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Anatomic variation—A bony canal for the median nerve at the distal humerus: A case report
Anatomic Variation—A Bony Canal for the Median Nerve at the Distal Humerus: A Case Report Kenichi Kazuki, MD, Takeshi Egi, MD, Mitsuhiro Okada, MD, Kunio Takaoka, MD, Osaka, Japan
We report a rare anatomic variation in which the median nerve travels in a bony canal of the distal humerus, separating from the brachial artery. We encountered this during neurolysis for posttraumatic median nerve palsy in a 10-year-old boy. We suggest that this anatomic variation was related strongly to this patient’s median nerve palsy. (J Hand Surg 2004;29A:953–956. Copyright © 2004 by the American Society for Surgery of the Hand.) Key words: Anatomic variation, humerus, supracondylar process, median nerve.
Osseous anatomic variation of the distal humerus in association with median nerve palsy is a rare condition. There have been some reports of median nerve neuropathy due to the humeral supracondylar process.1–9 Struthers described in detail the supracondylar process of the humerus and its associated ligament, which runs usually from this process to the medial condyle.4 The anatomic relationship between the process, with its associated Struthers’ ligament and the neurovascular bundle, is varied. Usually the neurovascular bundle is located under the arcade that is formed by the process and its associated ligament.1,2,4 – 8 Ay et al,3 however, reported an unusual case of a supracondylar process that was located beneath the neurovascular bundle. A case in which the brachial artery was not involved has also been From the Department of Orthopaedic Surgery, Osaka City University Graduate School of Medicine, Osaka, Japan. Received for publication April 7, 2004; accepted in revised form May 20, 2004. No benefits in any form have been received or will be received by a commercial party related directly or indirectly to the subject of this article. Reprint requests: Kenichi Kazuki, MD, Department of Orthopaedic Surgery, Osaka City University Graduate School of Medicine, 1-4-3 Asahimachi, Abeno-ku, Osaka 545-8585, Japan. Copyright © 2004 by the American Society for Surgery of the Hand 0363-5023/04/29A05-0028$30.00/0 doi:10.1016/j.jhsa.2004.05.018
reported.9 The supracondylar process is the homologue of the entepicondylar foramen of many animals.10 In climbing animals the supracondylar process normally is present and forms a foramen that serves to protect the neurovascular bundle and provide muscular attachment for the pronator teres muscle.5 We present a case of a 10-year-old boy with median nerve palsy in whom this variation was found at surgical exploration. Computed tomography (CT) scan suggested that a short osseous canal for the median nerve was formed at the medial condyle of the humerus.
Case Report A 10-year-old right-handed boy was brought to our clinic with incomplete median nerve palsy after an elbow injury. Three months earlier, while playing baseball, he was sliding headfirst and had hit his left elbow on a base. The elbow became swollen and mobility of the thumb and index finger were impaired. He was brought to the emergency department of another hospital but radiographs did not show any fractures or dislocations of the elbow. Although swelling disappeared after 3 weeks of immobilization and he regained the full range of motion of the elbow the median nerve palsy remained. Examination of his left elbow showed tenderness The Journal of Hand Surgery
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The Journal of Hand Surgery / Vol. 29A No. 5 September 2004
The cubital fossa was approached anteriorly. The brachial artery was identified at the cubital fossa but the median nerve was absent. The median nerve was found running parallel to the brachial artery along the medial border of the biceps in the distal arm. As the nerve and artery coursed distally the median nerve ran dorsally, separating from the brachial artery and penetrating the medial condyle of the humerus (Fig. 2). The anterior interosseous nerve was located in the normal position at the forearm level. Under a microscope we excised carefully bridging bone that was present between nerve funiculi and on the outside of the median nerve and moved the median nerve outside the osseous groove (Fig. 3). Continuity of the median nerve was preserved and no distinct neuroma was recognized. Postsurgical 3-dimensional CT showed an osseous groove located on the medial side of the physis of the medial epicondyle. This groove was the floor of an osseous canal, which was penetrated by the median nerve (Fig. 4). Neurologic findings
Figure 1. A presurgical radiograph showing an abnormal shadow on the medial condyle of the distal humerus (arrow).
on the medial side of the distal humerus but a bony process was not palpable. Incomplete sensory disturbance and muscle weakness were present in left median nerve distribution. Mild weakness of the pronator teres and flexor carpi radialis muscles and remarkable weakness of flexor digitorum superficialis, flexor pollicis longus, index flexor digitorum profundus, and abductor pollicis brevis muscles was found in muscular strength tests. Grip strength was 9.9 kg on the affected side and 19.6 kg on the unaffected side. Active flexion was impossible for both the thumb interphalangeal and index distal interphalangeal joints. There was thenar atrophy and thumb opposition was impossible. Hypesthesia was mild in the long and ring fingers, moderate in the index finger, and severe in the thumb. Tinel’s sign was present at the carpal tunnel level. The electrophysiologic examination was consistent with a median nerve palsy at the elbow. Conservative treatments for 6 months failed and the patient had surgical exploration of the median nerve. Presurgical radiography showed an abnormal shadow on the medial side of the physis of the medial epicondyle but we did not consider it related to the median nerve before surgery (Fig. 1).
