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Pathology International 2014; 64: 276–282
doi:10.1111/pin.12168
Original Article
Histopathology of tenosynovium in trigger fingers
Kazuyoshi Uchihashi,1 Toshiyuki Tsuruta,2 Hiroko Mine,2 Shigehisa Aoki,1 Aki Nishijima-Matsunobu,1 Mihoko Yamamoto,1 Akio Kuraoka3 and Shuji Toda1 Departments of 1Pathology and Microbiology and 3Anatomy and Physiology, Faculty of Medicine, Saga University, Saga and 2Tsuruta Orthopaedic Clinic, Ogi, Japan Stenosing flexor tenosynovitis, trigger finger, is a common clinical disorder causing painful locking or contracture of the involved digits, and most instances are idiopathic. This problem is generally caused by a size mismatch between the swollen flexor tendon and the thickened first annular pulley. Although hypertrophic pulleys have been histologically and ultrasonographically detected, little is known about the histopathology of the tenosynovium covering the tendons of trigger fingers. We identified chondrocytoid cells that produced hyaluronic acid in 23 (61%) fingers and hypocellular collagen matrix in 32 (84%) fingers around the tenosynovium among 38 specimens of tenosynovium from patients with trigger fingers. These chondrocytoid cells expressed the synovial B cell marker CD44, but not the chondrocyte marker S-100 protein. The incidence of these findings was much higher than that of conventional findings of synovitis, such as inflammatory infiltrate (37%), increased vascularity (37%), hyperplasia of synovial lining cells (21%), or fibrin exudation (5%). We discovered the following distinctive histopathological features of trigger finger: hyaluronic acid-producing chondrocytoid cells originated from fibroblastic synovial B cells, and a hypocellular collagen matrix surrounding the tenosynovium. Thus, an edematous extracellular matrix with active hyaluronic acid synthesis might increase pressure under the pulley and contribute to the progression of stenosis.
annular (A1) pulley of the flexor tendon sheath as a result of a discrepancy between the sizes of the flexor tendon sheath and the tendon (Fig. 1a).1–4 Primary stenosing tenosynovitis is usually idiopathic and it occurs more frequently in middle-aged women than in men.1 Secondary stenosing tenosynovitis can occur in patients with rheumatoid arthritis, diabetes mellitus, various tumors, and other entities that cause connective tissue disorders.1,4 However, the precise pathobiology of tenosynovium in trigger fingers remains unclear. The flexor tendon sheath is composed of retinacular and membranous (synovial) tissue components, called pulley and tenosynovium, respectively, which have separate and distinct functions. Histological and ultrasonographic findings of the affected pulley have shown hypertrophy resulting in constricting the osseofibrous tunnel through which the tendon runs (Fig. 1b).4–6 Unlike the affected pulley, the histopathology of tenosynovium in patients of trigger finger has never been studied. The present study aimed to characterize the histopathological features of tenosynovium associated with trigger finger. We found that chondrocytoid cells producing hyaluronic acid and hypocellular collagen matrix are distinctive histopathological findings of trigger finger.
Key word: chondrocytoid cell, histopathology, hyaluronic acid, tenosynovium, trigger finger
MATERIALS AND METHODS
Stenosing tenosynovitis of the flexor digitorum tendons (trigger finger) is a common clinical disorder that is characterized by a painful snapping, locking or contracture of the involved digits. The deficit originates at the level of the first
Correspondence: Kazuyoshi Uchihashi, MD, PhD, Nabeshima 5-1-1, Saga 849-8501, Japan. Email: [email protected] Disclosure statement: None declared. Received 25 December 2013. Accepted for publication 14 April 2014. © 2014 The Authors Pathology International © 2014 Japanese Society of Pathology and Wiley Publishing Asia Pty Ltd
Tissues and clinical data All techniques involving human materials proceeded in accordance with the Ethical Guidelines of Saga University and Tsuruta Orthopaedic Clinic. Tenosynovium specimens were collected from 38 fingers of 38 patients (mean age, 61.3 y (range, 35 to 79 y); female, n = 21; male, n = 17) who provided written, informed consent to participate in the study after undergoing surgery of the A1 pulley to release trigger finger at Tsuruta Orthopaedic Clinic during 2012. Control specimens were obtained at autopsy from six fingers at Saga University. All patients had tenderness and snapping at the A1 pulley. The range of motion (ROM) was limited in 27 (71%) patients and 16
Tenosynovium in trigger fingers
(a)
277
(b)
Figure 1 Schematic diagram of the digital pulley system of fingers (a) and location and microanatomy of the tenosynovium of flexor digitorum (b). Most trigger fingers are primarily idiopathic in which the site of obstruction is the first annular (A1) pulley at the level of MP joint (a). Tenosynovium covers surface of flexor digitorum (b). DIP, distal interphalangeal joint; PIP, proximal interphalangeal joint; MP, metacarpophalangeal joint; A, annular; C, cruciate.
(42%) had been treated by one to three local steroid injections before surgery. None of the patients had rheumatoid arthritis, chronic renal failure, trauma or infection. To assess the severity of the preoperative symptoms, we used the classification proposed by Newport et al.6,7 Stage I was considered a simple tenosynovitis with tenderness and pain, but without both palpable nodule and triggering. Stage II fingers demonstrated tenderness, a swelling or nodularity of the tendon, and occasional triggering. Stage III, the category with the most severe symptoms, included all manifestations of stage II, as well as frequent triggering or locking. Patients in stage III may present flexion contracture in their proximal inter phalangeal joint of involved digits. Thirteen (34%) fingers were categorized in stage II and 25 (66%) fingers were categorized in stage III.
