The influence of three-dimensional scapular kinematics on arm elevation angle in healthy subjects.

BACKGROUND: We often clinically observe individual differences in arm elevation angles, but the motion producing these differences remains unclear, partly because of the difficulty of accurately measuring scapular motion. The aim of this study was to determine whether the scapular or glenohumeral (GH) motion has more influence on differences in the arm elevation angles by capturing not only the humerus and scapula but also the trunk using two- (2D) and three-dimensional (3D) shape-matching registration techniques. METHODS: Fifteen healthy subjects (13 male and 2 female; mean age: 27.7 years) were instructed to elevate their arms in the sagittal, scapular, and coronal planes. They were divided into high and low groups based on the average of arm elevation angle measured by a goniometer. The 3D scapular, thoracohumeral, and glenohumeral motions were evaluated using 2D/3D single-plane registration. To compare 3D motions between groups, we performed a two-way repeated measures analysis of variance. RESULTS: Eight subjects were assigned to the high group, while seven subjects were assigned to the low groups based on an average elevation angle of 172°. The low group demonstrated a significant larger scapular protraction during elevation in all planes (P = 0.0002 for flexion; P = 0.0047 for scaption; P = 0.0314 for abduction), and smaller posterior tilting only during flexion (P = 0.0157). No significant differences occurred in scapular upward rotations or the glenohumeral positions and rotations. CONCLUSIONS: This study revealed that insufficient scapular retraction and posterior tilting results in lower arm elevation angles, suggesting that improving the flexibility and activation of muscles surrounding the scapula may be important to achieve complete arm elevation.

Open wedge high tibial osteotomy does not decrease patellar height relative to femur: A three-dimensional computer model analysis.

BACKGROUND: Patellar height, which decreases after open wedge high tibial osteotomy (OWHTO), has conventionally been assessed by tibial references using lateral radiographs of the knee; however, changes in the proximal tibia shape after OWHTO may affect this method. We aimed to evaluate the changes in patellar height position relative to the transepicondylar axis of the femur after OWHTO using in vivo three-dimensional (3D) computer models. METHODS: Fourteen patients who underwent 3D magnetic resonance imaging (MRI) at 30° and 50° knee flexion before OWHTO and after hardware removal were included. 3D computer models of the knee were created from the MRI scans and superimposed over the images taken in each position using voxel-based registration. For patellar height evaluation, a patellar reference point was established at each flexion angle and the femoral condylar planes (FCP) were set, including the transepicondylar axis. The patellar center angle was defined as the angle between an FCP that included the top of the intercondylar notch and an FCP that included the patellar reference point. The patellar center angle was evaluated at 30° and 50° knee flexion before and after OWHTO. RESULTS: The patellar center angle at 30° and 50° knee flexion did not significantly decrease after OWHTO, whereas the Caton-Deschamps index and Blackburne-Peel index based on tibia-referenced measurements significantly decreased postoperatively. CONCLUSION: Patellar height position relative to the femur in the 3D computer model did not decrease after OWHTO, whereas tibia-referenced conventional radiographic measurements significantly decreased. When evaluating patellar height, characteristics of each parameter should be considered.

In Vivo three-dimensional kinematics of normal knees during sitting sideways on the floor.

BACKGROUND: The normal knee kinematics during asymmetrical kneeling such as the sitting sideways remains unknown. This study aimed to clarify in vivo kinematics during sitting sideways of normal knees. METHODS: Twelve knees from six volunteers were examined. Under fluoroscopy, each volunteer performed a sitting sideways. A two-dimensional/three-dimensional registration technique was used. The rotation angle, varus-valgus angle, anteroposterior translation of the medial and lateral sides of the femur relative to the tibia, and kinematic pathway in each flexion angle was evaluated. RESULTS: Bilateral knees during sitting sideways showed a femoral external rotation relative to the tibia with flexion (ipsilateral: 13.7 ± 3.5°, contralateral: 5.8 ± 6.8°). Whereas the ipsilateral knees showed valgus movement of 4.6 ± 2.5° from 130° to 150° of flexion, and the contralateral knees showed varus movement of -3.1 ± 4.4° from 110° to 150° of flexion. The medial side of the contralateral knees was more posteriorly located than that of the ipsilateral knees beyond 110° of flexion. The lateral side of the contralateral knees was more anteriorly located than that of the ipsilateral knees from 120° to 150° of flexion. In the ipsilateral knees, a medial pivot pattern followed by a bicondylar rollback was observed. In the contralateral knees, no significant movement followed by a bicondylar rollback was observed. CONCLUSION: Even though the asymmetrical kneeling such as sitting sideways, the knees did not display asymmetrical movement.

