Optimal surgery sequence in the treatment of degenerative hip-spine syndrome: a propensity score-based inverse probability of treatment weighting analysis

Background: The coexistence of spinal degenerative diseases and hip joint degeneration is common among middle-aged and elderly individuals, causing significant suffering and economic burden for patients. Total hip arthroplasty (THA) and lumbar fusion (LF) are primary treatment options for this combined condition, but the impact of the surgical sequence on patient outcomes remains unclear. Hence, this study aims to evaluate the effects of the surgical sequence of THA and LF on symptom recovery, changes in sagittal spine-pelvis parameters, and the incidence of long-term complications in patients. Methods: A retrospective analysis was conducted on 104 patients diagnosed with hip-spine syndrome (HSS) who underwent THA and LF at the Chinese PLA General Hospital. IPTW was implemented to control potential confounding factors. The impact of surgical sequence on clinical function scores, radiological parameters, and long-term complications was evaluated before and after conducting IPTW. Patients who underwent THA surgery first, followed by LF surgery, were categorized as the THA→LF group; conversely, those who underwent LF surgery first, followed by THA surgery, were categorized as the LF→THA group. Clinical function scores included the Oswestry Disability Index (ODI), Japanese Orthopedic Association (JOA) score, and Harris Hip Score for both groups. Long-term complications assessed in this study included instances of Proximal Junctional Kyphosis (PJK), internal fixation loosening or failure, as well as hip prosthesis dislocation. Radiological parameters included Pelvic Tilt (PT), Pelvic Incidence (PI), Pelvic Incidence minus Lumbar Lordosis (PI-LL), Sacral Slope (SS), and Lumbar Lordosis (LL). Results: Before conducting IPTW, there were significant differences between the two groups across multiple variables, including age (P=0.035), fixation stage (P=0.042), preoperative PT (P=0.005), preoperative PI-LL (P=0.004), and preoperative LL (P=0.040). After conducting IPTW, all baseline data variables had P-values greater than 0.50, indicating that the baseline characteristics between the two groups were comparable. Following IPTW, the study found significant improvements in postoperative ODI, JOA score, and Harris Hip Score for both groups (P<0.001), indicating that both surgical sequences were effective in enhancing clinical functional activity. However, there were no significant differences between the groups. Additionally, there was no significant difference in the long-term complication rates between the two groups. Regarding radiological parameters, the PT in the THA→LF group was significantly lower than that in the LF→THA group (P=0.043), while the SS was significantly higher (P=0.028) at the last follow up after conducting IPTW. Conclusion: Compared to preoperative assessments, both surgical sequences significantly improve postoperative clinical function scores and radiological parameters for patients. When comparing between the two groups, the surgical sequence exhibits equivalent effects on functional improvement and complication rates. The radiological outcomes indicate that the THA→LF group shows more pronounced effects on PT and SS, suggesting a more favorable impact on pelvic alignment in patients undergoing this sequence. The use of the IPTW method successfully eliminates differences in baseline characteristics, enhancing the reliability of the results. Future research is warranted to further explore these findings and their implications for surgical decision-making in HSS patients.