Abstract
Introduction
Dislocation of an uncemented total hip replacement (THR) can cause damage to the femoral hear, when it passes through the rim of metal acetabular shell. This can lead to metal transfer on the surface of the head or chipping of bulk head material. Although dislocation is one of most common complications in total hip arthroplasty (THA), little is known if causes any further damage to the articulating surface of ceramic heads in long term observations.
Aim of the study
To evaluate, if dislocations of THR with ceramic on polyethylene bearing causes structural damage to the articulating surface of the femoral head in a follow-up of minium 10 years
Materials and methods
MATERIAL
This study included four groups of third generation (CeramTec Biolox forte) ceramic femoral heads with a diameter of 28 mm:
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8 heads dislocated in the first year(managed nonsurgically) where implants functioned for at least 10 years
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9 heads removed within 12 months after implantation because of recurrent dislocations
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11 heads retrieved after a minimum of 10 years from hips where no dislocation occurred
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8 unused heads
METHODS
Surface topography of retrieved heads was evaluated using Scanning Electron Microscopy with Energy – Dispersive X-ray Spectroscopy; roughness measurements were performed in three directions (0, 45,90 degrees) over a distance of 1,5 mm using a contact profilometer.
Results
On the dislocated heads dark stained scratches were present in the lower, non weight-bearing part; SEM studies demonstrated presence of multidirectional smear-like metal deposits (Fig 1) with a small number of chipped ceramic grains. EDS analysis of scratches indicated presence of Ti or Ti,Al,V - dependant on construction alloy of the acetabular component. There were no differences in morphology of scratched areas between heads removed within a few months after dislocation and components retrieved after at least 10 years.
Interestingly SEM findings within the weight-bearing part of dislocated heads were identical within corresponding areas of femoral heads articulating for 10 or more years as well as unused components (Fig 2). In these areas we observed a small number of pinholes and scratches, which we believe resulted from machining and subsequent polishing.
Roughness measurements were consistent with SEM findings (Table 1). Areas covered by metal deposits had a significantly higher roughness compared to undamaged area. We did not observe statistical differences between roughness of weight-bearing area in all examined groups.
Conclusions
Our study indicates, that dislocation of femoral head in a uncemented total hip replacement with ceramic on polyethylene bearing results in contained damage in the area which contacted the metal acetabular shell. Dislocation does not affect the weight-bearing surface of the head, even in a long-term follow-up
This study was financed by a National Science Centre grant No. 2012/05/D/NZ5/01840
