SCIENTIFIC ARTICLE
Anatomical Study of the Surgical Approaches to the Radial Tunnel Ekaterina Y. Urch, MD, Zina Model, BA, Scott W. Wolfe, MD, Steve K. Lee, MD
Purpose To provide a cadaveric analysis of 3 surgical approaches (anterior, anterolateral, posterior) used for decompression of the posterior interosseous nerve within the radial tunnel. The aim of the study was to determine whether the number of compression sites visualized and safely released differed between approaches. We hypothesized that no single approach is adequate for visualization of all key compression sites. Methods Thirty fresh-frozen cadaveric specimens were used to perform 10 anterior, 10 anterolateral, and 10 posterior approaches to the radial tunnel. For each approach, key anatomical structures and the 5 documented anatomical sites of nerve compression that were clearly visualized within the surgical exposure were recorded. The portion of the supinator that was directly visualized in each approach was released. A second window was then created to expose the remaining uncut portion of the supinator. Measurements were taken from each specimen. Results Statistical analysis demonstrated that the anterior and anterolateral approaches were best for visualizing the fibrous bands of the radial head, the leash of Henry, the origin of the extensor carpi radialis brevis, and the arcade of Frohse. The posterior approach was best for visualizing the distal border of the supinator. The relative uncut supinator distance varied with approach. The anterior approach left a larger relative uncut portion than the posterior approach. Conclusions No single approach was adequate for complete visualization and release of all compression points of the radial tunnel. In cases of radial tunnel release, complete visualization of the posterior interosseous nerve compression sites is best achieved through multiple windows. (J Hand Surg Am. 2015;-(-):-e-. Copyright Ó 2015 by the American Society for Surgery of the Hand. All rights reserved.) Type of study/level of evidence Therapeutic IV. Key words Anatomy, radial tunnel, nerve compression, radial nerve, posterior interosseous nerve.
R
is classically defined as compression of the posterior interosseous nerve (PIN) within the radial tunnel.1e3 The radial tunnel is a 5-cm-long potential space along ADIAL TUNNEL SYNDROME (RTS)
From the Division of Hand and Upper Extremity Surgery, Department of Orthopaedic Surgery, Hospital for Special Surgery, New York, NY. Received for publication November 5, 2014; accepted in revised form March 3, 2015. No benefits in any form have been received or will be received related directly or indirectly to the subject of this article. Corresponding author: Steve K. Lee, MD, Division of Hand and Upper Extremity Surgery, Department of Orthopaedic Surgery, Hospital for Special Surgery, Weill Cornell Medical College, 535 East 70th St., New York, NY 10021; e-mail: [email protected]. 0363-5023/15/---0001$36.00/0 http://dx.doi.org/10.1016/j.jhsa.2015.03.009
the anterior aspect of the proximal radius, originating at the radiocapitellar joint (RCJ) and running distally between the deep and the superficial heads of the supinator.4 Through numerous anatomical and clinical studies, various compression sites have been identified, including the fibrous bands proximal to the radial head, the leash of Henry, the extensor carpi radialis brevis (ECRB), the arcade of Frohse, and the supinator superficial head, ending with the distal edge of the supinator.4e8 The arcade of Frohse may be the primary site of PIN compression in RTS; however, the remaining 4 sites also may play key roles in the syndrome.4,9 The 3 pathognomonic signs of RTS are pain over the radial tunnel, pain during resisted extension of the middle finger, and pain during resisted supination.4,5 The first
Ó 2015 ASSH
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Published by Elsevier, Inc. All rights reserved.
r
1
2
ANATOMICAL STUDY OF RADIAL TUNNEL APPROACHES
FIGURE 1: Four classic approaches to the radial tunnel.
