The contribution of E3D imaging integrated with robotic navigation: analysis of the first 80 consecutive posterior spinal fusion cases.

Eighty consecutive complex spinal robotic cases utilizing intraoperative 3D CT imaging (E3D, Group 2) were compared to 80 age-matched controls using the Excelsius robot alone with C-arm Fluoroscopic registration (Robot Only, Group 1). The demographics between the two groups were similar-severity of deformity, ASA Score for general anesthesia, patient age, gender, number of spinal levels instrumented, number of patients with prior spinal surgery, and amount of neurologic compression. The intraoperative CT scanning added several objective factors improving patient safety. There were significantly fewer complications in the E3D group with only 3 of 80 (4%) patients requiring a return to the operating room compared to 11 of 80 (14%) patients in the Robot Only Group requiring repeat surgery for implant related problems (Chi squared analysis = 5.00, p = 0.025). There was a significant reduction the amount of fluoroscopy time in the E3D Group (36 s, range 4-102 s) compared to Robot only group (51 s, range 15-160 s) (p = 0.0001). There was also shorter mean operative time in the E3D group (257 ± 59.5 min) compared to the robot only group (306 ± 73.8 min) due to much faster registration time (45 s). A longer registration time was required in the Robot only group to register each vertebral level with AP and Lateral fluoroscopy shots. The estimated blood loss was also significantly lower in Group 2 (mean 345 ± 225 ml) vs Group 1 (474 ± 397 ml) (p = 0.012). The mean hospital length of stay was also significantly shorter for Group 2 (3.77 ± 1.86 days) compared to Group 1 (5.16 ± 3.40) (p = 0.022). There was no significant difference in the number of interbody implants nor corrective osteotomies in both groups-Robot only 52 cases vs. 42 cases in E3D group.Level of evidence: IV, Retrospective review.

100 Complex posterior spinal fusion cases performed with robotic instrumentation.

Robotic navigation has been shown to increase precision, accuracy, and safety during spinal reconstructive procedures. There is a paucity of literature describing the best techniques for robotic-assisted spine surgery for complex, multilevel cases or in cases of significant deformity correction. We present a case series of 100 consecutive multilevel posterior spinal fusion procedures performed for multilevel spinal disease and/or deformity correction. 100 consecutive posterior spinal fusions were performed for multilevel disease and/or deformity correction utilizing robotic-assisted placement of pedicle screws. The primary outcome was surgery-related failure, which was defined as hardware breakage or reoperation with removal of hardware. A total of 100 consecutive patients met inclusion criteria. Among cases included, 31 were revision surgeries with existing hardware in place. The mean number of levels fused was 5.6, the mean operative time was 303 min, and the mean estimated blood loss was 469 mL. 28 cases included robotic-assisted placement of S2 alar-iliac (S2AI) screws. In total, 1043 pedicle screws and 53 S2AI screws were placed with robotic-assistance. The failure rate using survivorship analysis was 18/1043 (1.7%) and the failure rate of S2AI screws using survivorship analysis was 3/53 (5.7%). Four patients developed postoperative wound infections requiring irrigation and debridement procedures. None of the 1043 pedicle screws nor the 53 S2AI screws required reoperation due to malpositioning or suboptimal placement. This case series of 100 multilevel posterior spinal fusion procedures demonstrates promising results with low failure rates. With 1043 pedicle screws and 53 S2AI screws, we report low failure rates of 1.7% and 5.7%, respectively with zero cases of screw malpositioning. Robotic screw placement allows for accurate screw placement with no increased rate of postoperative infection compared to historical controls. Level of evidence: IV, Retrospective review.

Accuracy of Robotic-Assisted Spinal Surgery-Comparison to TJR Robotics, da Vinci Robotics, and Optoelectronic Laboratory Robotics.

