Surgical anatomy of the radial nerve at the elbow. Surg Radiol Anat. 2009;31:101-106. [PMID: 18795220 DOI: 10.1007/s00276-008-0412-8]

Two fingerbreadths, one finger's width: on the proximity of the radial nerve to the deltoid tuberosity

INTRODUCTION

The aim of this study was to find a convenient technique to evaluate the location of the radial nerve (RN) with reference to the deltoid tuberosity (DT).

MATERIALS AND METHODS

Sixty-eight upper extremities, embalmed using a modified version of Thiel's method, were included in the study. The interval between the tip of the greater tubercle of the humerus and the distal tip of the lateral humeral epicondyle (LE) was defined as humeral length (HL). The most prominent point of the DT was used as the point of reference. Through this point, a horizontal reference line which met the humeral axis at the dorsal side of the humeral shaft was simulated. The longitudinal distance between the crossing point of the horizontal line and the humeral axis and the RN was measured (distance 1). The interval between the intersection point and the reference point at the DT was measured (distance 2). Data were evaluated in centimeters.

RESULTS

For the whole sample, the HL averaged 31.0 cm (SD: 2.3; range 26.2-36.9). Distance 1 averaged 2.2 cm (SD: 0.3; range 1.6-3.1), and distance 2 averaged 1.2 cm (SD: 1.0; range 0-2.8). The HL was larger in the male group when compared to females (p < 0.001; males mean: 32.2 cm; females mean 29.5 cm). There was no difference regarding distance 2 (p = 0.59; males mean: 1.2 cm; females mean: 1.3 cm) between the sexes. Distance 1 was significantly (p = 0.02) larger in the male group (mean: 2.3 cm) when compared to females (mean: 2.1 cm). Concerning sides, there were no differences regarding all evaluated parameters (HL: p = 0.6; Distance 1: p = 0.6; distance 2: p = 0.8).

CONCLUSIONS

This study provides an easily applicable technique to localize the RN with reference to the DT.

Fractures of the humeral shaft caused by arm wrestling: a systematic review

Background

Arm wrestling is a popular sport/game that may result in various injuries. The most common arm wrestling injury in adults is humeral shaft fracture. This study aimed to elucidate the current understanding of humeral shaft fracture caused by arm wrestling and propose the possible mechanism.

Methods

The PubMed and Web of Science databases were searched using the terms "arm wrestling" and "humeral fracture" as well as "sports" and "humeral fracture" in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. The inclusion criteria were English full-text articles and notable full-text articles in other languages concerning humeral shaft fracture caused by arm wrestling that described the patients' characteristics and presented adequate images or a detailed description of the fracture to confirm the fracture details. The exclusion criterion was a lack of appropriate images or detailed description of the fracture. Fifty-seven studies were identified. The patients' demographics were evaluated. The details of fractures, primary radial nerve palsy, match status, provided fracture treatment, and outcomes were evaluated using the chi-squared test. The relationship between fracture site and the patient's age was analyzed using Student's t-test.

Results

One hundred fifty-three patients, 82% of whom were males aged 15-34 years, were identified. With only a few exceptions, almost all patients were injured in recreational matches. The injured limb was the right arm in 65% of patients (n = 141). The patient's physical characteristics, the opponent's physical characteristics compared with those of the patient, and the match status at the time of injury varied between cases. Among the 46 patients with known match details, all were injured when one of the wrestling opponents suddenly added more force in an attempt to change the match status. The fracture configuration was spiral in all cases, and 48% of fractures had an associated medial butterfly fragment. The fracture site was the distal third or the junction between the distal and middle thirds in 90% of cases. Although primary radial nerve palsy was recognized in 19 of 103 patients (18.4%), all resolved spontaneously.

Conclusion

Although humeral shaft fracture caused by arm wrestling occurred mostly in male players aged 15-34 years, this injury may affect any player regardless of the match status, player's and opponent's physical characteristics, and age. The direct cause is torsional force generated by the internal rotators. A sudden change from concentric to eccentric contraction of the internal rotators is likely to cause fracture.

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.

Measurement of the Radial Nerve Danger Zone in Filipino Adults: A Cadaveric Study

Introduction

The radial nerve danger zone (RNDZ) is an important anatomic consideration to anticipate or prevent injury in trauma assessment or surgical fixation. No published estimate currently exists for Filipinos. In this study, we sought to provide a local estimate and explore potential predictors of this anatomic region in Filipino adult cadavers.

Materials and methods

Posterior dissection to expose and measure the radial nerve, from the lateral epicondyle to the lateral intermuscular septum, was performed in 60 upper limbs from 30 formalin-preserved cadavers in the laboratory of the Department of Anatomy, College of Medicine, University of the Philippines Manila. Univariate and multivariate linear regression modelling was performed with RNDZ as the dependent variable and age, sex, height and humeral length as potential independent variables individually and in combinations.

Results

The mean radial nerve length from the lateral epicondyle to the lateral intermuscular septum was estimated at 10.6 cm (95% confidence interval: 10.3 cm, 10.9cm). Height and humeral length were statistically significant univariate predictors in female cadavers, while only height was significant in male cadavers. In addition, all multivariate regression models were statistically significant and accounted for more than 57% of the variability in female RNDZ estimates. In comparison, only models that included height and age were statistically significant predictors of RNDZ and accounted for at most 22% of the variability of the estimate in males.