Novak1 (Fig. 1). The transbrachioradialis approach was omitted from the study owing to its similarity to the anterior approach. The radial tunnel begins at the RCJ and terminates at the distal aspect of the supinator. The floor of the tunnel is the anterior surface of the radiocapitellar joint proximally and the deep head of the supinator distally. The roof is marked by a fibrofatty layer between the brachialis and the brachioradialis proximally, then the medial edge of the ECRB, and finally the superficial head of the supinator.1,9 This definition spans all documented areas of possible nerve compression, including the fibrous bands proximal to the radial head, the leash of Henry, the insertion of the ECRB, the arcade of Frohse, and the superficial head of the supinator including the distal edge of the supinator. The anterior approach created a window between the brachioradialis and the brachialis and biceps tendons with the forearm supinated. The dissection was carried down to visualize the RCJ, the motor branch to the ECRB, and the superficial radial nerve. The RCJ was marked with an 18-gauge needle that was inserted into the joint. The distance from the needle to the arcade of Frohse (the entry point of the PIN into the supinator) was measured using a 15-cm stainless steel ruler. All measurements were made jointly by 2 investigators (E.Y.U. and Z.M.). This measurement, denoted as the distance between the RCJ and the arcade of Frohse, would later be used to derive the total length of the radial tunnel as it runs from the radial head to the distal edge of the supinator. Direct visualization of key anatomical landmarks and possible compression sites was noted.
line of treatment of RTS is nonsurgical and includes rest, activity modification, anti-inflammatories, and corticosteroid injections.4,8 In certain patients who are refractory to nonsurgical management, surgical exploration and release of the nerve may be indicated. Unfortunately, prior clinical series documenting the efficacy of surgical release have shown only moderate success in patient outcomes, with some studies reporting good or excellent results from 50% to 95% of patients.5,8,10e13 This is partly due to the inherent difficulty in identifying an isolated RTS.1,3,13 In cases in which the appropriate diagnosis is made, inadequate visualization and release of the nerve within the tunnel may play a role in unsatisfactory outcomes. Four different approaches to the radial tunnel have been described. These include the anterior, the anterolateral, the transbrachioradialis, and the posterior approaches.1,8 The purpose of our study was to perform 3 approaches (anterior, anterolateral, and posterior) used for surgical release of the PIN and evaluate the effectiveness of each in exposure and decompression of the PIN within the radial tunnel. METHODS Cadaveric dissection A total of 30 fresh-frozen cadaveric arms (4 female, 26 male; average age, 64 y) with no previous trauma, surgery, or obvious abnormality was used for dissection. One of 3 approaches (anterior, anterolateral, and posterior) was randomly performed on the 30 specimens for a total of 10 times per approach. The approaches were as described by Mackinnon and J Hand Surg Am.
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ANATOMICAL STUDY OF RADIAL TUNNEL APPROACHES
These included fibrous bands of the radial head, tendinous insertion of the ECRB, leash of Henry, superficial sensory branch of the radial nerve, the arcade of Frohse, and the distal border of the supinator. The PIN was then released by cutting the portion of the supinator muscle that was directly visualized within the anterior window. The radial and ulnar edges of the cut supinator were reapproximated and the cut length was measured using the 15-cm ruler. Next, a posterior window was developed using the interval between the ECRB and the extensor digitorum communis. The uncut supinator, from the end point of the previous cut to the distal exit point of the PIN, was then measured. Complete exposure of the muscle was confirmed by visualizing the entry and exit points of the PIN into the supinator. Finally, the circumferential diameter of the muscle bellies of the brachioradialis, extensor carpi radialis longus (ECRL), and ECRB was measured as a way to objectively quantify the muscularity, or bulkiness, of the specimen. This was done by passing a vessel loop around these muscles at the level of the arcade of Frohse and measuring directly off of the vessel loop with the 15-cm ruler. The anterolateral approach was performed by creating a window between the ECRL and the brachioradialis with the forearm in neutral. All of the same measurements and points of compression were noted as described previously, and a posterior second window was made to visualize and measure any unreleased portion of the PIN. The posterior approach was performed by creating a window between the ECRB and the extensor digitorum communis with the forearm pronated. All of the same measurements and points of compression were noted as described previously. In this instance, however, an anterolateral second window was made through the ECRL and the brachioradialis to visualize and measure any unreleased portion of the PIN.
