Since the year 2000, minimally invasive techniques for total hip
arthroplasty have generated substantial interest among patients and surgeons
alike. The various techniques are predicated on the concept that a smaller
skin incision and less dissection of the muscles, tendons, and other soft
tissues around the hip should cause less postoperative pain and facilitate a
quicker recovery for patients. The concepts surrounding minimally invasive
techniques are inherently appealing to patients and surgeons alike. However,
the true value of these approaches remains the subject of considerable debate.
Most reports on minimally invasive techniques have coupled changes in the
surgical technique with substantial changes in anesthesia, pain management,
patient education, and rehabilitation protocols, making it difficult to
quantify the contribution of the change in surgical technique alone to any
observed improvements in outcome.
The standard posterior approach for total hip arthroplasty is familiar to
many surgeons, and the mini-posterior approach represents a logical refinement
of that technique. The mini-posterior approach is differentiated from the
standard posterior approach on the basis of a smaller skin incision, less
muscle dissection, no capsular excision, no incision in the iliotibial band,
and no incision of the gluteus maximus insertion. Should difficulties be
encountered intraoperatively, the mini-posterior approach can be converted to
a standard posterior approach, allowing rapid, wide exposure of the femoral
and acetabular sides of the hip joint.
The two-incision technique is a substantially different approach to total
hip arthroplasty. The patient is positioned supine on the operating table, and
a small, anteriorly-based incision is used to access the interval between the
rectus femoris and the tensor fasciae latae to expose and prepare the
acetabulum under direct vision. Many surgeons have found acetabular
preparation to be relatively straightforward with the two-incision technique.
Femoral preparation is done through a small posterior incision to access the
piriformis fossa and to prepare the femur as one might perform closed femoral
intramedullary nailing. While fluoroscopy can be used at various intervals and
small glimpses of the femur can be obtained through the anterior incision, the
femoral preparation is largely done in a blind fashion. Many surgeons have
found femoral preparation to be technically challenging, and most of the
reported complications associated with the two-incision technique have
occurred on the femoral side. Early claims that the technique could be done
without damaging hip muscle or tendon have been discounted on the basis of
cadaver-based and clinical evidence of measurable muscle damage.
Mini-Posterior-Incision Total Hip Arthroplasty
Anteroposterior and lateral hip radiographs are templated prior to surgery
to determine anticipated implant sizes and the level of the femoral neck cut
relative to the superior margin of the lesser trochanter
(Figs. 1-A and 1-B).
The patient is placed in the lateral decubitus position and is translated
toward the posterior edge of the operating table. Pelvic support devices are
positioned to hold the pelvis firmly. The posterior pelvic support is tall
enough to cross the midline and to support the operative side of the pelvis,
whereas the anterior pelvic support is shorter and is placed against the
anterior superior iliac spine of the contralateral (uninvolved) hip and the
pubis. The chest and the shoulders are supported such that the tip of the
shoulder and the high point of the iliac crest on the operative side are
collinear with the long axis of the operating table. The hip is then placed
through a range of motion to ensure that the pelvic supports will hold the
pelvis firmly but will not interfere with intraoperative testing of hip
stability. This is confirmed by testing the hip in full extension with maximum
external rotation, in 45° of flexion with maximum adduction, and at
90° of flexion with maximum internal rotation.
Our approach involves slight modifications to the technique advocated by
Inaba et al.1. The
initial skin incision is made along the posterior border of the greater
trochanter and typically measures 7 to 10 cm in length. Extending the incision
proximal to the tip of the greater trochanter improves visualization of the
femur, whereas extending the incision distal to the vastus lateralis tubercle
(which corresponds to the vastus lateralis origin) improves visualization of
the acetabulum (Fig. 2).
The fascia of the gluteus maximus is incised in line with the posterior
border of the greater trochanter to expose the lateral part of the femur
(Fig. 3). Care should be taken
not to make this fascial incision too far anteriorly as it will involve the
thicker tissue of the iliotibial band itself and will make subsequent tissue
retraction more difficult. The fascial incision is carried proximally to the
tip of the greater trochanter and then slightly posteriorly to split the
gluteus maximus fibers in line with the posterior border of the underlying
gluteus medius muscle. A more anterior fascial split leaves excess gluteus
maximus muscle that must be retracted posteriorly and interferes with
acetabular exposure. Conversely, a more posterior fascial split leaves excess
gluteus maximus muscle that must be retracted anteriorly and interferes with
femoral exposure during reaming and component insertion.
