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Does Total Hip Arthroplasty Reduce the Risk of Secondary Surgery Following the Treatment of Displaced Acetabular Fractures in the Elderly Compared to Open Reduction Internal Fixation? A Pilot Study

Weaver, Michael J. MD*,†; Smith, Raymond Malcolm MD†,‡; Lhowe, David W. MD†,‡; Vrahas, Mark S. MD§

Author Information
Journal of Orthopaedic Trauma: February 2018 - Volume 32 - Issue - p S40-S45
doi: 10.1097/BOT.0000000000001088

Abstract

INTRODUCTION

Open reduction and internal fixation (ORIF) of acetabular fractures, particularly in the elderly patient, can be technically challenging and is associated with a relatively high rate of morbidity and mortality.1 The goal of surgery is to anatomically reduce the facture and maintain a congruent hip joint.2,3 In the elderly patient, osteopenia or osteoporosis is associated with fracture comminution and impaction of the articular surface.4–6 In these situations, achieving and maintaining an anatomic reduction may not be possible. The outcomes of elderly patients with acute acetabular fractures treated both nonoperatively and with traditional ORIF have been generally poor.7 Some authors have recommended reconstruction with total hip arthroplasty (THA) in select fractures to overcome the obstacles encountered in ORIF.8–12

Treatment of acetabular fractures by reconstruction with THA presents a number of potential challenges, including the risk of loosening of the femoral or acetabular components and the possibility of dislocation of the hip prosthesis.13 The limited case series available indicate the importance of achieving a stable construct to allow for the proper seating of an acetabular component and highlight the significant complication rates.14–19

At our institutions, we routinely treat displaced acetabular fractures with ORIF and reconstruction with acute THA. The primary purpose of this study was to compare their rate of postoperative complications requiring reoperation after the treatment of displaced acetabular fractures in the elderly with either ORIF or acute THA. The secondary purpose was to evaluate the self-reported functional outcomes of elderly patients treated with either ORIF or THA for displaced acetabular fractures.

MATERIALS AND METHODS

We performed a retrospective study of all consecutive patients aged 65 or older surgically treated for an acetabular fracture from January 2002 to January 2009. Seventy-three patients were identified. All but 3 patients had at least 6 months of follow-up and were included in the study, yielding a total cohort of 70 patients.

Demographic data were collected by review of the medical record. Fractures were classified as described by Letournel20 based on the preoperative radiographs and computed tomography. Treatment and complication data were abstracted from the medical record. Patients were contacted and asked to complete outcome measures, including SF-36 and patient self-reported Harris Hip Scores. The SF-36 instrument is a patient-reported outcome tool that involves 36 questions that provides information on 8 domains.21 Of interest to this study are the domains' physical function and bodily pain. The patient self-reported Harris Hip Score was developed to allow patients to report on their function as it related to their hip without the need for a physical examination and range of motion testing.22 It asks questions related to hip pain, limp, use of walking supports, distance walked, difficulty with sitting in a chair, difficulty putting on shoes and socks, and difficulty with climbing stairs. It is scored on the same 100 point scale as the formal Harris Hip Score, with score between 90 and 100 indicating excellent function, 80–89 good function, 70–79 fair function, and <70 being poor function. Postoperative radiographs at most recent follow-up were evaluated by a single surgeon (M.J.W.) for evidence of prosthetic loosening (in the case of THA) and to evaluate the presence of heterotopic ossification using the Brooker classification.23–25

The medical record was reviewed and patients were interviewed regarding the need for additional surgery after the treatment of their acetabular fracture. Patient outcome was measured using the patient self-reported Harris Hip Score to assess hip function and the bodily pain and functional domains of the SF-36 instrument to assess overall functional outcome.21,22 Additional secondary outcomes included mortality, infection, heterotopic ossification, and joint dislocation. The Social Security Death Index was queried to determine mortality in patients with less than 1-year follow-up. The χ2 test was used to compare demographic variables, rates of reoperation, mortality, infection, and heterotopic ossification. The outcome scores, patient-reported Harris Hip Score and SF-36, and patient age were analyzed using the Student t test.

