Femoral Neck Fracture Nonunion

Confirming the nonunion, and excluding the things that change the plan

When to call it. A femoral neck fracture that has not united by six months is a nonunion, but the decision rarely waits that long: progressive varus collapse, screw back-out or cut-out, and a fracture line that is widening rather than fading at three to four months are declaring failure early, and in a young patient there is nothing to gain by waiting for the calendar. Conversely, radiographs alone over-call it - the screws obscure the line and an apparently persistent lucency may be healing. CT is the test that settles whether the neck has united, and it also shows the bone stock, the position of the hardware and any posterior comminution that will matter for planning.

Exclude infection before you reconstruct anything. A nonunion around retained metal is a septic nonunion until shown otherwise, and this is the single omission that turns a valgus osteotomy into a disaster. Check CRP and ESR, ask specifically about wound problems or prolonged discharge after the index operation, and if there is any doubt aspirate the hip or take intra-operative samples for culture (multiple, off separate instruments) and histology before committing to a reconstruction. Infection changes the plan completely - towards debridement, hardware removal and staged treatment - and it is far better found before a blade plate is inserted than after.

Screen the patient's biology. An atrophic nonunion deserves the standard metabolic work-up: vitamin D, calcium, phosphate, parathyroid hormone and thyroid function, with smoking cessation, nutritional assessment and a review of medications (NSAIDs, steroids) - the same principles set out in Nonunion Management. It is unusual for a metabolic abnormality alone to explain a femoral neck nonunion, where mechanics and vascularity dominate, but correcting one is cheap and failing to look is indefensible in a nonunion that has already defeated one operation.

Arthroplasty is the commoner operation in this situation, and it is consistently underestimated: a total hip replacement after failed femoral neck fixation is a reconstructive procedure with higher complication rates than a primary, and the exam question is usually about exactly why.

• The hardware has to come out, and it may be broken, buried or stripped - have extraction sets available, and accept that removal can take longer than the arthroplasty.
• Screw holes are stress risers. Empty tracks in the lateral cortex and neck concentrate stress, and a fracture through one during broaching or in early weight-bearing is a recognised event. Consider a stem that bypasses the most distal hole by two cortical diameters, and be deliberate about it rather than hoping.
• Exposure is harder: scarring from the previous approach, capsular contracture, heterotopic bone and a shortened, adducted limb with contracted abductors all make dislocating the hip and restoring length more difficult than in a primary.
• Restoring leg length and offset is a genuine challenge when the neck has resorbed or collapsed into varus, and getting it wrong leaves the abductors weak and the patient with a limp and a Trendelenburg gait.
• Dislocation and infection rates are higher than primary arthroplasty - previous surgery, altered soft tissues and longer operative time all contribute - so implant choice should account for stability, and the patient should be counselled with these figures rather than primary-hip figures.
• Total hip replacement is generally preferred to hemiarthroplasty here: these patients are usually younger and more active than the typical acute hip-fracture patient, and the acetabular cartilage has often already been damaged by the collapsed head or protruding metal.