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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.

BACKGROUND: Periprosthetic osteolysis resulting in aseptic loosening is a leading cause of THA revision. Individuals vary in their susceptibility to osteolysis and heritable factors may contribute to this variation. However, the overall contribution that such variation makes to osteolysis risk is unknown. QUESTIONS/PURPOSES: We conducted two genome-wide association studies to (1) identify genetic risk loci associated with susceptibility to osteolysis; and (2) identify genetic risk loci associated with time to prosthesis revision for osteolysis. METHODS: The Norway cohort comprised 2624 patients after THA recruited from the Norwegian Arthroplasty Registry, of whom 779 had undergone revision surgery for osteolysis. The UK cohort included 890 patients previously recruited from hospitals in the north of England, 317 who either had radiographic evidence of and/or had undergone revision surgery for osteolysis. All participants had received a fully cemented or hybrid THA using a small-diameter metal or ceramic-on-conventional polyethylene bearing. Osteolysis susceptibility case-control analyses and quantitative trait analyses for time to prosthesis revision (a proxy measure of the speed of osteolysis onset) in those patients with osteolysis were undertaken in each cohort separately after genome-wide genotyping. Finally, a meta-analysis of the two independent cohort association analysis results was undertaken. RESULTS: Genome-wide association analysis identified four independent suggestive genetic signals for osteolysis case-control status in the Norwegian cohort and 11 in the UK cohort (p ≤ 5 x 10(-6)). After meta-analysis, five independent genetic signals showed a suggestive association with osteolysis case-control status at p ≤ 5 x 10(-6) with the strongest comprising 18 correlated variants on chromosome 7 (lead signal rs850092, p = 1.13 x 10(-6)). Genome-wide quantitative trait analysis in cases only showed a total of five and nine independent genetic signals for time to revision at p ≤ 5 x 10(-6), respectively. After meta-analysis, 11 independent genetic signals showed suggestive evidence of an association with time to revision at p ≤ 5 x 10(-6) with the largest association block comprising 174 correlated variants in chromosome 15 (lead signal rs10507055, p = 1.40 x 10(-7)). CONCLUSIONS: We explored the heritable biology of osteolysis at the whole genome level and identify several genetic loci that associate with susceptibility to osteolysis or with premature revision surgery. However, further studies are required to determine a causal association between the identified signals and osteolysis and their functional role in the disease. CLINICAL RELEVANCE: The identification of novel genetic risk loci for osteolysis enables new investigative avenues for clinical biomarker discovery and therapeutic intervention in this disease.

BACKGROUND: The risk of early complications is high after monoblock acetabular metal-on-metal (MoM) THA revisions. However, there is a paucity of evidence regarding clinical complications after isolated head-liner exchange of modular MoM THA. QUESTIONS/PURPOSES: The purposes of this study were (1) to describe the frequency of early complications after an isolated head-liner exchange revision of modular MoM THA; and (2) to determine whether patients who experienced complications or dislocation after head-liner exchanges had higher serum chromium (Cr) or cobalt (Co) ion levels than those who did not. METHODS: A review of our institution’s total joint registry retrospectively identified 53 patients who underwent 54 liner exchange revisions of a modular acetabular MoM THA. The study period was from April 2008 to April 2016 at a single tertiary care center. During this period, isolated head-liner exchanges (rather than more extensive revisions) were performed in patients if they did not have evidence of loosening of the acetabular or femoral components. Reasons for revision surgery included pain, mechanical symptoms, radiographic evidence of osteolysis, elevated serum metal ions, and MRI abnormalities with 40 of the 54 hips having pain or mechanical symptoms and 38 of 54 hips having multiple reasons for revision before surgery. Patients were excluded if they did not meet the minimum postrevision followup or had the modular liner exchange secondary to infection. All revisions were from a single manufacturer with one head-liner exchange of a MoM THA from another manufacturer excluded during the study period. The mean time from index MoM THA to modular exchange was 96 (SD ± 36) months. Because the focus of this study was early complications, we had a minimum 90-day followup duration for inclusion. Mean followup after revision was 15 months (SD ± 12); a total of 56% (30 of 54) had followup of at least 12 months’ duration. Complications (dislocation, infection) and reoperations were obtained by chart review performed by individuals other than the treating physician(s). Serum metal ion levels were obtained before head-liner exchange. The median serum Cr and Co levels were 6 µg/L (range, 0-76 µg/L) and 12 µg/L (range, 0-163 µg/L), respectively. RESULTS: Of the 54 revision THAs, 15 (28%) developed complications. Nine (17%) occurred within 90 days of the revision surgery and 11 (20%) resulted in reoperation. The most common complication was dislocation (12 of 54 [22%]) with recurrent dislocation noted in eight of these 12 patients. All patients with recurrent dislocation continued to dislocate and underwent repeat revision. Patients with dislocation had higher median serum Cr and Co ion levels than those without dislocation (Cr: 24 [range, 11-76] versus 4 [range, 0-70], p = 0.001 [95% confidence interval {CI}, 10-57]; Co: 41 [range, 6-163] versus 8 [range, 0-133], p = 0.016 [95% CI, 6-141]). Three (6%) of the 54 patients underwent repeat surgery for deep space infection. CONCLUSIONS: Complications and reoperations are common after modular head-liner exchange in the setting of a failed MoM THA. Our study likely underestimates the frequency of complications and revisions because the followup period in this report was relatively short. Dislocation is the most common complication and elevated serum metal ion levels may be a predictor of dislocation. These findings are concerning and surgeons should be aware of the high complication risk associated with this procedure. LEVEL OF EVIDENCE: Level IV, therapeutic study.

