Revision THA — Femoral Impaction Bone Grafting

Indication. Femoral impaction bone grafting is a biological reconstruction for contained cavitary femoral bone loss — a loose stem sitting in an expanded, brittle-walled canal where the surrounding cortices still form a closed envelope. The goal is not just a stable stem today but restored proximal bone stock for the patient's future revisions. It is the operation of choice for the physiologically young revision candidate. Absolute indications - Contained cavitary femoral bone loss (Paprosky Type II or IIIA) in a patient younger than 65 years where restoration of bone stock is a priority for future revisions.

• Failed primary or revision stem with contained osteolysis and adequate proximal femoral support for impaction.
• Need for biological reconstruction rather than mechanical distal fixation in a physiologically young patient. Relative indications - Paprosky Type IIIA defects with greater than 4 cm of intact isthmus, when combined with mesh containment of any segmental component.
• Patient preference for bone-stock restoration over an extensively porous-coated stem that sacrifices proximal bone.
• Revision of a cemented stem where the cement mantle has failed but the surrounding bone is cavitary rather than segmental. Contraindications - Absolute: uncontained segmental defects (Paprosky IIIB or IV) that cannot be converted into a contained cavity with mesh or strut allograft; active periprosthetic joint infection; inadequate distal femoral isthmus (less than 4 cm) for stable trial impaction.
• Relative: elderly low-demand patient where an uncemented modular fluted tapered stem offers faster recovery; severe osteoporosis with cortical thickness less than 2 mm (high fracture risk); previous pelvic radiation or a poor soft-tissue envelope increasing infection risk. The one decision that matters — which femoral reconstruction? Impaction grafting is one of three established strategies for the revision femur; the choice turns on whether the defect can be contained, how much isthmus remains, and whether the patient's priority is restored bone stock or early mobilisation.

Consent specifically for intraoperative fracture (5–15 percent), subsidence (acceptable 1–3 mm; concerning greater than 5 mm), dislocation (5–10 percent), infection (2–5 percent), sciatic nerve injury (1–3 percent), leg-length discrepancy, and the possibility of converting intraoperatively to an alternative reconstruction if impaction grafting proves unstable. Setup. Lateral decubitus on a radiolucent table with the operative hip uppermost, pelvis stabilised with pubic and sacral supports so the limb moves freely and leg length can be assessed. Regional (spinal/epidural) plus general anaesthesia for muscle relaxation and controlled hypotension; invasive arterial monitoring for lengthy revisions. Tranexamic acid (1 g IV at induction and 1 g at closure) reduces blood loss. Have on the back table a full revision hip set, cerclage wires/cables, titanium or tantalum mesh, fresh-frozen morcellised allograft (minimum 4–6 femoral heads), distal cement restrictors, a polished tapered cemented stem system (Exeter or equivalent), and a backup modular fluted tapered stem.

The goal is to convert an uncontained, defect-laden canal into a contained cavity, pack it densely with morcellised allograft, and cement a polished tapered stem into that restored envelope so the stem subsides 1–3 mm into a self-locking wedge while the graft revascularises by creeping substitution. The exposure is the posterior (Moore-Southern) approach — chosen because it gives extensile access to both femur and acetabulum and allows direct visualisation and protection of the sciatic nerve, which lies immediately posterior to the greater trochanter and is tethered by scar in revision surgery. An extended trochanteric osteotomy is added when distal cement removal or deformity correction is required. Neurovascular structures at risk through the case: the sciatic nerve posteriorly (traction or lengthening greater than 4 cm); the femoral nerve and profunda femoris artery anteriorly (during anterior-column exposure or mesh placement); and the superior gluteal neurovascular bundle (during an extended trochanteric osteotomy or abductor reconstruction). The abductor mechanism is frequently deficient or detached in revision surgery, so plan for a constrained liner or dual-mobility construct from the outset.

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Rehabilitation — protected weight-bearing is mandatory; early full weight-bearing increases fracture and subsidence risk even with a stable reconstruction. | Phase | Timing | Weight-bearing | Precautions & milestones | |------|--------|----------------|--------------------------| | 1 | 0–6 weeks | Touch or 20 kg partial weight-bearing | Posterior hip precautions; drain out at 24–48 h; wound review at 14–16 days | | 2 | 6–12 weeks | Progress to full weight-bearing by 12 weeks | Posterior precautions continue to 12 weeks; DVT prophylaxis for 35 days | | 3 | 3–6 months | Full, light activity | Driving once an emergency stop is safe (about 6–8 weeks); sedentary work | | 4 | 6 months onward | Full | Low-impact sport only; avoid running or jumping indefinitely; manual work from 6 months | Radiographic surveillance. Films at 6 weeks, 3, 6 and 12 months, then annually for 5 years and every 2 years thereafter. Assess graft incorporation (hazy interface at 3 months becoming trabecular continuity by 6–12 months, with remodelling to normal density by 2–3 years), stem subsidence (acceptable 1–3 mm; concerning greater than 5 mm), cement-mantle integrity, and any lucent lines. Long-term outcomes. 85–95 percent survivorship free of aseptic loosening at 10–15 years in contained defects performed in high-volume centres. Outcomes are inferior when mesh is required for segmental defects or when an intraoperative fracture occurs. The defining advantage over distal-fixation stems is that successful impaction grafting restores proximal bone stock, making the patient's next revision technically easier. Complications

Principle and rationale. Fresh-frozen morcellised allograft impacted densely around a polished tapered cemented stem restores proximal femoral bone stock by creeping substitution — the graft is progressively revascularised and remodelled by host osteoclasts and osteoblasts until it is replaced by living bone, while maintaining structural support to the stem during incorporation. The polished stem is deliberately non-bonded to the cement and subsides within the mantle to achieve a self-locking wedge; this is the opposite philosophy to a roughened or precoated stem that depends on immediate cement interlock. The Exeter and Nijmegen (Slooff) groups pioneered the technique, reporting greater than 85 percent survivorship at 10–15 years for contained defects. Why the defect must be contained. The medial calcar and the anterior and posterior metaphyseal cortices form the envelope that holds the graft under load. In revision surgery the calcar is often deficient or sclerotic, so mesh or strut augmentation is required to restore containment before any graft is introduced. The isthmus — the narrowest point of the diaphysis — provides the distal anchor for the trial during impaction; a minimum of 4 cm of intact isthmus is required for stable trial seating, and the anterior femoral bow must be respected when selecting stem length to avoid anterior cortical perforation. Paprosky femoral defect classification — the map that drives reconstruction choice.