The morphological variability of the piriformis muscle.

BACKGROUND: The aim of the study is to create several classifications of the piriformis muscle (PM): proximal and distal attachments, potential fusions, and the relationship with the sciatic nerve. It is the first comprehensive anatomical examination of this subject. MATERIALS AND METHODS: One hundred and twenty-four lower limbs from 62 cadavers, fixed in 10% formalin, were examined. RESULTS: The piriformis muscle was present in 120 limbs (96.8% of cases). Four types of proximal attachment were described (I-IV). The most common type was Type I, in which the proximal attachment was at the anterior surface of the sacrum, between S2 and S4 (52 lower limbs; 43.3%). The rarest type was Type IV, in which the proximal attachment was at the gluteal surface of the ilium near the margin of the greater sciatic notch and from the gluteus medius (12 cases; 10%). Three types of distal attachment were distinguished. The most common was Type 1, a single tendon. This type comprised two subtypes: A and B (105 lower limbs; 87.5%). The other two types accounted for 12.5% of the total. Fusions were noted between the piriformis muscle and adjacent muscles in 31.7%. Four patterns were observed in which the sciatic nerve ran against the piriformis muscle. The most common variation in the relationship was the common fibular nerve exiting superior to the piriformis muscle and the tibial nerve passing inferior to it (10 cases; 8.3%). CONCLUSIONS: The piriformis muscle is highly morphologically variable in both its proximal and distal attachments and its relationship with the sciatic nerve. There are four types of proximal attachment and three types of distal attachment. The piriformis muscle shows numerous fusions with its adjacent muscles: gluteus medius or minimus or superior gemellus. A new (fourth) type of relationship was demonstrated between the piriformis muscle and sciatic nerve. The piriformis muscle was absent in four cases.

Morphological variability of the pectoralis minor muscle. Study in human fetuses.

BACKGROUND: The pectoralis minor muscle is located in the anterior thoracic wall. Typically, is constituted by a single belly originating from the 3rd to the 5th rib and inserted into the coracoid process near the origins of the biceps brachii shorth head and of the coracobrachialis muscle. The current study, on human fetuses, aims to detect all morphological muscle variants and to create a new classification system. MATERIAL AND METHODS: Classical dissection of the thoracic wall and the upper limb was bilaterally performed on 25 (13 male and 12 female) human formalin-fixed fetuses aged 18-38 weeks of gestation. The spontaneously aborted fetuses were donated after parental consent to the Medical University anatomy program. The pectoralis minor muscle's morphology, the number of the muscle's bellies, their origins, and insertions, as well as the morphometric details of each belly of the pectoralis minor, were assessed. RESULTS: The pectoralis minor was bilaterally found in all fetuses (50 cases). Three types of muscle were identified based on the number of muscle bellies. In type, I (typical anatomy), were classified the cases with a single belly (in 66%). This type was divided into two subtypes (Ia and Ib). In the subtype Ia, the single belly had a typical course, and in Ib, a proximal attachment was characterized by two small bellies connecting together and creating one muscular mass. In type II, two bellies (24%), and in type III, three bellies (10%) were identified. CONCLUSIONS: Pectoralis minor is morphologically variable in the number of its bellies, its course, its origins, its insertions, and the location of its proximal attachments. The most common type (typical anatomy) was the type I represented by one belly. Other identified variants in the number of bellies by the present study may be hypothetically a result of prematurely terminated embryogenesis.

An unreported innervation of the coracobrachialis longus by the radial nerve: a potential pitfall for clinicians.

PURPOSE: The aim of the presented case is to describe an unprecedented innervation of the coracobrachialis longus muscle by the radial nerve. METHODS: An 82-year-old body donor at death was subjected to a routine anatomical dissection for teaching and research purposes at the Department of Anatomical Dissection and Donation in Lodz, Poland. RESULTS: We have found an additional branch of the radial nerve, which departed from it just below its beginning. Its initial section ran alongside the radial nerve in the axilla, then headed medially accompanying superior ulnar collateral artery. Then, it reaches the coracobrachialis longus muscle and is the only one to innervate it. CONCLUSIONS: The brachial plexus (BP) is very variable and well understood. Nevertheless, we must remember that there may still be variations in its structure, which may involve problems at every stage of diagnosis and treatment of diseases associated with its structures. Their knowledge is extremely important.

