| Abstract / Summary | Total hip arthroplasty (THA) has improved the life of millions of patients with debilitating conditions of the hip such as osteoarthritis (OA). The positive effect on quality of life and function has led THA to become one of the most frequently performed surgical procedures, a frequency that is projected to rise, especially among young patients. Although the survival of THAs is constantly improved, giving a long enough timeline all THA will eventually wear, break, loosen etc. 25 years after surgery 58-74% of all patients still have their primary THA. However, the survival of THAs is the lowest among young patients compared to all other age groups. Although revision surgery is possible the functional outcome is inferior compared to primary surgery and young patients risk undergoing multiple revisions in their lifetime. This is problematic as young patient likely have the highest demand for functional outcome compared to older patients. To improve the survival of THAs in young patient different bearings have been used. At the turn of the millennium and the following decade, metal-on-metal (MoM) THAs were used, but later showed inferior survival, tendency to metal ion release into the blood and formation of adverse reaction the metal debris (ARMD) in the form of pseudotumors (PTs). The MoM bearings are almost no longer used, and most countries have implemented lifelong follow-up programs in patients with MoM where metal ion levels and radiological findings such as PTs can lead to revision surgery.
Study I
We aimed to investigate the sensitivity and specificity when an orthopedic surgery resident after a short training program performed US scans on patients with THA to detect PTs compared with MARS-MRI as a gold standard. Secondly, we investigated the sensitivity and specificity for US to detect PTs in obese and non-obese patients. We examined 205 patients with 50 pseudotumors on MARS-MRI. We found that the orthopedic resident had a good sensitivity and specificity in both obese and non-obese patients.
Study II
Our aim was to investigate how patient-reported outcome (PRO), metal ion blood levels and ARMD changes over time in hip resurfacing arthroplasties (HRA), MoM and metal-on-polyethylene (MoP) THA at 4 and 13 years. We included 98 hips arthroplasties in 78 patients. The prevalence of PT declined in HRA and MoM THA but increased in MoP THA over time. New PTs were just as common in HRA and MoP THA. Blood levels of cobalt and chromium was higher in HRA and MoM THA compared to MoP THA, but were stable over time. No difference in PROM scores was found between HRA, MoM and MoP THA at first or second examination. Blood levels of cobalt and chromium or PROM scores were not associated with the presence of PTs. In perspective, surgeons should be cautious with using the presence of long-term pseudotumors as revision causes.
Study III
Our aim was to compare the survival and hazard ratio (HR) of revision of primary stemmed cementless THA with MoM, ceramic-on-ceramic (CoC) and ceramic-on-highly crosslinked polyethylene (CoXLP) to that of metal-on- highly crosslinked polyethylene (MoXLP) bearings in patients aged 20-55 years diagnosed with osteoarthritis or childhood hip disorders. We included 21,594 patients from the Nordic Arthroplasty Register Association dataset. MoXLP had higher survival and lower HR for revision than MoM - mainly for revision causes we cannot specify. MoXLP, CoC and CoXLP had similar survival and HR for revision, but longer follow-up is needed to investigate whether CoC and CoXLP have better, equal or worse performance as both CoC and CoXLP tended to have increased HRs. In perspective, we currently believe that either MoXLP, CoC or CoXLP could be the standard bearings in patients aged 20-55 years.
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