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Review
Outcomes of post-operative periprosthetic acetabular fracture around total hip arthroplasty Expert Rev. Med. Devices 12(3), 307–315 (2015)
Todd P Pierce, Jeffrey J Cherian, Julio J Jauregui, Randa DK Elmallah and Michael A Mont* Center for Joint Preservation and Replacement, Sinai Hospital of Baltimore, Rubin Institute for Advanced Orthopedics, 2401 West Belvedere Avenue, Baltimore, MD 21215, USA *Author for correspondence: Tel.: +1 410 601 8500 Fax: +1 410 601 8501 [email protected]; [email protected]
Post-operative periprosthetic acetabular fractures are rare, but serious complication following total hip arthroplasty (THA). As the number of THA performed each year increases so will the expected number of periprosthetic fractures, thus making the treatment of these fractures an important topic for discussion. The purpose of this review is to analyze the recent evidence on risk factors, fracture classification schemes and treatment strategies that have been used for periprosthetic acetabular fractures around THA. The modified Paprosky classification is the most widely used and is a useful guide for management strategies. This classification system provides the guidelines for developing multiple treatment algorithms for decision making. Treatment options for surgical management include open reduction and internal fixation with plating, use of reconstruction cages, trabecular metal augments and bone grafting as needed. Treatment decisions are still an area of controversy and current research. KEYWORDS: acetabulum . arthroplasty . fracture . hip . periprosthetic . post-operative
Although rare, post-operative periprosthetic acetabular fractures can be a disastrous complication following total hip arthroplasty (THA). By the year 2030, it is projected that the number of THA’s performed in the USA will increase by 137% [1,2]. As this number increases, the post-operative complications such as periprosthetic acetabular fractures will continue to grow [3,4]. Currently, there is a paucity of population-based studies on periprosthetic acetabular fractures, thus the true prevalence and incidence of these fractures remain unknown. However, a registry-based study stated that approximately 6% of revision hip arthroplasties performed in the USA are due to periprosthetic fractures [5]. Moreover, given the growing elderly population, the increasing prevalence of osteopenia, and the rising popularity of certain acetabular implants such as cementless and monoblock constructs [6], these fractures will continue to rise in incidence. In general, the etiology of a post-operative periprosthetic acetabular fracture is multifactorial and may have some association with the characteristics of the implant used [6–8].
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10.1586/17434440.2015.991313
Typically, these fractures are caused by trauma or any pathological process that weakens the surrounding bone [6]. Of these, patients with underlying pathological processes may have fractures with low energy trauma, most commonly from a fall from ground level [6]. As the number of periprosthetic fractures increases, their treatment will become an increasingly important topic for discussion. As previously stated, these fractures may result in a revision procedure, which places a substantial economic burden on healthcare systems due to their high procedural costs [9]. Therefore, identifying risk factors and establishing appropriate treatment algorithms for periprosthetic acetabular fractures is imperative to minimizing complications while maximizing outcomes. Currently, there is a paucity of literature regarding the treatment of periprosthetic acetabular fractures, particularly those occurring post-operatively. Therefore, the purpose of this review is to analyze the recent evidence on: risk factors, fracture classification schemes and treatment strategies that have been used for fractures around THA.
2014 Informa UK Ltd
ISSN 1743-4440
307
Review
Pierce, Cherian, Jauregui, Elmallah & Mont
Expert Review of Medical Devices Downloaded from informahealthcare.com by University of Hong Kong Libraries on 05/10/15 For personal use only.
Methods
A review of the literature was performed using three electronic databases – PubMed, EBSCO Host and SCOPUS. Reports from January 1999 to July 2014 were included. Preference was given to randomized control trials, meta-analyses and data from national registries. Nevertheless, all relevant studies were included in this review. For the purposes of this review, the following manuscripts were excluded: non-English and reports that exclusively addressed the management of intra-operative periprosthetic acetabular fractures. The search was conducted using the following key terms: periprosthetic [title] AND acetabul*[title] AND fractur*[title]. Then, the following key terms were used: pelvic [title] AND discontinuity [title]. From these search strings, 47 reports were identified. These manuscripts were reviewed for data, and 18 were relevant to this review. For additional reports, the references of these 18 peerreviewed journal articles were reviewed and an additional 24 were used for this manuscript, resulting in a total of 42 applicable studies. Risk factors
Risk factors specific to post-operative periprosthetic acetabular fractures can be sub-divided into patient and implant-related [1]. Patient-related
Periprosthetic acetabular fractures may occur in the postoperative period secondary to trauma or to a stress fracture occurring at or adjacent to an area of significant osteolysis [1,10,11]. In a case series of three patients treated with THA by Sanchez-Sotelo et al. [12], it was noted that there was severe osteolysis in the areas where their periprosthetic acetabular fractures were located. They concluded that untreated severe pelvic osteolysis may lead to a fracture around acetabular prostheses. In contrast, there are studies which have demonstrated trauma as the predominant risk factor [8,13]. Unlike the previously mentioned studies, Peterson and Lewallen [13] evaluated the etiology of a series of 11 acetabular fractures. They found that eight of their post-operative acetabular fractures were caused by trauma, four by a motor vehicle accident and four by a fall from ground level, though none were associated with osteolysis. In addition to trauma and osteolysis, some studies report that female gender may be associated with an increased risk of periprosthetic acetabular fractures. Meek et al. [14] calculated the incidence of periprosthetic fractures around THA using data collected from the Scottish Arthroplasty Project. The authors found that women were more likely than men to have a fracture with a calculated hazard ratio of 1.5 (95% CI: 1.3–1.7) (p < 0.001). This might be attributed to the higher reported prevalence of falls in women when compared to men [1,14]. In addition, the authors believed the higher incidence of osteoporosis and osteopenia that women have relative to men would place them at an increased risk of fracturing at their prosthesis from low energy trauma such as a fall from 308
