Search

Study Design: An in vitro biomechanical human cadaveric study of T1-T12 thoracic specimens was performed with 4 conditions (with and without rib cage, instrumented and uninstrumented) in flexion-extension, lateral bending, and axial rotation., Objective: The objective was to understand the influence of the rib cage on motion and stiffness parameters of the human cadaveric thoracic spine. Hypotheses tested for overall motion in all modes of bending for both uninstrumented and instrumented specimens were (i) in-plane range of motion and neutral and elastic zones will be greater without the rib cage, (ii) neutral and elastic zone stiffness values will be different for specimens without the rib cage, and (iii) out-of-plane rotations will be different for specimens without the rib cage., Summary of Background Data: The rib cage is presumed to provide significant stability to the thoracic spine, but no studies have been conducted to determine the influence of the rib cage in both uninstrumented and instrumented conditions in the full thoracic human cadaveric specimens., Methods: Seven human cadaveric spine specimens (T1-T12) with 4 conditions (with and without rib cage, instrumented and uninstrumented) were subjected to 5 N·m pure moments in flexion-extension, lateral bending, and axial rotation. Range of motion, neutral and elastic zones, neutral and elastic zone stiffness values, and out-of-plane rotations were calculated for the overall specimen., Results: In-plane range of motion was significantly higher without a rib cage for most modes of bending. Out-of-plane motions were also influenced by the rib cage. Neutral zone stiffness was significantly higher with a rib cage present., Conclusion: Testing without a rib cage yields different motion and stiffness measures, directly impacting the translation of research results to clinical interpretation. Researchers should consider these differences when evaluating the mechanical impact of surgical procedures or instrumentation in cadaveric or computational models., Level of Evidence: 5.

Study Design: Computer simulations to analyze the biomechanics of a novel compression-based fusionless device (hemistaple) that does not cross the disc for the treatment of adolescent idiopathic scoliosis., Objective: To biomechanically model, simulate, and analyze the hemistaple action using a human finite element model (FEM)., Summary of Background Data: A new fusionless growth sparing instrumentation device (hemistaple), which locally compresses the growth plate without spanning the disc, was previously developed and successively tested on different animal models., Methods: Patient-specific FEMs of the spine, rib cage, and pelvis were built using radiographs of 10 scoliotic adolescents (11.7 ± 0.9 yr; Cobb thoracic: 35° ± 7°, lumbar: 24° ± 6°). A validated algorithm allowed simulating the growth (0.8-1.1 mm/yr/vertebra) and growth modulation process (Hueter-Volkmann principle) during a period of 2 years. Four instrumentation configurations on the convex curves were individually simulated (Config 1: 5 thoracic vertebrae with hemistaples on superior endplates; Config 2: same as Config 1 with hemistaples on both endplates; Config 3: same as Config 1 + 4 lumbar vertebrae; Config 4: same as Config 2 + 4 lumbar vertebrae)., Results: Without hemistaples, on average the thoracic and lumbar Cobb angles, respectively, progressed from 35° to 56° and 24° to 30°, whereas the vertebral wedging at curve apices progressed from 5° to 12°. With the hemistaple Config 1, the Cobb angles progressed but were limited to 42° and 26°, whereas the wedging ended at 8°. With Config 3, Cobb and wedging were kept nearly constant (38°, 21°, 7°). With hemistaples on both endplates (Config 2, Config 4), the Cobb and wedging were all reduced (thoracic Cobb for Config 2 and 4: 24° and 15°; lumbar Cobb: 21° and 11°; wedging: 2° and 1°)., Conclusion: This study suggests that the hemistaple has the biomechanical potential to control the scoliosis progression and highlights the importance of the instrumentation configuration to correct the spinal deformities. It biomechanically supports the new fusionless device concept as an alternative for the early treatment of idiopathic scoliosis., Level of Evidence: 5.

