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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.
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Miembros Artificiales , Disco Intervertebral , Humanos , Vértebras Lumbares/cirugía , Implantación de Prótesis , Disco Intervertebral/cirugía , Rango del Movimiento Articular , Fenómenos Biomecánicos , CadáverRESUMEN
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.
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Disco Intervertebral , Vértebras Lumbares , Humanos , Disco Intervertebral/fisiología , Fenómenos Biomecánicos/fisiología , Soporte de Peso/fisiologíaRESUMEN
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.
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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.
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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.
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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.
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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.
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Miembros Artificiales , Vértebras Lumbares , Fenómenos Biomecánicos , Análisis de Elementos Finitos , Humanos , Vértebras Lumbares/diagnóstico por imagen , Rango del Movimiento ArticularRESUMEN
Compensatory hyperhidrosis is the leading cause of patients' dissatisfaction after thoracic sympathicotomy. The study aimed to reduce compensatory hyperhidrosis to increase patients' satisfaction. A prospective randomized study on palmar hyperhidrosis, May 2016-September 2019. Twenty-one patients T3-T4 sympathicotomy and 21 T3-T4 gray ramicotomy. Data prospectively collected. Analysis at study's end. Focus on the sweating, temperature, quality of life baseline and postoperatively, compensatory hyperhidrosis, hand dryness, patients' satisfaction, and if they would undergo the procedure again and recommend it. No baseline differences between groups. Hyperhidrosis was controlled postoperatively in all patients. No mortality, serious complications, or recurrences. Sympathicotomy worse postoperative quality of life (49.05 (SD: 15.66, IR: 35.50-63.00) versus ramicotomy 24.30 (SD: 6.02, IR: 19.75-27.25). After ramicotomy, some residual sweating on the face, hands, and axillae. Compensatory sweating worse with sympathicotomy. Satisfaction higher with ramicotomy. Better results with ramicotomy than sympathicotomy regarding hand dryness, how many times a day the patients had to shower or change clothes, intention to undergo the procedure again or recommend it to somebody else, and how bothersome compensatory hyperhidrosis was. T3-T4 gray ramicotomy had better results than T3-T4 sympathicotomy, with less compensatory sweating and higher patients' satisfaction.
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Hiperhidrosis/cirugía , Calidad de Vida , Adulto , Femenino , Humanos , Masculino , Satisfacción del Paciente , Estudios Prospectivos , Sudoración , Simpatectomía/métodos , Resultado del Tratamiento , Adulto JovenRESUMEN
Background: Sympathetic chain interruption is the gold standard treatment for essential hyperhidrosis. Postoperative compensatory hyperhidrosis, the main reason for patients' dissatisfaction, is reduced by selectively lesioning white and grey rami communicantes (ramicotomy).Objective: To develop an endoscopic surgical technique that interrupts only T3 and T4 grey rami communicantes to minimize compensatory hyperhidrosis.Material and Methods: T3 and T4 grey rami communicantes ramicotomy in fifteen cold-preserved cadavers through a uniportal axillary endoscopic approach. The sympathetic chain, its ganglia, and white rami communicantes were left intact. On opening the chest, the sympathetic chain, rami communicantes and ganglia were dissected, photographed, measured and excised for histological examination.Results: Dissecting the grey rami communicantes is feasible as they consistently lie between the intercostal nerve and the homonymous sympathetic ganglion. At some levels, Kuntz nerves, as well as more than one grey ramus communicans, can be found. White rami communicantes are more medial, therefore damaging them can be avoided. Intercostal veins can be obstructive, but these can be controlled via coagulation or clipping if necessary.Conclusion: Uniportal endoscopic selective excision of the T3 and T4 grey rami communicantes is feasible without damaging the white rami communicantes, the sympathetic chain or its ganglia. Clipping the grey rami communicantes is technically possible but not reliable due to their thin diameter. This study confirms that T3 and T4 grey rami sympathetic block is technically feasible. Its application might reduce compensatory hyperhidrosis, but clinical studies are needed.
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Hiperhidrosis , Simpatectomía , Cadáver , Estudios de Factibilidad , Ganglios Simpáticos/anatomía & histología , Humanos , Hiperhidrosis/cirugía , Resultado del TratamientoRESUMEN
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.