Age-related differences in morphology and kinematics of the native hip.

Our objectives were to clarify morphology of the hip as well as infinitesimal femoral head movement in specific positions in young and elderly volunteers without joint degeneration. Both hips of 20 young and 20 elderly healthy volunteers were examined. Magnetic resonance imaging was performed at four different positions for each hip: neutral, 45° flexion, 15° extension, and the Patrick position. Femoral and pelvic bone images were separately extracted when in the neutral position and superimposed over the images of each different position by using voxel-based registration. The distance between the acetabular center and the femoral head center (FHC) at the neutral position was defined as 3D-migration. The distance between FHCs at neutral position and that at each different position was defined as 3D-translation. The x-, y-, and z-axes pointed in the anterior, cranial, and lateral directions, respectively. 3D-migration-y in the elderly was more caudal than that in the young (P < .001). 3D-translation of 45° flexion in the elderly was larger than that in the young with statistical significance (P = .001), while 3D-translation of the Patrick position in the elderly was smaller than that in the young (P = .012). Age was significantly correlated with 3D-translation in 45° flexion (r = .431; P < .001) and that in Patrick (r = -.296; P = .008). These results can be used as a basis for the natural course with aging of morphometry and kinematics of the hip, as well as for potential disease progression in osteoarthritis of the hip.

Kinematics of bicruciate stabilized and cruciate retaining total knee arthroplasty.

Few studies have been reported about kinematic comparison between bicruciate stabilized and cruciate retaining total knee arthroplasty with the same anatomical surface geometry. The aim of this study was to demonstrate the in vivo kinematics and postoperative patient-reported outcomes of these two surgeries with the same anatomical surface geometry. We analyzed 17 bicruciate stabilized and 18 cruciate retaining total knee arthroplasties using single-plane fluoroscopic surveillance with two- to three-dimensional registration techniques during squatting from minimum to maximum flexion. Flexion angle, femoral external rotation, anteroposterior position of the medial and lateral sides, and postoperative 2011 Knee Society Scores were analyzed. Maximum flexion angles were larger for bicruciate stabilized than for cruciate retaining total knee arthroplasties. There was no significant difference in femoral external rotation between the two types. The medial and lateral femoral condyles in bicruciate stabilized type translated more posteriorly during deeper flexion and at maximum flexion angle, respectively, than those in cruciate retaining total knee arthroplasty. Both groups revealed medial pivots in early flexion, but during deep flexion, bicruciate stabilized total knee arthroplasty revealed bicondylar roll-back and cruciate retaining total knee arthroplasty revealed paradoxical anterior motion. Both groups exhibited similar results in postoperative 2011 Knee Society Scores. Bicruciate stabilized and cruciate retaining total knee arthroplasties with the same anatomical articular surfaces demonstrated different kinematics patterns during squatting. However, there were no significant differences in postoperative 2011 Knee Society Scores between the two types of surgery.

Comparison of in vivo kinematics of total knee arthroplasty between cruciate retaining and cruciate substituting insert.

