While knee osteoarthritis (OA) is now recognized as a complex disease affecting the whole joint, not just the cartilages, there remains a paucity of data regarding the interactions between knee components. One relationship of particular interest is between the spatial variations in cartilage thickness (CTh) and subchondral bone mineral density (BMD). Indeed, bone and cartilage are two mechanosensitive tissues that interact as a functional unit and there is evidence of a biomechanical coupling between both tissues. Particularly, a recent in vivo study has shown a positive relationship in non-OA knees with thicker cartilage where bone is denser, and an alteration of this relationship in OA knees. These observations support the concept of an osteochondral unit and warrant additional research to assess the influence of bone depth. Therefore, this study aimed to characterize the relationship between spatial variations in CTh and BMD measured at various depths below the bone surface.

CT-arthrography of 20 non-OA tibias and 20 severe medial-compartment OA tibias were segmented to build 3D mesh models of the bones and cartilages. Each individual tibia model was registered to a reference tibia, allowing to calculate BMD maps at 1, 3, 5 and 10mm below the bone-cartilage interface in the medial compartment. Pearson correlations between CTh maps and the four BMD maps were then calculated for each knee. Lastly, differences in correlation coefficients between successive bone layers were assessed using Wilcoxon signed-rank tests.

In both OA and non-OA tibias, the correlation coefficients were higher with the BMD measured in the 1mm layer, and followed a pattern of statistically significant decrease with bone layers of increasing depth (p < 0.021). In non-OA tibias, the median relationship was positive with a strong effect size in the 1, 3 and 5mm layers, while in OA tibias the median relationship was positive only in the 1mm layer and with a medium effect size. In the OA tibias, the median relationship was negative with a weak effect size in the 3 and 5mm layers, and it was negative with a medium effect size in the 10mm layer.

In conclusion, the results of the present study support the value of considering bone and cartilage as a unit, and more generally support OA pathophysiology models based on relationships among knee properties.

While osteophytes are a hallmark feature of knee osteoarthritis (OA), there is limited information regarding their location. In particular, it is unknown whether osteophytes develop in patient-specific locations or if there are consistent osteophyte locations among OA knees. This lack of data mainly stems from the fact that osteophytes have been mostly assessed with scores quantifying their size or severity but not their location. Given the important role that bone could play in OA development and the option it offers for OA treatment, there is a need to better understand the osteophyte locations. This study aimed to develop a method to compare osteophyte locations among knees and determine the overlapping ratio. CT arthrogram of 11 medial-compartment OA tibias (Kellgren-Lawrence grade ≥ 3) were segmented to locate the osteophytes and a bone matching technique was used to report the osteophyte locations of the 11 knees on a single reference tibia. This newly proposed method was highly reproducible (intra-operator ICC = 0.89). When used to compare the 11 tibias, it showed that more than 60% of the overall subosteophytal area, defined as the reference bone area covered by at least one osteophyte from one knee, was common to less than two tibias. Moreover, less than 20% of the overall subosteophytal area was common to five or more tibias. The results of this study suggest that osteophyte locations are specific to each knee. Future work should determine the relationships with mechanical loading, as this could explain the high inter-patient variability.

Background

Some models of knee osteoarthritis (OA) suggest that the properties of knee tissues are adapted in healthy joints, and that OA development is due to a breakdown in the equilibrium among tissue properties. Cartilage thickness and bone density are particularly important properties in this regard because both are related to the mechanical environment. This study tested the hypothesis that locations of thickest cartilage are associated with locations where bone density is the highest in non-OA tibias.

Knee osteoarthritis (OA) is a serious health concern, requiring novel therapeutic options. Walking mechanics has long been identified as an important factor in the OA process. Specially, a larger peak knee adduction moment during the first half of stance (KAM) has been associated with the progression of medial knee OA. Consequently, various gait interventions have been designed to reduce the KAM, including walking with a decreased foot progression angle (FPA). Other gait variables have recently been associated with medial knee OA progression, particularly a larger peak knee flexion moment during stance (KFM) and a larger knee flexion angle at heel-strike (KFA). Currently, there is a paucity of data regarding the effect of reducing the FPA on the KFM and KFA.

This study aimed to test for correlations between the FPA and the KAM, KFM and KFA. It was hypothesized that reducing the FPA is beneficial with respect to these three OA-related gait variables.

