Biomedical subjects

Luiz Pimenta

Publications and source records attributed to Luiz Pimenta.

9 recordsLinked to original sources

PubMed2007

Posterior cervical spine surgery for radiculopathy.

It is now common knowledge that cervical radiculopathy, frequently caused by disc herniation and/or degeneration, will often improve without surgical intervention. Only a small percentage of patients with the severity of symptoms necessitate surgical treatment. Surgery for radiculopathy is indicated for motor weakness, progressive neurological deficits, and progressive symptoms that do not improve with nonoperative treatment. Advantages and disadvantages exist for both ventral and dorsal approaches in the surgical treatment of cervical radiculopathy. Indications and results for dorsal nerve root decompression are discussed, and a review of our preferred techniques, including use of minimally invasive technology, is presented.

Cervical Vertebrae↗

PubMed2006

Porous coated motion cervical disc replacement: a biomechanical, histomorphometric, and biologic wear analysis in a caprine model.

STUDY DESIGN: The biomechanical, histopathologic, and histomorphometric characteristics of cervical disc replacement were assessed in a caprine animal model. OBJECTIVE: To investigate the biomechanical, porous ingrowth, and histopathologic characteristics of the Porous Coated Motion (PCM) Cervical Disc replacement (Cervitech, Inc., Rockaway, NJ). SUMMARY OF BACKGROUND DATA: As an alternative to anterior cervical interbody arthrodesis, an artificial cervical disc serves to replace the symptomatic degenerated disc, restore the functional biomechanical properties of the motion segment, and preserve neurologic function. METHODS: There were 12 mature Nubian goats divided into 2 groups based on postoperative survival periods of 6 (n = 6) and 12 months (n = 6). Using an anterior surgical approach, a complete discectomy was performed at the C3-C4, followed by implantation of the PCM device. Functional outcomes of the disc prosthesis were based on computerized tomography (CT), multidirectional flexibility testing, undecalcified histology, histomorphometric, and immunocytochemical analyses. RESULTS: There was no evidence of prosthesis loosening, or neurologic or vascular complications. CT showed the ability to image and assess the cervical spinal canal for the presence of compressive pathology in the area of the CoCrMo prosthesis. Multidirectional flexibility testing under axial rotation and lateral bending indicated no differences in the full range of intervertebral motion between the disc prosthesis and nonoperative controls (P > 0.05). Based on immunohistochemical and histologic analysis, there was no evidence of particulate debris, cytokines, or cellular apoptosis within the local or systemic tissues. Moreover, review of the spinal cord at the operative levels indicated no evidence of cord lesions, inflammatory reaction, wear particles, or significant pathologic changes in any treatment. Histomorphometric analysis at the metal-bone interface indicated the mean trabecular ingrowth of 40.5% +/- 24.4% and 58.65% +/- 28.04% for the 6 and 12-month treatments, respectively. CONCLUSION: To our knowledge, this serves as the first in vivo time-course study investigating the use of the PCM device for cervical arthroplasty. All 12 animals undergoing cervical disc replacement had no evidence of implant loosening, subluxation, or inflammatory reactions. PCM cervical arthroplasty permits unobstructed visualization of the spinal canal based on CT imaging. Segmental intervertebral motion was preserved under axial rotation and lateral bending loading conditions, while at the same time permitting porous osseointegration at the prosthesis-bone interface. Based on histopathologic review of all local and systemic tissues, there was no evidence of particulate wear debris, cytokines, cellular apoptosis, or significant pathologic changes in any treatment.

Animals↗

PubMed2006

A novel minimally invasive presacral approach and instrumentation technique for anterior L5-S1 intervertebral discectomy and fusion: technical description and case presentations.

OBJECT: The authors describe a new paracoccygeal approach to the L5-S1 junction for interbody fusion with transsacral instrumentation. The purpose of this technical note is to demonstrate a novel surgical approach, technique, and instrumentation system for the treatment of L5-S1 instability in degenerative disc disease and spondylolisthesis. METHODS: This technical note highlights the AxiaLif (TranS1) transsacral system as an alternative method to transforaminal lumbar interbody fusion or posterior lumbar interbody fusion. Via a novel presacral approach corridor, a truly percutaneous L5-S1 discectomy, interbody distraction, and fixation are achieved, and retroperitoneal viscera and dorsal neural elements are avoided. Percutaneous pedicle screw fixation is then used to provide additional stabilization at the treated level. CONCLUSIONS: This novel technique of interbody distraction and fusion via a truly percutaneous approach corridor allows for circumferential treatment of the lower lumbar segments with minimal risk to the anterior organs and dorsal neural elements.

Adult↗

PubMed2006

Anatomy of the percutaneous presacral space for a novel fusion technique.

