Aseptic loosening is the main complication after cemented hip arthroplasty. Therefore, it is very important to explore its pathogenesis so as to prevent the aseptic loosening.OBJECTIVE:
To observe the prosthesis stem and cement mantles retrieved at revision surgery, in combination with clinical and radiographic data, to explore the pathogenesis of aseptic loosening following hip arthroplasty.DESIGN, TIME AND SETTING:
Observation experiment. The study was performed at Baylor College of Medicine and the Institute of Orthopedic Research, Houston, USA between July 2002 and November 2003.PARTICIPANTS:
Thirty six patients undergoing cemented hip arthroplasty in Department of Orthopedics, Methodist Hospital at Houston were selected, including 20 males, 16 females, aged 38-92 years. There were 24 cases of aseptic loosening, 10 cases of infection, 1 of dislocation and 1 of fracture.METHODS:
The cemented femoral stems with complete cement mantles from the revision surgery of 36 cases were observed. The outer and inner surfaces of the cement mantle and the surface of the femoral component were carefully examined with stereo microscopy. The area, location and degree of surface abrasion and cement cracking were recorded by Gruen zone. The predominant displacement mode of each implant was classified as torsional, varus-bending, end-loading and/or collar loading.MAIN OUTCOME MEASURES:
The area, location and degree of surface abrasion and cement cracking.RESULTS:
Wearing of the stem and the matching surface of the cement mantle were found in all patients except two, independent of the duration of implantation. Regions of polishing of the outer surface of the cement mantle were observed in all implants revised for aseptic loosening, but only one of the components revised for other causes. The volume of cement removed by external abrasion of mantle was greater than that removed through stem contact by at least an order of magnitude. Cracks were visible within 13 cases of the mantles revised secondary to loosening, but none was found in infected or dislocated cases.CONCLUSION:
Early debonding and stem/cement motion appear to be a universal characteristic of cemented femoral stems. The osteolysis caused by particles generated from abrasive wearing of the outer surface of the cement mantle further accelerates wearing of cement mantle.