A 43 year old female presents with radial side forearm pain after working in her garden for several days. MRI was obtained with axial fat-suppressed fast spin-echo T2-weighted (1a) and coronal inversion recovery-weighted (1b) images.
A 60 year old female returned from a week long ski vacation with a tender palpable mass over the dorsal wrist. She does not recall any specific wrist injury during the trip. MRI was obtained with axial (2a) and coronal (2b) inversion recovery-weighted images.
A 20 year old male runner developed plantar midfoot pain while training for a marathon. MRI was obtained with sagittal fat-suppressed fast spin-echo T2-weighted (3a), coronal inversion recovery-weighted (3b), and axial fat-suppressed fast spin-echo proton density-weighted (3c) images.
What are the findings? What is your diagnosis? What do all three cases have in common?
Intersection syndrome of the forearm.
Distal intersection tenosynovitis of the wrist.
Flexor hallucis longus tenosynovitis at the knot of Henry.
All three cases can be categorized as tendon intersection syndromes.
INTERSECTION SYNDROME OF THE FOREARM
Forearm pain and swelling at the junction of the first and second dorsal extensor tendon compartments due to overuse was first described by Velpeau in 1841, and subsequently termed “intersection syndrome” by Dobyns et al. in 1978.1 This entity has been known by numerous other names, including “crossover syndrome” or “APL syndrome” for its anatomic location, “peritendinitis crepitans” or “squeaker’s wrist” due to audible crepitus in some patients, “oarsmen’s wrist” or “Bugaboo forearm” from associated activities, and “subcutaneous perimyositis” as a description of the pathology.2,3,4
The main abnormality is noninfectious peritendinous inflammation in the first and second dorsal extensor tendon compartments around their site of intersection, located 4 to 8 cm proximal to Lister’s tubercle. The etiology was originally thought to be due to mechanical friction between the two tendon compartments.5 In 1985, Grundberg et al. proposed stenosis of the second extensor compartment as the underlying primary abnormality, with secondary inflammation and involvement of the adjacent first compartment tendons. Surgical release of only the second extensor compartment resulted in relief of symptoms in their series.6 Subsequent research by Idler et al. suggested that the extensor fascia of the forearm may also contribute to stenosis of the tendon compartments in this region.7 The exact etiology is still unclear, and may be multifactorial.8
Most patients report activities involving repetitive flexion and extension of the wrist. Athletes performing rowing, weightlifting, skiing and racquet sports are frequently seen.9,10,11 Patients working with agricultural or digging tools have been specifically reported in the literature, along with carpenters, secretaries, and supermarket checkout clerks.12,13 Onset and tempo of the disorder is highly variable, with some patients presenting after a single ski run or a brief episode of activity.2,10 Other patients have harvested rice with hand tools for weeks before reporting symptoms.13 Severity is also variable, with most cases being mild and responsive to conservative treatment. Severe cases can lead to complications such as tendon rupture or stenosing tenosynovitis, which may require surgical intervention.13,14,15
The abductor pollicis longus and extensor pollicis brevis muscles originate from the posterior radius and interosseous membrane. The tendons course in the first dorsal extensor tendon compartment toward their insertions on the thumb. The extensor carpi radialis brevis and longus originate at the lateral humeral epicondyle, and course in the second dorsal extensor tendon compartment toward their metacarpal insertions. The first compartment tendons cross over the second compartment tendons in the radial dorsal forearm, approximately 4 cm proximal to Lister’s tubercle.4,5,16 This intersection creates a mechanically disadvantageous arrangement where thumb and wrist motion results in friction between the crossing tendons.17,18
Because the crossover is located on average 4 cm proximal to the radiocarpal joint, most standard wrist MRI protocols will not include the intersection. Additional images of the forearm may be needed to evaluate this region if the clinician orders a wrist examination. Marking the area of symptoms can be useful to ensure imaging of the correct anatomic region.4,5
The most commonly reported MR finding in intersection syndrome is peritendinous edema and fluid around the abductor pollicis longus (APL), extensor pollicis brevis (EPB), extensor carpi radialis brevis (ECRB) and extensor carpi radialis longus (ECRL) tendons at the point of intersection. Adjacent subcutaneous edema, proximal and distal extension of peritendinous edema and fluid from the intersection are also common findings.4,5,17,18,19 (Case 12) Tendinosis, muscular edema, adjacent adventitial bursitis, ganglion cyst and periosteal edema are less commonly seen.18 (Cases 13 and 14) After intravenous contrast, enhancement is usually present in the areas of peritendinous edema, but is not particularly helpful in the diagnosis.5
