I. M. Pinder

Survivorship Analysis of the Uncemented Porous-Coated Anatomic Knee Replacement

Ninety-six patients who had a total of 108 replacements with an uncemented porous-coated anatomic knee prosthesis were followed for an average of sixty-four months (range, thirty-nine to ninety-three months). At the time of the most recent follow-up, twenty-one implants (19 per cent) had failed, all due to problems with the tibial component. A patellar component was not used, and no noteworthy patellar problems were encountered after the operation. There were no infections about the prostheses, and no femoral implant was revised. The most common cause of failure was collapse of the anteromedial part of the tibial plateau, which occurred in fourteen knees. The prosthesis loosened without collapse of bone in two knees, and five knees were revised because of gross wear of the polyethylene. When the time of failure was defined as the point at which revision of the prosthesis was recommended, the cumulative rate of survival was 84 per cent (95 per cent confidence interval, +/- 7 per cent) at five years and 77 +/- 10 per cent at six years. When the time of failure was defined as the point at which the knee replacement was actually done, the five-year rate of survival was the same. No significant differences were demonstrated between groups that were stratified by age, sex, weight, or primary diagnosis. We therefore do not recommend the use of an uncemented porous-coated anatomic knee replacement of the design that was evaluated in this study.

Results of uncemented porous-coated anatomic total hip replacement

We reviewed a consecutive series of 241 uncemented, porous-coated anatomic (PCA) hip replacements at an average follow-up of five years (2 to 9). Of these, 32 had failed (13%), 26 at the acetabular component (11%) and six at the femoral component (2%). Acetabular failure was associated with local osteolysis and excessive polyethylene wear in 20 cases: in these histological examination showed giant macrophages incorporating numerous particles of high-density polyethylene. The femoral failures were related to a poor intramedullary fit with subsequent subsidence. Using the recommendation for revision as the end point, the cumulative survival rate for prostheses was 91% at six years (95% CI +/- 6%), 73% (+/- 11%) at seven years, and 57% (+/- 20%) at eight years. The result of uncemented PCA hip replacement is satisfactory up to six years, but then increasing failure of the acetabular component appears to be due to polyethylene wear, leading to osteolysis, loosening and component migration. At first, failure is often asymptomatic; routine follow-up of uncemented hip replacement is essential, especially after five years.

Polyethylene wear in uncemented knee replacements

Isolated wear of the polyethylene tibial component led to failure in five of a series of 108 uncemented porous-coated knee replacements. The clinical features included pain, effusion and instability with progressive varus deformity. In all cases there was extensive wear on the medial side of the polyethylene surface of the prosthesis. The mechanism of such wear is complex, being due in part to the unconstrained nature of the joint and the incongruity of its surfaces. Other design characteristics may have contributed.

The incidence of fatal pulmonary embolism after knee replacement with no prophylactic anticoagulation

We made a prospective study of the incidence of fatal pulmonary embolism in patients after total knee replacement with no prophylactic anticoagulation. There were 499 consecutive patients having 527 knee replacements. They all wore anti-thromboembolic stockings and were mobilised 48 hours after surgery. No patient was lost to follow-up. One patient died of pulmonary embolism 22 days after operation. There were no other deaths within three months of operation. The incidence of fatal pulmonary embolism was 0.19% (95% confidence interval: 0 to 0.6%). Fatal pulmonary embolism is rare after total knee replacement without prophylactic anticoagulation and the routine anticoagulation of these patients is of doubtful value.

Health outcome after total knee replacement in the very elderly

Between 1992 and 1994 we performed a prospective study of the effect of total knee replacement (TKR) on the health status of 119 patients over the age of 80 years who had had a primary unilateral TKR. The Nottingham Health Profile was used to assess this before and at three and 12 months after operation. We found a significant improvement in the scores for pain, emotional reaction, sleep and physical mobility at three months. After 12 months, the scores for pain and sleep were well maintained. The other factors had deteriorated slightly but remained better than before operation. Our findings show that TKR leads to a significant improvement in the general health status of the very elderly.

Ankle arthrodesis in rheumatoid arthritis : 30 cases followed for 5 years

We have reviewed the results of 30 ankle arthrodeses performed on 26 patients with rheumatoid arthritis. This procedure was associated with a high morbidity, with wound breakdown and infection occurring in 12 cases. Eighteen ankles had fused, six had pain-free fibrous union, and six required further surgery for nonunion. Clinical evaluation, at an average follow-up of 5 years, was based on a modified ankle-grading system with good or excellent results in 14, fair results in nine, and poor in two. Only 4 patients had some residual pain in the ankle, and so, despite the high complication rate, arthrodesis is an effective method of treating the painful, rheumatoid ankle.

All-polyethylene compared with metal-backed tibial components in total knee arthroplasty at ten years. A prospective, randomized controlled trial.