Figure 2. Intraoperative findings. (A) The median nerve penetrates the medial condyle of the distal humerus. White arrow points to the bridging bone over the median nerve. (B) Schema of the photograph to illustrate anatomic relationships.
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were improved after surgery. Thumb abduction did not recover but both thumb interphalangeal and index distal interphalangeal joint flexion were possible at the 3-month postsurgical examination. Grip strength was 15.7 kg on the affected side and 20.1 kg on the unaffected side. Moderate hypesthesia remained in the long finger but sensory disturbance of the other fingers and thumb showed remarkable improvement. The location of Tinel’s sign moved to the level of the distal palmar crease. The patient did not have noteworthy difficulty with the activities of daily living.
Discussion
Figure 3. Intraoperative findings after the bridging bone excision. (A) The tip of the forceps points to the osseous groove. (B) Schema of the photograph to illustrate anatomic relationships.
The supracondylar process is a rare anatomic variation of the distal humerus10 and has been reported as an osseous anatomic variation in association with median nerve compression neuropathy.1–9 It occurs usually unilaterally but Subasi et al8 reported a bilateral case. It may be found incidentally in radiographs taken for another reason. Occasionally isolated fracture of the process occurs.11A process was found in 7 of 1000 in Terry’s study.12 Al-Qattan and Husband2 reported that Lund first described median nerve compression at the level of the supracondylar process and ligament of Struthers in 1930. In the present case the supracondylar process was not seen in radiographs and the region was more distal than the supracondylar process. The lesion in the present
Figure 4. (A) Schema of the distal humerus before surgery. The black area indicated by the arrow shows the excised bridging bone. (B) Axial CT scan after surgery. (C) Postsurgical 3-dimensional CT scan of the distal humerus. Arrow points to the osseous groove.
956
The Journal of Hand Surgery / Vol. 29A No. 5 September 2004
case is better described as a short canal or a foramen of the medial condyle of the distal humerus. Although it is unclear whether the elbow injury in the present case contributed to the formation of a canal or a foramen it seems unlikely that a canal or foramen containing the median nerve was formed solely by the elbow injury. We consider 2 different possibilities for the present lesion. It may be a completely new anatomic variation different from the supracondylar process or it may be a subgroup of the supracondylar process in a child. Schrader and Reina6 reported a case of a supracondylar process in a child; in their report the supracondylar process was located more distally than usually seen in adults. The median nerve palsy in the present case was occasioned by an unusual injury. It might be that the bony canal was present and as the child grew the canal became too small to accomodate the nerve, which was enlarging. The minor elbow trauma may have caused some mild swelling adjacent to the median nerve leading to the onset of symptoms of median nerve palsy. Therefore an anatomic variation such as that in the present case should be included in the differential diagnosis of median nerve palsy, especially when associated with an unusual elbow injury.
References 1. Al-Naib I. Humeral supracondylar spur and Struthers’ ligament. A rare cause of neurovascular entrapment in the upper limb. Int Orthop 1994;18:393–394. 2. Al-Qattan MM, Husband JB. Median nerve compression by the supracondylar process: a case report. J Hand Surg 1991; 16B:101–103. 3. Ay S, Bektas U, Yilmaz C, Diren B. An unusual supracondylar process syndrome. J Hand Surg 2002;27A:913– 915. 4. Ivins GK. Supracondylar process syndrome: a case report. J Hand Surg 1996;21A:279 –281. 5. Kessel L, Rang M. Supracondylar spur of the humerus. J Bone Joint Surg 1966;48B:765–769. 6. Schrader PA, Reina CR. Struthers’ ligament neuropathy in a juvenile. Orthopaedics 1994;17:723–725. 7. Sener E, Takka S, Cila E. Supracondylar process syndrome. Arch Orthop Trauma Surg 1998;117:418 – 419. 8. Subasi M, Kesemenli C, Necmioglu S, Kapukaya A, Demirtas M. Supracondylar process of the humerus. Acta Orthop Belg 2002;68:72–75. 9. Symeonides PP. The humerus supracondylar process syndrome. Clin Orthop 1972;82:141–143. 10. Williams PL, Warwick R, Dyson M, Bannister LH, eds. Gray’s Anatomy. 37th ed. New York: Churchill Livingstone, 1989:409. 11. Spinner RJ, Lins RE, Jacobson SR, Nunley JA. Fractures of the supracondylar process of the humerus. J Hand Surg 1994;19A:1038 –1041. 12. Terry RJ. A study of the supracondyloid process in the living. Am J Phys Anthropol 1921;4:129 –139.
