Abstract
In primary total hip replacements there are numerous options available for providing hip stability in difficult situations i.e. Down's syndrome, Parkinson's disease. However, in the revision situation, in general, and in revision for recurrent dislocation situations specifically, it is important to have all options available including dual mobility constrained liners in order to optimise the potential for hip stability as well as function of the arthroplasty. Even with the newer options available dislocation rates of higher than 5% have been reported in the first two years following revision surgery at institutions where high volumes of revision surgery are performed [Della Valle, Sporer, Paprosky unpublished data]. Because of the deficient abductors, other soft tissue laxity and the requirement for large diameter cups, revision cases will always have more potential for dislocation. In these situations in the lower demand patient and where, a complex acetabular reconstruction that requires time for ingrowth before optimal implant bone stability to occur isn't present, dual mobility with constraint has provided excellent success in terms of preventing dislocation and maintaining implant construct fixation to bone at intermediate term follow-up. Hence in these situations dual mobility with constraint remains the option we utilise. We are also confident in using this device in cases with instability or laxity where there is a secure well-positioned acetabular shell. We cement a dual mobility constrained liner in these situations using the technique described below.
Present indication for dual mobility constrained liners: low demand patient, abductor muscle deficiency or soft tissue laxity, large outer diameter cups, multiple operations for instability, and instability with well-fixed shells that are adequately positioned.
Technique of cementing liner into shell: score acetabular shell if no holes; score liner in spider web configuration; all one or two millimeters of cement mantle.
Results
Constrained Dual Mobility Liner
For Dislocation: 56 Hips 10 yr average f/u, 7% failure of device, 5% femoral loosening, 4% acetabular loosening.
For Difficult Revisions: 101 hips 10 yr average f/u, 6% failure of device, 4% femoral loosening, 4% acetabular loosening
Cementing Liner into Shell: 31 hips 3.6 yr average f/u (2–10 years), 2 of 31 failures
