The assessment and treatment of nerve dysfunction after trauma around the elbow remains a challenging and controversial topic. The anatomic positions of the radial, median, and ulnar nerves and their major branches make them vulnerable at several sites as they course the upper extremity.42 This explains the classic relationships between particular nerve injuries and fracture patterns such as radial nerve palsy with Holstein-Lewis distal 1/3 humeral shaft fractures,40 posterior interosseous nerve injury with Monteggia fracture-dislocations,4,10,13,21,78,80,82,85 ulnar nerve and/or anterior interosseous nerve injuries with elbow dislocations,6,15,44,45,52,59,98 median nerve and/or radial nerve injuries with supracondylar and medial epicondyle fractures in children,3,5,7,14,16,18,20,36,37,51,56,61,63,71,83,97 and ulnar nerve injury at the cubital tunnel.30,85,94 When recognized as a paralysis after elbow trauma, it is not always clear how severe the nerve injury may be, although most lower energy injuries are fully recoverable. Although the time frame to intervention remains controversial for specific injuries, long-standing dysfunction necessitates surgical exploration and either neurolysis, transposition, repair, and/or reconstruction with tendon transfers. Considerable controversy remains as to the need for early exploration in closed humeral shaft or supracondylar fractures and Monteggia fracture-dislocations in children, and the role of ulnar nerve transposition after elbow trauma.
CLASSIFICATION OF NERVE INJURIES
In 1943, Seddon74 published his classification of nerve injuries as a description of the degree of injury and the likelihood of spontaneous recovery. Neurapraxias in motor nerves involve dyesthesias and/or paralysis without loss of nerve sheath continuity and peripheral Wallerian degeneration. Recovery may take months but usually is complete. Axonotmesis involves internal nerve fiber damage with complete Wallerian degeneration. The neural tube (endoneurium) remains intact and can guide the regenerating nerve fibers to their target. Spontaneous functional recovery is expected. Neurotmesis describes the division of the nerve. Functional recovery without surgical intervention is not possible.
In 1951, Sunderland88 expanded this description to include three subsets of neurotmesis. The Sunderland classification involves five degrees of nerve injury where the first two degrees correspond to neurapraxia and axonotmesis as described by Seddon. A third degree injury involves axon discontinuity with loss of the endoneurial tubes and incomplete spontaneous recovery. A fourth degree injury involves complete disorganization of nerve structure but preservation of nerve sheath continuity. A fifth degree injury involves complete division of the nerve trunk and requires surgical repair.
These classifications are useful in that they allow a prediction of spontaneous nerve recovery. Patients with Sunderland Grade 1 (neurapraxia) and Grade 2 (axonotmesis) injuries would be expected to recover fully whereas patients with Grades 3 to 5 (neurotomesis) would require surgery. Trauma around the elbow leading to nerve dysfunction attributable to transient stretching after dislocation or transient compression by a direct blow, bony fragments, or compartment syndrome (hematoma), is most often attributable to a Sunderland Grade 1 or 2 injury with expected full spontaneous resolution. High-energy fractures associated with motor vehicle accidents and high-velocity gunshot wounds may cause a high-degree nerve injury. Excessive traction with marked displacement, chronic compression, or penetrating injury with laceration are associated with neurotomesis with no spontaneous recovery.72,73,89
Diagnosis always begins with a careful examination and documentation. Evolution of nerve injuries is important in indicating the need for open treatment. Nerve conduction velocities after neurapraxic injuries initially may be normal but slowing usually occurs at 1 to 3 weeks. Conduction velocities may stay within normal limits as many as 7 days after axonotmesis. Denervation changes are seen at approximately 1 month with rein-nervation potentials seen at 6 to 8 weeks.31,87 The authors recommend that nerve conduction studies be delayed until 3 to 4 weeks after injury. One major disadvantage of electrodiagnostic studies is that although Wallerian degeneration can be detected, the status of the connective tissue component of the nerve cannot be assessed without direct exploration.87
One goal in the assessment of nerve dysfunction in the acute setting after trauma around the elbow is to accurately classify which injuries are first or second degree. These injuries will recovery spontaneously and unnecessary early exploration will be avoided. Patients with higher-grade nerve injuries (neurotmesis) associated with trauma may benefit from early intervention. In the chronic setting, compression or traction neuropathy may develop if a nerve is tethered by scar tissue or enveloped by a developing fracture callus. Additionally, nerves already injured may be more vulnerable to dissection with disruption of their vascularity.
