Julien Wegrzyn

Contribution of Trabecular and Cortical Components to Biomechanical Behavior of Human Vertebrae: An Ex Vivo Study

Whereas there is clear evidence for a strong influence of bone quantity (i.e., bone mass or bone mineral density) on vertebral mechanical behavior, there are fewer data addressing the relative influence of cortical and trabecular bone microarchitecture. The aim of this study was to determine the relative contributions of bone mass, trabecular microarchitecture, and cortical thickness and curvature to the mechanical behavior of human lumbar vertebrae. Thirty‐one L3 vertebrae (16 men, 15 women, aged 75 ± 10 years and 76 ± 10 years, respectively) were obtained. Bone mineral density (BMD) of the vertebral body was assessed by lateral dual energy X‐ray absorptiometry (DXA), and 3D trabecular microarchitecture and anterior cortical thickness and curvature was assessed by micro‐computed tomography (µCT). Then compressive stiffness, work to failure, and failure load were measured on the whole vertebral body. BMD was correlated with compressive stiffness (r = 0.60), failure load (r = 0.70), and work to failure (r = 0.55). Except for the degree of anisotropy, all trabecular and cortical parameters were correlated with mechanical behavior (r = 0.36 to 0.58, p = .05 to .001, and r = 0.36 to 0.61, p = .05 to .0001, respectively). Stepwise and multiple regression analyses indicated that the best predictor of (1) failure load was the combination of BMD, structural model index (SMI), and trabecular thickness (Tb.Th) (R = 0.80), (2) stiffness was the combination of BMD, Tb.Th, and curvature of the anterior cortex (R = 0.82), and (3) work to failure was the combination of anterior cortical thickness and BMD (R = 0.68). Our data imply that measurements of cortical thickness and curvature may enhance prediction of vertebral fragility and that therapies that improve both vertebral cortical and trabecular bone properties may provide a greater reduction in fracture risk.

Pelvic balance in sagittal and Lewinnek reference planes in the standing, supine and sitting positions.

INTRODUCTION Sagittal pelvic balance is a recognized factor influencing targeted acetabular-component anteversion during total hip arthroplasty implantation. However, no studies in the literature have systematically reported pelvic parameters data in the standing, sitting and supine positions. HYPOTHESIS Variations in acetabular cup orientation can be traced to eventual pelvic balance changes in one of these three usual positions. MATERIALS AND METHODS In these three positions (supine, standing and sitting), pelvic anatomical parameters and reference planes were radiologically defined from a group of 67 patients (average age: 70.2+/-3.2 years). The complete X-rays individual sets were digitized and measurements were obtained by a single operator using a Spineview software (previously, strictly validated for these kind of measurements). Positioning according to the Lewinnek pelvic coordinate system, which is considered as a possible source of errors when vertically standing or horizontally lying, was also investigated. RESULTS The average pelvic incidence of 59.6 degrees did not vary in the sitting, supine or standing positions, with no statistically significant difference between sexes. The Legaye equation--pelvic incidence is equals to pelvic version plus sacral slope--was verified. Pelvic version increased by an average 22 degrees from the sitting to the supine or standing positions. Sacral slope varied in a reverse order. Pelvic-femoral angle (PFA) decreased by 20 degrees from the standing to the supine position. The Lewinnek plane was located 4 degrees posterior to the vertical plane. Whatever the position adopted, pelvi-Lewinnek angle appeared constant, averaging 12 degrees. DISCUSSION The average pelvic incidence in this series was high, most probably associated with advancing patient age and/or pathology. The concept of functional anteversion appeared critical when taking into account pelvic version variations (according to the position, sitting, supine or standing) positions. The Lewinnek plane, commonly accepted as the reference plane for hip navigation, was individualised to each patient and should not be mistaken with the vertical plane; positioning of the femur in relation to the Lewinnek plane was also specific to each patient. Cumulative approximation on these two parameters at surgery resulted in a combined imprecision of 26 degrees when standing and 36 degrees when lying down. We have thus defined crucial parameters to be integrated in computer-assisted hip surgery softwares: positional variations of the pelvic version (functional anteversion), positioning of the Lewinnek plane, and PFA value (both specifically patients dependant). If integration of these parameters into new sofwares versions appears possible, this would represent a reliable compromise between maximum prosthetic stability, maximum joint amplitudes and elimination of possible prosthetic conflict.

