Abstract
Background:
The aims of the study were (1) to determine the cumulative two to twenty-year survivorship of the hip after open reduction and internal fixation of displaced acetabular fractures, (2) to identify factors predicting conversion to total hip arthroplasty or hip arthrodesis, and (3) to create a predictive model that calculates an individual’s probability of early need for total hip arthroplasty or hip arthrodesis.
Methods:
Eight hundred and sixteen acetabular fractures treated with open reduction and internal fixation by one surgeon over a twenty-six-year period were analyzed. Cumulative two to twenty-year Kaplan-Meier survivorship analyses of the hip, including best and worst-case scenarios, were performed with total hip arthroplasty or hip arthrodesis as the end point. Univariate and multivariate Cox regression analyses were performed to identify negative predictors, which were then used to construct a nomogram for predicting an individual’s probability of needing an early total hip arthroplasty.
Results:
The cumulative twenty-year survivorship of the 816 hips available for follow-up was 79% at twenty years. The best and worst-case scenarios corresponded to cumulative twenty-year survivorship of 86% and 52%, respectively. Significant independent negative predictors were nonanatomical fracture reduction, an age of more than forty years, anterior hip dislocation, postoperative incongruence of the acetabular roof, involvement of the posterior acetabular wall, acetabular impaction, a femoral head cartilage lesion, initial displacement of the articular surface of ≥20 mm, and utilization of the extended iliofemoral approach.
Conclusions:
Open reduction and internal fixation of displaced acetabular fractures was able to successfully prevent the need for subsequent total hip arthroplasty within twenty years in 79% of the patients. The results represent benchmark comparative data for any future and past studies on the outcome of surgical fixation of acetabular fractures.
Level of Evidence:
Prognostic Level II. See Instructions for Authors for a complete description of levels of evidence.
Acetabular fractures are life-altering injuries that commonly occur in young, active, and productive members of society, although the number of elderly patients sustaining acetabular fractures has increased. The general aim of surgical treatment of these challenging fractures is the preservation of the native hip joint so that it can continue to function for the remainder of the patient’s life1. Except for the contribution of Letournel and Judet2, this outcome has not been demonstrated in a comprehensive study involving a large number of patients with long-term follow-up spanning two decades.
The aims of this study were (1) to determine the cumulative survivorship of the hip two to twenty years after operative treatment of displaced acetabular fractures, (2) to identify predictors indicating the future need for total hip arthroplasty or hip arthrodesis, and (3) to create a model for prediction of the hip survivorship probability of an individual patient with a specific acetabular fracture.
Study Group
This study was approved by our local institutional review board. The study was based on the data for 1319 consecutive acetabular fractures (1307 patients) treated by the senior author (J.M.M.) over a twenty-six-year period (July 1980 to December 2006). Acetabular fractures that were treated nonoperatively (eighty-seven hips [eighty-five patients]), those that required acute primary total hip arthroplasty (twelve hips [twelve patients]), and those in which the acetabular fracture was periprosthetic (twelve hips [twelve patients]) were excluded. Of the remaining 1208 acetabular fractures (1198 patients), 259 fractures (249 patients) had less than two years of follow-up and 133 hips (133 patients) were lost to follow-up, and these were excluded. Hips that were converted to a total hip arthroplasty or hip arthrodesis at any time point were included. This left 816 surgically treated displaced acetabular fractures (810 patients) with complete data for analysis.
Data Collection
Data were acquired and saved in a digital format according to a standardized documentation protocol established in 19801. The created database included information on demographics, mechanism of injury, associated injuries including neurologic and vascular injuries, any previous surgical treatment, timing of surgery, classification of the fracture, preoperative and postoperative radiographic evaluation, intraoperative and perioperative data, and complications as well as follow-up (see Appendix).