Conclusion

The estimated length of the radial nerve danger zone generated in this study should be strongly considered over other published estimates in surgical fixation procedures performed in adult Filipinos.

One-year follow-up after treatment of proximal and/or middle one-third humeral shaft fractures with a helical plate: healing rates, complications and functional outcome measures

Background

Conventional plate osteosynthesis is a valuable treatment option in displaced proximal and/or middle one-third humeral shaft fractures. Nonetheless, this procedure can be complicated by a radial nerve palsy. To date, many surgical techniques have been developed in an attempt to minimize this high-impact complication. A helical plate has the potential to avoid an iatrogenic radial nerve palsy due to its design. This article aims to evaluate safety and functional outcomes of patients treated with a helical plate compared to conventional plate osteosynthesis. In particular healing rates, complications and functional outcome measures.

Methods

We retrospectively included all patients with displaced proximal and/or middle one-third humeral shaft fractures who were treated with a helical plate from October 2016 until August 2018 at a single level-1 trauma center (AZ Groeninge, Kortrijk, Belgium). A self-molded long PHILOS plate (DePuy Synthes®) or a pre-contoured A.L.P.S proximal humeral plating system (Zimmer Biomet®) were used. Patient baseline characteristics and standard radiographs were obtained pre- and postoperatively. We retrospectively searched for complications. Patients were reassessed using the Disabilities of the Arm, Shoulder and Hand (DASH), Constant Murley (CMS) and EQ-5D-5L scores with a minimal follow-up of 1 year.

Results

The humeral shaft fractures of all sixteen patients consolidated within 3 months and no iatrogenic radial nerve palsies were observed. One plate had to be removed after 1 year due to a late deep infection. With a minimum follow up of 1 year, the mean DASH score was 22 ± 19 and the mean normalized CMS was 80 ± 19.

Conclusion

Operative treatment of proximal and/or middle one-third humeral shaft fractures with a helical plate is a safe procedure with good to excellent shoulder function at one-year follow-up. Contrary to conventional plate osteosynthesis, a helical plate has the potential to completely avoid a radial nerve palsy, while maintaining similar healing rates and functional outcomes.

Trial registration

Retrospective cohort study. B396201939564. Registered on 10 MAY 2019.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12891-021-04774-9.

Location of the radial nerve along the humeral shaft between the prone and lateral decubitus positions at different elbow positions

Identification of the radial nerve is important during the posterior approach to a humerus fracture. During this procedure, the patient can be placed in the prone or lateral decubitus position depending on the surgeon’s preference. The distance from the radial nerve to the osseous structures will be different in each position. The purpose of this study was to identify the safety zones in various patient and elbow flexion positions. The distances from the olecranon to the center of the radial groove and intermuscular septum and lateral epicondyle to the lateral intermuscular septum were measured using a digital Vernier caliper. The measurements were performed with cadavers in the lateral decubitus and prone positions at different elbow flexion angles. The distance from where the radial nerve crossed the posterior aspect of the humerus measured from the upper part of the olecranon to the center of the radial nerve in both positions at different elbow flexion angles varied from a mean maximum distance of 130.00 mm with the elbow in full extension in the prone position to a minimum distance of 121.01 mm with the elbow in flexion at 120° in the lateral decubitus position. The mean distance of the radial nerve from the upper olecranon to the lateral intermuscular septum varied from 107.13 to 102.22 mm. The distance from the lateral epicondyle to the lateral edge of the radial nerve varied from 119.92 to 125.38 mm. There was not significant contrast in the position of the radial nerve with osseous landmarks concerning different degrees of flexion, except for 120°, which is not significant, as this flexion angle is rarely used.

Nerve transfer in the spastic upper limb: anatomical feasibility study

PURPOSE

Nerve transfers represent an innovative tool in the surgical treatment of upper limb paralysis. Well-documented for brachial plexus sequalae and under evaluation for tetraplegic patients, they have not yet been described for spastic upper limbs. The typical spastic deformity involves active and spastic flexor, adductor and pronator muscles, associated with paralysed extensor and supinator muscles. Experience with selective neurectomy has shown an effective decrease in spasticity together with preservation of muscle strength. We conceptualized a combination of neurectomy and nerve transfer, by performing a partial nerve transfer from a spastic elbow flexor muscle to a paralyzed wrist extensor muscle, hypothesizing that this would reduce the spasticity of the former and simultaneously activate the latter.

METHODS

Ten cadaveric dissections were performed in order to establish the anatomic feasibility of transferring a motor branch of the brachioradialis (BR) onto the branch of the extensor carpi radialis longus (ECRL) or brevis (ECRB). We measured the emergence, length, muscle entry point and diameter of each branch, and attempted the transfer.

RESULTS

We found 1-4 motor nerve for the BR muscle and 1-2 for the ECRL muscle. In all cases, the nerve transfer was achievable, allowing a satisfactory coaptation. The ECRB branch emerged too distally to be anastomosed to one of the BR branches.

CONCLUSION

This study shows that nerve transfers from the BR to the ECRL are anatomically feasible. It may open the way to an additional therapeutic approach for spastic upper limbs.

Surgical anatomy of the radial nerve in the arm: a cadaver study

PURPOSE

The purpose of this study was to analyse the anatomic course of the radial nerve (RN) in the arm, in order to minimize the potential risk of surgical injury.

