Biomechanical Comparison of Multilevel Stand-Alone Lumbar Lateral Interbody Fusion With Posterior Pedicle Screws: An In Vitro Study.

OBJECTIVE: Lumbar lateral interbody fusion (LLIF) allows placement of large interbody cages while preserving ligamentous structures important for stability. Multiple clinical and biomechanical studies have demonstrated the feasibility of stand-alone LLIF in single-level fusion. We sought to compare the stability of 4-level stand-alone LLIF utilizing wide (26 mm) cages with bilateral pedicle screw and rod fixation. METHODS: Eight human cadaveric specimens of L1-5 were included. Specimens were attached to a universal testing machine (MTS 30/G). Flexion, extension, and lateral bending were attained by applying a 200 N load at a rate of 2 mm/sec. Axial rotation of ± 8° of the specimen was performed at 2°/sec. Three-dimensional specimen motion was recorded using an optical motion-tracking device. Specimens were tested in 4 conditions: (1) intact, (2) bilateral pedicle screws and rods, (3) 26-mm stand-alone LLIF, (4) 26-mm LLIF with bilateral pedicle screws and rods. RESULTS: Compared to the stand-alone LLIF, bilateral pedicle screws and rods had 47% less range of motion in flexion-extension (p < 0.001), 21% less in lateral bending (p < 0.05), and 20% less in axial rotation (p = 0.1). The addition of bilateral posterior instrumentation to the stand-alone LLIF resulted in decreases of all 3 planes of motion: 61% in flexion-extension ( p < 0.001), 57% in lateral bending (p < 0.001), 22% in axial rotation (p = 0.002). CONCLUSION: Despite the biomechanical advantages associated with the lateral approach and 26 mm wide cages, stand-alone LLIF for 4-level fusion is not equivalent to pedicle screws and rods.

Characterization of ion release from a novel biomaterial, Molybdenum-47.5Rhenium, in physiologic environments.

BACKGROUND CONTEXT: Metals from spinal implants are released into surrounding tissues by various mechanisms. Metal ion release has been associated with clinical implant failure, osteolysis, and remote site accumulation with adverse events. Significant corrosion and associated metal ion release has been described with currently used spinal implant alloys. A novel metal alloy, Molybdenum-47.5Rhenium alloy (MoRe®), was approved for use in medical implants in 2019 by the FDA. PURPOSE: To evaluate the metal ion release profile of MoRe alloy after immersion in both a stable physiologic, as well as in an inflammatory environment. STUDY DESIGN: In vitro study. METHODS: The ion release profile of the MoRe alloy was comprehensively evaluated in-vitro after prolonged immersion in physiologic and inflammatory environments. Ion concentration analyses were then conducted using inductively coupled plasma-mass spectrometry (ICP-MS) methods. Comparative testing of titanium (Ti-6Al-4V) and cobalt chromium (Co-28Cr-6Mo) was also performed. RESULTS: Under baseline physiologic conditions, the MoRe alloy demonstrates very low molybdenum and rhenium ion release rates throughout the 30-day test period. During the first time interval (day 0-1), low levels of molybdenum and rhenium ions are detected (<0.3 µg/cm2 day) followed by a rapid reduction in the ion release rates to <0.05 µg/cm2 day during the second time interval (days 1-3) followed by a further reduction to very low steady-state rates <0.01 µg/cm2 day during the third time interval (days 3-7), which were maintained through 30 days. In the inflammatory condition (H2O2 solution), there was a transient increase in the release of molybdenum and rhenium ions, followed by a return to baseline ion release rates (days 2-4), with a further reduction to low steady-state rates of ∼0.01 µg/cm2 day (days 4-8). The measured molybdenum and rhenium ion release rates in both steady state (<0.01 µg/cm2 day), and inflammatory environments (0.01 µg/cm2 day) were far below the established FDA-permitted daily exposure (PDE) of 1,900 µg/cm2 day for molybdenum and 4,400 µg/cm2 day for rhenium. In contrast, titanium and cobalt chromium approached or exceeded their established PDE values in an inflammatory environment. CONCLUSIONS: The novel biomaterial MoRe demonstrated a lower metal ion release profile in both a physiologic and inflammatory environment and was well below the established PDE.  Comparative testing of the cobalt-chromium and titanium alloys found higher levels of ion release in the inflammatory environment that exceeded the PDE for cobalt and vanadium.

