Diagnosis: Carpal Tunnel

Patients predominantly complain of paresthesias or numbness, or both, in the area supplied by the median nerve, at the volar aspect of the thumb, index, long, and radial side of ring fingers. Patients frequently note nocturnal symptoms. The paresthesias may be aggravated on wrist movement or prolonged wrist posture in a bent position, such as when holding a baby or driving a car. As the disease progresses, patients may describe weakness of grasp and pinch and, later, atrophy of the thenar muscle ( Fig. 1 ). Thumb opposition becomes weak because of weakness of the opponens pollicis. Median nerve–innervated lumbricals may also become atrophic. Because all of these clinical manifestations are also seen with proximal median nerve compression, clinically, attention should be paid not to mistakenly diagnose nerve compression caused by cervical disk herniation, thoracic outlet structures, and median nerve compression in the forearm and at the elbow as CTS.

Median nerve compression in the left wrist with thenar muscle atrophy. Arrows indicate the thenar eminence.

The Phalen test (wrist flexion test) or reverse Phalen test is frequently positive. The Tinel sign (ie, nerve percussion test) is also frequently positive. Other tests can be useful, including the wrist compression test, tourniquet test, closed fist test, flick sign, and hand elevation test. The most sensitive test is the Phalen test, whereas Tinel sign is the most specific yet the least sensitive. The positive rate of Tinel sign was 81.9%, but that of Phalen test was 53% in the authors’ patients. Popinchalk and Schaffer reviewed the literature and reported that the sensitivity and specificity of Phalen test are 46% to 80% and 51% to 91%, respectively, and of the Tinel sign 28% to 73% and 44% to 95%, respectively. The carpal compression test was more specific (90%) and more sensitive (87%) than the Phalen test and the Tinel sign. The diagnosis is primarily a clinical one based on a combination of symptoms and characteristic physical examination findings.

In 2006, Graham and colleagues performed a literature review that yielded 6 clinical criteria (nocturnal numbness, median nerve paresthesia, thenar muscle atrophy, positive Phalen test, positive Tinel test, and loss of 2-point discrimination [2PD]) that proved to correlate positively with a diagnosis of CTS. They stated that the value added by electrodiagnostic testing was minimal. Electrodiagnostic testing, however, is helpful in confirming the diagnosis, assessing the degree of nerve compression to predict the rate of recovery, differentiating from other clinical conditions, and eliminating coexisting lesions. Similar to all other diagnostic tests, false-positive and false-negative results occur. The false-negative rate of nerve conduction studies has been reported to be between 16% and 34%. No significant relationships exist between nerve conduction study results, symptoms, and function in patients with CTS.

MRI generates images of high soft tissue contrast in the carpal tunnel and is a sensitive diagnostic tool but it is rarely used, because clinical tests are sufficient for making the diagnosis. Ultrasound is easy to perform and used as a first-line tool to assist diagnosis. Injection of local anesthetic into the carpal tunnel can help eliminate the possibility of other syndromes, especially cervical disk or thoracic outlet syndrome.

Treatment: Carpal Tunnel

Nonoperative treatment options range from wrist splinting to corticosteroid injections. If the symptoms are mild and there is no thenar muscle atrophy, splinting the wrist in neutral or serial steroid injections frequently decreases symptoms, at least transiently. Corticosteroid injection is used by some surgeons. A few studies show that it improved the symptoms 1 month after injection, but 2 local injections do not have added benefit compared with 1 injection. A recent study showed that 30 of the 120 patients (25%) had a good outcome with a single injection, 11 patients (9%) needed a second injection, and 5 patients (4%) needed a third injection. Of patients with an initial good treatment response, 28 (52%) had a good outcome after 1 year compared with 18 (27%) who had an initially moderate or no response to treatment. One-third of patients had a long-term beneficial effect from corticosteroid injection, mostly when they had a good initial response. If signs and symptoms persist or progress after conservative treatment, especially if thenar atrophy develops, surgical decompression of the median nerve is indicated. For acute CTS after trauma, such as carpal bone dislocation, crush injury, or forearm compartment syndrome, immediate surgical release is always indicated.

