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Purpose: A deep knowledge of the variations of the posterior forearm musculature is crucial for assessing and diagnosing conditions in this region. Extensor indicis (EI) is one of the muscles in this region, which exhibits diverse anatomical variations. This report documents an extremely unusual form of the EI with an accessory head on the dorsum of the hand., Methods: During routine dissection, an extremely rare presentation of the EI was found in the left forearm of a 94-year-old female cadaver., Results: This unusual EI consisted of two muscle bellies. The traditional belly originated from the distal two-thirds of the ulna. The muscle became tendinous around the carpal area, distal to the extensor retinaculum. The tendon was subsequently joined by an accessory muscle belly originating from the distal radioulnar ligament. The EI tendon inserted onto the dorsal expansion of the index finger, ulnar to that of the extensor digitorum. The posterior interosseous nerve innervated the muscle., Conclusion: Herein, we report an extremely rare form of the EI. To our knowledge, EI with an accessory head has only been reported rarely over the past 200 years. Moreover, our report appears to be the first case with photographic details of this anatomical variation. Clinicians should be aware of this variation for proper diagnosis and treatment., (© 2024. The Author(s), under exclusive licence to Springer-Verlag France SAS, part of Springer Nature.)

The fibularis brevis muscle belongs to the lateral compartment of the leg. It originates from the lower two-thirds of the lateral surface of the fibula bone and it also is attached to the anterior intermuscular septum. Its insertion is normally located on the tuberosity at the base of the fifth metatarsal bone, on its lateral side. However, distal attachment of this muscle is morphologically variable. Different variations have been identified and some classification systems have been created for both adults and foetuses. Based on various literature references, we have created a new classification system and compared the frequency of each type. The main aim of this review is to present morphological variations of the fibularis brevis tendon with their clinical significance, especially in autografting in case of surgical treatment of fibularis brevis tendon rupture. The clinical aspect of this pathology and some medical cases will also be presented., Competing Interests: Declaration of Competing Interest The authors declare that they have no competing interests., (Copyright © 2024 Elsevier GmbH. All rights reserved.)

The short lateral rotators of the thigh found in the gluteal region can have morphological variations. During anatomical dissection of a right lower limb, two variant structures were found in this region. The first of these accessory muscles originated from the external surface of the ramus of the ischium. Distally, it was fused with the gemellus inferior muscle. The second structure comprised tendinous and muscular parts. The proximal part originated from the external part of the ischiopubic ramus. It inserted on the trochanteric fossa. Both structures were innervated by small branches of the obturator nerve. The blood supply was via branches of the inferior gluteal artery. There was also a connection between the quadratus femoris and the superior part of the adductor magnus. These morphological variants could be clinically important.

The sartorius muscle belongs to the anterior compartment of the thigh. Morphological variations of this muscle are very rare, few cases being described in the literature. An 88-year-old female cadaver was dissected routinely for research and teaching purposes. However, an interesting variation was found during anatomical dissection. The proximal part of the sartorius muscle had the normal course, but the distal part bifurcated into two muscle bellies. The additional head passed medially to the standard head; thereafter, there was a muscular connection between them. This connection then passed into the tendinous distal attachment. It created a pes anserinus superficialis, which was located superficially to the distal attachments of the semitendinosus and gracilis muscles. This superficial layer was very wide and attached to the medial part of the tibial tuberosity and to the crural fascia. Importantly, two cutaneous branches of the saphenous nerve passed between the two heads. The two heads were innervated by separate muscular branches of the femoral nerve. Such morphological variability could be clinically important.

The variant plantaris muscle has itself been reported to have variable presentations. Here, we report an unusual finding of the plantaris muscle and report its gross and histological findings. A duplicated head of the plantaris muscle was identified in the right leg of an adult cadaver age and sex. The more anterior head of the muscle was in the typical location and originated from the superolateral condyle of the femur. However, the more posteriorly located head arose from the iliotibial band at the level of the distal thigh. The two heads united and continued as the typical distal tendon of the plantaris muscle to insert into the calcaneus tendon (Achilles). The normally positioned head of the plantaris muscle was found to be composed of typical skeletal muscle fibres. However, the accessory head of the plantaris muscle was found to be severely degenerated and infiltrated with adipose tissue. We report a duplicated head of the plantaris muscle. Histologically, the accessory head was degenerated and infiltrated with adipose tissue. To our knowledge, this is the first report of such a case. Further cases are now necessary to further elucidate this finding., (© 2023 Wiley-VCH GmbH. Published by John Wiley & Sons Ltd.)

Purpose: Variations of the extensor pollicis longus are rare. When present, these include a separate extensor pollicis longus muscle, tendon or an intertendinous connection with nearby tendons within the deep extensor compartment of the forearm. Here, we report an extremely rare variation of an accessory extensor pollicis longus originating from the extensor digitorum., Methods: An unusual muscle was found during the routine dissection forearm of a 71 year-old at death male cadaver., Results: This variant muscle originated from part of the extensor digitorum muscle belly that supplies the index finger. It became tendinous and entered the third extensor compartment of the wrist before joining the ulnar side of the extensor pollicis longus tendon. Traction on the muscle belly resulted in simultaneous extension of both the thumb and the index finger., Conclusion: This study documents an extremely rare extensor tendon to the thumb originating from the extensor digitorum, with a unique attachment to the normal extensor pollicis tendon. There have been minimal accounts of this variation, and the present report adds to the limited literature. Furthermore, the report suggests a new subtype, 1f, be included in the existing classification system. Surgeons should be aware of this rare variant for proper evaluation, diagnosis and surgical treatment. Further anatomical studies are needed to study the prevalence of this variant., (© 2023. The Author(s), under exclusive licence to Springer-Verlag France SAS, part of Springer Nature.)

Knowledge of anatomical variations can be of use to clinicians and surgeons when, for example, viewing images of a patient or performing operations. Such knowledge can minimise the risk of iatrogenic complications. Herein, we present a case of a variant atlantomastoid muscle. The muscle was identified on the left side in an adult cadaver. The muscle's measurements and anatomical relationships are presented as well as a review of salient literature. We hope that increased knowledge of anatomical variants in the suboccipital region can improve patient care.