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BACKGROUND: A cadaveric feasibility study was carried out. Osteotomies to correct fixed sagittal imbalance are usually performed at L3/ L4. OBJECTIVE: To investigate the feasibility of S1 pedicle subtraction osteotomy to correct spinal deformity and spinopelvic parameters, achieving better results with more limited exposure. The data obtained will allow a fixation construct specific for this osteotomy to be designed. METHODS: S1 pedicle subtraction osteotomy was performed on 12 cadaveric specimens. Baseline and postprocedural computed tomography and biomechanical studies were performed. Data were analyzed with a fixation system SolidWorks model, and the redesigned fixation construct was described and analyzed with an ANSYS model. RESULTS: S1 pedicle subtraction osteotomy is technically feasible. The fixation can be achieved with L4, L5, and iliac screws connected with bars. The system can be reinforced with a polyetheretherketone cage placed anteriorly in the S1 body osteotomy site, a cross-connecting bar, a double iliac screw, or an anterior interbody cage placed at the L5-S1 disc. The fixation strength is improved by angulating the iliac rod channel 10°, adding a semi-sphere to the locking screw contact surface and 2 fins to its saddle. The redesigned construct showed suitable stress and deformation levels, achieving the expected biomechanical requirements. DISCUSSION: Compared with surgery on higher levels, S1 pedicle subtraction osteotomy allows greater correction with shorter fixation, because the osteotomy is performed at a more caudal level, modifying the spinopelvic parameters. CONCLUSIONS: S1 pedicle subtraction osteotomy is technically feasible. Finite element analysis results indicate that it has appropriate biomechanical properties.
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Osteotomía/métodos , Sacro/cirugía , Curvaturas de la Columna Vertebral/cirugía , Anciano , Fenómenos Biomecánicos , Diseño Asistido por Computadora , Estudios de Factibilidad , Femenino , Análisis de Elementos Finitos , Humanos , Fijadores Internos , Masculino , Ensayo de Materiales , Persona de Mediana Edad , Diseño de Prótesis , Estrés MecánicoRESUMEN
Axillary nerve injury is common after brachial plexus injuries, particularly with shoulder luxation. Nerve grafting is the traditional procedure for postganglionic injuries. Nerve transfer is emerging as a viable option particularly in late referrals. At the proximal arm the radial and axillary nerves lie close by. Sacrificing one of the triceps muscle nerve branches induces little negative consequences. Transferring the long head of the triceps nerve branch is a good option to recover axillary nerve function. The surgical technique is presented in a video, stressing the steps to achieve a successful result. The video can be found here: https://youtu.be/WbVbpMuPxIE .
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Axila/lesiones , Axila/cirugía , Plexo Braquial/lesiones , Plexo Braquial/cirugía , Transferencia de Nervios/métodos , Nervio Radial/trasplante , Humanos , Masculino , Persona de Mediana EdadRESUMEN
BACKGROUND: In situ decompression and transposition are equally effective in cubital tunnel syndrome treatment. Both are traditionally performed in the supine position. OBJECTIVE: To validate our surgical technique for in situ decompression in the lateral decubitus position, comparing results with other techniques used in our institutions. METHODS: A retrospective study was performed from January 2009 to February 2016, of 188 patients with cubital tunnel syndrome 115 males, 73 females; mean age, 53.44 ± 12.12 years standard deviation (range, 18-84 years) treated with in situ decompression in the lateral or supine positions or transposition (subcutaneous or submuscular). The lateral decubitus group received local anesthesia and the remainder received a brachial plexus block. Clinical and electrophysiologic results between these 4 groups were compared. RESULTS: There were no statistically significant demographic differences between groups. Results were better in in situ decompression groups compared with transpositions. Mean follow-up was 1511.1 ± 770.57 days standard deviation (range, 310-4203 days). There were no recurrences or residual elbow pain/dysesthesia/anesthetic scar/hyperesthesia/neuroma in the lateral decubitus group. Complication and recurrence rates were in direct correlation to incision size. The worst results were seen in transpositions, particularly in the submuscular group. In situ decompression in the supine position had better results than transpositions but worse than those performed in lateral decubitus. Smaller surgical wound correlates with a reduction in operating time, costs, complication rates, and time out of work. CONCLUSIONS: In situ decompression is equally as effective as ulnar nerve transpositions but with fewer complications and recurrences. In the lateral decubitus position, the retroepicondylar tunnel is more accessible, allowing smaller incisions and better results.
