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Topographic Localization of the Motor Branch of the Median Nerve
Topographic Localization of the Motor Branch of the Median Nerve Metin Manouchehr Eskandari, MD, Cengiz Yilmaz, MD, Volkan Oztuna, MD, Fehmi Kuyurtar, MD, Mersin, Turkey
Purpose: To redefine the localization of the thenar branch (TB) of the median nerve in relation to the surface landmarks that are in routine use. Methods: The study was performed in 37 hands of 34 patients who had carpal tunnel release. All of the patients were women and the mean age was 50 years (range, 35– 67 y). A radiologic marking technique was used to determine the localization of the TB, the middle finger radial side line, and Kaplan’s cardinal line. The TB was marked by circumscribing with a soft radiopaque yarn and the surface landmark lines were shown by taping a K-wire to the hand for each line. An imageintensifier–printed image was obtained for each case and the distances between the markers of the TB and the wires were measured. Results: The TB had a mean ulnar offset of 12.6 mm (range, 4.0 –19.7 mm) from the middle finger radial side line and was located 4.4 mm (range, 0 –9.5 mm) proximal to the cardinal line. Conclusions: During carpal tunnel release surgery the surgeon must pay more attention to the localization of the TB of the median nerve because it was found to be 12.6 mm more ulnar than the location described in the literature. (J Hand Surg 2005;30A:803– 807. Copyright © 2005 by the American Society for Surgery of the Hand.) Key words: Carpal tunnel, localization, median nerve, motor branch, surface landmarks.
During surgery of the hand there are surface landmarks that are used to estimate the localization of deep structures and to minimize injury. The thenar branch (TB) of the median nerve is one of these deep structures that should be protected. This branch innervates the thenar muscles that contribute to the From the Department of Orthopedics and Traumatology, University of Mersin, School of Medicine, Mersin, Turkey. Received for publication August 10, 2004; accepted in revised form March 10, 2005. 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. Corresponding author: Metin Manouchehr Eskandari, MD, Mersin ¨ niversitesi Tip Fakültesi Hastanesi, Ortopedi ve Travmatoloji U AD, Zeytinlibahce cad. 33079, Mersin, Turkey; e-mail: mmeskandari@ yahoo.com. Copyright © 2005 by the American Society for Surgery of the Hand 0363-5023/05/30A04-0024$30.00/0 doi:10.1016/j.jhsa.2005.03.010
opposition of the thumb, which is the most important function of the hand. Topographic localization of this branch according to surface landmarks was defined by Kaplan in 1953 and 19651 and this definition still is used.2–5 Kaplan1 described his cardinal line as the line drawn from the apex of the interdigital fold between the thumb and the index finger toward the ulnar side of the hand, parallel with the middle crease of the palm. He stated that if a line is drawn continuing along the radial side of the middle finger in a proximal direction then its intersection by the cardinal line corresponds to the emergence of the motor branch of the median nerve.1 The study presented here was planned after observation of the TB in a more ulnar location than described in the literature. The aim of this study was to redefine the localization of this branch by using the well-known surface markers described by Kaplan.1 The Journal of Hand Surgery
803
804
The Journal of Hand Surgery / Vol. 30A No. 4 July 2005
edges of the TCL and skin then were approximated with a temporary suture to mimic the position of structures before the release. To represent the middle finger radial side and Kaplan’s1 cardinal lines 2 1.2-mm K-wires were taped on the palm (Fig. 2). While the wrist and fingers were held without forcing to any deviations an anteroposterior radiologic print of the hand was obtained using a C-arm image intensifier (Fig. 3). To ensure that the image truly was anteroposterior the forearm was held in full supination, and the dorsum of the wrist and the dorsal aspects of the second and fifth metacarpal heads were kept in contact with the surface of the C-arm image intensifier surface. The distances between the marker of the TB and the images of the 2 K-wires were measured on the prints of the hands and measurements were calculated by taking the reduction and the magnification rates of the images into consideration. A schematic diagram was drawn and the TB markers were placed by using the measurements referencing the middle finger radial side and cardinal lines (Fig. 4). The time spent to mark the structures and to obtain radiologic images was less than 5 minutes. Fol-
Figure 1. Exploration and marking of the TB of the median nerve during carpal tunnel release surgery. The radiopaque yarn (black arrowhead) is circumscribed around the branch at its emergence.
