Orthopedic Disorders: Fractures and Dislocations of the Mandible and Maxilla PDF

Orthopedic Disorders 22 CH A P TE R Patricia A. Schenck It is not possible to pr...

Orthopedic Disorders 22 CH A P TE R Patricia A. Schenck It is not possible to provide a complete review of the II. Clinical signs: Asymmetry of the jaw, oral hemor- anatomy, surgical approaches to the bones and joints, rhage and pain, crepitus, concurrent head and and surgical procedures in this review text. The reader is thoracic trauma encouraged to review surgical techniques, approaches, III. Diagnosis: Based on history and radiographs; CT can and anatomy using a surgery text. provide a three-dimensional (3-D) impression IV. Surgical procedures A. Preoperative considerations: Monitor neurologic FRACTURES OF THE SKULL function, and check for diaphragmatic hernia, I. Zygomatic arch fracture pneumothorax, and other conditions A. Preoperative considerations B. Anesthetic considerations: Place an endotracheal 1. Perform a neurologic examination tube through a pharyngotomy incision. Give 2. Confirm that the optic nerve and vision is antibiotics because most mandibular fractures intact before surgery are open 3. Computed tomography (CT) provides the best C. Surgical principles: Restore normal dental occlu- assessment sion. Intramedullary pinning is not recommended B. Surgical procedure: Reduce fractures that cause D. Postoperative care: Maintain nutrition with an compression of the eye esophagostomy or gastrostomy feeding tube. If C. Postoperative care and complications: Monitor not using a feeding tube, feed a soft gruel for neurologic function. Degenerative joint disease 4 weeks post surgery. Flush the mouth daily (DJD) of the temperomandibular joint (TMJ) may with dilute chlorhexidine solution result long-term. Prognosis is good E. Complications: Malocclusion is the most impor- II. Extracranial fractures: Fractures of the nuchal crest, tant complication; osteomyelitis occurs rarely sagittal crest, or frontal sinus V. Mandibular symphyseal separations A. Preoperative considerations: Perform neurologic A. Occurs often in cats examination B. Wire stabilization is the technique of choice B. Treatment: Most are managed conservatively. VI. Mandibular body fractures Surgery is performed if displacement is severe A. Create a muzzle using tape (Figure 22-1) C. Postoperative care and complications: Monitor 1. Can be used if there is minimal displacement neurologic function. Subcutaneous emphysema of fragments may occur secondary to frontal sinus fracture 2. Difficult to do in cats or in brachycephalic III. Intracranial fractures breeds A. Preoperative considerations 3. Feed soft gruel 1. Perform a neurologic examination B. Maxillary-mandibular fixation: Either wire the 2. Most are closed fractures maxilla to the mandible or use acrylic bonding of 3. Calvarial fractures are usually associated with the canine teeth to keep the mouth closed central nervous system (CNS) compromise C. Interfragmentary wiring: For fracture fragments B. Surgical procedure: Elevate depressed calvarial that are stable without loss of bone or fractures, and remove comminuted pieces comminution C. Postoperative care and complications: Monitor D. Intraoral acrylic splint neurologic function. Prognosis is guarded for neu- E. External skeletal fixation: Best used for fractures rologic recovery that are open, comminuted, or involve bone loss F. Bone plating VII. Mandibular ramus fractures FRACTURES AND DISLOCATIONS A. Usually do not require surgical treatment because OF THE MANDIBLE displacement is minimal I. Anatomy B. Condylectomy can be performed in those that A. About 15% of all fractures in cats are of the mandible develop an inability to open the mouth B. The mandibular canal contains the mandibular ar- VIII. TMJ dislocations tery and vein and the mandibular alveolar nerve A. Usually occurs from trauma 305 306 SECTION II SMALL ANIMAL C. Midline maxillary separations (traumatic cleft palate) 1. Occurs frequently in cats 2. Wide defects should be surgically closed D. Maxillary body fractures: Most do not require sur- gical treatment. Stabilization techniques used for mandibular fractures can be used for maxillary body fractures E. Postoperative care: Maintain adequate nutrition. Use gastrostomy or esophagostomy feeding tube. If not using a feeding tube, feed soft gruel F. Complications include dental malocclusion and osteomyelitis NEOPLASIA OF THE MAXILLA AND MANDIBLE I. Causes A. The oropharyngeal region is the fourth most com- mon site of malignant neoplasia in the dog B. The most common oral neoplasms in the dog are malignant melanoma, squamous cell carcinoma (SCC), fibrosarcoma, and epulides. SCC is the most common in cats Figure 22-1 Procedure for creating a tape muzzle. (From Birchard SJ, C. Boxers, golden retrievers, and cocker spaniels are Sherding RG, editors. Saunders Manual of Small Animal Practice, 3rd ed. predisposed to oral tumors. Small-breed dogs are St Louis, 2006, Saunders.) more prone to develop malignant melanomas, and large-breed dogs are more prone to SCC and fibrosarcoma D. Surgical resection is the first line of therapy for all B. Use closed reduction to replace, then stabilize with oral tumors either a muzzle of tape, or maxillary-mandibular II. Diagnosis fixation A. History includes drooling, halitosis, and dyspha- IX. TMJ dysplasia gia. Deformity of the muzzle may be present. A. Jaw locks in the open position. Reported in Most are painful, so anorexia is common Irish setters, cocker spaniels, and basset B. Physical examination: Consider sedation. Most hounds metastasize via the lymphatic system so examine B. May require condylectomy or resection of the lymph nodes zygomatic arch C. Diagnostic evaluation includes complete blood cell count, chemistry profile, radiographs of skull and chest. CT and magnetic resonance imaging FRACTURES OF THE MAXILLA (MRI) are helpful in evaluating the extent of I. Etiology invasion. Biopsy is important in determining A. Most are the result of trauma treatment B. More likely in young dogs and cats III. Tumor types II. Clinical signs include asymmetry of the maxilla, oral A. Benign nonodontogenic neoplasms pain and bleeding, nasal hemorrhage 1. Epulis III. Diagnosis a. Fibrous tumor originating from the A. History and radiographs. More than one fracture periodontal ligament may be present b. Rare in cats, common in dogs. The boxer is B. CT gives a 3-D view predisposed IV. Preoperative considerations 2. Other tumors include fibroma, hemangioma, li- A. Manage concurrent head, airway, and thoracic poma, chondroma, osteoma, and histiocytoma trauma. Maintain an airway and treat shock B. Malignant nonodontogenic neoplasms B. Complete a neurologic examination 1. Malignant melanoma V. Anesthetic considerations a. Often is locally invasive with early A. Place endotracheal tube through a pharyngotomy metastasis incision b. May be pigmented or nonpigmented B. Give antibiotics because many maxillary fractures c. Usually ulcerated, so oral bleeding and are open halitosis are common VI. Surgical fixation d. Treatment is complete surgical resection. A. Restore dental occlusion Radiation therapy has moderate success. B. Maintain patent nasal passages Chemotherapy is not effective  CHAPTER 22 Orthopedic Disorders 307 2. Squamous cell carcinoma (SCC) FRACTURES AND DISLOCATIONS a. Second most common oral tumor in dogs, OF THE SPINE most common tumor in cats b. Nontonsillar SCC is locally invasive and I. Atlantoaxial instability slow to metastasize. Tonsillar SCC is very A. Anatomy aggressive, with early metastasis to lymph 1. A pivot joint that allows the head to rotate nodes and lungs around an axis c. Wide surgical resection is the treatment 2. The dens is on the ventral surface of C2 (the of choice, with or without radiation axis) that projects into the floor of C1 (atlas) therapy. Chemotherapy may be added B. Causes to treatment 1. Congenital causes are most common and are d. Prognosis is guarded as recurrence