The role of ultrasound and isotope scanning in the management of irritable hips

European Journal of Radiology, 15 (1992) 113- 117

113

0 1992 Elsevier Science Publishers B.V. All rights reserved. 0720-048X/92/$05.00

EURRAD

00295

The role of ultrasound and isotope scanning in the management of irritable hips T.S. Gopakumar

a, R. Vaishya”, L. Klenerman a and H. Cartyb

The Universitv Departments of a Orthopaedic Surgery and b Radiologbv. Royal Liverpool Children k Hospital, Liverpool, UK

(Received 3 July 1991; accepted after revision 2 March 1992)

Key words: Irritable hips, ultrasound;

Irritable hips, radiosotope

study; Irritable hips, diagnosis; Ultrasound,

hip; Radiosotopes,

hip

Abstract Patients (n = 181) with the irritable hip syndrome were reviewed. Four of these were found to have Perthes disease and 3 cases had septic arthritis. Ultrasonography provides accurate information as to the presence or absence of an effusion in children with an irritable hip syndrome. The likelihood of a positive result is higher in the early course of the disease process (i.e. within 3 days). Bone scanning, if done routinely will help in the early diagnosis of Perthes disease. Recurrence of the symptoms occurred in IS:/ of patients and most of them were within 12 months of the first onset of symptoms.

Introduction Irritable hip is a common disorder of childhood. Since its first description a century ago by Lovett and Morse [ I] its nomenclature, aetiology, diagnosis and treatment have remained controversial. Hardinge in 1970 in a careful study of children with irritable hips failed to establish any connection with bacterial or viral infections, allergy or trauma [ 21. The diagnosis is inevitably speculative and retrospective [ 31. There are no pathognomic physical signs and the clinical picture mimics many other disorders such as Perthes disease, septic arthritis, osteomyelitis, slipped femoral epiphysis, juvenile chronic arthritis, turnours, trauma and nonaccidental injury. It is important to establish the underlying pathology so that a definitive diagnosis can be made and treatment started at the right time [4]. Radiographs and laboratory findings do not allow a definite diagnosis to be made in the early stages of the disease. Hence in the past decade there has been increasing enthusiasm for the use of ultrasonography Correspondence

to: Professor

L. Klenerman, Department of Orthopaedic and Accident Surgery, University of Liverpool, P.O. Box 147, Liverpool, L69 3BX, UK.

[ 5-101 and isotope scanning [4-131 to identify and/or to exclude the important and serious disorders like septic arthritis and Perthes disease. The present study was done to assess the role of ultrasonography and isotope bone scanning in the management of irritable hip syndrome. Patients and methods This retrospective study included 181 patients with suspected irritable hip syndrome admitted to hospital between January 1988 and June 1989. All patients with a painful limp, limitation of hip movements, pyrexia, or suspected infection in the hip joint were admitted. Following clinical examination, the degree of hip irritability was classified as mild, moderate or severe. Mild irritability was defined as pain with or without a slight limp, no muscle spasm and terminal limitation of hip movements. Severe irritability included significant pain requiring analgesia, inability to bear weight on the affected leg and gross restriction of hip movements. All intermediate cases were classified in the moderate group. A white count (WCC) and erythrocyte sedimentation rate (ESR; Westergren method) and plain AP ra-

114

diographs of the hip joint were performed on presentation. Eighty patients had an ultrasound examination of the hips and 107 an isotope scan, the policy of investigation being decided by the consultant. The ultrasound scans and the isotope bone scan were performed and reported by a consultant radiologist. The ultrasound scans were performed with a 5 mHz linear probe placed along the line of the femoral neck. The upper femoral epiphysis, growth plate, metaphysis and femoral neck were identified. Both hips were scanned for comparison. In a normal hip there is a distance of 2-3 mm between the bone and capsule (Fig. la). With an effusion there was an obvious increase in the distance between bone and capsule along the intracapsular portion of the femoral neck (Fig. lb). A discrepancy of 2 mm or more in measurement between the sides was regarded as an effusion. Isotope bone scans were done using 99”Tc MDP (technetium labelled methylene diphosphonate) according to a previously described technique modified to include a posterior view of the pelvis and lumbar spine to exclude a site of referred pain. All images were interpreted by a consultant radiologist with knowledge of the clinical information but no knowledge of plain radiographs or ultrasound findings. All children diagnosed as having irritable hips following exclusion of other serious conditions (e.g. Perthes disease and septic arthritis) were treated by bed rest followed by early mobilisation. All patients were followed up for periods ranging from 6-24 months (average 7 months).

