Development of an image-based technique to examine joint congruency at the elbow

Identifying joint contact in articular joints is important for both the biomechanical investigation of joint mechanics and the study of osteoarthritis. The purpose of this study is to develop a proximity mapping technique to non-invasively determine joint congruency, as a surrogate of joint contact. To illustrate the capabilities of this algorithm, a cadaveric upper extremity was positioned at varying degrees of elbow flexion. This technique was validated using a gold standard experimental casting technique. The pattern of the cast showed an excellent agreement with the generated proximity map using the inter-bone distance algorithm. The results from this study agree with the results of previous studies examining joint contact at the elbow both in the location and in the tracking of the joint contact throughout elbow flexion. Ultimately, this technique will lead to an increased understanding of the effect of malalignment and instability of the joint on contact mechanics.     

Massive infectious soft-tissue injury: diagnosis and management of necrotizing fasciitis and purpura fulminans

Learning Objectives: After studying the article, the participant should be able to: 1. Describe the most common bacteriology of necrotizing fasciitis and purpura fulminans. 2. Describe the "finger test" in the diagnosis of necrotizing fasciitis. 3. Discuss the three presentation patterns of necrotizing fasciitis. 4. Discuss the pathophysiology of acute infectious purpura fulminans. 5. Discuss the treatment strategies for necrotizing fasciitis and purpura fulminans, including the use of artificial skin substitutes.Necrotizing fasciitis and purpura fulminans are two destructive processes that involve skin and soft tissues. The plastic and reconstructive surgeon may frequently be called on for assistance in the diagnosis, treatment, and/or reconstruction of patients with these conditions. Understanding the natural history and unique characteristics of these processes is essential for effective surgical management and favorable patient outcome. A comprehensive review of the literature pertaining to these two conditions is presented, outlining the different pathophysiologies, the patterns of presentation, and the treatment strategies necessary for successful management of these massive infectious soft-tissue diseases.     

Teleconsultation with the mobile camera-phone in digital soft-tissue injury: a feasibility study

The purpose of this study was to examine the feasibility of teleconsultation using a mobile camera-phone to evaluate the severity of digital soft-tissue injury and to triage the injury with regard to management recommendations. With a built-in 110,000-pixel digital camera, pictures of the injured digit(s) or radiograph were taken by surgical residents in the emergency room and transmitted to another camera-phone to be viewed by the remote consultant surgeon. A brief medical and trauma history of each patient was relayed also by mobile phone. The consultant surgeon then reviewed all of these patients in the emergency room shortly after the initial telemedicine referral. Separate triaging for each digital injury into three groups was recorded during remote teleconsultation and according to actual treatment by the attending surgeon as follows: group I, the injury could be managed with conservative treatment, such as secondary intention wound healing, or primary closure with or without bone shortening; group II, skin grafting or local flap coverage was required for management of the injury; and group III, microsurgery such as replantation or free flap coverage was necessary to deal with the injury. Later, triaging was also performed individually by three junior plastic residents according to image review and patient referral information. Teleconsultation through a mobile camera-phone was performed for 45 patients with injuries of 81 digits from January to May of 2003. Of these 81 digital injuries, there were 12 cases (15 percent) where disagreement of triaging occurred between the teleconsultation and the actual treatment by the attending surgeon. In image reviewing, there was 79 percent sensitivity and 71 percent specificity in remote diagnosis of the skin defect and 76 percent sensitivity and 75 percent specificity in remote identification of the bone exposure regarding the concordance of opinions of all three surgeons; there was significant discordance in triaging in 20 cases (25 percent), and the difference in triaging was partly attributed to the inability to show instances of tiny exposed digital bone or tendon in some cases under the low-resolution digital image and the situation of a bloody oozing wound. In some cases, the difficulty in evaluating the probability of primary closure of severely avulsed skin edges or the probability of executing replantation for finger amputation also contributed to different triaging outcomes. Two neglected diagnoses of transected digital nerves were found and influenced triaging, highlighting the importance of on-site physical examination during teleconsultation. The telemedicine system using a mobile camera-phone based on the global system for mobile communication is feasible and valuable for early diagnosis and triaging of digital soft-tissue injury in emergency cases, with on-line verbal communication and review of the transmitted captured image. This system has the advantages of ease of use, low cost, high portability, and mobility. With advances in hardware for digital imaging and transmission technology and the development of the third-generation advanced mobile phone system in the foreseeable future, this system has potential for future applications in telemedicine and telecare.     

