Diaphyseal Impaction Grafting Combined with Metaphyseal Cones: Outcomes in 88 Revision Total Knee Arthroplasties.

BACKGROUND: Metaphyseal cones with cemented stems can be successfully utilized in most revision total knee arthroplasties (TKAs). However, if the diaphysis has been previously violated, fixation of the cemented stem, which is important for cone ingrowth and construct survival, can be compromised. The initial results of our novel technique combining diaphyseal impaction bone-grafting with a metaphyseal cone were promising but required additional study. The purpose of the present study was to assess results of this technique in a larger cohort. METHODS: A metaphyseal cone combined with diaphyseal impaction grafting and a cemented stem was utilized in 88 revision TKAs at our institution, including 35 from our prior study. The mean age at the time of revision was 67 years, and 67% of patients were male. Patients had had a mean of 4 prior knee arthroplasty procedures. The 2 most common reasons for revision were aseptic loosening (78%) and 2-stage reimplantation for periprosthetic joint infection (PJI) (19%). The mean follow-up was 4 years. RESULTS: At the time of the latest follow-up, no cone-impaction grafting constructs required re-revision for aseptic loosening. Five-year survivorship free from any revision of the cone-impaction grafting construct and free from any reoperation was 95% and 65%, respectively. A total of 25 knees (28%) underwent reoperation, with the 2 most common indications being PJI and periprosthetic fracture. All cones were osseointegrated, and all bone graft appeared stable or incorporated. One patient had radiographic evidence of tibial component loosening despite a well-fixed cone; however, this patient was asymptomatic and had not undergone revision at 9 years. CONCLUSIONS: When presented with a sclerotic, polished diaphyseal canal with deficient cancellous bone and concomitant metaphyseal bone loss, our technique of combining diaphyseal impaction grafting with a metaphyseal cone proved extremely durable in this larger series of patients. No cone-impaction grafting constructs required re-revision for aseptic loosening. LEVEL OF EVIDENCE: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Porous Tantalum Tibial Metaphyseal Cones in Revision Total Knee Arthroplasty: Excellent 10-Year Survivorship.

BACKGROUND: Highly porous metal tibial metaphyseal cones (TMCs) are commonly utilized in revision total knee arthroplasty (TKA) to address bone loss and obtain biologic fixation. Mid-term (5 to 10 year) studies have previously demonstrated excellent survivorship and high rates of osseointegration, but longer-term studies are lacking. We aimed to assess long-term (≥ 10 year) implant survivorship, complications, and clinical and radiographic outcomes after revision TKA with TMCs. METHODS: Between 2004 and 2011, 228 revision TKAs utilizing porous tantalum TMCs with stemmed tibial components were performed at a single institution and were retrospectively reviewed. The mean age at revision was 65 years, the mean body mass index was 33, and 52% were women. Implant survivorship, complications, and clinical and radiographic outcomes were assessed. The mean follow-up was 6.3 years. RESULTS: The 10-year survivorship free of aseptic loosening leading to TMC removal was 97%, free of any TMC removal was 88%, free of any re-revision was 66%, and free of any reoperation was 58%. The most common indications for re-revision were periprosthetic joint infection, instability, and aseptic femoral component loosening. The 10-year nonoperative complication rate was 24%. The mean Knee Society scores increased from 38 preoperatively to 69 at 10 years. There were 8 knees that had evidence of partial, progressive tibial radiolucencies at 10 years. CONCLUSIONS: Porous tantalum TMCs demonstrated persistently durable longer-term survivorship with a low rate of implant removal. The rare implant removals for component loosening or instability were offset by those required for periprosthetic joint infection, which accounted for 80% of cone removals. Porous tantalum TMCs provide an extremely reliable tool to address tibial bone loss and achieve durable long-term fixation in revision TKA. LEVEL OF EVIDENCE: IV.

Highly Porous Acetabular Cup and Augment Constructs in Complex Revision Total Hip Arthroplasty: What Predicts 10-Year Implant Survivorship?

