Total Knee Arthroplasty System Research Articles

Influence of surgical factors on patient satisfaction after bi\u2010cruciate stabilized total knee arthroplasty: retrospective examination using multiple regression analysis

BackgroundOne of the causes of dissatisfaction following total knee arthroplasty (TKA) is abnormal knee kinematics. A newly designed bi-cruciate stabilized (BCS) TKA system has been developed to produce close-to-normal kinematics because of its anatomic tibiofemoral articular geometry and cam-post mechanism. Although BCS TKA is expected to improve patient satisfaction, no reports have described the appropriate technique or soft tissue handling required to achieve excellent satisfaction with BCS TKA. This study is to identify intraoperative surgical predictors of patient satisfaction after BCS TKA.MethodsWe studied 104 knees with primary varus knee osteoarthritis that underwent BCS TKA with a navigation system retrospectively. Surgical parameters including coronal, sagittal and axial alignment and joint laxity in each compartment that affected patient satisfaction was evaluated. Satisfaction score was evaluated with use of the 2011 Knee Society Scoring system. The multivariate regression analysis included age, gender, body mass index and intraoperative parameters that correlated with satisfaction scores in the univariate analysis (P < 0.05). The current study focused on the patient satisfaction score at 1 year postoperatively and didn’t evaluate the long term clinical results nor survivorship.ResultsThe postoperative satisfaction score was 28.6 ± 8.1. Multivariate analysis showed that medial joint laxity at 30° flexion (P = 0.003), tibial excessive external rotation alignment (P = 0,009) and tibial varus alignment (P = 0.029) were predictors of poor satisfaction score.ConclusionsWhen performing BCS TKA, surgeons should pay attention to maintaining proper stability of the medial compartment at mid flexion range and should avoid tibial varus and excessive external rotational alignment.

Extramedullary femoral alignment system in total knee arthroplasty: Accuracy in relation of severity and different types of varus

ObjectivesWe assessed the accuracy of an extramedullary guide system for femoral component alignment in TKA. MethodsWe retrospectively analysed 87 total knee arthroplasties using a newly developed extramedullary guide system. ResultsCorrect postoperative coronal plane femoral component, with deviation from neutral alignment by 3° or less, was found in 87% of the study population. The percentages were 100%, 91% and 79% for HKA of 0–3°, 3–10° and >10°respectively. ConclusionThe correct use of the extramedullary guide system allows the restoration of the neutral mechanical axes of the lower limb, especially in cases of limited varus deformity.

Usefulness of an accelerometer-based navigation system in bilateral one-stage total knee arthroplasty

BackgroundBilateral one-stage total knee arthroplasty (BTKA) have increased because it provides a number of advantages. Recently, Accelerometer-based navigation (ABN) system which guide the cutting plane without intramedullary disturbance might result in less endothelial and microvascular damage. Therefore, we hypothesized that the ABN may reduce blood loss, reduce postoperative pain, and better restore BTKA alignment compared to conventional instruments.MethodsWe retrospectively compared 44 consecutive patients receiving ABN assisted BTKA (iBTKA) to 57 patients with conventional instruments (cBTKA). Identical pre- and post-operative care was utilized to all patients. The outcome measures assessed were hemoglobin (Hb), calculated blood loss (CBL), blood transfusion, VAS score for pain, morphine consumption, knee flexion angle, and length of stay (LOS). Radiographic assessment included mechanical axis (MA) and component positioning at 3–6 months of follow up.ResultsBoth iBTKA and cTKA groups had equivalent demographic data. Postoperative Hb of the cBTKA group was significantly lower than those in the iBTKA group at 24 h (p = 0.02), but there was no significant difference in drain volume, CBL, and blood transfusion rate. For radiographic measures, the iBTKA group had more accurate MA and component orientation, and had a lower number of outliers than those in the cBTKA group (p ≤ 0.01), except for the sagittal femoral component angle.ConclusionThe ABN assisted BTKA could not reduce blood loss or postoperative pain more than cBTKA, nor improve functional recovery. However, the ABN significantly improved the accuracy of MA and prostheses positioning.Trial registrationThe protocol of this study was registered in the Thai Clinical Trials Registry database No. TCTR20180731001# on 25 July 2018.

