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Introduction Osteolysis is a common problem in the long-term outcome after total hip arthroplasty, since the wear of a polyethylene liner is an inevitable process. However, its pace depends on many factors and not all of them have been proven. In particular, many studies do not find a connection between the wear rate of the liner and the position of the acetabular component. The purpose of this publication is to demonstrate the importance of correct acetabular component positioning. Methods A clinical case of bilateral total hip arthroplasty with follow-ups after 17 and 19 years is presented. The patient was operated being 31 and 33 years old, respectively, by one surgeon. The same type of the acetabular component was installed with the same type of polyethylene and friction pair diameter. It eliminates implant or surgical approach factors and patient characteristics. The position of the implant components is then remains the most important factor. For analysis, there were radiographs before the operation, at different times after it, CT data and intraoperative photos during the revision surgery. Results At the time of the last examination, there were minor manifestations of retroacetabular osteolysis that were better seen in CT and were more pronounced on the right. CT radiometry data on the angles of inclination of the acetabular components were 50.6° and 46.7° on the right and left, respectively, and the anversion was 40.3° and 25.4°. Revision of the right total hip arthroplasty was performed and it was found that the liner wear extended till the metal layer. Given good fixation of the cup, only the liner was exchanged and osteolytic cavities were filled with allogenic bone chips. Discussion The case can be considered a very good result of primary arthroplasty as revision surgery in this young patient was performed only after 17 years. However, in the contralateral joint the implant with the same pair of friction has survived for 19 years and at the moment it is early to decide on its revision. In our opinion, this case is an excellent illustration of the importance of the correct positioning of implant components.

Implant survival is a very important outcome measure of surgical treatment of patients with severe degenerative joint disease in the hip. The aim of this review is to summarize the present knowledge on the possibilities for earlier laboratory diagnosis of osteolysis and prognostic approaches to prevent aseptic loosening of prosthetic implants. Results Periprosthetic osteolysis is often seen as an early sign of an adverse event associated with the development of unstable total hip arthroplasty (THA). A lot of data support the concept of osteolysis as a condition caused by biomechanical stresses, surgery specific factors, preoperative decrease and postoperative loss of bone mineral density, vascular impairment and chronic inflammation. Hemostasiological, biochemical and immunological parameters of patients were explored before and after THA. Surgical intervention was treated as the cause of secondary immunodeficiency, and results of the recovery period evaluated with regard to the extent to which immunodeficiency appeared to be compensated. Dynamics in stress related bone remodeling around the implant was found to be be a marker for early detection of osteolysis and prediction of aseptic loosening of THA, as well as control over the "target" of drug exposure. Conclusion Literature review suggests that there is a common understanding of the pathogenesis of osteolysis and the development of aseptic loosening of THA, and there is scanty data on the laboratory markers for early diagnosis and prediction of the complication that would require further study.

Background: Modern total ankle arthroplasty (TAA) prostheses are uncemented press-fit designs whose stability is dependent on bone ingrowth. Preoperative insufficient bone density reduces initial local stability at the bone-implant interface, and we hypothesized that this may play a role in periprosthetic osteolysis. We aimed to investigate the preoperative bone density of the distal tibia and talus and compare these in patients with and without osteolysis. Methods: We enrolled 209 patients (218 ankles) who underwent primary TAA using the HINTEGRA prosthesis. The overall mean follow-up duration was 66 (range, 24-161) months. The patients were allocated into 2 groups according to the presence of periprosthetic osteolysis: the osteolysis group (64 patients, 65 ankles) and nonosteolysis group (145 patients, 153 ankles). Between the 2 groups, we investigated and compared the radiographic outcomes, including the Hounsfield unit (HU) value around the ankle joint and the coronal plane alignment. Results: HU values of the tibia and talus measured at 5 mm from the reference points were higher than those at 10 mm in each group. However, comparing the osteolysis and nonosteolysis groups, we found no significant intergroup difference in HU value at every measured level in the tibia and talus ( P > .05). Concerning the coronal plane alignment, there were no significant between-group differences in the tibiotalar and talar tilt angles ( P > .05). Conclusion: Patients with osteolysis showed similar preoperative bone density of the distal tibia and talus compared with patients without osteolysis. Our results suggest that low bone density around the ankle joint may not be associated with increased development of osteolysis. Level of Evidence: Level III, retrospective cohort study.

Background It is often challenging to decide whether to revise only the bearing or femoral acetabular component in the setting of progressive osteolysis without component loosening in revision total hip arthroplasty (THA). In this study, we aimed to (1) compare the survivorship of isolated bearing exchange and single/both component revision for patients with periprosthetic osteolysis without component loosening, and (2) identify potential risk factors associated with failures of isolated bearing exchange. Methods A total of 228 consecutive cases of revision THA for progressive osteolysis without component loosening was evaluated in 2 groups: (1) 124 component revision and (2) 104 isolated bearing exchange. The primary outcome was survival, with failure defined as repeat revision or reoperation for any reason. Patient risk factors, such as demographics and medical comorbidities, were also analyzed. Results There was no significant difference in survivorship between the component revision group and the bearing exchange group at 10 years (85% vs 82%; P = .89). There was no progression of osteolysis on radiographs at last follow-up for patients with isolated bearing change. Univariate regression modeling demonstrated that renal disease was associated with failure of isolated bearing exchange after revision THA. Conclusion This study demonstrated that isolated bearing exchange is associated with similar outcomes compared with component revision for aseptic osteolysis without loosening, demonstrating that isolated bearing exchange is a viable option for selected patients with osteolysis in the setting of well-fixed THA components. This provides clinically useful information for surgeons in the surgical treatment of THA patients with wear and osteolysis without component loosening.

BACKGROUND: Peri-prosthetic bone loss can result from chemical, biological, and mechanical factors. Mechanical stimulation via fluid pressure and flow at the bone–implant interface may be a significant cause. Evidence supporting mechanically induced osteolysis continues to grow, but there is no synthesis of published clinical and basic science data. QUESTIONS/PURPOSES: We sought to review the literature on two questions: (1) What published evidence supports the concept of mechanically induced osteolysis? (2) What is the proposed mechanism of mechanically induced osteolysis, and does it differ from that of particle-induced osteolysis? METHODS: A systematic review was performed of the PubMed and Web of Science databases. Additional relevant articles were recommended by the senior authors based on their expert opinion. Abstracts were reviewed and the manuscripts pertaining to the study questions were read in full. Studies showing support of mechanically induced osteolysis were quantified and findings summarized. RESULTS: We identified 49 articles of experimental design supporting the hypothesis that mechanical stimulation of peri-prosthetic bone from fluid pressure and flow can induce osteolysis. While the molecular mechanisms may overlap with those implicated in particle-induced osteolysis, mechanically induced osteolysis appears to be mediated by distinct and parallel pathways. CONCLUSIONS: The role of mechanical stimuli is increasingly recognized in the pathogenesis of peri-prosthetic osteolysis. Current research aims to elucidate the molecular mechanisms to better target therapeutic interventions. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1007/s11420-018-9641-5) contains supplementary material, which is available to authorized users.