BACKGROUND: Porous tantalum acetabular cup and augment constructs have demonstrated favorable outcomes up to 5 years postsurgery despite severe bone loss during revision total hip arthroplasty (THA). Prior literature lacks long-term studies with substantial case numbers. This study aims to assess long-term clinical and radiographic outcomes 10 years postsurgery in patients undergoing revision THA with porous tantalum acetabular cup-augment constructs and determine factors associated with long-term survivorship. METHODS: Between 2000 and 2012, 157 revision THAs were performed in cases with major acetabular defects (mainly Paprosky type IIIA and IIIB) utilizing porous tantalum cup-augment constructs. Pelvic discontinuity was noted intraoperatively in 17 hips (11%). Postoperative radiographs were evaluated at regular intervals for implant stability and radiolucent lines. There were 49 patients who had complete radiographic follow-up at 10 years or longer postsurgery. RESULTS: The 10-year survivorship free of revision of the cup-augment construct for aseptic loosening was 93%, free of any acetabular construct revision was 91%, free of any hip rerevision was 77%, and free of any reoperation was 75%. Pelvic discontinuity was associated with increased risk of reoperation (hazard ratio [HR] = 2.8), any hip rerevision (HR = 3.2), any cup-augment construct revision (HR = 11.8), and aseptic construct revision (HR = 10.0). Of unrevised cases with radiographs at 10 years, 4 hips showed radiographic loosening. Mean Harris hip scores improved from 47 preoperatively to 79 at 10 years. CONCLUSIONS: Porous tantalum acetabular cup-augment constructs used in revision THA with severe acetabular bone loss provide excellent implant survivorship at 10 years when the acetabulum is intact. Due to lower survivorship of cup-augment constructs in cases of pelvic discontinuity, additional construct fixation or stabilization methods are recommended, when a discontinuity is present. LEVEL OF EVIDENCE: IV.

Is the Rise of Medicare Advantage Impacting the Fidelity of Traditional Medicare Claims Data? Implications for Reporting of Long-Term Total Hip Arthroplasty Survivorship.

BACKGROUND: Arthroplasty registries often use traditional Medicare (TM) claims data to report long-term total hip arthroplasty (THA) survivorship. The purpose of this study was to determine whether the large number of patients leaving TM for Medicare Advantage (MA) has compromised the fidelity of TM data. METHODS: We identified 10,962 THAs in 9,333 Medicare-eligible patients who underwent primary THA from 2000 to 2020 at a single institution. Insurance type was analyzed, and 83% of patients had TM at the time of THA. Survivorship free from any revision or reoperation was calculated for patients who have TM. The same survivorship end points were recalculated with censoring performed when a patient transitioned to an MA plan after their primary THA to model the impact of losing patients from the TM dataset. Differences in survivorship were compared. The mean follow-up was 7 years. RESULTS: From 2000 to 2020, there was a decrease in TM insurance (93 to 73%) and a corresponding increase in MA insurance (0 to 19%) among THA patients. Following THA, 23% of TM patients switched to MA. For patients who had TM at the time of surgery, 15-year survivorship free from any reoperation or revision was 90% and 93%, respectively. When censoring patients upon transition from TM to MA, survivorship free from any reoperation became significantly higher (92 versus 90% at 15 years; hazard ratio = 1.16, P = .033), and there was a trend toward higher survivorship free from any revision (95 versus 93% at 15 years; hazard ratio = 1.16, P = .074). CONCLUSIONS: Approximately 1 in 4 patients left TM for MA after primary THA, effectively making them lost to follow-up within TM datasets. The mass exodus of patients out of TM appears to have led to a slight overestimation of survivorship free from any reoperation and trended toward overestimating survivorship free from any revision. If MA continues to grow, efforts to obtain MA data will become even more important.

Cemented dual-mobility constructs in uncemented revision acetabular components.

