Biomechanical evaluation of an expandable meshed bag augmented with pedicle or facet screws for percutaneous lumbar interbody fusion

Objective

To evaluate the biomechanics of lumbar motion segments instrumented with stand-alone OptiMesh system augmented with posterior fixation using facet or pedicle screws and the efficacy of discectomy and disc distraction.

Background context

OptiMesh bone graft containment system has been used for vertebral compression fractures and percutaneous lumbar interbody fusion. The filled mesh bag serves as the interbody device providing structural support to the motion segment being fused. No biomechanical data of this new device are available in the literature.

Methods

Twenty-four fresh human cadaveric lumbar motion segments were divided into two groups. In the control group, multidirectional flexibility testing was conducted after an intact condition and standard transforaminal lumbar interbody fusion (TLIF) procedure. In the OptiMesh group, testing was performed following intact, stand-alone OptiMesh procedure, OptiMesh with facet screws (placed using the transfacet approach), and OptiMesh with pedicle screws and rods. Range of motion (ROM) was calculated for each surgical treatment. The lordosis and disc height change of intact and instrumented specimens were measured in the lateral radiographs to evaluate the disc space distraction. In the OptiMesh group, cyclic loading in flexion extension (FE) was applied to measure cage subsidence or collapse (10,000 cycles at 6 Nm). After biomechanical testing, all the specimens were dissected to inspect the discectomy and end plate preparation. The area of discectomy was measured.

Results

The mean ROM of the intact specimens was 2.7°, 7.4°, and 7.2° in axial torsion (AT), lateral bending (LB), and FE, respectively. There was no difference between the control group and OptiMesh group. The mean ROM of the stand-alone OptiMesh system decreased to 2.4°, 5.1°, and 4.3° in AT, LB, and FE. The ROM decreased to 0.9° in AT, 2.2° in LB, and 0.9° in FE with OptiMesh system and facet screws. On average, OptiMesh system with pedicle screws and rods reduced the ROM to 1.3° in AT, 1.6° in LB, and 1.1° in FE. Compared with the intact condition and stand-alone OptiMesh system, both posterior fixation options had significant statistical difference (p<.001). In AT, ROM of facet screws was lower than that of pedicle screws (p<.05). There was no statistical difference between the facet and pedicle screws in LB and FE (p>.05). The mean volume of bone graft packed into each bag was 8.3±1.5 cc. The average increase of lordosis was 0.6°±1.0° after meshed bag was deployed. The average distraction achieved by the OptiMesh system was 1.0±0.6 mm. The average prepared area of discectomy was 42% of the total disc. The disc height change after cyclic loading was 0.2 mm. No subsidence or collapse was noticed.

Conclusions

The OptiMesh system offers large volume of bone graft in the disc space with small access portals. The OptiMesh system had similar construct stability to that of standard TLIF procedure when posterior fixation was applied. However, the amount of distraction was limited without additional distraction tools. With the anterior support provided by the expandable meshed bag, facet screws had comparable construct stability to that of pedicle screws. Slightly higher stability was observed in facet screws in AT.     

The biomechanical impact of facet tropism on the intervertebral disc and facet joints in the cervical spine

Background Context

Facet tropism is defined as the angular difference between the left and the right facet orientation. Facet tropism was suggested to be associated with the disc degeneration and facet degeneration in the lumbar spine. However, little is known about the relationship between facet tropism and pathologic changes in the cervical spine and the mechanism behind.

Influence of an auxiliary facet system on intervertebral discs and adjacent facet joints

Background context

Facet supplementation stabilizes after facetectomy and undercutting laminectomy. It is indicated in degenerative spondylolisthesis with moderate disc degeneration and dynamic stenosis.

Purpose

To determine the influence of an auxiliary facet system (AFS) on the instrumented disc, adjacent levels' discs, and facet joints and to compare it with fusion.

Study design

Finite element study.

Methods

L3–L4, L4–L5, and L5–S1 were studied using a validated finite element model with prescribed displacements for an intact spine, lesion by facetectomy and undercutting laminectomy, AFS, and fusion at L4–L5. The distribution of segmental range of motion (ROM) and applied moments, von Mises stress at the annulus, and facet joint contact forces were calculated with rotations in all planes. Institutional support for implant evaluation and modeling was received by Clariance.