Background: Thoracic transverse process is an important anatomic structure of the spine. Several anatomic studies have investigated the adjacent structures of the thoracic transverse process. But there is still a blank on the morphology of the thoracic transverse processes. The purpose of the cadaveric study is to investigate the morphology of thoracic transverse processes and to provide morphology basis for the pedicle-rib unit (extrapedicular) screw fixation method., Methods: Forty-five adult dehydrated skeletons (T1-T10) were included in this study. The length, width, thickness, and the tilt angle (upward and backward) of the thoracic transverse process were measured. The data were then analyzed statistically. On the basis of the morphometric study, 5 fresh cadavers were used to place screws from transverse processes to the vertebral body in the thoracic spine, and then observed by the naked eye and on computed tomography scans., Results: The lengths of thoracic transverse processes were between 16.63±1.59 and 18.10±1.95 mm; the longest was at T7, and the shortest was at T10. The widths of thoracic transverse processes were between 11.68±0.80 and 12.87±1.48 mm; the widest was at T3, and the narrowest was at T7. The thicknesses of thoracic transverse processes were between 7.86±1.24 and 10.78±1.35 mm; the thickest was at T1, and the thinnest was at T7. The upward tilt angles of thoracic transverse processes were between 24.9±3.1 and 3.0±1.56 degrees; the maximal upward tilt angle was at T1, and the minimal upward tilt angle was at T7. The upward tilt angles of T1 and T2 were obviously different from the other thoracic transverse processes (P<0.01). The backward tilt angles of thoracic transverse processes gradually increased from 24.5±2.91 degrees at T1 to 64.5±5.12 degrees at T10. The backward tilt angles were significantly different between each other, except between T5 and T6. In the validation study, screws were all placed successfully from transverse processes to the vertebrae of thoracic spine., Conclusions: The length, width, and thickness of the thoracic transverse processes are suitable for screw placement. And the obvious upward and backward tilt angles provide an excellent screw passage from transverse process to the vertebral body. Screw placement from the transverse processes to the vertebral body is feasible in the thoracic spine. However, there is still some place for improvement of the pedicle-rib unit screw fixation method.

Study Design: Cadaver dissection and measurement., Objective: To describe a previously undocumented intracostal ligament that limits the potential space through which the T1 ventral ramus passes before joining the C8 ventral ramus., Summary of Background Data: Preclavicular entrapment of the T1 ventral ramus can lead to radiculopathy, neurogenic thoracic outlet syndrome, or both, the so called "double crush" phenomenon. The usual sites of entrapment include the neural foramen, the interscalene interval, an aberrant cervical rib, the first rib itself, or an apical thoracic mass., Methods: A total of 42 shoulders from 21 embalmed cadavers (13 male, 8 female) were dissected. The presence of the ligament was noted and its anatomic characteristics were measured with digital calipers by 3 independent investigators. Means, ranges, and standard deviations were calculated., Results: The average ligament length was 31.0 mm (SD, 4.3). The ligament was trapezoidal in shape, and wider anteriorly. The mean anterior width was 7.1 mm (SD, 3.8), midsubstance width 3.6 mm (SD, 1.5), and posterior width 3.5 mm (SD, 1.3). The mean thickness was 0.5 mm (SD, 0.3), and the maximal opening through which the T1 nerve passed between the first rib and the ligament was 6.3 mm (SD, 1.6). The ligament was present on at least one side in 81% of individuals (67% of shoulders): 52% bilateral and 29% unilateral., Conclusion: This previously undescribed ligament is a robust structure, present on at least one side in over 80% of the individuals studied. When present, the ligament creates a narrow interval between the ligament and the first rib that the T1 ventral ramus traverses before crossing the first rib superiorly and contributing to the inferior trunk of the brachial plexus. Although the actual clinical significance has not been demonstrated, this ligament may represent another entrapment site for the T1 ventral ramus.

Study Design: Morphology comparisons between the pedicle and pedicle rib unit in the immature spine were conducted through computed tomographic scans., Objective: To establish reference data concerning the dimensions of the pedicle rib unit for normal children., Summary of Background Data: Until recently, studies on extrapedicular fixation were mostly based on adults. No published study has assessed the morphology of the pedicle rib unit in the normal immature population. Establishment of the basic morphometric characteristics may be beneficial in treating immature patients with spinal disorders., Methods: Measurements were carried out on the chest computed tomography scans of the immature Chinese patients without any spinal disorder findings. The width, chord length, and transverse angle of the pedicle rib unit were obtained and compared with the corresponding pedicle index. Difference between sex groups was measured, and significant statistical correlations were carefully studied to determine potentially important clinical relationships., Results: The mean values and the standard deviations obtained for each thoracic segment were determined. The width, chord length, and transverse angle of the pedicle rib unit were significantly larger than corresponding pedicle measurements at all levels. Significant difference for measurements between sexes was found at some segments. Compared with the sex, age seemed to have a more significant effect on the measurements. Linear pedicle and pedicle rib unit dimensions had good correlations with age, whereas the transverse angle seemed to change little with age., Conclusion: Compared with the dimensions of the immature pedicle, the significantly larger size of the corresponding pedicle rib unit provides a more ample space, which accommodates screws with larger diameters. Extrapedicular vertebral body fixation was anatomically feasible for the immature spine. The new procedure should be cautiously applied to avoid potential implant failures or a new deformity because of the growth of the immature spine.

