Safe zones in dorsal portals for wrist arthroscopy: a cadaveric study.

The standard dorsal portals are the most commonly used in wrist arthroscopy. This cadaveric study aims to determine safe zones, by quantitatively describing the neurovascular relationships of the dorsal wrist arthroscopy portals: 1-2, 3-4, midcarpal radial, midcarpal ulnar, 4-5, 6-radial and 6-ulnar. The neurovascular structures of twenty-one fresh frozen human cadaveric upper limbs were exposed, while the aforementioned portals were established with needles through portal sites. The minimum distance between portals and: dorsal carpal branch of radial artery, superficial branch of radial nerve, posterior interosseous nerve and dorsal branch of ulnar nerve, were measured accordingly with a digital caliper, followed by statistical analysis of the data. The median and interquartile range for each portal to structures at risk were determined and a safe zone around each portal was established. Free of any neurovascular structure safe zones surrounding 1-2, 3-4, midcarpal radial, midcarpal ulnar, 4-5, 6-radial and 6-ulnar portals were found at 0.46mm, 2.33mm, 10.73mm, 11.01mm, 10.38mm, 5.95mm and 0.64mm respectively. Results of statistical analysis from comparisons between 1-2, 3-4 and midcarpal radial portals, indicated that 1-2 was the least safe. The same analysis among 3-4, midcarpal radial, midcarpal ulnar and 4-5 portals indicated that midcarpal portals were safer, while 3-4 was the least safe. Results among midcarpal ulnar, 4-5, 6-radial and 6-ulnar portals indicated that 6-radial and specifically 6-ulnar were the least safe. This study provides a safe approach to the dorsal aspect of the wrist, enhancing established measurements and further examining safety of the posterior interosseous nerve.

A bilateral four-headed brachialis muscle with a variant innervation: a cadaveric report with possible clinical implications.

PURPOSE: Anterior compartment muscles of the arm present high morphological variability, with possible clinical significance. The current cadaveric report aims to describe a bilateral four-headed brachialis muscle (BM) with aberrant innervation. Emphasis on the embryological background and possible clinical significance are also provided. METHODS: Classical upper limb dissection was performed on an 84-year-old donated male cadaver. The cadaver was donated to the Anatomy Department of the National and Kapodistrian University of Athens. RESULTS: On the left upper limb, the four-headed BM was supplied by the musculocutaneous and the median nerves after their interconnection. On the right upper limb, the four-headed BM received its innervation from the median nerve due to the musculocutaneous nerve absence. A bilateral muscular tunnel for the radial nerve passage was identified, between the BM accessory heads and the brachioradialis muscle. CONCLUSION: BM has clinical significance, due to its proximity to important neurovascular structures and frequent surgeries at the humerus. Hence, knowledge of these variants should keep orthopedic surgeons alert when intervening in this area. Further dissection studies with a standardized protocol are needed to elucidate the prevalence of BM aberrations and concomitant variants.

Anatomical considerations for nerve transfer in axillary nerve injury.

This study investigated the anatomical details of the axillary and radial nerves in 50 upper limbs from 29 adult formalin-embalmed cadavers, and ten fresh upper limbs. The focus was on understanding the course, division, and ramifications of these nerves to improve treatment of shoulder dysfunction caused by axillary nerve damage. The axillary nerve divided anteriorly and posteriorly before passing the quadrangular space in all specimens, with specific distances to the first ramifications. It was found that the deltoid muscle's clavicular and acromial parts were always innervated by the anterior division of the axillary nerve, whereas the spinous part was variably innervated. The longest and thickest branches of the radial nerve to the triceps muscles were identified, with no statistically significant differences in fiber numbers among triceps branches. The study concludes that nerve transfer to the anterior division of the axillary nerve can restore the deltoid muscle in about 86% of shoulders, and the teres minor muscle can be restored by nerve transfer to the posterior division. The medial head branch and long head branch of radial nerve were identified as the best donor options.

Clinical anatomy of the lateral antebrachial cutaneous nerve: Is there any safe zone for interventional approach?

