Estimating joint contact areas and ligament lengths from bone kinematics and surfaces

We present a novel method for modeling contact areas and ligament lengths in articulations. Our approach uses volume images generated by computed tomography and allows the in vivo and noninvasive study of articulations. In our method, bones are modeled both implicitly (scalar distance fields) and parametrically (manifold surfaces). Using this double representation, we compute interbone distances and estimate joint contact areas. Using the same types of representation, we model ligament paths; in our model, the ligaments are approximated by the shortest paths in a three-dimensional space with bone obstacles. We demonstrate the method by applying our contact area and ligament model to the distal radioulnar joints of a volunteer diagnosed with malunited distal radius fracture in one forearm. Our approach highlights focal changes in the articulation at the distal radioulnar joint (location and area of bone contact) and potential soft-tissue constraints (increased "length" of the distal ligaments and ligament-bone impingement in the injured forearm). Results suggest that the method could be useful in the study of normal and injured anatomy and kinematics of complex joints.

Animal models of tendon and ligament injuries for tissue engineering applications

Animal modeling continues to be an important component to the critical evaluation of new techniques to treat tendon and ligament injuries. Appropriate choice and analysis of these models is essential. Factors that should be considered in assessing a potential model include the tissue type (ligament versus tendon and intrasynovial versus extrasynovial), the type of injury to be modeled, the techniques of measuring the response to treatment, the ease of comparison to previously published models and finally, the ease of translation to human trials and eventually to clinical usage.

Intrathecal ligaments and nerve root tension: possible sources of lumbar pain during spaceflight

Lumbar intrathecal ligaments have recently been demonstrated to randomly bind dorsal nerve roots to the dura within the lumbar vertebral column. Lengthening of the vertebral column and associated lumbar back pain experienced by astronauts is common in microgravity. This study was designed to investigate the relationship of lumbar intrathecal ligaments in spinal lengthening as a possible mechanism for back pain.

METHODS

A two-part study was designed using 36 vertebral columns from embalmed cadavers. There were 12 vertebral columns studied in mid-sagittal section to demonstrate the possible movement of the spinal cord during lengthening of the vertebral column. The remainder were assessed for the amount of tension placed on a dorsal nerve root by the lumbar intrathecal ligament during lengthening of the vertebral column.

RESULTS

The spinal cord moves in a cephalic direction approximately 2.8 mm with 4 cm lengthening of the vertebral column. During lengthening, a loss of thoracic and lordotic curvature was noted with an increase in disk height. Tension was significantly increased on the dorsal nerve roots being tethered by the lumbar intrathecal ligaments in comparison to non-tethered nerve roots during lengthening of the vertebral column.

CONCLUSION

A significant amount of tension is placed on dorsal nerve roots tethered by intrathecal ligaments within the lumbar spine during spinal lengthening. These ligaments randomly bind dorsal nerve roots in the lumbar spine and may be involved in the back pain experienced by astronauts in microgravity.

Functional Tissue Engineering for Ligament Healing: Potential of Antisense Gene Therapy

