Revision Total Hip Replacement - Acetabular Component

The operation in one line. Revision of a failed acetabular component is a defect-driven reconstruction: rule out infection, classify the bone loss, remove the old component while preserving every millimetre of host bone, then rebuild with the simplest implant that achieves stable biologic fixation on healthy bleeding bone. The whole strategy flows from the Paprosky classification. ### Indications for Acetabular Revision Absolute indications - Aseptic loosening (most common, 40-50%): progressive weight-bearing pain with radiographic lucencies greater than 2mm in all three DeLee-Charnley zones, component migration greater than 3mm vertical or 5mm horizontal on serial films, or cup tilt / change in position versus the post-operative baseline.

• Polyethylene wear with osteolysis: wear rate exceeding 0.2mm per year (the critical threshold), progressive osteolysis despite a well-fixed shell, or impending structural failure with large cavitary lesions.
• Recurrent instability: multiple dislocations (typically 3 or more) despite closed reduction and conservative care, requiring cup revision to correct malposition — often combined with a dual mobility or constrained liner.
• Infection: chronic periprosthetic joint infection requiring 2-stage revision (explantation, antibiotic spacer, then reimplantation) with acetabular involvement confirmed on culture and imaging.
• Component malposition: symptomatic position outside the Lewinnek safe zone (inclination 30-50 degrees, anteversion 5-25 degrees) causing instability, impingement, or accelerated wear; or a high hip center with progressive superior migration and abductor insufficiency. Relative indications - Liner dissociation or locking-mechanism failure (liner exchange alone if the shell is stable)
• Adverse reaction to metal debris (ARMD) from metal-on-metal bearings, revised to a non-metal bearing
• Pelvic discontinuity with acetabular instability
• Severe metallosis requiring debridement and component revision ### Mandatory pre-operative infection workup Infection must be excluded before any aseptic revision — a missed infection leads to a catastrophic, chronically infected revision. ESR and CRP are first-line, but ESR and CRP alone miss 30 percent of infections, so joint aspiration is mandatory whenever either marker is elevated or there is any clinical concern. Aspirate OFF antibiotics for a minimum of 2 weeks (6 weeks preferred), under fluoroscopic or ultrasound guidance via a lateral approach, and send for cell count with differential, Gram stain, and aerobic and anaerobic cultures held for 14 days. Use alpha-defensin when the standard panel is equivocal — it is unaffected by prior antibiotics.

• Lateral hip and Judet obliques: the obturator oblique (45 degrees away from the affected side) shows the anterior column and posterior wall; the iliac oblique (45 degrees toward the affected side) shows the posterior column and anterior wall. Essential for column integrity and screw planning.
• CT with 3D reconstruction: indicated for Paprosky IIIA/IIIB — accurate bone stock, defect morphology, containment, pelvic discontinuity, screw trajectories, and custom triflange templating.
• MRI: limited role — metal artifact degrades the image; useful only for soft-tissue collections or abductor tears. Key landmarks to identify on every film: the transverse acetabular ligament (the true anatomic floor), the teardrop (medial wall integrity — obliteration equals severe loss), Kohler's / ilioischial line (medial migration), the ischium (inferior support), and the ilioischial line along the posterior column (discontinuity). ### Setup and consent Position. Lateral decubitus with the affected hip uppermost, the pelvis held perpendicular to a radiolucent table with rigid anterior and posterior positioners — accurate cup orientation depends on a true perpendicular pelvis. Confirm position with fluoroscopy before draping. Consent specifically for instability (the commonest early complication), infection, sciatic nerve palsy, leg-length discrepancy, and the possibility of re-operation / re-revision.

The goal is a stable, biologically fixed reconstruction at the anatomic hip centre. The exposure is the foundation of the whole case: through the posterior approach you identify the sciatic nerve, deliver the femur, remove the failed component while preserving host bone, classify the defect, and rebuild it. The reconstruction follows the Paprosky grade (see the table in Background and Evidence).

