Changing the definition of treatment success alters treatment outcomes in periprosthetic joint infection: a systematic review and meta-analysis.

Background: Variability in the definition of treatment success poses difficulty when assessing the reported efficacy of treatments for hip and knee periprosthetic joint infection (PJI). To address this problem, we determined how definitions of PJI treatment success have changed over time and how this has affected published rates of success after one-stage and two-stage treatments for hip and knee PJI. Methods: A systematic review following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines was conducted to identify one-stage and two-stage revision hip and knee PJI publications in major databases (2006-2021). Definition of treatment success, based on Musculoskeletal Infection Society tier criteria, was identified for each study. Publication year, number of patients, minimum follow-up, and study quality were also recorded. The association of success definitions and treatment success rate was measured using multi-variable meta-regression. Results: Study quality remained unchanged in the 245 publications included. Over time, no antibiotics (tier 1) and no further surgery (tier 3) (40.7 % and 54.5 %, respectively) became the two dominant criteria. After controlling for type of surgery, study quality, study design, follow-up, and year of publication, studies with less strict success definitions (tier 3) reported slightly higher odds ratios of 1.05 [1.01, 1.10] ( p = 0.009 ) in terms of treatment success rates compared to tier 1. Conclusions: PJI researchers have gravitated towards tier-1 and tier-3 definitions of treatment success. While studies with stricter definitions had lower PJI treatment success, the clinical significance of this is unclear. Study quality, reflected in the methodological index for non-randomized studies (MINORS) score, did not improve. We advocate for improving PJI study quality, including clarification of the definition of treatment success.

Nearly 14-Fold Increased Risk of Manipulation Under Anesthesia After Total Knee Arthroplasty When Previous Contralateral Total Knee Arthroplasty Required Manipulation Under Anesthesia.

BACKGROUND: Stiffness remains a common complication after primary total knee arthroplasty (TKA). Manipulation under anesthesia (MUA) is the gold standard treatment for early postoperative stiffness; however, there remains a paucity of data on the risk of MUA after primary TKA if a prior contralateral TKA required MUA. METHODS: We performed a retrospective review of 3,102 patients who had staged primary TKAs between 2016 and 2021. The mean body mass index was 33 (range, 18 to 59) and the mean age was 67 years (range, 24 to 91). The mean preoperative range of motion for the first TKA was 2 to 104°, and for the contralateral TKA was 1 to 107°. The primary outcomes were MUA following first and second primary TKAs. Multivariable Poisson regressions were used to evaluate associations between risk factors and outcomes. RESULTS: The rate of MUA after the first TKA was 2.6% (n = 83 of 3,102) and 1.3% (n = 40 of 3,102) after the contralateral TKA. After adjustment, there was a nearly 14-fold higher rate of MUA after the second TKA if the patient had an MUA after the first TKA (relative risk, 13.80; 95% CI [confidence interval], 7.14 to 26.66). For the first TKA, increasing age (adjusted risk ratio [ARR], 0.65; 95% CI, 0.50 to 0.83) and increasing body mass index (ARR, 0.65; 95% CI, 0.47 to 0.90) were associated with lower risk for MUA. For the second TKA, increasing age was associated with a lower risk of MUA (ARR, 0.60; 95% CI, 0.45 to 0.80). CONCLUSIONS: For patients undergoing staged bilateral TKA, patients who undergo MUA following the first primary TKA are nearly 14-fold more likely to undergo an MUA following the contralateral primary TKA than those who did not have an MUA after their first TKA.

A Comparison of Clinical Outcomes After Total Knee Arthroplasty in Patients Who Have and Do Not Have Self-Reported Nickel Allergy: Matched and Unmatched Cohort Comparisons.

