대한내과학회지 : 제 83 권제 2 호 2012 http://dx.doi.org/10.3904/kjm.2012.83.2.178 특집 (Special Review) - 관절염환자의진단적접근 관절염의영상검사 한림대학교성심병원영상의학과 고성혜 Imaging of Arthritis Sung Hye Koh Department of Radiology, Hallym University Sacred Heart Hospital, Anyang, Korea Imaging study of joint is important to differentiate various kinds of arthritis, and to evaluate the treatment response of the arthritis. Radiograph is the basic and first line imaging study of the joint, but there are overlapped imaging findings between arthritis. The objective of this review is to present a simplified approach to radiographic evaluation of arthritis and to help in making adequate decision to choose a further imaging study among ultrasonography, CT and MRI. (Korean J Med 2012;83:178-189) Keywords: Arthritis; Osteoarthritis; Computed tomography; Rheumatoid arthritis; Ankylosing spondylitis 서 론 본 론 관절염의종류에따라관절을이루는관절연골과연골하골, 활액막, 힘줄과인대의변화가각각다른양상으로나타나므로임상소견과더불어영상소견은관절염의감별진단에도움이되며, 영상검사가관절염의진행정도를평가하고치료경과를관찰하는데중요한역할을한다. 영상검사에서관절연골손상에따른관절강협착 (joint space narrowing) 과대칭성 (symmetricity), 관절주위골다공증, 관절주위골경화 (sclerosis), 골미란 (bone erosion), 연골하낭종 (subchondral cyst), 관절주위연부조직변화, 석회질침착, 관절모양의변화, 침범관절의개수와분포등을평가한다. 관절염을감별하는데있어서여러가지방법들이있으나영상소견을중심으로정리한 Jacobson 등 [1] 이보고한것을기본으로몇가지수정하여소개하고자한다 (Fig. 1) [1,2]. 그림 1의흐름도는전형적이고특징적인소견을기준으로한것이므로비전형적인경우와각질환의초기소견은포함하지않고있기때문에임상소견과더불어판단하는것이필요하다. 여기서가장중요한것은세균성관절염 (septic arthritis) 을다른관절염과감별하여조기에적절한치료를하는것인데, 급성단일관절염증인경우에는임상소견으로세균성관절염을다른질환과감별하는것이중요하다 [3]. 관절염이단일관절인지아닌지평가하는데있어서손목과같이한 Correspondence to Sung Hye Koh, M.D. Department of Radiology, Hallym University Sacred Heart Hospital, 22, Gwanpyeong-ro 170beon-gil, Dongan-gu, Anyang 431-796, Korea Tel: +82-31-380-3898, Fax: +82-31-380-3878, E-mail: jnsunghye@hallym.or.kr - 178 -
- Sung Hye Koh. Imaging of arthritis - 부위에여러구획이존재하는경우에는한구획을단일관절로평가해야한다 (Table 1) (Fig. 2) [4]. 세균성관절염의경우단일구획에서시작하여치료가적절하게되지않은경우주변구획으로진행되고, 류마티스관절염에서는초기에양쪽손목에대칭적으로여러구획에관절염이생기고결국모든구획에관절염이생긴다 (Fig. 2B). 특정한구획을침범하는관절염들이있는데, 골관절염 (osteoarthritis) 과 CPPD는모두퇴행성변화를보이는관절염이지만골관절염은 carpometacarpal 구획과 trapezioscaphoid 구획을주로침범하고 CPPD 는 radiocarpal 구획을침범한다 (Fig. 2C and 2D). 염증성관절염관절내염증이있을때세균에의한감염에의한경우와류마티스또는척추관절병증과같은비세균성원인에의한경우모두대칭적인관절강협착, 골미란, 관절주변연부조직부종을동반한다. 골미란은염증성관절염을시사하는소견으로연골하골피질의흰선의일부가끊어져보이는것을말한다. 염증이없다면심한골다공증이있어도연골하골피질의하얀 선은유지되어야한다. 골미란이관절면의가장자리에있는경우를가장자리골미란 (marginal erosion) 이라고하는데, 이는관절면의가장자리에노출부 (bare area) 가있기때문이다. 이노출부는관절내부에위치하지만유리연골 (hyaline cartilage) 이덮고있지않기때문에관절내의염증이이노출부에가장먼저골미란을생기게하므로영상검사에서관절의가장자리를여러각도에서확인하는것이필요하다. 염증이진행되어연골과연골하부골의파괴가진행되면서관절강협착을유발하는데염증이관절강내에서전체적으로균일하게일어나므로대칭적관절강협착 (symmetric joint space narrowing) 이생긴다. 또한주변연부조직에염증이동반되므로연부조직부종이생긴다. 세균성관절염균일한관절강협착, 골미란, 연부조직부종등의염증성관절염의소견이있을때침범된관절이하나인경우에는가장먼저세균성관절염의가능성을생각하여임상적검사가진행되어야한다 (Fig. 1). 그러나세균성관절염이여러관절성으로생기는경우가약 20% 까지보고되어있으므로두개이상의관절이침범되더라도염증성관절염의감별진 Figure 1. Flow chart shows approach to radiographic evaluation of arthritis (modified from Jacobson, et al. Radiology 2008;248:378-389 [1]). - 179 -
