Complications and outcomes after three-column osteotomy: a 5-year follow-up.

BACKGROUND: Three-column spinal osteotomies (3-CO) are powerful techniques used to correct spinal deformity. These surgeries are associated with an elevated risk of complications. While outcomes have been reported in the literature with 2 years follow-up, longer-term outcomes of three-column osteotomies remain understudied. OBJECTIVES: This study aims to examine patient reported outcomes and complications for three-column osteotomies at 5 years. STUDY DESIGN: Retrospective review of a prospectively collected spinal deformity cases database. PATIENT SAMPLE: All consecutive adult patients at a single spine surgery center treated with either a pedicle subtraction osteotomy (PSO) or vertebral column resection (VCR) for spinal deformity, and with a minimum 5-year follow-up were included. OUTCOME MEASURES: Visual-analog scale (VAS) for back pain score (0 to 10), Oswestry Disability Index (ODI) score (0 to 100), number of complications, revision rate, sagittal balance, lumbar lordosis at preoperative and at 5-year visit. METHODS: Data was extracted from a prospectively collected spinal deformity surgery database continuously updated since 2002 with data from operative reports, patients' medical visit notes and patients' self-reported VAS and ODI questionnaires completed at each office visit. Radiographic measurements were performed on standing full-length spine radiographs taken at pre-op and 5-year visits. Descriptive statistics, comparison of means and proportions among groups, and a logistic regression analysis were conducted using the statistical software package SPSS version 28. Statistical significance was set at p<.05. RESULTS: Of 127 consecutive adult patients with minimum of 5-year follow-up undergoing a 3-CO posterior spinal surgery for spinal deformity were identified and included in the study, 79 (62%) were treated with PSO, and 48 (38%) with VCR. Both PSO and VCR groups demonstrated significant improvements in VAS (PSO pre-op: 6.7, 5-year: 4.6, p<.001; VCR pre-op: 7.1, 5-year: 5.2, p<.001), and ODI (PSO pre-op: 52.9, 5-year: 45.4, p<.001; VCR pre-op: 57.5, 5-year 43.0, p<.001) that were maintained at 5 years. Major and minor complications occurring within 5 years were not statistically different between the PSO and VCR groups (major: 59.5% vs 56.3%, p=.85; minor: 45.6% vs 37.5%, p=.46). The rate of revision surgery within 5 years was 39.4% overall. Of the fifty patients requiring revision, 37.5% were for nonunion, 27.1% instrumentation failure, 14.6% proximal junctional kyphosis (PJK), 12.5% vertebral fracture, 6.3% motor weakness, and 2.1% infection. Improvements in lumbar lordosis were maintained at 5 years in both the PSO (29.9° vs 47.2°, p<.001) and VCR (34.6° vs 48.5°, p<.001) groups while sagittal balance maintained significant improvement in the VCR group (9.5 cm vs 6.3 cm, p=.008) but not the PSO (11.4 cm vs 9.3 cm, p=.065). CONCLUSION: Patients undergoing three-column osteotomies had a major complication rate of 57.5% and a minor complication rate of 42.5% after 5 years. Improvements in lumbar lordosis were maintained at 5-year follow-up, but sagittal balance was only maintained in the VCR group. Despite these radiographic findings, both VCR and PSO groups maintained significant clinical improvements in both VAS and ODI scores at 5-year follow up.

Laminectomy Adjacent to Instrumented Fusion Increases Adjacent Segment Disease.

STUDY DESIGN: Retrospective cohort. OBJECTIVE: To determine if performing a simultaneous laminectomy at an unfused level adjacent to an instrumented fusion increases the risk of adjacent segment disease(ASD). SUMMARY OF BACKGROUND DATA: Laminectomy adjacent to instrumented fusion has uncertain outcomes. The increased mechanical forces at the unfused laminectomy may lead to more ASD. Few studies have examined the development of ASD with regards to laminectomy performed adjacent to instrumented fusions. METHODS: 789 patients underwent instrumented lumbar fusion and laminectomy at the same level(s) (n=676) or with an additional adjacent level laminectomy (n=113) with a minimum of 2-year follow-up. Diagnoses were degenerative spondylosis (n=241), degenerative spondylolisthesis (n=485) and isthmic spondylolisthesis (n=63) in addition to central stenosis. Primary outcome measures included development of ASD, time to development of ASD, revision surgery, and time to revision surgery. RESULTS: The adjacent laminectomy group developed ASD at a significantly greater rate of 57.5% (n=65), compared with 35.2% (n=238) of the non-adjacent laminectomy group (P<0.001). Revision surgery rate was also greater in the adjacent laminectomy group (22.1% v 13.5%, P<0.001). There was no difference in time to revision surgery (31.1 v 32.6 mo, P=0.71) or time to ASD development (31.2 v 32.3 mo, P=0.72). ODI and VAS scores did not differ, nor did patient baseline demographics including sex, BMI, Charleston Comorbidity Index, and tobacco use. The exception was the adjacent laminectomy group average age was 67.6 while the non-adjacent laminectomy group average age was 62.3 (P<0.001). However, age was not found to be an independent predictor of ASD development (P=0.44). CONCLUSION: Surgeons should be cautious when performing a laminectomy adjacent to an instrumented fusion, as this increases the rate of ASD as well as revision surgery.

