Triceps brachii insertional footprint: Under-estimated complexity

Abstract

Background: The detailed complexity of triceps brachii insertional footprint continues to challenge surgeons as evidenced by continued reports of triceps-associated complications following elbow procedures. The purpose of this study is to describe the three-dimensional footprint of the triceps brachii at its olecranon insertion at the elbow.

Methods: 22 cadaveric elbows were dissected leaving only the distal insertion of the triceps intact. The insertion was defined and probed with a three-dimensional digitizer to create a digital three-dimensional footprint allowing width, height, and surface area of the footprint to be recorded relative to the bare area. The insertional soft tissues of tendon versus muscle along with the shape of the footprints were qualitatively described.

Results: The mean width and surface area of the lateral segment was greater in males than in females (30.07 mm vs. 24.37 mm, p = 0.0339 and 282.1 mm vs. 211. 56 mm, p = 0.0181, respectively). No other statistically significant differences between the sexes were noted. The triceps insertional footprint was "crescent-shaped" and consisted of three regions: central tendon, medial muscular extension, and lateral muscular extension.

Discussion: These findings can help explain the importance of avoiding these muscular structures during triceps-off approaches and provides the framework for future clinical studies. Clinical Relevance: Basic Science, anatomy study, cadaver dissection.

Keywords: Triceps; anatomy; distal triceps; footprint; tendon.

Figure 1.

Typical representation of triceps distal anatomy and insertion in most literature.

Figure 2.

Triceps fully dissected, with preservation of all elements of the musculotendinous unit, with the accompanying digitized medial, posterior, and lateral insertional views (MTE- medial triceps extension, LTE- lateral triceps extension, TFP- central tendon footprint, ST- sublime tubercle, LSN- lesser sigmoid notch, O- olecranon tip, C- coronoid).

Figure 3.

Figure 3a: Anterior view of Triceps insertion and olecranon, figure 3b: anterior view with demarcation between central tendon insertion to bone (blue) and muscle fibres inserting to bone (red), figure 3c: posterior view, figure 3d: posterior view with demarcation between central tendon insertion to bone (blue) and muscle fibres inserting to bone (red) (MTE-medial triceps extension, TFP-central tendon foot print, LTE – lateral triceps extension, O-olecranon tip, BA-Bare Area, C-Coronoid).

Figure 4.

3D reconstructions of the digitized data of triceps insertion, depicting muscular extensions of the medial and lateral heads that insert into the olecranon without a significant length of tendinous material at the interface. C-Coronoid, LSN-Lesser Sigmoid Notch, ST-Sublime Tubercle, BA-Bare Area, THP-Central Tendon Footprint, LTE-Lateral Triceps Extension, MTE-Medial Triceps Extension.

Figure 5.

A reference plane was constructed on the central ridge of the greater sigmoid notch. All subsequent measurements were based on this reference plane. C-Coronoid, LSN-Lesser Sigmoid Notch, ST-Sublime Tubercle, BA-Bare Area, TFP-Central Tendon Footprint, LTE-Lateral Triceps Extension, MTE-Medial Triceps Extension.

Figure 6.

3D extraction of the digitized whole triceps insertional footprint.

Figure 7.

3D rendered image of the triceps insertion from three different viewpoints.

Figure 8.

(a) Graphic rendered image of the triceps insertion with a “croissant” like 3D shape wrapped around the posterior, medial, and lateral olecranon process. (b) A more accurate illustration of the triceps insertional footprint, with the superficial aponeurosis of the lateral muscular extension removed.