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Selected AbstractsThe intertarsal joint of the ostrich (Struthio camelus): Anatomical examination and function of passive structures in locomotionJOURNAL OF ANATOMY, Issue 6 2009Nina U. Schaller Abstract The ostrich (Struthio camelus) is the largest extant biped. Being flightless, it exhibits advanced cursorial abilities primarily evident in its characteristic speed and endurance. In addition to the active musculoskeletal complex, its powerful pelvic limbs incorporate passive structures wherein ligaments interact with joint surfaces, cartilage and other connective tissue in their course of motion. This arrangement may enable energy conservation by providing joint stabilisation, optimised limb segment orientation and automated positioning of ground contact elements independently of direct muscle control. The intertarsal joint is of particular interest considering its position near the mid-point of the extended limb and its exposure to high load during stance with significant inertial forces during swing phase. Functional-anatomical analysis of the dissected isolated joint describes the interaction of ligaments with intertarsal joint contours through the full motion cycle. Manual manipulation identified a passive engage-disengage mechanism (EDM) that establishes joint extension, provides bi-directional resistance prior to a transition point located at 115° and contributes to rapid intertarsal flexion at toe off and full extension prior to touch down. This effect was subsequently quantified by measurement of intertarsal joint moments in prepared anatomical specimens in a neutral horizontal position and axially-loaded vertical position. Correlation with kinematic analyses of walking and running ostriches confirms the contribution of the EDM in vivo. We hypothesise that the passive EDM operates in tandem with a stringently coupled multi-jointed muscle-tendon system to conserve the metabolic cost of locomotion in the ostrich, suggesting that a complete understanding of terrestrial locomotion across extinct and extant taxa must include functional consideration of the ligamentous system. [source] Using real-time MRI to quantify altered joint kinematics in subjects with patellofemoral pain and to evaluate the effects of a patellar brace or sleeve on joint motionJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 5 2009Christine E. Draper Abstract Abnormal patellofemoral joint motion is a possible cause of patellofemoral pain, and patellar braces are thought to alleviate pain by restoring normal joint kinematics. We evaluated whether females with patellofemoral pain exhibit abnormal patellofemoral joint kinematics during dynamic, weight-bearing knee extension and assessed the effects of knee braces on patellofemoral motion. Real-time magnetic resonance (MR) images of the patellofemoral joints of 36 female volunteers (13 pain-free controls, 23 patellofemoral pain) were acquired during weight-bearing knee extension. Pain subjects were also imaged while wearing a patellar-stabilizing brace and a patellar sleeve. We measured axial-plane kinematics from the images. Females with patellofemoral pain exhibited increased lateral translation of the patella for knee flexion angles between 0°and 50° (p,=,0.03), and increased lateral tilt for knee flexion angles between 0° and 20° (p,=,0.04). The brace and sleeve reduced the lateral translation of the patella; however, the brace reduced lateral displacement more than the sleeve (p,=,0.006). The brace reduced patellar tilt near full extension (p,=,0.001), while the sleeve had no effect on patellar tilt. Our results indicate that some subjects with patellofemoral pain exhibit abnormal weight-bearing joint kinematics and that braces may be effective in reducing patellar maltracking in these subjects. Published by Wiley Periodicals, Inc. J Orthop Res 27: 571,577, 2009 [source] Knee biomechanics after UKA and its relation to the ACL,a robotic investigationJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 4 2006Jeremy F. Suggs Abstract Unicompartmental knee arthroplasty (UKA) has regained popularity in recent years. However, limited data exist on how UKA affects knee biomechanics. The role of the anterior cruciate ligament (ACL) after fixed bearing UKA remains controversial. In this study, a robotic testing system was used to apply a quadriceps/hamstrings load to cadaveric knee specimens in the intact state, after medial UKA, and after transection of the ACL in UKA. The load was applied to the knee from full extension to 120° of flexion in 30° increments. UKA generally did not affect anterior,posterior (AP) femoral position, but did cause external tibial rotation and variations in varus,valgus rotation compared to the intact knee. ACL transection after UKA shifted the femur posteriorly compared to the intact and UKA knees and increased internal tibial rotation compared to the UKA knee at low flexion. The AP motion of the articular contact position in the implant was increased after ACL transection. These data might help explain the mechanism of tibial component loosening and provide insight into further investigations of polyethylene wear in UKA. Based on the kinematic data, the ACL should be functional to provide patients the greatest opportunity for long-term success after medial UKA. © 2006 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res [source] Distribution of in situ forces in the anterior cruciate ligament in response to rotatory loadsJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 1 2004Mary T. Gabriel Abstract The anterior cruciate ligament (ACL) can