Related Experiment Video
Updated: May 10, 2025
In Vivo Quantification of Hip Arthrokinematics during Dynamic Weight-bearing Activities using Dual Fluoroscopy
Published on: July 2, 2021
Amount of mechanical hip-knee-ankle (mHKA) angle correction by fixed-bearing medial UKA can be predicted using a new
Naoki Nakano1, Masanori Tsubosaka2, Tomoyuki Kamenaga2
1Kobe University, Kobe, Japan. gnaokix1981@gmail.com.
Introduction:
The amount of change in coronal alignment by unicompartmental knee arthroplasty (UKA) is important when considering its long-term results. This study investigated whether the amount of change in mechanical hip-knee-ankle (mHKA) angle by medial fixed-bearing UKA can be predicted based on the arithmetic hip-knee-ankle (aHKA) angle, an indicator of bony nature that is independent of soft tissue balance.
Materials And Methods:
The research involved 101 patients (125 knees) who underwent medial fixed-bearing UKA with the spacer-block technique. Pre- and postoperative mHKA angles, aHKA angle (180°- lateral distal femoral angle + medial proximal tibial angle), insert thickness, and the amount of bone cuts were measured. The component gap in extension was measured using a UKA tensor, and the pre-osteotomy gap was calculated. The correlation between aHKA angle minus preoperative mHKA angle and changes in mHKA angle, as well as the pre-osteotomy gap, were analysed. Additionally, changes in mHKA angle and total osteotomy volume were compared based on insert thickness.
Results:
A positive correlation was found between aHKA angle minus preoperative mHKA angle and the change in mHKA angle. The pre-osteotomy gap was also positively correlated with aHKA angle minus preoperative HKA angle. Greater changes in mHKA angle occurred in cases with inserts ≥ 9 mm compared to 8 mm inserts, though osteotomy volume did not significantly differ between the groups.
Conclusions:
In fixed-bearing UKA, postoperative changes in mHKA angle are likely to be more pronounced when there is a significant difference between aHKA angle and preoperative mHKA angle. Surgical planning should account for this factor to optimise outcomes.
