The method to measure the market risk (which stocks are exposed) by the slope coefficient of a linear regression model (that relates the returns of the asset and the returns of a market index) is known as Market Model. When applying this method it is extremely important to check the stability of the parameters (the slope, the intercept and the variance) over the time to neutralize the market risk. Procedures known in statistical quality control as analysis of linear profiles are presented for such purpose. By statistical tests based on the F -statistics, it is possible to identify the sources of variation and also out-of-control samples. Numerical examples illustrate the proposed procedures.

Article informationBackground: Transcervical neck fracture is common in daily orthopedic practice.Internal fixation is the curative option. However, there is controversy exists regarding the ideal fixation device. The aim of the work:This study aims to compare the clinical, functional and radiological results of cannulated screws versus dynamic locking plate in fixations of femoral neck fractures.Patients and Methods: Thirty patients with transcervical fracture neck femur were included. They were divided into two groups; the first for dynamic locked plate, and the second for cannulated screws. All were assessed preoperatively by radiological and clinical methods. Postoperative care consisted of routine vital data recording, intravenous antibiotics and appropriate analgesia. X-rays were done in the first postoperative to check fixation and after 12 weeks to check for union. The followup evaluation included questioning the patient about pain during activity and rest and about ability to walk and stand determining the range of motion of the hip joint using modified Harris Hip Scoring System. Results:The mean operative time in screws group was 38 minute compared to 72 minutes in plate group with significant difference between both groups. Both groups showed high successful union rate with no significant difference. In the screw group, 3 cases fail to union while in plate group only one case failed. The mean union time in screws group was 19.7 weeks while in plate group was 18.3 weeks. Screws group showed 8 cases of complication, compared to 5 cases in the plate group. There was a significant blood loss [more than 500ml] in plate group. Conclusion:Although both groups were comparable regarding union rate, the screw group was associated with significantly shorter operative time, and lower blood loss. The anatomical reduction is the main determining factor of success regardless the type of device used in fixation.

Article informationBackground: With the advancement of hip surgery and increased life span in many nations, the need for acetabular revision surgery is expected to grow. Many options are available for such surgery, including the use of impacted bone graft.The Aim of The Work: This work aimed to assess the clinical results of impacted bone graft in reconstructing the acetabular bone defect after a failed hip surgery.Patients and Methods: Between 2013 and 2019, we performed reconstructions of the acetabulum for 20 patients, who had at least one acetabular operation before revision. Surgical reconstruction was conducted using an impacted cancellous bone graft. Each patient was directed to long-term clinical [primary outcome] and radiological evaluations. The direct postoperative clinical and radiographic outcomes were evaluated and the patient continued regular follow up visits for at least 12 months after surgery. Results: According to the modified Harris-Hip [MHH] score, the results rated as excellent [35%], good [25%], fair [25%] and poor [15%]. No pain was recorded for 40%, slight pain for 30%. Thirteen patients [65%] were able to walk alone without support, while the remaining 7 used a support in the form of a cane [25%] or crutches [10%]. Leg-length discrepancy [>2.5 cm] was reported in two patients. Conclusion:Successful results were obtained using the impaction technique for acetabular reconstruction, with restoration of near normal mechanics. The union rate is satisfactory. Augmentation of the grafting technique by mesh or rings added more stability to the cup component.