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Wayne G Paprosky,1,2 Jeffrey M Muir3 1Department of Orthopedics, Section of Adult Joint Reconstruction, Department of Orthopedics, Rush University Medical Center, Rush–Presbyterian–St Luke’s Medical Center, Chicago, 2Central DuPage Hospital, Winfield, IL, USA; 3Intellijoint Surgical, Inc, Waterloo, ON, Canada Abstract: Total hip arthroplasty is an increasingly common procedure used to address degenerative changes in the hip joint due to osteoarthritis. Although generally associated with good results, among the challenges associated with hip arthroplasty are accurate measurement of biomechanical parameters such as leg length, offset, and cup position, discrepancies of which can lead to significant long-term consequences such as pain, instability, neurological deficits, dislocation, and revision surgery, as well as patient dissatisfaction and, increasingly, litigation. Current methods of managing these parameters are limited, with manual methods such as outriggers or calipers being used to monitor leg length; however, these are susceptible to small intraoperative changes in patient position and are therefore inaccurate. Computer-assisted navigation, while offering improved accuracy, is expensive and cumbersome, in addition to adding significantly to procedural time. To address the technological gap in hip arthroplasty, a new intraoperative navigation tool (Intellijoint HIP®) has been developed. This innovative, 3D mini-optical navigation tool provides real-time, intraoperative data on leg length, offset, and cup position and allows for improved accuracy and precision in component selection and alignment. Benchtop and simulated clinical use testing have demonstrated excellent accuracy, with the navigation tool able to measure leg length and offset to within

Background: Chronic pelvic discontinuity is a challenge during revision total hip arthroplasty due to the loss of structural continuity of the superior and inferior aspects of the acetabulum from severe acetabular bone loss. Acetabular distraction provides an alternative surgical treatment by stabilizing the acetabular component through elastic recoil of the pelvis, which may be supplemented with modular porous augments for addressing major acetabular defects. This study reports 2-year radiographic findings following acetabular distraction for the treatment of chronic pelvic discontinuity., Methods: Patients undergoing acetabular distraction performed by 5 surgeons from 2002 to 2021 were identified across 5 institutions. Demographic, surgical, and postoperative outcomes, including radiographic component stability, were recorded. There were 53 of 91 (58.2%) patients (5 deceased, 33 lost to follow-up) consisting of 4 Paprosky IIC (7.5%), 8 Paprosky IIIA (15.1%), and 41 Paprosky IIIB (77.4%) defects included, with a mean follow-up time of 4.8 years (range, 2 to 13.5). Modular porous augments were used in 33 (62.3%) cases. Failure was defined as a subsequent revision of the acetabular construct., Results: Among the 13 (24.5%) patients who returned to the operating room, 6 (46.2%) had a prior history of revision total hip arthroplasty before undergoing acetabular distraction. Only 5 (9.4%) patients underwent acetabular revision following acetabular distraction, leading to an overall cup survivorship of 90.6%. Of the remaining 48 patients, 46 (95.8%) had evidence of radiographic bridging callus of the chronic pelvic discontinuity at their last clinical follow-up., Conclusions: To our knowledge, in the largest series to date, acetabular distraction has proven to be a viable treatment for acetabular bone loss with a chronic pelvic discontinuity, with excellent early survivorship and radiographic evidence of bridging callus. Future studies with longer follow-ups are needed to further monitor the efficacy of this technique., Level of Evidence: Level III, Retrospective Comparative Study., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Background: Severe acetabular bone loss encountered during revision total hip arthroplasty (THA) poses a clinical challenge. In cases involving pelvic discontinuity, where the ilium is separated superiorly from the inferior ischiopubic segment through the acetabulum, acetabular distraction may be used to restore the biomechanics of the hemipelvis. This technique allows for correct sizing of the acetabulum, and the subsequent peripheral distraction and medial compression at the discontinuity provide initial mechanical stability and biological fixation as bone in growth occurs. Accordingly, this study aimed to assess long-term 5-year outcomes following acetabular distraction across 2 institutions., Methods: We retrospectively identified all patients who underwent revision THA in which the acetabular distraction technique was performed for the treatment of chronic pelvic discontinuity between 2002 and 2018. Demographic, operative, and clinical postoperative data were collected. Clinical endpoints included postoperative radiographic outcomes, complications requiring additional surgery, and reoperation for all causes. Only patients who had a minimum 5-year follow-up were included in this study., Results: A total of 15 patients (Paprosky IIC: one patient, 6.7%; Paprosky IIIA: 5 patients, 33.3%; Paprosky IIIB: 9 patients, 60%) who had a mean follow-up time of 9 years (range, 5.1 to 13.5) were analyzed. Porous tantalum augments were used in 11 (73.3%) cases to primarily address posteriorsuperior defects (100%). There were 4 (26.7%) patients that required reoperation, only 2 of which were for indications related to the acetabular construct, leading to an overall survivorship of 86.7%. Both patients had a prior revision THA before the implementation of the distraction technique. Evidence of bridging callus formation was reported radiographically for 14 (93.3%) patients at the time of the last clinical follow-up., Conclusions: For patients who have chronic pelvic discontinuity, acetabular distraction shows promising long-term outcomes. Even so, larger multi-center studies are needed to better support the efficacy of this technique., Level of Evidence: Level III, retrospective comparative study., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Acetabular bone loss continues to be one of the most complex and challenging scenarios facing the orthopaedic surgeon. Preoperative planning and classification systems essentially have remained the same, with the Paprosky classification still being the most commonly used. Careful radiological assessment with well-defined criteria can accurately diagnose acetabular bone loss patterns with an associated chronic pelvic discontinuity before surgery. The use of cemented reconstruction techniques has declined, and contemporary practice trends have involved the increasing use of highly porous hemispherical shells in conjunction with modular porous metal augments, which can successfully treat most acetabular revisions. Noncemented treatment options for the management of acetabular bone loss during revision include conventional porous/modular highly porous hemispherical implants, nonmodular highly porous implants with cementable acetabular liners, cup-cage reconstruction, oblong cups, and triflange reconstruction. These options can be combined with modular porous metal augments, structural allografts, impaction grafting, or reconstruction cages. Acetabular distraction is a newer technique for chronic pelvic discontinuity, which is used in conjunction with off-the-shelf revision acetabular shells and modular porous metal augments. This review is an update over the past decade, highlighting studies with mid to long-term follow-up, and presents the advantages, disadvantages, and principles associated with each of the most commonly used reconstructive techniques., (Copyright © 2024 by the American Academy of Orthopaedic Surgeons.)

