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Ultrasound findings in injuries of dorsal extensor hood: Correlation with MR and follow-up findings
European Journal of Radiology 77 (2011) 249–253
Contents lists available at ScienceDirect
European Journal of Radiology journal homepage: www.elsevier.com/locate/ejrad
Ultrasound findings in injuries of dorsal extensor hood: Correlation with MR and follow-up findings Mimoun Kichouh a,b , Michel De Maeseneer a,∗ , Tjeerd Jager b , Stefaan Marcelis c , Eddy Van Hedent b , Peter Van Roy d , Johan De Mey a a
Department of Radiology, Vrije Universiteit Brussel, Laarbeeklaan 101, 1090 Jette, Brussel, Belgium Department of Radiology, Aalsters Stedelijk Ziekenhuis, Aalst, Belgium Department of Radiology, Sint Andries Ziekenhuis, Tielt, Belgium d Department of Experimental Anatomy, Vrije Universiteit Brussel, Brussel, Belgium b c
a r t i c l e
i n f o
Article history: Received 18 February 2010 Received in revised form 18 May 2010 Accepted 21 May 2010 Keywords: Dorsal hood Extensor hood Sagittal band injuries Extensor retinaculum system MCP joint injuries
a b s t r a c t Objective: The aim of this study was to use ultrasound to examine the dorsal hood in nine patients with a clinical suspicion of dorsal hood injuries. Material and methods: Clinical and imaging files from interesting case logbooks of nine patients were reviewed. Ultrasound was performed by one of the three radiologists experienced in musculoskeletal ultrasound. The examinations were also performed in flexion and in flexion with resistance. MR correlation was obtained in six patients. One patient underwent surgery. To obtain anatomical correlation of the normal dorsal hood 2 embalmed hand specimens were dissected. Results: The sagittal bands were easily depicted in the transverse plane on ultrasound images and presented as hypoechoic bands on both sides of the extensor communis tendons. Injuries of the sagittal bands were seen on ultrasound as hypoechoic thickening of the sagittal bands at the side of the extensor tendons. The normal shape of the sagittal bands was also no longer recognizable. Subluxations or dislocations of the extensor tendons were also seen. When the injuries were located in the fibrous slips between the extensor indicis and the extensor communis of the second finger, subluxations with an increased distance between these 2 tendons were seen, especially in flexion, or in flexion with resistance. Conclusion: Ultrasound is a valuable tool for the assessment of the injuries of the dorsal hood and is an easily available method for the diagnosis of the fine soft tissue components of the dorsal hood region. © 2010 Elsevier Ireland Ltd. All rights reserved.
1. Introduction The dorsal hood or extensor hood is a retinacular system that stabilizes the extensor tendon at the dorsal aspect of the metacarpophalangeal joint (MCP) aiding to keep the tendon in place during flexion and extension. It is formed by three retinacular structures: the sagittal, oblique, and transverse bands. The latter two correspond to a fibrous extension of the lumbrical and interosseous muscles. The sagittal band (SB) is the most important structure of the extensor hood. It restricts proximal displacement of the extensor tendon and contributes to the extension of the digit [1–4]. The sagittal bands run circumferentially around the MCP joint and insert ventrally on the palmar plate and the deep transverse metacarpal ligament (DTML). Dorsally, the sagittal band is divided into a superficial and deep layer forming a tunnel through which the extensor digitorum tendon courses.
∗ Corresponding author. Tel.: +32 2 477 5323; fax: +32 2 477 5362. E-mail address: [email protected] (M. De Maeseneer). 0720-048X/$ – see front matter © 2010 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.ejrad.2010.05.015
Ruptures of the sagittal bands are reported to occur spontaneously or in association with metacarpophalangeal joint trauma such as boxer knuckle. They have also been reported with synovial disorders such as rheumatoid arthritis and psoriasis. Congenitally absent or lax sagittal bands have also been described [5,6]. These individuals may have pain or a snapping sensation or may be asymptomatic. Although dislocations are uncommon, dorsal hood injuries may lead to persistent disability. Therefore prompt diagnosis of these lesions is essential. Ultrasound imaging is an easily available technique allowing diagnosis of various soft tissue injuries. There are several publications about MR imaging of the dorsal hood [1,4,7,8]. However the role of ultrasound in the diagnosis of sagittal band injury has only been addressed in a few articles [6,9,10]. A previous case series reports on ultrasound findings in three patients [6]. Although there are a few articles dealing with evaluation of soft tissue structures of the hand including, tendons, ligaments, and retinaculum the literature on the dorsal hood is limited. The aim of this study was to assess the role of ultrasound in the diagnosis of injuries of the dorsal hood and describe the ultrasound
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imaging signs of such injuries. We correlated our findings with magnetic resonance imaging and follow-up. We also discuss the clinical findings and MR imaging findings of injuries of the dorsal hood. Cadaveric dissections were performed to better understand the normal anatomy of the uninjured dorsal hood. 2. Material and methods 2.1. Cadaveric study Dissection of two embalmed hand specimens obtained from the department of anatomy and amputated at the level of the distal forearm was performed. After the skin and subcutaneous connective and fatty tissues were removed, the dorsal hood was exposed. One specimen was frozen at −40 ◦ C and sliced in the transverse plane at the MCP level. Before dissection, ultrasound imaging was performed on an Acuson Antares (Siemens Medical Systems, Erlangen, Germany).
