Accurate prediction of spontaneous lumbar curve correction following posterior selective thoracic fusion in adolescent idiopathic scoliosis using logistic regression models and clinical rationale.

INTRODUCTION: Accurate prediction of spontaneous lumbar curve correction (SLCC) after selective thoracic fusion (STF) remains difficult. This study sought to improve prediction accuracy of SLCC. The hypothesis was preoperative and intraoperative variables could predict SLCC < 20°. METHODS: A multicenter observational prospective analysis was conducted to determine predictors of SLCC in AIS patients that had posterior STF. Curve types included major thoracic curves (Lenke 1, 3-4).The primary outcome variable was to establish prediction models, and a postoperative lumbar curve (LC) ≤ 20° was defined as the target variable. Multivariate logistic regression models were established to study the relationship between selected variables and a LC ≤ 20° versus a LC > 20° at ≥ 2-year follow-up. Single and dual thresholds models in perspective of clinical rationales were applied to find models with the highest positive/negative predictive values (PPV/NPV). The secondary outcome measure was SRS scores at ≥ 2-year follow-up. RESULTS: 410 patients were included. At ≥ 2-year follow-up 282 patients had LC ≤ 20°. These patients had better SRS-22 scores than those with LC > 20° (P = 0.02). The postoperative LC and LC ≤ 20° were predicted by preoperative LC and LC-bending Cobb angle (P < 0.01, r = 0.4-0.6). Logistic regression models could be established to identify patients at risk for failing the target LC ≤ 20°.For preoperative LC and LC-bending, the prediction model achieved a NPV/PPV of 80%/72%. If the postoperative main thoracic curve is combined with the preoperative LC and a gray area for difficult decisions was allowed, model accuracy could even be improved (NPV/PPV = 96%/81%). CONCLUSION: An accurate prediction model for postoperative SLCC was established based on a large analysis of prospective STF cases. These models can support prediction and understanding of postoperative SLCC aiding in surgical decision making when contemplating a selective thoracic fusion. These slides can be retrieved under Electronic Supplementary Material.

Titanium elastic nailing of fractures of the femur in children. Predictors of complications and poor outcome.

Between 1996 and 2003 six institutions in the United States and France contributed a consecutive series of 234 fractures of the femur in 229 children which were treated by titanium elastic nailing. Minor or major complications occurred in 80 fractures. Full information was available concerning 230 fractures, of which the outcome was excellent in 150 (65%), satisfactory in 57 (25%), and poor in 23 (10%). Poor outcomes were due to leg-length discrepancy in five fractures, unacceptable angulation in 17, and failure of fixation in one. There was a statistically significant relationship (p = 0.003) between age and outcome, and the odds ratio for poor outcome was 3.86 for children aged 11 years and older compared with those below this age. The difference between the weight of children with a poor outcome and those with an excellent or satisfactory outcome was statistically significant (54 kg vs 39 kg; p = 0.003). A poor outcome was five times more likely in children who weighed more than 49 kg.

Spinal lordosis with marked opisthotonus secondary to dystonia musculorum deformans: case report with surgical management.

STUDY DESIGN: A case report of severe spinal lordosis with marked opisthotonus and retrocollis secondary to dystonia musculorum deformans is presented. OBJECTIVE: To describe a case of dystonia musculorum deformans with progressive spinal lordosis and its surgical treatment. SUMMARY OF BACKGROUND DATA: Four patients with correction of coronal spinal deformity associated with dystonia musculorum deformans have been reported in the literature. No reports of sagittal spinal deformity treated with surgical instrumentation and fusion were found. METHODS: A retrospective chart and radiographic review of a single case was conducted. RESULTS: Orthotic management and pharmacologic therapy with botulinum toxin injections were unsuccessful in controlling the deformity. Severe spinal lordosis (170 degrees ) from occiput to sacrum was corrected surgically, allowing an upright posture. CONCLUSION: Dystonia musculorum deformans is a rare condition resulting in coronal or sagittal plane deformities. When other treatment methods are unsuccessful, surgical instrumentation and arthrodesis may correct the deformity and improve function.

Ender nail fixation of pediatric femur fractures: a biomechanical analysis.

SUMMARY: Biomechanical testing was performed to determine the effects of flexible intramedullary nail fixation on simulated transverse and comminuted midshaft femur fractures using two Ender nails. A synthetic adolescent-size femur model was used. The axial and rotational stiffness values for the simulated comminuted fracture were equivalent to those of the transverse fracture under "touch-down weight-bearing" loads. These data suggest that length and rotational control of comminuted midshaft femur fractures with two divergent Ender nails may be sufficient for early mobilization.

