Differences in the strain applied to Achilles tendon fibers when the subtalar joint is overpronated: a simulation study

Absolute reliability of Young's modulus of the soleus muscle and Achilles tendon measured using shear wave elastography in healthy young males

Background

Stiffness of the soleus muscle (SOL) and Achilles tendon (AT) are associated with Achilles tendinitis and medial tibial stress syndrome. Therefore, reliable SOL and AT stiffness measurements are important for monitoring clinical progress. However, little is known about the absolute reliability of the stiffness measurements of SOL and AT in different ankle positions. This study aimed to determine the absolute reliability of the Young's modulus measurements of the SOL and AT in different ankle positions in healthy young males.

Methods

This study included 33 healthy young males. SOL and AT stiffnesses were measured using Young's modulus and shear-wave elastography (SWE). Measurements were taken while the participants were kneeling, with their knees flexed to 90°, and the upper body supported by a table. Ultrasound images were recorded at ankle dorsiflexion angles of -10°, 0°, and 10°. The same measurements were repeated 15 min after the first measurement. Bland-Altman plots were used to verify the type or amount of error and 95 % confidence interval of the minimal detectable change (MDC95) values of the measurements.

Results

Bland-Altman plots identified that there was no fixed or proportional bias and that there was good agreement between the first- and second-time measurements of the SOL and AT, respectively, among all angles. The MDC95 of the Young's modulus of SOL at -10°, 0°, and 10° of ankle dorsiflexion were 5.6 kPa, 7.0 kPa, and 10.1 kPa, respectively, and AT were 15.8 kPa, 16.4 kPa, and 17.8 kPa, respectively.

Conclusion

Young's modulus measurements of the SOL and AT using SWE can be used to quantify elastic properties with high confidence. Clinically, assessing changes in the Young's moduli of the SOL and AT using SWE may help determine the effectiveness of interventions.

Classification by degree of twisted structure of the fetal Achilles tendon

BACKGROUND

The purpose of this study was to classify the twisted structure of the fetal Achilles tendon.

METHODS

The study was conducted using 30 legs from 15 Japanese fetuses (mean weight, 1764.6 ± 616.9 g; mean crown-rump length, 283.5 ± 38.7 mm; 16 males, 14 females). According to attachment to the deep layer of the calcaneal tuberosity, cases showing only soleus attachment were classified as least twist (Type I), cases showing both lateral head of the gastrocnemius and soleus were classified as moderate twist (Type II), and cases with only lateral head of the gastrocnemius were classified as extreme twist (Type III).

RESULTS

Viewing the Achilles tendon from cranially shows a structure twisted counterclockwise on the right side and clockwise on the left. The Achilles tendon was Type I in 4 legs (13%), Type II in 23 legs (77%), and Type III in 3 legs (10%).

CONCLUSIONS

The twisted structure of the Achilles tendon can be classified as early as the second trimester and is similar to that seen in adults.

The twisted structure of the fetal calcaneal tendon is already visible in the second trimester

INTRODUCTION

The progress in morphological science results from the greater possibilities of intra-pubic diagnosis and treatment of congenital disabilities, including the motor system. However, the structure and macroscopic development of the calcaneal tendon have not been investigated in detail. Studies on the adult calcaneal tendon showed that the calcaneal tendon is composed of twisted subtendons. This study aimed to investigate the internal structure of the fetal calcaneal tendon in the second trimester.

MATERIALS AND METHODS

Thirty-six fetuses fixed in 10% formaldehyde were dissected using the layer-by-layer method and a surgical microscope.

RESULTS

The twisted structure of the calcaneal tendon was revealed in all specimens. The posterior layer of the calcaneal tendon is formed by the subtendon from the medial head of the gastrocnemius muscle. In contrast, the anterior layer is formed by the subtendon from the lateral head of the gastrocnemius muscle. The subtendon from the soleus muscle constitutes the anteromedial outline of the calcaneal tendon. The lateral outline of the calcaneal tendon is formed by the subtendon originating from the medial head of the gastrocnemius muscle. In contrast, the medial outline is formed by the subtendon from the soleus muscle. In most of the examined limbs, the plantaris tendon attached to the tuber calcanei was not directly connected to the calcaneal tendon.

CONCLUSIONS

The twisted structure of the subtendons of the fetal calcaneal tendon is already visible in the second trimester and is similar to that seen in adults.

Morphological Features of the Ulnar Collateral Ligament of the Elbow and Common Tendon of Flexor-Pronator Muscles

Background:

The anterior bundle (AB) of the ulnar collateral ligament is the most important structure for valgus stabilization of the elbow. However, anatomic relationships among the AB, posterior bundle (PB) of the ulnar collateral ligament, and common tendon (CT) of the flexor-pronator muscles have not been fully clarified.

Purpose:

To classify the AB, PB, and CT and to clarify their morphological features.

Study Design:

Descriptive laboratory study.

Methods:

This investigation examined 56 arms from 31 embalmed Japanese cadavers. The CT investigation examined 34 arms from 23 embalmed Japanese cadavers with CTs remaining. Type classification was performed by focusing on positional relationships with surrounding structures. Morphological features measured were length, width, thickness, and footprint for the AB and PB and attachment length, thickness, and footprint for the CT.

Results:

The AB was classified as type I (44 elbows; 78.6%), can be separated as a single bundle, or type II (12 elbows; 21.4%), cannot be separated from the PB and joint capsule. The PB was classified as type I (28 elbows; 50.0%), can be separated as a single bundle; type IIa (6 elbows; 10.7%), posterior edge cannot be separated; type IIb (7 elbows; 12.5%), anterior edge cannot be separated; or type III (15 elbows; 26.8%), cannot be separated from the joint capsule. The CT was classified as type I (18 elbows; 52.9%), can be separated from the AB, or type II (16 elbows; 47.1%), cannot be separated from the AB. Significant differences in frequencies of AB, PB, and CT types were identified between men and women. Morphological features were measured only for type I of each structure, and reliability was almost perfect.

Conclusion:

These results suggest that the AB, PB, and CT each can be classified into an independent form and an unclear form. Presence of the unclear form was suggested as one factor contributing to morphological variation.

Clinical Relevance:

This study may provide basic information for clarifying functional roles of the AB, PB, and CT.