Publications by authors named "Pascal Swider"

42 Publications

Does a combined screw and dowel construct improve tibial fixation during anterior cruciate ligament reconstruction?

Eur J Orthop Surg Traumatol 2021 Jun 14. Epub 2021 Jun 14.

Department of Orthopaedics, Children's Hospital, CHU de Toulouse, Toulouse, France.

Purpose: The aims of the present study were to compare the biomechanical properties of tibial fixation in hamstring-graft ACL reconstruction using interference screw and a novel combination interference screw and dowel construct.

Material And Methods: We compared the fixation of 30 (2- and 4-stranded gracilis and semitendinosis tendons) in 15 fresh-frozen porcine tibiae with a biocomposite resorbable interference screw (Group 1) and a screw and dowel construct (Group 2). Each graft was subjected to load-to-failure testing (50 mm/min) to determine maximum load, displacement at failure and pullout strength.

Results: There were no significant differences between the biomechanical properties of the constructs. Multivariate analysis demonstrated that combination constructs (β = 140.20, p = 0.043), screw diameter (β = 185, p = 0.006) and 4-strand grafts (β = 51, p = 0.050) were associated with a significant increase in load at failure. Larger screw diameter was associated with increased construct stiffness (β = 20.15, p = 0.020).

Conclusion: The screw and dowel construct led to significantly increased fixation properties compared to interference screws alone in a porcine model. Increased screw diameter and utilization of 4-strand ACL grafts also led to improvement in load-to-failure of the construct. However, this is an in vitro study and additional investigations are needed to determine whether the results are reproducible in vivo.

Level Of Evidence: Level V; Biomechanical study.
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http://dx.doi.org/10.1007/s00590-021-03049-2DOI Listing
June 2021

MRI evaluation of the hydration status of non-pathological lumbar intervertebral discs in a pediatric population.

Orthop Traumatol Surg Res 2020 11 3;106(7):1281-1285. Epub 2020 Oct 3.

IMFT UMR 5502 CNRS, Toulouse, France.

Introduction: The intervertebral disc (IVD) is made up of the annulus fibrosus (AF) and the nucleus pulposus (NP) - an inert hydrated complex. The ability of the IVD to deform is correlated to that of the NP and depends on its hydration. As the IVD ages, its hydration decreases along with its ability to deform. In adolescent idiopathic scoliosis, one of the etiological hypotheses pertains to the IVD, thus making its condition relevant for the diagnosis and monitoring of this pathology.

Hypothesis: IVD hydration depends on sex, age and spine level in an asymptomatic pediatric population. The corollary is data on a control group of healthy subjects.

Material And Methods: A cohort of 98 subjects with normal spine MRI was enrolled; their mean age was 13.3 years. The disc volume and hydration of each IVD was evaluated on T2-weighted MRI sequences, using previously validated image processing software. This evaluation focused on the lumbar spine, from the thoracolumbar junction to the lumbosacral junction. It was assumed that IVD hydration was related to the ratio of NP and AF volumes. A mixed multivariate linear analysis was used to explore the impact of age, sex and spinal level on disc hydration.

Results: Disc hydration was higher overall in boys than in girls, but this difference was not significant. Hydration increased with age by +0.005 for each additional year (p=0.0213). Disc hydration appears to be higher at the thoracolumbar junction than the lumbar spine, although this difference was not significant.

Conclusion: Through this MRI study, we established a database of non-pathological lumbar disc hydration as a function of age, sex and spinal segment along with 95% confidence intervals.

Level Of Evidence: IV.
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http://dx.doi.org/10.1016/j.otsr.2019.11.034DOI Listing
November 2020

An energy approach describes spine equilibrium in adolescent idiopathic scoliosis.

Biomech Model Mechanobiol 2021 Feb 2;20(1):359-370. Epub 2020 Oct 2.

Institut de Mécanique des Fluides de Toulouse, IMFT, CNRS, Université de Toulouse, Toulouse, France.

The adolescent idiopathic scoliosis (AIS) is a 3D deformity of the spine whose origin is unknown and clinical evolution unpredictable. In this work, a mixed theoretical and numerical approach based on energetic considerations is proposed to study the global spine deformations. The introduced mechanical model aims at overcoming the limitations of computational cost and high variability in physical parameters. The model is constituted of rigid vertebral bodies associated with 3D effective stiffness tensors. The spine equilibrium is found using minimization methods of the mechanical total energy which circumvents forces and loading calculation. The values of the model parameters exhibited in the stiffness tensor are retrieved using a combination of clinical images post-processing and inverse algorithms implementation. Energy distribution patterns can then be evaluated at the global spine scale to investigate given time patient-specific features. To verify the reliability of the numerical methods, a simplified model of spine was implemented. The methodology was then applied to a clinical case of AIS (13-year-old girl, Lenke 1A). Comparisons of the numerical spine geometry with clinical data equilibria showed numerical calculations were performed with great accuracy. The patient follow-up allowed us to highlight the energetic role of the apical and junctional zones of the deformed spine, the repercussion of sagittal bending in sacro-illiac junctions and the significant role of torsion with scoliosis aggravation. Tangible comparisons of output measures with clinical pathology knowledge provided a reliable basis for further use of those numerical developments in AIS classification, scoliosis evolution prediction and potentially surgical planning.
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http://dx.doi.org/10.1007/s10237-020-01390-9DOI Listing
February 2021

Mechanical behavior of screw versus Endobutton for coracoid bone-block fixation.

Orthop Traumatol Surg Res 2020 Oct 8;106(6):1089-1093. Epub 2020 Aug 8.

Service d'orthopédie, CHU de Toulouse, place Baylac, 31059 Toulouse cedex 09, France; Laboratoire de biomécanique, institut de mécanique des fluides de Toulouse UMR CNRS 5502, Toulouse, France. Electronic address:

Introduction: Arthroscopic coracoid bone-block fixation by Endobutton was developed to avoid the complications associated with screwing. However, few studies have assessed the mechanical characteristics of the two. The aim of the present study was to assess and compare fixation rigidity by screw versus Endobutton. The study hypothesis was that rigidity is lower with Endobutton than with screws.

Material And Method: 3D print-outs of a glenoid and a coracoid process were obtained from CT scans of a patient showing anterior shoulder instability with significant bone defect. Four types of coracoid fixation were implemented: 1 or 2 4.5mm malleolar screws, and 1 or 2 Endobuttons. Three specimens per assembly were placed on a specific test bench. Lateromedial bone-block compression was exerted at 0.1mm/sec at 3 points: superior, central, inferior. The resultant force and bone-block displacement were recorded.

