Contemporary Total Knee Arthroplasty Research Articles

The Fate of Unresurfaced Patellae in Contemporary Total Knee Arthroplasty: Early to Midterm Results

BackgroundLeaving the patella unresurfaced in total knee arthroplasty (TKA) has increased significantly over the past decade in the United States, likely due to modern patella-friendly implants, complications with resurfacing, and the knowledge that historical studies were scientifically confounded. This study evaluated revision-free survivorship out to 8.5 years in a cohort of contemporary primary TKAs with patella-friendly femoral components and unresurfaced patellae. MethodsA total of 1,053 consecutive primary TKAs with unresurfaced patellae were retrospectively reviewed. A selective patellar nonresurfacing protocol was used for all cases. Kaplan-Meier survivorship estimates were calculated based on patellar revision and the latest follow-up. An aggressive lateral patellar facetectomy was performed in 78% (823 of 1,053) of cases. The cohort was 62% women and 43% American Society of Anesthesiologists physical status classification I or II with a mean age and body mass index of 65 years (range, 35 to 94) and 35 kg/m2 (range, 18 to 65), respectively. ResultsA total of 4 (0.4%, 4 of 1,053) unresurfaced patellae were revised. Three were resurfaced as part of other procedures: 2 for global instability and one for aseptic loosening at a mean of 1.6 years; and one patella was resurfaced by an outside surgeon for unexplained pain. The all-cause revision-free survivorship estimate specifically related to the patella was 98.9% (95% confidence interval, 98 to 100) out to 8.5 years. No significant difference in survivorship was related to patellae with or without a lateral patellar facetectomy (99.5 versus 98.1%, P ≥ .191); however, 3 of 4 patellar revisions occurred in TKAs without a lateral patellar facetectomy (P = .035). ConclusionsThe results of this study demonstrate excellent revision-free survivorship related to unresurfaced patellae, particularly when a lateral facetectomy was performed. These early to midterm results using modern patella-friendly femoral components are promising and comparable to resurfaced patellae in the literature. Level of EvidenceIV.

Variations in Trochlear Morphology of Contemporary and Legacy Total Knee Arthroplasty Prostheses: A Review of 22 Designs

BackgroundThe morphology of the trochlear compartment of total knee arthroplasty (TKA) prostheses is a major determinant of postoperative patello-femoral kinematics, particularly with unresurfaced patellae. The objective of this study was to quantify and compare the trochlear morphology of a large series of contemporary and legacy TKA designs. MethodsThe 3-dimensional surface models of 22 femoral components (13 contemporary and 9 legacy) were created using high-resolution laser scanning. The trochlear profile of each component was analyzed from proximal to distal in 15° increments around the trochlear axis. In each profile, the following variables were measured: sulcus angle, medio-lateral deviation of the sulcus, the height and width of the facets, and the trochlear groove orientation. ResultsIn the contemporary group, the sulcus angle decreased progressively along the trochlear arc to varying degrees, except for 2 symmetrical designs, whereas the sulcus angle of the legacy designs showed considerable variability. The height of the medial facet was very strongly correlated with that of the lateral facet in the contemporary group (R2 = 0.89), whereas the correlation was weak for the legacy designs (R2 = 0.36). Moreover, the trochlear sulcus deviated laterally from distal to proximal in 10 contemporary designs and 7 legacy designs, resulting in a trochlear groove orientation of 4.2 to 11.1° and 4.3 to 10.5°, respectively. In the remaining 5 designs (3 contemporary and 2 legacy), the sulcus was vertical. ConclusionsThere is more consistency in trochlear morphology of contemporary TKA designs compared to that of legacy designs, yet there are still large variations between different designs.

Simultaneous Evaluation of Tibiofemoral and Patellofemoral Mechanics in Total Knee Arthroplasty: A Combined Experimental and Computational Approach.

