Flexor-pronator Muscle Research Articles

Pre-Draft Elbow Magnetic Resonance Imaging in Major League Baseball Pitchers (127)

Objectives:Evaluate pre-draft elbow MRI on baseball pitchers who were entering the MLB draft to determine the presence or absence of pathology, and the associations between these pathologies and UCL tears, and inter-observer reliability regarding common MRI pathology.Methods:Pre-draft elbow MRI and X-Rays on prospective MLB pitchers between 2011-2017 were deidentified and reviewed by two separate authors. The authors graded the X-Rays MRI on several factors including presence or absence of ulnar collateral ligament (UCL) ossification, UCL appearance (heterogeneous or not), UCL thickening (and location), UCL tear (partial vs. full thickness and location), muscle strain, flexor tendon tear, posteromedial osteophyte, sublime tubercle enthesophyte, and osseous stress reactions.Results:Overall, 245 pre-draft elbow X-Rays and MRI were reviewed. On X-Ray: 12 (4.9%) had ossification within the UCL; 34 (13.9%) had an olecranon osteophyte; 14 (5.7%) had a sublime tubercle enthesophyte. MRI abnormalities were found in 70% (171/245) of pitchers. UCL thickening was found in 20% of pitchers. Regarding UCL tears, 3% had a full thickness tear and 24% had a partial thickness tear. Of full thickness tears, 86% were distal and one was midsubstance. Of partial thickness tears, 41% (24/58) were distal, 12% (7/58) were midsubstance, and 47% (27/58) were proximal. Periligamentous edema was present in 36% of pitchers while 14% had a flexor pronator muscle strain. Stress reactions were seen in 27% and most commonly involved the sublime tubercle. Based upon the presence of periligamentous edema, distal UCL pathology was more likely to be chronic than acute while proximal UCL pathology was more likely to be acute.Conclusions:The majority (70%) of pitchers entering the MLB draft had abnormal findings on their MRI, most commonly involving changes to the UCL. Interobserver reliability was acceptable following definition of pathology when reading pre-draft elbow MRI on MLB prospects.

High elasticity of the flexor carpi ulnaris and pronator teres muscles is associated with medial elbow injuries in youth baseball players

ABSTRACT Objectives The purpose of the present study was to measure the elasticities of the forearm flexor-pronator muscles in youth baseball players and examine their relationships with medial elbow injuries. Methods We examined the strain ratios (SR) of the flexor digitorum superficialis (FDS), flexor carpi ulnaris (FCU), and pronator teres (PT) in 89 youth baseball players with medial epicondylar fragmentation (injury group) and in 142 healthy baseball players (control group). An index of muscle elasticity was determined using ultrasound strain elastography. The SR of each muscles was compared between the injury and control groups, and the SR of the both side arms was compared within group. Moreover, multivariable logistic regression analyses were conducted to examine the association of forearm muscle elasticity with medial elbow injuries. Results The SR of the FCU and PT of the throwing arm were significantly higher in the injury group than in the control group (both P < .001). In the injury group, the SR of the FCU was higher in the throwing arm than in the non-throwing arm (P < .001), but no difference was noted for the PT. Multivariable logistic regression analyses showed that a 0.1 increase of the SR of the FCU of the throwing arm (odds ratio [OR] 1.30, 95% confidence interval [CI] 1.14–1.48) and PT of the throwing arm (OR 1.41, 95% CI 1.19–1.67) and the non-throwing arm (OR 1.31, 95% CI 1.12–1.54) was significantly associated with an increased prevalence of medial elbow injuries. Conclusion High elasticities of the FCU of the throwing arm and PT of both the arms were observed in individuals with medial elbow injuries, and were associated with increased prevalence of medial elbow injuries. These findings may be characteristic of medial elbow injuries in youth baseball players.

Elasticity of the Flexor Carpi Ulnaris Muscle After an Increased Number of Pitches Correlates With Increased Medial Elbow Joint Space Suppression.

