Distal insertional anatomy of the triceps brachii muscle: MRI assessment in cadaveric specimens employing histologic correlation and Play-doh® models of the anatomic findings.

OBJECTIVES: Assess the insertional anatomy of the distal aspect of the triceps brachii muscle using magnetic resonance imaging (MRI) in cadavers with histologic correlation and Play-doh® models of the anatomic findings. MATERIALS: Elbows were obtained from twelve cadaveric arm specimens by transverse sectioning through the proximal portion of the humerus and the midportion of the radius and ulna. MRI was performed in all elbows. Two of the elbow specimens were then dissected while ten were studied histologically. Subsequently, Play-doh® models of the anatomic findings of the distal attachment sites of the triceps brachii muscle were prepared. RESULTS: MRI showed a dual partitioned appearance of the distal attachment sites into the olecranon in all specimens. In the deeper tissue planes, the medial head muscle insertion was clearly identified while superficially, the terminal portion of the long and lateral heads appeared as a conjoined tendon. Histologic analysis, however, showed continuous tissue rather than separate structures attaching to the olecranon. CONCLUSION: Although MRI appeared to reveal separate and distinct attachments of the triceps brachii muscle into the olecranon, histologic analysis delineated complex but continuous tissue related to the attachments of the three heads of this muscle. The Play-doh® models were helpful for the comprehension of this complex anatomy and might serve as a valuable educational tool when applied to the analysis of other musculoskeletal regions.

A single simple position for ultrasound assessment of both common extensor and common flexor origin at the elbow.

OBJECTIVE: Is to evaluate the simplicity of 90° flexion/neutral position for ultrasonography assessment of both common extensor and common flexor origins in comparison with the standard position. MATERIAL AND METHODS: A standard questionnaire was distributed on 50 trainees, rheumatologists with No previous experience or training in ultrasonography. (They) were attending musculoskeletal training workshops at AL-Azhar rheumatology department musculoskeletal ultrasonography unit in 2016. Each participant then (was) asked to practice US examination of both common extensor and common flexor origins in both positions and then fill four questionnaires, two (of which are) for common flexor and (the other) two (are) for the common extensor origins, in the standard and the other proposed single position. Each questionnaire (whose) answer was graded on scale from 0 to 10, includes the following points: • Time needed to examine the tendon in minutes, • Difficulty in maintaining the probe contact to the skin, • Difficulty in getting good image of the tendon, • The overall impression of simplicity. RESULTS: Descriptive analysis of the questionnaire results shows that the participants favors the single position in all questionnaire parameters. Comparing means of the four questionnaire parameters in both positions shows highly significant difference in the four parameters at the level of both common flexor and extensor origins in favor of the single position as p > 0.005. CONCLUSION: The 90 degree flexion/neutral position appears to be simpler than the standard position for ultrasonography assessment of common extensor and common flexor tendons at the elbow.

Limitations of the radiocapitellar line for assessment of pediatric elbow radiographs.

BACKGROUND: The radiocapitellar line (RCL) is recommended for evaluating radiocapitellar alignment in skeletally immature elbows, yet its parameters have not been clearly defined. This study systematically assesses the RCL relationship in normal elbows, investigating the impacts of radiographic view, choice of anatomic landmarks, patient age, forearm position, and observer bias on the manner in which the RCL intersects the capitellum. METHODS: On radiographs of 20 normal elbows (age range, 1 to 8 y), 3 pediatric orthopaedic surgeons, blinded to clinical history, drew lines (RCLs) on anteroposterior and lateral projections, along the radial shaft and neck, and with and without the capitellum visible. Line placement was repeated 2 weeks later. The relationship of each RCL to the capitellum was assessed continuously using the perpendicular distance to the center of the capitellum, normalized to capitellar width [line-capitellar distance (LCD)], and categorically as passing through the middle third, outer two-thirds, or outside the capitellum. RESULTS: Of the 480 RCLs drawn, 23 (5%) missed the capitellum and 224 (47%) missed the middle third. More radial neck than shaft lines intersected the middle third on both anteroposterior and lateral views (P < 0.05, Fisher exact test), with the lowest LCD values for neck lines on the lateral view (P < 0.05, analysis of variance (ANOVA)). More RCLs intersected the middle third when the capitellum was visible than when it was obscured (P = 0.03, Fisher exact test), suggesting an effect of observer bias. Patient age correlated inversely with LCD (P < 0.001). The angle between the neck and shaft lines correlated positively with LCD (P < 0.001), suggesting an impact of forearm rotation position. Intraobserver and interobserver reliability was moderate-to-substantial (κ = 0.40-0.75). CONCLUSIONS: The RCL best defines normal radiocapitellar alignment when the line is drawn along the radial neck on the lateral view, although this relationship is affected by bias, patient age, and forearm rotation position. The RCL does not reliably intersect the middle third of the capitellum, arguing against its sufficiency for assessing precise radiocapitellar alignment. LEVEL OF EVIDENCE: Diagnostic Level 3.