Biomechanical analysis of cervical orthoses in flexion and extension: A comparison of cervical collars and cervical thoracic orthoses

The Role of Orthoses in Chronic Axial Spinal Conditions

PURPOSE OF REVIEW

Bracing represents a prevalent conservative, non-surgical approach used in the management of chronic spinal conditions such as spondylosis, degenerative disc disease, and spondylolisthesis. A wide variety of orthoses are available to aid in addressing cervical, thoracic, lumbar, thoracic, and SI joint pain. In this review, we aim to comprehensively examine brace types with their current applications and implications of usage.

RECENT FINDINGS

There are multiple cervical bracing options, such as soft and rigid collars, to assist in managing acute trauma and chronic degenerative conditions. The review highlights the nuanced decision-making process between hard and soft collars based on the severity of bone or ligamentous injury and neurological findings. Orthoses for low back pain are commonly used. The review highlights the challenges of chronic neck and lower back pain, emphasizing the importance of clinicians exploring all treatment strategies including braces which can improve function and reduce pain.

Comparison of outcomes after anterior cervical discectomy and fusion with and without a cervical collar: a systematic review and meta-analysis

PURPOSE

The clinical outcomes of patients who received a cervical collar after anterior cervical decompression and fusion were evaluated by comparison with those of patients who did not receive a cervical collar.

METHODS

All of the comparative studies published in the PubMed, Cochrane Library, Medline, Web of Science, and EMBASE databases as of 1 October 2023 were included. All outcomes were analysed using Review Manager 5.4.

RESULTS

Four studies with a total of 406 patients were included, and three of the studies were randomized controlled trials. Meta-analysis of the short-form 36 results revealed that wearing a cervical collar after anterior cervical decompression and fusion was more beneficial (P < 0.05). However, it is important to note that when considering the Neck Disability Index at the final follow-up visit, not wearing a cervical collar was found to be more advantageous. There were no statistically significant differences in postoperative cervical range of motion, fusion rate, or neck disability index at 6 weeks postoperatively (all P > 0.05) between the cervical collar group and the no cervical collar group.

CONCLUSIONS

This systematic review and meta-analysis revealed no significant differences in the 6-week postoperative cervical range of motion, fusion rate, or neck disability index between the cervical collar group and the no cervical collar group. However, compared to patients who did not wear a cervical collar, patients who did wear a cervical collar had better scores on the short form 36. Interestingly, at the final follow-up visit, the neck disability index scores were better in the no cervical collar group than in the cervical collar group. PROSPERO registration number: CRD42023466583.

A wearable system to assist impaired-neck patients: Design and evaluation

Patients with neurological disorders, such as amyotrophic lateral sclerosis, Parkinson's disease, and cerebral palsy, often face challenges due to head-neck immobility. The conventional treatment approach involves using a neck collar to maintain an upright head position, but this can be cumbersome and restricts head-neck movements over prolonged periods. This study introduces a wearable robot capable of providing three anatomical head motions for training and assistance. The primary contributions of this research include the design of an optimized structure and the incorporation of human-robot interaction. Based on human head motion data, our primary focus centered on developing a robot capable of accommodating a significant range of neutral head movements. To ensure safety, impedance control was employed to facilitate human-robot interaction. A human study was conducted involving 10 healthy subjects who participated in an experiment to assess the robot's assistance capabilities. Passive and active modes were used to evaluate the robot's effectiveness, taking into account head-neck movement error and muscle activity levels. Surface electromyography signals (sEMG) were collected from the splenius capitis muscles during the experiment. The results demonstrated that the robot covered nearly 85% of the overall range of head rotations. Importantly, using the robot during rehabilitation led to reduced muscle activation, highlighting its potential for assisting individuals with post-stroke movement impairments.

The Effects of Cervical Orthoses on Head and Intervertebral Range of Motion

STUDY DESIGN

Prospective Cohort.

OBJECTIVE

Quantify and compare the effectiveness of cervical orthoses in restricting intervertebral kinematics during multiplanar motions.

SUMMARY OF BACKGROUND DATA

Previous studies evaluating the efficacy of cervical orthoses measured global head motion and did not evaluate individual cervical motion segment mobility. Prior studies focused only on the flexion/extension motion.

METHODS

Twenty adults without neck pain participated. Vertebral motion from the occiput through T1 was imaged using dynamic biplane radiography. Intervertebral motion was measured using an automated registration process with validated accuracy better than 1 degree. Participants performed independent trials of maximal flexion/extension, axial rotation, and lateral bending in a randomized order of unbraced, soft collar (foam), hard collar (Aspen), and cervical thoracic orthosis (CTO) (Aspen) conditions. Repeated-measures ANOVA was used to identify differences in the range of motion (ROM) among brace conditions for each motion.

RESULTS

Compared with no collar, the soft collar reduced flexion/extension ROM from occiput/C1 through C4/C5, and reduced axial rotation ROM at C1/C2 and from C3/C4 through C5/C6. The soft collar did not reduce motion at any motion segment during lateral bending. Compared with the soft collar, the hard collar reduced intervertebral motion at every motion segment during all motions, except for occiput/C1 during axial rotation and C1/C2 during lateral bending. The CTO reduced motion compared with the hard collar only at C6/C7 during flexion/extension and lateral bending.

CONCLUSIONS

The soft collar was ineffective as a restraint to intervertebral motion during lateral bending, but it did reduce intervertebral motion during flexion/extension and axial rotation. The hard collar reduced intervertebral motion compared with the soft collar across all motion directions. The CTO provided a minimal reduction in intervertebral motion compared with the hard collar. The utility in using a CTO rather than a hard collar is questionable, given the cost and little or no additional motion restriction.

Posterior cervical foraminotomy versus anterior cervical discectomy for Cervical Brachialgia: the FORVAD RCT

Background

Posterior cervical foraminotomy and anterior cervical discectomy are routinely used operations to treat cervical brachialgia, although definitive evidence supporting superiority of either is lacking.

Objective

The primary objective was to investigate whether or not posterior cervical foraminotomy is superior to anterior cervical discectomy in improving clinical outcome.

Design

This was a Phase III, unblinded, prospective, United Kingdom multicentre, parallel-group, individually randomised controlled superiority trial comparing posterior cervical foraminotomy with anterior cervical discectomy. A rapid qualitative study was conducted during the close-down phase, involving remote semistructured interviews with trial participants and health-care professionals.

Setting

National Health Service trusts.

Participants

Patients with symptomatic unilateral cervical brachialgia for at least 6 weeks.

Interventions

Participants were randomised to receive posterior cervical foraminotomy or anterior cervical discectomy. Allocation was not blinded to participants, medical staff or trial staff. Health-care use from providing the initial surgical intervention to hospital discharge was measured and valued using national cost data.

