Femoral Component Research Articles

Total hip arthroplasty in patients with coxarthrosis due to developmental dysplasia of the hip: Is fixation of the subtrochanteric osteotomy necessary?

This study aims to analyze the clinical, functional, and radiographic results of patients with Crowe type IV developmental dysplasia of the hip (DDH) sequelae undergoing cementless total hip arthroplasty (THA) with transverse subtrochanteric shortening osteotomy without fixation at the osteotomy site. Between March 2013 and February 2020, a total of 42 hips of 34 patients (8 males, 26 females; mean age: 50.7±11.7 years; range, 27 to 76 years) with Crowe type IV DDH treated with subtrochanteric shortening osteotomy combined with primary cementless THA were retrospectively analyzed. Each case was evaluated to the Harris Hip Score (HHS). Crowe classification, location of the rotation center of hip, loosening of the implants, and union at the osteotomy line were evaluated radiologically. The mean follow-up was 57.9±31.5 (range, 24 to 192) months. The mean interval to complete bone union in 40 hips (95%) after surgery was 3.5±0.9 (range, 2 to 6) months. The mean preoperative HHS scores of the patients was 35.6±6.86, while the scores increased to 91.53±5.41 at the final follow-up (p<0.001). Our study results suggest that excellent clinical and radiological results can be obtained in Crowe type IV dysplastic hips in patients undergoing THA with the rectangular femoral component and transverse shortening osteotomy technique, without fixation at the osteotomy site.

Preoperative predictors of implant size in patients undergoing total knee arthroplasty: a retrospective cohort study

BackgroundTraditionally, the size of total knee arthroplasty (TKA) components is predicted by preoperative radiographic templating, which is of limited accuracy. This study aimed to evaluate the role of demographic data and ankle volume in predicting implant size in TKA candidates.MethodsIn a retrospective study, 415 patients who underwent TKA at a single institution were included. The mean age of the patients was 67.5 ± 7.1 years. The mean BMI of the patients was 31.1 ± 4.7 kg/m2. TKA implants were Zimmer Biomet NexGen LPS-Flex Knee in all cases. The demographic data included age, sex, height, weight, BMI, ethnicity, and ankle volume. Ankle volume was assessed with the figure-of-eight method. Multivariate linear regression analysis was used for predicting factors of implant size.ResultsMultivariate linear regression analysis showed that the Sex (β:1.41, P < 0.001), height (β:0.058, P < 0.001), ankle volume (β:0.11, P < 0.001), and Age (β:0.017, P = 0.004) were significant predictors of tibial component size. Sex (β:0.89, P < 0.001), height (β:0.035, P < 0.001), and ankle volume(β:0.091, P < 0.001) were significant predictors of femoral component size in the multivariate analysis.ConclusionDemographic data, adjunct with the ankle volume, could provide a promising model for preoperative prediction of the size of tibial and femoral components in TKA candidates.

The Effects of Different Femoral Component Materials on Bone and Implant Response in Total Knee Arthroplasty: A Finite Element Analysis.

Due to the high stiffness of the biomaterials used in total knee arthroplasty, stress shielding can lead to decreased periprosthetic bone mineral density and bone resorption. As different materials and 3D-printed highly porous surfaces are available for knee femoral components from the industry nowadays, this study aimed to compare the effects of two same-design cruciate-retaining femoral components, made with CoCr and titanium alloy, respectively, on periprosthetic bone stresses through a finite element model of the implanted knee in order to evaluate the induced stress shielding. Moreover, the effect of the cementless highly porous surface of the titanium implant was analyzed in comparison to the cemented interface of the CoCr implant. The von Mises stresses were analyzed in different periprosthetic regions of interest of the femur with different configurations and knee flexion angles. The titanium component induced higher bone stresses in comparison with the CoCr component, mostly in the medial compartment at higher knee flexion angles; therefore, the CoCr component led to more stress shielding. The model was revealed to be effective in describing the effects of different femoral component materials on bone stress, highlighting how a cementless, highly porous titanium femoral component might lead to less stress shielding in comparison to a cemented CoCr implant with significant clinical relevance and reduced bone resorption after total knee arthroplasty.

