Publications by authors named "David G Lewallen"

214 Publications

Is American Joint Replacement Registry Data Representative of National Data? A Comparative Analysis.

J Am Acad Orthop Surg 2021 Aug 25. Epub 2021 Aug 25.

From the American Academy of Orthopaedic Surgeons, Rosemont, IL (Porter), University of Wisconsin, Madison, WI (Illgen), OrthoCarolina Hip and Knee Center, Charlotte, NC (Springer), Dell Medical School at the University of Texas at Austin, Austin, TX (Bozic), Midwest Orthopedics at Rush University Medical Center, Chicago, IL (Sporer), Stanford University Medical Center, Palo Alto, CA (Huddleston), Mayo Clinic, Rochester, MN (Lewallen), and University of Virginia School of Medicine, Charlottesville, VA (Browne).

Introduction: The American Academy of Orthopaedic Surgeons American Joint Replacement Registry (AJRR) is the largest registry of total hip and knee arthroplasty (THA and TKA) procedures performed in the United States. The purpose of this study was to examine whether AJRR data are representative of the national experience with hip and knee arthroplasty as represented in the National (Nationwide) Inpatient Sample (NIS).

Methods: All patients undergoing a THA or TKA procedure between 2012 to 2018 (AJRR) and 2012 to 2016 (NIS) were identified. Cohen d effect sizes were computed to ascertain the magnitude of differences in demographics, hospital volume (in 50 patient increments), and geographic characteristics between the AJRR and NIS databases.

Results: The study included (NIS: 2,316,345 versus AJRR: 557,684) primary THA and (NIS: 3,417,700 versus AJRR: 809,494) TKA procedures. The magnitude of distribution, as determined by the Cohen d effect size, showed that the proportions of AJRR and NIS patients were similar based on overall sex (THAs [d = 0.03] and TKAs [d = 0.02]) and age (THAs [d = 0.17] and TKAs [d = 0.12]). Similarly, only small differences (d = 0.34 or less) were identified between databases considering hospital volume and geography. The AJRR was underrepresented in Southern regions and hospitals with low procedure volume and overrepresented in Northern hospitals and those with larger volume. Both the NIS and the AJRR followed a similar overall trend, with most procedures performed at hospitals with <50 cases per year.

Discussion: Distributions across hospital volume, age, and geography were proportionally similar between the AJRR and NIS databases, supporting the generalizability of AJRR findings to the larger US cohort.
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http://dx.doi.org/10.5435/JAAOS-D-21-00530DOI Listing
August 2021

Immortal Time Bias in the Analysis of Time-to-Event Data in Orthopedics.

J Arthroplasty 2021 Jun 21. Epub 2021 Jun 21.

Department of Quantitative Health Sciences, Mayo Clinic, Rochester, MN; Department of Orthopedic Surgery, Mayo Clinic, Rochester, MN.

Many outcomes in arthroplasty research are analyzed as time-to-event outcomes using survival analysis methods. When comparison groups are defined after a time-delayed exposure or intervention, a period of immortal time arises and can lead to biased results. In orthopedics research, immortal time bias often arises when a minimum amount of follow-up is required for study inclusion or when comparing outcomes in staged bilateral vs unilateral arthroplasty patients. We present an explanation of immortal time and the associated bias, describe how to correctly account for it using proper data preparation and statistical techniques, and provide an illustrative example using real-world arthroplasty data. We offer practical guidelines for identifying and properly handling immortal time to avoid bias.
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http://dx.doi.org/10.1016/j.arth.2021.06.012DOI Listing
June 2021

Migration Patterns for Revision Total Knee Arthroplasty in the United States as Reported in the American Joint Replacement Registry.

J Arthroplasty 2021 Jun 11. Epub 2021 Jun 11.

Department of Orthopaedic Surgery, Stanford University, Redwood City, CA.

Background: Revision total knee arthroplasty (TKA) is associated with a higher complication rate and a greater cost when compared to primary TKA. Based on patient choice, referral, or patient transfers, revision TKAs are often performed in different institutions by different surgeons than the primary TKA. The aim of this study is to evaluate the effect of hospital size, teaching status, and revision indication on the migration patterns of failed primary TKA in patients 65 years of age and older.

Methods: All primary and revision TKAs reported to the American Joint Replacement Registry from January 2012 through March 2020 were included and merged with the Centers for Medicare and Medicaid Services database. Migration was defined as a patient having a primary TKA and revision TKA performed at separate institutions by different surgeons.

Results: In total, 9167 linked primary and revision TKAs were included in the analysis. Overall migration rates were significantly higher from small (<100 beds; P = .019), non-teaching institutions (P = .002) driven primarily by patients diagnosed with infection. Infection patients had significantly higher migration rates from small (46.8%, P < .001), non-teaching (43.5%, P < .001) institutions, while migration rates for other causes of revision were statistically similar. Most patients migrated to medium or large institutions (84.7%) for revision TKA rather than small institutions (15.3%, P < .001) and to teaching (78.3%) rather than non-teaching institutions (21.7%, P < .001).

Conclusion: There is a diagnosis-dependent referral bias that affects the migration rates of infected primary TKA from small non-teaching institutions leading to a flow of more medically complex patients to medium and large teaching institutions for infected revision TKA.
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http://dx.doi.org/10.1016/j.arth.2021.06.005DOI Listing
June 2021

Synovial fluid α defensin has comparable accuracy to synovial fluid white blood cell count and polymorphonuclear percentage for periprosthetic joint infection diagnosis.

Bone Joint J 2021 Jun;103-B(6):1119-1126

Mayo Clinic, Rochester, Minnesota, USA.

Aims: The aim of this study was to determine the diagnostic accuracy of α defensin (AD) lateral flow assay (LFA) and enzyme-linked immunosorbent assay (ELISA) tests for periprosthetic joint infection (PJI) in comparison to conventional synovial white blood cell (WBC) count and polymorphonuclear neutrophil percentage (PMN%) analysis.

Methods: Patients undergoing joint aspiration for evaluation of pain after total knee arthroplasty (TKA) or total hip arthroplasty (THA) were considered for inclusion. Synovial fluids from 99 patients (25 THA and 74 TKA) were analyzed by WBC count and PMN% analysis, AD LFA, and AD ELISA. WBC and PMN% cutoffs of ≥ 1,700 cells/mm and ≥ 65% for TKA and ≥ 3,000 cells/mm and ≥ 80% for THA were used, respectively. A panel of three physicians, all with expertise in orthopaedic infections and who were blinded to the results of AD tests, independently reviewed patient data to diagnose subjects as with or without PJI. Consensus PJI classification was used as the reference standard to evaluate test performances. Results were compared using McNemar's test and area under the receiver operating characteristic curve (AUC) analysis.

Results: Expert consensus classified 18 arthroplasies as having failed due to PJI and 81 due to aseptic failure. Using these classifications, the calculated sensitivity and specificity of AD LFA was 83.3% (95% confidence interval (CI) 58.6 to 96.4) and 93.8% (95% CI 86.2 to 98.0), respectively. Sensitivity and specificity of AD ELISA was 83.3% (95% CI 58.6 to 96.4) and 96.3% (95% CI 89.6 to 99.2), respectively. There was no statistically significant difference between sensitivity (p = 1.000) or specificity (p = 0.157) of the two AD assays. AUC for AD LFA was 0.891. In comparison, AUC for synovial WBC count, PMN%, and the combination of the two values was 0.821 (sensitivity p = 1.000, specificity p < 0.001), 0.886 (sensitivity p = 0.317, specificity p = 0.011), and 0.926 (sensitivity p = 0.317, specificity p = 0.317), respectively.

