Clinical Radiology (1992) 45, 153 160
Intra-Articular Osteoid Osteoma V. N. C A S S A R - P U L L I C I N O ,
I. W. M C C A L L
a n d S. W A N
Department o f Diagnostic Imaging, The Institute of Orthopaedics, The Robert Jones & Agnes Hunt Orthopaedic Hospital, Oswestry O s t e o i d o s t e o m a s located within the capsule o f a j o i n t are uncommon and p r e s e n t challenging d i a g n o s t i c difficulties. T w e l v e patients with an intra-articular osteoid osteoma w e r e studied r e t r o s p e c t i v e l y to d e t e r m i n e the s p e c t r u m of clinical and radiological findings. T h e f e a t u r e s differ significantly from the well known classical hallmarks of the extra-articular lesion. The symptoms are non-specific with pain similar to other common joint disorders and the response to salicylate less precise. O n plain radiography intra-articular lesions are difficult to identify, lacking the florid periosteal new bone and intense p e r i f o c a l sclerotic reaction. A d e t e c t a b l e focal lesion is c o m m o n l y absent with considerable d e l a y between the onset o f symptoms and r a d i o l o g i c a l detection o f the t u m o u r nidus. Bone scintigraphy and computed tomography ( C T ) are essential for an accurate and early diagnosis. T h e s e i m a g i n g techniques reveal abnormalities in bone and cartilage growth, new bone formation and sclerosis distant from the tumour on either side o f the joint, and disruption of the articular surface. Radiological follow up after surgery shows t h a t these changes can be reversible, especially when the diagnosis is m a d e early. C a s s a r - P u l l i c i n o , V . N . , M c C a l l , I . W . & W a n , S. (1992). Clinical Radiology 45, 153-160. Intra-Articular Osteoid Osteoma
O s t e o i d os t e o m a is a small, h i g h l y cellular, b e n i g n t u m o u r o f b o n e , c o n t a i n i n g f i b r o v a s c u l a r tissue, i m m a t u r e b o n e and o s t e o i d , w h i c h is c a p a b l e o f g e n e r a t i n g a v i g o r o u s o s t e o b l a s t i c h o s t r e s p o n s e . It r e p r e s e n t s 11% o f all b e n i g n
b o n e t u m o u r s ( D a h l i n , 1986), is m o s t c o m m o n l y f o u n d in the d i a p h y s i s o f the l o n g b o n e s o f the l o w e r limb, a l t h o u g h a n y b o n e m a y p l a y host, a n d is f r e q u e n t l y l o c a t e d n e a r o r w i t h i n t h e periosteum_ I n its classical f o r m it p o s e s few d i a g n o s t i c p r o b l e m s , h a v i n g c h a r a c t e r i s t i c clinical, r a d i o l o g i c a l a n d h i s t o l o g i c a l features, a n d a c u r e c a n be e x p e c t e d f o l l o w i n g en bloc resection. W h e n the l o c a t i o n o f the o s t e o i d o s t e o m a is i n t r a a r t i c u l a r , d i a g n o s t i c difficulties m a y arise as it results in
Correspondence to: V. N. Cassar-Pullicino, Consultant Radiologist, Department of Diagnostic Imaging, The Robert Jones & Agnes Hunt Orthopaedic Hospital, Oswestry, Shropshire SY10 7AG.
Table 1 - Clinical features of intra-arlicularosteoid osteoma
Age Sex 6
F
40
M
16
M
52
M
20
M
24
F
18
M
32
F
34
M
24
F
39
F
14
F
Site
Main complaint
Duration Aggravating Analgesic Initial (years) factors response diagnosis
Femur, hip joint Acetabulum, hip joint Ulna, elbow joint TS, pars interarticularis, facet joint T5 spinallamina, facet joint Talus, ankle joint Talus, ankle joint Clavicle, S-C joint Scaphoid, carpal joints Capitate, carpal joints Base 2 metatarsal cuneiform joint Head 2 metatarsal phalangeal joint
Pain, limp Pain, sciatica Pain, swelling Girdle pain
i
Intercostal pain Pain, stiffness Pain, swelling Pain, swelling Pain, stiffness Pain, swelling Pain, stiffness Pain, swelling
3
Surgical findings
Follow-up (years) 3 Asymptomatic O 3 Minimal symptoms X 2 Asymptomatic X 2 Minor symptoms
Naproxen
? TB ? Still's
Synovitis
7
Movement, morning Movement
Naproxen
O.A.
Osteophytosis
3
Movement
--
3
Movements in bed
--
Osteochondritis dissecans O.A.
----
1¼
Rotational movements Movement, morning Movement
--
Myalgia
Naproxen
? Inflammatory arthritis ? Mono arthritis
Thickened capsule + 1 ligamentum flavum Asymptomatic O Pericapsular 2 thickening Minor symptoms O Synovitis 1 Asymptomatic O 2 Residual symptoms O
2 a ~ 5 221
Movement, coughing Morning
--NSAI
? Tietze's syndrome 9 Fracture
1
4
Gripping
--
Tenosynovitis
--
6
Walking, morning
Naproxen
? Stress lesion
Pericapsular thickening, osteophytosis Synovitis
1
Movement, walking
9 Freiberg's disease
--, None Specified; O, bone+soft tissue reverted to normal; X, bone changes persist unchanged.
Minimal symptoms 2 Asymptomatic O Occasional symptoms 1
Minor symptoms
154
CLINICAL RADIOLOGY
T a b l e 2 - Radiological features o f iutra-articular osteoid o s t e o m a
Abnormality
Plain film
CT*
Tumour nidus Bone sclerosis Perifocal Across joint Osteoporosis Osteophytosis Soft tissue swelling Joint space increase Articular erosion Metaphyseal widening Epiphyseal Enlargement Delayed fusion Tumour mineralization
5
11
1 1 4 3 4 2 1 4
5 4 4 3 6 2 6 4
2 1 2
2 1 11
* Twelfth IAOO shown by conventional tomography.
(a) (d) Fig. 1 (a) The plain film shows an increase in joint space. There is a localized area of lucency in the femoral neck (short arrow) with organized periosteal new bone formation in the region of the lesser tronchanter (long arrow). (b) CT of femoral neck shows the lucent osteoid osteoma elevating the cortex with adjacent sclerosis of the cortex. (c) CT of hip joint shows osteoporosis of the left femoral head and the widening of the joint space. (d) One year following en bloc removal of thc osteoid osteoma. The appearances of the bone and joint have returned to normal.
(b)
(c)
articular pain which is similar to other more common joint disorders, and which has a variable response to salicylate and non-steroidal anti-inflammatory therapy (Cohen et al., 1983; K a t t a p u r a m et al., 1983). The plain radiographic features of intra-articular osteoid osteoma (IAOO) are also rarely classical, which leads to further delayed or erroneous diagnosis. While the plain radiographic features of I A O O have been described (Sherman, 1947a; Marcove and Freiberger, 1966), there has been relatively little discussion of the value of more recent imaging techniques ( K a t t a p u r a m et al., 1983; N o r m a n et al., 1986). We therefore report a series of cases of I A O O in which the term intra-articular is used specifically to denote tumour nidus invading the intra-articular portion of bone. This is more selective than those of previous series where broader definitions of lesions 'at the ends of long bones' (Moser et al., 1990) or 'in or around the joints' ( K a t t a p u r a m et al., 1983) have been used. The imaging features in our series have been correlated with surgical findings and assessment of the post-treatment changes in the joint.
