A supernumerary muscle between the adductors brevis and minimus in humans

Comparison of three obturator nerve block techniques for injectate spread into the obturator canal: a randomized controlled trial

Purpose

The obturator nerve branches into the obturator canal; therefore, local anesthetic spread into the obturator canal predicts the success of the obturator nerve block (ONB). We compared three ONB techniques for the spread of local anesthetic mixed with contrast medium into the obturator canal.

Methods

We performed the ONB using the classical pubic approach (PA), inguinal approach (IA), or ultrasound-guided methodologic approach (UMA) in 143 patients undergoing transurethral resection of bladder tumors. The obturator nerve course and branching patterns of the UMA group were examined using ultrasound imaging. After injecting a local anesthetic mixed with a contrast medium, we evaluated its spread into the obturator canal using fluoroscopic imaging. P < 0.05 indicated statistical significance.

Results

Success rate of obturator canal enhancement was the greatest in the UMA group (84%; P < 0.001); the PA (42.6%; 20/47 patients) and IA (47.8%; 22/46 patients) groups did not differ significantly (P = 1.000). Both branches of the obturator nerve passed above the superior margin of the external obturator muscle (EOM), and the obturator canal was enhanced in 13 of 50 (26%) patients in the UMA group. The posterior branch of the obturator nerve passed between the superior and main fasciculi of the EOM in 37 of 50 patients (74%) in the UMA group; the obturator canal was enhanced in 29 of these 37 patients (78%).

Conclusion

Local anesthetic spread into the obturator canal using the UMA was superior to that using the PA and IA. Both branches of the obturator nerve could be blocked using the UMA.

Morphologic classification and innervation patterns of the pectineus muscle

The purpose of this study was to identify the frequency of pectineal hiatus and of pectineus innervations, including femoral, obturator, and/or accessory obturator nerves. Also, this study sought to detailed intramuscular nervous distributions, with a particular focus on the relationship of nerves in multi-innervated pectineus. One hundred (49 right and 51 left) thighs from 52 cadavers (25 men and 27 women) were dissected. The morphology and innervations of the pectineus were investigated. Modified Sihler's whole-mount nerve-staining method was employed for visualization of the intramuscular nerve-distribution patterns of the pectineus. Variation of the pectineus forming a hiatus was identified in 18% of the specimens. The femoral innervations to the pectineus were identified in all specimens. Additional innervation either by the obturator or the accessory obturator branch to the pectineus was identified in 10% or 2% of specimens, respectively. No case of triple innervation to the pectineus was observed. In cases of dually innervated pectineus, two nerves formed a communication system inside the muscle. Among the three nerves supplying the pectineus, the femoral nerve branched more than the other two nerves and covered the greatest area in the muscle. The pectineal hiatus appears to be a common variation. The femoral nerve branch in a dually innervated pectineus is the dominant nerve component that supplies the muscle when considering frequency, branching pattern, and area, even though cooperation between two nerve components is implied. This study serves to advance the existing anatomical knowledge about the pectineus muscle, which is of clinical value.

Variation of pectineus muscle forming a hiatus

Knowledge of the anatomic variations in the pectineus muscle is important for vascular surgeons to minimize complications following surgical approach to the distal part of the deep femoral artery. During routine dissection of the thigh, variations in the bilateral pectineus muscles were identified in an 82-year-old male cadaver. On both sides, the superficial and deep layers of the pectineus were divided at its distal part, forming a triangular-shaped hiatus between them and the femur shaft. Distally, the tendon of the superficial part intermingled with the tendon of the adductor longus. The tendon of the deep part was inserted into the pectineal line. On the right side, the deep femoral artery and its first perforating artery passed through the hiatus. On the left side, the deep femoral artery pierced the hiatus, and then, the first perforating artery was branched from the deep femoral artery. No reported case has described a pectineal hiatus. The variations observed in this study are an ontogenetic vestige of the two different origins of the pectineus. The insertion of the superficial layer into the adductor longus tendon suggests a close relationship between these muscles during prenatal development. Surgeons should be aware of the variation to minimize injury to the pectineus muscle while approaching the deep femoral artery.

The adductor minimus muscle revisited

The adductor minimus muscle has had scant and conflicting reports regarding its anatomy with some authors ignoring its existence altogether. The present study was conducted to more precisely describe the anatomy of this muscle. Forty human cadavers underwent dissection of the posterior thigh for observation of the adductor minimus muscle. When identified, this muscle was measured and relationships to the muscle documented. Additionally, five fetuses were dissected to observe for the presence of the adductor minimus muscle. The adductor minimus muscle was found in roughly one half of our specimens and was seen in all fetal specimens. When absent, the quadratus femoris muscle was always more prominent and extended more inferiorly toward the territory of the adductor minimus muscle. The average maximal length, width and thickness for the adductor minimus muscle was 14.6 cm, 7 cm, and 2.25 mm, respectively. Such data may be of consequence to clinicians who rehabilitate posterior thigh musculature or surgeons who operate this region.

A morphological study on the human obturator externus muscle with reference to anomalous muscle and anomalous fasciculus originating from the obturator externus muscle

To elucidate the essential nature of the human obturator externus muscle (OE), the gross anatomy of the anomalous muscle and anomalous fasciculus originating from this muscle as well as the posterior division of the obturator nerve (P) were examined in 73 thighs of 45 Japanese adult cadavers. The investigation of anomalous muscle and anomalous fasciculus was effected by observation of the supernumerary muscular branch and supernumerary muscular twig from the P. The anomalous muscle occurring between the adductor brevis muscle (AB) and adductor minimus muscle (AMi) (37/73 thighs; 50.7%) and the anomalous fasciculus fused to the posterior surface of the AMi (18/73 thighs; 24.7%) were detected. It was demonstrated by the course of the P and the suppling nerve, that the OE was divided into its superior fasciculus (or fasciculi) (SF) and main belly by the P, moreover the anomalous muscle originated from the former and the anomalous fasciculus from the latter. Presumably, in the process of ontogeny, the SF of the original OE retained its original morphology (23/73 thighs; 31.5%), a part of the SF was converted to anomalous muscle (27/73 thighs; 37.0%), the entire SF was converted to anomalous muscle (10/73 thighs; 13.7%), and the entire SF underwent retrogression and disappeared (13/73 thighs; 17.8%). The presence (50/73 thighs; 68.5%) or absence (23/73 thighs; 31.5%) of piercing of the OE by the P seemed to depend upon the circumstances surrounding the morphological change in the SF. The original OE was considered to occur as an OE pierced by the P not possessing any supernumerary muscular branch or twig. Actually, the original OE was confirmed to occur with a low frequency (15/73 thighs; 20.5%). It was inferred that the original OE readily underwent variation in the process of ontogeny due to the influence of the obturator nerve. The segmental composition of the obturator nerve was considered not to be involved in the morphological change in the OE.