2015 ISAKOS Biennial Congress ePoster #1703

Factors Associated With the Discrepancy Between Preoperative Plan and Postoperative Alignment in Closed Wedge High Tibial Osteotomy

Hyuk-Soo Han, MD, PhD, Seoul KOREA, REPUBLIC OF
Seong-Hwan Kim, MD, Seoul KOREA, REPUBLIC OF
In-Woong Park
Kee Yun Chung, Seoul KOREA, REPUBLIC OF
Ki Bum Kim
Sahnghoon Lee, MD, PhD, Seoul KOREA, REPUBLIC OF
Sang Cheol Seong, MD, PhD, mapo-gu, Seoul city KOREA, REPUBLIC OF
Myung Chul Lee, MD, PhD, Prof., Seoul KOREA, REPUBLIC OF

Department of Orthopedic Surgery, Seoul National University College of Medicine, Seoul, KOREA

FDA Status Cleared

Summary: The 1.5° valgus overcorrection of postoperative mechanical HKA axis angle was found compared with planned correction angle in tibia. The preoperative measurements could predict the overcorrection of mechanical HKA axis compared with real correction angle in tibia. By the equation, every 2.5° of joint convergence angle, every 2.4mm of medio-lateral joint width discrepancy and one grade of K-L gradi

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Abstract:

The alignment after HTO is affected not only by the bony correction but also by soft tissues around the knee. For successful HTO, accurate analysis of the deformity with the hip–knee–ankle (HKA) axis using a whole-leg radiograph is important. Adequate planning, including height of wedge base and correction angle of osteotomy, is also a mandatory factor for successful HTO. The purpose of the study was to evaluate the difference between preoperative plan and postoperative alignment after closed wedge HTO and determine the factors associated with the difference. This is a retrospective cohort study included 118 cases with a mean age of 50.1 years who have undergone closed wedge HTO. The following radiographic parameters were measured preoperatively and postoperatively: mechanical HKA axis angle, anatomical HKA axis angle, mechanical medial proximal tibia angle (mPTA), bowing angle of femur, mechanical lateral distal femoral angle (LDFA), joint line convergence angle, medio-lateral joint width discrepancy, Kellgren-Lawrens (K-L) grade, and discrepancy between the correction angle in tibia and correction angle in mechanical HKA axis. Paired t-test and independent t-test were used for comparison of mean values. Simple and multiple linear regression analysis using stepwise technique were used for the preoperative and demographic factors that affect the discrepancy in correction angle in tibia and mechanical HKA axis angle between preoperative plan and postoperative alignment. Preoperative mechanical and anatomical HKA axis angle was varus 8.3° (SD 3.7) and varus 1.9° (SD 3.8). Postoperative mechanical and anatomical HKA axis angle was valgus 3.1° (SD 2.6) and valgus 9.1° (SD 2.9). The mPTA angle was varus 6.2° (SD 3.1) preoperatively, valgus 3.7° (SD: 3.0) postoperatively. The medio-lateral joint width discrepancy was 3.1 mm (SD 1.8) preoperatively and 1.8 mm (SD 1.4) postoperatively. The K-L grade was 1.52 (SD 0.7) preoperatively. The discrepancy between correction angle in tibia and correction angle in mechanical HKA axis was 1.5° (valgus in mechanical HKA, SD 2.3). By multiple regression analysis, the equation was -0.922-0.169*preK-L+0.770*joint convergence angle+0.077* medio-lateral joint width discrepancy. By the simple regression analysis, 1° of valgus overcorrection was found to be related with every 2.5° of joint convergence angle(r2=0.396), 2.4mm of medio-lateral joint width discrepancy(r2=0.310) and one grade of K-L grading(r2=0.107) as preoperative measurement. The 1.5° valgus overcorrection of postoperative mechanical HKA axis angle was found compared with planned correction angle in tibia. The preoperative measurements could predict the overcorrection of mechanical HKA axis compared with real correction angle in tibia. By the equation, every 2.5° of joint convergence angle, every 2.4mm of medio-lateral joint width discrepancy and one grade of K-L grading preoperatively could predict 1° of valgus overcorrection compared with preoperative planning.