Anatomy of the distal biceps tendon: an in vivo 3-T magnetic resonance imaging study.

BACKGROUND: On the basis of the current literature, the optimal surgical technique for distal biceps tendon tears remains controversial. Cadaveric studies have investigated distal biceps anatomy but are limited by cohort size and tissue factors. We sought to investigate distal biceps anatomy in vivo by retrospectively reviewing magnetic resonance imaging (MRI) scans. An improved understanding of the anatomy of the distal biceps tendon will lead to better definition of the optimal anatomic surgical repair. METHODS: Two independent observers retrospectively reviewed 3-T MRI scans of elbows. Basic demographic data were collected, and measurements of tendon length, footprint width, footprint length, and footprint angle were taken using simultaneous tracker lines and a standardized technique. From the biceps muscle belly distally, the presence of a single tendon or double tendons was recorded and the tendon interdigitation point was measured if relevant. RESULTS: A total of 106 3-T MRI scans of 106 elbows of 103 patients were included. There were 71 male and 32 female patients, and the mean age was 44.7 years. Most distal biceps tendons exited the biceps muscle belly as separate entities (91%, 96 of 106 elbows) and then coalesced prior to insertion on the radial tuberosity (91%, 87 of 96 elbows). There was a positive correlation between tendon length and footprint length (P < .05), as well as between tendon length and footprint width (P < .05). The mean tendon length was 65.2 mm (95% confidence interval [CI], 63.3-66.8 mm; range, 44.3-86.8 mm), the mean distance from the musculotendinous junction to the interdigitation point was 38.3 mm (95% CI, 35.8-40.9 mm; range, 8.9-64.8 mm), the mean footprint width was 10.3 mm (95% CI, 9.9-10.7 mm; range, 5.9-16.3 mm), the mean footprint length was 16.2 mm (95% CI, 15.6-16.9; range, 7.3-25.4 mm), and the mean footprint angle was 32.1° (95% CI, 29.5°-34.6°; range, 8.5°-84.3°). CONCLUSION: An in vivo, high-resolution study of the anatomy of the distal biceps tendon improves our understanding of its complex morphology and hence our ability to perform an anatomic "footprint repair."

Defining the proximity of the axillary nerve from defined anatomic landmarks: an in vivo magnetic resonance imaging study.

BACKGROUND: The location of the axillary nerve in the shoulder makes it vulnerable to traumatic or iatrogenic injury. Cadaveric studies have reported the location of the axillary nerve but are limited because of tissue compression, dehydration, and decay. Three-Tesla (T) magnetic resonance imaging (MRI) allows high anatomic resolution of neural structures. The aim of our study was to better define the location of the axillary nerve from defined bony surgical landmarks in vivo, using MRI scan. METHODS: Using MRI, we defined a number of anatomic points and measured the distance from these to the perineural fat surrounding the axillary nerve using simultaneous tracker lines on both images. Two observers were used. RESULTS: A total of 187 consecutive 3-T MRI shoulder scans were included. Mean age was 57.9 years (range 18-86). The axillary nerve was located at a mean of 14.1 mm inferior from the bony glenoid at the anterior border, 11.9 mm from the midpoint, and 12.0 mm from the posterior border. There was a significant difference between distance at the anterior border and midpoint (P < .001), and between the anterior and posterior borders (P < .001). The axillary nerve was located at a mean of 12.6 mm medial to the humeral shaft at the anterior border, 9.9 mm at the midpoint, and 8.6 mm from the posterior border. There was a significant difference between distance at the anterior border and midpoint (P = .008) and between the anterior and posterior borders (P = .002). The mean distance of the axillary nerve from the anterolateral edge of the acromion was 53.3 mm (95% confidence interval [CI] 52.3, 54.2; range 33.9-76.3). The mean distance of the axillary nerve from the inferior edge of the capsule was 2.7 mm (95% CI 2.9, 3.1; range 0.3-9.9). There was a positive correlation between humeral head diameter and axillary nerve distance from the inferior glenoid (R2 = 0.061, P < .001). There was a positive correlation between humeral head diameter and distance from the anterolateral edge of the acromion (R2 = 0.140, P < .001). CONCLUSION: Our study has defined the proximity of the axillary nerve from defined anatomic landmarks. The proximity of the axillary nerve to the inferior glenoid and medial humeral shaft changes as the axillary nerve passes from anterior to posterior. The distance of the axillary nerve from the anterolateral edge of the acromion remains relatively constant. Both sets of distances may be affected by humeral head size. The study has relevance to the shoulder surgeon when considering "safe zones" during arthroscopic or open surgery.

A Ruptured Digital Epidermal Inclusion Cyst: A Sinister Presentation.

Epidermal inclusion cysts are benign cutaneous lesions caused by dermal or subdermal implantation and proliferation of epidermal squamous epithelium as a result of trauma or surgery. They are typically located on the scalp, face, trunk, neck, or back; however they can be found anywhere on the body. Lesions are asymptomatic unless complicated by rupture, malignant transformation to squamous cell carcinoma, or infection at which point they can clinically appear as more sinister pathologies. We present the case of a 45-year-old laborer with a ruptured epidermal inclusion cyst, manifesting clinically and radiographically as a malignancy. Following MRI, definitive surgical management may appear to be a logical progression in management of the patient. This case however is a good example of why meticulously following surgical protocol when evaluating an unknown soft tissue mass is imperative. By following protocol, an alternate diagnosis was made and the patient has since gone on to a make a full recovery without life transforming surgery.