IRRITABLE Age 70

HIPS

groups

NO of patients

Fig. 2. Chart showing distribution of age groups. Range 11 months to 14 years, (mean = 6.64 years).

Results Of the 181 cases included in this study, 4 cases (2%) later had Perthes disease diagnosed and 3 cases (2%) septic arthritis of the hip joint. The patients were aged between 11 months to 14 years (mean 7 years). The maximum incidence (64 %) of presentation was between 3 and 8 years (Fig. 2). The male to female ratio was 2: 1. The duration of symptoms prior to presentation varied from 1 to 20 days (mean 3 days). Early presentation i.e., within 3 days of the onset of symptoms was the most frequent in this series. The right hip was marginally more commonly affected than the left (5:4). Only 3 patients had bilateral involvement. The hospital stay of these children ranged from 1 to 15 days (mean 3.9 days). The majority of children (57%) were dis- . charged within 3 days of admission. There was a decrease in numbers presenting between November to April relative to April to October (Fig. 3). Only 16 cases

IRRITABLE

HIPS

Mclnth

30,

Fig. 1. (a) Normal ultrasound scan of the hip joint at the level of femoral capital epiphysis. (b) An effusion in the hip joint on ultrasound scan in an irritable hip.

No of patients

Jan

feb

mar

aPr

may

jun

jul

aug

=P

Months

Fig. 3. Chart showing seasonal variation

cd

“0”

de-C

115 TIME

ULTRASOUND

;;I 6-

OF

RECURRENCE

--+

/’

/’ 4-

_+’ _*-r

2+**-\.,o,, 0 2

3

4

5

6

7

P

Days

01 O-6

Fig. 4. Chart showing relationship of time of scanning and presence of effusion.

had severe irritability (9%). Of these 16 hips, 2 ultimately had a diagnosis of septic arthritis. None of the patients who developed Perthes disease had severe irritability. The majority of patients were apyrexial on admission (74”/b). 23% had mild pyrexia and only 3% had significant pyrexia (38°C). Of the cases with significant pyrexia, 2 had septic arthritis. The WCC was 4.2-28.8 x 109/L (mean 9 x 109/L). ESR was 1-55 mm/h (mean 13 mm/h). All cases with septic arthritis had a high ESR (mean 70 mm/h). There was no statistically significant difference in the value of ESR in patients with Perthes disease compared with irritable hips (P = 0.005). Eighty cases had an ultrasound scan of the hip done 2-11 days after the onset of symptoms. 33 hips (41%) had an effusion in the joint on ultrasound scan. An

7-12

13-24

15 -36

37-48

2.

Months

Fig. 6. Chart showing time of recurrence.

effusion was most often detected in the early course of the disease. Most positive scans (70%) were done within 3 days of onset of symptoms (Fig. 4). A bone scan was done for 107 (59%) hips. In 52 (49%) there was an increased uptake (Fig. 5a), in 4 cases (2%) there was reduced uptake in the lateral : of the femoral head (Fig. Sb) and in the remaining 51 hips, a normal scan. All the 4 cases who had a cold scan developed radiologically evident Perthes disease later. Initially only one case had established changes of Perthes disease radiologically diagnosed on plain radiographs. However on retrospective analysis of the radiographs by a consultant radiologist early subtle evidence of Perthes disease was noted in two out of three reported ‘normal’ radiographs. None of these four cases had a demonstrable effusion on ultrasound scan. 33 cases (18 %) had l-4 recurrences of pain. Of these the majority had only one recurrence (76%). Recurrences mostly occurred (54%) within 12 months of the onset of symptoms (Fig. 6). Discussion

(b)

Fig. 5. (a) A generalised increased uptake in the left hip on bone scan. (b) A cold scan involving the left femoral head in a patient with irritable hip. He later developed radiological changes of Perthes disease.