hypothesis that the entire supinator was visualized and cut through a single window was tested with signed rank tests for each approach. Statistical analyses set a level of significance of a ¼ 0.05. RESULTS The 30 specimens consisted of 4 female and 26 male cadaveric limbs. The average age was 64 years (range, 29e86 y). There was no difference in the muscularity of the limbs between the 3 groups. The superficial branch of the radial nerve was visualized in all anterior and anterolateral approaches, whereas it was visualized in only 4 posterior approaches. This difference was statistically significant (P ¼ .023). Likewise, whereas the fibrous bands of the radial head, the leash of Henry, the tendinous origin of the ECRB, and the arcade of Frohse were visualized in all anterior and anterolateral approaches, these were not consistently seen in the posterior approach (Table 1). Conversely, the distal border of the supinator was clearly visualized in all 10 posterior approaches, whereas this was the case in only 3 anterolateral approaches and in none of the anterior approaches. This difference was statistically significant (P < .001). The average distances between anatomical landmarks are present in Table 2. Using these 3 measurements, the average length of the radial tunnel was 79 mm (range, 53e103 mm; SD ¼ 14). Out of the 30 specimens, the supinator was completely released in 8 (27%) specimens via the single-window approach (7 from the posterior approach and 1 from the anterolateral approach). The average total supinator length was 50 mm (range, 28e76 mm; SD ¼ 12) and total supinator length did not differ between exposures (P ¼ .38). The relative uncut supinator distance, calculated as uncut length as a percentage of total supinator length, varied significantly across the 3 approaches, with the anterior approach having a significantly larger relative uncut distance than the posterior approach (P ¼ .008) (Table 2).
Statistical analysis Descriptive statistics for the ability to visualize branches and compression points are presented as the number and percentage of samples in which each feature is present in each approach. Distance measurements are presented as means and SD for each approach. Associations between the approach and the ability to visualize branches and compression points were assessed with Fisher exact tests. Differences in distance measurements between approaches were assessed with Kruskal-Wallis tests. Post hoc tests were conducted pairwise and the multiple test error incidence was controlled with the Bonferroni method. The null J Hand Surg Am.
3
DISCUSSION Our study demonstrated that the anterior and anterolateral approaches were best for visualizing the fibrous bands of the radial head, the leash of Henry, the origin of the ECRB, and the arcade of Frohse. The posterior approach was best for visualizing the distal border of the supinator. Furthermore, our results indicate that no single approach was consistently adequate for visualizing and releasing all compression points of the radial tunnel. The data show that, on average, nearly r
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ANATOMICAL STUDY OF RADIAL TUNNEL APPROACHES
TABLE 1.
Radial Tunnel Features Visualized in Each Approach Approach Anterolateral Count
Anterior %
Posterior
Count
%
Count
%
SBRN
P Value .023
No
0
0
0
0
4
40
Yes
10
100
10
100
6
60 < .001
Radial head No
0
0
0
0
10
100
Yes
10
100
10
100
0
0
No
0
0
0
0
5
50
Yes
10
100
10
100
5
50
Leash of Henry
.005
Origin of ECRB
.005
No
0
0
0
0
5
50
Yes
10
100
10
100
5
50
No
0
0
0
0
4
40
Yes
10
100
10
100
6
60
Arcade of Frohse
.023
< .001
Distal supinator No
7
70
10
100
0
0
Yes
3
30
0
0
100
100
SBRN, superficial branch of the radial nerve.
TABLE 2.
Summary of Various Measured Distances Within the Radial Tunnel as Seen in Each Approach
RCJ to Frohse (mm)
Approach
n
Mean
SD
Lower 95% CI for Mean
Upper 95% CI for Mean
P Value
Anterolateral
10
26
6
21.8
30.8
.791
Anterior
10
27
4
24.0
30.0
0
.
.
.
.
Anterolateral
10
21
18
8.9
34.6
Anterior
10
40
19
26.3
54.8
Posterior* Relative uncut supinator (%)
Relative cut supinator (%)
Posterior
10
8
21
e6.2
23.8
Anterolateral
10
78
18
65.4
91.1
Anterior
10
60
20
45.2
73.7
Posterior
10
91
21
76.2
106.2
.003
.003
CI, confidence interval. *RCJ not visualized in posterior approach.
1.2 cm of the PIN was not released through a single approach. This number can go up to as high as an average of 2 cm if only the anterior approach was used. Just as important, our results revealed that none of the 3 approaches guaranteed complete visualization of all 5 points of compression within the radial tunnel. J Hand Surg Am.