Main outcome measures

The primary outcome measure was clinical outcome, as measured by patient-reported Neck Disability Index score 52 weeks post operation. Secondary outcome measures included complications, reoperations and restricted American Spinal Injury Association score over 6 weeks post operation, and patient-reported Eating Assessment Tool-10 items, Glasgow-Edinburgh Throat Scale, Voice Handicap Index-10 items, PainDETECT and Numerical Rating Scales for neck and upper-limb pain over 52 weeks post operation.

Results

The target recruitment was 252 participants. Owing to slow accrual, the trial closed after randomising 23 participants from 11 hospitals. The qualitative substudy found that there was support and enthusiasm for the posterior cervical FORaminotomy Versus Anterior cervical Discectomy in the treatment of cervical brachialgia trial and randomised clinical trials in this area. However, clinical equipoise appears to have been an issue for sites and individual surgeons. Randomisation on the day of surgery and processes for screening and approaching participants were also crucial factors in some centres. The median Neck Disability Index scores at baseline (pre surgery) and at 52 weeks was 44.0 (interquartile range 36.0-62.0 weeks) and 25.3 weeks (interquartile range 20.0-42.0 weeks), respectively, in the posterior cervical foraminotomy group (n = 14), and 35.6 weeks (interquartile range 34.0-44.0 weeks) and 45.0 weeks (interquartile range 20.0-57.0 weeks), respectively, in the anterior cervical discectomy group (n = 9). Scores appeared to reduce (i.e. improve) in the posterior cervical foraminotomy group, but not in the anterior cervical discectomy group. The median Eating Assessment Tool-10 items score for swallowing was higher (worse) after anterior cervical discectomy (13.5) than after posterior cervical foraminotomy (0) on day 1, but not at other time points, whereas the median Glasgow-Edinburgh Throat Scale score for globus was higher (worse) after anterior cervical discectomy (15, 7, 6, 6, 2, 2.5) than after posterior cervical foraminotomy (3, 0, 0, 0.5, 0, 0) at all postoperative time points. Five postoperative complications occurred within 6 weeks of surgery, all after anterior cervical discectomy. Neck pain was more severe on day 1 following posterior cervical foraminotomy (Numerical Rating Scale - Neck Pain score 8.5) than at the same time point after anterior cervical discectomy (Numerical Rating Scale - Neck Pain score 7.0). The median health-care costs of providing initial surgical intervention were £2610 for posterior cervical foraminotomy and £4411 for anterior cervical discectomy.

Conclusions

The data suggest that posterior cervical foraminotomy is associated with better outcomes, fewer complications and lower costs, but the trial recruited slowly and closed early. Consequently, the trial is underpowered and definitive conclusions cannot be drawn. Recruitment was impaired by lack of individual equipoise and by concern about randomising on the day of surgery. A large prospective multicentre trial comparing anterior cervical discectomy and posterior cervical foraminotomy in the treatment of cervical brachialgia is still required.

Trial registration

This trial is registered as ISRCTN10133661.

Funding

This project was funded by the National Institute for Health and Care Research (NIHR) Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 27, No. 21. See the NIHR Journals Library website for further project information.

Neck Collar Assessment for People Living With Motor Neuron Disease: Are Current Outcome Measures Suitable?

A majority of people living with motor neuron disease (MND) experience weakness of the neck and as a result, experience head drop. This exacerbates problems with everyday activities (eating, talking, breathing, etc). Neck collars are often used to support head drop; however, these are typically designed for prehospitalization settings to manage and brace the cervical region of the spine. As a result, it has been recorded that people living with MND often reject these collars for a variety of reasons but most notably because they are too restricting. The current standardized outcome measures (most notably restricting cervical range of motion) used for neck collars are summarized herein along with whether they are suitable for a bespoke neck collar specifically designed for people living with MND.

The Influence of Cervical Spine Angulation on Symptoms Associated With Wearing a Rigid Neck Collar

Introduction:

Rigid cervical spine collars can be used to maintain the position of the cervical spine following injury or surgery. However, they have been associated with difficulty swallowing, pressure sores and pain, particularly in older patients. We aimed to investigate the relationship between cervical spine angulation, a rigid neck collar and neck pain in healthy young and older adults.

Methods:

Twenty healthy young adults aged 25 ± 3 years and 17 healthy older adults aged 80 ± 8 years were tested. Magnetic resonance imaging scans of their cervical spines were taken before and after the rigid neck collar was worn for 1 hour. Measurement of vertebral angulation involved digitization of the scans and joint angle calculations using image processing software. Pain was quantified before and after the collar was worn, using a visual analogue scale.

Results:

Pain scores increased in the young group after the collar was worn (p = 0.001). The older group showed no difference in pain score after the collar was worn. Statistical tests showed no significant correlations between the change in cervical angles and the change in pain scores after the collar was worn.

Discussion:

The aging process may contribute to the changing distribution of subcutaneous tissue and increase risk of symptoms associated with wearing a collar. Oesophageal compression is not a result of collar use.

Conclusion:

There is no correlation between cervical spine vertebrae angulation and symptoms associated with wearing a neck collar. Generally, older individuals have greater cervical lordosis angles, and more straight and lordotic neck shapes. Older individuals may be more prone to skin-interface pressures from the neck collar than younger individuals.

Effect of 5 different cervical collars on optic nerve sheath diameter: A randomized crossover trial

BACKGROUND

There is considerable evidence that prolonged use of cervical collars potentially cause detrimental effects including increase in optic nerve sheath diameter (ONSD) among healthy volunteers. Different types of cervical collars immobilize cervical spine variably well and may presumably differently influence the venous compression and hence the intracranial pressure. We therefore aimed to evaluate the influence of cervical spine immobilization with 5 different types of cervical collars on ONSD measured noninvasively by ultrasound on healthy volunteers.

METHODS

We conducted a randomized crossover trial including 60 adult healthy volunteers. Control assessment of the optic nerve sheath thickness was performed in both sagittal and transverse planes. Patient was placed supine on a transport stretcher, cervical collar was placed, and ONSD measurement was performed after 5 and 20 minutes. During the next days, the procedure was repeated with random allocation of participants and random cervical collar.