Conclusion: The diagnostic accuracy of synovial AD for PJI diagnosis is comparable and not statistically superior to that of synovial WBC count plus PMN% combined. Cite this article:  2021;103-B(6):1119-1126.
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http://dx.doi.org/10.1302/0301-620X.103B6.BJJ-2020-1741.R1DOI Listing
June 2021

Patellar Bone-Grafting for Severe Patellar Bone Loss During Revision Total Knee Arthroplasty.

JBJS Essent Surg Tech 2020 Jul-Sep;10(3). Epub 2020 Sep 18.

Mayo Clinic, Rochester, Minnesota.

Background: Treatment of severe patellar bone loss during revision total knee arthroplasty (TKA) is difficult. Patellar bone-grafting is a simple procedure that can improve patient outcomes following revision TKA.

Description: The patient is prepared and draped in the usual sterile fashion. The previous longitudinal knee incision is utilized for exposure. Scar tissue is excised from the medial gutter. However, tissue in the lateral gutter is largely maintained. An assessment of the surrounding quadriceps and patellar scar tissue ensues. This tissue can be utilized to create an envelope for holding the bone graft in place. If insufficient tissue is present, fascia from the iliotibial band or vastus medialis, allograft fascia, or synthetics can be used.A careful assessment of component fixation and rotation is critical to the success of patellar bone-grafting. Component revision for aseptic loosening or malrotation should be performed in the usual fashion. During component revision, it is recommended to preserve any additional bone as autograft for the patellar bone-grafting procedure. Common sites of autograft harvest include the femoral box cut and proximal tibial resection.The patella is then addressed by carefully removing the previous implant to avoid additional bone loss. This step is performed with a combination of an oscillating saw, osteotomes, and high-speed burr. The retropatellar bone is then prepared by debriding excess soft tissue, cysts, or cement. A high-speed burr is then utilized to produce a punctate bleeding surface for bone-graft incorporation.The harvested tissue is closed around the perimeter of the patella with use of interrupted nonabsorbable sutures, leaving a window to pack in the bone graft. The bone graft (allograft and autograft) is morselized and place through the window.The optimal patellar thickness is variable. After packing the bone graft through the soft-tissue window, the thickness is measured with a caliper. It is recommended to acquire a thickness of >20 mm because bone-graft resorption and remodeling occur with knee range of motion. The remaining soft-tissue window is closed with use of nonabsorbable sutures. The knee is cycled through a range of motion to ensure optimal patellofemoral tracking. If necessary, a lateral release or medial soft-tissue advancement can be performed to ensure patellofemoral tracking is adequate. Finally, the wound is irrigated and closed in layers.

Alternatives: Nonsurgical:Patellar knee braceHinged knee braceSurgical:Gull-wing osteotomyPatellar resurfacing with biconvex patellaBulk allograft reconstructionPartial or complete patellectomyPatelloplastyInterpositional arthroplastyTantalum metal-backed reconstruction.

Rationale: There is a myriad of surgical options for severe patellar bone loss following TKA. Patellar bone-grafting is simple, reproducible, and relatively cost-effective, and avoids the need for the amount of bone for reconstruction that may be required for metal-backed or biconvex patellar implants. The procedure allows for the restoration of the quadriceps lever arm, which may not be restored with other techniques, such as gull-wing osteotomy or patellectomy. Patellar bone-grafting avoids the cost and risks of disease transmission associated with allograft reconstruction. Finally, the procedure provides excellent long-term survivorship and patient-reported outcomes.

Expected Outcomes: Following this procedure, patients should experience a reduction in knee pain and improved patient-reported outcomes, with a prior study showing that the percentage of patients reporting anterior knee pain decreased from 51% to 27% following patellar bone-grafting. Patients also demonstrated an improvement in knee range of motion, with a mean increase in knee flexion of 7 and knee extension of 2. Complications related to this procedure are minimal. Bone stock restoration can be utilized for patellar resurfacing in the future. Radiographically, patellar bone resorption, loss of patellar height, and patellar remodeling do occur; however, despite these radiographic changes, Knee Society scores increased from 50 to 85 at the time of the latest follow-up.

Important Tips: Careful preoperative physical examination should document range of motion, areas of pain, and patellofemoral tracking and/or instabilityBe prepared to revise the femoral and/or tibial components if malrotated in order to optimize patellofemoral trackingRetain any autogenous bone harvested during component revision to use as patellar bone graftEnsure that allograft bone is available to ensure sufficient restoration of patellar thicknessConsider having allograft tissue available in the event that scar tissue in situ is not adequate to create an envelope for packing the bone graftA bleeding retropatellar surface prepared with a high-speed burr will increase the chance of bone incorporationA watertight closure of the soft-tissue envelope is critical to avoid loss of bone graft during knee range of motion.
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http://dx.doi.org/10.2106/JBJS.ST.19.00065DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8154392PMC
September 2020

Synovial Fluid Metal Ion Levels are Superior to Blood Metal Ion Levels in Predicting an Adverse Local Tissue Reaction in Failed Total Hip Arthroplasty.

J Arthroplasty 2021 Sep 1;36(9):3312-3317.e1. Epub 2021 May 1.

Department of Orthopedic Surgery, Mayo Clinic, Rochester, MN.

Background: Adverse local tissue reactions (ALTR) are associated with total hip arthroplasty (THA) failure in patients with metal-on-metal bearings and/or taper corrosion, which can also occur in metal-on-polyethylene articulations. Patients are monitored with blood cobalt (Co) and chromium (Cr) concentrations which do not always correlate with the degree of soft tissue reaction at revision THA. The purpose of this study was to determine how the blood and prosthetic hip synovial fluid levels of Co and Cr correlate with one another, and determine which concentration is more predictive of ALTR.

Methods: Synovial fluid and blood samples were collected at the time of revision THA in patients with (n = 26) and without ALTR (n = 27). Whole blood, serum, and synovial fluid metal ion concentrations were correlated with one another and clinical findings.

Results: The ratio of synovial fluid to whole blood Co concentration in ALTR and non-ALTR hips was 120:1 and 18:1 (P = .006). The mean ratio of synovial fluid to whole blood Cr concentration in ALTR and non-ALTR hips was 414:1 and 24:1 (P = .01). The mean synovial fluid Co/Cr concentrations were elevated in patients with ALTR compared with those without (2007.3 vs. 12.4 ppb, P = .007) and (3188.2 vs. 10.3 ppb, P = .02). The synovial fluid Co concentration was the most accurate test for detecting ALTR (cut off: 19.75 PPB, AUC 0.973).

Conclusion: In patients with ALTR, synovial fluid Co and Cr levels were 120 times higher and 414 times higher than whole blood Co and Cr levels. Synovial fluid Co ion concentration was the most accurate in predicting ALTR.

Level Of Evidence: Diagnostic level II.
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http://dx.doi.org/10.1016/j.arth.2021.04.034DOI Listing
September 2021

Surface Roughness of Titanium Orthopedic Implants Alters the Biological Phenotype of Human Mesenchymal Stromal Cells.

Tissue Eng Part A 2021 Aug 16. Epub 2021 Aug 16.

Department of Orthopedic Surgery, Mayo Clinic, Rochester, Minnesota, USA.