- 대한내과학회지 : 제 83 권제 2 호통권제 624 호 2012 - Table 1. Major compartments of the wrist Compartment Location Radiocarpal Between the distal end of the radius and the proximal carpal row Midcarpal Between the distal and the proximal carpal rows Common carpometacarpal Between the distal carpal row and the bases of the four ulnar metacarpals First carpometacarpal Between the trapezium and the base of the first metacarpal Inferior radioulnar Between the distal ends of the radius and ulna, separated from the radiocarpal compartment by the triangular fibrocartilage of the wrist Pisiform triquetral Between the pisiform and triquetrum Modified from Resnick D, Kransdorf MJ. Target area approach to articular disorders. In: Bone and Joint Imaging. 3rd ed. Philadelphia: Elsevier Saunders, 2005:519-539 [4]. A B C D Figure 2. (A) Compartments of the wrist. The pisiform-triquetral compartment is not shown. The trapezioscaphoid region of the midcarpal joint is separated from the remainderof this joint. CCMC, common carometacarpal compartment; CMC, first carpometacarpal compartment; IRU, inferior radioulnar compartment; MC, midcarpal compartment; RC, radiocarpal compartment. (B) Rheumatoid arthritis. (C) Osteoarthritis. (D) CPPD (modified from Resnick D, Kransdorf MJ. Target area approach to articular disorders. In: Bone and Joint Imaging. 3rd ed. Philadelphia: Elsevier Saunders, 2005:519-539 [4]). 단이확실하게되기전까지는항상세균성관절염의가능성을염두에두어야한다 [5]. 세균성관절염이임상적으로확인되면골수의염증여부를확인하기위해서 MRI를시행한다. MRI 에서골수의염증이있는경우에는 T1 강조영상에서저신호강도, 조영증강후에신호증강을보이며부종만있는경우에는신호증강은없다 (Fig. 3). 세균성관절염의영상소견은염증성관절염의소견을보이지만관절면의대칭적협착 (symmetric narrowing), 가장자리골미란, 관절주위연부조직부종, 관절하연골의골다공증등이모두나타나지않는경우도있다. 급성기에는골미란이보이지않을수도있고, 관절강내의삼출액에의해오히려관절강이넓어질수도있다. 결핵성관절염의경우에는관절강협착이천천히나타나기도한다 (Fig. 4) [2]. 류마티스관절염염증성관절염이두개이상의관절에있을때류마티스관절염의가능성과음성혈청반응척추관절증 (seronegative spondyloarthropathy) 을생각해야한다. 손과발에관절염이있을때방사선검사에서염증성관절염의소견이여러개의관절에서양측성그리고대칭적으로근위부 (proximal) 에분포하고골증식이없으면류마티스관절염일가능성이높다 (Fig. 5). MRI 는조기의류마티스관절염을평가하고, 동반된건염여부를확인하고, 활액막의두께와골수와연부조직염증정도를기준으로치료반응을관찰하는데유용하다 (Fig. 6) [6]. 만성기에는관절주위골다공증, 균질한관절강협착, 골미란, 연부조직부종외에관절의아탈구와연골하낭종이동반되기도한다. 류마티스관절염은활액막의전반적으로염증을일으키는질환이기때문에 retrocalcaneal bursa - 180 -
