Proximal Junction Research Articles

Return to Play Prediction Accuracy of the MLG-R Classification System for Hamstring Injuries in Football Players: A Machine Learning Approach.

Muscle injuries are one of the main daily problems in sports medicine, football in particular. However, we do not have a reliable means to predict the outcome, i.e. return to play from severe injury. The aim of the present study was to evaluate the capability of the MLG-R classification system to grade hamstring muscle injuries by severity, offer a prognosis for the return to play, and identify injuries with a higher risk of re-injury. Furthermore, we aimed to assess the consistency of our proposed system by investigating its intra-observer and inter-observer reliability. All male professional football players from FC Barcelona, senior A and B and the two U-19 teams, with injuries that occurred between February 2010 and February 2020 were reviewed. Only players with a clinical presentation of a hamstring muscle injury, with complete clinic information and magnetic resonance images, were included. Three different statistical and machine learning approaches (linear regression, random forest, and eXtreme Gradient Boosting) were used to assess the importance of each factor of the MLG-R classification system in determining the return to play, as well as to offer a prediction of the expected return to play. We used the Cohen's kappa and the intra-class correlation coefficient to assess the intra-observer and inter-observer reliability. Between 2010 and 2020, 76 hamstring injuries corresponding to 42 different players were identified, of which 50 (65.8%) were grade 3r, 54 (71.1%) affected the biceps femoris long head, and 33 of the 76 (43.4%) were located at the proximal myotendinous junction. The mean return to play for grades 2, 3, and 3r injuries were 14.3, 12.4, and 37days, respectively. Injuries affecting the proximal myotendinous junction had a mean return to play of 31.7days while those affecting the distal part of the myotendinous junction had a mean return to play of 23.9days. The analysis of the grade 3r biceps femoris long head injuries located at the free tendon showed a median return to play time of 56days while the injuries located at the central tendon had a shorter return to play of 24days (p = 0.038). The statistical analysis showed an excellent predictive power of the MLG-R classification system with a mean absolute error of 9.8days and an R-squared of 0.48. The most important factors to determine the return to play were if the injury was at the free tendon of the biceps femoris long head or if it was a grade 3r injury. For all the items of the MLG-R classification, the intra-observer and inter-observer reliability was excellent (k > 0.93) except for fibres blurring (κ = 0.68). The main determinant for a long return to play after a hamstring injury is the injury affecting the connective tissue structures of the hamstring. We developed a reliable hamstring muscle injury classification system based on magnetic resonance imaging that showed excellent results in terms of reliability, prognosis capability and objectivity. It is easy to use in clinical daily practice, and can be further adapted to future knowledge. The adoption of this system by the medical community would allow a uniform diagnosis leading to better injury management.

Upper versus Lower Lumbar Lordosis Corrections in Relation to Pelvic Tilt - An Essential Element in Surgical Planning for Sagittal Plane Deformity.

Retrospective study of a multicenter Adult Spinal Deformity (ASD) Database. To investigate the change in Pelvic tilt (PT) imparted by regional changes in lumbar lordosis at 2-year minimum follow up. The distribution of lumbar lordosis between L1-4 and L4-S1 is known to vary based on pelvic incidence (PI). However, the extent to which regional changes effect PT is not clearly elucidated. This information can be useful for ASD surgical planning. Operative patients from a multicenter ASD database were included with Lowest Instrumented Vertebrae (LIV) S1/Ilium, >5 levels of fusion, Proximal Junction Kyphosis (PJK) angle < 20, and >5 degrees of change in lumbar lordosis from L4-S1 and L1-4. Radiographic analysis was performed evaluating Thoracic Kyphosis (TK), T10-L2 kyphosis (TL), L1-S1 lordosis (LL), L4-S1 lordosis, L1-4 lordosis, sagittal vertical axis (SVA) and PI-LL from preoperative to postoperative, and change at 2-years follow-up. Stepwise regression analysis was performed in order to determine the relationship between PT and the above radiographic parameters. Health-related quality of life (HRQOL) outcomes were also compared between preoperative and postoperative timepoints at 2 years. 103 patients met inclusion for the study. There was improvement in all the radiographic parameters and HRQOLs at 2 years follow-up (p < 0.01). Stepwise regression model showed an inverse relationship between PT and LL change (r = 0.71, p < 0.01). Regionally, an increase in 10 degrees from L4-S1 correlated with a 2.4 degree decrease in PT (p < 0.01), while an increase in 10 degrees from L1-4 resulted in a 1.6 degree decrease in PT (p < 0.01). In the surgical planning for ASD, our data demonstrated significant correlational difference between corrections in the upper (L1-4) and lower (L4-S1) lumbar spine and PT changes. These calculations can be useful in planning sagittal plane corrections for ASD.

