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The wrist consists of eight carpal bones arranged in two rows: proximal and distal. Starting from the outer side and moving towards the inner side, the proximal row includes the scaphoid, lunate, triquetrum, and pisiform, while the distal row consists of the trapezium, trapezoid, capitate, and hamate. These bones form a concave shape on the front side, which forms the carpal tunnel when the transverse carpal ligament is stretched across it.
In the wrist, there are three joints that normally don't connect: the distal radio-ulnar joint, radiocarpal joint, and midcarpal joint. Wrist movements are achieved by the combined action of the radiocarpal and midcarpal joints. For instance, wrist flexion and extension are divided equally between these joints, whereas radial and ulnar deviation (moving the wrist towards or away from the body's centerline) mainly involves the midcarpal joint to a greater extent (about 60%).
Distal Radio-ulnar Joint:
The distal radio-ulnar joint connects the rounded head of the ulna with the ulnar notch of the distal end of the radius and the triangular fibrocartilage.
Its cavity has an L-shaped configuration and is separated from the radiocarpal joint by the triangular fibrocartilage.
The joint capsule comprises ventral and dorsal bands extending from the radius to the ulna, including a proximal pouch.
It functions as a pivotal type of articulation, allowing pronation and supination movements of the hand.
Radiocarpal Joint:
Also known as the "wrist joint," the radiocarpal joint is a condyloid synovial joint situated between the distal end of the radius and the carpal bones.
The proximal concave articular surface is formed by the articular facet of the radius and the distal surface of the triangular fibrocartilage.
The distal surface consists of the convex surfaces of the scaphoid, lunate, and triquetrum.
On the ulnar side, the radiocarpal joint may communicate with the piso-triquetral joint, involving the pisiform and the anterior facet of the triquetrum.
The joint capsule attaches to the distal margins of the radius and ulna, as well as to the proximal row of carpal bones, reinforced by extrinsic carpal ligaments.
Midcarpal Joint:
Situated between the proximal and distal rows of carpal bones, the midcarpal joint's capsule connects both rows and is strengthened by numerous intrinsic ligaments.
It enhances the range of movements of the radiocarpal joint and aids in hand grasp.
Distally, the carpometacarpal joints articulate the bases of the metacarpals with the distal row of carpal bones, often communicating with the midcarpal joint.
Wrist Ligaments and Triangular Fibrocartilage Complex:
Wrist ligaments can be categorized as extrinsic and intrinsic. Extrinsic ligaments stabilize the wrist by connecting the radius, ulna, and metacarpal bases to the carpal bones. They are stronger on the palm side of the wrist, but they have limited clinical importance as they are located outside the joint's synovial layer.
Intrinsic ligaments connect and stabilize the carpal bones, particularly the proximal row, during hand movements. The scapholunate and lunotriquetral ligaments are crucial among them. Tears in these ligaments can cause joint instability, leading to restricted movement, impaired function, and pain.
The triangular fibrocartilage complex consists of soft-tissue structures in the ulnar-carpal space, providing stability to the wrist's ulnar side and the distal radio-ulnar joint. It absorbs mechanical forces during wrist loading. The complex includes the triangular fibrocartilage, along with supporting structures like the meniscus homologus, ulnar collateral ligament, and ligaments around the radio-ulnar joint.
Proper assessment of wrist ligaments often requires advanced imaging techniques like MRI, MR arthrography, or spiral CT arthrography, as they are not easily visible with ultrasound. However, structures like the scapholunate ligament and triangular fibrocartilage complex can be examined using ultrasound, which is clinically relevant.
Tendons and Retinacula:
The wrist houses flexor and extensor tendons on its front and back sides respectively. There are nine flexor tendons and nine extensor tendons that extend towards the fingers without attaching to the carpal bones. Additionally, there are two main wrist flexors and three wrist extensors that insert onto the distal carpal row and the metacarpals. One tendon, the palmaris longus tendon, attaches to the transverse carpal ligament and the palmar aponeurosis.
Extensor Tendons:
Extensor tendons run along the back of the wrist, within fibrous tunnels formed by the bones and extensor retinaculum.
The extensor retinaculum is a thickening of the dorsal fascia, attached to the radius and ulna on one end and the pisiform and triquetrum on the other.
