Safe Zone for Superolateral Entry Pin Into the Distal Humerus in Children: An MRI Analysis (original) (raw)
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PLOS ONE
Iatrogenic nerve injury during fracture surgery of the upper arm is a well-known complication. Prevention of this type of injuries would be of great value. The literature describes several methods to reduce this type of injury, but no perfect solution is at hand. In this study we introduce a new radiographic evaluation of the course and variation of the radial nerve in the distal part of the humerus in relation to bony landmarks as observed on a plain (trauma) radiographs. Aim of this new approach is to reduce the chance of iatrogenic nerve injury by defining of a danger zone in the distal upper arm regarding the radial nerve and hence give an advise for future implant fabrication. Methods and findings Measurements were done on both arms of ten specially embalmed specimens. Arms were dissected and radiopaque wires attached to the radial nerve in the distal part of the upper arm. Digital radiographs were obtained to determine the course of the radial nerve in the distal 20 cm of the humerus in relation to bony landmarks; medial epicondyle and capitellumtrochlea projection (CCT). Analysis was done with ImageJ and Microsoft Excel software. We also compared humeral nail specifications from different companies with the course of the radial nerve to predict possible radial nerve damage. Results The distance from the medial epicondyle to point where the radial nerve bends from posterior to lateral was 142 mm on AP radiographs and 152 mm measured on the lateral radiographs. The average distance from the medial epicondyle to point where the radial nerve bends from lateral to anterior on AP radiographs was 66 mm. On the lateral radiographs where the nerve moves away from the anterior cortex 83 mm to the center of capitellum and
Clinical Anatomy, 2009
The percutaneous placement of lateral distal humeral pins risks injury to the radial nerve. We aimed to provide a reliable and safe parameter for the insertion of lateral distal humeral pins. A secondary aim of this study was to investigate the effect of pin/screw placement in the intended zone of fixation at the lateral distal humerus. We dissected 70 fresh cadaveric upper limbs and the radial nerve was identified and its course followed into the anterior compartment. The point where the radial nerve crosses humerus in mid lateral plane was identified and the distance between this point and lateral epicondyle was measured, as was the maximum trans-epicondylar distance, along with the olecranon fossa height. Statistical analysis was performed using the Pearson correlation coefficient. The average trans-epicondylar distance was measured at 62 ± 6 mm (range 52–78 mm), and the average lateral radial nerve height was 102 ± 10 mm (range 75–129 mm). The ratio of the lateral nerve height to the trans-epicondylar distance was an average of 1.7 ± 0.2 (range 1.4–2.0). The Pearson correlation coefficient between the lateral nerve height and the trans-epicondylar distance was r = 0.95. A relative dimension, the trans-epicondylar distance is both reliable and easily accessible to the operating surgeon. The absolute safe zone for pin entry into the lateral distal humerus is that area lying within the caudad 70% of a line, equivalent in length to the patient's own trans-epicondylar distance, when projected proximally from the lateral epicondyle. Clin. Anat. 22:684–688, 2009. © 2009 Wiley-Liss, Inc.
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
Journal of Bone and Joint Surgery, 2019
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. A confident surgeon has an intimate understanding of applied anatomy and an excellent knowledge of anatomic relationships. Avoiding iatrogenic injury is critically important. Hence, various publications have described "safe zones" and reference distances from anatomic landmarks 1. These points of reference help surgeons anticipate the positions of critical structures such as nerves before they are encountered, thereby reducing the chance of iatrogenic injury 2-4. The surgical anatomy of peripheral nerves in the upper extremity has been well described in adults 5. Fleming et al. described the "one-third, two-thirds rule" to reliably identify the radial nerve as it crosses from the posterior to the anterior compartment of the upper arm 6. Uhl et al. established the 13-cm rule to avoid iatrogenic radial nerve injury when approaching the humerus posteriorly 7. Cetik et al. elucidated a "safe zone" for the axillary nerve when approaching the proximal part of the humerus through a deltoid-split approach 8. These rules simplify complex anatomy and can be easily committed to memory to avoid iatrogenic nerve injury and increase patient safety 9 .
JOURNAL OF CLINICAL AND DIAGNOSTIC RESEARCH, 2018
Introduction: Identification of the radial nerve and preventing injury to it is crucial, while surgically approaching the humerus from the posterior aspect to treat fractures of the midshaft or the distal third of the bone. Aim: To identify certain anatomic landmarks, using which the radial nerve could be identified during surgical intervention, in order to prevent iatrogenic injury to the nerve. Materials and Methods: Twenty-eight arms belonging to 14 adult cadavers (10 male and 4 female) were used for this study. The distance between the radial nerve on the posterior humerus and the point of confluence of the long and lateral heads of the triceps with the triceps aponeurosis was measured. Statistical analysis using Student's paired t-test was done between the right and left sides. In the distal third of the humerus, the distance of the radial nerve and the lateral border of the triceps aponeurosis at four sites were determined. Results: The mean distance from the point of confluence to the radial nerve along the posterior humerus was 39.7±11.8 mm. The radial nerve passed adjacent to the lateral border of the triceps aponeurosis at a distance of 12-19.5 (±3.27) mm. It was never found to be closer than 4.6±2.54 mm to the aponeurosis. Conclusion: The present study is useful for orthopaedicians while undertaking the surgical management of humeral fractures. The point of confluence and the triceps aponeurosis are two anatomic landmarks that can be used to locate the radial nerve.
JSES international, 2022
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. A confident surgeon has an intimate understanding of applied anatomy and an excellent knowledge of anatomic relationships. Avoiding iatrogenic injury is critically important. Hence, various publications have described "safe zones" and reference distances from anatomic landmarks 1. These points of reference help surgeons anticipate the positions of critical structures such as nerves before they are encountered, thereby reducing the chance of iatrogenic injury 2-4. The surgical anatomy of peripheral nerves in the upper extremity has been well described in adults 5. Fleming et al. described the "one-third, two-thirds rule" to reliably identify the radial nerve as it crosses from the posterior to the anterior compartment of the upper arm 6. Uhl et al. established the 13-cm rule to avoid iatrogenic radial nerve injury when approaching the humerus posteriorly 7. Cetik et al. elucidated a "safe zone" for the axillary nerve when approaching the proximal part of the humerus through a deltoid-split approach 8. These rules simplify complex anatomy and can be easily committed to memory to avoid iatrogenic nerve injury and increase patient safety 9 .
JAAOS: Global Research and Reviews, 2019
Introduction: The purpose of this study was to investigate whether a safe zone rule could be applied to prevent iatrogenic injuries to the radial nerve (RN); and determine whether there is a relationship between the diameter of the radial head and capitellum and the distance of the posterior interosseous nerve (PIN) to the radiocapitellar joint. Methods: Ten fresh-frozen cadaveric specimens were used to measure the distances between the RN and the lateral epicondyle; the PIN and the radiocapitellar joint; the lateral epicondyle and the PIN as it crossed the ulnohumeral joint; the diameter of the radial head; the width of the capitellum; and the fingerbreadths of the specimens. Results: Four fingerbreadths determined a safe zone between the lateral epicondyle and the RN proximally at the point at which it pierced the intermuscular septum and the mid-lateral portion of the humeral shaft. Two fingerbreadths provided a safe zone for the PIN from the radiocapitellar joint to the midpoint of the axis of the radius only with the forearm in pronation. Conclusion: A four-finger rule, two-finger rule, and radial head diameter or capitellum size may predict a safe zone for the RN and PIN except for the segment of the nerve where it crosses the anterior cortex of either the humerus or radius.