Saito, A, Namiki, Y, and Okada, K. Elasticity of the flexor carpi ulnaris muscle after an increased number of pitches correlates with increased medial elbow joint space suppression. J Strength Cond Res 35(9): 2564-2571, 2021-This study aimed to measure the medial elbow joint space and elasticity of the forearm flexor-pronator muscles in repetitive pitching and to determine which of the forearm flexor-pronator muscles contribute to elbow valgus stability during pitching. Twenty-six collegiate baseball players performed 7 sets of 15 pitches. The medial elbow joint space and elasticity of the pronator teres, flexor carpi radialis, flexor digitorum superficialis (FDS), and flexor carpi ulnaris (FCU) were measured using ultrasonography before pitching and after every 15 pitches. Correlations among the rate of change of these parameters were analyzed using Pearson's correlation coefficients. The medial elbow joint space increased after 60 or more pitches compared with that before pitching (all p < 0.001; effect size [ES]: 0.44-1.22). FDS and FCU elasticity increased after 45 and 60 pitches or more in contrast to that before pitching, respectively (FDS: p = 0.047 and p < 0.001, respectively; ES: 1.05-1.42, FCU: p = 0.011 and p < 0.001, respectively; ES: 1.11-1.48). After 75 or more pitches, the rate of change of FCU elasticity correlated negatively with that of the medial elbow joint space (r = -0.395, r = -0.454, and r = -0.404, after 75, 90, and 105 pitches, respectively). Increased FCU elasticity after repetitive pitching correlated with suppression of the increase of the medial elbow joint space. The FCU may be the primary dynamic stabilizer against the elbow valgus force, and evaluation of the FCU elasticity may be important for preventing elbow injuries.

Ulnar Collateral Ligament Laxity After Repetitive Pitching: Associated Factors in High School Baseball Pitchers

Background: Medial elbow injury is common in baseball pitchers, with evidence of elbow valgus instability after only 60 consecutive pitches. However, the tissue-specific effects of repetitive pitching on medial elbow stabilizers are largely unknown. Purpose/Hypothesis: This study aimed to investigate changes in the ulnar collateral ligament (UCL) and forearm flexor-pronator muscles (FPMs) during repetitive pitching and factors that relate to identified change. We hypothesized that repetitive pitching would increase elasticity of the medial elbow stabilizers and therefore induce laxity. Study Design: Descriptive laboratory study. Methods: A total of 30 high school baseball pitchers participated (mean ± SD age, 16.6 ± 0.5 years). Each participant pitched 100 times (5 blocks of 20 pitches). The strain ratio, indicating elasticity in the UCL and FPMs, was measured using ultrasound before pitching and after every 20-pitch block. Data for each pitch block were compared using analysis of variance. Multiple regression analysis was used to investigate factors related to the change rate of the strain ratio. Results: The strain ratio of the UCL after 100 pitches was significantly less than that before pitching (before pitching, 4.83 ± 1.70; after 100 pitches, 3.59 ± 1.35; P = .013), but this was not the case for the FPMs (before pitching, 0.57 ± 0.24; after 100 pitches, 0.43 ± 0.18; P = .07). The ratio of the strain ratio in the UCL and FPMs (UCL/FPMs) before pitching (β = −0.385; P = .031) and the elbow flexion range of motion before pitching (β = −0.352; P = .046) were significantly and independently correlated with the change rate of the UCL. Conclusion: Elasticity significantly increased for the UCL, indicating laxity, but not for the FPMs after 100 pitches. Furthermore, the ratio of elasticity (UCL/FPMs) and the elbow flexion range of motion before pitching were significantly related to the change rate of UCL elasticity. Clinical Relevance: To reduce laxity of the UCL, pitchers should be limited to <100 pitches per game. Sustaining a lower level of relative FPMs to UCL elasticity at rest and maintaining a large muscle volume to avoid excessive elbow flexion range of motion may prevent UCL laxity that develops during repetitive pitching.

The Effects of Differences in the Morphologies of the Ulnar Collateral Ligament and Common Tendon of the Flexor-Pronator Muscles on Elbow Valgus Braking Function: A Simulation Study.

