How the spine differs in standing and in sitting-important considerations for correction of spinal deformity.

BACKGROUND CONTEXT: The current prevailing school of thought in spinal deformity surgery is to restore sagittal balance with reference to the alignment of the spine when the patient is standing. This strategy, however, likely accounts for increased rates of proximal junctional failure. PURPOSE: The purpose of this study was to investigate the differences between the spine in standing and sitting positions as these may elucidate reasons for deformity correction failure. STUDY DESIGN/SETTING: A prospective, comparative study of 58 healthy patients presenting to a tertiary hospital over a 6-month period was carried out. PATIENT SAMPLE: All patients presenting with a less than 3-month history of first episode lower back pain were included. Patients who had radicular symptoms, red flag symptoms, previous spine surgery, or visible spinal deformity during forward bending test were excluded. Pregnant patients were also excluded. OUTCOME MEASURES: Radiographic measurements including sagittal vertical axis (SVA), lumbar lordosis (LL), thoracolumbar angle (TL), thoracic kyphosis (TK), cervical lordosis (CL), pelvic incidence (PI), and pelvic tilt (PT) were collected. The sagittal apex and end vertebrae of all radiographs were also recorded. METHODS: Basic demographic data (age, gender, and ethnicity) was recorded. Lateral standing and sitting radiographs were obtained using EOS technology. Statistical analysis was performed to compare standing and sitting parameters using chi-square tests for categorical variables and paired t tests for continuous variables. RESULTS: Taking the standing position as the reference point, forward displacement of the SVA occurred during sitting by a mean of 6.39±3.87 cm (p<.001). This was accompanied by a reduction of LL and TK by a mean of 24.63±12.70° (p<.001) and 8.56±7.21°(p<.001), respectively. The TL became more lordotic by a mean of 3.25±7.30° (p<.001). The CL only reached borderline significance (p=.047) for increased lordosis by a mean of 3.45±12.92°. The PT also increased by 50% (p<.001). Despite relatively constant end vertebrae, the apex vertebra moved inferiorly for the thoracic curve (p<.006) and superiorly for the lumbar curve (p<.001) by approximately one vertebral level each. CONCLUSIONS: Sagittal spinal alignment changes significantly between standing and sitting positions. Understanding these differences is crucial to avoid overcorrection of LL, which may occur if deformity correction is based solely on the spine's standing sagittal profile.

Radiographical definition of the proximal tibiofibular joint - A cross-sectional study of 2984 knees and literature review.

BACKGROUND: Proximal tibiofibular joint (PTFJ) injuries are not uncommon but relatively understudied. This study evaluates the effectiveness of 2 radiographic methods in assessing the integrity of the PTFJ. STUDY DESIGN: This is a cross-sectional study of 2984 consecutive patients with knee X-rays done in a single institution over a 4-month period. A total of 5968 knee X-rays were assessed using 2 methods-[1] The direction in which the fibula points to in relation to the lateral femoral epicondyle on anteroposterior view and Blumensaat line on lateral view. [2] The degree of tibiofibular overlap as percentage of widest portion of the fibula head. Sensitivity and specificity of these methods in diagnosing a disrupted PTFJ are calculated. Variables including quality of X-rays, weight-bearing status of AP views and degree of knee flexion on lateral views are also recorded. Univariate analysis was carried out to investigate the association between variables using chi-square test for nominal data and student t-test for continuous data. RESULTS: The fibular points towards the lateral femoral epicondyle on AP view in 94.4% of the patients and points towards the posterior half of the Blumensaat line on lateral view in 98.1% of the patients. Using this method, weight-bearing X-rays are significantly associated with the direction the fibula is pointing (p<0.01) on the AP view and the degree of knee flexion is associated with the direction the fibula is pointing (p<0.01) on the lateral view. The AP tibiofibular overlap ranges from >0% to <75% in 94.1% of the patients and the lateral tibiofibular overlap ranges from >0% to <75% in 84.5% of the patients. This method is associated with whether true orthogonal X-rays of the knees are taken (p=0.048). CONCLUSION: The direction in which the fibula is pointing and the percentage of tibiofibular overlap are highly specific radiographic methods useful in defining the PTFJ. The first method requires a weight-bearing view on AP assessment and >20 degrees of flexion on lateral assessment. True orthogonal AP and lateral views are required for the second method to be used.