METHODS

The study was performed in 19 embalmed upper extremities of 11 adult human cadavers. We measured: distance from deltoid insertion (DI) into the humerus to lateral epicondyle (LE); distance from RN piercing point into the lateral intermuscular septum (LIS) to three other points-DI, LE and RN division into superficial and deep terminal branches; distance between the LE and the RN division. To assess variability, we correlated the distances between the landmarks to the overall length of the arm.

RESULTS

The RN was found to pierce the LIS within 31.6 mm of the most distal DI into the humerus. The mean distance between the entry point of RN in the LIS and the LE was 107.2 mm. The mean distance between RN perforating point in the LIS and RN division in its terminal branches was 86.4 mm. The DI-LE and the LIS-LE showed a moderate positive correlation with the length of the arm.

CONCLUSION

We describe the DI relationship to the RN course and also report its proportion within overall arm length which has not been previously described. Using the arm length as reference, our results show that RN can be found to perforate on the LIS at a point distal to the DI by 11% and proximal to the LE by 38%.

Radial Nerve Neuropraxis due to Compression by C-Arm Fluoroscopy in Spine Surgery: A Case Report

Introduction

Peripheral nerve injury is a well-known surgical complication related to the position of the patient. Moreover, in spine surgery, prone position for prolonged period places the patient at increased risk. The aim of this study was to report a case of a radial nerve neuropraxis due to compression by C-arm fluoroscopy during spine surgery. Case Presentation. An 81-year-old-female underwent a posterior spinal fixation L2-S1 due to lumbar spinal stenosis. In the recovery room, she presented an hematoma at the posterolateral part of her arm associated with a wrist drop due to radial nerve neuropraxis. The patient was referred to an occupational therapist and fully recovered four months later. After analysis of the patient positioning during the intervention, we came to the conclusion that this radial nerve injury was very possibly due to a compression by the C-arm fluoroscopy during the surgery.

Conclusion

Our case describes a rare case of compression of the radial nerve during lumbar spine surgery, which is an unexpected complication as the site of the nerve injury is not at all related to the surgery itself, but to the position of the patient. Although C-arm fluoroscopy is essential, spine surgeons should be aware of this possible complication related to its use in order to avoid it.

A morphologic and histologic study of the radial nerve and its branches at potential compression sites

Objectives

This study examined variations in the termination level of the radial nerve (RN) and the morphometry of the RN and its branches at potential compression sites. Additionally, we digitally analysed histological sections of the RN, the superficial branch of the radial nerve (SBRN), and the posterior interosseous nerve (PIN).

Methods

We conducted this study on 14 formalin fixed adult cadavers. The lengths of the RN, SBRN, and PIN were measured up to potential compression sites, using appropriate surface skeletal landmarks as reference points. We histologically evaluated the fascicular and non-fascicular areas and the number of axons in each nerve. All parameters were statistically analysed using a paired t-test.

Results

We found variations in the bifurcation of the RN with respect to the biepicondylar line (BEL). However, the course of RN terminal branches was constant in the forearm. There was a significant histological difference between the fascicular and non-fascicular areas of the PIN. There was no significant difference in the total number of axons in the SBRN and PIN. Finally, we observed that the intramuscular length of the PIN within the supinator muscle was variable and that the SBRN had more fascicles compared to the RN and PIN.

Conclusions

In our study, the RN and PIN had more variable morphometry compared to that of the SBRN. The histologic evaluation and quantification of these nerves at their potential compression sites could serve as a guide for surgeons planning nerve reconstruction procedures.

Identification of most consistent and reliable anatomical landmark to locate and protect radial nerve during posterior approach to humerus: a cadaveric study

The location of the radial nerve (RN) is described with various bony landmarks, but such may be disturbed in the setting of fracture and dislocation of bone. Alternative soft tissue landmarks would be helpful to locate the nerve in such setting. To recognize certain anatomic landmarks to identify, locate and protect RN from any iatrogenic injury during surgical intervention such as open reduction and internal fixation. Forty arms belonging to 20 adult cadavers were used for this study. We measured the distance of RN from the point of confluence of triceps aponeurosis (TA), tip of the acromion and tip of the lateral epicondyle along the long axis of the humerus. These distances were correlated with the upper arm length (UAL). The average UAL was 32.64±0.64 cm. The distance of the RN from the point of confluence of TA (tricepso-radial distance, TRD), tip of acromion (acromion-radial distance) and tip of lateral epicondyle of humerus (condylo-radial distance, CRD) was 3.59±0.16 cm, 14.27±0.59 cm, and 17.14±1.29 cm respectively. No correlation was found with UAL. Statistically, TRD showed the least variability and CRD showed maximum variability. The minimum TRD was found to be 3.00 cm. So this should be considered as the maximum permissible length of the triceps split. The point of confluence of the TA appears to be the most stable and reliable anatomic landmark for localization of the RN during the posterior approach to the humerus.

Establishing Safe Zones to Avoid Nerve Injury in the Approach to the Humerus in Pediatric Patients: A Magnetic Resonance Imaging Study

BACKGROUND

The surgical anatomy of upper-extremity peripheral nerves in adults has been well described as "safe zones" or specific distances from osseous landmarks. In pediatrics, relationships between nerves and osseous landmarks remain ambiguous. The goal of our study was to develop a model to accurately predict the location of the radial and axillary nerves in children to avoid iatrogenic injury when approaching the humerus in this population.