ground level [1,14,15]. However, because there were many more women receiving THA’s (nearly eight women for every five men), this may have been a confounder [14]. In addition, in a case series reported by Springer et al. [8], all patients who suffered a spontaneous periprosthetic transverse acetabular fracture were women. Also, all of the fractures occurred upon the resumption of physical activity. The authors also concluded that osteoporotic bone was a contributing factor. Another important risk factor to consider is age ‡70 years. In the previously mentioned epidemiological study performed in the UK, patients 70 years of age or older were more likely than those under 70 to be the victim of a periprosthetic fracture following THA (hazard ratio = 1.6; 95% CI: 1.4–1.9) (p < 0.001) [14]. Although older age has long been considered a risk factor for suffering from these fractures, there is some conflicting evidence for this assertion [1]. Singh et al. [16] associated increased age with a decrease risk of suffering a periprosthetic fracture (p < 0.001) due to the tendency of the elderly to live in a more sedentary manner [17,18]. In contrast, younger patients were more likely to fracture their prosthesis due to their more physically demanding lifestyles [17,18]. Implant-related
It is important to understand what implant characteristics may increase fracture risk. Multiple clinical studies have suggested that uncemented THA’s are at a higher risk of acetabular fracture compared to their cemented counterparts [7,8,19,20]. Haidukewych et al. [7] reported that there was a 0.4% prevalence of periprosthetic acetabular fracture in patients treated with cementless components (n = 21 out of 5329 patients), whereas there were no fractures in patients treated with cemented cups. In addition, monoblock implants have been found to be associated with an increased risk of periprosthetic acetabular fractures. These implants are uncemented acetabular components that are composed of a metal shell abutting the native acetabulum and a fitted polyethylene cup adjacent to the shell. Haidukewych et al. [7] reported a 0.09% prevalence rate of acetabular fractures with the use of hemispheric modular cups. That prevalence increased to 3.5% with THA’s that used elliptic monoblock cups (p < 0.001). The monoblock cups may increase the risk of fracture because they require more force to be inserted appropriately. Some fractures noticed on the post-operative follow-up visits not seen immediately after THA were non-displaced fractures that may have later propagated and became recognizable in the post-operative course after minor trauma. Larger cup sizes may be associated with an increased risk of periprosthetic acetabular fractures. Springer et al. [8] reported seven cases of spontaneous post-operative periprosthetic acetabular fracture after revision surgery. All of these cases involved an uncemented cup with a diameter greater than 58 mm. A biomechanical study examined the effect of placing different vertical loads on a finite elemental model of a pelvis and showed that increasing cup size in relation to the reamed acetabulum will intensify stress forces on the native acetabular Expert Rev. Med. Devices 12(3), (2015)
Post-operative periprosthetic acetabular fracture
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bone [21]. The authors noted that these stresses were below the level needed to cause a fracture, but this might be different in the presence of poor bone quality [21]. In summary, implants that are cementless, monoblock and have larger cup diameters may be associated with an increased risk of suffering from periprosthetic acetabular fractures. As new generation cementless designs become available, these risk factors may become less prevalent, but this remains an area of ongoing investigation.
Table 1. Modified Paprosky classification for periprosthetic acetabular fractures. Type
Description
I
Intra-operative during component insertion A: recognized, stable component, undisplaced fx B: recognized, displaced fx, cup instable C: not recognized intra-operatively
II
Classification
Although there have been several attempts to create a system to classify these types of fractures, the modified Paprosky classification scheme created by Della Valle et al. [22] has been the most widely used in the past decade (TABLE 1) [1,13]. This classification system for periprosthetic acetabular fractures is different from prior classification systems in two ways. It includes a scheme for classifying post-operative fractures. Previously constructed classification systems such as the Davidson system only classified intra-operative periprosthetic acetabular fractures [1]. It also provides surgeons with a guide to operative and nonoperative fracture management [1,6]. The Paprosky classification scheme for periprosthetic acetabular fractures has five fracture types. Type I and II are intra-operative fractures around the acetabulum, and their management will not be discussed in this review. Types III, IV and V are post-operative, and their current management will be described in detail. Type III fractures are those caused by post-operative trauma. They are sub-divided into types A and B based on acetabular component stability. Type IIIA fractures have a stable component, whereas Type IIIB fractures have an unstable component. Type IV fractures, or spontaneous fractures, are those associated with osteolysis. They are further sub-classified into types A and B. Type IVA fractures are those with less than 50% of the native host acetabulum lost. Type IVB fractures have greater than 50% of host bone lost. Type V fractures are any that show pelvic discontinuity, regardless of their etiology. They are sub-divided into types A, B and C. Like Type IV fractures, sub-types A and B are separated by the amount of host acetabulum bone that remains: sub-type A having more than 50% of host bone remaining, whereas sub-type B has less than 50% of the native acetabulum remaining. Type VC fractures are those associated with pelvic radiation, and they are managed exactly like Type VB fractures when using treatment algorithms. Management Type III – traumatic
When treating Type III fractures, it is essential to determine whether there is stability of the prosthetic component. This may not always be achieved through diagnostic imaging and clinical exam. Therefore, delineating between fracture Type IIIA and IIIB can be challenging because determining component stability may not always be possible without an intrainformahealthcare.com
Review
Intra-operative during removal A: less than 50% bone stock loss B: greater than 50% bone stock loss
III
Traumatic A: component stable B: component unstable
IV
Spontaneous A: less than 50% bone stock loss B: greater than 50% bone stock loss
V
Pelvic discontinuity A: less than 50% bone stock loss B: greater than 50% bone stock loss C: associated with pelvic radiation
fx: Fracture. Data taken from [22].
