Treatment of periprosthetic acetabular fractures after previous hemi- or total hip arthroplasty: Introduction of a new implant

Abstract

Objective: Treatment of displaced periprosthetic acetabular fractures in elderly patients. The goal is to stabilize an acetabular fracture independent of the fracture pattern, by inserting the custom-made roof-reinforcement plate and starting early postoperative full weight-bearing mobilization.

Indications: Acetabular fracture with or without previous hemi- or total hip arthroplasty.

Contraindications: Non-displaced acetabular fractures.

Surgical technique: Watson-Jones approach to provide accessibility to the anterior and supraacetabular part of the iliac bone. Angle-stable positioning of the roof-reinforcement plate without any fracture reduction. Cementing a polyethylene cup into the metal plate and restoring prosthetic femoral components.

Postoperative management: Full weight-bearing mobilization within the first 10 days after surgery. In cases of two column fractures, partial weight-bearing is recommended.

Results: Of 7 patients with periprosthetic acetabular fracture, 5 were available for follow-up at 3, 6, 6, 15, and 24 months postoperatively. No complications were recognized and all fractures showed bony consolidation. Early postoperative mobilization was started within the first 10 days. All patients except one reached their preinjury mobility level. This individual and novel implant is custom made for displaced acetabular and periprosthetic fractures in patients with osteopenic bone. It provides a hopeful benefit due to early full weight-bearing mobilization within the first 10 days after surgery.

Limitations: In case of largely destroyed supraacetabular bone or two-column fractures according to Letournel additional synthesis via an anterior approach might be necessary. In these cases partial weight bearing is recommended.

Keywords: Acetabulum; Mobilization; Osteoporosis; Prosthesis; Weight-bearing.

Fig. 1

Custom-made roof-reinforcement plate showing the outer (a) and inner (b) surface with angle-stable screw holes. Courtesy of 41medical AG, Bettlach, Switzerland

Fig. 2

The surgical intervention takes place in general anesthesia and supine position. As surgical approach serves the classic anterolateral Watson-Jones approach which provides a perfect accessibility to the anterior and middle supra-acetabular part of the iliac bone. The landmarks for the skin incision include the anterior superior iliac spine, the greater trochanter and the plain of the femur. The incision starts 2.5 cm posterior and inferior to the anterior superior iliac spine and is slightly curved dorsally to the greater trochanter prolonged to the femoral shaft for about 5 cm

Fig. 3

The triangle of the tensor fascie latae, gluteus medius, and lateral vastus muscle is then identified and opened midway between the anterior spine and greater trochanter. Subsequently, the ridge of the lateral vastus muscle is revealed

Fig. 4

After exposure of the prosthesis, the leg is brought into second position while dislocating carefully the prosthetic head. Retractors are placed anteriorly, posteriorly, and inferiorly, to optimize visualization of the acetabular fracture. In patients with non-periprosthetic fractures, the capsule is exposed and resected by a T-shape incision. Furthermore, femoral neck osteotomy and acetabular cartilage removal is performed before stepwise socket reaming, starting from 44 up to 52 mm, and implant insertion. In periprosthetic fractures after total hip arthroplasty, the acetabular component is removed with or without all the cement, depending on the type of prosthesis. In case of hemiarthroplasty, only the prosthetic head has to be removed

Fig. 5

Next, 5 cm of the anterosuperior and superior part of the acetabular roof are freed from soft-tissue for positioning of the fin. Regardless of fracture type, the roof-reinforced plate is installed without any anterior-superior reduction of the fracture and carefully pressed with a tappet to the acetabular roof for good contact. In case of an anterior column fracture reaching up superiorly into the acetabular roof, the fin is positioned further posteriorly to purchase screw fixation. The fin is then fixed to the iliac bone by inserting 3.5-mm angle-stable screws aimed in different directions. The drill is guided by the 3.5-mm boring bush and should always penetrate the opposite cortex. The length of the screws is determined by means of a measuring instrument. Furthermore, additional screws are inserted through the upper holes in the ring and, if possible, through inferior holes as well

Fig. 6

In periprosthetic fractures no bon grafting is performed. A Prolene® mesh graft (Ethicon, Johnson & Johnson Medical, Norderstedt, Germany) is now sutured to the inner aperture of the implant ring to cover it and prevent cement leakage into the pelvis. In cases of an isolated acetabular fracture, slices of the resected femoral head are placed at the bottom of the implant ring to provide better bony stabilization and improve bony healing

Fig. 7

Subsequently, a polyethylene cup with diameter 46 mm is cemented into the metal cage and the prosthetic femoral components are restored in typical manner

Fig. 8

Postoperative AP X‑ray