Patients’ loss to follow-up seemed to be a common phenomenon in clinical orthopaedic studies [10, 18, 23]. It has been suggested that lower than 5% loss probably leaded to little bias, whereas greater than 20% loss might potentially pose serious threats to the sensitivity and the validity of the data in research . From the clinical standpoint, patients discontinued to follow-up might have worse function and poorer prognosis [10, 22, 25]. From the investigative perspective, loss of follow-up would potentially bring about bias, decrease statistical power [11, 26, 27], and lead to underestimates or overestimates of therapeutic effects [28, 29]. Based on an analysis of 235 published reports, a systematic review concluded that plausible hypotheses about patients’ outcomes of LTFU could change the interpretation of results of randomized controlled trials .
Many factors including socio-economic demographic features and patients’ related factors might impact patients’ follow-up after surgery. It was found that the average age in LTFU group was higher than that in FU group (P < 0.001). Older patients were more likely to be lost to follow-up in our study. Compared with the elderly, younger patients might be easier to attend follow-up visits on their own without relying on their family members. Berg and Ring found that unmarried status (single or divorced) and unemployment status were independent predictors of loss to follow-up in a cohort study of 335 patients treated for metacarpal fractures . They considered it attributed to social deprivation [5, 31–33]. But 89.9% patients in FU group and 85.4% in LTFU group didn't live alone, and 84.9% in FU group and 80.2% in LTFU group were unemployed in our study. The patients’ age and living status of ours were significantly different from theirs, which greatly reduced the impact of social deprivation on follow-up. Additional risk for loss to follow-up related to fracture type and surgical methods. It was suggested that patients with femoral neck fracture and those who underwent hemiarthroplasty were more likely to be loss of follow-up. In Norquist et al’s research, patients treated non-operatively were significantly more likely to be non-responders . Similarly, in a follow-up study of patients with distal radius fractures, it was also showed that patients with non-surgical treatment were less likely to follow-up . However, all the patients in our study were treated surgically. The probable reason might be that, patients with femoral neck fracture underwent hemiarthroplasty were older than those underwent internal fixation or THA, which made them less likely to follow-up. On the other hand, compared with those with intertrochanteric fracture, they could weight-bearing move early after operation and were more likely feeling well.
In our series comprised of 1041 patients, 212(20.37%)were lost to follow-up, which was similar to previously reported LTFU rates [19, 34]. LTFU was thought associated with poor clinical outcomes under the assumption that the patients might be unsatisfied and quested for further care elsewhere. Murray et al. declared that patients underwent total hip arthroplasty who lost to follow-up had worse outcomes and radiographic features . Joshi et al.  found lower failure rates of revision surgery and higher satisfactory results in patients lost to follow-up compared with those had completing follow-up after total knee arthroplasty. Therefore, they thought that the patients who didn’t continue follow-up visits did not necessarily have poor results. A national multicenter follow-up study suggested that the improvement of patients’ symptoms during follow-up may lead them to believe that follow-up was no longer necessary . Similarly, a notable finding in our study was that more than 1/3 patients in LTFU group (75/212, 35.4%) were satisfied with treatment results and discontinued the scheduled follow-up by their own decision, when they were asked for the reasons of noncompliance with clinic visits.
Previous studies from traumatic surgery and emergency medicine found that distance to hospital and transportation expense were important factors for noncompliance with follow-up [37, 38]. Geng et al. also concluded that inconvenient transportation and long distance to clinic were the most common reasons for not continuing follow-up . Similar to previous literatures, distance to hospital correlated with our patients’ noncompliance with scheduled follow-up, and patients from LTFU group lived further away from the hospital. Inversely, 307 patients underwent surgical treatment after orthopaedic injuries were analyzed retrospectively, and there was no correlation between distance from the hospital and noncompliance . But the geographic area that their trauma center served was relatively larger than ours, which generated possible further effect on patients’ traffic affairs, that making more patients loss of follow-up. Due to the difficulty to calculate the transportation costs accurately, we only recorded the way to hospital. It was found that convenience of patients’ coming to follow-up was the main reason, as the patients LTFU were more likely to take traffic coach or bus to hospital. Moreover, with infirmity or advanced age, many patients (26.9%) from LTFU group declared that they had no ability to follow up, which also explained that convenience did play an important role. And 23 (10.8%) patients in LTFU group responded that they chose an alternate health care institution, due to inconvenience to our hospital. Finally, in our study, the payment methods of patients' medical expenses were also analyzed. Although the proportion of patients with rural cooperative medical insurance or at their own expense were higher in LTFU group, but no statistic difference were found in the logistic regression analysis. It was different from the observations by Berg and Zelle, lack of commercial health insurance was associated with the risk of noncompliance [5, 17]. It might be related to different medical costs and insurance systems in each region, which still needed further study.
Our study had several potential limitations. Firstly, our study was a retrospective cohort study that was inherently limited by data collection and sample size. Another inherent issue in this study was its dependence on accurate entry of databases. Therefore, we were unable to analyze other potential factors (e.g. life style, household income , education level ) due to lack of detailed information. Secondly, as the significant socioeconomic and geographic differences, the findings in our study might not necessarily generalize to other clinics. Moreover, as 1-year follow-up visit was considered as a main observation time point in most clinical research, our study focused on incomplete regular attendance within the first 1 year after surgery. Hence, we could not make any assumptions about nonattendance with long-term follow-up. Moreover, our study merely provided information on the demographics of hip-fracture patients after operation. Therefore, we could not make any assumptions about patients by conservative treatment, who were at high risk for noncompliance with their follow-up visits. Finally, the collection of patients’ questionnaire data in the present study was conducted more than 1 year after surgery, and therefore it could lead to recall bias by patients.
In conclusion, loss to follow-up was a common problem in patients underwent surgery for hip fractures. Our research indicated that there were multiple reasons for noncompliance. Advanced age, fracture type, long distance and inconvenience to hospital were risk factors of loss to follow-up at 1 year postoperatively. It was also suggested that most patients lost to follow-up after surgery were likely satisfied with their clinical results and might think it unnecessary for further follow-up.