The role of the elbow musculature, forearm rotation, and elbow flexion in elbow stability: an in vitro study

Elastic textile-based wearable modulation of musculoskeletal load: A comprehensive review of passive exosuits and resistance clothing

Elastic textiles play a critical role in passive wearable solutions for musculoskeletal load management in both passive exosuits and resistance clothing. These textiles, based on their ability to stretch and retract, can exhibit ambivalence in their load-modulating effects when used in occupational, rehabilitation, exercise, or everyday activity settings. While passive exosuits and resistance garments may appear similar in design, they have opposing goals: to reduce the musculoskeletal load in the case of exosuits and to increase it in the case of resistance clothing. Despite this intrinsic connection, these two approaches have not been extensively linked together. This review aims to fill this gap by examining the common and distinct principles of elastic textiles in passive exosuits and resistance clothing, shedding light on their interactions and the complex dynamics of musculoskeletal load systems. The effectiveness of different designs in passive exosuits that mimic musculoskeletal function and resistance clothing that increase the workload for strength training are critically reviewed. Current challenges in practical implementation and opportunities to improve critical issues, such as preload, thermal comfort, skin friction, and donning and doffing are also highlighted.

Comparative study of open elbow arthrolysis with and without hinge external fixation for the treatment of post-traumatic elbow stiffness

BACKGROUND

The present study aimed to compare the functional outcomes of hinged external fixators and non-external fixation in open elbow arthrolysis (OEA) for post-traumatic elbow stiffness (PTES) and to evaluate their applicability and limitations in patients with posttraumatic elbow stiffness.

METHODS

The clinical data of patients with PTES treated with OEA at our hospital between March 2015 and June 2022 were retrospectively analyzed. The assessed variables were the operation time, intraoperative blood loss volume, duration of hospitalization, and treatment costs. The elbow range of motion (ROM), Mayo Elbow Performance Score (MEPS), shortened disabilities of the arm, shoulder and hand questionnaire (Q-DASH) score, Oxford Elbow score (OES), Broberg and Morrey score (BMS), visual analog scale (VAS) for pain, and complications such as pin tract infection and heterotopic ossification were compared between patients with and without hinge external fixation. We also compared the baseline characteristics and functional outcomes of patients with and without hinge external fixation.

RESULTS

A total of 156 patients (48 patients with hinged external fixators and 108 patients without external fixators) diagnosed with PTES were included in this study. The mean follow-up was 15.8 ± 3.6 months. Compared with patients without external fixators, those with external fixators showed significantly greater improvements in elbow flexion and extension ROM (59.6° ± 26.1° vs. 46.2° ± 26.2°, p = 0.004) but had a significantly longer duration of hospitalization (p < 0.001), significantly longer operation time (p < 0.001), significantly higher treatment costs (p < 0.001), and significantly greater intraoperative blood loss volume (p < 0.001). There were no significant differences between the two groups in terms of improvement in elbow rotation ROM, MEPS score, VAS score for pain, OES score, Q-DASH score, BMS score, or incidence of complications.

CONCLUSION

The use of a hinged external fixator in open arthrolysis for posttraumatic elbow stiffness may result in short-term improvements in flexion-extension range of motion but is accompanied by increased blood loss, longer operative time, extended hospitalization, and higher costs. Further studies are needed to confirm these findings.

CLINICAL TRIAL NUMBER

Not applicable.

Upper arm muscle activity is influenced by both forearm posture and wrist exertion direction during isometric wrist flexion and extension

The purpose of this study was to determine how wrist exertion direction and forearm posture independently influence upper arm muscle activity during isometric wrist contractions. Surface electromyography was recorded from three muscles of the upper-limb: biceps brachii, triceps brachii, and brachioradialis. Participants were seated with their forearm supported in one of three postures (supinated/neutral/pronated) with an adjustable force transducer that could be placed either above, below, or to the right/left of the participant's hand. Participants performed randomized trials of isometric wrist flexion or extension at five relative intensities: 20, 40, 60, 80, or 100% of maximal force. Trials lasted 4.5 s and both wrist force and electromyography data were assessed. In general, the elbow flexors were more active during wrist flexion, while the triceps were more active in wrist extension, but this pattern reversed in certain forearm postures and wrist exertion directions. Both forearm posture and wrist exertion direction resulted in unique effects on upper arm muscle activity. These findings suggest that muscle activity of the upper arm muscles is influenced independently by both posture and force direction, which should be carefully considered by both motor control specialists and ergonomists.

Morphological changes in the interosseous membrane of the forearm during forearm rotation

[Purpose] Changes in forearm interosseous membrane dynamics during forearm rotation relative to the shoulder joint position remain poorly understood. The purpose of this study was to clarify interosseous membrane dynamics during forearm rotation in shoulder abduction and external rotation positions. [Participants and Methods] We conducted open magnetic resonance imaging on 17 healthy forearms in the prone position. Three limb positions were set for measuring the forearm rotation angle: intermediate, maximum pronation, and maximum supination. Images were obtained with the shoulder joint abducted at 90°and externally rotated at 90°. The forearm interosseous membrane angle was measured at three points: the apex of the forearm interosseous membrane, the radius, and the ulna. The measurement of the interosseous angle was repeated thrice. [Results] Sufficient intra-rater reliability was confirmed for the forearm interosseous membrane angle measurement. The interosseous membrane of the forearm showed a mean dorsal convex shape during forearm pronation (141.7° ± 0.83°), and the mean palmar convex shape during forearm supination (-141.6° ± 0.64°). [Conclusion] This study provides useful information for future research by quantifying the dynamics of the interosseous membrane of the forearm, which is an important soft tissue for forearm rotation. The establishment of a quantitative evaluation method for forearm interosseous morphological changes will help further elucidate forearm rotation movements during sports activities.

Quality control of elbow joint radiography using a YOLOv8-based artificial intelligence technology

BACKGROUND

To explore an artificial intelligence (AI) technology employing YOLOv8 for quality control (QC) on elbow joint radiographs.

METHODS

From January 2022 to August 2023, 2643 consecutive elbow radiographs were collected and randomly assigned to the training, validation, and test sets in a 6:2:2 ratio. We proposed the anteroposterior (AP) and lateral (LAT) models to identify target detection boxes and key points on elbow radiographs using YOLOv8. These identifications were transformed into five quality standards: (1) AP elbow positioning coordinates (XA and YA); (2) olecranon fossa positioning distance parameters (S17 and S27); (3) key points of joint space (Y3, Y4, Y5 and Y6); (4) LAT elbow positioning coordinates (X2 and Y2); and (5) flexion angle. Models were trained and validated using 2,120 radiographs. A test set of 523 radiographs was used for assessing the agreement between AI and physician and to evaluate clinical efficiency of models.

RESULTS

The AP and LAT models demonstrated high precision, recall, and mean average precision for identifying boxes and points. AI and physicians showed high intraclass correlation coefficient (ICC) in evaluating: AP coordinates XA (0.987) and YA (0.991); olecranon fossa parameters S17 (0.964) and S27 (0.951); key points Y3 (0.998), Y4 (0.997), Y5 (0.998) and Y6 (0.959); LAT coordinates X2 (0.994) and Y2 (0.986); and flexion angle (0.865). Compared to manual methods, using AI, QC time was reduced by 43% for AP images and 45% for LAT images (p < 0.001).

CONCLUSION

YOLOv8-based AI technology is feasible for QC of elbow radiography with high performance.

RELEVANCE STATEMENT

This study proposed and validated a YOLOv8-based AI model for automated quality control in elbow radiography, obtaining high efficiency in clinical settings.

KEY POINTS

QC of elbow joint radiography is important for detecting diseases. Models based on YOLOv8 are proposed and perform well in image QC. Models offer objective and efficient solutions for QC in elbow joint radiographs.

The influence of a single 30-pitch session on elbow laxity in adolescent and collegiate baseball pitchers

BACKGROUND

Ulnar collateral ligament (UCL) injuries are a source of significant injury among baseball players, and are increasingly evaluated under ultrasound. The purpose of this study is to determine the effect of a single session of pitching upon UCL thickness and laxity via a cross sectional, controlled ultrasonographic study. We hypothesize that a single session of pitching will cause the ulnar collateral ligament to thicken and become more lax.

METHODS

This was a cross sectional comparative study of collegiate and high school pitchers. Pitchers underwent an ultrasonographic assessment of the UCL before and after a thirty-pitch bullpen warm-up. Laxity was measured as the change in the distance between the ulna and the trochlea with and without a 5-pound weight held in hand with the elbow at 30° of flexion. Pre- and post-throwing UCL thickness and medial laxity were statistically compared with paired tests.