BACKGROUND: The decision to choose cruciate retaining (CR) insert or cruciate substituting (CS) insert during total knee arthroplasty (TKA) remains a controversial issue. We hypothesized that there are different knee kinematics between CR and CS inserts and that a raised anterior lip design would offer a potential minimization of the paradoxical movement and provide joint stability. The objective of this study was to evaluate and compare kinematics of a CR and CS TKA of the same single-radius design. METHODS: We investigated the in vivo knee kinematics of 20 knees with a CR TKA (10 knees in the CR insert and 10 knees in the CS insert). Patients were examined during deep knee flexion using fluoroscopy and femorotibial motion was determined using a 2- to 3-dimensional registration technique, which used computer-assisted design models to reproduce the spatial positions of the femoral and tibial components. We evaluated the knee range of motion (ROM), femoral axial rotation relative to the tibial component, anteroposterior translation, and kinematic pathway of the nearest point of the medial and lateral femoral condyles on the tibial tray. RESULTS: The average ROM was 121.0 ± 17.3° in CR and 110.8 ± 12.4° in CS. The amount of femoral axial rotation was 7.2 ± 3.9° in CR, and 7.4 ± 2.7° in CS. No significant difference was observed in the amount of anterior translation between CR and CS. The CR and CS inserts had a similar kinematic pattern up to 100° flexion that was central pivot up to 70° flexion and then paradoxical anterior femoral movement until 100° flexion. CONCLUSION: The present study demonstrated that there was no significant difference between the inserts in knee kinematics. These kinematic results suggested that the increased anterior lip could not control anterior movement in the CS insert.

Weight-bearing status affects in vivo kinematics following mobile-bearing unicompartmental knee arthroplasty.

PURPOSE: The effects of weight bearing (WB) on knee kinematics following mobile-bearing unicompartmental knee arthroplasty (UKA) remain unknown. The purpose of this study was to clarify the effects of WB on in vivo kinematics of mobile-bearing UKA during high knee flexion activities. METHODS: The kinematics of UKA were evaluated under fluoroscopy during squatting (WB) and active-assisted knee flexion (non-weight bearing, NWB). Range of motion, femoral axis rotation relative to the tibia, anteroposterior (AP) translation of the medial and lateral sides, and kinematic pathway were measured. RESULTS: There were no differences in knee flexion range and external rotation of the femur in each flexion angle between the WB conditions. The amount of femoral external rotation between minimum flexion and 60° of flexion during WB was significantly larger than that during NWB, and that between 60° and 130° of flexion during NWB was significantly larger than that during WB. There were no differences in medial AP translation of the femur in each flexion angle between the WB conditions. However, on the lateral side, posterior translation of 52.9 ± 12.7% was observed between minimum flexion and 130° of flexion during WB. During NWB, there was no significant translation between minimum flexion and 60° of flexion; beyond 60° of flexion, posterior translation was 41.6 ± 8.7%. Between 20° and 80° of flexion, the lateral side in WB was located more posteriorly than in NWB (p < 0.05). CONCLUSION: Mobile-bearing UKA has good anterior stability throughout the range of knee flexion. WB status affects the in vivo kinematics following mobile-bearing UKA. LEVEL OF EVIDENCE: III.

Kinematics of bicruciate and posterior stabilized total knee arthroplasty during deep knee flexion and stair climbing.

Second-generation bicruciate stabilized (BCS) total knee arthroplasty (TKA) was developed to substitute both anterior and posterior cruciate ligaments and replicate physiological kinematics. This study aimed to evaluate if the postcam mechanism and the surface geometry function effectively. Seventeen and twelve knees implanted with BCS TKA and posterior stabilized (PS) TKA, respectively, were analyzed. In vivo kinematics during deep knee flexion were estimated from single-plane fluoroscopic images using a 2-dimensional to 3-dimensional image registration technique. Flexion angle, anteroposterior translation, femoral external rotation (ER), and postcam engagement were compared between the groups. Postoperative 2011 Knee Society Score (KSS) was obtained at the last follow-up. The medial femoral condyle in BCS was positioned more anteriorly than that in PS from minimum flexion to maximum flexion. Posterior motion of the lateral femoral condyle was observed in both groups. ER of BCS was significantly larger compared to PS from minimum flexion to 100°. However, the amount of ER from minimum flexion to maximum flexion was similar: 6.2° ± 4.5° and 7.7° ± 4.1° in BCS and PS, respectively (P = .364). Anterior postcam engagement was observed in 76.5% and 25.0% in BCS and PS, respectively (P = .006). Posterior postcam engagement was observed in all cases in BCS and PS. There were no significant differences in KSS between the groups. The kinematic differences were likely a result of variations in articular surface geometry.

