Variability of the femoral mechanical-anatomical axis angle and its implications in primary and revision total knee arthroplasty.

Aims: Distal femoral resection in conventional total knee arthroplasty (TKA) utilizes an intramedullary guide to determine coronal alignment, commonly planned for 5° of valgus. However, a standard 5° resection angle may contribute to malalignment in patients with variability in the femoral anatomical and mechanical axis angle. The purpose of the study was to leverage deep learning (DL) to measure the femoral mechanical-anatomical axis angle (FMAA) in a heterogeneous cohort. Methods: Patients with full-limb radiographs from the Osteoarthritis Initiative were included. A DL workflow was created to measure the FMAA and validated against human measurements. To reflect potential intramedullary guide placement during manual TKA, two different FMAAs were calculated either using a line approximating the entire diaphyseal shaft, and a line connecting the apex of the femoral intercondylar sulcus to the centre of the diaphysis. The proportion of FMAAs outside a range of 5.0° (SD 2.0°) was calculated for both definitions, and FMAA was compared using univariate analyses across sex, BMI, knee alignment, and femur length. Results: The algorithm measured 1,078 radiographs at a rate of 12.6 s/image (2,156 unique measurements in 3.8 hours). There was no significant difference or bias between reader and algorithm measurements for the FMAA (p = 0.130 to 0.563). The FMAA was 6.3° (SD 1.0°; 25% outside range of 5.0° (SD 2.0°)) using definition one and 4.6° (SD 1.3°; 13% outside range of 5.0° (SD 2.0°)) using definition two. Differences between males and females were observed using definition two (males more valgus; p < 0.001). Conclusion: We developed a rapid and accurate DL tool to quantify the FMAA. Considerable variation with different measurement approaches for the FMAA supports that patient-specific anatomy and surgeon-dependent technique must be accounted for when correcting for the FMAA using an intramedullary guide. The angle between the mechanical and anatomical axes of the femur fell outside the range of 5.0° (SD 2.0°) for nearly a quarter of patients.

Factors that Influence Acquisition of Lower Extremity Braces in the Pediatric Orthopaedic Population.

BACKGROUND: Lower extremity brace-wear compliance has been studied in pediatrics, but failure to acquire a prescribed brace has not been included. The purpose of this study was to evaluate brace acquisition as a component of brace-wear compliance. METHODS: Records of patients (0 to 21 y) prescribed lower extremity braces from 2017 to 2019 were reviewed. Diagnoses included cerebral palsy, spina bifida, short Achilles tendon, clubfoot, and other. Brace type was categorized as clubfoot foot abduction orthosis, ankle-foot orthosis, knee, hip, or custom/other braces. Brace prescription and acquisition dates were recorded. Insurance was classified as government, private, or uninsured. Patient demographics included age, sex, race, and calculated area deprivation index. RESULTS: Of the 1176 prescribed lower extremity braces, 1094 (93%) were acquired while 82 (7%) were not. The odds ratios (OR) of failure to acquire a prescribed brace in Black and Hispanic patients were 1.64 and 2.71 times that in White patients, respectively (95% confidence interval: 1.01-2.71, P=0.045; 1.23-5.6, P=0.015); in patients without insurance, the OR was 8.48 times that in privately insured patients (95% confidence interval: 1.93-31.1, P=0.007). The ORs of failure to acquire were 2.12 (P=0.003) in patients 4 years or more versus 0 to 3 years, 4.17 (P<0.0001) in cerebral palsy versus clubfoot, and 4.12 (P=0.01) in short Achilles tendon versus clubfoot. There was no significant association between sex or area deprivation index and failure of brace acquisition. CONCLUSIONS: In our cohort, 7% of prescribed braces were not acquired. Black or Hispanic race, lack of insurance, and older age were associated with failure to acquire prescribed braces. Braces prescribed for clubfoot were acquired more often than for cerebral palsy or short Achilles tendon. Brace-wear compliance is an established factor in treatment success and recurrence. This study identified risk factors for failed brace acquisition, a critical step for improving compliance. These results may help effect changes in the current system that may lead to more compliance with brace wear. LEVEL OF EVIDENCE: Level III-retrospective cohort study.

Mechanical Testing of a Novel Fastening Device to Improve Scoliosis Bracing Biomechanics for Treating Adolescent Idiopathic Scoliosis.