As indications for total hip arthroplasty (THA) continue to expand, and patients continue to live longer with more active lifestyles, the incidence of revision THA is expected to rise. General orthopaedic surgeons are now beginning to consider doing revision THA surgery because of the increased revision burden being experienced nationwide. While classical approaches to the hip can be used for simple revisions, extensile exposure techniques in conjunction with selective soft-tissue releases are often required for adequate visualization for more complex revision cases. This review provides a systematic approach to surgical exposure for revision THA using the posterior approach. The surgeon should follow a stepwise progression to obtain safe, adequate, and reproducible visualization of both the acetabulum and the proximal femur., (Copyright © 2023 by the American Academy of Orthopaedic Surgeons.)

Background: Anteroposterior (AP) pelvic radiographs are subject to errors that may cause measurement inaccuracy in total hip arthroplasty (THA). Such errors may be detected by measuring pre- to postoperative leg-length changes in the nonoperative leg, which experiences no physical changes during THA., Methods: From AP pelvic radiographs, we measured pre- to postoperative leg-length changes (LLC) in the nonoperative legs of 67 patients who underwent primary THA using the trans-ischial line method., Results: An LLC of 0 mm was observed in the nonoperative leg in only 14 cases (21%). A LLC ⩾ 2 mm was observed in 27% (18/67) of cases, including 13% (9/67) with LLC ⩾ 3 mm and 6% (4/67) with LLC ⩾ 4 mm. A post-hoc analysis used a validated method to measure change in pelvic tilt between pre- and postoperative images and found that changes in pelvic tilt ⩾ 4° in the anterior and posterior directions created apparent lengthening (2.0 ± 1.4 mm, p   <  0.001 vs. 0-3° of tilt) and shortening (-2.1 ± 1.6 mm, p   <  0.001 vs. 0-3° of tilt) of the nonoperative leg, respectively., Conclusions: The current study provides evidence of measurement errors in leg length using AP pelvic radiographs following THA. Changes in pelvic tilt may be in part responsible for these errors, with the direction of change in pelvic tilt influencing the apparent lengthening or shortening of the lower limb. Ultimately, these findings may influence the radiographic measurement and interpretation of leg-length changes following THA.

Purpose: The dome technique is a technique used in performance of revision total hip arthroplasty (THA) involving intraoperative joining of two porous metal acetabular augments to fill a massive anterosuperior medial acetabular bone defect. While excellent outcomes were achieved using this surgical technique in a series of three cases, short-term results have not been reported. We hypothesized that excellent short-term clinical and patient reported outcomes could be achieved with use of the dome technique., Materials and Methods: A multicenter case series was conducted for evaluation of patients who underwent revision THA using the dome technique for management of Paprosky 3B anterosuperior medial acetabular bone loss from 2013-2019 with a minimum clinical follow-up period of two years. Twelve cases in 12 patients were identified. Baseline demographics, intraoperative variables, surgical outcomes, and patient reported outcomes were acquired., Results: The implant survivorship was 91% with component failure requiring re-revision in only one patient at a mean follow-up period of 36.2 months (range, 24-72 months). Three patients (25.0%) experienced complications, including re-revision for component failure, inter-prosthetic dual-mobility dissociation, and periprosthetic joint infection. Of seven patients who completed the HOOS, JR (hip disability and osteoarthritis outcome score, joint replacement) survey, five patients showed improvement., Conclusion: Excellent outcomes can be achieved using the dome technique for management of massive anterosuperior medial acetabular defects in revision THA with survivorship of 91% at a mean follow-up period of three years. Conduct of future studies will be required in order to evaluate mid- to long-term outcomes for this technique., Competing Interests: CONFLICT OF INTEREST: T.J.H. and C.M.B. have no conflicts to disclose. C.M.M. is a speaker and paid consultant for Smith & Nephew and receives research support from Zimmer Biomet. H.S.B. receives royalties from and is a paid consultant for Exactech and Smith & Nephew, has stock options in Exactech, receives research support from Zimmer Biomet, and receives royalties from Wolters Kluwer. N.P.S. is a board or committee member of AAOS and the Eastern Orthopaedic Association, has publishing royalties with Elsevier, and is a paid consultant for Medacta, Microport, Smith & Nephew, and Zimmer. P.M.C. is a board or committee member of AAOS and the American Association of Hip and Knee Surgeons, is a paid consultant for DePuy, A Johnson & Johnson Company, Stryker, Hip Innovation Technology, and Zimmer, is a paid presenter or speaker for Smith & Nephew, and has stock or stock options in Parvizi Surgical Innovation. W.G.P. is a paid consultant for CeramTec and ConvaTec, has IP royalties from Innomed, is a paid consultant and has stock options in Intellijoint, is on the editorial board of Journal of Arthroplasty, is a paid consultant for Next Science, receives publishing royalties, financial or material support from Wolters Kluwer Health - Lippincott Williams & Wilkins; and receives IP royalties and is a paid consultant for Zimmer., (Copyright © 2023 by Korean Hip Society.)

Purpose: Computer navigation in total hip arthroplasty (THA) offers potential for more accurate placement of acetabular components, avoiding impingement, edge loading, and dislocation, all of which can necessitate revision THA (rTHA). Therefore, the use of computer navigation may be particularly beneficial in patients undergoing rTHA. The purpose of this study was to determine if the use of computer-assisted hip navigation reduces the rate of dislocation in patients undergoing rTHA., Methods: A retrospective review of 72 patients undergoing computer-navigated rTHA between February 2016 and May 2017 was performed. Demographics, indications for revision, type of procedure performed, and incidence of postoperative dislocation were collected for all patients. Clinical follow-up was recorded at 3 months, 1 year and 2 years., Results: All 72 patients (48% female; 52% male) were included for analysis. The mean age was 70.4 ± 11.2 years and mean BMI was 26.4 ± 5.2 kg/m 2 . 22 of 72 patients (31%) required a rTHA procedure due to instability resulting in dislocation. At 3 months, 1 year, and 2 years, there were no dislocations (0%). There was a significant reduction in dislocation rate after computer-navigated rTHA (0%) relative to that following primary THA in the same patient cohort (31%; p  < 0.05)., Conclusion: Our study demonstrates a significant reduction in dislocation rate following rTHA with computer navigation. Although the cause of postoperative dislocation is often multifactorial, the use of computer navigation may help to curtail femoral and acetabular malalignment in rTHA., Level of Evidence: Level III: retrospective., Competing Interests: Conflict of InterestAbhinav K. Sharma declares that he has no conflict of interest. Zlatan Cizmic, M.D., declares that he has no conflict of interest. Kaitlin M. Carroll reports having stock ownership in Orthalign. Seth Jerabek, M.D., reports having stock ownership in Stryker and Imagen and receiving IP royalties, personal fees, and research funding from Stryker. Wayne Paprosky, M.D., reports having stock ownership in Intellijoint Surgical and receiving fees from Intellijoint Surgical, Zimmer Biomet, Microport, and Ceramtec. Peter Sculco, M.D., reports receiving fees from EOS Imaging, Intellijoint Surgical, and Lima Corp. Alejandro Gonzalez Della Valle, M.D., reports receiving IP royalties and fees from OrthoDevelopment, IP royalties, fees, and research support from OrthoSensor, and fees from Johnson & Johnson and Link Orthopaedics. Ran Schwarzkopf, M.D., reports having stock ownership in PSI and receiving fees and grants from Smith & Nephew and Intellijoint Surgical. David Mayman, M.D., reports having stock ownership in Imagen, Insight, Wishbone, and Orthalign, receiving IP royalties, fees, and research funding from Smith & Nephew, and receiving IP royalties from Orthalign. Jonathan M. Vigdorchik, M.D., reports stock ownership in Intellijoint Surgical and Motion Insights, fees and research funding from Corin Group, and fees from Intellijoint Surgical, Medacta, and Zimmer., (© Indian Orthopaedics Association 2022.)

