Flexional distance index: A new prognostic indicator of neurological outcomes at 4 years after cervical laminoplasty for K-line (+) ossification of the posterior longitudinal ligament.

OBJECTIVE: We aimed to investigate whether K-line in the neck flexion (FK-line), flexion angle (FA), or flexion distance index (FDI) could predict the recovery rate of the Japanese Orthopedic Association score (RR-JOA) at 4 years after cervical laminoplasty (LP) for ossification of the posterior longitudinal ligament (OPLL). METHODS: A new index, i.e., the FDI, which is based on the degree of neck flexion and the OPLL size on a lateral radiograph. "Flexional distance" is the distance from C2 to C7 in neck flexion, and "distance to OPLL" is the maximal distance from the line of the flexional distance to OPLL. FDI was defined as follows: FDI = flexional distance/distance to OPLL. Twenty-three patients with K-line (+) OPLL were evaluated at 4 years after LP (follow-up rate, 92%). We investigated the relationships between preoperative radiological factors, including FK-line, FA, and FDI, and RR-JOA at 4 years postoperatively. RESULTS: Preoperative FK-line and FA were significantly related with the RR-JOA at 1 year postoperatively, but not at 4 years postoperatively. Preoperative FDI was significantly positively correlated with the RR-JOA at 1 year and 4 years postoperatively (P = 0.0132, r = 0.504 and P = 0.0183, r = 0.484, respectively). Preoperative FDI < 2.5 was associated with worsening of the RR-JOA at 4 years postoperatively, with a probability of 80% DISCUSSIONS: FDI could predict the RR-JOA at 4 years after LP for OPLL. Decompression with fusion may be recommended for patients with preoperative FDI < 2.5. LEVEL OF EVIDENCE: 4.

The impact of ossification spread on cervical spine function in patients with ossification of the posterior longitudinal ligament.

Ossification of the posterior longitudinal ligament (OPLL) is a progressive disease. The bridging of ossified lesions to the vertebral body gradually increases, thereby decreasing the mobility of the cervical spine; thus, cervical spine function may decrease over time. However, cervical spine function in patients with cervical OPLL has not been evaluated in large prospective studies. Therefore, we conducted a prospective multicenter study to clarify whether ossification spread can influence cervical spine function and quality of life (QOL) in patients with cervical OPLL. In total, 238 patients (162 men, 76 women; mean age, 63.9 years) were enrolled from 16 institutions. Each patient underwent whole spine computed tomography and was evaluated for cervical spine function and QOL using the Japanese Orthopaedic Association Cervical Myelopathy Evaluation Questionnaire (JOACMEQ). In the multivariate regression analysis, a higher neck VAS score and a larger number of bridge formations of OPLL in the whole spine were significant predictors of adverse outcomes related to cervical spine function. This is the first prospective multicenter study to reveal the impact of ossification spread on cervical spine function. These findings are important to understand the natural course of OPLL and can serve as controls when evaluating postoperative cervical spine function.

Low Back Pain Induced by Posterior Longitudinal Ligament Incision in Percutaneous Transforaminal Endoscopic Lumbar Discectomy.