Contemporary total knee arthroplasty (TKA) has not fully restored natural patellofemoral (P-F) mechanics across the patient population. Previous experimental simulations have been limited in their ability to create dynamic, unconstrained, muscle-driven P-F articulation while simultaneously controlling tibiofemoral (T-F) contact mechanics. The purpose of this study was to develop a novel experimental simulation and validate a corresponding finite element model to evaluate T-F and P-F mechanics. A commercially available wear simulator was retrofitted with custom fixturing to evaluate whole-knee TKA mechanics with varying patella heights during a simulated deep knee bend. A corresponding dynamic finite element model was developed to validate kinematic and kinetic predictions against experimental measurements. Patella alta reduced P-F reaction forces in early and midflexion, corresponding with an increase in T-F forces that indicated an increase in extensor mechanism efficiency. Due to reduced wrapping of the extensor mechanism in deeper flexion for the alta condition, peak P-F forces in flexion increased from 101% to 135% of the applied quadriceps load for the baja and alta conditions, respectively. Strong agreement was observed between the experiment and model predictions with root-mean-square errors (RMSE) for P-F kinematics ranging from 0.8 deg to 3.3 deg and 0.7 mm to 1.4 mm. RMSE for P-F forces ranged from 7.4 N to 53.6 N. By simultaneously controlling dynamic, physiological loading of the T-F and P-F joint, this novel experimental simulation and validated model will be a valuable tool for investigation of future TKA designs and surgical techniques.

Optimizing Asymmetric Native Knee Flexion Gap Balance Promotes Superior Outcomes in Primary Total Knee Arthroplasty.

Replicating native knee kinematics remains the ultimate goal of total knee arthroplasty (TKA). Technology, such as robotics, provides robust intraoperative data; however, no evidence-based targets currently exist for improved clinical outcomes. Furthermore, some surgeons target a rectangular flexion space in TKA unlike the native knee. This study evaluated the effect of in vivo flexion gap asymmetry on patient-reported outcome measures (PROMs) in contemporary TKA. In vivo tibiofemoral joint space dimensions were measured during 129 TKAs using a calibrated tension device before and after complete posterior cruciate ligament resection. PROMs were compared based on the final dimensions and the change in flexion gap dimensions at 90° of flexion: (1) equal laxity, (2) lateral laxity, and (3) medial laxity. Groups did not differ by demographics ( P ≥ 0.347), clinical follow-up ( P = 0.134), tibiofemoral alignment ( P = 0.498), or preoperative PROMs ( P ≥ 0.093). Mean follow-up for the cohort was 1.5 years (range, 1-3). Pain with climbing stairs, pain while standing upright, and knees "always feeling normal" scores were superior for patients with equal or lateral laxity compared with medial laxity ( P ≤ 0.064). Pain with level walking, University of California Los Angeles activity level, KOOS JR, and satisfaction scores also tended to be superior for patients with equal or lateral laxity, although it lacked statistical significance ( P ≥ 0.111). Results of this study suggest that patients with either an equally tensioned rectangular flexion space or with later-flexion lateral laxity after posterior cruciate ligament resection may achieve superior PROMs. Findings support the clinical benefit of facilitating posterolateral femoral roll back in flexion, which mimics native knee kinematics and further helps define targets for advanced technology.

Coronal and Sagittal Component Position in Contemporary Total Knee Arthroplasty: Targeting Native Alignment Optimizes Clinical Outcomes

BackgroundAdvanced technologies, like robotics, provide enhanced precision for implanting total knee arthroplasty components; however, optimal component position and limb alignment remain unknown. This study sought to identify sagittal and coronal alignment targets that correlate with minimal clinically important differences (MCIDs) in patient-reported outcome measures (PROMs). MethodsA total of 1,311 consecutive total knee arthroplasties were retrospectively reviewed. Posterior tibial slope (PTS), femoral flexion (FF), and tibio-femoral alignment (TFA) were measured radiographically. Patients were grouped based on whether they achieved multiple MCIDs for PROM scores. Classification and regression tree machine learning models were utilized to identify optimal alignment zones. The mean follow-up was 2.4 years (range, 1 to 11). ResultsThe change in PTS and postoperative TFA were most predictive for achieving MCIDs in 90% of the models. Approximating native PTS within 4° correlated with MCID achievement and superior PROMs. Preoperative varus and neutral aligned knees were more likely to meet MCIDs and superior PROM scores when not overcorrected into valgus postoperatively (≥7°). Preoperative valgus-aligned knees correlated with MCID achievement when postoperative TFA was not overcorrected into substantial varus (<0°). Albeit less impactful, FF ≤ 7° correlated with MCID achievement and superior PROMs regardless of preoperative alignment. Sagittal and coronal alignment measurements had moderate to strong interactions in 13 of 20 models. ConclusionOptimized PROM MCIDs correlated with approximating native PTS while maintaining similar preoperative TFA and incorporating moderate FF. Study findings demonstrate interactions between sagittal and coronal alignment which may optimize PROMs, highlighting the importance of three-dimensional implant alignment targets. Level of EvidenceIII.