Specifically, the distal border of the supinator, which is a critical compression point of the PIN, was consistently not visualized through the anterior and anterolateral approaches. Conversely, the posterior approach was absolutely insufficient for visualizing the fibrous bands of the radial head. The posterior r
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ANATOMICAL STUDY OF RADIAL TUNNEL APPROACHES
approach was likewise inconsistent in exposing the leash of Henry, the tendinous border of the ECRB tendon, and the arcade of Frohse. Based on these data, a single approach for PIN decompression is inadequate for visualizing all compression within the radial tunnel. This finding has noteworthy implications for clinical practice because incomplete decompression and partial release of the supinator risks residual postoperative symptoms. This may account for the inconsistent clinical outcomes reported in prior studies.10,11,14 Our results suggest that a double-window approach for radial tunnel decompression allows for consistent exposure and careful release of all compression points within the radial tunnel. For example, through a single incision, the surgeon can use the anterior or anterolateral window for complete exposure of proximal compression sites. The senior author’s (S.K.L.) preferred method is a single 7-cm incision centered over the mobile wad, beginning 5 cm distal to the lateral epicondyle to expose the intermuscular plane between the brachioradialis and the ECRL. Next, working through the same skin incision, a posterior window can be developed to safely release the distal border of the supinator. In our dissections, the use of a second window did not require extension of the skin incision nor did it present any anatomical barriers that precluded completion of the dissection. The anterolateralposterior double-window technique is our preferred method of radial tunnel decompression clinically. A limitation of this study is that it is not known if a 2-window technique would have superior clinical outcomes to the single-window technique. For this, a randomized controlled trial is required. However, we do not believe there is equipoise of surgical release to make this an ethical study. Alternatively, a retrospective review of outcomes in patients treated with the double-window technique could provide clinical insight on the efficacy of the method compared with the classic single-window approach. Another limita-
J Hand Surg Am.
5
tion of this study is that measurements were made jointly by the authors during dissection. Therefore, we are unable to perform a reproducibility assessment. ACKNOWLEDGMENT The authors thank Jayme C. Burket, PhD, for assistance with statistical analysis. This study was partially funded by the Hospital for Special Surgery Surgeonin-Chief Fund. REFERENCES 1. MacKinnon SE, Novak CB. Compression neuropathies. In: Wolfe SW, Hotchkiss RN, Pederson WC, Kozin SH, eds. Green’s Operative Hand Surgery. 6th ed. Philadelphia: Churchill Livingstone; 2011:977e1092. 2. Sarhadi NS, Korday SN, Bainbridge LC. Radial tunnel syndrome: diagnosis and management. J Hand Surg Br. 1998;23(5):617e619. 3. Younge DH, Moise P. The radial tunnel syndrome. Int Orthop. 1994;18(5):268e270. 4. Dang AC, Rodner CM. Unusual compression neuropathies of the forearm, part I: radial nerve. J Hand Surg Am. 2009;34(10):1906e1914. 5. Lister GD, Belsole RB, Kleinert HE. The radial tunnel syndrome. J Hand Surg Am. 1979;4(1):52e59. 6. Portilla Molina AE, Bour C, Oberlin C, Nzeusseu A, Vanwijck R. The posterior interosseous nerve and the radial tunnel syndrome: an anatomical study. Int Orthop. 1998;22(2):102e106. 7. Prasartritha T, Liupolvanish P, Rojanakit A. A study of the posterior interosseous nerve (PIN) and the radial tunnel in 30 Thai cadavers. J Hand Surg Am. 1993;18(1):107e112. 8. Arle JE, Zager EL. Surgical treatment of common entrapment neuropathies in the upper limbs. Muscle Nerve. 2000;23(8):1160e1174. 9. Markiewitz AD, Merryman J. Radial nerve compression in the upper extremity. J Hand Surg Am. 2005;5(2):87e89. 10. Jebson PJ, Engber WD. Radial tunnel syndrome: long-term results of surgical decompression. J Hand Surg Am. 1997;22(5):889e896. 11. Lawrence T, Mobbs P, Fortems Y, Stanley JK. Radial tunnel syndrome. A retrospective review of 30 decompressions of the radial nerve. J Hand Surg Br. 1995;20(4):454e459. 12. Ritts GD, Wood MB, Linscheid RL. Radial tunnel syndrome. A tenyear surgical experience. Clin Orthop Relat Res. 1987;219:201e205. 13. Roles NC, Maudsley RH. Radial tunnel syndrome: resistant tennis elbow as a nerve entrapment. J Bone Joint Surg Br. 1972;54(3): 499e508. 14. Sotereanos DG, Varitimidis SE, Giannakopoulos PN, Westkaemper JG. Results of surgical treatment for radial tunnel syndrome. J Hand Surg Am. 1999;24(3):566e570.