INTRA-ARTICULAR OSTEOID OSTEOMA
155
p A T I E N T S AND M E T H O D S Clinical and Radiological Features Twelve patients, with a diagnosis of osteoid osteoma involving the intra-capsular portion of bone, have been investigated over a 5 year period. The age range was 6-52 years, and there was an even sex distribution. All patients presented with joint pain and articular dysfunction. The duration of symptoms ranged from 9 months to 7 years, with a mean of 3.5 years. Specific nocturnal pain was not a feature although pain was worse in the morning and on joint movement. The pain was not specifically relieved by aspirin but a moderate response was noted to Naproxen in five patients. Physical examination revealed a reduction in the whole range of joint movement. There was soft tissue swelling around the joint in five patients and muscle atrophy in three. The delay in diagnosis ranged from 9 months to 7 years, and the alternative diagnoses, based on clinical and radiological findings, are identified in Tables 1 and 2. Review of the initial plain radiographs demonstrated a focal lesion in only five patients, four of which were lucencies in the proximal femur, talus, scaphoid and metatarsal head. However, in the initial radiographic interpretation only two of these lesions were recognized (Figs 1 and 2)_ Bone density in the joint was variable with osteoporosis being present in four patients (Figs 1, 3 and 4), increased sclerosis in two patients (Fig. 5) and no abnormality was demonstrated in six patients. A uniform and congruent increase in the joint space was present (Figs 1 and 3) in the two cases involving the hips. In one case when the tumour disrupted the articular surface, the joint space was narrowed (Fig. 5). The fascial planes were normal in eight cases, but in four cases there was displacement of the pericapsular fat line and a marked intra-articular proliferation of synovium was subsequently confirmed at surgery in three patients (Table 1) (Figs 4 and 6). Bone growth was altered in four cases, with two cases each of increased metaphyseal width in the femoral neck and the metatarsals (Fig. 3). Epiphyseal enlargement was present in one hip and one metatarsal (Fig. 3). New bone formation and sclerosis was seen distant from the turnout on both sides of the adjacent joint. The new bone formation was especially prominent in three patients, taking the form of 'osteophytes' at the chondro-osseous junction in the hip (Fig. 3) and elbow, and a bone spur arising from the base of the second metatarsal_ There was partial delay in fusion of the metatarsal epiphyseal plate adjacent to the tumour site in one patient. In one patient osteochondritis dissecans was present in the elbow, which was coincidental but symptoms were initially attributed to this diagnosis. All lesions were detected by two-phase 99mTcscintigraphy, and the tumour was invariably active on both the diffusion and static phase. In two cases the increase in uptake in the affected joint was more generalized but localized activity was present at the site of the lesion in the remainder (Figs 3, 4 and 7)_ The balance of activity between the diffusion and bone phase varied with the duration of symptomatology, the former being less active in those cases with a significant delay in diagnosis. Increased isotope activity occurred at sites of marginal new bone formation (Fig. 3) and was more widespread in lesions associated with osteoporosis (Fig. 4). Computed tornography (CT) in 11 patients and conventional t o m o -
Fig. 2 A classical osteoid osteoma is seen in the scaphoid which is resulting in localized thinning of the subchondral plate.
graphy in one patient demonstrated all of the tumours clearly and delineated the alteration in bone architecture on both sides of the joint (Fig. 3), the exact relationship of the tumour to the eroded cortex (Fig. 1), joint surface (Figs 5 and 7) or epiphyseal plate, and the extent of the soft tissue reaction (Figs 4 and 6) (Table 2). The proportion of tumour mineralization was predominantly related to the duration of symptoms, indicating that dense calcification occurs in the more mature lesions (Figs 3, 5 and 7). M R I was obtained in one patient with a lesion within the scaphoid bone. The lesion was not clearly identifiable and did not show any alteration following IV gadolinium enhancement. In one of the patients with an early hip lesion the indreased joint space and os teoporosis returned to normal within 1 year (Fig. 1), while in the other, a lesion only diagnosed after 7 years delay, there was no change. The juxta-articular cancellous sclerosis abated in all cases (Figs 1 and 8) 1 2 years after en bloc tumour resection. DISCUSSION This series confirms that I A O O is difficult to diagnose unless there is a high index of suspicion for the lesion and confirms the findings of K a t t a p u r a m et al. (1983) where 23 out of 25 patients had a diagnostic delay of years rather than months. The signs and symptoms of the lesion may be present long before the tumour becomes visible on plain radiographs, which usually occurs when it attains a diameter of 4 m m or more ( K a t t a p u r a m et al., 1983). Furthermore, the classical nocturnal quality of pain found in around 80% of extra-articular osteoid osteoma (Cohen et al., 1983) is absent and the pain is less responsive to salicylates when the osteoid osteoma is intra-articular. Some relief however may occur from nonsteroidal anti-inflammatory drugs but a similar response may be expected from other inflammatory disorders.
156
CLINICAL RADIOLOGY
(a)
(b)
(c)
(a)
Fig. 3 - (a) Plain film of the pelvis demonstrates osteoporosis with increase in size of the joint space in the right hip. The left hip is normal. (b) Scintigram of pelvis shows focal increased activity in the floor of the acetabulum (short arrow) and to a lesser extent on the inferior margin of the femoral head (curved arrow). There is a mild generalized increase in activity throughout the joint. (c) CT of the right hip shows the osteophyte formation at the chondro-osseous junction (arrows) of the femoral head which correlates with the activity on the isotope study. (d) CT of the right hip. The osteoid osteoma is clearly defined in the floor of the acetabulum (arrow). Muscle wasting and osteoporosis are demonstrated on both sides of the joint.
N u m e r o u s published reports highlight the similarity o f the clinical findings to a variety o f acute, subacute and chronic inflammatory arthritides, including septic arthritis and tuberculosis ( C a p a n n a et al., 1986), PVNS, synovial chondromatosis and gout (Cohen et al., 1983), rheumatoid arthritis (Marcove and Freiberger, 1966; Snarr et al., 1973) and osteoarthritis (Sherman, 1947a,b; N o r m a n et al., 1986), all o f which resulted in unrewarding diagnostic procedures and inappropriate treatment. S y m p t o m s m a y also be referred to another joint, causing confusion with regard to the area o f investigation (Sim et al., 1975). The frequency o f intra-articular location in previous series of osteoid osteoma has varied from 0/40 (Kendrick and Evarts, 1967), 4/95 over a 10 year period (Cohen et al., 1983), and 30 hip lesions out o f 182 cases o f osteoid osteomas seen over a 24 year period ( N o r m a n et al., 1986). An under-estimation o f the true incidence of I A O O m a y have resulted f r o m the difficulties in making the diagnosis, as the natural history o f the lesion is benign, with a tendency to spontaneous involution after an interval of 5-10 years (Moberg, 1951; Golding, 1954;
Freiberger et al., 1959; Vickers et al., 1959). O u r findings o f 12 cases in a 5 year period probably reflect the value of the newer c o m p u t e r based diagnostic imaging systems. The difficulties in radiological diagnosis depend firstly on the absence on plain films o f the substantial, perifocal sclerosis that is normally associated with extra-articular osteoid osteoma. Secondly, the complexity o f articular a n a t o m y in some joints m a y result in difficulties in t u m o u r identification due to bone overlap as the focus of the t u m o u r m a y be extremely small. Thirdly, the regional articular osteoporosis, which m a y go unrecognized if comparative films o f corresponding joints are not available, is most m a r k e d in the early stage and in conjunction with erosions at the chondro-osseous junction, m a y be misinterpreted as an inflammatory erosive arthritis. In the hands and feet, the osteoporotic appearances are indistinguishable f r o m reflex sympathetic dystrophy because o f the close proximity o f multiple bones. Scintigraphy m a y b e less specific when the lesion is intra-articular, as the increase in activity can be generalized within the joint, due to the associated synovitis, osteoporosis and hyperae-
157
INTRA-ARTICULAR OSTEOID OSTEOMA
(b) (a)
(c)
(d)
Fig. 4 - (a) A lateral radiograph of the ankle shows generalized osteoporosis with a localized lucency on' the anterior aspect of the trochlear surface resembling an erosion (arrow). Previous plain films over a 9 m o n t h period had been normal. (b), (c) Scintigram of ankle on diffusion phase (b) and at 3 h (c) shows wide spread uptake throughout the ankle joint, although activity is greater in the anterior part of the joint. (d) Axial CT of the talus shows the classical osteoid osteoma with erosion of the overlying cortex and cartilage associated with a localized soft tissue swelling (arrows). Osteoporosis is again demonstrated.
mia. On the bone phase the activity was localized although diffuse uptake did occur, which was similar to three of 12 cases in the series of Kattapuram et al. (1983), who only identified a focal area of activity from the tumour on a repeat scan 6-12 months later. The activity was less prominent in our cases which had a long clinical history, although sufficient localized activity for diagnosis was present on the initial scan. Focal activity may also be seen in the osteophyte as occurred in our two cases and care should be taken not to confuse this with the tumour on the scintigrams. This increased uptake reflects the active bone production and is in contradistinction to the common osteophyte formation seen in jomt instability which results from longstanding osteoarticular degenerative changes (Watt and Dieppe, 1990). Unlike cortically situated osteoid osteoma, tumours in the medulla invoke only a mild osteoblastic response in surrounding trabecular bone (Edeiken et al., 1966) and
this lS particularly the case in intra-articular lesions due to the absence of adjacent periosteum (Sissons et al., 1984). In the intra-articular lesions trabecular bone formation may also be generated in the subchondral bone on the opposite side of the joint and this is well demonstrated by CT. This trabecular bone response may also occur in vertebrae across the primary cartilaginous joints of the spine (Heiman et al., 1976). Even when the joint lesion is cortical, the absence of intra-articular periosteum precludes a localized response although periosteal bone formation may occur in the diaphysis on either side of the joint (Moberg, 1952). The mechanism behind these distant reactions is poorly understood but may be related to associated vascular changes or to local metabolite production by the tumour. The intra-articular location also provokes a proliferation of the synovium, and capsular and extracapsular tissues have been found to be oedematous, thickened and
158
CLINICAL RADIOLOGY
(a)
(b) Fig. 7 (a) There is a dense nidus in the base of the metatarsal in a patient with a 6 year history of pain. The CT scan demonstrates the lesion crossing the joint space into the intermediate cuneiform, (b) The scintigram demonstrates focal activity at the t u m o u r site.