Overview of the Surgical Technique

For the acute THA procedure, a stable construct between the anterior and posterior column was created before implantation of the acetabular component. Reduction of the fracture was achieved by direct manipulation of the fracture fragments. In general, the fracture reduction was fairly simple once the femoral head was removed and the deforming force of the leg was absent. Once reduced, fixation was typically achieved with lag screws and reconstruction plates. In cases of extensive comminution, an antiprotrusio cage was used.

When a comminuted, isolated posterior wall fracture was treated by THA, the fracture was ignored if a stable cup could be placed in an anatomic position. In instances of large posterior wall defects, where it was felt that a stable cup could not be placed, the posterior wall was reconstructed with native bone or with femoral head autograft before placement of the acetabular component.

In all cases, every effort was made to achieve a reasonable press fit, and acetabular component fixation was supplemented with multiple screws. Bony defects were managed by impacting bone graft. Most often the femoral head was used as autograft and was morselized and reverse reamed into the defect before implantation of the acetabular component. Obtaining stable acetabular component, fixation at the time of its implantation is critical to prevent failure of ingrowth and subsequent acetabular component migration or loosening (Fig. 1E). In most cases, nonmodular femoral components were used. If the acetabular fracture precluded positioning of the acetabular component in a standard amount of anteversion, a conically tapered femoral stem was used to allow modification of the femoral version to improve hip stability.

FIGURE 1.
FIGURE 1.:
Preoperative anteroposterior radiograph of a 66-year-old man is shown with a posterior column/posterior wall acetabular fracture (A). Computed tomography shows an articular free fragment and an impaction fracture of the femoral head (B). The hip was exposed through a Kocher–Langenbeck approach. The femoral neck was cut based on preoperative templating. The posterior column component of the fracture was reduced and provisionally fixed with a reconstruction plate (C). A second plate was used to fix the posterior wall component and further secure the posterior column fracture, and the acetabulum was then reamed to accept the acetabular component. An excellent press fit was achieved (D). Six months postoperatively, the patient had returned to full weight bearing and normal activities with no hip pain (E). Although the patient had developed Brooker II heterotopic ossification, he had no functional limitations to hip motion.

Placement of the acetabular component based on standard anatomic landmarks can be challenging due to fracture comminution. We placed our acetabular components under fluoroscopic guidance, for fracture and primary cases, to improve position.26 When using this technique, it is important to position the c-arm and patient to match the appearance and contour of the pelvis on the c-arm image to the preoperative anteroposterior radiograph. If the fluoroscopic image is more of an inlet or outlet view compared with the preoperative film, the cup may be malpositioned.

In cases of ORIF, the treating surgeon determined the approach and method of fixation. In all cases, an attempt was made at achieving an anatomic reduction. In this series, all fractures were reduced and fixed through either a standard Kocher–Langenbeck approach or an Ilioinguinal approach. No extended approaches were used.

The postoperative rehabilitation protocol depended on the quality of fixation and the press fit achieved. In those treated with an acute THA, our expectation was that approximately half of patients would be able to weight bear as tolerated. In those treated with ORIF, all patients were limited to touch-down weight bearing for 10–12 weeks.

RESULTS

Of the 70 patients included in the study, 33 were treated with ORIF and 37 were treated with THA. The mean follow-up was 22 (range: 6–89 months). None of the 3 patients excluded due to short follow-up were noted to have undergone secondary surgery at the time of their last office visit. Demographic and injury data are presented in Table 1. The mean age in the ORIF group was 73 years (range: 65–88) compared with 79 years (66–90, P < 0.01) in the THA group. Patients treated with ORIF were less likely to sustain their injury from a simple fall (33%) compared with those treated with THA (78%, P < 0.01). Although there was a range of fracture patterns represented in each group, the most common pattern in those treated with ORIF was posterior wall, whereas the most common pattern in those treated with THA was anterior column (Table 2). All the patients treated with ORIF were kept touch-down weight bearing for 10–12 weeks, whereas 48% (18/37) of those treated with an acute THA were made weight bear as tolerated. Mortality within 1 year of the index injury was not significantly different comparing those treated with ORIF (15%) and THA (24%, P = 0.43).