operative examination [6]. When considered stable, Type IIIA fractures may be treated non-operatively with limited weight bearing for 3 months or until there is appropriate fracture union seen radiographically. All type IIIB fractures, those with unstable prosthetic components, require surgery [6,13,23]. When deciding how to best manage type IIIA fractures, there is controversy as to whether operative or non-operative management is optimal. There remains a paucity of prospective studies evaluating the progression of traumatic fractures to union or the incidence of required surgical correction. Peterson and Lewallen [13] evaluated patients who sustained periprosthetic acetabular fractures (n = 11 THA’s; 8 IIIA) at a mean of approximately 6 years (range, 1–13 years) after THA. The surgeons managed these fractures with restricted weight bearing and activity modification. Of the eight traumatically caused fractures, six of them progressed to fracture union after a mean of 20 weeks (range, 6–40 weeks). However, after a mean follow-up of 62 months (range, 27–112 months), of the six that initially reached fracture union, four patients required early revision due to progressive pain and component loosening. Of the original eight fractures, two required acetabular component revision with bone grafting due to nonunion. Although the outcomes of nonoperative management have not been uniformly successful, the authors of both of these studies believe that non-operative management may be considered for type IIIA fractures because of its decreased cost, non-invasive nature and low risk to the patient’s long-term prognosis [24]. 309
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Pierce, Cherian, Jauregui, Elmallah & Mont
Based on the stability of the acetabular component, Helfet and Ali [25] described a treatment algorithm that can be used for type III fractures. If the acetabular component is stable and the fracture has minimal displacement, they recommend protected weight bearing for 6–8 weeks. After attempted nonoperative treatment, if the patient remains symptomatic or has radiographic evidence of nonunion or malunion, an open reduction and internal fixation (ORIF) with plates/screws and bone grafting should be performed. However, when the implant is stable, but the fracture is displaced, whether or not the patient should undergo operative or non-operative management is determined by evaluating pelvic stability. When pelvic evaluation demonstrates a stable pelvis, current standards recommend a trial of 6–8 weeks of protected weight bearing. Conversely, an unstable pelvis would be ideally treated with an ORIF and placement of bone graft as needed. When considering how to best accomplish ORIF for posttraumatic fractures, there has been some research regarding the use of double posterior plating, with eventual grafting and cemented THA. Recently, Laflamme et al. [26] retrospectively assessed the treatment strategies used for periprosthetic acetabular fractures (n = 32 fractures). After a mean follow-up of 36 months (range, 9–82 months), they found that those who had posterior wall fractures addressed with posterior column plating had no incidences of fixation failure of plate migration. Similarly, Bronsema et al. [27] evaluated the long-term outcomes of a cohort of patients with acetabular fractures treated using bone grafting and a cemented cup (n = 20 fractures). After a mean follow-up of 18 years (range, 12–26 years), with the endpoint being revision for any reason, the survival rate at 20 years was approximately 75% with a mean Harris hip score of 82 points (range, 56–100 points). Despite the positive results seen with this particular management strategy, there remains a paucity of studies that show its effectiveness in post-operative fractures. Furthermore, these studies did not detail the stability of the acetabular component, which may also guide management. Hence, the results of the aforementioned studies should be interpreted cautiously as further research is conducted on this treatment modality. Unlike type IIIA fractures, all type IIIB fractures require operative management due to prosthetic instability [6,25]. The goals of surgical intervention are to attempt to restore pelvic stability and adequate bone stock, and to securely fix the implant/constructs [6]. Furthermore, in cases of intra-pelvic migration of the acetabular component, the patient may need a pre-operative vascular assessment as these fractures are sometimes associated with vascular injuries [23]. With the risk to major vascular structures in mind, Patil et al. [24] recommends extraction of the cup using a distinct ilioinguinal approach. This allows direct visualization and protection of the common iliac vessels. For implants that are considered unstable, the Helfet and Ali [25] treatment algorithm supports using the displacement of the fracture to guide the operative plan. For minimally displaced fractures, the patient should undergo ORIF with bone grafting and revision of the acetabular component. 310
If the fracture is displaced and there is significant bone loss (greater than 50%), they recommend restoring the bone stock using allograft and conducting a cage fixation along with component revision. Currently, there are no studies detailing the use of bone graft and reconstruction cages specifically with type IIIB fractures. However, there are multiple studies on their use with type IV and type V fractures, and evidence about implementing these constructs will be discussed in detail with the management of type IV and V fractures. The management of Type III fractures is guided by the stability of the acetabular component. Stable acetabular component fractures may be managed non-operatively, but surgical intervention may eventually be required. Those with unstable components require surgical intervention using bone graft and fixation using a reconstruction cage. Type IV – spontaneous
These fractures are much less common than Type III or V; therefore, literature regarding their management is limited. However, it is generally agreed that these fractures require surgical management regardless of their sub-classification [6]. Unlike Type III fractures, the sub-types of Type IV fractures are differentiated by the amount of native bone that remains within the acetabulum, but distinguishing between type A and B can be difficult using plain radiographs as they tend to underestimate the amount of bone loss [22,28,29]. In general, although computerized tomography can be helpful in distinguishing the sub-types of Type IV fractures [30], the definitive fracture classification and operative plan are formulated based on a thorough intra-operative assessment of the remaining native acetabular bone [22,28]. If there is loss of less than 50% of acetabular host bone (Type A), it is recommended the patient undergo revision using a porous-coated hemispherical cup with screws and appropriate bone grafting [22]. Furthermore, among the Type IVA fractures, those that are isolated to the medial wall and do not extend into the anterior or posterior columns may be treated with morcellized bone graft. As such, these isolated fractures may not require plate fixation. Sanchez-Sotelo et al. [12] described the successful use of this technique for two such fractures. However, if the patient has more than 50% loss of acetabular bone (Type B), there are a large armamentarium of constructs that can potentially be used, including trabecular metal augments, reconstruction cages and trabecular metal revision cups [6,22,24]. If required, bone grafting and plating/screw fixation can be utilized to stabilize the fracture [22]. Winter et al. [31] evaluated the use of bone grafting along with a BurchSchneider reconstruction cage model in an attempt to reconstruct these defects when there was more than 50% bone loss (n = 38). After a mean follow-up of approximately 7 years (range, 4–9 years), none of the subjects had radiographic signs of component loosening and all reported significant improvements in the following functional outcomes: pain, negotiating stairs, range of motion and walking capacity without supportive Expert Rev. Med. Devices 12(3), (2015)
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Post-operative periprosthetic acetabular fracture
device (p < 0.001). The sole use of porous-coated hemispheric components is not recommended for Type IVB fractures as they have been associated with high failure rates [22]. The higher failure rates of these constructs are possibly due to the lack of native bone, resulting in poor host bone ingrowth, hence, difficulty achieving adequate biologic fixation [22,32–36]. In general, the amount of host bone remaining in Type IV fractures will direct the operative management of the patient. Type IVA fractures have progressed to union through the use of porous-coated hemispheric cups, and isolated bone graft may be considered depending on the location of the fracture. However, Type IVB fractures require different constructs, and most reports suggest the use of reconstruction cages in conjunction with bone grafts. Type V – pelvic discontinuity
Among all of the group classifications constructed by the Della Valle et al. [22], modified Paprosky classification, the most extensive amount of research has been done on the treatment of pelvic discontinuity. Similar to Type IV fractures, management of Type V fractures is guided by the amount of acetabular host bone that remains. All fractures leading to pelvic discontinuity require surgical treatment. However, unlike Type IV fractures, the use of different methods of component revision for Type VB and VC fractures remain an area of controversy. With this in mind, management decisions are guided by the following principles [37–39]: . . . .
Restoring continuity of the acetabulum (connect ilium to ischium). Grafting of any bony deficiencies or fracture lines. Optimizing contact of remaining viable bone to component surfaces with potential for bony ingrowth. Obtaining a mechanically stable reconstruction.