Biomechanical Comparison of Unilateral and Bilateral Pedicle Screw Fixation after Multilevel Lumbar Lateral Interbody Fusion.

STUDY DESIGN: Human Cadaveric Biomechanical Study. OBJECTIVES: Lumbar Lateral Interbody Fusion (LLIF) utilizing a wide cage has been reported as having favorable biomechanical characteristics. We examine the biomechanical stability of unilateral pedicle screw and rod fixation after multilevel LLIF utilizing 26 mm wide cages compared to bilateral fixation. METHODS: Eight human cadaveric specimens of L1-L5 were included. Specimens were attached to a universal testing machine (MTS 30/G). Three-dimensional specimen range of motion (ROM) was recorded using an optical motion-tracking device. Specimens were tested in 3 conditions: 1) intact, 2) L1-L5 LLIF (4 levels) with unilateral rod, 3) L1-L5 LLIF with bilateral rods. RESULTS: From the intact condition, LLIF with unilateral rod decreased flexion-extension by 77%, lateral bending by 53%, and axial rotation by 26%. In LLIF with bilateral rods, flexion-extension decreased by 83%, lateral bending by 64%, and axial rotation by 34%. Comparing unilateral and bilateral fixation, LLIF with bilateral rods reduced ROM by a further 23% in flexion-extension, 25% in lateral bending, and 11% in axial rotation. The difference was statistically significant in flexion-extension and lateral bending (P < .005). CONCLUSIONS: Considerable decreases in ROM were observed after multilevel (4-level) LLIF utilizing 26 mm cages supplemented with both unilateral and bilateral pedicle screws and rods. The addition of bilateral fixation provides a 10-25% additional decrease in ROM. These results can inform surgeons of the incremental biomechanical benefit when considering unilateral or bilateral posterior fixation after multilevel LLIF.

The impact of mental health on patient-reported outcomes in cervical radiculopathy or myelopathy surgery.

Optimizing functional outcomes and disability status are essential for effective surgical treatment of cervical spine disorders. Mental impairment is common among patients with cervical spine complaints; yet little is known about the impact of baseline mental status with respect to overall patient-reported outcomes. This was a retrospective analysis of patients with cervical spondylosis with myelopathy(CM) or radiculopathy(CR: cervical disc herniation, stenosis, or spondylosis without myelopathy) at 2-year follow-ups. Patients were assessed for several health-related quality of life HRQOL) measures at baseline and 24-months post-operatively: Neck Disability Index (NDI), Visual Analog Scale(VAS), Short Form-36(SF) Physical(PCS) and Mental(MCS) Components. Patients were dichotomized by MCS score: LOW-MCS(SF-MCS < 40th percentile) vs. HIGH-MCS(SF-MCS > 60th percentile). Independent and paired t-tests compared improvement in each group for HIGH-MCS and LOW-MCS cohorts. 375 patients were analyzed(65.4yrs, 67.6%F). LOW-MCS radiculopathy patients showed significant improvement in NDI, VAS Neck and Arm Pain(p < 0.05). HIGH-MCS radiculopathy patients showed greater improvement in NDI score, VAS Neck and Arm Pain, and improvement in PCS(all p < 0.05). Comparing baseline and 2-year follow-up, LOW-MCS CM patients showed significant improvement in PCS, NDI, VAS Neck and Arm Pain(p < 0.05). HIGH-MCS myelopathy patients group showed marked improvement in NDI scores, VAS Neck and Arm Pain(p < 0.05). LOW-MCS CR patients were more likely to be less satisfied 2-years post-op(p < 0.001). Postoperative CR patients with lower baseline mental status saw less improvement and significantly worse outcomes than patients with higher baseline mental status. Improving baseline mental health may improve post-operative recovery. Implementing additional screening and care can optimize functional outcomes and disability status for patients with CR.

Impact of a Bundled Payment System on Resource Utilization During Spine Surgery.

