Trabecular bone score as an assessment tool to identify the risk of osteoporosis in axial spondyloarthritis: a case-control study.

OBJECTIVES: To compare the trabecular bone score (TBS) between patients with axial spondyloarthritis (axSpA) and matched normal controls and identify risk factors associated with a low TBS. METHODS: TBS and BMD were assessed in the two groups (axSpA and control) using DXA. Osteoporosis risk factors and inflammatory markers were also assessed. Disease activity and radiographic progression in the sacroiliac joint and spine were evaluated in the axSpA group. Multivariate linear regression analysis was performed to identify risk factors associated with TBS. RESULTS: In the axSpA group, 248 subjects were enrolled; an equal number of age- and sex-matched subjects comprised the control group. The mean TBS was 1.43 (0.08) and 1.38 (0.12) in the control and axSpA groups, respectively (P < 0.001); BMD at the lumbar spine did not differ between the two groups. The TBS was negatively correlated with ESR and CRP levels in the axSpA group only (P < 0.001 and P = 0.007, respectively). Syndesmophytes in the axSpA group was associated with lower TBS (P < 0.001) but higher lumbar BMD (P = 0.021) vs controls. In the multivariate analyses, ESR, CRP and spinal radiographic progression were significantly associated with TBS. CONCLUSION: TBS assessments revealed poor bone quality in patients with axSpA compared with the matched controls. In axSpA, systemic inflammatory markers were negatively correlated with TBS and spinal radiographic progression and inflammatory markers were independently correlated with low TBS. TBS may, therefore, be a useful clinical tool to identify the risk of osteoporosis in patients with axSpA.

Transpedicular screw fixation for type II Hangman's fracture: a motion preserving procedure.

Opinions have varied regarding the optimal treatment of an unstable Hangman's fracture. C2 pedicle screw instrumentation is a biomechanically strong fixation which although done through a simple posterior approach, is a technically demanding procedure. This prospective, non-randomized multicentre study included 15 consecutive patients with displaced type II traumatic spondylolisthesis of the axis. There were nine males and six females with a mean age of 37 years at surgery. The cause of injury was a road traffic accident in 11 patients and a fall from height in 4 patients. All patients had a single stage reduction and direct transpedicular screw fixation through the C2 pedicles. During follow-up, clinical evaluation and plain X-rays were performed at each visit; at 6-month follow-up, additional dynamic lateral flexion/extension views and a CT scan were performed. The average follow-up period was 32 months (range 25-56 months). At final follow-up, all patients were asymptomatic and regained a good functional outcome with no limitation of range of motion; all the patients showed solid union with no implant failure. There were no neurological complications. At 6-month follow-up, CT evaluation showed fusion in all patients and an adequate position of 28 screws. Two pedicle screws (6.6%) showed minimal (defined as <2 mm) intrusion; one into the spinal canal and the other into the vertebral foreamen. Transpedicular screw fixation through the C2 pedicles is a safe and effective method in treating type II traumatic spondylolisthesis of the axis resulting in good clinical and radiological outcomes. Adequate reduction was achieved and motion segments were preserved with its use.

Os Odontoideum in Children.

Os odontoideum is a rare entity of the second cervical vertebra, characterized by a circumferentially corticated ossicle separated from the body of C2. The ossicle is a distinct entity from an odontoid fracture or a persistent ossiculum terminale. The diagnosis may be made incidentally on imaging obtained for the workup of neck pain or neurologic signs and symptoms. Diagnosis usually can be made with plain radiographs. MRI and CT can assess spinal cord integrity and C1-C2 instability. The etiology of os odontoideum is a topic of debate, with investigative studies supporting both congenital and traumatic origins. A wide clinical range of symptoms exists. Symptoms may present as nondescript pain or include occipital-cervical pain, myelopathy, or vertebrobasilar ischemia. Asymptomatic cases without evidence of radiologic instability are typically managed with periodic observation and serial imaging. The presence of atlantoaxial instability or neurological dysfunction necessitates surgical intervention with instrumentation and fusion for stability.

C2-fractures: part II. A morphometrical analysis of computerized atlantoaxial motion, anatomical alignment and related clinical outcomes.

