Background: Disruption of the rotator cuff muscles compromises concavity compression force, which leads to superior migration of the humeral head and loss of stability. A novel idea of using the magnetic force to achieve shoulder stabilization in massive rotator cuff tears (MRCTs) was considered because the magnets can stabilize two separate entities with an attraction force. This study aimed to investigate the biomechanical effect of the magnetic force on shoulder stabilization in MRCTs. Methods: Seven fresh frozen cadaveric specimens were used with a customized shoulder testing system. Three testing conditions were set up: condition 1, intact rotator cuff without magnets; condition 2, an MRCT without magnets; condition 3, an MRCT with magnets. For each condition, anterior-posterior translation, superior translation, superior migration, and subacromial contact pressure were measured at 0°, 30°, and 60° of abduction. The abduction capability of condition 2 was compared with that of condition 3. Results: The anterior-posterior and superior translations increased in condition 2; however, they decreased compared to condition 2 when the magnets were applied (condition 3) in multiple test positions and loadings (p <0.05). Abduction capability improved significantly in condition 3 compared with that in condition 2, even for less deltoid loading (p < 0.05). Conclusions The magnet biomechanically played a positive role in stabilizing the shoulder joint and enabled abduction with less deltoid force in MRCTs. However, to ensure that the magnet is clinically applicable as a stabilizer for the shoulder joint, it is necessary to thoroughly verify its safety in the human body and to conduct further research on technical challenges.

OBJECTIVE: Low back pain, caused intervertebral disc degeneration has been treated by thermal annuloplasty procedure, which is a non-surgical treatement. The theoretical backgrounds of the annuloplasty are thermal destruct of nociceptor and denaturization of collagen fiber to induce contraction, to shrink annulus and thus enhancing stability. This study is about temperature and its distribution during thermal annuloplasty using 1414 nm Nd : YAG laser. METHODS: Thermal annuloplasty was performed on fresh human cadaveric lumbar spine with 20 intact intervertebral discs in a 37℃ circulating water bath using newly developed 1414 nm Nd : YAG laser. Five thermocouples were attached to different locations on the disc, and at the same time, temperature during annuloplasty was measured and analyzed. RESULTS: Thermal probe's temperature was higher in locations closer to laser fiber tip and on lateral locations, rather than the in depth locations. In accordance with the laser fiber tip and the depth, temperatures above 45.0℃ was measured in 3.0 mm depth which trigger nociceptive ablation in 16 levels (80%), in accordance with the laser fiber end tip and laterality, every measurement had above 45.0℃, and also was measured temperature over 60.0℃, which can trigger collagen denaturation at 16 levels (80%). CONCLUSION: When thermal annuloplasty is needed in a selective lesion, annuloplasty using a 1414 nm Nd : YAG laser can be one of the treatment options.
Baths ; Cadaver* ; Collagen ; Humans ; Intervertebral Disc Degeneration ; Intervertebral Disc* ; Lasers, Solid-State ; Low Back Pain ; Nociceptors ; Spine ; Water

