Aims. Femoral stems with exchangeable (modular) necks were introduced
to offer surgeons an increased choice when determining the version,
offset and length of the femoral neck during total hip arthroplasty
(THA). It was hoped that this would improve outcomes and reduce
complications, particularly dislocation. In 2010, the Australian Orthopaedic
Association National Joint Replacement Registry (AOANJRR) first
reported an increased rate of revision after primary THA using femoral
stems with an exchangeable neck. The aim of this study was to provide
a more comprehensive up-to-date analysis of primary THA using femoral
stems with exchangeable and fixed necks. Materials and Methods. The data included all primary THA procedures performed for osteoarthritis
(OA), reported to the AOANJRR between 01 September 1999 and 31 December
2014. There were 9289 femoral stems with an exchangeable neck and
253 165 femoral stems with a fixed neck. The characteristics of
the patients and prostheses including the bearing surface and stem/neck
metal combinations were examined using Cox proportional hazard ratios
(HRs) and Kaplan-Meier estimates of survivorship. . Results. It was found that prostheses with an exchangeable neck had a
higher rate of revision and this was evident regardless of the bearing
surface or the size of the femoral head.
This study aimed to characterise and qualitatively grade the severity of the corrosion particles released into the hip joint following taper corrosion. The 26 cases examined were CoC/ABG Modular (n = 13) and ASR/SROM (n = 13). Blood serum metal ion levels were collected before and after revision surgery. The haematoxylin and eosin tissue sections were graded on the presence of fibrin exudates, necrosis, inflammatory cells and corrosion products. The corrosion products were identified based on visible observation and graded on abundance. Two independent observers blinded to the clinical patient findings scored all cases. Elemental analysis was performed on corrosion products within tissue sections. X-Ray diffraction was used to identify crystalline structures present in taper debris.Objectives
Methods
Dislocation after Total Hip Replacement (THR) remains the second most common reason for revision in the Australian Orthopaedic Association National Joint Replacement Registry (AOA NJRR) and is the most common reason out to 3 years post operatively. There are many causes and associations of dislocation, including patient behaviour and (often unrecognized) spinal pathology leading to adverse component orientation. Femoral ball head size along with the head:neck ratio and the head:cup ratio are all important. Data from the AOA NJRR demonstrates a lower revision rate for dislocation with larger head sizes in all bearing surface combinations. Data from the AOA NJRR confirms that the revision rate for replaced hips using non cross-linked polyethylene cups increases along with the head size, but this is not seen with cross-linked polyethylene cups. THR using cross-linked polyethylene has a lower revision rate than THR using non cross-linked polyethylene, this difference is evident after only 3 months and the difference increases with time. The 12 year Cumulative Revision Rate (CRR) is 5.3% compared to 10.1%. This lower rate of revision is due to a reduced revision rate for both dislocation and loosening/lysis. The revision rate for dislocation at 1 year was 0.4% for THR with cross-linked polyethylene and 0.7% with non cross-linked polyethylene. Head sizes of 32mm and greater were used in 56.5% of THR with cross-linked polyethylene but only 12.7% of those with non cross-linked polyethylene. There was no difference in the revision rate for dislocation when head sizes of 32mm and less were compared, the difference was due to the higher proportion of larger head sizes used with cross-linked polyethylene. However there are reasons why the benefits of larger femoral ball heads may not increase with increasing head size, this is chiefly because of altered cup subtended angles (and femoral head offset) geometries incorporated into cup and liner designs, especially the ceramic on ceramic bearings. Larger head sizes may also increase the risk of taper disease, especially with smaller tapers and softer metal alloys.