is high seen in young, small and toy-breed dogs. Insta- 3. Fibrosarcoma bility arises from malformation of the dens, lack a. Third most common oral tumor in dogs; of ligamentous support, or congenital absence second most common in cats of the transverse or atlantoaxial ligaments b. Slow-growing, locally aggressive, late to 2. Acquired causes are the result of trauma and metastasize can happen at any age or breed of dog or cat c. Local recurrence is common C. Clinical signs d. Surgical resection is the treatment of 1. Vary from pain to ataxia or tetraplegia. The se- choice. Radiation and chemotherapy can verity is dependent on the degree of subluxation also be used in conjunction 2. If the dens luxates dorsally into the spinal 4. Other malignant nonodontogenic neoplasms cord, the signs are more severe include osteosarcoma (OSA), adenocarcinoma, 3. If the spinal cord suppression is severe, transmissible venereal tumor, mast respiratory arrest and death can occur cell tumor, hemangiosarcoma, and tonsillar D. Diagnosis lymphosarcoma 1. Radiographs are necessary and reveal a widened 5. Malignant odontogenic neoplasms space between the dorsal arch of C1 and the a. Ameloblastoma arises from the dental lami- dorsal spine of C2 nar epithelium. Rare tumors but more com- 2. CT and MRI are not required mon in younger dogs E. Surgical procedures b. Odontomas can invade all dental tissues 1. Do not flex the spine, which can exacerbate and are rare cord compression c. Surgical resection is the treatment of 2. Objectives are to remove the fractured or un- choice united dens, stabilize the C1-C2 articulation, IV. Surgery and prevent spinal cord injury A. Preoperative considerations 3. A dorsal approach or ventral approach can be 1. Knowledge of anatomy is necessary used. The ventral approach is more difficult 2. Maxillectomies are associated with significant but has a higher success rate blood loss, so have a source of blood 4. Complications include infection, dysphagia, replacement laryngeal paralysis, or surgical failure 3. Administer nonsteroidal antiinflammatory 5. Manage pain, administer antibiotics, and place drugs (NSAIDs) and fentanyl patches to an Elizabethan collar for 2 weeks. Restrict minimize postoperative pain exercise for 4 to 6 weeks 4. Use cuffed endotracheal tube II. Caudal cervical spondylomyelopathy (wobbler 5. Give antibiotics syndrome) B. Objectives are to resect completely the neoplasm A. Anatomy and preserve local blood supply 1. The dorsal components that play a role in- C. Procedures for surgery include maxillectomy clude the dorsal vertebral lamina, the articular (unilateral or bilateral), hemimaxillectomy, and facets and joint capsule, and the ligamentum mandibulectomy flavum D. Postoperative care 2. The ventral components that play a role in- 1. Pain control clude the vertebral bodies, the dorsal fibers of 2. Elizabethan collar to prevent self-mutilation the annulus fibrosus of the intervertebral disc, 3. Feed soft gruel for 1 month post surgery. Flush and the dorsal longitudinal ligament the oral cavity after eating. Maintain nutrition B. Causes 4. Reevaluate every 3 months for the first year. 1. Two populations of dogs get wobbler disease. Watch for metastasis About 10% to 15% are young Great Danes with E. Complications osseous malformations of the cervical spine. 1. Transient facial edema resolves after a few The remainder are middle-aged to older dogs weeks with acquired disease secondary to cervical 2. Nasal discharge, facial swelling, noisy respira- vertebral instability. Doberman pinschers tion, and inappetence often occur make up about 80% of this group. Labradors 3. The most common complication is dehiscence and dalmatians are also predisposed. 308 SECTION II SMALL ANIMAL 2. Pathologic changes 2. The choice of procedure is based on where the a. With congenital osseous malformation, compression is located (dorsal or ventral), the there is malformation or malarticulation of number of spaces involved, and whether it is the articular facets and vertebral bodies, dynamic or static which causes dorsal and lateral stenosis of F. Postoperative care and complications the spinal canal. C3 to C7 bodies are most 1. Manage pain (Fentanyl patch); give NSAIDs often affected. Stenosis is seen and gets 2. Administer antibiotics for 5 days post surgery worse with age. Heredity, nutritional 3. Provide nursing care for the recumbent patient imbalance, or trauma may play a role 4. Restrict activity for 3 to 6 months post b. Vertebral tipping is seen in middle-aged to surgery. Use a harness rather than a collar older patients. There is a malposition of for a dog the vertebral body caudal to the affected 5. Obtain radiographs monthly until there is intervertebral disc. The cranial aspect of complete bony fusion at the atlantoaxial joint the affected vertebra is displaced dorsally, (usually in 8-12 weeks) causing spinal compression. The C5 to C6 6. There is usually about an 80% return of function, and C6 to C7 spaces are most commonly but about 30% have recurrences within 2 years affected III. Spinal fractures and dislocations c. Chronic degenerative disc disease with A. Introduction cervical vertebral instability occurs most 1. Most are due to trauma in Doberman pinschers and is caused by 2. Repair depends on the region of the lesion, concurrent dorsal annulus and dorsal amount of neurologic dysfunction, body size, longitudinal ligament hypertrophy. The and other injuries caudal cervical intervertebral disc spaces 3. The thoracolumbar and lumbosacral junctions are affected most commonly are prone to fracture and luxation d. Ligamentum flavum hypertrophy causes dy- B. Causes namic dorsal spinal canal compression and is 1. Hyperextension is due to direct trauma to associated with vertebral arch abnormalities the dorsal spine, with collapse of the dorsal e. Hourglass compression is associated with compartment dorsal, ventral, and lateral compression and 2. Hyperflexion results in a wedge compression occurs most commonly in young Great Danes fracture of the vertebra, sparing the dorsal com- C. Clinical signs partment. These fractures are usually stable 1. A chronic, progressive history of neck pain, hy- 3. Compression occurs with an axial load force, permetria, ataxia, and tetraparesis is common and fragments and extruded nucleus pulposus 2. Compression worsens with neck extension can be driven into the spinal cord 3. The clinical signs may wax and wane; occa- 4. Rotation is usually associated with hyperexten- sionally there will be an acute deterioration sion, and disruption of both ventral and dorsal 4. Ataxia is usually worse in the rear limbs. Pro- compartments occur prioceptive deficits are present, with parapare- C. Clinical signs may range from pain or propriocep- sis progressing to tetraparesis. In the thoracic tion loss to loss of motor function limb, there is usually muscle atrophy of the D. Diagnosis spinatus muscle of the shoulder 1. Perform a complete physical examination, D. Diagnosis including a neurologic examination 1. Differentials include degenerative spinal cord 2. Obtain thoracic and abdominal radiographs. disease, ischemic myelopathy, discospondyli- Myelography is not indicated. CT is best for tis, congenital spinal cord disease, inflamma- identifying bony pathology; MRI is best for soft tory CNS disease, spinal neoplasia, brachial tissue visualization plexus tumor, subarachnoid cysts, and trauma. 