Following implant removal and débridement, an antibiotic-impregnated
polymethylmethacrylate spacer is implanted. After the proximal part of the
femur is removed, the greater trochanter is fixed to the spacer to prevent
shortening of the gluteal muscles. During this first stage, either an
immediate hip disarticulation with reconstruction of an above-the-knee stump
is performed (Case 1) or the extremity is preserved (Case 2). The former
should be considered for a patient with a severe periprosthetic fracture,
severe vascular compromise distally, or inadequate soft-tissue coverage.
Following treatment with intravenous antibiotics, the patient is managed
with reconstruction of an above-the-knee stump with use of a modular proximal
femoral replacement implant (MUTARS; Implantcast, Buxtehude, Germany) and a
bipolar head. In general, the original lateral incision is preferred and
distally a fish-mouth skin incision is used for the amputation. The end of the
reconstruction is covered with an anterior flap that is large enough so that
the scar lies posteriorly. However, a reconstruction with use of a medial or
an anterior flap is possible if the lateral soft tissues are severely
scarred3. Depending
on the quality of the soft-tissue coverage, every effort should be made to
preserve a stump length of at least 25 cm, which requires an implant length of
at least 20 cm. The proximal femoral replacement implant has a special rounded
end piece on the distal aspect to prevent penetration of the soft-tissue
envelope. The implant has a diameter of 2.5 cm. The adductor magnus muscle and
the iliotibial band should be preserved for a distance of 5 cm distal to the
skin incision. Care should be taken to preserve the insertion of the abductor
muscles for later fixation to the implant. To facilitate soft-tissue
attachment, a Trevira stocking (Implantcast) is pulled over the implant and is
fixed to it with use of number-6 Ethibond nonabsorbable sutures (Ethicon,
Somerville, New
Jersey)4. The
Trevira stocking is a polyethylene terephthalate knitted stocking, which is
characterized by a porous structure of 200 µm and a tensile strength of
4000 N4. The Trevira
stocking is also fixed to the osseous acetabulum to prevent implant
dislocation, with use of nonabsorbable sutures into the labrum or suture
anchors (Mitek, Norwood, Massachusetts) placed in the periacetabular bone.
While other means of securing the soft tissues are
available5, we
believe that the use of this stocking is essential to ensure effective fitting
of an external prosthesis.
The musculature is fixed to the Trevira stocking with use of nonabsorbable
sutures. The lateral part of the incision is closed, with the vastus lateralis
sutured to the posterior musculature and to the Trevira stocking. After the
subcutaneous tissues are reapproximated with use of absorbable sutures, the
skin is closed with staples.
Case 1. A seventy-year-old woman was admitted to the
hospital, in May 2002, with clinical signs of a deep infection around the
implant following treatment of a periprosthetic fracture with an
intramedullary total femoral replacement
(Fig. 1, A). After
implant removal and reconstruction with a gentamicin-loaded
polymethylmethacrylate cement spacer, the patient was started on intravenous
antibiotics. Because of a severely compromised wound, the patient underwent a
modified hip disarticulation, leaving the proximal soft tissues for
reconstruction of an above-the-knee stump with a gentamicin-loaded
polymethylmethacrylate spacer three weeks after the initial procedure
(Fig. 1, B). In
November 2002, the patient had no evidence of infection and underwent
implantation of a modular proximal femoral replacement implant (MUTARS,
Implantcast), which was 24 cm in length with a 52-mm-diameter bipolar head
(Fig. 1, C). Six weeks
later, she began a program of strengthening exercises and stump-wrapping to
decrease edema and shape the stump. She was then fitted with a transfemoral
modular prosthesis, which had an ischial containment socket to reduce implant
loading and the risk of dislocation and a single-axis knee joint with a
weight-activated friction brake. Nineteen months after surgery, the patient
had no pain and was wearing the prosthesis without interruption for up to six
hours. She walked with one crutch inside the house and was able to walk
outside with two crutches for approximately 500 m. Occasionally, she used a
wheelchair for longer distances. The patient had no discomfort sitting in a
wheelchair or a chair.