RADIAL NERVE PALSY WITH FRACTURES OF THE HUMERUS
Controversy and debate continue as to the optimal treatment and the role of immediate nerve exploration for patients with radial nerve palsy associated with fractures of the humerus. It is clear that exploration and assessment of the nerve is warranted when the fracture requires open treatment. Noncontro-versial indications for early exploration include: (1) fractures with unacceptable alignment (gross shortening, angulation or both) after closed treatment; (2) open fractures; (3) fractures with associated vascular injuries; and (4) multiple limb involvement in patients with polytrauma. The literature remains divided concerning closed fractures that are otherwise amenable to bracing and casting treatment.1,8,9,19,33,40
Radial nerve palsy after fractures of the humerus is the most common nerve lesion in long bone fractures.73,89 The reported incidence varies from 1.8% to 15.2%. Green33 reported that this variation may be attributable to different patient sources, that is, consecutive series of patients from tertiary referral centers versus patients from trauma center consecutive series. The literature review of Pollack et al68 shows an average incidence of 11% and suggests the true incidence may be even less.
The course of the radial nerve makes it particularly vulnerable to injury at the middle and distal 1/3 of the humerus. Motor branches to the triceps are given off proximally and patients often will have active triceps contraction. Contrary to some descriptions in standard textbooks,32,105 Whitson100 observed in 24 cadavers that the radial nerve is separated from the humerus along most of its length by 1 to 5 cm of triceps, brachialis muscle, or both. Only as the nerve approaches the supracondylar ridge is it in direct contact with the humerus. The clinical significance of these findings is that the nerve rarely is trapped within the fracture but can be tethered as it pierces the lateral intermuscular septum distally.
The vulnerability of the nerve at the distal aspect of the humerus was reported by Holstein and Lewis in 1963.40 Six of 341 fractures of the humeral shaft were associated with radial nerve palsy (1.8%) and five of these had a specific spiral fracture configuration in the distal 1/3 of the humerus. The distal fragment displaces into varus whereas the proximal end is abducted. Holstein and Lewis warned that the nerve could be trapped in the fracture site and attempts at closed reduction could lead to additional injury. However, the cause of most of these injuries seems to be local stretching caused by fracture displacement. Rarely is the nerve entrapped as described originally.75
Contrary to what might be expected by anatomic vulnerability, most reported series of radial nerve lesions are associated with fractures of the middle 1/3 of the humerus (Fig 1).
The review of the literature by Pollack et al68 stated that 60% of radial nerve lesions were found in midshaft fractures whereas 28% were found in distal 1/3 fractures. Pollock et al68 and others,75 however, reported the predominance of radial nerve lesions in the distal 1/3 (63%). No correlation in recovery related to the level of the humeral fracture was seen.68,75
Because of the nerves' anatomic vulnerability, Holstein and Lewis40 recommended early exploration for all injuries involving the distal 1/3 fracture. Other authors have advocated early exploration of the nerve regardless of the fracture level.64,77 Several advantages to early exploration have been proposed64: (1) stabilization of the fracture protects the nerve from additional trauma; (2) the nerve can be separated from the inevitable scar tissue and callus; (3) the status of nerve integrity can be ascertained and needless delay for the third degree to fifth degree lesions can be avoided; and (4) early surgery is technically easier and safer and the necessity of nerve grafting late lesions may be avoided.
Packer et al64 reported 89% complete recovery in a group of patients treated with early exploration within 2 weeks of injury compared with a 38% complete recovery for those patients who were treated conservatively or who underwent late exploration. They reported that even patients with midshaft fractures had a 50% incidence of nerve entrapment between bone ends at the fracture site. Sim et al77 concluded that correctable lesions of the nerve such as entrapment in the fracture or complete laceration were frequent and recommended early exploration. Shaw and Sakellarides76 reviewed a series of 45 patients and found four with complete radial nerve transections and two with partial lesions. They recommended early exploration for patients with Holstein-Lewis type fractures and observation for patients with midshaft injuries.
