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Purpose: Total knee arthroplasty (TKA) stands as a primary intervention for severe knee ailments, yet concerns remain regarding postoperative patient satisfaction and flexion instability. This study aims to evaluate the in‐vivo kinematics of medial‐pivot (MP) and posterior‐stabilised (PS) designs during step‐up activity, in comparison to the kinematics of the nonoperated contralateral knee. Methods: Sixteen patients with PS‐TKA and 14 with MP‐TKA were retrospectively examined. Clinical outcomes were assessed using patient‐completed questionnaires. Motion during step‐up was captured using a dual fluoroscopic system. Statistical analysis was applied to evaluate the in‐vivo tibiofemoral six‐degree‐of‐freedom kinematics and articular contact positions between the two groups. Results: Despite being older, patients in the MP group reported higher postoperative subjective scores for weight‐bearing functional activities. The axial rotation centres of MP‐TKA located on the medial tibial plateau exhibited less variance compared to PS‐TKA and contralateral knees. Compared to the contralateral knee (contralateral to medial‐pivot [C‐MP] or contralateral to posterior‐stabilised [C‐PS]), the MP group exhibited limited range of motion in terms of anteroposterior translation (MP: 3.6 ± 1.3 mm vs. C‐MP: 7.4 ± 2.5 mm, p < 0.01) and axial rotation (MP: 6.6 ± 1.9° vs. C‐MP: 10.3 ± 4.9°, p = 0.02), as well as in the PS group for anteroposterior translation (PS: 3.9 ± 1.7 mm vs. C‐PS: 7.2 ± 3.7 mm, p < 0.01). Conclusion: The MP group with better postoperative ratings demonstrated a more stable MP axial rotation pattern during step‐up activity compared to the PS group, underscoring the pivotal role of prosthetic design in optimising postoperative rehabilitation and functional recovery. Level of Evidence: Level III. [ABSTRACT FROM AUTHOR]

Squatting is a common daily activity and fundamental exercise in resistance training and closed kinetic chain programs. The aim of this study was to investigate the effects of an experimentally induced weakness of the gluteal muscles on joint kinematics, reactions forces (JRFs), and dynamic balance performance during deep bilateral squats in healthy young adults. Ten healthy adults received sequential blocks of (1) branch of the superior gluteal nerve to the tensor fasciae latae (SGNtfl) muscle, (2) superior gluteal nerve (SGN), and (3) inferior gluteal nerve (IGN) on the dominant right leg. At the control condition and following each block, the participants were instructed to perform deep bilateral squats standing on two force plates. Hip, knee, ankle, and pelvis kinematics did not differ significantly following iatrogenic weakness of gluteal muscles. The most important finding was the significant differences in JRFs following SGN and IGN block, with the affected hip, patellofemoral, and ankle joint demonstrating lower JRFs, whereas the contralateral joints demonstrated significantly higher JRFs, especially the patellofemoral joint which demonstrated an average maximum difference of 1.43 x body weight compared with the control condition. When performing a deep bilateral leg squat under SGN and IGN block, the subjects demonstrated an increased center of pressure (CoP) range and standard deviation (SD) in mediolateral compared with the control condition. These results imply that squat performance changes significantly following weakness of gluteal muscles and should be considered when assessing and training athletes or patients with these injuries. [ABSTRACT FROM AUTHOR]

Purpose: A new CR TKA design with concave medial and convex lateral tibial polyethylene bearing components was introduced recently to improve functional outcomes. This study aimed to investigate in-vivo articular contact kinematics in unilateral asymmetrical tibial polyethylene geometry CR TKA patients during strenuous knee flexion activities. Methods: Fifteen unilateral CR TKA patients (68.4 ± 5.8 years; 6 male/9 female) were evaluated for both knees during sit-to-stand, single-leg deep lunges and step-ups using validated combined computer tomography and dual fluoroscopic imaging system. Medial and lateral condylar contact positions were quantified during weight-bearing flexion activities. The Wilcoxon signed-rank test was performed to determine if there is a significant difference in articular contact kinematics during strenuous flexion activities between CR TKA and the non-operated knees. Results: Contact excursions of the lateral condyle in CR TKAs were significantly more anteriorly located than the contralateral non-operated knee during sit-to-stand (3.7 ± 4.8 mm vs − 7.8 ± 4.3 mm) and step-ups (− 1.5 ± 3.2 mm vs − 6.3 ± 5.8 mm). Contact excursions of the lateral condyle in CR TKAs were significantly less laterally located than the contralateral non-operated knee during sit-to-stand (21.4 ± 2.8 mm vs 24.5 ± 4.7 mm) and single-leg deep lunges (22.6 ± 4.4 mm vs 26.2 ± 5.7 mm, p < 0.05). Lateral condyle posterior rollback was not fully restored in CR TKA patients during sit-to-stand (9.8 ± 6.7 mm vs 12.9 ± 8.3 mm) and step-ups (8.1 ± 4.8 mm vs 12.2 ± 6.4 mm). Lateral pivoting patterns were observed in 80%, 73% and 69% of patients during sit-to-stand, step-ups and single-leg deep lunges respectively. Conclusion: Although lateral femoral rollback and lateral pivoting patterns were observed during strenuous functional daily activities, asymmetric contact kinematics still persisted in unilateral CR TKA patients. This suggests the specific investigated contemporary asymmetrical tibial polyethylene geometry CR TKA design evaluated in this study does not fully replicate healthy knee contact kinematics during strenuous functional daily activities. Level of evidence: III. [ABSTRACT FROM AUTHOR]