Histochemical study We resected tenosynovium around the flexor digitorum tendons for decompression during surgery to release the A1 pulley. Specimens were immediately fixed in 10% formaldehyde. Sections (5 μm thick) prepared from paraffin-embedded specimens were stained with hematoxylin-eosin (HE) and then we assessed the presence of hyperplastic synovial lining cells, inflammatory infiltrate, vascularity, fibrin exudation, hypocellular collagen matrix and chondrocytoid cells. The intensity of inflammatory cells was assessed as none, absent; mild, scattered infrequent mononuclear infiltrates not obvious at low magnification; moderate, frequent mononuclear infiltrates recognizable at low magnification; or severe, dense mononuclear infiltrates. The vascularity was analyzed by immunostaining of CD34 antibody. Then more than 10
vessels/high power fields was judged as increased vascularity. The sections were stained with Mallory’s azan and phosphotungstic acid hematoxylin (PTAH) to detect fibrosis and fibrin, respectively. We detected hyaluronic acid using alcian blue (pH 2.5) staining with or without prior hyaluronidase digestion. Two pathologists (K.U and S.T.) independently assessed the histological features.
Immunohistochemistry We used a mouse monoclonal antibody against leukocyte common antigen (LCA) (Nichirei, Tokyo, Japan) to confirm whether or not infiltrating mononuclear cells were leukocytes. Vascularity was assessed by immunostaining of CD34 (DakoCytomation, Glostrup, Denmark). As the chondrocytoid cells were located within eosinophilic matrix around the perisynovial space, we immunohistochemically assessed using procollagen (Takara Bio, Otsu, Japan), S-100 protein (DakoCytomation), and CD44 (Binding Site, Birmingham, UK) as markers of collagen synthesized de novo,8 chondrocytes and fibroblastic synovial B cells,9,10 respectively. Deparaffinized sections were immunostained using the avidin-biotin complex (ABC) with immunoperoxidase as described.11
Transmission electron microscopy We examined the fine structures of chondrocytoid cells in the other three specimens fixed with 2.5% glutaraldehyde, using standard transmission electron microscopy as described.12
© 2014 The Authors Pathology International © 2014 Japanese Society of Pathology and Wiley Publishing Asia Pty Ltd
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Statistical analysis
RESULTS
All statistical analyses were carried out using Stat View for Windows Version 5.0 (SAS Institute Inc, Cary, NC, USA). Categorical analysis of variables was performed using either the χ2 test (with Yates’s correction) or Fisher exact test, as appropriate. P < 0.05 was considered statistically significant.
Table 1 fingers
Histopathological findings of the tenosynovium from trigger Case number (%)
Histopathological findings Hyperplasia of synovial lining cells Inflammatory infiltrate Mild Moderate Severe Increased vascularity Fibrin exudation Hypocellular collagen matrix Chondrocytoid cells
8 (21) 14 (37) 12 (36) 2 (5) 0 (0) 14 (37) 2 (5) 32 (84) 23 (61)
a
b
c
d
e
f
Table 1 summarizes the histopathological findings. None of the control specimens had significant abnormalities and were thus suitable for comparison with the pathological specimens. The surface of tenosynovium from control specimens was covered by a single synovial lining cell layer without inflammatory cells (Fig. 2a). Only one of six control specimens has increased vascularity. Synovial lining cells were hyperplastic in eight (21%) specimens of trigger fingers (Fig. 2b,c), inflammatory infiltrate was found in 14 (37%) specimens and the magnitude was mild and moderate in 12 and 2 specimens, respectively (Fig. 2b). All expressed cytoplasmic LCA (Fig. 2d). Fourteen (37%) specimens showed increased vascularity (Fig. 2e). The synovial surface had PTAH-positive fibrin exudation in two (5%) specimens (Fig. 2c,f). Hypocellular collagen matrix around the tenosynovium was identified in 32 (84%) specimens (Fig. 3a,b), the matrix of
Figure 2 Histology of tenosynovium from normal (a) and trigger finger (b-g). The tenosynovial surface of control specimens is covered by synovial lining cell layer without inflammatory cells (a). Moderate perivascular infiltration by lymphocytes and increased vascularity in trigger finger (b). Synovial lining cells are hyperplastic and stratified (black arrowheads) (c). Fibrin exudates at surface of tenosynovium (white arrowheads) (c). Infiltrating mononuclear cells are positive for LCA (d). CD34 immunostaining confirms increased vascularity (e). PTAH staining shows fibrin exudation (f). LCA, leukocyte common antigen; PTAH, phosphotungstic acid hematoxylin.
