Cemented versus uncemented total hip arthroplasty for failed proximal femoral nail anti-rotation fixation in patients with intertrochanteric femur fractures: 5-year results of a retrospective observational study


 Background: Cemented or uncemented total hip arthroplasty (CTHA or UTHA) is being increasingly performed in patients with intertrochanteric femur fractures (IFFs) who failed to be treated with proximal femoral nail anti-rotations (PFNA) fixation. The purpose of this study is to compare the clinical outcomes of CTHA or UTHA following prior failed PFNA fixation in patients with IFFs.Methods: Data from 244 patients with IFFs who underwent a conversion of PFNA to CTHA (PCA, n =120) or to UTHA (PUA, n = 124) due to pain and hip disfunction during 2008-2018 were retrospectively analysed. Follow-up occurred 1, 3, 6, and 12 months postoperatively and yearly thereafter. The mean follow-up was 64 months (range, 57 – 71 months). The Harris hip score (HHS) was the primary outcome; the incidence of major orthopaedic complications was the secondary outcome.Results: At the final follow-up, HHS was 79.54±18.85 vs 75.26±18.27 (PCA vs PUA, p = 0.014). There were significant differences between groups regarding the incidence of prosthesis revision, prosthesis loosening, and periprosthetic fracture (5.8% for PCA vs 14.5% for PUA, p = 0.025; 10.0% for PCA vs 20.1% for PUA, p = 0.027; 3.3% for PCA vs 10.5% for PUA, p = 0.028, respectively). Conclusion: The results of the study demonstrated a significant advantage with respect to HHS and major orthopaedic complication rate in favor of CTHA, as compared to UTHA in patients with a failed PFNA treatment.


Background
Therapeutic advances in proximal femoral nail anti-rotation (PFNA) have substantially improved the outcomes for an increasing number of patients with a clinical diagnosis of intertrochanteric femur fractures (IFFs), a subtype of proximal femoral fractures, which was previously associated with poor prognoses [1][2][3]. The number of IFFs treated with PFNA during the past decade has increased dramatically and will substantially increase, not only as a consequence of an ageing population but also owing to its increasing use in young patients [4,5]. Hence, the number of failed PFNA that requires revision procedures may also increase accordingly [2]. Regrettably, the available options for revising a failed PFNA are limited [2]. When a failed PFNA intervention is indicated, the treatment strategies remain challenging and controversial [1]. Conversion from PFNA to cemented or uncemented total hip arthroplasty (CTHA or UTHA) tends to be an acknowledged method [6,7]. In the limited literature, however, the choice of implant material (CTHA or UTHA) is often blurred and unclear [8,9]. Revision of PFNA to CTHA or UTHA has been reported in some recent comparative studies [10,11]. However, most of those reports have been from a highly specialised medical institution, with a limited number of cases [12]. The irresolution as to which type of implant (CTHA or UTHA) is optimal in treating patients with a failed PFNA led to a significant distinction in the application of each intervention internationally [13]. No study that assesses the long-term clinical outcomes of CTHA versus UTHA regarding the treatment selection for failed PFNA currently exists.
In this retrospective cohort study, we used data from the China Southern Medical Centre database (CSMC) and compared the clinical and radiographic outcomes of Asian patients with failed PFNA who were treated by conversion to CTHA or UTHA.

Study population
The data from the period of July 1, 2008 to July 31, 2018 were obtained from the CSMC database, which is a government-funded initiative that began in 2002. The registry records of 312 patients who had undergone a conversion from PFNA to CTHA (PCA) or to UTHA (PUA) during the study period were retrospectively analysed. The conversion 4 procedure was carried out as stated by the manufacturers' instructions at three medical institutions by 6 surgeons, who were all experienced in arthroplasty. The technical details and postoperative protocol have been reported in our prior study [2]. The inclusion criteria were as follows: active elderly patients aged ≥ 60 years old; patients with a prior IFF  [14], and an American  The patient-specific details and preoperative data were collected and are shown in Table   1.

Clinical and radiographic analysis
The clinical and radiographic evaluations were retrospectively reviewed by two authors (SM and BC) at 1, 3, 6, and 12 months postoperatively and yearly thereafter. The primary 5 outcome measure was the HHS (range, 0 -100), which was used to determine the functional level and evaluate pain. The secondary outcome measure was the rate of major orthopaedic complications, including prosthesis revision, loosening, periprosthetic fracture, dislocation, periprosthetic infection, intolerable hip pain, lower limb shortening, and thrombotic events. Radiographic analysis consisted of anteroposterior views of the hip and pelvis and a true lateral view of the hip.

