Clinical consequences of pseudotumors in hip arthroplasty

Joint arthroplasty has increased over the last decades as an effective treatment option for hip and knee osteoarthritis. Significant evolution in techniques and materials offer a better quality of life and long-lasting improvement in wellselected patients. Metal on metal (MoM) hip arthroplasty and especially resurfacing arthroplasty has gained a wide interest and the main reason is the increased head-neck implant ratio which provides an increased range of motion and decreased femoral neck impingement and dislocation rate. Despite the fact that many surgeons tend to use implants like ceramic heads and High-density crosslinked polyethylene, the MoM articulation remains still appreciable. Adverse effects can been seen to all types MoM arthroplasties, Including Total Hip Arthroplasty (THA) with small (<36 mm) or large (≥36 mm) head diameter and Resurfacing Hip Arthroplasty (HRA). The incidence of local reactions is higher in articulations with large diameter heads. Some of these reactions include metallosis, aseptic lymphocytic vasculitis associated lesion (ALVAL) and pseudotumors. The term pseudotumor has been used to describe non neoplastic cystic or solid mass around a MoM hip arthroplasty. These masses form as a result of a reaction to metal debris from the implants surfaces. Second and third generation MoM hip implants use new articulation surfaces made by improved materials and have been associated with only minimal problems concerning durability like wear which can lead to aseptic loosening and revision surgery. Nonetheless side effects still exist. Metal ions release from the articulation surfaces especially when larger heads (larger loads) used lead on to local reactions which can present clinically in many ways. In 2012 Natu et al. made an effort to investigate the Adverse Reactions to Metal Debris (ARMD) after MoM hip arthroplasty. This umbrella term includes conditions like metallosis ALVAL (perivascular inflammatory infiltration of lymphocytes), granulomatous inflammation and pseudotumors. In this review are included only articles referring in the term pseudotumor and not the other reactions mentioned above.