Defining the pediatric spinal thoracoscopy learning curve: sixty-five consecutive cases.

STUDY DESIGN: Consecutive case prospective chart and radiographic review. OBJECTIVES: The purpose of this study was to define the learning curve of spinal thoracoscopy. SUMMARY OF BACKGROUND DATA: Thoracoscopy is an alternative to open thoracotomy in the treatment of pediatric spinal deformity. The learning curve for spinal thoracoscopy has not been described. METHODS: In this prospective study 65 consecutive cases of thoracoscopic anterior release with discectomy and fusion performed by one surgeon for the treatment of pediatric spinal deformity were reviewed. The patients were, on average, 14 +/- 3 years old and had the following diagnoses: idiopathic scoliosis (n = 13), Scheuermann's kyphosis (n = 9), neuromuscular spinal deformity (n = 35), congenital scoliosis (n = 4), and tumor/syrinx (n = 4). RESULTS: The average operative time for the thoracoscopic procedure was 161 +/- 41 minutes (range, 50-240 minutes). There was a slight decrease in the average operative time as the series progressed. The average number of discs excised was 6.5 +/- 1.5 (range, 3-10), and the number increased as the series progressed. The average operative time per disc was 29.3 +/- 7.7 minutes in the first 30 patients compared with 22.3 +/- 4.7 minutes in the next 35 patients (P < 0.01). The average blood loss during the thoracoscopic procedure was 301 +/- 322 mL (range, 25-2000 mL) and did not decrease as the series progressed. Initial postoperative scoliosis and kyphosis corrections were 59% +/- 17% and 92% +/- 12%, respectively. Complications occurred in six patients (cases 4, 8, 17, 31, 39, and 46) and were evenly distributed throughout the series. CONCLUSIONS: The learning curve for thoracoscopy is substantial, but not prohibitive. This technique provides a safe and effective alternative to thoracotomy in the treatment of pediatric spinal deformity.

Anesthesia of six-week-old New Zealand White rabbits for thoracotomy.

Many methods of administering surgical anesthesia to rabbits have been described. We are studying the effects of anterior thoracic spinal procedures on the growth of young rabbit spines. We introduce a method for intubation using direct laryngoscopy without the need for specially manufactured or costly equipment and for administration of anesthesia applicable to six-week-old New Zealand White (NZW) rabbits. Induction of anesthesia was initiated with 5% isoflurane in a sealed plastic anesthesia box. No premedication was given. We performed direct laryngoscopy by using an otoscope. Under direct visualization, a 5-French polypropylene catheter was passed through the speculum of the otoscope and advanced through the vocal cords. The endotracheal tube without the adapter then was advanced over this guide. A vigorous cough reflex was noted as the tube passed through the vocal cords. We have found this cough reflex to be a very reliable indicator of correct placement. Throughout the surgical procedure, anesthesia was maintained with isoflurane delivered from a standard small-animal anesthetic machine using pediatric breathing hoses, y-piece, and ventilator. Recovery after surgery was rapid.

Hemodilution as a method to reduce transfusion requirements in adolescent spine fusion surgery.

STUDY DESIGN: A case-control study. OBJECTIVES: 1) To determine if hemodilution adequately meets the transfusion needs in children who undergo posterior spinal fusion for idiopathic scoliosis and 2) to compare the efficacy of the various methods used to reduce the risk of allogeneic blood transfusion at the authors' institution. SUMMARY OF BACKGROUND DATA: Methods to reduce blood loss and avoid allogeneic blood transfusion caused by extensive spinal surgery in adolescents include 1) autologous blood predonation, 2) controlled hypotensive anesthesia, 3) intraoperative salvage of shed blood (cell saver), 4) acute normovolemic hemodilution, and 5) transfusion decisions by clinical judgment rather than by a preset value of hemoglobin. Although all methods have some efficacy, it is not clear which methods, separate or combined, are best in the adolescent scoliosis population. METHODS: Hemodilution, hypotensive anesthesia, and cell saver were used in 43 children between June 1996 and July 1997. A comparison group (43 children) underwent similar surgery with hypotensive anesthesia and cell saver, but no hemodilution (between July 1995 and December 1996). These two groups were similar with respect to means of age, levels of instrumentation, magnitude of curvature, estimated blood volume, mean arterial pressure, duration of surgery, duration of anesthesia, estimated blood loss, volume returned from cell saver, volume in the hemovac drain, and length of hospitalization. The groups differed in preoperative hemoglobin and hematocrit and in volume of crystalloid used. RESULTS: Transfusions were given to 34 of 43 patients (79%) in the nonhemodilution group. These patients received 61 units of packed cells (57 autologous, 2 donor directed, and 2 allogeneic). In comparison, 16 of 43 patients (37%) in the hemodilution group required transfusion. They received 16 units of packed cells (15 autologous and 1 allogeneic). There was no significant difference between the groups with respect to postoperative hemoglobin and hematocrit immediately after surgery (hemodilution, 10.2/29.2; nonhemodilution, 10.0/29.1), postoperative day 1 (hemodilution, 9.2/26.9; nonhemodilution, 9.2/27.3), and postoperative day 2 (hemodilution 9.0/26.4; nonhemodilution, 9.2/27.1). There were non complications related to the technique of hemodilution in the 43 patients of this group. Cell saver was used in all patients, but sufficient volume to return blood to the patient was available in only 23 hemodilution patients (mean volume, 230 mL) and 25 nonhemodilution patients (mean volume, 215 mL). In only two patients of each group (< 5%) did the volume returned prevent the absolute need for additional transfusions. CONCLUSIONS: Hemodilution was safely used as a method to satisfy the perioperative transfusion requirements of adolescents undergoing extensive spinal surgery. By allowing patients to arrive at surgery with a higher preoperative hemoglobin and hematocrit, and by decreasing the quantity of predonated autologous blood-collected and therefore used, the hemodilution method may indirectly decrease the quantity of postoperative autologous transfusions in this population. Cell saver was not shown to be effective, and its selective use is recommended.

