- Email: [email protected]
Unusual origin of the motor branch of the ulnar nerve to the flexor carpi ulnaris
J Shoulder Elbow Surg (2008) 18, e38-e39
www.elsevier.com/locate/ymse
Unusual origin of the motor branch of the ulnar nerve to the flexor carpi ulnaris Aydıner Kalacı, MD*, Yunus Dog˘ramacı, MD, Teoman Toni Sevinc¸, MD, Ahmet Nedim Yanat, MD Department of Orthopaedics and Traumatology, Mustafa Kemal University Faculty of Medicine, Antakya, Hatay, Turkey Cubital tunnel syndrome is the second most common entrapment neuropathy in the upper extremity after carpal tunnel syndrome.3 When conservative measures fail,2 a variety of surgical options have been described, ranging from simple decompression to ulnar nerve transposition. The dissection must expose the ulnar nerve from the arcade of Struthers to the flexor carpi ulnaris. Knowledge of local anatomy of the ulnar nerve and its variations is important to prevent complications related to anatomic variations during ulnar nerve release. Nerve branches close to the elbow, which may be sensory branches to the elbow or motor branches to the flexor carpi ulnaris, must be identified. Furthermore, crossing branches from the medial antebrachial cutaneous nerve should be protected.7 Significant variations of the ulnar nerve have been identified that may contribute to iatrogenic injury during ulnar nerve release surgery.4 We report a patient undergoing in situ surgical decompression of the ulnar nerve in which a motor branch to the flexor carpi ulnaris originated from the ulnar nerve about 3 cm above the medial epicondyle.
Case report A 54-year-old man, who did manual labor, presented to our outpatient clinic with insidious onset of hypoesthesia and tingling in the entire small and ulnar side of the ring fingers, as well as *Reprint requests: Aydıner Kalacı, MD, Assistant Professor. Mustafa Kemal University Faculty of Medicine, Dept of Orthopaedics and Traumatology, 31100 Antakya, Hatay, Turkey. E-mail addresses: [email protected], [email protected] (A. Kalacı).
weakness in flexion of the little and ring fingers of 1-year duration. Despite of 3 months of conservative treatment, he stated that the symptoms were getting worse for 2 months, with night symptoms interfering with his sleep. The patient had no history of trauma or a relevant medical condition. Physical examination revealed tenderness at the ulnar notch in his left elbow, normal range of elbow motion, but no instability or deformity. Tinel’s sign was positive. Froment’s sign was positive. The peripheral vascular examination revealed normal pulses and negative (AdsoneRoos tests). Radiographic examination of left elbow revealed no bony lesion. A detailed physical and radiographic examination of the cervical spine revealed no pathologic findings. Nerve conduction and electromyographic studies of left upper extremity showed moderate compromise of the nerve at the elbow with decreased conduction velocity (motor conduction velocity of the ulnar nerve at the above-elbow to below-elbow segment was 36.1 m/s), consistent with cubital tunnel syndrome. After preoperative assessment, the patient was admitted for surgical treatment under the diagnosis of cubital tunnel syndrome. The operation was done under general anesthesia, using a pneumatic tourniquet. The surgical approach was performed through a curved 8-cm-long skin incision on the posteromedial aspect of the elbow. With careful dissection, the ulnar nerve was traced along its course, proximally from the medial intermuscular septum down to the origin of superficial flexor muscles of the forearm. A variant branch of the ulnar nerve was found originating from the ulnar nerve at a distance of 30 mm above the medial epicondyle, originating from the ulnar aspect of the nerve, and crossing it at the level of the epicondyle to the radial aspect, to enter the fascia of the flexor carpi ulnaris muscle (Figure 1). During full flexion of the elbow, the ulnar nerve was found to be under pressure from the constricting effect of aberrant branch. In situ surgical decompression was performed, because motor branches to the flexor carpi ulnaris of the ulnar nerve prevented anterior transposition of the ulnar nerve. The symptoms were
1058-2746/2008/$34.00 - see front matter Ó 2008 Journal of Shoulder and Elbow Surgery Board of Trustees. doi:10.1016/j.jse.2008.07.015
Unusual origin of the motor
Figure 1 Intraoperative specimen of the left elbow shows the variant branch of the ulnar nerve above the medial epicondyle.
relieved within the first 3 weeks after the operation. On clinical and electromyographic examination, no recurrence was seen at the time this report was written.
