Risk factors for in-hospital mortality in geriatric patients aged 80 and older with axis fractures: a nationwide, cross-sectional analysis of concomitant injuries, comorbidities, and treatment strategies in 10,077 cases

Informed Consent and Investigational Review Board (IRB) were not required for this cross-sectional study as it used data from an anonymous, de-identified, administrative database.

Data are presented as total numbers and as percentages of the total. The Chi-Square test was used for statistical comparison between groups (A and B). To analyze the association between potential risk factors and the outcome parameter of in-hospital mortality the odds ratios (OR) with 95% confidence intervals (95% CI) were calculated for the previously identified factors.

In total, N = 10,077 hospital admissions cases were pooled from 2019 to 2021 and analyzed. Only patients aged 80 years or older were included. In total n = 843 cases of in-hospital deaths were documented, giving an in-hospital mortality rate of 8.4%. The proportion of male patients was 35.2% (n = 3544) and 64.8% (n = 6533) for female patients (p < 0.001). In the deceased group, 47.7% (n = 402) were male and 52.3% (n = 441) were female patients. Among all cases, n = 201 (2.0%) were classified as short-stay patients, n = 8876 (88.1%) as normal-stay patients, and n = 1000 (9.9%) as long-stay patients. Ten-point seven percent of cases (n = 1076) had severe motor function impairment (Barthel Index: 20–55 points). Mild to moderate motor function impairment (Barthel Index: 60–75) was documented in 4.1% of cases (n = 417) and 1.4% of cases (n = 142) had mild motor function impairment (Barthel Index: 80–95 points). A significantly higher proportion of cases were classified as having ´very severe´ motor function impairment (Barthel Index: 0–15 points), whereas significantly fewer cases with ´mild,´ ´moderate,´ and ´moderately severe´ motor function impairment were documented in the deceased group (all p < 0.01; Table 1).

A total of n = 3178 (31.5%) patients in this cohort were treated surgically. The in-hospital mortality rate in the surgically treated patients was 9.4% (n = 298 cases with in-hospital deaths vs. n = 545; 7.9% in the non-surgically treated group). The OR for in-hospital mortality depending on the surgical treatment was 1.13 (95% CI: 0.99–1.3; p = 0.103). In n = 1954 (61.5%) cases a dorsal approach was used and in n = 1266 (39.8%) cases a ventral approach was, which indicates, that a 360° approach was applied in n = 42 (1.3%) cases. Most frequently, screw fixation for one segment was applied (n = 1404 cases, 44.2%) followed by fixation with a screw-rod system for 1 segment (n = 919 cases; 28.9%). Multisegmented fixation with a screw-rod system of up to 5 segments was conducted in n = 728 (22.9%) cases. A dorsal fusion of 1–5 segments was coded in n = 823 (25.9%) cases. Decompression at one segment was only documented in n = 62 (2.0%) cases (Table 3).

Comorbidities indicating frailty and severe illness were associated with higher in-hospital mortality, such as essential hypertension, atrial fibrillation, left-sided heart failure, chronic kidney disease, dementia, and very severe motor dysfunction (Barthel index: 10–15 pts.). These findings are consistent with previous studies that have shown the importance of comorbidities and concomitant injuries in predicting mortality in elderly patients with axis fractures [6, 18]. In general, comorbidities are known to be associated with elevated risk for mortality after cervical spine fractures [19]. Concordant with our findings, chronic kidney disease is one of the key prognostic factors for early mortality in older patients with traumatic cervical spine injuries [20]. Shafafy et al. identified several predictors of mortality in elderly patients with fractures of the odontoid process [21]. They found that head injury and the presence of other spinal injuries increase the risk of mortality after 30 days [21]. Similarly, we revealed that concomitant injuriese such as SCI, traumatic brain injuries, atlas fractures, subaxial vertebral fractures, and rib cage fractures were indicators for high-risk in-hospital mortality. The knowledge of these factors can help to identify patients at risk, which should be monitored very carefully. Anyhow, there was no statistically significant difference in mortality rates between surgically treated (9.4%) and non-surgically treated patients (7.9%; p = 0.103) in the current cohort. Smith et al. retrospectively analyzed the complications of surgical versus conservative treatment of isolated type II odontoid fractures in octogenarians and found, that no relevant difference in the acute in-hospital mortality rate between 15.0% in the nonsurgical group and 12.5% in the surgical group [22]. These findings are in line with other retrospective studies [23]. Similarly, a meta-analysis by Deng et al. on the treatment of odontoid fractures in the octogenarians on 22 cases series and retrospective studies including 248 patients reports on a higher mortality rate of 10.1% for non-surgery vs. 5.4% for surgery, but without statistical significance [12]. Yang et al. conducted a meta-analysis to grade the evidence on conservative versus surgical treatment for type II odontoid fractures in the elderly. Analyzing twelve studies involving 730 patients aged 60 years or older, they did not find a difference with regard to the mortality between the two procedures [16]. In a prospective study on 336 patients, Rizvi et al. identified major comorbidities and older age as significant factors contributing to physicians’ decision to refrain from the surgical fixation of odontoid fractures [6]. Prospective trials are emerging to better understand the outcomes associated with different treatment options. Currently Robinson et al. are conducting the Uppsala Study on Odontoid Fracture Treatment (USOFT) which is one of the first randomized controlled trials comparing non-surgical and surgical management of type II odontoid fractures in the elderly [24]. Regarding stability and fusion rates meta-analysis see an advantage for the surgical treatment [12].

