Vincent Pomero

No Benefit of Patient-specific Instrumentation in TKA on Functional and Gait Outcomes: A Randomized Clinical Trial

BackgroundAlthough some clinical reports suggest patient-specific instrumentation in TKA may improve alignment, reduce surgical time, and lower hospital costs, it is unknown whether it improves pain- and function-related outcomes and gait.Questions/purposesWe hypothesized that TKA performed with patient-specific instrumentation would improve patient-reported outcomes measured by validated scoring tools and level gait as ascertained with three-dimensional (3-D) analysis compared with conventional instrumentation 3 months after surgery.MethodsWe randomized 40 patients into two groups using either patient-specific instrumentation or conventional instrumentation. Patients were evaluated preoperatively and 3 months after surgery. Assessment tools included subjective functional outcome and quality-of-life (QOL) scores using validated questionnaires (New Knee Society Score© [KSS], Knee Injury and Osteoarthritis Outcome Score [KOOS], and SF-12). In addition, gait analysis was evaluated with a 3-D system during level walking. The study was powered a priori at 90% to detect a difference in walking speed of 0.1 m/second, which was considered a clinically important difference, and in a post hoc analysis at 80% to detect a difference of 10 points in KSS.ResultsThere were improvements from preoperatively to 3 months postoperatively in functional scores, QOL, and knee kinematic and kinetic gait parameters during level walking. However, there was no difference between the patient-specific instrumentation and conventional instrumentation groups in KSS, KOOS, SF-12, or 3-D gait parameters.ConclusionsOur observations suggest that patient-specific instrumentation does not confer a substantial advantage in early functional or gait outcomes after TKA. It is possible that differences may emerge, and this study does not allow one to predict any additional variances in the intermediate followup period from 6 months to 1 year postoperatively. However, the goals of the study were to investigate the recovery period as early pain and functional outcomes are becoming increasingly important to patients and surgeons.Level of EvidenceLevel I, therapeutic study. See the Instructions to Authors for a complete description of levels of evidence.

Volumic patient-specific reconstruction of muscular system based on a reduced dataset of medical images.

Three-dimensional mechanical modelling of muscles is essential for various biomechanical applications and clinical evaluation, but it requires a tedious manual processing of numerous images. A muscle reconstruction method is presented based on a reduced set of images to generate an approximate parametric object from basic dimensions of muscle contours. A regular volumic mesh is constructed based on this parametric object. The approximate object and the corresponding mesh are deformed to fit the exact muscles contours yielding patient-specific geometry. Evaluation was performed by comparison of geometry to that obtained by contouring all computed tomography (CT) slices, and by quantification of the mesh quality criteria. Muscle fatty infiltration was estimated using a threshold between fat and muscle. Volumic fat index (VFI) of a muscle was computed using first all the complete CT scan slices containing the muscle (VFIref) and a second time only the slices used for reconstruction (VFIrecons). Mean volume error estimation was 2.6% and hexahedron meshes fulfilled quality criteria. VFIrecons respect the individual variation of fat content.

Peut-on se fier à l’angle poplité chez l’enfant paralysé cérébral marchant ?

