Our analysis revealed that reports of X-rays and CT scans often do not provide enough information about possible implant loosening in femoral PPF. In 60% of the X-rays and 80% of the CT scans, no reliable statement could be made about implant loosening. Since implant stability is difficult to assess for both X-ray and CT scans, our results are in line with findings with reported inter- and intra-observer reliability and validity of the Vancouver classification system. For this classification system, which is well-known and widespread within the orthopedic community, low levels of reliability have been reported. Naqvi and coworkers report Kappa values of 0.61–0.69 for the interobserver agreement and 0.74–0.90 for the intra-observer agreement for the entire Vancouver classification system . Baba and colleagues could explain poorer interobserver reliability in Vancouver classification-based assessment with 0.41 for X-rays and 0.48 for CT scans . Cohen’s kappa value of 0.6–0.79 represents a moderate agreement (35–63% of the data are reliable), while a kappa value of 0.40–0.59 represents a weak agreement, meaning that only 15–35% of the data are reliable . About implant loosening, the higher rates of ambiguous CT scans may be because of distortion, as more CT scans are performed in patients where loosening was difficult to assess in X-ray diagnostics. The need of carrying out CT scans must be justified as indispensable for the decision on therapy. The repositioning for examining patients with dislocated femur fractures carries the risk of nerve and vascular injuries caused by dislocated fracture fragments. In addition, the additional examination can once again place a heavy load on patients who are already suffering from noticeable pain and discomfort. This should be considered especially in treating fragile, elderly patients.
For radiation exposure, the dose in older patients, who represent the majority in PPF, is considered insignificant for the carcinogenic effect. However, to reduce the cancer risk associated with medical imaging irradiation, a stricter suggestion is needed, especially for younger patients . The reasons for CT may be better fracture morphology assessment and estimation of bone quality. However, assessment of bone quality by CT seems to be difficult. The prevalence of B2 and B3 fractures in our study (38.6% vs. 2.7%) was different in comparison to the reported numbers in other studies with similar patient collectives (B2 17.2% vs. B3 13.2%) [14, 37% vs. 5%) . This leads to the assumption that the difficulty in distinguishing between good and poor bone quality on imaging may be reason for the observed difference of reported numbers of B2 and B3 fractures. In this case, quantitative CT-based measurements would be helpful. Metal artifacts reduce the diagnostic value of CT’s . Such artifacts can result in damage of the informative value while assessing implant stability. Special software can help to better evaluate bone quality and reduce artifacts around the implants.
The demographic figures of our collective by age and sex of patients are comparable to those in the literature [14, 16, 17]. The length of hospital stay was comparable to a cohort of PPF patients in Ireland . An average time of 6 days to surgery after admission was somewhat later, as Sellan et al. reported with a duration of 4 days. The data showed no influence of time of fixation or revision of the arthroplasty on the duration of the hospital stay and the one-year mortality. Since the additional CT has no influence on length of hospital stay, the additional diagnostics does not bring any additional benefit for management of PPF.
The intraoperative examination of the implant loosening is based on a trivial mechanical examination. If the prosthesis needs to be exposed intraoperatively due to fracture morphology, stability can be easily checked. However, if the implant is not easily accessible or exposure is not primarily necessary, no reliable statement can be made intraoperatively about possible implant loosening. Finally, this may lead to different intraoperative findings compared to the implant stability assessed preoperatively by imaging. Besides manual mechanical testing, a practical tool is needed for the intraoperative examination of prosthesis loosening, especially in uncertain radiological findings. Resonance frequency analysis, an established method that tests the loosening of dental implants and is easy to perform, could contribute to better assessment intraoperatively . While revision arthroplasty of fixed prostheses may lead to an unnecessarily more complex operation, erroneously performed osteosynthesis in implant loosening may lead to complications and necessary follow-up procedures.
The limitation of the present study is its retrospective design. The study cohort is therefore inhomogeneous. All different kinds of femoral orthopedic implants in patients suffering from PPF have been included to the study. Also, retrospective design not only results in changes in CT protocols over the study period of 8 years but also in differences in X-ray machines, CT scanners, emitted radiation and associated picture quality. Different radiologists as well as trauma and orthopedic surgeons diagnosing X-rays, CTs, the latter planning treatment on those findings, have to be mentioned as well. This study presents an unavoidable problem of no output value of implant loosening. Nonetheless, this clinical diagnostic study resembles daily routine and problems both surgeons as well as radiologists are faced with each day. A prospective study using standardized approach would be necessary to consolidate the results of this study to overcome the drawbacks.