Strategies used to stabilize the elbow joint challenged by inverted pendulum loading

The stiffness of activated muscles may stabilize a loaded joint by preventing perturbations from causing large displacements and injuring the joint. Here the elbow muscle recruitment patterns were compared with the forearm loaded vertically (a potentially unstable inverted pendulum configuration) and with horizontal loading. Eighteen healthy subjects were studied with the forearm vertical and supinated and the elbow flexed approximately 90 degrees. In the first experiment EMG electrodes recorded activity of biceps, triceps, and brachioradialis muscles for joint torques produced (a) by voluntarily exerting a horizontal force isometrically (b) by voluntarily flexing and extending the elbow while the forearm was loaded vertically with 135N. The relationship between the EMG and the torque generated was quantified by the linear regression slope and zero-torque intercept. In a second experiment a vertical load increasing linearly with time up to 300N was applied.In experiment 1 the EMG-torque relationships for biceps and triceps had an intercept about 10% of maximum voluntary effort greater with the vertical compared to the horizontal force, the inverse was found for Brachioradialis, but the EMG-torque slopes for both agonist and antagonistic muscles were not different. In experiment 2 there were 29 trials with minimal elbow displacement and all the three muscles activated on the order of 11% of maximum activation to stabilize the elbow; 19 trials had small elbow extension and 14 trials small flexion requiring altered muscle forces for equilibrium; 7 trials ended in large unstable displacement or early termination of the test. An analysis indicate that the observed levels of muscle activation would only provide stability if the muscles' short-range stiffness was at the high end of the published range, hence the elbow was marginally stable. The stability analysis also indicated that the small elbow extension increased stability and flexion decreased stability.     

Prescribing joint co-ordinates during model preparation to improve inverse kinematic estimates of elbow joint angles

To appropriately use inverse kinematic (IK) modelling for the assessment of human motion, a musculoskeletal model must be prepared 1) to match participant segment lengths (scaling) and 2) to align the model׳s virtual markers positions with known, experimentally derived kinematic marker positions (marker registration). The purpose of this study was to investigate whether prescribing joint co-ordinates during the marker registration process (within the modelling framework OpenSim) will improve IK derived elbow kinematics during an overhead sporting task. To test this, the upper limb kinematics of eight cricket bowlers were recorded during two testing sessions, with a different tester each session. The bowling trials were IK modelled twice: once with an upper limb musculoskeletal model prepared with prescribed participant specific co-ordinates during marker registration – MR_PC – and once with the same model prepared without prescribed co-ordinates – MR; and by an established direct kinematic (DK) upper limb model. Whilst both skeletal model preparations had strong inter-tester repeatability (MR: Statistical Parametric Mapping (SPM1D)=0% different; MR_PC: SPM1D=0% different), when compared with DK model elbow FE waveform estimates, IK estimates using the MR_PC model (RMSD=5.2±2.0°, SPM1D=68% different) were in closer agreement than the estimates from the MR model (RMSD=44.5±18.5°, SPM1D=100% different). Results show that prescribing participant specific joint co-ordinates during the marker registration phase of model preparation increases the accuracy and repeatability of IK solutions when modelling overhead sporting tasks in OpenSim.     

Physiological considerations of muscle force through the elbow joint

An analytical model for the determination of muscle forces across the elbow joint during isometric loading conditions has been developed. The model incorporates the muscle length-tension relationship, while considering the muscle architecture. Sensitivity analyses were performed to study the effects of the geometric and architectural factors of the muscles on the distribution of muscle forces.     

Computed tomography analysis of radiostereometric data to determine flexion axes after total joint replacement: Application to the elbow joint

Kinematic analysis for in vivo assessment of elbow endoprostheses requires knowledge of the exact positions of motion axes relative to bony landmarks or the prosthesis. A prosthesis-based reference system is required for comparison between individuals and studies. The primary aim of this study was to further develop an earlier described algorithm for fusion of radiostereometric analysis (RSA) data and data obtained in 3D computed tomography (CT) for application to the elbow after total joint replacement. The secondary aim was to propose a method for marking of prostheses in 3D CT, enabling definition of a prosthesis-based reference system. Six patients with elbow endoprostheses were investigated.The fusion of data made it possible to visualize the motion axes in relation to the prostheses in the 3D CT volume. The differences between two repeated positioning repetitions of the longitudinal prosthesis axis were less than 0.6° in the frontal and sagittal planes. Corresponding values for the transverse axis were less than 0.6° in the frontal and less than 1.4° (in four out of six less than 0.6°) in the horizontal plane.This study shows that by fusion of CT and RSA data it is possible to determine the accurate position of the flexion axes of the elbow joint after total joint replacement in vivo. The proposed method for implant marking and registration of reference axes enables comparison of prosthesis function between patients and studies.     

Oxygen consumption in the lungs of dogs with a closed thoracic injury

The experiments on dogs have demonstrated that lung contusion and injury of the rib cage cause the increase in overall oxygen consumption and lung oxygen consumption within the first hours after trauma. During the next week in dogs with contusion lung gradual recovery of the initial levels is observed. In convalescents with rib cage injury the indices in this period remain increased, reaching maximal level in animals with fatal outcome several hours before death. The authors believe that the early posttraumatic period in closed chest trauma is characterized by the increase in the lung oxygen consumption.     

