Endoscopic carpal tunnel release: A cadaveric study Five surgeons performed endoscopic (Dyonics) carpal tunnel releases on 24 fresh cadaver wrists. In 50% of the specimens, transection of the transverse carpal ligament was incomplete. The average amount of incomplete release was 31 % (range, 0% to 53%). Three types of incomplete release were noted: (I) release of Guyon's canal release-one, (2) Incomplete distal ligament release-five, and (3) incomplete central or superficial release-six. Other technical errors were noted in nine of 24 specimens. There were no nerve lacerations. Endoscopic carpal tunnel release is either a technically demanding procedure, commonly results in incompletely released ligaments, or both. Proper training, followed by practice on several cadaver specimens before Its clinical use, is recommended. (J HAND SURG 1992;17A:I003-8.)
Donald H. Lee, MD, Victoria R. Masear, MD, Richard D. Meyer, MD, David M. Stevens, MD, and Sherri Colgin, MD, Birmingham, Ala.
Carpal tunnel syndrome is one of the most commonly encountered peripheral compression neuropathies. An estimated I % of the general population has had carpal tunnel syndrome, and up to 10% of all adults may have occasional carpal tunnel symptoms.' Carpal tunnel syndrome has gained wide attention as a common occupational cumulative trauma disorder. Open surgical release of the transverse carpal ligament for the treatment of carpal tunnel syndrome is widely used. 2·5 More recently, endoscopic release of the transverse carpal ligament (TCL) has been introduced as an alternative to an open ligament release.r" The purpose of this cadaver study was to (1) evaluate the adequacy of endoscopic carpal tunnel release (ECTR) on fresh cadaver specimens, (2) determine the common errors (if any) associated with ECTR, and (3) determine whether several different surgeons could perform complete ECTRs.
From the Divisions of Orthopedic Surgery and Plastic Surgery, University of Alabama at Birmingham, and BMC Montclair Hospital, Bunting Plastic Surgery Clinic, Birmingham, Ala. Received for publication Oct. 29, 1991; accepted in revised form Jan. 15, 1992. 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. Reprint requests: Donald H. Lee, MD, Division of Orthopedic Surgery, University of Alabama at Birmingham, Birmingham, AL 35233.
3/1/37705
Material and methods Twenty-four undissected fresh frozen cadaver arms, transected at the midhumerus level, were thawed before endoscopic carpal tunnel release. A Dyonics (ECTRA) endoscopic carpal tunnel release system was used. Five hand surgeons (three staff members and two hand fellows) each performed three to six endoscopic ligament releases. The three staff surgeons had the opportunity to observe the developer of the technique perform several clinical endoscopic ligament releases. The hand fellows were subsequently trained by the staff surgeons. The operative technique, as previously described,":" involves the use of two transverse incisions, one proximal and one distal. The proximal incision (approximately 1 em in length) is located 0.25 to 0.5 em proximal and 0.25 to 0.5 em to the radial side of the pisiform (Fig. 1). Through this incision, the ulnar neurovascular bundle is identified, isolated, and retracted ulnarly. With the wrist and fingers fully extended, an obturator and a slotted endoscopic cannula are introduced into the incision, under the TeL. The base of the hook of the hamate is palpated with the tip of the obturator. The obturator is then advanced both palmarly and distally toward a second skin incision. This incision is located along a line formed by the bisection of two lines drawn along a fully abducted thumb and the third web space. A small incision is made 0.25 to 0.5 em proximal to the junction of these lines (Fig. 2). The hand and forearm are placed on a special holder with the wrist held in an extended position. The obturator is removed, leaving the slotted cannula in poTHE JOURNAL OF HAND SURGERY
1003
The Journal of 1004
HAND SURGERY
Lee et al,
Pisiform
t (3\ 0.'em \.j/
-t f
0 .5 em
'-"1.0 om
Incision
Fig. 3. A slotted cannula is positioned directly beneath the transverse carpal ligament.
Fig. 1. A 1 em transverse proximal sk in incision is located 0 .25 to 0 .5 cm proximal and radial to the pisiform.
Fig. 4. Release of the transverse carpal ligament is performed under direct endoscopic visualization with specially designed knives .
