Varus-valgus Angle Research Articles

Extensor hallucis longus tendon is a new distal landmark for coronal tibial component alignment in total knee arthroplasty: A study of magnetic resonance imaging.

In total knee arthroplasty (TKA), various landmarks are generally used to ensure correct osteotomy. In this study, we examined whether the tibialis anterior tendon (TAT) or the extensor hallucis longus tendon (EHLT) could be used as a landmark of the center of the ankle joint in patients with knee osteoarthrosis (OA), using magnetic resonance imaging (MRI). The subjects were 61 patients with OA in 79 knees (males: 8 with 9 knees and females: 53 with 70 knees). With the ankle joint secured in the intermediate position, MRI from the knee joint to the ankle joint was performed in the same foot position. We prepared individual lines connecting the center of the ankle joint with the TAT or EHLT to measure the angle difference (ΔA) from Akagi's line in the knee joint. We analyzed whether the ΔA might be affected by deformity of the knee joint or foot region, and tibial torsion. At the ankle joint level, the ΔA of EHLT was the smallest, with an average of 1.6 ± 3.4°. The ΔA for the femorotibial angle, hallux valgus angle, and varus-valgus angle showed no correlations with deformity of the knee joint and foot region, or tibial torsion. MRI findings showed that EHLT would be useful as a landmark of the ankle joint center in extramedullary tibial osteotomy in TKA for medial knee OA. It was also clarified that the landmark would not be affected by severe deformity of the knee joint, deformity of the foot region, or external torsion of the tibia.

In Vivo Kinematics of Bicruciate-Retaining Total Knee Arthroplasty with Anatomical Articular Surface under High-Flexion Conditions.

Bicruciate-retaining total knee arthroplasty (BCR-TKA) recreates normal knee movement by preserving the anterior cruciate and posterior cruciate ligaments. However, in vivo kinematics of BCR-TKA with the anatomical articular surface remains unknown. The objective of this study was to evaluate in vivo kinematics of BCR-TKA with the anatomical articular surface during high-flexion activities. For this purpose, 17 knees after BCR-TKA with an anatomical articular surface were examined. Under fluoroscopy, each patient performed squatting and cross-legged sitting motions. To estimate the spatial position and orientation of the knee, a two-dimensional or three-dimensional registration technique was used. Rotation, varus-valgus angle, and anteroposterior translation of medial and lateral contact points of the femoral component relative to the tibial component were evaluated in each flexion angle. The results showed that from 80 to 110° of flexion, the femoral external rotation during squatting was significantly larger than that during cross-legged sitting. At maximum flexion, the knees during sitting indicated significantly more varus alignment than during squatting. During squatting, a medial pivot pattern was observed from minimum flexion to 10° flexion, with no significant movement beyond 10° of flexion. Conversely, during cross-legged sitting, no significant movement was detected from minimum flexion to 60° of flexion, with a medial pivot beyond 60° of flexion. Therefore, the knees showed relatively normal kinematics after BCR-TKA with an anatomical articular surface; however, it varied during high-flexion activities depending on the activity.

Repeatability, reproducibility, and agreement of three computational methods to approximate the functional flexion-extension axis of the tibiofemoral joint using 3D bone models of the femur

Background: Closely approximating the functional flexion-extension (FE) axis of the tibiofemoral joint in 3D models of the femur is important when computing joint motions which are physiologic. The objectives were to 1) develop methods to approximate the functional FE axis based on fitting circles, a tapered cylinder, and spheres to the posterior condyles, 2) determine the repeatability and reproducibility of each method, and 3) determine limits of agreement between pairs of axes.Methods: For each method, the respective axis was determined in forty 3D bone models of the distal femur. Varus-valgus angles and internal-external axial angles were computed relative to standard planes.Results: Repeatability and reproducibility were comparable for the tapered cylinder-based and sphere-based methods and better than that for the circle-based method. Limits of agreement were tightest when comparing the sphere-based and tapered cylinder-based axes. However, limits of agreement for the internal-external axial angle were wide at +3.6° to −3.9° whereas limits of agreement were tighter at +1.4° to −0.7° for the varus-valgus angle.Conclusion: The tapered cylinder-based and sphere-based methods offer advantages of better repeatability and reproducibility over the circle-based method. However, the sphere-based and tapered cylinder-based axes are not interchangeable owing to wide limits of agreement for the internal-external axial angle. The tapered cylinder-based axis is preferred intuitively over the sphere-based axis because the spheres require fitting in both the sagittal and coronal planes whereas the tapered cylinder requires fitting in the sagittal plane only which is the plane of motion in flexion-extension.

