summary Adult Dysplasia of the Hip is a disorder of abnormal development of the hip joint resulting in a shallow acetabulum with lack of anterior and lateral coverage. Diagnosis is made with plain radiographs of the hip joint. Treatment typically involves periacetabular osteotomies for those with concentrically reduced hips with congruous joint space and total hip arthroplasty for those presenting with end stage osteoarthritis. Epidemiology Incidence US: 3-5% estimated that 10% of all THA are performed as a result of dysplasia Demographics females > males 2-4x relative risk increase Risk factors breech presentation, female sex, primiparity, and family history Etiology Pathophysiology abnormal movement of the femoral head within the acetabulum due to both osseous and soft tissue abnormalities leads to overload of the acetabular rim leading to secodnary OA Associated conditions increased femoral anteversion, coxa valga, head-neck junction deformitites, femoral head asphericity, hypoplasia of the femoral intramedullary canal, posterior displacement of the greater trochanter Anatomy Acetabulum normal anteversion 15°, abduction 45° Proximal femur femoral head center of the femoral head should be at level of the greater trochanter proximal femur normal femoral neck anteversion: 15° relative to the femoral condyles normal neck shaft angle: 125° Classification Crowe Classfication Grade Proximal displacement Femoral head subluxation I <10% vertical height of pelvis Proximal migration of head neck junction from inter-teardrop line <50% of femoral head vertical diameter II 10-15% 50-75% III 15-20% 75-100% IV > 20% >100% Hartofilakidis Classification Dysplasia (Type A) Femoral head within acetabulum despite some subluxation. Segmental deficiency of the superior wall. Inadequate depth of true acetabulum. Low dislocation (Type B) Femoral head creates a false acetabulum superior to the true acetabulum. There is a complete absence of the superior wall. Inadequate depth of true acetabulum. High dislocation (Type C) Femoral head is completely uncovered by the true acetabulum and has migrated superiorly and posteriorly. There is a complete deficiency of the acetabulum and excessive anteversion of the true acetabulum. Presentation Symptoms hip or groin pain with insidious onset exacerbating activitis include hip flexion or external rotation in weight bearing stance lateral hip pain and a limp or Trendelenburg gait may occur with abductor fatigue Physical exam insepction evaluation of gait; abductor fatigue or Trendelnburg sign overall ligamentous laxity; Beighton score motion increased internal rotation with the hip in flexion increased femoral anteversion provocative tests anterior apprehension sign lateral decubitus position, hip placed in extension as examiner applies progressive external rotation and adduction positive with apprehension and/or pain prone external rotation tests anterior-directed force on the posterior greater trochanter Imaging Radiographs recommended views AP lateral false-profile view findings asphericity of the femoral head coxa valga (increase neck-shaft angle) narrow femoral canal measurements lateral center-edge angle (LCEA) of Wiberg assesses superolateral coverage of the femoral head on the AP view angle between a verticle line through the center of the femoral head and the acetabular edge dysplastic: <20° 20-25° "borderline" 25-39° normal Tonnis angle inclination of the weight bearing portion of the acetabulum angle formed between the horizontal and a line along the superior acetabulum evaluated on the AP view dysplastic: >10° normal: <10° anterior center-edge angle of Lequesne assesses anterior coverage of the femoral head angle created between a vertical line through the center of the femoral head and the anterior acetabulum evaluated on the false-profile view dysplastic: <20° normal 25-40° >40° indicative of femoroacetabular impingement (FAI) Femoro-Epiphyseal Acetabular Roof (FEAR) index angle formed between the horizontal portion of the central proximal femoral physeal scar and the acetabular index evaluated on the AP view FEAR index <5° indicative of a stable hip not requiring treatment CT indications preoperative planning should only be ordered by treating surgeon findings adequate assessment of acetabular and proximal femoral osseous morphology including excessive anteversion or retroversion distal femur should be included in patients with clinical signs of femoral anteversion diameter of femoral canal may be over-estimated on AP radiographs and underestimated on lateral radiographs due to rotational mismatch of the metaphysis and diaphysis Prevention Identification and prevention of infantile developmental dysplasia (DDH) Pavlik harness, closed and open reductions, spica casting, proximal femoral osteotomies Treatment Nonoperative supportive measures role of long-term nonsurgical management in symptomatic dysplasia is limited given premature progression of secondary OA Operative hip arthroscopy indications controversial adjunct procedure to PAO for enhanced visualization and management of chondral, labral and proximal femoral cam-type lesions contraindicated in the setting of moderate to severe dysplasia outcomes chondral and labral pathology is a sequelae of osseous instability and may recur or progress if