Indications,Survivorship, and Clinical Outcomes of a Rotating Hinge Total Knee and Distal Femoral Arthroplasty System

BackgroundRotating hinge knee prostheses (with or without distal femoral replacement) are indicated in cases of unreconstructible bony or soft tissue compromise. Despite their versatility, these implants have demonstrated high rates of mechanical failure. We aimed to review clinical outcomes of a novel hinged knee arthroplasty system.MethodsWe reviewed all cases in a prospective database of hinged total knee arthroplasty (with and without distal femoral arthroplasty) involving a single manufacturer’s implant system at a large tertiary-level academic health sciences center. We collected reasons for surgery, implant survivorship, reasons for revision, and clinical outcomes (Short Form 12, Western Ontario and McMaster Universities Osteoarthritis Index, and Knee Society Scores).ResultsSeventy-six cases of hinged knee implants using the knee system under investigation were performed (39 hinged total knee and 37 distal femoral replacements) between 2011 and 2018, inclusive. Indications for surgery varied, with second-stage reimplantation most common for rotating hinge and fracture most common for distal femoral arthroplasty. There were 6 revisions in the rotating hinge group (none for aseptic loosening) and 5 in the distal femoral arthroplasty group (1 for aseptic loosening). Average follow-up was 2.89 ± 2.09 years. Postoperative Short Form 12 (Physical Component), Western Ontario and McMaster Universities Osteoarthritis Index, and Knee Society Scores were 30.12 ± 10.17, 55.90 ± 21.51, and 115.62 ± 45.20, respectively.ConclusionThis novel hinged knee system is a highly durable option for complex and revision knee arthroplasty. Early failures tend to be secondary to infection. We observed only a single case of aseptic loosening. Although these early results are encouraging, ongoing follow-up is required to determine long-term prognosis in patients receiving this implant.     

Inter and intra-system size variability of reverse shoulder arthroplasty polyethylene inserts

Background:As the incidence of reverse shoulder arthroplasty (RSA) increases, so will the revision burden. At times, the revision surgeon may be faced with a well-fixed component on one side of the joint and revision implants from a different manufacturer. The ability to use glenoid and humeral implants from different manufacturers could simplify the revision procedure. This study hypothesized that across a range of RSA systems, some implants would demonstrate high size compatibility and others would demonstrate low compatibility.Results:The intersystem polyethylene articular surface deviations between same-size systems were not significantly different (P = 0.61) and were a mean maximum of 60 ± 16 μm (range: 30-80 μm). Intrasystem manufacturing variability was equivalent between all but two models, averaging 49 ± 17 μm (range: 23-99 μm).Discussion:Differences in articular geometry between same-size inserts from different systems were on the same scale as intrasystem manufacturing variability, suggesting that different implant systems of the same nominal diameter could potentially be used interchangeably in revision or extenuating circumstances.Conclusion:The results of this study suggest that surgeons can theoretically interchange same-sized implant components from the different RSA systems tested when conducting revisions.     

Retrieval Analysis of Polyethylene Components in Rotating Hinge Knee Arthroplasty Implants

BackgroundThis study examined a cohort of retrieved rotating hinge (RH) total knee arthroplasty implants of four different designs with emphasis on the surface damage observed on the polyethylene components. Our purpose was to determine if differences in polyethylene damage existed among the designs, and if those differences could be explained by differences in design characteristics.Materials and MethodsSeventy-two RH implants from four manufacturers (DePuy LPS/SROM, Zimmer NexGen, Stryker Howmedica MRH, and Biomet Finn-OSS) removed at the time of revision performed between 2002 and 2017 were identified in our institutional retrieval registry. Damage to the surfaces of the polyethylene was assessed using a subjective grading system and evaluated in multiple zones. Design characteristics that were evaluated included the following: location of the dwell point on the polyethylene component, posterior position of the axle, and amount of hyperextension and rotation allowed by the implant.ResultsThere were no differences in total damage scores between the four implant groups (P = .45). The Stryker Howmedica MRH group showed the least backside wear of all implants but significantly more articular-sided wear compared with two of the other three groups. All implants except NexGen showed increased total damage scores in implants revised for mechanical (vs nonmechanical) reasons and in implants with a longer duration of implantation.ConclusionNo single implant design emerged as superior in terms of minimizing polyethylene wear damage. Polyethylene damage existed in various locations but was not different in severity across designs, suggesting that there is no clear superior RH design that minimizes overall articular surface wear compared with other designs.     