Purpose: The aim of the present study was to trace knee position at the time of bone bruise (BB) and investigate how much this position departed from the knee biomechanics of an in vivo flexion–extension. Methods: From an original cohort of 62 patients, seven (11%) presented bicompartmental edemas and were included in the study. 3D models of bones and BB were obtained from MRI. Matching bone edemas, a reconstruction of the knee at the moment of BB was obtained. For the same patients, knee kinematics of a squat was calculated using dynamic Roentgen sterephotogrammetric analysis (RSA). Data describing knee position at the moment of BB were compared to kinematics of the same knee extrapolated from RSA system. Results: Knee positions at the moment of BB was significantly different from the kinematics of the squat. In particular, all the patients' positions were out of squat range for both anterior and proximal tibial translation, varus–valgus rotation (five in valgus and two in varus), tibial internal–external rotation (all but one, five externally and one internally). A direct comparison at same flexion angle between knee at the moment of BB (average 46.1° ± 3.8°) and knee during squat confirmed that tibia in the former was significantly more anterior (p < 0.0001), more externally rotated (6.1 ± 3.7°, p = 0.04), and valgus (4.1 ± 2.4°, p = 0.03). Conclusion: Knee position at the moment of Bone bruise position was out of physiological in-vivo knee range of motion and could reflect a locked anterior subluxation occurring in the late phase of ACL injury rather than the mechanism leading to ligament failure. Level of evidence: Level IV [ABSTRACT FROM AUTHOR]

This in vivo study investigated the effect of axial load on lunate and scaphoid kinematics during flexion–extension and radial–ulnar deviation of the uninjured wrist using four-dimensional computed tomography. We found that applying axial load to the wrist results in a more flexed, radially deviated and pronated position of the lunate and scaphoid during flexion–extension of the wrist compared with when no load is applied. A larger pronation and supination range of the lunate and scaphoid was seen when the wrist was flexed and extended under axial load, whereas a larger flexion and extension range of the lunate and scaphoid occurred during radial–ulnar deviation of the wrist when axial load was applied. [ABSTRACT FROM AUTHOR]

• New algorithm was able to register with an accuracy of <1 mm (in-plane) and <2°. • The algorithm could not register all images successfully. • Semi-automatic or manual registration is still required to obtain good results. The accurate quantification of in-vivo tibio-femoral kinematics is essential for understanding joint functionality, but determination of the 3D pose of bones from 2D single-plane fluoroscopic images remains challenging. We aimed to evaluate the accuracy, reliability and repeatability of an intensity-based 2D/3D registration algorithm. The accuracy was evaluated using fluoroscopic images of 2 radiopaque bones in 18 different poses, compared against a gold-standard fiducial calibration device. In addition, 3 natural femora and 3 natural tibiae were used to examine registration reliability and repeatability. Both manual fitting and intensity-based registration exhibited a mean absolute error of <1 mm in-plane. Overall, intensity-based registration of the femoral bone model revealed significantly higher translational and rotational errors than manual fitting, while no statistical differences (except for y-axis translation) were found for the tibial bone model. The repeatability of 108 intensity-based registrations showed mean in-plane standard deviations of 0.23–0.56 mm, but out-of-plane position repeatability was lower (mean SD: femur 7.98 mm, tibia 6.96 mm). SDs for rotations averaged 0.77–2.52°. While the algorithm registered some images extremely well, other images clearly required manual intervention. When the algorithm registered the bones repeatably, it was also accurate, suggesting an approach that includes manual intervention could become practical for efficient and accurate registration. [ABSTRACT FROM AUTHOR]

