JBJS | Selective Restoration of Motor Function in the Ulnar Nerve by Transfer of the Anterior Interosseous Nerve : An Anatomical Feasibility Study

The Journal of Bone & Joint Surgery, Volume 83, Issue 4

Articles | April 01, 2001

Selective Restoration of Motor Function in the Ulnar Nerve by Transfer of the Anterior Interosseous Nerve : An Anatomical Feasibility Study

Mehmet Erkan Üstün, MD; Tunç Cevat Ögün, MD; Mustafa Büyükmumcu, PhD; Ahmet Salbacak, PhD

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Investigation performed at Selçuk University Medical School, Konya, Turkey
Mehmet Erkan Üstün, MD Tunç Cevat Ögün, MD Mustafa Büyükmumcu, PhD Ahmet Salbacak, PhD Department of Neurosurgery (M.E.Ü.), Division of Hand-Upper Extremity-Microsurgery, Department of Orthopedics and Traumatology (T.C.Ö.), and Department of Anatomy (M.B. and A.S.), Selçuk University, Kennedy cad. Billur sok., 44/10 06700, G.O.P. Ankara, Turkey. E-mail address for T.C. Ögün: tunccevat@hotmail.com.
No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article. No funds were received in support of this study.

The Journal of Bone & Joint Surgery. 2001; 83:549-549

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Abstract

Background:

Proximal ulnar-nerve lesions have an unfavorable prognosis. The goal of the present study was to evaluate the feasibility of selective restoration of motor function of the ulnar nerve by the transfer of the anterior interosseous nerve or one of its branches to the motor branch of the ulnar nerve.

Methods:

Ten cadaveric arms were used in the present study. The ulnar nerve and its motor and sensory branches as well as the anterior interosseous nerve and its branches were dissected. The widths of the motor branch of the ulnar nerve and the anterior interosseous nerve and its motor branches as well as the relevant distances from the points of divergence were measured. The axons were counted, and the distances from the end of the main anterior interosseous nerve, its motor branches, and the motor branch of the ulnar nerve to the level of the dorsal sensory branch of the ulnar nerve were measured.

Results:

Our results indicate that the length, width, and number of axons of the branch of the anterior interosseous nerve to the pronator quadratus make it suitable for transfer to the motor branch of the ulnar nerve. The use of the main anterior interosseous nerve or its motor branches to the flexor pollicis longus and the flexor digitorum profundus is less feasible because of the need to graft a long segment and the longer distance from the level of transfer to the motor end points.

Conclusions:

The findings of the present study confirm the feasibility of motor-nerve transfer for reconstruction after an injury of the ulnar nerve. Nerve-grafting would be needed for injuries distal to the level of the dorsal sensory branch of the ulnar nerve.

Figures in this Article

Introduction

Introduction | Materials and Methods | Results | Discussion | References

The ulnar nerve may be injured at any point along its course. Motor recovery is more important than sensory recovery after ulnar nerve injury^1-4. Optimal matching of motor and sensory fascicles is a challenge in the repair of a mixed motor and sensory nerve, although it is essential for a good functional outcome. When the gap between the proximal and distal ends of the ulnar nerve increases and the level of injury is proximal to the elbow, the recovery of motor function decreases⁵. This, in turn, may necessitate secondary operations for restoration of motor function^2-6.

The search for a better outcome led us to study the feasibility of a transfer of the anterior interosseous nerve, which contains mainly motor fibers, to the motor branch of the ulnar nerve in order to innervate the intrinsic muscles of the hand. Nerve transfer, in which a healthy but less valuable nerve or its proximal stump is transferred in order to reinnervate a more important sensory or motor territory, has been previously described^7-15. However, a survey of the current literature revealed only a few laboratory and clinical studies in which nerve transfer was used to treat an irreparable injury of the ulnar nerve^1,16,17.

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Fig. 1:: Median (M), ulnar (U), and anterior interosseous nerve (A) with its branches dissected in the forearm. The open arrows indicate the pronator quadratus branch; the large arrow, the flexor digitorum profundus branch; and the small arrow, the flexor pollicis longus branch.

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TABLE I: Results of Measurement*

*The values are given as the mean and the standard deviation. †Measured from the point of divergence at Guyon’s canal. ‡Extended distal to the level of the dorsal sensory branch of the ulnar nerve.

