Aims: To study functional outcome and survivorship of custom designed knee implants for primary and revision TKR where off-the-shelf prostheses were unsuitable. Methods: Clinical and radiological results of twenty-three custom-designed total knee prosthesis in twenty patients were prospectively reviewed. The indications were bone loss following multiple revisions of total knee prosthesis and debridement for infection, periprosthetic fractures, bone deformity with rickets and small bones with juvenile chronic arthritis. All implants designed and manufactured at Centre for Biomedical Engineering, Stanmore, U.K. Four different designs of knee prosthesis used: Condylar knee of miniature size, CAD-CAM knee, Superstabiliser and Rotating Hinges. Hospital for Special Surgery (HSS) score taken preoperatively, at 3 months, and yearly by an independent research physiotherapist. Duration of follow up: 62.5 months (28–126 months) Results: Average HSS score improved from 13.5 points (range 0–48) pre-operatively to 86.5 points postoperatively (range 62–96) (p=0.025). Average maximum flexion post operatively: 86.4° (range 60°–122°). Sixteen knees had excellent, five good and two poor results. Extension lag of 15°–25° in three patients. One patient with juvenile chronic arthritis needed revision at five years after index arthroplasty. Conclusions: Clinical and radiological results for custom designed prostheses compare favourably with standard knee prosthesis for similar indications. Our results support the use of a custom designed knee implant as salvage prosthesis and also as an alternative to arthrodesis or amputation.

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.

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.

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.