BACKGROUND: The optoelectronic camera source and data interpolation serve as the foundation for navigational integrity in the robotic-assisted surgical platform. The objective of the current systematic review serves to provide a basis for the numerical disparity that exists when comparing the intrinsic accuracy of optoelectronic cameras: accuracy observed in the laboratory setting versus accuracy in the clinical operative environment. It is postulated that there exists a greater number of connections in the optoelectronic kinematic chain when analyzing the clinical operative environment to the laboratory setting. This increase in data interpolation, coupled with intraoperative workflow challenges, reduces the degree of accuracy based on surgical application and to that observed in controlled musculoskeletal kinematic laboratory investigations. METHODS: Review of the PubMed and Cochrane Library research databases was performed. The exhaustive literature compilation obtained was then vetted to reduce redundancies and categorized into topics of intrinsic optoelectronic accuracy, registration accuracy, musculoskeletal kinematic platforms, and clinical operative platforms. RESULTS: A total of 147 references make up the basis for the current analysis. Regardless of application, the common denominators affecting overall optoelectronic accuracy are intrinsic accuracy, registration accuracy, and application accuracy. Intrinsic accuracy of optoelectronic tracking equaled or was less than 0.1 mm of translation and 0.1° of rotation per fiducial. Controlled laboratory platforms reported 0.1 to 0.5 mm of translation and 0.1°-1.0° of rotation per array. There is a huge falloff in clinical applications: accuracy in robotic-assisted spinal surgery reported 1.5 to 6.0 mm of translation and 1.5° to 5.0° of rotation when comparing planned to final implant position. Total Joint Robotics and da Vinci urologic robotics computed accuracy, as predicted, lies between these two extremes-1.02 mm for da Vinci and 2 mm for MAKO. CONCLUSIONS: Navigational integrity and maintenance of fidelity of optoelectronic data is the cornerstone of robotic-assisted spinal surgery. Transitioning from controlled laboratory to clinical operative environments requires an increased number of steps in the optoelectronic kinematic chain and error potential. Diligence in planning, fiducial positioning, system registration, and intraoperative workflow have the potential to improve accuracy and decrease disparity between planned and final implant position. The key determining factors limiting navigation resolution accuracy are highlighted by this Cochrane research analysis.

Middle-Column Gap Balancing and Middle-Column Mismatch in Spinal Reconstructive Surgery.

BACKGROUND: Middle-column gap balancing (MCGB) is a reference measurement of the path of the posterior longitudinal ligament (PLL), which is reconstructed under tension and balanced by the combined height of the posterior one-third of the vertebral bodies and the posterior one-third of the disks, including any intervening load-sharing spacers. This measurement allows for a comparison of the ligamentous component of the middle column (PLL) with the load-sharing components (posterior one-third vertebral body + disk ). This difference gives rise to a "middle-column mismatch," which provides a linear measurement of the redundancy of the ligaments and neural elements, which relates to the correct cage, spacer, or load-bearing height, which is optimized. METHODS: For phase 1 measurement testing, 24 consecutive patients underwent reliable flexion, extension, and neutral lateral radiographic studies with a calibrated marker. The anterior, middle, and posterior columns were measured using a custom software program capable of measuring the length of curved lines specifically written for this purpose. For phase 2 measurement testing, 21 consecutive patients undergoing surgery with multilevel deformities for cervical, thoracic, and lumbar procedures had MCGB height pre- and postoperatively measured by 3 blinded observers. The preoperative and postoperative measurements were compared using a linear regression analysis and Pearson product-moment correlation. RESULTS: In phase 1 measurement testing the flexion, extension, and neutral bending radiographs of spinal segments not containing deformities showed that the middle column had the most reliable measurements of spinal axial height both in the actual measurements of change from flexion to extension (mm) and in percentage of change. In phase 2 measurement testing, a Pearson product-moment correlation was run between each individual's pre- and postoperative middle-column measurements. There was a strong positive correlation between preoperative and postoperative measurements, which was statistically significant (r = 0.983, n = 21, P < .01). CONCLUSIONS: This consecutive series of 21 deformity patients demonstrated the utility of measuring the preoperative middle-column length in predicting the optimal height of the spacers and intervertebral disks, and posterior vertebral body height, simultaneously restoring sagittal and coronal plane alignment. Key points of this study include the following: (1) Spinal balance requires optimizing spinal height, which is a curved line in order to accommodate cervical lordosis, thoracic kyphosis, and lumbar lordosis. (2) Software programs can allow measurement of the preoperative curved circuitous course of the PLL and vertebral body misalignment; this curved length is predictive of the optimal postoperative middle-column height after spinal osteotomies and intervertebral spacer insertion. (3) All 3 dimensions are important to optimize in deformity correction: sagittal plane, coronal plane, and axial spinal height.

The SPOT GRADE: A New Method for Reproducibly Quantifying Surgical Wound Bleeding.