Acetabular bone loss continues to be a challenging clinical problem faced by the revision total hip arthroplasty surgeons. The presence of a chronic pelvic discontinuity further complicates this clinical entity. Several surgical techniques have been described for the management of severe acetabular bone loss with an associated chronic pelvic discontinuity, with increasing enthusiasm for noncemented reconstruction. The focus is on noncemented reconstruction of Paprosky type IIIB acetabular defects with a chronic pelvic discontinuity.

Aims: Recent total knee arthroplasty (TKA) designs have featured more anatomical morphologies and shorter tibial keels. However, several reports have raised concerns about the impact of these modifications on implant longevity. The aim of this study was to report the early performance of a modern, cemented TKA design., Methods: All patients who received a primary, cemented TKA between 2012 and 2017 with a minimum two-year follow-up were included. The implant investigated features an asymmetrical tibial baseplate and shortened keel. Patient demographic details, Knee Society Scores (KSS), component alignment, and the presence of radiolucent lines at final follow-up were recorded. Kaplan-Meier analyses were performed to estimate survivorship., Results: A total of 720 of 754 primary TKAs (95.5%) were included with a mean follow-up of 3.9 years (SD 1.3); 562 (78.1%) were cruciate-retaining and 158 (21.9%) were posterior-stabilized. A total of 11 (1.5%) required reoperation for periprosthetic joint infection and seven (1.0%) for aseptic tibial loosening (five cruciate-retaining, two posterior-stabilized). Loosening occurred at a mean of 3.3 years (0.9 to 6.5). There were no cases of loosening in the 33 patients who received a 14 mm × 30 mm tibial stem extension. All-cause survivorship was 96.6% at three years (95% confidence interval (CI) 95.3% to 98.0%) and 96.2% at five years (95% CI 94.8% to 97.7%). Survivorship with revision for aseptic loosening was 99.6% at three years (95% CI 99.1% to 100.0%) and 99.1% at five years (95% CI 98.4% to 99.9%). Tibial components were in significantly more varus in those with aseptic loosening (mean 3.4° (SD 3.7°) vs 1.3° (SD 2.0°); p = 0.015). There were no other differences in demographic, radiological, or surgical characteristics between revised and non-revised TKAs for aseptic loosening (p = 0.293 to 1.00). Mean KSS improved significantly from 57.3 (SD 9.5) preoperatively to 92.6 (SD 8.9) at the final follow-up (p < 0.001)., Conclusion: This is the largest series to date of this design of implant. At short-term follow-up, the rate of aseptic tibial loosening is not overly concerning. Further observation is required to determine if there will be an abnormal rate of loosening at mid- to long-term follow-up. Cite this article: Bone Joint J  2021;103-B(6 Supple A):51-58.

»: Appropriate total hip arthroplasty (THA) reconstruction must simultaneously address component position, restoration of biomechanics, and soft-tissue balance., »: Preoperative planning for complex THA cases should include radiographic templating, a detailed case plan that contains backup implant options, and a thorough understanding of the patient's preoperative examination., »: Using a systematic approach to soft-tissue balancing in THA enhances the ability to intraoperatively execute the preoperative plan., »: In patients with preexisting deformities (e.g., dysplasia or prior surgery), increased attention to abductor function is necessary when assessing acetabular component placement and offset., Competing Interests: Disclosure: No external funds were received in support of this work. On the Disclosure of Potential Conflicts of Interest forms, which are provided with the online version of the article, one of more o the authors checked “yes” to indicate that the author had a relevant financial relationship in the biomedical arena outside the submitted work (http://links.lww.com/JBJSREV/A668)., (Copyright © 2021 by The Journal of Bone and Joint Surgery, Incorporated.)

Background: Acetabular bone loss in revision total hip arthroplasty can be very challenging even for fellowship-trained surgeons. Although it is uncommon, massive anterosuperior medial defects may be encountered, but treatment options have been limited and better ones are needed., Questions/purposes: The primary purpose of this case series is to describe a novel surgical treatment, which we call the dome technique, that can be used to address these challenging defects. The dome technique allows for the systematic reconstruction of massive anterosuperior medial defects of the acetabulum. We sought to illustrate the utility of this procedure in three patients with failed acetabular components and massive anterosuperior medial defects., Methods: We undertook a retrospective chart review of three patients who had had Paprosky 3B bone defects and undergone revision total hip arthroplasty by the senior author between 2013 and 2016 using the dome technique. The procedure involved the use of tantalum metal augments pieced together to fill the medial defect and recreate the column support needed for jumbo cup placement. The dome technique is unusual because it allows for intra-operative customization to obtain the proper fit., Results: At a mean of 23.6 months' follow-up (range, 10 to 37 months), all patients had good functional outcomes; none was in need of further revision., Conclusions: In three patients, the dome technique allowed for the anterosuperior column to be recreated by piecing together two porous metal augments to fill the medial bony void and create a stable column for a jumbo cup to be press fit. By recreating the deficient anterosuperior medial bone, the acetabulum can be downsized in a stepwise manner (with further surgery) and reconstructed in a stable fashion. This novel procedure is a unique option for the treatment of this challenging problem., Competing Interests: Conflict of InterestChristopher M. Melnic, MD, Matthew Knedel, MD, and Neil P. Sheth, MD, declare that they have no conflicts of interest. P. Maxwell Courtney, MD, reports receiving consulting fees from Hip Innovation Technology and educational support from the Journal of Bone and Joint Surgery, outside the submitted work. Wayne G. Paprosky, MD, reports receiving consulting fees and royalties from Zimmer Biomet and Stryker, royalties from Innomed and Wolters Kluwer, and consulting fees and stock or stock options from Intellijoint Surgical, outside the submitted work., (© Hospital for Special Surgery 2019.)

