Femoral Head Penetration Rates of Second-Generation Sequentially Annealed Highly Cross-Linked Polyethylene at Minimum Five Years

Background Highly cross-linked polyethylene (HXLPE) liners in total hip arthroplasty (THA) have demonstrated decreased wear rates, resilience to cup orientation, and reduced osteolysis compared to conventional polyethylene. Sequential irradiation and annealing below the melting temperature is unique compared to most HXLPE which is irradiated and remelted. This study purpose is to provide minimum 5-year femoral head penetration rates of sequentially annealed HXLPE in primary THA. Methods A retrospective review of a prospectively collected database identified 198 consecutive, cementless primary THAs utilizing sequentially annealed HXLPE (X3; Stryker, Mahwah, NJ). Operative technique was standardized. Radiographs were analyzed utilizing the Martell method with minimum 5-year and 1-year radiographs as baseline to minimize the initial bedding-in period. Results Seventy-seven hips with minimum 5-year follow-up were analyzed. Mean steady state linear and volumetric head penetration rates were 0.095 mm/y and 76 mm3/y, respectively. Volumetric head penetration was significantly less for 32-mm compared to 36-mm (P = .028). In addition, less head penetration was observed for ceramic 32-mm heads at nearly half the rate compared to cobalt-chromium 36-mm heads (P ≥ .092). No correlations existed between penetration rates and age, body mass index, University of California Los Angeles Activity Level, polyethylene thickness, cup inclination, or anteversion (P ≥ .10). No radiographic osteolysis was observed. Conclusion Surprisingly, linear head penetration rates of sequentially annealed HXLPE were nearly identical to the osteolysis threshold for conventional polyethylene and greater than reports of irradiated and remelted HXLPE. Furthermore, these data corroborate reports that HXLPE is resilient to cup orientation and demographic variables. Longer term follow-up is recommended

Contemporary Dual Mobility Head Penetration at Five Years: Concern for the Additional Convex Bearing Surface?

Background Dual mobility (DM) bearings are increasingly popular and second-generation designs contain highly cross-linked polyethylene. The purpose of this study is to report head penetration rates in modern DM bearings. Methods A review of 63 consecutive DM bearings was performed. Radiographs were analyzed for head penetration using Martell methodology at regular postoperative intervals. Results Thirty-four DM bearings were analyzed. Mean linear head penetration was 1.59 mm/y at 1 year, 1.07 mm/y at 2 years, and 0.27 mm/y at 5 years following an exponential regression model (R2 = 0.999). Mean volumetric wear was 783 mm3/y at 1 year, 555 mm3/y at 2 years, and 104 mm3/y at 5 years following an exponential regression model (R2 = 0.986). Conclusion Initial head penetration of DM bearings is larger than contemporary cross-linked polyethylene bearings; however, rates approach steady state after 2 years, analogous to traditional bearings. The larger “bedding-in” head penetration may be due to the additional convex bearing surface, creating 2 surfaces for deformation/wear

A Dual-Pivot Pattern Simulating Native Knee Kinematics Optimizes Functional Outcomes After Total Knee Arthroplasty

Background Kinematics after total knee arthroplasty (TKA) have been studied for decades; however, few studies have correlated kinematic patterns to patient reported outcomes. The purpose of this study was to determine if a pattern of lateral pivot motion in early flexion and medial pivot motion in high flexion, simulating native knee kinematics, produces superior clinical outcomes. A second study objective was to determine if a specific kinematic pattern throughout the various ranges of flexion produces superior function and patient satisfaction. Methods 120 consecutive TKAs were performed using sensor embedded tibial trials to record intraoperative knee kinematics through the full range of motion. Established criteria were used to identify lateral (L) or medial (M) pivot kinematic patterns based on the center of rotation within three flexion zones -- 0 to 45° (early flexion), 45 to 90° (mid flexion) and 90° to terminal flexion (late flexion). Knee Society Scores, pain scores, and patient satisfaction were analysed in relationship to kinematic patterns. Results Knee Society function scores were significantly higher in TKAs with early lateral pivot/late medial pivot intraoperative kinematics compared to all other kinematic patterns (p = 0.018) at minimum one-year follow-up. There was a greater decrease in the proportion of patients with early lateral/late medial pivot kinematics who reported that their knee never feels normal (p = 0.011). Higher mean function scores at minimum one-year follow-up (p < 0.001) and improvement from preoperative baseline (p = 0.008) were observed in patients with the most ideal “LLM” kinematic pattern (lateral pivot 0 to 45o and 45 to 90o; medial pivot beyond 90o) compared to those with the least ideal “MLL” kinematic pattern. All patients with the optimal “LLM” kinematic pattern compared to none of those with the “MLL” kinematic pattern reported that they were very satisfied with their TKA (p = 0.003). Conclusion Patients who exhibited an early flexion lateral pivot kinematic pattern accompanied by medial pivot motion in later flexion, as measured intraoperatively, reported higher functional outcome scores along with higher overall patient satisfaction. Replicating the dual-pivot kinematic pattern observed in native knees may improve function and satisfaction after TKA. Further study is warranted to explore a correlation with in-vivo kinematic patterns

