Flexural-torsional buckling initiates idiopathic scoliosis.

Initiation of the spinal deformity in idiopathic scoliosis (IS) has been attributed to an abnormal pattern of spinal growth during development. However, recent findings suggest that the earliest observable event in the pathogenesis of IS is a change in the shape of intervertebral discs with alterations in the shape of vertebrae being considered a secondary event. Starting from the previous description of the spinal deformity in IS as 'buckling' of the spine a new hypothesis describing the initial spinal deformity in IS as flexural-torsional buckling, a three-dimensional type of failure of axially loaded columns, is proposed. According to the new hypothesis the initiating event (the earliest observable event) in IS is flexural-torsional buckling developing from the flexible parts (intervertebral discs and ligaments) of the affected spinal motion segments. Since flexural-torsional buckling occurs in columns with a cross-section of one axis of symmetry characterised by a much greater in-plane than out-of-plane bending stiffness the new hypothesis predicts that the initiating condition (the condition promoting the initiation) of IS is 'flexibility anisotropy' namely significantly higher bending stiffness in lateral bending than bending stiffness in flexion-extension of a part of the spine. The parameter of 'flexibility anisotropy' as a factor for initiation of IS has never been suggested or tested before. The present hypothesis has implications in the research on the pathogenesis of IS as well as in the development of new methods for its treatment.

Minimally invasive therapeutic interventional procedures in the spine: an evidence-based review.

This chapter evaluates the current evidence on common minimally invasive therapeutic spinal procedures based on the Levels of Evidence and Grades of Recommendation developed by the Centre for Evidence-Based Medicine (Oxford, United Kingdom). The results of the evaluation of current clinical evidence allow the following recommendations to be made: epidural adhesiolysis performed repeatedly every 3 months to 4 months is effective in the "post lumbar laminectomy" syndrome; epidural steroid injections may provide only short-term relief from pain in lumbar radiculopathy but have no long-term effect; selective nerve root injections of corticosteroids have no therapeutic effect on the long-term natural history of radiculopathy symptoms; intra-articular facet joint injections of corticosteroids have no therapeutic effect on lower back pain (grade of recommendation: A). Furthermore, percutaneous vertebroplasty and balloon kyphoplasty provide immediate pain relief from osteoporotic spinal fractures but no significant long-lasting benefit (grade of recommendation: B). Finally, there is limited evidence (grade of recommendation: C) of the value of medial branch (facet) neurotomy, sacroiliac joint injection of steroids, and intradiscal electrothermal therapy, as well as of the advantages of percutaneous endoscopic lumbar discectomy over open microdiscectomy. As the level of evidence is generally low, more prospective randomized-controlled studies are needed to establish the value of the considered methods.

Factors affecting the timing of recovery from whiplash neck injuries: study of a cohort of 134 patients pursuing litigation.

INTRODUCTION: A cohort of 134 patients presenting in medico-legal practice with whiplash neck injury following a motor vehicle accident was studied prospectively by personal interviewing. MATERIALS AND METHODS: Injury- and patient-related factors with possible influence to the timing of recovery were analysed with univariate and multivariate statistical methods. RESULTS: Logistic regression showed significant association between high physical demand patient occupation and recovery within 6 months from injury (P = 0.036, coefficient 1.5, odds ratio 4.47) while initiation of physiotherapy treatment was associated with prolongation of symptoms for more than 6 months following injury (P < 0.001, coefficient -2.6, odds ratio 0.08). An association between development of arm pain (P = 0.01), upper limb numbness or paraesthesia (P = 0.03) and bilateral trapezius pain (P = 0.04) and persistence of whiplash-related symptoms was also observed. These findings must be taken into account in evaluation and treatment of patients with acute whiplash injuries pursuing litigation.

Correlation between wrist loads and the distal radius volar tilt angle.

BACKGROUND: Based on the phenomenon of bone adaptation to mechanical stimuli (Wolff's law) this study investigates a previously unreported correlation between the maximum wrist joint reaction force and the volar tilt angle of the distal radius. METHODS: Free body analysis of the sagittal-plane forces acting on the supinated distal radius during lifting and radiographic measurements in thirty normal wrists are used to analyse the correlation between the theoretically calculated maximum wrist joint reaction force and the radiographically measured volar tilt angle. FINDINGS: Non-statistically significant difference (p=0.33, 95% confidence interval -0.64 degrees to 0.22 degrees) and statistically significant correlation (R(2)=0.74, r=0.86, p<0.001) between the angle of the maximum wrist force and the volar tilt angle of the distal radius and inverse relationship between the volar tilt angle and the magnitude of the maximum wrist force (R(2)=0.71, r=-0.84, P<0.001) were found. INTERPRETATION: The radiographically measured volar tilt angle of the distal radius appears not to differ significantly from the theoretically calculated angle of the maximum wrist joint reaction force, a possible explanation for the phylogenetical development of the volar tilt angle. Also, an inverse relationship between the volar tilt angle and the magnitude of the maximum joint reaction force was observed suggesting that wrists characterized by a low volar tilt angle may be subjected during lifting activities to maximum joint reaction forces up to 50% higher than those in wrists with a high volar tilt and emphasising the importance of accurate restoration of the volar tilt during treatment of all distal radius fractures.

Secondary patellar resurfacing in total knee arthroplasty: results of multivariate analysis in two case-matched groups.

Although patellofemoral symptoms after patellar-retaining knee arthroplasty are common, no evidence has been published in the literature on the potential benefit from patellar resurfacing at a later stage. This study evaluates the effect of secondary (delayed) patellar resurfacing using comparisons between 2 case-matched groups of patients with primary and secondary patellar resurfacing. Furthermore, multivariate statistical methods were applied to study factors that may influence the final outcome. Our results suggest that although significant clinical improvement was seen after delayed patella resurfacing, the outcome of secondary patellar resurfacing is inferior to that expected for a similar group of patients with primary resurfacing. Furthermore, the timing (delay period) of the secondary resurfacing procedure appears to negatively affect the final outcome. This suggests that secondary patellar resurfacing, when indicated, should be considered at an early stage.

Access to the medullary canal in closed antegrade femoral nailing: a technical report.

Although general recommendations exist regarding the correct placement of the skin incision and the direction of deep dissection for closed antegrade intramedullary nailing of the femur, in surgical practice simultaneously establishing the correct entry point and exact direction for insertion of the entry instrument in the lateral (sagittal) plane may be difficult. This is due to sub-optimal radiographic images in the lateral plane as a result of the overlying shadows of the pelvis, variations in the degree of rotation of the femur during patient positioning and fracture reduction manoeuvres, variations in the degree of anterior bowing of the femoral shaft and the anatomy of the greater trochanter, and deviations of the plane of deep dissection caused by the glutei muscle fibres. This may lead to the need for several attempts with increased damage to the glutei muscles, high exposure to radiation and the risk of an iatrogenic fracture. The present technical note describes a simple method for swift, easy and accurate access to the medullary canal during closed antegrade femoral nailing.

Computer Modeling in Bone Research.

Computer modeling has had an undoubtedly enormous impact on the field of bone research in recent years. Development of advanced computer based models has permitted researchers to explore a vast area of musculoskeletal science from the complex biophysical stimuli at the cellular level to the mechanical behavior of heterogeneous skeletal structures. Furthermore, computer modeling has given significant impetus to the impressive progress of modern bone implant development. With recent advances in computers, faster hardware and increasingly sophisticated software, the prospects for the future of computer-based bone research appear more exciting than ever.