Edward Diao
DEFINITION
Carpal tunnel syndrome (CTS) is the most common nerve compression condition in the upper extremity.
Carpal tunnel release (CTR) is one of the most commonly performed procedures in the United States.
CTS is a compressive neuropathy of the median nerve at the wrist.
Early stages of CTS are reversible with treatment.
Later or more severe stages of CTS may not be (fully) reversible.
ANATOMY
The carpal tunnel or carpal canal is a space bounded by the carpal bones dorsally, the trapezium and scaphoid radially, the hook of the hamate ulnarly, and the transverse carpal ligament palmarly (FIG 1A).
The carpal canal contains the median nerve and nine digital flexor tendons, along with the accompanying tenosynovium (FIG 1C).
Anatomic anomalies include the following:
A persistent median artery
Muscle anomalies
Median nerve branching anomalies (FIG 1B)
Extraneous masses or structures may be found within the carpal canal, including sarcoid and ganglion cysts.
PATHOGENESIS
Most cases of CTS are idiopathic.9
Some cases are associated with systemic conditions, such as rheumatoid arthritis, diabetes, thyroid disease, chronic renal failure, and sarcoidosis. CTS is associated with pregnancy.
There is an association of CTS with cumulative trauma and repetitive use.9
Increased pressure within the carpal canal is associated with CTS.2,6,11
Peripheral neuropathy and CTS have also been associated with shear forces on the nerve, such as with a traction injury.7
FIG 1 • A. Cross-section of the carpal tunnel. B. The carpal tunnel has been fully released and the median nerve motor branch is seen branching from the nerve proximally and penetrating the radial portion of the transverse carpal ligament. C. Cross-section of the carpal tunnel with the ulnar artery and nerve superficial to the TCL. (B: Copyright Thomas R. Hunt III, MD.)
NATURAL HISTORY
CTS may have a variable course. It can improve, remain stable, or get more severe.
Patients with severe CTS have motor and sensory changes and may have muscle weakness and atrophy.9
Patients with extremely advanced CTS frequently have little pain but constant numbness and weakness.
HISTORY AND PHYSICAL FINDINGS
Presenting symptoms can be variable: some patients with mild CTS present with moderate to severe pain, numbness, and paresthesias, whereas other patients have minimal symptoms until their syndrome is severe and there is thenar muscle atrophy.
A common finding that drives patients toward a remedy is nocturnal waking.
The surgeon should obtain a full medical history to identify for risk factors for CTS such as hypothyroidism and diabetes.
The surgeon must understand the patient's occupational and recreational hand activities and any antecedent trauma that might contribute to symptoms.
The surgeon should inquire about activity triggers for the CTS.
The surgeon should obtain a sense of symptom progression and severity.
Questions should be asked about sensory and motor function, pain pattern, and nocturnal waking.
The physical examination includes the neck and shoulder girdle; the supraclavicular, infraclavicular, and axillary area; the humerus and elbow; the forearm; and the wrist and hand.
It is important to generate a list of findings that may be responsible for the pain or paresthesias other than CTS.
In addition to the standard joint evaluation with range of motion and assessments of stability, it is important to palpate the course of the nerves and elicit the Tinel sign along the course of the paracervical, brachial plexus, median, ulnar, and radial nerves.
The Tinel sign is mild, moderate, or severe subjective findings of radicular pain. The mechanical external stimulus threshold for depolarization–repolarization is lowered in a nerve that has a peripheral neuropathy. Anatomic distribution also is important.
Phalen's sign: Wrist flexion decreases the anatomic volume of the carpal canal and raises pressure in patients with CTS. The pattern of paresthesia can be important.
Carpal tunnel compression test: The mechanical external stimulus threshold for depolarization–repolarization is lowered in a nerve that has a peripheral neuropathy.
Two-point discrimination: In peripheral neuropathy the ability to distinguish one or two points is diminished.
Decreased range of motion and palmar wrist swelling can be indirect indications of tenosynovium in the carpal canal, and also any intra-articular wrist pathology.