Seven healthy subjects participated in this study after providing informed consent (4 male; 24 ± 5 years old; 21.9 ± 1.5 kg/m^2). Their walking mechanics was determined using a validated procedure based on a camera-based system (Vicon) and floor-mounted forceplates (Kistler). Participants were first asked to walk without instructions and these initial trials were used to determine their normal footstep characteristics. Then, footsteps with the same characteristics as during the normal trials, except for the FPA, were displayed on the floor and participants were requested to walk following these footsteps. Nine trials with visual instructions were collected for each participant, corresponding to FPA modifications in the range ± 20° compared to the normal FPA, with 5° increment. For each participant, the associations between FPA and knee biomechanics (KAM, KFM and KFA) were assessed using Pearson correlations based on the data from the 9 trials with FPA variations. Significant level was set a priori to 5%.

Significant correlations were noted between FPA and KAM for 5 out of the 7 participants, with R comprised between 0.75 and 0.96. Four participants also reported significant correlations between FPA and KFA (−0.88<R<−0.69). Significant correlations between FPA and KFM were observed in 2 participants, with inconsistent R (−0.68 and 0.78). There was no significant correlation between FPA and walking speed for none of the participants.

While the results confirmed that decreasing the FPA (toeing in) is often associated with a KAM reduction, they also showed relationships between decreased FPA and increased KFA. Therefore, this study suggests that reducing the FPA should be done in consideration of the possible negative changes in KFA. Similarly, although only one participant increased the KFM when decreasing the FPA, it seems important monitoring the effects FPA modifications could have on the KFM. The large variations observed among participants further suggest individualized gait modifications. This study should be extended to medial knee OA patients and longitudinal research is necessary to better understand the effects of decreasing the FPA.

Knee osteoarthritis (OA) affects an estimated 250 million people worldwide, with a cure yet to be found. Consequently, there is an urgent need to improve our understanding of OA physiopathology. While knee OA has long been mostly described as a loss of cartilage thickness (CTh) and research has focused on this characteristic, the role of bone alterations is rapidly gaining in interest. Analyzing subchondral bone mineral density (sBMD) is particularly interesting because this could inform on the mechanical environment at the knee. However, there is a paucity of data on sBMD in literature mainly because of the lack of prior methods to measure this parameter. A method for 3D sBMD assessment based on computed tomography (CT) scans was recently proposed, thus allowing testing for sBMD differences in knee OA. This study aimed at comparing non-OA and medial OA knees in terms of tibial sBMD and CTh. Specifically, it was hypothesized that sBMD and CTh differ with OA.

Ten knees with severe medial OA and 10 matched non-OA knees were analyzed after ethical approval (50% male; 60 ± 3 years old). The arthro-CT scans of the 20 knees were segmented using custom software to build 3D mesh models of the tibial bone and cartilage. CTh maps were obtained by calculating the distance between cartilage and bone meshes, while sBMD maps were calculated based on the intensity of the CT in the first 3mm of bone. For each knee, the average CTh and sBMD values over the entire medial and lateral compartments were calculated and used to determine the medial-to-lateral (M/L) CTh and sBMD ratios. Unpaired t-tests and receiver operating characteristic (ROC) were used for statistical analysis.

The M/L sBMD ratio was significantly higher in OA compared to non-OA knees (1.14 ± 0.04 vs. 1.08 ± 0.03; p<0.01), whereas the CTh ratio was not significantly different between groups (0.70 ± 0.21 vs. 0.85 ± 0.10; p=0.06). No significant differences were found between OA and non-OA knees for the average medial CTh and sBMD (p>0.4). High classification performance was obtained for the sBMD ratio and low performance for the average sBMD in the medial compartment (areas under the ROC curve of 0.9 and 0.6, respectively). CTh ratio and medial compartment average provided medium classification performances (areas under the curve of 0.7).

This study showed that sBMD differed between non-OA and severe medial OA knees and that sBMD M/L ratio was more sensitive to OA severity than CTh variables. These results brought new insights into the pathogenesis of knee OA, by supporting the idea that sBMD is altered with OA and suggesting that sBMD could play a role in disease development. Indeed, the mechanical stresses on the cartilages are related to the mechanical characteristics of the bones. Indirectly, this study also demonstrated the value of arthro-CT scans to simultaneously assess sBMD and CTh. Additional studies with larger cohorts of patients at different stages of the disease are necessary to better understand when changes in sBMD occur.