Aims: Dislocation remains a leading cause of failure following revision total hip arthroplasty (THA). While dual-mobility (DM) bearings have been shown to mitigate this risk, options are limited when retaining or implanting an uncemented shell without modular DM options. In these circumstances, a monoblock DM cup, designed for cementing, can be cemented into an uncemented acetabular shell. The goal of this study was to describe the implant survival, complications, and radiological outcomes of this construct. Methods: We identified 64 patients (65 hips) who had a single-design cemented DM cup cemented into an uncemented acetabular shell during revision THA between 2018 and 2020 at our institution. Cups were cemented into either uncemented cups designed for liner cementing (n = 48; 74%) or retained (n = 17; 26%) acetabular components. Median outer head diameter was 42 mm. Mean age was 69 years (SD 11), mean BMI was 32 kg/m2 (SD 8), and 52% (n = 34) were female. Survival was assessed using Kaplan-Meier methods. Mean follow-up was two years (SD 0.97). Results: There were nine cemented DM cup revisions: three for periprosthetic joint infection, three for acetabular aseptic loosening from bone, two for dislocation, and one for a broken cup-cage construct. The two-year survivals free of aseptic DM revision and dislocation were both 92%. There were five postoperative dislocations, all in patients with prior dislocation or abductor deficiency. On radiological review, the DM cup remained well-fixed at the cemented interface in all but one case. Conclusion: While dislocation was not eliminated in this series of complex revision THAs, this technique allowed for maximization of femoral head diameter and optimization of effective acetabular component position during cementing. Of note, there was only one failure at the cemented interface.

Obesity and Primary Total Hip Arthroplasty: The Absolute versus Relative Risk of Periprosthetic Joint Infection at 15 Years.

BACKGROUND: To make an informed decision about total hip arthroplasty (THA), surgeons and patients need to understand the absolute and relative risks of periprosthetic joint infection (PJI). We sought to evaluate the long-term risk of PJI following primary THA stratified by body mass index (BMI) and PJI-related risk factors. METHODS: We identified 21,550 primary THAs performed from 2000 to 2021 at a single institution. Patients were stratified as having 0, 1, or ≥ 2 PJI risk factors (diabetes, chronic kidney disease, nonprimary osteoarthritis, immunosuppression, or active smoking) and into BMI categories. The 15-year cumulative risk of PJI was evaluated by BMI and PJI risk factors. RESULTS: For the entire cohort, the 15-year absolute risk of PJI was 2%. For patients who did not have PJI risk factors, the absolute risk of PJI at 15 years was 1% in normal weight, 2% in class III obesity, and 4% in class IV obesity. Patients who had class III and IV obesity had a 3-times and 9-times higher relative risk of PJI, respectively (P = .03, P < .001). Among patients who had ≥ 2 PJI risk factors, the absolute risk of PJI at 15 years was 2% in normal weight, 4% in class III obesity, and 18% in class IV obesity. CONCLUSIONS: Healthy patients who had class III and IV obesity had a 3-times and 9-times increased risk of PJI at 15 years relative to normal weight patients. However, the absolute risk of PJI at 15 years was 2 and 4%, respectively. Given emerging data questioning whether BMI modification decreases PJI risk, surgeons and patients must consider both a 3-times to 9-times increased relative risk of PJI and a 2 to 4% absolute risk of PJI at 15 years for healthy patients who had a BMI ≥ 40. LEVEL OF EVIDENCE: IV.

Whole Blood Metal Levels in the Setting of an Oncologic Endoprosthesis: Is There Cause for Concern?