Background Aseptic loosening and periprosthetic osteolysis are frequent complications in total hip arthroplasty requiring revision surgery. Highly crosslinked polyethylene (HXLPE) implants have improved wear resistance, permitting larger femoral heads. However, such implants may experience surface cracking, mechanical failure, and oxidative damage. Vitamin E-infused HXLPE (VEPE) implants were therefore developed to reduce oxidation without compromising mechanical strength. We addressed the following questions: (1) Does femoral head size affect the midterm annual polyethylene wear rates of VEPE acetabular cups? (2) Does femoral head size affect the midterm migration rates of VEPE acetabular cups? (3) Are clinical outcomes affected by femoral head size? Hypothesis Annual wear rate, migration rate, and clinical outcomes of VEPE acetabular cups are independent of femoral head size. Patients and methods This was a prospective, multicenter, observational study of patients that underwent total hip arthroplasty. Hips were grouped according to the size of femoral head implanted (28 mm, 32 mm, and 36 mm). We determined annual wear rate and migration rate of VEPE acetabular cups using the Einzel-Bild-Rontgen-Analyse software. Clinically, we assessed the Harris Hip Score and visual analog score for pain and satisfaction. Results We followed 253 patients (267 hips) for a mean of 55.0 ± 20.6 months in the 28 mm, 46.2 ± 21.4 months in the 32 mm, and 43.8 ± 22.6 months in the 36 mm group. The annual wear rate was 0.025 mm per year from 1 year to the last follow-up and remained similar between the groups (p > 0.05). Also, mean two-dimensional migration rates did not exceed 0.05 mm from 2 years to the last follow-up and remained similar between the groups (p = 0.355). Finally, clinical outcomes also did not differ between the groups (p > 0.05). Two patients required revision surgery. Discussion Femoral head size did not influence midterm annual wear rate, migration rate, and clinical outcomes of VEPE acetabular cups. Furthermore, wear and cup migration rates were below the reported values leading to osteolysis and aseptic loosening. Nevertheless, studies with extended follow-up periods will be necessary to confirm these results in the long term. Level of evidence IV.

Sir,—In a recent correspondence, Dr. Mjoberg questions the role of wear particles in the pathogenesis of periprosthetic osteolysis (Mjoberg et al. 2017). In Dr. Mjoberg’s view, implant wear and wea...

Aseptic loosening of implants remains the most common reason for revision surgery for hip, knee, or ankle prostheses. Although a great scientific effort has been made to explain the underlying mechanisms it remains poorly understood, complex, and multifactorial. Many factors, including age, body weight, activity lesions, implant design, fixation methods, material proprieties, immunologic responses, and biomechanical adaptations to total ankle replacement all contribute to the development of periprosthetic osteolysis.

Background and purpose ��� The long-term survival of arthroplasty components may be limited by polyethylene wear-related problems such as periprosthetic osteolysis and aseptic loosening. Highly cross-linked polyethylene (HXLPE) blended with vitamin E was introduced to improve oxidative stability and to avoid long-term embrittlement. This study clinically compares the tribological behavior and clinical outcome of vitamin E blended HXLPE with ultra-high molecular weight polyethylene (UHMWPE) in an isoelastic monoblock cup for uncemented total hip arthroplasty. Patients and methods ��� In this randomized controlled trial (RCT), 199 patients were included: 102 patients received the vitamin E blended HXLPE cup, 97 patients the UHMWPE cup. Clinical and radiographic parameters were obtained preoperatively, directly postoperative and at 3, 12, and 24 months. Wear rates were compared using the mean linear femoral head penetration (FHP) rate. Results ��� 188 patients (94%) completed the 2-year follow-up. Mean patient satisfaction was higher in the vitamin E blended HXLPE group (8.9 [1]) than in in the control group (8.5 [2], p = 0.03). The Harris Hip Score (HHS) was higher in the vitamin E blended HXLPE group (95 [8]) than in the control group (92 [11], p = 0.3). The FHP rate was lower in the vitamin E blended HXLPE group: 0.046 mm/year compared with 0.056 mm/year in the control group (p = 0.05). No adverse reactions associated with the clinical application of vitamin E blended HXLPE were observed during follow-up, with an excellent 2-year survival to revision rate of 98% for both cups. Interpretation ��� This study shows the superior performance of the HXLPE blended with vitamin E acetabular cup with lower linear femoral head penetration rates and better clinical results compared with the UHMWPE acetabular cup after 2 years.

Highlights • Osteolysis can occur in the patella without a patellar prosthesis. • Increased shelf-age and lower sterilization dose of inserts predispose for osteolysis. • Conventional radiographs lack sensitivity in detecting and monitoring osteolysis. • Insert exchange, implant anchorage/alignment and bone defects are surgical priorities. • Although bone defects can be massive, no total revision is needed with good anchorage., Introduction and importance Periprosthetic osteolysis (PPOL) is a common complication after total knee arthroplasty (TKA) and is most commonly caused by wear-induced particles. Case presentation We report an unusual case of massive bilateral PPOL in the posterior flanges of the femur and patellae 4 years after bilateral uncemented TKA without patellar resurfacing in a 71-year old female. Bilateral staged revision surgery including polyethylene exchange and allograft morselized bone impaction was performed to treat the osteolytic lesions. There were no signs of implant malalignment, polyethylene wear or component loosening. Clinical discussion Several factors are associated with an increased risk on PPOL (e.g. polyethylene sterilization method, patient age, male gender). Surgical intervention in the context of massive PPOL should include replacement of a potential particle generator (most often polyethylene), correction of potential malalignment, treatment of bone defects and assessment of implant anchorage. Conclusion This report highlights the available evidence on clinical presentation, associated risk factors and preferred treatment strategy of massive osteolytic lesions after TKA according to available evidence.

The natural course of adverse events following the use of metal-on-metal (MoM) bearings in total hip arthroplasty (THA) is not well known. In this article, we report the case of a patient with asymptomatic major acetabular osteolysis following MoM THA that diminished gradually without any surgical intervention. A 58-year-old male underwent one-stage bilateral MoM THA for bilateral osteoarthritis. Four years after THA, major acetabular osteolysis developed in his right hip without any local or systemic symptoms. The patient underwent a careful radiographic and clinical observation without any surgical intervention because he did not want to undergo revision surgery. The lesion gradually diminished after 7 years, and most of the osteolytic area was replaced by newly formed bone at 10 years. He continues to be followed with no evidence of cup loosening or migration. Our observation suggests that a periprosthetic osteolytic change related to the use of MoM bearings has the potential for natural remission.

Background: Larger articulations reduce the risk of dislocation following primary total hip arthroplasty, leading to increased use of these articulations. The wear rate of highly cross-linked polyethylene (XLPE) is low in standard-diameter articulations but remains unclear in larger articulations. The aim of this randomized controlled trial was to compare the mean wear rates of 36-mm and 28-mm metal-on-XLPE articulations between 1 and 3 years postoperatively. Methods: Fifty-six elderly patients undergoing primary total hip arthroplasty were randomized intraoperatively to receive either a 36-mm or 28-mm metal-on-XLPE articulation. Factors that may affect wear were controlled by study design. Wear was measured using radiostereometric analysis. Results: Mean annual proximal wear rates between 1 and 3 years were 0.00 and 0.01 mm/yr for the 36 and 28-mm articulation cohorts, respectively. No patient had a proximal wear rate of >0.1 mm/yr. Mean wear was very low in all directions, and the wear rate of 36-mm articulations was not significantly greater than that of 28-mm articulations on the basis of proximal, medial 2-dimensional, and 3-dimensional wear. Conclusions: The wear rate of a larger 36-mm metal-on-XLPE articulation between 1 and 3 years following primary total hip arthroplasty was low and no greater than that of a 28-mm articulation. However, before a 36-mm metal-on-XLPE articulation is widely recommended, particularly in young active patients, long-term wear rates and association between wear and periprosthetic osteolysis should be determined. Level of Evidence: Therapeutic Level II. See Instructions for Authors for a complete description of levels of evidence.

