Journal of orthopaedic research : official publication of the Orthopaedic Research Society
-
At the end ranges of motion, the glenohumeral capsule limits translation of the humeral head in multiple directions. Since the 6-degree of freedom kinematics of clinical tests are commonly utilized to diagnose shoulder injuries, the objective of this study was to determine the magnitude and repeatability of glenohumeral joint kinematics during a simulated simple anteroposterior translation test in the anterior and posterior directions. A magnetic tracking system was used to determine the kinematics of the humerus with respect to the scapula in eight cadaveric shoulders. ⋯ Based on the data obtained, performing a simulated simple translation test should result in coupled inferior translations and anterior translations that are a function of external rotation. The low standard deviations demonstrate that the observed translations should be repeatable. Furthermore, capsular stretching or injury to the anterior-inferior region of the capsule should be detectable during clinical examination if excessive coupled translations exist or no posterior shift of the reference position with external rotation is noted.
-
Altered patellofemoral joint contact pressures are thought to contribute to patellofemoral joint symptoms. However, little is known about the relationship between tibiofemoral joint kinematics and patellofemoral joint contact pressures. The objective of this paper was to investigate the effect of tibiofemoral joint kinematics on patellofemoral joint pressures using an established in vitro robotic testing experimental setup. ⋯ These results imply that excessive strength conditioning with the hamstring muscles might not be beneficial to the patellofemoral joint. Knee pathology that causes an increase in tibial posterior translation and external rotation might contribute to degeneration of the patellofemoral joint. These results suggest that conservative treatment of posterior cruciate ligament injury should be reconsidered.
-
In an effort to prevent degeneration of articular cartilage associated with meniscectomies, both meniscal allografts and synthetic replacements have been studied. A number of biomechanical criteria may be important for a meniscal replacement to restore normal tibiofemoral contact pressure in the knee joint and hence be clinically successful. One of these criteria is geometric similarity. ⋯ Finally, less than a 0.5 mm change in the medial meniscal height and greater than a 1 mm change in the lateral meniscal height could be tolerated before the relative difference in the contact variables from those for the original geometry exceeded 10%. Thus in the design or selection of meniscal replacements, each of the four parameters should be measured when sizing a replacement tissue. Also tighter tolerances should be placed on the medial meniscal parameters compared to the lateral meniscal parameters.
-
The influence of cyclic compression and distraction on the healing of experimental tibial fractures.
Interfragmentary displacement has a main effect on callus formation in fracture healing. To test whether compressive or distractive displacements have a more pronounced effect on new bone formation, a sheep osteotomy model was created whereby the gap tissue was subjected to constant bending displacement. A diaphyseal osteotomy with a gap of 2 mm was created in 18 sheep tibiae and stabilized with a special unilateral actuator-driven external fixator. ⋯ Solid periosteal bridging of the gap was observed in two sheep in the control group, whereas bridging in the cycled groups was observed exclusively at the medullary side. In conclusion, cyclic compressive displacements were found to be superior over distractive displacements. A higher number of enforced and maintained compressive displacements enhanced periosteal callus formation but did not allow bony bridging of the gap.
-
The viability of chondrocytes in press-fit glycerol-preserved osteochondral allografts was compared to that in fresh autografts, after transplantation into load-bearing and non-load-bearing sites in mature sheep stifle joints. We used macroscopic grading, tonometer pen indentation testing, histology, sulfate uptake and viability as determined by confocal-microscopy to assess cartilage condition. Despite there being no statistical differences between macroscopic appearance and tonometer testing of all grafts, confocal microscopy and histology demonstrated a positive effect of load-bearing placement on cryopreserved osteochondral allografts. ⋯ Load-bearing allografts had a greater amount of fibrocartilage than autografts or adjacent cartilage but less fibrocartilage than non-load-bearing allografts. Both autografts and allografts had non-significant increases in metabolism compared to adjacent cartilage as measured by sulfate-uptake. Load-bearing placement improved chondrocyte viability of glycerol cryopreserved osteochondral allograft following a press-fit implantation.