Most cases (4/5) were females (Table 1). Two of 5 patients had evidence of hip instability before injury. One patient had a constrained liner placed for recurrent hip dislocation. The patient had 2 previous revisions with deficient abductors and a vertical cup. Interestingly, 3 of 4 women in the study had hypothyroidism and 3 of 5 patients were smokers which could contribute to subtle undiagnosed metabolic bone abnormalities.
Patients sustained a variety of acetabular fracture patterns. All the fractures had substantial radiographic displacement (>1 cm) on the initial injury radiographs. For this article’s purposes, pelvic discontinuity was defined as a complete separation of the acetabulum into superior and inferior portions and synonymous with an acute transverse acetabulum fracture.11 All patients had hip imaging an average of 3.9 months before traumatic fracture (range 17 days–10.7 months), which showed no radiographic evidence of acetabular component migration, pelvic discontinuity, or bone loss.
According to the Judet and Letournel classification system, the fracture types were 2 transverse, 2 posterior column, and 1 posterior wall. The surgical approach used for fixation of fracture was posterior in 4 of 5 cases. In the posterior wall case (Fig. 1), the cup was significantly displaced and, consistent with our protocol, through a Kocher–Langenbeck surgical approach, the acetabular component was revised first and then the posterior wall fragments were fixed to the posterior column using a buttress plate with the cup used as a template. In the remaining fractures, 1 ilioinguinal and 3 Kocher–Langenbeck were used to best approach the fracture. In one patient (case 2) treated with an ilioinguinal approach for a transverse fracture, the principle displacement was anterior for the inferior portion of fracture. Because the acetabular prosthetic component remained affixed to the superior half of the fracture when intraoperatively tested with a ball-spike pusher through the fracture site, the acetabular component did not require revision.
In all the posterior approach cases (2 posterior columns, one posterior wall and one transverse fracture), the head components were replaced along with the liner. Three of 4 had the acetabular component revised to an average size of 55 (56, 56, and 54 mm) (Fig. 2). In one case, a displaced posterior column fracture resulted in no revision of the acetabular component because it remained affixed and stable to the posterior column fracture (Table 2). On reduction and plate/screw fixation of the posterior column, the acetabular component was stable and 2 supplemental screws were placed through the existing acetabular component. In these 4 cases, the average number of screws through the prosthetic acetabular cup were 2.8. Nonstructural bone graft was used in all cases (synthetic in 3 and autograft in 2).
Average time to clinical and radiographic union was 3 months. Average time of follow-up was 76.0 months with a range of 13–134 months (Table 2). There were no postoperative hip dislocations, fracture nonunions, or acetabular component revisions required within the follow-up period. There were no infections.
Acute periprosthetic traumatic fractures of the acetabulum are rare, as illustrated by an incidence of 0.07% quoted over a 20-year period from the Mayo Clinic Registry.2 Such injuries are a distinct entity from the more commonly reported periprosthetic defects involving chronic osteolysis, bone loss, and pelvic discontinuity secondary to wear, and revision surgery with acetabular component over-medialization.
In 1972, Miller et al12 reported 9 periprosthetic acetabulum fractures treated nonoperatively. However, only one case had a significant force associated with the “fracture,” so preexisting conditions, such as infection, osteolysis and component loosing, could not be excluded. None of the fractures in this series progressed to osseous union and many required subsequent resection arthroplasty. In one of the largest series to date, Peterson et al2 reported on 11 patients who sustained fractures of the acetabulum around a total hip component over a 20-year period. At the time of initial evaluation, there was no evidence of an atraumatic causal component including osteolysis or component migration identified radiographically.2 Eight of these patients were reported to have a stable hip prosthesis based on clinical and radiographic examination. In this cohort of 8 with radiographically stable “type 1” fractures, nonoperative treatment with limited weight-bearing was used. Six of these 8 patients went on to what the author defined as “successful treatment,” meaning radiographic union at a mean of 20 weeks with conservative management.2 Despite this, only 18% of patients (regardless of treatment) retained the same acetabular component as prior to the fracture at 5-year follow-up, the majority requiring acetabular component revision based on nonunion, pain, or loosening.2 Attempts in this study to treat transverse “fractures” using the cup as a so-called “internal plate” to achieve stability of the fracture and cup fixation with the use of anchoring screws failed. This highlights the high failure rate with nonoperative treatment after periprosthetic fractures regardless of initial displacement. This differs from our series in which, no patient required a revision of their acetabular component during the follow-up period; however, our study did not include nonoperatively treated fractures.
Complications after open reduction and internal fixation of periprosthetic acetabular fractures, as reported in the available literature, have focused on the difficulty achieving union and the ultimate need for revision within a short time period.2,12,13 Peterson et al2 reported a nonunion rate of 25% and a cup revision rate of 80%. In contrast, our series (centered on strict adherence to the principles of appropriate fracture fixation for cup stability) did not find any cases of nonunion. Interestingly, in Peterson's series, 2 patients with bicolumnar involvement who underwent plate fixation went on to experience uneventful fracture healing.2 This seems to highlight the importance of obtaining bony stability in such fractures to achieve union.