Proximal junctional failure after surgical instrumentation in adult spinal deformity: biomechanical assessment of proximal instrumentation stiffness.

STUDY DESIGN: Assessment of different proximal instrumentation stiffness features to minimize the mechanical proximal junctional failure-related risks through computer-based biomechanical models. OBJECTIVE: To biomechanically assess variations of proximal instrumentation and loads acting on the spine and construct to minimize proximal junctional failure (PJF) risks. The use of less-stiff fixation such as hooks or tensioned bands, compared to pedicle screws, at the proximal instrumentation level are considered to allow for a gradual transition in stiffness with the adjacent levels, but the impact of such flexible fixation on the loads balance and complications such as PJF remain uncertain. METHODS: Six patients with adult spine deformity who underwent posterior spinal instrumentation were used to numerically model and simulate the surgical steps, erected posture, and flexion functional loading in patient-specific multibody analyses. Three types of upper-level fixation (pedicle screws (PS), supralaminar hooks (SH), and sublaminar bands (SB) with tensions of 50, 250, and 350 N) and rod stiffness (CoCr/6 mm, CoCr/5.5 mm, Ti/5.5 mm) were simulated. The loads acting on the spine and implants of the 90 simulated configurations were analyzed using Kruskal-Wallis statistical tests. RESULTS: Simulated high-tensioned bands decreased the sagittal moment at the adjacent level proximal to the instrumentation (1.3 Nm at 250 N; 2.5 Nm at 350 N) compared to screws alone (PS) (15.6 Nm). At one level above, the high-tensioned SB increased the sagittal moment (17.7 Nm-SB vs. 15.5 Nm-PS) and bending moment on the rods (5.4 Nm and 5.7 Nm vs. 0.6 Nm) (p < 0.05). SB with 50 N tension yielded smaller changes in load transition compared to higher tension, with moments of 8.1 Nm and 16.8 Nm one and two levels above the instrumentation. The sagittal moment at the upper implant-vertebra connection decreased with the rod stiffness (1.0 Nm for CoCr/6 mm vs. 0.7 Nm for Ti/5.5 mm; p < 0.05). CONCLUSION: Simulated sublaminar bands with lower tension produced smaller changes in the load transition across proximal junctional levels. Decreasing the rod stiffness further modified these changes, with a decrease in loads associated with bone failure, however, lower stiffness did increase the rod breakage risk. LEVEL OF EVIDENCE: N/A.

Early Gender Differences in Pain and Functional Recovery Following Thoracolumbar Spinal Arthrodesis.

BACKGROUND: To analyze gender differences regarding the recovery experience (pain, function, complications) after spinal arthrodesis surgery. METHODS: Pre-operative and post-operative gender-based differences in patient-reported outcomes for open posterior spinal arthrodesis at 6 weeks, 3 months, 6 months, and 1 year were studied, including age, comorbidities, body mass index (BMI), diagnosis, number of vertebrae fused, type of surgery, primary vs. revision surgery, and complications. Statistical analysis included the use of Student's t-test, Chi square, linear regression, Mann-Whitney U test, and Spearman's rho. RESULTS: Primary or revision posterior arthrodesis was performed on 1931 consecutive adults (1219 females, 712 males) for deformity and degenerative pathologies. At surgery, females were older than males (61.7 years vs. 59.7 years, p < 0.01), had slightly more comorbidities (1.75 vs. 1.5, p < 0.01), and were more likely to undergo deformity correction (38% vs. 22%, p < 0.01). Females described more pre-op pain (female VAS = 6.54 vs. male VAS = 6.41, p < 0.01) and lower pre-op function (female ODI = 49.73 vs. male ODI = 46.52, p < 0.01). By 3 months post-op, there was no significant gender difference in VAS or ODI scores. Similar pain and function scores between males and females continued through 6 months and 12 months. CONCLUSION: Although females have more pain and dysfunction before undergoing spinal surgery, the differences in these values do not reach the Minimum Clinically Important Difference (MCID). Post-operatively, there is no difference in pain and function scores among males and females at 3, 6, and 12 months.

Does Interbody Support at L5-S1 Matter in Long Fusions to the Pelvis?: A 5-year Analysis.