Knowledge on the outcome of C2-fractures is founded on heterogenous samples with cross-sectional outcome assessment focusing on union rates, complications and technical concerns related to surgical treatment. Reproducible clinical and functional outcome assessments are scant. Validated generic and disease specific outcome measures were rarely applied. Therefore, the aim of the current study is to investigate the radiographic, functional and clinical outcome of a patient sample with C2-fractures. Out of a consecutive series of 121 patients with C2 fractures, 44 met strict inclusion criteria and 35 patients with C2-fractures treated either nonsurgically or surgically with motion-preserving techniques were surveyed. Outcome analysis included validated measures (SF-36, NPDI, CSOQ), and a functional CT-scanning protocol for the evaluation of C1-2 rotation and alignment. Mean follow-up was 64 months and mean age of patients was 52 years. Classification of C2-fractures at injury was performed using a detailed morphological description: 24 patients had odontoid fractures type II or III, 18 patients had fracture patterns involving the vertebral body and 11 included a dislocated or a burst lateral mass fracture. Thirty-one percent of patients were treated with a halo, 34% with a Philadelphia collar and 34% had anterior odontoid screw fixation. At follow-up mean atlantoaxial rotation in left and right head position was 20.2 degrees and 20.6 degrees, respectively. According to the classification system of posttreatment C2-alignment established by our group in part I of the C2-fracture study project, mean malunion score was 2.8 points. In 49% of patients the fractures healed in anatomical shape or with mild malalignment. In 51% fractures healed with moderate or severe malalignment. Self-rated outcome was excellent or good in 65% of patients and moderate or poor in 35%. The raw data of varying nuances allow for comparison in future benchmark studies and metaanalysis. Detailed investigation of C2-fracture morphology, posttreatment C2-alignment and atlantoaxial rotation allowed a unique outcome analysis that focused on the identification of risk factors for poor outcome and the interdependencies of outcome variables that should be addressed in studies on C2-fractures. We recognized that reduced rotation of C1-2 per se was not a concern for the patients. However, patients with worse clinical outcomes had reduced total neck rotation and rotation C1-2. In turn, C2-fractures, especially fractures affecting the lateral mass that healed with atlantoaxial deformity and malunion, had higher incidence of atlantoaxial degeneration and osteoarthritis. Patients with increased severity of C2-malunion and new onset atlantoaxial arthritis had worse clinical outcomes and significantly reduced rotation C1-2. The current study offers detailed insight into the radiographical, functional and clinical outcome of C2-fractures. It significantly adds to the understanding of C2-fractures.

Sleep apnea in rheumatoid arthritis patients with occipitocervical lesions: the prevalence and associated radiographic features.

Since sleep apnea is a risk factor for high mortality of rheumatoid arthritis (RA) patients, this study examined the prevalence in RA patients with occipitocervical lesions, and the associated radiographic features. Twenty-nine RA patients requiring surgery for progressive myelopathy due to occipitocervical lesions (3 males, 26 females, average age 65 years) were preoperatively evaluated. Twenty-three (79%) had sleep apnea defined as apnea-hypopnea index >5 events per hour measured by a portable monitoring device, and all of them were classified as the obstructive type. Among gender, age, bone mass index (BMI), and radiographic parameters related to occipitocervical lesions: atlantodental interval (ADI), cervical angles (O/C1, C1/2, and C2/6), and cervical lengths (O-C2 and O-C6), the ADI and cervical lengths were shown to be significantly associated with the presence of sleep apnea by parametric statistical analysis. Since there were positive correlations between the ADI and cervical lengths by Pearson's test, we performed a multivariate logistic regression analysis after adjustment for confounding factors and found that small ADI was the principle parameter associated with sleep apnea. We therefore conclude that the prevalence of sleep apnea is higher than that in a general RA population that was reported previously, and believe that occipitocervical lesions are an independent risk factor for this condition. Small ADI and short neck, secondary to the vertical translocation by RA, may cause obstructive sleep apnea, probably through mechanical or neurological collapse of the upper airway.

Biomechanical assessment of bilateral C1 laminar hook and C1-2 transarticular screws and bone graft for atlantoaxial instability.