OBJECTIVE: To illustrate the posterior longitudinal ligament is one of the tissue candidates who can contribute to low back pain (LBP). METHODS: This is a retrospective study. A series of 72 patients who underwent single-level percutaneous endoscopic lumbar discectomy performed for lumbar disc herniation with LBP from June 2014 to June 2016 were examined. There are 42 males and 30 females. The ages of patients were 40 to 57 years, and the mean age was 49.8 years. The symptomatic disc level was at L4-5 in 43 patients and L5 S1 in 29 patients. Thirty-two patients (19 patients in L4-5 disc level, 13 patients in L5 S1 disc level) had LBP (which was limited to the lower back and buttock area) before the operation. All of the operative approaches were performed under local anesthesia. A posterior body diagram (15 cm × 10 cm) was made for this study to record the pain distribution. The centered foci of low back pain were subjectively recorded before, during, and after the operation. The transforaminal endoscopic spine system technology was used in this study. Radiological examinations (X-ray, computed tomography, and magnetic resonance imaging) were performed prior to and after surgery. The Visual Analogue Score (VAS) and Oswestry Disability Index (ODI) scores were taken before and after the surgery to observe the degree of pain. The VSA and ODI score before and after operation were expressed as mean ± SD, and compared by t-test for statistical analysis. RESULTS: When inciting the posterior longitudinal ligament during the operation, all 72 patients had provoked low back pain. Forty-three patients with symptomatic discs at L4-5 had pain foci in the lower back and upper gluteal region under the L4 spinous process. Twenty-nine patients with symptomatic discs at L5 S1 had pain foci in the gluteal region under the S1 spinous process. The pain localizations of L4-5 and L5 S1 were different. After the surgery, the provoked low back pain disappeared, and had not returned in any of the patients at the 6-month follow-up. After the operation, one patient suffered from lower limb pain that he did not have before the operation, and the lower limb pain abated a few days later. Three patients had cerebrospinal fluid leakage and were treated with higher pressure applied on the incision and bed rest for 10 days. During the 6-months follow-up period, the mean VAS decreased from 5.97 ± 1.10 to 2.13 ± 0.78. The mean ODI score decreased from 23.14 ± 3.28 to 7.92 ± 1.85. CONCLUSIONS: The intervertebral posterior longitudinal ligament may be one of the tissues from which low back pain originates.

Association between ossification of the longitudinal ligament of the cervical spine and arteriosclerosis in the carotid artery.

Although several risk factors have been reported for cervical ossification of the longitudinal ligament (OPLL), most evaluations made in the past were based on plain X-ray, not on computed tomography (CT) scan. In this study, we aimed to clarify novel risk factors for cervical OPLL in asymptomatic subjects undergoing CT scan as their routine medical checkups. A total of 1789 Japanese asymptomatic subjects who underwent CT scan for the whole body as their routine medical checkups were retrospectively reviewed. The medical checkup also included laboratory examinations, bone mineral status, and ultrasound of the carotid artery. As a result, cervical OPLL was seen in 120 subjects (6.7%). As we compared the demographic and clinical data between subjects with and without OPLL, OPLL group showed older age, higher proportion of male sex, higher BMI, higher incidence of hypertension, higher levels of blood HbA1c and triglyceride, and higher incidence of plaques in the carotid artery. A multivariate logistic regression analysis revealed that age (Odds ratio (OR):1.03), male sex (OR: 1.91), and the presence of plaque in the carotid artery (OR: 1.71) were risk factors for OPLL. To the best of our knowledge, this is the first report to reveal an association between OPLL and arteriosclerotic lesions.

Tissue discrimination by bioelectrical impedance during PLL resection in anterior decompression surgery for treatment of cervical spondylotic myelopathy.

BACKGROUND: The electrical properties of biological tissues differ depending on their physical properties. This study aimed to explore if bioelectrical impedance (modulus and phase) would discriminate tissues relevant to resection of the posterior longitudinal ligament (PLL) in anterior cervical decompression surgery. METHODS: PLL resection via an anterior approach was performed on the C4/5 segments in six mini-pigs. The bioelectrical impedance measurements were performed for two tissue groups (annulus fibrosus, endplate cartilage, sub-endplate cortical bone, and PLL; PLL, dura mater, spinal cord, and nerve root) using a novel probe and a precision inductance-capacitance-resistance meter. For each group, impedance was analyzed in terms of modulus and phase along a broad spectrum of frequencies (200-3000 kHz) using a nonparametric statistical analysis (Kruskal-Wallis). RESULTS: The analysis showed a clear difference among the tissues. The modulus and phase show the same changing trend with frequency and present lower values at higher frequencies. Among annulus fibrosus, endplate cartilage, sub-endplate cortical bone, and PLL, it was possible to discriminate each tissue at every frequency point, considering the phase (p < 0.05), while this was not always the case (i.e., annulus fibrosus vs PLL at frequency of 200 kHz, 400 kHz, and 3000 kHz, p > 0.05) for modulus. Among PLL, dura mater, spinal cord, and nerve root, for every comparison, a statistically significant difference was reported in the modulus, phase, or both (p < 0.05). CONCLUSIONS: The results indicated the potential of bioelectrical impedance to provide real-time tissue differentiation and enhance safe PLL resection in anterior cervical decompression surgery, particularly in robot-assisted minimally invasive surgery (RMIS).

