Intra-operative deviation in limb alignment occurring at implantation in total knee arthroplasty

BackgroundLong-term survival of knee replacement depends on accurate alignment. Despite improvements in cut accuracy mal-alignment of 3° or more is still seen. All methods share common implantation techniques. This study examines the effect of implantation on overall limb alignment relating it to cut alignment and trial alignment.MethodsA retrospective review of navigated primary knee replacements was undertaken (n = 113). Overall coronal limb alignments for the aggregated cuts, trial and final implanted components were examined.ResultsAll 113 knees had coronal aggregated cut alignment within 2° of neutral (range: 2° varus to 2° valgus). With trial components 99 knees (88%) had an overall coronal limb alignment within 2° of neutral (range: 3° varus to 4° valgus). After final implantation 106 knees (94%) were within 2° of neutral (range: 4° varus to 4° valgus). Forty eight knees (42%) showed no alignment deviation occurring between trial and the final implanted prostheses and 16 knees (14%) shoed a deviation of 2° or more. There was a correlation of both aggregated cut (r = 0.284, p = 0.002) and trial (r = 0.794, p < 0.001) with final alignment. There was no significant difference between the final alignment and the aggregated cut alignment(mean difference = − 0.15°, p = 0.254) or trial alignment (mean difference − 0.13°, p = 0.155).ConclusionsEven when the aggregated alignment produced by the bone cuts is accurate, inaccuracy in final alignment can result from the implantation process. It may be productive for surgeons to concentrate on the implantation process to improve alignment and reduce outliers.