[A prospective randomized controlled study of total knee arthroplasty via mini-subvastus and conventional approach]

To compare the clinical and radiographic results between primary total knee arthroplasty (TKA) via mini-subvastus or conventional approach through a prospective randomized controlled study.

Ninety-four patients (104 knees) undergoing primary TKA between January 2011 and April 2012 were evaluated and randomly divided into 2 groups. Forty-six patients (52 knees) underwent TKA via conventional approach (conventional approach group), and 48 patients (52 knees) underwent TKA via mini-subvastus approach (mini-subvastus approach group). In these patients, 45 cases (51 knees) in conventional approach group and 45 cases (49 knees) in mini-subvastus approach group were followed up and recruited in the final analysis. There was no significant difference in age, gender, body mass index, sides, osteoarthritis grading, American Knee Society Score (KSS), Hospital for Special Surgery (HSS) score, visual analogue scale (VAS), range of motion (ROM) of knee between 2 groups ( P>0.05). The clinical indexes were recorded and analyzed, including the operation time, length of incision, total blood loss, blood transfusion after operation, hospital stay time, the time of performing straight leg raise, incision condition, VAS score, ROM of knee, HSS score, and KSS score, hip-knee-ankle angle (HKA), femoral anatomic axis and the femoral prosthesis joint angle (femoral angle), tibia anatomic axis and tibial prosthesis joint angle (tibial angle), femoral prosthesis flexion angle (FPFA), and posterior slope angle (PSA) of the tibial plateau.

All patients were followed up. The average follow-up time was 66.4 months (range, 60.0-72.5 months) in conventional approach group and 65.6 months (range, 60.0-71.2 months) in mini-subvastus approach group. Compared with the conventional approach group, the incision of mini-subvastus approach group shortened, the operation time prolonged, and the time when patients started straight leg raise exercises was earlier; showing significant differences between 2 groups ( P<0.05). There was no significant difference in hospital stay time, total blood loss, and numbers of blood transfusion between 2 groups ( P>0.05). The complication rate was 8.2% (4/49) in mini-subvastus approach group and 0 in conventional approach group, showing no significant difference between 2 groups ( P=0.054). At 1 and 3 days, the VAS and the ROM of knee in mini-subvastus approach group were significantly better than those in conventional approach group ( P<0.05); but there was no significant difference in above indexes between 2 groups at 14 day ( P>0.05). There was no significant difference in HSS and KSS scores between 2 groups at the 1, 3, 6, 12 months and 3, 5 years ( P>0.05). X-ray film showed no aseptic loosening in all cases. There was no significant difference in the measured values and incidence of abnormal patient of HKA, femoral angle, tibial angle, FPFA, and PSA at last follow-up between 2 groups ( P>0.05).

TKA via mini-subvastus approach is helpful to the early function recovery of knee, but the long-term effectiveness is consistent with TKA via conventional approach. As the limited exposure, TKA via mini-subvastus spproach may has high risk of operative complications.