Erik Estivalèzes

Assessment of hindfoot deformity by three-dimensional MRI in infant club foot

In 12 infants aged under 16 months with unilateral club foot we used MRI in association with multiplanar reconstruction to calculate the volume and principal axes of inertia of the bone and cartilaginous structures of the hindfoot. The volume of these structures in the club foot is about 20% smaller than that in the normal foot. The reduction in volume of the ossification centre of the talus (40%) is greater than that of the calcaneus (20%). The long axes of both the ossification centre and the cartilaginous anlage of the calcaneus are identical in normal and club feet. The long axis of the osseous nucleus of the talus of normal and club feet is medially rotated relative to the cartilaginous anlage, but the angle is greater in club feet (10 degrees v 14 degrees). The cartilaginous structure of the calcaneus is significantly medially rotated in club feet (15 degrees) relative to the bimalleolar axis. The cartilaginous anlage of the talus is medially rotated in both normal and club feet, but with a smaller angle for club feet (28 degrees v 38 degrees). This objective technique of measurement of the deformity may be of value preoperatively.

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

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.

Percutaneous catheterization of the long bones: experimental study

The objective of this study was to develop a technique which would permit access to the entire contents of long bones using a minimally invasive approach. Vascular catheterization techniques were used to allow access to the entire marrow cavity through a minimal percutaneous approach. A new device was also developed to reach the epiphysis of the long bone. The study was performed on animal and human anatomical specimens. A percutaneous approach was made through the bone shaft from a remote entry site using principles from endoscopy in an ex vivo experiment. This method may become an alternative technique when a direct approach to lesional sites in long bones is dangerous or impossible. For example, it could be used in cases of preventive cement injections in weakened bones.

Mechanical coupling effects into a L3-L5 vertebral segment.

In the surgery of the adolescent idiopathic scoliosis (AIS), it has been shown that arthrodesis was increasing the intervertebral disc volume of discs below spine fusion post-operatively. Another consequence was the variation of hydration of disc remained free. The surgery induced a redistribution of strain energy but it is challenging to identify the mechanical loadings in-vivo. We hypothesized that the direct simulation of a vertebral segment under compression, bending and shear supported the analysis of mechanical transfers in-vivo.