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

BackgroundNatural 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.MethodsWithin 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.ResultsNLP 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%.ConclusionsNLP 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 EvidenceLevel III.     

Is a Titanium Implant for Total Knee Arthroplasty Better? A Randomized Controlled Study

BackgroundLighter weight and lower modulus are potential advantages of titanium (Ti) implants over cobalt chrome (CoCr) implants in total knee arthroplasty (TKA). This study was conducted to determine whether Ti implants in TKA resulted in better clinical outcomes and radiologic results.MethodsOne hundred and eight patients (216 knees) with knee arthritis warranting bilateral primary TKA were randomly allocated to undergo Ti rotating-platform TKA in one knee and CoCr rotating-platform TKA in the contralateral knee. The mean follow-up period was 5.3 years (range, 1-7 years). The weight of Ti implants was one-third lighter than that of CoCr implants (133.9 g vs 390.1 g, P < .01). Clinical outcomes were evaluated using clinical scores, patient preferences (lightness, comfort, naturalness, and satisfaction), gait analysis (kinetic and kinematic data), range of motion, and degree of pain. Radiologic results were evaluated based on the radiolucent line (RLL), degree of medial tibial bone loss, and loosening as seen on X-ray.ResultsNo significant differences were observed in clinical scores or patient preference. Regarding implant weight, approximately 70% of patients did not perceive the Ti implant as lighter. No significant differences were observed in gait analysis, range of motion, or degree of pain. The RLL was seen in 9% of the Ti implant group and 19% of the CoCr implant group.ConclusionThe lighter Ti implant did not show any clinical benefit over CoCr implants. The lightness of the Ti implant is not sufficient to matter or be noticeable. However, the Ti implant showed lower rate of RLL than the CoCr implant.Level of Evidencelevel I, randomized controlled trial.     

Modular Augmentation in Varus-Valgus–Constrained Knee Arthroplasty—Do We Need Sleeves to Avoid Femoral Loosening After Excessive Distal Augmentation?

BackgroundIn revision total knee arthroplasty, zonal fixation methods with a combination of augments, press-fit stems, and sleeves are popular. We hypothesized that high distal femoral augmentation with diaphyseal press-fit stems leads to an increased rate of early aseptic loosening and that femoral metaphyseal sleeves improve implant survival. Therefore, we retrospectively investigated implant survival in relation to augment heights and sleeves.MethodsA total of 136 patients with mean clinical follow-up of 50 months (range, 28-85) who underwent modular total knee arthroplasty and revision total knee arthroplasty with semiconstrained implants between January 2012 and July 2018 were retrospectively evaluated. Implant survival with 4, 8, and 12 mm distal femoral augments was compared to no distal augmentation. Subsequently, a subgroup analysis was performed for femoral sleeve implantation.ResultsWe observed an implant survival rate of 97.0%, 87.5%, and 69.2% for 4, 8, and 12 mm distal femoral augmentation, respectively (P = .73; P = .19; P = .008). The implant survival rate with femoral sleeves was 95.8% for the 8 mm augments and 85.7% for the 12 mm augments (P = .42; P = .96). Without femoral sleeves, the implant survival rate was 78.3% with the 8 mm augments and 50.0% with the 12 mm augments (P = .02; P < .001).ConclusionHigher rates of aseptic femoral loosening were identified for distal femoral augmentation of 8 mm or more without metaphyseal sleeve fixation in semiconstrained implants. Thus, in cases with femoral metaphyseal bone damage requiring high distal femoral augmentation, metaphyseal sleeves should be used to avoid early aseptic femoral loosening.     

