Rib-on-Pelvis Deformity and Reported Pain in Neuromuscular Early-Onset Scoliosis.

BACKGROUND: Neuromuscular early-onset scoliosis (N-EOS) often presents with a long sweeping thoracolumbar scoliosis and pelvic obliquity. With severe pelvic obliquity, the ribs come into contact with the high side of the pelvis, termed rib-on-pelvis deformity (ROP). The goal of this study is to evaluate whether ROP is associated with reported pain and other health-related quality of life (HRQOL) measures. We hypothesize that ROP is associated with increased pain and negative HRQOL. METHODS: A multicenter international registry was queried for all nonambulatory patients with N-EOS from 2012 to 2022. Both surgical and nonsurgical patients were included. ROP was classified as a binary radiographic assessment of preoperative (surgical patients) and most recent follow-up (nonsurgical patients) upright radiographs. Reported pain and other HRQOL measures were assessed through the 24-Item Early Onset Scoliosis Questionnaire (EOSQ-24). Patients with nonupright radiographs or EOSQ-24 questionnaires and corresponding radiographs >4 months apart were excluded. RESULTS: Totally, 225 patients (8.4±3.1 y, 55% female) were included. The median major curve was 63.3 (IQR: 40.6 to 81.2) degrees and median pelvic obliquity was 15.5 degrees (IQR: 8.8 to 26.4). Eighty-three patients (37%) had ROP. ROP was associated with both frequency (P<0.001) and severity (P<0.001) of pain. ROP was associated with worse general health (P=0.01), increased difficulty with vocalization (P=0.02), increased frequency of shortness of breath (P=0.002), and increased difficulty sitting upright (P=0.04). Regarding overall EOSQ-24 domains, ROP was associated with worse general health, pain/discomfort, pulmonary function, and physical function (P<0.01). In a subanalysis of 76 patients who underwent surgical intervention with at least 2 years of follow-up, patients with preoperative ROP experienced significantly greater improvements in both frequency (P=0.004) and severity (P=0.001) of pain than the patients without preoperative ROP at 2 years postoperatively. CONCLUSIONS: The overall incidence of ROP in N-EOS is about 37%. ROP is associated with greater pain and worse HRQOL through the EOSQ-24 questionnaire. Furthermore, these patients experienced a greater reduction in pain after surgery. Clinicians and parents must be aware that ROP is possibly a pain generator, but responds positively to surgical intervention. LEVEL OF EVIDENCE: Level III.

Clinical Relevance of Painful Congenital Early-onset Scoliosis: A Magnetic Resonance Image-based Study.

BACKGROUND: Back pain, as a clinical marker in scoliosis, has been associated with underlying pathology for many years, warranting further magnetic resonance imaging (MRI). Failures of segmentation, mixed defects, female gender, rib anomalies, congenital thoracic anomalies, and neurocutaneous markers are known risk factors for abnormal MRI pathology findings in patients with congenital early-onset scoliosis (Congenital-EOS). Yet, back pain has not been evaluated as a risk factor for underlying MRI pathology in patients with Congenital-EOS. This study aimed to assess back pain as a risk factor for underlying pathology in Congenital-EOS using MRI as a diagnostic tool. METHODS: A retrospective database review from the Pediatric Spine Study Group (PSSG) of all patients with Congenital-EOS who reported a back pain complaint, and underwent a spinal MRI study before surgical intervention was performed. Patients were divided into those with an underlying MRI pathology and those without. Demographics were compared between groups. RESULTS: From a total of 2355 patients with Congenital-EOS registered in PSSG, 107 patients reported a back pain complaint, with only 42 patients fulfilling the inclusion criteria (being evaluated with an MRI study). Overall group mean age was 8.1±4.5 years, with 25 of the 42 patients (60%) being females. Twenty-four of 42 patients (57%) had a comorbidity reported such as cardiac problems, musculoskeletal complaints, neurological deficits/myelopathy, gastrointestinal symptoms, developmental delay, respiratory problems, craniofacial abnormalities, and chromosomal conditions. An underlying MRI pathology was found in 21 of 42 patients with Congenital-EOS (50%) with back pain. The underlying MRI pathologies found were tethered spinal cord, spinal canal stenosis, syringomyelia, Arnold-Chiari malformation, and arachnoid cyst. CONCLUSIONS: Abnormal MRI findings are common in patients with Congenital-EOS who report back pain. Gender, age, major coronal curve angle, thoracic or lumbar predominance deformity, and comorbidities type or amount were not associated with abnormal MRI findings. LEVEL OF EVIDENCE: Level II-Prognostic study.

