Severe osteolysis after third-body wear due to hydroxyapatite particles from acetabular cup coating

Abstract

O ne concern about the fixation of HA-coated implants is the possible disintegration of the surface, with the migration of HA granules into the joint space, producing third-body wear. We report a study of six revisions of HA-coated polyethylene RM cups at 9 to 14 years after successful primary arthroplasty. In all six hips, we found HA granules embedded in the articulating surface of the polyethylene, with abrasive wear of the cup and the metal femoral head. The cup had loosened in four hips and three showed severe osteolysis of the proximal femur. Third-body wear due to HA particles from implant coating may produce severe clinical problems with few early warning signs. Further clinical, radiological and histological observations are needed to determine the possible incidence of this late complication in the various types of coating of a variety of substrates.

Inferior Survival of Hydroxyapatite versus Titanium-coated Cups at 15 Years

“…The cases of high PE wear in our study could be related to HA particles separating from the coating leading to increased backside wear and articulate wear on the PE, a mechanism described by Bauer, Morscher et al, and Rokkum et al [4,33,43]. Disintegration of the HA coating is influenced by numerous factors, including the purity of HA, manufacturing, crystallinity, porosity, method of coating, the thickness of the HA coating, the surface on which HA is deposited (smooth or rough), the adhesive strength of HA to the substrate [33], and the speed of resorption [8,35,45]. Calcium phosphate coatings have been applied plasma-sprayed with different quality and coating thicknesses ranging from 300 lm [33,43], over 150 lm [42], to 40 lm [41].…”

“…However, theories of coating degradation resulting in particulate HA-induced third-body wear [5,8,33] have long been discussed. This study was initiated to evaluate the potential disadvantages of HA-coated implants for THA including (1) survival, (2) increased wear, and (3) increased osteolysis.…”

“…Numerous authors have described a larger main group of well-performing cups with a smaller group of cup failures attributable to osteolysis, wear, aseptic loosening, and PE fracture (Table 3). Apparently, there is no clear association between worn failing implants and the clinical performance [29,33], and thus expansile (cystic) osteolysis and loosening may progress without warning signs [5,33,42].…”

“…Disintegration of the HA coating is influenced by numerous factors, including the purity of HA, manufacturing, crystallinity, porosity, method of coating, the thickness of the HA coating, the surface on which HA is deposited (smooth or rough), the adhesive strength of HA to the substrate [33], and the speed of resorption [8,35,45]. Calcium phosphate coatings have been applied plasma-sprayed with different quality and coating thicknesses ranging from 300 lm [33,43], over 150 lm [42], to 40 lm [41]. Thinner plasma-sprayed HA coatings (50 lm) have been recommended, as they give a stronger fixation and reduce the risk of HA fracture [44].…”

“…Supporting this concern, HA particles have been detected on the PE surface of retrieved components [4,9], and loose HA particles may increase production of excessive PE particles, leading to increased PE wear and liner revision, premature periprosthetic osteolysis, and aseptic implant loosening [4,33]. In general, release of HA particles from the implant surface could generate a clinical problem with few, if any, early warning signs [6,33].…”