Lecture 8-VCS80630-2023 Stifle Part 2-S.Malek PDF

DISEASES OF STIFLE PART 2 Dr. Sarah Malek VCS 80630- Small Animal Surgery Fall 2023 LEARNING OBJECTIVES • Describe the anatomical anomalies that contribute to development of patella luxation • Outline how to clinically diagnose patella luxation in a patient • Define the clinical grades (I-IV) used...

DISEASES OF STIFLE PART 2 Dr. Sarah Malek VCS 80630- Small Animal Surgery Fall 2023 LEARNING OBJECTIVES • Describe the anatomical anomalies that contribute to development of patella luxation • Outline how to clinically diagnose patella luxation in a patient • Define the clinical grades (I-IV) used for classification of patella luxation • Describe which grades of patella luxation require surgical intervention and why • Outline the goal of surgical treatment options for patella luxation and their associated complications • Know the differences in patella luxation in cats OUTLINE Patella luxation • Anatomy • Etiopathogenesis • Epidemiology • Concurrent anomalies • Diagnosis • Treatment ANATOMY • Patella • Ossified sesamoid in quadriceps tendon insertion • Quadriceps muscles • Extensor apparatus of stifle> hip flexion • Origins • Rectus femoris (of ilium) • Vastus medialis, lateralis, intermedius (of femur) • Insertion • Tibial tuberosity • Trochlear groove • Medial and lateral trochlear ridges FUNCTIONAL ANATOMY Patella stability A. Extensor mechanism alignment with • Femoral shaft • Trochlear groove • Tibial tuberosity B. Periarticular tissues • Medial and lateral retinaculum • Merging muscle fascia • Femoropatellar ligaments • Joint capsule CLASSIFICATION OF PATELLA LUXATION MPL/LPL is a result of one or more anomalies • Extensor malalignment due to deformities • Femur • Tibia • Both • Periarticular soft tissue imbalance Direction • Medial patella luxation (MPL) • Lateral patella luxation (LPL) CLASSIFICATION OF PATELLA LUXATION Etiology • Non-traumatic • Developmental not congenital • Hereditary • Musculoskeletal abnormalities • Traumatic • Periarticular soft tissue disruption • +/- pre-existing non-traumatic form • Iatrogenic • Complication of surgeries on tibia or femur ETIOPATHOGENESIS • Non-traumatic > traumatic> iatrogenic • Differences in small versus large breed dogs • Incidence • Type • Gender INCIDENCE OF PATELLA LUXATION • Most common type is MPL • Bilateral MPL also common: ~50% • MPL is more common small breed dogs • Small breeds: ~95% MPL, ~5% LPL • Large breeds: ~80%MPL, ~20% LPL • LPL is more common in large compared to small breeds • Gender • Small breed dogs: female>male • Large breed dogs: male>female Make sure you understand this slide well! EXTENSOR MALALIGNMENT IN MPL Femur • Genu varum • Out bowing of leg at stifle (tibia and femur involved) • Distal femoral varus • More common in large breeds • Shallow trochlear groove Shallow groove • Underdeveloped • <50% of patella in groove • Femoral neck anomalies • Coxa vara • Retroversion *LPL deformities are mirror image of those in MPL FEMORAL NECK VARIATIONS Possible anomalies in MPL Normal anteversion Excessive anteversion Retroversion EXTENSOR MALALIGNMENT IN MPL Tibia • • • • Medially positioned tibial tuberosity Internal torsion of tibia Proximal tibial varus> valgus Genu varum • Out bowing of leg at stifle (tibia and femur involved) • Result in medial insertion of patella tendon *LPL deformities are mirror image of those in MPL PERIARTICULAR SOFT TISSUES Traumatic patella luxation (acute) • Unilateral tear in medial or lateral retinaculum • Patella luxates to the opposite side of tear Non-traumatic luxation (progressive) • Retinaculum stretches opposite to the luxation • Retinaculum fibrosis (contracture) on the luxation side Contracted medial retinaculum Stretched lateral retinaculum PATELLA LUXATION GRADES Clinical grading system Grade I • Patella resides in the groove but can be luxated manually Grade II • Patella self-reduces but luxates intermittently Grade III • Patella luxated permanently but can be manually reduced Grade IV • Permanently luxated and cannot be manually reduced CONCURRENT ABNORMALITIES Cranial cruciate ligament (CrCL) tear • Theory: MPL may increase stress on CrCL • CrCL instability should not be missed Concurrent angular deformities • Femoral and tibial deformities • May not need correction DIAGNOSIS OF PATELLA LUXATION History • Trauma? Signalment • Breed • Age: immature- adult Physical examination • Orthopedic examination • Awake +/- sedated • Neurologic examination Diagnostic imaging DIAGNOSIS: ORTHOPEDIC EXAMINATION • +/- Lameness Beware of superimposed • Chronic and progressive CrCL rupture! • Mild to severe • Skipping lameness • Intermittent luxation and reduction of the patella during ambulation • +/- Limb muscle atrophy • +/- Visible or palpable limb deformity • Palpate stifle both in standing and lateral recumbency DIAGNOSIS: ORTHOPEDIC EXAMINATION Top differentials for non-traumatic hind limb lameness • Hip related • Developmental • Hip dysplasia • Legg-Calve-Perthes disease • Stifle related • Developmental • OC/OCD lesions • CrCL tear +/-meniscal damage • Patella luxation DIAGNOSIS: ORTHOPEDIC EXAMINATION Examination maneuvers • Palpate for both MPL and LPL • If patella in the groove, extend the stifle • For MPL • Internally