Comparison of cementless twin-peg, cemented twin-peg and cemented single-peg femoral component migration after medial unicompartmental knee replacement: a 5-year randomized RSA study

BackgroundThe component design and fixation method of joint arthroplasty may affect component migration and survival. The aim of this study was to compare fixation of cementless twin-peg (CLTP), cemented twin-peg (CTP) and cemented single-peg (CSP) femoral components of medial unicompartmental knee replacement (UKR).MethodsEighty patients (mean age = 63 years, 48 males) with medial knee osteoarthritis were randomized in three ways to CLTP (n = 25), CTP (n = 26) or CSP (n = 29) femoral UKR components. The patients were followed 5 years postoperatively with RSA, bone mineral density (BMD), PROMs and radiological evaluation of radiolucent lines (RLL), femoral component flexion angle and complications.ResultsAt the 5-year follow-up, femoral component total translation was comparable between the three groups (p = 0.60). Femoral component internal rotation was 0.50° (95% CI 0.3; 0.69) for the CLTP group, 0.58° (95% CI 0.38; 0.77) for the CTP group and 0.25° (95% CI 0.07; 0.43) for the CSP group (p = 0.01). BMD decreased peri-prosthetically (range − 11.5%; − 14.0%) until 6-month follow-up and increased toward the 5-year follow-up (range − 3.6%; − 5.8%). BMD change did not correlate with component migration. Lower flexion angle was correlated with higher 5-year subsidence, total translation, varus rotation and maximum total point motion (p = 0.01). Two patients (1 CLTP, 1 CTP) had RLL in the posterior zone. There were two revisions.ConclusionAt 5-year follow-up, fixation of UKA femoral components with twin-peg was not superior to the single-peg design. Cementless and cemented twin-peg femoral components had similar fixation. A lower flexion angle was correlated with higher component migration.

Image-free handheld robotic-assisted technology improved the accuracy of implant positioning compared to conventional instrumentation in patients undergoing simultaneous bilateral total knee arthroplasty, without additional benefits in improvement of clinical outcomes

PurposeThe purpose of this study was to compare the clinical and radiological outcomes in patients who underwent simultaneous bilateral total knee arthroplasty (SB-TKA) using either robotic-assisted TKA (RA-TKA) or conventional TKA (C-TKA).MethodsIncluded were the patients who underwent SB-TKA between January 2018 and January 2020 and had a minimum follow-up of 2 years. Of 151 patients included, 117 patients were operated using an image-free handheld robotic sculpting system (RA-TKA group) and 34 patients operated using conventional instrumentation (C-TKA group). The key outcomes noted were multiple patient-reported outcomes (PROs), adverse events, and radiological outcomes. Two investigators independently measured the radiological outcomes on pre- and post-operative radiographs in coronal plane (medial proximal tibial angle [MPTA] and anatomic lateral distal femoral angle [aLDFA]) and sagittal plane (posterior tibial slope [PTS] and posterior condylar offset [PCO]). The chi-square test was used to examine categorical variables. Student’s t test was used to analyze the continuous variables.ResultsPatients in both groups were similar in baseline characteristics (gender, body mass index, incidence of comorbidities, and length of hospital stay) except that RA-TKA group patients younger (66.7 ± 8.9 vs 70.4 ± 10.5, P = 0.037) than C-TKA group. The operative time was longer in RA-TKA group as compared to C-TKA (189.3 ± 37.1 vs 175.0 ± 28.2, P = 0.040). The final PROs at each were similar between the two groups (P > 0.05). The values of PROs at final follow-up in RA-TKA compared to C-TKA were VAS pain (0.4 ± 0.9 vs 0.4 ± 0.5), KOOS-JR (89.3 ± 5.8 vs 87.1 ± 5.3), and physical (55.9 ± 2.8 vs 55.4 ± 3.2), mental (61.1 ± 4.4 vs 60.2 ± 4.7) component of VR-12 scores, and KSS satisfaction (37.5 ± 1.1 vs 37.1 ± 2.2) (all P > 0.50 or non-significant [n.s.]). While one patient in RA-TKA required revision of femoral component for peri-prosthetic fracture, none of the patient in conventional group were revised (0.85% vs 0%, P = n.s.). The proportion of patients with outliers in RA-TKA group was lower for aLDFA (2.6% vs 22.1%, P < 0.01) and PTS (0% vs 35%, P < 0.01).ConclusionThis comparative study in patients undergoing SB-TKA found reduction of outliers in femoral and tibial implant positioning with RA-TKA as compared to C-TKA. There were no differences in both groups for pain, function, and satisfaction at a minimum of 2 years of follow-up.Level of evidenceIII Therapeutic Study.

