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Original Report
November 2003

MRI Features of Intersection Syndrome of the Forearm

Abstract

OBJECTIVE. The purpose of this original report is to describe the MRI findings in patients with intersection syndrome of the forearm.
CONCLUSION. Intersection syndrome is an overuse disorder of the dorsal distal forearm, presenting with particular symptoms and signs that may be clinically misdiagnosed. MRI can perform an important role in establishing the diagnosis. Peritendinous edema (peritendinitis) around the first and second extensor compartment tendons, extending proximally from the crossover point, is the most characteristic finding that should suggest a diagnosis of intersection syndrome. Chronic cases may be subtle and not show substantial MRI findings likely reflecting the development of a stenosing tenosynovitis.

Introduction

Pain of the dorsal aspect of the distal forearm and wrist is common. Symptoms may arise from either joint structures or periarticular soft tissue. The most frequent differential diagnoses include wrist ligament sprain, ganglion cyst, tendinitis, and muscle strain [1]. History and physical examination often provide a specific diagnosis or limit the differential, but the diagnosis remains uncertain in a subset of patients because of an atypical presentation or because of a rarely encountered or unrecognized entity. MRI can improve the evaluation of forearm and wrist symptoms.
The intersection syndrome is a noninfectious inflammatory process of the second extensor compartment tendons of the forearm, characterized by the presence of pain and swelling proximal to the Lister tubercle of the distal radius. Symptoms occur where the first extensor compartment tendons (the abductor pollicis longus and the extensor pollicis brevis tendons), crosses over the second extensor compartment tendons (the extensor carpi radialis longus and the extensor carpi radialis brevis tendons) (Fig. 1).
Fig. 1. Diagram of anatomy of intersection point of first extensor compartment (abductor pollicis longus and extensor pollicis brevis tendons) and second extensor compartment (extensor carpi radialis longus and brevis tendons) in distal forearm.
Our purpose is to report and illustrate the MRI findings of intersection syndrome and review the literature concerning this condition.