TABLE 1.
TABLE 1.:
Patient Demographic Information
TABLE 2.
TABLE 2.:
Fracture Patterns According to the System of Letournel20

Those patients treated with ORIF had a higher rate of reoperation (10/33, 30%) compared with those treated with THA (5/37, 14%). This difference did not reach statistical significance (P = 0.12); however, with the numbers available, post hoc power analysis revealed a power of only 35% to detect a difference between ORIF and acute THA at the P < 0.05 level. Of those treated with ORIF, 6/33 (21%) required conversion to THA for posttraumatic arthritis or failure of fixation at a median of 7 months (range 1–19). There were 4/33 that had an infection requiring operative debridement, and 1 patient required operative excision of heterotopic ossification due to symptomatic loss of hip motion (1 patient required both debridement for infection and later conversion to a hip replacement and was counted only once for the overall reoperation rate). Of those treated with acute THA, 4/37 (11%) had at least 1 dislocation, and 2/37 (5%) required revision surgery to address chronic instability. There were 3/37 that had an infection requiring operative debridement, and 1 patient required operative excision of heterotopic ossification due to symptomatic loss of hip motion (1 patient required both debridement for infection and later revision for recurrent instability and was counted only once for the overall reoperation rate). None of the patients treated with an acute THA had migration or loosening of the femoral or acetabular components. Radiographically severe heterotopic ossification (Brooker grade 3 or 4) developed in 3/33 (9%) of those patients treated with ORIF and 4/37 (11%, P = 0.86) of those treated with THA.

Twenty-four of the 37 patients treated with acute THA were living at the time of this study, and 13 (54%) completed the questionnaires. Twenty-five of the 33 patients treated with ORIF were living at the time of the study, and 9 (36%) responded. Patient reported Harris Hip Scores (Table 3) of the uninjured limb of those treated with THA were not statistically different from those treated with ORIF (mean values 81 and 82, respectively; P = 0.83). Although the findings did not reach statistical significance, there was a trend toward improved Harris Hip Scores of the injured limb in those treated with THA compared with ORIF (mean values 82 and 63, respectively; P = 0.06). However, there were significantly better SF-36 bodily pain scores in the THA group compared with the ORIF group (mean values 48 and 39, respectively; P = 0.04). The findings did not reach statistical significance in physical summary scores between THA group (mean 43) compared with the ORIF group (mean values 43 and 35, respectively; P = 0.15).

TABLE 3.
TABLE 3.:
Outcome Questionnaire Results, Harris Hip Score, and SF-36

DISCUSSION

The treatment of a displaced acetabular fracture in the elderly is challenging.19 Obtaining an anatomic reduction can be extremely difficult in the setting of fracture comminution and impaction of the articular surface. Reconstruction with a THA avoids the issue of obtaining an anatomic acetabular reduction but introduces the possible complications of prosthetic component loosening or dislocation of the hip.9 Although some authors have advocated for the selective use of THA in the treatment of displaced acetabular fractures in the geriatric population, to the best of our knowledge, there are no data regarding the functional outcome in these patients.

Our series highlights the difficulty in treating elderly patients with displaced acetabular fractures. We found a higher rate of reoperation in the ORIF group (10/33, 30%) compared with the THA group (5/37, 14%). However, this difference in reoperation did not reach statistical significance (P = 0.12). There is a high rate of deep infection in both groups (4/33 treated with ORIF and 3/37 treated with acute THA). These factors point toward the poor generalized health status of this patient population and the challenges these injuries present. Further study is required to determine whether the higher rate of reoperation seen here is a real finding given the limited number of patients and power of this study, as the post hoc power analysis, revealed a power of only 35% to detect a difference in reoperation rates between ORIF and acute THA.