Vertical fibrous bands from the retinaculum divide the extensor tunnel into six compartments, each containing synovial sheaths surrounding tendons.
The compartments house various extensor tendons: abductor pollicis longus and extensor pollicis brevis (first compartment), extensor carpi radialis longus and brevis (second compartment), extensor pollicis longus (third compartment), extensor digitorum and extensor indicis proprius (fourth compartment), extensor digiti quinti proprius (fifth compartment), and extensor carpi ulnaris (sixth compartment).
The Lister tubercle, located between the second and third compartments, serves as a landmark for identifying these compartments.
Flexor Tendons:
At the palm side of the wrist, nine flexor tendons enter the carpal tunnel to reach the fingers. These include four tendons from the flexor digitorum superficialis for the second to fifth fingers, four from the flexor digitorum profundus for the same fingers, and the flexor pollicis longus tendon.
The flexor digitorum superficialis tendons arise from the distal radius and pass through the carpal tunnel to reach the fingers. During finger movements, they can be felt at the wrist between the flexor carpi radialis and ulnaris tendons.
The flexor digitorum profundus tendons traverse the wrist just beneath the superficialis tendons. In the carpal tunnel, the index finger tendon is separate, while the others may become independent only in the palm. The lumbrical muscles in the palm arise from the profundus tendons.
The flexor pollicis longus tendon lies deep to the flexor carpi radialis and runs on the radial side of the index finger tendons in the carpal tunnel. It shares a synovial sheath with the superficialis and profundus tendons.
The primary wrist flexors, flexor carpi radialis and flexor carpi ulnaris, lie outside the carpal tunnel and are easily palpable. The flexor carpi radialis tendon originates between the elbow and wrist, has its own synovial sheath, and inserts on the palm side of the second metacarpal. It allows wrist flexion and radial deviation.
The flexor carpi ulnaris tendon, smaller and shorter than the radial counterpart, courses on the ulnar side of the wrist, housing the pisiform bone, and inserts on the hamate and fifth metacarpal. It allows wrist flexion and ulnar deviation, essential for tasks like using a screwdriver.
The palmaris longus tendon passes superficially to the transverse carpal ligament, often absent in about 20% of individuals, and splits into bundles distally, mingling with the aponeurosis.
Neurovascular Structures:
Median Nerve:
The median nerve runs along the forearm between the flexor digitorum profundus and superficialis muscles. As it nears the wrist, it shifts radially and moves superficially along the lateral margin of the flexor digitorum superficialis before entering the carpal tunnel.
Inside the tunnel, it runs superficially to the flexor pollicis longus and flexor digitorum superficialis tendons. The nerve tends to flatten as it progresses through the tunnel.
Covered by the transverse carpal ligament inside the carpal tunnel, the median nerve provides sensory supply to the palm's radial half and the first three fingers, and motor supply to the muscles of the thenar eminence.
Just before entering the carpal tunnel, it gives off a palmar cutaneous branch supplying the radial half of the palm.
Ulnar Nerve:
In the forearm, the ulnar nerve lies on the radial side of the flexor carpi ulnaris and the ulnar artery, giving off palmar and dorsal cutaneous branches.
It passes superficially to the transverse carpal ligament, traversing the Guyon tunnel, which lies medially relative to the carpal tunnel. Here, it bifurcates into superficial sensory and deep motor branches.
The ulnar nerve supplies sensation to the medial palm, little finger, and medial half of the ring finger, while the deep motor branch innervates intrinsic hand muscles.
Distal to the Guyon tunnel, the superficial branch continues straight, while the deep branch curves across the palm to reach the first interosseous space.
Radial Nerve (Cutaneous Terminal Branch):
Emerging between the extensor carpi radialis longus and brachioradialis tendons in the distal forearm, the superficial cutaneous branch of the radial nerve provides sensory supply to the dorsum of the wrist, hand, thumb, and proximal radial fingers.
Covered by a fascial band, it traverses the extensor tendons of the first compartment to reach the subcutaneous tissue.
Radial and Ulnar Arteries:
The brachial artery bifurcates into two terminal branches: the radial artery and the ulnar artery. In the distal forearm, the radial artery runs superficially over the ventral aspect of the distal radius, where its pulse is easily palpable. It then curves dorsally over the radial aspect of the wrist, passes beneath the extensor tendons of the first compartment, and traverses the floor of the anatomical snuffbox.
