Lesson 4 - Fractures and Bone Healing PDF

Orthopedics (Berlusconi) B&J – Lesson 8 Ratti - Rizzardi Fractures and bone healing A long bone is made generally by three components: the diaphysis or shaft, the epiphysis at the proximal and distal extremities and a narrow portion in between called metaphysis1. The rationale of subdividing the...

Orthopedics (Berlusconi) B&J – Lesson 8 Ratti - Rizzardi Fractures and bone healing A long bone is made generally by three components: the diaphysis or shaft, the epiphysis at the proximal and distal extremities and a narrow portion in between called metaphysis1. The rationale of subdividing the bone in regions is that each part differs in vascularization and thus, in time required for bone healing. Epiphyses are faster than diaphysis in healing since the formers are very well vascularized while the latter is supplied by only one vessel. When a bone is cross-cut, it is possible to recognize 2 portions: the cortex (or compact bone) and the cancellous bone (or trabeculated part). The periosteum is wrapped around the bone in close contact with the compact bone; this structure is crucial in many homeostatic processes of the bone including bone healing. The Wolff’s law states that a bone is able to remodel, changing its density, in response to the applied forces; the main consequence of this law is that where there are flexion (compression) forces the bone is thicker due to adaptive changes in the internal architecture of the trabeculae followed by secondary changes in the external cortex. For example, the medial part of the femur figured on the left, being weightbearing, will be thicker than the lateral one that is subjected to tension. In case of fracture, a metal device should be applied in the lateral side in order to sustain the lateral wall in tension and antagonize the compression in the medial site. Thus, when treating a fracture, it is important to know where are both the compression and the tension side of the bone in order to apply forces against the normal biomechanics that wouldn’t allow the fracture to heal. Another important implication of the Wolff’s law is that in children when there is a fracture there may be remodelling of the bone, also if the bone is displaced in respect to the axis. Fractures A fracture is an interruption of bone continuity and it can be traumatic (caused by a force superior to the bone resistance), pathologic (caused by a reduced bone strength) or surgical (performed in order to achieve any therapeutic aim). The bone can undergo a fracture either where the force has been applied (direct trauma fractures) or at a distant site (indirect trauma fractures that are divided into Flexion fractures, Torsion fractures, Compression fractures, and Avulsion fractures). Fractures due to their heterogeneity are classified according to various features: • basing on lesion level (diaphysis, epiphysis and metaphysis). • basing on joint involvement, fractures can be articular or extra-articular. 1 The Metaphysis contains the growth plate, the part of the bone that grows during childhood, and as it grows it ossifies near the diaphysis and the epiphyses. 16/10/2020 Pag. 1 of 8 Orthopedics (Berlusconi) B&J – Lesson 8 Ratti - Rizzardi • basing on fragment contact, fractures can be displaced or non-displaced. In a displaced fracture, the bone snaps into two or more parts and moves so that the two ends are not lined up straight. The contact between the fragments is fundamental for healing, thus in displaced fractures the surgeon has to align the segments. • basing on skin involvement fractures can be closed or open (compound fracture). In open fractures, the bone is exposed to external environment and they can be due either to the bone that punctures the skin or to laceration of the skin from outside. Open fractures can be complicated by bacterial infections and their healing can be delayed/absent (non-union) due to impaired blood flow caused by soft tissue damage. According to Gustilo-Anderson classification - that bases on the extent of soft tissue damage, the extent of contamination and energy of the trauma - open fractures can be of 5 grades: - Grade 1: open fracture, clean wound smaller than 1 cm in length. - Grade 2: open fracture, wound in between 1 and 10 cm in length without extensive soft-tissue damage, flaps, avulsions. - Grade 3: open fracture with adequate soft tissue coverage of a fractured bone despite extensive soft tissue laceration or flaps, or high-energy trauma (gunshot and farm injuries) regardless of the size of the wound. The surgeon is able to close it. - Grade 3b: open fracture with