?Nerve	No. of Axons	Width (mm)	Length from Point of Divergence (mm)	Length from End of Nerve to Level of Dorsal Branch of Ulnar Nerve (mm)
Motor branch of ulnar nerve	1216 ± 108	1.9 ± 0.17	—	??96 ± 4.3†
Main anterior interosseous nerve	1695 ± 170	3.0 ± 0.35	?10 ± 0.66	?113 ± 3.8
Motor branch to pronator quadratus	?912 ± 88	1.5 ± 0.15	114 ± 5.80	??10 ± 0.08‡
Motor branch to flexor pollicis longus	?962 ± 110	1.6 ± 0.18	?35 ± 1.90	??78 ± 2.9
Motor branch to flexor digitorum profundus	??872 ± 92	1.4 ± 0.12	?20 ± 1.20	87 ± 3.1

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TABLE I: Results of Measurement*

?Nerve	No. of Axons	Width (mm)	Length from Point of Divergence (mm)	Length from End of Nerve to Level of Dorsal Branch of Ulnar Nerve (mm)
Motor branch of ulnar nerve	1216 ± 108	1.9 ± 0.17	—	??96 ± 4.3†
Main anterior interosseous nerve	1695 ± 170	3.0 ± 0.35	?10 ± 0.66	?113 ± 3.8
Motor branch to pronator quadratus	?912 ± 88	1.5 ± 0.15	114 ± 5.80	??10 ± 0.08‡
Motor branch to flexor pollicis longus	?962 ± 110	1.6 ± 0.18	?35 ± 1.90	??78 ± 2.9
Motor branch to flexor digitorum profundus	??872 ± 92	1.4 ± 0.12	?20 ± 1.20	87 ± 3.1

Materials and Methods

Introduction | Materials and Methods | Results | Discussion | References

Ten arms of five cadavera were used in the study. The anterior interosseous nerve was dissected, revealing its branches to the flexor pollicis longus, the flexor digitorum profundus to the index and long fingers, and the pronator quadratus (Fig. 1). Afterward, the ulnar nerve was exposed throughout the forearm with its motor branch dissected intraneurally in a proximal direction to the point where the dorsal sensory branch emerged. Thereafter, the motor branch of the ulnar nerve became less identifiable. Thus, the level of the dorsal sensory branch was used as a reference point. After the dissection was completed, the width and length (from the point of divergence) of the main anterior interosseous nerve, and its motor branches to the flexor pollicis longus, the flexor digitorum profundus, and the pronator quadratus, and the width of the motor branch of the ulnar nerve were measured with use of calipers. The distances from the end of the main anterior interosseous nerve, its motor branches, and the motor branch of the ulnar nerve to the level of the dorsal sensory branch of the ulnar nerve were measured. Specimens of the nerves were obtained for axon counts; they were immersed in Heidenhain’s Susa fixative for twenty-four hours and then transferred to a solution of 80% alcohol and iodine for twenty-four hours for the removal of mercury. Sections of each nerve were stained with hematoxylin and eosin and processed for semiautomatic computer-aided determination of axon number. The feasibility of transferring the main anterior interosseous nerve and its branches, from the level of the antecubital region to the level of the pronator quadratus innervation, to the ulnar nerve was determined.

Results

Introduction | Materials and Methods | Results | Discussion | References

The results of the measurements are given in Table I. From an anatomical aspect, the main anterior interosseous nerve and its motor branches could be transferred to the ulnar nerve or the ulnar nerve could be mobilized and approximated to them. However, only the pronator quadratus branch reached distal to the critical level of the dorsal sensory branch of the ulnar nerve.

Discussion

Introduction | Materials and Methods | Results | Discussion | References

Nerve transfer after facial nerve or brachial plexus injury is a well-established method of neural reconstruction. Different motor nerves, such as the intercostal, phrenic, spinal accessory, medial pectoral, thoracodorsal, long thoracic, and subscapular nerves, and nerve roots, such as the ipsilateral seventh cervical, contralateral seventh cervical, and fourth cervical nerve roots, have been used for transfer^8-15. Transfer of one or two fascicles of the ulnar nerve to the motor branch of the biceps muscle to provide elbow flexion after brachial plexus injury has also been reported¹².

After repair of a proximal injury of the ulnar nerve, approximately half of patients can be expected to have a return of function of the long flexors of the fingers and the wrist¹¹. However, only about 5% of such patients recover useful intrinsic function¹¹. The results of ulnar nerve-grafting have been less than optimum, and they have deteriorated as the graft length has increased^6,11.

Transfer of a functionally expendable motor nerve to the motor branch of the ulnar nerve may be an appropriate solution. To our knowledge, Wang and Zhu¹⁶ were the first to study the transfer of the pronator quadratus branch of the anterior interosseous nerve to the recurrent branch of the median nerve and the deep branch of the ulnar nerve to restore the functions of the intrinsic hand muscles. Battiston and Lanzetta¹, reporting on clinical applications of the procedure, used a distal connection of the anterior interosseous nerve and the superficial sensory palmar branch of the median nerve to the motor and sensory components of the ulnar nerve at Guyon’s canal.

