Serena S. Hu

Surgical Compared with Nonoperative Treatment for Lumbar Degenerative Spondylolisthesis: Four-Year Results in the Spine Patient Outcomes Research Trial (SPORT) Randomized and Observational Cohorts

BACKGROUNDnThe management of degenerative spondylolisthesis associated with spinal stenosis remains controversial. Surgery is widely used and has recently been shown to be more effective than nonoperative treatment when the results were followed over two years. Questions remain regarding the long-term effects of surgical treatment compared with those of nonoperative treatment.nnnMETHODSnSurgical candidates from thirteen centers with symptoms of at least twelve weeks duration as well as confirmatory imaging showing degenerative spondylolisthesis with spinal stenosis were offered enrollment in a randomized cohort or observational cohort. Treatment consisted of standard decompressive laminectomy (with or without fusion) or usual nonoperative care. Primary outcome measures were the Short Form-36 (SF-36) bodily pain and physical function scores and the modified Oswestry Disability Index at six weeks, three months, six months, and yearly up to four years.nnnRESULTSnIn the randomized cohort (304 patients enrolled), 66% of those randomized to receive surgery received it by four years whereas 54% of those randomized to receive nonoperative care received surgery by four years. In the observational cohort (303 patients enrolled), 97% of those who chose surgery received it whereas 33% of those who chose nonoperative care eventually received surgery. The intent-to-treat analysis of the randomized cohort, which was limited by nonadherence to the assigned treatment, showed no significant differences in treatment outcomes between the operative and nonoperative groups at three or four years. An as-treated analysis combining the randomized and observational cohorts that adjusted for potential confounders demonstrated that the clinically relevant advantages of surgery that had been previously reported through two years were maintained at four years, with treatment effects of 15.3 (95% confidence interval, 11 to 19.7) for bodily pain, 18.9 (95% confidence interval, 14.8 to 23) for physical function, and -14.3 (95% confidence interval, -17.5 to -11.1) for the Oswestry Disability Index. Early advantages (at two years) of surgical treatment in terms of the secondary measures of bothersomeness of back and leg symptoms, overall satisfaction with current symptoms, and self-rated progress were also maintained at four years.nnnCONCLUSIONSnCompared with patients who are treated nonoperatively, patients in whom degenerative spondylolisthesis and associated spinal stenosis are treated surgically maintain substantially greater pain relief and improvement in function for four years.

Patient outcomes after decompression and instrumented posterior spinal fusion for degenerative spondylolisthesis.

STUDY DESIGNnA retrospective study of patient outcomes after decompression and fusion for degenerative spondylolisthesis, using the SF-36 survey and a functional questionnaire.nnnSUMMARY OF BACKGROUND DATAnIn recent studies, patient outcomes have been examined more specifically; however, detailed functional outcomes are not available nor have widely used outcomes instruments been administered.nnnMETHODSnThirty patients aged more than 40 years (average, 60.1 years) who had degenerative spondylolisthesis were evaluated after decompression and instrumented posterior fusion. Charts and radiographs were also reviewed. Questionnaires were administered by telephone, and consisted of the Medical Outcomes Study short form (SF-36) and 27 questions designed to evaluate function, quality of life, medication usage, and satisfaction with surgical results.nnnRESULTSnNinety-three percent of patients were satisfied with their outcomes. Patients improved significantly in their ability to perform heavy and light activities, participate in social activities, sit, and sleep (P < 0.001) and also improved in pain, depression, and medication usage (P < 0.0001). SF-36 data showed significantly better overall assessment of health in all categories than that in a published cohort of patients with low back pain. The current study group also showed no difference in seven of eight categories when compared with the general population. Fusion rate was 93% at an average of 128 days. Three patients required reoperation: two for pseudarthrosis and one for a deep infection. A poorer outcome, scored by the SF-36, was associated with greater preoperative stenosis (P < 0.05) or occurrence of a complication (P < 0.05).nnnCONCLUSIONSnPatients treated with decompression and fusion for degenerative spondylolisthesis had improved functional outcomes, when measured by a disease-specific questionnaire and by widely used instruments.