Fig. 1. Transverse ultrasound at MC II level of contralateral hand. The extensor tendons at metacarpal 2 level are shown (E). The curved arrow points to the ulnar sagittal band. The superficial fibrous slips are seen (arrowhead). Also note the deep fibrous slips (short bold arrow). The deep layer of the sagittal band is seen (straight arrow).
2.2. Clinical study During a 1-year period, nine patients (5 males, 4 females; age range, 27–54 years) were examined in our institution for pain at the dorsal aspect of the metacarpophalangeal joint and with a clinical suspicion of dorsal hood injuries. The patients were identified from interesting case logbooks. MR imaging was performed on a 1.5 T system (Symphony, Siemens, Erlangen, Germany) and consisted of two or more of the following sequences: axial T2 turbo spin echo (TR/TE, 3700/84; NEX, 3; FOV, 140 × 80; matrix size, 256 × 256; slice thickness, 3.0 mm; TA, 3.03), axial T1 spin echo (TR/TE, 521/22; NEX, 1; FOV, 140 × 80; matrix size, 512 × 307; slice thickness, 3 mm; TA, 2.03), and axial T2 turbo spin echo with fat suppression (TR/TE, 2450/75; NEX, 3; FOV, 140 × 80; matrix size, 256 × 192; slice thickness, 2.7 mm; TA, 2,38). The MR images were reviewed by consensus by 2 experienced musculoskeletal radiologists. Ultrasound imaging was performed by one of the three musculoskeletal radiologists experienced in musculoskeletal ultrasound. The radiologist who performed the ultrasound study was mostly aware of the MR findings. The ultrasound system employed was an Aloka Alpha 10 (Aloka, Japan) with a 15 MHz linear transducer. A standoff pad or ultrasound gel was used depending on the case. The metacarpophalangeal joints were examined in the axial and longitudinal plane. We assessed the joints, extensor communis tendons, and the dorsal hoods. A comparison was made with the asymptomatic contralateral finger. In our study, ultrasound imaging was performed in flexion and extension of the MCP joints. When a tear of the sagittal band was diagnosed, an additional assessment in flexion with resistance was performed to exclude subluxation or luxation of the tendons. Luxation of the tendon was defined as a position of the tendon to the side of the finger. Subluxation was defined as an intermediate position between the normal dorsal position of the extensor tendon and the luxated position. Six patients underwent an ultrasound follow-up examination 6 months after the first assessment.
Fig. 2. Normal transverse image of the third metacarpophalangeal joint in contralateral hand. The common extensor tendon is seen (star). Note the radial and ulnar sagittal bands (arrows).
Fig. 3. Normal transverse image in contralateral hand of the fourth metacarpophalangeal joint. Note the common extensor tendon (E) and the radial and ulnar sagittal band (curved arrows).
and the proximal interphalangeal joints. The latter two are very thin and therefore much more difficult to depict on ultrasound imaging. The sagittal bands are easily visualized in the transverse plane at ultrasound imaging. They present as hypoechoic bands on both sides of the extensor communis tendons (Figs. 1–4). The superficial layer of the SB runs over the extensor tendons. Together with a layer running under the tendons, the superficial layer forms a tunnel in which the extensor digitorum tendons are located (Fig. 1). The layers appear as fine linear hypoechoic structures oriented circumferentially and coursing from the extensor tendons to the palmar plates. The sagittal bands are best seen in the axial plane with the
3. Results 3.1. Cadaveric results and findings in normal hands The extensor tendons are strongly attached at the MCP level by the sagittal bands which are thick and oriented perpendicularly to the tendons (Figs. 1–4). The transverse and the oblique bands correspond to fibrous extensions respectively of the interosseous and lumbrical muscles and are located more distally, between the MCP
Fig. 4. Transverse ultrasound image of metacarpal 5 (MC V) in contralateral hand. Note the extensor tendons (E). Radial and ulnar sagittal bands are seen (curved arrows).
