Component In Total Knee Arthroplasty Research Articles

Validation and performance of a machine-learning derived prediction guide for total knee arthroplasty component sizing.

Anticipation of patient-specific component sizes prior to total knee arthroplasty (TKA) is essential to avoid excessive cost associated with additional surgical trays and morbidity associated with imperfect sizing. Current methods of size prediction, including templating, are inconsistent and time-consuming. Machine learning (ML) algorithms may allow for accurate TKA component size prediction with the ability to make predictions in real-time. Consecutive patients receiving primary TKA between 2012 and 2020 from two large tertiary academic and six community hospitals were identified. The primary outcomes were the final femoral and tibial component sizes extracted from automated inventory systems. Five ML algorithms were trained with routinely corrected demographic variables (age, height, weight, body mass index, and sex) using 80% of the study population and internally validated on an independent set of the remaining 20% of patients. Algorithm performance was evaluated through accuracy, mean absolute error (MAE), and root mean-squared error (RMSE). A total of 17,283 patients that received one of 9 TKA implants from independent manufacturers were included. The SGB model accuracy for predicting ± 4-mm of the true femoral anteroposterior diameter was 83.6% and for ± 1 size of the true femoral component size was 95.0%. The SGB model accuracy for predicting ± 4-mm of the true tibial medial/lateral diameter was 83.0% and for ± 1 size of the true tibial component size was 97.8%. Patient sex was the most influential feature in terms of informing the SGB model predictions for both femoral and tibial component sizing. A TKA implant sizing application was subsequently created. Novel machine learning algorithms demonstrated good to excellent performance for predicting TKA component size. Patient sex appears to contribute an important role in predicting TKA size. A web-based real-time prediction application was created capable of integrating patient specific data to predict TKA size, which will require external validation prior to clinical use.

Preoperative planning of total knee arthroplasty: reliability of axial alignment using a three-dimensional planning approach.

Preoperative templating of total knee arthroplasty (TKA) can nowadays be performed three-dimensionally with software solutions using computed tomography (CT) datasets. Currently there is no consensus concerning the axial orientation of TKA components in three-dimensional (3D) planning. To assess intra-/inter-observer reliability of detection of different bony landmarks in planning axial component alignment using axial CT images and 3D reconstructions. Intra- and inter-observer reliability of determination of four predefined axial femoral and tibial axes was calculated using data from CT scans. Axes determination was performed on the axial slices and on the 3D reconstruction using preoperative planning software. In summary, 61 datasets were analyzed by one medical student (intra-observer reliability) and 15 datasets were analyzed by four different observers independently (inter-observer reliability). For the femur, clinical epicondylar axis and posterior condylar axis showed the best reliability with an inter-observer variability of 0.7° and 0.5°, respectively. For the tibia, posterior condylar axis provided best reliability (inter-observer variability: 1.7°). Overall variability was greater for tibial than for femoral axes. Reliability of axis determination was more accurate using axial CT slices rather than 3D reconstructions. The femoral clinical epicondylar axis is highly reliable. Landmarks for the tibia are not as easily identifiable as for the femur. The tibial posterior condylar axis presents the axis with highest reliability. Based on these results, clinical epicondylar axis for orientation of the femoral TKA component and posterior condylar axis for the tibial implant, both defined on axial slices can be recommended.

The effect of anatomical tibia vara on the coronal alignment of tibial component in total knee arthroplasty: A radiographic analysis