Optimizing Expansion Clinic for Patients With Magnetic Controlled Growth Rods.

In 2017, members of the Pediatric Spine Study Group reported that 80% of new growth-friendly implants inserted were magnetically controlled growing rods (MCGRs). MCGRs are usually expanded more often than every 6 months, as was general practice with traditional growth rods. The growing volume of expansion visits is managed variably at different centers. Although there is existing research comparing MCGRs with traditional systems for efficacy and complications, there is limited literature regarding how expansion clinics are managed. This article reviews current practices such as scheduling, expansion verification, billing, and other key parameters for running expansion clinics.

How low can you go? Implant density in posterior spinal fusion converted from growing constructs for early onset scoliosis.

STUDY DESIGN: Retrospective, multicenter comparative. OBJECTIVES: Our purpose was to compare early onset scoliosis (EOS) patients treated with ultra-low, low, and high implant density constructs when undergoing conversion to definitive fusion. Larson et al. demonstrated that implant density (ID) at fusion does not correlate with outcomes in the treatment of adolescent idiopathic scoliosis, but did not address growth-friendly graduates. METHODS: EOS patients treated with growth-friendly constructs converted to fusion between 2000 and 2017 were reviewed from a multicenter database. ID was defined as number of pedicle screws, hooks, and sublaminar/bands per level fused. Patients were divided into ultra-low ID (< 1.3), low (≥ 1.3 and < 1.6), and high ID (≥ 1.6). EXCLUSION CRITERIA: < 2 years follow-up from fusion or inadequate radiographs. RESULTS: A total of 152 patients met inclusion criteria with 39 (26%) patients in the high ID group, 33 (22%) patients in the low ID group, and 80 (52%) in the ultra-low ID group. Groups were similar in operative time (p = 0.61), pre-fusion major curve (p = 0.71), mean number of levels fused (p = 0.58), clinical follow-up (p = 0.30), and radiographic follow-up (p = 0.90). Patients in the low ID group (11.6 ± 1.5 years) were slightly younger at the time of definitive fusion than patients in the ultra-low ID group (12.9 ± 2.2 years) and high ID group (12.5 ± 1.7 years) (p = 0.009). There was significantly more blood loss in the high ID group than the other two groups (high ID: 946.8 ± 606.0 mL vs. low ID: 733.9 ± 434.5 mL and ultra-low ID: 617.4 ± 517.2 mL; p = 0.01), but there was no significant difference with regard to percent of total blood volume lost (high ID: 59.3 ± 48.7% vs. low ID: 54.5 ± 37.5% vs. ultra-low ID: 51.7 ± 54.9%; p = 0.78). There was a difference in initial improvement in major curve between the groups (high ID: 21.6° vs. low ID: 18.0° vs. ultra-low ID: 12.6°; p = 0.01). However, during post-fusion follow-up, correction decreased 7.1° in the high ID group, 2.6 in the low ID group, and 2.8 in the ultra-low ID group (p = 0.19). At final follow-up, major curve correction from pre-fusion was similar between groups (high ID: 14.5° vs. low ID: 15.5° vs. ultra-low ID: 9.7°, p = 0.14). At final follow-up, there was no difference in T1-T12 length gain (p = 0.85), T1-S1 length gain (p = 0.68), coronal balance (p = 0.56), or sagittal balance (p = 0.71). The revision rate was significantly higher in the ultra-low ID group (13.8%; 11/80) versus the high ID group (2/39; 5.1%) and low ID group (0/33; 0%) (p = 0.04). CONCLUSIONS: Although an ID < 1.3 in growth-friendly graduates produces similar outcomes with regard to curve correction and spinal length gain as low and high ID, this study suggests that an ID < 1.3 is associated with an increased revision rate. LEVEL OF EVIDENCE: III.

Risk of early complication following anterior vertebral body tethering for idiopathic scoliosis.

