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Management of Radial Nerve Palsy Following Fractures of the Humerus
Management of Radial Nerve P a l s y F o l l o w i n g Fr a c t u re s o f th e H umer us Genghis E. Niver, MD, Asif M. Ilyas, MD* KEYWORDS Radial nerve Humerus fracture Holstein-Lewis fracture
KEY POINTS A radial nerve palsy is the most common peripheral nerve injury following a humerus fracture, occurring in up to 2% to 17% of cases. Surgical exploration is recommended in cases with open or complex fractures, particularly those associated with penetrating trauma. Radial nerve palsies associated with closed fractures of the humerus have traditionally been recommended to be treated with observation, with late exploration restricted to cases without spontaneous nerve recovery at 3 to 6 months. Advocates for early exploration believe that late exploration can result in increased muscular atrophy, motor endplate loss, compromised nerve recovery on delayed repair, and significant interval loss of patient function and livelihood. Early exploration can hasten nerve injury characterization and repair, as well as facilitate early fracture stabilization and rehabilitation.
In the United States, more than 237,000 humerus fractures occur each year. Humeral shaft fractures represent between 1% and 5% of all fractures.1,2 Initial retrospective studies by Mast and colleagues3 described humeral shaft fractures as being most common among male patients younger than 35 involved in high-energy trauma.2 However, more recent studies have described a bimodal incidence with women older than 50 years suffering these fractures from low-energy injuries, such as falls from a standing height.4,5 Complicating these fractures are radial nerve injuries, which are the most common peripheral
nerve injuries associated with humeral fractures.6,7 The incidence of radial nerve injuries with humerus fractures has been documented between 2% and 17%.8–10 A prospectively collected database of more than 5700 patients with polytrauma revealed the radial nerve to be the most frequently injured peripheral nerve, seen in 9.5% of humeral fractures.11 However, this polytrauma population also included open fractures. Controversy still exists in the treatment of humeral shaft fractures with associated radial nerve injuries. Algorithms have been proposed to provide recommendations with regard to management and treatment of these nerve injuries. However, pros and cons are associated with each of these algorithms.
All named authors hereby declare that they have no conflicts of interests to disclose related to the topic of this article. Hand and Upper Extremity Surgery, Rothman Institute, Thomas Jefferson University, 925 Chestnut Street, Philadelphia, PA 19107, USA * Corresponding author. E-mail address: [email protected] Orthop Clin N Am 44 (2013) 419–424 http://dx.doi.org/10.1016/j.ocl.2013.03.012 0030-5898/13/$ – see front matter Ó 2013 Elsevier Inc. All rights reserved.
orthopedic.theclinics.com
BACKGROUND
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Niver & Ilyas ANATOMY The humeral shaft is defined as the region “between the superior border of the pectoralis major insertion and the area immediately above the supracondylar ridge.”12 Prior descriptions historically have placed the radial nerve and profunda brachial artery in the musculospiral groove and lateral intermuscular septum of the humerus.9 However, the spiral groove is truly the origin of the brachialis muscle. Fibers of the medial head of the triceps and brachialis separate the radial nerve from the humeral cortex. Direct contact with the humerus typically most consistently occurs as the nerve approaches the lateral supracondylar ridge.13 Humeral shaft fractures can be described by their anatomic location by dividing the humeral shaft into thirds or fifths. The level of the fracture can provide the initial evidence of a radial nerve injury.3 Holstein and Lewis described an association of a radial nerve injury with a spiral fracture of the distal third humeral shaft fracture, since referred to as a Holstein-Lewis fracture.8 However, 1 to 5 cm of muscle separates the humerus and radial nerve at a level just proximal to the distal third of the humerus.14 Due to the force of injury, the proximal segment moves distally, causing displacement of the intermuscular septum. The radial nerve, which runs through this septum, may subsequently get tethered and injured. The nerve may also get lacerated when the apex of the distal fragment moves radially and proximally.8 Although this mechanism of radial nerve injury has been widely accepted, many recent studies dispute the constant relationship between the Holstein-Lewis fracture fragment and radial nerve injury.9,14,15 Similarly, a study by Bono and colleagues16 noted that the radial nerve has a more proximal decussation than previously reported. Their conclusion was that the nerve travels the distal half of the humerus along a superficial course. In addition, the AO classification can be used to describe fractures and their associated patterns.1 The AO classification divides diaphyseal humeral shaft fractures into 3 categories depending on the amount of contact between the major fracture fragments. Simple fractures with more than 90% contact between the main fracture fragments are known as AO Type A fractures. AO Type B fractures (wedge fractures) and AO Type C fractures (complex fractures) have little or no contact between major fragments. Subtypes also exist based on direction and fracture extent within the 3 major categories. According to Tytherleigh-Strong and colleagues,5 fractures of the middle third of the
humeral shaft arise with an incidence of 64.2% and AO Type A fractures have a similar incidence of 63.3%. Researchers differ in their incidence of radial nerve injury with regard to location of the humeral shaft fracture. For instance, Bostman and colleagues15 noted an equal incidence of radial nerve injuries in fractures of the middle and distal third humeral shaft. However, some have reported that a higher likelihood of neurovascular injuries occurs in middle third of humerus fractures,9 whereas others have observed an increase in neurovascular injuries in distal third humeral shaft fractures.17 Fracture pattern associated with radial nerve palsies is also variable; most occur in the presence of a spiral fracture, although transverse and oblique fractures can also result in a radial nerve injury.9,15,17