Chitranjan S. Ranawat Award: Motion During Total Knee Cementing Significantly Decreases Tibial Implant Fixation Strength.

Aseptic tibial loosening following primary total knee arthroplasty persists despite technique and device-related advancements. The mechanisms for this mode of failure are not well understood. We hypothesized that knee movement while the cement was curing dispersed lipids at the implant-cement interface and would result in decreased tibial fixation strength. A cadaveric study was performed utilizing 32 torso-to-toe specimens (64 knees). Four contemporary total knee arthroplasty designs were evaluated. Each implant design was randomly assigned to a cadaveric specimen pair with side-to-side randomization. Specimen densitometry was recorded. Each tibial implant was cemented using a standard technique. On one side, the tibial component was held without motion following impaction until complete cement polymerization. The contralateral knee tibial implant was taken through gentle range of motion and stability assessment 7 minutes after cement mixing. Axial tibial pull-out strength and interface failure examination was performed on each specimen. The average pull-out strength for the no motion cohort (5,462 N) exceeded the motion cohort (4,473 N) (P= .001). The mean pull-out strength between implant designs in the no motion cohort varied significantly (implant A: 7,230 N, B: 5,806 N, C: 5,325 N, D 3,486 N; P= .007). Similarly, the motion cohort inter-implant variance was significant (P ≤ .001). Intra-implant pull-out strength was significantly higher in implant A than D. The average pull-out strength was significantly lower in specimens that failed at the implant-cement interface vs bone failures (4,089±2,158 N vs 5,960±2,010 N, P < .0025). Knee motion during cement polymerization is associated with significant decreases in tibial implant fixational strength. Reduction in implant pull-out strength was identified with each implant design with motion and varied between designs. Across all tested designs, we recommend limiting motion while cementing the tibial implant to improve fixation strength.

Osteoarthritic Severity in Unresurfaced Patellae Does Not Adversely Affect Patient-reported Outcomes in Contemporary Primary TKA.

Introduction:The degree of osteoarthritis (OA) acceptable to leave in a native patella during unresurfaced total knee arthroplasty (TKA) remains unknown. This study's purpose was to examine the effect of patellofemoral OA severity on patient-reported outcome measures (PROMs) in primary TKAs performed without patellar resurfacing.Methods:One hundred ninety-three primary TKAs performed without patellar resurfacing were retrospectively reviewed. Preoperative patellofemoral OA severity was graded on severity, marginal osteophytes, joint space narrowing, and chondral damage using accepted grading systems. Patellar tilt and tibiofemoral alignment were measured radiographically. PROMs were evaluated at a minimum of 1-year follow-up.Results:In multivariate regression, preoperative lateral patella Kellgren-Lawrence grade ≥2 was associated with superior change in Knee Society Score pain with level walking, higher absolute change in Knee Injury and Osteoarthritis Outcome Score for Joint Replacement (P ≤ 0.029), and knees ‟always feeling normal” (odds ratio [OR] 3.12; P = 0.005). Osteoarthritis Research Society International atlas grades and Outerbridge classification scores did not significantly influence PROMs.Discussion:Worse preoperative OA severity in the lateral patellar facet, graded with the Kellgren-Lawrence system, predicted superior knee-specific PROMs in patients with unresurfaced patellae after contemporary TKA. This observation supports the clinical finding that patients with more severe OA have optimized patient outcomes and highlights the minimal contribution of patella OA to knee function after primary TKA.

Flip Autograft Technique for Anterolateral Femoral Deficiency in Total Knee Arthroplasty.

