Abstract
The alignment rod is widely used as an index for intraoperative alignment but alignment
error is inevitable. The purpose of this study was to verify the accuracy of lower
limb alignment correction by measurement of mechanical medial proximal tibial angle
(MPTA) as an index in open-wedge high tibial osteotomy (OWHTO). This study was retrospective
case series. This study involved 152 patients undergoing OWHTO for primary medial
osteoarthritis. Alignment rod or MPTA measurement board was used as an index of optimal
correction in OWHTO. Alignment rod was used from October 2013 to May 2017, and MPTA
measurement board was used from June 2017 to April 2020. The correction using an alignment
rod was that the weight-bearing line ratio (WBLR) passed through 62.5% of the tibial
plateau which was defined as Fujisawa's point under intraoperative fluoroscopy (A
rod group). The correction using MPTA measurement board was aligning the intraoperative
MPTA to the preplanned angle (MPTA group). Preplanned optimal alignment was defined
as Fujisawa's point in all patients. Knee injury and osteoarthritis outcome measure
(KOOS), Knee Society scoring system objective knee score (KSS), 3-m timed up-and-go
test (TUG), single-limb standing test (SLS), and isometric muscle strength of quadriceps
and hamstrings were assessed as clinical results. WBLR, MPTA, joint-line convergence
angle (JLCA), and joint-line obliquity (JLO) were assessed as radiological results
preoperatively and at 1 year after surgery. The clinical and radiological results
after OWHTO were compared with both groups. Postoperative WBLR in A rod group was
closer to the target alignment (Fujisawa's point: 62.5) than in the MPTA group at
all stage (A rod group vs. MPTA group: 63.1 vs. 54.6 at 6 months; 62.0 vs. 53.4 at
1 year; p < 0.001). There were no significant differences in the clinical results between both
groups. The intraoperative measurement of medial proximal tibial angle has a risk
of undercorrection after OWHTO. His study is a retrospective case series and reflects
level of evidence IV.
Keywords alignment rod - open-wedge high tibial osteotomy - medial proximal tibial angle
