Normative 3D acetabular orientation measurements by the low-dose EOS imaging system in 102 asymptomatic subjects in standing position: Analyses by side, gender, pelvic incidence and reproducibility.

BACKGROUND: Three-dimensional (3D) acetabular orientation is a fundamental topic in orthopedic surgery. Computed tomography (CT) allows 3D measurement of native acetabular orientation, but with a substantial radiation dose. The EOS imaging system was developed to perform this kind of evaluation, but has not been validated in this indication with specific attention to the acetabulum. We therefore performed a prospective study using EOS to assess: (1) the reproducibility of the 3D acetabulum orientation measures; (2) normative asymptomatic acetabular morphology in standing position, according to side and gender; and (3) the relationship between acetabular anteversion and pelvic incidence. HYPOTHESIS: The low-dose EOS imaging system is a reproducible method for measuring 3D acetabular orientation in standing position. PATIENTS AND METHODS: In a previous prospective study of spine sagittal balance, 165 asymptomatic volunteers were examined on whole-body EOS biplanar X-ray; 102 had appropriate images for pelvic and acetabular analysis, with an equal sex-ratio (53 female, 49 male). These EOS images were reviewed using sterEOS 3D software, allowing automatic measurement of acetabular parameters (anteversion and inclination) and pelvic parameters (pelvic incidence, pelvic tilt and sacral slope) in an anatomical (anterior pelvic plane: APP) and a functional reference plane (patient vertical plane: PVP). RESULTS: Both intra- and inter-observer analysis showed good agreement (ICC>0.90); Bland-Altman plot distributions were good. Acetabular anatomical anteversion and inclination relative to APP (AAAPP and AIAPP, respectively) were significantly greater in women than in men, with no effect of side (right AAA: women 21.3°±3.4° vs. men 16.1°±3.3° (P<0001); right AIAPP: women 55.3°±3.7° vs. men 52.5°±3.0° (P<0001); left AAAPP: women 20.9°±3.5° vs. men 15.6°±4.0° (P<0001); left AIAPP: women 54.6°±3.5° vs. men 52.7°±2.8° (P=0003)). The same differences between men and women were observed when measurements were related to PVP. Pelvic incidence subgroup (<44°; 44-62°; >62°) correlated significantly with functional acetabular orientation in standing position: PVP functional anteversion decreased by 5° relative to APP anteversion with incidence <44°, was equal to APP with incidence 44-62°, and or was greater by 4° relative to APP with incidence >62°. DISCUSSION: The use of a 3D sterEOS software prototype version for 3D reconstruction of the native acetabulum from standard EOS X-ray was shown to be a reliable and reproducible method. This innovative method enabled the reference values of 3D acetabular orientation in standing position to be measured for the first time. The results reinforced the concept of hip-spine relationships, and involved very low radiation dose. LEVEL OF EVIDENCE: IV prospective study without control group.

Clinical and radiological outcomes of lumbar posterior subtraction osteotomies are correlated to pelvic incidence and FBI index : Prospective series of 63 cases.

PURPOSE: Pedicle subtraction osteotomy (PSO) is one of the surgical options for treating alignment disorders of the fused spine (due to post-surgical fusion or related to arthritis). It enables satisfactory sagittal realignment and improved function due to economic sagittal balance. The aim of this study was to analyze clinical and radiological results of PSO after a minimum follow-up of 2 years and demonstrate the benefit of sub-group analysis as a function of pelvic incidence (PI). METHODS: A descriptive prospective single center study of 63 patients presenting with spinal global malalignment who underwent correction by PSO. Function was assessed by the Oswestry disability index (ODI), a visual analog scale of lumbar pain (VAS) and a SF-36 questionnaire. Radiographic analyses of pre- and post-operative pelvic-spinal parameters were performed on X-rays obtained by EOS(®) imaging after 3D modeling. Global analysis and analysis of sub-groups as a function of pelvic incidence were performed and the full balance integrated index (FBI) was calculated. RESULTS: this series showed a marked clinical improvement and significant progress of functional scores. Global post-operative radiological analysis showed a significant improvement in all pelvic and spinal parameters. The mean correction obtained after PSO was 31.7° ± 8.4°, hence global improvement of lumbar lordosis of 22°. The sagittal vertical angle (SVA) decreased from +9 cm before surgery to +4.3 cm after surgery. Sub-group analysis demonstrated greater improvement in pelvic tilt, sacral slope and spinal parameters of patients with a small or moderate pelvic incidence; all had an FBI index <10°. Most of the pelvic and spinal parameters of patients with a large pelvic incidence were insufficiently corrected and they had an FBI index >10° CONCLUSION: PSO is a surgical procedure enabling correction of multiplane rigid spinal deformities that require major sagittal correction. It was seen to be highly effective in patients with a small or moderate pelvic incidence (PI <60°) but was sometimes less effective in patients with large pelvic incidence due to insufficient lordosis correction. Clinical results were highly correlated with the value of the FBI index.