BACKGROUND: In a bundled payment system, a single payment covers all costs associated with a single episode of care. Spine surgery may be well suited for bundled payments because of clearly defined episodes of care, but the impact on current practice has not been studied. We sought to examine how a theoretical bundled payment strategy with financial disincentives to resource utilization would impact practice patterns. METHODS: A multiple-choice survey was administered to spine surgeons describing eight clinical scenarios. Respondents were asked about their current practice, and then their practice in a hypothetical bundled payment system. Respondents could choose from multiple types of implants, bone grafts, and other resources utilized at the surgeon's discretion. RESULTS: Forty-three respondents completed the survey. Within each scenario, 24%-49% of respondents changed at least one aspect of management. The proportion of cases performed without implants was unchanged for four scenarios and increased in four by an average of 8%. Use of autologous iliac crest bone graft increased across all scenarios by an average of 18%. Use of neuromonitoring decreased in all scenarios by an average of 21%. Differences in costs were not statistically significant. CONCLUSIONS: Financial disincentives to resource utilization may result in some changes to surgeons' practices but these appear limited to items with less clear benefits to patients. Choices of implants, which account for the majority of intra-operative costs, did not change meaningfully. A bundling strategy targeting peri-operative costs solely related to surgical practice may not yield substantive savings while rationing potentially beneficial treatments to patient care. LEVEL OF EVIDENCE: 5.

Direct Measurement of Tissue Oxygenation as a Method of Diagnosis of Acute Compartment Syndrome.

OBJECTIVE: The aim of this study was to investigate the utility of direct measurement of tissue oxygenation during compartment syndrome (CS) and tourniquet-induced ischemia in a large animal model. We hypothesize that as compartment pressure (CP) rises, circulation within the compartment will decrease resulting in a decreased level of oxygen in the muscle. METHODS: This study used a dog model of both CS- and tourniquet-based ischemia. In 15 animals, CS was induced in 1 hind limb with varying degrees of severity using an infusion model. Tourniquet ischemia was induced in the contralateral hind limb for varying durations. The partial pressure of oxygen (PmO2) was continuously monitored using a polarographic oxygen probe in the muscle of both hind limbs. CP was monitored in the CS limb. PmO2 and CP were analyzed after fasciotomy, performed after approximately 7 hours of warm ischemia, or release of tourniquet. RESULTS: With the application of tourniquet ischemia, PmO2 fell from 38.40 to 1.30 mm Hg (P < 0.001) and subsequently rose after release of the tourniquet to 39.81 mm Hg (P < 0.001). Elevated CP induced by infusion was relieved by fasciotomy (52.04-11.37 mm Hg postfasciotomy, P < 0.001). PmO2 readings in the infusion model were significantly higher in pre-CS than during CS (31.77 mm Hg vs. 3.88 mm Hg, P < 0.001) and rebounded after fasciotomy (50.24 mm Hg, P < 0.001), consistent with hyperemic response. CONCLUSIONS: Increased CP caused an observable decrease in PmO2 that was reversed by fasciotomy. PmO2 can be directly measured in real time with a polarographic tissue pO2 probe. This study is the first step of evaluating an alternative method for diagnosing acute CS.

How Effective is Physical Therapy for Common Low Back Pain Diagnoses?: A Multivariate Analysis of 4597 Patients.

STUDY DESIGN: A retrospective review. OBJECTIVE: The aim of this study is to evaluate whether the treatment of low back pain with physical therapy results in clinically significant improvements in patient-reported pain and functional outcomes. SUMMARY OF BACKGROUND DATA: Low back pain is a major cause of morbidity and disability in health care. Previous studies have found poor efficacy for surgery in the absence of specific indications. A variety of nonoperative treatments are available; however, there is scant evidence to guide the practitioner as to the efficacy of these treatments. METHODS: Four thousand five hundred ninety-seven patients who underwent physical therapy for the nonoperative treatment of low back pain were included. The primary outcome measures were pre-and post-treatment scores on the Oswestry Disability Index (ODI), Numeric Pain Rating Scale (NPRS) during activity, and NPRS during rest. Previously published thresholds for minimal clinically important difference (MCID) were used to determine the proportion of patients meeting MCID for each of our outcomes. Patients with starting values below the MCID for each variable were excluded from analysis. Logistic regression analysis was used to determine patient risk factors predictive of treatment failure. RESULTS: About 28.5% of patients met the MCID for improvement in ODI. Presence of night symptoms, obesity, and smoking were predictors of treatment failure for ODI. Fifty-nine percent of patients met the MCID for improvement in resting NPRS, with a history of venous thromboembolism, night symptoms, psychiatric disease, workers' compensation status, smoking, and obesity predictive of treatment failure. Sixty percent of patients met the MCID for improvement in activity NPRS, with night symptoms, workers' compensation status, and smoking predictive of treatment failure. CONCLUSION: We observed that a substantial percentage of the population did not meet MCID for pain and function following treatment of low back pain with physical therapy. Common risk factors for treatment failure included smoking and presence of night symptoms. LEVEL OF EVIDENCE: 4.

