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Shu B.,Stanford University | Johnston T.,Stanford University | Lindsey D.P.,Bone and Joint Center | McAdams T.R.,Stanford University
American Journal of Sports Medicine | Year: 2012

Background: Enhancing anterior-posterior (AP) stability in acromioclavicular (AC) reconstruction may be advantageous.Purpose: To compare the initial stability of AC reconstructions with and without augmentation by either (1) a novel "reverse" coracoacromial (CA) ligament transfer or (2) an intramedullary AC tendon graft.Hypothesis: Reverse CA transfer will improve AP stability compared with isolated coracoclavicular (CC) reconstruction.Study Design: Controlled laboratory study.Methods: Six matched pairs of cadaveric shoulders underwent distal clavicle resection and CC reconstruction. Displacement (mm) was measured during cyclic loading along AP (±25 N) and superior-inferior (SI; 10-N compression, 70-N tension) axes. Pairs were randomized to receive each augmentation and the same loading protocol applied.Results: Reverse CA transfer (3.71 ± 1.3 mm, standard error of the mean [SEM]; P =.03) and intramedullary graft (3.41 ± 1.1 mm; P =.03) decreased AP translation compared with CC reconstruction alone. The SI displacement did not differ. Equivalence tests suggest no difference between augmentations in AP or SI restraint.Conclusion: Addition of either reverse CA transfer or intramedullary graft demonstrates improved AP restraint and provides similar SI stability compared with isolated CC reconstruction.Clinical Relevance: Reverse CA ligament transfer may be a reasonable alternative to a free tendon graft to augment AP restraint in AC reconstruction. © 2012 American Orthopaedic Society for Sports Medicine.


Jacobs C.R.,Columbia University | Temiyasathit S.,Stanford University | Castillo A.B.,Bone and Joint Center
Annual Review of Biomedical Engineering | Year: 2010

An impressive range of tissues and cells are regulated by mechanical loading, and this regulation is central to disease processes such as osteoporosis, atherosclerosis, and osteoarthritis. However, other than a small number of specialized excitable cells involved in hearing and touch, cellular mechanosensing mechanisms are generally quite poorly understood. A lack of mechanistic understanding of these processes is one of the primary foci of the nascent field of mechanobiology, which, as a consequence, enjoys enormous potential to make critical new insights into both physiological function and etiology of disease. In this review we outline the process in bone by tracing mechanical effects from the organ level to the cellular and molecular levels and by integrating the biological response from molecule to organ. A case is made that a fundamental roadblock to advances in mechanobiology is the dearth of Information in the area of pericellular mechanics. © 2010 by Annual Reviews. All rights reserved.


Youm T.,New York University | Takemoto R.,Bone and Joint Center | Park B.K.-H.,New York University
Journal of the American Academy of Orthopaedic Surgeons | Year: 2014

The shoulder joint has the greatest range of motion of any joint in the body. However, it relies on soft-tissue restraints, including the capsule, ligaments, and musculature, for stability. Therefore, this joint is at the highest risk for dislocation. Thorough knowledge of the shoulder's anatomy as well as classification of dislocations, anesthetic techniques, and reduction maneuvers is crucial for early management of acute shoulder dislocation. Given the lack of comparative studies on various reduction techniques, the choice of technique is based on physician preference. The orthopaedic surgeon must be well versed in several reduction methods and ascertain the best technique for each patient. © the American Academy of Orthopaedic Surgeons.


Scanlan S.F.,Stanford University | Favre J.,Stanford University | Andriacchi T.P.,Stanford University | Andriacchi T.P.,Bone and Joint Center
Journal of Biomechanics | Year: 2013

Reports that knee cartilage health is sensitive to kinematic changes, combined with reports of extension loss following ACL reconstruction, underscores the importance of restoring ambulatory knee extension in the context of preventing premature osteoarthritis. The purpose of this study was to test the relationship between individual variations in peak knee extension at heel-strike of walking and the anterior-posterior location of thickest cartilage in the medial and lateral femoral condyles of healthy contralateral and ACL reconstructed knees. In vivo gait analysis and knee MR images were collected from 29 subjects approximately 2 years after unilateral ACL reconstruction. Knee extension was measured at heel-strike of walking and 3-D femoral cartilage thickness models were reconstructed from MR images. The ACL reconstructed knees had significantly reduced knee extension (-1.5±4.2°) relative to the contralateral knees (-4.6±3.4°) at heel-strike of walking but did not have side-to-side differences in the anterior-posterior location or magnitude of thickest medial and lateral femoral cartilage. The anterior-posterior location of the thickest medial femoral cartilage was correlated with knee extension at heel-strike in both the healthy contralateral (R2=0.356, p<0.001) and reconstructed (R2=0.234, p=0.008) knees. These results suggest that ACL reconstruction can impair terminal extension at periods of ambulatory loading known to be related to cartilage morphology in healthy joints. The fact that the femoral cartilage thickness distribution had not changed at 2 years post-op, even in the subset of subjects with extension loss, suggests that loads may be shifted to thinner cartilage regions, which could have important implications on long-term joint health. © 2013 Elsevier Ltd.


Zabala M.E.,Stanford University | Favre J.,Stanford University | Scanlan S.F.,Stanford University | Donahue J.,Sports Orthopedic and Rehabilitation SOAR | And 2 more authors.
Journal of Biomechanics | Year: 2013

Changes in knee mechanics following anterior cruciate ligament reconstruction (ACLR) have been implicated as a contributor to the development of premature osteoarthritis (OA). However, changes in ambulatory loading in this population have not been well documented. While the magnitude of the external knee moment vector is a major factor in loading at the knee, there is not a comprehensive understanding of the changes in the individual components of the vector following ACL reconstruction. The purpose of this study was to test for differences in the three components of the external knee moment during walking and stair locomotion between ACLR, contralateral and healthy control knees. Forty-five ACLR and 45 healthy control subjects were tested during walking, stair ascent and descent. ACLR knees had a lower first peak adduction moment than contralateral knees during all three activities. Similarly, additional cases of significant differences between ACLR and contralateral knees consisted of lower peak moments for the ACLR than the contralateral knees. These differences were due to both ACLR and contralateral knees as the ACLR knees indicated lower and the contralateral knees greater peak moments compared to healthy control knees. The results suggest a compensatory change involving greater loading in the contralateral knee, perhaps due to lower loading of the ACLR knee. Further, lower knee moments of the ACLR knee suggest that increased joint loading may not be the initiating factor in the development of OA following ACL reconstruction; but rather previous described kinematic or biological changes might initiate the pathway to knee OA. © 2012 Elsevier Ltd.

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