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Síndrome del Túnel Cubital/cirugía , Descompresión Quirúrgica/métodos , Articulación del Codo/inervación , Articulación del Codo/cirugía , Posicionamiento del Paciente/métodos , Nervio Cubital/cirugía , Adolescente , Adulto , Anciano , Anciano de 80 o más Años , Síndrome del Túnel Cubital/diagnóstico , Femenino , Estudios de Seguimiento , Humanos , Masculino , Persona de Mediana Edad , Conducción Nerviosa/fisiología , Estudios Retrospectivos , Adulto JovenRESUMEN
BACKGROUND: measuring intracranial pressure (ICP) is considered the gold standard of care for brain injury. While supratentorial ICP monitoring has been adopted everywhere, posterior fossa ICP monitoring is rarely performed. In this study, we aimed to evaluate the feasibility of inserting ICP sensors into the posterior fossa of cadavers, to measure ICP in the posterior fossa. METHODS: An ICP sensor was transcranially implanted into the posterior fossa of fifteen fresh adult cadavers. An extracranial point was defined in the retroauricular area 2 cm behind the tip of the mastoid process and 2 cm below the transverse sinus, in order to implant an ICP probe. The cranial cavity was opened and measures were taken of the distance that the ICP sensor had penetrated inside the posterior fossa, as well as the distance to nearby venous sinuses (lateral, transverse, sigmoid, inferior petrosal sinus, and jugular bulb). The cerebellar hemisphere was searched for any possible damage. RESULTS: the selected extracranial point (2 cm behind the tip of the mastoid process and 2 cm below the transverse sinus) was a safe location. Intracranial structures such as the brainstem and the cerebellar hemisphere were not damaged. The implanted ICP probe was at least 2 cm away from the venous sinuses, which were not damaged. CONCLUSION: ICP monitoring is safe and reliable at the described ICP probe placement site of the posterior fossa.
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Presión Intracraneal/fisiología , Adulto , Cadáver , Fosa Craneal Posterior/cirugía , Senos Craneales/cirugía , Estudios de Factibilidad , Femenino , Humanos , Masculino , Persona de Mediana Edad , Monitoreo Fisiológico/métodos , Seguridad del Paciente , Cráneo/cirugía , Adulto JovenRESUMEN
OBJECTIVE: Surgical treatment of trigeminal neuralgia (TN) associated with vertebrobasilar dolichoectasia is challenging. We analyze the treatments for this disease, discussing the advantages and drawbacks, and present our own technique and series. METHODS: This retrospective study covered the period January 2006 through January 2016. Vertebrobasilar dolichoectasia deviation from midline, basilar artery (BA) and vertebral artery diameter, and BA apex distance above the posterior clinoid process were measured on preoperative and postoperative magnetic resonance imaging. The BA was repositioned and kept in place with coagulation of the clival dura, Teflon pledgets, and fibrin glue. We also performed a thorough literature review using PubMed. RESULTS: Our cases included 5 men and 3 women with mean age 64.88 years ± 10.32 (range, 48-81 years); 7 cases were TN, and 1 case was painful tic convulsif. Pain was on the left side in 6 cases and on the right in 2 cases. All cases affected cranial nerve V2 and/or V3 divisions. Both V2 and V3 were affected in 4 cases, V3 was affected in 3 cases, and V2 was affected in 1 case. Hypertension was present in 5 cases. TN disappeared postoperatively in all cases. One patient took clonazepam 2 mg/24 hours for 3 months because of facial dysesthesia. Postoperative complications included hearing loss in 1 patient; facial paresis plus diplopia in 1 patient, which resolved in 3 months; and arterial hypertension. Postoperative arterial hypertension improved in all affected patients, although only 2 patients discontinued antihypertensive medications. Mean follow-up time was 56.50 months ± 40.08 (range, 14 months to 9 years 9 months). No patient showed pain recurrence. CONCLUSIONS: TN associated with vertebrobasilar dolichoectasia can be treated surgically with minimal morbidity. BA repositioning has the highest success rate. Our technique of inducing a dural scar to fix the BA in its new position away from the trigeminal nerve is simple, not technically demanding, and highly effective.