Core Decompression — Femoral Head AVN

Core decompression is a joint-preserving operation for the pre-collapse hip. By drilling a track from the lateral femoral cortex into the necrotic segment it relieves intraosseous pressure, stimulates reperfusion and removes a sample of bone for histology. The aim is to prevent collapse and buy time before an inevitable arthroplasty in a young patient — because once the head collapses, total hip arthroplasty in this group carries a markedly higher revision burden than arthroplasty for osteoarthritis. The single decision that governs everything: decompress the pre-collapse hip, replace the collapsed hip. A crescent sign (subchondral fracture, Ficat/ARCO Stage III) means the mechanical failure has already happened — decompression will not rescue it. Detailed staging lives in Background & Evidence, but the eligibility test is this:

Why preserve at all? National joint registries (AOANJRR, NJR, AJRR, SHAR, NZJR) consistently show that THA for osteonecrosis carries a higher revision burden than THA for primary osteoarthritis, driven by the younger, higher-demand population — commonly cited as roughly 25–30 percent revision at 10 years in AVN patients under 55, against 5–7 percent for OA. That risk is the rationale for an aggressive preservation attempt in the pre-collapse hip of a young patient. Consent specifically for: a realistic success rate that depends on stage and lesion size (not a guarantee), the possibility of progression to collapse and eventual arthroplasty, a small but serious risk of articular penetration or periprosthetic fracture, protected weight-bearing for 12 weeks, and (if a graft or rod is used) donor-site or hardware-related morbidity. Setup. Supine on a radiolucent table, hip in neutral rotation (a slight 10–15 degree internal rotation may relax the anterior capsule and improve visualisation). The whole operation depends on biplanar fluoroscopy, so test AP and lateral imaging and confirm a perfectly circular femoral head before draping. A first-generation cephalosporin (cefazolin 2 g IV, weight-adjusted) is given within 60 minutes of incision; vancomycin if beta-lactam-allergic or MRSA risk.

The goal: pass a guidewire from the lateral femoral cortex, across the neck, into the centre of the necrotic segment in the anterosuperior weight-bearing dome, and decompress it to within 5 mm of the subchondral bone — without breaching the joint, the femoral neck cortices, or the posterior neurovascular structures. The exposure is a small percutaneous lateral approach through vastus lateralis, laid out in full as the first steps below.

View larger

Technique choice — single large core versus multiple small cores

Five danger structures you protect during the approach

Weight-bearing is the make-or-break of success. The decompressed head needs 3–6 months to revascularise; uncontrolled loading during that window is a direct cause of collapse. The protected-weight-bearing window is therefore non-negotiable.

Recognising failure and the salvage options. Most failures declare within 18–24 months (but can occur up to 3–5 years) as progressive collapse, joint-space narrowing beyond 1 mm, or worsening pain despite initial improvement. Salvage options: - Total hip arthroplasty — the standard and most common salvage; good outcomes but a high revision rate in young AVN patients (registries: roughly 25–30 percent at 10 years versus 5–7 percent for OA).

• Vascularised fibula graft — a salvage attempt for the very young (less than 35) with small–medium lesions who have failed core decompression (60–80 percent success in carefully selected cases); buys time before an inevitable THA.
• Hip resurfacing — controversial; bone-quality concerns and inferior registry survivorship in osteonecrosis versus OA; not mainstream for AVN.
• Rotational osteotomy (Sugioka / transtrochanteric) — mainly in specialist East-Asian centres; rotates the defect away from the weight-bearing zone; only for small contained anterosuperior lesions; technically demanding with unpredictable outcomes.

Epidemiology. Non-traumatic osteonecrosis of the femoral head is a disease of younger adults (peak 30–50 years) driven by corticosteroid use, alcohol excess, sickle-cell disease and other haemoglobinopathies, decompression sickness, and idiopathic causes; traumatic AVN follows femoral-neck and displaced femoral-head fractures. Non-traumatic disease is bilateral in 30–70 percent of cases, so the contralateral hip must always be imaged and counselled about. Pathoanatomy — why the head dies and collapses. The femoral head is supplied predominantly by the medial femoral circumflex artery (MFCA, 80–90 percent via the posterosuperior retinacular vessels), with a minor contribution from the lateral femoral circumflex artery (10–20 percent) and a negligible adult contribution from the artery of the ligamentum teres. The typical AVN lesion sits in the anterosuperior weight-bearing dome — the watershed zone between MFCA and LFCA territories — which is the operative target. Interruption of the MFCA supply (trauma, emboli, thrombosis) leads to ischaemia, osteocyte death, a necrotic zone, then mechanical failure of the dead bone, a subchondral fracture (the crescent sign) and finally collapse and arthritis. Core decompression intervenes in the pre-collapse phase by relieving intraosseous pressure and stimulating reperfusion. Staging — know both systems (and the size quantification).

Success rates by combined stage and size (the most predictive pairing):

Key evidence — the honest message on adjuncts. Mont and colleagues established that joint-preserving procedures are indicated for pre-collapse disease and that, once collapse has occurred, THA gives excellent results beyond ten years — the paradigm that anchors the decompress-versus-replace rule. The systematic review by Marker showed core decompression is safe and effective for early disease, with the best results in small lesions and Stage I, and that improvement over historical results came substantially from better patient selection rather than technique alone. The network meta-analysis of RCTs by Liu (17 RCTs, 784 patients, 918 hips) found core decompression with cell therapy ranked best for limiting radiographic progression, but no significant difference between any joint-preserving method and non-surgical treatment for conversion to THA — which tempers claims that structural adjuncts outperform core decompression alone. Tanzer's retrieval analysis of 15 failed porous tantalum implants explained why: residual osteonecrosis in 14 of 15, subchondral fracture in all, collapse in 60 percent, and minimal bone ingrowth (mean 1.9 percent). Yoo's long-term vascularised-fibula series (124 hips, mean 13.9 years) supports the fibula as a durable option for selected hips, including some post-collapse disease, accepting microsurgical complexity and donor morbidity. This consistent evidence base is why core decompression alone is the default for small lesions and why adjuncts are reserved for medium–large lesions or salvage. Guidelines, registries and global practice. - Registry evidence (arthroplasty for AVN). AOANJRR (Australia), NJR (England, Wales and Northern Ireland), AJRR (USA), SHAR (Sweden) and NZJR all report osteonecrosis as a risk factor for earlier revision relative to OA, with age the dominant confounder; common failure modes are aseptic loosening, instability or dislocation, and periprosthetic fracture. This underpins the rationale for joint-preserving surgery in the pre-collapse hip.

• Diagnosis and staging consensus. The ARCO 2019 revised classification is the current international consensus staging system; stage and lesion size or location remain the key prognostic determinants, and MRI is the most sensitive modality for pre-collapse disease across all guidelines.
• Pharmacological adjuncts — global view. Bisphosphonates (alendronate, or annual IV zoledronic acid) are used in many centres for corticosteroid-associated osteonecrosis to slow progression, though evidence is mixed and they are not a substitute for joint-preserving surgery in symptomatic pre-collapse disease; statins and anticoagulants have been trialled for prophylaxis in high-risk steroid users with limited evidence.
• Surgical antibiotic prophylaxis — side by side. Most national guidance (AAOS, BOA or UK, AO Foundation, WHO surgical safety) recommends a first-generation cephalosporin (cefazolin 2 g IV, weight-adjusted) within 60 minutes of incision; for beta-lactam allergy or MRSA risk, vancomycin (15–20 mg/kg over 60–120 minutes) or teicoplanin per local protocol. A single dose is sufficient for this short percutaneous procedure; routine post-operative antibiotics are not indicated.