Clare Satterly November 16, 2016

In a recent study in the Netherlands, all 12 patients who underwent an acetabular reconstruction of large Paprosky type 3 defects using the Materialise aMace custom 3D printed acetabular implant, were recorded as being satisfied with the results of their procedure. The study, by Marieke Baauw, MD, Gijs Gerard van Hellemondt, MD and Maarten Spruit, MD, PhD from the Department of Orthopaedic Surgery at Sint-Maartenskliniek in Nijmegen, the Netherlands reported on their use of the aMace as part of an integral approach which included “a detailed approach to defect analysis, including measurement of bone deficiency and bone quality”. As reported in Helio Orthopaedics, the study presents positive results from a follow up of the 12 patients at least 18 months after surgery.

Materialise aMace acetabular cup

The study included patients with failed acetabular reconstructions and bone defects to such an extent that the use of regular techniques for reconstruction of large defects (ie, bone impaction grafting, solid bone graft, and anti-protrusio cages) was precluded. The authors comment in the article that they “were always able to introduce the custom device in the series of 12 and never had to resort to standard techniques.”

The surgical technique used in the study required a CT scan and special software to ascertain the degree of bone deficiency in the acetabulum and create a detailed plan “to restore the center of rotation and to compensate for the missing bone volume.” This enabled a 3D-printed porous augment and a cage (as either a monoblock or a modular construct) to be designed. The surgical plan provided “exact screw trajectories and screw lengths through the cup and flanges to the host bones of the ilium, ischium, and pubis, taking into account the bone quality for optimal screw purchase.” The surgeons were provided with an anatomical plastic model of the hemipelvis, trial implants in modular and monoblock fashion, and drill guides to identify the defect as assessed in the computed tomography scan analysis. The authors commented that “Using the trial implants, the pre-planned fit of the final implant to the acetabular defect was achieved.” Finally, the acetabular cup was introduced into the defect and fixed with the flange and cup screws using the drill guides provided.

Materialise aMace_augment

During a review of the 12 patients they completed a questionnaire and were all reported to be satisfied with their custom-made implant. The authors go on to comment that “The final implant matches the patient’s anatomy not only with the custom-made augment filling the acetabular defect perfectly but also with the precisely outlined flanges over the ilium, ischium, and pubic bone. Traditional augments and cages cannot accomplish this."

The full article “A Custom-made Acetabular Implant for Paprosky Type 3 Defects”, by Marieke Baauw, MD; Gijs Gerard van Hellemondt, MD; Maarten Spruit, MD, PhD appeared in Orthopedics: Now, Sep 2016, Volume 8, pp 1- 4, copyright Slack Incorporated.

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