Biomechanics Research Today is a free monthly online journal that collates and summarizes the latest research about Biomechanics, including details on mechanics of living organisms, movement, locomotion, prosthetic limbs. | ||||||
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Effects of patellar position and defect healing on in vitro stifle joint kinematics following removal of the central one-third of the patellar tendon in an ovine model.Bertollo N, Bell DJ, Yu Y, Walsh WR Surgical and Orthopaedic Research Laboratories, Prince of Wales Hospital, University of New South Wales, Sydney, New South Wales, Australia. n.bertollo@unsw.edu.au Harvest of the central one-third of the patella tendon (PT) is routinely performed for anterior cruciate ligament reconstruction (ACLR). Patella infera may ensue. In this study we unilaterally resected the central one-third of the PT in 20 sheep, without reconstructing or defunctionalizing the native ACL, and examined the effects at 3, 6, 12, and 24 weeks postoperatively on PT length, histological appearance of the donor defect and in vitro stifle joint kinematics. Mean length increases (p > 0.263) in the operated tendons of 0.3%, 2.8%, 0.5%, and 2.4% were observed at 3, 6, 12, and 24 weeks. A significant proximal shift of the patella correlated well with a mean 2.35° retardation of patellar flexion (r = 0.440, p = 0.001). A mean net 4.9° decrease in medial patellar tilt was also observed (p < 0.001), but was not coupled with changes in tibial rotation. Donor defect tissue showed a distinct progression of healing with time, remodeling from dense scar tissue at 3 weeks to bundles of well-organized collagen enveloped by vascularized loose connective tissue at 24 weeks but was not associated with the restoration of kinematics. These results suggest that resection of the central one-third of the PT and leaving the defect open in the ovine stifle joint may be associated with increased PT length and changes in patellar kinematics which do not recover 6 months postoperatively. The lack of patella infera may render this animal model unsuitable for the interpretation of joint kinematics following PT resection for human ACLR. Published 21 February 2011 in J Orthop Res, 29(4): 572-81. Articles on Biomechanics published 21 February 2011: Movement kinematics of prepotent response suppression in aging during conflict adaptation. J Gerontol B Psychol Sci Soc Sci, 66(2): 185-94. Effects of patellar position and defect healing on in vitro stifle joint kinematics following removal of the central one-third of the patellar tendon in an ovine model. J Orthop Res, 29(4): 572-81. Harvest of the central one-third of the patella tendon (PT) is routinely performed for anterior cruciate ligament reconstruction (ACLR). Patella infera may ensue. In this study we unilaterally resected the central one-third of the PT in 20 sheep, without reconstructing or defunctionalizing the native ACL, and examined the effects at 3, 6, 12, and 24 weeks postoperatively on PT length, histological appearance of the donor defect and in vitro stifle joint kinematics. Mean length increases (p > ... [Abstract] [Full-text] Articles on Biomechanics published 21 December 2010: Robust mechanosensing and tension generation by myosin VI. J Mol Biol, 405(1): 105-12. Myosin VI is a molecular motor that is thought to function both as a transporter and as a cytoskeletal anchor in vivo. Here we use optical tweezers to examine force generation by single molecules of myosin VI under physiological nucleotide concentrations. We find that myosin VI is an efficient transporter at loads of up to ∼2 pN but acts as a cytoskeletal anchor at higher loads. Our data and the resulting model are consistent with an indirect coupling of global structural motions to ... [Abstract] [Full-text] Robust mechanosensing and tension generation by myosin VI. J Mol Biol, 405(1): 105-12. Myosin VI is a molecular motor that is thought to function both as a transporter and as a cytoskeletal anchor in vivo. Here we use optical tweezers to examine force generation by single molecules of myosin VI under physiological nucleotide concentrations. We find that myosin VI is an efficient transporter at loads of up to ∼2 pN but acts as a cytoskeletal anchor at higher loads. Our data and the resulting model are consistent with an indirect coupling of global structural motions to ... [Abstract] [Full-text] Robust mechanosensing and tension generation by myosin VI. J Mol Biol, 405(1): 105-12. Myosin VI is a molecular motor that is thought to function both as a transporter and as a cytoskeletal anchor in vivo. Here we use optical tweezers to examine force generation by single molecules of myosin VI under physiological nucleotide concentrations. We find that myosin VI is an efficient transporter at loads of up to ∼2 pN but acts as a cytoskeletal anchor at higher loads. Our data and the resulting model are consistent with an indirect coupling of global structural motions to ... [Abstract] [Full-text] Articles on Biomechanics published 25 October 2010: Role of mechanical loading in healing of massive bone autografts. J Orthop Res, 28(12): 1657-64. We assessed healing of a 3.5 cm autograft transport segment, denuded of periosteum, and docked to the healthy distal femur with an intramedullary nail. We hypothesized that healing relates to proximity to the healthy distal femur and to mechanical loading patterns. Total bone area, area of new bone apposition, and quality of new bone formed in the 2 weeks after surgery, and area and degree of perfusion 16 weeks after surgery were measured as a function of proximity and loading patterns (as ... [Abstract] [Full-text] Collagen and mineral deposition in rabbit cortical bone during maturation and growth: effects on tissue properties. J Orthop Res, 28(12): 1626-33. We characterized the composition and mechanical properties of cortical bone during maturation and growth and in adult life in the rabbit. We hypothesized that the collagen network develops earlier than the mineralized matrix. Growth was monitored, and the rabbits were euthanized at birth (newborn), and at 1, 3, 6, 9, and 18 months of age. The collagen network was assessed biochemically (collagen content, enzymatic and non-enzymatic cross-links) in specimens from the mid-diaphysis of the tibia ... [Abstract] [Full-text] Role of mechanical loading in healing of massive bone autografts. J Orthop Res, 28(12): 1657-64. We assessed healing of a 3.5 cm autograft transport segment, denuded of periosteum, and docked to the healthy distal femur with an intramedullary nail. We hypothesized that healing relates to proximity to the healthy distal femur and to mechanical loading patterns. Total bone area, area of new bone apposition, and quality of new bone formed in the 2 weeks after surgery, and area and degree of perfusion 16 weeks after surgery were measured as a function of proximity and loading patterns (as ... 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