An analysis of spine fusion outcomes in sheep pre-clinical models.

PURPOSE: The ovine model is often used to evaluate new spine fusion technologies prior to clinical testing. An important aspect of designing sheep surgery protocols is to select the appropriate postoperative time period for comparing fusion outcomes. Unfortunately, determining the ideal study endpoint is complicated by the fact that prior published studies have not used consistent timeframes. Thus, the primary aim of this study was to provide a reference for investigators as to the expected fusion outcomes of control groups at varying timepoints in sheep spine surgery models. METHODS: We identified published sheep fusion studies using autograft, interbody cages, and/or instrumentation. Fusion data were extracted, converted to a common scale, and analyzed across studied timepoints. RESULTS: Overall, 29 studies of 360 fusion levels were identified: 11 ALIF (158 levels), 3 PLIF/TLIF (28 levels), 8 PLF (90 levels), and 7 ACDF (84 levels). Studied timepoints ranged from 4 to 48 weeks postoperative. In general, fusion rates varied across techniques and instrumentation. The time to reach solid fusion differed by as many as 20 weeks between control groups. CONCLUSIONS: Recommended timeframes for future studies designed to show either superiority over controls or equivalent outcomes with controls were developed based on aggregate results. Designating ideal study endpoints for sheep fusion models has both ethical implications associated with responsible use of animals in research, and economic implications given the cost of animal research. The current results can guide the development of future research methods and help investigators choose appropriate study timelines for various control groups.

A new 3-dimensional method for measuring precision in surgical navigation and methods to optimize navigation accuracy.

PURPOSE: Description of a novel method for evaluation of pedicle screws in 3 dimensions utilizing O-arm(®) and StealthStation(®) navigation; identifying sources of error, and pearls for more precise screw placement. METHODS: O-arm and StealthStation navigation were utilized to place pedicle screws. Initial and final O-arm scans were performed, and the projected pedicle probe track, projected pedicle screw track, and final screw position were saved for evaluation. They were compared to evaluate the precision of the system as well as overall accuracy of final screw placement. RESULTS: Thoracolumbar deformity patients were analyzed, with 153 of 158 screws in adequate position. Only 5 screws were malpositioned, requiring replacement or removal. All 5 were breached laterally and no neurologic or other complications were noted in any of these patients. This resulted in 97 % accuracy using the navigation system, and no neurological injuries or deficits. The average distance of the screw tip and angle of separation for the predicted path versus the final pedicle screw position were analyzed for precision. The mean screw tip distance from the projected tip was 6.43 mm, with a standard deviation of 3.49 mm when utilizing a navigated probe alone and 5.92 mm with a standard deviation of 3.50 mm using a navigated probe and navigated screwdriver (p = 0.23). Mean angle differences were 4.02° and 3.09° respectively (p < 0.01), with standard deviations of 2.63° and 2.12°. CONCLUSIONS: This new technique evaluating precision of screw placement in 3 dimensions improves the ability to define screw placement. Pedicle screw position at final imaging showed the use of StealthStation navigation to be accurate and safe. As this is a preliminary evaluation, we have identified several factors affecting the precision of pedicle screw final position relative to that predicted with navigation.

Long-term Treatment Effects of Lumbar Arthrodeses in Degenerative Disk Disease: A Systematic Review With Meta-Analysis.

