Tendinous Inscriptions of the Rectus Abdominis: A Comprehensive Review

Intercostal nerve electrodiagnostic testing in rib fractures

INTRODUCTION/AIMS

Intercostal nerve injury can occur after rib fractures, resulting in denervation of the abdominal musculature. Loss of innervation to the rectus abdominis and intercostal muscles can cause pain, atrophy, and eventual eventration, which may be an underrecognized and thus undertreated complication of rib fractures. We investigated the clinical utility of intercostal nerve electrodiagnostic testing following rib fractures to diagnose and localize nerve injury at levels T7 and below.

METHODS

Five patients with displaced bicortical rib fractures involving the 7th-11th ribs and clinical eventration of the ipsilateral abdominal wall underwent intercostal nerve conduction studies (NCS) and needle electromyography (EMG) on the affected side. EMG of the rectus abdominis and intercostal muscles was performed with ultrasound guidance, and ultrasound measurements of rectus abdominis thickness were obtained to assess for atrophy.

RESULTS

Average patient age was 59.4 years and average body mass index (BMI) was 31.5 kg/m2. Intercostal NCS and EMG were able to reliably diagnose and localize intercostal nerve damage after rib fractures. Ultrasound demonstrated an average rectus abdominis transverse cross-sectional thickness of 0.534 cm on the affected side, compared with 1.024 cm on the non-affected side.

DISCUSSION

Intercostal electrodiagnostic studies can diagnose and localize intercostal nerve damage after displaced rib fractures. Musculoskeletal ultrasound can be used to diagnose and quantify rectus abdominis atrophy and to accurately and safely guide needle EMG to the intercostal and rectus abdominis muscles.

Investigation of Structural Changes in Rectus Abdominis Muscle According to Curl-Up Angle Using Ultrasound with an Extended Field of View

The rectus abdominis (RA) muscle is related to abdominal muscle contraction and is divided into three sub-sections. In this study, changes in each section according to the curl-up angles were measured using ultrasound with an extended field of view (EFOV) scan and compared with the conventional scan. The results showed that the locations of the measurement position center were consistently detected only with the EFOV scan and that the change ratios in thickness and length between sections at the same angles were not significantly different, suggesting that each section was selectively activated. Furthermore, the ratios of the thickness and length changes in each section were significantly different between the rest position and curl-up angles. Specifically, in the section 2 there was a significant difference in the thickness and length changes between different angles, reflecting the characteristics of RA during contraction, and their variations were less than in the section 3. Therefore, the results suggest that changes in only a section of RA cannot be representative of overall RA activation, EFOV scan method can be useful for investigating the structural characteristics of RA in detail, and the proposed method can obtain various information about muscle contraction for efficient muscle treatment and muscle strengthening.

Fetal development and growth of the human erector spinae with special reference to attachments on the surface aponeurosis

PURPOSE

The longissimus (LO) and iliocostalis (IC) of adults consist of myofibers extending from the superolateral to the inferomedial side of the back and, because of the same course, they are fused in the thoracolumbar region. The LO also has a medial attachment to the long myofibers of the transversospinalis (TS) showing a course from the superomedial to the inferolateral side. However, there is apparently no information regarding when and how these similar longitudinal muscles differentiate from a cluster of dorsomedial myotome cells.

METHODS

We examined sagittal and horizontal sections of the trunks of 39 human embryos and fetuses (18-330 mm crown-rump length).

RESULTS

At 6-7 weeks gestational age (GA), the surface aponeurosis appeared prior to and independent of the thoracolumbar fascia. At 6-9 weeks GA, the LO myofibers had a postero-inferior course, from the transverse process to the initial aponeurosis, whereas the TS myofibers had a postero-superior course, from a lateral extension of the intertransverse ligament to the aponeurosis. However, the IC consisted of supracostal longitudinal myofibers and was distant from the LO until 12 weeks GA. Because of the lack of ligamentous attachments and ribs, myofibers of the TS, LO, and IC took a similar inferior course in the lumbar region. When the early TS was represented by the transverso-aponeurotic muscle, consequently, the LO corresponded to the aponeuro-transversal muscle and was independent from the IC.

CONCLUSION

The classical model of TS and LO development does not recognize the essential role of the aponeurosis identified here.

The Effect of Additional External Resistance on Inter-Set Changes in Abdominal Muscle Thickness during Bridging Exercise

Bridging exercises with abdominal hollowing are often used as a regimen for improving spinal stability. Lately, this type of training has become very popular among elite athletes, creating a need for more demanding exercises. The purpose of this study was to investigate whether the use of additional external resistance is beneficial for abdominal muscle recruitment during bridge exercise. Tissue movement of the transversus abdominis (TrA) and the rectus abdominis (RA) was recorded with the use of two synchronized ultrasonic devices, in 20 healthy college students. From the hook-lying position participants were examined in eight different exercise conditions: a) rest, b) abdominal drawing-in maneuver (ADIM), c) bridge, d) bridge- ADIM, e) bridge with 10KG, f) bridge- ADIM with 10KG, g) bridge with 20KG and h) bridge-ADIM with 20KG. Analysis of variance (ANOVA) showed a statistically significant increase in TrA thickness when performing the bridge exercise combined with ADIM compared to rest mode (p < .05). RA thickness decreased when the ADIM was performed, compared to rest (p < 0.05). No significant difference in TrA and RA thickness when exercising with and without external resistance was observed (p > 0.05). The main outcome of this study was that external loading provided some extra level of difficulty, yet it was not beneficial for abdominal muscle recruitment, when performing a supine bridge exercise.

Umbilicus and the rectus sheath: a study using human fetuses

PURPOSE

The newborn umbilicus is provided by a fibrous ring after closure with a scar at the bottom. Since it is believed to be embedded in the linea alba, a specific connection with the rectus sheath was not yet hypothesized for the umbilicus. However, there are no or few descriptions about the development and growth.

METHODS

We histologically examined 28 fetuses at 8-40 weeks: 6 fetuses at 8 weeks, 12 at 10-14 weeks and 10 at 31-40 weeks.

RESULTS

An initial rectus sheath issued a linear mesenchymal condensation toward the umbilical cord at 10-14 weeks and, an established sheath provided a fibrous band around the umbilical cord at 31-40 weeks. The rectus sheath margins made an acute turn toward the skin at the superior and lateral rims of umbilicus and dispersed into a loose tissue of the cord. In contrast, the sheath margin changed its direction gradually to the superficial side at the inferior rim and inserted at a border between the skin epidermis and a mesothelium-like covering of the cord. The developing umbilical ring contained no or few elastic fibers.

CONCLUSION

Instead of the underdeveloped linae alba, the rectus sheath seemed to be tightly connected with the umbilicus at birth. Rather than an expected elasticity, the rectus muscle contraction was likely to play a critical role in the closure after birth. Via the umbilical ring, the fetal rectus sheath also seemed to tightly connect with the skin at the inferior rim of umbilicus.