The anterior bundle (AB) and posterior bundle (PB) of the ulnar collateral ligament and the anterior common tendon (ACT) and posterior common tendon (PCT) of the flexor-pronator muscles have an independent form and an unclear form. The purpose of this study was to clarify the effect of differences in the morphologies of the AB, PB, ACT, and PCT on the elbow valgus braking function. This investigation examined three elbows. In the classification method, the AB, PB, ACT, and PCT with independent forms constituted Group I; the AB, ACT, and PCT with independent forms and the PB with an unclear form constituted Group II; the AB, PB, ACT, and PCT with unclear forms constituted Group III. The strains were calculated by simulation during elbow flexion at valgus at 0° and 10°. At 0° valgus, Group I and Group II showed similar AB and PCT strain patterns, but Group III was different. At 10° valgus, most ligaments and tendons were taut with increasing valgus angle. The average strain patterns of all ligaments and tendons were similar for the groups. The AB, PB, ACT, and PCT may cooperate with each other to contribute to valgus braking.

Relationship between pain, elbow valgus instability, and the function of flexor pronator muscles in baseball players.

HypothesisWe hypothesize that ulnohumeral joint space distance due to gravity valgus stress may not be related to pain in the medial elbow of the dominant arm in baseball players.MethodsThirty-one male baseball players were divided into an ulnar collateral ligament (UCL) injury group (n = 16) and a Healthy group (n = 15). The injury groups were diagnosed with UCL injury by magnetic resonance imaging, and was defined as having pain during throwing. The medial elbow of each player's throwing arm was imaged by ultrasonography under valgus stress. The ulnohumeral joint space was measured for horizontal and vertical distances. The examiner added resistance force on the subject in order to produce isometric contraction of the forearm pronator muscles (FPMs). Measurements were taken at rest and at FPM isometric contraction. The Mann-Whitney U test was used to compare data between the dominant and nondominant sides, and between the UCL injury group and the Healthy group.ResultsThe horizontal and vertical distance at rest on the dominant side was not significantly different between 2 groups. The vertical distance during contraction of the flexor carpi radialis (FCR), flexor carpi ulnaris (FCU), and pronator teres (PT) muscles was significantly different between the UCL injury group and the Healthy group (P < .05) and was shifted laterally. A shift in the lateral direction indicates an increase in valgus instability.ConclusionsThe dominant side suggested that the space in the ulnohumeral joint space was wider, with or without pain. It was suggested that players with medial elbow pain may have impaired FCR, FCU, and PT function.

Morphological Features of the Ulnar Collateral Ligament of the Elbow and Common Tendon of Flexor-Pronator Muscles.

Background:The anterior bundle (AB) of the ulnar collateral ligament is the most important structure for valgus stabilization of the elbow. However, anatomic relationships among the AB, posterior bundle (PB) of the ulnar collateral ligament, and common tendon (CT) of the flexor-pronator muscles have not been fully clarified.Purpose:To classify the AB, PB, and CT and to clarify their morphological features.Study Design:Descriptive laboratory study.Methods:This investigation examined 56 arms from 31 embalmed Japanese cadavers. The CT investigation examined 34 arms from 23 embalmed Japanese cadavers with CTs remaining. Type classification was performed by focusing on positional relationships with surrounding structures. Morphological features measured were length, width, thickness, and footprint for the AB and PB and attachment length, thickness, and footprint for the CT.Results:The AB was classified as type I (44 elbows; 78.6%), can be separated as a single bundle, or type II (12 elbows; 21.4%), cannot be separated from the PB and joint capsule. The PB was classified as type I (28 elbows; 50.0%), can be separated as a single bundle; type IIa (6 elbows; 10.7%), posterior edge cannot be separated; type IIb (7 elbows; 12.5%), anterior edge cannot be separated; or type III (15 elbows; 26.8%), cannot be separated from the joint capsule. The CT was classified as type I (18 elbows; 52.9%), can be separated from the AB, or type II (16 elbows; 47.1%), cannot be separated from the AB. Significant differences in frequencies of AB, PB, and CT types were identified between men and women. Morphological features were measured only for type I of each structure, and reliability was almost perfect.Conclusion:These results suggest that the AB, PB, and CT each can be classified into an independent form and an unclear form. Presence of the unclear form was suggested as one factor contributing to morphological variation.Clinical Relevance:This study may provide basic information for clarifying functional roles of the AB, PB, and CT.