extensive soft-tissue loss, periosteal stripping and bone damage. Usually associated with massive contamination. Will often need further soft-tissue coverage procedure. Surgery is not enough to close the skin. - Grade 3c: open fracture associated with a vessels and nerves injury requiring repair, irrespective of degree of soft-tissue injury. The preferred approach for open fractures is surgery that consists in anatomical reduction of the fracture (realignment of bone portions) if it is displaced followed by wound cleaning and positioning of external fixator (internal fixators are not used as they may increase soft tissue damage). Antibiotic prophylaxis with broad-spectrum antibiotics is always performed. • basing on damage entity, fractures can be: - complete, further divided in: o transverse fracture when the trauma is in a specific point and the break occurs at a right angle to the axis of the bone. A transverse pattern indicates a high energy fracture. o oblique fracture which occurs at an angle other than right angle to the axis of the bone. o spiral fracture2 which is caused by twisting a bone excessively. This type of fracture heals faster than others since the contact may be maintained. A spiral pattern indicates a low energy fracture. o comminuted high-energy fractures, characterized by the presence of multiple lines of fractures. o complex - incomplete further divided in green stick and infraction. 2 The torsion of the bone can occur due to leg sprain while walking, running or jumping or due to the turn of the upper while playing iron arm. 16/10/2020 Pag. 2 of 8 Orthopedics (Berlusconi) B&J – Lesson 8 Ratti - Rizzardi Bone healing The bone is able to heal itself with 2 different mechanisms according to the type of fracture: • sanatio per primam intentionem (primary healing) can occur only in case the fragments are in perfect strict contact with each other and the fracture line is simple3.The process consists in the formation by osteoclasts of tunnels between the 2 fragments, in which eventually osteoblasts migrate and start to fill the tunnels with new bone. For this process, absolute stability is required: the two fragments must never move one against the other. At x-ray, no deformities or growth can be seen. • secondary intention/healing occurs in case the fracture line is not simple or there are multiple fragments not in contact between them. This process relies on the formation of a callus that requires few steps: 1) Inflammatory Phase: characterized by the presence of hematoma and the granulation tissue around the bone, which is not really visible on plain films. 2) Fibrocartilaginous Callous (aka soft callus) Formation: fibroblasts, recruited during inflammatory phase, from the periosteum invade the fracture site and start proliferating, forming a fibrocartilaginous bridge with collagen fibers around the fracture. This process is not visible on plain films either. 3) Endochondral ossification which is the process by which cartilage is turned into bone 4) Bony Callous Formation: osteoblasts start producing spongy bone trabeculae, and the fibrous tissue is slowly converted into spongy bone. The area starts becoming more radiopaque. 5) Bone Remodeling is a long process of restitutio ad integrum and may require few years. Compact bone replaces spongy bone around the periphery of the fracture. According to the type of bone healing (per primam or per secondary intention) we want to achieve, a different kind of therapeutic approach is chosen. The rules that regulate the choice are based on Strain Theory by Stephan Perren. This theory states that: • If there is a narrow simple fracture line, absolute stability is required, which can be achieved by inter-fragmentary compression together with neutralization. This results in a Per primam intentionem healing. • If there is a wide complex fracture line, relative stability is required, which can be achieved just with a bridge fixation, this technique essentially consists in the application of some devices (nail, external fixation, cast, plating) in order to bridge the 2 (or more) fragments of the bone in order to keep them together. This results in secondary healing with callus formation. If the two principles are mixed, the fracture will never heal. 3 Comminuted fractures cannot have per primam healing. 