Proximal Junction Kyphosis in Adult Scoliosis: Best Postoperative Radiological Predictors-A Retrospective Cohort Study.

Background Proximal junction kyphosis (PJK) is the postsurgical radiographic event seen in the surgical plane after the fusion of a spinal deformity. Unfavorable health outcomes have been reported in symptomatic PJK patients compared to non-PJK patients. Methods The data for adult scoliosis patients who underwent curve correction were extracted from the hospital database. Pelvic and spinal parameters were measured and calculated to compare four predictive formulae for occurrences of PJK. Formula 1. Restoration of hypothetical values of lumbar lordosis (LL) and thoracic kyphosis (TK) according to pelvic incidence (PI). Formula 2. Evaluation of global sagittal alignment. Formula 3. Restoration of the apex of LL to its hypothetical position according to the spine shape. Formula 4. Evaluation of positive-sum and negative-sum of (LL + TK). Results A total number of cases were 52. There were 14 cases of PJK. The incidence of PJK was 26.9%, and the mean age for PJK cases was 63.2 ± 5.2. The excellent predictor for occurrences of PJK was formula 3. Postsurgical sagittal apexes of lumbar lordosis were located in their hypothetical position in 24 cases, and 12.5% of these cases developed PJK. While sagittal apexes were not located in their hypothetical position in 28 patients, PJK occurred in 39.3% of them (P=0.03, OR: 4.53, (95% CI: 1.09–18.9)). The second good predictor for occurrences of PJK was formula 2 (GSA >45° versus GSA <45° OR = 2.5, (95% CI: 0.67–9.38), P=0.17). The other two formulae (1 and 4) were not good predictors for occurrences of PJK. Conclusion Among the four proposed formulae for predicting occurrences of PJK, the position of the sagittal apex of lumbar lordosis is an excellent predictor of the development of PJK, followed by GSA. Hypothetical values of LL and TK, and positive or negative-sum of (LL + TK), are weak predictors for occurrences of PJK.

Correlation Between Different Sagittal Parameters in Patients With Degenerative Kyphosis.

ObjectiveTo explore the relationship between different sagittal parameters and identify the fitting formula of spino-pelvic parameters in patients with degenerative kyphosis (DK).Summary of BackgroundSagittal balance is increasingly recognized as a predictor of clinical outcomes in patients with DK, while the relationship between different sagittal parameters in patients with DK remains unidentified.MethodsA retrospective study with 279 participants was conducted. There were 168 DK patients which were divided into a sagittal balance group (SB:52 cases) and sagittal imbalance (SIB:116 cases). Radiographic measurements included thoracolumbar kyphosis (TLK), lumbar lordosis (LL), thoracic kyphosis (TK), pelvic incidence (PI), and pelvic tilt (PT). The correlations were analyzed between different sagittal parameters.ResultsThere were significant differences between the SB and SIB groups in terms of TLK, LL, PI-LL, PT, SVA, sacral slope (SS), and TK. For patients with DK, the LL was correlated with PT and TK. The linear regression was LL = 22.76−0.28 × PT + 0.62 × TK. In the SB group, TK was the influencing factor for LL and the linear regression analysis showed that LL = 33.57 + 0.33 × TK. While in the SIB group, PT and TK were in synergistic effect with PI-LL, the linear regression analysis showed that LL = 22.76−0.28 × PT + 0.62 × TK.ConclusionFrom the present study, we can see that LL has a significant correlation with PT and TK in patients with DK, while in SB, the LL was only correlated with TK. Therefore, the correction of LL in a different group should be calculated to avoid the incidence of proximal junction kyphosis (PJK).