Traumatic knee injuries frequently involve the disruption of multiple ligaments, such as a complete tear of the medial collateral ligament (MCL) together with a rupture of the anterior cruciate ligament (ACL) (Miyasaka, K., D. M. Daniel, M. L. Stone, and P. Hirshman. Am. J. Knee Surg. 4:3-8, 1991). Despite the high incidence, clinical management of this type of injury is still debated. Laboratory studies have shown that the ACL and MCL share the responsibility of stabilizing the knee, especially in response to valgus and other rotatory torques as well as anterior tibial loads (Inoue, M., E. McGurk-Burleson, J. M. Hollis, and S. L-Y. Woo. Am. J. Sports Med. 15:15-21, 1987; Kanamori, A., M. Sakane, J. Zeminski, T. W. Rudy, and S. L-Y. Woo. J. Ortho. Sci. 5:567-571, 2000; Ma, C. B., C. D. Papageogiou, R. E. Debski, and S. L. Woo. Acta Orthop. Scand. 71:387-393, 2000; Sakane, M., G. A. Livesay, R. J. Fox, T. W. Rudy, T. J. Runco, and S. L-Y. Woo. Knee Surg. Sports Traumatol. Arthrosc. 7:93-97, 1999). When one structure is deficient, the force in the other increases significantly to compensate. The injured ACL does not heal and requires surgical replacement by tissue grafts. On the other hand, after an isolated MCL tear or in a combined MCL and ACL injury, the MCL can heal spontaneously without surgical intervention and can function well in most cases. Nevertheless, the biomechanical and biochemical properties as well as the histomorphological appearance of the healing MCL are substantially different to those of normal tissue (Bray, R. C., D. J. Butterwick, M. R. Daschak, and J. V. Tyberg. J. Orthop. Res. 14:618-625, 1996; Loitz-Ramage, B. J., C. B. Frank, and N. G. Shrive. Clin. Orthop.:272-280, 1997; Weiss, J. A., S. L-Y. Woo, K. J. Ohland, S. Horibe, and P. O. Newton. J. Orthop. Res. 9:516-528, 1991). In an effort to improve the outcome of injuries to these and other ligaments, therapeutic strategies associated with improving biomechanical, biochemical, and histomorphological properties of ligaments have been investigated in recent years. These therapeutic strategies include growth factor stimulation (Conti, N. A., and L. E. Dahners. Presented at Orthopaedic Research Society, San Francisco, CA; Deie, M., T. Marui, C. R. Allen, K. A. Hildebrand, H. I. Georgescu, et al. Mech. Ageing Dev. 97:121-130, 1997), cell therapy (Menetrey, J., C. Kasemkijwattana, C. S. Day, P. Bosch, F. H. Fu, et al. Tissue Eng. 5:435-442, 1999; Watanabe, N., S. L-Y. Woo, C. Papageorgiou, C. Celechovsky, and S. Takai. Microsc. Res. Tech. 58:39-44, 2002), as well as gene stherapy (Nakamura N., D. A. Hart, R. S. Boorman, Y. Kaneda, N. G. Shrive, et al. J. Orthop. Res. 18:517-523, 2000; Shimomura, T., F. Jia, C. Niyibizi, and S. L-Y. Woo. Connect. Tissue Res.:2003). The knowledge gained by studying these therapeutic strategies could potentially be applied to other ligaments and tendons. In this article, antisense gene therapy to alter gene expression by using antisense oligonucleotides will be examined as a possible solution.

Facet joint kinematics and injury mechanisms during simulated whiplash

STUDY DESIGN

Facet joint kinematics and capsular ligament strains were evaluated during simulated whiplash of whole cervical spine specimens with muscle force replication.

OBJECTIVES

To describe facet joint kinematics, including facet joint compression and facet joint sliding, and quantify peak capsular ligament strain during simulated whiplash.

SUMMARY OF BACKGROUND DATA

Clinical studies have implicated the facet joint as a source of chronic neck pain in whiplash patients. Prior in vivo and in vitro biomechanical studies have evaluated facet joint compression and excessive capsular ligament strain as potential injury mechanisms. No study has comprehensively evaluated facet joint compression, facet joint sliding, and capsular ligament strain at all cervical levels during multiple whiplash simulation accelerations.

METHODS

The whole cervical spine specimens with muscle force replication model and a bench-top trauma sled were used in an incremental trauma protocol to simulate whiplash of increasing severity. Peak facet joint compression (displacement of the upper facet surface towards the lower facet surface), facet joint sliding (displacement of the upper facet surface along the lower facet surface), and capsular ligament strains were calculated and compared to the physiologic limits determined during intact flexibility testing.