Summary Statment

The dual-mobility cup seems to bring more stability without changing the gait pattern.

INTRODUCTION

Mobile-bearing knee prostheses have been designed in order to provide less constrained knee kinematics compared to fixed-bearing prosthesis. Currently, there is no evidence to confirm the superiority of either of the two implants with regard to walking performances. It has been shown that subjective outcome scores correlate poorly with real walking performance and it has been recommended to obtain an additional assessment of walking ability with objective gait analysis.

Purpose of the study: Reconstruction of the anterior cruciate ligament (ACL) controls laxity but does not enable restoration of strictly normal 3D kinematics. The purpose of this study was to compare the kinematics of the pathological knee with that of the healthy knee after ACL plasty. This study applied a new ambulatory system using miniature captors.

Material and method: Five patients with an isolated injury of the ACL participated in this study. The patients were assessed after injury (T1), at five months (T2), and at 14 months (T3) after surgery. The assessment included laxity (KT-1000), the IKDC score and the Lysholm score. The 3D angles of the knees were measured when walking 30 m on flat ground using a system composed of to small inertia units (3D accelerometer and 3D gyroscope) and a portable recorder. Functional settings were optimised and validating to ensure easy precise measurement of the 3D angles. Symmetry of the two knees was quantified using a symmetry index (SI) (difference in amplitude normalised in relation to mean amplitude) and the correlation coefficient CC.

Results: Clinical indicators improved during the follow-up (IKDC T1: 3C, 2C; T2: 5B; T3: 2A, 3B; subjective IKD: 53–95; Lysholm 67–96). Mean laxity improved from 8.6m to 2.5 mm. The gait analysis showed increased symmetry in terms of amplitude for flexion-extension (SI: −17% at T1, −1% at T2, 1% at T3), and an increase in symmetry in terms of the rotation signature (CC: 0.16 at T1, 0.99 at T2, 0.99 at T3). There was no trend to varus-valgus.

Discussion: This study demonstrates the clinical application of the new ambulatory system for measuring 3D angles of the knee joint. Joint symmetry increased after ACL plasty but still showed some perturbation at 14 months. The results observed here are in agreement with the literature. Other patients and other types of gait are being analysed.

Conclusion: This portable system allows gait analysis outside the laboratory, before and after ACL injury. It is very useful for follow-up after surgery.

Recently, many mathematical descriptors were proposed to quantify 3D motions of the foot and ankle complex. However, since the ranges of rotation in foot joints are rather small, the reliability of these kinematic assessments is questionable. Particularly, achievement of acceptable results for clinical decision makings demands to extract repeatable features. In this study, repeatability of kinematics assessment of multi-segment foot by means of different mathematical descriptors was investigated.

25 tiny markers were mounted on dominant anatomical landmarks of the foot and ankle complex. Six young healthy subjects were asked to walk over a forceplate surrounded by six infra-red cameras. Marker trajectories were captured during one stance phase and several trials per subject were recorded. Foot and ankle complex was considered as six rigid segments:

Shank,

3D angles between each pair of segments (i.e., 1~2, 2~3, 3~4, 3~5 and 4~6) were calculated based on three common mathematical descriptors:

helical angle,

Then, the coefficient of multiple correlations (CMC) was used to estimate the degree of similarity among joint angle patterns for intra-subject and inter-subjects trials.

It was observed that the three angle calculation methods had comparable repeatability for both intra-subject and inter-subjects kinematics. No significant difference among their repeatability was noticed. Most of angles showed good pattern repeatability intra-subject and acceptable pattern repeatability inter-subjects. In conclusion, all three calculation methods for foot joint angles can be reliably applied. Further studies enrolling patients with foot and ankle pathology are necessary to investigate the relevance of these measurements for clinical evaluations.

The FIRST knee prosthesis (Free Insert in Rotation Stabilized in Translation, Symbios SA) is a new ultra congruent, postero-stabilized total knee arthroplasty (TKA) with a mobile bearing expected to reduce significantly polyethylene wear, to improve the range of motion and the overall stability of the knee while ensuring a physiological ligament balance. We compared subjective and really objective results of this new TKA with two other widespread models of TKA.

