Ulnar nerve injury associated with trampoline injuries.

Objective: This study reports three cases of ulnar neuropathy after trampoline injuries in children.

Methods: A chart review was performed on children who sustained an ulnar nerve injury from a trampoline accident. In all cases, surgical intervention was required.

Results: Injuries included upper-extremity fractures in two cases and an upper-extremity laceration in one case. All cases required surgical exploration with internal neurolysis and ulnar nerve transposition. Nerve grafts were used in two cases and an additional nerve transfer was used in one case. All patients had return of intrinsic hand function and sensation after surgery.

Conclusion: Children should be followed for evolution of ulnar nerve neuropathy after upper-extremity injury with consideration for electrical studies and surgical exploration if there is no improvement after 3 months.

Key Words: injury, retrospective study, ulnar nerve

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Trampolines have become extremely popular for recreation and gymnastics training since their introduction in 1936. As reported by the U.S. Consumer Product Safety Commission, there has been a significant increase in trampoline injuries in children. (1, 2) The most common injuries include soft tissue injury, fracture or dislocation, and lacerations. (3) There have been no reports of ulnar nerve neuropathy associated with trampoline-related injuries. The purpose of this study was to report cases of ulnar nerve injury sustained from trampoline injuries.

Methods

After approval from the institutional human studies committee, a chart review was performed on children who sustained an ulnar nerve injury from a trampoline accident. In all cases, surgical intervention was required.

Results

Three cases of ulnar nerve injury sustained in children younger than 10 years of age are presented (Tables 1 and 2). A variety of injury patterns resulted in a spectrum of ulnar nerve injuries (Table 3). Surgical exploration and repair was required in all cases to correct unresolved ulnar nerve motor and sensory deficits (Table 4).

Case Reports

Case 1

A 4-year-old boy who fell onto his arm while jumping supervised on a trampoline sustained a displaced supracondylar fracture. He was evaluated in the emergency room and taken to the operating room for crossed percutaneous pinning under general anesthesia. He was treated with an above-elbow splint for 2 weeks and casted for 2 weeks. A pin tract infection resolved with oral antibiotics. He developed numbness in the ulnar nerve distribution, with weakness in the right hand for the next month. After 4 months without improvement he underwent exploration of the ulnar nerve. There was significant scarring found around the ulnar nerve directly behind the medial epicondyle in the cubital tunnel region. Intraoperative electrical studies were performed. An action potential was obtained across the area of scarring. Internal neurolysis demonstrated that all fascicles were in continuity. An anterior submuscular transposition of the ulnar nerve was performed. He experienced recovery of distal sensation and ulnar nerve extrinsic and intrinsic muscle function to his hand.

Case 2

A 9-year-old girl who fell onto her left arm while jumping supervised on a trampoline sustained minimally displaced closed proximal radial and ulnar fractures. She was evaluated in the emergency room and received casting only. She experienced immediate numbness in the ulnar nerve distribution, with weakness in the left hand. After 5 months without improvement, she underwent exploration with intraoperative electrical studies. There was significant scarring, with the ulnar nerve found directly adherent to the ulna fracture site, and an action potential obtainable across only one fascicle. Internal neurolysis with anterior submuscular transposition of the ulnar nerve was performed with three fascicular grafts across a 3-cm gap at the level of the proximal forearm. She ultimately experienced recovery of distal sensation and ulnar extrinsic and intrinsic muscle function to her hand.

Case 3

A 9-year-old boy who fell off a trampoline received a laceration to the proximal forearm. He was evaluated in the emergency room and his laceration was repaired. He experienced immediate numbness in the ulnar nerve distribution and weakness to his hand. With no improvement, he was referred 9 months after injury and underwent exploration with intraoperative electrical studies. There was 90% transection of the ulnar nerve and with an action potential obtainable across only one uninvolved fascicle. Internal neurolysis with anterior submuscular transposition of the ulnar nerve was performed, with four fascicular grafts across a 3-cm gap. In addition, a nerve transfer of the anterior interosseous branch of the median nerve to the deep motor branch of the distal ulnar nerve was performed. (4) He ultimately experienced recovery of distal sensation and ulnar extrinsic and intrinsic muscle function to his hand.

