Cervical spine facet tropism (CFT) defined as the facets’ joints angles difference between right and left sides of more than 7 degrees. This study aims to investigate the relationship between cervical sagittal alignment parameters and cervical spine facets’ tropism. A retrospective cross-sectional study carried out in a tertiary center where cervical spine magnetic resonance imaging (MRI) radiographs of patients in orthopedics/spine clincs were included. They had no history of spine fractures. Images’ reports were reviewed to exclude those with tumors in the c-spine. A total of 96 patients was included with 63% of them were females. The mean of age was 45.53± 12.82. C2-C7 cobb's angle (CA) and C2-C7 sagittal vertical axis (SVA) means were −2.85±10.68 and 1.51± 0.79, respectively. Facet tropism was found in 98% of the sample in at least one level on either axial or sagittal plane. Axial C 2–3 CFT and sagittal C4-5 were correlated with CA (r=0.246, P 0.043, r= −278, P 0.022), respectively. In addition, C2-C7 sagittal vertical axis (SVA) was moderately correlated with axial c2-3 FT (r= −0.330, P 0.006) Also, several significant correlations were detected in our model Cervical vertebral slopes and CFT at the related level. Nonetheless, high BMI was associated with multi-level and multiplane CFT with higher odd's ratios at the lower levels. This study shows that CFT at higher levels is correlated with increasing CA and decreasing SVA and at lower levels with decreasing CA. Obesity is a risk factor for CFT

Mechanical failure of spine posterior fixation in the lumbar region Is suspected to occur more frequently when the sagittal balance is not properly restored. While failures at the proximal extremity have been studied in the literature, the lumbar distal junctional pathology has received less attention. The aim of this work was to investigate if the spinopelvic parameters, which characterize the sagittal balance, could predict the mechanical failure of the posterior fixation in the distal lumbar region. All the spine surgeries performed in 2017-2019 at Rizzoli Institute were retrospectively analysed to extract all cases of lumbar distal junctional pathology. All the revision surgeries performed due to the pedicle screws pull-out, or the breakage of rods or screws, or the vertebral fracture, or the degenerative disc disease, in the distal extremity, were included in the junctional (JUNCT) group. A total of 83 cases were identified as JUNCT group. All the 241 fixation surgeries which to date have not failed were included in the control (CONTROL) group. Clinical data were extracted from both groups, and the main spinopelvic parameters were assessed from sagittal standing preoperative (pre-op) and postoperative (post-op) radiographs with the software Surgimap (Nemaris). In particular, pelvic incidence (PI), sagittal vertical axis (SVA), pelvic tilt (PT), T1 pelvic angle (TPA), sacral slope (SS) and lumbar lordosis (LL) have been measured. In JUNCT, the main failure cause was the screws pull-out (45%). Spine fixation with 7 or more levels were the most common in JUNCT (52%) in contrast to CONTROL (14%). In CONTROL, PT, TPA, SS and PI-LL were inside the recommended ranges of good sagittal balance. For these parameters, statistically significant differences were observed between pre-op and post-op (p<0.0001, p=0.01, p<0.0001, p=0.004, respectively, Wilcoxon test). In JUNCT, the spinopelvic parameters were out of the ranges of the good sagittal balance and the worsening of the balance was confirmed by the increase in PT, TPA, SVA, PI-LL and by the decrease of LL (p=0.002, p=0.003, p<0.0001, p=0.001, p=0.001, respectively, paired t-test) before the revision surgery. TPA (p=0.003, Kolmogorov-Smirnov test) and SS (p=0.03, unpaired t-test) differed significantly in pre-op between JUNCT and CONTROL. In post-op, PI-LL was significantly different between JUNCT and CONTROL (p=0.04, unpaired t-test). The regression model of PT vs PI was significantly different between JUNCT and CONTROL in pre-op (p=0.01, Z-test). These results showed that failure is most common in long fused segments, likely due to long lever arms leading to implant failure. If the sagittal balance is not properly restored, after the surgery the balance is expected to worsen, eventually leading to failure: this effect was confirmed by the worsening of all the spinopelvic parameters before the revision surgery in JUNCT. Conversely, a good sagittal balance seems to avoid a revision surgery, as it is visible is CONTROL. The mismatch PI-LL after the fixation seems to confirm a good sagittal balance and predict a good correction. The linear regression of PT vs PI suggests that the spine deformity and pelvic conformation could be a predictor for the failure after a fixation