Short- to Midterm Outcomes of a Novel Guided-Motion Rotational Hinged Total Knee Arthroplasty.

Hinged prostheses have been increasingly utilized in complex and revision total knee arthroplasty (TKA) cases requiring additional mechanical support and global stability. However, there is limited data detailing the outcomes of modern hinge designs in these procedures. The aim of this study is to report a minimum 2-year functional outcomes and survivorship of a novel-guided motion-hinged knee TKA system. A multicenter, retrospective cohort study was conducted on consecutive TKA patients between March 2013 and August 2017 with a novel-guided motion-hinged knee system. Demographics, change in range of motion (ΔROM), quality metrics, and implant survivorship were collected with a minimum of 2-year follow-up. Implant survival was analyzed by using the Kaplan-Meier method. Overall, 147 hinged knee cases (18 complex primaries and 129 revisions) were identified with an average follow-up duration of 3.8 ± 1.2 years. Patients presented with an average of 2.4 ± 1.6 prior knee surgeries, and 51 (34.7%) had a history of knee infections. The ROM improved postoperatively: Δ extension = 2 ± 1 degrees, Δflexion = 7 ± 3 degrees, Δtotal ROM = 9 ± 4 degrees. Kaplan-Meier survivorship analysis for implant revision at 2- and 5-year follow-up showed a survival rate of 100 and 98.5% (95% confidence interval: 94.3-99.6%), respectively, with one patient undergoing two-stage revision for infection and another undergoing femoral revision for aseptic loosening. Survivorship for aseptic all-cause reoperation at 2- and 5-year follow-up was 93.2% (87.7-96.3%) and 88.2% (80.0-93.2%), respectively. Fourteen patients underwent aseptic reoperation (patellar complications: n = 7 [4.8%]; instability: n = 5 [3.4%]; tuberosity fixation: n = 1 [0.7%]; extensor mechanism failure: n = 1 [1.1%]). Survivorship for all-cause reoperation at 2- and 5-year follow-up were 85% (78.2-90.0%) and 77.7% (68.8-84.3%), respectively. Fifteen patients underwent reoperation for infection (DAIR: n = 14 (9.5%); two-stage revision: n = 1 [0.7%]). Despite some reoperations, this guided-motion hinged-knee TKA system demonstrates excellent survivorship for component revision compared to other modern hinged knee implants reported in the literature. Patients also displayed an improvement in knee ROM at their latest follow-up.

An animal experimental study on domestic robot-assisted total knee arthroplasty

To evaluate the performance, safety, and precision of the Yuanhua robotic-assisted total knee arthroplasty system (YUANHUA-TKA) through animal experiments, which will provide reference data for human clinical trials. Six 18-month-old goats, weighing 30-35 kg, were used in this study. The experimental study was divided into two parts: the preoperative planning and intraoperative bone resection. CT scans of the goats' lower extremities were firstly performed before the experiments. Then the CT scans were segmented to generate the femoral and tibial three-dimensional (3D) models in the YUANHUA-TKA system. The volumes and angles of each resection plane on the femur and tibia were planned. The bone resection was finally implemented under the assistance of the YUANHUA-TKA system. After completing all bone resections, the lower extremities of each goat were taken to have CT scans. By comparing the femoral and tibial 3D models before and after the experiments, the actual bone resection volumes and angles were calculated and compared with the preoperative values. During the experiments, no abnormal bleeding was found; the YUANHUA-TKA system ran smoothly and stably and was able to stop moving and keep the osteotomy in the safe zone all the time. After the experiment, the resection planes were observed immediately and found to be quite flat. There was no significant difference between the planned and actual osteotomy thickness and osteotomy angle ( P>0.05); the error of the osteotomy thickness was less than 1 mm, and the error of the osteotomy angle was less than 2°. The YUANHUA-TKA system can assist the surgeons to perform osteotomy following the planned thickness and angle values. It is expected to assist surgeons to implement more accurate and efficient osteotomy in the future clinical applications.