STUDY DESIGN: Benchtop model with prospective surgeon video testing. OBJECTIVE: To create a surface bleeding severity scale, the SPOT GRADE (SG), for quantitative assessment of target bleeding site (TBS) blood loss. This is of particular interest for spinal surgery due to epidural bleeding and an inability to use diathermy and radiofrequency cautery close to nerve roots. SUMMARY OF BACKGROUND DATA: A novel apparatus perfusable at known flow rates and simulating different sized wounds was used to create movies to educate surgeons on specific degrees of bleeding. METHODS: Training (36) and testing (108) videos were created using a benchtop apparatus employing different bleeding severities based on the six-level SG (none, minimal, mild, moderate, severe, and extreme) and TBS sizes (1, 10, and 50 cm). Fourteen surgeons in four specialties (cardiothoracic, abdominal, spine, and orthopedic lower extremity) were trained and tested to evaluate SG characteristics including inter-rater and intrarater reliability. RESULTS: The interclass correlation coefficient was estimated to be 0.89840 (95% confidence interval [CI]: 0.85771, 1), whereas the intraclass correlation coefficient was estimated to be 0.93673 (95% CI: 0.89603, 1). In 98% of cases (95% CI: 0.9736, 0.9927), surgeons correctly identified eligible bleeds for a future clinical trial (scores = 1, 2, or 3) and in 91% of cases (95% CI: 0.8895, 0.9344), surgeons correctly identified noneligible bleeds (scores = 4 or 5). In 98.6% of cases (95% CI: 0.9777, 0.9945), physicians correctly identified true hemostasis (score = 0). Based upon these data the probability of a physician rating a bleed incorrectly as hemostasis (score = 0) is estimated to be 1.51% (95% CI: 0.0061, 0.0363). CONCLUSION: This SG is reproducible and reliable providing a basis for educating surgeons on TBS blood loss. It appears to be a new standard for evaluating wound blood loss. LEVEL OF EVIDENCE: 2.

In vitro biomechanical evaluation of four fixation techniques for distractive-flexion injury stage 3 of the cervical spine.

PURPOSE: Anterior plate fixation has been reported to provide satisfactory results in cervical spine distractive flexion (DF) injuries stages 1 and 2, but will result in a substantial failure rate in more unstable stage 3 and above. The aim of this investigation was to determine the biomechanical properties of different fixation techniques in a DF-3 injury model where all structures responsible for the posterior tension band mechanism are torn. METHODS: The multidirectional three-dimensional stiffness of the subaxial cervical spine was measured in eight cadaveric specimens with a simulated DF-3 injury at C5-C6, stabilized with four different fixation techniques: anterior plate alone, anterior plate combined with posterior wire, transarticular facet screws, and a pedicle screw-rod construct, respectively. RESULTS: The anterior plate alone did not improve stability compared to the intact spine condition, thus allowing considerable range of motion around all three cardinal axes (p > 0.05). The anterior plate combined with posterior wire technique improved flexion-extension stiffness (p = 0.023), but not in axial rotation and lateral bending. When the anterior plate was combined with transarticular facet screws or with a pedicle screws-rod instrumentation, the stability improved in flexion-extension, lateral bending, and in axial rotation (p < 0.05). CONCLUSIONS: These findings imply that the use of anterior fixation alone is insufficient for fixation of the highly unstable DF-3 injury. In these situations, the use of anterior fixation combined with a competent posterior tension band reconstruction (e.g. transarticular screws or a posterior pedicle screws-rod device) improves segmental stability.

Comparison of 2 lumbar total disc replacements: results of a prospective, randomized, controlled, multicenter Food and Drug Administration trial with 24-month follow-up.

