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. 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: 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.

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.

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.

Purpose: Dislocation is a short-term complication frequently encountered after implantation of a total hip arthroplasty (THA). Different strategies can be used to limit the influence of technical, particularly surgical, factors. The position of the acetabular element is a key factor, particularly the anteversion angle and the abduction angle. The purpose of this work was to determine the precision, the reproducibility, and the ease of use of a new mechanical guide for insertion of the acetabular cup.

Material and methods: After calculating the sample size necessary to achieve 90% statistical power for a 5% type I error, we had five surgeons who regularly implanted THA implant 310 press-fit hip cups on a plastic anatomic model of the pelvis. A new mechanical guide was developed using the constant direction of gravity as the reference frame. We determined the precision of acetabular cup implantation, its reproducibility, and ease of use compared with that of the Müller mechanical guide during in vitro implantation of 310 cups via a posterolateral approach that allowed the usual vision of the operative field.

Results: The error of cup anteversion relative to the reference set at 15 was 10.4±5.0 (range 3–21) for the Müller guide and 0.4±0.7 (range 1–3) for the new guide. Cup abduction, relative to the reference set at 45, was −4.7±2.3 (range 7–11) for the Müller guide and 0.3±0.5 (range 0–3) for the new guide. Mean time for positioning the cup was comparable with the two guides (mean 6s for the Müller guide and 5s for the new guide).

Discussion: The precision and reproducibility of cup positioning obtained with the new guide are better than those obtained with mechanical guides currently available on the market (p< 0.00001 with the Müller guide). They are more comparable with values found in in vitro studies using computer-assisted surgery techniques. Use of the new guide was also found to be rapid and simple.

Conclusion: The excellent results obtained with this new mechanical guide, as assessed in terms of cup position for THA, should be confirmed with in vivo trials.

Background: We evaluate the role of percutaneous þxation of Acetabular fractures in a selected group of patients in which conservative management seemed unlikely to yield a satisfying outcome. Method: Between July 1998 and July 2001, 17 consecutive patients having suffered an Acetabular fracture underwent ßuoroscopic guided percutaneous þxation to stabilize the fracture. The mean age of the patients was 81 years (range 67 to 90). In all cases the fracture was non-displaced or minimally displaced (< 2 mm). The operative indication was based on our experience that these patients would have a less favorable outcome with conservative management due to their diminished general health and important associated morbidity. Percutaneous þxation was performed at a mean of four days post injury (range 2–6). In all cases, 2 cannulated cancellous 7.3 mm were used, one to þx the anterior column and the other, inserted in a retrograde fashion to stabilize the posterior column. Bed to armchair transfer began after 24 hours. Weight bearing as tolerated was allowed at 4 weeks from surgery. Two patients died of unrelated causes in the postoperative period and one patient was lost to follow-up, leaving fourteen patients who could be followed for a mean of 1,5 years (range 6 months-3 years). Results: Soft tissue dissection was minimal. There were no intra-operative or post-operative complications. At latest follow-up there was no evidence radiographically of displacement of fragments, degenerative changes or screw failure. Fracture union was achieved at a mean period of 12 weeks (range, 8–15 weeks) after surgery. In one case the tip of the posterior screw penetrated the sacroiliac joint, but no clinical adverse effects were noted. Clinical results was satisfactory in thirteen patients, and fair in one patient, as assessed by the Matta modiþcation of the rating system described by dñAubigne and Postel. Conclusion: Our results show that the percutaneous þxation is a valid therapeutic option in selected Acetabular fractures, and in the future broader indications may be found for this technique.

Purpose: To determine if multidetector-row CT (MDCT) can replace conventional radiographs and be performed alone in severe trauma patients for the depiction of thoracolumbar spine fractures. Materials and Methods: One hundred consecutive severe trauma patients who underwent conventional radiographs of the thoracolumbar spine as well as thoraco-abdominal MDCT were prospectively identiþed. Conventional radiographs were reviewed independently by 3 radiologists and 2 orthopedic surgeons, and MDCT by 3 radiologists. Reviewers were blinded both to each other and to the results of the initial evaluation of these examinations. Presence, location and stability of fractures, as well as quality of reviewed imaging methods were assessed. Statistical analysis was performed to determine sensitivity and inter-observer agreement of each procedure, with clinical and radiological follow-up chosen as the reference standard. Time to perform each examination as well as involved radiation doses were also evaluated. Finally, a resource cost analysis was performed. Results: Sixty-seven fractured vertebrae in 26 of the patients were diagnosed. Twelve patients showed unstable spine fractures. Sensitivity and inter-observer agreement for unstable fractures amounted to 97.2% and 95.1% with MDCT, and 33.3% and 36.8% with conventional radiology. Average times in the performance of conventional radiographs and MDCT examinations amounted to 33 minutes and 40 minutes, respectively. Effective radiation doses involved in conventional radiographs of the spine and thoraco-abdominal MDCT amounted to 6.36 mSv and 19.42 mSv, respectively. MDCT afforded identiþcation of 145 associated traumatic lesions. Finally, costs of conventional radiographs and of MDCT amounted to 145 US$ and 880 US$ per patient, respectively. Conclusion: MDCT is a better test for depicting spine fractures than conventional radiographs. It can replace conventional radiographs and be performed alone in severe trauma patients.