Results

In flexion-extension and lateral bending, fusion decreased L4–L5 ROM and increased adjacent levels' ROM. Range of motion was similarly distributed with intact lesion and AFS. In axial rotation, L4–L5 ROM represented 33% with intact, 55% after lesion, 25% with AFS, and 21% with fusion. Fusion increased annulus stress at adjacent levels in flexion-extension and lateral bending, but decreased stress at L4–L5 compared with AFS. In axial rotation, von Mises stress was similar with fusion and AFS. Facet loading increased in extension and lateral bending with fusion. It was comparable for fusion and AFS in axial rotation.

Conclusions

This study suggests that the AFS stabilizes L4–L5 in axial rotation after facetectomy and undercutting laminectomy as fusion does. This is because of the cross-link that generates an increased annulus stress in axial rotation at adjacent levels. With imposed displacements, without in vivo compensation of the hips, the solicitation at adjacent levels' discs and facet joints is higher with fusion compared with AFS. Fusion decreases intradiscal stress at the instrumented level.     

Biomechanics of lateral plate and pedicle screw constructs in lumbar spines instrumented at two levels with laterally placed interbody cages

Background context

The lateral transpsoas approach to interbody fusion is gaining popularity because of its minimally invasive nature and resultant indirect neurologic decompression. The acute biomechanical stability of the lateral approach to interbody fusion is dependent on the type of supplemental internal fixation used. The two-hole lateral plate (LP) has been approved for clinical use for added stabilization after cage instrumentation. However, little biomechanical data exist comparing LP fixation with bilateral pedicle screw and rod (PSR) fixation.

Purpose

To biomechanically compare the acute stabilizing effects of the two-hole LP and bilateral PSR fusion constructs in lumbar spines instrumented with a lateral cage at two contiguous levels.

Study design

Biomechanical laboratory study of human cadaveric lumbar spines.

Methods

Eighteen L1–S1 cadaveric lumbar spines were instrumented with lateral cages at L3–L4 and L4–L5 after intact kinematic analysis. Specimens (n=9 each) were allocated for supplemental instrumentation with either LP or PSR. Intact versus instrumented range of motion was evaluated for all specimens by applying pure moments (±7.5 Nm) in flexion/extension, lateral bending (LB) (left+right), and axial rotation (AR) (left+right). Instrumented spines were later subjected to 500 cycles of loading in all three planes, and interbody cage translations were quantified using a nonradiographic technique.

Results

Lateral plate fixation significantly reduced ROM (p<.05) at both lumbar levels (flexion/extension: 49.5%; LB: 67.3%; AR: 48.2%) relative to the intact condition. Pedicle screw and rod fixation afforded the greatest ROM reductions (p<.05) relative to the intact condition (flexion/extension: 85.6%; LB: 91.4%; AR: 61.1%). On average, the largest interbody cage translations were measured in both fixation groups in the anterior-posterior direction during cyclic AR.

Conclusions

Based on these biomechanical findings, PSR fixation maximizes stability after lateral interbody cage placement. The nonradiographic technique served to quantify migration of implanted hardware and may be implemented as an effective laboratory tool for surgeons and engineers to better understand mechanical behavior of spinal implants.     

Reducing subsidence risk by using rapid manufactured patient-specific intervertebral disc implants

Background context

Intervertebral disc implant size, shape, and position during total disc replacement have been shown to affect the risk of implant subsidence or vertebral fracture. Rapid manufacturing has been successfully applied to produce patient-specific implants for craniomaxillofacial, dental, hip, and knee requirements, but very little has been published on its application for spinal implants.

Purpose

This research was undertaken to investigate the improved load distribution and stiffness that can be achieved when using implants with matching bone interface geometry as opposed to implants with flat end plate geometries.

Study design

The study design comprises a biomechanical investigation and comparison of compressive loads applied to cadaveric vertebrae when using two different end plate designs.

Methods

Four spines from male cadavers (ages 45–65 years, average 52 years), which had a total of n=88 vertebrae (C3–L5), were considered during this study. Bone mineral density scans on each spine revealed only one to be eligible for this study. Twenty remaining vertebrae (C3–L3) were potted and subjected to nondestructive compression tests followed by destructive compression tests. Custom-made nonfunctional implants were designed for this experiment. Ten implants were designed with matching end plate-to-bone interface geometry, whereas the other 10 were designed with flat end plates. Testing did not incorporate the use of a keel in either design type. I-Scan pressure sensors (Tekscan, Inc., MA, USA) were used during the nondestructive tests to assess the load distribution and percentage surface contact.

Results

Average percent contact area measured during nondestructive tests was 45.27% and 10.49% for conformal and flat implants, respectively—a difference that is statistically significant (p<.001). A higher percent contact area was especially observed for cervical vertebrae because of their pronounced end plate concavity. During destructive compression tests, conformal implants achieved higher failure loads than flat implants. Conformal implants also performed significantly better when stiffness values were compared (p<.0001).