(b) Fig. 5 (a) An anteroposterior radiograph of the wrist shows sclerosis in the capitate which is localized but ill-defined (black arrows. (b) Axial CT of the carpus demonstrates a well defined sclerotic focus on the posterior margin of the capitate which is causing an erosion of the adjacent articular surface of the hamate (arrow).
Fig. 6 Axial C T of the metatarsophalangeal joint shows extensive synovial hypertrophy (arrows).
fibrotic at surgery (Chandler and Kaell, 1950), Histologically the synovium has been designated as chronic nonspecific synovitis (Sherman, 1947b), and Snarr et al. (1973) described it as lymphofollicular synovitis indistinguishable from rheumatoid synovium, a feature which differentiates it from the synovial response generated by other bone tumours involving joints such as aneurysmal bone cyst, osteosarcoma, chondroblastoma and giant cell tumour. It has been postulated that the inflammation of synovial tissues in IAOO may be caused by a specific activator substance (Snarr et al., 1973), and the increased prostaglandin (PGE2) levels found in osteoid osteoma at other sites may be of relevance (Makley and Dunn, 1982). The histocompatibility markers (HLA) namely DR4, DR7 and MT3 found commonly in rheumatoid arthritis, have also been demonstrated (Norman et al., 1986) in some patients with IAOO of the hip, and when present, were associated with a higher incidence of concomittant arthritis. The joint space was increased in both cases involving the hip, a feature which has also been illustrated radiographically (Spence and Lloyd-Roberts, 1961) and in a case report by MRI (Glass et al., 1986). Similar change may have been present in the elbow, wrist and feet of other cases, but the overlapping joint contours and the lack of comparative views of the normal side make this difficult to confirm. It is possible that the synovitis or associated joint effusion may be responsible but it is more likely to be due to chondral hypertrophy and proliferation of articular cartilage which was associated with osteophytes in two of our cases. The combination of increased cartilage thickness and osteophytosis is also a feature of acromegaly which again raises the question as
INTRA-ARTICULAR OSTEOID OSTEOMA
(a)
(b) Fig. 8 - (a) and (b) The axial CT demonstrates a portion of the osteoid osteoma which extends from the joint into the pars interar ticularis. The pedicle, vertebral body (long arrows) and adjacent articular process (short arrow, (b)) are sclerotic. This sclerosis resolved once the tumour itself had been removed.
159
to whether a humoral growth stimulus is occurring in osteoid osteoma. The same process may also explain the enlargement of the femoral head and deformity of the hip joint in two young patients with symptoms of 7 and 8 years reported by Guistra and Freiberger (1970). Joint asymmetry may also be caused by premature epiphyseal closure which has been demonstrated in the hands and feet (Rosborough 1966; Bordelon et al., 1975; Blair and Kube, 1977) and elbow (Shifrin and Reynolds, 1971), although to our knowledge there has not been an example of a delay in fusion of the epiphysis as in our series. The lack of typical pain patterns and responses is in keeping with the findings of Kattapuram et al. (1983), Cohen et al. (1983) and Moser et al. (1990) although Norman et al. (1986) describe a number of cases with IAOO of the hip and classic symptomatology. The mechanism of the pain in osteoid osteoma is still speculative. Chandler and Kaell (1950) were first to demonstrate nerve fibres in the nidus and Sherman and McFarland (1965) identified abundant autonomic fibres in both the highly vascular nidus and the surrounding fibrovascular connective tissue. These findings were confirmed later by Shulman and Dorfman (1970), but their relationship with pain production remains to be clarified. The nerve rich periosteum plays a significant role in mediating pain associated with an intracortical diaphyseal osteoid osteoma, but in IAOO this mechanism is not operable. In IAOO the pattern of response, which is probably dictated by the synovitis, may initially be intermittent but quickly assumes the constant non-specific chronic pain of articular dysfunction and may be referred to other joints. The reason for the specificity of aspirin in the intracortical osteoid osteoma is not clear but increased PGE2 levels up to 1000-fold compared with normal bone have been found in extra-articular osteoid osteoma (Makley and Dunn, 1982), and prostaglandin inhibition by aspirin may be relevant. There is, however, a significant difference in the pain response to aspirin between intra- and extraarticular lesions. The lack of aspirin specificity in IAOO, along with the effectiveness on non-steroidal anti-inflammatory agents, supports an alternative pain mechanism. The natural history of osteoid osteoma is not fully understood but regardless of site, enlargement of the nidus ceases once it has reached about 1 cm and this finite growth potential is unusual for a neoplasm. Despite this limitation in size, the nidus is constantly remodelling with active osteoclastic and osteoblastic resorption and formation of bone, which governs the overall density of the lesion (Mirra, 1989). This activity may in part be orchestrated by prostaglandin release, which regulates bone resorption and production in both normal and pathological states (Healey and Ghelman, 1985). Spontaneous subsidence of pain and tumour regression of lesions in an extra-articular location are infrequently reported (Sherman, 1947b; Dockerty et al., 1951 ; Golding, 1954; Jaffe, 1958; Jackson et al., 1977; Norman et al., 1986) but when they occur, the radiological appearances can either persist unchanged or the nidus can disappear while the host bone returns to normal (Sherman, 1947b; Flaherty et al., 1956). The clinicoradiological picture is probably dependent on the age of the lesion, with synovial proliferation being predominant in the early stages_ This subsequently subsides but the IAOO initiates polypeptide release which promotes proliferation of chondrocytes in the degenerate cartilage, induces migration and differentiation of mesenchymal cells, and promotes angiogenesis
160
CLINICAL RADIOLOGY
from subchondral bone leading to the formation of osteophytes. In the subchondrally sited tumours, mesenchymal proliferation causes subsequent osteoarthritis in t h e l a t e r u n d i a g n o s e d cases w h i c h d e s p i t e r e g r e s s i o n o f t h e t u m o u r is n o t r e v e r s i b l e . P r e m a t u r e o s t e o a r t h r i t i s c a n still d e v e l o p a f t e r r e m o v a l o f a n I A O O f r o m a n o t h e r w i s e n o r m a l j o i n t ( S h e r m a n , 1947a; N o r m a n et al., 1986), a n d extensive joint destruction has been reported (Dahlin and J o h n s o n , 1954; M o r t o n a n d B a r t l e t t , 1966). F a c e t j o i n t arthritis has also been previously described (Maclellan a n d W i l s o n , 1967; C o r b e t t et al., 1974), b u t t h e r e w e r e n o f e a t u r e s w h i c h w e r e specific i n r e l a t i o n t o t h e j o i n t s . O n c e d i a g n o s e d a n o s t e o i d o s t e o m a is b e s t r e m o v e d b y en bloc resection, but this may not always be feasible when the l e s i o n is i n t r a - a r t i c u l a r . T h e r e is n o e v i d e n c e o f r e c u r r e n c e s f o l l o w i n g en bloc r e s e c t i o n b u t r e c u r r e n c e h a s b e e n r e p o r t e d a f t e r c u r e t a g e ( H e a l e y a n d G h e l m a n , 1985). S i m et al. ( 1 9 7 5 ) p o s e d t h e p r o b l e m o f p a t i e n t s w i t h c l i n i c a l histories and radiographic charactertstics of an osteoid osteoma, but in whom surgical exploration failed to r e m o v e t h e lesion. S e v e r a l p a t i e n t s (36) o b t a i n e d c l i n i c a l r e l i e f d e s p i t e t h e f a i l u r e to c o n f i r m t h e n i d u s h i s t o l o g i cally. I n n i n e p a t i e n t s w i t h p e r s i s t i n g s y m p t o m s f u r t h e r resection with histological confirmation of a nidus r e l i e v e d t h e s y m p t o m s in all p a t i e n t s . I A O O g e n e r a t e s d i a g n o s t i c difficulties b y v i r t u e o f t h e protean clinical and radiological manifestations and n e e d s t o b e c o n s i d e r e d as t h e c a u s e o f n o n - s p e c i f i c o r s e e m i n g l y specific m o n o - a r t i c u l a r a r t h r i t i s . T h e s e diffic u l t i e s a r e u n l i k e l y t o b e o v e r c o m e b y M R I w h i c h is p o i s e d t o b e c o m e t h e i n i t i a l m e t h o d o f c h o i c e in i m a g i n g joint disorders. The exquisite depiction by MRI of the extensive intra-articular, peri-articular, osseous and bone marrow reactive changes may overshadow the presence of t h e r e l a t i v e l y s m a l l I A O O . T h e m a t r i x c a l c i f i c a t i o n , so characteristic of the tumour nidus, may be absent on MRI, rendering the appearances non-specific and increasing the potential for misdiagnosis.