OBJECTIVES: Lumbar fusion has been widely used to treat unstable spinal disorders. Methods are evolving from open procedures to less invasive methods to avoid soft tissue trauma. Recently, a soft tissue sparing method to access the axial lumbosacral spine has been developed. It is crucial to determine structures potentially at risk for injury during this fusion technique. The anatomy of the presacral space and safety of the paracoccygeal approach were evaluated through cadaveric dissection and radiographic studies. The objective was to evaluate the safety of a paracoccygeal approach to the axial lumbosacral spine and determine structures that could potentially be injured. METHODS: The paracoccygeal approach was performed on two cadavers, followed by dissection. Distances from the midline trajectory of the approach to surrounding vascular structures were determined. Similar distances were also measured on computed tomography (CT) and magnetic resonance imaging (MRI) of 12 patients, as well as CT images of two additional patients. A "safe zone" was determined using the sagittal length of the presacral space and the distance between the most medial internal iliac vessel on the right and left, respectively. RESULTS: The coronal safe zone averaged 6.9 and 6.0 cm on MRI and CT, respectively. The mean distance from the anterior sacral margin to the rectum at the S3-S4 level was 1.2 and 1.3 cm on MRI and CT, respectively. CONCLUSION: In this study, we defined the "coronal safe zone" within the presacral space. This "safe zone" may guide surgeons when utilizing the percutaneous paracoccygeal approach.

Cadaver↗

PubMed2006

Charité lumbar artificial disc retrieval: use of a lateral minimally invasive technique. Technical note.

Indications for total disc replacement (TDR) may include implant loosening, malposition, displacement, early wear, and infection. Each indication is likely to require different preoperative planning, testing, and strategies. Preoperative planning is the first and most important step in performing a TDR revision. An organized approach reduces operative time, minimizes risks, decreases stress, and increases the success rate. Primary revision of a failed total disc arthroplasty can be planned as a posterior fusion, leaving the TDR device in place, but an unstable anterior column may require retrieval and revision of the interbody device. An anterior revision approach is associated with significant risk due to scarring and adhesions resulting from the primary procedure, making mobilization of the vessels very difficult, especially at the L4-5 bifurcation. The authors describe a new alternative for retrieval and revision of a TDR device. They present the details of two cases of TDR device revision in which they performed a minimally invasive extreme-lateral interbody fusion to effect a safer access route that avoids vascular structures and the creation of scar tissue.

Adult↗

PubMed2003

Cervical disc replacement-porous coated motion prosthesis: a comparative biomechanical analysis showing the key role of the posterior longitudinal ligament.

STUDY DESIGN: Benchtop cadaveric biomechanical comparative testing and caprine animal model in vivo implantation. OBJECTIVE: To evaluate the role of the posterior longitudinal ligament in cervical arthroplasty and to understand the relative contribution of this ligament in nonfusion applications. SUMMARY OF BACKGROUND DATA: Rauschning refers to the posterior longitudinal ligament as "The Kleenex Ligament" due to its apparent anatomic insignificance. White and Panjabi found the posterior longitudinal ligament ranked only fourth in importance in tensile load-to-failure biomechanical testing. In the postoperative situation following anterior cervical diskectomy fusion, posterior longitudinal ligament integrity is overlooked by physicians because the entire disc space usually fuses into a homogeneous block of bone. PURPOSE: This biomechanical study was undertaken to determine the relative importance of the posterior longitudinal ligament following two different degrees of anterior decompression, anterior disc replacement, and anterior arthrodesis procedures. METHODS: A total of seven fresh frozen human cadaveric cervical spines (C3-C7) (mean age 68 +/- 19 years) were used for biomechanical testing. Each vertebra was equipped with three non-colinear light emitting diodes designed for detection by an optoelectronic motion measurement system (3020 Optotract System). To determine the multidirectional flexibility, six pure moments (flexion, extension, right + left lateral bending, right + left axial rotation) and axial compression were applied using a servohydraulic 858 Bionix testing device configured with a six-degree-of-freedom spine simulator. Range of motion was defined as the peak displacement from the initial neutral position to the maximum load, whereas the neutral zone represents the motion from the initial neutral position to the unloaded position at the beginning of the third cycle. Seven groups of (N = 7 each) constructs at C5-C6 were: 1) intact "native" C5-C6 level; 2) anterior diskectomy (posterior longitudinal ligament intact); 3) a Low Profile Porous Coated Motion cervical disc replacement; 4) posterior longitudinal ligament resected; 5) Porous Coated Motion cervical disc replacement fixed with anterior flanges and screws; 6) tricortical structural allograft; and 7) an anterior cervical translational plate + allograft. The caprine model was evaluated for suitability as an animal model with 12 goats undergoing C3-C4 anterior cervical Porous Coated Motion disc replacement. RESULTS: Group 2 (anterior diskectomy alone) was significantly more stable than Group 4 (anterior diskectomy + posterior longitudinal ligament resection) in flexion-extension, 18.7 +/- 4.76 degrees versus 24.8 +/- 4.42 degrees (P < 0.05) and in lateral bending, 5.9 +/- 1.79 degrees versus 10.7 +/- 2.8 degrees (P < 0.05). The comparison for the two conditions for axial rotation, 10.4 +/- 13.9 degrees versus 13.9 +/- 2.7 degrees, and axial compression, 1.19 +/-.98 degrees versus 1.52 +/- 1.14 degrees, showed the same trend. Twelve goats undergoing porous coated motion cervical disc replacement had no evidence of prosthesis loosening, neurologic complications, or experienced inflammatory reactions from particulate wear debris after 6 months of implantation. DISCUSSION: This study confirms the pivotal role of the posterior longitudinal ligament in postsurgical stability of the cervical spine following anterior diskectomy. This is because the lateral anulus, uncovertebral ligaments, and lateral capsular ligaments are stretched and plastically deformed in the surgical distraction process of restoring the disc space height following anterior surgical decompression. There should be a separate determination of the range of motion of cervical disc replacements depending of the integrity and the amount of the posterior longitudinal ligament that has been resected. CLINICAL RELEVANCE: There are two basic types of total knee replacements, posterior cruciate ligament-preserving and posterior cruciate ligament-sacrificing designs. In the cervical spine, an analogous situation exists biomechanically depending on whether the posterior longitudinal ligament needs to be removed in its entirety as part of the spinal cord decompression part of the procedure--it may be helpful to conceptually differentiate between posterior longitudinal ligament-preserving and posterior longitudinal ligament-sacrificing total cervical disc replacements.

