Ehsan Jazini

Alterations in T2 relaxation magnetic resonance imaging of the ovine intervertebral disc due to nonenzymatic glycation.

Study Design. An in vitro study using ovine intervertebral discs to correlate the effects of increasing advanced glycation end-products (AGEs) with disc hydration evaluated by magnetic resonance imaging (MRI). Objective. To determine the relationship between the level of AGEs and tissue water content in intervertebral discs using T2 relaxation MRI. Summary of Background Data. AGEs result from nonenzymatic glycation, and AGEs have been shown to accumulate in the intervertebral disc tissue with aging and degeneration. AGEs can alter biochemical properties, including the hydrophobicity of the extracellular matrix. Because one of the degenerative signs of the intervertebral disc (IVD) is reduced hydration, we hypothesized that increased levels of tissue AGEs contribute to disc hydration. T2 relaxation MRI has been shown to be sensitive to the hydration status of the disc and may be valuable in detecting the changes in the IVD mediated by the increase of AGEs. Methods. Thirty-eight IVDs were obtained from 4 ovine spines, and the annulus fibrosis (AF) and nucleus pulposus (NP) tissues were isolated from these discs. The tissues were incubated in either a ribosylation or control solution for up to 8 days to induce the formation of AGEs. T2 relaxation times were obtained from these tissues after ribosylation. These tissues were subsequently analyzed for hydration, proteoglycan, collagen, and AGEs content. Results. In vitro ribosylation led to the increased accumulation of AGEs and reduced water content in both the AF and NP in a dose-dependent manner, but did not affect the proteoglycan and collagen composition. When analyzed by MRI, ribosylation significantly altered the mean T2 relaxation times in the NP (P = 0.001), but not in the AF (P = 0.912). Furthermore, the mean T2 values in the NP significantly decreased with increasing periods of incubation time (P < 0.001). Conclusion. This study demonstrates that levels of AGEs in the IVD may affect the tissue water content. Moreover, these ribosylation-mediated changes in tissue hydration were detectable using T2 relaxation MRI. T2 relaxation MRI may provide a noninvasive tool to measure in vivo changes in disc hydration that are negatively correlated with the accumulation of AGEs.

Positional Change in Displacement of Midshaft Clavicle Fractures: An Aid to Initial Evaluation.

Objectives: To determine how change in position affects displacement of midshaft clavicle fractures. Design: Retrospective review. Setting: Level I Trauma Center. Patients: Eighty patients with displaced midshaft clavicle fractures and presence of supine and semiupright or upright chest radiographs taken within 2 weeks of each other. Intervention: Supine, semiupright, and upright chest radiographs. Main Outcome Measurements: Fracture shortening and vertical displacement on supine, semiupright, and upright radiographs. Results: Mean vertical displacement was 9.42 mm [95% confidence interval (95% CI), 8.07–10.77 mm], 11.78 mm (95% CI, 10.25–13.32 mm), and 15.72 mm (95% CI, 13.71–17.72 mm) in supine, semiupright, and upright positions, respectively. Fracture shortening was −0.41 mm (95% CI, −2.53 to 1.70 mm), 2.11 mm (95% CI, −0.84 to 5.07), and 4.86 mm (95% CI, 1.66–8.06 mm) in supine, semiupright, and upright positions, respectively. Change in position from supine to upright significantly increased both vertical displacement and fracture shortening (P < 0.001). In the upright position, the proportion of patients who met operative indications (fracture shortening >20 mm) was 3 times greater when compared with that in the supine position (upright 17.65%; supine 5.88%, P = 0.06). Positional changes in fracture displacement were not associated with body mass index, age, or gender. Conclusions: Patient position is associated with significant changes in fracture displacement. Over 3 times more patients meet operative indications when placed in the upright versus supine position. An upright chest radiograph should be obtained to evaluate midshaft clavicle fracture displacement, as it represents the physiologic stress across the fracture when considering nonoperative management. Level of Evidence: Prognostic level IV. See Instructions for Authors for a complete description of levels of evidence.

Finding the right fit: studying the biomechanics of under-tapping with varying thread depths and pitches

BACKGROUND CONTEXT Compromise of pedicle screw purchase is a concern in maintaining rigid spinal fixation, especially with osteoporosis. Little consistency exists among various tapping techniques. Pedicle screws are often prepared with taps of a smaller diameter, which can further exacerbate inconsistency. PURPOSE The objective of this study was to determine whether a mismatch between tap thread depth (D) and thread pitch (P) and screw D and P affects fixation when under-tapping in osteoporotic bone. STUDY DESIGN This study is a polyurethane foam block biomechanical analysis. MATERIALS AND METHODS A foam block osteoporotic bone model was used to compare pullout strength of pedicle screws with a 5.3 nominal diameter tap of varying Ds and Ps. Blocks were sorted into seven groups: (1) probe only; (2) 0.5-mm D, 1.5-mm P tap; (3) 0.5-mm D, 2.0-mm P tap; (4) 0.75-mm D, 2.0-mm P tap; (5) 0.75-mm D, 2.5-mm P tap; (6) 0.75-mm D, 3.0-mm P tap; and (7) 1.0-mm D, 2.5-mm P tap. A pedicle screw, 6.5 mm in diameter and 40 mm in length, was inserted to a depth of 40 mm. Axial pullout testing was performed at a rate of 5 mm/min on 10 blocks from each group. RESULTS No significant difference was noted between groups under axial pullout testing. The mode of failure in the probe-only group was block fracture, occurring in 50% of cases. Among the other six groups, only one screw failed because of block fracture. The other 59 failed because of screw pullout. CONCLUSIONS In an osteoporotic bone model, changing the D or P of the tap has no statistically significant effect on axial pullout. Osteoporotic bone might render tap features marginal. Our findings indicate that changing the characteristics of the tap D and P does not help with pullout strength in an osteoporotic model. The high rate of fracture in the probe-only group might imply the potential benefit of tapping to prevent catastrophic failure of bone.