Background Highly cross-linked polyethylene was introduced to decrease periprosthetic osteolysis and reoperation, but this has not been conclusively proven. Methods One surgeon performed 513 consecutive primary total hip arthroplasties (450 patients) using 1 modern, cementless, titanium-mesh acetabular component with screw fixation. This study analyzed the differences in the rate of reoperation and incidence of osteolysis between 133 hips with standard and 112 hips with highly cross-linked polyethylene at minimum 10-year follow-up time. Results Of the entire cohort of 513 hips, no acetabular component was removed or revised for aseptic loosening. There were significantly more reoperations in the cohort with standard polyethylene (11 of 133, 8%) than highly cross-linked polyethylene (1 of 112, 1%; P = .03). Osteolysis was seen in 24% (32 of 133 hips) with standard polyethylene, compared with 13% (15 of 112 hips) with highly cross-linked polyethylene ( P = .02). These differences occurred despite the presence of patients with greater BMI and higher activity in the cohort with highly cross-linked polyethylene. Conclusion We continue to use this acetabular component with highly cross-linked polyethylene. Longer follow-up is required to determine the progression of osteolysis.

Category: Ankle Arthritis; Ankle Introduction/Purpose: Periprosthetic osteolysis in total ankle arthroplasty (TAA) is a substantial problem. It may cause implant failure and has potential to affect long-term implant survival. To prevent major revisional arthroplasty, it is important to make an early diagnosis of osteolysis and decide an appropriate timing of surgical intervention such as bone graft. We report our updated result of bone graft for osteolysis after TAA associated with clinical and radiologic outcome. Methods: We retrospectively evaluated our consecutive series of 440 primary TAAs performed between May 2004 and August 2018 and identified those who had a subsequent bone graft procedure. A total of 38 bone graft procedures for periprosthetic osteolysis after TAA were performed. Mean time-interval between primary TAA and bone graft was 5.09 years (range 17.0 to 127.0 months). Location of osteolysis, bone grafting method and clinical outcome parameters using visual analog scale (VAS), American Orthopaedic Foot & Ankle Society (AOFAS) score were recorded. Results: Radiographs revealed periprosthetic osteolysis in 51.8% (58/112) of distal tibial lesions and 41.1% (46/112) of talar lesions. Autogenous iliac bone graft was used in most of procedures. Both mean VAS and AOFAS scores improved significantly at the last follow-up (pConclusion: Bone graft for periprosthetic osteolysis may improve patient’s clinical outcome and give support to the structures surrounding the implant. Bone grafting in optimal timing may also improve implant survivorship. However, further study is needed for the etiology of newly developed painless osteolysis even after the bone graft.

Supracondylar periprosthetic femoral fractures after total knee arthroplasty are very rare, but very difficult to treat. They occur most often as a result of low energy trauma (slips and fall) in older patients with present osteoporosis and periprosthetic osteolysis. The treatment of these fractures is very difficult due to reduced biological capacity for healing in most cases. Surgical treatment of these fractures is accompanied by severe complications (prolonged healing, nonunion and disintegration osteosintets material) in 25 to 70% of the cases. The aim of this paper is to present the treatment of supracondylar femur fractures after total knee arthroplasty in men aged 72 with selfdynamisable internal fixator Mitkovic. Surgical treatment of fracture performed on the six day after the injury with minimally invasive surgical technique through two incisions. Verticalization and walking with crutches with non-weight-bearing started the first postoperative day. Patient discharged from hospital fifth postoperative day. Full weight-bearing on the operated leg is allowed after 6 weeks. The patient started a stationary physical therapy 6 weeks after surgery. Postoperative follow-up was 10 months. The fractures healed with an excellent functional result. Application of selfdynamisable internal fixator Mitkovic with minimally invasive technique in the treatment of these complex fractures provides excellent biomechanical conditions for healing.

Periprosthetic osteolysis and subsequent aseptic loosening of total joint replacements are driven by byproducts of wear released from the implant. Wear particles cause macrophage-mediated inflammation that culminates with periprosthetic bone loss. Most current animal models of particle-induced osteolysis are based on the acute inflammatory reaction induced by wear debris, which is distinct from the slowly progressive clinical scenario. To address this limitation, we previously developed a murine model of periprosthetic osteolysis that is based on slow continuous delivery of wear particles into the murine distal femur over a period of 4 weeks. The particle delivery was accomplished by using subcutaneously implanted osmotic pumps and tubing, and a hollow titanium rod press-fit into the distal femur. In this study, we report a modification of our prior model in which particle delivery is extended to 8 weeks to better mimic the progressive development of periprosthetic osteolysis and allow the assessment of interventions in a setting where the chronic particle-induced osteolysis is already present at the initiation of the treatment. Compared to 4-week samples, extending the particle delivery to 8 weeks significantly exacerbated the local bone loss observed with μCT and the amount of both peri-implant F4/80+ macrophages and tartrate-resistant acid phosphatase-positive osteoclasts detected with immunohistochemical and histochemical staining. Furthermore, systemic recruitment of reporter macrophages to peri-implant tissues observed with bioluminescence imaging continued even at the later stages of particle-induced inflammation. This modified model system could provide new insights into the mechanisms of chronic inflammatory bone loss and be particularly useful in assessing the efficacy of treatments in a setting that resembles the clinical scenario of developing periprosthetic osteolysis more closely than currently existing model systems.

Category: Ankle Arthritis Introduction/Purpose: Periprosthetic osteolysis in total ankle arthroplasty (TAA) is a substantial problem. It may cause implant failure and has potential to affect long-term implant survival. To prevent major revisional arthroplasty, it is important to make an early diagnosis of osteolysis and decide an appropriate timing of surgical intervention such as bone graft. We report our experience of bone graft for osteolysis after TAA associated with clinical and radiologic outcome. Methods: Between May 2004 and Oct. 2013, 238 primary TAA were performed on 219 patients. We excluded 37 ankles with follow-up less than 24 months; thus, 201 ankles in 185 patients with mean follow-up of 61.9 (range, 24-130) months were included in the study. Nineteen patients were treated with a total of 21 bone graft procedures for periprosthetic osteolysis after TAA. Of these patients, 12 (57.1%) were males with mean follow-up length after bone graft 35.0 months. Location of osteolysis, bone grafting method and clinical outcome parameters using visual analog scale (VAS), American Orthopaedic Foot and Ankle Society (AOFAS) score were recorded. Results: Radiographs revealed total of 62 osteolysis lesions in 19 patients; 35 (56.5%) distal tibial lesions, 23 (37.0%) talar lesions. Autogenous iliac bone graft was used in 18 procedures (85.7%). The mean scores (and standard deviation) improved for the VAS from 4.8 ± 1.23 points before bone graft to 3.0 ± 0.94 points at the last follow-up (pConclusion: Bone graft for periprosthetic osteolysis may improve patient’s clinical outcome and give support to the structures surrounding the implant. Bone grafting in optimal timing may also improve implant survivorship. However, further study is needed for the etiology of newly developed painless osteolysis even after the bone graft.

