Mick J. Perez-Cruet

Microendoscopic lumbar discectomy: technical note.

OBJECTIVE The microendoscopic discectomy (MED) technique was initially developed in 1997 to treat herniated lumbar disc disease. Since then, thousands of cases have been successfully performed at more than 500 institutions. This article discusses the technical aspects of this procedure and presents a consecutive case series. METHODS A total of 150 consecutive patients underwent MED. MED is performed by a muscle-splitting approach using a series of tubular dilators with consecutively increasing diameters. A tubular retractor is then inserted over the final dilator, and a specially designed endoscope is placed inside the tubular retractor. The microdiscectomy is performed endoscopically while the surgeon views the procedure on a video monitor. RESULTS Clinical outcomes were determined using a modified MacNab criteria, which revealed that 77% of patients had excellent, 17% had good, 3% had fair, and 3% had poor outcomes. The average hospital stay was 7.7 hours. The average return to work period was 17 days. Complications primarily included dural tears, which occurred in 8 patients (5%) and were seen early on in the patient series. Complication rates diminished as the surgeon’s experience with this technique increased. CONCLUSION MED for lumbar herniated disc disease can be performed safely and effectively, resulting in a shortened hospital stay and faster return to work; however, there is a learning curve to this procedure.

Treatment of Dissecting Pseudoaneurysm of the Cervical Internal Carotid Artery Using a Wall Stent and Detachable Coils: Case Report.

OBJECTIVE AND IMPORTANCE This case illustrates the use of an endovascular stent and coiling combination to treat a giant wide-necked pseudoaneurysm of the cervical internal carotid artery. CLINICAL PRESENTATION A 20-year-old male patient presented with a bilateral dissection of the cervical internal carotid artery and a right giant wide-necked pseudoaneurysm of the cervical segment of the internal carotid artery after a high-speed motor vehicle collision. INTERVENTION After failing conservative therapy, the patient was treated by endovascular placement of a Palmaz wall stent at the level of the pseudoaneurysm and filling of the pseudoaneurysm with multiple Guglielmi detachable coils. Obliteration of the pseudoaneurysm was achieved, and patency of the right internal carotid artery was maintained. CONCLUSION The patients neurological symptoms resolved completely after treatment, and he sustained no neurological complications during the 20-month follow-up period. This case illustrates the successful treatment of a wide-based giant pseudoaneurysm by using a combination of an endovascular stent and coil embolization.

Review: complications of minimally invasive spinal surgery.

COMPLICATIONS OF MINIMALLY invasive spinal surgery can be related to anesthesia, patient positioning, and surgical technique. The performance of successful minimally invasive spinal surgery is beset with several technical challenges, including the limited tactile feedback, two-dimensional video image quality of three-dimensional anatomy, and the manual dexterity needed to manipulate instruments through small working channels, which all account for a very steep learning curve. Knowledge of possible complications associated with particular minimally invasive spinal procedures can aid in their avoidance. This article reviews complications associated with minimally invasive spinal surgery in the cervical, thoracic, and lumbar spine by reviewing reported data of sufficient detail or with sufficient numbers of patients. In addition, possible complications associated with anesthesia use, patient positioning, and surgical techniques during thoracoscopic and laparoscopic spinal procedures are reviewed.

In vivo intervertebral disc regeneration using stem cell-derived chondroprogenitors

OBJECT There is currently no biologic therapy to repair or restore a degenerated intervertebral disc. A potential solution may rest with embryonic stem cells (ESCs), which have a potential to grow indefinitely and differentiate into a variety of cell types in vitro. Prior studies have shown that ESCs can be encouraged to differentiate toward specific cell lineages by culture in selective media and specific growth environment. Among these lineages, there are cells capable of potentially producing nucleus pulposus (NP) in vivo. In this investigation, the authors studied ESCderived chondroprogenitors implanted into a degenerated disc in a rabbit. For this purpose, a rabbit model of disc degeneration was developed. METHODS A percutaneous animal model of disc degeneration was developed by needle puncture of healthy intact discs in 16 New Zealand white rabbits. Series of spine MR imaging studies were obtained before disc puncture and after 2, 6, and 8 weeks. Prior to implantation, murine ESCs were cultured with cis-retinoic acid, transforming growth factor beta, ascorbic acid, and insulin-like growth factor to induce differentiation toward a chondrocyte lineage. After confirmation by MR imaging, degenerated disc levels were injected with chondrogenic derivatives of ESCs expressing green fluorescent protein. At 8 weeks post-ESC implantation, the animals were killed and the intervertebral discs were harvested and analyzed using H & E staining, confocal fluorescent microscopy, and immunohistochemical analysis. Three intervertebral disc groups were analyzed in 16 rabbits, as follows: 1) Group A, control: naïve, nonpunctured discs (32 discs, levels L4-5 and L5-6); 2) Group B, experimental control: punctured disc (16 discs, level L2-3); and 3) Group C, experimental: punctured disc followed by implantation of chondroprogenitor cells (16 discs, level L3-4). RESULTS The MR imaging studies confirmed intervertebral disc degeneration at needle-punctured segments starting at approximately 2 weeks. Postmortem H & E histological analysis of Group A discs showed mature chondrocytes and no notochordal cells. Group B discs displayed an intact anulus fibrosus and generalized disorganization within fibrous tissue of NP. Group C discs showed islands of notochordal cell growth. Immunofluorescent staining for notochordal cells was negative for Groups A and B but revealed viable notochordal-type cells within experimental Group C discs, which had been implanted with ESC derivatives. Notably, no inflammatory response was noted in Group C discs. CONCLUSIONS This study illustrates a reproducible percutaneous model for studying disc degeneration. New notochordal cell populations were seen in degenerated discs injected with ESCs. The lack of immune response to a xenograft of mouse cells in an immunocompetent rabbit model may suggest an as yet unrecognized immunoprivileged site within the intervertebral disc space.