CLASSIFICATION/DIAGNOSIS Radial nerve palsies can be classified as either partial or complete. To begin determining the type of palsy, one must perform a complete physical examination. A thorough baseline examination consists of sensory and motor evaluation of the median, ulnar, and radial nerves. Radial nerve sensation can be tested to light touch and pinprick on the dorsal hand at the level of the first web space. Radial nerve motor function can be determined by testing active extension of the wrist and of the fingers (including the thumb) at the metacarpophalangeal joints. In addition, the absence of brachioradialis or extensor carpi radialis longus firing may indicate a proximal injury at the level of the humeral shaft.18 After a thorough physical examination, complete motor loss has been noted to occur in 50% to 68% of radial nerve palsies.9,17 Primary nerve palsies noted during the initial physical examination usually have occurred at the time of injury. Secondary nerve palsies may arise at any point during the active treatment of the fracture; these can represent up to 20% of all nerve palsies.15,19 The Seddon or Sunderland classification system can be used in further defining the type of peripheral nerve injury.20,21 The initial definition of a radial nerve injury as primary or secondary may be a prognostic factor in the ultimate recovery of the nerve. One study demonstrated 40% recovery in patients with a primary palsy and 100% recovery in patients with a secondary palsy after treatment of a humeral shaft fracture (closed or open reduction with internal fixation).22 Other studies with primary radial nerve palsies have demonstrated spontaneous recovery in 85% after closed fractures of the humerus.15 Secondary nerve palsies after humeral shaft fractures may occur during closed treatment or
Following Fractures of the Humerus after surgical fixation. Shah and Bhatti23 reviewed 62 patients with radial nerve palsies and humeral shaft fractures, of which 17 patients developed a secondary nerve palsy. Of these 17 patients, 11 of them had true closed management of their fractures consisting of cast/splint treatment, with or without manipulation of their fracture; 4 patients were treated with olecranon pin traction. Eight of these 17 patients had surgical exploration of their nerves, with all of them demonstrating intact nerves; however, 3 patients had nerves impinging on fracture fragments and 1 patient had the radial nerve entrapped in scar. All 17 patients who had secondary nerve palsy demonstrated complete recovery of their radial nerve function. This study demonstrated that closed management of humeral shaft fractures can lead to secondary nerve palsies, all of which recovered. Surgical management of humeral shaft fractures can also lead to secondary palsies of the radial nerve. The least invasive technique is intramedullary nailing; however, this is not recommended in radial nerve palsies associated with humeral shaft fractures, as potential entrapment of the nerve in the fracture site leaves it vulnerable to further damage. The incidence of radial nerve injury following this technique has been reported to be between 0% and 5%.24 Other series examining radial nerve palsy following intramedullary nailing has identified that most palsies are temporary and resolve spontaneously.25–27 Alternatively, open reduction with compression plating is the most common procedure for humeral shaft fracture fixation. This technique can lead to radial nerve injury in up to 10% of cases.28,29 This approach allows for an anatomic reduction with the most predictable rate of fracture union.30,31 Routine exploration of the radial nerve is recommended during compression plating of the humerus, particularly in cases with preoperative radial nerve palsies.24
MANAGEMENT/TREATMENT To begin evaluating the status of a radial nerve injury and what type of treatment should be used, an electrodiagnostic study can be helpful. These studies are not useful in the acute setting, but may have a role in the subacute setting in determining the level and extent of nerve injury.18 It can also be used to determine a baseline nerve function at the 3-week point to guide treatment during the observation period. These baseline electrodiagnostic studies may demonstrate “fibrillation potentials, positive sharp waves, and monophasic action potentials of short duration.”32 Most patients with spontaneous recovery begin to demonstrate recovery during the first few months;
however, an electrodiagnostic study may serve as an adjunct study for those lacking nerve recovery at the 6-week or 12-week point.23,33,34 If a follow-up electrodiagnostic study at the 12-week point shows similar findings as the baseline, then exploration may be indicated. However, if the 12-week follow-up study shows “improved nerve function with larger polyphasic motor unit action potentials of longer duration,” then some degree of spontaneous recovery may be expected.32 However, the course of this subset of patients is not predictable. Significant controversy persists with regard to the management of a radial nerve palsy associated with a humeral shaft fracture. Currently, noncontroversial and generally well-accepted indications for early exploration include open fractures, radial nerve palsy after closed reduction, associated vascular injuries, high-velocity gunshot wounds, penetrating injuries, severe soft tissue injuries, or any case with a high suspicion of a direct nerve laceration (Box 1).8–10,17,29,35–39 Ring and colleagues40 retrospectively reviewed patients with a high-energy humeral shaft fracture with an associated complete radial nerve palsy. All 6 patients with a transected radial nerve had a complex open fracture. However, the management of a radial nerve palsy with a closed humerus fracture can be divided into 2 treatment camps: 1. Late exploration 2. Early exploration.