BACKGROUND: Massive modular endoprostheses have become a primary means of reconstruction after oncologic resection of a lower extremity tumor. These implants are commonly made with cobalt-chromium alloys that can undergo wear and corrosion, releasing cobalt and chromium ions into the surrounding tissue and blood. However, there are few studies about the blood metal levels in these patients. QUESTION/PURPOSE: What is the whole blood cobalt and chromium ion level in patients with massive modular endoprostheses? METHODS: We performed a cross-sectional study of our total joints registry to identify patients with a history of an endoprosthetic reconstruction performed at our institution. Patients who were alive at the time of our review in addition to those undergoing an endoprosthetic reconstruction after an oncologic resection were included. Whole blood samples were obtained from 27 (14 male and 13 female) patients with a history of a lower extremity oncologic endoprosthesis. The median time from surgery to blood collection was 8 years (range 6 months to 32 years). Blood samples were collected and stored in metal-free ethylenediaminetetraacetic acid tubes. Samples were analyzed on an inductively coupled plasma mass spectrometer in an International Organization for Standardization seven-class clean room using polytetrafluoroethylene-coated instruments to reduce the risk of metal contamination. The analytical measuring range was 1 to 200 ng/mL for chromium and cobalt. Cobalt and chromium levels were considered elevated when the blood level was ≥ 1 ppb. RESULTS: Cobalt levels were elevated in 59% (16 of 27) of patients, and chromium levels were elevated in 26% (seven of 27). In patients with elevated metal ion values, 15 of 17 patients had a reconstruction using a Stryker/Howmedica Global Modular Replacement System implant. CONCLUSION: Blood metal levels were elevated in patients who received reconstructions using modular oncology endoprostheses Future work is needed to establish appropriate follow-up routines and determine whether and when systemic complications occur because of elevated metal levels and how to potentially address these elevated levels when complications occur. Prospective and retrospective collaboration between multiple centers and specialty societies will be necessary to address these unknown questions in this potentially vulnerable patient group. LEVEL OF EVIDENCE: Level IV, therapeutic study.

Long-term outcome of total hip arthroplasty in patients with multiple hereditary exostosis.

BACKGROUND: Multiple hereditary exostosis (MHE) is a rare autosomal dominant disorder characterized by multiple osteochondromas. There is a paucity of literature concerning total hip arthroplasty (THA) in patients with MHE. The aim of this study is to report long-term outcomes of THA in patients with MHE. METHODS: Fourteen patients undergoing 15 THA's for the treatment of osteoarthritis in the presence of osteochondromas and proximal femoral deformity secondary to MHE were reviewed. Mean age at the time of surgery and follow-up was 56 and 12 years. Seven (47%) had uncemented femoral components. Eleven hips had coxa valga on preoperative imaging. Clinical outcomes were assessed with both Harris hip scores (HHS) and Musculoskeletal Tumor Society Scores (MSTS). RESULTS: Following surgery, there was an improvement in the HHS (48-82, p < 0.01) and MSTS scores (41-70%, p < 0.01). Complications occurred in 5 patients leading to reoperation in 3 patients, of which 2 patients underwent a revision procedure at 19 and 20-years postoperative. The 10-year revision free survival was 100%. CONCLUSIONS: THA in the setting of MHE reliably improves patient function. One in three patients will have a postoperative complication; however, the long-term incidence of revision is low.

Total Hip Arthroplasty Following Operative Fixation of Acetabular Fracture: A Contemporary Series.

BACKGROUND: Total hip arthroplasty (THA) is the operation of choice for salvage of post-traumatic arthritis following acetabular fracture. While high failure rates have been reported for these procedures, existing literature reports mainly on historical implant designs and techniques. We aimed to describe implant survivorships, complications, radiographic results, and clinical outcomes of contemporary THA following prior open reduction internal fixation (ORIF) of an acetabular fracture. METHODS: We identified 104 patients undergoing THA following prior ORIF of an acetabular fracture from 2000 to 2015 via our institutional total joint registry. Mean age at THA was 50 years (range, 18 to 79 years), 71% were men, and mean body mass index was 27 (range, 18 to 52). All patients were implanted with uncemented acetabular components, and 89% had uncemented stems. Some hardware from prior fixation was retained in 94% of cases. Mean follow-up was 10 years (range, 2 to 21 years). RESULTS: The 10-year survivorships free of any revision and any reoperation were 98% and 97%, respectively. There were 4 revisions: 1 each for psoas tendonitis, dislocation, acetabular aseptic loosening, and periprosthetic joint infection. There were 9 complications that did not lead to reoperation: 5 dislocations, 2 periprosthetic femur fractures, 1 sciatic nerve palsy, and 1 case of symptomatic heterotopic ossification. All unrevised components appeared radiographically well-fixed. Mean Harris Hip Score improved from mean 50 preoperatively to mean 82 at 5 years (P < .001). CONCLUSIONS: In this series of contemporary THAs following prior acetabular fracture ORIF, revision-free survivorship was excellent with only a single case of acetabular aseptic loosening. These results are encouraging and suggest that contemporary implants and techniques have notably improved on historic results. LEVEL OF EVIDENCE: Therapeutic, Level IV.