IMAGING AND OTHER DIAGNOSTIC STUDIES
AP, lateral, and oblique radiographs are not mandatory in the workup if the wrist examination is completely normal. If there is any possibility of wrist pathology, these studies should be obtained.
Other imaging studies are not indicated in routine cases. In cases of recurrent CTS, MRI should be obtained to gain further information regarding a complete versus incomplete release of the transverse carpal ligament (TCL) or evidence of median nerve compression, tenosynovitis, and scarring.1
Electrodiagnostics: Nerve conduction studies (NCS) and electromyography (EMG) are important. CTS can be graded based on NCS and EMG findings:
CTS mild: Increased sensory or motor distal latency; may see decreased amplitude
CTS moderate: Increased nerve conduction velocity
CTS severe: EMG shows signs of chronic denervation with positive fibrillations and sharp waves or unobtainable recordings on the electrodes to median innervated muscles.
Although some experts believe the absence of any of the above electrodiagnostic findings means that there is no CTS, others believe that false-negatives exist due to sensitivity issues with NCS and EMG.4
DIFFERENTIAL DIAGNOSIS
Cervical radiculitis
Cervical pathology, joint disease, disc disease, facet disease with foramina stenosis
Thoracic outlet syndrome
Brachial plexopathy
Syringomyelia, motor neuron disease, myelopathy
“Double crush syndrome”
Shoulder pain related to instability, intra-articular pathology, subacromial impingement
Acromioclavicular joint pathology
Medial epicondylitis
Lateral epicondylitis
Cubital tunnel syndrome
Radial tunnel syndrome
Pronator syndrome
Elbow pathology instability or contracture
Forearm or wrist tenosynovitis
Wrist tenosynovitis, extensor, flexor, or De Quervain tenosynovitis
Digital tenosynovitis (trigger finger)
Guyon canal syndrome
Hypothenar hammer syndrome
Wrist or carpal fracture
Intra-articular wrist pathology
NONOPERATIVE MANAGEMENT
Mild CTS can often be modulated through conservative means.5,16
Any systemic conditions should be identified and treated.5,16
Activity modification can be attempted, especially if the activity includes highly repetitive loading of the hand, wrist, and upper extremity.
Wrist splints can be introduced.
The physician can recommend or prescribe nonsteroidal anti-inflammatory drugs (NSAIDs).
Corticosteroid injection into the carpal canal can be considered (FIG 2).
Temporary relief from such an injection indicates that surgical decompression is likely to be successful.
Hand therapy can be considered.
Some believe oral vitamin B12 treatment can be helpful in some cases.
FIG 2 • Cortisone injection.
SURGICAL MANAGEMENT
The diagnosis of CTS is confirmed by either the presence of classic clinical symptoms and signs or positive NCS or EMG studies.
If the NCS or EMG findings are negative, at least one trial of corticosteroid injection should be given to evaluate the clinical response.
The surgeon should confirm that a trial of conservative treatment has been undertaken without a cure.
The surgeon should confirm that differential diagnoses have been considered.
The surgeon should understand that the presence of other diagnoses and conditions will affect the overall results of CTS treatment; this needs to be discussed with the patient before, not after, surgery. In fact, one should strongly consider delaying CTS treatment to control or improve other conditions that may be amenable to nonoperative treatment.
If the above conditions are met, CTR should have good to excellent results in more than 90% of cases.14
In the case of recurrent CTS, the key to success is patient selection. Although there are scant data to correlate the preoperative evaluation with results, the patient's clinical course, response to conservative treatment, and interpretation of electrodiagnostic studies and MRI should be carefully considered before revision surgery.
Positioning
CTR surgery is performed with the arm outstretched on a hand table.
Pneumatic tourniquet use facilitates accurate identification of critical anatomic structures.
Loupe magnification is recommended.
Anesthesia can be by general anesthesia or regional anesthesia such as an axillary block or Bier block.
Experienced surgeons can perform CTS safely under wrist block or local infiltration.
Approach
The goal of CTR surgery is to decompress the median nerve at the carpal canal by complete division of the TCL to allow the carpal tunnel to expand.