In vivo length change of ligaments of normal knees during dynamic high flexion.

BACKGROUND: Few studies compared the length change of ligaments of normal knees during dynamic activities of daily living. The aim of this study was to investigate in vivo length change of ligaments of the normal knees during high flexion. METHODS: Eight normal knees were investigated. Each volunteer performed squatting, kneeling, and cross-leg motions. Each sequential motion was performed under fluoroscopic surveillance in the sagittal plane. The femoral, tibial, and fibular attachment areas of the anterior cruciate ligament (ACL), posterior cruciate ligament (PCL), deep medial collateral ligament (dMCL), superficial medial collateral ligament (sMCL), and lateral collateral ligament (LCL) were determined according to osseous landmarks. After 2D/3D registration, the direct distance from the femoral attachment to the tibial or fibular attachment was measured as the ligament length. RESULTS: From 20° to 90° with flexion, the ACL was significantly shorter during cross-leg motion than during squatting. For the PCL, dMCL, sMCL, and LCL, there were no significant differences among the 3 motions. CONCLUSION: The ACL was shorter during cross-leg motion than during squatting in mid-flexion. This suggests that the ACL is looser during cross-leg motion than during squatting. On the other hand, the length change of the PCL, MCL, and LCL did not change even though the high flexion motions were different.

In vivo three-dimensional scapular kinematic alterations after reverse total shoulder arthroplasty.

BACKGROUND: In vivo three-dimensional (3D) kinematics of the scapula after reverse total shoulder arthroplasty (rTSA) have been sparsely investigated. The aim of this study was to analyze static and dynamic kinematic alterations of the scapula after rTSA in vivo with the use of computer-aided 3D reconstruction program. METHODS: A total of 15 patients with cuff tear arthropathy treated by rTSA participated. Scapulae with rTSA and the contralateral scapulae were evaluated with computed tomography scan data in 0° and 120° forward flexion positions of the glenohumeral joint. To examine static scapular kinematic alterations, the angular position and distance from the thorax were evaluated in the shoulder neutral position. 3D rotational and translational movements of the scapula in relation to the thorax were also measured during arm elevation to evaluate dynamic scapular kinematic alterations. RESULTS: Scapulae with rTSA were more anteriorly tilted in the sagittal plane and more internally rotated in the axial plane than were the contralateral scapulae. However, no significant differences were observed in the upward rotated position in the coronal plane or in the distance from the thorax in any plane between the scapulae with rTSA and the contralateral scapulae. In dynamic analyses, upward rotational movement in the coronal plane, external rotation in the axial plane, and posterior tilting in the sagittal plane showed significant differences between the scapulae with rTSA and the contralateral scapulae during elevation. In contrast, translational movements in coordination revealed no statistical differences between the two scapular groups except for lateral translation. CONCLUSION: Data from the 3D reconstruction program showed that rTSA might result in static positional changes and dynamic movement alterations. LEVEL OF EVIDENCE: Therapeutic, IV.

In vivo kinematic comparison before and after mobile-bearing unicompartmental knee arthroplasty during high-flexion activities.

BACKGROUND: Many patients who undergo unicompartmental knee arthroplasty (UKA) have an expectation that their knee flexion would increase following its replacement. Additionally, the survival rate of mobile-bearing UKA (MB-UKA) is high. However, the effect on the patient's kinematics remains unknown. This study aimed to clarify the kinematic effect of MB-UKA knees during high-flexion activities by comparing the in vivo kinematics before and after surgery. METHODS: A squatting motion was performed under fluoroscopic surveillance in the sagittal plane before and after MB-UKA. To estimate the spatial position and orientation of the knee, a two-dimensional/three-dimensional registration technique was used. The femoral rotation and varus-valgus angle relative to the tibia and anteroposterior (AP) translation of the medial and lateral side of the femur on the plane perpendicular to the tibial mechanical axis in each flexion angle were evaluated. RESULTS: Regarding the varus-valgus angle, the preoperative knees indicated a significant varus alignment compared with the postoperative knees from 10° to 60° of flexion. There were no significant differences in the femoral rotation angle, AP translation, and kinematic pathway before and after MB-UKA in the mid-flexion of the range of motion. CONCLUSION: There were differences between the varus-valgus knee kinematics before and after MB-UKA, from 10 to 60° of flexion, but no difference from midrange of flexion to deep flexion. In addition, the rotational knee kinematics before and after MB-UKA was not significantly different.