RESULTS

Our study included 15 pitchers, 8 collegiate and 7 high school level athletes. All played baseball at least 6 days a week, and nearly all played for at least 10 months a year. Pitchers reported a peak velocity of 89 ± 6 (77 to 98) miles per hour. In the prior season, these pitchers pitched 56 ± 33 (10 to 120) games, throwing 62 ± 34 (25-140) pitches per game on average. After throwing, there was significantly less UCL laxity (P = .013). Post-throwing laxity was significantly positively correlated with both peak pitch velocity (P = .009) and an average number of pitches thrown per game (P = .10).

CONCLUSION

Throwing 30 pitches significantly decreases medial elbow laxity with stress, possibly due to flexor-pronator activation. Post-throwing medial laxity is correlated with both peak pitch velocity and average number of pitches thrown per game. Future studies should be conducted to determine the number of throws at which laxity begins to increase, as this may provide a workload management guideline for injury prevention.

Evaluation of skeletal muscle elasticity using color Doppler shear wave imaging

PURPOSE

This study aimed to (1) assess the precision and reproducibility of color Doppler shear wave imaging (CD SWI) by comparing it with shear wave elastography (SWE) via elasticity phantom measurements, and (2) investigate the potential clinical applications of CD SWI in the upper limb muscles by assessing the reproducibility of skeletal muscle elasticity evaluations.

METHODS

Four elastography phantoms of different stiffness (6.0-7.5 wt%) were used to assess the precision and reproducibility of CD SWI (compared with SWE) at depths. Typical upper limb muscles of 24 men were also assessed for this comparison.

RESULTS

At superficial depths (0-2 cm), the phantom measurements obtained using CD SWI and SWE were similar at all levels of stiffness. Furthermore, both methods were highly reliable, with almost perfect intra- and inter-operator reliabilities. At greater depths (2-4 cm), measurements obtained using both methods were similar at all stiffness levels. Although standard deviations (SDs) of the phantom measurements obtained using both methods at lower stiffness were similar, those at higher stiffness were different. The SD of the CD SWI measurements was < 50% of that of the SWE measurements. However, both methods were highly reliable in the phantom test, with almost perfect intra- and inter-operator reliabilities. The intra- and inter-operator reliabilities of the shear wave velocity measurements for typical muscles of the upper limbs were also substantial in clinical settings.

CONCLUSION

CD SWI is a valid method for measuring elasticity, with precision and reliability as high as those of SWE.

Prevalence, diagnosis and management of musculoskeletal disorders in elite athletes: A mini-review

Musculoskeletal injuries in elite sports are ones of the most impact issue because their remarkable impact on performance caused by drastic absence of training and competition and a progressive deterioration in physical health, emotional and social athletes' dimensions. Also, the prevalence of epidemiologic research found an incidence of musculoskeletal disorders vary within sports and in elite athletes which is even higher as a consequence of higher demand physical performance. This way, the loss of physical performance due to an sport injury impacts not only the individual economic sphere of the professional but also that ofsports entities, reaching, according to some studies, a loss estimated in the range of 74.7 million pounds. Thus, the purpose of this article is to review and to provide an overview of the most common musculoskeletal injuries in elite sports precipitating factors, clinical presentation, evidence-based diagnostic evaluation, and treatment recommendations with a view to preventing medical conditions or musculoskeletal injuries that may alter performance and general health in the elite athletes.

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

Little is known about gender differences in stiffness of forearm muscles during voluntary actions. This study aimed to investigate the effect of forearm rotation on flexor carpi ulnaris (FCU) stiffness in men and women during submaximal handgrip contractions. During a single session, measurements were made on 20 young participants (9 females). Two positions of the forearm were compared in random order with the elbow flexed 90 degrees: (i) neutral position and (ii) maximal supination. In each position, participants performed two submaximal handgrip contractions at 25% and 50% of maximal voluntary contraction, while compressive stiffness was collected using a hand myometer (MyotonPRO). A mixed repeated measurement ANOVA was applied to assess the interaction between gender, forearm position, and contraction intensity. The FCU stiffness is affected by handgrip contraction intensity (p < 0.001), gender (p < 0.001), BMI (p = 0.009), and forearm rotation (p = 0.007). Only the gender factor was found to have significant interaction with forearm rotation (p = 0.037). Men's FCU was stiffer than women's in both positions and contraction intensities (p < 0.05). Only in men a significant increase in FCU stiffness was observed when comparing contraction intensities at both forearm positions (p < 0.05), as well as when the forearm was rotated from neutral to supine at both intensities (p < 0.05). In conclusion, FCU stiffness during handgrip contraction differed significantly between men and women. Women have fewer stiffness changes in FCU when performing different levels of handgrip contraction. We also observed that only men increased FCU stiffness by changing the forearm position from neutral to supine position for both handgrip intensities.

Ulnohumeral joint static cartilage compression is affected by radial head implant size

INTRODUCTION

Radiocapitellar joint arthroplasty is a commonly performed procedure, which often leads to early failure or instability. Few studies assess the effect of radiocapitellar joint arthroplasty on the ulnohumeral joint. We hypothesized that static forces of contact (compressing cartilage, or cartilage relaxation contact force) would reveal the effect of varying radial head implant size and elbow position on the ulnohumeral joint.

METHODS

A minimally-invasive method of measuring cartilage relaxation contact force was utilized in 10 fresh-frozen human cadaveric specimens that did not require significant dissection or intraarticular sensor placement. Specimens were rigidly fixed in various positions of elbow flexion and forearm pronosupination with increasing radial head implant lengths. Uniaxial distracting forces were applied and displacement was repeatedly measured with resultant best-fit polynomial curves to determine inflections corresponding to the force required to overcome static cartilage relaxation as in previous work.

FINDINGS

Baseline mean (intra-cadaver) cartilage relaxation contact force was 11.8 N (standard error of the mean = 0.3) at 90° of elbow flexion and neutral rotation. There was little variation within specimens (Intraclass correlation coefficient > 0.94). Cartilage relaxation contact force increased at the ulnohumeral joint with radial head implant overstuffing (> 4 mm, P < 0.05) and elbow flexion (120°, P < 0.001). Pronosupination altered cartilage relaxation contact force in an implant-length independent manner (P < 0.05).

INTERPRETATION

Radiocapitellar joint arthroplasty implant length and elbow joint position independently contribute to increased cartilage relaxation contact force at the ulnohumeral joint. This further supports attempts at anatomic reconstruction of the radiocapitellar joint to prevent pathologic ulnohumeral joint loading.

Characteristics of upper limb mass, muscle CSA and stiffness in adolescent baseball players with and without elbow injury

Since elbow injuries are common in adolescent baseball players, this study aimed to determine the relationship between musculoskeletal status and elbow injuries in 47 baseball players aged 12-14 years. Participants answered a questionnaire and had their general body measurements taken. Magnetic resonance imaging was used to evaluate muscle cross sectional areas (CSA) of the upper arm flexor and extensor muscles, and x-ray absorptiometry was used to determine the mass of the upper arm and the total mass of the forearm and hand. Shear wave elastography was used to determine muscle stiffness of the biceps brachii, brachialis, pronator teres, and brachioradialis. An orthopedic surgeon performed a clinical assessment and elbow ultrasonography for each participant to diagnose elbow injuries. The measured values were compared between the elbow injury and control groups using two-sample t-tests. The elbow injury group had significantly higher muscle stiffness in the brachialis (p < 0.001) and brachioradialis (p = 0.004) muscles and greater elbow flexor CSA of the distal upper arm (p = 0.004) than the control group. The total mass of the forearm and hand and the mass ratio of the forearm and hand to the upper arm were significantly greater in the elbow injury group than in the control group (p = 0.002 and p < 0.001). Thus, it may be necessary to increase flexibility of the brachialis and brachioradialis flexible by stretching and massaging in addition to evaluating the mass distal to the elbow and the elbow flexor muscle size of the distal upper arm to manage elbow injury in youth baseball players. Characteristics of Upper Limb Mass, Muscle Cross-Sectional Area and Stiffness in Adolescent Baseball Players with and without Elbow Injury.