Flexor pronator muscles' contribution to elbow joint valgus stability: ultrasonographic analysis in high school pitchers with and without symptoms

BackgroundFew researchers have examined the different contributions of flexor-pronator muscles to valgus stress in high school baseball pitchers with and without elbow symptoms. This study used ultrasonography to assess these muscles' dynamic contributions to elbow valgus joint stability in high school pitchers.MethodsA self-administered questionnaire on throwing-related elbow joint pain sustained during the prior year was completed by 89 high school baseball pitchers. Gravity stress ultrasonographic elbow examinations with 30° of flexion were done before and after isometric contraction of the flexor-pronator muscles. For study participants with and without a history of elbow symptoms, we compared differences of ulnohumeral joint space without gravity stress and isometric contraction of the flexor-pronator muscles and with gravity stress only and with isometric contraction of the flexor-pronator muscles under gravity stress.ResultsFor each pitcher, the ulnohumeral joint space in the condition with valgus stress was significantly larger than in the condition without valgus stress. Also, the ulnohumeral joint space in the condition with valgus stress was significantly larger than in the condition with valgus stress and flexor-pronator isometric muscle contraction. Participants with and without elbow symptom history showed no differences of ulnohumeral joint space in the unloaded and loaded flexor-pronator muscle contracted conditions.ConclusionUltrasonographic assessment demonstrated that flexor-pronator muscles contribute to elbow valgus stability. No difference was found in the flexor-pronator muscle contribution in high school baseball pitchers with and without elbow symptom history.

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

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. 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. 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). 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.

Medial elbow anatomy: A paradigm shift for UCL injury prevention and management.

To improve the management outcomes and diagnostic accuracy of the ulnar collateral ligament (UCL) injury, the anatomy of the medial side of the elbow joint is necessary to be understood in terms of the periarticular surroundings rather than the specific ligaments. The aim of this study was to anatomically clarify the medial side of the elbow joint in terms of the tendinous structures and joint capsule. We conducted a descriptive anatomical study of 23 embalmed cadaveric elbows. We macroscopically analyzed the relationship between the flexor pronator muscles (FPMs) and the joint capsule in 10 elbows, histologically analyzed in 6 elbows, and observed the bone morphology through micro computed tomography in 7 elbows. The two tendinous septa (TS) were found: between the pronator teres (PT) and flexor digitorum superficial (FDS) muscles, and between the FDS and flexor carpi ulnaris (FCU) muscles. These two TS are connected to the medial part of the brachialis tendon, deep aponeurosis of the FDS, and FCU to form the tendinous complex, which linked the humeroulnar joint and could not be histologically separated from each other. Moreover, the capsule of the humeroulnar joint under the tendinous complex had attachment on the ST of 7 mm width. The two TS, the brachialis tendon, the deep FDS and FCU aponeuroses, and the joint capsule linked the humeroulnar joint. These anatomical findings could lead to a paradigm shift in the prevention, diagnosis, and treatment of UCL injuries in baseball players. Clin. Anat. 32:379–389, 2019. © 2018 The Authors. Clinical Anatomy published by Wiley Periodicals, Inc. on behalf of American Association of Clinical Anatomists.

Analysis of magnetic resonance imaging–confirmed soft tissue injury pattern in simple elbow dislocations

The elbow is the second most commonly dislocated joint. Stability depends on the degree of soft tissue injury, with 2 proposed patterns, one starting laterally and the other medially. The purpose of this study was to describe the injured structures observed in magnetic resonance images (MRIs) in a prospective cohort of simple elbow dislocations. We evaluated 17 consecutive cases of simple elbow dislocations. Two musculoskeletal radiologists assessed the initial x-ray images and MRIs performed for all elbows. Radiologists evaluated the following soft tissue structures: medial collateral ligament complex (MCL), flexor-pronator muscle mass origin, anterior capsule (AC), posterior capsule, lateral collateral ligament complex (LCL), and extensor muscle mass origin. The radiologists were blinded to the study hypothesis. The initial radiographs in 16 patients showed the dislocation was posterolateral in 12, posterior in 3, and posteromedial in 1. We observed complete AC tear in 12 patients, MCL in 10, and LCL in 9. The inter-rater reliability for the radiologists was 0.70 (substantial) for MRI. In our series after simple elbow dislocation, complete AC tears were most common, followed by MCL and LCL tears. No single mechanism-related soft tissue injury pattern of simple elbow dislocation was observed, and different grades of soft tissue injury exist.

