Regression models are commonly used in spine research today, and they can be used to explain or predict an outcome. A regression model can indicate the relative impact of each variable on the expected outcome, so when the model has been developed, it can be used to predict the outcome for a hypothetical patient.

Significant changes are occurring in the health care field, and spine surgeons must have an understanding of business strategy if they are going to adapt to the new health care environment. Spine surgeons will be required to demonstrate how their service provides a unique value to their patients or else the patients will obtain care from competitors. Classic methods for demonstrating value such as academic prestige and superior clinical outcomes may no longer be sufficient in the evolving health care field, and surgeons will need to demonstrate a comprehensive and cost-effective treatment algorithm for a diagnosis. This article will discuss the basics of business strategy for the spine surgeon, and ways in which the surgeon may demonstrate value to their patients.

Temple University, Philadelphia, PA The author declares no conflict of interest. Reprints: William E. Aaronson, PhD, Temple University, Philadelphia, PA (e-mail: [email protected]). Received May 13, 2015 Accepted May 13, 2015

Minimally invasive transforaminal lumbar interbody fusion (MIS-TLIF) has become a popular alternative to traditional methods of lumbar decompression and fusion. When compared with the open technique, the minimally invasive approach can result in decreased pain and blood loss as well as a shorter length of hospitalization. However, the narrower working channel through the tubular retractor increases the difficulty of decortication and bone grafting. Therefore, recombinant human bone morphogenetic proteins (rhBMP-2) is often utilized (although this is off-label) to create a more favorable interbody fusion environment. Recently, the use of rhBMP-2 has been associated with excessive bone growth in an MIS-TLIF. If this bone growth compresses the neighboring neural structures, patients may present with either new or recurrent radicular pain. Computed tomographic (CT) imaging can demonstrate heterotopic bone growth extending from the disk space into either the ipsilateral neuroforamen or lateral recess, which may result in the compression of the exiting or traversing root, respectively. The purpose of this article and the accompanying video is to demonstrate a technique for defining and resecting rhBMP-2-induced heterotopic bone growth following a previous MIS-TLIF.

Journal of Spinal Disorders & Techniques 28(4):p E250, May 2015. | DOI: 10.1097/01.bsd.0000464894.64288.85

This was a cadaveric biomechanical experiment. To compare the pull-out strength of polyaxial screws that are either hubbed or not hubbed when inserted into the lateral mass. It has been shown in a study on pedicle screws in the thoracic spine that "hubbing" the head of the screw against the dorsal laminar cortex results in significantly lower pull-out strength of the screws. Fifteen segments of the human cervical spine (from C3 to C7) were prepared. Polyaxial screws 3.5 mm in diameter were used. On one side screws 12 mm in length were inserted until the screw head touched the lateral mass; they were then turned 2.5 more times until they were fully hubbed (hubbed screws). On the other side screws 14 mm in length were inserted until the screw head just touched the lateral mass (nonhubbed screws). The 2 mm difference in length was to ensure that the screws were buried to the same length. All screws inserted into the lateral masses underwent tensile pull-out by applying a tensile force down the long axis of the screw. The difference in pull-out strength between the 2 groups was evaluated using a nonparametric paired test (the Wilcoxon signed rank test), which compared side to side on each vertebra. One specimen was excluded because of cement breakage during the biomechanical test. A total of 14 vertebrae were tested. Four vertebrae in the hubbed group showed small fractures or cracks around the screw hole after screw insertion. In a side to side comparison, the hubbed screws had significantly lower pull-out strengths as compared with the nonhubbed screws (P=0.033). Hubbing of lateral mass screws lowers the potential pull-out strength of the screws as compared with the pull-out strength of nonhubbed screws. Thus, hubbing of lateral mass screws, on the basis of the parameters applied in this study, is not recommended.

Retrospective cohort study. To assess the concomitance of cervical spondylosis and thoracolumbar spinal deformity. Patients with degenerative cervical spine disease have higher rates of degeneration in the lumbar spine. In addition, degenerative cervical spine changes have been observed in adult patients with thoracolumbar spinal deformities. However, to the best of our knowledge, there have been no studies quantifying the association between cervical spondylosis and thoracolumbar spinal deformity in adult patients. Patients seen by a spine surgeon or spine specialist at a single institution were assessed for cervical spondylosis and/or thoracolumbar spinal deformity using an administrative claims database. Spinal radiographic utilization and surgical intervention were used to infer severity of spinal disease. The relative prevalence of each spinal diagnosis was assessed in patients with and without the other diagnosis. A total of 47,560 patients were included in this study. Cervical spondylosis occurred in 13.1% overall, but was found in 31.0% of patients with thoracolumbar spinal deformity (OR=3.27, P<0.0001). Similarly, thoracolumbar spinal deformity was found in 10.7% of patients overall, but was increased at 23.5% in patients with cervical spondylosis (OR=3.26, P<0.0001). In addition, increasing severity of disease was associated with an increased likelihood of the other spinal diagnosis. Patients with both diagnoses were more likely to undergo both cervical (OR=3.23, P<0.0001) and thoracolumbar (OR=4.14, P<0.0001) spine fusion. Patients with cervical spondylosis or thoracolumbar spinal deformity had significantly higher rates of the other spinal diagnosis. This correlation was increased with increased severity of disease. Patients with both diagnoses were significantly more likely to have received a spine fusion. Further research is warranted to establish the cause of this correlation. Clinicians should use this information to both screen and counsel patients who present for cervical spondylosis or thoracolumbar spinal deformity.