Does Lumbopelvic Fixation Add Stability? A Cadaveric Biomechanical Analysis of an Unstable Pelvic Fracture Model

Objective: We sought to determine the role of lumbopelvic fixation (LPF) in the treatment of zone II sacral fractures with varying levels of sacral comminution combined with anterior pelvic ring (PR) instability. We also sought to determine the proximal extent of LPF necessary for adequate stabilization and the role of LPF in complex sacral fractures when only 1 transiliac–transsacral (TI–TS) screw is feasible. Materials and Methods: Fifteen L4 to pelvis fresh-frozen cadaveric specimens were tested intact in flexion-extension (FE) and axial rotation (AR) in a bilateral stance gliding hip model. Two comminution severities were simulated through the sacral foramen using an oscillating saw, with either a single vertical fracture (small gap, 1 mm) or 2 vertical fractures 10 mm apart with the intermediary bone removed (large gap). We assessed sacral fracture zone (SZ), PR, and total lumbopelvic (TL) stability during FE and AR. The following variables were tested: (1) presence of transverse cross-connector, (2) presence of anterior plate, (3) extent of LPF (L4 vs. L5), (4) fracture gap size (small vs. large), (5) number of TI–TS screws (1 vs. 2). Results: The transverse cross-connector and anterior plate significantly increased PR stability during AR (P = 0.02 and P = 0.01, respectively). Increased sacral comminution significantly affected SZ stability during FE (P = 0.01). Two versus 1 TI–TS screw in a large-gap model significantly affected TL stability (P = 0.04) and trended toward increased SZ stabilization during FE (P = 0.08). Addition of LPF (L4 and L5) significantly improved SZ and TL stability during AR and FE (P < 0.05). LPF in combination with TI–TS screws resulted in the least amount of motion across all 3 zones (SZ, PR, and TL) compared with all other constructs in both small-gap and large-gap models. Conclusions: The role of LPF in the treatment of complex sacral fractures is supported, especially in the setting of sacral comminution. LPF with proximal fixation at L4 in a hybrid approach might be needed in highly comminuted cases and when only 1 TI–TS screw is feasible to obtain maximum biomechanical support across the fracture zone.

Outcomes of lumbopelvic fixation in the treatment of complex sacral fractures using minimally invasive surgical techniques

BACKGROUND CONTEXT Complex sacral fractures with vertical and anterior pelvic ring instability treated with traditional fixation methods are associated with high rates of failure and poor clinical outcomes. Supplemental lumbopelvic fixation (LPF) has been applied for additional stability to help with fracture union. PURPOSE The study aimed to determine whether minimally invasive LPF provides reliable fracture stability and acceptable complication rates in cases of complex sacral fractures. STUDY DESIGN/SETTING This is a retrospective cohort study at a single level I trauma center. PATIENT SAMPLE The sample includes 24 patients who underwent minimally invasive LPF for complex sacral fracture with or without associated pelvic ring injury. OUTCOME MEASURES Reoperation for all causes, loss of fixation, surgical time, transfusion requirements, length of hospital stay, postoperative day at mobilization, and mortality were evaluated. METHODS Patient charts from 2008 to 2014 were reviewed. Of the 32 patients who underwent minimally invasive LPF for complex sacral fractures, 24 (12 male, 12 female) met all inclusion and exclusion criteria. Outcome measures were assessed with a retrospective chart review and radiographic review. The authors did not receive external funding for this study. RESULTS Acute reoperation was 12%, and elective reoperation was 29%. Two (8%) patients returned to the operating room for infection, one (4.2%) required revision for instrumentation malposition, and seven (29%) underwent elective removal of instrumentation. No patient experienced failure of instrumentation or loss of correction. Average surgical time was 3.6 hours, blood loss was 180 mL, transfusion requirement was 2.1 units of packed red blood cells, and postoperative mobilization was on postoperative day 5. No mortalities occurred as a result of the minimally invasive LPF procedure. CONCLUSIONS Compared with historic reports of open LPF, our results demonstrate reliable maintenance of reduction and acceptable complication rates with minimally invasive LPF for complexsacral fractures. The benefits of minimally invasive LPF may be offset with increased elective reoperations for removal of instrumentation.