The glenohumeral micromotion and influence of the glenohumeral ligaments during axial rotation in varying abduction angle.

BACKGROUND: The patients with shoulder instability or disorders in overhead athletes have been considered to have an abnormal micromotion at the glenohumeral joint. However, the normal range of the micromotion has not been available during axial rotation with various abduction angles, especially above 90° abduction. This study aimed to investigate the glenohumeral translation and influence of the glenohumeral ligaments during axial rotation with up to maximum abduction. METHODS: Fourteen healthy volunteers performed active axial rotations at 0°, 90°, 135°, and maximal abduction angles. The positions of the humeral head center relative to the glenoid at maximally external, neutral, and maximally internal rotations (ER, NR, IR, respectively) for each abduction angle were evaluated using two- (2D) and three-dimensional (3D) shape matching registration techniques. The shortest pathway and its length between the origin and insertion of the superior, middle, and inferior glenohumeral ligaments (SGHL, MGHL, and IGHL, respectively) were calculated for each position. RESULTS: The glenohumeral joint showed 3.1 mm of superoinferior translation during axial rotation at 0° abduction (P < 0.0001), and 2.6 mm and 4.5 mm anteroposterior translation at 135° and maximal abduction (P < 0.0001), respectively. The SGHL and MGHL reached a maximum length at ER with 0° abduction, and the anterior and posterior bands of the IGHL reached a maximum at ER with 90° abduction and IR with 0° abduction. CONCLUSIONS: These findings indicated that the SGHL played a role as an inferior suppressor at 0° abduction, while the anterior band of IGHL played a role as an anterior stabilizer at 90° abduction. Every glenohumeral ligament did not get taut and the anteroposterior translation became greater with increasing abduction angle, above 90°. These results could be used as a reference when comparing with the pathological shoulders in the future study.

Semi-constrained posterior stabilized total knee arthroplasty reproduces natural deep knee bending kinematics.

BACKGROUND: The Flexible Nichidai Knee Posterior Stabilized (FNK-PS) system was designed to provide relatively high varus-valgus stabilities without the stem extensions to patients with severe knee joint disorders. This is a combination of a large tibial post and high femoral cam adapted to a PS system. The aim of our study was to analyze the in vivo two-dimensional/three-dimensional registration kinematics of the FNK PS-total knee arthroplasty (TKA) system during deep knee bending. METHODS: Nineteen knees from 15 total knee arthroplasty (TKA) patients who were able to squat with enough knee flexion were selected. During deep knee bending under weight bearing (WB) and non-weight bearing (NWB) conditions, we quantified range of motion, axial rotation, femoral anteroposterior translation, and post-cam engagement angle. RESULTS: The maximum-flexion was significantly different between the two conditions. The mean axial femoral external rotation was 4.8° and 6.2° under WB and NWB conditions, respectively, at 120° flexion. Anteroposterior translation based on bicondylar posterior roll-back patterns was noted with increasing knee flexion. Both the medial and lateral femoral aspects were significantly more posterior during early to mid-flexion. Initial post-cam engagement occurred significantly earlier during flexion under NWB than under WB conditions. Under WB, the timing of the post-cam engagement correlated with the maximum flexion . CONCLUSIONS: The kinematics of the semi-constrained PS system reproducibly exhibited a mild external rotation with smooth posterior roll-back. This was assisted by the engagement of the large tibial post and high femoral cam during the early phase of flexion.

