# Natural History of Nonoperatively Treated Borderline Acetabular Dysplasia in Young Adults and Factors Associated With Inferior Functional Outcome

## TL;DR

This study examines long-term outcomes of non-surgical treatment for borderline hip dysplasia in young adults, finding that most experience ongoing symptoms and mild osteoarthritis over 10 years.

## Contribution

The study provides the first long-term follow-up data on nonoperatively treated borderline acetabular dysplasia in young adults.

## Key findings

- 9% of nonoperatively treated borderline hips showed mild OA progression after 15 years.
- Acetabular retroversion and labrum hypertrophy were linked to worse functional outcomes but not OA progression.
- 21% of borderline hips required preservation surgery within 15 years.

## Abstract

The long-term outcomes of nonoperatively treated borderline acetabular dysplasia (BHD) in young adults remain unexplored. This study aimed to investigate the natural history of nonoperatively treated borderline hips over a minimum 10-year follow-up.

Most patients with nonoperatively treated BHD would exhibit persistent symptoms and radiological evidence of hip osteoarthritis (OA) for at least 10 years.

Case series (prognosis); Level of evidence, 4.

Medical records and radiographs of patients aged 14 to 39 years with BHD, defined as a lateral center-edge angle (LCEA) of 18° to 25°, who presented with hip pain between January 2005 and December 2012, were retrospectively reviewed. Patients treated nonoperatively returned for clinical examination, pelvic radiograph, and hip magnetic resonance imaging (MRI) at a minimum of 10-year follow-up. Medical records, pelvis radiographs, and MR images of patients with borderline hips who underwent surgery, either hip arthroscopy (HAS) for predominantly femoroacetabular impingement (FAI) or periacetabular osteotomy (PAO), were retrospectively reviewed.

Among 45 hips (30 patients) treated nonoperatively (mean age, 23 ± 7 years), 4 hips (9%) showed progression to OA grade 1 at a mean of 15 ± 1 years of follow-up. The mean modified Harris Hip Score (mHHS) was 88 ± 12 at the last follow-up, with only 1 patient scoring <70. Of the surgical group (19 hips, 15 patients), procedures included PAO (5 hips) and HAS (14 hips). Acetabular retroversion (odds ratio [OR], 13 [95% CI, 1.4-122.9]; P = .02) and labrum hypertrophy (OR, 17.9 [95% CI, 1.4-228.1]; P = .03) correlated with lower mHHS but not with OA progression.

At a mean 15-year follow-up, 19 of 90 (21%) of borderline hips required preservation surgery. Of the 45 nonsurgical hips, 4 (9%) exhibited mild OA progression, and 3 of 4 hips (75%) maintained excellent functional outcomes. Acetabular retroversion and labrum hypertrophy were associated with poorer function but did not predict OA progression. Persistent symptoms were common in patients with labrum hypertrophy after HAS for FAI.