3. Most important for prognosis is the presence Ischemic myelopathy is not associated with of deep pain. If deep pain sensation is intact, cervical pain, however there is an 85% to 90% chance of recovering 2. Myelography is helpful in identifying the site of normal neurologic function. If deep pain is ab- compression sent, there is only a 15% chance of neurologic 3. CT may be helpful in identifying dorsal arch function recovery abnormalities and osseous malformations in 4. Immobilize the patient to prevent additional the Great Dane spinal cord damage 4. MRI is the gold standard for imaging of the E. Preoperative considerations spine because MRI gives the greatest detail of 1. If the fracture is stable with minimal soft tissue structures displacement and the patient has good motor E. Surgical procedures function, the patient can be managed without 1. The three primary decompressive surgeries are surgery ventral decompression using a ventral slot tech- 2. Surgery is indicated if the fracture is unstable nique, ventral distraction and fusion using a or significantly displaced, if motor function is polymethylmethacrylate (PMMA) plug, and dor- diminished, or there is evidence of declining sal decompression using a dorsal laminectomy neurologic function  CHAPTER 22 Orthopedic Disorders 309 F. Surgical procedures 3. Prevent pneumothorax 1. For cervical fractures, most occur at the dorsal 4. Monitor for hemorrhage, seroma formation, spine or body of C2. A ventral approach to and pneumothorax. Manage pain the cervical spine provides the best bone 5. Neoplasms are usually malignant. Consider structure for fixation chemotherapy if excision was not complete 2. The thoracolumbar junction and lower 6. Metastases may have occurred even if the lumbar-lumbosacral space are the most tumor has been resected common locations of fracture or luxation in B. Pelvic neoplasia the thoracic and lumbar spine. The most 1. The ileal wing can be resected for localized common techniques are dorsal spinous tumors. Avoid hemorrhage and nerve damage process plating using plastic spinal plates 2. Monitor for seroma formation and infection and pin and PMMA fixation 3. Manage pain 3. Fractures of L6, L7, and the sacrum are 4. Consider chemotherapy if the tumor is malignant common; signs are related to sciatic, femoral, C. Vertebral neoplasia and sacral nerve deficits. A dorsal approach is 1. Remove as much of the tumor as possible and used for fixation decompress the spinal cord G. Postoperative care and complications 2. Administer dexamethasone prior to surgery to 1. Minimize pain, begin antibiotic therapy, and minimize spinal cord edema from manipulation provide nursing care for the recumbent patient 3. Perform multiple neurologic examinations 2. Begin physical therapy soon after surgery 4. Monitor for urine retention 3. Make sure there is urinary control; if not, 5. Consider chemotherapy express the bladder every 6 hours. Avoid 6. The prognosis for malignant vertebral tumors indwelling urinary catheters is poor 4. If deep pain sensation is present, about 85% will regain near-normal neurologic function FRACTURES OF THE SHOULDER I. Anatomy NEOPLASIA OF THE AXIAL SKELETON A. Fractures are often associated with brachial I. Causes plexus injuries or soft tissue injury A. OSA and chondrosarcoma are the most common B. Suprascapular nerve crosses the scapular neck neoplasms beneath the acromion B. Hemangiosarcoma and fibrosarcoma should also C. Cephalic vein is on the superficial craniolateral be considered aspect of the greater tubercle of the humerus C. Multilobular osteoma is the most common tumor D. Circumflex humeral vessels are distal to the teres of the skull minor, beneath the deltoideus muscle II. Clinical signs II. Diagnosis A. Usually presented for a swelling over a bone A. Clinical signs include lameness of the forelimb B. Neoplasias of the rib may lead to respiratory signs and pain or crepitus on palpation of the scapulo- C. Skull tumors may lead to neurologic signs humeral joint D. Pelvic tumors may result in constipation B. Radiography is required for diagnosis. CT is III. Diagnosis useful because of the 3-D views A. Radiographic signs may range from primarily lytic III. Fractures of the scapula to proliferative lesions A. Fracture of the scapular body is most common B. Polyostotic lytic lesions are seen with lymphoma B. If there is minimal displacement, treat with strict and multiple myeloma cage confinement C. Determine whether metastases are present; C. Because there are many tendons and muscles especially check regional lymph nodes and lungs around the scapulohumeral joint, osteotomy D. OSA or multilobular osteoma of the of the acromion or greater tubercles may be re- cranium appears as proliferative bony lesion of quired. These can then be reattached by screws flat bones D. Scapular body fractures are often transverse or E. Cerebrospinal fluid evaluation is usually oblique. Because the scapula is thin, treat with normal but may reveal increased levels of protein cage rest if at all possible and elevated pressure with vertebral neoplasia E. Fractures of the spine of the scapula do not F. Myelography and CT can determine the exact site require surgery of the tumor and how much spinal cord compres- F. Fractures involving the acromion require surgery sion is present with tension band or lag screw fixation G. Bone biopsy is necessary for a histopathologic G. Fractures of the scapular neck require surgery for diagnosis fixation. Be careful to protect the suprascapular IV. Treatment nerve A. Rib neoplasia H. Supraglenoid tubercle fractures require surgical 1. Completely remove the mass with wide normal fixation. In immature animals, the secondary margins center of ossification of the supraglenoid tubercle 2. Prevent abnormal chest wall movement can be confused with a fracture 310 SECTION II SMALL ANIMAL I. Glenoid fractures require surgical fixation C. Postoperative care involves pain control, minimiz- J. The prognosis is good for healing and normal ing postsurgical inflammation, and encouraging function if there is good stabilization movement of the distal extremity. Provide strict K. Restrict activity for about 8 to 12 weeks crate confinement for 3 weeks with leash walks L. Complications include suprascapular nerve D. The prognosis is good if stabilization is adequate injury, osteoarthritis (OA), and decreased limb function. Suprascapular nerve injury results in FRACTURES OF THE HUMERUS atrophy of the supraspinatus muscle IV. Proximal humeral fractures I. Anatomy A. These fractures are uncommon but occur A. The radial nerve lies within the musculospiral mostly in immature animals (Salter-Harris groove of the humerus type I, II, or III fractures). The physis of the B. On the lateral side, identify the lateral head of the proximal humerus is radiographically closed by triceps, the brachialis, the brachiocephalicus, and 10 months of age acromial head of the deltoid muscles. The radial B. If there is a proximal humeral fracture in an older nerve is also more lateral dog, evaluate for bone lysis or cortical thinning, C. On the medial side, identify the medial head of which could indicate OSA the triceps, the biceps brachii, and the median C. Surgery is required. Repair is usually with and ulnar nerves Steinmann pins and wire II. Causes. Most are due to trauma (hit by a car) or a D. Avulsion fractures of the greater or lesser fall from excessive heights tubercle occasionally occur in immature III. Diagnosis animals A. Diagnosis is based on radiographic findings E. For Salter-Harris I or II fractures, do a craniolat- B. Check for other thoracic trauma such as pneumo- eral approach. In young animals, use Steinmann thorax, diaphragmatic hernia pins and Kirschner wires. In older animals, use IV. Proximal humeral physeal fractures lag screws and Kirschner wire A. Seen in young dogs before physeal closure takes F. For Salter-Harris III fractures, in young animals, place use lag screws and Kirschner wire. In older B. Surgery is usually required for fixation animals, screws and a T plate can be used C. Use a cranial approach and fix with Kirschner G. Fractures of the humeral neck occur in older wires or Steinmann pins animals. Stabilize with a T plate or with Rush D. Restrict activity but encourage range of motion pins or Kirschner wires. Restrict to cage rest activity until signs of healing are seen on radiographs. V. Proximal diaphyseal fractures Malunion occurs rarely. If there is good A. Least common diaphyseal fracture stabilization, these fractures heal rapidly B. Evaluate