STUDY DESIGN: This was a prospective, randomized, controlled multicenter study with 24-month follow-up. OBJECTIVE: The purpose of this study was to evaluate the safety and efficacy in a Food and Drug Administration Investigation Device Exemption of a new lumbar total disc replacement (TDR) by comparing it to an earlier TDR approved for sale. SUMMARY OF BACKGROUND DATA: Randomized trials have reported TDR to produce results similar or superior to lumbar fusion. Results for various TDRs seem to be similar, but differences in study design and outcome measures pose challenges in definitively comparing devices. The purpose of this study was to perform a direct comparison of 2 lumbar TDRs in a prospective, randomized trial. METHODS: TDR was performed in 457 patients from 21 sites (261 patients in the investigational group (Kineflex-L Disc; metal-on-metal design anchored with keels, 204 randomized and 57 nonrandomized training cases), and 196 in the control group (CHARITE artificial disc; metal with polyethylene core with teeth for anchoring; 190 randomized and 6 nonrandomized training cases). All patients were treated nonoperatively for single-level symptomatic disc degeneration for at least 6 months prior to surgery. Perioperative data were collected. Clinical outcome data were collected prospectively, as approved by the Food and Drug Administration, through 24-month follow-up. Primary outcome measures used were the Oswestry Disability Index, visual analogue scales assessing pain, patient satisfaction, and reoperations. Success was defined to be at least 15-point improvements in Oswestry Disability Index scores, no reoperation, and no major adverse events. Radiographical measures included range of motion, disc space height, and assessment for device migration, subsidence, and fusion at the TDR level. RESULTS: There were no significant differences between the groups when comparing operative time, blood loss, or length of hospital stay. Both groups improved significantly on Oswestry Disability Index and visual analogue scale scores (P < 0.01) with no differences between the groups. Success rates were similar (68.1% investigational vs. 67.4% control). At 24-month follow-up, 94.1% of the investigational group and 91.9% of controls were satisfied with outcome. Reoperation was performed in 10.3% of the investigational group and 8.4% of the control group. CONCLUSION: This prospective, randomized, controlled study comparing 2 TDRs, the first to the authors' knowledge, found the devices produced very similar clinical outcomes. Both groups improved significantly by 6 weeks postoperatively and remained improved throughout follow-up with a high patient satisfaction rate.

Epidural application of spinal instrumentation particulate wear debris: a comprehensive evaluation of neurotoxicity using an in vivo animal model.

OBJECT: The introduction and utilization of motion-preserving implant systems for spinal reconstruction served as the impetus for this basic scientific investigation. The effect of unintended wear particulate debris resulting from micromotion at spinal implant interconnections and bearing surfaces remains a clinical concern. Using an in vivo rabbit model, the current study quantified the neural and systemic histopathological responses following epidural application of 11 different types of medical-grade particulate wear debris produced from spinal instrumentation. METHODS: A total of 120 New Zealand White rabbits were equally randomized into 12 groups based on implant treatment: 1) sham (control), 2) stainless steel, 3) titanium alloy, 4) cobalt chromium alloy, 5) ultra-high molecular weight polyethylene (UHMWPe), 6) ceramic, 7) polytetrafluoroethylene, 8) polycarbonate urethane, 9) silicone, 10) polyethylene terephthalate, 11) polyester, and 12) polyetheretherketone. The surgical procedure consisted of a midline posterior approach followed by resection of the L-6 spinous process and L5-6 ligamentum flavum, permitting interlaminar exposure of the dural sac. Four milligrams of the appropriate treatment material (Groups 2-12) was then implanted onto the dura in a dry, sterile format. All particles (average size range 0.1-50 µm in diameter) were verified to be endotoxin free prior to implantation. Five animals from each treatment group were sacrificed at 3 months and 5 were sacrificed at 6 months postoperatively. Postmortem analysis included epidural cultures and histopathological assessment of local and systemic tissue samples. Immunocytochemical analysis of the spinal cord and overlying epidural fibrosis quantified the extent of proinflammatory cytokines (tumor necrosis factor-α, tumor necrosis factor-ß, interleukin [IL]-1α, IL-1ß, and IL-6) and activated macrophages. RESULTS: Epidural cultures were negative for nearly all cases, and there was no evidence of particulate debris or significant histopathological changes in the systemic tissues. Gross histopathological examination demonstrated increased levels of epidural fibrosis in the experimental treatment groups compared with the control group. Histopathological evaluation of the epidural fibrous tissues showed evidence of a histiocytic reaction containing phagocytized inert particles and foci of local inflammatory reactions. At 3 months, immunohistochemical examination of the spinal cord and epidural tissues demonstrated upregulation of IL-6 in the groups in which metallic and UHMWPe debris were implanted (p < 0.05), while macrophage activity levels were greatest in the stainless-steel and UHMWPe groups (p < 0.05). By 6 months, the levels of activated cytokines and macrophages in nearly all experimental cases were downregulated and not significantly different from those of the operative controls (p > 0.05). The spinal cord had no evidence of lesions or neuropathology. However, multiple treatments in the metallic groups exhibited a mild, chronic macrophage response to particulate debris, which had diffused intrathecally. CONCLUSIONS: Epidural application of spinal instrumentation particulate wear debris elicits a chronic histiocytic reaction localized primarily within the epidural fibrosis. Particles have the capacity to diffuse intrathecally, eliciting a transient upregulation in macrophage/cytokine activity response within the epidural fibrosis. Overall, based on the time periods evaluated, there was no evidence of an acute neural or systemic histopathological response to the materials included in the current project.

