The role of the flexor pronator muscles as dynamic stabilizers against elbow valgus stress in patients with medial ulnar collateral ligament insufficiency

Background: There is consensus that most complete ulnar collateral ligament (UCL) injuries in throwers would benefit from surgical intervention. Optimal treatment for partial UCL tears remains controversial. Stress ultrasonography has become a well-accepted diagnostic modality for assessing UCL injury. Hypothesis: Partial UCL tears will result in an intermediate increase in ulnohumeral joint space gapping as compared with that of an intact UCL and a complete UCL tear, but the degree of joint space gapping will vary by anatomic location of the partial tear. Study Design: Controlled laboratory study. Methods: Twenty-one cadaveric elbows were divided into 7 groups representing different anatomic locations of UCL partial tears. Partial tears were simulated by cutting 50% of the measured width of the UCL at 6 locations: distal anterior/posterior, midsubstance anterior/posterior, and proximal anterior/posterior. A seventh partial tear was created by partially elevating the undersurface of the distal UCL to simulate the radiographic “T-sign.” Valgus stress (15 daN) was applied to each cadaveric elbow at 30° of flexion using a standardized device. Each specimen was tested intact, partially torn, and completely torn. At each state, joint space was measured using stress ultrasonography, and the difference in joint space from unstressed to stressed (delta) was recorded. Results: There were 10 right and 11 left upper extremity specimens. The mean delta was 0.58 mm for the intact state and <0.75 mm in all groups. Both distal partial tear groups had mean deltas <0.75 mm, similar to intact elbows. Proximal tears and the T-sign demonstrated intermediate deltas (0.99-1.23 mm). Midsubstance partial tears demonstrated the largest deltas (1.57-2.03 mm), similar to those of the complete tears. All complete tear groups had a mean delta >1.5 mm (1.54-3.03 mm). Conclusion: These findings suggest that partial tears introduce a spectrum of instability from functionally intact to completely torn. As a result, some may be biomechanically amenable to nonoperative treatment, while others would be indicated for early reconstruction. Further research into the biological and biomechanical determinants of nonoperative treatment failure will assist with more precise treatment recommendations. Clinical Relevance: Describing the biomechanical consequences of different, clinically significant partial UCL tears potentially allows more precise recommendations for operative and nonoperative treatment.

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Comparison of the Biomechanical Profile of the Intact Ulnar Collateral Ligament with the Modified Jobe and the Docking Reconstructed Elbow

The American Journal of Sports Medicine ◽

10.1177/0363546508331136 ◽

2009 ◽

Vol 37 (5) ◽

pp. 974-981 ◽

Cited By ~ 46

Author(s):

Michael G. Ciccotti ◽

Sorin Siegler ◽

John A. Kuri ◽

John H. Thinnes ◽

Daniel J. Murphy

Keyword(s):

Degrees Of Freedom ◽

Ulnar Collateral Ligament ◽

Elbow Flexion ◽

Collateral Ligament ◽

Valgus Stress ◽

Anterior Portion ◽

Reconstructive Procedures ◽

Kinematic Coupling ◽

Loading System ◽

4 Degrees Of Freedom

Background The modified Jobe and Docking techniques are commonly used to reconstruct the elbow's ulnar collateral ligament. Hypothesis Valgus laxity and kinematic coupling after these reconstructive procedures are similar to those of the native ulnar collateral ligament. Study Design Controlled laboratory study. Methods Testing was conducted on 10 pairs of cadaver elbows using a 4 degrees of freedom loading system. Subfailure valgus loads were applied to the native elbows at different flexion angles; motion and ligament elongation were measured. The elbows were then loaded to failure in valgus at 90° of flexion. The reconstructive techniques were then applied and testing was repeated. Results Only the resting length of the anterior portion of the ulnar collateral ligament anterior bundle remained isometric throughout range of motion. Valgus laxity was nearly equal for the native and reconstructed ligaments at flexion angles of 90° or higher. However, both reconstructions provided less valgus stability than the native ulnar collateral ligament at low flexion angles. Kinematic coupling decreased with increased flexion for both native and reconstructed ligaments. Conclusion The modified Jobe and Docking techniques reconstruct restraint of the native ulnar collateral ligament to valgus laxity and kinematic coupling at 90° of flexion and higher angles where peak valgus torque is experienced in the throwing elbow. Clinical Relevance Both reconstructions provide valgus stability comparable to that of the native ulnar collateral ligament at 90° and higher, helping to explain their success in treating throwing athletes. Both reconstructions provide less valgus stability than the native ulnar collateral ligament at low flexion angles, suggesting that patients undergoing ulnar collateral ligament reconstruction should be cautioned against activities that provide valgus stress at low elbow flexion angles, such as side-arm throwing. This study suggests caution against overtightening the reconstructions at the common 30° of flexion.