Conclusions

One of the main expected benefits from customizing the end plate geometry of disc implants is the reduced risk and potential for subsidence into the vertebral bone end plate. Subsidence depends in part on the stiffness of the implant-bone construct, and with a 137% increase in stiffness, the results of this study show that there are indeed significant potential benefits that can be achieved through the use of customization during the design and manufacture of intervertebral disc implants.     

Axial plane analysis of Lenke 1A adolescent idiopathic scoliosis as an aid to identify curve characteristics

Background context

Adolescent idiopathic scoliosis (AIS) is a complex three-dimensional (3D) deformity of the spine involving deviations in the frontal plane, modifications of the sagittal profile, and rotations in the transverse plane. Although Lenke classification system is based on 2D radiographs and includes sagittal thoracic and coronal lumbar modifiers, Lenke et al. suggested inclusion of axial thoracic and lumbar modifiers in the analysis.

Purpose

To analyze axial plane of Lenke 1A curves to identify curve characteristics.

Study design

Retrospective study.

Patient sample

Seventy patients (49 women, 21 men) with Lenke Type 1A idiopathic scoliosis were analyzed.

Outcome measures

Coronal, sagittal, and axial parameters were measured from plain radiographs that were obtained at initial medical examination of the patients.

Methods

Coronal and sagittal plane and whole spine segmental vertebra rotations from thoracic 1 to lumbar 5 were evaluated in 70 AIS patients with Lenke 1A curves by using Drerup method. Three different subgroups were identified according to magnitude and direction of lower end vertebra (LEV) rotation.

Results

In Group 1 (Lenke 1A1), the direction of LEV rotation was same with other vertebrae in the main curve and the magnitude of the LEV rotation was less than −0.5°. In Group 2 (Lenke 1A2), the rotation of LEV was between −0.5° and 0.5° and so was accepted as neutral. In Group 3 (Lenke 1A3), the rotation of LEV had opposite direction with vertebrae in the main curve and the magnitude of LEV rotation was more than 0.5°. The mean thoracic Cobb angle of patients with Lenke 1A idiopathic scoliosis was 51.1° (range 37°–80°), whereas the mean lumbar Cobb angle was 16.4° (range 0°–32°). The mean angle of trunk rotation of the patients was 5.7° (range 1°–16°). In terms of maximum thoracic vertebra rotation, the mean rotation angle of Lenke 1A idiopathic curves was −18.9° (range −(9.8°–44.7°)). The mean maximum lumbar vertebra rotation was 4.5° (range −7.2° to 15.1°).

Conclusions

Addition of axial plane analysis to conventional coronal and sagittal evaluations in patients with Lenke 1A curves may reveal inherent structural differences that are not apparent in single planar radiographic assessments and may necessitate a different surgical strategy.     

Does normalized signal intensity of cervical discs on T2 weighted MRI images change in whiplash patients?

Purpose

We tested the hypothesis that whiplash trauma leads to changes of the signal intensity of cervical discs in T2-weighted images.

Methods and materials

50 whiplash patients (18–65 years) were examined within 48 h after motor vehicle accident, and again after 3 and 6 months and compared to 50 age- and sex-matched controls. Signal intensity in ROI's of the discs at the levels C2/3 to C7/T1 and the adjacent vertebral bodies were measured on sagittal T2 weighted MR images and normalized using the average of ROI's in fat tissue. The contrast between discs and both adjacent vertebrae was calculated and disc degeneration was graded by the Pfirrmann-grading system.

Results

Whiplash trauma did not have a significant effect on the normalized signals from discs and vertebrae, on the contrast between discs and adjacent vertebrae, or on the Pfirrmann grading. However, the contrast between discs and adjacent vertebrae and the Pfirrmann grading showed a strong correlation. In healthy volunteers, the contrast between discs and adjacent vertebrae and Pfirrmann grading increased with age and was dependent on the disc level.

Conclusion

We could not find any trauma related changes of cervical disc signal intensities. Normalized signals of discs and Pfirrmann grading changed with age and varied between disc levels with the used MR sequence.     

Bilateral cervical spondylolysis of C7

Background context

Cervical spondylolysis, which is defined as a cleft between the superior and inferior articular facets of the articular pillar, is a rare condition. The sixth cervical vertebra (C6) is the level most commonly affected. Cases involving C2, C3, C4, or C5 have also been reported. However, to date, no case of C7 spondylolysis has been reported.

Purpose

To present a rare case of bilateral spondylolysis of the seventh cervical vertebra (C7) in a 58-year-old man.