brachial plexus and radial nerve C. Many occur secondary to metabolic bone disease D. Surgery is necessary SCAPULOHUMERAL LUXATION E. Use a cranial approach. A single intermedullary I. Causes pin may not provide rotational stability. Can use A. Occurs uncommonly two Rush pins, Steinmann pins, or a bone plate B. Medial luxation is most common, especially in F. Encourage early range of motion with restricted small-breed dogs exercise C. Lateral luxation occurs in larger dogs VI. Diaphyseal fractures II. Clinical sign is forelimb lameness A. These fractures are often spiral and can entrap III. Diagnosis is based on physical examination and the radial nerve radiography B. Muscle contraction causes overriding of fragments IV. Closed reduction C. Closed reduction can be attempted early after injury A. Medial luxation D. For surgery, use a lateral approach 1. Flex elbow and pull limb laterally while E. In small breeds, a combination of pins, wires, or exerting pressure on the scapular spine external fixation can be attempted. When using 2. Use general anesthesia pins, retrograde the pins into the proximal frag- 3. Place in a Velpeau sling for 2 weeks ment from the fracture site 4. Restrict exercise for another month. Swimming F. In large breeds, interlocking nails have been used. is a good exercise Plate fixation can be successful but is difficult be- B. Lateral luxation cause of the vessels and nerves present. Medial 1. Use general anesthesia plate placement is easier 2. Flex elbow and extend the shoulder while G. If external fixation is used, remove it in 4 to rotating the humeral head upward 6 weeks. Remove intramedullary pins following 3. Use spica splint for 2 weeks fracture healing V. Open reduction VII. Supracondylar fractures A. Use general anesthesia A. Rigid internal fixation is necessary B. Open reduction can be challenging and involves B. Steinmann pins or double Rush pins can be used. surgery to stabilize the joint In larger dogs, small bone plates can be used  CHAPTER 22 Orthopedic Disorders 311 VIII. Condylar fractures 2. Use small intramedullary pins or K-wires A. Most condylar fractures involve the lateral across the fracture, then place wire around portion of the condyle, which carries most of the pins in a figure-eight fashion the force through the elbow joint because of the G. Trochlear notch fractures articulation with the radial head 1. Because this is an articular fracture, there B. Spaniels and rottweilers have a heritable defect must be good alignment of the fracture with in which the humeral condyle does not com- rigid fixation pletely ossify. This predisposes them to this 2. Counteract the forces of the triceps by using fracture the tension band principle C. Surgery is usually necessary 3. Use intramedullary pins, K-wires, or bone D. Transcondylar lag screws with Kirschner wire plates. Contour the bone plate to the caudal or are used. Using crossed Kirschner wires is not caudolateral side of the ulna recommended H. Radial head fractures E. Arthritis and reduced range of motion are 1. Precise reduction with rigid fixation is necessary common complications 2. Use K-wires and lag screws to fix IX. Intercondylar fractures of the humeral condyles I. Radial neck and proximal physeal fractures A. These are very difficult to repair, as the condyles 1. In immature animals, stabilize without com- are split, in addition to the supracondylar pression to prevent premature closure of the fracture growth plate B. Fix the two condyles together first, then fix the 2. Stabilize so that the radial head articulates supracondylar fracture properly with the humeral condyle C. Lameness and OA are common complications 3. Use K-wires. Do not penetrate the articular surface of the radius 4. Remove the K-wires in 3 to 4 weeks FRACTURES AND GROWTH J. Monteggia fractures DEFORMITIES OF THE RADIUS 1. Refers to a fracture of the ulna with a radial AND ULNA, LUXATION OF THE ELBOW head luxation I. Fractures of the radius and ulna 2. Stabilize the ulnar fracture and reduce the A. Introduction radial head luxation 1. Commonly seen K. Mid-shaft radial and ulnar fractures 2. Usually the result of trauma or from falling or 1. Maintain proper angulation, rotation, and jumping length of the limb 3. Open fractures of the distal part of the radius 2. Prevent synostosis of the radius and ulna in and ulna are common immature animals B. Anatomy 3. Closed reduction and cast fixation 1. The radius is the main weight-bearing bone of a. Used for minimally displaced transverse the forelimb and is shorter than the ulna. The fractures ulna is the longest bone in the body b. Flex the elbow in a functional angle, and 2. The radial and interosseous arteries provide place the carpus is a slight varus position the main arterial supply. The radial, median, c. Apply a fiberglass cast, working from distal and ulnar nerves supply the antebrachium to proximal and paw 4. External fixation is used for comminuted C. Preoperative considerations fractures and simple fractures 1. Evaluate for concurrent injuries a. Reduce the fracture closed if possible 2. Evaluate neurologic function b. Place three or four pins on each side of the D. General objectives of surgery fracture line 1. Allow early return to weight bearing L. Plate fixation for distal metaphyseal fractures 2. Preserve neurovascular structures 1. Occur primarily in small dogs E. General postoperative care and complications 2. High incidence of nonunion if the fracture is 1. Use a soft padded bandage for 3 to 10 days to not stable reduce postoperative swelling 3. Align the fracture with compression, and insert 2. Reevaluate with radiographs every 3 to a cancellous bone graft 4 weeks. Restrict activity until the fracture M. Fractured styloid process of the ulna has healed 1. Reduce and stabilize the fracture with K-wires 3. Complications include delayed healing and and wire in a figure-eight configuration nonunion. If the fracture has not been stable, 2. Splint for 3 to 4 weeks postoperatively DJD can occur. If the animal is immature, there II. Growth deformities of the radius and ulna may be premature closure of the growth plates A. Anatomy F. Olecranon fractures 1. Deformities result from trauma and disruption 1. The triceps attached to the olecranon. of the blood supply to the physis, with synos- Counteract the forces of the triceps by using tosis of the radius and ulna the tension band principle and converting it 2. The physes of the radius and ulna close at into a compressive force about 7 to 9 months of age in dogs 312 SECTION II SMALL ANIMAL 3. The distal ulnar physis contributes about 85% and flexion and extension of the elbow are not to the longitudinal growth, and the proximal possible physis (olecranon) contributes about 15% to C. Diagnosis is via radiography the growth of the ulna D. Most elbow luxations can be treated by closed 4. The distal radial physis contributes about 60% reduction if treatment is initiated within the first and the proximal radial physis contributes 40% 3 days after the injury (Figure 22-2) to the longitudinal growth of the radius E. If elbow fractures are present, then surgery is 5. The radius and ulna must grow in a synchro- indicated. Surgical reduction is difficult nous fashion to attain a normal shape F. Keep the elbow extended to maintain reduction, B. Preoperative considerations obtain radiographs to confirm reduction. Put in a 1. Early recognition and treatment are important lateral splint to maintain elbow extension. Main- 2. Obtain radiographs and determine whether tain the splint for 2 weeks, then allow leash walks physes are open or closed for another 2 weeks C. General postoperative care and complications 1. In immature dogs, splint the limb, and FRACTURES AND DISLOCATIONS reevaluate radiographically every 3 weeks OF THE CARPUS 2. The prognosis is guarded, especially for mature dogs with severe deformities I. Introduction D. Surgical procedure to correct premature closure A. Usually the result of trauma. Isolated fractures