Materials and Methods The study was performed in 37 hands from 34 patients with carpal tunnel syndrome who had surgery between September 2002 and April 2004. All of the patients were women with a mean age of 50 years (range, 35– 67 y). Surgeries were performed under regional intravenous anesthesia and a minimal-incision approach was used. This incision was performed longitudinally over a line parallel to the radial side of the ring finger passing 2 mm ulnar to the thenar crease. The transverse carpal ligament (TCL) was cut near the most ulnar edge. After a routine carpal tunnel release the TB was explored and evaluated regarding the classification of the courses and anatomic variations described by Lanz.6 After that the TB was marked by circumscribing a soft radiopaque yarn placed on the site of its emergence from the median nerve (Fig. 1). By using a gentle surgical handling technique we did not disturb the TB’s position during the circumscribing procedure. The cut
Figure 2. The middle finger radial and Kaplan’s cardinal lines are shown by K-wires taped on the palm. The K-wire showing the middle finger radial side line is in touch and parallel with the radial border of the middle finger. The K-wire showing the cardinal line is placed parallel to the middle crease of the hand.
Eskandari et al / Localization of Motor Branch of Median Nerve
805
The localization of the images of the TB was either over or proximal to the cardinal line. The average proximal offset was 4.4 mm (minimum, 0.0 mm; maximum, 9.5 mm; SD, 2.3 mm). The overall localizations of the TBs made up an obliquely oriented oval with vertical and horizontal diameters of 10 and 15 mm, respectively, ulnar and slightly proximal to the intersection of Kaplan’s1 cardinal and middle finger radial side lines. This overall localization is shown in Figure 4. Another noteworthy point was related to the orientation of the cardinal line. Kaplan1 claims that this line would run ulnarly over the hook of hamate and distal to the pisiform. In the series presented here all of the images of the K-wires representing the cardinal line had a more distal orientation, passing over the base of the fifth metacarpal.
Figure 3. Anteroposterior radiograph of a hand with the TB, middle finger radial, and cardinal lines marked. The image of the TB is more ulnar and proximal to the intersection point of the 2 wires.
low-up evaluation was performed for a mean period of 9 months (range, 4 –18 mo). The patients were evaluated before surgery and at the last follow-up control for their symptom severity and functional status scores on a self-administered questionnaire described by Levine et al (Boston scale)7 and also for the presence of thenar atrophy and weakness of opposition. The Boston scales showed marked improvement in all patients and there was no patient with postoperative progressive thenar atrophy or weakness of opposition that might have occurred in relation to iatrogenic TB injury8 during the circumscribing procedure.
Results In all of the cases the TB arose from the anteroradial aspect of the median nerve. The course of the TB was extraligamentous in 18, transligamentous in 11, and subligamentous in 8 of the hands. One case of duplicate extraligamentous TB was seen but not included in the study. Evaluation of the radiographic prints showed that the localization of the image of the TB was on the ulnar side of the middle finger radial side line in all cases. The mean ulnar offset was 12.6 mm (minimum, 4.0 mm; maximum, 19.7 mm; SD, 4.1 mm).
Figure 4. Hand with surface creases and the middle finger radial side (A) and the cardinal lines (B). The distribution of 37 TBs is shown (small black points) in relation to each of the 2 lines. The overall area of the localization of the TBs is shown by an oval-shaped striped area. This area has vertical and horizontal diameters of 10 and 15 mm, respectively.