Metal orthopedic implants are largely biocompatible and generally achieve long-term structural fixation. However, some orthopedic implants may loosen over time even in the absence of infection. fixation failure is multifactorial, but the fundamental biological defect is cellular dysfunction at the host-implant interface. Strategies to reduce the risk of short- and long-term loosening include surface modifications, implant metal alloy type, and adjuvant substances such as polymethylmethacrylate cement. Surface modifications (e.g., increased surface rugosity) can increase osseointegration and biological ingrowth of orthopedic implants. However, the localized responses of cells to implant surface modifications need to be better characterized. As an model for investigating cellular responses to metallic orthopedic implants, we cultured mesenchymal stromal/stem cells on clinical-grade titanium disks (Ti6Al4V) that differed in surface roughness as high (porous structured), medium (grit blasted), and low (bead blasted). Topological characterization of clinically relevant titanium (Ti) materials combined with differential mRNA expression analyses (RNA-seq and real-time quantitative polymerase chain reaction) revealed alterations to the biological phenotype of cells cultured on titanium structures that favor early extracellular matrix production and observable responses to oxidative stress and heavy metal stress. These results provide a descriptive model for the interpretation of cellular responses at the interface between native host tissues and three-dimensionally printed modular orthopedic implants, and will guide future studies aimed at increasing the long-term retention of such materials after total joint arthroplasty.
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http://dx.doi.org/10.1089/ten.TEA.2020.0369DOI Listing
August 2021

Living With Survival Analysis in Orthopedics.

J Arthroplasty 2021 Apr 22. Epub 2021 Apr 22.

Department of Quantitative Health Sciences, Mayo Clinic, Rochester, MN; Department of Orthopedic Surgery, Mayo Clinic, Rochester, MN.

Time to event data occur commonly in orthopedics research and require special methods that are often called "survival analysis." These data are complex because both a follow-up time and an event indicator are needed to correctly describe the occurrence of the outcome of interest. Common pitfalls in analyzing time to event data include using methods designed for binary outcomes, failing to check proportional hazards, ignoring competing risks, and introducing immortal time bias by using future information. This article describes the concepts involved in time to event analyses as well as how to avoid common statistical pitfalls.
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http://dx.doi.org/10.1016/j.arth.2021.04.014DOI Listing
April 2021

Competing Risk Analysis: What Does It Mean and When Do We Need It in Orthopedics Research?

J Arthroplasty 2021 Apr 21. Epub 2021 Apr 21.

Department of Quantitative Health Sciences, Mayo Clinic, Rochester, MN; Division of Rheumatology, Mayo Clinic, Rochester, MN.

Most orthopedic studies involve survival analysis examining the time to an event of interest, such as a specific complication or revision surgery. Competing risks commonly arise in such studies when patients are at risk of more than one mutually exclusive event, such as death, or when the rate of an event depends on the rates of other competing events. In this article, we briefly describe the survival analysis censoring methodology, common fatal and nonfatal competing events, and define circumstances where standard survival analysis can fail in the setting of competing risks with real-world examples from orthopedics.
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http://dx.doi.org/10.1016/j.arth.2021.04.015DOI Listing
April 2021

Biconvex Patellar Components: 96% Durability at 10 Years in 262 Revision Total Knee Arthroplasties.

J Bone Joint Surg Am 2021 Jul;103(13):1220-1228

Department of Orthopedic Surgery, Mayo Clinic, Rochester, Minnesota.

Background: The optimal strategy to address osseous deficiencies of the patella during revision total knee arthroplasty (TKA) remains controversial. One possible solution is a cemented biconvex patellar component used such that the non-articular convexity both improves fixation and makes up for bone loss. The aim of this study was to determine the outcomes of the use of biconvex patellar components in a large series of revision TKAs.

Methods: From 1996 to 2014, 262 revision TKAs were performed at a single institution using a biconvex patellar component. Implant survivorship, clinical and radiographic results, and complications were assessed. The mean patient age at the TKA revision was 69 years, and 53% of the patients were female. The mean follow-up was 7 years.

Results: The 10-year survivorship free of revision of the biconvex patellar component due to aseptic loosening was 96%. The 10-year survivorship free of any revision of the biconvex patellar component was 87%. The 10-year survivorship free of any rerevision and free of any reoperation was 75% and 70%, respectively. The mean Knee Society Score (KSS) improved from 45.4 before the index revision to 67.7 after it. The mean residual composite thickness seen on the most recent radiographs was 18.1 mm. In addition to the complications leading to revision, the most common complications were periprosthetic patellar fracture (6%), of which 3 required revision; superficial wound infection (6%) requiring antibiotic therapy only or irrigation and debridement; and arthrofibrosis (3%).

Conclusions: In this cohort of 262 revision TKAs, biconvex patellar components used to treat marked patellar bone loss demonstrated excellent durability with a 10-year survivorship free of patellar rerevision due to aseptic loosening of 96%. The biconvex patellar components were reliable as evidenced by substantial improvements in clinical outcomes scores and a low risk of complications.

Level Of Evidence: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.
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http://dx.doi.org/10.2106/JBJS.20.01064DOI Listing
July 2021

Total Femur Antibiotic Spacers: Effective Salvage for Complex Periprosthetic Joint Infections.

J Arthroplasty 2021 07 6;36(7):2567-2574. Epub 2021 Mar 6.

Department of Orthopedic Surgery, Mayo Clinic, Rochester, MN.

Background: A simultaneous periprosthetic joint infection (PJI) of an ipsilateral hip and knee arthroplasty is a challenging complication of lower extremity reconstructive surgery. We evaluated the use of total femur antibiotic-impregnated polymethylmethacrylate (PMMA) bone cement spacers in the staged treatment of such limb-threatening PJIs.

Methods: Thirteen patients were treated with a total femur antibiotic spacer. The mean age at the time of spacer placement was 65 years. Nine patients had polymicrobial PJIs. All spacers incorporated vancomycin (3.0 g/40 g PMMA) and gentamicin (3.6 g/40 g PMMA), while 8 also included amphotericin (150 mg/40 g PMMA). Eleven spacers were biarticular. Twelve spacers were implanted through one longitudinal incision, while 8 of 12 reimplantations occurred through 2 smaller, separate hip and knee incisions. Mean follow-up after reimplantation was 3 years.

Results: Twelve (92%) patients underwent reimplantation of a total femur prosthesis at a mean of 26 weeks. One patient died of medical complications 41 days after spacer placement. At latest follow-up, 3 patients had experienced PJI recurrence managed with irrigation and debridement. One required acetabular component revision for instability. All 12 reimplanted patients retained the total femur prosthesis with no amputations. Eleven (91%) were ambulatory, and 7 (58%) remained on suppressive antibiotics.

Conclusion: Total femur antibiotic spacers are a viable, but technically demanding, limb-salvage option for complex PJIs involving the ipsilateral hip and knee. In the largest series to date, there were no amputations and 75% of reimplanted patients remained infection-free. Radical debridement, antimicrobial diversity, prolonged spacer retention, and limiting recurrent soft tissue violation are potential tenets of success.

Level Of Evidence: IV.
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http://dx.doi.org/10.1016/j.arth.2021.02.072DOI Listing
July 2021

A Deep Learning Tool for Automated Radiographic Measurement of Acetabular Component Inclination and Version After Total Hip Arthroplasty.

J Arthroplasty 2021 07 16;36(7):2510-2517.e6. Epub 2021 Feb 16.

Department of Health Sciences Research, Mayo Clinic, Rochester, MN; Department of Orthopedic Surgery, Mayo Clinic, Rochester, MN.