PURPOSE OF THE STUDY In clinical practice, it is generally accepted that hamstring tightness results in incomplete knee extension when the hip is in flexion and in smaller conventional and modified popliteal angles. Similarly, a difference between the conventional popliteal angle and the modified popliteal angle (popliteal differential) would be associated with a permanent deficit in knee extension. The purpose of this study was to determine whether these two hypothesis correlate with clinical findings. MATERIAL AND METHODS The series was composed of 35 walking cerebral palsy children, 16 girls and 19 boys, mean age 11+/-3.6 years with a pathological conventional popliteal angle. These children walked using the jump knee (n=24) or the crouch knee (n=11) pattern. Permanent hip flexion and the conventional and modified popliteal angles were noted. SPSS version 10.1.3 for Window was used to search for a correlation between the popliteal differential and the presence of permanent hip flexion using several values for the popliteal differential (5, 10, 15, 20, and 30 degrees ). Data were adjusted for age and gender. RESULTS The statistical analyses demonstrated a significant relationship between the presence of permanent hip flexion and a popliteal differential strictly less than 10 degrees and between the absence of permanent hip flexion and a popliteal angle greater or equal to 10 degrees . These statistically significant results, which demonstrated the opposite of what was expected, were independent of age and gender. DISCUSSION Our findings demonstrate that examination of the knee joint is indispensable but insufficient. The conventional popliteal angle is not a reliable indicator of hamstring tightness. The normal value of the modified popliteal angle has not been established so that it is impossible to determine what a pathological angle is. We do not know whether measurement of this angle is sufficient to establish indications for surgery. In the future, the development of muscle models coupled with gait analysis should enable more reliable prediction of outcome after surgery. At the present time, we recommend repeated physical examination using a standardized protocol, taking into consideration, several parameters including spasticity, selectivity and muscle force and to perform quantified gait analysis before scheduling hamstring lengthening surgery for walking cerebral palsy children.

A subject-specific biomechanical control model for the prediction of cervical spine muscle forces

Background: The aim of the present study is to propose a subject‐specific biomechanical control model for the estimation of active cervical spine muscle forces. Methods: The proprioception‐based regulation model developed by Pomero et al. (2004) for the lumbar spine was adapted to the cervical spine. The model assumption is that the control strategy drives muscular activation to maintain the spinal joint load below the physiological threshold, thus avoiding excessive intervertebral displacements. Model evaluation was based on the comparison with the results of two reference studies. The effect of the uncertainty on the main model input parameters on the predicted force pattern was assessed. The feasibility of building this subject‐specific model was illustrated with a case study of one subject. Findings: The model muscle force predictions, although independent from EMG recordings, were consistent with the available literature, with mean differences of 20%. Spinal loads generally remained below the physiological thresholds. Moreover, the model behavior was found robust against the uncertainty on the muscle orientation, with a maximum coefficient of variation (CV) of 10%. Interpretation: After full validation, this model should offer a relevant and efficient tool for the biomechanical and clinical study of the cervical spine, which might improve the understanding of cervical spine disorders. HighlightsA personalized proprioception‐based model estimating neck muscle forces is proposed.Consistent predictions are obtained independently from electromyogram‐recordings.The feasibility of building the subject‐specific model was assessed for one subject.Spine muscle response depends on the intervertebral joint load threshold.The model allows studying the effect of postural disorders or poor muscle quality.

Three-dimensional analysis of the vertebral rotation associated with the lateral deviation in Marfan syndrome spinal deformity.

Marfan syndrome (MFS) is a genetic disease often marked with the presence of scoliosis, which is poorly described in the literature. No three-dimensional analysis of the deformity in the literature is observed. Thirty patients diagnosed with MFS were prospectively included in our series. Each patient was proposed to undergo a stereoradiographic examination of the spine. Personalized three-dimensional reconstruction from T1 to L5 of the spine were made. The Cobb angle of each curve and the axial rotation of each vertebra were assessed. Our aim was to assess whether there is a correlation between the Cobb angle and the axial vertebral rotation at the apex of the curves associated with MFS. Fourteen females and 16 males were included. The mean age was 25.9 years, ranging from 4 to 65 years. Eleven patients were under 16 years. Nineteen patients were defined as scoliotic (Cobb angle over 10°), and 11 were defined as nonscoliotic (Cobb angle under 10°). A strong correlation (Pearson) between the Cobb angle and the axial vertebral rotation at the apex of the curves associated with MFS was observed. This is the first step of a three-dimensional analysis of the scoliosis associated with MFS. This study pointed out that the vertebral axial rotation in scoliosis associated with MFS compared with that observed in adolescent idiopathic scoliosis and in scoliosis associated with cerebral palsy patients. Level of evidence: II (Diagnostic Study).

Sagittal balance in scoliosis associated with Marfan syndrome: a stereoradiographic three-dimensional analysis.