RESULTS

Sixty healthy volunteers were included in our study. ONSD left diameter [mm] for the baseline was 3.8 [interquartile range (IQR): 3.65-3.93)] mm. Using AMBU after 5 min, ONSD was changed up to 4.505 (IQR 4.285-4.61; P < .001) mm. The largest change at 5 minutes and 20 minutes was using Philly 4.73 (IQR: 4.49-4.895; P < .001) and 4.925 (IQR: 4.65-5.06; P < .001), respectively. Necklite reported the lower change in ONSD: 3.92 (IQR: 3.795-4; P = 1.0) mm in 5 minutes and 3.995 (IQR: 3.875 - 4.1; P = 1.0) mm in 20 minutes. ONSD right diameter [mm] for the baseline was 3.8 (IQR 3.675-3.9) mm. Using AMBU after 5 minutes, ONSD was changed up to 4.5 (IQR 4.21-4.6) mm. The largest change at 5 minutes and 20 minutes was using Philly 4.705 (IQR 4.455-4.9) and 4.93 (IQR 4.645-5.075), respectively. Necklite reported the lower change in ONSD -33.9 (IQR 3.795-3.99) mm in 5 minutes and 3.995 (IQR 3.86-4.09) mm in 20 minutes.

CONCLUSION

We report significant increase of ONSD from the baseline after cervical collar placement among healthy volunteers at 5 minutes and 20 minutes interval. In addition, no significant difference was noted between ONSD measurements at 5 and 20 minutes. Clinicians should take proactive steps to assess the actual need of cervical collar case by case basis. Nonetheless, when needed, Necklite moldable neck brace seems to be a reasonable option.Registration: ClinicalTrials database (www.clinicaltrials.gov, NCT03609879).

Utility of Cervical Collars Following Cervical Fusion Surgery. Does It Improve Fusion Rates or Outcomes? A Systematic Review

BACKGROUND

The use of postoperative cervical collars following cervical fusions is common practice. Its use has been purported to improve fusion rates and outcomes. There is a paucity in the strength of evidence to support its clinical benefit. Our objective is to critically evaluate the published literature to determine the strength of evidence supporting the use of postoperative cervical collar use following cervical fusions.

METHODS

A systematic review using Preferred Reporting Items for Systematic Reviews and Meta-Analyses (also known as PRISMA) was performed. An online search using Medline and Cochrane Central Register of Controlled Trials databases was used to query prospective and retrospective clinical trials evaluating cervical fusions with or without postoperative collar.

RESULTS

The search identified 894 articles in Medline and 65 articles in the Cochrane database. From these articles, 130 were selected based on procedure and collar use. Only 3 studies directly compared between collar use and no collar use. Our analysis of the mean improvement in neck disability index scores and improvement over time intervals did not show a statistically significant difference between collar versus no collar (P = 0.86).

CONCLUSIONS

We found no strong evidence to support the use of cervical collars after 1- and 2-level anterior cervical discectomy and fusion procedures, and no studies comparing collar use and no collar use after posterior cervical fusions. Given the cost and likely impact of collar use on driving and the return to work, our study shows that currently there is no proven benefit to routine use of postoperative cervical collar in patients undergoing 1- and 2-level anterior cervical discectomy and fusion for degenerative cervical pathologies.

A comfort assessment of existing cervical orthoses

PURPOSE

Identify location and intensity of discomfort experienced by healthy participants wearing cervical orthoses.

METHOD

Convenience sample of 34 healthy participants wore Stro II, Philadelphia, Headmaster, and AspenVista^® cervical orthoses for four-hour periods. Participants reported discomfort level (scale 0-6) and location.

RESULTS

Participants reported mean discomfort for all orthoses over the four-hour test between 'a little discomfort' and 'very uncomfortable' (mean discomfort score = 1.64, SD = 1.50). Seven participants prematurely stopped tests due to pain and six reported maximum discomfort scores. Significant linear increase in discomfort with duration of wear was found for all orthoses. Significantly less discomfort was reported with Stro II than Headmaster and Philadelphia. Age correlated with greater perceived discomfort. Orthoses differed in the location discomfort was experienced.

CONCLUSION

Existing cervical orthoses cause discomfort influenced by design and duration of wear with orthoses' design the more significant factor. This work informed the design of a new orthosis and future orthoses developments. Practitioner Summary: The purpose of this study was to gain greater knowledge about the discomfort caused by wearing of existing neck orthoses in order to inform the design and development of a new neck orthosis. This study gathers empirical data from a surrogate population and concludes that orthosis design is more influential than the duration of wear.

Restriction of Cervical Intervertebral Movement With Different Types of External Immobilizers: A Cadaveric 3D Analysis Study

STUDY DESIGN

Cadaveric radiostereometric analysis study.

OBJECTIVE

To quantify the ability of five commonly used immobilizers to restrict cervical spine movement, including intervertebral movement, in three directions.

SUMMARY OF BACKGROUND DATA

Evidence about the ability of many clinically used cervical immobilizers to restrict cervical movement is limited. Furthermore, their effect on intervertebral movement is unknown.

METHODS

Radiographic inert beads were implanted in the cervical vertebral bodies of five fresh-frozen human cadavers. After application of different immobilizers (Stifneck, Sternal Occipital Mandibular Immobilizer (SOMI), halo-traction, spineboard, halo-vest) and controlled flexion-extension, lateral bending, and rotation torques, radiostereometric analysis was used to determine the overall and intervertebral three-dimensional movement of each vertebral level. Restriction of cervical movement was described as a mean restriction percentage (MRP) and classified on an arbitrary basis (poor: <20%, fair: 20%-40%, moderate: 40%-60%, substantial: 60%-80%, nearly complete: >80%).

RESULTS

Most of the restriction of flexion/extension was observed at C0-C1, while most rotational restriction was seen at C1-C2. Lateral bending was restricted at C1 to C7.The Stifneck provided the least immobilization with a moderate restriction of flexion-extension (MRP: 41%, SD: 14%), fair restriction of lateral bending (MRP: 29%, SD: 13%), and substantial restriction of rotation (MRP: 64%, SD: 15%). The halo-vest was the most restrictive immobilizer and reduced movement of the cervical spine substantially for flexion-extension (MRP: 70%, SD: 11%), substantially for lateral bending (MRP: 77%, SD: 14%), and nearly complete for rotation (MRP: 92%, SD: 3%).

CONCLUSION

The restriction of movement from lowest to highest was: Stifneck, SOMI, halo-traction, head blocks on a spine board, and halo-vest. Notably, the standard deviations of the restrictions were smaller for the cranio-thoracic devices than for the cervico thoracic devices. With this new knowledge of external immobilizers and their ability to restrict intervertebral cervical movement, their indication and application in clinical practice can be improved for all patients with (suspected) cervical injury.

LEVEL OF EVIDENCE

N/A.

