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Updated: May 28, 2026
Individualized Stem-positioning in Calcar-guided Short-stem Total Hip Arthroplasty
Published on: February 27, 2018
Classification and management of the unstable total hip arthroplasty
Glenn D Wera1, Nick T Ting, Mario Moric
1Department of Orthopaedic Surgery, Case Western Reserve University, Cleveland, Ohio 44116, USA.
Insights
Instability after total hip arthroplasty revisions is often due to component malposition or abductor deficiency. Acetabular revisions improve outcomes, while prior surgeries and failed liners increase redislocation risk.
Area of Science:
- Orthopedic Surgery
- Biomedical Engineering
- Arthroplasty Research
Background:
- Total hip arthroplasty (THA) instability is a significant complication requiring revision surgery.
- Understanding the etiologies of instability is crucial for improving revision THA outcomes.
Purpose of the Study:
- To classify the primary etiologies of instability in revision total hip arthroplasty.
- To identify risk factors for redislocation and evaluate the effectiveness of different revision strategies.
Main Methods:
- Retrospective review of 75 revision THA cases for instability.
- Classification of instability etiologies into 6 types.
- Analysis of redislocation rates, risk factors, and implant survivorship.
Main Results:
- The most common causes of instability were acetabular component malposition (33%) and abductor deficiency (36%).
- Redislocation occurred in 14.6% of cases; acetabular revisions were protective (P < .015).
- Previous operations and failed constrained liners were risk factors for failure. Tripolar constrained liners showed better survivorship than locking ring types.
Conclusions:
- Acetabular component malposition and abductor deficiency are leading causes of THA instability requiring revision.
- Revision acetabular surgery and specific liner types (tripolar, modular) can improve outcomes.
- Abductor insufficiency presents the highest risk of failure in revision THA.
Abstract:
Seventy-five total hip arthroplasty revisions for instability were classified into 6 primary etiologies: I, acetabular component malposition; II, femoral component malposition; III, abductor deficiency; IV, impingement; V, late wear; or VI, unresolved etiology. The most common etiologies were cup malposition (type I; 33%) and abductor deficiency (type III; 36%). At a mean of 35.3 months, 11 redislocations occurred (14.6%). Acetabular revisions were protective against redislocation (P < .015). The number of previous operations (P = .0379) and previously failed constrained liners (P < .02) were risk factors for failure. Tripolar constrained liners demonstrated improved survivorship vs locking ring types (P < .02); cemented constrained liners failed more often than modular constrained liners (P < .0018). The highest risk of failure was in patients with abductor insufficiency with revisions for other etiologies having a success rate of 90%.
