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Abstract Purpose Previous studies reported that anterior knee pain (AKP) occurs with an incidence of 32% after opening-wedge high tibial osteotomy (OWHTO). However, the biomechanical effects of this procedure on patellofemoral joints (PFJs) remain unclear. We aimed to quantify the changes in the kinematics and cartilage conditions of the PFJ during stair climbing before and after OWHTO. Methods We recruited 15 patients who underwent unilateral OWHTO. All patients performed continuous stair climbing under the surveillance of a dual fluoroscopic imaging system to determine accurate 6-degree-of-freedom (6-DOF) PFJs and 3D hip-knee-ankle (HKA) angles before and 6 months after OWHTO. The volume penetration centres between the patellar and femoral cartilage models were defined as contact centres. Eleven of these patients underwent quantitative T2 relaxation MRI to determine whether and how PFJ cartilage degeneration progressed. Results After OWHTO, patella valgus (mean − 3.73°, P = 0.02) and internal rotation (mean 3.14°, P = 0.03) increased compared with the preoperative conditions during the stair climbing motion. In addition, the patellae of OWTHO knees were located more laterally after surgery (1.56 ± 2.24 mm, P = 0.02) at knee flexion. Moreover, lateral shifts in the contact patterns of both the medial and lateral patellar facets together with increased T2 values (207.10 ± 21.84 ms, P = 0.04) of the lateral patella cartilage were found after surgery. Finally, the lateral patellar shift increased with decreasing varus 3D-HKA after surgery (R= -0.79, P

Abstract Purpose To determine the optimal angles for independent femoral tunnel drillings in single-bundle anterior cruciate ligament reconstruction (ACLR) in different races and genders with the aim of preventing damage to lateral femoral anatomic structures (LFAS), posterior cortex and medial femoral condyle. Methods This study included 180 volunteers, including 90 Caucasian and 90 matched Chinese. Magnetic resonance imaging (MRI) was used to scan the knees to create three-dimensional bone models, the ACL femoral footprint centre and the LFAS. In each femur model, femoral tunnels were established using a set of 16 distinct angular combinations: 15°, 30°, 45°, and 60° in the axial plane, as well as 15°, 30°, 45°, and 60° in the coronal plane. The minimum distance from the tunnel exit to the LFAS was evaluated, and the tunnel length, posterior cortex damage and medial femoral condyle injury were assessed. Results Among the 180 patients with simulated ACL femoral tunnels, there was damage to the anatomical structure in parts of the model. According to the Cochran Q test results (P

Objective Cartilage and meniscus are important structures that maintain the health of the knee joint. Early detection of changes in the internal components of cartilage and meniscus before morphological changes occur is essential to prevent and delay the development of osteoarthritis (OA). This study was designed to determine the changes in the matrix composition of morphologically intact cartilage and meniscus during the acute phase of an anterior cruciate ligament (ACL) rupture, as well as the effect of different states of meniscus (intact or tear) on adjacent cartilage during the acute phase. Methods This cross‐sectional study compared and analyzed 50 patients in the acute phase of ACL rupture who underwent surgical treatment and 66 age‐, weight‐ and height‐matched healthy volunteers from May 2022 to May 2023 at our institution. Mean T2 relaxation times and effect sizes in different regions of tibiofemoral articular cartilage and meniscus were compared between the two groups using the Mann–Whitney nonparametric t‐test, and correlations between different meniscal states and adjacent cartilage were analyzed. Results Both in the lateral and medial compartments of the knee, T2 relaxation times were significantly higher in all subregions of cartilage and meniscus in the ACL rupture group (p

Objectives It is now understood that pedicle screw loosening at the implant‐bone interface can lead to poor screw–bone interface purchase and decreased fixation stability. Previous biomechanical tests used cadaveric vertebrae and pull‐out or torque loads to assess the effect of the insertional direction of pedicle screws on screw loosening. However, these tests faced challenges in matching biomechanical differences among specimens and simulating in vivo loads applied on pedicle screws. This study aimed to evaluate the effect of the insertional direction of pedicle screws on screw loosening using tension‐compression‐bending loads and synthetic bone vertebrae. Methods Polyaxial pedicle screws were inserted into nine synthetic bone vertebrae in three directions (three samples per group): cranial, parallel, and caudad (−10°, 0°, +10° of the pedicle screw rod to the upper plane of the vertebra, respectively). Pedicle screws in the vertebrae were loaded using a polyethylene block connected to a material testing machine. Tension‐compression‐bending loads (100N–250N) with 30,000 cycles were applied to the pedicle screws, and displacements were recorded and then cycle‐displacement curve was drawn based on cycle number. Micro‐CT scans were performed on the vertebrae after removing the pedicle screws to obtain images of the screw hole, and the screw hole volume was measured using imaging analysis software. Direct comparison of displacements was conducted via cycle‐displacement curve. Screw hole volume was analyzed using analysis of variance. The correlation between the displacement, screw hole volume and the direction of pedicle screw was assessed by Spearman correlation analysis. Results The smallest displacements were observed in the caudad group, followed by the parallel and cranial groups. The caudad group had the smallest screw hole volume (p

Abstract Purpose To determine whether posterior cruciate ligament (PCL) buckling (angular change) is associated with anterior cruciate ligament (ACL) status (intact or ruptured), meniscal bone angle (MBA), anterior tibial translation (ATT), body weight, femoral-tibial rotation (FTR), posterior tibial slope (PTS), PCL length and femoral-tibial distance (FTD) and to identify the factors that have the greatest influence. Methods All enrolled participants were scanned with a 3.0 T, 8-channel coil MRI system (Magnetom Verio; Siemens). Bone and soft tissue parameters were measured by MIMICS software for each subject and each measured parameter was correlated with PCL buckling phenomena. The correlated and statistically significant parameters were then analyzed by multiple linear regression to determine the magnitude of the effect of the different parameters on the PCL buckling phenomenon. Results A total of 116 subjects (50 ACL ruptured and 66 age, weight and height matched volunteers with uninjured knees) were enrolled. Among all measured parameters, there were 8 parameters that correlated with PCL angle (PCLA), of which ACL status had the strongest correlation with PCLA (r = − 0.67, p =