Valgus instability of the elbow: acute and chronic form.

There has been an increase in thrower-specific elbow injuries in recent years. High valgus stresses during the late cocking and acceleration phases of throwing need to be compensated by the flexor pronator muscles as these can exceed the tensile strength of the medial collateral ligament complex. Prevention of injuries is the priority, with a focus on strengthening, reducing throwing frequency, decreasing force, and promoting a technique. The spectrum of thrower injuries ranges from a simple sprain to complete failure of the valgus stabilizing factors. The medial collateral ligament can stretch, leading to posteromedial impingement and radiocapitellar compression forces. This in turn can result in arthrosis and the formation of osteophytes. Ligament failure may eventually occur, making it impossible for the athlete to continue their throwing activities. The outcome of conservative treatment with strengthening, improvement of technique, and relative rest is often disappointing. Direct repair may no longer be possible in these acute-on-chronic injuries and a reconstruction with a tendon graft may be necessary.

The 7 Structures Distal to the Elbow That Are Critical to Successful Anterior Transposition of the Ulnar Nerve.

Background: Ulnar nerve transposition (UNT) surgery is performed for the treatment of cubital tunnel syndrome. Improperly performed UNT can create iatrogenic pain and neuropathy. The aim of this study is to identify anatomical structures distal to the medial epicondyle that should be recognized by all surgeons performing UNT to prevent postoperative neuropathy. Methods: Ten cadaveric specimens were dissected with attention to the ulnar nerve. Intramuscular UNT surgery was simulated in each. Distal to the medial epicondyle, any anatomical structure prohibiting transposition of the ulnar nerve to a straight-line course across the flexor-pronator mass was noted and its distance from the medial epicondyle was measured. Results: Seven structures were found distal to the medial epicondyle whose recognition is critical to ensuring a successful anterior transposition of the ulnar nerve: (1) Branches of the medial antebrachial cutaneous (MABC) nerve; (2) Osborne's fascia; (3) branches from the ulnar nerve to the flexor carpi ulnaris (FCU); (4) crossing vascular branches from the ulnar artery to the FCU; (5) the distal medial intermuscular septum between the FCU and flexor digitorum superficialis (FDS); (6) the combined muscular origins of the flexor-pronator muscles; and (7) the investing fascia of the FDS. Measurements are given for each structure. Conclusions: Poor outcomes and unnecessary revision surgeries for cubital tunnel syndrome can be avoided with intraoperative attention to 7 structures distal to the medial epicondyle. Surgeons should expect to dissect up to 12 cm distal to the medial epicondyle to adequately address these and prevent kinking of the nerve in transposition.

Quantifying the Center of Elbow Rotation: Implications for Medial Collateral Ligament Reconstruction.

Medial collateral ligament (MCL) reconstruction of the elbow mandates precise characterization of where the centerline of elbow rotation projects onto the medial epicondyle (ME). A muscle-splitting approach allows the flexor-pronator muscles to remain attached to the ME and facilitates visualization of the MCL remnant, the sublime tubercle, and the ulnohumeral joint line. Knowledge of where the centerline of rotation intersects the ME relative to the ulnohumeral joint line may assist the surgeon during placement of the proximal drill hole. Models were created from the computed tomography scans of 29 normal elbows. The centerline of rotation, center of the trochlea, sublime tubercle, and ulnohumeral joint line were identified. Measurements were taken from the ulnohumeral joint line to the center of the trochlea and to the centerline of rotation in the sagittal view and along the course of the MCL. The centerline of rotation intersected the ME in a consistent location. With the elbow flexed 90°, the trochlea center and the centerline of rotation are essentially in line with each other. There are significant differences between the distances from the ulnohumeral joint line to the center of the trochlea and to the centerline of rotation in both the sagittal view and along the course of the MCL. The centerline of rotation is located 14.31 mm (1.70) from the ulnohumeral joint line in the sagittal view and 16.54 mm (2.09) from the ulnohumeral joint line along the course of the MCL.