Os acromiale fixation: a biomechanical comparison of polyethylene suture versus stainless steel wire tension band

BACKGROUND Symptomatic hardware is a commonly reported complication after surgical fixation of an unstable meso-type os acromiale. This study compared the biomechanical properties of a cannulated screw tension band construct using a metal wire tension band vs. a suture tension band, considering that the suture construct could allow for decreased hardware burden in the clinical setting. METHODS A meso-type os acromiale was created in 16 cadaveric shoulders. Two cannulated 4-mm screws were placed in each specimen. Tension band augmentation was accomplished with a 1-mm stainless steel wire (wire group) or a #5 braided polyethylene suture (suture group), with 8 specimens in each group. An inferiorly directed force was applied to the anterior acromion at 1 mm/s on a materials testing machine. Stiffness and ultimate failure load were recorded and analyzed. RESULTS No significant difference (P = .22) was observed in the ultimate failure load between the wire (228  ± 85 N; range, 114-397 N) and the suture (275 ± 139 N; range, 112-530 N). No significant difference (P = .17) was observed in the stiffness between the wire (28  ± 12 N/mm; range, 18-53 N/mm) and the suture (38  ± 25 N/mm; range, 10-83 N/mm). CONCLUSIONS Stainless steel wire and polyethylene suture have similar biomechanical strength in the cannulated screw tension band fixation of meso-type os acromiale at time zero.

Low-Density Pedicle Screw Constructs for Adolescent Idiopathic Scoliosis: Evaluation of Effectiveness and Cost:

Introduction Optimal screw density and technique in treatment of idiopathic scoliosis remain unknown. We sought to find if low-density (LD) screw construct can achieve curve correction similar to that achieved with high-density (HD) constructs in adolescent scoliosis at substantial cost savings. Materials and Methods Patients treated operatively for idiopathic scoliosis at our center between 2007 and 2011 were identified through a retrospective database review. Each patient was treated with an LD screw construct. Radiographic outcomes included assessment of screw density, percent correction of major and fractional lumbar curves at follow-up, T5−T12 kyphosis, and angle of lowest instrumented vertebra (LIV). Costs were calculated and compared with costs of HD constructs. Results Forty-five patients met inclusion criteria. Ages ranged from 12 to 19 years (mean age, 14.9 years). Average construct density was 1.2 screws per fused level (range, 1.07−1.33 screws). Mean percent curve correction at latest follow-up: major curve, 67.2%; fractional lumbar curve, 69%. Average postoperative thoracic kyphosis: 30 degrees. Mean LIV angle: 5.6 degrees. Total screw cost was

Cost-effectiveness of circumferential fusion for lumbar spondylolisthesis: propensity-matched comparison of transforaminal lumbar interbody fusion with anterior-posterior fusion

13,370 per case in the LD group compared with

Anatomical Relationship of the Axillary Nerve to the Pectoralis Major Tendon Insertion

22,340 per case if all levels had been instrumented with 2 screws. Conclusions Our LD screw construct is among the lowest density constructs reported in the literature and achieves curve correction comparable to that reported for HD constructs at substantially lower cost.

The Growing Spine in Marfan and Loeys–Dietz Syndromes

BACKGROUND CONTEXT Transforaminal lumbar interbody fusion (TLIF) and dual-approach anteroposterior (AP) are common techniques to achieve circumferential fusion for lumbar spondylolisthesis. It is unclear which approach is more cost-effective. PURPOSE Our goal was to determine the incremental cost-effectiveness ratio (ICER) by calculating the cost per quality-adjusted life year (QALY) for each approach. STUDY DESIGN/SETTING This study is a propensity-matched cost-effectiveness comparison. PATIENT SAMPLE Patients with lumbar spondylolisthesis undergoing single-level AP fusion or TLIF and enrolled in a prospective observational surgical database were included in this study. OUTCOME MEASURES The outcome measures in this study were the Oswestry Disability Index (ODI) and the Short Form-6D (SF-6D). METHODS From a prospective surgical database, patients with lumbar spondylolisthesis undergoing single-level AP fusion were propensity matched to a TLIF cohort based on age, gender, body mass index, smoking status, workers compensation, preoperative ODI, and back and leg pain numeric scores. Quality-adjusted life years gained were determined using baseline and 1- and 2-yearpostoperative SF-6D scores. Cost was calculated from actual, direct hospital costs and included subsequent postsurgical costs (epidural spinal injections, spine-related emergency department visits, readmissions, and revision surgery). RESULTS Thirty-one cases of AP fusions were identified and propensity matched to 31 TLIF patients. Patients undergoing TLIF had a shorter mean operative time (270 vs. 328 minutes, p=.039) but no difference in estimated blood loss (526 vs. 548 cc, p=.804) or hospital length of stay (4.5 vs. 6.1 days, p=.146). Quality-adjusted life years gained at 2 years were also similar (0.140 vs. 0.130, p=.672). The mean index surgery and the total 2-year costs were lower for TLIF compared with AP (index: