Functional Outcomes of a Musculoskeletal Integrated Practice Providing Comprehensive Whole Person Care for Hip Osteoarthritis.

BACKGROUND: Outcomes of hip osteoarthritis (OA) management within integrated practice units (IPUs) are lacking. This study reports 6-month and 1-year patient-reported outcomes (PROs) of IPU care, the proportion of patients achieving minimal clinically important difference (MCID) and substantial clinical benefit (SCB) at 1 year, and baseline factors associated with the likelihood of achieving MCID and SCB. METHODS: We retrospectively evaluated 1009 new patients presenting to an IPU with hip OA between October 2017 and June 2020. Patients experienced multidisciplinary team-based management. Individuals with baseline and 6-month PROs or baseline and 1-year PROs (Hip Disability and Osteoarthritis Outcome Score Joint Replacement, HOOS JR) were included. We used anchor-based MCID and SCB thresholds and multivariable binary logistic regression models to identify baseline factors associated with achieving 1-year MCID and SCB. RESULTS: HOOS JR increased from baseline to 6 months (Δ = 19.1 ± 2.1, P = .065) and baseline to 1 year (Δ = 35.8 ± 2.9, P < .001). At 1 year, 72.7% (IPU only) and 88% (IPU-based total hip arthroplasty [THA]) achieved MCID (P < .001), and 62.3% (IPU only) and 88% (IPU-based THA) achieved SCB (P < .001). In multivariable regression, lower baseline HOOS JR scores (r = 0.96, P = .04), undergoing THA (r = 0.213, P < .001), and fewer symptoms of generalized anxiety (r = 0.932, P = .018) were independently associated with achieving MCID at 1 year. The same factors were independently associated with achieving SCB at 1 year. Lower baseline anxiety (Generalized Anxiety Disorder Questionnaire-7 item) and greater hip-related preoperative limitations result in greater likelihood of achieving MCID and SCB. CONCLUSION: Significant improvements in patient outcomes can be achieved by IPUs providing comprehensive care for hip OA including the management of psychological distress. Future prospective studies should compare the outcomes of IPUs with traditional care in managing diverse patient phenotypes.

Which Preoperative Factors are Associated with Not Attaining Acceptable Levels of Pain and Function After TKA? Findings from an International Multicenter Study.

BACKGROUND: Although TKA is a common and proven reliable procedure for treating end-stage knee osteoarthritis, a minority of patients still do not achieve satisfactory levels of pain relief and functional improvement. Even though several studies have attempted to identify patients at risk of having poor clinical outcomes, few have approached this issue by considering the outcome of the patient-acceptable symptom state (PASS), defined as the value on a patient-reported outcome measure scale above which the patient deems their current symptom state acceptable. QUESTIONS/PURPOSES: (1) What is the proportion of patients who do not attain the PASS in pain and function at 1 year after TKA? (2) Which preoperative patient factors are associated with not achieving the PASS in pain at 1 year after TKA? (3) Which preoperative patient factors are associated with not achieving the PASS in function at 1 year after TKA? METHODS: This retrospective study is a secondary analysis of the 1-year follow-up data from a prospective, international, multicenter study of a single TKA system. Inclusion criteria for that study were patients diagnosed with primary osteoarthritis or post-traumatic arthritis and who were able to return for follow-up for 10 years; exclusion criteria were infection, osteomyelitis, and failure of a previous joint replacement. Between 2011 and 2014, 449 patients underwent TKA at 10 centers in five countries. At 1 year, 13% (58 of 449) were lost to follow-up, 2% could not be analyzed (eight of 449; missing 1-year KOOS), leaving 85% (383 of 449) for analysis here. The primary outcomes were not surpassing evidence-derived PASS thresholds in the Knee Injury and Osteoarthritis Outcome Score (KOOS) Pain and Activities in Daily Living (ADL) sub-scores. Multivariate binary logistic regressions considering preoperative demographic, radiographic, and patient-reported outcome measure data were constructed using a forward stepwise elimination algorithm to reach the simplest best-fit regression models. RESULTS: At 1 year after TKA, 38% of the patients (145 of 383) did not reach the PASS in KOOS Pain, 36% (139 of 383) did not reach the PASS in KOOS ADL, and 29% (110 of 383) did not achieve the PASS in either KOOS Pain or ADL. After controlling for potentially confounding variables such as gender, age, BMI, and comorbidity scores, we found that men (odds ratio 2.09; p = 0.01), and patients with less-than-advanced radiographic osteoarthritis (OR 2.09; p = 0.01) were strongly associated with not achieving the PASS in pain. After controlling for the same potentially confounding variables, we found that patients with less-than-advanced radiographic osteoarthritis (OR 2.09; p = 0.01) were also strongly associated with not achieving the PASS in function. CONCLUSIONS: We found that patients with less severe osteoarthritis were much less likely to attain the PASS in pain and function at 1 year after TKA, and that men were much less likely to achieve the PASS in pain at 1 year after TKA. Based on these findings, surgeons should strongly consider delaying surgery in patients who present with less-than-severe osteoarthritis, with increased caution in men. Surgeons should counsel their patients on their expectations and their chances of achieving meaningful levels of pain and functional improvement. Future regional and national registry studies should assess the true proportion of patients attaining PASS in pain and function after TKA and confirm if the preoperative factors identified in this study remain significant in larger, more diverse patient populations. LEVEL OF EVIDENCE: Level III, therapeutic study.