PURPOSE: The purpose of this study was to determine peri-operative morbidity associated with anterior vertebral body tethering (aVBT) for idiopathic scoliosis. METHOD: Of 175 patients treated with aVBT, 120 patients had 2 year follow up and were included in this study. Prospectively collected clinical and radiographic data was analyzed retrospectively. RESULTS: Pre-operatively, the mean patient age was 12.6 year (8.2-15.7 year), Risser 0-3, with main thoracic scoliosis 51.2° (40-70°). Immediately post-operative, scoliosis improved to 26.9° (6-53°; p < 0.05), at 1-year post-operative was 23.0° (- 11 to 50°; p < 0.01 vs immediate post-op) and at 2-year post-operative was 27.5° (- 5 to 52; p = 0.64 vs immediate post-op). Pre-operative T5-T12 kyphosis was 16.0° (- 23 to 52°), post-operative was 16.9° (- 7 to 44°), at 1-year was 17.5° (- 14 to 61°) and at 2-year was 17.0° (- 10 to 50°; p = 0.72 vs pre-op). All patients underwent thoracoscopic approach, EBL 200 ml (20-900 ml), surgical time 215.3 min (111-472 min), anesthesia time 303.5 min (207-480 min), ICU stay of 0.2 day (0-2 days), and post-operative hospital stay 4.5 days (2-9 days). During the in-hospital peri-operative period, there were no unplanned return to the operating room (UPROR) and there was a 0.8% rate of complication: one pneumothorax requiring reinsertion of chest tube. By 90 days post-operative, there was no UPROR and a 5% rate of complication. Five additional patients developed complications after discharge: one CSF leak treated with blood patch injection in the clinic and resolved, two pleural effusions requiring chest tubes, one superficial wound infection and one pneumonia treated with outpatient antibiotics. By 1-year post-op, there was a 1.7% rate of UPROR and 8.3% rate of complication. Four additional patients developed complications beyond 90 days: two upper limb paresthesia required outpatient medical management, one CSF leak which initially treated blood patch injection in the clinic initially which then required UPROR, and one compensatory lumbar curve add on that was treated with extension of the tether. By 2-years post-op, there was a 6.7% rate of UPROR and 15.8% rate of complication. 9 additional complications developed after 1 year. One curve progression, one keloid scar, one right leg weakness, 4 cable failures and 2 curve overcorrections. CONCLUSION: This large, multicenter series of aVBT demonstrated a 15.8% complication rate and a 6.7% UPROR rate at 2 year post-operatively. This early study during the learning curve of aVBT found higher rates of CSF leaks and overall complications than would be expected for PSFI at 1 year post-operatively and a higher rate of overall complications and of UPROR than would be expected for PSFI at 2 year post-operatively. As is common with new procedures, the complication rate may fall with further experience.

Serial Casting in Neuromuscular and Syndromic Early-onset Scoliosis (EOS) Can Delay Surgery Over 2 Years.

BACKGROUND: The primary goal in managing early-onset scoliosis (EOS) is delaying/preventing surgical intervention while allowing improved spinal growth and chest wall and lung development to improve life expectancy. The effectiveness of serial casting for patients with neuromuscular and syndromic EOS is unclear. METHODS: Patients from 2 multicenter registries who underwent serial casting for nonidiopathic scoliosis (NIS) were reviewed retrospectively. Comparisons were made between precasting and postcasting major and compensatory curves and spine height. The need for surgical intervention and any treatment complications were documented. Risk factors for major curve progression from baseline to casting cessation were evaluated via univariate analysis. RESULTS: Forty-four patients (23 females; 21 males) with NIS (26 syndromic, 18 neuromuscular) and a mean age of 3.2 years at baseline were included. Mean follow-up and casting duration was 3.9 and 2.0 years, respectively. There were no statistically significant differences between mean precasting and postcasting major curve (55 vs. 60 degrees; P=0.348), minor curve (31 vs. 33 degrees; P=0.510), or rib-vertebra angle difference (18 vs. 29 degrees; P=0.840). However, thoracic height (15.5 vs. 16.8 cm; P=0.031) and lumbar height (8.9 vs. 9.8 cm; P=0.013) were significantly greater upon casting cessation. Currently, 13 patients (30%) have had successful casting (improvement of major curve ≥10 degrees) while 24 patients (55%) experienced major curve progression (worsening), and 19 patients (43%) required surgical intervention. Mean time from first casting to surgery was 34.5±15.1 months. There were no statistically significant predictors for major curve progression on univariate analysis. CONCLUSIONS: Spinal deformity progression despite casting and the subsequent need for surgical intervention for NIS were significantly higher compared with those reported for idiopathic EOS. However, serial casting did afford a substantial delay in surgical intervention. Ultimately, serial casting for neuromuscular or syndromic EOS is an effective strategy for delaying surgical intervention, despite suboptimal radiographic outcomes. LEVEL OF EVIDENCE: Level III.