underlying pathology is not corrected associated with accelerated progression of arthritis, hip subluxation, less functional improvement, as well as increased risk of surgical failure and reoperation periacetabular osteotomy (PAO) indications symptomatic dysplasia in an adolescent or adult with a concentrically reduced hip and congruous joint space preserved range of motion intraoperative dynamic testing of hip motion is needed to determine the need for femoral osteotomy minimum of 90° flexion and 15° internal rotation to prevent FAI advantages provides hyaline cartilage coverage preserved integrity of the posterior column, which allows patients to weight bear as tolerated postoperatively large multidirectional corrections preserves external rotators delays need for arthroplasty outcomes reliably improves radiographic parameters and symptomatology 92% survivorship at 15 years in avoiding THA salvage pelvic osteotomy (Chiari, Shelf) indications unreduced hip recommended for patients with inadequate femoral head coverage and an incongruous joint (a salvage procedure) outcomes 84% survivorship at 17 years with advanced OA as an endpoint advanced DDH and asphericity of the femoral head associated with poor outcomes hip resurfacing indications can be used for Crowe type I or II disease outcomes unable to address leg-length discrepancy 10% revision rate at 6 years higher revision and complication rate with hip resufracing in patients with DDH compared to general population total hip arthroplasty (THA) indications treatment of choice for patients with end-stage OA secondary to dysplasia may need small acetabular components outcomes improves Harris Hip scores and pain outcomes for Crowe I and II patients are in similar to those of THA for primary OA in the short term revision rates for Crowe III and IV are higher than non-dysplastic hips long term follow up demonstrates a higher revision rate for THA in dysplastic hips increased complication profile: infection, instability and neruovascular injury risk of sciatic nerve injury if limb length changed by >4cm may need to perform femoral shortening (trochanteric or subtrochanteric) Techniques Supportive measures technique weight loss, NSAIDs, activity modification, intra-articular injections Hip arthroscopy technique should not be performed in isolation as it does not treat underlying pathologic cause hip arthroscopy performed concomitantly with PAO to address labral pathology or evaluate for chondral injuries if significant chondral injury is identified, PAO can be abandoned with minimal morbidity continues to be controversial Periacetabular osteotomy (PAO) (Ganz, Bernese) approach modified Smith-Petersen technique involves osteotomies in the pubis, ilium, and ischium near the acetabulum allows significant three-dimensional correction of the acetabulum complications hip arthroplasty performed after PAO may lead to increased incidence of a retroverted acetabular cup Salvage Osteotomies Chiari Osteotomy technique make cut above acetabulum to sciatic notch and shift ilium lateral beyond the edge of acetabulum depends on metaplastic bone (fibrocartilge) for successful results. complications shortens limb Shelf Osteotomy approach modified Smith-Petersen technique places extra-articular buttress of bone to the lateral acetabulum over the subluxed femoral head increases weight bearing surface cover femoral head with fibrocartilage (metaplastic bone), not articular cartilage Hip Resurfacing technique posterior approach with release from the piriformis to the gluteus maximus tendon partial gluteus maximus tendon release aids in exposure unable to address limb length complications postoperative femoral neck fracture Total Hip Arthroplasty approach anterior, lateral or posterior based approaches may be used technique trochanteric osteotomy may be needed to improve visualization, especially in Crowe type III or IV dysplastics goal is to place the acetabular component in the true acetabulum to restore normal hip center of rotation and biomechanics this may cause significant leg lengthening, which would subsequently require femoral shortening (trochanteric or subtrochanteric) components may need to be medialized or used with augments to gain adequate coverage and stability of the acetabulum can use uncemented cup if there is less than 30% uncoverage a high hip center can be used to gain adequate bony stability, but is less ideal biomechanically modular femoral components allow for correction of rotational deformities complications increased risk of loosening with a high hip center increased risk of neurovascular injury and infection Complications Sciatic nerve palsies 10 times increased incidence of sciatic nerve palsy (5-15%) lengthening of greater than 4 cm can lead to sciatic nerve palsy that will present clinically as a foot drop Nonunion 29% nonunion with greater trochanter osteotomy subtrochanteric osteotomy and trochanter advancement lowers nonunion rate Hip Dislocation increased risks of hip dislocation after arthroplasty (5-10%), especially when high hip center is used Component loosening placement of the acetabular component in a high hip position associated with increased risk of loosening Periprosthetic femur fx Infection Prognosis 48% of THA in patients < 50-years-old are a result of dysplasia