Survivorship in total knee arthroplasty depends on the restoration of the coronal alignment of its components. Failure to restore this may decrease the longevity of TKR. The prevalence of tibia vara in patients with osteoarthritis of the knee undergoing TKA is quite high. We wanted to assess the effect of the varus angulation in the proximal metaphysis of the tibia on tibial component malposition in the coronal plane in patients undergoing total knee replacement. Patients who underwent TKA for primary osteoarthritis of the knee and with more than two years of follow-up were included. The extra-articular tibial deformity was assessed by measuring the angle between the anatomical and mechanical axis of the tibia. The coronal alignment of the femoral and tibial components was measured using lateral distal femoral angle and medial proximal tibial angle.Preoperatively,73 (90.12%) patients were having a neutral tibial anatomical axis and 8(9.9%) patients were having varus angulation in the proximal tibia.Postoperatively,18(22.2%) patients had a neutral mechanical axis. There were 14(17.2%) patients with more than 3 degrees of varus mechanical axis and 41(50.6%) patients had less than 3 degrees of varus mechanical axis alignment. 2 (2.5%) patients had more than 3-degree valgus mechanical axis and 6 (7.4%) had less than 3 degrees valgus mechanical axis. Postoperatively, out of 8 patients with pre-operative tibia vara, only 2(25%) patients had neutral placement of the tibial component. 6 (75%) had both tibial and femoral component malalignment. Out of the 73 patients with pre-operatively neutral tibial axis, 40(54.7%) patients had both tibial and femoral component malalignment. 8 (11%) patients had only tibial and 9(12.3%) patients had only femoral component malalignment. In 16 (19.1%) patients, there was no malalignment of both. There was no significant relationship between the tibial anatomical axis malalignment and the tibial component alignment in patients undergoing TKA for primary osteoarthritis.

Treatment Approach for Knee Osteoarthritis with Ipsilateral Femoral Cartilage Tumor: A Case Series

Osteoarthritis (OA) is a common pathology affecting the knee joint. Twenty percent of the cartilaginous tumors of bone are in the distal femur. This presents a challenge for treating patients with knee OA who also have ipsilateral distal femur cartilage tumors. We propose a classification system for knee OA with ipsilateral cartilaginous tumor and a treatment approach to address this issue. Intramedullary guides are avoided when performing total knee arthroplasty (TKA) in these patients so as not to further contaminate the femur with tumor cells. A non-image-based stereotactic surgical system is favored at our institution to achieve this goal. Seven patients underwent classification and treatment with TKA utilizing this approach. Average final follow-up was 15.3 months. Component alignment averaged 89.2° and all patients had 0° of extension with an average flexion to 107.5°. There were no postoperative complications and no radiographic evidence of component complication, tumor recurrence, or tumor expansion. Few studies have reported on the treatment of knee OA with concurrent cartilaginous tumor of the distal femur. All patients treated with the proposed approach had their OA successfully treated without complication related to their cartilaginous tumor or TKA components. This case series presents a novel classification and treatment algorithm to potentially guide arthroplasty surgeons in approaching these often-concurrent occurring pathologies.

Soft tissue impingement at the femorotibial joint after a posterior cruciate ligament-retaining total knee arthroplasty

Abstract Introduction: Impingement of soft tissue at the femorotibial (FT) joint after a total knee arthroplasty (TKA) can lead to poor postoperative performance and pain. In this report, we have described a case of FT joint impingement by scar tissue formation extending over the anterior surface of the intercondylar fossa after a posterior cruciate ligament (PCL)-retaining TKA. Patient concerns: A 78-year-old woman developed crepitations and discomfort during left knee extension and stair climbing at about 10 months after TKA. Diagnosis: Plain radiographs of her knee revealed that the patella baja present from before her TKA had progressed. Impression marks in the distal pole of the patella caused by the impingement of the scar tissue between the femoral component of PCL-retaining TKA and the PCL insertion during knee extension were also observed. The impingement was confirmed by direct arthroscopy. Interventions: We treated her by performing a resection of the scar tissue, excision of the distal pole of the patella, and replacement of the patella. Outcomes: Recovery period was unremarkable, with no recurrence of symptoms over the subsequent 5-year follow-up period. Conclusion: Our case demonstrates that a chronic mechanical irritation can induce proliferation of the residual synovial tissue at the insertion of the PCL. This, in turn, could result in the growth of a scar-like tissue, which could extend over the anterior surface of the intercondylar fossa and grow into the distal pole of the patella, causing an impingement at the FT joint. The presence of a patella baja before TKA could be a risk factor for FT impingement after PCL-retaining TKA, warranting a careful follow-up of these patients.