Background: Mechanically assisted crevice corrosion (MACC) at modular junctions can cause a spectrum of adverse local tissue reactions (ALTRs) in patients who have undergone total hip arthroplasty (THA). The purpose of this study is to describe the presentation, treatments, and related complications of a cohort of patients presenting with late instability following metal-on-polyethylene THA due to underlying MACC and ALTR., Methods: This multicenter retrospective case series presents 17 patients (12 women, mean age 62.6, range 42-73) presenting with late instability secondary to ALTR and MACC. All patients had a metal (Cobalt Chrome)-on-polyethylene bearing surface. Patients experienced a mean 2.7 dislocations (range 1-6) at mean 4.3 years (range 0.4-17.0) following their index surgery. Serum metal levels (n = 12) demonstrated a greater elevation of cobalt (mean 6.9, range 0.13-20.88 ng/mL) than chromium (mean 1.9, range 0.13-3.23 ng/mL)., Results: Patients were revised for instability at a mean of 6.8 years (range 2.1-19.4) following their index surgery. ALTR was encountered in every case and the modular head-neck junction demonstrated visible corrosion. An exchange of the CoCr head to a ceramic head with a titanium sleeve and placement of a constrained liner was performed for a majority of patients (n = 15, 88.2%). Five patients (29.4%) had complications postoperatively including peroneal palsy (n = 2), periprosthetic joint infection (n = 2), and ALTR recurrence (n = 1)., Conclusion: Recurrent instability in the setting of otherwise well-positioned THA components and without another obvious cause should raise concern for ALTR as a potential underlying etiology., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Background: Previous reports on the outcomes of isolated head and liner exchange in revision total hip arthroplasty have found high rates of instability after these surgeries. Most reports have studied constructs using ≤28 mm femoral heads. The purpose of this study was to determine if modern techniques with the use of larger head sizes can improve the rate of instability after head and liner exchange., Methods: We identified 138 hips in 132 patients who underwent isolated head and liner exchange for polyethylene wear/osteolysis (57%), acute infection (27%), metallosis (13%), or other (2%). All patients underwent revision with either 32 (23%), 36 (62%), or 40 (15%) mm diameter heads. Cross-linked polyethylene was used in all revisions. Lipped and/or offset liners were used in 104 (75%) hips. Average follow-up was 3.5 (1.0-9.1) years. Statistical analyses were performed with significance set at P < .05., Results: Revision-free survivorship for any cause was 94.6% and for aseptic causes was 98.2% at 5 years. 11 (8%) hips experienced a complication with 7 (5%) hips requiring additional revision surgery. After revision, 4 (3%) hips experienced dislocation, 5 (4%) hips experienced infection, and 1 (1%) hip was revised for trunnionosis. No demographic or surgical factors significantly affected outcomes., Conclusion: Our study shows that isolated head and liner exchange using large femoral heads and modern liners provides for better stability than previous reports. The most common complication was infection. We did not identify specific patient, surgical, or implant factors that reduced the risk of instability or other complication., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Acetabular bone loss, and specifically when it is associated with a chronic pelvic discontinuity, presents a difficult clinical challenge at the time of revision total hip arthroplasty. Most centers have advocated the use of noncemented constructs in an effort to achieve biologic fixation. The authors prefer noncemented fixation with use of the acetabular distraction technique in conjunction with modular porous metal augments for the treatment of severe acetabular bone loss and an associated chronic pelvic discontinuity.

Introduction: Identifying the source of pain is paramount for determining appropriate treatment and ensuring successful outcome in terms of management and relief of pain. The difficulty is that each surgeon has his or her own way of seeing the problem, and there is no consensus for the evaluation of these patients. The study hypothesis was that it is possible to find the cause of the pain in most cases., Patients and Methods: All patients consulting for unexplained painful hip arthroplasty were included and followed a decision tree to assess the cause of the pain. The primary endpoint was the final diagnosis. Secondary endpoints were subgroup comparison between main causes and assessment of risk factors., Results: Two hundred one hips of 194 patients were included as unexplained painful hip arthroplasty 6 months postoperatively. Final diagnoses comprised periarticular pain in 53 cases (26.4%): 40 cases of trochanteric bursitis, 5 of iliopsoas tendinitis, 5 of abductor deficiency, 1 of ischial tuberosity tendinitis, and 2 of heterotopic ossification; projected pain in 49 (24.4%): 45 cases of back pain with or without neuropathy, 3 of knee osteoarthritis, and 1 of metabolic neuropathy; wear in 40 (19.9%), in the polyethylene liner; loosening in 20 (10.0%): loosening of the femoral component in 8 and that of the cup in 12; material problems in 17 (8.5%): trunnionosis in 13 and metallosis in metal-on-metal implants in 4; no diagnosis in 7 hips (3.5%); infection in 6 (3.0%), all chronic; instability without real dislocation in 3 (1.5%); misplacement in 3 (1.5%), all for leg-length discrepancy; fracture in 2 (1.0%): 1 of greater trochanter and 1 of ilio-ischiopubic ramus; complex regional pain syndrome in 1 (0.5%)., Discussion: To our knowledge, this is the first study on the causes of painful hip arthroplasty in clinical practice, whether leading to revision or not. A systematic approach, including physical examination, radiographic assessment and laboratory studies, is needed to find the cause of the pain. It is important to understand the pain so that it can be treated appropriately. Revision surgery can sometimes help-but the worst thing is to make the patient worse., Level of Evidence: level 4, retrospective study., (Copyright © 2019 Elsevier Inc. All rights reserved.)

As the demand for total hip arthroplasty (THA) continues to increase, the burden of revision THA is also expected to increase. Although the quality of polyethylene has improved markedly, osteolysis continues to be a risk for older designs and younger, active patients. Although progressive but typically asymptomatic in early stages, osteolysis can result in component failure and complicate revision surgery. Serial radiographs are paramount for monitoring progression. Although select cases may be treated with observation, surgery should be considered based on age, activity level, and projected life span. Well-fixed, noncemented modular acetabular components may be treated with curettage and bone grafting, as well as having to bear liner exchange with retention of the acetabular shell. However, in the setting of osteolysis, it is controversial whether bone grafting and component retention is superior to cup revision. This review explores the pathophysiology of osteolysis after THA and provides a comprehensive analysis of the evaluation and treatment of patients with osteolysis.

