Sagittal alignment in lumbosacral fusion: relations between radiological parameters and pain.

The objective of this study was to conduct a radiological analysis of posture before and after lumbosacral fusion to evaluate the influence of spinal alignment on the occurrence and pattern of post surgical pain. The study included 81 patients, of whom 51 had a history of previous low back surgery. We excluded patients with suspected or confirmed nonunion. In the fusion group, the 27 patients who were pain free after the procedure were compared to the 54 patients with residual pain. Thirty patients had pain only or primarily when they were standing immobile, 18 when they were sitting immobile, and six in both positions. Measurements were done on full-length lateral radiographs of the spine, with the patient standing according to Duval Beaupère criteria. The subgroup with postfusion pain was characterized at baseline by a more vertical sacrum with less sacral tilt (ST) (P < 0.0062) and more pelvic tilt (PT) (P < 0.0160). PT at last follow-up (PT fu) correlated with the presence of postfusion pain (NP: P = 0.0003). In the patients with postfusion pain, PT was almost twice the normal value. ST at last follow-up (ST fu) in the standing position was also correlated with the presence of postfusion pain (P < 0.0001) indicating that the sacrum remained abnormally vertical in the subjects with postfusion pain. Using logistic regression, the only prognostic factor for residual pain at last follow-up was ST fu. Both at pre-operative evaluation and at last follow-up, patients with pain in the standing position or in both the standing and sitting positions were characterized at pre-operative status by a more vertical sacrum with less sacral tilt. The results of this study indicate that, achieving a strong fusion should not be the only goal. Appropriate position of the fused vertebrae is also of paramount importance to minimize muscle work during posture maintenance. The main risk is failing to correct or to causing excessive pelvic retroversion with a vertical sacrum leading to a sagittal alignment that replicates the sitting position. This situation is often accompanied by loss of lumbar lordosis and adversely affects stiff or degenerative hips.

Anatomic bases of a new technique of juxta-acetabular osteotomy. Technical principles and performance.

Pelvic osteotomies were developed to increase or restructure the acetabular surface. Periacetabular osteotomies are considered the most difficult from the technical point of view and necessitate sufficient residual cartilaginous surface. Juxta-acetabular osteotomies avoid major disorganization of the pelvic framework and allow easier reorientation of the acetabulum. The authors present a technical variant that preserves the entire posterior column, as in the Ganz osteotomy. The effects on the vascularisation of the periacetabular region are strictly the same and there is no necrosis of the subchondral bone. This osteotomy is easier to perform, because of a single positioning associating two simultaneous approaches. The osteotomies are rectilinear and easy to check peroperatively by fluoroscopy thanks to this positioning. Another valuable aspect of this double approach consists of very easy correction of "automatic" unwanted retroversion due to the lowering of the acetabular roof. This unintended displacement is rarely reported in the literature, despite its anatomic evidence in 3-dimensional CT-scan reconstructions for pre- and peroperative evaluation.

Dynamic anatomy of the acetabulum: an experimental approach and surgical implications.

The deformations and stresses acting on the acetabular rim have not been very precisely documented. The authors present a study based on an experimental simulation of hip loading with anatomic correlations. 122 dissections were performed in order to define the anatomic aspect of the roof (and especially of Byers's "area 17") and the intermediate area between the anterior and posterior acetabular cornua. Ten fresh cadavers were tested on the lines of previous studies on monopodal or bipodal loading. An extensometric study was performed with special attention to the transverse acetabular ligament, supra-acetabular area and obturator foramen. The area 17 of Byers is a transitional zone and the mobility of the posterior cornu is 3 times that of the anterior cornu. Resection of the acetabular ligament modifies the displacement of the posterior cornu under loading but has no influence on deformation of the oburator foramen. The biomechanical behavior of the acetabular roof in the standing position is influenced by the conditions of monopodal or bipodal loading and by femoral rotation, but a tendency to extrusion was constantly noted.

[Validity of the Pauwels theory: Focus on experimental methods for studying deformations of the hip joint during unilateral and bilateral weight-bearing]. / Validité de la théorie de Pauwels: mise au point de méthodes d'approches expérimentales sur l'étude des déformations du cotyle humain en appui monopodal et bipodal.

A critical analysis is proposed between two experimental studies of the hip joint. Is it very important to respect the PAUWELS theory? The authors try to answer this question.

[Cartilaginous and bony anatomy of the human cotyloid cavity: preliminary study for the analysis of the specific dynamics of cotyloid cornua]. / L'anatomie cartilagineuse et osseuse du cotyle humain: étude préliminaire à l'analyse de la dynamique spécifique des cornes cotyloïdiennes.

Recent studies on acetabular and periacetabular deformations help to understand hip functioning. They encourage a new anatomic analysis of the bony and cartilagenous frameworth of the hip. The authors report as biomechanical preleminary, a radiological and anatomical study on the behavior of the periacetabular region. The results are compared to the anatomical litterature and conclusions are drawn.