The Depuy Sigma Total Knee Arthroplasty (TKA) was introduced in 1997 as a modification of the Pressed Fit Condylar (PFC) TKA. It is the most commonly used TKA in England and Wales, accounting for 34.9% of all primary TKAs performed in 2006. The PFC has reported 10-year survival rates of 90–95%. This study reports the first clinical and radiological outcomes at 7–9 years following TKA using the PFC Sigma prosthesis.

Three hundred and eighteen consecutive Sigma TKAs were performed in 275 patients between October 1998 and March 2000. Patients were prospectively followed up in a specialist nurse-led clinic. Final review was performed in December 2007 or January 2008, i.e. 7–9 years post surgery. Outcome measures included American Knee Society Scores, Radiographic Scores and Oxford Knee Scores. Survival analysis was performed using the life table method.

Of 318 Sigma knees, 225 (193 patients) were alive at 7–9 years. 6 knees in 5 patients were lost to follow up. 7 knees (2.2%) were revised: 6 for infection within the first two years and 1 at 59 months who underwent isolated change of polyethylene insert. The 9-year survival was 97.7% with revision for any reason as endpoint and 99.6% with revision for aseptic failure as endpoint. The mean American Knee Society Knee score was 84/100 at 7–9 years compared with 33/100 pre-operatively. 0f 140 radiographs, 48 knees had radiolucent lines but no knee showed radiological evidence of loosening.

These results suggest that the Sigma TKA gives excellent clinical results up to 9-years.