Spine Evaluation Is Critical in Reducing Dislocations in Revision THA Patients

    Total hip arthroplasty (THA) is a highly successful operation for restoring mobility, relieving pain, and improving quality of life. But failures do occur, leading to the need for revision procedures. One of the most common reasons for revision is recurrent instability, [1] although the incidence of revisions due to these dislocations is decreasing as a result of better techniques and technologies. [2]

    Researchers from NYU Langone Health and the Hospital for Special Surgery have been studying the spine-hip connection and its role in dislocations after THA for years: [3-9]

    • At the 2017 Annual Meeting of the American Academy of Orthopaedic Surgeons, they showed that spinal deformity is a significant risk factor for dislocation and subsequent revision surgery. Their study demonstrated 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.
    • At the 2018 Annual Meeting, they unveiled a novel risk assessment tool – the Hip-Spine Classification in Revision Total Hip Arthroplasty – that helps identify which patients undergoing THA may be at higher risk for implant dislocation after surgery. Their study was detailed in a poster and scientific exhibit at the meeting, with poster being selected as the best poster in the adult reconstruction hip classification and as 1 of 3 best scientific exhibits at the meeting.

    Now, the researchers have applied the risk assessment tool in a protocol they’ve developed for patients undergoing revision THA due to instability. The protocol allows surgeons to evaluate spinal function and mobility preoperatively and then address the relevant pathology during the revision procedure.

    For the new study presented at the 2019 Annual Meeting of the American Academy of Orthopaedic Surgeons, the researchers prospectively collected data on 222 patients who underwent revision THA for recurrent instability between January 2014 and January 2017 at NYU Langone Health and Hospital for Special Surgery. The 111 patients in the protocol group were matched 1:1 with 111 patients for a control group.

    The protocol includes an analysis of supine, sitting, and standing radiographs:

    • Supine anteroposterior (AP) pelvis radiograph
    • Standing AP pelvis radiograph
    • Sitting and standing lateral radiographs

    This analysis, which includes calculating the changes in pelvic tilt between sitting and standing positions, gives surgeons more information about how a patient’s spine function affects hip alignment than they would have with a standard assessment that only includes supine radiographs. Advanced imaging equipment (EOS Imaging; Cambridge, Massachusetts) was used for the radiographs in the study, but standard radiographs can also be used.

    Once the radiographs have been analyzed, the assessment tool is used to assign a simple score consisting of a number for alignment and a letter for mobility:

    • 1 for normal spinal alignment (PI-LL ± 10°)
    • 2 for flatback deformity (PI-LL > 10°)
    • 3 for hyperlordosis (PI-LL < -10)
    • A for normal spinal mobility
    • B for stiff spine (<20° change in pelvic tilt or sacral slope from standing to sitting)

    The score informs the approach for revision surgery, with a treatment recommendation for each number and letter combination.

    Among the protocol group, only 3 patients had experienced a dislocation by 2 years after surgery, for a 97% survivorship rate. The 3 dislocations occurred in the first 3 postoperative months. Survivorship was only 84% in the control group (18 dislocations).

    “We were very surprised that the dislocation rate was only 3% for patients who received the new pre-surgical assessment compared with 16% for those who did not,” said Jonathan M. Vigdorchik, MD, from Hospital for Special Surgery. “We knew that spine function affects hip replacement outcomes, but not to this magnitude.”

    Dr. Vigdorchik and colleagues also found that without this new evaluation method, 77% of inappropriately positioned hip implants would not have been identified.

    Surgeons at NYU Langone Health and Hospital for Special Surgery began adopting the new assessment approach in 2014. “We hope our study draws awareness to the need for spinal evaluation and that more centers conducting hip replacement surgery will implement our protocol to help their patients,” Dr. Vigdorchik said.

    “Based on our work to date, we are collaborating with colleagues at Stanford University and the Mayo Clinic to conduct a multi-center study to collect more evidence. We hope that one day, this approach becomes the standard of care.”


    Vigdorchik JM, Eftekhary N, Elbuluk AM, Abdel MP, Buckland A, Schwarzkopf R, Jerabek SA, Mayman DJ. Evaluation of the Spine is Critical in Patients with Recurrent Instability after Total Hip Arthroplasty (Paper 184). Presented at the 2019 Annual Meeting of the American Academy of Orthopaedic Surgeons, March 12-16, Las Vegas, Nevada.


      1. Gwam CU, Mistry JB, Mohamed NS, et al. Current epidemiology of revision total hip arthroplasty in the United States: national inpatient sample 2009 to 2013. J Arthroplasty. 2017 Jul;32(7):2088-2092. doi: 10.1016/j.arth.2017.02.046. Epub 2017 Feb 27.
      2. Rajaee SS, Campbell JC, Mirocha J, Paiement GD. Increasing burden of total hip arthroplasty revisions in patients between 45 and 64 years of age. J Bone Joint Surg Am. 2018;100(6):449-58. doi: 10.2106/JBJS.17.00470.
      3. Buckland AJ, Vigdorchik J, Schwab FJ, et al. Acetabular anteversion changes due to spinal deformity correction: bridging the gap between hip and spine surgeons. J Bone Joint Surg Am. 2015 Dec 2;97(23):1913-20. doi: 10.2106/JBJS.O.00276.
      4. Vigdorchik J, DelSole E, Buckland A, Schwarzkopf R. The hip-spine relationship: what hip surgeons need to know. Published June 6, 2016, on ICJR.net. Accessed March 18, 2019.
      5. Buckland AJ, Puvanesarajah V, Vigdorchik J, et al. Dislocation of a primary total hip arthroplasty is more common in patients with a lumbar spinal fusion. Bone Joint J. 2017 May;99-B(5):585-591. doi: 10.1302/0301-620X.99B5.BJJ-2016-0657.R1.
      6. DelSole EM, Vigdorchik JM, Schwarzkopf R, Errico TJ, Buckland AJ. Total hip arthroplasty in the spinal deformity population: does degree of sagittal deformity affect rates of safe zone placement, instability, or revision? J Arthroplasty. 2017 Jun;32(6):1910-1917. doi: 10.1016/j.arth.2016.12.039. Epub 2016 Dec 27.
      7. Luthringer TA, Vigdorchik JM. A preoperative workup of a “hip-spine” total hip arthroplasty patient: a simplified approach to a complex problem. J Arthroplasty. 2019 Jan 18. pii: S0883-5403(19)30039-7. doi: 10.1016/j.arth.2019.01.012. [Epub ahead of print]
      8. 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.
      9. 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.