The Patient Acceptable Symptom State for the Harris Hip Score Following Total Hip Arthroplasty: Validated Thresholds at 3-Month, 1-, 3-, 5-, and 7-Year Follow-Up.

BACKGROUND: The Patient Acceptable Symptom State (PASS) represents the value on a patient-reported outcome measure scale beyond which patients consider themselves well or in a satisfactory state. The aim of this study is to define and validate the PASS threshold for the HHS at 3 months, 1, 3, 5, and 7 years after THA. METHODS: A total of 976 patients from 14 centers in 7 countries were enrolled into a prospective study. Patients completed the HHS and a numerical rating scale for satisfaction at each follow-up. PASS thresholds for the HHS were calculated at each follow-up interval using the anchor-based, 80% specificity method. A bootstrapping method was used to internally validate the primary PASS thresholds. A patient sample sourced from an institutional registry was used for external validation. RESULTS: The HHS was an excellent predictor of satisfaction at each time point (area under the curve > 0.8; P < .001). PASS thresholds for the HHS were 76 points at 3 months, 89 points at 1 year, 93 points at 3 years, 94 points at 5 years, and 93 points at 7 years. When applied to the internal and external validation cohorts, all PASS thresholds showed acceptable or excellent ability to predict satisfaction (area under the curve = 0.73-80; P < .001). CONCLUSION: The present study is the first to present validated PASS thresholds for the HHS following THA. These findings will serve as a useful reference for future THA outcome studies and as benchmarks for surgeons in their assessment of their patients' clinical success.

Changes in Patient Satisfaction Following Total Joint Arthroplasty.

BACKGROUND: The primary aim is to identify the degree to which patient satisfaction with the outcome of total hip arthroplasty (THA) or total knee arthroplasty (TKA) changes between 1 and 3 years from the procedure. The secondary aim is to identify variables associated with satisfaction. METHODS: Data were sourced from 2 prospective international, multicenter studies (919 THA and 450 TKA patients). Satisfaction was assessed by a 10-point numerical rating scale, at 1- and 3-year follow-up. Linear mixed-effects models were used to assess factors associated with satisfaction. RESULTS: For the THA cohort, higher preoperative joint space width (odds ratio [OR] = 0.28; P = .004), pain from other joints (OR = 0.26; P = .033), and lower preoperative health state (OR = -0.02; P < .001) were associated with consistently lower levels of satisfaction. The model also showed that patients with preoperative anxiety/depression improved in satisfaction between 1 and 3 years (OR = -0.26; P = .031). For the TKA cohort, anterior (vs neutral or posterior) tibial component slope (OR = 0.90; P = .008), greater femoral component valgus angle (OR = 0.05; P = .012), less severe osteoarthritis (OR = -0.10; P < .001), and lower preoperative health state (OR = -0.02; P = .003) were associated with lower levels of satisfaction across the study period. In addition, patients with anterior tibial component slope improved in satisfaction level over time (OR = -0.33; P = .022). CONCLUSION: Changes in satisfaction following THA and TKA are rare between 1- and 3-year follow-up. The findings of this study can be used to guide patient counseling preoperatively and to determine intervals of routine follow-up postoperatively.

The AAHKS Clinical Research Award: No Evidence for Superior Patient-Reported Outcome Scores After Total Hip Arthroplasty With the Direct Anterior Approach at 1.5 Months Postoperatively, and Through a 5-Year Follow-Up.

BACKGROUND: The direct anterior approach to total hip arthroplasty (THA) may result in superior early postoperative patient-reported outcome measures (PROMs). This study compared PROMs between THA patients treated with the direct anterior or posterolateral approach between 1.5 months and 5 years, using literature-derived patient acceptable symptom state (PASS) and minimal clinically important improvement (MCII) thresholds. METHODS: A propensity score match of 93 direct anterior patients to 93 posterolateral patients from a multicenter US collaboration (6 centers, 398 patients) was performed. The Harris Hip Score (HHS), the Short-Form 36, and a Numerical Rating Scale for Pain were collected preoperatively, postoperatively (mean days: 47), and at 1, 3, and 5 years. The proportion of patients reaching the HHS PASS, Pain MCII, and Function MCII in the direct anterior and posterolateral groups was compared using binary logistic regressions, controlling for age, gender, body mass index, and Charnley score. RESULTS: Direct anterior patients were less likely to reach the HHS PASS at the postoperative visit (P = .015; odds ratio = 0.454), but not at later visits (P > .082). Direct anterior patients had no difference from posterolateral patients in their tendency to reach the Pain MCII postoperatively or at 1 year (P > .090). The direct anterior patients were less likely to reach the Function MCII at the postoperative visit (P = .011; odds ratio = 0.422), but not at 1 year (P = .958). CONCLUSION: No evidence was found of superior early postoperative PROM scores in THA patients treated with the direct anterior approach. No PROM differences were found at or beyond 1 year, indicating that patients reach similar final symptom states, regardless of surgical approach.