M. Kichouh et al. / European Journal of Radiology 77 (2011) 249–253
Fig. 5. (a) Transverse ultrasound image in 50-year-old man with pain along metacarpal 3 (MCP III). Note hypoechoic thickening of the radial portion of the sagittal band (arrow). The extensor tendon (E) was not displaced. Note connective tissue (C). (b) Transverse proton density weighted image in same 50-year-old man. Note increased signal intensity and thickening of the radial band corresponding to a focal rupture of the radial portion of the sagittal band (arrow).
hand in extension and the MCP in slight flexion. The probe should be placed just proximal from the MCP joint. The connective tissue and the joint capsules located deep to the central tendons appear as a thick hyperechoic structure (Figs. 1–4). The extensor tendons are in close proximity to the sagittal bands (Figs. 1–4). 3.2. Clinical study There were 5 men and 4 women with a mean age of 43 years (range, 27–54 years). The clinical symptoms were pain and swelling. The injured fingers included the second finger (n = 2), the third finger (n = 4), the fourth finger (n = 1), and the fifth finger (n = 2). In five patients there was a history of acute trauma whereas in four patients there was no trauma. In one of the latter patients there was a history of psoriasis. Hypoechoic thickening of the dorsal hood was present in all patients (Figs. 5–7). In four patients the radial band was involved, in one patient the ulnar band was involved, and in four patients the entire dorsal hood was involved. The extensor tendons were thickened in two patients and were ruptured in one patient (Fig. 7). At the fifth finger there was an increased distance between the two tendons in the two patients (Fig. 8). Ulnar subluxation was present in two patients (Fig. 7). On MR imaging (n = 5) there was increased signal intensity on T2 weighted images at the radial side of the dorsal hood in two patients and on the ulnar side in one patient. There was high signal of the entire dorsal hood in two patients. On T1 weighted imaging hypoechoic soft tissue infiltration with non-recognizable architecture of the sagittal band was seen with injury. In one patient the collateral ligament was injured, in one patient the extensor digitorum com-
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Fig. 6. (a) Transverse ultrasound image in 37-year-old woman. Note markedly thickened radial sagittal band (arrow), corresponding to tear. Note extensor tendon (E) and normal ulnar band (curved arrow). (b) Corresponding transverse T1 weighted image. Note marked soft tissue thickening in region of radial band (long arrow). Compare to normal sagittal band in third finger (curved arrow). Note extensor tendon (short arrow).
munis was ruptured and in one patient there was diffuse soft tissue edema. When a rupture of the dorsal hood was present a hypoechoic mass is seen in the location of the sagittal bands. The normal architecture of the SB is no longer seen at the side of the extensor tendons (Figs. 5–7). These findings are seen without subluxation of the tendons towards the contralateral side (Fig. 7). Two out of nine patients show a subluxation (Fig. 7). Injury of the dorsal hood is associated with tendon rupture in one patient (Fig. 7). With a rupture of the fibrous slips between the indicis proprius and the extensors communis of the second finger, a hypoechoic mass is present at the level of these fibrous slips. In addition an increased distance between the two tendons is evident (subluxation) (Fig. 8). The distance between the two tendons is considered abnormal based on a comparison with the contralateral side. In the six patients who underwent MR, the lesions seen on MR are correctly diagnosed on ultrasound imaging. Two patients have respectively a luxation and a subluxation on ultrasound imaging that cannot be diagnosed on MR because these lesions can only be detected in flexion with resistance. Six patients underwent clinical and ultrasound follow-up 6 months after the first assessment. One patient was treated by surgery and the others were managed conservatively. Surgical findings confirmed the tear of the fibrous slips and a repair was performed. The patient had a fast recovery of hand function with rapid resolution of pain at 3 months and was completely symptom-
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Fig. 7. (a) Transverse ultrasound of the second metacarpophalangeal joint. Tear of the radial band (straight arrow) is seen. Rupture of the common extensor (C) is noted, with ulnar luxation (curved arrow) of the extensor indices (EI). (b) Longitudinal ultrasound of second metacarpophalangeal joint (MCP) in same patient. A rupture (curved arrow) of the common extensor is seen with retraction and thickening of the tendon (arrows).
Fig. 8. Transverse ultrasound in 38-year-old man after a fall with clenched wrist. Note hypoechoic thickening of the dorsal hood (curved arrows). Also tear (long arrow) of the fibrous slips between the extensor tendons (E) is seen.
free after 6 months. Recovery of hand function in the patients treated conservatively was less rapid. Four of five patients had painful mobilization at 3 months and three had persistent hand dysfunction 6 six months. 4. Discussion Accurate diagnosis of sagittal band rupture, as well as assessment of severity of injury, may be difficult without imaging because clinical symptoms are often nonspecific and include pain and swelling, as shown in the patients in this study. Also swelling of soft tissues severely limits clinical examination. Tendon luxation or subluxation is not always observed, even with complete rupture of the sagittal band which was also demonstrated in our series, further making clinical diagnosis difficult [1,4].