A volar exposure is used, but incision position and length vary.
The locations of critical deep structures are defined using superficial landmarks and a line drawn down the ulnar border of the second ray and another drawn obliquely across the palm in line with the ulnar border of the abducted thumb (Kaplan cardinal line) (FIG 3).
FIG 3 • Surface landmarks are critical when contemplating surgical release of the median nerve.
TECHNIQUES
OPEN CARPAL TUNNEL RELEASE
Exposure
Mark the skin incision location, beginning at the intersection of the Kaplan cardinal line and a line drawn along the radial border of the fourth ray, and ending at the wrist flexion crease (TECH FIG 1A).
Use a longitudinal hypothenar crease if available.
The incision may be placed anywhere along this mark (TECH FIG 1B), depending on the surgeon's preference. I prefer the midpoint of the proximal third of the palm.
The incision should be long enough to allow full access to the proximal to distal extent of the TCL to ensure full TCL division. This generally can be achieved without having the incision extend proximal to the wrist flexion crease.
Dissect in line with the incision using a scalpel or scissors, through the subcutaneous fat and the palmar fascia down to the TCL (TECH FIG 1C).
Frequently, the palmaris brevis muscle is encountered directly superficial to the TCL. It is incised and “feathered” from the ligament for adequate visualization of the TCL.
Incise the TCL over a small segment, avoiding injury to deep structures (TECH FIG 1D).
Contents of the carpal canal will have a characteristic appearance due to the tenosynovium.
Place an instrument such as a mosquito clamp or Carroll elevator into the carpal canal, just deep to the TCL (TECH FIG 1E).
This defines the undersurface of the TCL, the location of the hamate hook, and the proposed direction for release.
Visualize the superficial surface of the TCL along its course and place a right-angle retractor to protect the critical structures located between the skin and the ligament (TECH FIG 1F,G).
TECH FIG 1 • A. A longitudinal incision is marked for an open carpal tunnel release. B. Either all or a limited portion of this incision may be used, depending on the surgeon's preference. C. The palmar fascia has been incised, the deep fat retracted ulnarly, and the palmaris brevis muscle fibers dissected revealing the transverse fibers of the TCL. D. The distal portion of the TCL is carefully incised with a no. 15 knife blade. E. A mosquito clamp is placed deep to the TCL in a distal to proximal direction. F. A right angle retractor is utilized to visualize the proximal TCL and the distal forearm fascia. G. The same retractor is then utilized to visualized the distal TCL to allow complete release. (B–G: Copyright Thomas R. Hunt, III, MD.)
Transverse Carpal Ligament Release
Staying ulnar in the canal but still leaving a 2-mm cuff of TCL attached to the hamate hook, release the TCL under direct vision proximally and distally with a scalpel, scissors, or mini-meniscotome Beaver blade.
Keep a radially based TCL leaflet over the median nerve.
Release the distal forearm fascia proximally (see Tech Fig 1F).
This tissue may be a secondary compression site, especially in patients with two wrist flexion creases.
Completely divide the TCL and inspect the median nerve and canal contents (see Tech Fig 1G).
In rare instances a space-occupying lesion will require removal (ie, “billowing” synovium in a patient with rheumatoid arthritis).
In primary CTR procedures without systemic disease, there is no role for internal neurolysis or tenosynovectomy (TECH FIG 2).3,8,10
The wound is closed and sterile dressings are applied.
Use of a splint is based on the surgeon's preference.
TECH FIG 2 • Open CTR with divided leaflets of the TCL retracted by the retractor jaws. The instrument is on the median nerve which is adherent to the undersurface of the TCL via tenosynovium.
SINGLE-INCISION ENDOSCOPIC CARPAL TUNNEL RELEASE (MODIFIED AGEE TECHNIQUE) 14
Exposure
Mark out the palmaris longus, the flexor carpi radialis, and the flexor carpi ulnaris.
Make a transverse 1- to 2-cm incision in a wrist flexion crease centered over or just ulnar to the palmaris longus (TECH FIG 3A).
If the palmaris longus is not present, incise halfway between the flexor carpi radialis and the flexor carpi ulnaris.