Regional differences between the US, Scandinavia, and South Korea in patient demographics and patient-reported outcomes for primary total knee arthroplasty.

INTRODUCTION: Differences in total knee arthroplasty (TKA) patient demographics and clinical outcomes may exist between international regions, yet research is limited. The aim of this study was, therefore, to compare TKA patient demographics and patient-reported outcome measure (PROM) scores between the US, Scandinavia, and South Korea. MATERIALS AND METHODS: A total of 398 TKA patients from three regions were assessed: 169 in Scandinavia (3 centers), 129 in the US (3 centers), and 100 patients in South Korea (2 centers). Regional variation in patient demographics was assessed using Kruskal-Wallis H tests. Regional variation in PROM scores from preoperative, 1-, 3- and 5-year visits was assessed using piecewise linear mixed effect models. The PROMs analyzed were a numerical rating scale for satisfaction and the Knee Osteoarthritis Outcome Score. RESULTS: South Korean patients were the oldest (p < 0.001) and had the highest Charnley class (p < 0.001); US patients had the highest BMI (p < 0.001); Scandinavian patients had the lowest preoperative KL grade (p < 0.001). Scandinavian patients were associated with better preoperative and worse postoperative PROM scores. Scandinavian patients were also associated with moderately lower levels of satisfaction. These differences were lessened but remained significant after controlling for relevant demographic and surgical factors. CONCLUSIONS: Regional differences were found in TKA patient demographics and PROMs between the US, Scandinavia, and South Korea. The regional differences in patient demographics support the need for more research and clear guidelines related to TKA appropriateness criteria. The better preoperative and worse postoperative Scandinavian PROM scores may have been related to their less severe KL grade but might also reflect cultural differences in how patients reflect on their health state when answering PROMs. Clinicians should be aware of these international differences in PROM scores when interpreting studies conducted in different international regions. Future studies should investigate TKA variation between more international regions and assess intraregional variation. LEVEL OF EVIDENCE: Level III.

Patient-acceptable symptom state for the Oxford Hip Score and Forgotten Joint Score at 3 months, 1 year, and 2 years following total hip arthroplasty: a registry-based study of 597 cases.

Background and purpose - Patient-acceptable symptom states (PASS) represent the level on a patient-reported outcome measure (PROM) at which patients are satisfied with postoperative outcomes. We defined the PASS for the Oxford Hip Score (OHS) and Forgotten Joint Score (FJS-12) at 3-month, 1-year, and 2-year intervals after primary total hip arthroplasty (THA).Patients and methods - Between July 2018 and April 2019, primary THA patients in an academic medical center's registry completed the OHS, FJS-12, and a satisfaction anchor question at 3-month (n = 230), 1-year (n = 180), or 2-year (n = 187) postoperative intervals. PASS thresholds were derived with receiver operating characteristic analysis using the 80% specificity method. 95% confidence intervals (CI) were calculated using 1,000 non-parametric bootstrap replications.Results - 74%, 85%, and 86% of patients reported having a satisfactory symptom state at 3 months, 1, and 2 years after surgery, respectively. At 3-month, 1-year, and 2-year intervals, PASS thresholds were 34 (CI 31-36), 40 (CI 36-44), and 39 (CI 35-42) points for the OHS and 59 (CI 54-64), 68 (CI 61-75), and 69 (CI 62-75) points for the FJS-12.Interpretation - PASS thresholds varied with time for both the OHS and the FJS-12, with lower 3-month compared with 1-year and 2-year thresholds. These PASS thresholds represent OHS and FJS-12 levels at which the average patient is satisfied with THA outcomes, helping to interpret PROMs and serving as clinically significant benchmarks and patient-centered outcomes for research.

What Is the Clinical Presentation of Adverse Local Tissue Reaction in Metal-on-metal Hip Arthroplasty? An MRI Study.