Classically, the open technique is a standard practice. Under direct visualization through a large incision, the transverse carpal ligament is divided and the nerve decompressed. Over the past 20 years, surgical releases with smaller incisions (termed limited open or mini-open ) were popularized to minimize surgical morbidity and expedite return to work. Currently, limited open carpal tunnel release (OCTR) is a common practice ( Fig. 2 A ). Fewer surgeons now use tradition carpal tunnel release through a large incision.

( A ) OCTR with a mini-incision. ( B ) The incision site of single-portal endoscopic release. ( C ) The portals for making a 2-portal endoscopic release.

In 1989, Okutsu and colleagues described an ECTR technique using a single small incision 3 cm proximal to the wrist crease. They released the transverse carpal ligament longitudinally under endoscopic visualization using a hook knife. Chow introduced a technique using 2 skin incisions, with 1 incision just proximal to the wrist flexion crease ulnar to the palmaris longus tendon, and a second longitudinal incision 4 to 5 mm distal to the distal edge of the transverse carpal ligament. In 1993, Agee and colleagues modified this into what is called the Agee technique by using a single incision but introduced a trigger-deployed blade system to improve safety of the procedure.

Endoscopic techniques avoid midpalm incisions, preserving the palmar musculature and skin (see Fig. 2 B, C). Their shorter incisions also mean less scar tenderness and pillar pain. The disadvantages of ECTR are its learning curve and higher cost.

Multiple randomized controlled trials showed limited open procedure and the endoscopic approach to have similar rates of complications and parallel functional recovery. A 2004 meta-analysis of 13 randomized clinical trials by Thoma and colleagues compared OCTR with ECTR and analyzed data pooled from 3 studies without a significant difference observed between the 2 techniques. Immediate postoperative advantages of the endoscopic technique in grip strength and pain relief disappeared after 12 weeks. In a recent study, 52 patients with bilateral CTS had 1 hand randomized to undergo endoscopic release and the other to undergo mini-incision release. Despite similar improvements in subjective scores after endoscopic and open techniques at 3 months postoperatively, a majority of patients preferred the endoscopic technique because of the smaller scar and less pillar pain. Meta-analysis performed on 3 studies slightly favors ECTR in terms of symptom severity scores and functional scores at 12 weeks. Atroshi and colleagues compared the outcome of carpal tunnel release with 2 different techniques in 128 patients, showing carpal tunnel release with endoscopic and midpalm mini-incision having no difference in improvement in symptoms and hand-related disability over a 5-year follow-up. Recent reports about outcomes of these methods are detailed in Table 2 .

In the authors’ practice, the mini-OCTR is preferred. A 2- to 3-cm incision is made directly above the transverse carpal ligament. Such an incision usually is sufficient to expose and release the ligament. Care is taken to preserve any median nerve branches over or through the transverse carpal ligament. The incision is closed with absorbable suture and immediate postoperative motion is encouraged. The authors agree that both mini-open and endoscopic approaches provide an excellent outcome. Therefore, the decision as to which technique should be performed should be left up to patient and surgeon, depending on training and experience. The authors’ colleagues are split into those who perform ECTR and those who perform limited OCTR. No one continues with the conventional large open incisions for carpal tunnel release. In the authors’ experience, the surgical times for ECTR and limited OCTR are similar and ECTR is safe if a surgeon confirms the structure of transverse carpal ligament before cutting. In those cases of severe symptom, severe muscle atrophy, and suspicion of other causes of compression, OCTR is preferred by all surgeons in the authors’ group.