Background: Inappropriate acetabular component angular position is believed to increase the risk of hip dislocation after total hip arthroplasty. However, manual measurement of these angles is time consuming and prone to interobserver variability. The purpose of this study was to develop a deep learning tool to automate the measurement of acetabular component angles on postoperative radiographs.

Methods: Two cohorts of 600 anteroposterior (AP) pelvis and 600 cross-table lateral hip postoperative radiographs were used to develop deep learning models to segment the acetabular component and the ischial tuberosities. Cohorts were manually annotated, augmented, and randomly split to train-validation-test data sets on an 8:1:1 basis. Two U-Net convolutional neural network models (one for AP and one for cross-table lateral radiographs) were trained for 50 epochs. Image processing was then deployed to measure the acetabular component angles on the predicted masks for anatomical landmarks. Performance of the tool was tested on 80 AP and 80 cross-table lateral radiographs.

Results: The convolutional neural network models achieved a mean Dice similarity coefficient of 0.878 and 0.903 on AP and cross-table lateral test data sets, respectively. The mean difference between human-level and machine-level measurements was 1.35° (σ = 1.07°) and 1.39° (σ = 1.27°) for the inclination and anteversion angles, respectively. Differences of 5⁰ or more between human-level and machine-level measurements were observed in less than 2.5% of cases.

Conclusion: We developed a highly accurate deep learning tool to automate the measurement of angular position of acetabular components for use in both clinical and research settings.

Level Of Evidence: III.
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http://dx.doi.org/10.1016/j.arth.2021.02.026DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8197739PMC
July 2021

Deep Learning Artificial Intelligence Model for Assessment of Hip Dislocation Risk Following Primary Total Hip Arthroplasty From Postoperative Radiographs.

J Arthroplasty 2021 06 16;36(6):2197-2203.e3. Epub 2021 Feb 16.

Department of Radiology, Radiology Informatics Laboratory, Mayo Clinic, Rochester, MN.

Background: Dislocation is a common complication following total hip arthroplasty (THA), and accounts for a high percentage of subsequent revisions. The purpose of this study is to illustrate the potential of a convolutional neural network model to assess the risk of hip dislocation based on postoperative anteroposterior pelvis radiographs.

Methods: We retrospectively evaluated radiographs for a cohort of 13,970 primary THAs with 374 dislocations over 5 years of follow-up. Overall, 1490 radiographs from dislocated and 91,094 from non-dislocated THAs were included in the analysis. A convolutional neural network object detection model (YOLO-V3) was trained to crop the images by centering on the femoral head. A ResNet18 classifier was trained to predict subsequent hip dislocation from the cropped imaging. The ResNet18 classifier was initialized with ImageNet weights and trained using FastAI (V1.0) running on PyTorch. The training was run for 15 epochs using 10-fold cross validation, data oversampling, and augmentation.

Results: The hip dislocation classifier achieved the following mean performance (standard deviation): accuracy = 49.5 (4.1%), sensitivity = 89.0 (2.2%), specificity = 48.8 (4.2%), positive predictive value = 3.3 (0.3%), negative predictive value = 99.5 (0.1%), and area under the receiver operating characteristic curve = 76.7 (3.6%). Saliency maps demonstrated that the model placed the greatest emphasis on the femoral head and acetabular component.

Conclusion: Existing prediction methods fail to identify patients at high risk of dislocation following THA. Our radiographic classifier model has high sensitivity and negative predictive value, and can be combined with clinical risk factor information for rapid assessment of risk for dislocation following THA. The model further suggests radiographic locations which may be important in understanding the etiology of prosthesis dislocation. Importantly, our model is an illustration of the potential of automated imaging artificial intelligence models in orthopedics.

Level Of Evidence: Level III.
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http://dx.doi.org/10.1016/j.arth.2021.02.028DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8154724PMC
June 2021

Comparison of reconstructive techniques after acetabular resection for pelvic chondrosarcoma.

Bone Joint J 2021 Feb;103-B(2):391-397

Department of Orthopedic Surgery, Mayo Clinic, Rochester, Minnesota, USA.

Aims: Hip reconstruction after resection of a periacetabular chondrosarcoma is complex and associated with a high rate of complications. Previous reports have compared no reconstruction with historical techniques that are no longer used. The aim of this study was to compare the results of tantalum acetabular reconstruction to both historical techniques and no reconstruction.

Methods: We reviewed 66 patients (45 males and 21 females) with a mean age of 53 years (24 to 81) who had undergone acetabular resection for chondrosarcoma. A total of 36 patients (54%) underwent acetabular reconstruction, most commonly with a saddle prosthesis (n = 13; 36%) or a tantalum total hip arthroplasty (THA) (n = 10; 28%). Mean follow-up was nine years (SD 4).

Results: There was no difference in the mean age (p = 0.63), sex (p = 0.110), tumour volume (p = 0.646), or type of resection carried out (p > 0.05) between patients with and without reconstruction. Of the original 66 patients, 61 (92%) were ambulant at final follow-up. There was no difference in the proportion of patients who could walk in the reconstruction and 'no reconstruction' groups (p = 0.649). There was no difference in the mean Musculoskeletal Tumor Society (MSTS) score between patients who were reconstructed and those who were not (61% vs 56%; p = 0.378). Patients with a tantalum THA had a significantly (p = 0.015) higher mean MSTS score (78%) than those who were reconstructed with a saddle prosthesis (47%) or who had not been reconstructed (56%). Patients who had undergone reconstruction were more likely to have complications (81% vs 53%; p = 0.033).

Conclusion: Reconstruction after resection of the acetabulum is technically demanding. In selected cases, reconstruction is of benefit, especially when reconstruction is by tantalum THA; however, the follow-up for these patients remains mid-term. When not feasible, patients with no reconstruction have an acceptable functional outcome. Level of Evidence: Level III Therapeutic. Cite this article: 2021;103-B(2):391-397.
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http://dx.doi.org/10.1302/0301-620X.103B2.BJJ-2020-1012.R1DOI Listing
February 2021

Direct Inpatient Medical Costs of Operative Treatment of Periprosthetic Hip and Knee Infections Are Twofold Higher Than Those of Aseptic Revisions.

J Bone Joint Surg Am 2021 Feb;103(4):312-318

Departments of Orthopedic Surgery (M.H., D.G.L., D.J.B., and H.M.K.) and Health Sciences Research (S.L.V., J.E.R., and H.M.K.), Mayo Clinic, Rochester, Minnesota.

Background: Periprosthetic joint infections (PJIs) following total hip arthroplasty (THA) and total knee arthroplasty (TKA) are associated with substantial morbidity. A better understanding of the costs of PJI treatment can inform prevention, treatment, and reimbursement strategies. The purpose of the present study was to describe direct inpatient medical costs associated with the treatment of hip and knee PJI.

Methods: At a single tertiary care institution, 176 hips and 266 knees that underwent 2-stage revisions for the treatment of PJI from 2009 to 2015 were compared with 1,611 hips and 1,276 knees that underwent revisions for aseptic indications. In addition, 84 hips and 137 knees that underwent irrigation and debridement (I&D) with partial component exchange were compared with 39 hips and 138 knees that underwent partial component exchange for aseptic indications. Line-item details of services billed during hospitalization were retrieved, and standardized direct medical costs were calculated in 2018 inflation-adjusted dollars.

