Conservative Treatment
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Complete clinical evaluation for the entire upper extremity
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Decrease carpal tunnel pressure/Improve local neural circulation
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Proper orthosis geometry
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Wrist position 2 degrees of flexion, 3 degrees of ulnar deviation
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Lumbrical block if Berger’s test is positive or flexor synovitis present
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Thumb kinetic chain included in neutral in presence of associated carpometacarpal (CMC) joint osteoarthritis
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Full night resting pan orthosis for exquisite nocturnal pain
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Activity adjustment to minimize effects of posture, tendon load, lumbrical incursion, and flexor synovitis or tendinitis
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Avoid repetitive gripping, pinching, or strengthening
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Refer for electrodiagnostic testing or surgical consult if any atrophy of the opponens muscle, Semmes–Weinstein monofilaments above 3.61 for long finger, constant daytime paresthesia, no improvement in nocturnal pain, or provocative testing after a week of nocturnal orthotic use.
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Therapy inappropriate beyond a few sessions unless other tissues are being treated.
Postoperative Treatment
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Wrist control positioning to decrease incisional tension and to prevent over use
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Proper wound care to promote uneventful healing
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Suture removal at 15 to 17 days after surgery when tensile strength adequate to prevent wound dehiscence
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One-inch Micropore paper tape (3M) to minimize skin–incision line tension for 4 to 6 weeks full time; longitudinal to incision
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Gentle tendon and nerve gliding, allow tissues to strengthen slowly, avoid activity for repetitive grip. No value in testing grip strength
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Modalities only indicated if scar is painful or with flexor inflammation other than functional electrical stimulation to promote flexor tendon glide
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Short-term therapy is usually sufficient, but in some cases not necessary
It is interesting to note that this most common of all treated disorders in the upper extremity (which experience teaches that with a knowledgeable therapist and skilled surgeon is, in most cases, easy to diagnose, operate, and bring to functional recovery) is the subject of so much controversy and research. With this perspective in mind, a practical approach to the therapist’s management of carpal tunnel syndrome (CTS) is suggested based on literature review and my clinical experience.
Despite its frequency, many issues concerning this symptom complex are in question. Controversy exists in the literature regarding cause, techniques of evaluation, results with conservative care, technique of surgery, and the value of postoperative care.
A passionate debate rages concerning the effect of occupation on CTS and other injuries that may be a result of cumulative-type injuries, with many questions concerning this common and debilitating problem having no clear-cut answer.
Several updated reviews of anatomy, pathophysiology, diagnosis with clinical and electrodiagnostic testing, conservative and surgical treatment, and evidence for the same, are suggested for the interested reader.
The introduction of managed care, with changes in referral patterns to therapy, has increased the number of inappropriate referrals and the number of patients referred with either no diagnosis or incorrect diagnosis by the primary care physician or a physician from another specialty area. This increases the demands for clinical evaluation and treatment skills for therapists. In today’s climate, upper extremity therapists must be able to perform a clinical examination equal to that of a hand surgeon in order to provide appropriate treatment and suitable recommendations for the patient. In addition the therapist must be able to provide acceptable outcomes within treatment parameters set by third-party payers. These pressures can best be met by correct diagnosis and treatment procedures that are based on current medical science.
Conservative mismanagement of CTS by the therapist is most commonly related to the inability to diagnose it or to identify associated problems that have been missed or misdiagnosed, to inappropriate orthosis geometry, and to exercise regimens that increase rather than decrease carpal tunnel pressure (CTP).
The purpose of this chapter is not to review the obvious or to repeat what is elsewhere in this text, but to focus the attention of the hand clinician and physicians from other specialty areas on the variables that affect intratunnel pressures in the carpal canal, which can be influenced with conservative therapeutic management, and to offer a perspective from clinical experience and literature review on therapeutic interventions that have some or no benefit for this peripheral nerve compression. A few points are made on postoperative management, which may prevent complications and decrease the expense of treatment and lost time from work. Chapter 48 covers surgical management of CTS.
Treatment for CTS includes both conservative and operative interventions, with the goal being to decrease pressure on the median nerve so as to improve neural circulation and decrease symptoms. Conservative options have some support for short-term symptom relief if treated early, but ultimately surgical intervention is necessary for complete resolution of symptoms in most cases.
