A. Nick Shamie

One-year outcomes after minimally invasive sacroiliac joint fusion with a series of triangular implants: a multicenter, patient-level analysis

Background Sacroiliac joint (SI) pain is an often-overlooked cause of lower-back pain, due in part to a lack of specific findings on radiographs and a symptom profile similar to other back-related disorders. A minimally invasive surgical (MIS) approach to SI joint fusion using a series of triangular, titanium plasma spray-coated implants has shown favorable outcomes in patients with SI joint pain refractory to conservative care. The aim of this study was to provide a multicenter experience of MIS SI joint fusion using a patient-level analysis. Patients and methods We report a patient-level analysis from 144 patients with a mean of 16 months postoperative follow-up. Demographic information, perioperative measures, complications, and clinical outcomes using a visual analog scale for pain were collected prospectively. Random-effects regression models were used to account for intersite variability. Results The mean age was 58 years, 71% of patients were female, and 62% had a history of lumbar spinal fusion. Mean (95% confidence interval [CI]) operative time was 73 minutes (25.4–118), blood loss was minimal, and hospital stay was 0.8 days (0.1–1.5). At follow-up, mean (95% CI) visual analog scale pain scores improved by 6.1 points (5.7–6.6). Substantial clinical benefit, defined as a decrease in pain by >2.5 points or a score of 3.5 or less, was achieved in 91.9% of patients (95% CI 83.9%–96.1%), and 96% (95% CI 86.3%–98.8%) of patients indicated they would have the same surgery again. Conclusion When conservative measures fail to relieve symptoms resulting from degeneration or disruption of the SI joint, MIS SI joint fusion using a series of triangular, porous, titanium plasma spray-coated implants is a safe and effective treatment option.

Propionibacterium acnes biofilm is present in intervertebral discs of patients undergoing microdiscectomy.

Background In previous studies, Propionibacterium acnes was cultured from intervertebral disc tissue of ~25% of patients undergoing microdiscectomy, suggesting a possible link between chronic bacterial infection and disc degeneration. However, given the prominence of P. acnes as a skin commensal, such analyses often struggled to exclude the alternate possibility that these organisms represent perioperative microbiologic contamination. This investigation seeks to validate P. acnes prevalence in resected disc cultures, while providing microscopic evidence of P. acnes biofilm in the intervertebral discs. Methods Specimens from 368 patients undergoing microdiscectomy for disc herniation were divided into several fragments, one being homogenized, subjected to quantitative anaerobic culture, and assessed for bacterial growth, and a second fragment frozen for additional analyses. Colonies were identified by MALDI-TOF mass spectrometry and P. acnes phylotyping was conducted by multiplex PCR. For a sub-set of specimens, bacteria localization within the disc was assessed by microscopy using confocal laser scanning and FISH. Results Bacteria were cultured from 162 discs (44%), including 119 cases (32.3%) with P. acnes. In 89 cases, P. acnes was cultured exclusively; in 30 cases, it was isolated in combination with other bacteria (primarily coagulase-negative Staphylococcus spp.) Among positive specimens, the median P. acnes bacterial burden was 350 CFU/g (12 - ~20,000 CFU/g). Thirty-eight P. acnes isolates were subjected to molecular sub-typing, identifying 4 of 6 defined phylogroups: IA1, IB, IC, and II. Eight culture-positive specimens were evaluated by fluorescence microscopy and revealed P. acnes in situ. Notably, these bacteria demonstrated a biofilm distribution within the disc matrix. P. acnes bacteria were more prevalent in males than females (39% vs. 23%, p = 0.0013). Conclusions This study confirms that P. acnes is prevalent in herniated disc tissue. Moreover, it provides the first visual evidence of P. acnes biofilms within such specimens, consistent with infection rather than microbiologic contamination.

A comprehensive subaxial cervical spine injury severity assessment model using numeric scores and its predictive value for surgical intervention.

Multiple factors contribute to the determination for surgical intervention in the setting of cervical spinal injury, yet to date no unified classification system exists that predicts this need. The goals of this study were twofold: to create a comprehensive subaxial cervical spine injury severity numeric scoring model, and to determine the predictive value of this model for the probability of surgical intervention. In a retrospective cohort study of 333 patients, neural impairment, patho-morphology, and available spinal canal sagittal diameter post-injury were selected as injury severity determinants. A common numeric scoring trend was created; smaller values indicated less favorable clinical conditions. Neural impairment was graded from 2-10, patho-morphology scoring ranged from 2-15, and post-injury available canal sagittal diameter (SD) was measured in millimeters at the narrowest point of injury. Logistic regression analysis was performed using the numeric scores to predict the probability for surgical intervention. Complete neurologic deficit was found in 39 patients, partial deficits in 108, root injuries in 19, and 167 were neurologically intact. The pre-injury mean canal SD was 14.6 mm; the post-injury measurement mean was 12.3 mm. The mean patho-morphology score for all patients was 10.9 and the mean neurologic function score was 7.6. There was a statistically significant difference in mean scores for neural impairment, canal SD, and patho-morphology for surgical compared to nonsurgical patients. At the lowest clinical score for each determinant, the probability for surgery was 0.949 for neural impairment, 0.989 for post-injury available canal SD, and 0.971 for patho-morphology. The unit odds ratio for each determinant was 1.73, 1.61, and 1.45, for neural impairment, patho-morphology, and canal SD scores, respectively. The subaxial cervical spine injury severity determinants of neural impairment, patho-morphology, and post-injury available canal SD have well defined probability for surgical intervention when scored separately. Our data showed that each determinant alone could act as a primary predictor for surgical intervention.