Accuracy and outcome of a handheld accelerometer-based navigation device compared to conventional alignment method in total knee arthroplasty in a Chinese population

Background Total knee arthroplasty (TKA) is a successful procedure in treatment of degenerative disease of the knee, and optimal component placement is essential for long-term implant survival. The purpose of this study was to compare the accuracy of the accelerometer-based KneeAlign 2 (KA2) navigation system against conventional methods for accurate positioning of the femoral and tibial components in TKA in a Chinese population. Methods A total of 123 (37 conventional and 86 KA2) cases of elective primary TKA were reviewed. Hip-knee-ankle (HKA) angle, mechanical lateral distal femoral angle (mLDFA), and anatomical lateral distal femoral angle (aLDFA) were measured from hip-to-ankle EOS radiographs. Accuracy of conventional alignment and KA2 navigation system was assessed by measuring the difference between intraoperative goal and postoperative radiographic measurements of the components for each respective case. Results There was no significant difference between conventional alignment methods and KA2 navigation in achieving a neutral mechanical alignment of the lower limb. KA2 navigation was significantly more accurate than conventional alignment methods for optimal positioning of the tibial component in both the coronal and sagittal plane, while no significant difference between the two groups was appreciated in the positioning of the femoral component in the coronal plane. Conclusions TKA using the accelerometer-based KA2 system was found to offer a high degree of accuracy in component alignment, and in particular, significantly improved tibial component alignment in comparison with conventional alignment methods in a Chinese population. However, no significant improvements were observed in neutral mechanical axis of the lower limb alignment and femoral component placement in the coronal plane.

A 15-YEAR SURVIVAL ANALYSIS OF OXIDIZED ZIRCONIUM TOTAL KNEE ARTHROPLASTY

AbstractBackgroundOxidized zirconium (OxZr) has been introduced as an alternative bearing for femoral components in Total Knee Arthroplasty (TKA). It has a ceramic-like zirconium oxide outer layer with a low coefficient of friction. Early studies have found OxZr TKA to have a low incidence of early failure in young high demand patients. Currently no study has reported on the outcome of these implants beyond ten years.ObjectivesThe purpose of our study was to present an in-depth 15-year survival analysis of cemented Profix II OxZr TKA.Study Design &amp; MethodsData was collected prospectively and survival analysis undertaken with multiple strict end points. Complication rates were recorded and patient reported outcomes were measured.Results617 Profix II OxZr TKAs were performed over four years. Forty-nine patients underwent reoperation. Aseptic tibial loosening was the most common cause of failure (32.7%) on average occurring 2.8 years post primary procedure. There was one recorded failure due to loosening of the zirconium femoral component. Revision rate at 15-years was 6.38%. Cumulative survivorship was 91.52% with failure considered to be reoperation for any reason. WOMAC score improved in 86% of patients by year 1. The average score improved by 21.2 points and met the standard for minimum clinically important difference.ConclusionsThis study presents the first 15-year survival analysis of cemented Profix II OxZr TKA. Our data supports current literature on the long-term survivorship of oxidised zirconium total knee replacements.

POLYETHYLENE BEARING WEAR OF THE OXFORD UNICOMPARTMENTAL KNEE ARTHROPLASTY: TEN-YEAR RESULTS OF A RANDOMIZED CONTROLLED TRIAL COMPARING CEMENTED AND CEMENTLESS FIXATION

AbstractIntroductionThe Oxford Unicompartmental Knee Replacement's (OUKR's) fully-congruent design minimises polyethylene wear. Consequently, wear is a rare failure mechanism. Phase-3 OUKR linear wear at 5 years was higher than previous OUKR phases, but very low compared to fixed-bearing UKRs. This study aimed to measure OUKR bearing wear at 10 years and investigate factors that may affect wear.MethodologyBearing thickness for 39 OUKRs from a randomised study was calculated using radiostereometric analysis at regular intervals up to 10 years. Data for 39 and 29 OUKRs was available at 5 and 10 years, respectively. As creep occurs early, wear rate was calculated using linear regression between 6 months and 10 years. Relationships between wear and patient factors, fixation method, Oxford Knee Score (OKS), bearing position, and component position were analysed.ResultsThe mean wear rate was 0.06mm/year. Fixation method, age, OKS, component size, and bearing size had no correlation with wear. A higher BMI was associated with lower wear (p=0.01). Bearings more than 4mm from the wall had significantly more wear (p=0.04) than those less than 4mm from the wall. There was a linear correlation between the femoral component contact area on the bearing and wear (p=0.04).ConclusionsPhase-3 bearing wear rate is constant, significantly higher than previous OUKR phases at 10 years, and may increase the risk of long-term bearing failure. To minimise complications associated with wear, size 4 bearings should be used in young patients and manufacturing bearings from more durable, highly crosslinked polyethylene should be studied.