Objective The femoral tunnel position is crucial to anatomic single‐bundle anterior cruciate ligament (ACL) reconstruction, but the ideal femoral footprint position are mostly based on small‐sized cadaveric studies and elderly patients with a single ethnic background. This study aimed to identify potential race‐ or gender‐specific differences in the ACL femoral footprint location and ACL orientation, determine the correlation between the ACL orientation and the femoral footprint location. Methods Magnetic resonance images (MRIs) of 90 Caucasian participants and 90 matched Chinese subjects were used for reconstruction of three‐dimensional (3D) femur and tibial models. ACL footprints were sketched by several experienced orthopedic surgeons on the MRI photographs. The anatomical coordinate system was applied to reflect the ACL footprint location and orientation of scanned samples. The femoral ACL footprint locations were represented by their distance from the origin in the anteroposterior (A/P) and distal‐proximal (D/P) directions. The orientation of the ACL was described with the sagittal, coronal and transverse deviation angles. The ACL orientation and femoral footprint position were compared by the two‐sided t‐test. Multiple regression analysis was used to study the correlation between the orientation and femoral footprint position. Results The average femur footprint A/P position was −6.6 ± 1.6 mm in the Chinese group and −5.1 ± 2.3 mm in the Caucasian group, (p

Abstract Background The aim of the present study was to identify potential race- or gender-specific differences in anterior cruciate ligament (ACL) tibial footprint location from the tibia anatomical coordinate system (tACS) origin, investigate the distances from the tibial footprint to the anterior root of the lateral meniscus (ARLM) and the medial tibial spine (MTS), determine how reliable the ARLM and MTS can be in locating the ACL tibial footprint, and assess the risk of iatrogenic ARLM injuries caused by using reamers with various diameters (7–10 mm). Patients and methods Magnetic resonance images of 91 Chinese and 91 Caucasian subjects were used for the reconstruction of three-dimensional (3D) tibial and ACL tibial footprint models. The anatomical coordinate system was applied to reflect the anatomical locations of scanned samples. Results The average anteroposterior (A/P) tibial footprint location was 17.1 ± 2.3 mm and 20.0 ± 3.4 mm in Chinese and Caucasians, respectively (P

Objective Understanding the morphology of the distal femur is essential for improving bone‐implant match in total knee arthroplasty (TKA) and understanding the mechanisms behind knee kinematics. However, little is known about the asymmetry of the posterior condyles. Thus, this study aimed to thoroughly investigate asymmetries in sizes and shapes between the medial and lateral posterior condyles before and after femoral resections during TKA in osteoarthritic (OA) knees. Methods Three‐dimensional femoral models of 74 OA knees were constructed using computed tomography images. The morphologic measurements of the posterior condyle pre‐ and post‐simulated osteotomy for TKA included the radii of the posterior condyles fitted to a circle on the sagittal and axial planes of the femoral coordinate system, the inclination angle of the articular surface and resected surface, and the width and height of the resected surface. Differences in the data were assessed using Student's t‐test, and correlations were evaluated using the Pearson product–moment correlation. Results The radii of the medial posterior condyles fitted to the circle were, on average, 6 mm larger than those of the lateral condyles on the axial plane (p 0.107). Conclusions This study found asymmetrical inclination of the resected surface and coronal radii between the medial and lateral posterior condyles, which may relate to the posterolateral overhang of the lateral condyle after TKA and the progression of the knee OA. These findings provides valuable morphological information and may help improve the implant designs for TKA.

BackgroundThis study aimed to explore whether pre- or postoperative hip structures or surgical changes significantly influence hip range of motion (ROM) symmetry in patients with hip dysplasia during gait after total hip arthroplasty (THA) and provide possible surgical suggestions.MethodsFourteen patients with unilateral hip dysplasia underwent computed tomography before and after surgery to create three-dimensional hip models. Pre- and postoperative acetabular and femoral orientations, hip rotation centers (HRC), and femoral lengths were measured. Bilateral hip ROM during level walking after THA was quantified using dual fluoroscopy. The ROM symmetry in flexion-extension, adduction-abduction, and axial rotation was calculated using the symmetry index (SI). The relationship between SI and the above anatomical parameters and demographic characteristics was tested using Pearson's correlation and linear regression.ResultsThe average SI values for flexion-extension, adduction-abduction, and axial rotation during gait were −0.29, −0.30, and −0.10, respectively. Significant correlations were detected mainly in the postoperative HRC position. A distally placed HRC was associated with increased SI values for adduction-abduction (R = −0.47, p = 0.045), while a medially placed HRC was associated with decreased SI values for axial rotation (R = 0.63, p = 0.007). A regression analysis indicated that horizontal HRC positions significantly determined axial rotational symmetry (R2 = 0.40, p = 0.015). Normal axial rotation SI values were achieved with HRC between 17 mm medially and 16 mm laterally.ConclusionsPostoperative HRC position was significantly correlated with gait symmetry in the frontal and transverse planes in patients with unilateral hip dysplasia after THA. Surgical reconstruction of the HRC to between 17 mm medially and 16 mm laterally may contribute to gait symmetry.

Background: Osteoporosis is a common degenerative disease with high incidence among aging populations. However, in regular radiographic diagnostics, asymptomatic osteoporosis is often overlooked and does not include tests for bone mineral density or bone trabecular condition. Therefore, we proposed a highly generalized classifier for osteoporosis radiography based on the multiscale fractal, lacunarity, and entropy distributions.Methods: We collected a total of 104 radiographs (92 for training and 12 for testing) of lumbar spine L4 and divided them into three groups (normal, osteopenia, and osteoporosis). In parallel, 174 radiographs (116 for training and 58 for testing) of calcaneus from health and osteoporotic fracture groups were collected. The texture feature data of all the radiographs were pulled out and analyzed. The Davies–Bouldin index was applied to optimize hyperparameters of feature counting. Neighborhood component analysis was performed to reduce feature dimension and increase generalization. A support vector machine classifier was trained with only the most effective six features for each binary classification scenario. The accuracy and sensitivity performance were estimated by calculating the area under the curve.Results: Interpretable feature trends of osteoporotic pathological changes were depicted. On the spine test dataset, the accuracy and sensitivity of binary classifiers were 0.851 (95% CI: 0.730–0.922), 0.813 (95% CI: 0.718–0.878), and 0.936 (95% CI: 0.826–1) for osteoporosis diagnosis; 0.721 (95% CI: 0.578–0.824), 0.675 (95% CI: 0.563–0.772), and 0.774 (95% CI: 0.635–0.878) for osteopenia diagnosis; and 0.935 (95% CI: 0.830–0.968), 0.928 (95% CI: 0.863–0.963), and 0.910 (95% CI: 0.746–1) for osteoporosis diagnosis from osteopenia. On the calcaneus test dataset, they were 0.767 (95% CI: 0.629–0.879), 0.672 (95% CI: 0.545–0.793), and 0.790 (95% CI: 0.621–0.923) for osteoporosis diagnosis.Conclusion: This method showed the capacity of resisting disturbance on lateral spine radiographs and high generalization on the calcaneus dataset. Pixel-wise texture features not only helped to understand osteoporosis on radiographs better but also shed new light on computer-aided osteopenia and osteoporosis diagnosis.