Time to revisit contraindications of vertebroplasty- A retrospective study of osteoporotic burst fracture operated with vertebroplasty and short segment fixation

BackgroundTo evaluate the safety and efficacy of vertebroplasty with short segmented cement augmented pedicle screws fixation for severe osteoporotic vertebral compression fractures (OVCF) with posterior/anterior wall fracture patients. MethodsA retrospective study of 48 patients of DGOU type-4 (vertebra plana) OVCF with posterior/anterior wall fracture, were treated by vertebroplasty and short segment PMMA cement augmented pedicle screws fixation. Radiological parameters (kyphosis angle and compression ratio) and clinical parameters Visual analogue scale (VAS) and Oswestry disability index (ODI) were analysed. ResultsA significant improvement was noted in VAS (preoperative, 7.90±0.60; final follow-up 2.90±0.54) and ODI (77.10±6.96 to 21.30±6.70), (P<0.05). Neurological improvement was noted in all patients. Kyphosis corrected significantly from preoperative 23.20±5.90 to 5.30±1.40 postoperative with 5% (3.30±2.95) loss of correction at final follow-up. Anterior vertebral height restored significantly from 55.80±11.9% to 87.6±13.1% postoperative with 4.5±4.0% loss at final follow-up. Two cases of cement leakage were found, but both patients were asymptomatic. One patient had implant backout, one had Screw breakage and two had proximal junction kyphosis at final follow-up. No iatrogenic dural or nerve injury. ConclusionsTreatment with vertebroplasty with cement augmented screw fixation and direct decompression is a great option in treating such a complex situation in fragile age with fragile bones because. Vertebroplasty is a viable option for restoring vertebral anterior columns in patients who are considered as contraindications for vertebroplasty, like DGOU-4. It provides anterior support avoiding corpectomy, minimise blood loss, and also the duration of surgery. The addition of short segment fixation gives adequate support with less stress risers at the junctional area.

Front Cover: Resonant Oscillations of Josephson Current in Nb‐Bi2Te2.3Se0.7‐Nb Junctions (Adv. Quantum Technol. 3/2022)

In article number 2100124, Vasily S. Stolyarov and colleagues have observed unexpectedly fine (≈1 Oe) resonant oscillations of the critical Josephson current in the magnetic field in ballistic Nb-Bi2Te2.3Se0.7-Nb proximity junctions at temperatures below 500 mK. The peaked maxima of oscillations are attributed to the resonant transmission of quasiparticles through low-lying Andreev bound states forming at the superconductor-topological insulator interfaces owing to the p-wave component of the induced superconducting order.

Resonant Oscillations of Josephson Current in Nb‐Bi2Te2.3Se0.7‐Nb Junctions

AbstractJosephson proximity junctions and devices employing topological insulators are promising candidates for realizing topological superconductivity and topologically protected quantum circuits. Here, the new type of oscillations of the critical Josephson current in the ballistic Nb‐Bi2Te2.3Se0.7‐Nb junctions subject to the magnetic fields is reported. The oscillations appear below ≈400 mK and have a very unusual sharp‐peaked shape. Their ultra‐short period ≈1 Oe, by orders of magnitude shorter than the expected periodicity due to fluxoid quantization in the device, corresponds to the extremely low energy scale ≈1 eV. It is established that the observed effect is due to the resonant transmission of Andreev quasiparticles via the peculiar energy levels forming near the S‐TI interfaces.