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The Journal of Hand Surgery / Vol. 30A No. 4 July 2005
Discussion In the literature there are a large number of studies dealing with the morphology, anatomy, course, variations, branching patterns, and orientations of the TB of the median nerve8 –17—pioneered by the classic article by Lanz6—manifesting a comprehensive classification for anatomic courses and variations of the median nerve and its branches in the carpal tunnel. There are only a few studies, however, that consider the localization of this branch.11,12,15,16 Excluding Kaplan’s1 book we could find only 1 report in the English literature about the topographic localization of the TB.16 In this cadaveric study Olave et al16 calculated the mean distance of the TB from the distal wrist crease as 35 mm. These investigators did not consider the localization of the branch in an ulnar-radial direction. Kaplan1 included valuable information about the functional, surgical, and topographic anatomy of the hand. Along with other deep structures of the hand he described detailed techniques to localize the TB regarding the surface markers of the palm.1 His technique or its modified forms are used in recent published textbooks of hand surgery.2,4,5 In 2 of these books Brown and Gelberman2 and Szabo4 prefer to refer to the intersection of the cardinal line with the middle finger flexed onto the thenar eminence as the localization of the TB. The study presented here was planned when the TB was observed to be located very close to the cut edge of the TCL during the standard open carpal tunnel release surgeries. We objectively determined that the TB is located a mean of 12.6 mm ulnar to the location described in the literature. We emphasize that this localization also is ulnar to the point established by the flexed middle fingertip. This finding requires attention in surgeries such as a carpal tunnel release, which are performed in a longitudinal direction. This study also showed reliability of the cardinal line in locating the TB. The average distance of the motor branch from the cardinal line was 4.4 mm. In 5 cases the images of the motor branch were on the cardinal line but in the remaining 32 cases the localization was more proximal. On the other hand, in contrast to the literature1 the cardinal line passed over the base of the fifth metacarpal distal to both the hook of hamate and pisiform. All of our patients were women with a diagnosis of carpal tunnel syndrome. Because these 2 characteristics represent a relatively homogenous group that
constitutes the majority of the carpal tunnel syndrome cases requiring prediction of the course of the TB, we believe the case series contributes to the scientific strength of the study. Kaplan1 referred to a hypothetical man of average age. The surgical compromises in relation to the TB are investigated in 2 major topics: ulnar take-off variation and isolated or concomitant entrapment of the TB. Ulnar take-off variation, although rare, increases the risk for iatrogenic injury of the TB.6,9 –11,13,15,17–19 Defined sites of entrapment of the TB are the entrance point of the branch into the TCL in a transligamentous type and at the distal edge of the TCL where the TB might show an acute back angulation. These cases require additional release of the TB.6,8,9,14,19 Surgical vulnerability of the TB caused by its proximity to the surgical incision is studied in a single article by Lee and Strickland,12 who calculated the distance between a standard longitudinal incision and the TB as 5.5 ⫾ 2.0 mm. More ulnar localization of the TB relative to the classic definition of the surface topographic measures, discovered in the study presented here, leads to the question of whether the frequency of iatrogenic injury to this branch is more than known. For further evaluation of this topic we prefer close postoperative follow-up evaluation of opposition strength and thenar atrophy. In suspected cases additional functional testing or even electrodiagnostic measures might be necessary.19,20 We postulate that an oval-shaped area with vertical and horizontal diameters of 10 and 15 mm, respectively, represents the localization of the TB across the palm. This area is situated ulnar and slightly proximal to the intersection of Kaplan’s cardinal line with the radial side line of the middle finger and also might be pointed out by the fingertip contact area of both the middle and ring fingers in an unforced fist with the distal interphalangeal joints in extension, taking physiologic radial deviation of the flexed fingers into account.
References 1. Kaplan EB. Functional and surgical anatomy of the hand. Philadelphia: JB Lippincott, 1965:265–270. 2. Brown RA, Gelberman RH. Carpal tunnel release: open technique. In: Blair WF, ed. Techniques in hand surgery. 1st ed. Baltimore: Williams & Wilkins, 1996:703–710. 3. Keenan MAE, Botte MJ. Technique of percutaneous phenol block of the recurrent motor branch of the median nerve. J Hand Surg 1987;12A:806 – 807. 4. Szabo RM. Entrapment and compression neuropathies. In:
Eskandari et al / Localization of Motor Branch of Median Nerve
5.
6. 7.
8.
9.
10.
11. 12.