Introduction: Thoracolumbar kyphosis (TLK) is a common feature in patients with spinal deformities. However, due to limited studies, the impacts of TLK on gait have not been reported. The objective of the study was to quantify and evaluate the impacts of gait biomechanics of patients with TLK secondary to Scheuermann’s disease.Methods: Twenty cases of Scheuermann’s disease patients with TLK and twenty cases of asymptomatic participants were recruited into this study. And the gait motion analysis was conducted.Results: The stride length was shorter in the TLK group compared to control group (1.24 ± 0.11 m vs. 1.36 ± 0.21 m, p = 0.04). Compared to control group, the stride time and step time were more prolonged in the TLK group (1.18 ± 0.11s vs. 1.11 ± 0.08 s, p = 0.03; 0.59 ± 0.06 s vs. 0.56 ± 0.04 s, p = 0.04). The gait speed of the TLK group was significantly slower than it of control group (1.05 ± 0.12 m/s vs. 1.17 ± 0.14 m/s, p = 0.01); In the sagittal plane, the range of motion (ROM) of the hip in the TLK group was significantly smaller than that of the control group (37.71 ± 4.35° vs. 40.05 ± 3.71°, p = 0.00). In the transverse plane, the adduction/abduction ROMs of the knee and ankle, as well as the internal and external rotation of the knee, were smaller in TLK group than ROMs in the control group (4.66 ± 2.21° vs. 5.61 ± 1.82°, p = 0.00; 11.48 ± 3.97° vs. 13.16 ± 5.6°, p = 0.02; 9.00 ± 5.14° vs. 12.95 ± 5.78°, p = 0.00).Discussion: The main finding of this study was that measurements of gait patterns and joint movement of the TLK group were significantly lower than those of the control group. And these impacts have the potential to exacerbate degenerative progress of joints in the lower extremities. These abnormal features of gait can also serve as a guideline for physicians to focus on TLK in these patients.

Background: Shoulder ultrasound is a well-established point-of-care diagnostic modality in orthopaedic and sports medicine. Despite offering measurements of high-quality morphology, this methodology has faced several challenges, including variability in ultrasound systems, operator dependency, and lack of reliable and objective quantitative measures to track disease progression and responses to therapeutic interventions. Computer-aided quantitative ultrasound algorithm (CAQUSA) is an emerging novelty that automates the detection of normal and abnormal structures. Although CAQUSA has been shown to improve detections and diagnoses of soft tissue lesions, the proof-of-concept of utilizing CAQUSA to measure subacromial space width and its encroachment to the rotator cuff tendon have not been tested to assist in clinical decision-making for subacromial pain syndrome.Objective: This study aimed to develop a CAQUSA that measured the acromiohumeral distance (AHD) and test the algorithm’s reliability and agreement with manual measurements in wheelchair users with spinal cord injury (SCI).Methods: 116 ultrasound video clips recorded from 10 manual wheelchair users with SCI were evaluated manually by an experienced examiner with expertise in AHD examination and by the CAQUSA, which was developed for bone segmentation with probability mapping. The reliability and agreement of the diagnostic performance between the examiner and the CAQUSA were calculated and compared in both groups of AHD measurements.Results: The CAQUSA achieved a satisfactory agreement between computer-aided (11.95 ± 2.29 mm) and manual (11.33 ± 2.48 mm) measurements. The intraclass correlation coefficient between the two measures was excellent (ICC = 0.95). The sensitivity was 0.2 mm, with 95% true positives and 5% false positives at the fixed threshold of CAQUSA.Conclusion: AHD measurements made by the clinical observer were similar to that of the CAQUSA for assessing the clinical metrics related to subacromial pain syndrome. However, the CAQUSA showed greater reliability in its unclear or misleading image analysis. Based on the findings of this proof-of-concept study, the CAQUSA has promise for clinical utilization and interchangeability to minimize examiner-dependent errors and potentially reduce the cost of care.

In vitro biomechanical experiments utilizing cadaveric specimens are one of the most effective methods for rehearsing surgical procedures, testing implants, and guiding postoperative rehabilitation. Applying dynamic physiological muscle force to the specimens is a challenge to reconstructing the environment of bionic mechanics in vivo, which is often ignored in the in vitro experiment. The current work aims to establish a hardware platform and numerical computation methods to reproduce dynamic muscle forces that can be applied to mechanical testing on in vitro specimens. Dynamic muscle loading is simulated through numerical computation, and the inputs of the platform will be derived. Then, the accuracy and robustness of the platform will be evaluated through actual muscle loading tests in vitro. The tests were run on three muscles (gastrocnemius lateralis, the rectus femoris, and the semitendinosus) around the knee joint and the results showed that the platform can accurately reproduce the magnitude of muscle strength (errors range from −6.2% to 1.81%) and changing pattern (goodness-of-fit range coefficient ranges from 0.00 to 0.06) of target muscle forces. The robustness of the platform is mainly manifested in that the platform can still accurately reproduce muscle force after changing the hardware combination. Additionally, the standard deviation of repeated test results is very small (standard ranges of hardware combination 1: 0.34 N~2.79 N vs. hardware combination 2: 0.68 N~2.93 N). Thus, the platform can stably and accurately reproduce muscle forces in vitro, and it has great potential to be applied in the future musculoskeletal loading system.