NOVEL ROBOTIC TECHNIQUE TO INVESTIGATE TOTAL KNEE ARTHROPLASTY STABILITY

AbstractIntroductionMid-flexion instability may cause poor outcomes following TKA. Surgical technique, patient-specific factors, and implant design could all contribute to it, with modelling and fluoroscopy data suggesting the latter may be the root cause. However, current implants all pass the preclinical stability testing standards, making it difficult to understand the effects of implant design on instability. We hypothesized that a more physiological test, analysing functional stability across the range of knee flexion-extension, could delineate the effects of design, independent of surgical technique and patient-specific factors.MethodsUsing a SIMvitro-controlled six-degree-of-freedom robot, a dynamic stability test was developed, including continuous flexion and reporting data in a trans-epicondylar axis system. 3 femoral geometries were tested: gradually reducing radius, multi-radius and single-radius, with their respective tibial inserts. 710N of compression force (body weight) was applied to the implants as they were flexed from 0–140° with three levels of anterior/posterior (AP) tibial force applied (−90N,0N,90N).ResultsWhile in static tests, the implants performed similarly, functional stability testing revealed different paths of motion and AP laxities throughout the flexion cycle. Some designs exhibited mid-flexion instability, while others did not: the multi-radius design allowed increased AP laxity as it transitioned to each arc of reduced femoral component radius; the single-radius design had low tibial bearing conformity, allowing 16mm difference in the paths of mid-flexion versus extension motion.ConclusionsPreclinical lab testing reveals functional differences between different design philosophies. Implant design impacts kinematics and mid-flexion stability, even before factoring in surgical technique and patient-specific factors.

The Accuracy of Digital Preoperative Templating in Primary Total Hip Replacements.

Background​ Digital templating is an essential part of preoperative planning in elective total hip replacement (THR) surgery. The goals of templating are to predict femoral and acetabular implant sizes, to assess leg length, offset, and implant positioning. Templating markers such as the KingMark device (Brainlab, Munich, Germany) have been developed to improve the accuracy. Although templating is commonly used in many centres, there are challenges related to the accuracy of the process, such as true magnification ideal positioning of the pelvis and hips/body habit (obesity). Objectives The aim of this study was to assess the accuracy of preoperative templating in THR patients, and to assess the difference between templating performed with and without the KingMark device. Methods​ Our retrospective study included 642 consecutive patients who had primary THR at the Royal Bournemouth Hospital in the UK. Four hundred fifty-three (71%) of patients had the KingMark device on their templated radiographs. Patients who had hybrid total hip replacements using an uncemented acetabular component and cemented femoral component were included in the study. Digital templating was done using TraumaCad software (Brainlab). Analysis of the accuracy of predicting component size has been evaluated by comparing preoperative planned sizes with implanted sizes as documented by the surgeons and labels attached to the operative note. ​ ​Results​ The templated size corresponded to the actual femoral implant used in approximately 65.2% of cases. When femoral prostheses within one size above or below the templated size were included,​the accuracy of preoperative templating rose to 97.2%. Regarding the uncemented acetabular component, the templated size corresponded to the actual acetabular implant used in 46.3% of cases. When acetabular cup within one size above or below the templated size were included, the accuracy of preoperative templating rose to 87.5%. Similarly, there was minimal difference between the predicted templated sizes using the KingMark device compared to templating performed without it. ​Conclusions​ Preoperative templating is an essential part in optimizing the outcome of THRs. Templating allows the surgeon to estimate the size of the components to be used. It also provides a starting point, from which the surgeon can proceed from, and saves valuable intraoperative time by assessing the level of the femoral neck osteotomy and the degree of lateral rasping. Multiple factors affect the accuracy of preoperative templating including the patient BMI, external rotation of the hip and surgeon's experience. Although there are different methods of templating, digital templating with 2D radiographs is likely the most cost-effective and efficient process available at this time.

