Spinal deformity in myelodysplasia. Correction with posterior pedicle screw instrumentation

The surgical treatment of spinal deformity in children with myelomeningocele: the role of personalized three-dimensional printed models

This study was carried out to evaluate the benefits of personalized three-dimensional printing as an aid to the performance of surgery for the correction of spinal deformity in children with myelomeningocele. We performed a retrospective review to include all such children for whom personalized three-dimensional spine models were used for surgical planning (group A) and compared them through subjective and objective criteria to a similar group that had no models (group B). The seven children in group A were younger and had more complex deformities than the 10 children in group B. The models provided a markedly improved appreciation of the complex anatomy and enabled the planning and performance of patient-specific spinal instrumentation that was secure and low profile. The efficiency of the surgery as measured by intraoperative fluoroscopy time and blood loss and the extent of the deformity correction was comparable or superior in group A.

A Novel Groove-Entry Technique for Inserting Thoracic Percutaneous Pedicle Screws

STUDY DESIGN

Surgical technique.

OBJECTIVE

To evaluate the efficacy of a novel groove-entry technique for thoracic percutaneous pedicle screw (PPS) insertion.

SUMMARY OF BACKGROUND DATA

Minimally invasive spine stabilization (MISt) using posterior thoracolumbar instrumentation has many advantages over open procedures. Because of the variability among PPS entry points, the sloped cortex of the transverse process, and the narrow thoracic pedicle, thoracic PPS placement is technically challenging.

MATERIALS AND METHODS

A retrospective review of 24 patients who underwent minimally invasive spine stabilization procedures involving 165 thoracic PPS placements using the novel technique was performed. The thoracic PPS entry is a groove formed by 3 bony elements: the cranial portion of the base of the transverse process, the rib neck, and the posterolateral wall of the pedicle. This groove can be easily identified under fluoroscopy with a Jamshidi needle allowing thoracic PPS insertion in the craniocaudal direction.

RESULTS

Of the 165 thoracic PPSs placed, "Good" or "Acceptable" PPS placement accuracy was achieved in 152 (92.1%) and 164 (99.4%) placements, respectively. No complications such as organ injury, and screw loosening or breakage were observed with thoracic PPS insertion.

CONCLUSIONS

This novel technique is both safe and reliable, with low misplacement and complication rates. In hospitals in which computer image guidance or navigation is unavailable, this groove-entry technique may become the standard for thoracic PPS insertion.

Morphometric analysis of lumbar pedicles in patients with spinal dysraphism

BACKGROUND

In patients with open neural tube defects, the incidence of scoliosis and requirement for spinal fusions are increased. Historically, there has been no standardized measurement of vertebral morphometry in these patients. However, anecdotally, patients with open neural tube defects have a more medially oriented lumbar pedicle trajectory than the average population.

METHODS

A single-institution retrospective review of patients with open neural tube defects was conducted. The demographic parameters and functional and anatomical levels of the defects were noted. CT and MRI scans of the lumbar spine were analyzed; the pedicles from L 1 to S 1 were measured for width (W), length (L) and midline angle (α). The measurements were compared bilaterally, at each level, and with data from previously published reports.

RESULTS

16 scans of pediatric patients (mean = 3.0 ・} 4.3; age range = 7 days to 14.4 years; 7 males, 9 females) with a diagnosis of either myelomeningocele or lipomyelomeningocele were assessed. Most defects occurred in the lumbar region, with L 2 and L 5 accounting for 37.5% each. All angles demonstrated a quadratic increase from L 1 to S 1 (means: L 1 = 28.3 ・} 5.24° ; L 2 = 29.1 ・} 6.2°; L 3 = 33.2 ・} 6.0°; L 4 = 36.8 ・} 5.6°; L 5 = 43.8 ・} 5.9°; S 1 = 52.0 ・} 3.6°) and were more medially angulated than those reported previously; no significant difference existed between right and left measurements (W = 0.65 ≤ p ≤ 0.94; L = 0.91 ≤ p ≤ 1; α = 0.24 ≤p ≤0.86).

CONCLUSIONS

Patients with open neural tube defects had more medially angled pedicle trajectories in the lumbar spine when compared to previously reported values.

Management of spinal deformity in cerebral palsy

An understanding of the three-dimensional components of spinal deformity in children with cerebral palsy is necessary to recommend treatments that will positively affect these patients' quality of life. Management of these deformities can be challenging and orthopedic surgeons should be familiar with the different treatments available for this patient population. This article discusses the incidence, causes, natural history, and treatment of patients with scoliosis.

