Specific Risks of Total Hip Replacement

Part of The Joint Replacement Guide — Phase 3: Understanding the Risks · Article 14 of 42 · Hip

Key Points

• Dislocation, leg length difference, and nerve injury are the main risks specific to hip replacement, on top of the general surgical risks covered previously.
• Dislocation risk has fallen significantly with modern techniques and is now uncommon.
• Small leg length differences are common and usually well tolerated; larger differences are actively avoided during planning.
• Nerve injury is uncommon, and most cases improve, at least partially, over time.

Dislocation

Dislocation occurs when the ball of the new hip joint comes out of the socket, and is one of the risks specific to hip replacement. It is more likely in the early weeks after surgery, before the surrounding soft tissues have fully healed, which is part of the reasoning behind hip precautions in the initial recovery period (covered in a dedicated article later in this guide, including how that advice has evolved). Risk factors include the surgical approach used, implant positioning, and individual factors such as soft tissue laxity. If a dislocation does occur, it is usually treated by manipulating the hip back into place (closed reduction), often without the need for further surgery; recurrent dislocation is uncommon but can occasionally require revision surgery to address the underlying cause.

Leg Length Discrepancy

This is one of the most common concerns patients raise before surgery. Surgeons aim to match your leg length as closely as possible, but this has to be balanced against achieving a stable, well-fitting joint — occasionally a small amount of deliberate lengthening is needed to achieve good stability and reduce dislocation risk. Differences of a few millimetres are common and usually not noticeable in day-to-day life; most patients adapt within a matter of months as muscles and gait adjust. Very rarely, a persistent, symptomatic difference may need addressing with a simple shoe insert, and further surgery for this reason alone is unusual.

Nerve Injury

The sciatic nerve, which runs close to the back of the hip, is the nerve most at risk during hip replacement, particularly with a posterior surgical approach; the femoral nerve at the front of the hip is less commonly affected. Nerve injury typically presents as numbness or weakness — for example, difficulty lifting the foot (foot drop) if the sciatic nerve is affected. Most cases improve, at least partially, over weeks to months as the nerve recovers, and permanent, significant nerve injury is uncommon.

Other Hip-Specific Risks

A fracture around the implant (periprosthetic fracture) can occasionally occur during surgery or afterwards, particularly in bone that is already weakened by osteoporosis, and is managed according to its severity, sometimes with additional fixation at the time of surgery. Over the longer term, implants can loosen or wear — this is a separate topic covered in the articles on implant fixation and bearing surfaces, and in the later article on revision surgery.

In More Depth

National joint registry data allows dislocation and other complication rates to be tracked over time and by surgical approach, and these figures have generally trended downwards over the past two decades as surgical technique, implant design, and post-operative protocols have improved. There is an ongoing evidence debate about whether particular surgical approaches (discussed in detail in the next phase of this guide) carry meaningfully different dislocation risks — some studies favour certain muscle-sparing approaches, while others show that careful soft tissue and capsule repair, regardless of approach, is at least as important a factor. This is an area where surgeon experience and technique arguably matter more than the specific approach chosen.

This article is general information and does not replace individual clinical advice.

Sources

• National Joint Registry — Annual Report, hip replacement outcomes
• British Hip Society — patient information resources
• Cochrane Database of Systematic Reviews — surgical approach and outcomes in total hip replacement

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