Acknowledgements. We are grateful to Miss Wendy Owen for typing the manuscript and the Medical Photography Department at the Robert Jones & Agnes Hunt Orthopaedic Hospital for the photographic prints.
REFERENCES Blair, WF & Kube, WJ (1977). Osteoid osteoma in a distal radial epiphysis Case Report. Clinical Orthopaedics and Related Research, 126, 160 161. Bordelon, RL, Cracco, A & Book, KM (1975). Osteoid osteoma producing premature fusion of the epiphysis of the distal phalanx of the big toe. Journal of Bone and Joint Surgery, 57, 120-121. Capanna, R, Van Horn, JR, Ayala, A, Picci, P & Bettelli, G (1986). Osteoid osteoma and osteoblastoma of the talus. Skeletal Radiology, 15, 360 364. Chandler, FA & Kaell, HI (1950). Osteoid osteoma. Archives of Surgery, 60, 294-304. Cohen, MD, Harrington, TM & Ginsburg, WW (1983). Osteoid osteoma: 95 cases and a review of the literature. Seminars in Arthritis and Rheumatism, 12, 265 281. Corbett, JM, Wilde, AH, McCormack, LJ & Evarts, CM (1974). Intraarticular osteoid osteoma: a diagnostic problem. Clinical Orthopaedics and Related Research, 98, 225-230. Dahlin, DC (1986). Bone Tumors. 4th ed. Chap. 7, pp_ 88-101, Thomas, Springfield. Dahlin, DC & Johnson, EW (1954). Giant osteoid osteoma. Journal of Bone and Joint Surgery, 36-A, 559 576. Dockerty, MB, Ghormley, RK & Jackson, AE (1951). Osteoid osteoma: clinicopathologic study of 20 cases. Annals of surgery, 133, 77-89. Edeiken, J, DePalma, AF & Hodes, PJ (1966). Osteoid osteoma
(roentgenographic emphasis). Clinical Orthopaedics and Related Researe4z, 49, 201 206. Flaherty, RA, Pugh, DG & Dockerty, MB (1956). Osteoid osteoma. American Journal of Roentgenology, 76, 1041-1051. Freiberger, RH, Loitman, BS, Helpern, M & Thompson, TC (1959). Osteoid osteoma: a report of 80 cases. American Journal of Roentgenology, 82, 194 205. Glass, RBJ, Poznanski, AK, Fisher, MR, Shkolnik, A & Dias, L (1986). Case report: MR imaging of osteoid osteoma. Journal of Computer Assisted Tomography, 10, 1065-1067. Golding, JSR (1954). The natural history of osteoid osteoma with a report of 20 cases. Journal of Bone and Joint Surgery, 36, 218 229. Guistra, PE & Freiberger, RH (1970). Severe growth disturbances with osteoid osteoma. Radiology, 96, 285-288. Healey, JH & Ghelman, B (1985). Osteoid osteoma and osteoblastoma. Current concepts and recent advances. Clinical Orthopaedics and Related Research, 204, 77-85. Heiman, ML, Cooley, CJ & Bradford, DS (1976). Osteoid osteoma of a vertebral body: report of a case with extension across the intervertebral disk. Clinical Orthopaedics and Related Research, 118, 159-163. Jackson, RP, Reckling, FW & Mantz, FA (1977). Osteoid osteoma and osteoblastoma: similar histologic lesions with different natural histories. Clinical Orthopaedics and Related Research, 128, 303-313. Jaffe, HL (1958). Tumours and Tumourous Conditions of the Bones and Joints. p. 65, Lea and Febiger, Philadelphia. Kattapuram, SU, Kushner, DC, Phillips, WC & Rosenthal, DI (1983). Osteoid osteoma: an unusual cause of articular pain. Radiology, 147, 383-387. Kendrick, Jl & Evarts, CM (1967). Osteoid osteoma: a critical analysis of forty tumours. Clinical Orthopaedics and Related Research, 54, 51 59. Maclellan, DI & Wilson, FC (1967). Osteoid osteoma of the spine: a review of the literature and report of six new cases. Journal of Bone and Joint Surgery, 49-A, 111 121, Makley, JT & Dunn, M (1982). Prostaglandins a mechanism for pain mediation in osteoid osteoma. Orthopaedic Transections, 6, 72. Marcove, RC & Freiberger, RH (1966). Osteoid osteoma of the elbow a diagnostic problem report of four cases. Journal of Bone and Joint Surgery, 48-A, 1185-1190. Mirra, JM (1989). Bone Turnouts: Clinical Radiologic and Pathologic Correlations. pp. 226 245. Lea & Febiger, Philadelphia. Moberg, E (1951). The natural course of osteoid osteoma. Journal of Bone and Joint Surgery, 33, 166-170. Moberg, E (1952). Further observations on "corticalisosteoid" or "osteoid osteoma". Acta Radiologica, 38, 279 293. Morton, KS & Bartlett, LH (1966). Benign osteoblastic change resembling osteoid osteoma. Journal of Bone and Joint Surgery, 488, 478-484. Moser, RP, Kransdorf, M J, Brower, AC, Hudson, T, Aoki, J, Hudson Berrey, Bet al. (1990). Osteoid osteoma of the elbow: a review of six cases. Skeletal Radiology, 19, 181 186. Norman, A, Abdelwahab, IF, Buyon, J & Matzkin, E (1986), Osteoid osteoma of the hip stimulating an early onset of osteoarthritis. Radiology, 158, 417 420. Rosborough, D (1966). Osteoid osteoma report of a lesion in the terminal phalanx of a finger. Journal of Bone and Joint Surgery, 488, 485 -487. Sherman, MS (1947a). Osteoid osteoma associated with changes in an adjacent joint. Journal of Bone and Joint Surgery, 29, 483 490. Sherman, MS (1947b). Osteoid osteoma: review of the literature and report of 30 cases. Journal of Bone and Joint Surgery, 29, 918 930 Sherman, MS & McFarland, G (1965). Mechanism of pain in osteoid osteomas. Southern Medical Journal, 58, 163-166. Shift-in, LZ & Reynolds, WA (197 I). lntra-articular osteoid osteoma of the elbow: a case repor t. Clinical Orthopaedics and Related Research, 81, 126 129. Shulman, L & Dorfman, HD (1970). Nerve fibres in osteoid osteoma. Journal of Bone and Joint Surgery, 52-A, 1351--1356. Sim, FH, Dahlin, DC & Beabout, JW (1975). Osteoid osteoma diagnostic problems. Journal of Bone and Joint Surgery, 57, 154- 159. Sissons, HA, Murray, RO & Kemp, HBS (1984). Orthopaedic Diagnosis. Ex21, p. 187. Springer Verlag, Berlin. Snarr, JW, Abell, M R & M artel, W (I 973). Lympholollicular synovltlS with osteoid osteoma. Radiology, 106, 557 560. Spence, AJ & Lloyd-Roberts, GC (1961). Regional osteoporosis in osteoid osteoma. Journal of Bone and Joint Surgery, 43-B, 501 507. Vickers, CW, Pugh, DC & luans, JC (1959). Osteoid osteoma: a 15 year follow-up of an untreated patient. Journal of Bone and Joint Surgery, 41,357-358. Watt, I & Dieppe, P (1990). Osteoarthrltis revisited. Skeletal Radiology, 19,1 3.