In our study, only one patient out of nine (patient 7) had an extensor tendon dislocation after sagittal band injury a finding which is in accordance with the literature. According to the literature the sagittal band is the most important structure of the dorsal hood to maintain the stability of the extensor tendon. Currently there are no data available in the literature about the role of the oblique and transverse bands. These structures are also difficult to depict on ultrasound and MR and we were unable to assess whether they were intact. The volar part of the sagittal band is also difficult to assess due to interposition of adjacent fingers. If exclusively the sagittal band is ruptured, the transverse and oblique bands together are able to stabilize the extensor tendon over the MCP joint. This fact may explain why dislocation of the extensor tendon after sagittal band rupture is not common. Our study seems to confirm this finding. Different structures that also may contribute to the stability of the extensor tendon after sagittal band rupture are the intertendinous connections which are located in the second to fourth intermetacarpal spaces. These structures are very thin and are also likely difficult to detect on imaging. Tears involving the radial sagittal band occur with severe injuries and lead to ulnar subluxation of the extensor tendon [1,11,12]. Ulnar subluxation was present in two patients in our study. Radial subluxation is uncommon and is only observed when the mechanism of trauma occurs in a forced valgus position [1,4]. We did not observe radial subluxations. Koniuch et al. [13] reported in an anatomical study that ulnar dislocation of the extensor tendon was apparent after radial sagittal band transsection in the second to fourth fingers. However, only minimal radial subluxation was produced with transsection of the ulnar sagittal band. In the normal situation, the second and third fingers show 10–15◦ of ulnar deviation which is felt to represent a predisposing factor for sagittal band rupture [12,6]. The treatment of dorsal hood injuries remains controversial. Nevertheless, surgery may give better results than conservative treatment [11,14,9]. In our study one patient underwent surgery in the acute phase and had a good outcome. Ultrasound findings of a rupture of the dorsal hood in this study were focal hypoechoic thickening of the sagittal bands and disappearance of the normal architecture of the sagittal band. Luxation of the extensor tendon to the contralateral side was not systematically noticed. MR correlation was performed in six patients in order to evaluate the dorsal hood and extensor tendons. The lesions seen on MRI were correctly diagnosed on ultrasound. An advantage of ultrasound is the possibility to dynamically assess the extensor tendon and dorsal hood. Flexion/extension manoeuvre and flexion/extension with resistance in ulnar or radial direction can be performed. In our study two patients had respectively a luxation and a subluxation on sonography not seen on MR because these lesions were only seen in flexion with resistance. MR of the MCP joint could be performed in flexion because a dislocation may not be evident in extension [6]. One of our patients had a history of psoriasis and the dorsal hood was involved in the inflammation of the soft tissues. The synovial membrane is a predominant target of the seronegative spondyloarthropathies. In our study injuries of the third and fifth fingers involved six of nine patients, which is in accordance with previous studies that have shown a predilection for these two fingers [12,3,6]. Limitations of this study are due to the limited number of patients. However findings were relatively consistent in all patients. MR was used as our gold standard for correlation because imaging of the dorsal hood with MR has been extensively described in the literature. Surgical correlation was only obtained in one patient. Surgery would have been a better gold standard, but unfor-
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tunately many patients were treated conservatively. Future studies should address dorsal hood injuries with greater patient numbers and extensive surgical correlation. To understand the normal appearance of the dorsal hood and enable us to identify lesions of this structure we performed dissections and ultrasound in two cadaveric specimens and correlated our findings with the normal contralateral side. In conclusion, ultrasound may be used for the assessment of tears of the dorsal hood. A hypoechoic mass at the side of the extensor tendon with non-recognizable architecture of the sagittal band suggests a rupture. A rupture of the fibrous slips between the extensor proprius and the extensor communis of the second finger is suggested in the presence of a hypoechoic mass at the level of these fibrous slips with an increased distance between the two tendons. Conflict of interest. The authors have no conflict of interest. References [1] Drape JL, Dubert T, Silbermann O, Theleu P, Thivet A, Benacerraf R. Acute trauma of the extensor hood of the metacarpophalangeal joint: MR imaging evaluation. Radiology 1994;192:469–76.