Morphological evaluation of the scapula by three-dimensional computed tomography to elucidate shoulder joint function.

INTRODUCTION: There are many variations of scapula morphology. Evaluation of scapula morphology is necessary to elucidate shoulder joint movement. We aimed to analyze the bone morphology of various parts constituting the scapula to identify certain conserved features among them. MATERIALS AND METHODS: Thirty-one healthy individuals were the subjects. We created a scapular three-dimensional (3D) model using computed tomography (CT). X and Y axes were set on a glenoid surface. We measured the approximate plane of the upper and lower scapular bodies and scapular spine and the central axis of the coracoid and acromion. The anatomical position of the scapular spine, upper and lower bodies, coracoid, and acromion was measured. The positional relationship between the upper and lower bodies and scapular spine and the coracoid and acromion was evaluated. The average angle of the upper and lower scapular bodies and the scapular spine with respect to the XZ plane was calculated. The average angle of the coracoid and acromion with the X-axis on the XY plane and Z-axis on the YZ plane was calculated. RESULTS: On the XY plane, approximate planes of the upper and lower part of the body and the scapular spine were significantly correlated to each inclination. On the XY plane, inclinations of the central axes of the coracoid and acromion were significantly correlated. CONCLUSIONS: The findings revealed for the first time the correlation between the inclinations of the scapular body and scapular spine and the inclination angle between the coracoid and acromion.

Assessment of the talar deformity and alignment in congenital clubfoot using three-dimensional MRI after Ponseti method.

BACKGROUND: Ponseti method have been widely accepted as the initial treatment of congenital idiopathic clubfoot because its excellent primary result. On the other hand, relapses after Ponseti method are not uncommon and the cause of relapses have not been fully elucidated. We investigated detailed morphology and alignment of tarsal bones in clubfoot after Ponseti method using three-dimensional MRI analysis. METHODS: We performed MRI with 10 patients of unilateral clubfoot at three months after Achilles tenotomy. Based on the MRI volume data, we reconstructed three-dimensional bone surface model using the marching cubes method. We evaluated the volume of the talus and navicular bone, medial and planter deviation of the talar head and neck, medial deviation of the navicular bone, and internal rotation angle of the distal tibiofibular joint. RESULTS: In clubfoot, the volume of talus and navicular bone were significantly smaller compared with the contralateral side. Deviation of the talar head and neck varied from medially to almost the same as that on the contralateral side. The degree of deformity of the talus and alignment of the navicular bone and distal tibiofibular joint showed correlations. CONCLUSIONS: Patients with the medial deviated talar neck might have the alignment change of navicular bone and distal tibiofibular joint. Deformity of talar neck might to be compensated by talonavicular joint and distal tibiofibular joint through the manipulation of Ponseti method.

Regional Distribution of Articular Cartilage Thickness in the Elbow Joint: A 3-Dimensional Study in Elderly Humans.

During elbow procedures, reconstruction of the joint (including the articular cartilage) is important in order to restore elbow function; however, the regional distribution of elbow cartilage is not completely understood. The purpose of the present study was to investigate the 3-dimensional (3-D) distribution patterns of cartilage thickness of elbow bones (including the distal part of the humerus, proximal part of the ulna, and radial head) in order to elucidate the morphological relationship among them. METHODS: Two 3-D surface models were created with use of a laser scanner: (1) a cartilage-bone model based on 20 elderly cadaveric elbows exhibiting normal cartilaginous conditions and (2) a bone model that was created after dissolving the cartilage. The 2 models were superimposed, and cartilage thickness was measured as the interval distance on the articular surface. Measurements were made at categorized anatomical points of the individual bones, and 3-D distributions on the entire articular surface were analyzed. The spatial relationship among individual bones was also assessed. RESULTS: In the distal part of the humerus, the cartilage was thickest in the intermediate region between the capitellum and the trochlea (mean [and standard deviation], 1.27 ± 0.17 mm); in the proximal part of the ulna, it was thickest at the anterolateral edge of the coronoid (2.20 ± 0.39 mm) and the anteroproximal edge of the proximal sigmoid notch (2.49 ± 0.55 mm); and in the radial head, it was thickest at the articular zone on the rim circumference within the dish (1.10 ± 0.17 mm) and on the proximal circumference around the side (1.02 ± 0.17 mm) (p < 0.001 for all). These thicker cartilage regions gathered on the joint center, facing each other. CONCLUSIONS: The present study demonstrated regional variations in elbow cartilage thickness. The combined findings in individual bones showed "cartilage gathering" at the center of the elbow joint, which we believe to be a novel anatomical finding. CLINICAL RELEVANCE: An enhanced understanding of elbow cartilage geometry will provide additional insights into elbow procedures in elderly individuals, such as hemiarthroplasties, in which anatomical contours could help to restore normal joint function and improve postoperative outcomes.