Effects of Spinal Fusion for Idiopathic Scoliosis on Lower Body Kinematics During Gait.

STUDY DESIGN: Prospective. OBJECTIVES: The purpose of this study was to compare gait among patients with scoliosis undergoing posterior spinal fusion and instrumentation (PSFI) to typically developing subjects and determine if the location of the lowest instrumented vertebra impacted results. SUMMARY OF BACKGROUND DATA: PSFI is the standard of care for correcting spine deformities, allowing the preservation of body equilibrium while maintaining as many mobile spinal segments as possible. The effect of surgery on joint motion distal to the spine must also be considered. Very few studies have addressed the effect of PSFI on activities such as walking and even fewer address how surgical choice of the lowest instrumented vertebra (LIV) influences possible motion reduction. METHODS: Individuals with scoliosis undergoing PSFI (n = 38) completed gait analysis preoperatively and at postoperative years 1 and 2 along with a control group (n = 24). Comparisons were made with the control group at each time point and between patients fused at L2 and above (L2+) versus L3 and below (L3-). RESULTS: The kinematic results of the AIS group showed some differences when compared to the Control Group, most notably decreased range of motion (ROM) in pelvic tilt and trunk lateral bending. When comparing the LIV groups, only minor differences were observed, and the results showed decreased coronal trunk and pelvis ROM at the one-year visit and decreased hip rotation ROM at the two-year visit in the L3- group. CONCLUSIONS: Patients with AIS showed decreased ROM preoperatively with further decreases postoperatively. These changes remained relatively consistent following the two-year visit, indicating that most kinematic changes occurred in the first year following surgery. Limited functional differences between the two LIV groups may be due to the lack of full ROM used during normal gait, and future work could address tasks that use greater ROM. LEVEL OF EVIDENCE: Level II.

Effect of Surgical Fusion on Volitional Weight-Shifting in Individuals With Adolescent Idiopathic Scoliosis.

STUDY DESIGN: Prospective. OBJECTIVES: The goals of this study were to (1) evaluate the differences in weightbearing symmetry between individuals with adolescent idiopathic scoliosis (AIS) and typically developing controls; (2) observe the effect of posterior spinal fusion and instrumentation (PSFI) on volitional weight-shifting at 1 and 2 years postoperatively; and (3) evaluate whether lowest instrumented fusion level (ie, lowest instrumented vertebra [LIV]) in PSFI has an effect on volitional weight-shifting. SUMMARY OF BACKGROUND DATA: Previous studies have conflicting findings with regard to the effect of scoliosis on postural control tasks as well as the effect of surgery. They have also noted an inconsistent effect of PSFI at different LIVs, with more distal LIVs exhibiting greater reductions in postoperative range of motion. METHODS: The study was designed with an AIS group of 41 patients (8 males and 33 females) with AIS who underwent PSFI, along with a Control Group of 24 age-matched typically developing participants (12 male and 12 female). Both groups performed postural control tasks (static balance and volitional weight-shifting), with the AIS group repeating the tasks at 1 and 2 years postoperatively. RESULTS: At baseline, the AIS group showed increased weightbearing asymmetry than the Control Group (p = .01). The AIS group showed improvements in volitional weight-shifting at 2 years over baseline (p < .01). There was no effect of LIV on volitional weight-shifting by the second postoperative year. CONCLUSIONS: Individuals with AIS have greater weightbearing asymmetry but improved volitional weight-shifting over typically developing controls. PSFI improves volitional weight-shifting beyond preoperative baseline but does not differ significantly by LIV.

Effect of Lowest Instrumented Vertebra on Trunk Mobility in Patients With Adolescent Idiopathic Scoliosis Undergoing a Posterior Spinal Fusion.