BackgroundPrecise preoperative planning improves postoperative outcomes in total hip arthroplasty (THA), especially in developmental dysplasia of the hip (DDH) cases. Previous studies used the T-line and midcortical-line as preoperative landmarks to predict postoperative stem anteversion (PSA). However, the most reliable landmark in predicting PSA in DDH patients remains unclear. To find the most reliable measurement to predict the PSA in DDH patients, this study compared the midcortical-line and T-line at different femoral neck levels.MethodsPre- and postoperative Computed Tomography (CT) scans of 28 hips in 21 DDH patients who received THA were obtained for three-dimensional femoral models. The preoperative CT scan was used to measure the anteversion of the midcortical-line on the axial cross-sectional plane images (AM-CT), the anteversion of the midcortical-line from 3D models (AM-3D), and the T-line from 3D models (AT-3D) at simulated osteotomy planes at 5 and 10 mm heights proximal to the base of the lesser trochanter. The correlation between the preoperative femoral anteversion (AM-CT, AM-3D, AT-3D) and the PSA was assessed to evaluate the prediction accuracy.ResultsThe correlations between the AM-CT and the PSA were 0.86 (mean difference (MD) = 1.9°) and 0.92 (MD = −3.0°) at 5 and 10 mm heights, respectively. The correlation between the AM-3D and the PSA were 0.71 (MD = −11.6°) and 0.61 (MD = −12.9°) at 5 and 10 mm heights. The AT-3D was significantly greater (MD = 15.4°) than the PSA (p-value

Purpose: To develop and evaluate a deep learning-based method to localize and classify anterior cruciate ligament (ACL) ruptures on knee MR images by using arthroscopy as the reference standard.Methods: We proposed a fully automated ACL rupture localization system to localize and classify ACL ruptures. The classification of ACL ruptures was based on the projection coordinates of the ACL rupture point on the line connecting the center coordinates of the femoral and tibial footprints. The line was divided into three equal parts and the position of the projection coordinates indicated the classification of the ACL ruptures (femoral side, middle and tibial side). In total, 85 patients (mean age: 27; male: 56) who underwent ACL reconstruction surgery under arthroscopy were included. Three clinical readers evaluated the datasets separately and their diagnostic performances were compared with those of the model. The performance metrics included the accuracy, error rate, sensitivity, specificity, precision, and F1-score. A one-way ANOVA was used to evaluate the performance of the convolutional neural networks (CNNs) and clinical readers. Intraclass correlation coefficients (ICC) were used to assess interobserver agreement between the clinical readers.Results: The accuracy of ACL localization was 3.77 ± 2.74 and 4.68 ± 3.92 (mm) for three-dimensional (3D) and two-dimensional (2D) CNNs, respectively. There was no significant difference in the ACL rupture location performance between the 3D and 2D CNNs or among the clinical readers (Accuracy, p < 0.01). The 3D CNNs performed best among the five evaluators in classifying the femoral side (sensitivity of 0.86 and specificity of 0.79), middle side (sensitivity of 0.71 and specificity of 0.84) and tibial side ACL rupture (sensitivity of 0.71 and specificity of 0.99), and the overall accuracy for sides classifying of ACL rupture achieved 0.79.Conclusion: The proposed deep learning-based model achieved high diagnostic performances in locating and classifying ACL fractures on knee MR images.

Traditional optical motion capture (OMC) with retroreflective markers is commonly used to measure joint kinematics but was also reported with unavoidable soft tissue artifacts (STAs) when quantifying the motion of the spine. Additionally, the patterns of the STA on the lumbar spine remain unclear. This study aimed to 1) quantify the in vivo STAs of the human lower back in three-dimensional directions during weight-bearing forward–backward bending and 2) determine the effects of the STAs on the calculated flexion angles between the upper and lower lumbar spines and adjacent vertebrae by comparing the skin marker (SM)- and virtual bone marker (VM)-based measurements. Six healthy volunteers were imaged using a biplanar radiographic system, and thirteen skin markers were mounted on every volunteer’s lower back while performing weight-bearing forward–backward bending. The STAs in the anterior/posterior (AP), medial/lateral (ML), and proximal/distal (PD) directions were investigated. The flexion angles between the upper and lower lumbar segments and adjacent intervertebral segments (L2–L5) throughout the cycle were calculated. For all the participants, STAs continuously increased in the AP direction and exhibited a reciprocal trend in the PD direction. During flexion, the STA at the lower lumbar region (L4–L5: 13.5 ± 6.5 mm) was significantly higher than that at the upper lumbar (L1–L3: 4.0 ± 1.5 mm) in the PD direction (p < 0.01). During extension, the lower lumbar (L4–L5: 2.7 ± 0.7 mm) exhibited significantly less STAs than that exhibited by the upper lumbar region (L1–L3: 6.1 ± 3.3 mm) (p < 0.05). The STA at the spinous process was significantly lower than that on both sides in the AP direction (p < 0.05). The present results on STAs, based on dual fluoroscopic measurements in healthy adult subjects, presented an anatomical direction, marker location, and anatomic segment dependency, which might help describe and quantify STAs for the lumbar spine kinematics and thus help develop location- and direction-specific weighting factors for use in global optimization algorithms aimed at minimizing the effects of STAs on the calculation of lumbar joint kinematics in the future.

Deep-learning methods provide a promising approach for measuring in-vivo knee joint motion from fast registration of two-dimensional (2D) to three-dimensional (3D) data with a broad range of capture. However, if there are insufficient data for training, the data-driven approach will fail. We propose a feature-based transfer-learning method to extract features from fluoroscopic images. With three subjects and fewer than 100 pairs of real fluoroscopic images, we achieved a mean registration success rate of up to 40%. The proposed method provides a promising solution, using a learning-based registration method when only a limited number of real fluoroscopic images is available.

Background: The complexity of the spatial dynamic flexion axis (DFA) of the elbow joint makes the elbow prosthesis design and humeral component alignment challenging. This study aimed to 1) investigate the variations of the spatial DFA during elbow flexion and 2) investigate the relationship between the distal humeral trochlear geometry and the in vivo spatial variation of the DFA.Methods: Ten healthy subjects participated in this study. Each subject performed a full elbow extension to maximum flexion with hand supination under dual fluoroscopic imaging system (DFIS) surveillance. The 2D fluoroscopic images and the 3D bone models were registered to analyze the in vivo elbow kinematics and DFAs. The spatial DFA positions were defined as inclination with the medial and lateral epicondyle axes (MLA) in the transverse and coronal planes. The range of the DFA positions was also investigated during different flexion phases. The Spearman correlation method was used to analyze the relationship between the distal humeral trochlear’s morphological parameters and the position of DFAs during different flexion phases.Results: The pathway of the DFAs showed an irregular pattern and presented individual features. The medial trochlear depth (MTD) (r = 0.68, p = 0.03) was positively correlated with the range of the DFA position (2.8° ± 1.9°) in the coronal plane from full extension to 30° of flexion. Lateral trochlear height (LTH) (r = −0.64, p = 0.04) was negatively correlated with the DFA position (−1.4° ± 3.3°) in the transverse plane from 30° to 60° of flexion. A significant correlation was found between LTH with the DFA position in the coronal (r = −0.77, p = 0.01) and transverse planes (r = −0.76, p = 0.01) from 60° to 90° of flexion.Conclusion: This study showed that the pathway of the dynamic flexion axis has an individual pattern. The medial and lateral trochlear sizes were the key parameters that might affect the elbow joint flexion function. When recovering complex distal humeral fractures or considering the implant design of total elbow arthroplasty, surgeons should pay more attention to the medial and lateral trochlea’s geometry, which may help restore normal elbow kinematics.

