Cadaveric biomechanical studies of ADDISC total lumbar disc prosthesis.

BACKGROUND: Most total disc replacements provide excessive mobility and not reproduce spinal kinematics, inducing zygapophyseal joint arthritic changes and chronic back pain. In cadaveric lumbosacral spines, we studied if a new lumbar disc prosthesis kinematics mimics the intact intervertebral disc. METHODS: In eight cold preserved cadaveric lumbosacral spines, we registered the movement ranges in flexion, extension, right and left lateral bending, and rotation in the intact status, post-discectomy, and after our prosthesis implantation, comparing them for each specimen. FINDINGS: Comparing the intact lumbosacral spine with the L4-L5 prosthesis implanted specimens, we saw statistically significant differences in lateral bending and right rotation but not in the full range of rotation. Analyzing segments, we also noticed statistically significant differences at L4-L5 in flexion-extension and rotation. On the other hand, the L4-L5 discectomy, compared to the baseline spine condition, showed a statistically significant mobility increase in flexion, extension, lateral bending, and axial rotation, with an abnormal instantaneous center of rotation, which destabilizes the segment partly due to anterior annulus surgical removal. Disc prosthesis implantation reversed these changes in instantaneous center of rotation, but the prosthesis failed to restore the initial range of motion due to the destabilization of the ligaments in the operated disc. INTERPRETATION: The ADDISC total disc replacement reproduces the intact disc kinematics and Instantaneous Center of Rotation, but the prosthesis fails to restore the initial range of motion due to ligament destabilization. More studies will be necessary to define a technique that restores the damaged ligaments when implanting the prosthesis.

Bionate® nucleus disc replacement: bench testing comparing two different designs.

BACKGROUND: Intervertebral disc nucleus degeneration initiates a degenerative cascade and can induce chronic low back pain. Nucleus replacement aims to replace the nucleus while the annulus is still intact. Over time, several designs have been introduced, but the definitive solution continues to be elusive. Therefore, we aimed to create a new nucleus replacement that replicates intact intervertebral disc biomechanics, and thus has the potential for clinical applications. MATERIALS AND METHODS: Two implants with an outer ring and one (D2) with an additional midline strut were compared. Static and fatigue tests were performed with an INSTRON 8874 following the American Society for Testing and Materials F2267-04, F2346-05, 2077-03, D2990-01, and WK4863. Implant stiffness was analyzed at 0-300 N, 500-2000 N, and 2000-6000 N and implant compression at 300 N, 1000 N, 2000 N, and 6000 N. Wear tests were performed following ISO 18192-1:2008 and 18192-2:2010. GNU Octave software was used to calculate movement angles and parameters. The statistical analysis package R was used with the Deducer user interface. Statistically significant differences between the two designs were analyzed with ANOVA, followed by a post hoc analysis. RESULTS: D1 had better behavior in unconfined compression tests, while D2 showed a "jump." D2 deformed 1 mm more than D1. Sterilized implants were more rigid and deformed less. Both designs showed similar behavior under confined compression and when adding shear. A silicone annulus minimized differences between the designs. Wear under compression fatigue was negligible for D1 but permanent for D2. D1 suffered permanent height deformation but kept its width. D2 suffered less height loss than D1 but underwent a permanent width deformation. Both designs showed excellent responses to compression fatigue with no breaks, cracks, or delamination. At 10 million cycles, D2 showed 3-times higher wear than D1. D1 had better and more homogeneous behavior, and its wear was relatively low. It showed good mechanical endurance under dynamic loading conditions, with excellent response to axial compression fatigue loading without functional failure after long-term testing. CONCLUSION: D1 performed better than D2. Further studies in cadaveric specimens, and eventually in a clinical setting, are recommended. Level of evidence 2c.

Barbed Dental Ti6Al4V Alloy Screw: Design and Bench Testing.

BACKGROUND CONTEXT: Dental implants are designed to replace a missing tooth. Implant stability is vital to achieving osseointegration and successful implantation. Although there are many implants available on the market, there is room for improvement. PURPOSE: We describe a new dental implant with improved primary stability features. STUDY DESIGN: Lab bench test studies. METHODS: We evaluated the new implant using static and flexion-compression fatigue tests with compression loads, 35 Ncm tightening torque, displacement control, 0.01 mm/s actuator movement speed, and 9-10 Hz load application frequency, obtaining a cyclic load diagram. We applied variable cyclic loadings of predetermined amplitude and recorded the number of cycles until failure. The test ended with implant failure (breakage or permanent deformation) or reaching five million cycles for each load. RESULTS: Mean stiffness was 1151.13 ± 133.62 SD N/mm, mean elastic limit force 463.94 ± 75.03 SD N, and displacement 0.52 ± 0.04 SD mm, at failure force 663.21 ± 54.23 SD N and displacement 1.56 ± 0.18 SD mm, fatigue load limit 132.6 ± 10.4 N, and maximum bending moment 729.3 ± 69.43 mm/N. CONCLUSIONS: The implant fatigue limit is satisfactory for incisor and canine teeth and between the values for premolars and molars for healthy patients. The system exceeds five million cycles when subjected to a 132.60 N load, ensuring long-lasting life against loads below the fatigue limit.