STUDY DESIGN: Retrospective review of prospectively collected data. OBJECTIVE: To determine if the addition of L5-S1 interbody support in long fusion deformity constructs is associated with superior long-term clinical and radiographic outcomes. To compare the 5-year clinical and radiographic outcomes and complications between long fusion constructs with L5-S1 interbody support versus posterolateral fusion (PLF) alone. SUMMARY OF BACKGROUND DATA: Cadaveric biomechanical studies have suggested that an interbody fusion at L5-S1 is beneficial in long fusion constructs with sacropelvic fixation. However, there is limited data reflecting the superiority of interbody support augmentation in optimizing arthrodesis and deformity correction relative to PLF alone. METHODS: Eighty-eight consecutive adults with spinal deformity who underwent at minimum T11-pelvis posterior pedicle screw instrumentation with 5-year follow-up were included. Two cohorts were compared based on technique used at the lumbosacral junction (L5-S1): (A) no interbody (PLF; n = 23), or (B) interbody support at L5-S1 (IB; n = 65). Radiographic measurements and clinical outcome measures were compared at multiple time points. Complications were recorded and compared. RESULTS: No differences in baseline patient characteristics between cohorts. One nonunion occurred at L5-S1 in the PLF group (P = 0.091). Initial postop sagittal alignment was better in the IB group (PLF: 6.46 cm, IB: 2.48 cm, P = 0.007); however, this was not maintained over long-term follow-up. No significant differences in proximal junctional kyphosis (PLF: 7/23, IB: 9/65, P = 0.076). Proximal junctional failure was more frequent in the PLF group (PLF: 6/23, IB: 6/65, P = 0.043). No significant differences in complications were found. Both cohorts had improvement from baseline pain and functional scores. CONCLUSION: There is no absolute long-term advantage for lumbar interbody support in adult spinal deformity patients undergoing spinal arthrodesis to the pelvis.Level of Evidence: 3.

Does Local Administration of Liposomal Bupivacaine Reduce Pain and Narcotic Consumption in Adult Spinal Deformity Surgery?

STUDY DESIGN: Retrospective cohort study. OBJECTIVE: To determine if local administration of liposomal bupivacaine (LB) reduces postoperative pain scores and narcotic use in spinal deformity patients. METHODS: Adult patients undergoing elective spinal fusion (7 or more levels) for scoliosis or kyphosis were selected for inclusion. Patients received either periincisional injections of combined liposomal and standard bupivacaine (n = 90, group L) or standard bupivacaine only (n = 69, group C). Perioperative pain scores (VAS [visual analogue scale]), opioid use, length of stay, functional outcome (ODI [Oswestry Disability Index]), and perioperative complications were recorded. No external funding was received for this study. RESULTS: A total of 159 patients met inclusion criteria (mean age was 54.2 years of age). No significant baseline demographic differences were noted between the 2 groups. Group L experienced slight improvements in pain control on postoperative day (POD) 1 (P = .02). No difference in pain scores were otherwise noted. Group L transitioned off of intravenous (IV) narcotics faster with 52.6% less IV use by POD3 (P = .03). No differences in total narcotic consumption, perioperative complications, lengths of stay, and functional outcome scores were otherwise noted between the 2 cohorts. CONCLUSIONS: The use of LB in adult spinal deformity surgery does not appear to provide clinically important improvements in postoperative pain at the manufacturer's recommended dosage. Furthermore, while patients receiving LB may transition more quickly off of IV narcotics, this does not appear to translate into an overall decrease in narcotic consumption, hasten return of bowel function, or decrease hospital lengths of stay. Future prospective randomized control trials are warranted. The use of varying dosages of LB may also help further clarify the true efficacy of LB in the setting of spinal deformity surgery.

Adult spine deformity surgery in elderly patients: are outcomes worse in patients 75 years and older?

STUDY DESIGN: Retrospective study of a prospectively collected database at one center. OBJECTIVES: Assess the outcomes and complications of adult spinal deformity (ASD) surgery in patients that are 75 years and older compared with patients of 65-75 years of age. With increasing amounts of ASD surgery being performed on elderly patients, it is important to assess how age plays a factor in corrective reconstruction surgery. METHODS: Inclusion criteria for the study were all patients ≥ 65 years of age that underwent thoracolumbar deformity correction involving ≥ four levels at a single institution by two surgeons. Patients were divided based on age into 65-74.9 or ≥ 75 groups. Radiographic parameters were measured preoperatively, postoperatively, and at 2 years. The Numeric Rating Scale (NRS) and Oswestry Disability Index (ODI) were collected preoperatively, at 1 year, and 2 years. Comorbidities included were based around the Charlson Comorbidity Index (CCI) and compared to the incidence of complications and need for further surgery. RESULTS: Both age groups had improvements in their radiographic parameters postoperatively which was maintained at 2 years. Comparing the different age groups with similar comorbidity burden in regard to complications and need for additional surgery yielded no statistically significant difference between groups. Both groups had comparable decreases in NRS and increases in ODI at 2 years. CONCLUSIONS: Analysis of our study population indicates that there is no difference between the outcomes and complications of deformity surgery in patients 75 years and older when compared to a younger elderly population. It also does not appear that a ≥ 3 comorbidity burden has a significant impact on the complications or need for additional surgery in our elderly spinal deformity surgery population. LEVEL OF EVIDENCE: Level IV.

Biomechanical analysis of sagittal correction parameters for surgical instrumentation with pedicle subtraction osteotomy in adult spinal deformity.