ObjectiveSeveral needleless techniques have been developed to outcome the inherent disadvantages of the traditional needle stitching technique for graft preparation, such as tendon damage through the needle, time consumption, and the potential risk of needlestick injury. The purpose of the present study is to compare the graft preparation time and the biomechanical performance between an efficient needleless technique and the traditional needle stitching technique for graft preparation in anterior cruciate ligament reconstruction (ACLR).MethodsThe time required to perform a complete suture on 20 hamstring tendons during ACLRs was measured. The grafts from one side were prepared using the needle stitching technique. The grafts from the other side used the needleless grasping suture technique. For the second part of the study, 12 fresh-frozen porcine flexor tendons were divided into two groups using two techniques and were mounted in an electric tensile test system. Each group was pretensioned to 100 N to simulate the maximum initial graft tension. The suturing state of sutures and graft (intact and damaged) and the load-elongation curve were recorded for each group. A Student’s t-test was used to compare the means of the two groups.ResultsIn operation, the needleless grasping suture technique group (19.8 ± 4.8, range: 13.5–32.9 s) was significantly faster (p 0.05).ConclusionThe needleless grasping suture technique was a convenient and efficient method for graft preparation in ACLR.

Abstract Background The purpose of this study was to investigate the association between the severity of Developmental dysplasia of the hip (DDH) and the abnormality in pelvic incidence (PI). Methods This was a retrospective study analyzing 53 DDH patients and 53 non-DDH age-matched controls. Computed tomography images were used to construct three-dimensional pelvic model. The Crowe classification was used to classify the severity of DDH. The midpoint of the femoral head centers and sacral endplates were projected to the sagittal plane of the pelvis. The PI was defined as the angle between a line perpendicular to the sacral plate at its midpoint and a line connecting this point to the axis of the femoral heads. Independent sample t-tests were used to compare the differences between the PI of DDH group and the non-DDH controls group. Kendall’s coefficient of concordance was used to determine the correlation between the severity of DDH and PI. Results Patients with DDH had a significantly (p = 0.041) higher PI than the non-DDH controls (DDH 47.6 ± 8.2°, normal 44.2 ± 8.8°). Crowe type I patients had a significantly (p = 0.038) higher PI (48.2 ± 7.6°) than the non-DDH controls. No significant difference between the PI in Crowe type II or III patients and the PI in non-DDH controls were found (Crowe type II, 50.2 ± 9.6°, p = 0.073; Crowe type III, 43.8 ± 7.2°, p = 0.930). No correlation was found between the severity of DDH and the PI (r = 0.091, p = 0.222). Conclusions No correlation was found between the severity of DDH and the PI. The study confirmed that the PI in DDH (Crowe type I) group was higher than that of the non-DDH control group, while the PI does not correlate with the severity of DDH.

Abstract Background Precise evaluation of the hip abductor and adductor muscles function in total hip arthroplasty (THA) patients during gait could help prevent postoperative complications and optimize the rehabilitation training program. The purpose of this study was to elucidate the effects of THA on the hip abductor and adductor muscle lengths and moment arms of in vivo patients during gait. Methods Ten unilateral THA patients received CT scans and dual fluoroscopic imaging for the hip kinematics during gait. The hip abductor and adductor muscle insertions were digitized on the 3D hip model for the determination of their dynamic lines of action and moment arms. Changes in the hip abductor and adductor muscle lengths and moment arms of THA patients between the implanted and non-implanted sides were quantified during gait. Results The adductor longus, adductor brevis, and pectineus of the implanted hips had significantly (P < 0.05) less elongation than that of the non-implanted side during the stance phase. The gluteus medius, gluteus minimus, and piriformis moment arms of the implanted side were significantly shorter. The piriformis muscle moment arm was significantly larger. In the double support phase, the adductor magnus and adductor longus moment arms of the implanted sides were significantly decreased. Conclusions Results suggested that the adverse effects of THA on hip stability. Development of a rehabilitation program considering the effects of THA is essential. Accurate surgical techniques may reduce the impact of THA on the peripheral muscles.

The purpose of this study was to introduce a new reference axis for tibial rotation in total knee arthroplasty (TKA) and verify its reliability. A consecutive series of 80 knees that underwent TKA from 2018 to 2020 as well as 80 healthy knees were analyzed using a three-dimensional tibial model. A coordinate system was established based on the standard TKA tibial cut. The line connecting the lateral-tibial eminence and the medial 1/3rd of the tibial tubercle or the medial border of the tibial tubercle was identified as the lateral eminence line (LE line) and the medial lateral eminence line (MLE line), respectively. To evaluate the reliability of the new reference axis, Akagi's line, the medial third of the tibial tubercle (1/3 line) was compared with the LE and MLE lines by measuring the angle between the lines and the Z-axis. In the coronal view, the intersection angle (TPA), which is composed of the line connecting the center of the medial and lateral tibial plateau with the Z-axis, was measured. The mean angle between Akagi's line and the Z-axis in the healthy group and the osteoarthritis (OA) group was 87.57 ± 3.48° and 87.61 ± 3.47°, respectively. The mean angle between the LE line and Z-axis in the healthy and OA groups was 87.15 ± 4.13° and 86.78 ± 3.95°, respectively. A weak correlation was found between the TPA and Akagi's line and the 1/3 line. A moderate correlation was observed between the TPA and LE lines. There were no significant differences between the healthy and OA groups (P > 0.05) in any of the four reference axes. The LE line showed excellent intra- and inter-observer reliability and reproducibility. The novel and easily drawn LE line is a preferable option for tibial component rotational alignment in TKA.

