Computer-assisted total knee replacement after medial opening wedge high tibial osteotomy: medium-term results in a series of ninety cases

Purpose The aim of this study was to evaluate the medium-term results of total knee replacements (TKRs) after medial opening wedge valgising tibial osteotomy to those of primary TKR (TKR1). The hypothesis being that there would be no difference in results between these groups. Methods Series 1 was made up of 45 TKRs after medial opening wedge high tibial osteotomy (MHTO)-30 men and ten women at an average age of 69 +/- seven years (54-82). This was compared to a second series of TKR1s-30 men and ten women at an average age of 69 +/- seven years (55-78). The average IKS scores were 91 +/- 22.5 points (42-129) and 86 +/- 18 points (38-116) in the two groups respectively. The average pre-operative HKA angle was 179 +/- 5 degrees (169-193 degrees) in group 1, and 173 +/- 7.5 degrees (161-193 degrees) in group 2. Tibial mechanical axes were 90.5 +/- 4 degrees (of which 24 knees had a valgus angle) and 85.05 +/- 3.5 degrees (79-93 degrees) in the two groups respectively. Results All patients were reviewed at an average follow-up of 47 +/- 24.5 months for series 1 and 185 +/- 8.5 months for series 2. The average IKS score was 184 +/- 6 for series 1 (172-200) and 185 +/- 8.5 (163-200) for series 2 (p-0.872). Thirty-seven patients in series 1 and 38 patients in series 2 were either extremely satisfied or satisfied with the intervention. The average post-operative HKA angle was 180.5 +/- 2.5 degrees and 181 +/- 2 degrees (p-0.122) and the average tibial mechanical axis was 89 +/- 1.5 degrees against 90 +/- 1 degrees (p-0.001). The results of the 24 knees with a valgus tibial mechanical axis were statistically no different. Conclusions TKRs post medial opening wedge high tibial osteotomy have identical results to primary TKRs even in knees with a valgus tibial mechanical axis.