Cranio-cervical connection is a well-established biomechanical concept. However, literature of this connection and its impact on cervical alignment is scarce. Chin incidence (CI) is defined as a complementary to the angle between chin tilt (CHT) and C2 slope (C2S) axes. This study aims to investigate the relationship between cervical sagittal alignment parameters and CI with its derivatives. A retrospective cross-sectional study carried out in a tertiary center. CT-neck radiographs of non-orthopedics patients were included. They had no history of spine related symptoms or fractures in cranium or pelvis. Images’ reports were reviewed to exclude those with tumors in the c-spine or anterior triangle of the neck. A total of 80 patients was included with 54% of them were males. The mean of age was 30.96± 6.03. Models of predictability for c2-c7 cobb's angle (CA) and C2-C7 sagittal vertical axis (SVA) using C2S, CHT, and CI were significant and consistent r20.585 (f(df3,76) =35.65, P ≤0.0001, r=0.764), r20.474 (f(df2,77) =32.98, P ≤0.0001, r=-0.550), respectively. In addition, several positive significant correlations were detected in our model in relation to sagittal alignment parameters. Nonetheless, models of predictability for CA and SVA in relation to neck tilt (NT), T1 slope (T1S) and thoracic inlet axis (TIA) were less consistent and had a significant marginally weaker attributable effect on CA, however, no significant effect was found on SVA r20.406 (f(df1,78) =53.39, P ≤0.0001, r=0.620), r20.070 (f(df3,76) =1.904, P 0.19), respectively. Also, this study shows that obesity and aging are linked to decreased CI which will result in increasing SVA and ultimately decreasing CA. CI model has a more valid attributable effect on the sagittal alignment in comparison to TIA model. Future investigations factoring this parameter might enlighten its linkage to many cervical spine diseases or post-op complications (i.e., trismus)

To describe a staged surgical technique to correct significant progressive sagittal malalignment, without the need for 3-column osteotomy, in patients with prior long thoracolumbar instrumentation for scoliosis and to evaluate the radiographic and clinical outcome from this surgical strategy. A small cohort study (n=6) of patients with significant sagittal malalignment following extensive thoracolumbar instrumented fusions for scoliotic deformity. Radiographic parameters analysed included pelvic incidence, pelvic tilt, sacral slope, lumbar lordosis, thoracic kyphosis and sagittal vertical axis. Clinical outcome measures collected included EQ-5D, ODI, SRS 22 and VAS Pain Scores. 3 patients had 2-stage anterior release and instrumented fusion followed by a posterior instrumented fusion 3 patients with a large sagittal plane deformity had a 3-stage surgical technique. All patients achieved an excellent correction of sagittal alignment, with no surgical complications and excellent health related quality of life (HRQOL) outcome measures at follow-up. There was no symptomatic non-unions or implant failures including rod breakages. We present a safe and effective surgical strategy to treat the complex problem of progressive sagittal malalignment in the previously instrumented adult deformity patient, avoiding the need for 3-column osteotomies in the lumbar spine

Aims. The aim of this study was to evaluate the reliability and validity of a patient-specific algorithm which we developed for predicting changes in sagittal pelvic tilt after total hip arthroplasty (THA). Methods. This retrospective study included 143 patients who underwent 171 THAs between April 2019 and October 2020 and had full-body lateral radiographs preoperatively and at one year postoperatively. We measured the pelvic incidence (PI), the sagittal vertical axis (SVA), pelvic tilt, sacral slope (SS), lumbar lordosis (LL), and thoracic kyphosis to classify patients into types A, B1, B2, B3, and C. The change of pelvic tilt was predicted according to the normal range of SVA (0 mm to 50 mm) for types A, B1, B2, and B3, and based on the absolute value of one-third of the PI-LL mismatch for type C patients. The reliability of the classification of the patients and the prediction of the change of pelvic tilt were assessed using kappa values and intraclass correlation coefficients (ICCs), respectively. Validity was assessed using the overall mean error and mean absolute error (MAE) for the prediction of the change of pelvic tilt. Results. The kappa values were 0.927 (95% confidence interval (CI) 0.861 to 0.992) and 0.945 (95% CI 0.903 to 0.988) for the inter- and intraobserver reliabilities, respectively, and the ICCs ranged from 0.919 to 0.997. The overall mean error and MAE for the prediction of the change of pelvic tilt were -0.3° (SD 3.6°) and 2.8° (SD 2.4°), respectively. The overall absolute change of pelvic tilt was 5.0° (SD 4.1°). Pre- and postoperative values and changes in pelvic tilt, SVA, SS, and LL varied significantly among the five types of patient. Conclusion. We found that the proposed algorithm was reliable and valid for predicting the standing pelvic tilt after THA. Cite this article: Bone Joint J 2024;106-B(1):19–27