A prospective, randomized, controlled clinical investigation comparing PCM cervical disc arthroplasty with anterior cervical discectomy and fusion. 2-year results from the US FDA IDE clinical trial.

STUDY DESIGN: Prospective, multicenter, randomized Food and Drug Administration approved investigational device exemption clinical trial. OBJECTIVE: To evaluate the safety and effectiveness of the PCM Cervical Disc compared with anterior cervical discectomy and fusion (ACDF) in the treatment of patients with degenerative spondylosis and neurological symptoms at 1 level between C3-C4 and C7-T1. SUMMARY OF BACKGROUND DATA: Cervical disc arthroplasty in the treatment of symptomatic cervical spondylosis has been studied in other series. The PCM Cervical Disc is a nonconstrained motion-sparing alternative to ACDF. METHODS: Patients 18 to 65 years of age with single-level symptomatic cervical spondylosis with radiculopathy and/or myelopathy unresponsive to nonoperative treatment were enrolled, including patients with prior nonadjacent or adjacent single-level fusions. The per-protocol patient sample at 2 years included 342 patients (189 PCM, 153 ACDF). Longitudinal outcomes were comparatively evaluated. RESULTS: At 2 years postoperatively, clinical measures-neck and arm pain visual analogue scale, Neck Disability Index (NDI), SF-36, and neurological status-were significantly improved from preoperative baselines in both groups. Mean NDI score at 2 years was significantly lower in PCM group (P = 0.029). There were no statistical differences between groups in rates of surgery-related serious adverse events (5.6% PCM, 7.4% ACDF) or secondary surgical procedures (5.2% PCM, 5.4% ACDF). Patients with PCM reported lower dysphagia scores (8.8/100 vs. 12.1/100; P = 0.045) and higher patient satisfaction (82.8/100 vs. 81.4/100). Overall success, a composite endpoint including minimum 20% NDI improvement, no major complications, no neurological worsening, no secondary surgical procedures, and meeting radiographical criteria of motion for PCM and fusion for ACDF, was significantly greater in the PCM group (75.1% vs. 64.9%; P = 0.020). CONCLUSION: The treatment of symptomatic single-level cervical spondylosis with PCM achieves clinical outcomes that are at least equivalent to ACDF while maintaining motion. At 2 years, patients with PCM had lower NDI scores, statistically lower rate of prolonged dysphagia, greater patient satisfaction, and superior overall success.

Multilevel extreme lateral interbody fusion (XLIF) and osteotomies for 3-dimensional severe deformity: 25 consecutive cases.

BACKGROUND: This is a retrospective review of 25 patients with severe lumbar nerve root compression undergoing multilevel anterior retroperitoneal lumbar interbody fusion and posterior instrumentation for deformity. The objective is to analyze the outcomes and clinical results from anterior interbody fusions performed through a lateral approach and compare these with traditional surgical procedures. METHODS: A consecutive series of 25 patients (78 extreme lateral interbody fusion [XLIF] levels) was identified to illustrate the primary advantages of XLIF in correcting the most extreme of the 3-dimensional deformities that fulfilled the following criteria: (1) a minimum of 40° of scoliosis; (2) 2 or more levels of translation, anterior spondylolisthesis, and lateral subluxation (subluxation in 2 planes), causing symptomatic neurogenic claudication and severe spinal stenosis; and (3) lumbar hypokyphosis or flat-back syndrome. In addition, the majority had trunks that were out of balance (central sacral vertical line ≥2 cm from vertical plumb line) or had sagittal imbalance, defined by a distance between the sagittal vertical line and S1 of greater than 3 cm. There were 25 patients who had severe enough deformities fulfilling these criteria that required supplementation of the lateral XLIF with posterior osteotomies and pedicle screw instrumentation. RESULTS: In our database, with a mean follow-up of 24 months, 85% of patients showed evidence of solid arthrodesis and no subsidence on computed tomography and flexion/extension radiographs. The complication rate remained low, with a perioperative rate of 2.4% and postoperative rate of 12.2%. The lateral listhesis and anterior spondylolisthetic subluxation were anatomically reduced with minimally invasive XLIF. The main finding in these 25 cases was our isolation of the major indication for supplemental posterior surgery: truncal decompensation in patients who are out of balance by 2 cm or more, in whom posterior spinal osteotomies and segmental pedicle screw instrumentation were required at follow up. No patients were out of sagittal balance (sagittal vertical line <3 cm from S1) postoperatively. Segmental instrumentation with osteotomies was also more effective for restoration of physiologic lumbar lordosis compared with anterior stand-alone procedures. CONCLUSIONS: This retrospective study supports the finding that clinical outcomes (coronal/sagittal alignment) improve postoperatively after minimally invasive surgery with multilevel XLIF procedures and are improved compared with larger extensile thoracoabdominal anterior scoliosis procedures.