Expose the palmaris longus and retract it radially with a Ragnell retractor.
Identify the flexor retinaculum deep to this structure (TECH FIG 3B).
Incise the flexor retinaculum and create a distally based U-shaped flap 1 cm wide. Elevate and retract it with a mosquito clamp.
On the undersurface of the retinaculum adherent tenosynovium is frequently seen.
Visible deep to the opening should be the tenosynovium-covered digital flexor tendons and median nerve.
Pass small and large hamate finders down the carpal canal in an antegrade manner to evaluate the space and the location of the hamate (TECH FIG 3).
Palpate the tip of the instruments as they become subcutaneous distal to the distal edge of the TCL at the Kaplan cardinal line.
Make sure these instruments are not palpable subcutaneously in the proximal third of the palm, which would indicate incorrect placement superficial to the TCL and carpal canal and probably within the canal of Guyon.
Use the tenosynovial elevator and pass it proximally and distally a dozen times along the axis of the fourth ray to dissect tenosynovium from the undersurface of the TCL.
A “washerboard effect” should be felt with this maneuver.
TECH FIG 3 • A. The key landmarks for ECTR are shown here: FCR, PL, FCU. The transverse incision is inscribed. B. The skin incision has been made and the fascia has also been incised. (Copyright Ekkehard Bonatz, MD.)
Device Insertion
Introduce the assembled Agee endoscopic carpal tunnel release (ECTR) device into the carpal canal, with the scope directed palmarly.
The undersurface of the TCL with its characteristic transverse striations is visible.
While viewing the monitor, advance the instrument until the distal edge of the TCL is identified.
The distal edge is noted by a transition from the white, transverse fibers of the TCL to the yellow amorphous midpalmar fat, which often contains visible vessels and nerves.
Using your nondominant hand on the palm, perform a ballottement maneuver to help distinguish the transition between the midpalmar fat and the distal edge of the TCL while viewing the signal from the endoscope within the carpal canal on the monitor.
In the palm, palpate the tip of the ECTR device as it emerges into the subcutaneous space just distal to the TCL. Drive the device with the other dominant hand (TECH FIG 4).
The transillumination pattern from the ECTR device light source changes from underneath the TCL to the midpalmar fat.
Transverse Carpal Ligament Release
Elevate the blade and withdraw the device slowly, cutting the TCL from distal to proximal. Keep the device pressed up against the undersurface of the TCL so no structures come between the blade and the TCL; cut only the TCL (TECH FIG 5).
Cut only when visualization is excellent. If needed, withdraw the device and redefine the undersurface of the TCL in the manner detailed above until visualization is ideal.
TECH FIG 4 • The surgeon's nondominant index and long digits palpate the tip of the endoscopic carpal tunnel release device as it emerges into the subcutaneous space just distal to the transverse carpal tunnel ligament. The transillumination pattern from the device light source changes from underneath the transverse carpal ligament to the midpalmar fat.
Repeat the above step as needed until there is a full release of the TCL, with good separation of radial and ulnar leaflets from proximal to distal.
With a full release, it should not be possible to visualize the radial and ulnar leaflets simultaneously with the ECTR device up against the palmar tissues. Also, the ECTR device should be able to be placed within the trough between the radial and ulnar leaflets so neither leaflet is visible, just the fascia overlying the thenar muscles and the subcutaneous space.
TECH FIG 5 • After careful identification of the distal edge of the transverse carpal ligament (A), the ligament is released from distal to proximal (B). C. This is the start of the TCL division using the Agee device. The blade is elevated (center) and is shown starting to divide the TCL from distal to proximal. The median nerve is just seen radial to the blade. (Copyright Ekkehard Bonatz, MD.)
After full TCL release, withdraw the ECTR device.
Confirm increased volume of the carpal canal by reintroducing the hamate finders down the carpal canal.
Divide the proximal antebrachial fascia with long tenotomy scissors under direct vision.
Adson forceps help to deliver the tissue for cutting.
The incision is closed and a soft dressing applied.