Recently, ultrasound is used in the treatment of CTS. McShane and colleagues and Rojo-Manaute and colleagues reported the new technique of sonographically guided percutaneous needle release of the carpal tunnel and ultraminimally invasive carpal tunnel release, respectively. New devices have also been developed in recent years. McCormack and colleagues developed the MANOS device (Thayer Intellectual Property, Inc., San Francisco, CA) to divide the transverse carpal ligament using wrist and palm skin punctures. Preliminary results suggest this device as safe and effective. Pereira and colleagues introduced a modified Tsai 2-portal technique, creating a “fixed surgical tunnel” for decompression and a custom-made plastic tube used to check the quality of the release. Fechner and colleagues developed a new guiding cannula with raised borders to prevent accidental injury to the median nerve. Ip and colleagues used a new single-portal technique with instruments originally designed for endoscopic cubital tunnel release and reported no neurovascular or tendon injuries.

Complications in Carpal Tunnel

The complications of carpal tunnel release include infection, hypertrophic scar, scar tenderness, neuropraxias, and injury to nerve, artery, and tendon. Benson and colleagues reviewed 80 publications from 1966 through 2001. They found complication rates for carpal tunnel release, through either an endoscopic or open approach, to be very low. The incidence of structural damage to nerves, arteries, or tendons is 0.49% during OCTR and 0.19% during ECTR. Major nerve injuries were seen in 0.13% for ECTR and 0.10% for OCTR patients. ECTR had a rate of 0.03% for digital nerve injuries and 0.39% for OCTR. Arterial arch injuries occurred in 0.02% of the ECTR patients, with no cases in the OCTR patients. The most striking difference after open or endoscopic approach was in the rate of transient neuropraxias, which were reported in 1.45% of ECTR cases compared with 0.25% of OCTR cases. OCTR had more wound problems, such as infection, hypertrophic scar, and scar tenderness. The American Academy of Orthopaedic Surgeons report found 8 studies regarding wound-related complications, with 7 of 8 favoring ECTR, but the report failed to show a statistical difference in general complications or infection.

Pillar pain (the pain around the surgical incision of the carpal tunnel area) is relatively frequent after surgery ( Fig. 3 ). Its cause remains unknown although neurogenic inflammation is a possible cause. In the authors’ department, 30 cases after OCTR were followed for 10 to 30 months between December 2006 and October 2008; 11 cases of numbness and 8 cases of pillar pain around the incision were found. The analysis showed the length of incision positively correlated with the area of pillar pain; the type of approach (distal-mini or proximal-mini incisions) had no correlation with the presence of pillar pain. Cellocco and colleagues reported that mini-incision carpal tunnel release (<2 cm incision) showed advantages over standard technique (3–4 cm incision) in pillar pain. The treatment of pillar pain includes rest, bracing, and physiotherapy; however, all have uncertain effects and the pain can last quite long.

The complication of pillar pain after carpal tunnel release. The area of pillar pain ( blue dots ) after limited open technique.

Prognosis and Recovery: Carpal Tunnel Release

Louie and colleagues followed 113 cases of OCTR for an average of 13 years and concluded that a majority of patients are satisfied and free of symptoms. In a prospective study of Tan and Tan of 74 cases, 72% showed complete symptomatic relief, 74% showed improvement in function, and 66% showed gain in grip strength; overall, 82% were very satisfied with the results at 6 months after surgery. Additionally, they found older patients and patients with weakness in muscle power had poorer outcomes. Higher preoperative symptom severity and functional severity scores were also associated with less improvement in symptoms and function, respectively. Zyluk and Puchalski reported patients older than 60 years showed less improvement in total grip strength of the hand. Cowan and colleagues found that job type is the most important determinant of return to full work after surgery, but that psychological factors, such as patient expectations, catastrophic thinking, and anxiety in response to pain, also play a role. Follmar and colleagues reported that patients receiving narcotic pain medication chronically for nonhand pain experienced a longer recovery period but ultimately achieved the same outcomes as patients without chronic pain.