Results: Mean fixation rigidity with 1 screw, 2 screws, 1 Endobutton and 2 Endobuttons was respectively 158N/mm (range, 133-179), 249N/mm (241-259), 10N/mm (5-13) and 14N/mm (13-15), with significant difference between the screw and Endobutton groups (p<0.001). Displacement was greater with 1 than 2 Endobuttons under superior or inferior force, while the difference was non-significant under central force (7.45 vs 6.93mm; p=0.53) CONCLUSIONS: Screw fixation showed greater rigidity, while the Endobutton assembly showed less tension, leading to greater bone-block mobilization. The interest of using two Endobuttons is to reduce displacement under polar pressure. the present biomechanical study confirmed the mechanical vulnerability of bone-blocks fixed by endobutton until consolidation is achieved.

Level Of Evidence: Biomechanical study.
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http://dx.doi.org/10.1016/j.otsr.2020.03.035DOI Listing
October 2020

Foot and ankle compensation for anterior cruciate ligament deficiency during gait in children.

Orthop Traumatol Surg Res 2020 Feb 13;106(1):179-183. Epub 2019 Sep 13.

Service d'orthopédie, hôpital des Enfants, CHU de Toulouse, 330, avenue de Grande Bretagne, 31059 Toulouse, France.

Background: Anterior cruciate ligament (ACL) injuries are common in adults and cause knee instability, pain, and an increased risk of osteoarthritis. Previous studies demonstrated changed gait patterns in adult patients with ACL deficiency. In paediatric patients, ACL injuries were once thought to be rare but are being increasingly diagnosed due to greater involvement of children in contact sports and to the introduction of more effective diagnostic tools such as magnetic resonance imaging (MRI). However, little is known about gait adaptation in children with ACL deficiency. The objective of this study was to look for compensatory foot and ankle behaviours during gait in paediatric patients with symptomatic ACL deficiency.

Hypothesis: Compensation for ACL deficiency during gait occurs at the foot and ankle in children, because compensation at the hip and pelvis would require greater energy expenditure.

Material And Methods: We included 47 patients, 33 males and 14 females, ranging in age from 9 to 17 years (mean, 14.1 years). The patients had a history of unilateral ACL injury documented by MRI and initially treated by immobilisation and physical therapy. They were allowed to walk with full weight-bearing on the affected limb and were not taking medications at the time of the study. All patients had pain, knee instability, or functional limitation. The physical examination showed joint laxity indicating surgical ACL reconstruction. None had neurological conditions, congenital musculoskeletal abnormalities, or a history of knee surgery. Gait analysis (GA) was performed using a Vicon 460 system. Kinematic data for the ankle and foot were compared to those in a control group of 37 healthy children. Ankle angular positions were calculated for each group at the following stance time points: initial contact (0% of gait cycle [GC]), mid-stance (25% GC), terminal stance (60% GC), and swing (83% GC). Foot progression data were recorded at mid-stance (25% GC) and swing (70% GC). Student's t test was applied to compare the results to reference values obtained at our laboratory and to data from the control group.

Results: Compared to the reference values, the ankle was in plantar flexion at initial contact in 41 patients, and ankle dorsiflexion during the stance phase was diminished in 39 patients. The external foot progression angle was increased in 23 patients during the stance phase and 38 patients during the swing phase. Compared to the control group (mean age, 9.1 years), the patients had plantar flexion of the ankle at initial contact (3.43°±3.5° vs. 0.74°±3.6°, p<0.05) and decreased dorsiflexion during the stance phase (3.43°±3.5° vs. 0.74°±3.6°, p<0.05). No significant differences were found for any of the other parameters.

Discussion: Children with ACL deficiency developed compensatory foot and ankle behaviours during gait that improved knee stability. Understanding these compensations may guide treatment optimisation.

Level Of Evidence: III, retrospective comparative study.
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http://dx.doi.org/10.1016/j.otsr.2019.07.009DOI Listing
February 2020

Biomechanical Comparison of Two Locking Plate Constructs Under Cyclic Loading in Four-Point Bending in a Fracture Gap Model: Two Screws versus Three Screws Per Fragment.

Vet Comp Orthop Traumatol 2019 Jan 15;32(1):59-66. Epub 2019 Jan 15.

Unité de Chirurgie, Ecole Nationale Veterinaire de Toulouse, Toulouse, France.

Objectives:  The number of locking screws required per fragment during bridging osteosynthesis has not been fully determined in the dog. The purpose of this study was to assess the survival of two constructs, with either two or three screws per fragment, under cyclic bending.

Methods:  A 10-hole, 3.5-mm stainless steel locking compression plate was fixed 1 mm away from a bone surrogate in which the fracture gap was 47 mm. Two groups of 10 constructs, prepared with either two or three bicortical locking screws placed at the extremities of each fragment, were tested in a load-controlled 4-point bending test (range 0.7 to + 7 Nm) until failure.

Results:  The 3-screw constructs were stiffer than the 2-screw constructs (19.73 ± 0.68 N/mm vs. 15.52 ± 0.51 N/mm respectively) and the interfragmentary relative displacements were higher for the 2-screw constructs (11.17 ± 0.88%) than for the 3-screw constructs (8.00 ± 0.45%). The difference between the number of cycles to failure for the 3-screw constructs (162,448 ± 30,073 cycles) and the 2-screw constructs (143,786 ± 10,103 cycles) was not significant. Failure in all constructs was due to plate fracture at the level of the compression holes.

Clinical Significance:  Omission of the third innermost locking screw during bridging osteosynthesis subjected to bending forces led to a 20% reduction in construct stiffness and increased relative displacement (+39.6%) but did not change fatigue life.
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http://dx.doi.org/10.1055/s-0038-1676335DOI Listing
January 2019

Results of arthroscopic Bankart repair with Hill-Sachs remplissage for anterior shoulder instability.

Int Orthop 2017 12 11;41(12):2573-2580. Epub 2017 May 11.

Département d'Orthopédie Traumatologie du CHU de Toulouse, Hôpital Riquet, Place Baylac, 31052, Toulouse, France.

Purpose: The aim of this study was to evaluate mid-term outcomes of Bankart repair with Hill-Sachs remplissage (BHSR) and to highlight prognostic factors of failure.

Methods: Thirty-four patients operated on for anterior shoulder instability with BHSR were enrolled in a prospective non-randomised study. Clinical and radiographic evaluation was performed at 1.5, three, six months and yearly thereafter. Outcome measures included Rowe and Walch-Duplay score.

Results: At mean follow-up of 35 months (24-63), the Rowe and Walch-Duplay scores reached respectively 92.7 and 88.2 points. The mean deficit in external rotation was 6° in ER1 and 1° in ER2 (p = 0.4, p = 0.9 respectively). Five patients (14.7%) had a recurrence of instability and three others had a persistent anterior apprehension. In the failure group, the Hill-Sachs lesion was deeper (26% vs 19% of the humeral diameter; p = 0.04) and range of motion at 1.5 months postoperatively was greater. Age at surgery, pre-operative instability severity index score (ISIS), hyperlaxity, type and level of sport, amount of glenoid bone loss had no correlation with failure rate.