Anterior Cervical Discectomy With Fusion Using a Local Source for Cancellous Autograft: A Biomechanical Analysis of Vertebral Body Stability in an Osteopenic Bone Model

BACKGROUND

Anterior cervical discectomy with fusion is an effective treatment for patients having cervical radiculopathy and myelopathy. To reduce morbidity associated with autograft taken from the iliac crest without sacrificing high fusion rates, a novel technique that harvests bone from the vertebral body adjacent to the operative disc space has been proposed. The effects of square and round bone graft harvest techniques on the mechanical stability of the osteopenic donor vertebrae are unknown. We analyzed the biomechanical implications of the technique by subjecting osteopenic models to uniaxial compression to compare yield strengths of surgically altered and unaltered specimens.

METHODS

Biomechanical grade polyurethane foam was cut into 60 different 12 mm × 17 mm × 20 mm blocks. The foam had a density of 10 pounds per cubic foot, simulating osteoporotic bone. Rectangular prism (4 mm × 4 mm × 6 mm) and cylindrical cores (r = 2 mm, h = 8 mm) were removed from 20 blocks per group. Twenty samples were left intact as a control group. Anterior plate screws were applied to the models and a Polyether ether ketone (PEEK) interbody spacer was placed on top. Samples underwent uniaxial compression at 0.1 mm/s until mechanical failure. Points of structural failure were determined using a 0.1% offset on a force-displacement curve and compared to determine the reductions in compressive strength.

RESULTS

The mean force eliciting structural failure for intact samples was 450.6 N. Average failure forces for rectangular prisms and cylindrical cores removed were 383.2 and 395.4 N, respectively. Removal of a rectangular prismatic core of the necessary volume resulted in a 15.0% reduction in compressive strength, while removal of a cylindrical core of comparable volume facilitated a reduction of 12.2%.

CONCLUSION

Local autograft harvested from adjacent vertebrae reduces morbidity associated with a second surgical site while minimally reducing the compressive strength of the donor vertebra in an osteopenic model, lending credence to the efficacy of this technique in elderly patient populations.

Evaluation of the efficiency of cervical orthoses on cervical fracture: A review of literature

Background:

Various methods have been used to stabilize the vertebra in cervical fractures, including the use of various orthoses and surgery. However, it is not cleared which type of orthosis is more suitable for the subjects with cervical fractures to best immobilize the vertebra and to decrease the associated side effects. Therefore, the aim of this study was to evaluate the efficiency of various orthoses based on the available literature.

Materials and Methods:

A search was done in some databases include PubMed, ISI Web of Knowledge, EBSCO, Embasco, and Google Scholar. The search was done with some key words such as: Cervical spine injuries; odontoid fractures; hangman's fractures; axis fracture; axis, atlas, cervical fractures; trauma; neck fracture; neck injury in combination with cervical orthoses. The quality of the studies was evaluated by use of Downs and Black assessment and Assessment of Multiple Systematic Reviews (AMSTAR) for original research and review articles, respectively.

Results:

Based on the aforementioned key words, 25 papers were selected. The quality of the studies varies 10-24. Most of the studies were on the use of the halo vest orthosis, its side effects and also on complications associated with various orthoses.

Discussion:

Halo orthoses provide a high degree of restriction and immobilization; however, there are some side effects associated with this orthosis, including swallowing, pin loosening, and infection. It should be emphasized that other types of orthoses fewer complications, with reasonable outputs on motion restrictions.

Comparison of Cervical Range-of-Motion Restriction and Craniofacial Tissue-Interface Pressure With 2 Adjustable and 2 Standard Cervical Collars

STUDY DESIGN

Randomized controlled trial.

OBJECTIVE

The aim of the study was to compare and contrast the restrictiveness and tissue-interface pressure (TIP) characteristics of 2 standard and 2 adjustable cervical collars.

SUMMARY OF BACKGROUND DATA

This study compared the restrictiveness and TIP of 4 commercially available cervical collars (2 standard and 2 adjustable). Adjustable collars offer potential advantages of individualized fit for patients and decreased inventory for institutions. The overall goal was to determine whether the adjustable collars provided the same benefits of cervical range-of-motion (CROM) restriction as the standard collars without increasing TIP and risk of pressure-related complications.

METHODS

A total of 48 adult volunteer subjects (24 men and 24 women) were fitted with 4 collars (Aspen, Aspen Vista, Miami J, and Miami J Advanced) in random order. Data collection included assessment of CROM restrictiveness and measurement of TIP on the mandible and occiput in upright and supine positions. The experimental, repeated measures design stratified the sample by body mass index (BMI) and sex.

RESULTS

All collars restricted CROM as compared with no collar (P ≤ 0.001 each). Aspen was more restrictive than Aspen Vista and Miami J in 4 movement planes (P ≤ 0.003 each), but not significantly different from Miami J Advanced. The Miami J standard collar was associated with significantly lower peak TIPs on all sites and in all positions compared with Aspen (P ≤ 0.001), Miami J Advanced (P < 0.001), and Aspen Vista (P = 0.01 for mandible site and upright position, P < 0.001 for remaining sites and positions). Increased peak TIP correlated with high BMI across all collar types, but was significantly lower for the Miami J collar than the Aspen collar.

CONCLUSION

All collars, compared with no collar, significantly restricted CROM. Although the collar-to-collar comparisons were statistically significant, the differences may have little clinical significance in the acutely injured trauma patient. The Miami J standard collar had the lowest overall TIP in both sites and positions. Ongoing effort should be devoted to staff education in proper sizing and fit, particularly for patients with high BMI.

Assessment of the Sheffield Support Snood, an innovative cervical orthosis designed for people affected by neck muscle weakness

BACKGROUND

This study aimed at quantifying the biomechanical features of the Sheffield Support Snood, a cervical orthosis specifically designed for patients with neck muscle weakness. The orthosis is designed to be adaptable to a patient's level of functional limitation using adjustable removable supports, which contribute support and restrict movement only in desired anatomical planes.

METHODS

The snood was evaluated along with two commercially available orthoses, the Vista and Headmaster, in a series of flexion, extension, axial-rotation and lateral flexion movements. Characterization was performed with twelve healthy participants with and without the orthoses. Two inertial-magneto sensors, placed on the forehead and sternum, were used to quantify the neck's range of motion.

FINDINGS

In its less supportive configuration, the snood was effective in limiting movements to the desired planes, preserving free movement in other planes. The Headmaster was only effective in limiting flexion. The range of motion achieved with the snood in its rigid configuration was equivalent (P>0.05, effect size<0.4) to that achieved with the Vista, both in trials performed reaching the maximum amplitude (range of motion reduction: 25%-34% vs 24%-47%) and at maximum speed (range of motion reduction: 24%-29% vs 25%-43%).

INTERPRETATION

The Sheffield Support Snood is effectively adaptable to different tasks and, in its most supportive configuration, offers a support comparable to the Vista, but providing a less bulky structure. The chosen method is suitable for the assessment of range of motions while wearing neck orthoses and is easily translatable in a clinical context.