Late Exploration Although early reports recommended surgical management with exploration for primary radial nerve palsies after humeral shaft fractures,8,35 with time, investigators have leaned toward no immediate exploration of the radial nerve following closed fractures of the humerus because of a high rate of recovery (over 70%).3,17,19,22,29,35,41 One study found an incidence of 87.3% functional recovery after primary radial nerve palsies
Box 1 Indications for early exploration of a radial nerve palsy following fracture of the humerus Radial nerve palsy after a closed reduction Open fracture Vascular injury High-velocity gunshot wound Associated severe soft tissue injury
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Niver & Ilyas managed with no immediate surgical exploration.42 Similarly, many studies have noted that the radial nerve is usually contused and does not require immediate exploration.9,15,19,22 During routine exploration of radial nerve palsies associated with humeral shaft fractures, one study found a transection rate of only 12%.9 Another study, by Sonneveld and colleagues,43 reviewed 17 cases of radial nerve palsies after humeral shaft fractures. Fourteen fractures were explored, with 13 of the radial nerves noted to be undamaged. Clinical recovery was seen in 12 of the 14 patients with nerve exploration. In a systematic literature review of radial nerve palsy associated with fractures of the humeral shaft, Shao and colleagues44 identified a spontaneous radial nerve recovery rate of 70.7% in patients treated nonoperatively, and an overall recovery rate of 88.1% regardless of treatment and timing of intervention. Furthermore, they did not find a difference in outcome among patients treated with early or late exploration. In short, proponents of late exploration may argue that delaying surgical exploration can decrease the risk of the usual surgical complications, such as infection or scarring, in patients who may otherwise recover radial nerve spontaneously anyway. Another potential advantage of delaying surgery is to permit thickening of the neurilemmal sheath, making future nerve repair easier.18
Early Exploration Advocates of early exploration of a radial nerve palsy may argue that a sufficient number of radial nerve injuries requiring treatment after closed humeral shaft fractures routinely exist, warranting early exploration. Moreover, early exploration and expedient repair of a radial nerve laceration will result in a more superior outcome than a delayed repair. Series with late exploration have revealed nerve laceration or entrapment to be present 6% to 25% of the time.9,19,20,22,35,45 Moreover, the systematic review performed by Shao and colleagues44 identified a spontaneous recovery rate of 70% but an overall recovery rate of only 88%. In addition, Pollock and colleagues9 noted nerve lacerations in 20% to 42% of cases after late exploration. They also noted poor results clinically after late repair. Evidence has also been shown that delays of more than 5 months can result in poorer outcomes.10 Delaying surgery may result in irreversible nerve damage without motor endplate reinnervation within 12 to 18 months of injury for useful return of function.18 Similarly, if no improvement is seen after 7 months, then spontaneous recovery is not likely to occur.46
Box 2 Potential advantages of early exploration of a radial nerve palsy following a closed fracture of the humerus Earlier nerve injury characterization and repair Immediate fracture stabilization and earlier rehabilitation Less muscular atrophy and endplate loss Earlier return to function
Subsequently, advocates for early exploration of a radial nerve palsy with a simple closed humerus fracture would argue that after consideration of the plethora of available series, including a number of series that have documented the risk of a nerve laceration or incarceration with a closed fracture of the humerus to be as high as 25%, that expectant or delayed nerve exploration can compromise ultimate recovery (Box 2). Prolonged observation of cases with a lacerated or incarcerated radial nerve will result in no radial nerve recovery, potential atrophy and motor endplate loss, compromised nerve recovery on late exploration and repair, and significant interval loss of patient function and livelihood. In contrast, early exploration and repair performed earlier can facilitate better characterization of the nerve injury, quicker nerve recovery on repair with less distal endplate loss, less muscular atrophy, quicker return to function, and peace of mind. Moreover, after fracture fixation and stabilization is achieved, a neurolysed or repaired nerve will potentially benefit from a better environment for recovery with less tension, motion, or callus formation to impede nerve healing.17,35
SUMMARY A radial nerve palsy is the most common peripheral nerve injury following a humerus fracture, occurring in up to 2% to 17% of cases.8–10 These injuries can be classified as either partial or complete, depending on the extent of physical examination findings, as well as primary or secondary, depending on the palsy’s timing of presentation. Surgical exploration is recommended in cases with open or complex fractures, particularly those associated with penetrating trauma. Radial nerve palsies associated with closed fractures of the humerus have traditionally been recommended to be treated with observation, with late exploration restricted to cases without spontaneous nerve recovery at 3 to 6 months. Advocates for early
Following Fractures of the Humerus exploration believe that late exploration can result in increased muscular atrophy, motor endplate loss, compromised nerve recovery on delayed repair, and significant interval loss of patient function and livelihood. In contrast, early exploration maximizes nerve injury characterization and repair as well as facilitates early fracture stabilization, which can avoid late nerve injury or incarceration. Moreover, early exploration yielding a nerve injury that is repaired can lead to quicker nerve recovery with less motor endplate loss, less muscular atrophy, and quicker return to function.