BACKGROUND: The impact of a preoperative self-reported nickel allergy in patients undergoing primary total knee arthroplasty (TKA) remains unclear. The aim of this study was to compare the revision rates and outcomes of patients who have a self-reported nickel allergy undergoing primary TKA to patients who do not have a self-reported nickel allergy. METHODS: Over 5 years, a total of 284 TKAs in patients who have and 17,735 in patients who do not have a self-reported nickel allergy were performed. Revision rates and differences in preoperative and postoperative patient-reported outcome measures, including Knee Osteoarthritis Outcome Score Joint Replacement (KOOS JR), Visual Analog Scale, Lower Extremity Activity Scale, and the Patient-Reported Outcomes Measurement Information System Mental and Physical Scores, were compared. RESULTS: Survivorship free of all-cause revision at 1 year was similar for patients who have and do not have a self-reported nickel allergy (99.5% [95% CI (confidence interval): 98.6 to 100.0] versus 99.3% [95% CI: 99.1 to 99.4]), P = .49). Patients who have a self-reported nickel allergy undergoing primary TKA had no difference in KOOS JR, Visual Analog Scale, or Lower Extremity Activity Scale scores at 6 weeks and 1 year and slightly worse Patient-Reported Outcomes Measurement Information System mental and physical scores at 6 weeks compared to patients who did not have an allergy. Matched analysis revealed no difference in 6-week or 1-year KOOS, JR scores between patients who did and did not have a self-reported nickel allergy when stratified by implant class (nickel-free versus standard cobalt-chromium) (P = .113 and P = .415, respectively). CONCLUSIONS: Patients who have a self-reported nickel allergy can be advised that, on average, their clinical outcome scores will improve similarly to patients who do not have a self-reported nickel allergy, and revision rates will be similar.

Characterizing the Magnitude and Risk Factors of Functional and Anatomic Limb Lengthening in Patients Undergoing Revision Total Knee Arthroplasty.

BACKGROUND: In revision total knee arthroplasty (TKA), there is little information on the magnitude of potential limb lengthening, risk factors for lengthening, or its impact on patient-reported outcome measures. We aimed to quantify limb length alteration during revision TKA and assess risk factors for lengthening. METHODS: We identified 150 patients over a 3-year period who underwent revision TKA and had preoperative and postoperative EOS hip-to-ankle standing radiographs. The average patient age was 64 years, 51% were women; 68% had a preoperative varus deformity and 21% had a preoperative valgus deformity. Outcomes assessed included change in functional and anatomic limb length, risk factors for lengthening, and clinical outcome scores, including the Knee Osteoarthritis Outcome Score Joint Replacement, and the Veterans RAND 12-item Physical and Mental Scores. RESULTS: There were 124 patients (83%) who had functional limb lengthening, and 108 patients (72%) had anatomic limb lengthening. Patients had an average functional limb lengthening of 7 mm (range, -22 to 35) and an average anatomic limb lengthening of 5 mm (range, -16 to 31). Patients undergoing revision for instability experienced significantly greater anatomic lengthening (7.6 versus 4.6, P = .047). Patients who had ≥ 10° of deformity were more likely to be functionally lengthened (91 versus 79%) and had significantly greater average functional lengthening (12 versus 6 mm; P = .003). There was no significant change in clinical outcome scores at 6 weeks and 1 year for patients lengthened ≥ 5 or 10 mm compared to those not lengthened as substantially. CONCLUSIONS: There is major potential for functional and anatomic limb lengthening following revision TKA, with greater preoperative deformity and revision for instability being risk factors for lengthening.

Clinical Outcomes of Isolated Polyethylene Exchange Versus Full Component Revision for the Management of Instability Following Total Knee Arthroplasty.

BACKGROUND: Instability following total knee arthroplasty (TKA) is a common cause for revision. Isolated polyethylene exchange (IPE) can be performed to increase knee joint stability, but results have been mixed. The purpose of this study was to compare the survivorship and patient-reported outcomes of patients undergoing revision TKA for instability with IPE versus full component revision. METHODS: We reviewed 280 primary TKAs undergoing revision TKA for instability. There were 181 knees that underwent revision with IPE, compared to 99 knees treated with full component revision. The mean follow-up was 32.8 months (range, 24.8 to 82.5). Patient demographics, radiographic parameters, prosthesis constraints, reoperations for instability, and patient-reported outcomes were compared. RESULTS: The survivorship for instability was significantly higher at 2 years (99 versus 92%, P = .024) and 5 years (94 versus 84%, P = .024) for patients undergoing full component revision. Although there was no difference in Knee Injury and Osteoarthritis Outcome Score for Joint Replacements and Veterans RAND 12 physical component scores between the 2 groups at 6 weeks, 1 year, and 2 years after surgery, full revision patients reported greater pain relief (P = .006) and greater improvements in Veterans RAND 12 physical component scores (P = .027) at 1 year and Knee Injury and Osteoarthritis Outcome Score for Joint Replacements scores at 2 years (P = .017) compared to IPE patients. Men were associated with an increased risk for recurrent instability following IPE (hazard ratio 3.3, 95% confidence interval: [1.0 to 10.6]). CONCLUSIONS: Isolated polyethylene exchange was not as reliable or durable compared to full component revision for the management of postoperative instability. These procedures should only be reserved in cases with competent collaterals and when component position, offset, and rotation are optimized.