Clinical Evaluation
Eighty-six patients (11%) had a nerve palsy preoperatively. The sciatic nerve was involved in seventy-eight (10% of the total cohort) of these patients and the femoral or superior gluteal nerve in eight (1%). A fracture-dislocation occurred in 203 hips (25%); the dislocation was anterior in six hips (1% of the total cohort) and posterior in 197 (24%). One hundred and fifty-two dislocations (six anterior and 146 posterior, 75%) were treated with closed reduction before the fracture surgery, and the remaining fifty posterior dislocations were reduced at the time of the fracture reduction. Preoperative traction was generally not used except in certain fracture patterns that put the hip at risk for posterior dislocation or raised concern of femoral head wear against a fracture edge (e.g., transtectal-T and transverse patterns; sixty-two fractures, 8%).
Radiographic Evaluation
All patients were evaluated with the use of five standard radiographic views including an anteroposterior radiograph, two Judet views, and cephalad and caudad views of the pelvis3. All patients who were managed after 1983 were further evaluated with computed tomography (CT) of the pelvis (737 acetabular fractures, 90%). The maximum displacement of the fracture on any of the five radiographs was recorded without adjustment for magnification. The mean displacement (and standard deviation) was 20 ± 10 mm (range, 2 to 70 mm). Two hundred and twenty-six acetabular fractures (28%) had a displacement of ≥20 mm.
Classification of Fractures
Each fracture was classified on the basis of an evaluation of the five radiographs as well as the CT scan according to the method of Letournel and Judet2. Of the 816 acetabular fractures, 241 (30%) had a simple fracture pattern and 575 (70%) had an associated fracture pattern (Table I).
Surgical Technique
Three standard approaches were used: Kocher-Langenbeck, ilioinguinal, and extended iliofemoral. The approach was chosen according to a previously established surgical protocol1 and the recommendations of Letournel and Judet2, which were based on the classification and configuration of the fracture. The AMSCO and Kirschner orthopaedic tables (no longer manufactured) were used from the initiation of the study in 1980 until 1985. The Judet Tasserit table (no longer manufactured) was used from 1985 until 2006. The PROfx table (Mizuho OSI, Union City, California) has been in use after 2003. The prone position was used for the Kocher-Langenbeck surgical approach, the supine position was used for the ilioinguinal approach, and the lateral position was used for the extended iliofemoral approach. The goal of the surgery was fracture reduction and fixation through a single approach when possible. When the fracture reduction was deemed achievable through a single approach, an ilioinguinal or Kocher-Langenbeck approach alone was preferred rather than the extended iliofemoral approach or a combined approach to minimize the negative effect of the more extensive dissection and soft-tissue injury in the latter approaches. The surgical approach selected was generally consistent for six of the fracture types (Table I). An ilioinguinal approach was typically utilized for anterior wall, anterior column, and anterior column plus posterior hemitransverse fracture patterns. The Kocher-Langenbeck approach was typically selected for posterior wall, posterior column, and posterior column plus posterior wall fractures. The approach for treatment of transverse, T-shaped, transverse plus posterior wall, and both-column fractures was individualized (Table I). The choice of surgical approach during the study varied slightly over time. There was an increase in utilization of the ilionguinal and Kocher-Langenbeck approaches and a decrease in utilization of the extended iliofemoral approach over time (Fig. 1-A). The orthopaedic table served as an important reduction aid and was a major factor in decreasing the number of combined approaches and extended iliofemoral approaches.
Reduction and Fixation
The fracture reduction was initiated with the help of intraoperative longitudinal and/or lateral traction provided by means of the orthopaedic table. The reduction was fine-tuned by direct manipulation of the bone with bone forceps to achieve an anatomical reduction of the acetabulum and the innominate bone.
A plate and screw construct was utilized for fracture fixation in 721 hips (88%). Screw-only fixation was utilized in the remaining ninety-five hips (12%) in which large fragments and good bone quality were present. The duration of the operation and the estimated blood loss varied according to the operative approach (Table I). The intraoperative findings included free intra-articular fragments in 169 hips (21%), injury to the cartilage and/or bone of the femoral head in 190 hips (23%), and acetabular articular impaction in 163 hips (20%).
Accuracy of Reduction
The accuracy of reduction was assessed on the basis of measurements of the greatest residual displacement of any of the six acetabular reference lines of Letournel and Judet2 on the anteroposterior and two Judet radiographs without adjustment for magnification. The reduction was graded as anatomical (0 to 1 mm of residual displacement), imperfect (2 to 3 mm), or poor (>3 mm). In both-column fractures in which the acetabulum was reduced anatomically but the displacement of the innominate bone altered the position of the joint, the reduction was categorized as surgical secondary congruence. In addition, congruency of the acetabular roof with the femoral head was assessed postoperatively.