© 2014 The Authors Pathology International © 2014 Japanese Society of Pathology and Wiley Publishing Asia Pty Ltd
Tenosynovium in trigger fingers
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d
b
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Figure 3 Histology of tenosynovium from trigger finger. Hypocellular eosinophilic matrix (a, b) stained blue by Mallory’s azan (c). Chondrocytoid cells are observed in this matrix. Oval- to short spindle-shaped cells have pericellular basophilic mucoid material (d). Alcian blue staining without (e) or with (f) prior hyaluronidase digestion is positive and negative, respectively, for mucoid material.
which 23 (61%) contained chondrocytoid cells (Fig. 3d). The incidences of collagen matrix and chondrocytoid cells were similar between patients with and without steroid injection before the surgery (eosinophilic matrix: 88% and 82%, injected and non-injected group, respectively; chondrocytoid cells: 56% and 64%, respectively). The matrix was colored blue by Mallory’s azan stain (Fig. 3c), and negative for Dylon staining (data not shown), indicating that the matrix contained collagen fibers. Mucoid material around chondrocytoid cells was positive for alcian blue, which was abolished by prior hyaluronidase digestion (Fig. 3e,f). The chondrocytoid cells did not express S-100 protein (Fig. 4a), but they were positive for CD44 (Fig. 4b) and procollagen I (Fig. 4c). These results suggest that the chondrocytoid cells producing hyaluronic acid originated from fibroblastic synovial B cells,9,10 but did not undergo apparent cartilaginous differentiation. Electron microscopy showed degenerated collagen fibrils in the matrix
(Fig. 5a). The chondrocytoid cells were surrounded by a collagen fibril layer that had pericellular lacunae containing mucoid material (Fig. 5a,b). The cells also had abundant rough endoplasmic reticulum, pinocytic vesicles, mucin-laden granules and foot processes, but no lysosomes (Fig. 5c). These findings suggested that the cells originated from fibroblastic, rather than histiocytic cells.13,14 None of the clinical data, including sex, age (>60 years vs ≤60 years), preoperative local steroid injection (present vs absent), and the clinical stage (Stage II vs Stage III) are statistically correlated with the histological findings.
DISCUSSION We presented histopathological details of the tenosynovium affected by trigger finger. That is, both chondrocytoid cells
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a
b
c
Figure 4 Immunohistochemistry of chondrocytoid cells. Immunohistochemical staining of chondrocytoid cells is negative for S-100 (a) and positive for CD44 (b) and procollagen I (c).
that produce hyaluronic acid and hypocellular collagen matrix are characteristic findings of the disorder and suggest that the histopathological features are associated with stenosing mechanisms in trigger finger. The limitation of our study is the number of controls. However, it is ethically impossible to resect tenosynovium from normal fingers. The pathophysiology of trigger fingers can be explained as the container that is the anatomically available space,
and the contents that comprise the flexor tendon. Published reports have emphasized constriction of the container. That is, ultrasonographic studies have focused on hypertrophy of the pulley.4,15 A histological study of the A1 pulley of trigger finger has also shown fibrous thickening5 and some investigators have identified chondrocytoid cells in the innermost layer of the pulley.16,17 Sampson et al.16 demonstrated immunoreactivity for S-100 protein and the ultrastructural characteristics of chondrocytes in pulleys, indicating fibrocartilaginous metaplasia. Chondrocytoid cells have also been found in the transverse carpal ligament of carpal tunnel syndrome18 and in the tendon sheath of the extensor pollicis brevis and abductor pollicis longus from patients with De Quervain’s disease.13 On the basis of morphology of histochemistry or electron microscopy with or without immunoreactivity for S-100 protein, the authors above suggested that these cells displayed chondroid or cartilaginous metaplasia. However, the origins of these cells in the retinaculum have remained unknown. Here, we have first showed hyaluronic acid-producing chondrocytoid cells in tenosynovium, and these cells expressed CD44 and procollagen I, but not S-100, suggesting that these cells originated from fibroblastic tenosynovial cells.8–10 Electron microscopy confirmed the fibroblastic tenosynovial origin. We used CD44 antibody as a marker of synovial B cells in accordance with previous report,9,10 and confirmed its reaction to synovial lining cells. However, because CD44 is also known as a receptor for hyaluronic acid,19 it is likely that CD44 antibody react with the synthesized hyaluronic acid. Given these results and anatomical discontinuity between tenosynovium and the innermost layer of the pulley,16,20 the origins of chondrocytoid cells in tenosynovium may differ from the chondrocytoid cells in pulleys, as has been reported previously.13,14 The eosinophilic material around chondrocytoid cells was degenerated collagen matrix according to the findings of Mallory’s azan staining and electron microscopy. Immunoreactivity for procollagen I suggested that collagen fibrils formed de novo are included in the matrix just around chondrocytoid cells. Hyaluronic acid is one of the most hydrophilic molecules in nature and thus it can be described as a moisturizer for the extracellular matrix,21 and it contributes to lubrication of the tendon and pulley.22,23 Hyaluronic acid inhibits fibroblast proliferation, and it does not affect the production of either collagen or proteoglycan.24 Our histological findings support these results because the eosinophilic material around chondrocytoid cells contains few fibroblastic spindle cells (Fig. 3b). The edematous extracellular matrix in conjunction with hyaluronic acid synthesis may increase the pressure under the pulley in the trigger finger. Although there is no correlation between vascularity and other histological features, increased vascularity may contribute to edematous thickening of tenosynovium. We assumed that mutual inter-
© 2014 The Authors Pathology International © 2014 Japanese Society of Pathology and Wiley Publishing Asia Pty Ltd
Tenosynovium in trigger fingers
a
Figure 5 Transmission electron microscopy of chondrocytoid cells. Degenerated collagen fibrils are seen in the matrix (white arrows) (a). Chondrocytoid cells surrounded by collagen fibril layer (black arrows) have pericellular lacunae that contain mucoid material (arrowheads) (a, b), abundant rough endoplasmic reticulum (yellow arrows), pinocytic vesicles (black arrowheads), mucin-laden granules (red arrows) and foot processes (white arrowheads) but no lysosomes (c). These findings suggest that the cells are of fibroblastic, rather than macrophage origin.