The efficacy and safety of early exploration has been challenged by numerous authors.1,8,9,33,47,48,68,76,79 The rationale for delaying operative treatment includes: (1) avoiding unnecessary surgery in patients who are likely to spontaneously regain function; (2) surgery entails risks of anesthesia, infection, nonunion, and iatrogenic nerve injury; (3) delay allows the demarcation of nerve injury with thickening of the neurilemmal sheath and allows better visual and tactile cues for assessment of neurolysis versus nerve repair or grafting; (4) entrapment by callus does not preclude complete recovery; and (5) results of late exploration are similar to results of early intervention.64,72
Pollack et al reported a 68% incidence of complete recovery after early exploration, which is similar to the 73% rate of spontaneous recovery in their study.68 Their own series of 24 patients showed a 92% rate of spontaneous recovery.68 Omer62 reported that 80% or more of these nerve injuries will recover within 4 months as they usually are of neurapraxic or axonotmetic types. The incidence of surgically correctable lesions for nonpenetrating injuries seems to be small. Kettelkamp and Alexander47 explored 16 radial nerves and found no surgically correctable lesions or mechanical impingement in the case of closed fractures. Sonneveld et al79 explored 14 nerves and found 13 to be visibly normal with one contusion. Dabezies et al19 advocated early exploration but found nine of 10 nerves in continuity in closed fractures. A compilation of published data showed that the yield of surgically correctable lesions (complete lacerations) found at early exploration was only 12%, compared with 19% correctable lesions found at late exploration.68 Bostman et al8,9 found that entrapment of the nerve in callus was seen in 46% of their Holstein-Lewis fractures at exploration but, results were not improved over observation. Szalay and Rockwood90 presented a series of 15 patients with the Holstein-Lewis type fracture and radial nerve palsy. Eleven nerves recovered spontaneously and the four nerves explored all were in continuity and eventually recovered. Shah and Bhatti75 reported on 62 patients, 11 of whom had Holstein-Lewis fractures with radial nerve palsy. Nine of 11 patients were treated conservatively and had complete nerve recovery. It seems that closed humeral shaft fractures with radial nerve palsy can be observed safely if the fracture is amenable to bracing.
There is a higher incidence of high-grade nerve injuries with open fractures and the literature suggests early exploration for these injuries as stated above. Foster et al26 presented 14 open humeral shaft fractures and found that in 64% the nerve was either lacerated (seven patients) or interposed (two patients) between fracture fragments. This incidence seemed equal for Gustilo Types 1, 2, and 3 open fractures.35 Epineural nerve repair done primarily or secondarily, or neurolysis and decompression of the entrapped nerve led to full motor recovery in 10 of 13 patients available for followup. Three patients with contused or stretched nerves or both did not recover after exploration and ultimately required tendon transfers.
Although the need for immediate exploration of a secondary nerve palsy after manipulation of a closed fracture is cited frequently, there is sparse data in the literature to suggest that these palsies involve a higher incidence of surgically correctable (neurotmesis) lesions.33 Shah and Bhatti75 observed that secondary paralysis could not be predicted by localization or type of fracture. Their series included 17 patients with secondary paralysis after closed manipulation. Nine of these patients were treated without exploration and eventually regained full function. The eight secondary palsies that were explored were found to be in continuity and the patients eventually regained full function. Shah and Bhatti75 recommend initial observation in these patients, even in patients with Holstein-Lewis fractures. However, medical liability issues may indicate early exploration despite the reports noted above.
Unresolved Radial Palsy-Surgical Timing
The recommended time frame for late exploration in patients without functional recovery of the radial nerve has ranged from 8 weeks to 5 months.33 The treatment paradigm is to allow sufficient time for spontaneous recovery without jeopardizing the results of late repair.
Shaw and Sakellarides76 advocated exploration at 7 to 8 weeks. They reported that all patients in their series showed some signs of recovery within the first 2 months. Goldner and Kelley31 gave a similar recommendation, although in some patients, the onset of spontaneous clinical recovery did not begin for 5 months. Amillo et al1 recommend exploration at 3 months. Green33 has argued, based on Seddon's work that an observation period of up to 5 months may be warranted. Assuming that the nerve regenerates at a rate of 1 mm per day, injuries at the midshaft level may have to traverse as many as 16 cm (> 5 months) before innervating the brachioradialis or wrist extensors. Given this argument, Green stated that there may be no sound rationale for exploration as early as 3 months.33 Also, nerve conduction studies may be helpful in assessing the earliest signs of muscle regeneration before clinically significant muscular contraction is evident.31,87
Contrary to earlier reports,64,68 the results of delayed exploration and secondary repair or nerve grafting can produce results similar to acute intervention. Fisher and McGeoch25 reported functional recovery at 26 months post injury following nerve grafting in six patients with sural nerve grafts from 7 to 14 cm. Surgical variabilities of the radial nerve that predict good functional outcome after repair include: (1) homogeneous motor axons; (2) precise topographic localization of fibers to forearm muscles; (3) large funicular area; and (4) tolerance of cross innervation with misdirection which still results in extension of the wrist and fingers because patients can be retrained.31,72
Samardzic et al72 reported that 92% of radial nerve lesions could be restored to fair or better motor return after late exploration. Fair results were defined as M3 motor strength for extension of the wrist and fingers and M1 to M2 motor strength for abduction of the thumb. Their series included 24 patients with interfascicular neurolysis (at average of 4 months) and 13 patients with interfascicular grafting (at average of 6 months). Twelve injuries were iatrogenic from osteosynthesis of the humerus (Fig 2). Patients with nerves in continuity did best, with 96% regaining useful functional muscle recovery (> M3). Patients with lesions requiring nerve grafting had an 85% rate of recovery (> M3). Amillo et al1 reported on 12 patients who underwent exploration for radial nerve palsy after humeral shaft fractures at 25 days to 15 months after injury. Excellent and good results were obtained in 91% of patients, including six patients who underwent repair with sural nerve graft. Amillo et al1 recommended sural grafts for their ease of harvesting, good functional results, and minimal donor deficits. Secondary repairs require tensionless junctures. Thus after resection of scarred nerve, grafting is preferable and will facilitate recovery.