The aim was to evaluate if motion between the scaphoid bone fragments is related to the position of the fracture line and if a scaphoid nonunion results in the uncoupling of the proximal and distal carpal row during wrist motion. The influence of dorsal intercalated segment instability on interfragmentary motion was also analysed. In this study, 12 patients were included with unilateral scaphoid nonunion. Four-dimensional computerized tomography was used to analyse flexion–extension and radioulnar deviation motion of both wrists. We found that an increased instability of the scaphoid fragments is associated with the presence of dorsal intercalated segment instability and is not dependent on the position of the fracture line relative to the scaphoid apex. Additionally, a scaphoid nonunion results in an uncoupling of the carpal rows. [ABSTRACT FROM AUTHOR]

Additional fixation of the palmar scapholunate interosseous ligament has been advocated to improve the long-term results of dorsal scapholunate interosseous ligament reconstruction. To investigate the validity of this approach, we determined normal scapholunate motion patterns and calculated the location of the scapholunate rotation axis. We hypothesized that the optimal location of the scapholunate interosseous ligament insertion could be determined from the scapholunate rotation axis. Four-dimensional computerized tomography was used to study the wrist motion in 21 healthy participants. During flexion–extension motions, the scaphoid rotates 38° (SD 0.6°) relative to the lunate; the rotation axis intersects the dorsal ridge of the proximal pole of the scaphoid and the dorsal ridge of the lunate. Minimal scapholunate motion is present during radioulnar deviation. Since the scapholunate rotation axis runs through the dorsal proximal pole of the scaphoid, this is probably the optimal location for attaching the scapholunate ligament during reconstructive surgery. [ABSTRACT FROM AUTHOR]

Abstract Computational modeling of polyethylene wear based on patient-specific gait kinematics and component orientation remains lacking. This study aimed to quantify the polyethylene wear among 48 total hip arthroplasty (THA) using patient-specific data through a computational model incorporating the cross-shear effect. Strong patient variations were observed in volumetric wear rate (54.1 ± 13.9 mm3/year) and linear wear rate (0.20 ± 0.08 mm/year). Regression analysis demonstrated that axial plane rotation, in light of its influence on cross-shear effect, plays an important role in polyethylene wear. The computational model based on patient-specific gait kinematics and component orientation provides a useful tool to investigate the in-vivo polyethylene wear. Highlights • A THA wear model based on patient-specific data was developed. • The sliding-distance and cross-shear effect was incorporated based on 48 THA. • Strong variations in wear rates and locations across subjects were observed. • Increased axial RoM represents the leading factor to accelerated wear rate. • Acetabular component orientations are significant predictors to wear locations. [ABSTRACT FROM AUTHOR]

Polyethylene remains the most popular bearing material for total knee arthroplasty (TKA). Despite its widespread use, wear continue to be one of major factors implicated in revision surgery. Sliding distance, cross-shear, and contact stress are the major factors influencing polyethylene wear. As previous studies have either relied on wear simulations, computational modeling, or in vitro measurements to quantify sliding distance and cross-shear, in vivo subject-specific sliding distance and cross-shear after bi-cruciate retaining (BCR) TKA has not been previously reported. The objective of this study was to quantify the 6°-of-freedom (6DOF) in vivo kinematics, sliding distance, and cross-shear in BCR TKA patients during gait. Twenty-nine unilateral BCR TKA patients performed level walking on a treadmill under dual fluoroscopic imaging system (DFIS) surveillance. Cumulative normalized sliding distances between the lateral and medial compartments did not change significantly (p > 0.05) during the gait cycle. Although the total normalized sliding distance was similar between the lateral and medial compartments, the cross-shear at the lateral compartment differed significantly from that at the medial compartment (p < 0.001). Significant differences in the relative length positions of the peak sliding distance and cross-shear were found between the lateral and medial bearing components. The flexion-extension motion of the reconstructed knee was more associated with the linear displacements (anterior-posterior, R 2  = 0.6; lateral-medial, R 2  = 0.8, proximal-distal, R 2  = 0.7) than the angular displacement (varus-valgus, R 2  = 0.18; internal-external rotation, R 2  = 0.28). Despite some differences in peak sliding distance and cross-shear positons, our results suggest similar articular contact patterns between the lateral and medial compartments in BCR TKA patients during gait. The data could provide insights into understanding the potential wear patterns in BCR TKAs. [ABSTRACT FROM AUTHOR]