METHODS

We conducted a retrospective review of 116 magnetic resonance imaging (MRI) scans of entire humeri of skeletally immature patients; 53 of these studies met our inclusion criteria. Two independent observers reviewed all scans. Arm length was measured as the distance between the lateral aspect of the acromion and the lateral epicondyle. We then calculated the distances (defined as the percentage of arm length) between the radial nerve and distal osseous landmarks (the medial epicondyle, transepicondylar line, and lateral epicondyle) as well between the axillary nerve and the most lateral aspect of the acromion.

RESULTS

The axillary nerve was identified at a distance equaling 18.6% (95% confidence interval [CI], ±0.62%) of arm length inferior to the lateral edge of the acromion. The radial nerve crossed (1) the medial cortex of the posterior part of the humerus at a distance equaling 63.19% (95% CI: ±0.942%) of arm length proximal to the medial epicondyle, (2) the middle of the posterior part of the humerus at a distance equaling 53.9% (95% CI: ±1.08%) of arm length proximal to the transepicondylar line, (3) the lateral cortex of the posterior part of the humerus at a distance equaling 45% (95% CI: ±0.99%) of arm length proximal to the lateral epicondyle, and (4) from the posterior to the anterior compartment at a distance equaling 35.3% (95% CI: ±0.92%) of arm length proximal to the lateral epicondyle. A strong linear relationship between these distances and arm length was observed, with an intraclass correlation coefficient of >0.9 across all measurements.

CONCLUSIONS

The positions of the radial and axillary nerves maintain linear relationships with arm lengths in growing children. The locations of these nerves in relation to palpable osseous landmarks are predictable.

CLINICAL RELEVANCE

Knowing the locations of upper-extremity peripheral nerves as a proportion of arm length in skeletally immature patients may help to avoid iatrogenic injuries during surgical approaches to the humerus.

Safe zone for lateral pin placement for external fixation of the distal humerus

External fixation is a common, efficient technique used for humeral shaft stabilization and elbow fractures. There are reports of radial nerve injuries associated with this procedure. In this study, we investigated the course and variability of the radial nerve along the lateral humerus in relation to the elbow joint to determine a relatively safe zone for lateral pin placement in external fixation. Twenty upper extremities from 10 cadavers were studied. The nerve branches and course of the radial nerve along the lateral humerus were carefully dissected. Straight lines (a, b, and c) were made connecting three landmarks (the acromion, coracoid process, and anterior wall of the axilla) in the proximal upper extremity to the lateral condyle (LC) of the humerus; their intersections with the radial nerve (A, B, and C) were marked. We analyzed whether the intersection positions were correlated with the connecting line lengths. The mean lengths of the connecting lines were (a) 27.24 ± 2.57, (b) 26.18 ± 2.79, and (c) 20.95 ± 1.44 cm; the distance between the intersection points and the LC of the humerus were (Aa) 7.56 ± 1.31, (Bb) 6.90 ± 2.27, and (Cc) 5.01 ± 0.83 cm; and the measured intersection points of the radial nerve in the lateral aspect of the humerus were (A) 18.48%-34.82%, (B) 13.48%-40.00%, and (C) 19.27%-28.05% of the lengths of lines a, b, and c, respectively. Our data provide a more reliable reference to predict the course of the radial nerve on the lateral humerus and define a safe zone for pin placement. Clin. Anat., 33:637-642, 2020. © 2019 Wiley Periodicals, Inc.

CT Analysis of a Potential Safe Zone for Placing External Fixator Pins in the Humerus

BACKGROUND

Iatrogenic radial nerve injures are a common complication during the placement of external fixator pins at the lateral aspect of the humeral shaft. This study uses a three-dimensional measurement technique to locate a safe entry point for humeral pins when externally fixating the elbow. Methods: We fixed a guide wire to the radial nerve by a suture string, and used computed tomography (CT) to scan the upper limbs of cadaver specimens. Then, we measured the deviation angles of the radial nerve on the CT scans, and the distance from the radial nerve to the "elbow rotation center" (ERC). Result: The average distance from the radial nerve to the ERC was 87.3 ± 8.5 mm (range: 68-100 mm), 58.3 ± 11.3 mm (range: 32.12-82.84 mm), 106.3 ± 5.8 mm (range: 86.93-115.08 mm), and 113.9 ± 4.8 mm (range: 97.93-120.22 mm) at radial nerve deviation angles of 0°, -30°, 30°, and 45°, respectively. The average radial nerve deviation angle was -37.7° ± 7.7° and 123.9° ± 19.9° at 50 and 150 mm, respectively. Relative to 0°, the distance between the radial nerve and the ERC at radial nerve deviation angles of -30°, 30°, and 45° showed a significant difference (t = 18.20, p < 0.05; Z = 6.07, p < 0.001; Z = 6.40, p < 0.001, respectively). Conclusions: Pins inserted into the proximal humerus should be about 150 mm from the ERC with a radial nerve deviation angle of 30° anteriorly, and 50 mm from the ERC with a deviation angle of 30°-45° posteriorly.

Effects of the Elbow Flexion Angle on the Radial Nerve Location around the Humerus: A Cadaver Study for Safe Installation of a Hinged External Fixator

Background: This study aimed to investigate whether the distance between the radial nerve and rotational center of the elbow joint when observing from the lateral surface of the humerus changes according to passive elbow joint flexion for safe external fixation with a hinged fixator of the elbow joint.

