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Comparison between single injection transthecal and subcutaneous digital blocks
COMPARISON BETWEEN SINGLE INJECTION TRANSTHECAL AND SUBCUTANEOUS DIGITAL BLOCKS C. K. LOW, H. P. WONG and Y. P. LOW
From the Department of Orthopaedic Surgery, Tan Tock Seng Hospital, Singapore A randomized double blinded study was performed on 142 patients to evaluate two different techniques of single injection digital anaesthesia. In group A, 86 digits in 71 patients were anaesthetized by a single injection transthecal technique using 3 ec of lignoeaine and bupivaeaine mixture. Anaesthesia of the whole digit was achieved in 83 (97%) digits. In group B, 80 digits in 71 patients were anaesthetized with a single injection subcutaneous technique using the same amount of anaesthetic mixture. Total anaesthesia of the digit was achieved in 75 (94%) digits. These two techniques were found to have no differences in effectiveness, distribution, onset and duration of anaesthesia.
Journal of Hand Surgery (British and European Volume, 1997) 22B." 5." 582~84 The single injection transthecal digital block was first described by Chiu in 1990. The technique involves using the flexor tendon sheath for anaesthetic infusion. It has the advantages of providing anaesthesia of the entire digit with a single injection, requires a relatively small amount of anaesthetic agent, gives rapid onset of the anaesthesia and has no risk of direct mechanical trauma to the neurovascular bundles. Chiu (1990), Morrison (1993) and Morros et al (1993) had reported that anaesthesia of the entire digit was achieved in 91 to 99% of cases. In contrast, Chevaleraud et al (1993) in a series of 350 transthecal blocks reported that there was no anaesthesia of the dorsal digital nerves. Harbison (1991) has described an alternative single injection technique that uses a subcutaneous location. It is purported to be easier to administer, yet offers similar advantages to Chiu's technique. The only disadvantage is that the dorsal digital nerves are not always anaesthetized. Hill et al (1995) in a prospective randomized controlled blinded human study concluded that the transthecal block was clinically equal to the traditional two injection digital method in terms of time of anaesthesia and visual-analogue pain score. There was no study
comparing the subcutaneous block with the traditional method. As anaesthesia to the dorsum of the digit following the transthecal technique has not been achieved consistently (Chevaleraud et al 1993) and there has been no prospective controlled study comparing it with the subcutaneous technique, the aim of this double blinded study was to compare the transthecal and the subcutaneous single injection digital block techniques. MATERIALS AND M E T H O D S Between January and December 1996, a study was performed on 142 patients who required operations on fingers. The protocol used was in compliance with and approved by the Tan Tock Seng Hospital H u m a n Research Committee. The patients were randomly divided into two groups of equal size. The characteristics of both groups are summarized in Tables 1 and 2. In group A, a single injection transthecal block was used to anaesthetize the fingers that required surgery. 1% lignocaine was mixed with 1% bupivacaine in equal proportions. Three cc of the anaesthetic mixture was injected into the tendon
Table 1--Characteristics of transthecal and subcutaneous groups
Transthecal
Subcutaneous
Number of patients Male:Female Age: Mean (Standard deviation) years Right:Left hand Single digit Two, three or four digits Number of digits Thumb:Index:Middle:Ring:Little Number of digits with total anaesthesia
71 62:9 32.9 (11.7) 42:29 59 10:1:1 86 9:20:18:19:20 83
71 66:5 34.0 (12.5) 46:25 63 7:1:0 80 16:19:16:14:15 75
Onset of total anaesthesia Mean (Standard deviation) minutes
2.1 (2.4)
2.3 (2.7)
Duration of anaesthesia Mean (Standard deviation) hours
6.6 (1.5)
6.7 (2.0)
582
COMPARISON OF DIGITAL BLOCKS
583
Table 2--Operative procedures and zones
Operativeprocedure
Transthecal
Subcutaneous
Arthrodesis of finger joint Extensor tendon surgery Cross finger flap* Excision of finger lump Full thickness skin graft Nail surgery Local flap Fracture fixation Corrective osteotomy Removal of implants Repair of digital nerve Repair of ligament of joint Wound debridement and repair Operation zone: Dorsal Proximal:Middle:Distal phalanx Operation zone: Palmar Proximal:Middle:Distal phalanx
3 9 5 9 7 8 1 16 5 6 1 2 9
2 7 4 6 6 10 5 12 2 7 7 1 7
34:14:8
28:11:9
7:13:10
9:18:5
*Surgery involves two digits Thumb has only proximal and distal phalanges
sheath of the finger at the A1 pulley according to the technique described by Chiu (1990). In group B, a single injection subcutaneous technique was used. The same amount of anaesthetic mixture was injected into the subcutaneous tissue of the finger superficial to the A1 pulley. The injection was performed by a single investigator. The patients did not know the technique used. The patients were operated upon by two other investigators who were not aware of the technique used. The anaesthetized digits were examined by pin prick at 1 and 5 minutes and 5-minute intervals subsequently for 30 minutes following injection. Surgery was performed once the operation site was fully anaesthetized. The onset, distribution and duration of anaesthesia were documented. Failure of anaesthesia was defined as no loss of pain sensation at the operation site 30 minutes after the injection and supplementary injection of local anaesthetic mixture was required to proceed with surgery. The patients were instructed to report if any complications occurred during the first 2 weeks after operation.