Background Numerous studies have reported on the tibiofemoral articular cartilage contact kinematics, however, no data has been reported on the articular cartilage geometry at the contact area. This study investigated the in-vivo tibiofemoral articular cartilage contact biomechanics during a dynamic step-up motion. Methods Ten healthy subjects were imaged using a validated magnetic resonance and dual fluoroscopic imaging technique during a step-up motion. Three-dimensional bone and cartilage models were constructed from the magnetic resonance images. The cartilage contact along the motion path was analyzed, including cartilage contact location and the cartilage surface geometry at the contact area. Findings The cartilage contact excursions were similar in anteroposterior and mediolateral directions in the medial and lateral compartments of the tibia plateau ( P > 0.05). Both medial and lateral compartments were under convex (femur) to convex (tibia) contact in the sagittal plane, and under convex (femur) to concave (tibia) contact in the coronal plane. The medial tibial articular contact radius was larger than the lateral side in the sagittal plane along the motion path ( P < 0.001). Interpretations These data revealed that both the medial and lateral compartments of the knee experienced convex (femur) to convex (tibia) contact in sagittal plane (or anteroposterior direction) during the dynamic step-up motion. These data could provide new insight into the in-vivo cartilage contact biomechanics research, and may provide guidelines for development of anatomical total knee arthroplasties that are aimed to reproduce normal knee joint kinematics. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this study was to determine in-vivo kinematics of our developed posterior-stabilized (PS) total knee prosthesis for Asian populations in comparison with a popular high-flexion PS prosthesis.Methods: We analyzed 62 osteoarthritic knees: 31 knees with the new PS prosthesis (group A) and 31 knees with a popular high-flexion PS prosthesis (group B). Radiographic knee images were taken during standing, lunge, and kneeling activities. The three-dimensional position and orientation of the implant components were determined using model-based shape matching techniques.Results: Group A showed slightly greater implant flexion angles compared with knees with conventional prosthesis at maximum lunge (average: 119 vs. 110°, p = 0.001), and at maximum kneeling (121 vs. 114°, p = 0.004), although the range of motion was not significantly different. The femoral centre positions were more posterior in group A at standing, at 90° lunge, at maximum lunge (-9 and -7 mm, p = 0.004), at 90° kneeling, and at maximum kneeling (-9 vs. -7 mm, p = 0.016), and posterior translations of the femoral center were greater at 90° knee flexion postures. The femoral centre positions had a strong negative correlation with implant flexion angles at maximum lunge in group B (r = -0.893, p < 0.001), but not in group A (p = 0.242).Conclusions: The new PS prosthesis designed for Asian knee morphology achieved flexion angles and range of motion at least comparable to that of conventional high-flexion PS prosthesis. The femoral roll-back pattern, however, is different from a conventional knee, reflecting the post/cam design. [ABSTRACT FROM AUTHOR]

An equal knee joint height during flexion and extension is of critical importance in optimizing soft-tissue balancing following total knee arthroplasty (TKA). However, there is a paucity of data regarding the in-vivo knee joint height behavior. This study evaluated in-vivo heights and anterior–posterior (AP) translations of the medial and lateral femoral condyles before and after a cruciate-retaining (CR)-TKA using two flexion axes: surgical transepicondylar axis (sTEA) and geometric center axis (GCA). Eleven osteoarthritis (OA) knee patients were studied during a weight-bearing single leg lunge, using a validated dual fluoroscopic imaging system (DFIS) based tracking technique. Eight healthy subjects were recruited as controls. The results demonstrated that following TKA, the medial and lateral femoral condyle heights were not equal at mid-flexion (15–45°, medial condyle lower then lateral by 2.4 mm at least, p <0.01), although the knees were well-balanced at 0° and 90°. While the femoral condyle heights increased from the pre-operative values (>2 mm increase on average, p <0.05), they were similar to the intact knees except that the medial sTEA was lower than the intact medial condyle between 0° and 90°. At deep flexion (>90°), both condyles were significantly higher (>2 mm, p <0.01) than the healthy knees. Anterior femoral translation of the TKA knee was more pronounce at mid-flexion, whereas limited posterior translation was found at deep flexion. These data suggest that a well-balanced knee intra-operatively might not necessarily result in mid-flexion and deep flexion balance during functional weight-bearing motion, implying mid-flexion instability and deep flexion tightness of the knee. [ABSTRACT FROM AUTHOR]

