De Maeseneer et al. Sonography of the Extensor Pollicis Longus Tendon

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1 Sonography of the Extensor Pollicis Longus Tendon Michel De Maeseneer 1,2,3 Stefaan Marcelis 2 M. Osteaux 2 Tjeerd Jager 2,4 Freddy Machiels 5 Peter Van Roy 3 De Maeseneer M, Marcelis S, Shahabpour M, Jager T, Machiels F, Van Roy P Received December 12, 2003; accepted after revision June 7, Supported by the A. L. Baert Prize, Katholieke Universiteit Leuven, 2001; the Department of Experimental Anatomy, Vrije Universiteit Brussel, Brussels, Belgium. 1 Department of Radiology, Vrije Universiteit Brussel, Laarbeeklaan 101, Brussels 1090, Belgium. Address correspondence to M. De Maeseneer (michel.demaeseneer@az.vub.ac.be). 2 Department of Radiology, Sint Andries, Tielt, Belgium. 3 Department of Experimental Anatomy, Vrije Universiteit Brussel, Brussels, Belgium. 4 Present address: Aalsters Stedelijk Zienkenhuis, Alast, Belgium. 5 Department of Radiology, Parc Leopold, Brussels, Belgium. AJR 2005;184: X/05/ American Roentgen Ray Society Sonography of a Rupture of the Tendon of the Extensor Pollicis Longus Muscle: Initial Clinical Experience and Correlation with Findings at Cadaveric Dissection OBJECTIVE. The objectives of our study were to report our initial clinical experience with sonography of the wrist for diagnosing a proximal rupture of the of the extensor pollicis longus (EPL) muscle and to perform sonographic anatomic correlation of the EPL. MATERIALS AND METHODS. Clinical and imaging files of five patients who underwent sonography and subsequent open wrist surgery were reviewed retrospectively. Imaging was performed by four radiologists experienced in musculoskeletal sonography. Tendon retraction was evaluated on sonography and at surgery. In cadavers, sonography was performed in concert by two musculoskeletal radiologists during progressive stages of dissection of four embalmed specimens. One specimen was sliced in the transverse plane. RESULTS. In cadavers, the EPL was located on or adjacent to Lister s tubercle and extended to the base of the thumb. The EPL crossed over the extensor carpi radialis s where it exhibited a flattened aspect. In the five patients in the study, a tubular-shaped hypoechoic area was evident at the position of the ruptured EPL on sonograms. At surgery, this area corresponded to fluid, hemorrhage, and scar tissue in the EPL sheath. The assessment of retraction on sonography correlated with findings at surgery. CONCLUSION. Sonography may aid in diagnosing a rupture of the EPL and in the preoperative assessment of gap size and position of the retracted ends. A characteristic tubular hypoechoic area may be seen crossing over the extensor carpi radialis s. arious conditions have been implicated in the proximal rupture V of the of the extensor pollicis longus (EPL) muscle at the wrist. Spontaneous ruptures of the EPL include wrist fractures, callus formation, and rheumatoid arthritis [1 5]; performing push-ups [1 5], prominent orthopedic fixation screws [1 5], and spontaneous ruptures of the EPL also have been reported [6, 7]. Often accurate diagnosis is delayed. In addition, it is not possible to assess the size of the tear on the basis of clinical findings or to determine the precise position of the retracted ends of the. Accurate diagnosis and assessment of the size of the tear are essential because these findings may show that a direct suture of the is possible, thus avoiding a graft procedure [8]. In addition, the position of the retracted ends determines the site of the surgical incision, which should be as small as possible for cosmetic concerns. The aims of our study were to diagnose the EPL rupture on sonography, evaluate associated lesions, and determine the degree of retraction. Hence, we studied the EPL using sonographic anatomic correlation during dissection of cadaveric specimens and report our initial clinical experience with sonography. Materials and Methods Cadaveric Study Five embalmed hand specimens were obtained from the department of anatomy (Vrije Universiteit Brussel). Embalming was performed immediately after death of the individuals (age range, years; mean age, 68 years). Before dissection, sonography was performed on an ATL HDI 5000 system (Philips) with a 12-MHz transducer in concert by two experienced musculoskeletal radiologists. Compound imaging was used liberally. The EPL was investigated in a transverse and longitudinal imaging plane from Lister s tubercle to the base of the thumb. We assessed the obliquity, thickness, and sonographic pattern of the. The second phase of the investigation consisted of a progressive dissection of four specimens: first, removal of skin; second, removal of subcutaneous AJR:184, January