Aims. Sagittal plane imbalance (SPI), or asymmetry between extension and flexion gaps, is an important issue in total knee arthroplasty (TKA). The purpose of this study was to compare SPI between kinematic alignment (KA), mechanical alignment (MA), and functional alignment (FA) strategies. Methods. In 137 robotic-assisted TKAs, extension and flexion stressed gap laxities and bone resections were measured. The primary outcome was the proportion and magnitude of medial and lateral SPI (gap differential > 2.0 mm) for KA, MA, and FA. Secondary outcomes were the proportion of knees with severe (> 4.0 mm) SPI, and resection thicknesses for each technique, with KA as reference. Results. FA showed significantly lower rates of medial and lateral SPI (2.9% and 2.2%) compared to KA (45.3%; p < 0.001, and 25.5%; p < 0.001) and compared to MA (52.6%; p < 0.001 and 29.9%; p < 0.001). There was no difference in medial and lateral SPI between KA and MA (p = 0.228 and p = 0.417, respectively). FA showed significantly lower rates of severe medial and lateral SPI (0 and 0%) compared to KA (8.0%; p < 0.001 and 7.3%; p = 0.001) and compared to MA (10.2%; p < 0.001 and 4.4%; p = 0.013). There was no difference in severe medial and lateral SPI between KA and MA (p = 0.527 and p = 0.307, respectively). MA resulted in thinner resections than KA in medial extension (mean difference (MD) 1.4 mm, SD 1.9; p < 0.001), medial flexion (MD 1.5 mm, SD 1.8; p < 0.001), and lateral extension (MD 1.1 mm, SD 1.9; p < 0.001). FA resulted in thinner resections than KA in medial extension (MD 1.6 mm, SD 1.4; p < 0.001) and lateral extension (MD 2.0 mm, SD 1.6; p < 0.001), but in thicker medial flexion resections (MD 0.8 mm, SD 1.4; p < 0.001). Conclusion. Mechanical and kinematic alignment (measured resection techniques) result in high rates of SPI. Pre-resection angular and translational adjustments with functional alignment, with typically smaller distal than posterior femoral resection, address this issue. Cite this article: Bone Jt Open 2024;5(8):681–687

Introduction. Interactions between hip, pelvis and spine, as abnormal spinopelvic movements, have been associated with inferior outcomes following total hip arthroplasty (THA). Changes in pelvis position lead to a mutual change in functional cup orientation, with both pelvic tilt and rotation having a significant effect on version. Hip osteoarthritis (OA) patients have shown reduced hip kinematics which may place increased demands on the pelvis and the spine. Sagittal and coronal planes assessments are commonly done as these can be adequately studied with anteroposterior and lateral radiographs. However, abnormal pelvis rotation is likely to compromise the outcome as they have a detrimental effect on cup orientation and increased impingement risk. This study aims to determine the association between dynamic motion and radiographic sagittal assessments; and examine the association between axial and sagittal spinal and pelvic kinematics between hip OA patients and healthy controls (CTRL). Methods. This is a prospective study, IRB approved. Twenty hip OA pre-THA patients (11F/9M, 67±9 years) and six CTRL (3F/3M, 46±18 years) underwent lateral spinopelvic radiographs in standing and seated bend-and-reach (SBR) positions. Pelvic tilt (PT), pelvic-femoral-angle (PFA) and lumbar lordosis (LL) angles were measured in both positions and the differences (Δ) between standing and SBR were calculated. Dynamic SBR and seated maximal-trunk-rotation (STR) were recorded in the biomechanics laboratory using a 10-infrared camera and processed on a motion capture system (Vicon, UK). Direct kinematics extracted maximal pelvic tilt (PT. max. ), hip flexion (HF. max. ) and (mid-thoracic to lumbar) spinal flexion (SF. max. ). The SBR pelvic movement contribution (ΔPT. rel. ) was calculated as ΔPT/(ΔPT+ΔPFA)∗100 for the radiographic analysis and as PT. max. /(PT. max. +HF. max. ) for the motion analyses. Axial and sagittal, pelvic and spinal range of motion (ROM) were calculated for STR and SBR, respectively. Spearman's rank-order determined correlations between the spinopelvic radiographs and sagittal kinematics, and the sagittal/axial kinematics. Mann-Whitney U-tests compared measures between groups. Results. Radiograph readings correlated with sagittal kinematics during SBR for ΔPT and PT. max. (ρ=0.64, p<0.001), ΔPFA and HF. max. (ρ=0.44, p<0.0002), and ΔLL and SF. max. (ρ=0.34, p=0.002). Relative pelvic movements (ΔPT. rel. ) were not different between radiographic (11%±21) and biomechanical (15%±29) readings (p=0.9). Sagittal SRB spinal flexion correlated with the axial STR rotation (ρ=0.43, p<0.0001). Although not seen in CTRL, sagittal SRB pelvic flexion strongly correlated with STR pelvic rotation in OA patients (ρ=0.40, p=0.002). All spinopelvic parameters were different between the patients with OA and CTRL. CTRLs exhibited significantly greater mobility and less variability in all 3 segments (spine, pelvis, hip) and both planes (axial and sagittal) (Table 1). Conclusion. Correlation between sagittal kinematics and radiographical measurements during SBR validates the spinopelvic mobility assessments in the biomechanics laboratory. Axial kinematics of both pelvis and spine correlated significantly in OA patients, suggesting that patients with abnormal sagittal mobility are likely to also exhibit abnormal axial mobility, which can further potentiate any at-risk kinematics. Significantly lower OA ROM must be investigated post-THA. Pre-THA variability of both sagittal and axial movements indicates that both planes must be considered ahead of surgical planning with navigation and/or robotics. For any figures or tables, please contact the authors directly