Normative values for the L5 incidence in a subgroup of transitional anomalies extracted from 147 asymptomatic subjects.

PURPOSE: Pelvic incidence angle is not always measurable due to lumbosacral transitional vertebrae (LSV). The fifth lumbar vertebra (L5) is rarely abnormal. The purpose of this study was to quantify from full-body standing X-rays, the L5 incidence angle (L5I) in a normal asymptomatic population and to correlate it with standard spino-pelvic parameters taking the sacrum (S1) as a reference. METHODS: One hundred and forty seven asymptomatic volunteers were enrolled. The ethics committee approved the study protocol. Subjects underwent a low-dose full spine X-ray. 3D reconstructions were obtained and L5I was measured using the upper L5 endplate as the reference instead of the S1 endplate. A group of subjects with LSV was identified and subdivided in two subgroups. Standard spino-pelvic parameters and normative values for the L5 parameters were obtained. Statistical correlations were calculated between the standard and L5 parameters as well as L5I with L1-L5 lordosis in both subgroups. RESULTS: Twenty two (14.96 %) subjects with LSV were found. Ten of these had an unidentifiable S1 endplate due to a sacralisation of L5. Mean values for the L5I, L5 tilt, L5 slope and L1-L5 lordosis were, respectively, 22.43, 4.65, 17.73, and 45.51 for normal subjects (N = 137) and 32.75, 6.63, 26.38, and 55.02 for sacralisation of L5 subjects (N = 10). Mathematical relationship found: L5I = 0.7641 * PI - 17.725 (R = 0.83) and L1-L5 = 0.67 * L5I + 30.7 (R = 0.64). CONCLUSION: This prospective study is first to provide normative spino-pelvic values at the L5 level in an asymptomatic population, particularly in case of (LSV) sacralisation of L5 (N = 10) where L5I and L1-L5 lordosis appears to be 10° more important than in normal population. We propose L5I as a new spino-pelvic parameter to restore in case of L5-S1 disk disease. These normative values will help to control peri-operatively the adequate lordosis restoration, in the presence of LSV.

Sagittal parameters of global cervical balance using EOS imaging: normative values from a prospective cohort of asymptomatic volunteers.

OBJECTIVE: To define reference parameters for analyzing sagittal balance of the cervical spine in asymptomatic volunteers. METHODS: Prospective study after Bioethics Committee approval. Imaging performed using a low-dose radiographic system (EOS Imaging, Paris, France). The absence of pain was assessed using the Oswestry Questionnaire and VAS. 106 subjects were included of whom 55.66 % were men. The parameters measured were: pelvic incidence, pelvic tilt, sacral slope, thoracic and lumbar curvature, C7 plumb line position and the spino-sacral angle. The C7 slope and new parameters were measured: cranial incidence, defined in relation to the McGregor line and the sella turcica allowing to define cranial slope and tilt, and the spino-cranial angle (SCA). RESULTS: This study demonstrated a close correlation between the C7 slope and the cranio-cervical system. Economic sagittal balance in the asymptomatic population was defined by a constant SCA angle of 83° ± 9°. To maintain this balance, a spine with a marked C7 slope will present lordosis and vice versa. Cranial incidence is an anatomical parameter characteristic of the cranio-cervical system which makes it possible to analyze the spatial positioning of the head and to predict the desired value of cervical lordosis which is closely correlated to cranial slope. CONCLUSION: The C7 slope has a predictive value of the shape of the cervical spine in the sagittal plane. One-third of the asymptomatic population had cervical kyphosis. Our results could be used to study sagittal balance before and after arthrodesis, or cervical prosthesis.