The authors examined recovery of pinch strength in 31 patients having OCTR between 2008 and 2011. The pinch strength of all the cases did not return to normal 1 to 3 years after surgery; the recovery level of the pinch strength correlated significantly with the severity of muscle atrophy and severity and duration of compression before surgery. Subjective scores, however, such as Disabilities of the Arm, Shoulder, and Hand (DASH) scores, do not show patient dissatisfaction. All patients satisfied with the surgery and had remarkable improvement in function. After carpal tunnel release, subtle impairment of nerve and intrinsic muscle function can persist for years postoperatively.

Revision Surgery for Carpal Tunnel Release

Carpal tunnel release is one of the most frequently performed hand operations. Persistent, recurrent, or new symptoms after carpal tunnel release may require revision surgery. Revision surgery is indicated if there is only temporary or partial improvement in the symptoms or when classic carpal tunnel symptoms persist postoperatively. The surgical approach is to extend the previous incision into normal tissue to allow proximal or distal identification of the median nerve. The transverse carpal ligament is explored, and if the transverse fibers are remaining or reconstituted flexor retinaculum, these structures should be divided. Scar formation is frequent and can be severe and compressive to the nerve. A neurolysis may be indicated in these cases. Several procedures may help protect the nerve from recurrent scar, including vascularized soft tissue coverage (hypothenar fat pad flaps and synovial flaps) or autologous (vein grafts) or synthetic nerve wraps. Strickland and colleagues reported excellent results in 58 patients with 62 wrists who underwent revision carpal tunnel surgery using the hypothenar fat pad flap, with 37 of the 43 patients returning to their presurgery employment. Tollestrup and colleagues reported hypothenar fat pad flap can provide protective covering and a gliding surface for the median nerve. Chrysopoulo and colleagues modified this technique, so that the hypothenar fat pad transposition flap provides a reliable source of vascularized local tissue. Synovial flaps are frequently used. Vein wrapping and synthetic nerve conduit wrapping are additional methods for preventing scarring of the nerve.

Pronator Syndrome

From the elbow down to the forearm, the median nerve is located anterolateral to the brachial artery, passes deep to the ligament of Struthers (if present), and continues into the antecubital region. The ligament of Struthers (present in approximately 1% of the population) is an anatomic variant that extends from a small, vestigial supracondylar process on the anteromedial diaphysis of the humerus to the medial epicondyle.

Pronator syndrome is the compression of the median nerve as it passes between the 2 heads of the pronator teres muscle. Pronator syndrome is characterized by vague volar forearm pain, with median nerve paresthesias and minimal motor findings. Despite its name, the nerve can also be compressed beneath the proximal arch of the flexor digitorum superficialis (FDS), bicipital aponeurosis, the Struthers ligament, or an accessory head of the flexor pollicis longus (FPL) (ie, the Gantzer muscle).

Anterior Interosseous Nerve Syndrome

The AIN may be compressed by the tendinous origin of the deep head of the pronator teres, other variant tendinous structures, fibrous bands, or collateral vessels. Spontaneous and traumatic causes have been described.

Diagnosis: Anterior interosseous nerve

AIN syndrome is manifested as vague forearm pain and spontaneous loss of function of any or all of the AIN-innervated muscles. AIN innervates forearm flexor muscles except those innervated by the ulnar nerve. Therefore, weakness of power of the innervated muscles is common. Initial complaints include forearm pain and clumsiness with fine motor skills, such as writing and pinching. The FDP function of the middle finger may be preserved because of cross-innervation by the ulnar nerve. Because the AIN does not innervate the skin, the syndrome is not associated with any loss of sensibility. A characteristic finding in physical examination is a patient’s inability to make a rounded O between the thumb and index finger when asked by an examiner to flex the thumb interphalangeal joint and index finger distal interphalangeal joint ( Fig. 4 ).

( A ) A hand with normal AIN function. ( B ) With the AIN palsy, the hand is not able to complete tip pinch by making an O between the thumb and index finger. Instead, the tip pinch is compensated by extension of the interphalangeal joints and pulp pinch.

