DEPARTMENT OF TECHNIQUE
A safe, reliable method of carpal tunnel injection The injection of steroid preparations into the carpal canal is a recognized practice in the management of carpal tunnel syndrome. This procedure is associated with a risk of temporary or permanent damage to the median nerve. We present a new method of carpal tunnel injection based on anatomic dissections. We have used this technique successfuJly for more than 10 years, and there have been no cases of median nerve injury. (J HAND SURG 1992jI7A:1160-1.)
N. R. M. Kay, FRCS, Sheffield, England, and P. D . Marshall, FRCS , Cardiff, Wales
T
he injection of steroid preparations into the carpal canal in the management of patients with carpal tunnel syndrome is well accepted. If the nerve is injected, however, either temporary or permanent damage may result. It is not the purpose of this article to discuss the indications for steroid injections into the carpal canal. If an individual case is considered to be suitable for such treatment, then clearly a safe and reliable technique is necessary. Median nerve injury as a complication of carpal tunnel injection has been reported by Phalen, 1 Posch and Marcotte," and recently by Linskey and Segal. 3 There is no overall consensus in the literature regarding the safest method of injection. Although the distal skin crease of the wrist represents the surface landmark of the proximal limit of the carpal ligament, there is no overall agreement as to where on this crease the needle should be inserted. Phalen, I Green," and Wood" recommend that the needle be inserted to the ulnar aspect of the palmaris longus tendon in line with the fourth ray ; Gelberrnan et al." recommend that the needle be inserted on the radial aspect of the palmaris longus tendon, between this tendon and that of the flexor carpi radialis. From the Royal Hallamshire Hospital, Sheffield , England . Received for publication June 28 , 1991; accepted in revised form Feb. 10, 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: N.R.M. Kay, FRCS , Department of Orthopaedic Surgery, Royal Hallamshire Hospital , Sheffield S10 2JF, England. 3/1138409
1160
THE JOURNAL OF HAND SURGERY
Fig. 1. Diagram illustrating point of entry and direction of injecting needle. Note that the tip of the needle lies deep to the median nerve.
Failure of hydrocortisone inject ions to provide symptomatic relief of carpal tunnel syndrome may be due to poor injection technique. Wood' showed that it is surprisingly easy for even experienced operators to miss the carpal tunnel on occasion. By inserting a needle
Vol. 17A, No.6 November 1992
Safe, reliable method of carpal tunnel injection
1161
ANTERIOR
Median nerve
Fig. 3. Diagrammatic representation illustrating transmitted movement of needle and syringe when tip is embedded in flexor tendon and fingers are flexed and extended.
POSTERIOR Fig. 2. Diagrammatic representation of a section through the carpus illustrating that the needle tip is embedded in the paratenon of one of the flexor tendons. immediately before surgical decompression and then exploring to determine the location of the needle tip, he found that in 2 of 26 cases (8%) the carpal tunnel had been completely missed. Our method of carpal tunnel injection is based on anatomic dissections performed on cadaver wrists. This technique has been used successfully for 10 years. We have reviewed the last 250 patients, and there have been no cases of median nerve injury. Method Anatomic studies of cadaver wrists revealed that the carpal tunnel could be consistently entered if the needle was inserted just distal to the distal skin crease of the wrist in line with the fourth ray. The needle should be directed distally by approximately 45 degrees and in a radial direction by approximately 45 degrees (Fig. 1). This ensures that the needle enters the carpal canal with the tip lying deep to the median nerve, usually embedded in one of the flexor tendons or its synovium (Fig. 2). Penetration of the flexor tendons or their synovium can be demonstrated by transmitted movement of the needle when the fingers are slowly flexed and extended (Fig. 3). To avoid injection into the substance of the tendon itself, the needle is gradually withdrawn until finger flexion no longer causes movement of the needle. The fingers are then extended, and the easy injection
of the steroid preparation confirms that the needle tip is within the carpal canal but not within either the median nerve or the flexor tendons. For the technique to be successful, it is essential that the patient be fully aware of what will be required. We have found it useful to ask the patient to rehearse the necessary slow, smooth flexion and extension of the fingers before the injection itself. It is our practice to position the hand on a suitable surface and then to cleanse the skin of the wrist with an alcohol solution. The patient is asked to fully extend the fingers and thumb and then to flex the fingers slowly and smoothly until the tips touch the palm. The fingers are then extended in the same controlled, smooth manner. After this rehearsal we inject 1 ml of a solution containing 40 mg of triamcinolone acetonide (Kenalog, E.R. Squibb & Sons, Ltd., Hounslow, Middlesex, England) with a 21-gauge needle in the manner described. We do not add local anesthetic to the steroid preparation and have found it to be unnecessary to infiltrate the skin with local anesthetic before making the injection. REFERENCES I. Phalen GS. The carpal tunnel syndrome: seventeen years experience in diagnosis and treatment of six hundred and fifty four hands. J Bone Joint Surg 1966;48A:211-28. 2. Posch JL, Marcotte DR. Carpal tunnel syndrome: ananalysis of 1,201 cases. Orthop Rev 1976;5:25-35. 3. Linskey ME, Segal R. Median nerve injury from local steroid injection in carpal tunnel syndrome. Neurosurgery 1990;26:5 I 2-5. 4. Green DP. Diagnostic and therapeutic value of carpal tunnel injection. J HAND SURG 1984;9A:850-4. 5. Wood MR. Hydrocortisone injections for carpal tunnel syndrome. Hand 1980;12:62-4. 6. Gelberman RH, Aronson 0, Weisman MH. Carpal tunnel syndrome: results of a prospective trial of steroid injection and splinting. J Bone Joint Surg 1980;62A: 1181-4.