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[2] Young CM, Rayan GM. The sagittal band: anatomic and biomechanical study. J Hand Surg [Am] 2000;25:1107–13. [3] Scott SC. Closed injuries to the extension mechanism of the digits. Hand Clin 2000;16:367–73. [4] Clavero JA, Golano P, Farinas O, Aloma X, Monill JM, Esplugas M. Extensor mechanism of the fingers: MR imaging—anatomic correlation. Radiology 2003;23:593–611. [5] Inoue G, Tamura Y. Dislocation of the extensor tendons over the metacarpophalangeal joints. J Hand Surg [Am] 1996;21:464–9. [6] Lopez-Ben R, Lee DH, Nicolodi DJ. Boxer knuckle (injury of the extensor hood with extensor tendon subluxation): diagnosis with dynamic US—report of three cases. Radiology 2003;228:642–6. [7] Theumann NH, Pfirrmann CWA, Drapé JL, Trudell DJ, Resnick D. MR imaging of the metacarpophalangeal joints of the fingers. Part I. Conventional MR imaging and MR arthrographic findings in cadavers. Radiology 2002;222: 437–45. [8] Pfirrmann CWA, Theumann NH, Botte MJ, Drapé JL, Trudell DJ, Resnick D. MR imaging of the metacarpophalangeal joints of the fingers. Part II. Detection of simulated injuries in cadavers. Radiology 2002;222:447–52. [9] Moschilla G, Breidahl W. Sonography of the finger. Am J Roentgenol 2002;178:1451–7. [10] Bianchi S, Martinoli C, Abdelwahab IF. High-frequency ultrasound examination of the wrist and hand. Skeletal Radiol 1999;28:121–9. [11] Watson HK, Weinzweig J, Guidera PM. Sagittal band reconstruction. J Hand Surg [Am] 1997;22:452–6. [12] Araki S, Ohtani T, Tanaka T. Acute dislocation of the extensor digitorum communis tendon at the metacarpophalangeal joint. J Bone Joint Surg Am 1987;69:616–9. [13] Koniuch MP, Primer CA, VanGorder T, et al. Closed crush injury of the metacarpophalangeal joints. J Hand Surg [Am] 1987;12:750–7. [14] Ishizuki M. Traumatic and spontaneous dislocation of extensor tendon of the long finger. J Hand Surg Am 1990;15:967–72.
Contents lists available at ScienceDirect
European Journal of Radiology journal homepage: www.elsevier.com/locate/ejrad
Ultrasound findings in injuries of dorsal extensor hood: Correlation with MR and follow-up findings Mimoun Kichouh a,b , Michel De Maeseneer a,∗ , Tjeerd Jager b , Stefaan Marcelis c , Eddy Van Hedent b , Peter Van Roy d , Johan De Mey a a
Department of Radiology, Vrije Universiteit Brussel, Laarbeeklaan 101, 1090 Jette, Brussel, Belgium Department of Radiology, Aalsters Stedelijk Ziekenhuis, Aalst, Belgium Department of Radiology, Sint Andries Ziekenhuis, Tielt, Belgium d Department of Experimental Anatomy, Vrije Universiteit Brussel, Brussel, Belgium b c
a r t i c l e
i n f o
Article history: Received 18 February 2010 Received in revised form 18 May 2010 Accepted 21 May 2010 Keywords: Dorsal hood Extensor hood Sagittal band injuries Extensor retinaculum system MCP joint injuries
a b s t r a c t Objective: The aim of this study was to use ultrasound to examine the dorsal hood in nine patients with a clinical suspicion of dorsal hood injuries. Material and methods: Clinical and imaging files from interesting case logbooks of nine patients were reviewed. Ultrasound was performed by one of the three radiologists experienced in musculoskeletal ultrasound. The examinations were also performed in flexion and in flexion with resistance. MR correlation was obtained in six patients. One patient underwent surgery. To obtain anatomical correlation of the normal dorsal hood 2 embalmed hand specimens were dissected. Results: The sagittal bands were easily depicted in the transverse plane on ultrasound images and presented as hypoechoic bands on both sides of the extensor communis tendons. Injuries of the sagittal bands were seen on ultrasound as hypoechoic thickening of the sagittal bands at the side of the extensor tendons. The normal shape of the sagittal bands was also no longer recognizable. Subluxations or dislocations of the extensor tendons were also seen. When the injuries were located in the fibrous slips between the extensor indicis and the extensor communis of the second finger, subluxations with an increased distance between these 2 tendons were seen, especially in flexion, or in flexion with resistance. Conclusion: Ultrasound is a valuable tool for the assessment of the injuries of the dorsal hood and is an easily available method for the diagnosis of the fine soft tissue components of the dorsal hood region. © 2010 Elsevier Ireland Ltd. All rights reserved.
1. Introduction The dorsal hood or extensor hood is a retinacular system that stabilizes the extensor tendon at the dorsal aspect of the metacarpophalangeal joint (MCP) aiding to keep the tendon in place during flexion and extension. It is formed by three retinacular structures: the sagittal, oblique, and transverse bands. The latter two correspond to a fibrous extension of the lumbrical and interosseous muscles. The sagittal band (SB) is the most important structure of the extensor hood. It restricts proximal displacement of the extensor tendon and contributes to the extension of the digit [1–4]. The sagittal bands run circumferentially around the MCP joint and insert ventrally on the palmar plate and the deep transverse metacarpal ligament (DTML). Dorsally, the sagittal band is divided into a superficial and deep layer forming a tunnel through which the extensor digitorum tendon courses.
