Extramedullary versus intramedullary femoral alignment technique in total knee arthroplasty: a meta-analysis of randomized controlled trials

Background: There is no consensus whether the use of the extramedullary femoral cutting guide takes advantage over the intramedullary one in total knee arthroplasty. The aim of this study was to compare the extramedullary femoral alignment guide system with the conventional intramedullary alignment guide system for lower limb alignment, blood loss, and operative time during total knee arthroplasty. Methods: The Medline, Embase, Cochrane Library, China National Knowledge Infrastructure (CNKI), Wan Fang Chinese Periodical, Google, and reference lists of all the included studies were searched for randomized controlled trials. The following parameters were compared between the extramedullary technique and the intramedullary technique: (1) lower limb coronal alignment, (2) coronal alignment of femoral component, (3) sagittal alignment of femoral component, (4) blood loss, (5) and operation time. Results: Four randomized controlled trials consisting of 358 knees were included in our study. There was no significant difference between the extramedullary and intramedullary groups for the lower limb coronal alignment (RR = 1.20, 95% CI 0.28 similar to 5.21, n. s.), coronal alignment of femoral component (RR = 0.65, 95% CI 0.19 similar to 2.22, n. s.), and sagittal alignment of femoral component (RR = 0.73, 95% CI 0.38 similar to 1.41, n. s.). A reduced blood loss was associated with the use of the extramedullary guide (MD = -120.34, 95% CI -210.08 similar to-30.59, P = 0.009). No significant difference in operation time was noted between the two groups (MD = 1.41, 95% CI -1.82 similar to 4.64, n. s.). Conclusions: Neither extramedullary nor intramedullary femoral alignment is more accurate than the other in facilitating the femoral cut in total knee arthroplasty. Use of the extramedullary guide results in less blood loss and exhibits a similar operation time as compared with the intramedullary guide.