Study design

A case report.

Methods

A 58-year-old man visited our hospital with chronic posterior neck pain radiating to the left upper extremity. Magnetic resonance imaging (MRI) study revealed left foraminal disc herniations at C5–C6 and C6–C7. Cervical spondylolysis involving C7 was discovered incidentally during computed tomography (CT)–guided transforaminal steroid injection. Plain radiographs, CT images, and MRIs were reviewed thoroughly once again.

Results

The patient’s symptoms were relieved after he received CT-guided transforaminal steroid injections. Plain radiographs revealed a radiolucent defect in the articular pillar and cleft at the spinous process of C7. Computed tomography confirmed bilateral spondylolysis and spina bifida occulta of the C7 vertebra. Magnetic resonance imaging revealed absence of edema, which was suggestive of a chronic lesion.

Conclusion

Involvement of C7 is not exceptional in a case of cervical spondylolysis.     

Laparoscopic Approach for Artificial Urinary Sphincter Implantation in Women with Intrinsic Sphincter Deficiency Incontinence: A Single-Centre Preliminary Experience

Background

Implantation of an artificial urinary sphincter (AUS) is used as a last resort in women with stress urinary incontinence (SUI).

Objective

To assess the early functional outcome after laparoscopic placement of an AUS in women.

Design, setting, and participants

Twelve women with type 3 SUI underwent a laparoscopic AUS placement between 2006 and 2008. Eleven (92%) had previously undergone anti-incontinence procedures.

Intervention

The AUS was implanted with laparoscopic access either preperitoneally or intraperitoneally. The cuff was placed around the bladder neck between the periurethral fascia and the vagina.

Measurements

Perioperative complications were reviewed. To assess resolution of urinary incontinence, all patients were seen at 1, 3, 6, and 12 mo after the surgery and yearly thereafter.

Results and limitations

The mean age of subjects was 56.7 ± 12 yr (33–78). The mean body mass index was 24 ± 2.3 (20–25). The mean preoperative closure pressure was 22 ± 10.9 cmH₂O (4–35). The mean operative time was 181 ± 39 min [110–240]. Intraoperative complications occurred in three women (25%), with bladder (n = 2) and vaginal (n = 2) injuries. These complications required open conversion. AUS implantation was postponed in one case. The mean hospital stay was 7 ± 2.3 d (3–11). The bladder catheter was removed after a mean time of 10 ± 8 d (2–30). Urinary retention was observed in five cases (45%) after bladder catheter removal. AUS activation was done 4–14 wk after implantation. Mean follow-up was 12.1 ± 8 mo (5.2–27). Incontinence was completely resolved in eight women (88%) who underwent complete laparoscopic procedure. The main limitation of the study was the limited length of follow-up.

Conclusions

AUS implantation can be successfully achieved by laparoscopy. It appears to be technically feasible. These results are still preliminary, and further studies of larger populations with longer follow-up are needed to make any statement regarding surgical strategy.     

Measuring surface temperature and grading pathological changes of airway tissue in a canine model of inhalational thermal injury

Background

Airway tissue shows unexpected invulnerability to heated air. The mechanisms of this phenomenon are open to debate.

Objective

This study was designed to measure the surface temperatures at different locations of the airway, and to explore the relationship between the tissue's surface temperature and injury severity.

Method

Twenty dogs were randomly divided into four groups, including three experimental groups (six dogs in each) to inhale heated air at 70–80 °C (group I), 150–160 °C (group II) and 310–320 °C (group III) and a control group (two dogs, only for histological observation). Injury time was 20 min. Mucosal surface temperatures of the epiglottis (point A), cricoid cartilage (point B) and lower trachea (point C) were measured. Dogs in group I–III were divided into three subgroups (two in each), to be assayed at 12, 24 and 36 h after injury, respectively. For each dog, four tissue parts (epiglottis, larynx, lower trachea and terminal bronchiole) were microscopically observed and graded according to an original pathological scoring system (score range: 0–27).

Result

Surface temperatures of the airway mucosa increased slowly to 40.60 ± 3.29 °C, and the highest peak temperature was 48.3 °C (group III, point A). The pathological score of burned tissues was 4.12 ± 4.94 (0.0–18.0), suggesting slight to moderate injuries. Air temperature and airway location both influenced mucosal temperature and pathological scores very significantly, and there was a very significant positive correlation between tissue temperature and injury severity.

Conclusion

Compared to the inhalational air hyperthermia, airway surface temperature was much lower, but was still positively correlated with thermal injury severity.     