A biomechanical comparison of open and thoracoscopic anterior spinal release in a goat model.

STUDY DESIGN: A biomechanical assessment of anterior release and discectomy in the thoracic spine was performed on an animal model using thoracoscopic and open thoracotomy techniques. OBJECTIVES: To compare the relative efficacy of these two techniques of release in achieving increased spinal mobility. BACKGROUND DATA: The clinical use of video-assisted thoracoscopy in the correction of spinal deformity is increasing. The effectiveness of thoracoscopic anterior spinal release with discectomy has not been evaluated biomechanically. METHODS: Anterior release with discectomy was performed on six midthoracic motion segments in five mature goats. The thoracoscopic technique was used for three levels on one side, and an open thoracotomy was used for the alternating three levels of the contralateral side. The duration of surgery for disc excision and the amount of blood loss for each technique were recorded. The intact cranial and caudal motion segments served as controls. The motion segments were individually subjected to nondestructive biomechanical testing. Torsional, sagittal, and coronal bending torques were applied, and the resulting angular displacement was measured. RESULTS: The duration of surgery to remove a disc thoracoscopically decreased as experience was gained by the surgeon. The amount of intraoperative blood loss was comparable using the two methods. There was significantly increased flexibility in the released segments with both techniques, compared with the flexibility in the intact levels for all three loading directions. There was no difference in the motion obtained after release between the two techniques. CONCLUSION: Open and thoracoscopic anterior release and discectomy have been demonstrated, through biomechanical in vitro testing, to increase the flexibility of the spine to a similar extent.

Anterior release and fusion in pediatric spinal deformity. A comparison of early outcome and cost of thoracoscopic and open thoracotomy approaches.

STUDY DESIGN: A consecutive series of patients undergoing thoracoscopic anterior spinal release and fusion for scoliosis or kyphosis was compared with a consecutive series of patients treated with an open thoracotomy approach. OBJECTIVES: To compare the early clinical results, costs, and charges of performing an anterior thoracic spinal release and fusion with the two approaches. SUMMARY OF BACKGROUND DATA: The thoracoscopic approach to the spine is gaining acceptance, yet there are little data comparing the technique with standard open methods for the treatment of spinal deformity. METHODS: The first 14 thoracoscopic cases performed at the authors' hospital were compared with 18 open thoracotomy cases treated during the previous 12-month period. In each case the discs were excised and bone grafted before performing a posterior fusion. The early clinical outcomes and the hospital charges/costs were analyzed. RESULTS: The percent curve correction was similar between the thoracoscopic and open methods: scoliosis 56% and 60%, respectively; kyphosis, 88% and 94%, respectively. The blood loss and complication rates were similar between the two groups; however, the chest tube output was greater in the thoracoscopic group. The length of hospital stay was not reduced, and the cost of the open procedure is 29% less than the thoracoscopic approach. The minimally invasive thoracoscopic approach avoids cutting the chest/shoulder musculature, greatly decreasing the morbidity of anterior spinal surgery. CONCLUSIONS: The thoracoscopic technique is a safe and effective alternative to open thoracotomy in the approach to the anterior thoracic spine for the treatment of pediatric and adolescent spinal deformity.