The coracobrachialis muscle belongs to the anterior group of the brachial region. Its main functions are flexion and adduction at the glenohumeral joint. It is highly morphologically variable, especially in the number of bellies, place of origin or insertion, and its relationship to the musculocutaneous nerve. Accessory structures associated with the coracobrachialis muscle include the coracobrachialis brevis or coracobrachialis longus muscle. The present case describes a three-headed coracobrachialis muscle with two such additional structures. One of these has a tendinous origin connected to the periosteum and located on the surgical neck of the humerus. Its insertion is fused with the third head of the coracobrachialis muscle. The other has a proximal attachment fused with the capsule of the shoulder joint, and its distal attachment is fused with the third head of the coracobrachialis muscle in place of its connection with the short head of the biceps brachii. This could result in better stabilisation of the glenohumeral joint; on the other hand, it could limit operational access during treatment of subscapularis tears.

Purpose: The aim of the present case is to describe an interesting variation of the additional head of the rectus femoris., Methods: A male body donor, 81 years old at death, was subjected to routine anatomical dissection for research and teaching purposes at the Department of Anatomical Dissection and Donation, Medical University of Lodz, Poland., Results: We have found an example of an accessory head of the quadriceps femoris, a double-headed rectus femoris in which the proximal attachment is connected to the rectus femoris muscle originating from the anterior inferior iliac spine. The muscle belly of this additional structure is separate but fused distally with the vastus lateralis muscle. It then passes into the patellar ligament inserted into the tibial tuberosity., Conclusions: Knowledge of the possible occurrence of an additional head is nevertheless important for clinicians, especially for orthopedists performing reconstructive surgeries. It could also be significant for physiotherapists arranging rehabilitation plans after such surgeries because it could potentially help to achieve faster recovery., (© 2022. The Author(s), under exclusive licence to Springer-Verlag France SAS, part of Springer Nature.)

The evolution and variations of human anatomy are of great interest to physicians and anatomists. Variations can be categorized as vestigial, accessory or atavistic structures. Vestigial muscles are frequently encountered structures that are normally present but have become rudimentary through evolution. Muscles that disappeared during evolution sometimes arise again, although rarely; such muscles are referred to as atavistic. They arise from failure of suppression of genetic loci. Some common atavistic muscles seen clinically are the extensor digitorum brevis manus, chondroepitrochlearis and plantaris. Atavistic muscles appear more frequently in the upper limb than in any other region of the human body. One explanation for the appearance of these muscles, mainly within the upper limbs, is based on the evolution of the complex upper extremities formed in humans today. Often, the presence of atavistic muscles is asymptomatic, but they can compromise the function of normal anatomical structures and complicate clinical situations if their presence is unknown. They can cause complications if they are confused with soft tissue pathology, if they compress or displace surrounding structures, or if they require an additional blood supply during times of exercise and stress. The purpose of this paper was to describe the common atavistic muscles, their hypothesized evolutionary origins, their potential complications and possible treatments for the diagnosing clinician., (© 2022 Wiley-VCH GmbH.)

Background: On the basis of the available literature, we proposed the hypothesis that the number of muscle bellies is morphologically constant. The main purpose of this study was to examine the morphological variability of the SM and to create a new classification of it based on number of muscle bellies., Methods: Sixty-six adult cadavers of Central European population (45 females, 21 males) were obtained and fixed in 10% formalin before examination., Results: The SM was found in all 66 specimens (45 females, 21 males, 31 left and 35 right sides). After meticulous dissection, we distinguished nine types on the basis of number of bellies. Type I was characterized by single belly and occurred in 1.5%. Type II had a double belly and was present in 3%. Type III, the most common type, occurring in almost 32% of the studied population, had three bellies. The frequency of type IV, characterized by four bellies, was also high, just over 30%. The following types were less frequent: type V with five bellies (18.2%), type VI with six bellies (7.6%), type VII with seven bellies (3%), type VIII with eight bellies (1.5%), and type IX with nine bellies (3%). All of the types had origin on the anterior surface of the scapula., Conclusions: The SM is morphologically variable in the number of its bellies. Evolutionary changes are probably the reason. The most common type was the SM with three bellies, in line with Larson's model of the division of the SM into three parts. Subsequent studies should be carried out based on MRI or ultrasonography examination to confirm if it is possible to show all types (presented in this study) among group of patients during MRI., Competing Interests: There is no conflict of interest., (Copyright © 2021 Nicol Zielinska et al.)

The plantaris muscle is located in the posterior aspect of the superficial compartment of the lower leg, running from the lateral condyle of the femur to the calcaneal tuberosity. Classically, it is characterized by a small and fusiform muscle belly, which then changes into a long slender tendon. From the evolutionary point of view, the muscle is considered vestigial. However, it has recently been suspected of being a highly specialized sensory muscle because of its high density of muscle spindles. It has a noticeable tendency to vary in respect of both origin and insertion. Researchers have published many reports on the potential clinical significance of the muscle belly and tendon, including mid-portion Achilles tendinopathy, 'tennis leg syndrome', and popliteal artery entrapment syndrome. The right knee joint area was subjected to classical anatomical dissection, during which an atypical plantaris muscle was found and examined in detail. Accurate morphometric measurements were made. The muscle belly was assessed as bifurcated. Morphologically, superior and inferior parts were presented. There was a tendinous connection (named band A) with the iliotibial tract and an additional insertion (named band B) to the semimembranosus tendon. Both bands A and B presented very broad fan-shaped attachments. The human plantaris muscle is of considerable interest and has frequent morphological variations in its proximal part. Its specific characteristics can cause clinical problems and lead to confusion in diagnosis. More studies are needed to define its actual features and functions.

The flexor pollicis longus (FPL) is located in the anterior compartment of the forearm. It is morphologically variable in both point of origin and insertion. An additional head of the FPL can lead to anterior interosseous syndrome. This report presents a morphological variation of the FPL (additional head in proximal attachment and bifurcated tendinous insertion in distal attachment) and an unrecognized structure that has not so far been described in the literature. This structure originates in six heads (attached to the FPL or interosseous membrane) that merge together, and inserts on to the FPL. All the variations noted have clinical significance, ranging from potential nerve compression to prevention of tendon rupture.