BACKGROUND: High complication rate has been documented in spinal instrumentation with pedicle subtraction osteotomy. The objective was to analyze the biomechanics of spinal instrumentation with pedicle subtraction osteotomy as functions of three instrumentation parameters. METHODS: Patient-specific biomechanical computer models of 3 adult patients who were instrumented with pedicle subtraction osteotomy were used to simulate the actual instrumentations and alternative instrumentations derived by varying instrumentation parameters: pedicle subtraction osteotomy wedge angle and rod contouring angle, location of the osteotomy, and number of rods (2 vs. 4). FINDINGS: A change of the sagittal correction by +7.5° (-7.5°) resulted in a change in the screw axial forces and rods bending loads around the osteotomy by +38% (-19%) and +28% (-11%), respectively. The bending moments in the rods were 31% lower at the osteotomy site when it was located at one level above, and 20% higher when it was located at a level below. Additional rods allowed the rod bending and screw axial loads to be reduced by 24% and 22%, respectively. INTERPRETATION: The amount of sagittal correction was positively correlated with loads sustained by the screws and rods. Rods were subjected to higher bending loads at the pedicle subtraction osteotomy site when it was done at a lower level. A 4-rod construct is an effective way to reduce the risk of rod breakage by reducing the loads sustained by the rods.

Preoperative Dehydration does not Increase the Risk of Complications Following Elective Lumbar Surgery.

STUDY DESIGN: A retrospective cohort study. OBJECTIVE: The aim of this study was to evaluate the effect of preoperative dehydration on hospital length of stay (LOS), rates of 30-day postoperative complications, related reoperations, and readmissions. SUMMARY OF BACKGROUND DATA: Preoperative dehydration has long been associated with postoperative infection, deep vein thrombosis (DVT), acute renal failure, and an increased hospital LOS. To our knowledge, the effect of preoperative dehydration on complication rates for patients undergoing elective lumbar spine surgery has not been well described. METHODS: An analysis of American College of Surgeons National Surgical Quality Improvement Program (ACS-NSQIP) data from 2006 to 2013 was performed. Patients undergoing elective lumbar procedures were identified and exclusion criteria eliminated patients who underwent any emergency procedures, infections, tumor cases, or revision surgeries. Patient dehydration was defined as preoperative blood urea nitrogen/creatinine (BUN/Cr) ratio greater than 20. RESULTS: Patients (4698; 34.5%) with preoperative dehydration based on BUN/Cr ratio were identified. Univariate analysis was suggestive of an association between preoperative dehydration and an increased risk of DVT (1.1% compared with 0.6%; P = 0.002), urinary tract infection (2.5% compared with 1.6%; P < 0.001), and need for transfusion postoperatively (17.6% compared with 14.4%; P < 0.001). However, on the basis of multivariate regression, no significant association between dehydration and increased odds of aforementioned outcomes was identified. CONCLUSION: Preoperative dehydration does not appear to negatively affect perioperative outcomes or readmission in patients undergoing elective lumbar spine surgery. LEVEL OF EVIDENCE: 3.

Preservation of Spine Motion in the Surgical Treatment of Adolescent Idiopathic Scoliosis Using an Innovative Apical Fusion Technique: A 2-Year Follow-Up Pilot Study.

BACKGROUND: This trial reports the 2-year and immediate postremoval clinical outcomes of a novel posterior apical short-segment (PASS) correction technique allowing for correction and stabilization of adolescent idiopathic scoliosis (AIS) with limited fusion. METHODS: Twenty-one consecutive female AIS patients were treated at 4 institutions with this novel technique. Arthrodesis was limited to the short apical curve after correction with translational and derotational forces applied to upper and lower instrumented levels. Instrumentation spanned fused and unfused segments with motion and flexibility of unfused segments maintained. The long concave rods were removed at maturity. Radiographic data collected included preoperative and postoperative data for up to 2 years as well as after long rod removal. RESULTS: All 21 patients are beyond 2 years postsurgery. Average age at surgery was 14.2 years (11-17 years). A mean of 10.5 ± 1 levels per patient were stabilized and 5.0 ± 0.5 levels (48%) were fused. Cobb angle improved from 56.1° ± 8.0° to 20.8° ± 7.8° (62.2% improvement) at 1 year and 20.9° ± 8.4°, (62.0% improvement) at 2 years postsurgery. In levels instrumented but not fused, motion was 26° ± 6° preoperatively compared to 10° ± 4° at 1 year postsurgery, demonstrating 38% maintenance of mobility in nonfused segments. There was no report of implant-related complications. CONCLUSIONS: PASS correction technique corrected the deformity profile in AIS patients with a lower implant density while sparing 52% of the instrumented levels from fusion through the 2-year follow-up.

Biomechanical Analysis of Acute Proximal Junctional Failure After Surgical Instrumentation of Adult Spinal Deformity: The Impact of Proximal Implant Type, Osteotomy Procedures, and Lumbar Lordosis Restoration.