We report a rare anatomic variation in which the median nerve travels in a bony canal of the distal humerus, separating from the brachial artery. We encountered this during neurolysis for posttraumatic median nerve palsy in a 10-year-old boy. We suggest that this anatomic variation was related strongly to this patient’s median nerve palsy. (J Hand Surg 2004;29A:953–956. Copyright © 2004 by the American Society for Surgery of the Hand.) Key words: Anatomic variation, humerus, supracondylar process, median nerve.
Osseous anatomic variation of the distal humerus in association with median nerve palsy is a rare condition. There have been some reports of median nerve neuropathy due to the humeral supracondylar process.1–9 Struthers described in detail the supracondylar process of the humerus and its associated ligament, which runs usually from this process to the medial condyle.4 The anatomic relationship between the process, with its associated Struthers’ ligament and the neurovascular bundle, is varied. Usually the neurovascular bundle is located under the arcade that is formed by the process and its associated ligament.1,2,4 – 8 Ay et al,3 however, reported an unusual case of a supracondylar process that was located beneath the neurovascular bundle. A case in which the brachial artery was not involved has also been From the Department of Orthopaedic Surgery, Osaka City University Graduate School of Medicine, Osaka, Japan. Received for publication April 7, 2004; accepted in revised form May 20, 2004. No benefits in any form have been received or will be received by a commercial party related directly or indirectly to the subject of this article. Reprint requests: Kenichi Kazuki, MD, Department of Orthopaedic Surgery, Osaka City University Graduate School of Medicine, 1-4-3 Asahimachi, Abeno-ku, Osaka 545-8585, Japan. Copyright © 2004 by the American Society for Surgery of the Hand 0363-5023/04/29A05-0028$30.00/0 doi:10.1016/j.jhsa.2004.05.018
reported.9 The supracondylar process is the homologue of the entepicondylar foramen of many animals.10 In climbing animals the supracondylar process normally is present and forms a foramen that serves to protect the neurovascular bundle and provide muscular attachment for the pronator teres muscle.5 We present a case of a 10-year-old boy with median nerve palsy in whom this variation was found at surgical exploration. Computed tomography (CT) scan suggested that a short osseous canal for the median nerve was formed at the medial condyle of the humerus.
Case Report A 10-year-old right-handed boy was brought to our clinic with incomplete median nerve palsy after an elbow injury. Three months earlier, while playing baseball, he was sliding headfirst and had hit his left elbow on a base. The elbow became swollen and mobility of the thumb and index finger were impaired. He was brought to the emergency department of another hospital but radiographs did not show any fractures or dislocations of the elbow. Although swelling disappeared after 3 weeks of immobilization and he regained the full range of motion of the elbow the median nerve palsy remained. Examination of his left elbow showed tenderness The Journal of Hand Surgery
953
954
The Journal of Hand Surgery / Vol. 29A No. 5 September 2004
The cubital fossa was approached anteriorly. The brachial artery was identified at the cubital fossa but the median nerve was absent. The median nerve was found running parallel to the brachial artery along the medial border of the biceps in the distal arm. As the nerve and artery coursed distally the median nerve ran dorsally, separating from the brachial artery and penetrating the medial condyle of the humerus (Fig. 2). The anterior interosseous nerve was located in the normal position at the forearm level. Under a microscope we excised carefully bridging bone that was present between nerve funiculi and on the outside of the median nerve and moved the median nerve outside the osseous groove (Fig. 3). Continuity of the median nerve was preserved and no distinct neuroma was recognized. Postsurgical 3-dimensional CT showed an osseous groove located on the medial side of the physis of the medial epicondyle. This groove was the floor of an osseous canal, which was penetrated by the median nerve (Fig. 4). Neurologic findings
Figure 1. A presurgical radiograph showing an abnormal shadow on the medial condyle of the distal humerus (arrow).
on the medial side of the distal humerus but a bony process was not palpable. Incomplete sensory disturbance and muscle weakness were present in left median nerve distribution. Mild weakness of the pronator teres and flexor carpi radialis muscles and remarkable weakness of flexor digitorum superficialis, flexor pollicis longus, index flexor digitorum profundus, and abductor pollicis brevis muscles was found in muscular strength tests. Grip strength was 9.9 kg on the affected side and 19.6 kg on the unaffected side. Active flexion was impossible for both the thumb interphalangeal and index distal interphalangeal joints. There was thenar atrophy and thumb opposition was impossible. Hypesthesia was mild in the long and ring fingers, moderate in the index finger, and severe in the thumb. Tinel’s sign was present at the carpal tunnel level. The electrophysiologic examination was consistent with a median nerve palsy at the elbow. Conservative treatments for 6 months failed and the patient had surgical exploration of the median nerve. Presurgical radiography showed an abnormal shadow on the medial side of the physis of the medial epicondyle but we did not consider it related to the median nerve before surgery (Fig. 1).