Discussion The superficial crossing branches of the medial antebrachial cutaneous nerve as well as branches of the ulnar nerve itself may be at risk during surgery. Regardless of the different surgical techniques for cubital tunnel syndrome, the surgical incision remains same, and the proximity of surgical incision to the nerve makes all the underlying structures vulnerable to injury.1 Avoiding damage to these branches decreases the morbidity and increases the clinical outcome of cubital tunnel surgery.5 Several anatomic investigations have tried to elucidate the clinical anatomy of the nerves at the elbow. Sunderland and Hughes10 examined branching of the ulnar nerve at the elbow in 20 specimens. They noted that the flexor carpi ulnaris was innervated by multiple branches in all but 1 specimen, in which a single branch was noted. They also found that the branches to the flexor carpi ulnaris were distal to the epicondyle in 18 of the 20 specimens, but in 1 case, a branch arose at the level of the epicondyle, and in another, a branch arose 4 cm above the epicondyle. In a cadaveric study of 39 arms from deceased donors, Gonzalez et al4 reported that motor branches to the flexor carpi ulnaris muscle originated at a distance ranging from 6 mm proximal to 73 mm distal to the medial epicondyle. The origin of the motor branch was proximal to the epicondyle in only 2 specimens. Regarding sensory branches, they reported a range of 0 to 3 capsular nerve branches arising from the ulnar nerve at an average distance of 7 mm proximal to the medial epicondyle (range, 45 mm proximal-24 mm distal). The first branch of the ulnar nerve provides sensory innervation to the elbow capsule.9 This capsular branch has
e39 been described as J-shaped, which is given off at a variable point; there might not be just one, but rather, a few small branches to the joint capsule.6 In a prospective observational anatomic study in 97 patients who underwent primary cubital tunnel surgery, Lowe et al7 found 1 superficial crossing branch of the medial antebrachial cutaneous nerve in 27 patients, 2 in 58, 3 in 8, and 4 in 4. The branches were noted to cross at or proximal to the medial humeral epicondyle 6% of the time, and at an average proximal distance of 1.8 cm distal to the medial humeral epicondyle 100% of the time at an average distal distance of 3.1 cm. In another study of 37 forearms, Marur et al8 found 4 in which the origin of the motor branch to the flexor carpi ulnaris muscle was proximal to the interepicondylar line, and in 1 it measured 12 mm. In our patient a variant branch of ulnar nerve originated 30 mm proximal to the medial epicondyle. The branch arose from the ulnar aspect of the nerve and was crossing the main trunk at the medial epicondyle. Then, it turned radially and interiorly to penetrate the fascia of flexor carpi ulnaris muscle. Stimulation showed that this was a motor branch to the flexor carpi ulnaris. In conclusion, few cases of this type of anatomic variation of the ulnar nerve have been described in the literature. A good knowledge of anatomy of ulnar nerve and its variations is necessary to prevent iatrogenic injury to this nerve and its aberrant branches during ulnar nerve release at the elbow.
References 1. Bartels RH. History of the surgical treatment of ulnar nerve compression at the elbow. Neurosurgery 2001;49:391-400. 2. Brady RL, Catalano LW, Barron OA. Ulnar nerve entrapment and cubital tunnel syndrome: do’s and don’ts. Curr Opin Orthop 2003;14: 296-301. 3. Fernandez E, Pallini R, Lauretti L, Scogna A, La Marca F. Neurosurgery of the peripheral nervous system: cubital tunnel syndrome. Surg Neurol 1998;50:83-5. 4. Gonzalez MH, Lotfi P, Bendre A, Mandelbroyt Y, Lieska N. The ulnar nerve at the elbow and its local branching: an anatomic study. J Hand Surg [Br] 2001;26:142-4. 5. Jackson LC, Hotchkiss RN. Cubital tunnel surgery. Complications and treatment of failures. Hand Clin 1996;12:449-56. 6. Khoo D, Carmichael SW, Spinner RJ. Ulnar nerve anatomy and compression. Orthop Clin North Am 1996;27:317-38. 7. Lowe JB 3rd, Maggi SP, Mackinnon SE. The position of crossing branches of the medial antebrachial cutaneous nerve during cubital tunnel surgery in humans. Plast Reconstr Surg 2004;114:692-6. 8. Marur T, Akkin SM, Alp M, Demirci S, Yalc¸in L, Ogu¨t T, Akgu¨n I. The muscular branching patterns of the unlar nerve to the flexor carpi ulnaris and flexor digitorium profundus muscles. Surg Radiol Anat 2005;27:322-6. 9. Mazurek MT, Shin AY. Upper extremity peripheral nerve anatomy: current concepts and applications. Clin Orthop Relat Res 2001;383: 7-20. 10. Sunderland S, Hughes ESR. Metrical and non-metrical features of the muscular branches of the ulnar nerve. J Comp Neurol 1946;85:113-23.