STUDY DESIGN: Prospective. OBJECTIVES: The goal of this study was to evaluate the effect of posterior spinal fusion surgery terminating at different lowest instrumented vertebrae (LIV) on trunk mobility in individuals with adolescent idiopathic scoliosis (AIS). SUMMARY OF BACKGROUND DATA: Posterior spinal fusion with instrumentation is the standard surgical technique employed in AIS for correcting spine deformities with Cobb angles exceeding 50°. Surgical correction of curve deformity reduces trunk mobility and range of motion. However, conflicting findings from previous studies investigating the impact of different LIV levels on the reduction in trunk mobility after surgery have been reported. METHODS: The study was designed as a prospective study with 47 patients (7 males and 40 females) with AIS who underwent posterior spinal fusion. Patients were classified into 5 groups based on their surgical LIV level (ie, T12, L1, L2, L3, and L4). Trunk flexion-extension (sagittal plane), lateral bending (coronal plane), and axial rotation (transverse plane) kinematics were assessed during preoperative, 1 year postoperative, and 2 years postoperative evaluation visits. RESULTS: There were postoperative reductions of 41%, 51%, and 59% in trunk range of motion in the sagittal, coronal, and transverse planes, respectively (p < .0001). A trend toward greater postoperative reductions in peak forward flexion at more distal LIVs was observed (p = .04). CONCLUSIONS: Fusion reduces trunk mobility in the sagittal, coronal, and transverse planes. More distal LIV fusions limit peak forward flexion to a greater extent which is considered clinically significant. After fusion, the reductions seen in axial rotation, lateral bending, and backward extension do not differ significantly at more distal LIVs.

A rare anesthetic complication involving central line access during lumbar spine surgery: a case report and review.

STUDY DESIGN: A case report describing a rare perioperative complication involving the intrathoracic placement of a central venous catheter during spine surgery leading to hemodynamic instability. OBJECTIVE: To review the efficacy of central line use in perioperative spine patients and to describe the diagnosis, emergent treatment, and postoperative care of a unique case of intrathoracic extravasation of propofol. SUMMARY OF BACKGROUND DATA: Although placement of central line access is a safe procedure, complications can occur. A case in which a venous catheter delivering propofol into the thorax has never been documented. METHODS: A 48-year-old woman presented for revision spine surgery, and a central line was placed. After placement of spinal instrumentation, she became hemodynamically unstable secondary to mediastinal compression caused by pressure from intraoperative propofol and fluid insufflation. RESULTS: A chest tube was placed, and with aggressive pulmonary toilet and physical therapy, she did well and was discharged without noted symptoms. CONCLUSION: The efficacy of central line use should be carefully considered in perioperative spine surgery, and in patients with significant risk factors, placement of central venous access should be radiographically confirmed.

Quantification of a meaningful change in low back functional impairment.

STUDY DESIGN: Repeated measures study design. OBJECTIVE: Determine a meaningful change in low back functional impairment as measured with the lumbar motion monitor. SUMMARY OF BACKGROUND DATA: A quantitative functional performance probability (P(n)) measure has been developed and is scored from 0.00 to 1.00. Previous research has shown that a 0.5 cut-off provides excellent sensitivity and specificity for identifying impaired and healthy low back function. However, a meaningful change in the P(n) measure has not been defined. METHODS: The lumbar motion monitor was used to repeatedly measure P(n) in 3 groups of subjects including (1) asymptomatic, (2) recovering low back pain (LBP) and, (3) nonrecovering LBP. The asymptomatic group had 20 subjects. The recovering and nonrecovering LBP had 18 and 8 subjects, respectively. The asymptomatic group was tested 5 times at 1-week intervals. The 2 LBP groups were tested every 2 weeks for 3 months (6 evaluations). RESULTS: The P(n) in the asymptomatic group did not significantly change over the observed period. On the basis of the variability in the asymptomatic group it was hypothesized that a meaningful change in P(n) was 0.14. The defined meaningful change was evaluated in 2 patient with LBP populations. The P(n) in the recovered LBP group significantly improved during the 3 month observation period and there was a corresponding reduction of symptoms. In the recovering LBP group the within subject standard deviation was 0.14 and all patients had at least 1 visit to visit change greater than 0.14. Furthermore, 11 of the 18 recovering patients with LBP had a meaningful change between the first 2 visits. In contrast, none of the nonrecovering LBP group had a meaningful change between the first 2 visits. CONCLUSION: A meaningful change in P(n) was defined as 0.14.

Static versus dynamic plating for multilevel anterior cervical discectomy and fusion.

