Purpose:

Crosslinking of polyethylene has become synonymous with longevity in total hip replacement. In the USA 70–85% of all polyethylene cups underwent crosslinking since 2008. Three publications appeared in the autumn 2011 volume of the “SA Orthopaedic Journal,” on the 10–33 year follow-up of the original SA crosslinked implant. The purpose of this study is to illustrate and confirm statistically, the improvement of the bone cement interface, provided that wear of polyethylene can be reduced to an absolute minimum.

Far too many cases of instability and recurrent dislocation occur after primary total hip replacement. The motivation for this paper came from yet another three cases of recurrent dislocation on our theatre list in a single month (March 2006). All three were recurrent dislocations after primary hip replacements. Since these were not three isolated cases we realised that there is an urgent need to improve the situation. In all three cases surgical or implant factors were responsible.

We take a fresh look at the causes; which are implant, surgeon and patient related. Of these only patient related issues cannot always be corrected. The design of a stable implant is discussed and revolves around head size, head neck ratio and cup depth. The surgeons’ contribution can be equally important and controllable – it embodies correct peri-articular soft tissue tension, orientation of components and patient selection. Finally, patient factors are neuromuscular, anatomical and patient compliance. In this respect some unresolved factors should be identified pre-operatively.

Especially for the occasional hip surgeon this is an extremely important issue. The recurrent dislocation results in extremely poor quality of life, often leading to revision surgery. These aged patients usually suffer multiple inherent risks and massive financial losses. Above all we believe that the great majority of these dislocations can be prevented by simply keeping to the clear and well proven principles of stability in total hip replacement.

This study investigates the relationship between the quality of the arthroplasty and the radiological appearance of the interface. Of special interest is the prognostic value of sustained stability and of improvement in the interface, a phenomenon we have not previously seen.

At 1 week and at 6 and 24 months postoperatively, we assessed radiographs of 20 randomly selected patients in whom cross-linked polyethylene cups had been implanted. We classified them into three stages: in stage 0 there was no interface in any zone, in stage I less than 2 mm and in stage II more than 2 mm. This was not a comparative study, but an important feature was the sustainment and/or improvement of the interface. In 16 patients a complete ‘white-out’ of interfaces in postoperative x-rays was sustained for the duration of the study. In three patients imperfect postoperative interfaces clearly improved. In only one patient, who had developed infection, was there deterioration. Widening was seen only in cases of gross mechanical failure or sepsis.

We postulate that cross-linking of polyethylene results in virtual absence of HDP debris and that this is the main reason for interface improvement. It is polythene particles that cause osteolysis, and their elimination dramatically improves the prognosis for total joint replacement. The results reconfirm that, provided fixation is complete, cement is not the main reason for interface failure.

We believe that this method makes total joint replacement viable even in young patients.

There is no consensus on the management of the most lethal complication of total joint replacement. One school follows the traditional ‘prophylaxis without compromise’ policy, while the other, realising the dangers of prophylactic drugs, especially in total joint replacement, goes to the other extreme of ‘no prophylaxis and no anti-thrombotic drugs even for pulmonary embolism’.

We follow a middle of the road principle, believing that ‘surveillance determines anticoagulation therapy’. Our treatment protocol divides patients into high and low-risk cases. Regular surveillance (Doppler and blood examination) determines the method and extent of prophylaxis for high-risk cases and the therapeutic handling of positive clot formation in low-risk patients. Treating over 1055 patients over 8 years, we selectively administered anticoagulants only when clinically indicated and after positive Duplex diagnosis. Mortality due to pulmonary embolism was reduced by this regime from 1.0% to less than 0.05% (two cases in 6 years).

Guidelines have been laid down regarding the value of blood tests in combination with Duplex in an effective and affordable way, not only to detect thrombo-embolism but also to manage treatment, even after discharge.

Introduction and Aims: Wear of ultra-high molecular weight polyethylene (UHMWPE) acetabular cups is a well-known cause of osteolysis and loosening of the components. Improvement of the wear resistance of UHMWPE could extend the clinical life of total hip arthroplasty (THA). Chemical cross-linking in acetylene with gamma radiation is a cheap and effective way of increasing wear resistance of UHMWPE.

Method: This study is a report on 132 patients operated between 1977 and 1984, using the Pretoria monobloc stainless steel hip with 30mm metal head. Acetabular cups were machined from RAM extruded rectangular bars (RCH 1000). Final cups were gamma irradiated in stainless steel containers filled with acetylene gas. Three hundred microns surface cross-linking was achieved at 100kG. At that time, 1059 hip replacements were performed by the two first authors. The retrospective study consisted of measurement of the radiological wear. The criteria was to compare and measure the wear from early post-op radiograph and longest follow-up radiograph. Linear wear was measured according to the Livermore methods. Exclusion criteria included follow-up less than 10 years, sepsis, dislocation and other non wear-related causes of failure. The rarely retrieved cross-linked ace-tabular cups were analysed individually using spectrum electron microsope (SEM).