Defining intraoperative hypothermia in ventral hernia repair

Background

Intraoperative normothermia, a single measurement of core body temperature ≥36°C, is an important quality metric outlined by the World Health Organization for the reduction of surgical site infections (SSIs). Hypothermia has been linked to SSI in colorectal and trauma patients, but the effect in ventral hernia repair (VHR) is unknown.

Materials and methods

Patients who underwent VHR at a single institution between 2005 and 2012 were included. Temperature data were matched with National Surgical Quality Improvement Program SSI data. Novel definitions of hypothermia were explored: patient temperature nadir, percentage of time spent at the nadir, mean temperature, and time spent <36°C. Multivariable regression models were performed.

Results

Five hundred fifty-three patients were included with temperature recorded every 8–15 min. Mean temperature nadir was 35.7°C (±1.3°C [standard deviation]) and was not associated with SSI (odds ratio [OR], 0.938; 95% confidence interval, 0.778–1.131). The percentage of readings spent at the nadir was 31% (±31%) and was not predictive of SSI (OR, 1.471; 95% CI, 0.983–2.203). As mean temperature increased, the risk of SSI increased (OR, 1.115; 95% CI, 0.559–2.225). Percentage of temperature readings <36°C was 29% (±38%) and was not associated with SSI (OR, 1.062; 95% CI, 0.628–1.796). In all models, body mass index, smoking, and length of surgery were predictive of SSI.

Conclusions

Our results demonstrate no association between temperature and SSI in VHR. Efforts to reduce SSI should focus on factors such as smoking cessation, weight loss, and length of surgery. Our study suggests that maintenance of perioperative normothermia may only decrease SSIs in certain at-risk populations.     

Biomechanical evaluation of fracture fixation constructs using a variable-angle locked periprosthetic femur plate system

Background

In the United States there are more than 230,000 total hip replacements annually, and periprosthetic femoral fractures occur in 0.1–4.5% of those patients. The majority of these fractures occur at the tip of the stem (Vancouver type B1). The purpose of this study was to compare the biomechanically stability and strength of three fixation constructs and identify the most desirable construct.

Methods

Fifteen medium adult synthetic femurs were implanted with a hip prosthesis and were osteotomized in an oblique plane at the level of the implant tip to simulate a Vancouver type B1 periprosthetic fracture. Fractures were fixed with a non-contact bridging periprosthetic proximal femur plate (Zimmer Inc., Warsaw, IN). Three proximal fixation methods were used: Group 1, bicortical screws; Group 2, unicortical screws and one cerclage cable; and Group 3, three cerclage cables. Distally, all groups had bicortical screws. Biomechanical testing was performed using an axial–torsional testing machine in three different loading modalities (axial compression, lateral bending, and torsional/sagittal bending), next in axial cyclic loading to 10,000 cycles, again in the three loading modalities, and finally to failure in torsional/sagittal bending.

Results

Group 1 had significantly greater load to failure and was significantly stiffer in torsional/sagittal bending than Groups 2 and 3. After cyclic loading, Group 2 had significantly greater axial stiffness than Groups 1 and 3. There was no difference between the three groups in lateral bending stiffness. The average energy absorbed during cyclic loading was significantly lower in Group 2 than in Groups 1 and 3.

Conclusions

Bicortical screw placement achieved the highest load to failure and the highest torsional/sagittal bending stiffness. Additional unicortical screws improved axial stiffness when using cable fixation. Lateral bending was not influenced by differences in proximal fixation.

Clinical relevance

To treat periprosthetic fractures, bicortical screw placement should be attempted to maximize load to failure and torsional/sagittal bending stiffness.     

Factors Predicting the Usefulness of Deceased Donors

Background

Preoperative management for deceased donation is important. Deceased donation can failed for several reasons. We analyzed the clinical data of deceased donation after consent for cadaveric donation to evaluate the reasons of failure of organ procurement.

Material and Methods

We retrospectively reviewed the medical records of 112 deceased donors in a single institution between January 1998 and September 2012. There were no organs from cardiac death donors.

Results

Of 112 deceased donors, 51 (45.5%) were traumatic brain deaths and 33 (29.5%), nontraumatic brain hemorrhages. The overall mean age was 37.2 (±16.6) years with 35 (30.7%) of female gender. There were 15 (13.3%) donation failures for all organs. Significant factors for failure were histories of cardiopulmonary resuscitation (odds ratio [OR], 0.17; 95% confidence interval [CI], 0.05–0.58; P = .005), cardiac arrest (OR, 0.03; 95% CI, 0.006–0.14; P < .001), or acute renal failure (OR, 0.05; 95% CI, 0.006–0.42; P = .006). The nonsignificant factors included the time from intensive care unit to brain death (mean time, 105.1 ± 153.4); diabetes insipidus; hypotension despite inotrophic therapy, hypothermia (<35°C), arrhythmia, infection, metabolic acidosis, disseminated intravascular coagulopathy, and brain death cause.