- 고성혜. 관절염의영상검사 - A B C D E Figure 3. Septic arthritis (A) AP view and (B) lateral radiographs of the 3rd finger of a hand show symmetric joint space narrowing, periarticular soft tissue swelling and bone erosion (arrow) of the PIP joint. (C) Ultrasonography of the dorsal portion of the PIP joint of the finger shows cortical erosion (arrowhead) and periarticular soft tissue inflammation (arrows). (D, E) On MRI of the finger, the proximal phalangeal head, mid phalangeal base and periarticular soft tissue of the PIP joint show low signal intensity on T1-weighted image (D). After contrast infusion, fat suppressed T1-weighted image shows signal enhancement of the proximal phalangeal head and periarticular soft tissue sparing mid phalangeal base. The area of low signal intensity of the mid phalangeal base suggests reactive bone marrow edema not inflammation. 같은윤활낭 (bursa) 과건초 (tendon sheath) 에도염증을일으킨다. 손과발외에도무릎관절, 고관절, 천장관절, 견관절에도관절염이있을수있으며, 척추에서 C1-2에윤활관절에염증성관절염이생겨서 odontoid process에골미란이생기고 (Fig. 7), 윤활관절에인접한 C1-2를연결하는인대손상으로 atalantodental space가 3 mm 이상넓어지는 atlantoaxial subluxation이생기기도한다 (Fig. 8). 이때방사선검사에서경추를굴곡한자세에서만 atlantoaxial subluxation 이나타나는경우도있다. 음성혈청반응척추관절증 (seronegative spondyloarthropathy) 염증성관절염이여러관절에생기며, 손과발에생기는 경우에원위부관절을침범하고골증식의소견을보이면음성혈청반응척추관절증을먼저의심해야한다. 강직성척추염, Psoriatic arthritis, Reiter syndrome (Reactive arthritis) 등이이에해당하고 Psoriatic arthritis와 Reiter syndrome은비교적드물다. 강직성척추염은 axial skeleton을주로침범하고 peripheral joint를침범하기도한다 (Fig. 9). 척추에서는골염 (osteitis), syndesmophyte 형성, 척추후관절 (facet joint) 염증, 그리고척추제융합이생긴다 (Fig. 10). 천장관절에서는양측성대칭적으로염증이생기며대체로척추의염증보다먼저생긴다. 처음에는관절면의연골하골피질의하얀선이끊어지거나희미해지는것으로시작하여골미란의크기가커지게된다 - 181 -
- The Korean Journal of Medicine: Vol. 82, No. 2, 2012 - A B C Figure 4. Tuberculous dactylitis. (A) AP view and (B) lateral radiographs of the 3rd finger of a hand show osteomyelitis with cold abscess of the proximal phalanx. The joints space of the PIP joint of the finger is relatively preserved (arrow) (C) Ultrasonography of the volar portion of the PIP joint shows effusion (arrow) in the joint and large erosion of the proximal phalangeal head (arrowhead). Figure 5. Rheumatoid arthritis of hand and wrist. Radiograph of a hand shows joint space narrowing, bone erosion (arrow heads) and periarticular soft tissue swelling (arrow) in pancompartment of the wrist and metacarphophalangeal and proximal interphalangeal joints of the hand. (Fig. 11). 골미란주변에는골경화가보일수있고관절내의염증이진행되면서결국관절강이좁아지고골융합이생긴다 (Fig. 12). 단순방사선검사에서천장관절이정상으로보이거나이상소견이뚜렷하지않을때 MRI 로관절내부삼출액과관절주변골수부종이있으면진단할수있다 (Fig. 13). 또한단순방사선검사에서이상소견이보이지만염증성관절염인지퇴행성관절염인지구분하기힘들때는 CT로감별할수있다. 척추를침범하는경우에는초기에추간판과척추체인접부 (Discovertebral junction) 에전방가장자리에골미란이있다가골경화가심해지는데이를 shiny corner sign 이라고한다 (Fig. 10). 