If you cannot safely visualize the structures with the ECTR device, conversion to a two-incision or open CTR method is strongly suggested.
TWO-INCISION ENDOSCOPIC CARPAL TUNNEL RELEASE (CHOW TECHNIQUE)
Make the proximal incision and create the distally based U-shaped flap of antebrachial fascia in the manner described for the single-incision ECTR technique.
Introduce a clamp, elevator, or trocar under the TCL.
Advance the instrument until it is palpable in the palm subcutaneously distal to the TCL.
Make a second small incision to expose the tip of the instrument, usually at the junction of the middle and proximal thirds of the palm.
Take care to identify the superficial arch, common digital nerves, and fibers of the distal TCL in the area.
A variety of techniques (open or scope-assisted) can be used at this point, including slotted trocars for two-incision endoscopic release, or use of a mini-meniscotome blade or scissor or other cutting instrument with a retractor or elevator to protect the median nerve and flexor tendons from the TCL cutting instrument.
The complete distal TCL division can be ascertained by direct visualization, also taking note that the vessels and nerves have not been injured.
A pitfall of the two incision techniques, aside from the potential injury to the palmar arterial arch and/or the branches of median or ulnar nerve, is incomplete release of the TCL distally. Therefore, inspection of the operative site with magnifying loupes at the distal incision is important.
REVISION RELEASE FOR RECURRENT OR RESIDUAL CARPAL TUNNEL SYNDROME
If the recurrent CTS is due to prior incomplete release, revision surgery can be attempted using an ECTR technique; otherwise, open release is indicated (TECH FIG. 6A,B).
Use a generous skin incision, incorporating previous incisions as needed.
Perform the release using a similar technique to that described for primary open CTR.
Scarring often requires scalpel dissection, and separation of superficial tissues from the TCL is difficult.
Carefully separate the TCL (in the area of its previous division) from the underlying median nerve.
Dense scarring of the median nerve to the TCL is expected and will place the nerve in jeopardy during this exposure.
Completely release the TCL and the scarred median nerve, taking great care to protect the median nerve motor branch.
Use an operating microscope to inspect the median nerve for signs of damage or scarring.
TECH FIG 6 • A, B. Revision of prior endoscopic carpal tunnel release with open technique. C. Revision carpal tunnel release with NeuraGen tube around scarred branch of median nerve.
An external epineurotomy to expose the bands of Fontana on the surface fascicles of the median nerve is recommended in the case of significant nerve scarring.
If there is minimal nerve scarring or damage, the wound can be closed in the usual manner.
If nerve injury is dramatic and rescarring seems likely, cover the damaged nerve with a hypothenar fat pad flap, palmaris brevis muscle flap, vein wrapping, or neural conduit (TECH FIG 6C).
Create a TCL flap through Z-lengthening and tissue rearrangement if flexor tendon prolapse or palmar migration of the median nerve seems likely.
Hypothenar Fat Pad
When revision CTR reveals median nerve scarring, surgical tactics to improve the environment around the nerve after the neurolysis to reduce rescarring are attractive. Strickland12 has described this technique in several publications. The tissue is readily available and has been shown to be of benefit. In a 1996 article,12 62 patients were reviewed. Results were good based on preand postoperative patient satisfaction scores, with only three transient minor complications.
Dissect the fat pad to the level of the ulnar nerve and artery, and advance the radial edge to cover the median nerve.
Sew this edge to the radial flap of the TCL.
Palmaris Brevis Flap
Rose et al described this flap in 1991.
Expose the thin palmaris brevis muscle on the ulnar side of the CTR incision.
Divide it from its insertion in the subcutaneous space and transpose or rotate it into a position covering the median nerve.
POSTOPERATIVE CARE
Traditionally, CTR patients were managed in wrist splints for 1 to 3 weeks after surgery. However, multiple studies have shown that faster recovery occurs when the wrist is not splinted postoperatively.
Temporary postoperative splints may still be indicated in specific clinical scenarios, such as open revision surgery.
Hand therapy is helpful in the postoperative period, especially if the patient is having difficulty with full digital active and passive motion.