Algorithm based automatic templating is less accurate than manual digital templating in total knee arthroplasty

The purpose of the study was to evaluate the accuracy of a commercial automatic digital templating algorithm compared to manual digital templating in total knee arthroplasty (TKA). The study also evaluated if race and the presence of a standardized calibration marker on preoperative radiographs effect the accuracy of digital templating. One hundred twenty-five consecutive patients undergoing primary TKA were included in the study. Patient demographics, etiology of arthritis, and the presence of a standardized calibration marker on preoperative anteroposterior (AP) and lateral radiographs was recorded. Manual digital templating and the use of the “auto-knee” templating algorithm with “Traumacad” software was performed and recorded. Intraoperative sizes of the actual implants used were recorded. Pearson χ2 test was used to evaluate the accuracy of auto versus manual templating. Manual templating was within 1 size of the implant used intraoperatively for femoral and tibial implants 97.6% and 94.2% of the time, respectively. The “auto-knee” algorithm was within one size of the implant used for femoral and tibial implants 51.2% and 71.2% of the time, respectively. The presence of a standardized calibration marker on the AP view did not change accuracy of templating for both components. There was no difference in accuracy of templating between races. We caution surgeons from exclusively using an automatic algorithm as it is less accurate than manual templating for TKA.     

Process Mapping Total Knee Arthroplasty: A Comparison of Instrument Designs

BackgroundTotal knee arthroplasty (TKA) is commonly performed with proprietary, manual instrumentation provided by the surgical implant manufacturer. Registry studies and meta-analysis, with few outliers, have consistently shown similar functional outcomes and implant survival after TKA regardless of implant manufacturer, implant design, or surgical technique. We hypothesized that process mapping could identify areas for improvement in TKA instrumentation.MethodsSeventeen TKA implant systems from 10 companies representing over 90% of all TKAs performed in the United States were evaluated. Instrumentation required for femoral, tibial, and patellar preparation was compared. The number of steps including surgical technician assembly steps, instrument handoffs, and surgeon steps were tabulated based off application of a standardized surgical flow, adjusted for manufacturer-recommended steps during completion of a TKA operation.ResultsCruciate-retaining (CR) knee instrumentation in studied systems required 158-225 discrete steps and posterior-stabilized (PS) knees required 181-230 steps. With the fewest steps for femoral, tibial, and patellar instrumentation, CR and PS knee systems could be improved to 145 and 163 steps, respectively. The Arthrex iBalance and the Biomet Vanguard Microplasty required fewest steps among CR systems; the OrthoDevelopment Balanced and the Corin Unity required fewest steps among PS systems.ConclusionsProcess mapping identified potential areas for improved instrumentation in all studied systems, suggesting the possibility to reduce operative steps broadly across the TKA industry. Patient outcomes were not evaluated by system. Future implant system design changes may do well to reduce unnecessary steps and instrumentation.     

Prospective Mid-Term Results of a Completely Metal-Free Ceramic Total Knee Endoprosthesis: A Concise Follow-Up of a Previous Report

