Abstract
Introduction: The Sheehan total knee endoprosthesis has been widely used since 1971. It incorporates a semi-constrained hinge with intramedullary stems cemented into the femur and tibia for fixation. This gives a stable polycentric knee mechanism that allows axial rotation as well as stimulating other knee movements. This design has certain disadvantages including the large amount of bone resected for implantation and its constrained nature, which predisposes to loosening. While clinically excellent results have been reported in 95% of patient by some authors, other papers have reported much lower rates of successful outcome and revision rates of up to 30%. Few papers however report the difficulties encountered during revision or the techniques that need to be used to overcome these.
Patients and Methods: We reviewed the records of 21 patients who required revision of Sheehan TKR’s between 1987 and 2001. Reason for revision was recorded and all patients were scored using the Knee Society Index and Severity Instrument (Saleh et al CORR 2001). The operative details were examined and technical difficulties at the time of surgery recorded. Per-operative and early post-operative complications related to the revision procedure were also noted.
Results: The average age of patients requiring revision was 65 years old (range 39–79). The average time from primary surgery to revision was 16.2 years (range 8–20 years). The reasons for primary surgery were rheumatoid arthritis in 9 and osteoarthritis in 12. Revision surgery was required for pain associated with tibial subsidence and painful bone contact in 14. Five of these also had varus/valgus instability in excess on 30°. Two patients had dislocation of their tibial on femoral component. One patient had a one-stage revision for infection and one had revision for a fractures tibial intramedullary stem. Three patients had revision to anterior flanged femoral components to facilitate patellar resurfacing for patello-femoral pain. In 14 patients the knee was revised to a second Sheehan prosthesis as the degree of bone loss was insufficient to allow cement removal and bone stock reconstruction. Three patients were revised to stemmed Co-ordinate (DepuyTM) revision prostheses, one to a standard AMK surface replacing prosthesis and one to a hinged Finn prosthesis due to global instability. Seven patients required impaction bone grafting and required structural grafting for severe bone loss. The overall complication rate approached 80%! Two patients had wound breakdown, one required grafting. Five patients had persistent wound ooze successfully treated with antibiotics alone. To patients had cortical perforation, which was bypassed by the prosthetic stem, two suffered post-operative fractures, one requiring ORIF, one bracing. Four patient required re-revision, two to kinemax prostheses and two to further Sheehan prostheses.
Discussion: While the Sheehan TKR was of great benefit to a large number of patients it is not without its problems. These results show that prostheses coming to revision did not necessarily fail early and so with time we can expect more to present for revision. The high complication rate and the need for complex reconstructive techniques attest to the difficulty of revising these prostheses. Some of these problems are the legacy of the prosthetic design and should be borne in mind when taking on these cases.
The abstracts were prepared by Raymond Moran. Correspondence should be addressed to him at the Irish Orthopaedic Assocation, c/o Cappagh National Orthopaedic Hospital, Finglas, Dublin 11, Ireland.
