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.

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.

Selective T3-T4 sympathicotomy versus gray ramicotomy on outcome and quality of life in hyperhidrosis patients: a randomized clinical trial.

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.

Selective block of grey communicantes in upper thoracic sympathectomy. A feasibility study on human cadaveric specimens.

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.

High frequency of lumbar fusion in patients denied surgical treatment of the sacroiliac joint.

PURPOSE: Effective treatment of medical conditions relies on proper diagnosis. Clinical trials show the safety and effectiveness of sacroiliac joint (SIJ) fusion in patients with chronic SI joint dysfunction. To what extent is the condition under recognised? OBJECTIVE: To determine whether under recognition of SIJ pain affects healthcare trajectories in Spanish patients with low back pain. METHODS: Retrospective study of characteristics and consequences of 189 patients with persistent SIJ pain seen in an outpatient neurosurgery clinic. RESULTS: Patients with SIJ pain who were denied surgical treatment had a longer pain duration, higher likelihood of prior lumbar fusion, and a high rate (63%) of lumbar fusion within 2 years prior to SIJ pain diagnosis, which, in most cases, provided little benefit. CONCLUSIONS: Lack of knowledge of the role of the SIJ in chronic low back pain probably results in diagnostic confusion and may lead to misdirected treatment.

Minimally Invasive Sacroiliac Joint Fusion, Radiofrequency Denervation, and Conservative Management for Sacroiliac Joint Pain: 6-Year Comparative Case Series.

BACKGROUND: Sacroiliac joint (SIJ) pain is an under-recognized condition. Substantial information supports the safety and effectiveness of SIJ fusion (SIJF). Long-term follow-up after SIJF has not been reported. OBJECTIVE: To determine responses to conservative management (CM), SIJ denervation, and SIJF in patients with SIJ pain unresponsive to CM. METHODS: Retrospective study with long-term (up to 6 yr) follow-up of 137 patients with SIJ pain seen in an outpatient neurosurgery clinic who received either CM (n = 63), sacroiliac denervation (n = 47), or minimally invasive SIJF (n = 27). At each routine clinic visit, patients completed pain scores and Oswestry Disability Index. Additional data were extracted from medical charts. RESULTS: Patients treated with continued CM had no long-term improvement in pain (mean worsening of 1 point) or disability (mean Oswestry Disability Index worsened by 4-6 points), increased their use of opioids, and had poor long-term work status. SIJF patients had large improvements in SIJ pain (mean 6 points), large improvements in disability (mean 25 points), a decrease in opioid use, and good final work status. Sacroiliac denervation patients had intermediate responses (0-1 and 1-2 points, respectively). CONCLUSION: In patients with SIJ pain unresponsive to CM, SIJF resulted in excellent long-term clinical responses, with low opioid use and better work status compared to other treatments.

Can we safely monitor posterior fossa intracranial pressure? A cadaveric study.

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.

Biplanar x-ray fluoroscopy for sacroiliac joint fusion.

Chronic pain originating from the sacroiliac joint (SI) can cause severe dysfunction. Although many patients respond to conservative management with NSAIDs, some do need further treatment in the form of SI joint fusion (SIJF). To achieve safe and successful SIJF, intraoperative x-ray fluoroscopy is mandatory to avoid serious damages to nearby vascular and neural structures. Each step of the procedure has to be confirmed by anteroposterior (AP) and lateral projections. With a single-arm x-ray, the arch has to be moved back and forth for the AP and lateral projections, and this lengthens the procedure. To achieve the same results in less time, the authors introduced simultaneous biplanar fluoroscopy with 2 x-ray arches. After the patient is positioned prone with the legs spread apart in the so-called Da Vinci position, one x-ray arch for the lateral projection is placed at a right angle to the patient, and a second x-ray machine is placed with its arch between the legs of the patient. This allows simultaneous AP and lateral x-ray projections and, in the authors' hands, markedly speeds up the procedure. Biplanar fluoroscopy allows excellent AP and lateral projections to be made quickly at any time during the surgical procedure. This is particularly useful in cases of bilateral SI joint fusion if both sides are done at the same time. The video can be found here: https://youtu.be/TX5gz8c765M .

Percutaneous lumbar sympathectomy in the treatment of erectile dysfunction secondary to cavernous adrenergic hypertone: initial results of an original technique.

Corporeal smooth muscle tone is regulated by a delicate balance between contraction and erectile smooth muscle. An abnormal balance in basal conditions, due to an augmented contraction of erectile smooth muscle, defined "dysfunctional antagonism", may be responsible of a particular condition of erectile dysfunction (ED), secondary to cavernous adrenergic hypertone (CAY). In order to investigate the possibility to treat CAY with a definitive inhibition of adrenergic innervation to corpora cavernosa, we evaluated the results of an original technique of percutaneous lumbar sympathectomy (PLS) in a group of patients with clinical signs and symptoms of CAY In our study, 14 patients were selected and treated with PLS. Pre-treatment evaluation was designed to identify patients with ED caused by CAY, eligible for surgical treatment, and consisted of medical history, the self administered International Index of Erectile Function and Doppler sonography evaluation of cavernous arteries. Were considered eligible to the surgical treatment the patients with normal PSV values and abnormal EDV values after first injection of alprostadil, but reduced to zero after redosing with alprostadil and phentolamine. All these patients were treated with percutaneous bilateral lumbar ganglionic block with mepivacaine and, at a successive time, phenol 4% and evaluated after I and 4 months. Each evaluation consisted of a self-administered IIEF questionnaire, physical examination and Doppler sonography evaluation. Among the 14 patients selected and treated with temporary block with mepivacaine, 3 reported significant adverse events, consisting of loss of ejaculation (2 patients) and severe lumbar pain (1 patient). In all the other patients treated, only mild to moderate lumbar pain was reported. 10 patients out of the 14 treated with mepivacaine accepted to undergo the successive step of ganglionic block with phenol. Nine patients reported improved erections at both visits, as assessed by the GEQ. Moreover, the analysis of responses to IIEF questions 2-3 showed a highly significant improvement in erectile function compared to scores at baseline. Doppler sonography showed normal flow parameters at both visits in 8 patients. No significant adverse events were recorded after the procedures, except for mild to moderate lumbar pain. Clinical data collected in this study seem to confirm chemical sympathesctomy as a reliable, effective and safe therapeutic option in ED secondary to CAY.