The biomechanical role of the lacertus fibrosus of the biceps brachii Muscle

Abstract

Purpose The lacertus fibrosus (LF) is involved in various surgeries. However, the biomechanical contribution of the LF remains unclear. The aim of this study was to determine the role of the lacertus fibrosus on the elbow and forearm kinematics and on the biceps brachii muscle lever arms. Methods This biomechanical study was performed on seven fresh-frozen upper limbs of cadavers. Elbow flexion, forearm supination, and biceps brachii muscle lever arms were analyzed in the intact conditions (I) and after superficial (R) and deep part (R2) of the lacertus fibrosus release, respectively. Results Elbow flexion shows a significant difference (p < 0.0001) between I, R, R2. Abduction/adduction shows a significant difference between I-R (p < 0.0001) and I-R2 (p < 0.0001). Supination does not show a significant difference in mean maximum amplitude, but between 40 and 70%, there are significant differences. There is a significant mean decrease of lever arm in flexion (28%) and supination (50%) after superficial and deep part of the lacertus fibrosus release. ConclusionThe results of this study show that the lacertus fibrosus increases the lever arm during flexion and supination. It limits the flexion and abduction of the elbow and supination of the forearm. Lacertus fibrosus maintains the rhythmicity between the elbow flexion and supination of the forearm. Level of evidence Basic science study, biomechanics

Gender differences on effects of forearm rotation on compressive stiffness of flexor carpi ulnaris during submaximal handgrip contractions

“…These findings can also be explained by the factors mentioned above (muscle volume, connective tissue, and intramuscular fat). Furthermore, they may also be related to structural in‐series continuity described between the biceps and medial forearm muscles via the antebrachial fascia and the lacertus fibrosus (Snoeck, 2021; Snoeck et al, 2014; Stecco, Gagey, Belloni, et al, 2007; Stecco, Gagey, Macchi, et al, 2007). Also, a mechanical interaction between the biceps and brachialis muscles during passive forearm rotation has been reported (Yoshitake et al, 2018).…”

“…Also, a mechanical interaction between the biceps and brachialis muscles during passive forearm rotation has been reported (Yoshitake et al, 2018). The action as supination of the biceps through the antebrachial fascia and the tension on the lacertus fibrosus may increase the FCU during handgrip (Konschake et al, 2017; Snoeck, 2021; Snoeck et al, 2014) (See Figure 2). Another possible explanation for our results may be the muscle length of FCU.…”

“…For instance, in vitro has been reported that passive tension of the medial forearm musculature increases elbow stability when the forearm is supinated (Seiber et al, 2009). Certain researchers, including Konschake et al and Snoeck et al, have proposed that different structures, such as biceps brachii muscle (biceps) and antebrachial fascia, may be related to changes in the stiffness of the medial forearm muscle (Konschake et al, 2017; Snoeck, 2021; Snoeck et al, 2014). The biceps as supinator may increase the passive tension of the medial forearm musculature through the antebrachial fascia (Konschake et al, 2017, Snoeck, 2021, Snoeck et al, 2014).…”

“…Certain researchers, including Konschake et al and Snoeck et al, have proposed that different structures, such as biceps brachii muscle (biceps) and antebrachial fascia, may be related to changes in the stiffness of the medial forearm muscle (Konschake et al, 2017; Snoeck, 2021; Snoeck et al, 2014). The biceps as supinator may increase the passive tension of the medial forearm musculature through the antebrachial fascia (Konschake et al, 2017, Snoeck, 2021, Snoeck et al, 2014). The antebrachial fascia via the lacertus fibrosus (i.e., bicipital aponeurosis) releases a strong fascial adhesion to the medial forearm musculature (Snoeck, 2021, Snoeck et al, 2014).…”

“…The biceps as supinator may increase the passive tension of the medial forearm musculature through the antebrachial fascia (Konschake et al, 2017, Snoeck, 2021, Snoeck et al, 2014). The antebrachial fascia via the lacertus fibrosus (i.e., bicipital aponeurosis) releases a strong fascial adhesion to the medial forearm musculature (Snoeck, 2021, Snoeck et al, 2014). The lacertus fibrosus has been shown to increase the lever arm of biceps during flexion and supination (Snoeck, 2021) and transmitted forces between the antebrachial fascia and medial forearm muscles (e.g., FCU) (Snoeck, 2021).…”