The extremities of patients who present with closed humeral shaft fractures with radial nerve palsy should be placed in a brace and observed unless the character or instability of the fracture dictates otherwise. Most lesions are neurapraxic and will recover spontaneously within 2 to 5 months. Nerve palsy after manipulation may necessitate exploration to allay the patient's anxiety. The results of exploration with neurolysis, repair, or nerve graft in a delayed setting are equivalent to primary repair. In patients in whom nerve grafting has failed or myostatic contracture has occurred, good functional results can be achieved through tendon transfers.
There has been great variation in the reported incidence of nerve injury and the degree of spontaneous recovery after Monteggia fractures of the elbow. Most large series mix pediatric and adult patients and various types of Monteggia fractures and their equivalents.4,10,13,21,78,82,85 These injuries have been classified based on the direction of the ulnar angulation and the radial head dislocation: Type 1, anterior; Type 2, posterior; Type 3, lateral; and Type 4, proximal radial fracture.4 Because mechanisms of nerve injury are varied for different Monteggia fracture types, the literature dictates a careful review of the adult and pediatric population. Boyd and Boals10 found only five cases of nerve injury in 159 fractures in pediatric and adult patients. There was no categorization of these nerve injuries between children or adults. Smith78 reported on six cases of nerve injury in 25 consecutive fractures. All of his patients were 6 to 9 years of age. Bruce et al13 found 11 of 35 cases of nerve palsy in a mixed population of patients. The six nerve injuries at presentation were not classified additionally, although three of five injuries in patients nerve after initial treatment occurred in children. Stein et al85 reported seven nerve injuries in a series of 11 fractures in patients between 20 and 25 years of age.
Etiology of Nerve Injury
Dysfunction of the posterior interosseous nerve is the most commonly reported nerve injury. The nerve is at risk as it traverses around the radial neck proximally where it can be stretched or compressed by the typically anterior dislocation of the radial head.85 In addition, the nerve can be compressed or tethered at the arcade of Froshe as it passes between the two heads of the supinator as described by Spinner.81,82 Stein et al85 thought that the latter was the most likely etiology. They reported four patients recovered completely after release of the fibrous band at the proximal edge of the superficial head of the supinator, whereas the radial nerve in one patient appeared to be injured by stretching over the displaced radial head. Stein et al85 described identification of the site of injury by clinical examination, as the sensory branch of the radial nerve and motor branches to the extensor carpi radialis longus come off proximal to the arcade of Froshe. Six of seven patients in the series of Stein et al85 had anterior dislocations of the radial head. No nerve injuries were reported in two series of patients with Type 2 Monteggia fractures with posterior head dislocations,65,66 although Bado4 thought that neurologic deficits seemed to occur more frequently with posterior head dislocations compared with anterior head dislocations as suggested by Spar.80 Spar presented a patient with posterior interosseous palsy who had a lateral dislocation of the radial head (Type 3), with looping of the nerve around the head which prevented closed reduction.80 He reproduced the laterally dislocated radial head in cadavers and found that the nerve could wrap around the radial neck and block reduction. Bado4 has reported a 20% incidence of radial nerve palsy with lateral radial head dislocations. Spar summarized the possible mechanisms of nerve injury to include: (1) direct trauma; (2) compression at the arcade of Froshe; (3) entrapment between the radius and ulna; (4) stretching of the nerve around the radial neck during closed reduction; and (5) tardy palsy caused by scarring from an unreduced radial head. The iatrogenic injury risk can be significant; Smith78 reported five cases of palsy after surgical treatment. Late palsy after closed treatment has been reported by Bruce et al.13 Lichter and Jacobsen50 reported a case of nerve palsy 38 years after an unreduced Monteggia fracture.
Treatment in Children
The literature suggests that most posterior interosseous nerve injuries associated with closed Monteggia fractures of all types are neurapraxias that will resolve spontaneously after closed reduction.10,13,21,78,82 In the series reported by Boyd and Boals,10 all patients recovered spontaneously (mixed ages).10 The six children presented by Smith78 all recovered within 3 to 9 weeks. Spinner82 reported three cases of posterior interosseous nerve injuries in children, all of whom recovered spontaneously after closed reduction. The three children who were identified by Bruce et al13 as presenting with late palsy after initial treatment all recovered spontaneously. The one child in the series of Hirachi et al38 recovered spontaneously after conservative treatment.