Robot-assisted total knee arthroplasty is associated with a learning curve for surgical time but not for component alignment, limb alignment and gap balancing.

The application of robotics in the operating theatre for total knee arthroplasty (TKA) remains controversial. As with all new technology, the introduction of new systems is associated with a learning curve and potentially associated with extra complications. Therefore, the aim of this study is to identify and predict the learning curve of robot-assisted (RA) TKA. A RA TKA system (MAKO) was introduced in April 2018 in our service. A retrospective analysis was performed of all patients receiving a TKA with this system by six surgeons. Operative times, implant and limb alignment, intraoperative joint balance and robot-related complications were evaluated. Cumulative summation (CUSUM) analyses were used to assess learning curves for operative time, implant alignment and joint balance in RA TKA. Linear regression was performed to predict the learning curve of each surgeon. RA TKA was associated with a learning curve of 11-43 cases for operative time (p < 0.001). This learning curve was significantly affected by the surgical profile (high vs. medium vs. low volume). A complete normalisation of operative times was seen in four out of five surgeons. The precision of implant positioning and gap balancing showed no learning curve. An average deviation of 0.2° (SD 1.4), 0.7° (SD 1.1), 1.2 (SD 2.1), 0.2° (SD 2.9) and 0.3 (SD 2.4) for the mLDFA, MPTA, HKA, PDFA and PPTA from the preoperative plan was observed. Limb alignment showed a mean deviation of 1.2° (SD 2.1) towards valgus postoperatively compared to the intraoperative plan. One tibial stress fracture was seen as a complication due to suboptimal positioning of the registration pins. RA TKA is associated with a learning curve for surgical time, which might be longer than reported in current literature and dependent on the profile of the surgeon. There is no learning curve for component alignment, limb alignment and gap balancing. IV.

Patient Demographics and Anthropometric Measurements Predict Tibial and Femoral Component Sizing in Total Knee Arthroplasty

BackgroundAccurate sizing is critical for the overall success of a total knee arthroplasty (TKA). This study's primary purpose was to investigate the ability to predict the tibial and femoral component size in a single implant system from patient demographics and anthropometric data. A secondary goal was to compare the predicted tibial and femoral component sizes from our statistical model with a previously validated electronic application used to predict the implant size. MethodsA consecutive series of 484 patients undergoing a primary TKA at a single institution was reviewed. Data on height, weight, body mass index, sex, age, and component size were collected. A proportional odds model was developed to predict tibial and femoral component sizes. The relationship between the proportional odds model predictions was also compared with the component sizes determined by the Arthroplasty Size Predictor electronic application. ResultsWeight, height, and sex predicted the implanted component size with an accuracy of 54.0% (n = 247/484) for the tibia and 51.1% (n = 231/484) for the femur. The accuracy improved to 94.4% (n = 457/484) for the tibia and 93.4% (n = 452/484) for the femur within ±1 component size. Our data are highly correlated to the Arthroplasty Size Predictor for the predicted tibial component size (ρ = 0.91, P < .001) and femoral component size (ρ = 0.89, P < .001). ConclusionsOur novel templating model may improve operative efficiency for a single TKA system. Our findings have a high concordance with a widely available electronic application used to predict implant sizes for a variety of TKA systems.

An Academic Orthopaedic Specialty Hospital Provides the Shortest Operative Times within a Single Health System for Primary and Revision Total Knee Arthroplasty.