Conclusions: The rate of failure at mid-term follow-up of BHSR was higher than commonly reported. The premature recovery of range of motion seems to be a clinical sign of failure at follow-up. Moreover, in case of deep Hill-Sachs lesion (>20%) an alternative procedure should be considered.

Level Of Evidence: Level IV.
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http://dx.doi.org/10.1007/s00264-017-3491-5DOI Listing
December 2017

BMI-related microstructural changes in the tibial subchondral trabecular bone of patients with knee osteoarthritis.

J Orthop Res 2017 08 24;35(8):1653-1660. Epub 2016 Oct 24.

Department of Orthopaedic and Trauma Surgery, Hôpital Pierre Paul Riquet, Centre Hospitalier Universitaire de Toulouse, Place du Docteur Baylac, TSA 40031, 31059 Toulouse cedex 9, France.

Overweight is a risk factor for osteoarthritis on the knees. Subchondral trabecular bone (SCTB) densification has been shown to be associated with cartilage degeneration. This study analyzed the microarchitectural changes in the SCTB of tibial plateaus to validate the hypothesis that the degree of remodeling is correlated with a patient's body weight. Twenty-one tibial plateaus were collected during total knee arthroplasty from 21 patients (15 women and 6 men). These patients had a mean age of 70.4 years (49-81), mean weight of 74.7 kg (57-93) and mean body mass index (BMI) of 28.4 kg/m (21.3-40.8). One cylindrical plug was harvested in the center of each tibial plateau (medial and lateral). Micro-CT parameters (7.4 μm resolution) were determined to describe the SCTB structure. On the medial plateau, there were significant correlations between BMI and bone volume fraction BV/TV (r = 0.595, p = 0.004), structure model index SMI (r = -0.704 p = 0.0002), trabecular space Tb.Sp (r = 0.600, p = 0.04) and trabecular number Tb.N (r = 0.549, p = 0.01). SCTB densification during osteoarthritis is associated with a reduction in its elastic modulus, which could increase cartilage stress, and accelerate cartilage loss. SCTB densification has been shown to precede cartilage degeneration. The correlation of SCTB microarchitecture and body weight may explain why knee osteoarthritis is more common in overweight or obese patients. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:1653-1660, 2017.
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http://dx.doi.org/10.1002/jor.23459DOI Listing
August 2017

Bernoulli's Principle Applied to Brain Fluids: Intracranial Pressure Does Not Drive Cerebral Perfusion or CSF Flow.

Acta Neurochir Suppl 2016 ;122:107-11

Department of Porous Media, Institute of Fluid Mechanics of Toulouse, Toulouse, France.

In line with the first law of thermodynamics, Bernoulli's principle states that the total energy in a fluid is the same at all points. We applied Bernoulli's principle to understand the relationship between intracranial pressure (ICP) and intracranial fluids. We analyzed simple fluid physics along a tube to describe the interplay between pressure and velocity. Bernoulli's equation demonstrates that a fluid does not flow along a gradient of pressure or velocity; a fluid flows along a gradient of energy from a high-energy region to a low-energy region. A fluid can even flow against a pressure gradient or a velocity gradient. Pressure and velocity represent part of the total energy. Cerebral blood perfusion is not driven by pressure but by energy: the blood flows from high-energy to lower-energy regions. Hydrocephalus is related to increased cerebrospinal fluid (CSF) resistance (i.e., energy transfer) at various points. Identification of the energy transfer within the CSF circuit is important in understanding and treating CSF-related disorders. Bernoulli's principle is not an abstract concept far from clinical practice. We should be aware that pressure is easy to measure, but it does not induce resumption of fluid flow. Even at the bedside, energy is the key to understanding ICP and fluid dynamics.
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http://dx.doi.org/10.1007/978-3-319-22533-3_21DOI Listing
July 2017

Characterisation of Supra- and Infratentorial ICP Profiles.

Acta Neurochir Suppl 2016 ;122:37-40

Department of Neurosurgery, Hôpital Purpan, Place du Dr Baylac TSA 40031, 31059, Toulouse, France.

In pathophysiology and clinical practice, the intracranial pressure (ICP) profiles in the supratentorial and infratentorial compartments are unclear. We know that the pressure within the skull is unevenly distributed, with demonstrated ICP gradients. We recorded and characterised the supra- and infratentorial ICP patterns to understand what drives the transtentorial ICP gradient.A 70-year-old man was operated on for acute cerebellar infarction. One supratentorial probe and one cerebellar probe were implanted. Both signals were recorded concurrently and analysed off-line. We calculated mean ICP, ICP pulse amplitude, respiratory waves, slow waves and the RAP index of supra- and infratentorial ICP signals. Then, we measured transtentorial difference and performed correlation analysis for every index.Supratentorial ICP mean was 8.5 mmHg lower than infratentorial ICP, but the difference lessens for higher values. Both signals across the tentorium showed close correlation. Supra- and infratentorial pulse amplitude, respiratory waves and slow waves also showed a high degree of correlation. The compensatory reserve (RAP) showed good correlation. In this case report, we demonstrate that the mean value of ICP is higher in the posterior fossa, with a strong correlation across the tentorium. All other ICP-derived parameters display a symmetrical profile.
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http://dx.doi.org/10.1007/978-3-319-22533-3_7DOI Listing
July 2017

Cadaveric Study Comparing the Biomechanical Properties of Grafts Used for Knee Anterolateral Ligament Reconstruction.

Arthroscopy 2016 11 7;32(11):2288-2294. Epub 2016 May 7.

Service de Chirurgie Orthopédique et de Traumatologie, Hôpital P.P.R., Toulouse, France. Electronic address:

Purpose: To measure the biomechanical properties (maximum load, stiffness, and elongation) of the anterolateral ligament (ALL), gracilis, and iliotibial band (ITB) within the same subject.

Methods: Thirteen unpaired knees were used (7 women, 6 men). The donors had a mean age at death of 54 years (range: 37 to 70 years). The mechanical properties of two types of ALL grafts were evaluated: ITB and two-strand gracilis. The mechanical properties of ALL were also measured. Validated methods were used to perform the tensile tests to failure and to record the results. Student's t-test was used to compare the various samples.

Results: The maximum load to failure was 141 N (±40.6) for the ALL, 200.7 N (±48.7) for the gracilis, and 161.1 N (±27.1) for the ITB. Only the gracilis had a significantly higher failure load than ITB and ALL (P = .001 and P = .03). The stiffness was 21 N mm (±8.2) for the ALL, 131.7 N mm (±43.7) for the gracilis, and 39.9 N mm (±6) for the ITB. The elongation at failure was 6.2 mm (±3.2) for the ALL, 19.9 mm (±6.5) for the gracilis, and 20.8 mm (±14.7) for the ITB.

Conclusions: The gracilis had the highest maximum load to failure. The ITB's mechanical properties most closely resemble those of the ALL.