A method for measuring muscle strength in restraining valgus joint angulation: Elbow varus muscle strength against valgus loading

Skeletal muscle works as a dynamic joint stabilizer, assisting the underlying ligaments in restricting joint angulation by actively resisting external loads. Despite its clinical importance, little is known about the muscle strength required to produce torque to help ligaments restrict joint angulation within the physiological range permitted by the joint structure. In this study, we introduce a method for measuring the strength of the elbow musculature in restraining valgus angulation and present the values obtained in 20 healthy young men. Each participant was fastened to a Biodex dynamometer, with the elbow joint flexed to 90° and the varus-valgus axis aligned to the dynamometer's rotation axis. Maximal voluntary isometric ramp contraction of shoulder internal rotators was performed while the humeroulnar joint gap was monitored with an ultrasound apparatus. The largest torque recorded while the humeroulnar joint gap did not exceed a predetermined individualized threshold was considered to be the elbow varus strength of the participant. The elbow varus strength of the dynamic stabilizer was found to be 41 ± 12 Nm, which agreed with the value estimated by our musculoskeletal model. The inter-operator reliability test indicated excellent reliability (ICC (2,1) = 0.91). These findings suggest that the present method is valid for measuring the strength of the elbow musculature in restraining the valgus angulation. Measurements of this aspect of strength are expected to provide insights for understanding and preventing elbow injuries.

The loads developed by epicondylar and epitrochlear muscles across the elbow joint. A dynamic simulated model

The radio-humeral joint has traditionally been believed to support most of the loads transmitted through the elbow. Load transfer through the elbow has been a controversial issue since the publication of the first biomechanical studies on the subject, most of which were based on extrinsic forces acting on the extended joint. The present study analyzes load distribution across the six different compartments in the elbow while the joint is flexed, as well as the intrinsic forces generated in the epicondylar and epitrochlear muscles. Ten cadaveric elbows were positioned at 90° of flexion, forearm in a neutral position and wrist at 0°. Tekscan sensors were used for measuring intraarticular pressures. Forces generated by epitrochlear muscles results in a series of loads that affect mainly the anteromedial facet (40%), followed by the posterolateral facet (34%) of the ulnohumeral joint, with the flexor carpi ulnaris generating the heaviest loads (43% on the anteromedial and 38% on the posterolateral facets). Conversely, the forces generated by the epicondylar muscles, similar in behavior but with an opposite direction, convey heavier loads to the elbow's anterolateral facet (45%), followed by the radiohumeral joint (26%) with the extensor carpi ulnaris generating the heaviest loads (54% on the anterolateral facet and 17% on the radiohumeral joint). Our results indicate that the elbow joint exhibits a characteristic load distribution pattern that depends on the muscles, as intrinsic forces are generated by the epicondylar and epitrochlear muscles. The anterior portion of the ulnohumeral joint is the area bearing the heaviest loads.

Musculoskeletal simulation of elbow stability for common injury patterns

Elbow stability is derived from a combination of muscular, ligamentous, and bony structures. After an elbow trauma the stability of the joint is an important decision criterion for the subsequent treatment. The decision regarding nonoperative/operative care depends mostly on subjective assessments of medical experts. Therefore, the aim of this study is to use musculoskeletal simulations as an objective assessment tool to investigate the extent to which failure of different stabilizers affects the elbow stability and how these observations correspond to the assessment from clinical practice. A musculoskeletal elbow simulation model was developed for this aim. To investigate the stability of the elbow, varus/valgus moments were applied under 0°, 45°, and 90° flexion while the respective cubital angle was analyzed. This was performed for nine different injury scenarios, which were also evaluated for stability by clinical experts. With the results, it can be determined by which injury pattern and under which flexion angle the elbow stability is impaired regarding varus/valgus moments. The scenario with a complete failure of the medial and lateral ligaments and a fracture of the radial head was identified as having the greatest instability. The study presented a numerical determination of elbow stability against varus/valgus moments regarding clinical injury patterns, as well as a comparison of the numerical outcome with experience gained in clinical practice. The numerical predictions agree well with the assessments of the clinical specialists. Thus, the results from musculoskeletal simulation can make an important contribution to a more objective assessment of the elbow stability.

Finite Element Analysis of Elbow Joint Stability by Different Flexion Angles of the Annular Ligament

Objective

The injury of the annular ligament can change the stress distribution and affect the stability of the elbow joint, but its biomechanical mechanism is unclear. The present study investigated the biomechanical effects of different flexion angles of the annular ligament on elbow joint stability.

Methods

A cartilage and ligament model was constructed using SolidWorks software according to the magnetic resonance imaging results to simulate the annular ligament during normal, loosened, and ruptured conditions at different buckling angles (0°, 30°, 60°, 90°, and 120°). The fixed muscle strengths were 40 N (F1), 20 N (F2), 20 N (F3), 20 N (F4), and 20 N (F5) for the triceps, biceps, and brachial tendons and the base of the medial collateral ligament and lateral collateral ligament. The different elbow three‐dimensional (3D) finite element models were imported into ABAQUS software to calculate and analyze the load, contact area, contact stress, and stress of the medial collateral ligament of the olecranon cartilage.

Results

The results showed that the stress value of olecranon cartilage increased under different conditions (normal, loosened, and ruptured annular ligament) with elbow extension, and the maximum stress value of olecranon cartilage was 2.91 ± 0.24 MPa when the annular ligament was ruptured. The maximum contact area of olecranon cartilage was 254  mm² with normal annular ligament when the elbow joint was flexed to 30°, while the maximum contact area of loosened and ruptured annular ligament was 283 and 312 mm² at 60° of elbow flexion, and then decreased gradually. The maximum stress of the medial collateral ligament was 6.52 ± 0.23, 11.51 ± 0.78, and 18.74 ± 0.94 MPa under the different conditions, respectively.

Conclusion

When the annular ligament ruptures, it should be reconstructed as much as possible to avoid the elevation of stress on the surface of the medial collateral ligament of the elbow and the annular cartilage, which may cause clinical symptoms.

The radiological findings in complex elbow fracture-dislocation injuries

Elbow fracture-dislocation is a complex injury which can lead to significant bony and soft tissue damage. Surgical intervention is guided towards restoring joint stability, allowing early mobilization and preventing long-term joint stiffness. The most common types are posterolateral, posteromedial, Monteggia type (and variants), and anterior trans-olecranon fracture-dislocations. Posterolateral fracture-dislocation is characterized by a radial head fracture (± anterolateral coronoid fracture) and typically capsuloligamentous disruption (lateral collateral ligaments injury is the most common). A posterolateral fracture-dislocation with radial head and coronoid anterolateral facet fractures is termed a terrible triad injury. In posteromedial fracture-dislocation, there is a fracture of the anteromedial facet of the coronoid, typically with proximal avulsion of the lateral collateral ligaments (± injury to the posterior bundle of the ulnar collateral ligament). Monteggia fracture-dislocation injuries demonstrate proximal ulnar fracture (with possible involvement of the olecranon and the coronoid) and radial head dislocation. These can be divided into apex anterior or apex posterior variants. The latter are commonly associated with radial head fractures and lateral ligamentous injury, and have a worse prognosis. In trans-olecranon fracture-dislocation, there is significant disruption of the greater sigmoid notch and the olecranon, with various involvement of the coronoid and the proximal ulna. The article describes the radiological findings and outlines the management principles in complex elbow fracture-dislocation injuries.

Establishing the Role of Elbow Muscles by Evaluating Muscle Activation and Co-contraction Levels at Maximal External Rotation in Fastball Pitching

Background: Baseball pitching is associated with a high prevalence of ulnar collateral ligament injuries, potentially due to the high external valgus load on the medial side of the elbow at the instant of maximal shoulder external rotation (MER). In-vitro studies show that external valgus torque is resisted by the ulnar collateral ligament but could also be compensated by elbow muscles. As the potential active contribution of these muscles in counteracting external valgus load during baseball pitching is unknown, the aim of this study is to determine whether and to what extent the elbow muscles are active at and around MER during a fastball pitch in baseball.

Methods: Eleven uninjured pitchers threw 15 fastball pitches. Surface electromyography of six muscles crossing the elbow were measured at 2000 Hz. Electromyography signals were normalized to maximal activity values. Co-contraction index (CCI) was calculated between two pairs of the flexor and extensor elbow muscles. Confidence intervals were calculated at the instant of MER. Four ranges of muscle activity were considered; 0–20% was considered low; 21–40% moderate; 41–60% high and over 60% as very high. To determine MER, the pitching motion was captured with a highspeed camera at 240 Hz.

Results: The flexor pronator mass, pronator teres, triceps brachii, biceps brachii, extensor supinator mass and anconeus show moderate activity at MER. Considerable variation between participants was found in all muscles. The CCI revealed co-contraction of the two flexor-extensor muscle pairs at MER.