Methods: Twenty fresh-frozen cadaveric arms were dissected. The points where the radial nerve crosses over the posterior aspect of the humerus, crosses through the lateral center, and crosses over the anterior aspect of the humerus were defined in the lateral view of the elbow joint, using fluoroscopy, as R1, R2, and R3, respectively. The distances between the rotational center and each point on the radial nerve were measured when the flexion angle of the elbow joint was 10°, 50°, 90°, and 130°.

Results: The distances between the rotational center and R1, R2, and R3 were 118 mm, 94 mm, and 65 mm, respectively, when the flexion angle was 10°; 112 mm, 93 mm, and 74 mm, respectively, for 50°; 108 mm, 93 mm, and 77 mm, respectively, for 90°; and 103 mm, 94 mm, and 83 mm, respectively, for 130°. The distance between the rotational center and R2 was constant regardless of the flexion angle. With elbow joint extension, the distances between R1 and R3 increased; the safe zone, a region where the radial nerve would not be located on the humerus, was the smallest in extension. When the elbow joint was flexed, the distances between R1 and R3 decreased; the safe zone was the largest in flexion.

Conclusions: This study showed that the radial nerve location on the humerus varied based on the flexion angle of the elbow joint; the safe zone may change. A half-pin can be likely inserted safely, avoiding the elbow joint extension position.

Safe zone for the posterior interosseous nerve with regard to the lateral and posterior approaches to the proximal radius

PURPOSE

The posterior interosseous nerve (PIN) is at risk during the posterior and lateral approaches to the proximal radius. We aimed to define a safe zone for these approaches to avoid injury of the PIN and to evaluate their close and changing relationship to the nerve during forearm rotation.

METHODS

The study collective consisted of 50 upper limbs. After performance of the lateral approach, the distance between the tip of the radial head and the PIN's exit point from the supinator (= distance 1) and the shortest interval between the nerve's exit to the radial margin of the ulna (= distance 2) were measured in maximum pronation and supination. Then, the dorsal approach was conducted and again distance 1 and the interval between the distal margin of the anconeus and the nerve's exit point (distance 2) were evaluated (pronation and supination).

RESULTS

There were significantly shorter distances during supination in comparison to pronation. Regarding the lateral approach, distance 1 changed from a mean of 60.3 mm (supination) to 62.7 mm in pronation (p < 0.001). For the dorsal approach, distance 1 decreased significantly (p < 0.001) from 62.9 mm (pronation) to 60.2 mm (supination).

CONCLUSION

Supination during the lateral and dorsal approaches to the proximal radius needs to be avoided to protect the PIN. Furthermore, the nerve appeared at an interval between 45 and 84.1 mm (lateral approach) and 47.5-93.8 mm (dorsal approach), respectively. Therefore, care must be taken at this height during extension of the approaches in a distal direction.

Posterior interosseous nerve localization within the proximal forearm - a patient normalized parameter

AIM

To provide a “patient-normalized” parameter in the proximal forearm.

METHODS

Sixty-three cadaveric upper extremities from thirty-five cadavers were studied. A muscle splitting approach was utilized to locate the posterior interosseous nerve (PIN) at the point where it emerges from beneath the supinator. The supinator was carefully incised to expose the midpoint length of the nerve as it passes into the forearm while preserving the associated fascial connections, thereby preserving the relationship of the nerve with the muscle. We measured the transepicondylar distance (TED), PIN distance in the forearm’s neutral rotation position, pronation position, supination position, and the nerve width. Two individuals performed measurements using a digital caliper with inter-observer and intra-observer blinding. The results were analyzed with the Wilcoxon-Mann-Whitney test for paired samples.

RESULTS

In pronation, the PIN was within two confidence intervals of 1.0 TED in 95% of cases (range 0.7-1.3 TED); in neutral, within two confidence intervals of 0.84 TED in 95% of cases (range 0.5-1.1 TED); in supination, within two confidence intervals of 0.72 TED in 95% of cases (range 0.5-0.9 TED). The mean PIN distance from the lateral epicondyle was 100% of TED in a pronated forearm, 84% in neutral, and 72% in supination. Predictive accuracy was highest in supination; in all cases the majority of specimens (90.47%-95.23%) are within 2 cm of the forearm position-specific percentage of TED. When comparing right to left sides for TEDs with the signed Wilcoxon-Mann-Whitney test for paired samples as well as a significance test (with normal distribution), the P-value was 0.0357 (significance - 0.05) indicating a significant difference between the two sides.

CONCLUSION

This “patient normalized” parameter localizes the PIN crossing a line drawn between the lateral epicondyle and the radial styloid. Accurate PIN localization will aid in diagnosis, injections, and surgical approaches.

Radial nerve location at the posterior aspect of the humerus: an anatomic study of 100 specimens

PURPOSE

Radial neuropathy represents a devastating complication in a posterior approach to the distal humerus. This study aimed to propose "safe zones" regarding the radial nerve (RN) location at the posterior aspect of the humerus to minimize the risk of iatrogenic injury.

METHODS

In 100 embalmed specimens, the distances of the proximal edge of the olecranon fossa (OF) to the radial nerve at the medial edge (R1), at the center (R2) and at the lateral edge (R3) of the posterior aspect of humeral shaft were measured. Humeral length (HL) and transcondylar width (TW) were evaluated and correlated to R1, R2 and R3.

