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    PRACTICE PEARLS: Evaluating and Treating Recurrent THA Dislocation

    One of the most common complications of total hip arthroplasty (THA) is recurrent dislocation, occurring in 2% to 3% of patients. Of those, 30% to 50% occur within 3 months of surgery, and about 75% occur within the first year after surgery. Due to the multiple potential causes, recurrent dislocation can be difficult to diagnose and treat.

    The initial treatment for THA dislocation is closed reduction combined with abduction pillow or brace or a knee immobilizer, according to Rajesh N. Maniar, MD, from the Lilavati Hospital and Breach Candy Hospital in Mumbai, India, who reviewed his protocols for diagnosing and treating patients with recurrent THA dislocation at ICJR’s Pan Pacific Orthopaedic Congress. Surgical intervention, he said, is only needed after more than 2 dislocations.

    When a patient presents with multiple dislocations, the first step is a complete evaluation, including history and physical, and radiographic examination to find the cause of the dislocation. Based on the findings, the surgeon can plan the treatment to specifically address the cause.

    Evaluation

    The history should include a review of previous surgical notes and notation of the number and timing of dislocations. The chance of recurrence is 39% when the first dislocation occurred less than 5 weeks after surgery, increasing to 58% when it occurred more than 5 weeks after surgery.

    The physical examination should include evaluation of:

    • Leg length difference
    • Gait
    • Range of motion
    • Abductor strength
    • Neurovascular status

    Laboratory tests – including a C-reactive protein level and an erythrocyte sedimentation rate – should be ordered to rule out infection as a cause of recurrent dislocation.

    Radiographic imaging will provide additional information. Dr. Maniar recommends low AP pelvis view, AP of the hip, and cross-table lateral views, as well as CT scan. The radiographic imaging is scrutinized for the following:

    • Abduction/anteversion
    • Liner disassociation
    • Femoral offset
    • Component geometry, including head-to-neck ratio
    • Bone quality and integrity
    • Osteophytes
    • Osteolysis
    • Eccentric wear

    Treatment Options

    There are multiple causes of recurrent dislocation, and the choice of treatment must address the root cause.

    Component malposition: The surgical procedure is fairly straight forward in cases of malposition of the acetabular component, and research has shown good outcomes of repositioning the acetabulum. Reorientation of the femoral component, however, is a more difficult procedure with higher morbidity because it involves the removal of a well-fixed component.

    Inadequate soft tissue tension: Inadequate femoral offset or inadequate leg length restoration are the most common causes of inadequate soft tissue tension. Either of these causes can be addressed by exchanging components. On the acetabular side, elevated rim liners, face-changing liners, or lateral offset liners can be used. On the femoral side, neck length/offset or head diameter can be changed. These exchange procedures can only be done if the components are well fixed, abductor strength is good, and there are no neurologic disorders.

    Abductor muscle deficiency: This can be caused by trochanteric non-union or abductor muscle loss. In recent years, abductor muscle deficiency has been successfully treated with either vastus lateralis transfer or the use of jumbo femoral heads.

    Impingement: Impingement can occur between the femoral neck and the acetabulum, between the greater trochanter and the pelvis, or between the femur and the ischium. Impingement between the femoral neck and the acetabulum can be treated by improving the implant position, optimizing the head-neck ratio, removing an elevated liner, or increasing the femoral head size.

    The surgeon should intraoperatively check for impingement between the greater trochanter and the pelvis and between the femur and ischium. Each of these conditions is treated by excising the impinging bone: the anterior part of the greater trochanter, a prominent ischium, or a hypertrophic posterior-inferior capsule.

    Liner wear in cases with late dislocation: In case of liner wear, the treatment is a modular component exchange or upsizing the femoral head, the acetabular liner, or both.

     Compliance issues or multifactorial/unclear: Constrained liners, dual-mobility cups, or bipolar hemiarthroplasty can be used if the cause of dislocation is compliance issues, unclear, or multifactorial. Constrained liners have significantly increased the success rates of revision for dislocation, Dr. Maniar said. However, there are 2 concerns with constrained liners: (1) early acetabular loosening caused by the increased stresses at the bone-implant interface, and (2) an increased risk of component disassembly.

     The large head of dual-mobility hips increases the joint stability, making dual-mobility hips another good option for recurrent hip dislocation. The literature shows good outcomes for dual-mobility hips with low rates of recurrent dislocation. However, whether the long-term results for these prostheses hold up, particularly in younger patients, remains to be seen, Dr. Maniar said.

    Bipolar hemiarthroplasty is a rare procedure used for recurrent dislocation in patients with reduced capacity for bony ingrowth, such as avascular necrosis and irradiated pelvis. The procedure generally has good outcomes.

    Last resort: A girdlestone arthroplasty is a last-resort option for some recurrent dislocation patients.

    Recurrent dislocation in THA needs a systematic approach for the treatment to be successful. Through a thorough evaluation of the patient, it is usually possible to find the cause of and determine the right treatment option for these patients. If the cause is unclear or if the regular treatment options fail, constrained liners or dual-mobility components are alternatives that will usually provide good results.

    Click the image above to watch Dr. Maniar’s presentation from the Pan Pacific Orthopaedic Congress.

    Disclosures

    Dr. Maniar has disclosed that he is a consultant to Depuy Synthes.