Aims. We aimed to assess the reliability and validity of OpenPose, a posture estimation algorithm, for measurement of knee range of motion after total knee arthroplasty (TKA), in comparison to radiography and goniometry. Methods. In this prospective observational study, we analyzed 35 primary TKAs (24 patients) for knee osteoarthritis. We measured the knee angles in flexion and extension using OpenPose, radiography, and goniometry. We assessed the test-retest reliability of each method using intraclass correlation coefficient (1,1). We evaluated the ability to estimate other measurement values from the OpenPose value using linear regression analysis. We used intraclass correlation coefficients (2,1) and Bland–Altman analyses to evaluate the agreement and error between radiography and the other measurements. Results. OpenPose had excellent test-retest reliability (intraclass
Aims. Accurate identification of the ankle joint centre is critical for estimating tibial coronal alignment in total knee arthroplasty (TKA). The purpose of the current study was to leverage artificial intelligence (AI) to determine the accuracy and effect of using different radiological anatomical landmarks to quantify mechanical alignment in relation to a traditionally defined radiological ankle centre. Methods. Patients with full-limb radiographs from the Osteoarthritis Initiative were included. A sub-cohort of 250 radiographs were annotated for landmarks relevant to knee alignment and used to train a deep learning (U-Net) workflow for angle calculation on the entire database. The radiological ankle centre was defined as the midpoint of the superior talus edge/tibial plafond. Knee alignment (hip-knee-ankle angle) was compared against 1) midpoint of the most prominent malleoli points, 2) midpoint of the soft-tissue overlying malleoli, and 3) midpoint of the soft-tissue sulcus above the malleoli. Results. A total of 932 bilateral full-limb radiographs (1,864 knees) were measured at a rate of 20.63 seconds/image. The knee alignment using the radiological ankle centre was accurate against ground truth radiologist measurements (inter-class
Abstract. Rehabilitation exercise is critical for patients’ recovery after knee injury or post-surgery. Unfortunately, adherence to exercise is low due to a lack of positive feedback and poor self-motivation. Therefore, it is crucial to monitor their progress and provide supervision. Inertial measurement unit (IMUs) based sensing technology can provide remote patient monitoring functions. However, most current solutions only measure the range of knee motion in one degree of freedom. The current IMUs estimate the orientation-angle based on the integrated raw data, which might lack accuracy in measuring knee motion. This study aims to develop an IMU-based sensing system using the absolute measured orientation-angle to provide more accurate comprehensive monitoring by measuring the knee rotational angles. An IMU sensing system monitoring the knee joint angles, flexion/extension (FE), adduction/abduction (AA), and internal/external (IE) was developed. The accuracy and reliability of FE measurements were validated in human participants during squat exercise using measures including root mean square error (RMSE) and
Aims. Joint registries classify all further arthroplasty procedures to a knee with an existing partial arthroplasty as revision surgery, regardless of the actual procedure performed. Relatively minor procedures, including bearing exchanges, are classified in the same way as major operations requiring augments and stems. A new classification system is proposed to acknowledge and describe the detail of these procedures, which has implications for risk, recovery, and health economics. Methods. Classification categories were proposed by a surgical consensus group, then ranked by patients, according to perceived invasiveness and implications for recovery. In round one, 26 revision cases were classified by the consensus group. Results were tested for inter-rater reliability. In round two, four additional cases were added for clarity. Round three repeated the survey one month later, subject to inter- and intrarater reliability testing. In round four, five additional expert partial knee arthroplasty surgeons were asked to classify the 30 cases according to the proposed revision partial knee classification (RPKC) system. Results. Four classes were proposed: PR1, where no bone-implant interfaces are affected; PR2, where surgery does not include conversion to total knee arthroplasty, for example, a second partial arthroplasty to a native compartment; PR3, when a standard primary total knee prosthesis is used; and PR4 when revision components are necessary. Round one resulted in 92% inter-rater agreement (Kendall’s W 0.97; p < 0.005), rising to 93% in round two (Kendall’s W 0.98; p < 0.001). Round three demonstrated 97% agreement (Kendall’s W 0.98; p < 0.001), with high intra-rater reliability (interclass
