Abstract
Recently, pathological changes in the fat pad on the anterior inferior iliac spine (AIIS), between the proximal rectus femoris and joint capsule, have been highlighted as a cause of anterior hip pain. However, precise fat pad features, such as the spatial distribution distal to the AIIS, histological features, and in vivo tissue elasticity, remain unclear. This study aimed to investigate the morphological characteristics of the fat pad on the AIIS. Four hips from four cadaveric donors were both macroscopically and histologically investigated, and eight hips from four volunteers were assessed using ultrasonography. The fat pad on the AIIS was also surrounded by the iliopsoas and gluteus minimus, extending distally to the superficial portion of the vastus lateralis, and the anterior portion of the gluteus maximus tendon. Histological analysis revealed that the fat pad was composed of loose connective tissue. Based on the ultrasonography, the shear wave velocity in the fat pad was significantly lower than that in the joint capsule. Conclusively, the pathological adhesion between the joint capsule and pericapsular muscles, if caused by fat pad fibrosis, may occur following the abovementioned fat pad spatial distribution.
Highlights
Pathological changes in the fat pad on the anterior inferior iliac spine (AIIS), between the proximal rectus femoris and joint capsule, have been highlighted as a cause of anterior hip pain
This study aimed to investigate the morphological features of the fat pad on the AIIS, focusing on its spatial distribution distal to the AIIS, histological features, and in vivo tissue elasticity
The present study revealed that the fat pad between the proximal rectus femoris and the joint capsule— surrounded by the iliopsoas and gluteus minimus—extended distally deep to the gluteus minimus tendon and superficial to the vastus lateralis, and posterolaterally to the anterior portion of the gluteus maximus tendon
Summary
Pathological changes in the fat pad on the anterior inferior iliac spine (AIIS), between the proximal rectus femoris and joint capsule, have been highlighted as a cause of anterior hip pain. The precise characteristics of the fat pad—histological features and in vivo tissue elasticity, as assessed by shear wave elastography during ultrasound imaging10—remain unclear. Both the spatial distribution and the abovementioned characteristics of the fat pad on the AIIS may clarify the pathological changes in the fat pad that play a role in anterior hip pain development. This study aimed to investigate the morphological features of the fat pad on the AIIS, focusing on its spatial distribution distal to the AIIS, histological features, and in vivo tissue elasticity. We hypothesized that the fat pad on the AIIS spreads distal to the joint capsule, is composed of loose connective tissue, and is significantly less elastic than the joint capsule, which is a dense connective tissue
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