Aetiology Of Closed Radial Nerve Injury

Mononeuropathies of the Radial Nerve take places in multiple sites, and the mechanism of injury is various and complicated. This paper intends to retrospectively analyzed a large sample of cases with the purpose to sum up common clinical causes and injury sites of CNORN to provide a basis to the diagnosis of this disease.We studied the cases diagnosed with Closed Mononeuropathy of the Radial Nerve and treated in our hospital from December 1997 to December 2007,while ruling out open injury cases. Patients with a total number of 30 cases were flowed up and was analysed according to radial nerve function evaluation trial standards of Chinese Medical Association of Hand Surgery Institute. We arranged excellent, fine, and good as effective while poor as ineffective.Anterolateral incision was applied in radial nerve injury located in upper arm, anterolateral incision in elbow and dorsal forearm incision in forearm to expose the nerve and anatomical injury causes.Finally 42 cases consistent with the selection criteria, of which 16 cases were completely radial nerve palsy, accounting for 38.1 %, 26 cases were incomplete radial nerve palsy, accounting for 61.9 %. Trauma is still the most common cause, responsible for45.2 % of the cases, of which the most common is the humeral fractures. In juvenile Monteggia fracture is the main factor causing radial nerve injury. There are all 5 cases under the age of 18, 4 cases caused by Monteggia fractureand one caused by oppression in fixed posture sleep. There are 8 cases of primary nerve injury accounting for 19.6% of all cases. All eight cases of iatrogenic injury were secondary to the humerus fracture fixation or external fixation and transferred from the grassroots medical units.Previous reports indicated that the neural groove is the most common site radial nerve injury takes place, mainly secondary to the humeral fractures. In our statistic radial nerve injury in this site rates 57.1%. vulnerability of radial nerve injury in this position is relevant to the two following factors, first, the radial nerve in the neural groove coursed a long distance along humerus closely; Second radial is fixed solid by the surrounding muscle tendon when penetrating the lateral muscul compartment. The distance that radial nerve accompanied the humerus arange from 2.2 cm-12.0 cm; about more than 70 % in the crowd the lateral head of triceps forms fiber arch, under which the radial nerve courses. Due to fixation by the fibers in lateral muscul compartment & this arch and constraint of the humeral, radial nerve is of little mobility. So exogenous traction will make the nerve suffer from a greate tensile force. So the radial nerve is most vulnerable in the middle 1/3 humeral shaft and distal 1/3 humeral shaft of fractures or external compression. Timely neurolysis and adjustments operation had a good effect. Many scholars believe that the safer approach is the posterior approach for humeral fractures on the middle 1/3 and distal 1/3. currently AO system plates used to fix humeral are all longer than the length of the radial nerve parallel to humerus, so radial nerve compression or traction injury are prone to happen. Our Statistics show 2 cases whose radial nerve fractured due to direct compress by plate or screw, which leads to totally radial nerve palsy. Therefore, carefully marking acromion, medial epicondyle, lateral epicondyle trip of radial nerve before surgery, estimating whether built-in plate is located in the course of nereve, revealing radial nerve clearly and a slight shift of nerve help to avoid the occurrence of iatrogenic injury.After penetrating the lateral muscul compartment the radial nerve Travels superficially, gradually courses from lateral side to anterior side , where the nerve formed a Obtuse-Angle opening towards medial side. And due to fixation in the lateral muscul compartment, the radial has minimum rotation. So a placeholder such as malreduction, internal fixation plates and other abnormal bone callus will cause Obtuse-Angle up, shift of nerve or change in course which lead to radial nerve bearing greater traction force or compression of the nerve. Our statistics show five cases in which radial nerve accompanying the plate, and three cases in which radial nerve was embedded in the bone callus entrapment. Direct contacts with foreign bodies or bone callus entrapment and a greater tension in nerve track, eventually led to the delayed radial nerve injury in these cases. Remove the plate, remove bone callus or a reasonable adjustment to the radial nerve in the above-mentioned cases all had a good therapeutic effect.Elbow is the second most important position where radial nerve injury takes place, accounding for 33.3%. The concept of radial tunnel has been widely accepted. MRINALINI KONJENGBA's study shows that in about 60% of the crowd Frohse arch is of tendon structure, in about 30% is of membrane structure and in the vast majority of the subjects superficial lamella of musculus supinator is tendon organizations; most superficial medial head of musculus extensor carpi radialis brevis is comprised of tendon tissue. If the forearm completely pronation, these structures can produce compression on the nerve. Occupational overuse, chronic repetitive irritation precipitated by alternating pronation and supination, acute injury with compression and pathology involving the structures of the radial tunnel etc may change the normal nature of the anatomic entities along the radial tunnel into causative factors for entrapment neuropathy of the DBRN or posterior in terosseous nerve at the proximal forearm. Our statistics show 8 cases of this kind. There are 5 radial nerve fracture cases caused by compression of fiber tissue, among which there were obvious constrictions on the nerve. There are 3 cases caused by capitulum radii forward dislocation, in which condition the shearing force produced by the dislocated capitulum radii and Frohse archreset lead to PIN injury finally. After reduction and strengthening articulatio cubiti, the patients all gained a good recovery. Ganglion cyst is a common cause for the damage, the cyst lies dorsal of the deep branch, which will press the deep branch towards the palm side, make deep branch of the radial nerve and the sharp edge of Frohse arch to contact directly, and after repeated friction, fracture will take place.However, there are still some spontaneous radial nerve injury of which the mechanism is not entirely clear. Our statistics show 3 cases in whom exploration revealed not obvious exogenous radial nerve compression and more than two funnel-like constrictions where no nerve fibers were detected when explored, the distance between constrictions varied from 4cm to 6 cm. Pan Yongwei and Fujio Umehara also reported several similar cases, and histologic anatomy shows that the outer membrane of nerve was infiltrated with inflammatory cells, their inference is that local limited nerve inflammation of the nerve membrane caused such lesions. This specific pathogenesis of these diseas need to be further clarifiedThomas W. Wright's studie show that when the elbow rotate from 15 degrees radial side to 90 degrees ulnar side, the radial nerve in elbow experienced an average 8.8 mm displacement. And congenital anatomical structures in the elbow limit the radial nerve movement, so when the upper extremity especially articulatio cubiti and wrist joints need repetitive activities, these anatomical structures become causative factors for entrapment neuropathy. This clarifies why the workers comprise most of non-traumatic CMORV cases.Radial nerve disease is not the most common upper extremity peripheral nerve disease, but the diagnosis and treatment of CMORN is more difficult due to the following reasons. First the etiological factors of CMORN is more complex, we found humeral fractures, radial head anterior dislocation (common in Monteggia fracture), spontaneous radial nerve injury, pressure of surrounding tissues, iatrogenic injury, external crush injury, endogenous foreign body entrapment are all common causes. Second the radial nerve injury sites are rather scattered, along the humerus, in radial tunnel and in radial tunnel in the elbow, the incidence of CMORN does not vary much. Furthermore currently there are some of the CMORN pathogenesis is not clear, which mainly includes Primary radial nerve injury. So only if the causes of CMORN is clarified, diagnosis and treatment can be made earlier and the patients can resume best.