The aim of this study was to evaluate the relationship between the location of the insertion point of the AT into the posterior aspect of the calcaneus and the PF. Two hundred and two feet were evaluated from MRI scans. Ninety-seven women and one hundred and five men with a mean age of 40.15±18.58 were included in this study. Two independent investigators measured the horizontal distance from the most anterior point of the calcaneus to the most posterior part of the PF (A), including the horizontal length of the calcaneus (B). Moreover, distance between the most inferior point of the calcaneus and the most inferior part of the AT insertion into the calcaneus (C) and height of the posterior aspect of the calcaneus (D) were measured. Patients were divided into three groups based on age (I - patients younger than 18, II − 18–65, III - older than 65The all obtained mean values showed high sexual dimorphism between genders. However, when standardized ratios were compared, no statistically significant sexual differences were noted (p>0.05). Although previous studies have reported a correlation between the PF, age and gender, this correlation was not found in our study. Based on the obtained results, this study concludes that age and sex do not influence the morphology of the PF. However, aging strongly affects the location of the AT insertion point. Therefore, we believe this is the key factor which influence the relationship between the AT and PF.

Change in forearm muscle length can be used to predict muscle function during pronosupination. In ten fresh cadaveric specimens, markers were placed at fifteen muscle origins and insertions. The forearm was positioned at 10° increments from 80° of pronation to 90° of supination with the elbow flexed at 90°. An electromagnetic tracking system was used to digitally collect 3D origin and insertion coordinates. These coordinates were used to create a vector representing muscle length as a straight line from the muscle origin to the muscle insertion. To normalize the data, all lengths were normalized as a percentage of the maximum muscle length for each specimen. Differences in the data were determined through paired t-test analysis.

The muscles which exhibited a significant decrease in length from pronation to supination throughout the entire range were the biceps brachii and the palmaris longus. Muscles exhibiting a significant increase over the range were the pronator teres at both the humeral and ulnar origins as well as the pronator quadratus. The brachialis also exhibited an increase, though not as pronounced. The supinator, extensor indicis and the extensor carpi ulnaris all exhibited maximum length at the neutral position while length decreased in both pronation and supination directions. The only muscle to exhibit minimal length at neutral with increasing length in each direction was the brachioradialis. The extensor carpi radialis longus kept a consistent length during pronation and increased during supination. Muscles that remained consistent during pronation but decreased their length during supination included the extensor policis longus, the flexor carpi ulnaris, and the radial and ulnar origins of the abductor policis longus. The extensor carpi radialis brevis and the flexor carpi radialis exhibited no significant change in muscle length during forearm rotation.

Forearm Rotation involves a complex interaction between the Radius and Ulna. Multiple muscles traverse the forearm en route to the hand. Many muscles change significantly in length during pronosupination. These muscles

Must adapt to this change in length to allow coordinated Upper Extremity function.

Clinical Relevance- Rehabilitation following Injury needs to take into account the effect of forearm rotation, Splint position may vary depending on which Muscle or Tendon is injured, Surgical Procedures and Implants need to be designed to take into account transverse and longitudinal forces on the forearm.

The objectives of this study were to elucidate the function of Brachioradialis during forearm rotation to determine whether it is a neutralizing muscle and a protector of hyper-rotation by eccentric contraction.

The distance from the brachioradialis (BRAR) origin to insertion was measured on 10 left fresh frozen cadaveric arms using an electromagnetic tracking system. This was done in 10¢^aincrements over the full range of forearm rotation. In addition, fine-wire electrodes were placed in the BRAR of twelve living subjects. EMG data was collected as the subject rotated the forearm in both a pronating and a supinating direction.

The muscle length data shows that length is shortest at neutral and greatest closer to full rotation in either direction. When rotating from full pronation to neutral the EMG data show a steady increase while the muscle length decreases indicating a concentric contraction. When rotating from neutral to full pronation the muscle length increased and with load the EMG level increased indicating an eccentric contraction. During rotation from full supination to neutral, the EMG activity increased slightly with the muscle length, indicating a concentric contraction. When rotating from neutral to full supination, the EMG level remained variable while the muscle length increased indicating an eccentric contraction or a passive stretch.

EMG activity can occur during isometric, eccentric, or concentric contractions, the accompanying muscle length data is useful for establishing the direction of the activity. We conclude BRAR is a neutralizing muscle as it has a linear relationship with EMG activity when returning the forearm to neutral. It also acts eccentrically slowing extreme pronation and thus it has a dynamic effect on DRUJ stability.

This knowledge will assist surgeons in Tendon Transfer surgery and injury to the Brachioradialis muscle.