Conservative intervention by the hand therapist might have potential influence on pressures in the carpal tunnel (in cases treated early) by altering postures, tendon load, muscle activity, and external forces, through activity modification and orthotic positioning. Flexor tendon inflammation, one probable cause of CTS, can be decreased with medication, changes in load to the flexor system, and a lumbrical positional orthosis Modalities and nerve gliding as conservative treatments are without strong support and are discussed in the next section.
Clinical Examination
Early and accurate diagnosis is important for providing the correct or appropriate conservative treatment, for identifying the correct surgical candidate, and for minimizing potential disability. The duration of symptoms is a key determinant in estimating the predictive factors of recovery and postsurgical outcomes. Conservative treatment is of most value when instituted in the earliest stages of compression. It is critical to identify and treat this compression syndrome before axonal loss occurs in the median nerve, and equally important to consider the pathophysiologic changes occurring with the different stages of nerve compression when interpreting diagnostic test results and predicting response to conservative management.
My experience is that patients referred to hand therapy by the primary care physician, and even the neurologist, are often misdiagnosed with CTS for complaints of “hand pain,” making a complete clinical evaluation of the upper extremity by the therapist critical to the delivery of appropriate care. Symptoms associated with basilar thumb arthritis, flexor tendon inflammation at the A1 pulley or carpal tunnel level, or de Quervain’s tendinitis or tendinosis may be the origin of the hand pain. The clinical evaluation should include a directed history to identify any systemic or metabolic problems that could be contributory, assessment of mechanical forces imposed on the extremity in the course of work or avocational activity, a review of symptoms, and treatment to date. The initial interview usually includes asking the patient questions about pain, paresthesias, and motor weakness. Patient complaints of pain, “numbness and tingling” in the median nerve distribution, and complaints of hand swelling are often easy to diagnose after a few provocative tests. Complaints of increased symptoms at night are a good diagnostic predictor for CTS. The initial stages of CTS usually occur at night as revealed by serial overnight recordings of intracarpal tunnel pressure in patients suffering from CTS. Tissue fluid in the arms is redistributed at night when there is no active muscle pump, and both intraneural blood pressure and systemic blood pressure are decreased during sleep. Wrist flexion position during sleep may also contribute to median nerve ischemia.
Author’s Approach
My approach in a busy clinical practice is to follow history taking with a clinical examination beginning with Semmes–Weinstein monofilament testing (Semmes–Weinstein Pressure Aesthesiometer Kit, North Coast Medical, Campbell, CA) to determine light touch and deep pressure thresholds of both median and ulnar nerve distribution. Testing is performed both with the upper extremity joints in neutral position (especially the forearm) and also following Phalen’s testing, which positions the wrist in flexion for 60 seconds. A quick screen includes Tinel’s test (percussion over the carpal tunnel), lumbrical incursion, or the Berger test (the patient holds a full fist position with the wrist at neutral for 30 to 40 seconds, which creates lumbrical incursion into the carpal canal), Durkan’s test (external pressure applied over the transverse carpal ligament using a calibrated piston (Gorge Medical, Hood River, Oregon), or more practically, with digital pressure, and observation of soft edema.
Tests specific to CTS are then supplemented with a screen including provocative tests for proximal compression (distal to proximal) in the fibrous bridge between the heads of the flexor digitorum superficialis (FDS), between the humeral and ulnar heads of the pronator teres, beneath the lacertus fibrosis, thoracic outlet, and for C6 through C8 radiculopathy. The various sites of median nerve compression—brachialis muscle, Struthers’ ligament, the bicipital aponeurosis, pronator teres, FDS, the accessory head of the flexor pollicis longus (FPL), and vascular structures—are recently reviewed. As previously noted a quick screen is performed for commonly seen associated problems of first CMC arthritis, de Quervain’s tendinitis, stenosing tenosynovitis (trigger fingers), wrist or digital tendinitis, epicondylitis, or ulnar nerve compression.
I recommend (for the primary care physician) that a patient be sent for electrodiagnostic studies and surgical consult with symptoms of nocturnal pain, daytime paresthesia, positive provocative tests (Phalen’s, Tinel’s, Berger’s test, or paresthesia with sustained index-to-thumb pinch); middle finger Semmes–Weinstein readings of 3.61 or greater, and of course with any atrophy in the opponens pollicis muscle. These patients’ pain may be helped by treatment of associated tenosynovits, changes in activity level, and nocturnal positioning, but need release of the transverse carpal ligament to become asymptomatic.