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Dynamic Sonography with Valgus Stress to Assess Elbow Ulnar Collateral Ligament Injury in Baseball Pitchers

Ultrasound Quarterly ◽

10.1097/00013644-200306000-00005 ◽

2003 ◽

Vol 19 (2) ◽

pp. 99

Author(s):

&NA;

Keyword(s):

Ulnar Collateral Ligament ◽

Ligament Injury ◽

Collateral Ligament ◽

Valgus Stress ◽

Ulnar Collateral Ligament Injury ◽

Baseball Pitchers

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Elbow valgus stability of the transverse bundle of the ulnar collateral ligament

BMC Musculoskeletal Disorders ◽

10.1186/s12891-021-04760-1 ◽

2021 ◽

Vol 22 (1) ◽

Author(s):

Mutsuaki Edama ◽

Kanta Matsuzawa ◽

Hirotake Yokota ◽

Ryo Hirabayashi ◽

Chie Sekine ◽

...

Keyword(s):

Subcutaneous Tissue ◽

Load Condition ◽

Ulnar Collateral Ligament ◽

Joint Space ◽

Collateral Ligament ◽

Valgus Stress ◽

Limb Position ◽

Intact State ◽

Significant Difference ◽

Telos Stress Device

Abstract Background The purpose of this study was to clarify elbow valgus stability of the transverse bundle (TB). We hypothesized that the transverse bundle is involved in elbow valgus stability. Methods Twelve elbows of six Japanese Thiel-embalmed cadavers were evaluated. The skin, subcutaneous tissue and origin of forearm flexors were removed from about 5 cm proximal to the elbow to about 5 cm distal to the elbow, and the ulnar collateral ligament was dissected (intact state). The cut state was defined as the state when the TB was cut in the middle. The joint space of the humeroulnar joint (JS) was measured in the intact state and then in the cut state. With the elbow flexed to 30°, elbow valgus stress was gradually increased to 30, 60 N using the Telos Stress Device, and the JS was measured by ultrasonography under each load condition. Paired t-testing was performed to compare the JS between the intact and cut states under each load. Results No significant difference in JS was identified between the intact and cut state at start limb position. The JS was significantly higher in the cut state than in the intact state at both 30 N and 60 N. Conclusion The findings from this study suggested that the TB may be involved in elbow valgus stability.

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Biomechanical Analysis of Thumb Ulnar Collateral Ligament Tear Kinematics

Hand ◽

10.1177/1558944719868518 ◽

2019 ◽

pp. 155894471986851

Author(s):

Charles C. Lin ◽

Nilay A. Patel ◽

Yasuo Itami ◽

Michelle H. McGarry ◽

Steven S. Shin ◽

...

Keyword(s):

Ulnar Collateral Ligament ◽

Biomechanical Analysis ◽

Collateral Ligaments ◽

Collateral Ligament ◽

Valgus Stress ◽

Ligament Tear ◽

Partial Tear ◽

Complete Tear ◽

Valgus Instability ◽

The Stability

Background: Thumb ulnar collateral ligament (UCL) injuries are common, but the kinematics of these injuries have not been comprehensively described, especially regarding kinematic changes with progressive UCL injury. Methods: Eleven cadaveric thumbs underwent kinematic testing under 4 conditions: intact, partial tear (50%) of the proper UCL, full tear of the proper UCL, and complete tear of both the proper and accessory UCL. Kinematic testing parameters included varus/valgus stress, pronation/supination, and volar/dorsal translation at −10 degree, 0 degree, 15 degree, and 30 degree of metacarpophalangeal flexion. Results: Partial tear of the proper UCL did not result in significant increases in laxity in any direction compared with intact ( P ≥ .132). Full tear of the proper UCL resulted in a significant increase in valgus angulation (18.8° ± 1.7° vs 11.5° ± 1.5°; P = .024) and pronation (15.4° ± 2.5° vs 12.6° ± 2.3°; P = .034) at 30 degree of flexion relative to intact. Complete tear of both the proper and accessory collateral ligaments resulted in increased valgus angulation at all degrees of flexion ( P < .001). Complete tear also resulted in a significant volar translation at 0 degree, 15 degree, and 30 degree of flexion ( P ≤ .016). Conclusion: Partial tear of the proper UCL does not significantly affect the stability of the joint, but full tear of the proper UCL increases valgus instability at 30 degree of flexion. Complete tear of the UCL is necessary for increased varus/valgus instability at all degrees of flexion and results in significant increases in pronation/supination and volar translation.

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