The study aimed to optimize value-based health care practices in total joint arthroplasty (TJA), and we need to understand how the surgical setting can influence efficiency of care. While this has previously been investigated, the purpose of this study was to clarify if these findings are generalizable to an institution with an orthopaedic specialty hospital. A retrospective review was conducted of 6,913 patients who underwent primary or revision total knee arthroplasty (TKA) at one of four hospitals within a single, urban, and academic health system: a high volume academic (HVA) hospital, a low volume academic (LVA) hospital, a high volume community (HVC) hospital, or a low volume community (LVC) hospital. Patient demographics were collected in an arthroplasty database, as were operating room (OR) times and several specific time points during the surgery. The HVA (orthopaedic specialty) hospital had the shortest total primary TKA OR times and the LVC that had the longest times (156.69 vs. 174.68, p < 0.0001). The HVA hospital had the shortest total revision TKA OR times, and the LVC had the longest times (158.20 vs. 184.95, p < 0.0001). In our health system, the HVA orthoapedic specialty hospital had the shortest overall OR time, even when compared with the HVC hospital. This is in contradistinction to prior findings that HVC institutions had the shortest OR times in a health system that did not have an orthopaedic specialty hospital. This provides evidence that an orthopaedic specialty hospital can be a model for efficient care, even at an academic teaching institution.

Early clinical outcome and learning curve following unilateral primary total knee arthroplasty after introduction of a novel total knee arthroplasty system.

BACKGROUNDNew implants for total knee arthroplasty (TKA) are continuously introduced with the proposed benefit of increased performance and improved outcome. Little information exists on how the introduction of a novel arthroplasty implant affects the perioperative and surgical outcome immediately after implementation. AIMTo investigate how surgery-related factors and implant positioning were affected by the introduction of a novel TKA system.METHODSA novel TKA system was introduced at our institution on 30th November 2015. Seventy-five TKAs performed with the Persona TKA immediately following its introduction by 3 different surgeons (25 TKAs/surgeon) were identified as the Introduction Group. Moreover, the latest 25 TKAs performed by each surgeon prior to introduction of the Persona TKA were identified as the Control Group. A Follow-up Group of 25 TKAs/surgeon was identified starting 1-year after the end of the introduction period. Demographics, surgery-related factors and alignment data were recorded, and intergroup differences compared.RESULTSFollowing introduction of the novel implant, Persona TKA was utilized in 69% (71%), 53% (54%), and 45% (75%) of primary TKA procedures by the three surgeons, respectively (Follow-up Group). Mean surgery time was increased by 28% (P < 0.0001) and mean intra-operative blood loss by 25% (P = 0.002) in the Introduction Group, while only the mean surgery time was increased in the Follow-up Group by 18% (P < 0.0001). Overall alignment was similar between the groups apart from femoral flexion (FF) and tibial slope (TS). The number of FF outliers was reduced in the Introduction Group with a more pronounced decrease in the Follow-up Group.CONCLUSIONIntroduction of the new TKA implant increased surgical time and intraoperative blood loss immediately after its introduction. These differences diminished one year after introduction of the new implant. Fewer outliers with respect to FF and TS were seen when using the novel TKA implant. Further studies are needed to investigate if these differences persist over time and correlate with patient reported outcomes.

Usefulness of an Accelerometer-Based Portable Navigation System for Total Knee Arthroplasty: A Multicenter Prospective Randomized Controlled Trial.

