An investigation of range of motion preservation in fusionless anterior double screw and cord constructs for scoliosis correction.

PURPOSE: To evaluate the motion-preserving properties of vertebral body tethering with varying cord/screw constructs and cord thicknesses in cadaveric thoracolumbar spines. METHODS: In vitro flexibility tests were performed on six fresh-frozen human cadaveric spines (T1-L5) (2 M, 4F) with a median age of 63 (59-to-80). An ± 8 Nm load was applied to determine range of motion (ROM) in flexion-extension (FE), lateral bending (LB), and axial rotation (AR) in the thoracic and lumbar spine. Specimens were tested with screws (T5-L4) and without cords. Single (4.0 mm and 5.0 mm) and double (4.0 mm) cord constructs were sequentially tensioned to 100 N and tested: (1) Single 4.0 mm and (2) 5.0 mm cords (T5-T12); (3) Double 4.0 mm cords (T5-12); (4) Single 4.0 mm and (5) 5.0 mm cord (T12-L4); (6) Double 4.0 mm cords (T12-L4). RESULTS: In the thoracic spine (T5-T12), 4.0-5.0 mm single-cord constructs showed slight reductions in FE and 27-33% reductions in LB compared to intact, while double-cord constructs showed reductions of 24% and 40%, respectively. In the lumbar spine (T12-L4), double-cord constructs had greater reductions in FE (24%), LB (74%), and AR (25%) compared to intact, while single-cord constructs exhibited reductions of 2-4%, 68-69%, and 19-20%, respectively. CONCLUSIONS: The present biomechanical study found similar motion for 4.0-5.0 mm single-cord constructs and the least motion for double-cord constructs in the thoracic and lumbar spine suggesting that larger diameter 5.0 mm cords may be a more promising motion-preserving option, due to their increased durability compared to smaller cords. Future clinical studies are necessary to determine the impact of these findings on patient outcomes.

Assessing clinical trunk change with surface topography: anterior scoliosis correction as a model to evaluate curve progression.

PURPOSE: Previous work has suggested that surface topography can be used for repeated measurements of deformity during curve monitoring following an initial radiograph. Changes in deformity during natural curve progression may be subtle. An important preemptive question to answer is whether topography can follow a large change in spine deformity, as in scoliosis correction. We assess the ability of surface topography to track the evolution of spine deformity during anterior scoliosis correction relative to traditional radiographs. Anterior scoliosis correction was chosen for this analysis because it changes the shape of the trunk without leaving a surgical scar and muscle atrophy along the posterior spine. METHODS: Following IRB approval, 18 patients aged 14.6 ± 2.0 years at surgery were enrolled in a retrospective review of coronal radiographs and topographic scans acquired before and after scoliosis correction. Radiographic and topographic measures for the coronal curve angle before and after surgery were compared. RESULTS: Surface topography estimates correlate with radiographic measures of the pre- (r = 0.7890, CI = [0.4989 0.9201], p < 0.00001), postsurgical (r = 0.7485, CI = [0.4329 0.9006], p = 0.0004), and the change in the coronal curve angle (r = 0.6744, CI = [0.3028 0.8680], p = 0.0021) due to surgery. CONCLUSIONS: We provide evidence open for further extension that topography can follow changes in the coronal curve angle comparably to radiographs. LEVEL OF EVIDENCE: Level IV.

Progressive double major scoliotic curve with concurrent lumbosacral spondylolisthesis in a skeletally immature patient with Marfan syndrome treated with anterior scoliosis correction.

STUDY DESIGN: Case report (review of patient records, imaging, and pulmonary function tests) and literature review. OBJECTIVES: To describe the case of a skeletally immature patient with Marfan syndrome who underwent anterior scoliosis correction (ASC) and muscle-sparing posterior far lateral interbody fusion (FLIF) in a two-stage procedure to correct progressive severe double major scoliosis and spondylolisthesis. Patients with Marfan syndrome suffer from rapidly progressive scoliosis and spondylolisthesis. Operative treatment has typically been limited to PSF, but newer techniques may be less invasive and provide more spine motion. METHODS: A 12-year-old girl with Marfan syndrome, spondylolisthesis, and severe progressive scoliosis underwent a two-stage procedure to achieve correction. Muscle-sparing posterior FLIF of the spondylolisthesis from L4-S1 was initially performed, followed 1 week later by ASC from right T4-T11 and left T11-L3 using an anterior screw/cord construct. RESULTS: Follow-up from the index procedures for the spondylolisthesis and scoliosis is 35 months. No significant complications occurred in perioperative and postoperative follow-up periods. At the 13-month follow-up, the double major scoliosis showed continued curve correction via growth modulation and overcorrection of the lumbar to - 13°. A revision lengthening procedure of the anterior cord from T11-L3 was performed. An asymptomatic elevated hemidiaphragm was discovered at 6 weeks postoperation, which was believed to be secondary to retraction neuropraxia and subsequently improved. At 21 months postlengthening and 35 months postindex procedure, she is skeletally mature and the curves have maintained correction in both the coronal and sagittal planes without any further complications. CONCLUSIONS: Anterior scoliosis correction of both a thoracic and lumbar curve combined with an L4-S1 PSF was effective for this patient and may be promising for patients with Marfan syndrome, progressive scoliosis, and spondylolisthesis. Overcorrection can be planned for and easily corrected by inserting a new cord of a different length.

