Indications And Diagnostic Accuracy

Schindler et al. reviewed 21 children and adolescents undergoing 24 arthroscopies for varied diagnoses. In this study, arthroscopy supported the presumed diagnosis in 56%, concluding that hip arthroscopy may not be useful as a diagnostic tool.13 This finding was corroborated in a large series, in which it was concluded that the diagnostic use of hip arthroscopy remains viable only in specific cases. Furthermore, Dorfmann and Boyer suggested that the improvements in imaging modalities have decreased and may continue to decrease the indications for diagnostic arthroscopy in the hip.9

Although hip scope for diagnosis alone may have limited applications, Schindler went on to conclude that arthroscopy in children is helpful in obtaining synovial biopsies and removing loose bodies and should decrease the need for open surgery with dislocation of the hip and its associated risk of avascular necrosis. The reported complication rate in Schindler's series was no higher than in the adult population, which has been reported to be 1% to 2%, with two patients having transient pudendal nerve dysesthesias and no infections or cases of residual stiffness being observed.12,13 More recent information has placed the surgeon in a more informed position when considering the role of hip arthroscopy. The surgeon can weigh the small risk of complications associated with hip arthroscopy, the merits of imaging alternatives such as magnetic resonance imaging, and the emerging data on accuracy of diagnosis and outcomes of treatment using hip ar-throscopy. To properly take advantage of maximum benefit given the defined risk for hip arthroscopy, it is extremely important to consider which preopera-tive factors might portend a better outcome. Awareness of predictive factors such as mechanical symptoms is especially important in cases of occult pain in the young active patient who does not have an underlying developmental disorder, childhood aliment, or a revealing imaging study. In a review of patients treated at our institution, we concluded that regardless of the preoperative diagnosis, the presence of definite mechanical symptoms is an important prognostic indicator of symptomatic relief following operative hip arthroscopy. Removal of loose bodies, manage ment of labral tears, and debridement of focal chon-dral injury were found to be associated with better outcomes. Less-desirable results were achieved in patients with osteonecrosis and degenerative arthritis. However, mechanical symptoms in these patients, including pediatric and adolescent patients, may still signal potentially treatable pathology because treatment with arthroscopy may prevent or delay the need for open arthrotomy in children or arthroplasty in adults.21

HISTORY AND physical examination

Pediatric and adolescent patients do not frequently complain of hip pain. In fact, it is not uncommon for hip pathology to be discovered after complaints of knee pain in the young patient. This pattern of referred pain occurs frequently enough that the treating physician should have a high index of suspicion that hip pathology or hip injury may be the causative factor for knee pain in the patient with a normal examination of the knee. Another frequent presentation is limping in a child who has suffered no known injury. When this scenario occurs, a history of preceding illness, which is found in up to 40% of patients, directs the examiner toward a diagnosis of transient synovi-tis of the hip. In one study of 243 children seen in the emergency department, 39.5% subsequently had this diagnosis.22

In the pediatric or adolescent patient, as with any orthopedic patient, the history with careful attention to mechanism of injury can be revealing. Running, jumping, and kicking-based activities are frequently involved, especially in causing labral pathology. A patient with a labral tear often reports an acute twisting injury, but an axial load on a flexed hip can also result in trauma to the labrum. In our series of 86 hip arthroscopies, only 17% of patients gave a definite history of traumatic event preceding the onset of symptoms. Of the patients diagnosed at arthroscopy with labral tears, 36% had antecedent trauma, whereas 44% of patients with loose bodies attributed their pain to trauma.21 McCarthy's analysis revealed a 44% incidence of traumatic injury in his patients with labral tears.23 Again, it should be stressed that because hip injury is an infrequent occurrence in pediatric patients, underlying hip disorders should be investigated thoroughly.

In our experience and that of others, subjective complaints of catching, locking, popping, and giving way are helpful at defining those patients who may benefit from surgery.9,21,23,24 We found the presence of mechanical symptoms to be suggestive of treatable intraarticular pathology in 100% of our patients who had labral tears, loose bodies, or chondral injury. How ever, in one study, only 64% of patients with a labral tear diagnosed at arthroscopy had mechanical symp-toms.24 McCarthy found a positive correlation between giving-way or locking episodes with labral tears and the presence of locking episodes correlated with chondral injury.23 Selection bias toward these patients was undoubtedly present in our study because mechanical symptoms were considered an indication for surgery.21 Locking or catching symptoms should be distinguished from popping or snapping symptoms because the latter may herald extraarticular pathology that is not amenable to arthroscopic surgery, such as anteromedial catching or psoas tendon bursitis.9 Anec-dotally, complaints of the hip feeling tired or weak have been helpful as an indicator of intraarticular pathology in our series.

Physical examination of the injured hip can be quite vexing, likely because of the complex anatomy both within and surrounding the hip joint. Examination frequently reveals pain in provocative positions, but this is individualized and entirely patient dependent. Reproducible pain with passive flexion and medial or internal rotation of the hip has been identified as predictors of intraarticular pathology.24 This finding has been corroborated in young athletic patients.2 The direction of these provocative maneuvers does not correlate well with the location of labral tears, according to Farjo et al.24 McCarthy noted painful clicks in 56% of patients during a Thomas hip flexion-to-extension test and concluded that this finding had a significant positive correlation with acetabular labral tear on arthroscopic evaluation. He states that pertinent physical findings such as these represent the best predictors of treatable intraarticular pathology.23

We believe that decreased range of motion as compared with the contralateral unaffected hip is also a useful sign of significant hip pathology. Flexion and internal rotation appear to be affected most and earliest in these patients. These findings on physical examination are obviously nonspecific, as internal rotation of the hip is often lost early in degenerative conditions of the hip. Most would agree that limited abduction in flexion is a cardinal indication for treatment of LCP, and this examination should be performed on all pediatric patients with hip pain. Furthermore, a reduction in adduction of the flexed hip has been described as being the earliest physical sign of hip irritability, whether the underlying diagnosis is LCP or other causes.25

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