Results of revision surgery and causes of unstable total knee arthroplasty

Abstract

Background: The aim of this study was to evaluate causes of unstable total knee arthroplasty and results of revision surgery.

Methods: We retrospectively reviewed 24 knees that underwent a revision arthroplasty for unstable total knee arthroplasty. The average follow-up period was 33.8 months. We classified the instability and analyzed the treatment results according to its cause. Stress radiographs, postoperative component position, and joint level were measured. Clinical outcomes were assessed using the Hospital for Special Surgery (HSS) score and range of motion.

Results: Causes of instability included coronal instability with posteromedial polyethylene wear and lateral laxity in 13 knees, coronal instability with posteromedial polyethylene wear in 6 knees and coronal and sagittal instability in 3 knees including post breakage in 1 knee, global instability in 1 knee and flexion instability in 1 knee. Mean preoperative/postoperative varus and valgus angles were 5.8°/3.2° (p = 0.713) and 22.5°/5.6° (p = 0.032). Mean postoperative α, β, γ, δ angle were 5.34°, 89.65°, 2.74°, 6.77°. Mean changes of joint levels were from 14.1 mm to 13.6 mm from fibular head (p = 0.82). The mean HSS score improved from 53.4 to 89.2 (p = 0.04). The average range of motion was changed from 123° to 122° (p = 0.82).

Conclusions: Revision total knee arthroplasty with or without a more constrained prosthesis will be a definite solution for an unstable total knee arthroplasty. The solution according to cause is very important and seems to be helpful to avoid unnecessary over-constrained implant selection in revision surgery for total knee instability.

Keywords: Revision arthroplasty; Total knee instability; Unstable total knee.

Fig. 1

(A) The radiograph shows coronal plane instability and varus deformity on both postoperative knees. (B) We found posteromedial bearing wear in the operative field. (C) We performed a revision total knee arthroplasty with femoral and tibial component change.

Fig. 2

Radiographs demonstrating sagittal plane instability (A) and coronal plane instability (B). We presumed posterior cruciate ligament and medial collateral ligament attenuation. (C) We performed a revision arthroplasty with femoral component change.

Fig. 3

The right knee shows posterior instability (A) and valgus instability (B) suggesting coronal and sagittal instability. We found a post fracture of the polyethylene insert (C) and performed a revision surgery with femoral and tibial component change (D).

Fig. 4

The left knee showed global instability on radiography and clinical examination (A). We performed a revision arthroplasty on the left knee with femoral and tibial component change (B).