REFERENCES 1. Browner BD. 3rd edition. Skeletal trauma: basic science, management, and reconstruction, vol. 2. Philadelphia: Saunders; 2003. p. xxiii, 2626, xli. 2. Ekholm R, Adami J, Tidermark J, et al. Fractures of the shaft of the humerus. An epidemiological study of 401 fractures. J Bone Joint Surg Br 2006;88(11): 1469–73. 3. Mast JW, Spiegel PG, Harvey JP Jr, et al. Fractures of the humeral shaft: a retrospective study of 240 adult fractures. Clin Orthop Relat Res 1975;112: 254–62. 4. Rose SH, Melton LJ 3rd, Morrey BF, et al. Epidemiologic features of humeral fractures. Clin Orthop Relat Res 1982;168:24–30. 5. Tytherleigh-Strong G, Walls N, McQueen MM. The epidemiology of humeral shaft fractures. J Bone Joint Surg Br 1998;80(2):249–53. 6. Omer GE Jr. Results of untreated peripheral nerve injuries. Clin Orthop Relat Res 1982;163:15–9. 7. Samardzic M, Grujicic D, Milinkovic ZB. Radial nerve lesions associated with fractures of the humeral shaft. Injury 1990;21(4):220–2. 8. Holstein A, Lewis GM. Fractures of the humerus with radial-nerve paralysis. J Bone Joint Surg Am 1963; 45:1382–8. 9. Pollock FH, Drake D, Bovill EG, et al. Treatment of radial neuropathy associated with fractures of the humerus. J Bone Joint Surg Am 1981;63(2):239–43. 10. Amillo S, Barrios RH, Martı´nez-Peric R, et al. Surgical treatment of the radial nerve lesions associated with fractures of the humerus. J Orthop Trauma 1993;7(3):211–5. 11. Noble J, Munro CA, Prasad VS, et al. Analysis of upper and lower extremity peripheral nerve injuries in a population of patients with multiple injuries. J Trauma 1998;45(1):116–22. 12. DeFranco MJ, Lawton JN. Radial nerve injuries associated with humeral fractures. J Hand Surg Am 2006;31(4):655–63. 13. Whitson RO. Relation of the radial nerve to the shaft of the humerus. J Bone Joint Surg Am 1954;36(1): 85–8.
14. Rockwood CA, Green DP, Bucholz RW. Rockwood and Green’s fractures in adults. 6th edition. Philadelphia: Lippincott Williams & Wilkins; 2006. 15. Bo¨stman O, Bakalim G, Vainionpa¨a¨ S, et al. Radial palsy in shaft fracture of the humerus. Acta Orthop Scand 1986;57(4):316–9. 16. Bono CM, Grossman MG, Hochwald N, et al. Radial and axillary nerves. Anatomic considerations for humeral fixation. Clin Orthop Relat Res 2000;373:259–64. 17. Garcia A Jr, Maeck BH. Radial nerve injuries in fractures of the shaft of the humerus. Am J Surg 1960; 99:625–7. 18. Lowe JB 3rd, Sen SK, Mackinnon SE. Current approach to radial nerve paralysis. Plast Reconstr Surg 2002;110(4):1099–113. 19. Kettelkamp DB, Alexander H. Clinical review of radial nerve injury. J Trauma 1967;7(3):424–32. 20. Seddon HJ. Nerve lesions complicating certain closed bone injuries. J Am Med Assoc 1947;135(11):691–4. 21. Sunderland S. A classification of peripheral nerve injuries producing loss of function. Brain 1951;74(4): 491–516. 22. Shaw JL, Sakellarides H. Radial-nerve paralysis associated with fractures of the humerus. A review of forty-five cases. J Bone Joint Surg Am 1967; 49(5):899–902. 23. Shah JJ, Bhatti NA. Radial nerve paralysis associated with fractures of the humerus. A review of 62 cases. Clin Orthop Relat Res 1983;172:171–6. 24. Farragos AF, Schemitsch EH, McKee MD. Complications of intramedullary nailing for fractures of the humeral shaft: a review. J Orthop Trauma 1999;13(4): 258–67. 25. Crolla RM, de Vries LS, Clevers GJ. Locked intramedullary nailing of humeral fractures. Injury 1993; 24(6):403–6. 26. Ingman AM, Waters DA. Locked intramedullary nailing of humeral shaft fractures. Implant design, surgical technique, and clinical results. J Bone Joint Surg Br 1994;76(1):23–9. 27. Rommens PM, Verbruggen J, Broos PL. Retrograde locked nailing of humeral shaft fractures. A review of 39 patients. J Bone Joint Surg Br 1995;77(1):84–9. 