Treatment in Adults
Stein et al85 recommended exploration at 12 weeks if no sign of spontaneous recovery was present. They reported unresolved nerve injuries complicating Monteggia fractures in six patients requiring surgical exploration. However, four of these patients underwent exploration before 3 months (range, 12 days-9 weeks). There was only one patient with persistent nerve dysfunction after 3 months (18 weeks), and that patient improved after release at the arcade of Froshe. In the series of Galbraith and McCullough30 of 1540 closed fractures or dislocations of the elbow, all posterior interosseous nerves recovered spontaneously. In the series of Bruce et al13 six of 11 patients, adults and children with palsy on presentation all recovered spontaneously. There were two residual paresthesia in adults who presented with paralysis after initial closed treatment. One patient required exploration with neurolysis at 8 months but eventually fully recovered. Hirachi et al38 presented a series of 17 patients with traumatic posterior interosseous nerve lesions. Seven patients had Monteggia fractures (six adults, three Type 1 lesions) and all but one showed some signs of clinical recovery within 6 weeks with complete spontaneous resolution. They recommend exploration at 6 weeks if no signs of recovery are present. Spar80 reported a case of spontaneous recovery as late as 1 year after the initial injury but gave no details regarding this patient. Young et al103 presented a series of 40 patients who underwent operative intervention for posterior interosseous nerve palsy of greater than 3 months duration. However, their series included only three patients with "miscellaneous fractures or dislocations" around the elbow, suggesting that long-term palsy in these patients is rare.
Other Nerve Injuries
Injuries to the median, anterior interosseous, and ulnar nerves also have been reported in patients with Monteggia fractures, although with much less frequency.24,34,85,96 The ulnar nerve can be tethered at the cubital tunnel and as it enters the forearm between the two heads of the flexor carpi ulnaris. The series of Stein et al85 included three patients with ulnar neuritis diagnosed 2 to 3 weeks after the initial injury who responded to surgical release of the flexor carpi ulnaris aponeurosis. The anterior interosseous nerve is at risk proximally, as it lies on the interosseous membrane in close proximity to the ulna and can be injured by stretching or tethering over the anteriorly angulated fracture as described by Engber and Keene.24 Watson and Singer96 presented a patient with an irreducible Monteggia fracture in whom the median nerve was trapped between the fragments of the ulna. They caution against repeated attempts at closed reduction of the ulna.
Posterior interosseous nerve injury complicating Monteggia fractures of all types in children and adults can be treated with a period of observation after closed reduction of the radial head and reduction of the ulna. Most lesions are neurapraxias that will resolve spontaneously within 3 months. Chronic dislocation or subluxation of the radial head may necessitate open reduction for the fracture deformity and exploration of the posterior interosseous nerve.39,50 Inability to reduce the radial head acutely may signify nerve entrapment as described by Spar.80 Hirachi et al38 reported one patient with a chronically unreduced radial head and entrapment of the nerve between the radius and capitellum. In those patients who do not have spontaneous recovery, exploration of the nerve with release of the arcade of Froshe and complete exploration distal to the radio-capitellar joint has yielded good results.
NERVE INJURIES AFTER PROXIMAL FOREARM TRAUMA
The incidence of nerve injuries in series of patients with closed forearm fractures treated by plating varies from 1% to 10%. Often it is difficult to determine whether the injury resulted from the fracture or from the operative intervention.2,41,60,69,86
Warren95 described two cases of complete anterior interosseous nerve palsy in patients with closed forearm fractures treated without internal fixation. Iatrogenic damage to the anterior interosseous nerve can occur if the proximal dissection of the radius is extraperiosteal. The nerve also can be injured by excessive retraction of the flexors during plating (Fig 3). Hope41 presented three patients with anterior interosseous nerve palsy after plating of the proximal radius. The lesions were thought to be neurapraxias because all patients spontaneously improved. Hope did not recommend reexploration and suggested that tendon transfers may be the best course of action in the unlikely event that the nerve did not recover.