Influence of radiation conditions on the wear behaviour of Vitamin E treated UHMWPE gliding components for total knee arthroplasty after extended artificial aging and simulated daily patient activities

The long term performance of total knee arthroplasty (TKA) with regards to the bearing materials is related to the aging behaviour of these materials. The use of highly crosslinked materials in hip arthroplasty improved the clinical outcome. Nevertheless, the outcome for these materials compared to conventional UHMWPE (ultra-high molecular weight polyethylene) remains controversial in TKA and alternative bearing materials may be advantageous to improve its outcome in the second and third decade.The aim of this study is the evaluation of the influence of radiation conditions on the wear behaviour of Vitamin E blended UHMWPE gliding components for TKA by simulation of extended aging and high demanding daily patient activities. For a medium radiation dose (30 kGy), the influence of the irradiation type (E-beam or Gamma radiation) and the thermal conditions (room temperature (RT) or heated to 115 °C) are evaluated in comparison to non-irradiated material.Significant influences on the wear behaviour were found for the radiation source and temperature during irradiation. Furthermore, no relevant degradation of the tested materials was observed after extended artificial aging. There was a good correspondence between the wear pattern in this study and retrievals.

'Skywalker' surgical robot for total knee arthroplasty: An experimental sawbone study.

Currently, robot-assisted surgical systems are used to reduce the error range of total knee arthroplasty (TKA) osteotomy and component positioning. We used 20 sawbone models of the femur and 20 sawbone models of the tibia and fibula to evaluate the osteotomy effect of 'Skywalker' robot-assisted TKA. The maximal movement of the cutting jig was less than 0.25mm at each osteotomy plane. The mean and standard deviation values of the angle deviation between the planned osteotomy plane and the actual osteotomy plane at each osteotomy plane were not more than 1.03° and 0.55°, respectively. The mean and standard deviation values of absolute error of resection thickness at each osteotomy position were less than 0.78 and 0.71mm, respectively. The 'Skywalker' system has good osteotomy accuracy, can achieve the planned osteotomy well and is expected to assist surgeons in performing accurate TKA in clinical applications in future.

Pain associated with cemented and uncemented long-stemmed tibial components in revision total knee arthroplasty.

Stemmed tibial components are frequently used in revision total knee arthroplasty (TKA). The purpose of this study was to evaluate patient satisfaction, overall pain, and diaphyseal tibial pain in patients who underwent revision TKA with cemented or uncemented stemmed tibial components. This is a retrospective cohort study involving 110 patients with revision TKA with cemented versus uncemented stemmed tibial components. Patients who underwent revision TKA with stemmed tibial components over a 15-year period at a single institution with at least two-year follow-up were assessed. Pain was evaluated through postal surveys. There were 63 patients with cemented tibial stems and 47 with uncemented stems. Radiographs and Knee Society Scores were used to evaluate for objective findings associated with pain or patient dissatisfaction. Postal surveys were analyzed using Fisher's exact test and the independent-samples t-test. Logistic regression was used to adjust for age, sex, and preoperative bone loss. No statistically significant differences in stem length, operative side, or indications for revision were found between the two cohorts. Tibial pain at the end of the stem was present in 25.3% (16/63) of cemented stems and 25.5% (12/47) of uncemented stems (p = 1.000); 74.6% (47/63) of cemented patients and 78.7% (37/47) of uncemented patients were satisfied following revision TKA (p = 0.657). There were no differences in patient satisfaction, overall pain, and diaphyseal tibial pain in cemented and uncemented stemmed tibial components in revision TKA. Patient factors, rather than implant selection and surgical technique, likely play a large role in the presence of postoperative pain. Stemmed tibial components have been shown to be a possible source of pain in revision TKA. There is no difference in patient satisfaction or postoperative pain with cemented or uncemented stemmed tibial components in revision TKA. Cite this article: Bone Joint J2021;103-B(6 Supple A):165-170.