Is the lateral jack-knife position responsible for cases of transient neurapraxia?

OBJECTIVE: The lateral jack-knife position is often used during transpsoas surgery to improve access to the spine. Postoperative neurological signs and symptoms are very common after such procedures, and the mechanism is not adequately understood. The objective of this study is to assess if the lateral jack-knife position alone can cause neurapraxia. This study compares neurological status at baseline and after positioning in the 25° right lateral jack-knife (RLJK) and the right lateral decubitus (RLD) position. METHODS: Fifty healthy volunteers, ages 21 to 35, were randomly assigned to one of 2 groups: Group A (RLD) and Group B (RLJK). Motor and sensory testing was performed prior to positioning. Subjects were placed in the RLD or RLJK position, according to group assignment, for 60 minutes. Motor testing was performed immediately after this 60-minute period and again 60 minutes thereafter. Sensory testing was performed immediately after the 60-minute period and every 15 minutes thereafter, for a total of 5 times. Motor testing was performed by a physical therapist who was blinded to group assignment. A follow-up call was made 7 days after the positioning sessions. RESULTS: Motor deficits were observed in the nondependent lower limb in 100% of the subjects in Group B, and no motor deficits were seen in Group A. Statistically significant differences (p < 0.05) were found between the 2 groups with respect to the performance on the 10-repetition maximum test immediately immediately and 60 minutes after positioning. Subjects in Group B had a 10%-70% (average 34.8%) decrease in knee extension strength and 20%-80% (average 43%) decrease in hip flexion strength in the nondependent limb. Sensory abnormalities were observed in the nondependent lower limb in 98% of the subjects in Group B. Thirty-six percent of the Group B subjects still exhibited sensory deficits after the 60-minute recovery period. No symptoms were reported by any subject during the follow-up calls 7 days after positioning. CONCLUSIONS: Twenty-five degrees of right lateral jack-knife positioning for 60 minutes results in neurapraxia of the nondependent lower extremity. Our results support the hypothesis that jack-knife positioning alone can cause postoperative neurological symptoms.

Evaluation of immediate postoperative complications and outcomes among military personnel treated for spinal trauma in Afghanistan: a cohort-control study of 50 cases.

STUDY DESIGN: Retrospective case-control study. OBJECTIVE: The objective of the study was to compare neurological outcomes and complication rates between a series of combat-injured patients treated in Afghanistan (AFG) and those treated at Landstuhl Regional Medical Center (LRMC). SUMMARY OF BACKGROUND DATA: At present, no studies have addressed the ideal timing and setting for surgical stabilization in combat-injured soldiers who sustain spinal trauma. METHODS: Soldiers who sustained spine injuries while deployed to Afghanistan and who underwent surgery in theater or at LRMC between 2010 and 2011 were identified. Demographic information, injury-specific data, neurological status, type of surgical intervention, postoperative complications, and need for additional surgery were abstracted for all patients. Neurological improvement was the primary dependent variable. Secondary variables included the risk of developing complications and the need for additional surgery. Statistical analysis was performed using t tests, and the Fisher exact test was used for categorical variables. RESULTS: Between 2010 and 2011, 30 individuals were treated in AFG, and 20 received surgery at LRMC. Neurological improvement occurred in 10% of AFG patients and 5% of those treated at LRMC. Complications occurred in 40% of AFG patients and in 20% of the LRMC group. Twenty-three percent of AFG patients required additional spine surgery after leaving Afghanistan. There was no statistical difference in neurological improvement between the AFG and LRMC groups (P=0.64). Soldiers who received surgery in AFG were at significantly increased risk of requiring additional procedures (P=0.03). CONCLUSIONS: Soldiers treated in theater did not have statistically higher rates of neurological improvement as compared with those treated at LRMC. Patients treated in-theater were at elevated risk for the need for additional surgery. This study is among the first to evaluate clinical outcomes after surgical intervention for war-related spinal trauma. LEVEL OF EVIDENCE: Level III (case-control).