INTRODUCTION: The lateral antebrachial cutaneous nerve (LACN) is a somatosensory nerve coursing in the lateral portion of the forearm. The nerve is located in a close proximity to the cephalic vein (CV) all along its course with a danger of being injured during venipuncture. The LACN also overlaps and communicates with the superficial branch of the radial nerve (SBRN) in the distal forearm and hand, making the awareness of their relationship of great importance in the treatment of neuroma. The aim of the study was to observe the relationship of the LACN to surrounding structures as well as its branching pattern and distribution. MATERIALS AND METHODS: Ninety-three cadaveric forearms embalmed in formaldehyde were dissected. The relationship of the LACN to surrounding structures was noted and photographed, and distances between the structures were measured with a digital caliper. The cross-sectional relationships of the LACN and SBRN to the CV were described using heatmaps. RESULTS: The emerging point of the LACN was found distally, proximally or at the level of the interepicondylar line (IEL). The LACN branched in 76 cases (81.7 %) into an anterior and posterior branch at mean distance of 47.8 ± 34.2 mm distal to the IEL. The sensory distribution was described according to the relationship of the LACN branches to the medial border of the brachioradialis muscle. The LACN supplying the dorsum of the hand was observed in 39.8 % of cases. The LACN and the SBRN intersected in 86 % of upper limbs with communications noticed in 71 % of forearms. The LACN was stated as the most frequent donor of the communicating branch resulting in neuroma located distal to the communication and being fed from the LACN. The relationship of the LACN and the CV showed that the IEL is the most appropriate place for the venipuncture due to maximal calibers of the CV and deep position of the LACN. The LACN was adjacent to the cubital perforating vein and the radial artery in all cases. The medial border of the brachioradialis muscle was observed less than 1.8 mm from the LACN. CONCLUSION: The study provides morphological data on the LACN distribution, branching pattern and relationship to surrounding structures in a context of clinical use in different spheres of medicine. The branching pattern of the LACN appears to be more constant compared to data provided by previous authors. We emphasized the meaning of cross-sectional relationship of the LACN to the CV to avoid venipuncture outside the cubital fossa if possible. The posterior branch of the LACN was predicted as appropriate donor of the graft for a digital nerve. The LACN appeared to be in a close proximity within the whole length of the brachioradialis muscle what the orthopedic surgeons must be concerned of. The meaning of the donor-nerve of the communicating branch in neuroma treatment was also introduced.

Restoration of intrinsic hand function by superficial radial nerve: an anatomical study.

BACKGROUND: The contralateral seventh cervical (cC7) nerve root transfer represents a cornerstone technique in treating total brachial plexus avulsion injury. Traditional cC7 procedures employ the entire ulnar nerve as a graft, which inevitably compromises its restorative capacity. OBJECTIVE: Our cadaveric study seeks to assess this innovative approach aimed at preserving the motor branch of the ulnar nerve (MBUN). This new method aims to enable future repair stages, using the superficial radial nerve (SRN) as a bridge connecting cC7 and MBUN. METHODS: We undertook a comprehensive dissection of ten adult cadavers, generously provided by the Department of Anatomy, Histology, and Embryology at Fudan University, China. It allowed us to evaluate the feasibility of our proposed technique. For this study, we harvested only the dorsal and superficial branches of the ulnar nerve, as well as the SRN, to establish connections between the cC7 nerve and recipient nerves (both the median nerve and MBUN). We meticulously dissected the SRN and the motor and sensory branches of the ulnar nerve. Measurements were made from the reverse point of the SRN to the wrist flexion crease and the coaptation point of the SRN and MBUN. Additionally, we traced the MBUN from distal to proximal ends, recording its maximum length. We also measured the diameters of the nerve branches and tallied the number of axons. RESULTS: Our modified approach proved technically viable in all examined limbs. The distances from the reverse point of the SRN to the wrist flexion crease were 8.24 ± 1.80 cm and to the coaptation point were 6.60 ± 1.75 cm. The maximum length of the MBUN was 7.62 ± 1.03 cm. The average axon diameters in the MBUN and the anterior and posterior branches of the SRN were 1.88 ± 0.42 mm、1.56 ± 0.38 mm、2.02 ± 0.41 mm,respectively. The corresponding mean numbers of axons were 1426.60 ± 331.39 and 721.50 ± 138.22, and 741.90 ± 171.34, respectively. CONCLUSION: The SRN demonstrated the potential to be transferred to the MBUN without necessitating a nerve graft. A potential advantage of this modification is preserving the MBUN's recovery potential.

The communication patterns between the lateral antebrachial cutaneous nerve and the superficial branch of the radial nerve.