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Anatomical Study of the Surgical Approaches to the Radial Tunnel Ekaterina Y. Urch, MD, Zina Model, BA, Scott W. Wolfe, MD, Steve K. Lee, MD
Purpose To provide a cadaveric analysis of 3 surgical approaches (anterior, anterolateral, posterior) used for decompression of the posterior interosseous nerve within the radial tunnel. The aim of the study was to determine whether the number of compression sites visualized and safely released differed between approaches. We hypothesized that no single approach is adequate for visualization of all key compression sites. Methods Thirty fresh-frozen cadaveric specimens were used to perform 10 anterior, 10 anterolateral, and 10 posterior approaches to the radial tunnel. For each approach, key anatomical structures and the 5 documented anatomical sites of nerve compression that were clearly visualized within the surgical exposure were recorded. The portion of the supinator that was directly visualized in each approach was released. A second window was then created to expose the remaining uncut portion of the supinator. Measurements were taken from each specimen. Results Statistical analysis demonstrated that the anterior and anterolateral approaches were best for visualizing the fibrous bands of the radial head, the leash of Henry, the origin of the extensor carpi radialis brevis, and the arcade of Frohse. The posterior approach was best for visualizing the distal border of the supinator. The relative uncut supinator distance varied with approach. The anterior approach left a larger relative uncut portion than the posterior approach. Conclusions No single approach was adequate for complete visualization and release of all compression points of the radial tunnel. In cases of radial tunnel release, complete visualization of the posterior interosseous nerve compression sites is best achieved through multiple windows. (J Hand Surg Am. 2015;-(-):-e-. Copyright Ó 2015 by the American Society for Surgery of the Hand. All rights reserved.) Type of study/level of evidence Therapeutic IV. Key words Anatomy, radial tunnel, nerve compression, radial nerve, posterior interosseous nerve.
R
is classically defined as compression of the posterior interosseous nerve (PIN) within the radial tunnel.1e3 The radial tunnel is a 5-cm-long potential space along ADIAL TUNNEL SYNDROME (RTS)
From the Division of Hand and Upper Extremity Surgery, Department of Orthopaedic Surgery, Hospital for Special Surgery, New York, NY. Received for publication November 5, 2014; accepted in revised form March 3, 2015. No benefits in any form have been received or will be received related directly or indirectly to the subject of this article. Corresponding author: Steve K. Lee, MD, Division of Hand and Upper Extremity Surgery, Department of Orthopaedic Surgery, Hospital for Special Surgery, Weill Cornell Medical College, 535 East 70th St., New York, NY 10021; e-mail: [email protected]. 0363-5023/15/---0001$36.00/0 http://dx.doi.org/10.1016/j.jhsa.2015.03.009
the anterior aspect of the proximal radius, originating at the radiocapitellar joint (RCJ) and running distally between the deep and the superficial heads of the supinator.4 Through numerous anatomical and clinical studies, various compression sites have been identified, including the fibrous bands proximal to the radial head, the leash of Henry, the extensor carpi radialis brevis (ECRB), the arcade of Frohse, and the supinator superficial head, ending with the distal edge of the supinator.4e8 The arcade of Frohse may be the primary site of PIN compression in RTS; however, the remaining 4 sites also may play key roles in the syndrome.4,9 The 3 pathognomonic signs of RTS are pain over the radial tunnel, pain during resisted extension of the middle finger, and pain during resisted supination.4,5 The first
Ó 2015 ASSH
r
Published by Elsevier, Inc. All rights reserved.
r
1
2
ANATOMICAL STUDY OF RADIAL TUNNEL APPROACHES
FIGURE 1: Four classic approaches to the radial tunnel.
