Purpose: Anterior hip pain raises difficult diagnostic and therapeutic problems. Several diagnostic hypotheses are currently put forward to explain the origin of this pain: subcondral cysts, labrum problems and anterior bone impingement, an association of these mechanisms. We report our operative observations in thirteen cases and examined the findings in light of the clinical data and imaging results in order to search for aetiopathogenic factors leading to this type of pain and to elucidate possible therapeutic options.

Material and methods: Thirteen video-assisted miniarthrotomy procedures were performed using a novel technique in patients presenting anterior hip pain. The preoperative work-up included physical examination, standard radiographs, and MRI and/or arthroscan to rule out an extraarticular cause and identify any lesion of the superomedial border of the hip joint (acetabular rim and/or labrum).

Results: Physical examination was not greatly contributive excepting the two posttrauma cases. Four patients had unique lesions of the labrum with no associated bone lesions and no argument in favour of anterior bony impingement identifiable from the preoperative data. Regularisation of the labrum improved the pain in these four patients. Isolated chondroplasty of the femoral head in one patient was very partially improved. The eight other patients had lesions of the labrum associated with a femoral head imprint, bony defects or osteophytes at the head-neck junction, or actetabular defects, or an association of these three types of lesions. The patients raised major diagnostic problems because it was difficult to identify the initially causal mechanism: anterior mechanical conflict with a cam effect and secondary disinsertion of the labrum due to microtrauma (five of the patients had an insufficiently concave head-neck junction or an osteophyte which may have been the cause); or an initial lesion of the labrum causing secondary subchondral acetabular defects resulting from the disinsertion (this hypothesis was compatible with the presentation of three patients who had no femoral anomalies, notably absence of any defect and a normal head-neck junction).

Discussion: Video-assisted mini-arthrotomy of the hip enables careful inspection of the entire hip joint and facilitates any therapeutic measures necessary. Isolated lesions of the labrum are exceptional and generally are associated with remodelling of the anterosuperior border of the acetabulum. The primary mechanism of a labrum lesion or an anterior cam effect is difficult to demonstrate in these patients who are often seen late in the process. Better knowledge of the aetiopathogenesis of anterior hip pain is needed to propose adapted and effective treatment.