Sequential analysis of three-dimensional tibiofemoral relationship through anatomic anterior cruciate ligament reconstruction with gravity-assisted radiographic technique in prone position.

BACKGROUND/OBJECTIVES: It is important to restore the tibiofemoral relationship as well as the anterior knee laxity for more successful anterior cruciate ligament (ACL) reconstruction, since a residual abnormality in the tibiofemoral relationship would lead an abnormal stress on the articular cartilages/menisci and consequently increase the risk of osteoarthritis in the future. This study aimed to sequentially clarify the three-dimensional tibiofemoral relationship before and after anatomic anterior cruciate ligament (ACL) reconstruction under an anterior tibial load with a gravity-assisted radiographic technique in the prone position. METHODS: Fifteen patients with unilateral ACL injury participated in the study. Anatomic triple-bundle ACL reconstruction was performed using semitendinosus tendon autografts. During the computed tomography scans that were performed preoperatively, and those performed at 3 weeks and at 6 months postoperatively, the patients lay in the prone position with the knee flexed at 15°, wherein the calf weight could exert an anterior drawer force on the tibia due to gravity. Three-dimensional the tibial position relative to the femur were evaluated for each time point, followed by calculation of side-to-side differences in the parameters between the ACL-deficient/ACL-reconstructed knees and the contralateral intact knees. Seven healthy volunteers were enrolled in the control group and the side-to-side differences (right minus left) in these parameters were calculated. RESULTS: The tibia in the ACL-deficient knee was located anteriorly by 3.5 ±â€¯1.1 mm and rotated internally by 2.4° ± 2.3°; these values were significantly larger than the corresponding values of -0.2 ±â€¯1.5 mm and 0.1° ± 2.2° in the control group. However, at 3 weeks postoperatively, the tibia in the ACL-reconstructed knee was over-constrained as compared to that in the control group; it was located posteriorly by 2.5 ±â€¯1.4 mm and rotated externally by 3.4° ± 3.4°. At 6 months postoperatively, no significant difference was observed in the tibial displacements/rotations between the patient and control groups. The side-to-side difference in the anterior knee laxity at the manual maximum anterior load was 0.1 ±â€¯1.2 mm at 6 months postoperatively, with a significant improvement over the preoperative value of 7.4 ±â€¯2.5 mm. CONCLUSIONS: Anatomic ACL reconstruction could restore not only the normal anterior knee laxity, but also the normal tibiofemoral relationship even under an anterior tibial load.

Evaluation of errors in measurements of infantile hip radiograph using digitally reconstructed radiograph from three-dimensional MRI.