2 fat; and third, removal of the extensor retinaculum. Dissections were performed in concert by a musculoskeletal radiologist and an anatomist. We assumed that if a structure was removed and then no longer seen on sonograms, its absence on sonography was proof that this structure corresponded to that present on sonography before removal. One specimen was frozen at 40 C and sliced in the transverse plane using a band saw. Clinical Study Sonography of the wrist was performed by musculoskeletal radiologists from four institutions, each of whom had at least 10 years of experience in musculoskeletal sonography. Informed consent was obtained to search patients records retrospectively. Five consecutive patients were identified during a 6-month period by searching the databases of the four institutions. The radiologists were given each patient s clinical history of pain, difficulty extending the thumb, or both. Different clinical systems were used (Prosound 5500, Aloka; ATL HDI 5000, Philips; Technos, Esaote; Elegra, Siemens) with 12-MHz transducers. A standoff pad was not used by any of the radiologists; instead, transmission gel was used liberally. For each sonographic evaluation, the patient sat on a chair in front of the examinator and placed the pronated wrist on the examination table. First, Lister s tubercle was identified as a bony protrusion on the dorsoradial aspect of the radius by placing the probe in the transverse plane. This tubercle was used as a landmark to identify the EPL. When the transducer is placed in an oblique plane extending from Lister s tubercle to the base of the first metacarpus, the normal course of the EPL can be identified. We continued with an assessment of the presence of the extensor indicis proprius. In addition, the extensor carpi radialis brevis and longus s were imaged in the transverse and longitudinal plane. On sonography the diagnosis of EPL rupture was made when a defect was noted in the normal fibrillar structure. A dynamic examination was performed to confirm the absence of continuity. The distance between the reappearance of fibrillar structures proximally and distally was assessed and indicated the degree of retraction. A diagnosis of extensor carpi radialis brevis and longus tenosynovitis was made when these s were thickened and heterogeneous and fluid was present in the synovial sheath. Results Anatomic Study After the skin and subcutaneous connective and fatty tissues were removed, the extensor retinaculum was exposed. On further dissection at the level of the first carpal row, the EPL crossed over the extensor carpi radialis brevis and longus s (Fig. 1). Anatomic slices showed the thin and flattened aspect of the extensor pollicis longus (Fig. 2). When reaching the base of the first metacarpal bone, the EPL joined the extensor pollicis brevis. At this position, the EPL was covered by fibrous dorsal reinforcements (Fig. 3). The oblique position of the EPL relative to the extensor carpi radialis brevis and longus s also was shown. The EPL was located on top of Fig. 1. Photograph of specimen 1 after partial removal of extensor retinaculum during dissection shows extensor pollicis longus (P) at intersection with extensor carpi radialis brevis (B) and longus (L) s. Tendon of extensor indicis proprius (i) is seen. On more radial aspect of wrist, extensor pollicis brevis and abductor pollicis longus s (arrowheads) are shown. Lister s tubercle in two of the five specimens and on the ulnar side of Lister s tubercle in the remaining three specimens. Sonography of Cadaveric Specimens The EPL was located either on the top of Lister s tubercle or on the ulnar side of the latter (Fig. 4). From this position, the EPL showed a 50 oblique course toward the base of the first metacarpal bone. In the longitudinal plane, a 2-mm-thick structure with a fibrillar pattern was recognized [8]. On sonography, the EPL was visualized in a transverse plane by rotating the probe 90 from the previously described position. When the described position of the ultrasound probe is used along the transverse aspect of the, the EPL appears either hypoechoic or hyperechoic depending on the obliquity of the ultrasound beam. The extensor s of the second digit also were depicted clearly [9]. Before and during all phases of dissection, the EPL was clearly identifiable in the longitudinal and transverse planes. Clinical Study The clinical and