Intra-Articular Osteoid Osteoma V. N. C A S S A R - P U L L I C I N O ,
I. W. M C C A L L
a n d S. W A N
Department o f Diagnostic Imaging, The Institute of Orthopaedics, The Robert Jones & Agnes Hunt Orthopaedic Hospital, Oswestry O s t e o i d o s t e o m a s located within the capsule o f a j o i n t are uncommon and p r e s e n t challenging d i a g n o s t i c difficulties. T w e l v e patients with an intra-articular osteoid osteoma w e r e studied r e t r o s p e c t i v e l y to d e t e r m i n e the s p e c t r u m of clinical and radiological findings. T h e f e a t u r e s differ significantly from the well known classical hallmarks of the extra-articular lesion. The symptoms are non-specific with pain similar to other common joint disorders and the response to salicylate less precise. O n plain radiography intra-articular lesions are difficult to identify, lacking the florid periosteal new bone and intense p e r i f o c a l sclerotic reaction. A d e t e c t a b l e focal lesion is c o m m o n l y absent with considerable d e l a y between the onset o f symptoms and r a d i o l o g i c a l detection o f the t u m o u r nidus. Bone scintigraphy and computed tomography ( C T ) are essential for an accurate and early diagnosis. T h e s e i m a g i n g techniques reveal abnormalities in bone and cartilage growth, new bone formation and sclerosis distant from the tumour on either side o f the joint, and disruption of the articular surface. Radiological follow up after surgery shows t h a t these changes can be reversible, especially when the diagnosis is m a d e early. C a s s a r - P u l l i c i n o , V . N . , M c C a l l , I . W . & W a n , S. (1992). Clinical Radiology 45, 153-160. Intra-Articular Osteoid Osteoma
O s t e o i d os t e o m a is a small, h i g h l y cellular, b e n i g n t u m o u r o f b o n e , c o n t a i n i n g f i b r o v a s c u l a r tissue, i m m a t u r e b o n e and o s t e o i d , w h i c h is c a p a b l e o f g e n e r a t i n g a v i g o r o u s o s t e o b l a s t i c h o s t r e s p o n s e . It r e p r e s e n t s 11% o f all b e n i g n
b o n e t u m o u r s ( D a h l i n , 1986), is m o s t c o m m o n l y f o u n d in the d i a p h y s i s o f the l o n g b o n e s o f the l o w e r limb, a l t h o u g h a n y b o n e m a y p l a y host, a n d is f r e q u e n t l y l o c a t e d n e a r o r w i t h i n t h e periosteum_ I n its classical f o r m it p o s e s few d i a g n o s t i c p r o b l e m s , h a v i n g c h a r a c t e r i s t i c clinical, r a d i o l o g i c a l a n d h i s t o l o g i c a l features, a n d a c u r e c a n be e x p e c t e d f o l l o w i n g en bloc resection. W h e n the l o c a t i o n o f the o s t e o i d o s t e o m a is i n t r a a r t i c u l a r , d i a g n o s t i c difficulties m a y arise as it results in
Correspondence to: V. N. Cassar-Pullicino, Consultant Radiologist, Department of Diagnostic Imaging, The Robert Jones & Agnes Hunt Orthopaedic Hospital, Oswestry, Shropshire SY10 7AG.
Table 1 - Clinical features of intra-arlicularosteoid osteoma
Age Sex 6
F
40
M
16
M
52
M
20
M
24
F
18
M
32
F
34
M
24
F
39
F
14
F
Site
Main complaint
Duration Aggravating Analgesic Initial (years) factors response diagnosis
Femur, hip joint Acetabulum, hip joint Ulna, elbow joint TS, pars interarticularis, facet joint T5 spinallamina, facet joint Talus, ankle joint Talus, ankle joint Clavicle, S-C joint Scaphoid, carpal joints Capitate, carpal joints Base 2 metatarsal cuneiform joint Head 2 metatarsal phalangeal joint
Pain, limp Pain, sciatica Pain, swelling Girdle pain
i
Intercostal pain Pain, stiffness Pain, swelling Pain, swelling Pain, stiffness Pain, swelling Pain, stiffness Pain, swelling
3
Surgical findings
Follow-up (years) 3 Asymptomatic O 3 Minimal symptoms X 2 Asymptomatic X 2 Minor symptoms
Naproxen
? TB ? Still's
Synovitis
7
Movement, morning Movement
Naproxen
O.A.
Osteophytosis
3
Movement
--
3
Movements in bed
--
Osteochondritis dissecans O.A.
----
1¼
Rotational movements Movement, morning Movement
--
Myalgia
Naproxen
? Inflammatory arthritis ? Mono arthritis
Thickened capsule + 1 ligamentum flavum Asymptomatic O Pericapsular 2 thickening Minor symptoms O Synovitis 1 Asymptomatic O 2 Residual symptoms O
2 a ~ 5 221
Movement, coughing Morning
--NSAI
? Tietze's syndrome 9 Fracture
1
4
Gripping
--
Tenosynovitis
--
6
Walking, morning
Naproxen
? Stress lesion
Pericapsular thickening, osteophytosis Synovitis
1
Movement, walking
9 Freiberg's disease
--, None Specified; O, bone+soft tissue reverted to normal; X, bone changes persist unchanged.
Minimal symptoms 2 Asymptomatic O Occasional symptoms 1
Minor symptoms
154
CLINICAL RADIOLOGY
T a b l e 2 - Radiological features o f iutra-articular osteoid o s t e o m a
Abnormality
Plain film
CT*
Tumour nidus Bone sclerosis Perifocal Across joint Osteoporosis Osteophytosis Soft tissue swelling Joint space increase Articular erosion Metaphyseal widening Epiphyseal Enlargement Delayed fusion Tumour mineralization
5
11
1 1 4 3 4 2 1 4
5 4 4 3 6 2 6 4
2 1 2
2 1 11
* Twelfth IAOO shown by conventional tomography.
(a) (d) Fig. 1 (a) The plain film shows an increase in joint space. There is a localized area of lucency in the femoral neck (short arrow) with organized periosteal new bone formation in the region of the lesser tronchanter (long arrow). (b) CT of femoral neck shows the lucent osteoid osteoma elevating the cortex with adjacent sclerosis of the cortex. (c) CT of hip joint shows osteoporosis of the left femoral head and the widening of the joint space. (d) One year following en bloc removal of thc osteoid osteoma. The appearances of the bone and joint have returned to normal.
(b)
(c)
articular pain which is similar to other more common joint disorders, and which has a variable response to salicylate and non-steroidal anti-inflammatory therapy (Cohen et al., 1983; K a t t a p u r a m et al., 1983). The plain radiographic features of intra-articular osteoid osteoma (IAOO) are also rarely classical, which leads to further delayed or erroneous diagnosis. While the plain radiographic features of I A O O have been described (Sherman, 1947a; Marcove and Freiberger, 1966), there has been relatively little discussion of the value of more recent imaging techniques ( K a t t a p u r a m et al., 1983; N o r m a n et al., 1986). We therefore report a series of cases of I A O O in which the term intra-articular is used specifically to denote tumour nidus invading the intra-articular portion of bone. This is more selective than those of previous series where broader definitions of lesions 'at the ends of long bones' (Moser et al., 1990) or 'in or around the joints' ( K a t t a p u r a m et al., 1983) have been used. The imaging features in our series have been correlated with surgical findings and assessment of the post-treatment changes in the joint.