A clinical prospective monocentric cohort study of 100 consecutive patients (47–88 yrs) undergoing a FIRST TKA for primary osteoarthritis is currently being done. Pre- and post-operative follow-ups (6 weeks, 4,5 months and 1 year) are done with well-recognized subjective evaluations (EQ-5D and WOMAC scores) and semi-objective questionnaires (KSS score and radiography evaluation) as well as with a really objective evaluation using gait parameters from 6 walking trials, performed at different speeds with an ambulatory in field gait analysis system (Physilog®, BioAGM CH). The outcomes after one year of follow-up of 32 FIRST TKA are compared to 29 NexGen® postero-stabilized TKA (Zimmer Inc) with a fixed bearing and to 26 NexGen® TKA with a mobile bearing using the same methods.

The gait cycle time of the FIRST TKA was statistically significantly shorter at normal speed of walk, as well as double-support periods, as compared to both standard models. The normal walking speed was significantly higher with faster swing speed and stride lengths for the new TKA. Significantly better coordination scores were observed at normal walking speed for the FIRST TKA as compared to the fixed-bearing TKAs.

The FIRST TKA showed statistically significantly better really objective outcomes in terms of gait after one year of follow-up and similar subjective and semi-objective evaluations compared to two widespread TKA designs.

Introduction: Ankle arthropathy is associated with a decreased motion of the ankle-hindfoot during ambulation. Ankle arthrodesis was shown to result in degeneration of the neighbour joints of the foot. Inversely, total ankle arthroplasty conceptually preserves the adjacent joints because of the residual mobility of the ankle but this has not been demonstrated yet in vivo. It has also been reported that degenerative ankle diseases, and even arthrodesis, do not result in alteration of the knee and hip joints. We present the preliminary results of a new approach of this problem based on ambulatory gait analysis.

Patients and Methods: Motion analysis of the lower limbs was performed using a Physilog® (BioAGM, CH) system consisting of three-dimensional (3D) accelerometer and gyroscope, coupled to a magnetic system (Liberty©, Polhemus, USA). Both systems have been validated. Three groups of two patients were included into this pilot study and compared to healthy subjects (controls) during level walking: patients with ankle osteoarthritis (group 1), patients treated by ankle arthrodesis (group 2), patients treated by total ankle prosthesis (group 3).

Results: Motion patterns of all analyzed joints over more than 20 gait cycles in each subject were highly repeatable. Motion amplitude of the ankle-hindfoot in control patients was similar to recently reported results. Ankle arthrodesis limited the motion of the ankle-hindfoot in the sagittal and horizontal planes. The prosthetic ankle allowed a more physiologic movement in the sagittal plane only. Ankle arthritis and its treatments did not influence the range of motion of the knee and hip joint during stance phase, excepted for a slight decrease of the hip flexion in groups 1 and 2.

Conclusion: The reliability of the system was shown by the repeatability of the consecutive measurements. The results of this preliminary study were similar to those obtained through laboratory gait analysis. However, our system has the advantage to allow ambulatory analysis of 3D kinematics of the lower limbs outside of a gait laboratory and in real life conditions. To our knowledge this is a new concept in the analysis of ankle arthropathy and its treatments. Therefore, there is a potential to address specific questions like the difficult comparison of the benefits of ankle arthroplasty versus arthrodesis. The encouraging results of this pilot study offer the perspective to analyze the consequences of ankle arthropathy and its treatments on the biomechanics of the lower limbs ambulatory, in vivo and in daily life conditions.

Introduction. Quantification of daily upper-limb activity is a key determinant in evaluation of shoulder surgery. For a number of shoulder diseases, problem in performing daily activities have been expressed in terms of upper-limb usage and non-usage. Many instruments measure upper-limb movement but do not focus on the differentiations between the use of left or right shoulder. Several methods have been used to measure it using only accelerometers, pressure sensors or video-based analysis. However, there is no standard or widely used objective measure for upper-limb movement. We report here on an objective method to measure the movement of upper-limb and we examined the use of 3D accelerometers and 3D gyroscopes for that purpose.