Role of Trabecular Microarchitecture and Its Heterogeneity Parameters in the Mechanical Behavior of Ex Vivo Human L3 Vertebrae

Low bone mineral density (BMD) is a strong risk factor for vertebral fracture risk in osteoporosis. However, many fractures occur in people with moderately decreased or normal BMD. Our aim was to assess the contributions of trabecular microarchitecture and its heterogeneity to the mechanical behavior of human lumbar vertebrae. Twenty‐one human L3 vertebrae were analyzed for BMD by dual‐energy X‐ray absorptiometry (DXA) and microarchitecture by high‐resolution peripheral quantitative computed tomography (HR‐pQCT) and then tested in axial compression. Microarchitecture heterogeneity was assessed using two vertically oriented virtual biopsies—one anterior (Ant) and one posterior (Post)—each divided into three zones (superior, middle, and inferior) and using the whole vertebral trabecular volume for the intraindividual distribution of trabecular separation (Tb.Sp*SD). Heterogeneity parameters were defined as (1) ratios of anterior to posterior microarchitectural parameters and (2) the coefficient of variation of microarchitectural parameters from the superior, middle, and inferior zones. BMD alone explained up to 44% of the variability in vertebral mechanical behavior, bone volume fraction (BV/TV) up to 53%, and trabecular architecture up to 66%. Importantly, bone mass (BMD or BV/TV) in combination with microarchitecture and its heterogeneity improved the prediction of vertebral mechanical behavior, together explaining up to 86% of the variability in vertebral failure load. In conclusion, our data indicate that regional variation of microarchitecture assessment expressed by heterogeneity parameters may enhance prediction of vertebral fracture risk.

Can Dual Mobility Cups prevent Dislocation in All Situations After Revision Total Hip Arthroplasty

UNLABELLED The outcome of a single design of dual mobility cup was prospectively evaluated in a continuous series of 994 revision THAs with respect to dislocation and intra-prosthetic dislocation (IPD). At a 7.3-year mean follow-up, the dislocation rate was 1.5% and the IPD rate was 0.2%. The 2 IPD occurred in acetabular-only revisions and were related to a poor head-to-neck ratio with early impingement and wear at the polyethylene mobile component chamfer. Dual mobility cups demonstrated a low dislocation rate in revision THA but did not compensate for potential perioperative technical errors. In addition, IPD did not appear to be a concern with respect to the benefit in term of instability prevention though caution is advised in acetabular-only revision associated with a poor head-to-neck ratio. LEVEL OF EVIDENCE Therapeutic study-Level IV.

Repeat Revision of Anterior Cruciate Ligament Reconstruction A Retrospective Review of Management and Outcome of 10 Patients With an Average 3-Year Follow-Up