28. Bell MJ, Beauchamp CG, Kellam JK, et al. The results of plating humeral shaft fractures in patients with multiple injuries. The Sunnybrook experience. J Bone Joint Surg Br 1985;67(2):293–6. 29. Dabezies EJ, Banta CJ 2nd, Murphy CP, et al. Plate fixation of the humeral shaft for acute fractures, with and without radial nerve injuries. J Orthop Trauma 1992;6(1):10–3. 30. Chapman JR, Henley MB, Agel J, et al. Randomized prospective study of humeral shaft fracture fixation: intramedullary nails versus plates. J Orthop Trauma 2000;14(3):162–6. 31. McCormack RG, Brien D, Buckley RE, et al. Fixation of fractures of the shaft of the humerus by dynamic
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compression plate or intramedullary nail. A prospective, randomised trial. J Bone Joint Surg Br 2000; 82(3):336–9. Mohler LR, Hanel DP. Closed fractures complicated by peripheral nerve injury. J Am Acad Orthop Surg 2006;14(1):32–7. Robinson LR. Traumatic injury to peripheral nerves. Muscle Nerve 2000;23(6):863–73. Robinson LR. Role of neurophysiologic evaluation in diagnosis. J Am Acad Orthop Surg 2000;8(3): 190–9. Packer JW, Foster RR, Garcia A, et al. The humeral fracture with radial nerve palsy: is exploration warranted? Clin Orthop Relat Res 1972;88:34–8. Vander Griend R, Tomasin J, Ward EF. Open reduction and internal fixation of humeral shaft fractures. Results using AO plating techniques. J Bone Joint Surg Am 1986;68(3):430–3. Foster RJ, Swiontkowski MF, Bach AW, et al. Radial nerve palsy caused by open humeral shaft fractures. J Hand Surg Am 1993;18(1):121–4. Modabber MR, Jupiter JB. Operative management of diaphyseal fractures of the humerus. Plate versus nail. Clin Orthop Relat Res 1998;347:93–104.
39. Bercik MJ, Kingsbery J, Ilyas AM. Peripheral nerve injuries following gunshot fracture of the humerus. Orthopedics 2012;35(3):e349–52. 40. Ring D, Chin K, Jupiter JB. Radial nerve palsy associated with high-energy humeral shaft fractures. J Hand Surg Am 2004;29(1):144–7. 41. Dameron TB Jr, Grubb SA. Humeral shaft fractures in adults. South Med J 1981;74(12):1461–7. 42. Heim D, Herkert F, Hess P, et al. Surgical treatment of humeral shaft fractures—the Basel experience. J Trauma 1993;35(2):226–32. 43. Sonneveld GJ, Patka P, van Mourik JC, et al. Treatment of fractures of the shaft of the humerus accompanied by paralysis of the radial nerve. Injury 1987; 18(6):404–6. 44. Shao YC, Harwood P, Grotz MR, et al. Radial nerve palsy associated with fractures of the shaft of the humerus: a systematic review. J Bone Joint Surg Br 2005;87(12):1647–52. 45. Klenerman L. Fractures of the shaft of the humerus. J Bone Joint Surg Br 1966;48(1):105–11. 46. Gelberman RH. Operative nerve repair and reconstruction, vol. 2. Philadelphia: Lippincott; 1991. p. xxix, 1625, 37.
KEY POINTS A radial nerve palsy is the most common peripheral nerve injury following a humerus fracture, occurring in up to 2% to 17% of cases. Surgical exploration is recommended in cases with open or complex fractures, particularly those associated with penetrating trauma. Radial nerve palsies associated with closed fractures of the humerus have traditionally been recommended to be treated with observation, with late exploration restricted to cases without spontaneous nerve recovery at 3 to 6 months. Advocates for early exploration believe that late exploration can result in increased muscular atrophy, motor endplate loss, compromised nerve recovery on delayed repair, and significant interval loss of patient function and livelihood. Early exploration can hasten nerve injury characterization and repair, as well as facilitate early fracture stabilization and rehabilitation.
