Halldór Jónsson

Assessment of Total Hip Arthroplasty by Means of Computed Tomography 3D Models and Fracture Risk Evaluation

Total hip arthroplasty (THA) can be achieved by using a cemented or noncemented prosthesis. Besides patients age, weight, and other clinical signs, the evaluation of the quality of the bones is a crucial parameter on which orthopedic surgeons base the choice between cemented and noncemented THA. Although bone density generally decreases with age and a cemented THA is preferred for older subjects, the bone quality of a particular patient should be quantitatively evaluated. This study proposes a new method to quantitatively measure bone density and fracture risk by using 3D models extracted by a preoperative computed tomography (CT) scan of the patient. Also, the anatomical structure and compactness of the quadriceps muscle is computed to provide a more complete view. A spatial reconstruction of the tissues is obtained by means of CT image processing, then a detailed 3D model of bone mineral density of the femur is provided by including quantitative CT density information (CT must be precalibrated). A finite element analysis will provide a map of the strains around the proximal femur socket when solicited by typical stresses caused by an implant. The risk for structural failure due to press-fitting and compressive stress during noncemented THA surgery was estimated by calculating a bone fracture risk index (ratio between actual compressive stress and estimated failure stress of the bone). A clinical trial was carried out including 36 volunteer patients (ages 22-77) who underwent unilateral THA surgery for the first time: 18 received a cemented implant and 18 received a noncemented implant. CT scans were acquired before surgery, immediately after, and after 12 months. Bone and quadriceps density results were higher in the healthy leg in about 80% of the cases. Bone and quadriceps density generally decrease with age but mineral density may vary significantly between patients. Preliminary results indicate the highest fracture risk at the calcar and the lowest at the intertrocanteric line, with some difference between patients. An analysis of the results suggest that this methodology can be a valid noninvasive decision support tool for THA planning; however, further analyses are needed to tune the technique and to allow clinical applications. Combination with gait analysis data is planned.

Parents' perspectives on otitis media and antibiotics A qualitative study

Background - Judicious use of antibiotics is an important factor in decreasing the current increase in bacterial resistance. Discussion with patients and their guardians on whether to use antibiotics or not can be expected to increase in the future. Objective - To explore the views and feelings of parents of children with acute otitis media towards the disease and its treatment. Design - A qualitative study with semi-structured interviews. Subjects - Twenty-one parents of pre-school children with newly diagnosed acute otitis media who had attended a primary care centre in Reykjavík. Results - The parents did not consider the disease a threat. They generally thought the disease was caused by environmental factors or by a disturbance in body mechanism. The majority thought that treatment with antibiotics could harm their children. Conclusion - The parents of young children hold views on acute otitis media and antibiotics which are markedly different from the medical model.

Bone Mineral Density and Fracture Risk Assessment to Optimize Prosthesis Selection in Total Hip Replacement

The variability in patient outcome and propensity for surgical complications in total hip replacement (THR) necessitates the development of a comprehensive, quantitative methodology for prescribing the optimal type of prosthetic stem: cemented or cementless. The objective of the research presented herein was to describe a novel approach to this problem as a first step towards creating a patient-specific, presurgical application for determining the optimal prosthesis procedure. Finite element analysis (FEA) and bone mineral density (BMD) calculations were performed with ten voluntary primary THR patients to estimate the status of their operative femurs before surgery. A compilation model of the press-fitting procedure was generated to define a fracture risk index (FRI) from incurred forces on the periprosthetic femoral head. Comparing these values to patient age, sex, and gender elicited a high degree of variability between patients grouped by implant procedure, reinforcing the notion that age and gender alone are poor indicators for prescribing prosthesis type. Additionally, correlating FRI and BMD measurements indicated that at least two of the ten patients may have received nonideal implants. This investigation highlights the utility of our model as a foundation for presurgical software applications to assist orthopedic surgeons with selecting THR prostheses.