Conclusion: The South African contribution to the method of cross-linking is important. This is a cheap and effective way to improve the quality of the polyethylene. Results of this long-term group of patients with cross-linked UHMWPE show a significant decrease in the wear rate, significantly increasing the longevity of the THR.

In February and March 2004, 35 hip and 15 knee arthroplasties were performed. Indications for surgery included primary OA, avascular necrosis and fractures. Revision surgery was performed for aseptic loosening and recurrent dislocations. There were three revision hip arthroplasties and three arthroplasties were done for subcapital femoral fractures. The mean age of the patients was 64.2 years (33 to 84). The male to female ratio was 1:1.5. Both cemented and uncemented implants were used.

In the hip arthroplasties, the mean intraoperative blood loss was 515 ml (300 to 1520 ml). Intraoperative blood loss was minimal in the knee arthroplasties. Postoperative suction drainage averaged 477 ml for the hips and 925 ml for the knees. Postoperative blood transfusions were administered in seven patients. The mean time to mobilisation was 3 days postoperatively, and discharge was on day seven.

Early complications included superficial cellulitis in four patients, who were treated with intravenous antibiotics. After a knee replacement one patient developed a haematoma, which drained spontaneously. One patient had an early dislocation. Three patients developed upper respiratory tract infections. One 32-year-old man developed intraoperative pulmonary fat embolism and required ventilation for 24 hours. Following a knee replacement, one patient developed a transient drop foot, which improved after 24 hours. No incidence of clinical DVT was encountered.

Hip and knee arthroplasties are major procedures. Adequate preoperative evaluation to identify potential risks could limit major complications.

Revision THA is guaranteed to throw some light on the question of longevity of implants. This study takes a fresh look at the materials that we have used in 30 years of joint replacement.

We studied four consecutive revision arthroplasties performed in one week. Patient 1 was a 55-year-old woman who in 1994 received a titanium-backed acetabular cup with virgin HDP insert and an alumina femoral head on a titanium stem. Polyethylene osteolysis was obvious and histological assessment confirmed the presence of polyethylene granulomata. Patient 2 was a 28-year-old man who had bilateral ceramic-on-ceramic hip replacements 18 and 19 years previously. The prosthesis on the left became loose and showed a typical alumina-ceramic problem. Patient 3 was a 51-year-old woman with stage-III polyethylene disease after 19 years. Substantial granulomata were seen on histological sections. Patient 4, a 52-year-old woman, had received a gamma cross-linked cup and stainless steel head 22 years previously. She presented with dislocation but no tribological problems. There was no wear and interfaces were perfect.

These four cases highlight the importance of proper selection of tribological materials. Polyethylene disease was an important cause of medium-term or late failure and acrylic debris was only a secondary problem. Literature reports on titanium metallosis seem over-rated, but titanium performance is questionable with cement. Finally, cross-linking of ultra-high molecular weight polyethylene is a simple, cheap and effective way of enhancing long-term performance in joint replacement surgery.

The longevity of hip arthroplasty is especially important in young patients. High quality polythene and metals, coupled with improved bone cement and cementing techniques, have led to increased longevity. Of particular importance has been the cross-linking of ultra-high molecular weight polyethylene, which almost completely eliminates implant wear and projects the lifespan beyond the second decade.

In a three to four-year follow-up of patients, including a random sample of females under the age of 20 years, we have found the entire arthroplasty unchanged. The interface often becomes better integrated with time. The fact that there is no polythene debris is likely to have a direct effect on the longevity of the arthroplasty.

These results suggest that surgery can be contemplated in very young patients.

Evaluating 30 years of total hip arthroplasty, we analyse the factors that determine longevity in terms of implant, design, materials, instrumentation and operative technique.

Simple implant design is important. Cups should be thick-walled and cemented. Particularly when cross-linked polyethylene is used, the size of the head bears little relation to the prevention of wear, but using too small a head seriously impairs stability. Improved cement and cementing techniques now facilitate exact placement. Traction instrumentation controls leg length equalisation and periarticular tissue tension, and further enhances stability.

We give the preliminary results of 22 consecutive shoulder replacements done over a two-year period using a locally-produced prosthesis. Most of the replacements were done for traumatic reasons.

This paper examines research over three decades.