STUDY DESIGN: Computer biomechanical simulations to analyze risk factors of proximal junctional failure (PJF) following adult scoliosis instrumentation. OBJECTIVE: To evaluate the biomechanical effects on the proximal junctional spine of the proximal implant type, tissue dissection, and lumbar lordosis (LL) restoration. SUMMARY OF BACKGROUND DATA: PJF is a severe proximal junctional complication following adult spinal instrumentation requiring revision surgery. Potential risk factors have been reported in the literature, but knowledge on their biomechanics is still lacking to address the issues. METHODS: A patient-specific multibody and finite-element hybrid modeling technique was developed for a 54-year-old patient having undergone instrumented spinal fusion for multilevel stenosis resulting in PJF. Based on the actual surgery, 30 instrumentation scenarios were derived and simulated by changing the implant type at the upper instrumented vertebra (UIV), varying the extent of proximal osteotomy and the degree of LL creation. Five functional loads were simulated, and stresses and strains were analyzed for each of the 30 tested scenarios. RESULTS: There was 80% more trabecular bone with stress greater than 0.5 MPa in the UIV with screws compared to hooks. Hooks allowed 96% more mobility of the proximal instrumented functional unit compared to screws. The bilateral complete facetectomy along with posterior ligaments dissection caused a significant increase of the range of motion of the functional unit above the UIV. LL creation increased the flexion moment applied on the proximal vertebra from 7.5 to 17.5 Nm, which generated damage at the bone-screw interface that affected the screw purchase. CONCLUSION: Using hooks at UIV and reducing posterior proximal spinal element dissection lowered stress levels in the proximal junctional spinal segment and thus reduced the biomechanical risks of PJF. LL restoration was associated with increased stress levels in postoperative functional upper body flexion.

Metabolic Syndrome and 30-Day Outcomes in Elective Lumbar Spinal Fusion.

STUDY DESIGN: A retrospective cohort study. OBJECTIVE: The aim of this study was to evaluate the effect of metabolic syndrome (MetS) on 30-day morbidity and mortality following elective lumbar spinal fusion. SUMMARY OF BACKGROUND DATA: MetS is a variable combination of hypertension, obesity, elevated fasting plasma glucose, and dyslipidemia.MetS has been associated with an increased risk of postoperative morbidity and mortality in multiple surgical settings. To our knowledge, the effect of MetS on 30-day outcomes following elective lumbar spinal fusion has not been well studied. METHODS: An analysis of ACS-NSQIP data was performed between 2006 and 2013. Patients undergoing elective posterior lumbar fusion were identified. Emergency procedures, infections, tumor cases, and revision surgeries were excluded. Patients were defined as having MetS if they had a history of hypertension requiring medication, diabetes, and a body mass index (BMI) ≥30 kg/m. RESULTS: One thousand five hundred ninety (10.2%) patients with MetS were identified. A mild increase in major (P = 0.040) and minor complications (P = 0.003) in patients with MetS was noted. MetS was associated with increased rates of pulmonary complications (1.9% compared with 1.0%; P = 0.001), sepsis (1.7% compared with 0.9%; P = 0.005), and acute post-op renal failure (0.4% compared with 0%; P < 0.001). Multivariate analysis confirmed MetS to be an independent predictor of pulmonary complications [odds ratio (OR) 1.51; 95% confidence interval (95% CI 1.00-2.27); P = 0.048], sepsis (OR 1.56; 95% CI 1.01-2.42; P = 0.039), and acute postoperative renal failure (OR 6.95; 95% CI 2.23-21.67; P = 0.001). MetS status was associated with a mild increase in total hospital length of stay (4.38 compared with 3.81 days; P < 0.001). CONCLUSION: While MetS is a predictor of postoperative acute renal failure, it only slightly increases the risk of overall complications and is not associated with increased rates of 30-day reoperations or readmissions following elective lumbar fusion. LEVEL OF EVIDENCE: 3.

Biomechanical effect of pedicle screw distribution in AIS instrumentation using a segmental translation technique: computer modeling and simulation.

BACKGROUND: Efforts to select the appropriate number of implants in adolescent idiopathic scoliosis (AIS) instrumentation are hampered by a lack of biomechanical studies. The objective was to biomechanically evaluate screw density at different regions in the curve for AIS correction to test the hypothesis that alternative screw patterns do not compromise anticipated correction in AIS when using a segmental translation technique. METHODS: Instrumentation simulations were computationally performed for 10 AIS cases. We simulated simultaneous concave and convex segmental translation for a reference screw pattern (bilateral polyaxial pedicle screws with dorsal height adjustability at every level fused) and four alternative patterns; screws were dropped respectively on convex or concave side at alternate levels or at the periapical levels (21 to 25% fewer screws). Predicted deformity correction and screw forces were compared. RESULTS: Final simulated Cobb angle differences with the alternative screw patterns varied between 1° to 5° (39 simulations) and 8° (1 simulation) compared to the reference maximal density screw pattern. Thoracic kyphosis and apical vertebral rotation were within 2° of the reference screw pattern. Screw forces were 76 ± 43 N, 96 ± 58 N, 90 ± 54 N, 82 ± 33 N, and 79 ± 42 N, respectively, for the reference screw pattern and screw dropouts at convex alternate levels, concave alternate levels, convex periapical levels, and concave periapical levels. Bone-screw forces for the alternative patterns were higher than the reference pattern (p < 0.0003). There was no statistical bone-screw force difference between convex and concave alternate dropouts and between convex and concave periapical dropouts (p > 0.28). Alternate dropout screw forces were higher than periapical dropouts (p < 0.05). CONCLUSIONS: Using a simultaneous segmental translation technique, deformity correction can be achieved with 23% fewer screws than maximal density screw pattern, but resulted in 25% higher bone-screw forces. Screw dropouts could be either on the convex side or on the concave side at alternate levels or at periapical levels. Periapical screw dropouts may more likely result in lower bone-screw force increase than alternate level screw dropouts.