16/10/2020 Pag. 3 of 8 Orthopedics (Berlusconi) B&J – Lesson 8 Ratti - Rizzardi The process of bone healing is strongly variable regarding the timing and the efficiency; many factors related to the patient influence either positively or negatively the process: for example, age. Indeed, in children the biological process of bone remodelling is more active than in adults; this grants to children to have, even in case of dislocated fractures, a correct and faster healing even without anatomical reduction. This is possible until the growth plate is still open, so up until 10 years of age. If a child experiences a femur fracture (image on the right), after 3 weeks the callus starts to form, then calcifying process begins and in 12 weeks it becomes a bony callus. In 6 months, bone remodelling occurs following the Wolff law. Active life (sportsmen) favors healing increasing blood circulation while healing is delayed by immobility and absence of gravity. Also, diet4 can influence bone healing. Hormones have different actions for example, corticosteroids5 slow healing while Estrogens6, PTH7 and GH improve healing. Patient comorbidities, such as diabetes, neuropathies, anemia, vitamin deficiencies (A, C, D and K especially), infections and drugs (anti-inflammatory, anti-hypertensive and anti-coagulative) slow healing as well as habits as smoking and alcohol. Local factors include infections, tumors, necrosis, denervation, local damage (soft tissues and vascularity), bone loss, type of bone and blood supply. Bone portions that have a terminal blood supply (arterioles don’t have any collaterals but splits directly into capillaries) are more prone to face Avascular necrosis (AVN), examples are the distal tibia, the talus, the neck of the femur and the scaphoid bone. Surgical factors include surgical damage of the periosteum (as it harbours the precious blood flow), hardware (since the choice of the right implant is crucial), gap (as a too large gap impedes the healing), weightbearing (a little weightbearing is crucial for the healing process) and stability of fixation. Absence of pain together with remodelling phase at x-ray are indicative of complete healing. The process of healing is defined as union or consolidation. Nonunion is permanent failure of healing unless surgery is performed; nonunion may occur when the fracture moves too much, has a poor blood supply or gets infected. A fracture with nonunion generally resembles, in structure, to a fibrous joint, and is therefore often called a "false joint" or pseudoarthrosis. The diagnosis of nonunion is generally done when there is no progress between two x-rays. Still it is possible to predict nonunion by seeing the fracture able to move during the remodelling phase e.g. femoral fractures usually heal in 3 months, thus if after the 3rd month there is still movement at the fracture site, healing cannot occur without external intervention. Radiological evaluation of traumas Dislocations and Sprain The dislocation (in Italian lussazione) is the complete loss of contact between articular ends of 2 bones within a joint, while a subluxation is only a partial loss of contact between the 2 articular ends. Instead, a sprain (in Italian distorsione) is defined as wrenching or twisting of a joint, with partial or complete rupture of its ligaments. 4 Consuming 1200-1500 mg of calcium and 800-1000 IU vitamin D can help in keeping bones strong. Long-term use of corticosteroids is associated with 35% of all cases of nontraumatic AVN (avascular necrosis). Doctors think these drugs may affect your body's ability to break down fatty substances. These substances collect in the blood vessels -- making them narrower -- and reduce the amount of blood to the bone. That can lead to AVN. 6 Estrogen deficiency is known to increase osteoclast bone resorption, whereas estrogen replacement can reverse this effect. Estrogen seems to be an important factor in all stages of fracture healing. The application of estrogens enhances fracture healing of long bones at least in mice. 5 7 could increase bone mineral density to accelerate fracture healing. 16/10/2020 Pag. 4 of 8 Orthopedics (Berlusconi) B&J – Lesson 8 Ratti - Rizzardi Since the precise location of the injury may be difficult to understand, especially in the pelvis, when the patient refers trauma and pain, a visit followed by an x-ray is necessary. If an injury to a joint is suspected, the doctor when reading x-ray has to consider in order: 1. the joint line evaluating its size and continuity. 2. the relationship between the bones. 3. the shape of bones. Deformities can have several etiologies for example dysplasia. 