∗ Corresponding author. Tel.: +32 2 477 5323; fax: +32 2 477 5362. E-mail address: [email protected] (M. De Maeseneer). 0720-048X/$ – see front matter © 2010 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.ejrad.2010.05.015
Ruptures of the sagittal bands are reported to occur spontaneously or in association with metacarpophalangeal joint trauma such as boxer knuckle. They have also been reported with synovial disorders such as rheumatoid arthritis and psoriasis. Congenitally absent or lax sagittal bands have also been described [5,6]. These individuals may have pain or a snapping sensation or may be asymptomatic. Although dislocations are uncommon, dorsal hood injuries may lead to persistent disability. Therefore prompt diagnosis of these lesions is essential. Ultrasound imaging is an easily available technique allowing diagnosis of various soft tissue injuries. There are several publications about MR imaging of the dorsal hood [1,4,7,8]. However the role of ultrasound in the diagnosis of sagittal band injury has only been addressed in a few articles [6,9,10]. A previous case series reports on ultrasound findings in three patients [6]. Although there are a few articles dealing with evaluation of soft tissue structures of the hand including, tendons, ligaments, and retinaculum the literature on the dorsal hood is limited. The aim of this study was to assess the role of ultrasound in the diagnosis of injuries of the dorsal hood and describe the ultrasound
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imaging signs of such injuries. We correlated our findings with magnetic resonance imaging and follow-up. We also discuss the clinical findings and MR imaging findings of injuries of the dorsal hood. Cadaveric dissections were performed to better understand the normal anatomy of the uninjured dorsal hood. 2. Material and methods 2.1. Cadaveric study Dissection of two embalmed hand specimens obtained from the department of anatomy and amputated at the level of the distal forearm was performed. After the skin and subcutaneous connective and fatty tissues were removed, the dorsal hood was exposed. One specimen was frozen at −40 ◦ C and sliced in the transverse plane at the MCP level. Before dissection, ultrasound imaging was performed on an Acuson Antares (Siemens Medical Systems, Erlangen, Germany).
Fig. 1. Transverse ultrasound at MC II level of contralateral hand. The extensor tendons at metacarpal 2 level are shown (E). The curved arrow points to the ulnar sagittal band. The superficial fibrous slips are seen (arrowhead). Also note the deep fibrous slips (short bold arrow). The deep layer of the sagittal band is seen (straight arrow).
2.2. Clinical study During a 1-year period, nine patients (5 males, 4 females; age range, 27–54 years) were examined in our institution for pain at the dorsal aspect of the metacarpophalangeal joint and with a clinical suspicion of dorsal hood injuries. The patients were identified from interesting case logbooks. MR imaging was performed on a 1.5 T system (Symphony, Siemens, Erlangen, Germany) and consisted of two or more of the following sequences: axial T2 turbo spin echo (TR/TE, 3700/84; NEX, 3; FOV, 140 × 80; matrix size, 256 × 256; slice thickness, 3.0 mm; TA, 3.03), axial T1 spin echo (TR/TE, 521/22; NEX, 1; FOV, 140 × 80; matrix size, 512 × 307; slice thickness, 3 mm; TA, 2.03), and axial T2 turbo spin echo with fat suppression (TR/TE, 2450/75; NEX, 3; FOV, 140 × 80; matrix size, 256 × 192; slice thickness, 2.7 mm; TA, 2,38). The MR images were reviewed by consensus by 2 experienced musculoskeletal radiologists. Ultrasound imaging was performed by one of the three musculoskeletal radiologists experienced in musculoskeletal ultrasound. The radiologist who performed the ultrasound study was mostly aware of the MR findings. The ultrasound system employed was an Aloka Alpha 10 (Aloka, Japan) with a 15 MHz linear transducer. A standoff pad or ultrasound gel was used depending on the case. The metacarpophalangeal joints were examined in the axial and longitudinal plane. We assessed the joints, extensor communis tendons, and the dorsal hoods. A comparison was made with the asymptomatic contralateral finger. In our study, ultrasound imaging was performed in flexion and extension of the MCP joints. When a tear of the sagittal band was diagnosed, an additional assessment in flexion with resistance was performed to exclude subluxation or luxation of the tendons. Luxation of the tendon was defined as a position of the tendon to the side of the finger. Subluxation was defined as an intermediate position between the normal dorsal position of the extensor tendon and the luxated position. Six patients underwent an ultrasound follow-up examination 6 months after the first assessment.
Fig. 2. Normal transverse image of the third metacarpophalangeal joint in contralateral hand. The common extensor tendon is seen (star). Note the radial and ulnar sagittal bands (arrows).
Fig. 3. Normal transverse image in contralateral hand of the fourth metacarpophalangeal joint. Note the common extensor tendon (E) and the radial and ulnar sagittal band (curved arrows).
and the proximal interphalangeal joints. The latter two are very thin and therefore much more difficult to depict on ultrasound imaging. The sagittal bands are easily visualized in the transverse plane at ultrasound imaging. They present as hypoechoic bands on both sides of the extensor communis tendons (Figs. 1–4). The superficial layer of the SB runs over the extensor tendons. Together with a layer running under the tendons, the superficial layer forms a tunnel in which the extensor digitorum tendons are located (Fig. 1). The layers appear as fine linear hypoechoic structures oriented circumferentially and coursing from the extensor tendons to the palmar plates. The sagittal bands are best seen in the axial plane with the
3. Results 3.1. Cadaveric results and findings in normal hands The extensor tendons are strongly attached at the MCP level by the sagittal bands which are thick and oriented perpendicularly to the tendons (Figs. 1–4). The transverse and the oblique bands correspond to fibrous extensions respectively of the interosseous and lumbrical muscles and are located more distally, between the MCP
Fig. 4. Transverse ultrasound image of metacarpal 5 (MC V) in contralateral hand. Note the extensor tendons (E). Radial and ulnar sagittal bands are seen (curved arrows).
