202
· DOS Abstracts
Average cyst volume per cyst-patient decreases
over a 10-year period after periacetabular
osteotomy
Inger Mechlenburg, Jens R. Nyengaard, John Gelineck, Kjeld Søballe
Orthopaedic Research, Aarhus University Hospital; Stereology and Electron
Microscopy Laboratory and CSGB , Aarhus University; Department of
Radiology, Aarhus University Hospital
Background:
Bone cysts in patients with hip dysplasia are the results of degen-
eration or defects of the cartilage and local elevated stress in the subchondral
bone.
Purpose / Aim of Study:
To examine how many patients have acetabular or
femoral head cysts and investigate whether the volume of cysts change after
PAO.
Materials and Methods:
Magnetic resonance imaging (MRI) was performed in
a series of 26 consecutively included patients before periacetabular osteotomy
(PAO) and 1, 2½ and 10 years after. 26 patients had MRI preoperatively, 25
returned for MRI at 1 year, 21 at 2½ years and 18 at 10 year follow up. The
number of cysts was noted and the total cyst volume in each patient was esti-
mated with a design-unbiased stereology. The Hip disability and Osteoarthritis
Outcome Score (HOOS) was collected 4 and 10 years after PAO.
Findings / Results:
Preoperative, 12 patients had acetabular or femoral head
cysts (22 cysts), 1 year postoperative, 15 patients had cysts (23 cysts), 2½
years postoperative, 15 patients had cysts (18 cysts) and 10 years after PAO 9
patients had cyst (9 cysts). Mean total acetabular cyst volume per cyst-patient
at the time of MRI was: 3.44 + 6.71 cm3 (1.96 + 3.97 cm3) 0.96 + 1.70 cm3
(0.43 + 0.26 cm3) (p=0.04). All acetabular cysts were located anterolaterally
in the acetabulum except for one that was posterolateral. At 4 and 10 years, the
mean subscores for HOOS were Pain 75/79, Symptoms 75/73, ADL 83/85,
Sport/recreation 63/68 and Quality Of Life 62/61.
Conclusions:
The mean total cyst volume per cyst- patient decreased signifi-
cantly over a 10-year period after PAO. We believe this is a result of decreased
local stress in the subchondral bone after PAO which also indicates that redirec-
tion of the acetabulum reduces the risk of progression of osteoarthritis in the
operated hip.
149.