Materials and Methods

We reviewed the clinical and imaging findings of patients in whom MRI of the distal forearm and wrist suggested the diagnosis of intersection syndrome. The subjects were identified by a radiology information system search of all MRIs performed at our institution over a 5-year period. Next, we determined which patients' findings had correlation with the referring health care provider's clinical examination or clinical follow-up after MRI. Clinical features used included point tenderness on the dorsum of the forearm, 3–8 cm proximal to the wrist joint; crepitus with passive or active motion; and visible swelling along the course of the affected tendons. Inclusion criteria required that a 3-month clinical follow-up was available to document therapeutic response and exclude other diagnoses. This selection methodology yielded three cases. The total number of MRI examinations of the wrist and forearm over a 5-year period were 1,815 (1,684 wrists and 131 forearms). The incidence of verified intersection syndrome in our referral population for MRI was 0.2% (3/1,815).
MRIs of the forearm of two patients were obtained on a 1.5-T scanner (Signa, General Electric Medical Systems, Milwaukee, WI) using an extremity coil. The forearm was scanned in a neutral position. The parameters for these MRI examinations were as follows: axial T1-weighted conventional spin-echo images (TR/TE, 400/14; matrix size, 256 × 128; excitations, 2; field of view, 12 cm; slice thickness, 5 mm; interslice gap, 1 mm); axial fat-suppressed T2-weighted fast spin-echo images (TR/TEeff, 2,300/88; echo-train length, 8; matrix size, 512 × 320; excitations, 2; field of view, 12 cm; slice thickness, 5 mm; interslice gap, 1 mm); sagittal fast spin-echo STIR (TR/TE, 3,350/43; inversion time, 150; matrix size, 256 × 192; excitations, 1.5; field of view, 14 cm; slice thickness, 4 mm; interslice gap, 1 mm); and coronal T1-weighted spin-echo images (400/14; matrix size, 256 × 192; excitations, 1.5; field of view, 12 cm; slice thickness, 3 mm; interslice gap, 1 mm). In one patient with a suspected mass of the forearm, the following sequences were additionally performed after IV administration of 0.1 mmol/kg of gadopentetate dimeglumine (Magnevist, Berlex Laboratories, Wayne, NJ): axial fat-suppressed T1-weighted images (450/11; matrix size, 256 × 128; excitations, 2; field of view, 18 cm; slice thickness, 4 mm; interslice gap, 1 mm); coronal fat-suppressed fast multiplanar spoiled gradient-echo (200/4; matrix size, 256 × 128; excitations, 2; field of view, 12 cm; slice thickness, 4 mm; interslice gap, 1 mm).
MRIs of the other patient were obtained on a 0.3-T scanner (Airis II, Hitachi Medical Systems America, Twinsburg, OH) using an extremity coil with the forearm in a neutral position. The protocol used was the following: axial T1-weighted conventional spinecho images (500/25; matrix size, 256 × 256; field of view, 16 cm; slice thickness, 5 mm; interslice gap, 2 mm); axial T2-weighted fast spin-echo images (6,000/125; echo-train length, 10; matrix size, 256 × 256; field of view, 16 cm; slice thickness, 5 mm; interslice gap, 2 mm); axial fast spin-echo STIR images (2,000/25; inversion time, 100 msec; matrix size, 256 × 256; field of view, 16 cm; slice thickness, 5 mm; interslice gap, 1 mm); sagittal T1-weighted conventional spin-echo images (500/25; matrix size, 256 × 256; field of view, 20 cm; slice thickness, 4 mm; interslice gap, 1.5 mm); sagittal T2-weighted fast spin-echo images (4,600/80; echo-train length, 8; matrix size, 256 × 256; field of view, 20 cm; slice thickness, 4 mm; interslice gap, 1.5 mm); coronal T1-weighted conventional spin-echo images (500/25; matrix size, 256 × 256; field of view, 20 cm; slice thickness, 4 mm; interslice gap, 1.5 mm); coronal fast spin-echo STIR images (2,000/25; inversion time, 100; matrix size, 256 × 256; field of view, 20 cm; slice thickness, 4 mm; interslice gap, 1.5 mm).
The scans were graded in consensus by two radiologists experienced in musculoskeletal MRI for the following features: thickness of the abductor pollicis longus (APL), extensor pollicis brevis (EPB), extensor carpi radialis longus (ECRL), and extensor carpi radialis brevis (ECRB) tendons; abnormal signal intensity within the tendons; peritendinous edema and fluid signal or enhancement; edema in surrounding subcutaneous tissue; and muscle signal abnormality. Tendon thickening was subjectively assessed by comparison to the tendons in extensor compartments 3–6 and by morphologic alteration from a comma-shaped structure to a more rounded configuration on axial images.

