J Korean Orthop Assoc.  2022 Aug;57(4):307-314. 10.4055/jkoa.2022.57.4.307.

Results of Primary Total Knee Arthroplasty in Osteoarthritis with Varus Thrust Knee and Severe Varus Deformity

• Sun D
• Song IS
• Kwon J
• Kim C

• KMID: 2532412
• DOI: http://doi.org/10.4055/jkoa.2022.57.4.307

Abstract

Purpose
Varus thrust is an posterolateral rotatory knee motion observed with severe varus patients. It shows a dynamic worsening of varus in the loading response (LR), while returning to a more neutral alignment during the initial contact (IC) of gait. This study examined the results of primary total knee arthroplasty in varus thrust osteoarthritis, including varus thrust motion, gait analysis.
Materials and Methods
From March 2009 to March 2019, among 2,391 total knee arthroplasty who underwent total knee arthroplasty, 84 knees from 68 patients with varus thrust and more than a 20° varus deformity were enrolled in this study. The pre-operative and postoperative varus thrust amount (VTA), proximal tibiofibular overlap (PTFOL), and implant position (α, β, γ, and δ) were examined. The gait pattern was analyzed before and after surgery using the footscan ^® (RSscan International, Olen, Belgium), evaluating the foot axis-center of pressure angle (FCA) of the ipsilateral foot at the IC and at the LR. The clinical outcomes were evaluated with Hospital for special surgery (HSS).
Results
The changes in the VTA were from a pre-operative mean of 5.1° (3.1–7.2) to a mean of 1.9° (0.3–2.8) at the last follow-up (p=0.017). PTFOL changed from pre-operative mean of 18.1 mm (9.0–29.1) to post-operative mean of 11.0 mm (4.2–20.7) (p=0.029). The mean α, β, γ, and δ angle in the last follow-up was 94.6°, 90.3°, 3.86°, and 89.7°, respectively. The FCA in IC was corrected from a pre-operative mean of -1.8° (-1.0 to -4.4) to a post-operative mean of 2.3° (-1.1 to 4.1) (p=0.013). FCA in LR was similar from a pre-operative mean of 5.2° (1.0–7.2) to a post-operative mean of 6.0° (1.1–7.4) (p=0.823). The HSS was changed from a pre-operative mean of 45.7 to a post-operative mean of 86.2 in the last follow-up (p=0.011).
Conclusion
Standard total knee arthroplasty in the varus thrust knee showed satisfactory correction of the varus thrust amount and gait pattern, without recurrence of the varus thrust gait. Better clinical results were achieved in total knee arthroplasty of osteoarthritis with a varus thrust without using a constraining implant.

Keyword

knee; varus thrust; gait analysis; total knee arthroplasty