Influence of kinematic analysis methods on detecting ankle and subtalar joint instability

Patients with subtalar joint instability may be misdiagnosed with ankle instability, which may lead to chronic instability at the subtalar joint. Therefore, it is important to understand the difference in kinematics after ligament sectioning and differentiate the changes in kinematics between ankle and subtalar instability. Three methods may be used to determine the joint kinematics; the Euler angles, the Joint Coordinate System (JCS) and the helical axis (HA). The purpose of this study was to investigate the influence of using either method to detect subtalar and ankle joints instability. 3D kinematics at the ankle and subtalar joint were analyzed on 8 cadaveric specimens while the foot was intact and after sequentially sectioning the anterior talofibular ligament (ATFL), the calcaneofibular ligament (CFL), the cervical ligament and the interosseous talocalcaneal ligament (ITCL). Comparison in kinematics calculated from sensor and anatomical landmarks was conducted as well as the influence of Euler angles and JCS rotation sequence (between ISB recommendation and previous research) on the subtalar joint. All data showed a significant increase in inversion when the ITCL was sectioned. There were differences in the data calculated using sensors coordinate systems vs. anatomic coordinate systems. Anatomic coordinate systems were recommended for these calculations. The Euler angle and JCS gave similar results. Differences in Euler angles and JCS sequence lead to the same conclusion in detecting instability at the ankle and subtalar joint. As expected, the HA detected instability in plantarflexion at the ankle joint and in inversion at the subtalar joint.

Treatment for carpal tunnel syndrome by coronal Z-type lengthening of the transverse carpal ligament

OBJECTIVE

To compare the effects of coronal Z-type lengthening of transverse carpal ligament with conventional open approach for carpal tunnel syndrome.

METHODS

A double-blinded study was conducted from January 2005 to August 2008 on 68 patients with a mean age of 41 years (range 27-55 years) diagnosed as severe carpal tunnel syndrome. They were randomized into two groups(A and B). Patients in group A underwent coronal Z-type lengthening of transverse carpal ligament; and patients in group B had conventional open approach surgery. Postoperative evaluation was scheduled at 1, 3, 6 and 12 months after the surgery and incidence rate of bowstring of the flexor tendons, improvement of grip strength and ADL activities of daily living) score were recorded.

RESULTS

Fifty-eight patients had been followed up successfully, 30 and 28 for group A and B respectively. The Scar Tissue Formation of the flexor tendons in group B was observed more than that in group A at 6 and 12 month after operation. Improvement of grip strength were observed in two groups, which was statistically different between 6 and 12 months after operation and no significant difference was seen between 1 and 3 months after operation. According to ADL, the satisfaction rates documented on form for patients were statistically different in the two groups at 6 and 12 months after operation and no difference was noted at 1 and 3 months after operation.

CONCLUSION

Excellent improvement of function and satisfaction were achieved by Coronal Z-type reconstruction of the flexor retinaculum for severe carpal tunnel syndrome. Our method offers a more effective alternative method for conventional carpal tunnel open decompression surgery.

Crystallization study and comparative in vitro-in vivo hydrolysis of PLA reinforcement ligament

In the present work, the crystallization behavior and in vitro-in vivo hydrolysis rates of PLA absorbable reinforcement ligaments used in orthopaedics for the repair and reinforcement of articulation instabilities were studied. Tensile strength tests showed that this reinforcement ligament has similar mechanical properties to Fascia Latta, which is an allograft sourced from the ilio-tibial band of the human body. The PLA reinforcement ligament is a semicrystalline material with a glass transition temperature around 61 °C and a melting point of ~178 °C. Dynamic crystallization revealed that, although the crystallization rates of the material are slow, they are faster than the often-reported PLA crystallization rates. Mass loss and molecular weight reduction measurements showed that in vitro hydrolysis at 50 °C initially takes place at a slow rate, which gets progressively higher after 30-40 days. As found from SEM micrographs, deterioration of the PLA fibers begins during this time. Furthermore, as found from in vivo hydrolysis in the human body, the PLA reinforcement ligament is fully biocompatible and after 6 months of implantation is completely covered with flesh. However, the observed hydrolysis rate from in vivo studies was slow due to high molecular weight and degree of crystallinity.