RESULTS

Peak facet joint compression was greatest at C4-C5, reaching a maximum of 2.6 mm during the 5 g simulation. Increases over physiologic limits (P < 0.05) were initially observed during the 3.5 g simulation. In general, peak facet joint sliding and capsular ligament strains were largest in the lower cervical spine and increased with impact acceleration. Capsular ligament strain reached a maximum of 39.9% at C6-C7 during the 8 g simulation.

CONCLUSIONS

Facet joint components may be at risk for injury due to facet joint compression during rear-impact accelerations of 3.5 g and above. Capsular ligaments are at risk for injury at higher accelerations.

Intracarpal steroid injection is safe and effective for short-term management of carpal tunnel syndrome

A double-blinded placebo-controlled trial was performed to evaluate the use of steroid injections beneath the transverse carpal ligament in the treatment of carpal tunnel syndrome (CTS) refractory to nonsurgical therapy. Forty-three patients received 6 mg betamethasone and lidocaine and 38 patients received 1 ml saline placebo and lidocaine. The primary outcome measure was satisfaction with symptom relief. Thirty patients (70%) in the steroid-treated group were satisfied or highly satisfied compared with 13 (34%) of placebo-treated patients (P < 0.001). Patients receiving steroids also showed significant improvement in median nerve conduction parameters and scores on validated symptom/function questionnaires. Forty-six patients were treated with serial injections for recurrent CTS symptoms. After 18 months, 17 patients reported adequate symptom relief with steroid injection, and 18 patients with unsatisfactory symptom relief were referred for carpal tunnel release surgery. We conclude that although steroid injections are safe and effective for temporary relief of CTS, most patients will eventually require surgery for long-term control of their symptoms.

Ligaments: a source of work-related musculoskeletal disorders

The mechanical and neurological properties of ligaments are reviewed and updated with recent development from the perspective which evaluates their role as a source of neuromusculoskeletal disorders resulting from exposure to occupational activities. Creep, tension-relaxation, hysteresis, sensitivity to strain rate and strain/load frequency were shown to result not only in mechanical functional degradation but also in the development of sensory-motor disorders with short- and long-term implication on function and disability. The recently exposed relationships between collagen fibers, applied mechanical stimuli, tissue microdamage, acute and chronic inflammation and neuromuscular disorders is delineated with special reference to occupational stressors.

Biomechanical consequences of lateral column lengthening of the calcaneus: Part I. Long plantar ligament strain

Lateral column lengthening of the calcaneus has been a powerful tool used to correct peritalar subluxation in symptomatic flat feet. The mechanical basis and limits for correction with this procedure are not well understood. A flatfoot model was created on 8 fresh-frozen cadaver feet by sectioning the deltoid ligament, talonavicular capsule, and spring ligament. Strain-gauge analysis of the long plantar ligament was performed (on 6 specimens) as the lateral column was sequentially lengthened from 4 to 12 mm in 2-mm increments. Results showed that only the lateral most one-third of the long plantar ligament measured positive strain during this procedure. The medial two-thirds of the long plantar ligament and plantar fascia decreased in tension and became fully lax during lengthening. Maximum tension in the long plantar ligament was measured after placing grafts 6 mm in thickness (P <.05). Larger grafts produced additional strain in the ligament, but were not significant. The authors conclude that grafts >6 mm have no additional corrective capacity without compromising the long plantar ligament. Either larger graft size or loss of the long plantar ligament could compromise the intrinsic stability of the lateral column of the foot. These findings may decrease the incidence of complications with this procedure, specifically lateral column pain, instability, and calcaneocuboid arthrosis.

Eccentric muscle contractions: their contribution to injury, prevention, rehabilitation, and sport

Muscles operate eccentrically to either dissipate energy for decelerating the body or to store elastic recoil energy in preparation for a shortening (concentric) contraction. The muscle forces produced during this lengthening behavior can be extremely high, despite the requisite low energetic cost. Traditionally, these high-force eccentric contractions have been associated with a muscle damage response. This clinical commentary explores the ability of the muscle-tendon system to adapt to progressively increasing eccentric muscle forces and the resultant structural and functional outcomes. Damage to the muscle-tendon is not an obligatory response. Rather, the muscle can hypertrophy and a change in the spring characteristics of muscle can enhance power; the tendon also adapts so as to tolerate higher tensions. Both basic and clinical findings are discussed. Specifically, we explore the nature of the structural changes and how these adaptations may help prevent musculoskeletal injury, improve sport performance, and overcome musculoskeletal impairments.

