Abstract
Background
Acetabular bone loss in revision total hip arthroplasty can be very challenging even for fellowship-trained surgeons. Although it is uncommon, massive anterosuperior medial defects may be encountered, but treatment options have been limited and better ones are needed.
Questions/Purposes
The primary purpose of this case series is to describe a novel surgical treatment, which we call the dome technique, that can be used to address these challenging defects. The dome technique allows for the systematic reconstruction of massive anterosuperior medial defects of the acetabulum. We sought to illustrate the utility of this procedure in three patients with failed acetabular components and massive anterosuperior medial defects.
Methods
We undertook a retrospective chart review of three patients who had had Paprosky 3B bone defects and undergone revision total hip arthroplasty by the senior author between 2013 and 2016 using the dome technique. The procedure involved the use of tantalum metal augments pieced together to fill the medial defect and recreate the column support needed for jumbo cup placement. The dome technique is unusual because it allows for intra-operative customization to obtain the proper fit.
Results
At a mean of 23.6 months’ follow-up (range, 10 to 37 months), all patients had good functional outcomes; none was in need of further revision.
Conclusions
In three patients, the dome technique allowed for the anterosuperior column to be recreated by piecing together two porous metal augments to fill the medial bony void and create a stable column for a jumbo cup to be press fit. By recreating the deficient anterosuperior medial bone, the acetabulum can be downsized in a stepwise manner (with further surgery) and reconstructed in a stable fashion. This novel procedure is a unique option for the treatment of this challenging problem.
Introduction
Massive anterosuperior medial acetabular bone loss is uncommon in revision total hip arthroplasty (THA). A significant feature of the condition is that the anterior column is no longer supportive, and it is consequently often classified as a Paprosky 3B defect [11]. Treatment options have been limited to date to a custom triflange implant, but results of such repairs have been mixed [2, 5, 17]. In the treatment of acetabular bone loss, good short- and intermediate-term results have been achieved with intra-cavitary porous metal augments [1, 8–10, 16]; however, to our knowledge, the fastening of porous tantalum augments to address large anterosuperior medial defects has yet to be addressed in the literature.
The etiology of acetabular bone loss is multifactorial, and the extent of the bone loss cannot be fully appreciated until the acetabular component has been removed [12, 13]. Patients typically present with deep groin pain, as patients who require acetabular revision do, and may or may not be able to ambulate.
Porous metal augments have been shown to be helpful when treating acetabular defects; however, the surgeon must understand how the augments are functioning. As previously discussed by some of us (C.M.M., N.P.S., W.G.P.), defects of the anterosuperior column are classified as intra-cavitary defects [13]. During a type A reconstruction, augments chosen are secured with screws before acetabular cup placement and are used for primary construct stability. When massive anterosuperior medial bone loss is present, two porous metal augments can be fashioned together (Figs. 1 and 2) and press fit into the pelvis to recreate the anterosuperior column and fill the large medial defect. Augments used in this manner provide primary stability.
Demonstration of how two trial augments can be customized and pieced together to treat anterosuperior medial acetabular bone loss.
We present a case series of three patients with failed acetabular components and Paprosky 3B bone defects with massive anterosuperior medial defects. We describe a novel treatment, which we call the dome technique, to address these challenging defects. The dome technique allows for reconstruction in a systematic manner of massive anterosuperior medial defects of the acetabulum.
Methods
This is a retrospective chart review of a series of three patients undergoing revision total hip arthroplasty performed by the senior author (W.G.P.) between the years 2013 and 2016 using the dome technique. This review was conducted by multiple authors. No patients were excluded from this case series. The authors obtained informed consent for publication of this manuscript from each patient.
Surgical Technique
Each patient was placed in the lateral decubitus position. In all three cases, the earlier THA was performed with a posterior approach to the hip, and our surgeon employed an extensile posterior approach using the previous incision. An aspiration, tissue culture, and frozen section were obtained to assess for infection or acute inflammation. A robust posterior capsule in conjunction with external rotators was tagged with a no. 5 Ethibond suture and repaired at the end of the procedure. After dislocation of the hip, the ball head was removed with an impactor, and a pocket anterior to the acetabular component was created for the trunnion. In all cases, the polyethylene liner was removed, all remaining screws in the acetabular component were extracted, and the acetabular component was found to be grossly loose and was gently removed after complete disruption of the bone-implant interface. The obturator foramen, defining the inferior margin of the native acetabulum, was identified, and the acetabulum was debrided of all remaining fibrous tissue using electrocautery and a Cobb elevator. The anterosuperior and posteroinferior columns were then carefully inspected. In each case, anterosuperior medial bone loss significant enough to be classified as a Paprosky 3B defect was encountered. At this point, trial augments were fashioned together to fill the defect.
