As individuals age, physical impairments may have a deleterious effect on the musculoskeletal system (1). Distal radius fractures (DRF) are a commonly encountered type of traumatic injury in daily practice. The incidence of osteoporosis-associated DRF has been reported to increase from approximately the age of 70 years (2). DRF associated with osteoporosis are frequently identified as the earliest manifestation of fragility fractures, which precede other osteoporotic fractures (3). The number of patients with DRF is expected to continue to rise due to the increasing age of the global population (2). The World Health Organization has recognized osteoporotic fractures and associated morbidity as important health issues globally (4).

Volar locking plate fixation enables early postoperative return to daily activities. It has increasingly been indicated not only for elderly patients but also for adolescents (5). However, from the patient's perspective, undergoing surgery can pose substantial challenges, such as psychological stressors associated with the illness itself, anesthesia, surgical outcomes and postoperative recovery (6). In particular, the perioperative period is considered a time of high psychological stress (6). Furthermore, preoperative patients with orthopedic diseases are concerned about their postoperative physical condition and anxious about postoperative restrictions on physical movement (7).

The central sensitization inventory (CSI) score is a patient-reported outcome used to identify symptoms associated with a central sensitization syndrome (8). It was recently reported that the CSI score can be used as an assessment tool for psychosocial factors in pain assessment (9). In the present study, the use of the CSI score to assess the psychosocial factors of patients' status before surgery for DRF was investigated. Furthermore, factors influencing the CSI score before surgery for DRF were investigated.

The present study investigated factors associated with the CSI scores before volar locking plate fixation for DRF. Factors investigated included patient features (sex, side of injury and age), fracture-related variables (fracture type and interval from injury to evaluation in days) and patient-reported outcomes (NRS and Q-DASH scores). It was found that the CSI score was significantly associated with age and NRS.

It has been reported that postoperative pain is more intense in female fracture patients than in male fracture patients (13). This suggests that sex may influence pain perception following trauma and it was included as a variable in the analysis. However, no significant association between the CSI score and sex was found. Iitsuka et al (14) investigated differences in postoperative functional recovery between dominant and non-dominant side injuries in patients who underwent volar locking plate fixation for DRF. They reported that patients with dominant-side injuries showed significantly greater postoperative improvement in hand joint range of motion and grip strength than those with non-dominant-side injuries (14). Therefore, it was hypothesized that the side of injury (dominant or non-dominant side) influences pain after fracture treatment and preoperative CSI score. However, no significant relationship was found between the side of injury and CSI score. DRF involving the articular surface have been reported to be associated with poorer functional outcomes compared with extra-articular fractures (15). Furthermore, at 6 months postoperatively, patients with complete intra-articular fractures (AO classification type C) have been shown to experience significantly greater pain than those with partial intra-articular fractures (AO classification type B) (16). Based on these findings, it was hypothesized that the fracture type influences preoperative CSI scores. On the other hand, as the cohort of the present study included only three type A fractures, five type B fractures and 14 type C fractures, types A and B were combined into a single group and compared with type C for statistical analysis. As a result, it was found that the type of fracture (extra-articular or intra-articular fractures) was not related to the preoperative CSI score. Wilson et al (17) reported that pain was inversely correlated with the interval from injury to initial consultation and initial response for DRF. Therefore, it was hypothesized that the interval (in days) from injury to evaluation influences preoperative CSI scores; however, no significant association was found. Patient-reported outcomes that assess pain and directly reflect quality of life have gained attention as important measures in evaluating wrist function. Kawamura et al (18) reported that the visual analogue scale and grip strength were associated with Q-DASH scores after volar locking plate fixation for DRF. The Q-DASH score is a widely used patient-reported outcome measure for the upper extremities and has been employed in previous studies that evaluated the outcomes of DRF (19). However, in the present study, no significant relationship was found between the Q-DASH and CSI scores.