Abstract. Introduction. There are several imaging-based measurements for patello-femoral height. Available methods rely predominantly on sagittal images. The latter can be misleading with sagittal oblique slices and when the patella is tilted and/or chronically subluxed. In this study we describe a simple method of patellar height measurement using axial MRI overlap. Materials and methods. A retrospective observational analysis of 97 knees from 251 patients was conducted. Cases were selected following the exclusion of scans with fractures, massive effusion, patello-femoral pathology. Axial patello-trochlear overlap (APTO) was measured on the axial MRI images as follows: (1) Patellar length (P): expressed as the number of axial images showing patellar articular surface (2) Trochlear overlap (T): the number of axial images showing overlap between patellar articular surface and articular surface of lateral trochlea. APTO is the ratio T/P. All measurements were carried out independently and on two separate occasions by 6 raters. As a control conventional patello-trochlear index were measured for all patients by a senior musculoskeletal radiologist. Results. The mean APTO value was 36.7 (range 14.2 to 66.6; SD 11.4). There was a positive correlation with patello-trochlear index (Pearson
Aims. The purpose of this study was to explore the correlation between femoral torsion and morphology of the distal femoral condyle in patients with trochlear dysplasia and lateral patellar instability. Methods. A total of 90 patients (64 female, 26 male; mean age 22.1 years (SD 7.2)) with lateral patellar dislocation and trochlear dysplasia who were awaiting surgical treatment between January 2015 and June 2019 were retrospectively analyzed. All patients underwent CT scans of the lower limb to assess the femoral torsion and morphology of the distal femur. The femoral torsion at various levels was assessed using the a) femoral anteversion angle (FAA), b) proximal and distal anteversion angle, c) angle of the proximal femoral axis-anatomical epicondylar axis (PFA-AEA), and d) angle of the AEA–posterior condylar line (AEA-PCL). Representative measurements of distal condylar length were taken and parameters using the ratios of the bianterior condyle, biposterior condyle, bicondyle, anterolateral condyle, and anteromedial condyle were calculated and correlated with reference to the AEA, using the Pearson
Introduction. Cementless fixation in total knee arthroplasty has been proposed to offer advantages long-term once osteointegration has occurred as there is no substrate between the implant and the bone to fail. Radiostereometric analysis (RSA) is a useful tool to study fixation, but typically focused on early migration in the first two post-operative years. Few studies have looked at 10-year RSA migration in cementless fixation and those that have contain small numbers of subjects. The objective of this study was to compare implant migration and inducible displacement between cemented and cementless TKA at 10 years and to compare the 10-year migration to the 2-year data in an effort to validate the predictive modelling of RSA. Methods. Subjects who had previously participated in RSA migration studies with 2-year follow-up were recruited to return for a long-term follow-up exam, at least 10 years from their surgery. The implants under study included two cemented designs from two manufacturers and one porous metal monoblock cementless design. At the 10-year visit, subjects had supine RSA exams to determine long-term migration as well as a loaded exam (single leg stance) to determine inducible displacement. Differences between cemented and cementless groups were evaluated with the Mann Whitney U test and Spearman's rank