Once the senior surgeon was pleased with the trial reconstruction, final porous metal augments were pieced together and inserted into the defect. Crushed cancellous bone graft can be added to the reconstruction; in one case (patient 2), the surgeon used 60 cc. It is essential to obtain a press fit of the augments, as stated above, before reaming. Sequential reaming in reverse was then used to appropriately size the acetabulum between the newly constructed column and the intact posteroinferior column. In all three cases, a revision jumbo tantalum shell was used and impacted into place in appropriate inclination and anteversion, and a goal of 50% contact between the acetabular shell and host bone was achieved. A minimum of four 6.5-mm screws were then placed in the acetabular component. The entire construct was then unitized with cement after a press fit had been obtained. Of note, intra-operative imaging was not used in these three cases.
A highly cross-linked polyethylene liner was cemented into each acetabular component, followed by a trial reduction. The femoral stems were found to be stable in all cases. An appropriate cobalt chromium or ceramic ball head with a titanium sleeve was impacted onto the trunnion, the hip was reduced, leg lengths and stability were assessed, and the wound was copiously irrigated and closed.
Results
Case 1
Case 1 involved a 53-year-old woman with a history of right THA in 2007 for developmental dysplasia of the hip. Her past medical history was significant for hypertension, dyslipidemia, depression, and anxiety. She presented with increasing and progressive groin pain 6 years after the index surgery. Radiographs demonstrated migration of her acetabular component and bone loss consistent with a Paprosky 3B defect. An infection workup including erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), and aspiration at the time of surgery yielded negative results. Right total hip acetabular revision using the dome technique was performed in October 2013 (Fig. 3). Toe-touch weight bearing for 3 months with progression to full weight bearing thereafter was prescribed. Results of a pre-operative 12-item Short-Form Health Survey (SF-12) were not available, but her post-operative SF-12 physical component summary score at 3 years was 49.9. At a 37-month follow-up appointment, the patient reported excellent function and painless hip range of motion.
The 
Case 2
Case 2 involved a 69-year-old man with a history of a primary left THA in 1998 and a two-stage revision for periprosthetic infection in 2006. The past medical history was significant for gout, basal-cell carcinoma, benign prostatic hyperplasia, gastroesophageal reflux disease, and hypertension. He suffered a fall from a height while deer hunting and presented with increasing pain. Radiographs demonstrated migration of the acetabular component consistent with Paprosky 3B bone loss. An infection workup including ESR, CRP, and aspiration at the time of surgery yielded negative results. He underwent revision of the left acetabular component in July 2015; the dome technique was used (Fig. 4). Toe-touch weight bearing for 3 months with progression to full weight bearing thereafter was prescribed. The patient's pre-operative SF-12 physical component summary score was 34.1; at 2 years after surgery, the score had increased to 53.5. He returned to deer hunting, frequently hiking several miles at a time.
The 
Case 3
Case 3 involved a 59-year-old man with a history of a right THA in 1998 and subsequent revision of his acetabular component in 2015, both by surgeons outside the senior author's institution. There was no significant past medical history. The patient presented with severe groin pain and an inability to fully bear weight. Radiographs demonstrated migration of the acetabular component with bone loss consistent with a Paprosky 3B defect and an apparent pelvic discontinuity. An infection workup including ESR, CRP, and aspiration at the time of surgery yielded negative results. He underwent a revision right THA in April 2016 that involved revision of the acetabular component via the dome technique and acetabular distraction [14] (Fig. 5). Toe-touch weight bearing for 3 months with progression to full weight bearing thereafter was prescribed. His pre-operative SF-12 physical summary score was 26.7, which increased to 29.1 at 10 months after surgery. At this follow-up, the patient reported continued weakness of the right (operative) hip for which he used a cane, but he reported minimal pain and was participating in outpatient physical therapy.
The 
Discussion
We have presented a case series of three patients who underwent revision THA with the dome technique to address large anterosuperior medial acetabular bone loss. At a mean of 23.6 months’ follow-up (range, 10 to 37 months), all patients were performing well clinically. Although pre-operative functional information was limited, patients showed clear improvement post-operatively, both in function and in pain level. The patients were also able to return to physical activity after reconstruction. At the time of this writing, all three constructs have remained radiographically stable and have not required subsequent revision.
Few treatment options for large medial acetabular defects located anterosuperiorly have been described in the literature. Given that an increase in the number of revision THAs is projected, this complex and challenging problem will most likely become more common [6, 7]. Although triflange reconstruction has been shown to be an option for these defects, it may not rely on biologic fixation to host bone and does not allow for intra-operative customization [3, 4, 12, 15]. The dome technique allows for the anterosuperior column to be recreated by piecing together two porous metal augments to fill the medial bony void and allow for a stable column for a jumbo cup to be press fit. Once the intra-cavitary defect has been addressed, the acetabular defect classification can be effectively improved from Paprosky 3B to Paprosky 3A. The recommendation of the senior author (who performed surgery in these cases) is treatment of the extra-cavitary defect with supplemental fixation to transform the Paprosky 3A defect into type 2 defect [13]. Such a stepwise treatment sequence is essential when tackling these complex problems.
We believe this reconstruction technique has no real limitations: given the numerous options for augment size and shape, the construct can be intra-operatively customized to treat the defect, no matter how large it is. This is an advantage over a custom triflange implant, which is created before surgery and cannot be customized intra-operatively.
