关键词: 全身骨骼三维建模成像系统, 膝关节参数, 脊柱矢状位失衡, 慢性下腰痛, 髌股关节痛

Abstract: BACKGROUND: With changing lifestyles and aging, sagittal spinal imbalance has become a common orthopedic issue significantly affecting knee and pelvic function. Understanding the impact of sagittal spinal imbalance and its compensatory mechanisms is crucial for improving the clinical management of chronic pain.
OBJECTIVE: To evaluate the alignment of the spine-pelvis-lower extremities using whole-body EOS imaging, analyze the correlation between spinal sagittal imbalance and knee joint parameters, and explore their compensatory mechanisms.
METHODS: A total of 71 patients with chronic low back pain or patellofemoral pain who visited Department of Orthopedics, First Affiliated Hospital of Soochow University between January 1, 2021 and December 31, 2023 were included. Radiographic measurements were performed using whole-body EOS to determine pelvic tilt, pelvic incidence, lumbar lordosis, sagittal vertical axis, global tilt, hip-knee-angle, knee flexion angle, lateral distal femoral angle, and medial proximal tibial angle. Patients were classified into normal group (pelvic incidence − lumbar lordosis < 10°), compensated group (10° ≤ pelvic incidence − lumbar lordosis ≤ 20°), and decompensated group (pelvic incidence − lumbar lordosis > 20°) based on the SRS-Schwab spinal deformity classification according to pelvic incidence − lumbar lordosis difference. The differences in radiographic parameters among the groups were analyzed. The differences in American Knee Society Knee Score and Oswestry Disability Index scores were compared among each group. Patients were divided into chronic low back pain group and non-chronic low back pain group, patellofemoral pain group and non-patellofemoral pain group based on clinical symptoms, and the relationship between radiographic parameter differences and clinical symptoms was analyzed.
RESULTS AND CONCLUSION: (1) When pelvic incidence − lumbar lordosis was less than 20°, lateral distal femoral angle and medial proximal tibial angle tended to stabilize. When pelvic incidence − lumbar lordosis was greater than 20°, it showed a linear correlation with lateral distal femoral angle and medial proximal tibial angle, with lateral distal femoral angle increasing and medial proximal tibial angle decreasing with increasing pelvic incidence − lumbar lordosis values. (2) Compared with the normal group, the compensated group had significantly increased pelvic tilt (P < 0.01), while knee joint parameters hip-knee-angle and knee flexion angle showed no significant differences; the decompensated group showed significant increases in pelvic tilt (P < 0.01), and decreases in hip-knee-angle, and knee flexion angle (P < 0.01). Compared with the compensated group, the decompensated group showed a significant decrease in hip-knee-angle (P < 0.05), but had no significant differences in pelvic tilt and knee flexion angle. (3) Compared with the non-patellofemoral pain group, patients with patellofemoral pain had significant decreases in spinal lumbar lordosis, lateral distal femoral angle, and medial proximal tibial angle (P < 0.05) and a significant increase in pelvic incidence − lumbar lordosis (P < 0.05). (4) Patients with low back pain had significant differences in radiographic parameters compared with the non-chronic low back pain group (P < 0.05). (5) Compared with the normal group, both the compensated and decompensated groups showed a significant decrease in American Knee Society Knee Score scores and a significant increase in Oswestry Disability Index scores (P < 0.05). Compared with the compensated group, the decompensated group showed a significant decrease in American Knee Society Knee Score scores and a significant increase in Oswestry Disability Index scores (P < 0.05). (6) Pelvic incidence − lumbar lordosis values increased with age and were higher in females compared with males. (7) This study systematically reveals the spine and lower limbs play an important role in disease progression and clinical symptoms. Associated symptoms low back pain and patellofemoral pain are related to the stability of the spine-pelvis-lower extremity alignment. Furthermore, spinal sagittal imbalance is more severe in elderly and female patients.

Key words: whole-body EOS imaging, knee joint parameter, spinal sagittal imbalance, chronic low back pain, patellofemoral pain