Background Periprosthetic osteolysis (PPO) is a frequent indication for total hip replacement (THR) failure. Currently, PPO diagnosis occurs in advanced stages that often necessitate complex revisions due to bone loss. PPO biomarkers could facilitate earlier diagnosis. Alternative macrophage activation pathway regulators, chitotriosidase (CHIT1) and CC chemokine ligand 18 (CCL18), have increased periprosthetic expression in patients undergoing revision THR for osteolysis. We hypothesized that synovial fluid and serum levels of CHIT1 and CCL18 would be increased in patients undergoing revision THR for PPO versus controls without osteolysis. Methods In this prospective case-control study, 60 patients undergoing revision metal-on-polyethylene THR at Hospital for Special Surgery were screened preoperatively from January 2013 to December 2014. Twenty “osteolysis” patients who underwent revision for PPO (based on imaging and operative reports) and 10 “control” patients (with stable implants) who underwent revision for recurrent dislocation or a mechanical etiology were included. Among osteolysis and control patients, 11/20 and 4/10 were male; average age was 68 and 63 years, respectively; 9/20 and 3/10 had cemented femoral components; and average implant longevity was 15 and 5 years, respectively. Preoperative serum and intraoperative synovial fluid samples were collected. CHIT1 and CCL18 were quantified via enzyme-linked immunosorbent assay. Significance was assessed via nonparametric Mann-Whiney U test. Results CHIT1 was significantly increased in both synovial fluid (3727 versus 731 nanomoles [nM]) and serum (98 versus 39 nM) in the osteolysis versus control patients. CCL18 levels were also significantly increased in osteolysis versus control patients’ synovial fluid (425 versus 180 nM) but not their serum. Conclusions In this prospective case-control study, CHIT1 was identified as a novel synovial fluid and serum biomarker of PPO. CHIT1 expression is induced during macrophage activation in response to wear debris. CHIT1 monitoring may facilitate early diagnosis of THR PPO. Furthermore, CHIT1 may represent a novel therapeutic target for PPO. Electronic supplementary material The online version of this article (10.1007/s11420-017-9598-9) contains supplementary material, which is available to authorized users.

Osteolysis around joint replacements may develop due to migration of wear particles from the joint space into gaps between the interface bone and the implant where they can accumulate in high concentrations to cause tissue damage. Osteolysis may appear in various postoperative times and morphological shapes which can be generalized into linear and focal. However, there are no clear explanations on the causes of such variations. Patients’ degree of sensitivity to polyethylene particles (osteolysis thresholds), the local particle concentration and the access route provided by the interface gaps have been described as determining factors. To study their effects, a 2D computational fluid dynamics model of the hip joint capsule in communication with an interfacial gap and the surrounding bone was employed. Particles were presented using a discrete phase model (DPM). High capsular fluid pressure was considered as the driving force for particle migration. Simulations were run for different osteolysis thresholds ranging from 5×1085×108 to 1×10121×1012 particle number per gram of tissue and fibrous tissue generation in osteolytic lesion due to particles was simulated for the equivalent of ten postoperative years. In patients less sensitive to polyethylene particles (higher threshold), osteolysis may be linear and occur along an interfacial gap in less than 5% of the interfacial tissue. Focal osteolysis is more likely to develop in patients with higher sensitivity to polyethylene particles at distal regions to an interfacial gaps where up to 80% of the interfacial tissue may be replaced by fibrous tissue. In these patients, signs of osteolysis may also develop earlier (third postoperative year) than those with less sensitivity who may show very minor signs even after ten years. This study shows the importance of patient sensitivity to wear particles, the role of interfacial gaps in relation to morphology and the onset of osteolysis. Consequently, it may explain the clinically observed variation in osteolysis development.

Biological responses to wear debris were largely elucidated in studies focused on conventional ultrahigh-molecular-weight polyethylene (UHMWPE) and some investigations of polymethymethacrylate cement and orthopaedic metals. However, newer bearing couples, in particular metal-on-metal but also ceramic-on-ceramic bearings, may induce different biological reactions.Does wear debris from the newer bearing surfaces result in different biological responses compared with the known responses observed with conventional metal-on-UHMWPE bearings?A Medline search of articles published after 1996 supplemented by a hand search of reference lists of included studies and relevant conference proceedings was conducted to identify the biological responses to orthopaedic wear debris with a focus on biological responses to wear generated from metal-on-highly crosslinked polyethylene, metal-on-metal, ceramic-on-ceramic, and ceramic-on-polyethylene bearings. Articles were selected using criteria designed to identify reports of wear debris particles and biological responses contributing to prosthesis failure. Case reports and articles focused on either clinical outcomes or tribology were excluded. A total of 83 papers met the criteria and were reviewed in detail.Biological response to conventional UHMWPE is regulated by the innate immune response. It is clear that the physical properties of debris (size, shape, surface topography) influence biological responses in addition to the chemical composition of the biomaterials. Highly crosslinked UHMWPE particles have the potential to alter, rather than eliminate, the biological response to conventional UHMWPE. Metal wear debris can generate elevated plasma levels of cobalt and chromium ions. These entities can provoke responses that extend to the elicitation of an acquired immune response. Wear generated from ceramic devices is significantly reduced in volume and may provide the impression of an "inert" response, but clinically relevant biological reactions do occur, including granulomatous responses in periprosthetic tissues.The material composition of the device, the physical form of the debris, and disease pathophysiology contribute to complex interactions that determine the outcome to all wear debris. Metal debris does appear to increase the complexity of the biological response with the addition of immunological responses (and possibly direct cellular cytotoxicity) to the inflammatory reaction provoked by wear debris in some patients. However, the introduction of highly crosslinked polyethylene and ceramic bearing surfaces shows promising signs of reducing key biological mechanisms in osteolysis.

Background and Literature Review Periprosthetic osteolysis (PPO) after second- or third-generation total wrist arthroplasty (TWA), with or without evident loosening of the implant components, has previously been reported in the literature, but rarely in a systematic way. Purpose The purpose of this study was to analyze the prevalence, location, and natural history of PPO following a TWA and to determine whether this was associated with prosthetic loosening. Patients and Methods We analyzed 44 consecutive cases in which a RE-MOTION TWA (Small Bone Innovations Inc., Morrisville, PA, USA) had been done. Results We found significant periprosthetic radiolucency (more than 2 mm in width) at the radial component side in 16 of the cases and at the carpal component side in 7. It developed gradually juxta-articularly around the prosthetic components regardless of the primary diagnosis, and seemed to stabilize in most patients after 1-3 years. In a small percentage of the patients, the periprosthetic area of bone resorption was markedly larger. In general, radiolucency was not related to evident loosening of the implant components, and only five carpal components and one radial had subsided or tilted. Conclusion Periprosthetic loosening is frequent following a TWA. In our series it was not necessarily associated with implant loosening and seemed to stabilize within 3 years. Close and continued observation is, however, recommended. Level of Evidence Therapeutic IV.

Intracapsular femoral neck fractures are very common orthopedic injuries; total hip arthroplasty has been demonstrated to be an optimal option, but one of the major concerns remains the fact that it may dislocate. The aim of this study is to retrospectively review patients with a displaced intracapsular femoral neck fracture who underwent total hip arthroplasty to realize whether the use of large-diameter ceramic-on-ceramic coupling has the potential to substantially reduce the risk of such a complication. Among 690 hip replacements performed in a period of 8 years, we have selected 86 total hip arthroplasties done for displaced intracapsular fracture of the femoral neck in 64 women and 22 men with a mean age at operation of 67.9 years. Ceramic-on-ceramic coupling was chosen in 38 cases, a 36-mm head was used in 36 cases. At the latest follow-up, there were no cases requiring revision surgery and periprosthetic osteolysis was undetectable. There were no cases of dislocations. New-generation ceramic-on-ceramic bearings with heads of large diameter should therefore be considered to address the problem of dislocation after total hip replacement is done for displaced femoral neck fracture.

To prevent periprosthetic osteolysis and subsequent aseptic loosening of artificial hip joints, we recently developed a novel acetabular highly cross-linked polyethylene (CLPE) liner with graft polymerization of 2-methacryloyloxyethyl phosphorylcholine (MPC) on its surface. We investigated the wear resistance of the poly(MPC) (PMPC)-grafted CLPE liner during 20 million cycles in a hip joint simulator. We extended the simulator test of one liner to 70 million cycles to investigate the long-term durability of the grafting. Gravimetric, surface, and wear particle analyses revealed that PMPC grafting onto the CLPE liner surface markedly decreased the production of wear particles and showed that the effect of PMPC grafting was maintained through 70 million cycles. We believe that PMPC grafting can significantly improve the wear resistance of artificial hip joints. © 2013 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 32:369–376, 2014.