Reliability of tibial anterior crest as the anatomical reference of rotating alignment for tibial component in total knee arthroplasty

This study aimed to research whether anterior tibial crest is a reliable anatomical reference for rotational alignment of tibial component in TKA. The study included 122 patients who underwent computed tomography angiography (CTA) examination for unilateral lower extremity trauma with normal contralateral lower extremities, including 89 males and 33 females, with an average age of(51.4±16.4) years old(ranged 18 to 81 years old). Picture archiving and communication system (PACS) was used to mark 11 lines including the surgical epicondylar axis (SEA) connecting the most prominent points of the lateral epicondyle and the deepest point of the sulcus on the medial epicondyle of the femur, axis of medial border of patellar tendon (MEPT)connecting the middle of the posterior cruciate ligament (PCL) and medial border of the patellar tendon at the level of a standard tibial cut from 8 mm distal of the lateral tibial joint surface, transverse axis of tibia (TAT) at the level of a standard tibial cut from 8 mm distal of the lateral tibial joint surface, Akagi line connecting the projected middle of the PCL and medial border of the patellar tendon at the tibial attachment, the axis of the medial 1/3 of patellar tendon(M1/3) connecting the projected middle of PCL and the medial 1/3 of the patellar tendon at the patellar tendon attachment level, Insall line connecting the projected middle of the PCL and the medial 1/3 of tibial tubercle, the axis of medial border of tibial tubercle (MBTT) connecting the projected middle of the PCL and medial border of tibial tubercle, as well as the axis of the proximal anterior tibial crest (PATC), axis 1 of the middle anterior tibial crest (MATC1), axis 2 of the middle anterior tibial crest (MATC2) and the axis of the distal anterior tibial crest (DATC) which were marked by connecting the 4 equidistant points on the sharp anterior tibial crest and the projected middle of the PCL. The angles between TAT and SEA as well as the angles between other axes and the perpendicular to SEA were measured. Pairwise differences among the 10 tibial axes were examined using One-Way ANOVA and paired t-test. The angles between the axes of MEPT, Akagi line, M1/3, Insall line, MBTT, PATC, MATC1, MATC2, DATC and the perpendicular to SEA were (-1.6 ±4.5)° , (1.4 ±5.0)° , (10.2±5.1)°, (11.9±5.4)°, (3.6±4.8)°, (12.0±6.9)°, (7.2±8.6)°, (7.1±10.4)°, (6.6±13.5)°, respectively. The angle between TAT and SEA was (4.1±5.3)°. MEPT was external rotation compared to SEA. M1/3, Insall line and PATC were significantly greater than Akagi line, MBTT, TAT (P<0.001). MATC1, MATC2 and DATC were also significantly greater than Akagi line, MBTT axis and TAT (P<0.001). However, MATC1, MATC2 and DATC were also significantly less than M1/3 axis, Insall line and PATC(P<0.01). There were no significant statistical differences between MATC1, MATC2 and DATC(P>0.05). The middle tibial anterior crest can be used as a reference for rotational alignment of tibial component in TKA, and its reliability is better than Insall line, but worse than Akagi line, TAT and MBTT.

Soft tissue releasing and serial casting for management of flexion contracture after primary total knee arthroplasty in a patient with hemophilia.

Introduction and importanceFlexion contracture following total knee arthroplasty (TKA) in patients with hemophilia is not uncommon, and this complication reduces knee range of motion and produces morbidity for the patient. This report states the success of treatment of flexion contracture after primary TKA in a patient with hemophilia; by open soft tissue contracture releasing and serial casting.Case presentationA 20-year-old-man presented with hemophilia type A. He had undergone TKA for treatment of secondary osteoarthritis, following chronic hemophilic arthropathy of his right knee. After surgery, the patient had progressive flexion contracture posture, until he had 45 degrees of knee flexion contracture at his 3 month follow up. The patient received open soft tissue releasing, then serial casting for 6 weeks. After this, the cast was removed and he continued with a home rehabilitation program. At 1 year follow, his knee flexion contraction contracture had improved up to 10 degrees. The patients function had recovered and he was satisfied with this treatment.Clinical discussionThe complications after TKA in patients with hemophilia are very challenging in there management; with flexion contracture after TKA being a common complication in patients with hemophilia.ConclusionIn severe flexion contracture following TKA, soft tissue releasing combined with serial casting is effective, and might be an option that is less invasive than revising all of the TKA components.

Two-year RSA migration results of symmetrical and asymmetrical tibial components in total knee arthroplasty: a randomized controlled trial.