Methods of fixation that have been investigated include the use of acetabular transplants, trabecular metal acetabular components and cup–cage constructs [37,40]. In the treatment of Type VA fractures, one commonly used method is the use of reconstruction cages, which should bridge the superior and inferior portions of the pelvis. This should allow the temporary stabilization of the fracture during bone graft incorporation and fracture healing [1]. Nevertheless, the literature appears to favor the use of reconstruction cages with Type VA fractures, but it discourages its use with Type VB fractures. One of the first published uses of reconstruction cages for Type VA fractures was carried out by Berry et al. [41]. They evaluated 27 patients who had pelvic discontinuity that were fixed using reconstruction cages with uncemented components and compared them to those with cemented components without cages at a mean follow-up of 3 years. A satisfactory result was defined as no additional operations on the acetabulum, a stable acetabular component, definite or possible healing of the discontinuity and the absence of severe pain. None of the patients undergoing reconstruction using cemented components informahealthcare.com
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had satisfactory outcomes. However, 77% of patients in the cage group had satisfactory outcomes with the most success found in those who had more host bone remaining (greater than 50% native acetabulum). Similarly, Kosashvili et al. [42] evaluated 24 patients with no segmental defects in the acetabulum (Type VA fractures), who were diagnosed with discontinuity (n = 26 discontinuities). After a mean follow-up of 45 months (range, 24–68 months), where failure was defined as migration of the component by greater than 5 mm, 12% failed (n = 3 out of 24 hips). The surgeons concluded that reconstructive cages were a reliable option for patients who had pelvic discontinuity whenever most of their native acetabulum is intact. Paprosky et al. [43] constructed an operative treatment algorithm for patients who have pelvic discontinuity [40,43]. The authors formulated this plan by dividing pelvic discontinuity into two types – acute (synonymous with Type VA fractures) and chronic (synonymous with Type VB fractures). For those grouped into acute discontinuity, or Type VA fractures, bony apposition of fragments can be achieved by compression of the opposing fracture segments together. This can be performed with an ORIF with plating. For Type VB and VC fractures, the use of reconstruction cages may not be ideal because the design may not allow for the bony ingrowth necessary for fixation in the presence of significant bone loss [40,43]. Paprosky et al. [40] reported that with the use of acetabular cages for patients with pelvic discontinuity and with greater than 50% of the native acetabulum lost (n = 15), there was a 31% revision rate and 44% of the patients presented with aseptic loosening at a mean follow-up of 5 years (range, 2–8 years). The authors attributed this poor success rate to the difficulty of restoring the massive bone loss with bone graft and the inability to achieve the perfect contact between the cage and remaining native bone [38]. Furthermore, Paprosky et al. [43] conducted an evaluation of the pain level of a group of patients with acetabular defects that were associated with pelvic discontinuity. The treatment group was surgically corrected using trabecular metal acetabular components along with augments, if needed (n = 12), and they were compared with patients who had defects treated by applying a reconstruction cage (n = 12). After a 2-year mean follow-up (range, 1–3 years), six of the patients who had cage reconstruction reported moderate or severe pain. Of those treated with trabecular metal acetabular prosthetics, 11 claimed to have no pain or mild pain. Paprosky et al. [43] formulated a plan for treating what are currently classified as Type VB fractures. It is unlikely that these patients have the potential to progress to union. Therefore, a reconstruction cage is not considered ideal for achieving stability. Hence, stability is achieved by distraction of the discontinuity. The successful use of distraction for patients in chronic discontinuity was recently described by Sporer et al. [44] from an investigation of a series of revision THA’s in pelvic discontinuity. The authors achieved a re-revision rate of only 5% (n = 1 out of 20 THA’s), which led them to recommend the use of distraction for Type VB fractures. Paprosky et al. [43] 311
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Pierce, Cherian, Jauregui, Elmallah & Mont
15–84%) for the cage only group (p = 0.009). The authors believe that their construct will be a focus of continued research and long-term follow-up studies. Reconstruction cages can be used for Type VA fractures. However, newer constructs such as cup–cage models may be necessary to appropriately treat Type VB and VC fractures.
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Author’s preferred treatment
Figure 1. Jumbo cup for Type IVB fracture.
recommend using a modular trabecular metal acetabular component with one or two augments to span the discontinuity and provide internal fixation of the pelvis. In a recent report, this recommendation was supported by the American Academy of Orthopaedic Surgeons [45,46]. Nehme et al. [37] explored the use of modular trabecular metal components for 16 revision THA, and at a mean follow-up of nearly 32 months (range, 24–39 months), there was no evidence of implant migration or loosening. Given the extensive literature regarding the need to find different ways to surgically revise Type VB and VC fractures, the use of cup–cage reconstruction models for revision remains an area of increased research focus. Abolghasemian et al. [47] evaluated the use of the cup–cage model compared with standard ilio–ischial reconstruction cage for those in pelvic discontinuity (n = 26 discontinuities in 24 patients). The cup–cage constructs had a significantly higher 7-year survivorship of 87.2% (95% CI: 71–103%) compared with 49.9% (95% CI:
The modified Paprosky classification that was first described by Della Valle et al. [22] provides an effective tool that can be used in the guidance of management. Upon initial evaluation, it is essential to perform a thorough history and physical. In addition, anterior, posterior and lateral radiographs should be obtained and compared with previous radiographs for evidence of component migration, fractures or pelvic discontinuity. Although not necessarily required, it is common practice for a CT scan to be performed because of its ability to quantify the amount of bone loss and to assist in operative planning. Due to the difficulty in classifying these fractures, it is common practice to have a large armamentarium of treatment options while in the operating room, including, but not limited to, trabecular augments, reconstruction cages and bone grafts. For Type IIIA fracture, it is not uncommon to proceed with non-operative management with toe-touch weight-bearing for at least 12 weeks. If there is no radiographic evidence of progression to union, the senior author would recommend ORIF with bone grafting of the defect. For Type IIIB fractures, operative management is seen as imperative to patient care, sometimes in conjunction with a pre-operative vascular assessment. In patients with a substantial amount of component migration, which is considered at or past Ko¨hler’s line, a vascular consult would be obtained and along with a computed tomography angiogram of the pelvis and lower extremities bilaterally. All Type IV fractures are operatively managed. For Type IVA fractures, porous-coated hemispherical cups are used with bone graft available if needed. However, trabecular augments and reconstruction cages are kept in the operating room (FIGURES 1 & 2). Type V fractures, regardless of sub-classification, require operative management. If the fracture is Type VB, reconstruction cages are considered insufficient to achieve the stability necessary for adequate fixation. The senior author believes that the use of trabecular metal acetabular components supplemented with augments to bridge the discontinuity should be further explored. In addition to obtaining the proper alignment and to reconstruct the native anatomy of the acetabulum, limiting soft tissue disturbance surrounding the fracture location is just as important as the construct chosen for fixation. With this in mind, using less invasive techniques offers the benefit of minimizing soft tissue disruption and protecting the blood supply to promote fracture union. Expert commentary & five-year review
Figure 2. Reconstruction cage for Type IVB facture.