Results: The mean direct medical cost of 2-stage revision THA performed for the treatment of PJI was significantly higher than that of aseptic revision THA ($58,369 compared with $22,846, p < 0.001). Similarly, the cost of 2-stage revision TKA performed for the treatment of PJI was significantly higher than that of aseptic revision TKA ($56,900 compared with $24,630, p < 0.001). Even when the total costs of aseptic revisions were doubled for a representative comparison with 2-stage procedures, the costs of PJI procedures were 15% to 28% higher than those of the doubled costs of aseptic revisions (p < 0.001). The mean direct medical cost of I&D procedures for PJI was about twofold higher than of partial component exchange for aseptic indications.

Conclusions: The direct medical costs of operative treatment of PJI following THA and TKA are twofold higher than the costs of similar aseptic revisions. The high economic burden of PJI warrants efforts to reduce the incidence of PJI. Reimbursement schemes should account for the high costs of treating PJI in order to ensure sustainable patient care.

Level Of Evidence: Economic Level IV. See Instructions for Authors for a complete description of levels of evidence.
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http://dx.doi.org/10.2106/JBJS.20.00550DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8327701PMC
February 2021

Migration Patterns for Revision Total Hip Arthroplasty in the United States as Reported in the American Joint Replacement Registry.

J Arthroplasty 2021 04 6;36(4):1401-1406. Epub 2020 Nov 6.

Department of Surgery and Perioperative Care, Dell Medical School at the University of Texas at Austin, Austin, TX.

Background: Revision total hip arthroplasty (revTHA) is associated with higher rates of complications and greater costs than primary procedures. The aim of this study is to evaluate the effect of hospital size, teaching status, and indication for revTHA, on migration patterns in patients older than 65 years old.

Methods: All THAs and revTHAs reported to the American Joint Replacement Registry from 2012 to 2018 were included and merged with the Centers for Medicare and Medicaid Services database. Migration rate was defined as a patient's THA and revTHA procedures that were performed at separate institutions by different surgeons. Migratory patterns were recorded based on hospital size, teaching status, and indication for revTHA. Analyses were performed by statisticians.

Results: The number of linked procedures included was 11,906. Migration rates in revTHA due to infection were higher for small hospitals than large hospitals (46.6% vs 28.6%, P < .0001). Migration rates were higher comparing non-teaching with teaching hospitals (55% vs 34%, P < .0001). This difference was significant for periprosthetic fractures (70.6% vs 37.2%, P = .005), instability (56.5% vs 35.5%, P = .04), and mechanical complications (88.9% vs 34.7%, P < .05). Most patients migrated to medium or large hospitals rather than small hospitals (89% vs 11%, P < .0001) and to teaching rather than non-teaching institutions (82% vs 18%, P < .0001).

Conclusion: Hospital size and teaching status significantly affected migration patterns for revTHA. Migration rates were significantly higher in small non-teaching hospitals in revTHA due to infection, periprosthetic fracture, instability, and mechanical complications. Over 80% of patients migrated to larger teaching hospitals.
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http://dx.doi.org/10.1016/j.arth.2020.10.030DOI Listing
April 2021

Use of Natural Language Processing Algorithms to Identify Common Data Elements in Operative Notes for Knee Arthroplasty.

J Arthroplasty 2021 03 10;36(3):922-926. Epub 2020 Oct 10.

Department of Health Sciences Research, Mayo Clinic, Rochester, MN; Department of Orthopedic Surgery, Mayo Clinic, Rochester, MN.

Background: Natural language processing (NLP) methods have the capability to process clinical free text in electronic health records, decreasing the need for costly manual chart review, and improving data quality. We developed rule-based NLP algorithms to automatically extract surgery specific data elements from knee arthroplasty operative notes.

Methods: Within a cohort of 20,000 knee arthroplasty operative notes from 2000 to 2017 at a large tertiary institution, we randomly selected independent pairs of training and test sets to develop and evaluate NLP algorithms to detect five major data elements. The size of the training and test datasets were similar and ranged between 420 to 1592 surgeries. Expert rules using keywords in operative notes were used to implement NLP algorithms capturing: (1) category of surgery (total knee arthroplasty, unicompartmental knee arthroplasty, patellofemoral arthroplasty), (2) laterality of surgery, (3) constraint type, (4) presence of patellar resurfacing, and (5) implant model (catalog numbers). We used institutional registry data as our gold standard to evaluate the NLP algorithms.

Results: NLP algorithms to detect the category of surgery, laterality, constraint, and patellar resurfacing achieved 98.3%, 99.5%, 99.2%, and 99.4% accuracy on test datasets, respectively. The implant model algorithm achieved an F1-score (harmonic mean of precision and recall) of 99.9%.

Conclusions: NLP algorithms are a promising alternative to costly manual chart review to automate the extraction of embedded information within knee arthroplasty operative notes. Further validation in other hospital settings will enhance widespread implementation and efficiency in data capture for research and clinical purposes.

Level Of Evidence: Level III.
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http://dx.doi.org/10.1016/j.arth.2020.09.029DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7897213PMC
March 2021

Automated Detection of Periprosthetic Joint Infections and Data Elements Using Natural Language Processing.

J Arthroplasty 2021 02 5;36(2):688-692. Epub 2020 Aug 5.

Department of Health Sciences Research, Mayo Clinic, Rochester, MN; Department of Orthopedic Surgery, Mayo Clinic, Rochester, MN.

Background: Periprosthetic joint infection (PJI) data elements are contained in both structured and unstructured documents in electronic health records and require manual data collection. The goal of this study is to develop a natural language processing (NLP) algorithm to replicate manual chart review for PJI data elements.

Methods: PJI was identified among all total joint arthroplasty (TJA) procedures performed at a single academic institution between 2000 and 2017. Data elements that comprise the Musculoskeletal Infection Society (MSIS) criteria were manually extracted and used as the gold standard for validation. A training sample of 1208 TJA surgeries (170 PJI cases) was randomly selected to develop the prototype NLP algorithms and an additional 1179 surgeries (150 PJI cases) were randomly selected as the test sample. The algorithms were applied to all consultation notes, operative notes, pathology reports, and microbiology reports to predict the correct status of PJI based on MSIS criteria.

Results: The algorithm, which identified patients with PJI based on MSIS criteria, achieved an f1-score (harmonic mean of precision and recall) of 0.911. Algorithm performance in extracting the presence of sinus tract, purulence, pathologic documentation of inflammation, and growth of cultured organisms from the involved TJA achieved f1-scores that ranged from 0.771 to 0.982, sensitivity that ranged from 0.730 to 1.000, and specificity that ranged from 0.947 to 1.000.

Conclusion: NLP-enabled algorithms have the potential to automate data collection for PJI diagnostic elements, which could directly improve patient care and augment cohort surveillance and research efforts. Further validation is needed in other hospital settings.

Level Of Evidence: Level III, Diagnostic.
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http://dx.doi.org/10.1016/j.arth.2020.07.076DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7855617PMC
February 2021

Intermediate to Long-Term Follow-up of Cementing Liners into Well-Fixed Acetabular Components.

J Bone Joint Surg Am 2020 Aug;102(16):1397-1404

Department of Orthopedic Surgery, Mayo Clinic, Rochester, Minnesota.

Background: The cementation of a new liner into a well-fixed acetabular component is common during revision total hip arthroplasty (THA) for many indications, but most commonly for lack of a modern, compatible, highly cross-linked polyethylene (HXLPE) liner. However, little is known about the intermediate-term to long-term durability of this strategy. The purpose of this study was to evaluate the implant survivorship, risk of complications, clinical outcomes, and radiographic results of cementing a new HXLPE liner into a well-fixed acetabular component.