Novak1 (Fig. 1). The transbrachioradialis approach was omitted from the study owing to its similarity to the anterior approach. The radial tunnel begins at the RCJ and terminates at the distal aspect of the supinator. The floor of the tunnel is the anterior surface of the radiocapitellar joint proximally and the deep head of the supinator distally. The roof is marked by a fibrofatty layer between the brachialis and the brachioradialis proximally, then the medial edge of the ECRB, and finally the superficial head of the supinator.1,9 This definition spans all documented areas of possible nerve compression, including the fibrous bands proximal to the radial head, the leash of Henry, the insertion of the ECRB, the arcade of Frohse, and the superficial head of the supinator including the distal edge of the supinator. The anterior approach created a window between the brachioradialis and the brachialis and biceps tendons with the forearm supinated. The dissection was carried down to visualize the RCJ, the motor branch to the ECRB, and the superficial radial nerve. The RCJ was marked with an 18-gauge needle that was inserted into the joint. The distance from the needle to the arcade of Frohse (the entry point of the PIN into the supinator) was measured using a 15-cm stainless steel ruler. All measurements were made jointly by 2 investigators (E.Y.U. and Z.M.). This measurement, denoted as the distance between the RCJ and the arcade of Frohse, would later be used to derive the total length of the radial tunnel as it runs from the radial head to the distal edge of the supinator. Direct visualization of key anatomical landmarks and possible compression sites was noted.
line of treatment of RTS is nonsurgical and includes rest, activity modification, anti-inflammatories, and corticosteroid injections.4,8 In certain patients who are refractory to nonsurgical management, surgical exploration and release of the nerve may be indicated. Unfortunately, prior clinical series documenting the efficacy of surgical release have shown only moderate success in patient outcomes, with some studies reporting good or excellent results from 50% to 95% of patients.5,8,10e13 This is partly due to the inherent difficulty in identifying an isolated RTS.1,3,13 In cases in which the appropriate diagnosis is made, inadequate visualization and release of the nerve within the tunnel may play a role in unsatisfactory outcomes. Four different approaches to the radial tunnel have been described. These include the anterior, the anterolateral, the transbrachioradialis, and the posterior approaches.1,8 The purpose of our study was to perform 3 approaches (anterior, anterolateral, and posterior) used for surgical release of the PIN and evaluate the effectiveness of each in exposure and decompression of the PIN within the radial tunnel. METHODS Cadaveric dissection A total of 30 fresh-frozen cadaveric arms (4 female, 26 male; average age, 64 y) with no previous trauma, surgery, or obvious abnormality was used for dissection. One of 3 approaches (anterior, anterolateral, and posterior) was randomly performed on the 30 specimens for a total of 10 times per approach. The approaches were as described by Mackinnon and J Hand Surg Am.
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ANATOMICAL STUDY OF RADIAL TUNNEL APPROACHES
These included fibrous bands of the radial head, tendinous insertion of the ECRB, leash of Henry, superficial sensory branch of the radial nerve, the arcade of Frohse, and the distal border of the supinator. The PIN was then released by cutting the portion of the supinator muscle that was directly visualized within the anterior window. The radial and ulnar edges of the cut supinator were reapproximated and the cut length was measured using the 15-cm ruler. Next, a posterior window was developed using the interval between the ECRB and the extensor digitorum communis. The uncut supinator, from the end point of the previous cut to the distal exit point of the PIN, was then measured. Complete exposure of the muscle was confirmed by visualizing the entry and exit points of the PIN into the supinator. Finally, the circumferential diameter of the muscle bellies of the brachioradialis, extensor carpi radialis longus (ECRL), and ECRB was measured as a way to objectively quantify the muscularity, or bulkiness, of the specimen. This was done by passing a vessel loop around these muscles at the level of the arcade of Frohse and measuring directly off of the vessel loop with the 15-cm ruler. The anterolateral approach was performed by creating a window between the ECRL and the brachioradialis with the forearm in neutral. All of the same measurements and points of compression were noted as described previously, and a posterior second window was made to visualize and measure any unreleased portion of the PIN. The posterior approach was performed by creating a window between the ECRB and the extensor digitorum communis with the forearm pronated. All of the same measurements and points of compression were noted as described previously. In this instance, however, an anterolateral second window was made through the ECRL and the brachioradialis to visualize and measure any unreleased portion of the PIN.