12. Intersection syndrome with associated muscular edema and subcutaneous edema.
13. Ganglion cyst associated with intersection syndrome.
14. Periosteal reaction and marrow edema associated with intersection syndrome
Intersection syndrome needs to be differentiated from de Quervain’s tenosynovitis, as treatment of de Quervain’s tends to be more aggressive with earlier utilization of injections and surgery.3 Usually, the distal location of symptoms in de Quervain’s tenosynovitis is sufficient to make the correct diagnosis, but occasionally the symptoms may overlap, or both entities may be present. (Case 15) In these cases, MRI can be very helpful for accurate diagnosis. Other causes of forearm pain such as Wartenberg’s syndrome, muscle strain, or ganglion cyst can also be differentiated from intersection syndrome by MRI.5,16
15. Coexistence of intersection syndrome and de Quervain’s tenosynovitis.
Initial treatment is similar to most overuse syndromes with rest and modification of activity, oral NSAIDs, ice, and splinting with the wrist in mild extension.3,14 Taping the forearm has also been reported to reduce symptoms.20
A course of oral corticosteroids and injection of a local anesthetic and corticosteroid mixture adjacent to the site of swelling may be performed in patients who do not respond to conservative treatment.3,4,14 Most patients will respond to nonoperative treatment, but some may require surgical synovectomy and decompression.15
DISTAL INTERSECTION TENOSYNOVITIS OF THE WRIST
Noninfectious tenosynovitis involving the extensor pollicis longus (EPL), extensor carpi radialis brevis (ECRB) and longus (ECRL) tendons over the wrist is less commonly reported in the literature than the classic forearm intersection syndrome. Patients present with dorsal wrist pain and swelling, sometimes after a traumatic event. Anecdotal occupational or recreational overuse in skiers and kickboxers has been reported. Symptoms may mimic those of osteoarthritis or a ganglion cyst.21,22,23 Autoimmune diseases such as rheumatoid arthritis or lupus may predispose to tendinopathy in this region, particularly involving the EPL.21,24
Severity is variable; most cases are mild and respond to conservative treatment, but some patients are much more symptomatic and may progress to a complete tear of the extensor pollicis longus. Synovectomy and tendon repair may be necessary in these cases.22
The EPL, ECRB and ECRL tendons intersect distal to the radiocarpal joint and Lister’s tubercle. The tubercle acts as a pulley, altering the angle of the EPL tendon so that it crosses superficially over the ECRB and ECRL. This creates a mechanically disadvantageous arrangement, where motion of the thumb and hand may cause friction between the tendons.21,22,24
Several other anatomic factors may contribute to pathology in this location. Lister’s tubercle can irritate the EPL due to mechanical friction, particularly if there has been previous fracture or deformity of the tubercle.24 The second and third extensor compartments communicate with each other in this area, allowing inflammation in one compartment to spread to the adjacent compartment. The extensor retinaculum may limit the space available around the tendons in this region, constricting the compartments and resulting in increased pressure on the tendons. Finally, the EPL tendon has a watershed vascular supply in this region, making it vulnerable to ischemia.21,22,24
The main finding is peritendinous edema, fluid and distention of the tendon compartments of the EPL, ECRB and ECRL at their point of intersection. Associated findings include tendinosis with thickening and/or increased signal in the involved tendons, partial tendon tears, and reactive marrow edema in adjacent osseous structures such as Lister’s tubercle.21,22 (Cases 17 and 18) Complete tear with discontinuity of the EPL and retraction of the proximal fragment may be seen in severe cases. (Case 19) Distal intersection tenosynovitis can coexist with the more proximal forearm intersection syndrome. (Case 20) Anomalous position of the EPL lateral to Lister’s tubercle is rare, but predisposes patients to tenosynovitis.25 (Case 21)