Methods: We retrospectively identified 323 revision THAs in which a nonconstrained HXLPE liner was cemented into a well-fixed acetabular component. The mean age at the time of the revision THA was 63 years, and 50% of patients were female. The most common indications for revision THA were polyethylene wear and osteolysis (48%), aseptic femoral loosening (35%), and hip instability (8%). The mean follow-up was 9 years.

Results: Polyethylene liner failure occurred in 11 cases (3%). In all cases, the cemented liner dissociated from the acetabular component. At 10 years, the survivorship free from any revision was 80% (95% confidence interval [CI], 75% to 84%) and the survivorship free from any reoperation was 77% (95% CI, 72% to 82%). The most common reason for re-revision was dislocation (45% of reoperations). A dislocation occurred in 17% of cases. Hips that underwent revision for instability were significantly more likely to dislocate compared with hips that underwent revision for liner wear (hazard ratio [HR], 2.3 [95% CI, 1.2 to 4.5]; p = 0.02). Elevated rim or face-changing liners were significantly more likely to dissociate than flat liners (HR, 9.0 [95% CI, 1.2 to 70.6]; p = 0.04).

Conclusions: Cementation of a nonconstrained HXLPE liner into a well-fixed acetabular component during revision THA provided durable fixation with only a small number of failures at the cement interface (3%). Instability after this procedure remains a concern, but this is multifactorial in nature. These data support the continued use of this technique, when necessary, during revision THA.

Level Of Evidence: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.
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http://dx.doi.org/10.2106/JBJS.19.01441DOI Listing
August 2020

Phage Therapy for Limb-threatening Prosthetic Knee Klebsiella pneumoniae Infection: Case Report and In Vitro Characterization of Anti-biofilm Activity.

Clin Infect Dis 2021 07;73(1):e144-e151

Division of Infectious Diseases, Mayo Clinic, Rochester, Minnesota, USA.

Background: Prosthetic joint infection (PJI) is a potentially limb-threatening complication of total knee arthroplasty. Phage therapy is a promising strategy to manage such infections including those involving antibiotic-resistant microbes, and to target microbial biofilms. Experience with phage therapy for infections associated with retained hardware is limited. A 62-year-old diabetic man with a history of right total knee arthroplasty 11 years prior who had suffered multiple episodes of prosthetic knee infection despite numerous surgeries and prolonged courses of antibiotics, with progressive clinical worsening and development of severe allergies to antibiotics, had been offered limb amputation for persistent right prosthetic knee infection due to Klebsiella pneumoniae complex. Intravenous phage therapy was initiated as a limb-salvaging intervention.

Methods: The patient received 40 intravenous doses of a single phage (KpJH46Φ2) targeting his bacterial isolate, alongside continued minocycline (which he had been receiving when he developed increasing pain, swelling, and erythema prior to initiation of phage therapy). Serial cytokine and biomarker measurements were performed before, during, and after treatment. The in vitro anti-biofilm activity of KpJH46Φ2, minocycline and the combination thereof was evaluated against a preformed biofilm of the patient's isolate and determined by safranin staining.

Results: Phage therapy resulted in resolution of local symptoms and signs of infection and recovery of function. The patient did not experience treatment-related adverse effects and remained asymptomatic 34 weeks after completing treatment while still receiving minocycline. A trend in biofilm biomass reduction was noted 22 hours after exposure to KpJH46Φ2 (P = .063). The addition of phage was associated with a satisfactory outcome in this case of intractable biofilm-associated prosthetic knee infection. Pending further studies to assess its efficacy and safety, phage therapy holds promise for treatment of device-associated infections.
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http://dx.doi.org/10.1093/cid/ciaa705DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8246933PMC
July 2021

Comparison of Porous Tantalum Acetabular Implants and Harrington Reconstruction for Metastatic Disease of the Acetabulum.

J Bone Joint Surg Am 2020 Jul;102(14):1239-1247

Department of Orthopedic Surgery, Mayo Clinic, Rochester, Minnesota.

Background: The periacetabular region is a common location for metastatic disease. Although large lytic acetabular defects are commonly treated with a hip arthroplasty with a cemented component according to a Harrington-style reconstruction, the use of highly porous uncemented tantalum acetabular components has been described. Currently, there are no direct comparisons of these reconstructive techniques. The purpose of this study was to compare the outcomes of the Harrington technique and tantalum acetabular component reconstruction for periacetabular metastases.

Methods: From 2 tertiary sarcoma centers, we retrospectively reviewed 115 patients (70 female and 45 male) with an acetabular metastatic defect who had been treated between 2002 and 2015 with a total hip arthroplasty using either the cemented Harrington technique (78 patients) or a tantalum acetabular reconstruction (37 patients). The mean patient age was 61 years, and the most common Eastern Cooperative Oncology Group status was 3 (39 patients). The mean follow-up for surviving patients was 4 years.

Results: An additional surgical procedure was performed in 24 patients (21%). Harrington-style reconstructions were more likely to require a reoperation compared with tantalum reconstructions (hazard ratio [HR], 4.59; p = 0.003). The acetabular component was revised in 13 patients (11%); 5 patients (4%) underwent revisions that were due to loosening of the acetabular component. The 10-year cumulative incidence of revision of the acetabular component for loosening was 9.6% in the Harrington group and 0% in the tantalum group (p = 0.09). The mean Harris hip score significantly improved following reconstruction (31 to 67 points; p < 0.001), with no significant difference (p = 0.29) between groups.

Conclusions: In patients with periacetabular metastatic disease treated with total hip arthroplasty, an acetabular reconstruction strategy utilizing highly porous tantalum acetabular components and augments successfully provided patients with a more durable construct with fewer complications compared with the cemented Harrington-style technique.

Levels Of Evidence: Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.
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http://dx.doi.org/10.2106/JBJS.19.01189DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7431144PMC
July 2020

Modular Fluted Tapered Stems in Aseptic Oncologic Revision Total Hip Arthroplasty: A Game Changer?

J Arthroplasty 2020 12 18;35(12):3692-3696. Epub 2020 Jun 18.

Department of Orthopedic Surgery, Mayo Clinic Rochester, Rochester, MN.

Background: Modular fluted tapered (MFT) stems are the most frequently used femoral component in revision total hip arthroplasties (THAs). Despite this, no data are available on how they perform in revision THA for oncologic salvage. This is a unique population, often with severe bone loss and prior radiation that extends the limits of uncemented femoral reconstruction. The aims of this study were to evaluate the implant survivorship, radiographic results, and clinical outcomes of MFT stems used for revision oncologic salvage.

Methods: We identified 17 patients treated initially with primary THA for an oncologic diagnosis (15 primary oncologic, 2 metastatic disease) who underwent subsequent femoral revision with an MFT stem. Mean age at revision was 66 years and 35% of patients were female. Mean follow-up was 4 years. Before revision, 5 of 17 had undergone local radiation.

Results: Ten-year survivorship free from aseptic loosening was 100%. The survivorship free of any reoperation was 76%. There were no femoral component fractures. Three patients were revised for recurrent instability, and 1 patient underwent irrigation and debridement for an acute infection. At most recent follow-up, no patient had radiographic evidence of progressive femoral component subsidence or failure of osteointegration. The mean Harris Hip Score improved from 29 preoperatively to 76 postoperatively (P < .0001).

Conclusion: In this series of patients with cancer, many of whom had severe bone loss and/or prior local radiation, being treated with revision THA, there were no revisions for femoral component loosening and no cases of implant fracture.