UNLABELLED: STUDYDESIGN: In vitro biomechanical test was conducted to compare the stability of 5 different atlantoaxial posterior fusion techniques. OBJECTIVE: To evaluate the biomechanical stability of an atlas laminar hook combined with transarticular (TA) screws relative to 4 different conventional fusion techniques. SUMMARY OF BACKGROUND DATA: The atlantoaxial instability caused by fractures, rheumatoid arthritis, congenital deformity, or traumatic lesions of the transverse ligament often result in acute or chronic spinal cord compression, a possible threat to a patient's life. Posterior atlantoaxial fixations are used to reconstruct the stability of atlantoaxial articulation. Conventional posterior atlantoaxial fixations are associated with high rates of pseudoarthrosis and carry the potential risk of neurologic complication. TA screw fixation can provide an excellent biomechanical stability. As a modified 3-point fixation technique, the bilateral C1-2 TA screws have been combined with C1 laminar hook and bone grafts. This modified technique had carried good clinical outcomes. METHODS: Eight human specimens (C0-C4) were loaded nondestructively with pure moments and the range of motion at the level of C1-C2 was measured. Eight specimens were implanted with each of the following techniques, respectively: Gallie fixation, C1-2 TA screw fixation combined with Gallie fixation, C1-2 TA screw fixation, C1 laminar hook combined with C1-2 TA screw fixation plus bone grafts, and the C1 lateral mass screws in the atlas combined with C2 isthmic screws in axis. RESULTS: Although the C1-2 TA screws best restricted lateral bending and axial rotation, the modified 3-point fixation technique additionally restricted flexion-extension and provided the excellent stability. Differences in axial rotation and lateral bending (with + or - 1.5 Nm load) were observed when the 3-point fixation techniques (TA + Gallie and TA + hook) were compared with atlas lateral mass screws in the atlas combined with isthmic screws in axis. CONCLUSIONS: The modified C1 laminar hook combined with C1-2 TA screws and bone graft fixation provided the best biomechanical stability. The C1 lateral mass screws in the atlas combined with isthmic screws in axis fixation is a sound alternative when the C1-2 TA screw fixation is not feasible.

The C0-C2 axial rotation test: normal values, intra- and inter-rater reliability and correlation with the flexion rotation test in normal subjects.

OBJECTIVES: Impairment in upper cervical spine mobility is associated with cervicogenic headache severity and disability. Measures of such mobility include the flexion-rotation test (FRT), which requires full cervical flexion and may be influenced by lower cervical spine dysfunction. The C0-C2 axial rotation test also evaluates upper cervical mobility but normal values and reliability have not been reported. Our objective is to determine normal values, and intra-rater and inter-rater reliability of the C0-C2 axial rotation test. METHODS: Two therapists independently evaluated the FRT and C0-C2 axial rotation test with an iPhone compass application on 32 asymptomatic subjects with mean age 40.53 (SD 11.64) years on two occasions. Measurement procedures were standardized; and order of testing randomized. RESULTS: For the FRT and C0-C2 axial rotation test reliability was high (ICC > 0.88). For rater one, Mean range to the left during the FRT and C0-C2 axial rotation test was 45.0° (6.04) and 14.43° (2.94), respectively, while range to the right was 44.6° (6.57) and 15.44° (2.68). For the FRT and C0-C2 axial rotation test the standard error of measurement was at most 2°, while the minimum detectable change was at most 4°. A strong positive correlation exists between the FRT and C0-C2 axial rotation test (r = 0.84, P < 0.01). DISCUSSION: The range recorded during the C0-C2 axial rotation test and FRT have high levels of reliability when evaluated using an iPhone. The strong correlation between the FRT and C0-C2 axial rotation test indicate that both may be measuring similar constructs, but each test needs to be referenced to normal values.

Spontaneous rotatory atlantoaxial dislocation without neurological compromise in a child with Down syndrome: a case report.

Spontaneous atlantoaxial dislocation is a rare recognised complication of Down syndrome. In the majority of cases, dislocation takes place in an anteroposterior direction and is often associated with abnormalities of odontoid development or ossification. Rotatory atlantoaxial dislocation is extremely rare in Down syndrome and this is to our knowledge the first reported case in which modern imaging methods have been described; surface shaded reformats derived from a multislice CT scan were of fundamental importance in making the diagnosis.