Cervical total disk replacement: complications and avoidance.

Anterior cervical diskectomy and fusion for neurologic deficits, radicular arm pain, and neck pain refractory to conservative management are successful. The approach and procedure were first described in 1955 and have become the anterior cervical standard of care for orthopedic surgeons and neurosurgeons. Advancements and innovations have addressed disease processes of the cervical spine with motion-preserving technology. The possibility of obtaining anterior cervical decompression while maintaining adjacent segment motion led to the advent of cervical total disk replacement. The Food and Drug Administration has approved 3 cervical devices with other investigational device exemption trials under way.

A meta-analysis of comparative outcomes following cervical arthroplasty or anterior cervical fusion: results from 4 prospective multicenter randomized clinical trials and up to 1226 patients.

STUDY DESIGN: Meta-analysis of 4 prospective randomized controlled Food and Drug Administration (FDA) Investigational Device Exemption (IDE) clinical trials. OBJECTIVE: To maximize the information available from 4 IDE studies by analyzing the combined outcomes of cervical arthroplasty versus fusion at 24-month follow-up. SUMMARY OF BACKGROUND DATA: To date, 4 randomized clinical trials have been completed in the United States under FDA IDE protocols to study cervical arthroplasty. Each trial reported arthroplasty to be at least as successful as fusion controls based on noninferiority trial designs. However, sample sizes in any given trial may not be sufficient to demonstrate superiority of treatment effect. Meta-analysis enables pooling of results from comparable trials, which may lead to more precise and statistically significant estimates of treatment effect. METHODS: Four cervical arthroplasty randomized clinical trials with comparable enrollment criteria and outcome measures were conducted independently by 3 separate sponsors to study the following devices: Bryan, Prestige, ProDisc-C, and PCM cervical disc replacements. A total of 1608 patients were treated across 98 investigative sites. Data were available for 1352 treated patients, of which 1226 were evaluable at 24 months. Assessments included clinical success definitions based on neck disability index, maintenance or improvement of neurological status, subsequent surgery or intervention at the index level (survivorship), and a composite score comprising these as well as serious device-related adverse events. Trial endpoint comparisons were made at 24 months postoperatively. For each endpoint, a random-effects meta-analysis was performed to compare the success rates of cervical arthroplasty with anterior cervical discectomy and fusion (ACDF). Also, supportive frequentist and bayesian analyses were performed. RESULTS: The pooled primary overall success results indicated a statistically significant treatment effect favoring arthroplasty compared with ACDF. Overall success was achieved by 77.6% of the arthroplasty patients and by 70.8% of the ACDF patients (pooled odds ratio [OR]: 0.699, 95% confidence interval [CI]: 0.539-0.908, P = 0.007). The results of the individual subcomponent meta-analyses, all of which favored arthroplasty, were neck disability index success (OR: 0.786, 95% CI: 0.589-1.050, P = 0.103), neurological status (OR: 0.552, 95% CI: 0.364-0.835, P = 0.005), and survivorship (OR: 0.510, 95% CI: 0.275-0.946, P = 0.033). Only the survivorship endpoint suggested low heterogeneity. CONCLUSION: These findings suggest that cervical arthroplasty is superior to ACDF in overall success, neurological success, and survivorship outcomes at 24 months postoperatively.

An attempt at clinically defining and assessing minimally invasive surgery compared with traditional "open" spinal surgery.