4. the position of tuberosities. For example, in a femur it is important to check if the greater and the lesser trochanter are in place. In case of trauma to the pelvis it is important to assess if the head of the femur is inside the socket (hip joint) and if there is a good line in the symphysis pubis and in sacro-iliac joint. In the X-ray on the right, the head of the femur is not in place. If the x-ray is not informative enough to assess the direction in which the head has been displaced, CT, MRI or x-ray in other projections are indicated. Displacement direction is fundamental to choose the maneuver to put the head back in the socket. The x-ray on the left shows that the patient has undergone a prosthetic surgery (total joint replacement) of the right hip joint, since screws (viti) and metal are present. Whenever screws are present, surgeons and radiologists have to pay attention since screws may go over the ileo-pectineal line where iliac vessels pass. On the left there’s a clear deformation of the femoral head together with its upward displacement resulting in a length difference of the 2 lower limbs (this can be assessed by comparing the position of the left and right trochanters). This total asymmetry quite surely is physically visible with the limping of the patient. In case of trauma to the knee, the doctor has to evaluate the relationships between the tibia & the fibula, the patella which is visible in AP view and medial & lateral condyles which are visible in lateral view. The medial condyle is located where the tibia has a concave shape in strict contact with the convex part of the femur while The lateral condyle is located where the convex tibia profile is near the concave part of the femur. The x-ray on the left shows a dislocation of the knee: the tibia has moved anteriorly. An antero-medial dislocation of the tibia may cause severe damage to the arteries and also nerves. Thus, a dislocation must be reduced immediately in order to prevent damage to the very important structures. 16/10/2020 Pag. 5 of 8 Orthopedics (Berlusconi) B&J – Lesson 8 Ratti - Rizzardi On the top there’s a normal ankle joint while in the bottom there’s the x-rays of a patient that reported a fracture of the distal fibula (lateral malleolus) and an anterior dislocation of both the fibula and the tibia. Probably, this patient puts the foot in a bad way on the floor resulting in the torsion of the ankle joint in the articulation of the knee joint: sprain and torsion create a spiral fracture. In these settings, the first concern is soft tissues around. Fractures • Shaft. A whole bone x-ray in both AP and lateral view is necessary to evaluate a fracture of the shaft. For example, in case of fracture of the shaft of the femur the x-ray has to comprise both the hip joint and the knee joint to assess direction of displacement, presence of metal in the knee or the hip, asymmetry in shaft and/or in epiphysis either of the femur or of the tibia. Afterwards, cortex shape, continuity and thickness and bone shape have to be evaluated. The picture on the left is a good example of a stress fracture8, that may be the result of long usage of an external fixator. The external fixator indeed can cause microfracture of the lateral tension side, leaving the medial weightbearing side more stable. The fracture is incomplete as the line does not span the entirety of the bone and it can be classified as close and undisplaced. The axis, rotation and length of the bone are normal. Moreover, it should be classified as transverse, but usually this type of fractures are the result of high energy trauma. This condition requires an external intervention (surgery aimed at increase the tension side thickness) since it is not of traumatic origin, but it is the result of the failure of the internal biomechanics of the bone. Moreover, surgery is required since in this situation the stabilization of the bone needs the activation of the intrinsic healing potential of the organ. On the right, an oblique displaced fracture is present. The femur is shortened and externally rotated and the patella is lateral translocated. The latter is the result of the incapability of the shortened femur to bear gravity force. This condition can be assessed in the initial part of the physical examination, since during inspection of the patient in lying position, he will have the foot externally rotated (result of femoral fracture) with the hip in normal position (otherwise a problem in the hip or in the muscles could be suspected). What is peculiar of this image is the density of the cortex; in fact, the proximal part is normal but getting distal, the cortex is not anymore smooth and with a normal thickness. This anomaly was revealed to be a metastasis from a squamous-cellular carcinoma of the lung. • Epiphysis evaluation starts with the assessment in 2 view x-rays of the intraarticular line, density of the bone and relationship between bones. 