Amorphous calcium deposits of the hip joint: current observations and state of the scientific discussion.

INTRODUCTION

As a result of increasing hip arthroscopies, rare pathologies as intra-articular amorphous calcium deposits in the capsule-labral (perilabral) recess can be recognized. There is a lack of publications on this pathology. The largest case series included 18 patients. An association between femoroacetabular impingement syndrome (FAIS) and female sex was observed. Furthermore, a correlation between the size of the calcific deposit and the preoperative hip function score was reported. Our hypothesis was that the data of our patient collective with intraoperative amorphous calcium deposits of the hip joint are comparable to the existing data to confirm previous observations.

MATERIALS AND METHODS

From 01/2018 to 08/2020, a total of 714 hip arthroscopies were performed. 12 (1.7%) patients who presented intra-articular amorphous calcium deposits during arthroscopy were included. On radiographs, signs of impingement and osteoarthritis were determined. Characteristics and size of the calcific deposits were examined. Preoperative and at the time of follow-up (23 months), patient-reported outcome scores (PROS) were evaluated. Duration of symptoms, pain medication, comorbidities, and return-to-work were evaluated too.

RESULTS

The PROS of the four female and eight male patients improved significantly. The average size of the calcific deposit was 6.9 mm in the anteroposterior radiographs. Separation of the calcific deposit from the acetabular rim was seen in nine cases. No correlation between deposit sizes and PROS was found. Cam morphology was treated in ten cases. All patients returned to work after a median of 7 weeks (2.5-13 weeks).

CONCLUSION

Amorphous calcium deposits were found in approximately 1% of all hip joints with indication for hip arthroscopy. They are not consistently associated with gender, intra-articular hip pathologies or comorbidities. The clustered occurrence in cam FAI can be justified solely by the fact that impingement is by far the most common indication for hip arthroscopy.