How Does Spinal Deformity Impact Hip Stability? Interview with:

Dr Aaron J. Buckland Spinal and scoliosis surgeon and assistant professor Orthopedic surgery NYU Langone Medical Center

Dr. Aaron Buckland

Dr Aaron J. Buckland
Spinal and scoliosis surgeon and
Assistant professor
Orthopedic surgery
NYU Langone Medical Center What is the background for this study?

Response: For decades, surgeons performing hip replacements have placed the acetabular component adjacent to the pelvis in a “safe zone” which has been shown to reduce dislocation risk. However, beginning in residency, I would notice that several of my patients with spinal deformities or lumbar fusions, would experience dislocations despite the safe zone placement of these implants. Our initial research demonstrated that there was an increased dislocation risk in patients with lumbar fusions, particularly if they underwent spinal realignment. We investigated this phenomenon further by retrospectively reviewing 107 patients who met the criteria for sagittal spinal deformity, including 139 hip replacements collectively. What are the main findings?

Response: We found among them an 8 percent dislocation rate for implants in patients with some degree of spinal stenosis; 5.8 percent of the same patient cohort required revision surgery due to recurrent dislocation. This compares to a one to three percent dislocation risk in the normal population.

Patients who sustained dislocations had significantly higher standing spinopelvic (posterior) tilt, T1-pelvic angle, and mismatch of lumbar lordosis and pelvic incidence. Among all patients, 78 percent had safe zone anteversion while lying down (supine), which decreased significantly, to 58 percent when standing due to increases in spinopelvic tilt. Among dislocating hip replacements, 80 percent had safe anteversion, 80 percent had safe inclination, and 60 percent had both parameters within the ‘safe zone’. What should readers take away from your report?

Response: Until now, no studies of this hip-spine relationship have focused on the subgroup of patients with a diagnosis of sagittal spinal deformity. This research suggests that placing the cup in the safe zone may not be enough to prevent dislocation in patients with spinal deformity. Surgeons should anticipate potential instability after performing a hip replacement in patients with spinal deformity, and they should adjust their surgical plans accordingly. There are preoperative planning technologies and patient-specific implants they can utilize to further reduce the risk of dislocation and need for reoperation. What recommendations do you have for future research as a result of this study?

Response: Our future research will examine postural analysis more closely to develop algorithms for patient-specific or pathology-specific safe zones. We also plan to investigate optimizing hip replacements in terms of offset and impingement-free range of motion, or using a dual-mobility bearing implant in patients with sagittal spinal deformity. Thank you for your contribution to the community.

Citation: Abstract presented at 2017 AAOS meeting March 2017

Total Hip Arthroplasty in the Spinal Deformity Population: Does Degree of Deformity Affect Hip Stability? Aaron Buckland, FRACS, New York, NY Edward M. Delsole, MD, New York, NY Thomas J. Errico, MD, New York, NY Ran Schwarzkopf, MD, New York, NY Jonathan Vigdorchik, MD, New York, NY In this study, we report an elevated dislocation rate and risk factors for dislocation among patients with sagittal spinal deformity.

Note: Content is Not intended as medical advice. Please consult your health care provider regarding your specific medical condition and questions.

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Last Updated on March 17, 2017 by Marie Benz MD FAAD