STUDY DESIGN: Systematic review with meta-analysis. OBJECTIVE: To (1) evaluate long-term patient-centered clinical outcomes after lumbar arthrodesis with or without decompression for lumbar spondylosis (LS); and (2) compare these outcomes with those of alternative treatments, including nonsurgical and surgical which maintain mobility of the lumbar spine. SUMMARY OF BACKGROUND DATA: The effective treatment of LS is a complex clinical and economic concern for patients and health care providers. SELECTION CRITERIA: (1) randomized controlled clinical trials (RCTs) comparing treatment effects of lumbar arthrodesis with other interventions; (2) participants: skeletally mature adults with lumbar degenerative disk disease. SEARCH METHODS: Ovid MEDLINE, Embase, the Cochrane Library, and others. All years through February of 2013 were included. Patient-centered clinical outcomes before treatment, at 12, 24, or >24 months of follow-up, and rate of complications and additional surgical treatment were collected. A meta-analysis was performed to evaluate pooled treatment effects. The GRADE approach was applied to evaluate the level of evidence. RESULTS: The review included 38 studies of 5738 participants. All studies showed strong or at least moderate treatment effects of lumbar arthrodesis at 12, 24, and 48-72 months of follow-up. The level of evidence was moderate at 12 and 24 months, and low at 48-72 months. The pooled long-term treatment effect of lumbar arthrodesis exceeded those of: nonsurgical treatment (P<0.0001) with a moderate level of evidence, and decompression without fusion (P=0.005) with a low level of evidence. The treatment effect of lumbar arthrodesis showed a small inferiority versus arthroplasty at 12 and 24 months of follow-up (P<0.001), but not after 24 months postoperative. CONCLUSIONS: This review indicates that surgical stabilization of the lumbar spine is an effective treatment for LS; in particular, for patients with severe chronic low back pain that has been resistant to ≥3 months of conservative therapy.

Perioperative and long-term clinical outcomes for bone morphogenetic protein versus iliac crest bone graft for lumbar fusion in degenerative disk disease: systematic review with meta-analysis.

STUDY DESIGN: Systematic review with meta-analysis. OBJECTIVES: To compare the perioperative and long-term postoperative effectiveness of bone morphogenetic protein (BMP) for lumbar arthrodesis in skeletally mature adults with degenerative disk disease (DDD) to that of the current golden standard treatment, iliac crest autologous bone graft (ICBG). SUMMARY OF BACKGROUND DATA: The treatment efficacy of lumbar arthrodesis in DDD is a complex clinical and economic issue for patients and health care providers. METHODS: Comprehensive electronic literature search was performed using following databases: Ovid MEDLINE; Embase; Cochrane Library; Central Register of Controlled Trials (CENTRAL); Database of Abstracts of Reviews of Effects; Methodology Register; Technology Assessment Database; and Economic Evaluation Database. The full year ranges of each database until May of 2012 were included. RESULTS: Eight randomized controlled clinical trials of 383 citations were selected. The included studies involved 1138 participants. The pooled 2-year postoperative clinical outcomes were equivalent in BMP and ICBG groups, and exceeded minimum clinically important differences for Oswestry Disability Index, SF-36 (physical scale), and numeric rating scale (back pain). ICBG was associated with increased pain and complications at the donor site (P<0.01). The pooled average operative time was 21 minutes less in BMP versus ICBG (P<0.001). The pooled rate of additional surgical treatment was 2 times less in the BMP than in the ICBG groups (P=0.006). The pooled risk of nonunion at 24-month follow-up was 2 times less in the BMP than in the ICBG groups (P=0.037), however, this effect was likely biased. CONCLUSIONS: BMP, in particular rhBMP-2, is a good alternative to autogenous bone graft, especially in cases when harvesting of autologous bone is contraindicated or undesirable, operation time is limited, and there are no contraindications for BMP use.However, the current study did not reveal evidence robust enough to develop strong medical recommendations concerning BMP use for lumbar arthrodesis in degenerative disk disease.

Mineralization and collagen orientation throughout aging at the vertebral endplate in the human lumbar spine.

