The Ring total knee replacement--a comparison of survivorship.

Long term results of joint replacement are frequently expressed as survivorship; it therefore becomes increasingly important to have the ability to make valid comparisons between survivorship tables in order to determine accurately the statistical significance of published differences. We present a statistical method for direct comparison of survivorship tables. We have applied this technique to evaluate the survivorship of the unconstrained, uncemented Ring total knee replacement first implanted in 1975 and compare this to contemporaneous constrained prostheses. There is a significant improvement in survival, which suggests a beneficial long-term effect on the bone/implant interface of this changing design concept.

Venous thromboembolic disease in uncemented total hip replacement surgery--a one-year follow-up of 490 patients.

A retrospective study of the morbidity and mortality from deep vein thrombosis (DVT) and pulmonary embolus (PE) in 490 consecutive patients undergoing uncemented total hip replacement was carried out in a district general hospital. Special diagnostic tests for DVT and PE were not available. Patients were followed up for one year. There were three deaths in hospital and eight further deaths during the first year, all unrelated to DVT and PE. The clinical incidence of venous thromboembolism was 2.04%. While clinical diagnosis of venous thromboembolic disease probably underestimates its incidence, the figures for mortality are accurate. With every patient accounted for one year after operation, there were no deaths attributable to PE in this series.

Reduction in blood loss in total hip arthroplasty using topical Colgen.

Blood loss associated with uncemented total hip arthroplasty can be considerable, and any simple and safe means of reducing this loss and hence the volume of blood transfused during surgery would be valuable. The authors conducted a randomized trial using Colgen, a nondenatured collagen with hemostatic properties, in 76 patients undergoing uncemented total hip arthroplasty. Thirty-eight patients had Colgen sprinkled around the reduced hip joint after arthroplasty and 38 patients acted as controls. Analysis, using Student's t-test, showed no difference between the groups in measured blood loss at operation. However, after surgery in the Colgen group both visible measured blood loss (P less than .05) and total calculated blood loss (P less than .01) were significantly reduced. These results are particularly relevant today, when blood transfusion itself is a potential danger and should be kept to the necessary minimum.

The Ring total knee replacement.

A prospective study of the Ring Total Knee Replacement is presented. The senior author (P.A. Ring) designed this prosthesis and began to apply it clinically in 1974. The Ring prosthesis is a resurfacing, unconstrained type of knee prosthesis and is designed for use without cement. It comprises two components, femoral and tibial, both made of titanium. A polyethylene liner is attached to the tibial component. The method was used for treatment of osteoarthritis and rheumatoid arthritis of the knee on 149 patients (178 knees) in the period from 1974 to 1985. Seventeen patients were lost to follow-up, leaving 132 patients (161 knees) for review. During the last review, 75.2% of the knees were pain free and 72% had full correction of the deformity. The average follow-up period was 5.1 years and the survival rate of the prosthesis during the same period was 94.4%. To evaluate the method we used computer analysis of preoperative and postoperative assessment cards with 153 observations. The result was excellent in 92 (57.2%) knees, good in 38 (23.6%) knees, and poor in 31 (19.2%) knees. Loosening of the components occurred in 3.7% knees, and the total revision rate was 5%. One knee was arthrodesed.

Uncemented acetabular cups in dysplastic and protrusio acetabuli.

Total hip arthroplasties using the Ring uncemented polyethylene to metal system were carried out in 84 hips with either protrusio or dysplasia of the acetabulum. The results of the operation, the stability and function of the acetabular implant, and radiologic changes in the medial wall of the acetabulum in the protrusio hips were assessed over a two- to five-year follow-up period. Annual assessment over the follow-up period showed that an excellent functional result was achieved in all patients. Six of the eight hips with severe protrusio showed an increase in the thickness of the medial acetabular wall one year from the time of operation. Lack of bony cover over the lateral surface of the acetabular cup in the dysplastic hips did not have any adverse effect on the stability and function of these hips.

Anaesthesia for hip replacement in ankylosing spondylitis.

Thirteen total hip replacements in 8 patients with ankylosing spondylitis are reviewed. Complications of the disease which can lead to anaesthetic difficulties are discussed, and the importance of a preoperative visit and the value of indirect laryngoscopy emphasized. As intubation problems may occur, especially in undiagnosed cases, equipment for emergency intubation should always be readily available. The results fully justify the operation.

Osteolytic changes in the upper femoral shaft following porous-coated hip replacement.

Ten uncemented total hip replacements were performed in 1975 using an implant in which the cobalt-chrome femoral stem was coated to give a porous surface. In all but one case a high-density polyethylene head was used. The radiological changes in the upper femoral shafts were assessed between three and nine years later. Seven showed extensive stress-relieving changes, loss of calcar, stress fractures at the root of the lesser trochanter with subsequent detachment, and osteoporosis followed by avulsion of the greater trochanter. In these seven patients the lower part of the stem appeared to be soundly embedded, although in only one was there evidence of bony incorporation. It is suggested that if the fixation of a fully coated implant of this sort remains sound, gross atrophy of the upper femoral shaft develops after five years. This atrophy, associated with an implant which can be removed only at the expense of further bone destruction, presents substantial problems if revision is needed.

Cementless acetabular replacement using a pegged polyethylene prosthesis.

