Uncemented femoral stems. Studies on periprosthetic bone remodelling and prevention of bone loss in total hip arthroplasty.

Introduction Tapered uncemented femoral stems are popular implants in total hip arthroplasty (THA). They are easy to use and excellent long-term results have been reported for patients with primary osteoarthritis of the hip (OA). The disadvantages of these devices include post-operative periprosthetic bone loss, the clinical importance of which is still uncertain, and an increased risk of early periprosthetic fractures. These stems rely on initial primary stability to achieve biological fixation to bone. Poor bone quality, such as in patients with previous surgery of the hip or osteoporosis, is therefore generally considered to be a contraindication. Hypotheses We hypothesized that (1) femoral periprosthetic bone loss occurs after implantation of these devices and is related to the stem size used as well as the pre-operative bone mineral density (BMD) of the hip, (2) that femoral hip revision surgery using these implants is a reliable procedure with predictable mid-term results despite compromised proximal femoral bone stock prior to revision, (3) that a bisphosphonate will reduce the femoral periprosthetic bone loss and finally (4) that a tapered, uncemented, hydroxyapatite-(HA) coated femoral stem can provide durable fixation and good clinical outcome in elderly patients with osteoporotic fractures of the femoral neck. Materials and methods Two similar tapered uncemented HA-coated femoral stems were used in the studies. Bone mineral density (BMD) was measured using Dual-energy X-ray Absorptiometry (DXA), migration was assessed using radiostereometry (RSA) and Einzel-Bild-Röntgen-Analyse (EBRA). Clinical outcome was evaluated using the Harris hip score (HHS) and health related quality of life (EQ-5D) Results Study I In a retrospective study, a single cohort of 138 patients with a unilateral THA was examined 3 years after surgery with DXA. It was found that periprosthetic proximal bone loss was related to stem size. Patients with the larger stem sizes lost more bone than patients with smaller stems. Study II In a retrospective analysis of 60 patients, who were examined 6 years after uncemented femoral stem revision surgery due to aseptic loosening, we found a 95% survival rate of the stem and no cases of aseptic loosening. We also noted that all stems were stable according to radiological parameters and that the clinical outcome was acceptable. Study II In a randomized, double-blind, placebo-controlled trial of 73 patients with hip OA, risedronate was given once weekly for 6 months following THA surgery. Risedronate reduced the proximal femoral bone loss by 7% up to 12 months postoperatively. In both groups, patients with a low pre-operative BMD lost significantly more bone than patients whose initial BMD was high. Study IV In a prospective single-cohort study of 50 cognitively intact elderly patients operated with a new HA-coated stem due to a displaced FNF, we found stable stems after 3 months. We also found a continuous decrease in BMD around the stems up to 2 years after surgery. Patients with osteoporosis lost more bone than patients with a normal BMD. Conclusions Periprosthetic bone loss after THA can be reduced with bisphosphonate treatment. Future studies on prevention of bone loss after THA should focus on patients who have a low pre-operative BMD of the hip. An uncemented, tapered HA-coated stem can be used successfully for elderly patients with osteoporotic fractures of the femoral neck. Further studies are needed to ascertain whether uncemented femoral stems are superior, equivalent or inferior to cemented stems in the treatment of FNFs in the elderly

Unsupervised Contact Learning for Humanoid Estimation and Control

This work presents a method for contact state estimation using fuzzy clustering to learn contact probability for full, six-dimensional humanoid contacts. The data required for training is solely from proprioceptive sensors - endeffector contact wrench sensors and inertial measurement units (IMUs) - and the method is completely unsupervised. The resulting cluster means are used to efficiently compute the probability of contact in each of the six endeffector degrees of freedom (DoFs) independently. This clustering-based contact probability estimator is validated in a kinematics-based base state estimator in a simulation environment with realistic added sensor noise for locomotion over rough, low-friction terrain on which the robot is subject to foot slip and rotation. The proposed base state estimator which utilizes these six DoF contact probability estimates is shown to perform considerably better than that which determines kinematic contact constraints purely based on measured normal force.Comment: Submitted to the IEEE International Conference on Robotics and Automation (ICRA) 201

The Ringloc liner compared with the Hexloc liner in total hip arthroplasty

The aim of this study was to compare the 10-year survival rate, pelvic osteolysis frequency and linear head penetration rate of the Hexloc and Ringloc liners used together with a partially threaded porous and hydroxyapatite coated cup and the Bi-Metric uncemented femoral stem. The 15-year results for the cup with the Hexloc liner are also reported. We included 332 consecutive hips (166 Hexloc and 166 Ringloc) on 281 patients in the study. Revisions of prosthesis components were recorded and pelvic osteolytic lesions were assessed using radiographs and computed tomography. The linear head penetration rate was measured using the Martell method. The 10-year survival rate of the liner with revision due to liner wear and/or osteolysis as endpoint was 88% for the Hexloc liner and 98% for the Ringloc liner. The 15-year survival rate of the Hexloc liner was 67%. Pelvic osteolysis was found in 27% of the Hexloc and 19% of the Ringloc hips. After 15 years, 53% of the Hexloc hips had developed an osteolytic lesion. The linear head penetration rate was 0.16 mm/year for the Hexloc liner and 0.12 mm/year for the Ringloc liner. This paper is the first to describe the rapidly deteriorating survival up to 15 years with the old generation gamma-in-air sterilized polyethylene used in Hexloc liners. The newer Ringloc liner with the ArCom™ polyethylene has superior clinical results but a linear wear rate and frequency of osteolytic lesions that is higher than expected