hypothesis that the entire supinator was visualized and cut through a single window was tested with signed rank tests for each approach. Statistical analyses set a level of significance of a ¼ 0.05. RESULTS The 30 specimens consisted of 4 female and 26 male cadaveric limbs. The average age was 64 years (range, 29e86 y). There was no difference in the muscularity of the limbs between the 3 groups. The superficial branch of the radial nerve was visualized in all anterior and anterolateral approaches, whereas it was visualized in only 4 posterior approaches. This difference was statistically significant (P ¼ .023). Likewise, whereas the fibrous bands of the radial head, the leash of Henry, the tendinous origin of the ECRB, and the arcade of Frohse were visualized in all anterior and anterolateral approaches, these were not consistently seen in the posterior approach (Table 1). Conversely, the distal border of the supinator was clearly visualized in all 10 posterior approaches, whereas this was the case in only 3 anterolateral approaches and in none of the anterior approaches. This difference was statistically significant (P < .001). The average distances between anatomical landmarks are present in Table 2. Using these 3 measurements, the average length of the radial tunnel was 79 mm (range, 53e103 mm; SD ¼ 14). Out of the 30 specimens, the supinator was completely released in 8 (27%) specimens via the single-window approach (7 from the posterior approach and 1 from the anterolateral approach). The average total supinator length was 50 mm (range, 28e76 mm; SD ¼ 12) and total supinator length did not differ between exposures (P ¼ .38). The relative uncut supinator distance, calculated as uncut length as a percentage of total supinator length, varied significantly across the 3 approaches, with the anterior approach having a significantly larger relative uncut distance than the posterior approach (P ¼ .008) (Table 2).
Statistical analysis Descriptive statistics for the ability to visualize branches and compression points are presented as the number and percentage of samples in which each feature is present in each approach. Distance measurements are presented as means and SD for each approach. Associations between the approach and the ability to visualize branches and compression points were assessed with Fisher exact tests. Differences in distance measurements between approaches were assessed with Kruskal-Wallis tests. Post hoc tests were conducted pairwise and the multiple test error incidence was controlled with the Bonferroni method. The null J Hand Surg Am.
3
DISCUSSION Our study demonstrated that the anterior and anterolateral approaches were best for visualizing the fibrous bands of the radial head, the leash of Henry, the origin of the ECRB, and the arcade of Frohse. The posterior approach was best for visualizing the distal border of the supinator. Furthermore, our results indicate that no single approach was consistently adequate for visualizing and releasing all compression points of the radial tunnel. The data show that, on average, nearly r
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4
ANATOMICAL STUDY OF RADIAL TUNNEL APPROACHES
TABLE 1.
Radial Tunnel Features Visualized in Each Approach Approach Anterolateral Count
Anterior %
Posterior
Count
%
Count
%
SBRN
P Value .023
No
0
0
0
0
4
40
Yes
10
100
10
100
6
60 < .001
Radial head No
0
0
0
0
10
100
Yes
10
100
10
100
0
0
No
0
0
0
0
5
50
Yes
10
100
10
100
5
50
Leash of Henry
.005
Origin of ECRB
.005
No
0
0
0
0
5
50
Yes
10
100
10
100
5
50
No
0
0
0
0
4
40
Yes
10
100
10
100
6
60
Arcade of Frohse
.023
< .001
Distal supinator No
7
70
10
100
0
0
Yes
3
30
0
0
100
100
SBRN, superficial branch of the radial nerve.
TABLE 2.
Summary of Various Measured Distances Within the Radial Tunnel as Seen in Each Approach
RCJ to Frohse (mm)
Approach
n
Mean
SD
Lower 95% CI for Mean
Upper 95% CI for Mean
P Value
Anterolateral
10
26
6
21.8
30.8
.791
Anterior
10
27
4
24.0
30.0
0
.
.
.
.
Anterolateral
10
21
18
8.9
34.6
Anterior
10
40
19
26.3
54.8
Posterior* Relative uncut supinator (%)
Relative cut supinator (%)
Posterior
10
8
21
e6.2
23.8
Anterolateral
10
78
18
65.4
91.1
Anterior
10
60
20
45.2
73.7
Posterior
10
91
21
76.2
106.2
.003
.003
CI, confidence interval. *RCJ not visualized in posterior approach.
1.2 cm of the PIN was not released through a single approach. This number can go up to as high as an average of 2 cm if only the anterior approach was used. Just as important, our results revealed that none of the 3 approaches guaranteed complete visualization of all 5 points of compression within the radial tunnel. J Hand Surg Am.