www.elsevier.com/locate/ymse
Unusual origin of the motor branch of the ulnar nerve to the flexor carpi ulnaris Aydıner Kalacı, MD*, Yunus Dog˘ramacı, MD, Teoman Toni Sevinc¸, MD, Ahmet Nedim Yanat, MD Department of Orthopaedics and Traumatology, Mustafa Kemal University Faculty of Medicine, Antakya, Hatay, Turkey Cubital tunnel syndrome is the second most common entrapment neuropathy in the upper extremity after carpal tunnel syndrome.3 When conservative measures fail,2 a variety of surgical options have been described, ranging from simple decompression to ulnar nerve transposition. The dissection must expose the ulnar nerve from the arcade of Struthers to the flexor carpi ulnaris. Knowledge of local anatomy of the ulnar nerve and its variations is important to prevent complications related to anatomic variations during ulnar nerve release. Nerve branches close to the elbow, which may be sensory branches to the elbow or motor branches to the flexor carpi ulnaris, must be identified. Furthermore, crossing branches from the medial antebrachial cutaneous nerve should be protected.7 Significant variations of the ulnar nerve have been identified that may contribute to iatrogenic injury during ulnar nerve release surgery.4 We report a patient undergoing in situ surgical decompression of the ulnar nerve in which a motor branch to the flexor carpi ulnaris originated from the ulnar nerve about 3 cm above the medial epicondyle.
Case report A 54-year-old man, who did manual labor, presented to our outpatient clinic with insidious onset of hypoesthesia and tingling in the entire small and ulnar side of the ring fingers, as well as *Reprint requests: Aydıner Kalacı, MD, Assistant Professor. Mustafa Kemal University Faculty of Medicine, Dept of Orthopaedics and Traumatology, 31100 Antakya, Hatay, Turkey. E-mail addresses: [email protected], [email protected] (A. Kalacı).
weakness in flexion of the little and ring fingers of 1-year duration. Despite of 3 months of conservative treatment, he stated that the symptoms were getting worse for 2 months, with night symptoms interfering with his sleep. The patient had no history of trauma or a relevant medical condition. Physical examination revealed tenderness at the ulnar notch in his left elbow, normal range of elbow motion, but no instability or deformity. Tinel’s sign was positive. Froment’s sign was positive. The peripheral vascular examination revealed normal pulses and negative (AdsoneRoos tests). Radiographic examination of left elbow revealed no bony lesion. A detailed physical and radiographic examination of the cervical spine revealed no pathologic findings. Nerve conduction and electromyographic studies of left upper extremity showed moderate compromise of the nerve at the elbow with decreased conduction velocity (motor conduction velocity of the ulnar nerve at the above-elbow to below-elbow segment was 36.1 m/s), consistent with cubital tunnel syndrome. After preoperative assessment, the patient was admitted for surgical treatment under the diagnosis of cubital tunnel syndrome. The operation was done under general anesthesia, using a pneumatic tourniquet. The surgical approach was performed through a curved 8-cm-long skin incision on the posteromedial aspect of the elbow. With careful dissection, the ulnar nerve was traced along its course, proximally from the medial intermuscular septum down to the origin of superficial flexor muscles of the forearm. A variant branch of the ulnar nerve was found originating from the ulnar nerve at a distance of 30 mm above the medial epicondyle, originating from the ulnar aspect of the nerve, and crossing it at the level of the epicondyle to the radial aspect, to enter the fascia of the flexor carpi ulnaris muscle (Figure 1). During full flexion of the elbow, the ulnar nerve was found to be under pressure from the constricting effect of aberrant branch. In situ surgical decompression was performed, because motor branches to the flexor carpi ulnaris of the ulnar nerve prevented anterior transposition of the ulnar nerve. The symptoms were
1058-2746/2008/$34.00 - see front matter Ó 2008 Journal of Shoulder and Elbow Surgery Board of Trustees. doi:10.1016/j.jse.2008.07.015
Unusual origin of the motor
Figure 1 Intraoperative specimen of the left elbow shows the variant branch of the ulnar nerve above the medial epicondyle.
relieved within the first 3 weeks after the operation. On clinical and electromyographic examination, no recurrence was seen at the time this report was written.