OBJECTIVE: When the pedicle screw insertion technique is failed or not applicable, C7 intralaminar screw insertion method has been used as an alternative or salvage fixation method recently. However, profound understanding of anatomy is required for safe application of the bilaterally crossing laminar screw at C7 in clinic. In this cadaveric study, we evaluated the anatomic feasibility of the bilateral crossing intralaminar screw insertion and especially focused on determination of proper screw entry point. METHODS: The C7 vertebrae from 18 adult specimens were studied. Morphometric measurements of the mid-laminar height, the minimum laminar thickness, the maximal screw length, and spino-laminar angle were performed and cross-sectioned vertically at the screw entry point (spino-laminar junction). The sectioned surface was equally divided into 3 parts and maximal thickness and surface area of the parts were measured. All measurements were obtained bilaterally. RESULTS: The mean mid-laminar height was 13.7 mm, mean minimal laminar thickness was 6.6 mm, mean maximal screw length was 24.6 mm, and mean spinolaminar angle was 50.8+/-4.7degrees. Based on the measured laminar thickness, the feasibility of 3.5 mm diameter intralaminar screw application was 83.3% (30 sides laminae out of total 36) when assuming a tolerance of 1 mm on each side. Cross-sectional measurement results showed that the mean maximal thickness of upper, middle, and lower thirds was 5.0 mm, 7.5 mm, and 7.3 mm, respectively, and mean surface area for each part was 21.2 mm2, 46.8 mm2, and 34.7 mm2, respectively. Fourteen (38.9%) sides of laminae would be feasible for 3.5 mm intralaminar screw insertion when upper thirds of C7 spino-laminar junction is the screw entry point. In case of middle and lower thirds of C7 spino-laminar junction, 32 (88.9%) and 28 (77.8%) sides of laminae were feasible for 3.5 mm screw insertion, respectively. CONCLUSION: The vertical cross-sectioned area of middle thirds at C7 spinolaminar junction was the largest area and 3.5 mm screw can be accommodated with 77.8% of feasibility when lower thirds were the screw entry point. Thus, selection of middle and lower thirds for each side of screw entry point in spino-laminar junction would be the safest way to place bilateral crossing laminar screw within the entire lamina. This anatomic study result will help surgeons to place the screw safely and accurately.
Adult ; Cadaver* ; Humans ; Spine

We present a case of angiographically confirmed transection of the cisternal segment of the anterior choroidal artery (AChA) associated with a severe head trauma in a 15-year old boy. The initial brain computed tomography scan revealed a diffuse subarachnoid hemorrhage (SAH) and pneumocephalus with multiple skull fractures. Subsequent cerebral angiography clearly demonstrated a complete transection of the AChA at its origin with a massive extravasation of contrast medium as a jet trajectory creating a plume. We speculate that severe blunt traumatic force stretched and tore the left AChA between the internal carotid artery and the optic tract. In a simulation of the patient's brain using a fresh-frozen male cadaver, the AChA is shown to be vulnerable to stretching injury as the ipsilateral optic tract is retracted. We conclude that the arterial injury like an AChA rupture should be considered in the differential diagnosis of severe traumatic SAH.
Angiography ; Arteries* ; Brain ; Cadaver ; Carotid Artery, Internal ; Cerebral Angiography ; Choroid* ; Craniocerebral Trauma ; Diagnosis, Differential ; Humans ; Male ; Pneumocephalus ; Rupture ; Skull Fractures ; Subarachnoid Hemorrhage ; Subarachnoid Hemorrhage, Traumatic* ; Visual Pathways

OBJECTIVE: To compare two testing protocols for evaluating range of motion (ROM) changes in the preloaded cadaveric spines implanted with a mobile core type Charite(TM) lumbar artificial disc. METHODS: Using five human cadaveric lumbosacral spines (L2-S2), baseline ROMs were measured with a bending moment of 8 Nm for all motion modes (flexion/extension, lateral bending, and axial rotation) in intact spine. The ROM was tracked using a video-based motion-capturing system. After the Charite(TM) disc was implanted at the L4-L5 level, the measurement was repeated using two different methods : 1) loading up to 8 Nm with the compressive follower preload as in testing the intact spine (Load control protocol), 2) loading in displacement control until the total ROM of L2-S2 matches that when the intact spine was loaded under load control (Hybrid protocol). The comparison between the data of each protocol was performed. RESULTS: The ROMs of the L4-L5 arthroplasty level were increased in all test modalities (p < 0.05 in bending and rotation) under both load and hybrid protocols. At the adjacent segments, the ROMs were increased in all modes except flexion under load control protocol. Under hybrid protocol, the adjacent segments demonstrated decreased ROMs in all modalities except extension at the inferior segment. Statistical significance between load and hybrid protocols was observed during bending and rotation at the operative and adjacent levels (p < 0.05). CONCLUSION: In hybrid protocol, the Charite(TM) disc provided a relatively better restoration of ROM, than in the load control protocol, reproducing clinical observations in terms of motion following surgery.
Arthroplasty ; Cadaver ; Chimera ; Displacement (Psychology) ; Humans ; Range of Motion, Articular ; Spine ; Track and Field