[The value of MRI in diagnosis of ligament injuries of knee joint]

OBJECTIVE

To study the performance of MRI and its diagnostic value for ligament injuries of knee joint.

METHODS

Form June 2008 to February 2010, the MRI of 74 patients with ligament injuries of knee joint were retrospectively analyzed. There were 47 males and 27 females in the group, which course was from 2 h to 10 d, with an average age of 37.3 years (ranged from 12 to 76). The clinical symptom included knee swelling, pain, joint instability, extension-flexion movement disorder. The physical examination showed valgus test or drawer test positive, and tenderness of medial knee positive.

RESULTS

There were ligament injuies in 74 cases, among them, 19 cases were anterior cruciate ligament (25.7%),18 were posterior cruciate ligament (24.3%), 13 were lateral collateral ligament (17.6%), 24 were medial collateral (32.4%), the ligament of 12 cases were completely broken (included 8 cases cruciate ligament and 4 cases collateral ligament presented as discontinued signals of the ligament, and swelling and thickening of the ligament with medium signal in PDWI and high signal intensity in T2WI and in SPIR). The MRI of 62 patients with partial longitudinal tearing ligaments showed continuity, swelling and thickening of the ligaments with medium signal in PDWI and high signal intensity in T2WI and in SPIR. Forty-four cases were examined with surgery and arthroscopy, 41 ligaments were accorded with MRI, diagnosis rate of MRI was 95%.

CONCLUSION

MRI can accurately diagnose the ligament injuries of knee joint,which is an ideal technique in the diagnosis of ligament injuries of knee joint, and should be used as a routine examining method.

[Clinical significance of nuchal ligament calcification and the discussion on biomechanics]

OBJECTIVE

To improve the cognition about X-ray characteristics of nuchal ligament calcification, and discuss biomechanical properties.

METHODS

From September 2008 to August 2009, the X-rays of 163 cases showed nuchal ligament calcification, which datas were analyzed. There were 91 males and 72 females, the age from 38 to 68 with an average of 53.6 years. And the number of calcification segment, related vertebral level, and vertebral hyperosteogeny, intervertebral space or intervertebral foramen stenosis, anterior or posterior longitudinal ligament calcification, cervical instability in the relative segment were observed.

RESULTS

One hundred forty-one patients occurred degeneration in the relative segment. The characteristics of X-ray: the multiple nuchal ligament calcification existed single segment and the C5,6 and C4,5 were readily occurred, which multiple related vertebral sclerotin, intervertebral space or intervertebral foramen, anterior or posterior longitudinal ligament occurred pathological changes, moreover, it was main segment of pathological changes. The X-rays of 93 cases showed vertebral hyperosteogeny 72 intervertebral space or intervertebral foramen stenosis, 49 anterior or posterior longitudinal ligament calcification, 66 cervical instability in the relative segment. The percentage was respectively 65.96%, 51.06%, 34.75%, 46.81%.

CONCLUSION

Cervical X-ray examination could discover characteristics of nuchal ligament calcification in the relative segment, also is helpful to diagnosis of cervical spondylosis.