BACKGROUND: Adverse local tissue reaction (ALTR) is not only a prominent cause of metal-on-metal (MoM) implant revision, but may also compromise the result of revision surgery. Patients treated with MoM arthroplasty and subsequently revised as a result of ALTR have been shown to experience worse patient-reported outcomes, inferior survivorship, and more complications when compared with patients receiving MoM implants who were revised for reasons other than ALTR. There is conflicting evidence as to whether the presence of symptoms is associated with ALTR in patients with MoM implants. Blood metal ions are associated with ALTR, but a consensus on appropriate thresholds associated with ALTR risk is lacking. QUESTIONS/PURPOSES: (1) Was the presence of symptoms as measured by patient-reported outcome measures associated with ALTR presence and severity as noted on metal artifact reduction sequence (MARS)-MRI in patients treated with one design of MoM THA or hip resurfacing arthroplasty (HRA)? (2) Could reliable thresholds for blood metal ion levels be determined that were associated with ALTR presence on MARS-MRI? METHODS: This retrospective study presents a secondary analysis of data drawn from a prospective, international, multicenter study of the recalled Articular Surface Replacement (ASR) hip system. This larger study aims to identify risk factors for revision and provide followup guidelines for the many unrevised ASR patients. A total of 1721 patients were enrolled from 16 centers in six countries after the device was recalled and are followed annually for 5 years. In the present analysis, data from the enrollment visit (mean time from index surgery, 7.5 years; SD 3.5 years) were considered. Only patients from two centers conducting MARS-MRI on all patients regardless of clinical presentation as a standard of care were included to avoid selection bias. A total of 327 unilateral patients fulfilled our inclusion criteria (90% of those eligible). The level of symptoms was systematically determined using the Harris hip score and a visual analog scale for pain, and whole blood metal ion levels were collected from all patients. MARS-MRIs were analyzed by a single reader for ALTR presence (Anderson classification), diameter, and synovial thickness. A validation series of 35 MARS-MRIs indicated excellent intrareader reproducibility of the evaluations (intraclass correlation = 0.82) and substantial agreement (κ coefficient = 0.64) was achieved between the MARS-MRI reader and a musculoskeletal radiologist with > 10 years of experience with MARS-MRI. Binary logistic regression was used to determine variables independently associated with ALTR. Receiver operator characteristic curves were used to determine sensitive and specific cut points for cobalt and chromium. RESULTS: After controlling for confounding variables, presence of symptoms was determined to be a risk factor for ALTR (odds ratio, 2.9; p = 0.007) in patients treated with ASR MoM THA. Moreover, among patients undergoing ASR MoM THA with ALTR, synovial thickness correlated with symptomaticity (p = 0.030). For patients undergoing ASR MoM HRA, we found no association between symptoms and ALTR prevalence or severity. A cobalt cutoff of 3.2 parts per billion (ppb) was associated with increased risk of ALTR (p < 0.001; sensitivity, 68%; specificity, 71%) in ASR MoM THA. In patients with ASR MoM HRA, a cobalt threshold of 2.9 ppb was indicative of ALTR (p < 0.001; sensitivity, 79%; specificity, 69%). CONCLUSIONS: The risk factors identified in the current study may be used to stratify patients receiving MoM implants in terms of ALTR risk. We found that symptoms are associated with an increased likelihood of ALTR presence in ASR MoM THA and that cobalt ion level is associated with ALTR in ASR MoM THA as well as ASR MoM HRA. Importantly, MoM HRA followup protocols that exempt asymptomatic patients from annual followup are not justified because asymptomatic patients are no less likely to have ALTR than symptomatic patients. Blood metal ion levels may reliably be used to screen patients undergoing MoM HRA. For patients undergoing MoM THA, a combination of symptom state and blood metal ion levels may be used to determine ALTR risk. LEVEL OF EVIDENCE: Level III, diagnostic study.

What Preoperative Factors are Associated With Not Achieving a Minimum Clinically Important Difference After THA? Findings from an International Multicenter Study.