Pressure mapping as an outcome measure for spinal surgery in patients with myelomeningocele

STUDY DESIGN

A retrospective analysis of prospectively collected data on a cohort of 19 myelomeningocele patients undergoing spino-pelvic deformity surgery.

OBJECTIVE

To examine if greater curve correction with third generation spinal implants correlate with improved pressure distribution and resolution, or prevention of skin ulcerations in myelomeningocele patients.

SUMMARY OF BACKGROUND DATA

Children born with myelomeningocele have often complex spino-pelvic deformities leading to skin ulcerations.

METHODS

A cohort of 19 consecutive wheelchair dependent patients with myelodisplastic spinal deformities, who underwent spinal surgery, was prospectively followed with regular pressure mappings for a minimum of 2 years. Standard spino-pelvic radiologic measurements were obtained. Sitting pressure mappings were obtained over the study period using the Force Sensitive Applications from Vista Medical (Winnipeg, Manitoba, Canada). Statistical analysis was done using SAS (SAS Institute Inc, Cary, NC). Paired t-test and Wilcox on Signed Rank test was used where applicable. Significance was taken to be P<0.05.

RESULTS

Surgery significantly corrected radiographic parameters, specifically, Cobb angle (52%), pelvic obliquity (89%), and to a lesser degree pelvic tilt. Stratifying the data based on fixation type showed that the M-W construct was able to significantly correct pelvic obliquity. While significant changes in radiographic variables were observed after surgery, this was not the case with the various pressure mapping variables. Only minor changes after surgery were observed in the average pressure, maximum pressure, and variable coefficient of pressure. What was observed was an improvement in the overall distribution from anterior/posterior and right/left. While the values only approached statistical significance (P=0.053) for right/left, however, this did not appear to be clinically significant regarding skin ulceration.

CONCLUSION

Despite significant surgical corrections in radiographic parameters, these resulted in small changes in pressure distributions and do not appear to influence skin ulceration in the myelomeningocele patient. Pressure mapping may not be a useful tool in predicting outcome of spinal surgery. Factors which were proven to influence pressure distribution are the sagittal pelvic orientation and also achieving coronal spine balance.

Surgical complications in neuromuscular scoliosis operated with posterior- only approach using pedicle screw fixation

Background

There are no reports describing complications with posterior spinal fusion (PSF) with segmental spinal instrumentation (SSI) using pedicle screw fixation in patients with neuromuscular scoliosis.

Methods

Fifty neuromuscular patients (18 cerebral palsy, 18 Duchenne muscular dystrophy, 8 spinal muscular atrophy and 6 others) were divided in two groups according to severity of curves; group I (< 90°) and group II (> 90°). All underwent PSF and SSI with pedicle screw fixation. There were no anterior procedures. Perioperative (within three months of surgery) and postoperative (after three months of surgery) complications were retrospectively reviewed.

Results

There were fifty (37 perioperative, 13 postoperative) complications. Hemo/pneumothorax, pleural effusion, pulmonary edema requiring ICU care, complete spinal cord injury, deep wound infection and death were major complications; while atelectesis, pneumonia, mild pleural effusion, UTI, ileus, vomiting, gastritis, tingling sensation or radiating pain in lower limb, superficial infection and wound dehiscence were minor complications. Regarding perioperative complications, 34(68%) patients had at least one major or one minor complication. There were 16 patients with pulmonary, 14 with abdominal, 3 with wound related, 2 with neurological and 1 cardiovascular complications, respectively. There were two deaths, one due to cardiac arrest and other due to hypovolemic shock. Regarding postoperative complications 7 patients had coccygodynia, 3 had screw head prominence, 2 had bed sore and 1 had implant loosening, respectively. There was a significant relationship between age and increased intraoperative blood loss (p = 0.024). However it did not increased complications or need for ICU care. Similarly intraoperative blood loss > 3500 ml, severity of curve or need of pelvic fixation did not increase the complication rate or need for ICU. DMD patients had higher chances of coccygodynia postoperatively.

Conclusion

Although posterior-only approach using pedicle screw fixation had good correction rate, complications were similar to previous reports. There were few unusual complications like coccygodynia.