척추체전면과측면에골증식이일어나면 squared 모양을보이며, annulus fibrosus의외측에골화가진행되면 syndesmophyte가나타나는데, 이때척추의전면에출렁거리는듯한전종인대의골화를보이는 diffuse idiopathic skeletal hyperostosis (DISH) 의경우와감별해야한다 (Fig. 14). Syndesmophyte가두꺼워지고연결되면 bamboo spine 의소견이보이고비교적척추골절이쉽게일어난다 (Fig. 10). 후관절 (facet joint) 의염증은진행하여관절의융합이생기고, 척추의 AP view 에서후방극간인대 (posterior interspinous ligament) 의골화로 dagger sign 이보이며후관절 (facet joint) 의융합과극간인대 (interspinous ligament) 의골화는 trolleytrack sign 으로보인다 (Fig. 12). Peripheral joint를침범하는경우에는양측성으로균일한관절강협착을보이고고관절 - 182 -
- Sung Hye Koh. Imaging of arthritis - A B C Figure 6. Rheumatoid arthritis of wrist. (A) Radiograph shows marginal erosions (arrow heads) in midcarpal compartment and radiocarpal compartment. (B) On fat suppressed T1-weighted MR coronal scan of the wrist, pannus formation (curved arrow). is noted in distal radioulnar compartment with effusion. (C) On T2-weighted MR axial scan shows tenosynovitis of extensor tendons (open arrows). Figure 7. Rheumatoid arthritis of C1-2. Sagittal CT scan of C-spine shows a bone erosion of the anterior portion of odontoid process of C2 (arrow). - 183 -
- 대한내과학회지 : 제 83 권제 2 호통권제 624 호 2012 - A B C D Figure 8. Rheumatoid arthritis of C1-2 with subluxation. (A, B) Lateral views of C-spine show C1-2 subluxation (arrows) not with neck extension (A) but with neck flexion (B). (C, D) Sagittal scan of CT (C) and MR T2-weighted image (D) of C-spine show C1-2 subluxtion (arrows) with narrowing of spinal canal. Spinal cord shows high signal intensity on MR T2-weighted image suggesting compressive myelopathy (arrowhead). 의경우에서는 acetabular protrusion과연골하낭종이생기고대퇴골경부에골증식이보인다 (Fig. 12). 퇴행성관절염퇴행성관절염은비대칭성관절강협착, 골경과와골극, 염증성관절염에서보이는골미란이없는연골하낭종이특징적이소견이다. 가장자리골극이퇴행성관절염을진단하는데도움을주는소견이라고하면, 관절강협착, 골경화, 연골하낭종은중증정도를평가하는데사용된다. 퇴행성 관절염이영상소견에서보일때침범된관절의위치, 환자의나이와기타영상소견으로퇴행성변화를동반하는다른종류의관절염의가능성을생각해야한다. 골관절염 (Typical osteoarthritis) 관절의퇴행성변화는일상생활에서생기는미세하고반복적인외상으로인해관절연골이손상되고닳고파괴되는것으로서환자의자세의습관과행동에따라퇴행성변화의차이가생긴다. 퇴행성변화는주로 40대전후에생기기시 - 184 -
- 고성혜. 관절염의영상검사 - A B Figure 9. Ankylosing spondylitis of peripheral joints. (A, B) Radiographs of a foot (A) and a knee (B) show marginal bone erosions (arrowheads) and bony proliferations (arrows). Figure 11. Ankylosing spondylitis of SI joint. Axial scan of CT of pelvis shows bone erosions of both SI joints (arrows). Figure 10. Ankylosing spondylitis of L-spine. Lateral radiograph of L-spine shows syndesmophyte formation (arrowhead), ankylosis of facet joints (curved arrow), ossification of posterior interspinous ligament (double arrows), osteitis of anterior corner of discovertebral junction (shiny-corner sign) (arrow), and a distractive fracture of L2-3 (open arrow). 작하며무릎의경우관절강협착이내측에비대칭성으로나타나고고관절의경우상방에관절강협착이오면서대퇴골두가상방으로이동한다. 손에서는사용하는동작과정도에따라서 first carpometacarpal joint 또는 interphalangeal joint 에퇴행성변화가생긴다 (Figs. 2 and 15). - 185 -