Anterolateral bone loss of the femur within the trochlear groove presents a unique and rare issue in primary total knee arthroplasty (TKA). Unlike distal and posterior femur bone loss for which most contemporary TKA systems have modular augments, the same does not exist for anterolateral bone loss. We present a technique in which a patient’s host bone from the standard distal femoral cuts was used to augment and provide a stable base for cementing of final femoral implants. Currently, the patient has 3-year follow-up with excellent results in terms of pain control with no evidence of component failure on the most recent radiographs. This technique provides a simple solution to a complex problem within primary TKA.

Avoiding Femoral Canal Instrumentation in Computer-Assisted Total Knee Arthroplasty With Contemporary Blood Management Had Minimal Differences in Blood Loss and Transfusion Rates Compared to Conventional Techniques

BackgroundComputer-assisted surgery that does not utilize femoral canal instrumentation is theorized to have less blood loss. However, there is a paucity of data on this, particularly in the era of tranexamic acid use. We sought to analyze the association of computer navigation with total calculated blood loss and transfusion rate in patients undergoing primary total knee arthroplasty (TKA). MethodsWe identified 14,890 patients who underwent unilateral primary TKA at a single institution from 2016 to 2020. Computer-assisted surgery in the form of an accelerometer or robotics was utilized in 4,165 TKAs (28%). Drains were utilized in 4,860 TKAs (32%). We used multivariate logistic regression analysis to determine if computer navigation reduced the rate of blood transfusion and linear regression analysis to determine the impact of computer navigation on blood loss. ResultsIn total, 542 patients (3.6%) underwent a transfusion. The average change in hemoglobin (Hgb) was 2.1 g/dL (standard deviation [SD] 0.91) and average total calculated blood loss was 310 mL (SD = 154). In a multivariate regression model, computer navigation was not protective of transfusion (odds ratio [OR] 1.04, P = .73). Preoperative Hgb <10 (OR 10.5, P < .0001) and drain use (OR 2.25, P < .0001) were the most significant risk factors for transfusion. In a linear regression model, computer navigation reduced blood loss by 19 mL (SD 2.94, P < .0001) per case. ConclusionIn this large retrospective cohort analysis of contemporary TKA patients, computer-assisted surgery that eliminates intramedullary femoral canal instrumentation during primary TKA was not associated with reduced transfusion rates and had minimal differences in overall blood loss.

Comparison of Cruciate-Sacrificing vs Posterior-Stabilized Total Knee Replacement Using a Contemporary Total Knee System.

The use of highly conforming polyethylene tibial inserts in cruciate-retaining total knee arthroplasty (TKA) often requires posterior cruciate ligament (PCL) release/sacrifice for balancing (CS TKA). The CS TKA relies on the posterior capsule, collateral ligaments, and articular conformity without a cam or post to achieve stability. Using prospectively collected data we compared clinical outcomes of CS TKA to posterior-stabilized (PS) TKA utilizing a contemporary TKA system. Sixty-nine consecutive CS TKAs were compared to 45 consecutive PS TKAs at 2-year minimum follow-up. CS knees were balanced with the PCL released. Preoperative/postoperative range of motion (ROM), Knee Society Scores (KSS), stair function, and squatting ROM were analyzed. At minimum 2-year follow up, CS and PS TKA demonstrated significant improvement in ROM (P < .001), KSS (Pain, P < .001; Function, P < .001), and KSS stair function (P < .001), with no revisions. There was no difference in preoperative to postoperative improvements for passive knee ROM (10° (0°-20°) vs 13° (5°-25°); P= .16), KSS Pain (34 (21-42) vs 38 (24-46); P= .22), KSS Function (35 (30-50) vs 35 (18-50); P= .34), and KSS stair function (10 (10-20) vs 10 (0-20); P= .37) for CS and PS TKA, respectively. CS TKA had higher squatting ROM (P= .02) at minimum 2-year follow-up compared to PS TKA. Both PS and CS TKA provided significant improvement in clinical outcomes, with no differences in passive ROM, KSS, or stair function postoperatively. Our data support that with proper articular conformity and balancing, cruciate-retaining TKA in a PCL-deficient knee (CS TKA) is appropriate. This may be design specific and further prospective randomized studies are needed to corroborate these findings.

