Superimposition of maximal stress and necrosis areas at the top of the femoral head in hip aseptic osteonecrosis.

INTRODUCTION: Recent reports described possible mechanical factors in the development and aggravation of osteonecrosis of the femoral head (OFH), but these have yet to be confirmed on dedicated mechanical study. We therefore developed a 3D finite element model based on in-vivo data from patients with incipient OFH, with a view to determining whether the necrosis area was superimposed on the maximal stress area on the femoral head. HYPOTHESIS: The location of the necrosis area is determined by stress on the femoral head. MATERIAL AND METHOD: All patients from the rheumatology department with early stage OFH in our center were investigated. Analysis of CT scans showed stress distribution on the head by 3D finite elements models, enabling determination of necrosis volume within the maximal stress area and of the percentage intersection of necrosis within the stress area (%I n/s: necrosis volume in stress area divided by total stress area volume and multiplied by 100) and of stress within the necrosis area (%I s/n: stress volume in necrosis area divided by total necrosis area volume and multiplied by 100). RESULTS: Nineteen of the 161 patients assessed retrospectively for the period between 2006 and 2015 had incipient unilateral OFH, 10 of whom (4 right, 6 left) had CT scans of sufficient quality for inclusion. Mean age was 52 years (range, 37-81 years). Mean maximal stress was 1.63MPa, mean maximal exported stress volume was 2,236.9 mm3 and mean necrosis volume 6,291.1 mm3. Mean %I n/s was 83% and mean %I s/n 35%, with no significant differences according to gender, age, side or stress volume. There was a strong inverse correlation between necrosis volume and %I s/n (R2=-0.92) and a strong direct correlation between exported stress volume and %I s/n (R2=0.55). %I s/n was greater in small necrosis (<7,000mm3). CONCLUSION: OFH seems to develop within the maximal stress area on the femoral head. The present results need confirmation by larger-scale studies. We consider it essential to take account of these mechanical parameters to reduce failure rates in conservative treatment of OFH. LEVEL OF EVIDENCE: IV.

Can three-dimensional patient-specific cutting guides be used to achieve optimal correction for high tibial osteotomy? Pilot study.

INTRODUCTION: Treatment of medial tibiofemoral osteoarthritis with a high-tibial osteotomy (HTO) is most effective when the optimal angular correction is achieved. However, conventional instrumentation is limited when multiplanar correction is needed. HYPOTHESIS: Use of patient-specific cutting guides (PSCGs) for HTO provides an accurate correction (difference<2°) relative to the preoperative planning. MATERIALS AND METHODS: Between February 2014 and February 2015, 10 patients (mean age: 46 years [range: 31-59]; grade 1 or 2 osteoarthritis in Ahlbäck's classification) were included prospectively in this reliability and safety study. All patients were operated using the same medial opening-wedge osteotomy technique. Preoperative planning was based on long-leg radiographs and CT scans with 3D reconstruction. The PSGCs were used to align the osteotomy cut and position the screw holes for the plate. The desired correction was achieved in the three planes when the holes on the plate were aligned with the holes drilled based on the PSCG. Preoperatively, the mean HKA angle was 171.9° (range: 166-179°), the mean proximal tibial angle was 87° (86-88°) and the mean tibial slope was 7.8° (1-22°). The postoperative correction was compared to the planned correction using 3D CT scan transformations. Intraoperative and postoperative complications were assessed at a minimum follow-up of 1 year. RESULTS: The procedure was successfully carried out in all patients with the PSCGs. On postoperative long-leg radiographs, the mean HKA was 182.3° (180-185°); on the CT scan, the mean tibial mechanical angle was 94° (90-98°) and the mean tibial slope was 7.1° (4-11°). In 19 out of 20 postoperative HKA and slope measurements, the difference between the planned and achieved correction was <2° based on the 3D analysis of the three planes in space; in the other case, the slope was 13° instead of the planned 10°. The intra-class correlation coefficients between the postoperative and planned parameters were 0.98 [0.92-0.99] for the HKA and 0.96 [0.79-0.99] for the tibial slope. There were no surgical site infections; one patient had a postoperative hematoma that resolved spontaneously. DISCUSSION: The results of this study showed that use of PSCGs in HTO procedures helps to achieve optimal correction in a safe and reliable manner. LEVEL OF EVIDENCE: IV - Prospective cohort study.

[Vascular complications during surgery of lumbar disk herniation. Apropos of 3 personal cases and 37 cases from a national investigation]. / Accidents vasculaires au cours de la chirurgie de la hernie discale lombaire. A propos de 3 cas personnels et de 37 cas colligés dans une enquête nationale.

Three personal cases of iatrogenic vascular complications (two arterial wounds and one arteriovenous fistula) induced by lumbar herniation surgery led to a French national investigation among vascular and neurosurgical units where 37 other such cases have been discovered over 10 years (1984-1994). In 23 cases, the initial symptomatology was collapses by arterial (22 cases) or venous (one case) hemorrhage requiring emergency vascular repair surgery; in 17 cases an arterio-venous fistula was found in a period varying from a few hours to 5 years after surgery; it was revealed by cardiac failure, lower limb edema or abdominal thrill. Among the 40 cases, 77% occurred at the L4-L5 level; the mortality was 5%, and the morbidity was 27%. Origin, causes and prevention are discussed.