Conclusions

Failure of deceased donation was associated with cardiac arrest while awaiting organ procurement and the presence of an history of cardiopulmonary resuscitation or presence of acute renal failure.     

Circulational heat dissipation of upper airway: Canine model of inhalational thermal injury

Background

The upper airway has powerful heat-absorbing ability, in which the blood circulation may play an important role.

Objective

This study aimed to explore the circulational heat-dissipating ability, and to investigate the contribution of blood circulation to the heat-absorbing ability of upper airway.

Methods

18 adult, male Beagle dogs were divided into three groups to inhale thermal dry air of 70–80 °C, 150–160 °C or 310–320 °C for 20 min. Blood temperatures and blood flow rates of bilateral common jugular veins (CJVs) were measured. Dogs’ breathing rates and air temperatures in middle trachea were also measured. According to the formula “Q = c·m·ΔT”, the heat dissipated by blood (Q_-blood) and the heat release by air (Q_-air) were calculated out. The contribution of circulational heat dissipation to the heat-absorbing ability of upper airway was defined as “C_-blood”.

Results

The blood temperature rise of CJV was 2.24 ± 0.60 °C. The blood flow rate of CJV was 44.5 ± 5.9 ml/min. The air temperature in middle trachea was 63.5 ± 18.9 °C. The mean breathing rate was 51.8 ± 7.5/min. The calculated “Q_-blood” and “Q_-air” were 13197.3 ± 4408.6 J and 33540.2 ± 24578.7 J, and the “C_-blood” was 55.2 ± 25.0% (21.7–88.8%).

Conclusion

Circulational heat dissipation plays an important role in the heat-absorbing process of upper airway when inhaled air is less than 160 °C. However, for air higher than 160 °C, some other mechanism might be dominant in the upper airway's heat-absorbing ability.     

Biomechanical analysis of a novel posterior construct in a transforaminal lumbar interbody fusion model an in vitro study

Background context

Spinal fusion is a commonly performed surgical procedure. It is used to treat a variety of spinal pathologies, including degenerative disease, trauma, spondylolisthesis, and deformities. A mechanically stable spine provides an ideal environment for the formation of a fusion mass. Instrumented spinal fusion allows early ambulation with minimal need for a postoperative external immobilizer. Several biomechanical and clinical studies have evaluated the stability offered by different posterior instrumentation techniques and the effects of reduced instrumentation.

Purpose

The aim of the study was to compare the biomechanics of a novel pedicle and translaminar facet screw (TLFS) construct. Also, in this study, comparisons were made with the more common pedicle screw/TLFS constructs for posterior fixation.

Study design

Human cadaveric lumbar spines were tested in an in vitro flexibility experiment to investigate the biomechanical stability provided by a novel pedicle and TLFS construct after transforaminal lumbar interbody fusion (TLIF).

Methods

Seven fresh human lumbar spines (L2–L5) were tested by applying pure moments of ±8 Nm. After intact specimen testing, a left-sided TLIF with a radiolucent interbody spacer was performed at L3–L4. Each specimen was then tested for the following constructs: bilateral pedicle screws (BPS) and rods at L3–L4; unilateral pedicle screws (UPS) and rods at L3–L4; UPS and rods and TLFS at L3–L4 (UPS+TLFS); and unilateral single pedicle screw and TLFS and rod at L3–L4 (V construct). The L3–L4 range of motion (ROM) and stiffness for each construct were obtained by applying pure moments in flexion, extension, lateral bending, and axial rotation.

Results

All instrumented constructs significantly reduced ROM in flexion-extension and lateral bending compared with the intact specimen. In axial rotation, only BPS constructs significantly reduced ROM compared with intact specimen. The V construct was able to achieve more reduction in ROM compared with UPS construct and was comparable to UPS+TLFS construct. Unilateral pedicle screws construct was the least stable in all loading modes and was significantly different than BPS construct in lateral bending.

Conclusions

The V construct exhibited enhanced stability compared with UPS construct in all loading modes. It provides bilateral fixation and preserves the anatomic integrity of the superior facet joint. The novel construct may offer advantages of less invasiveness, significant reduction in operation time, duration of hospitalization, and costs of implants, which would require further clinical evaluation.     