of of the distal ulnar physis the carpus are rare, usually occurring in grey- 1. In immature dogs, remove a section of the ulna hounds or working dogs to allow unrestrained growth of the radius, and B. Fractures usually involve the articular surface so prevent regrowth by placement of a fat graft rigid fixation is necessary 2. In mature dogs, there is cranial or medial II. Anatomy bowing, carpal valgus, limb shortening, and A. Osseous structures malalignment of the radius/ulna in the elbow 1. The seven bones are arranged in two rows. 3. Objectives are to correct the angular deformi- The proximal row includes the radial, ulnar, ties, and maintain as much limb length as and accessory carpal bones. The distal row possible consists of the C1, C2, C3, and C4 carpal bones 4. Perform an osteotomy of the radius at the 2. The radial bone is the largest, is located medi- point of maximal curvature ally, and articulates with the radius proximally, E. Surgical procedure to correct premature closure and with C1, C2, C3, and C4 distally of the proximal radial physis 3. The ulnar carpal bone is lateral and articulates 1. Usually not recognized until after the bone with the radius and ulna proximally, the acces- growth of the radius is finished sory carpal bone on the palmar side, and with 2. There is distal luxation of the radial head from C4 and the 5th metacarpal bone distally the humerus, and the leg is straight 4. C4 is the largest bone of the distal row, and it ar- 3. The objective is to articulate the radial head ticulates with the 4th and 5th metacarpal bones with the humerus and ulna B. Articulations F. Surgical procedure to correct premature closure 1. The antebrachiocarpal joint is between the of the distal radial physis distal radius and ulna and the proximal row of 1. In the immature dog with complete closure, carpal bones. It provides about 70% of the there is distal luxation of the radial head, and range of motion the limb is shortened. The leg remains straight, 2. The middle carpal joint is between the proxi- and the radius and ulna bow rarely. The objec- mal and distal row of carpal bones, and it pro- tive is to remove a section of the radius to al- vides about 25% of the range of motion low unrestricted growth of the ulna 3. The carpometacarpal joint is between the 2. In the immature dog with partial lateral closure, distal row of carpal bones and the metacarpal there is carpal valgus with external rotation, bones, and it provides only about 5% of the cranial and medial bowing of the forelimb, and range of motion shortening of the limb. The objective is to 4. The intercarpal joints are those between the car- remove the closed portion of the distal radial pal bones. There is little motion in these joints physis and prevent bony bridging of the C. Ligamentous structures removed physis 1. There is no continuous collateral ligament that 3. In mature dogs, the objective is to reestablish spans all three joints congruity to the elbow joint and to correct the 2. The radial collateral ligament spans from the angular deformity of the limb styloid process of the radius to the radial III. Traumatic luxation of the elbow carpal bone A. Lateral luxation is common because the medial 3. The ulnar collateral ligament spans from the condyle of the humerus is larger which prevents styloid process of the ulna to the ulnar carpal medial luxation bone B. Clinical signs include acute non-weight-bearing 4. The flexor retinaculum supports the palmar lameness; the foot and antebrachium are abducted, part of the carpus  CHAPTER 22 Orthopedic Disorders 313 100° Anconeal process Medial pressure on olecranon Lateral humeral epicondyle Inwardly rotate A B antebrachium Flex Medial epicondyle Anconeal process medial to epicondyle Pressure on radial head Outwardly rotate antebrachium C Extend Figure 22-2 A, For closed reduction of a laterally luxated elbow (B), flex the elbow and inwardly rotate the antebrachium to hook the anconeal process into the olecranon fossa. C, Then extend the elbow slightly and abduct and outwardly rotate the antebrachium while placing pressure on the radial head. (From Fossum TW. Small Animal Surgery, 3rd ed. St Louis, 2007, Mosby.) 5. The palmar carpal fibrocartilage crosses the IV. Fractures of the ulnar carpal bone and C1, C2, C3, or C4 palmar surface and attaches to all the bones A. Very rare except the accessory carpal bone. It also at- B. Most are small chip fractures from hyperexten- taches to the metacarpals sion injury II. Fractures of the radial carpal bone C. Treatment is fragment removal, splinting, and A. Most often occur in working dogs resulting from exercise restriction jumps or falls. Fractures may be chip fractures, V. Luxations, subluxations, and hyperextension injuries slab fractures, or avulsion fractures rarely. Lame- of the carpus ness is noted immediately following the injury. A. Clinical signs and diagnosis Bone fragments rarely reattach 1. Most common injury of the carpus in nonwork- B. Nondisplaced fractures can be treated with a ing dogs; usually the result of a fall or jumping splint for 6 to 8 weeks from a height. Tears or the palmar joint capsule, C. Surgery is indicated to remove small fracture ligaments, and fibrocartilage also occur with the fragments. Larger fragments can be fixed fracture using screws or Kirschner wires. A splint is 2. Most have acute, non–weight-bearing lameness, used for several weeks postoperatively. with soft tissue swelling. Carpal hyperextension Restrict exercise for 6 to 8 weeks. OA is a is present, so the carpal pad touches the ground common sequel when standing III. Fractures of the accessory carpal bone B. Treatment A. Uncommon except in racing greyhounds 1. Splinting is not usually successful because B. These are usually avulsion fractures and need there are soft tissue injuries present with little internal fixation support for the carpus C. Use screws and Kirschner wires 2. Arthrodesis is the treatment of choice. If the D. Splint for 4 to 6 weeks postoperatively, and antebrachiocarpal joint can be preserved, restrict exercise for 12 to 16 weeks there will be little gait alteration after surgery 314 SECTION II SMALL ANIMAL 3. If plates are used, splint for 6 to 8 weeks post 6. Fractures of the ischium that entrap the sciatic surgery. Once soft tissue swelling has sub- nerve sided, the splint can be changed to a cast if 7. Fracture of the pubis with herniation necessary 8. Gross displacement of the iliac crest or C. Postoperative complication ischiatic tuberosity 1. Soft tissue swelling is common for a few days V. Special considerations post surgery. Monitor the tightness of the A. Fractures of the ilium bandage and splint 1. Damage to the sciatic nerve may be 2. Complications are rare once bony fusion has present occurred 2. Surgical repair is usually recommended because most are displaced or unstable, and the ilium is weight bearing FRACTURES OF THE PELVIS 3. Plates and screws are usually used I. Causes 4. Seroma formation is common. Use warm A. Very common compresses to treat B. Severe trauma (e.g., hit by car) is usually the cause 5. Restrict activity to leash walks for 6 to C. Concurrent injuries are common 8 weeks II. Anatomy 6. The prognosis is good with good stabilization A. Major weight-bearing regions are the sacroiliac B. Fractures of the acetabulum joint, body of the ilium, and acetabulum 1. Usually accompanied by other pelvic B. Each half of the pelvis is composed of the ilium, fractures ischium, pubis, and acetabulum 2. These are difficult fractures to repair; the surgi- III. Diagnosis cal approach is difficult, and rigid fixation is A. Determine whether there are other concurrent necessary injuries. Treat shock, perform radiographs 3. The treatment of choice is surgical (especially of the chest), perform an electrocar- stabilization diogram, make sure that the urinary tract is 4. Femoral head and neck ostectomy can be intact. Caudal abdominal hernias can occur in performed if it is not possible to reconstruct conjunction with pelvic fractures an acetabular fracture B. When the patient is stable, radiograph the pelvis 5. Restrict activity to leash walks for 6 to to evaluate bony injury. Perform a neurologic 8 weeks examination to evaluate spinal reflexes, anal tone, 6. If there is good stabilization, prognosis and perineal sensation is good. If stabilization is poor, the IV. Treatment prognosis is fair to poor; OA usually A. Malunions are common. Repair fractures as develops. If femoral head ostectomy is soon as the patient is stable and are a good performed, the prognosis is guarded anesthetic risk to fair B. Nonsurgical treatment C. Sacroiliac fracture or luxation 1. Used for unilateral fractures, fractures with 1. Surgical treatment is difficult, so manage minimal displacement, fractures of the nonsurgically if possible non–weight-bearing portion of the pelvis. 