Case 2. In January 2002, a seventy-six-year-old woman presented
with a recurrent infection following a total knee replacement, proximal and
distal femoral fractures (Fig. 2,
A), and partial peroneal and tibial nerve palsies. The
patient was managed with intravenous antibiotics and was taken to the
operating room for removal of all implants, careful débridement, and
subsequent implantation of a gentamicin-loaded polymethylmethacrylate spacer
(Fig. 2, B). After
twenty-four days, the patient underwent a modified hip disarticulation,
leaving the proximal soft tissues attached for reconstruction of an
above-the-knee stump with use of a modular proximal femoral replacement
implant that was 19 cm long and had a 48-mm-diameter bipolar head
(Fig. 2, C).
Initially, she was managed with a prosthesis as described for the first
patient (Case 1). However, she later was diagnosed as having breast cancer and
underwent surgical and medical treatments. Afterward, refitting of the
prosthesis was necessary because of a change in stump volume and a reduction
in physical fitness. The prosthetic knee joint with a weight-activated
friction brake had to be replaced with a manually locked joint. At the latest
follow-up examination, the patient was able to walk with one cane in the house
and used a wheelchair outside. She had no discomfort sitting in a wheelchair
or a chair.
Preservation of the hip joint is the main advantage of this modified
hip disarticulation and stump reconstruction. Although it is not intended that
the end of the stump be used for weight-bearing, it provides a lever arm for
hip flexion and extension as the proximal soft tissues remain attached to the
replacement implant. The main disadvantages of a hip disarticulation are its
unappealing appearance; the discomfort of the basket-shaped prosthetic socket,
which incorporates nearly one-half of the pelvis; and the 82% increase in
energy consumption required for walking compared with that in a normal
person6. Considering
the age and the preoperative functional level of both patients in this study,
it is likely that they would have become dependent on a wheelchair following
hip disarticulation without stump reconstruction. The functional results in
these two patients compare well with an above-the-knee amputation performed
for a failed total knee
replacement7,8,
and we believe these results are superior to the functional outcome after hip
disarticulation.
In the salvage of a limb with an infection around a total hip replacement
with loss of femoral bone stock secondary to a periprosthetic fracture, a
type-B-IIIb rotationplasty as described by Winkelmann might be
considered2. After
removal of the entire femur, a femoral component is cemented into the tibia
and a rotationplasty is performed. However, after multiple procedures and
recurrent infections, this technique is surgically demanding. In addition, in
our experience, its functional outcome in elderly patients is less
predictable.
Preservation of a functional above-the-knee stump following a hip
disarticulation with use of an Austin-Moore prosthesis (Smith and Nephew,
Memphis, Tennessee) in the treatment of bone and soft-tissue tumors was
described by Marcove et al. in
19799. Because of
the pointed stem of this implant, three of the twelve patients complained of
stem penetration through the skin. Brooks et
al.5 and Gosheger et
al.3 further
developed the technique and showed improved functional results. In the latter
study, all patients used an above-the-knee prosthesis within three months
after surgery3.
Compared with the two patients described in the present report, all of those
in previous reports who were treated for malignant tumors were younger (range,
eighteen to fifty-nine years) and had a better preoperative functional
level3,5,9.
Although the patients described by Gosheger et
al.3 and those in
our report had gradual stump shrinkage requiring readjustments of the
prosthetic socket, no patient had skin irritation or problems distally around
the end piece of the specially designed femoral component.
We used a bipolar head with a large diameter to decrease the risk of
dislocation. The dislocation risk is further diminished as the ischial
containment socket offers protection against lateral displacement of the
femoral component by holding the greater trochanter against the ischium.
Acetabular reconstruction with use of a bipolar implant and bonegrafting in
revision total hip replacement has been associated with high rates of implant
migration and groin
pain10. However,
considering the low functional demands of patients such as ours and the
benefits of load transfer after an above-the-knee amputation from the external
prosthesis to the ischial tuberosity, we believe that implant migration and
groin pain should not be major concerns.
We believe that this technique is a valuable option to preserve a stump
that can improve both appearance and function. The technique is
contraindicated whenever adequate implant coverage with a viable
musculocutaneous tissue flap is not possible. Placement of a metal implant, a
Trevira stocking, and nonabsorbable sutures in a previously infected limb may
predispose to recurrent infection. However, conversion to a hip
disarticulation is always possible if infection recurs. ?