Morphological variability of the pectoralis major muscle in human fetuses.

BACKGROUND: The pectoralis major muscle is located in the anterior chest wall. In most cases, it is divided into clavicular, sternal (sternocostal) and abdominal heads. The aim of this study is to demonstrate and classify the morphological variability of the pectoralis major muscles in human fetuses. MATERIAL AND METHODS: Classical anatomical dissection was performed on 35 human fetuses aged 18-38 weeks of gestation at death were examined. (17 female, and 18 male, 70 sides; fixed in 10% formalin solution). The fetuses were obtained from spontaneous abortion after informed consent of both parents and through deliberate donation to the Medical University anatomy program. Upon dissection, the following morphological features were assessed: the morphology of the pectoralis major, the possible occurrence of accessory heads, the possible absence of some head, and morphometric measurements of each head of the pectoralis major muscle. RESULTS: Five types of morphology (based on number of bellies) were observed in the fetuses. Type I was characterized by a single claviculosternal belly (10% of all samples). Type II comprised the clavicular and sternal heads (37.1%). Type III comprised three clavicular, sternal and abdominal heads (31.4%). Type IV (17.2%) was characterized by four muscle bellies and was divided into four subtypes. Type V (4.3%), was represented by five parts, and was divided into two subtypes. CONCLUSIONS: Due to its embryological development, the PM demonstrates great variability in the numbers of its parts. The most common type was the PM with two bellies, in line with previous studies which also distinguished only clavicular and sternal heads.

Accessory part of the deltoid muscle.

The shoulder and arm region has numerous morphological variations. The deltoid muscle usually consists of three parts: anterior, middle and posterior. This case report describes a very rare deltoid muscle variant, an addition to the spinal part that is attached proximally at the infraspinatus fascia and the spine of the scapula. The distal attachment transforms directly into the brachialis muscle. Additional parts can affect the biomechanics and function of the joints significantly.

An unreported infraspinatus muscle variation-two-headed infraspinatus minor muscle and three-headed fusion with the teres minor muscle.

The infraspinatus muscle is situated under the scapular spine in the infraspinous fossa and inserts into the greater tuberosity of the humerus. It is a component of a crucial shoulder muscle group, the rotator cuff. There are a few interesting additional muscles in the infraspinal region. In the literature they are called the infraspinatus superficialis, infraspinatus minor and infraspinatus accessory muscles. The infraspinatus minor muscle is described as a superficial muscle bundle running under the scapular spine. During routine anatomical dissection, an unreported variation of the infraspinatus minor muscle was found. It derived from the inferior surface of the scapular spine and the infraspinous fossa. It had two heads. The superior head inserted on the greater tuberosity of the humerus. The inferior head inserted on the tendinous part of the infraspinatus muscle. There was also an unusual fusion of the infraspinatus muscle with the teres minor muscle. In this paper we will discuss the anatomical and physiological relationships of this morphological variation.

A newly reported muscle: an accessory infraspinatus or a deep layer of the latissimus dorsi?

The infraspinatus muscle is a component of the rotator cuff; the latissimus dorsi muscle is the largest muscle of the back. These muscles are not considered very morphologically variable. However, the latissimus dorsi has more frequent variations than the infraspinatus. During anatomical dissection, an additional muscle structure was found. It originated on the medial border of the scapula, ran under the scapular spine, and ended on the greater tubercle next to the infraspinatus attachment. We will discuss the anatomical and physiological relationships of this muscle. We believe that our finding underlines the importance of different muscle variants in the rotator cuff region. Level of evidence: II basic science research.