Cervical radiculopathy: epidemiology, etiology, diagnosis, and treatment

Cervical radiculopathy is a relatively common neurological disorder resulting from nerve root dysfunction, which is often due to mechanical compression; however, inflammatory cytokines released from damaged intervertebral disks can also result in symptoms. Cervical radiculopathy can often be diagnosed with a thorough history and physical examination, but an magnetic resonance imaging or computed tomographic myelogram should be used to confirm the diagnosis. Because of the ubiquity of degenerative changes found on these imaging modalities, the patient's symptoms must correlate with pathology for a successful diagnosis. In the absence of myelopathy or significant muscle weakness all patients should be treated conservatively for at least 6 weeks. Conservative treatments consist of immobilization, anti-inflammatory medications, physical therapy, cervical traction, and epidural steroid injections. Cervical radiculopathy typically is self-limiting with 75%-90% of patients achieving symptomatic improvement with nonoperative care. For patients who are persistently symptomatic despite conservative treatment, or those who have a significant functional deficit surgical treatment is appropriate. Surgical options include anterior cervical decompression and fusion, cervical disk arthroplasty, and posterior foraminotomy. Patient selection is critical to optimize outcome.

Effectiveness of Adjustable Cervical Orthoses and Modular Cervical Thoracic Orthoses in Restricting Neck Motion: A Comparative In vivo Biomechanical Study

STUDY DESIGN

In vivo biomechanical study.

OBJECTIVE

To compare the effectiveness of adjustable cervical orthoses (COs) and modular cervical thoracic orthoses (CTOs) with standard devices in restricting neck motion in all 3 anatomical planes.

SUMMARY OF BACKGROUND DATA

No literature is available regarding the effectiveness of adjustable COs and modular CTOs in restricting neck motion, and existing in vivo evaluation methodologies lack consistency and objectivity.

METHODS

The effectiveness of adjustable COs (Vista collar and Vista multipost collar) and modular CTOs (Vista TS, Vista TS with multipost, and Vista TS4 with multipost) in comparison with standard devices (Aspen collar [AC] and Aspen cervical thoracic orthosis) in restricting neck motion across 3 anatomical planes was studied in vivo in 27 healthy participants across prescribed loading levels ranging from 0.5 to 2.0 N·m. Neck range of motion allowed was compared between devices using Tukey post hoc test. The compliance of devices in restricting flexion and extension was obtained via a linear regression model.

RESULTS

When compared with modular CTOs, Aspen CTO was significantly more effective at motion restriction in both sagittal and frontal planes under loading level higher than 1.5 N·m. Modular CTOs outperformed adjustable COs in most of the cases but were fairly comparable with the standard CO (i.e., AC). Adjustable COs were just as effective as standard COs. The compliances of devices in restricting neck flexion ranked in ascending order were 0.83 (Aspen CTO), 1.53 (Vista TS with multipost), 1.60 (Vista TS4 with multipost), 1.77 (Vista multipost collar), 1.78 (AC), 1.99 (Vista TS), and 2.43 (Vista Collar) degrees per N·m.

CONCLUSION

Overall, modular CTOs had poorer performance in neck restriction than their standard counterpart (ACTO), whereas adjustable COs showed overall comparable performance to their standard counterpart (AC). The outcomes may assist clinicians in selecting appropriate devices.

LEVEL OF EVIDENCE

N/A.

Occipital Condyle Fracture with Associated Hypoglossal Nerve Injury

Occipital condyle fracture (OCF) is a rare injury that was first described by Bell in 1817. In fact, there have been only 96 more reported cases of occipital condyle fractures from 1817 to 1994 of which only 58 survived. Occipital condyle fractures can sometimes go unnoticed or under-diagnosed as they are not always evident on plain radiographs of the cervical spine. Also, in rare cases OCFs can cause damage to the hypoglossal nerve which passes through the hypoglossal canal which is near the occipital condyle. The presence of specific symptoms and clinical signs should lead to the correct diagnosis. This paper describes a patient who was diagnosed with OCFs, but not hypoglossal nerve damage until 20 days following admission to hospital. We point out many factors that contributed to this delayed diagnosis, which ultimately caused severe discomfort to the patient.

Motion in the unstable cervical spine when transferring a patient positioned prone to a spine board

CONTEXT

Two methods have been proposed to transfer an individual in the prone position to a spine board. Researchers do not know which method provides the best immobilization.

OBJECTIVE

To determine if motion produced in the unstable cervical spine differs between 2 prone logrolling techniques and to evaluate the effect of equipment on the motion produced during prone logrolling.

DESIGN

Crossover study.

SETTING

Laboratory.

PATIENTS OR OTHER PARTICIPANTS

Tests were performed on 5 fresh cadavers (3 men, 2 women; age = 83 ± 8 years, mass = 61.2 ± 14.1 kg).

MAIN OUTCOME MEASURE(S)

Three-dimensional motions were recorded during 2 prone logroll protocols (pull, push) in cadavers with an unstable cervical spine. Three equipment conditions were evaluated: football shoulder pads and helmet, rigid cervical collar, and no equipment. The mean range of motion was calculated for each test condition.

RESULTS

The pull technique produced 16% more motion than the push technique in the lateral-bending angulation direction (F1,4 = 19.922, P = .01, η(2) = 0.833). Whereas the collar-only condition and, to a lesser extent, the football-shoulder-pads-and-helmet condition demonstrated trends toward providing more stability than the no-equipment condition, we found no differences among equipment conditions. We noted an interaction between technique and equipment, with the pull maneuver performed without equipment producing more anteroposterior motion than the push maneuver in any of the equipment conditions.

CONCLUSIONS

We saw a slight difference in the motion measured during the 2 prone logrolling techniques tested, with less lateral-bending and anteroposterior motion produced with the logroll push than the pull technique. Therefore, we recommend adopting the push technique as the preferred spine-boarding maneuver when a patient is found in the prone position. Researchers should continue to seek improved methods for performing prone spine-board transfers to further decrease the motion produced in the unstable spine.

Do cervical collars and cervicothoracic orthoses effectively stabilize the injured cervical spine? A biomechanical investigation

STUDY DESIGN

In vitro biomechanical study.

OBJECTIVE

Our objective was to determine the effectiveness of cervical collars and cervicothoracic orthoses for stabilizing clinically relevant, experimentally produced cervical spine injuries.

SUMMARY OF BACKGROUND DATA

Most previous in vitro studies of cervical orthoses used a simplified injury model with all ligaments transected at a single spinal level, which differs from real-life neck injuries. Human volunteer studies are limited to measuring only sagittal motions or 3-dimensional motions only of the head or 1 or 2 spinal levels.