Biomechanical comparison of anatomic trajectory pedicle screw versus injectable calcium sulfate graft-augmented pedicle screw for salvage in cadaveric thoracic bone

Many salvage options for failed thoracic pedicle screws exist including the use of a different trajectory or the augmentation of the screw with polymethylmethacrylate cement. Although polymethylmethacrylate immediately increases the construct stiffness and the pull-out strength, it may cause bone necrosis, toxin relaxation, and/or neural injury. On the other hand, calcium sulfate bone grafts have a high potential for biologic incorporation and no thermal damage effect. In the current study, polyaxial pedicle screws were first inserted with a straightforward approach on both sides in 17 fresh human cadaveric thoracic vertebrae. The maximal insertion torque for each screw was measured and then the pull-out strengths were recorded. Afterward, these pedicle screws were randomly assigned to be replaced either by graft augmentation or by anatomic trajectory technique for salvage. The graft-augmented screws were placed using the previous holes. The maximum insertional torque for each anatomic trajectory screw was measured. Finally, the pull-out strengths of the revision screws were recorded. The mean maximum insertional torque decreased with the anatomic trajectory salvage technique when compared with the straightforward approach, 0.23 versus 0.38 Nm, respectively (P=0.003). The anatomic trajectory revision resulted in decreased pull-out strength when compared with the pull-out strength of the straightforward technique, 297 versus 469 N, respectively (P=0.003). The calcium sulfate graft augmentation increased the pull-out strength when compared with the pull-out strength of the straightforward technique, 680 versus 477 N, respectively (P=0.017). The mean pull-out strength ratio of revised screw to original was 0.71 for anatomic trajectory and 1.8 for graft-augmented screws, a statistically significant difference (P=0.002).

Congenital and developmental deformities of the spine in children with myelomeningocele

The treatment of spinal deformities in children with myelomeningocele poses a formidable task. Multiple medical comorbidities, such as insensate skin and chronic urinary tract infection, make care of the spine difficult. A thorough understanding of the natural history of these deformities is mandatory for appropriate treatment to be rendered. A team approach that includes physicians from multiple specialties provides the best care for these patients. The two most challenging problems are paralytic scoliosis and rigid lumbar kyphosis. The precise indications for surgical intervention are multifactorial, and the proposed benefits must be weighed against the potential risks. Newer spinal constructs now allow for fixation of the spine in areas previously difficult to instrument. Complications appear to be decreasing with improved understanding of the pathophysiology associated with myelomeningocele.

Thoracic pedicle screws: postoperative computerized tomography scanning assessment

OBJECT

The authors evaluated the accuracy of placement of thoracic pedicle screws by performing postoperative computerized tomography (CT) scanning. A grading system is presented by which screw placement is classified in relation to neurological, bone, and intrathoracic landmarks.

METHODS

One hundred eighty-five thoracic pedicle screws were implanted in 27 patients with the assistance of computer image guidance or fluoroscopy. Postoperative CT scanning was conducted to determine a grade for each screw: Grade I, entirely contained within pedicle; Grade II, violates lateral pedicle but screw tip entirely contained within the vertebral body (VB); Grade III, tip penetrates anterior or lateral VB; Grade IV, breaches medial or inferior pedicle; and Grade V, violates pedicle or VB and endangers spinal cord, nerve root, or great vessels and requires immediate revision. Based on anatomical morphometry, the spine was subdivided into upper (T1-2), middle (T3-6), and lower (T7-12) regions. Statistical analyses were performed to compare regions. The mean follow-up period was 37.6 months. The following postoperative CT scanning-documented grades were determined: Grade I, 160 screws (86.5%); Grade II, 15 (8.1%); Grade III, six (3.2%); Grade IV, three (1.6%); and Grade V, one (0.5%). Among cases involving screw misplacements, Grade II placement was most common, and this occurred most frequently in the middle thoracic region.

CONCLUSIONS

The authors' grading system has advantages over those previously described; however, further study to determine its reliability, reproducibility, and predictive value of clinical sequelae is warranted. Postoperative CT scanning should be considered the gold standard for evaluating thoracic pedicle screw placement.

An extrapedicular approach to the placement of screws in the thoracic spine: an anatomic and radiographic assessment

STUDY DESIGN

A radiographic and anatomic study of an extrapedicular method of screw placement in cadaveric thoracic spines.

OBJECTIVE

To evaluate an alternative method of thoracic vertebral body screw fixation using an extrapedicular screw technique. To evaluate the anatomic safe zones and proper starting point for this alternative approach to the placement of screw fixation in the thoracic spine.

SUMMARY OF BACKGROUND DATA

Despite the clinical successes reported with thoracic pedicle screw-rod constructs, controversy exists about the safety of this technique in pedicles that are anatomically too small for transpedicular fixation. An alternative method of extrapedicular screw fixation was evaluated in this present study.