Anterior cervical discectomy and corpectomy.

OBJECTIVE: The objective of this review article is to describe the authors’ operative technique for performing anterior cervical corpectomy and fusion. METHODS: The authors reviewed their operative technique and experience to clearly detail the general methods utilized to safely and effectively perform anterior cervical corpectomy and fusion. Specific nuances peculiar to the authors’ technique were identified and highlighted. RESULTS: The operative technique for anterior cervical corpectomy, including nuances for enhancing ease or outcome of surgery, is described in detail. Drawings and photographs are included where appropriate to highlight specific aspects of the procedural technique. CONCLUSION: Anterior cervical corpectomy and fusion is a well known technique that proceeds in a consistent and logical sequence of maneuvers. Specific technical nuances at various points enhance the ease and safety of the technique, as well as the completeness of the eventual result.

Simplified three-dimensional culture system for long-term expansion of embryonic stem cells

AIM To devise a simplified and efficient method for long-term culture and maintenance of embryonic stem cells requiring less frequent passaging. METHODS Mouse embryonic stem cells (ESCs) labeled with enhanced yellow fluorescent protein were cultured in three-dimensional (3-D) self-assembling scaffolds and compared with traditional two-dimentional (2-D) culture techniques requiring mouse embryonic fibroblast feeder layers or leukemia inhibitory factor. 3-D scaffolds encapsulating ESCs were prepared by mixing ESCs with polyethylene glycol tetra-acrylate (PEG-4-Acr) and thiol-functionalized dextran (Dex-SH). Distribution of ESCs in 3-D was monitored by confocal microscopy. Viability and proliferation of encapsulated cells during long-term culture were determined by propidium iodide as well as direct cell counts and PrestoBlue (PB) assays. Genetic expression of pluripotency markers (Oct4, Nanog, Klf4, and Sox2) in ESCs grown under 2-D and 3-D culture conditions was examined by quantitative real-time polymerase chain reaction. Protein expression of selected stemness markers was determined by two different methods, immunofluorescence staining (Oct4 and Nanog) and western blot analysis (Oct4, Nanog, and Klf4). Pluripotency of 3-D scaffold grown ESCs was analyzed by in vivo teratoma assay and in vitro differentiation via embryoid bodies into cells of all three germ layers. RESULTS Self-assembling scaffolds encapsulating ESCs for 3-D culture without the loss of cell viability were prepared by mixing PEG-4-Acr and Dex-SH (1:1 v/v) to a final concentration of 5% (w/v). Scaffold integrity was dependent on the degree of thiol substitution of Dex-SH and cell concentration. Scaffolds prepared using Dex-SH with 7.5% and 33% thiol substitution and incubated in culture medium maintained their integrity for 11 and 13 d without cells and 22 ± 5 d and 37 ± 5 d with cells, respectively. ESCs formed compact colonies, which progressively increased in size over time due to cell proliferation as determined by confocal microscopy and PB staining. 3-D scaffold cultured ESCs expressed significantly higher levels (P < 0.01) of Oct4, Nanog, and Kl4, showing a 2.8, 3.0 and 1.8 fold increase, respectively, in comparison to 2-D grown cells. A similar increase in the protein expression levels of Oct4, Nanog, and Klf4 was observed in 3-D grown ESCs. However, when 3-D cultured ESCs were subsequently passaged in 2-D culture conditions, the level of these pluripotent markers was reduced to normal levels. 3-D grown ESCs produced teratomas and yielded cells of all three germ layers, expressing brachyury (mesoderm), NCAM (ectoderm), and GATA4 (endoderm) markers. Furthermore, these cells differentiated into osteogenic, chondrogenic, myogenic, and neural lineages expressing Col1, Col2, Myog, and Nestin, respectively. CONCLUSION This novel 3-D culture system demonstrated long-term maintenance of mouse ESCs without the routine passaging and manipulation necessary for traditional 2-D cell propagation.