• Robotic surgical systems can predict post-op kinematics using intra-op measurements. • Correlation between intra-op and post-op weight bearing kinematics is unknown. • We compared intra-op and post-op implant contact paths after medial knee arthroplasty. • Contact paths primarily differ at low knee flexion angles during daily activities. Robot-assisted surgical systems can predict post-operative kinematics based upon intra-operative passive kinematics, planned implant position and alignment, and soft-tissue tension. It is currently unknown how well the intra-operative passive kinematics replicate the post-surgical weight bearing active kinematics. This study compared intra-operative and post-operative tibiofemoral implant contact paths after medial unicompartmental knee arthroplasty (mUKA). Passive intraoperative and active postoperative tibiofemoral contact path data was collected from eight patients who underwent mUKA. Intraoperative contact path data was measured using a navigation system. Postoperative contact path data was measured during walking, chair rise, stair ascent, and stair descent using a biplane radiography system and a validated tracking process. A total of 86 movement trials were included in the analysis. The contact point on the femur implant was up to 9.8 mm more medial and up to 8.3 mm less anterior at low flexion angles during activities of daily living than during passive extension intra-operatively, and the contact point on the tibia implant was up to 13.8 mm less lateral and up to 5.8 mm less posterior at low flexion angles during activities of daily living than during intra-operative passive extension. Femoral contact paths primarily differed between 3° and 42° of flexion; and tibial contact paths differed between 3° and 50° of flexion. This pilot study is the first to compare intra-operative and post-operative weight bearing contact paths. The primary conclusions from this study are that contact points on the femur implant are more medial and less anterior at low flexion angles during activities of daily living than during passive extension intra-operatively, and that the contact points on the tibia implant are less lateral at low flexion angles during activities of daily living than during intra-operative passive extension. [ABSTRACT FROM AUTHOR]

Wrist pathology is often diagnosed by using the contralateral wrist as a comparison of baseline motion and strength. However, recent range of motion studies suggest that females have different carpal motion patterns compared to males and that the dominant carpal bones have different motion patterns. The purpose of this study is to evaluate the effect of sex and hand dominance on in vivo kinematics of the scaphoid, lunate and capitate using four-dimensional computed tomography (4D-CT) analysis in healthy uninjured volunteers. In this prospective study, both wrist of 20 uninjured Caucasian volunteers (11 men and 9 women) were assessed using 4D-CT during active flexion–extension and radial-ulnar deviation. A linear mixed model was used to compare the carpal motion patterns. Sex had no influence on carpal kinematics. Hand-dominance in males did have a significant effect on carpal kinematics. During flexion–extension of the male wrist, more radial-ulnar deviation of the lunate, scaphoid and capitate of the non-dominant hand was seen. During radial-ulnar deviation of the male wrist, radial-ulnar deviation and pro-supination of the lunate was more in the dominant hand. This study provides a better understanding of carpal kinematics and the effect of sex and hand-dominance on the scaphoid, lunate and capitate in uninjured wrists. [ABSTRACT FROM AUTHOR]

Introduction: To better understand cervical kinematics following cervical disc replacement (CDR), the in vivo behavior of a minimally constrained CDR was assessed. Methods: Radiographic analysis of 19 patients undergoing a 1-level CDR from C4-5 to C6-7 (DISCOVER, Depuy-Spine, USA) was performed. Neutral-lateral and flexion-extension radiographs obtained at preop, postop and late follow-up were analyzed for segmental angle and global angle (GA C2-7). Flexion-extension range of motion was analyzed using validated quantitative motion analysis software (QMA®, Medical Metrics, USA). The FSU motion parameters measured at the index and adjacent levels were angular range of motion (ROM), translation and center of rotation (COR). Translation and COR were normalized to the AP dimension of the inferior endplate of the caudal vertebra. All motion parameters, including COR, were compared with normative reference data. Results: The average patient age was 43.5 ± 7.3 years. The mean follow-up was 15.3 ± 7.2 months. C2-7 ROM was 35.9° ± 15.7° at preop and 45.4° ± 13.6° at follow-up (∆ p < .01). Based on the QMA at follow-up, angular ROM at the CDR level measured 9.8° ± 5.9° and translation was 10.1 ± 7.8 %. Individuals with higher ROM at the CDR level had increased translation at that level ( p < .001, r = 0.97), increased translation and ROM at the supra-adjacent level ( p < .001, r = .8; p = .005, r = .6). There was a strong interrelation between angular ROM and translation at the supra-adjacent level ( p < .001, r = .9) and caudal-adjacent level ( p < .001, r = .9). The location of the COR at the CDR- and supra-adjacent levels was significantly different for the COR-X ( p < .001). Notably, the COR-Y at the CDR level was significantly correlated with the extent of CDR-level translation ( p = .02, r = .6). Shell angle, which may be influenced by implant size and positioning had no impact on angular ROM but was correlated with COR-X ( p = .05, r = −.6) and COR-Y ( p = .04, r = −.5). Conclusion: The COR is an important parameter for assessing the ability of non-constrained CDRs to replicate the normal kinematics of a FSU. CDR size and location, both of which can impact shell angle, may influence the amount of translation by affecting the location of the COR. Future research is needed to show how much translation is beneficial concerning clinical outcomes and facet loading. [ABSTRACT FROM AUTHOR]