Discussion

Trampolines continue to be sold in increasing numbers to the private consumer. According to a 2001 U.S. Consumer Product Safety Review, trampoline sales have increased by 350% from 140,000 in 1990 to 640,000 in 1998. It is estimated that there are more than 3 million trampolines in use in the United States today. (5)

Accompanying the increase in trampoline sales has been an increase in the number of trampoline-related injuries in the pediatric population of epidemic proportions. One study cited one child injured every 3 days. (1) The setting for more than 96% of these injuries was in the privately owned backyard trampoline. (6) Unfortunately, most trampoline injuries involve children, approximately 88% of whom are younger than 14 years old. (7) Children are at increased risk for injury in such high-energy falls compared with adults, because of immature judgment, coordination, strength, and open growth plates. (8) Injuries range from mild to severe and 4% are associated with hospitalization. (5) The most common injuries include soft tissue injury, lacerations, dislocation, and fracture. Fractures are the most common reason for hospitalization and surgery (83%). (9) Fortunately, devastating cervical spine injuries with paraplegia or quadriplegia are rare at a reported rate of 0.5%. (8) Eleven cases of death have been reported since 1991. (2) In a literature search, there were no reports of peripheral nerve injury.

The ulnar nerve is particularly at increased risk in its superficial location in the region of the medial elbow. Ulnar nerve injury may follow an injury to the upper extremity either at the time of injury, at the time of intervention, or delayed beyond the time of injury. Blunt injury may cause contusions, and sharp injury may cause direct nerve laceration. Laceration by bony shards may occur to the ulnar nerve after fractures of the humerus (10) or ulna. (11, 12) Fracture of any upper-extremity bone may result in a compartment syndrome. At the time of intervention, the ulnar nerve may become entrapped with attempts at closed reduction or closed percutaneous pinning. (13, 14) Although rare, ulnar neuropathy may occur beyond the time of injury, with entrapment by scar or callus formation. (15) Most injuries result in temporary nerve dysfunction and resolve within weeks. (16) However, all injuries should be followed closely for evolution of ulnar nerve neuropathy after upper-extremity injury with consideration for electrical studies if there is no clinical improvement after 3 months. (11) If electrical studies show no evidence of reinnervation, surgical exploration is indicated.

We report three cases of ulnar nerve injury sustained in children younger than 10 years old. The mechanism of ulnar nerve injury was different in each case; however, surgical exploration and repair were required for all cases to correct unresolved motor and sensory deficits. A mixed pattern of nerve injuries was found. (17) Onset of symptoms occurred immediately in two cases and delayed 1 month in one case. Exploration was required in all three cases after no improvement in symptoms after a period of observation. All three cases required intraoperative electrical studies with internal neurolysis and ulnar nerve transposition. Additional nerve grafts were used in two cases for nerve discontinuity and neuroma in continuity. Nerve transfer was added in the third case to improve recovery after prolonged intrinsic muscle denervation of 9 months. (4) In each case, there was return of intrinsic and extrinsic motor function and sensation to the hand after surgery.

Ulnar nerve injuries associated with closed injuries should receive physical therapy and be closely followed for a period of at least 3 months for evidence of improvement. Most injuries are first- or second-degree and resolve completely. If there is no evidence of resolution, electrodiagnostic studies for degree and level of injury should be sought and surgical exploration planned after 3 months with no evidence of reinnervation. Open injuries associated with open fractures, lacerations, or open reduction are candidates for early surgical exploration. If the nerve is found disrupted, repair or grafting is performed. If the nerve is in continuity and if some electrical continuity is present, partial laceration, neuroma in continuity, or entrapment by callus are possibilities. Internal neurolysis and anterior transposition are used to free nerve fascicles from scar or callus and reduce tension across the lesion. If electrical continuity is not present, fascicular nerve grafts are usually required after internal neurolysis. Vastamaki et al (18) cited nerve grafts longer than 7.5 cm and duration of injury longer than 16 months as poor prognostic factors. We perform nerve transfer (anterior interosseous branch of the median nerve to deep motor branch of the distal ulnar nerve) to improve intrinsic motor recovery for high ulnar nerve injuries. (4)

These cases with prolonged muscle denervation demonstrate that severe ulnar nerve injuries can occur after trampoline-related accidents. In conclusion, children should be followed closely for evolution of ulnar nerve neuropathy after upper-extremity injury. We recommend consideration for electrical studies and early surgical exploration if there is no improvement after 3 months.

Our greatest glory is not in never falling but in rising every time we
fall.
--Confucius

Table 1. Demographics and initial injury (a)

                                                            Onset of
      Age       Injury and initial                          ulnar nerve
Case  (yr)/sex  treatment                 Level             symptoms

1     4/M       Right closed Type III     Distal humerus    1 mo
                  supracondylar fracture
                K-wire and casting
2     9/F       Left closed proximal      Proximal forearm  Immediate
                  radius/ulnar fracture
                Casting
3     9/M       Left full-thickness       Proximal forearm  Immediate
                  laceration
                Laceration repair

(a) M, male; F, female; K, kirschner.

Table 2. Presenting physical examination (a)

                                                       Pinch/grip (lb)
                                                       (affected versus
Case  Clawing  Sensory         Froment  Tinel          unaffected)

1     +        No light touch  +        At pin site    Not done
               No 2pd
2     +        No light touch  +        None           7/20 versus 9/25
               No 2pd
3     +        No light touch  +        At laceration  4/10 versus 8/15
               No 2pd                     level

(a) 2pd, two-point discrimination.