The roles of growth factors in tendon and ligament healing

Tendon healing is a complex and highly-regulated process that is initiated, sustained and eventually terminated by a large number and variety of molecules. Growth factors represent one of the most important of the molecular families involved in healing, and a considerable number of studies have been undertaken in an effort to elucidate their many functions. This review covers some of the recent investigations into the roles of five growth factors whose activities have been best characterised during tendon healing: insulin-like growth factor-I (IGF-I), transforming growth factor beta (TGFbeta), vascular endothelial growth factor (VEGF), platelet-derived growth factor (PDGF), and basic fibroblast growth factor (bFGF). All five are markedly up-regulated following tendon injury and are active at multiple stages of the healing process. IGF-I has been shown to be highly expressed during the early inflammatory phase in a number of animal tendon healing models, and appears to aid in the proliferation and migration of fibroblasts and to subsequently increase collagen production. TGFbeta is also active during inflammation, and has a variety of effects including the regulation of cellular migration and proliferation, and fibronectin binding interactions. VEGF is produced at its highest levels only after the inflammatory phase, at which time it is a powerful stimulator of angiogenesis. PDGF is produced shortly after tendon damage and helps to stimulate the production of other growth factors, including IGF-I, and has roles in tissue remodelling. In vitro and in vivo studies have shown that bFGF is both a powerful stimulator of angiogenesis and a regulator of cellular migration and proliferation. This review also covers some of the most recent studies into the use of these molecules as therapeutic agents to increase the efficacy and efficiency of tendon and ligament healing. Studies into the effects of the exogenous application of TGFbeta, IGF-I, PDGF and bFGF into the wound site singly and in combination have shown promise, significantly decreasing a number of parameters used to define the functional deficit of a healing tendon. Application of IGF-I has been shown to increase in the Achilles Functional Index and the breaking energy of injured rat tendon. TGFbeta and PDGF have been shown separately to increase the breaking energy of healing tendon. Finally, application of bFGF has been shown to promote cellular proliferation and collagen synthesis in vivo.

Celiac artery compression by the median arcuate ligament: a pitfall of end-expiratory MR imaging

PURPOSE

To measure the prevalence and degree of celiac artery compression during breath-hold imaging at end inspiration and end expiration in patients referred to undergo magnetic resonance (MR) imaging of the abdomen for reasons unrelated to intestinal ischemia.

MATERIALS AND METHODS

A series of 100 patients underwent routine MR imaging of the upper abdomen at 1.5 T; imaging included multiple dynamic contrast-enhanced fat-suppressed transverse three-dimensional spoiled gradient-echo acquisitions (3.6-4.5/1.5-1.9 [repetition time msec/echo time msec], 12 degrees flip angle). Arterial phase acquisitions were obtained during suspended respiration at end expiration (n = 50) or at end inspiration (n = 50), and venous phase acquisitions were obtained at the opposite respiratory phase. Two radiologists, blinded to patient identity and the phase of respiration, independently assessed the degree of narrowing on reconstructed oblique sagittal images. Radiologists reached consensus in 97 patients, who formed the cohort for this study. The percentage of stenosis of the celiac artery relative to its origin and the angle formed by the proximal celiac artery and the aorta were also measured in all patients. This angle and the arcsine transformation of the percentage of stenosis were compared for the two respiratory phases by using a paired Student t test. chi2 analysis was used to evaluate whether the degree of narrowing was independent of the breath-hold protocol that was used.