The objective of this study was to compare the two-year migration pattern and clinical outcomes of a total knee arthroplasty (TKA) with an asymmetrical tibial design (Persona PS) and a well-proven TKA with a symmetrical tibial design (NexGen LPS). A randomized controlled radiostereometric analysis (RSA) trial was conducted including 75 cemented posterior-stabilized TKAs. Implant migration was measured with RSA. Maximum total point motion (MTPM), translations, rotations, clinical outcomes, and patient-reported outcome measures (PROMs) were assessed at one week postoperatively and at three, six, 12, and 24 months postoperatively. A linear mixed-effect model using RSA data of 31 asymmetrical and 38 symmetrical TKAs did not show a difference in mean MTPM migration pattern of the tibial or femoral components. Mean tibial component MTPM at two years postoperative of the asymmetrical TKA design was 0.93 mm and 1.00 mm for the symmetrical design. For the femoral component these values were 1.04 mm and 1.14 mm, respectively. No significant differences were observed in other migration parameters or in clinical and PROM measurements. The TKA design with an asymmetrical tibial component has comparable component migration with the proven TKA with a symmetrical tibial component. This suggests the risk of long-term aseptic loosening of the two designs is comparable. Cite this article: Bone Joint J2021;103-B(5):855-863.

Correlations of typical pain patterns with SPECT/CT findings in unhappy patients after total knee arthroplasty

PurposeThe diagnostic process in patients after painful total knee arthroplasty (TKA) is challenging. The more clinical and radiological information about a patient with pain after TKA is included in the assessment, the more reliable and sustainable the advice regarding TKA revision can be. The primary aim was to investigate the position of TKA components and evaluate bone tracer uptake (BTU) using pre-revision SPECT/CT and correlate these findings with previously published pain patterns in painful patients after TKA.MethodsA prospectively collected cohort of 83 painful primary TKA patients was retrospectively evaluated. All patients followed a standardized diagnostic algorithm including 99m-Tc-HDP-SPECT/CT, which led to a diagnosis indicating revision surgery. Pain character, location, dynamics and radiation were systematically assessed as well as TKA component position in 3D-CT. BTU was anatomically localized and quantified using a validated localization scheme. Component positioning and BTU were correlated with pain characteristics using non-parametric Spearman correlations (p < 0.05).ResultsBased on Spearman’s rho, significant correlations were found between pain and patients characteristics and SPECT/CT findings resulting in nine specific patterns. The most outstanding ones include: Pattern 1: More flexion in the femoral component correlated with tender/splitting pain and patella-related pathologies. Pattern 3: More varus in the femoral component correlated with dull/heavy and tingling/stinging pain during descending stairs, unloading and long sitting in patients with high BMI and unresurfaced patella. Pattern 6: More posterior slope in the tibial component correlated with constant pain.ConclusionThe results of this study help to place component positioning in the overall context of the "painful knee arthroplasty" including specific pain patterns. The findings further differentiate the clinical picture of a painful TKA. Knowing these patterns enables a prediction of the cause of the pain to be made as early as possible in the diagnostic process before the state of pain becomes chronic.Level of evidenceLevel III

Intra- and inter\u2010observer reliability of implant positioning evaluation on a CT-based three\u2010dimensional postoperative matching system for total knee arthroplasty

BackgroundThe evaluation of postoperative total knee arthroplasty (TKA) alignment mainly relies on measurement data obtained from plain radiographs. The aim of this retrospective observational study was to document the intra- and inter-observer reliability in assessment of TKA component positioning after surgery using a three-dimensional (3D) computed tomography (CT) image matching system.MethodsFourteen knees from 14 patients who received primary TKA were included, and images were analyzed by blinded readers not associated with the surgeries. The examiner digitized the reference points according to defined landmarks, and the designated size component was superimposed to the 3D reconstructed CT model for measurement. In addition to the evaluation of implant position against the coronal and sagittal lower limb mechanical axes that were defined based on bony landmarks, implant position against axes connecting implant-based reference points that are easier to indicate was evaluated.ResultsThe overall intra- and inter-observer reliabilities determined by the intraclass correlation coefficients (ICC) of the implant alignment measurement for both femoral and tibial components were good (ICC > 0.60), except in the direction of femoral flexion and extension, for both mechanical and implant-based axes. The difference between implant alignment measurements according to the traditional mechanical axis and the implant-based axis ranged between means of 0.08o and 1.70o and were statistically significantly different.ConclusionsThe postoperative evaluation of implant position in the coronal and sagittal planes using 3D-CT image matching is reliable and has good reproducibility except for the sagittal alignment assessment of the femoral component. The measured implant position according to the traditional mechanical axis and the implant-based axis were slightly but significantly different.