INTRA-ARTICULAR OSTEOID OSTEOMA
155
p A T I E N T S AND M E T H O D S Clinical and Radiological Features Twelve patients, with a diagnosis of osteoid osteoma involving the intra-capsular portion of bone, have been investigated over a 5 year period. The age range was 6-52 years, and there was an even sex distribution. All patients presented with joint pain and articular dysfunction. The duration of symptoms ranged from 9 months to 7 years, with a mean of 3.5 years. Specific nocturnal pain was not a feature although pain was worse in the morning and on joint movement. The pain was not specifically relieved by aspirin but a moderate response was noted to Naproxen in five patients. Physical examination revealed a reduction in the whole range of joint movement. There was soft tissue swelling around the joint in five patients and muscle atrophy in three. The delay in diagnosis ranged from 9 months to 7 years, and the alternative diagnoses, based on clinical and radiological findings, are identified in Tables 1 and 2. Review of the initial plain radiographs demonstrated a focal lesion in only five patients, four of which were lucencies in the proximal femur, talus, scaphoid and metatarsal head. However, in the initial radiographic interpretation only two of these lesions were recognized (Figs 1 and 2)_ Bone density in the joint was variable with osteoporosis being present in four patients (Figs 1, 3 and 4), increased sclerosis in two patients (Fig. 5) and no abnormality was demonstrated in six patients. A uniform and congruent increase in the joint space was present (Figs 1 and 3) in the two cases involving the hips. In one case when the tumour disrupted the articular surface, the joint space was narrowed (Fig. 5). The fascial planes were normal in eight cases, but in four cases there was displacement of the pericapsular fat line and a marked intra-articular proliferation of synovium was subsequently confirmed at surgery in three patients (Table 1) (Figs 4 and 6). Bone growth was altered in four cases, with two cases each of increased metaphyseal width in the femoral neck and the metatarsals (Fig. 3). Epiphyseal enlargement was present in one hip and one metatarsal (Fig. 3). New bone formation and sclerosis was seen distant from the turnout on both sides of the adjacent joint. The new bone formation was especially prominent in three patients, taking the form of 'osteophytes' at the chondro-osseous junction in the hip (Fig. 3) and elbow, and a bone spur arising from the base of the second metatarsal_ There was partial delay in fusion of the metatarsal epiphyseal plate adjacent to the tumour site in one patient. In one patient osteochondritis dissecans was present in the elbow, which was coincidental but symptoms were initially attributed to this diagnosis. All lesions were detected by two-phase 99mTcscintigraphy, and the tumour was invariably active on both the diffusion and static phase. In two cases the increase in uptake in the affected joint was more generalized but localized activity was present at the site of the lesion in the remainder (Figs 3, 4 and 7)_ The balance of activity between the diffusion and bone phase varied with the duration of symptomatology, the former being less active in those cases with a significant delay in diagnosis. Increased isotope activity occurred at sites of marginal new bone formation (Fig. 3) and was more widespread in lesions associated with osteoporosis (Fig. 4). Computed tornography (CT) in 11 patients and conventional t o m o -
Fig. 2 A classical osteoid osteoma is seen in the scaphoid which is resulting in localized thinning of the subchondral plate.
graphy in one patient demonstrated all of the tumours clearly and delineated the alteration in bone architecture on both sides of the joint (Fig. 3), the exact relationship of the tumour to the eroded cortex (Fig. 1), joint surface (Figs 5 and 7) or epiphyseal plate, and the extent of the soft tissue reaction (Figs 4 and 6) (Table 2). The proportion of tumour mineralization was predominantly related to the duration of symptoms, indicating that dense calcification occurs in the more mature lesions (Figs 3, 5 and 7). M R I was obtained in one patient with a lesion within the scaphoid bone. The lesion was not clearly identifiable and did not show any alteration following IV gadolinium enhancement. In one of the patients with an early hip lesion the indreased joint space and os teoporosis returned to normal within 1 year (Fig. 1), while in the other, a lesion only diagnosed after 7 years delay, there was no change. The juxta-articular cancellous sclerosis abated in all cases (Figs 1 and 8) 1 2 years after en bloc tumour resection. DISCUSSION This series confirms that I A O O is difficult to diagnose unless there is a high index of suspicion for the lesion and confirms the findings of K a t t a p u r a m et al. (1983) where 23 out of 25 patients had a diagnostic delay of years rather than months. The signs and symptoms of the lesion may be present long before the tumour becomes visible on plain radiographs, which usually occurs when it attains a diameter of 4 m m or more ( K a t t a p u r a m et al., 1983). Furthermore, the classical nocturnal quality of pain found in around 80% of extra-articular osteoid osteoma (Cohen et al., 1983) is absent and the pain is less responsive to salicylates when the osteoid osteoma is intra-articular. Some relief however may occur from nonsteroidal anti-inflammatory drugs but a similar response may be expected from other inflammatory disorders.
156
CLINICAL RADIOLOGY
(a)
(b)
(c)
(a)
Fig. 3 - (a) Plain film of the pelvis demonstrates osteoporosis with increase in size of the joint space in the right hip. The left hip is normal. (b) Scintigram of pelvis shows focal increased activity in the floor of the acetabulum (short arrow) and to a lesser extent on the inferior margin of the femoral head (curved arrow). There is a mild generalized increase in activity throughout the joint. (c) CT of the right hip shows the osteophyte formation at the chondro-osseous junction (arrows) of the femoral head which correlates with the activity on the isotope study. (d) CT of the right hip. The osteoid osteoma is clearly defined in the floor of the acetabulum (arrow). Muscle wasting and osteoporosis are demonstrated on both sides of the joint.
N u m e r o u s published reports highlight the similarity o f the clinical findings to a variety o f acute, subacute and chronic inflammatory arthritides, including septic arthritis and tuberculosis ( C a p a n n a et al., 1986), PVNS, synovial chondromatosis and gout (Cohen et al., 1983), rheumatoid arthritis (Marcove and Freiberger, 1966; Snarr et al., 1973) and osteoarthritis (Sherman, 1947a,b; N o r m a n et al., 1986), all o f which resulted in unrewarding diagnostic procedures and inappropriate treatment. S y m p t o m s m a y also be referred to another joint, causing confusion with regard to the area o f investigation (Sim et al., 1975). The frequency o f intra-articular location in previous series of osteoid osteoma has varied from 0/40 (Kendrick and Evarts, 1967), 4/95 over a 10 year period (Cohen et al., 1983), and 30 hip lesions out o f 182 cases o f osteoid osteomas seen over a 24 year period ( N o r m a n et al., 1986). An under-estimation o f the true incidence of I A O O m a y have resulted f r o m the difficulties in making the diagnosis, as the natural history o f the lesion is benign, with a tendency to spontaneous involution after an interval of 5-10 years (Moberg, 1951; Golding, 1954;
Freiberger et al., 1959; Vickers et al., 1959). O u r findings o f 12 cases in a 5 year period probably reflect the value of the newer c o m p u t e r based diagnostic imaging systems. The difficulties in radiological diagnosis depend firstly on the absence on plain films o f the substantial, perifocal sclerosis that is normally associated with extra-articular osteoid osteoma. Secondly, the complexity o f articular a n a t o m y in some joints m a y result in difficulties in t u m o u r identification due to bone overlap as the focus of the t u m o u r m a y be extremely small. Thirdly, the regional articular osteoporosis, which m a y go unrecognized if comparative films o f corresponding joints are not available, is most m a r k e d in the early stage and in conjunction with erosions at the chondro-osseous junction, m a y be misinterpreted as an inflammatory erosive arthritis. In the hands and feet, the osteoporotic appearances are indistinguishable f r o m reflex sympathetic dystrophy because o f the close proximity o f multiple bones. Scintigraphy m a y b e less specific when the lesion is intra-articular, as the increase in activity can be generalized within the joint, due to the associated synovitis, osteoporosis and hyperae-
157
INTRA-ARTICULAR OSTEOID OSTEOMA
(b) (a)
(c)
(d)
Fig. 4 - (a) A lateral radiograph of the ankle shows generalized osteoporosis with a localized lucency on' the anterior aspect of the trochlear surface resembling an erosion (arrow). Previous plain films over a 9 m o n t h period had been normal. (b), (c) Scintigram of ankle on diffusion phase (b) and at 3 h (c) shows wide spread uptake throughout the ankle joint, although activity is greater in the anterior part of the joint. (d) Axial CT of the talus shows the classical osteoid osteoma with erosion of the overlying cortex and cartilage associated with a localized soft tissue swelling (arrows). Osteoporosis is again demonstrated.
mia. On the bone phase the activity was localized although diffuse uptake did occur, which was similar to three of 12 cases in the series of Kattapuram et al. (1983), who only identified a focal area of activity from the tumour on a repeat scan 6-12 months later. The activity was less prominent in our cases which had a long clinical history, although sufficient localized activity for diagnosis was present on the initial scan. Focal activity may also be seen in the osteophyte as occurred in our two cases and care should be taken not to confuse this with the tumour on the scintigrams. This increased uptake reflects the active bone production and is in contradistinction to the common osteophyte formation seen in jomt instability which results from longstanding osteoarticular degenerative changes (Watt and Dieppe, 1990). Unlike cortically situated osteoid osteoma, tumours in the medulla invoke only a mild osteoblastic response in surrounding trabecular bone (Edeiken et al., 1966) and
this lS particularly the case in intra-articular lesions due to the absence of adjacent periosteum (Sissons et al., 1984). In the intra-articular lesions trabecular bone formation may also be generated in the subchondral bone on the opposite side of the joint and this is well demonstrated by CT. This trabecular bone response may also occur in vertebrae across the primary cartilaginous joints of the spine (Heiman et al., 1976). Even when the joint lesion is cortical, the absence of intra-articular periosteum precludes a localized response although periosteal bone formation may occur in the diaphysis on either side of the joint (Moberg, 1952). The mechanism behind these distant reactions is poorly understood but may be related to associated vascular changes or to local metabolite production by the tumour. The intra-articular location also provokes a proliferation of the synovium, and capsular and extracapsular tissues have been found to be oedematous, thickened and
158
CLINICAL RADIOLOGY
(a)
(b) Fig. 7 (a) There is a dense nidus in the base of the metatarsal in a patient with a 6 year history of pain. The CT scan demonstrates the lesion crossing the joint space into the intermediate cuneiform, (b) The scintigram demonstrates focal activity at the t u m o u r site.
