The principal findings of this study were as follows: (1) patient compliance with osteoporosis treatment after TKA was high, and (2) there was no significant difference in the degree of improvement in the DEXA results between the OPD and TKA groups.
Successful osteoporosis treatment requires the selection of the appropriate treatment method and enhanced treatment compliance. Low compliance is generally due to concerns regarding drug-induced adverse effects. While the exact factors influencing compliance remain unknown, treatment compliance is higher with injectable agents than with oral agents, and among injectable agents, compliance is generally high when injection is required once every 6 months. Osteoporosis treatment compliance is higher when it is treated by a specialist and in cases of enhanced doctor-patient communication.[19–21] Further, compliance with osteoporosis treatment is higher when compliance with the treatments of concomitant diseases is high. In this study, we believed that treatment compliance in the TKA group would be high because patients in this group had increased interactions with doctors, and treatment compliance of patients who performed TKA was relatively high.
In the present study, the compliance rate in the TKA group was very high at 100%, even considering the small number of patients included. This rate was much higher than the general TKA 1-year outpatient follow-up rate of approximately 70%.[15, 16] Osteoporosis treatment compliance in the OPD group was also approximately 70% higher than the general one-year follow-up rate of 50%. We believe that because the hospital involved in the study is a public hospital, treatment cost is relatively low, which can increase the follow-up rate. Further, as mentioned, the high compliance rate in the TKA group may be because patients in the TKA group had more interactions with the doctor; the relatively high 1-year follow-up rate of TKA may have also affected osteoporosis treatment compliance. The use of denoxumab, which is used for injection once every 6 months and showed relatively good compliance, is also considered to be one of the reasons for the good compliance.
Previous studies have demonstrated a decrease in BMD 1 year after TKA; osteoporosis treatment after TKA can prevent BMD loss.[9, 10, 24] In this study, BMD increased significantly at 1 year after treatment in the OPD group. However, in the TKA group, only the lowest average T-score at two or more points on the L-spine showed a statistically significant increase, and although there was an increase at other sites, the difference was not statistically significant. There was no statistical difference in the degree of increase in the T-scores between the two groups. The use of denoxumab after TKA was not statistically significant 1 year after TKA, but it helped prevent the decrease in BMD.
Previous studies have reported on the change in BMD when osteoporosis treatment is performed after TKA, but there is no report on the number of patients who continue to receive osteoporosis treatment. In particular, denoxumab has been reported to have high compliance; however, there are no reports on postoperative compliance. In this study, TKA increased compliance with osteoporosis treatment. While TKA is not required to increase compliance, if osteoporosis is treated after TKA, various complications, such as periprosthetic fracture, aseptic loosening, and postoperative pain can be reduced; thus, osteoporosis treatment is required. In such cases, enhanced treatment effects can be expected because the treatment compliance is much higher than that before TKA. Moreover, osteoporosis is undertreated in a large number of patients undergoing TKA. A greater effect can be expected in the detection and treatment of patients with osteoporosis.
The present study has some limitations. First, the number of patients included in this study was small. To solve this problem, more data will be collected prospectively and additional research results will be published based on the current study. Second, the DEXA results did not indicate the BMD status around the knee implant. However, since DEXA results are generally used to indicate the outcomes of osteoporosis treatment, we believe that the overall osteoporosis treatment results in this study can be judged using DEXA evaluation. Third, as this was a retrospective study, the selection bias was likely to be high.