An accelerometer-based portable navigation system was recently introduced to improve prosthetic alignment during total knee arthroplasty (TKA). The purpose of this multicenter prospective randomized controlled trial (RCT) was to evaluate the effects of this accelerometer-based portable navigation system for achieving more accurate alignment during TKA in the clinical setting. One hundred patients with primary varus osteoarthritis of the knee were enrolled in this prospective RCT conducted in 5 hospitals. A navigation system was utilized in 50 patients (navigation group), and a conventional intramedullary femoral guide and an extramedullary tibial guide were utilized in 50 patients (conventional group). At 6 months postoperatively, weight-bearing radiographs were obtained of the whole operative leg. An experienced surgeon who was blinded to the treatment assignments then measured the alignment to 1 decimal place with use of computer software. Power analysis showed that 41 knees were required in each group. There were no complications as a result of the use of the accelerometer-based portable navigation system. Postoperative radiographs were obtained in 45 patients from each group. There were no significant differences in sex, age, height, body weight, body mass index, preoperative femorotibial angle, and operative time between groups. The absolute differences of the femoral prosthesis (p = 0.01), tibial prosthesis (p < 0.01), and hip-knee-ankle angle (p < 0.01) from a neutral mechanical axis were less in the navigation group compared with those in the conventional group. Alignment outliers (>2° away from the neutral mechanical axis) of the tibial prosthesis and hip-knee-ankle angle were less in the navigation group (9% and 27%, respectively) compared with those in the conventional group (31% and 49%; p = 0.01 and p = 0.04, respectively). To our knowledge, this is the first multicenter prospective RCT to evaluate an accelerometer-based portable navigation system. An accelerometer-based portable navigation system provides more accurate prosthetic and limb alignment in the coronal plane than conventional techniques, without extended operative time or an increased rate of complications. The results of this study may help orthopaedic surgeons decide whether or not to use an accelerometer-based portable navigation system. Therapeutic Level I. See Instructions for Authors for a complete description of levels of evidence.

MAKO CT-based robotic arm-assisted system is a reliable procedure for total knee arthroplasty: a systematic review.

The aim of this study was to investigate the clinical and radiological results of the MAKO CT-based robotic-assisted system for total knee arthroplasty (TKA). A PRISMA systematic review was conducted using four databases (MEDLINE, EMBASE, Pubmed, GOOGLE SCHOLAR) to identify all clinical and radiological studies reporting information regarding the use and results of the CT-based robotic-assisted system to perform TKA between 2016 and 2020. The main investigated outcome criteria were postoperative pain, analgesia requirements, clinical scores, knee range of motion, implant positioning and the revision rate. The ROBINS-I tool (Risk Of Bias In Non-randomized Studies of Interventions) was used to evaluate the quality of included studies and the risk of bias. A total of 36 studies were identified, of which 26 met inclusion criteria. Of these 26 studies, 14 were comparative. The follow-up varied from 30days to 17months. This CT-based, saw cutting Robotic TKA is associated with a significantly lower postoperative pain score (2.6 versus 4.5) and with significantly reduced time to hospital discharge (77h versus 105), compared with conventional TKA. The two comparative studies assessing functional outcomes at 1year reported significantly better functional scores with CT-based robotic TKA compared with conventional TKA (WOMAC score: 6 ± 6 versus 9 ± 8 (p < 0.05); KSS function score: 80 versus 73 (p = 0.005)). Only three comparative studies assessed implant positioning, and these reported better implant positioning with CT-based robotic-assisted TKA. The CT-based robotic-assisted system for TKA reduced postoperative pain and improved implant positioning with equal or slightly superior improvement of the functional outcomes at one year, compared to conventional TKA. Systematic review level IV.

Survivorship of constrained polyethylene inserts in primary total knee replacements