The effects of a semiconstrained integrated artificial disc on zygapophyseal joint pressure and displacement.

Study Design. Measurement of zygapophyseal joint pressure and displacement was performed after placement of a semiconstrained integrated artificial disc (SIAD) in a cadaver model. Objective. To understand the likelihood of accelerated zygapophyseal joints degeneration as a result of the implant. Summary of Background Data. A SIAD has been developed to treat lumbar spondylosis secondary to segmental disc degeneration and spinal stenosis. The SIAD replaces the stenotic segments disc. Previous studies have demonstrated that nonconstrained artificial disc (NAD) replacements fail to achieve their optimal long-term outcomes likely because of significantly increased zygapophyseal joint pressure and displacement at the implanted level. Moreover, clinical studies have reported an increased incidence of zygapophyseal joint degeneration after lumbar disc replacement. Methods. Eight cadaver lumbar specimens (L2–L5) were loaded in flexion, neutral, extension, left bend, and right rotation. Zygapophyseal joint pressure and displacement were measured during each of the 5 positions at each of the 3 levels with the ratio of deformation calculated under the different loads. An artificial disc was placed at the L3–L4 level, and the measurements were repeated. Results. After L3–L4 segment implantation, the pressure in the zygapophyseal joint at operative segment was not significantly changed by SIAD and NAD implantation in axial compression and flexion, compared with physiological disc. Notable differences in zygapophyseal joint pressure between the SIAD and NAD were identified at the operative level in extension, left bend, and right rotation. The adjacent-level effect of NAD was significantly greater than that of SIAD. The ratio of deformation difference between the 2 discs was increased by load experienced in extension, flexion, left bend, and right rotation. Conclusion. The SIAD provided a superior biomechanical milieu for zygapophyseal joints at the implanted and adjacent levels compared with NAD, which may avoid the acceleration of postoperative zygapophyseal joint degeneration. Level of Evidence: 1

Use of the subcutaneous lumbar spine (SLS) index as a predictor for surgical complications in lumbar spine surgery

BACKGROUND CONTEXT Lumbar spine surgeries require adequate exposure to visualize key structures and limited exposure can make surgery more technically difficult, thus increasing the potential for complications. Body mass index and body mass distribution have been shown to be associated with worse surgical outcomes. PURPOSE This study aims to further previous investigations in elucidating the predictive nature of body mass distribution with peri- and postoperative complications in lumbar surgery. STUDY DESIGN/SETTING This is a retrospective study conducted at a single institution. PATIENT SAMPLE Two hundred eighty-five patients who underwent lumbar laminectomy, laminotomy, or posterior lumbar interbody fusion or transforaminal lumbar interbody fusion procedures between 2013 and 2016. OUTCOME MEASURES Magnetic resonance imaging (MRI) results and electronic medical records were reviewed for measurements and relevant complications. METHODS Previously known risk factors were identified and MRI measurements of subcutaneous adipose depth (SAD) relative to spinous process height (SPH) were measured at the surgical site to generate the subcutaneous lumbar spine (SLS) index. This measurement was then analyzed in association with recorded surgical complications. RESULTS The SLS index was found to be a significant risk factor for total complications (0.292, p=.041), perioperative complications (0.202, p=.015), and need for revision surgery (0.285, p<.001). The SAD alone proved to be negatively associated with perioperative complications (-0.075, p=.034) and need for revision surgery (-0.104, p=.001), with no predictive association seen for total or postoperative complications. Linear regression revealed an SLS index of 3.43 as a threshold value associated with a higher risk of total complications, 5.8 for perioperative complications, and 3.81 for the need for revision surgeries. CONCLUSION Body mass distribution of the surgical site as indicated by SAD to SPH (SLS index) is significantly associated with increasing risk of postoperative and perioperative complications as well as increased likelihood for necessary revision surgery. This relationship was shown to be a more accurate indication of perioperative risk than previous standards of body mass index and SAD alone, and may allow spine surgeons to assess surgical risk when considering lumbar spine surgery using simple calculations from standard preoperative MRI results.