Methods. We studied 8 subjects with unilateral pathological shoulder (8 rotator cuff disease: 53 years old ± 8) and compared them to 18 control subjects (10 right handed, 8 left handed: 32 years old ± 8, younger than the patient group to be almost sure they don_t have any unrecognized shoulder pathology). The Simple Shoulder Test (SST) and Disabilities of the Arm and Shoulder Score (DASH) questionnaires were completed by each subject.

Two modules with 3 miniature capacitive gyroscopes and 3 miniature accelerometers were fixed by a patch on the dorsal side of the distal humerus, and one module with 3 gyroscopes and 3 accelerometers were fixed on the thorax. The subject wore the system during one day (8 hours), at home or wherever he/she went. We used a technique based on the 3D acceleration and the 3D angular velocities from the modules attached on the humerus.

Results. As expected, we observed that for the stand and sit postures the right side is more used than the left side for a healthy right-handed person(idem on the left side for a healthy left-handed person). Subjects used their dominant upper-limb 18% more than the non-dominant upper-limb. The measurements on patients in daily life have shown that the patient has used more his non affected and non dominant side during daily activity if the dominant side = affected shoulder. If the dominant side ≠ affected shoulder, the difference can be showed only during walking period.

Discussion-Conclusion. The technique developed and used allowed the quantification of the difference between dominant and non dominant side, affected and unaffected upper-limb activity. These results were encouraging for future evaluation of patients with shoulder injuries, before and after surgery. The feasibility and patient acceptability of the method using body fixed sensors for ambulatory evaluation of upper limbs kinematics was shown.

Introduction: Registration of complications in a Department of Orthopaedic Surgery or Traumatology has always been the concern of surgeons as a simple feedback to improve the quality of care they provide to their patients. However, it has not been made through a systematic approach in Switzerland to date. The literature shows only one study which proposes to set up a database and software for general surgery complications.

The purpose of this study was to show the feasibility of setting up a computerized register of complications for a whole Department of Orthopaedic Surgery and Traumatology, based on a simple, user-friendly and upto-date scientific approach.

Methods: After a systematic literature review, the definitions, types and classification of complications were determined. A protocol for data registration was defined as well as the tasks for the people involved. A client-server software was chosen and further developped, in close collaboration with the Information Technology Department to benefit from an automatic download of patients’ administrative data.

Results: The classification of complications by de Waal Maletfijt was adapted and the coefficient of severity proposed by Clavien was used. A definition of each complication was communicated to all staff involved. A self-developed Microsoft Access application with a local database as back-end was developed. A new strategy to capture the complications efficiently was developed and used after staff approval. Data collection was done before surgery (prehospitalisation), on the day of surgery and after the operation until the end of the stay in hospital.

Conclusions: This systematic approach to record complications was found feasible, efficient and a useful tool for the assessment of quality of care.

Introduction: Coordination is a strategy chosen by the central nervous system to control the movements and maintain stability during gait. Coordinated multi-joint movements require a complex interaction between nervous outputs, biomechanical constraints, and pro-prioception. Quantitatively understanding and modeling gait coordination still remain a challenge. Surgeons lack a way to model and appreciate the coordination of patients before and after surgery of the lower limbs. Patients alter their gait patterns and their kinematic synergies when they walk faster or slower than normal speed to maintain their stability and minimize the energy cost of locomotion. The goal of this study was to provide a dynamical system approach to quantitatively describe human gait coordination and apply it to patients before and after total knee arthroplasty.

Methods: A new method of quantitative analysis of interjoint coordination during gait was designed, providing a general model to capture the whole dynamics and showing the kinematic synergies at various walking speeds. The proposed model imposed a relationship among lower limb joint angles (hips and knees) to parameterize the dynamics of locomotion of each individual. An integration of different analysis tools such as Harmonic analysis, Principal Component Analysis, and Artificial Neural Network helped overcome high-dimensionality, temporal dependence, and non-linear relationships of the gait patterns.

Ten patients were studied using an ambulatory gait device (Physilog®). Each participant was asked to perform two walking trials of 30m long at 3 different speeds and to complete an EQ-5D questionnaire, a WOMAC and Knee Society Score. Lower limbs rotations were measured by four miniature angular rate sensors mounted respectively, on each shank and thigh. The outcomes of the eight patients undergoing total knee arthroplasty, recorded pre-operatively and post-operatively at 6 weeks, 3 months, 6 months and 1 year were compared to 2 age-matched healthy subjects.