Classification of thoracolumbar fractures and dislocations

A classification of injuries is necessary in order to develop a common language for treatment indications and outcomes. Several classification systems have been proposed, the most frequently used is the Denis classification. The problem of this classification system is that it is based on an assumption, which is anatomically unidentifiable: the so-called middle column. For this reason, few years ago, a group of spine surgeons has developed a new classification system, which is based on the severity of the injury. The severity is defined by the pathomorphological findings, the prognosis in terms of healing and potential of neurological damage. This classification is based on three major groups: A = isolated anterior column injuries by axial compression, B = disruption of the posterior ligament complex by distraction posteriorly, and group C = corresponding to group B but with rotation. There is an increasing severity from A to C, and within each group, the severity usually increases within the subgroups from .1, .2, .3. All these pathomorphologies are supported by a mechanism of injury, which is responsible for the extent of the injury. The type of injury with its groups and subgroups is able to suggest the treatment modality.

[The morphological characteristics of osteoarthrosis]

Osteoarthrosis (OA) is a group of overlapping diseases that have various etiologies, but equal biological, morphological, and clinical outcomes. OA is characterized by degenerative and destructive changes in the articular hyaline cartilage, subchondral bone, spongiosis, synovium, capsule, and articular ligamentous apparatus. The clinical symptoms of OA are closely associated with morphological changes in articular tissue elements, primarily in the articular hyaline cartilage. Six stages that reflect the magnitude of changes in the hyaline cartilage and 4 degrees of the extent of the process along the articular surface are identified.

[Iris suture fixation of posterior-chamber elastic intraocular lens in ligament apparatus laxity]

An original MIOL-23 multifocal elastic intraocular lens (IOL) was used to operate 5 eyes with acquired lens dislocation and traumatic cataract. By making self-sealing tunnel incision, ILO was implanted into the capsular sac and sutured to the iris. MIOL-23 implantation caused an increase in mean visual acuity. The IOL took up a correct position. Elastic IOL implantation with iris suture fixation is an efficient and safe mode of additional ILO support.

Successful treatment of meralgia paresthetica with pulsed radiofrequency of the lateral femoral cutaneous nerve

BACKGROUND

Meralgia paresthetica is a rarely encountered sensory mononeuropathy characterized by paresthesia, pain or sensory impairment along the distribution of the lateral femoral cutaneous nerve caused by entrapment or compression of the nerve as it crosses the anterior superior iliac spine and runs beneath the inguinal ligament.

OBJECTIVE

We describe the first reported use of pulsed radiofrequency neuromodulation to relieve the intractable pain associated with meralgia paresthetica.

CASE REPORT

A 33-year-old morbidly obese female with a history of lower back pain and previous spinal fusion presented with sensory dysesthesias and paresthesias in the right anterolateral thigh, consistent with meralgia paresthetica. Temporary relief occurred with multiple lateral femoral cutaneous nerve and fascia lata blocks at 2 different institutions. The patient expressed dissatisfaction with her previous treatments and requested "any" therapeutic intervention that might lead to long-lasting pain relief. At this time, we located the anterior superior iliac spine and reproduced concordant dysesthesia. Pulsed radiofrequency was then undertaken at 42 degrees C for 120 seconds followed by dexamethasone and bupivicaine. The patient reported exceptional and prolonged pain relief at 6-month follow-up.

LIMITATIONS

Since this case report is not a prospective, randomized, controlled or blinded study, no conclusions may be drawn from the results attained on behalf of this single individual. Additional, larger group analyses studying this technique while eliminating bias from patient variables would be essential prior to assuming any validity to using pulsed radiofrequency techniques of neuromodulation for managing peripheral neuropathic pain processes.

CONCLUSION

The patient had experienced long-standing pain that was recalcitrant to conservative/pharmacologic therapy and multiple nerve blocks with local steroid instillations. A single treatment with pulsed radiofrequency resulted in complete and sustained cessation of pain. No side effects were evident. Pulsed radiofrequency of the LFCN may offer an effective, low risk treatment in patients with meralgia paresthetica who are refractory to conservative medical management or are unwilling or unfit to undergo surgery.