BACKGROUND: The advent of value-based care, in which surgeons and hospitals accept more responsibility for clinical and financial results, has increased the focus on surgeon- and hospital-specific outcomes. However, methods to identify high-quality, low-cost surgeons are not well developed. QUESTIONS/PURPOSES: (1) Is there an association between surgeon THA volume and 90-day Centers for Medicare & Medicaid Services (CMS) Part A payments, readmissions, or mortality? (2) What proportion of THAs in the United States is performed by low- and high-volume surgeons? METHODS: We performed a retrospective analysis of the CMS Limited Data Set on all primary elective THAs performed in the United States (except Maryland) between January 2013 and June 2016 on patients insured by Medicare. This represented 409,844 THAs totaling more than USD 7.7 billion in direct CMS expenditures. Surgeons were divided into five groups based on annualized volume of CMS elective THAs over the study period. Using linear and logistic regression, we calculated and compared 90-day CMS Part A payments, readmissions, and mortality among the groups. For each episode, demographic information (age, sex, and race), geographic location, and Elixhauser comorbidities were calculated to control for major confounding factors in the regression. RESULTS: When compared with the highest volume group, each lower volume group had increased payments, increased readmission rates, and increased mortality rates in a stepwise fashion when controlling for patient-specific variables including Elixhauser comorbidity index, demographic information, region, and background trend. The lowest volume group resulted in 27.2% more CMS payments per case (p < 0.001; 95% confidence interval [CI], 26.6%–27.8%), had an increased readmission odds ratio (OR) of 1.8 (p < 0.001; 95% CI, 1.7–1.9), and an increased mortality OR of 4.7 (p < 0.001; 95% CI, 4.0–5.5) when compared with the highest volume group. There was also variation within volume groups: some lower volume surgeons had lower payments, readmissions, and mortality than some higher volume surgeons despite the general trend. In terms of CMS volume, surgeons who were at least moderate volume (11+ annual cases) performed 78% of THAs and represented 26% of operating surgeons. The low- and lowest volume surgeons (10 or fewer annual cases) performed only 22% of THAs in the United States while representing 74% of unique operating surgeons. CONCLUSIONS: There is a strong association between a surgeon’s Medicare volume and lower CMS payments, readmissions, and mortality. Furthermore, the majority of Medicare THAs in the United States are performed by surgeons who perform > 10 CMS operations annually. Compared with previous work, these results suggest a trend toward higher volume surgeons in the Medicare population. The results also suggest a benefit to the shift toward higher volume surgeons in reducing payments, readmissions, and mortality for elective THA in the United States. However, given that payments, readmission, and mortality of surgeons varied widely, it is important to note that available individual CMS data can be used to directly evaluate each individual surgeon based on their actual results well as through association with volume. LEVEL OF EVIDENCE: Level III, therapeutic study.