Fig. 2. A I ern transverse distal palmar skin incision is located along a line formed by the bisection of two lines drawn along a fully abducted thumb and the third web space. The incis ion is located 0.25 to 0.5 em proximal to the junction of these lines.
sition directly beneath the TCL (Fig. 3) . The endoscope is inserted into the cannula proximally. Care is taken to ensure that no tissue is interposed between the slot within the cannula and the TCL. The slot may be rotated 5 to 10 degrees to the ulnar side to protect the median
nerve and flexor tendons . With direct visualization of the undersurface of the TCl, the ligament is released (Fig. 4). Three specially designed knives (probe, triangular, and hook type) are used to perform the release. The distal edge of the ligament is cut first, followed by the midportion , and finally the proximal portion. The area is carefully reexamined to ensure complete release of the ligament. The obturator is reinserted, and the cannula is removed. Several topographic measurements were made (Fig. 5). These included (I) the distance between the distal palmar skin crease and the distal palmar incision (DPl), (2) the distance between the proximal palmar skin crease and the DPI, and (3) the distance between the most radial aspect of the first web space and the midportion of the DPI.
Vol. 17A, No.6 November 1992
Endoscopic carpal funnel release
SKIN MEASUREMENTS
1005
OPEN DISSECTION
V
U
U
I
..- "
~i~~----' @ Fig. 6. Open dissection measurements. 4, Distance between distal palmar incision (DPO and superficial palmar arch (SPA); 5, distance between DPI and distal edge of transverse carpal ligament (TCL); 6, distance between distal edge of TCL and SPA.
Fig. 5. Topographic measurements. 1, Distance between distal palmar skin crease and distal palmar incision (DPI); 2, distance between proximal palmar skin crease and DPI; 3, distance between most radial aspect of first web space and midportion of DPr.
Several open dissection measurements were made after the TCL was endoscopically released (Fig. 6). These included (4) the distance between the DPI and the superficial palmar arch (SPA), (5) the distance between the DPI and the distal edge of the TCL, and (6) the distance between the distal edge of the TCL and the SPA. Other measurements included the length and estimated width of the TCL. The estimated width of the reapproximated ligament was made between its attachment from the scaphoid tubercle to the hamate hook. The specimens were evaluated for complete versus incomplete TCL releases. The cut and uncut portions of the TeL were measured. Several errors in surgical technique were noted; these included improper location of the ligamentous cut, improper trocar and cannula placement, and unwanted structural injuries. The number of errors produced by each surgeon was determined.
Results The results of the topographic measurements showed that the distance between the distal palmar skin crease and the DPI (distance I) averaged 2.8 em, the distance between the proximal palmar skin crease and the DPI (distance 2) averaged 2.1 cm., and the distance between the most radial aspect of the first web space and the
midportion of the distal palmar skin incision (distance 3) averaged 5.4 em. (Table I). The results of the open dissection showed that the distance between the DPI and the SPA (distance 4) averaged 0.4 cm., the distance between the DPI and the distal edge of the TeL (distance 5) averaged 0.8 em, and the distance between the distal edge of the TCL and the SPA (distance 6) averaged 1.2 ern (Table II). A negative value meant that the DPI was located distal to the level of the SPA or that the distal edge of the TCL was located distal to the DPr. The length of the transverse carpal ligament averaged 2.9 em (range, 1.9 to 5.5 cm). The estimated width of the TCL averaged 1.3 ern (range, 1.0 to 1.9 ern). The level of the DPI was noted to be at or distal to the superficial palmar arch (SPA) in 10 specimens (range, 0.0 to 1.1 em). The level of the distal edge of the transverse carpal ligament (TCL) was noted to be at or distal to the distal palmar incision in three specimens (range, 0.0 to 0.4 ern), Complete release of the ligament was noted in 50% of the specimens. Incomplete release was noted in the other 50%. In the specimens that had incomplete ligament releases, the average amount of ligament released was 61 %. The portion of ligament not released in these twelve specimens averaged 39% (range, 9% to 100%) (Table III). Three types of incomplete release were noted: (1) release of Guyon's tunnel-one specimen, (2) incomplete distal ligament release-five specimens, and (3) incomplete central (superficial) ligament release-six specimens.
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HAND
Table I. Topographic measurements Specimen I
R
2 3 4 5 6 7 8 9 10
L
R L R
L R L
R L
II
R
12 13 14 15 16 17 18 19 20 21 22 23 24
L L
Average
R
L R
L R
L L L
L L R
Table II. Open dissection measurements Distance 3:j: (cm)
Specimen
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24. Average
2.5 3.2 3.1 2.7 3.2 3.1 2.6 3.5 1.5 3.0 2.4 2.6 2.8 3.6 3.5 1.5 2.5 3.0 2.5 3.2 2.1 2.4 3.6 3.1
2.0 2.6 2.6 2.1 3.0 2.1 1.8 2.8 1.1 2.4 2.0 2.1 1.5 2.1 2.7 1.5 2.0 2.0 1.3 2.2 2.2 2.5 2.5
5.5 5.6 5.7 5.9 6.5 6.1 5.9 6.0 5.5 6.0 4.2 4.4 5.7 5.7 5.2 4.0 5.5 3.7 5.2 5.7 5.5 6.3 5.5 4.3
2.8
2.1
5.4
l.l
SURGERY
·Distance between the distal palmar skin crease and the distal palmar incision. tDistance between the proximal palmar skin crease and the distal palmar incision. ~Distance between the most radial aspect of the first web space and the mid. portion of the distal palmar incision.