Aims. This study aimed to evaluate sagittal spinopelvic alignment (SSPA) in the early stage of rapidly destructive coxopathy (RDC) compared with hip osteoarthritis (HOA), and to identify risk factors of SSPA for destruction of the femoral head within 12 months after the disease onset. Methods. This study enrolled 34 RDC patients with joint space narrowing > 2 mm within 12 months after the onset of hip pain and 25 HOA patients showing femoral head destruction. Sharp angle was measured for acetabular coverage evaluation. Femoral head collapse ratio was calculated for assessment of the extent of femoral head collapse by RDC. The following parameters of SSPA were evaluated using the whole spinopelvic radiograph: pelvic tilt (PT), sacral slope (SS), pelvic incidence (PI), sagittal vertical axis (SVA), thoracic kyphosis angle (TK), lumbar lordosis angle (LL), and PI-LL. Results. The HOA group showed higher Sharp angles compared with the RDC group. PT and PI-LL were higher in the RDC group than the HOA group. SS and LL were lower in the RDC group than the HOA group. No difference was found in PI, SVA, or TK between the groups. Femoral head collapse ratio was associated with PT, SS, SVA, LL, and PI-LL. A PI-LL > 20° and a PT > 30° correlated with greater extent of femoral head destruction by RDC. From regression analysis, SS and SVA were significantly associated with the femoral head collapse ratio within 12 months after disease onset. Conclusion. Compared with HOA, RDC in the early stage correlated with sagittal spinopelvic malalignment. SS and SVA may partially contribute to the extent of femoral head destruction by RDC within 12 months after the onset of hip pain. The present study indicates a potential role of SSPA assessment in identification of RDC patients at risk for subsequent bone destruction. Cite this article: Bone Jt Open 2022;3(1):77–84

In healthy subjects, respiratory maximal volumes are highly dependent on the sagittal range of motion of the T7-T10 segment. In AIS, the abolition of T7-T10 dynamics related to the stiffness induced by the apex region in Lenke IA curves could harm ventilation during maximal breathing. The aim of this study was to analyze the dynamics of the thoracic spine during deep breathing in AIS patients and in healthy matched controls. This is a cross-sectional, case-control study. 20 AIS patients (18 girls, Cobb angle, 54.7±7.9°; Risser 1.35±1.2) and 15 healthy volunteers (11 girls) matched in age (12.5 versus 15.8 yr. mean age) were included. In AIS curves, the apex was located at T8 (14) and T9 (6). Conventional sagittal radiographs of the whole spine were performed at maximal inspiration and exhalation. The ROM of each spinal thoracic functional segment (T1-T7, T7-T10, T10-T12) and the global T1-T12 ROM were measured. In healthy subjects, the mean T1-T12 ROM during forced breathing was 16.7±3.8. AIS patients showed a T1-T12 ROM of 1.1±1.5 (p<0.05), indicating a sagittal stiffness of the thoracic spine. A wide T7-T10 ROM (15.3±3.0) was found in healthy controls (91.6% of the T1–T12 ROM). AIS patients showed only 0.4±1.4 ROM at T7-T10 (36.4% of the T1-T12 ROM) (p<0.001). There was a significant positive correlation between the magnitude of T7-T10 kyphosis in maximal exhalation and both FVC (% of predicted FVC) and FEV1. In conclusion, Lenke 1A AIS patients show a restriction of the thoracic spine motion with an almost complete abolition of T7-T10 ROM, a crucial segment for deep breathing. T7-T10 stiffness could explain the ventilatory limitations found in AIS patients

Tibial plateau fracture reduction involves restoration of alignment and articular congruity. Restorations of sagittal alignment (tibial slope) of medial and lateral condyles of the tibial plateau are independent of each other in the fracture setting. Limited independent assessment of medial and lateral tibial plateau sagittal alignment has been performed to date. Our objective was to characterize medial and lateral tibial slopes using fluoroscopy and to correlate X-ray and CT findings. Phase One: Eight cadaveric knees were mounted in extension. C-arm fluoroscopy was used to acquire an AP image and the C-arm was adjusted in the sagittal plane from 15° of cephalad tilt to 15 ° of caudad tilt with images captured at 0.5° increments. The “perfect AP” angle, defined as the angle that most accurately profiled the articular surface, was determined for medial and lateral condyles of each tibia by five surgeons. Given that it was agreed across surgeons that more than one angle provided an adequate profile of each compartment, a range of AP angles corresponding to adequate images was recorded. Phase Two: Perfect AP angles from Phase One were projected onto sagittal CT images in Horos software in the mid-medial compartment and mid-lateral compartment to determine the precise tangent subchondral anatomic structures seen on CT to serve as dominant bony landmarks in a protocol generated for calculating medial and lateral tibial slopes on CT. Phase Three: 46 additional cadaveric knees were imaged with CT. Tibial slopes were determined in all 54 specimens. Phase One: Based on the perfect AP angle on X-ray, the mean medial slope was 4.2°+/-2.6° posterior and mean lateral slope was 5.0°+/-3.8° posterior in eight knees. A range of AP angles was noted to adequately profile each compartment in all specimens and was noted to be wider in the lateral (3.9°+/-3.8°) than medial compartment (1.8°+/-0.7° p=0.002). Phase Two: In plateaus with a concave shape, the perfect AP angle on X-ray corresponded with a line between the superiormost edges of the anterior and posterior lips of the plateau on CT. In plateaus with a flat or convex shape, the perfect AP angle aligned with a tangent to the subchondral surface extending from center to posterior plateau on CT. Phase Three: Based on the CT protocol created in Phase Two, mean medial slope (5.2°+/-2.3° posterior) was significantly less than lateral slope (7.5°+/-3.0° posterior) in 54 knees (p<0.001). In individual specimens, the difference between medial and lateral slopes was variable, ranging from 6.8° more laterally to 3.1° more medially. In a paired comparison of right and left knees from the same cadaver, no differences were noted between sides (medial p=0.43; lateral p=0.62). On average there is slightly more tibial slope in the lateral plateau than medial plateau (2° greater). However, individual patients may have substantially more lateral slope (up to 6.8°) or even more medial slope (up to 3.1°). Since tibial slope was similar between contralateral limbs, evaluating slope on the uninjured side provides a template for sagittal plane reduction of tibial plateau fractures