The abductor muscles are identified, and the interval between the gluteus
medius and minimus is developed by means of gentle blunt dissection with the
surgeon's index finger. A Deaver retractor or 90°-bent Hohmann retractor
is then placed in this interval to retract the gluteus medius anteriorly and
to expose the underlying piriformis tendon along the inferior border of the
gluteus minimus (Fig. 4-A). The
involved lower extremity is positioned in neutral abduction-adduction, is
flexed approximately 30°, and is placed in gentle internal rotation to put
some, but not excessive, tension on the external rotators and the posterior
capsule. Any prominent vessels coursing along the external rotator muscles are
identified and coagulated.
The external rotators and the underlying posterior hip capsule are incised
(Fig. 4-B) and preserved as one
layer (Fig. 5). The incision is
made with electrocautery by releasing the piriformis and the underlying
capsule from their insertion on the greater trochanter and then extending the
capsular split proximally and slightly posteriorly, parallel to the posterior
edge of the gluteus minimus muscle, stopping at the osseous margin of the
acetabulum after incising the labrum. Attention is then turned distally.
Beginning at the piriformis fossa, the hip capsule and the external rotators
are incised as one layer from the posterior border of the greater trochanter
down to the proximal border of the quadratus femoris muscle. In many patients,
the quadratus femoris can be left intact and the underlying hip capsule can be
released with electrocautery. In very stiff hips, the quadratus femoris may
need to be released as part of the exposure. A number-5 suture is placed
through the posterosuperior hip capsule and the piriformis tendon as a tag
suture on a clamp to facilitate retraction of the posterior capsule and the
external rotators during trial reduction of the hip later in the procedure
(Fig. 6).
The hip is dislocated, and the femoral head and neck are exposed. A second
Deaver retractor or 90°-bent Hohmann retractor can be placed along the
femoral head to retract the skin posteriorly. A specialized double-bent
Hohmann retractor is placed under the quadratus femoris, with its tip on the
lesser trochanter to facilitate visualization of the psoas tendon insertion on
the lesser trochanter (Fig. 7).
A ruler can be used to measure the position of the femoral neck cut proximally
from the lesser trochanter or distally from the center of the femoral head. We
often pre-bend a paper ruler to the appropriate neck length as measured in
millimeters on the basis of our preoperative planning and then slide that
ruler in the small incision and mark the neck cut with electrocautery (Figs.
8 and
9).
The femoral neck cut is made with a single-sided reciprocating saw to avoid
damaging the skin edges (Fig.
10). The femoral head is then removed in a single piece without
substantial difficulty (Fig.
11).
Femoral preparation with the mini-posterior approach requires a specialized
femoral retractor that will translate the skin and the posterior portion of
the gluteus maximus posteriorly (Fig.
12). That retractor is placed on the anterior surface of the
femoral neck, just distal to the neck cut
(Fig. 13). The assistant then
flexes the hip to position the neck optimally in the incision by following the
rule that more distally-based incisions will require more hip flexion for
ideal femoral exposure, whereas more proximally-based incisions will require
less hip flexion. The hip should be internally rotated to >90°. When
the hip is rotated to >90°, the greater trochanter and the attached
gluteus medius tendon are moved more laterally away from the edges of reamers
and broaches that are targeted down the middle of the femoral canal
(Fig. 14). Care must be taken
not to damage the proximal skin margin, which is under substantial tension,
when inserting and removing femoral reamers and broaches. In most cases, the
reamers are best introduced in a slight varus position and are advanced until
the proximal cutting teeth are safely past the skin and abductor muscle before
being brought back into a neutral position to carry out the reaming. Similar
precautions are taken when inserting and removing femoral broaches
(Fig. 15).
After appropriate rotational and axial stability have been obtained, the
femoral broach is left in place and attention is turned to the acetabular side
(Fig. 16).
A narrow short-tipped cobra retractor is placed along the anterior margin
of the acetabulum, just distal to the anterior inferior iliac spine
(Fig. 17). The tip is placed
through the soft tissue of the capsule in that region and rests on the bone of
the anterior wall of the acetabulum, which provides excellent leverage for
translating the femur anteriorly (Fig.
18). This narrow cobra retractor then rests against the medial
edge of the femoral neck, which is protected by the femoral broach that was
left in place, and the entire femur typically can be translated anteriorly to
facilitate reaming of the acetabulum under direct vision.