Statistical analysis Student's t, Z2 and Fisher's test were used in the statistical analysis. P values of less than 0.05 were considered statistically significant. RESULTS In the transthecal group, 86 digits in 71 patients were anaesthetized with the transthecal technique. Anaesthesia of the whole digit was achieved in 83 digits. Two thumbs and one index finger had no dorsal anaesthesia, requiring
an additional 2 cc of anaesthetic mixture to be given into the dorsal subcutaneous tissue at the base of the digit. In the subcutaneous group, 80 digits in 71 patients were anaesthetized with the subcutaneous technique. Anaesthesia of the entire finger was achieved in 75 digits. Three thumbs and two index fingers had no dorsal anaesthesia and a supplementary dorsal injection with 2 cc of anaesthetic mixture was given. The onset and duration in digits with total anaesthesia are summarized in Table 1. The differences between the two techniques with regards to effectiveness, distribution, onset and duration of anaesthesia are not significant. No complications such as haematoma, infection or trauma to the neurovascular bundle were reported with either technique. DISCUSSION The traditional digital ring block involves injecting 2 cc of 1% lignocaine on each side of the base of the digit. It requires two injections and a total of 4 cc of anaesthetic solution. It also has the potential hazard of causing sustained elevation of compartmental pressure, leading to compression of the neurovascular bundles. The single injection transthecal digital block described by Chiu (1990) uses the flexor tendon sheath for anaesthetic infusion. It was claimed that it had advantages of requiring a single injection for anaesthesia of the entire digit and no risk of direct mechanical trauma to the neurovascular bundles. Anaesthesia of the entire digit was achieved in 416 of 420 cases. Morrison (1993) performed 46 transthecal blocks and 'total analgesia of the digit' was achieved in 45 cases. In a series of
584
65 cases, Morros et al (1993) reported that this technique gave "total anaesthesia to the finger" in 59. Five patients had slight discomfort which did not interfere with the operation and in only one case was additional anaesthesia required. However, Chevaleraud et al (1993) in a series of 350 transthecal blocks reported that there was "no" anaesthesia of the dorsal digital nerves. The volumes of anaesthetic used by Chiu (1990), Morrison (1993), Morros et al (1993) and Chevaleraud et al (1993) were 2, 2, 3 and 3 to 4 cc respectively. In our study, 3 cc of a mixture of lignocaine and bupivacaine in equal proportions was used. Ninety-seven percent of the digits had total anaesthesia. Lignocaine is fast acting but has a short duration, whereas bupivacaine is slow acting but has a long duration of action. A mixture of both agents would be rapid in onset and with a long duration of action, thus providing a prolonged period of postoperative analgesia. Two of nine thumbs and one of 20 index fingers had no dorsal anaesthesia. In these three cases, the investigator who gave the block felt that the needle had penetrated too deep and entered into the metacarpophalangeal joint. Harbison (1991) described an alternative single injection technique that was subcutaneous and said to be easier to administer than the transthecal digital block, yet offering similar advantages to Chiu's technique (1990). The injection was given into the crease at the base of the finger which was at the level of the A2 pulley. He did not report on the incidence of total anaesthesia or absence of anaesthesia in the dorsal digital nerves. In our study, the subcutaneous injection was in the palm at the level of A1 pulley. Ninety-four percent of the subcutaneous blocks had total anaesthesia. This may be because the dorsal tissue is loose and offers less tissue resistance. The anaesthetic agent is then pushed from the palmar to the dorsal side of the digit during injection. Three of 16
T H E J O U R N A L OF H A N D SURGERY VOL. 22B No. 5 O C T O B E R 1997
