BACKGROUNDAccuracy of implant placement in total knee arthroplasty (TKA) is crucial. Traditional extramedullary alignment instruments are fairly effective for achieving the desired mean tibial component coronal alignment. We modified the traditional tibial plateau resection technique and evaluated its effect on alignment restoration.

METHODSTwo hundred and eighty-two primary TKAs in our hospital between January 2013 and December 2014 were enrolled in this retrospective study. Group A consisted of 128 primary TKAs performed by one senior surgeon. Preoperative measurement of the tibial resection was conducted on radiographs, and the measured thicknesses of the lateral and medial plateau resection were used to place the tibial alignment guide. Group B consisted of 154 primary TKAs performed by the other senior surgeon, using a traditional tibial plateau resection technique. In all patients, an extramedullary guide was used for tibial resection, and preoperative and postoperative full-leg standing radiographs were used to assess the hip-knee-ankle angle (HKA), femoral component alignment angle (FA), and tibial component alignment angle (TA). A deviation ≥3° was considered unsatisfactory. Data were analyzed by unpaired Student's t-test.

RESULTSThe mean postoperative HKA and TA angles were significantly different between Groups A and B (178.2 ± 3.2° vs. 177.0 ± 3.0°, t = 2.54, P = 0.01; 89.3 ± 1.8° vs. 88.3 ± 2.0°, t = 3.75, P = 0.00, respectively). The mean postoperative FA was 88.9 ± 2.5° in Group A and 88.9 ± 2.6° in Group B, and no significant difference was detected (t = 0.10, P = 0.92). There were 90 (70.3%) limbs with restoration of the mechanical axis to within 3° of neutral alignment and 38 (29.7%) outliers (>3° deviation) in Group A, whereas there were 89 (57.8%) limbs with restoration of the mechanical axis to within 3° of neutral alignment and 65 (42.2%) outliers (>3° deviation) in Group B. The severity of the preoperative alignment deformity was a strong predictor for postoperative alignment.

CONCLUSIONSUsing conventional surgical instruments, preoperative measurement of resection thickness of the tibial plateau on radiographs could improve the accuracy of conventional surgical techniques.