Characterization of scaffold carriers for BMP9-transduced osteoblastic progenitor cells in bone regeneration.

Successful bone tissue engineering at least requires sufficient osteoblast progenitors, efficient osteoinductive factors, and biocompatible scaffolding materials. We have demonstrated that BMP9 is one of the most potent factors in inducing osteogenic differentiation of mesenchymal progenitors. To facilitate the potential use of cell-based BMP9 gene therapy for bone regeneration, we characterize the in vivo osteoconductive activities and bone regeneration potential of three clinically used scaffold materials, type I collagen sponge, hydroxyapatite-tricalcium phosphate (HA-TCP), and demineralized bone matrix (DBM), using BMP9-expressing C2C12 osteoblastic progenitor cells. We find that recombinant adenovirus-mediated BMP9 expression effectively induces osteogenic differentiation in C2C12 cells. Although direct subcutaneous injection of BMP9-transduced C2C12 cells forms ectopic bony masses, subcutaneous implantation of BMP9-expressing C2C12 cells with collagen sponge or HA-TCP scaffold yields the most robust and mature cancellous bone formation, whereas the DBM carrier group forms no or minimal bone masses. Our results suggest that collagen sponge and HA-TCP scaffold carriers may provide more cell-friendly environment to support the survival, propagation, and ultimately differentiation of BMP9-expressing progenitor cells. This line of investigation should provide important experimental evidence for further preclinical studies in BMP9-mediated cell-based approach to bone tissue engineering.

Psychological distress in the active duty military spine patient.

Disorders of the spine are a substantial burden to the military health care system that degrades readiness in the overall force. Because treatment outcomes are affected by psychosocial factors, assessment of psychological distress is important for patients with spine complaints. The incidence of psychological distress in the unique military population is not well described. The purpose of this retrospective case-control study was to determine the rate of psychological distress and identify associated patient characteristics among many variables collected in the military health system. A consecutive cohort of active duty service members presenting to a spine specialty clinic was assessed as Normal, At Risk, or Distressed using the Distress and Risk Assessment Method. Of 74 active duty patients (63 male, 11 female), 43 (58%) had some level of psychological distress: 29 (39%) At Risk, 12 (16%) Distressed-Depressive, and 2 (3%) Distressed-Somatic. Multivariate regression analysis identified female gender (odds ratio [OR] 7.90), higher disability as measured by Oswestry Disability Index/Neck Disability Index (OR 8.0 per 13.8 point increase), and assignment to a Warrior Transition Unit or Medical Evaluation Board (OR 7.35) as statistically significant variables. The results indicate that active duty patients are subject to similarly high levels of psychological distress as their civilian counterparts.

Effect of vacuum spine board immobilization on incidence of pressure ulcers during evacuation of military casualties from theater.