281
c
b
ference between fibrous thickening of the A1 pulley and the increased volume of tenosynovium comprises one cause of this disorder. We should also consider that the synthesis of hyaluronic acid in synovial cells is secondary to the stenosing condition by thickened pulleys. Unfortunately, we could not demonstrate the correlation between the clinical parameters and the histological findings. One of the reason for this may be that all of our cases are categorized in an advanced clinical stage (stage II and III), and are resistant to conservative treatment. Drossos et al. reported that the outer layer of A1 pulley has no inflammatory infiltrate, indicating that tenosynovitis may not be a suitable term for pathophysiology of trigger finger.6 On the other hand, our series showed inflammatory infiltrate in 37%. Inflammation seems to depend on its anatomical site. This suggests that inflammatory cell infiltration may be greater in tenosynovium than in pulley. In conclusion, we identified chondrocytoid cells that produce hyaluronic acid and a hypocellular collagen matrix in the tenosynovium of trigger finger, suggesting that excess hyaluronic acid synthesis and an edematous swollen collagen matrix are involved in the progression of trigger finger. Thus, the attenuation of the collagen matrix or hyaluronic acid synthesis might be an effective non-surgical therapeutic modality for treating trigger finger.
ACKNOWLEDGMENTS This study was supported in part by Grants-in-Aid from the Japanese Ministry of Education, Culture, Sports, Science and Technology for Scientific Research no. 22791387, 24791553 (to KU), and 23591050 (to ST). We thank Fumihiro
Mutoh, Shinichi Nakahara, Hiroyuki Ideguchi and Masako Ikenaga for excellent technical assistance. REFERENCES 1 Nimigan AS, Ross DC, Gan BS. Steroid injections in the management of trigger fingers. Am J Phys Med Rehabil 2006; 85: 36–43. 2 Lundin AC, Eliasson P, Aspenberg P. Trigger finger and tendinosis. J Hand Surg Eur Vol 2011; 37: 233–6. 3 Ryzewicz M, Wolf JM. Trigger digits: Principles, management, and complications. J Hand Surg Am 2006; 31: 135–46. 4 Vuillemin V, Guerini H, Bard H, Morvan G. Stenosing tenosynovitis. J Ultrasound 2012; 15: 20–28. 5 Meachim G, Roberts C. The histopathology of stenosing tendovaginitis. J Pathol 1969; 98: 187–92. 6 Drossos K, Remmelink M, Nagy N, de Maertelaer V, Pasteels JL, Schuind F. Correlations between clinical presentations of adult trigger digits and histologic aspects of the A1 pulley. J Hand Surg Am 2009; 34: 1429–35. 7 Newport ML, Lane LB, Stuchin SA. Treatment of trigger finger by steroid injection. J Hand Surg Am 1990; 15: 748–50. 8 Qu Z, Garcia CH, O’Rourke LM, Planck SR, Kohli M, Rosenbaum JT. Local proliferation of fibroblast-like synoviocytes contributes to synovial hyperplasia. Results of proliferating cell nuclear antigen/cyclin, c-myc, and nucleolar organizer region staining. Arthritis Rheum 1994; 37: 212–20. 9 Suzuki A, Nozawa-Inoue K, Amizuka N, Ono K, Maeda T. Localization of CD44 and hyaluronan in the synovial membrane of the rat temporomandibular joint. Anat Rec A Discov Mol Cell Evol Biol 2006; 288: 646–52. 10 Henderson KJ, Edwards JC, Worrall JG. Expression of CD44 in normal and rheumatoid synovium and cultured synovial fibroblasts. Ann Rheum Dis 1994; 53: 729–34. 11 Uchihashi K, Aoki S, Shigematsu M et al. Organotypic culture of human bone marrow adipose tissue. Pathol Int 2010; 60: 259– 67. 12 Uchihashi K, Aoki S, Matsunobu A, Toda S. Osteoblast migration into type I collagen gel and differentiation to osteocyte-like cells within a self-produced mineralized matrix: A novel system
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14 15 16
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for analyzing differentiation from osteoblast to osteocyte. Bone 2013; 52: 102–10. Ippolito E, Postacchini F, Scola E, Bellocci M, De Martino C. De Quervain’s disease. An ultrastructural study. Int Orthop 1985; 9: 41–7. Revell PA. Synovial lining cells. Rheumatol Int 1989; 9: 49–51. Guerini H, Pessis E, Theumann N et al. Sonographic appearance of trigger fingers. J Ultrasound Med 2008; 27: 1407–13. Sampson SP, Badalamente MA, Hurst LC, Seidman J. Pathobiology of the human A1 pulley in trigger finger. J Hand Surg Am 1991; 16: 714–21. Sbernardori MC, Bandiera P. Histopathology of the A1 pulley in adult trigger fingers. J Hand Surg Eur Vol 2007; 32: 556–9. Nakamichi K, Tachibana S. Histology of the transverse carpal ligament and flexor tenosynovium in idiopathic carpal tunnel syndrome. J Hand Surg Am 1998; 23: 1015–24. Lesley J, Hyman R. CD44 can be activated to function as an hyaluronic acid receptor in normal murine T cells. Eur J Immunol 1992; 22: 2719–23.