INTRODUCTION: The superficial branch of the radial nerve (SBRN) and the lateral antebrachial cutaneous nerve (LACN) are sensory nerves coursing within the forearm in a close relationship. This high degree of overlap and eventual communication between the nerves is of great surgical importance. The aim of our study is to identify the communication pattern and overlap of the nerves, to localize the position of this communication in relation to a bony landmark, and to specify the most common communication patterns. MATERIALS AND METHODS: One hundred and two adult formalin-fixed cadaveric forearms from 51 cadavers of Central European origin were meticulously dissected. The SBRN, as well as the LACN, were identified. The morphometric parameters concerning these nerves, as well as their branches and connections, were measured with a digital caliper. RESULTS: We have described the primary (PCB) and secondary communications (SCB) between the SBRN and the LACN and their overlap patterns. One hundred and nine PCBs were found in 75 (73.53%) forearms of 44 (86.27%) cadavers and fourteen SCBs in eleven hands (10.78%) of eight cadavers (15.69%). Anatomical and surgical classifications were created. Anatomically, the PCBs were classified in three different ways concerning: (1) the role of the branch of the SBRN within the connection; (2) the position of the communicating branch to the SBRN; and (3) the position of the LACN branch involved in the communication to the cephalic vein (CV). The mean length and width of the PCBs were 17.12 mm (ranged from 2.33 to 82.96 mm) and 0.73 mm (ranged from 0.14 to 2.01 mm), respectively. The PCB was located proximally to the styloid process of the radius at an average distance of 29.91 mm (ranged from 4.15 to 97.61 mm). Surgical classification is based on the localization of the PCBs to a triangular zone of the SBRN branching. The most frequent branch of the SBRN involved in the communication was the third (66.97%). Due to the frequency and position of the PCB with the third branch of the SBRN, the danger zone was predicted. According to the overlap between the SBRN and the LACN, we have divided 102 forearms into four types: (1) no overlap; (2) present overlap; (3) pseudo-overlap; and (4) both present and pseudo-overlap. Type 4 was the most common. CONCLUSION: The patterns of communicating branch arrangements appeared to be not just a rare phenomenon or variation, but rather a common situation highlighting clinical importance. Due to the close relationship and connection of these nerves, there is a high probability of simultaneous lesion.

Deep branch of the radial nerve: effect of pronation/supination on longitudinal nerve alignment.

OBJECTIVE: To evaluate the effect of maximal pronation and supination of the forearm on the alignment and anatomic relationship of the deep branch of the radial nerve (DBRN) at the superior arcade of the supinator muscle (SASM) by using high-resolution ultrasound (HRUS). MATERIALS AND METHODS: In this cross-sectional study, HRUS in the long axis of the DBRN was performed in asymptomatic participants enrolled from March to August 2021. DBRN alignment was evaluated by measuring angles of the nerve in maximal pronation and maximal supination of the forearm independently by two musculoskeletal radiologists. Forearm range of motion and biometric measurements were recorded. Student t, Shapiro-Wilk, Pearson correlation, reliability analyses, and Kruskal-Wallis test were used. RESULTS: The study population included 110 nerves from 55 asymptomatic participants (median age, 37.0 years; age range, 16-63 years; 29 [52.7%] women). There was a statistically significant difference between the DBRN angle in maximal supination and maximal pronation (Reader 1: 95% CI: 5.74, 8.21, p < 0.001, and Reader 2: 95% CI: 5.82, 8.37, p < 0.001). The mean difference between the angles in maximal supination and maximal pronation was approximately 7° for both readers. ICC was very good for intraobserver agreement (Reader1: r ≥ 0.92, p < 0.001; Reader 2: r ≥ 0.93, p < 0.001), as well as for interobserver agreement (phase 1: r ≥ 0.87, p < 0.001; phase 2: r ≥ 0.90, p < 0.001). CONCLUSION: The extremes of the rotational movement of the forearm affect the longitudinal morphology and anatomic relationships of the DBRN, primarily demonstrating the convergence of the nerve towards the SASM in maximal pronation and divergence in maximal supination.

Is the radial groove a myth? Is the radial nerve in direct contact with the posterior humerus?

