Abstract
The purposes of this study were (1) to evaluate the relationship between lumbosacral flexibility and the effects of total knee arthroplasty (TKA) on whole-body alignment; and (2) to determine the prerequisites of the adjacent joints for successful TKA. A total of 116 patients (156 cases) who had whole-body X-ray and flexion-extension lumbar radiograph available were enrolled. For the sagittal alignment evaluation, hip–knee–ankle (HKA) angle, pelvic tilt (PT), sacral slope (SS), lumbar lordosis (LL), thoracic kyphosis (TK), and C7 plumb line-sacrum distance (SVA) were evaluated on the whole-body radiographs. Lumbar flexibility (LF) was evaluated using the flexion-extension lumbar radiographs, and pelvic flexibility (PF) was evaluated using the pelvic incidence (PI). The disparities in the knee joint between postoperative passive motion and weight-bearing posture were assessed. LF was significantly correlated with ΔLL and ΔSVA (LL: p = 0.039, SVA: p = 0.040; Pearson correlation coefficient (PCC): −0.206 and 0.205, respectively). There were correlations between PF and ΔSS (p < 0.001, PCC: −0.362), and between the disparity and LF (p = 0.005, PCC = −0.275). Linear regression analysis demonstrated that LF was significantly associated with the presence of disparity (p = 0.005, β = −0.205). LF is an important factor for improved spinal and lower limb alignment after TKA. Additionally, reduced LF may result in knee joint disparity between passive extension and standing extension status. Therefore, surgeons should consider spinopelvic alignment, including lower limb alignment preoperatively, to be able to predict possible changes in whole-body alignment following TKA.
Highlights
As the aging population increases, many patients experience multi-site degenerative changes, with the knee and spine being the two most commonly affected sites
Total knee arthroplasty (TKA) is a well-established procedure in osteoarthritic knee patients [4,5,6] and TKA patients commonly present with spinal problems, such as lower back pain (LBP)
As mentioned above, poor outcomes after TKA can often be predicted because spinal problems can be aggravated or a negative effect can be imparted on the knee joint, such as recurrence of flexion deformity
Summary
As the aging population increases, many patients experience multi-site degenerative changes, with the knee and spine being the two most commonly affected sites. [2] many patients have improved spinal problems after TKA, some complain of aggravated spinal problems or recurrence of knee flexion deformity for the standing body balance, even if it was previously solved with TKA. This may imply that multiple joints can affect each other; it is very important to consider these effects after TKA. As mentioned above, poor outcomes after TKA can often be predicted because spinal problems can be aggravated or a negative effect can be imparted on the knee joint, such as recurrence of flexion deformity. The EOSTM whole-body X-ray system was introduced as a method of whole-body alignment assessment and has been used to develop a new modality for clinical alignment analysis
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