One hundred sixty-eight patients (168 knees) underwent CAS TKA by two surgeons at a single institution with 2 years follow-up. The final change in joint line was calculated from the verified tibial resection and distal femoral cuts. Group A patients had joint line changes of less than 4 mm and Group B patients had joint line changes of more than 4 mm. Post-operative Oxford scores, Knee scores, Function scores and SF-36 scores were obtained at 6 months and 2 years post TKA.
There was significant linear correlation between joint line changes and Oxford scores (P = 0.0001), Function scores (P = 0.0001) and Knee scores (P = 0.0001) at 6 months and Oxford scores (P = 0.0001) alone at 2 years with increasing joint line changes having poorer outcome scores. Group A compared to Group B patients demonstrated better Oxford scores (P = 0.0001), Function scores (P = 0.0001), Knee scores (P = 0.0001) and total SF-36 scores (P = 0.003) at 6 months as well as better Oxford scores (P = 0.0001) and Knee scores (P = 0.014) at 2 years.
CAS is a useful intra-operative tool for assessing the final joint line in TKA. Outliers in joint line changes of ¡Ý 4 mm are associated with poorer clinical outcome scores.
Level of evidence: Prognostic Study, Level II-1.