312
The prevalence rates of post-operative periprosthetic acetabular fractures will continue to increase over time. This is most Expert Rev. Med. Devices 12(3), (2015)
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Post-operative periprosthetic acetabular fracture
Review
Periprosthetic likely due to the growing number of >50% acetabular Unstable No native bone indications of THA, longer life expecfracture lost tancy, the rising number of patients under 65 years of age who are obtaining THA’s and the stresses placed on the Yes
Review
Outcomes of post-operative periprosthetic acetabular fracture around total hip arthroplasty Expert Rev. Med. Devices 12(3), 307–315 (2015)
Todd P Pierce, Jeffrey J Cherian, Julio J Jauregui, Randa DK Elmallah and Michael A Mont* Center for Joint Preservation and Replacement, Sinai Hospital of Baltimore, Rubin Institute for Advanced Orthopedics, 2401 West Belvedere Avenue, Baltimore, MD 21215, USA *Author for correspondence: Tel.: +1 410 601 8500 Fax: +1 410 601 8501 [email protected]; [email protected]
Post-operative periprosthetic acetabular fractures are rare, but serious complication following total hip arthroplasty (THA). As the number of THA performed each year increases so will the expected number of periprosthetic fractures, thus making the treatment of these fractures an important topic for discussion. The purpose of this review is to analyze the recent evidence on risk factors, fracture classification schemes and treatment strategies that have been used for periprosthetic acetabular fractures around THA. The modified Paprosky classification is the most widely used and is a useful guide for management strategies. This classification system provides the guidelines for developing multiple treatment algorithms for decision making. Treatment options for surgical management include open reduction and internal fixation with plating, use of reconstruction cages, trabecular metal augments and bone grafting as needed. Treatment decisions are still an area of controversy and current research. KEYWORDS: acetabulum . arthroplasty . fracture . hip . periprosthetic . post-operative
Although rare, post-operative periprosthetic acetabular fractures can be a disastrous complication following total hip arthroplasty (THA). By the year 2030, it is projected that the number of THA’s performed in the USA will increase by 137% [1,2]. As this number increases, the post-operative complications such as periprosthetic acetabular fractures will continue to grow [3,4]. Currently, there is a paucity of population-based studies on periprosthetic acetabular fractures, thus the true prevalence and incidence of these fractures remain unknown. However, a registry-based study stated that approximately 6% of revision hip arthroplasties performed in the USA are due to periprosthetic fractures [5]. Moreover, given the growing elderly population, the increasing prevalence of osteopenia, and the rising popularity of certain acetabular implants such as cementless and monoblock constructs [6], these fractures will continue to rise in incidence. In general, the etiology of a post-operative periprosthetic acetabular fracture is multifactorial and may have some association with the characteristics of the implant used [6–8].
informahealthcare.com
10.1586/17434440.2015.991313
Typically, these fractures are caused by trauma or any pathological process that weakens the surrounding bone [6]. Of these, patients with underlying pathological processes may have fractures with low energy trauma, most commonly from a fall from ground level [6]. As the number of periprosthetic fractures increases, their treatment will become an increasingly important topic for discussion. As previously stated, these fractures may result in a revision procedure, which places a substantial economic burden on healthcare systems due to their high procedural costs [9]. Therefore, identifying risk factors and establishing appropriate treatment algorithms for periprosthetic acetabular fractures is imperative to minimizing complications while maximizing outcomes. Currently, there is a paucity of literature regarding the treatment of periprosthetic acetabular fractures, particularly those occurring post-operatively. Therefore, the purpose of this review is to analyze the recent evidence on: risk factors, fracture classification schemes and treatment strategies that have been used for fractures around THA.
2014 Informa UK Ltd
ISSN 1743-4440
307
Review
Pierce, Cherian, Jauregui, Elmallah & Mont
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Methods
A review of the literature was performed using three electronic databases – PubMed, EBSCO Host and SCOPUS. Reports from January 1999 to July 2014 were included. Preference was given to randomized control trials, meta-analyses and data from national registries. Nevertheless, all relevant studies were included in this review. For the purposes of this review, the following manuscripts were excluded: non-English and reports that exclusively addressed the management of intra-operative periprosthetic acetabular fractures. The search was conducted using the following key terms: periprosthetic [title] AND acetabul*[title] AND fractur*[title]. Then, the following key terms were used: pelvic [title] AND discontinuity [title]. From these search strings, 47 reports were identified. These manuscripts were reviewed for data, and 18 were relevant to this review. For additional reports, the references of these 18 peerreviewed journal articles were reviewed and an additional 24 were used for this manuscript, resulting in a total of 42 applicable studies. Risk factors
Risk factors specific to post-operative periprosthetic acetabular fractures can be sub-divided into patient and implant-related [1]. Patient-related
Periprosthetic acetabular fractures may occur in the postoperative period secondary to trauma or to a stress fracture occurring at or adjacent to an area of significant osteolysis [1,10,11]. In a case series of three patients treated with THA by Sanchez-Sotelo et al. [12], it was noted that there was severe osteolysis in the areas where their periprosthetic acetabular fractures were located. They concluded that untreated severe pelvic osteolysis may lead to a fracture around acetabular prostheses. In contrast, there are studies which have demonstrated trauma as the predominant risk factor [8,13]. Unlike the previously mentioned studies, Peterson and Lewallen [13] evaluated the etiology of a series of 11 acetabular fractures. They found that eight of their post-operative acetabular fractures were caused by trauma, four by a motor vehicle accident and four by a fall from ground level, though none were associated with osteolysis. In addition to trauma and osteolysis, some studies report that female gender may be associated with an increased risk of periprosthetic acetabular fractures. Meek et al. [14] calculated the incidence of periprosthetic fractures around THA using data collected from the Scottish Arthroplasty Project. The authors found that women were more likely than men to have a fracture with a calculated hazard ratio of 1.5 (95% CI: 1.3–1.7) (p < 0.001). This might be attributed to the higher reported prevalence of falls in women when compared to men [1,14]. In addition, the authors believed the higher incidence of osteoporosis and osteopenia that women have relative to men would place them at an increased risk of fracturing at their prosthesis from low energy trauma such as a fall from 308