Background: Knowledge of potential compression sites of peripheral nerves is important to the clinician and surgeon alike. One anatomical location for potential compression of the radial nerve, which is rarely mentioned in the literature, is at the proximal humeral attachment of the lateral head of the triceps brachii at the level of the proximal spiral groove. As no anatomical studies have been devoted to this band, the present study was conducted., Methods: Ten adult fresh-frozen cadavers were dissected and the lateral head's attachment onto the posterior humerus evaluated for a band. This anatomy and its relation to the radial nerve during range of motion of the elbow and forearm were evaluated., Results: A band was found on 15 of 20 arms. On five sides, the band was comprised of grossly muscle fibers of the lateral head of the triceps brachii and was not tendinous. The bands were crescent-shaped, straight, and duplicated on nine, five, and one arm, respectively. The length of the bands ranged from 1.1 to 2.2 cm (mean 1.54 cm). The width of the bands ranged from 0.5 to 1.1 cm (mean 0.8 cm). With elbow extension and the forearm in neutral, all bands were lax. With elbow extension and the forearm supinated, the bands became tauter less the muscular bands. In elbow extension and with the forearm in supination, the bands became most taut less the muscular bands., Conclusions: The presence of a fibrous band extending from the lateral head of the triceps brachii is common and should be among the differential diagnoses of anatomical sites for potential proximal radial nerve compression when other more common locations are ruled out.

Anatomical variations are routinely encountered during dissections of muscles and in clinical practice, so anatomists and clinicians need to be aware of them. One such muscle is the tensor fascia suralis, a very rare muscle located in the popliteal fossa. It can originate from any of the hamstring muscles and it inserts into the fascia of the leg. This report presents a case of a variant muscle located very deep to the biceps femoris; it originated from the posterior surface of the femur and inserted into the fascia of the leg. It is unclear whether this is a rare variant of the tensor fascia suralis or a completely new muscle.

The plantaris is a small muscle that typically originates at the lateral supracondylar line of the femur and the knee joint capsule, from where it continues distally, forming a long and slender tendon. However, considerable controversy surrounds the status of this seemingly inconspicuous muscle: is it a residual muscle, or one that it is just developing? In addition, both the proximal and distal attachments are highly morphologically variable. These variations can lead to many diseases. Interestingly, the course of the PM tendon is also variable. The present case study presents a new description of a complex origin type and a rare course of the PM tendon. Understanding of the PM and its tendon has clear clinical value and is a significant indicator of the development of interest in this overlooked muscle.

Purpose: The plantaris muscle is a morphologically variable structure with regard to both its origin and insertion, and the course of the tendon. We here determined the pattern of branching and distribution of intramuscular nerves of the plantaris muscle to determine its usability for autologous transplantation. No information exists on the innervation of the plantaris muscle using Sihler's staining technique, and hence its intramuscular nerves. The main purpose of the work is to determine the pattern of branching and distribution of the intramuscular nerves of the plantaris muscle. Is the plantaris muscle a good transplant candidate?, Materials and Methods: Eighty lower limbs from cadavers (40 left, 40 right, 40 male, 40 female, age range 41-94 years) were fixed in 10% formalin solution and examined macroscopically as well as morphometrically with regard to the innervation pattern of the respective plantaris muscle. Afterwards Sihler's staining was used in all 80 plantaris muscles to identify the exact distribution of the muscular branch originating from the main nerve trunk in the muscle belly., Results: Two patterns of branching and nerve distribution could be intensified in the plantaris muscle: Type I, with a single pattern entire up to the muscle and then divided into superior and inferior intramuscular branches.; type II with a double innervation pattern (superior and inferior). The superior and inferior pattern were not connected to each other., Conclusion: The plantaris muscle reveals variability with two different innervation patterns. Type II is ideally suited for autologous transplantation. New classifications of innervation are desirable for individual muscles rather than a generalized approach., (Copyright © 2020 Elsevier GmbH. All rights reserved.)

Objective: Anatomic assessment of the medial upper arm to identify potential sites for insertion of the etonogestrel (ENG) implant., Study Design: Forty female cadaveric arms were dissected. Two rows of 1×2-cm dissection windows were created in the inner arm overlying the triceps approximately 2-3 and 4-5 cm posterior to the bicipital sulcus (sulcus). The primary window was 8-10 cm proximal to the medial epicondyle and approximately 2-3 cm posterior to the sulcus. Neurovascular structures within each window were identified. The entire medial upper arm was dissected to visualize underlying structures., Results: Mean age (± SD) of cadavers at death was 72.0±11.0 years. Arm measurements at the primary window were circumference 28.2±4.8 cm [range: 21-41], skin thickness 0.6±0.2 mm [0.3-1.0] and subcutaneous tissue thickness: 12.3±4.9 mm [4.7-21]. The basilic vein and the medial brachial cutaneous, ulnar and medial antebrachial cutaneous nerves were located in 40%, 58%, 40% and 18% of the primary windows, respectively. No major neurovascular structures were located 3-5 cm posterior to the sulcus. More neurovascular structures were identified overlying the biceps than triceps. Elbow flexion with the hand underneath the head displaced the ulnar nerve anteriorly towards the sulcus., Conclusion: As no major neurovascular structures were identified overlying the triceps 8-10 cm proximal to the medial epicondyle and 3-5 cm posterior to the sulcus, ENG implant insertion at this location may minimize risk of injury associated with improper deep insertion. Elbow flexion deflects the ulnar nerve away from this area and may further decrease risk of injury secondary to inadvertent deep insertion., Implications: Although a limited cadaver study, this anatomic assessment provides rationale for insertion of the ENG implant overlying the triceps 8-10 cm proximal to the medial epicondyle and 3-5 cm posterior to the sulcus. This area is theoretically safer for insertion of the ENG implant than areas of the inner arm where major neurovascular structures are commonly located., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Ulnar neuropathy at the cubital tunnel is common. However, a rare form of ulnar neuropathy here is due to compression from an accessory muscle, the anconeus epitrochlearis. Reports in the literature regarding the details of this muscle's innervation are vague, so the aim of the present study was to characterize this anatomy more clearly. This was a combined review of magnetic resonance imaging (MRI) from patients with an anconeus epitrochlearis and ulnar neuropathy and cadaveric dissections to characterize the innervation of this variant muscle. A review of 11 patients and three reports of ulnar neuropathy and an anconeus epitrochlearis in the literature revealed no MRI changes consistent with acute denervation of this muscle. However, in two cases, there were signs of chronic denervation of the muscle. Dissection of five cadavers revealed that the nerve supply to the anconeus epitrochlearis originated proximal to the medial epicondyle, traveled parallel to the ulnar nerve, terminated on the deep aspect of this muscle, and had a mean length of 60 mm. This clinicoanatomical study provides evidence that the innervation of the anconeus epitrochlearis is proximal to the muscle and on its deep aspect. Clin. Anat. 32:218-223, 2019. © 2018 Wiley Periodicals, Inc., (© 2018 Wiley Periodicals, Inc.)