Clinical Relevance: The biomechanical properties of each potential ALL graft can be factored in when deciding which type of graft to use.
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http://dx.doi.org/10.1016/j.arthro.2016.03.004DOI Listing
November 2016

Adipose stromal cells improve healing of vocal fold scar: Morphological and functional evidences.

Laryngoscope 2016 08 14;126(8):E278-85. Epub 2016 Apr 14.

CNRS UMR5273 STROMALab, University of Toulouse, Toulouse Cedex, France.

Objectives/hypothesis: Adipose derived stromal cells (ASCs) are abundant and easy to prepare. Such cells may be useful for treating severe vocal disturbance caused by acute vocal fold scars.

Study Design: Prospective animal experiments with controls.

Methods: Twenty New-Zealand white rabbits were used in the present study. We evaluated vocal fold healing, with or without injection of autologous ASCs, after acute scarring. A defined lesion was created and the ASCs were immediately injected. Vocal fold regeneration was evaluated histomorphometrically and via viscoelastic analysis using an electrodynamic shaker.

Results: Six weeks after ASC injection, vocal folds exhibited significantly less inflammation than control folds (P < 0.005). In addition, hypertrophy of the lamina propria and fibrosis were significantly reduced upon ASC injection (P < 0.02). The decrease in viscoelastic parameters was less important in the ASC injected group compared to the noninjected group (P = 0.08).

Conclusion: Injection of autologous ASCs improved vocal fold healing in our preclinical model. Further studies are needed, but this method may be useful in humans.

Level Of Evidence: NA. Laryngoscope, 126:E278-E285, 2016.
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http://dx.doi.org/10.1002/lary.25867DOI Listing
August 2016

Experimental and Numerical Models of Complex Clinical Scenarios; Strategies to Improve Relevance and Reproducibility of Joint Replacement Research.

J Biomech Eng 2016 Feb;138(2):021008

This research review aims to focus attention on the effect of specific surgical and host factors on implant fixation, and the importance of accounting for them in experimental and numerical models. These factors affect (a) eventual clinical applicability and (b) reproducibility of findings across research groups. Proper function and longevity for orthopedic joint replacement implants relies on secure fixation to the surrounding bone. Technology and surgical technique has improved over the last 50 years, and robust ingrowth and decades of implant survival is now routinely achieved for healthy patients and first-time (primary) implantation. Second-time (revision) implantation presents with bone loss with interfacial bone gaps in areas vital for secure mechanical fixation. Patients with medical comorbidities such as infection, smoking, congestive heart failure, kidney disease, and diabetes have a diminished healing response, poorer implant fixation, and greater revision risk. It is these more difficult clinical scenarios that require research to evaluate more advanced treatment approaches. Such treatments can include osteogenic or antimicrobial implant coatings, allo- or autogenous cellular or tissue-based approaches, local and systemic drug delivery, surgical approaches. Regarding implant-related approaches, most experimental and numerical models do not generally impose conditions that represent mechanical instability at the implant interface, or recalcitrant healing. Many treatments will work well in forgiving settings, but fail in complex human settings with disease, bone loss, or previous surgery. Ethical considerations mandate that we justify and limit the number of animals tested, which restricts experimental permutations of treatments. Numerical models provide flexibility to evaluate multiple parameters and combinations, but generally need to employ simplifying assumptions. The objectives of this paper are to (a) to highlight the importance of mechanical, material, and surgical features to influence implant-bone healing, using a selection of results from two decades of coordinated experimental and numerical work and (b) discuss limitations of such models and the implications for research reproducibility. Focusing model conditions toward the clinical scenario to be studied, and limiting conclusions to the conditions of a particular model can increase clinical relevance and research reproducibility.
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http://dx.doi.org/10.1115/1.4032368DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4844079PMC
February 2016

Can the gracilis replace the anterior cruciate ligament in the knee? A biomechanical study.

Int Orthop 2016 Aug 5;40(8):1647-1653. Epub 2015 Nov 5.

Laboratoire de Biomécanique, Faculté de Médecine, Toulouse, France.

Purpose: The purpose of this study was to determine whether a four-strand gracilis-only construct possesses the biomechanical properties needed to act as an anterior cruciate ligament (ACL) reconstruction graft.

Methods: This was a pilot study with 32 cadaver specimens. The biomechanical properties of three types of grafts were determined using validated tensile testing methods: patellar tendon (BTB), both hamstring tendons together (GST4) and gracilis alone (G4).

Results: The maximum load at failure of the G4 was 416.4 N (±187.7). The GST4 and BTB had a maximum load at failure of 473.5 N (±176.9) and 413.3 N (±120.4), respectively. The three groups had similar mean maximum load and stiffness values. The patellar tendon had significantly less elongation at failure than the other two graft types.

Conclusions: The biomechanical properties of a four-strand gracilis construct are comparable to the ones of standard grafts. This type of graft would be useful in the reconstruction of the anteromedial bundle in patients with partial ACL ruptures.
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http://dx.doi.org/10.1007/s00264-015-3027-9DOI Listing
August 2016

Spino-pelvic alignment influences disc hydration properties after AIS surgery: a prospective MRI-based study.

Eur Spine J 2015 Jun 2;24(6):1183-90. Epub 2015 Apr 2.

Department of Spine Surgery, CMCR des Massues, Croix Rouge Française, 92 rue Edmond Locard, 69322, Lyon Cedex 05, France,

Purpose: To analyze the disc hydration and volumetric changes of the intervertebral disc after scoliosis surgery depending on the sagittal spino-pelvic organization.

Methods: We conducted a prospective MRI study in 45 patients with surgically treated adolescent idiopathic scoliosis (AIS) with a minimum 2-year follow-up. Fusion ended at L1 (n = 13), L2 (n = 14), L3 (n = 11) or L4 (n = 7). Total disc (Vd) and nucleus volumes (Vn) were extrapolated from 3D reconstruction using a custom-made image processing software (Biomechlab, Toulouse, France). Nucleus and external disc contours were semi-automatically detected on turbo spin echo T2-weighted sequence joined 3-mm sagittal cuts. Disc hydration was extrapolated from the nucleus-disc volume ratio (Vn/Vd). Radiographic sagittal parameters were measured pre- and post-operatively on full spine standing views (pelvic incidence, sacral slope, L1S1 lumbar lordosis). Lumbo-pelvic congruity was calculated by the ratio LL/SS according to Stagnara.

Results: Mean PI of the cohort was 55° (34°-85°). After surgical correction, lumbar lordosis was slightly increased by 3° (p = 0.02) decreasing lumbo-pelvic congruity from 1.37 to 1.27 (p < 0.01). When pelvic incidence was less than 55° (mean PI 46°), nucleus volumes have increased on average by 30 % compared to the preoperative status in the unfused lumbar discs, while the total disc volumes has remained stable. Five-year follow-up (n = 13) confirmed the constant improvement of the disc hydration ratio. When PI was high (mean PI 64°), volumetric changes were very mild and significant changes in nucleus volumes and disc hydration ratio concerned only the intermediate lumbar levels (L2L3, L3L4 and L4L5).

