Hip arthroscopy for the management of osteoid osteoma of the acetabulum: a systematic review of the literature and case report

Systematic review

The initial search revealed 21 studies. Out of these studies, seven duplicates were
removed, and two articles were removed after title review. In addition, one article
was excluded after abstract review since there was no available full text; the research
was an abstract that was presented in a scientific meeting. Out of the 11 remaining
articles, one article was removed after full text review because it described the
use of arthroscopy for diagnostic purposes only. Eventually, ten studies were included
in our review (Fig. 1). No further studies were found to be eligible for inclusion in our review after
screening of the references of the ten included studies.

Fig. 1. Outline of the systematic search strategy used in this study

A meta-analysis was not performed due to the inconsistency of the data in the included
studies of this review. All studies were case reports. The two reviewers of this study
had no disagreements throughout all stages of the systematic review.

The included studies were conducted in North America, Europe and Asia. Each study
reported only one case of acetabular OO that was treated using hip arthroscopy (Table 1) 20]–29]. Only two patients were females, and the age of all patients ranged from 7 to 47 years.
The left hip was involved in the majority of the patients, and different locations
of the mass in the acetabulum were reported. Most patients were operated in the supine
position, and underwent hip arthroscopy for excision of the tumor and synovectomy.
Two out of the ten patients had arthroscopic guided-RFA of the mass. The follow-up
period ranged from six months to 2 years, with one article not reporting the follow-up
duration. Success rate was 100 %, and no recurrence of the tumor was noted in any
of the patients. In addition, none of the patients required any additional surgical
procedure. Complications developed in one patient only in the form of transient post-operative
impotence and perineal numbness for 4 weeks.

Table 1. Summary of the available literature about the use of hip arthroscopy for the treatment
of acetabular osteoid osteoma

Case report

An otherwise healthy 31-year-old male presented with left hip pain of more than one
year duration. The pain was mainly located lateral in the iliac area, with minimal
pain in the groin, and was radiating to the thigh. The pain was worse at night and
waked the patient up from sleep every night. Physical examination of the affected
hip revealed normal extension, and limited flexion at 100°, abduction at 30°, adduction
at 10°, external rotation at 30° and internal rotation at 15°. The hip was spontaneously
adopting an external rotation and abduction position. Plain radiographs suggested
osteopenia and joint space thinning and loss of sphericity of the femoral head, but
failed to show any tumor (Fig. 2a). The CT scan, MRI and bone scan demonstrated findings suggestive of OO of the left
acetabular fossa (Fig. 3).

Fig. 2. Initial and follow-up radiographs of the left hip of a 31 year-old male with acetabular
osteoid osteoma. a Plain x-ray of the left hip before undergoing radiofrequency ablation or hip arthroscopy
showing mild degenerative changes of the hip joint; b Plain x-ray of the left hip of the same patient 44 months following hip arthroscopy
and radiofrequency ablation of the acetabular osteoid osteoma not showing further
progression of the osteoarthritic changes

Fig. 3. Axial (a), coronal (b) and sagittal (c) views of a computed tomography scan showing a round nidus of osteoid osteoma at
the superomedial aspect of the left acetabulum, lying immediately superior and posterior
to the fovea in a 31 year-old male with left hip pain

The patient has tried several NSAIDs before his presentation to our clinic. Nevertheless,
all medication trials (including the use of naproxen) failed to relieve his symptoms.
Radiofrequency ablation therapy, consisting of three cycles for two minutes at 90 °C
with an interval of one minute rest time between each cycle, was performed under CT
guidance to treat the lesion. Following the procedure, the patient started to complain
of severe pain that was limiting his ability to walk and stand normally even with
continuation of NSAIDs. The OO appeared to be unchanged on a CT scan of the left hip
that was done 4 months following the RFA. With the possible higher rate of complications
of open surgery that requires hip dislocation, the patient agreed for an attempt of
arthroscopic excision of the tumor. Based on the CT scans, the tumor was located posterior
and superior within the acetabular fossa; therefore, hip arthroscopy was performed
using the anterior, anterolateral and posterior portals. The region of the tumor was
identified with irregularities of the cartilage at the posterior/superior edge of
the fovea. Under fluoroscopic and direct guidance, a burr was placed in the identified
region of the tumor. This region was burred, and the cavity of the nidus was identified.
The burr could not be placed deeper inside the cavity due to its angulation, thus,
the radiofrequency chisel was placed in the region and ablation involved the entire
cavity. No intra- or post-operative complications were encountered.

Six weeks after surgery, the patient reported no relief of his pain. A new CT scan
of his left hip showed that the OO was still there, while the burned area appeared
slightly posterior to the lesion. The patient underwent a second attempt of CT guided
RFA of the lesion three weeks later. Improvement of his pain and increased range of
motion of the hip were recorded two weeks following that. During the last follow-up
visit, 44 months after the last procedure, he reported ignorable mild discomfort during
activity. The nocturnal pain was gone, and he regained his ability to walk and stand
without any pain. His range of motion improved fully with the exception of adduction
at 10° and abduction at 30°. His latest follow-up x-rays showed no progression of
the mild degenerative joint changes of the left hip which were noted in the first
images (Fig. 2b).