The piriformis muscle is clinically implicated in pain disorders, posterior approaches for total hip arthroplasty, and iatrogenic injury to the muscle and the surrounding nerves. The piriformis muscle has been said to receive innervation from L5 to S3 ventral rami with most sources using S1 and S2 ventral rami as the most common innervation this muscle. However, descriptions of the nerve in the literature are vague. Therefore, the aim of this study was to clarify the anatomy of the nerve supply to the piriformis muscle. Twenty sides from ten fresh-frozen cadavers were studied. Specifically, via anterior dissection of the sacral plexus, branches to the piriformis were identified. Once identified, the nerves to the piriformis muscle were traced proximally to clarify their origin. Nerves supplying the piriformis muscle existed on all sides. On 80% of sides, the piriformis was innervated by two to three nerves. The origin of these nerves was from the superior gluteal nerve on 14 sides (70%), inferior gluteal nerve on one side (5%), L5 ventral ramus on one side (5%), S1 ventral ramus on 17 sides (85%), and S2 ventral ramus on 14 sides (70%), respectively. The most common nerve branches to the piriformis are from the superior gluteal nerve, and the ventral rami of S1 and S2. Based on our study, a single "nerve to piriformis" does not exist in the majority of specimens thus this term should be abandoned. Clin. Anat. 32:282-286, 2019. © 2018 Wiley Periodicals, Inc., (© 2018 Wiley Periodicals, Inc.)

Purpose: The following research aimed to investigate the prevalence and anatomical features of the axillary arch (AA) - a muscular, tendinous or musculotendinous slip arising from the latissimus dorsi and that terminates in various structures around the shoulder girdle. The AA may complicate axillary lymph node biopsy or breast reconstruction surgery and may cause thoracic outlet syndrome., Methods: Major electronic databases were thoroughly searched for studies on the AA and its variations. Data regarding the prevalence, morphology, laterality, origin, insertion and innervation of the AA was extracted and included in this meta-analysis. The AQUA tool was used in order to assess potential risk of bias within the included studies., Results: The AA was reported in 29 studies (10,222 axillas), and its pooled prevalence estimate in this meta-analysis was found to be 5.3% of the axillas: unilaterally (61.6%) and bilaterally (38.4%). It was predominantly muscular (55.1% of the patients with the AA), originated from the latissimus dorsi muscle or tendon (87.3% of the patients with the AA), inserted into the pectoralis major muscle or fascia (35.2% of the patients with the AA), and was most commonly innervated by the thoracodorsal nerve (39.9% of the patients with the AA)., Conclusion: The AA is a relatively common variant, hence it should not be neglected. Oncologists and surgeons should consider this variant while diagnosing an unknown palpable mass in the axilla, as the arch might mimic a neoplasm or enlarged lymph nodes., (Copyright © 2018 Royal College of Surgeons of Edinburgh (Scottish charity number SC005317) and Royal College of Surgeons in Ireland. Published by Elsevier Ltd. All rights reserved.)

The inferior gluteal nerve has been traditionally described as a solely motor branch innervating the gluteus maximus. However, during routine dissection of the gluteal region, a cutaneous branch of the inferior gluteal nerve was identified. As the gluteal region is vulnerable to the development of pressure ulcers and iatrogenic injury with for example, surgical approaches and injection therapies, a comprehensive understanding of its cutaneous innervation is important. Therefore, the aim of this study was to elucidate the anatomy of this cutaneous branch of the inferior gluteal nerve in a series of cadavers. Twelve sides from six fresh-frozen cadaveric specimens were dissected. When a cutaneous branch was identified piercing the gluteus maximus, its origin from the inferior gluteal nerve was verified and the diameter and length of it measured. Additionally, for localization, the distance from the midline to the exit point of the cutaneous branch from the gluteus maximus was measured. One to two cutaneous branches were identified as arising from the inferior gluteal nerve on nine sides (75%). The branch(es) were usually located in the lower outer quadrant of the gluteus maximus. These branches had a mean distance of 12.5 cm from the midline. Their mean diameter and length was 0.7 mm and 28.6 cm, respectively. On all sides with a cutaneous branch of the inferior gluteal nerve, the skin over the posterior aspect of the greater trochanter was innervated by superior and inferior cluneal nerves and supplemented by cutaneous branch(es) of the inferior gluteal nerve. Side or sex was not a predictor of the presence of a cutaneous branch of the inferior gluteal nerve. To our knowledge, a cutaneous branch derived from the inferior gluteal nerve has not been previously described. Based on our cadaveric findings, the majority of individuals will have the area of skin over the greater trochanter innervated by this nerve. Therefore, surgeons and pain specialists should be aware of its presence and might develop surgical procedures that help avoid it or develop technical advances that target it for various pain syndromes in this area. We propose naming these cutaneous branches the lateral cluneal nerves, which would necessitate renaming the middle cluneal nerves to medial cluneal nerves. Clin. Anat. 31:937-941, 2018. © 2018 Wiley Periodicals, Inc., (© 2018 Wiley Periodicals, Inc.)