'Congenital anomalies of craniovertebral junction presenting after 50 years of age': An oxymoron or An unusual variation?

OBJECTIVES: Manifestation of congenital anomalies of cranio-vertebral junction (CVJ) in the later half of life is unusual and intriguing. Coexisting cervical spondylotic changes with multilevel compression, poorer bone quality as well as less smooth post-surgical recuperation make management of elderly Congenital Atlantoaxial Dislocation/ Basilar Invagination (CAAD/BI) challenging. The clinico-radiological presentation, pathogenesis and outcome are analysed here. PATIENTS AND METHODS: Clinico-radiological data of 20 patients of CAAD/BI (with markers of congenital anomalies) presenting after 50 years of age, the challenges faced and outcomes after C1-C2 fusion have been analysed. RESULTS: Three distinct groups were identified. Seven patients with Os-odontoideum had reducible AAD (Type I). Seven patients had assimilated C1, C2-3 fusion and deformed C1-2 joints with irreducible AAD/BI (Type II). In type III, 4 patients had similar segmentation defects but with compression at both cervico-medullary junction and subaxial spine, although clinical localisation pointed to the CVJ. Spastic quadriparesis was the commonest presentation. All underwent C1-2 fusion alone. There was significant improvement in 18, including those with compression at additional level. Bony fusion was documented in all patients followed up beyond one year. CONCLUSION: Congenital CVJ anomalies may present in later half of life, though attempts at reasoning remain speculative. These patients improve after multiplanar realignment and C1-2 fusion. Careful clinico-radiological evaluation is required in those with additional subaxial compression. Bone quality in elderly is not a deterrent for instrumentation. Fusion eventually occurs in most.

Low bone mineral density predicts the formation of new syndesmophytes in patients with axial spondyloarthritis.

BACKGROUND: This study aimed to investigate whether the presence of low bone mineral density (BMD) in patients with axial spondyloarthritis (axSpA) predicts formation of new syndesmophytes over 2 years. METHODS: One hundred and nineteen patients fulfilling the imaging arm of the Assessment of SpondyloArthritis International Society axSpA criteria were enrolled. All patients were under 50 years of age. The modified Stoke Ankylosing Spondylitis Spinal Score (mSASSS) was assessed by two trained readers blinded to the patients' data. BMD (lumbar spine, femoral neck or total hip) at baseline was assessed using dual-energy absorptiometry. Low BMD was defined as Z score ≤ - 2.0. Spinal radiographic progression was defined as worsening of the mSASSS by ≥ 2 points over 2 years. Logistic regression analyses were performed to identify predictors associated with development of new syndesmophytes and spinal radiographic progression. RESULTS: At baseline, 19 (16%) patients had low BMD. New syndesmophytes had developed in 22 (21%) patients at 2-year follow-up. New syndesmophyte formation after 2 years occurred more in patients with low BMD than in those with normal BMD (p = 0.047). In the multivariable analysis, current smoking, existing syndesmophytes and low BMD at baseline were associated with spinal radiographic progression (OR (95% CI) 3.0 (1.1, 7.7), 4.6 (1.8, 11.8) and 3.6 (1.2, 11.2), respectively). The presence of syndesmophytes at baseline and low BMD were predictors of new syndesmophytes over the following 2 years (OR (95% CI) 5.5 (2.0, 15.2) and 3.6 (1.1, 11.8), respectively). CONCLUSIONS: Low BMD and existing syndesmophytes at baseline were independently associated with the development of new syndesmophytes in young axSpA patients.

Using peripheral stimulation to reduce the pain of C2-mediated occipital headaches: a preliminary report.