ground level [1,14,15]. However, because there were many more women receiving THA’s (nearly eight women for every five men), this may have been a confounder [14]. In addition, in a case series reported by Springer et al. [8], all patients who suffered a spontaneous periprosthetic transverse acetabular fracture were women. Also, all of the fractures occurred upon the resumption of physical activity. The authors also concluded that osteoporotic bone was a contributing factor. Another important risk factor to consider is age ‡70 years. In the previously mentioned epidemiological study performed in the UK, patients 70 years of age or older were more likely than those under 70 to be the victim of a periprosthetic fracture following THA (hazard ratio = 1.6; 95% CI: 1.4–1.9) (p < 0.001) [14]. Although older age has long been considered a risk factor for suffering from these fractures, there is some conflicting evidence for this assertion [1]. Singh et al. [16] associated increased age with a decrease risk of suffering a periprosthetic fracture (p < 0.001) due to the tendency of the elderly to live in a more sedentary manner [17,18]. In contrast, younger patients were more likely to fracture their prosthesis due to their more physically demanding lifestyles [17,18]. Implant-related
It is important to understand what implant characteristics may increase fracture risk. Multiple clinical studies have suggested that uncemented THA’s are at a higher risk of acetabular fracture compared to their cemented counterparts [7,8,19,20]. Haidukewych et al. [7] reported that there was a 0.4% prevalence of periprosthetic acetabular fracture in patients treated with cementless components (n = 21 out of 5329 patients), whereas there were no fractures in patients treated with cemented cups. In addition, monoblock implants have been found to be associated with an increased risk of periprosthetic acetabular fractures. These implants are uncemented acetabular components that are composed of a metal shell abutting the native acetabulum and a fitted polyethylene cup adjacent to the shell. Haidukewych et al. [7] reported a 0.09% prevalence rate of acetabular fractures with the use of hemispheric modular cups. That prevalence increased to 3.5% with THA’s that used elliptic monoblock cups (p < 0.001). The monoblock cups may increase the risk of fracture because they require more force to be inserted appropriately. Some fractures noticed on the post-operative follow-up visits not seen immediately after THA were non-displaced fractures that may have later propagated and became recognizable in the post-operative course after minor trauma. Larger cup sizes may be associated with an increased risk of periprosthetic acetabular fractures. Springer et al. [8] reported seven cases of spontaneous post-operative periprosthetic acetabular fracture after revision surgery. All of these cases involved an uncemented cup with a diameter greater than 58 mm. A biomechanical study examined the effect of placing different vertical loads on a finite elemental model of a pelvis and showed that increasing cup size in relation to the reamed acetabulum will intensify stress forces on the native acetabular Expert Rev. Med. Devices 12(3), (2015)
Post-operative periprosthetic acetabular fracture
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bone [21]. The authors noted that these stresses were below the level needed to cause a fracture, but this might be different in the presence of poor bone quality [21]. In summary, implants that are cementless, monoblock and have larger cup diameters may be associated with an increased risk of suffering from periprosthetic acetabular fractures. As new generation cementless designs become available, these risk factors may become less prevalent, but this remains an area of ongoing investigation.
Table 1. Modified Paprosky classification for periprosthetic acetabular fractures. Type
Description
I
Intra-operative during component insertion A: recognized, stable component, undisplaced fx B: recognized, displaced fx, cup instable C: not recognized intra-operatively
II
Classification
Although there have been several attempts to create a system to classify these types of fractures, the modified Paprosky classification scheme created by Della Valle et al. [22] has been the most widely used in the past decade (TABLE 1) [1,13]. This classification system for periprosthetic acetabular fractures is different from prior classification systems in two ways. It includes a scheme for classifying post-operative fractures. Previously constructed classification systems such as the Davidson system only classified intra-operative periprosthetic acetabular fractures [1]. It also provides surgeons with a guide to operative and nonoperative fracture management [1,6]. The Paprosky classification scheme for periprosthetic acetabular fractures has five fracture types. Type I and II are intra-operative fractures around the acetabulum, and their management will not be discussed in this review. Types III, IV and V are post-operative, and their current management will be described in detail. Type III fractures are those caused by post-operative trauma. They are sub-divided into types A and B based on acetabular component stability. Type IIIA fractures have a stable component, whereas Type IIIB fractures have an unstable component. Type IV fractures, or spontaneous fractures, are those associated with osteolysis. They are further sub-classified into types A and B. Type IVA fractures are those with less than 50% of the native host acetabulum lost. Type IVB fractures have greater than 50% of host bone lost. Type V fractures are any that show pelvic discontinuity, regardless of their etiology. They are sub-divided into types A, B and C. Like Type IV fractures, sub-types A and B are separated by the amount of host acetabulum bone that remains: sub-type A having more than 50% of host bone remaining, whereas sub-type B has less than 50% of the native acetabulum remaining. Type VC fractures are those associated with pelvic radiation, and they are managed exactly like Type VB fractures when using treatment algorithms. Management Type III – traumatic
When treating Type III fractures, it is essential to determine whether there is stability of the prosthetic component. This may not always be achieved through diagnostic imaging and clinical exam. Therefore, delineating between fracture Type IIIA and IIIB can be challenging because determining component stability may not always be possible without an intrainformahealthcare.com
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Intra-operative during removal A: less than 50% bone stock loss B: greater than 50% bone stock loss
III
Traumatic A: component stable B: component unstable
IV
Spontaneous A: less than 50% bone stock loss B: greater than 50% bone stock loss
V
Pelvic discontinuity A: less than 50% bone stock loss B: greater than 50% bone stock loss C: associated with pelvic radiation
fx: Fracture. Data taken from [22].