Purpose: The extensor indicis proprius (EIP) is a muscle of the forearm that originates from the posterior surface of the ulna and the adjacent interosseous membrane and attaches to the index finger. Many anatomical variations of this muscle have been reported in the literature. The extensor digitorum brevis manus (EDBM) is a variant muscle found on the back of the wrist and hand. These muscle variants should be considered in the context of clinical syndromes and reconstructive hand surgery. The aim of the present study was to describe in detail the normal and variant anatomy of these muscles and propose new systematic classifications., Materials and Methods: Formol-carbol-fixed Europid upper limbs (n = 176) were examined in the Department of Anatomy, Histology and Embryology at the Medical University of Sofia for variations of the EIP and occurrences of the EDBM., Results: We found normal anatomy in 147 (84%) of the specimens examined and we measured the length and width of the muscle belly and tendon of the EIP. Variations of the EIP in the other 29 upper limbs (16%) included replacement of the EIP by an EIB, coexistence of the EIP and EIB, presence of accessory tendons, and additional muscles., Conclusions: Knowledge of anatomical variations of forearm muscles is important because they can cause clinical syndromes or have implications for reconstructive surgery, most often as tendon transfers in response to functional loss of other forearm muscles.

OBJECTIVE The authors hypothesized that when the anatomical variant of an anconeus epitrochlearis is present, the risk of developing cubital tunnel syndrome would be reduced by replacing the normal roof of the cubital tunnel (Osborne's ligament) with a more forgiving muscular structure, the anconeus epitrochlearis. The authors further hypothesized that when the presence of an anconeus epitrochlearis contributes to ulnar neuropathy, it would be secondary to muscular hypertrophy, thereby making it more likely to occur in the dominant arm. Therefore, the goal of the present study was to evaluate these hypotheses. METHODS This retrospective cohort study was performed by reviewing the records of all adult patients who underwent operative intervention for cubital tunnel syndrome between 2005 and 2014 as the experimental group and all asymptomatic patients in the medical literature who were part of a series reporting the prevalence of an anconeus epitrochlearis as the control group. The primary outcome of interest was the presence of an anconeus epitrochlearis in asymptomatic individuals versus patients with cubital tunnel syndrome. RESULTS During the study period, 168 patients underwent decompression of the ulnar nerve for cubital tunnel syndrome, and an anconeus epitrochlearis was found at surgery in 9 (5.4%) patients. The control group consisted of 634 asymptomatic patients from the medical literature, and an anconeus epitrochlearis was present in 98 (15.5%) of these patients. An anconeus epitrochlearis was present significantly less frequently in the symptomatic patients than in asymptomatic individuals (p < 0.001). Among patients undergoing surgical decompression, an anconeus epitrochlearis was associated with symptoms in the dominant arm (p = 0.037). CONCLUSIONS The authors found that an anconeus epitrochlearis was present significantly less often in patients with cubital tunnel syndrome than in asymptomatic controls. The mechanism of protection may be that this muscle decreases the rigidity of the entrance into the cubital tunnel. When an anconeus epitrochlearis does contribute to cubital tunnel syndrome, it is significantly more likely to occur in the dominant arm, possibly due to repetitive use and hypertrophy of the anconeus epitrochlearis. The presence of an anconeus epitrochlearis may be protective against the development of cubital tunnel syndrome, although this is a preliminary finding.

The aim of this study was to explore the anatomical variations of the nerve to the levator ani (LA) and to relate these findings to LA dysfunction. One hundred fixed human female cadavers were dissected using transabdominal, gluteal, and perineal approaches, resulting in two hundred dissections of the sacral plexus. The pudendal nerve and the sacral nerve roots were traced from their origin at the sacral foramina to their termination. All nerves contributing to the innervation of the LA were considered to be the nerve to the LA. Based on the spinal nerve components, the nerve to the LA was classified into the following categories: 50% (n = 100) originated from S4 and S5 (type I); 19% (n = 38) originated from S5 (type II); 16% (n = 32) originated from S4 (type III); 11% (n = 22) originated from S3 and S4 (type IV); 4% (n = 8) originated from S3, S4, and S5 (type V). Two patterns of nerve termination were observed. In 42% of specimens, the nerve to the LA penetrated the coccygeus muscle and assumed an external position along the inferior surface of the LA muscle. In the remaining 58% of specimens, the nerve crossed the superior surface of the coccygeus muscle and continued along the superior surface of the iliococcygeus muscle. Damage to the nerve to LA has been associated with various pathologies. In order to minimize injuries during surgical procedures, a thorough understanding of the course and variations of the nerve to the LA is extremely important., (© 2015 Wiley Periodicals, Inc.)

The thoracoabdominal diaphragm is a composite musculotendinous structure, separating the thoracic and abdominal cavities. Reemphasis of the already well-delineated variations of the muscular and tendinous portions, and blood and nerve supply of the diaphragm is becoming apparent. Scientific reports concerning reconstruction of the pericardium, activation of the muscle and the phrenic nerves by use of laparoscopically placed intramuscular electrodes, and repair of congenital and traumatic hernias reemphasize the importance of the muscular to tendinous relationships. The objective of this study, therefore, was to measure the ratio of the surface area of the tendinous central region to the muscular region of the diaphragm and provide a clear description across various specimens. We classified diaphragmatic measurements from 104 adult human diaphragms into six classes (I-VI) based on the ratio of surface area between its tendinous and muscular components. The majority of specimens, 56.7%, was attributed to class II and indicated a tendon-to-muscle ratio of between 10 and 15%; however, a small number of specimens indicated a very large tendon area at the expense of muscle bulk. Future research should be geared toward assessing the relationship between surface area of the musculature and its motor points with focus on interventions for herniation repair and recovery. Our results have shown that surgical interventions should be tailored to the individual, as diaphragm size may not necessarily predict tendon-to-muscle ratio.

The sternalis muscle is a well documented but rare muscular variation of the anterior thoracic wall. It lies between the superficial fascia and the pectoral fascia and is found in about 8% of the population. It presents in several morphological variants both unilaterally and bilaterally and has no apparent physiological function. There is still much disagreement about its nerve supply and embryological origin. With the advent of medical imaging and thoracic surgery the clinical importance of this muscle has been re-emphasized. It has been implicated in misdiagnosis of breast masses on routine mammograms owing to its parasternal location and relative unfamiliarity among radiologists. When undetected before any thoracic surgery, it has the potential to interfere with and prolong such procedures. When present and detected preoperatively it can be used as a muscular flap in reconstructive surgeries of the breast and neck. This article will present the sternalis muscle with special emphasis on its morphology, homology, and clinical significance., (© 2014 Wiley Periodicals, Inc.)