Impact of Selective Posterior Cruciate Ligament Fiber Release on Femoral Rollback in Cruciate-Retaining Total Knee Arthroplasty: A Computational Study.

BACKGROUND: Partial or total release of the posterior cruciate ligament (PCL) is often performed intraoperatively in cruciate-retaining total knee arthroplasty (CR-TKA) to alleviate excessive femoral rollback. However, the effect of the release of selected fibers of the PCL on femoral rollback in CR-TKA is not well understood. Therefore, we used a computational model to quantify the effect of selective PCL fiber releases on femoral rollback in CR-TKA. METHODS: Computational models of 9 cadaveric knees (age: 63 years, range 47 to 79) were virtually implanted with a CR-TKA. Passive flexion was simulated with the PCL retained and after serially releasing each individual fiber of the PCL, starting with the one located most anteriorly and laterally on the femoral notch and finishing with the one located most posteriorly on the medial femoral condyle. The experiment was repeated after releasing only the central PCL fiber. The femoral rollback of each condyle was defined as the anterior-posterior distance between tibiofemoral contact points at 0° and 90° of flexion. RESULTS: Release of the central PCL fiber in combination with the anterolateral (AL) fibers, reduced femoral rollback a median of 1.5 [0.8, 2.1] mm (P = .01) medially and by 2.0 [1.2, 2.5] mm (P = .04) laterally. Releasing the central fiber alone reduced the rollback by 0.7 [0.4, 1.1] mm (P < .01) medially and by 1.0 [0.5, 1.1] mm (P < .01) laterally, accounting for 47 and 50% of the reduction when released in combination with the AL fibers. CONCLUSIONS: Releasing the central fibers of the PCL had the largest impact on reducing femoral rollback, either alone or in combination with the release of the entire AL bundle. Thus, our findings provide clinical guidance regarding the regions of the PCL that surgeons should target to reduce femoral rollback in CR-TKA.

Contemporary Isolated Bearing Exchange for the Management of Hip Instability Following Primary Total Hip Arthroplasty.

BACKGROUND: Isolated ball and liner exchanges (IBLEs) can be performed to increase hip joint stability, but historical results have been mixed due to a lack of head size options or dual mobility articulations. The purpose of this study was to evaluate the contemporary results of IBLEs in patients who have instability following primary total hip arthroplasty (THA). METHODS: We retrospectively reviewed 65 primary THAs from 2016 to 2020 with hip instability undergoing IBLE or conversion to dual mobility articulation. There were 31 men and 34 women who had an average age of 70 years (range, 26 to 92). The mean time to revision from primary was 40.1 months (range, 1 to 120). In 52 cases, IBLE was performed using conventional bearings, while 13 hips were converted to dual mobility. Radiographic factors, including acetabular component orientation, reproduction of hip joint offset, leg lengths, and outcomes such as recurrent instability requiring subsequent revision and patient-reported outcome measure, were recorded and compared. RESULTS: There were 12 (18.4%) hips that experienced subsequent instability and required another revision (17.3% ball and liner exchange versus 23.1% dual mobility articulation, P = .615). The mean time to rerevision for instability was 17.1 months. There were no significant differences in either acetabular component anteversion (P = .25) or restoration of hip joint offset (P = .87) in patients who required another revision for instability compared to those who did not, respectively. At 1 year, patients undergoing conventional bearing exchange reported higher Hip Dysfunction Osteoarthritis Outcome Score for Joint Replacements (P = .002) and Veterans Rand physical component (P = .023) scores compared to those who underwent a conversion to dual mobility articulation. Only age > 75 years at the time of surgery was associated with increased risk for dislocation (odds ratio 7.2, confidence interval 1.2 to 43.7, P = .032). CONCLUSIONS: Isolated bearing exchanges for instability following THA remained at high risk for subsequent instability. Conversion to dual mobility articulations did not reduce the risk of reoperation.