There are limitations to this study. First, because it is a retrospective case review, it is inherently biased. Second, there are only three patients in this case series. Fortunately, this problem is very uncommon.
In conclusion, the dome technique is a novel procedure that allows for the recreation of the anterosuperior column; two porous metal augments are pieced together to fill the medial bony void, which creates a stable column that allows fixation of a jumbo cup. The dome technique is a unique option for the treatment of this uncommon but challenging problem. Further long-term follow-up of a larger patient population is needed to determine whether the dome technique will be a superior treatment for massive anterosuperior medial acetabular defects.
Electronic supplementary material
Electronic supplementary material
Electronic supplementary material, 11420_2019_9730_MOESM1_ESM - The Dome Technique, an Option for Massive Anterosuperior Medial Acetabular Bone Loss: A Retrospective Case Series
Electronic supplementary material, 11420_2019_9730_MOESM1_ESM for The Dome Technique, an Option for Massive Anterosuperior Medial Acetabular Bone Loss: A Retrospective Case Series by, Christopher M. Melnic, MD, Matthew Knedel, MD, P. Maxwell Courtney, MD, Neil P. Sheth, MD, Wayne G. Paprosky, MD, in HSS Journal: The Musculoskeletal Journal of Hospital for Special Surgery
Electronic supplementary material
Electronic supplementary material, 11420_2019_9730_MOESM2_ESM - The Dome Technique, an Option for Massive Anterosuperior Medial Acetabular Bone Loss: A Retrospective Case Series
Electronic supplementary material, 11420_2019_9730_MOESM2_ESM for The Dome Technique, an Option for Massive Anterosuperior Medial Acetabular Bone Loss: A Retrospective Case Series by, Christopher M. Melnic, MD, Matthew Knedel, MD, P. Maxwell Courtney, MD, Neil P. Sheth, MD, Wayne G. Paprosky, MD, in HSS Journal: The Musculoskeletal Journal of Hospital for Special Surgery
Electronic supplementary material
Electronic supplementary material, 11420_2019_9730_MOESM3_ESM - The Dome Technique, an Option for Massive Anterosuperior Medial Acetabular Bone Loss: A Retrospective Case Series
Electronic supplementary material, 11420_2019_9730_MOESM3_ESM for The Dome Technique, an Option for Massive Anterosuperior Medial Acetabular Bone Loss: A Retrospective Case Series by, Christopher M. Melnic, MD, Matthew Knedel, MD, P. Maxwell Courtney, MD, Neil P. Sheth, MD, Wayne G. Paprosky, MD, in HSS Journal: The Musculoskeletal Journal of Hospital for Special Surgery
Electronic supplementary material
Electronic supplementary material, 11420_2019_9730_MOESM4_ESM - The Dome Technique, an Option for Massive Anterosuperior Medial Acetabular Bone Loss: A Retrospective Case Series
Electronic supplementary material, 11420_2019_9730_MOESM4_ESM for The Dome Technique, an Option for Massive Anterosuperior Medial Acetabular Bone Loss: A Retrospective Case Series by, Christopher M. Melnic, MD, Matthew Knedel, MD, P. Maxwell Courtney, MD, Neil P. Sheth, MD, Wayne G. Paprosky, MD, in HSS Journal: The Musculoskeletal Journal of Hospital for Special Surgery
Electronic supplementary material
Electronic supplementary material, 11420_2019_9730_MOESM5_ESM - The Dome Technique, an Option for Massive Anterosuperior Medial Acetabular Bone Loss: A Retrospective Case Series
Electronic supplementary material, 11420_2019_9730_MOESM5_ESM for The Dome Technique, an Option for Massive Anterosuperior Medial Acetabular Bone Loss: A Retrospective Case Series by, Christopher M. Melnic, MD, Matthew Knedel, MD, P. Maxwell Courtney, MD, Neil P. Sheth, MD, Wayne G. Paprosky, MD, in HSS Journal: The Musculoskeletal Journal of Hospital for Special Surgery
Footnotes
Electronic supplementary material
Compliance with Ethical Standards
Conflict of Interest:
Christopher M. Melnic, MD, Matthew Knedel, MD, and Neil P. Sheth, MD, declare that they have no conflicts of interest. P. Maxwell Courtney, MD, reports receiving consulting fees from Hip Innovation Technology and educational support from the Journal of Bone and Joint Surgery, outside the submitted work. Wayne G. Paprosky, MD, reports receiving consulting fees and royalties from Zimmer Biomet and Stryker, royalties from Innomed and Wolters Kluwer, and consulting fees and stock or stock options from Intellijoint Surgical, outside the submitted work.
Human/Animal Rights:
All procedures followed were in accordance with the ethical standards of the responsible committee on human experimentation (institutional and national) and with the Helsinki Declaration of 1975, as revised in 2013.
Informed Consent:
Informed consent was obtained by all patients included in this case series.
Required Author Forms
Disclosure forms provided by the authors are available with the online version of this article.