Пойкилодермия пигментная сетчатая Сиватта: клинический случай

КОЖНЫЕ БОЛЕЗНИМЕЛАНОЗСиватта пойкилодерми

Increased Long-Term Cardiovascular Risk After Total Hip Arthroplasty: A Nationwide Cohort Study

Abstract Total hip arthroplasty is a common and important treatment for osteoarthritis patients. Long-term cardiovascular effects elicited by osteoarthritis or the implant itself remain unknown. The purpose of the present study was to determine if there is an increased risk of late cardiovascular mortality and morbidity after total hip arthroplasty surgery. A nationwide matched cohort study with data on 91,527 osteoarthritis patients operated on, obtained from the Swedish Hip Arthroplasty Register. A control cohort (n = 270,688) from the general Swedish population was matched 1:3 to each case by sex, age, and residence. Mean follow-up time was 10 years (range, 7–21). The exposure was presence of a hip replacement for more than 5 years. The primary outcome was cardiovascular mortality after 5 years. Secondary outcomes were total mortality and re-admissions due to cardiovascular events. During the first 5 to 9 years, the arthroplasty cohort had a lower cardiovascular mortality risk compared with the control cohort. However, the risk in the arthroplasty cohort increased over time and was higher than in controls after 8.8 years (95% confidence interval [CI] 7.0–10.5). Between 9 and 13 years postoperatively, the hazard ratio was 1.11 (95% CI 1.05–1.17). Arthroplasty patients were also more frequently admitted to hospital for cardiovascular reasons compared with controls, with a rate ratio of 1.08 (95% CI 1.06–1.11). Patients with surgically treated osteoarthritis of the hip have an increased risk of cardiovascular morbidity and mortality many years after the operation when compared with controls

Measurement of migration of a humeral head resurfacing prosthesis using radiostereometry without implant marking: An experimental study

Today, the shoulder joint is the third most commonly replaced joint after the hip and knee joints and the incidence is increasing. In Sweden, 1863 primary Shoulder Arthroplasties and 195 revisions were performed in 2017. The most common diagnoses are Osteoarthritis and irreparable tears of the rotator cuff, with or without arthropathy, often referred to as cuff tear arthropathy. Different Shoulder Arthroplasty (SA) concepts include anatomical total shoulder arthroplasty (TSA), hemiarthroplasty (HSA) and reversed shoulder arthroplasty, but also humeral head resurfacing (HHR) and stemless arthroplasties. All concepts offer pain relief, improvement of function and in quality of life for the different diagnoses. Unfortunately, there are sometimes complications after SA. They involve periprosthetic joint infection, humeral and glenoid fractures, stress shielding, loosening of the glenoid and humeral component but also glenoid erosion and cuff rupture. Some of these complications are most common within 1 year after operation, some after several years, both may lead to a revision. This, together with the fact that new designs of implants and methods of fixation of SA continues to develop, stresses the importance of continuous monitoring of implant survival and follow-up. The overall aim of this thesis was to describe clinical examples of different methods to assess the outcome after Shoulder Arthroplasty. The most common methods are clinical examination, radiographic assessment, Patient Reported Outcome Measure (PROM), National Joint registries, where revisions are an important outcome, but also Clinical Trials. All of these methods are used in one or more of the 4 papers in this thesis and shows the complexity of the topic and the practical work. In paper I we used Radio Stereometric Analysis (RSA) in an experimental set-up and concluded that marker-free RSA can be used for a humeral head resurfacing arthroplasty. In paper II we used data from the Swedish Shoulder Arthroplasty Registry (SSAR) with PROM and revisions to conclude that age is the only factor that affects revision when comparing HSA and HHR. Paper III is a long-time follow-up of a Randomized controlled study where we used radiological assessment, PROM and revisions. The conclusion was that both TSA and HSA develop severe radiological changes 10 year after primary operation. Paper IV is a prospective RSA cohort study where we also evaluated PROM and revisions. The conclusion is that HHR seems to obtain a secure fixation in the humerus, after an initial migration. But also that the prostheses shows continuous glenoid wear. The main conclusion of this thesis is that patient’s operated with SA needs continuous monitoring and several methods may be used to evaluate the outcome