The neuronal protective effects of local brain cooling at the craniectomy site after lateral fluid percussion injury in a rat model

Background

The aim of the present study is to investigate whether local brain cooling at the craniectomy site causes attenuation of traumatic brain injury (TBI) induced by fluid percussion injury (FPI).

Methods

Anesthetized male Sprague–Dawley rats were divided into two major treatment groups. Immediately after the onset of fluid percussion TBI, a craniectomy window of 6 × 8 mm was made at the right parietal, and a cold water bag (0°C–1°C or 5°C–6°C) was applied locally for 30 min. Additional groups of rats were used as craniectomy and craniectomy + FPI controls. Physiological parameters, such as brain and colonic temperature, mean arterial pressure, and heart rate, were monitored during FPI. Functional motor outcomes were evaluated using the inclined plane test (maximal grasp angle). Cellular infarction volume was calculated using triphenyltetrazolium chloride staining. Apoptosis and neuronal marker–positive cells in the cortex were measured by immunofluorescence staining. All functional and morphologic parameters were assessed 72 h after injury.

Results

Compared with the craniectomy + FPI control groups, the groups treated with 5°C–6°C local cold water therapy showed significant attenuation of the FPI-induced motor deficits, weight loss, and cerebral infarction but no effect on colonic temperature. The FPI-induced apoptosis and neuronal loss were also significantly reduced by local cooling.

Conclusions

Our results suggest that local cooling with 5°C–6°C cold water therapy may ameliorate TBI in rats by reducing infarction volume, neuronal cell loss, and apoptosis, resulting in improved functional outcome. We propose that the use of local cooling at the craniectomy site after FPI might have clinical benefits in the future.     

Accuracy and reliability of coronal and sagittal spinal curvature data based on patient-specific three-dimensional models created by the EOS 2D/3D imaging system

Background context

Three-dimensional (3D) deformations of the spine are predominantly characterized by two-dimensional (2D) angulation measurements in coronal and sagittal planes, using anteroposterior and lateral X-ray images. For coronal curves, a method originally described by Cobb and for sagittal curves a modified Cobb method are most widely used in practice, and these methods have been shown to exhibit good-to-excellent reliability and reproducibility, carried out either manually or by computer-based tools. Recently, an ultralow radiation dose–integrated radioimaging solution was introduced with special software for realistic 3D visualization and parametric characterization of the spinal column.

Purpose

Comparison of accuracy, correlation of measurement values, intraobserver and interrater reliability of methods by conventional manual 2D and sterEOS 3D measurements in a routine clinical setting.

Study design/setting

Retrospective nonrandomized study of diagnostic X-ray images created as part of a routine clinical protocol of eligible patients examined at our clinic during a 30-month period between July 2007 and December 2009.

Patient sample

In total, 201 individuals (170 females, 31 males; mean age, 19.88 years) including 10 healthy athletes with normal spine and patients with adolescent idiopathic scoliosis (175 cases), adult degenerative scoliosis (11 cases), and Scheuermann hyperkyphosis (5 cases). Overall range of coronal curves was between 2.4° and 117.5°. Analysis of accuracy and reliability of measurements were carried out on a group of all patients and in subgroups based on coronal plane deviation: 0° to 10° (Group 1, n=36), 10° to 25° (Group 2, n=25), 25° to 50° (Group 3, n=69), 50° to 75° (Group 4, n=49), and more than 75° (Group 5, n=22).

Methods

Coronal and sagittal curvature measurements were determined by three experienced examiners, using either traditional 2D methods or automatic measurements based on sterEOS 3D reconstructions. Manual measurements were performed three times, and sterEOS 3D reconstructions and automatic measurements were performed two times by each examiner. Means comparison t test, Pearson bivariate correlation analysis, reliability analysis by intraclass correlation coefficients for intraobserver reproducibility and interrater reliability were performed using SPSS v16.0 software (IBM Corp., Armonk, NY, USA). No funds were received in support of this work. No benefits in any form have been or will be received from a commercial party related directly or indirectly to the subject of this article.

Results

In comparison with manual 2D methods, only small and nonsignificant differences were detectable in sterEOS 3D–based curvature data. Intraobserver reliability was excellent for both methods, and interrater reproducibility was consistently higher for sterEOS 3D methods that was found to be unaffected by the magnitude of coronal curves or sagittal plane deviations.

Conclusions

This is the first clinical report on EOS 2D/3D system (EOS Imaging, Paris, France) and its sterEOS 3D software, documenting an excellent capability for accurate, reliable, and reproducible spinal curvature measurements.     