On the other hand, the ulnar artery enters the wrist on the lateral side of the ulnar nerve and accompanies the nerve through the Guyon tunnel, superficial to the transverse carpal ligament. Like the nerve, the ulnar artery divides into a superficial palmar branch and a deep palmar branch.
Essentials of Clinical History and Physical Examination:
History Investigation: Before undergoing ultrasound examination, it's crucial to thoroughly investigate the patient's history. This includes ruling out any potential systemic joint disorders like rheumatoid arthritis, as well as considering sporting or occupational activities that may be related to tendonitis or overuse syndromes. Additionally, any history of local trauma, such as occult fractures, tendon ruptures, or ligament sprains, should be noted.
Physical Examination: During physical examination, assessing the range of wrist movements, including flexion-extension, ulnar-radial deviation, and pronation-supination, is essential. This evaluation helps in understanding the extent of mobility and identifying any limitations or discomfort. Accurately pinpointing the site of pain, especially in cases of tendinitis, can provide valuable diagnostic clues. Movements that exacerbate pain should also be tested to better understand the underlying pathology.
Radiographic Review: Reviewing recent standard radiographs, if available, is an integral part of the evaluation process. These radiographs can reveal signs of joint and bone diseases, such as osteoporosis, marginal erosions, or focal bone lesions. Abnormal bone positions, which may indicate ligament tears, as well as soft tissue thickening and calcifications, should be carefully examined for diagnostic insights.
Space-Occupying Masses: When encountering a space-occupying mass on the dorsal or palmar aspects of the wrist, observing intermittent variations in its size over time can suggest the possibility of a ganglion cyst. Furthermore, if the mass is associated with an adjacent tendon and moves along with-it during wrist movements, the presence of an intratendinous ganglion should be considered.
Carpal Tunnel Syndrome:
Symptoms: Patients with carpal tunnel syndrome typically experience night tingling and burning pain in the radial aspect of the hand and the first three fingers. These symptoms may also occur during the day, especially when the hand is held in a fixed position, such as when holding a heavy book or gripping a telephone receiver. The tingling sensation can sometimes lead patients to mistake the condition for a vascular disorder.
Diagnostic Tests:
Tinel Test: This test involves tapping the volar aspect of the carpal tunnel with a reflex hammer. A positive result occurs if this tapping reproduces the patient's symptoms.
Phalen Test: In the Phalen test, the wrist is fully flexed and maintained in this position for one minute. If this maneuver reproduces the patient's symptoms, the test is considered positive.
Considerations: It's important to note that while these clinical tests can be helpful in establishing a diagnosis, false negatives may occur, especially in cases of chronic entrapment disease.
Normal Ultrasound Anatomy:
Patient Positioning: The patient is seated comfortably in front of the examiner, with both wrists and elbows resting on the examination table. Alternatively, aged or traumatized patients may lie supine with the arms resting at the sides of the body, although this position may pose challenges for examining the opposite side. For dynamic scanning of the extensor tendons, the hand is best positioned on a gel tube, with the fingers hanging over its edge to facilitate finger movements.
Examination Sequence:
The routine ultrasound examination of the wrist typically begins with evaluation of its dorsal aspect, followed by the palmar aspect.
Depending on the specific clinical presentation, ultrasound images can be obtained in different positions of the wrist, including flexion and extension, radial and ulnar deviation, and pronation and supination.
Dorsal Wrist Ultrasound Examination:
Transverse Imaging: Transverse ultrasound images are ideal for detecting and accurately identifying the extensor tendons. Assessment of individual tendons relies on their anatomical position and behavior during dynamic examination.
Extensor Tendons:
Detection of the extensor tendon for the third finger is straightforward during transverse ultrasound scans obtained while actively flexing and extending this finger while others are held fixed.
The extensor carpi radialis and extensor carpi ulnaris can be distinguished based on their anatomical position, as they are not influenced by finger movements.
Imaging:
Begin by obtaining ultrasound images at the level of the distal epiphysis of the radius, with the Lister tubercle serving as a useful landmark.
The extensor tendons appear as oval or rounded hyperechoic structures of varying sizes.