PURPOSE: Plain hip radiograph is commonly used for the diagnosis of infantile acetabular dysplasia. Many infants are unable to maintain adequate position during radiography. Besides, the infantile hip is much smaller and has a higher cartilage component in the acetabulum and proximal femur compared with the adult hip. In this study, we developed a digitally reconstructed radiograph synthesized from magnetic resonance imaging (MRI) and investigated errors of hip radiographic measurements in different pelvic positions. PATIENTS AND METHODS: MRI of both hips was performed in 10 patients (mean age 3.9 years). Three-dimensional (3D) bone models were created from MRI data. We tilted 3D pelvic bone models between 10° anteversion and retroversion and through 10° rotation on the affected and contralateral sides using 3D axes. Following this, we created digitally reconstructed radiographs in each pelvic position and calculated the acetabular index (AI), center-edge angle (CEA), migration percentage (MP), and teardrop distance (TDD). RESULTS: AI tended to increase with pelvic retroversion and did not change with pelvic rotation. CEA tended to decrease with pelvic retroversion and rotation on the contralateral side. MP increased with pelvic retroversion and rotation on the contralateral side. TDD did not change significantly with pelvic tilt and rotation. CONCLUSIONS: Radiographic measurements of hip in infants were highly influenced by pelvic movement. AI was influenced by pelvic tilt; CEA and MP were influenced by both pelvic tilt and rotation. We need to keep in mind that infantile hip radiographs could have about ±5° errors in AI and CEA.

Three-Dimensional In Vivo Analysis of Malunited Distal Radius Fractures With Restricted Forearm Rotation.

Malunited distal radius fractures (DRFs) occasionally restrict forearm rotation, but the underlying pathology remains unclear. We aimed to elucidate the mechanism of rotational restriction by retrospective analysis of 23 patients with unilateral malunited DRFs who presented restricted forearm rotation. We conducted computed tomography during forearm rotation on both sides. Three-dimensional (3D) bone surface models of the forearm were created, and 3D deformity of the distal radius, translation of the distal radius relative to the ulna, distal radioulnar joint (DRUJ) contact area, and estimated path length (EPL) of distal radioulnar ligaments (DRUL) during forearm rotation were evaluated. In total, 18 patients had dorsal angular deformities (DA group) and five had volar angular deformities (VA group). In the DA group, the closest point between the distal radius and ulna on DRUJ was displaced to the volar side during supination and pronation (p < 0.001); DRUJ contact area was not significantly different between the DA and normal groups. In bone-ligament model simulation, the EPL of dorsal DRUL was longer in the DA group than in the normal group (p < 0.001); opposite phenomena were observed in the VA group. In the DA group, translation of the distal radius in a volar direction relative to the ulna during pronation was impaired presumably due to dorsal DRUL tightness. Anatomical normal reduction of the distal radius by corrective osteotomy may improve forearm rotation by improving triangular fibrocartilage complex tightness and normalizing translation of the distal radius relative to the ulna. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:1881-1891, 2019.

Comparison of finite helical axes of normal and anatomically designed prosthetic knees.

BACKGROUND: Describing three-dimensional joint motion using the finite helical axis has an advantage in understanding unknown coupling motion in prosthetic knee joints. We aimed to examine the differences in the orientations of finite helical axis of normal and anatomically designed cruciate-retaining and posterior-stabilized prosthetic knees after total knee arthroplasty. METHODS: Ten normal, 40 cruciate-retaining prosthetic knees of 33 patients and 19 posterior-stabilized prosthetic knees of 14 patients enabling to flex > 120° were analyzed during a squatting motion with deep knee bending. The motion was recorded by a fluoroscopic imaging system, and the pose of the bone and prostheses were determined by an image registration technique. The finite helical axes were calculated using 30° window. FINDINGS: The finite helical axis in the early flexion phase of the normal knees had a greater inferior inclination (mean - 19.0° (SD 7.2°)) than those of the cruciate-retaining (mean - 1.7 (SD 5.0°)) and posterior-stabilized (mean - 2.9° (SD 5.5°)) prosthetic knees (p < 0.001), and became almost horizontal and constant in the mid to deep flexion phases. In contrast, the cruciate-retaining and posterior-stabilized prosthetic knees demonstrated slightly inclined and almost constant vertical angles throughout the all phases. INTERPRETATION: These results demonstrate that, in the normal knee, a clear coupling motion occurs during the early flexion phase. For the cruciate-retaining and posterior-stabilized prosthetic knees, an unclear coupling motion exists during all phases. These results suggest that the physiological motion is not possible to reproduce using shape-guided motion only even in an anatomically designed prosthetic knee.