Introduction and Objective. Up to 30% of thoracolumbar (TL) fractures are missed in the emergency room. Failure to identify these fractures can result in neurological injuries up to 51% of the casesthis article aimed to clarify the incidence and risk factors of traumatic fractures in China. The China National Fracture Study (CNFS. Obtaining sagittal and anteroposterior radiographs of the TL spine are the first diagnostic step when suspecting a traumatic injury. In most cases, CT and/or MRI are needed to confirm the diagnosis. These are time and resource consuming. Thus, reliably detecting vertebral fractures in simple radiographic projections would have a significant impact. We aim to develop and validate a deep learning tool capable of detecting TL fractures on lateral radiographs of the spine. The clinical implementation of this tool is anticipated to reduce the rate of missed vertebral fractures in emergency rooms. Materials and Methods. We collected sagittal radiographs, CT and MRI scans of the TL spine of 362 patients exhibiting traumatic vertebral fractures. Cases were excluded when CT and/or MRI where not available. The reference standard was set by an expert group of three spine surgeons who conjointly annotated (fracture/no-fracture and AO Classification) the sagittal radiographs of 171 cases. CT and/or MRI were used confirm the presence and type of the fracture in all cases. 302 cropped vertebral images were labelled “fracture” and 328 “no fracture”. After augmentation, this dataset was then used to train, validate, and test deep learning classifiers based on the ResNet18 and VGG16 architectures. To ensure that the model's prediction was based on the correct identification of the fracture zone, an Activation Map analysis was conducted. Results. Vertebras T12 to L2 were the most frequently involved, accounting for 48% of the fractures. Accuracies of 88% and 84% were obtained with ResNet18 and VGG16 respectively. The sensitivity was 89% with both architectures but ResNet18 had a significantly higher specificity (88%) compared to VGG16 (79%). The fracture zone used was precisely identified in 81% of the heatmaps. Conclusions. Our AI model can accurately identify anomalies suggestive of TL vertebral fractures in sagittal radiographs precisely identifying the fracture zone within the vertebral body

Spinal deformations are posture dependent. Official data from the Netherlands show that youth are encountering increasing problems with the musculoskeletal system (>40% back pain, and sport injury proneness). Prolonged sloth and slumped sitting postures are causative factors. Dutch youth are “champion sitting” in Europe. The effects of sitting on the development of posture and function of locomotion (stiffness) during growth have only been reported clearly in classic textbooks (in German) of practical anatomy and orthopaedics. Research with relevant clinical examinations is being done to understand epidemiological data on the increasing posture-dependent problems. A cohort of adolescents (15–18 years) in secondary school was assessed for sagittal postural deviations while bending. 248 children completed a questionnaire, and tests were done on neuromuscular tightness. The femorotibial angle was used to measure hamstring tightness. Measurement of the dorsiflexion of the foot was used to assess the tightness of calf muscles and Achilles tendons. All adolescents were photographed laterally while performing the finger–floor test (used to test flexibility), assessed as a knockout test: “Can you reach the floor or not?” The spinal profiles while bending were classified as abnormal arcuate or angular kyphosis. Hamstring tightness was present in 62.1% of the cohort in both legs, and in 18.2% unilaterally. Achilles tendon tightness was present bilaterally in 59.3%, and unilaterally in 19.4%. Activities with presence of stiffness (finger–floor distance), in descending order, were football, running, no sports, field hockey, tennis, dance, and gymnastics. 93.5% of the soccer players had tight hamstrings in both legs compared with none of those performing gymnastics. The correlation of the finger–floor test with tight hamstrings was 73.2%. For sagittal bending deformities, the correlation between form and function deficits cannot be made yet. 80 of 248 spines were rated by the examiners as having deformed flexion. Since Andry (1741) and at the zenith of continental orthopaedics and anatomy around 1900, the prolonged flexed positions of a young spine were indicated as being the main cause of deformity by overload and shear loads on immature discs and cartilage, preventing normal development of the discs. Nachemson proved that the intradiscal pressure in sitting adults was extremely high, so it follows that children must also be at risk. Evidence suggests that youth, generally because of their sedentary and “screenful lifestyle”, will encounter serious problems in growth, manifesting as incongruent neuro-osseous growth (Roth), serious neuromuscular tightness (being prone to injury), and spinal deformations, leading to pain

