Abstract
Musculoskeletal ultrasound imaging (MSKUI) has become an increasing studied assessment tool in orthopedic sports medicine. Several studies have investigated ulnar collateral ligament (UCL) integrity and morphology in the throwing arm of baseball players with MSKUI. Research data has indicated that UCL thickening and medial joint space (MJS) widening occurs in athletes during sustained competition. Purpose: The purpose of this study was to examine acute UCL thickness and MJS adaptations in the throwing arm of Division I collegiate baseball pitchers with MSKUI following one in-game performance. Methods: This was a non-experimental descriptive quantitative repeated measures study in which ten NCAA Division I collegiate baseball pitchers (mean age 20.4 ± 1.4 yrs) with no history of significant upper extremity injuries participated. Musculoskeletal ultrasound images were obtained with a GE LOGIQ e ultrasound unit before and immediately after (< 15 minutes) pitching performance during each subject’s first game of the season. A 3 kg valgus force was applied with a handheld dynamometer (Hoggan Scientific microFET 2) 20 cm distal to the medial epicondyle of the throwing arm during imaging. Post-imaging ligament thickness measurements were performed at the mid-substance of UCL and at the apex of the trochlea. Post-imaging MJS width measurements were performed from the apex of the trochlea to the apex of the ulna. Maximum power Doppler imaging quantification (PDIQ) ratios were also assessed to measure localized perfusion changes. Changes in UCL thickness (mid-substance and apex of the trochlea), MJS width, max PDIQ ratio, along with mid-substance to trochlea ratio and the PDIQ area assessed were analyzed using paired samples t-tests. Results: There was no significant difference in mid-substance UCL thickness width before (5.72 ± 0.7mm) and after performance (5.70 ± 0.7mm; t (9)= .36, p = .73). With respect to apex of trochlea UCL thickness, no significant differences were found before (2.67 ± 0.7mm) and after (2.61 ± 0.6mm; t (9)= 1.30, p = .23) performance. When assessing MJS, a significant change of ~4% was observed before (6.30 ± 1.5mm) and after (6.60 ± 1.5mm; t (9)= -3.70; p= .005). There was no significant difference in max PDIQ ratio before (.08 ± .06) and after (.22 ± .29; t (9)= -1.37; p= .20) performance. Controlling for the pitch count [F (1,9) = .17, p = .69], innings pitched [F (1,9) = .06, p = .81], and change in max PDIQ ratio [F (1,9) = .18, p = .68] did not affect change in MJS. Discussion: While there was a significant change in MJS, there were no significant UCL thickness changes following first competitive play of the season. Increase in MJS width is likely attributed to increased tissue extensibility due to temperature and circulation increases during sport participation but more research is needed to explore this relationship. Conclusion: A significant MJS widening did occur after one pitching outing at the start of the season; whereas, no changes were observed in UCL thickness measured at two different locations or in local perfusion as measured by PDIQ. Further research is needed to understand the etiology of increased medial elbow joint widening in pitchers following competition at the start of the collegiate baseball season.