thumbs and two of 19 index fingers had no dorsal anaesthesia. The tissue over the radial border of the thumb and the radial side of the index finger is firmer than on the web space side. Higher resistance over the non-web space side and the size of the thumb and index finger might have influenced the distribution of the local anaesthetic. The transthecal technique of Chiu (1990) and our subcutaneous block require only one injection. In our study, both techniques gave high success rates for anaesthesia of the entire digit with a single injection, requiring a relatively small amount of anaesthetic agent, rapid onset of the anaesthesia and no risk of direct mechanical trauma to the neurovascular bundles. There were no differences in effectiveness, distribution, onset and duration of anaesthesia. The subcutaneous block would appear to be a better choice as it is easier to administer and has no risk of intraarticular injection. References Chevaleraud E, Ragot J M, Brunelle E, Dumontier C, Brunelli F (1993). Local anaesthesia of the finger using the flexor tendon sheath. Annales Francaises d'Anesth6sie et de R6animation, 12: 237-240. Chiu D T (1990). Transthecal digital block. Flexor tendon sheath used for anaesthetic infusion. Journal of Hand Surgery, 15A: 471~473. Harbison S (1991). Transthecal digital block. Flexor tendon sheath used for anaesthetic infusion (letter). Journal of H a n d Surgery, 16A: 957. Hill R G, Patterson J W, Parker J C, Bauer J, Wright E, Heller M (1995). Comparison of transthecal digital block and traditional digital block for anesthesia of the finger. Annals of Emergency Medicine, 25:604 607. Morrison W G (1993). Transthecal digital block. Archives of Emergency Medicine, 10:35 38. Morros C, Perez D, Raurell A, Rodriques J E (1993). Digital anaesthesia through the flexor tendon sheath at the palmar level. International Orthopaedics, 17: 2 7 3 2 7 4 .
Received: 5 February 1997 Accepted after revision: 7 April 1997 Dr Low Chee Kwang, Department of Orthopaedic Surgery,Tan Tock Seng Hospital, Moulmein Road, Singapore 308433. © 1997The British Society for Surgery of the Hand
From the Department of Orthopaedic Surgery, Tan Tock Seng Hospital, Singapore A randomized double blinded study was performed on 142 patients to evaluate two different techniques of single injection digital anaesthesia. In group A, 86 digits in 71 patients were anaesthetized by a single injection transthecal technique using 3 ec of lignoeaine and bupivaeaine mixture. Anaesthesia of the whole digit was achieved in 83 (97%) digits. In group B, 80 digits in 71 patients were anaesthetized with a single injection subcutaneous technique using the same amount of anaesthetic mixture. Total anaesthesia of the digit was achieved in 75 (94%) digits. These two techniques were found to have no differences in effectiveness, distribution, onset and duration of anaesthesia.
Journal of Hand Surgery (British and European Volume, 1997) 22B." 5." 582~84 The single injection transthecal digital block was first described by Chiu in 1990. The technique involves using the flexor tendon sheath for anaesthetic infusion. It has the advantages of providing anaesthesia of the entire digit with a single injection, requires a relatively small amount of anaesthetic agent, gives rapid onset of the anaesthesia and has no risk of direct mechanical trauma to the neurovascular bundles. Chiu (1990), Morrison (1993) and Morros et al (1993) had reported that anaesthesia of the entire digit was achieved in 91 to 99% of cases. In contrast, Chevaleraud et al (1993) in a series of 350 transthecal blocks reported that there was no anaesthesia of the dorsal digital nerves. Harbison (1991) has described an alternative single injection technique that uses a subcutaneous location. It is purported to be easier to administer, yet offers similar advantages to Chiu's technique. The only disadvantage is that the dorsal digital nerves are not always anaesthetized. Hill et al (1995) in a prospective randomized controlled blinded human study concluded that the transthecal block was clinically equal to the traditional two injection digital method in terms of time of anaesthesia and visual-analogue pain score. There was no study
comparing the subcutaneous block with the traditional method. As anaesthesia to the dorsum of the digit following the transthecal technique has not been achieved consistently (Chevaleraud et al 1993) and there has been no prospective controlled study comparing it with the subcutaneous technique, the aim of this double blinded study was to compare the transthecal and the subcutaneous single injection digital block techniques. MATERIALS AND M E T H O D S Between January and December 1996, a study was performed on 142 patients who required operations on fingers. The protocol used was in compliance with and approved by the Tan Tock Seng Hospital H u m a n Research Committee. The patients were randomly divided into two groups of equal size. The characteristics of both groups are summarized in Tables 1 and 2. In group A, a single injection transthecal block was used to anaesthetize the fingers that required surgery. 1% lignocaine was mixed with 1% bupivacaine in equal proportions. Three cc of the anaesthetic mixture was injected into the tendon