The extensor retinaculum is visualized as thin transversely oriented bands adjacent to the tendons due to anisotropy, with the retinaculum of the fourth compartment often being the thickest and most visible.
The synovial membrane enveloping the tendons and the synovial fluid within the sheath cannot be visualized under normal conditions.
Examination Technique:
Each tendon or tendon group should be assessed separately, evaluating different compartments sequentially.
Initially recognize the tendon, then follow it on short-axis planes down to its distal insertion.
Longitudinal ultrasound images may provide additional details regarding the fibrillar pattern of tendons and their dynamic motion.
Dorsal Compartments - First Compartment: Second Compartment: Third Compartment: Fourth and Fifth Compartments: Sixth Compartment:
In the first compartment, the abductor pollicis longus and extensor pollicis brevis tendons (APL & EPB) lie side by side over the lateral aspect of the radial styloid.
Anatomical variants such as a central septum and accessory tendons may be encountered, influencing the pathogenesis of local tendinitis.
Longitudinal ultrasound images over the radial styloid demonstrate these tendons resting on the radial cortex, forming a bridge between the radius and the base of the first metacarpal.
The radial artery, veins, and radial nerve can also be assessed in this region, with dynamic scanning demonstrating nerve snapping dorsally and ventrally over the tendons during pronation and supination movements.
Proximal Carpal Tunnel:
Bony Landmarks: Identification of the proximal carpal tunnel is aided by locating the pisiform at its ulnar side and the scaphoid at its radial side, an Lunate Bone Below. These bones appear as round hyperechoic structures with posterior acoustic shadowing on ultrasound.
Probe Adjustment: Once these landmarks are visible in a single image, the probe's orientation should be adjusted to optimize soft tissue visualization within the tunnel. Tilting the probe back and forth helps distinguish the hypoechoic median nerve from adjacent tendons.
Tendon Positioning: Relative to the flexor carpi radialis, the flexor pollicis longus tendon lies deeper, slightly closer to the midline. Oblique longitudinal ultrasound images can show these tendons in the same plane.
Carpal Tunnel Size: The proximal carpal tunnel is larger compared to the distal tunnel. Ultrasound accurately evaluates its diameter, outline, and cross-sectional area, as well as the median nerve.
Transverse Carpal Ligament: This ligament appears as a thin convex band, easily visualized with ultrasound. It attaches to the pisiform and scaphoid, but its lateral division holding the flexor carpi radialis tendon may not be visible.
Flexor Tendons: The nine flexor tendons (four from the flexor digitorum superficialis, four from the flexor digitorum profundus, and the flexor pollicis longus) can be imaged individually inside the carpal tunnel based on their anatomic position and dynamic scanning.
Median Nerve: This nerve courses superficially and parallel to the second and third flexor tendons, just deep to the transverse carpal ligament. Its cross-section is usually elliptical but can vary in shape and size depending on wrist position and subject.
Dynamic Movements: During finger flexion or fist clenching, ultrasound shows passive shifting movements of the median nerve on the underlying gliding flexor tendons.
Anatomic Variants: Ultrasound identifies clinically relevant anatomic variants within the carpal tunnel, such as accessory flexor muscles, bifid median nerves, and persistent median arteries. These anomalies can be easily assessed and detailed in the ultrasound report, alerting hand surgeons to potential risks during procedures.
Distal Carpal Tunnel:
Bony Landmarks: The tubercle of the trapezium on the radial side and the hook of the hamate on the ulnar side serve as the main bony landmarks for the distal carpal tunnel. The trapezium has a flat palmar surface, while the hamate hook is more centrally located.
Size and Appearance: The distal tunnel is smaller and has a thicker, straighter appearance compared to the proximal tunnel. As the tunnel narrows, the median nerve flattens out, making it more challenging to differentiate the flexor tendons, which lie deeper and are closely apposed.
Ultrasound Imaging: With ultrasound, the flexor carpi radialis tendon can be seen under the tubercle of the trapezium, with the flexor pollicis longus tendon located immediately medial to it. The median nerve's size can be estimated by comparing its cross-section with the underlying tendons.
Nerve Structure: The median nerve's fascicular echotexture is more evident proximally, where it runs parallel to the skin, compared to the distal tunnel, where it has a downward oblique course. Adjustments in probe orientation or wrist flexion may be necessary for better visualization.