Clinical Evaluation: Literature Review
Some authors conclude that there is little scientific evidence regarding the reliability and validity for comprehensive upper extremity clinical examination and that sensitivity and specificity vary greatly with comparison subjects within the various studies, but others have demonstrated the value of clinical diagnostic testing for CTS. * However, the existence of a gold standard for the evaluation of CTS is still in question.
* See references .
The American Academy of Orthopaedic Surgeons approved Evidence-Based Clinical Practice Guidelines on May 18, 2007, for the diagnosis of CTS with recommendations for diagnosis including patient history, physical examination (sensory testing, manual muscle testing, provocative testing), discriminatory tests for alternative diagnoses, and electrodiagnostic tests. The guidelines do not include MRI, computerized axial tomography, or pressure-specified sensorimotor devices in the wrist and hand (PSSD).Through meta-analysis the German Societies of Hand Surgery; Neurosurgery; Neurology; Orthopaedics; Clinical Neurophysiology and Functional Imaging; Plastic, Reconstructive and Aesthetic Surgery; and Surgery for Traumatology recommend similar guidelines for diagnosis, including an accurate history and clinical neurologic examination (including clinical tests) and electrophysiologic investigations (distal motor latency and sensory neurography). They regard radiography, MRI, and high-resolution ultrasonography as optional supplementary investigations.
Szabo and colleagues have concluded that if a patient has (in descending order for sensitivity) a positive Durkan’s test, abnormal sensibility with Semmes–Weinstein testing, an abnormal hand diagram (patient mapping of discomfort and quality of their symptoms), and nocturnal pain, the probability of a correct CTS is 0.86. If all four of these conditions are normal, the probability that the patient has CTS is 0.0068. They found that the addition of electrodiagnostic tests did not increase the diagnostic power of the four clinical tests. Their work is supported by others.
MacDermid determined in a systematic review of the properties of clinical tests for CTS that although 60 studies were reviewed in detail, many were of poor quality (mean quality score was 6.6 of 12, with only 15 of 60 obtaining a score of 8 or greater). The most frequently studied test was Phalen’s, with an overall estimate of 68% sensitivity and 73% specificity. Next was Tinel’s, with estimates of 50% and 77%, and then carpal compression, with estimates of 64% and 83% for sensitivity and specificity, respectively. Two-point discrimination and testing of atrophy or strength of the abductor pollicis brevis proved to be specific but not very sensitive.
Berger suggested that provocative testing to produce lumbrical incursion may be as sensitive and specific as Phalen’s test for CTS. The test is performed by asking the patient to make a fist with the wrist in the neutral position. The test is positive if pain and paresthesia occur within 30 to 40 seconds. A full fist results in approximately 3 cm of lumbrical muscle incursion into the carpal tunnel and can increase the carpal tunnel contents, possibly contributing to median nerve compression.
Other studies have introduced the complaint of subjective swelling of the affected hand as an important diagnostic and prognostic factor with CTS, and the distal metacarpal compression maneuver as being helpful in diagnosis and orthosis design. Goloborod’ko describes a provocative test in which the examiner uses his or her fingers to simultaneously exert dorsal pressure on the first metacarpal and pisotriquetral complex and volar pressure on the lunate. The test is considered positive if symptoms of CTS are reproduced. The Hand Elevation Test has been found to be 88% sensitive and 98% specific and is recommended in conjunction with other known tests to assist in the diagnosis of CTS. Paresthesias with the first three provocative tests indicate a positive result.
The effect of tenosynovitis as both a contributing cause of CTS, and recurrent CTS, and its effect on commonly used clinical screening tests for CTS emphasizes the importance for the therapist of being able to both diagnose and treat the symptoms of flexor tendon inflammation as opposed to, or in conjunction with, CTS. A recent experimental study speculates that noninflammatory fibrosis of the subsynovial connective tissue is related to CTS and that a change in the subsynovial connective tissue volume or stiffness may be the source of median nerve compression. El Miedany and associates in a study of provocative testing in patients with confirmed forearm symptoms and tenosynovitis found that the sensitivity of Tinel’s, Phalen’s, reverse Phalen’s, and carpal tunnel compression tests was higher for the diagnosis of tenosynovitis than for the diagnosis of CTS (Tinel’s, 46% vs. 30%; Phalen’s, 92% vs. 47%; reverse Phalen’s, 75% vs. 42%; carpal tunnel compression test, 95% vs. 46%). Similarly, higher specificity of these tests was found with tenosynovitis than CTS. They suggested that these tests can be used as an indicator for medical management of the condition of tenosynovitis.