Aims. The aim of this study was to assess the effect of posterior cruciate ligament (PCL) resection on flexion-extension gaps, mediolateral soft-tissue laxity, fixed flexion deformity (FFD), and limb alignment during posterior-stabilized (PS) total knee arthroplasty (TKA). Patients and Methods. This prospective study included 110 patients with symptomatic osteoarthritis of the knee undergoing primary robot-assisted PS TKA. All operations were performed by a single surgeon using a standard medial parapatellar approach. Optical motion capture technology with fixed femoral and tibial registration pins was used to assess gaps before and after PCL resection in extension and 90° knee flexion. Measurements were made after excision of the anterior cruciate ligament and prior to bone resection. There were 54 men (49.1%) and 56 women (50.9%) with a mean age of 68 years (. sd. 6.2) at the time of surgery. The mean preoperative hip-knee-ankle deformity was 4.1° varus (. sd. 3.4). Results. PCL resection increased the mean flexion gap significantly more than the extension gap in the medial (2.4 mm (. sd. 1.5) vs 1.3 mm (. sd. 1.0); p < 0.001) and lateral (3.3 mm (. sd. 1.6) vs 1.2 mm (. sd. 0.9); p < 0.01) compartments. The mean gap differences after PCL resection created significant mediolateral laxity in flexion (gap difference: 1.1 mm (. sd. 2.5); p < 0.001) but not in extension (gap difference: 0.1 mm (. sd. 2.1); p = 0.51). PCL resection significantly improved the mean FFD (6.3° (. sd. 4.4) preoperatively vs 3.1° (. sd. 1.5) postoperatively; p < 0.001). There was a strong positive correlation between the preoperative FFD and change in FFD following PCL resection (Pearson’s
Aims. The purpose of this investigation was to determine the relationship between height, weight, and sex with implant size in total knee arthroplasty (TKA) using a multivariate linear regression model and a Bayesian model. Methods. A retrospective review of an institutional registry was performed of primary TKAs performed between January 2005 and December 2016. Patient demographics including patient age, sex, height, weight, and body mass index (BMI) were obtained from registry and medical record review. In total, 8,100 primary TKAs were included. The mean age was 67.3 years (SD 9.5) with a mean BMI of 30.4 kg/m. 2. (SD 6.3). The TKAs were randomly split into a training cohort (n = 4,022) and a testing cohort (n = 4,078). A multivariate linear regression model was created on the training cohort and then applied to the testing cohort . A Bayesian model was created based on the frequencies of implant sizes in the training cohort. The model was then applied to the testing cohort to determine the accuracy of the model at 1%, 5%, and 10% tolerance of inaccuracy. Results. Height had a relatively strong correlation with implant size (femoral component anteroposterior (AP) Pearson
Aims. Although knee osteoarthritis (OA) is diagnosed and monitored radiologically, actual full-thickness cartilage loss (FTCL) has rarely been correlated with radiological classification. This study aims to analyze which classification system correlates best with FTCL and to assess their reliability. Methods. A prospective study of 300 consecutive patients undergoing unilateral total knee arthroplasty (TKA) for OA (mean age 69 years (44 to 91; standard deviation (SD) 9.5), 178 (59%) female). Two blinded examiners independently graded preoperative radiographs using five common systems: Kellgren-Lawrence (KL); International Knee Documentation Committee (IKDC); Fairbank; Brandt; and Ahlbäck. Interobserver agreement was assessed using the intraclass correlation coefficient (ICC). Intraoperatively, anterior cruciate ligament (ACL) status and the presence of FTCL in 16 regions of interest were recorded. Radiological classification and FTCL were correlated using the Spearman
Introduction. Patient reported outcome measures (PROMs) are increasingly used as quality benchmarks in total joint arthroplasty (TJA). The objective of this study was to investigate whether PROMs correlate with patient satisfaction, which is arguably the most important and desired outcome. Methods. An institutional joint database was queried for patients who underwent primary, elective, unilateral TJA. Eligible patients were asked to complete a satisfaction survey at final follow-up.