ADDISC lumbar disc prosthesis: Analytical and FEA testing of novel implants.

The intact intervertebral disc is a six-freedom degree elastic deformation structure with shock absorption. "Ball-and-socket" TDR do not reproduce these properties inducing zygapophyseal joint overload. Elastomeric TDRs reproduce better normal disc kinematics, but repeated core deformation causes its degeneration. We aimed to create a new TDR (ADDISC) reproducing healthy disc features. We designed TDR, analyzed (Finite Element Analysis), and measured every 500,000 cycles for 10 million cycles of the flexion-extension, lateral bending, and axial rotation cyclic compression bench-testing. In the inlay case, we weighted it and measured its deformation. ADDISC has two semi-spherical articular surfaces, one rotation centre for flexion, another for extension, the third for lateral bending, and a polycarbonate urethane inlay providing shock absorption. The first contact is between PCU and metal surfaces. There is no metal-metal contact up to 2000 N, and CoCr28Mo6 absorbs the load. After 10 million cycles at 1.2-2.0 kN loads, wear 140.96 mg (35.50 mm3), but no implant failures. Our TDR has a physiological motion range due to its articular surfaces' shape and the PCU inlay bumpers, minimizing the facet joint overload. ADDISC mimics healthy disc biomechanics and Instantaneous Rotation Center, absorbs shock, reduces wear, and has excellent long-term endurance.

Bionate Lumbar Disc Nucleus Prosthesis: Biomechanical Studies in Cadaveric Human Spines.

DESIGN: cadaveric spine nucleus replacement study. OBJECTIVE: determining Bionate 80A nucleus replacement biomechanics in cadaveric spines. METHODS: in cold preserved spines, with ligaments and discs intact, and no muscles, L3-L4, L4-L5, and L5-S1 nucleus implantation was done. Differences between customized and overdimensioned implants were compared. Flexion, extension, lateral bending, and torsion were measured in the intact spine, nucleotomy, and nucleus implantation specimens. Increasing load or bending moment was applied four times at 2, 4, 6, and 8 Nm, twice in increasing mode and twice in decreasing mode. Spine motion was recorded using stereophotogrammetry. Expulsion tests: cyclic compression of 50-550 N for 50,000 cycles, increasing the load until there was extreme flexion, implant extrusion, or anatomical structure collapse. Subsidence tests were done by increasing the compression to 6000 N load. RESULTS: nucleotomy increased the disc mobility, which remained unchanged for the adjacent upper level but increased for the lower adjacent one, particularly in lateral bending and torsion. Nucleus implantation, compared to nucleotomy, reduced disc mobility except in flexion-extension and torsion, but intact mobility was no longer recovered, with no effect on upper or lower adjacent segments. The overdimensioned implant, compared to the customized implant, provided equal or sometimes higher mobility. Lamina, facet joint, and annulus removal during nucleotomy caused more damaged than that restored by nucleus implantation. No implant extrusion was observed under compression loads of 925-1068 N as anatomical structures collapsed before. No subsidence or vertebral body fractures were observed under compression loads of 6697.8-6812.3 N. CONCLUSIONS: nucleotomized disc and L1-S1 mobility increased moderately after cadaveric spine nucleus implantation compared to the intact status, partly due to operative anatomical damage. Our implant had shallow expulsion and subsidence risks.

Bionate Biocompatibility: In Vivo Study in Rabbits.

Response to foreign materials includes local tissue reaction, osteolysis, implant loosening, and migration to lymph nodes and organs. Bionate 80A human explants show minor wear and slight local tissue reaction, but we do not know the response at the spinal cord, nerve roots, lymph nodes, or distant organs. This study aims to figure out reactions against Bionate 80A when implanted at the spinal epidural space of 24 20-week-old New Zealand white rabbits. In one group of 12 rabbits, we implanted Bionate 80A on the spinal epidural space, and another group of 12 rabbits was used as the control group. We studied tissues, organs, and tissue damage markers on blood biochemistry, urine tests, and necropsy. The animals' clinical parameters and weight showed no statistically significant differences. At 3 months, the basophils increased slightly in the implant group, platelets decreased in all, and at 6 months, implanted animals showed slight eosinophilia, but none of these changes was statistically significant. External, organ, and spinal tissue examination showed neither toxic reaction, inflammatory changes, or noticeable differences between groups or survival periods. Under microscopic examination, the Bionate 80A particles induced a chronic granulomatous response always outside the dura mater, with giant multinucleated cells holding phagocytized particles and no particle migration to lymph nodes or organs. Thus, it was concluded that Bionate particles, when implanted in the rabbit lumbar epidural space, do not generate a significant reaction limited to the surrounding soft tissues with giant multinucleated cells. In addition, the particles did not cross the dura mater or migrate to lymph nodes or organs.