Changes at the sternal extremity of the fourth rib have already been established as reliable indicators of age at death. Still now, the Iscan "phase method," based on the morphologic changes at the sternal extremity of the fourth rib, is one of the best effective for age estimation at death. The present study was carried out to develop an alternative method considering the morphologic characteristics of articular surface (A), anterior/posterior walls (B), and superior/inferior edges (C) of the sternal extremity of the fourth rib. For each parameter a numerical score was assigned and some regression formulae was elaborated. The best correlation between morphologic characteristics and age was obtained through the formula Age = 10.43 (AB)(0.53). The sample consisted of sternal extremities of the fourth rib obtained at autopsy from 49 white males of known age.

Study Design: A cadaver study comparing 3 different minimally invasive approaches to the anterior thoracic spine., Objective: To assess the feasibility of minimally invasive thoracic corpectomy from a posterolateral approach and to compare surgical results from 3 approaches., Summary of Background Data: Traditional posterolateral approaches to the thoracic spine are effective but are associated with a high rate of operative morbidity., Methods: Thoracic corpectomies were performed using a modified tubular retractor starting at 3, 6, and 9 cm off of midline. Postoperative computed tomography scans were performed and analyzed to assess the extent of corpectomy and ventral decompression., Results: From 3 to 6 to 9 cm, a significant difference in extent of corpectomy (65.8%, 81.5%, and 82.6%, P=0.02) and ventral decompression (83.6%, 90.4%, 94.6%, P=0.05) was noted between 3 cm and the more lateral approaches. The 9 cm approach required more rib resection and average working distances of 8.4 to 11.3 cm, which made the procedure more difficult technically and less suited to the length of standard instruments., Conclusions: Minimally invasive thoracic corpectomy is feasible and a 6 cm approach off of midline appears optimal.

Study Design: A case report., Objective: To report the successful nonoperative management of a patient with progressive ankylosing spondylitis who sustained a three-column flexion-distraction injury of the upper thoracic spine with an intact sternal-rib complex, thereby emphasizing the existence and clinical relevance of the fourth-column concept in such patients., Summary of Background Data: Three-column injuries of the cervical and lumbar spine are typically unstable and require surgical stabilization. Patients with ankylosing spondylitis are at an increase risk to sustain three-column injuries of the spine due to their progressive inflammatory disease, a state that renders the spine brittle and alters its biomechanical function. A fourth-column model of the thoracic spine has been proposed and incorporates the sternal-rib complex; however, such a model has rarely been addressed in the literature and its role regarding three-column upper thoracic spine injury with an intact sternal-rib complex in patients with ankylosing spondylitis is unknown. METHODS.: A 68-year-old white man with ankylosing spondylitis and Pickwickian body habitus sustained a three-column flexion-distraction injury at T5 following a ground-level fall. The patient complained of midthoracic back pain; however, he was neurologically intact and ambulated without aids., Results: Because of the patient's numerous active medical issues that substantially increased his perioperative risks combined with symptomatic improvement of his pain, the patient refused surgical stabilization. In addition, because of the patient's body habitus and pulmonary issues, external brace immobilization was not tolerated. At 17 months of follow-up, the patient remained neurologically intact, ambulated well, his midthoracic back pain had subsided, and no progressive kyphosis was noted., Conclusions: This case confirms the existence and clinical relevance of the fourth column of the thoracic spine and its role in providing added spinal stability in the patient with ankylosing spondylitis. As such, it is still possible to achieve a favorable clinical outcome in a select subpopulation of patients with ankylosing spondylitis that sustain three-column flexion-distraction injuries who are neurologically intact and are not candidates for surgical stabilization.

Objectives: To evaluate the usefulness of the method of counting ribs by assessing anatomic variations of the attachments of costal cartilages to the proximal xiphoid., Materials and Methods: From January to September 2005, 224 subjects (136 men, 88 women, age 13 to 89 years, mean age 55 years) underwent computed tomography examination of the chest. Axial images of the chest were obtained on a 16-slice multidetector computed tomography. Counting ribs was performed by using the medial clavicle as an anatomic landmark to identify the first costal cartilage. We analyzed variety and incidence of the attachment patterns of costal cartilages to the proximal xiphoid., Result: Out of the 224 patients, the last costal attachments to the proximal xiphoid were the sixth costal cartilages bilaterally for 2 (0.9%) subjects, one 6th and one 7th for 4 (1.8%) subjects, bilateral seventh for 191 (85.3%) subjects, one 7th and one 8th for 15 (6.7%) subjects, and bilateral eighth for 12 (5.4%) subjects., Conclusions: The method of counting ribs from the proximal xiphoid is inaccurate because the sixth, seventh, and eighth costal cartilages may each attach to the proximal xiphoid.