Revision total hip arthroplasty is a costly procedure accounting for approximately 14% of all hip arthroplasties. Compounding the cost considerations is the potential for serious injury to the patient when removing existing components. Such injury can result in not only increased morbidity but also dramatically increased costs. The use of computer-assisted navigation in revision total hip arthroplasty, while relatively uncommon, offers surgeons the ability to measure component position and orientation intraoperatively, thus allowing them the opportunity to modify their surgical plan, with the potential for decreasing both costs and iatrogenic injury. Here, we report a case of revision total hip arthroplasty where the use of computer-assisted navigation as a diagnostic tool allowed for intraoperative alterations in surgical plan and resulted in improved post-operative outcomes., Competing Interests: Declaration of conflicting interests: The author(s) declared the following potential conflicts of interest with respect to the research, authorship, and/or publication of this article: W.G.P has received consultancy fees from Intellijoint Surgical, Inc. J.M.M. is an employee of Intellijoint Surgical, Inc. J.V. and J.R.S. report no potential conflicts.

Background: Midlevel providers (i.e. physician assistants [PAs] and nurse practitioners [NPs]) are being integrated into systems of care due to the exponentially increasing demand for orthopaedic care. There is a lack of studies which investigate orthopaedic patients' perspectives regarding midlevel providers., Methods: An anonymous questionnaire was administered to 538 first-time patients of four orthopaedic surgeons before their new patient visit. Content included patient perspectives regarding: optimal scope of practice, midlevel provider importance in physician selection, and reimbursement equity with physicians., Results: Of 538 consecutive patients, 415 (77%) responded. 57% were female with an average age of 63.9 ± 11.4 years. Most patients (68%) considered the training background of the surgeon's midlevel provider when initially choosing an orthopaedic surgeon. 34% of all patients perceived PAs to be more highly trained than NPs while 17% perceived the opposite. Patients had specific preferences regarding which services should be surgeon-provided: follow-up for abnormal tests (82%), initial postoperative appointment (81%), new patient visits (81%), and determining the need for advanced diagnostic studies (e.g. MRI) (76%). Patients had specific preferences regarding which services could be midlevel-provided: preoperative teaching (73%), minor in-office procedures (65%), long term postoperative appointments (61%), and prescriptions (61%). Patients lacked a consensus on reimbursement equity for midlevel providers and orthopaedic surgeons, despite most patients (78%) reporting the surgeon provides a higher-quality consultation., Conclusions: As health care becomes increasingly consumer-centric and value-driven, a databased utilization of midlevel staff will allow orthopaedic physicians to optimize efficiency and patient satisfaction. Surgeons may consider our results in division of clinical duties among midlevel staff since patients had specific preferences regarding which services should be physician-provided or midlevel-provided. Orthopaedic surgeons may also consider including the midlevel provider in marketing efforts, as most patients considered the midlevel provider's training background when initially choosing a surgeon and perceived PAs to be more highly trained than NPs. Patients lacked a consensus towards reimbursement equity for orthopaedic surgeons and midlevels, despite reporting that the surgeon provides a higher quality consultation. These findings are important as the midlevel workforce grows in response to the rising demand for orthopaedic care. Level of Evidence: IV., Competing Interests: Disclosures: The authors report no potential conflicts of interest related to this study.

Background: The purpose of this study was to examine the outcomes of repeat revision after failure of a constrained liner., Methods: We reviewed 1212 consecutive revisions and identified 74 (6%) revisions of a failed constrained liner in 46 patients with a mean age of 65 years. The most common reasons for revision of a constrained liner were recurrent instability (64.9%) and infection (25.7%)., Results: At a mean of 35 months, 42 of the 74 hips (57%) required repeat revision. Kaplan-Meier revision-free survival was 24% at 10 years. Thirty-two of the 74 revisions (43%) had a dislocation event after the index revision. Kaplan-Meier dislocation-free survival was 43% at 10 years. There was a higher failure rate among the 34 patients with abductor deficiency (hazard ratio 1.90, 95% confidence interval, 1.06-3.43; P = .032)., Conclusion: Patients undergoing revision of a failed constrained liner have a high likelihood of recurrent dislocation and repeat revision surgery., Level of Evidence: Level IV., (Copyright © 2018. Published by Elsevier Inc.)

Aims The aim of this study was to examine the results of the acetabular distraction technique in achieving implantation of a stable construct, obtaining biological fixation, and producing healing of chronic pelvic discontinuity at revision total hip arthroplasty. Patients and Methods We identified 32 patients treated between 2006 and 2013 who underwent acetabular revision for a chronic pelvic discontinuity using acetabular distraction, and who were radiographically evaluated at a mean of 62 months (25 to 160). Of these patients, 28 (87.5%) were female. The mean age at the time of revision was 67 years (44 to 86). The patients represented a continuous series drawn from two institutions that adhered to an identical operative technique. Results Of the 32 patients, one patient required a revision for aseptic loosening, two patients had evidence of radiographic loosening but were not revised, and three patients had migration of the acetabular component into a more stable configuration. Radiographically, 22 (69%) of the cohort demonstrated healing of the discontinuity. The Kaplan-Meier construct survivorship was 83.3% when using revision for aseptic acetabular loosening as an endpoint. At the time when one patient failed due to aseptic loosening (at 7.4 years), there were a total of seven patients with a follow-up of seven years or longer who were at risk of failure. Conclusion The acetabular distraction technique demonstrates encouraging radiographic outcomes, with healing of the discontinuity in over two-thirds of our series. This surgical technique permits biological fixation and intraoperative customization of the construct to be implanted based on the pattern of the bone loss identified following component removal. Cite this article: Bone Joint J 2018;100-B:909-14.