Although the ulnar nerve is closely associated with the triceps brachii muscle, the literature does not normally describe it as supplying this muscle. However, recent research has examined the ulnar nerve in the upper arm and identified branches supplying the medial head of the triceps brachii muscle. This study aims to expand upon this research by describing the course and incidence of these branches in a larger sample size. We examined 50 specimens in 25 cadavers. Ulnar innervation of the medial head of the triceps brachii was identified in 14 specimens (28%). The mean distance of the ulnar nerve branch midpoint was 26% along a line between the surgical neck and an epicondyle line, with a range of 11-39%. Innervation of the triceps brachii muscle by the ulnar nerve has important clinical and surgical implications., (Copyright © 2013 Wiley Periodicals, Inc.)

Background and Study Aims: Little information can be found in the literature regarding the relationships of the posterior interosseous nerve (PIN) while it traverses the supinator muscle. Because compression syndromes may involve this nerve at this site and researchers have investigated using branches of the PIN to the supinator for neurotization procedures, the authors' aim was to elucidate information about this anatomy., Materials and Methods: Dissection was performed on 52 cadaveric limbs to investigate branching patterns of the PIN within the supinator muscle., Results: On 29 sides, the PIN entered the supinator muscle as a single nerve and from its medial side provided two to four branches to the muscle. On 23 sides, the nerve entered the supinator muscle as two approximately equal-size branches that arose from the radial nerve on average 2.2 cm from the proximal edge of this muscle. In these cases, the medial of the two branches terminated on the supinator muscle, and the lateral branch traveled through the supinator muscle; in 13 specimens, it provided additional smaller branches to the supinator muscle. The length of PIN within the supinator muscle was 4 cm on average, and the diameter of its branches to the supinator muscle ranged from 0.8 to 1.1 mm. In 10 specimens, the PIN left the supinator muscle before the most distal aspect of the muscle. In two specimens with a single broad PIN, muscle fibers of the supinator muscle pierced the PIN as it traveled through it., Conclusion: This knowledge of the anatomy of the PIN as it passes through the supinator muscle may be useful to neurosurgeons during decompressive procedures or neurotization., (Georg Thieme Verlag KG Stuttgart · New York.)

Details of piriformis syndrome, including the proper diagnosis and most effective form of treatment, continue to be controversial. While the cause, diagnosis, and treatment of piriformis syndrome remain elusive, many studies have been conducted to investigate newly developed diagnostic techniques as well as various treatment options for piriformis-induced sciatica. Despite the quantity of literature, few studies have demonstrated statistically significant results that support one form of treatment over another. Thus, despite the evidence supporting the newer treatment methodologies for piriformis syndrome, research should continue. It is important not only to evaluate treatment outcomes based on associated pain relief, but also to investigate the functional and anatomical return that patients experience from these studied treatments in order to fully explore the most effective form of therapy for piriformis syndrome.

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.

Object: Various donor nerves have been used for brachial plexus neurotization procedures. To the authors' knowledge, neurotization of median nerve branches to the pronator teres to the radial nerve at the elbow have not been explored., Methods: In an attempt to identify an additional nerve donor candidate for neurotization procedures of the upper limb, 20 cadaveric upper limbs underwent dissection of the cubital fossa and identification of branches of the median nerve to the pronator teres. Measurements were made of such branches, and distal transection was then performed to determine the appropriate length so that the structure could be brought to the laterally positioned radial nerve via tunneling deep to the biceps brachii muscle., Results: All specimens were found to have a median nerve branch to the pronator teres that was long enough to reach the radial nerve in the cubital fossa. Neural connections remained tension free with full pronation and supination. The mean length of these branches to the pronator teres was 3.6 cm. The overall mean diameter of these nerves was 1.5 mm. The mean proximal, midpoint, and distal diameters were 2.0, 1.8, and 1.5 mm, respectively. The mean distance between the origin of these branches to the pronator teres and the medial epicondyle of the humerus was 4.1 cm., Conclusions: Based on the results of our cadaveric study, the use of the branch of the median nerve to the pronator teres muscle may be considered for neurotization of the radial nerve in the cubital fossa.

Object: The sublime bridge is a potential site of entrapment of the median nerve in the forearm. To the authors' knowledge, this structure and its relationship to the median nerve have not been studied. The aim of the present study was to quantitate this structure and elucidate its relationship to the median nerve., Methods: Sixty adult cadaveric forearms underwent dissection of the sublime bridge. Relationships of this structure were observed, and measurements of its anatomy were made. The relationship of the median nerve to the sublime bridge was observed with range of motion about the forearm., Results: The sublime bridge was found to be tendinous in the majority (45 [75%]) of specimens and muscular in the remaining forearms (15 [25%]). The maximal mean width of the sublime bridge was 7 cm proximally, and the minimal mean width was 3 cm distally. The mean distance from the medial epicondyle to the apex of the sublime bridge was found to be 8.1 cm. The relation of the median nerve to the bridge was always intimate. On 2 sides (1 left and 1 right) from different male specimens, the median nerve was attached to the deep aspect of the sublime bridge by a strong connective tissue band, thus forming a tunnel on the deep aspect of this structure. With range of motion of the forearm, increased compression of the median nerve by the overlying sublime bridge was seen with extension but no other movement., Conclusions: Based on the authors' study, pronator syndrome is an incorrect term applied to compression of the median nerve at the sublime bridge. This potential site of median nerve compression is distinct and has characteristics that can clinically differentiate it from compression of the median nerve between the heads of the pronator teres. The authors hope that these data will be of use to the surgeon in the evaluation and treatment of patients with proximal median nerve entrapment.