BACKGROUND: Despite innovations in THA, there remains a subgroup of patients who experience only modest pain relief and/or functional improvement after the procedure. Although several studies have previously sought to identify factors before surgery that were associated with achieving or not achieving a meaningful improvement after THA, there is no consensus on which factors are most associated; many studies have relied on single-center or single-country multicenter studies for their cohorts. QUESTIONS/PURPOSES: We sought to identify (1) the proportion of patients who do not achieve a minimum clinically important difference (MCID) in pain and function 1 year after THA, and (2) the preoperative factors that were associated with not achieving MCIDs in pain and function 1 year after THA. METHODS: This retrospective study analyzed data gathered from a prospective international, multicenter study examining the long-term clinical outcomes of two different polyethylene liners and two different acetabular shells. A total of 814 patients from 12 centers across four countries were enrolled in the study, with the final cohort consisting of 594 patients (73%) who all had complete preoperative and 1-year PROMs as well as a valid preoperative radiograph used to measure minimum joint space width. The outcomes in this study were achieving evidence-derived MCIDs in (1) pain, defined as a reduction of two points on an 11-point (0 = very little, 10 = worst imaginable) numerical rating scale (NRS) for hip-related pain or reporting a 1 year NRS-pain score of 0, and (2) function, defined as an increase equal to or greater than 8.3 on the SF-36 Physical Function subscore (range: 0 to 100; 0 = maximum disability, 100 = no disability) or reporting a 1-year SF-36 Physical Function subscore within the 95th percentile of scores in our cohort. All demographic variables, such as age, sex, country; surgical factors, including body mass index (BMI), surgical approach, acetabular liner type, and preoperative PROMs, were included as covariates in a binary logistic regression model. We used a backwards stepwise elimination algorithm to reach the simplest, best-fit model. RESULTS: In the final analysis cohort of 594 patients, 54 patients (9%) did not achieve the MCID in pain and 146 (25%) patients did not achieve the MCID in physical function after THA. After controlling for potential confounding variables such as age, BMI, and preoperative PROMs, we found that higher joint space width (odds ratio (OR) = 2.19; 95% confidence interval (CI) = 1.49-3.22; p < 0.001), lower preoperative SF-36 Mental Component Summary (MCS) (OR = 0.95; 95% CI = 0.93-0.98; p = 0.001), and female sex (OR = 2.04; 95% CI = 1.08-3.82; p = 0.027) were associated with failing to achieve a MCID in pain. It is important to note that the effect size of having a higher preoperative SF-36 MCS is small, with a 1- or 10-point increase in SF-36 MCS decreasing the odds of a patient not achieving the pain MCID by 5% or 63%, respectively.In a separate multivariable model, after controlling for potential confounding variables such as age, BMI, and preoperative PROMs, we found that higher joint space width (OR = 1.54; 95% CI = 1.18-2.02; p = 0.002), higher preoperative Harris hip score (HHS) (OR = 1.01; 95% CI = 1.00-1.03; p = 0.019) and undergoing surgery in Scandinavia (OR = 1.73; 95% CI = 1.17-2.55; p = 0.006) were associated with failing to achieve a MCID in physical function. It is important to note that the effect size of having a higher preoperative HHS is very small, with a 1- or t10-point increase in HHS increasing the odds of not achieving the physical function MCID by only 1% or 15%, respectively. CONCLUSIONS: These findings suggest that surgeons should counsel patients with high joint space width, female patients, and patients undergoing surgery in Scandinavia that they may be much less likely to experience meaningful pain relief or functional improvement after THA, and in light of that, determine whether indeed surgery should be postponed or avoided in those patients. Lower SF-36 MCS score and higher HHS before surgery were also found to be associated with not achieving MCIDs in pain and physical function, respectively, after surgery, but both had relatively small effect sizes. Future prospective studies may consider exploring the relationship between less pain relief or functional improvement and the risk factors identified in this study, such as high joint space width, to validate our findings and determine if the variables we identified are truly predictive of worse postoperative outcomes. Future retrospective studies of regional or national registry data should use the analysis methods presented within this study to both identify the portion of the THA patients who do not achieve a MCID in pain or physical function after surgery and confirm if the preoperative risk factors for poor improvement identified within our international, multicenter cohort are also found in a larger patient population with more diverse implants and comorbidities. LEVEL OF EVIDENCE: Level III, therapeutic study.

The Benefits of National and Regional Arthroplasty Registries.

Since the first arthroplasty registries were established in the 1970s, they have become powerful tools in improving the efficiency of health care delivery and patient outcomes. As demonstrated over the past decades, registries can offer benefits not only to patients and surgeons but also to a variety of other stakeholders, such as hospitals, payers, and implant manufacturers. Registry data may be leveraged to address a variety of pressing concerns in the field of arthroplasty. These examples include the role of registries in (1) informing the financial aspects of an increasingly value-based payment system, (2) identifying best clinical practices, (3) improving the outcomes of individual health care providers, and (4) selecting new technologies through outlier detection and benchmarking. As registries continue to mature by improving data coverage and quality, they will play a central role in shaping the future of arthroplasty as well as orthopaedics in general.

Promising early outcomes of a novel anatomic knee system.

PURPOSE: The primary aim of this study was to report the early clinical and radiographic outcomes of patients who have been treated with total knee arthroplasty (TKA) using the Persona knee system. The secondary aim was to compare patient-reported outcomes (PROs) of the Persona knee system to those of the NexGen implant. METHODS: A registry-based study of a consecutive series of 112 patients (129 knees) treated with the Persona knee system from a single center was conducted. Preoperative, 1-year, and 2-year radiographs and PROs were analyzed. Postoperative radiographs were assessed for radiolucency and component positioning. Patients were monitored for postoperative complications and revision. Two-year PROs were compared to a 1:1 propensity score-matched cohort of patients treated with the NexGen knee system. RESULTS: Ninety-five percent of knees were within literature-defined safe ranges of the anatomical tibiofemoral axis, tibial varus/valgus angle, femoral flexion/extension angle, and tibial slope. Radiolucency was observed in 0.9% and 1.3% of knees at one and 2 years, respectively. Two-year PRO values demonstrated clinically meaningful improvements from the preoperative values. The cumulative 2-year percent revision was 3.0% (95% confidence interval 1.9-3.8%); there were no revisions due to implant mechanical failure. Patients treated with the Persona knee system had higher KOOS symptom (p = 0.037) and KOOS QOL (p < 0.001) scores compared to patients with the NexGen knee system. CONCLUSIONS: This knee design demonstrates excellent clinical outcomes, similar or better than the NexGen knee system, at early follow-up. LEVEL OF EVIDENCE: III.