The Reliability of the Divergence Angle for Evaluating Rotational Implant Positioning in Medial Unicompartmental Knee Replacement.

Background Unicompartmental knee arthroplasty (UKA) is a highly effective surgical procedure used to treat patients with osteoarthritis affecting a single knee compartment. UKA has gained significant popularity, accompanied by an expansion of its surgical indications. This increasing trend can be attributed to the consistently excellent clinical outcomes associated with UKA, which rival those achieved with total knee arthroplasty (TKA). However, despite these advancements, implant rotation malposition remains a prevalent factor contributing to early failure in UKA cases. The aim of this study is to analyze the rotational positioning of femorotibial implants in UKA and to identify an appropriate angle formed by the femoral component and the tibial component using a newly described angle. Methods This was a retrospective study of patients' data of 40 medial UKA cases of 33 patients who were operated on in our hospital between October 1998 and March 2019. The study introduces a new angle called the "divergence angle." This angle is formed between the lateral portion of the femoral component and the lateral part of the tibial component, as measured on a patellofemoral Merchant view at 30 degrees of knee flexion. The divergence angle was evaluated through radiographic assessment by two independent reviewers. Results According to statistical analysis, the divergence angle was highly reliable with both intra- and inter-observer reproducibility. Intra-observer reproducibility was excellent with an intra-class correlation coefficient(ICC) between 0.901 and 0.933 (p < 0.001). The inter-observer reproducibility was excellent with an ICCof 0.92 (p < 0.001).The Gaussian curve confirmed the normal distribution of the divergence angle values with moderate dispersion of values. The majority of the angles of divergence (85%) measured between the femoral and tibial components were less than 10 degrees (n = 34), with a mean angle of 6.3 ± 4.5°. Conclusion The divergence angle between the femoral and tibial components, measured at 30 degrees of knee flexion using the Merchant view, is an easily accessible, reliable, and reproducible method. This technique enables the assessment of the optimal rotational positioning of implants in medial UKA.

Combined femoral and tibial component total knee arthroplasty device rotation measurement is reliable and predicts clinical outcome

BackgroundThe optimal total knee arthroplasty (TKA) rotational alignment and how best to obtain and measure it are debatable. The aim was to analyse the reliability of the Berger femoral, three different tibial and four different combined two-dimensional computer tomography (2D-CT) TKA component rotation measurements, and to ascertain which rotational values best predict a successful clinical outcome.MethodsThe 2D-CT scans were obtained post-operatively on 60 patients who had TKA. We determined one femoral [Berger’s femoral angle (BFA)], three tibial [Berger’s tibial angle (BTA), anatomical tibial angle (ATA) and bimalleolar posterior tibial component angle (BM_PTCA)] and four combined [transepicondylar posterior tibial component angle (TE_PTCA), bicondylar posterior tibial component angle (BC_PTCA, transepicondylar bimalleolar angle (TE_BM) and bicondylar bimalleolar angle (BC_BM)] TKA rotation angles. We made all measures in 23 patients twice by three observers and determined inter- and intra-observer agreement using the Bland–Altman plot method. We analysed measures of 55 patients using the area under the ROC curve (AUC) analysis to ascertain the discriminative capacity of BFA, ATA, TE_PTCA and BC_PTCA for predicting a successful clinical outcome according to the Knee Society Score (KSS) threshold.ResultsATA showed the smaller inter- and intra-observer average of differences (−0.1° and 1.6°, respectively) of the studied methods followed by BFA (−0.9° and 1.4°), TE_PTCA (−2.1° and 2.7°) and BC_PTCA (−0.5° and 1.8°). BFA (−4° to 2.1° and −6.1° to 8.8°) and BC_PTCA (−4.4° to 3.4° and −7.9° to 4.4°) showed the narrower inter- and intra-observer limits of agreement. A TKA device rotation (BC_PTCA) < 0.8° of external rotation (ER) predicted a KSS and KSS knee successful outcome, and < 3.8° ER for KSS functional (AUC = 0.889; 0.907 and 0.764, respectively). BFA and ATA < 0.9° ER and < 3.9° internal rotation (IR) predicted a successful KSS knee outcome (AUC = 0.796 and 0.889, respectively).ConclusionThe ATA tibial component rotation measurement was the most reliable of those studied. BFA, TE_PTCA and BC_PTCA were reliable measures for TKA femoral and combined rotation. The presence of a minimal rotation between the TKA components (BC_PTCA) and a small femoral ER or tibial IR predicted a successful KSS outcome.Level of evidence II.