In one specimen the cannula was placed into Guyon's canal, with its subsequent release. The TeL was not released at all. Five specimens had incomplete release of the distal portion of the TCL. The average portion of the ligament not released was 0.82 em (range, 0.2 to 1.5 em) or 27% of the ligament (range, 9% to 53%). Six specimens had incomplete release of the central and most superficial (palmar) portion of the ligament. The average portion of the ligament not released was I ern (range, 0.5 em to 2.2 ern) or 38% of the ligament (range, 23% to 51%). Twelve errors in technique were noted in 9 of 24 specimens. Six types of error were noted: (1) improper placement of trocar (into Guyon's canal)-one specimen, (2) placement of the ligament cut too far ulnarward over the hook of the hamate-six specimens, (3) ulnar artery laceration proximally-one specimen, (4) ulnar neurovascular bundle looped around the cannula proximally-two specimens, (5) superficial palmar arch looped around the cannula-one specimen, and
Distance 4* (cm)
0.5 1.3 0.5 0.7
Distance (em)
st
Distance (cm)
1.0 0.0 0.7 -0.5§ 1.0 1.2 1.5 0.0 0.3 0.9 0.7 0.0 -0.5§ -0.3§ -0.8§ -l.l§ 0.0 0.0 0.4
0.5 0.3 l.l 1.5 0.1 -0.2 11 1.6 0.0 1.7 1.0 0.7 -00411 l.l 0.8 -0.211 2.0 1.5 1.5 1.5 0.3 1.7 0.8 0.3 0.0
1.0 1.6 1.6 2.1 1.2 0.8 1.6 0.7 1.2 2.0 1.9 l.l 1.1 1.1 0.7 2.7 1.5 1.0 1.2 1.1 0.0 0.8 0.3 004
0.4
0.8
1.2
1.1
6:t
.Distance between the distal palmar incision and the superficial palmar arch. tDistance between the distal palmar incision and the distal edge of the transverse carpal ligament. ~Distance between the distal edge of the transverse carpal ligament and the superficial palmar arch. §Distal palmar incision located distal to level of superficial palmar arch. [Distal edge of transverse carpal ligament located distal 10 level of distal palmar incision.
(6) flexor tendon (small finger) looped around the cannula-one specimen. Placement of the ligamentous cut too far ulnarly usually resulted in an incomplete release of the TCL centrally. A portion of the periosteum overlying the hook of the hamate and the attachment of the TCL to the hook of the hamate was usually released. The superficial or most palmar portion of the ligament was not released. In specimens with incomplete ligament releases distally, usually no portion of the ligament was released in that area. There were no digital or median nerve injuries. The technical errors were relatively equally distributed between the five surgeons (Table IV). Discussion
Three types of endoscopic carpal ligament release system have been described to date."" These include
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Endoscopic carpal tunnel release
Table III. Open dissection measurements Length TCL Specimen
(em)
I 2
2.9 2.6 2.7 3.2
3 4
5 6 7
8 9 10 II 12
13 14 15 16 17 18 19 20
Length TeL CUI (em)
1.9
2.9 2.6 2.7 3.2
1.6
1.0 1.0
3.5 3.0
1.7 1.7
2.6 3.2 2.2 2.7
1.2 1.0 1.2
3.5 3.1 4.0 3.7 5.5 2.3 3.5
1.3
1.1 1.3
1.3
1.4
2.2
1.5 1.5 1.7 l.l 1.3
1.9
1.2
1.2 1.2
24
2.7 2.2 2.0 2.3
1.2 1.1
Average
2.9
1.3
21 22 23
1 2 3 4 5 6
Width TCL (em) estimated
2.1
Area uncut
100 100 100 100 0 73 100 47 59 100 49 65 88 100 60 91 100 100 100 100 70
0.0 2.2 2.6 1.5 1.3 2.7
1.7 2.0 3.5 3.7 3.3 2.1
3.5 2.1 2.2
1.9 1.9 1.7 1.1
Entire TCL Distal Distal Central Central Distal Distal
2
3,4 3 3,5
Central Distal
3 Central Central Central
77
55 100 81
2.3
Errors
5,6 3 3
= Release of Guyon's tunnel.
= Cannula under superficial
palmar arch.
