Joint replacement

The aims of joint replacement are to reduce pain and improve mobility and quality of life. Joint replacements allow patients to maintain their independence, may reduce

Figure 22.20. Posterior fracture-dislocation of the hip pre (a) and post (b) reduction.

their reliance on walking aids and may even allow the housebound patients to re-enter the community.

Indications for joint replacement include severe pain interfering with the patient's activities of daily living and quality of life, increasing severity of deformity and joint stiffness, and loss of independence. The requirement of large doses of analgesics to control symptoms, interruption to sleep pattern due to persistent pain and failure of conservative means of treatment such as the use of walking aids, physiotherapy and possibly bracing are also relevant.

The disease process may be an isolated phenomenon affecting a particular joint or be part of a generalized arthropathy (e.g. rheumatoid arthritis) where multiple limbs may be affected either symetrically or asymetrically. As such the patient may require multiple joint arthroplasty involving both upper and lower limbs, and if this is the case, the sequence and timing of joint replacement are important considerations. Bilateral joint replacements can also be performed sequentially or at the same operation (e.g. bilateral total hip replacements).

The decision to perform joint replacement or arthroplasty, whether it involves the upper or lower limb, depends on both local and general factors. The latter relate mainly to an assessment of whether the patient requires a joint replacement, his general fitness and suitability for major surgery and extensive rehabilitation. The patient's loss of independence through an inability to perform daily activities of living and its impact on him must be enquired about. Age is not generally a contraindication to joint replacement. In generalized disease processes such as diabetes or patients who are immunocompromised, for example renal transplant patients on immunosuppressive agents, there is an increased risk of complications of joint arthroplasty, particularly infection.

The local factors which need to be assessed prior to joint replacement surgery include an assessment of the quality of soft tissues and bone, the neurovascular status of the limb, particularly where the surgery involves the lower limb and the alignment of the limb together with associated deformity of the joint. If there are any concerns regarding the vascular status of the limb, then a preoperative vascular opinion should be sought.

Evaluation, especially in the context of patients who have had previous surgery to the affected joint, involves: • Skin: previous surgical scars, especially if there have been multiple operations around the joint, may affect the surgical approach to the joint. The surgeon needs to be aware of the presence of chronic skin conditions, especially chronic ulcers, around the joint that may be in close proximity to the surgical incision as this can predispose to infection.

Figure 22.21. Total hip arthroplasty for osteoarthritis of the hip.

• The quality of the subcutaneous tissues and muscles is important as adequate coverage of the prosthesis is needed. This is usually a problem in the knee and elbow or small joints of the hand. Ligamentous stability also needs to be assessed as this may affect which type of prosthesis is used.

• The amount and quality of bone is carefully assessed radiographically as this is the main supporting tissue for any prosthetic implant (Fig. 22.21). Patients with poor bone stock or quality due to generalized bone disorders (e.g. osteoporosis) may require a specialized prosthesis or a different surgical technique compared with those who have good bone quality without major loss of the bone stock.

• Alignment of the joint or loss thereof due to deformity secondary to loss of bone stock and soft-tissue contracture is important in the weight-bearing joints of the lower limbs. Alignment is assessed both clinically and radiologically and influences the surgical technique as well as choice of prothetic implant. In the case of the knee joint, only one compartment may be involved in degenerative disease.

Unicompartmental prostheses are available to allow the most affected compartment to be addressed while preserving bone stock. Following clinical assessment, appropriate radiographs of the involved joint, and if necessary the contralateral joint, are taken for comparison. In some cases, full-length films of the limb may be required, particularly with regards to total knee arthroplasty.

Once the decision has been made to proceed with joint replacement surgery, on the basis of clinical and radiological findings, a lengthy discussion needs to be undertaken with the patient to inform him of the details of the procedure to be undertaken, the expected outcome and the complications involved. Only under these circumstances, can a patient give informed consent to undergo a major surgical procedure. The patient also needs to be informed of the usual postoperative course, any rehabilitation that will be required, the expected life of any prosthetic implant and the consequences of having to undergo revision surgery. The patient should be advised that implants can dislocate and loosen (Fig. 22.22) or fail (Fig. 22.23). The patient should

Figure 22.22. Total hip arthroplasty for osteoarthritis of the hip-arthroplasty now painful and possibly loose.

either be reviewed on a regular basis long term or advised as to what symptoms to expect in the event of problems with the implant.

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