The distribution of brachial plexus lesions after experimental traction: a cadaveric study

Anatomical damages in the spinal nerve roots and the spinal cord after brachial plexus injury: descriptive study from a cohort of consecutive patients who underwent DREZ-lesioning for pain-practical implications

BACKGROUND

Systematic descriptions of anatomical damage after brachial plexus injury (BPI) at the intradural level have been scarcely reported in detail. However, considering these damages, not only in the spinal nerve roots but also in the spinal cord itself, is crucial in determining the appropriate surgical approach to restore upper limb function and address refractory pain. Therefore, the authors present a descriptive study focusing on intradural findings observed during microsurgical DREZ-lesioning.

METHODS

This study enrolled 19 consecutive patients under the same protocol. Microsurgical observation through exposure of C4 to Th1 medullary segments allowed to describe the lesions in spinal nerve roots, meninges, and spinal cord. Electrical stimulation of the ventral roots checked the muscle responses.

RESULTS

Extensive damage was observed among the 114 explored roots (six roots per patient), with only 21 (18.4%) ventral (VR) and 17 (14.9%) dorsal (DR) roots retaining all rootlets intact. Damage distribution varied, with the most frequent impairments in C6 VRs (18 patients) and the least in Th1 VRs (14 patients), while in all the 19 patients for the C6 DRs (the most frequently impaired) and in 14 patients for Th1 DRs (the less impaired). C4 roots were found damaged in 12 patients. Total or partial avulsions affected 63.3% and 69.8% of DRs and VRs, respectively, while 15.8% and 14.0% of the 114 DRs and VRs were atrophic, maintaining muscle responses to stimulation in half of those VRs. Pseudomeningoceles were present in 11 patients but absent in 46% of avulsed roots. Adhesive arachnoiditis was noted in 12 patients, and dorsal horn parenchymal alterations in 10.

CONCLUSIONS

Knowledge of intradural lesions post-BPI helps in guiding surgical indications for repair and functional neurosurgery for pain control.

Prescriptive and proscriptive lessons for managing shoulder dystocia: a technical and videographical tutorial

This tutorial of the intrapartum management of shoulder dystocia uses drawings and videos of simulated and actual deliveries to illustrate the biomechanical principles of specialized delivery maneuvers and examine missteps associated with brachial plexus injury. It is intended to complement haptic, mannequin-based simulation training. Demonstrative explication of each maneuver is accompanied by specific examples of what not to do. Positive (prescriptive) instruction prioritizes early use of direct fetal manipulation and stresses the importance of determining the alignment of the fetal shoulders by direct palpation, and that the biacromial width should be manually adjusted to an oblique orientation within the pelvis-before application of traction to the fetal head, the biacromial width is manually adjusted to an oblique orientation within the pelvis. Negative (proscriptive) instructions includes the following: to avoid more than usual and/or laterally directed traction, to use episiotomy only as a means to gain access to the posterior shoulder and arm, and to use a 2-step procedure in which a 60-second hands-off period ("do not do anything") is inserted between the emergence of the head and any initial attempts at downward traction to allow for spontaneous rotation of the fetal shoulders. The tutorial presents a stepwise approach focused on the delivering clinician's tasks while including the role of assistive techniques, including McRoberts, Gaskin, and Sims positioning, suprapubic pressure, and episiotomy. Video footage of actual deliveries involving shoulder dystocia and permanent brachial plexus injury demonstrates ambiguities in making the diagnosis of shoulder dystocia, risks of improper traction and torsion of the head, and overreliance on repeating maneuvers that prove initially unsuccessful.

Effect of Scapular Fixation on Lateral Movement and Scapular Rotation during Glenohumeral Lateral Distraction Mobilisation

BACKGROUND

Glenohumeral lateral distraction mobilisation (GLDM) is used in patients with shoulder mobility dysfunction. No one has examined the effect of scapular fixation during GLDM. The aim was to measure and compare the lateral movement of the humeral head and the rotational movement of the scapula when three different magnitudes of forces were applied during GLDM, with and without scapular fixation.