Inferior Radiographic and Functional Outcomes With Modular Stem in Metal-on-Metal Total Hip Arthroplasty.

BACKGROUND: Data on the association between stem type and metal-on-metal (MoM) total hip arthroplasty (THA) performance are limited. The aim of this study is to investigate the effect of stem type on the prevalence of osteolysis and radiolucency, blood metal ion levels, and functional outcomes in patients with Articular Surface Replacement THA (ASR XL), a type of MoM THA. METHODS: We analyzed 539 unilateral MoM THAs coupled with Summit (48%), Corail (35%), or S-ROM (17%) hip stems at a mean follow-up of 6.4 years. Fifty-four percent of the patients were male, and the mean age was 60 years. We studied radiographs, patient-reported outcome measures, and ion levels. RESULTS: Patients with S-ROM hip stems were 3.8 times more likely to have osteolysis (P = .003) and 7.6 times more likely to have radiolucency (P < .001) than those treated with Summit hip stems. In addition, patients treated with S-ROM hip stems scored worse than those with Summit hip stems in 4 of the 5 patient-reported outcome measures: Harris Hip Score, Visual Analog Scale pain, University of California at Los Angeles activity, and EQ-5D index. All these differences were statistically significant and ranged from 5% to 10%, which is clinically significant. CONCLUSION: Patients with S-ROM hip stems had inferior functional and radiographic results compared to patients with Summit hip stems. Retrieval studies on large diameter head MoM THA and close follow-up of these patients with hip stems are needed to understand the mechanism causing the differences in outcomes between these stem types.

The Cobalt/Chromium Ratio Provides Similar Diagnostic Value to a Low Cobalt Threshold in Predicting Adverse Local Tissue Reactions in Patients With Metal-on-Metal Hip Arthroplasty.

BACKGROUND: A higher cobalt/chromium (Co/Cr) ratio is thought to be associated with corrosion of the trunnion and increased adverse local tissue reaction (ALTR) risk in patients treated with metal-on-metal (MoM) hip arthroplasty. The main aim of this study was to investigate the diagnostic value of Co/Cr ratio in identifying ALTR in patients treated with MoM hip resurfacing arthroplasty and total hip arthroplasty (THA). METHODS: A total of 310 unilateral patients were included. All patients received a metal artifact reduction sequence magnetic resonance imaging to detect ALTR. Blood Co and Cr levels were measured. RESULTS: MoM THA patients had a higher Co/Cr ratio than MoM hip resurfacing arthroplasty patients (1.7, interquartile range 1.2-3.1 vs 0.9, interquartile range 0.7-1.3, P < .001). The continuous Co/Cr ratio, continuous Co, and Co ≥ 7 ppb were predictive of ALTR when tested in receiver-operating characteristic analyses. The most sensitive and specific cutoffs were found to be 1.4 for Co/Cr ratio (sensitivity = 80.0%; specificity = 48.7%) and 2.4 ppb for Co (sensitivity = 77.8%; specificity = 46.2%). In multivariate analysis, continuous Co, Co ≥ 7 ppb, and the receiver-operating characteristic analysis-generated cutoffs were associated with ALTR prevalence. CONCLUSION: Blood metal ions are strong, but not perfect, predictors of ALTR in patients with MoM hip arthroplasty. Higher Co/Cr ratios are associated with increased risk for ALTR in MoM THA. However, blood Co levels alone are as good a predictor of ALTR as the Co/Cr ratio. The most ALTR-sensitive cutoffs are lower than previously reported in the literature.

Indications for MARS-MRI in Patients Treated With Articular Surface Replacement XL Total Hip Arthroplasty.

BACKGROUND: The purpose of this study was to identify which patient and clinical factors are predictive of adverse local tissue reaction (ALTR) and to use these factors to create a highly sensitive algorithm for indicating metal artifact reduction sequence magnetic resonance imaging (MARS-MRI) in Articular Surface Replacement (ASR) XL total hip arthroplasty patients. Our secondary aim was to compare our algorithm to existing national guidelines on when to take MARS-MRI in metal-on-metal total hip arthroplasty patients. METHODS: The study consisted of 137 patients treated with unilateral ASR XL implants from a prospective, multicenter study. Patients underwent MARS-MRI regardless of clinical presentation at a mean of 6.2 (range, 3.3-10.4) years from surgery. Univariate and multivariate analyses were conducted to determine which variables were predictive of ALTR. Predictors were used to create an algorithm to indicate MARS-MRI. Finally, we compared our algorithm's ability to detect ALTR to existing guidelines. RESULTS: We found a visual analog scale pain score ≥2 (odds ratio [OR] = 2.53; P = .023), high blood cobalt (OR = 1.05; P = .023), and male gender (OR = 2.37; P = .034) to be significant predictors of ALTR presence in our cohort. The resultant algorithm achieved 86.4% sensitivity and 60.2% specificity in detecting ALTR within our cohort. Our algorithm had the highest area under the curve and was the only guideline that was significantly predictive of ALTR (P = .014). CONCLUSION: Our algorithm including patient-reported pain and sex-specific cutoffs for blood cobalt levels could predict ALTR and indicate MARS-MRI in our cohort of ASR XL metal-on-metal patients with high sensitivity. LEVEL OF EVIDENCE: Level II, diagnostic study.