Causes of traumatic posterior interosseous nerve injury around the proximal forearm include open and closed fractures of the radius, gunshot wounds, contusions, lacerations, and iatrogenic damage.38 The nerve is at risk as it travels between the two heads of the supinator down the radial shaft. Lacerations of the proximal forearm can produce muscle damage and lesions of the posterior interosseous nerve. The series of Hirachi et al38 of posterior interosseous palsies included six patients with forearm fractures (three in the proximal radius), two patients with lacerations, and two patients with contusions. Seven of 10 of these patients required operative exploration; two required tendon transfers for reconstruction. The authors recommend exploration for all patients with open fractures, lacerations, and closed injuries who do not have spontaneous recovery at 6 weeks. Hirachi et al38 reported that functional results may be suboptimal after forearm trauma because of the associated muscle damage and the difficulty in finding the distal nerve branches for grafting. They suggest tendon transfers as a reasonable alternative for functional recovery.38 Young et al103 presented operative treatments in 40 patients with posterior interosseous nerve palsy of the forearm, 31 of which were posttraumatic. Sixteen of the posttraumatic injuries were iatrogenic, four were lacerations, and eight were crush injuries. The average time to surgery was 4.5 months. Neurolysis was done in 23 patients, nerve grafting was done in 12, and tendon transfer was done in four. All but three patients had excellent or good results. The patients who had a nerve graft had results similar to the patients who had neurolysis. Given their results, the authors thought that exploration and repair of the nerve at 3 months was preferable to tendon transfers as initial treatment of the paralysis. Cravens and Kline17 presented 32 posterior interosseous nerve palsies, 15 of which were posttraumatic (six lacerations, six fractures, three contusions). In the operative series of 28 nerves, all patients recovered at least 3/5 function with active wrist, finger and thumb extension, and finger abduction. Given their favorable results with nerve exploration, the authors recommend exploration and repair at 3 months rather than primary tendon transfer. Zook et al104 used sural nerve grafts in three patients to bridge posterior interosseous nerve deficits measuring 2.5 to 4.5 cm 4, 5, and 7 months after injury. All three patients recovered full function of the hand at 1 year and the authors think the results of nerve grafting are superior to the results of tendon transfers.
Nerve injuries after shotgun or military high velocity gunshot wounds around the elbow are placed in a separate category because the incidence of these injuries is higher than in closed or other open injuries.11 Permanent nerve loss is not uncommon in patients with these injuries because many tend to be neurotmetic lesions. Omer62 reported on 917 nerve injuries involving the upper extremity and found that the incidence of spontaneous recovery was only 69% for patients with high velocity gunshot wounds compared with 85% for patients with fractures, dislocations, or both. The time for recovery in patients with fracture-dislocations was 1 to 4 months. Recovery took 3 to 9 months in patients in whom nerves recovered after gunshot wounds. Luce and Griffin53 found approximately 50% of nerve deficits after high velocity shotgun injuries to the upper extremity involve complete transections. Brannon et al11 presented a series of 26 patients with gunshot wounds to the elbow, five of whom had associated nerve lesions (four ulnar, one radial). They recommend exploration for all patients requiring open reduction. Nerves that are transected should be tagged for delayed repair.
NERVE INJURY WITH DISLOCATIONS OF THE ELBOW
Although well described, the true incidence of nerve injury after elbow dislocation is difficult to determine. The literature is full of case reports and series that combine children with adults and simple dislocations with fracture and/or dislocations.15,30,44,45,52,59,98 The most common injury seems to be an ulnar nerve neurapraxia that spontaneously resolves after closed reduction.
Nerve Injuries in Adults
Mehlhoff et al59 reported 52 cases of simple elbow dislocations, all in adults, with nine cases of nerve injury: five ulnar; three median and ulnar combined; and one isolated median. All nerves recovered spontaneously except for one patient who continued to have ulnar dysesthesia at 14 months. A less favorable outcome was presented by Galbraith and McCullough30 in their series of 1546 closed fractures or dislocations about the elbow. Of the nine patients with ulnar nerve lesions, six had persistent symptoms and two required nerve transposition.
Nerve Injuries in Children
Watson-Jones97 presented a series of 16 nerve injuries in 97 elbow dislocations. The patients ranged in age from 12 to 57 years. There were 13 ulnar nerve palsies, one median nerve palsy, and two radial nerve palsies. All patients with palsies eventually recovered fully but ulnar nerve transposition was done in nine patients; some as early as 1 day after injury. Watson-Jones thought that the mechanism of ulnar nerve injury was direct traction of the nerve in the cubital tunnel after posterolateral displacement of the radius and ulna. Linscheid and Wheeler52 reported 24 nerve injuries in 110 dislocations in children and adults. There were 16 ulnar nerve injuries, three median nerve injuries, and four combined nerve lesions. In a subsequent series of 37 dislocations (including intraarticular fractures) by the same authors, three transient ulnar palsies and one transient median nerve palsy that subsequently resolved were reported. There was one tardy ulnar nerve palsy that required anterior transposition at 1 year.99 Anterior interosseous nerve palsy has been reported by Beverly and Fearn.6
There have been numerous case reports describing entrapment of the median nerve after dislocation,3,7,20,36,51,61,63,83,92,98 which have occurred almost exclusively in children. The patterns of entrapment as described by Hallett36 are as follows: in Type 1, the nerve is caught within the joint between the humerus and ulna as it slips posteriorly behind a torn medial collateral ligament or fractured medial epicondyle; in Type 2, the nerve runs through a healed fracture of the medial epicondyle; and in Type 3, the nerve is looped into the humeroulnar joint by becoming trapped through a tear in the anterior aspect of the joint capsule. Most lesions involve a Type 1 pattern.
