Diagnosis, causes and treatments of instability following total knee arthroplasty

Abstract

Instability following total knee arthroplasty is one of the major causes of revision surgery. In most cases, it can be prevented by using an appropriate prosthesis and a good surgical technique. Particular attention should be given to confirmation of diagnosis for which thorough history taking, complete physical examination and radiographic evaluation are needed. With regard to treatment, identification of the etiology of instability is crucial for establishing proper treatment plans; instability would persist without correction of the cause of the initial instability. For successful revision surgery, balanced medio-lateral and flexion-extension gaps should be achieved. Constrained or rotating-hinge total knee prosthesis should also be considered as an alternative option for certain subsets of patients with instability.

Keywords: Arthroplasty; Instability; Knee; Prosthesis failure.

Fig. 1

Varus-valgus stress radiographs of the knee with instability showing medial femoral condyle avulsion fracture caused by severe osteolysis (A) and lift off in the lateral compartment due to combined lateral laxity (B). (C, D) Revision total knee arthroplasty was performed using a constrained condylar implant.

Fig. 2

(A, B) Radiographs of the knee with instability after total knee arthroplasty using a cruciate-retaining knee implant. (C, D) Conversion of the femoral component to a posterior stabilized femoral component was performed in revision sugery.

Fig. 3

Radiographs of the knee with severe bone loss and osteolysis combined with recurvatum (A) and global instability (B). (C, D) Revision surgery was performed using a rotating hinge knee prosthesis.