Case #3 - Patient-Matched Tri-Flange Case Study
Dr. Edward McPherson M.D.
University of Southern California Medical Center
Chief complaint:
Left hip pain
History:
J.K. is a 52-year-old female referred to me for evaluation of progressive radiolucencies in her left hip. She suffers from developmental dysplasia of both hips.
J.K. has developed left hip pain in the last several months. The pain was particularly bothersome but settled down as she cut down on her activity level. She has been followed by a local orthopedist in the desert area, and the alarming issue has been that of progressive radiolucencies in her superior acetabulum as well as in her femoral stem. Radiographs taken recently compared to one year ago show a dramatic change in bone density of the proximal femur.
Currently, she is able to ambulate with a walker or crutches, but for long distance ambulation in the community she uses a wheelchair. She has been doing this for over four to five years.
X-rays:
X-rays brought in by the patient were reviewed. X-rays from August of 1997 and August of 1998 are used for comparison. The left hip shows a cemented all-polyethylene cup with a superolateral bone graft secured with screws. A long cemented stem is seen down the mid-diaphysis (see figure 1). A flexion deformity is seen in the femur due to a prior prosthetic fracture, which is now healed. Osteolytic lesions are seen in the superolateral acetabulum, ischium and pubis and the acetabular cup. Osteolysis is seen in several areas about the cement stem. Most striking is the change in density in the bone in the femoral shaft, more in the distal half than in the proximal half, indicative of progressive bone resorption.
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Figure 1
Treatment Plan:
The patient underwent a resection arthroplasty of her hip, and at the time of surgery severe bone deficiencies were seen in her acetabulum and femur due to infection and prior osteolysis. The segmental deficiencies of the acetabulum included the entire rim and underlying bone. The medial wall was completely deficient. The posterior wall remained intact along with the column. The anterior rim was deficient, but the anterior column was partially intact. The patient had high-dose antibiotic cement placed in the acetabulum, forming a neo acetabulum (see figure 2). The patient was then placed into a brace thereafter. The wound healed without event. She was treated for six weeks with antibiotics. After completing six weeks of I.V. antibiotics, the patient was left off of antibiotics for a total of three weeks. Repeat serum labs, consisting of Westergren sed rate and C-reactive protein, normalized. An aspiration culture was negative. She was then scheduled for reimplantation.
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Figure 2
Reconstruction Plans:
She has significant problems in terms of her reconstructive process. Her pelvis is very small and dysplastic in general. She has very shallow iliac width above her acetabulum. In addition, her bone is osteopenic due to her osteolysis and prior to infection. Because of her very young age, I was not in favor of using a bulk allograft as the incorporation of a bulk allograft may not do as well in the face of damaged tissues from infection. Furthermore, a bulk allograft is a three-dimensional porous structure, which has a high likelihood of hiding any bacteria that may still exist within the wound at the time of reimplantation. Her bone deficiencies in the acetabulum were too great to accept a reconstructed porous-coated hemi-shere, even in the deep profile design. Therefore, the design choice was a custom tri-flange cup with porous coating on the back side, filling out all bony defects as much as possible. Superior dome screws were placed to allow bicortical fit of long screws of up to 80 to 90mm in length to come up the bicortical area up to the iliac wing anteriorly and posteriorly.
On the femoral side, the bone defect in the proximal femur would require a modular revision system. The choice was a Mallory/Head® modular calcar replacement stem, as she was deficient proximally.
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Intraoperative Course:
The porous-coated tri-flange cup was placed with small modifications in the ischial area to allow the tri-flange cup to sit flush. The small gaps that remained were filled with fresh frozen allograft cancellous bone, which was lavaged with antibiotic solution prior to insertion. The cup was inserted and secured with superior 6.5 cancellous screws into the ilium for a length of 80 and 90mm, based on preoperative planning. The ischium was also secured with cancellous screws. No cement was used (see figures 3, 4, 5, and 6).
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 Figure 3 |
 Figure 4 |
 Figure 5 |
 Figure 6 |
She was allowed to stand to tolerance up until she could not stand for 20 minutes. At that point a spica cast was placed around here waist and thigh with hinges at the knee. The foot was incorporated into a long leg lower cast to preserve rotational stability of the osteotomy site. The patient was maintained touch weightbearing for six weeks and then progressed with weightbearing thereafter.
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