Contributions of the Third and Fourth Digits and the Second and Fifth Digits of the Flexor Digitorum Superficialis Muscle to Elbow Valgus Stability

Abstract

Background: Thiel cadavers have been reported to have lifelike flexibility and mechanical properties, but whether they are useful for measurement of the ulnohumeral joint space (JS) is unclear. The contributions of the third and fourth digits and the second and fifth digits of the flexor digitorum superficialis (FDS) to elbow valgus stability are also unknown. Purpose: To (1) clarify whether Thiel cadavers can be used for JS measurement on ultrasound and (2) identify the contributions to valgus stability of the third and fourth digits and the second and fifth digits of the FDS. Study Design: Descriptive laboratory study. Methods: In experiment 1 (12 elbows from human volunteers and 12 elbows from Thiel cadavers), valgus stress was increased gradually from 0 to 30 to 60 N, and the JS was compared on ultrasound between groups at each load. In experiment 2 (13 elbows from Thiel cadavers), specimens were divided into 2 groups, and the JS was measured for group 1 with the FDS intact, with tendinous insertions of the third and fourth digits cut (3/4-cut state), and with tendinous insertions of all fingers cut (all-cut state); and for group 2 at intact FDS, with tendinous insertions of the second and fifth digits cut (2/5-cut state), and at all-cut. Results: In experiment 1, the rate of change of the JS increased significantly with elbow valgus stress in both humans and Thiel cadavers, with no significant difference between groups. In experiment 2, the JS was significantly greater in the 3/4- and 2/5-cut states compared with the intact state at both 30 N (Δ3/4-cut vs intact = 0.23 mm [ P = .01]; Δ2/5-cut vs intact = 0.32 mm [ P = .02]) and 60 N (Δ3/4-cut vs intact = 0.33 mm [ P = .002]; Δ2/5-cut vs intact = 0.37 mm [ P = .04]). There was no significant difference in JS measurements between the 3/4- and 2/5-cut states at any load. Conclusion: Thiel cadavers showed JS changes similar to those of humans when valgus stress was applied. The third and fourth digits and the second and fifth digits of the FDS were involved in valgus stability, and there was no difference in their respective contributions. Clinical Relevance: This study may help in identifying function of the FDS based on structure.

Evaluation of flexor digitorum superficialis function in adolescent baseball players

“… 25 , 29 Recently, studies have reported that increasing FDS function increases the medial-side stability in valgus stress and helps to improve baseball players with ulnar collateral ligament injury. 9 , 18 , 22 , 24 Regarding finger movements during pitching motion, the force of the thumb and ring fingers is greatest just before the maximum shoulder external rotation, whereas the force produced from the index and middle fingers reaches the peak just before the maximum shoulder external rotation and ball release. 11 Previous studies using cadavers have reported that the index, small, and independent small fingers adhere to the anterior oblique ligament of the MCL.…”

Acute Effect of Four Stretching Protocols on Change of Direction in U-17 Male Soccer Players

“…The CV% was calculated for each athlete and then averaged out across the team through the division of the standard deviation by the mean of COD (CV = 100 (SD/M)). The minimum detectable difference at the 95% CI (MDD) was calculated using the following equation: MDD = z × standard error of measurement × √2, where z is 1.96 and the standard error of measurement is SD√(1−ICC) [ 47 , 48 , 49 ]. Effect size was presented using partial eta squared (η p 2 ), were 0.01 < η p 2 < 0.06 is defined as a small effect, 0.06 < η p 2 < 0.014 is defined as medium, and η p 2 > 0.14 resembled a large effect [ 50 ].…”