Midterm outcomes of total hip arthroplasty after internal hemipelvectomy and iliofemoral arthrodesis.

BACKGROUND AND OBJECTIVES: Recent studies have reported acceptable outcomes after arthrodesis takedown and conversion to total hip arthroplasty (THA); however, there are no reports on outcomes after oncologic resection, which are inherently complex and may portend poorer outcomes. The purpose of this study was to examine the surgical and functional outcomes of patients who underwent prior hemipelvectomy for tumor resection and were later converted to THA. METHODS: All patients who had prior iliofemoral arthrodesis after oncologic resection that were later converted to THA at a single institution were examined. Charts were reviewed for demographic information, operative information, functional outcomes, and complications/reoperations. RESULTS: All three patients in this study were males who underwent internal hemipelvectomies for chondrosarcoma. Patients were converted to THA at a mean of 26 years after arthrodesis. Mean follow-up after conversion to THA was 7.4 years. During this follow-up period, two of the three patients required revision surgery. At last follow-up, the mean Harris Hip Score was 81 and the mean Mayo Hip Score was 67, and all patients were ambulatory without significant pain. CONCLUSIONS: Overall, patients who undergo iliofemoral arthrodesis after oncologic hemipelvectomy and are later converted to THA can expect to have a reasonable outcome, despite a high rate of complications and revision surgery.

Correlation of Blood Metal Concentrations with Cognitive Scores and Neuroimaging Findings in Patients with Total Joint Arthroplasty.

Total joint arthroplasty (TJA) implants are composed of metals, ceramics, and/or polyethylene. Studies suggest that the debris released from metal implants may possess neurotoxic properties with reports of neuropsychiatric symptoms and memory deficits, which could be relevant to Alzheimer's disease and related dementias. This exploratory study examined the cross-sectional correlation of blood metal concentrations with cognitive performance and neuroimaging findings in a convenience sample of 113 TJA patients with history of elevated blood metal concentrations of either titanium, cobalt and/or chromium. Associations with neuroimaging measures were observed but not with cognitive scores. Larger studies with longitudinal follow-up are warranted.

Primary total knee arthroplasty in patients with post-polio syndrome.

Aims: Knowledge on total knee arthroplasties (TKAs) in patients with a history of poliomyelitis is limited. This study compared implant survivorship and clinical outcomes among affected and unaffected limbs in patients with sequelae of poliomyelitis undergoing TKAs. Methods: A retrospective review of our total joint registry identified 94 patients with post-polio syndrome undergoing 116 primary TKAs between January 2000 and December 2019. The mean age was 70 years (33 to 86) with 56% males (n = 65) and a mean BMI of 31 kg/m2 (18 to 49). Rotating hinge TKAs were used in 14 of 63 affected limbs (22%), but not in any of the 53 unaffected limbs. Kaplan-Meier survivorship analyses were completed. The mean follow-up was eight years (2 to 19). Results: The ten-year survivorship free from revision was 91% (95% confidence interval (CI) 81 to 100) in affected and 84% (95% CI 68 to 100) in unaffected limbs. There were six revisions in affected limbs: three for periprosthetic femoral fractures and one each for periprosthetic joint infection (PJI), patellar clunk syndrome, and instability. Unaffected limbs were revised in four cases: two for instability and one each for PJI and tibial component loosening. The ten-year survivorship free from any reoperation was 86% (95% CI 75 to 97) and 80% (95% CI 64 to 99) in affected and unaffected limbs, respectively. There were three additional reoperations among affected and two in unaffected limbs. There were 12 nonoperative complications, including four periprosthetic fractures. Arthrofibrosis occurred in five affected (8%) and two unaffected limbs (4%). Postoperative range of motion decreased with 31% achieving less than 90° knee flexion by five years. Conclusion: TKAs in post-polio patients are complex cases associated with instability, and one in four require constraint on the affected side. Periprosthetic fracture was the main mode of failure. Arthrofibrosis rates were high and twice as frequent in affected limbs.

