Fracture Malunion

Fracture malunion is healing of a fracture in an unacceptable position, with angulation, rotation, shortening or translation beyond the limits tolerated for the bone. Union has occurred, but the alignment is wrong.

The limits vary by bone. For example: over 10 degrees of angulation in the femoral or tibial shaft, any rotation over 10 degrees in the forearm or femur, over 2 cm of leg shortening, and over 2 mm of articular step off.

It follows inadequate reduction, loss of reduction in a cast or after fixation, inadequate or failed fixation, poor bone quality (osteoporosis), non-operative treatment of an unstable fracture, delayed presentation, and treatment by traditional bone setters. It is common in low resource settings. Fractures of the distal radius, clavicle, femoral neck, tibia, forearm, humerus and ankle are the usual sites.

Complications are functional limitation, pain, deformity, altered joint loading with early arthritis, limb length discrepancy, gait disorder, nerve and tendon problems, and cosmetic concerns. Intra-articular malunion causes post-traumatic arthritis.

Pathophysiology.

Fracture healing proceeds normally in the displaced position through callus formation and remodelling. Remodelling can correct some angulation in children (up to 20 to 30 degrees close to a growing physis in the plane of motion of the nearby joint), but not rotation. It has little effect in adults.

Malalignment alters the joint reaction forces and the line of the mechanical axis, which overloads cartilage.

Visible deformity, pain on loading, limp, limb shortening or rotation deformity, limited range of motion (for example, loss of forearm rotation), reduced grip, and joint pain adjacent to the malunion. Neurological symptoms may arise from a displaced fragment or callus (ulnar neuropathy after a malunited distal humerus or elbow fracture; carpal tunnel syndrome after a distal radius malunion).

Examine alignment (standing, including the adjacent joints), rotation (compare the feet or hands with the opposite limb), leg length, range of motion, gait, nerve function, and skin. Check for associated infection or nonunion.

• Radiographs of the whole bone including both adjacent joints, in two planes; long leg standing alignment films for the lower limb to measure the mechanical axis, joint orientation angles and length.
• CT with 3D reconstruction defines the deformity, rotation (compare with the opposite side) and articular malunion.
• Rotational profile CT of the femur or tibia in rotational malunion.
• Exclude infection (white cell count, C-reactive protein, erythrocyte sedimentation rate) and nonunion before correction, and bone health tests (calcium, vitamin D) in fragility fractures.
• Nerve conduction studies for neuropathy.

Differential diagnosis.

• Nonunion or delayed union with deformity.
• Post-traumatic arthritis and avascular necrosis.
• Growth plate arrest.
• Congenital deformity and rickets.

Decide whether to treat. Many malunions are asymptomatic and need only observation, particularly in older or low demand patients (for example, a distal radius malunion in a frail patient, or a clavicle malunion). Treat when there is pain, loss of function, a deformity that is unacceptable, a risk of arthritis from malalignment, or nerve compression.

Corrective osteotomy.

• Plan with templates from long leg films (CORA method) and 3D CT, and with patient specific guides in complex cases.
• Open wedge, closing wedge, dome or derotation osteotomy at the apex of the deformity (or adjacent to it), with plate or intramedullary nail fixation.
• Distal radius: opening wedge dorsal or volar plate osteotomy with bone graft; forearm: osteotomy with plate fixation; femur and tibia: intramedullary nail, with derotation as needed.
• Intra-articular malunion: intra-articular osteotomy within 3 to 4 months of injury; late arthritis needs arthroplasty or arthrodesis.
• Limb length discrepancy over 2 to 3 cm: lengthening (ring fixator, magnetic nail) or shoe raise.
• Fix the fracture by the Ilizarov method for complex deformity with shortening and bone loss.
• Postoperative: protection until union (8 to 12 weeks), then rehabilitation.

Non-operative. Orthotics, shoe raise, physiotherapy and analgesia for symptomatic mild deformity. Corticosteroid injection for adjacent joint pain is considered.

Give methylprednisolone acetate 40 mg with 3 to 5 mL of lidocaine 1% into a large joint, once, under aseptic technique. Repeat no sooner than 3 months, maximum 3 injections in 12 months. Check glucose in diabetes, and avoid with infection.

Operative antibiotic prophylaxis. Give cefazolin 2 g intravenously (3 g when weight is 120 kg or over) within 60 minutes before incision as a single dose. Repeat after 4 hours or blood loss over 1500 mL.

With severe penicillin allergy, give vancomycin 15 mg/kg intravenously starting 90 to 120 minutes before incision as a single dose. Check levels and creatinine in prolonged cases.

Thromboprophylaxis. Give enoxaparin 40 mg subcutaneously once daily, started 6 to 12 hours after surgery. Continue for 10 to 14 days for upper limb and tibial surgery, and 28 to 35 days for femoral surgery or when mobility is reduced. Use mechanical prophylaxis until then.

Use 20 mg once daily at creatinine clearance under 30 mL/min. Adjust by anti-Xa level in obesity and renal impairment. Check the platelet count on days 5 to 14 for heparin induced thrombocytopenia.

Analgesia.

• Paracetamol 1 g orally every 6 hours as needed for up to 5 to 7 days (maximum 4 g daily; 3 g daily when weight is under 50 kg, with chronic alcohol use or hepatic impairment).
• Ibuprofen 400 mg orally every 8 hours with food for up to 5 days (maximum 1200 mg daily); avoid with eGFR under 30 mL/min/1.73 m2, peptic ulcer, heart failure or anticoagulant use. Avoid NSAIDs when union is delayed.
• Oral morphine 5 to 10 mg every 4 hours as needed for severe pain for up to 3 days. Start 2.5 to 5 mg with age over 75 or eGFR under 30 mL/min/1.73 m2. Avoid exceeding 60 mg in 24 hours without senior review. Monitor sedation and respiration and prescribe a laxative.

Secondary prevention after a fragility fracture. Alendronate 70 mg orally once weekly, taken fasting with a full glass of water and kept upright for 30 minutes, for 5 years then reassess (maximum 70 mg weekly).

Check calcium, 25-hydroxyvitamin D and creatinine before starting and yearly. Avoid alendronate with eGFR under 35 mL/min/1.73 m2, uncorrected hypocalcaemia or oesophageal stricture.

Zoledronic acid 5 mg intravenously over at least 15 minutes once yearly (for 3 years, then reassess) when oral therapy is not tolerated and eGFR is 35 mL/min/1.73 m2 or over. Check creatinine and calcium before each dose.

Colecalciferol 800 to 2000 IU orally daily with dietary calcium to a total of 1000 to 1200 mg daily (maximum total 2000 mg daily). Correct vitamin D deficiency first.

Monitoring. Radiographs at 2 weeks, 6 weeks, 3 months, 6 months and 12 months after osteotomy to confirm union and alignment. Wound, neurovascular state and range of motion at each visit. Gait and leg length. Late arthritis on follow up films.

Referral and escalation. Refer symptomatic or functionally limiting malunion to orthopaedics (or a limb reconstruction service for complex deformity) for planning. Urgent referral for neurological deficit, infection, or loss of reduction of a recent fracture still correctable by manipulation (within 2 to 3 weeks).

Special groups.

• Children: observe malunions near the physis that can remodel; correct rotational malunion and those far from the physis.
• Older adults: treat only when symptomatic, balancing surgical risk; assess bone health.
• Low resource settings: malunion after traditional bone setting is common; osteotomy remains effective months to years later.
• Kidney impairment: avoid ibuprofen and bisphosphonates at eGFR under 35 mL/min/1.73 m2, and reduce morphine doses.