Predictive factors for proximal junctional kyphosis in long fusions to the sacrum in adult spinal deformity

Study Design. A retrospective study. Objective. To assess the mechanisms and the independent risk factors associated with proximal junctional kyphosis (PJK) in patients treated surgically for adult spinal deformity with long fusions to the sacrum. Summary of Background Data. The occurrence of PJK may be related to preoperative and postoperative sagittal parameters. The mechanisms and risk factors for PJK in adults are not well defined. Methods. Consecutive patients who underwent long instrumented fusion surgery (≥6 vertebrae) to the sacrum with a minimum of 2 years of follow-up were retrospectively studied. Risk factors included patient factors, surgical factors, and radiographical parameters such as thoracic kyphosis (TK), lumbar lordosis (LL), sagittal vertical axis, pelvic tilt, and pelvic incidence. Results. Ninety consecutive patients (mean age, 64.5 yr) met inclusion criteria. Radiographical PJK occurred in 37 of the 90 (41%) patients with a mean follow-up of 2.9 years. The most common mechanism of PJK was fracture at the upper instrumented vertebra (UIV) in 19 (51%) patients. Twelve (13%) patients with PJK were treated surgically with proximal extension of the instrumented fusion. Preoperative TK more than 30°, preoperative proximal junctional angle more than 10°, change in LL more than 30°, and pelvic incidence more than 55° were identified as predictors associated with PJK. Achievement of ideal global sagittal realignment (sagittal vertical axis <50 mm, pelvic tilt <20°, and pelvic incidence-LL <±10°) protected against the development of PJK (19% vs. 45%). A multivariate regression analysis revealed changes in LL more than 30°, and preoperative TK more than 30° were the independent risk factors associated with PJK. Conclusion. Fracture at the UIV was the most common mechanism for PJK. Change in LL more than 30° and pre-existing TK more than 30° were identified as independent risk factors. Optimal postoperative alignment of the spine protects against the development of PJK. A surgical strategy to minimize PJK may include preoperative planning for reconstructions with a goal of optimal postoperative alignment. Level of Evidence: 3

Revision of Failed Lumbar Fusions: A Comparison of Anterior Autograft and Allograft

Study Design. The radiographic and clinical results of two different anterior structural grafts were compared in 38 patients who had combined anterior‐posterior revision surgery for failed lumbar fusion. Objectives. Failed lumbar fusion surgery, such as pseudarthrosis or flatback deformity, may result in disabling pain. The optimum revision technique has yet to be defined. The authors of the current study sought to determine which of two different types of anterior graft yields the best results. Summary of Background Data. Posterior procedures for revision of a failed lumbar fusion have not yielded reliably successful results. A combined anterior‐posterior approach may be effective in restoring sagittal balance and enhancing fusion rates. Recent studies have shown femoral ring allografts to be effective in lumbar fusion revision, but no studies have compared these with other types of structural grafts. Methods. Thirty‐eight patients with pseudarthrosis were treated with combined anterior‐posterior lumbar spine fusion using either femoral ring allografts (26 patients) or tricortical iliac autografts (12 patients). Radiographic follow‐up examination and retrospective patient self‐assessment questionnaires were used to evaluate outcomes. Results were assessed by independent reviewers after a mean follow‐up period of 35 months. Results. Radiographic follow‐up examination revealed acceptably low pseudarthrosis rates for structural autografts (0%) and allografts (6%). The questionnaires revealed significant improvement in pain for both groups. Allograft patients showed greater improvement in function, less pain medication usage, and higher overall success rates (83%) than autograft patients (64%). Conclusions. Femoral ring allografts are as effective, clinically and radiographically, as tricortical iliac autografts when used as an anterior structural element in revision lumbar spine fusion in patients who have undergone multiple surgical procedures for pseudarthrosis or flatback deformity. The slightly greater improvement for the allograft group needs to be confirmed in a larger study.