METHODS

Seventeen volunteers were recruited (n = 25 shoulders). Three magnitudes of GLDM force (low, medium, and high) were applied under fixation and non-fixation scapular conditions in the open-packed position. Lateral movement of the humeral head was assessed with ultrasound, and a universal goniometer assessed scapular rotation.

RESULTS

The most significant increase in the distance between the coracoid and the humeral head occurred in the scapular fixation condition at all three high-force magnitudes (3.72 mm; p < 0.001). More significant scapular rotation was observed in the non-scapular fixation condition (12.71°). A difference in scapula rotation (10.1°) was observed between scapular fixation and non-scapular fixation during high-force application.

CONCLUSIONS

Scapular fixation resulted in more significant lateral movement of the humeral head than in the non-scapular fixation condition during three intensities of GLDM forces. The scapular position did not change during GLDM with the scapular fixation condition.

Two clinical tests assessing long thoracic nerve function to determine C5 and C6 root graft eligibility in patients with brachial plexus injury

OBJECTIVE

Identifying roots available for grafting is of paramount importance prior to reconstructing complex injuries involving the brachial plexus. This is traditionally achieved by combining input from both clinical examinations and imaging studies. In this paper, the authors describe and evaluate two new clinical tests to study long thoracic nerve function and, consequently, to predict the status of the C5 and C6 roots after global brachial plexus injuries.

METHODS

From March 2020 to December 2020, in 41 patients undergoing brachial plexus repair, preoperative clinical assessments were performed using modified C5 and C6 protraction tests, C5 and C6 Tinel's signs, and MRI findings to predict whether graft-eligible C5 and C6 roots would be identified intraoperatively. Findings from these three assessments were then combined in a logistic regression model to predict graft eligibility, with overall predictive accuracies calculated as areas under receiver operating characteristic curves.

RESULTS

In the 41 patients, the pretest probability of C5 root availability for grafting was 85% but increased to 92% with a positive C5 protraction test and to 100% when that finding was combined with a positive C5 Tinel's sign and favorable MRI findings. The pretest probability of C6 root availability was 40%, which increased to 84% after a positive C6 protraction test and to 93% when the protraction test result concurred with Tinel's test and MRI findings.

CONCLUSIONS

Combining observations of the protraction tests with Tinel's sign and MRI findings accurately predicts C5 and C6 root graft eligibility.

Effects of Prestretch on Neonatal Peripheral Nerve: An In Vitro Study

Background  Characterizing the biomechanical failure responses of neonatal peripheral nerves is critical in understanding stretch-related peripheral nerve injury mechanisms in neonates. Objective  This in vitro study investigated the effects of prestretch magnitude and duration on the biomechanical failure behavior of neonatal piglet brachial plexus (BP) and tibial nerves. Methods  BP and tibial nerves from 32 neonatal piglets were harvested and prestretched to 0, 10, or 20% strain for 90 or 300 seconds. These prestretched samples were then subjected to tensile loading until failure. Failure stress and strain were calculated from the obtained load-displacement data. Results  Prestretch magnitude significantly affected failure stress but not the failure strain. BP nerves prestretched to 10 or 20% strain, exhibiting significantly lower failure stress than those prestretched to 0% strain for both prestretch durations (90 and 300 seconds). Likewise, tibial nerves prestretched to 10 or 20% strain for 300 seconds, exhibiting significantly lower failure stress than the 0% prestretch group. An effect of prestretch duration on failure stress was also observed in the BP nerves when subjected to 20% prestretch strain such that the failure stress was significantly lower for 300 seconds group than 90 seconds group. No significant differences in the failure strains were observed. When comparing BP and tibial nerve failure responses, significantly higher failure stress was reported in tibial nerve prestretched to 20% strain for 300 seconds than BP nerve. Conclusion  These data suggest that neonatal peripheral nerves exhibit lower injury thresholds with increasing prestretch magnitude and duration while exhibiting regional differences.