Developmental Dysplasia Treated With Cementless Total Hip Arthroplasty Utilizing High Hip Center Reconstruction: A Minimum 13-Year Follow-up Study.

BACKGROUND: The primary aim of this study was to determine the clinical outcomes at 13-year follow-up of patients diagnosed with developmental dysplasia of the hip and subsequently treated with total hip arthroplasty (THA). The secondary aim was to investigate the effect of hip center location on clinical outcomes and polyethylene wear. METHODS: We reviewed data from a consecutive series of 104 patients (123 hips) from a single center. Patients were treated with THA with the high hip center (HHC) technique using cementless acetabular shells and highly cross-linked liners. Radiographs were collected preoperatively and through 13-year follow-up to assess degree of dysplasia (Crowe classification), component positioning, occurrence of bone resorption, and polyethylene wear. The Harris Hip Score (HHS) was administered at 4 and 13 years. RESULTS: No patients were lost to follow-up, and one was revised for femoral loosening. Radiolucency was seen in 20% of patients and was not associated with HHC (P = .560). No patients developed osteolysis. The wear rate was low for all patients (mean: 3 ± 19 µm/y) and not associated with HHC (P = .852). The median 13-year HHS was 91.9 (interquartile range: 84.8-97.0). There was a statistically significant decline from the 4- to 13-year HHS (P < .001) for the Crowe II-IV group, although 82% of these patients remained above 80 points at 13 years. The nondysplastic and Crowe I group showed no longitudinal change in HHS (P = .243). CONCLUSION: This cup design and highly cross-linked polyethylene liner combination demonstrates excellent clinical outcomes, similar to THA for primary osteoarthritis, through 13-year follow-up in patients with various degrees of developmental dysplasia of the hip and HHC reconstructions.

Indications for MARS-MRI in Patients Treated With Metal-on-Metal Hip Resurfacing Arthroplasty.

BACKGROUND: Currently, there are no universally accepted guidelines on when to obtain metal artifact reduction sequence magnetic resonance imaging (MARS-MRI) in metal-on-metal (MoM) hip resurfacing arthroplasty (HRA) patients. Our primary aims were to identify which patient and clinical factors are predictive of adverse local tissue reaction (ALTR) and create an algorithm for indicating MARS-MRI in patients with Articular Surface Replacement (ASR) HRA. The secondary aim was to compare our algorithm to existing guidelines on when to perform MARS-MRI in MoM HRA patients. METHODS: The study cohort consisted of 182 patients with unilateral ASR HRA from a prospective, multicenter study. Subjects received MARS-MRI at a mean of 7.8 years from surgery, regardless of symptoms. We determined which variables were predictive of ALTR and generated cutoffs for each variable. Finally, we created an algorithm to predict ALTR and indicate MARS-MRI in ASR HRA patients using these cutoffs and compared it to existing guidelines. RESULTS: We found high blood cobalt (Co) (odds ratio = 1.070; P = .011) and high blood chromium (Cr) (odds ratio = 1.162; P = .002) to be significant predictors of ALTR presence. Our algorithm using a blood Co cutoff of 1.15 ppb and a Cr cutoff of 1.09 ppb achieved 96.6% sensitivity and 35.3% specificity in predicting ALTR, which outperformed the existing guidelines. CONCLUSION: Blood Co and Cr levels are predictive of ALTR in ASR HRA patients. Our algorithm considering blood Co and Cr levels predicts ALTR in ASR HRA patients with higher sensitivity than previously established guidelines.

Periprosthetic acetabular radiolucency progression in mid-term follow-up of the articular surface replacement hip system.

