# Length ratios of the distal triceps tendon: an anatomical study for the assessment of tendon length in chronic defect situations

## TL;DR

This study provides anatomical measurements and correlations to help surgeons accurately assess triceps tendon length during chronic defect repairs.

## Contribution

The study introduces reliable anatomical references for triceps tendon length assessment in chronic ruptures.

## Key findings

- The lateral aponeurosis length strongly correlates with ulna length, making it a reliable reference for triceps length.
- Moderate to strong correlations were found between tendon/aponeurosis lengths and bony landmarks like the distal humerus and olecranon.
- Accurate tendon length restoration is critical for maintaining elbow function and stability.

## Abstract

Chronic triceps tendon ruptures are rare but challenging to treat due to limited muscle mobilization and difficulty in accurately assessing tendon length. Proper tendon length restoration is essential for maintaining physiological muscle tension, as excessive tendon length may lead to weakness and extension lag with reduced functional stability during elbow extension, whereas insufficient length can restrict elbow flexion and alter joint kinematics. This study aimed to examine the length ratios of the distal triceps tendon and aponeurosis in relation to bony landmarks to provide an intraoperative reference for tendon length assessment in chronic defect situations.

A total of 54 embalmed cadaveric upper limbs (male: 54%, female: 46%) were dissected. The following anatomical parameters were measured: the length of the distal triceps tendon from the olecranon (OL) tip to the musculotendinous junction, the lengths of the medial and lateral distal triceps aponeurosis, the length of the ulna (UL) and radius (RA), and the width of the OL and the distal humerus (intercondylar width). Pearson correlation coefficients were used to analyze relationships between tendon/aponeurosis lengths and bony landmarks.

The mean length of the distal triceps tendon was 40 ± 15 mm, while the medial and lateral triceps aponeurosis measured 150 ± 17 mm and 115 ± 18 mm, respectively. Moderate correlations were observed between the distal triceps tendon length and both the width of the distal humerus (r = 0.42, P = .002) and the width of the OL (r = 0.36, P = .007). The lateral aponeurosis length showed strong correlations with UL length (r = 0.64, P < .001), RA length (r = 0.54, P < .001), and distal humerus width (r = 0.51, P < .001), while a moderate correlation was found with OL width (r = 0.41, P = .002). The medial aponeurosis length strongly correlated with the OL width (r = 0.54, P < .001) and UL length (r = 0.52, P < .001), and moderately with the RA length (r = 0.49, P < .001) and distal humerus intercondylar width (r = 0.44, P < .001).

This study demonstrates that the lateral aponeurosis length correlates strongly with UL length, making it a particularly reliable reference for estimating the physiological triceps length in chronic defect situations. These findings provide an important anatomical basis for achieving precise triceps length restoration, which is essential for optimal clinical outcomes in reconstructive surgery.