Discussion The superficial crossing branches of the medial antebrachial cutaneous nerve as well as branches of the ulnar nerve itself may be at risk during surgery. Regardless of the different surgical techniques for cubital tunnel syndrome, the surgical incision remains same, and the proximity of surgical incision to the nerve makes all the underlying structures vulnerable to injury.1 Avoiding damage to these branches decreases the morbidity and increases the clinical outcome of cubital tunnel surgery.5 Several anatomic investigations have tried to elucidate the clinical anatomy of the nerves at the elbow. Sunderland and Hughes10 examined branching of the ulnar nerve at the elbow in 20 specimens. They noted that the flexor carpi ulnaris was innervated by multiple branches in all but 1 specimen, in which a single branch was noted. They also found that the branches to the flexor carpi ulnaris were distal to the epicondyle in 18 of the 20 specimens, but in 1 case, a branch arose at the level of the epicondyle, and in another, a branch arose 4 cm above the epicondyle. In a cadaveric study of 39 arms from deceased donors, Gonzalez et al4 reported that motor branches to the flexor carpi ulnaris muscle originated at a distance ranging from 6 mm proximal to 73 mm distal to the medial epicondyle. The origin of the motor branch was proximal to the epicondyle in only 2 specimens. Regarding sensory branches, they reported a range of 0 to 3 capsular nerve branches arising from the ulnar nerve at an average distance of 7 mm proximal to the medial epicondyle (range, 45 mm proximal-24 mm distal). The first branch of the ulnar nerve provides sensory innervation to the elbow capsule.9 This capsular branch has
e39 been described as J-shaped, which is given off at a variable point; there might not be just one, but rather, a few small branches to the joint capsule.6 In a prospective observational anatomic study in 97 patients who underwent primary cubital tunnel surgery, Lowe et al7 found 1 superficial crossing branch of the medial antebrachial cutaneous nerve in 27 patients, 2 in 58, 3 in 8, and 4 in 4. The branches were noted to cross at or proximal to the medial humeral epicondyle 6% of the time, and at an average proximal distance of 1.8 cm distal to the medial humeral epicondyle 100% of the time at an average distal distance of 3.1 cm. In another study of 37 forearms, Marur et al8 found 4 in which the origin of the motor branch to the flexor carpi ulnaris muscle was proximal to the interepicondylar line, and in 1 it measured 12 mm. In our patient a variant branch of ulnar nerve originated 30 mm proximal to the medial epicondyle. The branch arose from the ulnar aspect of the nerve and was crossing the main trunk at the medial epicondyle. Then, it turned radially and interiorly to penetrate the fascia of flexor carpi ulnaris muscle. Stimulation showed that this was a motor branch to the flexor carpi ulnaris. In conclusion, few cases of this type of anatomic variation of the ulnar nerve have been described in the literature. A good knowledge of anatomy of ulnar nerve and its variations is necessary to prevent iatrogenic injury to this nerve and its aberrant branches during ulnar nerve release at the elbow.
References 1. Bartels RH. History of the surgical treatment of ulnar nerve compression at the elbow. Neurosurgery 2001;49:391-400. 2. Brady RL, Catalano LW, Barron OA. Ulnar nerve entrapment and cubital tunnel syndrome: do’s and don’ts. Curr Opin Orthop 2003;14: 296-301. 3. Fernandez E, Pallini R, Lauretti L, Scogna A, La Marca F. Neurosurgery of the peripheral nervous system: cubital tunnel syndrome. Surg Neurol 1998;50:83-5. 4. Gonzalez MH, Lotfi P, Bendre A, Mandelbroyt Y, Lieska N. The ulnar nerve at the elbow and its local branching: an anatomic study. J Hand Surg [Br] 2001;26:142-4. 5. Jackson LC, Hotchkiss RN. Cubital tunnel surgery. Complications and treatment of failures. Hand Clin 1996;12:449-56. 6. Khoo D, Carmichael SW, Spinner RJ. Ulnar nerve anatomy and compression. Orthop Clin North Am 1996;27:317-38. 7. Lowe JB 3rd, Maggi SP, Mackinnon SE. The position of crossing branches of the medial antebrachial cutaneous nerve during cubital tunnel surgery in humans. Plast Reconstr Surg 2004;114:692-6. 8. Marur T, Akkin SM, Alp M, Demirci S, Yalc¸in L, Ogu¨t T, Akgu¨n I. The muscular branching patterns of the unlar nerve to the flexor carpi ulnaris and flexor digitorium profundus muscles. Surg Radiol Anat 2005;27:322-6. 9. Mazurek MT, Shin AY. Upper extremity peripheral nerve anatomy: current concepts and applications. Clin Orthop Relat Res 2001;383: 7-20. 10. Sunderland S, Hughes ESR. Metrical and non-metrical features of the muscular branches of the ulnar nerve. J Comp Neurol 1946;85:113-23.