SCREENING PROTOCOL FOR DETECTION OF ISCHAEMIC DISEASE OF THE GROWING HIP AND PREVENTION OF LEGG-CALVE-PERTHES DISEASE.

TRADUÇÃO EM PORTUGUÊS

SCREENING PROTOCOL FOR DETECTION OF ISCHAEMIC DISEASE OF THE GROWING HIP AND PREVENTION OF LEGG-CALVÉ-PERTHES DISEASE.

Nuno Craveiro Lopes, M.D.

Paediatric Orthopaedic Unit, Garcia de Orta Hospital, Almada-PORTUGAL

E-mail: nuno.lopes@mail.netvisao.pt Home Page: http://clientes.netvisao.pt/nfrancac/pagedlcp/index.html

INTRODUCTION

LCPD is perhaps a multifactorial disease, but what is sure today is that you need two or more ischaemic episodes, occurring within some months to provoke the illness. Those episodes are symptomatic: There is pain and signs one can detect if one is aware of. We call that stage before the onset of LCPD, Ischaemic Disease of the Growing Hip (IDGH).

After studding for 10 years both experimentally and clinically the effect of intermittent tamponade of the intra-articular vascular flow to the epiphysis (Fig.1) and the effect of transphyseal neck-head femoral drilling to supplement the vascular flow to the epiphysis (Fig.2), we introduced on our unit a screening protocol to detect the cases of IDGH at risk of evolve to LCPD and prevent the evolution of those cases to LCPD.

MATERIAL AND METHODS

All paediatricians and general practitioners of the area of influence of our hospital were informed of the protocol and advised to send all children complaining of a painful hip or thigh, to the paediatric emergency unit of our hospital.

From January 1993 to December 1995 (3 years), from a population of 70 thousand under 16 years of age, we have screened 123 patients, 3 to 12 years old, presenting with a painful hip syndrome of unknown origin.

The protocol included a first screening by ultrasound, to identify the cases with a pattern of IDGH, which includes effusion, synovial and articular cartilage thickening (Fig.3). The second screening procedure was done at the beginning with a nuclide bone scan and nowadays with a MRI bone scan, to detect a necrotic episode in evolution (Fig.4).

As a predictor of probability of evolution to LCPD we consider three stages of IDGH:

Stage I - Detection of an old episode of necrosis. Signs of minimal flatten epiphysis, head within a head, irregular contour on the XR and ultrasound signs of chronic irritation (Fig.5). Have a low probability of evolution to LCPD.

Stage II - Detection of an old episode and a new necrotic episode in evolution. The MRI confirms the actual necrotic episode (Fig.6). The probability is fair.

Stage III - Detection of a new necrotic episode in evolution over another recent one, with signs of epiphyseal fragility. The XR shows epiphyseal porosis and sometimes a subchondral crescent sign (Fig.7). The probability of evolution to LCPD is almost 100%.

The hips, where we have detected IDGH Stage III or Stage II in children over 6 years of age, have been submitted to a transphyseal neck-head drilling with a 5mm drill or trephine, guided by image intensifier. Those cases had a mean follow-up of 4 years and 4 months (3 years to 5 years and 4 months).

RESULTS

From the 123 screened cases, 32 (26%) where easily diagnosed as LCPD (18), SFCE (3), Septic (3), Rheum (3), Trauma (2) and extra-articular (3).

On the remaining 91, the first screening procedure by ultrasound confirmed the diagnose of transient synovitis in 48 cases (53%) and permitted us to identify 43 cases (47%) suspicious of IDGH. From those 43 suspected cases, MRI confirmed the diagnose of IDGH stage II and III in 6 cases, which represents 6,5% of those 91 hips (Fig.8). The total of transient synovitis cases on our series was 85 cases (93,5%)

The 6 hips diagnosed as IDGH Stage II and III were submitted to a transphyseal neck-head drilling and none have evolved to LCPD or had impairment of growth of the proximal femur (Fig.9).

Recent epidemiological data from the area of influence of our unit, comparing the incidence of LCPD on the years 93 to 95 and 96 to 98, have shown a decrease from 8.5/100.000 to 1.8/100.000 per year, on the population under 16 years of age.

CONCLUSION

Early detection of LCPD is essential to get a good end result with a spherical head.

The best method to detect a necrotic episode is MRI, but the costs do not permit its use on all children with a painful hip syndrome.

The first screening procedure of our protocol utilizing ultrasound, having a high sensitivity but low specificity, permitted us to identify 43 cases suspicious of IDGH within a total of 91 cases. This enabled the selection of cases where MRI, a method with a high sensitivity and specificity, can be used to diagnose IDGH with a better cost/effectiveness relation.

The cases of IDGH stage II and III, were transphyseal neck-head drilling have been used, did not progressed to LCPD, and the preliminary study of the epidemiological data seemed to show a decrease on the incidence of the illness on our population. Those facts point to a preventive effect of this intervention on the onset of LCPD. We have begun now a prospective double blind study to confirm those results.

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