Surgical site infection in spinal surgery: description of surgical and patient-based risk factors for postoperative infection using administrative claims data.

Study Design. Retrospective analysis. Objective. The objective of this study was to investigate the accuracy of using an automated approach to administrative claims data to assess the rate and risk factors for surgical site infection (SSI) in spinal procedures. Summary of Background Data. SSI is a major indicator of health care quality. A wide range of SSI rates have been proposed in the literature depending on clinical setting and procedure type. Methods. All spinal surgeries performed at a university-affiliated tertiary-care center from July 2005 to December 2010 were identified using diagnosis-related group, current procedural terminology, and International Classification of Diseases, Ninth Revision (ICD-9) codes and were validated through chart review. Rates of SSI and associated risk factors were calculated using univariate regression analysis. Odds ratios were calculated through multivariate logistic regression. Results. A total of 6628 hospital visits were identified. The cumulative incidence of SSI was 2.9%. Procedural risk factors associated with a statistically significant increase in rates of infection were the following: sacral involvement (9.6%), fusions greater than 7 levels (7.8%), fusions greater than 12 levels (10.4%), cases with an osteotomy (6.5%), operative time longer than 5 hours (5.1%), transfusions of red blood cells (5.0%), serum (7.4%), and autologous blood (4.1%). Patient-based risk factors included anemia (4.3%), diabetes mellitus (4.2%), coronary artery disease (4.7%), diagnosis of coagulopathy (7.8%), and bone or connective tissue neoplasm (5.0%). Conclusion. Used individually, diagnosis-related group, current procedural terminology, and ICD-9 codes cannot completely capture a patient population. Using an algorithm combining all 3 coding systems to generate both inclusion and exclusion criteria, we were able to analyze a specific population of spinal surgery patients within a high-volume medical center. Within that group, risk factors found to increase infection rates were isolated and can serve to focus hospital-wide efforts to decrease surgery-related morbidity and improve patient outcomes.

Parametric finite element analysis of verterbral bodies affected by tumors

The vertebral column is the most frequent site of metastatic involvement of the skeleton. Due to the proximity to the spinal cord, from 5% to 10% of all cancer patients develop neurologic manifestations. As a consequence, fracture risk prediction has significant clinical importance. In this study, we model the metastatically involved vertebra so as to parametrically investigate the effects of tumor size, material properties and compressive loading rate on vertebral strength. A two-dimensional axisymmetric finite element model of a spinal motion segment consisting of the first lumbar vertebral body (no posterior elements) and adjacent intervertebral disc was developed to allow the inclusion of a centrally located tumor in the vertebral body. After evaluating elastic, mixed, and poroelastic formulations, we concluded that the poroelastic representation was most suitable for modeling the metastatically involved vertebras response to compressive load. Maximum principal strains were used to localize regions of potential vertebral trabecular bone failure. Radial and axial vertebral body displacements were used as relative indicators of spinal canal encroachment and endplate failure. Increased tumor size and loading rate, and reduced trabecular bone density all elevated axial and radial displacements and maximum tensile strains. The results of this parametric study suggest that vertebral tumor size and bone density contribute significantly to a patients risk for vertebral fracture and should be incorporated in clinical assessment paradigms.

Percutaneous plasma decompression alters cytokine expression in injured porcine intervertebral discs