No Difference in Limb Alignment Between Kinematic and Mechanical Alignment Robotic-Assisted Total Knee Arthroplasty.

BACKGROUND: Individualized alignment techniques have gained major interest in an effort to increase satisfaction among total knee arthroplasty patients. This study aimed to compare postoperative alignment between kinematic alignment (KA) and mechanical alignment (MA) and assess whether KA significantly deviates from the principle of aligning the limb as close to neutral alignment as possible. METHODS: There were 234 patients who underwent robotic-assisted total knee arthroplasty using an unrestricted KA and a strict MA technique (KA: 145, MA: 89). The lateral distal femoral angle, medial proximal tibia angle, and the resultant arithmetic hip-knee-ankle angle (aHKA) were measured. The aHKA < 0 indicated varus alignment, while the aHKA > 0 indicated valgus knee alignment. The primary outcome was the frequency of cases that resulted in an aHKA of ± 4° of neutral (0°), as assessed on full-leg standing radiographs obtained at 6 weeks postoperatively. The secondary outcome was the change in coronal plane alignment of the knee classification type from preoperative to postoperative between the MA and KA groups. RESULTS: The mean preoperative aHKA was similar between the 2 groups (P = .19). The KA group had a mean postoperative aHKA of -1.4 ± 2.4°, while the MA group had a mean postoperative aHKA of -0.5 ± 2.1°. No significant difference in limb alignment was identified between KA and MA cases that resulted in hip-knee-ankle angle of ± 4° being neutral (91.7 versus 96.6%, P = .14). There were 97.2% of cases in the KA group that fell within the ± 5° range. The MA group was associated with a significantly higher rate of coronal plane alignment of the knee classification type change from preoperatively to postoperatively (P < .001). CONCLUSIONS: Kinematic alignment achieved similar postoperative aHKA compared to MA, and thus did not significantly deviate from the principle of aligning the limb as close to neutral alignment as possible. Surgeons should feel comfortable starting to introduce individualized alignment techniques. Without being restricted by boundaries, postoperative alignment will be within 5 degrees of neutral 97% of the time.

Is Tibial Bone Mineral Density Related to Sex, Age, Preoperative Alignment, or Fixation Method in Primary Total Knee Arthroplasty?

BACKGROUND: Cementless total knee arthroplasty (TKA) has regained interest for its potential for long-term biologic fixation. The density of the bone is related to its ability to resist static and cyclic loading and can affect long-term implant fixation; however, little is known about the density distribution of periarticular bone in TKA patients. Thus, we sought to characterize the bone mineral density (BMD) of the proximal tibia in TKA patients. METHODS: We included 42 women and 50 men (mean age 63 years, range: 50 to 87; mean body mass index 31.6, range: 20.5 to 49.1) who underwent robotic-assisted TKA and had preoperative computed tomography scans with a BMD calibration phantom. Using the robotic surgical plan, we computed the BMD distribution at 1 mm-spaced cross-sections parallel to the tibial cut from 2 mm above the cut to 10 mm below. The BMD was analyzed with respect to patient sex, age, preoperative alignment, and type of fixation. RESULTS: The BMD decreased from proximal to distal. The greatest changes occurred within ± 2 mm of the tibial cut. Age did not affect BMD for men; however, women between 60 and 70 years had higher BMD than women ≥ 70 years for the total cut (P = .03) and the medial half of the cut (P = .03). Cemented implants were used in 1 86-year-old man and 18 women (seven < 60 years, seven 60 to 70 years, and four ≥ 70 year old). We found only BMD differences between cemented or cementless fixation for women < 60 years. CONCLUSIONS: To our knowledge, this is the first study to characterize the preoperative BMD distribution in TKA patients relative to the intraoperative tibial cut. Our results indicate that while sex and age may be useful surrogates of BMD, the clinically relevant thresholds for cementless knees remain unclear, offering an area for future studies.

A novel computational workflow to holistically assess total knee arthroplasty biomechanics identifies subject-specific effects of joint mechanics on implant fixation.