Green DP, Hotchkiss RN, Pederson WC, eds. Green’s operative hand surgery. 4th ed. Philadelphia: Churchill Livingstone, 1999:1404 –1447. Wright PE II. Carpal tunnel and ulnar tunnel syndromes and stenosing tenosynovitis. In: Canale ST, ed. Campbell’s operative orthopaedics. 9th ed. St. Louis: Mosby, 1998:3685– 3702. Lanz U. Anatomical variations of the median nerve in the carpal tunnel. J Hand Surg 1977;2:44 –53. Levine DW, Simmons BP, Koris MJ, Daltory LH, Hohl GG, Fossel AH, et al. A self-administered questionnaire for the assessment of severity of symptoms and functional status in carpal tunnel syndrome. J Bone Joint Surg 1993;75A:1585– 1592. Bennett JB, Crouch CC. Compression syndrome of the recurrent motor branch of the median nerve. J Hand Surg 1982;7:407– 409. Ahn DS, Yoon ES, Koo SH, Park SH. A prospective study of the anatomic variations of the median nerve in the carpal tunnel in Asians. Ann Plast Surg 2000;44:282–287. Cavallo AV, Slattery PG, Barton RJ. Endoscopic carpal tunnel release and congenital anomalies of the median nerve. Hand Surg 2003;8:265–270. Kozin SH. The anatomy of the recurrent branch of the median nerve. J Hand Surg 1998;23A:852– 858. Lee WPA, Strickland JW. Safe carpal tunnel release via a
13.
14.
15.
16.
17.
18.
19.
20.
807
limited palmar incision. Plast Reconstr Surg 1998;101:418 – 424. Lindley SG, Kleinert JM. Prevalence of anatomic variations encountered in elective carpal tunnel release. J Hand Surg 2003;28A:849 – 855. Mackinnon SE, Dellon AL. Anatomic investigations of nerves at the wrist: I. Orientation of the motor fascicle of the median nerve in the carpal tunnel. Ann Plast Surg 1988;21: 32–35. Mumford J, Morecraft R, Blair WF. Anatomy of the thenar branch of the median nerve. J Hand Surg 1987;12A:361– 365. Olave E, Prates JC, Gabrielli C, Pardi P. Morphometric studies of the muscular branch of the median nerve. J Anat 1996;189:445– 449. Werschkul JD. Anomalous course of the recurrent motor branch of the median nerve in a patient with carpal tunnel syndrome. J Neurosurg 1977;47:113–114. Chow JCY, Hantes ME. Endoscopic carpal tunnel release: thirteen years’ experience with the Chow technique. J Hand Surg 2002;27A:1011–1018. Ueno H, Kaneko K, Taguchi T, Fuchigami Y, Fujimoto H, Kawai S. Endoscopic carpal tunnel release and nerve conduction studies. Int Orthop 2001;24:361–363. Szabo RM, Slater RR Jr, Farver TB, Stanton DB, Sharman WK. The value of diagnostic testing in carpal tunnel syndrome. J Hand Surg 1999;24A:704 –714.
Purpose: To redefine the localization of the thenar branch (TB) of the median nerve in relation to the surface landmarks that are in routine use. Methods: The study was performed in 37 hands of 34 patients who had carpal tunnel release. All of the patients were women and the mean age was 50 years (range, 35– 67 y). A radiologic marking technique was used to determine the localization of the TB, the middle finger radial side line, and Kaplan’s cardinal line. The TB was marked by circumscribing with a soft radiopaque yarn and the surface landmark lines were shown by taping a K-wire to the hand for each line. An imageintensifier–printed image was obtained for each case and the distances between the markers of the TB and the wires were measured. Results: The TB had a mean ulnar offset of 12.6 mm (range, 4.0 –19.7 mm) from the middle finger radial side line and was located 4.4 mm (range, 0 –9.5 mm) proximal to the cardinal line. Conclusions: During carpal tunnel release surgery the surgeon must pay more attention to the localization of the TB of the median nerve because it was found to be 12.6 mm more ulnar than the location described in the literature. (J Hand Surg 2005;30A:803– 807. Copyright © 2005 by the American Society for Surgery of the Hand.) Key words: Carpal tunnel, localization, median nerve, motor branch, surface landmarks.