Figure 2. Intraoperative findings. (A) The median nerve penetrates the medial condyle of the distal humerus. White arrow points to the bridging bone over the median nerve. (B) Schema of the photograph to illustrate anatomic relationships.
Kazuki et al / Anatomic Variation of the Distal Humerus
955
were improved after surgery. Thumb abduction did not recover but both thumb interphalangeal and index distal interphalangeal joint flexion were possible at the 3-month postsurgical examination. Grip strength was 15.7 kg on the affected side and 20.1 kg on the unaffected side. Moderate hypesthesia remained in the long finger but sensory disturbance of the other fingers and thumb showed remarkable improvement. The location of Tinel’s sign moved to the level of the distal palmar crease. The patient did not have noteworthy difficulty with the activities of daily living.
Discussion
Figure 3. Intraoperative findings after the bridging bone excision. (A) The tip of the forceps points to the osseous groove. (B) Schema of the photograph to illustrate anatomic relationships.
The supracondylar process is a rare anatomic variation of the distal humerus10 and has been reported as an osseous anatomic variation in association with median nerve compression neuropathy.1–9 It occurs usually unilaterally but Subasi et al8 reported a bilateral case. It may be found incidentally in radiographs taken for another reason. Occasionally isolated fracture of the process occurs.11A process was found in 7 of 1000 in Terry’s study.12 Al-Qattan and Husband2 reported that Lund first described median nerve compression at the level of the supracondylar process and ligament of Struthers in 1930. In the present case the supracondylar process was not seen in radiographs and the region was more distal than the supracondylar process. The lesion in the present
Figure 4. (A) Schema of the distal humerus before surgery. The black area indicated by the arrow shows the excised bridging bone. (B) Axial CT scan after surgery. (C) Postsurgical 3-dimensional CT scan of the distal humerus. Arrow points to the osseous groove.
956
The Journal of Hand Surgery / Vol. 29A No. 5 September 2004
case is better described as a short canal or a foramen of the medial condyle of the distal humerus. Although it is unclear whether the elbow injury in the present case contributed to the formation of a canal or a foramen it seems unlikely that a canal or foramen containing the median nerve was formed solely by the elbow injury. We consider 2 different possibilities for the present lesion. It may be a completely new anatomic variation different from the supracondylar process or it may be a subgroup of the supracondylar process in a child. Schrader and Reina6 reported a case of a supracondylar process in a child; in their report the supracondylar process was located more distally than usually seen in adults. The median nerve palsy in the present case was occasioned by an unusual injury. It might be that the bony canal was present and as the child grew the canal became too small to accomodate the nerve, which was enlarging. The minor elbow trauma may have caused some mild swelling adjacent to the median nerve leading to the onset of symptoms of median nerve palsy. Therefore an anatomic variation such as that in the present case should be included in the differential diagnosis of median nerve palsy, especially when associated with an unusual elbow injury.
References 1. Al-Naib I. Humeral supracondylar spur and Struthers’ ligament. A rare cause of neurovascular entrapment in the upper limb. Int Orthop 1994;18:393–394. 2. Al-Qattan MM, Husband JB. Median nerve compression by the supracondylar process: a case report. J Hand Surg 1991; 16B:101–103. 3. Ay S, Bektas U, Yilmaz C, Diren B. An unusual supracondylar process syndrome. J Hand Surg 2002;27A:913– 915. 4. Ivins GK. Supracondylar process syndrome: a case report. J Hand Surg 1996;21A:279 –281. 5. Kessel L, Rang M. Supracondylar spur of the humerus. J Bone Joint Surg 1966;48B:765–769. 6. Schrader PA, Reina CR. Struthers’ ligament neuropathy in a juvenile. Orthopaedics 1994;17:723–725. 7. Sener E, Takka S, Cila E. Supracondylar process syndrome. Arch Orthop Trauma Surg 1998;117:418 – 419. 8. Subasi M, Kesemenli C, Necmioglu S, Kapukaya A, Demirtas M. Supracondylar process of the humerus. Acta Orthop Belg 2002;68:72–75. 9. Symeonides PP. The humerus supracondylar process syndrome. Clin Orthop 1972;82:141–143. 10. Williams PL, Warwick R, Dyson M, Bannister LH, eds. Gray’s Anatomy. 37th ed. New York: Churchill Livingstone, 1989:409. 11. Spinner RJ, Lins RE, Jacobson SR, Nunley JA. Fractures of the supracondylar process of the humerus. J Hand Surg 1994;19A:1038 –1041. 12. Terry RJ. A study of the supracondyloid process in the living. Am J Phys Anthropol 1921;4:129 –139.