Can knee flexion contracture affect cervical alignment and neck tension? A prospective self-controlled pilot study

• Published in: The spine journal 2020-02, Vol.20 (2), p.251-260
• Main Authors: Ding, Yi, Liu, Baoge, Qiao, Hui, Yin, Lu, He, Wen, Si, Fangda, Wang, Dian
• Format: Article
• Language: English
• Subjects: Cervical alignment; Compensation mechanism; Flexion-relaxation ratio; Horizontal gaze; Knee flexion contracture; Neck tension; Shear wave elastography; Surface electromyography
• ISSN: 1529-9430; 1878-1632
• DOI: 10.1016/j.spinee.2019.09.008

The coordination of the alignment between the lower extremities and cervical spine helps to achieve balance and horizontal gaze during standing and walking. Malalignment in any segment can disturb the global balance, causing compensation in another segment. Knee flexion contracture (KFC) can cause spine inclination with increased C7 tilt or C7 SVA (sagittal vertical axis). Cervical alignment and the posterior muscles are essential for maintaining the horizontal gaze which is closely related to neck tension (NT). This study aimed to determine whether KFC can affect cervical alignment and its potential effects on the posterior muscles and NT. A prospective pilot study was carried out in preoperative (pre-op) and postoperative (post-op) phases. This study included 22 consecutive patients with KFC and 12 control subjects in our department who agreed to participate from between August 1, 2018 and February 28, 2019 in our department. Visual analog scale (VAS) and neck disability index (NDI) were used. The sagittal alignment parameters and cervical range of motion (ROM) were measured on radiographic images, and included the C0–C2 lordosis (C0–2L), C2–C7 lordosis (C2–7L), C2 SVA, C7 SVA, T1 slope, thoracic kyphosis, lumbar lordosis (LL), pelvic tilt, sacral slope, and knee flexion angle (KA). Surface electromyography-based flexion-relaxation ratio (FRR) and ultrasound-based shear wave elastography (SWE) were performed. The control group was matched for age, sex, and body mass index with the KFC group. Patients in the KFC group underwent arthroscopic surgery to correct knee alignment. Comparisons between pre-op and post-op phases were performed using paired sample t tests, comparisons between KFC and control groups were performed using independent samples t tests. The correlation analysis between the parameters was performed using Spearman analysis. Funding for this study was provided by the National Natural Science Foundation of China (60,000 USD), Beijing Municipal Administration of Hospitals Incubating Program (50,000 USD), and Beijing Municipal Administration of Hospitals Clinical Medicine Development of Special Funding Support (20,000 USD). There were no conflicts of interest associated with this study. The average follow-up time for this pilot study was 11.4±1.5 days. Pre-op, the KFC group had higher KA, T1S, C7 SVA, C2 SVA, C0–2L, SWE, VAS, and NDI compared with the control group, but all of these parameters were decreased significantly post-op. The LL, FRR