Insufficient restoration of lumbar lordosis and FBI index following pedicle subtraction osteotomy is an indicator of likely mechanical complication.

PURPOSE: Pedicle subtraction osteotomies (PSO) enable correction of spinal deformities but remain difficult and are associated with high complication rates. This study aimed to prospectively review different post-operative complications and mechanical problems in patients who underwent PSO as treatment for sagittal imbalance as sequelae of degenerative disc disease or previous spinal fusion. METHOD: This was a descriptive prospective single center study of 63 patients who underwent sagittal imbalance correction by PSO. Radiographic analysis of pre- and post-operative pelvic and spinal parameters was completed based on EOS images following 3D modeling. Global and sub-group analyses were completed based on the Roussouly classification. A systematic analysis of post-operative complications was conducted during hospital stay and at follow-up visits. RESULTS: Complications included 15 cases (20.2%) of bilateral leg pain, with transient neurological deficit in 6 cases (9.5%), and 9 cases (12.5%) of early surgical site infections. Intra-operative complications included five tears of the dura mater and two cases of excessive blood loss (>5,000 mL). Two mortalities occurred from major intracerebral bleeds in the early post-operative period. Mechanical complications were principally non-union (9 cases) and junctional kyphosis (3 cases). All 19 post-operative complications (28.1%) were revised at an average of 2 years following surgery. All mechanical complications were found in the patients who had insufficient imbalance correction and this was mainly associated with high PI (>60°) or a moderate PI (45-60º) combined with excess FBI pre-operatively that remained >10° post-operatively. CONCLUSION: Infection and neurologic complications following PSO are relatively common, and frequently reported in the literature. The principal cause of mechanical complications, such as non-union or junctional kyphosis, was insufficient sagittal correction, characterized by post-operative FBI >10°. The risks of insufficient correction are greater in patients with higher pelvic incidence and those patients who required very high correction.

Total elbow arthroplasty for acute distal humeral fractures in patients over 65 years old - results of a multicenter study in 87 patients.

INTRODUCTION: Fractures of the distal humerus represent 5% of osteoporosis fragility fractures in subjects over the age of 60. Osteoporosis, comorbidities and intra-articular comminution make management of this entity difficult. HYPOTHESIS: The hypothesis was that total elbow arthroplasty could be a reliable treatment option in subjects over the age of 65 presenting with a fracture of the distal humerus. MATERIALS AND METHODS: Eight-seven patients (80 women and 7 men) mean age 79 years old (65-93) underwent total elbow arthroplasty for the treatment of an AO type A fracture in 9 cases, type B in 8 and type C in 70. RESULTS: After a mean follow-up of 37.5 months (6-106) the Mayo Elbow Performance Score MEPS was 86±14, the quick-DASH score was 24±19 and the Katz score was 5±1.5 points. The MEPS was better in patients with a high preoperative Katz score and a history of inflammatory arthritis who were living at home. Fifty-five patients (63%) presented with a pain-free elbow, and 20 (24%) with slight pain. The flexion-extension range of motion was 97±22° and 48% presented with a flexion-extension arc of at least 100°. Function was normal in 69 patients. Complications were identified in 20 cases (23%) and revision surgery was necessary in 8 (9%). Two arthroplasties had to be changed, one for a fracture of the humeral stem component and the other for loosening. Only one infection occurred in this series. CONCLUSION: Total elbow arthroplasties provide fractured patients with immediate satisfactory results and a stable, painless and functional elbow. These results seem to be reliable and durable. The rate of complications is low with revision surgery in approximately 10%. LEVEL OF EVIDENCE: Level IV.