The Effect of Tourniquet Use and Sterile CO2 Gas Bone Preparation on Cement Penetration in Primary Total Knee Arthroplasty

Introduction Tourniquetless total knee arthroplasty (TKA) is experiencing resurgence in popularity due to potential pain control benefits. Further, optimal cement technique and implant fixation remain paramount to long-term cemented TKA success, as aseptic loosening continues to be a leading cause of revision. The purpose of this study was to determine how tourniquet use and/or novel bone preparation using sterile, compressed carbon dioxide (CO2) gas affected cement penetration in TKA. Methods A retrospective review was performed on 303 consecutive primary TKAs with the same implant in three groups: (1) a tourniquet without sterile CO2 compressed gas used for bone preparation, (2) no tourniquet with CO2 gas, and (3) tourniquet use and CO2 gas bone preparation. Cement penetration was measured on radiographs by two independent, blinded raters across seven zones defined by the Knee Society Radiographic Evaluation System. Results The three groups did not differ on age, BMI, or sex (p≥0.1). Cement penetration was greater in six of seven zones with significantly greater cement penetration in three zones (Tibial AP Zone 2, Femoral Lateral Zones 3A and 3P) in groups that utilized CO2 gas bone preparation compared to the tourniquet only group (p≤0.039). Conclusion Bone prepared with CO2 gas showed significantly more cement penetration in three zones with greater cancellous bone. The results suggest use of CO2 gas bone preparation may achieve greater cement penetration than using a tourniquet with lavage only

Safety of Same and Next Day Discharge Following Revision Hip and Knee Arthroplasty Using Modern Perioperative Protocols

Introduction: Advances in perioperative care have enabled early discharge and outpatient primary total joint arthroplasty (TJA). However, the safety of early discharge after revision TJA (rTJA) remains unknown and the COVID-19 pandemic will force decreased hospitalization. This study compared 90-day outcomes in patients undergoing aseptic rTJA discharged the same or next day (early) to those discharged two or three days postoperatively (later). Methods: 530 aseptic rTJAs performed at a single tertiary referral center (12/5/2011-12/30/2019) were identified. Early and later discharge patients were matched as closely as possible on procedure type, sex, ASA-PS classification, age, and BMI. All patients were optimized using modern perioperative protocols. The rate of 90-day ED visits and hospital admissions was compared between groups. Results: 183 early discharge rTJAs (54 hips, 129 knees) in 178 patients were matched to 183 later discharge rTJAs (71 hips, 112 knees) in 165 patients. 62% of the sample was female, with an overall average age and BMI of 63±9.9 (range: 18-92) years and 32±6.9 (range: 18-58) kg/m2. There was no statistical difference in 90-day ED visit rates between early (6/178, 3.4%) and later (11/165, 6.7%) discharge patients (p=0.214). 90-day hospital admission rates for early (7/178, 3.9%) and later (4/165, 2.4%) did not differ (p=0.545) Conclusions: Using modern perioperative protocols and with appropriate patient selection, early discharge following aseptic rTJA does not increase 90-day readmissions or ED visits. As hospital inpatient capacity remains limited due to COVID-19, select rTJA patients may discharge home the same or next day to preserve hospital beds and resources for more critical medically related illness

Do Medial Pivot Kinematics Correlate With Patient-Reported Outcomes After Total Knee Arthroplasty?