- The Korean Journal of Medicine: Vol. 82, No. 2, 2012 - Figure 12. Ankylosing spondylitis of SI joint. Radiograph of pelvis shows bony ankylosis of both SI joints, Symmetric joint space narrowing of both hip joints, bony proliferations (arrows) of both pelvic bones and both proximal femurs. There is a white vertical line at the midline of lumbosacral spine; dagger sign (arrowhead). Figure 14. DISH (Diffuse idiopathic skeletal hyperostosis) of thoracolumbar spine. Lateral radiograph of thoracolumbar spine shows flowing ossification (arrows) of anterior longitudinal ligament at the anterior portion of the thoracolumbar spine. Figure 13. Ankylosing spondylitis of SI joint. On MR oblique coronal scan of pelvis, fat suppressed contrast enhancement T1-weighted image shows signal enhancement (arrows) in joint spaces and periarticular bones of the lower portion of both SI Figure 15. Osteoarthritis of hand. Radiograph shows spurs (arrows) and sclerosis of the 1st interphalangeal joint, the 1st carpometacarpal joint, and trapezioscaphoid joint. - 186 -
- Sung Hye Koh. Imaging of arthritis - joints. Figure 16. CPPD of knee. Radiograph shows chondral calcinosis in lateral meniscus (arrow) with large spurs (open arrow) and severe subchondral sclerosis (arrow head). Figure 18. Neuropathic joint. Oblique radiograph of a foot of a DM patient shows fragmentation, disorganization and sclerosis of mid foot. Figure 17. CPPD of wrist. Radiograph shows chondral calcinosis in trigangular fibrocartilage (arrow head) and ligament calcification in lunotriquetral ligament (arrow). 이차성골관절염 (Secondary osteoarthritis) 퇴행성변화가흔히발생하는위치가아닌곳에생기거나, 중증정도가심하고, 나이도비교적어린경우에는다른원인에의한퇴행성변화가있는지살펴보아야한다. 외상은가장흔한이차성골관절염의원인으로연골손상을동반하는외상이있었거나운동선수의경우나직업적으로과도하게관절연골에손상이생기는경우에퇴행성변화가 일찍오고좌, 우한쪽에만나타난다. CPPD는연골, 활액막, 힘줄과인대에석회질이침착되는질환으로결정침작이관절연골을손상시켜서퇴행성변화를나타나게한다 (Fig. 16). 무릎은 CPPD가가장흔히발견되는곳으로외측무릎관절또는무릎뼈대퇴골관절에만변화가있으면골관절염과감별이가능하다. 분포양상은일반적으로양측성이다. 영상소견이일부분골관절염과유사하나다음의몇가지의차이점을보인다 [7]. 침범하는관절부위의차이관절질환이몸무게가실리는관절에발생하기도하지만퇴행성관절질환이흔히나타나지않는손목, 팔꿈치, 어깨관절에서도발견된다. 관절내부에서침범하는위치의차이손목에서 radiocarpal에만퇴행성변화가단독으로생기거 - 187 -
