When a hip cartilage defect is too large for standard repair

A small cartilage injury inside the hip joint — the kind measuring less than about two square centimetres — can often be addressed with techniques such as microfracture or an osteochondral autograft taken from elsewhere in the same joint. Once a defect grows larger than that, or involves significant loss of the bone immediately beneath the cartilage surface, those options run out of reach. The lesion is simply too wide and too deep for what those procedures can reliably fill.

For defects of the femoral head — the rounded ball of the hip — in the range of 400 mm² or above (roughly the area of a circle 2.2 cm across), the clinical answer is osteochondral allograft transplantation, or OCA. In plain terms, a precisely matched piece of donor bone and cartilage, taken from a carefully screened tissue bank, is shaped to fit the defect and fixed into place in a single surgical session. Unlike a marrow-stimulation technique, which encourages the body to fill a hole with fibrocartilage, OCA delivers intact hyaline cartilage — the same tissue the hip is designed to move on — together with the underlying bone scaffold that keeps it alive and load-bearing.

The causes of these larger defects include traumatic femoral head injuries, femoroacetabular impingement, avascular necrosis, and developmental conditions such as Legg-Calvé-Perthes disease. Across published series, the typical patient is in their early twenties, and hip replacement carries documented concerns about implant longevity at that age. OCA's explicit purpose is to preserve the joint for as long as possible — deferring rather than bypassing the patient's natural hip.

The patients who are most likely to benefit

Most people assessed for osteochondral allograft transplantation of the hip are in their twenties. Published series report mean ages of 21 to 22 years — young enough that the expected lifespan of a hip replacement implant becomes a genuine concern rather than a theoretical one. Arthroplasty at that age is not ruled out, but surgeons and patients generally work through every joint-preserving option first.

For many, the problem arrives without warning. Post-traumatic femoral head damage — from a fracture-dislocation in a road traffic collision, a sports impact, or a fall — accounts for roughly 31% of OCA cases in recent series. The developmental and structural conditions discussed in the previous section make up much of the remainder, but the point worth noting here is that OCA is not solely a pathway for gradual, predictable deterioration. It is equally relevant after a single acute event that leaves a young adult with a defect too large for earlier repair options.

Previous surgery on the same hip does not disqualify someone. In published cohorts, nearly half of OCA patients had already undergone at least one prior operation on that side, so OCA frequently functions as a second-line or later preservation step rather than a first response.

Where a matched femoral head allograft is not immediately available — as may happen in an urgent trauma setting — surgeons have used osteochondral plugs from a fresh-frozen proximal humerus allograft, supplemented with demineralised bone matrix, as a workable alternative. A published case report of a 21-year-old who sustained a traumatic fracture-dislocation in a road traffic collision documented full strength and no pain at two years following this approach.

Why allograft rather than the patient's own tissue

The most direct answer to 'why not use my own cartilage?' is one of geometry. Autograft mosaicplasty — in which small cylindrical plugs are harvested from a lower-load area of the same joint and transferred to the defect — works well for lesions up to roughly 1.6 × 1.0 cm. Beyond that, the harvest sites cannot safely provide enough tissue without creating a secondary problem where the plugs were taken.

Femoral head defects treated with OCA in published series average 2.8 × 2.1 cm — nearly three times the surface area handled by autograft in the same multicenter comparison — with graft depths of around 8.5–8.8 mm. There is simply no equivalent donor region in the hip that can fill a gap of those dimensions without meaningful morbidity at the harvest site.

The outcome data from the same study offer some reassurance: despite the larger defect size, allograft and autograft cohorts achieved comparable functional scores (mHHS approximately 86–87; HOS-ADL approximately 92–93), with no statistically significant difference between them. That finding should not be taken as proof of equivalence — these are Level 4 case-series, and numbers are modest — but it does suggest that using donor tissue for larger lesions does not automatically produce inferior results.

Allograft does introduce a different consideration: the biological viability of the donor cartilage at the time of implantation. That is addressed separately in the graft quality section below.

What the operation involves: surgical hip dislocation

Hearing the phrase 'surgical hip dislocation' can sound alarming before anyone explains what it actually means — so it is worth being clear about why the approach is necessary and what a controlled, planned dislocation involves in practice.

To reach a large defect on the femoral head, the surgeon needs to see the entire surface of the ball, not just the portion visible through an arthroscope. For defects above roughly 400 mm² — the sizes typical in OCA — a keyhole approach does not provide that access. Instead, a small section of the greater trochanter (the bony prominence on the outer side of the hip) is carefully detached and set aside. This temporary step allows the hip to be gently and safely dislocated under full anaesthesia, exposing the complete femoral head surface. The damaged area is then prepared, and the donor graft is shaped and press-fitted into position. Once the graft is secure, the trochanter is reattached — usually with screws — and the incision closed.