Background To the authors’ knowledge, no previous published study has focused on management and outcome of repeat revision of anterior cruciate ligament reconstruction in terms of functional result and meniscus and articular cartilage status. Hypothesis Repeat revision of anterior cruciate ligament reconstruction improves knee stability, but with inferior results for functional outcome compared with primary anterior cruciate ligament reconstruction. Meniscal tears and subsequent articular cartilage degeneration are more prevalent with successive revisions due to recurrent laxity. Study Design Case series; Level of evidence, 4. Materials and Methods: Between February 2003 and November 2006, a consecutive series of 10 patients with an average age at 30 years (range, 17-48) were operated on for a repeat revision of anterior cruciate ligament reconstruction (2 revisions after a primary reconstruction) with arthroscopic procedures. A clinical and a radiographic evaluation were performed to assess anterior cruciate ligament reconstruction failures, outcome of revisions, and causes of failures. Meniscal tears and articular cartilage lesions were analyzed. Results The average follow-up of the second revision was 38 months (range, 12-61). At latest follow-up, final International Knee Documentation Committee assessment was excellent or good in 7 cases. Postoperatively, only 2 patients recovered to the same sports activity level they had before their first anterior cruciate ligament reconstruction. Four had a lower level, and 4 discontinued sports activity. The postoperative average side-to-side KT-1000 arthrometer maximum manual difference was 1.3 ± 1.9 mm. Nine patients had meniscal tears and 7 had articular cartilage lesions. Meniscal tears, meniscectomies, and articular cartilage degeneration increased after the second revision (P = .016, P = .0098, and P = .0197, respectively). Severe articular cartilage degeneration (International Cartilage Repair Society grade III and IV lesions) was found in patients with bad functional outcome (final International Knee Documentation Committee assessment C or D) (P = .0472). Incidence of articular cartilage degeneration was found to be more prevalent in cases of meniscal tears and partial meniscectomy at the same tibiofemoral compartment (P = .0157). Index anterior cruciate ligament reconstruction and first revision failures were caused by recurrent trauma (60% and 70%, respectively) or a surgical technical error with tunnel malpositioning (40% and 10%, respectively). Conclusion Outcome of repeat revision of anterior cruciate ligament reconstruction was excellent or good in 70% of the cases, although decreased after the second revision, in relation to the occurrence of meniscal tears and articular cartilage lesions. Meniscal and articular cartilage lesions were more frequent and more severe with recurrent laxity. The cause of failures was mainly recurrent trauma, followed by surgical technical errors.

Acetabular Reconstruction Using a Kerboull Cross-Plate, Structural Allograft and Cemented Dual-Mobility Cup in Revision THA at a Minimum 5-Year Follow-Up

The current study aimed to evaluate the outcome of a continuous and prospective series of 61 revision THAs with AAOS grade III and IV acetabular bone defect reconstruction using a Kerboull cross-plate, structural allograft and cemented dual mobility cup (Saturne, Amplitude, Valence, France). At a 7.5-year mean follow-up, no instability was reported after revision. In addition, no failure of the acetabular reconstruction was observed in 98% of the patients with complete allograft osseointegration and no evidence of mechanical rupture of the Kerboull cross-plate and/or loosening of the cemented dual mobility cup. In conclusion, such reconstruction technique demonstrated excellent results at mid-term follow-up in terms of prevention of instability after revision, restoration of the acetabular bone stock, and stable cemented fixation of the dual mobility cup.

Repair of insertional achilles tendinosis with a bone-quadriceps tendon graft

Background: While conservative treatment may be successful in most cases, partial rupture at the calcaneal insertion point is a significant concern with insertional Achilles tendinopathy. We report on the outcomes of a surgical technique for Achilles tendon augmentation using a bone-tendon graft harvested from the knee extensor system. Materials and Methods: Our retrospective case series includes 25 surgical procedures performed in 24 patients, 19 males and five females, with a mean age of 47 (range, 30 to 59) years, 18 of whom were athletes. The mean followup period was 52 (range, 12 to 156) months. All patients underwent MRI examination prior to surgery which showed partial Achilles tendon rupture. The Achilles tendon was debrided through a posterolateral approach. The bone-quadriceps tendon graft was harvested, then the bone plug of the graft was inserted into a blind tunnel drilled into the calcaneus and fixed with an interference screw. The fibers of the quadriceps tendon were sutured to the residual part of the Achilles tendon with the foot at an angle of 90 degrees. Results: Patients were able to resume their sporting activity after an average of 6.7 months. At last followup examination, physical activity was scored 5.2 on the 10-point Tegner Scale; the mean AOFAS score was 98.4. MRI examination showed good graft integration 1 year postoperatively. Conclusion: The bone-quadriceps tendon grafting technique was a good alternative for the insertional Achilles lesions with partial detachment which we felt required augmentation. Level of Evidence: IV, Retrospective Case Series

Determinants of the Mechanical Behavior of Human Lumbar Vertebrae After Simulated Mild Fracture