Interpretation: The muscle activation of the flexor and pronator muscles at MER indicates a direct contribution of forearm muscles crossing the medial side of the elbow in counteracting the external valgus load during fastball pitching. The activation of both flexor and extensor muscles indicates an in-direct contributory effect as the combined activity of these muscles counteract opening of the humeroulnar joint space. We believe that active muscular contributions counteracting the elbow valgus torque can be presumed to relieve the ulnar collateral ligament from maximal stress and are thus of importance in injury risk assessment in fastball pitching in baseball.

Comparative study of the functional outcomes of combined medial-lateral approach arthrolysis with or without external fixation for severe elbow stiffness

BACKGROUND

To evaluate and compare the functional outcomes of combined medial-lateral approach open arthrolysis with and without hinged external fixation.

METHODS

We retrospectively collected and analyzed the clinical data of patients with severe elbow stiffness who were treated in our institution from January 2018 to January 2019. All of them were treated with combined medial-lateral approach arthrolysis. There were 20 patients who had the hinged external fixation placed and 29 patients without the placement of the external fixation. Their baseline characteristics and functional outcomes were evaluated and compared.

RESULTS

The average follow-up time was 28.4 ± 3.7 months. There were no significant differences in the ROM of the elbow, MEPS, VAS, DASH, or complications between the two groups. The operation time and treatment cost of the patients without external fixation were significantly lower than patients with external fixation.

CONCLUSION

Combined medial-lateral approach open elbow arthrolysis without external fixation is a safe and effective way to treat elbow stiffness.

LEVEL OF EVIDENCE

Therapeutic Level III; Retrospective Cohort Comparison; Treatment Study.

The role of the brachialis muscle in elbow stability with collateral ligament injury: A biomechanical investigation

BACKGROUND

The brachialis muscle lies in close anatomic relation to the anterior capsule of the elbow joint. The contribution of the brachialis muscle to elbow stability has not yet been fully investigated. Therefore, the aim of this biomechanical in-vitro study was to analyze its influence on joint stability.

METHODS

Nine fresh frozen cadaveric elbows were evaluated for stability against valgus and varus/posterolateral rotatory forces. Brachialis loading was measured indirectly using strain gauges. Three distinct scenarios were analyzed: A) with intact lateral ulnar and ulnar collateral ligaments B) with a ruptured lateral ulnar collateral ligament C) with ruptured lateral ulnar and ulnar collateral ligaments.

FINDINGS

In all scenarios, an increased strain was observed under posterolateral rotatory/varus forces. The maximum measured strain occurred with elbow flexion of 30° and pronation of the forearm. The strain was significantly higher with dual-ligament rupture (mean - 210.5 μm/m; min. 97.8 μm/m; max. -310 μm/m; SD 107.8 μm/m; p = .034) compared to intact ligaments (mean - 106.9 μm/m; min. -32.51 μm/m, max. -287 μm/m; SD 100.2 μm/m) and single-ligament rupture (mean - 109.5 μm/m; min. - 96.7 μm/m; max - 130.4 μm/m; SD 18.2).

INTERPRETATION

A strain of the brachialis muscle was observed under varus/posterolateral rotatory forces with a pronated forearm and the strain increased significantly in the event of a dual-ligament rupture. This suggests that the brachialis muscle may influence varus/posterolateral rotatory stability of the elbow. Hence, a concomitant tear of the brachialis muscle might result in pronounced instability following simple elbow dislocation.

LEVEL OF EVIDENCE

Basic Science Study, Biomechanics.

Grip Strength Measurement in Baseball Pitchers: A Clinical Examination to Indicate Stride Length Inefficiency

BACKGROUND

Ulnar collateral ligament injuries are rampant in the sport of baseball where kinetic chain impacts, stemming from misappropriation of stride length or changes that occur in competition due to fatigue, have not been evaluated for dynamic elbow stability effects.

HYPOTHESIS/PURPOSE

To examine the relationship between clinical measures of grip strength and altered stride length in baseball pitchers. It is believed that shorter stride lengths would reduce grip strength in baseball pitchers.

STUDY DESIGN

Crossover Study Design.

METHODS

A total of 19 uninjured pitchers (15 collegiate and 4 high school) (age 18.63 ± 1.67 years, height 1.84 ± 0.054 m, mass 82.14 ± 0.054 kg) threw two simulated 80-pitch games at ±25% of their desired stride length recorded by motion capture with two force plates and a radar gun to track each throw. A handheld grip dynamometer was used to record the mean change in grip strength after games from baseline measures. Pairwise comparisons at baseline and post-game denoted grip strength changes and dominant grip strength offsets for stride length conditions.

RESULTS

Subjects with shorter stride lengths revealed a significant decline in grip strength in the dominant arm from baseline (pre-game; 45.1 kg vs. post-game; 43.2 kg, p=0.017, ES=0.28), however all other tests involving dominant grip strength changes and offset analyses were not statistically different for under-stride and over-stride length conditions.

CONCLUSIONS

Clinical evaluation of grip strength has the potential to identify altered lower body mechanics and may be considered as a safe and effective monitoring strategy to integrate with motion capture in determining optimal stride lengths for baseball pitchers.

LEVEL OF EVIDENCE

Level 3.

Pronation and palmar pinch improve the stability of the medial elbow joint space in high school baseball pitchers

HYPOTHESIS

We aimed to investigate the contributions of grip, pronation, and pinch to stabilization of the medial elbow joint space; examine their relationship with muscle strength; and assess the effect of stabilization on the medial elbow joint space in baseball pitchers.

METHODS

In this controlled laboratory study, we measured the medial elbow joint space using ultrasound during the following conditions: unloading; loading; and loading with grip, pronation, and pinch. To evaluate changes in the medial elbow joint space as a result of various conditions, 1-way repeated-measures analysis of variance and post hoc analysis for multiple comparisons were performed. To investigate whether strong or weak muscle strength improved the medial elbow joint space during the loaded condition, Pearson correlation analysis was performed. Finally, a post hoc power analysis was performed.

RESULTS

We enrolled 121 pitchers. The medial elbow joint space in the loaded condition, loaded condition with full grip, and loaded condition with full pinch was significantly larger than that in the unloaded condition. The medial elbow joint space in the loaded condition with full grip, loaded condition with full pronation, and loaded condition with full palmar pinch was significantly smaller than that in the loaded condition. A post hoc power analysis showed that the power of the 1-way repeated-measures analysis of variance was 100%. The strengths of the full grip and palmar pinch were significantly correlated with a reduced gap distance of the medial elbow joint space (P < .001 for both).

CONCLUSION

In high school baseball pitchers, pronation and palmar pinch contraction significantly improved the gap distance of the medial elbow joint space in the loaded condition and during grip contraction. Moreover, the grip and palmar pinch strengths were significantly correlated with stabilizing effects on the medial elbow joint space.

The three-column concept of elbow joint stability and the Wrightington elbow fracture-dislocation classification, emphasizing the role of cross-sectional imaging

Elbow fracture-dislocation is a complex injury with a combination of osseous and soft tissue disruption. Different classification systems have been used to describe the injury pattern and help guide the management. The article describes the important cross-sectional findings in complex elbow fracture-dislocation injuries based on the relatively new Wrightington classification. This includes the various elements and patterns seen in elbow fracture-dislocations providing a simple and comprehensive system to classify these injuries and help guide the surgical management. The article also describes the three-column concept of elbow joint stability, dividing the elbow joint osseous structures into lateral, middle and medial columns. Detailed radiological assessment of the fractures pattern is vital to understand the mechanism of injury, allowing clinicians to predict the associated capsuloligamentous injury and help guide the management decisions. The Wrightington elbow fracture-dislocation classification categorizes the injuries according to the ulnar coronoid process and radial head fractures. Type A is an anteromedial coronoid fracture. Type B is a bifacet or basal coronoid fracture, with B + indicating associated radial head fracture. Type C is a combined anterolateral facet and radial head or comminuted radial head fractures. Type D is a diaphyseal ulnar fracture, with D + indicating associated radial head fracture.

Lateral Elbow Laxity Is Affected by the Integrity of the Radial Band of the Lateral Collateral Ligament Complex: A Cadaveric Model With Sequential Releases and Varus Stress Simulating Everyday Activities

BACKGROUND

An elongation of the radial lateral collateral complex (R-LCL) can provoke symptomatic minor instability of the lateral elbow leading to lateral elbow pain. Biomechanical models investigating the effects of elongation and partial or complete lesions of the R-LCL on lateral elbow stability are lacking.