= Cut placed too far ulnarly over hock of hamate. = Ulnar artery laceration. = Cannula under ulnar NV bundle proximally. = Flexor tendon (small finger) looped over cannula.
the Agee Inside Job (3-M) carpal tunnel release system, the Chow (Dyonics) ECTRA endoscopic carpal tunnel release system, and the Okutsu universal subcutaneous endoscope (USE). The Agee Inside Job carpal tunnel release system uses a pistol grip handpiece that has a disposable blade assembly, The blade assembly features a retractable blade that is viewed through an endoscopic window at the tip of the disposable blade. A single incision, at the wrist level, is used. The blade assembly is introduced under the transverse carpal ligament. With the blade assembly in the proper position, the blade is elevated and the ligament is released under direct visualization. The Chow ECTRA and Okutsu USE systems use an obturator and a cannula. The ECTRA system uses a slotted cannula. The carpal ligament is endoscopically visualized through the slot. The ligament is released with specially designed knives placed within the slotted
Table IV. Number of errors per surgeon Surgeon No. I 2
3 4 5
No. releases performed
Errors
6
3
3
6 5
3
3 3
4 3
24
2 3
1
1 2
12
12
cannula, This system uses a two-incision techniqueone incision proximally at the wrist and one distally in the palm. The Okutsu USE system uses a clear nonslotted plastic tube placed through a single proximal wrist incision. The endoscope is inserted through the plastic tube to visualize the carpal ligament. A hook knife is placed
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Lee et al.
parallel and outside the tube. Under direct visualization the ligament is released in a retrograde fashion. The theoretical advantages of all of these systems is that they decrease the amount of postoperative pain, scarring, and loss of grip and pinch strength, thus permitting an earlier return to daily activities and work. Overall, cosmetic results and patient satisfaction should be improved. The technical aspects of any new procedure, including its potential complications, must be learned before it is applied clinically. An endoscopic procedure presents several potential difficulties. These include problems with surgical instruments and surgical technique. In the former, failure ofthe instrumentation (video camera, light source, etc.), resulting in poor visualization, may occur. In the latter, failure of the surgical procedure may include incomplete ligament releases and inadvertent arterial, nerve, and tendon injuries. In contrast to open procedures, these complications may not be recognized at the time of surgery. The fresh cadavers used in this study are similar to those used in the endoscopic surgical skills workshops. The minimum of three to six endoscopic releases performed by each surgeon in this study is generally more than the number of releases performed in the workshops. The results of open dissection after the endoscopic releases showed an incomplete ligament release in 50% of the specimens. Incomplete releases were generally due to errors in technique, either too superficial placement of the cannula or placement too ulnarly of the cutting slot in the cannula. Incomplete proximal or distal ligament releases were attributed, in part, to penetration of the ligament with the cannula or inability to distinguish the proximal and distal ends of the ligament. The number of incomplete releases and technical errors appeared to be evenly distributed among the several surgeons. The relatively small number of specimens used did not allow us to determine whether a definite learning curve was present. It did appear, though, that with more experience the number of error-free ligament
releases increased. However, no definite trend was noticed. Errors occurred in earlier as well as later releases for some of the surgeons. Surgical adaptations are currently being tried. These include larger proximal and distal incisions with direct visualization of the proximal and distal edges of the TCL, the SPA, and the ulnar neurovascular bundle and placement of the cutting slot slightly radial to the hook of the hamate. Endoscopic carpal tunnel release may be a useful alternative to open release. However, the technique is either technically demanding, commonly results in incompletely sectioned ligaments, or both. Proper training in the use of ECTR, followed by practice on several cadaver specimens before its clinical use, is recommended. A high learning curve is suspected. The authors thank Dr. James Chow for allowing them to observe his surgical approach to the treatment of carpal tunnel syndrome.
REFERENCES I. Kasdan ML. Occupational hand and upper extremity injuries and diseases. Philadelphia: Hanley & Belfus, 1991:341-402. 2. Phalen GS. The carpal tunnel syndrome: seventeen years' experience in diagnosis and treatment of 654 hands. J Bone Joint Surg 1966;48A:211-28. 3. Phalen GS. The carpal tunnel syndrome: clinical evaluation of 598 hands. Clin Orthop 1972;83:29-40. 4. Kendall D. Aetiology, diagnosis and treatment of paraesthesias in the hands. Br Med J 1960;2:1633-40. 5. Lichtman OM, Floro RL, Mack GR. Carpal tunnel release under local anesthesia: evaluation of the outpatient procedure. J HAND SURG 1979;4:544-6. 6. Chow JCY. Endoscopic release of the carpal ligament: a new technique for carpal tunnel syndrome. Arthroscopy 1989;5:19-24. 7. Chow JCY. Endoscopic release of the carpal ligament for carpal tunnel syndrome: 22-month clinical trial. Arthroscopy 1990;6:288-96. 8. Okutusu I, NinorniyaS, Takatori Y, Ugawa Y. Endoscopic management of carpal tunnel syndrome. Arthroscopy 1989;5:11-8.