BackgroundHypersensitivity reactions are suspected to cause premature aseptic loosening in susceptible patients after total knee arthroplasty. In response, metal-free implants have been developed. The aim of this prospective, observational midterm study was the assessment of a completely metal-free ceramic knee replacement system as a concise follow-up of a previous report.MethodsThirty-eight patients, with anamnestic suspected or documented allergy to the metal used in prosthetic alloys, participated in this 4-year follow-up of the metal-free BPK-S (Peter Brehm) total knee replacement system with ceramic femoral and tibial components. Clinical assessment included Knee Society Score (KSS), Oxford Knee Score, Euro Quol-5D-Visual Analogue Scale (EQ-5D-VAS), and perioperative or postoperative complications and need for revision. The position of the implant, signs of loosening, and leg alignment were assessed radiographically.ResultsAll postoperative clinical scores improved significantly from baseline to 48-month follow-up examination. The Oxford Knee Score improved from 39 to 15 points. The KSS improved from 99 to 195 points (the KSS knee score 42.5 to 96 and the KSS function score 60 to 100). The EQ-5D improved from 12 to 7 points; the EQ-VAS improved from 52.5 to 97 points. No allergic reactions could be detected. Radiologically, a median preoperative varus deformity of 5° improved to 0° at 4-year follow-up. Radiolucent lines appeared around uncemented areas with no clinical symptoms.ConclusionThe fully metal-free BPK-S Integration ceramic knee replacement system exhibits excellent immuno-allergological compatibility, offering a safe option for patients with prior hypersensitivity reactions to metallic materials. Full cementation of all components is recommended to avoid radiolucent lines around the implant.     

Synchronous Periprosthetic Joint Infections: High Mortality,Reinfection, and Reoperation

BackgroundSynchronous periprosthetic joint infections (PJIs) are a catastrophic complication with potentially high mortality. We aimed to report mortality, risk of reinfection, revision, reoperation, and implant survivorship after synchronous PJIs.MethodsWe identified 34 patients treated for PJI in more than one joint within a single 90-day period from 1990 to 2018. PJIs involved bilateral knee arthroplasty (27), bilateral hip arthroplasty (4), 1 knee arthroplasty and 1 elbow arthroplasty (1), 1 knee arthroplasty and 1 shoulder arthroplasty (1), and bilateral hip and knee arthroplasty (1). Irrigation and debridement with component retention was performed in 23 patients, implant resection in 10 patients, and a combination of irrigation and debridement with component retention and implant resection in 1 patient. A competing risk model was used to analyze implant survivorship, and Kaplan-Meier survival was used for patient mortality. Mean follow-up was 6 years.ResultsMortality was high at 18% at 30 days and 27% at 1 year. The 1-year cumulative incidence of any reinfection was 13% and 27% at 5 years. The 1-year cumulative incidence of any revision or implant removal was 6% and 20% at 5 years. The 1-year cumulative incidence of unplanned reoperation was 25% and 35% at 5 years. Rheumatoid arthritis was associated with increased risk of mortality (HR 7, P < .01), as was liver disease (HR 4, P = .02).ConclusionIn the largest series to date, patients with synchronous PJIs had a high 30-day mortality rate of 18%, and one-fourth underwent unplanned reoperation within the first year.     

Diagnosis of infection after total hip arthroplasty

Forty-eight total hip arthroplasties for which revision surgery was performed were reviewed to determine the accuracy of laboratory tests, plain radiographs, hip aspiration, and technetium-99m MDP and gallium-67 scans in demonstrating the presence or absence of infection of the prosthesis. Six of the 48 hips were diagnosed as having an infection at the revision surgery. The erythrocyte sedimentation rate and the C-reactive protein levels were significantly higher in the patients with infected prostheses. The difference in the white blood cell count was not significant. There was no signifi-cant relationship between the presence of infection and the severity of loosening and instability of the implants diagnosed by plain radiographs. The accuracy of hip aspiration in diagnosing the infection was 83%, with a sensitivity of 40% and a specificity of 92%. The accuracy of technetium-99m MDP bone scan was 79%, with a sensitivity of 83%, and a specificity of 79%. Gallium-67 scan had an accuracy of 96%, a sensitivity of 67%, and a specificity of 100%. The findings in the present study indicated that diagnostic tests consisting of laboratory tests and plain radiography, followed by hip aspiration and sequential use of technetium-99m MDP and gallium-67 scintigraphies, are suitable for differentiation between mechanical loosening and infection of total hip arthroplasty. Received: November 17, 2000 / Accepted: February 14, 2001     

Additive manufacturing of porous titanium metaphyseal components: Early osseointegration and implant stability in revision knee arthroplasty