Computational studies of total knee arthroplasty (TKA) often focus on either joint mechanics (kinematics and forces) or implant fixation mechanics. However, such disconnect between joint and fixation mechanics hinders our understanding of overall TKA biomechanical function by preventing identification of key relationships between these two levels of TKA mechanics. We developed a computational workflow to holistically assess TKA biomechanics by integrating musculoskeletal and finite element (FE) models. For our initial study using the workflow, we investigated how tibiofemoral contact mechanics affected the risk of failure due to debonding at the implant-cement interface using the four available subjects from the Grand Challenge Competitions to Predict In Vivo Knee Loads. We used a musculoskeletal model with a 12 degrees-of-freedom knee joint to simulate the stance phase of gait for each subject. The computed tibiofemoral joint forces at each node in contact were direct inputs to FE simulations of the same subjects. We found that the peak risk of failure did not coincide with the peak joint forces or the extreme tibiofemoral contact positions. Moreover, despite the consistency of joint forces across subjects, we observed important variability in the profile of the risk of failure during gait. Thus, by a combined evaluation of the joint and implant fixation mechanics of TKA, we could identify subject-specific effects of joint kinematics and forces on implant fixation that would otherwise have gone unnoticed. We intend to apply our workflow to evaluate the impact of implant alignment and design on TKA biomechanics.

The Efficacy and Safety of Tranexamic Acid in Total Hip and Knee Arthroplasty: A Literature Review.

Historically, total hip arthroplasty (THA) and total knee arthroplasty (TKA) have been associated with significant perioperative blood loss and a relatively high rate of allogeneic blood transfusions. However, in recent years, tranexamic acid (TXA), a competitive inhibitor of tissue plasminogen activator, inhibiting fibrinolysis of existing thrombi, has substantially decreased the need for blood transfusion in THA and TKA. Various administration strategies have been studied, but there remains a lack of consensus on an optimal route and dosing regimen, with intravenous and topical regimens being widely used. A growing body of literature has demonstrated the safety and efficacy of TXA in primary and revision THA and TKA to reduce blood loss, allogeneic transfusions, and complications; it is associated with lowered lengths of stay, costs, and readmission rates.

Joint Replacement Technology in the Ambulatory Surgery Center: Current and Future Applications.

Total joint replacement (TJR) surgery in the ambulatory surgery centers (ASCs) has grown significantly over the past several years, along with the ability to improve the value of care. Standardization of high-quality, perioperative care is pivotal to the success of a TJR ASC program. As surgeons are experiencing increasing overhead with decreasing reimbursement, technology integration can provide major advantages. In this article, we will therefore highlight several examples of technologies that are changing the field and improving care in the preoperative, intraoperative, and postoperative settings.

Isolated Liner Exchange Versus All-Component Revision for Instability After Total Knee Arthroplasty.

BACKGROUND: Instability is a common cause for revision total knee arthroplasty (TKA). The risks and benefits of polyethylene liner exchange (LE) as compared to full metal component revision continue to be debated. The purpose of this study was to investigate the success rate and complication profiles of revision TKA for instability based on surgical procedure. METHODS: This was a retrospective study of patients undergoing revision TKA for instability from 2015 to 2019. Patients with prior revisions were excluded. 42 patients undergoing isolated polyethylene LE without an increase in constraint were compared with 48 patients undergoing full component revision revision (FCR) of both tibial and femoral components. The primary outcome was differences in rerevision for instability. Noninstability reoperations, 90-day readmissions, and lengths-of-stay were also compared. RESULTS: LEs had a 10.1% higher rerevision for instability rate that approached statistical significance (LE 14.3% versus FCR 4.2%, P = .092). Additionally, FCR had a 4.2% rate of aseptic loosening and a 4.2% rate of periprosthetic-joint-infection, whereas LE had none (P = .181). FCR also had a longer length-of-stay (FCR 3.0 ± 1.3 versus LE: 1.8 ± 0.9 days, P < .001). No differences were found in 90-day readmissions (LE 7.1% versus FCR 4.2%, P = .661). CONCLUSION: All component revision may have a higher success rate than isolated LE in addressing instability but is associated with higher rates of surgical complications. With appropriate patient selection and risk-benefit discussion, isolated LE may be a reasonable surgical option for TKA instability with a lower complication profile and length-of-stay.

Total Hip Arthroplasty: An Update on Navigation, Robotics, and Contemporary Advancements.

