A clinical and roentgenographic study of Little League elbow.

BACKGROUND: Comparisons of medial elbow injury rate and the incidence of clinical and radiographic findings among Little League baseball players have not been documented. HYPOTHESIS: Injury rate and clinical and radiographic findings in Little Leaguers of different positions may be similar. STUDY DESIGN: Survey and retrospective review. METHODS: Altogether, 343 Little Leaguers (120 pitchers, 40 catchers, and 183 fielders) participated in the study. The survey (including age, playing position, playing experience, and symptoms), clinical examination, and roentgenogram of both elbows were obtained for analysis using Pearson's chi-square test. RESULTS: Clinically, 58% of the pitchers presented with soreness compared to 63% in catchers and 47% in fielders. Radiographic examination revealed hypertrophy of the medial humeral epicondyle in all pitchers and catchers and 90% of the fielders. Separation of the medial epicondyle was found in 63% of pitchers, 70% of catchers, and 50% of fielders, while fragmentation was found in 19% of pitchers, 40% of catchers, and 15% of fielders. In subjects with separation or fragmentation, 49% and 56% complained of elbow soreness, respectively. CONCLUSION: Similar rates of medial elbow changes in Little Leaguers may imply that the roentgenological changes of the medial epicondyle could be an adaptive yet physiological reaction to the excessive valgus stress of throwing. The higher incidence of medial epicondylar separation and fragmentation in catchers that has not been reported before may be secondary to the increased stress placed on the elbow when throwing from the squatting position.

The application potential of sintered beta-dicalcium pyrophosphate in total joint arthroplasty.

An in vitro bone cell culture model was used to evaluate the potential application of sintered beta-dicalcium pyrophosphate (SDCP) in arthroplasty surgery. Primary osteoclasts and osteoblasts were cocultured with different sizes of SDCP particles. The changes in cell counts and the synthesis and secretion of alkaline phosphatase, acid phosphatase, and prostaglandin E(2) in response to the SDCP particles were monitored. When bone cells were cultured with SDCP particles smaller than 53 microm, both the osteoblast and osteoclast cell counts decreased significantly. When the SDCP particles were larger than 177 microm, although the osteoblast population increased significantly, the osteoclast population decreased significantly. Simultaneously, the titer of prostaglandin E(2) in the medium and the cytoplasmic prostaglandin E(2) increased significantly. We concluded that SDCP is a potentially useful bioceramic for the prevention of osteoclast-mediated periprosthetic osteolysis.

The effects of cyclic stretching on tensile properties of the rabbit's skeletal muscle.

OBJECTIVE: To define the threshold of muscle injury with cyclic passive stretch. DESIGN: The changes in the load-deformation curve of muscle-tendon unit were monitored until the failure point by an in vivo rabbit model. BACKGROUND: Muscle injuries range in severity from a simple strain to complete rupture. Although strains occur more frequently than complete failures, only a few studies have investigated the phenomena of these sub-failure injuries. Monitoring of the continuum for stretch-induced injury allows us to define the threshold of stretch injury. METHODS: Thirty rabbits' triceps surae muscle-tendon unit preparations were used. One of the pairs (control) was stretched until failure; the other (experimental) was first cyclic stretched to either 12, 20 or 25% of the initial length of the muscle-tendon unit and then stretched to failure. Comparisons were made between the load-deformation curves of the experimental and control specimens. RESULTS: When cyclic stretched to 12 or 20%, there were no significant changes existed in the biomechanical parameters except the deformation at the peak load. In contrast, all the biomechanical parameters except the ration of the energy absorption changed significantly after 25% strain cyclic stretch. CONCLUSIONS: A threshold for stretch-induced injury does exist. This can be reproduced at the 25% strain of the triceps surae muscle-tendon unit.

Morphological changes of the triceps surae muscle-tendon unit during passive extension: an in vivo rabbit model.

OBJECTIVE: To elucidate the morphological and biomechanical manifestation of the triceps surae muscle-tendon unit during passive extension. DESIGN: The instantaneous changes within the load-deformation curve of muscle-tendon unit were analyzed by an in vivo rabbit model. BACKGROUND: Although muscle strains occur more frequently than complete failures, the failure mechanism of these sub-failure injuries is rarely investigated. Monitoring of the instantaneous changes in the load-deformation curve allows correlation with the morphological changes that occur during passive extension. METHODS: After anesthesia, the triceps surae muscle of rabbit was dissected and then stretched to failure by a MTS Bionix 858 machine. The morphological changes in failure patterns were recorded by photographs. RESULTS: The morphological and biomechanical manifestations of the triceps surae muscle-tendon unit was divided into five different portions: first, the viscoelastic portion with minimal morphologic change; second, the portion of micro-failure with local ecchymosis; third and fourth, the portions of macrofailure with sequential rupture of the muscle fibers; and fifth, the portion of rupture and separation of muscle parenchyma. CONCLUSIONS: A threshold for stretch-induced injury does exist. The threshold of the initiation of micro-failure in this model was 16.5% of the strain, which corresponded to 16.6% of the maximal sustainable force. RELEVANCE: Elucidation of the existence of micro-failure in skeletal muscle gives a good reference point to determine the functional capabilities and limitation of muscular tissue. With this, the deleterious effect of muscle stretching can be avoided by limiting muscle stretching to below this limit.

The postural stability control and gait pattern of idiopathic scoliosis adolescents.

OBJECTIVE: The static postural equilibrium and gait patterns between idiopathic scoliotic (IS) patients and normal subjects were studied to verify the best method to identify the functional disability in IS patients. DESIGN: The static stability in six postures and gait patterns among normal subjects and IS patients were compared. BACKGROUND: Postural stability control and gait analysis are non-invasive methods to identify many diseases. However, the dysfunction of IS patients in postural stability control and gait pattern is not clear. The results of this research may lead to further understanding of the etiology of idiopathic scoliosis in the postural equilibrium influencing aspects. METHODS: Thirty IS patients and fifteen normal subjects were recruited for postural stability control test and gait analysis using the force plate and 3-D motion analysis system. RESULTS: The IS patients generally produced higher sway area, lateral sway, sagittal sway, and sway radius than normal subjects. The cadence is smaller in the IS patients, but the stance phase and stride phase are similar to normal subjects. CONCLUSIONS: The IS patients are poor in postural stability control but their gait pattern is similar to that of normal subjects. Standing with trunk at full flexion is the most effective position to identify the postural stability control of IS patient.