operative examination [6]. When considered stable, Type IIIA fractures may be treated non-operatively with limited weight bearing for 3 months or until there is appropriate fracture union seen radiographically. All type IIIB fractures, those with unstable prosthetic components, require surgery [6,13,23]. When deciding how to best manage type IIIA fractures, there is controversy as to whether operative or non-operative management is optimal. There remains a paucity of prospective studies evaluating the progression of traumatic fractures to union or the incidence of required surgical correction. Peterson and Lewallen [13] evaluated patients who sustained periprosthetic acetabular fractures (n = 11 THA’s; 8 IIIA) at a mean of approximately 6 years (range, 1–13 years) after THA. The surgeons managed these fractures with restricted weight bearing and activity modification. Of the eight traumatically caused fractures, six of them progressed to fracture union after a mean of 20 weeks (range, 6–40 weeks). However, after a mean follow-up of 62 months (range, 27–112 months), of the six that initially reached fracture union, four patients required early revision due to progressive pain and component loosening. Of the original eight fractures, two required acetabular component revision with bone grafting due to nonunion. Although the outcomes of nonoperative management have not been uniformly successful, the authors of both of these studies believe that non-operative management may be considered for type IIIA fractures because of its decreased cost, non-invasive nature and low risk to the patient’s long-term prognosis [24]. 309
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Based on the stability of the acetabular component, Helfet and Ali [25] described a treatment algorithm that can be used for type III fractures. If the acetabular component is stable and the fracture has minimal displacement, they recommend protected weight bearing for 6–8 weeks. After attempted nonoperative treatment, if the patient remains symptomatic or has radiographic evidence of nonunion or malunion, an open reduction and internal fixation (ORIF) with plates/screws and bone grafting should be performed. However, when the implant is stable, but the fracture is displaced, whether or not the patient should undergo operative or non-operative management is determined by evaluating pelvic stability. When pelvic evaluation demonstrates a stable pelvis, current standards recommend a trial of 6–8 weeks of protected weight bearing. Conversely, an unstable pelvis would be ideally treated with an ORIF and placement of bone graft as needed. When considering how to best accomplish ORIF for posttraumatic fractures, there has been some research regarding the use of double posterior plating, with eventual grafting and cemented THA. Recently, Laflamme et al. [26] retrospectively assessed the treatment strategies used for periprosthetic acetabular fractures (n = 32 fractures). After a mean follow-up of 36 months (range, 9–82 months), they found that those who had posterior wall fractures addressed with posterior column plating had no incidences of fixation failure of plate migration. Similarly, Bronsema et al. [27] evaluated the long-term outcomes of a cohort of patients with acetabular fractures treated using bone grafting and a cemented cup (n = 20 fractures). After a mean follow-up of 18 years (range, 12–26 years), with the endpoint being revision for any reason, the survival rate at 20 years was approximately 75% with a mean Harris hip score of 82 points (range, 56–100 points). Despite the positive results seen with this particular management strategy, there remains a paucity of studies that show its effectiveness in post-operative fractures. Furthermore, these studies did not detail the stability of the acetabular component, which may also guide management. Hence, the results of the aforementioned studies should be interpreted cautiously as further research is conducted on this treatment modality. Unlike type IIIA fractures, all type IIIB fractures require operative management due to prosthetic instability [6,25]. The goals of surgical intervention are to attempt to restore pelvic stability and adequate bone stock, and to securely fix the implant/constructs [6]. Furthermore, in cases of intra-pelvic migration of the acetabular component, the patient may need a pre-operative vascular assessment as these fractures are sometimes associated with vascular injuries [23]. With the risk to major vascular structures in mind, Patil et al. [24] recommends extraction of the cup using a distinct ilioinguinal approach. This allows direct visualization and protection of the common iliac vessels. For implants that are considered unstable, the Helfet and Ali [25] treatment algorithm supports using the displacement of the fracture to guide the operative plan. For minimally displaced fractures, the patient should undergo ORIF with bone grafting and revision of the acetabular component. 310
If the fracture is displaced and there is significant bone loss (greater than 50%), they recommend restoring the bone stock using allograft and conducting a cage fixation along with component revision. Currently, there are no studies detailing the use of bone graft and reconstruction cages specifically with type IIIB fractures. However, there are multiple studies on their use with type IV and type V fractures, and evidence about implementing these constructs will be discussed in detail with the management of type IV and V fractures. The management of Type III fractures is guided by the stability of the acetabular component. Stable acetabular component fractures may be managed non-operatively, but surgical intervention may eventually be required. Those with unstable components require surgical intervention using bone graft and fixation using a reconstruction cage. Type IV – spontaneous
These fractures are much less common than Type III or V; therefore, literature regarding their management is limited. However, it is generally agreed that these fractures require surgical management regardless of their sub-classification [6]. Unlike Type III fractures, the sub-types of Type IV fractures are differentiated by the amount of native bone that remains within the acetabulum, but distinguishing between type A and B can be difficult using plain radiographs as they tend to underestimate the amount of bone loss [22,28,29]. In general, although computerized tomography can be helpful in distinguishing the sub-types of Type IV fractures [30], the definitive fracture classification and operative plan are formulated based on a thorough intra-operative assessment of the remaining native acetabular bone [22,28]. If there is loss of less than 50% of acetabular host bone (Type A), it is recommended the patient undergo revision using a porous-coated hemispherical cup with screws and appropriate bone grafting [22]. Furthermore, among the Type IVA fractures, those that are isolated to the medial wall and do not extend into the anterior or posterior columns may be treated with morcellized bone graft. As such, these isolated fractures may not require plate fixation. Sanchez-Sotelo et al. [12] described the successful use of this technique for two such fractures. However, if the patient has more than 50% loss of acetabular bone (Type B), there are a large armamentarium of constructs that can potentially be used, including trabecular metal augments, reconstruction cages and trabecular metal revision cups [6,22,24]. If required, bone grafting and plating/screw fixation can be utilized to stabilize the fracture [22]. Winter et al. [31] evaluated the use of bone grafting along with a BurchSchneider reconstruction cage model in an attempt to reconstruct these defects when there was more than 50% bone loss (n = 38). After a mean follow-up of approximately 7 years (range, 4–9 years), none of the subjects had radiographic signs of component loosening and all reported significant improvements in the following functional outcomes: pain, negotiating stairs, range of motion and walking capacity without supportive Expert Rev. Med. Devices 12(3), (2015)
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Post-operative periprosthetic acetabular fracture
device (p < 0.001). The sole use of porous-coated hemispheric components is not recommended for Type IVB fractures as they have been associated with high failure rates [22]. The higher failure rates of these constructs are possibly due to the lack of native bone, resulting in poor host bone ingrowth, hence, difficulty achieving adequate biologic fixation [22,32–36]. In general, the amount of host bone remaining in Type IV fractures will direct the operative management of the patient. Type IVA fractures have progressed to union through the use of porous-coated hemispheric cups, and isolated bone graft may be considered depending on the location of the fracture. However, Type IVB fractures require different constructs, and most reports suggest the use of reconstruction cages in conjunction with bone grafts. Type V – pelvic discontinuity
Among all of the group classifications constructed by the Della Valle et al. [22], modified Paprosky classification, the most extensive amount of research has been done on the treatment of pelvic discontinuity. Similar to Type IV fractures, management of Type V fractures is guided by the amount of acetabular host bone that remains. All fractures leading to pelvic discontinuity require surgical treatment. However, unlike Type IV fractures, the use of different methods of component revision for Type VB and VC fractures remain an area of controversy. With this in mind, management decisions are guided by the following principles [37–39]: . . . .
Restoring continuity of the acetabulum (connect ilium to ischium). Grafting of any bony deficiencies or fracture lines. Optimizing contact of remaining viable bone to component surfaces with potential for bony ingrowth. Obtaining a mechanically stable reconstruction.
