Dysplastic Hip in Adults

Definition

Radiographic Definitions (Box 5.1)

AP pelvis radiograph showing the lateral CE angle and acetabular index. Both hips show shallow socket dysplasia. The acetabular index should normally be horizontal; the lateral CE angle should be ~30°. (Miller's Review of Orthopaedics, 9th Ed.)

Anatomy of Adult Hip Dysplasia

1. Acetabular Side

• Shallow acetabulum with deficient anterior and lateral coverage
• Decreased acetabular depth (socket less than a hemisphere; upsloping acetabular index)
• Varying degrees of superolateral subluxation and lateralization of the femoral head
• High articular contact stresses concentrated near the superolateral rim - the mechanical basis for early cartilage damage

2. Proximal Femur

• High neck-shaft angle (coxa valga)
• Increased femoral anteversion

Crowe Classification

Crowe classification for adult DDH showing progressive proximal displacement of the femoral head center of rotation. (Miller's Review of Orthopaedics, 9th Ed.)

Natural History

• Many mild cases are asymptomatic and go unrecognized on radiographs in childhood
• Hip pain in adults younger than 50 years is often the result of an underlying structural problem (dysplasia or FAI)
• Initial presentation of symptoms may be soon followed by rapid degeneration
• Abnormal biomechanics leads to progressive chondral damage and labral tears
• Untreated dysplasia progresses to secondary osteoarthritis (OA) - the main long-term sequela

Clinical Presentation (Spectrum)

• Presentation is often subtle; patients may describe it as a "groin pull"
• Anterior groin pain, aggravated by activity
• Mechanical symptoms (clicking, catching, giving way) from associated labral pathology
• Chondral surface delamination and chondral flap tears may also produce symptoms
• Examination: positive impingement test (flexion + adduction + internal rotation elicits groin pain), positive Stinchfield test

Investigations

Treatment

Goals of Surgical Correction

1. Relieve pain
2. Correct anatomic deformity
3. Long-term: reduce the occurrence of degenerative joint disease (DJD)

Options

• Activity modification, physiotherapy, analgesia
• Appropriate in mild/asymptomatic cases or those unfit for surgery

• For mild dysplasia with labral tears and early chondral damage
• Minimally invasive; rapid recovery but steep learning curve
• Limited role - does not address the underlying bony deformity

• The posterior column is preserved - maintains pelvic stability
• Does not violate the abductors
• Allows early weight bearing
• Permits significant correction of acetabular tilt and version
• Allows joint medialization (repositions center of hip rotation medially, lowering joint reactive forces)

• Acetabular roof index to zero
• Lateral CE angle restored to normal range
• Appropriate socket anteversion restored
• Overcorrection (retroversion → secondary FAI) must be avoided

• Previous hardware may be left in place if it does not interfere with acetabular component placement
• A retroverted socket from prior osteotomy means internal landmarks may not be reliable for cup positioning

• Varus femoral osteotomy corrects excessive valgus neck-shaft angle (coxa valga) and lateral uncovering
• Typically reserved for pediatric patients; less commonly used in adults
• Can be combined with PAO in selected cases

• Reserved for patients with established degenerative joint disease (DJD) who are no longer candidates for hip preservation
• Technical challenges in dysplastic THA: small true acetabulum, high-riding femoral head, short femoral canal, increased anteversion

Summary Table

• Miller's Review of Orthopaedics, 9th Edition, Section 2: Structural Hip Disorders in the Adult, pp. 422-425
• Bailey and Love's Short Practice of Surgery, 28th Edition, Ch. 39: Hip dysplasia in young adults, p. 575

Recent evidence note: A 2024 systematic review (PMID: 38919352) found that PAO in patients over 40 remains a viable option with acceptable outcomes in appropriately selected patients without significant pre-existing arthritis.