2. Perform neurologic examination and evaluate Nonsurgical treatment is best in animals with bladder function, anal tone, and perineal intact neurologic function and no soft tissue sensation injuries that require surgery 3. If neurologic deficits are present, the prognosis 2. Nursing care can be extensive. Many are is guarded reluctant to stand or turn over. A padded bed D. Fractures of the ischium should be used; turn the patient regularly, and 1. Usually associated with fractures of other keep the patient clean and dry weight-bearing regions of the pelvis 3. Provide pain control 2. Surgical repair is usually unnecessary unless 4. Prevent constipation with stool softeners or there is severe pain or displacement that mild laxatives impacts function of the hip 5. Empty the urinary bladder regularly E. Fractures of the pubis 6. Restrict activity to cage rest for 3 to 4 weeks 1. More common in young animals in which the 7. Physical therapy will help lessen disuse atrophy pelvic symphysis has not yet fused C. Surgical treatment indications 2. Surgery is usually unnecessary unless 1. Fracture of the ilium with fracture of the there is herniation of abdominal or pelvic pubis and ischium that creates an unstable organs acetabulum F. Narrowed pelvic canal associated with healed 2. Fractures of the acetabulum pelvic fractures 3. Displaced or unstable sacroiliac fractures 1. Obstipation and dystocia are most common in 4. Severe bilateral fractures of the pelvis cats and small dogs 5. Pelvic fracture associated with hip luxation or 2. Subtotal colectomy may be necessary if there femoral fracture is obstipation  CHAPTER 22 Orthopedic Disorders 315 III. Avascular necrosis of the femoral head DISORDERS OF THE COXOFEMORAL JOINT A. Causes I. Anatomy 1. Also known as Legg-Perthes or Legg-Calve- A. Ball-and-socket joint made up of the acetabulum Perthes disease and femoral head 2. Most common in young small-breed dogs B. The fossa of the acetabulum and the fovea of the 3. No history of trauma; lameness is bilateral in femoral head may be mistaken for radiographic about 15% of animals abnormalities 4. Cause is unknown C. The femoral head has an extensive blood 5. Weight bearing causes the bone to collapse supply with fracture of the cartilage D. The major muscles of the thigh all have insertions B. Diagnosis or origins close to this joint 1. Diagnosis is based on physical examination II. Coxofemoral luxation and radiographs A. Diagnosis 2. Limb may be shortened and muscles atrophied 1. Animals will usually not bear weight on the 3. On radiographs, decreased bone density is limb noted, with a widened joint space 2. If you pull the hindlimbs directly caudally, they C. Treatment should be the same length in a normal animal. 1. Surgery is usually necessary If they are different lengths, the coxofemoral 2. Excision arthroplasty (removal of the femoral joint is most likely dislocated head and neck) is the most common procedure B. Closed reduction because dogs with such injury are usually small 1. Replace the femoral head into the acetabulum IV. Hip dysplasia with the patient under general anesthesia using A. Causes rotation and traction 1. The most common disorder of the hip in the 2. Once the hip is back in place, use a flexion dog and the most common cause of OA sling if the luxation was craniodorsal; use hob- 2. Most commonly affects large- and giant-breed bles if the luxation was caudoventral. Restrict dogs, although all breeds can be affected motion for 7 to 14 days, depending on the age 3. There is a polygenic mode of inheritance of the animal. Limit exercise for an additional 4. Joint instability results as the stresses at the 2 to 4 weeks (Figure 22-3) hip joint exceed the support of the surrounding 3. Reluxation is not uncommon. If reluxation soft tissues occurs, use an open reduction B. Diagnosis C. Open reduction 1. Lameness and gait abnormalities are usually 1. If there is an avulsion fracture, surgery should seen, especially after exercise be performed 2. Ortolani sign: Place a hand on the knee and 2. The typical approaches are the cranial lateral apply dorsal pressure to the femur while approach to the hip or the trochanteric moving the leg from an adducted to an ab- osteotomy approach ducted position. If a click is heard, this is a 3. Reduce the femoral head, and then anchor it to positive Ortolani sign and indicates joint laxity prevent relaxation 3. Radiographic findings range from subluxation 4. Reluxation is not uncommon. If this occurs of the femoral head to severe secondary DJD then excision arthroplasty or total hip replace- C. Treatment ment is considered 1. Medical treatment involves weight control, 5. Restrict activity for 1 month alleviation of pain, reduction of inflammation, and restriction of activity 2. Surgery is considered when medical manage- ment is no longer effective 3. Surgical procedures a. Triple pelvic osteotomy: Used in patients with little evidence of DJD. Osteotomies of the ilium, pubis, and ischium are performed, and the acetabulum is rotated so that it pro- vides more coverage of the femoral head. Restrict activity for 8 weeks b. Femoral head and neck excision arthro- plasty: This is a salvage procedure used in smaller dogs (i.e., less than 40 lb). The femo- ral head and neck are removed, which re- moves the painful contact points in the joint. Figure 22-3 After reduction, use a flexion (Ehmer) sling for a craniodorsal Encourage use of the limb within 1 week of luxation (left) and hobbles for a caudoventral luxation (right). (From Birchard SJ, surgery. It will take 2 to 3 months for the Sherding RG, editors. Saunders Manual of Small Animal Practice, 3rd ed. limb to reach a functional level. There may St Louis, 2006, Saunders.) be muscle atrophy or a post-legged gait 316 SECTION II SMALL ANIMAL c. Pectineal myectomy: The entire pectineus femur. The peroneal and saphenous nerves run muscle is removed, which decreases ten- caudal to the femur sion on the medial aspect of the coxofemo- B. Evaluate for ligament injuries to the stifle ral joint capsule and may relieve some of C. Most of the fractures are physeal fractures the associated pain. Restrict activity for D. Lateral, medial, or cranial approaches can be 2 weeks. Seroma formation is common used. Pins, plates, or screws may be chosen for d. Total hip replacement: Growth plates must fixation be closed. Performed in dogs weighing more E. Restrict activity for at least 24 hours; if the fixa- than about 40 lb. Strict asepsis must be ad- tion is stable, start leash walks 1 to 2 days after hered to, and the dog must be free of infec- surgery tion. Restrict activity for 2 months. About F. Contracture of the quadriceps can occur from ad- 95% of dogs will have satisfactory function hesions, usually when the leg is fixed in an ex- tended position. DJD can result if the fixation is not stable. In young animals, there may be limb FRACTURES OF THE FEMUR shortening from physeal closure I. Proximal femur A. The proximal femur includes the femoral head, ORTHOPEDIC DISORDERS OF THE STIFLE the femoral neck, the trochanters, and their at- tachments to the femoral