Branches: After exiting the distal edge of the transverse carpal ligament, the median nerve divides into two or three branches, known as the common palmar digital nerves, which further divide into digital nerves for the fingers.
Guyon Tunnel:
Location and Boundaries: The Guyon tunnel is located in a medial and superficial position relative to the carpal tunnel, delimited by the dorsal aspect of the transverse carpal ligament and the superficial palmar carpal ligament on the radial side, and the lateral aspect of the pisiform on the ulnar side.
Ultrasound Imaging: The pisiform and the ulnar artery are easily detected with ultrasound. The ulnar nerve lies between these two structures and appears as a small hypoechoic structure containing internal fascicles.
Anomalous Muscle: An accessory abductor digiti minimi muscle may be encountered in the tunnel.
Terminal Branches: Distally, the ulnar nerve divides into two terminal branches: the superficial sensory branch continues alongside the ulnar artery, while the deep motor branch courses along the medial surface of the hamate hook. Similarly, the ulnar artery splits into superficial and deep branches, following the respective nerve bundles.
Dorsal Wrist Pathology:
Tendinitis and Tendinopathies: Tendinitis and tendinopathies of the dorsal wrist, often termed as tenosynovitis, are common conditions, frequently caused by overuse related to sports or occupational activities. These conditions can also be associated with systemic musculoskeletal disorders.
De Quervain Disease:
Description: De Quervain disease is a form of overuse tenosynovitis affecting the wrist, particularly affecting individuals who perform repetitive thumb movements.
Etiology: It often results from chronic microtrauma at the radial styloid, leading to localized thickening of the extensor retinaculum and subsequent impingement and inflammation of tendons.
Clinical Presentation: Patients typically experience tenderness and pain over the radial styloid, exacerbated by thumb movements and forceful pinching.
Diagnostic Tests: The Finkelstein test, involving passive ulnar deviation of the wrist with the thumb maximally flexed, is commonly used for diagnosis.
Treatment: Treatment options include anti-inflammatory drugs, splinting, local injections, and surgical release of the retinaculum in resistant cases.
Proximal intersection syndrome
Proximal intersection syndrome is an overuse tenosynovitis that occurs at the intersection of the first extensor compartment (abductor pollicis longus and extensor pollicis brevis) and the second extensor compartment (extensor carpi radialis longus and extensor carpi radialis brevis) within the forearm.
Clinical Presentation:
Patients often report a history of overuse due to repetitive wrist flexion and extension, or occasionally, direct trauma.
Activities such as weightlifting, rowing, racket sports, horseback riding, and skiing are commonly associated with this condition.
Typical symptoms include radial wrist or forearm pain worsened by flexion and extension, along with swelling and tenderness at the intersection area.
Pathology:
The musculotendinous junctions of the first extensor compartment tendons intersect with the second extensor compartment tendons at an angle of around 60°, approximately 4 cm proximal to Lister’s tubercle.
In intersection syndrome, there is tenosynovitis primarily affecting the tendons of the second extensor compartment, possibly due to friction from the overlying tendons of the first compartment.
Radiographic Features:
Diagnosis is usually based on clinical evaluation, but imaging modalities such as ultrasound and MRI can provide additional information.
Ultrasound may reveal fluid within the tendon sheaths, peritendinous edema, disruption of the hyperechoic plane dividing the two tendon groups, subcutaneous edema, and ganglion cysts.
MRI may show peritendinous edema surrounding both the first and second extensor compartments, centered around the intersection point approximately 4 cm proximal to Lister’s tubercle. Increased intrasubstance tendon signal may indicate tendinosis.
Treatment and Prognosis:
Conservative management includes immobilization, modifying activities, and using anti-inflammatory medications.
Local corticosteroid injections can also be beneficial.
Surgical intervention may be considered for cases that do not respond to conservative treatment.
Distal intersection syndrome -
Distal intersection syndrome is a specific type of tenosynovitis that affects the extensor pollicis longus (EPL) tendon as it crosses over the extensor carpi radialis longus (ECRL) and extensor carpi radialis brevis (ECRB) tendons within the forearm. Let’s delve deeper into this condition:
Clinical Presentation:
Patients typically present with pain and swelling over Lister’s tubercle.
Some may also notice crepitus during thumb movements.