High Rates of Aseptic Loosening in Modern Posterior-stabilized Femoral Components From a Single Manufacturer.

Total knee arthroplasty (TKA) is one of the most commonly performed surgical procedures in the United States. There are concerns and reports of early aseptic loosening due to debonding at the cement-implant interface in a specific posterior-stabilized femoral design. This study describes failure at the cement-implant interface with 2 femoral implant designs produced by a single manufacturer. This is a review of failed primary total knee arthroplasties performed with Optetrak Logic and Truliant posterior-stabilized femoral components between 2010 and 2020. Cases with revision surgery performed for femoral component loosening were reviewed. Seventeen of 896 knees were revised for femoral component loosening. The mean time from index arthroplasty to revision was 73 months. Patients presented with knee pain and recurrent aseptic effusions. More than half of patients had no evidence of component loosening on plain radiographs. Bone scans were positive in 77% of patients with loosening. Femoral components were easily disimpacted from the cement mantle at the time of revision surgery. Patients were treated with femoral only revision or femoral and tibial revision. Two complications occurred in this series. Providers should maintain vigilance in the surveillance of patients with these implants. Clinicians should have a low threshold for additional diagnostic testing if these patients develop pain and/or recurrent effusions. Isolated femoral or complete revision both seem to be acceptable treatment strategies for this failure mechanism.

Cementless tapered wedge stems in patients undergoing primary total hip arthroplasty with Dorr C bone-are complication risks increased?

The use of cementless femoral stems in patients undergoing primary total hip arthroplasty (THA) with Dorr C bone remains controversial for fear of fracture or subsidence. Purpose of this multicenter study was to compare clinical outcomes and complications of THA using a tapered femoral prosthesis in patients with Dorr C bone versus Dorr A/B bone. A total of 1,030 patients underwent primary THA with a tapered wedge femoral stem at a minimum one year follow up. Forty-eight patients with Dorr C bone (mean age 68.7 years) were compared with a matched cohort of patients with Dorr A/B bone (mean age 69.9 years). Mean follow-up was approximately 4 years in both cohorts. There were no differences in sex, age, body mass index (BMI), Harris Hip Score (HHS), complications, and radiographic outcomes including subsidence and aseptic loosening were evaluated. Postoperative HHSs were a mean of 82 points in the Dorr C cohort compared to 84 points in the Door A/B cohort (P=0.2653). There was no significant difference in complication or revision rates for any reason (P=0.23). Mean subsidence for the Dorr C and Dorr A/B was 1.4 and 1.2 mm, respectively (P=0.5164), and there was no aseptic loosening of the femoral component found in either group. Current generation tapered wedge cementless femoral stems provide stable fixation for patients with Dorr C bone quality without increased complications with respect to fracture or subsidence and can be considered an alternative to cemented stems in patients with compromised bone quality.

Does preoperative 3D CT planning helps in predicting the component size determination and alignment in automatic robotic total knee arthroplasty (RA-TKA)

PurposeImage-based Robotic Total knee Arthroplasty (RA-TKA)was developed with the purpose of enhancing the accuracy in determining the component sizes preoperatively and helping surgeons in minimizing errors and improve patient outcomes. The research aims to find the reliability of robotic-assisted TKR based on images in determining the correct component sizes using preoperative three-dimensional (3D) computer tomography. MethodAfter ethical approval, we conducted a prospective study from March 2022 to December 2022. A total of 100 knees underwent image-based RA-TKA having grade 4 Osteoarthritis knee (Kellegren Lawrence classification). A single senior surgeon performed on all patients. Postoperative implant sizes and fit were assessed by five radiographic markers by an independent observer. ResultsIn our study, we found the mean age was (64.96 ± 7.3) years, with female to male ratio of 43:22. The preoperative 3D CT accuracy is 100% for femoral component sizing and 97% for the tibial component. There was a statistically significant improvement in varus deformity from preoperative 7.370 ± 3.70° to 1.24 0 ± 0.910° after surgery., p = 0.001. Improvement in flexion deformity correction was from preoperative 6.50 ± 6.30 to postoperative 1.640 ± 1.770, p = 0.001. ConclusionOur study concludes that the use of pre-operative 3D CT helps in predicting the component sizes, minimizes surgical time, and enhances implant position accuracy, as well as improves postoperative limb alignment in the coronal and sagittal planes.