Level Of Evidence: III.
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http://dx.doi.org/10.1016/j.arth.2020.06.038DOI Listing
December 2020

Acetabular Distraction Technique for the Treatment of Chronic Pelvic Discontinuities: Excellent Short-Term Implant Survivorship and Good Clinical Outcomes.

J Arthroplasty 2020 10 28;35(10):2966-2971. Epub 2020 May 28.

Department of Orthopedic Surgery, Mayo Clinic, Rochester, Minnesota.

Background: Pelvic discontinuity is a challenging complication in revision total hip arthroplasty. One technique that has garnered enthusiasm with limited data is acetabular distraction. Acetabular distraction provides stability via elastic recoil of the pelvis. The aim of this study is to report implant survivorship, radiographic results, clinical outcomes, and complications in the largest independent series of discontinuities treated with acetabular distraction.

Methods: We retrospectively identified all revision total hip arthroplasties with a pelvic discontinuity between 2005 and 2017. Of the 162 patients, 31 were treated with distraction. Mean age was 67 years, with 71% female. Mean body mass index was 28 kg/m, and mean follow-up was 3 years.

Results: The 2-year survivorship free from revision for aseptic loosening, re-revision for any reason, and reoperation were 97%, 93%, and 87%, respectively. There were 3 re-revisions including 1 for aseptic loosening, 1 conversion to a dual mobility for instability, and 1 two-stage exchange for infection. At last follow-up, 3 acetabular components did not have evidence of osteointegration. Only patients with osteointegration to both the ilium and ischium had evidence of a healed discontinuity. The mean Harris Hip Score improved from 43 preoperatively to 77 postoperatively (P < .0001). The most common complication was a partial sciatic nerve palsy that occurred in 4 patients.

Conclusion: In this series utilizing pelvic distraction, there was excellent 2-year survivorship free from revision for aseptic loosening. Despite several discontinuities persisting, 90% of patients had radiographic evidence of implant osteointegration, and clinical outcomes improved significantly. The most common complication was a partial sciatic nerve palsy.

Level Of Evidence: IV Case Series.
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http://dx.doi.org/10.1016/j.arth.2020.05.048DOI Listing
October 2020

Outcomes of a technique combining diaphyseal impaction grafting and metaphyseal cones for severe bone loss in revision total knee arthroplasty.

Bone Joint J 2020 Jun;102-B(6_Supple_A):116-122

Department of Orthopedic Surgery, Mayo Clinic, Rochester, Minnesota, USA.

Aims: Metaphyseal cones with cemented stems are frequently used in revision total knee arthroplasty (TKA). However, if the diaphysis has been previously violated, the resultant sclerotic canal can impair cemented stem fixation, which is vital for bone ingrowth into the cone, and long-term fixation. We report the outcomes of our solution to this problem, in which impaction grafting and a cemented stem in the diaphysis is combined with an uncemented metaphyseal cone, for revision TKA in patients with severely compromised bone.

Methods: A metaphyseal cone was combined with diaphyseal impaction grafting and cemented stems for 35 revision TKAs. There were two patients with follow-up of less than two years who were excluded, leaving 33 procedures in 32 patients in the study. The mean age of the patients at the time of revision TKA was 67 years (32 to 87); 20 (60%) were male. Patients had undergone a mean of four (1 to 13) previous knee arthroplasty procedures. The indications for revision were aseptic loosening (80%) and two-stage reimplantation for prosthetic joint infection (PJI; 20%). The mean follow-up was four years (2 to 11).

Results: Survival free from revision of the cone/impaction grafting construct due to aseptic loosening was 100% at five years. Survival free from any revision of the construct and free from any reoperation were 92% and 73% at five years, respectively. A total of six patients (six TKAs, 17%) required a further revision, four for infection or wound issues, and two for periprosthetic fracture. Radiologically, one unrevised TKA had evidence of loosening which was asymptomatic. In all unrevised TKAs the impacted diaphyseal bone graft appeared to be incorporated radiologically.

Conclusion: When presented with a sclerotic diaphysis and substantial metaphyseal bone loss, this technique combining diaphyseal impaction grafting with a metaphyseal cone provided near universal success in relation to implant fixation. Moreover, radiographs revealed incorporation of the bone graft and biological fixation of the cone. While long-term follow-up will be important, this technique provides an excellent option for the management of complex revision TKAs. Cite this article: 2020;102-B(6 Supple A):116-122.
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http://dx.doi.org/10.1302/0301-620X.102B6.BJJ-2019-1511.R1DOI Listing
June 2020

Constrained Liners Implanted Simultaneously at the Time of Acetabular Shell Revision with a Highly Porous Implant: Surprisingly Good Fixation at 10 Years.

J Bone Joint Surg Am 2020 Sep;102(17):1521-1529

Department of Orthopedic Surgery, Mayo Clinic, Rochester, Minnesota.

Background: Many surgeons are reluctant to use a constrained liner at the time of acetabular component revision because of concerns that doing so might result in early acetabular component loosening related to high bone-implant interface stresses transmitted from the constrained liner. We hypothesized that, with appropriate initial implant stabilization using highly porous acetabular components with robust supplemental screw fixation, constrained liners could be safely used at the time of acetabular revision.

Methods: We retrospectively identified 148 revision total hip arthroplasties (THAs) in which a constrained liner of 1 design was cemented into a newly placed highly porous acetabular component fixed with supplemental screws (mean, 5 screws). The mean age at the time of revision THA was 69 years, and 68% of the patients were female. The most common indications for revision were 2-stage reimplantation (33%), recurrent dislocation (30%), and aseptic loosening of the acetabular component (22%) or both the acetabular and femoral components (9%). The mean duration of follow-up was 7 years.

Results: There were no failures at the bone-implant interface. No cases of acetabular metal shell loosening were identified on radiographic analysis. The 10-year survival rates with acetabular revision and any reoperation as the end points were 75% and 67%, respectively. Overall, 33 hips (22%) required revision or reoperation because of infection or wound complications (n = 12), dislocation or mechanical failure of the constrained liner (n = 11), periprosthetic femoral fracture (n = 4), femoral loosening (n = 3), or other reasons (n = 3). The 10-year survival rate with re-revision for instability as the end point was 88% overall, which was similar to the 85% 10-year survival rate with re-revision for instability as the end point among hips that were specifically revised because of instability during index revision THA (p = 0.9).

Conclusions: Implanting a constrained liner at the time of acetabular revision in high-risk patients resulted in no cases of aseptic metal acetabular component loosening in this large series. This finding is likely related to the fact that a highly porous acetabular component was utilized with robust supplemental screw fixation in each case. Such information is valuable as these data favor a paradigm shift when compared with some traditionally held tenets.

Level Of Evidence: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.
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http://dx.doi.org/10.2106/JBJS.19.01332DOI Listing
September 2020

Primary and revision total hip arthroplasty with uncemented acetabular components in patients with Paget's disease.

Hip Int 2020 Apr 28:1120700020920178. Epub 2020 Apr 28.

Department of Orthopaedic Surgery, Mayo Clinic, Rochester, MN, USA.

Introduction: Paget's disease affects 3-4% of the population; however, literature describing outcomes of total hip arthroplasty (THA) in this population are limited. Given the known concerns with bleeding, heterotopic ossification (HO), and component loosening, we describe our results with primary and revision THAs in Paget's disease with emphasis on implant survivorship, radiographic results, and clinical outcomes.

Methods: We identified 25 THAs performed with contemporary uncemented acetabular components in patients with Paget's disease from 1999 to 2014. Mean age and follow-up were 78 and 7 years.

