Conversion of Prior Surgery to Total Hip Arthroplasty

CASE STUDY

A 50-year-old male presented with severe right hip pain, Trendelenberg gait, and limb length discrepancy. He had an open reduction with internal fixation for a childhood hip fracture. Radiographic evaluation demonstrated severe arthritic changes with proximal femoral deformity, retained hardware, and a limb length discrepancy ( Fig. 67.1 ). The patient elected to undergo total hip replacement. A cementless socket was utilized; while in the femur, a modular, cementless implant was utilized with distal fixation. The screws were removed from the plate, while the proximal end of the plate was resected to minimize hardware irritation ( Fig. 67.2 ).

$FIGURE 67.1, Radiograph depicts severe arthritic conditions of the hip with proximal femoral deformity, retained hardware, and subsequent limb length discrepancy from childhood hip fracture.$

FIGURE 67.2, Postoperative radiograph demonstrating conversion to total hip arthroplasty with bone grafting of the medial defect, removal of impinging hardware, and placement of modular taper femoral implant.

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Chapter Synopsis

This chapter addresses the major issues encountered during conversion to total hip arthroplasty (THA) after an earlier nonarthroplastic procedure.

Important Points

Although each case requires individualized attention, a thorough physical examination should be standard.
The most common reasons for conversion procedures are childhood osteotomies and failed repairs of hip fractures.
Issues to consider include leg length discrepancies, functional status of the abductors, anatomic distortions and old hardware that may affect implant selection, and choice of implants to achieve stability and functional range of motion.

Clinical/Surgical Pearls

Preoperative evaluation of periarticular infection should be considered.
Patients should be educated about expectations regarding function, gait abnormalities, and leg length discrepancy.
Standard extensile approaches should be considered in conversion procedures.
A trochanteric slide or osteotomy may improve exposure and avoid traumatic abductor rupture.
Hardware should be left in situ when possible before hip dislocation to prevent iatrogenic fracture.
Knowledge about the retained hardware can aid in its efficient removal.

Clinical/Surgical Pitfalls

Standard implants may not be appropriate, and specialty implants that provide stability without hardware removal may be a reasonable option.
In the early postoperative period, weight bearing may be limited, and hip abduction braces may be required.

Introduction

Conversion of a prior nonarthroplasty procedure to a total hip arthroplasty (THA) can be difficult due to retained hardware, anatomic distortions, and contractures that have developed. Each case requires individualized treatment and surgical techniques. Standard revision or specialty implants may be needed to accomplish stability and a functional range of motion (ROM). Creative planning may be necessary to achieve the appropriate outcome while minimizing the risk of perioperative complications.

Indications and Contraindications

Indications for conversion to a THA include previous pelvic or femoral osteotomies for hip containment, failed hip fracture repairs, and takedown of hip fusions. The cause of failure, which typically is specific for each patient, may be degenerative changes in the childhood osteotomy patient, articular cartilage damage, articular penetration of hardware in failed hip fracture repair, and development of ipsilateral joint arthritis after hip arthrodesis. Most patients can tolerate leg length discrepancies, limited hip ROM, and a Trendelenburg gait pattern.

A detailed history and physical examination can determine the condition that necessitated the prior surgery, any complications that occurred, and the durability of the procedure. The physical examination should include the assessment of the prior skin incisions, limb length discrepancies, abductor function, gait pattern, and neurologic status.

Leg length discrepancies should be measured and assessed as true or apparent. True leg length discrepancies are measured from the anterior superior iliac spine (ASIS) to the medial malleolus. Anatomic landmarks may be difficult to palpate, making clinical measurements inaccurate. Long leg computed tomography (CT) scanograms may be necessary for a more accurate assessment. Apparent leg length discrepancies stem from conditions that give the appearance of a shorter limb, such as pelvic obliquity from a lumbar spine condition, hip or knee flexion contractures, and hip abduction contractures.

Patients should be instructed about the difference between true and apparent leg length discrepancies and the goals of surgical intervention. The limits of limb lengthening should be explained. Rarely, a limb may need to be shortened. If shortening by more than 2 cm is required, a trochanteric advancement is required to obtain adequate abductor tension and decrease the risk of dislocation.

Abductor function and gait patterns should be assessed, and patients should be counseled about the results expected after surgical intervention. A shortened limb or decreased offset may decrease the abductor moment arm, producing a Trendelenburg gait pattern. Childhood osteotomies or hip fusions may lead to abductor atrophy or complete dysfunction. Clinical examination may not predict the overall function of the abductors. Electromyography (EMG) may provide further evidence about abductor function.

Finally, there must be a low threshold to rule out sepsis as a cause of failure. Rapid failure after hip fracture repair or a history of postoperative infection should trigger an evaluation for sepsis. Routine studies may include determinations of the erythrocyte sedimentation rate (ESR), C-reactive protein (CRP) level, and white blood cell (WBC) count. Further evaluation can be done with CT and magnetic resonance imaging (MRI) with contrast enhancement. In cases with retained hardware, nuclear medicine scans may demonstrate a reasonable level of specificity. Elevated blood test results or a high index of suspicion necessitates preoperative culture of a hip aspirate. Intraoperative cultures should also be performed on a routine basis.

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