Introduction. Spinopelvic mobility has been associated with THA outcome. To-date spine assessments have been made quasi-statically, using radiographs, in standing and seated positions but dynamic spinopelvic mobility has not been well explored. This study aims to determine the association between dynamic (motion analysis) and quasi-static (radiographic) sagittal assessments and examine the association between axial and sagittal spinal kinematics in hip OA patients and controls. Methods. This is a prospective, IRB approved, cohort study of 12 patients with hip OA pre-THA (6F/6M, 67±10 years) and six healthy controls (3F/3M, 46±18 years). All underwent lateral spinopelvic radiographs in standing and seated bend-and-reach (SBR) positions. Pelvic tilt (PT), pelvic-femoral-angle (PFA) and lumbar lordosis (LL) angles were measured in both positions and the differences (Δ) in angles between SBR and standing were computed. All participants performed two dynamic tasks at the motion laboratory: seated maximal trunk rotation (STR) and seated bend and reach (SBR). Three-dimensional joint motion data were collected and processed by a 10-camera infrared motion analysis system (Vicon, Nexus 2.10, UK). Total axial and sagittal spine (mid-thoracic to lumbar) range of motion (ROM) were calculated for STR and SBR, respectively. Results. ΔLL for SBR and motion analysis spinal flexion for SBR moderately correlated (ρ=0.4, p=0.007). Dynamic spinal rotation and flexion significantly, strongly, correlated (ρ=0.6 p=0.007). OA patients compared to healthy participants showed significant less ΔPFA (53°±21° vs. 77°±14°; p<0.001); ΔPT (−17°±8° vs. 9°±15°; p<0.001), ΔLL (35°±15° vs. 43° ±9°; p<0.001), axial spinal rotation during STR (62° ±12°vs. 79° ±8°, p<.001) and less, but not significant, spine flexion during SBR (36° ±15° vs. 44° ±10°, P=.1). Conclusion. Dynamic sagittal and axial spinal ROM showed moderately correlated. Motion analysis can provide valid assessments for spine mobility. OA patients compared to healthy participants showed significant less ΔPFA, ΔPT, ΔLL, axial spinal rotation during STR. Surgeons should be aware that patients with less spine mobility that could affect the stability of THA and increase the risk of poor outcomes

The spinopelvic alignment is often assessed via the Pelvic Incidence-Lumbar Lordosis (PI-LL) mismatch. Here we describe and validate a simplified method to evaluating the spinopelvic alignment through the L1-Pelvis angle (L1P). This method is set to reduce the operator error and make the on-film measurement more practicable. 126 standing lateral radiographs of patients presenting for Total Hip Arthroplasty were examined. Three operators were recruited to label 6 landmarks. One operator repeated the landmark selection for intra-operator analysis. We compare PI-LL mismatch obtained via the conventional method, and our simplified method where we estimate this mismatch using PI-LL = L1P - 90°. We also assess the method's reliability and repeatability. We found no significant difference (p > 0.05) between the PI-LL mismatch from the conventional method (mean 0.22° ± 13.6) compared to L1P method (mean 0.0° ± 13.1). The overall average normalised root mean square error (NRMSE) for PI-LL mismatch across all operators is 7.53% (mean -3.3° ± 6.0) and 6.5% (mean -2.9° ± 4.9) for the conventional and L1P method, respectively. In relation to intra-operator repeatability, the correlation coefficients are 0.87 for PI, 0.94 for LL, and 0.96 for L1P. NRMSE between the two measurement sets are PI: 9.96%, LL: 5.97%, and L1P: 4.41%. A similar trend is observed in the absolute error between the two sets of measurements. Results indicate an equivalence in PI-LL measurement between the methods. Reproducibility of the measurements and reliability between operators were improved. Using the L1P angle, the classification of the sagittal spinal deformity found in the literature translates to: normal L1P<100°, mild 100°<L1P<110°, and severe L1P>110°. Surgeons adopting our method should expect a small improvement in reliability and repeatability of their measurements, and a significant improvement of the assessment of the mismatch through the visualisation of the angle L1P

Abstract. Objectives. The objective of this proof of concept study was to explore whether some total hip arthroplasty (THA) patients with well-functioning implants achieve normal sagittal plane hip kinematics during walking gait. Methods. Sagittal plane hip kinematics were recorded in eleven people with well-functioning THA (71 ± 8 years, Oxford Hip Score = 46 ± 3) and ten healthy controls (61 ± 5 years) using a three-dimensional motion capture system as they walked over-ground at a self-selected velocity. THA patients were classified as high- or low-functioning (HF and LF, respectively) depending on whether the mean absolute difference between their sagittal plane hip kinematics was within one standard deviation of the control group (5.4°) or not. Hedge's g effect size was used to compare the magnitude of the difference from the control group for the HF and LF THA groups. Results. Five THA patients were identified as HF and 6 as LF. The mean absolute difference in sagittal plane hip kinematics between the THA groups and the control group was on average 6.2° larger for the LF THA patients compared to the HF, with this difference associated with a large effect size (g = 1.84). Conclusions. The findings of this study challenge the findings of previous work which suggests THA patients do not achieve normal sagittal plane hip kinematics. Five patients were classified as HR and achieved motion patterns that were on average within the variance of the asymptomatic control group, suggesting normative sagittal plane hip kinematics. Understanding why some THA patients achieve motion patterns more comparable to healthy controls than others would help to develop means of maximising functional recovery, and potentially enhance both patient quality of life and implant survivorship through more normal loading of the implant