When a nerve transfer is performed, the function gained should be greater than the function lost. If the pronator quadratus branch is transferred, the functional loss will be minimal as the pronator teres and the secondary pronators can easily compensate for it. This transfer can reach about 1 cm distal to the level of the dorsal sensory branch of the ulnar nerve. Of the three motor branches of the anterior interosseous nerve, the pronator quadratus branch provides the most distal level for possible transfer and also the level closest to the motor end points. If the injury is more distal, interfascicular nerve-grafting between the two motor nerves would be required. The pronator quadratus branch had a slightly smaller width and a smaller number of axons compared with the motor branch of the ulnar nerve.

If the procedure were carried out at the level of the flexor digitorum profundus branch, the function of the deep flexors of the index and long fingers would be sacrificed. Suturing these tendons to the nearby deep flexors of the ring and little fingers could compensate for the loss of function if the ulnar nerve injury was distal to the level of innervation of these muscles. If the long flexor of the thumb is expended, the motor branch to the flexor pollicis longus can also be considered for transfer, although arthrodesis or tenodesis of the interphalangeal joint of the thumb would then be required. Approximation does not constitute a major problem, since the ulnar nerve can easily be drawn beside these nerves. However, the drawback with a transfer at this level is that the motor branch of the ulnar nerve becomes difficult to differentiate intraneurally. Thus, the flexor pollicis longus and flexor digitorum profundus branches would need to be extended with nerve grafts to the level of the dorsal sensory branch of the ulnar nerve. Such a procedure has the inherent disadvantages associated with long-segment nerve-grafting. The main anterior interosseous nerve, before it branches, is also appropriate for transfer in terms of both width and number of axons. However, use of that nerve has the same drawbacks as use of the flexor pollicis longus and flexor digitorum profundus branches as well as the disadvantage that all of its distal branches are sacrificed.

Clinical studies are needed to support these findings. Wang et al.¹⁷ reported good results in a series of twenty patients in whom the pronator quadratus branch of the anterior interosseous nerve was transferred to the recurrent branch of the median nerve and the motor branch of the ulnar nerve. They used intraneural dissection to differentiate motor and sensory branches. We propose the use of intraoperative stimulation of the fascicles and either observation of muscle contractions or recording of compound muscle-action potentials as an alternative to intraneural dissection. Recently, in a series of seven patients, Battiston and Lanzetta¹ transferred the pronator quadratus branch of the anterior interosseous nerve and the palmar sensory branch of the median nerve to the motor branch of the ulnar nerve at Guyon’s canal. They reported good motor and sensory recovery in six patients after a follow-up period of one to 3.5 years. Longer-term studies with more patients are needed to support these encouraging results.

Transfer of the pronator quadratus branch of the anterior interosseous nerve to the motor branch of the ulnar nerve may be a viable option for the treatment of a patient with an injury of the ulnar nerve who has diminished likelihood of motor recovery. This procedure has several distinct advantages. Motor function is reestablished with use of a donor nerve that possesses mainly motor axons, the mean widths and numbers of axons of the donor and recipient nerves are similar, and the loss of function is small and easily compensated for. Sensory recovery can be achieved with nerve-grafting, cross innervation from the median nerve, or transfer of the palmar cutaneous branch of the median nerve¹⁸.

References

Introduction | Materials and Methods | Results | Discussion | References

Battiston B, and Lanzetta M: Reconstruction of high ulnar nerve lesions by distal double median to ulnar nerve transfer. J Hand Surg Am,1999.24: 1185-91, 241185 1999 [PubMed]

Birch R, and Raji AR: Repair of median and ulnar nerves. Primary suture is best. J Bone Joint Surg Br,1991.73: 154-7, 73154 1991 [PubMed]

Bolitho DG; Boustred M; Hudson DA; and Hodgetts K: Primary epineural repair of the ulnar nerve in children. J Hand Surg Am,1999.24: 16-20, 2416 1999 [PubMed]

Chow JA; Van Beek AL; Bilos ZJ; Meyer DL; and Johnson MC: Anatomical basis for repair of ulnar and median nerves in the distal part of the forearm by group fascicular suture and nerve-grafting. J Bone Joint Surg Am,1986.68: 273-80, 68273 1986 [PubMed]

Vastamaki M; Kallio PK; and Solonen KA: The results of secondary microsurgical repair of ulnar nerve injury. J Hand Surg Br,1993.18: 323-6, 18323 1993 [PubMed]