Special mention is given to material research and basic implant design. In South Africa there were unique opportunities to conduct engineering and biological research on materials, close examining the interface – the key to total joint replacement success. It seems there is now more clarity on the longevity of implants and on how to avoid certain pitfalls.

In the past, many high tibial osteotomies were done to relieve symptoms of osteoarthritis. These osteotomies have largely been replaced by total knee arthroplasty (TKA).

This paper presents the long-term results of 270 osteotomies followed up for 10 years and discusses the complications involved in subsequent conversion to TKA.

At the same time as the LCS knee, the ARD knee was developed. We aimed to assess whether over a 10 to 15-year period the SS 86 rotational platform knee system stood the test of time.

In a retrospective study, we followed up 250 patient, assessing patient satisfaction, range of motion and radiological appearance. Patient satisfaction was high and range of motion and radiological appearances very good.

Thromboembolism is a potentially fatal complication of total joint replacement. Some surgeons follow a ‘prophylaxis without compromise’ policy, while others, who realise that there are risks attached to the use of prophylactic drugs, go to the opposite extreme and administer no prophylaxis and no anti-thrombotic drugs, even for pulmonary embolism.

We believe the results of surveillance should determine the administration of anticoagulation therapy. In over 1 500 patients, anticoagulants have been administered only when clinically indicated and after positive Duplex diagnosis. Death due to pulmonary embolism has occurred in only two patients in six years, a reduction from 1.0% to less than 0.05%.

Our treatment protocol divides our patients into high and low risk cases. The results of Doppler and blood tests dictate the method and extent of prophylaxis for high-risk cases, and the therapeutic handling of positive clot formation in the low-risk population.

In a retrospective study, we examine the occurrence and management of sepsis in total knee arthroplasty. Histological examination and MCS play important roles.

In the past many high tibial osteotomies were done to relieve symptoms of osteoarthritis. Total knee arthroplasty (TKA) has largely taken the place of these osteotomies.

Aiming to evaluate the long-term results of these osteotomies and assess the complications involved on conversion to TKA, we followed up 207 patients over a 10-year period.

Wear of ultra-high molecular weight polyethylene (UHMWP) acetabular cups is a well-known cause of osteolysis and loosening of the components. Improvement of the wear resistance of UHMWP could extend the clinical life of total hip arthroplasty (THA). Chemical cross-linking in acetylene with gamma radiation is a cheap and effective way of increasing wear resistance of UHMWP.

This study is a report on 263 patients (123 males and 140 females) on whom Dr Weber performed THA between 1977 and 1984, using the Pretoria (Grobbelaar) monobloc stainless steel hip with 30-mm metal head. There were 96 patients (107 prostheses) available for follow-up at a mean of 18.3 years, with 89 surviving prosthesis in 79 patients (83.2%).

We collected complete sets of radiographs of 54 patients (mean age 71.4 years) for a radiological survey in 1999. In 41 patients (76%) we found no wear. The mean age of these patients was 72 years. Wear was noted in the other 13 patients (24%), whose mean age was 75 years. The mean follow-up time was 16 years (8 to 23). The mean magnification in the radiological study was 18%. Mean wear for the total group was 1.29 mm and mean annual wear 0.17 mm.

A similar analysis performed on a group of 64 of Dr Grobbelaar’s patients at 15.5 year mean follow-up shows remarkable similarity, with mean wear of 0.172 mm for a group of 64 patients and annual wear 0.11 mm. Dr Oonishi of Japan, who has conducted the only other long-term follow-up, found similarly promising results.

At the same time as the LCS knee, the ARD knee was developed. We aimed to assess whether over a 10 to 15-year period the SS 86 rotational platform knee system stood the test of time.

In a retrospective study, we followed up 250 patient, assessing patient satisfaction, range of motion and radiological appearance. Patient satisfaction was high and range of motion and radiological appearances very good.

The radiation crosslinking of high-density polyethylene prostheses was investigated over a wide range of doses in the presence and absence of gaseous crosslinking agents. It was found that in the bulk polymer the crosslinking pattern is completely different from the homogeneous crosslinking that occurs in polymer films. The presence of crosslinking agents causes highly crosslinked polymer to be formed on the surface while the bulk of the polymer is largely unaffected--which is explained in terms of diffusion phenomena. This surface crosslinking has a profound effect on the mechanical properties of the prostheses and restricts cold flow and deformation of the polymer without sacrificing the excellent abrasion-resistance properties of the polyethylene when subjected to high pressures. Based on this research a number of high-density polyethylene knee prostheses have been radiation-crosslinked and the results in vitro appear to be very promising.