shaft. The sciatic nerve I. Anatomy runs caudal to the hip on top of the gemelli, inter- A. Patella luxation, cruciate disruptions, and menis- nal obturator, and quadratus femoris muscles. cal problems account for about 95% of stifle The femoral artery, nerve, and vein are very su- disorders in dogs and cats perficial in the femoral triangle B. The cranial stifle is made up of the quadriceps B. Preoperatively, stabilize the patient, take radio- muscles, patella, patellar tendon, and tibial graphs, and administer antibiotics tuberosity, aligned with the coxofemoral joint, C. The most common approach is the craniolateral talocrural joint, and paw. There should be no approach. Fractures can be repaired, or a femoral medial or lateral deviation head and neck ostectomy can be performed C. Neurovascular structures run longitudinally and D. The proximal femur is subject to many stresses, close to the caudal joint capsule and stability can be a problem. Prevent weight II. General preoperative considerations bearing for the first few weeks, then start non- A. Do a complete orthopedic evaluation weight-bearing physical therapy after that. Repeat 1. Palpate the patellar tendon. If the edges feel radiographs before initiating significant activity indistinct, this indicates stifle effusion which is E. There will be a period of increased vascularity associated with cranial cruciate rupture or DJD and decreased bone density of the femoral neck secondary to rupture postoperatively. Monitor with serial radiographs 2. Determine range of motion of the stifle. Clicks II. Femoral diaphysis may be heard that indicate crepitus and menis- A. The femoral artery and nerve pass medially down cal pathology the length of the shaft. The sciatic nerve is lo- 3. Attempt cranial movement of the tibia while cated caudal to the vastus lateralis muscle and holding the femur motionless (the drawer sign lateral to the semimembranosus muscle or Lachman test). Movement indicates laxity of B. Preoperatively, stabilize the patient, take radio- the cranial cruciate ligament graphs, and administer antibiotics 4. With the femur held motionless, grasp the C. A combination of intramedullary pins and cer- hock and rotate the tibia. Normally there is clage wires are typically used for fixation. If the 20 to 30 degrees of internal rotation, with 5 to fracture is highly comminuted, external fixation 10 degrees of external rotation will probably be necessary to provide stability 5. Exert medial and lateral digital pressure on the D. Maintain soft tissue attachments to bone frag- patella while moving the stifle to detect patel- ments. Use avascular bone fragments only if they lar luxation are needed to obtain stability 6. Exert pressure on the lateral side and medial E. If the fracture repair is stable, start leash walks side to detect increased laxity of the joint 3 to 5 days after fixation, and increase activity space and laxity of the collateral ligaments slowly over 4 weeks. Remove implants if needed 7. Exert deep pressure on the stifle to determine about 6 to 8 weeks after repair focal pain F. Healing may fail if stability is not good or osteomy- B. Obtain radiographs elitis occurs. Nonstable, devitalized bone fragments III. Principles of stifle surgery can lead to draining tracts. Excessive periosteal re- A. Place dog in dorsal recumbency action with large callus formation may occur B. Perform an arthrotomy to identify and examine III. Distal femur all structures A. Includes the metaphysis, condyles, trochlea, and IV. Patellar luxation patella. The femoral artery divides into the poplit- A. Commonly affects miniature breeds. Medial patel- eus and saphenous arteries, which run laterally lar luxations are most common; lateral luxations and medially on the caudal aspect of the distal almost always occur in large and giant breeds  CHAPTER 22 Orthopedic Disorders 317 B. Generally congenital or developmental. Contribut- F. Lateral retinacular imbrication technique: ing factors include decrease or increase in the an- Most common extracapsular technique; can be gle formed by the head and neck of the femurs, performed on any size patient bowing of the distal part of the femur, a shallow G. TPLO: This procedure is gaining in popularity. It trochlear groove, increased internal or external is designed to eliminate tibial thrust where the tibial rotation, and malpositioned tibial tuberosity tibia moves forward during active weight bearing C. Classification of luxations in the stifle with cranial cruciate ligament laxity. 1. Grade I: The patella lies in the trochlear groove The tibial plateau is leveled to nearly perpendicu- but can be manually subluxated or luxated lar to the long axis of the tibia. An intact caudal 2. Grade II: There is clinical spontaneous luxation; cruciate ligament is required. It is probably best the patella can be luxated manually but reduces suited for large or giant breeds or very active spontaneously or with minimal manipulation dogs. TPLO requires specialized equipment and 3. Grade III: The patella is luxated most of the expertise time but can be reduced manually H. Postoperative care 4. Grade IV: Patellar luxation cannot be reduced 1. Administer analgesics manually 2. Padded bandage for 1 to 2 days to reduce D. Diagnosis is based on a history of intermittent swelling rear-leg lameness, particularly during exercise 3. With a fascial strip, use a lateral splint, leash E. Surgical procedures vary; some require parapatel- walk for 3 months, return to normal function lar arthrotomy and release to diminish the tension after 6 to 9 months on tissue, and some require arthrotomy with tight- 4. With lateral retinacular imbrication, limit ening of surrounding tissues exercise for 6 weeks, and gradually return to F. The objective is to stabilize the patella and main- normal activity over the next 2 to 4 weeks tain a full range of motion 5. With TPLO, limit exercise for 8 weeks, then G. Surgical techniques radiograph to assess bone healing 1. Trochleoplasty: Deepening of the trochlear VI. Caudal cruciate ligament rupture groove. Begin physical therapy on the day of A. Extremely rare. There is acute lameness and a surgery; restrict activity for 1 month caudal drawer sign with 90 degrees of stifle flexion 2. Chondroplasty: Used in dogs less than 6 months B. Avulsion of the bony attachment is also present of age VII. Meniscal problems 3. Wedge resection: Remove a piece of the troch- A. Isolated meniscal tears are rare in dogs. Meniscal lea, then cut a piece below to deepen, and pathology is usually associated with partial or replace the first removed wedge complete cranial cruciate tear 4. Imbrication: After creating increased depth in B. With cruciate injury, there is craniocaudal and the trochlear groove, perform imbrication rotational laxity, which allows the femoral (tightening) of the lax side using either the condyles to traumatize the caudal horn of the DeAngelis technique or Flo technique medial meniscus 5. Tibial tuberosity translocation C. Diagnosed by hearing or palpating a click during V. Cranial cruciate ligament rupture range of motion A. There is usually an acute onset of rear-limb lame- D. Surgery indicated to remove or repair the menisci ness, usually during exercise. Chronic lameness VIII. Collateral ligament disruptions may be present in older overweight dogs. There A. Occur as a result of severe varus (medial) or is firm swelling on the medial aspect of the joint valgus (lateral) stress to the stifle with a chronic cruciate ligament rupture B. Classification B. The cranial drawer sign will be present with 1. First degree: Stretching and minor disruption rupture of the cranial cruciate ligament of collagen fibers; responds to rest and re- C. Tibial compression: Use one hand to hold the femur stricted exercise motionless with a finger resting on the tibial tuber- 2. Second degree: Partial tearing; responds to osity, then gently dorsiflex the hock with the other rest and restricted exercise hand. If cranial