Subsidence analysis of a cementless short stem THA using EBRA-FCA - A seven-year prospective multicentre study

BackgroundMetaphyseal fixation of short stem THA allows for minimally invasive surgery, less bone removal, improved bone load transfer and reduced stress shielding. Short stems facilitate the anatomic restoration i.a. of leg length, femoroacetabular offset, and center of rotation. However, metaphyseal fixation might cause impaired primary and/or secondary stability resulting in an inherent tendency for early axial migration and aseptic loosening eventually. The objective of this study was to investigate the long-term outcome and migration pattern of a calcar-guided short stem. MethodsIn a prospective multicenter study, 213 patients (224 THAs) were enrolled. Patients were followed for up to 84 months postoperatively. Clinical outcome was assessed using the Harris Hip Score and the VAS for pain and satisfaction. Standardized and calibrated radiographs were screened i.a. for stress shielding and loosening. Einzel-Bild-Roentgen-Analyse – femoral component analysis (EBRA-FCA) was used to detect longitudinal subsidence. ResultsAt 7 year follow-up, n = 139/224 cases were available for analysis. All clinical parameters improved significantly (p < 0.001) and improvement persisted. There were no radiographic changes indicating stress shielding. EBRA-FCA revealed a mean subsidence of −1.44 mm followed by a stabilization. Weight >80 kg (p = 0.115), BMI <30 kg/m2 (p = 0.282), male gender (p = 0.246), and age <65 years (p = 0.304) seemed to be associated with a higher risk for migration. The cumulative revision rate was 2.23%. Revisions due to stem migration (0.89%) occurred early (mean time between index surgery and revision: 3.3 months). ConclusionsIf at all, there appears to be a pronounced initial subsidence, which stabilizes thereafter. Stem migration was rarely a compelling reason for failure or revision. Demographics do not seem to have a significant effect on migration pattern. The absence of radioluce lines, resorption or hypertrophy of the proximal femora support the hypothesis of a reduced stress shielding for metaphyseal anchoring short stems.

A robotic-assisted simulation of kinematic alignment in TKA leads to excessive valgus and internal rotation in valgus knees.

Strategies to further improve patient satisfaction after total knee arthroplasty include the introduction of new alignment philosophies and more precise instruments such as navigation and robotics. The aim of this study was to investigate the effect of a combination of image-based robotic assistance and the use of modern alignment strategies on the resulting joint line obliquity as well as femoral component rotation and to compare this between varus, neutral and valgus knees. This retrospective study included 200 patients who received a robotic-assisted total knee arthroplasty (MAKO®, Stryker) using functional alignment between 2018 and 2020. The patients were divided into a varus (103 patients), neutral (57 patients) and valgus (40 patients) group. The intraoperatively recorded bone cuts and resulting joint line obliquity were identified and compared to values obtained with a robotic computer simulation of kinematic alignment. The mean femoral coronal alignment of the varus, neutral and valgus group, respectively, equalled 0.5° (± 1.1°), 1.1° (± 0.8°) and 1.6° (± 0.7°) of valgus with functional alignment and 2.1° (± 2.1°), 4.1° (± 1.7°) and 6.2° (± 1.7°) of valgus with kinematic alignment. The mean femoral axial alignment of the valgus group resulted in 0.8° (± 2.0°) of internal rotation with functional alignment and 3.9° (± 2.8°) of internal rotation with kinematic alignment. Overall, 186 knees (93%) could be balanced while respecting certain safe zones by using functional alignment as opposed to 54 knees (27% and none in the valgus group) when applying kinematic alignment. Kinematic alignment led to a combination of femoral component valgus and internal rotation of more than 3° in 22 valgus knees (55%), 10 neutral knees (18%) and 3 varus knees (3%) compared to none in each group when applying functional alignment with safe zones. Robotic-assisted kinematic alignment leads to a combination of excessive valgus and internal rotation of the femoral component in valgus and to a lesser extent also in neutral knees when compared with functional alignment. IV.