The Technological Development of Minimally Invasive Spine Surgery

Minimally invasive spine surgery has its roots in the mid-twentieth century with a few surgeons and a few techniques, but it has now developed into a large field of progressive spinal surgery. A wide range of techniques are now called “minimally invasive,” and case reports are submitted constantly with new “minimally invasive” approaches to spinal pathology. As minimally invasive spine surgery has become more mainstream over the past ten years, in this paper we discuss its history and development.

Isolation and Characterization of Mesenchymal Stromal Cells from Human Umbilical Cord and Fetal Placenta

The human umbilical cord (UC) and placenta are non-invasive, primitive and abundant sources of mesenchymal stromal cells (MSCs) that have increasingly gained attention because they do not pose any ethical or moral concerns. Current methods to isolate MSCs from UC yield low amounts of cells with variable proliferation potentials. Since UC is an anatomically-complex organ, differences in MSC properties may be due to the differences in the anatomical regions of their isolation. In this study, we first dissected the cord/placenta samples into three discrete anatomical regions: UC, cord-placenta junction (CPJ), and fetal placenta (FP). Second, two distinct zones, cord lining (CL) and Whartons jelly (WJ), were separated. The explant culture technique was then used to isolate cells from the four sources. The time required for the primary culture of cells from the explants varied depending on the source of the tissue. Outgrowth of the cells occurred within 3 - 4 days of the CPJ explants, whereas growth was observed after 7 - 10 days and 11 - 14 days from CL/WJ and FP explants, respectively. The isolated cells were adherent to plastic and displayed fibroblastoid morphology and surface markers, such as CD29, CD44, CD73, CD90, and CD105, similarly to bone marrow (BM)-derived MSCs. However, the colony-forming efficiency of the cells varied, with CPJ-MSCs and WJ-MSCs showing higher efficiency than BM-MSCs. MSCs from all four sources differentiated into adipogenic, chondrogenic, and osteogenic lineages, indicating that they were multipotent. CPJ-MSCs differentiated more efficiently in comparison to other MSC sources. These results suggest that the CPJ is the most potent anatomical region and yields a higher number of cells, with greater proliferation and self-renewal capacities in vitro. In conclusion, the comparative analysis of the MSCs from the four sources indicated that CPJ is a more promising source of MSCs for cell therapy, regenerative medicine, and tissue engineering.

Potential of Human Nucleus Pulposus-Like Cells Derived From Umbilical Cord to Treat Degenerative Disc Disease

Abstract BACKGROUND Degenerative disc disease (DDD) is a common spinal disorder that manifests with neck and lower back pain caused by the degeneration of intervertebral discs (IVDs). Currently, there is no treatment to cure this debilitating ailment. OBJECTIVE To investigate the potential of nucleus pulposus (NP)-like cells (NPCs) derived from human umbilical cord mesenchymal stem cells (MSCs) to restore degenerated IVDs using a rabbit DDD model. METHODS NPCs differentiated from MSCs were characterized using quantitative real-time reverse transcription polymerase chain reaction and immunocytochemical analysis. MSCs and NPCs were labeled with fluorescent dye, PKH26, and transplanted into degenerated IVDs of a rabbit model of DDD (n = 9 each). Magnetic resonance imaging of the IVDs was performed before and after IVD degeneration, and following cell transplantation. IVDs were extracted 8 wk post-transplantation and analyzed by various biochemical, immunohistological, and molecular techniques. RESULTS NPC derivatives of MSCs expressed known NP-specific genes, SOX9, ACAN, COL2, FOXF1, and KRT19. Transplanted cells survived, dispersed, and integrated into the degenerated IVDs. IVDs augmented with NPCs showed significant improvement in the histology, cellularity, sulfated glycosaminoglycan and water contents of the NP. In addition, expression of human genes, SOX9, ACAN, COL2, FOXF1, KRT19, PAX6, CA12, and COMP, as well as proteins, SOX9, ACAN, COL2, and FOXF1, suggest NP biosynthesis due to transplantation of NPCs. Based on these results, a molecular mechanism for NP regeneration was proposed. CONCLUSION The findings of this study demonstrating feasibility and efficacy of NPCs to regenerate NP should spur interest for clinical studies to treat DDD using cell therapy.