Progressive Neuromuscular Scoliosis Secondary to Spinal Cord Injury in a Young Patient Treated With Nonfusion Anterior Scoliosis Correction.

Ninety-eight percent of skeletally immature patients with spinal cord injury (SCI) suffer from progressive neuromuscular scoliosis (NMS). Operative treatment has typically been limited to posterior spinal fusion (PSF), but a newer technique as described may be less invasive and preserve more function. A PSF of the entire spine to the pelvis is standard of care. However, maintenance of spinal flexibility, motion, and potential growth is desirable. We present a case for proof-of-concept of utilizing a surgical motion-preserving technique to treat progressive NMS in an 11year-old girl with T10 level (AIS B) paraplegia with a progressive 60° NMS of the lumbar spine. She had anterior scoliosis correction (ASC) from T11-L5 without fusion. Over 24 months, the curve growth-modulated to a residual of 12° with continued modulation to 7° at 3-year follow-up (skeletal maturity).

Vertebral Body Stapling versus Bracing for Patients with High-Risk Moderate Idiopathic Scoliosis.

PURPOSE: We report a comparison study of vertebral body stapling (VBS) versus a matched bracing cohort for immature patients with moderate (25 to 44°) idiopathic scoliosis (IS). METHODS: 42 of 49 consecutive patients (86%) with IS were treated with VBS and followed for a minimum of 2 years. They were compared to 121 braced patients meeting identical inclusion criteria. 52 patients (66 curves) were matched according to age at start of treatment (10.6 years versus 11.1 years, resp. [P = 0.07]) and gender. RESULTS: For thoracic curves 25-34°, VBS had a success rate (defined as curve progression <10°) of 81% versus 61% for bracing (P = 0.16). In thoracic curves 35-44°, VBS and bracing both had a poor success rate. For lumbar curves, success rates were similar in both groups for curves measuring 25-34°. CONCLUSION: In this comparison of two cohorts of patients with high-risk (Risser 0-1) moderate IS (25-44°), in smaller thoracic curves (25-34°) VBS provided better results as a clinical trend as compared to bracing. VBS was found not to be effective for thoracic curves ≥35°. For lumbar curves measuring 25-34°, results appear to be similar for both VBS and bracing, at 80% success.

Cervical sagittal plane decompensation after surgery for adolescent idiopathic scoliosis: an effect imparted by postoperative thoracic hypokyphosis.

OBJECT: Several studies have characterized the relationship among postoperative thoracic, lumbar, and pelvic alignment in the sagittal plane. However, little is known of the relationship between postoperative thoracic kyphosis and sagittal cervical alignment in patients with adolescent idiopathic scoliosis (AIS) treated with all pedicle screw constructs. The authors examined this relationship and associated factors. METHODS: A prospective database of pediatric patients with AIS undergoing spinal fusion between 2003 and 2005 was reviewed for those who received predominantly pedicle screw constructs for Lenke Type 1 or Type 2 curves. Parameters analyzed on pre- and postoperative radiographs were the fusion levels; cervical, thoracic, and lumbar sagittal balance; and C-2 and C-7 plumb lines. RESULTS: Preoperatively, 6 (Group A) of the 22 patients included in the study had frank cervical kyphosis (mean angle 13.0°) with mean associated thoracic kyphosis of 27.2° (range 16°-37°). Postoperatively, cervical kyphosis (13.0°) remained in the patients in Group A along with mean thoracic kyphosis of 17.7° (range 4°-26°, p < 0.05). Preoperatively, the remaining 16 of 22 patients had neutral to lordotic cervical alignment (mean -13.8°) with thoracic kyphosis (mean 45°, range 30°-76°). Postoperatively, 8 (Group B) of these 16 patients demonstrated cervical sagittal decompensation (> 5° kyphosis), with 6 showing frank cervical kyphosis (10.5°, p < 0.05). In Group B, the mean postoperative thoracic kyphosis was 25.6° (range 7°-49°, p < 0.05). The other 8 patients (Group C) had mean postoperative thoracic kyphosis of 44.1° (range 32°-65°), and there was no cervical decompensation (p < 0.05). CONCLUSIONS: The sagittal profile of the thoracic spine is related to that of the cervical spine. The surgical treatment of Lenke Type 1 and 2 curves by using all pedicle screw constructs has a significant hypokyphotic effect on thoracic sagittal plane alignment (19 [86%] of 22 patients). If postoperative thoracic kyphosis is excessively decreased (mean 25.6°, p < 0.05), the cervical spine may decompensate into significant kyphosis.