Object: Other than very simple descriptions of the existence of the lateral intermuscular septum (LIS), the literature offers almost nothing about its detailed anatomy, relationships to the radial nerve, and proximal branches. To further elucidate its morphological characteristics, the present cadaveric study was performed., Methods: The lateral arm was bilaterally dissected from 25 adult fixed cadavers (50 sides). Specifically, a detailed evaluation of the LIS was made, and this structure's attachments and relationships to the radial nerve were analyzed and measured., Results: In addition to the previously described muscles arising from the LIS, the authors identified the extensor carpi radialis brevis muscles as partially arising from this structure. The deep and posterior portion of the deltoid tendon was confluent with the superior aspect of the LIS. The mean thickness of the LIS was 1.0 mm. Distally, the LIS attached strongly to the lateral epicondyle of the humerus and became confluent with the annular ligament encircling the head of the radius. The distal attachment of the LIS was confluent with the capsule of the elbow joint. All radial nerves traveled through a defect (mean diameter 1 cm) in the LIS. With traction on the nerve from proximal and distal to this defect, there was free excursion. In 85% of the specimens, however, the posterior antebrachial cutaneous nerve traveled through a tunnel within the LIS and pierced the septum at a mean of 5 cm proximal to the lateral epicondyle. The lower lateral brachial cutaneous nerve proximally pierced the LIS near its origin, occurring a mean of 3.2 cm distal to the LIS's origin from the humerus., Conclusions: To the authors' knowledge, the details regarding the LIS and its relationships to the radial nerve have not been reported. Such information may be of use to surgeons who operate in this region, for example, during neural repair or entrapment procedures.

Axillary arch muscles have been described as having variable and sometimes multiple insertions. We report a 90-year-old female cadaver with an axillary arch muscle that originated from the latissimus dorsi and was inserted into the pectoralis major, pectoralis minor and coracoid process. Recognising that axillary arch muscles can be present in such complex forms is important in clinical practice.

Reports place the frequency of axillary nerve injury at 6% for all brachial plexus injuries, emphasizing the importance of an accurate anatomic description of this nerve within the deltoid in order to reduce iatrogenic injury. The aim of the present study was to explore the anatomic variations of the axillary nerve within the deltoid muscle. Fifty human cadavers were dissected, resulting in 100 nerve specimens. The anterior and posterior branches of the axillary nerve were identified and their length measured from their point of origin (split from the axillary nerve) to their termination in the deltoid muscle. In 65% of cases, the axillary nerve split into two branches (anterior and posterior) within the quadrangular space, and in the remaining 35% split within the deltoid muscle. The posterior branch of the deltoid muscle irrespectively of origin gave off a branch to the teres minor and the superior lateral brachial cutaneous nerve in 100% of cases. The branch to the posterior part of the deltoid muscle was present in 90% of cases, and the branch to the middle part of the deltoid was present in 38% of cases. The anterior branch of the deltoid muscle provided a branch to the joint capsule, a branch to the anterior part of the deltoid muscle and the middle part of the deltoid in 100% of cases. In 18% of the cases, the anterior branch of the axillary nerve provided a branch to the posterior part of the deltoid muscle. The middle part of the deltoid muscle received dual innervation in 38% of cases and the posterior part of the deltoid muscle in 8% of the cases.

Variations within the musculature of the lateral compartment of the leg are uncommon. However, clinicians and radiologists should be aware of anatomical alterations in this region when involved in diagnosis or imaging interpretation. The present report describes a well-developed muscle of the lateral compartment of the leg that inserted distally onto the talus and calcaneus. This muscle could be considered a variation of the so-called peroneus quartus muscle. To the authors' knowledge this muscle variation has not been described as having an attachment onto the talus thus the term 'peroneotalocalcaneus muscle' is proposed.

The levator claviculae is an uncommon anatomical variant found in the posterior cervical triangle. In this report we present a 78-year-old man with this muscular variation, which was found during gross anatomical dissection. While sites of insertion and origin have been variable, in the present case the muscle originated from the left transverse processes of C3 and C4, and inserted onto the lateral third of the ipsilateral clavicle. Clinical considerations of this variant anatomy are of interest, as they may present in patients as a supraclavicular mass and may also mimic pathology on cross-sectional imaging.

Introduction: To date, only scant data has been reported regarding the anatomy of the radial nerve and profunda brachii artery and their relationships while within the triangular interval of the posterior arm. As this area has recently gained attention for using motor branches of the triceps muscle for nerve transfers, the present study was conducted., Materials and Methods: Fifteen adult cadavers (30 sides) underwent dissection, observation and quantitation of their triangular intervals and its contents. The relationship between the profunda brachii and radial nerve in the proximal one half and distal one half of this area was documented., Results: The length of the triangular interval had a mean of 6 cm and the width of this area was on average 2.5 cm. Within the triangular interval, we identified on average, 2.5 arterial branches and 2.3 nerve branches from the profunda brachii and radial nerve, respectively. The maximal number of branches of either the artery or nerve within this geometric region was five. In the proximal one half of this area, 75% of the arteries were found anterior to the radial nerve whereas in the distal one half of the interval most nerves were flanked by arterial branches on both medial and lateral sides. Not all branches of the profunda brachii artery were muscular in this region as some were found to supply the adjacent radial nerve. Communication between the profundi brachii artery in the triangular interval and the posterior humeral circumflex artery was found on two left sides (6.7%)., Conclusions: We hope that these anatomical data may be useful to the surgeon who utilizes branches of the proximal radial nerve for neurotization procedures or branches of the profunda brachii for flap procedures.

The tibial nerve has been reported to be often iatrogenically injured during fibular graft harvest, high tibial osteotomy and fascial release procedures. Despite this complication, there are limited data available in the literature concerning the surgical anatomy of tibial nerve branches in the deep posterior compartment of the leg. The aim of the present study was to quantitative and localize the motor nerve points for the flexor hallucis longus (FHL), tibialis posterior (TP) and flexor digitorum longus muscles (FDL) in relation to a regional bony landmark. The range for the number of branches of the tibial nerve and the terminal motor points of each muscle were identified and measurements were made with a digital caliper from these points to the apex of the head of fibula. Three particular types in the branching of tibial nerve were determined. In 55.6% of the cases there were separate branches to each of the muscles in the deep posterior compartment of the leg (Type I). In 30.6% of the cases there were two main branches of the tibial nerve that provided motor branches (Type II). Finally, the tibial nerve had one main branch, which gave rise to separate motor branches to each of the muscles in 13.8% (Type III). In 61.1% of the cases the FHL was innervated by proximal and distal branches of the tibial nerve. In 38.9% of the cases, it was innervated only by one proximal branch. In all of our cases, the TP was innervated by both proximal and distal branches and the FDL innervated only distally. This provided a detailed anatomical description of the tibial nerve in the deep posterior compartment of the leg. Knowledge of the variable peripheral course of the tibial nerve, as well as the detailed anatomy of its motor branches may decrease iatrogenic injuries and motor loss of the foot during surgical procedures.

