A twenty-eight-year-old man was seen at another hospital because of
right hip pain with walking, which had lasted for six months. A diagnosis of
solitary bone cyst was made at that institution, and he was treated with core
decompression. The pain did not decrease postoperatively, and he subsequently
consulted our hospital.
On examination, the patient walked with an antalgic limp on the affected
side and had mild limitation of the range of motion of the right hip joint
(100° of flexion, 15° of adduction, 15° of internal rotation, and
20° of external rotation) because of pain. Plain radiographs showed a
large radiolucent area with marginal sclerosis that extended from the superior
subchondral bone of the femoral head to the neck of the femur. The volume of
this lesion, as measured with a digitizer on the anteroposterior radiograph,
was 40% of the femoral head volume. In addition, we noted developmental
dysplasia (a center-edge angle of 18° and an acetabular head index of 63%)
and 1 mm of collapse of the femoral head compared with the contralateral side.
There was no loss of joint space, but there were marginal osteophytes of the
femoral head (Figs. 1-A and
1-B). We interpreted these
findings as being consistent with early osteoarthritis in a patient with
developmental dysplasia. In addition, the bone tumor was located directly
under the weight-bearing surface, and the femoral head was already aspherical
in its superolateral aspect. Magnetic resonance imaging showed a hypointense
lesion of the femoral head and neck on T1-weighted images
(Fig. 2-A) and a hyperintense
lesion on T2-weighted images (Fig.
2-B). The patient underwent needle biopsy of the lesion, which was
interpreted as a chondroblastoma.
Although extensive curettage of the tumor and packing of the defect with
bone grafts is the usual treatment for this lesion, we suspected that the
early osteoarthritic changes, the slight collapse of the femoral head
secondary to the lesion, and the acetabular dysplasia would lead to rapid
progression of degenerative osteoarthritis and femoral head collapse if that
treatment was used alone. For those reasons, we thought that additional
reconstructive surgery was indicated to reduce the load on the affected part
of the femoral head. As the lateral portion of the femoral head was not
affected, we sought to improve the acetabular coverage of that portion with a
rotational acetabular osteotomy to redistribute the weight-bearing force to
this intact area. To avoid seeding of tumor cells, we performed the osteotomy
before the curettage. It was carried out as described by Ninomiya and
Tagawa8. The
osteotomy line was drawn at 1 to 1.5 cm from the acetabular rim, and then the
osteotomy was performed anteriorly, laterally, and posteriorly around the
acetabulum with use of a special curved osteotome that was designed to
approximate the acetabular curvature. Two trapezoidal bone grafts, each about
5 mm thick, were taken from the external wall of the ilium and were used to
fill the gap between the ilium and the rotated acetabular fragment. After
adequate coverage of the femoral head was achieved by moving the acetabulum 35
mm laterally, two Kirschner wires (2 mm in diameter) were inserted to fix the
rotated acetabulum and the cortical bone struts to the ilium. Cancellous bone
chips were also used to fill the gaps between the osteotomized bone
surfaces.
After completion of the osteotomy, curettage of the tumor with a surgical
burr was done through a fenestration in the great trochanter under
fluoroscopic guidance. After complete curettage and washing with phenol,
cancellous bone chips and granular
hydroxyapatite9 were
packed into the cavity (Fig.
3). The tissue removed by curettage was examined histologically,
and a diagnosis of benign chondroblastoma was made
(Fig. 4).
The Kirschner wires were removed through a small skin incision in the sixth
postoperative week. Partial weight-bearing with two crutches was allowed two
months postoperatively, and full weight-bearing began five months
postoperatively. The range of motion of the involved hip was increased
postoperatively, to 110° of flexion, 25° of adduction, 45° of
internal rotation, and 60° of external rotation.
At the time of the latest follow-up (4.5 years after the operation), there
had been no recurrence of the tumor and no progression of femoral head
collapse (Fig. 5). The patient
had no discomfort in the right hip and had returned to his previous work as a
driver of a tractor.
Chondroblastoma is a rare lesion, accounting for approximately 1% to
2% of all benign bone tumors. The majority of patients with chondroblastoma
are younger than twenty years of age and may still have an open
physis1-7.
Although the usual treatment is curettage, local recurrence is not unusual,
with a recurrence rate as high as 21% following curettage and
bone-grafting6.
While the recurrences usually occur within the first three years after
curettage, they have been reported after much longer periods of
time2,5.
In discussing the use of proximal femoral osteotomy for treatment of
osteonecrosis of the femoral head, Mont and
Hungerford10 stated
that its purpose was to move the necrotic segment away from the major
weight-bearing part of the acetabulum and redistribute the load to articular
cartilage that is still supported by healthy subchondral bone. Although we
were treating a bone tumor, we subscribed to those principles. Ito et
al.11 reported
that, if a necrotic femoral head has an intact lateral bone cortex at the
femoral neck, varus osteotomy alone can achieve sufficient coverage of the
intact part of the femoral head. However, Ito et al. found that three of four
patients with >25° of varus correction and three of fifteen with
<25° of correction had a permanent limp. Thus, by performing a
rotational acetabular osteotomy in our patient, we utilized the intact lateral
cortex of the femoral head, as proposed by Ito et al., and shifted the
weight-bearing sector of the femoral head to intact articular cartilage and
subchondral bone while, at the same time, preserving a satisfactory range of
motion, improving the lateral coverage of the femoral head in a patient with
acetabular dysplasia, and avoiding limb-length discrepancy and abductor
insufficiency.
To date, we have treated twenty-one young patients (twenty-five hips,
followed for a minimum of three years) with extensive osteonecrosis of the
femoral head with a rotational acetabular osteotomy. We found the procedure to
be effective for preventing further collapse of the femoral head and for
controlling
symptoms12. The
good clinical outcome seems to be related to adequate postoperative acetabular
coverage of the lateral part of the femoral head by living bone. While we are
not aware of any reports on the use of this osteotomy for the treatment of
tumors of the femoral head, we thought that, given the constellation of
problems posed by the tumor and the hip dysplasia in our patient, it was the
best surgical option.
Even though curettage was performed under fluoroscopic guidance, it was
unclear whether the tumor was completely removed. With a follow-up of 4.5
years, we cannot rule out the possibility of a recurrence in the future, and
it will be necessary to follow our patient carefully. Collapse of the femoral
head and progression of the osteoarthritis of the hip joint had not occurred
at the time of writing. ?
The authors did not receive grants or outside funding in support of their
research or preparation of this manuscript. They did not receive payments or
other benefits or a commitment or agreement to provide such benefits from a
commercial entity. No commercial entity paid or directed, or agreed to pay or
direct, any benefits to any research fund, foundation, educational
institution, or other charitable or nonprofit organization with which the
authors are affiliated or associated.