BACKGROUND: The goal of this editorial and literature review is to define the term "minimally invasive surgery" (MIS) as it relates to the spine and characterize methods of measuring parameters of a spine MIS technique. METHODS: This report is an analysis of 105,845 cases of spinal surgery in unmatched series and 95,161 cases in paired series of open compared with MIS procedures performed by the same surgeons to develop quantitative criteria to analyze the success of MIS. RESULTS: A lower rate of deep infection proved to be a key differentiator of spinal MIS. In unmatched series the infection rate for 105,845 open traditional procedures ranged from 2.9% to 4.3%, whereas for MIS, the incidence of infection ranged from 0% to 0.22%. For matched paired series with the open and MIS procedures performed by the same surgeons, the rate of infection in open procedures ranged from 1.5% to 10%, but for spine MIS, the rate of deep infection was much lower, at 0% to 0.2%. The published ranges for open versus MIS infection rates do not overlap or even intersect, which is a clear indication of the superiority of MIS for one specific clinical outcome measure (MIS proves superior to open spine procedures in terms of lower infection rate). CONCLUSIONS: It is difficult, if not impossible, to validate that an operative procedure is "less invasive" or "more minimally invasive" than traditional surgical procedures unless one can establish a commonly accepted definition of MIS. Once a consensus definition or precise definition of MIS is agreed upon, the comparison shows a higher infection rate with traditional spinal exposures versus MIS spine procedures.

Minimally invasive surgery: lateral approach interbody fusion: results and review.

STUDY DESIGN: A retrospective review of patients treated at 2 institutions with anterior lumbar interbody fusion using a minimally invasive lateral retroperitoneal approach, and review of literature. OBJECTIVE: To analyze the outcomes from historical literature and from a retrospectively compiled database of patients having undergone anterior interbody fusions performed through a lateral approach. SUMMARY OF BACKGROUND DATA: A paucity of published literature exists describing outcomes following lateral approach fusion surgery. METHODS: Patients treated with extreme lateral interbody fusion (XLIF) were identified through retrospective chart review. Treatment variables included operating room (OR) time, estimated blood loss (EBL), length of hospital stay (LOS), complications, and fusion rate. A literature review, using the National Center for Biotechnology Information databases PubMed/MEDLINE and Google Scholar, yielded 14 peer-reviewed articles reporting outcomes scoring, complications, fusion status, long-term follow-up, and radiographic assessments related to XLIF. Published XLIF results were summarized and evaluated with current study data. RESULTS: A total of 84 XLIF patients were included in the current cohort analysis. OR time, EBL, and length of hospital stay averaged 199 minutes, 155 mL, and 2.6 days, respectively, and perioperative and postoperative complication rates were 2.4% and 6.1%. Mean follow-up was 15.7 months. Sixty-eight patients showed evidence of solid arthrodesis and no subsidence on computed tomography and flexion/extension radiographs. Results were within the ranges of those in the literature. Literature review identified reports of significant improvements in clinical outcomes scores, radiographic measures, and cost effectiveness. CONCLUSION: Current data corroborates and contributes to the existing body of literature describing XLIF outcomes. Procedures are generally performed with short OR times, minimal EBL, and few complications. Patients recover quickly, requiring minimal hospital stay, although transient hip/thigh pain and/or weakness is common. Long-term outcomes are generally favorable, with maintained improvements in patient-reported pain and function scores as well as radiographic parameters, including high rates of fusion.

Multidirectional flexibility of the spine following posterior decompressive surgery after single-level cervical disc arthroplasty: an in vitro biomechanical investigation.