Cost-Effectiveness of Bone Cement With and Without Antibiotics: A Broader Perspective

Background Periprosthetic joint infections (PJIs) and periprosthetic femur fractures (PFFs) increase total costs of care. Retrospective registry/institutional studies with selection bias and underpowered meta-analyses have corrupted the evidence base regarding antibiotic-laden bone cement (ALBC) use in total knee arthroplasties (TKAs). Clinical practice guidelines (CPGs) recommend using cement fixation of femoral components in hip fracture patients to prevent PFFs, but have no recommendations regarding ALBC. Hip osteoarthritis CPGs have no bone cement recommendations regarding prevention of PJIs or PFFs. ALBC is potentially cost-effective by reducing PJIs, PFFs, and reducing implant costs. Methods A systematic review was conducted to identify randomized controlled trials (RCTs), meta-analyses, and registry reports related to the efficacy of ALBC in reducing PJIs and cemented femoral fixation in reducing PFFs. Numbers needed to treat (NNT) are calculated. Cost-effectiveness margins per case are calculated. Results A pooled analysis of four TKA RCTs found ALBC reduces PJI by 0.94% (p=0.027), NNT 106. A total hip arthroplasty (THA) meta-analysis found ALBC reduces PJI by 0.58% (p&lt;0.0001), NNT 172. A hip hemiarthroplasty (HH) RCT found high-dose dual-antibiotic ALBC reduces PJI by 2.35% (p=0.0474), NNT 43. A THA registry report found that cemented fixation compared to ingrowth fixation reduced PFFs by 0.44% (p&lt;0.0001), NNT 229. A pooled analysis of three HH RCTs found that cemented femoral stem fixation reduced PFFs by 5.09% (p-0.0099), NNT 20. Mean PJI treatment costs are $80,000. Mean PFF treatment costs are $27,596. Mean HH cemented femoral stem cost reduction: $685. Using ALBC: TKA margin/case is $755; THA margin/case is $586; and HH margin/case is $3,925. Using plain bone cement: TKA margin/case is $0; THA margin/case is $121; and HH margin/case is $2,065. Conclusions A broader perspective demonstrates that ALBC provides significant financial margins in TKAs, THAs, and hip hemiarthroplasties. ALBC is cost-effective when including the additional costs of using ALBC in TKAs, THAs, and hip hemiarthroplasties. Hand-mixed ALBC is more cost-effective than pre-mixed ALBC in all scenarios.

An experimental study on the impact of prosthesis temperature on the biomechanical properties of bone cement fixation

PurposeTo investigate the effect of the femoral component and tibial plateau component temperature on the strength of cement fixation during total knee arthroplasty (TKA).MethodsFemoral prosthesis, tibial plateau prosthesis, and polypropylene mold base were used to simulate TKA for bone cement fixation. Pre-cooling or pre-warming of femoral and tibial plateau components at different temperatures (4 °C, 15 °C, 25 °C, 37 °C, 45 °C), followed by mixing and stirring of bone cement at laboratory room temperature (22 °C), were performed during research. The prosthesis and the base adhered together, and the bone cement was solidified for 24 h at a constant temperature of 37 °C to verify the hardness of the bone cement with a push-out test.ResultsThe push-out force of the femoral prosthesis after fixation was higher than that of the tibial plateau prosthesis, and with the increase of the prosthesis temperature, the push-out force after fixation of the bone cement also increased linearly and the porosity of the prosthetic cement in the tibia and femur decreased as the temperature increased.ConclusionWithout changing the mixing temperature and solidification temperature, the fixation strength of the femoral prosthesis is higher than that of the tibial plateau prosthesis. Properly increasing the temperature of the prosthesis can increase the push-out force of the fixation strength.

Overall Accuracy of Radiological Digital Planning for Total Hip Arthroplasty in a Specialized Orthopaedics Hospital

Preoperative radiological planning is a key factor in the prediction of implant size and positioning that influences surgical time, the risk of complications, and functional outcomes. We have tested the accuracy of the digital templating performed in our hospital for a sample of 215 patients that underwent total hip arthroplasty. We assessed the accuracy of correctly predicting implant size for the femoral and acetabular components, as well as the stem neck length. We found that our method of templating proved accurate (within one size) in 95.8% of cases for the stem and 94.9% for the cup when using the anteroposterior view only, while the lateral view was accurate in 95.8% of cases for the stem and 97.2% for the cup. Exact prediction of the stem size was obtained in 77.7% of cases using the anteroposterior view and 67.0% of cases on the lateral view, and 73.0% and 74.4% of cases for the cup on the AP and LL views, respectively. Stem neck size was predicted exactly in 75.35% of cases and within one size in 93.49% of cases. We concluded that our method of digital templating using dedicated software is highly effective in accurately predicting implant size.