BACKGROUND CONTEXT: Dynamic anterior plates have been popularized to promote cervical spine fusion by allowing controlled settling, thereby promoting load sharing across the construct. To date these proposed benefits have been largely theoretical and there are no studies confirming any benefits over more traditional static plates. PURPOSE: To compare the clinical and radiographic outcomes of patients undergoing an instrumented multilevel anterior cervical discectomy and fusion (ACDF) with either a static or dynamic plate design. STUDY DESIGN: A retrospective clinical and radiographic study. PATIENT SAMPLE: From 1997 to 2002, 52 patients with either radiculopathy or myelopathy underwent two- or three-level ACDF with either static or dynamic plate fixation. OUTCOME MEASURES: Functional outcome, fusion status, radiographic measurements. METHODS: A statically locked plating system was used in 21 patients, and a dynamic plating system was used in 31 patients. Functional outcome, fusion status, plate migration, settling, and adjacent-level disc space impingement were evaluated. RESULTS: Clinical outcome was found to be similar between the statically and dynamically plated groups. Eighty-four percent of patients in both groups experienced good or excellent results at final follow-up. We observed a higher rate of nonunion in patients treated with a dynamic plate (16% [5 of 31]) compared with a rate of 5% (1 of 21) in those patients treated with a static plate (p=.05). Settling of the construct and plate migration was similar between the study groups at all time points. CONCLUSIONS: This study failed to confirm our hypothesis that a dynamic plate (that allows angular motion between the screws and plate) confers any clinical or radiographic advantage over earlier design static plates. A higher rate of nonunion was actually seen in the dynamically plated patients; however, clinical results were similar between the two groups.

Unusual presentation of osteoblastoma in a patient with idiopathic scoliosis after posterior spinal fusion.

BACKGROUND CONTEXT: Few studies have described the diagnosis of osteoblastoma of the spine as a cause of scoliosis. These reports have described the tumor in conjunction with initial presentation of painful scoliosis. This case report presents a case of osteoblastoma 9 years removed from diagnosis and fusion of idiopathic scoliosis in the thoracic spine. PURPOSE: To report the late presentation of an osteoblastoma of the thoracic spine 9 years after posterior spinal fusion for scoliosis. STUDY DESIGN: Case report. METHODS: A 25-year-old man presented with thoracolumbar back pain and progressive neurological deficit 9 years after posterior spinal fusion for idiopathic scoliosis. Magnetic resonance imaging of the thoracic spine indicated the presence of a mass in the spinal canal causing cord compression. The patient underwent decompression with resection of the mass which was found to be an aggressive osteoblastoma. RESULTS: The patient enjoyed a full neurological recovery and has subsequently developed a recurrence at 13 months. CONCLUSIONS: We present osteoblastoma as a possible cause of low back pain and neurological deficit postfusion that should be considered in a differential diagnosis.

Functional impairment as a predictor of spine loading.

STUDY DESIGN: Spine loadings during a variety of lifting exertions were compared with individual torso kinematic abilities. Relationships were evaluated between these measures. OBJECTIVE: To determine if trunk kinematic status (functional impairment) is indicative of spine loading increases in patients with low back pain (LBP) compared to asymptomatic individuals. SUMMARY OF BACKGROUND DATA: Recurrent LBP is a common and costly problem that may be related to increased spine loads in those individuals with LBP. Previous studies suggest that patients with LBP had greater loading than their asymptomatic counterparts when performing work. However, we know little about how to identify when a patient with LBP can resume lifting tasks without having exaggerated spine loading. METHODS: Sixty-two patients with LBP and 61 who were asymptomatic were evaluated for signs of kinematic compromise (i.e., inability to generate normal trunk kinematic patterns) during a prelift test. All subjects were then asked to perform a variety of lifting exertions that varied in lift origin (region), lift asymmetry position, and weight lifted. An electromyography-assisted model was used to evaluate spine loading in each subject during the lifting exertions. Statistical models were used to assess the relationship between kinematic compromise and spine loading. RESULTS: Patients with LBP had greater spine loading as well as greater kinematic compromise. The degree of kinematic compromise was related to the degree of spine loading increases in those individuals with LBP. A statistical model was developed that was able to describe 87% of the variability in compression, 61% in anteroposterior shear, and 65% in lateral shear. CONCLUSIONS: Those patients with greater kinematic compromise used higher levels of antagonistic muscle coactivation that not only reduced trunk motion but also resulted in increases in spine loading. Given the degree of kinematic compromise and the lifting task conditions, a method has been devised to predict the increase in spine loading above and beyond that of an asymptomatic individual when performing typical materials handling tasks.

Differences in motor recruitment and resulting kinematics between low back pain patients and asymptomatic participants during lifting exertions.