Donald H. Lee, MD, Victoria R. Masear, MD, Richard D. Meyer, MD, David M. Stevens, MD, and Sherri Colgin, MD, Birmingham, Ala.
Carpal tunnel syndrome is one of the most commonly encountered peripheral compression neuropathies. An estimated I % of the general population has had carpal tunnel syndrome, and up to 10% of all adults may have occasional carpal tunnel symptoms.' Carpal tunnel syndrome has gained wide attention as a common occupational cumulative trauma disorder. Open surgical release of the transverse carpal ligament for the treatment of carpal tunnel syndrome is widely used. 2·5 More recently, endoscopic release of the transverse carpal ligament (TCL) has been introduced as an alternative to an open ligament release.r" The purpose of this cadaver study was to (1) evaluate the adequacy of endoscopic carpal tunnel release (ECTR) on fresh cadaver specimens, (2) determine the common errors (if any) associated with ECTR, and (3) determine whether several different surgeons could perform complete ECTRs.
From the Divisions of Orthopedic Surgery and Plastic Surgery, University of Alabama at Birmingham, and BMC Montclair Hospital, Bunting Plastic Surgery Clinic, Birmingham, Ala. Received for publication Oct. 29, 1991; accepted in revised form Jan. 15, 1992. 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. Reprint requests: Donald H. Lee, MD, Division of Orthopedic Surgery, University of Alabama at Birmingham, Birmingham, AL 35233.
3/1/37705
Material and methods Twenty-four undissected fresh frozen cadaver arms, transected at the midhumerus level, were thawed before endoscopic carpal tunnel release. A Dyonics (ECTRA) endoscopic carpal tunnel release system was used. Five hand surgeons (three staff members and two hand fellows) each performed three to six endoscopic ligament releases. The three staff surgeons had the opportunity to observe the developer of the technique perform several clinical endoscopic ligament releases. The hand fellows were subsequently trained by the staff surgeons. The operative technique, as previously described,":" involves the use of two transverse incisions, one proximal and one distal. The proximal incision (approximately 1 em in length) is located 0.25 to 0.5 em proximal and 0.25 to 0.5 em to the radial side of the pisiform (Fig. 1). Through this incision, the ulnar neurovascular bundle is identified, isolated, and retracted ulnarly. With the wrist and fingers fully extended, an obturator and a slotted endoscopic cannula are introduced into the incision, under the TeL. The base of the hook of the hamate is palpated with the tip of the obturator. The obturator is then advanced both palmarly and distally toward a second skin incision. This incision is located along a line formed by the bisection of two lines drawn along a fully abducted thumb and the third web space. A small incision is made 0.25 to 0.5 em proximal to the junction of these lines (Fig. 2). The hand and forearm are placed on a special holder with the wrist held in an extended position. The obturator is removed, leaving the slotted cannula in poTHE JOURNAL OF HAND SURGERY
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The Journal of 1004
HAND SURGERY
Lee et al,
Pisiform
t (3\ 0.'em \.j/
-t f
0 .5 em
'-"1.0 om
Incision
Fig. 3. A slotted cannula is positioned directly beneath the transverse carpal ligament.
Fig. 1. A 1 em transverse proximal sk in incision is located 0 .25 to 0 .5 cm proximal and radial to the pisiform.
Fig. 4. Release of the transverse carpal ligament is performed under direct endoscopic visualization with specially designed knives .
Fig. 2. A I ern transverse distal palmar skin incision is located along a line formed by the bisection of two lines drawn along a fully abducted thumb and the third web space. The incis ion is located 0.25 to 0.5 em proximal to the junction of these lines.
sition directly beneath the TCL (Fig. 3) . The endoscope is inserted into the cannula proximally. Care is taken to ensure that no tissue is interposed between the slot within the cannula and the TCL. The slot may be rotated 5 to 10 degrees to the ulnar side to protect the median
nerve and flexor tendons . With direct visualization of the undersurface of the TCl, the ligament is released (Fig. 4). Three specially designed knives (probe, triangular, and hook type) are used to perform the release. The distal edge of the ligament is cut first, followed by the midportion , and finally the proximal portion. The area is carefully reexamined to ensure complete release of the ligament. The obturator is reinserted, and the cannula is removed. Several topographic measurements were made (Fig. 5). These included (I) the distance between the distal palmar skin crease and the distal palmar incision (DPl), (2) the distance between the proximal palmar skin crease and the DPI, and (3) the distance between the most radial aspect of the first web space and the midportion of the DPI.