USO DAS UNIDADES HOUNSFIELD NO PLANEJAMENTO DA CIRURGIA ESPINHAL: REVISÃO SISTEMÁTICA E META-ANÁLISE

ABSTRACT Bone mineral density is a crucial factor in the success or failure of osteosynthesis in spine surgery; it shows the onset of osteoporosis and related complications. Its evaluation is verified by dual-energy X-ray absorptiometry (DEXA) and Hounsfield Unit (HU) measurement by CT scan. Objective: Determine the use of HU in surgical planning; compare utility in diagnosing osteoporosis by DEXA; and evaluate sensitivity in predicting complications. Method: A systemic literature review was conducted on PubMed, in line with PRISMA methodology. Including those who justified the use of pre-surgical planning, compared HU/DEXA, and assessed complications. For the statistical analysis, the χ2 was used. Results: 57 articles were identified by selecting nine that met the inclusion criteria. In patients undergoing spinal surgery for fixation and fusion for degenerative pathology, HU measurement showed a prevalence of osteoporosis of 58.5% (sensitivity 93.26%; specificity 90.22%), osteoporosis-associated complications of 24.5%, proper diagnosis of 71.98%, and screw release rate of 82.31%. Conclusions: UH measurement for the diagnosis of osteoporosis turns out to be more sensitive, specific, and predictive compared to DEXA, especially in elderly patients; it represents a useful tool in planning spinal surgery, minimizing the risk of complications such as screw release, fractures, pseudoarthrosis, subsidence of intersomatic devices, and kyphosis of the proximal junction. Level of evidence II; Study Design: Systematic Review and meta-analysis.

Multiple andreev reflections in topological insulator nanoribbons

Superconducting proximity junctions made of topological insulator (TI) nanoribbons (NRs) provide a useful platform for studying topological superconductivity. We report on the fabrication and measurement of Josephson junctions (JJs) using Sb-doped Bi2Se3 NRs in contact with Al electrodes. Aharonov–Bohm and Altshuler–Aronov–Spivak oscillations of the axial magneto-conductance of TI NR were observed, indicating the existence of metallic surface states along the circumference of the TI NR. We observed the supercurrent in the TI NR JJ and subharmonic gap structures of the differential conductance due to multiple Andreev reflections. The interface transparency of the TI NR JJs estimated based on the excess current reaches τ = 0.83, which is among the highest values reported for TI JJs. The temperature dependence of critical current is consistent with the short and ballistic junction model confirming the formation of highly transparent superconducting contacts on the TI NR. Our observations would be useful for exploring topological Josephson effects in TI NRs.

Proximal junctional kyphosis

Proximal Junctional Kyphosis (PJK) is defined as a proximal junctional sagittal Cobb angle of ≥ 10° or a proximal junctional sagittal Cobb angle at least 10° greater than the preoperative measurement. There are several risk factors for the development of PJK identified in literature using univariate analysis. Majority of these risk factors are no longer significant after multivariate analysis. Pointing to the fact that proximal junction kyphosis arises from a multifactorial etiology, further studies with long term follow-up are needed for patients with PJK to elicit risk factors in terms of patients, spinopelvic parameters, and surgical techniques.

Influence of the femoral artery-graft junction patient-specific geometry on blood flow structure and wall shear stress

The paper presents a comparative numerical study of pulsatory blood flow in five patient-specific models of femoral-popliteal artery anastomosis. Three-dimensional geometric models of a proximal junction of the common femoral artery/graft were constructed on the bases of CT angiography. The influence of junction geometry on the blood flow and wall shear stress is analyzed. The ratio of the measured CFA and graft diameters and the junction angle are considered as the major geometrical parameters. Numerically calculated velocity fields are analyzed, and stagnant zones in the anastomoses flow are identified. Time-averaged distributions of wall shear stress and oscillatory shear index obtained for five patient-specific model are compared.