PURPOSE

To evaluate how partial and complete R-LCL release affects radiocapitellar joint stability in a setting of controlled varus load and progressive soft tissue release.

STUDY DESIGN

Controlled laboratory study.

METHODS

Ten fresh-frozen cadaveric specimens were obtained and mounted on a custom-made support to control elbow flexion and extension and to allow for controlled varus loading. Stress tests were performed on all intact specimens under gravity load alone, a 0.5-kg load applied to the hand, and a 1-kg load applied to the hand. After load application, anteroposterior radiographs were obtained. The following release sequence was applied to all specimens: release of the anterior half of the common extensor origin, pie crusting of the R-LCL, and R-LCL release. After each release, stress tests and radiographs were performed. The varus joint angulation of the elbow (α) was measured by 2 examiners as the main outcome parameter.

RESULTS

Significant changes in α from the initial condition occurred after each release, and a significant effect of varus load on α was documented for all release steps. A significant effect of the releases on α could be documented for all identical varus load conditions. A linear regression model was generated to describe the effect of varus load on α.

CONCLUSION

Varus loads simulating everyday activities produce changes in the varus joint angulation of the elbow already in the intact specimen, which are linearly dependent on the applied moment and persist after release of the lateral stabilizing structures. With progressive load, a pie crusting of the R-LCL is the minimal procedure able to provoke a significant change in the varus joint angulation, and a complete R-LCL release produces additional increase in the varus joint angulation in all testing conditions.

CLINICAL RELEVANCE

These findings confirm the role of the R-LCL as static lateral stabilizer, supporting a pathological model based on its insufficiency and culminating with a symptomatic minor instability of the lateral elbow.

The ulnar collateral ligament loading paradox between in-vitro and in-vivo studies on baseball pitching (narrative review)

Ulnar collateral ligament (UCL) weakening or tears occur in 16% of professional baseball pitchers. To prevent players from sustaining a UCL injury, it is important to understand the relationship between the UCL properties and elbow stabilizers with the load on the UCL during pitching. In-vitro studies showed that the ultimate external valgus torque of 34 Nm would rupture the UCL, which is in apparent conflict with the reported peak valgus torques in pitching (40–120 Nm). Assuming both observations are correct, the question rises why ‘only’ 16 out of 100 professional pitchers sustain a UCL rupture. Underestimation of the effect of other structures in in-vivo studies is most likely the explanation of this mismatch because the calculated in-vivo torque also includes possible contributions of functional and structural stabilizers. In-vitro studies show that the flexor-pronator mass has the potential to counteract valgus torque directly, whereas the elbow flexor-extensor muscles combined with the humeroradial joint might have an indirect effect on valgus torque by increasing the joint compression force. Accurate experimental electromyography data and a more detailed (musculoskeletal)mechanical model of the elbow are needed to investigate if and to what extent the structural and functional stabilizers can shield the UCL during pitching.

Rehabilitation Following Ulnar Collateral Ligament Reconstruction in Overhead-Throwing Athletes

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The prevalence of ulnar collateral ligament (UCL) injury and UCL reconstruction (UCL-R) continues to rise, causing morbidity in overhead-throwing athletes.

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Postoperative rehabilitation protocols are essential for proper healing of the reconstructed ligament and safely returning athletes to competition, yet there is no uniformly accepted standard of care.

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UCL-R rehabilitation has traditionally been guided by expert opinion and conventional wisdom rather than scientific studies, resulting in substantial variability in rehabilitation practices, time to return to play, and outcomes.

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Current research efforts aim to closely investigate the biomechanical implications of UCL-R and overhead throwing to better guide rehabilitation and to improve competitive performance and outcomes.

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Additional biomechanical and scientific studies on rehabilitation modalities and timing are warranted for systematic analysis, optimization, and standardization of UCL-R rehabilitation.

The ulnar collateral ligament responds to stress in professional pitchers

BACKGROUND

Our purpose with this study was to determine the response of the ulnar collateral ligament (UCL) in professional pitchers after exposure to a season of pitching and to rest during an off-season.

METHODS

In a prospective study supported by Major League Baseball, all pitchers within a single professional baseball club were enrolled. An ultrasound of the ligament was then performed by a single fellowship-trained ultrasonographer at the beginning of the season (T1), the end of the season (T2), and the beginning of the following season (T3). We measured the UCL thickness and ulnotrochlear joint opening at 30° of flexion with and without stress. Two ultrasound images were saved. Inter- and intra-rater reliability were determined. A multivariable analysis was conducted.

RESULTS

A total of185 total pitchers were included: 94 pitchers at T1, 83 at T2, and 118 at T3. These pitchers had 12 [7, 15] (median [interquartile range]) years of pitching experience and had a peak velocity of 95 [93, 97] miles/hour. Intra- and inter-rater reliability were excellent. The baseline UCL thickness was associated with peak velocity (P = .031) and prior UCL reconstruction (P = .024). After accounting for pitching experience, peak velocity, and prior UCL reconstruction, thickness increased during the season (P = .002) and decreased during the off-season (P = .001). After accounting for these same variables, valgus laxity at 30° increased during the season (P = .002) and decreased during the off-season (P = .029).

CONCLUSION

The UCL responds to stress in professional pitchers by becoming thicker and more lax, and responds to rest by becoming thinner and less lax.

Ultrasound evaluation shows increase in laxity after partial common extensor origin detachment but not after additional lesion of the radial band of the lateral collateral ligament

PURPOSE

The lateral elbow musculature conveys a dynamic valgus moment to the elbow, increasing joint stability. Muscular or tendinous lesions to the anterior half of the common extensor origin (CEO) may provoke a deficiency in the elbow dynamic stabilizers, regardless of their traumatic, degenerative, or iatrogenic aetiology. Furthermore, a role for the radial band of the lateral collateral ligament (R-LCL) has been postulated in the aetiology of lateral elbow pain. This study aimed to evaluate the effects of sequential lateral releases with dynamic ultrasound, evaluating its capability to detect lesions of the CEO and of the R-LCL.

METHODS

Ultrasound investigation of the lateral compartment of the elbow was performed on nine cadaveric specimens with a 10 MHz linear probe in basal conditions, after the release of the anterior half of the CEO and after complete R-LCL release. The lateral joint line widening (λ) was the primary outcome parameter, measured as the linear distance between the humeral and radial articular surfaces.

RESULTS

The release of the anterior half of the CEO significantly increased λ by 200% compared to the starting position (p = 0.0008) and the previously loaded position (p = 0.0015). Conversely, further release of the R-LCL caused only a marginal, non-significant increase in λ.

CONCLUSIONS

Ultrasound evaluation can detect changes related to tendon tears or muscular avulsions of the CEO and can depict lateral elbow compartmental patholaxity by assessing articular space widening while scanning under dynamic stress. However, it cannot reliably define if the R-LCL is injured. Iatrogenic damage to the CEO should be carefully avoided, since it causes a massive increase in compartmental laxity.

State of the Union on Ulnar Collateral Ligament Reconstruction in 2020: Indications, Techniques, and Outcomes

PURPOSE OF REVIEW

There has been a marked increase in the number of ulnar collateral ligament reconstructions performed annually and an associated increase in the amount of recent literature published. It is paramount that surgeons remain up to date on the current literature, as modern indications and surgical techniques continue to improve clinical outcomes.

RECENT FINDINGS

Our understanding of ulnar collateral ligament (UCL) injuries, treatment indications, and surgical techniques for UCL reconstruction continues to evolve. Despite the rapidly increasing amount of published literature on the topic, a clear and concise surgical algorithm is lacking. Studies have suggested a trend towards improved clinical outcomes and decreased complications with various modifications in UCL reconstruction techniques. Current sport-specific outcome studies have reported conflicting results regarding the effect of UCL reconstruction on an athlete's performance upon returning to sport. With the rising incidence of UCL reconstruction and growing media attention, UCL injuries, reconstruction techniques, and return to sport following UCL surgery are timely topics of interest to clinicians and overhead throwing athletes. Several technique modifications have been reported, and these modifications may lead to improved outcomes and lower complication rates. Studies assessing sport-specific outcome measures will be necessary to provide a more critical and informative analysis of outcomes following UCL reconstruction.

Chronic complex persistent elbow instability: a consecutive and prospective case series and review of recent literature

BACKGROUND

Chronic complex persistent elbow instability (CCPEI) is a condition that even expert elbow surgeons find challenging to treat. The results of the few studies that have dealt with the treatment of this condition are conflicting. We describe the surgical results of a consecutive prospective series of patients with CCPEI and provide a review of the recent literature.