Although opinions and results vary from study to study, most agree that clinical evaluation of CTS has value in itself or as an adjunct to electrodiagnostic testing, and that early diagnosis is critical to good outcomes in the treatment of CTS.
Conservative Management: Literature Review and Implications for Treatment
Even with early detection, the value of conservative treatment has not been proven. Many patients experience relief of symptoms with orthotic positioning, local corticosteroid injection, anti-inflammatory medications, and changes in applied forces, † but eventually require surgical decompression of the median nerve. The efficacy of surgical decompression over conservative measures has been substantiated by a number of investigators, and has been demonstrated to be more cost-effective than orthotic positioning.
† See references .
Clinical research for conservative interventions for CTS include use of local and oral steroids, NSAIDs, positioning with orthoses, ultrasound, phonophoresis, iontophoresis, lidocaine patches, exercise therapy, yoga, manual mobilization, neural mobilization, vitamin B 6 , workplace adjustment, low-level laser therapy, and weight loss.Increased weight or body mass index (BMI) have been identified as risk factors for CTS. Individuals classified as obese (BMI > 29) are 2.5 times more likely than slender individuals (BMI < 20) to be diagnosed with CTS. Other studies have found statistically significant correlations between BMI and CTS. The importance of aerobic activity and overall fitness should be stressed, especially for those with sedentary occupations and weight problems.
There is increased interest in “neurodynamic maneuvers” or neural mobilization techniques for nonoperative treatment of CTS. Median nerve excursions have been measured and are the basis for clinical exercise regimens that combine cervical, shoulder, elbow, forearm, wrist, and digital motions to effect various degrees of nerve excursion. It is postulated that CTP is reduced by combining intermittent active wrist and digital flexion and extension exercises and that differential flexor tendon gliding exercises serve to reduce tenosynovial edema and improve the venous return from the nerve bundles, thus reducing CTP. The physiologic rationale for nervous system mobilization supports the concept that nerve excursion or gliding improves local tissue nutrition by encouraging axonal transport and thus may improve nerve conduction. A recent study concludes that forearm supination is the preferred position for passive median nerve gliding exercise because of large distally oriented nerve gliding, whereas active full digital grip may produce proximally oriented median nerve gliding.
Although some evidence supports the efficacy of nerve gliding exercise, well-respected clinicians in the discipline caution that we should not be “overzealous” with active and passive maneuvers and should be responsive to clinical nerve-related symptoms with exercise that could potentially increase strain to the entrapped nerve. Walsh notes that “there is limited evidence reporting favorable outcomes when using neural mobilization to treat specific patient populations, and the appropriate parameters of dosage (i.e., duration, frequency, and amplitude) remain to be confirmed.” At this point the efficacy of nerve gliding is not clear.
Michlovitz has provided us with a general review of available literature and cited the difficulty in making conclusions about the literature regarding success of treatment for CTS “due to variations in outcome measures, severity of CTS, and inconsistencies in duration, dosage, and follow-up time for interventions.” Based on literature review she recommended that patients with mild or moderate CTS be provided with a conservative program of positioning the wrist in neutral for nocturnal wear. She suggested that intermittent exercise (nerve gliding exercises), activity modification, and pain-relieving modalities could be helpful in modulating pain and reducing symptoms. Her review is supported by a randomized controlled trial by Baysal and coworkers which supports a combination of orthotic positioning, exercise, and ultrasound therapy in the conservative treatment of CTS.
Meta-analysis of these many studies on conservative treatment yields inconclusive support for these interventions. The lack of clinical heterogeneity was cited as a significant problem, making comparisons and conclusions difficult. Our best available evidence for conservative interventions based on these analyses of literature review follows.
In a systematic review of randomized, controlled trials Gerritsen and colleagues found that diuretics, vitamin B 6 , nonsteroidal anti-inflammatory drugs, yoga, and laser acupuncture seem to be ineffective in providing short-term symptom relief (varying levels of evidence), but steroid injections seem to be effective (limited evidence). They found conflicting evidence for the efficacy of ultrasound and oral steroids, and limited evidence that ultrasound is effective for long-term relief. Orthotic positioning was found to be less effective than surgery. They concluded that there is little known about the efficacy of most conservative treatment options for CTS.
O’Conner and associates in a meta-analysis of conservative treatments other than steroid injection concluded that current evidence shows significant short-term benefit from oral steroids, positioning, ultrasound, yoga, and carpal bone mobilization. Other nonsurgical treatments did not produce significant benefit. Trials of magnet therapy, laser acupuncture, exercise, or chiropractic care did not demonstrate symptom benefit compared with placebo or control.
