Anterior interosseous nerve syndrome after shoulder arthroscopy: report of 3 cases

J Shoulder Elbow Surg (2016) 25, e348–e352

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Anterior interosseous nerve syndrome after shoulder arthroscopy: report of 3 cases Maria Florencia Deslivia, MDa,b, Hyun-Joo Lee, MDc, Seong-Man Lee, MDd, Bin Zhu, MDe, In-Ho Jeon, MD, PhDf,* a

Department of Human Computer Interaction and Robotics, University of Science and Technology, Daejeon, Republic of Korea b Korea Institute of Science and Technology, Seoul, Republic of Korea c Department of Orthopedic Surgery, Kyungpook National University Hospital, Daegu, Republic of Korea d Department of Orthopedic Surgery, Goodssen Hospital, Daegu, Republic of Korea e Department of Hand Surgery, Ningbo No. 6 Hospital, Ningbo, China f Department of Orthopedic Surgery, Asan Medical Center, University of Ulsan, Seoul, Republic of Korea Keywords: Shoulder arthroscopy; anterior interosseous nerve palsy; anterior interosseous nerve syndrome; median nerve; flexor pollicis longus; flexor digitorum profundus; arthroscopy complication; case report

In 2006, there were 257,541 cases of shoulder arthroscopy (excluding those for rotator cuff repair) in the United States alone.5 Among the possible complications, anterior interosseous nerve (AIN) syndrome is an underdiagnosed one. There was only 1 case report, with 3 patients, reporting the occurrence of AIN syndrome after shoulder arthroscopy procedures.9 The previous study described traction-type neurapraxia in patients predisposed with a fibrous band over the nerve as a possible etiology. Because of the rarity of AIN syndrome, neither standardized diagnostic criteria nor treatment exists for this entity. It is also largely accepted that the definite etiology of this syndrome is still elusive. We report 3 cases of AIN palsy after shoulder arthroscopy with potential risks and clinical outcomes of the patients.

This study was approved by the Ethical Committee of Asan Medical Center, Seoul, Korea. *Reprint requests: In-Ho Jeon, MD, PhD, Department of Orthopaedic Surgery, College of Medicine, Asan Medical Center University of Ulsan, 86 Asanbyeongwon-gil, Songpa-gu, Seoul 138-736, Republic of Korea. E-mail address: [email protected] (I.-H. Jeon).

Materials and methods We reviewed the records of patients with AIN syndrome after shoulder arthroscopy managed in our centers from 2010-2015. The eligibility criteria were AIN syndrome based on clinical assessment with paralysis of the flexor pollicis longus (FPL) and flexor digitorum profundus (FDP) of the second finger on the same side of the hand undergoing shoulder arthroscopy. Given the rarity of the condition, we included all cases consecutively.

Results A summary of the patient demographic characteristics and original shoulder procedures in our study and the previous study by Sisco and Dumanian9 is shown in Table I. The characteristics of AIN syndrome presented by each patient are displayed in Table II.

Case 1 A 61-year-old man was diagnosed with a rotator cuff tear and underwent shoulder arthroscopy. General anesthesia was

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Summary of patient demographic characteristics and initial shoulder procedures in our study and that of Sisco and Dumanian9

Case

Age, y

Sex

Shoulder procedure

Anesthesia

Position

Traction

Current patients 1

61

M

Capsular release, acromioplasty, and rotator cuff repair

Lateral decubitus

Spider traction and 60–mm Hg pump

58 41

M F

Bursectomy and synovectomy Bursectomy and synovectomy

General anesthesia without interscalene block General anesthesia General anesthesia without interscalene block

Lateral decubitus NA

Spider traction and 60–mm Hg pump NA

44

M

Debridement, subacromial decompression, and release of coracoacromial ligament

Regional anesthesia with interscalene block

Lateral decubitus

2

52

M

Regional anesthesia with interscalene block

Lateral decubitus

3

35

M

Debridement of humeral head and labrum, subacromial decompression, and repair of supraspinatus and infraspinatus portions of rotator cuff Labral and rotator cuff debridement and subacromial decompression

Regional anesthesia with interscalene block

Beach chair

Traction of 4.5 kg applied with boom attached to adhesive foam sling on distal part of forearm Traction of 4.5 kg applied with boom attached to adhesive foam sling on distal part of forearm Not clear

2 3 Patients in case report of Sisco and Dumanian 1

AIN syndrome after shoulder arthroscopy

Table I

F, female; M, male; NA, not available.