ObjectiveTo assess the difference between the posterior condylar angle (PCA) and the mechanical lateral distal femoral angle (mLDFA) in the osseous and cartilaginous contours in a non-arthritic Chinese population.MethodsComputed tomography (CT) and magnetic resonance imaging (MRI) were obtained from 83 patients with knee injuries before arthroscopy, and femur and distal femoral cartilage three-dimensional (3D) models were constructed. The 3D cartilage model was arranged to share physical space with the 3D femoral model, and then PCA and mLDFA were measured on the osseous and cartilaginous contours, respectively. The differences between the measurements with and without cartilage were evaluated.ResultsThe average PCA with cartilage was 2.88 ± 1.35° and without was 2.73 ± 1.34°. The difference was significant in all patients and females but not in males. The average mLDFA with cartilage was 84.73 ± 2.15° and without cartilage was 84.83 ± 2.26°, but the difference was statistically insignificant in all groups.ConclusionPCA on the osseous and cartilaginous contours significantly differed with and without cartilage in the female group, suggesting that cartilage thickness should be considered during preoperative femoral rotational resection planning.

Background: Total hip arthroplasty (THA) for hip dysplasia patients is sometimes complex and compromises pathomorphological changes in these patients. However, it remains unclear whether it is preoperative deformities or postoperative structures or anatomic changes during THA that have the most remarkable correlation with the hip dynamic function during gait. The purpose of this study was to investigate this relationship and propose insights into the surgical reconstruction strategy in patients with developmental dysplasia of the hip.Methods: A total of 21 unilateral hip dysplasia patients received computed tomography scans for the creation of 3D hip models before surgery and at the last follow-up. Acetabular and femoral orientations, hip center positions, and femoral length were measured before and after THA. Hip kinematics of the operated side during gait was quantified using a dual fluoroscopic imaging technique. Pearson correlation and multiple linear regression were performed to evaluate the relationship between hip maximum range of motion in six directions and demographics characters and above hip anatomic parameters before and after THA and their changes in surgery.Results: Pearson correlation analysis found significant correlations with the gait range of motion mainly in postoperative structures, including postoperative hip center positions and acetabulum and combined anteversion. Further multiple linear regression indicated that a laterally placed hip center was significantly correlated with an increased internal rotation (R2 = 0.25, p = 0.021), which together with increased postoperative acetabulum anteversion explained 45% of external rotation decreasing (p = 0.004). A proximally placed hip center was correlated with more extension (R2 = 0.30, p = 0.010). No significant demographic characters or preoperative deformities or surgical changes were included into other multiple regression models.Conclusion: Strong correlations between postoperative structures, especially hip center positions and gait range of motion in unilateral hip dysplasia patients after THA were found. It indicated that postoperative prosthesis structures, particularly hip center positions had significant impact on the hip gait motion range and should be treated with particular caution in surgery.

The concepts of “optimal posture (OP)” and “harmful posture (HP)” are commonly used, and specific spinal postures can contribute to back pain. However, quantitative descriptions of optimal and harmful standing (StP) and sitting (SP) postures are currently lacking, particularly for different body mass indices (BMIs). Therefore, this study aimed to identify and quantify the OPs and HPs of StP and SP at different BMIs and investigate the attitudes and beliefs of rehabilitation practitioners toward OPs and HPs. Overall, 552 rehabilitation practitioners were recruited to participate in a questionnaire survey to select the optimal position from seven sitting and five standing postures for each BMI healthy volunteer. The segmental relationships of each posture were qualified using the Vicon software. For normal BMI, the physiotherapists chose two SPs (48.19% and 49.64%) and one StP (80.42%) as the OP. One sitting SP (83.7%) and two standing StPs (43.48% and 48.19%) were selected as optimal for obese BMI. All the most commonly selected OPs had an upright lordotic posture, while the postures with slouched spinal curves or forward head postures were almost all selected as HP. Additionally, 96.74% of participants considered education about optimal SP and StP to be “quite” or “very” important. The OP of the StP and SP postures was mostly based on the vertical alignment of gravity lines and sagittal balance. For obese people, the rehabilitation practitioners’ observations may be erroneous, and further physical examination is necessary. Rehabilitation practitioners generally believe that postural education is essential in clinical practice.

This study aimed to compare the in-vivo kinematics and articular contact status between medial-pivot total knee arthroplasty (MP-TKA) and posterior stabilized (PS) TKA during weight-bearing single-leg lunge. 16 MP-TKA and 12 PS-TKA patients performed bilateral single-leg lunges under dual fluoroscopy surveillance to determine the in-vivo six degrees-of-freedom knee kinematics. The closest point between the surface models of the femoral condyle and the polyethylene insert was used to determine the contact position and area. The nonparametric statistics analysis was performed to test the symmetry of the kinematics between MP-TKA and PS-TKA. PS-TKA demonstrated a significantly greater range of AP translation than MP-TKA during high flexion (p = 0.0002). Both groups showed a significantly greater range of lateral compartment posterior translation with medial pivot rotation. The contact points of PS-TKA were located significantly more posterior than MP-TKA in both medial (10°–100°) and lateral (5°–40°, 55°–100°) compartments (p < 0.0500). MP-TKA had a significantly larger contact area in the medial compartment than in the lateral compartment. In contrast, no significant differences were observed in PS-TKA. The present study revealed no significant differences in clinical outcomes between the MP and PS groups. The PS-TKA demonstrated significantly more posterior translations than MP-TKA at high flexion. The contact points are located more posteriorly in PS-TKA compared with MP-TKA. A larger contact area and medial pivot pattern during high flexion in MP-TKA indicated that MP-TKA provides enhanced medial pivot rotation.

Purpose: The aims of this study were to 1) investigate the effects of femoral drilling angle in coronal and sagittal planes on the stress and strain distribution around the femoral and tibial tunnel entrance and the stress distribution on the graft, following anterior cruciate ligament reconstruction (ACLR), 2) identify the optimal femoral drilling angle to reduce the risk of the tunnel enlargement and graft failure.Methods: A validated three-dimensional (3D) finite element model of a healthy right cadaveric knee was used to simulate an anatomic ACLR with the anteromedial (AM) portal technique. Combined loading of 103.0 N anterior tibial load, 7.5 Nm internal rotation moment, and 6.9 Nm valgus moment during normal human walking at joint flexion of 20° was applied to the ACLR knee models using different tunnel angles (30°/45°/60° and 45°/60° in the coronal and sagittal planes, respectively). The distribution of von Mises stress and strain around the tunnel entrances and the graft was calculated and compared among the different finite element ACLR models with varying femoral drilling angles.Results: With an increasing coronal obliquity drilling angle (30° to 60°), the peak stress and maximum strain on the femoral and tibial tunnel decreased from 30° to 45° and increased from 45° to 60°, respectively. With an increasing sagittal obliquity drilling angle (45° to 60°), the peak stress and the maximum strain on the bone tunnels increased. The lowest peak stress and maximum strain at the ACL tunnels were observed at 45° coronal/45° sagittal drilling angle (7.5 MPa and 7,568.3 μ-strain at the femoral tunnel entrance, and 4.0 MPa and 4,128.7 μ-strain at the tibial tunnel entrance). The lowest peak stress on the ACL graft occurred at 45° coronal/45° sagittal (27.8 MPa) drilling angle.Conclusions: The femoral tunnel drilling angle could affect both the stress and strain distribution on the femoral tunnel, tibial tunnel, and graft. A femoral tunnel drilling angle of 45° coronal/ 45° sagittal demonstrated the lowest peak stress, maximum strain on the femoral and tibial tunnel entrance, and the lowest peak stress on the ACL graft.