The human vertebral body and intervertebral disc interface forms the region where the cartilaginous endplate, annulus fibrosis and bone of the vertebral body are connected through an intermediate calcified cartilage layer. While properties of both the vertebral body and components of the disc have been extensively studied, limited quantitative data exists describing the microstructure of the vertebral body-intervertebral disc interface in the spine throughout development and degeneration. Quantitative backscattered scanning electron and second harmonic generation confocal imaging were used to collect quantitative data describing the mineral content and collagen fiber orientation across the interface, respectively. Specimens spanned ages 56 days to 84 years and measurements were taken across the vertebral endplate at the outer annulus, inner annulus and nucleus pulposis. In mature and healthy endplates, collagen fibers span the calcified cartilage layer in all regions, including the endplate adjacent to the central nucleus pulposis. We also observed an abrupt transition from high mineral volume fractions (35-50%) to 0% over short distances measuring 3-15 microns in width across the transition from calcified cartilage to unmineralized cartilage. The alignment of collagen fibers at the outer annulus and thickness of the CC layer indicated that collagen fiber mineralization adjacent to the bone may serve to anchor the soft tissue without a gradual change in material properties. Combining backscattered scanning electron microscopy and second harmonic generation imaging on the same sections thus enable a novel assessment of morphology and properties in both mineralized and soft tissues at the vertebral body-intervertebral disc throughout development and aging.

Alternative Uses of O-Arm and Stealth Navigation Technology Over 10 Years: The University of Colorado Experience.

Intraoperative computed tomography scanning with O-arm and use of Stealth navigation can improve surgical outcomes in a variety of orthopedic subspecialties. In spine surgery, the accuracy, precision, and safety of pedicle screw and interbody implant placement has improved. This technology is now routinely used in percutaneous pedicle screw placement and minimally invasive sacroiliac joint fusion. Other applications include, but are not limited to, isthmic pars defect repair, lumbosacral pseudoarticulation resection in Bertolotti's syndrome, radiofrequency ablation, and en bloc tumor resection. Intraoperative navigation has numerous applications, and use of this technology should continue to evolve as the technology advances. [Orthopedics. 2023;46(2):e89-e97.].

Catastrophic acute failure of pelvic fixation in adult spinal deformity requiring revision surgery: a multicenter review of incidence, failure mechanisms, and risk factors.

OBJECTIVE: There are few prior reports of acute pelvic instrumentation failure in spinal deformity surgery. The objective of this study was to determine if a previously identified mechanism and rate of pelvic fixation failure were present across multiple institutions, and to determine risk factors for these types of failures. METHODS: Thirteen academic medical centers performed a retrospective review of 18 months of consecutive adult spinal fusions extending 3 or more levels, which included new pelvic screws at the time of surgery. Acute pelvic fixation failure was defined as occurring within 6 months of the index surgery and requiring surgical revision. RESULTS: Failure occurred in 37 (5%) of 779 cases and consisted of either slippage of the rods or displacement of the set screws from the screw tulip head (17 cases), screw shaft fracture (9 cases), screw loosening (9 cases), and/or resultant kyphotic fracture of the sacrum (6 cases). Revision strategies involved new pelvic fixation and/or multiple rod constructs. Six patients (16%) who underwent revision with fewer than 4 rods to the pelvis sustained a second acute failure, but no secondary failures occurred when at least 4 rods were used. In the univariate analysis, the magnitude of surgical correction was higher in the failure cohort (higher preoperative T1-pelvic angle [T1PA], presence of a 3-column osteotomy; p < 0.05). Uncorrected postoperative deformity increased failure risk (pelvic incidence-lumbar lordosis mismatch > 10°, higher postoperative T1PA; p < 0.05). Use of pelvic screws less than 8.5 mm in diameter also increased the likelihood of failure (p < 0.05). In the multivariate analysis, a larger preoperative global deformity as measured by T1PA was associated with failure, male patients were more likely to experience failure than female patients, and there was a strong association with implant manufacturer (p < 0.05). Anterior column support with an L5-S1 interbody fusion was protective against failure (p < 0.05). CONCLUSIONS: Acute catastrophic failures involved large-magnitude surgical corrections and likely resulted from high mechanical strain on the pelvic instrumentation. Patients with large corrections may benefit from anterior structural support placed at the most caudal motion segment and multiple rods connecting to more than 2 pelvic fixation points. If failure occurs, salvage with a minimum of 4 rods and 4 pelvic fixation points can be successful.

A biomechanical study on the effects of rib head release on thoracic spinal motion.