Results

MRI and medical record documentation were reviewed for the three cases of intersection syndrome. The patients were all men, 22, 28, and 59 years old. The mean age was 36 years old. All patients were referred for MRI, but none had an initial clinical diagnosis of intersection syndrome.
One patient (Fig. 2A, 2B, 2C) was a tennis player referred for evaluation of a new-onset painful mass. The second patient (Fig. 3A, 3B, 3C) had new-onset forearm pain in which a pronator tendon rupture was suspected after skiing. The final patient (Fig. 4) presented with chronic pain and swelling of the distal forearm, occurring over the previous several months, which was believed to be occupationally related because he was an industrial worker whose job required repetitive wrist flexion and extension.
Fig. 2A. 28-year-old male tennis player who presented with tender mass on distal forearm. Axial T2-weighted fat-suppressed fast spin-echo image (TR/TEeff, 2,300/88) shows peritendinous and subcutaneous edema (arrow) in region of intersection of first extensor compartment and second extensor compartment tendons. Individual tendons are not well discerned.
Fig. 2B. 28-year-old male tennis player who presented with tender mass on distal forearm. Axial fat-suppressed T1-weighted image (450/11) shows tendon anatomy at crossover junction. First extensor compartment tendons, abductor pollicis longus (black arrow) and extensor pollicis brevis tendons (black arrowhead), cross superficial relative to second extensor compartment tendons, extensor carpi radialis longus (white arrow) and extensor carpi radialis brevis tendons (white arrowhead).
Fig. 2C. 28-year-old male tennis player who presented with tender mass on distal forearm. Contrast-enhanced axial fat-suppressed T1-weighted image (450/11) shows enhancement predominantly in interval between first and second extensor compartment tendons (arrowhead) very likely reflecting inflammation from focal friction and advential bursitis.
Fig. 3A. 59-year-old man with new-onset forearm pain after skiing in whom pronator tendon rupture was suspected clinically. Axial T1-weighted spin-echo image (TR/TE, 500/25) shows extensor carpi radialis longus (arrow) and extensor carpi radialis brevis (arrowhead) tendons to be separately discernible because of tenosynovial fluid.
Fig. 3B. 59-year-old man with new-onset forearm pain after skiing in whom pronator tendon rupture was suspected clinically. Axial STIR fast spin-echo image (2,000/25; inversion time, 100 msec) shows marked peritendinous soft-tissue edema present on this fluid-sensitive sequence (arrow) at crossover point between first and second extensor compartment tendons.
Fig. 3C. 59-year-old man with new-onset forearm pain after skiing in whom pronator tendon rupture was suspected clinically. Axial T2-weighted fast spin-echo image (6,000/125) shows more discrete circumferential fluid signal collection to be evident around extensor carpi radialis longus tendon likely reflecting associated tenosynovitis (arrowhead).
Fig. 4. 22-year-old man who presented with chronic pain and swelling of distal forearm believed to be occupationally related. Axial fat-suppressed T2-weighted fast spin-echo image (TR/TEeff, 2,300/88) shows minimal thickening (arrow) of second extensor compartment tendons (extensor carpi radialis longus and brevis tendons are not separately discernible) and minimal peritendinous edema (arrowhead) surrounding both second and first extensor compartment tendons (abductor pollicis longus and extensor pollicis brevis tendons are not separately discernible). In this case, morphologic alterations are subtle, and edema is not prominent or conspicuous because of chronicity and likely development of stenosing-type tenosynovitis. However, after findings on MRI suggested diagnosis of intersection syndrome, specific therapy, including local corticosteroid injection, was initiated. The patient responded to therapy.
Review of the MRIs showed tendon thickening in two patients, one minimal (Fig. 4) and one mild. There was no signal alteration in any of the tendons of interest. All patients had peritendinous edema of some degree (minimal, moderate, or severe) involving one or more of the first or second extensor compartment tendons (Figs. 2A, 2B, 2C, 3A, 3B, 3C, 4). Peritendinous edema surrounding the junction of the abductor pollicis longus and extensor pollicis brevis tendons (first extensor compartment tendon) with the extensor carpi radialis longus and extensor carpi radialis brevis tendons (second extensor compartment tendon) was present in two patients; in one of these patients, the appearance of tenosynovitis with a discrete fluid-filled tendon sheath was visible (Fig. 3A, 3B, 3C). The edema–fluid characteristically began at the crossover point and extended proximally for an average of 3.5 cm. Adjacent mild subcutaneous edema was present in two patients. In the patient who had imaging performed after the administration of IV contrast material, peritendinous enhancement was observed at the intersection (Fig. 2A, 2B, 2C). This enhancement was focally more prominent in the interval between the first and second extensor compartment tendons. There was no signal abnormality in the muscles of any patient. Distal tenosynovitis at the level of the extensor retinaculum and fibroosseous tunnels on the dorsum of the wrist were not present for either the first or second extensor compartment tendons.
Review of the follow-up medical records revealed that all patients underwent medical treatment. Therapy for all patients consisted of avoiding exacerbating activities and taking a regimen of nonsteroidal antiinflammatory drugs. Two patients used a wrist splint for 2–3 weeks. One patient underwent rehabilitation consisting of range-of-motion exercises and wrist extensor strengthening. Two patients responded to therapy within a few weeks. The third patient responded to therapy after subsequently receiving a local corticosteroid injection. None of the patients underwent surgery. For all patients, it was only after the MRI evaluation that the diagnosis of intersection syndrome was made and specific therapy was instituted. In retrospect, all patients had clinical symptoms or a clinical context that was typical for intersection syndrome.