During surgery of the hand there are surface landmarks that are used to estimate the localization of deep structures and to minimize injury. The thenar branch (TB) of the median nerve is one of these deep structures that should be protected. This branch innervates the thenar muscles that contribute to the From the Department of Orthopedics and Traumatology, University of Mersin, School of Medicine, Mersin, Turkey. Received for publication August 10, 2004; accepted in revised form March 10, 2005. 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. Corresponding author: Metin Manouchehr Eskandari, MD, Mersin ¨ niversitesi Tip Fakültesi Hastanesi, Ortopedi ve Travmatoloji U AD, Zeytinlibahce cad. 33079, Mersin, Turkey; e-mail: mmeskandari@ yahoo.com. Copyright © 2005 by the American Society for Surgery of the Hand 0363-5023/05/30A04-0024$30.00/0 doi:10.1016/j.jhsa.2005.03.010
opposition of the thumb, which is the most important function of the hand. Topographic localization of this branch according to surface landmarks was defined by Kaplan in 1953 and 19651 and this definition still is used.2–5 Kaplan1 described his cardinal line as the line drawn from the apex of the interdigital fold between the thumb and the index finger toward the ulnar side of the hand, parallel with the middle crease of the palm. He stated that if a line is drawn continuing along the radial side of the middle finger in a proximal direction then its intersection by the cardinal line corresponds to the emergence of the motor branch of the median nerve.1 The study presented here was planned after observation of the TB in a more ulnar location than described in the literature. The aim of this study was to redefine the localization of this branch by using the well-known surface markers described by Kaplan.1 The Journal of Hand Surgery
803
804
The Journal of Hand Surgery / Vol. 30A No. 4 July 2005
edges of the TCL and skin then were approximated with a temporary suture to mimic the position of structures before the release. To represent the middle finger radial side and Kaplan’s1 cardinal lines 2 1.2-mm K-wires were taped on the palm (Fig. 2). While the wrist and fingers were held without forcing to any deviations an anteroposterior radiologic print of the hand was obtained using a C-arm image intensifier (Fig. 3). To ensure that the image truly was anteroposterior the forearm was held in full supination, and the dorsum of the wrist and the dorsal aspects of the second and fifth metacarpal heads were kept in contact with the surface of the C-arm image intensifier surface. The distances between the marker of the TB and the images of the 2 K-wires were measured on the prints of the hands and measurements were calculated by taking the reduction and the magnification rates of the images into consideration. A schematic diagram was drawn and the TB markers were placed by using the measurements referencing the middle finger radial side and cardinal lines (Fig. 4). The time spent to mark the structures and to obtain radiologic images was less than 5 minutes. Fol-
Figure 1. Exploration and marking of the TB of the median nerve during carpal tunnel release surgery. The radiopaque yarn (black arrowhead) is circumscribed around the branch at its emergence.
Materials and Methods The study was performed in 37 hands from 34 patients with carpal tunnel syndrome who had surgery between September 2002 and April 2004. All of the patients were women with a mean age of 50 years (range, 35– 67 y). Surgeries were performed under regional intravenous anesthesia and a minimal-incision approach was used. This incision was performed longitudinally over a line parallel to the radial side of the ring finger passing 2 mm ulnar to the thenar crease. The transverse carpal ligament (TCL) was cut near the most ulnar edge. After a routine carpal tunnel release the TB was explored and evaluated regarding the classification of the courses and anatomic variations described by Lanz.6 After that the TB was marked by circumscribing a soft radiopaque yarn placed on the site of its emergence from the median nerve (Fig. 1). By using a gentle surgical handling technique we did not disturb the TB’s position during the circumscribing procedure. The cut
Figure 2. The middle finger radial and Kaplan’s cardinal lines are shown by K-wires taped on the palm. The K-wire showing the middle finger radial side line is in touch and parallel with the radial border of the middle finger. The K-wire showing the cardinal line is placed parallel to the middle crease of the hand.
Eskandari et al / Localization of Motor Branch of Median Nerve
805
The localization of the images of the TB was either over or proximal to the cardinal line. The average proximal offset was 4.4 mm (minimum, 0.0 mm; maximum, 9.5 mm; SD, 2.3 mm). The overall localizations of the TBs made up an obliquely oriented oval with vertical and horizontal diameters of 10 and 15 mm, respectively, ulnar and slightly proximal to the intersection of Kaplan’s1 cardinal and middle finger radial side lines. This overall localization is shown in Figure 4. Another noteworthy point was related to the orientation of the cardinal line. Kaplan1 claims that this line would run ulnarly over the hook of hamate and distal to the pisiform. In the series presented here all of the images of the K-wires representing the cardinal line had a more distal orientation, passing over the base of the fifth metacarpal.
Figure 3. Anteroposterior radiograph of a hand with the TB, middle finger radial, and cardinal lines marked. The image of the TB is more ulnar and proximal to the intersection point of the 2 wires.
low-up evaluation was performed for a mean period of 9 months (range, 4 –18 mo). The patients were evaluated before surgery and at the last follow-up control for their symptom severity and functional status scores on a self-administered questionnaire described by Levine et al (Boston scale)7 and also for the presence of thenar atrophy and weakness of opposition. The Boston scales showed marked improvement in all patients and there was no patient with postoperative progressive thenar atrophy or weakness of opposition that might have occurred in relation to iatrogenic TB injury8 during the circumscribing procedure.