Decreased Pain and Improved Dynamic Knee Instability Mediate the Beneficial Effect of Wearing a Soft Knee Brace on Activity Limitations in Patients With Knee Osteoarthritis.

ObjectiveTo evaluate whether improvement of proprioception, pain, or dynamic knee instability mediates the effect of wearing a soft knee brace on activity limitations in patients with knee osteoarthritis (OA).MethodsWe conducted an analysis of data for 44 patients with knee OA who were enrolled in a laboratory‐based trial evaluating the effect of wearing a commercially available soft knee brace. Activity limitations were assessed with the 10‐meter walk test and the Get Up and Go test. Knee joint proprioception was assessed by an active joint position sense test; pain was assessed on a numeric rating scale (NRS) (range 0–10); pressure pain threshold (PPT) was assessed with a hand‐held pressure algometer; dynamic knee instability was expressed by the perturbation response, i.e., a measure reflecting a deviation in mean knee varus–valgus angle after a controlled mechanical perturbation on a treadmill, with respect to level walking. Mediation analysis was conducted using the product of coefficients approach. Confidence intervals were calculated with a bootstrap procedure.ResultsA decrease in pain (scored on an NRS) and a decrease in dynamic knee instability mediated the effect of wearing a soft knee brace on the reduction of activity limitations (P < 0.05), while changes in proprioception and PPT did not mediate this effect (P > 0.05).ConclusionThis study shows that decreased pain and reduced dynamic knee instability are pathways by which wearing a soft knee brace decreases activity limitations in patients with knee OA.

Role of the anconeus in the stability of a lateral ligament and common extensor origin–deficient elbow: an in vitro biomechanical study

The role of the anconeus in elbow stability has been a long-standing debate. Anatomic and electromyographic studies have suggested a potential role as a stabilizer. However, to our knowledge, no clinical or biomechanical studies have investigated its role in improving the stability of a combined lateral collateral ligament and common extensor origin (LCL + CEO)-deficient elbow. Seven cadaveric upper extremities were mounted in an elbow motion simulator in the varus position. An injured model was created by sectioning of the CEO and the LCL. The anconeus tendon and its aponeurosis were sutured in a Krackow fashion and tensioned to 10 N and 20 N using a transosseous tunnel. Varus-valgus angles and ulnohumeral rotations were recorded using an electromagnetic tracking system during simulated active elbow flexion with the forearm pronated and supinated. During active motion, the injured model resulted in a significant increase in varus angulation (P = .0001 for pronation; P = .001 for supination) and external rotation (P = .001 for pronation; P = .003 for supination) of the ulnohumeral articulation compared with the intact state. Tensioning of the anconeus significantly decreased the varus angulation (P = .006 for 10 N pronation; P = .0001 for 20 N pronation; P = .0001 for 10 N supination; P = .0001 for 20 N supination) and external rotation angle (P = .008 for 10 N pronation; P = .0001 for 20 N pronation; P = .0001 for 10 N supination; P = .0001 for 20 N supination) of the injured elbow. In the highly unstable varus elbow orientation, anconeus tensioning restores the in vitro stability of a combined LCL + CEO-deficient elbow during simulated active motion with the forearm in both pronation and supination. These results may have several clinical implications in managing symptomatic lateral elbow instability.

A Comparison of Knee Abduction Angles Measured by a 3D Anatomic Coordinate System Versus Videographic Analysis: Implications for Anterior Cruciate Ligament Injury.