Analysis of Segmental Mobility Following a Novel Posterior Apical Short-Segment Correction for Adolescent Idiopathic Scoliosis.

STUDY DESIGN: A prospective, nonrandomized, multicenter study. OBJECTIVES: The purpose of this study was to evaluate the amount of motion present at instrumented but unfused segments and at motion segments adjacent to the instrumentation following application of a new posterior apical short-segment correction technique for correcting adolescent idiopathic scoliosis (AIS). SUMMARY OF BACKGROUND DATA: High-density pedicle screw instrumentation and posterior arthrodesis of all instrumented levels is the most common surgical treatment for AIS stabilization. The consequence of long fusion is an abnormal load on adjacent levels with an increased risk of future adjacent segment degeneration. METHODS: This new system applied translational and derotational forces over a short apical segment. The short apical region was prepared for fusion while maintaining motion of unfused vertebral segments. Radiographic data were collected pre-operatively, at surgery, and at 3, 6, and 12 months after surgery. RESULTS: Twenty-one female patients, mean age of 14.2 years (10.6-16.9 years) with Lenke 1A/1B curves, were enrolled. The range of motion in the unfused instrumented segment was significantly higher than the apical fused segment (11 vs. 0.9, P < 0.001). The range of motion of unfused vertebral levels distal to the construct at one year did not differ significantly from their respective pre-op values. When the analysis was extended to understand the impact of lower instrumented vertebra (LIV) on motion of unfused segments distal to the construct, it appeared that (1) the change in motion from pre-op to 12 months post-op as a function of LIV is not statistically significant; and (2) The motion of the unfused distal vertebral segments at 12 months does not statistically increase with a lower LIV. CONCLUSION: Through one year, this novel technique achieved and maintained similar AIS correction to current posterior fusion techniques while maintaining the mobility of unfused motion segments with less implant density. LEVEL OF EVIDENCE: 4.

Associations Between Body Mass and Revision Surgical Outcomes in Adult Scoliosis.

STUDY DESIGN: Retrospective cohort study. OBJECTIVE: To determine whether an association exists between high body mass index (BMI>25 kg/m) and surgical outcomes in revision adult scoliosis patients. SUMMARY OF BACKGROUND DATA: Obesity is thought to be associated with increased surgical complications and inferior clinical outcomes in adults. There are no studies analyzing the effect of obesity on surgical outcomes in revision patients for adult scoliosis. METHODS: Forty-five consecutive revision adult scoliosis patients (35 women and 10 men; mean age, 62.7±9.3 y) with a minimum follow-up of 2 years were included in this study. Patients were divided into 2 groups according to BMI: overweight (BMI≥25 kg/m, n=27) and nonoverweight (<25 kg/m, n=18). Radiographic measures, Oswestry Disability Index (ODI), Visual Analog Scale (VAS), as well as comorbidities and complications were reviewed and compared at preoperative and 2-year follow-up. RESULTS: No significant differences in surgical methods, complication rates, or radiographic measures were found between the 2 groups except for the greater preoperative and final follow-up thoracic kyphosis in the overweight group (P<0.05). A higher comorbidity rate of circulatory disorders (33.3% vs. 0%, P=0.018) and diabetes (25.9% vs. 0%, P=0.053) was observed in the overweight group, as well as a higher preoperative VAS score (7.1±1.7 vs. 5.2±2.9, P=0.031). At 2-year follow-up, VAS and ODI improvements for both groups showed significant and similar improvement from preoperative (P<0.01). CONCLUSIONS: Overweight revision adult scoliosis patients had higher thoracic kyphosis and more significant preoperative pain compared with normal-weight individuals. Overweight patients also had significantly higher rates of medical comorbidities. However, BMI did not affect the functional outcome of surgical correction or perioperative complication rates. Overweight patients benefited from surgery just as much as nonoverweight patients at 2-year follow-up.

Does obesity affect surgical outcomes in degenerative scoliosis?