Anatomy:
The intersection of the second extensor compartment (ECRL, ECRB) occurs just distal to Lister’s tubercle.
A communicating foramen connects the tendon sheaths of the EPL and ECRB, allowing inflammation from one tendon to spread to the other.
Pathology and Etiology:
Distal intersection syndrome can be caused by:
Biomechanical attrition: Resulting from repetitive movements causing a pulley effect at Lister’s tubercle (overuse syndrome).
Direct blunt trauma to the EPL tendon.
Distal radius fractures, even without displacement.
Trauma is the most common cause, and EPL tenosynovitis can persist for years after an injury.
Radiographic Features:
Ultrasound may reveal peritendinous edema and fluid within the tendon sheaths where the EPL crosses the ECRL and ECRB tendons.
MRI typically shows peritendinous edema around the second and third extensor compartment tendons, extending proximally from the crossover point of the EPL in the dorsal wrist.
Treatment and Prognosis:
Early operative release is recommended due to the high risk of EPL tendon rupture, also known as “drummer boy’s palsy.”
Wartenberg Disease:
Description: Wartenberg disease refers to the neuropathy affecting the superficial terminal branch of the radial nerve at the wrist.
Etiology: It may result from trauma, iatrogenic events, or nerve entrapment between tendons.
Clinical Presentation: Patients may experience pain over the dorsoradial surface of the wrist and distal forearm radiating to the dorsum of the hand and thumb.
Diagnostic Tools: High-resolution ultrasound examination can reveal subtle abnormalities of the superficial cutaneous branch of the radial nerve.
Treatment: Corticosteroid injection at the site of tenderness along the nerve is often effective, and end-range pronation should be avoided to prevent nerve entrapment.
Extensor Pollicis Longus Tenosynovitis:
Description: This condition involves tenosynovitis of the extensor pollicis longus tendon, commonly due to mechanical friction over the Lister tubercle.
Clinical Presentation: Patients may experience pain over the Lister tubercle and crepitus during thumb movements.
Diagnostic Tools: Ultrasound can reveal synovial sheath effusion proximal to the Lister tubercle.
Treatment: Treatment options include anti-inflammatory drugs, splinting, and surgical intervention if untreated.
Extensor Carpi Ulnaris Tenosynovitis:
Description: Tenosynovitis of the extensor carpi ulnaris tendon is often secondary to instability of the retinaculum of the sixth compartment.
Clinical Presentation: Patients typically complain of localized pain over the dorsum of the ulna.
Diagnostic Tools: Ultrasound can measure tendon size and identify longitudinal splits related to tendon subluxation.
Treatment: Corticosteroid injection and avoiding end-range pronation are common treatment strategies.
Extensor Carpi Ulnaris Instability:
Description: Instability of the extensor carpi ulnaris tendon can result from tears in the retinaculum, leading to anterior dislocation of the tendon.
Diagnosis: High-resolution ultrasound can confirm tendon instability, either subluxation or intermittent dislocation.
Treatment: Treatment depends on the cause and may include conservative measures or surgical intervention.
Ventral Wrist Pathology
Introduction:
Similar to the dorsal wrist, ventral wrist tendinopathies are common, primarily affecting the flexor tendons.
Compression neuropathy of the median nerve at the carpal tunnel is the most prevalent wrist pathology.
Carpal Tunnel Syndrome (CTS)
Prevalence and Etiology:
CTS is the most common entrapment syndrome of the upper limb, with an estimated prevalence of approximately 125×10^6 new cases per year.
Compression of the median nerve at the wrist leads to CTS, with predisposing factors including anatomical variants, systemic disorders (e.g., diabetes), and space-occupying lesions within the carpal tunnel.
Clinical Presentation:
Typically affects late middle-aged women.
Symptoms include tingling, numbness, and burning pain in the thumb, index, middle, and radial half of the ring finger.
Symptoms worsen with prolonged manual work and may include night pain (brachialgia paresthetica nocturna) due to wrist flexion during sleep.
Pathophysiology and Progression:
Early CTS may lack gross morphological abnormalities of the median nerve, but later stages exhibit nerve swelling, shape changes, demyelination, and fibrosclerosis.
Chronic disease can lead to permanent sensory and motor deficits, with muscle wasting observed, termed "ape hand."