Acetabular replacement without cement using three types of pegged polyethylene prostheses was begun as a prospective trial by Morscher (August 1977). Ring (June 1979), and Freeman (January 1980); 1878 hips have been replaced using this technique and are reviewed. Follow-up averaged 2 years (range: 6 months-6 years). Successful pain relief and satisfactory walking ability were present in 97% and adequate flexion in 90%. Radiographic review showed the consistent development of a stable, uniform sclerotic line adjacent to the prosthesis. No component migration could be documented. Ten hips have been revised for obvious femoral loosening, and two acetabula showed slight motion during revision for femoral failure and were revised. Deep infection (0.37%) occurred only in patients not receiving perioperative antibiotics and not operated upon in unidirectional filtered air-flow enclosures. Postmortem histological evaluation of eight hips showed a thin fibrous membrane separating the prosthesis from viable bone. These results are preliminary, but nevertheless at least as good as those in any large series of cemented acetabula with the same follow-up. The advantages of this technique are its reproducible results, low complication rate, limited invasion of the skeleton, and easy revision should failure occur.

Osteosarcoma in association with total hip replacement.

The occurrence of an osteosarcoma at the site of a cobalt-chrome total hip replacement is described, and the possibility of the tumour arising as a result of the liberation of cobalt particles is discussed. The experimental and clinical evidence relating tumour formation to the presence of particulate metals, and to the presence of solid and particulate polyethylene, is presented. It is considered that the risk of tumour formation at the site of any total hip replacement is very small.

Blood loss associated with Ring uncemented total knee replacement: comparison between continuous and intermittent suction drainage.

In a retrospective comparison of blood loss following uncemented total knee replacement, in which either continuous or intermittent suction drainage was used, measured blood loss was significantly greater with continuous drainage. However, a method of calculating actual blood loss demonstrated no significant difference. With intermittent drainage, more blood remains undetected around the knee joint; this technique should therefore be abandoned in favour of continuous suction drainage.

Ring UPM total hip arthroplasty.

It is apparent that failure at the cement-bone interface is an increasing problem with total hip arthroplasty. This failure may be difficult or impossible to rectify. The risk of infection at the cement-bone interface and the difficulty of revisional surgery in the cemented articulation appear to justify fully an attempt to develop a reliable, uncemented total hip prosthesis. During the period from 1980 to 1982, 471 uncemented metal-on-plastic total hip arthroplasties have been performed. The results were compared with those for earlier metal-on-metal articulations and a comparable group of cemented metal-on-plastic joints. The short-term results for this procedure appear better than those obtained with the uncemented metal-on-metal articulation and comparable with those of the cemented joint, while retaining the relative freedom from complications of the uncemented articulation. The implant relies on the axial location of the pelvic component, and it is designed to be revised with ease, should revision prove necessary.

Uncemented acetabular replacement.

An uncemented Polyethylene acetabular component has been developed using a cup of conical outer configuration locked in position with the Freeman osseous peg. This cup is available in four sizes and is normally used with an uncemented femoral component. During the last 3 years 875 implants of this sort have been inserted and the results in these patients who are between 1 and 3 years post-operatively have been compared with the results in 236 replacements of a similar configuration but secured with bone cement in the usual way. The two groups have been demonstrated to be comparable in pre-operative diagnosis, age and sex. The results using the uncemented articulation are broadly the same as those using the cemented joint during the period of study but the acetabular component in 30% of the cemented joints showed a zone of demarcation between cement and bone whereas only one of the uncemented acetabular components showed similar radiological changes. The examination of the radiographs of the uncemented group suggests that the pelvic bone responds favourably to the stresses which are imposed upon it provided that the centre of the joint movement is relocated in the anatomical position, under these circumstances bone will usually build up to support the cup in a dysplastic acetabulum and in the floor of a central protrusion.

Uncemented total hip replacement.

During the last 20 years almost 3000 uncemented total hip replacements have been used in the treatment of osteoarthritis and rheumatoid arthritis. The development of an axially located prosthesis is outlined, and the causes of failure indicated. Uncemented prostheses have the advantage of a relatively low mortality and morbidity and the rate of infection in particular is low. Interface pain, with or without frank prosthetic loosening, is the commonest cause of failure, but revisional surgery is relatively easy, and usually successful. Loss of function without significant pain may occur after many years from distal migration of the femoral component. The development of an uncemented metal-on-plastic joint has produced better short-term results than the metal-on-metal articulation, probably because of its lower frictional coefficient and the use of a wider range of pelvic and femoral components.

Uncemented surface replacement of the knee joint.

A method of surface replacement of the knee joint using an uncemented titanium-on-high-density-polyethylene prosthesis has been investigated in 61 patients. The results show that pain is relieved in the vast majority of cases. Overall, the joint range is marginally improved. Preoperative deformities can be considerably correced. The procedure appears to give a functional result that is comparable with other types of replacement arthroplasty and leaves complete freedom for revisional surgery at a later date should it become necessary.

Five to fourteen year interim results of uncemented total hip arthroplasty.

One thousand eight hundred eight uncemented total hip replacements have been performed during the last 14 years. The prototype and early models, 11-14 years later have retained a satisfactory result in 56% of cases, and the valgus prostheses, 6-11 years after implantation retain a satisfactory result in 85% of cases. The models in current use, with a standard neck shaft angle, and a range of implants to fit the medullary canal securely, have given a satisfactory result in 94% of patients in a one to 6 year survey. Of the whole series 101 hips (5.5%) have required further surgical treatment, mainly for interface pain but only 9 patients (0.5%) have finally ended with a resection-pseudarthrosis, all for infection. The overall results of the operation appear comparable with those of cemented metal on metal implants, but the frequency of minor discomfort on weightbearing is probably greater than that which follows a cemented on plastic articulation. Against this must be balanced the low risk of infection, and the ease with which revisional surgery can be performed.