Grip and pinch strength, subjective symptom measures, and functional evaluations are helpful to manage the postoperative course.
Some patients have prolonged periods of tenderness under the TCL, or pillar pain on the thenar or hypothenar side of the proximal palm, and require extended hand therapy and periods of time to gradually increase hand strength and endurance for hand activities.
OUTCOMES
There should be greater than 95% good or excellent results.14 This randomized, double-blinded multicenter study compared open and single portal endoscopic CTR and showed statistically significant improvements in the endoscopic group between 6 weeks and 3 months postoperatively in terms of pain and hand strength compared to that of the open group, and equivalent good results in both groups at 1 year.
Stutzetal13 reported on a retrospective series of 200 patients who underwent a secondary exploration during a 26-month period at a single institution for persistent or recurrent CTS symptoms after CTR. There were 108 cases of incomplete release of the TCL. Twelve patients had evidence of median nerve laceration during the index procedure. Forty-six patients had scarring of the nerve to surrounding tissues. In 13 patients the cause of their problem could not be determined.
Varitimidisetal15 reviewed 22 patients (24 wrists) who underwent revision open CTR after an initial ECTR and who had persistent CTS. Twenty-two patients had incomplete TCL release. One patient had a partial and another a complete median nerve transection. One patient had a Guyon canal release instead of a CTR. Twenty patients returned to work, 15 at the previous level and 5 at lighter duty. The two patients with nerve injuries continued to do poorly, one requiring a vein-wrapping procedure.
COMPLICATIONS
Incomplete TCL release
Median nerve scarring or damage (especially the common digital nerve to the third web space and the thenar motor branch)
Ulnar nerve or artery damage
Sympathetically mediated pain syndrome
Damage to palmar arterial arch
REFERENCES
1. Ablove RH, Peimer CA, Diao E, et al. Morphologic changes following endoscopic and two-portal subcutaneous carpal tunnel release. J Hand Surg Am 1994;19A:821–826.
2. Diao E, Shao F, Liebenberg E, et al. Carpal tunnel pressure alters median nerve function in a dose-dependent manner: a rabbit model for carpal tunnel syndrome. J Orthop Res 2005;23:218–223.
3. Gelberman RH, Pfeffer GB, Galbraith RT, et al. Results of treatment of severe carpal-tunnel syndrome without internal neurolysis of the median nerve. J Bone Joint Surg Am 1987;69A:896–903.
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7. Lundborg G, Rydevik B. Effects of stretching the tibial nerve of the rabbit: a preliminary study of the intraneural circulation and the barrier function of the perineurium. J Bone Joint Surg Br 1973;55B:390–401.
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10. Rhoades CE, Mowery CA, Gelberman RH. Results of internal neurolysis of the median nerve for severe carpal tunnel syndrome. J Bone Joint Surg Am 1985;67A:253–256.
11. Rydevik B, Lundborg G, Bagge U. Effects of graded compression on intraneural blood flow: an in vivo study on rabbit tibial nerve. J Hand Surg Am 1981;6A:3–12.
12. Strickland JW, Idler RS, Lourie GM, et al. The hypothenar fat pad flap for management of recalcitrant carpal tunnel syndrome. J Hand Surg Am 1996;21A:840–848.
13. Stutz N, Gohritz A, Van Schoonhoven J, et al. Revision surgery after carpal tunnel release: analysis of the pathology in 200 cases during a 2-year period. J Hand Surg Br 2006;31B:68–71.
14. Trumble TE, Diao E, Abrams RA, et al. Single-portal endoscopic carpal tunnel release compared with open release: a prospective, randomized trial. J Bone Joint Surg Am 2002;84A:1107–1115.
15. Varitimidis SE, Herndon JH, Sotereanos DG. Failed endoscopic carpal tunnel release: operative findings and results of open revision surgery. J Hand Surg Br 1999;24B:465–467.
16. Weiss AP, Sachar K, Gendreau M. Conservative management of carpal tunnel syndrome: a reexamination of steroid injection and splinting. J Hand Surg Am 1994;19A:410–415.