Verdugo and colleagues, in a review for the Cochrane Database, found that a significant proportion of people treated medically require surgery, and the risk of reoperation in surgically treated people is low. They concluded that surgical treatment of CTS relieves symptoms significantly better than orthotic positioning.
In a qualitative systematic review of 24 studies, chosen from 2027 articles on conservative management for CTS, Muller and coworkers found grade B evidence (recommendation for an intervention based on evidence that is consistent with two or three randomized controlled studies) to support interventions of orthotic positioning, ultrasound, nerve gliding, carpal bone mobilization, magnetic therapy, and yoga for people with CTS.
Piazzini and associates conducted a meta-analysis for reviews of conservative treatment of CTS from January 1985 to May 2006 and found (1) strong evidence (level 1) on efficacy of local and oral steroids; (2) moderate evidence (level 2) that vitamin B 6 is ineffective and that orthoses are effective, and (3) limited or conflicting evidence (level 3) that NSAIDs, diuretics, yoga, laser, and ultrasound are effective, whereas exercise therapy and botulinum toxin B injection are ineffective.
Evidence-based guidelines from the German Societies of Hand Surgery; Neurosurgery; Neurology; Orthopaedics; Clinical Neurophysiology and Functional Imaging; Plastic, Reconstructive and Aesthetic Surgery; and Surgery for Traumatology determined that among conservative treatment methods, treatment with a nocturnal orthosis and local infiltration of a corticosteroid preparation are effective; that oral steroids, positioning, and ultrasound show only short-term benefit; and that surgical treatment is clearly superior to all conservative methods. They found that open and endoscopic procedures (when the endoscopic surgeon has sufficient experience) are equivalent, and that a routine epineurotomy and interfascicular neurolysis cannot be recommended. They also concluded that early functional treatment postoperatively is important.
A Practical Approach to Reducing Carpal Tunnel Pressure and Associated Symptoms
The goal of all these interventions is to decrease CTP, which will theroretically improve vascular permeability, tissue nutrition, and decrease symptoms. It is therefore important for the hand therapist to understand the effects of therapeutic interventions on CTP to avoid treatments that are ineffective or excessive.
Effect of Posture, Load, and External Pressure on Carpal Tunnel Pressures
A review of experimental work on CTP may offer some insight into reducing these mechanical pressures with positioning, alterations in work or avocational postures, and load applied to the structures that sit within the carpal tunnel. CTPs are affected by changes in the posture of the wrist, fingers, thumb, and forearm; by loads applied to the palmaris longus (PL), flexor digitorum profundus (FDP), FDS, flexor pollicis longus (FPL), and the lumbrical muscles; by externally applied forces to the palm and wrist area; and with exposure to vibration.
Effect of Wrist Posture
We observe clinically that wrist position with CTS is critical and that changes in position by as much as 20 degrees can alter nerve compression symptoms. Prefabricated orthoses with metal bar inserts often increase paresthesias and pain if the wrist is positioned in too much extension. We also observe the effect of extreme or sustained work postures on CTS and tendon inflammation.
The shape of the carpal tunnel changes with wrist posture. A posture of wrist flexion decreases cross-sectional area in the region of the pisiform and hamate, whereas extension decreases cross-sectional area at the level of the pisiform. The PL, by virtue of its insertion into the palmar aponeurosis (i.e., the distal portion of the flexor retinaculum), may alter the shape of the carpal tunnel as it applies tension to the retinaculum when the wrist is extended.
CTPs depend on tendon load through the carpal tunnel as well as wrist position. Regardless of loading condition, catheter pressures have been found to be higher with wrist extension than with wrist flexion. This has been shown previously for wrist postures associated with unloaded conditions. Changes in flexor tendon trajectories due to wrist posture may also increase contact forces on the median nerve, subjecting it to shear pressure.
Keir and Bach explored the hypothesis that the extrinsic finger flexor muscles have the potential to move into the proximal end of the carpal tunnel with wrist extension. Muscle excursions of the FDP and FDS were measured relative to the pisiform during wrist extension in cadaveric specimens. They found that the extrinsic finger flexor muscles have the potential to enter the carpal tunnel during wrist extension, possibly contributing to elevated CTPs during this activity. They conclude that the use of finger flexors when the wrist and fingers are extended should be avoided.