rotate tibia • Push patella medially • For LPL • Externally rotate tibia • Push patella laterally • If patella not in the groove, extend stifle • Push patella back in the groove if possible • Assign grade I-IV if luxating or luxated DIAGNOSIS: ORTHOPEDIC EXAMINATION Assess CrCL stability • ~20% CrCL tears concurrent with patella luxation • Stability tests • Cranial drawer test and tibial compression test • +/-medial buttress • +/- meniscal click • +/- crepitus in flexion and extension Pain • Grades III, IV>II, I +/- effusion DIAGNOSIS: DIAGNOSTIC IMAGING Radiography • Orthogonal stifle views • Craniocaudal, mediolateral • +/-skyline (tangential) view of trochlear groove • Research and surgical planning • Findings • +/- effusion • +/- osteophytosis • Osteoarthritic changes correlate to grade of luxation • Goal is to rule out • Osteomyelitis, neoplasia, fractures, etc. TREATMENT • Grade and symptom based approach • Grade I • Incidental finding, asymptomatic = monitor • Grade II • Young: symptomatic, treat sooner than later • Older: If mild symptoms, monitor closely. Intervene if progressing • Grade III • Treat as soon as possible • Grade IV • Treat as soon as possible • Increased risk of CrCL tear if luxation is untreated? TREATMENT STRATEGIES Address underlying contributing factors • Shallow trochlear groove • Tibial tuberosity location • Periarticular soft tissues • Concurrent angular limb deformity correction SURGICAL PROCEDURES Same principles for LPL and MPL Main surgical techniques • Trochleoplasty • Tibial tuberosity transposition • Periarticular soft tissue adjustments • Angular limb deformity correction TROCHLEOPLASTY TECHNIQUES Modification of the shape of trochlear groove Types 1. Recession trochleoplasty • Cartilage preserving 2. Abrasion trochleoplasty (trochlear sulcoplasty) • No preservation of cartilage 3. Trochlear chondroplasty • Cartilage preserving RECESSION TROCHLEOPLASTY Common techniques 1. Wedge recession trochleoplasty 2. Block recession trochleoplasty Technique a) Wedge or block osteotomies b) Osteochondral graft removed c) Recipient bed deepened • To accommodate 50% thickness of patella d) Graft replaced e) Patella reduced Surgeon preference for chosen technique ABRASION TROCHLEOPLASTY No cartilage preservation in trochlear groove • Articular cartilage and subchondral bone removed • Debrided surface refills with fibrocartilage Questionable validity when cartilage is healthy Reasonable option in end stage grooves TROCHLEAR CHONDROPLASTY In dogs < 6 months of age Not commonly performed Technique • Elevation of cartilage flap • Deepening of the subchondral bone bed • Replacement of flap PATELLA GROOVE REPLACEMENT (PGR) Trochlear grooves with severe cartilage damage • Does not address patella lesions • Less frequent clinical use TIBIAL TUBEROSITY TRANSPOSITION 1. Osteotomy of tibial tuberosity 2. Transposition of the tuberosity • For MPL • Lateral transposition • For LPL • Medial transposition 3. Stabilization of osteotomy • Pin+/- tension band SOFT TISSUE ADJUSTMENTS A. Imbrication of stretched retinaculum • Lateral in MPL • Medial in LPL B. Desmotomy and capsulotomy of contracted side • Medial in MPL • Lateral in LPL MPL post- correction MPL pre- correction B Contracted medial retinaculum Stretched lateral retinaculum A ANGULAR LIMB DEFORMITY CORRECTION Performed if significantly contributes to luxation Requires more complex preoperative planning • +/- advanced imaging Better done right the first time • Higher complication rates Increased cost CONCURRENT CRCL TEAR Possible to address both patella luxation and CrCL deficiency • Extracapsular techniques • Osteotomy techniques • Examples: TPLO and TTA PROGNOSIS AND COMPLICATIONS Overall complication rates ~13-40% • Recurrence of patella luxation • Increased risk with higher grades • Others: seroma formation, fracture, infection, implant failure • Variable degrees of osteoarthritis PROGNOSIS AND COMPLICATIONS Single session versus staged bilateral procedures • Conflicting results • Ideally staged to allow recovery Addressing comorbidities preoperatively would increase success • Weight management • Controlling local and systemic infections • Managing endocrinopathies POSTOPERATIVE CARE AND FOLLOW UP Activity restriction for 6-8 weeks Postoperative rechecks • 2 weeks • Incision check • Check patella stability • 4-6 weeks • Check patella stability • If metallic implants present • Recheck radiographs PATELLA LUXATION IN CATS MPL is most common form (~95%) • Bilateral> unilateral • Association with hip luxation (~58%) Non-traumatic > traumatic Low grades can have significant lameness No gender predisposition Breed: Abyssinian, Devon Rex, commonly reported in DSH PATELLA LUXATION IN CATS Surgical treatment • Same approach as dogs • Parasagittal patellectomy may be needed • Similar complication rates to dogs TAKE HOME MESSAGES • Dogs and cats are predisposed to MPL>LPL • Patella luxation is a multifactorial, developmental disease • Clinically symptomatic patients benefit from surgery • Surgical treatment of patella luxation involves correction of femorotibial anomalies and periarticular soft tissue disruptions • Concurrent correction of patella luxation and stifle stabilization for CrCL deficiency is possible