Analysis and treatment of poor outcomes following in situ arthrodesis in adolescent spondylolisthesis.

In situ lumbosacral arthrodesis in the treatment of adolescent spondylolisthesis was evaluated in 39 patients. The clinical outcome an average of 4.7 years later was considered excellent or good in 82% of the cases based on their pain and gait. The quality of the fusion mass correlated with outcome. Those patients with the most severe kyphosis (slip angle) had the greatest chance of a poor result. Four patients required reoperation for pseudarthrosis or symptomatic compression of the cauda equina. Three of these were successfully treated with repeat arthrodesis or decompression with sacroplasty or both.

The use of modified Neufeld's skeletal traction in children and adolescents.

A modified form of Neufeld's skeletal traction is described. This technique is a useful method of treating children and adolescents with femoral or pelvic fractures. The advantage over standard femoral skeletal traction is early mobilization of the patient to a sitting position. Additionally, the patient can be placed in this form of traction at home, allowing earlier discharge from the hospital.

Immobilization of the knee joint alters the mechanical and ultrastructural properties of the rabbit anterior cruciate ligament.

The effects of immobilization of the knee joint on the mechanical and ultrastructural properties of the anterior cruciate ligament have not been well documented. Our goal was to determine these effects in a rabbit model and to assess the effect of knee flexion angle during immobilization. The knee joint was immobilized in either 170 degrees or 105 degrees of flexion, and new methodologies were utilized to determine the mechanical properties of the anterior cruciate ligament. In specimens from knees that had been immobilized, the cross-sectional area of the ligament was 74% of the control value. The stress-strain curve was altered slightly, and the strain at failure increased 32-40%. The modulus and stress at failure did not decrease significantly. There was no significant difference between the mechanical properties of the knees immobilized at 170 degrees and 105 degrees of flexion. Histological and ultrastructural evaluation demonstrated changes in the shape and intracellular make-up of the fibroblasts from the ligament after immobilization. This cellular response may account for the alterations in the mechanical properties of the anterior cruciate ligament.

Financial aspects of femoral shaft fracture treatment in children and adolescents.

The billing records of 58 children and adolescents with femoral shaft fractures treated during 1990 were analyzed. The treatment groups included early spica casting, skin traction, skeletal traction, home traction, and intramedullary rodding. The medical charges included both the hospital and physician (orthopedist, radiologist, and anesthesiologist) components. The total charges were lowest for the early spica group ($5,494) and highest for the skeletal traction and intramedullary rodding groups ($21,093 and $21,359, respectively). Both skin traction and home Neufeld traction were associated with significant savings over in-hospital skeletal traction and intramedullary rodding. With the continually rising cost of health care, it is the responsibility of the physician to know the charges for various treatment options.

Morphologic and biomechanical comparison of tendons used as free grafts.

The palmaris longus (n = 10), plantaris (n = 11), and extensor digitorum longus (n = 10) tendons were harvested from cadaver limbs for morphologic and biomechanical comparisons. Eleven flexor digitorum profundus tendons from the index finger were also harvested for comparison of biomechanical properties of the free graft tendons with those of a typical digital flexor. Maximal tendon length, cross-sectional area, volume, stiffness, and modulus of elasticity were determined by measurement, laser micrometry, and tensile testing. The plantaris and extensor digitorum longus yielded the longest grafts, 334 and 325 mm, respectively, compared with the palmaris longus, which yielded only 161 mm of length. Cross-sectional areas were as follows: palmaris longus, 3.1 mm2; plantaris, 1.4 mm2; extensor digitorum longus, 3.3 mm2; and flexor digitorum profundus, 10.6 mm2. Mean volumes were as follows: palmaris longus, 529 mm3; plantaris, 557 mm3; and extensor digitorum longus, 1006 mm3. The palmaris longus and the extensor digitorum longus showed greater stiffness, 42.0 and 47.8 N/mm, respectively, than the plantaris, which had a stiffness of 25.5 N/mm. However, the flexor digitorum profundus showed significantly greater stiffness than all of the graft tendons. The modulus of elasticity ranged from 1161.6 to 1673.0 MPa, with no significant difference between tendons tested. The findings in this study provide data that may be useful in the selection of a specific donor for free tendon grafting.

A comparative evaluation of the mechanical properties of the rabbit medial collateral and anterior cruciate ligaments.