Fung and associates determined in a recent study of wrist posture and motion that frequent flexion, extension, and sustained force of the wrist increase the risk of developing CTS, but that neutral wrist position and repetitive digital motion were not associated with CTS. Keir and colleagues provide guidelines for wrist posture that can be applied to the design of tools and hand-intensive tasks implicating fairly neutral postures. Their investigations defined postures of 26.6 degrees of extension, 37.7 degrees of flexion, radial deviation of 17.8 degrees, and ulnar deviation of 12.1 degrees to keep CTP below the critical 30 mm Hg.
Intratunnel pressures have been measured at 2.5 mm Hg with the wrist in neutral, 31 mm Hg with normal wrist flexion, and 30 mm Hg in maximal wrist extension in normal subjects. Burke and coworkers also found that wrist position had a significant effect on CTP and demonstrated that intratunnel pressures are the lowest with the wrist near neutral, most specifically at 2 degrees of wrist flexion and 3 degrees of ulnar deviation. They recommended this position for wrist control orthotic use. Weiss determined that the average position of the wrist associated with the lowest pressure was 2 ± 9 degrees of extension and 2 ± 6 degrees of ulnar deviation, and recommended an orthosis position similar to that recommended by Burke.
Other investigators support a neutral orthotic position for night only or full-time positioning.
Orthotic positioning has been found to be the most effective if applied within 3 months of symptom onset. Other investigators support the use of short-term nocturnal orthotic use for CTS regardless of the degree of median nerve impairment, demonstrating a reduction in wrist, hand, or finger discomfort. Symptom relief and neurophysiologic improvement after night-only orthotic wear therapy (in neutral position) has been found to last up to the 6-month follow-up visit by some investigators. Walker and associates in a study comparing full-time to part-time orthotic wear with wrist neutral found that physiologic improvement occurred with full-time wear; however, others have found no significant alterations in intratunnel pressures with or without orthoses.
Clinical Implication
The proper position for a wrist control orthosis is neutral, with the wrist postured at 2 degrees of flexion, and 3 degrees of ulnar deviation ( Fig. 49-1A ). Prefabricated orthoses that often position the wrist in extension may increase CTP ( Fig. 49-1B ). A working posture of wrist neutral to slight flexion when digital load is required may minimize intratunnel pressures. Orthoses applied at night with early symptoms are the most effective and are needed for daytime only if it is necessary to control work postures in neutral. Presurgical positioning with orthoses has value if applied early, if tenosynovitis is a coexisting problem, or as pain relief intervention as a precursor to surgery. These orthoses can be remolded for proper fit to wear postoperatively to control tension on the incision and to prevent overuse and associated inflammation.
Repetitive digital motions with work activity may be tolerated with wrist postures of neutral; positions of wrist extension combined with repetitive finger loads should be avoided.
Effect of Finger Position
We observe clinically that limiting finger motion is sometimes required to decrease the symptoms and pain associated with CTS and that in a number of cases wrist control positioning alone does not offer relief of pain. This is especially true in manual laborers with well-developed lumbricals or with anxious and often elderly patients who attempt to improve their symptoms by continually flexing their digits (i.e., the “compulsive gripper”). These same patients find relief of symptoms if the metacarpophalangeal (MCP) joints are positioned in moderate extension, which limits flexor tendon excursion and lumbrical incursion into the carpal tunnel.
With the wrist in neutral, intratunnel pressures are relieved by finger positions that pull the lumbricals up out of the tunnel. Several recent studies examine the dynamic relationship of the lumbrical muscles and the carpal tunnel.
Lumbrical incursion into the carpal tunnel that is associated with finger flexion movements increase intratunnel pressures by increasing the contents of the carpal canal.
The four lumbricals take their origin from the FDP tendons as the latter cross the palm. Anatomic studies have demonstrated that the lumbrical muscles originate distal to the carpal tunnel with the fingers held in extension, but that all four lumbrical muscles lie within the carpal canal when the fingers are actively flexed. As a composite fist is made, the FDP tendons pull the proximal portion of the lumbricals into the carpal canal.
Lumbrical incursion has been studied in four finger positions. The lumbrical muscle origins were found to be an average of 7.8 mm distal to the carpal tunnel with full finger extension, 14 mm into the tunnel with 50% finger flexion, 25.5 mm with 75% finger flexion, and 30 mm with 100% finger flexion. The lumbrical muscles were distal to the proximal aspect of the hook of the hamate only for the position of full digital extension and 50% finger flexion.
