Re-Revision THA Due to Dislocation: Does the Implant Matter?
Using data from the Australian Orthopaedic Association National Joint Replacement Registry, researchers evaluated whether implant choice in revision total hip arthroplasty for dislocation can reduce the risk of recurrent dislocations and, subsequently, the need for a second revision surgery.
Noah Kirschner, MD, and Ajit Deshmukh, MD
Hoskins W, Bingham R, Hatton A, de Steiger RN. Standard, large-head, dual-mobility, or constrained-liner revision total hip arthroplasty for a diagnosis of dislocation: an analysis of 1,275 revision total hip replacements. J Bone Joint Surg Am. 2020 Dec 2;102(23):2060-2067. doi: 10.2106/JBJS.20.00479. PMID: 33264216.
Total hip arthroplasty (THA) is the standard of care for patients with end-stage osteoarthritis of the hip. Outcomes following THA are excellent, and THA is considered to be one of the most successful procedures in orthopaedics. Orthopaedic surgeons need to be wary of the risk of dislocation associated with THA, however, as dislocation is one of the most common causes of revision and re-revision THA.
Numerous techniques and technologies have been used in revision procedures to prevent recurrence of instability following initial dislocation. In a recent retrospective study, Hoskins et al reviewed 9 years of data (1999 to 2018) from the Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR) to evaluate differences in re-revision rates for various types of prostheses following prior revision surgery for dislocation.
The researchers included all patients who had undergone a major revision procedure for the treatment of dislocation following primary THA, excluding thoses with a metal-on-metal bearing prosthesis. Patients were then divided into 4 group based on the prosthesis type used in the first revision surgery:
- Standard-size head (≤ 32 mm)
- Large-size head (≥ 36mm)
- Dual-mobility cup
- Constrained acetabular liner
The primary outcome measures were cumulative rate of second revision for all causes and cumulative rate of second revision for a diagnosis of dislocation.
A total of 1275 first revisions were performed for a diagnosis of dislocation: 335 in the standard-head group, 387 in the large-head group, 265 in the dual-mobility cup group, and 288 in the constrained acetabular liner group. The researchers found that among these patients:
- At 11 years following the first revision surgery, the cumulative rate of second revision related to dislocation for all prosthesis groups was 24%.
- The rate of all-cause second revision was significantly higher in the standard-head group when compared with the constrained acetabular liner group (hazard ratio [HR], 1.53).
- The rate of second revision for dislocation was significantly higher in the standard-head group than in the constrained acetabular liner (HR, 2.44), dual-mobility (HR, 2.04), and large-head groups (HR, 1.80).
Orthopaedic surgeons utilize many resources and exert tremendous effort to ensure THA implants are placed in the the most stable position possible, as dislocation is the most common cause of revision following THA. The dislocation rate has been reported to be between 0.3% and 10% in primary THA patients, with the dislocation rate climbing as high as 28% after revision THA. [1-3]
Following a dislocation event, non-operative intervention is often attempted. If dislocation is recurrent or malposition of the components is noted after closed reduction, revision surgery is typically recommended. The study by Hoskins et al provides insight into which prostheses surgeons can use to minimize both the risk of repeated dislocations following revision surgery and the need for a second revision procedure. The reserachers found that large femoral head size, dual-mobility components, and constrained acetabular liners are most likely to improve stability in patients undergoing first revision THA for dislocation.
Utilizing a larger head size has been associated with decreased risk of dislocation in primary THA. The larger head increases the range of motion of the components before impingement occurs.  The jump distance is also increased, requiring additional translation to dislocate the femoral head. 
Dual-mobility prostheses use a similar biomechanical concept and similarly have been shown to decrease instability in primary THA.  This type of implant incorporates an additional bearing, usually a polyethylene hemisphere, between the prosthetic head and the acetabular liner, maximizing the femoral head-to-neck ratio.
Acetabular constrained liners resist dislocation by locking the femoral head into the liner of the acetabular cup.  Although increasing the constraint may seem to be an obvious solution, forces are transmitted to other surfaces, creating the risk of liner damage, locking mechanism failure, and component loosening. 
The study by Hoskins et al demonstrates that the use of large heads, dual-mobility cups, and constrained liners are superior options to standard heads in the prevention of recurrent dislocations. No differences were reported among these 3 prostheses, and are all viable options for revision procedures. Further studies are needed, however, and surgeons should continue to individualize the revision prosthesis according to each patient situation and presentation.
Noah Kirschner, MD, is a second-year orthopaedic surgery resident in the Department of Orthopedic Surgery at NYU Langone Health, New York, New York. Ajit Deshmukh, MD, is a Clinical Associate Professor in the Department of Orthopedic Surgery at NYU Langone Health, New York, New York.
Disclosures: The authors have no disclosures relevant to this article.
- Dargel J, Oppermann J, Bruggemann GP, Eysel P. Dislocation following total hip replacement. Dtsch Arztebl Int. 2014 Dec 22;111(51-52):884-90. Epub 2015/01/20.
- Parvizi J, Picinic E, Sharkey PF. Revision total hip arthroplasty for instability: surgical techniques and principles. J Bone Joint Surg Am. 2008 May;90(5):1134-42. Epub 2008/05/03.
- Brooks PJ. Dislocation following total hip replacement: causes and cures. Bone Joint J. 2013 Nov;95-B(11 Suppl A):67-9. Epub 2013/11/06.
- Singh SP, Bhalodiya HP. Head size and dislocation rate in primary total hip arthroplasty. Indian J Orthop. 2013 Sep;47(5):443-8. Epub 2013/10/18.
- Kelley SS, Lachiewicz PF, Hickman JM, Paterno SM. Relationship of femoral head and acetabular size to the prevalence of dislocation. Clin Orthop Relat Res. 1998 Oct(355):163-70. Epub 1999/01/26.
- Ko LM, Hozack WJ. The dual mobility cup: what problems does it solve? Bone Joint J. 2016 Jan;98-B(1 Suppl A):60-3. Epub 2016/01/07.
- Werner BC, Brown TE. Instability after total hip arthroplasty. World J Orthop. 2012 Aug 18;3(8):122-30. Epub 2012/08/25.