Vol. 17A, No.6 November 1992
Endoscopic carpal funnel release
SKIN MEASUREMENTS
1005
OPEN DISSECTION
V
U
U
I
..- "
~i~~----' @ Fig. 6. Open dissection measurements. 4, Distance between distal palmar incision (DPO and superficial palmar arch (SPA); 5, distance between DPI and distal edge of transverse carpal ligament (TCL); 6, distance between distal edge of TCL and SPA.
Fig. 5. Topographic measurements. 1, Distance between distal palmar skin crease and distal palmar incision (DPI); 2, distance between proximal palmar skin crease and DPI; 3, distance between most radial aspect of first web space and midportion of DPr.
Several open dissection measurements were made after the TCL was endoscopically released (Fig. 6). These included (4) the distance between the DPI and the superficial palmar arch (SPA), (5) the distance between the DPI and the distal edge of the TCL, and (6) the distance between the distal edge of the TCL and the SPA. Other measurements included the length and estimated width of the TCL. The estimated width of the reapproximated ligament was made between its attachment from the scaphoid tubercle to the hamate hook. The specimens were evaluated for complete versus incomplete TCL releases. The cut and uncut portions of the TeL were measured. Several errors in surgical technique were noted; these included improper location of the ligamentous cut, improper trocar and cannula placement, and unwanted structural injuries. The number of errors produced by each surgeon was determined.
Results The results of the topographic measurements showed that the distance between the distal palmar skin crease and the DPI (distance I) averaged 2.8 em, the distance between the proximal palmar skin crease and the DPI (distance 2) averaged 2.1 cm., and the distance between the most radial aspect of the first web space and the
midportion of the distal palmar skin incision (distance 3) averaged 5.4 em. (Table I). The results of the open dissection showed that the distance between the DPI and the SPA (distance 4) averaged 0.4 cm., the distance between the DPI and the distal edge of the TeL (distance 5) averaged 0.8 em, and the distance between the distal edge of the TCL and the SPA (distance 6) averaged 1.2 ern (Table II). A negative value meant that the DPI was located distal to the level of the SPA or that the distal edge of the TCL was located distal to the DPr. The length of the transverse carpal ligament averaged 2.9 em (range, 1.9 to 5.5 cm). The estimated width of the TCL averaged 1.3 ern (range, 1.0 to 1.9 ern). The level of the DPI was noted to be at or distal to the superficial palmar arch (SPA) in 10 specimens (range, 0.0 to 1.1 em). The level of the distal edge of the transverse carpal ligament (TCL) was noted to be at or distal to the distal palmar incision in three specimens (range, 0.0 to 0.4 ern), Complete release of the ligament was noted in 50% of the specimens. Incomplete release was noted in the other 50%. In the specimens that had incomplete ligament releases, the average amount of ligament released was 61 %. The portion of ligament not released in these twelve specimens averaged 39% (range, 9% to 100%) (Table III). Three types of incomplete release were noted: (1) release of Guyon's tunnel-one specimen, (2) incomplete distal ligament release-five specimens, and (3) incomplete central (superficial) ligament release-six specimens.
The Journal of Lee et al,
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HAND
Table I. Topographic measurements Specimen I
R
2 3 4 5 6 7 8 9 10
L
R L R
L R L
R L
II
R
12 13 14 15 16 17 18 19 20 21 22 23 24
L L
Average
R
L R
L R
L L L
L L R
Table II. Open dissection measurements Distance 3:j: (cm)
Specimen
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24. Average
2.5 3.2 3.1 2.7 3.2 3.1 2.6 3.5 1.5 3.0 2.4 2.6 2.8 3.6 3.5 1.5 2.5 3.0 2.5 3.2 2.1 2.4 3.6 3.1
2.0 2.6 2.6 2.1 3.0 2.1 1.8 2.8 1.1 2.4 2.0 2.1 1.5 2.1 2.7 1.5 2.0 2.0 1.3 2.2 2.2 2.5 2.5
5.5 5.6 5.7 5.9 6.5 6.1 5.9 6.0 5.5 6.0 4.2 4.4 5.7 5.7 5.2 4.0 5.5 3.7 5.2 5.7 5.5 6.3 5.5 4.3
2.8
2.1
5.4
l.l
SURGERY
·Distance between the distal palmar skin crease and the distal palmar incision. tDistance between the proximal palmar skin crease and the distal palmar incision. ~Distance between the most radial aspect of the first web space and the mid. portion of the distal palmar incision.