Aims: All health care systems in the developed world are facing everincreasing health care costs and faced with this prospect, governments and other health care payers seek greater beneþts from existing health resources. An inexpensive alternative without excessive technical demands on physicians or operating room personnel, is two-dimensional (2D) computerassisted preoperative planning. The purpose of the study was to clinically validate the SYMBIOS X-Rays Preoperative Planning software for preoperative planning of cementless total hip replacement. Methods: For each of the thirty patients with osteoarthritis who underwent a total hip arthroplasty using an uncemented anatomic stem, the manual preoperative planning of the surgeon, the 2D computer-assisted one and the result after the real implantation were compared by an independent observer. Comparisons were based on stem and neck sizes as well as stem and rotation center position, using the deþnitive implantation as the reference standard. Results: There were no statistical differences between the results of the manual and 2D computer-assisted preoperative plans in terms of stem size and neck length (< 1 size) as well as for rotation center positioning (< 5mm) when compared to the deþnitive implantation. Conclusion: Two-dimensional computer-assisted preoperative planning seems to provide results as good as those of the manual procedure with the great advantage of allowing the surgeon to simulate various stem designs and to take into account biomechanical criteria.

Purpose of the study: After total hip replacement, the initial stability of the cementless femoral stem is a prerequisite for ensuring bone ingrowth and therefore long term fixation of the stem. For custom made implants, long term success of the replacement has been associated with reconstruction of the offset, antero/retro version of the neck orientation and its varus/valgus orientation angle. The goals of this study were to analyze the effects of the extra-medullary parameters on the stability of a noncemented stem after a total hip replacement, and to evaluate the change of stress transfer.

Material and methods: The geometry of a femur was reconstructed from CT-scanner data to obtain a three-dimensional model with distribution of bone density. The intra-medullary shape of the stem was based on the CT-scanner. Seven extra-medullary stem designs were compared: 1) Anatomical case based on the reconstruction of the femoral head position from the CT data; 2) Retroverted case of − 15° with respect to the anatomical reconstruction; 3) Anteverted case with an excessive anteversion angle of + 15° with respect to the anatomical case; 4) Medial case: shortened femoral neck length (− 10 mm) inducing a medial shift of the femoral head offset; 5) Lateral case: elongated femoral neck length (+ 10 mm) inducing lateral shift of the femoral head offset 6) Varus case with CCD angle 127°; 7) Valgus case with CCD angle 143°. The plasma sprayed stem surface was modeled with a frictional contact between bone and implant (friction coefficient: 0.6). The loading condition corresponding to the single limb stance phase during the gait cycle was used for all cases. Applied loads included major muscular forces (gluteus maximus, gluteus medius, psoas).

Results: Micromotions (debonding and slipping) of the stems relative to the femur and interfacial stresses (pressure and friction) were different according to the extra-medullary parameters. However, the locations of peak stresses and micromotions were not modified. The highest micromotions and stresses corresponded to the lateral situation and to the anteverted case (micro-slipping and pressure were increased up to 35 p.100). High peak pressure was observed for all designs, ranging from anatomical case (34 MPa) to anteverted case (44 MPa). The peak stresses and micromotions were minimal for the anatomical case. The maximal micro-debonding was not significantly modified by the extra-medullary design of the femoral stem.

Discussion: The extra-medullary stem design has been shown to affect the primary stability of implant and the stress transfer after THR. Most interfacial regions present small micro-slipping which normally allows the occurrence of bone ingrowth. The anatomical design presents the lowest micromotions and the lowest interfacial stresses. The worst cases correspond to the anteverted and lateralized cases. Probably, the anteverted situation involves higher torsion torque, which in turn may induce high torsion shear micro-motions and higher stress at the interface. Moreover, the lever arm of the weight bearing force on the femoral head is augmented for the augmented neck length situation. This increases the bending moment, and therefore may increase the stresses as well as the stem shear micromotions. In summary, the present results could be taken as biomechanical arguments for the requirement of anatomical reconstruction of not only the intra-medullary shape but also the extra-medullary parameters (reconstruction of the normal hip biomechanics).