Changes in medial elbow elasticity and joint space gapping during maximal gripping: reliability and validity in evaluation of the medial elbow joint using ultrasound elastography.

BACKGROUND: Medial elbow injuries are common in baseball pitchers. This study investigated the reliability of medial elbow elastography measurement and the characteristics of the medial elbow stabilizers. METHODS: Medial elbow joint space gapping and the strain ratios of the ulnar collateral ligament (UCL) and the forearm flexor-pronator muscle (FPM) were measured at rest and during gripping in 29 healthy college students. The intraclass correlation coefficients of elastography were calculated. The data were compared between tissues and between rest and gripping. RESULTS: The intraclass correlation coefficients (ICC1,3) of the elastography measurements were 0.91 and 0.83 for the UCL and 0.80 and 0.85 for the FPM for each examiner. Medial elbow joint space gapping during gripping (3.1 ± 0.6 mm) was significantly less than that at rest (3.8 ± 0.8 mm, P < .001). The strain ratios for both the UCL and FPM during gripping were significantly greater than those at rest (17.64 ± 10.97 during gripping vs. 3.94 ± 1.92 at rest for UCL, P < .001; 1.72 ± 0.99 during gripping vs. 0.35 ± 1.92 at rest for FPM, P < .001). The strain ratio for the UCL was significantly greater than that for the FPM both at rest (P < .001) and during gripping (P < .001). CONCLUSIONS: Elastography measurements of the UCL and FPM have almost perfect reliability. Gripping reduces medial elbow joint space gapping compared with rest. For both tissues, gripping reduces their elasticity compared with rest. The elasticity of the UCL is less than that of the FPM both at rest and during gripping.

Use of an Elbow Brace During Repetitive Pitching Does Not Cause an Increased Mechanical Burden on the Throwing Arm.

BACKGROUND: Repetitive pitching induces an increase in medial elbow joint space gapping and may consequently lead to local tissue stress and injury. Use of an elbow brace may prevent this from occurring by preventing an increase of medial elbow joint space gapping. However, an elbow brace adds weight to the limb and may increase the burden on the throwing arm. OBJECTIVE: To investigate whether use of an elbow brace during repetitive pitching reduces shoulder and arm range of motion and grip strength. DESIGN: Prospective crossover study. SETTING: University campus. PARTICIPANTS: Twenty-five healthy high school baseball players. METHODS: Each participant pitched 100 times under two conditions: without an elbow brace (control) and wearing an elbow brace. MAIN OUTCOME MEASUREMENTS: Shoulder and elbow range of motion (ROM) before pitching and after every block of 20 pitches. Grip strength before pitching and after 100 pitches. RESULTS: There was no significant main effect and interaction for ROM between the two conditions and between pitching sets. In both conditions, grip strength after 100 pitches was significantly lower than that before pitching (P < .05). When the two conditions were compared, there was no significant difference before pitching or after 100 pitches. CONCLUSIONS: Use of elbow brace does not alter shoulder and elbow ROM or decrease grip strength after repetitive pitching up to 100 times compared with a no brace condition. An elbow brace can be used during repetitive pitching without causing an increased mechanical burden on the throwing arm. LEVEL OF EVIDENCE: II.

The effect of repetitive baseball pitching on medial elbow joint space gapping associated with 2 elbow valgus stressors in high school baseball players.

BACKGROUND: To prevent elbow injury in baseball players, various methods have been used to measure medial elbow joint stability with valgus stress. However, no studies have investigated higher levels of elbow valgus stress. This study investigated medial elbow joint space gapping measured ultrasonically resulting from a 30 N valgus stress vs. gravitational valgus stress after a repetitive throwing task. METHODS: The study included 25 high school baseball players. Each subject pitched 100 times. The ulnohumeral joint space was measured ultrasonographically, before pitching and after each successive block of 20 pitches, with gravity stress or 30 N valgus stress. Two-way repeated measures analysis of variance and Pearson correlation coefficient analysis were used. RESULTS: The 30 N valgus stress produced significantly greater ulnohumeral joint space gapping than gravity stress before pitching and at each successive 20-pitch block (P < .01). For the 2 stress methods, ulnohumeral joint space gapping increased significantly from baseline after 60 pitches (P < .01). Strong significant correlations were found between the 2 methods for measurement of medial elbow joint space gapping (r = 0.727-0.859, P < .01). CONCLUSIONS: Gravity stress and 30 N valgus stress may produce different effects with respect to medial elbow joint space gapping before pitching; however, 30 N valgus stress appears to induce greater mechanical stress, which may be preferable when assessing joint instability but also has the potential to be more aggressive. The present results may indicate that constraining factors to medial elbow joint valgus stress matched typical viscoelastic properties of cyclic creep.