BackgroundVarus–valgus constrained (VVC) inserts are used in primary total knee arthroplasty (TKA) when stability cannot be achieved with a traditional insert. Concern has been raised regarding premature loosening and failure of these primary TKAs due to the increased load transfer through the prosthesis. This study seeks to assess the survival, clinical outcomes and radiographic assessment of VVC total knee inserts used in a single primary TKA system without diaphyseal stem extensions. MethodsA consecutive cohort of 74 primary TKAs with VVC inserts was identified from an institutional database. A two-to-one matched group of 136 posterior-stabilized (PS) primary TKAs was generated from the same database. Survival analysis was assessed for all-cause revision surgery. Patient outcome measures were the Oxford Knee Score (OKS) and patient reported satisfaction. Radiographs were assessed in accordance with the Knee Society radiographic scoring system for radiolucency. ResultsSurvival rates at three and five years were 98.1% and 95.1% for the VVC liner group and 98.1% and 98.1% for the PS liner group, respectively. OKS improved from pre-op to post-op for both groups (p < .001). OKS was reduced in the VVC liner group compared to the PS liner group at latest available follow-up (p = .012). However, clinical satisfaction rates did not differ between the two groups. Small, non-progressive radiolucent lines existed on several radiographs; however, no components in either group were deemed radiographically loose. ConclusionThe survivorship, clinical, and radiographic outcomes of VVC knees were similar to the PS comparison group at short- to mid-term follow-up.

Is the Patient-Reported Outcome Measurement Information System Feasible in Bundled Payment for Care Improvement Total Knee Arthroplasty Patients?

BackgroundSeveral bundled payment plans, like the Bundled Payment for Care Improvement (BPCI) initiative for total joint arthroplasty, have been introduced to decrease costs and improve clinical care. Measuring clinical outcomes with efficient, standardized methodologies is essential to determine the relative value of total joint arthroplasty care. We investigated feasibility and responsiveness of the recently developed Patient-Reported Outcomes Measurement Information System (PROMIS) in total knee arthroplasty (TKA) patients. MethodsWe included patients with preoperative and 1-year PROMIS Physical Function (PF), Pain Interference (PI), and Depression (DEP) scores who received unilateral primary TKA. Burden was assessed using the number of questions and time required for PROMIS completion. The minimum clinically important difference was defined as 5. Floor/ceiling effects were noted if more than 15% of patients responded with the lowest/highest possible score, respectively. Wilcoxon rank-sum test was used to compare categorical data. Analysis of variance was used for PROMIS comparisons. ResultsIn total, 172 knees (54 BPCI) were included. Floor effects were identified for DEP at baseline (non-BPCI) and follow-up (both groups), and for PI at follow-up only (BPCI). Patients required 140 seconds and 16 questions to answer all 3 PROMIS domains. Sixty-seven percent, 60%, and 44% of knees achieved minimum clinically important difference in PI, PF, and DEP scores respectively, with no significant difference between groups. The BPCI cohort was older (P < .001) with a higher American Society of Anesthesiologists score (P = .028). There were no significant differences in scores between BPCI and non-BPCI patients. ConclusionPROMIS is feasible and time-efficient in BPCI patients undergoing primary TKA. There were no significant differences in outcomes between BPCI and non-BPCI knees. Level of EvidenceLevel 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.

No reduced patellar loading with latest-generation cruciate-retaining total knee arthroplasty\u2014a comparative study of Attune and Press-Fit Condylar\xae

PurposeTo investigate if the latest-generation cruciate-retaining total knee arthroplasty (CR-TKA) systems through more patella-friendly femoral trochlea reduce the patellar bone loading.MethodsTwenty patients who underwent Attune CR-TKA were matched with twenty-one patients who underwent Press-Fit Condylar® (PFC) CR-TKA. The patella was always preserved. The in vivo patellar loading was measured twice by two blinded observers and localised on an 8-quadrant grid on 1-year post-operatively SPECT/CT images. The position of the TKA components, patella height, thickness, tilt, and tibial tuberosity-trochlear groove index were measured in 3D CT. Knee function was assessed pre-operatively, at 12 and 24 months post-operatively with the knee society score (KSS). All data were compared between groups with the Mann-Whitney U test and within groups with Spearman’s correlation.ResultsA significantly higher bone tracer uptake (BTU) was seen in the Attune group in the lateral non-articular patellar quadrants. No other significant differences of the BTU were seen. The post-operative KSS did not differ significantly. Spearman’s correlation showed no correlations between the significantly higher BTU of the lateral non-articular patellar quadrants and the position of the TKA and patellar measurements. All patellar measurements did not correlate with bone stress in SPECT/CT.ConclusionNo significant improvement in terms of in vivo patellar bone stress was seen with the latest-generation CR-TKA system. The increased bone stress at the non-articular lateral patellar quadrants of the Attune could be due to higher stabilising quadriceps forces.