STUDY DESIGN: Retrospective cohort analysis of prospectively collected data. OBJECTIVE: To determine whether an association exists between body mass and surgical outcomes in patients with degenerative scoliosis after long instrumented spinal arthrodesis (≥ 4 discs). SUMMARY OF BACKGROUND DATA: Obesity is thought to be associated with increased surgical complications and inferior clinical outcomes in adults. There are no studies analyzing the effect of obesity on surgical outcomes in patients with degenerative scoliosis after long instrumented spinal arthrodesis. METHODS: Eighty-four consecutive patients with degenerative scoliosis (69 females and 15 males; mean age, 68.6 ± 8.0 yr) with a minimum follow-up of 2 years were included in this study. Patients were divided into 3 groups according to body mass index (BMI): obese (BMI ≥ 30 kg/m², n = 19), overweight (BMI = 25-29.9 kg/m², n = 35), and normal weight (BMI < 25 kg/m², n = 30). Radiographical measures, Oswestry Disability Index, visual analogue scale score, as well as comorbidities and complications were reviewed and analyzed for all patients preoperatively and at 1- and 2-year follow-ups. RESULTS: Compared with the normal weight group, no significant differences in surgical methods, comorbidities, complication rates, curve correction, or radiographical measures were found in the obese and overweight groups, except for a greater preoperative lumbar lordosis in the overweight group (-40.3° ± 13.8° vs. -26.0° ± 18.9°, P < 0.05). At 2-year follow-up, Oswestry Disability Index and visual analogue scalescores improved significantly in all groups compared with preoperatively (P < 0.01). The changes of Oswestry Disability Index and visual analogue scalescores from preoperatively to final follow-up were similar in the 3 groups (P > 0.05). CONCLUSION: Obesity did not affect the amount of deformity correction and did not increase comorbidities and postoperative complication rates. Overweight patients had a greater lumbar lordosis before surgery than normal weight patients. Obese and overweight patients benefited from surgery just as much as normal weight patients at 2-year follow-up.

Comparative analysis of clinical outcomes and complications in patients with degenerative scoliosis undergoing primary versus revision surgery.

STUDY DESIGN: Retrospective cohort analysis of prospectively collected data. OBJECTIVE: To compare clinical outcomes and postoperative complications in patients with lumbar degenerative scoliosis who underwent primary (P) versus revision (R) surgery. SUMMARY OF BACKGROUND DATA: Revision surgery for spinal deformity is technically challenging and may be associated with greater risks of complications and inferior clinical outcomes. There is a paucity of data in the literature comparing primary versus revision surgery in patients with degenerative scoliosis with respect to their clinical outcomes and complications. METHODS: An analysis of 84 consecutive patients with degenerative scoliosis who underwent primary versus revision surgery between 2002 and 2010 with a minimum 2-year follow-up was performed. RESULTS: There were 53 patients in the primary group and 31 in the revision group. The average number of previously operated levels in the revision group was 3.5 ± 2.6. Mean age at surgery, sex, and body mass index were similar between the 2 groups, as well as comorbidities and postoperative complication rates (P > 0.05). Although a greater preoperative coronal imbalance was noticed in the revision group (P: 2.5 cm vs. R: 4.8 cm, P = 0.022), the final radiographical measures were comparable between the 2 groups. At 2-year follow-up, Oswestry Disability Index and visual analogue scale scores improved significantly in both groups compared with preoperatively (P < 0.001). The improvement in scores of Oswestry Disability Index and visual analogue scale preoperatively to final follow-up was similar between the 2 groups (P > 0.05). CONCLUSION: Revision patients achieved the same radiographical and clinical outcomes as primary patients. The complication rates were similar between primary and revision patients. Revision patients benefit from surgery just as much as primary patients at 2-year follow-up.

Revision spinal fusion in patients older than 75: is it worth the risks?

STUDY DESIGN: Retrospective clinical study of a prospective database. OBJECTIVE: This study aims to determine whether revision spinal fusion surgery is worthwhile in patients older than 75 from a risk-benefit perspective. SUMMARY OF BACKGROUND DATA: The benefits of spinal fusion in patients older than 65 is well documented. However, the clinical benefit to patients older than 75 of revision surgery, which often yields worse outcomes with higher complication rates, is uncertain. METHODS: Ninety-nine consecutive patients older than 75 with minimum 2-year follow-up underwent spinal fusion as either a primary (n = 58) or revision (n = 41) operation. Diagnoses were spondylolisthesis (n = 43), scoliosis (n = 28), kyphosis (n = 5), and other degenerative spinal disorders (n = 26). Outcomes were obtained prospectively by visual analogue scale (VAS) and Oswestry Disability Index (ODI) at preoperative, 1-year, 2-year, and latest follow-up. RESULTS: Revision patients had significantly worse scores compared with primary patients at all time intervals, for both VAS (preoperative: 6.4 vs. 5.8, 1 yr: 3.6 vs. 2.4, 2 yr: 4.7 vs. 2.5) and ODI (preoperative: 52.2 vs. 44.1, 1 yr: 37.3 vs. 25.6, 2 yr: 47.0 vs. 25.0). Both groups improved significantly at 1 year postoperatively. At 2 years, the results of revision surgery deteriorated (ΔVAS: -1.7, ΔODI: -5.2), whereas the benefits of primary procedures were maintained (ΔVAS: -3.3, ΔODI: -19.1). Complications were generally greater in the revision group and included revision surgery (8[19.5%] vs. 7[12.1%]), nonunion (2[4.9%] vs. 3[5.2%]), adjacent level fracture (4[9.8%] vs. 6[10.3%]), infection (6[14.7%] vs. 2[3.4%]), foot drop (0[0.0%] vs. 4[6.9%]), imbalance (4[9.8%] vs. 1[1.7%]), pulmonary failure (1[2.4%] vs. 1[1.7%]), and death (0[0.0%] vs. 1[1.7%]). CONCLUSION: Despite having worse initial ODI and VAS scores, revision patients older than 75 initially benefit as much as patients older than 75 undergoing primary operations. However, at 2 years, revision patients do not have a sustained benefit despite a higher complication rate. LEVEL OF EVIDENCE: 4.

