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Robot-Assisted TKA for Varus Knees: Post Hoc Exploratory Analysis of Alignment Strategy and Deformity Severity
Alexey Vladimirovich Lychagin1, Andrey Anatolyevich Gritsyuk1, Mikhail Pavlovich Elizarov1
1Department of Traumatology, Orthopedics, and Disaster Surgery, I.M. Sechenov First Moscow State Medical University (Sechenov University), Trubetskaya Str., 8-2, 119991 Moscow, Russia.
Robot-assisted total knee arthroplasty (raTKA) with limited/restricted kinematic alignment (lim.-KA) showed potential benefits in moderate varus knee osteoarthritis, but range of motion favored mechanical alignment (MA). Further research is needed to confirm these findings.
Area of Science:
- Orthopedic Surgery
- Robotics in Medicine
- Biomechanical Engineering
Background:
- Robot-assisted total knee arthroplasty (raTKA) enhances precision in component positioning and coronal alignment.
- The clinical impact of alignment strategies in varying varus knee phenotypes remains unclear.
- This study explores alignment strategy effects within specific varus deformity subgroups in raTKA.
Purpose of the Study:
- To evaluate the clinical outcomes of mechanical alignment (MA) versus limited/restricted kinematic alignment (lim.-KA) in robot-assisted total knee arthroplasty (raTKA).
- To conduct a post hoc exploratory analysis comparing alignment strategies across mild and moderate varus deformity subgroups.
- To assess the influence of deformity severity on the effectiveness of different alignment strategies in raTKA.
Main Methods:
- A single-center, open-label, randomized study of 296 patients undergoing raTKA for varus knee osteoarthritis.
- Patients were randomized to MA (n=149) or lim.-KA (n=147) alignment.
- Subgroup analysis stratified patients into mild (≤10° varus) and moderate (11-20° varus) deformity groups for post hoc comparison of outcomes including ROM, VAS, KSS, OKS, and FJS-12 at 12 months.
Main Results:
- The primary whole-cohort analysis showed no significant advantage for either alignment strategy.
- In the moderate-varus subgroup, lim.-KA demonstrated superior 12-month outcomes for KSS-knee, KSS-function, OKS, and FJS-12 compared to MA.
- Conversely, range of motion (ROM) favored MA in the moderate-varus subgroup, and VAS pain scores did not show a lim.-KA advantage.
Conclusions:
- The primary raTKA comparison did not reveal a clinical benefit of lim.-KA over MA.
- Post hoc analyses suggest a potential phenotype-dependent benefit of lim.-KA in moderate varus knees for certain patient-reported outcomes, while MA showed better ROM.
- These exploratory findings require prospective validation before altering clinical practice for alignment strategies in raTKA based on varus deformity severity.