In one specimen the cannula was placed into Guyon's canal, with its subsequent release. The TeL was not released at all. Five specimens had incomplete release of the distal portion of the TCL. The average portion of the ligament not released was 0.82 em (range, 0.2 to 1.5 em) or 27% of the ligament (range, 9% to 53%). Six specimens had incomplete release of the central and most superficial (palmar) portion of the ligament. The average portion of the ligament not released was I ern (range, 0.5 em to 2.2 ern) or 38% of the ligament (range, 23% to 51%). Twelve errors in technique were noted in 9 of 24 specimens. Six types of error were noted: (1) improper placement of trocar (into Guyon's canal)-one specimen, (2) placement of the ligament cut too far ulnarward over the hook of the hamate-six specimens, (3) ulnar artery laceration proximally-one specimen, (4) ulnar neurovascular bundle looped around the cannula proximally-two specimens, (5) superficial palmar arch looped around the cannula-one specimen, and
Distance 4* (cm)
0.5 1.3 0.5 0.7
Distance (em)
st
Distance (cm)
1.0 0.0 0.7 -0.5§ 1.0 1.2 1.5 0.0 0.3 0.9 0.7 0.0 -0.5§ -0.3§ -0.8§ -l.l§ 0.0 0.0 0.4
0.5 0.3 l.l 1.5 0.1 -0.2 11 1.6 0.0 1.7 1.0 0.7 -00411 l.l 0.8 -0.211 2.0 1.5 1.5 1.5 0.3 1.7 0.8 0.3 0.0
1.0 1.6 1.6 2.1 1.2 0.8 1.6 0.7 1.2 2.0 1.9 l.l 1.1 1.1 0.7 2.7 1.5 1.0 1.2 1.1 0.0 0.8 0.3 004
0.4
0.8
1.2
1.1
6:t
.Distance between the distal palmar incision and the superficial palmar arch. tDistance between the distal palmar incision and the distal edge of the transverse carpal ligament. ~Distance between the distal edge of the transverse carpal ligament and the superficial palmar arch. §Distal palmar incision located distal to level of superficial palmar arch. [Distal edge of transverse carpal ligament located distal 10 level of distal palmar incision.
(6) flexor tendon (small finger) looped around the cannula-one specimen. Placement of the ligamentous cut too far ulnarly usually resulted in an incomplete release of the TCL centrally. A portion of the periosteum overlying the hook of the hamate and the attachment of the TCL to the hook of the hamate was usually released. The superficial or most palmar portion of the ligament was not released. In specimens with incomplete ligament releases distally, usually no portion of the ligament was released in that area. There were no digital or median nerve injuries. The technical errors were relatively equally distributed between the five surgeons (Table IV). Discussion
Three types of endoscopic carpal ligament release system have been described to date."" These include
Vol. 17A, No.6 November 1992
1007
Endoscopic carpal tunnel release
Table III. Open dissection measurements Length TCL Specimen
(em)
I 2
2.9 2.6 2.7 3.2
3 4
5 6 7
8 9 10 II 12
13 14 15 16 17 18 19 20
Length TeL CUI (em)
1.9
2.9 2.6 2.7 3.2
1.6
1.0 1.0
3.5 3.0
1.7 1.7
2.6 3.2 2.2 2.7
1.2 1.0 1.2
3.5 3.1 4.0 3.7 5.5 2.3 3.5
1.3
1.1 1.3
1.3
1.4
2.2
1.5 1.5 1.7 l.l 1.3
1.9
1.2
1.2 1.2
24
2.7 2.2 2.0 2.3
1.2 1.1
Average
2.9
1.3
21 22 23
1 2 3 4 5 6
Width TCL (em) estimated
2.1
Area uncut
100 100 100 100 0 73 100 47 59 100 49 65 88 100 60 91 100 100 100 100 70
0.0 2.2 2.6 1.5 1.3 2.7
1.7 2.0 3.5 3.7 3.3 2.1
3.5 2.1 2.2
1.9 1.9 1.7 1.1
Entire TCL Distal Distal Central Central Distal Distal
2
3,4 3 3,5
Central Distal
3 Central Central Central
77
55 100 81
2.3
Errors
5,6 3 3
= Release of Guyon's tunnel.
= Cannula under superficial
palmar arch.