BACKGROUND: The radial groove is known as a sulcus on the posterior humerus and protects the radial nerve from adjacent muscle and soft tissue. In the literature, there exists heterogeneity regarding the presence of an actual radial groove and the radial nerve's interaction with the periosteum of the humerus. This study aimed to determine if there is a real radial groove, "sulcus," and define the relationship between the radial nerve and the periosteum of the posterior humerus. METHODS: Eighteen fresh-frozen cadaveric specimens were dissected using a posterior triceps splitting approach. The radial nerve's interaction with the periosteum of the humerus was determined. The presence of a visible and palpable radial groove was also examined. RESULTS: In 56% of specimens, the radial nerve was directly seated over the periosteum of the posterior humerus (direct contact between the nerve and bone). In comparison, 44% of specimens had a layer of the medial head of the triceps brachii muscle fibers interposition between the nerve and bone. 89% of specimens had no visible or palpable radial groove. In 11% of specimens, there was mild palpable depression. CONCLUSION: This study shows that the radial groove may not exist and is probably not a true anatomical structure. In addition, the nerve is in direct contact with the posterior periosteum of the humerus in most specimens. These anatomic relationships and findings add to the anatomical understanding of the radial nerve, which helps during operative approaches and fixation of the humerus.

Radial nerve compression: anatomical perspective and clinical consequences.

The radial nerve is the biggest branch of the posterior cord of the brachial plexus and one of its five terminal branches. Entrapment of the radial nerve at the elbow is the third most common compressive neuropathy of the upper limb after carpal tunnel and cubital tunnel syndromes. Because the incidence is relatively low and many agents can compress it along its whole course, entrapment of the radial nerve or its branches can pose a considerable clinical challenge. Several of these agents are related to normal or variant anatomy. The most common of the compressive neuropathies related to the radial nerve is the posterior interosseus nerve syndrome. Appropriate treatment requires familiarity with the anatomical traits influencing the presenting symptoms and the related prognoses. The aim of this study is to describe the compressive neuropathies of the radial nerve, emphasizing the anatomical perspective and highlighting the traps awaiting physicians evaluating these entrapments.

A rare variation of radial nerve coexisting with the intercalated ectopic muscle from latissimus dorsi muscle / Una rara variación del nervio radial que coexiste con el músculo ectópico intercalado del músculo latísimo del dorso

SUMMARY: The axilla is the main communication channel connecting the upper limbs, the neck and chest. Stabilization of the internal structure is essential for upper limb and shoulder mobility. In this case, we observed and recorded the characteristics of the variation of the radial nerve as well as the intercalated ectopic muscle from latissimus dorsi muscle. The position relationship between both, was also particularly noted by us. In view of the presence of the variation we reported, related clinical research, surgery and disease diagnosis are expected to take this case into account.

La axila es el principal canal de comunicación que conecta los miembros superiores, el cuello y el tórax. La estabilización de la estructura interna es fundamental para la movilidad del miembro superior y del hombro. En este caso observamos y registramos las características de la variación del nervio radial así como del músculo ectópico intercalado del músculo latísimo del dorso. La relación de posición entre ambas también fue significativa en este estudio. En vista de la presencia de la variación que informamos, se espera que la investigación clínica relacionada con la cirugía y el diagnóstico de la enfermedad tengan en cuenta este caso.

The posterior interosseous nerve at the proximal forearm: anatomical study and clinical correlation / El nervio interóseo posterior en el antebrazo proximal: estudio anatómico y correlación clínica

SUMMARY: The deep branch of the radial nerve (DBRN) runs through the radial tunnel, which is a muscle-aponeurotic structure that extends from the humeral lateral epicondyle to the distal margin of the supinator muscle (SM). The Posterior Interosseous Nerve (PIN) originates as a direct continuation of the DBRN as it emerges from the SM and supplies most of the muscles of the posterior compartment of the forearm. The PIN can be affected by compressive neuropathies, especially at the "Arcade of Frohse". Its preservation is of special interest in surgical approaches to proximal radius fractures and in compressive syndromes release, for which surgeons must have an adequate anatomical knowledge of its course. This descriptive cross-sectional study evaluated 40 upper limbs of fresh cadavers. The diameters of the DBRN, the length of the radial tunnel, and the distances to the supinator arch, PIN emergence and PIN bifurcation were measured. The deep branch of the radial nerve (DBRN) has a course of 23.8 ± 3.7 mm from its origin to the supinator arch, presenting a diameter of 2.2 ± 0.3 mm at that level. The length of the radial tunnel was 42.2 ± 4 mm. The PIN originated 70.7 ± 3.5 mm distal to the lateral epicondyle. Type I corresponds to the division of the PIN during its journey through the radial tunnel, presenting in 35 % of cases, and Type II corresponds to the division of the PIN distal to its emergence from the radial tunnel presenting in the remaining 65 %. This study enriches the knowledge of the PIN and provides useful reference information on a Latin American mestizo sample. We propose the division pattern of the PIN into two types. Future studies may use this classification not only as a qualitative variable, but also include quantitative morphometric measurements.