METHODS

Three-plane flexibility tests were performed to evaluate 2 cervical collars (Vista Collar and Vista Multipost Collar) and 2 cervicothoracic orthoses (Vista TS and Vista TS4) using a skull-neck-thorax model with 8 injured cervical spine specimens (manufacturer of orthoses: Aspen Medical Products Inc, Irvine, CA). The injuries consisted of flexion-compression at the lower cervical spine and extension-compression at superior spinal levels. Pair-wise repeated measures analysis of variance (P < 0.05) and Bonferroni post hoc tests determined significant differences in average range of motions of the head relative to the base, C7 or T1, among experimental conditions. RESULTS.: All orthoses significantly reduced unrestricted head/base flexion and extension. The orthoses allowed between 8.4% and 25.8% of unrestricted head/base motion in flexion/extension, 57.8% to 75.5% in axial rotation, and 53.8% to 73.7% in lateral bending. The average percentages of unrestricted motion allowed by the Vista Collar, Vista Multipost Collar, Vista TS, and Vista TS4 were: 14.0, 9.7, 6.1, and 4.7, respectively, for middle cervical spine extension and 13.2, 11.8, 3.3, and 0.4, respectively, for lower cervical spine flexion.

CONCLUSION

Successive increases in immobilization were observed from Vista Collar to Vista Multipost Collar, Vista TS, and Vista TS4 in extension at the injured middle cervical spine and in flexion at the injured lower cervical spine. Our results may assist clinicians in selecting the most appropriate orthosis based upon patient-specific cervical spine injuries.

Effects of cervical orthoses on neck biomechanical responses during transitioning from supine to upright

BACKGROUND

Our objectives were to use a hybrid cadaveric/surrogate model to evaluate the effects of the cervicothoracic orthosis and collar on head and neck biomechanical responses during transitioning from supine to upright.

METHODS

The model consisted of an adult-male surrogate dummy with its artificial neck replaced by a human neck specimen (n=10). The model was transitioned from supine to upright using a rotation apparatus. A high-speed digital camera tracked motions of the head, vertebrae, cervicothoracic orthosis, pelvis, and rotation apparatus. Head load cell data were used to compute occipital condyle loads. Average peak spinal loads and motions were statistically compared (P<0.05) among experimental conditions (cervicothoracic orthosis: anterior strut locked and unlocked; collar; and unrestricted).

FINDINGS

Loads at the occipital condyles consisted of anterior shear, compression, and extension moment. The most rigid device tested, cervicothoracic orthosis with anterior strut locked, significantly reduced axial compression neck force and increased anterior shear neck force and provided the greatest immobilization by significantly reducing spinal rotations as compared to other experimental conditions. Similar neck biomechanical responses were observed between the cervicothoracic orthosis, anterior strut unlocked, and collar.

INTERPRETATION

The simple maneuver of supine-to-upright transitioning, commonly performed clinically, produced complex neck loads and motions including head protrusion which caused cervical spine snaking. Neck motions consisted of extension at the upper cervical spine and flexion at the subaxial cervical spinal levels. Of the devices tested, the cervicothoracic orthosis, with anterior strut locked, provided the greatest cervical spine immobilization thereby reducing the risk of potential secondary neck injuries.

A 3D motion analysis study comparing the effectiveness of cervical spine orthoses at restricting spinal motion through physiological ranges

OBJECTIVE

To compare the effectiveness of the Aspen, Aspen Vista, Philadelphia, Miami-J and Miami-J Advanced collars at restricting cervical spine movement in the sagittal, coronal and axial planes.

METHODS

Nineteen healthy volunteers (12 female, 7 male) were recruited to the study. Collars were fitted by an approved physiotherapist. Eight ProReflex (Qualisys, Sweden) infrared cameras were used to track the movement of retro-reflective marker clusters placed in predetermined positions on the head and trunk. 3D kinematic data were collected during forward flexion, extension, lateral bending and axial rotation from uncollared to collared subjects. The physiological range of motion in the three planes was analysed using the Qualisys Track Manager System.

RESULTS

The Aspen and Philadelphia were significantly more effective at restricting flexion/extension than the Vista (p < 0.001), Miami-J (p < 0.001 and p < 0.01) and Miami-J Advanced (p < 0.01 and p < 0.05). The Aspen was significantly more effective at restricting rotation than the Vista (p < 0.001) and the Miami-J (p < 0.05). The Vista was significantly the least effective collar at restricting lateral bending (p < 0.001).

CONCLUSION

Our motion analysis study found the Aspen collar to be superior to the other collars when measuring restriction of movement of the cervical spine in all planes, particularly the sagittal and transverse planes, while the Aspen Vista was the least effective collar.

Effects of orthoses on three-dimensional load-displacement properties of the cervical spine

PURPOSE

Our objectives were to develop a skull-neck-thorax model capable of quantifying spinal motions in an intact human cadaver neck with and without cervical orthoses, determine the effect of orthoses on three-dimensional load-displacement properties of all cervical spinal levels, and compare and contrast our results with previously reported in vivo data.

METHODS

Load input flexibility tests were performed to evaluate two cervical collars (Vista(®) collar and Vista(®) Multipost collar) and two cervicothoracic orthoses (CTOs: Vista(®) TS and Vista(®) TS4) using the skull-neck-thorax model with 10 intact whole cervical spine specimens. The physiologic range of motion (RoM) limit was the peak obtained from flexibility tests with no orthosis. Pair-wise repeated measures, analysis of variance (p < 0.05), and Bonferroni post hoc tests determined significant differences in average peak RoM at each spinal level among the experimental conditions.

RESULTS

Significant reductions below physiologic limits were observed due to all orthoses in: three-dimensional head/T1 RoMs, all sagittal intervertebral RoMs, and lateral bending at C4/5 through C7/T1. Both CTOs significantly reduced C6/7 sagittal RoM as compared to both collars. Intervertebral RoMs with the orthoses could not be differentiated from physiologic limits at the upper cervical spine in lateral bending and throughout the entire cervical spine in axial rotation, with the exception of C1/2.

CONCLUSIONS

Our results indicate that cervical orthoses effectively immobilized the entire cervical spine in flexion/extension and the lower cervical spine in lateral bending. The CTOs improved immobilization of the lower cervical spine in flexion/extension as compared to the collars. The orthoses were least effective at restricting lateral bending of the upper spinal levels and axial rotation of all spinal levels, except C1/2. Understanding immobilization provided by orthoses will assist clinicians in selecting the most appropriate brace based upon patient-specific immobilization requirements.