Background: Periprosthetic osteolysis in total ankle arthroplasty (TAA) is a substantial problem. We report the incidence and characteristics of periprosthetic osteolysis and its association with clinical outcomes after TAA using the HINTEGRA ankle system. Methods: Between May 2004 and April 2010, 126 primary TAA were performed on 115 patients. We excluded 27 ankles with a follow-up of less than 24 months; thus, 99 ankles in 90 patients with a mean follow-up of 40.8 (range, 24–89) months were included in the study. Pain and clinical outcomes were assessed using the visual analog scale and the American Orthopaedic Foot and Ankle Society score. Fluoroscopy was used for optimum visualization of the bone-implant interfaces on radiographs. Computed tomography (CT) was conducted on 25 ankles that exhibited progression of osteolysis. Results: Radiographs revealed that 37 of the 99 ankles showed radiologic evidence of osteolysis; of these, 10 demonstrated continuous progression over the study period. Helical CT scans were more accurate than radiographs for identifying and measuring periprosthetic osteolysis in TAA. None of the demographic parameters were substantially different between the 2 groups of subjects (with or without osteolysis). No major association was found between the presence of osteolysis and clinical and radiologic outcomes. Conclusion: Osteolysis associated with TAA may indeed be common in the postoperative period. Although most of the osteolytic lesions observed here were relatively quiescent, these lesions raise concerns in contemporary TAA because of their incidence rate and the potential for later mechanical failure as compared to arthrodesis. Early diagnosis and careful evaluation of osteolysis may provide a clinical opportunity for limited revision surgery in ankles of impending prosthesis failure. Level of Evidence: Level IV, case series.

Patients with ASR implants (resurfacing and large-diameter (XL) metal-on-metal (MoM) total hip arthroplasty), even if asymptomatic and with a stable prosthesis, may present extremely high blood metal ion levels. We report on a consecutive series of fourteen ASR revisions, focusing on osteolysis and their radiographic correspondence and their correlation with blood metal ion levels. At revision, seven hips revealed severe periacetabular osteolysis which was radiographically undetectable in six and asymptomatic in five. Seven hips with no acetabular osteolysis had significantly lower serum Cr and Co ion concentrations (respectively 25.2, 41.1 μg/l) compared to the seven hips with severe acetabular bone loss (respectively 70.1, 147.0 μg/l). Elevated blood metal ion levels should be considered as a warning of undetectable and ongoing periprosthetic osteolysis in asymptomatic patients with ASR prosthesis.

Background Polyethylene acetabular components are common in hip arthroplasty. Highly cross-linked polyethylene (HXLPE) has lower wear than ultra-high molecular weight polyethylene (UHMWPE). Evidence suggests that wear particles induce inflammation causing periprosthetic osteolysis contributing to implant loosening with wear rates of 0.05 mm/y were considered safe. We aimed to compare incidence and volume of periacetabular osteolysis between HXLPE and UHMWPE using computed tomography. Methods Initially, 54 hips in 53 patients were randomized to HXLPE or UHMWPE acetabular liner. At 10 years, 39 hips in 38 patients remained for the radiostereometric analysis' demonstrating significantly lower wear in the HXLPE group. At 12 years, 14 hips in 13 patients were lost to follow-up leaving 25 hips for computed tomography assessment. Images were reconstructed to detect osteolysis and where identified, areas were segmented and volumized. Results Osteolysis was observed in 8 patients, 7 from the UHMWPE group and only 1 from the HXLPE group (Fisher exact, P = .042). There was no correlation between the amount of polyethylene wear and osteolysis volume; however, the radiostereometric analysis-measured wear rate in patients with osteolysis from both groups was significantly higher than overall average wear rate. Conclusion This data demonstrates lower incidence of periacetabular osteolysis in the HXLPE group of a small cohort. Although numbers are too low to estimate causation, in the context of lower wear in the HXLPE group, this finding supports the hypothesis that HXLPE may not elevate osteolysis risk, and hence does not suggest that HXLPE wear particles are more biologically active than those generated by earlier generations of polyethylene.

Loosening and periprosthetic osteolysis are some of the most common long-term complications after hip arthroplasty. The decision-making process and surgical treatment options are controversial.We retrospectively reviewed 96 acetabular revisions (91 patients) performed between 2002 and 2012, with a minimum of 2 years of follow-up and a mean of 5.7 years of follow-up. Clinical outcome was assessed using the Harris Hip Score. The size and location of osteolytic lesions were evaluated using the preoperative radiographs; healing of the defects was categorized using a standardized protocol.Thirty-three (34.4%) hips had isolated liner exchanges (ILEs), 10 (10.4%) hips had cemented liners into well-fixed shells (CLS), 45 (46.9%) hips had full acetabular revisions (FARs), and 8 (8.3%) hips had revision with a roof ring/antiprotrusio cage (RWC). All procedures showed significant improvement in Harris Hip Score after revision (P ≤ .001). Fifteen patients had moderate residual pain (pain score ≤20): 8 (24%) ILE, 3 (30%) CLS, and 4 (9%) FAR. Complete bone defect healing after grafting was lower with acetabular component retention procedures (ILE and CLS; 27%) compared with full acetabular component revision procedures (FAR and RWC; 57%). Fifteen patients underwent reoperation: 3 ILE, 1 CLS, 8 FAR, and 3 RWC.Acetabular component retention demonstrates a low risk of reoperation; however, residual pain and limited potential for bone graft incorporation are a concern. FAR is technically challenging and may have an elevated risk of reoperation; however, higher degrees of bone graft incorporation and satisfactory clinical outcome can be expected.

Polyethylene wear is an important factor in failure of total hip arthroplasty (THA). With increasing numbers of THAs being performed worldwide, particularly in younger patients, the burden of failure and revision arthroplasty is increasing, as well, along with associated costs and workload. Various radiographic methods of measuring polyethylene wear have been developed to assist in deciding when to monitor patients more closely and when to consider revision surgery. Radiographic methods that have been developed to measure polyethylene wear include manual and computer-assisted plain radiography, two- and three-dimensional techniques, and radiostereometric analysis. Some of these methods are important in both clinical and research settings. CT has the potential to provide additional information on component orientation and enables assessment of periprosthetic osteolysis, which is an important consequence of polyethylene wear.