20 Lundborg G, Myrhage R. The vascularization and structure of the human digital tendon sheath as related to flexor tendon function. An angiographic and histological study. Scand J Plast Reconstr Surg 1977; 11: 195–203. 21 Fakhari A, Berkland C. Applications and emerging trends of hyaluronic acid in tissue engineering, as a dermal filler and in osteoarthritis treatment. Acta Biomater 2013; 9: 7081–92. 22 Yagi M, Mitsui Y, Gotoh M, Sato N, Yoshida K, Nagata K. Role of the hyaluronan-producing tenosynovium in preventing adhesion formation during healing of flexor tendon injuries. Hand Surg 2012; 17: 13–17. 23 Taguchi M, Zhao C, Sun YL, Jay GD, An KN, Amadio PC. The effect of surface treatment using hyaluronic acid and lubricin on the gliding resistance of human extrasynovial tendons in vitro. J Hand Surg Am 2009; 34: 1276–81. 24 Yagi M, Sato N, Mitsui Y, Gotoh M, Hamada T, Nagata K. Hyaluronan modulates proliferation and migration of rabbit fibroblasts derived from flexor tendon epitenon and endotenon. J Hand Surg Am 2010; 35: 791–6.
© 2014 The Authors Pathology International © 2014 Japanese Society of Pathology and Wiley Publishing Asia Pty Ltd
Pathology International 2014; 64: 276–282
doi:10.1111/pin.12168
Original Article
Histopathology of tenosynovium in trigger fingers
Kazuyoshi Uchihashi,1 Toshiyuki Tsuruta,2 Hiroko Mine,2 Shigehisa Aoki,1 Aki Nishijima-Matsunobu,1 Mihoko Yamamoto,1 Akio Kuraoka3 and Shuji Toda1 Departments of 1Pathology and Microbiology and 3Anatomy and Physiology, Faculty of Medicine, Saga University, Saga and 2Tsuruta Orthopaedic Clinic, Ogi, Japan Stenosing flexor tenosynovitis, trigger finger, is a common clinical disorder causing painful locking or contracture of the involved digits, and most instances are idiopathic. This problem is generally caused by a size mismatch between the swollen flexor tendon and the thickened first annular pulley. Although hypertrophic pulleys have been histologically and ultrasonographically detected, little is known about the histopathology of the tenosynovium covering the tendons of trigger fingers. We identified chondrocytoid cells that produced hyaluronic acid in 23 (61%) fingers and hypocellular collagen matrix in 32 (84%) fingers around the tenosynovium among 38 specimens of tenosynovium from patients with trigger fingers. These chondrocytoid cells expressed the synovial B cell marker CD44, but not the chondrocyte marker S-100 protein. The incidence of these findings was much higher than that of conventional findings of synovitis, such as inflammatory infiltrate (37%), increased vascularity (37%), hyperplasia of synovial lining cells (21%), or fibrin exudation (5%). We discovered the following distinctive histopathological features of trigger finger: hyaluronic acid-producing chondrocytoid cells originated from fibroblastic synovial B cells, and a hypocellular collagen matrix surrounding the tenosynovium. Thus, an edematous extracellular matrix with active hyaluronic acid synthesis might increase pressure under the pulley and contribute to the progression of stenosis.
annular (A1) pulley of the flexor tendon sheath as a result of a discrepancy between the sizes of the flexor tendon sheath and the tendon (Fig. 1a).1–4 Primary stenosing tenosynovitis is usually idiopathic and it occurs more frequently in middle-aged women than in men.1 Secondary stenosing tenosynovitis can occur in patients with rheumatoid arthritis, diabetes mellitus, various tumors, and other entities that cause connective tissue disorders.1,4 However, the precise pathobiology of tenosynovium in trigger fingers remains unclear. The flexor tendon sheath is composed of retinacular and membranous (synovial) tissue components, called pulley and tenosynovium, respectively, which have separate and distinct functions. Histological and ultrasonographic findings of the affected pulley have shown hypertrophy resulting in constricting the osseofibrous tunnel through which the tendon runs (Fig. 1b).4–6 Unlike the affected pulley, the histopathology of tenosynovium in patients of trigger finger has never been studied. The present study aimed to characterize the histopathological features of tenosynovium associated with trigger finger. We found that chondrocytoid cells producing hyaluronic acid and hypocellular collagen matrix are distinctive histopathological findings of trigger finger.
Key word: chondrocytoid cell, histopathology, hyaluronic acid, tenosynovium, trigger finger
MATERIALS AND METHODS
Stenosing tenosynovitis of the flexor digitorum tendons (trigger finger) is a common clinical disorder that is characterized by a painful snapping, locking or contracture of the involved digits. The deficit originates at the level of the first
Correspondence: Kazuyoshi Uchihashi, MD, PhD, Nabeshima 5-1-1, Saga 849-8501, Japan. Email: [email protected] Disclosure statement: None declared. Received 25 December 2013. Accepted for publication 14 April 2014. © 2014 The Authors Pathology International © 2014 Japanese Society of Pathology and Wiley Publishing Asia Pty Ltd
Tissues and clinical data All techniques involving human materials proceeded in accordance with the Ethical Guidelines of Saga University and Tsuruta Orthopaedic Clinic. Tenosynovium specimens were collected from 38 fingers of 38 patients (mean age, 61.3 y (range, 35 to 79 y); female, n = 21; male, n = 17) who provided written, informed consent to participate in the study after undergoing surgery of the A1 pulley to release trigger finger at Tsuruta Orthopaedic Clinic during 2012. Control specimens were obtained at autopsy from six fingers at Saga University. All patients had tenderness and snapping at the A1 pulley. The range of motion (ROM) was limited in 27 (71%) patients and 16
Tenosynovium in trigger fingers
(a)
277
(b)
Figure 1 Schematic diagram of the digital pulley system of fingers (a) and location and microanatomy of the tenosynovium of flexor digitorum (b). Most trigger fingers are primarily idiopathic in which the site of obstruction is the first annular (A1) pulley at the level of MP joint (a). Tenosynovium covers surface of flexor digitorum (b). DIP, distal interphalangeal joint; PIP, proximal interphalangeal joint; MP, metacarpophalangeal joint; A, annular; C, cruciate.