Use of the orbicularis retaining ligament in lower eyelid reconstruction

INTRODUCTION

The orbicularis retaining ligament (ORL) is a distinct anatomical structure that has only been recently characterised. A variety of techniques, based on Hamra's concepts, now divide this ligament during lower lid blepharoplasty. This often produces a substantial skin excess which is discarded. We set out to investigate the validity of this surgical manoeuvre as a means of recruiting anterior lamella for the purposes of lower lid reconstruction.

MATERIALS AND METHODS

Between September 2002 and August 2004, 23 patients underwent reconstruction of the anterior lamella of their lower eyelid using this technique. The mean age of the patients was 56 years (range 26-86 years). The mean follow-up time was 20 months (range 12-36 months). Clinical evaluation was carried out preoperatively and postoperatively to assess the presence of palpebral non occlusion, epiphora, the sensation of a dry eye, ectropion, conjunctivitis and keratitis. Assessment of the tissue deficit was made clinically and with standardised digital photographs.

RESULTS

Satisfactory reconstruction of the anterior lamella of the lower eyelid was achieved in 19/23 patients. Preoperative symptoms of epiphora and lower lid position were improved. The visual analogue scale of appearance was improved postoperatively. In some cases, particularly in the atrophic lower lid, the results were short lived and further surgery was required to achieve optimal results.

CONCLUSION

In cases of isolated cutaneous deficit where the lid support mechanisms are intact, the procedure is both successful and aesthetically favourable for resurfacing this challenging area.

Contribution of biomechanics to management of ligament and tendon injuries

The contribution of biomechanics to the advancement of management of ligament and tendon injuries has been significant. Thanks to Professor Y.C. Fung's writing and guidance, our field of research has done fundamental work on anatomy and biology of ligaments and tendons, developed methods to accurately determine mechanical properties, identified various experimental factors which could change the outcome measurements as well as examined biological factors that change tissue properties in-vivo. Professor Fung also gave us his quasi-linear viscoelastic theory for soft tissues so that the time and history dependent properties of ligaments and tendons could be properly described. We have further adopted Professor Fung's eight steps on methods of approach for biomechanical investigation to understand as well as enhance the treatment of ligament and tendon injuries during work or sports related activities. Examples on how to better treat the tears of the medial collateral ligament of the knee, as well as how to improve reconstruction procedures for the anterior cruciate ligament are presented in detail. Currently the use of functional tissue engineering for ligament and tendon healing is a topic of great interest. Here the use of biological scaffolds, such as porcine small intestinal submucosa, has shown promise. For the last 35 to 40 years, the field of biomechanics has made great strides in the treatment of ligament and tendon injuries, and many patients have benefited. The future is even brighter because of what has been done properly in the past. Exciting advances can be made in the field of tissue engineering through novel in-vitro culture and bioscaffold fabrication techniques. Recent technology can also allow the collection of in-vivo data so that ligament and tendon injuries can be better understood. Yet, solving new and more complex problems must still follow the stepwise methods of approach as taught by Professor Fung.

[Angle-closed glaucoma secondary to bilateral spontaneous zonular laxity]

Changeable anterior chamber depth due to spontaneous zonular laxity of the lens is a rare abnormality in clinic. Here is a 25-year-old female with changeable anterior chamber depth due to bilateral spontaneous zonular laxity which also finally led to progressive myopia and angle-closure glaucoma is described. After using local anti-inflammation and dilation of the pupil, and carrying out "Phacoemulsification + anterior vitrectomy" putted intraocular lens (IOL) into the ravine of ciliary body, the woman's intraocular pressure was controlled and visual acuity was corrected to 20/20.

ASB clinical biomechanics award winner 2006 prospective study of the biomechanical factors associated with iliotibial band syndrome

BACKGROUND

Iliotibial band syndrome is the leading cause of lateral knee pain in runners. Despite its high prevalence, little is known about the biomechanics that lead to this syndrome. The purpose of this study was to prospectively compare lower extremity kinematics and kinetics between a group of female runners who develop iliotibial band syndrome compared to healthy controls. It was hypothesized that runners who develop iliotibial band syndrome will exhibit greater peak hip adduction, knee internal rotation, rearfoot eversion and no difference in knee flexion at heel strike. Additionally, the iliotibial band syndrome group were expected to have greater hip abduction, knee external rotation, and rearfoot inversion moments.

