What does the AOANJRR say about total hip replacement?

Total hip replacement has a strong claim to being one of the most successful surgical procedures ever developed. It reliably reduces pain, restores mobility, and improves quality of life — and Australia's national joint replacement registry gives us exceptional data on exactly how well it performs over time.

What is the AOANJRR?

The Australian Orthopaedic Association National Joint Replacement Registry has been collecting data on every hip and knee replacement performed in Australia since 1999. With capture rates approaching complete national coverage, the registry provides a uniquely reliable picture of long-term implant survival. When a patient asks how long their hip replacement is likely to last, the AOANJRR is where the most credible Australian answer comes from.

How common is hip replacement in Australia?

Total hip replacement is one of the most commonly performed elective surgical procedures in the country. Volumes have risen steadily over the registry's lifetime, reflecting both an ageing population and growing recognition that earlier intervention can improve patient outcomes and quality of life. The dataset the registry has accumulated is now one of the largest and most valuable in the world.

What are the long-term revision rates?

The AOANJRR tracks revision rates — how often a hip replacement requires reoperation to address a problem with the implant. For primary total hip replacement, the registry consistently shows a cumulative revision rate of approximately 5 per cent at ten years, approximately 8 to 9 per cent at fifteen years, and in the range of 12 per cent at twenty years.

Expressed the other way: roughly 95 per cent of hip replacements are still functioning without revision at the ten-year mark. That is an impressive track record for a mechanical implant operating inside a living body under considerable load over an extended period.

What are the most common reasons for revision?

Understanding why hip replacements are revised helps explain both the challenges of the operation and how practice has evolved to address them.

Instability (dislocation) has historically been one of the leading causes of revision after hip replacement. The hip is a ball-and-socket joint, and after surgery the soft tissue envelope needs time to recover. Dislocation is more likely in the early post-operative period and is influenced by both implant positioning and surgical approach. Advances in implant design and surgical technique — including the growing use of the direct anterior approach — have meaningfully reduced dislocation rates over the registry period.

Aseptic loosening is the gradual failure of the bond between implant and bone, most often due to wear particles from the bearing surface generating an inflammatory response that causes bone loss. This is typically a longer-term phenomenon, becoming more prominent beyond ten to fifteen years.

Infection is a serious complication that can occur early (in the weeks following surgery) or late (months to years later). It accounts for a meaningful proportion of revisions and remains one of the most challenging problems in joint replacement surgery.

Periprosthetic fracture — fracture of the bone around an implant — has become an increasingly recognised cause of revision, particularly as the population of patients with older hip replacements ages and becomes more susceptible to falls.

What does the registry show about bearing surfaces?

The material combination used for the ball-and-socket bearing surfaces significantly affects long-term implant performance, and the AOANJRR data on this has been influential in shaping clinical practice.

Ceramic-on-ceramic and ceramic-on-highly-crosslinked-polyethylene combinations show the best long-term performance in registry analyses, with low wear rates and low revision rates attributable to the bearing surface. These are now the most commonly used bearing surfaces in contemporary practice.

Metal-on-metal hip replacements — once promoted on the basis of low wear rates and the ability to use larger femoral heads — showed markedly elevated revision rates in the registry data, driven by adverse local tissue reactions to metal ion release. This evidence played a significant role in the withdrawal of metal-on-metal devices from primary hip replacement practice. The AOANJRR's ability to detect this signal earlier and more clearly than smaller studies is a demonstration of exactly why a national registry matters.

Does surgical approach affect outcomes?

The registry does not consistently show one surgical approach to be superior to another when overall revision rate is the primary measure. However, some analyses have identified lower dislocation rates associated with the direct anterior approach (DAA) compared to posterior approaches, which is consistent with what the biomechanical rationale for the DAA would suggest — the posterior capsule and external rotators are preserved rather than divided.

This is an area of active research, and the registry will continue to generate useful data as DAA volumes grow and longer-term follow-up accumulates.

Cemented versus cementless fixation

Both cemented and cementless hip replacement techniques have extensive long-term registry data supporting their use. Historically, cemented fixation was the standard; cementless fixation has grown significantly in prevalence over the past two decades, particularly in younger patients, and the registry supports its performance. The choice between them is influenced by patient age, bone quality, and surgeon experience — and both approaches, when used in the right patient, deliver excellent long-term results.

How does age affect outcomes?

Younger patients have higher revision rates than older patients, and this is consistently demonstrated across all joint replacement registries. The reason is straightforward: younger patients are more active and have longer lives ahead of them, during which a revision could occur. The relationship between age and revision rate does not mean younger patients should avoid hip replacement — it means the discussion about timing, implant selection, and activity modification needs to be more detailed and more tailored for this group.

Patient satisfaction after hip replacement

Total hip replacement consistently generates some of the highest patient satisfaction rates of any elective surgical procedure. Large outcome studies show that the great majority of patients — typically well over 90 per cent — report significant improvements in pain and function, and high overall satisfaction with the procedure. This places hip replacement in a different category to knee replacement, where dissatisfaction rates are somewhat higher.

The combination of strong registry survival data and high patient satisfaction makes total hip replacement one of the most evidence-supported interventions in elective surgery.

Hip replacement consistently produces some of the highest satisfaction rates of any elective surgical procedure — and the AOANJRR tells us why the data underpinning that confidence is real.

What this means in practice

The registry data provides a strong evidence base for hip replacement in appropriate patients. Choosing implants with a proven registry track record, selecting a bearing surface appropriate for the patient's age and activity level, and using a surgical technique that minimises dislocation risk are all informed by this data. The AOANJRR is not just a historical record — it is an active tool that shapes how hip replacement is performed in Australia today.