Bare medial epicondyle physeal fracture of the humerus: A case report

We identified an unusual case of the medial epiondyle physeal fracture, which has been caused by a direct blow, accompanied with complete stripping of soft tissue. Surgery was performed for open reduction and internal fixation of the medial epicondyle and reattachment of the anterior oblique bundle of medial collateral ligament and flexor muscle origin. Six months after the surgery, strength of wrist flexion and forearm pronation, range of motion and valgus stability of the left elbow had recovered. One year after the injury, radiographs showed atrophy and sclerosis of the medial epicondylar apophysis. In this type of injury, revascularization of medial epicondyle fracture is not essential for recovery of elbow function when reattachment of the medial collateral ligament and flexor-pronator muscle origin to the distal medial humerus successfully restores stability of the elbow joint.

Strength of Dynamic Stabilizers of the Elbow in Professional Baseball Pitchers Decreases during Baseball Season

Objectives:Injuries to the ulnar collateral ligament (UCL) are one of the most common and severe incurred by pitchers. Baseball pitchers of all ages and levels have seen an increase in the diagnosis of these injuries. Tears of the UCL are caused by high valgus forces at the elbow of which the UCL is the primary restraint. Biomechanical studies have demonstrated that baseball pitchers either approach or exceed the maximum tensile strength of the UCL while throwing. Valgus force is additionally resisted by the flexor pronator (FP) muscles: flexor carpi ulnaris (FCU), flexor digitorum superficialis (FDS), and pronator teres (PT), which act as secondary stabilizers. The importance of these secondary stabilizers has not been clearly demonstrated. The goal of this study was to monitor the strength changes in the secondary stabilizers of the elbow over the course of the baseball season and to attempt to correlate any of those changes to observed UCL injuries.Methods:With approval of the Institutional Review Board, 19 professional minor league baseball pitchers were evaluated in spring training and then at the conclusion of the season for flexor-pronator muscle strength. Additionally, their medical histories were assessed for incidents of ulnar collateral ligament injuries and days missed from baseball activities. Each player was assessed using custom testing devices measuring forearm pronation strength, wrist flexion strength, and isolated ring finger FDS strength. Both dominant and non-dominant arms were evaluated and the same testing procedure was performed both at spring training and at the conclusion of the baseball season. Strength was defined as the maximum isometric force generated over three trials. For each test, percentile rank was determined within the sample. A comparison between spring and fall assessments was done using a paired two sample T-test for means.Results:For all three tests, there was a demonstrated decrease of strength in both the pitching arm and non-pitching arm over the season. Pronation strength, wrist flexion strength, and FDS strength to the ring finger decreased 16.1%, 13.7%, and 4.9% respectively in the throwing arm. The decrease in pronation strength and wrist flexion strength in the throwing arm were statistically significant (p=0.001 and 0.003 respectively). Although the non-throwing arm also decreased in strength, it did not reach statistical significance. Two of the nineteen players were diagnosed with ulnar collateral ligament sprains during the season. The two injured players were the 1st and 3rd weakest in a composite percentile strength ranking from the spring assessment.Conclusion:In this study, we showed a diminution of strength of the muscles that act as secondary stabilizers of the ulnar collateral ligament over the course of the professional baseball season. The flexor pronator muscles (specifically the FCU, PT, and FDS) may help protect baseball pitchers from ulnar collateral ligament injuries and weakness of these muscles might make individuals prone to ulnar collateral ligament injuries and subsequent valgus overload syndrome. It is possible that this data would be helpful to predict individuals who are predisposed toward ulnar collateral ligament injuries, as well as in the development of comprehensive flexor-pronator muscle strengthening programs aimed at maintaining secondary stabilizer strength over the course of the baseball season.

Anatomical considerations of fascial release in ulnar nerve transposition: a concept revisited.

Surgical transposition of the ulnar nerve to alleviate entrapment may cause otherwise normal structures to become new sources of nerve compression. Recurrent or persistent neuropathy after anterior transposition is commonly attributable to a new distal compression. The authors sought to clarify the anatomical relationship of the ulnar nerve to the common aponeurosis of the humeral head of the flexor carpi ulnaris (FCU) and flexor digitorum superficialis (FDS) muscles following anterior transposition of the nerve. The intermuscular septa of the proximal forearm were explored in 26 fresh cadaveric specimens. The fibrous septa and common aponeurotic insertions of the flexor-pronator muscle mass were evaluated in relation to the ulnar nerve, with particular attention to the effect of transposition upon the nerve in this region. An intermuscular aponeurosis associated with the FCU and FDS muscles was present in all specimens. Transposition consistently resulted in angulation of the nerve during elbow flexion when this fascial septum was not released. The proximal site at which the nerve began to traverse this fascial structure was found to be an average of 3.9 cm (SD 0.7 cm) from the medial epicondyle. The common aponeurosis encountered between the FDS and FCU muscles represents a potential site of posttransposition entrapment, which may account for a subset of failed anterior transpositions. Exploration of this region with release of this structure is recommended to provide an unconstrained distal course for a transposed ulnar nerve.