Table II

Summary of AIN syndrome characteristics

Case Current patients 1 2 3 Patients in case report of Sisco and Dumanian9 1 2 3

AIN findings

AIN onset

Treatment

Abnormal findings

Recovery time

Notes

FPL and FDP2 FPL and FDP2 FPL and FDP2

1 mo after surgery Within 1 week after surgery Within 1 week after surgery

Surgical Conservative Surgical

No abnormalities NA Compressive fibrous band at proximal aspect of FDS

NA 18 mo 3 mo

Symptoms persisting after 1 y Complete recovery Complete recovery

FPL and FDP2 FPL and FDP2 FPL and FDP2

1 week Soon after surgery Several days

Conservative Surgical Surgical

NA Compressive fibrous band at proximal aspect of FDS Fibrous band along dorsum of superficial head of pronator teres muscle

9 mo 5 mo 7 mo

Complete recovery Complete recovery Complete recovery

AIN, anterior interosseous nerve; FDP2, flexor digitorum profundus of second finger; FDS, flexor digitorum superficialis; FPL, flexor pollicis longus; NA, not available.

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Figure 1 Axial cut of magnetic resonance imaging shows high signal change of the pronator teres muscle (arrows) in case 1.

performed without an interscalene block. The patient was placed in the lateral decubitus position. Spider traction was applied in accordance with a 60–mm Hg pump. Capsular release, acromioplasty, and rotator cuff repair were performed. One month after surgery, the doctor discovered that ipsilateral paralysis of the FPL and FDP of the second finger had developed. The exact onset was unclear because the patient wore a pillow brace after rotator cuff surgery, which may have masked the symptoms. Three months later, he regained flexion of the thumb interphalangeal joint partially (grade 1). Pronation weakness was grade 4. There was no Tinel sign in the median nerve territory at the elbow. These symptoms persisted; thus, 1 year after initial surgery, the AIN was explored along the upper forearm and elbow. Magnetic resonance imaging studies of the patient are displayed in Figures 1 and 2. During the exploration, compressive bicipital aponeurosis, fibrous pronator teres muscle, and bulging of the proximal nerve were encountered (Figs. 3 and 4). There was no abnormal thickening found in the nerve. Two months after surgery, the patient reported improved pronation (grade 4) and distal interphalangeal flexion of the second finger (grade 1). He also noted that the bulkiness of the ulnar forearm was slightly recovered. He did not have any further resolution of symptoms.

Case 2 A 58-year-old man had calcific tendinitis and bursitis. Shoulder arthroscopy with general anesthesia was performed with the patient placed in the lateral decubitus position. Spider traction and a 60–mm Hg pump were used during the surgical procedure. Within 1 week after surgery, the patient had ipsilateral paralysis of the FPL and FDP of the second finger. One month after surgery, he regained flexion (grade 3). However, he refused any further operation because of tolerance. Eighteen months after surgery, all neurologic symptoms resolved completely (grade 4+).

Figure 2 Forearm magnetic resonance imaging shows high signal change of the pronator quadratus muscle (arrows) at wrist level in case 1.

Case 3 A41-year-old woman underwent shoulder arthroscopy in another center with general anesthesia and without an interscalene block. The main diagnosis was synovitis, and thus bursectomy and synovectomy were performed. There was no information regarding traction and position applied because the procedure was performed in another center. Within 1 week after surgery, the patient had ipsilateral paralysis of the FPL and FDP of the second finger. These symptoms persisted for 1 year until the patient decided to come to our center. AIN exploration was performed. The intraoperative finding was a compressive fibrous band at the proximal aspect of the flexor digitorum superficialis (FDS), which was subsequently released. Postoperatively, there was immediate improvement of the thumb symptoms. Three months thereafter, all symptoms resolved.

Discussion AIN syndrome comprises weakness in the FPL, the FDP of the index finger, the pronator quadratus, and occasionally, the FDP of the middle finger.6 Patients may complain of weakness when writing or pinching, with a general inability to form

AIN syndrome after shoulder arthroscopy

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Figure 3 After release of the biceps aponeurosis, a focal lesion of the median nerve and anterior interosseous nerve (circle) could be confirmed in case 1.

Figure 4 Decompression was further achieved by releasing the arch at the flexor digitorum superficialis origin site (circle) in case 1.

the “O” sign with the thumb and index finger. In relation to shoulder arthroscopy, previous studies have described the relationship of this procedure with injuries to nerves, such as the musculocutaneous, median, ulnar, and radial nerves.2 However, AIN palsy is less common, with only one other study reporting it,9 and is potentially missed as a clinical diagnosis. From an anatomic perspective, the median nerve gives rise to the AIN just after coursing between the 2 heads of the pronator teres muscle. The AIN then courses beneath the fibrous arch of the FDS muscle and enters the FDP muscle belly at an average 30% the forearm length distal to the medial epicondyle. Approximately 4 cm distal to its takeoff from the

