[Complications with the acetabular cup in the CLS total hip joint endoprosthesis]

Abstract

Purpose of the study: The aim of the study is to present complications of acetabular component of CLS total hip replacement and their solution.

Material: In the period of 1986-1999 in total 219 cementless CLS total hip replacements and 2012 CLS cups in hybrid replacements were implanted at 1st Orthopaedic Department in Brno--primary surgeries--2026, revision surgeries--205. Of 2231 CLS cups we encountered 25 complications requiring a revision surgery (1.1% of all cases): 2 cases of the broken metal shell, 3 cases of cup penetration into pelvis, 4 cases of cup migration, 5 cases of aseptic loosening, 5 cases of dislocations and 6 cases of deep infections.

Method: Broken metal shells were treated by Müller and Eichler ring, cancellous bone grafting with a cemented PE cup. Penetration of cups into pelvis were managed by Girdlestone procedure. Migration of the cup was solved in 1 case by Burch-Schneider ring, other cases with a good function were left in situ. Aseptic loosening with defects of acetabulum was solved by means of metal rings, cancellous bone grafting and cemented PE cup. Dislocation was managed by adjustment of CLS cup in the correct position, longer or closed reduction and orthesis. In infections a two-step procedure was used with a repeated application of CLS cup, Prostalac technique or Girdlestone procedure.

Results: The results of cases solved by means of acetabular metal rings, cancellous bone grafting and cemented PE cup are after 2-5 years good. The patients are capable of full weight bearing and have no pains, Harris score is 83-89 points. The radiograph shows in all but one patients a stable implant without radiolucent interface. The function of all patients with dislocations of CLS implant is now very good or good. No recurrence was recorded in patients with infections. The function of the hip with Girdlestone procedure is in 2 patients low--Harris score is 58 and 63 points. Harris score in patients after a two-step revision with a repeated application of CLS cup is 80-89 points.

Discussion: In cases of the broken metal shell there occurred a proximolateral defect of the acetabular bone as a result of development dysplasia of the hip. The cup had inadequate circumferential support. The cases of cup penetration into pelvis are connected with a marked primary or subsequent deficiency of the acetabular floor, excessive reaming of subchondral bone and osteoporosis. Revision surgery with a metal ring requires a careful extensive cancellous bone grafting with a complete filling of all defects, support of the ring by the bone and development of a stable bone-ring-cemented PE cup composite. The best results in infections were achieved by a two-step revision with a repeated application of CLS cup.

Conclusion: Of the total number of 2231 implanted CLS cups in the period of 1986-1999 only 25 complications were recorded requiring a revision surgery, i.e. 1.1% of all cases. Complications relating to the cup were treated in case of acetabular defects by means of metal acetabular rings, cancellous bone grafting and cemented cups. In infections a two-step procedure was used with a repeated application of CLS cup, Prostalac technique or Girdlestone procedure.