Citing dislocation as the most common cause of revision arthroplasty, physicians from Hospital for Special Surgery (HSS) in New York wrote a review article covering the latest liner and shell options for primary total hip arthroplasty (THA). In the paper, the authors explain how liner design may affect functional anteversion, inclination, and jump distance.
Their study, “Acetabular Component and Liner Selection for the Prevention of Dislocation After Primary Total Hip Arthroplasty” appears in the December 2021 edition of JBJS Reviews.
“Dislocations after primary THA are devastating adverse events for patients that are potentially avoidable in many instances,” co-author Peter Sculco, M.D. told OTW. A hip and knee surgeon at HSS, Dr. Sculco added, “Recent years have seen a considerable increase in our understanding of prosthesis placement, design, and the spino-pelvic relationship as it relates to dislocation risk. In the setting of this new and developing understanding, we thought it would be valuable for the hip surgeon to have a comprehensive guide of currently available acetabular component and liner designs that may be applied at the individual patient level to help reduce dislocation risk.”
Naming the most up-to-date liner and shell options for primary THA (in order of increasing constraint and stability), the authors provided information for:
- neutral,
- lateralized,
- face-changing (oblique),
- lipped (high-wall) with or without lateralization,
- modular and anatomic dual-mobility, and
- constrained options.
The authors emphasized that “the design of these liners functions to either increase jump distance in any direction (dual-mobility) or in a specific region of the cup (high-wall liner) or capture the head entirely (constrained liner).”
They recommend that surgeons choose liners based on the patient-specific risk of dislocation. Variables to consider, they say, include:
- static anatomic (e.g., large anterior inferior iliac spine or greater trochanter morphology),
- dynamic anatomic (e.g., limited sitting-standing change in the sacral slope), and
- demographic or medical (e.g., neuro-cognitive disorders and obesity) risk factors.
The authors also pointed out that adult reconstruction surgeons should be able to recognize patients who are at risk for instability and dislocation after primary THA. They held out hope that “advancements in technology have the potential to increase component positioning accuracy, promote a better understanding of component position in relation to patient anatomy, and decrease the incidence of instability and dislocation after primary THA.”
Dr. Sculco added, “This review may alter practice by serving as a foundational source of knowledge for acetabular component and liner design and function, thereby allowing the hip surgeon to select the optimal liner characteristics to mitigate the risk of dislocation after primary THA for their own patients.”