METHODS

A group of healthy female recreational runners underwent an instrumented gait analysis and were then followed for two years. Eighteen runners developed iliotibial band syndrome. Their initial running mechanics were compared to a group of age and mileage matched controls with no history of knee or hip pain. Comparisons of peak hip, knee, rearfoot angles and moments were made during the stance phase of running. Variables of interest were averaged over the five running trials, and then averaged across groups.

FINDINGS

The iliotibial band syndrome group exhibited significantly greater hip adduction and knee internal rotation. However, rearfoot eversion and knee flexion were similar between groups. There were no differences in moments between groups.

INTERPRETATION

The development of iliotibial band syndrome appears to be related to increased peak hip adduction and knee internal rotation. These combined motions may increase iliotibial band strain causing it to compress against the lateral femoral condyle. These data suggest that treatment interventions should focus on controlling these secondary plane movements through strengthening, stretching and neuromuscular re-education.

Cervical myelopathy caused by soft-tissue mass in diffuse idiopathic skeletal hyperostosis

A rare case of cervical spinal cord compression in diffuse idiopathic skeletal hyperostosis (DISH or Forestier's Disease) caused by a craniocervical mass of soft-tissue is reported. The objective is to describe an uncommon mechanism of spinal cord compression in DISH. Three weeks after a cardiac infarction a 69-year-old man slowly developed spastic tetraparesis. Magnetic resonance tomography showed a craniocervical tumor compressing the spinal cord and a massive DISH of the cervical spine. An extended mass of yellowish amorphous material was removed from between the dura, the posterior odontoid process and the posterior aspect of vertebral body C2 reaching to the upper part of C3.The histologic appearance indicated connective tissue and cell-degenerated cartilaginous tissue. There was no inflammatory component and no evidence of neoplasia. No ossification of the posterior longitudinal ligament (OPLL) was found. After removal and craniocervical stabilization the patient's neurologic function improved remarkably. The increase of mechanical stress on the atlantoaxial segment and enhanced proliferation reaction of the connective tissue in DISH are suggested as the underlying pathomechanisms in the formation of this soft-tissue mass.

The dual etiology of ipsilateral shoulder pain after thoracic surgery⋆

Ipsilateral shoulder pain after thoracic surgery is a distressing problem and is associated with impairment of respiratory and shoulder function. The most suggested etiology for this shoulder pain is referred phrenic nerve pain. However, we have made clinical observations that suggest shoulder ligament strain as another cause of the shoulder pain.

Ventroaxial luxation of the apex of the corniculate process of the arytenoid cartilage in resting horses during induced swallowing or nasal occlusion

OBJECTIVE

To report ventroaxial luxation of the apex of the left or right corniculate process of the arytenoid cartilage under the contralateral corniculate process during resting endoscopic examination, and morphologic features of the larynx of 1 affected horse.

STUDY DESIGN

Retrospective study.

ANIMALS

Horses (n=8).

METHODS

Horses had endoscopic examination as part of a survey of Clydesdale horses (n=7), or investigation of poor performance in Thoroughbred horses (1). One Clydesdale was euthanatized and the larynx examined; 4 cadaver larynges from normal horses were also examined.

RESULTS

Ventroaxial luxation of the apex of the left or right corniculate process of the arytenoid cartilage was not detected during quiet breathing but was induced by swallowing or nasal occlusion. Prevalence in Clydesdales was 5.2% (7/133). A Thoroughbred with identical endoscopic appearance of the larynx at rest had progressive ventroaxial luxation of the apex of the arytenoid cartilage during high-speed treadmill endoscopy, associated with abnormal respiratory noise. Necropsy examination of an affected Clydesdale larynx revealed an excessively wide (10 mm) transverse arytenoid ligament that allowed easy separation of the apices of the corniculate processes. In normal cadaver larynges, the apices could not be separated with abaxial traction.