Rodolfo Perez Alamino, Carolina Casellini, Andrea Banos, Emilce Edith Schneeberger, Susana Alicia Gagliardi, José Antonio Maldonado Cocco, Gustavo CiteraSection of Rheumatology, Instituto de Rehabilitación Psicofísica, Buenos Aires, ArgentinaAbstract: Periprosthetic osteolysis (PO) is a frequent complication in patients with joint implants. There are no data regarding the prevalence of PO in patients with rheumatoid arthritis (RA), juvenile chronic arthritis (JCA), ankylosing spondylitis (AS), and osteoarthritis (OA).Objectives: To evaluate the prevalence of PO in patients with RA, JCA, AS, and OA, who have undergone total hip replacement (THR), and to identify factors associated with its development.Methods: The study included patients diagnosed with RA (ACR 1987), AS (modified New York criteria), JCA (European 1977 criteria), and osteoarthritis (OA) (ACR 1990 criteria) with unilateral or bilateral THR. Demographic, clinical, and therapeutic data were collected. Panoramic pelvic plain radiographs were performed, to determine the presence of PO at acetabular and femoral levels. Images were read by two independent observers.Results: One hundred twenty-two hip prostheses were analyzed (74 cemented, 30 cementless, and 18 hybrids). The average time from prosthesis implantation to pelvic radiograph was comparable among groups. PO was observed in 72 hips (59%). In 55% of cases, PO was detected on the femoral component, with a lower prevalence in RA (53%) vs AS (64.7%) and JCA (76.5%). Acetabular PO was more frequent in JCA patients (58.8%), compared with RA (11.6%) and OA (28.5%) patients (P = 0.0001 and P = 0.06, respectively). There was no significant association between the presence of PO and clinical, functional, or therapeutic features.Conclusion: The prevalence of PO was 59%, being more frequent at the femoral level. Larger studies must be carried out to determine the clinical significance of radiologic PO.Keywords: periprosthetic osteolysis, hip prosthesis, rheumatoid arthritis, juvenile chronic arthritis, ankylosing spondylitis

Aseptic and septic periprosthetic osteolysis following total hip arthroplasty has become increasingly recognized as a major clinical problem. An aggressive granulomatous tissue, the interfacial membrane, develops at the interface between the bone and the prostheses or the bone and the cement. Our hypothesis was that during the septic and aseptic loosening of the total hip arthroplasty, there is a clear pathological abnormality in the tissue elements building up the interfacial membrane, which is responsible for the different aetiologies of the disease and could be monitored besides the classical methods by differential scanning calorimetry. In our study, the interfacial membrane pieces removed during operations of revision hip arthroplasties in the cases of aseptic loosening and during prosthesis removals in the cases of septic implant loosening. We investigated stem parts of cemented hip arthroplasties only. Our measurements were carried out on eight septic and 12 aseptic samples. With our investigations, we could demonstrate that DSC is a useful and well-applicable method for the investigation of the interfacial membrane that develops in septic and aseptic loosening of hip arthroplasty. DSC scans clearly demonstrated significant differences between the different types and conditions of samples (aseptic membrane: T m = 62.2 °C and ΔH cal = 2.13 J/g, septic membrane: T m = 60.2 °C and ΔH cal = 3.22 J/g,). These investigations can help us make a correct diagnosis in the problematic cases of loosened total hip arthroplasty. To decide the possible septic feature of a given sample, calorimetry could serve as one of the quickest procedures available.

Periprosthetic osteolysis is one of the leading causes of total joint revision procedures. If allowed to progress in the absence of radiographic diagnosis and/or proper medical treatment, osteolysis may result in aseptic loosening yielding failure of the implant and the need for complex revision arthroplasty. The purpose of this review was to assess the current understanding of periprosthetic osteolysis with an emphasis on host factors and future directions. A PubMed search was conducted using the following key words; osteolysis, periprosthetic osteolysis, osteolysis imaging. Pertinent articles, as it pertained to the outline of the review, were selected. Periprosthetic osteolysis stems from numerous risk factors. Osteolysis host characteristic risk factors include gender, body weight, and genetics. Current implant designs have reduced the incidence of this disease; however no current design has been able to replicate the in vivo characteristics and therefore development of wear particles continues to be seen. Advanced methods of imaging diagnosis are on the rise, however early imaging diagnosis is currently ineffective. Pharmacologic intervention appears to be a logical avenue for medical intervention, but no approved drug therapy to prevent or inhibit periprosthetic osteolysis is currently available. Although the rate of periprosthetic osteolysis seems to be decreasing with advances in implant design and increased knowledge of the biological process of wear particle induced osteolysis, the rapid increase in the total number of total joint arthroplasties over the next two decades means that better ways of detecting and treating periprosthetic osteolysis are greatly needed.

Aseptic osteolysis has been the single most important factor limiting the longevity of a THA. A great deal of attention has been focused on the development of implants and materials that minimize the development of osteolysis. The monoblock porous tantalum acetabular cup was designed to minimize osteolysis, but whether it does so is unclear.We evaluated the incidence of osteolytic lesions after THA using a monoblock porous tantalum acetabular component.We retrospectively reviewed 51 patients who had a THA using a monoblock porous tantalum acetabular cup. At a minimum of 9.6 years postoperatively (average, 10.3 years; SD, 0.2 years; range, 9.6-10.8 years), a helical CT scan of the pelvis using a metal suppression protocol was obtained. This scan was evaluated for the presence of osteolysis.We found no evidence of osteolysis on CT scan at an average of 10.3 years.Osteolysis appears not to be a major problem at 10 years with this monoblock porous tantalum acetabular component, but longer term followup will be required to determine whether these findings persist.Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Introduction Magnetic resonance imaging (MRI) is useful in assessing bone and soft tissue lesions due to the production of wear particles. Our objective was to study the distribution of lesions in patients with one type of cementless acetabular component with this technique. Material and methods We included 40 total hip arthroplasty with press-fitted hydroxyapatite porous-coated cup and multiple optional screw holes performed over a mean of 13 years. We studied the presence, extent and continuity of the granulomatous lesion and osteolysis with MRI using special pulse sequences to reduce metal artefacts. Results One hip was not amenable to analysis. An isolated granulomatous lesion was found in 3 hips, associated osteolysis in 32, in the pelvis only in 10, in the femur only in 3 and in both segments in 19. By zones, the pelvis involvement was supra-acetabular ilium in 15, ischium-pubic branch in 24, ischium in 12 and retro-acetabular ischium in 21. Only two hips and two screws central lesions were isolated from the granulomatous mass. Comments and conclusions MRI osteolysis and soft tissue lesions secondary to wear to be studied. The distribution of osteolytic areas show a peripheral pattern typical of nonperforated acetabular cups frequently coexisting with proximal femoral involvement, highlighting few isolated lesions in the holes or around the implanted screws.

The long-term durability of polyethylene lining total hip arthroplasty (THA) mainly depends on periprosthetic osteolysis due to wear particles, especially in young active patients. In hip simulator study, reports revealed significant wear reduction of the alumina ceramic-on-polyethylene articulation of THA compared with metal-on-polyethylene bearing surfaces. However, medium to long-term clinical studies of THA using the alumina ceramic-on-polyethylene are few and the reported wear rate of this articulation is variable. We reviewed the advantages and disadvantages of ceramicon- polyethylene articulation in THA, hip simulator study and retrieval study for polyethylene wear,in vivoclinical results of THA using alumina ceramic-on-polyethylene bearing surfaces in the literature, and new trial alumina ceramic-onhighly cross linked polyethylene bearing surfaces.

This study determined the accuracy of plain radiography in detecting osteolytic lesions around total knee prostheses compared to multi-detector computed tomography (CT). Thirty-one patients diagnosed with periprosthetic osteolysis by multi-detector CT after total knee arthroplasty (TKA) were studied. Computed tomography for each patient was retrospectively reviewed in a blinded fashion. The plain radiographs for each patient that had been obtained prior to CT were reviewed in the same manner. The results of the CT were compared with the results of the radiographs. The number, size, and location of the lesions were compared. The multi-detector CT detected 48 lesions in 31 knees: 40 tibial lesions, 4 femoral lesions, and 4 patellar lesions. Radiographic diagnosis was made in 6 of the 40 tibial lesions, 2 of the 4 femoral lesions, and 0 of the 4 patellar lesions. Plain radiographs are inadequate for evaluating periprosthetic osteolysis in TKA with only 8 (17%) of 48 lesions detected by multi-detector CT visible on the standard radiographs. Multi-detector CT provides the surgeon with a diagnostic and preoperative planning tool when osteolysis is suspected.