The ability of a vertebra to carry load after an initial deformation and the determinants of this postfracture load‐bearing capacity are critical but poorly understood. This study aimed to determine the mechanical behavior of vertebrae after simulated mild fracture and to identify the determinants of this postfracture behavior. Twenty‐one human L3 vertebrae were analyzed for bone mineral density (BMD) by dual‐energy X‐ray absorptiometry (DXA) and for microarchitecture by micro–computed tomography (µCT). Mechanical testing was performed in two phases: initial compression of vertebra to 25% deformity, followed, after 30 minutes of relaxation, by a similar test to failure to determine postfracture behavior. We assessed (1) initial and postfracture mechanical parameters, (2) changes in mechanical parameters, (3) postfracture elastic behavior by recovery of vertebral height after relaxation, and (4) postfracture plastic behavior by residual strength and stiffness. Postfracture failure load and stiffness were 11% ± 19% and 53% ± 18% lower than initial values (p = .021 and p < .0001, respectively), with 29% to 69% of the variation in the postfracture mechanical behavior explained by the initial values. Both initial and postfracture mechanical behaviors were significantly correlated with bone mass and microarchitecture. Vertebral deformation recovery averaged 31% ± 7% and was associated with trabecular and cortical thickness (r = 0.47 and r = 0.64; p = .03 and p = .002, respectively). Residual strength and stiffness were independent of bone mass and initial mechanical behavior but were related to trabecular and cortical microarchitecture (|r| = 0.50 to 0.58; p = .02 to .006). In summary, we found marked variation in the postfracture load‐bearing capacity following simulated mild vertebral fractures. Bone microarchitecture, but not bone mass, was associated with postfracture mechanical behavior of vertebrae.

Fungaemia Caused by Fusarium proliferatum in a Patient Without Definite Immunodeficiency

Abstract Recent literature has shown the growing importance of opportunistic fungal infections due to Fusarium spp. However, disseminated fusariosis remains rare in patients without neutropenia. We report a case of fungaemia in a 78-year-old French woman without definite immunodeficiency. Fusarium proliferatum grew from both central and peripheral blood cultures. Fever was the only clinical sign of the infection. An appropriate antifungal therapy with voriconazole led to the recovery of the patient. An environmental investigation was undertaken but failed to find a reservoir of Fusarium spores. A contaminated central venous catheter might have been the source of fungaemia.

The role of bone intrinsic properties measured by infrared spectroscopy in whole lumbar vertebra mechanics: organic rather than inorganic bone matrix?

Whole bone strength is determined by bone mass, microarchitecture and intrinsic properties of the bone matrix. However, few studies have directly investigated the contribution of bone tissue material properties to whole bone strength in humans. This study assessed the role of bone matrix composition on whole lumbar vertebra mechanics. We obtained 17 fresh frozen human lumbar spines (8 W, 9 M, aged 76±11years). L3 bone mass was measured by DXA and microarchitecture by μ-CT with a 35 μm-isotropic resolution. Microarchitectural parameters were directly measured: Tb.BV/TV, SMI, Tb.Th, DA, Ct.Th, Ct.Po and radius of anterior cortical curvature. Failure load (N), stiffness (N/mm) and work to failure (N.mm) were extracted from quasi-static uniaxial compressive testing performed on L3 vertebral bodies. FTIRM analysis was performed on 2 μm-thick sections from L2 trabecular cores, with a Perkin-Elmer GXII Auto-image Microscope equipped with a wide band detector. Twenty measurements per sample were performed at 30∗100 μm of spatial resolution. Each spectrum was collected at 4 cm(-1) resolution and 50 scans in transmission mode. Mineral and collagen maturity, and mineralization and crystallinity index were measured. There was no association between the bone matrix characteristics and bone mass or microarchitecture. Mineral maturity, mineralization and crystallinity index were not related to whole vertebra mechanics. However, collagen maturity was positively correlated with whole vertebra failure load and stiffness (r=0.64, p=0.005 and r=0.54, p=0.025, respectively). The collagen maturity (3rd step) in combination with bone mass (i.e., BMC, 1st step) and microarchitecture (i.e., Tb.Th, 2nd step) improved the prediction of whole vertebra mechanical properties in forward stepwise multiple regression models, together explaining 71% of the variability in whole vertebra stiffness (p=0.001). In conclusion, we demonstrated a substantial contribution of collagen maturity, but not mineralization parameters, to whole bone strength of human lumbar vertebrae that was independent of bone mass and microarchitecture.