To investigate the effect of preoperative valgus or varus deformity on the prosthesis installation and alignment restoration in total knee arthroplasty (TKA).
Between January 2012 and December 2013, 198 patients (245 knees) with osteoarthritis underwent primary TKA, and the clinical data were retrospectively analyzed. There were 23 males and 175 females, with the average age of 67 years (range, 43-90 years). Single knee and double knees were involved in 151 and 47 cases respectively. The disease duration was from 1 month to 30 years (mean, 8.99 years). The anteroposterior X-ray films of whole lower limbs were taken, and the femorotibial angle (FT) was measured before operation and at 1 week after operation; the mechanical femoral angle (MF) and the anatomical tibial angle (AT) at 1 week after operation were measured. The correlation analysis was made for pre- and post-operative FT, MF, and AT. According to the valgus or varus deformity before operation, all patients were divided into 5 groups: ≥ 20 degrees varus (group A), 10-20 degrees varus (group B), ≤ 10 degrees varus (group C), < 10 degrees valgus (group D), and ≥ 10 degrees valgus (group E), and the above indicators were compared between groups. And the rate of the good limb alignment was recorded after operation.
The pre- and post-operative FT were (171.53 ± 9.12) and (177.38 ± 3.57)degrees respectively, and postoperative MF and AT were (89.00 ± 2.68) and (88.62 ± 2.16) respectively. Preoperative FT was associated with postoperative FT and MF (r = 0.375, P = 0.000; r = 0.386, P = 0.000), but it was not correlated with AT (r = 0.024, P = 0.710). Postoperative FT was associated with MF and AT (r = 0.707, P = 0.000; r = 0.582, P = 0.000). Postoperative FT was significantly increased when compared with preoperative FT in each group (P < 0.05). There were significant differences in preoperative FT between groups (P < 0.05). There were significant differences in postoperative FT when compared group A with groups B, C, D, and E (P < 0.05), and when compared groups B and C with groups D and E (P<0.05), but there was no significant difference between groups B and C, and between groups D and E (P > 0.05). The rate of good alignment was 70.2% (172/245); it was 27.8% (5/18), 66.0% (62/94), 74.4% (67/90), 88.9% (32/36), and 85.7% (6/7) in groups A, B, C, D, and E respectively, showing significant differences between groups (P < 0.05). There was no significant difference in postoperative AT between groups (P > 0.05). Except for between group D and group E (P > 0.05), significant difference in MF was shown between the other groups (P < 0.05).
The more severe deformity of lower limb before TKA, the higher risk of deviation for prosthesis installation and poor alignment in TKA.