Tibial and Fibular Fractures

Tibial and fibular fractures are disruptions in the continuity of the tibia and fibula, the two bones of the crus (lower leg). The tibia is the major weight-bearing bone, while the fibula provides minimal weight-bearing support and serves as an attachment site for muscles. These fractures are common in dogs and cats, often resulting from high-energy trauma such as vehicular accidents, falls from heights, or direct blows. They can be classified based on location (proximal, mid-diaphyseal, distal), configuration (transverse, oblique, spiral, comminuted, segmental), and whether they are open or closed. Surgical management is frequently required to restore limb alignment, length, and joint congruity, especially in comminuted or intra-articular fractures. The goal of treatment is early return to function with minimal complications, achieved through stable internal or external fixation.

The primary etiology of tibial and fibular fractures is trauma, with vehicular accidents being the most common cause in dogs, followed by falls from heights, kicks, and gunshot wounds. In cats, falls from high-rise buildings (high-rise syndrome) are a frequent cause. Pathological fractures can occur secondary to bone neoplasia (e.g., osteosarcoma), metabolic bone disease (e.g., hyperparathyroidism), or severe osteoporosis. Iatrogenic fractures may occur during surgery or manipulation of the limb, particularly in patients with weakened bone. Stress fractures are rare but can occur in athletic or racing animals due to repetitive loading. The tibia is particularly vulnerable due to its subcutaneous location and relatively thin soft tissue coverage, especially on the medial aspect.

Tibial and fibular fractures account for approximately 10-20% of all fractures in dogs and cats. They are more common in young, active animals, with a peak incidence between 1 and 3 years of age. There is no significant sex predisposition, but some studies suggest a higher incidence in males due to increased roaming and trauma exposure. Breed predispositions include small and toy breeds (e.g., Yorkshire Terriers, Toy Poodles) for distal tibial fractures, and large and giant breeds (e.g., Greyhounds, Labrador Retrievers) for comminuted diaphyseal fractures. In cats, non-pedigree domestic shorthairs are commonly affected due to outdoor access. Working dogs, such as police and military dogs, are at higher risk for traumatic fractures. The fibula is fractured in association with tibial fractures in the majority of cases, but isolated fibular fractures are rare and often managed conservatively.

The pathophysiology of tibial fractures involves direct or indirect application of force leading to bone failure. Direct trauma causes comminution and soft tissue damage, while indirect forces (e.g., bending, torsion) produce transverse or spiral fractures. The fracture disrupts the periosteal and endosteal blood supply, leading to ischemia of the fracture ends. The inflammatory phase begins immediately, with hematoma formation and release of cytokines, attracting inflammatory cells. Within days, a soft callus forms, composed of fibrous tissue, cartilage, and immature bone. The reparative phase involves endochondral and intramembranous ossification, leading to a hard callus. Remodeling occurs over months, restoring the bone's original shape and strength. In unstable fractures, excessive motion leads to delayed union or nonunion. Open fractures carry a risk of infection, osteomyelitis, and delayed healing. Concurrent soft tissue injury, such as vascular damage or compartment syndrome, can compromise limb viability.

Intrinsic factors include age (young animals have thicker periosteum and faster healing but are more prone to growth plate injuries), breed (small breeds have a higher risk of distal fractures due to thin cortices), and body weight (obesity increases stress on bones). Genetic factors, such as osteogenesis imperfecta, can predispose to fractures. Metabolic diseases like hyperparathyroidism or Cushing's syndrome weaken bone. Extrinsic factors include high-energy trauma, poor nutrition (calcium, vitamin D deficiency), and excessive activity. Prior orthopedic surgery or the presence of implants can create stress risers. Environmental factors, such as living in urban areas with high traffic, increase the risk of vehicular trauma.

Clinical signs include acute non-weight-bearing lameness of the affected hind limb, swelling, pain on palpation, crepitus, and abnormal mobility. The limb may appear shortened or angulated. Open fractures present with skin wounds, hemorrhage, and visible bone fragments. Neurological deficits may occur if the peroneal or tibial nerves are injured, resulting in dropped hock or loss of sensation. Systemic signs include tachycardia, tachypnea, and signs of shock in severe trauma. On physical examination, careful assessment of the entire limb, including joints above and below the fracture, is essential to rule out concurrent injuries such as cruciate ligament rupture or hip luxation.