(42%) had been treated by one to three local steroid injections before surgery. None of the patients had rheumatoid arthritis, chronic renal failure, trauma or infection. To assess the severity of the preoperative symptoms, we used the classification proposed by Newport et al.6,7 Stage I was considered a simple tenosynovitis with tenderness and pain, but without both palpable nodule and triggering. Stage II fingers demonstrated tenderness, a swelling or nodularity of the tendon, and occasional triggering. Stage III, the category with the most severe symptoms, included all manifestations of stage II, as well as frequent triggering or locking. Patients in stage III may present flexion contracture in their proximal inter phalangeal joint of involved digits. Thirteen (34%) fingers were categorized in stage II and 25 (66%) fingers were categorized in stage III.
Histochemical study We resected tenosynovium around the flexor digitorum tendons for decompression during surgery to release the A1 pulley. Specimens were immediately fixed in 10% formaldehyde. Sections (5 μm thick) prepared from paraffin-embedded specimens were stained with hematoxylin-eosin (HE) and then we assessed the presence of hyperplastic synovial lining cells, inflammatory infiltrate, vascularity, fibrin exudation, hypocellular collagen matrix and chondrocytoid cells. The intensity of inflammatory cells was assessed as none, absent; mild, scattered infrequent mononuclear infiltrates not obvious at low magnification; moderate, frequent mononuclear infiltrates recognizable at low magnification; or severe, dense mononuclear infiltrates. The vascularity was analyzed by immunostaining of CD34 antibody. Then more than 10
vessels/high power fields was judged as increased vascularity. The sections were stained with Mallory’s azan and phosphotungstic acid hematoxylin (PTAH) to detect fibrosis and fibrin, respectively. We detected hyaluronic acid using alcian blue (pH 2.5) staining with or without prior hyaluronidase digestion. Two pathologists (K.U and S.T.) independently assessed the histological features.
Immunohistochemistry We used a mouse monoclonal antibody against leukocyte common antigen (LCA) (Nichirei, Tokyo, Japan) to confirm whether or not infiltrating mononuclear cells were leukocytes. Vascularity was assessed by immunostaining of CD34 (DakoCytomation, Glostrup, Denmark). As the chondrocytoid cells were located within eosinophilic matrix around the perisynovial space, we immunohistochemically assessed using procollagen (Takara Bio, Otsu, Japan), S-100 protein (DakoCytomation), and CD44 (Binding Site, Birmingham, UK) as markers of collagen synthesized de novo,8 chondrocytes and fibroblastic synovial B cells,9,10 respectively. Deparaffinized sections were immunostained using the avidin-biotin complex (ABC) with immunoperoxidase as described.11
Transmission electron microscopy We examined the fine structures of chondrocytoid cells in the other three specimens fixed with 2.5% glutaraldehyde, using standard transmission electron microscopy as described.12
© 2014 The Authors Pathology International © 2014 Japanese Society of Pathology and Wiley Publishing Asia Pty Ltd
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Statistical analysis
RESULTS
All statistical analyses were carried out using Stat View for Windows Version 5.0 (SAS Institute Inc, Cary, NC, USA). Categorical analysis of variables was performed using either the χ2 test (with Yates’s correction) or Fisher exact test, as appropriate. P < 0.05 was considered statistically significant.
Table 1 fingers
Histopathological findings of the tenosynovium from trigger Case number (%)
Histopathological findings Hyperplasia of synovial lining cells Inflammatory infiltrate Mild Moderate Severe Increased vascularity Fibrin exudation Hypocellular collagen matrix Chondrocytoid cells
8 (21) 14 (37) 12 (36) 2 (5) 0 (0) 14 (37) 2 (5) 32 (84) 23 (61)
a
b
c
d
e
f
Table 1 summarizes the histopathological findings. None of the control specimens had significant abnormalities and were thus suitable for comparison with the pathological specimens. The surface of tenosynovium from control specimens was covered by a single synovial lining cell layer without inflammatory cells (Fig. 2a). Only one of six control specimens has increased vascularity. Synovial lining cells were hyperplastic in eight (21%) specimens of trigger fingers (Fig. 2b,c), inflammatory infiltrate was found in 14 (37%) specimens and the magnitude was mild and moderate in 12 and 2 specimens, respectively (Fig. 2b). All expressed cytoplasmic LCA (Fig. 2d). Fourteen (37%) specimens showed increased vascularity (Fig. 2e). The synovial surface had PTAH-positive fibrin exudation in two (5%) specimens (Fig. 2c,f). Hypocellular collagen matrix around the tenosynovium was identified in 32 (84%) specimens (Fig. 3a,b), the matrix of
Figure 2 Histology of tenosynovium from normal (a) and trigger finger (b-g). The tenosynovial surface of control specimens is covered by synovial lining cell layer without inflammatory cells (a). Moderate perivascular infiltration by lymphocytes and increased vascularity in trigger finger (b). Synovial lining cells are hyperplastic and stratified (black arrowheads) (c). Fibrin exudates at surface of tenosynovium (white arrowheads) (c). Infiltrating mononuclear cells are positive for LCA (d). CD34 immunostaining confirms increased vascularity (e). PTAH staining shows fibrin exudation (f). LCA, leukocyte common antigen; PTAH, phosphotungstic acid hematoxylin.