Spinal orthoses

External orthoses are used in the management of a variety of spinal disorders. Many types of brace are available to support the cervical, thoracic, and lumbar spine as well as junctional regions, which have special mechanical considerations. Many prefabricated and custom-made devices are available, made by a variety of manufacturers in this unregulated area of medical practice. Despite the widespread use of spinal orthoses, evidence of their efficacy in managing many spinal conditions is lacking. The most compelling indication for their use is in the management of traumatic spine injury. However, studies evaluating the efficacy of spinal orthoses have several shortcomings; many have evaluated orthoses that are no longer used. Recent data provide general guidelines to help the clinician choose the appropriate device.

Assessing range of motion to evaluate the adverse effects of ill-fitting cervical orthoses

BACKGROUND CONTEXT

Although previous studies have primarily focused on testing the effectiveness of cervical orthoses under properly fit conditions, this study focuses on analyzing the effects of an ill-fitted cervical orthosis (Miami J). This may have significance to health-care providers in understanding the effects of an improperly fitted neck brace.

PURPOSE

The aims of this study were threefold: first, to apply virtual reality (VR) feedback control to repeatedly measure orthoses effectiveness in the primary motions; second, to use this control methodology to test the orthoses ability to restrict flexion/extension (FE) as a function of axial rotation (AR); third, to test the effects of an ill-fitting Miami J on cervical motion.

STUDY DESIGN/SETTING

This study combines six degrees of freedom electromagnetic trackers and VR feedback to analyze the effectiveness of common cervical orthoses under less than optimal conditions.

PATIENT SAMPLE

Twelve healthy male subjects aged 21 to 35 (mean 29.44 years, SD 6.598) years with no previous spinal cord injuries or current neck pain participated in the study.

OUTCOME MEASURES

Cervical range of motion (CRoM) measurements were used to determine the amount of motion restriction for each of the fitted (too small, correct size, and too big) Miami J orthoses.

METHODS

One Nest of Birds (NOB) electromagnetic sensor (Ascension Technology) was placed on the head and another on the upper back to measure motion of the head relative to the torso. The VR goggles (i-O Display Systems) were worn so that real-time feedback was available to the subject for motion control. The subject executed the primary motions of FE, AR, and lateral bending (LB) in separate sets of five trials each. Next, in combined motion, the subject axially rotated to a set point and then FE to his maximums. This entire set of motions was repeated for each (soft collar, Miami J, Miami J with chest extension, Sternal Occipital Mandibular Immobilizer (AliMed, Inc.), (SOMI and Halo) as well as the Miami J (one size too small and one size too big); the fitting of each brace was done by a board certified orthotist. A repeated measures analysis of variance was used to determine differences between the tested states (*p=.05).

RESULTS

For the validation test, the primary motions recorded for subjects wearing each cervical brace, which demonstrated that the various orthoses all restricted CRoM. The soft collar restricted less motion than the other devices, whereas the Halo restricted the most motion throughout. For the ill-fitting cervical collar comparison, motion in the correct size collar was normalized to 1.0, and the correct size allowed less motion than either the too big or too small braces. In FE, the too big brace tended to allow more motion than the too small, but only the too big brace in extension was significantly different from the correct size. In AR, the too small brace seemed to allow more motion than the too big. Both the too big and too small braces were significantly different than the correct size in both left and right AR. In LB, the too big brace and too small brace were very similar in the amount of motion they were able to restrict. Both braces were significantly different than the correct size in right LB, whereas only the too small brace was significantly different from the correct size in left LB. In the combined motion data, both the too big and too small braces allowed more motion than the correct size. The too small brace seemed to allow more FE at all degrees of AR except for extreme right AR.

CONCLUSIONS

To our knowledge, the effects of improperly fitted cervical orthoses on CRoM are still unknown. Using the NOB electromagnetic tracking system combined with VR feedback, we were able to consider the motion restriction of ill-fitting Miami J orthoses for both primary and combined motions. For both motion types, increased motion was possible when the subject was improperly fitted with the Miami J. If not considered, these excessive motions could potentially have detrimental effects on patient satisfaction, clinical outcomes, or even lead to increased secondary injury.

Anterior cervical discectomy and fusion with a locked plate and wedged graft effectively stabilizes flexion-distraction stage-3 injury in the lower cervical spine: a biomechanical study

STUDY DESIGN

An in vitro three-dimensional (3D) flexibility test of human C3-C7 cervical spine specimens.

OBJECTIVE

To test the hypothesis that anterior cervical fusion with a wedged graft and a locked plate can effectively stabilize the cervical spine after complete anterior and posterior segmental ligamentous release.

SUMMARY OF BACKGROUND DATA

Distraction-flexion Stage 3 injuries of the lower cervical spine (bilateral facet dislocations) are usually reduced under awake cranial traction. When the magnetic resonance imaging reveals a traumatic disc prolapse, anterior cervical discectomy and fusion (ACDF) is usually recommended. Most authors advise combining ACDF with posterior instrumentation to address the insufficiency of the posterior elements. However, there is clinical evidence that ACDF with a locked plate alone suffices for the treatment of these injuries, especially in young patients. Still, there are no biomechanical studies on the effect of a locked plate on the complete anterior and posterior ligamentous-deficient young cervical spine under physiologic preload.

METHODS

Eight fresh frozen human lower cervical spines (C3-C7) from young donors (age, 44.5 years; range, 21-63 years) were used. A 3D flexibility test was conducted using a moment of 0.8 Nm without preload. Flexion-extension was additionally tested using a moment of 1.5 Nm under 0 and 150 N follower preload. Spines were tested first intact, then after complete C5-C6 discectomy with posterior longitudinal ligament resection and ACDF with a wedged bone graft and a rigid locked plate, and finally after complete release of the supraspinous, interspinous, and intertransverse ligaments; the facet capsules; and ligamentum flavum. RESULTS.: When tested under 0.8 Nm moment without preload, complete posterior and anterior ligamentous release did not significantly increase the ROM of the ACDF construct in flexion-extension (P > 0.025), lateral bending (P > 0.025), and axial rotation (P > 0.025). When tested under 1.5 Nm moment with or without a compressive preload, the complete posterior and anterior ligamentous release did not significantly affect the ROM of the ACDF construct (P > 0.01). The application of preload significantly reduced the motion at the C5-C6 ACDF construct with ligamentous disruption in comparison with the motion in the absence of a preload (P < 0.01).

CONCLUSION

Anterior cervical fusion with a wedged graft and a rigid constrained (locked) plate can effectively stabilize the nonosteoporotic cervical spine after complete posterior element injury when excessive ROM is prevented (for example, by the use of postoperative external immobilization). Even when the construct is subjected to higher moments, adequate stability can be achieved when physiologic preload is present. Osteoporosis and lack of sufficient preload due to poor neuromuscular control may affect long-term screw stability, and additional external immobilization may be needed until fusion matures.