Follow-up
Clinical and radiographic follow-up was generally performed at six weeks, three months, and one and two years after fracture reduction. All patients were advised to return for follow-up at regular two to three-year intervals thereafter. In addition to the regular follow-up, an attempt to contact every patient for the purposes of this study was made by phone, mail, and/or e-mail. This most recent study-specific follow-up information was acquired between October 2008 and September 2009. All patients were asked whether or not they had undergone conversion to a total hip arthroplasty or hip arthrodesis and the timing of such a procedure. Of the 1198 patients (1208 fractures), 810 patients (816 fractures, 68%) were successfully contacted. Postoperative nerve palsies were not specifically investigated since that was beyond the scope of this report. Eighty-seven (11%) of the patients with adequate follow-up had died by the time of the study follow-up. Only one hip in these patients had been converted to a total hip arthroplasty. Mortality and conversion to total hip arthroplasty in these patients were ascertained on the basis of the hospital’s demographic database and the follow-up information provided by relatives.
Worst and Best-Case Scenarios
Patients with insufficient follow-up (less than two years) or no follow-up were also analyzed to identify any differences with regard to demographics and clinical, radiographic, and intraoperative findings. A worst-case scenario was postulated on the basis of the assumption that all fractures with insufficient or no follow-up would fail. A best-case scenario was postulated on the basis of the assumption that no fractures with insufficient or no follow-up would fail.
Statistical Analysis
The chi-square test was used to calculate differences in categorical parameters between a pair of groups, and the unpaired t test was used for continuous parameters. The cumulative survivorship was analyzed according to the Kaplan-Meier method, with the end point defined as total hip arthroplasty or arthrodesis of the hip4. Univariate and multivariate Cox proportional-hazard modeling was used to identify factors predictive of a poor outcome and to calculate the corresponding hazard ratios. When a predictive factor with a non-nominal scale was identified, the difference in survivorship between the two groups was calculated with use of the log-rank test. The predictors from the final multivariate Cox regression model were used to construct a nomogram to predict the early need for total hip arthroplasty (by two years postoperatively). A p value of 0.05 was considered significant.
Source of Funding
One of the authors (M.T.) received personal funding from the Swiss National Science Foundation (SNF) and the Association for Orthopaedic Research (AFOR) to conduct this study.
Accuracy of Reduction (Table II)
The mean postoperative displacement at the level of the articular cartilage was 0.9 ± 1.9 mm (range, 0 to 20 mm). The postoperative reduction was graded as anatomical in 616 hips (75%), imperfect in 148 (18%), poor in thirty-six (4%), and surgical secondary congruence in sixteen (2%). The rate of anatomical reduction was significantly higher in hips with simple compared with associated fracture types, in hips without delayed treatment, and in patients younger than forty years at the time of the fracture (p < 0.001 for all). Posterior wall fractures and posterior column plus posterior wall fractures had a significantly higher rate of anatomical reduction (p < 0.001 and p = 0.04, respectively). Both-column fractures had a significantly lower rate of anatomical reduction (p = 0.001). The overall rate of anatomical reduction increased consistently over time from 40% in 1980 to 92% in 2006 (Fig. 1-B).
Survivorship Analysis (Table III)
One hundred and six hips were converted to total hip arthroplasty before the specified minimum two years of follow-up. The mean duration of follow-up for the remaining 710 hips was 10.3 ± 6.9 years (range, two to 28.6 years). The follow-up was two to five years in 188 hips (23% of the total cohort), five to ten years in 223 (27%), ten to fifteen years in 133 (16%), fifteen to twenty years in seventy-seven (9%), and more than twenty years in eighty-nine (11%). A total of 124 hips (15%) failed; 120 were converted to a total hip arthroplasty and four to a hip arthrodesis. The mean time to failure was 4.5 ± 6.2 years (range, 0.2 to 26.2 years), and the median was 1.5 years.