Ultrasonography of Extrathyroidal Diseases Mimicking Intrinsic Thyroid Lesions.

Some localized or multisystem diseases as well as congenital anomalies occasionally involve thyroid and unusual findings will be identified during thyroid ultrasonography. Recognition of these entities will minimize unnecessary complementary examination and lead to appropriate management for patients. Therefore, we aim to review sonographic features of these extrathyroidal diseases that affect thyroid in adults. Our review derives from cases diagnosed in our hospital and published literature, with pictures accessible using as illustration. These disorders included intrathyroidal parathyroid adenoma, intrathyroidal cystic findings of nonthyroid origin, metastases to the thyroid, esophageal diverticulum, paratracheal air cysts, and ossification of anterior longitudinal ligament.

Molecular characterization of known and novel ACVR1 variants in phenotypes of aberrant ossification.

Diffuse idiopathic skeletal hyperostosis (DISH) is a disorder principally characterized by calcification and ossification of spinal ligaments and entheses. Fibrodysplasia ossificans progressiva (FOP) is a rare autosomal dominant disabling disorder characterized by progressive ossification of skeletal muscle, fascia, tendons, and ligaments. These conditions manifest phenotypic overlap in the ossification of tendons and ligaments. We describe herein a patient with DISH, exhibiting heterotopic ossification of the posterior longitudinal ligament where clinical whole exome sequencing identified a variant within ACVR1, a gene implicated in FOP. This variant, p.K400E, is a novel variant, not identified previously, and occurs in a highly conserved region across orthologs. We used sequence-based predicative algorithms, molecular modeling, and molecular dynamics simulations, to test the potential for p.K400E to alter the structure and dynamics of ACVR1. We applied the same modeling and simulation methods to established FOP variants, to identify the detailed effects that they have on the ACVR1 protein, as well as to act as positive controls against which the effects of p.K400E could be evaluated. Our in silico molecular analyses support p.K400E as altering the behavior of ACVR1. In addition, functional testing to measure the effect of this variant on BMP-pSMAD 1/5/8 target genes was carried out which revealed this variant to cause increased ID1 and Msx2 expression compared with the wild-type receptor. This analysis supports the potential for the variant of uncertain significance to contribute to the patient's phenotype.

Effectiveness of posterior structures in the development of proximal junctional kyphosis following posterior instrumentation: A biomechanical study in a sheep spine model.