Mid- to long-term outcomes of contemporary total knee arthroplasty in Charcot neuroarthropathy: a systematic review and meta-analysis.

Total knee arthroplasty (TKA) is an effective procedure to treat many patients with end-stage knee arthropathy. However, the extension of TKA for patients with Charcot neuroarthropathy (CNA) is controversial, with relatively limited evidence defining optimal reconstruction techniques.This systematic review of relevant studies that were published from January 2000 to June 2020 aimed to define survivorship, complications, reoperation, and component revision rates of contemporary TKA performed for CNA.We identified 127 TKA performed for CNA in five studies that comprised ≥ 7 knees with ≥ 5 years of follow-up.Overall implant survivorship was 85.4%. The overall complication rate was 26.4%, with the most common complications including instability (24.0%), periprosthetic fracture (17.4%), infection (13.0%), ligament injury (10.9%) and aseptic loosening (10.9%).The aetiology of CNA and prosthesis type had no influence on clinical outcomes, whereas the effect of staging of disease and ataxia status was still inconclusive.Understanding the potential determinants, survivorship and risk of complications related to TKA performed in CNA may help surgeons to deal with patient expectations.Cite this article: EFORT Open Rev 2021;6:556-564. DOI: 10.1302/2058-5241.6.200103

Acquired Idiopathic Stiffness After Contemporary Total Knee Arthroplasty: Incidence, Risk Factors, and Results Over 25 Years

BackgroundAcquired idiopathic stiffness (AIS) remains a common failure mode of contemporary total knee arthroplasties (TKAs). The present study investigated the incidence of AIS and manipulation under anesthesia (MUA) at a single institution over time, determined outcomes of MUAs, and identified risk factors associated with AIS and MUA. MethodsWe identified 9771 patients (12,735 knees) who underwent primary TKAs with cemented, modular metal-backed, posterior-stabilized implants from 2000 to 2016 using our institutional total joint registry. Mean age was 68 years, 57% were female, and mean body mass index was 33 kg/m2. Demographic, surgical, and comorbidity data were investigated via univariate Cox proportional hazard models and fit to an adjusted multivariate model to access risk for AIS and MUA. Mean follow-up was 7 years. ResultsDuring the study period, 456 knees (3.6%) developed AIS and 336 knees (2.6%) underwent MUA. Range of motion (ROM) increased a mean of 34° after the MUA; however, ROM for patients treated with MUA was inferior to patients without AIS at final follow-up (102° vs 116°, P < .0001). Significant risk factors included younger age (HR 2.3, P < .001), increased tourniquet time (HR 1.01, P < .001), general anesthesia (HR 1.3, P = .007), and diabetes (HR 1.5, P = .001). ConclusionAcquired idiopathic stiffness has continued to have an important adverse impact on the outcomes of a subset of patients undergoing primary TKAs. When utilized, MUA improved mean ROM by 34°, but patients treated with MUA still had decreased ROM compared to patients without AIS. Importantly, we identified several significant risk factors associated with AIS and subsequent MUA. Level of EvidenceLevel III, retrospective comparative study.

Clinical Outcomes in Isolated Tibial Revision With Cruciate Retaining Total Knee Arthroplasty

BackgroundTibial component loosening is one of the most common modes of failure in contemporary total knee arthroplasty (TKA). Limited literature is available on the outcomes of isolated tibial revision with retention of the cruciate retaining (CR) femoral component. The purpose of this study was to determine the results of isolated tibial revisions in CR TKA. MethodsWe identified 135 patients who underwent an isolated tibial revision after a primary CR TKA from our institutional registry between January 2007 and January 2017. The mean time between the primary and revision was 2.9 years (range 0.1-15.4). Revision with a press-fit stem was performed in 79 patients and 56 patients were revised with a fully cemented stem. Patients were evaluated at a minimum of two years using Knee Society Score, Knee Injury and Osteoarthritis Score for Joint Replacement, and radiography. Implant survivorship was determined using Kaplan-Meier survival analysis. ResultsAt a mean follow-up of 5.1 years, there were six (4.4%) repeat revisions: three for periprosthetic infection (2.2%), two for instability (1.5%), and one for a fractured tibial stem (0.7%). The mean Knee Society Score and Knee Injury and Osteoarthritis Score for Joint Replacement increased from 51.6 and 56.1 preoperatively to 90.1 and 89.7 after surgery (P < .001). Survivorship free of repeat revision for any cause was 93.3% at 5 years, and aseptic revision survivorship was 95.8% at 5 years. No implants were radiographically loose. ConclusionIn patients with isolated tibial loosening and a well-fixed and well-positioned CR femoral component, isolated tibial revision provides excellent early to midterm implant survivorship and clinical outcomes with a low risk of instability and recurrent tibial loosening.