This information is important clinically because the hook of the hamate has been found to be the most constrictive portion of the carpal canal, therefore lumbrical incursion to this level could likely have the greatest effect on median nerve compression. Others have demonstrated that the median nerve is compressed and flattened to the greatest degree at the level of the hook of the hamate. So, with finger flexion greater than 50%, this already crowded area becomes even more crowded as the lumbricals move in to take up more space and apply more pressure to the median nerve.
Ham and colleagues have also studied the effect of finger flexion on lumbrical incursion and the median nerve. Successive cross-sectional areas of the carpal tunnel were measured using MRI with the fingers in both full extension and full flexion in 12 healthy volunteers. In this study the presence, amount, shape, and size of the lumbrical muscles influenced the alignment and shape of the median nerve in the carpal tunnel. Other changes that were noted in this study during finger flexion were fat compression, flattening and displacement of the median nerve in the presence of lumbrical muscles, and pressure from the superficial and deep flexor tendons.
Ditmars and Houin make the point that the lumbricals retract into the carpal tunnel with MCP flexion and actually contract during active interphalangeal (IP) joint extension, causing median nerve compression within the distal end of the tunnel. They state that this mechanism is suggested when the patient complains of intermittent numbness that occurs while writing, holding books, or carrying objects (as with an intrinsic-plus position) for a period of time.
A study on the effects of finger posture on CTP as it relates to wrist position demonstrated that an angle of 45 degrees flexion at the MCP joint may be optimum when designing orthoses or work postures.
Clinical Implication
The clinical implication from review of these studies and from clinical experience is that, in some cases, wrist control positioning alone may be insufficient to decrease intratunnel pressures (or to limit excursion in an inflamed flexor tendon system). A lumbrical block added to the wrist control orthosis that holds the MCP joints at 20 to 40 degrees of flexion decreases finger flexion by 50% and decreases intratunnel pressures. A recent study comparing the effects of a custom fabricated orthosis with the wrist in neutral and MCP joints in neutral to prefabricated wrist cock-up orthoses supports this concept of addressing lumbrical incursion with the addition of a lumbrical block.
In patients with well-developed lumbricals, a positive Berger’s test or swelling at the volar wrist indicating flexor synovitis or in patients who are “compulsive grippers,” the MCP joints should be blocked in moderate extension to decrease the effects of lumbrical incursion ( Fig. 49-2 ). I often fabricate a complete resting pan orthosis including the thumb kinetic chain, and digits in a neutral position for patients with severe nocturnal pain who cannot undergo surgery immediately or for those with associated triggering digits or with symptomatic basilar thumb arthritis ( Fig. 49-3 ). Limiting flexor tendon excursion in patients with flexor synovitis or hypertrophic synovium is critical to decreasing pain and inflammation and prevents triggering of digits with stenosing tenosynovitis often seen in association with CTS by forcing the patient to work the digits in a hook-fist position.
Work postures that require repetitive gripping in patients with CTS should be altered, as should postures that require sustained grip or pinch with an intrinsic-plus position. As noted in the previous section, activity requiring repetitive finger motions is best tolerated with the wrist in neutral. The use of therapy aids that encourage repetitive gripping, such as therapeutic putty or hand grippers, should be avoided as a part of a strengthening program for any hand that is inflamed or edematous as a result of other injury or for patients with the diagnosis of CTS. Repetitive flexion exercise increases intratunnel pressures and can contribute to CTS and trigger fingers. A better option is to strengthen the hand with isometric-type exercise or dowel use that allows less than 50% finger flexion. Strengthening should not be a part of a conservative management program for CTS.
Effects of Combined Tendon Load and Posture
Wrist and finger posture combined with load, as with gripping and pinching, have been found to elevate CTPs. Active-resistant flexion of the fingers creates ulnar sliding of the median nerve beneath the flexor retinaculum.
The combined effects of posture and tendon load have been studied in cadaveric wrists. It has been demonstrated that CTPs depend on wrist posture and the loading of tendons passing through the carpal tunnel. CTPs were measured in eight cadaveric wrists under four muscle loading conditions, with the thumb, index, and long finger in a pinch-grip posture measured with both zero load and 1-kg mass to the flexor tendons of the index and long fingers, the PL, and the FPL. This study demonstrated that muscle load elevated pressure in the carpal tunnel above the critical pressure. The effect of muscle loading from greatest to lowest was loading of the PL, the finger flexors, the FPL, and no load. The PL created the highest pressure with the wrist extended and only moderate pressure with the wrist in flexion. The authors speculate that the insertion of the PL into the flexor retinaculum may change the shape of the tunnel when the tendon is under pressure. Loading the finger flexors with the wrist flexed increases median nerve pressure 2.5 times that of loading the flexor tendons in neutral. Tendon load with the wrist in either 45 degrees of extension or flexion increased intratunnel pressure by 30 mm Hg. Loading the FPL in wrist flexion or extension induced pressures no different from zero load conditions, but when the FPL was loaded with the wrist in ulnar deviation, the pressure was twice that of the unloaded state. A forceful grip in ulnar deviation highly compressed the median nerve.