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Post-operative management Weight bearing. Weight-bearing as tolerated immediately when fixation is excellent (press-fit or a well-fixed cage), with a frame or crutches for the first 6 weeks. With large augments, structural graft or marginal stability, use touch-down weight bearing, progressing to partial weight bearing over 6-12 weeks guided by serial radiographs. Hip precautions (posterior approach) — 12 weeks (longer than a primary, because the soft tissues are compromised): no flexion greater than 90 degrees (avoid low chairs, deep sofas, tying shoes), no adduction across the midline (do not cross the legs), no internal rotation (no pivoting on the leg). Provide an abduction pillow at night for the first 6 weeks, an elevated toilet seat, and a reacher and sock aid. Thromboprophylaxis. Revision is high-risk: LMWH (enoxaparin 40mg SC daily) or a DOAC (rivaroxaban 10mg daily, apixaban 2.5mg twice daily) for 4-6 weeks, plus TED stockings and intermittent pneumatic compression. Antibiotics. Continue 24-48 hours post-operatively (cephazolin 2g eight-hourly, or vancomycin if MRSA risk); extend and involve infectious diseases if intra-operative cultures are concerning. Pain. Multimodal: regular paracetamol, an NSAID if tolerated, opioids sparingly, and a neuropathic adjunct if needed. Mobilisation. Day 1-2 sit out and walk with physiotherapy and precautions; weeks 1-6 progress mobility and begin abductor strengthening when allowed; weeks 6-12 wean the assistive device and advance function. Radiographic surveillance and monitoring. AP pelvis and lateral in recovery, then 6 weeks, 3 months, 6 months, and annually for life — monitoring position, ingrowth, lucencies, migration and osteolysis. Monitor sciatic nerve function (a palsy may have delayed onset; EMG at 3 weeks if suspected), wound healing (staples out at 14-21 days), and mobilisation progress. Red flags: new or progressive pain, instability, radiographic lucencies greater than 2mm, component migration, or expanding osteolysis. ### Complications — recognition, prevention and management

Epidemiology and the revision burden Aseptic loosening is the commonest single reason for acetabular revision (about 40-50 percent of cases), followed by instability and infection. Major registries (the NJR for England and Wales, AOANJRR for Australia, AJRR for the USA, and the Swedish and Nordic registries) put acetabular revision survival at around 85-90 percent at 10 years, with a re-revision rate of roughly 10-15 percent that rises with defect severity (Paprosky type) and the number of prior revisions. Cementless porous-metal revision cups consistently outperform cemented all-polyethylene revision cups at 10 years, and aseptic-loosening survival of trabecular-metal shells in complex (Paprosky III) defects is around 90 percent at 10 years. The reasons for re-revision follow a predictable distribution: aseptic loosening about 35 percent, dislocation about 30 percent, infection about 20 percent, periprosthetic fracture about 10 percent, and other causes (liner wear, component failure) about 5 percent. ### Paprosky classification and defect-driven survival The Paprosky grade sets both the reconstruction and the expected survival. It is the dominant intra-operative framework worldwide.

• Trabecular-metal shells in complex (Paprosky III) defects: durable biologic fixation, aseptic-loosening survival around 90 percent at 10 years; dislocation remains the leading re-operation, supporting liberal use of dual mobility or large-head bearings.
• Cup-cage construct: a workhorse for severe loss and pelvic discontinuity — the porous cup gives biologic fixation while the cage off-loads it across the discontinuity; 70-80 percent all-cause survival at 10 years, with re-revision driven by instability and infection rather than loosening.
• Custom triflange (Type IIIB): patient-specific flanges to ilium, ischium and pubis give immediate screw fixation and potential ingrowth; emerging data show 85-90 percent survival at 5-10 years, becoming the gold standard for massive loss and discontinuity. Drawbacks are implant cost and a 6-12 week design-and-manufacture lead time.
• Dual mobility bearings: a meta-analysis of revision THA shows a significantly lower dislocation rate and lower aseptic-loosening risk than fixed bearings, with no difference in infection; intraprosthetic dislocation is uncommon (less than 1 percent).
• Functional outcomes: pain relief is excellent in 80-90 percent, Oxford Hip Score 35-40 (versus 42-45 for primary THR), and 75-85 percent are satisfied (versus 90-95 percent for primary) — so expectation management is essential.