INTRODUCTION: Proximal junctional kyphosis - PJK has been defined by a 10 or greater increase in kyphosis at the proximal junction as measured by the Cobb angle from the caudal endplate of the uppermost instrumented vertebrae (UIV) to the cephalad endplate of the vertebrae 1 segments cranial to the UIV. In this biomechanical study, it is aimed to evaluate effects of interspinosus ligament complex distruption and facet joint degeneration on PJK development. MATERIALS AND METHODS: Posterior instrumentation applied between T2 - T7 vertebrae using pedicle screws to randomly selected 21 sheeps, divided into 3 groups. First group selected as control group (CG), of which posterior soft tissue and facet joints are protected. In second group (spinosus group, SG) interspinosus ligament complex which 1 segment cranial to UIV has been transected, and third group (faset group-FG) was applied facet joint excision. 25 N, 50 N, 100 N, 150 N and 200 N forces applied at frequency of 5 Hertz as 100 cycles axial to the samples. Then, 250 N, 275 N and 300 N forces applied static axially. Interspinosus distance, kyphosis angle and discus heights was measured in radiological evaluation. Abnormal PJK was defined by a proximal junctional angle greater than 100 and at least 100 greater than the corresponding preoperative measurement. RESULTS: In CG group, average interspinosus distance was 6,6 ± 1.54 mm and kyphosis angle was 2,2 ± 0.46° before biomechanical testing, and they were measured as 9,4 ± 1.21 mm and 3,3 ±0.44° respectively after forces applied to samples. In SG group, average interspinosus distance was 6,2 ± 1.72 mm and kyphosis angle was 2,7 ± 1.01° before experiment, and they were measured as 20,8 ± 5.66 mm and 15,1 ± 2.34° respectively after forces applied to samples. In FG group, average interspinosus distance was 4,8 ± 1.15 mm and kyphosis angle was -1 ± 4.14° before experiment, and they were measured as 11,1 ±1.96mm and 11 ± 2.87° respectively after forces applied to samples. In comparison to group CG, statistically significant junctional kyphosis was seen on both FG and SG group after statistical analysis. (p < 0.05). PJK was seen statistically significant more on SG group than FG group. (p < 0.05). Not any statistically significant difference was seen on measurement of disk distances among three groups. (p > 0.05) CONCLUSIONS: Protecting interspinosus ligament complex and facet joint unity during posterior surgical treatment for spine deformation is vital to prevent PJK development. Based on our literature review, this is the first biomechanical study that reveals interspinosus ligament complex are more effective on preventing PJK development than facet joints.

Anterior longitudinal ligament in diffuse idiopathic skeletal hyperostosis: Ossified or displaced?

Diffuse idiopathic skeletal hyperostosis (DISH) is often theorized to be an ossification of the anterior longitudinal ligament (ALL). Using computed tomography (CT) imaging and cryomacrotome sectioning, we investigated the spatial relationship between the ALL and newly formed bone in DISH to test this hypothesis. In the current study, four human cadaveric spines diagnosed with DISH using CT imaging were frozen and sectioned using a cryomacrotome. Photographs were obtained of the specimen at 125 µm intervals. Manual segmentations of the ALL on cryomacrotome photographs were projected onto the three-dimensional reconstructed CT scans. The presence and location of newly formed bone were assessed in relationship to the location of the ALL. The ALL could be identified and segmented on the photographs at all levels. The ALL was located at the midline at levels where no new bone had formed. At the locations where new bone had abundantly formed, the ALL was displaced towards to the contralateral side and not replaced by bony tissue. The displacement of the-morphologically normal appearing-ALL away from the newly formed bone implies that newly formed bone in DISH may not originate from the ALL. © 2018 The Authors. Journal of Orthopaedic Research® Published by Wiley Periodicals, Inc. on behalf of Orthopaedic Research Society J Orthop Res 36:2491-2496, 2018.

Effects of multilevel posterior ligament dissection after spinal instrumentation on adjacent segment biomechanics as a potential risk factor for proximal junctional kyphosis: a biomechanical study.

BACKGROUND: Spinous processes and posterior ligaments, such as inter- and supraspinous ligaments are often sacrificed either deliberately to harvest osseous material for final spondylodesis e.g. in deformity corrective surgery or accidentally after posterior spinal instrumentation. This biomechanical study evaluates the potential destabilizing effect of a progressive dissection of the posterior ligaments (PL) after instrumented spinal fusion as a potential risk factor for proximal junctional kyphosis (PJK). METHODS: Twelve calf lumbar spines were instrumented from L3 to L6 (L3 = upper instrumented vertebra, UIV) and randomly assigned to one of the two study groups (dissection vs. control group). The specimens in the dissection group underwent progressive PL dissection, followed by cyclic flexion motion (250 cycles, moment: + 2.5 to + 20.0 Nm) to simulate physical activity and range of motion (ROM) testing of each segment with pure moments of ±15.0 Nm after each dissection step. The segmental ROM in flexion and extension was measured. The control group underwent the same loading and ROM testing protocol, but without PL dissection. RESULTS: In the treatment group, the normalized mean ROM at L2-L3 (direct adjacent segment of interest, UIV/UIV + 1, PJK-level) increased to 104.7%, 107.3%, and 119.4% after dissection of the PL L4-L6, L3-L6, and L2-L6, respectively. In the control group the mean ROM increased only to 103.2%, 106.7%, and 108.7%. The ROM difference at L2-L3 with regard to the last dissection of the PL was statistically significant (P = 0.017) and a PL dissection in the instrumented segments showed a positive trend towards an increased ROM at UIV/UIV + 1. CONCLUSIONS: A dissection of the PL at UIV/UIV + 1 leads to a significant increase in ROM at this level which can be considered to be a risk factor for PJK and should be definitely avoided during surgery. However, a dissection of the posterior ligaments within the instrumented segments while preserving the ligaments at UIV/UIV + 1 leads to a slight but not significant increase in ROM in the adjacent cranial segment UIV/UIV + 1 in the used experimental setup. Using this experimental setup we could not confirm our initial hypothesis that the posterior ligaments within a long posterior instrumentation should be preserved.