Background Many total knee arthroplasty (TKA) implants are designed to facilitate a medial pivot kinematic pattern. The purpose of this study was to determine whether intraoperative medial pivot kinematic patterns are associated with improved patient outcomes. Methods A retrospective review of consecutive primary TKAs was performed. Sensor-embedded tibial trials determined kinematic patterns intraoperatively. The center of rotation (COR) was identified from 0° to 90° and from 0° to terminal flexion, and designated medial-pivot or non-medial pivot based on accepted criteria. Patient-reported outcomes were measured preoperatively and at minimum one-year follow-up. Results The analysis cohort consisted of 141 TKAs. Mean age and median BMI were 63.7 years and 33.8 kg/m2, respectively. Forty-percent of TKAs demonstrated a medial pivot kinematic pattern intraoperatively. A medial pivot pattern was more common with posterior cruciate-retaining (CR) and posterior cruciate-substituting/anterior lipped (CS) implants when compared to posterior stabilized (PS) TKAs (P ≤.0150). Regardless of bearing type, minimum one-year Knee Society scores and UCLA activity level did not significantly differ based on medial vs non-medial pivot patterns (P ≥.292). For patients with posterior cruciate-sacrificing implants, there were trends for greater median improvement in Knee Society objective (46 vs 31.5 points, P =.057) and satisfaction (23 vs 14 points, P =.067) scores in medial pivot knees. Conclusion A medial pivot pattern may not significantly govern clinical success after TKA based on intraoperative kinematics and modern outcome measures. Further research is warranted to determine if a particular kinematic pattern promotes optimal clinical outcomes

The Fate of Zone 2 Radiolucencies in Contemporary Highly Porous Acetabular Components: Not All Designs Perform Equally

Background: The enhanced frictional resistance of modern ultraporous acetabular components can impede complete seating; however, surgeons expect the enhanced ingrowth surface to resolve polar (zone 2) gaps over time via osseointegration. This study characterized zone 2 radiographic osseointegration in 3 acetabular component designs: 2 highly porous ingrowth and one traditional ongrowth. Methods: A consecutive cohort of primary total hip arthroplasties was reviewed which utilized 3 different acetabular cup designs: ongrowth titanium with hydroxyapatite (HA), highly porous titanium with machined radial grooves (MRG), and dual-porous titanium substrate with micropore (MP). Radiographic analysis was performed using accepted measurement criteria with particular attention to radiolucent lines. Results: Seven hundred ninety cases were available for analysis. Initial 1-month radiographs revealed 43.2% of HA, 78.2% of MRG, and 81.0% of MP cups exhibited zone 2 radiolucencies, consistent with incomplete seating. At 1 year, all HA radiolucencies resolved, whereas 46.2% and 34.7% of radiolucencies remained in MRG and MP cups, respectively (P ≤ .005). At minimum 2 years, a significant proportion of zone 2 radiolucencies remained in 46.0% of MRG compared with 23.9% of MP cups and 3.0% of HA cups (P ≤ .007). Conclusion: The resolution of zone 2 radiolucencies at 1-year and minimum 2-year follow-up signified osseointegration for nearly all HA and most MP cups. Highly porous titanium cups with machined radial grooves demonstrated persistent zone 2 radiolucencies at 1 year and beyond. Given reports of early loosening with this particular acetabular implant, further follow-up is warranted as this study highlights that not all contemporary highly porous metal acetabular components perform equally

Satisfaction and Functional Outcomes in Unicompartmental Compared with Total Knee Arthroplasty: Radiographically Matched Cohort Analysis