RESULTS

In total, 55 (57%) of 97 patients had at least mild artery narrowing at end expiration, of whom 40 (73%) had less narrowing at end inspiration and 11 (20%) had no change. The average percentage of stenosis at end expiration (21% +/- 16) was significantly higher than that at end inspiration (11% +/- 11; P <.001). At end expiration, the average celiac artery angle was significantly lower in patients with mild to severe narrowing (41 degrees +/- 19) than in those without narrowing (50 degrees +/- 19; P <.03).

CONCLUSION

Accentuation of celiac artery compression at end expiration can give rise to a potential pitfall of breath-hold abdominal imaging. When compression is suspected, imaging should be performed during inspiration.

A study of pelvic ligament strength

OBJECTIVES

To measure the strength at tearing of pelvic ligaments used in the cure of prolapse and urinary incontinence.

MATERIAL AND METHODS

We performed our measurements on pelvis ligaments from cadaveric specimens. We dissected 29 human female pelvis cadavers of which storage conditions differed. Ten were frozen, 10 fresh and 9 were stored in formalin. In each cadaver we dissected pre-vertebral ligaments at promontory and right and left symmetrical ligaments. These were the iliopectineal, sacrospinous and arcus tendineus of pelvic fascia. A subjective clinical evaluation of the ligament properties was performed by visual observation as well as finger palpation. Ligaments were classified into three groups. Group A contained high quality ligaments, in terms of thickness and apparent strength following finger palpation. Ligaments of doubtful quality were classified in group B and low apparent quality ligaments in group C. Then the ligaments were stitched by a suture taking the entire ligament and a force was applied on the vagina axis until tearing. The device used for strength measurement during traction was a SAMSON type force gauge, model EASY, serial number SMS-R-ES 300N manufactured by Andilog that was developed for the purpose of our study. Measurements were given in Newton (N).

RESULTS

There was a great variability in the values obtained at tearing with minimal values at around 20N and maximal values at 200N. Individually measured, ligament strength varied between individuals, and for the same patient between the type of ligaments and the side. The pre-vertebral ligament was on average the strongest. There was no significant difference according to the storage condition except for the pre-vertebral ligament in formalin cadavers. For bilateral ligaments, there was no difference between the left and right side. The iliopectineal ligament was statistically significantly stronger than the sacrospinous and arcus tendineus of pelvic fascia. There was a correlation between subjective evaluation and objective strength measurements.

DISCUSSION

No papers have been published on the strength of pelvic ligaments at tearing. These are however routinely used in the cure of prolapse and urinary incontinence. Our results show that there is a great variability in strength between individuals, and for a same patient between the types of ligaments and side. These observations could explain some of the surgical intervention failures and demonstrate the importance of per-operative strength evaluation. Per-operative subjective evaluation of strength is related to objective measurements and could be used to determine the type of ligaments to be used for surgical suspension. Freezing does not damage pre-vertebral ligament strength and further studies are required to evaluate elasticity of pelvic ligaments.

[Biomechanics of stress distribution and resistance of biological tissues: why use prostheses for the treatment of genital prolapse?]

BACKGROUND

Solidity and elasticity are the two main biomechanical properties of pelvic tissues involved in surgical cure of genital prolapse-prevertebral, pectinate, and sacrospinal ligaments, tendinous arcs of the pelvic fascia, vaginal tissue. We report data in the literature and personal studies concerning these autologous biological tissues.

MATERIAL AND METHODS

The resistance of pelvic tissues was tested on 29 cadavers. Measurements were also made on two 2-cm samples of vaginal tissue obtained during vaginal route surgery for prolapse cure in 20 menopaused women. Stress tests were conducted to determine resistance and level of rupture.

RESULTS

There was a wide variability in ligament resistance, ranging from a minimum of 22 Newtons to a maximum to the order of 200 Newtons. Results varied greatly from one woman to another and also between the two sides in the same woman. The prevertebral ligament exhibited the greatest resistance. The pectinate ligament was significantly more resistant than the sacrospinal ligaments and the tendinous arcs of the pelvic fascia. There was a significant relationship between the subjective assessment of ligament quality and objective measurements of resistance. For vaginal tissues, resistance varied greatly from 12 Newtons to a maximum to the order of 76 Newtons. Flexion values ranged from 14 to 130 Newtons.