Biomechanical investigation of post-operative C5 palsy due to ossification of the posterior longitudinal ligament in different types of cervical spinal alignment.

Post-operative C5palsies are among the most common complications seen after cervical surgery for ossification of the posterior longitudinal ligament (OPLL). Although C5 palsy is a well-known complication of cervical spine surgery, its pathogenesis is poorly understood and depends on many other factors. In this study, a finite element model of the cervical spine and spinal cord-nerve roots complex structures was developed. The changes in stress in the cord and nerve roots, posterior shift of the spinal cord, and displacement and elongation of the nerve roots after laminectomy for cervical OPLL were analyzed for three different cervical sagittal alignments (lordosis, straight, and kyphosis). The results suggest that high stress concentrated on the nerve roots after laminectomy could be the main cause of C5 palsy because ossification of ligaments increases spinal cord shifting and root displacement. The type of sagittal alignment had no influence on changes in cord stress after laminectomy, although cases of kyphosis with a high degree of occupying ratio resulted in greater increases in nerve root stress after laminectomy. Therefore, kyphosis with a high OPLL occupying ratio could be a risk factor for poor surgical outcomes or post-operative complications and should be carefully considered for surgical treatment.

Fatigue responses of the human cervical spine intervertebral discs.

Numerous studies have been conducted since more than fifty years to understand the behavior of the human lumbar spine under fatigue loading. Applications have been largely driven by low back pain and human body vibration problems. The human neck also sustains fatigue loading in certain type of civilian occupational and military operational activities, and research is very limited in this area. Being a visco-elastic structure, it is important to determine the stress-relaxation properties of the human cervical spine intervertebral discs to enable accurate simulations of these structures in stress-analysis models. While finite element models have the ability to incorporate viscoelastic material definitions, data specific to the cervical spine are limited. The present study was conducted to determine these properties and understand the responses of the human lower cervical spine discs under large number of cyclic loads in the axial compression mode. Eight disc segments consisting of the adjacent vertebral bodies along with the longitudinal ligaments were subjected to compression, followed by 10,000 cycles of loading at 2 or 4Hz frequency by limiting the axial load to approximately 150 N, and subsequent to resting period, subjected to compression to extract the stress-relaxation properties using the quasi-linear viscoelastic (QLV) material model. The coefficients of the model and disc displacements as a function of cycles and loading frequency are presented. The disc responses demonstrated a plateauing effect after the first 2000 to 4000 cycles, which were highly nonlinear. The paper compares these responses with the "work hardening" phenomenon proposed in clinical literature for the lumbar spine to explain the fatigue behavior of the discs. The quantitative results in terms of QLV coefficients can serve as inputs to complex finite element models of the cervical spine to delineate the local and internal load-sharing responses of the disc segment.

[The biomechanics of hyperextension injuries of the subaxial cervical spine]. / Biomechanik der Hyperextensionsverletzung der subaxialen Halswirbelsäule.