The anterior part of the inferior hip capsule, extending from the ischium
to the anterior aspect of the femoral neck, is then incised with
electrocautery down to, but not through, the transverse acetabular ligament
(Fig. 19). Care is taken to
not cut deeper than the capsule in this region as the medial circumflex artery
and vein run directly adjacent to the capsule. This incision allows the
posterior hip capsule and attached external rotators to be translated further
posteriorly, providing better visualization of the posteroinferior part of the
acetabulum. That exposure is maintained by placing a broad cobra retractor
adjacent to the transverse acetabular ligament inferiorly, with the tip of the
broad cobra retractor resting against the hard cortical bone of the cotyloid
notch inferiorly. Posteriorly, a specialized double-bent Hohmann retractor
with a short tip is impacted with a mallet into the bone of the posterior
column in the interval between the hip capsule and the labrum, with care being
taken not to direct the tip into the acetabulum, where it would interfere with
reaming (Fig. 20).
Acetabular reaming is carried out under direct vision, and the transverse
acetabular ligament is used as a guide to appropriate anteversion of the
reamer (Fig. 21). We typically
prepare the acetabulum by starting with a reamer that is 3 mm smaller than the
templated acetabular component size. We then finish the acetabular preparation
with a reamer that is 1 mm smaller than the actual acetabular component to
allow for a secure press-fit (Fig.
22). Preoperative templating of the acetabular component size
allows this simple two-reamer preparation to be done routinely. Minimizing the
number of reamers is efficient and reduces the risk of damaging the skin
edges. While specialized reamer-drivers with either a curved or offset shaft
and low-profile reamer heads are available, they are not required for routine
cases.
The acetabular component is then impacted into place under direct vision
with a goal of 20° anteversion and 40° to 45° inclination. The cup
is typically oriented parallel to the transverse acetabular ligament as a
guide to anteversion and is positioned such that 2 to 4 mm of the
posterosuperior edge of the component is uncovered by host bone. This
typically ensures that the cup is inclined 40° to 45° in the frontal
plane (Fig. 23). Supplemental
fixation of the cup with screws can be carried out at the discretion of the
surgeon. A trial acetabular liner or the final acetabular liner is then placed
according to surgeon preference (Fig.
24).
A trial reduction is then performed. The trial femoral neck and head can be
challenging to assemble through the small incision, particularly when using a
larger-diameter femoral head. Typically, the femur must be flexed 45° and
maximally internally rotated to expose the femoral neck for assembly. The tag
suture that was previously placed through the capsule and the piriformis
tendon is used to retract this tissue so that it does not become incarcerated
between the acetabular component and the trial femoral head. In cases in which
there is no intention to gain limb length, it is typical for the equator of
the femoral head to be lying on the posterosuperior edge of the acetabular
component prior to the reduction maneuver
(Fig. 25). Hip stability is
assessed by confirming an impingement-free range of motion that includes (1)
full extension with maximum external rotation (impingement occurs if the cup
is over-anteverted); (2) the position of sleep, with 45° of hip flexion
and maximum adduction (impingement occurs if there is insufficient offset);
and (3) 90° of hip flexion with 10° of abduction, allowing at least
75° of internal rotation (impingement occurs if the cup is not anteverted
enough or if there is insufficient offset)
(Fig. 26). We add one
additional test of soft-tissue tension. The hip is flexed to 30° and the
limb is held by the foot to allow maximum internal rotation to occur
(Fig. 27). If the hip
subluxates posterosuperiorly in this position, it indicates poor soft-tissue
tension that is typically occurring because of insufficient femoral
offset.
Once a stable configuration is obtained, the final femoral component is
impacted into place and the hip is reduced and is placed through a final range
of motion to confirm appropriate stability, limb length, and offset
(Fig. 28).
The wound is thoroughly irrigated with a pulsatile lavage system and is
closed in layers. The deep layer involves a soft-tissue repair of the
piriformis and the posterior capsule back to the anterosuperior capsule and
the posterior border of the gluteus minimus with use of a heavy nonabsorbable
suture (Fig. 29). This
soft-tissue repair has several theoretical advantages over a more traditional
osseous repair of the capsule and external rotators back to the greater
trochanter. First, it allows obliteration of any posterior dead space as the
capsule and external rotators are advanced directly against the edge of the
prosthetic femoral head (Fig.
30). Second, the repair will not pull apart with internal rotation
of the femur, as often occurs with osseous repairs through drill-holes in the
greater trochanter (Fig. 31).
Third, by suturing the posterior capsule and piriformis to the posterior
border of the gluteus minimus (in addition to the anterosuperior capsule),
some degree of dynamic stabilization may be conferred when the gluteus minimus
muscle fires.
The remainder of the wound is closed with multiple interrupted sutures in
the gluteus maximus fascia and subcutaneous tissues
(Fig. 32). The skin is closed
with a running absorbable suture and steri-strips, and an immediate
postoperative radiograph is made.
