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Published on: September 7, 2022
Dysplastic hips with a subchondral cyst demonstrate poorer functional scores and a trend toward increased benefit
Chiara Heller1, Quentin Karisch1, Justus Stamp1
1Department of Orthopaedic Surgery, Hannover Medical School, DIAKOVERE Annastift, Anna-von-Borries Str. 1-7, 30625, Hannover, Germany.
Background:
Subchondral cysts of the femoral head have been commonly regarded as indicators of joint degeneration in developmental dysplasia of the hip (DDH), attributed to excessive stress and mechanical overload. Whether such cysts constitute a contraindication to periacetabular osteotomy (PAO) in young hips remains controversial. The aim of this study was to determine early outcomes after PAO in young dysplastic hips in which a subchondral femoral head cyst with an intact cartilage cap was identified.
Methods:
An institutional PAO database was utilized, and hips undergoing PAO between January 2022 and December 2023 were identified. Preoperative magnetic resonance imaging (MRI) studies were reviewed for the presence of subchondral femoral cysts, and hips were stratified into groups with and without such cysts. Radiographic and demographic data were compared between groups. Preoperative and 1-year postoperative patient-reported outcome measures (PROMs; mHHS, iHOT-12) were collected and compared. Proportions of hips achieving the minimal clinically important difference (MCID) and patient acceptable symptom state (PASS) following PAO were calculated and compared.
Results:
A total of 107 hips were included; 21 (20%) were found to have subchondral femoral cysts and 86 (80%) were found not to have cysts. No significant differences in demographic or radiographic parameters were identified between groups. PROMs for hips with subchondral cysts were observed to be slightly lower pre- and postoperatively. Significant improvements in PROMs were observed in both groups at 1-year follow-up. A higher proportion of hips with subchondral cysts achieved MCID for both mHHS and iHOT-12. For PASS, the proportion of hips reaching the threshold was higher in the cyst group for mHHS, whereas it was higher in the non-cyst group for the iHOT-12.
Conclusion:
Periacetabular osteotomy yielded significant improvements in PROMs despite the presence of a structural cystic subchondral lesion under an intact cartilage cap. The greater improvements in mHHS and iHOT-12 observed among hips with subchondral cysts are suggested to reflect a higher baseline symptom burden, indicating that greater potential for functional improvement may be achieved once dysplastic biomechanics and associated overload and instability are corrected.