There is a difference of opinion as to the incidence of Perthes disease following irritable hips. It has been reported to occur in l-20% of cases [ 14-171. In this series the incidence was 2 %. Early diagnosis of Perthes disease on plain radiographs is often difficult. Absence of early radiological signs of Perthes disease at first presentation was reported in one fifth of patients by Jacobs [ 171 and in about one half by Wilk [ 181 and 2 in the is series. Early and subtle radiological changes are easily overlooked by radiologists and orthopaedic surgeons who are not exposed to a large paediatric practice. Isotope scanning helps to establish an accurate and earlier diagnosis of Perthes disease and the

116

irritable hip syndrome. A cold defect is indicative of early Perthes disease and indicates the initial infarct. The hot scan of the irritable hip syndrome is not specific for idiopathic synovitis and is also seen in infection, rheumatoid disease and post traumatic states and must always be interpreted against the clinical background. As a result of scanning, parents can be told at an early stage their child’s prognosis and once the initial pain subsides, the number of follow up appointments and attendances to hospital can be reduced [4]. Ultrasound scanning is considered to be the best non-invasive technique and follow-up of hip effusions. It is extremely sensitive in detecting small amounts (23 ml) of fluid [&lo]. Translucent lines seen around the hips on plain radiographs, displacement of which is traditionally taught to indicate an effusion are not diagnostic of an effusion but merely represent different muscle planes [9]. Despite being extremely sensitive in detecting an effusion, the ultrasound scan is non specific and cannot characterise the type of fluid present. It is surprising that some patients with irritable hips have a normal ultrasound scan (i.e. no effusion at presentation). About half the patients (49%) in this series had a normal scan. Similar findings have been reported by McGoldrick et al. [lo] in 61% of case and Bickerstti et al. [ 91 in 29% of cases. This could be due to the transient nature of the disease which results in the effusion disappearing in a few days. In most reported studies there is no mention of the time interval between the onset of symptoms and the ultrasound scan. This is an important factor, as in this study the majority of positive scans (70%) were performed within 3 days of the onset of symptoms. Effusions almost completely regress in 4- 11 days [ 81. No difference was found in the clinical presentation of patients with and without an effusion on ultrasound scan. However Adams et al. found that the severity of clinical symptoms and signs were directly related to the amount of effusion [ 61. No effusion was found in this series in any patients who developed Perthes disease. On the contrary, BickerstaB et al. reported an effusion in both their cases of Perthes disease, with persistence in one patient up to 42 days [ 91. As yet there is no clear cut evidence in the literature as to whether an effusion of transient synovitis of the hip is responsible for the vascular insult of Perthes disease [20]. If intra articular fluid is demonstrated on an ultrasound scan, the fluid may be aspirated under ultrasound control. A false positive tap (dry tap) implies that the joint has been missed and aspiration should be repeated [ 81. The recurrence rate of irritable hips has not been well documented. A recurrence rate of 18% in this series of patients compared with 29% in Jacobs’ series

[ 161. Recurrences are most frequent within 612 months of the first attack [21]. There are no features which distinguish an initial attack from recurrences, or can predict the likelihood of recurrence. Sharwood [ 171 reported no seasonal variation on the presentation of irritable hips. Laudin, et al. [22] noted a higher incidence in autumn and winter months and correlated this with an increased incidence of respiratory infection in these months. In this series a decreased incidence (27%) occurred in autumn and winter months (October to March) compared with 73 y0 in spring and summer months (April to September). In conclusion we recommend that all children who present with an irritable hip should have an ultrasound examination to investigate the incidence and relevance of an effusion. Radionuclide studies are recommended in children with X-ray changes suspicious of Perthes disease, pain in the hip lasting more than 48 hours, or those with pain but no effusion, as these children are more likely to have Perthes disease.

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117 13 Gordon I, Peters AM, Nunn R. The symptomatic hip in childhood: scintigraphic finding in presence of normal radiograph. Skeletal Radio1 1987; 16: 383-386. 14 Speck A. Transient synovitis of the hip joint in children. Paediatrics 1959; 24: 1042-1049. 15 Salter RB. Textbook of disorders and injuries of musculoskeletal system. Baltimore: Williams and Wilkins, 1970: 187. 16 Jacobs BW. Synovitis of hip in children and its significance. Paediatrics 1971; 47: 558-566. 17 Sharwood PJ. The irritable hip syndrome in children. Acta Orthop Stand 1981; 52: 633-638.

18 Jacobs BW. Early recognition of osteochondrosis of capital epiphysis of femur. JAMA 1965; 192: 527. 19 Wilk LH. Juvenile osteochondrosis of the hip. JAMA 1965; 192: 939. 20 Erken EHW, Katz K. Irritable hip and Perthes disease. J Paediatr Orthop 1990; 10: 322-326. 21 Illingworth CM. Recurrence of transient synovitis of the hip. Arch Dis Child 1983; 58: 620-623. 22 Landin LA, Danielson LG, Wattsgard C. Transient synovitis of hip: its incidence epidemiology and relation to Perthes disease. J Bone Joint Surg 1987; 69B: 238-242.