PURPOSE: Idiopathic scoliosis is generally treated by surgical derotation of the spine. A secondary goal of surgery is minimization of the "rib hump" deformity. Previous studies have evaluated the effects of surgical releases such as diskectomy, costo-vertebral joint release, facetectomy, and costoplasty on spine mobilization and overall contribution to thoracic stability. The present study was designed to evaluate the biomechanical effects of the rib head joints alone on axial rotation, lateral bending, and segmental rotation, without diskectomy or disruption of anterior or posterior elements. METHODS: Four female cadaver thoracic spines with intact sternums and rib cages were mounted in an Instron servo-hydraulic bi-axial MTS. In a 12-step sequence, the costo-vertebral and costo-transverse ligaments were released, first unilaterally from T10-T7, then bilaterally until complete disarticulation between the rib heads and the vertebral bodies. After each release, biomechanical testing, including axial rotation and lateral bending, was performed. Vertebral body displacement was also measured using electromagnetic trackers. RESULTS: We found that rib displacement during axial rotation was significantly increased by unilateral rib head release, and torque was decreased with each successive cut. We also found increased vertebral displacement with sequential rib head release. CONCLUSIONS: Our results show that sequential costo-vertebral joint releases result in a decrease in the force required for axial rotation and lateral bending, coupled with an increase in the displacement of vertebral bodies. These findings suggest that surgical release of the costo-transverse and costo-vertebral ligaments can facilitate segmental correction in scoliosis by decreasing the torso's natural biomechanical resistance to this correction.

Pre-Operative Planning in Complex Deformities and Use of Patient-Specific UNiD™ Instrumentation.

STUDY DESIGN: Review of current literature and authors experience. OBJECTIVE: Pre-operative planning is an integral part of complex spine surgery. With the advent of computer-assisted planning, multiple surgical plans can be evaluated utilizing alignment parameters, and the best plan for individual patients selected. However, the ability to evaluate and measure surgical correction goals intraoperatively are still limited. The use of patient-specific UNiD rods, created based on pre-operative plans, provided an initial tool for implementation of pre-operative plans in the operative setting. METHODS: A literature review for the use of patient-specific UNiD rods in thoracolumbar spine complex surgery was performed. The articles were selected and reviewed for the initial experience/outcomes of these techniques. Further, the initial experience of the authors at The University of Colorado is described. RESULTS: The use of UNiD patient-specific rods, in combination with pre-operative planning has been shown to provide a higher rate of patients with spinopelvic alignment parameters within currently accepted ranges. This includes improvement of sagittal vertical axis (SVA) < 50 mm and pelvic incidence (PI)-lumbar lordosis (LL) = ± 10°. Multiple authors have shown improvement in pelvic tilt to age adjusted values but note continued difficulties in obtaining correction goals. CONCLUSIONS: The use of pre-operative planning software and UNiD patient-specific rods has been shown to improve surgeon's ability to achieve spinopelvic alignment parameters, specifically SVA and PI-LL, along with other possible benefits. Further research is needed regarding long-term value of the technology.

Blockade of Osteoclast-Mediated Bone Resorption With a RANKL-Inhibitor Enhances Bone Formation in a Rat Spinal Fusion Model.

STUDY DESIGN: Rat spine fusion model. OBJECTIVE: The present study aimed to determine whether administration of osteoprotegerin (OPG) in a rat model of spinal fusion increases bone volume, bone density, and decreases osteoclasts in the fusion mass. SUMMARY OF BACKGROUND DATA: OPG is a soluble RANK-ligand inhibitor that blocks osteoclast differentiation and activation. This makes it a potential agent to control the remodeling process and enhance bone mass during spinal fusion. MATERIALS AND METHODS: Forty-eight male Sprague-Dawley rats received a one-level spinal fusion of L4-L5 with bone allograft. Rats were then divided into four groups according to initiation of treatment: (1) saline on day 0 (saline), (2) OPG on day 0 (OPG D0), (3) OPG on day 10 (OPG D10), and (4) OPG on day 21 (OPG D21) postsurgery. After their initial injection, rats received weekly subcutaneous injections of OPG (10 mg/kg) and were euthanized six weeks postsurgery. MicroCT analysis of the fusion site and histological analysis of bone surface for quantification of osteoclast lining was performed. RESULTS: Increased bone volume in the fusion site and around the spinous process was seen in OPG D0 and OPG D10 when compared with saline. Mean trabecular thickness was greater in all groups receiving OPG compared with saline, with OPG D0 and OPG D10 having significantly greater mean trabecular thickness than OPG D21. All OPG groups had less bone surface lined with osteoclasts when compared with Saline, with OPG D0 and OPG D10 having fewer than OPG D21. CONCLUSIONS: This study indicates that OPG inhibited osteoclast bone resorption, which led to greater bone at the fusion site. Future studies investigating OPG on its own or in combination with an osteogenic factor to improve spinal fusion outcomes are warranted to further elucidate its potential therapeutic effect.