Aged↗

PubMedDate not supplied

Choosing a cervical disc replacement.

BACKGROUND CONTENT: Three important basic scientific studies are presented that measured the volumetric density of longitudinal bony columns within the cervical vertebra. The most solid bone is lateral, adjacent to the uncovertebral joints in a radial pattern. PURPOSE: To characterize the best footprint, profile and biomaterials to construct a cervical disc replacement. STUDY DESIGN: A compilation of biomechanical and anatomical basic scientific studies. METHODS: Microcomputed tomographic imaging, trabecular density and mineral distribution were quantitated from human cervical vertebra. RESULTS: The lateral portions of the cervical vertebra are subjected to higher bending loads than the lumbar vertebral bodies. Therefore, the optimal prosthesis needs to be anchored in the lateral uncovertebral bone. To reduce the incidence of cervical subsidence, the prosthesis needs to be more rectangular than round to take advantage of the radially oriented lateral trabeculae. TiCaP (titanium/calcium phosphate) (Cervitech, Inc., Rockaway, NJ) bony ingrowth coating leads to 10% to 15% greater bony integration than plasma-sprayed titanium. TiCaP causes a supersaturated solution of CaP at the metal-bone interface, which enables reprecipitation of hydroxyapatite and superior bony integration. The optimum pore size of the ingrowth coating of the lumbar spine is 75 to 300 microns, whereas in the cervical spine the optimal ingrowth coating is 20 to 30 microns. This is an order of magnitude lower in pore size to match the smaller cervical trabecular architecture. CONCLUSIONS: Kinematic considerations for the cervical spine show the load is 1/9th the load carried by the lumbar spine or 50 N per segment. Knowing the sliding distance and wear characteristics of conventional biomaterials (ultrahigh molecular weight polyethylene and cobalt chrome) demonstrates that the generation of particulate debris should be a very minor consideration with cervical arthroplasty.

Arthroplasty, Replacement↗

PubMedDate not supplied

Clinical experience with the new artificial cervical PCM (Cervitech) disc.

The results of a pilot study performed between December 2002 and October 2003 in which 82 cervical disc arthroplasties were implanted in 53 patients are reviewed in detail. Visual Analog Scale (VAS) pain scale, Neck Disability Index (NDI), and Treatment Intensity Gradient Test (TIGT) scales were evaluated as were static and dynamic radiographs. Significant improvents in all scales were seen postoperatively. One device migration of 4 millimeters was seen at 3 months and observed. Eighty percent of patients had a good or excellent result at one week, improving to ninety percent of patients being judged to have a good or excellent result by one month (Odom's criteria), which then remained at ninety percent at 3 months.

Adult↗

PubMedDate not supplied

Extreme Lateral Interbody Fusion (XLIF): a novel surgical technique for anterior lumbar interbody fusion.

BACKGROUND: Minimally disruptive approaches to the anterior lumbar spine continue to evolve in a quest to reduce approach-related morbidity. A lateral retroperitoneal, trans-psoas approach to the anterior disc space allows for complete discectomy, distraction, and interbody fusion without the need for an approach surgeon. PURPOSE: To demonstrate the feasibility of a minimally disruptive lateral retroperitoneal approach and the advantages to patient recovery. METHODS/RESULTS: The extreme lateral approach (Extreme Lateral Interbody Fusion [XLIF]) is described in a step-wise manner. There have been no complications thus far in the author's first 13 patients. CONCLUSIONS: The XLIF approach allows for anterior access to the disc space without an approach surgeon or the complications of an anterior intra-abdominal procedure. Longer-term follow-up and data analysis are under way, but initial findings are encouraging.

Bone Diseases↗