Delayed Fracture Union

Delayed union is a fracture that has not healed in the expected time but is still showing signs of progression to union. The time frame varies by bone: for example, a tibial shaft fracture usually unites by 16 to 20 weeks, and a femoral shaft by 12 to 16 weeks. A fracture is delayed if it has not united by 1.5 times the average time and not yet nonunion (generally defined as no progress after 6 to 9 months).

It is common in the tibia, scaphoid, femoral neck, fifth metatarsal and clavicle. Causes are inadequate immobilisation, excess movement, fracture gap, infection, poor blood supply, soft tissue injury, comminution and distraction, with host factors including smoking, diabetes, malnutrition, vitamin D deficiency, NSAIDs, corticosteroids, older age, anticoagulants, chemotherapy and excess alcohol.

Complications are prolonged pain and disability, nonunion, implant failure, stiffness, muscle atrophy and loss of work.

Pathophysiology.

Bone healing passes through inflammation (haematoma, 1 to 7 days), soft callus (2 to 3 weeks), hard callus (3 to 4 months) and remodelling (months to years). Delay arises when the blood supply, stability or biology is compromised at any stage. Low grade movement stimulates callus but excess movement causes fibrous tissue; too rigid fixation with a gap can slow healing.

Persistent pain and tenderness at the fracture site on loading beyond the expected time, with swelling, and sometimes slight movement. Pain on weight bearing and ongoing need for support. Look for risk factors: smoking, diabetes, nutrition, medication, previous infection, and systemic disease.

Examine the fracture site for tenderness, movement, alignment, skin and signs of infection, as well as neurovascular state and the adjacent joint range.

• Serial radiographs in two planes every 4 to 6 weeks. Features are persistent fracture line, little or no bridging callus, and sclerotic or rounded ends. The RUST score of under 10 at 3 to 4 months suggests risk.
• CT assesses cortical bridging in unclear cases (union is likely when 3 of 4 cortices are bridged).
• Blood tests: full blood count, C-reactive protein, erythrocyte sedimentation rate, calcium, phosphate, 25-hydroxyvitamin D, albumin, HbA1c, thyroid stimulating hormone, parathyroid hormone and alkaline phosphatase.
• Exclude infection (inflammatory markers, MRI or nuclear imaging, and deep samples at surgery).

Differential diagnosis.

• Nonunion (hypertrophic, atrophic).
• Infected nonunion and pathological fracture.
• Stress fracture and avascular necrosis.
• Osteomalacia and metabolic bone disease.

Correct host and local factors (first 4 to 8 weeks).

• Smoking cessation, glucose control (HbA1c under 8% or 64 mmol/mol), protein and calorie nutrition, adequate calcium (1000 to 1200 mg daily total) and correction of vitamin D deficiency.
• Colecalciferol 50 000 IU orally once weekly for 6 to 8 weeks, then 800 to 2000 IU daily (maximum 4000 IU daily without monitoring); check 25-hydroxyvitamin D and calcium at 8 to 12 weeks. Avoid with hypercalcaemia.
• Stop NSAIDs and corticosteroids where possible.

Mechanical optimisation.

• Non-operative fractures: improve immobilisation, change the cast, use a functional brace or controlled loading as the fracture type allows. Weight bearing as tolerated promotes callus in the tibia (load sharing).
• Operative fractures with stable fixation: continue protected weight bearing and wait; with unstable fixation, dynamise the nail (remove locking screws) at 3 to 4 months or revise the fixation.
• Scaphoid and femoral neck: early surgical fixation or bone grafting for delay, because of the avascular necrosis risk.

Adjuncts. Low intensity pulsed ultrasound (20 minutes daily for 3 to 6 months) or pulsed electromagnetic fields have limited evidence. Teriparatide is not used routinely for delayed union.

Surgery. If no progress by 4 to 6 months (or earlier for high risk sites), proceed to nonunion surgery: exchange nailing, autograft, or revision of the fixation.

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).
• 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.
• Avoid NSAIDs while healing is delayed.

Monitoring. Radiographs every 4 to 6 weeks to 6 months, then every 3 months. Pain, weight bearing and function at each visit. Calcium and 25-hydroxyvitamin D at 8 to 12 weeks. Review sooner if pain increases, the implant loosens or a wound appears.

Referral and escalation. Refer to orthopaedics when a fracture shows no progression at 3 to 4 months (or earlier for scaphoid, femoral neck and tibia). Urgent referral for implant failure, signs of infection or neurovascular compromise.

Special groups.

• Smokers and diabetics: higher risk; intensify cessation and glucose control.
• Older adults: osteoporotic fractures heal more slowly; assess bone health.
• Children: delayed union is uncommon and should prompt a search for infection, metabolic disease or non-accidental injury.
• Kidney impairment: avoid NSAIDs, reduce morphine doses and adjust vitamin D.