Abstract Background The deformity of the proximal femur and acetabular in patients with developmental dysplasia of the hip (DDH) renders an intraoperative decision for ideal component placement challenging. We hypothesized that the altered morphology of calcar femorale (CF) in DDH patients changed the fixation mechanism of the cementless metaphyseal-filling stem and aimed to predict stem anteversion using proximal femoral anatomical parameters from preoperative CT. Methods Preoperative and postoperative CT scans of 34 DDHs with a metaphyseal-filling stem in THA were retrospectively analyzed. Proximal femoral anatomical parameters, including the femoral anteversion (FA) and the CF angles at the low femoral neck (LFN) and the center of the lesser trochanter (CLT) levels (FA-LFN, FA-CLT, CF-LFN, and CF-CLT) were measured. The dysplastic hips were divided into the CF group (n = 21) and the non-CF group (n = 13) according to the presence of the CF-LFN. The association between the anatomical parameters and the postoperative stem anteversion was statistically analyzed, and the predicted stem anteversion was compared with postoperative stem anteversion. Results In the CF group, the combination of the CF-LFN and FA-CLT exhibited a strong positive correlation (R = 0.870, p < 0.001) with the postoperative stem anteversion. In the non-CF group, only the FA-LFN had a strong positive correlation (R = 0.864, p < 0.001). Average prediction errors were 5.9° and 6.4° in the CF and non-CF groups. Conclusions The presence of CF-LFN is related to the press-fit mechanism of the metaphyseal-filling stem, and the preoperative measurements from CT images can be employed as a tool to predict postoperative stem anteversion in DDH patients.

Abstract Background The purpose of this study was to investigate the relationship between the three dimensional (3D) femoral head displacement in patients with developmental dysplasia of the hip (DDH) and Crowe classification. Methods Retrospectively, CT scans of 60 DDH patients and 55 healthy demography-matched healthy control subjects were analyzed. Using the anterior pelvic plane a pelvic anatomic coordinate system was established. The center coordinates of the femoral heads of both the DDH patients and control subjects were quantified relative to the pelvic coordinate system and were mapped proportionally to a representative normal pelvis for comparison. Results In the anteroposterior (AP) direction, the center of the femoral head was significantly more anterior in the DDH patients (type I, II, and III, respectively45.0 ± 5.5, 42.9 ± 7.1, and 43.9 ± 4.6 mm) when compared to the controls (50.0 ± 5.2 mm) (p

Background The medial-pivot (MP) prosthesis was developed to produce more physiological postoperative knee kinematics and better patient satisfaction than traditional prostheses, but outcomes are inconsistent in different studies of Caucasian patients. This study aimed to investigate the postoperative patient satisfaction and in vivo knee kinematics of the MP and posterior-stabilized (PS) prosthesis during gait activity in Chinese patients.Methods A retrospective analysis of 12 patients was received for this study in each MP group and PS group. Patient-reported satisfaction level and Forgotten Joint Score (FJS) were evaluated with questionnaires. A dual fluoroscopic imaging system was used to investigate in vivo knee kinematics of MP and PS total knee arthroplasty (TKA) during treadmill walking at a speed of 0.4 m/s.Results Comparable promising patient satisfaction and overall FJS (MP 60.7 ± 15.35 vs. PS 51.3 ± 17.62, p = 0.174) were found between the MP and PS groups. Peak flexion appeared at around 70% of gait cycle with values of 52.4 ± 7.4° for MP and 50.1 ± 3.6° for PS groups (no difference). Both groups maintained a stable position at the stance phase and began to translated anteriorly at toe-off with an amount of 4.5 ± 2.3 mm in the MP and 6.6 ± 2.7 mm in the PS (p = 0.08) group until late swing. The range of this external rotation motion was 5.9 ± 4.8 and 6.2 ± 4.1° (p = 0.79) for the MP and PS, respectively.Conclusion A similar knee kinematics pattern characterized by a loss of early-stance knee flexion and femoral rollback during walking was observed in the MP and PS TKAs. Our study confirmed similar effectiveness of MP TKA compared to PS TKA in Chinese patients, while the change of knee kinematics of both implants during slow walking should be noted.

Background: A comprehensive and thorough understanding of functional acetabular component orientation is essential for optimizing the clinical outcome after total hip arthroplasty (THA). This study aimed to quantify the functional acetabular anteversion and inclination of unilateral THA patients during walking and static standing and to determine whether the functional acetabular orientation falls within the Lewinnek safe zone.Methods: Seventeen patients with unilateral THA received a CT scan and dual fluoroscopic imaging during level walking and static standing to evaluate in vivo hip kinematics. The pelvic functional coordinate system of the 3D CT-based computer model was defined by the line of gravity and anterior pelvic plane (APP) to measure functional acetabular anteversion and inclination in different postures. The Lewinnek safe zone was used to determine the acetabular malposition during functional activities.Results: The THA side demonstrated an average of 10.1° (± 9.6°, range –7.5° to 29.9°) larger functional anteversion and 16.0° (± 9.2°, range –7.2° to 29.9°) smaller inclination than native hips during level walking. Functional acetabular anteversion in the THA side during level walking and static standing was significantly larger than anatomical measurements (p < 0.05). Acetabular orientation of most well-placed THA components anatomically in the Lewinnek safe zone fell outside the safe zone during more than half of the gait cycle and static standing.Conclusion: The current study revealed that an anatomically well-placed acetabular cup does not guarantee a well-functional orientation during daily activities. The in vivo mechanical performance and loading conditions of the THA component during other weight-bearing activities should be investigated in further studies.