In the United States, more than 237,000 humerus fractures occur each year. Humeral shaft fractures represent between 1% and 5% of all fractures.1,2 Initial retrospective studies by Mast and colleagues3 described humeral shaft fractures as being most common among male patients younger than 35 involved in high-energy trauma.2 However, more recent studies have described a bimodal incidence with women older than 50 years suffering these fractures from low-energy injuries, such as falls from a standing height.4,5 Complicating these fractures are radial nerve injuries, which are the most common peripheral
nerve injuries associated with humeral fractures.6,7 The incidence of radial nerve injuries with humerus fractures has been documented between 2% and 17%.8–10 A prospectively collected database of more than 5700 patients with polytrauma revealed the radial nerve to be the most frequently injured peripheral nerve, seen in 9.5% of humeral fractures.11 However, this polytrauma population also included open fractures. Controversy still exists in the treatment of humeral shaft fractures with associated radial nerve injuries. Algorithms have been proposed to provide recommendations with regard to management and treatment of these nerve injuries. However, pros and cons are associated with each of these algorithms.
All named authors hereby declare that they have no conflicts of interests to disclose related to the topic of this article. Hand and Upper Extremity Surgery, Rothman Institute, Thomas Jefferson University, 925 Chestnut Street, Philadelphia, PA 19107, USA * Corresponding author. E-mail address: [email protected] Orthop Clin N Am 44 (2013) 419–424 http://dx.doi.org/10.1016/j.ocl.2013.03.012 0030-5898/13/$ – see front matter Ó 2013 Elsevier Inc. All rights reserved.
orthopedic.theclinics.com
BACKGROUND
420
Niver & Ilyas ANATOMY The humeral shaft is defined as the region “between the superior border of the pectoralis major insertion and the area immediately above the supracondylar ridge.”12 Prior descriptions historically have placed the radial nerve and profunda brachial artery in the musculospiral groove and lateral intermuscular septum of the humerus.9 However, the spiral groove is truly the origin of the brachialis muscle. Fibers of the medial head of the triceps and brachialis separate the radial nerve from the humeral cortex. Direct contact with the humerus typically most consistently occurs as the nerve approaches the lateral supracondylar ridge.13 Humeral shaft fractures can be described by their anatomic location by dividing the humeral shaft into thirds or fifths. The level of the fracture can provide the initial evidence of a radial nerve injury.3 Holstein and Lewis described an association of a radial nerve injury with a spiral fracture of the distal third humeral shaft fracture, since referred to as a Holstein-Lewis fracture.8 However, 1 to 5 cm of muscle separates the humerus and radial nerve at a level just proximal to the distal third of the humerus.14 Due to the force of injury, the proximal segment moves distally, causing displacement of the intermuscular septum. The radial nerve, which runs through this septum, may subsequently get tethered and injured. The nerve may also get lacerated when the apex of the distal fragment moves radially and proximally.8 Although this mechanism of radial nerve injury has been widely accepted, many recent studies dispute the constant relationship between the Holstein-Lewis fracture fragment and radial nerve injury.9,14,15 Similarly, a study by Bono and colleagues16 noted that the radial nerve has a more proximal decussation than previously reported. Their conclusion was that the nerve travels the distal half of the humerus along a superficial course. In addition, the AO classification can be used to describe fractures and their associated patterns.1 The AO classification divides diaphyseal humeral shaft fractures into 3 categories depending on the amount of contact between the major fracture fragments. Simple fractures with more than 90% contact between the main fracture fragments are known as AO Type A fractures. AO Type B fractures (wedge fractures) and AO Type C fractures (complex fractures) have little or no contact between major fragments. Subtypes also exist based on direction and fracture extent within the 3 major categories. According to Tytherleigh-Strong and colleagues,5 fractures of the middle third of the
humeral shaft arise with an incidence of 64.2% and AO Type A fractures have a similar incidence of 63.3%. Researchers differ in their incidence of radial nerve injury with regard to location of the humeral shaft fracture. For instance, Bostman and colleagues15 noted an equal incidence of radial nerve injuries in fractures of the middle and distal third humeral shaft. However, some have reported that a higher likelihood of neurovascular injuries occurs in middle third of humerus fractures,9 whereas others have observed an increase in neurovascular injuries in distal third humeral shaft fractures.17 Fracture pattern associated with radial nerve palsies is also variable; most occur in the presence of a spiral fracture, although transverse and oblique fractures can also result in a radial nerve injury.9,15,17