Despite inaccuracies due to artifact and variations in patient positioning, anteroposterior (AP) radiographs remain the clinical standard for post-operative evaluation of component placement following total hip arthroplasty (THA). However, cup position, specifically anteversion, can be significantly affected by variations in patient positioning on an X-ray. A major cause of such artifact is unaccounted for pelvic tilt. Several methods for correcting the effects of pelvic tilt on radiographic anteversion have been proposed, with varying degrees of accuracy. The purpose of this study was to evaluate the accuracy and reliability of a commonly referenced method for correcting acetabular cup anteversion in a cohort undergoing total hip arthroplasty and determine its appropriateness for use in this population of patients. Radiographs from patients who underwent primary or revision hip arthroplasty between February 2016 and February 2017 were retrospectively reviewed. Corrected anteversion was calculated by measuring the vertical distance between the symphysis pubis and the sacrococcygeal joint, per the method outlined by Tannast et al. This symphococcygeal distance was then applied to Tannast's nomograms to calculate the magnitude of pelvic tilt. Corrected and uncorrected anteversion values were compared to anteversion values collected intraoperatively using an imageless computer-assisted navigation device. A total of 71 cases were initially eligible for inclusion in the study. The correction method could not be applied in 44% (31/71) of the cases, chiefly due to difficulties in visualizing the required landmarks. In cases where it could be applied, corrected values correlated very poorly with navigation measurements (r = -0.07). Mean corrected anteversion (36.9°, SD: 7.4°) differed from uncorrected anteversion (25.2°, SD: 7.6°) by an average of 13.5° (p<0.001). Mean navigated anteversion (27.4°, SD: 5.7°) differed from corrected values by an average of 10.8° (p=0.16). The evaluated correction method could not be consistently applied to radiographs and did not reliably correct anteversion due to pelvic tilt in this population of patients undergoing hip arthroplasty. This correction method does not appear to be appropriate for use in this patient population., Competing Interests: The authors have declared financial relationships, which are detailed in the next section.

Background: Radiostereometric analysis (RSA) accurately assesses arthroplasty implant performance and is routinely used for research purposes. Because of its efficacy in detecting implant failure in research subjects, we deployed the use of RSA beads for routine surveillance in all elective total hip and total knee arthroplasty patients., Methods: We retrospectively compared 143 patients who received RSA beads intraoperatively with 343 patients who did not receive RSA beads. Using RSA images, we assessed bead stability at 6 weeks and 1 year postoperatively., Results: There were no intraoperative complications in the RSA group and two in the control group. No differences were found between groups for the surgical time and the expected blood loss. At 6 weeks, 99.5% of beads were considered to be stable, with stability increasing to 99.7% of beads at 1 year., Conclusion: The routine use of RSA bead insertion is a safe procedure and may provide the ability to assess implant fixation in clinical practice.

Acetabular bone loss is commonly encountered in patients who undergo revision total hip arthroplasty. Severe bony defects may be associated with chronic pelvic discontinuity, which makes acetabular reconstruction considerably more difficult. Surgeons must understand the current treatment options for patients with severe acetabular bone loss and chronic pelvic discontinuity. Surgeons also should understand how to perform acetabular distraction with the use of a porous acetabular shell and porous, modular metal augments.

Revision total hip arthroplasty in patients with acetabular bone loss is a challenge and should only be performed by experienced surgeons. Correct classification of the acetabular bone loss pattern allows for the formulation and execution of a detailed treatment plan. However, reclassification of the bone loss pattern is essential if additional bone loss is discovered intraoperatively so that the patient is appropriately treated. Modular, uncemented, porous metal augments and a jumbo acetabular cup should be used to treat patients with severe acetabular bone loss (Paprosky type IIIA and type IIIB acetabular defects).

Background: Some authors have advocated for use of porous tantalum metaphyseal cones to manage bone defects during revision total knee arthroplasty (TKA). The purpose of this study is to compare results with porous metaphyseal cones to results with traditional hybrid stem fixation in revision TKA., Methods: Forty-nine patients undergoing revision TKA with femoral and/or tibial metaphyseal cones (39 tibial only, 3 femoral only, 7 both) were matched by surgical indication to 49 patients undergoing revision TKA with a traditional hybrid stem (non-cone) technique. Clinical and radiographic outcomes were compared at a minimum of two-year follow-up (mean 3.5 years) with adjustment for baseline characteristics., Results: Pre-revision bone defects and most baseline demographics were similar between the cone and non-cone cohorts suggesting appropriate matching. Patients in the non-cone cohort had greater pre- to post-operative increases in Knee Society Score (37.2 ± 18.6 vs 28.4 ± 17.8, P = .010) and Knee Society Functional Score (30.4 ± 24.3 vs 13.1 ± 27.6, P = .003). The cohorts did not differ with respect to complications, subsequent reoperation, subsequent revision, patient satisfaction, tibial overhang, the presence of radio-sclerotic lines, cortical hypertrophy around the stems, or tibial subsidence., Conclusion: In this series, metaphyseal cones were not associated with superior outcomes at short-term follow-up. Given the increased cost associated with use of cones compared to traditional techniques, this study cannot support the routine use of metaphyseal cones in revision TKA. Longer-term follow-up will be necessary to determine if construct durability differs over the long term., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Chronic pelvic discontinuity is a distinct and unique challenge seen during revision total hip arthroplasty (THA) in which the superior ilium is separated from the inferior ischiopubic segment through the acetabulum, rendering the anterior and posterior columns discontinuous. The operative management of acetabular bone loss in revision THA is one of the most difficult challenges today. Common treatment options include cage reconstruction with bulk acetabular allograft, custom triflange acetabular component, a cup-cage construct, jumbo acetabular cup with porous metal augments, or acetabular distraction with a porous tantalum shell with or without modular porous augments.

