Thesis (M.Sc.) - Cairo University - Faculty of Medicine - Department of Orthopedic Surgery

KPI is the third most frequent cause of failure of total knee arthroplasty. Moreover, the degree of constraint required to achieve immediate and long-term stability in TKA is frequently debated. KPI is defined as the abnormal and excessive displacement of the articular elements that leads to clinical failure of the arthroplasty and is one of the most common causes of aseptic failure following TKA. Instability may be early or late, but also may be in extension, in flexion, or global. Several specific patient-related risk factors have been identified and include gross deformity, general or regional neuromuscular pathology, hip or foot deformities, and obesity. Instability of the knee can be prevented in most cases with an adequate selection of implants and a good surgical technique. It is imperative to pre-operatively plan for anticipated instability to insure correct implant selection. The degree of constraint of the articulation in TKA should be dictated by the degree of disease and associated deformity. The prevention of instability after TKA is paramount. In this regard, careful femoral component size selection and placement can help balance flexion and extension gaps. Most cases of KPI require surgical treatment. Successful outcomes can be obtained in many of these cases, but without identifying the cause of instability, the surgeon risks repeating the mistakes that led to the instability after the initial total knee arthroplasty

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