CONCLUSION

Our findings illustrate pelvic tissue failure observed in patients with genital prolapse. Individual maximal resistance of the pelvic ligaments is vary variable, between ligaments and between subjects, and even between sides in a given subject. Pelvic ligaments used for cure of genital prolapse are moderately resistant with wide interindividual variability. The mechanical properties of vaginal tissue are also very variable, illustrating why these tissues may exhibit a certain resistance against dissociation when exposed to loading but much less resistance when exposed to traction by a surgical suture. These findings suggest a revision of classical surgical procedures.

The effect of plantar fascia release on strain in the spring and long plantar ligaments

The effect of plantar fascia release on strain in the spring and long plantar ligaments was investigated in 11 cadaveric feet. Strain gauges were placed in the spring and long plantar ligaments of each specimen, and cyclic axial loading was applied until reproducible hysteresis curves were observed in the ligaments before and after plantar fascia release. After release of the plantar fascia, the average strain observed in the spring ligaments at 920N of axial load increased by 52% (p < .001) and in the long plantar ligaments by 94% (p = .04). Longer resting lengths of the ligaments were also observed. Release of the plantar fascia significantly changed force distributions in the foot which may explain the development of deformities and symptoms observed clinically following this procedure.

Neuromuscular dysfunction elicited by cyclic lumbar flexion

An attempt was made to develop an in vivo model that could explain the neurophysiological and biomechanical processes active in the development of the idiopathic low back disorder common in workers who perform repetitive lifting tasks in industry. Passive cyclic flexion of the feline lumbar spine at 0.1 HZ for 20 min resulted in creep of the supraspinous ligament and other lumbar viscoelastic tissues as well as spasms superimposed on a decreasing electromyogram (EMG) elicited reflexly from the multifidus muscles. Rest for 7 h did not allow full recovery of the viscoelastic creep; the multifidus EMG gradually increased with initial and delayed hyperexcitability. Increasing the peak load of the cyclic flexion resulted in larger creep in the passive tissues and required a longer time for recovery of reflex EMG activity and longer delayed hyperexcitability, but development of spasms and hyperexcitability was unaffected. It is conceivable that damage to the viscoelastic tissues elicits an inflammatory process that in turn triggers a transient neuromuscular disorder. The present findings provide a biomechanical and neurophysiological explanation for a common idiopathic low back disorder as well as for the development of a cumulative trauma disorder often seen in workers engaged in repetitive lumbar flexion.

Carpal instability in rheumatoid wrists

This study was conducted to identify patterns of carpal instability in the rheumatoid wrist. One hundred patients with proven rheumatoid arthritis were randomly chosen, and posteroanterior and lateral radiographs of right wrists were taken. The most common isolated pattern was volar intercalated segmental instability, apparent in 16 wrists, while nine wrists had scapholunate dissociations. Larsen grading scores revealed a correlation between disease duration, carpal height ratio, and ulnar translocation index. In the early stages of disease, the scapholunate angle was significantly increased and the lunate rotated volarly due to loosening of the intrinsic carpal ligament. In later phases, the capitolunate angle significantly increased and the capitate rotated dorsally. Patterns of carpal instability in rheumatoid wrists seem to be complicated, involving combined laxity of the intrinsic and extrinsic carpal ligaments.