Noonan and Blair61 reviewed the literature on median nerve entrapment and reported that most nerve injuries were diagnosed late (3 months to 2.5 years after injury). They attributed this to the difficulty in interviewing and examining young patients. Acute or progressive high median nerve palsy after reduction, tardy palsy attributable to scarring and bony callus in a Type 2 pattern, difficulty in reduction, unusual pain, and acute limitation of motion all are suggestive of entrapment. Radiographically, a lucency in the supracondylar region as described by Matev57 may be present at 2 to 3 months after the injury. Matev first described this oblique stripe with sclerotic margins in two patients with Type 1 entrapment patterns and median nerve symptoms. The stripe corresponds to the position of the nerve and resolves after operative decompression. A fracture of the medial epicondyle or a widened medial joint space also is suggestive of nerve entrapment when combined with the above clinical signs. The key to successful outcome is early diagnosis as nerve decompression is superior to late excision and grafting of the chronically damaged segment.61
Fracture and Dislocation in Children
The literature contains only sporadic case reports of median nerve injuries with greenstick fractures of the forearm in children.29,43 Most of these are Monteggia equivalent type fractures with proximal ulna and/or proximal radius fractures with or without dislocations of the elbow. The nerve could be entrapped at the fracture site at the radius or the proximal ulna. Huang et al43 reviewed the literature and found five reported cases: two with median nerve entrapment in a greenstick fracture of the radius, two with entrapment in a greenstick fracture of the ulna, and one combined anterior interosseous and median nerve entrapment. Surgical intervention with either acute freeing of the nerve, neurolysis, direct repair, or nerve graft was needed in all reported cases with an average time to surgery of 4.5 months.
SUPRACONDYLAR FRACTURES IN CHILDREN
The reported incidence of nerve injury with supracondylar fractures in children has ranged from 12% to 16%.14,16,18,37,54,56 It seems that posteromedially displaced fractures are more likely to be associated with neural compromise. Brown and Zinar12 have suggested a higher incidence of nerve injury in patients with widely displaced fractures although nerve injury with complete transection has been reported even in patients with minimally displaced injuries.71 There is some debate as to the most frequently injured nerve. Involvement of the radial nerve with posteromedial displacement and involvement of the median nerve with tenting over a spike of metaphyseal bone in posterolateral displacement have been reported.37 Injury to the anterior interosseous nerve also has been reported.16
Several studies suggests that 86% to 100% of these injuries are neurapraxias that will recover spontaneously within 6 months in an average of 2 to 3 months.14,18,37,54 Campbell et al14 reported a 49% incidence of neurovascular injury after Type 3 fractures but there were no nerve transections and all symptoms resolved by 4 months. Brown and Zinar12 reported 18 acute neural injuries in 162 displaced fractures: 11 radial, five median, and two ulnar. All deficits resolved spontaneously within 6 months with an average of 2.3 months. The authors recommend a waiting period of 6 months before electrodiagnostic studies to determine whether exploration of the nerve is warranted. Brown and Zinar also reported five iatrogenic injuries, (a 3% incidence) four involving the ulnar nerve by impalement after percutaneous fixation of the medial epicondyle. They recommend a limited incision with placement of the pin in the medial epicondyle under direct visualization in patients with extreme swelling. The authors of the current study have expanded the indications for direct visualization of pin entry to include all patients who require medial pinning. Lyons et al54 reported 19 ulnar nerve injuries postoperatively with cross-pinning techniques used in 345 Type 3 supracondylar fractures. Urgent reexploration with freeing of the tangled nerve is recommended. Culp et al18 reviewed 101 displaced supracondylar fractures and found 18 associated neural injuries. Only nine injuries recovered spontaneously at a mean of 2.5 months. The remaining nine nerves required exploration at a mean of 7.5 months. Eight nerves were in continuity and recovered after neurolysis. There was one patient with complete transection of the radial nerve who did poorly after nerve grafting.