Unicompartmental and total knee arthroplasty (UKA and TKA) have demonstrated excellent mid- and long-term outcomes and have been compared in clinical series for decades; however, to our knowledge, no study has sufficiently matched UKA and TKA cohorts on preoperative osteoarthritis severity. The purpose of this study was to evaluate patient-reported outcomes of radiographically and demographically matched UKA and TKA cohorts. Methods: One hundred and thirty-five UKAs and 135 TKAs were matched by patient age, sex, body mass index, and American Society of Anesthesiologists Physical Status (ASA-PS) classification as well as preoperative osteoarthritis severity in medial and lateral tibiofemoral and patellofemoral compartments (Kellgren-Lawrence grading system). Patient-reported outcome measures for pain, function, activity level, and satisfaction were evaluated at minimum 1-year follow-up via components of the modern Knee Society Score, the University of California Los Angeles (UCLA) activity-level score, and a Likert satisfaction scale. Results: The patients in the UKA group reported significantly less pain, a higher activity level, and greater satisfaction while performing several functional activities and could walk for a longer amount of time before stopping due to knee discomfort compared with those in the TKA group (p ≤ 0.038). In addition, a greater proportion of patients in the UKA than in the TKA group were "satisfied or very satisfied" with their knee replacement surgery at minimum 1-year follow-up (90% versus 81%; p = 0.043). Conclusions: With minimum 1-year follow-up, patients who underwent UKA reported significantly higher function, less pain, and a greater level of patient satisfaction than a radiographically and demographically matched TKA cohort

Tibial baseplate position and posterior cruciate ligament status impact patient-reported outcomes in conforming dual-pivot bearing total knee arthroplasty

Background: In an effort to optimize clinical outcomes and enhance stability, ultracongruent bearings have been increasingly used in primary total knee arthroplasty (TKA). The importance of the posterior cruciate ligament (PCL) and optimal sagittal tibial baseplate position in ultracongruent bearing TKA remains unknown. This study sought to determine whether these modifiable, surgical-technique-dependent variables meaningfully impact patient-reported outcome measures. Methods: A total of 759 primary TKAs of the same dual-pivot design performed using a consistent surgical technique between January 2016 and April 2019 were retrospectively reviewed. PCL status was recorded, and anteroposterior (AP) tibial baseplate position and posterior tibial slope were measured by two independent blinded raters. Patient-reported outcomes related to pain, function, satisfaction, and activity level were analyzed in relationship to PCL status, posterior tibial slope, and AP tibial baseplate position, in addition to other pertinent covariates. Results: Median age and body mass index of the cohort were 68.3 years and 33.4 kg/m2, respectively, with 73% being female. In multivariate analysis, partial or full release of the PCL was predictive of a knee "always" feeling normal (odds ratio 1.42, P = .041). Furthermore, tibial baseplate position closer to the middle of the tibia was associated with greater improvements in pain with level walking, pain while climbing stairs, and Knee Injury and Osteoarthritis Outcome Score for Joint Replacement total scores (P ≤ .079). Conclusion: In congruent dual-pivot bearing TKA, partially or fully releasing the PCL and AP tibial baseplate position closer to the middle of the tibia may provide greater improvement in pain and function scores at minimum 1-year follow-up

The Effect of Large Femoral Heads and Acetabular Cup Position on PROMs after Modern Posterior Approach THA

INTRODUCTION: Use of large femoral heads (≥40mm) in total hip arthroplasty (THA) decreases postoperative dislocation by increasing impingement-free range of motion, however, may leave patients more susceptible to groin pain. Also, limited data exist for the effect of large femoral heads and acetabular cup position on modern patient-reported outcome measures (PROMs). Therefore, the purpose of this study was to evaluate the effect of large femoral heads (≥40mm) and acetabular cup position on PROMs after primary THA. METHODS: 328 primary THAs performed by a single surgeon were retrospectively reviewed. Acetabular cup inclination and anteversion were measured using Martell Hip Analysis Suite software. Femoral head and acetabular cup sizes were recorded from the electronic medical record. Prospectively collected PROMs (and covariates) related to activity level, satisfaction, and overall hip health were evaluated. RESULTS: Age, covariates related to PROMs, and acetabular cup position did not differ between ≥40mm and 90 and being ‘very satisfied or satisfied’ correlated with wide ranges and several combinations of acetabular cup inclination and anteversion. CONCLUSION: Patients achieved comparable PROMs regardless of femoral head size suggesting large femoral heads may not leave patients susceptible to groin pain in addition to reducing the risk of postoperative dislocation. Excellent patient outcomes correlated with wide ranges of acetabular cup position