BACKGROUND CONTEXTnDiscectomy is a surgical technique commonly used to treat bulging or herniated discs causing nerve root compression. Clinical data suggest discectomy may also help patients with contained discs and no clear neural compromise. However, the mechanisms of clinical efficacy are uncertain, and consequently bases for treatment optimization are limited.nnnPURPOSEnTo determine the effect of percutaneous plasma decompression on the histologic, morphologic, biochemical and biomechanical features of degenerating intervertebral discs.nnnSTUDY DESIGNnAn adult porcine model of disc degeneration was used to establish a degenerative baseline against which to evaluate discectomy efficacy.nnnOUTCOME MEASURESnCytokines interleukin (IL)-1, IL-6, IL-8, and tumor necrosis factor (TNF)-alpha were measured from tissue samples using enzyme-linked immunosorbent assay. Histology and morphology images were rated for degenerative findings (of cells and matrix) in both the nucleus and annulus. Proteoglycan content was determined, and intact specimen stiffness and flexibility were measured biomechanically. Magnetic resonance images were collected for biomechanical specimens.nnnMETHODSnUsing a retroperitoneal surgical approach, stab incisions were made in four or five lumbar discs per spine in 12 minipigs. Animals were allocated into one of three groups: 6-week recovery, 12-week recovery and percutaneous plasma decompression using an electrosurgical device at 6 weeks with recovery for 6 additional weeks. Four additional animals served as controls.nnnRESULTSnDiscs treated with discectomy had a significant increase in IL-8 and a decrease in IL-1 as compared with the 12-week, nontreated discs. There were no significant differences in morphologic and biomechanical parameters or proteoglycan content between treated discs and time-matched, nontreated discs.nnnCONCLUSIONSnOur results demonstrate that percutaneous plasma discectomy alters the expression of inflammatory cytokines in degenerated discs, leading to a decrease in IL-1 and an increase in IL-8. Whereas both IL-1 and IL-8 have hyperalgesic properties, IL-1 is likely to be a more important pathophysiologic factor in painful disc disorders than IL-8. Therefore, the alteration in cytokine expression that we observed is consistent with this effect as a mechanism of pain relief after discectomy. In addition, given that IL-1 is catabolic in injured tissue and IL-8 is anabolic, our results suggest that a percutaneous plasma discectomy may be capable of initiating a repair response in the disc.

Hospital readmission after spine fusion for adult spinal deformity.

Study Design. Retrospective cohort study. Objective. To assess the rate, causes, and risk factors of unplanned hospital readmission after spine fusion for the treatment of adult spinal deformity. Summary of Background Data. Hospital readmissions in the elderly are common, and with increasing emphasis on the quality of health care, readmission rates are used to assess hospital performance. Spine surgery has seen rapidly increased utilization during the past 2 decades. Surgical treatments of complex spinal deformity are known to have higher rates of complications than other types of spine surgery. However, there are no reports describing the rates and causes of hospital readmission after deformity surgery. Methods. Patients were identified at a single institution from 2006 through 2011 that received a spine fusion for the treatment of adult spinal deformity. All hospital readmissions within 90 days of discharge were reviewed for cause. Unplanned readmission rates were calculated via Kaplan-Meier failure analysis. Rates were compared across patients receiving different lengths of spine fusion (short: 2–3 vertebra, medium: 4–8, long: 9 or more). Risk factors were assessed using a Cox proportional hazards multivariate model. Results. Eight hundred thirty-six patients were enrolled (111 short, 402 medium, and 323 long fusions). The overall unplanned readmission rate was 8.4% at 30 days and 12.3% at 90 days. Patients with long spine fusion had higher rates of readmission than patients with medium or short length fusions. Surgical site infection accounted for 45.6% of readmissions. Risk factors for readmission include longer fusion length, higher patient severity of illness, and specific medical comorbidities. Conclusion. Unplanned hospital readmissions after spine fusion for adult spinal deformity are common, and are most often due to surgical site infection. Patient medical comorbidities are an important part of assessing risk and can be used by providers and patients to better assess individual risk prior to treatment. Level of Evidence: 3

Surgical site infections in spine surgery: identification of microbiologic and surgical characteristics in 239 cases.

