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The Spine Blog

Friday, May 1, 2020

Back vs. Hip: What to fix first?

Lumbar spine and hip pathology frequently co-exist, posing a challenge to joint replacement and spine surgeons. Sometimes the concomitant pathology leads to misdiagnosis and results in a failed operation. In other cases, patients clearly have symptoms attributable to both regions, and it can be difficult to determine which pathology to address first. The joint replacement literature has identified lumbar spine pathology, and specifically prior lumbar fusion, as a risk factor for dislocation. While hip replacement surgeons would prefer never to encounter patients with lumbar spine pathology, they do not have this luxury and need to know how to proceed when they encounter patients with both diagnoses. Hip pathology does not necessarily predispose spine surgeons to complications, and they generally worry little about hip pathology other than to warn patients that they might need a hip replacement after their lumbar fusion. In order to shed some light on this issue, Daniel Yang and colleagues from Brown University used the PearlDiver database to identify patients with concomitant hip and lumbar pathology. They created a cohort of about 86,000 patients who underwent total hip arthroplasty (THA) from 2007-2017. Ninety-four percent of these THA patients never underwent a lumbar fusion in the time interval under study. Less than 1% (about 600) of THA patients had undergone a remote lumbar fusion more than 2 years prior to THA, 2.4% (about 2,000) underwent THA within 2 years following a lumbar fusion, and 1.6% (about 1,400) underwent THA followed by lumbar fusion. Thirty-day complication rates including dislocation, infection, and DVT occurred at similar rates in the THA alone and THA after a remote lumbar fusion groups, though the latter group had a higher THA revision rate during the study period (8% vs. 4%, OR=1.9). In looking at the dual diagnosis patients who underwent THA and lumbar fusion relatively close together, the patients who underwent THA first tended to have worse outcomes. Compared to the THA only group, the THA first group had a higher revision rate (9.0% vs. 4.4%, OR=1.9), higher dislocation rate (5.4% vs. 2.0%, OR=2.5), and higher infection rate (6.7% vs. 2.3%, OR=2.7). The fusion first group had a higher revision rate than the THA only group (7.6% vs. 4.4%, OR=1.6), though 30 day complications were not significantly higher. All three groups undergoing both THA and lumbar fusion had higher pre- and post-operative opioid use compared to the THA alone group.

The authors have done a nice job using an administrative database to create a large enough cohort of patients undergoing both THA and lumbar fusion to attempt to answer the question of which operation should be done first. Given that only 6% of THA patients in this cohort had undergone lumbar fusion, it would be nearly impossible to have a large enough sample using anything other than an administrative database to address the question. However, this study design has significant limitations. For one, patients with both back and hip pathology were not randomized to the order of operations, so this choice could have been confounded by many unmeasured variables. The authors did attempt to control for some potential confounders, but the database did not include details such as severity of disease, length of fusion, or BMI. Additionally, patient reported outcomes were not included, so it is unclear if patients had better subjective outcomes (rather than just fewer complications) with one approach or the other. The limited time horizon likely affected the observed revision rates, as patients who had lumbar fusion first likely had THA later in the period under study and had less time in which to undergo a revision. A survival analysis may have been more appropriate for this analysis. The study design also missed THA patients who had underwent lumbar fusion prior to 2007. Additionally, the statistical comparisons were between the THA only group and the dual diagnosis groups, not between the THA first and fusion first groups. Despite these limitations, the data do suggest that dual diagnosis patients may have a lower rate of dislocations in the 30 days after surgery if lumbar fusion is performed prior to THA (3.3% vs. 5.4%). While patients with concomitant lumbar and hip pathology have higher complication rates than those with isolated hip disease, performing lumbar fusion prior to THA may be the preferred strategy for many patients in this challenging cohort.

Please read Mr. Yang's article on this topic in the May 15 issue. Does this change how you consider the order in which to perform lumbar fusion and THA?

Adam Pearson, MD, MS
Associate Web Editor