BACKGROUND CONTEXT: In the summer of 2009, the vacuum spine board (VSB) was designated by the US Air Force as the preferred method of external spinal immobilization during aeromedical transport of patients with suspected unstable thoracolumbar spine fractures. One purported advantage of the VSB is that, by distributing weight over a larger surface area, it decreases the risk of skin pressure ulceration. PURPOSE: To examine whether the rate of pressure ulcers has changed since the introduction of the VSB. STUDY DESIGN: Retrospective cohorts. PATIENT SAMPLE: Injured US service members undergoing spinal immobilization during evacuation from the Iraq and Afghanistan theaters to Landstuhl, Germany. OUTCOME MEASURES: Presence and stage of pressure ulceration, and deterioration in neurologic status. METHODS: Records of the initial 60 patients medically evacuated on the VSB to Landstuhl Regional Medical Center were retrospectively analyzed for patient demographics, injury characteristics, and incidence of pressure injury. The incidence of pressure ulcers after the use of VSB was compared with that in a historical control consisting of 30 patients with unstable spinal injuries evacuated before the introduction of the VSB. No sources of external funding were used for this investigation. RESULTS: The combined cohort had a mean age of 28.8 years and mean Injury Severity Score (ISS) of 20.63 and comprised 96% men. Most injury mechanisms were blunt (58%). The rate of neurological injury was 19%. There were no cases of progressive neurological deficit or deformity in either cohort. In the VSB group, using a broad definition of pressure ulcer, incidence was 13 of 60 patients (22%). Using a strict definition, incidence was eight of 60 (13%): five Stage I and three Stage II. In the non-VSB group, incidence of pressure ulcers was three of 30 (10%), using either definition, all Stage II. Difference in incidence between the groups was not statistically significant. Intubated patients had a significantly higher incidence of pressure ulcers. CONCLUSION: Both the VSB and historic means (non-VSB) of spinal immobilization appear to be safe and produce only transient morbidity despite an average of 9 to 10 hours of transport. Intubated status was identified as the most important risk factor for the development of a pressure ulcer.

Comparison of tissue oxygenation and compartment pressure following tibia fracture.

OBJECTIVE: We investigated the ability of direct continuous measurement of intramuscular tissue oxygenation (PmO(2)) to detect acute ischaemia in the leg in patients at risk for acute extremity compartment syndrome. Following tibia fracture treated by intramedullary nailing, we compared the proportions of PmO(2) and compartment pressure (CP) measurements that met the warning criteria for compartment syndrome. METHODS: Participants included 10 patients sustaining acute isolated closed tibia shaft fractures treated by intramedullary nailing. A tissue oxygenation probe and a CP probe were percutaneously placed into the anterior compartment of the leg. PmO(2) and CP in the anterior compartment were measured in the injured leg for 48 h postoperatively. Measurements meeting the warning criteria were defined as PmO(2) < 10 mmHg, CP > 30 mmHg and perfusion pressure ΔP < 30 mmHg. RESULTS: None of the patients developed compartment syndrome. Comparison of CP and PmO(2) showed a CP > 30 mmHg in 50.39% of CP measurements in all patients and a PmO(2) < 10 mmHg in 0.75% of PmO(2) measurements in two patients (P = 0.005). Comparison of ΔP and PmO(2) showed a ΔP < 30 mmHg in 31.01% of ΔP measurements in nine patients and a PmO(2) < 10 mmHg in 0.76% of PmO(2) measurements in one patient (P = 0.01). CONCLUSION: In the absence of compartment syndrome, pressure measurements following tibia fracture treated with intramedullary nailing often met the warning criteria, whereas PmO(2) did not, suggesting that measurement of intramuscular tissue oxygenation may represent a potential method for the identification of acute compartment syndrome that deserves continued investigation.

Lumbar plexus anatomy within the psoas muscle: implications for the transpsoas lateral approach to the L4-L5 disc.

BACKGROUND: The transpsoas lateral surgical approach has been advocated as an alternative to direct anterior approaches for less invasive or minimally invasive access to the spine. Postoperative thigh pain, paresthesia, and/or weakness have been described after the use of this surgical approach. The purpose of this cadaveric anatomic study is to provide a description of the lumbar plexus as it relates to the transpsoas lateral surgical approach. METHODS: Dissection of the lumbar plexus was performed in eighteen cadaveric specimens. Needle markers were placed in the L2-L3, L3-L4, and L4-L5 discs in the midcoronal plane. The anatomic structures were surveyed, and the proximity of the needle to the neural structures was observed. RESULTS: In thirteen of the eighteen specimens, the femoral nerve received its contributions from the L2 to L4 nerve roots and was formed at the L4-L5 disc space. In all specimens, the femoral nerve passed dorsal to or directly at the midpoint of the disc. In three specimens, the needle displaced or was immediately adjacent to the femoral nerve. The femoral nerve was found between the needle and the posterior aspect of the L4-L5 disc space in thirteen of the eighteen specimens. CONCLUSIONS: Because of the proximity of the neural elements, in particular the femoral nerve, to the center of the disc space, the transpsoas lateral surgical approach to the L4-L5 disc space will likely cause intraoperative displacement of neural structures from their anatomic course during retractor dilation. Careful attention should be paid to retractor placement and dilation time during transpsoas lateral access surgery, particularly at the L4-L5 disc.