be anatomically divided into anteromedial (AM) and posterolateral (PL) bundles. Current ACL reconstruction techniques focus primarily on reproducing the AM bundle, but are insufficient in response to rotatory loads. The objective of this study was to determine the distribution of in situ force between the two bundles when the knee is subjected to anterior tibial and rotatory loads. Ten cadaveric knees (50 ± 10 years) were tested using a robotic/universal forcemoment sensor (UFS) testing system. Two external loading conditions were applied: a 134 N anterior tibial load at full knee extension and 15°, 30°, 60°, and 90° of flexion and a combined rotatory load of 10 N m valgus and 5 N m internal tibial torque at 15° and 30° of flexion. The resulting 6 degrees of freedom kinematics of the knee and the in situ forces in the ACL and its two bundles were determined. Under an anterior tibial load, the in situ force in the PL bundle was the highest at full extension (67 ± 30 N) and decreased with increasing flexion. The in situ force in the AM bundle was lower than in the PL bundle at full extension, but increased with increasing flexion, reaching a maximum (90 ± 17 N) at 60° of flexion and then decreasing at 90°. Under a combined rotatory load, the in situ force of the PL bundle was higher at 15° (21 ± 11 N) and lower at 30° of flexion (14 ± 6 N). The in situ force in the AM bundle was similar at 15° and 30° of knee flexion (30 ± 15 vs. 35 ± 16 N, respectively). Comparing these two external loading conditions demonstrated the importance of the PL bundle, especially when the knee is near full extension. These findings provide a better understanding of the function of the two bundles of the ACL and could serve as a basis for future considerations of surgical reconstruction in the replacement of the ACL. © 2003 Orthopaedic Research Society. Published by Elsevier Ltd. All rights reserved. [source] Kinematics of the knee at high flexion angles: An in vitro investigationJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 1 2004Guoan Li Abstract Restoration of knee function after total knee, meniscus, or cruciate ligament surgery requires an understanding of knee behavior throughout the entire range of knee motion. However, little data are available regarding knee kinematics and kinetics at flexion angles greater than 120° (high flexion). In this study, 13° cadaveric human knee specimens were tested using an in vitro robotic experimental setup. Tibial anteroposterior translation and internal,external rotation were measured along the passive path and under simulated muscle loading from full extension to 150° of flexion. Anterior tibial translation was observed in the unloaded passive path throughout, with a peak of 31.2 ± 13.2 mm at 150°. Internal tibial rotation increased with flexion to 150° on the passive path to a maximum of 11.1 ± 6.7°. The simulated muscle loads affected tibial translation and rotation between full extension and 120° of knee flexion. Interestingly, at high flexion, the application of muscle loads had little effect on tibial translation and rotation when compared to values at 120°. The kinematic behavior of the knee at 150° was markedly different from that measured at other flexion angles. Muscle loads appear to play a minimal role in influencing tibial translation and rotation at maximal flexion. The results imply that the knee is highly constrained at high flexion, which could be due in part to compression of the posterior soft tissues (posterior capsule, menisci, muscle, fat, and skin) between the tibia and the femur. © 2003 Orthopaedic Research Society. Published by Elsevier Ltd. All rights reserved. [source] Does three months of nightly splinting reduce the extensibility of the flexor pollicis longus muscle in people with tetraplegia?PHYSIOTHERAPY RESEARCH INTERNATIONAL, Issue 1 2007Lisa Harvey Abstract Background and Purpose.,The extensibility of the paralysed flexor pollicis longus (FPL) muscle is an important determinant of an effective tenodesis grip in people with C6 and C7 tetraplegia. Therapists believe that splinting can reduce the extensibility of the FPL muscle and thus improve hand function. However, there remains much controversy around the optimal position of splinting and its effectiveness is yet to be verified. The aim of the present study was to determine whether a three-month thumb splinting protocol reduces extensibility of the FPL muscle in people with tetraplegia.,Method.,An assessor-blinded, within-subject, randomized controlled trial was undertaken. Twenty people with tetraplegia and bilateral paralysis of all thumb muscles were recruited from a sample of convenience. One randomly selected hand of each subject was splinted each night for three months. The splint immobilized the FPL muscle in a relatively shortened position by positioning the carpometacarpal and metacarpophalangeal joint of the thumb in flexion. The other hand remained unsplinted for the duration of the study. Carpometacarpal angle was measured with the application of a standardized torque by a blinded assessor at the beginning and end of the three-month study period. A device specifically designed for this purpose that stabilized the wrist and other joints of the thumb in full extension was used.,Results.,No subject withdrew from the study. The three-month splinting protocol had a mean treatment effect on carpometacarpal joint angle of 0° (95% CI, ,6° to 6°).,Conclusion.,Splinting the FPL muscle in a relatively shortened position each night for three months does not reduce its extensibility. Copyright © 2006 John Wiley & Sons, Ltd. [source] | ||||||||||