Medial elbow pain in the overhead athlete

This review aims to cover the anatomy, mechanics, injury mechanism, physical examination, imaging, diagnosis and treatment of medial elbow pain in overhead athletes. Due to the repetitive valgus stress overhead athletes place on their elbows, they are susceptible to common causes of medial elbow pain. These include ulnar collateral ligament tears, ulnar neuritis, medial epicondyle apophysitis or avulsion fractures, flexor-pronator muscle strains or tendinitis, and valgus extension overload syndrome. With a more detailed knowledge of the injury mechanisms and up-to-date treatment options for these patients, physicians will be able to prevent and better treat medial elbow pain in overhead athletes.

Ultrasonographic assessment of the flexor pronator muscles as a dynamic stabilizer of the elbow against valgus force.

Flexor pronator muscles (FPMs) play a key role in stabilizing the elbow joint against valgus forces. However, no studies have investigated the in vivo kinematics of FPMs against these forces on the elbow. This study aimed to clarify the in vivo contribution of each FPM as a dynamic stabilizer in a clinical situation.Twelve healthy volunteers participated in this study. Verbal informed consent was obtained from all subjects. The elbow was flexed to 90 degrees, and the forearm was placed in the neutral position. Manual valgus stress was applied to the elbow joint until maximal shoulder external rotation was achieved. The width of the ulnohumeral joint space and the ulnar shift of the sublime tubercle were measured before and after isometric contraction of FPMs using ultrasonography.The horizontal distances were decreased 1.1±0.6 mm after forearm pronation, 0.6±0.5 mm after wrist palmar flexion, 0.1±0.4 mm after wrist ulnar flexion, and 0.2±0.5 mm after finger flexion. Significant changes were observed during forearm pronation, wrist palmar flexion, and finger flexion but not during wrist ulnar flexion (p<0.05). The sublime tubercle was significantly shifted 0.5±0.1 mm medially after forearm pronation, 0.2±0.1 mm medially after wrist palmar flexion, and 0.1±0.1 mm laterally after wrist ulnar flexion and finger flexion (p<0.05). The FPMs, especially the pronator teres and the flexor carpi radialis, function as dynamic stabilizers against elbow valgus stress. The results of this study may be useful in developing injury prevention and rehabilitation strategies for throwing injuries of the elbow.

The proximal origins of the flexor–pronator muscles and their role in the dynamic stabilization of the elbow joint: an anatomical study

The purpose of this study was to anatomically investigate the proximal origin of flexor-pronator muscles (FPMs) and clarify their contribution to dynamic stabilization of the elbow joint during valgus stress. 52 elbows from 26 donated formalin-fixed cadavers were examined. The pronator teres muscle (PT), flexor carpi radialis muscle (FCR), palmaris longus muscle (PL), flexor digitorum superficialis muscle (FDS), and flexor carpi ulnaris muscle (FCU) were identified, and their proximal origin and relationship to the anterior bundle of the medial ulna collateral ligament (AOL) were macroscopically and histologically investigated. The PT, FCR, PL, and FDS converged and formed a common tendon at their proximal origin (the anterior common tendon: ACT). The ACT was attached to the medial epicondyle and the joint capsule, just anterior and parallel to the AOL. The histological morphology of the ACT was quite similar to that of the AOL. The ulnar head of the PT was observed in 48 of 52 elbows (92.3 %), just behind the humeral head of PT. It mainly originated from the anterior edge of the sublime tubercle, while the upper part of ulnar head transitioned directly into the thickened joint capsule just anterior to the AOL. The proximal attachment of the FPMs had a characteristic morphology. According to our results, the ACT and PT might assist the AOL by sharing static and dynamic traction forces applied to the medial elbow joint.