M. Kichouh et al. / European Journal of Radiology 77 (2011) 249–253
Fig. 5. (a) Transverse ultrasound image in 50-year-old man with pain along metacarpal 3 (MCP III). Note hypoechoic thickening of the radial portion of the sagittal band (arrow). The extensor tendon (E) was not displaced. Note connective tissue (C). (b) Transverse proton density weighted image in same 50-year-old man. Note increased signal intensity and thickening of the radial band corresponding to a focal rupture of the radial portion of the sagittal band (arrow).
hand in extension and the MCP in slight flexion. The probe should be placed just proximal from the MCP joint. The connective tissue and the joint capsules located deep to the central tendons appear as a thick hyperechoic structure (Figs. 1–4). The extensor tendons are in close proximity to the sagittal bands (Figs. 1–4). 3.2. Clinical study There were 5 men and 4 women with a mean age of 43 years (range, 27–54 years). The clinical symptoms were pain and swelling. The injured fingers included the second finger (n = 2), the third finger (n = 4), the fourth finger (n = 1), and the fifth finger (n = 2). In five patients there was a history of acute trauma whereas in four patients there was no trauma. In one of the latter patients there was a history of psoriasis. Hypoechoic thickening of the dorsal hood was present in all patients (Figs. 5–7). In four patients the radial band was involved, in one patient the ulnar band was involved, and in four patients the entire dorsal hood was involved. The extensor tendons were thickened in two patients and were ruptured in one patient (Fig. 7). At the fifth finger there was an increased distance between the two tendons in the two patients (Fig. 8). Ulnar subluxation was present in two patients (Fig. 7). On MR imaging (n = 5) there was increased signal intensity on T2 weighted images at the radial side of the dorsal hood in two patients and on the ulnar side in one patient. There was high signal of the entire dorsal hood in two patients. On T1 weighted imaging hypoechoic soft tissue infiltration with non-recognizable architecture of the sagittal band was seen with injury. In one patient the collateral ligament was injured, in one patient the extensor digitorum com-
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Fig. 6. (a) Transverse ultrasound image in 37-year-old woman. Note markedly thickened radial sagittal band (arrow), corresponding to tear. Note extensor tendon (E) and normal ulnar band (curved arrow). (b) Corresponding transverse T1 weighted image. Note marked soft tissue thickening in region of radial band (long arrow). Compare to normal sagittal band in third finger (curved arrow). Note extensor tendon (short arrow).
munis was ruptured and in one patient there was diffuse soft tissue edema. When a rupture of the dorsal hood was present a hypoechoic mass is seen in the location of the sagittal bands. The normal architecture of the SB is no longer seen at the side of the extensor tendons (Figs. 5–7). These findings are seen without subluxation of the tendons towards the contralateral side (Fig. 7). Two out of nine patients show a subluxation (Fig. 7). Injury of the dorsal hood is associated with tendon rupture in one patient (Fig. 7). With a rupture of the fibrous slips between the indicis proprius and the extensors communis of the second finger, a hypoechoic mass is present at the level of these fibrous slips. In addition an increased distance between the two tendons is evident (subluxation) (Fig. 8). The distance between the two tendons is considered abnormal based on a comparison with the contralateral side. In the six patients who underwent MR, the lesions seen on MR are correctly diagnosed on ultrasound imaging. Two patients have respectively a luxation and a subluxation on ultrasound imaging that cannot be diagnosed on MR because these lesions can only be detected in flexion with resistance. Six patients underwent clinical and ultrasound follow-up 6 months after the first assessment. One patient was treated by surgery and the others were managed conservatively. Surgical findings confirmed the tear of the fibrous slips and a repair was performed. The patient had a fast recovery of hand function with rapid resolution of pain at 3 months and was completely symptom-
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Fig. 7. (a) Transverse ultrasound of the second metacarpophalangeal joint. Tear of the radial band (straight arrow) is seen. Rupture of the common extensor (C) is noted, with ulnar luxation (curved arrow) of the extensor indices (EI). (b) Longitudinal ultrasound of second metacarpophalangeal joint (MCP) in same patient. A rupture (curved arrow) of the common extensor is seen with retraction and thickening of the tendon (arrows).
