New Assessment Tool Helps Identify the Risk for Postop Dislocation in THA Patients

    Orthopaedic researchers at NYU Langone Health have developed a novel risk assessment tool that helps identify which patients undergoing total hip arthroplasty (THA) may be at higher risk for implant dislocation after surgery.

    Their study is detailed in a poster and scientific exhibit at the 2018 Annual Meeting of the American Academy of Surgeons (AAOS) in New Orleans. The poster was selected by the AAOS Central Program Committee as the Best Poster in the Adult Reconstruction Hip classification and as 1 of 3 Best Scientific Exhibits at the meeting.

    At last year’s AAOS Annual Meeting, the NYU Langone researchers showed that spinal deformity was a significant risk factor for dislocation and subsequent revision surgery. They reported on a study showing that as the lumbar spine moves during posture changes – such as transitioning from sitting to standing – alterations occur in the spinopelvic relationship that change the position of the hip socket and may cause an implant to dislocate in a person with spinal deformity.

    This finding led the researchers to further develop a risk prediction tool to better identify which patients undergoing THA may be at higher risk for dislocation, and then implement a treatment algorithm to help reduce that risk.

    “Dislocation is a common reason for a total hip replacement to fail, and when it happens, sufferers can experience significant pain and require another surgery to fix the problem,” explained lead study author Jonathan Vigdorchik, MD, an assistant professor of orthopedic surgery at NYU School of Medicine and associate fellowship director of the Division of Adult Reconstructive Surgery at NYU Langone Orthopedic Hospital.

    “Orthopedic surgeons need to be more aware of this problem and think about the risk of dislocation prior to performing a hip replacement instead of just dealing with the complications after the surgery. We need to be proactive in our approach.”

    Some newer hip implants are designed with dual-mobility cups that allow for increased range of motion, which helps reduce dislocation risk. However, no guidelines currently exist to aid clinicians in deciding when to use these more constrained implants, which are often more expensive than conventional implants, may not be medically necessary, and may carry added risks of the bearings wearing out.

    For the study, the NYU Langone researchers reviewed data on 1082 THAs performed using computer navigation between January 2014 and December 2015, during which period no dual-mobility implants were used. The overall implant dislocation rate among this cohort was found to be 1.8%. Of this group, 320 patients had lumbar spinal degeneration or deformity as diagnosed by imaging scans, with 10 patients experiencing dislocations for a dislocation rate of 3.1%. This is about 3 times higher than in patients with normal lumbar spines.

    Beginning in 2016, surgeons at NYU Langone used the standardized risk prediction model and treatment algorithm, which factored in data collected from preoperative imaging taken while the patient was sitting and standing, as well as other measures that might affect risk for dislocation, including presence of degenerative spinal pathology, spinal deformity, or a prior lumbar fusion.

    Using the risk assessment tool, the researchers identified 192 of 1009 patients as high risk for a dislocation after surgery. All 192 patients underwent a THA through the high-risk algorithm, with dual-mobility implants being used in 143 of the cases. The researchers reported only 1 dislocation (0.5%) in this high-risk group, compared with 3.1% in the previous group not assessed with the risk assessment and treatment algorithm. These findings represent a 6-fold decrease in the rate of dislocation in the high-risk group.

    “There were significantly fewer dislocations in the high-risk group when treated via our new treatment algorithm,” explained study co-author Aaron J. Buckland, MD, an assistant professor of orthopedic surgery in the Division of Spine Surgery and director of spine research at NYU Langone.

    “We were able to prevent these implant dislocations from occurring in the first place, sparing our patients unplanned admissions, pain, disability, and revision surgery.”

    All patients who undergo THA at NYU Langone Orthopedic Hospital now go through the risk assessment screening and treatment algorithm prior to surgery. Other technologies, including laser-guidance, computer navigation, and robotic surgical devices, are used for the especially high-risk and complex cases identified through the algorithm to ensure the best possible outcome free of complications.

    Future studies aim to examine how the algorithm affects long-term outcomes and clinical benefits in patients at high risk for dislocation.


    Vigdorchik J, Elbuluk A, Carroll K, Mayman D, Iorio R, Buckland A, Jerabek S. A New Risk-Assessment Score and Treatment Algorithm for Patients at High-Risk of Dislocation following Total Hip Arthroplasty (Poster P0072). Presented at the 2018 Annual Meeting of the American Academy of Orthopaedic Surgeons, March 6-10, 2018, New Orleans, Louisiana.

    Eftekhary N, Elbuluk A, Delsole E, Aggarwal V, Iorio R, Buckland A, Schwarzkopf R, Vigdorchick J. The Spinopelvic Relationship: A Stepwise Approach to Ensuring Stability in High-Risk Dislocation Patients Undergoing Total Hip Arthroplasty (Scientific Exhibit SEO1). Presented at the 2018 Annual Meeting of the American Academy of Orthopaedic Surgeons, March 6-10, 2018, New Orleans, Louisiana.