cruciate ligament laxity is present, 3. Third degree: Complete discontinuity of the the tibia will move cranially. The cranial drawer test ligament; requires surgical repair is more consistent than the tibial compression test C. The objective is to restore the integrity of the in- D. Surgical techniques are classified as either intra- jured ligament and stability of the stifle capsular (stabilization from within the joint) or IX. Stifle luxation extracapsular (stabilization outside the joint) A. Severe trauma is necessary for stifle luxation to 1. Intracapsular techniques: Patellar tendon tech- occur. It is more common in cats. The patellar niques, over-the-top repairs, and under-and-over tendon is usually not disrupted repairs B. Repair ligaments and tendons to reestablish joint 2. Extracapsular techniques: Lateral imbrication stability technique, and tibial plateau leveling osteotomy C. Place an external fixator, setting pins in the distal fe- (TPLO) mur and proximal tibia, and maintain for 3 to 4 weeks. E. Fascial strip over-the-top technique: Suitable for Alternative to external fixation is to use a full cast. dogs that weigh less than 40 lb Place the stifle in a partially flexed position 318 SECTION II SMALL ANIMAL bearing because of injury to other limbs, FRACTURES OF THE TIBIA AND FIBULA restricted activity is not possible, and rigid I. Introduction fixation is necessary A. Account for about 15% to 20% of long bone V. Postoperative care and complications fractures in small animals A. Apply compressive wrap for 3 to 5 days to B. There is minimal soft tissue coverage of these prevent soft tissue swelling bones, so fractures are often open B. Cover connecting bars and clamps of external II. Anatomy fixation with tape and gauze A. Epiphysis: The epiphyseal regions are composed C. Do not routinely remove small pins, wires, of loosely woven, trabecular bone, which limits screws, but remove large intramedullary pins the holding power of fixation implants. Epiphyseal D. Remove plates if chronic infection and drainage regions serve as ligament and tendon insertions occur, if animal experiences pain when exposed and are subjected to tensile forces. Epiphyseal to cold ambient temperatures, or when the plate regions that support articular cartilage are sub- design induces bone atrophy jected to compressive loads. Fracture healing in E. Complications include nonunion, malunion, infec- this area is rapid due to the ample blood supply tion, and growth deformities B. Physis: This region exists only in young, growing F. Infection requires immediate aggressive therapy to animals. Injuries here can cause premature avoid progression to osteomyelitis and nonunion cessation of growth C. Metaphysis: This is an indistinct region between LUXATION, SUBLUXATION, AND SHEARING the physis and diaphysis INJURIES OF THE TARSAL JOINT D. Diaphysis: The tibial diaphysis is subjected to bending and torsional forces. Fractures here heal I. Anatomy slowly and require prolonged rigid fixation A. The tarsus consists of the tibia, fibula, metatarsal III. Preoperative considerations bones, and seven tarsal bones A. Evaluate cardiopulmonary function and neurologic B. The tarsocrural joint is between the tibia and fib- function. Look for other musculoskeletal injuries ula proximally and the talus and calcaneus distally B. Provide antibiotics if the fracture is open 1. Most luxations and subluxations involve this IV. Surgical procedures joint A. Pin and tension band wire fixation: Used for avul- 2. The major ligaments for stability on the medial sion fractures of the fibular head, tibial tubercle, side are the long medial ligaments and tibiotalar or lateral or medial malleolus short component ligament B. Interfragmentary lag screw fixation: Used for 3. The major ligaments for stability on the lateral intra-articular fractures of the proximal and distal side are the long lateral ligament and the calca- epiphysis and for reconstruction of comminuted neofibular short component ligament shaft fractures prior to plating C. The intertarsal joints are between the tarsal C. Cross pin and rush pin fixation: Used for trans- bones. The most common injury is damage to the verse fractures of the epiphysis, axially stable plantar ligaments and tarsal fibrocartilage fractures of the metaphysis, and Salter I and II II. Tarsocrural luxation and subluxation fractures of the proximal and distal physis A. Surgery is recommended D. Intramedullary pin and wire fixation B. Luxation results from combinations of injuries 1. Used for simple, axially stable fractures of the that fracture the malleoli and damage contralat- tibial diaphysis eral ligaments 2. Contraindicated in infected or contaminated C. Subluxation occurs from rupture or avulsion of open fractures, or in fractures that cannot be either the lateral or medial collateral ligament reconstructed complexes 3. The pin should be about 50% to 60% of the 1. With a medial rupture, the paw tilts laterally smallest medullary canal diameter with a lateral valgus force 4. Cerclage wires can be used on long oblique 2. With a lateral rupture, the paw tilts medially fracture line, which can be accurately reduced with a medial varus force 5. Interfragmentary wires can be used to stabilize D. Perform radiographs to check for other injuries short oblique patterns E. Double-prosthesis replacement E. External skeletal fixation 1. Reproduces the components of the medial and 1. Indicated in stable reducible and nonreducible lateral collateral ligament, allowing joint stability fracture patterns, open fractures with signifi- to be maintained cant soft tissue damage, or infected fractures 2. Double-ligament replacement yields better 2. Contraindicated in intra-articular fractures and results than conservative management avulsion fractures of ligament and tendon 3. After surgery, allow some weight-bearing mobi- epiphyseal attachments lization using a soft cast. Make sure the hock is 3. External fixation is usually placed on the in a functional standing angle. Maintain the medial side of the tibia cast for 4 to 12 weeks. Once the cast has been F. Plate and screw fixation: Indicated when the removed, slowly increase activity over the next stabilized limb is needed for immediate weight 4 to 12 weeks  CHAPTER 22 Orthopedic Disorders 319 III. Shear injury VIII. Distal intertarsal (tarsometatarsal) subluxation with A. The medial side is injured more often than the plantar instability lateral side A. Less common than proximal subluxation injury B. Joint arthrodesis is considered if extensive bone B. Usually associated with trauma and cartilage damage is present C. Treat with arthrodesis of the distal intertarsal C. Objectives of surgery are to prevent infection, joint stabilize the tarsocrural joint, eliminate pain, and D. After surgery, provide a soft-cast splint; remove maintain a functional range of motion when there is evidence of bony fusion D. Perform debridement as soon as possible. Irrigate IX. Intertarsal-tarsometatarsal subluxation injuries with copious amounts of fluids A. Proximal intertarsal subluxations E. Replace ligaments at this time, or do this later if 1. No evidence of trauma repeated debridement is necessary. Ligaments 2. Periodic lameness is present are replaced with bone anchors or screws and 3. Treat with rigid splints figure-eight sutures B. Distal intertarsal subluxation. Valgus deformity is F. Stabilize with a rigid splint; change dressing daily seen. Stabilize with tension band wire G. Postoperative care C. Tarsometatarsal subluxation. Stabilize with medi- 1. Firmly immobilize the tarsocrural joint until ally positioned tension band if there is dorsomedial there is granulation tissue or the wound is instability; if there is dorsal instability, manage with sutured. Avoid using external skeletal fixator rigid splints as this is detrimental to the joint. A rod incor- D. Luxation of talus, central tarsal bone, talocalca- porated into a wrap can be used neus. Treat with surgical fixation