No abstract

Background The single-leg step down task (SLSD) is a clinical tool to assess movement and control of the lower extremity and trunk. Hip abduction weakness may impact movement quality during the SLSD, however the relationships between movement and strength are unclear. Purpose To determine the relationship between hip abduction isometric strength and movement during the SLSD of trunk lean, pelvic drop, knee valgus, and hip flexion. Study Design Cross sectional, cohort study Methods One hundred-eighteen Minor League baseball players (age=21.6 ± 2.0 years; n=68 pitchers, n=50 position players) participated. Bilateral hip abduction isometric strength was measured using a handheld dynamometer (HHD), and then multiplied by distance from the greater trochanter to the HHD and expressed as hip abduction torque. Video cameras captured the SLSD, with participants standing on one leg while lowering their contralateral heel to touchdown on the floor from a 0.203m (8in.) step. Trunk lean, trunk flexion, pelvic drop, knee valgus, and hip flexion were measured using Dartfish at heel touchdown. A value of 180° indicated no knee valgus. Pearson correlations examined the relationships between hip abduction torque and SLSD motions. Results There were no significant correlations for position players. For pitchers, on the lead leg increased hip abduction torque weakly correlated with a decrease in knee valgus (r= 0.24, p=0.049). Also for pitchers on the trail leg, increased hip abduction torque weakly correlated with decreased pelvic drop (r= -0.28, p=0.021). Conclusion Hip abduction strength contributes to dynamic control of the trunk and legs. Specifically in pitchers, hip abduction weakness was related to increased movement of the lower extremity and lumbopelvic regions during the dynamic SLSD task. These deficits could translate to altered pitching performance and injury. Levels of Evidence 2.

No abstract

Objectives: The ulnar collateral ligament (UCL) is one of the most common sites of injury in baseball pitchers, with 25% of Major League Baseball (MLB) pitchers having undergone surgical reconstruction (UCLR). It remains unknown whether the ligament responds to the stress of pitching. The purpose of this study is to determine the response of the UCL in professional pitchers to pitching and rest through a prospective ultrasonographic study. Methods: This was a prospective study supported by the Major League Baseball Research Committee. All pitchers within a single professional baseball club were enrolled. Pitching exposure history data including number of years pitching and peak pitch velocity were collected. A full ultrasound (US) examination of the ligament was then performed by a single fellowship-trained ultrasonographer with extensive experience with UCL US. This US examination was performed at the beginning of the season, the end of the season, and the beginning of the following season. This US examination included measurement of UCL thickness and valgus laxity, as measured via ulnotrochlear joint opening at 30° of flexion to valgus stress of 10% of the mean pitching torque of 64 Nm. Two US images were saved for each measurement such that all measurements were made twice and analysis was performed on the average. Thirty ultrasounds were measured by a second experienced ultrasonographer to determine inter-rater reliability via intra-class correlation coefficients (ICC). Correlation analyses were performed between pre-season data and pitching exposure data. Paired analyses compared data between pre- and post-season one and between post-season one and pre-season two. Results: 185 total pitchers were included: 94 pitchers were included prior to season one, 83 were included at the end of season one, and 120 pitchers were included prior to season two. Excluding player movement in and out of the active roster, follow-up rate was 70% (46/66) during season one and 91% (49/54) between seasons. These pitchers were 23±4 years old (mean±standard deviation), had 12±6 years pitching experience, and had peak velocity of 95±3 miles per hour. 38 pitchers (21%) underwent UCLR either prior to enrollment or during the study. With examination of US data, ICCs were 0.851 for UCL thickness and 0.906 for UCL laxity at 30°. Peak pitch velocity positively correlated with UCL thickness (p=0.009) and valgus laxity at 30° (p=0.010). Within-subject UCL thickness increased during the season (mean difference [95% confidence intervals] 1.0 [0.3 to 1.7] mm, p=0.006) and decreased during the offseason (0.6 [0.3 to 0.9] mm, p<0.001). Within-subject valgus laxity at 30° increased during the season non-significantly (0.4 [-0.06 to 0.76] mm opening, p=0.069) and decreased significantly during the off season significantly (0.2 [-0.04 to 0.5] mm opening, p=0.039). Conclusion: The ulnar collateral ligament responds to stress and rest in professional pitchers. The UCL thickens and becomes more lax in response to higher pitch velocity and more years of pitching. The UCL thickens and valgus laxity increases with the stress of a single season of pitching, and these effects are partially reversed during the offseason.

Background: Hip strength is an important factor for control of the lumbo-pelvic-hip complex. Deficits in hip strength may affect throwing performance and contribute to upper extremity injuries. Hypothesis: Deficits in hip abduction isometric strength would be greater in those who sustained an upper extremity injury and hip strength would predict injury incidence. Study Design: Prospective cohort study. Level of Evidence: Level 3. Methods: Minor League baseball players (n = 188, age = 21.5 ± 2.2 years; n = 98 pitchers; n = 90 position players) volunteered. Hip abduction isometric strength was assessed bilaterally with a handheld dynamometer in side-lying position, expressed as torque using leg length (N·m). Hip abduction strength asymmetry was represented by [(trail leg/lead leg) × 100]. Overuse or nontraumatic throwing arm injuries were prospectively tracked. Poisson regression models were used to estimate relative risk ratios associated with hip asymmetry; confounders, including history of prior overuse injury in the past year, were included. Results: Hip abduction asymmetry ranged from 0.05% to 57.5%. During the first 2 months of the season, 18 players (n = 12 pitchers) sustained an upper extremity injury. In pitchers, for every 5% increase in hip abduction asymmetry, there was a 1.24 increased risk of sustaining a shoulder or elbow injury. No relationship between hip abduction strength and injury was observed for position players. Conclusion: Hip abduction asymmetry in pitchers was related to subsequent upper extremity injuries. The observed risk ratio indicates that hip abduction asymmetry may contribute a significant but small increased risk of injury. Clinical Relevance: Hip abduction muscle deficits may affect pitching mechanics and increase arm stress. Addressing hip asymmetry deficits that exceed 5% may be beneficial in reducing upper extremity injury rates in pitchers.