Hip prosthetic loosening and periprosthetic osteolysis:A commentary

Prosthetic loosening and periprosthetic osteolysis have been debated for decades,both in terms of the timing and nature of the triggering events.The hypothesis of wear-particle-induced loosening states that wear particles cause a foreign-body response leading to periprosthetic osteolysis and ultimately to late prosthetic loosening,i.e.,that the osteolysis precedes the loosening.The theory of early loosening,on the other hand,postulates that the loosening is already initiated during or shortly after surgery,i.e.,that the osteolysis is secondary to the loosening.This commentary focuses on the causal relationship between prosthetic loosening and periprosthetic osteolysis.

Hip prosthetic loosening:A very personal review

Hip prosthetic loosening is often difficult to detect at an early stage,and there has been uncertainty for a long time as to when the loosening occurs and thus to the basic causes.By comparing different diagnostic methods,we found that loosening is best defined as prosthetic migration and measured by radiostereometric analysis.Convincing evidence indicates that poor interlock,poor bone quality,and resorption of a necrotic bone bed may initiate loosening during or shortly after surgery;this forms the basis of the theory of early loosening.Biomechanical factors do affect the subsequent progression of loosening,which may increase subclinically during a long period of time.Eventually,the loosening may be detected on standard radiographs and may be interpreted as late loosening but should to be interpreted as late detection of loosening.The theory of early loosening explains the rapid early migration,the development of periprosthetic osteolysis and granulomas,the causality between wear and loosening,and largely the epidemiology of clinical failure of hip prostheses.Aspects discussed are definition of loosening,the pattern of early migration,the choice of migration threshold,the current understanding of loosening,a less exothermic bone cement,cemented taper-slip stems,a new exciting computed tomography-based technique for simpler implant migration studies,and research suggestions.

Outcome and revision rate of uncemented humeral head resurfacing:Mid-term follow-up study

BACKGROUND Glenohumeral osteoarthritis(OA)is a common cause of pain and disability affecting nearly a third of the world’s population over 60 years of age.As in other joints,shoulder arthroplasty appears to be the most effective treatment.The implant design has evolved during time transitioning to shorter humeral stem lengths or even stemless components.AIM To evaluate the medium-term outcome and survival of a cementless humeral head resurfacing(HHR)in a group of patients affected with OA or avascular necrosis.METHODS This is a retrospective study of prospectively collected data using HHR in 23 patients(15 female and 8 male)after a 7.4 year follow-up.The collected data included clinical and radiographical evaluation.The Constant score,the visual analogue scale,and a clinical evaluation of range of motion were registered preand postoperatively.Fifteen patients affected with OA(2 cases of mild,6 moderate,and 7 severe)and 10 with avascular necrosis(stage III according to Cruess classification)were enrolled.X-rays were evaluated to detect loosening signs,degenerative changes,and superior humeral head migration.Magnetic resonance preoperatively was also performed to assess the rotator cuff status.Tendon integrity was mandatory to implant the HHR.RESULTS In total,19 patients(21 shoulders)completed the follow-up.Data on 4 shoulders,in 4 patients,were lost because of prosthesis failure.The global revision rate was 16%.A statistically significant improvement in the mean Constant score,visual analogue scale,and range of motion have been reported.No signs of loosening were registered,while in 12 cases a glenoid erosion was found.The osteophytes appeared 7 times on the humeral side and 12 on the glenoid.Superior humeral migration was recorded in only 1 case.CONCLUSION HHR remains a reasonable option in patients with an intact rotator cuff for the treatment of OA and avascular necrosis.

Radiographic and clinical analysis of cementless acetabular fixation in total hip arthroplasty

Objective： To investigate the factors affecting the fixation, loosening and therapeutic effect of cementless acetabular prosthesis through following up the patients with total hip arthroplasty clinically and radiographically. Methods： From February 1998 to May 1999, 139 patients （148 hips） underwent total hip arthroplasty with cementless acetabular prosthesis in our department. In this study, the clinical therapeutic effect and the anteroposterior radiographs of the pelvis and anteroposterior and lateral radiographs of the hips of 109 patients （116 hips） made before operation, at 1 week operation and annually 3, 6, and 12 months after thereafter were analyzed retrospectively. The clinical therapeutic effects were evaluated with Harris hip score. Radiographs were used to observe the position of prostheses and the bone changes around the implant, and to measure the wearing speed and direction of the acetabular cup. All evaluations were made by an independent examiner who did not participate in the operation. The patients were followed up for 5-6 years. Results- The mean Harris score was 44 points （ range, 10-70 points ） before operation, but it increased to 92.4 points （ range, 80-100 points） at the latest review after operation, which was significantly higher than that before operation （P 〈 0.05 ）. No acetabular component was revised because of infection or aseptic loosening. And no acetabular component migrated. There was no revision of fixed acetabular component because of pelvic osteolysis secondary to polyethylene wear. The mean linear wear rate was 0.15 mm per year. All the acetabular prostheses were classified as stable on the radiographs. Conclusions ： In terms of fixation, total hip arthroplasty with cementlcss acetabular components was successful. Although there is no aseptic loosening and a low incidence of osteolysis at the latest follow-up evaluation, polyethylene wear cannot be avoided and can lead to expansile osteolysis near the cups. This kind of osteolysis usually had no obvious clinical symptoms but it can be diagnosed early on radiographs. So radiographical follow-up for cementless acetabular components is very important.