Optimising femoral component rotation using Equiflex instrumentation: a clinical review.

Although there is agreement that flexion and extension spaces should be symmetrical and that rotation of the femoral component impacts outcome in a knee replacement, there is dispute over what is the 'correct' rotation and how best to achieve it (Akagi et al., Clin Orthop Relat Res 366:155-163, 1999; Anouchi et al., Clin Orthop Relat Res 287:170-177, 1993; Barrack et al., Clin Orthop Relat Res 392:46-55, 2001; Berger et al., Clin Orthop Relat Res 356:144-153, 1998; Jenny and Boeri, Acta Orthop Scand 75(1):74-77, 2004; Poilvache et al., Clin Orthop Relat Res 331:35-46, 1996; Siston et al., J Bone Joint Surg Am 87(10):2276-2280, 2005). Insall and Scuderi recommended placing a tensor in flexion and rotating the femoral cutting block so that its posterior edge is parallel to the cut tibia (Insall, Surgery of the knee, vol 2, 2nd edn., Churchill Livingstone, New York, 1993; Scuderi and Insall, Orthop Clin N Am 20:71-78, 1989). We feel Equiflex instrumentation will reliably achieve Insall and Scuderi's recommendation. To evaluate early results and lateral retinacular release rates using Equiflex instrumentation for TKR, we evaluated 209 consecutive knees (31 valgus, 178 varus) using this technique from 4 April 2005 until 19 September 2006. Pre and postop American Knee Society and Oxford scores, deformity, ROM, lateral retinacular release rates and complications were recorded. We could correct alignment and achieve our technical goals in 99% of cases. A lateral retinacular release was required in only five knees (2.4%). The complications are comparable to published data. The Equiflex instrumentation does help in equalising flexion-extension gaps, improves patellar tracking and reduces the incidence of lateral retinacular release.