Background:Knee positions involved in noncontact anterior cruciate ligament (ACL) injury have been studied via analysis of injury videos. Positions of high ACL strain have been identified in vivo. These methods have supported different hypotheses regarding the role of knee abduction in ACL injury.Purpose/Hypothesis:The purpose of this study was to compare knee abduction angles measured by 2 methods: using a 3-dimensional (3D) coordinate system based on anatomic features of the bones versus simulated 2-dimensional (2D) videographic analysis. We hypothesized that knee abduction angles measured in a 2D videographic analysis would differ from those measured from 3D bone anatomic features and that videographic knee abduction angles would depend on flexion angle and on the position of the camera relative to the patient.Study Design:Descriptive laboratory study.Methods:Models of the femur and tibia were created from magnetic resonance images of 8 healthy male participants. The models were positioned to match biplanar fluoroscopic images obtained as participants posed in lunges of varying flexion angles (FLAs). Knee abduction angle was calculated from the positioned models in 2 ways: (1) varus-valgus angle (VVA), defined as the angle between the long axis of the tibia and the femoral transepicondylar axis by use of a 3D anatomic coordinate system; and (2) coronal plane angle (CPA), defined as the angle between the long axis of the tibia and the long axis of the femur projected onto the tibial coronal plane to simulate a 2D videographic analysis. We then simulated how changing the position of the camera relative to the participant would affect knee abduction angles.Results:During flexion, when CPA was calculated from a purely anterior or posterior view of the joint—an ideal scenario for measuring knee abduction from 2D videographic analysis—CPA was significantly different from VVA (P < .0001). CPA also varied substantially with the position of the camera relative to the participant.Conclusion:How closely CPA (derived from 2D videographic analysis) relates to VVA (derived from a 3D anatomic coordinate system) depends on FLA and camera orientation.Clinical Relevance:This study provides a novel comparison of knee abduction angles measured from 2D videographic analysis and those measured within a 3D anatomic coordinate system. Consideration of these findings is important when interpreting 2D videographic data regarding knee abduction angle in ACL injury.

The Evidence of Crucifixion on the Shroud of Turin Through the Anatomical Traits of the Lower Limbs and Feet

The imprint of the feet and lower limbs, as well as the blood and rivulets, present on the Shroud of Turin were analysed with regard to anatomical and pathological characteristics. In the dorsal image of the cloth, the crucifixion position shows the left foot on top of the right one; in the frontal view, the feet are almost parallel. The nail used in the crucifixion was driven through the foot. In the frontal image, the knees, the tibiae and the ankles seem to be parallel with different varus–valgus angles; the left one is straighter than the right one, which shows a greater angle. Because of this parallelism, both ankles show a plantar flexion that is dissimilar in the dorsal images. We describe for the first time the anatomical study of the image of the Shroud through modern concepts. At the level of biomechanics and anatomy, the image on the Shroud of Turin does not comply with modern knowledge; in fact, the image fails with regard to some aspects that we cannot interpret yet.

In vivo three-dimensional kinematics of normal knees during different high-flexion activities.

AimsIn Asia and the Middle-East, people often flex their knees deeply in order to perform activities of daily living. The purpose of this study was to investigate the 3D kinematics of normal knees during high-flexion activities. Our hypothesis was that the femorotibial rotation, varus-valgus angle, translations, and kinematic pathway of normal knees during high-flexion activities, varied according to activity.Materials and MethodsWe investigated the in vivo kinematics of eight normal knees in four male volunteers (mean age 41.8 years; 37 to 53) using 2D and 3D registration technique, and modelled the knees with a computer aided design program. Each subject squatted, kneeled, and sat cross-legged. We evaluated the femoral rotation and varus-valgus angle relative to the tibia and anteroposterior translation of the medial and lateral side, using the transepicodylar axis as our femoral reference relative to the perpendicular projection on to the tibial plateau. This method evaluates the femur medially from what has elsewhere been described as the extension facet centre, and differs from the method classically applied. ResultsDuring squatting and kneeling, the knees displayed femoral external rotation. When sitting cross-legged, femurs displayed internal rotation from 10° to 100°. From 100°, femoral external rotation was observed. No significant difference in varus-valgus angle was seen between squatting and kneeling, whereas a varus position was observed from 140° when sitting cross-legged. The measure kinematic pathway using our methodology found during squatting a medial pivoting pattern from 0° to 40° and bicondylar rollback from 40° to 150°. During kneeling, a medial pivot pattern was evident. When sitting cross-legged, a lateral pivot pattern was seen from 0° to 100°, and a medial pivot pattern beyond 100°.ConclusionThe kinematics of normal knees during high flexion are variable according to activity. Nevertheless, our study was limited to a small number of male patients using a different technique to report the kinematics than previous publications. Accordingly, caution should be observed in generalizing our findings.Cite this article: Bone Joint J 2018;100-B:50–5.