Nerve injuries after supracondylar fractures in children generally are neurapraxias that will resolve spontaneously. Indications for early exploration include open fractures, vascular injuries, and irreducible fractures. Nerve injuries without recovery at 6 months should be explored. Most nerves are in continuity and recover after decompression and neurolysis. Complete nerve transection is exceedingly rare. The few reported cases have involved mainly the radial nerve with variable return of function after primary repair or nerve grafting.5,56
ULNAR NEUROPATHY AFTER ELBOW TRAUMA
Scarring in and around the cubital tunnel after elbow trauma can lead to compression and tethering of the ulnar nerve at any of the sites classically described: ligament of Struthers, medial intermuscular septum, medial epicondyle, or flexor carpi ulnaris muscular septa.42 The ulnar nerve has a longitudinal excursion of up to 11 mm proximal to the elbow.101 This gliding of the nerve is jeopardized as it adheres to the surrounding scar tissue and/or fracture callus or heterotopic bone. Immobilization of the elbow may potentiate scarring and fibrosis and exacerbate the problem, which is magnified after elbow release of contracture where increased joint motion is not matched by ulnar nerve glide.
Decompression with or without anterior transposition has been described as a treatment for ulnar neuropathy (Fig 4). There is no consensus as to the optimal location of the transposition although it has been suggested by Gabel and Amadio28 that submuscular positioning is better for patients undergoing revision surgery. Few reports deal specifically with the treatment of posttraumatic injury. Wang et al94 did routine anterior subcutaneous transposition in 20 intercondylar fractures of the distal humerus. At an average followup of 26 months, no patient had nerve symptoms. These results compared favorably with the 5% incidence of postoperative ulnar neuropathy that Wang et al94 reported for patients with similar fractures without transposition. The authors surmised that anterior transposition avoids compression from periarticular fibrosis and hardware impingement from around the medial epicondyle. Routine in situ release during the initial surgery is thought to decrease the need for future nerve surgery. McKee et al58 performed ulnar nerve neurolysis and subcutaneous transposition in 21 elbows with ulnar nerve symptoms during reconstruction for failed elbow fractures. Fourteen patients had intraarticular fractures of the distal humerus. Five patients had failed anterior transposition at a previous surgery. Nerves were found to be encased in periarticular fibrosis, compressed by metal implants, or trapped by bony fragments or suture material. Seventeen patients had good or excellent results. Only two patients had poor results. The authors conclude that good function can be achieved after neurolysis and anterior transposition during late reconstruction of the posttraumatic elbow. Of course if ulnar neuritis is present at initial treatment, decompression and/or transposition must be performed.
Decompression plus anterior transposition of the ulnar nerve has been recommended after acute trauma to prevent tardy ulnar neuritis in patients with or without pre-injury symptoms. The authors routinely isolate and decompress the ulnar nerve during initial fracture treatment but do not perform a routine transposition. Early motion may help prevent the development of scarring with subsequent neuropathy.
IATROGENIC AND MISCELLANEOUS CAUSES OF NERVE INJURY
Iatrogenic nerve injury as a result of closed treatment and surgical treatment of injuries around the elbow has been reported throughout the literature.46,49,67,84,91,93 The radial nerve is at risk as it courses down the humeral shaft during fracture exposure100 and because of callus formation23 or hardware27 in patients with late evolving nerve injury. Samardzic et al72 reported 12 iatrogenic injuries in their series of 37 radial nerve palsies associated with humeral shaft fractures. Entrapment of the nerve in the medullary canal of the proximal fragment has been reported, which would put it at risk during attempts at closed nailing, especially when inserting a reamed nail.102 Potential nerve injury by distal interlocking screws in the humerus has been shown in cadaver dissections by Rupp et al.70 Radial nerve paralysis after tourniquet use was reported by Kurihara and Goto49 in two patients with previous humeral shaft fractures. In the proximal forearm, the posterior interosseous nerve is at risk during plating of radius fractures (dorsal or volar approach), or open reduction and internal fixation of the radial head.42 The anterior interosseous nerve is at risk as it runs along the interosseous membrane during plating of proximal forearm fractures. Injury to the median nerve has been reported during catheterization of the brachial artery.46 The ulnar nerve can be injured during acute fracture treatment and delayed elbow reconstruction. Devascularization of the nerve can occur during transposition. Injury to the ulnar nerve during steroid injection for medial epicondylitis has been reported recently.84 Posterior interosseous and median nerve injury during elbow arthroscopy is well recognized.55,91 Perreault et al67 reviewed the literature on ulnar nerve palsy as a complication of anesthesia and stressed the importance of patient positioning with adequate padding of the axilla and the elbow. Compartment syndrome as a possible complication of trauma around the elbow should not be overlooked. Delays in assessment and treatment can lead to significant chronic dysfunction of the muscles and nerves of the forearm.
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