Table 1--Characteristics of transthecal and subcutaneous groups
Transthecal
Subcutaneous
Number of patients Male:Female Age: Mean (Standard deviation) years Right:Left hand Single digit Two, three or four digits Number of digits Thumb:Index:Middle:Ring:Little Number of digits with total anaesthesia
71 62:9 32.9 (11.7) 42:29 59 10:1:1 86 9:20:18:19:20 83
71 66:5 34.0 (12.5) 46:25 63 7:1:0 80 16:19:16:14:15 75
Onset of total anaesthesia Mean (Standard deviation) minutes
2.1 (2.4)
2.3 (2.7)
Duration of anaesthesia Mean (Standard deviation) hours
6.6 (1.5)
6.7 (2.0)
582
COMPARISON OF DIGITAL BLOCKS
583
Table 2--Operative procedures and zones
Operativeprocedure
Transthecal
Subcutaneous
Arthrodesis of finger joint Extensor tendon surgery Cross finger flap* Excision of finger lump Full thickness skin graft Nail surgery Local flap Fracture fixation Corrective osteotomy Removal of implants Repair of digital nerve Repair of ligament of joint Wound debridement and repair Operation zone: Dorsal Proximal:Middle:Distal phalanx Operation zone: Palmar Proximal:Middle:Distal phalanx
3 9 5 9 7 8 1 16 5 6 1 2 9
2 7 4 6 6 10 5 12 2 7 7 1 7
34:14:8
28:11:9
7:13:10
9:18:5
*Surgery involves two digits Thumb has only proximal and distal phalanges
sheath of the finger at the A1 pulley according to the technique described by Chiu (1990). In group B, a single injection subcutaneous technique was used. The same amount of anaesthetic mixture was injected into the subcutaneous tissue of the finger superficial to the A1 pulley. The injection was performed by a single investigator. The patients did not know the technique used. The patients were operated upon by two other investigators who were not aware of the technique used. The anaesthetized digits were examined by pin prick at 1 and 5 minutes and 5-minute intervals subsequently for 30 minutes following injection. Surgery was performed once the operation site was fully anaesthetized. The onset, distribution and duration of anaesthesia were documented. Failure of anaesthesia was defined as no loss of pain sensation at the operation site 30 minutes after the injection and supplementary injection of local anaesthetic mixture was required to proceed with surgery. The patients were instructed to report if any complications occurred during the first 2 weeks after operation.
Statistical analysis Student's t, Z2 and Fisher's test were used in the statistical analysis. P values of less than 0.05 were considered statistically significant. RESULTS In the transthecal group, 86 digits in 71 patients were anaesthetized with the transthecal technique. Anaesthesia of the whole digit was achieved in 83 digits. Two thumbs and one index finger had no dorsal anaesthesia, requiring
an additional 2 cc of anaesthetic mixture to be given into the dorsal subcutaneous tissue at the base of the digit. In the subcutaneous group, 80 digits in 71 patients were anaesthetized with the subcutaneous technique. Anaesthesia of the entire finger was achieved in 75 digits. Three thumbs and two index fingers had no dorsal anaesthesia and a supplementary dorsal injection with 2 cc of anaesthetic mixture was given. The onset and duration in digits with total anaesthesia are summarized in Table 1. The differences between the two techniques with regards to effectiveness, distribution, onset and duration of anaesthesia are not significant. No complications such as haematoma, infection or trauma to the neurovascular bundle were reported with either technique. DISCUSSION The traditional digital ring block involves injecting 2 cc of 1% lignocaine on each side of the base of the digit. It requires two injections and a total of 4 cc of anaesthetic solution. It also has the potential hazard of causing sustained elevation of compartmental pressure, leading to compression of the neurovascular bundles. The single injection transthecal digital block described by Chiu (1990) uses the flexor tendon sheath for anaesthetic infusion. It was claimed that it had advantages of requiring a single injection for anaesthesia of the entire digit and no risk of direct mechanical trauma to the neurovascular bundles. Anaesthesia of the entire digit was achieved in 416 of 420 cases. Morrison (1993) performed 46 transthecal blocks and 'total analgesia of the digit' was achieved in 45 cases. In a series of