Fusion of radiostereometric analysis data into computed tomography space: application to the elbow joint

Improvement of joint prostheses is dependent upon information concerning the biomechanical properties of the joint. Radiostereometric analysis (RSA) and electromagnetic techniques have been applied in previous cadaver and in vivo studies on the elbow joint to provide valuable information concerning joint motion axes. However, such information is limited to mathematically calculated positions of the axes according to an orthogonal coordinate system and is difficult to relate to individual skeletal anatomy. The aim of this study was to evaluate the in vivo application of a new fusion method to provide three-dimensional (3D) visualization of flexion axes according to bony landmarks. In vivo RSA data of the elbow joint's flexion axes was combined with data obtained by 3D computed tomography (CT). Results were obtained from five healthy subjects after one was excluded due to an instable RSA marker. The median error between imported and transformed RSA marker coordinates and those obtained in the CT volume was 0.22 mm. Median maximal rotation error after transformation of the rigid RSA body to the CT volume was 0.003 degrees . Points of interception with a plane calculated in the RSA orthogonal coordinate system were imported into the CT volume, facilitating the 3D visualization of the flexion axes. This study demonstrates a successful fusion of RSA and CT data, without significant loss of RSA accuracy. The method could be used for relating individual motion axes to a 3D representation of relevant joint anatomy, thus providing important information for clinical applications such as the development of joint prostheses.     

Development of an active elbow flexion simulator to evaluate joint kinematics with the humerus in the horizontal position

In-vitro simulation of active joint motion is useful to evaluate rehabilitation protocols and surgical procedures in the laboratory prior to their application in patients. To date, simulated active elbow flexion has been reliably achieved and well established only in the dependent position (humerus vertical with hand down). We have developed and evaluated the performance of a new elbow motion simulator capable of active flexion in the dependent, varus, valgus and horizontal positions. Muscle loading and motion control were achieved via a combination of motors and actuators attached to relevant tendons. Simulated active flexion was compared to passive flexion in terms of repeatability, motion pathways and joint laxity. The joint kinematics of active flexion were significantly more repeatable than passive flexion (p<0.05). Active flexion reduced varus–valgus joint laxity by 29% (supinated p<0.05) and 26% (pronated p<0.05) compared to passive flexion. Greater repeatability of simulated active flexion suggests that this mode of in-vitro testing should increase statistical power and decrease required sample sizes.     

Patterns of joint size dimorphism in the elbow and knee of catarrhine primates

Differences in body size between conspecific sexes may incur differences in the relative size and/or shape of load-bearing joints, potentially confounding our understanding of variation in the fossil record. More specifically, larger males may experience relatively greater limb joint stress levels than females, unless an increase in weight-related forces is compensated for by positive allometry of articular surface areas. This study examines variation in limb joint size dimorphism (JSD) among extant catarrhines to: 1) determine whether taxa exhibit JSD beyond that expected to simply maintain geometric similarity between sexes, and 2) test whether taxa differ in JSD (relative to body size dimorphism) with respect to differences in limb use and/or phylogeny. "Joint size" was quantified for the distal humerus and distal femur of 25 taxa. Analysis of variance was used to test for differences between sexes (in joint size ratios) and among taxa (in patterns of dimorphism). Multiple regression was used to examine differences in JSD among taxa after accounting for variation in body size dimorphism (BSD) and body size. Although degrees of humeral and femoral JSD tend to be the same within species, interspecific variation exists in the extent to which both joints are dimorphic relative to BSD. While most cercopithecoids exhibit relatively high degrees of JSD (i.e., positive allometry), nonhuman hominoids exhibit degrees of JSD closer to isometry. These results may reflect a fundamental distinction between cercopithecoids and hominoids in joint design. Overall, the results make more sense (from a mechanical standpoint) when adjustments to BSD are made to account for the larger effective female body mass associated with bearing offspring. In contrast to other hominoids, modern humans exhibit relatively high JSD in both the knee and elbow (despite lack of forelimb use in weight support). Estimates of BSD based on fossil limb bones will vary according to the extant analogue chosen for comparison.     

Quantitative trait loci analysis of osteochondrosis traits in the elbow joint of pigs

Osteochondrosis is a growth disorder in the cartilage of young animals and is characterised by lesions found in the cartilage and bone. This study identified quantitative trait loci (QTLs) associated with six osteochondrosis lesion traits in the elbow joint of finishing pigs. The traits were: thickening of the cartilage, lesion in the subchondral bone, irregular cartilage surface, fissure under the cartilage, an irregular sagittal central groove and depression of the proximal edge of the radius. The study comprised 7172 finishing pigs from crossing 12 Duroc boars with 600 crossbred Landrace × Large White sows and included 462 single nucleotide polymorphism markers. The results showed 18 QTLs exceeding the 5% genome-wide threshold. The QTLs associated with lesions in the medial part of the condylus humeri (assumed to be the four main osteochondrosis traits) were, in most cases, at common locations, whereas the QTLs associated with depression of the proximal edge of the radius in general were on the same chromosomes but at separate locations. The detected QTLs explain a large part of the genetic variation, which is promising for incorporating osteochondrosis into a breeding programme using marker-assisted selection.