The long-term results of Stanmore total knee replacements

Abstract

One hundred and three sequential Stanmore knee replacements were reviewed retrospectively on two occasions with a maximal follow-up period of nine years three months. This knee prosthesis, which is hinged, was successful In alleviating pain, stabilisIng an unstable knee and modestly IncreasIng the arc of flexion. Walking capacity was increased and flexion contractures were reduced. There were seven cases of Infection and four of fracture around the prosthesis. All these proved difficult to freat and two knees with both fracture and infection needed amputation. Eight knees were revised for aseptic loosening and a further 14 were found to have radiological signs ofloosening. The results have been analysed by the methods advocated by Tew and Waugh and give a cumulative success rate of 80 per cent at seven years, provided success is judged solely by whether the prosthesis is still in situ. The role of the Stanmore knee as a primary arthroplasty is discussed. The first metal Stanmore total knee replacement was performed in 1954 to replace the lower end of a femur in a young woman aged 20 suffering from recurrence of a giant-cell tumour. The prosthesis was bolted to the femur and the tibia and functioned successfully for 21 years (Burrows, Wilson and Scales 1975). Its commercial introduction for use outside the Institute of Orthopaedics at Stanmore was in 1971.

Is there a future for hinged prostheses in primary total knee arthroplasty?

“…24 The technique of survivorship analysis was applied only in the 1980s and there are few such analyses involving hinged prostheses. Most of the older designs of hinged prostheses yielded unacceptably poor results, 25,26 but those of the second-generation St Georg and the Blauth prosthesis are equal to, or better than, the best outcomes of resurfacing prostheses. We were able to examine the condylar surface, the polyethylene menisci and the polyethylene bush of a Blauth prosthesis which had been revised 150 months after insertion because of aseptic loosening.…”

Endoprosthetic replacement of the proximal tibia

“…26 The endoprostheses which we have used were initially based on the Stanmore hinged knee, the long-term results of which were not encouraging, with failure rates between 20% and 30% at eight years. 27,28 After resection of a tumour around the knee, all knee ligaments are removed and there may well be considerable muscle loss. Any endoprosthesis must replace the length of bone missing, provide a stable knee and allow sufficient hyperextension for the knee to 'lock'.…”

The Cost-Effectiveness of Limb Salvage for Bone Tumours

“…In conventional knee replacements for osteoarthritis these implants have been shown to have a very high failure rate and are not recommended for routine use. 20 Unwin et al 16 found that the failure rate for aseptic loosening alone in their large series of endoprostheses around the knee was 50% at 20 years which is a failure rate of 2.5% per year. This does not include other causes such as infection and implant failure which are responsible for an extra failure rate of 1.5% per annum.…”