BACKGROUND: Low back disorders are a prevalent problem in society today and may lead to chronic debilitating low back pain. Developing our understanding of temporal muscle and kinematic patterns during manual material handling tasks may provide insight for preventing the cascading series of events leading to chronic low back pain. METHODS: Sixty-two low back pain patients and 61 asymptomatic participants performed a variety of lifting exertions that varied in lift origin horizontal and vertical distance, lift asymmetry, and weight. Electromyographic activity of 10 trunk muscles as well as trunk and pelvic kinematics was recorded during each exertion. Differences in muscle activation and kinematic parameters were compared between low back pain patients and asymptomatic participants as a function of experimental conditions. FINDINGS: Both the left and right erector spinae activated significantly earlier and were on significantly longer in low back pain patients compared to asymptomatic participants. The horizontal and vertical location of the lift influenced the EMG and kinematic differences between the low back pain patients and asymptomatic participants. INTERPRETATION: These finding indicate that low back pain patients would be exposed to increase muscle activity resulting in higher spine loads for a greater length of time compared to asymptomatic participants. The longer exposure time to increased spine load may lead to greater risk of future low back injury and cascading events leading to debilitating low back pain. The longer muscle activation time suggests that low back pain patients have changed their motor program from an open to a closed loop system.

Spine loading in patients with low back pain during asymmetric lifting exertions.

BACKGROUND CONTEXT: Recurrent low back pain (LBP) is a common and costly problem that might be related to increased spine loads in those with LBP. However, we know little about how the spine is loaded when those with LBP perform lifting exertions. PURPOSE: Document spine loading patterns of patients with LBP performing symmetric and asymmetric lifting exertions compared with asymptomatic individuals performing the same tasks. STUDY DESIGN: Spine loadings during lifting exertions that varied in asymmetric origin as well as horizontal and vertical distance from the spine were compared between asymptomatic subjects and patients with LBP. METHODS: Sixty-two patients with LBP and 61 asymptomatic individuals performed a variety of lifting exertions that varied in lift origin horizontal and vertical position (region), lift asymmetry position and weight lifted. An electromyography-assisted model was used to evaluate spine loading in each subject during the lifting exertions. Differences in spine loading between the LBP and asymptomatic subjects were noted as a function of the experimental variables. RESULTS: Patients with LBP experienced greater spine compression and shear forces when performing lifting tasks compared with asymptomatic individuals. The least taxing conditions resulted in some of the greatest differences between LBP and asymptomatic individuals. CONCLUSIONS: Greater levels of antagonistic muscle coactivation resulted in increases in spine loading for patients with LBP. Specific lifting conditions that tend to exacerbate loading can be identified by means of physical workplace requirements. These findings may impact acceptable return-to-work conditions for those with LBP.

Effect of torso flexion on the lumbar torso extensor muscle sagittal plane moment arms.

BACKGROUND CONTEXT: Accurate anatomical inputs for biomechanical models are necessary for valid estimates of internal loading. The magnitude of the moment arm of the lumbar erector muscle group is known to vary as a function of such variables as gender. Anatomical evidence indicates that the moment arms decrease during torso flexion. However, moment arm estimates in biomechanical models that account for individual variability have been derived from imaging studies from supine postures. PURPOSE: Quantify the sagittal plane moment arms of the lumbar erector muscle group as a function of torso flexion, and identify individual characteristics that are associated with the magnitude of the moment arms as a function of torso flexion. STUDY DESIGN/SETTING: Utilization of a 0.3 Tesla Open magnetic resonance image (MRI) to image and quantify the moment arm of the right erector muscle group as a function of gender and torso flexion. METHODS: Axial MRI images through and parallel to each of the lumbar intervertebral discs at four torso flexion angles were obtained from 12 male and 12 female subjects in a lateral recumbent posture. Multivariate analysis of variance was used to investigate the differences in the moment arms at different torso flexion angles, whereas hierarchical linear regression was used to investigate associations with individual anthropometric characteristics and spinal posture. RESULTS: The largest decrease in the lumbar erector muscle group moment arm from neutral to 45-degree flexion occurred at the L5-S1 level (9.7% and 8.9% for men and women, respectively). Measures of spinal curvature (L1-S1 lordosis), body mass and trunk characteristics (depth or circumference) were associated with the varying moment arm at most lumbar levels. CONCLUSIONS: The sagittal plane moment arms of the lumbar erector muscle mass decrease as the torso flexes forward. The change in moment arms as a function of torso flexion may have an impact on prediction of spinal loading in biomechanical models.