BACKGROUND: Peripheral nerve stimulation (PNS) is an accepted treatment for neuropathic pain. Recent studies have focused on its potential for relieving headache pain. OBJECTIVES: To investigate the effectiveness of PNS in reducing occipital headache pain. DESIGN: A prospective, 12-week pilot study involving 11 patients evaluated before and after implantation of PNS systems to treat C2-mediated occipital headaches. METHODS: Prior to and at 4 and 12 weeks after implantation, patients completed the Short-Form McGill Pain Questionnaire (SF-MPQ), Visual Analog Scale (VAS), and Present Pain Index (PPI). Patients also answered questionnaires and kept diaries to record stimulator use, medication consumption, and numbers of headaches. RESULTS: A comparison of pre- and post-implantation evaluations showed statistically significant declines in scores on the SF-MPQ (64%; p = 0.0013), VAS (67%; p < 0.0001), and PPI (68%; p = 0.0009). Most patients (91% and 64% respectively) reported reductions in medication use and numbers of headaches. Patients also reported a reduction in headache symptoms and the impact of headaches on activities. Two adverse events were encountered, one due to a loose connection and, the other caused by lead migration. CONCLUSIONS: PNS reduced headache pain, headache frequency and medication use.

Intraoperative dynamic angiography to detect resolution of Bow Hunter's syndrome: Technical case report.

BACKGROUND: Bow Hunter's syndrome is a rare form of vertebrobasilar insufficiency that may be successfully treated by surgical intervention. Use of intraoperative dynamic transcranial Doppler ultrasound for surgical treatment of vertebrobasilar insufficiency has been described in literature. However, this technique was inconsistent and unreliable in some patients. We present a case of a patient with Bow Hunter's syndrome treated surgically and emphasize the valuable addition of intraoperative dynamic angiography to determine resolution of vertebral artery compromise. CASE DESCRIPTION: The patient was a 58-year-old man with complaints of dizziness, vertigo, and near-syncopal episodes that occurred when he rotated his head to the left. Imaging revealed compromise of the dominant left vertebral artery with leftward head rotation. An anterior cervical approach with decompression of the left subaxial vertebral artery was performed. Significant osteophyte formation was observed. Removal of bone and decompression of the vertebral artery was performed. Intraoperative dynamic angiography confirmed resolution of vertebral artery compression and minimized the amount of decompression. No further intervention was required. CONCLUSION: Intraoperative dynamic angiography is a definitive test to determine hemodynamic resolution of Bow Hunter's syndrome. It offers real-time feedback of vertebral artery decompression, potentially minimizes the amount of decompression, and can be performed safely.

Palpatory diagnosis of plagiocephaly.

INTRODUCTION: The term plagiocephaly, from the Greek plagios (oblique) and kephalê (head), means distortion of the head, and refers clinically to cranial asymmetry. Cranial Osteopathy, since it was first proposed, has focussed upon the diagnosis and treatment of birth trauma and cranial asymmetries, and consequently specific therapy for plagiocephalic deformities has been described. Osteopathic manipulation also has been proposed as a treatment for torticollis, a condition associated with plagiocephaly. For these reasons, we decided to look at the mechanics of the occipital bone and the adjacent atlas and bones of the cranial base, in relation to functional plagiocephaly. METHODS: The records of 649 children seen in an osteopathic practice in Lyon, France, were reviewed retrospectively, in compliance with the legal requirements of the Commission Nationale de l'Informatique et des Libertés (CRIL) and the Helsinki accord, for gender, age at presentation, birth history, obstetrical data (breech presentation, vacuum extraction, forceps delivery or Caesarean section), presenting complaint, side of posterior plagiocephaly, side of frontal plagiocephaly, torticollis, motion pattern of the occipital bone upon the atlas, and motion pattern of the spheno-occipital synchondrosis. RESULTS: We found significant correlations between plagiocephaly (right/left) and primipara (P=0.024), use of forceps (P=0.055) and extractor suction (P=0.055). Correlations were also found between flattening of the occiput (right/left) and lateral strain of the spheno-occipital synchondrosis (P=0.002) and between plagiocephaly (right/left) and occipito-atlantal motion (P=0.000). CONCLUSION: We found a significant correlation between the lateral strain pattern of the spheno-occipital synchondrosis and plagiocephaly and between rotational dysfunction of the occiput upon the atlas and the side of posterior plagiocephaly. We suggest that thorough neonatal osteopathic examination can identify individuals predisposed to develop posterior plagiocephaly.

Intended and non-intended kinematic effects of atlanto-axial rotational high-velocity, low-amplitude techniques.