© 2014 The Authors Pathology International © 2014 Japanese Society of Pathology and Wiley Publishing Asia Pty Ltd
Tenosynovium in trigger fingers
a
d
b
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c
e
f
Figure 3 Histology of tenosynovium from trigger finger. Hypocellular eosinophilic matrix (a, b) stained blue by Mallory’s azan (c). Chondrocytoid cells are observed in this matrix. Oval- to short spindle-shaped cells have pericellular basophilic mucoid material (d). Alcian blue staining without (e) or with (f) prior hyaluronidase digestion is positive and negative, respectively, for mucoid material.
which 23 (61%) contained chondrocytoid cells (Fig. 3d). The incidences of collagen matrix and chondrocytoid cells were similar between patients with and without steroid injection before the surgery (eosinophilic matrix: 88% and 82%, injected and non-injected group, respectively; chondrocytoid cells: 56% and 64%, respectively). The matrix was colored blue by Mallory’s azan stain (Fig. 3c), and negative for Dylon staining (data not shown), indicating that the matrix contained collagen fibers. Mucoid material around chondrocytoid cells was positive for alcian blue, which was abolished by prior hyaluronidase digestion (Fig. 3e,f). The chondrocytoid cells did not express S-100 protein (Fig. 4a), but they were positive for CD44 (Fig. 4b) and procollagen I (Fig. 4c). These results suggest that the chondrocytoid cells producing hyaluronic acid originated from fibroblastic synovial B cells,9,10 but did not undergo apparent cartilaginous differentiation. Electron microscopy showed degenerated collagen fibrils in the matrix
(Fig. 5a). The chondrocytoid cells were surrounded by a collagen fibril layer that had pericellular lacunae containing mucoid material (Fig. 5a,b). The cells also had abundant rough endoplasmic reticulum, pinocytic vesicles, mucin-laden granules and foot processes, but no lysosomes (Fig. 5c). These findings suggested that the cells originated from fibroblastic, rather than histiocytic cells.13,14 None of the clinical data, including sex, age (>60 years vs ≤60 years), preoperative local steroid injection (present vs absent), and the clinical stage (Stage II vs Stage III) are statistically correlated with the histological findings.
DISCUSSION We presented histopathological details of the tenosynovium affected by trigger finger. That is, both chondrocytoid cells
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Figure 4 Immunohistochemistry of chondrocytoid cells. Immunohistochemical staining of chondrocytoid cells is negative for S-100 (a) and positive for CD44 (b) and procollagen I (c).
that produce hyaluronic acid and hypocellular collagen matrix are characteristic findings of the disorder and suggest that the histopathological features are associated with stenosing mechanisms in trigger finger. The limitation of our study is the number of controls. However, it is ethically impossible to resect tenosynovium from normal fingers. The pathophysiology of trigger fingers can be explained as the container that is the anatomically available space,
and the contents that comprise the flexor tendon. Published reports have emphasized constriction of the container. That is, ultrasonographic studies have focused on hypertrophy of the pulley.4,15 A histological study of the A1 pulley of trigger finger has also shown fibrous thickening5 and some investigators have identified chondrocytoid cells in the innermost layer of the pulley.16,17 Sampson et al.16 demonstrated immunoreactivity for S-100 protein and the ultrastructural characteristics of chondrocytes in pulleys, indicating fibrocartilaginous metaplasia. Chondrocytoid cells have also been found in the transverse carpal ligament of carpal tunnel syndrome18 and in the tendon sheath of the extensor pollicis brevis and abductor pollicis longus from patients with De Quervain’s disease.13 On the basis of morphology of histochemistry or electron microscopy with or without immunoreactivity for S-100 protein, the authors above suggested that these cells displayed chondroid or cartilaginous metaplasia. However, the origins of these cells in the retinaculum have remained unknown. Here, we have first showed hyaluronic acid-producing chondrocytoid cells in tenosynovium, and these cells expressed CD44 and procollagen I, but not S-100, suggesting that these cells originated from fibroblastic tenosynovial cells.8–10 Electron microscopy confirmed the fibroblastic tenosynovial origin. We used CD44 antibody as a marker of synovial B cells in accordance with previous report,9,10 and confirmed its reaction to synovial lining cells. However, because CD44 is also known as a receptor for hyaluronic acid,19 it is likely that CD44 antibody react with the synthesized hyaluronic acid. Given these results and anatomical discontinuity between tenosynovium and the innermost layer of the pulley,16,20 the origins of chondrocytoid cells in tenosynovium may differ from the chondrocytoid cells in pulleys, as has been reported previously.13,14 The eosinophilic material around chondrocytoid cells was degenerated collagen matrix according to the findings of Mallory’s azan staining and electron microscopy. Immunoreactivity for procollagen I suggested that collagen fibrils formed de novo are included in the matrix just around chondrocytoid cells. Hyaluronic acid is one of the most hydrophilic molecules in nature and thus it can be described as a moisturizer for the extracellular matrix,21 and it contributes to lubrication of the tendon and pulley.22,23 Hyaluronic acid inhibits fibroblast proliferation, and it does not affect the production of either collagen or proteoglycan.24 Our histological findings support these results because the eosinophilic material around chondrocytoid cells contains few fibroblastic spindle cells (Fig. 3b). The edematous extracellular matrix in conjunction with hyaluronic acid synthesis may increase the pressure under the pulley in the trigger finger. Although there is no correlation between vascularity and other histological features, increased vascularity may contribute to edematous thickening of tenosynovium. We assumed that mutual inter-
© 2014 The Authors Pathology International © 2014 Japanese Society of Pathology and Wiley Publishing Asia Pty Ltd
Tenosynovium in trigger fingers
a
Figure 5 Transmission electron microscopy of chondrocytoid cells. Degenerated collagen fibrils are seen in the matrix (white arrows) (a). Chondrocytoid cells surrounded by collagen fibril layer (black arrows) have pericellular lacunae that contain mucoid material (arrowheads) (a, b), abundant rough endoplasmic reticulum (yellow arrows), pinocytic vesicles (black arrowheads), mucin-laden granules (red arrows) and foot processes (white arrowheads) but no lysosomes (c). These findings suggest that the cells are of fibroblastic, rather than macrophage origin.
