Luis Saura Beltran MD, Presenter: Nothing to Disclose

Jenny T. Bencardino MD, Abstract Co-Author: Nothing to Disclose

Amado Ross Sussmann MD, Abstract Co-Author: Nothing to Disclose

Zehava Sadka Rosenberg MD, Abstract Co-Author: Nothing to Disclose

James S. Babb PhD, Abstract Co-Author: Nothing to Disclose

Laith M. Jazrawi MD, Abstract Co-Author: Consultant, Knee Creations, LLC Consultant, Ferring Group Consultant, Core Essence Orthopaedics, Inc Consultant, ConMed Linvatec Consultant, Johnson & Johnson

Gregory Hall, Abstract Co-Author: Nothing to Disclose

Javier Beltran MD, Abstract Co-Author: Nothing to Disclose

Determine the prevalence of low-lying medial head of triceps muscle belly and tendon insertion.

IRB approval was obtained and informed consent was waived for this retrospective HIPAA-compliant study. 50 consecutive MR studies of the elbow were identified using a search of our department database: 32M, 18W, age: 20-79 mean 45. Exclusion criteria included medial elbow pain and medial elbow pathology on MR. 5 cadaveric specimen underwent high-resolution 3T elbow MRI. The following variables were measured: Medial triceps muscle belly (MTMB) and tendon insertion (MTTI) distance relative to the superior olecranon. Low-lying MTMB and MTTI distances were defined as extension below the superior olecranon line (<0). Subjects were divided into three groups: 1) low-lying muscle (<0) and low lying tendon (<0), 2) non low-lying muscle(≥0) and low lying tendon (< 0), and 3) non low-lying muscle and tendon (both ≥0). The prevalence of low lying MTMB and MTTI was calculated in the study group and cadaveric specimen. Pearson correlation test was performed.

In the MR study group, the prevalence of a low-lying MTMB and MTTI was 10% (5/50) and 92% (46/50), respectively. The range of MTMB distance with respect to the superior olecranon line was -5.2 to 7.4 mm (mean = 0.8, SD 2.7). The range of MTTI distance to the superior olecranon line was -8.2 to 0 mm (mean = -3.8, SD 2.0). Associated low lying MTMB and MTTI (group 1) was 20%; non-low lying MTMB and low-lying MTTI (Group 2) was 72% and associated non-low lying MTMB and MTTI was 8% of cases. There was a significant association between MTMB and MTTI distances r = 0.372 (p = 0.001).  In the cadaveric group, the prevalence of a low-lying MTMB and MTTI was 60% (3/5) and 100% (5/5), respectively.  The range of MTMB distance with respect to the superior olecranon line was -6.0 to 0 mm (mean = -2.4). The range of MTTI distance to the superior olecranon line was -7.7 to -2.4 mm (mean = -5.1). Figure shows MTMB (blue arrow) and low-lying MTTI (green arrow). Conjoined tendon: red arrow.

Conclusion: There is a high prevalence (92%) of low lying medial triceps tendon insertion in our patient population without medial elbow pain as well as in our cadaveric study (100%).

Anatomic variation with a third insertional contribution from the superficial medial head of triceps tendon below the superior olecranon line has not been reported.

Beltran, L, Bencardino, J, Sussmann, A, Rosenberg, Z, Babb, J, Jazrawi, L, Hall, G, Beltran, J, Prevalence of Low-lying Medial Head of Triceps Muscle and Tendon: MR Imaging and Cadaveric Study.  Radiological Society of North America 2012 Scientific Assembly and Annual Meeting, November 25 - November 30, 2012 ,Chicago IL. http://archive.rsna.org/2012/12032207.html