Finite Element Analysis of a Bionate Ring-Shaped Customized Lumbar Disc Nucleus Prosthesis.

Study design: Biomechanical study of a nucleus replacement with a finite element model. Objective: To validate a Bionate 80A ring-shaped nucleus replacement. Methods: The ANSYS lumbar spine model made from lumbar spine X-rays and magnetic resonance images obtained from cadaveric spine specimens were used. All materials were assumed homogeneous, isotropic, and linearly elastic. We studied three options: intact spine, nucleotomy, and nucleus implant. Two loading conditions were evaluated at L3-L4, L4-L5, and L5-S1 discs: a 1000 N axial compression load and this load after the addition of 8 Nm flexion moment in the sagittal plane plus 8 Nm axial rotation torque. Results: Maximum nucleus implant axial compression stresses in the range of 16-34 MPa and tensile stress in the range of 5-16 MPa, below Bionate 80A resistance were obtained. Therefore, there is little risk of permanent implant deformation or severe damage under normal loading conditions. Nucleotomy increased segment mobility, zygapophyseal joint and end plate pressures, and annulus stresses and strains. All these parameters were restored satisfactorily by nucleus replacement but never reached the intact status. In addition, annulus stresses and strains were lower with the nucleus implant than in the intact spine under axial compression and higher under complex loading conditions. Conclusions: Under normal loading conditions, there is a negligible risk of nucleus replacement, permanent deformation or severe damage. Nucleotomy increased segmental mobility, zygapophyseal joint pressures, and annulus stresses and strains. Nucleus replacement restored segmental mobility and zygapophyseal joint pressures close to the intact spine. End plate pressures were similar for the intact and nucleus implant conditions under both loading modes. Manufacturing customized nucleus implants is considered feasible, as satisfactory biomechanical performance is confirmed.

A new universal 3D-printable device to prevent excessive drilling in orthopedic surgery.

INTRODUCTION: The occurrence of vascular injury during drilling is a rare but severe complication. Unfortunately, drilling protection systems are not available in all hospitals. Thanks to the development of 3D printing in recent years, sharing devices and materials to solve surgical problems has become easy and inexpensive. The objective of our work is to evaluate a universal, freely accessible, 3D-printable drilling protection device. MATERIALS AND METHODS: A prospective, randomized, and triple-blind evaluation of excess drilling was evaluated in expert surgeons and resident surgeons without the use of the protection device. Subsequently, excess drilling was assessed using the device in both groups. The differences in drilling lengths between both groups with and without the device were analyzed to establish the reduction of excess drilling in both groups. RESULTS: The drilling in the expert surgeon without device group was 3.03 mm (SD 1.69 95% CI 2.40-3.66 p value = 9.89e-11), while the resident surgeon with device group performed excess drilling of 1.76 mm (SD 0.89 CI 95% 1.43-2.10). Results showed better results in the resident surgeon with device group than in the expert surgeons with device group (p value Ë‚ 0.01). The device improved drilling in both resident surgeons (5.77 mm) and expert surgeons (1.17 mm). CONCLUSIONS: The device improves drilling in both expert surgeons and resident surgeons, showing greater benefits in the latter. The device is printable with any 3D printer, making it universally accessible, inexpensive, and effective, allowing expert surgeons to improve precision in high-risk situations and resident surgeons to improve their technique without increasing risk to the patient.

Osteomyelitis, Venous Thrombosis, and Septic Emboli in a Pediatric Patient: A Case Report.

New virulence factors, such as the Panton-Valentine leukocidin (PVL), are appearing during Staphylococcus aureus infections occurring in the pediatric population. Such factors increase the aggressiveness and risk of dissemination of the bacteria, causing infections to be life-threatening. An early diagnosis is thus especially important. We present a case of osteomyelitis, venous thrombosis, and septic emboli occurring in a pediatric patient that should trigger suspicion of a PVL-positive strain. A multidisciplinary approach is necessary to enable rapid diagnosis and early treatment, which is essential for successful management of these infections. Management is based on broad-spectrum antibiotics, in combination with aggressive surgical treatment and antithrombotic therapy. In patients infected with S. aureus whose condition worsens quickly, PVL gene sequencing should be considered.

ICR in human cadaveric specimens: An essential parameter to consider in a new lumbar disc prosthesis design.