PurposeMarfan syndrome (MFS) is a genetic disease often marked by the presence of scoliosis. There is no three-dimensional analysis of the deformity in the literature. Our aim was to determine what kind of sagittal balance defines scoliosis associated with MFS, namely a flexion deformity, as it is in scoliosis associated with Chiari I or an extension deformity, as in adolescent idiopathic scoliosis (AIS). To address this issue, we compared the presence or absence of a thoracic scoliosis with the presence or absence of a segment in extension in the thoracic spine.MethodsIn our series, 30 patients diagnosed with Marfan syndrome were prospectively included. In each patient, personalized three-dimensional reconstruction from T1 to L5 of the spine was made using stereoradiography. The patients were first separated based on the presence or absence of thoracic scoliosis, in order to compare this with the presence or absence of a segment in extension in the thoracic spine. They were then classified into two groups based on the presence or absence of the segment in extension (meaning containing negative values of inter-vertebral sagittal rotation) in the thoracic spine.ResultsAmong scoliotic patients with a thoracic scoliosis (17 cases), there were 13 (76.5% cases) with a segment in extension in the thoracic spine and 4 with no segment in extension.ConclusionsOur results showed that scoliosis associated with MFS is somehow original, demonstrating a sagittal balance in extension (as AIS) in about 80% of thoracic curves, but without this characteristic feature in about 20%.

Cervical muscles forces and spinal loads estimation in standing position: Asymptomatic cases

Loads acting on the spine induce muscles recruitment. Estimation of muscles activation in the cervical spine and the regulation of their corresponding intervertebral loads is important to understand neck pathologies and risk of injuries, but these parameters are not yet well known. Loads due to gravity in cervical spine can be calculated (Saintonge 2004). The aim of this study is to analyse how the muscular system of the cervical spine may conterbalance loads due to gravity, at rest and in standing position.

Spinal alignment evolution with age: A prospective gait analysis study

AIM To describe, using gait analysis, the development of spinal motion in the growing child. METHODS Thirty-six healthy children aged from 3 to 16 years old were included in this study for a gait analysis (9 m-walk). Various kinematic parameters were recorded and analyzed such as thoracic angle (TA), lumbar angle (LA) and sagittal vertical axis (SVA). The kinetic parameters were the net reaction moments (N.m/kg) at the thoracolumbar and lumbosacral junctions. RESULTS TA and LA curves were not statistically correlated to the age (respectively, P = 0.32 and P = 0.41). SVA increased significantly with age (P < 0.001). Moments in sagittal plane at the lumbosacral junction were statistically correlated to the age (P = 0.003), underlining the fact that sagittal mechanical constraints at the lumbosacral junction increase with age. Moments in transversal plane at the thoracolumbar and lumbosacral junctions were statistically correlated to the age (P = 0.0002 and P = 0.0006), revealing that transversal mechanical constraints decrease with age. CONCLUSION The kinetic analysis showed that during growth, a decrease of torsional constraint occurs while an increase of sagittal constraint is observed. These changes in spine biomechanics are related to the crucial role of the trunk for bipedalism acquisition, allowing stabilization despite lower limbs immaturity. With the acquisition of mature gait, the spine will mainly undergo constraints in the sagittal plane.

The Effect of different techniques of decompression of spinal stenosis on Lumbar Spine biomechanical properties for different vertebral levels

Six L1–L2 and six L4–L5 functional human cadaveric spinal units were tested, intact and after different techniques of decompression (bilateral facetectomy, then bilateral arthrectomy). Vertebral body three-dimensional ranges of motion (ROM) under loads were measured. Flexion extension (FE), lateral bending (LB), axial torsion (AT) (maximum of 8 Nm in each case) and posteroanterior shear (maximum 300 N) were considered. Then, all specimens (after bilateral arthrectomy) were tested to failure under postero-anterior shear loads. Frontal and lateral calibrated X-rays were performed before tests, to exclude other than degenerative pathologies and a 3D reconstruction was performed in order to obtain the specimen geometry.