MATERIALS AND METHODS

Two fresh, unfixed, adult cadavers were obtained randomly; 6.0-mm AO Synthes pedicle screws were placed using an extrapedicular approach bilaterally from T3 to T10. The screws were placed according to one defined method described later. Computerized tomographic (CT) images were obtained. The position of each screw was analyzed. The cadavers were then dissected with the screw pathway exposed and the relation of the screw to surrounding anatomy documented.

RESULTS

All screws did not penetrate the spinal canal. All screws were within the pedicle rib unit and did not penetrate the neural foramen or pleura.

CONCLUSION

This study, although only introductory, indicates the potential for extrapedicular vertebral body fixation in the thoracic spine. Biomechanical evaluations are presently being conducted to evaluate the use of extrapedicular thoracic screw fixation.

The use of pedicle-screw internal fixation for the operative treatment of spinal disorders

Pedicle screws have dramatically improved the outcomes of spinal reconstruction requiring spinal fusion. Short-segment surgical treatments based on the use of pedicle screws for the treatment of neoplastic, developmental, congenital, traumatic, and degenerative conditions have been proved to be practical, safe, and effective. The Funnel Technique provides a straightforward, direct, and inexpensive way to very safely apply pedicle screws in the cervical, thoracic, or lumbar spine. Carefully applied pedicle-screw fixation does not produce severe or frequent complications. Pedicle-screw fixation can be effectively and safely used wherever a vertebral pedicle can accommodate a pedicle screw--that is, in the cervical, thoracic, or lumbar spine. Training in pedicle-screw application should be standard in orthopaedic training programs since pedicle-screw fixation represents the so-called gold standard of spinal internal fixation.

Treatment of selected neuromuscular patients with posterior instrumentation and arthrodesis ending with lumbar pedicle screw anchorage

STUDY DESIGN

This is a retrospective analysis of 23 patients with severe neuromuscular spinal deformity treated with posterior instrumentation and fusion ending in the lumbar spine.

OBJECTIVES

The purposes of this study were to determine the safety and efficacy of stopping posterior instrumentation constructs in the lumbar spine with pedicle screw anchorage.

SUMMARY OF BACKGROUND DATA

There are sparse data in the peer-reviewed literature regarding indications and outcomes in patients with neuromuscular disorders for instrumented fusion ended short of the pelvis with transpedicular fixation.

METHODS

The average age of patients at surgery was 18.4 years (range, 10-61 years). Additional anterior discectomy and fusion were performed in four patients with large, stiff curves. No patient received anterior instrumentation. Criteria for exclusion of the pelvis from the fusion were less than 15 degrees of pelvic obliquity as a result of a compensatory curve below the major curve(s), the absence of problematic lower extremity contractures, and, often, the potential for ambulation. Process and clinical outcomes and complications were analyzed.

RESULTS

Radiographic follow-up was available in 21 patients at an average of 62 months (range, 24-110 months) after surgery. Their average Cobb angle was 71 degrees before surgery, 25 degrees after surgery (64% correction), and 32 degrees at follow-up (54% correction). Their average spinal-pelvic obliquity was 6 degrees before surgery, 5 degrees after surgery, and 6 degrees at follow-up. The average lower instrumented vertebra was lumbar 3.7. Clinical follow-up was available for all 23 patients for an average of 61 months (range, 24-110 months). There were no perioperative deaths, deep wound infections, pseudarthroses, or instrument failures. Outcomes based on responses to questionnaires completed by patient, parent, or caregiver were highly satisfactory in 20 patients (87%), satisfactory in 2 patients (9%) and neither satisfactory nor unsatisfactory in 1 patient (4%).

CONCLUSION

Posterior instrumentation and arthrodesis using lumbar lower instrumented vertebra pedicle screw anchorage can be performed safely and effectively, in selected patients patients with scoliosis and minimal pelvic obliquity.

Stability of myelomeningocele spines treated with the mayfield two-stage anterior and posterior fusion technique

STUDY DESIGN

Retrospective review of the results of operative treatment for paralytic thoracolumbar lordoscoliosis in six consecutive myelomeningocele patients treated with the Mayfield two-stage combined anterior and posterior fusion and instrumentation technique.

OBJECTIVES

To assess the long-term stability of myelomeningocele spines treated with the Mayfield technique.

SUMMARY OF BACKGROUND DATA

An initial description of the technique by Mayfield and an early study of the evolution of the two-stage combined anterior and posterior instrumented fusion of paralytic lordoscoliosis in myelomeningocele spines are available.