Evaluation of an operation support system using the femoral anterior tangent line to determine intraoperative femoral component rotation in total knee arthroplasty

BackgroundThe femoral anterior tangent (FAT) line refers to a line parallel to the anterior surface of the distal femur in the axial plane. This study aimed to evaluate the effectiveness of a new operation support system which uses the FAT line to set the femoral component rotational alignment in total knee arthroplasty (TKA). MethodsA total of 170 consecutive knees in 139 patients undergoing primary TKA with the JIGEN (Jig Engaged Three-dimensional (3D) Pre-Operative Planning Software for TKA) operation support system was examined. The JIGEN system creates 3D models of bones using computed tomography data, allowing for surgical simulations such as positioning of implants while calculating positions of the intramedullary alignment rod (IM rod) and surgical jig. We retrospectively analyzed the FAT line angle relative to the surgical epicondylar axis (SEA) on the axis plane perpendicular to the IM rod and evaluated the accuracy of the femoral component alignment after TKA with the 3D measurement system. ResultsThe FAT line was 9.6° ± 3.7° (range, 1.4°–20.4°) internally rotated relative to the SEA. The average absolute error was 1.4° ± 1.1° in the coronal plane, 2.0° ± 1.5° in the sagittal plane, and 1.6° ± 1.3° in the axial plane. The femoral component outliers (i.e., >3° away from the goal alignment) were 7.7% in the coronal plane, 20.6% in the sagittal plane, and 10.3% in the axial plane. ConclusionsOur findings suggest that the FAT line is a reliable and reproducibly identifiable axis for the accurate determination of proper rotational alignment in TKA. An operation support system which uses the FAT line for determining intraoperative femoral component rotation can effectively achieve highly accurate positioning of the femoral component in TKA.

Comparing the effect of tourniquet and tranexamic acid on the tibial cement mantle thickness in total knee arthroplasty.

This study aims to determine the efficacy of both tranexamic acid (TXA) and tourniquet on the tibial cement mantlethickness in total knee arthroplasty (TKA). We retrospectively reviewed the recorded data of patients with primary end-stage knee osteoarthritis who underwent TKA procedure during 2014-2016 at a single institution to evaluate the tibial cement mantle. Patients were categorized in two groups based on the use of tourniquet (groups 1 and 2). In addition, these groups were categorized into two different subgroups based on the use of TXA in groups 1 and 2 (group 1-A, B and group 2-A, B). Four zones at the tibial baseplate on the anteroposterior view and two zones on the lateral view were measured at the 4-6-week postoperative visit. A total of 28 patients (30 knees) were operated using tourniquet and TXA (group 1-A), 29 (30 knees) using tourniquet without TXA (group 1-B), 24 (28 knees) using TXA without tourniquet (group 2-A), and 38 (42 knees) without using TXA and tourniquet (group 2-B). Although a significant difference was found in the cumulative cement mantle penetration on postoperative X-rays between groups 1 and 2, no significant differences were found between groups A and B in both groups. This study reports that tourniquet use in TKA increased cement mantle penetration of the tibial component in primary TKA. The main strength of this study was that the TXA use alone exhibited no significant effect on the cement thickness.

Tobacco Exposure Is Associated With Extremely Low Polyethylene Oxidation in Total Knee Arthroplasty Components.