Polyethylene wear of acetabular components is a key factor in the development of periprosthetic osteolysis and wear at the articular surface has been well documented and quantified, but fewer data are available about changes which occur at the backside of the liner. At revision surgery for loosening of the femoral component we retrieved 35 conventional modular acetabular liners of the same design. Linear and volumetric articular wear, backside volumetric change and the volume of the screw-head indentations were quantified. These volumes, clinical data and the results from radiological Ein Bild Röntgen Analyse migration analysis were used to identify potential factors influencing the volumetric articular wear and backside volumetric change. The rate of backside volumetric change was found to be 2.8% of the rate of volumetric articular wear and decreased with increasing liner size. Migrated acetabular components showed significantly higher rates of backside volumetric change plus screw-head indentations than those without migration. The backside volumetric change was at least ten times larger than finite-element simulation had suggested. In a stable acetabular component with well-anchored screws, the amount of backside wear should not cause clinical problems. Impingement of the screw-heads could produce more wear particles than those generated at the liner-shell interface. Because the rate of backside volumetric change is only 2.8% of the rate of volumetric articular wear and since creep is likely to contribute a significant portion to this, the debris generated by wear at the backside of the liner may not be sufficient to create a strong osteolytic response.

Polymethylmethacrylate (PMMA) particles generated from joint arthroplasties appear to contribute to aseptic implant loosening through inflammation-induced periprosthetic osteolysis. However, osteolysis appears to be multifactorial; whether a direct link exists between PMMA particles and osteolysis in vivo is unproven. With the aim to define the relationship between PMMA particles and osteolysis, the authors analyzed the bone mineral density, using microCT scans preoperatively, the first day postoperatively and then every 7–10 days for 32 days, and bone turnover, using 18F-fluoride positron emission tomography scanner (PET scan) at 8 weeks in four groups of mice that had undergone intramedullary femoral injection. The experimental group of five mice was injected with PMMA particles, and compared with two negative control groups (no injection and injection with the carrier, phosphate-buffered saline) and one positive control group (injection of PMMA particles contaminated with endotoxin). There was no significant change in bone mineral density with addition of PMMA particles, and no evidence of osteolysis. However, bone turnover was increased in the presence of PMMA particles. Even though a direct link between PMMA particles and osteolysis was not found in the short term, PMMA particles appear to influence the regenerative capacity of bone. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2009

Highly cross-linked polyethylene (XLPE) has been introduced in total hip arthroplasty in an effort to reduce polyethylene wear and the associated periprosthetic osteolysis. Our aim was to demonstrate these reduced wear rates in a 2-dimensional head penetration model and to perform a clinical comparison of both groups using the Harris Hip Score (and SF-36 questionnaire). Sixty hips with a Trilogy XLPE liner (Zimmer) were matched and compared to a control group of 20conventional Trilogy PE liners (Zimmer). No differences in clinical outcome were seen, but a statistically significant reduction in linear wear was observed in the XLPEgroup, after 5 years. It is clear that, because of the reduction and stabilization offree radicals in polyethylene, a reduction in annual wear can be achieved.

Joint replacements of the hip and knee are among the most clinically successful operations. According to figures compiled by the American Academy of Orthopaedic Surgeons, the number of primary total hip replacements performed in the USA was 220,000 in 2003. This was 38% more than in 1996 and this number is expected to rise to 572,000 (plus another 97,000 revisions) by 2030. The number of primary total knee replacements performed in 2003 was approximately 418,000 and is expected to rise exponentially with the increasing numbers of baby boomers and the aging population. Current research focuses not only on extending implant longevity, but also on improving function to meet the increased demands of today's patients, who are likely to be younger and more active than their predecessors two decades ago. Potential advancements in arthroplasty surgery include new, more wear-resistant bearing surfaces, porous metals to enhance osseointegration and replace lost bone stock, a clearer understanding of the biological processes associated with periprosthetic osteolysis, minimally invasive surgery and computer assisted surgery. Long-term studies are needed to establish the efficacy of these new technologies.

Understanding the complex cellular and tissue mechanisms and interactions resulting in periprosthetic osteolysis requires a number of experimental approaches, each of which has its own set of advantages and limitations. In vitro models allow for the isolation of individual cell populations and have furthered our understanding of particle-cell interactions; however, they are limited because they do not mimic the complex tissue environment in which multiple cell interactions occur. In vivo animal models investigate the tissue interactions associated with periprosthetic osteolysis, but the choice of species and whether the implant system is subjected to mechanical load or to unloaded conditions are critical in assessing whether these models can be extrapolated to the clinical condition. Rigid analysis of retrieved tissue from clinical cases of osteolysis offers a different approach to studying the biologic process of osteolysis, but it is limited in that the tissue analyzed represents the end-stage of this process and, thus, may not reflect this process adequately.

Periprosthetic osteolysis secondary to wear-induced particle generation is a common long-term complication of hip and knee replacement and frequently results in the need for revision surgery. Management of significant bone defects remains a surgical challenge. Surgical intervention must address the wear particle generator (usually, but not always, the bearing surface), the osteolytic defects, and implant-related issues, primarily fixation and alignment. Indications for surgical intervention in the absence of loosening and pain are not well established. In general, patient age and activity level, the location and size of the osteolytic defect, and the clinical record of the implant system will dictate treatment choices.

Periprosthetic osteolysis is most often diagnosed by plain radiographs. Because these radiographs routinely underestimate the extent of the lesion, three-dimensional imaging should be used early in the evaluation process to confirm the presenting extent of disease. If the osteolytic process is asymptomatic, scheduled regular follow-up should be instituted until the lesion can be confirmed to be stable or until the decision is made to proceed with surgery. Nonsurgical management with pharmacologic agents has not proved to be effective. If surgery is contemplated, a three-dimensional evaluation with magnetic resonance imaging or helical computed tomography can assist in preoperative planning. Surgical intervention requires complete débridement of the lesional membrane and removal of the wear-generator--with or without component removal and with or without bone grafting, depending on the individual circumstances. A standardized follow-up evaluation mechanism for all patients should be a part of total joint arthroplasty management.

Background:Inflammatory responses to wear debris cause osteolysis that leads to aseptic prosthesis loosening and hip arthroplasty failure. Although osteolysis is usually associated with aseptic loosening, it is rarely seen around stable implants. Aseptic implant loosening is a simple radiologic phenomenon, but a complex immunological process. Particulate debris produced by implants most commonly causes osteolysis, and this is called particle-associated periprosthetic osteolysis (PPO).Objective:The objective of this review is to outline the features of particle-associated periprosthetic osteolysis to allow the physician to recognise this condition and commence early treatment, thereby optimizing patient outcome.Methods:A thorough literature search was performed using available databases, including Pubmed, to cover important research published covering particle-associated PPO.Results:Although osteolysis causes bone resorption, clinical, animal, andin vitrostudies of particle bioreactivity suggest that particle-associated PPO represents the culmination of several biological reactions of many cell types, rather than being caused solely by the osteoclasts. The biological activity is highly dependent on the characteristics and quantity of the wear particles.Conclusion:Despite advances in total hip arthroplasty (THA), particle-associated PPO and aseptic loosening continue to be major factors that affect prosthetic joint longevity. Biomarkers could be exploited as easy and objective diagnostic and prognostic targets that would enable testing for osteolysis after THA. Further research is needed to identify new biomarkers in PPO. A comprehensive understanding of the underlying biological mechanisms is crucial for developing new therapeutic interventions to reverse or suppress biological responses to wear particles.