Study Design. Retrospective analysis. Objective. The objective of this study was to describe the microbiology of surgical site infection (SSI) in spine surgery and relationship with surgical management characteristics. Summary of Background Data. SSI is an important complication of spine surgery that results in significant morbidity. A comprehensive and contemporary understanding of the microbiology of postoperative spine infections is valuable to direct empiric antimicrobial treatment and prophylaxis and other infection prevention strategies. Methods. All cases of spinal surgery associated with SSI between July 2005 and November 2010 were identified by the hospital infection control surveillance program using Centers for Disease Control National Health Safety Network criteria. Surgical characteristics and microbiologic data for each case were gathered by direct medical record review. Results. Of 7529 operative spine cases performed between July 2005 and November 2010, 239 cases of SSI were identified. The most commonly isolated pathogen was Staphylococcus aureus (45.2%), followed by Staphylococcus epidermidis (31.4%). Methicillin-resistant organisms accounted for 34.3% of all SSIs and were more common in revision than in primary surgical procedures (47.4% vs. 28.0%, P = 0.003). Gram-negative organisms were identified in 30.5% of the cases. Spine surgical procedures involving the sacrum were significantly associated with gram-negative organisms (P < 0.001) and polymicrobial infections (P = 0.020). Infections due to gram-negative organisms (P = 0.002) and Enterococcus spp. (P = 0.038) were less common in surgical procedures involving the cervical spine. Cefazolin-resistant gram-negative organisms accounted for 61.6% of all gram-negative infections and 18.8% of all SSIs. Conclusion. Although gram-positive organisms predominated, gram-negative organisms accounted for a sizeable portion of SSI, particularly among lower lumbar and sacral spine surgical procedures. Nearly half of infections in revision surgery were due to a methicillin-resistant organism. These findings may help guide choice of empiric antibiotics while awaiting culture data and antimicrobial prophylaxis strategies in specific spine surgical procedures. Level of Evidence: 3

Do 1-year outcomes predict 2-year outcomes for adult deformity surgery?

BACKGROUND CONTEXTnHealth-related quality-of-life (HRQOL) measures are being used more frequently in the evaluation of the adult deformity patient. This is due in part to the validation of the deformity-specific Scolios Research Society-22 (SRS-22). Hence, relationships between HRQOL outcomes and traditional measures of success such as deformity correction, fusion healing, and complications are being established.nnnPURPOSEnTo examine the pattern of HRQOL outcome responses after adult deformity surgery.nnnSTUDY DESIGNnAnalysis of prospective multicenter cohort.nnnPATIENT SAMPLEnTwo hundred and eighty-three adult deformity patients with preoperative, 1-, and 2-year postoperative outcome measures.nnnOUTCOME MEASURESnSRS-22, Short Form-12 (SF-12), Oswestry Disability Index (ODI), and back and leg pain numeric rating scale scores.nnnMETHODSnPreoperative versus postoperative health status measures were evaluated by matched-pairs sample t test statistics and post hoc analysis of variance (ANOVA) findings.nnnRESULTSnSRS-22 improved from a mean 3.03 points at baseline to 3.21 points at 6 months, 3.71 points at 1 year, and 3.70 points at 2 years post-op. Mean ODI score was 37.0 points pre-op and improved to 27.0 points at 6 months, and 22.8 points at 1 and 2 years post-op. Mean SF-12 physical component score was 33.7 points at baseline, improving to 36.9 points at 6 months, 40.6 points at 1 year, and 40.5 points at 2 years post-op. Paired samples analysis comparing 6-month and 1-year post-op scores showed deterioration for numeric rating scale leg pain (p=0.05). There was a trend for improvement in SF-12 physical component score (p=0.06). Significant improvement between 6 months and 1 year post-op was noted for ODI (p=0.02) and SRS total score (p<0.0001). Comparison of 1- versus 2-year postoperative scores revealed no statistically significant differences for any of the HRQOL parameters.nnnCONCLUSIONSnThis study supports the application of HRQOL measures, including the deformity-specific SRS-22, as a valuable tool in the assessment of adult deformity patients. Change in outcome score stabilized after the 1-year postoperative interval, for most patients.