In the present study, it was found that age and NRS had a significant association with the CSI score. Furthermore, the NRS had a greater impact on the CSI scores than age. Older age decreases the ability of patients to cope with emotional stress and control their emotions in response to stressful events such as anxiety and depression (20). In the present study, patients' CSI scores were investigated in response to being informed of a DRF diagnosis and the subsequent recommendation for surgical treatment. It was found that the CSI score was significantly associated with age and was higher with increasing age. Pain is classified into three categories: Nociceptive pain, neuropathic pain and psychosocial pain (21). The results of the present study that the NRS, a measure of nociceptive pain, was related to the CSI score supports those of a previous study (22). The present findings suggest that nociceptive pain intensity is positively associated with central sensitization in the preoperative state before DRF surgery, highlighting the importance of pain assessment prior to surgery.

In the present study, the mean CSI score before volar locking plate fixation for DRF was 19.2±12.4, and 9.1% (2 patients) of the cohort had a CSI score of 40 or higher. A CSI score of 40 or higher has been proposed as a clinically relevant cutoff indicating the presence of central sensitization-related symptoms (10). Previous reports have shown that the mean CSI score was 16.1±11.1 in patients with chronic low back pain, with 4.4% scoring 40 or higher (22). In addition, the mean CSI score in patients with hip osteoarthritis was 19.5±11.3, with 5.0% scoring 40 or higher (23). Compared with these reports, the CSI scores of patients before volar locking plate fixation for DRF are not lower than those reported for other musculoskeletal disorders. Furthermore, CSI is used not only as a diagnostic indicator for central sensitization syndrome but also as an indicator of psychosocial factors, such as anxiety and depression (9). Therefore, in the present study, CSI scores were regarded as an indicator of psychosocial factors, and it was evaluated how CSI scores are associated with activities of daily living impairment in patients before volar locking plate fixation for DRF.

This study has several limitations. First, the sample size in this study was relatively small (n=22). Post-hoc power analysis demonstrated that the statistical power for the correlation between the NRS and CSI score was sufficient (power=0.882), whereas the power for the association between age and CSI score was moderate (power=0.522). In addition, the multivariable linear regression model showed high statistical power (power=0.99). Although the primary associations observed in this study appear to be statistically robust, the finding regarding age should be interpreted with caution due to its moderate power. Further studies with larger sample sizes are warranted to validate this association. Second, Multivariate analysis was performed; however, due to the small sample size (n=22), the number of covariates that could be included in the model was limited. Inclusion of additional variables in such a small cohort may increase the risk of model overfitting and unstable estimates, as described by Riley et al (24). Therefore, potential confounding factors such as psychological comorbidities (e.g., anxiety and depression), osteoporosis and psychosocial background were not included in the final model (25-27). Thus, a certain degree of residual confounding may remain. Previous studies have demonstrated that these factors may influence pain perception and central sensitization (25,26). Accordingly, an independent association between CSI and clinical outcomes cannot be definitively established. Future studies with larger sample sizes and multivariate models are warranted to confirm these findings. Furthermore, for the same reason, detailed subgroup analyses according to specific AO fracture classifications were not performed, as dividing this small cohort into multiple subgroups would substantially reduce statistical power and increase the risk of unstable estimates. Accordingly, the independent association between CSI and clinical outcomes cannot be definitively established. Future studies with larger sample sizes and multivariate models are warranted to confirm these findings. Third, this study evaluated only the preoperative clinical status. Therefore, the impact of preoperative CSI scores on postoperative pain and functional recovery remains elusive. Longitudinal studies with follow-up assessments are required to determine the predictive value of CSI. Finally, because the completion of the CSI score was voluntary, data were missing in a subset of eligible patients, which may have introduced selection bias.

In conclusion, CSI scores were significantly associated with age and NRS before volar locking plate fixation for DRF. Mental stress management and nociceptive pain relief for elderly patients may be useful in preoperative patient care.