Conclusions: This prospective MRI study showed a significant and sustainable improvement in T2 hypersignal of the disc, indirectly indicating improvement of disc hydration content after AIS surgery. Analysis of disc volumetric changes according to the pelvic incidence suggests that these changes are under the influence of the sagittal spino-pelvic alignment. PI seems to play a key role in the homeostasis of the discs under fusion and should be taken into account for preoperative planning. The restoration of the lumbo-pelvic congruence may help to limit early degenerative changes in the free-motion segment discs after AIS surgery. Hydration content was less sensitive to surgery when PI was high, suggesting higher shear stress in the lower discs. Longer follow-up is required to confirm this hypothesis.
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http://dx.doi.org/10.1007/s00586-015-3875-4DOI Listing
June 2015

Biomechanical study of ACL reconstruction grafts.

J Orthop Res 2015 Aug 21;33(8):1188-96. Epub 2015 May 21.

Service de Chirurgie Orthopédique et de Traumatologie, Hôpital P.P.R, Toulouse, France.

There are no published studies describing the strength quadrupled gracilis tendon alone and quadrupled semitendinosus tendon alone in the configuration used for anterior cruciate ligament (ACL) reconstruction. The primary objective was to compare the mechanical properties of grafts used for ACL reconstruction during a tensile failure test. The secondary objective was to evaluate the effect of uniform suturing on graft strength. Fifteen pairs of knees were used. The mechanical properties of five types of ACL grafts were evaluated: patellar tendon (PT), sutured patellar tendon (sPT), both hamstring tendons (GST4), quadrupled semitendinosus (ST4), and quadrupled gracilis (G4). Validated methods were used to perform the tensile tests to failure and to record the results. Student's t-test was used to compare the various samples. The maximum load to failure was 630.8N (± 239.1) for the ST4, 473.5N (± 176.9) for the GST4, 413.3N (± 120.4) for the sPT, and 416.4N (± 187.7) for the G4 construct. Only the ST4 had a significantly higher failure load than the other grafts. The sPT had a higher failure load than the PT. The ST4 construct had the highest maximum load to failure of all the ACL graft types in the testing performed here. Uniform suturing of the grafts improved their ability to withstand tensile loading.
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http://dx.doi.org/10.1002/jor.22889DOI Listing
August 2015

Wave front migration of endothelial cells in a bone-implant interface.

J Biomech 2011 Jul 20;44(10):1980-6. Epub 2011 May 20.

IMFT UMR CNRS 5502, 1 Allées Professeur Camille Soula, 31400 Toulouse, France.

The neo-vascularization of the host site is crucial for the primary fixation and the long-term stability of the bone-implant interface. Our aim was to investigate the progression of endothelial cell population in the first weeks of healing. We proposed a theoretical reactive model to study the role of initial conditions, random motility, haptotaxis and chemotaxis in interactions with fibronectin factors and transforming angiogenic factors. The application of governing equations concerned a canine experimental implant and numerical experiments based upon statistical designs of experiments supported the discussion. We found that chemotaxis due to transforming angiogenic factors was attracting endothelial cells present into the host bone. Haptotaxis conditioned by fibronectin factors favored cells adhesion to the host bone. The combination of diffusive and reactive effects nourished the wave front migration of endothelial cells from the host bone towards the implant. Angiogenesis goes together with new-formed bone formation in clinics, so the similarity of distribution patterns of mineralized tissue observed in-vivo and the spatio-temporal concentration of endothelial cells predicted by the model, tended to support the reliability of our theoretical approach.
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http://dx.doi.org/10.1016/j.jbiomech.2011.05.008DOI Listing
July 2011

Influence of growth modulation on the effective permeability of the vertebral end plate. A porcine experimental scoliosis model.

Clin Biomech (Bristol, Avon) 2011 May 10;26(4):337-42. Epub 2010 Dec 10.

Department of Paediatric Orthopaedic Surgery, Hôpital des Enfants, University Hospital, University of Toulouse, 330 avenue de Grande Bretagne, Toulouse Cedex 9, France.

Background: Abnormal mechanical loading occurs in scoliosis as compared to normal spines. Intervertebral disc degeneration has been correlated with alteration of bone density in adjacent vertebral bodies. How vertebral end plate remodels in scoliosis and the consequences on disc homeostasis are not well understood. Permeability is a relevant physical measure to quantify mass transport in porous media. We hypothesized that effective permeability of the vertebral end plate was modified by growth modulation in a scoliosis animal model.

Methods: Flexible asymmetric posterior instrumentation was undertaken on six healthy four-week-old pigs. Two sets of left pedicle screws were inserted and connected with a stainless steel cable. After two months, the apical intervertebral unit and three units located cranially and caudally, were harvested. One central and two lateral specimens were investigated using a previously validated method for measuring permeability.

Findings: A three-dimensional deformity was obtained in all six animals with an average of 42° right thoracic curve, 44° lordosis and 21° rotation. Permeability was significantly greater in the center of the end plates than in the periphery and it was decreased by -45% towards the apex of the deformity. Fluid flow direction did not play a significant role. No significant difference was found between the convex side and the concave side.

Interpretation: The end plate is a crucial zone for diffusive and convective transport and we showed in a scoliosis animal model that a growth modulation may decrease its effective permeability. The proposed methodology and associated results could help to understand degenerative changes in human spine.
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http://dx.doi.org/10.1016/j.clinbiomech.2010.11.007DOI Listing
May 2011

Sensitivity analysis of periprosthetic healing to cell migration, growth factor and post-operative gap using a mechanobiological model.

Comput Methods Biomech Biomed Engin 2011 Sep 24;14(9):763-71. Epub 2011 Jun 24.

IMFT UMR CNRS 5502, University of Toulouse, CHU Purpan, Amphithéâtre Laporte, Place Dr Baylac, 31056 Toulouse Cedex, France.

A theoretical rationale, which could help in the investigation of mechanobiological factors affecting periprosthetic tissue healing, is still an open problem. We used a parametric sensitivity analysis to extend a theoretical model based on reactive transport and computational cell biology. The numerical experimentation involved the drill hole, the haptotactic and chemotactic migrations, and the initial concentration of an anabolic growth factor. Output measure was the mineral fraction in tissue surrounding a polymethymethacrylate (PMMA) canine implant (stable loaded implant, non-critical gap). Increasing growth factor concentration increased structural matrix synthesis. A cell adhesion gradient resulted in heterogeneous bone distribution and a growth factor gradient resulted in homogeneous bone distribution in the gap. This could explain the radial variation of bone density from the implant surface to the drill hole, indicating less secure fixation. This study helps to understand the relative importance of various host and clinical factors influencing bone distribution and resulting implant fixation.
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http://dx.doi.org/10.1080/10255842.2010.494160DOI Listing
September 2011

Remodelling of vertebral endplate subchondral bone in scoliosis: a micro-CT analysis in a porcine model.