Methods of fixation that have been investigated include the use of acetabular transplants, trabecular metal acetabular components and cup–cage constructs [37,40]. In the treatment of Type VA fractures, one commonly used method is the use of reconstruction cages, which should bridge the superior and inferior portions of the pelvis. This should allow the temporary stabilization of the fracture during bone graft incorporation and fracture healing [1]. Nevertheless, the literature appears to favor the use of reconstruction cages with Type VA fractures, but it discourages its use with Type VB fractures. One of the first published uses of reconstruction cages for Type VA fractures was carried out by Berry et al. [41]. They evaluated 27 patients who had pelvic discontinuity that were fixed using reconstruction cages with uncemented components and compared them to those with cemented components without cages at a mean follow-up of 3 years. A satisfactory result was defined as no additional operations on the acetabulum, a stable acetabular component, definite or possible healing of the discontinuity and the absence of severe pain. None of the patients undergoing reconstruction using cemented components informahealthcare.com
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had satisfactory outcomes. However, 77% of patients in the cage group had satisfactory outcomes with the most success found in those who had more host bone remaining (greater than 50% native acetabulum). Similarly, Kosashvili et al. [42] evaluated 24 patients with no segmental defects in the acetabulum (Type VA fractures), who were diagnosed with discontinuity (n = 26 discontinuities). After a mean follow-up of 45 months (range, 24–68 months), where failure was defined as migration of the component by greater than 5 mm, 12% failed (n = 3 out of 24 hips). The surgeons concluded that reconstructive cages were a reliable option for patients who had pelvic discontinuity whenever most of their native acetabulum is intact. Paprosky et al. [43] constructed an operative treatment algorithm for patients who have pelvic discontinuity [40,43]. The authors formulated this plan by dividing pelvic discontinuity into two types – acute (synonymous with Type VA fractures) and chronic (synonymous with Type VB fractures). For those grouped into acute discontinuity, or Type VA fractures, bony apposition of fragments can be achieved by compression of the opposing fracture segments together. This can be performed with an ORIF with plating. For Type VB and VC fractures, the use of reconstruction cages may not be ideal because the design may not allow for the bony ingrowth necessary for fixation in the presence of significant bone loss [40,43]. Paprosky et al. [40] reported that with the use of acetabular cages for patients with pelvic discontinuity and with greater than 50% of the native acetabulum lost (n = 15), there was a 31% revision rate and 44% of the patients presented with aseptic loosening at a mean follow-up of 5 years (range, 2–8 years). The authors attributed this poor success rate to the difficulty of restoring the massive bone loss with bone graft and the inability to achieve the perfect contact between the cage and remaining native bone [38]. Furthermore, Paprosky et al. [43] conducted an evaluation of the pain level of a group of patients with acetabular defects that were associated with pelvic discontinuity. The treatment group was surgically corrected using trabecular metal acetabular components along with augments, if needed (n = 12), and they were compared with patients who had defects treated by applying a reconstruction cage (n = 12). After a 2-year mean follow-up (range, 1–3 years), six of the patients who had cage reconstruction reported moderate or severe pain. Of those treated with trabecular metal acetabular prosthetics, 11 claimed to have no pain or mild pain. Paprosky et al. [43] formulated a plan for treating what are currently classified as Type VB fractures. It is unlikely that these patients have the potential to progress to union. Therefore, a reconstruction cage is not considered ideal for achieving stability. Hence, stability is achieved by distraction of the discontinuity. The successful use of distraction for patients in chronic discontinuity was recently described by Sporer et al. [44] from an investigation of a series of revision THA’s in pelvic discontinuity. The authors achieved a re-revision rate of only 5% (n = 1 out of 20 THA’s), which led them to recommend the use of distraction for Type VB fractures. Paprosky et al. [43] 311
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15–84%) for the cage only group (p = 0.009). The authors believe that their construct will be a focus of continued research and long-term follow-up studies. Reconstruction cages can be used for Type VA fractures. However, newer constructs such as cup–cage models may be necessary to appropriately treat Type VB and VC fractures.
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Author’s preferred treatment
Figure 1. Jumbo cup for Type IVB fracture.
recommend using a modular trabecular metal acetabular component with one or two augments to span the discontinuity and provide internal fixation of the pelvis. In a recent report, this recommendation was supported by the American Academy of Orthopaedic Surgeons [45,46]. Nehme et al. [37] explored the use of modular trabecular metal components for 16 revision THA, and at a mean follow-up of nearly 32 months (range, 24–39 months), there was no evidence of implant migration or loosening. Given the extensive literature regarding the need to find different ways to surgically revise Type VB and VC fractures, the use of cup–cage reconstruction models for revision remains an area of increased research focus. Abolghasemian et al. [47] evaluated the use of the cup–cage model compared with standard ilio–ischial reconstruction cage for those in pelvic discontinuity (n = 26 discontinuities in 24 patients). The cup–cage constructs had a significantly higher 7-year survivorship of 87.2% (95% CI: 71–103%) compared with 49.9% (95% CI:
The modified Paprosky classification that was first described by Della Valle et al. [22] provides an effective tool that can be used in the guidance of management. Upon initial evaluation, it is essential to perform a thorough history and physical. In addition, anterior, posterior and lateral radiographs should be obtained and compared with previous radiographs for evidence of component migration, fractures or pelvic discontinuity. Although not necessarily required, it is common practice for a CT scan to be performed because of its ability to quantify the amount of bone loss and to assist in operative planning. Due to the difficulty in classifying these fractures, it is common practice to have a large armamentarium of treatment options while in the operating room, including, but not limited to, trabecular augments, reconstruction cages and bone grafts. For Type IIIA fracture, it is not uncommon to proceed with non-operative management with toe-touch weight-bearing for at least 12 weeks. If there is no radiographic evidence of progression to union, the senior author would recommend ORIF with bone grafting of the defect. For Type IIIB fractures, operative management is seen as imperative to patient care, sometimes in conjunction with a pre-operative vascular assessment. In patients with a substantial amount of component migration, which is considered at or past Ko¨hler’s line, a vascular consult would be obtained and along with a computed tomography angiogram of the pelvis and lower extremities bilaterally. All Type IV fractures are operatively managed. For Type IVA fractures, porous-coated hemispherical cups are used with bone graft available if needed. However, trabecular augments and reconstruction cages are kept in the operating room (FIGURES 1 & 2). Type V fractures, regardless of sub-classification, require operative management. If the fracture is Type VB, reconstruction cages are considered insufficient to achieve the stability necessary for adequate fixation. The senior author believes that the use of trabecular metal acetabular components supplemented with augments to bridge the discontinuity should be further explored. In addition to obtaining the proper alignment and to reconstruct the native anatomy of the acetabulum, limiting soft tissue disturbance surrounding the fracture location is just as important as the construct chosen for fixation. With this in mind, using less invasive techniques offers the benefit of minimizing soft tissue disruption and protecting the blood supply to promote fracture union. Expert commentary & five-year review
Figure 2. Reconstruction cage for Type IVB facture.
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The prevalence rates of post-operative periprosthetic acetabular fractures will continue to increase over time. This is most Expert Rev. Med. Devices 12(3), (2015)
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Post-operative periprosthetic acetabular fracture
Review
Periprosthetic likely due to the growing number of >50% acetabular Unstable No native bone indications of THA, longer life expecfracture lost tancy, the rising number of patients under 65 years of age who are obtaining THA’s and the stresses placed on the Yes