median nerve, the AIN innervates the FPL, the FDP of the second finger, and variably, the FDP of the third finger.3 Considering the AIN’s distal rise from the shoulder, it is important to analyze why AIN pathology might occur after shoulder arthroscopy procedures. Previous study described that the AIN fascicle can be traced up to the brachial plexus level. Magnetic resonance neurography also showed fascicular lesions at the upper arm level of the median nerve in patients with AIN syndrome.7 It is thus possible that procedures in the shoulder area might elicit pathology in more distal areas. Sisco and Dumanian9 have described mechanical factors as the cause of AIN syndrome after shoulder arthroscopy. The lateral decubitus position may generate excessive strain on the brachial plexus due to arm positioning and the use of traction, resulting in nerve injuries.8 Elongation of the nerve will in turn adversely affect the blood supply and electrical conduction velocity of the nerve.4 Consequently, there was a 10% incidence of transient paresthesias and/or true nerve palsies after the use of this position.8 Moreover, the lateral decubitus position in shoulder arthroscopy also uses a compression band around the forearm, thus creating compression in this area. All patients in our case report (3 of 3) and 2 of 3 patients in the case report of Sisco and Dumanian were placed in this position. Besides positioning, the irrigation fluid that is generally used in shoulder arthroscopy procedures has been recognized as a possible cause of neurologic injury.10 Sisco and Dumanian9 assumed that extravasated fluid traveling distally was the possible cause of AIN syndrome. However, the vulnerability of the AIN fascicle at the upper arm level7 makes it possible for even local fluid extravasation to cause neurologic disturbance. Our study agrees with the previous study by Sisco and Dumanian9 indicating that AIN syndrome is a possible

e352 complication in shoulder arthroscopy patients with anatomically at-risk nerves. Of our 3 cases, 2 showed anatomic abnormalities. The other case (case 2) had complete recovery with conservative treatment; thus, no confirmation of anatomic abnormality was performed. Our study also found that case 1 displayed additional abnormality in the pronator teres muscle, an uncommon finding for AIN palsy. We hypothesize that in case 1—combined with the absence of anatomic abnormalities during AIN exploration—the main etiology was located more proximal during the course of the median nerve. Finally, it is interesting to assume that 2 factors interplay in AIN syndrome patients with shoulder arthroscopy. The first is the existing anatomically at-risk nerves, and the second is the shoulder arthroscopy procedure, which stretches and swells the proximal part of the AIN fascicle and compresses the distal part. It is also important to note that the paucity of basic research makes it impossible to derive solid conclusions regarding the etiology and, thus, further investigations are required. To reduce the risk of neural complications, including AIN syndrome, after shoulder arthroscopy, the beach-chair position has been largely advocated.1 As for treatment, significant loss of AIN function might benefit from functional tendon transfers of the FDS of the ring or middle finger or of the brachioradialis,2 nerve transfer,7 and simple distal interphalangeal arthrodesis.

Conclusion Surgeons should keep in mind that shoulder arthroscopy might put additional stress on the AIN, which is anatomically at risk.

Disclaimer The authors, their immediate families, and any research foundations with which they are affiliated have not received any financial payments or other benefits from any commercial entity related to the subject of this article.

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References 1. Berjano P, González BG, Olmedo JF, Perez-España LA, Munilla MG. Complications in arthroscopic shoulder surgery. Arthroscopy 1998;14:785-8. 2. Boardman ND III, Cofield RH. Neurologic complications of shoulder surgery. Clin Orthop Relat Res 1999;(368):44-53. 3. Chin D, Meals R. Anterior interosseous nerve syndrome. J Am Soc Surg Hand 2001;1:249-57. 4. Driscoll PJ, Glasby MA, Lawson GM. An in vivo study of peripheral nerves in continuity: biomechanical and physiological responses to elongation. J Orthop Res 2002;20:370-5. http://dx.doi.org/10.1016/S0736 -0266(01)00104-8 5. Jain NB, Higgins LD, Losina E, Collins J, Blazar PE, Katz JN. Epidemiology of musculoskeletal upper extremity ambulatory surgery in the United States. BMC Musculoskelet Disord 2014;15:4. http://dx.doi.org/10.1186/1471-2474-15-4 6. Mackinnon SE, Novak CB. Compression neuropathies. In: Wolfe SW, Hotchkiss RN, Pederson WC, Kozin SH, editors. Green’s operative hand surgery. 6th ed. Philadelphia: Elsevier; 2011. p. 977-1014. (ISBN 978-1-4160-5279-1) 7. Pham M, Bäumer P, Meinck HM, Schiefer J, Weiler M, Bendszus M, et al. Anterior interosseous nerve syndrome: fascicular motor lesions of median nerve trunk. Neurology 2014;82:598-606. http://dx.doi.org/ 10.1212/WNL.0000000000000128 8. Rains DD, Rooke AG, Wahl CJ. Pathomechanism and complications related to patient positioning and anesthesia during shoulder arthroscopy. Arthroscopy 2011;27:532-41. http://dx.doi.org/10.1016/j.arthro .2010.09.008 9. Sisco M, Dumanian GA. Anterior interosseous nerve syndrome following shoulder arthroscopy. A report of three cases. J Bone Joint Surg Am 2007;89:392-5. http://dx.doi.org/10.2106/JBJS.F.00445 10. Weber SC, Abrams JS, Nottage WM. Complications associated with shoulder arthroscopy surgery. Arthroscopy 2002;18(Suppl 1):88-95. http://dx.doi.org/10.1053/jars.2002.31801