Specifically, the distal border of the supinator, which is a critical compression point of the PIN, was consistently not visualized through the anterior and anterolateral approaches. Conversely, the posterior approach was absolutely insufficient for visualizing the fibrous bands of the radial head. The posterior r
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ANATOMICAL STUDY OF RADIAL TUNNEL APPROACHES
approach was likewise inconsistent in exposing the leash of Henry, the tendinous border of the ECRB tendon, and the arcade of Frohse. Based on these data, a single approach for PIN decompression is inadequate for visualizing all compression within the radial tunnel. This finding has noteworthy implications for clinical practice because incomplete decompression and partial release of the supinator risks residual postoperative symptoms. This may account for the inconsistent clinical outcomes reported in prior studies.10,11,14 Our results suggest that a double-window approach for radial tunnel decompression allows for consistent exposure and careful release of all compression points within the radial tunnel. For example, through a single incision, the surgeon can use the anterior or anterolateral window for complete exposure of proximal compression sites. The senior author’s (S.K.L.) preferred method is a single 7-cm incision centered over the mobile wad, beginning 5 cm distal to the lateral epicondyle to expose the intermuscular plane between the brachioradialis and the ECRL. Next, working through the same skin incision, a posterior window can be developed to safely release the distal border of the supinator. In our dissections, the use of a second window did not require extension of the skin incision nor did it present any anatomical barriers that precluded completion of the dissection. The anterolateralposterior double-window technique is our preferred method of radial tunnel decompression clinically. A limitation of this study is that it is not known if a 2-window technique would have superior clinical outcomes to the single-window technique. For this, a randomized controlled trial is required. However, we do not believe there is equipoise of surgical release to make this an ethical study. Alternatively, a retrospective review of outcomes in patients treated with the double-window technique could provide clinical insight on the efficacy of the method compared with the classic single-window approach. Another limita-
J Hand Surg Am.
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tion of this study is that measurements were made jointly by the authors during dissection. Therefore, we are unable to perform a reproducibility assessment. ACKNOWLEDGMENT The authors thank Jayme C. Burket, PhD, for assistance with statistical analysis. This study was partially funded by the Hospital for Special Surgery Surgeonin-Chief Fund. REFERENCES 1. MacKinnon SE, Novak CB. Compression neuropathies. In: Wolfe SW, Hotchkiss RN, Pederson WC, Kozin SH, eds. Green’s Operative Hand Surgery. 6th ed. Philadelphia: Churchill Livingstone; 2011:977e1092. 2. Sarhadi NS, Korday SN, Bainbridge LC. Radial tunnel syndrome: diagnosis and management. J Hand Surg Br. 1998;23(5):617e619. 3. Younge DH, Moise P. The radial tunnel syndrome. Int Orthop. 1994;18(5):268e270. 4. Dang AC, Rodner CM. Unusual compression neuropathies of the forearm, part I: radial nerve. J Hand Surg Am. 2009;34(10):1906e1914. 5. Lister GD, Belsole RB, Kleinert HE. The radial tunnel syndrome. J Hand Surg Am. 1979;4(1):52e59. 6. Portilla Molina AE, Bour C, Oberlin C, Nzeusseu A, Vanwijck R. The posterior interosseous nerve and the radial tunnel syndrome: an anatomical study. Int Orthop. 1998;22(2):102e106. 7. Prasartritha T, Liupolvanish P, Rojanakit A. A study of the posterior interosseous nerve (PIN) and the radial tunnel in 30 Thai cadavers. J Hand Surg Am. 1993;18(1):107e112. 8. Arle JE, Zager EL. Surgical treatment of common entrapment neuropathies in the upper limbs. Muscle Nerve. 2000;23(8):1160e1174. 9. Markiewitz AD, Merryman J. Radial nerve compression in the upper extremity. J Hand Surg Am. 2005;5(2):87e89. 10. Jebson PJ, Engber WD. Radial tunnel syndrome: long-term results of surgical decompression. J Hand Surg Am. 1997;22(5):889e896. 11. Lawrence T, Mobbs P, Fortems Y, Stanley JK. Radial tunnel syndrome. A retrospective review of 30 decompressions of the radial nerve. J Hand Surg Br. 1995;20(4):454e459. 12. Ritts GD, Wood MB, Linscheid RL. Radial tunnel syndrome. A tenyear surgical experience. Clin Orthop Relat Res. 1987;219:201e205. 13. Roles NC, Maudsley RH. Radial tunnel syndrome: resistant tennis elbow as a nerve entrapment. J Bone Joint Surg Br. 1972;54(3): 499e508. 14. Sotereanos DG, Varitimidis SE, Giannakopoulos PN, Westkaemper JG. Results of surgical treatment for radial tunnel syndrome. J Hand Surg Am. 1999;24(3):566e570.
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