(b) Fig. 5 (a) An anteroposterior radiograph of the wrist shows sclerosis in the capitate which is localized but ill-defined (black arrows. (b) Axial CT of the carpus demonstrates a well defined sclerotic focus on the posterior margin of the capitate which is causing an erosion of the adjacent articular surface of the hamate (arrow).
Fig. 6 Axial C T of the metatarsophalangeal joint shows extensive synovial hypertrophy (arrows).
fibrotic at surgery (Chandler and Kaell, 1950), Histologically the synovium has been designated as chronic nonspecific synovitis (Sherman, 1947b), and Snarr et al. (1973) described it as lymphofollicular synovitis indistinguishable from rheumatoid synovium, a feature which differentiates it from the synovial response generated by other bone tumours involving joints such as aneurysmal bone cyst, osteosarcoma, chondroblastoma and giant cell tumour. It has been postulated that the inflammation of synovial tissues in IAOO may be caused by a specific activator substance (Snarr et al., 1973), and the increased prostaglandin (PGE2) levels found in osteoid osteoma at other sites may be of relevance (Makley and Dunn, 1982). The histocompatibility markers (HLA) namely DR4, DR7 and MT3 found commonly in rheumatoid arthritis, have also been demonstrated (Norman et al., 1986) in some patients with IAOO of the hip, and when present, were associated with a higher incidence of concomittant arthritis. The joint space was increased in both cases involving the hip, a feature which has also been illustrated radiographically (Spence and Lloyd-Roberts, 1961) and in a case report by MRI (Glass et al., 1986). Similar change may have been present in the elbow, wrist and feet of other cases, but the overlapping joint contours and the lack of comparative views of the normal side make this difficult to confirm. It is possible that the synovitis or associated joint effusion may be responsible but it is more likely to be due to chondral hypertrophy and proliferation of articular cartilage which was associated with osteophytes in two of our cases. The combination of increased cartilage thickness and osteophytosis is also a feature of acromegaly which again raises the question as
INTRA-ARTICULAR OSTEOID OSTEOMA
(a)
(b) Fig. 8 - (a) and (b) The axial CT demonstrates a portion of the osteoid osteoma which extends from the joint into the pars interar ticularis. The pedicle, vertebral body (long arrows) and adjacent articular process (short arrow, (b)) are sclerotic. This sclerosis resolved once the tumour itself had been removed.
159
to whether a humoral growth stimulus is occurring in osteoid osteoma. The same process may also explain the enlargement of the femoral head and deformity of the hip joint in two young patients with symptoms of 7 and 8 years reported by Guistra and Freiberger (1970). Joint asymmetry may also be caused by premature epiphyseal closure which has been demonstrated in the hands and feet (Rosborough 1966; Bordelon et al., 1975; Blair and Kube, 1977) and elbow (Shifrin and Reynolds, 1971), although to our knowledge there has not been an example of a delay in fusion of the epiphysis as in our series. The lack of typical pain patterns and responses is in keeping with the findings of Kattapuram et al. (1983), Cohen et al. (1983) and Moser et al. (1990) although Norman et al. (1986) describe a number of cases with IAOO of the hip and classic symptomatology. The mechanism of the pain in osteoid osteoma is still speculative. Chandler and Kaell (1950) were first to demonstrate nerve fibres in the nidus and Sherman and McFarland (1965) identified abundant autonomic fibres in both the highly vascular nidus and the surrounding fibrovascular connective tissue. These findings were confirmed later by Shulman and Dorfman (1970), but their relationship with pain production remains to be clarified. The nerve rich periosteum plays a significant role in mediating pain associated with an intracortical diaphyseal osteoid osteoma, but in IAOO this mechanism is not operable. In IAOO the pattern of response, which is probably dictated by the synovitis, may initially be intermittent but quickly assumes the constant non-specific chronic pain of articular dysfunction and may be referred to other joints. The reason for the specificity of aspirin in the intracortical osteoid osteoma is not clear but increased PGE2 levels up to 1000-fold compared with normal bone have been found in extra-articular osteoid osteoma (Makley and Dunn, 1982), and prostaglandin inhibition by aspirin may be relevant. There is, however, a significant difference in the pain response to aspirin between intra- and extraarticular lesions. The lack of aspirin specificity in IAOO, along with the effectiveness on non-steroidal anti-inflammatory agents, supports an alternative pain mechanism. The natural history of osteoid osteoma is not fully understood but regardless of site, enlargement of the nidus ceases once it has reached about 1 cm and this finite growth potential is unusual for a neoplasm. Despite this limitation in size, the nidus is constantly remodelling with active osteoclastic and osteoblastic resorption and formation of bone, which governs the overall density of the lesion (Mirra, 1989). This activity may in part be orchestrated by prostaglandin release, which regulates bone resorption and production in both normal and pathological states (Healey and Ghelman, 1985). Spontaneous subsidence of pain and tumour regression of lesions in an extra-articular location are infrequently reported (Sherman, 1947b; Dockerty et al., 1951 ; Golding, 1954; Jaffe, 1958; Jackson et al., 1977; Norman et al., 1986) but when they occur, the radiological appearances can either persist unchanged or the nidus can disappear while the host bone returns to normal (Sherman, 1947b; Flaherty et al., 1956). The clinicoradiological picture is probably dependent on the age of the lesion, with synovial proliferation being predominant in the early stages_ This subsequently subsides but the IAOO initiates polypeptide release which promotes proliferation of chondrocytes in the degenerate cartilage, induces migration and differentiation of mesenchymal cells, and promotes angiogenesis
160
CLINICAL RADIOLOGY
from subchondral bone leading to the formation of osteophytes. In the subchondrally sited tumours, mesenchymal proliferation causes subsequent osteoarthritis in t h e l a t e r u n d i a g n o s e d cases w h i c h d e s p i t e r e g r e s s i o n o f t h e t u m o u r is n o t r e v e r s i b l e . P r e m a t u r e o s t e o a r t h r i t i s c a n still d e v e l o p a f t e r r e m o v a l o f a n I A O O f r o m a n o t h e r w i s e n o r m a l j o i n t ( S h e r m a n , 1947a; N o r m a n et al., 1986), a n d extensive joint destruction has been reported (Dahlin and J o h n s o n , 1954; M o r t o n a n d B a r t l e t t , 1966). F a c e t j o i n t arthritis has also been previously described (Maclellan a n d W i l s o n , 1967; C o r b e t t et al., 1974), b u t t h e r e w e r e n o f e a t u r e s w h i c h w e r e specific i n r e l a t i o n t o t h e j o i n t s . O n c e d i a g n o s e d a n o s t e o i d o s t e o m a is b e s t r e m o v e d b y en bloc resection, but this may not always be feasible when the l e s i o n is i n t r a - a r t i c u l a r . T h e r e is n o e v i d e n c e o f r e c u r r e n c e s f o l l o w i n g en bloc r e s e c t i o n b u t r e c u r r e n c e h a s b e e n r e p o r t e d a f t e r c u r e t a g e ( H e a l e y a n d G h e l m a n , 1985). S i m et al. ( 1 9 7 5 ) p o s e d t h e p r o b l e m o f p a t i e n t s w i t h c l i n i c a l histories and radiographic charactertstics of an osteoid osteoma, but in whom surgical exploration failed to r e m o v e t h e lesion. S e v e r a l p a t i e n t s (36) o b t a i n e d c l i n i c a l r e l i e f d e s p i t e t h e f a i l u r e to c o n f i r m t h e n i d u s h i s t o l o g i cally. I n n i n e p a t i e n t s w i t h p e r s i s t i n g s y m p t o m s f u r t h e r resection with histological confirmation of a nidus r e l i e v e d t h e s y m p t o m s in all p a t i e n t s . I A O O g e n e r a t e s d i a g n o s t i c difficulties b y v i r t u e o f t h e protean clinical and radiological manifestations and n e e d s t o b e c o n s i d e r e d as t h e c a u s e o f n o n - s p e c i f i c o r s e e m i n g l y specific m o n o - a r t i c u l a r a r t h r i t i s . T h e s e diffic u l t i e s a r e u n l i k e l y t o b e o v e r c o m e b y M R I w h i c h is p o i s e d t o b e c o m e t h e i n i t i a l m e t h o d o f c h o i c e in i m a g i n g joint disorders. The exquisite depiction by MRI of the extensive intra-articular, peri-articular, osseous and bone marrow reactive changes may overshadow the presence of t h e r e l a t i v e l y s m a l l I A O O . T h e m a t r i x c a l c i f i c a t i o n , so characteristic of the tumour nidus, may be absent on MRI, rendering the appearances non-specific and increasing the potential for misdiagnosis.