There is a paucity of information regarding the detailed anatomy of the capsular part of the brachialis muscle in the extant literature. Our current study seeks to further elucidate the presence, morphology, and potential function of this muscle. Thirty-six cadaveric upper extremities underwent dissection of their anterior elbow joint capsule with special attention to any fibers attaching onto it from the brachialis muscle. We found that the majority of fibers of the brachialis simply passed superficial to the anterior elbow joint capsule. The highest concentration of fibers was noted to be onto the anteromedial joint capsule via connective tissue and not direct muscle attachment. No specimen was found to have a distinct muscle belly associated with these connections to the joint capsule. On all sides, such fibers were simply deeper attachments of the brachialis muscle. Following tension on these deeper fibers, retraction of the joint capsule was not noted. We would speculate, based on our study, that these fibers of the brachialis do not represent a separate muscle per se and do not retract the anterior elbow joint capsule with flexion of the forearm as has been theorized. These data may be of use to surgeons who operate this region so that attention to preservation of such fibers may be of less importance.

Variations of the muscles of the anterior forearm are common. We report the cadaveric findings of an unusual variant of flexor digitorum superficialis (FDS). The deep part of the FDS was found to be split and showed two distinct fusiform muscle bellies. The medial belly originated from the common flexor tendon from the medial condyle of the humerus and continued as a thin tendon at the middle of the forearm to insert onto the fifth digit. The lateral belly blended proximally with the deep surface of the superficial portion of the FDS and ended in a relatively thicker tendon, which was inserted onto the second digit. The median nerve passed between the medial and lateral bellies of the deep part of the FDS. To our knowledge, this is only the second report of a split FDS in the extant literature. A review of neuromuscular variations of the anterior forearm is presented.

In classical anatomy textbooks the serratus posterior superior muscle was said to elevate the superior four ribs, thus increasing the AP diameter of the thorax and raising the sternum. However, electromyographic and other studies do not support its role in respiration. In order to help resolve this controversy and provide some insight into their possible functionality, the present study aimed at examining the morphology, topography and morphometry of serratus posterior superior and inferior muscles in both normal specimens and those derived from patients with a history of chronic obstructive pulmonary disorder (COPD). These muscles were examined in 50 human cadavers with an age range of 58-82 years. In 18 of the cadavers their histories revealed that they were suffering from COPD. There was no significant difference between right and left sides, race, gender and age and positive COPD history in regard to dimensions and nerves supply of serratus posterior superior and inferior muscles (P > 0.05). Based upon our findings that no morphometric differences exist between the of serratus posterior superior and inferior muscles of COPD patients versus controls, we are suggesting that no respiratory function be attributed to either of the serratus posterior superior and inferior muscles.

There is significant paucity in the literature regarding vertebral aponeurosis. We were able to find only a few descriptions of this specific fascia in the extant medical literature. To elucidate further the anatomy of this structure, forty adult human cadavers were dissected. Both quantitation and anatomical observations were made of the vertebral aponeurosis. The vertebral aponeurosis was identified in 100% of specimens. This fascia was identified as a thin fibrous layer consisting of longitudinal and transverse connective tissue fibers blended together deep to the latissimus dorsi muscle. It attached medially to the spinous processes of the of the thoracic vertebrae; laterally to the angles of ribs; inferiorly to the fascia covering the serratus posterior inferior muscle (superficial lamina of the posterior layer of thoracolumbar fascia); superiorly it ran deep to the serratus posterior superior and splenius capitis muscles to blend with the deep fascia of the neck. At the level of the serratus posterior inferior muscle, the vertebral aponeurosis fused to form a continuous layer descending toward the sacrotuberous ligament covering the erector spinae muscle. Morphometrically, the mean length of the vertebral aponeurosis was 38 cm and the mean width was 24 cm. The mean thickness was three mm. There was no significant difference between left and right sides, gender or age with regard to vertebral aponeurosis length, width, or thickness (P > 0.05). During manual tension of the vertebral aponeurosis, the tensile force necessary for failure had a mean of 38.7 N. In all specimens, the vertebral aponeurosis was capable of holding sutures placed through its substance. We hope that these data will be of use for descriptive purposes and may potentially add to our understanding of the biomechanics involved in movements of the back. As back pain is perhaps the most common reason patients visit their physicians, additional knowledge of this anatomical region is important.

Few reports are found in the extant medical literature regarding the vastoadductor membrane. This membrane effectively creates a subcompartment within the subsartorial canal. The lower limbs of 16 embalmed adult cadavers were dissected to identify the vastoadductor membrane and note its measurements. A vastoadductor membrane was identified in all specimens and was derived from the medial intermuscular septum. This membrane connected the medial edge of the vastus medialis muscle to the lateral edge of the adductor magnus muscle. Membranes were all wider proximally and narrowed distally. The mean length of this structure was 7.6 cm. The mean width of the vastoadductor membrane at its proximal, midportion, and distal parts was 2.2, 1.7, and 0.5 cm, respectively. The mean distance from the anterior superior iliac spine to the proximal border of the vastoadductor membrane was 28 cm. The mean distance from the distal border of the membrane to the adductor tubercle was 10 cm. Seventy-five percent of specimens exhibited a fenestrated vastoadductor membrane. Branches of the saphenous nerve to the skin of the medial thigh pierced the vastoadductor membrane in 31% of specimens. Two specimens demonstrated branches derived from the branch of the obturator nerve that pierced this membrane en route to the skin of the medial thigh. Perforating venous branches from the great saphenous vein were identified in 22% of specimens. As compression of the femoral artery at the adductor hiatus is a well-recognized entity, the clinician may also try to explore potential compression of this vessel more proximally by an overlying vastoadductor membrane. The authors would also hypothesize that due to the interconnection between the adductor magnus and vastus medialis by the vastoadductor membrane that a potential synergy exists between the functions of these two muscles.

Giovanni Battista Canano was born in Italy in 1515 and his work has gone mostly unknown. Very few copies of this anatomist and physician's book are known to exist. Interestingly, Canano reported and depicted what we believe, to be the first description of the palmaris brevis muscle. This description would be some 200 years prior to what is thought to be the earliest mention of this muscle by William Cheselden in his book, The Anatomy of the Human Body, published in 1713.