Pressure has been measured within the carpal tunnel during nine functional positions of the hand and wrist, adding support to earlier work by Cobb and colleagues. Intratunnel pressures exceed normal pressures by more than 200 mm Hg when making a strong fist in normal subjects, and in fact making a fist increased the intratunnel pressure significantly more than variations of either wrist flexion or extension in normal subjects. Power grip was found to elevate intratunnel pressures to 223 mm Hg, isometric flexion of a finger against resistance to 41 mm Hg, wrist flexion to 56 mm Hg pressure, and wrist extension to 77 mm Hg.
Rempel and coworkers examined the relationship between CTP and fingertip force and found that (1) fingertip loading increased CTP for all 10 wrist postures tested, (2) fingertip loading elevated CTPs independent of wrist posture, and (3) relatively small fingertip loads have a large effect on CTP. They concluded that sustained pinch and grasp aggravate median nerve neuropathy at the wrist.
Clinical Implication
These measurements of intracarpal pressures vary some from study to study depending on the method of study, but all demonstrate that CTP changes with posture and load. The implication from these studies is that work postures should avoid the positions of forceful grip, pinching with the wrist ulnarly deviated, strong gripping with the wrist in more than 10 to 15 degrees of flexion, or positions of wrist extension. Isolated fingertip pressures and sustained grasp should be avoided in working situations. Again the case is made for working with the wrist and fingers in a neutral posture. We should be cautious as we ask the patients with other diagnoses (e.g., distal radius fractures or rotator cuff repair) that contribute to inflamed or swollen tissues to exercise with Theraband (which requires sustained hand grip), work simulation tools, work samples, exercise putty, and hand grippers.
The effect of tenosynovitis as both a contributing cause of CTS and recurrent CTS and its effect on commonly used clinical screening tests for CTS emphasizes the importance for the therapist being able to both diagnose and treat the symptoms of flexor tendon inflammation as opposed to, or in conjunction with, CTS. Therapists should be aware that some commonly utilized provocative tests for CTS (Tinel’s, Phalen’s, reverse Phalen’s, and carpal tunnel compression tests) have been found to be better diagnostic tools for tenosynovitis than CTS and can be an indicator for medical management for tenosynovitis.
Effect of Thumb Position
Clinically, we observe that some patients with inflammation at the first CMC joint also experience median nerve symptoms, and that patients, if questioned carefully, point out that median nerve paresthesias worsen with sustained pinch as when holding the newspaper or a pen. The effect of first CMC joint inflammation, the pull of the opponens muscle on the flexor retinaculum, and sustained intrinsic contraction as when holding a heavy book have been implicated as a source of increased intratunnel pressures.
It has been demonstrated that loading the FPL in wrist flexion or extension does not increase intracarpal pressures more than an unloaded state, but FPL load with the wrist ulnarly deviated increases pressures twice that of the unloaded state. Keir and associates allude to the possibility of the thenar muscle applying traction to the flexor retinaculum, much as the PL does, with load to the index finger in opposition.
Clinical Implication
All patients with median nerve symptoms should be evaluated for first CMC joint inflammation or basilar thumb arthritis, and if symptomatic, should be fitted with a short opponens orthosis for daytime ( Fig. 49-4A ) and a long opponens orthosis for night ( Fig. 49-4B ), and they should avoid work postures that combine pinch and wrist ulnar deviation . Positioning the thumb kinetic chain requires knowledge of thumb anatomy and kinematics and precision fabrication. Improper positioning within the orthosis contributes to CMC pain. As the orthosis is fabricated the therapist should manually seat the metacarpal in the trapezium, allow for slight flexion of the MCP joint, and ensure that the patient can oppose the thumb P2 to index P3 for function. Patients should avoid repetitive gripping and pinching with work and avocational activities. Adduction forces to the first CMC can be minimized by increasing the size of the writing pen or pencil, applying arthritic grips to golf clubs, or by increasing grip size on other tools.