OBJECTIVE: The goal of this study was to evaluate the biomechanical features of human cadaveric spines implanted with the Activ L prosthesis. METHODS: Five cadaveric human lumbosacral spines (L2-S2) were tested for different motion modes, i.e. extension and flexion, right and left lateral bending and rotation. Baseline measurements of the range of motion (ROM), disc pressure (DP), and facet strain (FS) were performed in six modes of motion by applying loads up to 8 Nm, with a loading rate of 0.3 Nm/second. A constant 400 N axial follower preload was applied throughout the loading. After the Activ L was implanted at the L4-L5 disc space, measurements were repeated in the same manner. RESULTS: The Activ L arthroplasty showed statistically significant decrease of ROM during rotation, increase of ROM during flexion and lateral bending at the operative segment and increase of ROM at the inferior segment during flexion. The DP of the superior disc of the operative site was comparable to those of intact spine and the DP of the inferior disc decreased in all motion modes, but these were not statistically significant. For FS, statistically significant decrease was detected at the operative facet during flexion and at the inferior facet during rotation. CONCLUSION: In vitro physiologic preload setting, the Activ L arthroplasty showed less restoration of ROM at the operative and adjacent levels as compared with intact spine. However, results of this study revealed that there are several possible theoretical useful results to reduce the incidence of adjacent segment disease.
Arthroplasty ; Biomechanics ; Cadaver ; Humans ; Incidence ; Prostheses and Implants ; Range of Motion, Articular ; Spine ; Sprains and Strains

OBJECTIVE: The aims of this study were to present the newly developed pedicle guidance system for minimally invasive pedicle screw fixation under endoscopic visualization and to evaluate the feasibility, safety, and efficacy of this device. METHODS: The authors designed a special guidance device that allows a pedicle screw to be inserted with ease and accuracy under endoscopic visualization. The system consists of a bone biopsy needle (Jamshidi type needle), fiducial pins, a pushing trocar, retriever, specialized awls, and probes. After making an inch-long paramedian skin incision, the bone biopsy needle was percutaneously inserted into the pedicle, as in vertebroplasty, and the fiducial pin was inserted through the needle after removing the inner cannula. The fiducial pin was advanced into the vertebral body until the threaded distal end was positioned 1-2 cm away from the posterior bony structure. The biopsy needle was removed, leaving the fiducial pin in position. The operative wound was then dilated with a step dilator, a tubular retractor was introduced, and an endoscope was placed. Decompressive laminectomy and interbody fusion were then performed. A tubular retractor was repositioned in order to visualize the fiducial pins. A cannulated awl was used to create a hole over the fiducial pin. The pedicle trajectory was prepared using a cannulated probe, and a pedicle screw was inserted under fluoroscopic and endoscopic guidance. RESULT: Fifteen patients underwent surgery using this method. In all cases, the screws were safely inserted without misplacement. The overall operative time ranged from 180 min to 260 min (mean 219.3 min). There were no procedure related complications. CONCLUSION: This newly designed device proved to be practical, time saving, and useful for endoscope-assisted pedicle screw fixation.
Biopsy ; Catheters ; Endoscopes ; Endoscopy ; Humans ; Laminectomy ; Lumbar Vertebrae ; Needles ; Operative Time ; Skin ; Spinal Fusion ; Surgical Instruments ; Vertebroplasty