STUDY DESIGN: Biomechanical study in cadaveric specimens. BACKGROUND: The commercially available lumbar disc prostheses do not reproduce the intact disc's Instantaneous centre of Rotation (ICR), thus inducing an overload on adjacent anatomical structures, promoting secondary degeneration. AIM: To examine biomechanical testing of cadaveric lumbar spine specimens in order to evaluate and define the ICR of intact lumbar discs. MATERIAL AND METHODS: Twelve cold preserved fresh human cadaveric lumbosacral spine specimens were subjected to computerized tomography (CT), magnetic resonance imaging (MRI) and biomechanical testing. Kinematic studies were performed to analyse range of movements in order to determine ICR. RESULTS: Flexoextension and lateral bending tests showed a positive linear correlation between the angle rotated and the displacement of the ICR in different axes. DISCUSSION: ICR has not been taken into account in any of the available literature regarding lumbar disc prosthesis. Considering our results, neither the actual ball-and-socket nor the withdrawn elastomeric nucleus models fit the biomechanics of the lumbar spine, which could at least in part explain the failure rates of the implants in terms of postoperative failed back syndrome (low back pain). It is reasonable to consider then that an implant should also adapt the equations of the movement of the intact ICR of the joint to the post-surgical ICR. CONCLUSIONS: This is the first cadaveric study on the ICR of the human lumbar spine. We have shown that it is feasible to calculate and consider this parameter in order to design future prosthesis with improved clinical and biomechanical characteristics.

Ankle torque-related fractures and its echo-fast diagnosis protocol.

Ankle torque is the most frequent injury mechanism encountered in traumatology. It usually develops as an ankle sprain, and often produces an ankle fracture. Signs and symptoms are very unspecific on the differential diagnosis, and conventional radiographs must be obtained to confirm it. This study compares ultrasound and standard X-ray images values found in ankle sprain-related fracture diagnoses. A 3-month prospective study was carried out on 52 patients with ankle torque. First, an ultrasound diagnosis was made by the first researcher at their arrival to the emergency department, usually consisting of a longitudinal section of the fibula, tibia, and V metatarsal. Then, a blinded independent investigator carried out the usual diagnosis protocol using traditional radiographs. When the required number was obtained, a third independent investigator evaluated the results. A Chi-squared test was used to contrast the outcomes between sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) comparing a non-inferiority hypothesis of our protocol against standard X-ray images screening. Echography showed to be at least as good as standard radiographs on the screening of ankle torque-related fractures (p = 0.02). In our series of patients, nearly 8% of fractures are misdiagnosed with plain radiographies, which concurs with the lower limit found in the bibliography. All the false negatives on radiographs were true positives in the first ultrasound assessment. The average time for the ultrasound protocol was 42 s. An ultrasound is at least as effective as conventional X-ray images when used in diagnosing ankle sprain-related fractures, regardless of age or sex and could in fact be better. The use of echography could reduce the number of radiographies performed when diagnosing these kinds of fractures, thereby reducing the amount of radiation exposure and expediting the diagnostic process as well as the "in situ diagnosis".Level of clinical evidence 2 [prospective cohort (N > 30 patients) study].

One-Stage vs Two-Stage Laparoscopic Roux-en-Y Gastric Bypass in Obese Patients with Body Mass Index >55 Kg/m2; 5-YEAR FOLLOW UP.

BACKGROUND: Surgical strategies in patients with BMI > 55 kg/m2 are not well established. OBJECTIVES: The objective of this study is to compare the long term results and complications of 1- vs. 2-stage laparoscopic "Roux-en-Y″ gastric bypass (LRYGB) for patients with BMI > 55 kg/m2. METHODS: Retrospective review of the complications and outcomes, between January 2007 and January 2010, for patients with a BMI > 55 kg/m2 who underwent directly a LRYGB (1-stage) or a LRYGB as a 2nd stage of a laparoscopic sleeve gastrectomy (LSG). RESULTS: Twenty-four patients were enrolled (no patient was lost during the 5-year follow-up). In the 1-stage LRYGB group, two patients had grade II complications according to Clavien-Dindo classification. In the 2-stage LRYGB group, complications of the first and the second surgery were summed. There were no differences between the two groups despite being heterogenous (more men with a higher BMI in the 2-stage group). There was a statistically significant difference in the final BMI in 1-stage LRYGB group compared to the 2-stage LRYGB group (34.46 ± 6.29 vs. 40.40 ± 3.47; p = 0.01, respectively) and in percentage of excess of BMI loss (%EBMIL; 69.80 ± 19.96 vs. 54.54 ± 13.93; p = 0.04, respectively). CONCLUSIONS: In patients with a BMI > 55 kg/m2, both 1- and 2-stage LRYGB give good long-term results. If feasible, a 1-stage LRYGB obtains a better percentage of excess of BMI loss but if not possible, the strategy of initially performing a laparoscopic sleeve gastrectomy followed by a LRYGB is safe and there were no differences in complications.