Adjacent segment motion after anterior cervical discectomy and fusion versus Prodisc-c cervical total disk arthroplasty: analysis from a randomized, controlled trial.

STUDY DESIGN: Post hoc analysis of data acquired in a prospective, randomized, controlled trial. OBJECTIVE: To compare adjacent segment motion after anterior cervical discectomy and fusion (ACDF) versus cervical total disc arthroplasty (TDA). SUMMARY OF BACKGROUND DATA: TDA has been designed to be a motion-preserving device, thus theoretically normalizing adjacent segment kinematics. Clinical studies with short-term follow-up have yet to demonstrate a consistent significant difference in the incidence of adjacent segment disease. METHODS: Two hundred nine patients at 13 sites were treated in a prospective, randomized, controlled trial of ACDF versus TDA for single-level symptomatic cervical degenerative disc disease (SCDD). Flexion and extension radiographs were obtained at all follow-up visits. Changes in ROM were compared using the Wilcoxon signed-rank test and the Mann-Whitney U test. Predictors of postoperative ROM were determined by multivariate analysis using mixed effects linear regression. RESULTS: Data for 199 patients were available with 24-month follow-up. The groups were similar with respect to baseline demographics. A significant increase in motion at the cranial and caudal adjacent segments after surgery was observed in the ACDF group only (cranial: ACDF: +1.4° (0.4, 2.4), P = 0.01; TDA: +0.8°, (-0.1, +1.7), P = 0.166; caudal: ACDF: +2.6° (1.3, 3.9), P < 0.0001; TDA: +1.3, (-0.2, +2.8), P = 0.359). No significant difference in adjacent segment ROM was observed between ACDF and TDA. Only time was a significant predictor of postoperative ROM at both the cranial and caudal adjacent segments. CONCLUSION: Adjacent segment kinematics may be altered after ACDF and TDA. Multivariate analysis showed time to be a significant predictor of changes in adjacent segment ROM. No association between the treatment chosen (ACDF vs. TDA) and ROM was observed. Furthermore clinical follow-up is needed to determine whether possible differences in adjacent segment motion affect the prevalence of adjacent segment disease in the two groups.

Admitting service and morbidity and mortality in elderly patients after hip fracture: finding a threshold for medical versus orthopedic admission.

Outcomes by admitting service of 355 consecutive patients admitted for hip fracture at an academic medical center were retrospectively studied. An adverse event occurred in 53 patients (14.9%): 10 in-hospital deaths, 37 intensive care unit transfers, and 25 deaths within 30 days. No significant difference was found between percentages of patients with adverse events admitted to a medical service versus an orthopedic service (52.8% vs 47.2%; P = .8). Criteria that determine admitting service based on medical acuity do not adequately allocate patients at risk for serious morbidity and early mortality to a medical service. Addition of American Society of Anesthesiologists grade 4 and men 85 or older to existing criteria would increase the percentage of patients with adverse events admitted to a medical service (72% vs 28%; P<.005).

Dynamic constructs for spinal fusion: an evidence-based review.

Dynamic stabilization of the spine has applications in cervical and lumbar degenerative disease and in thoracolumbar trauma. There is little evidence to support the use of dynamic cervical plates rather than rigid anterior cervical fixation. Evidence to support the use of dynamic constructs for fusion in the lumbar spine is also limited. Fusion rates, implant loosening, and failure are significant concerns that limit the adoption of current devices. This article provides a synopsis of the literature on human subjects. There is a need for high-quality evidence for interventions for spinal pathology. An evidence-based approach to the management of spinal disorders will require ongoing assessment of clinical outcomes and comparison of effectiveness between alternatives.

Delayed presentation of tetraparesis following posterior thoracolumbar spinal fusion and instrumentation for adolescent idiopathic scoliosis.