Clinical and radiologic evaluation of medial epicondylar osteotomy for varus total knee arthroplasty

BackgroundIn varus total knee arthroplasty (TKA), a pathologic contracture of the medial soft tissue should be released for ligament balancing. A medial epicondylar osteotomy has been performed as an alternative method for this. The purpose of this study was to demonstrate the clinical and radiologic results of medial epicondylar osteotomy for varus TKA, focusing on the union type of osteotomy site. MethodsThe study retrospectively evaluated 61 cases with a mean femorotibial angle of 10.4° varus and a mean flexion contracture angle of 8.5±9.8°. Intraoperative medial and lateral gap difference in extension and 90° flexion was accepted at <2mm. Clinical outcomes (Knee Society Scores, range of motion) and radiologic outcomes (coronal alignment and valgus stability) were compared between the two groups divided by the union type of osteotomy site (bony union or fibrous union). ResultsThe clinical and radiologic outcomes were significantly improved at the latest follow-up. Bony union was achieved in 39 (63.9%) patients, whereas 22 patients showed fibrous union. There was no difference in the varus–valgus angle on the stress radiographs between the bony union and fibrous union group (1.6±1.2° vs. 1.6±0.8°, P<0.916). The Knee Society Scores (knee, function), range of motion and radiographic alignment did not differ between the two groups. ConclusionMedial epicondylar osteotomy was a good option for gap balancing during TKA, as it provided satisfactory clinical and radiological results, regardless of union type of the osteotomy site.

The influence of sex and obesity on gait biomechanics in people with severe knee osteoarthritis scheduled for arthroplasty

BackgroundSex and body mass may influence knee biomechanics associated with poor total knee arthroplasty (TKA) outcomes for knee osteoarthritis (OA). This study aimed to determine if gait differed between men and women, and overweight and class I obese patients with severe knee OA awaiting TKA. Methods34 patients with severe knee OA (average age 70.0 (SD 7.2) years, body mass index 30.3 (4.1kg/m2)) were recruited from a TKA waiting list. Three-dimensional gait analysis was performed at self-selected walking speed. Comparisons were made between men and women, and overweight (body mass index (BMI) 25.0–29.9kg/m2) and class I obese (BMI 30.0–34.9kg/m2) participants. Biomechanical outcomes included absolute and body size-adjusted peak knee adduction moment (KAM), KAM impulse, peak knee flexion moment, as well as peak knee flexion and varus-valgus angles, peak varus-valgus thrust, and peak vertical ground reaction force (GRF). FindingsMen had a higher absolute peak KAM, KAM impulse and peak GRF compared to women, and this sex-difference in frontal plane moments remained after adjusting for body size. However, when additionally adjusting for static knee alignment, differences disappeared. Knee biomechanics were similar between obesity groups after adjusting for the greater body weight of those with class I obesity. InterpretationMen had greater KAM and KAM impulse even after adjustment for body size; however adjustment for their more varus knees removed this difference. Obesity group did not influence knee joint kinematics or moments. This suggests sex- and obesity-differences in these variables may not be associated with TKA outcomes.

Strain measurements of the tibial insert of a knee prosthesis using a knee motion simulator

ObjectiveThe longevity of a knee prosthesis is influenced by the wear of the tibial insert due to its posture and movement. In this study, we assumed that the strain on the tibial insert is one of the main reasons for its wear and investigated the influence of the knee varus-valgus angles on the mechanical stress of the tibial insert. MethodsKnee prosthesis motion was simulated using a knee motion simulator based on a parallel-link six degrees-of-freedom actuator and the principal strain and pressure distribution of the tibial insert were measured. In particular, the early stance phase obtained from in vivo X-ray images was examined because the knee is applied to the largest load during extension/flexion movement. The knee varus-valgus angles were 0° (neutral alignment), 3°, and 5° malalignment. ResultsUnder a neutral orientation, the pressure was higher at the middle and posterior condyles. The first and second principal strains were larger at the high and low pressure areas, respectively. Even for a 3° malalignment, the load was concentrated at one condyle and the positive first principal strain increased dramatically at the high pressure area. The negative second principal strain was large at the low pressure area on the other condyle. The maximum equivalent strain was 1.3–2.1 times larger at the high pressure area. For a 5° malalignment, the maximum equivalent strain increased slightly. ConclusionThese strain and pressure measurements can provide the mechanical stress of the tibial insert in detail for determining the longevity of an artificial knee joint.