Diagnosis:
Relies on clinical and electrodiagnostic findings, often not requiring imaging.
High-resolution ultrasound (Ultrasound) has become a valuable diagnostic tool, allowing rapid and accurate assessment of nerve compression in both static and dynamic states.
Ultrasound Findings:
Ultrasound reveals changes in median nerve shape and echotexture within the carpal tunnel, including swelling, flattening, and loss of fascicular pattern.
The "notch sign," indicating abrupt nerve caliber change at the entrance of the carpal tunnel, aids in diagnosis.
Various morphometric indices, such as nerve cross-sectional area and distal flattening ratio, help quantify abnormal nerve morphology.
Color and power Doppler imaging can depict hyperemic blood flow, indicative of intraneural inflammation.
Assessment of Transverse Carpal Ligament:
Ultrasound assesses the transverse carpal ligament, identifying bulging indicative of pathology.
Extraneous causes of nerve entrapment, such as tenosynovitis and space-occupying lesions (e.g., ganglion cysts, amyloidosis), are visualized.
Treatment:
Conservative management includes wrist splints, NSAIDs, and local corticosteroid injections.
Surgical decompression of the transverse carpal ligament is recommended for persistent or severe cases.
Ultrasound aids in postsurgical evaluation, assessing ligament sectioning completeness and identifying scarring tissue around the median nerve.
Conclusion:
Ultrasound serves as a valuable adjunct to clinical evaluation in diagnosing CTS, particularly in identifying anatomical variants and assessing the cause of nerve compression.
Its accuracy and non-invasiveness make it an attractive initial diagnostic tool, potentially replacing electrodiagnostic studies in some cases.
Guyon Tunnel Syndrome
Rare Condition:
Ulnar neuropathy at the Guyon canal is uncommon compared to carpal tunnel and cubital tunnel syndromes.
Anatomy and Pathophysiology:
The Guyon tunnel is anatomically divided into three zones:
Zone I (pisiform level): Contains the main trunk of the ulnar nerve with sensory and motor fibers.
Zones II and III (hamate level): Zone II houses the motor branch, while zone III contains the sensory branch.
Compression within these zones can lead to mixed symptoms or purely motor or sensory syndromes.
Causes:
Ganglion cysts are the primary cause, accounting for approximately 30-40% of cases.
Ganglia originates from the hamate-triquetrum or piso-triquetrum joints and expand into the Guyon tunnel.
High-resolution Ultrasound (Ultrasound) is effective in diagnosing ganglion cysts, visualizing them as well-delineated anechoic masses without internal flow signals.
Diagnostic Modalities:
Ultrasound is useful for initial diagnosis but may not accurately depict the ganglion's origin due to the pedicle's poor visualization.
Preoperative planning may require additional imaging modalities such as MRI and CT arthrography after contrast injection to assess the ganglion's origin and extension in detail.
Other Causes:
Injuries to the ulnar artery causing thrombosis and pseudoaneurysm formation can compress the ulnar nerve.
Anomalous muscles within the tunnel, like the accessory abductor digiti minimi, may also lead to ulnar nerve compression.
Flexor Carpi Radialis Tenosynovitis:
The flexor carpi radialis tendon passes through the carpal tunnel, with tenosynovitis often occurring near its insertion.
Middle-aged women are commonly affected, presenting with radial wrist pain and a palpable lump, sometimes mistaken for a volar ganglion.
Pathogenesis involves friction within the carpal tunnel, exacerbated by osteoarthritis of the carpometacarpal and scapho-trapezium joints.
Diagnostic imaging, such as ultrasound (US), helps differentiate from volar ganglia, revealing swollen and irregularly hypoechoic tendon with synovial effusion.
Treatment involves conservative measures like anti-inflammatory drugs and splinting; surgery is reserved for refractory cases.
Flexor Carpi Ulnaris Tendinopathy:
The flexor carpi ulnaris tendon lacks a synovial sheath and commonly presents with calcifying tendinitis, predominantly in young to middle-aged women.
Symptoms include acute pain proximal to the pisiform, often with a tender and inflamed pisiform.
Diagnosis relies on clinical examination and radiological findings, with ultrasound revealing calcifications and signs of inflammation.
Treatment includes anti-inflammatory medications, ice, and immobilization, with steroid injections for severe pain.