Background: The purpose of this study is to determine whether revision total hip arthroplasty (THA) is associated with increased rates of deep vein thrombosis (DVT) and pulmonary embolism (PE) when compared to primary THA., Methods: We queried the American College of Surgeons National Surgical Quality Improvement Program database for all primary and revision THA cases from 2011 to 2014. Demographic data, medical comorbidities, and venous thromboembolic rates within 30 days of surgery were compared between the primary and revision THA groups., Results: Revision THA had a higher rate of DVT than the primary THA (0.6% vs 0.4%, P = .016), but there was no difference in the rate of PE (0.3% vs 0.2%, P = .116). When controlling for confounding variables, revision surgery alone was not a risk factor for DVT (odds ratio 0.833, 95% confidence interval 0.564-1.232) or PE (odds ratio 1.009, 95% confidence interval 0.630-1.616). Independent risk factors for DVT include age >70 years, malnutrition, infection, operating time >3 hours, general anesthesia, American Society of Anesthesiologists classification 4 or greater, and kidney disease (all P < .05). Probability of DVT ranged from 0.2% with zero risk factors to 10% with all risk factors. Independent risk factors for PE included age >70 years, African American ethnicity, and operating time >3 hours (all P < .05) with probabilities of PE postoperatively ranging from 0.2% to 1.1% with all risk factors., Conclusion: Revision surgery alone is not a risk factor for venous thromboembolism after hip arthroplasty. Surgeons should weigh the risks and benefits of more aggressive anticoagulation in certain high-risk patients., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Background: Accurate cup positioning is one of the most challenging aspects of total hip arthroplasty (THA). Undetected movement of the patient during THA surgery can lead to inaccuracies in cup anteversion and inclination, increasing the potential for dislocation and revision surgery. Investigations into the magnitude of patient motion during THA are not well represented in the literature., Methods: We analyzed intraoperative pelvic motion using a novel navigation device used to assist surgeons with cup position, leg length, and offset during THA. This device uses an integrated accelerometer to measure motion in 2 orthogonal degrees of freedom. We reviewed the data from 99 cases completed between February and September 2016., Results: The mean amount of pitch recorded per patient was 2.7° (standard deviation, 2.2; range, 0.1°-9.9°), whereas mean roll per patient was 7.3° (standard deviation, 5.5; range, 0.3°-31.3°). Twenty-one percent (21 of 99) of patients demonstrated pitch of >4°. Sixty-nine percent (68 of 99) of patients demonstrated >4° of roll, and 25% (25 of 99) of patients demonstrated roll of ≥10°., Conclusion: Our findings indicate that while the majority of intraoperative motion is <4°, many patients experience significant roll, with a large proportion rolling >10°. This degree of movement has implications for acetabular cup position, as failure to compensate for this motion can result in placement of the cup outside the planned safe zone, thus, increasing the potential for dislocation. Further study is warranted to determine the effect of this motion on cup position, leg length, and offset., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Total knee arthroplasty (TKA) has become an increasingly common treatment option for patients who have debilitating knee arthritis. TKA is a relatively safe and efficient procedure that results in promising outcomes and has a positive effect on a patient's quality of life. More TKAs are being performed annually because the procedure substantially reduces pain and improves functionality; however, as the number of TKAs continues to rise, there is concern for potential complications that may result in prosthetic joint failure. Primary TKA failure may result in revision procedures that have high costs and an increased risk for additional complications. Infection is the second most common cause of primary TKA failure and the single most common cause of revision TKA failure. Surgeons who have a better understanding of the epidemiology, risk factors, and diagnostic modalities associated with periprosthetic knee infection will be able to implement preventive measures and treat patients in whom such a complication occurs.

Two-stage revision total knee arthroplasty (TKA) is the standard of care for patients who require a revision procedure for the mangement of a late or chronic periprosthetic knee infection. A careful examination of two-stage revision TKA is warranted as the number of patients who require revision TKA in the United States continues to rise. Surgeons should understand the intricacies involved in two-stage revision TKA, including the indications, procedural variations, and current deliberations on two-stage revision TKA in the literature. Surgeons also should understand the alternative treatments for periprosthetic knee infections.

Single-stage revision total knee arthroplasty has become an increasingly common treatment option for patients with failed knee prostheses. Periprosthetic knee infection is the leading and most devastating cause of revision total knee arthroplasty. Although periprosthetic knee infection has been extensively studied in the orthopaedic literature, the role of single-stage revision total knee arthroplasty for the treatment of periprosthetic knee infection warrants further research. As healthcare reform shifts from a volume-based to a value-based system, it is imperative that orthopaedic surgeons understand the procedural indications, risks, and benefits of single-stage revision total knee arthroplasty.

Total hip arthroplasty is an increasingly common procedure used to address degenerative changes in the hip joint due to osteoarthritis. Although generally associated with good results, among the challenges associated with hip arthroplasty are accurate measurement of biomechanical parameters such as leg length, offset, and cup position, discrepancies of which can lead to significant long-term consequences such as pain, instability, neurological deficits, dislocation, and revision surgery, as well as patient dissatisfaction and, increasingly, litigation. Current methods of managing these parameters are limited, with manual methods such as outriggers or calipers being used to monitor leg length; however, these are susceptible to small intraoperative changes in patient position and are therefore inaccurate. Computer-assisted navigation, while offering improved accuracy, is expensive and cumbersome, in addition to adding significantly to procedural time. To address the technological gap in hip arthroplasty, a new intraoperative navigation tool (Intellijoint HIP ® ) has been developed. This innovative, 3D mini-optical navigation tool provides real-time, intraoperative data on leg length, offset, and cup position and allows for improved accuracy and precision in component selection and alignment. Benchtop and simulated clinical use testing have demonstrated excellent accuracy, with the navigation tool able to measure leg length and offset to within <1 mm and cup position to within <1° in both anteversion and inclination. This study describes the indications, procedural technique, and early accuracy results of the Intellijoint HIP surgical tool, which offers an accurate and easy-to-use option for hip surgeons to manage leg length, offset, and cup position intraoperatively., Competing Interests: WGP has received consultancy fees from and is a shareholder in Intellijoint Surgical, Inc. JMM is an employee of Intel-lijoint Surgical, Inc. The authors report no other conflicts of interest in this work.

Background: The purpose of this study was to evaluate the performance of dual-mobility articulations in patients at high risk for dislocation after revision total hip arthroplasty., Methods: We reviewed the results of 36 consecutive revision total hip arthroplasties performed on patients considered high risk for instability. Indications for inclusion included abductor insufficiency, recurrent instability, failure of constrained liner, or inadequate intraoperative stability when trialing., Results: At a minimum of 2 years, there were 4 (11.1%) repeat revisions including both dual-mobility liners that were cemented into an acetabular shell and 2 for deep infection treated with a 2-stage exchange. There was one dislocation that was successfully closed reduced but no revisions for recurrent instability. The mean Harris hip score improved from 45 to 90 points (P < .001)., Conclusion: Dual-mobility articulations are associated with a low rate of failure with no revisions for instability in this challenging group of patients., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Background: Incompletely solved problems in hip and knee arthroplasty present ongoing practice challenges., Methods: Content experts summarized treatment options and preferred treatment methods for 4 incompletely solved problems in hip and knee arthroplasty., Results: The problems chosen for discussion in this symposium included 2 soft tissue problems: chronic extensor mechanism deficiency after total knee arthroplasty and abductor deficiency after total hip arthroplasty (THA), recurrent infection after a 2-stage procedure for infected THA or total knee arthroplasties, and pelvic discontinuity after THA., Conclusion: The approaches outlined may provide guidance on management of these different problems. For surgeons and others in the orthopedic community interested in innovation, these challenges also present ripe opportunities to improve the care of patients with unmet needs., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Background: Revision total hip arthroplasty in patients with a nonsupportive superior acetabulum often requires secondary augmentation beyond a hemispherical cup to achieve reliable fixation. Treatment options include using a higher hip center, jumbo cup, custom triflange implant, cages, or filling the superior defect with a bilobed implant, structural allograft, or metal augments. We previously reported a cohort of 31 patients treated with porous-coated hemispherical cups and distal femoral allograft for Paprosky type IIIA acetabular defects., Methods: The original cohort of 31 hips was retrospectively reviewed. Fourteen patients died with <15 years of follow-up, and 2 were lost to follow-up. This left 15 patients for evaluation including 5 males and 10 females, with an average age of 61 years (range: 37-74 years) at the time of surgery. Acetabular revision was performed with the use of a porous-coated hemispherical cup along with structural distal femoral allograft, cut to resemble the number 7, and secured with 6.5-mm cancellous screws with washers., Results: Overall, 7 hips failed, resulting in a Kaplan-Meier survivorship of 72% at 25 years of follow-up. In surviving patients, radiographs demonstrated components to be well fixed, and average Merle d'Aubigné score increased from 5 to 10 points. There were a subset of patients that failed early (median: 6.2 years), but the remaining patients demonstrated excellent clinical and radiographic results., Conclusions: The use of distal femoral allograft can be considered in young patients with type IIIA acetabular defects that could benefit from restoration of bone stock., (Copyright © 2016 Elsevier Inc. All rights reserved.)