INTRODUCTION: The study of neck kinematics during high-velocity, low-amplitude manipulations of the atlanto-axial segment is essential to understanding cervical motion mechanisms and their impact and possible risk for soft-tissue injuries during treatment of spine disorders. METHODS: Twenty fresh-frozen specimens were tested during manual application of an axial rotation technique. FINDINGS: The kinematics indicate the thrust induced motion components of approximately 1° at the treated segment around all three axes of the local embedded reference frame. Moreover, an equal amount of axial rotation motion took place at the adjacent atlanto-occipital joint. INTERPRETATION: Overall atlanto-axial motion remained below the level of slow regional mobilization of the cervical spine. These findings can be correlated to literature data concerning the limited increase in vertebral artery strain during high-velocity, low-amplitude manipulation.

Magnetic Resonance Imaging Analysis of Deep Cervical Flexors in Patients with Ossification of the Posterior Longitudinal Ligament and Clinical Implication.

OBJECTIVE: The purpose of this study was to analyze the cross-sectional area (CSA) of deep cervical flexors as measured by magnetic resonance imaging in ossification of the posterior longitudinal ligament (OPLL) patients with neck pain and, by implication, how this may relate to recruitment of the deep cervical flexors and sternocleidomastoid. DESIGN: A retrospective case-control study was conducted. All 72 subjects were imaged using plain radiography, computed tomography, and magnetic resonance imaging. RESULTS: There was a more limited cervical range of motion in the OPLL group than that in the control group. Cervical lordosis, T1 slope, and thoracic inlet angle values were significantly lower in the OPLL group than in the control group. Bilateral CSAs of the longus colli muscle and longus capitis muscle of the OPLL group were smaller than those of the control group. In addition, bilateral CSAs of the sternocleidomastoid of the OPLL subjects were greater than those of healthy subjects. CONCLUSIONS: The authors found that the OPLL patients with chronic neck pain had lesser lordotic cervical alignment, smaller deep cervical flexor CSAs, and larger sternocleidomastoid CSAs than the control group did. The authors' theory is that the sternocleidomastoids in these OPLL patients have compensatorily hypertrophied in response to presumably atrophied deep cervical flexors.

Validation and use of a finite element model of C-2 for determination of stress and fracture patterns of anterior odontoid loads.

OBJECT: The finite element (FE) method is a powerful tool for the analysis of stress patterns of anatomical structures. In this study a highly refined FE model of C-2 was created and validated. The model was then used to characterize stress patterns, predicted fracture patterns, and transitions between Type II and Type III odontoid fractures. METHODS: An anatomically accurate three-dimensional model of C-2 was created from computerized tomography data obtained from the Visible Human Project. The C-2 model was broken down into an FE mesh consisting of 32,815 elements and 40,969 nodes. For validation, the FE model was constrained and loaded to simulate that used in previous biomechanical studies. The validated model was then loaded in an iterative fashion, varying the orientation of the load within the validated range. A matrix of stress plots was created for comparative analysis. Results of the validation testing closely correlated with those obtained in previous biomechanical testing. Pure extension loading produced a Type III stress pattern with maximum stress of 134 MPa. Loading at 45 degrees produced a Type II stress distribution with a maximum stress of 123 MPa. These stresses are within 3% and 11%, respectively, of the reported yield stress of cortical bone (138 MPa). In the second portion of the study, systematic variation in the orientation of the load vector revealed that higher stresses were associated with increased lateral angulation and increasing upward inclination of the load vectors. A transition from a Type III to Type II pattern occurred with lateral orientations greater than 15 degrees and with compressive loads of 45 degrees. CONCLUSIONS: The validated C-2 FE model described in this study both qualitatively and quantitatively was able to simulate the behavior of the C-2 vertebra in biomechanical testing. In this study the authors demonstrate the utility of the FE method when used in conjunction with traditional biomechanical testing.

Chronic atlanto-axial instability in Down syndrome.