Autofusion in the immature spine treated with growing rods.

STUDY DESIGN: Retrospective case review of skeletally immature patients treated with growing rods. Patients received an average of 9.6 years follow-up care. OBJECTIVE: (1) to identify the rate of autofusion in the growing spine with the use of growing rods; (2) to quantify how much correction can be attained with definitive instrumented fusion after long-term treatment with growing rods; and (3) to describe the extent of Smith-Petersen osteotomies required to gain correction of an autofused spine following growing rod treatment. SUMMARY OF BACKGROUND DATA: The safety and use of growing rods for curve correction and maintenance in the growing spine population has been established in published reports. While autofusion has been reported, the prevalence and sequelae are not known. METHODS: Nine skeletally immature children with scoliosis were identified who had been treated using growing rods. A retrospective review of the medical records and radiographs was conducted and the following data collected: complications, pre- and postoperative Cobb angles at time of initial surgery (growing rod placement), pre- and postoperative Cobb angles at time of final surgery (growing rod removal and definitive fusion), total spine length as measured from T1-S1, % correction since initiation of treatment and at definitive fusion, total number of surgeries, and number of patients found to have autofusion at the time of device removal. RESULTS: The rate of autofusion in children treated with growing rods was 89%. The average percent of the Cobb angle correction obtained at definitive fusion was 44%. On average, 7 osteotomies per patient were required at the time of definitive fusion due to autofusion. CONCLUSION: Although growing rods have efficacy in the control of deformity within the growing spine, they also have adverse effects on the spine. Immature spines treated with a growing rod have high rates of unintended autofusion which can possibly lead to difficult and only moderate correction at the time of definitive fusion.

Accuracy of free-hand placement of thoracic pedicle screws in adolescent idiopathic scoliosis: how much of a difference does surgeon experience make?

The use of thoracic pedicle screws for the treatment of adolescent idiopathic scoliosis (AIS) has gained widespread popularity. However, the placement of pedicle screws in the deformed spine poses unique challenges, and surgeons experience a learning curve. The in vivo accuracy as determined by computed tomography (CT) of placement of thoracic pedicle screws in the deformed spine as a function of surgeon experience is unknown. We undertook a retrospective review to determine the effect of surgeon experience on the accuracy of thoracic pedicle screw placement in AIS. In 2005, we started to obtain routine postoperative CT scans on patients undergoing a spinal fusion. From a database of these patients, we selected AIS patients, who underwent a posterior spinal fusion. Fifteen consecutive patients for each of the following three groups stratified by attending surgeon experience were selected (N = 45): A) less than 20 cases of all pedicle screw constructs for AIS (surgeons <2 years of practice), B) 20-50 cases (surgeons 2-5 years of practice), and C) greater than 50 cases (surgeons greater than 5 years of practice). Intraoperative evaluation of all screws included probing of the pedicle screw tract, neurophysiologic monitoring, and fluoroscopic confirmation. A total of 856 thoracic pedicle screws were studied. Postoperative CT scans were evaluated by two spine surgeons and a consensus read established as follows: (1) In: intraosseous placement or 2-mm breach, either medial or lateral. Of the 856 screws, 104 demonstrated a >2-mm breach, for an overall rate of 12.1% (medial = 55, lateral = 49, P = 0.67). When the breach rates were stratified by surgeon experience, there was a trend toward decreased rate of breach for the most experienced surgeons, although this did not attain statistical significance (Group A: 12.7%, Group B: 12.9%, Group C: 10.8%, P = 0.58). However, the most experienced group (C) had a markedly decreased rate of medial breaches (3.5 vs. 7.4% and 8.4% for groups A and B, respectively, P < 0.01). The breach rate for the concave periapical screws was not statistically different from the overall breach rate (13.0% vs. 12.1%, P = 0.93). In conclusion, the overall accuracy of placement of pedicle screws in the deformed spine was 87.9%, with no neurologic, vascular, or visceral complications. Meticulous technique allows spine surgeons with a range of surgical experience to accurately and safely place thoracic pedicle screws in the deformed spine. The most experienced surgeons demonstrated the lowest rate of medial breaches.