CLINICAL RELEVANCE

The clinical relevance of this laryngeal observation in resting horses is unclear. Ventroaxial luxation of the corniculate process of the arytenoid cartilage during induced swallowing or nasal occlusion in resting horses or during high-speed treadmill exercise may be caused by an abnormally wide transverse arytenoid ligament.

Initial repair strengths of two methods for acute medial collateral ligament injuries of the elbow

The purposes of this study were to compare the initial repair strength of the medial collateral ligament (MCL) of the elbow using trans-osseous sutures and suture anchor methods and to determine the effect of repair pretensioning. Twelve, fresh-frozen upper extremities (66 +/- 5 years) were mounted in a valgus-loading system. MCL repairs were performed using trans-osseous suture and suture anchor methods with 20 N or 40 N pretensioning. A cyclic (0.5 Hz), valgus 40 N load was applied 12 cm distal to the elbow axis of flexion. The load was increased by 10 N every 200 cycles until a length increase of 5 mm or catastrophic failure of the repair occurred. Repairs pretensioned with 40 N endured a significantly higher number of cycles and failed at higher loads than those pretensioned with 20 N (p < 0.05). No difference was found in the cycles or load to failure between trans-osseous sutures and suture anchors (p > 0.05). A higher magnitude of pretensioning of MCL repairs was found to increase initial repair strength suggesting that pretensioning should be performed clinically. Despite the comparable failure loads of the trans-osseous suture and suture anchor methods, the failure mechanism differed between the two techniques. The suture anchors usually failed catastrophically when the sutures broke as they passed through the anchor eyelet, while the trans-osseous sutures gradually elongated to the defined failure length by stretching and sliding through the ligament. The use of different suture anchors, suture sizes, or suture materials would likely influence the findings of this study and should be considered when applying these findings clinically.

Hormones and growth factors in the pathogenesis of spinal ligament ossification

Ossification of the spinal ligaments (OSL) is a pathologic condition that causes ectopic bone formation and subsequently results in various degrees of neurological deficit, but the etiology of OSL remains almost unknown. Some systemic hormones, such as 1,25-dihydroxyvitamin D, parathyroid hormone (PTH), insulin and leptin, and local growth factors, such as transforming growth factor-beta (TGF-beta), and bone morphogenetic protein (BMP), have been studied and are thought to be involved in the initiation and development of OSL. This review article summarizes these studies, delineates the possible mechanisms, and puts forward doubts and new questions. The related findings from studies of genes and target cells in the ligament of OSL are also discussed. Although these findings may be helpful in understanding the pathogenesis of OSL, much more research needs to be conducted in order to investigate the nature of OSL.

Active Range of Motion as an Indicator for Ligament and Membrane Lesions in the Upper Cervical Spine after a Whiplash Trauma

In the present study, we examined whether active range of neck motion (AROM) differed between persons with and without a diagnosis of whiplash-associated disorder type 2 (WAD2) and explored whether magnetic resonance (MR)-verified lesions of specific ligaments or membranes at the craniovertebral junction was associated with increased or decreased motion in any particular direction among the WAD2 patients. A CROM goniometer was used for registration of flexion, extension, side bending (left and right) and rotation (left and right), respectively. The neck structures considered were the alar and the transverse ligaments, and the tectorial and the posterior atlanto-occipital membranes. Our study comprised 87 WAD2 patients and 29 control persons without any known neck injury. For comparing mean values of AROM between the groups, t-test and analysis of variance (ANOVA) were used. WAD patients had on average a shorter range of active motion for all movements compared with the control group. The difference was statistically significant for all measures considered, except side bending to the left. Among the WAD patients, increasing severity of lesions to the alar ligaments was associated with a decrease in maximal flexion and rotation. A similar pattern was seen for lesions to the transverse ligament, but the trend test was not significant. An abnormal posterior atlanto-occipital membrane was associated with shorter range of left rotation, with a significant trend test both in analyses with and without adjustment for lesions to other structures. No significant association was found in relation to lesions to the tectorial membrane, but very few persons had such lesions. These findings indicate that soft tissue lesions may affect neck motion as reflected by AROM. However, since lesions to different structures seem to affect the same movement, AROM alone is not a sufficient indicator for soft-tissue lesions to specific structure in the upper cervical spine.