Retrospective cohort study. To study the relationship between the proximal spine and shoulder levels in adolescent idiopathic scoliosis (AIS). It has been frequently observed that the shoulder levels do not correspond to the spinal curve direction in AIS. Eighty-five operated cases of AIS were analyzed retrospectively of which 69 were Lenke type I and II curves. Preoperative anteroposterior standing x-rays of the spine and clinical photographs were studied. T1 tilt and intercoracoid line (ICL) tilt and their mutual relationship were documented. The curve type (Lenke), magnitude, and direction of the proximal and main thoracic (PT and MT) curves were also noted. The shoulder level as depicted by the ICL showed 3 patterns-horizontal, left side elevated, or right side elevated. The T1-ICL relationship was either concordant or discordant. In the concordant case the T1 was tilted to the same side as the ICL; and vice versa in the discordant. The shoulder level was dependent on the MT curve if the ICL tilted to the same side as the MT curve and it was dependent on the PT curve if it tilted to the same side as the PT curve. This relationship appeared unrelated to curve type. Preoperative shoulder levels in AIS may be concordant with the T1 or discordant-each can have left or right shoulder elevation or balanced shoulders. Further, the shoulder might be MT dependent or PT dependent. Theoretically therefore, surgical balancing of the shoulder and upper instrumented vertebra placement should not depend only on the magnitude and stiffness of the PT curve.

Imaging study. X-ray and computed tomography (CT) sagittal reconstruction images are used to evaluate the stability of the spine. However, we did not know the extent of difference between them. The aim of the study was to compare the differences seen in thoracolumbar burst fractures on lateral radiographs and CT sagittal reconstruction images and investigate their clinical relevance. Lateral radiographs and CT sagittal reconstruction images of 45 patients with thoracolumbar burst fractures were used to record the following measurements: the compressed area of the fractured vertebrae, from lateral radiographs, and the sagittal compressed area, bony fragment area, and total fracture-involved area, from CT sagittal reconstruction images. The percentage of compressed area of fractured vertebrae was 29.32±13.80% on lateral radiographs and 27.93±12.21% on CT sagittal reconstruction images; there was no significant difference between them (P>0.05). The percentage of total fracture-involved area was 53.20±20.64% on CT sagittal reconstruction images, higher than the compressed area measured on lateral radiographs (P<0.01) and CT sagittal reconstruction images (P<0.01). The percentage of bony fragment area was 25.27±15.18% on CT sagittal reconstruction images; there was no significant relationship between bony fragment area and the compressed area (r=0.1258, P>0.05). The compressed area of fractured vertebrae on lateral radiographs could not represent the fracture-involved area and underestimated the total fracture-involved area. We suggested that the above 3 parameters could be easily obtained on CT sagittal reconstruction images, which might be better for assessing the potential instability of the thoracolumbar burst fracture and could become a valuable and indispensable examination for therapeutic decision making.

Systematic review. To provide a systematic review of published literature on the impact of subsidence on clinical outcomes and radiographic fusion rates after anterior cervical discectomy and fusion with plates or without plates. Subsidence of interbody implants is common after anterior cervical spine fusions. The impact of subsidence on fusion rates and clinical outcomes is unknown. Systematic literature review on published articles on anterior cervical discectomy and fusion, which objectively measured graft subsidence, radiographic fusion rates, and clinical outcomes between April 1966 and December 2010. A total of 35 articles that measured subsidence and provided fusion rates and/or clinical outcomes were selected for inclusion. The mean subsidence rate ranged from 19.3% to 42.5%. The rate of subsidence based on the type of implant ranged from 22.8% to 35.9%. The incidence of subsidence was not impacted by the type of implant (P=0.98). The overall fusion rate of the combined studies was 92.8% and was not impacted by subsidence irrespective of subsidence definition or the measurement technique used (P=0.19). Clinical outcomes were evaluated in 27 of 35 studies with all studies reporting an improvement in patient outcomes postoperatively. Subsidence irrespective of the measurement technique or definition does not appear to have an impact on successful fusion and/or clinical outcomes. A validated definition and standard measurement technique for subsidence is needed to determine the actual incidence of subsidence and its impact on radiographic and clinical outcomes.