The Importance of Timing for Total Hip Arthroplasty and Spinal Fusion
Managing a patient with degenerative disease in both the hip and the lumber spine – the hip-spine syndrome – presents a challenge: Which procedure should be done first? Should the surgeon start with a total hip arthroplasty (THA), or should the patient be referred to a spine surgeon for spinal fusion before THA?
Does it even matter?
Yes, it does, according to researchers from the Rubin Institute for Advanced Orthopedics at LifeBridge Health in Baltimore, Maryland, who presented data at the annual meeting of the American Association of Hip & Knee Surgeons showing that the timing of the 2 procedures is critical.
“Our hypothesis was that patients who had a prior fusion were at higher risk for dislocation after THA,” said senior study author Ronald E. Delanois, MD, the Jerome P. Reichmister, M.D., Endowed Chairman of Orthopedics for the Rubin Institute for Advanced Orthopedics and the division director of the Center for Joint Preservation and Replacement.
This hypothesis was based on what he and his colleagues were seeing in practice, and the study data confirmed their anecdotal observations: Patients who underwent THA after spinal fusion were much more likely to dislocate postoperatively than patients who had THA first.
Using the PearlDiver supercomputer, Dr. Delanois and colleagues identified 716,084 patients in the Symphony Health database who had undergone THA between 2010 and 2018. They narrowed the search to 13,996 patients who had also undergone lumbar fusion, 8890 before THA and 5016 after THA. Then, they divided these patients into 2 groups – spinal fusion before THA and spinal fusion after THA – and matched them 1:1 based on demographics, with 4510 patients in each group.
As they had hypothesized, the researchers found that patients who underwent spinal fusion before THA had significantly more dislocation episodes postoperatively than patients who underwent spinal fusion after THA: 387 (8.6%) for the spinal fusion before THA group and 335 (7.4%) for the spinal fusion after THA group (P=0.048). There were no significant differences between groups for other complications or for revisions.
Why more postoperative dislocations occur in patients who have spinal fusion before THA is still somewhat of a mystery.
“No one can say why this happens,” Dr. Delanois said, but he has some thoughts. Postoperatively, any THA patient is at some risk of dislocation when sitting down or standing up because the hip capsule has not yet reformed to the point of being protective, he said. In a patient who undergoes spinal fusion first, the hip is at greater risk after THA because the spine has lost some of the mobility that’s needed to compensate until the hip capsule is more robust.
For this reason, “We believe that when patients present with concomitant disease, the hip replacement should be done before the spine, unless there is a reason that the spine is at greater risk,” Dr. Delanois said.
The surgeon planning the THA should collaborate with the spine surgeon to work out the order of procedures and the timing between procedures, he said. If the spine fusion has to be done first, the surgeon planning the THA may want to order more than the traditional anteroposterior and frog-leg lateral radiographs. Sitting and standing radiographs will help to assess spinal motion and aid in planning how to protect the hip after THA, Dr. Delanois said.
The bottom line for surgeons whose THA patients have already undergone spinal fusion is to be cognizant of the higher risk for dislocations and be prepared to follow the patient more closely than with a typical THA patient, Dr. Delanois said.
Mohamed NS, Remily EA, Wilkie WA, Pervaiz SS, Douglas SJ, Stafford JA, Plate JF, Naziri Q, Nace J, Delanois RE. Spinal Fusion and Total Hip Arthroplasty: Why Timing Is Important (Paper 39). Presented at the 30th AAHKS Annual Meeting, November 5-8, 2020, Dallas, Texas.