The development of extendable prostheses has permitted limb salvage surgery in paediatric patients with bone tumours in proximity to the physis. Prostheses are extended to offset limb length discrepancy as the child grows. Aseptic loosening (AL) is a recognised complication. The implant stem must fit the narrow paediatric medullary canal and remain fixed while withstanding growth and increasing physical demands. Novel designs incorporate a hydroxyapatite (HA) coated collar that manufacturers claim improves bony ongrowth and stability, providing even stress distribution in stem and shoulder regions and providing a bone-implant seal, resulting in decreased AL and prolonged survival. This study aims to assess whether there is a relationship between bony ongrowth onto a HA collar and AL. Hypothesis: Bone ongrowth onto the HA collar of extendable prostheses is associated with more stable fixation and less AL despite patient growth. Retrospective review of 51 primary partial femoral extendable prostheses implanted over 12 years from 1994–2006 (followed up to death at a mean of 2.5±2.2 years or last clinical encounter at a mean of 8.6 years) and 24 subsequent revisions, to ascertain failure rate and mode, together with a cohort study reviewing bony ongrowth onto the HA coated collar in 10 loose and 13 well fixed partial femoral, humeral and tibial implants. Patient growth was measured as a change in bone:implant-width ratio.Background/Aims
Methods
Both from experimental studies and the large arthroplasty registries there is evidence that bacteria are more often involved in implant loosening then is currently reported. To further elucidate this potential problem, the current study investigated the hypothesis that many total hip arthroplasty revisions, classified as aseptic, are in fact low-grade infections missed with routine diagnostics. In 7 Dutch hospitals, 176 patients with the preoperative diagnosis of aseptic loosening of their total hip arthroplasty were enrolled. From each patient, the preoperative history was obtained. During surgery, between 14 and 20 tissue samples were obtained for routine culture, pathology analysis and broad range 16S rRNA PCR with reverse line blot hybridization (PCR-RLB). Samples were taken from the (neo-) capsule and acetabular and femoral interface tissue. Cultures were performed locally according to similar protocols. One specialized pathologist, blinded for all other results, analyzed all pathology samples. The PCR-RLB analysis was performed centrally, using a technique previously validated for orthopedic use. Patients were classified as not infected, suspect for infection or infected, according to strict, predefined criteria. Each patient had a follow-up visit after 1 year.Background
Methods