Results: The new method provided coordination scores at various walking speeds, ranged between 0 and 10. It determined the overall coordination of the lower limbs as well as the contribution of each joint to the total coordination. The difference between the pre-operative and post-operative coordination values were correlated with the improvements of the subjective outcome scores. Although the study group was small, the results showed a new way to objectively quantify gait coordination of patients undergoing total knee arthroplasty, using only portable body-fixed sensors.

Conclusion: A new method for objective gait coordination analysis has been developed with very encouraging results regarding the objective outcome of lower limb surgery.

The purpose of this study was to evaluate the mid- and long-term outcomes of total knee arthroplasty in adult patients who have advanced juvenile idiopathic arthritis (JIA).

Between 1989 and 2001, twenty-two knees of JIA adult patients were treated with primary arthroplasty. Surgical challenges included fixed valgus and flexion deformity. All patients were evaluated (mean 8.0 years) using established and new scoring systems.

Knee arthroplasty provided relief of pain and stiffness and moderate improvement in range of motion in this severely affected patients. Although outcomes were scored poorly on established instruments, patients rated their benefits of the operation highly.

To evaluate the mid- and long-term outcomes of total knee arthroplasty in adult patients who have advanced juvenile idiopathic arthritis (JIA).

Between 1989 and 2001, twenty-two knees in fourteen adult patients with severe JIA were treated with primary arthroplasty. Surgical challenges included relative condylar and patellar overgrowth within a contracted, inelastic soft tissue envelope, osteoporosis, small sized bones and fixed valgus and flexion deformity including ankylosis. All patients were evaluated (follow-up: mean 8.0 years) using established and new scoring systems (postoperatively at follow-up and preoperatively by recall)..

Patients’ postoperative pain and stiffness VAS were significantly less than preoperative scores, with mean changes of 8.8 and 7.2, respectively. A mean post-operative flexion arc of 77° (range 30°–130°) was observed. All lower limbs were post-operatively aligned between 0° and 5° of mechanical valgus. Incomplete radiolucent lines were present in 27% of knees, but were not associated with clinical symptoms. Final SF-36, EQ-5D and WOMAC scores were relatively low, but 82% of patients rated themselves satisfied with the functional outcome, 100% with pain relief, and 100% stated that the outcome met or exceeded their expectations. Issues deemed by JIA patients to be important were identified by the patient specific questionnaire (PASI-pg), but not by SF-36, EQ-5D or WOMAC.

Knee arthroplasty provided relief of pain and stiffness and moderate improvement in range of motion in this severely affected adult JIA patients. Although outcomes were scored poorly on established instruments, patients rated their satisfaction with and benefits of the operation highly.

Funding:

B. Jolles received a Ligue Vaudoise contre le Rhumatisme Award for her work on Rheumatoid Arthritis.

Background: Mobile-bearing knee replacements have some theoretical advantages over fixed-bearing devices. However, very few randomized controlled clinical trials have been published to date, and studies showed little clinical and subjective advantages for the mobile-bearing using traditional systems of scoring. The choice of the ideal outcome measure to assess total joint replacement remains a complex issue. However, gait analysis provides objective and quantifying evidences of treatment evaluation. Significant methodological advances are currently made in gait analysis laboratories and ambulatory gait devices are now available. The goal of this study was to provide gait parameters as a new objective method to assess total knee arthroplasty outcome between patients with fixed- and mobile-bearing, using an ambulatory device with minimal sensor configuration.

This randomized controlled double-blind study included to date 14 patients: the gait signatures of four patients with mobile-bearing were compared to the gait signatures of nine patients with fixed-bearing pre-operatively and post-operatively at 6 weeks, 3 months and 6 months. Each participant was asked to perform two walking trials of 30m long at his/her preferred speed and to complete a EQ-5D questionnaire, a WOMAC and Knee Society Score (KSS). Lower limbs rotations were measured by four miniature angular rate sensors mounted respectively, on each shank and thigh.

A new method for a portable system for gait analysis has been developed with very encouraging results regarding the objective outcome of total knee arthroplasty using mobile- and fixed-bearings.