El ramo profundo del nervio radial (RPNR) discurre por el túnel radial, que es una estructura músculo- aponeurótica que se extiende desde el epicóndilo lateral del húmero humeral hasta el margen distal del músculo supinador (MS). El nervio interóseo Posterior (NIP) se origina como una continuación directa del RPNR cuando emerge del MS e inerva la mayoría de los músculos del compartimiento posterior del antebrazo. El NIP puede verse afectado por neuropatías compresivas, especialmente en la "Arcada de Frohse". Su conservación es de especial interés en los abordajes quirúrgicos de las fracturas proximales de radio y en la liberación de síndromes compresivos, para lo cual los cirujanos deben tener un adecuado conocimiento anatómico de su curso. Este estudio descriptivo transversal evaluó 40 miembros superiores de cadáveres frescos. Se midieron los diámetros de la RPNR, la longitud del túnel radial y las distancias al arco supinador, la emergencia del NIP y la bifurcación del NIP. El RPNR tenía un recorrido de 23,8 ± 3,7 mm desde su origen hasta el arco supinador, presentando un diámetro de 2,2 ± 0,3 mm a ese nivel. La longitud del túnel radial fue de 42,2 ± 4 mm. El NIP se originó 70,7 ± 3,5 mm distal al epicóndilo lateral. El tipo I corresponde a la división del NIP durante su recorrido por el túnel radial presentándose en el 35 % de los casos, y el tipo II corresponde a la división del NIP distal a su salida del túnel radial presentándose en el 65 % restante. Este estudio enriquece el conocimiento del NIP y proporciona información de referencia útil sobre una muestra de mestizos latinoamericanos. Proponemos el patrón de división del NIP en dos tipos. Futuros estudios pueden utilizar esta clasificación no solo como una variable cualitativa, sino también incluir medidas morfométricas cuantitativas.

Entrapment of subscapular artery by the splitting of radial nerve- putative clinical implications.

The third part of the axillary artery has an intimate relationship with the cords of the brachial plexus. The subscapular artery, the largest branch of the axillary artery, arises from its third part. The radial nerve is a branch of the posterior cord of the brachial plexus and its supplies the extensors of the arm, forearm and dorsum of the hand. During routine undergraduate dissection of the axilla of a formalin-fixed cadaver of about 70 years, the subscapular artery was found sandwiched between two divisions of the radial nerve. These anterior and posterior divisions of the radial nerve arose immediately after the formation of the radial nerve and encircled the subscapular artery and fused to form a single nerve subsequently. This variant anatomy can lead to conditions like subscapular entrapment causing ischemia of the scapular region and radial nerve compression causing weakness of the extensors of the upper limb. Injury to the nerve and vessel can occur while performing diagnostic and therapeutic procedures in the area. Knowledge of these variations provides a precautious approach by surgeons and other interventionists while working on this area.

Duplicated superficial branch of the radial nerve and brachioradialis muscle belly: prevalence and significance.

BACKGROUND: The superficial branch of the radial nerve (SBRN) is a sensory nerve innervating the dorsoradial part of the hand. It originates in the cubital fossa, runs under the belly of the brachioradialis muscle (BM), emerges from underneath in the distal third of the forearm and continues in the subcutaneous tissue towards the hand. There exist several anatomical variations of its branching and course, including a rare variation of its duplication combined with a duplication of the brachioradialis muscle belly. The aim of this study was to find out the prevalence of this variation on a sample of cadaveric human bodies which has not been reported yet. MATERIALS AND METHODS: We have carefully dissected 208 cadaveric upper limbs (Central European population). All cases of limbs containing the variation of a double SBRN and/or a double BM belly were measured and documented. RESULTS: We have identified 2 cases of a double SBRN combined with a double BM belly (0.96%). Both were present in the right forearm of a male donor and in both cases the nerve was impinged by muscle bundles connecting the 2 muscle bellies together. Moreover, we have encountered 1 case of a double SBRN without a double BM belly (0.48%), i.e. the total prevalence of a double SBRN was 1.44%. CONCLUSIONS: The duplicated SBRN with the duplicated BM is a relatively rare anatomical variation that might cause complications while performing various surgical procedures in the forearm, moreover it might be a rare cause of Wartenberg's syndrome.