Statistical analysis
The follow-up time was defined as the time interval between the date that CTHA or UTHA was performed and the date of the final follow-up. The definition of loosening of either the stem or the acetabulum on radiography was based on a previous description [15].
Periprosthetic infection was determined according to the previously reported criteria [16].
Stress shielding was determined by the classification of Engh et al [17]. Osteolysis was evaluated by the criteria of McLaughlin et al [18]. Heterotopic ossification was assessed per the Brooker classification system [19]. Prosthesis revision was defined as removal of the CTHA or UTHA device for any reason [20]. Between-group differences in the HHS or the major orthopaedic complications were compared using the nonparametric independent samples t-test or the chi-squared test, respectively. A significant difference was defined as a two-sided p value < 0.05. All statistical analyses were performed in SPSS 24.0 software (IBM, Armonk, NY, USA).

Primary outcome
The HHSs after conversion surgery are shown in Table 2. At the final follow-up, the scores of the PCA and PUA groups were 79.54±18.85 and 75.26±18.27, respectively. From the three years after conversion surgery to the final follow-up, significant differences were detected in HHS between groups. CTHA had a noteworthy functional advantage compared 6 to UTHA in these cases. At each follow-up prior within three years after conversion surgery, noteworthy distinctions regarding the HHS failed to be found.

Secondary outcome
Forty-nine orthopaedic complications in 24  with CTHA [21]. While our analysis was able to statistically validate the difference in the HHS, it failed to validate the differences in the rate of major orthopaedic complications during the first 2 years, most likely owing to the short follow-up. The long-term outcomes of CTHA or UTHA for patients with failed PFNA is a matter of great debate [22]. However, a growing but still very limited body of literature has investigated the therapeutic role of these two endoprostheses in the setting of failed PFNA and has suggested that the differences between CTHA and UTHA were attributed to errors in surgical techniques or indications [23]. A previous study that included 203 patients with failed treatment for proximal femur fracture demonstrated that the higher HHS associated with CTHA did not increase the rate of short-term orthopaedic complications compared to that associated with UTHA [24]. A single-centre survival analysis of 2156 hips at 12-18 years confirmed a similar result [25].
The evidence in previous reports regarding the superior endoprosthesis that should be used to convert a failed PFNA is inconclusive [25,26]. Additionally, no literature has provided guiding principles to reduce or avert mechanical complications [27]. Consistent with previous randomised studies [28], we failed to observe conspicuous differences in the HHS at the end of the 3-year follow-up. Although this lack of differences could be attributed to the relatively short follow-up, not everyone was convinced by this explanation.
The outcomes regarding the rate of major orthopaedic complications were within acceptable limits [27]. Our findings are comparable to those of prior reports with at least a 2-year follow-up [7,26]. Nevertheless, the quantitative comparison is problematic for interpretation since a majority of prior reports included a mixed population of proximal femoral fractures and multi-ethnic, younger patients, and stress shielding of the proximal femur is especially age-dependent [3]. Previous literature has demonstrated that UTHA has 8 a higher rate of orthopaedic complications than CTHA [21,28]. Additionally, recent evidence favours UTHA for proximal femur fractures despite the high rate of orthopaedic complications [25].
Our findings are supported by previously available literature in this area that acknowledged an increased revision rate in UTHA cases [29]. Nevertheless, the majority of population reports that focus on this subject are based on 10-year follow-up data. Few prior studies have quantified the risk for re-revision in this setting [28]. Additionally, our study sheds light on the risk for re-revision surgery for patients with failed PFNA treated with UTHA. Although it has been previously recognised that this cohort has a higher 5-year revision rate than those undergoing CTHA, the true risk to a patient with failed PFNA treated with UTHA appears much higher than previously reported [28]. The higher rate of re-revision could be associated with dissimilarities in implant materials. For patients with failed PFNA, the decision about whether to proceed with surgery is mostly based on the balance between re-revision risks and benefits. Previous reports were commonly restricted to specific implants or small populations, without a definite focus on the results of patients with failed PFNA [30,31]. Hence, the decision-making process for such patients failed to be fully considered and could result in an inapposite intervention.
The inherent limitations of the current study are similar to those of other retrospective analyses. First, observational reports such as our study are susceptible to absent variables and the subsequent inability to adjust for certain biases inherent to the methodology. Assessing the superiority of one device over another tends to be restrictive in nature and could be compromised by a relatively small population, improper control of confounding factors, and moderately short follow-up. Second, the lack of a further analysis regarding the use of antibiotics could introduce another potentially confounding factor when considering periprosthetic infection as an endpoint. Third, although the omission of data on patient occupation types might not have a large effect on the prosthesis revision, it was not possible to adjust for prosthesis revision as a potential risk factor. We acknowledge that each patient's data after revision surgery tends to be more complex than both the simple HHS and the rate of major orthopaedic complications.

Conclusion
The goal of our study was to provide a possible explanation for the superiority of CTHA over UTHA in regard to HHS and major orthopaedic complication rate in Asian populations

Ethics approval and consent to participate
This study was approved by the Medical Ethics Committee (The First Affiliated Hospital, Sun Yat-sen University), and an exemption from informed consent was obtained from our responsible Investigational Ethics Review Board.

Consent for publication
Not applicable.

Competing interests
The authors declare that they have no competing interests.