BackgroundWhile in vitro wear simulation of unicompartmental knee arthroplasty (UKA) showed outstanding long-term wear performance, studies reported that polyethylene (PE) wear was responsible for 12% fixed-bearing (FB) UKA failure. This paper aimed to quantify the in vivo 6-degrees-of-freedom (6-DOF) knee kinematics and contact positions of FB UKA during daily activities and compare with the previous results of in vitro wear simulator.MethodsFourteen patients following unilateral medial FB UKA received a CT scan and dual fluoroscopic imaging during level walking, single-leg deep lunge, and sit-to-stand motion for evaluating in vivo 6-DOF FB UKA kinematics. The closest point between surface models of the femoral condyle and PE insert was determined to locate the medial compartmental articular contact positions, which were normalized relative to the PE insert length. The in vivo contact area was compared with the in vitro wear region in previous simulator studies.ResultsThe in vivo contact positions during daily activities were more anterior than those in the previous in vitro wear simulator studies (p < 0.001). Significant differences in the femoral anteroposterior translation and tibial internal rotation during the stance phase were observed and compared with those in lunge and sit-to-stand motions (p < 0.05). The in vivo contact position located anteriorly and medially by 5.2 ± 2.7 and 1.8 ± 1.6 mm on average for the stance phase, 1.0 ± 2.4 and 0.9 ± 1.5 mm for the lunge, and 2.1 ± 3.3 and 1.4 ± 1.4 mm for sit-to-stand motion. The in vivo contact position was in the more anterior part during the stance phase (p < 0.05).ConclusionThe current study revealed that the contact position of FB UKA was located anteriorly and medially on the PE insert during in vivo weight-bearing activities and different from previous findings of the in vitro wear simulator. We should take in vivo 6-DOF knee kinematics and contact patterns of FB UKA into account to reproduce realistic wear performance for in vitro wear simulator and to improve implant design.

ObjectiveFemoral offset (FO) restoration is significantly correlated with functional recovery following total hip arthroplasty (THA). Accurately assessing the effects of FO changes on hip muscles following THA would help improve function and optimize functional outcomes. The present study aimed to (1) identify the impact of FO side difference on the hip muscle moment arms following unilateral THA during gait and (2) propose the optimal FO for a physiological hip muscle function.MethodsIn vivo hip kinematics from eighteen unilateral THA patients during gait were measured with a dual-fluoroscopic imaging system. The moment arms of thirteen hip muscles were calculated using CT-based 3D musculoskeletal models with the hip muscles’ lines of actions. The correlation coefficient (R) between FO and hip muscle moment arm changes compared with the non-implanted hip was calculated. We considered that the FO reconstruction was satisfactory when the abductor moment arms increased, while the extensor, adductor, and flexor moment arms decreased less than 5%.ResultsA decreased FO following THA was significantly correlated with a decrease of the abductor and external rotator moment arms during the whole gait (R > 0.5) and a decrease of extensor moment arms during the stance phase (R > 0.4). An increased FO following THA was significantly associated with shorter flexor moment arms throughout the gait (R < −0.5) and shorter adductor moment arms in the stance phase (R < −0.4). An increase in FO of 2.3–2.9 mm resulted in increased abductor moment arms while maintaining the maximum decrease of the hip muscles at less than 5.0%.ConclusionAn increase of 2–3 mm in FO could improve the abductor and external rotator function following a THA. Accurate surgical planning with optimal FO reconstruction is essential to restoring normal hip muscle function in THA patients.

[This corrects the article DOI: 10.1371/journal.pone.0174663.].

Knee joint pain is a common symptom in obese individuals and walking is often prescribed as part of management programs. Past studies in obese individuals have focused on standing alignment and kinematics in the sagittal and coronal planes. Investigation of 6 degree-of-freedom (6DOF) knee joint kinematics during standing and gait is important to thoroughly understand knee function in obese individuals with knee pain. This study aimed to investigate the 6DOF knee joint kinematics in standing and during gait in obese patients using a validated fluoroscopic imaging system. Ten individuals with obesity and knee pain were recruited. While standing, the knee was in 7.4±6.3°of hyperextension, 2.8±3.3° of abduction and 5.6±7.3° of external rotation. The femoral center was located 0.7±3.1mm anterior and 5.1±1.5mm medial to the tibial center. During treadmill gait, the sagittal plane motion, i.e., flexion/extension and anterior-posterior translation, showed a clear pattern. Specifically, obese individuals with knee pain maintained the knee in more flexion and more anterior tibial translation during most of the stance phase of the gait cycle and had a reduced total range of knee flexion when compared to a healthy non-obese group. In conclusion, obese individuals with knee pain used hyperextension knee posture while standing, but maintained the knee in more flexion during gait with reduced overall range of motion in the 6DOF analysis.

Context: Arthrofibrosis after anterior cruciate ligament (ACL) reconstruction can be detrimental to the knee joint function and patient outcomes. However, the effects of arthrofibrosis on the in vivo tibiofemoral and patellofemoral joint kinematics after ACL reconstruction remain unclear. Objective: The objective of this study was to quantify the in vivo knee kinematics during a dynamic lunge task in the knee with arthrofibrosis after ACL reconstruction. Methods: Eleven patients with arthrofibrosis in one knee after ACL reconstruction participated in this study. Computed tomography and dual fluoroscopic imaging were used to evaluate in vivo kinematics of affected and contralateral knees during a lunge task. Differences in 6 degrees of freedom tibiofemoral kinematics and patellar tracking between limbs were assessed via repeated-measures analysis of variance. Results: Internal tibial rotation (5.2° vs 7.5°, respectively; P<.001) and inferior patellar shift (24.6 mm vs 28.9mm, respectively; P < .001) were significantly lower in the arthrofibrotic knee compared with the contralateral knee from 15° to 75° of knee flexion. The patella in the arthrofibrotic knee significantly less flexed by 9.1° (P = .009) throughout the measured ROM and less laterally tilted by 3° (P = .017) compared with the contralateral knee from 30° to 75° of knee flexion. Conclusions: A significant superior shift and medial tilt of the patella were found in the affected knee compared with those in the contralateral knee during the dynamic lunge. Decreased internal tibial rotation and patellar flexion were found in knees with arthrofibrosis following ACL reconstruction; whether these kinematic changes are caused by arthrofibrosis need further investigation. [ABSTRACT FROM AUTHOR]