BACKGROUND: Many patients undergo both THA and spinal arthrodesis, and those patients may not fare as well as those who undergo one procedure but not the other. The mechanisms of how spinal arthrodesis affects patient function after THA remain unclear. QUESTIONS/PURPOSES: The aims of our study were to (1) determine how patient-reported outcome measures (PROMs), including the Oxford hip score as well as dislocations and complications compare after THA between patients with and without spinal arthrodesis; (2) characterize sagittal pelvic changes in these patients that occur when moving between different functional positions and test for differences between patients with and without spinal arthrodesis; and (3) assess whether differences in sagittal pelvic dynamics are associated with PROMs, complications, and dislocations after THA. METHODS: In this case-control study, we identified 42 patients (60 hips) who had undergone both THA and spinal arthrodesis between 2002 and 2016 and who were available for followup at a minimum of 12 months (mean, 6 ± 5 years) after the later of the two procedures. These cases were case-control-matched for age, gender, and body mass index with 42 patients (60 hips) who underwent only THA and had no known spinal pathology. All patients completed PROMs, including the Oxford hip score, and underwent four radiographs of the pelvis and spinopelvic complex in three positions (supine, standing, and deep-seated). Cup orientation and various spinopelvic parameters, including pelvic tilt and pelvic-femoral angle, were measured. The difference in pelvic tilt between standing and seated allowed for patient classification based on spinopelvic mobility into normal (± 10°-30°), stiff (< ± 10°) or hypermobile (> ± 30°) groups. RESULTS: Compared with the THA-only group, the THA-spinal arthrodesis group had inferior PROMs (Oxford hip score, 33 ± 10 versus 43 ± 6; p < 0.001) and more surgery-related complications (such as dislocation, loosening, periprosthetic fracture or infection, psoas irritation) (12 versus 3; p = 0.013), especially dislocation (5 versus 0; p = 0.023). We detected no difference in change of pelvic tilt between supine and standing positions between the groups. When standing, patients undergoing THA-spinal arthrodesis had greater pelvic tilt (25° ± 11° versus 17° ± 8°; p < 0.001) and the hip was more extended (193° ± 22° versus 185° ± 30°; p = 0.012). We found that patients undergoing THA-spinal arthrodesis were more likely to have spinopelvic hypermobility (12 of 42 versus three of 42; odds ratio, 5.2; p = 0.02) with anterior tilting of the pelvis. Of all biomechanical parameters, only spinopelvic hypermobility was associated with inferior PROMs (Oxford hip score, 35 ± 9 versus 40 ± 7 in normal mobility; p = 0.049) and was also present in dislocating hips that underwent revision despite acceptable cup orientation. CONCLUSIONS: In patients with spinal arthrodesis who have undergone THA, spinopelvic hypermobility is associated with inferior outcomes, including hip instability. Spinopelvic hypermobility should be routinely assessed because these patients may have a narrow zone of optimum cup orientation that would require new technology to define and assist the surgeon in obtaining it. Level of Evidence Level III, therapeutic study.

Two-stage reimplantation arthroplasty is a commonly used approach for treating chronic periprosthetic joint infections. A prereimplantation threshold value of erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) to determine infection eradication and the proper timing of reimplantation remains ill defined. We theorized that rather than a specific numeric threshold, a percentage of improvement in these serology markers might improve diagnostic accuracy in determining the timing of reimplantation.We investigated if (1) the percent, or delta, change in ESR and CRP values from preresection to prereimplantation ([INCREMENT]ESR, [INCREMENT]CRP) is a useful marker of infection eradication and (2) whether the initial PJI causative organism (resistant, nonresistant, or culture-negative) is associated with serum ESR and CRP values before and after treatment with an antibiotic spacer and parenteral antibiotic therapy.We retrospectively reviewed 300 patients, nine of whom were lost to followup, treated with a two-stage revision THA or TKA protocol between 2005 and 2014 from two separate institutional arthroplasty registries. Serum ESR and CRP values were recorded at two designated points: (1) preresection and (2) after 6 weeks of intravenous antibiotic therapy with a drug-eluting spacer and completion of an organism-specific intravenous antibiotic regimen. Patient records were reviewed electronically for causative species of infection, revision surgeries, and recurrent/persistent infection based on Musculoskeletal Infection Society criteria for a minimum of 2 years. Forty-eight of 291 patients (16%) underwent a revision procedure for recurrent or persistent infection, whereas 31 patients (10%) were revised for noninfectious reasons. The [INCREMENT]ESR, [INCREMENT]CRP, culture results, and patient demographics were recorded and analyzed with receiver operator curves controlling for American Society of Anesthesiologists (ASA) class.Receiver operator characteristic area under the curves (AUC) demonstrated that both the [INCREMENT]ESR (AUC = 0.581) and [INCREMENT]CRP (AUC = 0.539) percentages were poor markers of recurrent or persistent infection. When comparing preresection with prereimplantation values, the median percent [INCREMENT]ESR was 50% (interquartile range [IQR], 17%-77%) for those patients who remained infection-free versus 59% (IQR, 29%-78%) for those who developed reinfection (p = 0.540). The median percent [INCREMENT]CRP was 77% (IQR, 47%-92%) for those patients who remained infection-free versus 79% (IQR, 46%-95%) for those who experienced reinfection (p = 0.634). Although no significant differences were found between organism type and CRP values at the two time points, the preresection ESR level was higher in patients infected with resistant bacteria (median, 69; IQR, 60%-85%) compared with nonresistant organisms (median, 55; IQR, 33%-83%; p = 0.020).The percent change in serum ESR and CRP inflammatory markers before and after two-stage reimplantation for PJI was not associated with reinfection risk when controlling for ASA class. Although a return to normal serology infrequently occurs before reimplantation, [INCREMENT]ESR and [INCREMENT]CRP provide no additional diagnostic accuracy to determine the timing of reimplantation. Furthermore, the pre- and postresection serology values have no meaningful relationship to resistant or nonresistant pathogens. Decisions for reimplantation must take into account multiple variables rather than a specific threshold change in serum inflammatory markers.Level III, diagnostic study.