Effect of Coronal Alignment on 10-Year Survivorship of a Single Contemporary Total Knee Arthroplasty.

Debate remains regarding the utility of mechanical axis alignment as a predictor of durability after total knee arthroplasty (TKA). Our study aimed to assess the effects of coronal alignment on implant durability, clinical outcomes, and radiographic results with a single fixed-bearing TKA design. All patients undergoing primary cemented TKA of a single design (Stryker Triathlon) from 2005–2007 with >10 years of follow-up and available pre-operative and post-operative hip–knee–ankle radiographs were included (n = 89). Radiographs were measured to determine coronal alignment and assessed for loosening. Mean preoperative mechanical axis alignment was −6° ± 6.7° (varus, range, −16°–23°), while mean post-operative alignment was −1° ± 2.7° (varus, range, −3°–15°). The aligned group was defined as knees with a post-operative mechanical axis of 0° ± 3° (n = 73) and the outlier group as those outside this range (n = 16). No patients underwent revision. Ten-year survivorship free from any reoperation was 99% and 100% in the aligned and outlier groups, respectively (p = 0.64). Knee Society scores improved significantly in both groups (p < 0.001) and did not differ at final follow-up (p = 0.15). No knees demonstrated radiographic evidence of loosening. Post-operative mechanical axis alignment within 3° of neutral was not associated with improved implant durability, clinical outcomes, or radiographic results at 10 years following primary TKA.

An Extramedullary Spacing Block Technique to Restore Native Coronal Limb Alignment in TKA

Background: Historically, the femoral and tibial preparation for a total knee arthroplasty (TKA) are executed in isolation and then soft tissue releases are used to obtain a balanced knee. We present the clinical outcomes associated with a novel surgical method that links the tibial and femoral resections, avoids soft tissue releases, is performed extramedullary, and does not require special scans, robotics, or rapid prototype blocks. Materials and Methods: We measured hip, knee, ankle alignment radiographs preoperatively and postoperatively on 433 consecutive TKAs performed between November 2016 and August 2019. A new surgical technique called the linked and tensioned extramedullary resections (LATER technique) for both extension and flexion gap balancing was utilized without any soft tissue releases. Results: One hundred thirty-four knees were found to have severe malalignment preoperatively (≥10 degrees of varus or valgus deformities). The average angular correction was 12 degrees toward neutral alignment. Of the entire cohort, 89.2% of patients reported being completely or mostly satisfied. Patients reported “a lot of improvement” or “back to normal” (92.3%). Conclusions: The LATER technique improves coronal alignment following a complex primary TKA. Contemporary TKA can be balanced without ligament releases. The avoidance of intramedullary violation and soft tissue releases decreased intraoperative blood loss and trauma. This technique also avoids the complexities of navigation, the complications associated with fat embolism, and the manufacturing of rapid prototype blocks. The LATER technique of coronally tensioned alignment is simple to use and has excellent patient-reported satisfaction and improvement scores.