17. Distal intersection tenosynovitis with tendinosis of the EPL and ECRB.
18. Severe distal intersection tenosynovitis with partial tears of the EPL, ECRB and ECRL.
19. Severe distal intersection tenosynovitis with complete tears of the EPL and ECRB.
20. Coexistence of forearm intersection syndrome and distal intersection tenosynovitis.
21. Anomalous lateral position of the EPL with tenosynovitis of the EPL and ECRB.
Most cases of distal intersection tenosynovitis not related to autoimmune disease or radial fracture tend to be mild, and respond well to conservative treatment. Severe cases may progress to EPL tendon rupture and require surgical treatment.21,22,23,24 Direct EPL tendon repair is often difficult due to tendon retraction and poor quality of remaining tendon tissue. Tendon transfer or graft may be necessary in such cases.24
FLEXOR HALLUCIS LONGUS TENOSYNOVITIS AT THE KNOT OF HENRY
The flexor hallucis longus tendon has a long course from its muscular origin to the distal insertion in the great toe, with several points of anatomic vulnerability to wear and friction. Tendinopathy is most commonly seen at the tibiotalar joint as the tendon curves over the posterior talus. Distal disease at the hallux sesamoids is next most frequent, followed by the intersection of the flexor hallucis longus with the flexor digitorum longus. This intersection is known variously as the “knot of Henry”, “Henry’s knot”, or the “master knot of Henry”.26
The flexor hallucis longus (FHL) muscle originates from the lower fibula and interosseous membrane, lateral to the flexor digitorum longus (FDL) muscle which originates from the inferior tibia. The FDL tendon crosses superficially over the FHL in the plantar midfoot at the knot of Henry, which is usually located over the navicular and medial cuneiform in most patients. This anatomic relationship creates a mechanically disadvantageous site similar to the intersection syndromes of the upper extremity.26,27,28 A fibrous slip connects the FHL and FDL at the knot of Henry, which tends to maintain their anatomic relationship at this location.29 The tendon sheaths of the FHL and FDL usually communicate, which allows inflammation of one structure to spread to the adjacent tendon.27
Another tendon intersection site has been identified in the lower leg as the FDL crosses superficially over the posterior tibial tendon, called the chiasma crurale. However, there is no reported clinical impingement syndrome at this site, and histologic examination of cadaveric tendons at this location did not reveal significant tendon degeneration.30
MRI findings in mild cases are typical of tenosynovitis, including peritendinous fluid and edema around the FHL and FDL at the knot of Henry.26,27 (Cases 23 and 24) More severe cases may demonstrate synovial hypertrophy in the tendon sheath, outpouching of the tendon sheath, tendinosis, partial or complete tendon tears. Stenosing tenosynovitis with thickening and fibrosis of the tendon sheath can be difficult to diagnose on MRI due to relatively scant peritendinous fluid signal; tenography may be useful for diagnosis and treatment in these patients.27,28,31
23. Flexor hallucis longus tenosynovitis.
24. Flexor hallucis longus and flexor digitorum longus tenosynovitis centered at the knot of Henry.
As with other overuse syndromes, mild FHL or FDL tenosynovitis is initially treated conservatively with rest and oral anti-inflammatory agents. Tenography can be diagnostic and therapeutic in persistently symptomatic patients. Injection of contrast material distends the tendon sheath and can visualize stenosis, synovial hypertrophy and outpouching. Injection of steroid and local anesthetic into the tendon sheath produces symptomatic improvement in most patients.27,28
Some cases, especially those with FHL tears and severe symptoms may require surgery. In these patients, surgical release of the knot of Henry with debridement of fibrotic tissue and tendon repair has been reported to produce symptomatic relief and functional improvement.28,32
Tendon intersection syndromes occur at several specific locations in the upper and lower extremities. Incidence is difficult to determine, since many cases are self-limited and may not come to clinical attention. Many patients are diagnosed based on clinical findings and treated conservatively, not requiring advanced imaging. Published reports in the radiology literature are sparse. Review of the Radsource experience over the past 8 years by keyword search revealed 38 cases of forearm intersection syndrome, 29 cases of distal intersection tenosynovitis, and 4 cases of flexor hallucis longus tenosynovitis at the knot of Henry.
MR imaging can be helpful in tendon intersection syndromes when history and physical examination are atypical or inconclusive. In some cases, intersection syndromes may coexist with other pathology which can also be diagnosed by MR. Early accurate diagnosis is important for appropriate treatment and optimal patient outcome.
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