Hindlimb unloading alters ligament healing

We investigated the hypothesis that hindlimb unloading inhibits healing in fibrous connective tissue such as ligament. Male rats were assigned to 3- and 7-wk treatment groups with three subgroups each: sham control, ambulatory healing, and hindlimb-suspended healing. Ambulatory and suspended animals underwent surgical rupture of their medial collateral ligaments, whereas sham surgeries were performed on control animals. After 3 or 7 wk, mechanical and/or morphological properties were measured in ligament, muscle, and bone. During mechanical testing, most suspended ligaments failed in the scar region, indicating the greatest impairment was to ligament and not to bone-ligament insertion. Ligament testing revealed significant reductions in maximum force, ultimate stress, elastic modulus, and low-load properties in suspended animals. In addition, femoral mineral density, femoral strength, gastrocnemius mass, and tibialis anterior mass were significantly reduced. Microscopy revealed abnormal scar formation and cell distribution in suspended ligaments with extracellular matrix discontinuities and voids between misaligned, but well-formed, collagen fiber bundles. Hence, stress levels from ambulation appear unnecessary for formation of fiber bundles yet required for collagen to form structurally competent continuous fibers. Results support our hypothesis that hindlimb unloading impairs healing of fibrous connective tissue. In addition, this study provides compelling morphological evidence explaining the altered structure-function relationship in load-deprived healing connective tissue.

Wrist kinetics after luno-triquetral dissociation: the changes in moment arms of the flexor carpi ulnaris tendon

Wrist biomechanics after luno-triquetral (LT) dissociation is important for understanding the clinical sequelae of the disease and for determining its treatment options. The LT interosseous ligament plays an important role in stabilizing the joint and damage to the ligament would be expected to significantly increase moment arms of tendon of the flexor carpi ulnaris (FCU), the principal ulnar wrist flexor. We investigated the changes in moment arms of FCU tendon after various amounts of sectioning of the ligaments proven to be associated with LT dissociation. In six fresh frozen cadaveric upper extremities, excursions of the FCU tendon were recorded simultaneously with wrist joint angulation during wrist flexion-extension and radioulnar deviation. Tendon excursions were measured in intact wrists, in wrists with sectioning of the dorsal portion of the LT interosseous ligament, in wrists with sectioning of the entire LT interosseous ligament, and finally in wrists with further sectioning of the dorsal radiotriquetral and intercarpal ligaments. Moment arms of the tendon were calculated from tendon excursions and joint motion angulations and expressed as percentage changes from those in the intact wrist. During wrist flexion-extension, moment arms of the FCU tendon after sectioning of the entire LT interosseous ligament and after sectioning of the two capsular ligaments were 112 +/- 7% and 114 +/- 8%, respectively; these values were significantly greater than those in the intact wrist. During radioulnar deviation, the moment arms were 114 +/- 11% after sectioning of the dorsal portion of the LT interosseous ligament, 134 +/- 15% after sectioning of the entire ligament, and 153 +/- 18% after sectioning of the capsular ligaments, again being significantly greater than the normal wrist. Increase in moment arms of the FCU tendon after loss of integrity of the LT interosseous ligament and dorsal capsular ligaments may contribute to clinical sequelae of LT dissociation and difficulty in treating this disorder.

Urogynecologic ultrasound is a useful aid in the assessment of female stress urinary incontinence--a prospective study with TVT procedure

The aims of the study were to study the suitability of certain urogynecologic ultrasound parameters, e.g. descent of the urethrovesical (UV) junction on Valsalva, posterior urethrovesical (PUV) angle both at rest and on Valsalva, and funneling of the vesical neck, in the pre- and postoperative assessment of stress urinary incontinence (SUI) and to evaluate the efficacy and safety of tension-free vaginal tape (TVT) for the surgical treatment of SUI. Forty-six consecutive women (mean age 61 years) with symptoms of SUI underwent TVT placement. The patients were examined prior to and on average of 11 weeks after the operation with perineal ultrasound. An upright coughing test on standing was performed every time. Operative success rate was 94% in this series. Urogynecologic perineal ultrasound examination seemed strongly to support an anamnestic diagnosis of genuine SUI, and TVT proved to be a safe and effective ambulatory procedure for the surgical treatment of SUI.

Clinical presentation of wandering spleen

BACKGROUND

Wandering spleen (WS) is an uncommon condition with a variety of clinical presentations.

