Survival of the Cementless Spotorno total hip arthroplasty

The total hip arthroplasty hugely improves the quality of life and is regarded
the most efficient and cost-effective surgical procedure in history1. In
orthopaedic science there is continuing need for evaluation of hip systems used
in the past to assess their survival and to determine the factors of failure in
order to improve the reliability of orthopaedic implants. Currently a 10-year
survival is a benchmark for quality.

During the last thirty years there has been an increase of the use of
cementless fixation in total hip arthroplasties (THA). Cementless hip
arthroplasties perform well at the mid-term and the long-term. Literature
suggests that the fixation of cemented acetabular components is more reliable
than that of cementless components beyond the first postoperative decade. Other
authors describe a better outcome of the femoral component and on the other
hand a lower survival rate of the uncemented acetabular component compared to
the cemented type.6 The main excepted reason for the increased use of the
uncemented prosthesis was the failure of cemented all polyethylene acetabular
component in the 1980*s. At that time the thought was that the use of bone
cement caused osteolysis, around the prosthesis. This phenomenon was called
*cement disease*. Today we know that polyethylene wear particles originated
from the cup are the problem instead of cement-disease*.

In our institution we have used the CementLess Spotorno (CLS) system. Recently,
this series was published in a peer reviewed journal, describing clinical
outcome after a ten to seventeen year follow-up.9 Our series of n=102 showed a
good mid-term to long-term survival.However little is known about the long-term
survival of cementless hip systems up to twenty years. By means of this
research we want to gain more knowledge about the long term survival of
cementless hip systems, in particular the CLS system.

We will evaluate this series again after a five-year interval. We expect that
radiologic loosening assessed with conventional X-ray of both the femoral and
acetabular component will increase since the last moment of follow up because
of an increase of polyethylene wear. Loosening will lead to lower clinical
evaluation scores.

The main objective of this study is to describe the long term results of a
non-designer series of the CLS total hip arthroplasty (with the use of a CLS
femoral stem and acetabular cup).

Primary Objective
Survival analysis of the CLS total hip arthroplasty system by assessment of the
incidence of revision and time to revision because of aseptic loosening of one
or both prosthetic components.

Secondary Objectives
Clinical assessment will be performed by physical examination, interview, and
using clinical scores (Charnley*s modification of the Merle d*aubigné-Postel,
Haris Hips Score and the EQ5D).

Radiological assessment will be performed using conventional X-rays of pelvis
and proximal femur. Radiogical loosening of the prosthesis is observed and
qualified by Gruen and Charnley. The acetabular cup inclination angle and
degree and angle of linear polyethylene wear will be measured by the method
described by Livermore et. al. Also heterotypic ossifications will be
classified with use of the system described by Brooker et. al.

The incidence of revision will be reported and analysed using the Kaplan Meyer
method.

Effects of preoperative clinical status, patient demographics, prosthetic
component size, and polyethylene wear on clinical outcome, aseptic loosening
and revision for any reason will be analysed.

Prospective cohort study design.
Two surgeons at our institution performed a consecutive series of 120 total hip
replacement procedures with the CLS system (CementLess Spotorno; Protek/Zimmer,
Zurich, Switzerland) in ninety-six patients between 1989 and 1997. The
indications for the procedure were osteoarthritis, rheumatoid arthritis, or
femoral head osteonecrosis. Inclusion criteria were an age of sixty-six years
or younger; a primary total hip arthroplasty for treatment of osteoarthritis,
rheumatoid arthritis, or femoral head osteonecrosis; and a trumpet-shaped femur
as defined by the morpho-cortical index (a measure characterizing femoral
morphology dysplastic, cylindrical, or trumpet-shaped] and femoral cortical
thickness). A trumpet-shaped femur with a thick cortex provides ideal
conditions for the CLS press-fit Stem. Exclusion criteria were primary or
secondary carcinoma in the last five years, unwilling to participate and a
lower extremity with neurovascular compromise. Patients were included in a
standardized follow-up protocol until 2007.

Patients* risks are negligible and the burden is minimal. All patients
underwent surgery 15-22 years ago. We will notify the patient by means of an
appointment letter for regular clinical evaluation. Regular clinical evaluation
consists of standardized digital X-rays of pelvis and hip, an interview and
physical examination.

We believe a routine follow up of patients should be performed every two to
three years, because relevant mechanical loosening of the prosthesis can
present with few clinical complaints. In these cases early surgery can be a
valid option to prevent more difficult revision procedures and the subsequent
risks.