Department of Brain Sciences, Imperial College London, UKFulltext PDF
The use of constrained liners has become increasingly popular as a method of managing recurrent hip dislocations. There are three common mechanisms of failure of these liners recorded. Type III failures are the most frequent and include damage to the locking mechanism. This case report discusses an uncommon mechanism of failure in which a total hip replacement with a constrained liner dislocated despite an intact locking ring. The mechanism of failure in this case was due to impingement of the neck of the femoral component against the rim of the liner, causing gradual wear of the anterior and posterior flanges. Factors that can lead to this type of impingement include a low head-neck offset ratio, reduced medial offset and poor orientation of the acetabular cup.
Theodoraki M. Mechanism of Type III Failure of Constrained Hip Arthroplasty with Intact Locking Ring. Ann Orthop Surg Res. 2019; 2(1): 1008..