BackgroundAdverse local tissue reaction (ALTR), characterized by a heterogeneous cellular inflammatory infiltrate and the presence of corrosion products in the periprosthetic soft tissues, has been recognized as a mechanism of failure in total hip replacement (THA). Different histological subtypes may have unique needs for longitudinal clinical follow-up and complication rates after revision arthroplasty. The purpose of this study was to describe the histological patterns observed in the periprosthetic tissue of failed THA in three different implant classes due to ALTR and their association with clinical features of implant failure.MethodsConsecutive patients presenting with ALTR from three major hip implant classes (N = 285 cases) were identified from our prospective Osteolysis Tissue Database and Repository. Clinical characteristics including age, sex, BMI, length of implantation, and serum metal ion levels were recorded. Retrieved synovial tissue morphology was graded using light microscopy. Clinical characteristics and features of synovial tissue analysis were compared between the three implant classes. Histological patterns of ALTR identified from our observations and the literature were used to classify each case. The association between implant class and histological patterns was compared.ResultsOur histological analysis demonstrates that ALTR encompasses three main histological patterns: 1) macrophage predominant, 2) mixed lymphocytic and macrophagic with or without features of associated with hypersensitivity/allergy or response to particle toxicity (eosinophils/mast cells and/or lymphocytic germinal centers), and 3) predominant sarcoid-like granulomas. Implant classification was associated with histological pattern of failure, and the macrophagic predominant pattern was more common in implants with metal-on-metal bearing surfaces (MoM HRA and MoM LHTHA groups). Duration of implantation and composition of periprosthetic cellular infiltrates was significantly different amongst the three implant types examined suggesting that histopathological features of ALTR may explain the variability of clinical implant performance in these cases.ConclusionsALTR encompasses a diverse range of histological patterns, which are reflective of both the implant configuration independent of manufacturer and clinical features such as duration of implantation. The macrophagic predominant pattern and its mechanism of implant failure represent an important subgroup of ALTR which could become more prominent with increased length of implantation.

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Aims Instability continues to be a troublesome complication after total hip arthroplasty (THA). Patient-related risk factors associated with a higher dislocation risk include the preoperative diagnosis, an age of 75 years or older, high body mass index (BMI), a history of alcohol abuse, and neurodegenerative diseases. The goal of this study was to assess the dislocation rate, radiographic outcomes, and complications of patients stratified as high-risk for dislocation who received a dual mobility (DM) bearing in a primary THA at a minimum follow-up of two years. Materials and Methods We performed a retrospective review of a consecutive series of DM THA performed between 2010 and 2014 at our institution (Hospital for Special Surgery, New York, New York) by a single, high-volume orthopaedic surgeon employing a single prosthesis design (Anatomic Dual Mobility (ADM) Stryker, Mahwah, New Jersey). Patient medical records and radiographs were reviewed to confirm the type of implant used, to identify any preoperative risk factors for dislocation, and any complications. Radiographic analysis was performed to assess for signs of osteolysis or remodelling of the acetabulum. Results There were 151 patients who met the classification of high-risk according to the inclusion criteria and received DM THA during the study period. Mean age was 82 years old (73 to 95) and 114 patients (77.5%) were female. Mean follow-up was 3.6 years (1.9 to 6.1), with five patients lost to follow-up and one patient who died (for a reason unrelated to the index procedure). One patient (0.66%) sustained an intraprosthetic dislocation; there were no other dislocations. Conclusion At mid-term follow-up, the use of a DM bearing for primary THA in patients at high risk of dislocation provided a stable reconstruction option with excellent radiographic results. Longer follow-up is needed to confirm the durability of these reconstructions.

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Background: A variety of classification systems have been developed to help surgeons treat patients with acetabular or femoral bone loss in total hip arthroplasty, yet no "gold standard" for classification has been agreed upon. Furthermore, the reliability and validity of the available classification systems remain unknown. Questions/Purpose: The aims of our study were to determine the reliability and validity of the three most common acetabular and femoral bone loss classification systems (Paprosky, American Academy of Orthopaedic Surgeons [AAOS], and Saleh and Gross). Methods: A systematic review of the literature was performed to identify studies that reported on the reliability or validity (or both) of the acetabular and femoral components of the three bone loss classification systems. Results: In all, seven articles met our inclusion criteria. Six studies reported on the reliability (all six studies) or validity (three studies) of acetabular bone loss rating systems (286 acetabula), and five analyzed reliability (all five studies) or validity (three studies) of femoral bone loss classification systems (364 femurs). In studies in which either the Paprosky or AAOS acetabular bone loss classifications were used, the classification systems were considered unreliable in 75% and 100% of them, respectively. On the femoral side, the Paprosky classification demonstrated moderate interobserver and good intraobserver reliability. The AAOS femoral bone classification was found to have good intraobserver reliability but poor interobserver reliability. The Saleh and Gross acetabular and femoral bone loss classification systems yielded mixed results, but each was considered reliable in one of the studies looking at these aspects of the systems. Conclusion: Although surgical techniques, treatment options, and advanced imaging available to the surgeon have evolved over the past few decades, the acetabular and femoral bone loss classification systems, first developed in the 1990s, have remained largely unchanged. Our results indicate that improvements to these systems are necessary in order for them to be as useful as possible in planning the surgical course.