Clin Biomech (Bristol, Avon) 2010 Aug 3;25(7):636-41. Epub 2010 Jun 3.

Orthopaedic Surgery Department, Toulouse University Hospital, Toulouse, France.

Background: Disc degeneration has been correlated with alteration of bone density of adjacent vertebral bodies. Abnormal mechanical loading appears in scoliosis as compared to normal spines. How vertebral endplate was remodelled in scoliosis is not well understood.

Methods: We conducted a micro-CT analysis of subchondral bone of the vertebral endplate at the curve apex in a porcine scoliosis model. Two adjacent thoracic T(5)-T(6) and lumbar L(1)-L(2) levels were instrumented in six four-week-old pigs with a custom offset implant connected by a flexible stainless steel wire. Two months after implantation, three cylindrical specimens were harvested into the vertebral endplate of each of the scoliosis levels: centre, convexity and concavity, and from the dorsal T(9)-T(10) vertebral units obtained from nine three-month-old non-instrumented pigs used as controls. Micro-CT analysis was carried out on each specimen.

Findings: In the concavity of the scoliotic spine, bone volume fraction, trabecular thickness, and trabecular separation significantly increased whereas in the convexity, only trabecular separation increased. Connectivity index and trabecular number decreased significantly.

Interpretation: This was the first micro-CT study of subchondral bone microarchitecture of the scoliotic vertebral end plate. At the curve apex, increased compression in the concavity induced an osteogenic process. In the convexity, diminished compression caused an osteolytic process with a local resorption. Clinically, the unbalanced tissue remodelling could play a role in the convective and diffusive transports into the end plate, which is of prime importance for the segment homeostasis in scoliosis treatment with or without surgery.
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http://dx.doi.org/10.1016/j.clinbiomech.2010.04.011DOI Listing
August 2010

Correlations between effective permeability and marrow contact channels surface of vertebral endplates.

J Orthop Res 2010 Sep;28(9):1229-34

Service de Chirurgie Orthopédique et Traumatologique, Institut Locomoteur, Centre Hospitalier Universitaire de Toulouse-Rangueil, 1 Avenue Jean Poulhès, TSA 50032, 31059 Toulouse Cedex 9, France.

Homeostasis of the intervertebral disc relies on nutrient supply and waste clearance through the dense capillary network that is in contact with the cartilage endplate (CEP). We developed a micro-computerized tomography (micro-CT) method to quantify the marrow contact channel surface (MCCS) with the CEP and to validate the hypothesis according to which MCCS was correlated to the effective permeability of the vertebral endplate (VEP) and influenced by the mechanical stimuli. The influence of compression loading on local vascularization was investigated. Six 4-week-old skeletally immature pigs were instrumented with left pedicle screws and rod at both T5-T6 and L1-L2 levels to create asymmetrical spine tethers. After 3 months of growth, three cylindrical specimens of the VEP (one central and two lateral right and left) were obtained from both the instrumented and the control levels. We used a previously validated method for measuring permeability. Micro-CT analysis (resolution 12 microm) yielded a gray-scale 2D-image of the discal end of each specimen converted into a binary 2D-image to derive the MCCS. Correlations between MCCS and effective permeability were assessed. Effective permeability and MCCS were significantly decreased compared to the control group especially on the tethered side (-41.5%, p = 0.004 and -52.5%, p = 0.0009, respectively). Correlations were significant and showed maximal value (r(2) = 0.430, p < 0.0001) on the tethered side involving maximal compressive loadings. Mechanical stimuli, due to unbalanced growth, altered the vascularization and the convective properties of the CEP. The cascade of mechanobiological events should offer perspectives for research on disc degeneration and attempted treatment.
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http://dx.doi.org/10.1002/jor.21137DOI Listing
September 2010

Micro-computed tomography study of the subchondral bone of the vertebral endplates in a porcine model: correlations with histomorphometric parameters.

Surg Radiol Anat 2010 Apr 8;32(4):335-41. Epub 2009 Oct 8.

Service de Chirurgie Orthopédique et Traumatologique, Institut Locomoteur, Centre Hospitalier Universitaire Rangueil, 1, avenue Jean Poulhès, TSA 50032, 31059, Toulouse Cedex 9, France.

Purpose: Subchondral bone (SCB) of the vertebral endplates (VEP) is the principal site of changes in vertebral trabecular microarchitecture secondary to intervertebral disc degeneration. However, the microstructure of this region has not yet been clearly characterized.

Methods: One thoracic and one lumbar vertebral unit (vertebra-disc-vertebra) was removed in nine pigs aged 4 months. Three samples (one central and two laterals) were taken from each VEP. Micro-CT examination and histomorphometric measurements of the subchondral trabecular bone of the VEP were carried out. Correlations between micro-CT and histological parameters were sought.

Results: Trabecular network was significantly denser [increased bone volume fraction (BV/TV) and trabecular number (Tb.N), decreased intertrabecular separation (Tb.Sp)] in the cranial endplates of the vertebral units. It was also significantly denser and less well organized [increased degree of anisotropy (DA)] in the centre of the VEP. The thickness of the cartilage endplate (CEP), SCB and growth cartilage were significantly lower in the centre of the VEP. There was a significant negative correlation between BV/TV, Tb.N and DA with the thicknesses of the CEP and SCB whereas Tb.Sp was positively correlated with these two parameters.

Conclusion: We observed densification of the trabecular network in the centre of the VEP overlying the nucleus pulposus, partly related to thinner hyaline cartilage. Densification is associated with more anisotropic architecture that could cause lower mechanical strength in this area. This study provides new information on the microarchitecture of the SCB of the VEP which will make it possible to validate future models.
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http://dx.doi.org/10.1007/s00276-009-0569-9DOI Listing
April 2010

Influence of asymmetric tether on the macroscopic permeability of the vertebral end plate.

Eur Spine J 2009 Dec 20;18(12):1971-7. Epub 2009 Aug 20.

Department of Orthopaedic Surgery, Toulouse Rangueil University Hospital, Toulouse, France.