The cumulative survivorship for the entire series was 88% (95% confidence interval [CI], 87% to 90%) at five years of follow-up, 85% (95% CI, 84% to 87%) at ten years, and 79% (95% CI, 76% to 81%) at twenty years (Table III, Fig. 2). The survivorship for both-column fractures at twenty years of follow-up was significantly greater (87% [95% CI, 83% to 90%], p = 0.002), and the survivorship for anterior wall fractures was significantly lower (34% [95% CI, 9% to 59%], p = 0.002). The other types of fractures were not significantly different in terms of survivorship. Survivorship was significantly lower in patients who had been older than forty years at the time of the surgery (70% [95% CI, 67% to 74%] at twenty years, p < 0.001), patients who had undergone previous unsuccessful surgical attempts at reduction (30% [95% CI, 6% to 54%] at five years, p < 0.001), and patients in whom an extended iliofemoral approach had been utilized (73% [95% CI, 75% to 83%] at fifteen years, p = 0.04).
Predictors of Outcome (see Appendix) and Nomogram for Predicting Early Failure
Univariate analysis of possible negative predictors identified nineteen factors, and nine of these were identified as independent significant predictors of outcome on the basis of the multivariate analysis. Six of those nine parameters were already predetermined at the time of injury or initial evaluation: an age of over forty years, anterior dislocation, femoral head cartilage lesion, involvement of the posterior wall, marginal impaction, and initial displacement of ≥20 mm. The three remaining negative predictors were directly related to the surgical intervention: nonanatomical reduction, postoperative incongruence of the acetabular roof, and utilization of the extended iliofemoral approach. The median time to failure ranged from 1.0 years for hips with incongruence of the acetabular roof to 10.9 years for hips with anterior dislocation.
A nomogram was constructed to allow prediction of the probability of the need for a total hip arthroplasty by two years postoperatively (Fig. 3).
Worst and Best-Case Scenarios
The worst-case scenario revealed a cumulative two-year survivorship of 61% (95% CI, 59% to 62%), a ten-year survivorship of 57% (95% CI, 55% to 58%), and a twenty-year survivorship of 52% (95% CI, 50% to 54%). The best-case scenario revealed a cumulative two-year survivorship of 94% (95% CI, 93% to 95%), a ten-year survivorship of 90% (95% CI, 9% to 91%), and a twenty-year survivorship of 86% (95% CI, 85% to 88%).
Patients without sufficient follow-up did not differ significantly from the analyzed patients with regard to their demographic, radiographic, and operative data except for a higher proportion of male patients (p = 0.025), a greater age at surgery (p < 0.001), fewer preoperative nerve palsies (p = 0.03), fewer posterior wall fractures (p = 0.034), fewer hips with <20 mm of initial displacement (p = 0.046), fewer hips with a nonanatomical reduction (p = 0.002), and fewer hips with incongruence of the acetabular roof postoperatively (p = 0.008) (see Appendix).
To our knowledge, no comprehensive study with long-term follow-up has previously analyzed negative predictors of outcome in a large series of consecutive patients with all subtypes of acetabular fractures. The aim of the present study was to document the cumulative long-term survivorship of the hip over a two-decade period after open reduction and internal fixation (ORIF) in a consecutive series of 816 displaced acetabular fractures. We found that 79% of the native hips could be preserved successfully at a follow-up of twenty years. When secondary total hip arthroplasty was necessary, 50% of all cases required joint replacement within 1.5 years after fixation of the fracture. Independent noncontrollable factors associated with the need for total hip arthroplasty were age, anterior dislocation, posterior wall involvement, a femoral head cartilage lesion, marginal impaction, and the amount of initial displacement. Independent controllable negative predictors of outcome were the accuracy of reduction, restoration of a congruent acetabular roof, and utilization of the extended iliofemoral approach. This statistical information was incorporated in a nomogram for clinical use; the nomogram predicts the need for early total hip arthroplasty after fixation of an acetabular fracture.