Comparative Survival of Contemporary Cementless Acetabular Components Following Revision Total Hip Arthroplasty.

BACKGROUND: The advent of highly porous ingrowth surfaces and highly crosslinked polyethylene has been expected to improve implant survivorship in revision total hip arthroplasty. Therefore, we sought to evaluate the survival of several contemporary acetabular designs following revision total hip arthroplasty. METHODS: Acetabular revisions performed from 2000 to 2019 were identified from our institutional total joint registry. We studied 3,348 revision hips, implanted with 1 of 7 cementless acetabular designs. These were paired with highly crosslinked polyethylene or dual-mobility liners. A historical series of 258 Harris-Galante-1 components, paired with conventional polyethylene, was used as reference. Survivorship analyses were performed. For the 2,976 hips with minimum 2-year follow-up, the median follow-up was 8 years (range, 2 to 35 years). RESULTS: Contemporary components with adequate follow-up had survivorship free of acetabular rerevision of ≥95% at 10-year follow-up. Relative to Harris-Galante-1 components, 10-year survivorship free of all-cause acetabular cup rerevision was significantly higher in Zimmer Trabecular Metarevision (hazard ratio (HR) 0.3, 95% confidence interval (CI) 0.2-0.45), Zimmer Trabecular MetaModular (HR 0.34, 95% CI 0.13-0.89), Zimmer Trilogy (HR 0.4, 95% CI 0.24-0.69), DePuy Pinnacle Porocoat (HR 0.24, 95% CI 0.11-0.51), and Stryker Tritanium revision (HR 0.46, 95% CI 0.24-0.91) shells. Among contemporary components, there were only 23 rerevisions for acetabular aseptic loosening and no rerevisions for polyethylene wear. CONCLUSION: Contemporary acetabular ingrowth and bearing surfaces were associated with no rerevisions for wear and aseptic loosening was uncommon, particularly with highly porous designs. Therefore, it appears that contemporary revision acetabular components have dramatically improved upon historical results at available follow-up.

Can the American Joint Replacement Registry Utilize Administrative Claims Data to Accurately Classify Revision Total Hip Arthroplasty (THA) Surgical Diagnoses?

BACKGROUND: The American Joint Replacement Registry (AJRR) is a valuable tool for studying revision total hip arthroplasty (rTHA). Currently, International Classification of Diseases-10 (ICD-10) codes are utilized by the AJRR for classifying surgical diagnoses. However, the validity of this methodology is unknown. The purpose of this study was to determine the accuracy of these codes, as used by AJRR, in classifying rTHA diagnoses. METHODS: We identified 908 rTHAs performed at our institution from 2015 to 2021 using our total joint registry (TJR). Revision diagnoses were obtained from the TJR, which contains prospectively recorded surgical diagnoses collected by trained abstractors, independent from ICD-10 data. The ICD-10 diagnosis codes, as submitted to AJRR, were retrieved for the same procedures. The accuracy of ICD-10 codes for classifying rTHA diagnoses as septic versus aseptic, instability, aseptic loosening, and periprosthetic fracture was assessed using Cohen's Kappa statistic, sensitivity, and specificity. RESULTS: Concordance between AJRR-submitted data and TJR for classifying rTHA as septic or aseptic was excellent (96.9%; k = 0.87). Agreement for aseptic diagnoses varied from very good for instability (k = 0.76) and loosening (k = 0.67) to moderate for periprosthetic fracture (k = 0.54). Specificity was high (>96%) for all 3 aseptic diagnoses, but sensitivity was lower at 74%, 68%, and 44% for instability, loosening, and periprosthetic fracture, respectively. CONCLUSION: The AJRR submitted ICD-10 data correctly classifies the infection status of rTHA procedures with outstanding accuracy, but the accuracy for more granular diagnoses was variable. These data demonstrate the potential for diagnosis specific limitations when utilizing ICD-10 administrative claims for registry reporting.

