Total Hip Replacement

A total hip replacement is a very successful procedure for patients with arthritis of the hip. Arthritis of the hip can be caused by osteoarthritis, inflammatory arthritis, or secondary arthritis due to an injury or deformity. Hip fractures are often treated with a hip replacement if screw and plate fixation can not be done.

Minimally invasive, muscle sparing surgery is performed by both surgeons at the Cape Joint Surgery. This ensures preservation of important muscle attachments in order to allow for early post-operative mobilization and optimal functioning very soon after surgery.

The Cape Joint Surgery surgeons are both super-specialist fellowship trained hip and knee surgeons with extensive experience in the diagnosis of hip problems in adults and children.

Please Click Here for information on other hip complaints and procedures.

The basic philosophy behind total hip replacement surgery is the removal of the femur neck and smoothing out of the acetabular cup, subsequent to which a metal femoral stem and an acetabular cup (usually also metal except in rare cases where a polyethylene cup is cemented into the acetabulum) are inserted. The acetabular cup is then fitted with a liner, which is usually either plastic (highly cross-linked polyethylene) or ceramic. There has been a recent move away from metal cup liners and these are not used in this practice. The next step in the procedure is insertion of a appropriately sized replacement femoral head (i.e. a metal or ceramic ball which it is accepted by a morse taper on the neck of the femoral stem). The hip is then reduced and stability of the implants in all leg positions is confirmed.

Recent advances in total hip replacement surgery have led to significantly improved outcomes. Some of these advances are:

Femoral stem as well as cup liner modularity allow us to compile a patient-specific implant in every case when we perform intraoperative trials of the various components discussed above. This enables us to achieve accurate length and excellent stability in most cases. Stability and patient satisfaction has much improved since the days of cemented monobloc femur implants and plastic acetabular cups, which had significant limitations in this regard. Another advantage of modular implants is the fact that revision operations are often simplified.

Implant fixation is of paramount importance and if this is not achieved will likely necessitate a revision procedure in the early stages. While the earlier prostheses relied on cement fixation of the stem and the cup , and while cement fixation still remains a viable option, modern ingrowth stems and cups are designed in such a way that immediate stability is achieved with press-fit insertion and long-term stability is insured with bony ingrowth into the implant coating. Various coating modalities are available and they may contain hydroxyapatite which is a type of ceramic, present in natural bone, which has been shown to increase the rate of bony ongrowth and ingrowth. A major advantage of these ingrowth implants is the fact that the potential joint space (a microscopic space between the implant and the cement mantle in cemented implants) is not present and therefore mechanical wear particles can not enter the femur or the pelvis and as a consequence, no inflammatory granulomas will form in the interface (a condition which can lead to implant loosening in cemented implants).

There are various implants available for total hip replacement with the available combinations of bearing surfaces being metal-on-polyethylene, metal-on-metal, ceramic-on-ceramic and metal-on-ceramic. The material that the hip replacement component is manufactured from could range from cobalt chrome, stainless steel to titanium, with or without hydroxyappertite coating (a material which encourages bone ingrowth). The implant selection should be left up to the surgeon, as there are various combinations and permutations available which may have to be ultimately selected only during surgery, based on the particular anatomical requirements of the patient.

Dr Engela and Dr Martin attend- and present papers regularly at international meetings and follow published literature closely in order to determine which implant is best for which patient. We do not prescribe to a phylosophy that one type of implant could- or should be used on all patients. Each patient has a different anatomical geometry and different circumstances and therefore each patient in our practice will be assessed individually and a suitable implant selected to match individual requirements.

Dr Engela’s experience was gained whilst he was involved in designing custom implants for each patient and supervising manufacturing of the custom implants during the years 1993 – 1995. These custom implants were part of a research project and did not become commercially viable due to the cost of manufacturing inidiviual implants. The design of more than 1000 custom implants and implantation of more than 500 implants at the time gave him a good understanding of how to select an implant for each patient individually.

At present most patients in our practice will have a cementless total hip replacement with the option of ceramic-on-polyethyle, ceramic-on-ceramic, or metal-on-polyethylene articulation surfaces. Implant selection and procedure of choice are based on several factors. We have to consult with the patient in order to determine the needs of the patient in terms of joint utilization, severity of disease and deformity. X-ray assessment forms a vital part of the pre-operative planning.

The accepted survivorship period of a total hip replacement after replacement is 98% at 10 years and this criterion is used when selecting an implant in our practice.

Complications of total hip replacements include implant related infection, aseptic (uninfected) loosening of the implants, dislocation and component wear or breakage as well as periprosthetic fractures. These complications often require revision surgery.

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