Posterior Cruciate Ligament Resection Does Not Consistently Increase the Flexion Space in Contemporary Total Knee Arthroplasty

IntroductionIt is accepted dogma in total knee arthroplasty (TKA) that resecting the posterior cruciate ligament (PCL) increases the flexion-space by approximately 4mm. Unfortunately, this doctrine is based on historical studies of limited size with variable technique. The aim of this study was to determine the effect of PCL-resection on in vivo tibiofemoral joint space dimensions in a cohort of modern TKAs. MethodsTibiofemoral joint space measurements were made during 129 standardized TKAs by two arthroplasty surgeons. A medial parapatellar approach, computer navigation and provisional bone cuts were performed in all cases with particular attention to preserving PCL integrity. The tibiofemoral gap was measured with a calibrated tension device at extension, 45-degrees, and 90-degrees before and after complete PCL-resection. Results51% of patients were female (66/129) with mean age and BMI of 69.5 years and 34.2 kg/m2, respectively. After PCL-resection, mean change in center joint space dimension increased 0.33mm at extension, 0.95mm at 45-degrees, and 1.71mm at 90-degrees (P < .001). The 90-degree flexion-space opened ≥4mm in only 10% of patients. Dividing the flexion-space change by femoral implant dimension to account for patient size, the flexion-space at 90-degrees significantly increased more in females compared to males (P = .020). ConclusionThe tibiofemoral joint space increased progressively from extension to mid-flexion through deep-flexion after PCL-resection, yet was substantially less than reported in historical studies. However, large variation in flexion-space opening was observed with some patients failing to increase the flexion-space whatsoever with PCL-resection. This runs counter to conventional TKA understanding and should be considered in modern surgical education. Level of EvidenceTherapeutic Level III.

Single Use Instruments for Implanting a Contemporary Total Knee Arthroplasty System Are Accurate, Efficient, and Safe

BackgroundSingle use instruments (SUI) is a potential mechanism to improve efficiency and reduce cost in total knee arthroplasty (TKA). New technology requires patient safety and surgical accuracy. A multi-center study of SUI vs reusable mechanical instrumentation (RUI) for a TKA system compared implant placement accuracy and operating room (OR) efficiency. MethodsFour surgeons implanted 88 primary TKAs, N = 44 RUI and N = 44 SUI. Accuracy was measured radiographically at 3 months. The primary endpoint was non-inferiority of absolute value of mechanical axis alignment. Radiographic endpoints, OR times, and adverse events were also evaluated. ResultsSeventy-five subjects completed the study (41 SUI/34 RUI). The primary endpoint non-inferiority of SUI vs RUI was met, with no significant difference between SUI and RUI in most radiographic parameters (distal femoral varus-valgus, proximal tibial varus-valgus, tibial slope, or subjects within 3° of target); there was a slight difference in femoral component flexion angle (P = .015). SUI and RUI mean (SD) OR set-up times were 18.8 (10.03) and 26.7 (6.93) (P <.001), and surgical times (first incision to last stitch) were 64.6 (16.95) and 60.5 (19.01) (P = .295), respectively. Differences in OR clean-down and anesthesia were not significant. There were no revisions, and there was no significant difference in the number of reported adverse events. ConclusionSUI resulted in similar accuracy of implant placement to RUI with decreased OR set-up time and no increase in adverse events. These results support the safety and efficacy of SUI for performing TKA. Further analysis of potential economic and technical advantages is warranted.

Superior Mid- to Long-Term Clinical Outcomes of Mobile-Bearing Total Knee Arthroplasty Compared to Fixed-Bearing: A Meta-Analysis Based on a Minimum of 5 Years of Study.

As more patients undergo total knee arthroplasty (TKA) each year, and the average age of patients gets younger, the patients are generally more active requiring a greater physiological demand and increasing range of motion on the prosthesis than the previous patients. However, there is no consensus on the optimal TKA tibial bearing design. We performed this systematic review to compare the clinical differences between mobile and fixed bearing constructs used in contemporary TKA. We searched PubMed, EMBASE, and Cochrane Library databases, identifying 515 total publications, including 17 randomized controlled trials (RCTs). A meta-analysis was performed, while the quality and bias of the evidence were rated according to the Grading of Recommendations Assessment Development and Evaluation (GRADE) guidelines and the Cochrane Database questionnaire. The meta-analysis was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines. Seventeen studies were included, with a total of 1505 knees receiving a mobile bearing TKA and 1550 knees receiving a fixed bearing TKA. The meta-analysis compared clinical outcomes between mobile bearing (MB)-TKA and fixed bearing (FB)-TKA using postoperative Knee Society Score, postoperative ROM, and survivorship and showed that there was a distinct difference in Knee Society Score between the mobile-bearing and fixed-bearing groups (overall standardized mean difference = 1.38; 95% confidence interval (CI): 0.50-2.25; p = 0.002; I2 = 60%). Patients treated with mobile-bearing prostheses were more likely to report good or excellent range of motion results (overall standardized mean difference = 2.06; 95% CI: 0.65-3.47; p = 0.004). No difference in implant survivorship or reoperation rate were identified. The fixed-bearing and mobile-bearing TKA designs are both capable of producing excellent long-term results with excellent clinical outcomes if properly implanted; however, the mobile-bearing TKA have superiority in mid- to long-term clinical results. Trial registration number for PROSPERO was CRD42019126402.

