Supinator Motor Branch Transfer To The Posterior Interosseous Nerve In C7-T1Brachial Plexus Palsies:the Experimental And Clinical Study

Part one The feasibility of transferring supinator motor branch to the posterior interosseous nerve in C7-T1brachial plexus palsiesExperiment one Spinal nerve origins of the muscular branches of the radial nerve:an electrophysiological studyObjective To determine the spinal nerve origins of the muscular branches of the radial nerve and to identify potential intraplexus donor nerves for neurotization of the posterior interosseous nerve in patients with lower brachial plexus injuries.Methods An intraoperative electrophysiological study was carried out during16contralateral C7nerve transfers using the Esaote Reporter4-channel electrophysiological apparatus (Esaote Biomedica, Italy). The CMAP(compound muscle action potential) of each muscle innervated by the radial nerve was recorded while the C5-T1nerves were individually stimulated.Results The triceps brachii muscle primarily received root contributions from C7. The C5and C6nerve roots displayed greater amplitudes for the brachioradialis and supinator muscles compared with those of the C7, C8and T1nerve roots (P<0.05) and there was no significant difference between C5and C6nerve roots (P>0.05). The extensor carpi radialis branch was innervated by C5, C6and C7, and no significant differences were detected between them (P>0.05). The amplitudes obtained for the extensor digitorum communis branch were the largest from C7and C8(P<0.05), without significant difference between them (P>0.05), while the amplitudes of the extensor carpi ulnaris and extensor pollicis longus were largest from the C8root (P<0.05).Conclusion Brachioradialis, extensor carpi radialis and supinator muscles received nerve fibers from C5and C6. Theoretically, these muscle branches can be used to repair damage to the posterior interosseous nerve in C7-T1palsies. Experiment two Surgical anatomy of the radial nerve at the elbow and in the forearmObjective To provide anatomical evidence of transferring the muscular branch of radial nerve to the posterior interosseous nerve in C7-T1brachial plexus palsies through the surgical anatomy of the radial nerve at the elbow and in the forearm.Methods The radial nerves were dissected on13formalin-fixed upper extremities of adult human cadavers. The radial nerve was exposed in the spiral groove, and its course and branches were dissected in a proximal to distal fashion. Asisted by the operating loup, the microanatomy and measurement were done. The following parameters were evaluated:(1) The number, distance between emergence point to the lateral epicondyle and to the arcade of Frohse, length and diameter of the branches(branches to the brachioradialis, extensor carpi radialis longus, superficial sensory, extensor carpi radialis brevis and supinator).(2) The transverse diameter and vertical diameter of the posterior interosseous nerve.(3) The number, distance between the exit point of the posterior interosseous nerve from the supinator muscle and the entry point into the innervated muscle of the muscular branches(branches to the extensor digitorum communis, extensor digiti minimi, extensor carpi ulnaris, abductor pollicis longus, extensor pollicis brevis, extensor pollicis longus and extensor indicis). In six arms, the branches to the brachioradialis, extensor carpi radialis longus, the supinator deep head branch, supinator superficial head branch and the posterior interosseous nerve were removed and stained with H&E for histological study. The specimens were fixed in paraffin, cross-sectioned and stained with H&E. The feature of the nerves can be observed and photographed using a digital camera coupled with an optical microscope(Olympus). An image analysis software(IPP6.0) was used for myelinated fibers counting. Additionally, the technique of transfering the supinator motor branch to the posterior interosseous nerve was designed and tested on six upper extremities.Results (1) After the radial nerve pierced the lateral intermuscular septum at the distal third humerus, the branches to the brachioradialis, extensor carpi radialis longus and superficial sensory emerged from the radial nerve above the lateral epicondyle and the extensor carpi radialis brevis branch emerged below the lateral epicondyle in a proximal to distal fashion. In most specimens, there was only one branch to innervate the brachioradialis, extensor carpi radialis longus and the extensor carpi radialis brevis, respectively.