Background: Mobile-bearing knee replacements have some theoretical advantages over fixed-bearing devices. However, very few randomized controlled clinical trials have been published to date, and studies showed little clinical and subjective advantages for the mobile-bearing using traditional systems of scoring.

The choice of the ideal outcome measure to assess total joint replacement remains a complex issue. However, gait analysis provides objective and quantifying evidences of treatment evaluation. Significant methodological advances are currently made in gait analysis laboratories and ambulatory gait devices are now available.

The goal of this study was to provide gait parameters as a new objective method to assess total knee arthroplasty outcome between patients with fixed- and mobile-bearing, using an ambulatory device with minimal sensor configuration.

Methods: This randomized controlled double-blind study included to date 31 patients: the gait signatures of 12 patients with mobile-bearing were compared to the gait signatures of 19 patients with fixed-bearing pre-operatively and post-operatively at 6 weeks, 3 months and 6 months. Each participant was asked to perform two walking trials of 30m long at his/her preferred speed and to complete a EQ-5D questionnaire, a WOMAC and Knee Society Score (KSS). Lower limbs rotations were measured by four miniature angular rate sensors mounted respectively, on each shank and thigh.

Results: Better relative differences between pre-operative and post-operative 3 months and 6 months KSS (122% vs 34% at 3 months, 138% vs 36% at 6 months) and KSS function (154% vs 8% at 3 months, 183% vs 42% at 6 months) scores were observed for the fixed-bearing compared to the mobile-bearing. The same better improvements for fixed-bearing were also found with the range of knee angles (Affected side: 31% vs −5% at 3 months, 47% vs 5% at 6 months), (Unaffected side: 16% vs 5% at 3 months, 15% vs 6% at 6 months) and peak swing speeds of shank (Affected side: 18% vs −2% at 3 months, 30% vs 4% at 6 months), (Unaffected side: 8% vs −3% at 3 months, 7% vs 4% at 6 months).

Conclusions: A new method for a portable system for gait analysis has been developed with very encouraging results regarding the objective outcome of total knee arthroplasty using mobile- and fixed-bearings.

Introduction The purpose of this study was to identify issues of importance to Juvenile Idiopathic Arthritis (JIA) patients before and after total hip arthroplasty (THA) and to determine if these issues are included in widely utilized, standardized outcome measures for THA (Western-Ontario and McMaster Universities Arthritis Index – WOMAC; Patient Specific Index – PASI).

Methods JIA patients who underwent THA between 1986 and 1999 in our institution participated in the study (n=31). An independent observer was asked to gather data forms including patient demographics, a postoperative WOMAC questionnaire, postoperative patient-generated items from the PASI, a retrospectively completed preoperative PASI form, and changes in items from pre-operative to postoperative PASI. Descriptive analysis was completed on demographic information and clinical outcomes as well as for the WOMAC and PASI scores. Spearmans rank correlation coefficients were calculated to describe the association between WOMAC and PASI scores

Results Issues deemed important by JIA patients included four symptom areas (pain, joint motion, strength, discomfort) and five activity areas (light household, leisure, clothing, sports, sex); some indicated they had no symptoms or difficulties. Issues relevant to patients shifted from predominantly symptoms before surgery, to recreational and social activities at follow-up. Comparison of postoperative WOMAC questionnaires with preoperative and postoperative PASI questionnaires revealed fundamental differences between items found in the standardized WOMAC and items deemed important by the patient. The WOMAC included less than 10% of the unweighted content deemed important by these patients at follow-up.The shift in the PASI towards more physically demanding activities after surgery indicates that patients improved, which is not reflected in the WOMAC. Correlations between postoperative WOMAC and PASI scores for pain sub-scales were low to moderate (Spearman‘s coefficient rs=0.53) and 63% of JRA patients had higher PASI than WOMAC normalized scores.

Conclusion The self-generated, self-reported portion of the PASI questionnaire provided a different perspective on the impact of THA in JIA patients. The WOMAC did not include content deemed to be important by JRA patients and did not correlate well with the patient specific instrument.

