Abstract
The purpose of this study was to present our experience with femoral neck fractures that occurred after metal-on-metal hybrid surface arthroplasty and to assess their causation.
Materials and Methods: A series of 600 metal-on-metal surface arthroplasties was performed from late 1996 to early 2003 by the primary author. Failures during this period were assessed radiographically and with implant retrieval analysis to determine the cause of failure. There were five femoral neck fractures in this series (0.83%).
In addition, a review of the femoral neck fracture cases identified from the Conserve+ Multi-Center IDE was performed (19 femoral neck fractures in 1203 cases, 1.6%).
Results: Lead Author Series: Four of the five fractures occurred at the component–neck junction in the first five months after surgery (average three months). All were associated with a traumatic episode but they also had structural and or technical risk factors, which weakened the constructs. The most important technical deficiency was failure to cover all of the reamed bone with the component in three of the five. One fracture was associated with histological changes consistent with osteonecrosis of the head in a case of overpenetration of cement in very soft bone.
Multi-Center IDE: Additional risk factors were identified among which impingement of the neck with the acetabular component, notching of the lateral femoral neck cortex, and leaving the femoral component proud (not completely seated).
Conclusion: It is important to avoid or at least minimize notching the femoral neck by performing the cylindrical reaming at the recommended angle of 140° and to stop reaming before the reamer touches the lateral cortex. Osteophytes should be judiciously removed only if there is a notable impingement when the hip is at 90° of flexion and internally rotated. We believe that understanding the factors that contribute to femoral neck fracture after surface arthroplasty may reduce the already low incidence of this mode of failure.
Theses abstracts were prepared by Professor Roger Lemaire. Correspondence should be addressed to EFORT Central Office, Freihofstrasse 22, CH-8700 Küsnacht, Switzerland.