Abstract: Background: The assessment of the joint space thickness is an important clinical parameter for diagnosing osteoarthritis. The accuracy of joint space thickness evaluation from radiographs is limited due to anatomical complexity of the wrist. We propose using distance maps estimated from 3-dimensional and 4-dimensional images reflecting joint space thickness distribution over the relevant part of the articular surface. Methods: In this paper we investigate the difference between joint space thicknesses acquired from dynamic distance maps to static distance maps. A dynamic distance map gives for every point on a subchondral bone surface the shortest distance to the opposing subchondral bone surface during wrist motion. We hypothesize that the joint space thickness calculated from dynamic distance maps provide a better reflection of the functional joint space thickness. The diagnostic potential of the dynamic joint space thickness measurement is illustrated by comparing data from distance maps of osteoarthritic wrists with normal wrists. Findings: In 10 healthy wrists which are examined, dynamic joint space thickness is smaller than static acquired joint space thickness suggesting that dynamic distance maps provide a better estimate of the measured joint space thickness than joint space thickness based on a static joint space thickness. In 3 examined osteoarthritic wrists the joint space thickness is smaller than in healthy individuals. Moreover, the difference between dynamic and static joint space thickness is smaller in pathological joint parts. Interpretation: The method presented in this paper demonstrates the feasibility of in vivo dynamic distance maps to detect joint space thickness in the radiocarpal joint of healthy individuals. [Copyright &y& Elsevier]

Abstract: Few studies have investigated the function of the patellar tendon in-vivo. This study quantified the three-dimensional (3D) kinematics of the patellar tendon during weight-bearing flexion. Eleven subjects were imaged using magnetic resonance (MR). Sagittal plane images were outlined to create a 3D model of the patella, tibia, and femur and included the attachment sites of the patellar tendon. Each attachment site was divided into central, medial, and lateral thirds. Next, the subjects were imaged using fluoroscopy from two orthogonal directions while performing a single-leg lunge. The models and fluoroscopic images were used to reproduce the motion of the patella, tibia, and femur. The apparent elongation, sagittal plane angle, and coronal plane angle of each third of the patellar tendon were measured from the relative motion of the attachment sites. All three portions of the patellar tendon deformed similarly with flexion. The length of the patellar tendon significantly from full extension to 30°. From 30°–110°, no significant change in the length of the patellar tendon was observed. The patellar tendon was oriented anteriorly at flexion angles less than 60° and posteriorly thereafter. From full extension to 60°, the medial orientation of the patellar tendon decreased significantly with flexion. These data may have important implications for anterior cruciate ligament reconstruction using patellar tendon autografts and for the design of rehabilitation regimens for patients of patellar tendon repair. [Copyright &y& Elsevier]

A photostereometric technology-based knee motion analysis system was developed and intraoperative kinematics during total knee arthroplasty (TKA) was investigated. Ten knees were evaluated and two different types of posterior-cruciate-retaining TKA (Genesis-I and Genesis-II) were used. Both TKA showed posterior translation of the medial and lateral femoral condyle with knee flexion. The motion pattern of the estimated contact point of Genesis-II was small initial rollback followed by sliding motion, then rollback again more than 60°. In Genesis-II, the amount of translation of the medial condyle was significantly larger than that of the lateral, suggesting that the lateral condyle acted as a rotational pivot. Our developed knee motion analysis system was non-contact, high resolution and can evaluate both kinematics and estimated contact pattern. The results of this study suggest that intraoperative measurement using this analysis system has advantages for the investigation of in-vivo kinematics and contact condition in TKA. [Copyright &y& Elsevier]