We studied the radiographs of thirty-two patients with Down syndrome for evidence of atlanto-axial instability. One of the patients had instability in 1970 and seven had it in 1983. The interval between the atlas and the odontoid process in the patients who demonstrated motion at that interval radiographically averaged 2.78 millimeters in 1970 and 6.93 millimeters in 1983 (p less than 0.005). Four patients whose radiographs showed atlanto-axial motion in 1970 lost that motion by 1983, and in seven patients who did not show atlanto-axial instability in 1970 it developed by 1983. Atlanto-axial instability was more likely to develop in boys who were more than ten years old. Accessory upper-cervical ossicles became evident in three patients, none of whom had atlanto-axial motion. However, one of these three patients had an abnormally wide atlanto-axial interval.

Lumbosacral spinal fusion. A biomechanical study.

The effects of spinal fusion on fused segment and the adjacent, unfused segments play a significant role in the clinical effectiveness of spinal fusion for low-back pain with or without sciatica. Much of the information on this important subject is derived from clinical impressions. The purpose of this biomechanical study is to investigate the altered kinematics and biomechanics of the three different types of spinal fusion (posterior, bilateral-lateral, and anterior) on the adjacent, unfused segment as well as within the fused segment and to investigate their clinical implications. Sixteen fresh human cadaver lumbosacral spines were tested under a simulated physiologic loading condition. The test specimens included three motion segments, L3-4, L4-5, and L5-S1. To study the mechanics of the lumbar spine under combined compression and bending loads, a special apparatus was designed. These loads were applied by an MTS machine through two sets of pulley systems. The loads, as well as displacement data from both actuators, were recorded. A video camera system was utilized to record the kinematics of the spinal motion segment. The unfused specimen was tested first, and the fused specimen then was retested under the identical loading conditions. A total of 16 spine specimens were tested and evaluated--five posterior, four bilateral-lateral, and seven anterior fusions. All types of fusion resulted in increased bending and axial stiffnesses. Overall, anterior fusion provided the largest increase in stiffness, followed by bilateral-lateral fusion and posterior fusion.(ABSTRACT TRUNCATED AT 250 WORDS)

CT-functional diagnostics of the rotatory instability of upper cervical spine. 1. An experimental study on cadavers.

Twelve specimens of the upper cervical spine were functionally examined by using radiography, cineradiography and computerized tomographic (CT) scan. The range of rotation was measured from CT images after maximal rotations to both sides. The left alar ligament was then cut and the examination repeated. The alar and transverse ligaments could be differentiated on CT images in axial, sagittal, and coronal views. Rotation at occiput-atlas was 4.35 degrees to the right and 5.9 degrees to the left and at atlas-axis it was 31.4 degrees to the right and 33 degrees to the left. After one-sided lesion of the alar ligament, there was an overall increase of 10.8 degrees or 30% of original rotation to the opposite side, divided about equally between the occiput-atlas and the atlas-axis. It is concluded that a lesion (irreversible overstretching or rupture of alar ligaments) can result in rotatory hypermobility or instability of the upper cervical spine.

Shear fracture through the body of the axis vertebra.

STUDY DESIGN: Three cases of a previously undescribed body fracture of the axis vertebra are presented. OBJECTIVES: To describe the radiographic features of the fracture are described, and to point out the differences to other axis body fractures regarding the mechanism of injury, stability, and treatment. SUMMARY OF BACKGROUND DATA: Fractures involving the odontoid process usually are caused by indirect forces, and they are considered unstable injuries. Anderson and D'Alonzo Type III odontoid fractures usually are hyperflexion injuries. Superior articular process fractures with or without associated odontoid peg fractures are caused by lateral hyperflexion injuries. METHODS: Three cases of body fractures of the axis vertebra are described. These fractures occur in an oblique plane shearing off in one piece the odontoid process together with one of the superior articular processes. The fragment displaces anterocaudally, and the odontoid process tilts toward the affected side. RESULTS: All fractures were managed nonsurgically. The two displaced fractures did not reduce in traction, and they had united in the displaced position after the 12 weeks of halo treatment. One patient reported only minor problems, but showed radiologic evidence of facet joint arthritis at 20 months. The second patient was lost to follow-up after discontinuation of halo treatment at 12 weeks. The only undisplaced fracture was managed in a halo body jacket for 10 weeks. The patient was pain free and had regained a full range of movement at 7 months. CONCLUSIONS: The presumed mechanism of injury in the described fracture is one of asymmetrical axial compression. The fracture can be managed safely in a halo jacket.