Custom total knee arthroplasty facilitates restoration of constitutional coronal alignment

PurposeTo describe a strategy for coronal alignment using a computed tomography (CT) based custom total knee arthroplasty (TKA) system, and to evaluate the agreement between the planned and postoperative Hip–Knee–Ankle (HKA) angle, Femoral Mechanical Angle (FMA) and Tibial Mechanical Angle (TMA).MethodsFrom a consecutive series of 918 primary TKAs, 266 (29%) knees received CT-based posterior-stabilized cemented custom TKA. In addition to a preoperative CT-scan, pre- and post-operative radiographs of weight-bearing long leg, anterior–posterior and lateral views of the knee were obtained, on which the FMA, TMA and HKA angles were measured. CT-based three-dimensional (3D) models enabled to correct for cases with bony wear by referring to the non-worn areas and to estimate the native pre-arthritic angles. The alignment technique aimed to preserve or restore constitutional alignment (CA) within predetermined limits, by defining a ‘target zone’ based on three criteria: 1) a ± 3° (range 87°–93°) primary tolerance for the femoral and tibial resections; 2) a ± 2° secondary tolerance for component obliquity, extending the bounds for FMA and TMA (range 85°–95°); 3) a planned HKA angle range of 175°–183°. Agreement between preoperative, planned and postoperative measurements of FMA, TMA and HKA angle were calculated using intra-class correlation coefficients (ICC).ResultsPreoperative radiograph and CT-scan measurements revealed that, respectively, 73 (28%) and 103 (40%) knees were in the ‘target zone’, whereas postoperative radiographs revealed that 217 (84%) TKAs were in the ‘target zone’. Deviation from the planned angles were − 0.5° ± 1.8° for FMA, − 0.5° ± 1.8° for TMA, and − 1.1° ± 2.1° for HKA angle. Finally, the agreement between the planned and achieved targets, indicated by ICC, were good for FMA (0.701), fair for TMA (0.462) and fair for HKA angle (0.472).ConclusionUsing this strategy for coronal alignment, 84% of custom TKAs were within the ‘target zone’ for FMA, TMA and HKA angles. These findings support the concepts of emerging personalized medicine technologies, and emphasise the importance of accurate strategies for preoperative planning, which are key to achieving satisfactory ‘personalised alignment’ that can further be improved by customisation of implant components.Level of evidenceIV.

Mechanical Axis Estimation System for Total Knee Arthroplasty Using a Three-Axis Inertial Measurement Unit Sensor

Mechanical Axis Estimation System for Total Knee Arthroplasty Using a Three-Axis Inertial Measurement Unit Sensor

Lack of small tibial component size availability for females in a highly utilized total knee arthroplasty system

Surgeons must rely on manufacturers to provide an appropriate distribution of total knee arthroplasty (TKA) sizes. There is a lack of literature regarding current appropriateness of tibial sizing schemes according to sex. As such, a study was devised assessing the adequacy of off-the-shelf tibial component size availability according to sex. A search was conducted to identify all primary TKAs between July 2012 and June 2019 performed using a single implant. Baseline patient characteristics were collected (age, weight, height, BMI, and race). Two cohorts were created according to patient sex. Tibial sizes for each cohort were collected. Tibial component bar graph and histogram were created according to component sizes. Skewness and kurtosis were calculated for each distribution. Overhang was noted and measured radiographically. A total of 864 patients were identified, 38.7% males and 61.3% females. Most patients were Caucasian, and BMI was similar between cohorts. Tibial size distribution for males was as follows: 0.3% C, 4.8% D, 16.5% E, 40.1% F, 31.4% G, 6.9% H. Tibial size distribution for females was as follows: 30.8% C, 42.8% D, 23.0% E, 2.6% F, 0.8% G, 0.0% H. Histograms and normal curves demonstrated a fairly symmetric distribution of sizes for males (skewness = - 0.31, kurtosis = - 0.03). The distribution for females was positively skewed (skewness = 0.57, kurtosis = 0.12). Overall, overhang was noted in 16.6% of all size C tibias. The results of this study highlight an implant-specific discrepancy in size availability affecting female patients which could result in inferior outcomes. The authors urge manufacturers to critically assess current implant size distribution availability to ensure both genders are adequately, and equally represented. IV.

