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Updated: Mar 7, 2026
In Vitro Application of a Wireless Sensor in Flexion-Extension Gap Balance of Unicompartmental Knee Arthroplasty
Published on: May 5, 2023
A newly developed patient-specific instrumentation system achieves consistent alignment accuracy in varising knee
Takaaki Hiranaka1, Peter D'Alessandro2, Peter McEwen3
1Sydney Orthopaedic Research Institute, Landmark Orthopaedics, St. Leonards, Sydney, Australia; Department of Orthopaedic Surgery, Section of Medicine, Division of Medicine, Dentistry and Pharmaceutical Sciences, Graduate School of Medicine, Okayama University, Okayama, Japan.
Background:
Patient-specific instrumentation (PSI) has been introduced to improve the accuracy of varising knee osteotomy. This study aimed to evaluate the correction accuracy of a newly developed PSI system for varising knee osteotomy, including medial closing-wedge distal femoral osteotomy (MCWDFO), lateral opening-wedge distal femoral osteotomy (LOWDFO), and medial closing-wedge high tibial osteotomy (MCWHTO).
Methods:
Twenty-three patients with valgus knee alignment who underwent varus osteotomy using the new PSI system were retrospectively analysed (MCWDFO, n = 10; LOWDFO, n = 7; MCWHTO, n = 6). The overall error was defined as the difference between the planned and achieved hip-knee-ankle angles (HKAs) at 6 months postoperatively (ΔHKA), reflecting the accuracy of overall lower limb alignment correction. Positive values indicated overcorrection, and negative values indicated undercorrection.
Results:
Across all procedures, the mean planned and achieved HKA were 178.9° ± 0.7° and 179.3° ± 0.7°, respectively, resulting in a mean overall error of -0.4° ± 1.7° (range, -4.5° to 2.5°). The mean overall error was -1.0° ± 1.7° for MCWDFO, -0.5° ± 1.6° for LOWDFO, and 0.6° ± 1.1° for MCWHTO, with no significant difference among techniques (P > 0.05). No major complications, including hinge fracture or delayed union, were observed.
Conclusions:
The newly developed PSI workflow achieved high correction accuracy and demonstrated consistent performance across various femoral and tibial osteotomy techniques for valgus correction. These findings indicate that the system provides a reliable and safe approach for achieving precise alignment correction in varus knee surgery.