Postoperative pelvic incidence (PI) change may impact sagittal spinopelvic alignment (SSA) after instrumented surgical correction of adult spine deformity (ASD).

OBJECTIVES: To study factors causing postoperative change of PI after surgical correction of ASD and to assess the effect of this variability on postoperative PI-LL mismatch. BACKGROUND: PI is used as an individual constant to define lumbar lordosis (LL) correction goal (PI-LL < 10). Postoperative changes of PI were shown but with opposite vectors. The impact of the PI variability on the postoperative PI-LL has not been studied. METHODS: The medical and radiographic data analyzed for patients who underwent long posterior instrumented spinal fusion. Inclusion criteria are age, ≥ 20 years old; ASD due to degenerative disk disease (DDD) or scoliosis (DS); ≥ 3 levels fused; and 2-year follow-up or revision. Studied parameters are LL (L1-S1), PI, sacral slope (SS), pelvic tilt (PT), and PI-LL. Measurement error and postoperative changes were defined. Statistical analysis includes ANOVA, correlation, regression, and risk assessment by odds ratio; P ≤ 0.05 considered statistically significant. RESULTS: Eighty patients were included: mean age, 62.4 years-old (SD, 11.1); female, 63.7%; mean body mass index (BMI), 27.1 (SD, 5.6). Distribution of patients by follow-ups includes preoperative 100%; postoperative (1-3 weeks), 100%; 11-13 months. 90%; 22-26 months, 58%; and revision: 24%. Pre- versus postoperative PI (∆PI) changed both positively and negatively and the absolute value of change|∆PI| exceeded measurement error (P ≤ 0.05) reaching as high as 31°, and progressed with time; R2 dropped from 0.73 to 0.45 (P < 0.001); ∆PI depended on disproportional changes of SS and PT, preoperative PI, and change of LL. Obesity, DS, and absence of sacroiliac fixation increased |∆PI|. The risk of LL insufficient correction (PI-LL > 10°) associated with a |∆PI|> 6°, P = 0.05. Sacroiliac fixation diminished PI variability only during the first postoperative year. CONCLUSION: Preoperative variability and postoperative instability of PI diminish the applicability of the PI-LL < 10° goal to plan correction of LL. An alternative method is offered. LEVEL OF EVIDENCE: IV.

Evaluation of ABM/P-15 versus autogenous bone in an ovine lumbar interbody fusion model.

A prospective, randomized study was performed in an ovine model to compare the efficacy of an anorganic bovine-derived hydroxyapatite matrix combined with a synthetic 15 amino acid residue (ABM/P-15) in facilitating lumbar interbody fusion when compared with autogenous bone harvested from the iliac crest. P-15 is a biomimetic to the cell-binding site of Type-I collagen for bone-forming cells. When combined with ABM, it creates the necessary scaffold to initiate cell invasion, binding, and subsequent osteogenesis. In this study, six adult ewes underwent anterior-lateral interbody fusion at L3/L4 and L4/L5 using PEEK interbody rings filled with autogenous bone at one level and ABM/P-15 at the other level and no additional instrumentation. Clinical CT scans were obtained at 3 and 6 months; micro-CT scans and histomorphometry analyses were performed after euthanization at 6 months. Clinical CT scan analysis showed that all autograft and ABM/P-15 treated levels had radiographically fused outside of the rings at the 3-month study time point. Although the clinical CT scans of the autograft treatment group showed significantly better fusion within the PEEK rings than ABM/P-15 at 3 months, micro-CT scans, clinical CT scans, and histomorphometric analyses showed there were no statistical differences between the two treatment groups at 6 months. Thus, ABM/P-15 was as successful as autogenous bone graft in producing lumbar spinal fusion in an ovine model, and it should be further evaluated in clinical studies.