RESULTS

R1 was 15.0 (±2.1; 10.6-19.5) cm, R2 averaged 12.7 (±1.6; 8.9-15.7) cm, R3 was 10.6 (±1.3; 7.6-13.7) cm. HL was 30.8 (±1.9) cm. TW averaged 6.3 (±0.6) cm. TW and HL correlate with R1, R2, R3 (r = 0.451-0.565 [95% CI 0.279-0.685]). The mean ratio was 2.3 (±0.18) for HL/R1, 2.6 (±0.23) for HL/R2 and 3.1 (±0.31) for HL/R3. The ratio averaged 2.2 (±0.20) for R1/TW, 1.9 (±0.18) for R2/TW and 1.6 (±0.15) for R3/TW.

CONCLUSIONS

We present the OF as an osseous landmark to reduce the risk of iatrogenic radial neuropathy. HL and TW can be reliably used to estimate the RN location. The consistent "safe zones" of the RN in relation to the OF are 10.5 cm at the medial edge, 9 cm at the center and 7.5 cm at the lateral edge of the posterior aspect of the humeral shaft.

Safe zone for superolateral entry pin into the distal humerus in children: an MRI analysis

BACKGROUND

The radial nerve is at risk for iatrogenic injury during placement of pins, screws, or wires around the distal humerus. Unlike adults, detailed anatomic information about the relationship of the nerve to the distal humerus is lacking in children.

QUESTION/PURPOSES

This study evaluates the relationship of the radial nerve to the distal humerus in a pediatric population on conventional MRI and proposes an anatomic safe zone using easily identifiable bony landmarks on an AP elbow radiograph.

METHODS

To determine the course of the radial nerve at the lateral distal humerus, we reviewed 23 elbow radiographs and MRIs of 22 children (mean age, 9 ± 4 years; range, 3-12 years) obtained as part of their workup for various elbow conditions. We described a technique using distance ratios calculated as a percentage of the patient's own transepicondylar distance, defined as the distance measured between the apices of the medial and lateral epicondyles, on the AP elbow radiograph and the midcoronal MR image. The cross-reference tool on a Picture Archiving and Communication System was then used to identify axial MR image at the level where the transepicondylar distance was measured. On this axial image, a line was drawn connecting the medial and lateral epicondyles (the transepicondylar axis) and its midpoint was determined. The radial nerve angle was measured by a line from the radial nerve to the midpoint of the transepicondylar axis and a line along the lateral half of the transepicondylar axis. On this axial slice, the closest distance from the nerve to the underlying cortex of the distal humerus was measured. To further localize the nerve along the distal humerus, predetermined percentages of the transepicondylar distance were projected proximally from the level of the transepicondylar axis along the longitudinal axis of the humerus on the midcoronal MR image. At these designated heights, the corresponding axial MR image was identified using the cross-reference tool and the nerve was mapped in a similar fashion. We then proposed a simpler method using a best-fit line drawn along the lateral supracondylar ridge on the AP radiograph to define the safe zone for lateral pin entry.

RESULTS

On axial MR images, the radial nerve was located in the anterolateral quadrant with a mean radial nerve angle of 54° (range, 35°-87) at 0% transepicondylar distance (23 MRIs), 41° (range, 24°-63°) at 50% transepicondylar distance (23 MRIs), and ≥ 10° at 75% transepicondylar distance (on the 13 MRIs that extended this far cephalad). The mean closest distance between the radial nerve and the underlying humeral cortex was 10 mm (range, 3-26 mm) at 0% transepicondylar distance and 7 mm (3-16 mm) at 50% transepicondylar distance. On the AP elbow radiograph, the height of the lateral supracondylar ridge, determined by a best-fit line drawn along the lateral cortex of the ridge, diverged from the most proximal extent of the ridge at a point located at 60% transepicondylar distance (range, 51%-76%). At the corresponding location on the axial MR image, the nerve was located anterolaterally with a mean radial nerve angle of 39° (range, 15°-61°) and a mean distance of 6 mm (range, 2-10 mm) from the underlying humerus.

CONCLUSIONS

Our data suggest that percutaneous direct lateral entry Kirschner wires and half-pins can be safely inserted in the distal humerus in children along the transepicondylar axis, either at or slightly posterior to the lateral supracondylar ridge, when placed caudal to the point located where the lateral supracondylar ridge line diverges from the proximal extent of the supracondylar ridge on AP elbow radiograph.

Upper extremity nerve entrapments: the axillary and radial nerves--clinical diagnosis and surgical treatment

BACKGROUND

Nontraumatic pain in the shoulder, arm, and hand (brachialgia) is a common complaint in the field of musculoskeletal disorders, where nerve entrapment constitutes a possible cause. The effect of nerve compression is dose-dependent; thus, a low-level compression will only result in decreased endoneurial circulation, neural edema, and a Seddon grade IV weakness, but will not be revealed in nerve conduction or magnetic resonance imaging studies. Because of technical limitations, several clinical options to diagnose compression neuropathies in the upper extremity have been proposed. These include blinded controlled studies on manual muscle testing to delineate the level of nerve compression, and the scratch collapse test to verify the level of compression. In this article, the authors describe the clinical examination and surgical techniques for diagnosing and treating entrapments of the axillary and radial nerves.

METHODS

A previously published clinical triad for diagnosis of nerve compressions has been used: (1) manual muscle testing to reveal weakness in specific muscles distal to the level of nerve compression; (2) pain on compression and/or positive Tinel sign; and (3) positive scratch collapse test at the level of nerve compression.

