Postoperative Radiographic Evaluation Following Adult Spine Deformity Correction

Abstract

Background

During the follow-up visits after Adult Spine Deformity (ASD) surgery, obtaining surveillance radiographs is a usual practice, and this study tried to identify evidence to support or refute such practice.

Methods

This is a retrospective, diagnostic case series (Level IV) of 49 patients. We identified the abnormal radiographic findings and their association with need for revision surgery. We determined the odds of obtaining an abnormal radiographs that lead to revision surgery at each of the given time intervals of follow-up. We also estimated the risk versus benefit of obtaining radiographs at each of the given time intervals of follow-up.

Results

We identified a total of 11 individual types of abnormal postoperative radiographic findings. Of them, the two radiographic findings that always needed revision surgery because of the associated clinical presentation were pedicle screw pullout and bilateral rod fracture. One abnormal radiographic finding that was never associated with revision surgery was the halo around a pedicle screw. In each of the given postoperative time intervals of follow-up at which the routine radiographs were obtained, we noted that the odds of noticing abnormal radiographic finding that lead to revision surgery was always >1. We found that the cumulative hazard rate for exposure to radiation was significantly higher during the initial follow-up visits when compared to subsequent follow-up visits.

Conclusion

This study finds evidence to support the practice of routine postoperative radiographic evaluation of patients who come for follow-up after ASD surgery.

Introduction

With more than 11 million baby boomers joining the population of over 60 years of age in the United States, the incidence of adult spine deformity (ASD) is greatly increasing [1]. In total, it has been estimated that the prevalence of ASD is 60% among the elderly and half as many (32%) are symptomatic [2]. From 2000 to 2010, the total number of spine surgeries with a principal diagnosis of “curvature of the spine” as per the International Classification of Diseases Ninth Edition (ICD-9) increased from 9,400 to more than 20,600 [3]. The same study showed that among Medicare beneficiaries there was a fivefold increase in surgeries during the same period from 1,100 to 5,800 per year. The rate of surgical management of multilevel spinal curvature in patients over age 60 years is also shown to exceed the growth of the 60+ age demographic during the same period [4]. A retrospective analysis using Nationwide Inpatient Sample (NIS) database showed that the annual number of ≥3-level spinal curvature fusions in patients older than age 60 years increased from 6,571 to 16,526, representing a 107.8% increase from 13.4 cases per 100,000 people in 2004 to 27.9 cases per 100,000 in 2011 (p < .001) [4].

Also significant is the fact that in the last two decades, from 1998 to 2008, the nationwide mean annual trend in the volume of spine fusion surgery is +7% [5]. When calculated separately, the nationwide mean annual trend in the volume of ≥3-level spinal curvature fusions is an astounding +16% [5]. To provide a perspective, the mean annual trend in the volume of the other most commonly done major surgical procedures, that is, laminectomy, hip arthroplasty, knee arthroplasty, percutaneous transluminal coronary angioplasty, and coronary artery bypass graft, is approximately +0.5%, +2.5%, +4%, +2%, and −2%, respectively [5].

The increase in volume of surgeries done for ASD directly increases the number of scheduled postoperative office follow-up visits. During each of the scheduled postoperative office follow-up visits after surgical correction of ASD, obtaining surveillance radiographs is a usual practice. Hence, the focus of this study was to look for evidence for obtaining routine postoperative radiographs during follow-up after adult spine deformity correction. These guidelines, we believe, would help both optimize the utilization of health care resources and avoid unnecessary exposure to radiation.

The specific aims of this study are threefold:

• Identifying the abnormal radiographic findings that can change the course of management due to the associated clinical symptoms, that is, “Which abnormal radiographic finding indicates a need for revision surgery and which abnormal radiographic finding indicates no need revision surgery?”

• Determining if there is any association between abnormal radiographic findings and time elapsed from the index procedure, that is, “At what time period during the follow-up after ASD surgery is it likely to find abnormal radiographs than not?”

• Estimating the cumulative hazard rate for routine postoperative radiographic evaluation, that is, “How many normal patients get exposed to radiation in order to identify one patient who needs revision surgery?”