Perioperative outcomes and complications related to teaching residents and fellows in scoliosis surgery.

STUDY DESIGN: Single-surgeon retrospective case series of 303 consecutive operative patients with idiopathic scoliosis (IS). OBJECTIVE: The purpose of this study is to evaluate the perioperative outcomes in patients undergoing surgery for IS as a function of the experience level of the surgical assistant. SUMMARY OF BACKGROUND DATA: The experience level of the surgical assistant, who is often a resident or fellow, has never before been evaluated as an independent factor in predicting perioperative outcomes and morbidity in scoliosis surgery. We hypothesize that there is no difference in perioperative outcomes with varying experience level of the surgical assistant. METHODS: We evaluated the clinical, radiographic, and operative records from 303 consecutive operative patients from consecutive patients with IS. Group I was comprised of residents or spine fellows as assistants (teaching service, n = 175), and Group II consisted of junior or senior attendings as assistants (private practice service, n = 128). Multivariable linear regression was used to evaluate the relationship between experience level of the assistant and curve correction, operative time, estimated blood loss (EBL), complications, transfusions, and length of stay. RESULTS: In the posterior spinal fusion group (PSF, n = 164), there were no statistically significant differences in operative times between Groups I and II. Group I operative time was significantly increased, however, in patients undergoing anterior spinal surgery (ASF, P = 0.01), video-assisted thoracoscopic surgery (P = 0.0004), and combined anterior/posterior surgeries (ASF/PSF, P = 0.0063). There were no differences in EBL in ASF, video-assisted thoracoscopic surgery, or PSF surgeries, however, Group I had significantly higher EBL in the ASF/PSF group (P = 0.0016). No group differences were detected with respect to curve correction, transfusion rates, length of stay, or early complication rates. CONCLUSION: The experience level of surgical assistant had little bearing on perioperative morbidity or radiographic outcomes in scoliosis surgery. Marginally increased operative times and EBL, without an increase in transfusions or complications, is an acceptably safe tradeoff for educating orthopedic residents and fellows.

A histologic study of fractured human vertebral bodies.

Twenty-seven fractured human vertebral bodies and 24 unfractured human vertebrae from adjacent levels were studied postmortem using histologic and high-resolution radiographic techniques. The findings were compared with those in the vertebral bodies of individuals without spinal fracture. Forty-six human thoracolumbar spines were obtained from individuals at autopsy. Standard radiographs were made of all specimens. Twelve of the 46 individuals had a total of 27 fractured vertebral bodies by plain radiographic criteria. Attention was focused on these fractured vertebrae as well as on 24 unfractured vertebral bodies that were harvested from a level immediately adjacent to the fractured vertebral bodies. Twelve vertebral bodies from four individuals with no evidence of fracture or inflammatory spondyloarthropathy were also studied for comparison. The vertebral bodies were graded by their mineral density as measured by dual-energy x-ray absorptiometry and sectioned into 3-mm sagittal cuts. High-resolution contact radiographs were prepared for each section prior to decalcification and tissue sectioning on a large format microtome. Mid-and parasagittal tissue sections of each vertebra were prepared for standard hematoxylin and eosin stains. A total of 126 sections were studied. The histologic characteristics of the fractured vertebrae (n = 27) were compared with those of adjacent unfractured levels (n = 24) and with vertebrae from individuals without fracture (n = 12). Vertebral bodies with fractures secondary to osteoporosis were consistently characterized histologically by focal areas of endochondral new bone formation adjacent to avascular necrotic bone and unreactive marrow. Such ongoing new bone and new vessel formation adjacent to nonhealing areas were also documented in radiographically unfractured vertebral bodies from individuals with osteoporotic fractures at adjacent levels. No areas of endochondral new bone formation or areas of focal necrosis were found in vertebral bodies from individuals without radiographic evidence of osteoporosis. A vascular necrosis of the vertebral body is a common histologic finding in individuals with osteoporosis. Indeed, our histologic observations suggest subclinical fractures and microfractures of the vertebral body may be the underlying pathologic process leading to avascular necrosis in individuals with osteoporosis. Microtrabecular fractures and endplate fractures were commonly seen in osteoporotic vertebral bodies, often in vertebrae that appeared to be uninvolved on specimen radiographs.