Failure patterns and related risk factors of sagittal reconstruction following pedicle subtraction osteotomy in patients with ankylosing spondylitis and thoracolumbar kyphosis

The aim of this study was to analyze the specific patterns and risk factors of sagittal reconstruction failure in ankylosing spondylitis (AS)-related thoracolumbar kyphosis after pedicle subtraction osteotomy (PSO). A retrospective study was performed in patients with AS and thoracolumbar kyphosis after lumbar PSO with a minimum follow-up of 2 years. Patients were classified as having successful realignment (group A), inadequate correction immediately postoperatively (group B), and sagittal decompensation during follow-up (group C) according to the immediately postoperative and latest follow-up sagittal vertical axis (SVA). Radiographic parameters and clinical outcomes were collected. Pelvic tilt (PT) was used to assess the magnitude of pelvic backward rotation. Hip structural damage and ossification of the anterior longitudinal ligament (ALL) at the proximal junction, PSO level, and distal junction were also evaluated on radiographs. Overall, 109 patients with a mean age of 35.3 years were included. Patients in both group B (n = 16) and group C (n = 13) were older than those in group A (n = 80) (mean ages 43.6 vs 32.9 years, p < 0.011; and 39.2 vs 32.9 years, p = 0.018; respectively). Age (OR 1.102, p = 0.011), and preoperative PT (OR 1.171, p = 0.041) and SVA (OR 1.041, p = 0.016) were identified as independent risk factors of inadequate correction. Additionally, a higher distribution of patients with adequate ALL ossification at the PSO level was found in group B than in group A (37.5% vs 22.5%, p = 0.003). Age (OR 1.101, p = 0.011) and preoperative SVA (OR 1.013, p = 0.020) were identified as independent risk factors of sagittal decompensation. Furthermore, compared with group A, group C showed a higher distribution of patients with severe hip structural damage (15.4% vs 0, p = 0.018) and higher incidences of rod fracture (RF) (38.5% vs 8.8%, p = 0.011) and pseudarthrosis (15.4% vs 0, p = 0.018). Additionally, the incidence of RF (19.6% vs 6.9%, p = 0.045) and changes in the proximal junctional angle (0.5° vs 2.2°, p = 0.027) and the distal junctional angle (0.3° vs 2.2°, p = 0.019) were lower during follow-up in patients with adequate ALL ossification than in those without adequate ossification. Sagittal reconstruction failure in patients with AS could be attributed to inadequate correction immediately after surgery (14.7%) and sagittal decompensation during follow-up (11.9%). Adequate ALL ossification was a risk factor of inadequate correction. However, adequate ALL ossification could decrease the development of RF and relieve the junctional kyphotic change during follow-up. Older age and greater baseline SVA were independent risk factors for both inadequate correction and sagittal decompensation.

Incidence of Chronic Periscapular Pain After Adult Thoracolumbar Deformity Correction and Impact on Outcomes.

ObjectiveExtension of the posterior upper-most instrumented vertebra (UIV) into the upper thoracic (UT) spine allows for greater deformity correction and reduced incidence of proximal junction kyphosis (PJK) in adult spinal deformity (ASD) patients. However, it may be associated with chronic postoperative scapular pain (POSP). The goal of this study was to assess the relationship between UT UIV and persistent POSP, describe the pain, and assess its impact on patient disability. MethodsASD patients who underwent multilevel posterior fusion were retrospectively identified then administered a survey regarding scapular pain and the Oswestry Disability Index (ODI), by telephone. Univariate and multivariate analysis were utilized. ResultsA total of 74 ASD patients were included in the study: 37 patients with chronic POSP and 37 without scapular pain. The mean age was 70.5 years, and 63.9% were women. There were no significant differences in clinical characteristics, including mechanical complications (PJK, pseudarthrosis, and rod fracture) or reoperation between groups. Patients with persistent POSP were more likely to have a UT than a lower thoracic UIV (p=0.018). UT UIV was independently associated with chronic POSP on multivariate analysis (p=0.022). ODI score was significantly higher in patients with scapular pain (p=0.001). Chronic POSP (p=0.001) and prior spine surgery (p=0.037) were independently associated with ODI on multivariate analysis. ConclusionA UT UIV is independently associated with increased odds of chronic POSP, and this pain is associated with significant increases in patient disability. It is a significant clinical problem despite solid radiographic fusion and the absence of PJK.