AimsMetaphyseal cones and sleeves are components used in revision knee arthroplasty to ensure load transfer, encourage bone on-growth and prevent stress shielding. Additive manufacturing of titanium alloy implants is a novel technique with limited clinical outcome reports in the literature. The aim of this study was to determine radiographic evidence of osseointegration and early results of a single manufacturer porous titanium metaphyseal components in the proximal tibia.MethodsWe retrospectively reviewed the prospectively collected database of two institutions. Patients who underwent revision knee arthroplasty using porous titanium components by a single manufacturer were identified. Immediate post-operative and latest follow-up radiographs were independently analysed by 2 reviewers to determine metaphyseal bone contact and level of osseointegration in relevant Knee Society Radiographic Evaluation and Scoring System zones.Results22 patients (15 males; 7 females) with a mean age of 71 (49–92) years were included. The mean follow-up period was 14 months (2–44 months). Cones were used in 16 patients and sleeves in 6. Interobserver reliability assessment showed substantial agreement (weighted Kappa 0.71, (95% CI: 0.60, 0.81). There was significant correlation between the bone contact in the immediate postop radiograph and osseointegration at final follow-up (kendall’s tau-b: 0.698, p < 0.001). Infection free prosthetic joint survival was 20/22 at final follow-up.ConclusionPorous titanium metaphyseal components produced with additive manufacturing provided excellent osseointegration and no early clinical failures. Partial or complete contact of the cone with native bone in the immediate postoperative radiograph resulted in osseointegration in all cases.     

Analysis of Biomechanical Differences Between Condylar Constrained Knee and Rotating Hinged Implants: A Numerical Study

BackgroundDifferent levels of constraint for total knee arthroplasty can be considered for revision surgeries. While prior studies have assessed the clinical impact and patient outcomes of condylar constrained knee (CCK) and rotating hinged (RTH) implants, nowadays little is known about the biomechanical effects induced by different levels of constraint on bone stress and implant micromotions.MethodsCCK and RTH implant models were analyzed using a previously validated numerical model. Each system was investigated during a squat and a lunge motor task. The force in the joint, the bone and implant stresses, and micromotions in this latter were analyzed and compared among designs.ResultsDifferent activities induced similar bone stress distributions in both implants. The RTH implant induces mostly high stress compared to the CCK implant, especially in the region close to tip of the stem. However, in the proximal tibia, the stresses achieved with the CCK implant is higher than the one calculated for the RTH design, due to the presence of the post-cam system. Accordingly, the condylar constrained design shows higher implant micromotions due to the greater torsional constraint.ConclusionDifferent levels of constraint in revision arthroplasty were always associated with different biomechanical outputs. RTH implants are characterized by higher tibial stress especially in the region close to the stem tip; condylar implants, instead, increase the proximal tibial stress and therefore implant micromotions, as a result of the presence of the post-cam mechanism. Surgeons will have to consider these findings to guarantee the best outcome for the patient and the related change in the bone stress and implant fixation induced by different levels of constrain in a total knee arthroplasty.     

Yearly incidence of unicompartmental knee arthroplasty in the United States

Our purpose was to estimate the incidence of unicompartmental knee arthroplasty in the United States. Three major implant manufacturers provided data over an 8-year period from 1998 to 2005. In addition, a database from 44 hospitals was used to derive national estimates for implants manufactured by all other companies. The incidence of unicompartmental knee arthroplasty ranged from 6570 implants in 1998 to 44990 in 2005. Unicompartmental knee arthroplasty increased at an average rate of 32.5% during the study period compared with a 9.4% average increase in rate of total knee arthroplasty over the same period. Although unicompartmental arthroplasty is growing at triple the rate of total knee arthroplasty in the United States, the data suggest that unicompartmental implants currently account for less than 8% of all knee arthroplasty procedures.     