METHODS

The medical files of 5 children who underwent operation for WS in the authors' department during the period 1996 through 2000 were retrospectively reviewed.

RESULTS

Splenic salvage procedures (retroperitoneal splenopexy) were performed in 4 patients. One patient underwent splenectomy because of splenic necrosis.

CONCLUSIONS

Early diagnosis and surgical treatment is mandatory to prevent complications. Every effort should be made to preserve the spleen, especially among the pediatric population, and splenopexy is the procedure of choice even in the asymptomatic patient.

Avulsion transverse ligament injuries in children: successful treatment with nonoperative management. Report of three cases

Neck injuries in children most commonly affect the upper cervical spine. Injuries of the transverse ligament and its attachments may result in C1-2 instability, but the optimum form of treatment is unknown. Three patients, who ranged in age from 5 to 11 years, sustained transverse atlantal ligament injuries with unilateral avulsion fracture of the osseous tubercle of C-1. One child was injured in a fall and two were involved in motor vehicle accidents. Although all patients presented with neck pain, none exhibited neurological deficits. Plain radiography demonstrated no evidence of osseous injury, but an increased predental interval was noted in each case. Computerized tomography (CT) scanning demonstrated the avulsion fractures, and magnetic resonance imaging revealed evidence of soft-tissue injuries in the occipital-C2 ligamentous complex. All children were managed with external immobilization (halo vest in two and a Sterno-Occipito-Mandibular Immobilizer brace in one), for 6 to 12 weeks. Follow-up CT scanning demonstrated reattachment of the avulsed osseous tubercle, and dynamic cervical spine radiographs revealed the absence of C1-2 instability. The results of these cases suggest a role for external immobilization in the treatment of osseous avulsion injuries of the transverse atlantal ligament in children.

Effects of aging and spinal degeneration on mechanical properties of lumbar supraspinous and interspinous ligaments

BACKGROUND CONTEXT

The effects of aging and spinal degeneration on the mechanical properties of spinal ligaments are still unknown, although there have been several studies demonstrating those of normal spinal ligaments.

PURPOSE

To investigate the mechanical properties of the human posterior spinal ligaments in human lumbar spine, and their relation to age and spinal degeneration parameters.

STUDY DESIGN/SETTING

Destructive uniaxial tensile tests were performed on the human supraspinous and interspinous ligaments at L4-5 level. Their mechanical properties were compared with age and spinal degeneration using several imaging modalities.

PATIENT SAMPLE

Twenty-four patients with lumbar degenerative diseases on whom posterior surgeries were performed, with the age ranging from 18 to 85 years.

OUTCOME MEASURES

The ultimate load and elastic stiffness as structural properties, the degree of disc degeneration, range of segmental motion, the disc height, disc space narrowing ratio and degree of facet degeneration as the parameters of spinal degeneration.

METHODS

Twenty-four supraspinous and interspinous ligaments at the L4-5 level were obtained from posterior surgeries of patients with lumbar degenerative disease. The mechanical tests of bone-ligament-bone complexes were performed in a uniaxial tensile fashion with a specially designed clamp device. The ultimate load and elastic stiffness were calculated as structural properties. The degree of disc degeneration, range of segmental motion, the disc height, disc space narrowing ratio and degree of facet degeneration were examined by using radiographs, computed tomography and magnetic resonance imaging.

RESULTS

The average and SD value of ultimate load, elastic stiffness, tensile strength and elastic modulus were 203+/-102.9 N, 60.6+/-36.7 N/mm, 1.2+/-0.6 Mpa and 3.3+/-2.1 Mpa, respectively. A significant negative correlation was found between age and tensile strength (p= 0.02). The specimens with facet degeneration showed lower values in tensile strength and elastic modulus than those without facet degeneration (p<0.04). However, no correlation was found between disc-related parameters and tensile strength.

CONCLUSIONS

The mechanical strength of human lumbar posterior spinal ligaments decreases with age and facet degeneration, particularly in the ligament substance.