The Prevalence of the Use of MIS Techniques in the Treatment of Adult Spinal Deformity (ASD) Amongst Members of the Scoliosis Research Society (SRS) in 2016.

STUDY DESIGN: Electronic survey administered to Scoliosis Research Society members. OBJECTIVE: To determine the prevalence of minimally invasive surgery (MIS) techniques for the treatment of adult spinal deformity. SUMMARY OF BACKGROUND DATA: There is a paucity of data available on the practice pattern, prevalence of minimally invasive spine surgery, and the preferred minimally invasive techniques in the treatment of adult spine deformity. METHODS: An electronic nine-question survey regarding individual usage pattern of minimally invasive spine surgery techniques was administered in 2016 to the members of the Scoliosis Research Society. Determinants included complexity in condition of patient population, prevalence of use of minimally invasive techniques in the surgeon's practice, prevalence of use of a particular MIS technique, strategy elected during surgery, adoption of staging of procedures and timing between staging of procedures. RESULTS: A total of 357 surgeons responded (61.3% response rate), and 154 (43.1%) of the respondents said that they use MIS as a part of their surgical treatment of adult spinal deformity. However, of these 154 respondents, 67 (43.5%) said that their MIS usage in deformity practice was between 1% and 20%. Only 11 (7.2%) said that they used MIS 81% to 100% of the time. The top MIS approaches that surgeons chose were MIS lateral lumbar interbody fusion 109 (70.59%) and MIS percutaneous screws 91 (58.8%). CONCLUSIONS: The low rate of adoption of these techniques among the SRS members may be due to the false perception that there is not enough data to support that MIS techniques are better. This and the fact that a practitioner needs to be facile at different MIS techniques may be the true impediment to the adoption of MIS techniques in the treatment of ASD. LEVEL OF EVIDENCE: Level IV.

Development of Bilateral Facet Cysts Causing Recurrent Symptoms After Decompression and the Placement of an Intralaminar Implant: A Case Report.

CASE: We report the development of bilateral symptomatic facet joint cysts in a 78-year-old man who had been treated with decompression and placement of a coflex device (Paradigm Spine) at L3-L4 and L4-L5. Preoperative imaging clearly demonstrated fluid in the facet joints without cysts. He underwent standard surgical treatment, but developed symptomatic facet joint cysts at 4 months postoperatively. The patient was treated with a revision decompression and replacement of the devices; there were no issues at the 32-month follow-up. CONCLUSION: While the coflex device has possible long-term biomechanical advantages, vigilance with adherence to appropriate decompression surgical technique is necessary.

Surgical Intervention for Cauda Equina Syndrome in the Second and Third Trimesters of Pregnancy: A Report of Three Cases.

CASE: Low back pain affects >50% of pregnant women. However, cauda equina syndrome (CES) during pregnancy is rare. Because a delay in treatment increases the risk of irreversible neurologic damage, acute onset is regarded as a surgical emergency. We describe 3 cases of CES in pregnant women at 24, 27, and 30 weeks' gestation, respectively. CONCLUSION: All 3 of the patients underwent surgical decompression in the prone position under general anesthesia with continuous external monitoring of the fetal heart rate. Intraoperative findings were noteworthy for epidural venous plexus engorgement in 2 of the patients. There were no complications for the patients or the fetuses, and all 3 of the patients had postoperative resolution of the neurologic symptoms.

One-step Minimally Invasive Pedicle Screw Instrumentation Using O-Arm and Stealth Navigation.

