Atlas of Primary Care Procedures, 1st Edition

Musculoskeletal Procedures

70

Carpal Tunnel Syndrome Injection

Carpal tunnel syndrome is the most common entrapment neuropathy. The syndrome is produced by compression of the median nerve within the carpal canal. The canal is an unyielding space bounded by the carpal bones inferiorly and the transverse carpal ligament superiorly. Conditions that enlarge structures within the canal or that shrink the canal can produce median nerve compression. Tumors, ganglia, or tenosynovitis of the flexor tendons all reduce the space within the canal. Edema can result from general medical conditions such as thyroid dysfunction or amyloidosis.

Carpal tunnel syndrome is more common in women (3:1 female-to-male ratio). Pregnant women and those in the later reproductive years appear to have the highest incidence. Underlying causes for tenosynovitis, such as repetitive work activities, gout, or rheumatoid arthritis should be corrected or treated. Improved control of diabetes or hypothyroidism also appears to benefit individuals with the disorder.

Most patients with carpal tunnel syndrome exhibit paresthesias and pain in the distribution of the median nerve. The nerve supplies sensation to the volar aspect of the first three fingers and the radial half of the fourth finger. Symptoms are worse with activity or at night, when individuals tend to sleep on the wrist or maintain the hand in flexion. More established cases may exhibit pain into the wrist or forearm, weakness in the hand, and atrophy of the thumb abductor muscles.

Provocative testing includes Tinel's test and Phalen's test. Tinel's test induces paresthesias by tapping over the median nerve at the wrist. Phalen's test is performed by maximally flexing the wrists (palmar flexed to 90 degrees) by placing the wrists together for 30 to 60 seconds, producing numbness, paresthesias, or reproducing the patient's symptoms. Poor sensitivity of these tests (tests are positive in 20% and 46% of normal individuals, respectively) limits their value. Electrophysiologic studies provide objective data. Nerve conduction tests reveal latency across the carpal canal, and electromyography of the thenar muscles can establish the presence of axonal damage. Electrophysiologic testing does not appear to identify those who will benefit from surgical intervention and may be unnecessary when the diagnosis is clinically apparent.

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Thenar muscle atrophy suggests the presence of severe, long-standing disease. Surgical decompression is indicated for severe disease or for severe, disabling pain. Milder disease can be treated with rest, ice, avoidance of offending activities, nighttime splinting, nonsteroidal antiinflammatory drugs (NSAIDs), and oral or injected corticosteroids.

The literature has confirmed the value of steroids injected into the canal. Slow and careful needle tip positioning avoids damage to the median nerve. Most studies document that more than 70% of patients receive significant short-term benefit from injection therapy. Patients with symptom recurrence can be reinjected, but a limit of two or three injections is advocated to limit the amount of crystalline substance in the canal, which can serve as an irritant. If a second injection fails, most authors recommend that the patient be referred for surgical intervention.

INDICATIONS

• Signs and symptoms suggesting median nerve compression in the carpal canal with the absence of severe symptoms or pain and absence of severe signs such as thenar muscle wasting

RELATIVE CONTRAINDICATIONS

• Uncooperative patient
• Signs and symptoms of carpal tunnel syndrome in the third trimester of pregnancy (spontaneous improvement after delivery is likely)
• Evidence of cellulites or bacteremia
• Presence of a mass in the carpal canal
• Coagulopathy or bleeding diathesis

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PROCEDURE

Note the location of the carpal tunnel in the proximal portion of the hand, not over the wrist.

The sensory distribution of the median nerve is shown in Figure 2A. Long-term compression of the median nerve can result in thenar muscle weakness and atrophy (Figure 2B).

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Tinel's sign is produced by tapping over the median nerve at the wrist (Figure 3A). Phalen's sign is performed by holding the wrists together for up to 60 seconds (Figure 3B).

PITFALL: Limit Phalen's test to 60 seconds. Severe disease often manifests with symptoms in less than 30 seconds. Phalen's test often is positive in normal individuals if the wrists are palmar flexed to 90 degrees for more than 60 seconds.

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The patient is laid supine, and the affected arm is fully extended. The practitioner must turn to face the patient's feet (Figure 4A). Ask the patient to make a fist and slightly flex the wrist against resistance. Most individuals have a palmaris longus tendon that elevates at the wrist (Figure 4B). The needle is inserted on either side (radial or ulnar) of the palmaris longus tendon.