OBJECTIVE: Expandable cage used for spinal reconstruction after corpectomy has several advantages over nonexpendable cages. Here we present our clinical experience with the use of this cage after anterior column corpectomy with an average of one year follow up. METHODS: Ten patients underwent expandable cage reconstruction of the anterior column after single-level or multilevel corpectomy for various cervical spinal disorders. Anterior plating with or without additional posterior instrumentation were performed in all patients. Functional outcomes, complications, and radiographic outcomes were determined. RESULTS: There was no cage-related complication. Functionally, neurological examination revealed improvement in 7 of 10 patients and no patient had neurological deterioration after the surgery. Immediate stability was achieved and maintained throughout the period of follow-up. There was minimal subsidence (<2mm) noticeable in three of the cases that underwent a two-level corpectomy. Subsidence was noted in osteoporotic patients and patients undergoing multi-level corpectomies. Average pre-operative kyphotic angle was 9 degrees. This was corrected to an average of 5.4 degrees in lordosis postoperatively. CONCLUSION: In conclusion, expandable cages are safe and effective devices for vertebral body replacement after cervical corpectomy when used in combination with anterior plating with or without additional posterior stabilization. The advantages of using expandable cages include its ability to easily accommodate itself into the corpectomy defect, its ability to tightly purchase into the endplates after expansion and thus minimizing the potential for migration, and finally, its ability to correct kyphosis deformity via its in vivo expansion properties.
Animals ; Congenital Abnormalities ; Follow-Up Studies ; Humans ; Kyphosis ; Lordosis ; Neurologic Examination ; Spinal Fusion ; Spine*

OBJECTIVE: The biomechanical stabilities between the anterior plate fixation after anterior discectomy and fusion (ACDFP) and the posterior transpedicular fixation after ACDF(ACDFTP) have not been compared using human cadaver in bilateral cervical facet dislocation. The purpose of this study is to compare the stability of ACDFP, a posterior wiring procedure after ACDFP(ACDFPW), and ACDFTP for treatment of bilateral cervical facet dislocation. METHODS: Ten human spines(C3-T1) were tested in the following sequence: the intact state, after ACDFP(Group 1), ACDFPW(Group 2), and ACDFTP(Group 3). Intervertebral motions were measured by a video-based motion capture system. The range of motion(ROM) and neutral zone(NZ) were compared for each loading mode to a maximum of 2.0Nm. RESULTS: ROMs for Group 1 were below that of the intact spine in all loading modes, with statistical significance in flexion and extension, but NZs were decreased in flexion and extension and slightly increased in bending and axial rotation without significances. Group 2 produced additional stability in axial rotation of ROM and in flexion of NZ than Group 1 with significance. Group 3 provided better stability than Group 1 in bending and axial rotation, and better stability than Group 2 in bending of both ROM and NZ. There was no significant difference in extension modes for the three Groups. CONCLUSION: ACDFTP(Group 3) demonstrates the most effective stabilization followed by ACDFPW(Group 2), and ACDFP(Group 1). ACDFP provides sufficient strength in most loading modes, ACDFP can provide an effective stabilization for bilateral cervical facet dislocation with a brace.
Braces ; Cadaver ; Diskectomy ; Dislocations* ; Humans ; Spine

This paper reviews the mechanisms of brachial plexus injury which includes the traumatic: stretch/contusions with or without avulsion, gunshot wounds(GSWs) and lacerations and the nontraumatic from tumors and the various etiologies of thoracic outlet syndrome(TOS). Another type of brachial plexus injury is that of obstetrical birth injury. The paper also reviews the anatomy of the brachial plexus and operative approaches with the anterior approach used in the majority of cases. The posterior subscapular approach with resection of the first rib is occasionally used for tumor resection, GSWs of the lower roots and trunk and the majority of patients with TOS. Surgical techniques and their indications in brachial plexus surgery are presented including nerve action potential(NAP) recording, neurolysis, end-to-end suture anastomosis repair and graft repair including split-repair. The mechanisms of brachial plexus injury are individually reviewed and results for each type of repair of same from the Louisiana State University Health Sciences Center(LSUHSC) experience with 1, 019 patients between 1968-1998 are summarized. There were 509 (49%) stretch/contusion injuries, which was the majority lesion followed in number by brachial plexus GSWs (12%) and lacerations (7%). Nontraumatic brachial plexus injuries included tumors (16%) and TOS (16%). Obstetrical brachial plexus injury though not included with the 1, 019 patients presented in a paper by Kim and Kline et al (J Neurosurg 98: 1005-1016, 2003) are presented and the LSUHSC experience with these are included as well.
Birth Injuries ; Brachial Plexus* ; Humans ; Lacerations ; Louisiana ; Ribs ; Sutures ; Transplants