Hyperextension injuries of the subaxial cervical spine are potentially hazardous due to relevant destabilization. Depending on the clinical condition, neurologic or vascular damage may occur. Therefore an exact knowledge of the factors leading to destabilization is essential. In a biomechanical investigation, 10 fresh human cadaver cervical spine specimens were tested in a spine simulator. The tested segments were C4 to 7. In the first step, physiologic motion was investigated. Afterwards, the three steps of injury were dissection of the anterior longitudinal ligament, removal of the intervertebral disc/posterior longitudinal ligament, and dissection of the interspinous ligaments/ligamentum flavum. After each step, the mobility was determined. Regarding flexion and extension, an increase in motion of 8.36 % after the first step, 90.45 % after the second step, and 121.67 % after the last step was observed. Testing of lateral bending showed an increase of mobility of 7.88 %/27.48 %/33.23 %; axial rotation increased by 2.87 %/31.16 %/45.80 %. Isolated dissection of the anterior longitudinal ligament led to minor destabilization, whereas the intervertebral disc has to be seen as a major stabilizer of the cervical spine. Few finite-element studies showed comparable results. If a transfer to clinical use is undertaken, an isolated rupture of the anterior longitudinal ligament can be treated without surgical stabilization.

Effect of posterior decompression extent on biomechanical parameters of the spinal cord in cervical ossification of the posterior longitudinal ligament.

Ossification of the posterior longitudinal ligament is a common cause of the cervical myelopathy due to compression of the spinal cord. Patients with ossification of the posterior longitudinal ligament usually require the decompression surgery, and there is a need to better understand the optimal surgical extent with which sufficient decompression without excessive posterior shifting can be achieved. However, few quantitative studies have clarified this optimal extent for decompression of cervical ossification of the posterior longitudinal ligament. We used finite element modeling of the cervical spine and spinal cord to investigate the effect of posterior decompression extent for continuous-type cervical ossification of the posterior longitudinal ligament on changes in stress, strain, and posterior shifting that occur with three different surgical methods (laminectomy, laminoplasty, and hemilaminectomy). As posterior decompression extended, stress and strain in the spinal cord decreased and posterior shifting of the cord increased. The location of the decompression extent also influenced shifting. Laminectomy and laminoplasty were very similar in terms of decompression results, and both were superior to hemilaminectomy in all parameters tested. Decompression to the extents of C3-C6 and C3-C7 of laminectomy and laminoplasty could be considered sufficient with respect to decompression itself. Our findings provide fundamental information regarding the treatment of cervical ossification of the posterior longitudinal ligament and can be applied to patient-specific surgical planning.

Failure properties and damage of cervical spine ligaments, experiments and modeling.

Cervical spine ligaments have an important role in providing spinal cord stability and restricting excessive movements. Therefore, it is of great importance to study the mechanical properties and model the response of these ligaments. The aim of this study is to characterize the aging effects on the failure properties and model the damage of three cervical spine ligaments: the anterior and the posterior longitudinal ligament and the ligamentum flavum. A total of 46 samples of human cadaveric ligaments removed within 24-48 h after death have been tested. Uniaxial tension tests along the fiber direction were performed in physiological conditions. The results showed that aging decreased the failure properties of all three ligaments (failure load, failure elongation). Furthermore, the reported nonlinear response of cervical ligaments has been modeled with a combination of the previously reported hyperelastic and damage model. The model predicted a nonlinear response and damage region. The model fittings are in agreement with the experimental data and the quality of agreement is represented with the values of the coefficient of determination close to 1.

Soft-tissue damage and segmental instability in adult patients with cervical spinal cord injury without major bone injury.