STUDY DESIGN: Case report. OBJECTIVE: We present a case of delayed tetraparesis in a patient after posterior spinal fusion for adolescent idiopathic scoliosis. SUMMARY OF BACKGROUND DATA: The reported rate of neural complications after scoliosis surgery is low. Intraoperative neuromonitoring is used to detect and prevent spinal cord injury. METHODS: Review of medical record. RESULTS: Delayed tetraparesis developed on the second postoperative day after unremarkable T3-L4 posterior fusion. MRI revealed evidence of cord ischemia at C4-C7. Angiogram revealed a hypervascular T4 body resulting in arteriovenous shunting into the epidural venous plexus. CONCLUSION: Venous congestive myelopathy due to arteriovenous shunting or unrecognized syrinx are presented as possible etiologies of this patient's spinal cord injury. A preoperative MRI may have helped discern the cause of this patient's spinal cord injury.

Reoperation after primary fusion for adult spinal deformity: rate, reason, and timing.

STUDY DESIGN: Retrospective cohort study of consecutive patients undergoing primary fusion with segmental fixation for adult spinal deformity. OBJECTIVE: We sought to determine the survivorship of primary fusion for adult spinal deformity and identify patient-specific predictors of complications requiring reoperation. SUMMARY OF BACKGROUND DATA: Compared with the adolescent population, surgery for adult deformity is often more complex and technically difficult, contributing to a high reported rate of complications that can result in the need for reoperation. Reported complication rates vary widely. METHODS: From 1999-2004 all patients who underwent primary instrumented fusion for nonparalytic adult spinal deformity at a single center were included. Inclusion criteria included minimum age at surgery of 20 years and minimum fusion length of 4 motion segments. Surgical, demographic, and comorbidity data were recorded. Reoperation was defined as any additional surgery involving levels of the spine operated on during the index procedure and/or adjacent levels. Comparisons were performed between patients who required reoperation and those who did not. RESULTS: Eighty-nine patients met inclusion criteria. Endpoint (minimum 2 years follow-up or reoperation) was reached for 91%. Mean follow-up was 3.8 years. Cumulative reoperation rate was 25.8%. Survival was 86.4% at 1 year, 77.2% at 2 years, and 75.2% at 3 years. Reasons for reoperation included infection (n = 8), pseudarthrosis (n = 3), adjacent segment problems (n = 5), implant failure (n = 4), and removal of painful implants (n = 3). Multivariate analysis showed smoking was significantly higher in the reoperation group. CONCLUSION: Using a strict definition of reoperation for a well-defined cohort, in the presence of relevant risk factors, many patients undergoing primary fusion for adult spinal deformity required reoperation. The results indicate that complex medical and surgical factors contribute to the treatment challenges posed by patients with adult spinal deformity. This represents the largest cohort reported to date of patients undergoing primary fusion using third-generation instrumentation techniques.

Clinical outcome of deep wound infection after instrumented posterior spinal fusion: a matched cohort analysis.

STUDY DESIGN: Retrospective case control study. OBJECTIVE: Determine the impact of infection on clinical outcome in patients undergoing posterior spinal fusion surgery. SUMMARY OF BACKGROUND DATA: The outcome of patients treated for infection after spinal surgery is not well established because of variability in cohort identification, definition of infection, outcomes instrument, use of a control group, and/or sample size. METHODS: Thirty-two patients were included. Sixteen patients ("infection group") met inclusion criteria of deep wound infection after spinal fusion with posterior segmental instrumentation (including combined approach). A 1:1 matched cohort ("control group") was created based on primary or revision status, length of fusion, diagnosis, and age. Postoperative patient outcomes were evaluated using the physical components of SF-36 v2.0 with minimum 2-year follow-up. RESULTS: No significant difference in the Physical Function, Role Physical, Bodily Pain, and General Health domains was detected between the infection group and control group. Mean follow-up was 62 months. Mean Physical Component Summary was 41.4 in the infection group and 44.3 in the control group (P = 0.6). Infection occurred early in 12 patients and late in 4 patients. Most common organisms isolated were Staphylococcus epidermidis, Enterococcus sp., and Staphylococcus aureus. Multiple debridements were significantly associated with polymicrobial infections and later pseudarthrosis requiring reoperation. CONCLUSION: An aggressive approach to deep wound infection emphasizing early irrigation and debridement allowed preservation of instrumentation and successful fusion in most cases. At the conclusion of treatment, patients can expect a medium-term clinical outcome similar to patients in whom this complication did not occur.