All about complex hip and knee revisions

A revisional surgery for a hip or knee replacement is sometimes needed if the original prosthesis fails. In this article, Mr Albert Ngu, an orthopaedic consultant at RNOH Stanmore, explains what may complicate a patient’s case, and how surgeons perform complex procedures on the hip and knees.

What is a hip or knee revision, and why would it be needed?

A hip or knee revision is a surgical procedure undertaken to replace or repair a previously implanted joint replacement that is no longer functioning as intended. While primary hip and knee replacements are highly successful, they are not designed to last indefinitely. Over time, components may wear out, loosen, or fail.

Patients may require revision surgery for several reasons. The most common include implant wear and loosening, which can lead to pain and instability, and infection, which may occur months or even years after the original procedure. Other indications include recurrent dislocation of a hip replacement, stiffness, fracture around the implant, or persistent pain without an obvious cause. In some cases, revision is necessary because the original implant has not provided adequate function or alignment.

What makes a case complex?

Not all revision procedures are the same. A case is considered complex when there are additional challenges that make the surgery more technically demanding and the outcome less predictable.

Complexity may arise from significant bone loss, which can occur as a result of long-term implant wear or previous surgeries. This makes it more difficult to secure a new implant firmly. Similarly, multiple previous operations can lead to scar tissue and altered anatomy, increasing surgical difficulty.

Other factors include infection requiring staged surgery, where the implant must be removed and replaced in separate procedures, and instability or deformity, particularly in cases where ligaments are no longer functioning properly. Patient-related factors such as poor bone quality, medical comorbidities, or obesity can also contribute to the complexity of the case.

How complex revisions are performed

Complex hip and knee revisions are highly specialised procedures that require careful planning and advanced surgical techniques. Pre-operative assessment typically includes detailed imaging such as X-rays and CT scans to evaluate bone stock and implant position.

During surgery, the existing implant is carefully removed, often requiring specialised instruments to minimise further bone loss. The surgeon then reconstructs the joint using revision implants, which differ from standard replacements. These may include longer stems, augments, or custom components designed to compensate for bone deficiency.

In cases of severe bone loss, techniques such as bone grafting or the use of metal augments and cages may be employed to rebuild structural support. For knee revisions, constrained or hinged implants may be necessary when ligaments are insufficient to stabilise the joint.

Where infection is present, a two-stage revision is commonly performed. This involves removing the implant, treating the infection with antibiotics and a temporary spacer, and then inserting a new prosthesis once the infection has resolved.

Risks and considerations

As with any major surgery, complex revision procedures carry certain risks. These include infection, blood clots, dislocation (in hip revisions), stiffness (in knee revisions), and nerve or blood vessel injury. The risks are generally higher than in primary joint replacement due to the complexity of the procedure and the patient’s underlying condition.

It is essential that patients are fully assessed and optimised prior to surgery. This may involve managing chronic conditions, improving nutrition, and addressing any sources of infection elsewhere in the body.

Recovery and patient expectations

Recovery following a complex hip or knee revision is typically longer and more demanding than after a primary joint replacement. Patients should expect a period of restricted mobility and structured rehabilitation, often supported by physiotherapy.

Hospital stays may be slightly longer, particularly in more complex or staged procedures. Weight-bearing status will depend on the stability of the reconstruction and the techniques used during surgery. Some patients may initially require walking aids for several weeks or months.

Pain relief is carefully managed, and most patients experience gradual improvement in function over time. However, it is important to recognise that the outcome of revision surgery may not match that of a primary replacement. The primary aim is often pain reduction and improved stability, rather than complete restoration of normal joint function.

With appropriate surgical expertise and patient engagement in rehabilitation, complex hip and knee revisions can provide meaningful improvements in quality of life, even in challenging circumstances.