STUDY DESIGN: Description of a navigated, single-step, minimally invasive technique for the placement of pedicle screws. OBJECTIVE: To describe a new technique for minimally invasive placement of pedicle screws in the lumbar spine using O-arm and StealthStation navigation in combination. SUMMARY OF BACKGROUND DATA: Minimally invasive surgical techniques are described in the literature as safe and effective methods for pedicle screw instrumentation. These techniques increase radiation exposure and prompt multiple instrument passes through the pedicle. MATERIALS AND METHODS: In total, 35 adult patients (187 screws) underwent lumbar surgery with pedicle screw placement using the 1- (8 patients/48 screws) or 2-step (27 patients/139 screws) technique. Complications associated with instrumentation were noted. Pedicle screw position was evaluated. RESULTS: Of 187 screws placed, 181 (96.8%) were found to be fully contained within the pedicle (grade 1) and 4 (2.1%) had a breach of <2 mm. In the 1-step technique, no screws were malpositioned. One screw at S1 with inadequate fixation was replaced with a screw 1 mm larger in diameter. In the 2-step technique, 2 screws (1.06% overall) were revised due to inferior breach of the pedicle. No neurological sequelae were noted. Also, 1 screw was deemed too long at S1 and was replaced with a shorter screw. None of the revised pedicle screws caused neuromonitoring changes and the breaches were found intraoperatively on 3D imaging. CONCLUSIONS: Using O-arm and StealthStation navigation with minimally invasive surgical technology for placement of posterior spinal instrumentation is safe, effective, and limits radiation exposure.

Stand-alone Anterior Lumbar Interbody, Transforaminal Lumbar Interbody, and Anterior/Posterior Fusion: Analysis of Fusion Outcomes and Costs.

Fusion outcomes and costs of stand-alone anterior lumbar interbody fusion (ALIF), transforaminal lumbar interbody fusion (TLIF) in association with posterior fusion, and anterior/posterior (A/P) fusion were compared using clinical, radiographic, and billing data. Adult patients with symptomatic 1- or 2-level degenerative disk disease in isolation or in association with a grade 1 or 2 degenerative or lytic spondylolisthesis and canal and/or foraminal stenosis who underwent elective stand-alone ALIF, TLIF, or A/P fusion were compared. The analysis focused primarily on fusion rates and costs and secondarily on radiographic and clinical parameters. One hundred six patients at least 2 years beyond surgery (ALIF, 53; TLIF, 17; A/P fusion, 36) were reviewed. Demographics were similar except for age, with the ALIF group being younger (mean, 37.8 years) than the other groups (TLIF, 53.1 years; A/P fusion, 48.2 years). There were no differences between the groups in fusion rates or outcomes as assessed by the Numeric Rating Scale. Compared with the other 2 groups, the ALIF group had a significantly shorter operative time, less blood loss, and a shorter stay (P<.0001). Evaluation of radiographic parameters revealed significant differences regarding disk angle (P<.001), disk height (P<.0001), and pelvic tilt (P=.001) favoring ALIF and A/P fusion over TLIF. Stand-alone ALIF should be considered in the management of patients with 1- or 2-level lumbar degenerative disk disease for which the pathology can be addressed adequately via this approach. [Orthopedics. 2018; 41(5):e655-e662.].

Calcium phosphates as bone graft extenders.

Although iliac crest autograft is the gold standard for fusion, many patien experience permanent pain at the donor site that is likely underestimated in the literature. As the population requiring reconstructive spine surgery increases, so does the need for a successful substitute for autologous bone. One such large surface bone graft substitute that has gained popularity in spine surgery is calcium phosphate. However, the characteristics of various calcium phosphate products have not been previously reviewed in the literature. Thus, this article presents a comparative analysis of the physiochemical attributes of calcium phosphate materials used in spine surgery.

Spinopelvic Parameters in Asymptomatic Subjects Without Spine Disease and Deformity: A Systematic Review With Meta-Analysis.

