This registry study investigated the occurrence of aseptic complications, which led to revision surgery, and the prevalence of postoperative pulmonary embolisms of cemented and uncemented HAs after FNF with a follow-up of up to 5 years by analyzing the German Arthroplasty Register (EPRD). A prospective investigation of a 3:1 matched population of patients with cemented and uncemented HA was obtained for the treatment of FNF. In addition, cross-validation and precise follow-up data acquisition was possible through data input by EPRD registered hospitals and data provided by health insurance companies.

Femoral stem fixation is controversial in the surgical management of FNF. In 2010, the working group around Parker et al. was able to clearly demonstrate the advantages of cemented treatment with faster mobilization and reduction of postoperative pain by means of a systematic review [20]. In addition to a reduction in postoperative pain and faster mobilization of patients after use of a partial arthroplasty with a cemented stem, a lower proportion of stem sintering was also described in the literature [20, 21]. Similarly, the proportion of aseptic revisions was significantly lower with HAs with cemented femoral stem fixation compared with the cementless alternative [12, 22,23,24]. Okike et al. described a significantly increased risk of aseptic revision for uncemented HA, with a hazards ratio of 1.77 (95% CI 1.43–2.19) [12]. Furthermore, a 2.1 times higher rate of revision surgeries for aseptic failure of HA were reported in an analysis of the Norwegian Hip Fracture Register [25]. The evaluation of the EPRD also demonstrated a significant difference for aseptic revisions with a hazard ratio of 0.56 for cemented partial prostheses. The replacement rate for cemented stems was 2.5% after 3 years, the same level as for uncemented HAs after 1 month. The literature cites a lower number of periprosthetic fractures with cemented stems as the main reason for the lower revision rate [22]. In particular, patients with risk factors for periprosthetic fractures, such as increased patient age, osteoporosis, and a recurrent tendency to fall benefit from cemented fixation [26]. This hypothesis could also be supported by the significant difference in periprosthetic fractures as the reason for replacement surgery in our study. While the proportion of periprosthetic fractures as a reason for revision in cemented HA was 5.2%, the proportion in the cementless variant was about tenfold higher, at 52.2%. In addition to the stabilizing effect of bone cement, the possibility of insufficient osseous integration of the cementless stem is discussed as a reason for this issue [26, 27]. Besides periprosthetic fractures, which were also reported as the main cause of aseptic revision surgery in the literature, dislocation of the prosthesis and acetabular wear were reported as important reasons for reoperations [28].

With regard to mortality, no clear advantage of a particular stem anchorage technique could be shown in previous studies over the long term [22, 24, 25, 29, 30]. However, there are some problems concerning a cemented fixation of a HA caused by side-effects of cemented fixation. Geographical differences are also noticeable in this context, with mainly cemented HA being used in Europe, whereas mainly uncemented HA are used in the USA. [3, 31]. Several studies reported an increased in-patient mortality for cemented joint replacement surgeries and demonstrated an increased mortality for cemented HA with an odds ratio of 1.64 (95% CI 1.35–2.00) within the first 48 h after surgery [30, 32]. Also, first signs of increased in-hospital mortality are apparent for cemented HA in the analysis of large register data. The theory for the increased mortality immediately after implantation is the bone cement implantation syndrome (BCIS). This occurs in up to 28% of cemented partial arthroplasties and is manifested by hypoxia, sudden loss of arterial pressure, pulmonary hypertension, and arrhythmias, potentially leading to cardiac arrest [33, 34]. However, the exact pathomechanism has not been fully elucidated, and a multifactorial cause seems most likely [34]. The frequently occurring intraoperative pulmonary emboli, that sometimes present only subclinically, seem to play a major role [35]. In 0.81% of the investigated cemented HAs in our study, a documented and clinically relevant pulmonary embolism occurred, which resulted in further diagnosis and therapy. There was no statistically significant difference (p = 0.057) compared with the uncemented stem anchorage variant; however, an odds ratio of 1.53 in terms of an increased risk for cemented HA was calculated. Li et al. showed a significantly increased rate of pulmonary embolism after cemented fixation in a meta-analysis [36]. Patients with pulmonary embolism subsequently show significantly increased mortality compared with patients without pulmonary embolism, both immediately postoperatively and after 1, 3 and even 6 months [37]. Preventive measures and the implementation of safety guidelines in the use of bone cement, especially in HA after femoral neck fracture, are therefore strongly recommended [38].

Despite many advantages of this study, some limitations must be mentioned. The quality of the registry depends on the quality of the information provided by the surgeons and the coding of the hospitals. Validation of the arthroplasty registry protocol with insurance and billing procedures can minimize, but not completely remove this effect.

In the analysis of pulmonary emboli, the registry is similarly dependent on correct coding and can only represent events during the first in-patient stay. However, the aim of the study was to investigate embolisms directly related to prosthesis implantation. Therefore, the period of acute in-patient treatment seems to be suitable. Another limitation is the patient follow-up period of 5 years for aseptic revisions. Due to the age of the register the investigation time is limited here.