Introduction. Several studies have evaluated surgical outcomes of lumbar degenerative disease by calculating minimum clinically important difference (MCID) of Japanese Orthopaedic Association Back Pain Evaluation Questionnaire (JOABPEQ), which is patient-reported outcomes (PROs). Previous reports have shown that PROs from elderly population declined even in healthy individuals and MCID threshold could also differ according to the type of pathology, treatment procedure, and age group, however, there are few studies that have been examined MCID of JOABPEQ specifically for lumbar spinal stenosis (LSS) by generation. The purpose of this study was to evaluate the difference of MCID values of the JOABPEQ between the 80s and 60s patients with LSS undergoing posterior decompression surgery without fusion using the Zurich Claudication Questionnaire (ZCQ) which is a LSS-specific outcome measurement as an anchor.
Methods. We retrospectively reviewed 629 consecutive patients who underwent posterior decompression surgery without fusion for LSS at our institution and completed JOABPEQ and ZCQ preoperatively and at 1-year follow-up.Patients with failed back syndrome and osteoporotic vertebral fracture were excluded. We used the symptom severity and physical function scores and the results for 13th question (How satisfied are you with the overall result of your back operation?) in ZCQ as anchors to determine MCID for each domain of the JOABPEQ using receiver operating characteristics (ROC) curve analysis. In order to focus on the clinical characteristics of the 80s patients, we compared them with the 60s patients, who are apart in age with the 80s patients.
Results. Of 629 patients, 92 were in the Group 80s (mean age: 83.3 ± 2.4 years) and 147 were in the Group 60s (mean age: 65.2 ± 2.7 years). In both groups, the symptom severity and the physical function were markedly improved at 1-year follow-up (P < 0.001). Preoperative and postoperative symptom severity and physical function and the satisfaction of ZCQ in the Group 80s were significantly lower than those in the Group 60s (P < 0.001). Regarding JOABPEQ, the effective rate in the walking ability domain was significantly lower in the Group 80s than in the Group 60s (P = 0,002). The ROC analysis revealed that MCID values of the JOABPEQ in the Group 80s and 60s were 21.4 and 14.3 for pain disorder, 4.2 and 4.2 for lumbar function, 25.0 and 39.3 for walking ability, 17.6 and 23.0 for social life, and 8.3 and 10.2 for psychological disorder. The AUC values were 0.695 and 0.729 for pain disorder, 0.737 and 0.752 for lumbar function, 0.803 and 0.870 for walking ability, 0.867 and 0.849 for social life, and 0.845 and 0.749 for psychological disorder.
Discussion. MCID values for walking ability, social life, psychological domain of the JOABPEQ in the 80s patients were lower than those in the 60s patients. On the other hand, MCID for pain disorder were higher in the 80s patients than the 60s patients. These results imply that elderly patients have higher expectations for pain improvement, while having lower expectations for physical functions such as walking ability and social function.