METHODS

We assessed 21 patients with previous failed surgical or conservative treatment, with a terrible-triad injury in 13, Monteggia-like lesion in 6, humeral shear fracture-dislocation in 1, and radial head fracture-dislocation in 1. Overall, 21 open débridement procedures, 15 ulnar nerve transpositions, 6 ulnar in situ neurolysis procedures, 7 total elbow arthroplasties, 8 radial head arthroplasties, 1 radial head resection with humeroradial anconeus interpositional arthroplasty, 4 coronoid graft reconstructions, 14 ligament retensioning procedures, 3 ulnar nonunion treatments, and 2 ulnar osteotomies were performed. Two dynamic external fixators were applied. The Mayo Elbow Performance Score, quick Disabilities of the Arm, Shoulder and Hand score, and modified American Shoulder and Elbow Surgeons score were used preoperatively and postoperatively.

RESULTS

The mean follow-up period was 29.4 months. A significant improvement was found between preoperative and postoperative clinical scores and range-of-motion values. The reintervention and major complication rates were 19% and 23%, respectively. Arthritic evolution was observed in 71% of the cases.

CONCLUSIONS

CCPEI is a challenging condition with an uncertain prognosis. The variability in patients' pathoanatomic conditions requires customized surgical treatment aimed at elbow stabilizer reconstruction when the ulnohumeral joint is preserved or aimed at joint replacement in case of severe articular degeneration. The time interval between the initial trauma and index surgical procedure significantly affects the feasibility of reconstructive procedures.

The column procedure preserves elbow stability on biomechanical testing

PURPOSE

The effect of open release of a post-traumatic elbow contracture on the stability of the joint has not been so far studied in vivo. Resection of elbow joint capsule, the key element of surgery, was reported to have no effect on the stability of cadaveric elbows. The joint capsule is yet known to participate in maintaining elbow stability as one of secondary stabilizers.

METHODS

We assessed elbow joint laxity in 39 patients who underwent an open contracture release via the 'column procedure' described by B. Morrey and P. Mansat within the preceeding three to nine months. The measurements were taken with an apparatus designed particularly for this experiment according to the predetermined protocol. A preliminary part of the experiment showed that there was no significant difference between laxity of two elbow joints in healthy volunteers. Laxity of the operated elbows could be then compared with the contralateral joints.

RESULTS

Mean absolute difference of laxity between healthy and operated elbows was 1.55° (0.1°-4.1°, SD = 1.1) being significantly lower than 2°, p = 0.0056. The difference of the joint laxity between the operated and healthy elbows did not differ statistically significantly by more than 0.6° from the difference of the laxity of two healthy elbows and, therefore, is not clinically noticeable.

CONCLUSIONS

Our experiment confirmed that the 'column procedure' is a safe procedure which does not compromise the stability of the elbow joint.

Changes in Muscle Activity in Response to Assistive Force during Isometric Elbow Flexion

This study investigated the muscle activity and force variability in response to perturbation of assistive force during isometric elbow flexion. Sixteen healthy right-handed young men (age: 22.0 ± 1.1 years; height: 171.9 ± 4.8 cm; weight 68.4 ± 11.2 kg) were recruited and the muscle activity of biceps brachii and triceps brachii were assessed using surface electromyography. Workload force and assistive force applied on isometric elbow flexion significantly affected the changes in both biceps and triceps muscle activities. A higher assistive force was shown to result in reduced biceps muscle activity compared to the unassisted period. In contrast, the efficiency of the assistive force acting on the biceps decreased as the assistive force increased. In general, the force variability of the biceps muscle remained approximately the same at lower workload force conditions than that at higher workload force conditions. In conclusion, higher assistive force may not yield a higher performance efficiency in human-assistive force interaction.

The Effectiveness of a Hinged Elbow Orthosis in Medial Collateral Ligament Injuries: An In Vitro Biomechanical Study

BACKGROUND

Medial collateral ligament (MCL) injuries are common after elbow trauma and in overhead throwing athletes. A hinged elbow orthosis (HEO) is often used to protect the elbow from valgus stress early after injury and during early return to play. However, there is minimal evidence regarding the efficacy of these orthoses in controlling instability and their influence on long-term clinical outcomes.

PURPOSE

(1) To quantify the effect of an HEO on elbow stability after simulated MCL injury. (2) To determine whether arm position, forearm rotation, and muscle activation influence the effectiveness of an HEO.

STUDY DESIGN

Controlled laboratory study.

METHODS

Seven cadaveric upper extremity specimens were tested in a custom simulator that enabled elbow motion via computer-controlled actuators and motors attached to relevant tendons. Specimens were examined in 2 arm positions (dependent, valgus) and 2 forearm positions (pronation, supination) during passive and simulated active elbow flexion while unbraced and then while braced with an HEO. Testing was performed in intact elbows and repeated after simulated MCL injury. An electromagnetic tracking device measured valgus angulation as an indicator of elbow stability.

RESULTS

When the arm was dependent, the HEO increased valgus angle with the forearm in pronation (+1.0°± 0.2°, P = .003) and supination (+1.5°± 0.0°, P = .006) during active motion. It had no significant effect on elbow stability during passive motion. In the valgus position, the HEO had no effect on elbow stability during passive or active motion in pronation and supination. With the arm in the valgus position with the HEO, muscle activation reduced instability during pronation (-10.3°± 2.5°, P = .006) but not supination (P = .61).

CONCLUSION

In this in vitro study, this HEO did not enhance mechanical stability when the arm was in the valgus and dependent positions after MCL injury.

CLINICAL RELEVANCE

After MCL injury, an HEO likely does not provide mechanical elbow stability during rehabilitative exercises or when the elbow is subjected to valgus stress such as occurs during throwing.

The elbow: review of anatomy and common collateral ligament complex pathology using MRI

The elbow is a complex joint whose stability is imparted by osseous and soft-tissue constraints. Anatomical and biomechanical knowledge of the supporting structures that provide stability to the medial and lateral elbow is essential to correctly interpret the pathological findings. Conventional MRI and MR arthrography are the imaging modalities of choice in the evaluation of elbow ligament injuries. Elbow instability can be classified according to timing (acute, chronic, or recurrent), the direction of displacement, the degree of displacement, and the articulations involved. This article reviews the MR imaging protocols recommended for each diagnosis and the normal anatomy and biomechanical aspects of the medial and lateral collateral ligament complex. We also present multiple cases of typical and atypical patterns of injury.

Effects of realistic sheep elbow kinematics in inverse dynamic simulation

Looking for new opportunities in mechanical design, we are interested in studying the kinematic behaviour of biological joints. The real kinematic behaviour of the elbow of quadruped animals (which is submitted to high mechanical stresses in comparison with bipeds) remains unexplored. The sheep elbow joint was chosen because of its similarity with a revolute joint. The main objective of this study is to estimate the effects of elbow simplifications on the prediction of joint reaction forces in inverse dynamic simulations. Rigid motions between humerus and radius-ulna were registered during full flexion-extension gestures on five cadaveric specimens. The experiments were initially conducted with fresh specimens with ligaments and repeated after removal of all soft tissue, including cartilage. A digital image correlation system was used for tracking optical markers fixed on the bones. The geometry of the specimens was digitized using a 3D optical scanner. Then, the instantaneous helical axis of the joint was computed for each acquisition time. Finally, an OpenSim musculoskeletal model of the sheep forelimb was used to quantify effects of elbow joint approximations on the prediction of joint reaction forces. The motion analysis showed that only the medial-lateral translation is sufficiently large regarding the measuring uncertainty of the experiments. This translation assimilates the sheep elbow to a screw joint instead of a revolute joint. In comparison with fresh specimens, the experiments conducted with dry bone specimens (bones without soft tissue) provided different kinematic behaviour. From the results of our inverse dynamic simulations, it was noticed that the inclusion of the medial-lateral translation to the model made up with the mean flexion axis does not affect the predicted joint reaction forces. A geometrical difference between the axis of the best fitting cylinder and the mean flexion axis (derived from the motion analysis) of fresh specimens was highlighted. This geometrical difference impacts slightly the prediction of joint reactions.

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.

Ultrasound-Assisted Assessment of Medial Elbow Stability

OBJECTIVES

An assessment of medial elbow stability is essential to the patient with an ulnar collateral ligament injury. Ultrasound imaging can be used to assess medial elbow stability. This study determined the effect of the elbow flexion angle on the medial elbow joint space during clinical tests of medial elbow stability.