Sonographic peripheral nerve cross-sectional area in adults, excluding median and ulnar nerves: A systematic review and meta-analysis.

INTRODUCTION/AIMS: Although electromyography remains the "gold standard" for assessing and diagnosing peripheral nerve disorders, ultrasound has emerged as a useful adjunct, providing valuable anatomic information. The objective of this study was to conduct a systematic review and meta-analysis evaluating the normative sonographic values for adult peripheral nerve cross-sectional area (CSA). METHODS: Medline and Cochrane Library databases were systematically searched for healthy adult peripheral nerve CSA, excluding the median and ulnar nerves. Data were meta-analyzed, using a random-effects model, to calculate the mean nerve CSA and its 95% confidence interval (CI) for each nerve at a specific anatomical location (= group). RESULTS: Thirty groups were identified and meta-analyzed, which comprised 16 from the upper extremity and 15 from the lower extremity. The tibial nerve (n = 2916 nerves) was reported most commonly, followed by the common fibular nerve (n = 2580 nerves) and the radial nerve (n = 2326 nerves). Means and 95% confidence interval (CIs) of nerve CSA for the largest number of combined nerves were: radial nerve assessed at the spiral groove (n = 1810; mean, 5.14 mm2 ; 95% CI, 4.33 to 5.96); common fibular nerve assessed at the fibular head (n = 1460; mean, 10.18 mm2 ; 95% CI, 8.91 to 11.45); and common fibular nerve assessed at the popliteal fossa (n = 1120; mean, 12.90 mm2 ; 95% CI, 9.12 to 16.68). Publication bias was suspected, but its influence on the results was minimal. DISCUSSION: Two hundred thirty mean CSAs from 15 857 adult nerves are included in the meta-analysis. These are further categorized into 30 groups, based on anatomical location, providing a comprehensive reference for the clinician and researcher investigating adult peripheral nerve anatomy.

Unusual sensory innervation of the dorsal hand and why we should bear this variation in mind.

Detailed knowledge of the anatomy and different variations of the superficial branch of the radial nerve could be of great importance not only to anatomists but also to clinicians. A predominant radial nerve supply to the dorsum of the hand is rare. Herein, we present an unusual case of unilateral sensory innervation of the dorsal hand found during routine anatomical dissection of a 72-year-old at death male Caucasian cadaver. We also present a brief discussion of the reported variation and emphasize its potential clinical implications.

Wrist Arthroscopy Using the 2R Portal: Is It Safer Than the 1,2 Portal?

BACKGROUD: The purpose of this study was to compare the 1,2 with a novel 2R portal in terms of proximity to critical structures. METHODS: Wrist arthroscopy was performed on 8 fresh frozen cadavers via the 1,2 and 2R portals. External anatomy was then dissected under loupe magnification. The closest distance between the portals and surrounding anatomical structures was measured in millimeters using digital calipers. RESULTS: The 1,2 portal was significantly closer to radial artery and first extensor compartment tendons than the 2R portal. The radial artery was on average 1.32 mm from the 1-2 portal and 14.25 mm from the 2R portal. The 2R portal was significantly closer to the second and third extensor compartment tendons. The closest branch of the superficial branch of the radial nerve (SBRN) was on average 2.04 mm from the 1-2 portal and 7.59 mm from the 2R portal, but this was not statistically significant. CONCLUSIONS: We advocate using the 2R portal preferentially to the 1,2 portal when treating radial sided wrist pathology to decrease the risk of iatrogenic radial artery and SBRN injury.

Anatomical variations in the sensory innervation of the dorsal surface of the first digit space, a cadaveric study with clinical consequences.