The Effect of Scapular Fixation on Scapular and Humeral Head Movements during Glenohumeral Axial Distraction Mobilization

Background and Objectives: Glenohumeral axial distraction mobilization (GADM) is a usual mobilization technique for patients with shoulder dysfunctions. The effect of scapular fixation on the movement of the scapula and the humeral head during GADM is unknown. To analyze the caudal movement of the humeral head and the rotatory movement of the scapula when applying three different intensities of GADM force with or without scapular fixation. Materials and Methods: Fifteen healthy subjects (mean age 28 ± 9 years; 73.3% male) participated in the study (twenty-eight upper limbs). Low-, medium- and high-force GADM in open-packed position were applied in scapular fixation and non-fixation conditions. The caudal movement of humeral head was evaluated by ultrasound measurements. The scapular rotatory movement was assessed with a universal goniometer. The magnitude of force applied during GADM and the region (glenohumeral joint, shoulder girdle, neck or nowhere) where subjects felt the effect of GADM mobilization were also recorded. Results: A greater caudal movement of the humeral head was observed in the non-scapular fixation condition at the three grades of GADM (p < 0.008). The rotatory movement of the scapula in the scapular fixation condition was practically insignificant (0.05−0.75°). The high-force GADM rotated scapula 18.6° in non-scapular fixation condition. Subjects reported a greater feeling of effect of the techniques in the glenohumeral joint with scapular fixation compared with non-scapular fixation. Conclusions: The caudal movement of the humeral head and the scapular movement were significantly greater in non-scapular fixation condition than in scapular fixation condition for the three magnitudes of GADM force.

A Systematic Review of the Tensile Biomechanical Properties of the Neonatal Brachial Plexus

Brachial plexus (BP) birth injury has a reported incidence of 1 to 4 per 1000 live births. During complicated deliveries, neonatal, maternal, and other birth-related factors can cause over-stretching or avulsion of the neonatal brachial plexus leading to injury. Understanding biomechanical responses of the neonate brachial plexus when subjected to stretch can offer insight into the injury outcomes while guiding the development of preventative maneuvers that can help reduce the occurrence of neonatal brachial plexus injuries. This review article aims to offer a comprehensive overview of existing literature reporting biomechanical responses of the brachial plexus, in both adults and neonates, when subjected to stretch. Despite the discrepancies in the reported biomechanical properties of the brachial plexus, available studies confirm the loading rate and loading direction dependency of the brachial plexus tissue. Future studies, possibly in vivo, that utilize clinically relevant neonatal large animal models can provide translational failure values of the biomechanical parameters for the neonatal brachial plexus when subjected to stretch.

C5 Palsy After Cervical Spine Decompression: Topographic Correlation With C6 Chassaignac Tubercle?: A Fresh-Cadaveric Study of the Cervical Spine and Rediscussion of Etiological Hypotheses

STUDY DESIGN

Cadaveric study on fresh unprocessed, nonpreserved, undyed specimens, which has not previously been reported.

OBJECTIVE

Our aim was to explore the possible topographic correlation of the C5 nerve root with regards to its course and regional relation to C6 Chassaignac tubercle.

SUMMARY OF BACKGROUND DATA

C5 palsy is reported amongst the most frequent postoperative complications of cervical spinal procedures. We hypothesized that etiologic mechanisms proposed thus far in the current literature, although with some plausible explanation, still cannot explain why the C5 nerve root and not any other level suffer a postoperative palsy.

METHODS

Six fresh cadavers had extensive layer by layer dissection performed by two surgeons (one of whom has experience as an anatomy demonstrator and dissector). Roots of brachial plexus were exposed in relation to cervical transverse processes. Photographs were taken at each stage of the exposure.

RESULTS

We observed a close relation of the path of the C5 nerve root with the C6 tubercle bilaterally. Moreover, we noted a steeper descent of C5 in comparison with the other adjacent roots.

