The purpose of this study was to compare selected rabbit tendons and ligaments morphologically and biochemically. Five representative structures from each of six age-and sex-matched rabbits were compared. Biochemical analyses included total collagen, reducible collagen cross-links, quantitative collagen typing, DNA, and glycosaminoglycans. Histological and chemical differences were demonstrated between the tendons and the ligaments. Smaller differences were also found between the individual ligaments (collateral and cruciate) and between the two tendons (patellar and Achilles) that were examined. These findings suggest that ligaments are more metabolically active than tendons, having more plump cellular nuclei, higher DNA content, larger amounts of reducible cross-links, and the presence of more type I11 collagen, as compared with tendons. They also contain slightly less total collagen than tendons and more glycosaminoglycans. We conclude that the tendons and ligaments studied have unique histological and biochemical characteristics, despite their gross similarities. Relatively increased metabolic activity in ligaments, implied by our findings, may be species specific, age related (transient), or may truly represent a structural expression of functional need for more rapid adaptation. Further investigation of other similarities or differences between particular ligaments (or tendons) is indicated, and attention is directed toward the importance of such variables in development of models for tendon and ligament studies. Key Words: Tendon-Ligament-DNA concentration-Collagen cross-linking-Glycosaminoglycans-Comparison.Chronic knee ligament instabilities are most commonly treated by functional replacement with other periarticular structures, mainly tendons. These replacements have included the use of various parts of the quadriceps tendon mechanism (1 1,20,28), pes anserinus (39), semitendinosis tendon (8,36), biceps femoris tendon (38), gracilis tendon (43), iliotibial bank (17,31,34), and lengths of fascia lata twisted or rolled into tendonlike forms (24,25).

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Background: Recent studies evaluating nonoperative treatment of elbow ulnar collateral ligament (UCL) injuries augmented with platelet-rich plasma (PRP) have shown promising results. To date, no comparative studies have been performed on professional baseball players who have undergone nonoperative treatment with or without PRP injections for UCL injuries. Hypothesis: Players who received PRP injections would have better outcomes than those who did not receive PRP. Study Design: Cohort study; Level of evidence, 3. Methods: The Major League Baseball (MLB) Health and Injury Tracking System identified 544 professional baseball players who were treated nonoperatively for elbow UCL injuries between 2011 and 2015. Of these, 133 received PRP injections (PRP group) before starting their nonoperative treatment program, and 411 did not (no-PRP group). Player outcomes and a Kaplan-Meier survival analysis were compared between groups. In addition, to reduce selection bias, a 1:1 matched comparison of the PRP group versus the no-PRP group was performed. Players were matched by age, position, throwing side, and league status: major (MLB) and minor (Minor League Baseball [MiLB]). A single radiologist with extensive experience in magnetic resonance imaging (MRI) interpretation of elbow injuries in elite athletes analyzed 243 MRI scans for which images were accessible for tear location and grade interpretation. Results: Nonoperative treatment of UCL injuries resulted in an overall 54% rate of return to play (RTP). Players who received PRP had a significantly longer delay in return to throwing ( P < .001) and RTP ( P = .012). The matched cohort analysis showed that MLB and MiLB pitchers in the no-PRP group had a significantly faster return to throwing ( P < .05) and the MiLB pitchers in the no-PRP group had a significantly faster RTP ( P = .045). The survival analysis did not reveal significant differences between groups over time. The use of PRP, MRI grade, and tear location were not statistically significant predictors for RTP or progression to surgery. Conclusion: In this retrospective matched comparison of MLB and MiLB pitchers and position players treated nonoperatively for a UCL tear, PRP did not improve RTP outcomes or ligament survivorship, although there was variability with respect to PRP preparations, injection protocols, time from injury to injection, and rehabilitation programs. MRI grade and tear location also did not significantly affect RTP outcomes or progression to surgery.

Experimental work has shown that dislocation of the shoulder may involve disruption of the capsule from its lateral humeral attachment. We report two patients with recurrent dislocation due to this injury. Lateral repair gave good results. It is suggested that this injury be considered and looked for when glenoid labral injury is minimal or absent.

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There was no difference in the rate of professional advancement among pitchers drafted by the MLB who had undergone UCLR as amateurs compared with controls. Both groups had similar statistical performance. Pitchers in the UCLR group had an increased risk of DL assignment but no increase in the number of days on DL or risk of DL placement for elbow injury.