Periprosthetic osteolysis is one of the most serious long-term problems in total hip arthroplasty. It has been primarily attributed to the body's inflammatory response to submicron polyethylene particles worn from the hip implant, and it leads to bone loss and structural deterioration in the surrounding bone. It was previously demonstrated that radiographic texture analysis (RTA) has the ability to distinguish between osteolysis and normal cases at the time of clinical detection of the disease; however, that analysis did not take into account the changes in texture over time. The goal of this preliminary analysis, however, is to assess the ability of temporal radiographic texture analysis (tRTA) to distinguish between patients who develop osteolysis and normal cases. Two tRTA methods were used in the study: the RTA feature change from baseline at various follow-up intervals and the slope of the best-fit line to the RTA data series. These tRTA methods included Fourier-based and fractal-based features calculated from digitized images of 202 total hip replacement cases, including 70 that developed osteolysis. Results show that separation between the osteolysis and normal groups increased over time for the feature difference method, as the disease progressed, with area under the curve (AUC) values from receiver operating characteristic analysis of 0.65 to 0.72 at 15 years postsurgery. Separation for the slope method was also evident, with AUC values ranging from 0.65 to 0.76 for the task of distinguishing between osteolysis and normal cases. The results suggest that tRTA methods have the ability to measure changes in trabecular structure, and may be useful in the early detection of periprosthetic osteolysis.

Bisphosphonates are promising in the treatment of periprosthetic osteolysis induced by particulate wear debris. The in vivo effects of pamidronate with different doses and durations of administration on bone-titanium attachment in the presence of endotoxin-coated polyethylene particles were examined in a rat model in this study. Titanium pins and endotoxin-coated polyethylene particles were introduced into rat femoral canals followed by intraperitoneal injection of pamidronate every other day. The treatment varied in the dose from 0 to 40 μg/kg and the duration of either 10 days or 6 weeks. Bilateral femurs were harvested after 6 weeks and examined by bone densitometer and MicroCT scan. Pamidronate increased the bone density of the left, unoperated femurs in a dose and duration dependent manner. Bone-titanium attachment significantly increased in all treatment groups compared to the control group. When pamidronate was administered for 10 days, the increase of bone-titanium attachment was significantly dose-dependent. However, when pamidronate was given for 6 weeks at 4 μg/kg, the bone-titanium attachment was significantly (p < 0.001) lower compared to the 10 day treatment of the same dose, although it was significantly higher than controls. Our results suggest that pamidronate effectively increase bone-titanium attachment even in the presence of endotoxin-coated polyethylene particles. However, long-term administration may reduce its efficacy. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2007

Gene therapy is a technique that draws on the introduction of new genes into cells for the purpose of treating disease by restoring or adding gene expression. Numerous growth factors and other proteins with the ability to promote the regeneration of tissues in the locomotive system have been identified, but their clinical use is often hindered by delivery problems. In principle, these problems can be overcome by delivering the relevant genes, as the therapeutic substances thereby can be persistently produced directly by local cells at the site of diseases.Articular chondrocytes are receptive to transduction using various gene delivery methods. Following genetic modification, they are capable of sustained expression of transgene products at biologically relevant levels. Our research has proved the AAV vector to be an effective tool for gene delivery to articular chondrocytes in vitro as well as in vivo. To this end, we have demonstrated that the AAV vector mediated TGFbeta1-overexpression stimulates cartilage anabolism. WEAR DEBRIS-INDUCED OSTEOLYSIS: The RANKL system may be a key therapeutic target in treatment of aseptic periprosthetic loosening. We investigated whether gene transfer of OPG using an AAV vector has protective effects against orthopaedic wear debris-induced bone loss. In osteoclastogenesis and in bone wafer resorption assays, the bioactivity of the transgene OPG was proven by depletion of osteoclastogenesis and reduced bone resorption. Using an in vivo model of debris-induced bone resorption, we demonstrated complete inhibition of osteolysis in animals receiving AAV-OPG gene therapy.The success of future OPG treatment of osteoporosis is highly dependent on its effects on fracture healing and remodelling. Using an in vivo fracture healing model, our studies demonstrated that AAV-OPG gene therapy did not conflict with normal bone healing, in contrast to high-dosage intravenous treatment with OPG. However, AAV-OPG therapy depressed remodelling and integration of the genuine cortical bone at the fracture line.Structural bone allografts often fracture due to their lack of osteogenic and remodelling potiential. To overcome these limitations, we utilized allografts coated with AAV-caALK2 vector that mediated in vivo gene transfer. We showed that the AAV vector was capable of transducing adjacent inflammatory cells and osteoblasts in the fracture callus and that BMP signals delivered via AAV-caALK2 coating induced bone formation directly on the cortical surface of the allograft.The presented research may be seen as initial steps towards development of gene therapeutic treatment options for complex orthopaedic diseases. As such, our studies represent proof-of-principle that the rAAV vector promotes efficient gene transfer in vitro to a spectrum of cells with orthopaedic relevance, and that in vivo targeting of somatic tissue with a single administration of a rAAV vector at the time of surgery could be sufficient for long-term expression of therapeutic proteins. Essential to the future success of transgene delivery by rAAV vectors is the absence of an immune response to either the vector or the gene product. Furthermore, development of rAAV vectors with regulatory gene expression needs further attention in future research.

L iu and colleagues compared retrieved tibial components from TKA prostheses that incorporated either conventional polyethylene (sterilized with ethylene oxide or gamma in low oxygen) or highly crosslinked polyethylenes (XLPEs). They found only minor differences in the types and amounts of surface damage, but slightly more thinning (penetration) on the XLPE polyethylene components. There are several reasons why the long-term clinical advantages that the XLPE polyethylenes were designed to provide would not be evident as a substantial reduction in these shortterm surface damage scores. Historically, the two main weaknesses of conventional polyethylene were wear on a submicron scale, which produced billions of particles that were the primary drivers of periprosthetic osteolysis, and (for those implants sterilized with gamma radiation) oxidative degradation that markedly weakened the polyethylene, potentially leading to fatigue wear and/or component fracture. Wear on the submicron scale results in polishing (burnishing) of the surface and thinning of the polyethylene component [5]. However, as Liu et al. note, thinning during the first few years in vivo is due primarily to creep deformation, which does not involve wear [7] and the initial (creep) thinning of an XLPE tibial plateau is expected to be comparable to, or slightly greater than, that of a conventional polyethylene plateau. Consequently, based the wear rates measured in knee simulator studies [3, 6, 9], the portion of the total thinning after 44 months or less in vivo that is due to debris-producing wear would likely be too small with either type of polyethylene for the difference between the two to be measured using the methods of Liu et al. The authors of the current study also report no delamination damage with XLPE or conventional polyethylene. Delamination can result from substantial oxidative degradation [8] and has been observed with XLPE tibial plateaus that were sequentially annealed (rather than remelted) [4]. This CORR Insights is a commentary on the article ‘‘Surface Damage Is Not Reduced With Highly Crosslinked Polyethylene Tibial Inserts at Short-term’’ by Liu and colleagues available at: DOI:10.1007/s11999-0154344-4. One of the authors (HAM) certifies that he has received or may receive patent arrangement benefits from DePuy Orthopaedics Inc, (Warsaw, IN, USA), and grants and personal fees from Depuy Orthopaedics Inc, outside the submitted work. All ICMJE Conflict of Interest Forms for authors and Clinical Orthopaedics and Related Research editors and board members are on file with the publication and can be viewed on request. The opinions expressed are those of the writer, and do not reflect the opinion or policy of CORR or The Association of Bone and Joint Surgeons. This CORR Insights comment refers to the article available at DOI:10.1007/s11999-0154344-4. H. A. McKellop PhD (&) UCLA & OIC Department of Orthopaedic Surgery, Orthopaedic Institute for Children, 403 West Adams Blvd, Los Angeles, CA 90007-2664, USA e-mail: HMcKellop@mednet.ucla.edu