= Cut placed too far ulnarly over hock of hamate. = Ulnar artery laceration. = Cannula under ulnar NV bundle proximally. = Flexor tendon (small finger) looped over cannula.
the Agee Inside Job (3-M) carpal tunnel release system, the Chow (Dyonics) ECTRA endoscopic carpal tunnel release system, and the Okutsu universal subcutaneous endoscope (USE). The Agee Inside Job carpal tunnel release system uses a pistol grip handpiece that has a disposable blade assembly, The blade assembly features a retractable blade that is viewed through an endoscopic window at the tip of the disposable blade. A single incision, at the wrist level, is used. The blade assembly is introduced under the transverse carpal ligament. With the blade assembly in the proper position, the blade is elevated and the ligament is released under direct visualization. The Chow ECTRA and Okutsu USE systems use an obturator and a cannula. The ECTRA system uses a slotted cannula. The carpal ligament is endoscopically visualized through the slot. The ligament is released with specially designed knives placed within the slotted
Table IV. Number of errors per surgeon Surgeon No. I 2
3 4 5
No. releases performed
Errors
6
3
3
6 5
3
3 3
4 3
24
2 3
1
1 2
12
12
cannula, This system uses a two-incision techniqueone incision proximally at the wrist and one distally in the palm. The Okutsu USE system uses a clear nonslotted plastic tube placed through a single proximal wrist incision. The endoscope is inserted through the plastic tube to visualize the carpal ligament. A hook knife is placed
1008
The Journal of HAND SURGERY
Lee et al.
parallel and outside the tube. Under direct visualization the ligament is released in a retrograde fashion. The theoretical advantages of all of these systems is that they decrease the amount of postoperative pain, scarring, and loss of grip and pinch strength, thus permitting an earlier return to daily activities and work. Overall, cosmetic results and patient satisfaction should be improved. The technical aspects of any new procedure, including its potential complications, must be learned before it is applied clinically. An endoscopic procedure presents several potential difficulties. These include problems with surgical instruments and surgical technique. In the former, failure ofthe instrumentation (video camera, light source, etc.), resulting in poor visualization, may occur. In the latter, failure of the surgical procedure may include incomplete ligament releases and inadvertent arterial, nerve, and tendon injuries. In contrast to open procedures, these complications may not be recognized at the time of surgery. The fresh cadavers used in this study are similar to those used in the endoscopic surgical skills workshops. The minimum of three to six endoscopic releases performed by each surgeon in this study is generally more than the number of releases performed in the workshops. The results of open dissection after the endoscopic releases showed an incomplete ligament release in 50% of the specimens. Incomplete releases were generally due to errors in technique, either too superficial placement of the cannula or placement too ulnarly of the cutting slot in the cannula. Incomplete proximal or distal ligament releases were attributed, in part, to penetration of the ligament with the cannula or inability to distinguish the proximal and distal ends of the ligament. The number of incomplete releases and technical errors appeared to be evenly distributed among the several surgeons. The relatively small number of specimens used did not allow us to determine whether a definite learning curve was present. It did appear, though, that with more experience the number of error-free ligament
releases increased. However, no definite trend was noticed. Errors occurred in earlier as well as later releases for some of the surgeons. Surgical adaptations are currently being tried. These include larger proximal and distal incisions with direct visualization of the proximal and distal edges of the TCL, the SPA, and the ulnar neurovascular bundle and placement of the cutting slot slightly radial to the hook of the hamate. Endoscopic carpal tunnel release may be a useful alternative to open release. However, the technique is either technically demanding, commonly results in incompletely sectioned ligaments, or both. Proper training in the use of ECTR, followed by practice on several cadaver specimens before its clinical use, is recommended. A high learning curve is suspected. The authors thank Dr. James Chow for allowing them to observe his surgical approach to the treatment of carpal tunnel syndrome.
REFERENCES I. Kasdan ML. Occupational hand and upper extremity injuries and diseases. Philadelphia: Hanley & Belfus, 1991:341-402. 2. Phalen GS. The carpal tunnel syndrome: seventeen years' experience in diagnosis and treatment of 654 hands. J Bone Joint Surg 1966;48A:211-28. 3. Phalen GS. The carpal tunnel syndrome: clinical evaluation of 598 hands. Clin Orthop 1972;83:29-40. 4. Kendall D. Aetiology, diagnosis and treatment of paraesthesias in the hands. Br Med J 1960;2:1633-40. 5. Lichtman OM, Floro RL, Mack GR. Carpal tunnel release under local anesthesia: evaluation of the outpatient procedure. J HAND SURG 1979;4:544-6. 6. Chow JCY. Endoscopic release of the carpal ligament: a new technique for carpal tunnel syndrome. Arthroscopy 1989;5:19-24. 7. Chow JCY. Endoscopic release of the carpal ligament for carpal tunnel syndrome: 22-month clinical trial. Arthroscopy 1990;6:288-96. 8. Okutusu I, NinorniyaS, Takatori Y, Ugawa Y. Endoscopic management of carpal tunnel syndrome. Arthroscopy 1989;5:11-8.
