Uncemented Metal-on-metal Acetabular Component. Follow up of 112 Hips For a Minimum of 5 Years

Vassan UT, Sharma S, Chowdary KP, Bhamra MS.
Acta Orthopaedica 2007;78 (4):470-478

Metal-on-metal bearings have previously been shown to have less volumetric and linear wear than metal-on-polyethylene implants. This study reports medium term results with a metal-on-metal implant with uncemented cup. One hundred and twelve hips were reviewed retrospectively. All were treated with a Fitmore uncemented cup with a polyethylene insert containing a cobalt chrome metal articulation. Sixty six patients had a CF-30 cemented stem and 35 a thrust plate prosthesis.

Mean age at implantation was 56 years. Mean follow up was seven years. Radiographic assessment was performed and radiolucent lines in Delee and Charnley regions measured. Failure was defined as revision or progressive radiolucent lines of more than 2mm in all three zones. Survivorship analysis was performed for patients undergoing revision of acetabular component for whatever reason.

Results showed a mean pre-operative Harris hip score of 38 and a mean post-operative Harris hip score of 91. Five patients had a posterior dislocation, one requiring revision. Two patients developed deep infection. In one patient the cup dislodged and this was attributed to a superior acetabular defect. Radiographic assessment was completed in 91 patients. Non-progressive radiolucent lines in one or more De Lee zones were seen in 5 cups. One patient had progressive radiolucent lines of more than 2mm secondary to infection. Overall 4 cups were revised, one for dislodged cup, one for persistent groin pain, one for septic loosening and one for recurrent dislocation. With revision for all causes as an endpoint 82% had survived at ten years. With revision for aseptic loosening as endpoint 100% survived ten years.

They conclude that the Fitmore acetabular cup gives good medium term results as far as aseptic loosening is concerned.


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