Background. Obesity has been shown to be an independent risk factor for aseptic loosening of the tibia and smaller implant size has been correlated with increased risk of failure of tibial components in obese patients [1,2]. Many surgeons have noted that obese patients, especially females, not uncommonly will have small implant sizes. As such, we hypothesized that obesity was not directly correlated with total knee arthroplasty (TKA) implant sizes. The purpose of this study was to determine if increasing body mass index (BMI), height, and/or weight is associated with implant size in primary TKA. Methods. The institutional registry of a single academic center was reviewed to identify all primary TKAs performed between 2005 and 2016. Those without minimum 2-year follow-up or with incomplete implant data were excluded. The different manufacturer's implant designs were categorized based on anteroposterior and mediolateral dimensions of the femoral and tibial component sizes and cross sectional area was determined. BMI was categorized by the World Health Organization (WHO) obesity scale (Class I: BMI 30 to <35, Class II: BMI 35 to <40, Class III: BMI 40 kg/m. 2. or greater). Patient demographics including sex, height, weight, and BMI were analyzed to evaluate correlations with implant size using Pearson
Introduction. The objective of this study was to assess the effect of PCL resection on flexion-extension gaps, mediolateral soft tissue laxity, fixed flexion deformity (FFD), and limb alignment during posterior-stabilised total knee arthroplasty (TKA). Methods. This prospective study included 110 patients with symptomatic knee osteoarthritis undergoing primary robotic-arm assisted posterior-stabilised TKA. All operative procedures were performed by a single surgeon using a standard medial parapatellar approach. Optical motion capture technology with fixed femoral and tibial registration pins was used to assess gaps pre- and post-PCL resection in knee extension and 90 degrees knee flexion. This study included 54 males (49.1%) and 56 females (50.9%) with a mean age of 68 ± 6.2 years at time of surgery. Mean preoperative hip-knee-ankle deformity was 6.1 ± 4.4 degrees varus. Results. PCL resection increased the flexion gap more than the extension gap in the medial (2.4 ± 1.5mm vs 1.3 ± 1.0mm respectively, p<0.001) and lateral (3.3 ± 1.6mm vs 1.2 ± 0.9mm respectively, p<0.01) compartments. The gap differences following PCL resection created mediolateral laxity in flexion (gap difference: 1.1 ± 2.5mm, p<0.001) but not in extension (gap difference: 0.1 ± 2.1mm, p=0.51). PCL resection improved overall FFD (6.3 ± 4.4° preoperatively vs 3.1 ± 1.5° postoperatively, p<0.001). There was a strong positive correlation between preoperative FFD and change in FFD following PCL release (Pearson
Introduction. As total knee arthroplasty incidence in the United States continues to increase, health care entities are looking to reform policy to decrease costs while improving efficiency and quality of care. The allocation of hospital and surgeon charges and payments is an important aspect of health care economics, but the trends and relationship between surgeon and hospital charges and payments for knee arthroplasty have not been well examined. The goal of this study is to report trends and variation in hospital charges and payments compared to surgeon charges and payments for total knee arthroplasty in a Medicare population. Methods. The 5% Medicare sample was used to capture hospital and surgeon charges and payments for total knee arthroplasty from 2005–2014. Two important values were calculated: (1) the charge multiplier (CM) which is the ratio of hospital to surgeon charges, and (2) the payment multiplier (PM), which is the ratio of hospital to surgeon payments. The year to year variation and regional trends in patient demographics, Charlson Comorbidity Index (CCI), length of stay (LOS), CM and PM were evaluated for all patients. Statistical significance of trends was evaluated using student's t-tests. Correlations between the financial multipliers and LOS were evaluated using a Pearson
This study validates the short-form WOMAC function scale for assessment of conservative treatment of osteoarthritis of the knee. Data were collected before treatment and six and nine months later, from 100 patients with osteoarthritis of the knee to determine the validity, internal consistency, test-retest reliability, floor and ceiling effects, and responsiveness of the short-form WOMAC function scale. The scale showed high correlation with the traditional WOMAC and other measures. The internal consistency was good (Cronbach α: 0.88 to 0.95) and an excellent test-retest reliability was found (Lin’s concordance
