The aim of this study was to determine the stability of a new
short femoral stem compared with a conventional femoral stem in
patients undergoing cementless total hip arthroplasty (THA), in
a prospective randomized controlled trial using radiostereometric
analysis (RSA). A total of 53 patients were randomized to receive cementless
THA with either a short femoral stem (MiniHip, 26 patients, mean
age: 52 years, nine male) or a conventional length femoral stem
(MetaFix, 23 patients, mean age: 53 years, 11 male). All patients
received the same cementless acetabular component. Two-year follow-up
was available on 38 patients. Stability was assessed through migration
and dynamically inducible micromotion. Radiographs for RSA were
taken postoperatively and at three, six, 12, 18, and 24 months.Aims
Patients and Methods
A possible solution for the management of proximal femoral bone
loss is a modular femoral endoprosthesis (EPR). Although the outcome
of EPRs in tumour surgery has been well described, the outcome of
their use in revision hip surgery has received less attention. The
aim of this study was to describe the outcome of using EPR for non-neoplastic
indications. A retrospective review of 79 patients who underwent 80 EPRs for
non-neoplastic indications was performed, including the rates of
complication and survival and the mean Oxford Hip Scores (OHS),
at a mean of five years post-operatively. The mean age at the time
of surgery was 69 years (28 to 93) and the mean number of previous operations
on the hip was 2.4 (0 to 17). The most common indications for EPR
implantation were periprosthetic joint infection (PJI) (n = 40),
periprosthetic fracture (n = 12) and failed osteosynthesis of a
proximal femoral fracture or complex trauma (n = 11).Objectives
Methods
Pseudotumours are a rare complication of hip resurfacing. They are thought to be a response to metal debris which may be caused by edge loading due to poor orientation of the acetabular component. Our aim was to determine the optimal acetabular orientation to minimise the risk of pseudotumour formation. We matched 31 hip resurfacings revised for pseudotumour formation with 58 controls who had a satisfactory outcome from this procedure. The radiographic inclination and anteversion angles of the acetabular component were measured on anteroposterior radiographs of the pelvis using Einzel-Bild-Roentgen-Analyse software. The mean inclination angle (47°, 10° to 81°) and anteversion angle (14°, 4° to 34°) of the pseudotumour cases were the same (p = 0.8, p = 0.2) as the controls, 46° (29° to 60°) and 16° (4° to 30°) respectively, but the variation was greater. Assuming an accuracy of implantation of ± 10° about a target position, the optimal radiographic position was found to be approximately 45° of inclination and 20° of anteversion. The incidence of pseudotumours inside the zone was four times lower (p = 0.007) than outside the zone. In order to minimise the risk of pseudotumour formation we recommend that surgeons implant the acetabular component at an inclination of 45° (± 10) and anteversion of 20° (± 10) on post-operative radiographs. Because of differences between the radiographic and the operative angles, this may be best achieved by aiming for an inclination of 40° and an anteversion of 25°.
We report 17 patients (20 hips) in whom metal-on-metal resurfacing had been performed and who presented with various symptoms and a soft-tissue mass which we termed a pseudotumour. Each patient underwent plain radiography and in some, CT, MRI and ultrasonography were also performed. In addition, histological examination of available samples was undertaken. All the patients were women and their presentation was variable. The most common symptom was discomfort in the region of the hip. Other symptoms included spontaneous dislocation, nerve palsy, a noticeable mass or a rash. The common histological features were extensive necrosis and lymphocytic infiltration. To date, 13 of the 20 hips have required revision to a conventional hip replacement. Two are awaiting revision. We estimate that approximately 1% of patients who have a metal-on-metal resurfacing develop a pseudotumour within five years. The cause is unknown and is probably multifactorial. There may be a toxic reaction to an excess of particulate metal wear debris or a hypersensitivity reaction to a normal amount of metal debris. We are concerned that with time the incidence of these pseudotumours may increase. Further investigation is required to define their cause.