Metaphyseal Stem Extension Improves Tibial Stability in Cementless Total Knee Arthroplasty

BackgroundThe goal was to determine if the addition of a metaphyseal stem extension limits micromotion of a cementless tibial component during cyclic loading in primary total knee arthroplasty. The hypothesis tested was that the use of a 50-mm stem extension on a cementless tibial component would limit motion compared with an identical cementless component without a stem extension. MethodsThe study used 3 variations of a tibial component from the same total knee arthroplasty system. Group 1 consisted of a cementless tibial component without a stem extension. Group 2 used the same cementless component as group 1, but with the addition of a short 50-mm stem. Group 3 consisted of a cemented tibial component without a stem extension to serve as a “control” (gold standard). The tibial specimens were implanted into a synthetic bone model and tested using a physiological medial-lateral 60/40 load distribution for 5000 cycles. ResultsThe results demonstrated a significant decrease in motion at the anterior region of the cementless stem extension (group 2) components compared with the cementless with no stem extension (group 1). The cementless with stem extension (group 2) demonstrated similar results at all cycles to the cemented (group 3) components at the anterior region. ConclusionThe addition of a short metaphyseal stem (50mm) to a keel plus 4-peg tibial component design provides a significant reduction in micromotion during cyclic loading of a cementless tibial baseplate in a synthetic foam bone model, similar to a cemented implant.

Comparable surgery time for robotic assisted total knee arthroplasty after initial learning curve

Aims and Objectives:In the past years, further development in knee replacement still continues. Computer-assisted surgery techniques in total knee arthroplasty (TKA) are on the rise. One point of criticism is the prolonged time of surgery and associated cost as known from old techniques like navigation. The primary objective of this study was to determine the learning curve for the time of surgery and accuracy in implant positioning for an imageless robotic system for TKA.Materials and Methods:In this prospective study, the first 30 robotic-assisted TKA from a single senior surgeon were analyzed with regard to time of surgery and accuracy of implant position on the basis of the intraoperative plan and the postoperative x-rays. This data was compared to the last 30 manual TKAs of the same surgeon with the same prosthesis. Evaluation of the learning curve was performed with CUSUM analysis. The time of surgery after finishing the learning curve in the robotic group was compared to the manual group.Results:The learning curve in the robotic group for surgery time was finished after 11 cases. The robotic experience did not affect the accuracy of implant positioning, such as limb alignment and restoration of the joint line. The mean absolute deviation of the postoperative limb alignment to the intraoperative plan was 2° (+/- 1,1). The mean absolute deviation of the medial proximal tibial (mPTA) and distal lateral femoral angle (dLFA) was 1° (+/- 0,9) for both. The mean surgery time in the robotic group after finishing the learning curve was 66 minutes (+/- 4,2) and in the total manual group 67 minutes (+/- 3,5) (n.s.).Conclusion:After finishing the initial learning curve of 11 cases for robotic-assisted TKA the time of surgery is equal to the manual conventional technique. However, there is no learning curve for implant positioning with the imageless robotic system. The implementation of the intraoperative plan is accurate to 1° with the robotic system.