Introduction. Tibial tuberosity and trochlear groove (TT-TG) distance has been investigated for the patients with primary patellofemoral subluxation/dislocation. To date, TT-TG distance after TKA has not been evaluated, and the effect of postoperative TT-TG distance on patellar tracking is unknown. The purpose of the current study was to investigate the effect of TT-TG distance and rotational position of the femoral and tibial components on patellar tilt after TKA. Methods. Consecutive 115 knees for the diagnosis of osteoarthritis were included in the current study. TKA was performed using posterior cruciate ligament sacrificed prosthesis. A total of 17 men and 96 women with an average age of 75.3 years were included at the time of the surgery. Computed tomography (CT) was taken after TKA in full extension. Postoperative TT-TG distance was measured as a reference of surgical epicondylar axis (SEA) of the femur. Patellar tilt was defined as the angle of the patellar component relative to SEA. Femoral and tibial component rotation was measured as the angle relative to SEA and tibial antero-posterior (AP) axis. Tibial AP axis was defined as the line connecting medial one-third of the tibial tuberosity and center of medial-lateral width. Pearson
Introduction. Tibial component malrotation is associated with pain, stiffness and altered patellofemoral kinematics in total knee arthroplasty (TKA). However, accurately measuring tibial component rotation following TKA is difficult. Proposed protocols utilizing computed tomography (CT) are not well validated and can be time consuming. This study aimed to; 1) Validate and compare the reproducibility of the Berger (2D-CT) and Mayo (3D-CT) protocols; 2) Validate a simple, and potentially rapid screening measurement using an anatomical distance on 2D axial CT- the Centre of Tibial Tray to Tibial Tubercle (CTTT) distance. Methods. Rotational alignment of 70 TKA patients were evaluated by 3 independent observers using the Berger, and Mayo protocols, which have been previously described, and a new CTTT protocol (Figure 1). The inter and intra-rater interclass
We have studied the concept of posterior condylar offset and the importance of its restoration on the maximum range of knee flexion after posterior-cruciate-ligament-retaining total knee replacement (TKR). We measured the difference in the posterior condylar offset before and one year after operation in 69 patients who had undergone a primary cruciate-sacrificing mobile bearing TKR by one surgeon using the same implant and a standardised operating technique. In all the patients true pre- and post-operative lateral radiographs had been taken. The mean pre- and post-operative posterior condylar offset was 25.9 mm (21 to 35) and 26.9 mm (21 to 34), respectively. The mean difference in posterior condylar offset was + 1 mm (−6 to +5). The mean pre-operative knee flexion was 111° (62° to 146°) and at one year postoperatively, it was 107° (51° to 137°). There was no statistical correlation between the change in knee flexion and the difference in the posterior condylar offset after TKR (Pearson
Smoking is known to have an adverse effect on wound healing and musculoskeletal conditions. This case-controlled study looked at whether smoking has a deleterious effect in the outcome of autologous chondrocyte implantation for the treatment of full thickness chondral defects of the knee. The mean Modified Cincinatti Knee score was statistically significantly lower in smokers (n = 48) than in non-smokers (n = 66) both before and after surgery (p <
0.05). Smokers experienced significantly less improvement in the knee score two years after surgery (p <
0.05). Graft failures were only seen in smokers (p = 0.016). There was a strong negative correlation between the number of cigarettes smoked and the outcome following surgery (Pearson’s
This study aimed to evaluate if total knee arthroplasty (TKA) femoral components aligned in either mechanical alignment (MA) or kinematic alignment (KA) are more biomimetic concerning trochlear sulcus orientation and restoration of trochlear height. Bone surfaces from 1,012 CT scans of non-arthritic femora were segmented using a modelling and analytics system. TKA femoral components (Triathlon; Stryker) were virtually implanted in both MA and KA. Trochlear sulcus orientation was assessed by measuring the distal trochlear sulcus angle (DTSA) in native femora and in KA and MA prosthetic femoral components. Trochlear anatomy restoration was evaluated by measuring the differences in medial, lateral, and sulcus trochlear height between native femora and KA and MA prosthetic femoral components.Aims
Methods