INTRODUCTION: Recent registry studies show that aseptic loosening secondary to osteolysis is the second leading cause of hip implant failure in patients implanted with metal-on-metal (MoM) bearings. The primary aim of our study was to report on the progression of acetabular osteolysis during mid-term follow-up in patients treated with MoM hip resurfacing arthroplasty (HRA) and MoM total hip arthroplasty (THA). The secondary aim was to identify independent predictors of osteolytic lesion progression. MATERIALS AND METHODS: A total of 805 patients (805 hips) were included in this study (541 MoM HRA, 264 MoM THA) from a prospective, international clinical registry of the Articular Surface Replacement Hip System. Patients were enrolled a median of 6.6 years from surgery. Osteolytic lesion progression was defined either as any lesion developing de novo, or as an existing lesion progressing from radiolucency to osteolysis during the study period (range 0.5-4.3 years). RESULTS: The number of cases with any osteolysis or radiolucency was 21 (3.9%) for ASR HRA and 29 (11.0%) for ASR XL THA at enrollment and increased to 69 (12.8%) for ASR HRA and 41 (15.5%) for ASR XL THA after follow-up. Osteolytic lesion progression was found in 66 (12.2%) ASR HRA patients and 31 (11.7%) ASR XL THA patients. Multivariate models determined that lower acetabular version angle (OR 0.963, p = 0.011) and elevated whole blood chromium (OR 1.110, p = 0.044) were independent predictors of osteolytic lesion progression in ASR HRA. CONCLUSION: We suggest that physicians of patients implanted with ASR HRA implants closely monitor patients with higher chromium levels and lower version angles, as they are at increased risk for osteolytic lesion progression, and we recommend annual radiographic follow-up on all patients with ASR implants.

Are Females at Greater Risk for Revision Surgery After Hip Resurfacing Arthroplasty With the Articular Surface Replacement Prosthesis?

BACKGROUND: Female patients undergoing hip resurfacing arthroplasties may be at greater risk of revision surgery than males, but it is unclear whether this is related to sex or other factors. We focused our analysis on data from a prospective multicenter cohort study monitoring the ASR(TM) hip resurfacing arthroplasty prosthesis on the potential association of sex on patient-reported outcome measures (PROMs), metal ion levels, revision surgery, and presence of adverse local tissue reaction. As thousands of patients with the ASR(TM) prosthesis are still undergoing followup it is critical to optimize the protocol for monitoring these patients. QUESTIONS/PURPOSES: We wished (1) to assess the associations between sex and implant survival, and adverse local tissue reaction; and (2) to report the differences between sexes in metal ion levels and patient-reported outcome measures. METHODS: One thousand two hundred fifty-two patients (1390 hips) who underwent hip resurfacing arthroplasty with implantation of the ASR(TM) prosthesis from April 2003 to July 2010 were eligible for enrollment in a multicenter followup study of the ASR(TM) Hip Resurfacing System after the voluntary recall of this device was initiated by DePuy in 2010. Nine hundred seventy patients (1098 hips) were enrolled at a mean of 7 years after surgery, with a mean followup of 2 years (range, 1-3.5 years). Nine hundred fifty-eight patients (1084 hips) met the inclusion criteria: ability to provide informed consent, complete PROMs, and continued routine followup. A subset of patients (150 patients, 171 hips), who all were from one center, with annual metal artifact reduction sequence MRI were analyzed. Ninety-three percent of patients from this center had routine MRI performed. The EuroQoL (EQ-5D), Harris hip score (HHS), University of California Los Angeles (UCLA) activity score, VAS pain, radiographs, patient and surgery details, and blood cobalt and chromium levels were obtained. Cox regression analysis was conducted to identify factors associated with implant survival, using any revision as the end point, and presence of adverse local tissue reaction. RESULTS: In patients who had unilateral surgery, the only variable found to be associated with revision surgery was HHS (hazard ratio [HR], 0.96; 95% CI, 0.94-0.97; p < 0.001). In patients who had bilateral surgery, only HHS (HR, 0.93; 95% CI, 0.90-0.97; p < 0.001) and cobalt level (HR, 1.02; 95% CI, 1.01-1.03; p < 0.001) were associated with risk for revision. In patients with metal artifact reduction sequence MRI, the only variable found to be associated with presence of adverse local tissue reaction was cobalt level (HR, 1.06; 95% CI, 1.02-1.10; p = 0.001). Cobalt and chromium concentrations were greater in female patients than in male patients (cobalt, median 1.89 versus median 1.12 parts per billion [ppb], p < 0.001; chromium, median 2.03 versus median 1.17 ppb, p < 0.001). Slight differences were observed between males and females in HHS (males median 96 versus females median 94, p < 0.001) and UCLA scores (median 8 versus median 6, p < 0.001); however, there was no difference between sexes for VAS pain (median 0.5 versus median 0.5, p = 0.405). Differences were identified between males and females in the distribution of EQ-5D scores, yet the medians were the same (median 1.0 versus median 1.0, p < 0.001). CONCLUSIONS: Male and female patients who had hip resurfacing arthroplasty with implantation of the ASR(TM) prosthesis should be followed with equal vigilance as both are at similar risk of revision surgery and adverse local tissue reaction. Metal ion levels and HHS should be obtained at followup to monitor for risk of revision and as a screening tool for MRI. Further research is necessary to evaluate if these relationships persist in patients with other metal-on-metal prostheses. LEVEL OF EVIDENCE: Level II, therapeutic study.