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Orthopaedic Surgery Hip
Increasing Intra-operative Flexibility and Optimising Total Hip Replacement with
Anatomical Uncemented Modular Femoral Implants
a report by
Gerard Asencio
Orthopaedic Department, University Hospital, Nîmes
One of the primary goals of cementless total hip arthroplasty (THA) is resultant forces across the joint and deleterious effects on wear rates.
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to obtain intimate contact between the prosthesis and the host bone A decrease in femoral offset reduces the abductor movement arm and
in order to provide both short- and long-term stability of the implants. therefore increases both the resultant force across the hip and the
Other important goals are to restore leg length, periarticular soft- energy required for normal gait.
tissue tension, range of motion, stability of the joint and function
required for diverse daily activities. The inability to restore femoral offset is also correlated with decreased
periarticular soft-tissue-structure tension and the subsequent
Cementless Fixation with Anatomical Femoral deleterious effects on stability of the head in the acetabulum. This
Components in Total Hip Arthroplasty leads to a significantly reduced resistive force, which limits
Cementless fixation with anatomical femoral components in THA has separation of the head from the acetabulum and prevents the femoral
been proved extremely reliable. The anatomical shape promotes prosthetic head from subluxating within the cup while walking and
proximal fill in the metaphyseal trabecular bone and maximal interface carrying out daily activities. The offset of the native femur depends on
stability, even with femoral anatomy variances. several factors, such as neck shaft angle, neck length and size of the
proximal femur, and covers a large range, as reported in the
literature.
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Modified offset in a reconstructed hip may result from an
inadequate, undersized or malpositioned femoral implant or,
The rotational relationship of the indirectly, from a modification of the cup placement. Different neck
neck to the acetabulum shell is
shaft angles and a great variety of implant sizes may be necessary in
order to restore proper offset and proper hip balance, particularly with
of paramount importance in the
uncemented implants.
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determination of total hip
Femoro–Acetabular Relationship and Hip Stability
arthroplasty stability.
Hip instability is an infrequent but frustrating complication of THA.
Most studies report dislocation rates of 2–5% after THA. Dislocation is
partly dependent on patient compliance, but also on surgical
The positive reports in the literature
1,2
have been confirmed by our technique and achievement of stability intra-operatively. Intra-
own experience from 1990 to the present, with the ABGI and then the operative factors contributing to hip instability include the type of
ABGII system (Stryker, Newbury, UK). The survival rate with ABGI surgical approach, final component positioning and repair of the soft-
stems over an average follow-up of 13 years was 97.3%, and the tissue structures, as well as anatomical and surgical femoral offset,
failure rate of the femoral stem due to aseptic loosening was only neck length and soft-tissue insufficiency, as described above. In
1.3%. Osteointegration was achieved in 98.7%. The main positive addition, the rotational relationship of the neck to the acetabulum
patterns of bone remodelling seen radiographically were endosteal shell is of paramount importance in the determination of THA stability.
apposition and cancellous bone densification in the mid-stem section. Femoral version contributes to the inherent stability of the hip joint,
However, the close metaphyseal fit required to achieve fixation does not and proper femoral version in conjunction with acetabular version
always allow definite articular adaptations – such as vertical translation, allows for hip stability and an unimpeded range of motion.
anteversion adjustment, medio-lateralisation in order to fine-tune leg
length, soft-tissue tension, stability and function – in the same way that Any impingement due to rotational mismatches will predispose to hip
a cemented stem does. According to Massin et al.,
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accurate restoration instability and also to possible premature loosening of the
of the centre of the hip and the femoral offset with a single neck shaft
angle would be achieved in fewer than 40% of cases.
Gerard Asensio is an Orthopaedic Surgeon and Professor of
Orthopaedic Surgery at the University of Montpellier-Nîmes.
Femoral Offset and Hip Balance Restoration
He is also Chief of the Department of Orthopaedic Surgery
Inadequate soft-tissue balancing is a major cause of failure of primary
and Trauma at the University Hospital of Nîmes. Professor
Ascensio is a member of the French Society of Orthopaedic
and revision THAs. Charnley
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described the importance of restoring the Surgery and Trauma (SOFCOT) and the French College of
femoral offset and abductor function and proposed the trochanteric
Orthopaedic and Trauma Surgeons (CFCOT).
osteotomy as the solution in his surgical technique. The inability to E:
gerard.asencio@chu-nimes.fr
restore femoral offset adequately has been correlated with increased
© TOUCH BRIEFINGS 2007 51
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