8 A stress fracture is a fatigue-induced fracture of the bone usually caused by repeated stress over time. Instead of resulting from a single impact, stress fractures are the result of accumulated trauma from repeated submaximal loading, such as running or jumping. Because of this mechanism, stress fractures are common overuse injuries in athletes. 16/10/2020 Pag. 6 of 8 Orthopedics (Berlusconi) B&J – Lesson 8 Ratti - Rizzardi On the right, there’s a patellar fracture that impairs the extension of the knee joint since the patella is the site of insertion of the quadriceps tendon and of the patellar tendon. This displacement needs surgical intervention to reconstruct the extensor mechanism. Clinical case 1: a 71 years old lady has been hitten by a car while walking. She comes to the ER in a wheelchair, she can’t walk and has a lot of pain on the knee. Soft tissues are not affected, the knee is not swollen, but it’s stiff. To make a first analysis of the X-rays (AP and lateral view): 1. Follow the joint line evaluating its size and continuity. 2. Look at the relationship between the bones: there’s no difference, they are in contact. 3. Look at the density and shape of bone. The cortex is thin because she’s 71 years old and probably she is affected by osteoporosis. Moreover, in both the projections there’s a white line that revels abnormalities in the density of the tibia (red circles). 4. Look at position of tuberosities. Lateral view allows to evaluate the alignment of two condyles: in a healthy subject the latters should overlap. Condyles may not align either because the condyle is divided in two parts or because the limb is externally rotated (the x-rays has been done wrongly). In this case, there’s the displacement of the lateral condyle of the tibia. The CT shows a big gap due to a loss of bone in the tibial lateral side and cartilage pulled downward (white line9): the fragment has gone at least 2 cm inside the tibia, it’s comminuted and rotated. Probably, the depression of cartilage occurs, during falling of the old woman, as a result of torsion associated to compression10 (the lateral condyle of the femur exerts a big force on the lateral meniscus that pushes the lateral cortex of the proximal tibia downwards). Without intervention the meniscus enters the bone. This condition is surgical: the fragments have to be reduced to assure the healing of the fracture and prevent the deviation of the knee. 9 The cartilage is harder in consistency than the epiphysis medulla so at X-ray it appears as a white line. This is what often happen in young patients in a skiing injury: a proximal tibial plateau fracture. 10 16/10/2020 Pag. 7 of 8 Orthopedics (Berlusconi) B&J – Lesson 8 Ratti - Rizzardi Clinical case 2: a 35ys old man cannot move the shoulder after a motorvehicle accident. In this x-ray it is not possible to assess properly the relationship between bones, the head cannot be precisely defined since the humerus is displaced and turned. With a tridimensional CT reconstruction, it is possible to determine that the head of the humerus is massively displaced posteriorly and that the shaft has been shortened. Moreover, the head of the humerus has a difficult blood flow, just like the main part of the epiphysis. Indeed, a fracture or especially a dislocation of the head may disrupt the vascular supply of the humeral head and, even if the surgeon reduces it perfectly, that head will lose its vitality because the blood flow has been disrupted in the accident. In this surgical image the clamp moves the head and it possible to appreciate the shaft of the humerus. It is also possible to observe the glenoid fossa which is empty: the femoral head needs to be moved from posteriorly into place where it is kept in place by an internal fixator. Clinical case 3 This is an open Gustilo 2 fracture at x-ray and CT. In this setting, the classification is important to understand if the fracture has interrupted the ligaments. The tibia is laterally dislocated and there’s a spiral fracture of the fibula with comminution on one side. For the fact that it’s a joint fracture it must be reduced anatomically to allow immediate movement and weight baring. In the first hospital setting, reduction of bone portion at the attachment of the deltoid ligament is carried out and the latter gets fixed by sutures too. Still, reduction was not successful and the internal fixation (x-ray on the left) of the lateral malleolus, that is shortened, externally rotated and comminuted, is necessary to allow absolute stability for the healing to be carried out. 16/10/2020 Pag. 8 of 8