Biomechanical Evaluation of Semi-rigid Junctional Fixation Using a Novel Cable Anchor System to Prevent Proximal Junctional Failure in Adult Spinal Deformity Surgery.

A porcine cadaveric biomechanical study. To biomechanically evaluate a novel Cable Anchor System as semi-rigid junctional fixation technique for the prevention of proximal junctional failure after adult spinal deformity surgery and to make a comparison to alternative promising prophylactic techniques. The abrupt change of stiffness at the proximal end of a pedicle screw construct is a major risk factor for the development of proximal junctional failure after adult spinal deformity surgery. A number of techniques that aim to provide a gradual transition zone in range of motion (ROM) at the proximal junction have previously been studied. In this study, the design of a novel Cable Anchor System, which comprises a polyethylene cable for rod fixation, is assessed. Ten T6-T13 porcine spine segments were subjected to cyclic 4 Nm pure-moment loading. The following conditions were tested: uninstrumented, 3 level pedicle screw fixation (PSF), and PSF with supplementary Cable Anchors applied proximally at 1-level (Anchor1) or 2-levels (Anchor2), transverse process hooks (TPH), and 2-level sublaminar tapes (Tape2). The normalized segmental range of motion in the junctional zone was compared using one-way analysis of variance and linear regression. Statistical comparison at the level proximal to PSF showed significantly lower ROMs for all techniques compared to PSF fixation alone in all movement directions. Linear regression demonstrated a higher linearity for Anchor1 (0.820) and Anchor2 (0.923) in the junctional zone in comparison to PSF (1-level: 0.529 and 2-level: 0.421). This linearity was similar to the compared techniques (TPH and Tape2). The Cable Anchor System presented in this study demonstrated a gradual ROM transition zone at the proximal end of a rigid pedicle screw construct similar to TPH and 2-level sublaminar tape semi-rigid junctional fixation constructs, while providing the benefit of preserving the posterior ligament complex.Level of Evidence: 5.

Anatomical retraction of the semitendinosus muscle following harvest of the distal semitendinosus tendon for ACL reconstruction.

Retraction of semitendinosus muscle has been reported after reconstruction of the anterior cruciate ligament with semitendinosus/gracilis-graft. However, very little data exist on the natural variation in side-to-side length symmetry. The purpose of this study was to investigate the side-to-side asymmetry of semitendinosus muscle length in individuals with ACL reconstruction (ACLR) using the semitendinosus/gracilis-graft compared to a group of healthy control subjects to establish the level of retraction that can confidently be ascribed the surgery. Eleven subjects aged 30 (19-39) years, with previous unilateral ACLR with the combined semitendinosus/gracilis tendon graft were recruited. Average follow-up was 6.8years (0.3-13.0) after reconstruction. Ten healthy subjects aged 30years (23-36) with no previous knee surgery served as controls. Bilateral magnetic resonance imaging (MRI) scans were obtained of the thigh from 60mm below the knee joint and 700mm proximal to this point with a slice thickness of 5mm with 5mm inter-slice distance. Semitendinosus length was measured on both legs between the distal and proximal musculotendinous junction of the semitendinosus. Length difference between legs was calculated for all participants. Percentage of shortening was expressed relative to the healthy leg. Subjects who had undergone ACLR had on average 81mm (25%) shortening of the semitendinosus on the reconstructed leg compared to the non-reconstructed side. The healthy subjects all had less than 10mm difference between legs (< 3%). The side-to-side difference was significantly different between the reconstructed patients and the healthy subjects (p < 0.001). This study indicates that retraction larger than 10mm is a consequence of the tendon harvest and not natural variation. It also supports that persistent retraction of the semitendinosus muscle occurs following harvest of the semitendinosus tendon for ACL graft. Level IV.