While total hip arthroplasty (THA) remains effective for improvement of pain and function in patients with osteoarthritis and avascular necrosis, there remain areas of continued pursuit of excellence, including decreasing rates of dislocation, leg length discrepancy, implant loosening, and infection. This review article covers several bearing surfaces and articulations, computer-assisted navigation and robotic technology, and minimally invasive surgical approaches that have sought to improve such outcomes. Perhaps the most significant improvement to THA implant longevity has been the broad adoption of highly cross-linked polyethylene, with low wear rates. Similarly, navigation and robotic technology has proven to more reproducibly achieve intraoperative component positioning, which has demonstrated clinical benefit with decreased risk of dislocation in a number of studies. Given the projected increase in THA over the coming decades, continued investigation of effective incorporation of technology, soft tissue-sparing approaches, and durable implants is imperative to continued pursuit of improved outcomes in THA.

Serum CD64 as a Marker for Chronic Periprosthetic Joint Infection.

Background: Serum cluster of differentiation 64 (CD64) has emerged as a diagnostic test for musculoskeletal infections. The purpose of this study was to evaluate the utility of serum CD64 in diagnosing periprosthetic joint infections (PJIs) compared to conventional markers like white blood count (WBC), C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), and interleukin-6 (IL-6). Methods: A prospective case-control study on patients undergoing revision hip or knee arthroplasty surgery >6 weeks after their index surgery was performed at a single institution. Whole blood samples were drawn within 24 hours prior to revision surgery for white blood count, ESR, CRP, IL-6, and CD64. Intraoperative cultures were obtained during the revision, and PJI was defined using the major criteria from the 2018 Musculoskeletal Infection Society criteria. Two-sample Wilcoxon rank-sum test and Fisher's exact test were used to determine if there were significant differences in serum laboratory values between patients with and without infection. The sensitivity, specificity, positive predictive value (PPV), negative predictive value, and accuracy of each test were calculated. Results: With an average age of 67 years, 39 patients with 15 revision THAs and 24 TKAs, were included. 19 patients (48.7%) were determined to have PJI. Patients with PJI had significantly higher CD64 (P = .036), CRP (P = .016), and ESR (P = .045). CD64 had the highest specificity (100%) and PPV (100%), moderate accuracy (69.2%), but low sensitivity (37.0%) and negative predictive value (62.5%). Conclusions: Given the high specificity, PPV, and accuracy, CD64 may be an excellent confirmatory test to help diagnose PJI.

A Comparison of Clinical Outcomes After Total Knee Arthroplasty in Patients With Preoperative Nickel Allergy Receiving Cobalt Chromium or Nickel-Free Implant.

BACKGROUND: The role of metal hypersensitivity reactions in total knee arthroplasty (TKA) failure is debated. There is no consensus on whether use of a more expensive nickel-free implant is indicated for patients who have preoperative nickel allergy. The purpose of this study was to examine the outcome of patients who have preoperative nickel allergy receiving nickel-free or cobalt chromium (CoCr) implants. METHODS: This was a retrospective review of 17,798 patients who underwent 20,324 unilateral primary TKAs between 2016 and 2020. Presence of preoperative nickel allergy was determined (n = 282). Patients were divided into 2 cohorts: those receiving (1) nickel-free or (2) CoCr implants. Clinical outcome scores and revision rates were assessed. RESULTS: 243 received a nickel-free implant and 39 received a CoCr implant. There was no significant difference in revision rate between the cohorts. Survivorship free of revision was 94% in the CoCr implant cohort and 98% in the nickel-free implant cohort (P = .9). When comparing clinical outcome scores between cohorts, there was no difference in preoperative, 6-week or 1-year Knee Osteoarthritis Outcome Score Joint Replacement, Visual Analog Scale (VAS), Lower Extremity Activity Scale, Patient-Reported Outcomes Measurement Information System (PROMIS), and Veterans RAND 12-item scores between cohorts. CONCLUSION: In this retrospective cohort study, there was no difference in revision rates or clinical outcomes in patients who had a nickel allergy undergoing primary TKA with CoCr or nickel-free implants. Further studies are needed to determine if nickel allergy is an independent risk factor for worse TKA outcomes in general.

Significantly Worse Fixation of Cemented Patellar Components on Multiacquisition Variable-Resonance Image Combination Magnetic Resonance Imaging Compared to Femoral and Tibial Components: A Cause for Concern?