Nonlinear finite element analysis for musculoskeletal biomechanics of medial and lateral plantar longitudinal arch of Virtual Chinese Human after plantar ligamentous structure failures

BACKGROUND

Musculoskeletal diseases of the foot such as stress fractures, tendonitis and subsequent pain are commonly associated with elevated stresses/strains of abnormal plantar arch after plantar ligamentous structure failures. The goal of this study was to develop anatomically detailed, finite element models of the medial and lateral plantar longitudinal arch, and to investigate bone and muscle stresses resulting from plantar fasciotomy and major plantar ligament injuries.

METHODS

Nonlinear finite element models of the second ray and the fifth ray of plantar longitudinal arches were constructed on the basis of CT and MR images of Virtual Chinese Human "female No. 1". The models assumed a balanced standing load configuration. Three different degrees of passive intrinsic muscle tensions (weak, moderate, or severe) were used in conjunction with simulations of plantar fasciotomy and major plantar ligament injury.

FINDINGS

Plantar fasciotomy caused von Mises stress increases in the bones and plantar ligaments while major plantar ligament injuries caused stress increases in the bones, flexor tendons, and plantar fascia. Increasing intrinsic muscle passive tensions decreased stress/strain levels in the medial and lateral arch, and adjusted abnormal tension/compression stress flows of both arches to close to the normal biomechanical states.

INTERPRETATION

This study shows that plantar longitudinal arches are concordant combination of bony structures, intrinsic muscles, plantar fascia and ligaments. After plantar ligamentous structure failures, intrinsic muscles have to contribute to stabilize the plantar arches. This mechanism may reduce the risk of developing stress fractures, tendonitis and pain syndrome.

Neck ligament strength is decreased following whiplash trauma

Background

Previous clinical studies have documented successful neck pain relief in whiplash patients using nerve block and radiofrequency ablation of facet joint afferents, including capsular ligament nerves. No previous study has documented injuries to the neck ligaments as determined by altered dynamic mechanical properties due to whiplash. The goal of the present study was to determine the dynamic mechanical properties of whiplash-exposed human cervical spine ligaments. Additionally, the present data were compared to previously reported control data. The ligaments included the anterior and posterior longitudinal, capsular, and interspinous and supraspinous ligaments, middle-third disc, and ligamentum flavum.

Methods

A total of 98 bone-ligament-bone specimens (C2–C3 to C7-T1) were prepared from six cervical spines following 3.5, 5, 6.5, and 8 g rear impacts and pre- and post-impact flexibility testing. The specimens were elongated to failure at a peak rate of 725 (SD 95) mm/s. Failure force, elongation, and energy absorbed, as well as stiffness were determined. The mechanical properties were statistically compared among ligaments, and to the control data (significance level: P < 0.05; trend: P < 0.1). The average physiological ligament elongation was determined using a mathematical model.