RESULTS

Detailed videos illustrate the examination techniques for diagnosing axillary entrapment in the shoulder and radial nerve entrapments in the upper arm and forearm (four levels), and the surgical techniques for each nerve release.

CONCLUSION

The clinical triad of muscle testing, scratch-collapse test, and pain at the level of nerve compression provides the clinician with a clinical foundation for analyzing patients with brachialgia in a structured fashion.

Course of the radial nerve in relation to the center of rotation of the elbow--the need for a rational safe zone for lateral pin placement

PURPOSE

To investigate the course and variability of the radial nerve along the lateral humerus in relation to the center of rotation of the elbow joint in the context of lateral pin placement for hinged external fixation.

METHODS

A total of 95 formalin-fixed upper extremities were dissected. The course of the radial nerve along the lateral aspect of the humerus was measured at 3 landmarks with respect to the center of rotation of the elbow. We analyzed the data and the landmark positions correlated with the length of the humerus.

RESULTS

The measured positions of 3 landmarks of the radial nerve in the lateral aspect of the humerus ranged from 19% to 43% of the length of the humerus and were located, on average, 6.0, 9.7, and 13.5 cm from the lateral center of rotation.

CONCLUSIONS

These data help predict the humeral course of the radial nerve and define a safe zone for pin implantation. However, because of variability in the course of the radial nerve, a safe zone cannot fully ensure prevention of iatrogenic injury to the nerve. The safest method of pin application remains mini-open dissection and visual implantation.

CLINICAL RELEVANCE

Based on this cadaveric study, it is not possible to define a rational safe zone. The safest method of pin application for dynamic external fixation of the elbow is to perform a mini-open dissection with direct visualization.

Modified combined approach for distal humerus shaft fracture: anterolateral and lateral bimodal approach

Background

Due to the anatomical nature of the radial nerve, dissection and attainment of an adequate operative field in mid to distal humerus fracture is dangerous and limited. We devised a combined anterolateral and lateral approach that ensures protection of the radial nerve. This is achieved by performing bimodal dissection of the proximal humerus anteriorly and the distal humerus laterally.

Methods

Thirty-five consecutive patients were treated using a combined anterolateral and lateral approach for a minimum follow-up period of 24 months. We analyzed time to bony union, time to return to daily work, range of motion, elbow joint function as assessed by the Mayo elbow performance index and complications.

Results

Radiologic bony union was observed at 11.2 weeks (range, 8 to 20 weeks) on average. Four cases of incomplete radial nerve palsy before surgery all recovered. Time to return to work was 10.2 weeks (range, 2 to 32 weeks) on average. The average range of motion of the elbow was 3.3° (range, 0° to 10°) of extension and 135.9° (range, 125° to 145°) of flexion. There were 21 cases of excellent and 13 cases of good or better recovery, comprising over 97.1% on the Mayo elbow performance index. There were no complications of radial nerve palsy, non-union, mal-union, or infection.

Conclusions

Our a modified combined anterolateral and lateral approach is a clinically effective surgical method of achieving protection of the radial nerve and securing easy and firm internal fixation.

Effect of elbow flexion on the proximity of the PIN during 2-incision distal biceps repair

The posterior interosseous nerve (PIN) is at risk for injury during surgical dissection for distal biceps repair, yet the optimal position of elbow flexion to avoid a PIN injury has never been established for the 2-incision approach. The purpose of this study was to determine the proximity of the PIN to the radial tuberosity during surgical dissection in different degrees of elbow flexion. Ten cadaveric specimens with an intact elbow and forearm were dissected in full pronation using a modified Boyd-Anderson approach. Half of the dissections were completed in 90° of flexion and the other half were completed in maximal flexion. To simulate the location of the PIN during a single-incision biceps repair, the distance of the PIN to the radial tuberosity was recorded in full extension and supination. Results from these measurements were assessed for differences using paired t tests, with differences deemed significant for P values less than .05. The PIN was not identified in any of the 2-incision surgical dissections. Based on these findings, the proximity of the PIN to the radial tuberosity is not significantly affected by the degree of elbow flexion in the muscle-splitting 2-incision approach. In addition, a safe zone exists for avoiding PIN injury in a single-incision technique for distal biceps repair because a drill bit exiting the radial tuberosity greater than 1 cm in a distal-radial direction would place the PIN at risk.

The supinator muscle: anatomical bases for deep branch of the radial nerve entrapment

PURPOSE

Our goals were to carry out an anatomical description of the internal architecture of the supinator muscle in order to describe potentially compressive structures for the deep branch of the radial nerve (DBRN) and to establish reference landmarks for the surgical treatment of radial tunnel syndrome.

METHODS

Thirty upper limbs were dissected. The pennation angle of proximal and distal arcades of the supinator to the radial shaft axis was measured. Possible compressive structures of both superficial and deep heads of supinator were recorded. Proximal and distal arcades of the superficial layer of the supinator were classified according to their fiber content as tendinous, musculo-tendinous, muscular or membranous. The distances of superficial layer of the supinator muscle to the humeroradial joint line and lateral epicondyle were measured.

RESULTS

Pennation angle was 33.6° (±4.2°) for the superficial layer and 50.2° (±6.6°) for the deep layer. The difference was statistically significant (p < 0.0001). The proximal arcade was purely tendinous in 20 cases (66.7 %). The distal arcade was mainly tendinous or musculo-tendinous (70 %). The average distance between the lateral epicondyle and the proximal arcade was 41.6 mm. We did not find any other potentially compressive structure within DBRN course between both layers.

