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

BACKGROUND CONTEXT: 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). PURPOSE: This study aimed to determine whether KFC can affect cervical alignment and its potential effects on the posterior muscles and NT. DESIGN: A prospective pilot study was carried out in preoperative (pre-op) and postoperative (post-op) phases. PATIENT SAMPLE: 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. OUTCOME MEASURES: 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. METHODS: 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. RESULTS: 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 of splenius capitis (FRRsc), and ROM of the KFC group pre-op were lower than the control group, and all of these were increased significantly post-op. There were no differences in pelvic tilt, sacral slope, C2-7 L, or TK between the KFC and control groups, or in FRR of splenius capitis (FRRutr) between pre-op and post-op phases. KA had strong correlations with LL (r=-0.83), which correlated well with C7 SVA (r=-0.75). C7 SVA correlated strongly with C2 SVA (r=0.79), which also correlated strongly with C0-2 L (r=0.76). C0-2 L correlated well with FRRsc (r=-0.65) and SWEsc (r=0.72), and both of them correlated well with VAS (r=-0.54, r=0.71) and NDI (r=-0.57, r=0.76). ROM correlated well with FRRsc (r=0.71), SWEsc (r=-0.74), VAS (r=-0.66), and NDI (r=-0.66). CONCLUSIONS: KFC may cause spine inclination and craniocervical malalignment, leading to NT and ROM reduction. The results of this pilot study may be helpful in guiding further studies concerning KFC and NT.

The Influence of Enhanced Side Impact Protection on Kinematics and Injury Measures of Far- or Center-Seated Children in Forward-Facing Child Restraints.

OBJECTIVE: To evaluate the influence of forward-facing child restraint systems' (FFCRSs) side impact structure, such as side wings, on the head kinematics and response of a restrained, far- or center-seated 3-year-old anthropomorphic test device (ATD) in oblique sled tests. METHODS: Sled tests were conducted utilizing an FFCRS with large side wings and with the side wings removed. The CRS were attached via LATCH on 2 different vehicle seat fixtures-a small SUV rear bench seat and minivan rear bucket seat-secured to the sled carriage at 20° from lateral. Four tests were conducted on each vehicle seat fixture, 2 for each FFCRS configuration. A Q3s dummy was positioned in FFCRS according to the CRS owner's manual and FMVSS 213 procedures. The tests were conducted using the proposed FMVSS 213 side impact pulse. Three-dimensional motion cameras collected head excursion data. Relevant data collected during testing included the ATD head excursions, head accelerations, LATCH belt loads, and neck loads. RESULTS: Results indicate that side wings have little influence on head excursions and ATD response. The median lateral head excursion was 435 mm with side wings and 443 mm without side wings. The primary differences in head response were observed between the 2 vehicle seat fixtures due to the vehicle seat head restraint design. The bench seat integrated head restraint forced a tether routing path over the head restraint. Due to the lateral crash forces, the tether moved laterally off the head restraint reducing tension and increasing head excursion (477 mm median). In contrast, when the tether was routed through the bucket seat's adjustable head restraint, it maintained a tight attachment and helped control head excursion (393 mm median). CONCLUSION: This testing illustrated relevant side impact crash circumstances where side wings do not provide the desired head containment for a 3-year-old ATD seated far-side or center in FFCRS. The head appears to roll out of the FFCRS even in the presence of side wings, which may expose the occupant to potential head impact injuries. We postulate that in a center or far-side seating configuration, the absence of door structure immediately adjacent to the CRS facilitates the rotation and tipping of the FFCRS toward the impact side and the roll-out of the head around the side wing structure. Results suggest that other prevention measures, in the form of alternative side impact structure design, FFCRS vehicle attachment, or shared protection between the FFCRS and the vehicle, may be necessary to protect children in oblique side impact crashes.