Potential use of Sox9 gene therapy for intervertebral degenerative disc disease.

STUDY DESIGN: A new recombinant adenoviral vector expressing Sox9, a chondrocyte-specific transcription factor, was tested in a chondroblastic cell line and primary human intervertebral disc cells in vitro. Direct infection of intervertebral disc cells then was assessed in a rabbit model. OBJECTIVES: To deliver a potentially therapeutic viral vector expressing Sox9 to degenerative human and rabbit intervertebral discs cells, and to assess the effect of Sox9 expression on Type 2 collagen production. SUMMARY OF THE BACKGROUND DATA: The concentration of competent Type 2 collagen, an essential constituent of the healthy nucleus pulposus, declines with intervertebral disc degeneration. Recent studies suggest that Sox9 upregulates Type 2 collagen production. Interventions that augment Type 2 collagen production by intervertebral disc cells may represent a novel therapeutic method for patients with degenerative disc disease. METHODS: Adenoviral delivery vectors expressing Sox9 and green fluorescent protein were constructed using the AdEasy system. The chondroblastic cell line, HTB-94, and cultured human degenerated intervertebral disc cells were infected with the vectors. Reverse transcriptase-polymerase chain reaction and immunohistochemical analyses were performed to document increased Type 2 collagen expression. The AdSox9 virus then was injected directly into the intervertebral discs of three rabbits. After 5 weeks, the injected discs were evaluated histologically. RESULTS: The AdSox9 virus efficiently transduced HTB-94 cells and degenerated human disc cells. Western blot analysis confirmed increased Sox9 production. Increased Type 2 collagen production was demonstrated in infected HTB-94 and human disc cells using both reverse transcriptase-polymerase chain reaction and immunohistochemical staining. In the rabbit model, cells infected with AdSox9 maintained a chondrocytic phenotype, and the architecture of the nucleus pulposus was preserved over a 5-week study period compared to control discs. CONCLUSIONS: A novel adenoviral vector efficiently increased Sox9 and Type 2 collagen synthesis in cultured chondroblastic cells and human degenerated disc cells. In a rabbit model, sustained Sox9 production preserved the histologic appearance of the nucleus pulposus cells in vivo. These findings suggest a potential role for Sox9 gene therapy in the treatment of human degenerative disc disease.

The impact of mental processing and pacing on spine loading: 2002 Volvo Award in biomechanics.

STUDY DESIGN: The impact of various levels of mental processing and pacing (during lifting) on spine loading was monitored under laboratory conditions. OBJECTIVES: To explore how mental demands and pacing influence the biomechanical response and subsequent spine loading and, to determine whether individual characteristics have a modifying role in the responses. SUMMARY OF BACKGROUND DATA: Modern work often requires rapid physical exertions along with demands of mental processing (both psychosocial stressors). While the effect of physical workplace factors on spine loading has been widely documented, few studies have investigated the impact that interaction of psychosocial factors and individual factors has on spine loads. METHODS: For this study, 60 subjects lifted boxes while completing two types of mental processing tasks: 1) series tasks with decisions occurring before the act of lifting, and 2) simultaneous tasks with decisions occurring concurrently with the lift. For both of these mental processing conditions, two intensities of mental load were evaluated: simple and complex. Task pacing was also adjusted under slow and fast conditions. Finally, individual characteristics (personality and gender) were evaluated as potential modifiers. An electromyographically assisted model evaluated the three-dimensional spine loads under the experimental conditions. RESULTS: Simultaneous mental processing had the largest impact on the spine loads, with the complex intensity resulting in increases of 160 N with lateral shear, 80 N with anteroposterior shear, and 700 N with compression. Increased task pace produced greater lateral shear (by 20 N), anteroposterior shear (by 60 N), and compression loads (by 410 N). Gender and personality also influenced loadings by as much as 17%. CONCLUSIONS: Mental processing stress acted as a catalyst for the biomechanical responses, leading to intensified spine loading. Mental stress appeared to occur as a function of time pressures on task performance and resulted in less controlled movements and increases in trunk muscle coactivation. These adjustments significantly increased spine loading. These results suggest a potential mechanism for the increase in low back pain risk resulting from psychosocial stress caused by modern work demands.