Relationship Between Grading With Magnetic Resonance Imaging and Radiographic Parameters in Posterior Tibial Tendon Dysfunction

The objective of the present study was to elucidate the relationship between the state of the posterior tibial tendon (PTT) on magnetic resonance images and foot deformity. The cases included 34 feet in 27 patients with PTT deformity and the controls included 18 feet in 12 patients who had undergone magnetic resonance imaging for other foot diseases. The PTT was closely examined on the magnetic resonance images and classified using the Conti classification. The control feet with no injury to the PTT were classified as grade 0. The talonavicular coverage angle, lateral talo-first metatarsal angle, medial cuneiform to fifth metatarsal height, calcaneal pitch angle, and varus–valgus angle were measured as radiographic parameters for flatfoot deformation, and the relation between the Conti classification and each parameter was examined statistically. A significant difference was observed in the talonavicular coverage angle between grade 0 and the other grades; the lateral talo-first metatarsal angle between grade 0 and the other grades and between grades 1 and 3; the medial cuneiform to fifth metatarsal height among grades 0, 2, and 3 and grades 1, 2, and 3; the calcaneal pitch angle between grades 1 and 3; and the varus–valgus angle among grades 0, 2, and 3 and between grades 1 and 3. Eversion of the forefoot was observed, along with an advanced collapse in the medial longitudinal arch, from an early stage of PTT injury.

An In Vitro Study of the Role of Implant Positioning on Ulnohumeral Articular Contact in Distal Humeral Hemiarthroplasty

To investigate the effect of implant positioning on ulnohumeral contact using patient-specific distal humeral (DH) implants. Seven reverse-engineered DH implants were manufactured based on computed tomography scans of their osseous geometry. Native ulnae were paired with corresponding native humeri and custom DH implants in a loading apparatus. The ulna was set at 90° of flexion and the humeral component (either native bone or reverse-engineered implant) was positioned from 5° varus to 5° valgus in 2.5° increments under a 100-N compressive load. Contact with the ulna was measured with both the native distal humerus and the reverse-engineered DH implant at all varus-valgus (VV) angles, using a joint casting method. Contact patches were digitized and analyzed in 4 ulnar quadrants. Output variables were contact area and contact pattern. Mean contact area of the native articulation was significantly greater than with the distal humeral hemiarthroplasty (DHH) implants across all VV positions. Within the native condition, contact area did not significantly change owing to VV angulation. Within the DHH condition, contact area also did not significantly change owing to VV angulation. Conversely, in the DHH condition, contact pattern did significantly change. Medial ulnar contact pattern was significantly affected by VV angulation. Lateral ulnar contact was variably affected, but generally decreased as well. Ulnar contact patterns were changed as a result of VV implant positioning using reverse-engineered DH implants, most notably on the medial aspect of the joint. Implant positioning plays a crucial role in producing contact patterns more like those observed in the native joint. Recent clinical evidence reports nonsymmetrical ulnar wear after DHH. This work suggests that implant positioning is likely a contributing factor and that more exact implant positioning may lead to better clinical outcomes.

Preoperative varus–valgus kinematic pattern throughout flexion persists more strongly after cruciate-retaining than after posterior-stabilized total knee arthroplasty

BackgroundRestoration of normal knee kinematics is key to improving patient satisfaction and functional outcomes after total knee arthroplasty (TKA). However, the effect of preoperative varus–valgus kinematics due to knee osteoarthritis on the postoperative kinematics is unclear. The function of the knee ligament contributes to both knee stability and kinematics. The aim of this study was to evaluate changes in varus–valgus kinematics before and after TKA using a navigation system, in addition to comparing the pre- and postoperative changes in kinematic patterns between cruciate-retaining (CR)- and posterior-stabilized (PS)-TKAs. MethodsForty knees treated with TKA were evaluated (CR-TKA 20; PS-TKA 20). Manual mild passive knee flexion was applied while moving the leg from full extension to flexion. The varus–valgus angle was automatically measured by a navigation system at every 10° of the flexion angle, and the kinematics were evaluated. ResultsKinematic patterns throughout flexion can be classified into five types. The pre- and postoperative kinematic patterns were similar in 60% of patients who underwent CR-TKA, whereas they were similar in only 25% of those who underwent PS-TKA. The mean change in the size of the varus–valgus angle throughout flexion did not differ between CR-TKA and PS-TKA. However, the distribution of changes in the size of the varus–valgus angle differed between CR-TKA and PS-TKA. ConclusionsWe obtained the following results: 1) some patterns of varus–valgus kinematics are noted under unloading conditions despite recovery of neutral alignment in extension and 2) the preoperative varus–valgus kinematic pattern persisted more strongly after CR-TKA than after PS-TKA.