This study has some limitations. We evaluated the long-term results by using conversion to total hip arthroplasty or hip fusion as an indirect indication of the development of posttraumatic osteoarthritis. We did not evaluate the clinical or radiographic follow-up data of the patients. Advantages of this approach include the clarity of the end point, the availability of follow-up information for patients who were unable to return for follow-up visits, the retrospective availability of follow-up information for patients who died, and the reduction of unnecessary radiation exposure in asymptomatic patients. Disadvantages include the lack of radiographic and clinical follow-up information for comparison with the literature. Symptomatic and asymptomatic cases of secondary osteoarthritis that did not lead to arthroplasty or arthrodesis are not reflected in the survivorship curve. In addition, indications for arthroplasty can vary among surgeons, making this analysis less generally applicable.
Another limitation is the relatively large number of patients with no or insufficient follow-up. Although the loss-to-follow-up quotient5 for this study was 3.2, the 79% overall cumulative survivorship of the hip after twenty years is noteworthy. The majority of the demographic, radiographic, and operative parameters did not differ between the groups with sufficient and insufficient follow-up (see Appendix). Moreover, a greater proportion of hips with negative predictive factors were identified in the evaluated group of 816 hips with adequate follow-up compared with those with inadequate follow-up (see Appendix). This comparison indicates that the actual survivorship after twenty years may be better than 79%.
Two sections of the survivorship curve could be identified. The first curve section showed an exponential decrease and covered the first 1.5 years after surgery, during which the first 50% of the failures occurred (see Appendix). Hips with multiple negative predictors typically failed during this early time period, as predicted by the nomogram. The second curve section showed a more linearly decreasing survivorship and covered the 18.5-year time period starting 1.5 years postoperatively. During this time, secondary osteoarthritis could develop even in the absence of negative predictors. Preexisting osteoarthritis6,7, natural wear of the joint, and substantial traumatic cartilage damage might lead to this phenomenon. A similar long-term survivorship pattern was assumed but not proven by other authors6,8,9. Studies of the outcome of acetabular fractures should have a follow-up of at least two years. When evaluating and comparing long-term outcomes, the linear decrease in survivorship over time should be taken into account.
The Cox regression analysis technique used in the present study is a powerful tool that allows prediction of the time-dependent probability that an individual patient will need a total hip arthroplasty. The constructed nomogram (Fig. 3) is a graphical representation of the numerical probability of the need for a total hip arthroplasty by two years. As shown in the two illustrative case examples in the Appendix, individual prognoses corresponded well with the actual patient follow-up. The knowledge of the individualized prognosis provides the patient and the treating orthopaedic surgeon with realistic expectations. These could influence the postoperative treatment regime, the future level of activity that is adopted, or even the choice of work. The two-year time point for the nomogram was chosen since an unfavorable early prognosis could justify acute primary total hip arthroplasty instead of ORIF6. The nomogram can be used as an adjunct to select patients in whom acute primary total hip arthroplasty could be more beneficial than ORIF. Primary total hip arthroplasty might be considered in such patients in whom early joint degeneration is highly probable. However, accurate fracture reduction is essential even if primary total hip arthroplasty is planned. The decision regarding the choice between ORIF and total hip arthroplasty must also take into account other factors in addition to the individual prognosis, such as the invasiveness of the procedure, the associated morbidity, and the costs associated with a second surgery.
Many of the identified negative predictors are consistent with those in the literature, including nonanatomical reduction1,6,10-12, incongruence of the acetabular roof1, an age of more than forty years1,6,9, a femoral head cartilage lesion6,7,9, marginal impaction6,12, delayed reconstruction6,10, and relocation of an associated dislocation after more than six hours13. We were also able to identify additional univariate and multivariate predictors of a poor outcome, including anterior or posterior fracture dislocation, initial displacement of ≥20 mm, the presence of free intra-articular fragments, involvement of the posterior acetabular wall, and utilization of the extended iliofemoral approach. The strongest predictors that were controllable by the surgeon were the accuracy of reduction and the restoration of a congruent acetabular roof.