sonographic findings (Figs. 5 and 6) for five patients who underwent sonography and open wrist surgery are shown in Table 1. At surgery, the patients were placed in the dorsal decubitus position with the involved arm on the hand table. Surgery was performed by one of four surgeons experienced in wrist and surgery. The surgeons were aware of the findings in the sonography report. A ruptured EPL was identified in all patients. All patients underwent a transfer procedure. The hypoechoic tubular area seen on sonography corresponded to an empty sheath filled with fluid, hemorrhage, or scar tissue at surgery. Retraction was measured and correlated with findings on sonography. Discussion Clinical findings of proximal ruptures of the EPL usually include pain and the inability to extend the thumb. The latter finding, however, may be difficult to elicit because of associated conditions, such as wrist fracture and arthritis. When Lister s tubercle is used as a bony landmark, the normal position of the can be identified easily. Although MRI has been used in the evaluation of wrist s, in our experience this technique is not suited for the diagnosis of 176 AJR:184, January 2005

3 Sonography of the Extensor Pollicis Longus Tendon Fig. 2. Photograph of transverse slice of specimen 3 at level of distal radius shows that extensor pollicis longus (EPL) (P) is situated on ulnar aspect of extensor carpi radialis brevis (B) and longus (white L) s. EPL is seen on top of Lister s tubercle (black L). Also note extensor digitorum group (D). EPL abnormalities. This is related to the finding that the EPL at the level of the wrist has a 50 oblique orientation relative to the routine MRI planes that results in significant magic angle effect artifact. This limitation renders accurate MRI evaluation of the difficult even with the use of dedicated surface coils. In addition, the EPL, in contradistinction to the adjacent s, is flat at its crossing point over the s; even in a normal setting, the EPL may be difficult to depict on MRI. In our experience, the use of surface coils and special imaging planes may yield good results on MRI but is more time-consuming. We explored the use of sonography to assist in the diagnosis of proximal rupture of A Fig. 3. Photograph of dissection in specimen 4 shows proximally (curved arrow) that extensor pollicis longus (EPL) crosses over extensor carpi radialis s. More distally (small black arrows), EPL reaches base of metacarpal head where it joins extensor pollicis brevis (arrowheads) and is covered by dorsal reinforcements (r). EPL (large black arrow) continues distally. the of the EPL. In contradistinction to proximal ruptures, the EPL also may be avulsed from the distal phalanx, a situation similar to mallet finger. Our results indicate that sonography of the wrist can be used to show proximal rupture of the EPL and can aid in the assessment of the amount of retraction of the ends. Accurate diagnosis of a tear of the EPL B Fig. 4. Sonograms of specimen 3. A, Transverse sonogram of dorsal aspect of radius at level of Lister s tubercle (Li) shows that extensor pollicis longus (calipers) is located on top of Lister s tubercle. B, Sonogram obtained before dissection in oblique imaging plane extending from Lister s tubercle (L) to base of first metacarpal shows fibrillar structures of extensor pollicis longus (arrowheads). Left side of image is caudal; right side, cranial. AJR:184, January

4 Fig. 5. Sonograms of 36-year-old woman with extension deficit of thumb (patient 2 in Table 1). Left side of images is proximal; right side, distal. A, In longitudinal plane, hypoechoic area with fusiform (R) aspect (between stars) is seen at normal position of extensor pollicis longus (EPL). B, In longitudinal plane, transition zone (asterisk) between rupture (R) and normal fibers (arrows) is shown at base of first metacarpal bone. is important, so proper surgical treatment may be prescribed. In addition, sonography may depict additional findings in the adjacent s [9]. A Fig. 6. Sonogram in 37-year-old man with extension deficit of thumb (patient 3 in Table 1). Longitudinal view of extensor pollicis longus (EPL) shows empty sheath of EPL (r). Area of rupture (between stars) is indicated. Deep in relation to ruptured EPL, extensor carpi radialis (e) is shown. Left side is proximal; right side, distal. TABLE 1 Clinical and Sonographic Findings in Five Patients with Rupture of the Tendon of the Extensor Pollicis Longus Patient Sex Age (yr) Clinical Findings Sonographic Findings 1 M 40 Extension deficit, corticosteroid injection 2 F 36 Extension