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ference between fibrous thickening of the A1 pulley and the increased volume of tenosynovium comprises one cause of this disorder. We should also consider that the synthesis of hyaluronic acid in synovial cells is secondary to the stenosing condition by thickened pulleys. Unfortunately, we could not demonstrate the correlation between the clinical parameters and the histological findings. One of the reason for this may be that all of our cases are categorized in an advanced clinical stage (stage II and III), and are resistant to conservative treatment. Drossos et al. reported that the outer layer of A1 pulley has no inflammatory infiltrate, indicating that tenosynovitis may not be a suitable term for pathophysiology of trigger finger.6 On the other hand, our series showed inflammatory infiltrate in 37%. Inflammation seems to depend on its anatomical site. This suggests that inflammatory cell infiltration may be greater in tenosynovium than in pulley. In conclusion, we identified chondrocytoid cells that produce hyaluronic acid and a hypocellular collagen matrix in the tenosynovium of trigger finger, suggesting that excess hyaluronic acid synthesis and an edematous swollen collagen matrix are involved in the progression of trigger finger. Thus, the attenuation of the collagen matrix or hyaluronic acid synthesis might be an effective non-surgical therapeutic modality for treating trigger finger.
ACKNOWLEDGMENTS This study was supported in part by Grants-in-Aid from the Japanese Ministry of Education, Culture, Sports, Science and Technology for Scientific Research no. 22791387, 24791553 (to KU), and 23591050 (to ST). We thank Fumihiro
Mutoh, Shinichi Nakahara, Hiroyuki Ideguchi and Masako Ikenaga for excellent technical assistance. REFERENCES 1 Nimigan AS, Ross DC, Gan BS. Steroid injections in the management of trigger fingers. Am J Phys Med Rehabil 2006; 85: 36–43. 2 Lundin AC, Eliasson P, Aspenberg P. Trigger finger and tendinosis. J Hand Surg Eur Vol 2011; 37: 233–6. 3 Ryzewicz M, Wolf JM. Trigger digits: Principles, management, and complications. J Hand Surg Am 2006; 31: 135–46. 4 Vuillemin V, Guerini H, Bard H, Morvan G. Stenosing tenosynovitis. J Ultrasound 2012; 15: 20–28. 5 Meachim G, Roberts C. The histopathology of stenosing tendovaginitis. J Pathol 1969; 98: 187–92. 6 Drossos K, Remmelink M, Nagy N, de Maertelaer V, Pasteels JL, Schuind F. Correlations between clinical presentations of adult trigger digits and histologic aspects of the A1 pulley. J Hand Surg Am 2009; 34: 1429–35. 7 Newport ML, Lane LB, Stuchin SA. Treatment of trigger finger by steroid injection. J Hand Surg Am 1990; 15: 748–50. 8 Qu Z, Garcia CH, O’Rourke LM, Planck SR, Kohli M, Rosenbaum JT. Local proliferation of fibroblast-like synoviocytes contributes to synovial hyperplasia. Results of proliferating cell nuclear antigen/cyclin, c-myc, and nucleolar organizer region staining. Arthritis Rheum 1994; 37: 212–20. 9 Suzuki A, Nozawa-Inoue K, Amizuka N, Ono K, Maeda T. Localization of CD44 and hyaluronan in the synovial membrane of the rat temporomandibular joint. Anat Rec A Discov Mol Cell Evol Biol 2006; 288: 646–52. 10 Henderson KJ, Edwards JC, Worrall JG. Expression of CD44 in normal and rheumatoid synovium and cultured synovial fibroblasts. Ann Rheum Dis 1994; 53: 729–34. 11 Uchihashi K, Aoki S, Shigematsu M et al. Organotypic culture of human bone marrow adipose tissue. Pathol Int 2010; 60: 259– 67. 12 Uchihashi K, Aoki S, Matsunobu A, Toda S. Osteoblast migration into type I collagen gel and differentiation to osteocyte-like cells within a self-produced mineralized matrix: A novel system
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