- 대한내과학회지 : 제 83 권제 2 호통권제 624 호 2012 - A Figure 19. Gout. (A) Radiograph shows soft tissue swelling (arrow) of the medial portion of the 1st metatarsal head with adjacent bone erosion. (B) US of the medial portion of the 1st MTP joint shows echogenic crystal deposition in the soft tissue swelling. 나또는무릎에서 patellofemoral compartment의병변이단독적으로생기거나또한심하게손상된경우에는 CPPD결절침착질환을의심할수있다 (Fig. 17). 크기가큰연골하낭종 심한골파괴성변화 다양한골극형성 Neuropathic joint는초기에골관절염과유사하나진행할수록골화, 골분절 (fragmentation), 아탈구 (subluxation) 가점점뚜렷해진다. 초기의 neuropathic joint와골관절염과의감별에도움이되는소견은신경손상이있는위치에관절변화가생기는것이다. 그러므로환자의병력이영상검사진단에필요하다. 예를들어 DM foot에서는 midfoot에 neuropathic joint 가생기는특징이다 (Fig. 18). 기타 통풍 (Gout) 은관절강협착이나골다공증을동반하지않는 monosodium urate cystal 침착에의한것으로통풍에서보이는골미란은특징적으로관절면가장자리에서벗어나서경계가잘그려지는 punched-out appearance를보인다. monosodium urate crystal이방사선검사에서고음영으로보이지않는경우가많기때문에결정침착이있는곳은연부조직의심한부종으로만보이고이때초음파검사에서결정침착이고음 B 영으로보여진단에유용하며 MRI에서는모든스캔에서저신호강도로보인다 (Fig. 19). 가장흔히침착되는곳은 first metatarsophalangeal joint이다. 초기에는한개의관절에서시작하나후기에는여러관절을침범한다. 손과발의다른관절에침착되는경우가드물지않고팔꿈치의 olecranon bursa에침착되기도한다. SLE (systemic lupus erythematosus) 는방사선검사에서관절면협착이흔하지않으며주로 metacarpophalangeal joint 의 subluxation 생기며 AP view 에서는잘보이지않고 oblique view를찍어야만알수있다. 관절주변골다공증과연부조직부종은보일수있다. 결론관절염이의심될때관절강협착이있는지먼저보고골미란이있는지골극이있는지살펴보아야한다. 관절강의협착이있을때골미란이있으면염증성관절염, 골극이있으면퇴행성관절염을고려하여야하며염증성관절염이하나의관절에생길때는가장먼저세균성관절염의가능성을확인하는것이중요하다. 여러개의관절에생길때는관절염의분포와골증식이있는지를평가하여류마티스관절염과음성혈청반응척추관절증 (seronegative spondyloarthropathy) 을구분한다. 퇴행성변화가있는관절에서는침범된관절의위치와진행정도, 나이등을고려하여이차성관절염이의심되면원인을찾아보아야한다. 관절강협착이없고경계가명확한관절주위골미란이있으며종괴모양의연부조직부종이있을때는통풍을고려하여야한다. 가장기본적인영상검사인단순방사선검사에서는관절염이진행되어관절주변뼈에변화가있을때이상소견이나타나고, CT는단순방사선검사보다예민하게이상소견을발견하는데도움이되며관절구조가복잡할때유리하다. US는관절내부삼출액과관절주변연부조직의변화를잘볼수있고단순방사선검사에서잘나타나지않는석회질침착을예민하게볼수있는장점이있으나연골과골파괴를평가하는데제한이있고다른검사에비해서검사결과가검사자에좌우되고재현성이떨어진다. MRI 는검사에포함된관절의관절연골, 골수의변화, 관절주위연부조직변화를평가하는데유용하며치료경과관찰에도움을준다. 이때조영증강검사를같이실시하여야활액막과삼출 - 188 -
- 고성혜. 관절염의영상검사 - 액을구분하여활액막의비후정도를평가할수있고골수와연부조직의염증범위를정확하게평가할수있으며감영성관절염인경우골수내부또는주변조직에농양이동반되었는지확인할수있다. 중심단어 : 관절염 ; 영상 ; 류마티스 ; 강직성척추염 REFERENCES 1. Jacobson JA, Girish G, Jiang Y, Resnick D. Radiographic evaluation of arthritis: inflammatory conditions. Radiology 2008;248:378-389. 2. Jacobson JA, Girish G, Jiang Y, Sabb BJ. Radiographic evaluation of arthritis: degenerative joint disease and variations. Radiology 2008;248:737-747. 3. Margaretten ME, Kohlwes J, Moore D, Bent S. Does this adult patient have septic arthritis? JAMA 2007;297:1478-1488. 4. Resnick D, Kransdorf MJ. Target area approach to articular disorders. In: Bone and Joint Imaging. 3rd ed. Philadelphia: Elsevier Saunders, 2005:519-539. 5. Learch TJ. Imaging of infectious arthritis. Semin Musculoskelet Radio l2003;7:137-142. 6. Narvaez JA, Narvaez J, De Lama E, De Albert M. MR imaging of early rheumatoid arthritis. Radiographics 2010; 30:143-163; discussion 63-65. 7. Resnick D. Kransdorf MJ. Calcium pyrophosphate dehydrate crystal deposition disease. In: Bone and Joint Imaging. 3rd ed. Philadelphia: Elsevier Saunders, 2005:459-473. - 189 -