Clinically Asymptomatic Patients Show a High Bacterial Colonization Rate of Osteosynthetic Implants Around the Knee but Not the Hip

BackgroundPatients with osteosynthetic implants around the hip and knee show higher infection rates after joint arthroplasty. Our aim was to evaluate the bacterial colonization of any osteosynthetic implants around the hip and knee in patients without clinical signs of infection.MethodsConsecutive patients with osteosynthetic implant removal because of related soft tissue irritations or before elective total joint arthroplasty of the hip and knee were prospectively included. Patients with signs of infection were excluded. Based on sonication fluid cultures, implants were classified according to microbial growth as negative (no growth), contaminated (nonsignificant growth), or colonized (significant growth).ResultsSonication cultures were positive in 54 of 203 implants (27%), including 8 of 34 (24%) after orthopedic and 46 of 169 (27%) after traumatological surgery. Of 203 sonication cultures, 22 (11%) grew significant bacterial counts. Most common microorganisms were coagulase-negative staphylococci (46%). Implants around the knee showed a significantly higher rate of positive sonication cultures compared with those around the hip (14% vs 2%, P = .017).ConclusionsWe detected high bacterial implant colonization rates regardless of the initial type of surgery. Predominant pathogens were staphylococci, the most common causative agents of periprosthetic joint infections. Positive sonication results do not necessarily lead to postoperative surgical complications and thus do not equal infection. It remains unclear if patients with evidence of bacterial implant colonization show a higher risk of periprosthetic joint infection after adjacent subsequent total joint arthroplasty. Nevertheless, surgeons should be aware of a significantly higher colonization rate of implants around the knee and take this into consideration when total knee arthroplasty is scheduled in patients with osteosynthetic devices.     

Imaging periprosthetic osteolysis around total knee arthroplasties using a human cadaver model

We examined the sensitivity and accuracy of measuring osteolysis around total knee arthroplasty (TKA) on radiographs, computed tomography (CT), and magnetic resonance imaging (MRI) in a cadaver model. Fifty-four simulated osteolytic defects ranging from 0.7 to 14 cm(3) were created in 6 cadaver knees implanted with either a cemented or an uncemented TKA. Three blinded investigators assessed the presence, location, and volume of defects on radiographs and CT and MRI scans with metal reduction protocols. Both CT and MRI had significantly higher sensitivities and specificities than did plain radiographs (P < .005). Overall, there was no difference in the accuracy of defect volume measurements between CT and MRI (P = .574). This study demonstrates the limitations of radiographs and the high sensitivity and specificity of both CT and MRI in assessing osteolysis around TKA.     

Revision Total Hip and Knee Arthroplasty Implant Identification: Implications for Use of Unique Device Identification 2012 AAHKS Member Survey Results

FDA's Unique Device Identification (UDI) Rule will mandate manufacturers to assign unique identifiers to their marketed devices. UDI use is expected to improve implant documentation and identification. A 2012 American Association of Hip and Knee Surgeons membership survey explored revision total hip and knee arthroplasty implant identification processes. 87% of surgeons reported regularly using at least 3 methods to identify failed implants pre-operatively. Median surgeon identification time was 20 min; median staff time was 30 min. 10% of implants could not be identified pre-operatively. 2% could not be identified intra-operatively. UDI in TJA registry and UDI in EMR were indicated practices to best support implant identification and save time. FDA's UDI rule sets the foundation for UDI use in patient care settings as standard practice for implant documentation.     

