Introduction

Numerous types of graft can be used for revision of anterior cruciate ligament (ACL) reconstruction. The goal of our studies was to analyze mid term outcomes of revision of anterior cruciate ligament reconstructions conducted by means of ipsilateral bone -patellar tendon -bone (B-PT-B) transplant.

Purpose of the study: The purpose of this study was to use weight-bearing radiographies to study the mobility of the polyethylene insert in relation to the femoral and tibial components of a total knee arthroplasty (TKA) with preservation of the posterior cruciate ligament and a mobile plateau with rotation and anterioposterior translation (INNEX^® Anterior-Posterior Glide, Zimmer).

Material and methods: A 3D kinematic study of the femoral and tibial component and the mobile insert was conducted on a series of 51 first-intention TKA using a computer-assisted matching system between 3D prosthetic models and the radiographic silhouette of the implants.

Results: At mean 23 months postoperatively, the poly-ethylene tibial insert exhibited an increase in its internal rotation during flexion. This rotation, knee extended, was limited to rotation between the insert and the tibial base. With increased flexion, there was an increase in the value and the portion of rotation involving the femoral component in relation with the mobile tibial insert.

Discussion: The degree of insert mobility has varied depending on the report. Certain authors have reported relatively limited mobility because of a minimally congruent superior surface allowing anteroposterior and mediolateral translation as the femur glided over the insert. Others report mobility of the mobile plateau in relation to the tibial base and minimal rotation of the femoral component. Rotation of the polyethylene insert in TKAs with a mobile plateau appears to be quite variable. With the LCS AP Glide prosthesis, anteroposterior translation of the mobile plateau was measured at a mean 5.6 mm (1–1.125 mm). Paradoxical anterior translation, rather than posterior translation, of the mobile plateau with flexion has been reported in a few patients.

Conclusion: The mobile plateau has exhibited progressive increase in internal rotation with flexion. We have concluded that the major part of the mobility occurs between the mobile plateau and the tibial base. However, with flexion, the femoral component increased its mobility over the plateau. During flexion, anteroposterior translation occurred between the femoral piece and the tibial insert, and between the tibial insert and the tibial base, but the direction of the translation of the mobile tibial insert appeared to be unpredictable with the non-constrained prosthesis used for this study.

Purpose: Dislocation of total hip arthoplasties is a sad reality. The incidence of this complication is estimated from 0.6 to 8%. Dislocation can be a single event that never recurs, but half of all dislocations will reoccur again. We analysed outcome after treating chronically unstable total hip arthroplasties using a double-mobility cup.

Material and methods: Between 1990 and 2000, we treated 42 cases of recurrent dislocation of total hip arthroplasties. Five were immediate, 33 early, and four late; five dislocations on the average. The prosthesis was implanted via the posterolateral approach for 36 patients. Thirteen patients treated in our unit had already had surgical treatment for chronic instability: 1 trochanteoplasty, 8 bone blocks, 5 restraining cups. A standing AP view of the pelvis was obtained in all patients before surgery to analyse shortening (gluteus medius insufficiency), cup tilt and anteversion, and stem lateralisation. Likewise a CT scan was performed systematically to analyse stem and cup anteversion. No position anomaly was found in 17 patients; at least one anomaly was found in the others. All patients were reoperated via the posterolateral approach. A double-mobility cup was implanted systematically without changing the stem.

Results: Among the 42 patients, we had two with recurrent dislocation, one in a neurologic patient and one in a patient with major anomalies in the position of the femoral component that was not changed. The incidence of recurrent dislocation was thus 4.75%.

Discussion: The therapeutic method used here can be compared with other solutions (trochanteroplasty, anti-dislocation crescent, antidislocation bone block, bipolar replacement). The double-mobility cup is particularly interesting for high-risk patients: neck fracture, tumour surgery, neurological disease, antecedent non-prosthetic surgery (dearthrodesis prosthesis). We advocate revision surgery after three dislocations.

Conclusion: The double-mobility cup appears to be a valid therapeutic option, both for the treatment and prevention of chronic instability of total hip arthroplasty.