STUDY DESIGN: A retrospective imaging and clinical study. OBJECTIVE: To evaluate the extraneural soft-tissue damage and its clinical relevance in patients with traumatic cervical spinal cord injury (SCI) without major bone injury. SUMMARY OF BACKGROUND DATA: To date, various kinds of cervical discoligamentous injuries have been demonstrated on magnetic resonance images in patients with SCI without bony injury. However, it has not been clear whether these magnetic resonance imaging abnormalities are actually related to spinal segmental instability and the patients' neurological status. METHODS: Eighty-eight adult patients with acute traumatic cervical SCI without major bone injury were examined by flexion-extension lateral radiographs and magnetic resonance images within 2 days after trauma. We excluded patients with flexion recoil injury; therefore, most of the patients included were considered to have sustained a hyperextension injury. Instability of the injured cervical segment was defined when there was more than 3.5-mm posterior translation and/or more than a 11° difference in the intervertebral angle between the site of interest and adjacent segments. The neurological status was evaluated according to the American Spinal Injury Association motor score. RESULTS: On magnetic resonance images, the damage to the anterior longitudinal ligament and intervertebral disc were apparent in 44 and 37 patients, respectively. Various degrees of prevertebral fluid collection (prevertebral hyperintensity) were demonstrated in 76 patients. These magnetic resonance imaging abnormalities were significantly associated with initial cervical segmental instability as judged by flexion-extension radiographs. Interestingly, the American Spinal Injury Association motor score had a significant association with either magnetic resonance imaging abnormalities or segmental instability but not with the cervical canal diameter. CONCLUSION: A considerable proportion of the patients with traumatic cervical SCI without major bone injury were shown to have various types of soft-tissue damage associated with cervical segmental instability at the early stages of the injury. The severity of paralysis greatly depended on these discoligamentous injuries.

[The crural diaphragm belongs to the pharyngeo-cardial continence organ (PET-CT and impedance measurements on the stretch sphincter and its fixation in the hiatus oesophageus of the diaphragm)]. / Das krurale Zwerchfell gehört zum ösophagokardialen Kontinenzorgan (PET-CT und Impedanzmessung am Dehnverschluss und seine Verankerung im Hiatus oesophageus des Zwerchfells).

This paper provides evidence that pharyngeo-cardial propulsion in the oesophagus follows similar principles as translocation of luminal contents in other locations in the body. In brief, the following statements are discussed in the paper: 1. Only animals with a lung-based respiratory system have an oesophagus. 2. Its bulky muscular wall is made up of the elastic fibres which ensure that the oesophagus stays elastic during an entire lifetime. 3. While short-segment ring sphincter systems exist in several locations in the body, the lower oesophageal sphincter is maximally elongated. This configuration helps with the propulsion of luminal contents in addition to this sphincter's opening and occlusive functions. 4. The musculature of the diaphragm is genetically related to the cervical muscles. The crural portion of the diaphragm works in coordination with the lower oesophageal stretch sphincter. 5. Gastro-oesophageal reflux disease is fairly common. In patients with this disorder, the oesophagus is too short and the stretch sphincter remains patent for abnormal periods of time. 6. When the stretch sphincter is surgically retightened by transposition of the oesophageal cardia into the abdomen, a proper function of the regulatory lower oesophageal stretch sphincter can be restored. 7.-9. All fundoplication procedures place the lower oesophageal sphincter under stretch, squeeze and create an oesophageal wrap out of gastric fundus tissue. X-ray images confirm in many patients undergoing fundoplication that the anatomic stretch sphincter already starts above and proximally to the plicated cuff.

CT and MRI-based diagnosis of craniocervical dislocations: the role of the occipitoatlantal ligament.