Differential diagnoses include: 1) Patellar luxation, which presents with intermittent lameness and a palpable luxating patella, but no fracture on radiographs. 2) Cranial cruciate ligament rupture, characterized by a positive cranial drawer sign and joint effusion, but no fracture. 3) Hip dysplasia or coxofemoral luxation, causing hind limb lameness but with pain localized to the hip. 4) Osteosarcoma, which may present with pathological fracture; radiographs show lytic bone lesions. 5) Panosteitis, causing shifting leg lameness in young dogs, with radiographs showing increased medullary density. 6) Septic arthritis, with joint swelling and fever, but no fracture. 7) Muscle or tendon injuries, such as Achilles tendon rupture, which may cause similar lameness but with a palpable defect. 8) Spinal cord disease, such as intervertebral disc herniation, causing proprioceptive deficits and paresis, but no fracture on limb palpation.

The diagnostic algorithm begins with a thorough history and physical examination, including assessment of the cardiovascular and respiratory systems to identify life-threatening injuries. Orthopedic examination should be performed after stabilization, with careful palpation of the entire limb to localize pain and crepitus. Neurological examination is essential to rule out nerve injury. Radiography is the primary imaging modality: standard mediolateral and craniocaudal views of the tibia and fibula, including the stifle and hock joints, are obtained. Stress views may be needed to evaluate joint stability. Advanced imaging, such as CT, is indicated for complex comminuted fractures, intra-articular fractures, or when surgical planning requires precise 3D reconstruction. MRI is rarely needed but may be used to assess soft tissue injuries. In cases of suspected infection, blood work and culture are performed. Exploratory surgery may be necessary to assess the fracture and soft tissue damage.

Laboratory findings are generally non-specific but are important for preoperative assessment. Complete blood count may show leukocytosis due to stress or infection. Serum biochemistry may reveal elevated muscle enzymes (creatine kinase) due to muscle trauma. Coagulation panel (PT/aPTT) is recommended to rule out coagulopathies, especially in patients with severe trauma. Blood gas analysis may show metabolic acidosis in shock. Inflammatory biomarkers such as C-reactive protein (CRP) and serum amyloid A (SAA) may be elevated. Synovial fluid analysis is not typically performed unless there is suspicion of septic arthritis. Urinalysis is routine to assess renal function and rule out concurrent urinary tract trauma.

Radiography is the cornerstone of diagnosis. Standard views include mediolateral and craniocaudal projections of the entire tibia and fibula, including the stifle and hock. Fracture configuration, displacement, and comminution are assessed. Stress views (e.g., varus/valgus stress) may be used to detect concurrent ligamentous injuries. CT with 3D reconstruction is invaluable for complex fractures, providing detailed information on fragment orientation and aiding in surgical planning. MRI is useful for evaluating soft tissue structures, such as the menisci or collateral ligaments, but is rarely indicated. Ultrasonography may be used to assess vascular integrity or soft tissue abscesses. Arthroscopy is not typically used for tibial fractures but may be employed for intra-articular fractures to assess articular surface reduction.

Cytology and histopathology are not routinely performed for tibial fractures unless there is suspicion of a pathological fracture due to neoplasia or infection. Fine-needle aspiration of any mass or lytic lesion may be performed, with cytology revealing neoplastic cells or inflammatory cells. Biopsy of bone lesions is indicated if osteosarcoma or other tumors are suspected. Histopathology of bone tissue can confirm the diagnosis and guide treatment. In cases of osteomyelitis, culture and sensitivity of bone or exudate are essential. Synovial fluid analysis may be performed if there is joint effusion, with findings of inflammation or sepsis.

Treatment options include conservative management for minimally displaced, stable fractures (e.g., greenstick or hairline fractures) in young animals, using a cast or splint. However, surgical stabilization is preferred for most tibial fractures to achieve anatomical reduction and early return to function. Surgical techniques include: 1) Internal fixation with bone plates and screws (e.g., dynamic compression plate, locking compression plate) for diaphyseal fractures; 2) Intramedullary pinning with or without cerclage wires for transverse or short oblique fractures; 3) External skeletal fixation (ESF) using a linear or circular fixator for comminuted or open fractures; 4) Interlocking nail for diaphyseal fractures. For proximal or distal fractures involving the joint, articular reconstruction with lag screws and neutralization plates is required. Open fractures require aggressive debridement, lavage, and stabilization, with delayed closure if necessary. Postoperative management includes pain control, antibiotics, and restricted activity. Physical rehabilitation, including passive range of motion exercises and controlled leash walks, is initiated early.