Results In all of the cases the TB arose from the anteroradial aspect of the median nerve. The course of the TB was extraligamentous in 18, transligamentous in 11, and subligamentous in 8 of the hands. One case of duplicate extraligamentous TB was seen but not included in the study. Evaluation of the radiographic prints showed that the localization of the image of the TB was on the ulnar side of the middle finger radial side line in all cases. The mean ulnar offset was 12.6 mm (minimum, 4.0 mm; maximum, 19.7 mm; SD, 4.1 mm).
Figure 4. Hand with surface creases and the middle finger radial side (A) and the cardinal lines (B). The distribution of 37 TBs is shown (small black points) in relation to each of the 2 lines. The overall area of the localization of the TBs is shown by an oval-shaped striped area. This area has vertical and horizontal diameters of 10 and 15 mm, respectively.
806
The Journal of Hand Surgery / Vol. 30A No. 4 July 2005
Discussion In the literature there are a large number of studies dealing with the morphology, anatomy, course, variations, branching patterns, and orientations of the TB of the median nerve8 –17—pioneered by the classic article by Lanz6—manifesting a comprehensive classification for anatomic courses and variations of the median nerve and its branches in the carpal tunnel. There are only a few studies, however, that consider the localization of this branch.11,12,15,16 Excluding Kaplan’s1 book we could find only 1 report in the English literature about the topographic localization of the TB.16 In this cadaveric study Olave et al16 calculated the mean distance of the TB from the distal wrist crease as 35 mm. These investigators did not consider the localization of the branch in an ulnar-radial direction. Kaplan1 included valuable information about the functional, surgical, and topographic anatomy of the hand. Along with other deep structures of the hand he described detailed techniques to localize the TB regarding the surface markers of the palm.1 His technique or its modified forms are used in recent published textbooks of hand surgery.2,4,5 In 2 of these books Brown and Gelberman2 and Szabo4 prefer to refer to the intersection of the cardinal line with the middle finger flexed onto the thenar eminence as the localization of the TB. The study presented here was planned when the TB was observed to be located very close to the cut edge of the TCL during the standard open carpal tunnel release surgeries. We objectively determined that the TB is located a mean of 12.6 mm ulnar to the location described in the literature. We emphasize that this localization also is ulnar to the point established by the flexed middle fingertip. This finding requires attention in surgeries such as a carpal tunnel release, which are performed in a longitudinal direction. This study also showed reliability of the cardinal line in locating the TB. The average distance of the motor branch from the cardinal line was 4.4 mm. In 5 cases the images of the motor branch were on the cardinal line but in the remaining 32 cases the localization was more proximal. On the other hand, in contrast to the literature1 the cardinal line passed over the base of the fifth metacarpal distal to both the hook of hamate and pisiform. All of our patients were women with a diagnosis of carpal tunnel syndrome. Because these 2 characteristics represent a relatively homogenous group that
constitutes the majority of the carpal tunnel syndrome cases requiring prediction of the course of the TB, we believe the case series contributes to the scientific strength of the study. Kaplan1 referred to a hypothetical man of average age. The surgical compromises in relation to the TB are investigated in 2 major topics: ulnar take-off variation and isolated or concomitant entrapment of the TB. Ulnar take-off variation, although rare, increases the risk for iatrogenic injury of the TB.6,9 –11,13,15,17–19 Defined sites of entrapment of the TB are the entrance point of the branch into the TCL in a transligamentous type and at the distal edge of the TCL where the TB might show an acute back angulation. These cases require additional release of the TB.6,8,9,14,19 Surgical vulnerability of the TB caused by its proximity to the surgical incision is studied in a single article by Lee and Strickland,12 who calculated the distance between a standard longitudinal incision and the TB as 5.5 ⫾ 2.0 mm. More ulnar localization of the TB relative to the classic definition of the surface topographic measures, discovered in the study presented here, leads to the question of whether the frequency of iatrogenic injury to this branch is more than known. For further evaluation of this topic we prefer close postoperative follow-up evaluation of opposition strength and thenar atrophy. In suspected cases additional functional testing or even electrodiagnostic measures might be necessary.19,20 We postulate that an oval-shaped area with vertical and horizontal diameters of 10 and 15 mm, respectively, represents the localization of the TB across the palm. This area is situated ulnar and slightly proximal to the intersection of Kaplan’s cardinal line with the radial side line of the middle finger and also might be pointed out by the fingertip contact area of both the middle and ring fingers in an unforced fist with the distal interphalangeal joints in extension, taking physiologic radial deviation of the flexed fingers into account.
