Currently, there is no consensus regarding which implant (a DHS or a PFNA) is the best implant for stable IFFs [10]. The study was initiated to compare DHS and PFNA for differences in outcomes, based on the hypothesis that DHS would have more complications and worse outcome than PFNA in the treatment of stable IFFs (type AO/OTA 31.A1). Many authors comparing DHS devices with PFNA devices in stable IFF pointed out no obvious differences among the results of treatments with either DHS or PFNA implant [2, 12, 13]. However, to our knowledge, no comparison was performed in terms of post-operative femoral fractures after implant removal, postoperative HHS, and reoperation rate during post-operative follow-up assessment of a minimum 4 years in literature.
In this study, we compared PFNA and DHS fixations for the treatment of stable IFFs. Our results suggested that PFNA device was better than DHS device, as indicated by significantly less total complications, less orthopaedic complications, less post-operative femoral fractures after implant removal, less reoperation rate, and higher postoperative HHS (Tables 2 and 3). Furthermore, our results highlight the fact that patients with stable IFFs may not always need DHS fixation, which, though a satisfactory short-term effect, carries an increased risk of post-operative problems and complications.
Despite some studies have shown there is the superiority of PFNA over DHS in the treatment of stable IFFs [2, 3, 14, 15], there has been a trend toward more DHSs in stable IFFs [2]. Historically, a higher reoperation rate have been observed after DHS compared with after PFNA. Our study showed a higher rate of post-operative femoral fractures after DHS removal than after PFNA removal for stable IFFs. Reoperation percentages of 6.4 and 13.4 % for the PFNA and DHS groups at last follow-up were comparable to rates in the most recent studies [5, 16, 17]. This finding parallels previous clinical findings for reoperation percentages. Most studies underlined that the rates of reoperation and post-operative femoral fractures after implant removal were higher after using a DHS than after a PFNA [1, 2, 18]. We also found the rates were slightly higher than those published for stable IFFs in many review studies but were lower than those published in the most recent studies [5, 19]. Although the rates of reoperations or post-operative femoral fractures after two implants removal are varied in many studies, the consistent difference in the two groups appears to have existed. In our study many patients underwent reoperations on account of post-operative femoral fractures after implant removal. Reoperation rate was higher in DHS devices, nevertheless, only implant removal was significant. Moreover, post-operative femoral fractures reported in many literature fail to give a clear distinction between peri-implant fractures and post-operative femoral fractures after implant removal in updated reviews [20, 21]. Zhang et al. [1] assessed the change of postoperative femoral fracture rates after implant (DHS or PFNA) removal with time and failed to observe more femoral fractures and differences between two implants. Also, their studies failed to conclude a similar time- dependent change for either implant. However, our study showed reoperation rate was higher after DHSs of stable IFFs, and 6 reoperations (5.4 %) in Group DHS in 1-year follow-up were caused by peri-implant fractures, which is in contrast to a 6 % rate in early study [22]. Currently, there is no consensus that DHS device in stable IFFs would reduce incidence of peri-implant fractures. However, it is abundantly clear that the design and composition of the implant affect bone loss and an important mechanism is through stress-shielding, which does not mean that the baseline bone mineral density value predicting subsequent peri-implant fractures is irrelevant [23]. When patient loads the skeleton with higher loads, it responds with greater stress-shielding. If this scenario would continue longer, it is hard to avoid fracture caused by stress-shielding. As the stress-shielding induced by DHS could lead to more bone loss than that by PFNA, it is easy to understand that, more often than not, post-operative femoral fractures after implant removal is observed in the DHS group at a later stage.
The assessment of functional outcome for patients with stable IFFs has been suggested to use postoperative HHS [24]. We found obvious difference in postoperative HHS existed between the groups after 1 postoperative year. In line with our results, two studies suggested that there were major differences in postoperative HHS between two implants in stable IFFs [1, 2]. Our finding of major differences in postoperative HHS between the groups seemed to indicate that reoperation rate was enough to influence postoperative HHS. After 1 postoperative year (after implant removal), but more patients in the two groups rated their postoperative HHS. Although the differences were temporary and minor, the postoperative HHS reflects important functional outcome related to an ability to maintain patient’s independence. Postoperative HHS has been inconsistent in many studies comparing the DHS and PFNA devices in stable IFFs [12, 13]. In a RCT comparing the PFNA devices versus the DHS devices in stable IFFs at 0.6–1 postoperative year, the authors pointed out no difference in postoperative HHS between the groups [25]. However, in another recent randomized clinical study, the authors found obvious difference in postoperative HHS at 1 postoperative year [4]. On the whole, the latest review of RCTs comparing the DHS and PFNA devices in stable IFFs reported no difference existed regarding postoperative HHS [6], which was not in line with our results (Table 2). This was likely due to their shorter duration of follow-up (0.6- 1 postoperative year), and a conclusion was drawn without implants removal, which might not be an objective assessment.
Most literature have reported that hip and thigh pain was common when patients were treated using DHS or PFNA [6, 26]. Our study demonstrated 58 % of patients with hip and thigh pain were observed during the follow-up period with no significant impact on postoperative function outcome. To our knowledge, the pain appeared to be associated with damage to the gluteus medius tendon.
Despite our consistent findings from the orthopaedic departments represented in our study, there were several limitations to our study. First, it is a retrospective study with all the problems inherent with this methodology. Second, patient- and surgeon-related confounders may have existed. Third, this study is observational and it is possible that we did not address every potential confounding variable in our analyses. Fourth, due to a retrospective study, it is possible that variables contribute to complications were unaccounted for in this study. Fifth, postoperative functional assessment using HHS instead of the EQ-5D questionnaire. Sixth, the follow-up period was relatively short. Potential long-time problems associated with implants may yet occur. Accordingly, the large number of patients in a long-time follow-up study could add valuable information.