CLASSIFICATION/DIAGNOSIS Radial nerve palsies can be classified as either partial or complete. To begin determining the type of palsy, one must perform a complete physical examination. A thorough baseline examination consists of sensory and motor evaluation of the median, ulnar, and radial nerves. Radial nerve sensation can be tested to light touch and pinprick on the dorsal hand at the level of the first web space. Radial nerve motor function can be determined by testing active extension of the wrist and of the fingers (including the thumb) at the metacarpophalangeal joints. In addition, the absence of brachioradialis or extensor carpi radialis longus firing may indicate a proximal injury at the level of the humeral shaft.18 After a thorough physical examination, complete motor loss has been noted to occur in 50% to 68% of radial nerve palsies.9,17 Primary nerve palsies noted during the initial physical examination usually have occurred at the time of injury. Secondary nerve palsies may arise at any point during the active treatment of the fracture; these can represent up to 20% of all nerve palsies.15,19 The Seddon or Sunderland classification system can be used in further defining the type of peripheral nerve injury.20,21 The initial definition of a radial nerve injury as primary or secondary may be a prognostic factor in the ultimate recovery of the nerve. One study demonstrated 40% recovery in patients with a primary palsy and 100% recovery in patients with a secondary palsy after treatment of a humeral shaft fracture (closed or open reduction with internal fixation).22 Other studies with primary radial nerve palsies have demonstrated spontaneous recovery in 85% after closed fractures of the humerus.15 Secondary nerve palsies after humeral shaft fractures may occur during closed treatment or
Following Fractures of the Humerus after surgical fixation. Shah and Bhatti23 reviewed 62 patients with radial nerve palsies and humeral shaft fractures, of which 17 patients developed a secondary nerve palsy. Of these 17 patients, 11 of them had true closed management of their fractures consisting of cast/splint treatment, with or without manipulation of their fracture; 4 patients were treated with olecranon pin traction. Eight of these 17 patients had surgical exploration of their nerves, with all of them demonstrating intact nerves; however, 3 patients had nerves impinging on fracture fragments and 1 patient had the radial nerve entrapped in scar. All 17 patients who had secondary nerve palsy demonstrated complete recovery of their radial nerve function. This study demonstrated that closed management of humeral shaft fractures can lead to secondary nerve palsies, all of which recovered. Surgical management of humeral shaft fractures can also lead to secondary palsies of the radial nerve. The least invasive technique is intramedullary nailing; however, this is not recommended in radial nerve palsies associated with humeral shaft fractures, as potential entrapment of the nerve in the fracture site leaves it vulnerable to further damage. The incidence of radial nerve injury following this technique has been reported to be between 0% and 5%.24 Other series examining radial nerve palsy following intramedullary nailing has identified that most palsies are temporary and resolve spontaneously.25–27 Alternatively, open reduction with compression plating is the most common procedure for humeral shaft fracture fixation. This technique can lead to radial nerve injury in up to 10% of cases.28,29 This approach allows for an anatomic reduction with the most predictable rate of fracture union.30,31 Routine exploration of the radial nerve is recommended during compression plating of the humerus, particularly in cases with preoperative radial nerve palsies.24
MANAGEMENT/TREATMENT To begin evaluating the status of a radial nerve injury and what type of treatment should be used, an electrodiagnostic study can be helpful. These studies are not useful in the acute setting, but may have a role in the subacute setting in determining the level and extent of nerve injury.18 It can also be used to determine a baseline nerve function at the 3-week point to guide treatment during the observation period. These baseline electrodiagnostic studies may demonstrate “fibrillation potentials, positive sharp waves, and monophasic action potentials of short duration.”32 Most patients with spontaneous recovery begin to demonstrate recovery during the first few months;
however, an electrodiagnostic study may serve as an adjunct study for those lacking nerve recovery at the 6-week or 12-week point.23,33,34 If a follow-up electrodiagnostic study at the 12-week point shows similar findings as the baseline, then exploration may be indicated. However, if the 12-week follow-up study shows “improved nerve function with larger polyphasic motor unit action potentials of longer duration,” then some degree of spontaneous recovery may be expected.32 However, the course of this subset of patients is not predictable. Significant controversy persists with regard to the management of a radial nerve palsy associated with a humeral shaft fracture. Currently, noncontroversial and generally well-accepted indications for early exploration include open fractures, radial nerve palsy after closed reduction, associated vascular injuries, high-velocity gunshot wounds, penetrating injuries, severe soft tissue injuries, or any case with a high suspicion of a direct nerve laceration (Box 1).8–10,17,29,35–39 Ring and colleagues40 retrospectively reviewed patients with a high-energy humeral shaft fracture with an associated complete radial nerve palsy. All 6 patients with a transected radial nerve had a complex open fracture. However, the management of a radial nerve palsy with a closed humerus fracture can be divided into 2 treatment camps: 1. Late exploration 2. Early exploration.