A safe, reliable method of carpal tunnel injection The injection of steroid preparations into the carpal canal is a recognized practice in the management of carpal tunnel syndrome. This procedure is associated with a risk of temporary or permanent damage to the median nerve. We present a new method of carpal tunnel injection based on anatomic dissections. We have used this technique successfuJly for more than 10 years, and there have been no cases of median nerve injury. (J HAND SURG 1992jI7A:1160-1.)
N. R. M. Kay, FRCS, Sheffield, England, and P. D . Marshall, FRCS , Cardiff, Wales
T
he injection of steroid preparations into the carpal canal in the management of patients with carpal tunnel syndrome is well accepted. If the nerve is injected, however, either temporary or permanent damage may result. It is not the purpose of this article to discuss the indications for steroid injections into the carpal canal. If an individual case is considered to be suitable for such treatment, then clearly a safe and reliable technique is necessary. Median nerve injury as a complication of carpal tunnel injection has been reported by Phalen, 1 Posch and Marcotte," and recently by Linskey and Segal. 3 There is no overall consensus in the literature regarding the safest method of injection. Although the distal skin crease of the wrist represents the surface landmark of the proximal limit of the carpal ligament, there is no overall agreement as to where on this crease the needle should be inserted. Phalen, I Green," and Wood" recommend that the needle be inserted to the ulnar aspect of the palmaris longus tendon in line with the fourth ray ; Gelberrnan et al." recommend that the needle be inserted on the radial aspect of the palmaris longus tendon, between this tendon and that of the flexor carpi radialis. From the Royal Hallamshire Hospital, Sheffield , England . Received for publication June 28 , 1991; accepted in revised form Feb. 10, 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: N.R.M. Kay, FRCS , Department of Orthopaedic Surgery, Royal Hallamshire Hospital , Sheffield S10 2JF, England. 3/1138409
1160
THE JOURNAL OF HAND SURGERY
Fig. 1. Diagram illustrating point of entry and direction of injecting needle. Note that the tip of the needle lies deep to the median nerve.
Failure of hydrocortisone inject ions to provide symptomatic relief of carpal tunnel syndrome may be due to poor injection technique. Wood' showed that it is surprisingly easy for even experienced operators to miss the carpal tunnel on occasion. By inserting a needle
Vol. 17A, No.6 November 1992
Safe, reliable method of carpal tunnel injection
1161
ANTERIOR
Median nerve
Fig. 3. Diagrammatic representation illustrating transmitted movement of needle and syringe when tip is embedded in flexor tendon and fingers are flexed and extended.
POSTERIOR Fig. 2. Diagrammatic representation of a section through the carpus illustrating that the needle tip is embedded in the paratenon of one of the flexor tendons. immediately before surgical decompression and then exploring to determine the location of the needle tip, he found that in 2 of 26 cases (8%) the carpal tunnel had been completely missed. Our method of carpal tunnel injection is based on anatomic dissections performed on cadaver wrists. This technique has been used successfully for 10 years. We have reviewed the last 250 patients, and there have been no cases of median nerve injury. Method Anatomic studies of cadaver wrists revealed that the carpal tunnel could be consistently entered if the needle was inserted just distal to the distal skin crease of the wrist in line with the fourth ray. The needle should be directed distally by approximately 45 degrees and in a radial direction by approximately 45 degrees (Fig. 1). This ensures that the needle enters the carpal canal with the tip lying deep to the median nerve, usually embedded in one of the flexor tendons or its synovium (Fig. 2). Penetration of the flexor tendons or their synovium can be demonstrated by transmitted movement of the needle when the fingers are slowly flexed and extended (Fig. 3). To avoid injection into the substance of the tendon itself, the needle is gradually withdrawn until finger flexion no longer causes movement of the needle. The fingers are then extended, and the easy injection
of the steroid preparation confirms that the needle tip is within the carpal canal but not within either the median nerve or the flexor tendons. For the technique to be successful, it is essential that the patient be fully aware of what will be required. We have found it useful to ask the patient to rehearse the necessary slow, smooth flexion and extension of the fingers before the injection itself. It is our practice to position the hand on a suitable surface and then to cleanse the skin of the wrist with an alcohol solution. The patient is asked to fully extend the fingers and thumb and then to flex the fingers slowly and smoothly until the tips touch the palm. The fingers are then extended in the same controlled, smooth manner. After this rehearsal we inject 1 ml of a solution containing 40 mg of triamcinolone acetonide (Kenalog, E.R. Squibb & Sons, Ltd., Hounslow, Middlesex, England) with a 21-gauge needle in the manner described. We do not add local anesthetic to the steroid preparation and have found it to be unnecessary to infiltrate the skin with local anesthetic before making the injection. REFERENCES I. Phalen GS. The carpal tunnel syndrome: seventeen years experience in diagnosis and treatment of six hundred and fifty four hands. J Bone Joint Surg 1966;48A:211-28. 2. Posch JL, Marcotte DR. Carpal tunnel syndrome: ananalysis of 1,201 cases. Orthop Rev 1976;5:25-35. 3. Linskey ME, Segal R. Median nerve injury from local steroid injection in carpal tunnel syndrome. Neurosurgery 1990;26:5 I 2-5. 4. Green DP. Diagnostic and therapeutic value of carpal tunnel injection. J HAND SURG 1984;9A:850-4. 5. Wood MR. Hydrocortisone injections for carpal tunnel syndrome. Hand 1980;12:62-4. 6. Gelberman RH, Aronson 0, Weisman MH. Carpal tunnel syndrome: results of a prospective trial of steroid injection and splinting. J Bone Joint Surg 1980;62A: 1181-4.
