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

Abstract

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

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

“…Therefore, the results of this study appear highly accurate. In addition, in previous research [ 13 , 14 ], the anatomical features of the AB, PB, and CT were examined by focusing on positional relationships with surrounding structures, and it was reported that the AB, PB, and CT were each classified into an independent form and an unclear form. In other simulation studies [ 15 , 16 ], the lateral collateral ligament of the ankle was classified based on morphological differences, and the strain during ankle movements has been reported to differ for each type.…”

“…In the dissection procedure, the skin, subcutaneous tissue, and muscular parts were removed, and the AB, PB, anterior common tendon (ACT), and posterior common tendon (PCT) were carefully dissected. Classification of the AB, PB, ACT, and PCT was performed with reference to previous studies [ 13 , 14 ]. Group I was classified as follows: the AB and PB could be separated as a single fiber bundle, and the AB, ACT, and PCT could be separated from each other.…”

“…The PB was digitized at a total of eight points of the origin and insertion, and they were defined as the anterior band, anterior central band, posterior central band, and posterior band. In previous research [ 13 , 14 ], the PB of Group I originated from the medial epicondyle of the humerus, and the average width of the origin was about 4 mm. Thus, the digitized parts of the anterior central band and posterior central band in Group II and Group III were the fiber bundles or joint capsules located about 2 mm anterior and 2 mm posterior from the medial epicondyle tips of the humerus, respectively.…”

“…Thus, the reported anatomical features of the AB, PB, and CT have been controversial. Therefore, in previous research [ 13 , 14 ] the anatomical features of the AB, PB, and CT were examined, and the AB, PB, and CT were found to have an independent form and unclear form. Other ligaments have been reported to have a different braking function due to differences in anatomical features [ 15 , 16 ].…”

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

“…The AB has been reported as a primary stabilizer for elbow valgus stress, with the posterior bundle as a secondary stabilizer [ 5 – 9 ]. Many anatomical studies [ 3 , 4 , 7 , 10 – 24 ] and biomechanical studies [ 25 – 30 ] have been reported on AB and PB. But there are few anatomical studies and biomechanical studies on TB [ 2 , 20 , 31 , 32 ].…”