We reviewed 27 patients who underwent revision for an adverse local tissue reaction (ALTR) secondary to corrosion at the head-neck junction with MoP bearings. Serum cobalt and chromium levels were elevated in all cases, with a mean cobalt of 11.2 ppb and chromium of 2.2 ppb. Patients underwent modular bearing exchange, including a ceramic head with a titanium sleeve in 23 of 27 cases with only one recurrence of ALTR in one of the four patients not treated with a ceramic head. The diagnosis of ALTR secondary to corrosion is associated with cobalt levels of >1 ppb with cobalt levels elevated above chromium. Retention of a well-fixed stem and modular exchange to a ceramic head leads to resolution of symptoms and decreases in metal levels., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Given the increasing number of total hip arthroplasty procedures being performed annually, it is imperative that orthopaedic surgeons understand factors responsible for instability. In order to treat this potentially complex problem, we recommend correctly classifying the type of instability present based on component position, abductor function, impingement, and polyethylene wear. Correct classification allows the treating surgeon to choose the appropriate revision option that ultimately will allow for the best potential outcome., (©2016 The British Editorial Society of Bone & Joint Surgery.)

Trabecular metal cones are one option for treating osseous defects during TKA. A total of 83 consecutive TKAs utilizing cones with an average of 40 months follow-up were reviewed. There were 24 males and 59 females, with an average age of 69 years old. Four were complex primary and 79 were revision procedures. Of 83 patients, 10 (12%) required repeat revision surgery (8 infections, one periprosthetic fracture, one aseptic loosening) and overall, 37 of 83 patients (45%) experienced at least one complication. Of 73 unrevised knees, 72 (99%) demonstrated radiographic evidence of osseointegration. Despite a high complication rate in this population, trabecular metal cones represent an attractive option for managing bone loss in complex primary and revision TKA with a high rate of osseointegration., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Femoral bone loss is a complex problem in revision total hip arthroplasty. The Paprosky classification is used when determining the degree and location of bone loss. Meticulous operative planning is essential where severe bone loss is a concern. One must correctly identify the bone loss pattern, safely remove the existing components, and proceed with the proper reconstruction technique based on the pattern of bone loss. This article discusses the etiology and classification of bone loss, clinical and radiographic evaluation, components of effective preoperative planning, and clinical results of various treatment options with a focus on more severe bone loss patterns., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Background: The diagnosis of periprosthetic joint infection (PJI) in patients with failed metal-on-metal (MoM) bearings and corrosion reactions in hip arthroplasties can be particularly difficult, because the clinical presentation of adverse local tissue reactions may mimic that of PJI, because it can also occur concurrently with PJI, and because common laboratory tests used to diagnose PJI may be elevated in patients with MoM THAs., Questions/purposes: We sought to determine the test properties of the serum erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), synovial fluid white blood cell (WBC) count, and synovial fluid differential (percent polymorphonuclear cells [PMNs]) in diagnosing PJI in either MoM hips undergoing revision for a variety of indications or in non-MoM hips undergoing revision for either corrosion reaction or full-thickness wear. Additionally, we sought to describe how MoM bearings, metal debris, and corrosion reactions can confound the analysis of the synovial fluid WBC count and affect its diagnostic use for PJI., Methods: We reviewed 150 revision hips meeting specified inclusion criteria (92 MoM total hips, 19 MoM hip resurfacings, 30 non-MoM bearings with corrosion, and nine full-thickness bearing surface wear with metallosis). In our review, we diagnosed 19 patients as infected using Musculoskeletal Infection Society (MSIS) criteria. Mean laboratory values were compared between infected and not infected patients and receiver operator characteristic curves were generated with an area under the curve (AUC) to determine test performance and optimal cutoffs., Results: After excluding the inaccurate synovial fluid samples, the synovial fluid WBC count (performed accurately in 102 patients) was the best test for the diagnosis of PJI (AUC=98%, optimal cutoff 4350 WBC/μL) followed by the differential (performed accurately in 102 patients; AUC=90%, optimal cutoff 85% PMN). The ESR (performed in 131 patients) and CRP (performed in 129 patients) both had good sensitivity (83% and 94%, respectively). Patients meeting MSIS criteria for PJI had higher mean serum ESR, CRP, synovial fluid WBC count, and differential than those not meeting MSIS criteria (p<0.05 for all). An observer blinded to the MSIS diagnosis of the patient assessed the synovial fluid samples for inaccuracy secondary to metal or cellular debris. Synovial fluid sample "inaccuracy" was defined as the laboratory technician noting the presence of metal or amorpous material, fragmented cells, or clots, or the sample having some defect preventing an automated cell count from being performed. Of the 141 patients who had a synovial fluid sample initially available for review, 47 (33%) had a synovial fluid sample deemed to be inaccurate. A synovial fluid WBC count was still reported; however, 35 of these 47 hips (75%) and 11 of these 35 (31%) were falsely positive for infection., Conclusions: The diagnosis of PJI is extremely difficult in patients with MoM bearings or corrosion and the synovial fluid WBC count can frequently be falsely positive and should be relied on only if a manual count is done and if a differential can be performed. A more aggressive approach to preoperative evaluation for PJI is recommended in these patients to allow for careful evaluation of the synovial fluid specimen, the integration of synovial fluid culture results, and repeat aspiration if necessary., Level of Evidence: Level III, diagnostic study. See Guidelines for Authors for a complete description of levels of evidence.