There are some discrepancies between our findings and the literature. In contrast to other reports9, we did not find superior survivorship of hips with simple fracture patterns. Consistent with one previous report6, anterior wall fractures had the worst survivorship. This might be related to the somewhat higher proportion of elderly patients, marginal impaction, and nonanatomical reduction associated with these fractures (see Appendix). Also, involvement of the posterior acetabular wall (often associated with substantial cartilage damage; see Appendix) was a negative predictor. Both-column fractures were the only fractures with a significantly better outcome at twenty years, despite the significantly higher proportion of nonanatomical reduction, large initial displacement, and more frequent utilization of the extended iliofemoral approach (see Appendix). An explanation for this better outcome is the secondary surgical congruence of the articular surface despite deficiencies in reduction. In both-column fractures, all articular fragments displace with the femoral head. The involvement of the innominate bone in the fracture might allow it to act as a crumple zone, resulting in less articular cartilage damage. Another explanation could be the more direct force transmission that occurs in acetabular wall fractures, in which the femoral head is displacing in relation to a stable fragment. This can create marginal impaction of the acetabulum, marked cartilage damage, and impaction of the femoral head.
As shown in our study, the extended iliofemoral surgical approach was directly associated with a higher risk of subsequent total hip arthroplasty. Although we did not evaluate the patient radiographs, one could suggest that the problem with the extended iliofemoral approach is osteonecrosis of the innominate bone with disconnection of the inner and outer pelvic tables6. However, this was not observed by the senior author when these patients returned for total hip arthroplasty. Over time, the use of this approach has decreased, whereas the use of the ilioinguinal and Kocher-Langenbeck approaches alone and the rate of anatomical reduction have increased (Figs. 1-A and 1-B). The primary reason for these trends was the use of the orthopaedic table, but a secondary reason was the development of sophisticated surgical reduction instruments for these approaches. More extensive dissection does not necessarily lead to a higher rate of anatomical reduction and a better prognosis. However, the extended iliofemoral surgical approach is still being used by the senior author in both-column fractures with involvement of the sacroiliac joint. A combined ilioinguinal and Kocher-Langenbeck approach is rarely necessary with this fracture pattern.
We observed several secular trends in our patient population (see Appendix). Five of the negative predictors in the multivariate analysis (a femoral head cartilage lesion, involvement of the posterior wall, an age of more than forty years, initial displacement of ≥20 mm, and marginal impaction) showed an increasing prevalence over time. Some of those factors might be the result of the aging population or the maturation of a highly selected referral practice.
In summary, 21% of all patients with operatively treated displaced acetabular fractures needed conversion to total hip arthroplasty within twenty years. Half of the conversions occurred within the first 1.5 years, with a slow and steady rate of total hip arthroplasty at longer follow-up. Factors that were predictive of the need for early conversion to total hip arthroplasty were greater age, anterior dislocation, posterior wall involvement, a femoral head cartilage lesion, marginal impaction, large initial displacement, nonanatomical reduction, failure to restore a congruent acetabular roof, and utilization of the extended iliofemoral surgical approach. We observed an increasing prevalence of many of the predictive factors over the twenty-six years encompassed by the study. A nomogram was constructed that can predict the likelihood of early conversion. This nomogram can be helpful in selecting patients who could potentially benefit from acute primary total hip arthroplasty instead of ORIF alone. To our knowledge, the number of evaluated fractures and the duration of follow-up in the present study are unique for acetabular fractures in particular and unusual for any type of articular fractures in general. The results represent benchmark comparative data for any future and past studies on the outcome after surgical fixation of acetabular fractures.
Tables showing demographic data for patients with and without sufficient follow-up, regression results, the distribution of negative predictive factors according to fracture type, and secular trends as well as figures showing illustrative examples of patients with good and poor predicted outcomes are available with the online version of this article as a data supplement at jbjs.org.
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Disclosure: One or more of the authors received payments or services, either directly or indirectly (i.e., via his or her institution), from a third party in support of an aspect of this work. In addition, one or more of the authors, or his or her institution, has had a financial relationship, in the thirty-six months prior to submission of this work, with an entity in the biomedical arena that could be perceived to influence or have the potential to influence what is written in this work. No author has had any other relationships, or has engaged in any other activities, that could be perceived to influence or have the potential to influence what is written in this work. The complete Disclosures of Potential Conflicts of Interest submitted by authors are always provided with the online version of the article.