Improving planning and post-operative assessment for Total Hip Arthroplasty

Total Hip Arthroplasty (THA) remains the gold standard of treatment for patients who suffer with a variety of hip-related pathological degeneration or trauma. These patients often exhibit significantly less post-operative pain and an increase in the range of motion of the joint, but there are still relatively common instances of debilitating periprosthetic complications that call into question the method for pre-surgical implant choice. Currently, there are two principal options for THA prostheses: cemented or non cemented. Utilizing the cemented procedure ensures a faster acquisition of adequate implant stability than with the non cemented procedure, but can eventually lead to an increased periprosthetic fracture risk. Non cemented prosthetic stems are more frequently revised within the first few years following THA due to periprosthetic fracture, but non cemented revision surgeries generally result in fewer complications than those of cemented implants. Surgeons typically rely on experience or simple patient metrics such as age and sex to prescribe which implant procedure is optimal, and while this may work for most patients, there is a clear need to analyze more rigoriously patient conditions that correlate to optimal post-THA outcomes. The results from the investigation reported herein indicate that an understanding of how the percent composition and quality of a patients quadriceps muscle in both healthy and operated legs may be a better indicator for prosthetic choice. Additionally, these data emphasize that the traditional metrics of age and sex inadequately predict changes in quadriceps composition and quality and thereby have comparatively minor utility in determining the patient-appropriate prosthetic type. Key Words: Total Hip Arthroplasty, Prosthetic selection, Muscle size and quality, Anatomical modeling, Surgical planning.

Effects of dietary intervention on serum lipids in factory workers.

OBJECTIVE To assess the effect of workplace-oriented dietary intervention on serum lipids. DESIGN A cohort study. Screening for blood lipids and subsequent dietary intervention performed at a ferro-alloy factory where all the workers have at least one meal per working day served by the factory kitchen. SETTING Employees at Grundartangi ferro-alloy factory, Iceland. SUBJECTS From 1 June 1989 to 1 June 1991, 155 workers participated in the screening and prevention programme. INTERVENTION Changing the food served by the kitchen to 200 workers by lowering the total number of calories and increasing the content of fibre and unsaturated fats in the diet. RESULTS The mean serum cholesterol was lowered from 6.64 to 6.09 mmol/l or by -8.28% for the whole group (p < 0.001) after two years of intervention. In the subgroups studied, serum high density lipoprotein (HDL) increased (p < 0.001), whereas serum low density lipoprotein (LDL) decreased. Cholesterol/HDL and LDL/HDL ratios were reduced. General dietary habits seemed to change in a favourable way. No significant change occurred in body mass index or smoking habits, and there was little effect on exercise habits. CONCLUSION Workplace dietary intervention seems to be effective in reducing cardiovascular risk factors. Information provided to the kitchen staff is of importance, as well as information given to the employees, in order to obtain beneficial results from dietary change.

CT and MRI Assessment and Characterization Using Segmentation and 3D Modeling Techniques: Applications to Muscle, Bone and Brain.

This paper reviews the novel use of CT and MRI data and image processing tools to segment and reconstruct tissue images in 3D to determine characteristics of muscle, bone and brain. This to study and simulate the structural changes occurring in healthy and pathological conditions as well as in response to clinical treatments. Here we report the application of this methodology to evaluate and quantify: 1. progression of atrophy in human muscle subsequent to permanent lower motor neuron (LMN) denervation, 2. muscle recovery as induced by functional electrical stimulation (FES), 3. bone quality in patients undergoing total hip replacement and 4. to model the electrical activity of the brain. Study 1: CT data and segmentation techniques were used to quantify changes in muscle density and composition by associating the Hounsfield unit values of muscle, adipose and fibrous connective tissue with different colors. This method was employed to monitor patients who have permanent muscle LMN denervation in the lower extremities under two different conditions: permanent LMN denervated not electrically stimulated and stimulated. Study 2: CT data and segmentation techniques were employed, however, in this work we assessed bone and muscle conditions in the pre-operative CT scans of patients scheduled to undergo total hip replacement. In this work, the overall anatomical structure, the bone mineral density (BMD) and compactness of quadriceps muscles and proximal femoral was computed to provide a more complete view for surgeons when deciding which implant technology to use. Further, a Finite element analysis provided a map of the strains around the proximal femur socket when solicited by typical stresses caused by an implant press fitting. Study 3 describes a method to model the electrical behavior of human brain using segmented MR images. The aim of the work is to use these models to predict the electrical activity of the human brain under normal and pathological conditions by developing detailed 3D representations of major tissue surfaces within the head, with over 12 different tissues segmented. In addition, computational tools in Matlab were developed for calculating normal vectors on the brain surface and for associating this information with the equivalent electrical dipole sources as an input into the model.

