Ultrasonographic and Electrophysiological Evaluation of Ulnar Nerve Instability and Snapping of the Triceps Medial Head in Healthy Subjects.
OBJECTIVE
To evaluate the relationship between ulnar nerve instability and snapping of the triceps medial head during elbow flexion.


METHODS
Twenty-six healthy individuals were recruited. The primary outcome measures were ultrasonographic and electrophysiological parameters of the ulnar nerve. Ulnar nerve instability was classified into three types based on the degree of ulnar nerve movement: no dislocation (Type N), subluxation (Type S), and dislocation (Type D).


RESULTS
In the elbow 90-degree position, the incidences of Type N, S, and D were 41 (78.8%), 8 (15.4%), and 3 (5.8%) elbows, respectively; in the full flexion position, the incidences of Types N, S, and D were 24 (46.2%), 19 (36.5%), and 9 (17.3%) elbows, respectively. Spearman's correlation coefficients between ulnar nerve instability and snapping of the triceps medial head in the elbow 90-degree and full flexion positions were 0.808 and 0.889 (P < 0.001), respectively. The ulnar sensory response in Type S was of prolonged latency and decreased amplitude compared with that in Type N or D in the elbow full flexion position.


CONCLUSIONS
Ulnar nerve instability increased with elbow flexion and correlated with snapping of the triceps medial head. Ultrasonography of the ulnar nerve is an important tool in ulnar nerve instability assessment.
From the Department of Internal Medicine, College of Medicine, Korea University, Seoul, Republic of Korea (JHK); Department of Neurology, Myongji Hospital, Seonam University School of Medicine, Gyeonggi-do, Republic of Korea (B-EJ); Department of Physical Medicine & Rehabilitation, College of Medicine, Korea University, Seoul, Republic of Korea (KHK, BKP, DHK); and Medical Science Research Center, Korea University Ansan Hospital, Gyeonggi-do, Republic of Korea (JC).
Jae Ho
JH
Kang
Byung-Euk
BE
Joo
Ki Hoon
KH
Kim
Byung Kyu
BK
Park
Jaehyung
J
Cha
Dong Hwee
DH
Kim
D000328:Adult; D001132:Arm / Q000000981:diagnostic imaging / Q000294:innervation / Q000503:physiopathology; D004551:Elbow Joint / Q000000981:diagnostic imaging / Q000294:innervation / Q000503:physiopathology; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D007593:Joint Instability / Q000000981:diagnostic imaging* / Q000503:physiopathology; D008297:Male; D018482:Muscle, Skeletal / Q000503:physiopathology; D009431:Neural Conduction / Q000502:physiology*; D056888:Patient Positioning; D016059:Range of Motion, Articular / Q000502:physiology; D014459:Ulnar Nerve / Q000000981:diagnostic imaging* / Q000503:physiopathology; D014463:Ultrasonography / Q000379:methods