Hentz VR; Rosen JM; Xiao SJ; McGill KC; and Abraham G: The nerve gap dilemma: a comparison of nerves repaired end to end under tension with nerve grafts in a primate model. J Hand Surg Am,1993.18: 417-25, 18417 1993 [PubMed]

Büyükmumcu M; Üstün ME; Seker M; Kocaogullari Y; and Sagmanligil A: The possibility of deep peroneal nerve neurotisation by the superficial peroneal nerve: an anatomical approach. J Anat,1999.194: 309-12, 194309 1999

Chen L, and Gu YD: An experimental study of contralateral C7 root transfer with vascularized nerve grafting to treat brachial plexus root avulsion. J Hand Surg Br,1994.19: 60-6, 1960 1994 [PubMed]

Chuang DC; Lee GW; Hashem F; and Wei FC: Restoration of shoulder abduction by nerve transfer in avulsed brachial plexus injury: evaluation of 99 patients with various nerve transfers. Plast Reconstr Surg,1995.96: 122-8, 96122 1995 [PubMed]

Gu YD, and Ma MK: Use of the phrenic nerve for brachial plexus reconstruction. Clin Orthop,1996.323: 119-21, 323119 1996 [PubMed]

Jobe TM, Wright PE 2nd. Peripheral nerve injuries. In: Canale ST, editor. Campbell’s operative orthopaedics. Volume 4. St. Louis: Mosby; 1998. p 3827-94

Leechavengvongs S; Witoonchart K; Uerpairojkit C; Thuvasethakul P; and Ketmalasiri W: Nerve transfer to biceps muscle using a part of the ulnar nerve in brachial plexus injury (upper arm type): a report of 32 cases. J Hand Surg Am,1998.23: 711-6, 23711 1998 [PubMed]

Narakas AO, and Hentz VR: Neurotization in brachial plexus injuries. Indication and results. Clin Orthop.,1988.237: 43-56, 23743 1988 [PubMed]

Samardzic M, Grujicic D, Antunovic V.: Nerve transfer in brachial plexus traction injuries. J Neurosurg.,1992.76: 191-7, 76191 1992 [PubMed]

Tonkin MA; Eckersley JR; and Gschwind CR: The surgical treatment of brachial plexus injuries. Aust N Z J Surg,1996.66: 29-33, 6629 1996 [PubMed]

Wang Y, and Zhu S: Transfer of a branch of the anterior interosseous nerve to the motor branch of the median nerve and ulnar nerve. Chin Med J,1997.110: 216-9, 110216 1997 [PubMed]

Wang Y; Zhu S; and Zhang B: Anatomical study and clinical application of transfer of pronator quadratus branch of anterior interosseous nerve in the repair of thenar branch of median nerve and deep branch of ulnar nerve. Zhongguo Xiu Fu Chong Jian Wai Ke Za Zhi.,1997.11: 335-7, Chinese11335 1997 [PubMed]

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TABLE I: Results of Measurement*

?Nerve	No. of Axons	Width (mm)	Length from Point of Divergence (mm)	Length from End of Nerve to Level of Dorsal Branch of Ulnar Nerve (mm)
Motor branch of ulnar nerve	1216 ± 108	1.9 ± 0.17	—	??96 ± 4.3†
Main anterior interosseous nerve	1695 ± 170	3.0 ± 0.35	?10 ± 0.66	?113 ± 3.8
Motor branch to pronator quadratus	?912 ± 88	1.5 ± 0.15	114 ± 5.80	??10 ± 0.08‡
Motor branch to flexor pollicis longus	?962 ± 110	1.6 ± 0.18	?35 ± 1.90	??78 ± 2.9
Motor branch to flexor digitorum profundus	??872 ± 92	1.4 ± 0.12	?20 ± 1.20	87 ± 3.1

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TABLE I: Results of Measurement*

?Nerve	No. of Axons	Width (mm)	Length from Point of Divergence (mm)	Length from End of Nerve to Level of Dorsal Branch of Ulnar Nerve (mm)
Motor branch of ulnar nerve	1216 ± 108	1.9 ± 0.17	—	??96 ± 4.3†
Main anterior interosseous nerve	1695 ± 170	3.0 ± 0.35	?10 ± 0.66	?113 ± 3.8
Motor branch to pronator quadratus	?912 ± 88	1.5 ± 0.15	114 ± 5.80	??10 ± 0.08‡
Motor branch to flexor pollicis longus	?962 ± 110	1.6 ± 0.18	?35 ± 1.90	??78 ± 2.9
Motor branch to flexor digitorum profundus	??872 ± 92	1.4 ± 0.12	?20 ± 1.20	87 ± 3.1