Patients are encouraged to sit up in a chair within four to six hours after
surgery and then begin walking the following morning with progressive
weight-bearing as tolerated.
Two-Incision Total Hip Arthroplasty
The patient is positioned supine on an operating table that is radiolucent
to allow fluoroscopic imaging of both the femur and the acetabulum
intraoperatively (Fig. 33). A
6-cm anterior incision is centered over the base of the femoral neck as
assessed fluoroscopically (Fig.
34). The Smith-Petersen interval is then used to expose the hip,
to cut the femoral neck, and to prepare the acetabulum
(Fig. 35). Fluoroscopy is used
intermittently to verify acetabular reaming depth, sizing, and positioning.
The acetabular component is then impacted into place
(Fig. 36). A second incision
measuring 3.8 to 5 cm is made in the buttock, and the abductors and external
rotators are identified (Fig.
37). The femur is sequentially reamed and broached through the
piriformis fossa in a blind fashion but with use of intraoperative fluoroscopy
at key intervals to aid in appropriate alignment and sizing
(Fig. 38). The posterior hip
capsule must be incised to allow passage of the trunnion of the femoral
component. The femoral component is then impacted into place in a blind
fashion. During femoral component insertion, the lesser trochanter and the
neck or collar of the femoral component can be palpated through the anterior
incision to help to guide the anteversion of the femoral stem
(Fig. 39). Trial reduction is
carried out, and limb length, offset, and hip stability are assessed. After
assembly of the final femoral head, the hip is reduced and the two incisions
are closed in layers.
CRITICAL CONCEPTS FOR THE MINI-POSTERIOR-INCISION TECHNIQUEINDICATIONS:Primary total hip arthroplasty in patients who are not morbidly obese and
who are without substantial osseous deformity that would require concomitant
osteotomyCONTRAINDICATIONS:Marked hip stiffness requiring extensive soft-tissue releasesSubstantial retained hardware that requires removalFragile skin that is at risk with moderate retraction forceExtreme obesitySubstantial osseous deformityPITFALLS:Limited skin incision puts the skin edges at risk of damage from saws,
reamers, and retractors.Limited exposure can make preservation of the full length of the piriformis
tendon and the external rotators more difficult.Limited exposure can make control of bleeding more difficult if the medial
femoral circumflex vessels are inadvertently injured during acetabular
preparation.Assembly of the trial femoral neck and head, as well as reduction of the
hip without incarcerating soft tissue in the acetabulum, can be more
difficult. That is particularly true when using a femoral head with a diameter
of >32 mm.AUTHOR UPDATE:On the basis of the results of our study, the two-incision technique for
total hip arthroplasty is no longer used at our institution.
CRITICAL CONCEPTS FOR THE MINI-POSTERIOR-INCISION TECHNIQUE
INDICATIONS:
Primary total hip arthroplasty in patients who are not morbidly obese and
who are without substantial osseous deformity that would require concomitant
osteotomy
Primary total hip arthroplasty in patients who are not morbidly obese and
who are without substantial osseous deformity that would require concomitant
osteotomy
CONTRAINDICATIONS:
Marked hip stiffness requiring extensive soft-tissue releasesSubstantial retained hardware that requires removalFragile skin that is at risk with moderate retraction forceExtreme obesitySubstantial osseous deformity
Marked hip stiffness requiring extensive soft-tissue releases
Substantial retained hardware that requires removal
Fragile skin that is at risk with moderate retraction force
Extreme obesity
Substantial osseous deformity
PITFALLS:
Limited skin incision puts the skin edges at risk of damage from saws,
reamers, and retractors.Limited exposure can make preservation of the full length of the piriformis
tendon and the external rotators more difficult.Limited exposure can make control of bleeding more difficult if the medial
femoral circumflex vessels are inadvertently injured during acetabular
preparation.Assembly of the trial femoral neck and head, as well as reduction of the
hip without incarcerating soft tissue in the acetabulum, can be more
difficult. That is particularly true when using a femoral head with a diameter
of >32 mm.
Limited skin incision puts the skin edges at risk of damage from saws,
reamers, and retractors.
Limited exposure can make preservation of the full length of the piriformis
tendon and the external rotators more difficult.
Limited exposure can make control of bleeding more difficult if the medial
femoral circumflex vessels are inadvertently injured during acetabular
preparation.
Assembly of the trial femoral neck and head, as well as reduction of the
hip without incarcerating soft tissue in the acetabulum, can be more
difficult. That is particularly true when using a femoral head with a diameter
of >32 mm.
AUTHOR UPDATE:
On the basis of the results of our study, the two-incision technique for
total hip arthroplasty is no longer used at our institution.