A maior rede de estudos do Brasil

354 pág.

Pré-visualização | Página 35 de 50

acetabular bone stock, as well as any deficiencies
in the dome or rim of the acetabulum influence
acetabular component size. Femoral templating
helps determine:
a. Level of femoral neck resection
b. Femoral component size
c. Distances from fixed points on the femur to the
center of hip rotation in order to help optimize
postoperative limb length
d. If femoral implant adequately reconstructs
femoral offset and proper hip mechanics
Special Instruments, Position, 
and Anesthesia
1. The preferred patient position for a posterolateral
approach to the hip joint is the lateral decubitus
position. Adequate padding of the axilla is neces-
sary to avoid injury to the brachial plexus. While
the patient must be secure on the operation room
table, avoid excessive tightening of pelvic posts,
1 2 3
C H A P T E R 2 0
Total Hip Arthroplasty
Hybrid and Uncemented
Douglas E. Padgett
which can compromise the neurovascular status of
the “down-leg” (Fig. 20–1).
2. All pressure points should be padded.
3. The procedure can be done with general, epidural,
or long-acting spinal anesthesia. There is some evi-
dence that epidural anesthesia decreases the risk of
deep-vein thrombosis as well as decreases blood loss
during total hip arthroplasty.
4. Instruments required for total hip arthroplasty
include self-retaining retractors, straight and bent
Hohman-type retractors, a femoral neck elevator to
facilitate exposure of the proximal femur, and bat-
tery powered reamers and power saws. In addition,
the specific instruments, broaches and trial compo-
nents unique to the prosthesis to be implanted
should be available.
5. Consider using enclosed helmets and body exhausts,
which may help minimize the risk of perioperative
6. Intravenous antibiotics appropriate for the hospi-
tal’s bacterial flora should be administered prior 
to tourniquet inflation and continued for at least 
24 hours after surgery.
Tips and Pearls
1. Extensile exposure is essential for success. The use
of short or “mini” incisions is to be avoided as it
may compromise component insertion.
2. The inability to anteriorly translate the femur
enough to achieve adequate visualization of the
acetabulum is usually due to insufficient release of
the gluteus maximus tendon at its femoral inser-
tion and/or of the reflected head of the rectus
femoris tendon at its insertion site into the supra-
3. Preoperative measurements (level of neck resec-
tion, distance from lesser trochanter to center of
hip rotation) should be reassessed during surgery
since radiographic magnification may vary as
much as 10 to 15%.
4. Ensure that all significant osteophytes are identified
and removed at the time of surgery. Medial acetab-
ular osteophytes can result in lateralization of 
the cup that may affect abductor mechanics.
Osteophytes located on the acetabular rim or on the
femoral neck can cause impingement leading either
to decreased hip motion and/or to hip instability.
5. Assess the stability of the hip prior to closure. Pay
particular attention to impingement from either
osteophytes or the prosthetic femoral neck on the
rim of the acetabular component. Stability often
reflects the adequacy of reconstruction of both
length and offset. Failure to restore offset, especially
in large individuals, may result in impingement and
hip instability. Hip motions evaluated should
a. Hip flexion of 90 degrees without rotation (sim-
ulating sitting in a chair)
b. Hip flexion of 45 degrees, hip adduction of 
15 degrees, and internal rotation of 15 degrees
(simulating sleeping position)
c. Hip extension, abduction and external rotation
to assess anterior instability
What To Avoid
1. Because of the problems associated with infection,
great care is taken to minimize this complication.
Operating room traffic should be minimized, and
preoperative antibiotics administered.
2. Avoid a vertical or retroverted alignment of the
acetabular component.
3. Avoid over-reaming the acetabulum and removing
excessive bone. Conversely avoid under-reaming
the acetabulum and using excessive force during
component impaction, thereby increasing the risk
of acetabular fracture. Controlled acetabular ream-
ing is preferred. If the press-fit stability of the
acetabular component is not satisfactory, the use 
of a supplemental acetabular fixation screw is
4. Avoid a varus or retroverted alignment of the
femoral component.
5. Avoid excessive broaching or reaming of the femur
especially when cement fixation of the femoral
component is planned. Over zealous removal of
cancellous bone will weaken the bone-cement
interface and may predispose to early component
loosening. Femoral preparation should be per-
formed in a controlled methodical fashion.
1 2 4 H I P A N D F E M U R
6. Avoid excessive force during femoral preparation
for an uncemented femoral component. Preparation
of the femur for an uncemented femoral compo-
nent requires patience in order to minimize the risk
of fracture.
If a fracture occurs, it is vital to assess component sta-
bility. If a fracture is recognized during either broach-
ing or implant insertion, remove the broach or implant
and expose the fracture. Consider obtaining intra-
operative radiographs. If the stem will adequately
bypass the fracture (at least 1.5 cortical diameters),
then the femur should be cerclaged with either 16-gauge
chrome cobalt wires or 2.0-mm cables. At this point,
the broach or final implant can be reinserted. If the
implant is axially or torsionally unstable, a larger
implant may be required. If stability is questionable,
consider insertion of a cemented stem.
7. Avoid inserting an undersized uncemented femoral
component. Use of an implant that is too small may
compromise initial implant stability, thereby result-
ing in implant motion and possibly predisposing
to early failure. Preoperative templating is useful to
help indicate the approximate size of the implant
to be inserted. If there is a significant discrepancy
between the preoperative projected implant size
and the apparent intraoperative implant size, con-
sider obtaining intraoperative radiographs. The lead-
ing cause for undersizing the femoral stem is not
positioning it sufficiently lateral in the trochanteric
bed and thus placing the stem in varus.
Postoperative Care Issues
1. While not mandatory, a suction-type drain can be
used and normally, safely discontinued the morn-
ing after surgery.
2. Thromboembolic precautions are recommended.
Options include intraoperative heparin, aspirin,
warfarin, low-molecular weight heparin, and inter-
mittent pneumatic compression.
3. Weight-bearing status may depend on the method
of femoral component fixation: full weight bearing
with cement fixation; partial weight bearing with
uncemented fixation.
4. “Hip precautions” such as avoiding excessive hip
flexion and/or hip rotation should be reviewed with
the patient.
Operative Technique 
(Posterolateral Approach)
1. Position the patient in the lateral decubitus posi-
tion. Pad all pressure points including the axilla.
While the patient must be secure on the operation
room table, avoid excessive tightening of pelvic
posts, which can compromise the neurovascular
status of the “down-leg” (Fig. 20–1).
2. Prepare and drape the limb in the hospital’s stan-
dard sterile fashion.
3. Make a straight lateral incision approximately 
15 cm in length. Center the incision over the lateral
shaft of the femur. The incision should start approx-
imately 5 cm proximal to the tip of the greater
trochanter and extend distally about 10 cm.
4. Carry the dissection directly through the subcuta-
neous tissue. Maintain adequate hemostasis.
Identify the fascia lata.
5. Incise the fascia lata longitudinally. Bluntly split the
fibers of the