Characteristics of immediate and fatigue strength of a dual-threaded pedicle screw in cadaveric spines.

BACKGROUND CONTEXT: Novel dual-threaded screws are configured with overlapping (doubled) threads only in the proximal shaft to improve proximal cortical fixation. PURPOSE: Tests were run to determine whether dual-threaded pedicle screws improve pullout resistance and increase fatigue endurance compared with standard pedicle screws. STUDY DESIGN/SETTING: In vitro strength and fatigue tests were performed in human cadaveric vertebrae and in polyurethane foam test blocks. PATIENT SAMPLE: Seventeen cadaveric lumbar vertebrae (14 pedicles) and 40 test sites in foam blocks were tested. OUTCOME MEASURES: Measures for comparison between standard and dual-threaded screws were bone mineral density (BMD), screw insertion torque, ultimate pullout force, peak load at cyclic failure, and pedicular side of first cyclic failure. METHODS: For each vertebral sample, dual-threaded screws were inserted in one pedicle and single-threaded screws were inserted in the opposite pedicle while recording insertion torque. In seven vertebrae, axial pullout tests were performed. In 10 vertebrae, orthogonal loads were cycled at increasing peak values until toggle exceeded threshold for failure. Insertion torque and pullout force were also recorded for screws placed in foam blocks representing healthy or osteoporotic bone porosity. RESULTS: In bone, screw insertion torque was 183% greater with dual-threaded than with standard screws (p<.001). Standard screws pulled out at 93% of the force required to pull out dual-threaded screws (p=.42). Of 10 screws, five reached toggle failure first on the standard screw side, two screws failed first on the dual-threaded side, and three screws failed on both sides during the same round of cycling. In the high-porosity foam, screw insertion torque was 60% greater with the dual-threaded screw than with the standard screw (p=.005), but 14% less with the low-porosity foam (p=.07). Pullout force was 19% less with the dual-threaded screw than with the standard screw in the high-porosity foam (p=.115), but 6% greater with the dual-threaded screw in the low-porosity foam (p=.156). CONCLUSIONS: Although dual-threaded screws required higher insertion torque than standard screws in bone and low density foam, dual-threaded and standard pedicle screws exhibited equivalent axial pullout and cyclic fatigue endurance. Unlike single-threaded screws, the mechanical performance of dual-threaded screws in bone was relatively independent of BMD. In foam, the mechanical performance of both types of screws was highly dependent on porosity.

Transforaminal lumbar interbody fusion with rhBMP-2 in spinal deformity, spondylolisthesis, and degenerative disease--part 1: Large series diagnosis related outcomes and complications with 2- to 9-year follow-up.

STUDY DESIGN: Retrospective review of prospectively collected data. OBJECTIVE: To evaluate long-term clinical outcomes and complications of the transforaminal lumbar interbody fusion (TLIF) procedure from a large consecutive series, without industry funding. Clinical outcomes and complications are analyzed by diagnosis and primary versus revision surgery to assess whether TLIF with bone morphogenic protein (BMP) is appropriate for common use in deformity, spondylolisthesis, and degenerative disease. SUMMARY OF BACKGROUND DATA: A common method for achieving spinal arthrodesis includes TLIF with a cage and off-label interbody BMP-2, supported by posterior arthrodesis and a pedicle screw construct. There are no large studies analyzing outcomes and complications after TLIF in different diagnoses, for primary and revision surgery, leading some to question the widespread use of TLIF. METHODS: A total of 509 consecutive adults underwent open posterior instrumented fusion, augmented with TLIF at 872 discs using a cage and rhBMP-2, with minimum 2-year follow-up. Cohort diagnoses included 179 degenerative, 207 spondylolisthesis, and 123 deformity patients. Patient age averaged 61 years, 207 had undergone prior decompression or fusion surgery. All patients underwent posterior instrumented fusion and pedicle screw instrumentation at average 3.6 levels (range, 1-16); all patients had TLIF 1.7 levels (range, 1-4 levels) with BMP and autograft, stabilized with an interbody cage. RESULTS: At average 59 months follow-up, 12 patients developed pseudoarthrosis, 8 at TLIF levels (8/872 discs, 0.92%) most commonly at L5-S1 (6/8). Significant clinical improvement was noted in patients with deformity, spondylolisthesis, and degenerative disease undergoing primary and revision surgery. Overall, visual analogue scale preoperative score was 6.6, at 1 year 3.8, at 2 years 3.5 (P < 0.001) and the preoperative ODI was 50.9, at 1 year 36.1, and at 2 years 35.0 (P < 0 0.001). Pain medication requirements also declined. CONCLUSION: The efficacy of TLIF with BMP is supported in this large series with long-term follow-up, independent of industry. Reliable fusion and improved outcomes can be expected in adults undergoing TLIF for deformity, spondylolisthesis, and degenerative disease. Most complications occurred in patients with deformity. LEVEL OF EVIDENCE: 3.