Is the American Joint Replacement Registry Able to Correctly Classify Revision Total Knee Arthroplasty Procedural Diagnoses?

BACKGROUND: The American Joint Replacement Registry (AJRR) is a powerful tool for the study of revision total knee arthroplasty (rTKA). The AJRR uses International Classification of Diseases-10 (ICD-10-CM) codes for recording surgical diagnoses. However, the validity of this methodology is unknown. The purpose of this study was to determine the accuracy of ICD-10-CM codes, as used by AJRR, in classifying rTKA diagnoses. METHODS: There were 988 rTKAs performed from 2015 to 2021 identified in our institutional total joint registry (TJR). Revision diagnoses were obtained from TJR, in which trained abstractors prospectively record diagnoses independent of ICD-10-CM data. The ICD-10-CM diagnosis codes submitted to AJRR were retrieved for the same procedures. The accuracy of ICD-10-CM codes for classifying rTKA diagnoses as septic versus aseptic, aseptic loosening, instability, and periprosthetic fracture was assessed using Cohen's Kappa statistics, sensitivities, and specificities. RESULTS: Concordance between AJRR-submitted codes and TJR was excellent (97.3%, k = 0.9) for identifying septic versus aseptic revisions. Agreement for aseptic diagnoses varied from very good for loosening (k = 0.65) and instability (k = 0.64) to fair for periprosthetic fracture (k = 0.36). Specificity was high (> 94%) for all three diagnoses, but sensitivity was lower at 71%, 63%, and 28% for loosening, instability, and periprosthetic fracture, respectively. CONCLUSION: The AJRR submitted ICD-10-CM diagnosis codes correctly classified rTKA cases as septic or aseptic with remarkable accuracy, but accuracy for more granular diagnoses varied. These data demonstrate the potential for diagnosis-specific limitations when using administrative claims data for registry reporting and have important implications for researchers using ICD-10-CM data.

John N. Insall Award: Randomized Clinical Trial of Cementless Versus Cemented Tibial Components: Durable and Reliable at a Mean 10-Years Follow-Up.

BACKGROUND: Cementless fixation is gaining popularity for primary total knee arthroplasties (TKAs). The prior 5-year results of our randomized clinical trial that included 3 different tibial designs found minimal differences. The purpose of the current study was to investigate the 10-year results in the same cohort. METHODS: Between 2003 and 2006, 389 primary TKAs were randomized: traditional modular cemented tibia (135); hybrid (cemented baseplate with uncemented pegs) monoblock tibia (128); and cementless monoblock tibia (126). Implant survivorships, radiographs, and clinical outcomes were analyzed. Mean age at TKA was 68 years (range, 41 to 85), 46% were male, and mean body mass index was 32 (range, 21 to 59). The mean follow-up was 10 years. RESULTS: The 10-year survivorship free of any revision was similar between the hybrid monoblock and cementless monoblock groups at 96%, but lower (89%) for the traditional modular cemented tibia (P = .05). The traditional modular cemented tibia group had significantly more revisions for aseptic tibial loosening than the other 2 groups (7 versus 0%) at 10 years (P = .003). The traditional modular cemented tibia group had significantly more nonprogressive radiolucent lines than the hybrid and cementless monoblock groups (24, 12, and 9%, respectively). Clinical outcomes were similar and excellent between all 3 groups. CONCLUSION: Cementless and hybrid monoblock tibial components have excellent implant survivorship (96%) with no cases of aseptic tibial loosening to date. The traditional cemented modular tibial group had a 7% cumulative incidence of aseptic loosening at 10 years. LEVEL OF EVIDENCE: Level I, Prospective Randomized Control Trial.

Intussusception Allograft Prosthetic Composites in Total Hip Arthroplasty: A Salvage Operation for Extensive Femoral Bone Loss.