Abstract. Introduction. In cementless UKR, early post-operative tibial fractures are 7x more common in very small tibias. A smaller keel has been shown to reduce this fracture risk, but its effect on fixation is unassessed. This mechanical study assesses the effect of keel interference and size on sagittal micromotion of the tibial component in physiological loading positions. Method. A high-resolution Digital Image Correlation setup was developed and validated to an accuracy of 50 micrometres. Variants of tibial components were 3D-printed: standard, no-interference, no-keel, and a new small keel. Components were implanted into bone-analogue foam which was machined to a CT-reconstructed small tibia, using surgical technique. Tibias were loaded to 200N in physiological loading positions: 8mm (step-up) and 15mm (lunge) posterior to midpoint, and micromotion was assessed. Results. In all tests, anterior lift-off was the largest micromotion observed. In ‘step-up’, a standard keel moved more than the no-interference and no-keel variants (340μm-vs-63μm-vs-30μm, p=0.002). In ‘lunge’ loading, the no-interference and no-keel variants moved more than the standard (826μm-vs-1003μm-vs-521μm, p=0.039). The small keel experienced less micromotion in ‘step-up’ (245μm-vs-340μm p=0.233, overall p=0.009) and ‘lunge’ (378μm-vs-521μm p=0.265, overall p=0.006) than the standard keel. Conclusion. The keel protects against large tibial micromotion during lunge movement. Counterintuitively, interference increases micromotion during step-up movement, likely due to implant pivoting around the bone-keel interface. Results suggest patients should be advised against lunge movements early post-operatively. The new smaller keel fixes similarly or better than the standard keel, making it viable for replacing the standard keel to potentially reduce fracture risk

Background. Surgical treatment of AIS includes several purposes such as arrest deformity progression through a solid fusion, obtain a permanent correction of the deformity and others. Objectives. To evaluate the improvement of sagittal spinopelvic parameters and clinical outcomes in patients with adolescent idiopathic scoliosis 2 years after corrective surgery. Methods. Radiological and clinical data of 134 consecutive scoliosis patients including 11 boys and 124 girls with the average age of 15.37 years, with AIS Lenke 1, 2, 3, 4, 5 or 6 were included in this retrospective study with 2-year follow-up. Whole spine anterior/posterior and lateral Xray, CT scan and MRI were taken preoperatively, immediately after surgery, at 3 months and 2 years after corrective surgery. Radiological parameters were evaluated and compared pre and post operatively. Result. In coronal plan, significant reduction was observed in main curve, proximal curve and distal curve P<0.001, 2 years after corrective surgery. Meanwhile, the translation of apex vertebra decreased p<0.001. But sagittal profile of the patients did not show obvious changes such as LL, TK. The pelvic parameters indicated that PI was 50.6 degrees, PT was 13.8, SS was 37.0 and TPA was 47.5 degrees preoperatively. Vertebral body height increased dramatically just after surgery and showed further in the last follow up. Conclusion. The changes in coronal plan was significant 2 years after correction surgery for AIS patients and were not correlated with restoration of sagittal profile. Conflict of interest. None. Sources of funding. None

Objectives. Normal sagittal spine-pelvis-lower extremity alignment is crucial in humans for maintaining an ergonomic upright standing posture, and pathogenesis in any segment leads to poor balance. The present study aimed to investigate how this sagittal alignment can be affected by severe knee osteoarthritis (KOA), and whether associated changes corresponded with symptoms of lower back pain (LBP) in this patient population. Methods. Lateral radiograph films in an upright standing position were obtained from 59 patients with severe KOA and 58 asymptomatic controls free from KOA. Sagittal alignment of the spine, pelvis, hip and proximal femur was quantified by measuring several radiographic parameters. Global balance was accessed according to the relative position of the C7 plumb line to the sacrum and femoral heads. The presence of chronic LBP was documented. Comparisons between the two groups were carried by independent samples t-tests or chi-squared test. Results. Patients with severe KOA showed significant backward femoral inclination (FI), hip flexion, forward spinal inclination, and higher prevalence of global imbalance (27.1% versus 3.4%, p < 0.001) compared with controls. In addition, patients with FI of 10° (n = 23) showed reduced lumbar lordosis and significant forward spinal inclination compared with controls, whereas those with FI > 10° (n = 36) presented with significant pelvic anteversion and hip flexion. A total of 39 patients with KOA (66.1%) suffered from LBP. There was no significant difference in sagittal alignment between KOA patients with and without LBP. Conclusions. The sagittal alignment of spine-pelvis-lower extremity axis was significantly influenced by severe KOA. The lumbar spine served as the primary source of compensation, while hip flexion and pelvic anteversion increased for further compensation. Changes in sagittal alignment may not be involved in the pathogenesis of LBP in this patient population. Cite this article: W. J. Wang, F. Liu, Y.W. Zhu, M.H. Sun, Y. Qiu, W. J. Weng. Sagittal alignment of the spine-pelvis-lower extremity axis in patients with severe knee osteoarthritis: A radiographic study. Bone Joint Res 2016;5:198–205. DOI:10.1302/2046-3758.55.2000538