Impact of Hypothermic Preservation on Tissue Yield and Viability in Pig Pancreata

Introduction

Chronic shortage of quality human cadaveric pancreata limits islet transplantation. Porcine islet xenotransplantation is being explored to increase the donor pool. For clinical-ready islets, centralized animal husbandry, Current Good Manufacturing Practice–regulated processing facilities, and organ transportation support are required. Amount of cold ischemia time (CIT) before isolation significantly affects transplantation. The goal of this study was to determine the maximum safe CIT of whole pancreata before islet isolation.

Materials and Methods

Pancreata were rapidly removed from Yorkshire pigs (age, 14–22 days) and stored in modified University of Wisconsin solution or in EuroCollins solution at 4^°C. Pancreata were processed with <1 hour CIT (control) or stored for 4 or 12 hours before isolation. Islet yield and percent purity and viability were determined after 7 days of in vitro tissue culture and maturation. Samples from nonprocessed pancreata were collected and snap-frozen in liquid nitrogen at 0, 3, 6, 9, 12, 15, and 24 hours of preservation, then analyzed for adenosine diphosphate/adenosine triphosphate ratio as a measure of tissue energetics.

Results

Up to 12 hours in cold storage had no significant impact on overall islet yield after 7 days of in vitro culture compared with controls; islet yield at the end of the maturation process was 28,700 ± 500 islet equivalents per pancreas (mean ± SEM control yield, 30,300 ± 900 islet equivalents per pancreas); islet purity was 75 ± 5% compared with 74 ± 5% in controls. Islet viability was significantly reduced at 12 hours compared with controls (80 ± 6% vs 96 ± 5%; P < .05). The tissue adenosine diphosphate/adenosine triphosphate ratio was maintained within the first 6 hours (1.6 ± 0.1 to 1.8 ± 0.2; P = NS) but was markedly increased during the 24-hour study (3.3 ± 0.1 at 24 hours), indicating a progressive loss of adenosine triphosphate tissue stores.

Conclusions

Young pig pancreata can be hypothermically stored for up to 12 hours without affecting islet yield and purity; however, islet viability is reduced. These data highlight the need for uniform shipping parameters to standardize islet quality, ideally with CIT <6 hours.     

Individual and contextual characteristics as determinants of sagittal standing posture: a population-based study of adults

Background context

Sagittal standing posture is associated with musculoskeletal symptoms and quality of life. However, the frequency and determinants of suboptimal sagittal alignment outside the clinical context remain to be clarified.

Purpose

To estimate the association of sociodemographic, anthropometric, and behavioral characteristics with sagittal standing posture among adults from the general population.

Study design

Cross-sectional evaluation of a population-based sample.

Patient sample

As part of the EPIPorto study, 489 adults were assessed during 2005 to 2008.

Outcome measures

Individual spinopelvic parameters were measured. Additionally, participants were classified into one of four types of sagittal postural patterns (Roussouly classification: Types 1, 2, and 4 corresponding to nonneutral postures and Type 3 to a neutral posture).

Methods

Spinopelvic parameters were recorded from 36-inch sagittal radiographs obtained in free-standing posture. Age, sex, education, occupation, body mass index (BMI), waist circumference, total physical activity, leisure time physical activity, time spent in sitting position, smoking status, and tobacco cumulative exposure were collected. Individual parameters and patterns of sagittal posture were compared across categories of participants' characteristics.

Results

Older age, lower educational level, blue collar occupation, and overall and central obesity were associated with increased sagittal vertical axis and pelvic tilt/pelvic incidence ratio. Taking the neutral postural pattern (Type 3) as reference for the outcome in a multinomial regression model, independently of age, sex, education, total physical activity, and smoking status, overweight adults had higher odds of Type 2 (odds ratio [OR]=1.92; 95% confidence interval [CI]: 1.13–3.27) and Type 4 (OR=2.13; 95% CI: 1.16–3.91) postural patterns in comparison with normal weight subjects. Overall and central obesity were positively related with Type 1 postural pattern (OR=6.10, 95% CI: 1.52–24.57 and OR=3.54, 95% CI: 1.13–11.11, respectively). There was also a weak direct association between female sex and Type 1 postural pattern. Regarding behavioral factors, subjects with total physical activity above the first third exhibited all nonneutral postural patterns less frequently, and current smokers were more likely to present a Type 4 postural pattern.

Conclusions

Higher BMI and central obesity were important potential determinants of nonneutral posture among adults from the general population. Future research should investigate the potential effectiveness of overweight prevention and management in avoiding sagittal misalignment conditions.