BACKGROUND: Craniocervical dislocations are rare, potentially devastating injuries. A diagnosis of craniocervical dislocations may be delayed as a result of their low incidence and paucity of diagnostic criteria based on CT and MRI. Delay in diagnosis may contribute to neurological injury from secondary displacement resulting from instability. The purpose of this study was to define CT and MRI-based diagnostic criteria for craniocervical dislocations to facilitate early injury recognition and stabilization. QUESTIONS/PURPOSES: Using CT and MRI, we (1) described the bony articular displacements characterize craniocervical injuries; (2) described the ligamentous injuries that characterize craniocervical injuries; and (3) determined whether neurologic injuries were associated with bony or ligamentous injury. METHODS: Using a prospectively collected spinal cord injury database, we identified 18 patients with acute, traumatic occipitocervical injuries. We reviewed CT scans and MR images to document the height of the occipitoatlantal and atlantoaxial joints and integrity of craniocervical ligaments. Medical records were reviewed for neurological status. The primary measurements were number of patients with articular displacement, location of bony displacement, and number of patients with ligamentous injury. RESULTS: Thirteen of 18 patients had displacement outside the normal range. Six patients demonstrated displacement of both occipitoatlantal and atlantoaxial joints, whereas five patients presented with displacement through the atlantoaxial joints only. Two patients had an abnormal basion-dental interval only. Of 17 patients with MR images, the cruciate ligament was injured in 11 patients, indeterminate in four, and intact in two. All five patients with occipitoatlantal articular displacement had injury to the occipitoatlantal capsule. No patient had occipitoatlantal capsular injury without occipitoatlantal articular displacement. Three cases of complete spinal cord injury were found after occipitoatlantal-atlantoaxial dislocations. Three patients with occipitoatlantal-atlantoaxial dislocations were neurologically intact. The five patients with atlantoaxial dislocations and patients without displacement or ligamentous injury were neurologically intact. Five patients had cruciate ligament rupture or indeterminate injury but no joint diastasis. CONCLUSIONS: The occipitoatlantal joint capsules stabilize the occipitoatlantal joint; disruption of the occipitoatlantal capsule may suggest the presence of instability. Based on these findings, we identified two distinct injury patterns: isolated atlantoaxial injuries (Type I) and combined occipitoatlantal-atlantoaxial injuries (Type II). Occipitoatlantal joint capsule integrity differentiated these subsets and Type II injuries had a higher percentage of complete spinal cord injuries on presentation.

Ossification of the posterior longitudinal ligament: genetics and pathophysiology.

Ossification of the posterior longitudinal ligament (OPLL) is a disease of progressive ectopic calcification of the PLL of the spine. It occurs most frequently in the cervical spine, followed by the thoracic spine. The disease was first described in the Japanese population, and the prevalence of OPLL is highest in Japan at a rate of 1.9%-4.3%. Note, however, that OPLL is also seen and is a known cause of cervical myelopathy in other Asian countries and in the white population. Research into the underlying cause of OPLL over the past few decades has shown that it is a multifactorial disease with significant genetic involvement. Genetic studies of OPLL have revealed several gene loci that may be involved in the pathogenesis of this disease. Genes encoding for proteins that process extracellular inorganic phosphate, collagen fibrils, and transcription factors involved in osteoblast and chondrocyte development and differentiation have all been implicated in the pathophysiology of OPLL. In this paper, the authors review current understanding of the genetics and pathophysiology of OPLL.

Biomechanical study of the effect of degree of static compression of the spinal cord in ossification of the posterior longitudinal ligament.

OBJECT: The authors evaluated the biomechanical effect of 3 different degrees of static compression in a model of the spinal cord in order to investigate the effect of cord compression in patients with ossification of the posterior longitudinal ligament (OPLL). METHODS: A 3D finite element spinal cord model consisting of gray matter, white matter, and pia mater was established. As a simulation of OPLL-induced compression, a rigid plate compressed the anterior surface of the cord. The degrees of compression were 10, 20, and 40% of the anteroposterior (AP) diameter of the cord. The cord was supported from behind by the rigid body along its the posterior border, simulating the lamina. Stress distributions inside of the cord were evaluated. RESULTS: The stresses on the cord were very low under 10% compression. At 20% compression, the stresses on the cord increased very slightly. At 40% compression, the stresses on the cord became much higher than with 20% compression, and high stress distributions were observed in gray matter and the lateral and posterior funiculus. The stresses on the compressed layers were much higher than those on the uncompressed layer. CONCLUSIONS: The stress distributions at 10 and 20% compression of the AP diameter of the spinal cord were very low. The stress distribution at 40% compression was much higher. The authors conclude that a critical point may exist between 20 and 40% compression of the AP diameter of the cord such that when the degree of the compression exceeds this point, the stress distribution becomes much higher, and that this may contribute to myelopathy.