The biomechanical properties of the medial collateral and anterior cruciate ligaments from 30 New Zealand White rabbits were measured. Because of its complex geometry, the ACL was divided into two portions (medial and lateral) to provide uniform loading. This allowed an examination of the intra-ligamentous properties. A laser micrometer system was used to measure the cross-sectional area for tensile stress and a video dimension analyzer was used to measure the strain. The mechanical properties (stress-strain curves) of the MCL and ACL were different, with the modulus (determined between 4 and 7% strain) in the MCL (1120 +/- 153 MPa) more than twice that of either portion of the ACL (516 +/- 64 and 516 +/- 69 MPa for the medial and lateral portions, respectively). This higher modulus correlated with the more uniform and dense appearance of the collagen fibrils examined with scanning electron microscopy (SEM).

Ultrastructural morphometry of anterior cruciate and medial collateral ligaments: an experimental study in rabbits.

This study presents morphometric analyses of collagen subfascicle area fraction and collagen fibril diameter distributions for the anterior cruciate (ACL) and medial collateral (MCL) knee ligaments from transmission electron micrographs of ligament cross sections of five mature, female New Zealand White rabbits. Statistically significant differences in subfascicular area fractions were found between the ACL and MCL (0.89 +/- 0.02, 0.97 +/- 0.01, respectively; p less than 0.001). Mean fibril diameters for the ACL and MCL were also significantly different (0.059 +/- 0.005, 0.085 +/- 0.011 microns, respectively; p less than 0.025). Fibril eccentricity (a measure of parallel alignment of collagen fibrils within the ligaments, defined as the ratio of minor to major axes of elliptical fibril outlines) was 0.89 +/- 0.03 and 0.85 +/- 0.08, respectively, for the ACL and MCL; these data were not significantly different (p greater than 0.1). The relative amount of variation in the pooled fibril diameter data due to variation between animals, ligaments, locations within ligaments, and among fibrils at individual locations are reported. The variation of fibril diameter distributions between the ACL and MCL was substantially greater than the variation between different locations within each ligament cross section as well as between different animals. The structural differences reported may help explain known differences in the biomechanical properties of the ACL and MCL.

Evaluation of a new injury model to study medial collateral ligament healing: primary repair versus nonoperative treatment.

The medial collateral ligament (MCL) of the rabbit left hindlimb was ruptured by a rod placed beneath it, resulting in a "mop-end" tear of the ligament substance with simultaneous injury to the insertion sites. Using this model, we compared primary ligament repair and nonoperative treatment using biomechanical and histologic techniques at time zero, 10 days, and 6 and 12 weeks postoperatively. Biomechanical evaluation included measurement of varus-valgus (V-V) knee rotation, in situ load on the MCL, and tensile testing of the femur-MCL-tibia complex (FMTC). The V-V rotation of all experimental knees decreased over time. At 12 weeks, V-V rotation of experimental knees was still 1.3 times larger than that of controls. Primary repair initially decreased V-V rotation, but at 6 and 12 weeks there was no statistical difference between operated and nonoperated knees. The in situ load on the MCL followed the same trends. There was no significant effect of MCL repair on any of the tensile properties. However, postoperative healing time significantly improved the FMTC structural properties in both experimental groups. Failure modes of the FMTCs and histologic sections of the ligament insertion sites indicated that after injury the ligament insertion to bone recovered more slowly than the ligament substance. Tensile testing of the FMTC showed that even at 12 weeks postoperatively the mechanical properties of the healed ligament material remained significantly different from those of the controls.

The use of a laser micrometer system to determine the cross-sectional shape and area of ligaments: a comparative study with two existing methods.

Determination of the tensile stresses in ligaments and tendons during uniaxial loading depends on accurate measurement of the cross-sectional area. In this study, a laser micrometer system was employed to evaluate the cross-sectional shape and area of the medial collateral ligament (MCL) at three locations and anterior cruciate ligament (ACL). In a New Zealand White (NZW) rabbit, morphologic sections of the ligaments were made to verify the cross-sectional shape reconstructed by the laser micrometer system. The areas obtained by the laser micrometer system from ten additional NZW rabbits were compared with those obtained by two other methods commonly used to measure the cross-sectional area of ligaments and tendons: one method uses digital calipers and the other a constant pressure (0.12 MPa) area micrometer. For the MCL, the digital calipers yielded results very similar to those of the laser micrometer, but the constant pressure area micrometer yielded values 20 percent lower. The area measured at the proximal site of the MCL was 13 percent greater than the area measured at the joint line and distal line. For the ACL, the values obtained by the digital calipers and constant pressure area micrometer were 16 and 20 percent lower, respectively. Because of the irregular shape exhibited by the rabbit ACL, the digital calipers could not accurately measure the cross-sectional area. The constant pressure area micrometer yielded lower values for the cross-sectional area of both the MCL and ACL, presumably due to the applied pressure which caused changes in both the cross-sectional shape and area.