AIN syndrome does not have a clear cause. It is most commonly attributed to a postinfectious neuritis or a compression of the AIN after it branches from the median nerve under the leading edge of the FDS origin. In most cases, it is the result of neuritis rather than being a mechanical compression. Electrodiagnostic studies serve an important role in the diagnosis because they can support the diagnosis and assess the severity of the neuropathy. Imaging studies, such as MRI, are not commonly used in the diagnosis of AIN syndrome.

Parsonage-Turner syndrome (brachial neuritis) should be considered in the differential diagnosis in patients with AIN syndrome. These patients typically have a history of severe pain in the shoulder and arm with weakness in shoulder and biceps muscles for several weeks after a viral infection, but those with AIN syndrome do not. In a neuritis involving the AIN, spontaneous recovery usually occurs, although sometimes up to 1 year may be needed. In patients with a spontaneous AIN palsy and no electrodiagnostic evidence of reinnervation after 6 months, surgeons should consider nerve exploration or nerve transfer (or both). In patients with concomitant nerve compression, local decompression in patients with Parsonage-Turner syndrome may accelerate recovery.

Diagnosis: Cubital Tunnel

In the early phases of the disease, patients complain of medial elbow pain and paresthesias or numbness in the small finger and ulnar aspect of the ring finger. The disease later evolves to intrinsic muscle weakness and later atrophy. Patients notice weakness with grip and/or pinch strength or hand clumsiness. Increasing degrees of elbow flexion are provocative, in that they cause dynamic changes to the cross-sectional area and volume, affecting intra- and extraneural pressures. Longstanding disease can lead to irreversible intrinsic muscle atrophy. The extent of ulnar nerve dysfunction is divided into 3 categories by McGowan and modified by Dellon : (1) mild nerve dysfunction implies intermittent paresthesias and subjective weakness; (2) moderate dysfunction presents with intermittent paresthesias and measurable weakness; and (3) severe dysfunction is characterized by persistent paresthesias and measurable weakness.

Clawing of the small and ring fingers is found in advanced stages ( Fig. 5 ). Atrophy of the intrinsic muscles of the hand and, in particular, the first dorsal interosseous muscle is common (see Fig. 5 ). The carrying angle may give a clue as to tracing back to prior trauma that increases the carrying angle and causes excess traction on the ulnar nerve. Careful sensory testing, such as touch 2PD testing, can help quantify early changes in sensibility. In the early stages of nerve compression, provocative testing (Tinel sign and elbow flexion-compression test) may be the only positive signs, followed by alteration of threshold testing (vibration and Semmes-Weinstein monofilaments). In the later stages, 2PD becomes abnormal. Motor strength should be assessed in all of the major upper extremity muscle groups, with particular attention paid to the intrinsic muscles of the hand and the deep flexors of the ring and small fingers.

The symptom of ulnar nerve compression at the elbow. ( A ) Atrophy of the intrinsic muscles of the right hand. ( B ) Clawing of the small and ring fingers in the right hand.

Two of the most frequently used provocative tests are the Tinel test along the course of the ulnar nerve and the elbow flexion-compression test. In 2008, Cheng and colleagues described the scratch collapse test ( Fig. 6 ). Sensitivity for this test was reported to be 69% compared with 54% and 46% for the Tinel test and the elbow flexion-compression test, respectively. The Tinel test, however, has the highest negative predictive value (98%) among all tests for cubital tunnel syndrome. These examination findings can be used in combination to best diagnose cubital tunnel syndrome.

The scratch collapse test. ( A ) With the elbow flexed, the patient can perform resisted bilateral shoulder external rotation as the examiner applies resistance to the motion to the forearm before scratch. ( B ) The examiner then scratches or swipes the fingertips lightly over the course of the affected ulnar nerve at the suspected compression site. ( C ) Then resisted shoulder external rotation was immediately repeated. When the patient temporarily unable to resist the internal rotation force applied by the examiner, being pushed easily to internal rotation, the test is positive.

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