Abstract
BACKGROUND
During revision hip arthroplasty, removal of a well-fixed, ingrown metal acetabular component may not be possible. Therefore, a new polyethylene liner can be cemented into the existing shell via the cement locking mechanism. We report the indications, technique, and results of cementing an acetabular liner into a well-fixed cementless acetabular shell.
PATIENTS AND METHODS
All patients were given informed consent to participate in this study, and the study was approved by our hospital institutional review board. Of 95 revision total hip arthroplasty (THA) between 2005 and 2014, five hips in 5 patients (4 female and a male) were operated by the cemented socket into metal shell technique. The mean age was 70.6 years (range, 59–84 years) (Table 1).
Operative Technique
All operations were performed with the patient in the lateral decubitus position and using a posterolateral approach without osteotomy of the greater trochanter. After removal of broken polyethylene liner, an all-polyethylene socket (manufactured by Kyocera Corporation, Osaka, Japan) was cemented in the metal shell. In case of small metal shell, bone bed around the shell were augmented by the use of an impaction morselized allogeneic bone grafting, and the socket was cemented both in the metal shell and in the bone bed (Fig. 1).
Postoperative Regimen
On the third postoperative day, the patients began a rehabilitation programmed by clinical path under the supervision of a physiotherapist. The use of crutches for ambulation was begun on the 10th to 14th postoperative day, with progressive weight-bearing as tolerated. Time to full weight-bearing was 3 to 4 weeks postoperatively.
RESULTS
All of the cemented sockets functioned well and there were no failure cases during average follow-up period of 5 years (range, 0.7–9.5 years).
DISCUSSION
Cementation of polyethylene liners into well-fixed metal shells has become a popular option during revision total hip arthroplasty (THA). Failure was always observed at the metal shell/cement interface whenever it did occur. The cement locking mechanism can be strengthened by roughening the backside of a smooth polyethylene liner to improve the cement-polyethylene interface, or by using an all-polyethylene acetabular component that is designed to be used with cement. Saw roughening of the polyethylene liner strengthens the poly-cement interface. We have used the all-polyethylene acetabular component with macrotexture anchoring form to cement fixation. To perform this procedure, an adequate shell diameter is necessary to accept an acetabular liner that will enable 2 mm of cement mantle around it. If an oversized polyethylene liner is cemented into a small acetabular metal shell, then there is the theoretical risk that the increased shear force will damage the cement locking mechanism, thus leading to failure of the construct. The case 1 in the current series, the hips had this situation, but no loosening occurred at final follow-up of 9.5 years postoperatively (Fig. 1).
CONCLUSIONS
We reported good results with the use of a “cemented cup in cementless cup” technique in revision THAs, although follow-up periods were short-term to midterm.
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