584
65 cases, Morros et al (1993) reported that this technique gave "total anaesthesia to the finger" in 59. Five patients had slight discomfort which did not interfere with the operation and in only one case was additional anaesthesia required. However, Chevaleraud et al (1993) in a series of 350 transthecal blocks reported that there was "no" anaesthesia of the dorsal digital nerves. The volumes of anaesthetic used by Chiu (1990), Morrison (1993), Morros et al (1993) and Chevaleraud et al (1993) were 2, 2, 3 and 3 to 4 cc respectively. In our study, 3 cc of a mixture of lignocaine and bupivacaine in equal proportions was used. Ninety-seven percent of the digits had total anaesthesia. Lignocaine is fast acting but has a short duration, whereas bupivacaine is slow acting but has a long duration of action. A mixture of both agents would be rapid in onset and with a long duration of action, thus providing a prolonged period of postoperative analgesia. Two of nine thumbs and one of 20 index fingers had no dorsal anaesthesia. In these three cases, the investigator who gave the block felt that the needle had penetrated too deep and entered into the metacarpophalangeal joint. Harbison (1991) described an alternative single injection technique that was subcutaneous and said to be easier to administer than the transthecal digital block, yet offering similar advantages to Chiu's technique (1990). The injection was given into the crease at the base of the finger which was at the level of the A2 pulley. He did not report on the incidence of total anaesthesia or absence of anaesthesia in the dorsal digital nerves. In our study, the subcutaneous injection was in the palm at the level of A1 pulley. Ninety-four percent of the subcutaneous blocks had total anaesthesia. This may be because the dorsal tissue is loose and offers less tissue resistance. The anaesthetic agent is then pushed from the palmar to the dorsal side of the digit during injection. Three of 16
T H E J O U R N A L OF H A N D SURGERY VOL. 22B No. 5 O C T O B E R 1997
thumbs and two of 19 index fingers had no dorsal anaesthesia. The tissue over the radial border of the thumb and the radial side of the index finger is firmer than on the web space side. Higher resistance over the non-web space side and the size of the thumb and index finger might have influenced the distribution of the local anaesthetic. The transthecal technique of Chiu (1990) and our subcutaneous block require only one injection. In our study, both techniques gave high success rates for anaesthesia of the entire digit with a single injection, requiring a relatively small amount of anaesthetic agent, rapid onset of the anaesthesia and no risk of direct mechanical trauma to the neurovascular bundles. There were no differences in effectiveness, distribution, onset and duration of anaesthesia. The subcutaneous block would appear to be a better choice as it is easier to administer and has no risk of intraarticular injection. References Chevaleraud E, Ragot J M, Brunelle E, Dumontier C, Brunelli F (1993). Local anaesthesia of the finger using the flexor tendon sheath. Annales Francaises d'Anesth6sie et de R6animation, 12: 237-240. Chiu D T (1990). Transthecal digital block. Flexor tendon sheath used for anaesthetic infusion. Journal of Hand Surgery, 15A: 471~473. Harbison S (1991). Transthecal digital block. Flexor tendon sheath used for anaesthetic infusion (letter). Journal of H a n d Surgery, 16A: 957. Hill R G, Patterson J W, Parker J C, Bauer J, Wright E, Heller M (1995). Comparison of transthecal digital block and traditional digital block for anesthesia of the finger. Annals of Emergency Medicine, 25:604 607. Morrison W G (1993). Transthecal digital block. Archives of Emergency Medicine, 10:35 38. Morros C, Perez D, Raurell A, Rodriques J E (1993). Digital anaesthesia through the flexor tendon sheath at the palmar level. International Orthopaedics, 17: 2 7 3 2 7 4 .
Received: 5 February 1997 Accepted after revision: 7 April 1997 Dr Low Chee Kwang, Department of Orthopaedic Surgery,Tan Tock Seng Hospital, Moulmein Road, Singapore 308433. © 1997The British Society for Surgery of the Hand