Conversion THA (Failed Hip Fracture Fixation)

The indication. Conversion THA is offered for a painful, failed hip fracture fixation that conservative management cannot rescue. The four presentation patterns are: - Nonunion or malunion — femoral-neck nonunion more than 6 months after cannulated-screw fixation, or a painful intertrochanteric nonunion after a DHS or cephalomedullary nail, or a varus malunion causing mechanical symptoms and secondary acetabular wear.

• Avascular necrosis with segmental collapse (Ficat Stage 3-4) of the femoral head following fixation, with progressive pain; combined head AVN and acetabular cartilage loss needs both components.
• Hardware failure — implant cut-out through the femoral head, broken plate or screws with loss of fixation, or symptomatic subsidence of a cephalomedullary nail.
• Post-traumatic arthritis — progressive joint-space narrowing after a periarticular fracture, or an intra-articular malunion causing impingement and accelerated cartilage wear. Absolute contraindications are active sepsis (raised inflammatory markers, positive cultures), medical instability precluding elective arthroplasty, and an irreversible sciatic palsy with a non-functional limb. Relative contraindications are recent infection (within 6 weeks of treatment), severe osteoporosis (T-score less than negative 4.0), significant abductor deficiency without reconstructable soft tissues, and patient factors such as poor compliance, active substance abuse or untreated psychiatric illness. Pre-operative planning is the operation. Three workstreams run in parallel. Imaging. AP pelvis and cross-table lateral to assess bone stock, hardware position and leg-length discrepancy; Judet views for acetabular columns and wall defects if the acetabulum needs a component; full-length femur AP and lateral to capture the whole nail, the distal locking screws and the femoral bow; and a CT with three-dimensional reconstruction for complex bone loss, templating and hardware localisation. Templating. Calibrate magnification against a known implant size or marker; account for medial calcar defects, greater-trochanter position and acetabular floor loss; select long-stem revision components, a dual-mobility cup and any constraint options; and document the planned offset and leg-length change against the contralateral hip. Hardware inventory. Confirm you will have screw extractors and conical extractors, a plate-removal set, a universal nail extraction device with a slap hammer and femoral hooks, fenestration equipment (high-speed burr, 8-12 mm trephines, cerclage cables) and modular revision implants with extended offset options. Consent specifically for the higher-than-primary risks in this group: dislocation, infection, intraoperative fracture, nerve palsy, leg-length discrepancy, and the possibility of further revision surgery.

The goal is to remove the failed hardware, reconstruct the deficient acetabulum and femur, and implant a stable, durable total hip — all while protecting a sciatic nerve that is often scarred from the index operation. The exposure is the foundation of the whole case: it is laid out in full as the first steps of the operative sequence below.

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Approach selection. The exposure is chosen around the hardware, the prior scars and the surgeon's experience. The posterior approach is the workhorse for conversion because it is familiar, extensile and gives the best access for hardware removal; the alternatives each trade something.

Rehabilitation and precautions. Weight-bearing is matched to fixation and bone quality: weight-bearing as tolerated for cementless fixation in good bone; toe-touch for 6 weeks for a cemented stem or poor bone; and partial weight-bearing with an abduction brace for 6 weeks after a trochanteric osteotomy. Posterior-approach precautions (no flexion greater than 90 degrees, no adduction, no internal rotation) run for 6 weeks. Give extended DVT prophylaxis for 35 days (aspirin or LMWH) — this group is higher-risk than primary THA. Image at 6 and 12 weeks to confirm component position, bone healing and no subsidence. Most patients return to low-impact activities within a year. Survivorship. Expect 5-year implant survival of 85-92 percent and 10-year survival of 75-85 percent — below primary THA because of the bone quality — with a reoperation rate of 15-25 percent. Mean Harris Hip Score reaches 75-85 at 2 years (versus 90-plus for primary THA), with a roughly 20-point Oxford Hip Score improvement; about 70-80 percent return to low-impact activities at a year.

Why conversion is harder than primary. Conversion THA after failed fracture surgery is a recognised, growing share of the complex-primary and revision workload; patients are often younger and more active than primary-OA patients, which raises the bar for durable fixation and bearing choice. International registries (NJR for England and Wales, AOANJRR Australia, AJRR USA, SHAR Sweden, plus the Norwegian and New Zealand registries) consistently classify it as a higher-risk indication than osteoarthritis, with elevated dislocation, infection and periprosthetic-fracture rates. The dominant failure modes are early instability (the leading early mode and the principal reason registries favour dual-mobility or large-head constructs), periprosthetic joint infection (higher than primary owing to prior surgery, scarring and dead space), periprosthetic fracture (driven by retained screw holes and diaphyseal stress risers), and later aseptic loosening (mitigated by diaphyseal-fixing long stems). Cementless cups and modern revision-type stems show good medium-term survival, though uniformly below matched primary THA; dual-mobility bearings show low dislocation rates with reassuring medium-term survival, while very-long-term wear and intraprosthetic-dislocation data are still maturing.

Evidence-based recommendations. On hardware-removal timing, Level III evidence requires a minimum of 6 weeks after recent infection treatment, and Level IV evidence allows asymptomatic non-interfering screws to be left. On stem selection, Level III evidence supports long stems (150 mm plus) to reduce subsidence in Type II/III bone loss, and Level IV evidence supports calcar-replacing stems to restore offset in medial-calcar deficiency. On bearing surface, Level III evidence shows dual mobility reduces dislocation versus conventional (relative risk about 0.25), and Level IV evidence prefers a large head (36 mm plus) if a conventional construct is used. On prophylaxis, Level I evidence supports extended VTE prophylaxis for 35 days (reducing symptomatic DVT/PE) and cefazolin 2 g pre-incision redosed every 4 hours intra-operatively.