Results: In primary THAs, survivorship free from aseptic acetabular and femoral loosening was 100% and 94% at 8 years. 7 patients (41%) received blood transfusions. HO was seen in 9 (53%). Mean Harris Hip Score (HHS) improved from 49 to 76. In revision THAs, survivorship free from acetabular and/or femoral aseptic loosening was 100% at 5 years. 3 patients (38%) received a transfusion. HO was seen in 5 (63%). Mean HHS improved from 52 to 77. There were no radiographic signs of aseptic loosening among unrevised cases in either group.

Discussion: Our investigation demonstrates that concerns with acetabular fixation in Paget's disease have been mitigated with contemporary uncemented acetabular components. Complications previously noted, namely intraoperative bleeding and HO, continue to be of concern.
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http://dx.doi.org/10.1177/1120700020920178DOI Listing
April 2020

Lymphedema: A Significant Risk Factor for Infection and Implant Failure After Total Knee Arthroplasty.

J Am Acad Orthop Surg 2020 Dec;28(23):996-1002

From the Department of Orthopedic Surgery, Mayo Clinic, Rochester, MN.

Background: Lymphedema is characterized by fluid buildup and swelling, leading to skin fibrosis and recurring soft-tissue infections. There is a paucity of data examining the impact of lymphedema in total knee arthroplasty (TKA). The purpose of this study was to review the outcomes of TKA in patients with lymphedema compared with a matched cohort with primary osteoarthritis.

Methods: One hundred forty-four knees underwent primary TKA with a preceding diagnosis of ipsilateral lymphedema. The mean follow-up was 7 years. A blinded 1:2 match of knees with lymphedema to a group of knees without lymphedema undergoing primary TKA was performed. Matching criteria included sex, age, date of surgery, and body mass index. The mean follow-up for the comparison cohort was 8 years.

Results: Lymphedema increased revision hazard ratio [HR] 7.60; P < 0.001), reoperation (HR, 2.87; P < 0.001), and infection (HR, 6.19; P < 0.001) in addition to periprosthetic fracture (P = 0.04) and tibial component loosening (P = 0.01). The mean time to infection trended toward later time points in knees with lymphedema (19 versus 2 months, P = 0.25).

Discussion: Lymphedema increased the risk of revision, reoperation, and infection. These data highlight the need for appropriate patient counseling and the need for further investigation into the effects of preoperative and postoperative optimization of lymphedema management in the TKA setting.

Level Of Evidence: Therapeutic Level III.
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http://dx.doi.org/10.5435/JAAOS-D-20-00005DOI Listing
December 2020

Four Challenges in Revision Total Knee Arthroplasty: Exposure, Safe and Effective Component Removal, Bone Deficit Management, and Fixation.

Instr Course Lect 2019 ;68:217-230

With utilization of both primary and revision total knee arthroplasty projected to increase in coming decades particularly in younger, more active patients, a determination of best surgical practices is vital to meet the burden of demand. Four challenges in surgical techniques for revision total knee arthroplasty include surgical exposure, careful removal of components, bone deficit management, and fixation options. Surgical exposure may be more complicated in patients presenting for revision who have a history of multiple prior surgeries, infection, scar tissue formation, stiffness, ligamentous deficiency, or vascular compromise. Removal of previous implants while preserving bone stock and ligamentous stabilizers requires adequate exposure of interfaces and visualization, and is facilitated with a variety of tools and techniques. Treatment options for management of bone deficits have expanded in recent years to include a wide range of porous metal sleeves, cones, and augments, in addition to the traditional arsenal of screws, cement, bone graft, metallic augments, offset adapters, and stems in various lengths and geometries. Stem fixation may be noncemented, cemented, or hybrid, with the goal of the stems to load share and enhance the mechanical stability of the reconstruction.
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February 2020

Contemporary Total Hip and Total Knee Arthroplasty Results in Patients with Hemochromatosis.

J Arthroplasty 2020 04 30;35(4):976-980. Epub 2019 Nov 30.

Department of Orthopedic Surgery, Mayo Clinic, Rochester, MN.

Background: Hemochromatosis can result in metabolic bone pathology (due to excessive iron absorption) and degenerative joint disease, leading to total joint arthroplasties. The aim of this study is to analyze the survivorship, complications, radiographic results, and clinical outcomes of patients with hemochromatosis who received either a total hip arthroplasty (THA) or a total knee arthroplasty (TKA).

Methods: We identified 34 lower extremity arthroplasties in 29 patients with hemochromatosis performed between 2000 and 2016. There were 17 primary THAs in 15 patients and 17 primary TKAs in 14 patients. Mean age at arthroplasty was 63 years with 76% being male. The mean body mass index was 28 kg/m. Mean follow-up was 5 years.

Results: The survivorship free from any revision for THAs was 94% at 10 years. One patient was revised for aseptic loosening of the femoral stem at 6 months. In THA patients, no infections, no other complications, and no radiographic evidence of aseptic loosening were identified. Harris Hip Scores improved from a mean of 55 preoperatively to 94 postoperatively (P < .001). The survivorship free from any revision for TKAs was 100% at 10 years. Two patients (12%) developed acquired idiopathic stiffness postoperatively; no infections were identified. There was no radiographic evidence of aseptic loosening in any TKA. Knee Society Scores improved from a mean of 61 preoperatively to 94 postoperatively (P < .001).

Conclusion: This study found excellent survivorship, significant improvements in clinical outcomes, and a very low complication profile for both THA and TKA in patients with hemochromatosis.
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http://dx.doi.org/10.1016/j.arth.2019.11.038DOI Listing
April 2020

Definitive Resection Arthroplasty of the Knee: A Surprisingly Viable Treatment to Manage Intractable Infection in Selected Patients.

J Arthroplasty 2020 03 19;35(3):855-858. Epub 2019 Oct 19.

Department of Orthopedic Surgery, Mayo Clinic, Rochester, MN.

Background: Resection arthroplasty of the hip is considered a viable option after multiple failed attempts to eradicate a prosthetic joint infection (PJI). However, much less information about resection arthroplasty of the knee is available. The goals of this study were to determine the success of infection eradication with a resection arthroplasty of the knee and subsequent functional outcomes in this group.

Methods: We retrospectively identified 25 knees (23 patients) treated with resection arthroplasty of the knee for PJI performed at a single institution between 1974 and 2016. The mean age at resection arthroplasty was 65 years. The mean body mass index was 37 kg/m, and the mean Charleston Comorbidity Index was 5. Patients had a mean of 5 operations on the knee (mean of 3 operations for infection) before the resection arthroplasty. Failure to eradicate the infection was defined as any reoperation for infection. Clinical outcomes were assessed via ambulatory status, use of gait aids, and ongoing pain. The mean follow-up was 4 years.

Results: At most recent follow-up, 84% (21 of 25) of knees were free of infection. Three patients had recurrent infection within the first year, and 1 patient had a late infection at 4 years postoperatively. However, only 1 patient required a subsequent amputation. Forty-five percent were community ambulators, 35% were household ambulators, and 20% were only able to transfer. All patients required knee bracing and assistive devices. Fifteen percent of patients were using long-term narcotics.

Conclusion: This large series demonstrates the results of selected use of resection arthroplasty as a treatment for recalcitrant periprosthetic knee infections that have failed multiple attempts to eradicate an ongoing PJI. The resection definitively solved the infection in 84% of patients. Functional results were variable but surprisingly good in some. All patients required bracing and assistive devices.
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http://dx.doi.org/10.1016/j.arth.2019.10.025DOI Listing
March 2020
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