In the current cohort 31.5% of the patients were treated surgically. Most frequently, a screw fixation for one segment was applied as used to encode for dens-screws or transarticular “Magerl” screws, followed by fixation with a screw-rod system for 1 segment as used to encode the dorsal Atlanto-axial fusion techniques. The role of comorbidities was less pronounced in this cohort of surgically treated patients. We revealed Pneumonia to be a relevant risk factor (OR = 2.12). The occurrence of pneumonia after surgery is a frequent complication that is linked with significant morbidity and mortality [25]. Aspiration may be partially accountable, which is associated with significantly greater length of stay, costs, and mortality and has been reported with an incidence of 5.3 cases of per 1000 cervical procedures [26]. The highest OR in this sudy of 4.62 for in-hospital mortality in surgically treated patients was associated with SCI, although it was only prevalent in 1.1% of the cases. SCI has been well recognized as a significant factor for a fatal outcome in cervical spine fractures, especially in the geriatric population [27, 28]. However, low case numbers of SCI in this cohort prevented statistical differentiation between complete and incomplete SCI. Furthermore, only SCI diagnoses coded as concomitant but not primary ICD-10 code could be analyzed. Acute renal failure was found to have an OR of 3.20 for mortality in our cohort and could potentially be suggested as another significant predictor. Acute renal failure is well-known to be associated with increased mortality and therefore should be meticulously screened for and treated as early as possible [29, 30]. The current analysis suggests that bleeding complications are likely to play a major role for the in-hospital mortality, with medication-induced hemorrhagic diathesis having a high OR of 1.98. The deceased group had a significantly higher prevalence of acute anemia due to hemorrhage and hemorrhagic diathesis compared with the survival group. The cases in which blood transfusion was indicated were associated with 2.02-fold increased odds of in-hospital mortality. However, no difference was found in the frequency of long-term anticoagulant therapy between the groups, which was present in 25.6% of all cases. It has been demonstrated, that massive intraoperative hemorrhage is an important risk factor for in-hospital mortality after spine surgery with a reported OR of 28.2 [31]. For planned spine surgery various guidelines on the perioperative management of anticoagulation have been published [32, 33]. The initial findings from the AO Spine Anticoagulation Global Survey recognized the challenge of offering consistent perioperative anticoagulation advice to patients due to the lack of universally acknowledged literature or guidelines [34]. Cutler et al. demonstrated, that next to age and white race the history of bleeding disorders were independently predictive of complications in the multivariate analysis in their retrospective cohort of 103 patients treated with anterior fixation for odontoid fractures with a significant OR of 4.4 [35]. Our results and the body of the literature suggest that investigating the peri-operative management of coagulopathies to mitigate adverse events and exploring the feasibility of bridging anticoagulants in the trauma setting should be further considered. Hemoglobin levels might be employed to identify high-risk patients for in-hospital mortality and could be integrated into a predictive score system [21].

The geriatric population is prone to an increased risk of complications during the peri-operative period caused by prevalent comorbidities and weak bone structure. Nonetheless, Robinson et al. propose, that surgical treatment improves survival of elderly with axis fracture based on their national population-based multi-registry cohort study on 3375 patients [37]. A systematic analysis of the literature on the morbidity and mortality related to odontoid fracture surgery in the elderly population showed that major complications after surgery include cardiac failure, deep vein thrombosis, stroke, pneumonia, respiratory failure, liver failure, and severe infection [38]. Notable, anterior surgery had a higher rate of site-specific complications such as nonunion and revision surgery [38]. Longo et al. report a mortality rate of 7.6% and a complication rate of 9.1% in elderly patients treated with anterior odontoid screw fixation and described functional dependency as one predictor for mortality, which is in line with our findings [36]. Interestingly, we identified the fixation using a screw-rod system for one segment (e.g., as in "Goel/Harms" technique) to be associated with a significantly decreased risk for in-hospital mortality (OR = 0.74). Based on the results of their retrospective study of 70 patients above 75 years of age with odontoid fractures Faure et al. conclude, that the Harms technique showed lower risk of complications and better mechanical stability compared to anterior screw fixation [39]. In line, Cutler et al. report on a high complication rate (37.9%) and relevant mortality rate of 6.8% of anterior fixation of odontoid fractures in a retrospective analysis of 103 patients aged 73.9 years at average [35].

One further protective surgical factor was the use of intraoperative navigation. Due to substantial improvements and rapidly increasing availability, computer-assisted navigation is establishing itself as the gold standard for instrumentation at the cervical spine. It has been reviewed to increases the accuracy of pedicle screw placement, to reduce screw mispositioning and leading to fewer revision surgeries [40]. Ishak et al. retrospectively analyzed 35 patients suffering type II odontoid fractures with an average age of 86.5 years, that were treated with a navigated C1-C2 fusion. They found no in-hospital deaths and the overall major complication rate was 11%, leading to their conclusion, that Atlanto-axial fusion by using intra-operative spinal navigation is a safe and effective procedure [41].