The Validity of a New Low-Dose Stereoradiography System to Perform 2D and 3D Knee Prosthetic Alignment Measurements.

IntroductionThe EOS stereoradiography system has shown to provide reliable varus/valgus (VV) measurements of the lower limb in 2D (VV2D) and 3D (VV3D) after total knee arthroplasty (TKA). Validity of these measurements has not been investigated yet, therefore the purpose of this study was to determine validity of EOS VV2D and VV3D.MethodsEOS images were made of a lower limb phantom containing a knee prosthesis, while varying VV angle from 15° varus to 15° valgus and flexion angle from 0° to 20°, and changing rotation from 20° internal to 20° external rotation. Differences between the actual VV position of the lower limb phantom and its position as measured on EOS 2D and 3D images were investigated.ResultsRotation, flexion or VV angle alone had no major impact on VV2D or VV3D. Combination of VV angle and rotation with full extension did not show major differences in VV2D measurements either. Combination of flexion and rotation with a neutral VV angle showed variation of up to 7.4° for VV2D; maximum variation for VV3D was only 1.5°. A combination of the three variables showed an even greater distortion of VV2D, while VV3D stayed relatively constant. Maximum measurement difference between preset VV angle and VV2D was 9.8°, while the difference with VV3D was only 1.9°. The largest differences between the preset VV angle and VV2D were found when installing the leg in extreme angles, for example 15° valgus, 20° flexion and 20° internal rotation.ConclusionsAfter TKA, EOS VV3D were more valid than VV2D, indicating that 3D measurements compensate for malpositioning during acquisition. Caution is warranted when measuring VV angle on a conventional radiograph of a knee with a flexion contracture, varus or valgus angle and/or rotation of the knee joint during acquisition.

Hindfoot alignment at one year after total knee arthroplasty.

PurposeIt has previously been found that valgus hindfoot alignment (HFA) improves 3 weeks following total knee arthroplasty (TKA) for varus knee osteoarthritis (OA). In the present study, HFA was evaluated prior to TKA, as well as 3 weeks and 1 year following TKA. Using these multiple evaluations, the chronological effects of TKA on HFA were investigated.MethodsThe study included 71 patients (73 legs) who underwent TKA for varus knee OA. Radiograph examinations of the entire limb and hindfoot were performed in the standing position prior to TKA, as well as 3 weeks and 1 year following TKA. The varus–valgus angle was used as an indicator of HFA in the coronal plane. Patients were divided into two groups according to the preoperative varus–valgus angle: a hindfoot varus group (varus–valgus angle <76°) and a hindfoot valgus group (varus–valgus angle ≥76°). The changes in the varus–valgus angle were evaluated and compared in both groups.ResultsIn the hindfoot valgus group, the mean ± standard deviation varus–valgus angle significantly declined from 80.5 ± 3.1° prior to TKA to 78.6 ± 3.7° 3 weeks following TKA and 77.1 ± 2.7° 1 year following TKA. However, in the hindfoot varus group, the mean varus–valgus angle prior to TKA (72.7 ± 2.6°) did not differ significantly from the mean varus–valgus angles 3 weeks (72.3 ± 3.3°) or 1 year (73.5 ± 3.0°) following TKA.ConclusionsHFA improved chronologically in legs with hindfoot valgus as a result of the alignment compensation ability of the hindfoot following TKA. However, no improvement was noted in legs with hindfoot varus because the alignment compensation ability of the hindfoot had been lost. The patients with hindfoot varus should be attended for ankle pain in the outpatient clinic after TKA.Level of evidenceIII.