Discussion

Intersection syndrome is a specific painful disorder of the forearm that is relatively common and sometimes not correctly clinically diagnosed [2]. First described by Velpeau in 1841, it has also been referred to in the literature by the terms “peritendinitis crepitans,” “oarsmen's wrist,” “crossover syndrome,” “subcutaneous perimyositis,” “squeaker's wrist,” “bugaboo forearm,” and “abductor pollicis longus bursitis” or “abductor pollicus longus syndrome.” Dobyns et al. [3] introduced the term “intersection syndrome,” an anatomic designation related to the area in which the musculotendinous junctions of the first extensor compartment tendons (abductor pollicis longus and extensor pollicis brevis tendons) intersect the second extensor compartment tendons (extensor carpi radialis longus and extensor carpi radialis brevis tendons), at an angle of approximately 60° (Fig. 1).
In this study, we provide a descriptive report of a small case series of three patients (two with acute symptoms and one with chronic symptoms) who presented for MRI primarily because the diagnosis of intersection syndrome was not initialy suspected. There was a selection bias because only patients who had MRI findings based on the radiology reports were included. We do not have any information regarding the frequency of patients referred to MRI with the diagnosis of intersection syndrome who did not have these reported MRI findings. If the clinical index of suspicion (i.e., pretest probability) for intersection syndrome is high, advanced imaging would probably not be obtained. It is in the context of an uncertain diagnosis that MRI is likely be used; therefore, it is relevant for a radiologist to be familiar with intersection syndrome and the imaging manifestations.
There is no consensus about the pathophysiology of this condition. Two main hypotheses regarding the pathogenesis have been postulated. One hypothesis considers intersection syndrome to be a result of friction between the muscle bellies of the first extensor compartment tendon and the adjacent tendons of the second extensor compartment [4]. Another hypothesis implicates entrapment from stenosis; in 1985, Grundberg and Reagan [2] studied 13 patients with surgical correlation, and proposed that the syndrome may result from tightness of the tendon sheath of the extensor carpi radialis longus and extensor carpi radialis brevis tendons, causing swelling and tenderness proximally. The proportional contribution of these two factors remains uncertain, and they are not necessarily mutually exclusive causes if one considers that the tempo of the disorder may be acute from a single inciting overuse event (e.g., a weekend of skiing) or chronic from repetitive unaccustomed activity (e.g., daily work of a machinist). Nevertheless, the common pathologic features are noninfectious peritendinitis [4] and an associated local tenosynovitis in the acute setting (Fig. 3A, 3B, 3C) with the potential to develop into a stenosing tenosynovitis in the chronic setting (Fig. 4). As in other musculoskeletal friction related disorders, an adventitial bursitis [5] may occur (Fig. 2A, 2B, 2C).
There is an association with sports-related activities, such as rowing, canoeing, playing racket sports, horseback riding, and skiing [6, 7]. In 1994, Palmer and Lane-Larsen [8] reported a prevalence of 11.9% in a group of 42 skiers, developing typical symptoms within the first 2 days of activity. Presentation is pain and swelling in a region about 4–8 cm proximal to the Lister tubercle, where the first and second extensor compartment tendons cross. In more severe cases, wrist motion and direct palpation may produce crepitus.
MRI is well suited to show the findings of intersection syndrome, especially with fluid-sensitive sequences. The most important finding is the presence of peritendinous edema concentrically surrounding the second and the first extensor compartments, beginning at the point of crossover, 4–8 cm proximal to the Lister tubercle and extending proximally. Peritendinitis may be a more appropriate broader term, given that there may not be tendon sheath fluid found in this location [4]; interstitial fluid may surround the tendons and tendon sheaths or may be found in the interval between them at the intersection point.
