Spine & Sports Institute

Abstract

Background: Hamstring muscle strains often recur. The authors studied the effect of the grade of initial injury on the subsequent risk of reinjury.

Hypothesis: No difference in reinjury rate between acute low-grade (grades I and II) and high-grade (III and IV) hamstring muscle strains would be seen.

Study Design: Cohort study (prognosis); Level of evidence, 1.

Methods: Between 1999 and 2007, the authors managed 165 elite track and field athletes with acute, first-time unilateral hamstring muscle strains. Strains were classified into 4 grades (I, II, III, and IV) based on knee active range of motion deficit at 48 hours. The same rehabilitation protocol was prescribed, and the rate of reinjury was recorded during the following 24 months.

Results: The average time to return to sport after initial injury was 7.4 days for grade I injuries, 12.9 days for grade II injuries, 29.5 days for grade III injuries, and 55.0 days for grade IV injuries. At follow-up, 23 of the 165 athletes (13.9%) had experienced a second hamstring muscle strain. Of the 75 athletes with a grade I injury, 7 (9.3%) had experienced a recurrence after 24 months. Of the 58 athletes with a grade II injury, 14 (24.1%) experienced a recurrence. Of the 26 athletes with a grade III injury, 2 (7.7%) experienced a recurrence, and of the 6 athletes with a grade IV injury, none had experienced a recurrence after 24 months.

Conclusion: Low-grade hamstring muscle lesions appear to lead to a higher risk of reinjury than high-grade hamstring muscle lesions. However, there were disproportionately fewer high-grade injuries than low-grade injuries. Objective clinical findings can accurately determine the risk of reinjury after acute hamstring muscle strains in elite track and field athletes.

Abstract

Background: Clinical studies claim that platelet-rich plasma (PRP) shortens recovery times because of its high concentration of growth factors that may enhance the tissue repair process. Most of these studies obtained PRP using different separation systems, and few analyzed the content of the PRP used as treatment.

Purpose: This study characterized the composition of single-donor PRP produced by 3 commercially available PRP separation systems.

Study Design: Controlled laboratory study.

Methods: Five healthy humans donated 100 mL of blood, which was processed to produce PRP using 3 PRP concentration systems (MTF Cascade, Arteriocyte Magellan, Biomet GPS III). Platelet, white blood cell (WBC), red blood cell, and fibrinogen concentrations were analyzed by automated systems in a clinical laboratory, whereas ELISA determined the concentrations of platelet-derived growth factor αβ and ββ (PDGF-αβ, PDGF-ββ), transforming growth factor β1 (TGF-β1), and vascular endothelial growth factor (VEGF).

Results: There was no significant difference in mean PRP platelet, red blood cell, active TGF-β1, or fibrinogen concentrations among PRP separation systems. There was a significant difference in platelet capture efficiency. The highest platelet capture efficiency was obtained with Cascade, which was comparable with Magellan but significantly higher than GPS III. There was a significant difference among all systems in the concentrations of WBC, PDGF-αβ, PDGF-ββ, and VEGF. The Cascade system concentrated leukocyte-poor PRP, compared with leukocyte-rich PRP from the GPS III and Magellan systems.

Conclusion: The GPS III and Magellan concentrate leukocyte-rich PRP, which results in increased concentrations of WBCs, PDGF-αβ, PDGF-ββ, and VEGF as compared with the leukocyte-poor PRP from Cascade. Overall, there was no significant difference among systems in the platelet concentration, red blood cell, active TGF-β1, or fibrinogen levels.

Clinical Relevance: Products from commercially available PRP separation systems produce differing concentrations of growth factors and WBCs. Further research is necessary to determine the clinical relevance of these findings.

Abstract

Background: The risk of elbow or shoulder injury for young baseball pitchers is unknown.

Purpose/Hypothesis: The purpose of this study was to quantify the cumulative incidence of throwing injuries in young baseball pitchers who were followed for 10 years. Three hypotheses were tested: Increased amount of pitching, throwing curveballs at a young age, and concomitantly playing catcher increase a young pitcher’s risk of injury.

Study Design: Cohort study; Level of evidence, 3.

Methods: In sum, 481 youth pitchers (aged 9 to 14 years) were enrolled in a 10-year follow-up study. Participants were interviewed annually. Injury was defined as elbow surgery, shoulder surgery, or retirement due to throwing injury. Fisher exact test compared the risk of injury between participants who pitched at least 4 years during the study and those who pitched less. Fisher exact tests were used to investigate risks of injury for pitching more than 100 innings in at least 1 calendar year, starting curveballs before age 13 years, and playing catcher for at least 3 years.

Results: The cumulative incidence of injury was 5.0%. Participants who pitched more than 100 innings in a year were 3.5 times more likely to be injured (95% confidence interval = 1.16 to 10.44). Pitchers who concomitantly played catcher seemed to be injured more frequently, but this trend was not significant with the study sample size.

Conclusion: Pitching more than 100 innings in a year significantly increases risk of injury. Playing catcher appears to increase a pitcher’s risk of injury, although this trend is not significant. The study was unable to demonstrate that curveballs before age 13 years increase risk of injury.

Clinical Relevance: The risk of a youth pitcher sustaining a serious throwing injury within 10 years is 5%. Limiting the number of innings pitched per year may reduce the risk of injury. Young baseball pitchers are encouraged to play other positions as well but might avoid playing catcher.