BackgroundWe evaluate whether patient exposures such as tobacco use are associated with high systemic or local in vivo oxidative state and with increased in vivo polyethylene oxidation.MethodsWe performed a case-control study which evaluated clinical factors associated with high systemic or local in vivo oxidative state among patients whose implants have been identified as demonstrating either extreme or minimal oxidation by our implant retrieval laboratory. Analysis of more than 2500 tibial inserts from explanted total knee arthroplasty demonstrated a wide spectrum of polyethylene oxidation. Components from some patients exhibited extremely high oxidation rates (super-oxidizers), and components from other patients demonstrated negligible oxidation (nonoxidizers). Patients’ clinical data were retrospectively investigated from a prospectively collected institutional database.ResultsEighteen patients met criteria as either super-oxidizers (9) or nonoxidizers (9). Average time in vivo was 6.6 (±4.4) years. Reasons for removal were aseptic loosening (10), instability (3), infection (2), component malposition (1), massive osteolysis (1), and other (1). Chi-square for categorical predictors demonstrated that nonoxidizer patients were significantly more likely to be current smokers than super-oxidizers (6 vs 0, P = .012). No other free radical–associated variables were significantly different across oxidation groups.ConclusionThere was a significant association between extremely low ultra-high-molecular-weight polyethylene oxidation and current smoking.

Custom-made 3D printed patient specific guides (PSG) improves component axial alignment in total knee arthroplasty (TKA)

BackgroundUsage of Patient Specific Instrumentation (PSI) or Patient Specific Guides (PSG) in TKA has evolved rapidly in the past decade. Restoration of Mechanical axis in TKA is vital to achieve good functional outcome and long term implant survival. We carried out a comparative study to assess the efficacy of PSG in achieving neutral axial alignment and its impact on early functional outcomes compared to Conventional Instrumentation (CI). MethodsPatients eligible as per study design (n = 100) undergoing TKA were randomized and divided in two equal groups which were matched in baseline demographics and clinical profile. All the patients in the PSG group (n = 50) and conventional instrumentation (CI) group (n = 50) underwent TKA with same implant. Pre-operative CT scans done as per specified protocol to acquire image data for 3D printing PSG. Duration of surgery and post-operative Hip-Knee-Ankle (HKA) angles achieved in the two groups was compared. Post-operative functional outcomes were assessed using WOMAC scores. ResultsThere was statistically significant difference in the mean post-operative axial alignment achieved between the two groups (p = 0.041). Outliers (180 ± 3 deg) of HKA angle were more in the CI Group (p = 0.007). There was no difference in functional outcomes between the two groups at one year. Duration of surgery was significantly less in PSG Group (p < 0.001). Conclusion3D printed PSG are superior in achieving neutral HKA axis as compared to CI in TKA. Better axial alignment of TKA components does not correlate with better patient reported functional outcomes. PSG use significantly reduces surgical time.

Circle-based model to estimate error in using the lowest points to indicate locations of contact developed by the femoral condyles on the tibial insert in total knee arthroplasty

A common method used to study tibiofemoral joint biomechanics following total knee arthroplasty (TKA) is the lowest point method, which finds the lowest points of each femoral condyle in relation to the plane of the resected tibia. The objectives of this paper were twofold: 1) to use a circle-based model to demonstrate the large inherent error introduced when the lowest points are used to indicate anterior-posterior (AP) positions of contact by the femur on the tibial insert, 2) to use the circle-based model to estimate the magnitude of error. A circle-based model was created to simulate articular surfaces of the tibial insert and condyles of the femoral component and to demonstrate the error. Equations relating the error to radii of tibial and femoral articular surfaces were derived. The magnitude of the error was estimated for common low-conforming TKA components by determining radii using best-fit circles to approximate curvature of articular surfaces. Error in AP tibial insert contact locations is caused by the slope of the tibial articular surface and the magnitude increases with increasing slope and increasing radius of the femoral condyle. For radii approximating articular surfaces of common low-conforming components, relative errors range from 45% to 109%. The circle-based model effectively demonstrates the cause of the large error in using lowest points to indicate AP tibial insert contact locations and enables an estimate of relative error. Because relative error exceeds 45%, the lowest point method should not be used to indicate the AP tibial insert contact locations.