Table 3. Intraoperative findings

      Degree of
      nerve
Case  injury     Findings                     Electrical studies

1     3          Dense scar encompassing      + across injury
                   nerve behind medial        + extrinsics/-intrinsics
                   epicondyle
2     4          Nerve adherent to ulna       + single fascicle only
                   fracture site with single
                   uninvolved fascicle
3     5          90% transection with         + single branch only
                   neuroma with small
                   uninvolved branch

Table 4. Operative procedures

                                                      Nerve
Case  Transposition  Neurolysis  Nerve graft          transfer

1     +              +           None                 None
2     +              +           3-cm gap, three      None
                                   fascicles (dorsal
                                   cutaneous and
                                   MABC donor)
3     +              +           3-cm gap, four       AIN to ulnar
                                   fascicles (sural     deep motor
                                   nerve graft)

(a) MABC, medial antebrachial cutaneous; AIN, anterior interosseous
nerve.

Accepted July 14, 2003.

References

1. Smith GA. Injuries to children in the United States related to trampolines, 1990-1995: A national epidemic. Pediatrics 1998;101:406-412.

2. U.S. Consumer Product Safety Commission. Consum Prod Safety Rev 2001 Winter;5(3).

3. Woodward GA, Furnival R, Schunk JE. Trampolines revisited: A review of 114 pediatric recreational trampoline injuries. Pediatrics 1992;89:849-854.

4. Novak CB, Mackinnon SE. Distal anterior interosseous nerve transfer to the deep motor branch of the ulnar nerve for reconstruction of high ulnar nerve injuries. J Reconstr Microsurg 2002;18:459-464.

5. U.S. Consumer Product Safety Commission. Trampolines. US Consum Prod Safety Commission Rep Sept 2000.

6. Smith GA, Shields BJ. Trampoline-related injuries to children. Arch Pediatr Adolesc Med 1998;152:694-699.

7. Larson BJ, Davis JW. Trampoline-related injuries. J Bone Joint Surg Am 1995;77:1174-1178.

8. Brown PG, Lee M. Trampoline injuries of the cervical spine. Pediatr Neurosurg 2000;32:170-175.

9. American Academy of Pediatrics, Committee on Injury and Poison Prevention and Committee on Sports Medicine and Fitness. Trampolines at home, school, and recreational centers. Pediatrics 1999;103:1053-1056.

10. Stahl S, Rosen N, Moscona R. Ulnar nerve palsy following fracture of the shaft of the humerus. J Orthop Trauma 1998;12:363-364.

11. Stahl S, Rozen N, Michaelson M. Ulnar nerve injury following midshaft forearm fractures in children. J Hand Surg [Br] 1997;22:788-789.

12. Neiman R, Maiocco B, Deeney VF. Ulnar nerve injury after closed forearm fractures in children. J Pediatr Orthop 1998;18:683-685.

13. Ikram MA. Ulnar nerve palsy: A complication following percutaneous fixation of supracondylar fractures of the humerus in children. Injury 1996;27:303-305.

14. Lyons JP, Ashley E, Hoffer MM. Ulnar nerve palsies after percutaneous cross-pinning of supracondylar fractures in children's elbows. J Pediatr Orthop 1998;18:43-45.

15. Prosser AJ, Hooper G. Entrapment of the ulnar nerve in a greenstick fracture of the ulna. J Hand Surg [Br] 1986;11:211-212.

16. Amillo S, Mora G. Surgical management of neural injuries associated with elbow fractures in children. J Pediatr Orthop 1999;19:573-577.

17. Sunderland Sir S. Nerves and Nerve Injuries. New York, Churchill Livingstone, 1978, ed 2.

18. Vastamaki M, Kallio PK, Solonen KA. The results of secondary microsurgical repair of ulnar nerve injury. J Hand Surg [Br] 1993;18:323-326.

RELATED ARTICLE: Key Points

* Children should be followed for evolution of ulnar nerve neuropathy after upper-extremity injury.

* Electrical studies and surgical exploration should be considered if there is no improvement after 3 months.

Melvin M. Maclin II, MD, Christine B. Novak, PT, MS, and Susan E. Mackinnon, MD

From the Division of Plastic and Reconstructive Surgery, Washington University School of Medicine, St. Louis, MO.

Reprint requests to Susan E. Mackinnon, MD, Division of Plastic and Reconstructive Surgery, Washington University School of Medicine, East Pavilion, Suite 17424, One Barnes-Jewish Hospital Plaza, St. Louis, MO 63110. Email: [e-mail]