ACL Repair of Femoral Osseous Avulsion in a 13-Year-Old Using Suture Pullout Technique

Background: The incidence of pediatric anterior cruciate ligament (ACL) injuries has been increasing over the past 20 years, with the majority comprised of mid substance tears or tibial eminence avulsion fractures. Pediatric femoral sided osseous avulsion is rarely reported in orthopedic literature and specific surgical indications and contraindications, as well as recommended surgical techniques and postoperative rehabilitation protocols, are underdefined. Indications: The surgical indications for femoral-sided repair of ACL osseous avulsion includes a displaced osseous fragment and ligamentous laxity on physical examination. There was no concomitant midsubstance tear necessitating reconstruction. Technique Description: Two sutures piercing the proximal ligamentous bony junction of the ACL were fed through 2.4-mm transphyseal tunnels and secured with cortical button and backup fixation with a 3.9-mm swivel lock anchor in the proximal lateral femoral metaphysis. The patient was immobilized in a hinged-knee brace locked in extension during ambulation and limited to 90 degrees of flexion while nonweightbearing for the first 6 weeks after surgery. Standard ACL protocol was followed thereafter. Results: Successful fixation and restoration of ligamentous tension and impingement-free range of motion were achieved without complication. There was stable Lachman, negative pivot shift, 125 degrees of knee flexion, and evidence of early healing at 3 months follow-up. Discussion/Conclusion: This report demonstrates successful reduction and fixation of proximal bony avulsion of the ACL. Although this patient exhibits stable physical examination and undisturbed growth at early follow-up, more research is required to establish treatment and rehabilitation guidelines for this rare injury.

Lower Limb Reconstruction Using Tibial Strut Autograft after Resection of Primary Malignant Bone Tumors in Skeletally Immature Patients.

Reconstruction of large bone defects in skeletally immature patients remains a surgical challenge. We report the long-term clinical outcomes of a novel surgical technique for lower limb reconstruction using the tibia as a strut autograft following resection of primary malignant bone tumors in skeletally immature patients. We retrospectively reviewed the medical records of six patients diagnosed with lower limb primary bone sarcoma. All patients underwent tumor resection and reconstruction using tibial strut autograft. The radiological and clinical outcomes including complications at the recipient and donor sites were assessed. The mean age at presentation was ten years (range 6-15 years). Two cases had osteosarcoma and four had Ewing sarcoma. The mean length of the resected tumor and tibial autografts were 20.83 and 19.33 cm respectively. Union at both ends was achieved in five grafts while one graft achieved union only at the distal end. The mean time for union of the proximal and distal junctions was 4 and 8.8 months respectively. The mean follow-up period was 8.4 years (range 14 months-20 years). One patient developed a foot drop, and three patients underwent subsequent joint arthrodesis (2 knees and 1 ankle). The mean musculoskeletal tumor society functional score was 80.8%. Two patients had clinically significant leg-length discrepancy that needs further lengthening procedure. Four patients survived with no evidence of disease and two patients died due to their primary oncologic disease. All donor sites regenerated, with the earliest signs of new bone formation at (2-4) weeks post-operatively. Reconstruction using non-vascularized‎ tibia strut autograft after resection of primary malignant lower limb bone tumors can be a viable alternative method for reconstructing large bone defects in the immature skeleton.