CONCLUSION

Steeper angle of the C5 nerve root and close proximity to C6 Chassaignac tubercle may play a role in predisposing it to neuropraxia. Detailed anatomical photographs on fresh unprocessed cadaveric specimens are novel. Peculiar anatomical features and recent experimental evidence discussed do highlight a postganglionic extraforaminal etiology corresponding well to the demographic meta-analysis data on clinical features of postoperative C5 palsy. Exploring an alternative unified "neurophysiologic stress and critical tipping point" etiological model that encompasses current theories and correlates known metanalyses observations, we believe further studies would be prudent to ascertain/refute these findings.

LEVEL OF EVIDENCE

3.

Intraoperative Shoulder Traction as Cause of C5 Palsy: Magnetic Resonance Imaging Study

OBJECTIVE

During surgery, shoulder traction is often used for better fluoroscopic imaging of the lower cervical spine. Traction on the C5 root has been implicated as a potential cause of C5 palsy after cervical spine surgery. Using magnetic resonance imaging, this study was undertaken to determine the impact of upper extremity traction on the C5 root orientation.

METHODS

In this study, 5 subjects underwent coronal magnetic resonance imaging of the cervical spine and left brachial plexus. Using a wrist restraint, sequential traction on the left arm with 10, 20, and 30 lb. was applied. Measurements of the angle between the spinal axis and C5 nerve root and the angle between the C5 nerve root and the upper trunk of the brachial plexus were obtained. The measurements were taken by a trained neuroradiologist and analyzed for significance.

RESULTS

The angle between the C5 nerve root and the vertical spinal axis remained within 3 and 4 degrees of the mean and was not found to be associated with increased traction weight (P = 0.753). The angle between the C5 root and the upper trunk increased with increasing weight and was found to be statistically significant (P = 0.003).

CONCLUSIONS

While the cause of C5 palsy is likely multifactorial, this study provides evidence that, in the awake volunteer, upper extremity traction leads to C5 root and upper trunk tension. These results suggest that shoulder traction in the anesthetized patient could lead to tension of the C5 nerve root and subsequent injury and palsy.

Contralateral C7 transfer to lower trunk via a subcutaneous tunnel across the anterior surface of the chest and neck for total brachial plexus root avulsion: a cadaveric study

BACKGROUND

Restoration of hand function after total brachial plexus root avulsion (tBPRA) is a difficult problem in surgical management. A new modified approach in repairing tBPRA is to use a subcutaneous tunnel across the anterior surface of the chest and neck, and then transfer the contralateral C7 root (cC7) to the lower trunk. However, the anatomical details of this method have not yet been fully described and assessed. The objective of this study was to quantitatively describe the nerve transfer using a cadaveric surgical simulation.

MATERIALS AND METHODS

Brachial plexuses were dissected from 12 adult cadavers, producing 24 sides of brachial plexuses for nerve transfer experiments. We performed simulated cC7 transfers to the lower trunk via a subcutaneous tunnel across the anterior surface of the chest and neck. Measurements of the nerves were made and transfers quantitatively documented.

RESULTS

With the affected shoulder and arm in a neutral position, cC7 and C8-T1 could be sutured directly together in 75% of the cadavers. A nerve graft length of 4.6 ± 1.18 cm was needed to bridge the gap in the remaining cadavers. For cadavers where distal cC7 was directly connected with the lower trunk, 54.17% could be sutured, and an average nerve graft length of 3.9 cm was needed in the remains.

CONCLUSIONS

For surgical management of total tBPRA, transfer of the cC7 nerve to the C8-T1 or lower trunk via a subcutaneous tunnel across the chest and neck will likely be superior to a conventional cC7 root transfer in the clinic. This approach shortens the nerve graft needed and nerve regeneration distance, decreases the number of neurorrhaphy sites, and makes full use of the donor nerves, which may benefit hand flexion restoration.