Effect of a realtime process for positioning the plug-in gait wand markers

Main topics: Technical developments in movement science, Experimental studies in human movement science Introduction and aim: Quality of the popular Plug-in Gait (PiG) model [1] outputs depends primarily on marker positioning. Among them, thewandmarkersplacedon the thighsandshanksare especially difficult to position because they involve non-palpable anatomical points: the hip and the knee joint centers, respectively. This communication presents an optimal method for positioningwandmarkers using a real-time process.We examine the effect of thismethod on two operators (expert and non-expert). This process is expected to reduce the inter-session variability [2] and the maximum of the varus-valgus knee angle during swing phase. Patients/materials and methods: Gait data were collected on ten healthy subjects (62±10kg, 1.69±0.09m) with an optoelectronic motion capture system (Vicon, Oxford Metrics). Except the wand markers, all the PiG markers, plus medial markers were placed by an expert operator (5-year experience in gait analysis). A custom program using the Vicon RealTime SDK was implemented in Matlab. It indicated when the thigh wand marker, for example, belonged to the plan formed by the hip joint center, the lateral and medial condyles, with a tolerance of ±1mm. Firstly, each subject participated in four gait sessions, two with and twowithout real-time positioning by the expert. Between each session, the wand markers were fully removed. Four other gait sessionswere then carried outwith non-experts as operator (physiotherapist students without experience in gait laboratory). Kinematics PiG data were calculated by the use of the Biomechanical toolkit [3]. A two-way mixed-anova examined the effect of the realtime process and operators. Results: Real-time positioning significantly reduced the intersession variability of knee angles for the non-expert (Fig. 1). For the expert, only the flexion-extension was different. Similarly, a significant difference of 6 degrees (Table 1) was observed for the maximal knee var/valgus angle provided from the non-expert positioning. Thanks to the real-time process, themaximal var/valgus of the non-expert did not differ from the expert one.

Alteration of Hindfoot Alignment After Total Knee Arthroplasty Using a Novel Hindfoot Alignment View

This study examined the coronal alignment of the hindfoot in varus osteoarthritis of the knee before and after total knee arthroplasty (TKA) in 100 legs using a novel imaging method. We categorized the preoperative hindfoot alignment into varus (30 legs) and valgus (70 legs) groups; imaging of the hindfoot was conducted preoperatively and postoperatively, and the varus–valgus angle (VVA) was measured as the hindfoot alignment. The femorotibial angle improved significantly after TKA. We found that the VVA improved significantly after TKA in the hindfoot valgus group (P<0.001), but not in the varus group (P=0.554), and we speculate that the hindfoot alignment in the valgus group improved as a result of a residual compensatory capacity in the hindfoot.

A new radiographic view of the hindfoot

BackgroundA new radiographic view was proposed to evaluate the coronal plane alignment of the hindfoot under weightbearing conditions.MethodsWe studied 46 feet of individuals with normal appearing asymptomatic feet. On the antero-posterior roentgenogram using this new method, the line from the top of the sustentaculum tali to the lateral-inferior end of the posterior articular surface of the talus was obtained as the standard line showing varus or valgus of the calcaneus. We defined the angle between the longitudinal axis of the tibia and the standard line as described above as Varus-Valgus angle (V-V angle).ResultsThe mean (±SD) V-V angle of the 46 feet studied was 76.4 (±3.6) degrees.ConclusionThe findings from this study indicate that it is possible to estimate the alignment of the hindfoot quantitatively by comparing individuals to the mean V-V angle that we calculated in our sample, which was 76.4 degrees.

Gait Differs Between Unilateral and Bilateral Knee Osteoarthritis

Creaby MW, Bennell KL, Hunt MA. Gait differs between unilateral and bilateral knee osteoarthritis. ObjectivesTo compare walking biomechanics in the most painful leg, and symmetry in biomechanics between legs, in individuals with (1) unilateral pain and structural osteoarthritis (OA), (2) unilateral pain, but bilateral structural OA, and (3) bilateral pain and structural OA and in (4) an asymptomatic control group. DesignCohort study. SettingLaboratory based. ParticipantsParticipants with symptomatic and/or radiographic medial tibiofemoral OA in one or both knees (n=91), and asymptomatic control participants (n=31). InterventionsNot applicable. Main Outcome MeasureThe peak knee adduction moment, peak knee flexion moment, knee varus-valgus angle, peak knee flexion angle, toe-out, and trunk lean were computed from 3-dimensional analysis of walking at a self-selected speed. ResultsAfter controlling for walking speed, greater trunk lean toward the more painful knee and reduced flexion in the more painful knee were observed in all OA groups compared with the control group. Between-knee asymmetries indicating greater varus angle and a lower external flexion moment in the painful knee were present in those with unilateral pain and either unilateral or bilateral structural OA. Knee biomechanics were symmetrical in those with bilateral pain and structural OA and in the pain free control group. ConclusionsThe presence of pain unilaterally appears to be associated with asymmetries in knee biomechanics. Contrary to this, bilateral pain is associated with symmetry. This suggests that the symptomatic status of both knees should be considered when contemplating unilateral or bilateral biomechanical interventions for medial knee OA.