Aims

The purpose of this study was to analyse the biomechanics of walking, through the ground reaction forces (GRF) measured, after first metatarsal osteotomy or metatarsophalangeal joint (MTP) arthrodesis.

Introduction: Many publications have already shown the great interest of dual-mobility concept which significantly reduces the rate of prosthetic dislocation and thus find its place for patients at high risk of post operative instability. The aim of our study is to evaluate the prevalence of prosthetic instability in revision total hip arthroplasty using a dualmobility cup.

Materials and Methods: Our multicentric series consists of 163 revision total hip arthroplasties performed between may 1999 and may 2004. The mean age at revision was 70 years and the mean follow-up period was 56 months.

The primary etiology necessitating revision is aseptic loosening.

According to the SOFCOT classification, the acetabular deficiency was grade IV 9 times, grade III 47 times, grade I or II 107 times.

All the implanted acetabular components are SERF dual-mobility implants. This system consists of a metal back which can be HA-coated and Press Fit or cemented in a Kerboull cross or in a Novae Arm. The mobile-bearing insert which allows a dual articulation between the head and the metal back is of polyethylene.

We implanted 119 HA-coated press-fit cups and cemented 44 dual-mobility cups in a support ring or in a Kerboull cross.

Results: The mean Merle d’Aubigné and Postel score is 14,1 at the last follow-up and 4,2 in the preoperative period.

We reported 8 complications: 6 early dislocations and 2 acetabular revisions for secondary mobilisation of the cup.

Discussion: According to Huten’s 1996 SOFCOT teaching conference, this rate ranges between 2 and 5% and we have already published a series of 106 dual-mobility with no dislocation at a 10 year follow-up period.

With 4% dislocations at a mean follow-up of 56 months, the dual-mobility cup seems to provide high stability in revision hip surgery when other factors such as muscular deficiency, extended synovectomies, difficult implant placement, encourage an uncertain postoperative prosthetic stability.

These results have to be compared to those of other systems such as constrained acetabular cups or tripolar cups.

Conclusion: This is why dual-mobility remains an efficient and reliable choice to avoid prosthetic dislocation in revision surgery. Moreover, we encourage the use of dual-mobility cup in any high risk situation in terms of post-operative instability such as for old or neurological patients.

Purpose: We report a prospective series of 70 explantations of the femoral pivot via a transfemoral approach required due to septic and aseptic loosening.

Material and methods: Aseptic loosening was observed in 61 cases, septic loosening in 9. The extended posterolateral approach was used to remove the implant in all cases and a femoral segment (Wagner method). Reconstruction of the femur was achieved with locked stems without cement (65 patients) or a long stem without cement (1 patient). Reimplantation was not attempted in four patients. Bone grafts were not used. Mean follow-up in this series was 3.5 years. The PMA score was used for clinical assessment. Radiographic assessment of segment healing and bone regrowth around the implant was done by measuring the cortical index.

Results: We observed a significant gain in the PMA score of more than 9 points. We had one intraoperative fracture of the femoral segment and two episodes of early dislocation. All femoral segments healed. Osteogenesis failed in three cases with fracture of the locking screw. There were also two cases of late fracture of the trochanter. At one year, bone regrowth measured from the cortical index was greater than 10% on the average.

Discussion: We discuss the characteristic features of this type of surgery in comparison with other solutions for femoral revision: operative time, blood loss, choice of implants, later weight bearing. We also found that this technique allows easier implant removal and more effective cleaning of the femoral shaft in the event of septic surgery with fewer cases of intraoperative accidents (malposition, femoral fractures). We were able to demonstrate that this method of femur reconstruction without bone graft provides a stimulation of osteogenesis in the floating segment. Stem locking provides primary stability in 100% of the cases. Secondary stability was achieved in 90% due to the quality of the newly formed bone.