(2) After the extensor carpi radialis brevis branch emerged from the radial nerve, one to three supinator branches arose from the posterior interosseous nerve proximal the arcade of Frohse to innervate the supinator muscle and usually there were one to two tiny branches innervating the supinator when the the posterior interosseous nerve traversed the muscle. We concluded five types of the supinator branches according to the number of the branches:Type Ⅰ (three branches7/13), Type Ⅲ (two branch2/13), Type Ⅲ(four branches2/13), Type Ⅳ(single branch1/13) and Type Ⅴ(five branches1/13).(3) After the posterior interosseous nerve exited from the supinator muscle, it divided into two groups of teminal branches to innervate the muscles of the posterior aspect of the forearm. The superficial group of branches emerged from the posterior interosseous nerve proximally and innervated the extensor digitorum communis, extensor digiti minimi and extensor carpi ulnaris in a proximal to distal fashion. The deep group of branches from the posterior interosseous nerve distally innervated the abductor pollicis longus, extensor pollicis brevis, extensor pollicis longus and extensor indicis orderly.(4) The numbers of the myelinated nerve fibers of the branches to brachioradialis, extensor carpi radialis longus, supinator deep head, supinator superficial head and the posterior interosseous nerve were224.17±95.89,161.83±59.05,201.5±72.67,182.67±44.89and1,472.17±428.94.(5) On all six upper extremities, after dividing the extra-tunnel branches to supinator at their muscle entry points, they could be transferred directly to the posterior interosseous nerve. There was no tension at the anastomotic stoma even with the passive activity of the elbow joint.Conclusion The branches to the brachioradialis, extensor carpi radialis longus and supinator can be transferred to the posterior interosseous nerve to restore thumb and finger extension in patients with C7-T1brchial plexus palsies, and the supinator branch is likely the best doner nerve, for no nerve graft, brief reinnervation delay, sufficient myelinated nerve fibers and no loss of supination with this transfer. Part two Supinator motor branch transfer to the posterior interosseous nerve in C7-T1brachial plexus palsies:the experimental study Experiment one Establishment of the model of supinator motor branch transfer to the posterior interosseous nerve in C7-T1brachial plexus palsies in the ratsObjective To establish the model of supinator motor branch transfer to the posterior interosseous nerve in C7-T1brachial plexus palsies in the rats.Methods (1) The radial nerves and muscular branches were dissected on10adult SD rats at the elbow and in the forearm. Asisted by the operating loup, the microanatomy and measurement were done to compare with those of the human being and the technique of transfering the supinator motor branch to the posterior interosseous nerve was designed and tested on the rats. Then, the supinator branch and the posterior interosseous nerve were removed and fixed in a solution of phosphate-buffered gluteraldehyde, cross-sectioned and stained with toluidine blue for histological study. The feature of the nerves can be observed and photographed using a digital camera coupled with an optical microscope(Olympus). An image analysis software(Leica FW4000) was used for myelinated fibers counting.(2) On10rats, the entire brachial plexus was exposed via a supraclavicular approach, and the C5-T1nerves were dissected to the intervertebral foramen. The supinator, extensor digitorum communis and extensor carpi ulnaris were exposed at the elbow and in the forearm. The CMAP(compound muscle action potential) of each muscle was recorded while the C5-T1nerves were individually stimulated using the Esaote Reporter4-channel electrophysiological apparatus to determine the spinal nerve origins of the supinator motor branch and the posterior interosseous nerve.(3) The models of C7-T1brachial plexus palsies were established in the10rats and were evaluated by the observation and nerve electrophysiology.Results (1) On the rats, after the extensor carpi radialis branch emerged from the radial nerve at the elbow, one supinator branche arose from the posterior interosseous nerve proximal the arcade of Frohse to innervate the supinator muscle. The numbers of the myelinated nerve fibers of the supinator motor branch and the posterior interosseous nerve were85±16.06and331.55±76.05, repectively. On all rats, after dividing the supinator branches at their muscle entry points, they could be transferred directly to the posterior interosseous nerve. There was no tension at the anastomotic stoma even with the passive activity of the elbow joint.(2) The amplitudes obtained for the supinator muscles were the largest from the upper trunk(P <0.05). We could detected CMAP for the supinator muscles in some rats when the middle trunk was stimulated, but there was no CMAP from the lower trunk. The lower trunk displayed greater amplitudes for the extensor digitorum communis and the extensor carpi ulnaris compared with those of middle trunk(P<0.05) and there was no CMAP detected from the upper trunk.