Biological Prosthesis for Total Hip Arthroplasty in Treatment of Adult Developmental Dysplasia of the Hip

Introduction

Developmental dysplasia of the hip (DDH), the most prevalent developmental childhood hip disorder, includes a complete spectrum of hip abnormalities from dysplasia to subluxation to dislocation of the hip joint1. As a result of weight bearing, displacement of the femoral head to the head side occurs. Depending on the severity, the displacement is classified as subluxation or dislocation. Long‐term weight bearing leads to severe hip dysplasia and hip dislocation in adulthood, with associated development of severe secondary osteoarthritis. In the early stages of DDH, a variety of techniques for acetabular osteotomy are available. However, most patients with osteoarthritis eventually need total hip arthroplasty2, 3.

Case Presentation and Surgical Procedure

We here present the case of a female patient aged 71 years who presented with right hip pain with no obvious precipitating factor for 2 years and failure to improve on non‐steroidal anti‐inflammatory drugs (NSAIDs). Her right hip pain had been getting worse for nearly six months. She could not tolerate the pain induced by walking 50 m. On physical examination she had hip joint flexion 80°, 10° of internal rotation, 20° of external rotation and Thomas Allis and Trendelenburg signs were all negative. X‐ray films showed right sided DDH of Crowe type II, joint dislocation, femoral head deformation, narrowing of the joint space and osteophytes on the acetabular rim. These are the typical findings in DDH secondary to osteoarthritis.

After admission, the patient underwent routine preoperative condition assessment and was considered fit for surgery. A modified Gibson incision was used to perform the procedure. Antibiotics were administered 30 min before surgery and 48 h after surgery. Multimodality analgesia was used after surgery, comprising iliac fascia nerve block combined with opioid analgesic and NSAIDS. Anti‐deep vein thrombosis (DVT) treatment was started on the first postoperative day; this included use of physical methods (foot pump, compression stockings) and drugs (low molecular weight heparin). Isometric quadriceps exercises started on the first postoperative day and the patient began weight bearing on the third postoperative day.

Discussion

In the advanced stages of DDH, hip pain becomes more severe and night pain and lameness develop. Hip joint function is limited, which severely affects the day‐to‐day life of patients. At this stage, total hip arthroplasty is the most appropriate treatment. Indications for surgery should be strictly limited to obvious hip pain and dysfunction that is not relieved by conservative treatment. It is inappropriate to perform total hip arthroplasty in patients with hip subluxation or dislocation without significant pain.

Preoperative Measurement and Prosthesis Design

Preoperative assessment requires measurement of the following on an anteroposterior (AP) plain X‐ray film of the pelvis.

1. The center‐edge (CE) angle. The normal hip CE angle is >25°; DDH can be diagnosed when it is <20°.

2. The acetabular index angle. Between 0°–10° is normal; this angle is generally >10° in patients with DDH.

3. The extent of osteoarthritis according to the following stages: (i) stage 0, acetabular dysplasia with no evidence of osteoarthritis; (ii) stage 1, slight changes in femoral head shape and slight joint space narrowing; (iii) stage 2, significant joint space narrowing, cystic changes in the femoral head; and (iv) stage 3, severe joint space narrowing, severe variant of the femoral head and curtain‐like osteophytes on the internal wall of the acetabulum.

More information can be provided by CT4, which can be used to assess bone quantity beneath the acetabulum, severity of acetabular osteophytes, and degree of femoral neck anteversion. Assessment of all these factors guides the choice of either a conventional prosthesis or a special one. We use appropriately magnified template contrast X‐ray films for preoperative prosthesis design. These enable determination of the size of the prosthesis, the location of the femoral neck osteotomy, the size of stem and cup and the center of rotation.

Surgical Techniques

It is generally thought that the failure rate of THA is higher in patients with DDH than in other patients5, 6. This is likely due to the complex anatomical abnormalities of hip dysplasia. Firstly, it is necessary to identify the true acetabular position. However the acetabulum is reconstructed, the acetabular cup must cover at least 75% of the area; otherwise the probability of acetabular component loosening will be significantly increased. Inward shift of the acetabular cup and use of a small prosthesis provides satisfactory support and reduces load distribution in the graft area. Secondly, the problem of proximal femur dysplasia must be addressed. These abnormalities include increased femoral anteversion and a straight or narrow medullary cavity. Conventional femoral prostheses adequately meet the treatment needs of patients with Crowe type II; however, specially designed prosthesis are often required for those with Crowe type IV7, 8. In patients with high dislocation, the sciatic nerve may be injured as a consequence of limb lengthening9. If there is serious shortening, osteotomy should be performed to prevent injury to the sciatic nerve10. As to selection of the acetabular component, Jasty et al. considers that cementless porous prostheses significantly improve long‐term outcomes11. The posterolateral approach has both advantages and shortcomings12, 13, 14. It is not technically difficult and provides good exposure. However, it is more difficult to control limb length with this procedure because posterior joint structures may be destroyed and this may cause joint dislocation. To correctly control the length of the limb, it is necessary to determine the rotation center of the acetabulum and the location of the osteotomy of the femoral neck preoperatively: doing so facilitates placing the prosthesis in the correct position. Both to reduce the incidence of postoperative dislocation and correctly handle the soft tissue balance around the joints, the prosthesis placement angle is particularly important. The acetabular cup anteversion angle and abduction angle should be confirmed intraoperatively, as should the anteversion angle of the femoral prosthesis. The joint capsule should be sutured carefully to reduce the incidence of dislocation.

Postoperative Treatment

Postoperative use of antibiotics, analgesia and the prevention of DVT are very important. Infection is a catastrophic complication, in addition to practicing strict asepsis during surgery, administration of preoperative antibiotics 30 min before surgery is also critical. Multimodality analgesia, including iliac fascia nerve block, opioid analgesics and NSAIDs, is recommended postoperatively. Early physical and drug therapy reduces the incidence of DVT.

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Supporting information

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