Results

For all whiplash-exposed ligaments, the average failure elongation exceeded the average physiological elongation. The highest average failure force of 204.6 N was observed in the ligamentum flavum, significantly greater than in middle-third disc and interspinous and supraspinous ligaments. The highest average failure elongation of 4.9 mm was observed in the interspinous and supraspinous ligaments, significantly greater than in the anterior longitudinal ligament, middle-third disc, and ligamentum flavum. The average energy absorbed ranged from 0.04 J by the middle-third disc to 0.44 J by the capsular ligament. The ligamentum flavum was the stiffest ligament, while the interspinous and supraspinous ligaments were most flexible. The whiplash-exposed ligaments had significantly lower (P = 0.036) failure force, 149.4 vs. 186.0 N, and a trend (P = 0.078) towards less energy absorption capacity, 308.6 vs. 397.0 J, as compared to the control data.

Conclusion

The present decreases in neck ligament strength due to whiplash provide support for the ligament-injury hypothesis of whiplash syndrome.

The Mechanisms of Atrial Fibrillation

In this article we have reviewed the mechanisms of atrial fibrillation (AF) with special emphasis on the thoracic veins. Based on a number of features, the thoracic veins are highly arrhythmogenic. The pulmonary vein (PV)-left atrial (LA) junction has discontinuous myocardial fibers separated by fibrotic tissues. The PV muscle sleeve is highly anisotropic. The vein of Marshall (VOM) in humans has multiple small muscle bundles separated by fibrosis and fat. Insulated muscle fibers can promote reentrant excitation, automaticity, and triggered activity. The PV muscle sleeves contain periodic acid-Schiff (PAS)-positive large pale cells that are morphologically reminiscent of Purkinje cells. These special cells could be the sources of focal discharge. Antiarrhythmic drugs have significant effects on PV muscle sleeves both at baseline and during AF. Both class I and III drugs have effects on wavefront traveling from PV to LA and from LA to PV. Separating the thoracic veins and the LA with ablation techniques also prevents PV-LA interaction. By reducing PV-LA interaction, pharmacological therapy and PV isolation reduce the activation rate in PV, intracellular calcium accumulation, and triggered activity. Therefore, thoracic vein isolation is an important technique in AF control. We conclude that thoracic veins are important in the generation and maintenance of AF.

Sensory – Motor control of ligaments and associated neuromuscular disorders

The ligaments were considered, over several centuries, as the major restraints of the joints, keeping the associated bones in position and preventing instability, e.g. their separation from each other and/or mal-alignment. This project, conducted over 25 years, presents the following hypothesis: 1. Ligaments are also major sensory organs, capable of monitoring relevant kinesthetic and proprioceptive data. 2. Excitatory and inhibitory reflex arcs from sensory organs within the ligaments recruit/de-recruit the musculature to participate in maintaining joint stability as needed by the movement type performed. 3. The synergy of the ligament and associated musculature allocates prominent role for muscles in maintaining joint stability. 4. The viscoelastic properties of ligaments and their classical responses to static and cyclic loads or movements such as creep, tension-relaxation, hysteresis and strain rate dependence decreases their effectiveness as joint restraint and stabilizers and as sensory organs and exposes the joint to injury. 5. Long-term exposure of ligaments to static or cyclic loads/movements in a certain dose-duration paradigms consisting of high loads, long loading duration, high number of load repetitions, high frequency or rate of loading and short rest periods develops acute inflammatory responses which require long rest periods to resolve. These inflammatory responses are associated with a temporary (acute) neuromuscular disorder and during such period high exposure to injury is present. 6. Continued exposure of an inflamed ligament to static or cyclic load may result in a chronic inflammation and the associated chronic neuromuscular disorder known as cumulative trauma disorder (CTD). 7. The knowledge gained from basic and applied research on the sensory - motor function of ligaments can be used as infrastructure for translational research; mostly for the development of "smart orthotic" systems for ligament deficient patients. Three such "smart orthosis", for the knee and lumbar spine are described. 8. The knowledge gained from the basic and applied research manifests in new physiotherapy modalities for ligament deficient patients. Ligaments, therefore, are important structures with significant impact on motor control and a strong influence on the quality of movement, safety/stability of the joint and potential disorders that impact the safety and health of workers and athletes.