CONCLUSION

Our anatomical results about pennation angle could be used as a basis for a thorough functional study about the supinator. Both proximal and distal arcades appeared as the two zones ables to compress the DBRN. Their localization should help the surgeon for the DBRN neurolysis.

Identification of the radial nerve during the posterior approach to the humerus: a cadaveric study

OBJECTIVE

Identification of the radial nerve is necessary during the posterior approach to the humerus in an effort to maintain its integrity. Other than anatomic descriptions of the radial nerve with respect to osseous structures, there are few superficial intraoperative landmarks along the course of the traditional triceps-splitting approach to provide facile nerve identification. The objective of this study was to determine the reliability of using the anatomic intersection of the long and lateral heads of the triceps and the triceps aponeurosis as a superficial reference point for radial nerve identification during the posterior approach to the humerus.

METHODS

Thirty adult human cadaver upper extremities as 15 matched pairs were used. Systematic identification and measurement from the point of intersection between the long and lateral heads of the triceps and the triceps aponeurosis to the distal most aspect of the radial nerve as it coursed the posterior humerus at its midaxial point was performed and recorded.

RESULTS

Mean distance was found to measure 39.0 ± 2.1 mm (range, 36-44 mm), approximating a fixed distance, two finger breadths proximal to our identified point of intersection. Statistical analysis between the two matched pair groups yielded no significant difference in measured distances (P = 0.88).

CONCLUSIONS

Our group has identified the point of intersection among three landmarks forming a point of intersection. This point is the confluence of the long and lateral heads of the triceps and the triceps aponeurosis. This serves as a visualized anatomic reference point during the posterior surgical exposure to the humerus and can be used to identify the radial nerve as it courses the posterior humerus.

A method to localize the radial nerve using the 'apex of triceps aponeurosis' as a landmark

BACKGROUND

The relationship of the radial nerve is described with various osseous landmarks, but such relationships may be disturbed in the setting of humerus shaft fractures. Alternative landmarks would be helpful to more consistently and reliably allow the surgeon to locate the radial nerve during the posterior approach to the arm.

QUESTIONS/PURPOSES

We investigated the relationship of the radial nerve with the apex of triceps aponeurosis, and describe a technique to locate the nerve.

MATERIALS AND METHODS

We performed dissections of 10 cadavers and gathered surgical details of 60 patients (30 patients and 30 control patients) during the posterior approach of the humerus. We measured the distance of the radial nerve from the apex of the triceps aponeurosis along the long axis of the humerus in cadaveric dissections and patients. This distance was correlated with the height and arm length. For all patients, we recorded time until first observation of the radial nerve, blood loss, and postoperative radial nerve function.

RESULTS

The mean distance of the radial nerve from the apex of the triceps aponeurosis was 2.5 cm, which correlated with the patients' height and arm length. The mean time until the first observation of the radial nerve from beginning the skin incision was 6 minutes, as compared with 16 minutes in the control group. Mean blood loss was 188 mL and 237 mL, respectively. With the numbers available, we observed no difference in the incidence of patients with postoperative nerve palsy: none in the study group and three in the control group.

CONCLUSION

The apex of the triceps aponeurosis appears to be a useful anatomic landmark for localization of the radial nerve during the posterior approach to the humerus.

Innervation of the supinator muscle and its relationship to two-incision distal biceps tendon repair: an anatomic study

Reinsertion of the ruptured distal biceps tendon has been performed using either a single-anterior incision or a two-incision approach. A systematic review of these two repair methods has identified a higher incidence of supination weakness following the two-incision approach. The objective of this study was to describe the innervation of the supinator muscle and its implications regarding a two-incision distal biceps repair. Twelve fresh upper extremity specimens from 12 males were dissected with the forearm in full pronation. The number of branches of the posterior interosseous nerve (PIN) to the supinator, their site of exit from the PIN trunk, and their distance from a variety of known anatomic landmarks were recorded. Specimens were characterized as high (<5 mm), moderate (6-10 mm), or low (>10 mm) risk of nerve branch injury depending on the proximity of nerve branches to the bicipital tuberosity. In general, we found the innervation of the supinator to be highly variable. There were from two to nine branches of the PIN which supplied the supinator, with 0-3 arising from the ulnar side of the nerve. Four specimens were at low, five at moderate, and three at high risk of nerve branch injury during dorsal exposure of the bicipital tuberosity. We conclude that there is a substantial amount of variability in the innervation of the supinator, with certain patterns being at higher risk of nerve branch injury if dissection of the supinator is carried out over the bicipital tuberosity.

The surgical anatomy of the radial nerve and the triceps aponeurosis

The radial nerve passes around the posterior aspect of the humerus where it is prone to injury in both humeral fractures and surgical exploration of this region. We examined 55 cadaveric limbs to determine whether the exact position of the radial nerve could be reliably predicted on the basis of superficial anatomical markings. We found that when there is considerable variability in the position of the nerve in relation to the lateral epicondyle, the nerve consistently passed adjacent to the lateral border of the triceps aponeurosis at a distance of 22-27 (+/-2) mm. It was never found to be closer than 13 (+/-1) mm to the aponeurosis. The lateral border of the triceps aponeurosis is easy to identify and our findings may help avoid iatrogenic injury to the radial nerve during exploration.