Machine Learning Algorithms Identify Optimal Sagittal Component Position in Total Knee Arthroplasty

BackgroundAdvanced technologies, like robotics, provide enhanced precision for implanting total knee arthroplasty (TKA) components; however, the optimal targets for implant position specifically in the sagittal plane do not exist. This study identified sagittal implant position which may predict improved outcomes using machine learning algorithms. MethodsA retrospective review of 1091 consecutive TKAs was performed. All TKAs were posterior cruciate ligament retaining or sacrificing with an anterior-lip (49.4%) or conforming bearing (50.6%) and performed with modern perioperative protocols. Preoperative and postoperative tibial slope and postoperative femoral component flexion were measured with standardized radiographic protocols. Analysis groups were categorized by satisfaction scores and the Knee Society Score question ‘does this knee feel normal to you?’ Machine learning algorithms were used to identify optimal sagittal alignment zones that predict superior satisfaction and knees “always feeling normal” scores. ResultsMean age and median body mass index were 66 years and 34 kg/m2, respectively, with 67% being female. The machine learning model predicted an increased likelihood of being “satisfied or very satisfied” and a knee “always feeling normal” with a change in tibial slope closer to native (−2 to +2°) and femoral component flexion 0 to +7°. Worse outcomes were predicted with any femoral component extension, femoral component flexion beyond +10°, and adding or removing >5° of native tibial slope. ConclusionSuperior patient-reported outcomes were predicted with approximating native tibial slope and incorporating some femoral component flexion. Deviation from native tibial slope and excessive femoral flexion or any femoral component extension were predictive of worse outcomes. Level of EvidenceTherapeutic level III.

Tibial component coverage affects tibial bone resorption and patient-reported outcome measures for patients following total knee arthroplasty

PurposeThe aim of this study is to investigate the prognostic value of tibial component coverage (over-hang and under-hang) and the alignment of total knee arthroplasty (TKA) components 1 week after surgery. We select patient-reported outcome measures (PROMS) (the Knee Society score (KSS score) and the Western Ontario and McMaster Universities Osteoarthritis Index-pain score (WOMAC pain score)) and tibial bone resorption (TBR) 2 years after surgery as the end points.MethodsThe study retrospectively analyzed 109 patients undergoing TKA (fixed-bearing prosthesis with asymmetrical tibial tray) from January 2014 to December 2017 in Huashan Hospital. By using standard long-leg X-rays, anteroposterior (AP) and lateral X-rays of the knee, tibial component coverage (under-hang or over-hang), AP tibial-femoral anatomical angle (AP-TFA), AP femoral angle (AP-FA), AP tibial angle (AP-TA), and lateral tibial angle (L-TA) were measured at 1 week after surgery, while TBR was measured through postoperative 1-week and 2-year AP and lateral radiographs of the knee on three sides (medial side, lateral side on AP radiograph, and anterior side on lateral radiograph). The Pearson correlation analysis, simple linear regression, multiple linear regression, the Student’s t test, and one-way ANOVA together with Tukey’s post hoc test (or Games-Howell post hoc test) were used in the analyses.ResultsTibial under-hang was more likely to appear in our patients following TKA (42%, medially, 39%, laterally, and 25%, anteriorly). In multivariate linear regression analysis of TBR, tibial under-hang (negative value) 1 week after surgery was positively correlated with TBR 2 years later on the medial (p = 0.003) and lateral (p = 0.026) side. Tibial over-hang (positive value) 1 week after surgery on the medial side was found negatively related with KSS score (p = 0.004) and positively related with WOMAC pain score (p = 0.036) 2 years later in multivariate linear regression analysis of PROMS. Both scores were better in the anatomically sized group than in the mild over-hang group (or severe over-hang) (p < 0.001). However, no significant relationship was found between the alignment of TKA components at 1 week after surgery and the end points (TBR and PROMS) 2 years later.ConclusionUnder-hang of the tibial component on both the medial and lateral sides can increase the risk of TBR 2 years later. Over-hang of tibial component on the medial side decreases the PROMS (KSS score and WOMAC pain score) 2 years later. An appropriate size of tibial component during TKA is extremely important for patient’s prognosis, while the alignment of components might not be as important.