This matched cohort study aims to (a) assess differences in spinopelvic characteristics of patients having sustained a dislocation following THA and a control THA group without dislocation; (b) identify spinopelvic characteristics associated with risk of dislocation and; (c) propose an algorithm to define the optimum cup orientation for minimizing dislocation risk. Fifty patients with a history of THA dislocation (29 posterior-, 21 anterior dislocations) were matched for age, gender, body mass index, index diagnosis, and femoral head size with 100 controls. All patients were reviewed and underwent detailed quasi-static radiographic evaluations of the coronal- (offset; center-of-rotation; cup inclination/anteversion) and sagittal- reconstructions (pelvic tilt, pelvic incidence, lumbar lordosis, pelvic-femoral-angle, cup ante-inclination). The spinopelvic balance (PI-LL), combined sagittal index (CSI= Pelvic-femoral-angle + Cup Anteinclination) and Hip-User-Index were determined. sagittal index (CSI= Pelvic-femoral-angle + Cup Anteinclination) and Hip-User-Index were determined. Parameters were compared between the two groups (2-group analysis) and between controls and per direction of dislocation (3-group analysis). There were marginal coronal differences between the groups. Sagittal parameters (lumbar-lordosis, pelvic-tilt, CSI, PI-LL and Hip-User-Index) differed significantly. PI-LL (>10°) and standing pelvic tilt (>18°) were the strongest predictors of dislocation risk (sensistivity:70%/specificity:70%). All hips with a standing CSI<195° dislocated posteriorly and all with CSI>260° dislocated anteriorly. A CSI between 200–245° was associated with significantly reduced risk of dislocation (OR:6; 95%CI:2.5–15.0; p<0.001). In patients with unbalanced and/or rigid lumbar spine, standing CSI of 215–245° was associated with significantly reduced dislocation risk (OR:10; 95%CI:3.2–29.8; p<0.001). PI-LL and standing pelvic-tilt determined from pre-operative, standing, lateral spinopelvic radiograph can be useful screening tools, alerting surgeons of patients at increased dislocation risk. Measurement of the pelvic-femoral angle pre-operatively provides valuable information to determine the optimum, cup orientation associated with reduced dislocation risk by aiming for a standing CSI of 200–245°

Aim. To investigate the effect of the eight plate position in sagittal plane on tibial slope in temporary epiphysiodesis technique applied to the proximal tibia and whether there is a rebound effect after removing the plate. Method. Forty New Zealand rabbits (6 weeks old) were divided into four groups. In all groups, two 1.3 mm mini plates and cortical screws implantation were placed on both medial and lateral side of the proximal epiphysis of the right tibia. In Group 1 and 3, the plates were placed on anterior of the proximal tibial anatomical axis in the sagittal plane, and placed posteriorly in Group 2 and 4. The left tibia was examined as control in all groups. Group 1 and Group 2 were sacrificed after four week-follow-up. In Group 3 and Group 4, the implants were removed four weeks after index surgery and the rabbits were followed four more weeks to investigate the rebound effect. The tibial slope was measured on lateral X-rays every two weeks. Both medial and lateral plateau slopes were evaluated on photos of the dissected tibia. Results. In Group 1, right MTPA (medial tibial plateau angle) and left MTPA, right LTPA (lateral tibial plateau angle) and left LTPA, and right 4wTPPA (the tibial proximal posterior angle at 4th week) and left 4wTPPA values were compared with each other. There was a significant difference in MTPA, LTPA, and 4wTPPA in Group 1 (p: 0.003, 0.006, 0.004). In Group 1, the medial and lateral slope significantly decreased after 4 weeks. There was no significant difference in MTPA, LTP and 4wTPPA measurements in Group 2 (p= 0.719, 0.306, 0.446, respectively). In Group 2, the slope did not change in four weeks. There was a significant difference in MTPA, LTPA, 4wTPPA, and 8wTPPA (tibial proximal posterior angle at 8th week) in Group 3 (p= 0.005, 0.002, <0.001, <0.001, respectively). In Group 3, the slope decreased at 4th week and remained stabile during the next four week-follow up and no rebound effect was observed. There was no significant difference in MTPA, LTPA, 4wTPPA, and 8wTPPA measurements in Group 4 (p= 0.791, 0.116, 0.232, 0.924), respectively. In group 4, slope did not change at 4th week of index surgery and no rebound effect was observed in the next four week-follow up. Conclusion. If eight plates were placed on anterior of lateral proximal tibia axis on both medial and lateral side, the tibial slope would reduce, and remain stabile after implant removal. Care should be taken to place the plates on the line of proximal tibial axis in sagittal plane in temporary epiphysiodesis technique performed due to angular knee deformities. Changing the slope due to plate placement can be used as a secondary gain for patients who will benefit from slope change, such as adolescent ACL surgery