Multimodal Quantitative Assessment for Pre-operative Prosthesis Selection in Total Hip Arthroplasty

Total Hip Arthroplasty (THA) is one of the most utilized and successful orthopedic surgical procedures, and with increasing life expectancies in many populations worldwide, THA rates are projected to continue to rise accordingly. Despite the procedure’s rising prevalence, many periprosthetic fracture and unloading events are still reported. While many investigations have recently focused on potential assessment modalities and metrics to observe and characterize periprosthetic pathophysiology in THA patients, there is no extant, reliable method for the quantitative assessment of patients prior to THA. In most cases, respective opinions of the physicians involved dictate this decision, and procedures are therefore founded upon both the surgeon’s own experiences and qualitative generalizations based on suggested indicators of bone quality (gender, age, and qualitative assessment of CT images). There is therefore a great need for a quantitative, multimodal gold standard to securely choose the appropriate implant on a patient-specific basis. The objective of the re- search presented herein was to describe a novel assembly of such data from a 72-patient cohort as a first step towards eventually creating a patient-specific, presurgical application that orthopedic surgeons can utilize for determining the optimal THA prosthesis procedure. Here, we report the use of 3D soft tissue segmentation of the Rectus femoris, Vastus lateralis, and the Vastus medialis muscles, the use of 3D FEA to compute Fracture Risk Indices (FRI), the pre-operative measurement and user-friendly assembly of 11 gait parameters, and the measurement and analyses of EMG activation data – all of which are presented herein as a comprehensive patient report for a representative 60 year-old female patient.

Monitoring Bone Density from Patients Undergoing Total Hip Arthroplasty using Computed Tomography and 3D Modeling Techniques.

A clinical trial was carried out including 36 volunteer patients which underwent unilateral THA surgery (50% cemented, 50% uncemented). Changes in bone mineral density after the operation are monitored to assess the outcome of the procedure. We found age and gender only to be a modest predictor of bone quality for our THA patients and since poor bone quality is known to be associated with a risk of revision surgery it needs to receive a higher weight in our preclinical assessment when choosing between cemented and uncemented THA.

Epidemiology of spinal fractures and associated spinal cord injuries in Iceland

Study designA retrospective epidemiological study.SettingLandspítali University Hospital, Iceland.ObjectivesAssessment of epidemiological data and risk factors for traumatic spinal fractures (SFs) and associated spinal cord injury (SCI).MethodsA retrospective review of hospital admissions due to traumatic SFs during a 5-year period, with analysis of epidemiological parameters and occurrence of concomitant SCI. Patients with asymptomatic SFs and non-traumatic SCI were excluded.ResultsA total of 487 patients were diagnosed with a SF or 310 PMI (per million inhabitants), 42 of them (9%, 27 PMI) with an associated SCI. The mean age was 56 years, males were 57%. Falls were the leading cause of both SFs (49%) and SCIs (43%). Low falls (<1 m) caused SFs more often in elderly women (67%, mean age 77 years) and more than 96% were without SCI. Road traffic accidents (RTA) caused 31% of SFs and 26% of SCIs. Seat belts were not used in 20% of car accidents, but information was missing in 27%. Sports/leisure-related accidents caused SFs in 12% of cases, whereof horseback riding accidents were the most common (36%).ConclusionsSFs led to SCI in 9% of patients. Several risk factors were common for SFs and SCIs but two major differences were seen: SFs without SCI were most common in older women due to low falls, while the risk of a concomitant SCI increased in young patients, in males, in falls from high levels and when driving without using seat belts. Preventive efforts should therefore be directed towards these risk factors.

Patient-specific mobility assessment to monitor recovery after total hip arthroplasty

Total hip arthroplasty is a ubiquitously successful orthopedic surgical procedure, whose prevalence is rising worldwide. While many investigations focus on characterizing periprosthetic pathophysiology, the objective of our research is to develop and describe multi-metric assemblies as a first step toward creating a patient-specific mobility index that rehabilitators and orthopedic surgeons can utilize for prescribing their respective procedures. In total, 48 total hip arthroplasty patients (both cemented and uncemented) undergoing unilateral, primary surgery went through computed tomographic scans and gait analysis measurements both before and 1 year following their surgery. Altogether, the reported quantitative metrics include 11 spatial and temporal gait parameters, muscle density, and electromyography signals from the rectus femoris, vastus lateralis, and vastus medialis, and bone mineral density values from bioimage analysis around the implant stem. We found that measured parameters from a subgroup were sensitive to changes observed during patient recovery, implicating the predictive sensitivity of these patient conditions. Most post-operative gait parameters changed significantly, while electromyography data indicated few significant differences. Moreover, results from bioimage analyses indicate a general reduction of periprosthetic bone mineral density after 1 year, in association with increasing density of the quadriceps muscles. Furthermore, this work identifies which quantitative metrics undergo the greatest variation after total hip arthroplasty and demonstrates the clinical feasibility of a multimodal approach to mobility assessment that may ultimately support decision-making for post-surgical rehabilitation protocols.