Velcro fastening straps are commonly used to secure a scoliosis brace around the upper body and apply corrective forces to the spine. However, strap loosening and tension loss have been reported that reduce spinal correction and treatment efficacy. A novel fastening device, or controlled tension unit (CTU), was designed to overcome these limitations. A scoliosis analog model (SAM) was used to biomechanically compare the CTU fasteners and posterior Velcro straps on a conventional brace (CB) as well as on a modified brace (MB) that included a dynamic cantilever apical pad section. Brace configurations tested were (1) CB with posterior Velcro straps, (2) CB with posterior CTU fasteners, (3) MB with posterior Velcro straps, and (4) MB with posterior CTU fasteners. MB configurations were tested with 0 N, 35.6 N, and 71.2 N CTU fasteners applied across the apical pad flap. Three-dimensional forces and moments were measured at both ends of the SAM. The CTU fasteners provided the same corrective spinal loads as Velcro straps when tensioned to the same level on the CB configuration and can be used as an alternative fastening system. Dynamically loading the apical flap increased the distractive forces applied to the spine without affecting tension in the fastening straps.

A mechanical analog thoracolumbar spine model for the evaluation of scoliosis bracing technology.

INTRODUCTION: Thoracolumbar braces are used to treat Adolescent Idiopathic Scoliosis. The objective of this study was to design and validate a mechanical analog model of the spine to simulate a thoracolumbar, single-curve, scoliotic deformity in order to quantify brace structural properties and corrective force response on the spine. METHODS: The Scoliosis Analog Model used a linkage-based system to replicate 3D kinematics of spinal correction observed in the clinic. The Scoliosis Analog Model is used with a robotic testing platform and programmed to simulate Cobb angle and axial rotation correction while equipped with a brace. The 3D force and moment responses generated by the brace in reaction to the simulated deformity were measured by six-axis load cells. RESULTS: Validation of the model's force transmission showed less than 6% loss in the force analysis due to assembly friction. During simulation of 10° Cobb angle and 5° axial rotation correction, the brace applied 101 N upwards and 67 N inwards to the apical connector of the model. Brace stiffness properties were 0.5-0.6 N/° (anteroposterior), 0.5-2.3 N/° (mediolateral), 23.3-26.5 N/° (superoinferior), and 0.6 Nm/° (axial rotational). CONCLUSIONS: The Scoliosis Analog Model was developed to provide first time measures of the multidirectional forces applied to the spine by a thoracolumbar brace. This test assembly could be used as a future design and testing tool for scoliosis brace technology.

A comparison of biological coatings for the promotion of corneal epithelialization of synthetic surface in vivo.

PURPOSE: To investigate the effect of a range of biological coatings on corneal epithelialization of a synthetic polymer surface in vivo. METHODS: Eight diverse biological factors (collagen I, collagen III, collagen IV, laminin, fibronectin, endothelial extracellular matrix, hyaluronic acid, and chondroitin sulfate) were coated individually onto the surface of polycarbonate membranes with a pore size of 0.1 micro m. The coated membranes were implanted on the anterior cornea of adult cats and were clinically assessed for rapidity and extent of and persistence of epithelial overgrowth. The membranes with persistent epithelial attachment were examined histologically by immunohistochemistry and routine light and electron microscopy. RESULTS: Collagen I, collagen IV, and laminin consistently enhanced migration and attachment of corneal epithelial cells in vivo. Multiple-layered epithelium over the collagen I-, collagen IV-, and laminin-coated membranes was demonstrated histologically. The collagen I-coated membranes performed best, in that they showed greater stratification and differentiation of the epithelium. Formation of basement membrane and adhesion complexes over the collagen I-coated membranes was detected by immunohistochemistry and electron microscopy up to 9 weeks after implantation. Membranes coated by fibronectin, endothelial extracellular matrix, hyaluronic acid, and chondroitin sulfate did not support persistent epithelial overgrowth. Compromised biostability of these coatings was mostly likely associated with postsurgical reactions of the host corneal tissue. CONCLUSIONS: A biologically modified polymer can support migration and adhesion of corneal epithelial cells in vivo. The collagen I-modified surface exhibited the most promising performance, both clinically and histologically.