Obtaining consistently an optimal cup orientation in THA is vital to obtain adequate head coverage and maximum impingement free range of motion and thus reduce the incidence of polyethylene wear, cup loosening, and dislocation rates associated with a limited range of motion. It is clear that THA instability, the most frequent cause of early failure, is a complex problem related to a wide range of causes. However cup orientation is one of the surgeon dependant potentially modifiable variables that continue to have an important influence due to the lack of reliable means of assuring an adequate orientation of the components, particularly the cup anteversion. Standard mechanical guides like Muller’s have been shown to be inaccurate and imprecise. Not surprisingly, dislocation is the most frequent short term complication after a THA. Acetabular cup orientation is a key factor determining joint stability and one of the most important ones under the surgeons’ control. An in vitro study was used to determine the precision, reproducibility and ease of use of a new mechanical guide in comparison to a standard mechanical guide Müllers. The new guide (Gravity Assisted Navigation System) consists of a simple to use navigation tool. It uses the constant direction of the force of gravity identified by two bulls’ eye levels providing real time intraoperative augmented reality thus controlling the orientation of the pelvis. Visualisation of the guide from a single perspective is enough to determine in real time, the orientation of the cup in abduction and anteversion. By using anatomic repairs within the pelvis its flexion/extension is taken into consideration. As part of an invitro study, 310 press-fit acetabular cups were impacted into a plastic model of a pelvis by 5 surgeons (Power 90%, Type I error 5%), The orientation obtained was measured with respect to a fixed reference of 15° of anteversion and 45° of abduction. Results: an average of 10.4° anteversion ,(Range 3°to 21°, Standard of Deviation 5.0°) for Müller s guide and of 0.4° anteversion (Range 1° to 3°, Standard of Deviation 0.7°) for the new guide and an average of −4.7° abduction (Range 7° to −11°, Standard of Deviation 2.3°) for Müllers guide and 0.3° abduction (Range 0° to 3°, Standard of Deviation 0.5°) for the new guide. The average time required for the orientation of the cups was similar with both guides. (6 seconds for Mullers guide and 5 seconds for the new guide) The precision and reproducibility of the cup orientation obtained with the new guide were significantly better than those obtained with Müllers guide (p< 0.00001). The results obtained with with the new mechanical guide are encouraging. The in vitro results are encouraging, the high precision and accuracy are comparable to results obtained by computer assisted navigation systems in similar studies.

Introduction and Aims: In this study, we identify issues of importance to adult Juvenile Rheumatoid Arthritis (JRA) patients before and after total hip arthroplasty (THA) and determine if these issues are included in widely utilised, standardised outcome measures for THA (Western-Ontario and McMaster Universities Arthritis Index – WOMAC; Patient Specific Index – PASI).

Method: Adult JRA patients who underwent THA between 1986 and 1999 at our institution participated in the study (n=31). An independent observer gathered data, including patient demographics, a post-operative WOMAC questionnaire, post-operative patient-generated items from the PASI, a retrospectively completed pre-operative PASI form, and changes in items from pre-operative to post-operative PASI. Descriptive analysis was completed on demographic information and clinical outcomes, as well as for the WOMAC and PASI scores. Spearman’s rank correlation coefficients were calculated to describe the association between WOMAC and PASI scores.

Results: Issues deemed important by JRA patients included four symptom areas (pain, joint motion, strength, discomfort) and five activity areas (light household, leisure, clothing, sports, sex); some patients indicated they had no symptoms or difficulties. Before surgery, issues identified as relevant by patients were predominantly symptoms, whereas at follow-up, patients primarily identified recreational and social activities as the issues relevant to them.

Comparison of post-operative WOMAC questionnaires with pre-operative and post-operative PASI questionnaires revealed fundamental differences between items found in the standardised WOMAC and items deemed important by the patient. The WOMAC included less than 10% of the unweighted content deemed important by these patients at follow-up. The shift in the PASI towards more physically demanding activities after surgery indicates that patients improved, which is not reflected in the WOMAC. Correlations between post-operative WOMAC and PASI scores for pain subscales were low to moderate (Spearman rank correlation coefficient: rs = 0.53) and 63% of JRA patients had higher PASI than WOMAC normalised scores.

Conclusion: The self-generated, self-reported portion of the PASI provided a different perspective on the impact of THA in adult JRA patients and more information on issues important to these patients. The WOMAC did not include content deemed to be important by JRA patients and did not correlate well with the PASI.