References 1. Kaplan EB. Functional and surgical anatomy of the hand. Philadelphia: JB Lippincott, 1965:265–270. 2. Brown RA, Gelberman RH. Carpal tunnel release: open technique. In: Blair WF, ed. Techniques in hand surgery. 1st ed. Baltimore: Williams & Wilkins, 1996:703–710. 3. Keenan MAE, Botte MJ. Technique of percutaneous phenol block of the recurrent motor branch of the median nerve. J Hand Surg 1987;12A:806 – 807. 4. Szabo RM. Entrapment and compression neuropathies. In:
Eskandari et al / Localization of Motor Branch of Median Nerve
5.
6. 7.
8.
9.
10.
11. 12.
Green DP, Hotchkiss RN, Pederson WC, eds. Green’s operative hand surgery. 4th ed. Philadelphia: Churchill Livingstone, 1999:1404 –1447. Wright PE II. Carpal tunnel and ulnar tunnel syndromes and stenosing tenosynovitis. In: Canale ST, ed. Campbell’s operative orthopaedics. 9th ed. St. Louis: Mosby, 1998:3685– 3702. Lanz U. Anatomical variations of the median nerve in the carpal tunnel. J Hand Surg 1977;2:44 –53. Levine DW, Simmons BP, Koris MJ, Daltory LH, Hohl GG, Fossel AH, et al. A self-administered questionnaire for the assessment of severity of symptoms and functional status in carpal tunnel syndrome. J Bone Joint Surg 1993;75A:1585– 1592. Bennett JB, Crouch CC. Compression syndrome of the recurrent motor branch of the median nerve. J Hand Surg 1982;7:407– 409. Ahn DS, Yoon ES, Koo SH, Park SH. A prospective study of the anatomic variations of the median nerve in the carpal tunnel in Asians. Ann Plast Surg 2000;44:282–287. Cavallo AV, Slattery PG, Barton RJ. Endoscopic carpal tunnel release and congenital anomalies of the median nerve. Hand Surg 2003;8:265–270. Kozin SH. The anatomy of the recurrent branch of the median nerve. J Hand Surg 1998;23A:852– 858. Lee WPA, Strickland JW. Safe carpal tunnel release via a
13.
14.
15.
16.
17.
18.
19.
20.
807
limited palmar incision. Plast Reconstr Surg 1998;101:418 – 424. Lindley SG, Kleinert JM. Prevalence of anatomic variations encountered in elective carpal tunnel release. J Hand Surg 2003;28A:849 – 855. Mackinnon SE, Dellon AL. Anatomic investigations of nerves at the wrist: I. Orientation of the motor fascicle of the median nerve in the carpal tunnel. Ann Plast Surg 1988;21: 32–35. Mumford J, Morecraft R, Blair WF. Anatomy of the thenar branch of the median nerve. J Hand Surg 1987;12A:361– 365. Olave E, Prates JC, Gabrielli C, Pardi P. Morphometric studies of the muscular branch of the median nerve. J Anat 1996;189:445– 449. Werschkul JD. Anomalous course of the recurrent motor branch of the median nerve in a patient with carpal tunnel syndrome. J Neurosurg 1977;47:113–114. Chow JCY, Hantes ME. Endoscopic carpal tunnel release: thirteen years’ experience with the Chow technique. J Hand Surg 2002;27A:1011–1018. Ueno H, Kaneko K, Taguchi T, Fuchigami Y, Fujimoto H, Kawai S. Endoscopic carpal tunnel release and nerve conduction studies. Int Orthop 2001;24:361–363. Szabo RM, Slater RR Jr, Farver TB, Stanton DB, Sharman WK. The value of diagnostic testing in carpal tunnel syndrome. J Hand Surg 1999;24A:704 –714.