METHODS

Ultrasound images of the nondominant elbow were collected during 3 tests of medial elbow stability: valgus stress test, weighted valgus test, and milking maneuver. The elbow flexion angle increased between the valgus stress test and milking maneuver. The width of the medial joint space was measured on ultrasound images collected in unstressed and stressed conditions.

RESULTS

Across test conditions, the medial joint width was greater in the stressed condition (mean ± SD, 3.7 ± 0.1 mm) than in the unstressed condition (2.9 ± 0.09 mm). The medial elbow joint space width was less (mean difference, 0.16 ± 0.01 mm; P = .01) in the milking maneuver position compared to the valgus stress test positions.

CONCLUSIONS

This study provides evidence that changes in the width of the medial elbow during clinical evaluation of the unimpaired elbow can be detected by ultrasound. Changing the elbow flexion angle did not affect the change in width of the medial elbow during valgus loading.

Medial Elbow Joint Space Increases With Valgus Stress and Decreases When Cued to Perform A Maximal Grip Contraction

BACKGROUND

Previous research indicates that the amount of valgus torque placed on the elbow joint during overhead throwing is higher than the medial ulnar collateral ligament (UCL) can tolerate. Wrist and finger flexor muscle activity is hypothesized to make up for this difference, and in vitro studies that simulated activity of upper extremity musculature, specifically the flexor digitorum superficialis and flexor carpi ulnaris, support this hypothesis.

PURPOSE

To assess the medial elbow joint space at rest, under valgus stress, and under valgus stress with finger and forearm flexor contraction by use of ultrasonography in vivo.

STUDY DESIGN

Controlled laboratory study.

METHODS

Participants were 22 healthy males with no history of elbow dislocation or UCL injury (age, 21.25 ± 1.58 years; height, 1.80 ± 0.08 m; weight, 79.43 ± 18.50 kg). Medial elbow joint space was measured by use of ultrasonography during 3 separate conditions: at rest (unloaded), under valgus load (loaded), and with a maximal grip contraction under a valgus load (loaded-contracted) in both limbs. Participants lay supine with their arm abducted 90° and elbow flexed 30° with the forearm in full supination. A handgrip dynamometer was placed in the participants' hand to grip against during the contracted condition. Images were reduced in ImageJ to assess medial elbow joint space. A 2-way (condition × limb) repeated-measures analysis of variance and Cohen's d effect sizes were used to assess changes in medial elbow joint space. Post hoc testing was performed with a Bonferroni adjustment to assess changes within limb and condition.

RESULTS

The medial elbow joint space was significantly larger in the loaded condition (4.91 ± 1.16 mm) compared with the unloaded condition (4.26 ± 1.23 mm, P < .001, d = 0.712) and the loaded-contracted condition (3.88 ± 0.94 mm, P < .001, d = 1.149). No significant change was found between the unloaded and loaded-contracted conditions ( P = .137).

CONCLUSION

Medial elbow joint space increases under a valgus load and then decreases when a maximal grip contraction is performed. This indicates that wrist and finger flexor muscle contraction may assist in limiting medial elbow joint space, a result similar to findings of previous research in vitro.

CLINICAL RELEVANCE

Muscle activation of the upper extremity limits the medial elbow joint space, suggesting that injury prevention programs for throwing athletes should incorporate exercises for the elbow, wrist, and hand to limit excessive medial elbow joint space gapping during activities that create high valgus load.

Simple elbow dislocation

The elbow is the second most commonly dislocated major joint in adults. Good long-term outcomes have been reported after non-operative management; however, a small proportion (<10%) of patients have a poor outcome and some do require surgical intervention. A review of the anatomy, pathoanatomy, management and outcomes of simple elbow dislocations is presented. Emphasis is placed on emerging concepts regarding the soft tissue injury, the stabilising structures that are injured, the sequence and mechanism of injury and the relationship to elbow stability. The benefits of nonsurgical and surgical management are discussed and a treatment algorithm based on the pathoanatomy is proposed.

Optimizing the rehabilitation of elbow lateral collateral ligament injuries: a biomechanical study

BACKGROUND

Elbow lateral collateral ligament (LCL) injury may arise after trauma or lateral surgical approaches. The optimal method of rehabilitating the LCL-insufficient elbow is unclear. Therapists often prescribe active motion exercises with the forearm pronated. Recently, overhead exercises have become popular as they may enable gravity to compress the elbow joint, improving stability, although this has not been proved biomechanically. This investigation aimed to quantify the effects of several variables used in LCL injury rehabilitation on elbow stability.

METHODS

Seven cadaveric specimens were tested in a custom elbow motion simulator in 3 arm positions (overhead, dependent, and varus) and 2 forearm positions (pronation and supination) during passive and simulated active elbow extension. Three injury patterns were studied (intact, LCL injury, and LCL with common extensor origin injury). An electromagnetic tracking device measured ulnohumeral kinematics.

RESULTS

Following combined LCL and common extensor origin injury, overhead positioning enhanced elbow stability relative to the other arm positions (P < .01 in pronation; P = .04 in supination). Active motion stabilized the LCL-deficient elbow in the dependent (P = .02) and varus (P < .01) positions. Pronation improved stability in the overhead (P = .05), dependent (P = .06), and varus (P < .01) positions.

CONCLUSIONS

Rehabilitation with the arm overhead improves elbow stability after LCL injury. Initiating earlier range of motion in this "safe position" might decrease elbow stiffness and allow optimal ligament healing. If exercises are done in the dependent position, active motion with forearm pronation should be encouraged. Varus arm positioning should be avoided.

In-Vitro Quantification of Medial Collateral Ligament Tension in the Elbow

The anterior bundle of the medial collateral ligament (AMCL) of the elbow is commonly injured in patients with elbow dislocations and in throwing athletes. This in-vitro study quantified tension in the native AMCL throughout elbow flexion for different arm positions. We conducted passive and simulated active elbow flexion in seven fresh-frozen cadaveric upper extremities using an established motion simulator. Motions were performed in the valgus and vertical positions from 20-120° while measuring AMCL tension using a custom transducer. Average AMCL tension was higher in the valgus compared to vertical position for both active (p = 0.03) and passive (p = 0.01) motion. Peak AMCL tension was higher in the valgus position for active (p = 0.02) and passive (p = 0.01) motion. There was no significant difference in AMCL tension between active and passive motion in the valgus (p = 0.15) or vertical (p = 0.39) positions. In the valgus position, tension increased with elbow flexion from 20-70° for both active (p = 0.04) and passive (p = 0.02) motion, but not from 70-120°. This in-vitro study demonstrated that AMCL tension increases with elbow flexion, and is greater in the valgus position relative to the vertical position. This information has important implications to the desired target strength of repair and reconstruction techniques.

Complications of Open Elbow Arthrolysis in Post-Traumatic Elbow Stiffness: A Systematic Review

Objective

The objective of this study was to systematically review the literature for a more comprehensive understanding of the complications of open elbow arthrolysis in patients with post-traumatic elbow stiffness and provide a reference for better prevention and treatment of them.

Methods

The PubMed, EMBASE, Cochrane Library, and Google Scholar databases were searched for therapeutic studies with a set of inclusion and exclusion criteria. Data were extracted from selected articles, and a statistical analysis was performed to evaluate related factors and management of the complications.

Results

Twenty-eight articles published between 1989 and 2013, involving 810 patients, were included. Most of the complications included in the selected articles were nerve complications, heterotopic ossification, elbow instability, infection, pin-related complications and repeat elbow contracture. The total complication rate was 24.3% ± 3.0%, and the reoperation rate was 34.0%. Furthermore, the statistical analysis revealed that preoperative range of motion (β = -0.004, P = 0.01) and proportion of female (β = 0.336, P = 0.04) were the independent factors affecting the total complication rate.

Conclusions

Various risk factors are related to each of the complications, and we found that patients with less preoperative ROM and a higher proportion of female gender may point to a higher total complication rate. Therefore, to further improve the overall outcomes of this procedure, more and larger prospective studies should be performed to further elucidate the effects of prophylactic interventions targeting the risk factors, thus improving the methods of prevention and treatment of complications.

Management of complex elbow dislocations: a mechanistic approach

Complex elbow dislocations (ie, fracture-dislocations) are challenging injuries to treat and may result in significant patient morbidity. Chronic instability, posttraumatic arthrosis, and poor functional outcomes are frequent. Orthopaedic surgeons should strive to optimize elbow function through restoration of articular congruity and stability coupled with early rehabilitation. Although most of these injuries require surgical management, not all complex elbow dislocations are equivalent. Understanding elbow biomechanics and the injury mechanism provides valuable insight into the variations of pathology that may be observed. Identifying the particular fracture pattern, such as an axial loading, valgus posterolateral rotatory, or varus posteromedial rotatory injury mechanism, helps guide appropriate treatment.