The key phrase is controlled and planned. This is not a traumatic event but a precise surgical manoeuvre performed to give the graft the best possible position and fixation.

Recovery is more gradual than after an arthroscopic hip procedure, because the reattached trochanter needs time to heal before full weight-bearing resumes. Protected weight-bearing — often with crutches — is standard during that bone-healing phase, followed by a structured physiotherapy programme. The overall timeline is longer than for keyhole surgery, and that is a practical consideration worth raising during any pre-operative consultation.

Outcomes: what the evidence shows and what it cannot yet tell us

The functional gains from OCA are meaningful and consistent across the two largest published series. Modified Harris Hip Score rises from a pre-operative mean of around 58–62 to approximately 84 after surgery (P<.001), with the iHOT-12 — a patient-reported quality-of-life measure — climbing from roughly 35 to 78. Between 67% and 84% of patients reach the minimum clinically important difference depending on the series, meaning the improvement is not merely statistical but felt as real change in daily life.

THA conversion is the other figure patients reasonably want to understand. Across published series, 13.7–25% of patients go on to hip replacement at a mean of 1.9–3.8 years after OCA — typically those with the most severe pre-operative joint damage. Put the other way: roughly 75–86% avoid or significantly delay hip replacement over the reported follow-up periods. OCA is not framed as a permanent solution, and this honestly reflects the biological challenge of restoring a large femoral head defect in a young, active person.

One finding that carries direct practical weight concerns how the donor graft is stored before surgery. In a 33-patient series, grafts preserved using the Missouri Osteochondral Preservation System (MOPS) achieved 100% success at one year or more, compared with 50% success for those stored using standard refrigeration — an odds ratio of approximately 47 (P=0.001). This is not a minor technical detail: how a graft has been handled from procurement to implantation is a clinical decision, and it is worth asking a surgeon where their grafts come from and under what storage conditions.

Longer-term data, beyond five years, remain sparse. What exists is sufficient to understand what OCA offers in the medium term; it is not yet enough to map the full trajectory for a patient now in their early twenties.

Is hip OCA the right next step for you

Several questions shape whether hip OCA is a realistic option for any given patient: How large is the defect, and what caused it? Has the joint already been treated surgically — and if so, how? What are the patient's activity goals, and how much recovery time is feasible?

OCA is most clearly indicated when a femoral head lesion exceeds roughly 400 mm², when trauma is the root cause, or when defect dimensions make autograft mosaicplasty geometrically insufficient. Smaller focal defects — particularly those below about two square centimetres — are generally better matched to OATS or a cell-based approach such as MACI. Diffuse osteoarthritis sits outside the scope of cartilage repair entirely; for those patients, the conversation shifts toward joint replacement rather than preservation.

Prior surgery on the same hip, the aetiology of the defect, graft storage protocols, and the patient's own recovery capacity all influence the decision. The published cohorts are predominantly young — mean age around 21–22 — and that demographic context matters: OCA is a bridge strategy most defensible when arthroplasty is genuinely premature.

None of these questions can be answered without cross-sectional imaging and a specialist hip-preservation assessment. For patients across Lincolnshire and the wider East Midlands and Yorkshire area, Lincolnshire Hip — part of the MSK Doctors group — offers that assessment without requiring a GP referral.

1. [1] Osteochondral Allograft and Autograft Transplant for Femoral Head Defects: A Multicenter Study. (2025). https://doi.org/10.1177/03635465251338062 https://doi.org/10.1177/03635465251338062
2. [2] Osteochondral Allograft Transplantation of the Femoral Head via Surgical Hip Dislocation: Survivorship and Patient Reported Outcome Measures at Minimum 2-Year Follow-Up. (2025). https://doi.org/10.1177/23259671251385115 https://doi.org/10.1177/23259671251385115
3. [3] FP5.7 Clinical Outcomes following Osteochondral Allograft Transplantation of the Femoral Head via Surgical Hip Dislocation. (2025). https://doi.org/10.1093/jhps/hnaf011.045 https://doi.org/10.1093/jhps/hnaf011.045
4. [4] Osteochondral Allograft Transplant in a Young Patient with a Traumatic Hip Fracture Dislocation: A Case Report. (2024). https://doi.org/10.3390/std13040032 https://doi.org/10.3390/std13040032
5. [5] Osteochondral Allograft Transplantation in Avascular Necrosis of the Hip. (2023). https://doi.org/10.4103/juoa.juoa_2_25 https://doi.org/10.4103/juoa.juoa_2_25