A brief description of the anatomy of the tendon sheaths in this location is relevant to the imaging findings. On the dorsal side of the wrist, the extensor tendons of the fingers and thumb pass underneath a band of fibrous tissue, the extensor retinaculum. As opposed to the palmar side, where most of the tendons go through a common carpal tunnel, the tendons on the extensor side are separated into six different compartments by septa of connective tissue. After passing the wrist, the tendons diverge on their way toward the digits. The tendon sheaths lining these compartments extend proximally relative to the extensor retinaculum to a level near the myotendinous junctions, but this is believed to be variable and not well documented in anatomic or imaging studies. The implication is that intersection syndrome may have findings of an associated reactive tenosynovitis (Fig. 3A, 3B, 3C). Mild subcutaneous edema adjacent to the intersection point is also a feature, probably resulting from surrounding hyperemia. Findings of tendinosis (thickening and signal abnormality) may not be present, reflecting principally a peritendinous phenomenon. Mild tendon thickening and morphologic alterations are often subjective and raise a set of observer performance issues when trying to apply these findings consistently in practice.
The treatment paradigm is similar to other overuse injuries. Conservative measures are the first line of treatment. Symptoms resolve within 2–3 weeks in 60% of patients with rest, administration of nonsteroid antiinflammatory drugs, and splinting. Surgery is indicated typically only for patients not responding to therapy [9]. When conservative treatment fails, a tenosynovectomy and a fasciotomy of abductor pollicis longus can be performed.
The main differential diagnosis is de Quervain's tenosynovitis, which may require an earlier surgical intervention [10]. De Quervain's tenosynovitis represents an inflammatory stenosing process of the first dorsal extensor compartment tendons and differs clinically from the intersection syndrome because the presence of pain and swelling is referred to a more distal location, at the radial styloid process. Finkelstein's test [11] is a pathognomonic physical examination finding of this condition, resulting in pain by “grasping the patients thumb and quickly abducting the hand ulnarward.” MRI features of de Quervain's disease are distinct, as described by Glajchen and Schweitzer [12]. The findings are increased tendon thickness within the first extensor compartment (abductor pollicis longus and extensor pollicis brevis tendons) at the level of the distal radius and increased signal within the surrounding synovial sheath, reflecting tenosynovitis. Surrounding subcutaneous edema is found in some patients.
In summary, intersection syndrome of the forearm can have unique MRI features, which have not been previously described, reflecting the proposed abnormality of peritendinous inflammation and irritation, particularly in the subacute setting. Radiologists should be aware of this condition because the clinical diagnosis may be enigmatic.

Footnote

Address correspondence to J. A. Carrino ([email protected]).

References

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2.
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Information & Authors

Information

Published In

American Journal of Roentgenology
Pages: 1245 - 1249
PubMed: 14573413

History

Submitted: November 18, 2002
Accepted: April 30, 2003

Authors

Affiliations

C. Rosalia Costa
Department of Radiology, Thomas Jefferson University Hospital, Ste. 3390, 111 S 11th St., Philadelphia, PA 19107.
Present address: Department of Radiology, Instituto Portugues de Oncologia de Francisco Gentil, Centro Regional Porto, Rua Dr. Antonio Bernardino de Almeida, Porto 4200, Portugal.
William B. Morrison
Department of Radiology, Thomas Jefferson University Hospital, Ste. 3390, 111 S 11th St., Philadelphia, PA 19107.
John A. Carrino
Department of Radiology, Thomas Jefferson University Hospital, Ste. 3390, 111 S 11th St., Philadelphia, PA 19107.
Present address: Department of Radiology, Brigham and Women's Hospital, 75 Francis St., Boston, MA 02155.

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