Computing muscle, ligament, and osseous contributions to the elbow varus moment during baseball pitching

Baseball pitching imposes a dangerous valgus load on the elbow that puts the joint at severe risk for injury. The goal of this study was to develop a musculoskeletal modeling approach to enable evaluation of muscle-tendon contributions to mitigating elbow injury risk in pitching. We implemented a forward dynamic simulation framework that used a scaled biomechanical model to reproduce a pitching motion recorded from a high school pitcher. The medial elbow muscles generated substantial, protective, varus elbow moments in our simulations. For our subject, the triceps generated large varus moments at the time of peak valgus loading; varus moments generated by the flexor digitorum superficialis were larger, but occurred later in the motion. Increasing muscle-tendon force output, either by augmenting parameters associated with strength and power or by increasing activation levels, decreased the load on the ulnar collateral ligament. Published methods have not previously quantified the biomechanics of elbow muscles during pitching. This simulation study represents a critical advancement in the study of baseball pitching and highlights the utility of simulation techniques in the study of this difficult problem.

Stability of severely stiff elbows after complete open release: treatment by ligament repair with suture anchors and hinged external fixator

BACKGROUND

Instability is a crucial issue in severe post-traumatic elbow stiffness during complete-release surgery. This study aimed to evaluate the efficacy of ligament repair using a suture anchor in the operative treatment of severely stiff elbows for which a hinged external fixator was indicated.

METHODS

We retrospectively reviewed 46 cases of severely stiff elbows (flexion arc <60°) undergoing open release. During the operation, all 46 elbows were noted to have instability. Suture anchors were applied to restore the ligament if it was impossible to repair the ligament directly, and a hinged external fixator was simultaneously applied to protect the vulnerable ligament and facilitate rehabilitation. No allograft or autograft was used in any of our cases. The stability, arc of motion, Mayo Elbow Performance Score, ulnar nerve symptoms, and radiographs were evaluated.

RESULTS

At a mean follow-up of 24.3 months, the postoperative Mayo Elbow Performance Score was 91 points, as compared with 63 points preoperatively. The mean flexion arc improved from 25° to 126°. Three patients presented with moderate elbow instability when the hinged external fixator was removed; however, all of them regained stability by the last follow-up. Furthermore, 7 cases of new-onset nerve palsy were noted; however, all of them resolved with conservative management. None of the patients required secondary surgery for any reason.

CONCLUSIONS

Repair of an avulsed collateral ligament with suture anchors and hinged external fixation was effective in restoring functional mobility in patients with severe post-traumatic elbow stiffness after complete release. This could be an option for treating ankylosed, severely or very severely stiff elbows.

Improper trunk rotation sequence is associated with increased maximal shoulder external rotation angle and shoulder joint force in high school baseball pitchers

BACKGROUND

In a properly coordinated throwing motion, peak pelvic rotation velocity is reached before peak upper torso rotation velocity, so that angular momentum can be transferred effectively from the proximal (pelvis) to distal (upper torso) segment. However, the effects of trunk rotation sequence on pitching biomechanics and performance have not been investigated.

PURPOSE

The aim of this study was to investigate the effects of trunk rotation sequence on ball speed and on upper extremity biomechanics that are linked to injuries in high school baseball pitchers. The hypothesis was that pitchers with improper trunk rotation sequence would demonstrate lower ball velocity and greater stress to the joint.

STUDY DESIGN

Descriptive laboratory study.

METHODS

Three-dimensional pitching kinematics data were captured from 72 high school pitchers. Subjects were considered to have proper or improper trunk rotation sequences when the peak pelvic rotation velocity was reached either before or after the peak upper torso rotation velocity beyond the margin of error (±3.7% of the time from stride-foot contact to ball release). Maximal shoulder external rotation angle, elbow extension angle at ball release, peak shoulder proximal force, shoulder internal rotation moment, and elbow varus moment were compared between groups using independent t tests (α < 0.05).

RESULTS

Pitchers with improper trunk rotation sequences (n = 33) demonstrated greater maximal shoulder external rotation angle (mean difference, 7.2° ± 2.9°, P = .016) and greater shoulder proximal force (mean difference, 9.2% ± 3.9% body weight, P = .021) compared with those with proper trunk rotation sequences (n = 22). No other variables differed significantly different between groups.

CONCLUSION

High school baseball pitchers who demonstrated improper trunk rotation sequences demonstrated greater maximal shoulder external rotation angle and shoulder proximal force compared with pitchers with proper trunk rotation sequences.

CLINICAL RELEVANCE

Improper sequencing of the trunk and torso alter upper extremity joint loading in ways that may influence injury risk. As such, exercises that reinforce the use of a proper trunk rotation sequence during the pitching motion may reduce the stress placed on the structures around the shoulder joint and lead to the prevention of injuries.

Arthrolysis combined with reconstruction for treatment of terrible triad injury with a poor outcome after surgical as well as conservative intervention

INTRODUCTION

The treatment of terrible triad injury with a poor outcome after intervention has not been successful thus far. The purpose of this study was to evaluate the efficacy of arthrolysis and reconstruction in the treatment of terrible triad injury with a poor outcome after surgical as well as conservative intervention.

MATERIALS AND METHODS

Twelve patients (12 elbows) with the diagnosis of terrible triad injury were respectively reviewed. All the 12 patients had elbow dysfunction after conservative and surgical treatment of the terrible triad injury. Preoperatively, the flexion arc and forearm rotation were 36.7° ± 28.5° and 51.3° ± 43.4°, respectively, and the Mayo Elbow Performance Score was 56.3 points. The mean interval between the primary injury and our surgical treatment was 6.6 months. Our surgical intervention included elbow arthrolysis, ulnar nerve transposition, radial head replacement, coronoid process and ligament repair, and hinged external fixation. Patients were encouraged to participate in rehabilitation training 24 h after surgery.

RESULTS

The mean follow-up duration was 20.1 months; the flexion arc and forearm rotation were 122° ± 18° and 140° ± 20°, respectively, and the mean Mayo Elbow Performance Score was 94.6 points (9 excellent, 3 good). Concentric stability was restored in all elbows. Complications included superficial pin tract infection (1), heterotopic ossification (3), and ulnar nerve palsy (1); the ulnar nerve symptoms had improved at the last follow-up.

CONCLUSIONS

The combination of open arthrolysis and reconstruction performed at a mean interval of 6-month posttrauma can restore functional mobility in cases of terrible triad injury with a poor outcome after surgical as well as conservative intervention. Thus, it may be an effective alternative for the treatment of the poor outcome terrible triad injury. We recommend early functional rehabilitation with adherence to the guidelines for hinged external fixation.

Percutaneous lateral ulnar collateral ligament reconstruction

PURPOSE

Open surgical reconstruction of the lateral ulnar collateral ligament is the standard treatment for symptomatic posterolateral rotatory instability of the elbow. It involves dissection and retraction of the lateral elbow muscles, which have been shown to be secondary stabilizers of the lateral elbow. We introduce a new muscle-protecting technique for single-strand lateral ulnar collateral ligament reconstruction and report on the isometry and primary stability when compared with a conventional muscle-splitting procedure. It was hypothesized that percutaneous lateral ulnar collateral ligament reconstruction provided isometry over the range of motion and that stability was comparable with a conventional open procedure.

METHODS

In sixteen human cadaver arms, the intact and the lateral collateral ligament complex-deficient situation was tested. Open lateral ulnar collateral ligament reconstruction was performed using a single-strand palmaris graft with humeral and ulnar tenodesis screw fixation. Posterolateral rotational stability was compared with a new reconstruction method, which percutaneously places a single-strand palmaris graft with humeral and ulnar tenodesis screw fixation.

RESULTS

Both open and percutaneous lateral ulnar collateral ligament reconstruction provided isometry over the range of motion and restored posterolateral stability to that of the intact situation. No significant differences between open and percutaneous reconstruction were found.

CONCLUSIONS

Percutaneous lateral ulnar collateral ligament reconstruction aims to preserve the lateral elbow muscles and to minimize soft tissue dissection. It has been shown that in an in vitro setup, this new procedure provides isometry over the range of motion and sufficiently restores posterolateral rotatory stability.