The prognosis for tibial and fibular fractures is generally good to excellent with appropriate treatment. For simple fractures, the success rate is over 90%. Comminuted fractures have a guarded prognosis, with a higher risk of complications such as nonunion, malunion, and infection. Open fractures have a worse prognosis due to the risk of osteomyelitis. Prognostic indicators include the degree of comminution, soft tissue damage, fracture location, and the presence of concurrent injuries. Negative prognostic factors include severe comminution, open fractures, delayed treatment, and poor owner compliance. With proper surgical technique and postoperative care, most animals regain full limb function within 8-12 weeks.

Postoperative follow-up includes serial radiographs at 4, 6, 8, and 12 weeks to assess bone healing. Suture removal is typically at 10-14 days. Restricted activity is maintained for 6-8 weeks, with gradual increase in exercise. Physical therapy, including passive range of motion exercises and swimming, is recommended. Long-term monitoring for implant failure or loosening is necessary, and implant removal may be considered after complete healing, especially in young animals. Owners should be advised to monitor for signs of infection, such as swelling, discharge, or lameness, and to return for re-evaluation if these occur.

Pearls: 1) Always obtain orthogonal radiographs of the entire tibia and fibula, including the stifle and hock, to rule out concurrent injuries. 2) For distal fractures, use a plate with locking screws to provide angular stability, especially in small breeds. 3) In open fractures, perform thorough debridement and lavage with sterile saline, and consider delayed primary closure. 4) Use a bone graft (autogenous cancellous bone) for comminuted fractures to enhance healing. 5) Protect the limb with a soft padded bandage postoperatively to reduce swelling. Pitfalls: 1) Failure to assess the entire limb for concurrent injuries, such as cruciate ligament rupture or hip luxation. 2) Inadequate fracture stabilization leading to delayed union or nonunion. 3) Over-tightening cerclage wires, causing vascular compromise. 4) Placing screws in the fracture line, weakening the bone. 5) Ignoring signs of compartment syndrome, which can lead to muscle necrosis and limb loss.

Perioperative antimicrobial prophylaxis: Cefazolin (22 mg/kg IV) administered 30 minutes before incision and repeated every 90 minutes during surgery. Postoperative antibiotics (e.g., amoxicillin-clavulanate 13.75 mg/kg PO q12h) are continued for 7-10 days for closed fractures, and longer for open fractures. Analgesia: Preoperative opioids (e.g., hydromorphone 0.05-0.1 mg/kg IV) and postoperative NSAIDs (e.g., carprofen 2.2 mg/kg PO q12h or meloxicam 0.1 mg/kg PO q24h) for 3-5 days. Local anesthesia: Femoral and sciatic nerve blocks with bupivacaine (1-2 mg/kg) provide intraoperative and postoperative analgesia. For severe pain, a constant rate infusion (CRI) of fentanyl (2-5 mcg/kg/hr) or lidocaine (25-50 mcg/kg/min) may be used. Muscle relaxants: Methocarbamol (20-40 mg/kg PO q8h) may be used for muscle spasms. Chondroprotectants: Polysulfated glycosaminoglycan (4.4 mg/kg IM or SC twice weekly) or oral glucosamine/chondroitin supplements may be used to support joint health, especially if there is articular involvement.

The literature supports the use of locking plates for the treatment of tibial fractures, particularly in comminuted cases, due to improved biomechanical stability and preservation of periosteal blood supply. A study by Dejardin et al. (2001) demonstrated superior outcomes with interlocking nails compared to plate fixation for diaphyseal fractures. External skeletal fixation is recommended for open fractures, with a study by Johnson et al. (2002) showing a low complication rate when using a hybrid fixator. The AO Principles of Fracture Management emphasize anatomical reduction, stable fixation, preservation of blood supply, and early mobilization. A meta-analysis by Boudrieau (2003) reported a 95% union rate for tibial fractures treated with internal fixation. Postoperative rehabilitation protocols have been shown to improve functional outcomes, as evidenced by a study by Marsolais et al. (2009). Overall, the evidence supports early surgical intervention and stable fixation for optimal outcomes.