INTRODUCTION: Radial nerve palsy is a classical complication of a humeral shaft fracture. In clinical practice, motor palsy of the radial nerve is sometimes observed without an abnormality felt in the sensory territory. HYPOTHESIS: We hypothesised that this dissociation between sensory and motor involvement is related to anatomical variations of the sensory innervation of the dorsal surface of the first digit space, thus, we decided to study the nature and frequency of these variations. MATERIAL AND METHOD: A cadaveric study was conducted on 24 upper limbs to analyse the truncal origin of the sensory branches innervating the dorsal surface of the first digit space. RESULTS: The sensory branch of the radial nerve (SBRN) participated in the innervation of the dorsal surface of the first digit space in 22 limbs, an anatomical variation was present in 2 cases with a mixed innervation by the SBRN and the lateral cutaneous nerve of forearm (LCNF) in 1 case and singular innervation by LCNF, with no SBRN involvement, in 1 case. Communications between SBRN and LCNF were found in 7 cases. DISCUSSION: Pure motor radial damage, without a sensory deficit of the dorsal surface of the first digit space, does not preclude a complete traumatic injury of the radial nerve. The sensory innervation of this region can be relayed by a branch of the LCNF. LEVEL OF EVIDENCE: IV; cadaveric study.

Surgical Anatomy of the Radial Nerve at the Dorsal Region of the Humerus: A Cadaveric Study.

BACKGROUND: Surgery for humeral shaft fractures is associated with a high risk of iatrogenic radial nerve palsy (RNP). Plausible causes are difficult anatomical conditions and variants. METHODS: We performed a cadaveric study with 23 specimens (13 female and 10 male Caucasian donors) to assess the course and anatomy of the radial nerve (RN) with its branches alongside the humeral shaft. The accuracy of identification of the RN in the surgical field was analyzed by measuring the location, course, diameter, and form of each nerve and vessel of interest. RESULTS: The RN is not a single structure running alongside the humeral shaft; at least 4 parallel structures crossed the dorsal humerus in all subjects. The RN was accompanied by 2 vessels and at least 1 other nerve, which we named the musculocutaneous branch (MCB). With an oval profile and an average diameter of 3.1 mm (range, 2.6 to 3.8 mm), the MCB was thinner but, in some cases, close to the average diameter of 4.7 mm (range, 4.0 to 5.2 mm) of the RN, which had a round profile. Both accompanying vessels had similar diameters: 3.5 mm (range, 2.6 to 4.2 mm) for the radial collateral artery and 4.0 mm (range, 2.9 to 4.4 mm) for the medial collateral artery. In 20 (87%) of the cases, the RN ran proximal to and in 3 (13%) of the cases, distal to the MCB. Furthermore, a distal safe zone of at least 110 mm (range, 110 to 160 mm) was found, measured from the radial (lateral) epicondyle proximally. CONCLUSIONS: The RN does not cross the dorsal humerus alone, as often stated in anatomical textbooks, but runs parallel to vessels and at least 1 nerve branch with a similar appearance. Thus, for reliable preservation of the RN, we recommend identification and protection of all crossing structures in posterior humeral surgeries 110 mm proximal to the radial epicondyle.

Optimal placement for needle electromyography of the supinator muscle: Cadaveric studies.

INTRODUCTION/AIMS: The existing methods for needle electromyography are confusing as to which is the safest and most effective. Our aim was to identify the optimal and safest needle electromyographic insertion site in the supinator muscle. METHODS: We performed a two-step cadaveric dissection of the supinator muscle and related neurovascular structures. The study was performed using 18 upper limbs of 9 fresh adult cadavers (step 1) and 14 upper limbs of 7 fresh adult cadavers (step 2). In step 1, an imaginary line connecting the radial head (RH) and midpoint of the dorsal wrist (RW line) was drawn, and the distance from the RH to the point where the RW line and posterior interosseous nerve (PIN) intersect (L_CROSS) was measured on the RW line. In step 2, the needle was inserted 30 mm distal to the RH according to the results of step 1. After injection with India ink, dissection was performed to measure the distance between the needle insertion site and PIN (L_CROSS_Inj) on the RW line. RESULTS: The median L_CROSS was 51.4 (35.5-65.6) mm. Needle insertion spared the PIN in all cases during step 2, and the needle was inserted into the supinator muscle in all cases. The median L_CROSS_Inj was 27.4 (13.2-39.8) mm. DISCUSSION: A safe and accurate needle insertion site for the supinator muscle is approximately 30 to 40 mm distal to the RH along the RW line.