STUDY DESIGN: A systematic review with meta-analysis. OBJECTIVE: To combine published data, focusing on the development of optimal spinopelvic parameters in adult asymptomatic subjects without spine deformity while taking into consideration the impact of potential confounders. SUMMARY OF BACKGROUND DATA: A well-grounded approach to define the optimal spinopelvic parameters is necessary for planning surgical correction of spine deformity. MATERIALS: Selection criteria: (1) randomized and nonrandomized prospective, cross-sectional, and retrospective studies; (2) participants: asymptomatic subjects without spine deformity aged above 18 years; (3) studied parameters: lumbar lordosis (LL), pelvic incidence, sacral slope, and pelvic tilt; (4) potential confounders: method of measurement, sex, age, ethnicity, weight, height, and body mass index. Search method: Ovid MEDLINE (1946-current) and EMBASE (1980-current), all years through October 2015 were included. Data were collected: number of enrolled subjects, means of the studied characteristics, SD, SE of the means, 95% confidence intervals. A meta-analysis was performed to evaluate the pooled means and range of optimal values (pooled mean±pooled SD) taking into consideration the impact of confounders. The GRADE approach was applied to evaluate the level of evidence. RESULTS: Seventeen of 1018 studies were included (2926 subjects from 9 countries). The pooled means and the optimal ranges were: LL (L1-S1), 54.6 (42-67) degrees; LL (L1-L5), 37.0 (22-53) degrees; pelvic incidence, 50.6 (39-62) degrees; sacral slope, 37.7 (28-48) degrees; pelvic tilt, 12.6 (3-22) degrees. The pooled results were statistically significant (P<0.001), but heterogeneous. Impact of the following confounders was revealed: method of measurement, ethnicity, age, and body mass index. A methodology was created to define an individualized optimal value and range of each studied parameter taking into consideration the influence of confounders. CONCLUSIONS: The pooled results and developed methodology can be used as diagnostic criteria for evaluation of the spinopelvic parameters, planning of surgical interventions and evaluation of the treatment effect.

Strain in Posterior Instrumentation Resulted by Different Combinations of Posterior and Anterior Devices for Long Spine Fusion Constructs.

STUDY DESIGN: Clinically related experimental study. OBJECTIVE: Evaluation of strain in posterior low lumbar and spinopelvic instrumentation for multilevel fusion resulting from the impact of such mechanical factors as physiologic motion, different combinations of posterior and anterior instrumentation, and different techniques of interbody device implantation. SUMMARY OF BACKGROUND DATA: Currently different combinations of posterior and anterior instrumentation as well as surgical techniques are used for multilevel lumbar fusion. Their impact on risk of device failure has not been well studied. Strain is a well-known predictor of metal fatigue and breakage measurable in experimental conditions. METHODS: Twelve human lumbar spine cadaveric specimens were tested. Following surgical methods of lumbar pedicle screw fixation (L2-S1) with and without spinopelvic fixation by iliac bolt (SFIB) were experimentally modeled: posterior (PLF); transforaminal (TLIF); and a combination of posterior and anterior interbody instrumentation (ALIF+PLF) with and without anterior supplemental fixation by anterior plate or diverging screws through an integrated plate. Strain was defined at the S1 screws, L5-S1 segment of posterior rods, and iliac bolt connectors; measurement was performed during flexion, extension, and axial rotation in physiological range of motion and applied force. RESULTS: The highest strain was observed in the S1 screws and iliac bolt connectors specifically during rotation. The S1 screw strain was lower in ALIF+PLF during sagittal motion but not rotation. Supplemental anterior fixation in ALIF+PLF diminished the S1 strain during extension. Strain in the posterior rods was higher after TLIF and PLF and was increased by SFIB; this strain was lowest after ALIF+PLF, as supplemental anterior fixation diminished the strain during extension, in particular, cages with anterior screws more than anterior plate. Strain in the iliac bolt connectors was mainly determined by direction of motion. CONCLUSIONS: Different devices modify strain in low posterior instrumentation, which is higher after transforaminal and posterior techniques, specifically with spinopelvic fixation. LEVEL OF EVIDENCE: N/A.