Bone wax can lead to foreign body reaction and local osteolysis after open femoroacetabular impingement (FAI) surgery.

Introduction Bone wax is a haemostatic agent, widely used to prevent bleeding from bone surfaces. Despite its effectiveness in haemostatic control, it can lead to foreign body granuloma and osteolysis. Therefore, the aim of this study was to assess the rate and progress of osteolysis after surgical bone wax application. Methods We included 425 patients between 01/2002 and 12/2006 that underwent offset correction for cam type femoroacetabular impingement with application of bone wax for homogeneous statistical cohort formation. Comparison was made to a similar cohort group undergoing offset correction without application of bone wax, including 479 patients between 01/2008 and 12/2012. Out of the study group, six hips in five patients presented with persisting pain and growing osteolysis on the X-rays in the area of the offset correction, and two underwent subsequent revision surgery. None of the patients in the cohort group presented with osteolysis. In both groups, patients who presented with persisting pain without radiological osteolysis had other determinable causes as labral tears, progressing osteoarthritis, trochanteric bursitis, and adhesions as suggested source of the pain. We measured the relative area of the osteolysis where present (area of osteolysis/area of femoral head in %) on lateral radiographs on the first postoperative X-rays and latest follow-up X-rays, with a mean follow-up time of 8.6 ± 2.5 years (range, 5-13 years). Histologic samples were taken at revision surgery. Results The relative area of osteolysis increased in all hips from a directly postoperative median of 5.5% ± 2.7% (2.3-10.7%) to 11.2% ± 3.9% (7.1-17.3%) at last follow-up. In patients undergoing revision surgery for osteolysis, remaining wax as a foreign material with attached multinucleated giant cells and abundant mononuclear cells was detected histologically. Conclusion The intra-articular use of bone wax should be approached with caution and with awareness of the possible complications. Trial Registration Number KEK 2018-00078, registered April 2018. Level Of Evidence level IV, retrospective case series.