Late Exploration Although early reports recommended surgical management with exploration for primary radial nerve palsies after humeral shaft fractures,8,35 with time, investigators have leaned toward no immediate exploration of the radial nerve following closed fractures of the humerus because of a high rate of recovery (over 70%).3,17,19,22,29,35,41 One study found an incidence of 87.3% functional recovery after primary radial nerve palsies
Box 1 Indications for early exploration of a radial nerve palsy following fracture of the humerus Radial nerve palsy after a closed reduction Open fracture Vascular injury High-velocity gunshot wound Associated severe soft tissue injury
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Niver & Ilyas managed with no immediate surgical exploration.42 Similarly, many studies have noted that the radial nerve is usually contused and does not require immediate exploration.9,15,19,22 During routine exploration of radial nerve palsies associated with humeral shaft fractures, one study found a transection rate of only 12%.9 Another study, by Sonneveld and colleagues,43 reviewed 17 cases of radial nerve palsies after humeral shaft fractures. Fourteen fractures were explored, with 13 of the radial nerves noted to be undamaged. Clinical recovery was seen in 12 of the 14 patients with nerve exploration. In a systematic literature review of radial nerve palsy associated with fractures of the humeral shaft, Shao and colleagues44 identified a spontaneous radial nerve recovery rate of 70.7% in patients treated nonoperatively, and an overall recovery rate of 88.1% regardless of treatment and timing of intervention. Furthermore, they did not find a difference in outcome among patients treated with early or late exploration. In short, proponents of late exploration may argue that delaying surgical exploration can decrease the risk of the usual surgical complications, such as infection or scarring, in patients who may otherwise recover radial nerve spontaneously anyway. Another potential advantage of delaying surgery is to permit thickening of the neurilemmal sheath, making future nerve repair easier.18
Early Exploration Advocates of early exploration of a radial nerve palsy may argue that a sufficient number of radial nerve injuries requiring treatment after closed humeral shaft fractures routinely exist, warranting early exploration. Moreover, early exploration and expedient repair of a radial nerve laceration will result in a more superior outcome than a delayed repair. Series with late exploration have revealed nerve laceration or entrapment to be present 6% to 25% of the time.9,19,20,22,35,45 Moreover, the systematic review performed by Shao and colleagues44 identified a spontaneous recovery rate of 70% but an overall recovery rate of only 88%. In addition, Pollock and colleagues9 noted nerve lacerations in 20% to 42% of cases after late exploration. They also noted poor results clinically after late repair. Evidence has also been shown that delays of more than 5 months can result in poorer outcomes.10 Delaying surgery may result in irreversible nerve damage without motor endplate reinnervation within 12 to 18 months of injury for useful return of function.18 Similarly, if no improvement is seen after 7 months, then spontaneous recovery is not likely to occur.46
Box 2 Potential advantages of early exploration of a radial nerve palsy following a closed fracture of the humerus Earlier nerve injury characterization and repair Immediate fracture stabilization and earlier rehabilitation Less muscular atrophy and endplate loss Earlier return to function
Subsequently, advocates for early exploration of a radial nerve palsy with a simple closed humerus fracture would argue that after consideration of the plethora of available series, including a number of series that have documented the risk of a nerve laceration or incarceration with a closed fracture of the humerus to be as high as 25%, that expectant or delayed nerve exploration can compromise ultimate recovery (Box 2). Prolonged observation of cases with a lacerated or incarcerated radial nerve will result in no radial nerve recovery, potential atrophy and motor endplate loss, compromised nerve recovery on late exploration and repair, and significant interval loss of patient function and livelihood. In contrast, early exploration and repair performed earlier can facilitate better characterization of the nerve injury, quicker nerve recovery on repair with less distal endplate loss, less muscular atrophy, quicker return to function, and peace of mind. Moreover, after fracture fixation and stabilization is achieved, a neurolysed or repaired nerve will potentially benefit from a better environment for recovery with less tension, motion, or callus formation to impede nerve healing.17,35
SUMMARY A radial nerve palsy is the most common peripheral nerve injury following a humerus fracture, occurring in up to 2% to 17% of cases.8–10 These injuries can be classified as either partial or complete, depending on the extent of physical examination findings, as well as primary or secondary, depending on the palsy’s timing of presentation. Surgical exploration is recommended in cases with open or complex fractures, particularly those associated with penetrating trauma. Radial nerve palsies associated with closed fractures of the humerus have traditionally been recommended to be treated with observation, with late exploration restricted to cases without spontaneous nerve recovery at 3 to 6 months. Advocates for early
Following Fractures of the Humerus exploration believe that late exploration can result in increased muscular atrophy, motor endplate loss, compromised nerve recovery on delayed repair, and significant interval loss of patient function and livelihood. In contrast, early exploration maximizes nerve injury characterization and repair as well as facilitates early fracture stabilization, which can avoid late nerve injury or incarceration. Moreover, early exploration yielding a nerve injury that is repaired can lead to quicker nerve recovery with less motor endplate loss, less muscular atrophy, and quicker return to function.
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