BACKGROUND: Allograft prosthetic composites (APCs) have been used to perform revision total hip arthroplasty (THA) for massive femoral bone loss or deformity. Intussusception, or "telescoping", APC techniques have been proposed to enhance the contact area of this interface and provide superior mechanical fixation over conventional methods. The purpose of this study is to present to our knowledge, the largest series of telescoping APC THAs, along with surgical technique details and midterm (average 5-10 years) clinical results. METHODS: Between 1994 and 2015, 46 revision THAs performed with proximal femoral telescoping APCs were retrospectively reviewed at a single institution. Overall survival, reoperation-free survival, and construct survival rates were calculated via Kaplan-Meier methods. In addition, radiographic analyses were performed to evaluate for component loosening, union at the APC-host interface, and resorption of the allograft. RESULTS: At 10 years, the overall patient survival was 58%, reoperation-free survival was 76%, and construct survival was 95%. Reoperation was performed in 20% (n = 9) and only 2 constructs required resection. Radiographic analyses performed at latest follow-up revealed no instances of radiographic femoral stem loosening, an 86% union rate at the APC-host site, 23% with signs of some allograft resorption, and a 54% trochanteric union. The mean postoperative Harris hip score was 71 points (range, 46-100). CONCLUSION: Telescoping APCs are technically demanding, but provide reliable mechanical fixation for the reconstructing of large proximal femoral bone deficits in revision THA with excellent construct survivorship, acceptable reoperation rates, and good clinical outcomes. LEVEL OF EVIDENCE: IV.

Cross-sectional association between systemic metal concentrations and immune markers in patients with total joint arthroplasty.

Total joint arthroplasty (TJA) implants are composed of metal components. Although they are regarded safe, the long-term immunological effects of chronic exposure to the specific implant materials are unknown. We recruited 115 hip and/or knee TJA patients (mean age 68 years) who provided a blood draw for measurement of chromium, cobalt, titanium concentrations, inflammatory markers and systemic distribution of immune cells. We examined differences between the immune markers and the systemic concentrations of chromium, cobalt and titanium. CD66-b neutrophils, early natural killer cells (NK), and eosinophils were present in higher percentages in patients with chromium and cobalt concentrations greater than the median. The opposite pattern was observed with titanium where the percentages of CD66-b neutrophils, early NK, and eosinophils were higher in patients with undetectable titanium. Cobalt concentrations were positively correlated with a higher percentage of gamma delta T cells. Both chromium and cobalt concentrations were positively correlated with higher percentages of plasmablasts. Titanium concentrations were positively correlated with higher CD4 effector memory T cells, regulatory T cell count and Th1 CD4 helper cells. In this exploratory study, we observed altered distribution of immune cells in TJA patients with elevated systemic metal concentrations. Although these correlations were not strong, these exploratory findings warrant further investigation into the role of increased metals circulating in blood and its role in immune modulation.

Propensity Scores: Confounder Adjustment When Comparing Nonrandomized Groups in Orthopaedic Surgery.

Many studies in arthroplasty research are based on nonrandomized, retrospective, registry-based cohorts. In these types of studies, patients belonging to different treatment or exposure groups often differ with respect to patient characteristics, medical histories, surgical indications, or other factors. Consequently, comparisons of nonrandomized groups are often subject to treatment selection bias and confounding. Propensity scores can be used to balance cohort characteristics, thus helping to minimize potential bias and confounding. This article explains how propensity scores are created and describes multiple ways in which they can be applied in the analysis of nonrandomized studies. Please visit the following (https://www.youtube.com/watch?v=sqgxl_nZWS4&t=3s) for a video that explains the highlights of the paper in practical terms.

How to Distinguish Correlation From Causation in Orthopaedic Research.

Correlations in observational studies are commonly misinterpreted as causation. Although correlation is necessary to establish a causal relationship between two variables, correlations may also arise due to chance, reverse causality, or confounding. There are several methods available to orthopaedic researchers to determine whether the observed correlations are causal. These methods depend on the key components of the study including, but not limited to, study design and data availability on confounders. In this article, we illustrate the main concepts surrounding correlation and causation using intuitive real-world examples from the orthopaedic literature. Please visit the following https://www.youtube.com/watch?v=WW7pFudZbHA&t=52s for a video that explains the highlights of the paper in practical terms.