STUDY DESIGN: In vitro human cadaveric biomechanical study. OBJECTIVE: This study quantifies the multidirectional flexibility of the spine following laminoplasty and laminectomy after cervical disc arthroplasty. SUMMARY OF BACKGROUND DATA: Posterior decompressive surgery may be used to treat recurrence of myeloradiculopathy following disc arthroplasty. This is the first study investigating the biomechanical effects of posterior decompressive surgery combined with cervical disc arthroplasty. METHODS: Seven human cervical spines were biomechanically evaluated under the following conditions: (1) intact; (2) discectomy (C5-C6); (3) disc arthroplasty (C5-C6); (4) arthroplasty + 3-level laminoplasty (C3-C5); (5) arthroplasty + 4-level laminoplasty (C3-C6); (6) arthroplasty + 5-level laminoplasty (C3-C7); (7) arthroplasty + 5-level laminoplasty (C3-C7) without hydroxyapatite spacers; and (8) arthroplasty + laminectomy (C3-C7). Multidirectional flexibility testing used unconstrained pure moments of ±2 Nm for flexion-extension, axial rotation, and lateral bending. Quantification of C5-C6 and C3-C7 range of motion (ROM) and neutral zone (NZ) were normalized to the intact spine (100%). RESULTS: Flexion-extension loading of the discectomy condition demonstrated ROM of 22.05° ± 4.17° at the operative level (P < 0.05). Implantation of the porous coated motion device restored segmental motion near the intact condition (ROM, 9.97° ± 6.44°; NZ, 5.82° ± 6.18°). There were no statistical differences between 3-level (13.79° ± 6.49°), 4-level (14.51° ± 5.76°), and 5-level (15.67° ± 5.71°) laminoplasty; however, additional levels demonstrated a trend toward increased motion at the arthroplasty level. Laminoplasty without spacers (17.45°) and laminectomy (18.27°) indicated even greater segmental motion (P > 0.05). Axial rotation and lateral bending indicated trends similar to those for flexion-extension. CONCLUSION: Posterior decompressive surgery increased ROM and NZ in all loading modes compared to arthroplasty alone, and laminectomy markedly increased motion compared with laminoplasty. Use of hydroxyapatite spacers and minimization of the extent of laminoplasty appear to be biomechanically favorable in this in vitro model.

The effect of spinal instrumentation on kinematics at the cervicothoracic junction: emphasis on soft-tissue response in an in vitro human cadaveric model.

OBJECT: Thoracic pedicle screw instrumentation is often indicated in the treatment of trauma, deformity, degenerative disease, and oncological processes. Although classic teaching for cervical spine constructs is to bridge the cervicothoracic junction (CTJ) when instrumenting in the lower cervical region, the indications for extending thoracic constructs into the cervical spine remain unclear. The goal of this study was to determine the role of ligamentous and facet capsule (FC) structures at the CTJ as they relate to stability above thoracic pedicle screw constructs. METHODS: A 6-degree-of-freedom spine simulator was used to test multidirectional range of motion (ROM) in 8 human cadaveric specimens at the C7­T1 segment. Flexion-extension, lateral bending, and axial rotation at the CTJ were tested in the intact condition, followed by T1­6 pedicle screw fixation to create a long lever arm inferior to the C7­T1 level. Multidirectional flexibility testing of the T1­6 pedicle screw construct was then sequentially performed after sectioning the C7­T1 supraspinous ligament/interspinous ligament (SSL/ISL) complex, followed by unilateral and bilateral FC disruption at C7­T1. Finally, each specimen was reconstructed using C5­T6 instrumented fixation and ROM testing at the CTJ performed as previously described. RESULTS: Whereas the application of a long-segment thoracic construct stopping at T-1 did not significantly increase flexion-extension peak total ROM at the supra-adjacent level, sectioning the SSL/ISL significantly increased flexibility at C7­T1, producing 35% more motion than in the intact condition (p < 0.05). Subsequent FC sectioning had little additional effect on ROM in flexion-extension. Surprisingly, the application of thoracic instrumentation had a stabilizing effect on the supra-adjacent C7­T1 segment in axial rotation, leading to a decrease in peak total ROM to 83% of the intact condition (p < 0.05). This is presumably due to interaction between the T-1 screw heads and titanium rods with the C7­T1 facet joints, thereby limiting axial rotation. Incremental destabilization served only to restore peak total ROM near the intact condition for this loading mode. In lateral bending, the application of thoracic instrumentation stopping at T-1, as well as SSL/ISL and FC disruption, demonstrated trends toward increased supraadjacent ROM; however, these trends did not reach statistical significance (p > 0.05). CONCLUSIONS: When stopping thoracic constructs at T-1, care should be taken to preserve the SSL/ISL complex to avoid destabilization of the supra-adjacent CTJ, which may manifest clinically as proximal-junction kyphosis. In an analogous fashion, if a T-1 laminectomy is required for neural decompression or surgical access, consideration should be given to extending instrumentation into the cervical spine. Facet capsule disruption, as might be encountered during T-1 pedicle screw placement, may not be an acutely destabilizing event, due to the interaction of the C7­T1 facet joints with T-1 instrumentation.