Smart sensor implant technology in total knee arthroplasty

Innovations in computer technology and implant design have paved the way for the development of smart instruments and intelligent implants in trauma and orthopaedics to improve patient-related functional outcomes. Sensor technology uses embedded devices that detect physical, chemical and biological signals and provide a way for these signals to be measured and recorded. Sensor technology applications have been introduced in various fields of medicine in the diagnosis, treatment and monitoring of diseases. Intelligent ‘Smart’ implants are devices that can provide diagnostic capabilities along with therapeutic benefits. In trauma and orthopaedics, applications of sensors is increasing because of the advances in microchip technologies for implant devices and research designs. It offers real-time monitoring from the signals transmitted by the embedded sensors and thus provides early management solutions. Smart orthopaedic implants have applications in total knee arthroplasty, hip arthroplasty, spine surgery, fracture healing, early detection of infection and implant loosening. Here we have explored the role of Smart sensor implant technology in total knee arthroplasty. Smart sensor assisted can be used intraoperatively to provide objective assessment of ligament and soft tissue balancing whilst maintaining the sagittal and coronal alignment to achieve desired kinematic targets following total knee arthroplasty. It can also provide post-implantation data to monitor implant performance in natural conditions and patient's clinical recovery during rehabilitation. The use of Smart Sensor implant technology in total knee arthroplasty appears to provide superior patient satisfaction rates and improved functional outcomes.     

Reference Pricing Reduces Total Knee Implant Costs

BackgroundReference pricing establishes a set price a hospital is willing to pay for total knee arthroplasty (TKA) components regardless of vendor. The hospital contracts with vendors that sell implants to the hospital at the hospital-dictated prices. Orthopedic surgeons are free to utilize any implant system that has met the reference price using their best clinical judgment. Our hypothesis is that vendors will meet the set price and selection of different vendors and technologies will not change.MethodsWe retrospectively analyzed the 12 months prior (May 2017-2018) and the most recent 12 months after (March 2019-2020) implementing reference pricing at our institution. We investigated differences in average prices for total implant and component costs. We evaluated cost of implants with respect to surgeon volume, assessed the rate of cementless TKAs used, and number of companies purchased from before and after reference pricing.ResultsIn total, 7148 TKAs were included in the study with 3790 arthroplasties before and 3358 after implementation of reference pricing. Overall implant costs decreased by 16.7% (P < .0001). All individual knee component costs decreased by at least 11% (P = .0003). No difference in prices were found among surgeons (P = .9758). Cementless knee use increased by 9% (P < .0001; odds ratio 1.94, 95% confidence interval = 1.69-2.24). No vendor business was lost.ConclusionThe strategy of reference pricing significantly reduced costs for TKA implants at our institution. The reduction in implant costs was regardless of surgeon volume. Newer technologies were utilized more often after reference pricing. This strategy represents a significant cost-savings approach for other hospitals.     

Could Novel Radiographic Findings Help Identify Aseptic Tibial Loosening?

BackgroundAseptic loosening following total knee arthroplasty remains one of the leading causes of long-term failure. Radiographic identification of loose implants can be challenging with standard views. The purpose of this study was to compare the incidence of novel radiographic findings of anterior heterotopic bone formation and medial or lateral cyst formation in patients who have aseptic loosening to patients who have well-fixed implants.MethodsA retrospective radiographic review was performed on 48 patients’ revised secondary to aseptic tibial loosening. This cohort was compared to two additional cohorts; 48 patients returning for routine postoperative follow-up (control 1), and 48 patients revised secondary to infection or instability who had well-fixed implants (control 2).ResultsThere were 41 of 48 (85%) patients who had implant loosening and were noted to have anterior heterotopic bone formation compared to 1 of 48 (2%) patients in control 1 and 3 of 48 (6%) patients in control 2 (P ≤ .0001). There were 43 of 48 (90%) patients who had implant loosening and had medial cyst formation compared to 3 of 48 (6%) patients in control 1 and 5 of 48 (10%) in control 2 (P ≤ .0001). There were 42 of 48 (88%) patients who had implant loosening and had lateral cyst formation compared to 2 of 48 (4%) patients in control 1 and 4 of 48 (8%) in control 2 (P ≤ .0001).ConclusionIn this study, we describe novel radiographic findings of anterior heterotopic bone formation and cysts that develop in patients who have aseptic loosening following primary total knee arthroplasty. We believe that these radiographic features may lead to easier identification of aseptic loosening.