Acknowledgements. We are grateful to Miss Wendy Owen for typing the manuscript and the Medical Photography Department at the Robert Jones & Agnes Hunt Orthopaedic Hospital for the photographic prints.
REFERENCES Blair, WF & Kube, WJ (1977). Osteoid osteoma in a distal radial epiphysis Case Report. Clinical Orthopaedics and Related Research, 126, 160 161. Bordelon, RL, Cracco, A & Book, KM (1975). Osteoid osteoma producing premature fusion of the epiphysis of the distal phalanx of the big toe. Journal of Bone and Joint Surgery, 57, 120-121. Capanna, R, Van Horn, JR, Ayala, A, Picci, P & Bettelli, G (1986). Osteoid osteoma and osteoblastoma of the talus. Skeletal Radiology, 15, 360 364. Chandler, FA & Kaell, HI (1950). Osteoid osteoma. Archives of Surgery, 60, 294-304. Cohen, MD, Harrington, TM & Ginsburg, WW (1983). Osteoid osteoma: 95 cases and a review of the literature. Seminars in Arthritis and Rheumatism, 12, 265 281. Corbett, JM, Wilde, AH, McCormack, LJ & Evarts, CM (1974). Intraarticular osteoid osteoma: a diagnostic problem. Clinical Orthopaedics and Related Research, 98, 225-230. Dahlin, DC (1986). Bone Tumors. 4th ed. Chap. 7, pp_ 88-101, Thomas, Springfield. Dahlin, DC & Johnson, EW (1954). Giant osteoid osteoma. Journal of Bone and Joint Surgery, 36-A, 559 576. Dockerty, MB, Ghormley, RK & Jackson, AE (1951). Osteoid osteoma: clinicopathologic study of 20 cases. Annals of surgery, 133, 77-89. Edeiken, J, DePalma, AF & Hodes, PJ (1966). Osteoid osteoma
(roentgenographic emphasis). Clinical Orthopaedics and Related Researe4z, 49, 201 206. Flaherty, RA, Pugh, DG & Dockerty, MB (1956). Osteoid osteoma. American Journal of Roentgenology, 76, 1041-1051. Freiberger, RH, Loitman, BS, Helpern, M & Thompson, TC (1959). Osteoid osteoma: a report of 80 cases. American Journal of Roentgenology, 82, 194 205. Glass, RBJ, Poznanski, AK, Fisher, MR, Shkolnik, A & Dias, L (1986). Case report: MR imaging of osteoid osteoma. Journal of Computer Assisted Tomography, 10, 1065-1067. Golding, JSR (1954). The natural history of osteoid osteoma with a report of 20 cases. Journal of Bone and Joint Surgery, 36, 218 229. Guistra, PE & Freiberger, RH (1970). Severe growth disturbances with osteoid osteoma. Radiology, 96, 285-288. Healey, JH & Ghelman, B (1985). Osteoid osteoma and osteoblastoma. Current concepts and recent advances. Clinical Orthopaedics and Related Research, 204, 77-85. Heiman, ML, Cooley, CJ & Bradford, DS (1976). Osteoid osteoma of a vertebral body: report of a case with extension across the intervertebral disk. Clinical Orthopaedics and Related Research, 118, 159-163. Jackson, RP, Reckling, FW & Mantz, FA (1977). Osteoid osteoma and osteoblastoma: similar histologic lesions with different natural histories. Clinical Orthopaedics and Related Research, 128, 303-313. Jaffe, HL (1958). Tumours and Tumourous Conditions of the Bones and Joints. p. 65, Lea and Febiger, Philadelphia. Kattapuram, SU, Kushner, DC, Phillips, WC & Rosenthal, DI (1983). Osteoid osteoma: an unusual cause of articular pain. Radiology, 147, 383-387. Kendrick, Jl & Evarts, CM (1967). Osteoid osteoma: a critical analysis of forty tumours. Clinical Orthopaedics and Related Research, 54, 51 59. Maclellan, DI & Wilson, FC (1967). Osteoid osteoma of the spine: a review of the literature and report of six new cases. Journal of Bone and Joint Surgery, 49-A, 111 121, Makley, JT & Dunn, M (1982). Prostaglandins a mechanism for pain mediation in osteoid osteoma. Orthopaedic Transections, 6, 72. Marcove, RC & Freiberger, RH (1966). Osteoid osteoma of the elbow a diagnostic problem report of four cases. Journal of Bone and Joint Surgery, 48-A, 1185-1190. Mirra, JM (1989). Bone Turnouts: Clinical Radiologic and Pathologic Correlations. pp. 226 245. Lea & Febiger, Philadelphia. Moberg, E (1951). The natural course of osteoid osteoma. Journal of Bone and Joint Surgery, 33, 166-170. Moberg, E (1952). Further observations on "corticalisosteoid" or "osteoid osteoma". Acta Radiologica, 38, 279 293. Morton, KS & Bartlett, LH (1966). Benign osteoblastic change resembling osteoid osteoma. Journal of Bone and Joint Surgery, 488, 478-484. Moser, RP, Kransdorf, M J, Brower, AC, Hudson, T, Aoki, J, Hudson Berrey, Bet al. (1990). Osteoid osteoma of the elbow: a review of six cases. Skeletal Radiology, 19, 181 186. Norman, A, Abdelwahab, IF, Buyon, J & Matzkin, E (1986), Osteoid osteoma of the hip stimulating an early onset of osteoarthritis. Radiology, 158, 417 420. Rosborough, D (1966). Osteoid osteoma report of a lesion in the terminal phalanx of a finger. Journal of Bone and Joint Surgery, 488, 485 -487. Sherman, MS (1947a). Osteoid osteoma associated with changes in an adjacent joint. Journal of Bone and Joint Surgery, 29, 483 490. Sherman, MS (1947b). Osteoid osteoma: review of the literature and report of 30 cases. Journal of Bone and Joint Surgery, 29, 918 930 Sherman, MS & McFarland, G (1965). Mechanism of pain in osteoid osteomas. Southern Medical Journal, 58, 163-166. Shift-in, LZ & Reynolds, WA (197 I). lntra-articular osteoid osteoma of the elbow: a case repor t. Clinical Orthopaedics and Related Research, 81, 126 129. Shulman, L & Dorfman, HD (1970). Nerve fibres in osteoid osteoma. Journal of Bone and Joint Surgery, 52-A, 1351--1356. Sim, FH, Dahlin, DC & Beabout, JW (1975). Osteoid osteoma diagnostic problems. Journal of Bone and Joint Surgery, 57, 154- 159. Sissons, HA, Murray, RO & Kemp, HBS (1984). Orthopaedic Diagnosis. Ex21, p. 187. Springer Verlag, Berlin. Snarr, JW, Abell, M R & M artel, W (I 973). Lympholollicular synovltlS with osteoid osteoma. Radiology, 106, 557 560. Spence, AJ & Lloyd-Roberts, GC (1961). Regional osteoporosis in osteoid osteoma. Journal of Bone and Joint Surgery, 43-B, 501 507. Vickers, CW, Pugh, DC & luans, JC (1959). Osteoid osteoma: a 15 year follow-up of an untreated patient. Journal of Bone and Joint Surgery, 41,357-358. Watt, I & Dieppe, P (1990). Osteoarthrltis revisited. Skeletal Radiology, 19,1 3.