(3) There was no significant difference of the amplitudes obtained for the supinator branches between the two sides on the rats four weeks postoperatively(P>0.05). No CMAP could detected for the extensor digitorum communis and the the extensor carpi ulnaris4weeks postoperatively.Conclusion (1) The anatomy of the radial nerve at the elbow and in the forearm on the rats was similar to that on the human being and the supinator motor branch matched the posterior interosseous nerve in terms of number of myelinated fibers. The technique of supinator motor branch transfer to the posterior interosseous nerve was conducted successfully in the rats.(2) Spinal nerve origins of the supinator motor branch and the posterior interosseous nerve in the rats is consistent with those in the human being.(3) Supinator motor branch transfer to the posterior interosseous nerve in the rats with C7-T1nerve root avulsion is a feasible and ideal model. Experiment two The outcome of supinator motor branch transfer to the posterior interosseous nerve in C7-T1brachial plexus palsies:the experimental studyObjective To evaluate the efficiency of supinator motor branch transfer to the posterior interosseous nerve in C7-T1brachial plexus palsies by the experiment on the rats.Methods One hundred and twenty adult SD rats were divided into three groups randomly. Group A was C7-T1nerve root avulsion without repairing. Group B was C7-T1nerve root avulsion with contralateral C7transfer to the lower trunk. Group C was C7-T1nerve root avulsion with supinator motor branch transfer to the posterior interosseous nerve. The ethology of the rats was observed in the1st,2nd,3rd,6th month postoperatively. The recovery rate of the latency and amplitude for the posterior interosseous nerve, the recovery rate of wet muscle weight and muscle fibers sectional area of the extensor digitorum communis and extensor carpi ulnaris, and the recovery rate of the myelinated nerve fibers and the sectional area of the posterior interosseous nerve were performed respectively.Results The rats of group A were not extending the finger constantly. We observed finger extension in group B61.6±5.66days afer surgery and in group C15.1±3.28days postoperatively. There was significant difference between the two groups. The restoration of finger extension in group C was better than that in group B in the first, second and third month afer surgery(P<0.05). In the6th month postoperatively, the recovery rate of the myelinated nerve fibers in group B was a little higher than that in group C, but there was no significant difference between the two groups(P>0.05). However, the other values of the rats in group B was inferior to those in group C and there was significant difference between the two groups(P<0.05).Conclusion The outcome of supinator motor branch transfer to the posterior interosseous nerve is better than that of contralateral C7transfer to the lower trunk in the rats with C7-T1nerve root avulsion, which provides experimental evidence for the clinical use of this innovative technique. Part three Supinator motor branch transfer to the posterior interosseous nerve in C7-T1brachial plexus palsies:the clinical studyObjective To design and apply a new technique of transferring the supinator motor branch to the posterior interosseous nerve in C7-T1brachial plexus palsies for finger extension and to evaluate the outcome.Methods Supinator motor branch transfer to the posterior interosseous nerve has been performed in4patients with C7-T1brachial plexus palsies and they underwent follow-up every3months postoperatively. The finger extension was observed and the measurements including the muscle power and nerve electrophysiology of the extensor digitorum communis, extensor pollicis longus and extensor carpi ulnaris were recorded.Results In all cases, the first sign of electrophysiological recovery, that is, nascent motor unit potential of extensor digitorum communis during voluntary contraction, appeared between3-6.5months, postoperatively. The finger extension appeared between5and9months in the4cases and the thumb extension between12and18months in the first3cases after surgery. The forearm supination was not affected in all cases. The electrophysiological and clinical outcome demonstrated promising improvement over time. The fourth patient was lost during the follow-up.Conclusion Supinator motor branch transfer to the posterior interosseous nerve can reliably restore thumb and finger extension in a timely fashion and should be considered as a new option in addressing C7-T1brachial plexus palsies.