BACKGROUND Several studies have described equivalent performance on radiostereometric analysis at two years for metal-backed compared with all-polyethylene stemmed tibial implants. The purpose of this study was to determine the ten-year survivorship results of these two designs from a large randomized controlled trial. METHODS Patients who were fifty years old or more, with no history of infection, and were undergoing primary total knee arthroplasty were randomized at the time of surgery to receive either an all-polyethylene or a metal-backed tibial component. Patients were assessed preoperatively and at one, three, five, eight, and ten years postoperatively. All assessments included a clinical history, a physical examination, and a radiographic evaluation. A total of 510 consecutive patients (566 knees) were recruited from August 1993 to January 1997. The mean age of the patients at the time of the index arthroplasty was 69.3 years, and 299 (59%) were women. The primary diagnosis was osteoarthritis for 458 knees (80.9%) and rheumatoid arthritis for 108 knees (19.1%). RESULTS Two hundred and ninety-three patients returned for the ten-year follow-up evaluation. A total of twenty-eight knees had been revised. Ten-year survivorship, with revision for any reason (or the time at which patients were documented as requiring revision but were unfit for surgery) as the end point, was 94.5% (95% confidence interval, 90.4% to 96.8%) for the all-polyethylene design and 96% (95% confidence interval, 92.6% to 97.8%) for the metal-backed design. Ten-year survivorship, with aseptic failure as the end point, was 97% (95% confidence interval, 93.3% to 98.7%) for the all-polyethylene design and 96.8% (95% confidence interval, 93.6% to 98.4%) for the metal-backed design. On the basis of the numbers available at ten years, there was no significant difference in survivorship between the two designs (p > 0.05). CONCLUSIONS The long-term results demonstrate excellent survivorship, with revision as the end point, for both the metal-backed and the all-polyethylene tibial component designs with no differences noted between the two.

The influence of femoral head surface roughness on the wear of ultrahigh molecular weight polyethylene sockets in cementless total hip replacement

A theoretical relationship was recently proposed relating the wear behavior of polymetric bearing materials articulating against hard counterfaces.(1) This model attempts to predict the influence of surface roughness on wear. Laboratory-based studies have been used to establish the validity of these relationships, but their application to the clinical situation has not been investigated fully. Forty-two retrieved PCA hip joints have been assessed. The total wear volume was calculated from the penetration measured using the shadowgraph method, and roughness of the articulating surfaces was recorded using noncontacting profilometry. The roughness of the explanted femoral heads was observed to increase (median S(a) - 10. 35 nm worn region, 3.05 nm peripheral region), while that of the acetabular liner fell dramatically (median S(a) - 41 nm worn region, 212 nm unworn region). No evidence of a relationship between the topography of the worn regions of the femoral head and that of the acetabular liner could be found. Similarly, the strength of the association between the surface roughness and the clinical wear factor was considerably poorer than that achieved in laboratory experiments. A number of reasons for this observation are proposed. Most deleterious was considered to be the inability of the roughness parameters to describe the damaging features of the surface adequately. Uncertainty as to when the surface of the component degrades during its life serves to introduce further doubt as to the application of the wear models in the clinical environment. In conclusion, this study fails to provide clinical evidence to substantiate the relationship between surface finish and wear rate. The adoption of standardized measurement parameters and techniques would facilitate the direct comparison of joint types and the selection of the most advantageous materials.

The role of the rotating hinge prosthesis in the salvage arthroplasty setting.

We have studied a consecutive series of 72 salvage knee procedures using a Kinematic rotating hinge prosthesis performed in a single arthroplasty unit between 1983 and 1997. Clinical and radiographic assessment of the survivorship of the Kinematic rotating hinge total knee arthroplasty (Howmedica, Rutherford, NJ) were analyzed. Survival analysis revealed a best-case 10-year implant survival of 90%. Concurrently, this group of patients exhibited a significant and sustained improvement in Knee Society Score and pain relief after implantation of a rotating hinge component. There were 10 deaths due to unrelated causes during the study period. This constrained hinged prosthesis remains a viable option in the face of gross deformity, bone loss, and failed multiple previous surgical procedures.

Quality of life after knee revision arthroplasty.

Background and purpose Radiographic and clinical survival analyses of revision total knee replacement (TKR) are considered acceptable outcome measures. However, the full influence of revision knee replacement on the overall health status of patients remains poorly defined. Methods We prospectively studied the health-related quality of life outcome in 94 patients who underwent revision knee replacement surgery over a 5-year period. Comparisons were drawn between the Nottingham health profile (NHP) scores and the Knee Society score pre-revision, and those obtained at 3 months, 1 year and 5 years after revision knee arthroplasty. Results We found a significant improvement in Knee Society score and NHP pain scores 3 and 12 months after revision TKR (p < 0.05). No other modalities of the NHP showed a significant change. 5 years after surgery, pain was less than before revision (p = 0.2), but energy level was considered worse (p = 0.07). Knee Society scores were found to be higher pre- and postoperatively for patients undergoing revision for reasons other than sepsis than for patients with sepsis. Patients requiring implantation of a hinged prosthesis also had lower Knee Society scores than those patients receiving a non-hinged implant. Repeated revision was associated with a downward trend in Knee Society score with each surgical intervention.