Patients tended toward better function in the patients treated with THA compared with ORIF (patient-reported Harris Hip Scores of 82 vs. 63, P = 0.06). This is a large clinical difference, with a score of 82 representing a good result and a score of 63 representing a poor result. Patients treated with THA had significantly better SF-36 bodily pain scores compared with those with ORIF (48.4 vs. 35.4, P = 0.04), also representing a large clinical difference. Given the poor response rate, it is difficult to draw any definite conclusions from this data; however, it seems that THA compares well with ORIF in terms of function and pain relief.

It is our belief that reconstruction with THA can lead to earlier mobilization and weight bearing. Furthermore, THA potentially provides a more durable result, with a lower rate of reoperation. Although reconstruction with a THA can be technically challenging in the setting of an acute acetabular fracture, if a stable acetabular construct can be created, it has been our experience that some patients can safely begin immediate weight bearing. As we have gained experience with this technique, we have become more comfortable allowing patients to bear weight earlier. Despite previous concerns for the risk of acetabular component migration or loosening, we did not find these issues to be a problem in our patient cohort.

Instability and dislocation are frequent complications encountered after THA for acetabular fractures. Four of the 37 patients treated with acute THA (11%) had at least 1 dislocation event, and 2 (5%) required revision surgery for recurrent instability. A high rate of instability has also been documented in patients treated with THA after fracture of the femoral neck.27 This may in part be due to the lack of pre-existing joint stiffness and a greater early range of motion in fracture patients. It may also be due to soft tissue compromise as a result of the injury. To help reduce the incidence of dislocation, it has become our practice to use c-arm fluoroscopy during placement of the acetabular component to attempt to avoid cup malposition.26 We typically use large femoral head sizes whenever possible to maximize the head-neck ratio and limit impingement. Further, if instability remains a concern, we will use conically tapered femoral components to optimize femoral version.

This study has a number of limitations. The primary limitation of this study is the small sample size. As has been noted, our post hoc power analysis revealed a power of only 35% to detect a difference in reoperation rates between ORIF and acute THA, should there actually be one. Therefore, our finding of no difference in reoperation rates, despite what seems to be a large difference in the raw data, may actually be due to a type II statistical error. Our small numbers are primarily due to the relative rare nature of these injuries treated at a single institution. However, this was expected. Therefore, this initial study was planned as a pilot to determine the potential value of a larger, multi-institutional study. We believe that we have succeeded in this objective because further study with a multi-institutional cohort would improve the ability to detect a significant difference in the rate of reoperation, should one in fact exist. Another important limitation was the low response rate to the functional outcome questionnaires. This problem highlights the difficulties in surveying the geriatric trauma population. Larger patient numbers would also mitigate this limitation. Certainly, our findings support further study in this regard.

In addition, there were potentially important differences in the demographics of the patient groups in mechanism of injury and age (Table 1). Patients treated with THA were older and more likely to have sustained their injury as a result of a ground level fall as opposed to an Motor Vehicle Collision (MVC). This may indicate selection bias for THA in these patients who may have had poorer bone quality because their fractures were the result of lower-energy injuries. In addition, there was likely a selection bias in that the treating surgeon was more likely to select patients with more articular impaction or comminution for reconstruction with THA compared with ORIF. However, we would have expected that these factors would have predisposed the THA group to worse outcomes.

ORIF and reconstruction with THA are options in the treatment of displaced fractures of the acetabulum in the elderly population. These are challenging injuries in this patient population and both treatments are associated with high rates of morbidity and mortality. THA seems similar to ORIF in terms of reoperation, mortality, and complications. However, patients treated by THA reported improved pain scores, and there was a high rate of conversion to THA in the short term (21% within 2 years injury), when patients were treated with ORIF. Therefore, the use of acute THA as primary treatment in this patient population merits further, more controlled, comparative study.

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Keywords:

acetabular fracture; total hip replacement; ORIF; post-traumatic arthritis; fracture

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