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Identify the second wrist crease on the volar surface (Figure 5A). Prepare a 5- to 6-mL syringe with injection solution, such as 0.5 mL of Celestone and 3 to 4 mL of 1% lidocaine without epinephrine. Lay the syringe flat on the forearm, with the needle directed toward the tip of the third finger (Figure 5B). Angle the needle slightly downward. The needle tip will lie approximately 1 cm below the surface of the hand overlying the carpal canal (Figure 5C).

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Many authors recommend insertion of the needle tip to the proximal canal; this means the needle is inserted only about 1 to 1.5 cm (Figure 6A). An alternate technique attempts to insert the needle within the canal, inserting the needle 2.0 to 2.5 cm (Figure 6B). Both techniques appear efficacious. After injection, the patient should experience immediate numbness from the lidocaine. NSAIDs and nighttime splinting should be prescribed in addition to the injection, unless NSAIDs are contraindicated.

PITFALL: Insert the needle slowly and gently. The needle should pass easily. If resistance is met, withdraw the needle, and redirect the tip, still aiming for the tip of the third finger.

PITFALL: The needle tip can touch or penetrate the median nerve. If the insertion is slow, magnified symptoms appear in the fingertips when the needle tip touches the nerve. Ask patients to report pain or numbness in the fingertips as the needle is inserted. If the needle tip touches the median nerve, withdraw the needle and then redirect slightly, still aiming for the tip of the third finger.

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CODING INFORMATION

INSTRUMENT AND MATERIALS ORDERING

Consult the ordering information that appears in Chapter 65. Needles, syringes, and splints are available from local surgical supply houses. A suggested tray for performing soft tissue aspirations and injections is listed in Appendix D. Skin preparation recommendations appear inAppendix H.

BIBLIOGRAPHY

Biundo JJ. Regional rheumatic pain syndromes. In: Klippel JH, Weyand CM, Wortmann RL, eds. Primer on the rheumatic diseases, 11th ed. Atlanta, Arthritis Foundation, 1997:136–148.

Buttaravoli P, Stair T. Minor emergencies: splinters to fractures. St. Louis: Mosby, 2000:267–270.

Dammers JW, Veering MM, Vermeulen M. Injection with methylprednisolone proximal to the carpal tunnel: randomized double blind trial.BMJ 1999;319:884–886.

Kasten SJ, Louis DS. Carpal tunnel syndrome: a case of median nerve injection injury and a safe and effective method for injecting the carpal tunnel. J Fam Pract 1996;43:79–82.

Katz RT. Carpal tunnel syndrome: a practical review. Am Fam Physician 1994;49:1371–1379.

Lee D, van Holsbeeck MT, Janevski PK, et al. Diagnosis of carpal tunnel syndrome: ultrasound versus electromyography. Radiol Clin North Am 1999;37:859–872.

Mercier LR, Pettid FJ, Tamisiea DF, et al. Practical orthopedics, 4th ed. St. Louis: Mosby, 1991:101–103.

Miller RS, Iverson DC, Fried RA, et al. Carpal tunnel syndrome in primary care: a report from ASPN. J Fam Pract 1994;38:337–344.

Murphy MS, Amadio PC. Carpal tunnel syndrome: evaluation and treatment. Fam Pract Recert 1992;14:23–40.

Olney RK. Carpal tunnel syndrome: complex issues with a “simple” condition [Editorial]. Neurology 2001;56:1431–1432.

Seiler JG. Carpal tunnel syndrome: update on diagnostic testing and treatment options. Consultant 1997;37:1233–1242.

Szabo RM. A management guide to carpal tunnel syndrome. Hosp Med 1994;30:26–33.

von Schroeder HP. Review finds limited evidence for electrodiagnosis to predict surgical outcomes in people with carpal tunnel syndrome.Evid Based Healthcare Sci Appr Health Pol 2000;4:92.

Wilson FC, Lin PP. General orthopedics. New York: McGraw-Hill, 1997:259–260.

Wong SM, Hui AC, Tang A, et al. Local vs. systemic corticosteroids in the treatment of carpal tunnel syndrome. Neurology 2001;56:1565–1567