Use of cervical collar after single-level anterior cervical fusion with plate: is it necessary?

STUDY DESIGN

Randomized clinical trial.

OBJECTIVE

This study is evaluates whether the use of a cervical collar after single-level anterior cervical fusion with plating increases the fusion rate and improved clinical outcomes.

SUMMARY OF BACKGROUND DATA

Plates limit motion between the graft and the vertebra in anterior cervical fusion. Still, the use of cervical collars after instrumented anterior cervical fusion is widely practiced.

METHODS

Patients enrolled in an FDA-regulated, multicenter trial in 32 centers treated with single-level decompression and arthrodesis using allograft and an anterior cervical plate were included in the analysis. Patients were divided into Braced and Nonbraced groups regardless of type of brace. SF-36, Neck Disability Index (NDI), Numerical Rating Scales (0-100) for neck and arm pain were determined before surgery, 1.5, 3, 6, 12, and 24 months after surgery. Fusion was assessed by independent radiologists at 6, 12, and 24 months after surgery using upright AP, lateral, and flexion-extension views. Fusion success was defined as the presence of bridging trabecular bone, angulation of less than or equal 4 degrees on flexion-extension radiographs; and absence of radiolucencies.

RESULTS

Two hundred fifty-seven patients were included in the analysis, 149 were braced and 108 were not. Demographic characteristics and baseline outcome measures of both groups were similar. There was also no statistically significant difference in any of the clinical measures at baseline except for SF-36 Physical Component Summary score. The SF-36 Physical Component Summary, NDI, neck, and arm pain scores were similar in both groups at all time intervals and showed statistically significant improvement when compared with preoperative scores. There was no difference in the proportion of patients working at any time point between the Braced and Nonbraced group. Independent radiologists reported higher rates of fusion in the Nonbraced group over all time intervals, none of which were statistically significant.

CONCLUSION

Our results show that the use of a cervical brace does not improve the fusion rate or the clinical outcomes of patients undergoing single-level anterior cervical fusion with plating.

Reduction in head and intervertebral motion provided by 7 contemporary cervical orthoses in 45 individuals

STUDY DESIGN

Biomechanical evaluation of cervical orthoses.

OBJECTIVE

To provide data to help clinicians select an orthosis for immobilization of the adult cervical spine.

SUMMARY OF BACKGROUND DATA

There are limited data on the effectiveness of cervical orthoses at restricting intervertebral motion, and many of the commonly used, contemporary braces have not been evaluated. Additionally, no data exist comparing the effectiveness of braces in the supine versus the upright position. New technology is available to measure intervertebral motion with greater accuracy.

METHODS

Overall range of motion of the head in 3 planes as well as intervertebral motion in the sagittal plane were measured in 45 healthy adult volunteers while wearing 7 cervical orthoses. Subject-reported comfort of each brace was also recorded.

RESULTS

All braces significantly reduced intervertebral motion. Effectiveness and comfort varied between braces. In general, orthoses could be grouped as cervical braces or cervicothoracic braces. The latter was consistently better at limiting motion, with some differences within these groups as well.

CONCLUSION

These data will help to guide the clinician in selecting the appropriate cervical orthosis for their adult patient based on comfort, morphologic considerations, and degree of immobilization required.

Restoring geometric and loading alignment of the thoracic spine with a vertebral compression fracture: effects of balloon (bone tamp) inflation and spinal extension

BACKGROUND CONTEXT

In patients with osteoporosis, changes in spinal alignment after a vertebral compression fracture (VCF) are believed to increase the risk of fracture of the adjacent vertebrae. The alterations in spinal biomechanics as a result of osteoporotic VCF and the effects of deformity correction on the loads in the adjacent vertebral bodies are not fully understood.

PURPOSE

To measure 1) the effect of thoracic VCFs on kyphosis (geometric alignment) and the shift of the physiologic compressive load path (loading alignment), 2) the effect of fracture reduction by balloon (bone tamp) inflation in restoring normal geometric and loading alignment and 3) the effect of spinal extension alone on fracture reduction and restoration of normal geometric and loading alignment.

STUDY DESIGN/SETTING

A biomechanical study using six fresh human thoracic specimens, each consisting of three adjacent vertebrae with all soft tissues and bony structures intact.

METHODS

In order to reliably create fracture, cancellous bone in the middle vertebral body was disrupted by inflation of bone tamps. After removal of the bone tamps, the specimen was compressed using bilateral loading cables until a fracture was observed with anterior vertebral body height loss of >/=25%. Fracture reduction was performed under a compressive preload of 250 N first under the application of extension moments, and then using inflatable bone tamps. The vertebral body heights, kyphotic deformity of the fractured vertebra and adjacent segments and location of compressive load (cable) path in the fractured and adjacent vertebral bodies were measured on video-fluoroscopic images.

RESULTS

The VCF caused anterior wall height loss of 37+/-15%, middle-height loss of 34+/-16%, segmental kyphosis increase of 14+/-7.0 degrees and vertebral kyphosis increase of 13+/-5.5 degrees (p<.05). The compressive load path shifted anteriorly by about 20% of anteroposterior end plate width in the fractured and adjacent vertebrae (p=.008). Bone tamp inflation restored the anterior wall height to 91+/-8.9%, middle-height to 91+/-14% and segmental kyphosis to within 5.6+/-5.9 degrees of prefracture values. The compressive load path returned posteriorly relative to the postfracture location in all three vertebrae (p=.004): the load path remained anterior to the prefracture location by about 9% to 11% of the anteroposterior end plate width. With application of extension moment (6.3+/-2.2 Nm) until segmental kyphosis and compressive load path were fully restored, anterior vertebral body heights were improved to 85+/-8.6% of prefracture values. However, the middle vertebral body height was not restored and vertebral kyphotic deformity remained significantly larger than the prefracture values (p<.05).

CONCLUSIONS

The anterior shift of the compressive load path in vertebral bodies adjacent to VCF can induce additional flexion moments on these vertebrae. This eccentric loading may contribute to the increased risk of new fractures in osteoporotic vertebrae adjacent to an uncorrected VCF deformity. Bone tamp inflation under a physiologic preload significantly reduced the VCF deformity (anterior and middle vertebral body heights, segmental and vertebral kyphosis) and returned the compressive load path posteriorly, approaching the prefracture alignment. Application of extension moments also was effective in restoring the prefracture geometric and loading alignment of adjacent segments, but the middle height of the fractured vertebra and vertebral kyphotic deformity were not restored with spinal extension alone.