A newly developed patient-specific instrumentation system achieves consistent alignment accuracy in varising knee osteotomy

Abstract

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.

Conclusion:

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.

What are the new findings?

• A PSI workflow was applied across femoral and tibial osteotomies, demonstrating versatility in varus correction.

• Alignment outcomes showed minimal deviation between planned and achieved correction, indicating high precision.

• Accuracy was consistent across different osteotomy techniques, supporting a standardised approach to planning and execution.

• Reliable results were achieved across multiple surgeons, suggesting reduced dependence on individual surgical technique.

• The workflow enabled predictable correction with a low complication profile, supporting its clinical reliability.

• The workflow integrates 3D planning with guide-based execution, enabling controlled and reproducible translation from plan to surgery.

*Corresponding author at:

Sydney Orthopaedic Research Institute
Level 2, 500 Pacific Highway
St Leonards, Sydney, 2065
Australia

Tel: +61 2 9904 7182
E-mail address: koumei.01.13@gmail.com (T. Hiranaka).

https://doi.org/10.1016/j.knee.2026.104414

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