MYOC Gene Sequencing Analysis in Primary Open-Angle Glaucoma Patients from the Centre Region of Portugal.

Primary open-angle glaucoma is the most frequent subtype of glaucoma. Relatives of primary open-angle glaucoma patients have an increased risk of developing the disease, suggesting a genetic predisposition to the disease. MYOC was the first primary open-angle glaucoma-causing gene identified. This study aimed to identify sequence variations in the MYOC gene that may be responsible for the phenotype in a group of primary open-angle glaucoma patients from the Centre Region of Portugal. The three coding exons and the proximal splicing junctions of the MYOC gene were studied using a PCR sequencingapproach in a group of 99 primary open-angle glaucoma patients. The sequencing analysis enabled the identification of 20 variants, including four in the promoter region, seven in the introns and nine in exons one and three, of which four were missense variants. Initially, all four missense sequence variations identified were considered candidates to glaucoma causing disease mutations. However, after literature review, only variant c.1334C>T (Ala445Val) remained as likely responsible for mild late-onset normal tension glaucoma. This is the first study performed in a group of primary open-angle glaucoma patients from the Centre Region of Portugal,contributing to the identification of one genetic variant in the MYOC gene and reinforcing the hypothesis that normal tension glaucomacould be also due to MYOC gene mutations.

Novel Distributed Loading Technique Using Multimaterial, Long-Segment Spinal Constructs to Prevent Proximal Junctional Pathology in Adult Spinal Deformity Correction—Operative Technique and Radiographic Findings

Proximal junctional kyphosis (PJK) and proximal junction failure are common and costly complications after long-segment adult spinal deformity (ASD) correction. Although much research has focused on the concept of "softening the landing" to prevent proximal junction pathologies, long-segment constructs largely deviate from the force-deformation curve of the physiologic spine. Our novel distributed loading technique for ASD correction is described using multimaterial, long-segment constructs to create a biomechanically sound, yet physiologic, decremental stiffness toward the rostral end. Operative steps detail the custom-designed constructs of dual-headed pedicle screws and varied rod diameters and materials (cobalt chromium or titanium) for an initial 20 patients (mean 66.6 ± 4.8 years). Standing scoliosis films were obtained preoperatively and at regular intervals postoperatively to assess for PJK. No patient had evidence of PJK or proximal junction failure at latest radiographic follow-up (mean 17.9 months, range 13-25 months). Radiographic findings for sagittal vertical axis averaged 11.2 ± 5.6 cm preoperatively and 3.6 ± 2.3 cm postoperatively. Compared with preoperative parameters, postoperative reductions in pelvic incidence-lumbar lordosis mismatch averaged 28.7 ± 12.9 degrees, and sagittal vertical axis averaged 7.6 ± 5.2 cm while PJA was essentially unchanged. Preliminary results suggest that the distributed loading technique is promising for prevention of PJK with stiffness gradients that mimic the force-deformation curve of the physiologic posterior tension band. Our technique may optimize the degree of stress at the proximal junction without overwhelming the anterior column bony while remodeling and mature arthrodesis takes place.

Credibility assessment of patient-specific biomechanical models to investigate proximal junctional failure in clinical cases with adult spine deformity using ASME V&V40 standard

Computational models are increasingly used to assess spine biomechanics and support surgical planning. However, varying levels of model verification and validation, along with characterization of uncertainty effects limit the level of confidence in their predictive potential. The objective was to assess the credibility of an adult spine deformity instrumentation model for proximal junction failure (PJF) analysis using the ASME V&V40:2018 framework. To assess model applicability, the surgery, erected posture, and flexion movement of actual clinical cases were simulated. The loads corresponding to PJF indicators for a group of asymptomatic patients and a group of PJF patients were compared. Model consistency was demonstrated by finding PJF indicators significantly higher for the simulated PJF vs. asymptomatic patients. A detailed sensitivity analysis and uncertainty quantification were performed to further establish the model credibility.