Case Series: The Dome Technique, an Option for Addressing Massive Anterosuperior Medial Acetabular Bone Loss
Key findings
- This case series reports on three patients who underwent revision total hip arthroplasty that included a novel solution for addressing large anterosuperior medial acetabular bone loss
- In the "Dome Technique," two porous metal augments are fashioned together and press-fit into the pelvis to recreate the anterosuperior column and fill the large medial bony void
- At an average of 23.6 months of follow-up (range, 10–37 months), all patients had minimal pain and had been able to return to physical activity
- At the time of publication, all three constructs remained radiographically stable and had not required subsequent revision
Massive anterosuperior medial acetabular bone loss is an uncommon but challenging problem that can be encountered in revision total hip arthroplasty (THA). Severe "up-and-in" defects, where the cup has migrated medially and the anterior column is no longer supportive, is classified as a Paprosky 3B defect.
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To date, treatment options are limited, and the results of such repairs have been mixed. In the case of triflanges, the implant is created preoperatively and cannot be customized during surgery, a potential problem because the extent of the bone loss cannot be fully appreciated until the acetabular component has been removed.
Orthopedic surgeon Christopher M. Melnic, MD, of the Center for Hip & Knee Replacement at Massachusetts General Hospital, and colleagues at Rush University recently reviewed three cases in which a novel solution for acetabular bone loss was used: the "Dome Technique." Their report appears in the HSS Journal.
The Technique
The article describes the Technique in detail. In brief, two porous metal augments are fashioned together and press-fit into the pelvis to recreate the anterosuperior column and fill the large medial bony void, allowing for intraoperative customization of the construct. This recreates the column for a revision jumbo tantalum cup to be impacted into place. Multiple screws are then placed into the inferior and superior hemipelvis to create a stable construct. If necessary, additional augments can be placed and then utilized by the acetabular component.
The Patients
The three patients included in this review had revision THA with the Dome Technique, performed by the same senior surgeon, between 2013 and 2016. No patients were excluded from the case series.
In all three cases, radiographs demonstrated migration of the acetabular component and bone loss consistent with a Paprosky 3B defect, and infection workup yielded negative results.
Case 1: A 53-year-old woman underwent right THA in 2007 for developmental dysplasia of the hip. Six years later, she presented with increasing and progressive groin pain, and right total hip acetabular revision was performed using the Dome Technique. No preoperative results of the 12-item Short-Form Health Survey (SF-12) were available, but her postoperative physical component summary score three years after revision surgery was 49.9. At the 37-month follow-up visit, the patient reported excellent, painless hip function and full range of motion.
Case 2: A 69-year-old man underwent primary left THA in 1998, and a two-stage revision for periprosthetic infection in 2006. He subsequently suffered a fall from a height while deer hunting and presented with increasing pain. In 2015, he underwent revision of the left acetabular component with the Dome Technique. His SF-12 physical component summary score was 34.1 preoperatively, and 53.5 two years after surgery. The patient returned to deer hunting, frequently hiking several miles at a time.
Case 3: A 59-year-old man underwent right THA in 1998, and revision of the acetabular component in 2015. He presented with severe groin pain and an inability to fully bear weight. Radiographs demonstrated an apparent pelvic discontinuity in addition to the acetabular defect. He underwent revision right THA in 2016 that involved revision of the acetabular component via the Dome Technique and acetabular distraction. His SF-12 physical summary score improved from 26.7 preoperatively to 29.1 at 10 months after surgery. At that follow-up, the patient reported continued weakness of the operative hip, for which he used a cane, but he had minimal pain and was participating in outpatient physical therapy.
Commentary
At the time this paper was written, all three constructs remained radiographically stable and had not required subsequent revision.
As the population ages, the number of THA revisions is expected to increase, and large anterosuperior medial acetabular defects might become more common. The Dome Technique seems to have no real limitations, and given the numerous options for augmenting size and shape, the construct can be intraoperatively customized to treat defects of any size.
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