deficit, previous wrist fracture Hypoechoic area, cm, tenosynovitis of Hypoechoic area, cm, tenosynovitis of 3 M 37 Extension deficit, Slightly heterogeneous, cm previous radius fracture 4 M 24 Extension deficit, corticosteroid infiltrations Hypoechoic area, cm, tenosynovitis of 5 F 18 Pain Hypoechoic area, cm Sonography results in this study were similar in all patients. We found in five consecutive cases of rupture of the EPL the normal was replaced by a tubular hypoechoic or slightly heterogeneous area at the level of the proximal carpal row. As shown intraoperatively, the hypoechoic area corresponded to a synovial sheath distended by fluid, hemorrhage, or scar tissue. The ends were retracted proximally and distally. Tenosynovitis of the extensor carpi radialis brevis and longus s was an additional finding in three cases. On the basis of anatomic descriptions, this finding may be expected given the fact that at the intersection there is a communication between the synovial sheets of the EPL and the extensor carpi radialis s [10, 11]. Sonography aided in assessing the amount of retraction of the ends, as shown by the findings at surgical exploration. When the diagnosis of an EPL tear is confirmed, surgical therapy is mandatory to restore thumb and hand function. If retraction of the ends is limited, a direct suture is performed. However, if retraction is significant, a graft procedure is unavoidable. Hence, most typically the extensor indicis proprius is sectioned and is reattached to the distal stump of the EPL [2, 8]. Limitations of this study include the small number of clinical cases. This limitation is related primarily to the fact that the use of sonography for the preoperative assessment of EPL tears has not been addressed previously, to our knowledge, in the surgical or radiology literature. Additional studies are required to confirm our findings in a larger number of patients. The number of anatomic specimens also was limited, and the specimens used for our study may not represent all possible anatomic variations. In addition, neither intra- nor interobserver variability was calculated because of the B 178 AJR:184, January 2005

5 Sonography of the Extensor Pollicis Longus Tendon limited number of patients. All radiologists, however, were experienced in musculoskeletal sonography. The use of embalmed specimens yielded good results. This is in contradistinction to the situation with MRI anatomic correlation for which fresh specimens are better [12, 13]. In conclusion, sonography may be used to diagnose EPL tears and assess the amount of retraction. In addition, the status of the s that may be used as a graft, such as the extensor indicis proprius, may be evaluated. A characteristic hypoechoic or slightly heterogeneous tubular area was observed at the normal position of the torn EPL. Tenosynovitis of the extensor carpi radialis s, related to communication with the sheath of the EPL, also may be present. References 1. Hove LM. Delayed rupture of the thumb extensor : a 5-year study of 18 consecutive patients. Acta Orthop Scand 1994;65: Bonatz E, Kramer TD, Masear VR. Rupture of the extensor pollicis longus. Am J Orthop 1996;25: Failla JM, Koniuch MP, Moed BR. Extensor pollicis rupture at the tip of a prominent fixation screw: report of three cases. J Hand Surg 1993;18: Haher JN, Haher TR, Devlin VJ, Armenti V. Bilateral rupture of extensor pollicis longus: a case report. Orthopedics 1987;10: Denman EE. Rupture of the extensor pollicis longus: a crush injury. Hand 1979;11: Lloyd TW, Tyler MP, Roberts AH. Spontaneous rupture of extensor pollicis longus in a kick boxer. Br J Sports Med 1998;32: Dawson WJ. Sports-induced spontaneous rupture of the extensor pollicis longus. J Hand Surg 1992;17: Low CK, Pereira BP, Chao VT. Optimum tensioning position for extensor indicis to extensor pollicis longus tranfer. Clin Orthop 2001;388: Chiou HJ, Chou YH, Chang CY. Ultrasonograpy of the wrist. Can Assoc Radiol J 2001;52: Landsmeer JMF. The hand and hominisation. Acta Morphol Neerl Scand 1987;25: Landsmeer JMF, ed. Carpal area: atlas of anatomy of the hand, 1st ed. Edinburgh, London: Churchill Livingstone, 1976: Hodler J, Trudell D, Kang HS, Kjellin I, Resnick D. Inexpensive technique for performing magnetic resonance pathologic correlation in cadavers. Invest Radiol 1992;27: De Maeseneer M, Jager T, Vanderdood K, Van Roy P, Shahabpour M, Marcelis S. Ultrasound during dissection of cadaveric specimens: a new method for obtaining ultrasound anatomic correlations in musculoskeletal radiology. Eur Radiol 2004;14: AJR:184, January