BACKGROUND: The etiology of anterior knee pain after total knee arthroplasty (TKA) remains unclear. Few studies have examined patellar fixation quality. The purpose of the present study was to evaluate the patellar cement-bone interface after TKA on magnetic resonance imaging (MRI) and to correlate the patella fixation grade with the incidence of anterior knee pain. METHODS: We retrospectively reviewed 279 knees undergoing metal artifact reduction MRI for either anterior or generalized knee pain at least 6 months after cemented, posterior-stabilized TKA with patellar resurfacing with one implant manufacturer. MRI cement-bone interfaces and percent-integration of the patella, femur, and tibia were assessed by a fellowship-trained senior musculoskeletal radiologist. The grade and character of the patella interface were compared to the femur and tibia. Regression analyses were used to determine the association between patella integration with anterior knee pain. RESULTS: There were more patellar components with ≥75% zones of fibrous tissue (50%) compared to the femur (18%) or tibia (5%) (P < .001). There were a greater number of patellar implants with poor cement integration (18%) compared to the femur (1%) or tibia (1%) (P < .001). MRI findings showed more evidence of patellar component loosening (8%) compared to the femur (1%) or tibia (1%) (P < .001). Anterior knee pain was correlated with worse patella cement integration (P = .01), with women predicted to have better integration (P < .001). CONCLUSION: The quality of the patellar cement-bone interface after TKA is worse compared to the femoral or tibial component interface. Poor patellar cement-bone interface may be a source of anterior knee pain after TKA, but further investigation is required.

Impact of Antibiotic-Impregnated Spacer Design in the Treatment of Periprosthetic Hip Infection.

Background: Although 2-stage exchange arthroplasty, consisting of temporary insertion of an antibiotic-impregnated cement spacer (AICS), is considered the standard of care for chronic periprosthetic joint infection (PJI) in total hip arthroplasty (THA), a consensus on the AICS design has not yet been established. Ceramic-on-polyethylene AICSs (Poly-AICS) are theorized to cause less pain and better function than cement-on-bone AICS (CemB-AICS) but use non-antibiotic-impregnated components that may harbor bacteria. This study evaluates the impact of spacer design on infection-free survivorship following THA reimplantation as well as pain and function during the interim AICS stage. Methods: A retrospective review was performed of all cases of THA PJI treated with either Poly-AICS or CemB-AICS at a single high-volume academic center. Data were collected until the final follow-up after THA reimplantation with an average follow-up duration of 2.6 years. The primary outcome was infection-free survivorship after the final reimplantation. Secondary outcomes included postoperative pain scores, opioid use, time to ambulation, length of stay, complications, and discharge disposition. Results: A total of 99 cases (67 CemB-AICS; 32 Poly-AICS) were included. There were no baseline differences between the 2 groups. There were no differences in infection-free survivorship after reimplantation in survivorship curve comparisons (P = .122) and no differences in postoperative inpatient pain scores, opioid use, length of stay, time to ambulation, complications, or discharge disposition during the AICS stage. Conclusions: Patients with THA PJI treated with Poly-AICS did not have worse infection-related outcomes despite the use of non-antibiotic-impregnated components but also did not appear to have less pain or improved function during the early AICS stage.

Liquid Phase 3D Printing: How This New Technology Can Help Bring 3D Printing to the Operating Room.

PURPOSE OF REVIEW: The purpose of this review is to discuss the state of technology in liquid phase three-dimensional (3D) metal printing, how this has affected the field of orthopedic surgery, and changes that we can expect in the future with the rise of this printing technology. We will also discuss how liquid phase metal printing can possibly bring three-dimensional printing to the operating room. RECENT FINDINGS: The use of liquid phase 3D metal printing may become commonplace for manufacturing orthopedic implants and devices. Traditional metal printing involved powder-based metals and high-energy beam technologies that are expensive, time-consuming, and potentially wasteful. This unfortunately leaves them out of reach for most end consumers such as orthopedic surgeons. Liquid phase metal printing is less expensive and faster. However, there is still major work required to bring this technology to the operating room and benefit patients. While major strides have been made in the field of liquid phase metal three-dimensional printing, there are still significant developments in the pipeline. These could lead to future production of personalized orthopedic implants and devices with optimal material properties for patients.