We implemented an experimental model of asymmetrical compression loading of the vertebral end plate (VEP) in vivo. The macroscopic permeability of the VEP was measured. We hypothesized that static asymmetrical loading on vertebrae altered the macroscopic permeability of the VEP. In scoliosis, solute transport to and from the disc is dramatically decreased especially at the apical intervertebral disc. The decrease in permeability could be induced by mechanical stress. Nine skeletally immature pigs were instrumented with left pedicle screws and compression rod at the T5/T6 and L1/L2 levels. After 3 months, three cylindrical specimens of the VEP were obtained from each of the tethered levels. A previously validated method for measuring permeability, based on the relaxation pressure due to a transient-flow rate was used. A pistoning device generated a fluid flow that fully saturated the cylindrical specimen. The decrease in upstream pressure was measured using a pressure transducer, which allowed the macroscopic permeability to be derived. A microscopic study completed the approach. Overall macroscopic permeability was lower for the tethered VEPs than for the VEPs of the control group, respectively -47% for flow-in (p = 0.0001) and -46% for flow-out (p = 0.0001). In the tethered group, macroscopic permeability of the specimens from the tethered side was lower than macroscopic permeability of those from the non-tethered side, -39% for flow-out (p = 0.024) and -47% for flow-in (p = 0.13). In the control group, the macroscopic permeability was greater in the center of the VEP than in its lateral parts for flow-out (p = 0.004). Macroscopic permeability of the center of the VEPs was greater for flow-out than for flow-in (p = 0.02). There was no significant difference between thoracic and lumbar. This study demonstrated that compression loading applied to a growing spine results in decreased permeability of the VEP. This result could be explained by local remodeling, such as calcification of the cartilage end plate or sclerosis of the underlying bone.
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http://dx.doi.org/10.1007/s00586-009-1140-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2899431PMC
December 2009

Micro-computed tomography evaluation of vertebral end-plate trabecular bone changes in a porcine asymmetric vertebral tether.

J Orthop Res 2010 Feb;28(2):232-40

Service de Chirurgie Orthopédique et Traumatologique-Institut Locomoteur, Centre Hospitalier Universitaire de Toulouse-Rangueil, 31059 Toulouse Cedex 9, France.

We conducted a micro-CT analysis of subchondral bone of the vertebral end-plates after application of compressive stress. Thoracic and lumbar vertebral units were instrumented by carrying out left asymmetric tether in eleven 4-week-old pigs. After 3 months of growth, instrumented units and control units were harvested. Micro-CT study of subchondral bone was performed on one central and two lateral specimens (fixated side and non-fixated side). In control units, bone volume fraction (BV/TV), number of trabeculae (Tb.N), trabecular thickness (Tb.Th), and degree of anisotropy (DA) were significantly higher, whereas intertrabecular space (Tb.Sp) was significantly lower in center than in periphery. No significant difference between the fixated and non-fixated sides was found. In instrumented units, BV/TV, Tb.N, Tb.Th, and DA were significantly higher in center than in periphery. BV/TV, Tb.N, and Conn.D were significantly higher in fixated than in non-fixated side, while Tb.Sp was significantly lower. We noted BV/TV, Tb.N, and Tb.Th significantly lower, and Tb.Sp significantly higher, in the instrumented levels. This study showed, in instrumented units, two opposing processes generating a reorganization of the trabecular network. First, an osteolytic process (decrease in BV/TV, Tb.N, Tb.Th) by stress-shielding, greater in center and on non-fixated side. Second, an osteogenic process (higher BV/TV, Tb.N, Conn.D, and lower Tb.Sp) due to the compressive loading induced by growth on the fixated side. This study demonstrates the densification of the trabecular bone tissue of the vertebral end-plates after compressive loading, and illustrates the potential risks of excessively rigid spinal instrumentation which may induce premature osteopenia.
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http://dx.doi.org/10.1002/jor.20974DOI Listing
February 2010

Adsorption and release of BMP-2 on nanocrystalline apatite-coated and uncoated hydroxyapatite/beta-tricalcium phosphate porous ceramics.

J Biomed Mater Res B Appl Biomater 2009 Nov;91(2):706-15

Université de Toulouse, CIRIMAT, UPS-INPT-CNRS, ENSIACET, 31077 Toulouse Cedex 4, France.

The association of bone morphogenetic proteins (BMPs) with calcium phosphate bioceramics is known to confer them osteoinductive properties. The aim of this study was to evaluate the surface properties, especially regarding recombinant human BMP-2 (rhBMP-2) adsorption and release, of commercial sintered biphasic calcium phosphate ceramics after coating with biomimetic nanocrystalline apatite. The raw and coated ceramics exhibited similar macroporous structures but different nanometer-sized pores contents. Both types of ceramics showed Langmuir-type adsorption isotherms of rhBMP-2. The coating noticeably increased the rate of adsorption and the total amount of growth factor taken up, but the maximum coverage per surface area unit as well as the affinity constant appeared lower for coated ceramics compared with raw ceramic surfaces. The limited advantage gained by coating the ceramics can be assigned to a lower accessibility of the surface adsorption sites compared with the raw ceramics. The quantity of rhBMP-2 spontaneously released in cell culture medium during the first weeks was lower for coated samples than for uncoated ceramics and represented a minor fraction of the total adsorbed amount. In conclusion, the nanocrystalline apatite coating was found to favor the adsorption of rhBMP-2 while providing a mean to fine tune the release of the growth factor.
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http://dx.doi.org/10.1002/jbm.b.31447DOI Listing
November 2009

Coxa magna quantification using MRI in Legg-Calve-Perthes disease.

Clin Biomech (Bristol, Avon) 2009 Jan 6;24(1):43-6. Epub 2008 Nov 6.

Children Hospital, Orthopedic Pediatric Department, Toulouse, France.

Background: The idiopathic avascular necrosis of the femoral epiphysis characterizes the Legg-Calve-Perthes disease in pediatric osteoarticular pathologies. The coxa magna, more frequently observed, corresponds to an enlargement and deformation of the femoral head. The volume extension induces a subluxation of the hip, which is a bad prognosis for the healthy function of the joint.

Methods: The aim of the study was to quantify the coxa magna in Legg-Calve-Perthes disease using magnetic resonance imaging. Twenty-five patients with unilateral Legg-Calve-Perthes disease were included in the clinical protocol and the volume properties of cartilaginous epiphyseal head were quantified using custom-made image processing software.

Findings: Difference in cartilage volume between healthy hips and pathological ones were significant. Excepting one patient, we observed a statistically significant volume increase for the pathological hip, the mean value being +13%.

Interpretation: Our results confirmed the effective three-dimensional properties of the coxa magna, which is clearly associated to a negative prognosis for the future of the joint. To our knowledge, the volume quantification of coxa magna has not been established before. The non-radiant MRI associated to three-dimensional investigation could potentially improve the clinical follow up of children to adapt the non-invasive treatment and to plan the surgery if necessary.
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http://dx.doi.org/10.1016/j.clinbiomech.2008.09.002DOI Listing
January 2009

Effects of physical activities on biochemical and biomechanical properties of tendons in two commercial types of chickens.

Connect Tissue Res 2008 ;49(2):76-84

Tissus Animaux, Nutrition, Digestion, Ecosystéme et Métabolisme, Université de Toulouse, Cedex, France.