Background: Although the Trendelenburg position and shoulder bracing are recommended for safe subclavian venipuncture, the optimal shoulder position remains unclear. The current study observed spatial relations between the subclavian vein and surrounding structures using multislice computed tomography to determine optimal shoulder position for safe subclavian venipuncture and then conducted a small follow-up clinical trial to confirm these findings., Methods: Thoracic multislice computed tomography was performed for seven adult volunteers at three shoulder positions: elevated (up); neutral; and lowered caudally (down). Overlap and distance between the clavicle and the subclavian vein and the diameter of the subclavian vein were measured. Anatomical relations between the subclavian artery and vein were also observed. The success rate for subclavian venipuncture was then compared between the up and down shoulder positions in 30 patients., Results: In the multislice computed tomography study, the mean overlap ratios between clavicle and subclavian vein in the up, neutral, and down positions were 33.5, 36.9, and 40.0%, respectively. Overlap increased with lower shoulder position (up < neutral < down; P < 0.05). The mean distances between the clavicle and the subclavian vein in the up, neutral, and down positions were 6.8, 5.0, and 3.6 mm, respectively. Again, distance decreased with lower shoulder position (up < neutral < down; P < 0.05). The diameter of the subclavian vein did not differ among the three shoulder positions. The success rate for subclavian venipuncture was significantly higher in the down position compared with the up position (P = 0.003)., Conclusions: Lowered shoulder position increases both overlap and proximity between the clavicle and the subclavian vein, producing a more constant relation between the clavicle and the subclavian vein, without affecting vein diameter. Proper use of a lowered shoulder position should thus increase the safety and reliability of subclavian venipuncture compared with other shoulder positions.

Catheter pinch-off syndrome is an uncommon and often unrecognized complication of central venous catheters. The cause, clinical diagnosis, and management of this unique catheter occlusion are reviewed. Nurses can play a key role in the early detection of catheter pinch-off syndrome as well as the prevention of subsequent catheter fracture and embolization.

Costochondral grafts are commonly used to restore dysplastic mandibular condyles. Despite their worldwide use, the growth of the condyle-ramus unit constructed with a costochondral graft is highly unpredictable, excess growth being the most common consequential problem. In a recent series of experiments on rats, it became evident that the amount of cartilage, more precisely the amount of germinative cells, in the rib graft has a direct bearing on its growth capacity. In the present study, the histology of the human costochondral junction of growing individuals was examined. It was implicit from the height of the proliferative plus hypertrophic cell zones of the junction that the grafts used clinically have always contained germinative cells, but in variable amounts. Thus the reported growth variability of the condyle-ramus unit may be due to the amount of cartilage included in the grafts.

Objectives: The authors evaluated the reduction of rib prominence in patients who underwent thoracoplasty versus matched control patients who underwent fusion without thoracoplasty., Summary of Background Data: Correction in rib prominence with thoracoplasty is not well quantified in the literature. The role of rib bone graft as an alternative to iliac crest is unknown., Methods: Fifty patients who underwent thoracoplasty were reviewed and compared with 26 patients who underwent fusion without thoracoplasty. Rib prominence, clinical data, and patient outcome were evaluated., Results: The mean reduction in rib prominence was 71% in the thoracoplasty group and 17% in the control group. There was no difference in estimated blood loss, operative time, and length of hospitalization. Satisfaction with thoracoplasty was high., Conclusions: Thoracoplasty is more effective than fusion alone for reduction of rib prominence in thoracic scoliosis; it provides ample, effective bone graft for fusion.

The effects of thoracic epidural anesthesia on the performance of the parasternal intercostal muscles were investigated by measuring electromyographic activity and length changes of the parasternals (EMG activities and length, respectively, of the parasternals) in seven pentobarbital anesthetized, spontaneously breathing dogs. Epidural injection of 0.1 mL/kg of 2% lidocaine decreased tidal volume and minute ventilation during unstimulated breathing. These changes were accompanied by complete abolishment of EMG activities of the parasternals and passive elongation of the parasternals during inspiration. At equivalent end-tidal PCO2 values (70 and 80 mm Hg) during CO2 rebreathing, tidal volume and minute ventilation were lower after epidural block compared to the corresponding values before the block. Thoracic epidural anesthesia impaired contraction of the parasternals and conceivably other respiratory muscles in the rib cage as well and could induce a distortion of the rib cage. The authors conclude that respiratory muscles in the rib cage contribute considerably to the maintenance of ventilation in anesthetized dogs.

Fresh cadaver dissections indicated that the anterior chest approach for obtaining a free osteocutaneous rib graft, based on the anterior intercostal vessels, would be feasible. Following this, a mandibular defect in radiated tissue was successfully repaired in one stage by a free osteocutaneous graft with microvascular anastomoses. A 22-cm segment of rib, with overlying muscle and skin measuring 10 X 30 cm, was transferred. Follow-up, with selective arteriography at 6 months, confirmed the belief that the periosteal blood supply alone could support the rib segment. The anterior chest approach, to obtain a free osteocutaneous rib graft, is easier, faster, and safer than the posterior approach.