The effect of fixation type on the survivorship of contemporary total knee arthroplasty in patients younger than 65 years of age: a register-based study of 115,177 knees in the Nordic Arthroplasty Register Association (NARA) 2000–2016

Background and purpose — Cemented fixation is regarded as the gold standard in total knee arthroplasty (TKA). Among working-age patients, there has been controversy regarding the optimal fixation method in TKA. To address this issue, we conducted a register-based study to assess the survivorship of cemented, uncemented, hybrid, and inverse hybrid TKAs in patients aged < 65 years.Patients and methods — We used the Nordic Arthroplasty Register Association data of 115,177 unconstrained TKAs performed for patients aged < 65 years with primary knee osteoarthritis over 2000–2016. Kaplan–Meier (KM) survival analysis with 95% confidence intervals (CI) and Cox multiple-regression model with adjustment for age, sex, and nation were used to compare fixation methods in relation to revision for any reason.Results — The 10-year KM survivorship of cemented TKAs was 93.6% (95% CI 93.4–93.8), uncemented 91.2% (CI 90.1–92.2), hybrid 93.0% (Cl 92.2–93.8), and inverse hybrid 96.0% (CI 94.1–98.1). In the Cox model, hybrid TKA showed decreased risk of revision after 6 years’ follow-up compared with the reference group (cemented) (hazard ratio [HR] 0.5 [CI 0.4–0.8]), while uncemented TKAs showed increased risk of revision both < 1 year (HR 1.4 [1.1–1.7]) and > 6 years’ (HR 1.3 [1.0–1.7]) follow-up compared to the reference.Interpretation — Both cemented and hybrid TKAs had 10-year survival rates exceeding 92–>93% in patients aged < 65 years. Cemented TKA, however, was used in the vast majority (89%) of the operations in the current study. As it performs reliably in the hands of many, it still deserves the status of gold standard for TKA in working-age patients.

Management of Gonarthrosis with a Rotating Hinge Prosthesis: Minimum 10-Year Follow-up.

BackgroundThe use of hinged designs is usually reserved for severe deformities or instability in contemporary total knee arthroplasty (TKA). Results have been mixed with some authors reporting relatively high incidences of complications. The aim of this study is to present the results of primary TKA performed with a hinged prosthesis with a minimum 10-year follow-up. We also examined the factors that influence survivorship of this prosthesis.MethodsA total of 238 primary TKA procedures were performed using hinged prostheses. Indications included osteoarthritis, rheumatoid arthritis, posttraumatic deformity, and arthritis. Clinical outcomes were assessed using the Hospital for Special Surgery score. Radiologic assessment was performed at each follow-up. Survivorship was calculated based on the Kaplan-Meier method. All complications were documented.ResultsMean follow-up was 13.5 years (standard deviation [SD], 3.4). Mean flexion at final review was 118° (SD, 20°). Fifty-four percent and 20% reported excellent and good functional scores, respectively. Survivorship was 94% at 13.5 years in patients over 60 years of age and 77% in patients less than 60 years of age. Survivorship in patients with preoperative varus deformity was 96% and that in valgus knees was 79%.ConclusionsThe results of this study suggest that when rotating hinges are used for primary TKA, the best results are achieved in patients over 60 years old. The indications for this design in the setting of primary TKA include significant deformities, severe bone loss, and ligamentous laxity.