The aim of our experiment was to study the effects of physical activities on the biochemical and biomechanical properties of tendons in 12 standard (S) broilers and 12 Label Rouge (LR) chickens. In the two types of birds no differences were found between control and active birds for body weights. Gastrocnemius (Gas) tendon and Pectoralis minor (Pm) tendons were harvested and processed for passive stretch tests prior to cooking or not. Some biochemical parameters also were determined. Results showed that total collagen content in Gas tendon was significantly higher in active than in control birds. However, no significant changes were found in collagen solubility in LR tendons while these values were increased in S ones. Active birds showed greater sGAGs content than control ones. Ultimate load was found to be significantly higher in active birds than in control. Deformability (defined by Poisson's ratio) of raw and heated at 80 degrees C Gas tendons increases in active groups because Poisson's ratio decreases. Physical activities also increase the rigidity (defined by elastic modulus) of raw and heated at 80 degrees C Gas tendons because elastic modulos values increase. Physical activity was not able to modify stiffness or maximum stress values in raw or heated at 80 degrees C Gas tendons from broilers whereas these two parameters were found to be slightly higher in active group from LR chickens only in raw tendons. All the biomechanical results recorded in Pm tendons from both types of chickens were not significantly different between control and active birds. A significant correlation was found between the total collagen content and stiffness in Gas tendon from LR active birds.
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http://dx.doi.org/10.1080/03008200801913593DOI Listing
May 2008

Influence of location, fluid flow direction, and tissue maturity on the macroscopic permeability of vertebral end plates.

Spine (Phila Pa 1976) 2008 Mar;33(6):612-9

Biomechanics Laboratory EA3697, Toulouse University Hospital, Toulouse, France.

Study Design: We implemented a pilot study in a growing animal model. The macroscopic permeability of the vertebral endplates was measured. The influence of location, tissue maturity, and fluid flow direction was quantified.

Objective: We hypothesized that the macroscopic permeability of vertebral endplate may decrease with maturity of the vertebral segment.

Summary Of Background Data: The alternation of loading induced by the diurnal cycle generates convective flux into the vertebral segment with the dominant flow path through the vertebral endplates. The alteration of mass transport at the disc-vertebrae interface may interrupt the mechanobiologic balance, and have an effect such as degenerative changes or scoliosis.

Methods: A previously validated method for measuring permeability, based on the relaxation pressure caused by a transient-flow rate was used. Three specimens were extracted from each L1 to L5 endplate. Seventy-one specimens were frozen, and 64 were stored fresh in a standard culture media. A microscopic analysis completed the biomechanical analysis.

Results: At 2, 4, and 6 months, the mean permeability (10(-14) m/N x s, flow-in/flow-out) of the central zone was respectively: 1.23/1.66, 1.03/1.29, and 0.792/1.00. Laterally, it was 1.03/1.19, 1.094/1.001, and 0.765/0.863. For all groups, cartilage endplate and growth plate were both thinner in the center of the plate. Weak differences of the vascular network were detected, except for a small increase of vascular density in the central zone.

Conclusion: The results from this animal study showed that the central zone of the vertebral endplate was more permeable than the periphery and the flow-out permeability was up to 35% greater than the flow-in permeability. Increase of permeability with decrease of cartilage thickness was noticed within the same age group. We also found a statistically significant decrease of the macroscopic permeability correlated with the tissue maturity.
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http://dx.doi.org/10.1097/BRS.0b013e318166e0d7DOI Listing
March 2008

Age- and gender-related distribution of bone tissue of osteoporotic humeral head using computed tomography.

J Shoulder Elbow Surg 2007 Sep-Oct;16(5):596-602. Epub 2007 Jul 23.

Department of Orthopedic Surgery Fujita Health University 2nd Hospital, Nagoya, Japan.

Treatment of proximal humeral fractures is very challenging in elderly patients with osteoporosis. Difficulty in obtaining a stable osteosynthesis remains the main problem for the surgeon. Knowing more details about the bone quality of the humeral head can be helpful for treatment. The purpose of this study was to evaluate the bone quality of the humeral head based on age, sex, and location. Three groups of patients were identified according to age: group A (aged <30 years), group B (aged >40 years but <60 years), and group C (aged >60 years). Computed tomography (CT) was performed on each patient to evaluate the humeral head bone quality. The distribution of bone density was assessed by the CT value expressed in Hounsfield units. The maximum, minimum, and mean CT values were calculated in the cancellous bone of the humeral head for each image. The humeral head was then divided into 3 equal zones, and a map of the 3 zones was made. The results showed that there was a significant difference between men and women in our series with regard to the percentage of bone tissue. There was also a significant difference among the 3 groups (age-related), as well as between the medial and lateral sides, with regard to the percentage of bone tissue. Osteopenic change in the humeral head has a negative correlation with aging. The medial side, especially the articular side, has more bone tissue than other areas. These results suggest that, when we treat humeral head fractures of elderly patients, we need to define bone quality for each case. We should then take care when establishing the site and angle of insertion for fixation to obtain optimal fixation on the lateral side.
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http://dx.doi.org/10.1016/j.jse.2007.01.006DOI Listing
January 2008

Quantification of intervertebral disc volume properties below spine fusion, using magnetic resonance imaging, in adolescent idiopathic scoliosis surgery.

Spine (Phila Pa 1976) 2007 Jul;32(15):E405-12

Department of Pediatric Surgery, Pontchaillou University Hospital, Rennes, France.

Study Design: Prospective clinical study. A quantification of volume and hydration variation of the intervertebral discs, using magnetic resonance imaging (MRI), in the lumbar spine before and after surgery performed in adolescent idiopathic scoliosis (AIS).

Objectives: To evaluate an objective quantification of volume and hydration of intervertebral discs below spine fusion in scoliosis surgery.

Summary And Background Data: Repercussion of long spine fusion on the free lower lumbar spine is one of the major concerns of scoliosis surgery. However, the evolution of lumbar intervertebral disc below thoracolumbar fusions remains unknown.

Methods: MRI performed in the clinical protocol, concerned 28 patients having an idiopathic scoliosis. They underwent posterior instrumentations. MRI was obtained before surgery, after surgery at 3 months and for 15 patients at 1 year. MRI data were posttreated using a custom-made image processing software to semiautomatically derive volume properties of disc, anulus fibrosus, and nucleus pulposus. The nucleus-disc volume ratio was also an indicator of the hydration level.

Results: The reliability of the three-dimensional reconstruction process was initially verified using an intraoperator reproducibility test. Original preoperative data on disc volume properties were then derived. Postoperative volume variations were quantified in discs below spine fusion taking into account the level of the arthrodesis and the disc location. It showed that the postoperative volume criteria increased significantly for nucleus, disc, and nucleus-disc volume ratio and some magnitude modulation could be conditioned by the location of surgical instrumentation. Some stabilization or reduction depending on disc level and arthrodesis size between 3 months and 1 year is observed in the follow-up. It tended to prove that the recovery of balance physiologic positioning and inherent biomechanical loads could induce a restored hydration of disc, which should favor the remodeling of free segments.

Conclusions: This work was the first report dealing with consequences of scoliosis surgery on subjacent disc in term of volume and hydration properties.
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http://dx.doi.org/10.1097/BRS.0b013e318074d69fDOI Listing
July 2007
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