Based on our experience, we propose a treatment algorithm for traumatic periprosthetic acetabular fractures (Fig. 3). As with all trauma situations, attention should first be centered on Advanced Trauma Life Support algorithms as highlighted by Harvie et al and Peterson et al.2,14 Vascular lacerations can occur from high-energy displaced acetabular fractures and/or acetabular components/screws.2 Once the patient is hemodynamically stable and medically optimized, primary decision-making revolves around the fracture. To achieve this, we agree with many authors who stress the importance of fixation of the acetabular columns and walls.1,15 We fixed the fracture in all cases as we would any acetabular fracture and do not rely solely on “the cup as a plate” philosophy. Through the fracture approach, we assess stability of the cup. If the acetabular component is stable at the time of operation, it is not mandatory to revise the cup. Columnar fixation alone in this case is considered adequate for healing and acetabular component durability. Although not the original intent of our study, we believe that this treatment algorithm is also applicable to cases of intraoperative fractures.
The limitations of this clinical series include the small case numbers, retrospective nature, selection bias, and lack of any control group. Nevertheless, although the case number is small with patients excluded lacking adequate follow-up, we had more strict inclusion criteria compared with previous publications that also had small numbers. We focused on acute fractures secondary to trauma of significant force after placement of a functioning THA, thereby eliminating all chronic cases and those with preexisting osteolysis, bone loss, and/or component migration. A study strength is that radiographs before fracture were available allowing for exclusion of specified preexisting conditions. Therefore, we are able to propose, within the confines of our average 76.0-month follow-up time, a treatment algorithm and surgical technique that can result in acetabular component retention secondary to a stable osseous foundation.
This approach resulted in satisfactory outcomes in our patients without need for revision implants. In fracture patterns with columnar involvement, the columns were restored with plates and screws. In fracture patterns with wall involvement, the acetabular component functioned as a template for wall reconstruction with use of a buttress plate. The acetabular component was revised when deemed loose during stress of the component through the surgical approach used for fracture fixation. Team-based surgical management with arthroplasty- and fracture-trained surgeon(s) is paramount for optimal outcome.
1. Cha E, Ertl JP, Mullis BH. A case report: periprosthetic acetabulum
fracture with combined pelvic ring injury. J Orthop Trauma. 2012;26:e43–e45.
2. Peterson CA, Lewallen DG. Periprosthetic fracture
of the acetabulum
after total hip arthroplasty
. J Bone Joint Surg Am. 1996;78:1206–1213.
3. Sanchez-Sotelo J, McGrory BJ, Berry DJ. Acute periprosthetic fracture
of the acetabulum
associated with osteolytic pelvic lesions: a report of 3 cases. J Arthroplasty. 2000;15:126–130.
4. Helfet DL, Ali A. Periprosthetic fractures of the acetabulum
. Instr Course Lect. 2004;53:93–98.
5. Gelalis ID, Politis AN, Arnaoutoglou CM, et al. Traumatic periprosthetic acetabular fracture treated by acute one-stage revision arthroplasty. A case report and review of the literature. Injury. 2010;41:421–424.
6. Letournel E, Judet R. Fractures of the Acetabulum
. New York, NY: Springer; 1993.
7. Haidukewych GJ, Jacofsky DJ, Hanssen AD, et al. Intraoperative fractures of the acetabulum
during primary total hip arthroplasty
. J Bone Joint Surg Am. 2006;88:1952–1956.
8. Simon P, von Roth P, Perka C. Treatment algorithm of acetabular periprosthetic fractures. Int Orthop. 2015;39:1995–2003.
9. Chalmers BP, Pallante GD, Taunton MJ, et al. Can dislocation of a constrained liner be salvaged with dual-mobility constructs in revision THA? Clin Orthop Relat Res. 2018;476:305–312.
10. Guyen O, Lewallen DG, Cabanela ME. Modes of failure of osteonics constrained tripolar implants: a retrospective analysis of forty-three failed implants. J Bone Joint Surg Am. 2008;90:1553–1560.
11. Issack PS, Nousiainen M, Beksac B, et al. Acetabular component revision in total hip arthroplasty
. Part II: management of major bone loss and pelvic discontinuity. Am Orthop (Belle Mead, NJ). 2009;38:550–556.
12. Miller AJ. Late fracture of the acetabulum
after total hip replacement. J Bone Joint Surg Br. 1972;54:600–606.
13. Sharkey PF, Hozack WJ, Callaghan JJ, et al. Acetabular fracture associated with cementless acetabular component insertion: a report of 13 cases. J Arthroplasty. 1999;14:426–431.
14. Harvie P, Gundle R, Willett K. Traumatic periprosthetic acetabular fracture: life threatening haemorrhage and a novel method of acetabular reconstruction. Injury. 2004;35:819–822.
15. Gras F, Marintschev I, Klos K, et al. Navigated percutaneous screw fixation of a periprosthetic acetabular fracture. J Arthroplasty. 2010;25:1169.e1161–1164.
Keywords:Copyright © 2019 Wolters Kluwer Health, Inc. All rights reserved.
periprosthetic fracture; acetabulum; total hip arthroplasty