Fig. 8. Transverse ultrasound in 38-year-old man after a fall with clenched wrist. Note hypoechoic thickening of the dorsal hood (curved arrows). Also tear (long arrow) of the fibrous slips between the extensor tendons (E) is seen.
free after 6 months. Recovery of hand function in the patients treated conservatively was less rapid. Four of five patients had painful mobilization at 3 months and three had persistent hand dysfunction 6 six months. 4. Discussion Accurate diagnosis of sagittal band rupture, as well as assessment of severity of injury, may be difficult without imaging because clinical symptoms are often nonspecific and include pain and swelling, as shown in the patients in this study. Also swelling of soft tissues severely limits clinical examination. Tendon luxation or subluxation is not always observed, even with complete rupture of the sagittal band which was also demonstrated in our series, further making clinical diagnosis difficult [1,4].
In our study, only one patient out of nine (patient 7) had an extensor tendon dislocation after sagittal band injury a finding which is in accordance with the literature. According to the literature the sagittal band is the most important structure of the dorsal hood to maintain the stability of the extensor tendon. Currently there are no data available in the literature about the role of the oblique and transverse bands. These structures are also difficult to depict on ultrasound and MR and we were unable to assess whether they were intact. The volar part of the sagittal band is also difficult to assess due to interposition of adjacent fingers. If exclusively the sagittal band is ruptured, the transverse and oblique bands together are able to stabilize the extensor tendon over the MCP joint. This fact may explain why dislocation of the extensor tendon after sagittal band rupture is not common. Our study seems to confirm this finding. Different structures that also may contribute to the stability of the extensor tendon after sagittal band rupture are the intertendinous connections which are located in the second to fourth intermetacarpal spaces. These structures are very thin and are also likely difficult to detect on imaging. Tears involving the radial sagittal band occur with severe injuries and lead to ulnar subluxation of the extensor tendon [1,11,12]. Ulnar subluxation was present in two patients in our study. Radial subluxation is uncommon and is only observed when the mechanism of trauma occurs in a forced valgus position [1,4]. We did not observe radial subluxations. Koniuch et al. [13] reported in an anatomical study that ulnar dislocation of the extensor tendon was apparent after radial sagittal band transsection in the second to fourth fingers. However, only minimal radial subluxation was produced with transsection of the ulnar sagittal band. In the normal situation, the second and third fingers show 10–15◦ of ulnar deviation which is felt to represent a predisposing factor for sagittal band rupture [12,6]. The treatment of dorsal hood injuries remains controversial. Nevertheless, surgery may give better results than conservative treatment [11,14,9]. In our study one patient underwent surgery in the acute phase and had a good outcome. Ultrasound findings of a rupture of the dorsal hood in this study were focal hypoechoic thickening of the sagittal bands and disappearance of the normal architecture of the sagittal band. Luxation of the extensor tendon to the contralateral side was not systematically noticed. MR correlation was performed in six patients in order to evaluate the dorsal hood and extensor tendons. The lesions seen on MRI were correctly diagnosed on ultrasound. An advantage of ultrasound is the possibility to dynamically assess the extensor tendon and dorsal hood. Flexion/extension manoeuvre and flexion/extension with resistance in ulnar or radial direction can be performed. In our study two patients had respectively a luxation and a subluxation on sonography not seen on MR because these lesions were only seen in flexion with resistance. MR of the MCP joint could be performed in flexion because a dislocation may not be evident in extension [6]. One of our patients had a history of psoriasis and the dorsal hood was involved in the inflammation of the soft tissues. The synovial membrane is a predominant target of the seronegative spondyloarthropathies. In our study injuries of the third and fifth fingers involved six of nine patients, which is in accordance with previous studies that have shown a predilection for these two fingers [12,3,6]. Limitations of this study are due to the limited number of patients. However findings were relatively consistent in all patients. MR was used as our gold standard for correlation because imaging of the dorsal hood with MR has been extensively described in the literature. Surgical correlation was only obtained in one patient. Surgery would have been a better gold standard, but unfor-
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tunately many patients were treated conservatively. Future studies should address dorsal hood injuries with greater patient numbers and extensive surgical correlation. To understand the normal appearance of the dorsal hood and enable us to identify lesions of this structure we performed dissections and ultrasound in two cadaveric specimens and correlated our findings with the normal contralateral side. In conclusion, ultrasound may be used for the assessment of tears of the dorsal hood. A hypoechoic mass at the side of the extensor tendon with non-recognizable architecture of the sagittal band suggests a rupture. A rupture of the fibrous slips between the extensor proprius and the extensor communis of the second finger is suggested in the presence of a hypoechoic mass at the level of these fibrous slips with an increased distance between the two tendons. Conflict of interest. The authors have no conflict of interest. References [1] Drape JL, Dubert T, Silbermann O, Theleu P, Thivet A, Benacerraf R. Acute trauma of the extensor hood of the metacarpophalangeal joint: MR imaging evaluation. Radiology 1994;192:469–76.
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