METHODS

Study of the six individual patients showed that the mean age at the time of surgery was 13 years and 8 months (range, 9 years 9 months to 15 years 10 months). At the time of surgery, the major lumbosacral curve averaged 81 degrees (range, 52-137 degrees ), pelvic obliquity was 28 degrees (range, 1-48 degrees ), torso decompensation was 2.8 cm (range, 0-6.0 cm), thoracic kyphosis was 60 degrees (range, 25-93 degrees ), lumbar lordosis was 106 degrees (range, 55-151 degrees ), and sacral anteflexion was 78 degrees (range, 22-117 degrees ). The mean duration of follow-up evaluation was 13 years 5 months (range, 8 years 10 months to 16 years 11 months).

RESULTS

Clinical and radiographic evaluation showed that immediately after surgery, the lumbosacral curve was corrected to an average of 25 degrees and at last follow-up evaluation was 25 degrees, for a final correction of 69%. Pelvic obliquity was corrected to 7 degrees, 5 degrees at last follow-up evaluation, for a 82% correction. Torso decompensation was corrected to 1.4 cm initially and finally to 0.3 cm, for an 89% correction. Kyphosis was corrected to 52 degrees, finally to 50 degrees (17% decrease); lordosis to 73 degrees and finally to 67 degrees (37 degrees decrease); and sacral anteflexion corrected to 51 degrees and finally to 56 degrees (28% decrease). In one patient, the tip of the longest rod displaced from the uppermost hook and was replaced with maintenance of correction. Another patient had dehiscence of the pelvic portion of the posterior wound, with secondary bacterial contamination, and healed by secondary intention.

CONCLUSIONS

The Mayfield technique effectively corrected and stabilized these difficult myelomeningocele spinal deformities, using distraction against square-holed hooks seated on the sacral alae, which contain the best-quality bone in these hypoplastic pelves.

The safety and efficacy of Isola-Galveston instrumentation and arthrodesis in the treatment of neuromuscular spinal deformities

BACKGROUND

Implant systems that realign and stabilize a deformed spine continue to evolve. The purpose of the study of this case series was to determine the safety and effectiveness of a system designed to integrate hook, wire, screw, and post anchors for the treatment of a wide spectrum of neuromuscular disorders associated with pelvic deformity or the potential for deformity.

METHODS

Forty-seven consecutive patients who had a spinal deformity that was due to cerebral palsy or an upper motor-neuron cerebral palsy-like disease (thirty-one patients), myelomeningocele (nine), Duchenne muscular dystrophy (four), or other disorders (three) were managed with Isola-Galveston instrumentation and arthrodesis. The average age at the time of the operation was fourteen years and three months (range, five years and four months to twenty-three years and nine months). Eight patients (17 percent) had an additional anterior discectomy and arthrodesis without instrumentation, and three (6 percent) had an additional decancellation egg-shell osteotomy. The forty-seven patients were followed for an average of forty-seven months (range, twenty-four to 100 months). The complications were tabulated to assess the safety of the procedure, and the correction of each deformity was calculated to determine the efficacy.

RESULTS

There were no deaths, acute wound infections, or serious neurological problems. Reoperation was necessary in five patients (11 percent). One reoperation was performed because of a delayed deep wound infection; one, because of delayed sterile drainage; and one, for a pseudarthrosis repair. The remaining two reoperations were done for removal of an implant because the cephalad portion had become prominent. In addition to the pseudarthrosis that required a reoperation, there were three possible pseudarthroses that did not require a reoperation (overall prevalence of pseudarthrosis, 9 percent). Postoperative bracing was used for eleven patients (23 percent); it did not influence the rate of pseudarthrosis or possible pseudarthrosis. The average preoperative scoliosis of 70 degrees was corrected to 24 degrees (a 66 percent correction) at the time of the latest follow-up, and the average preoperative pelvic obliquity of 27 degrees was corrected to 5 degrees (an 81 percent correction). A survey of the patients, parents, and caregivers indicated that 96 percent of them were satisfied or very satisfied with the result of the operation.

CONCLUSIONS

Isola-Galveston instrumentation seems as safe and effective as other types of instrumentation that have been studied in comparable series in the literature. Isola-Galveston instrumentation is probably more effective for the correction of pelvic obliquity and the maintenance of correction. Only a posterior procedure is used, and the instrumentation appears to decrease the need for an additional anterior approach. Spinal hook, wire, screw, and post anchors have been successfully integrated into one posterior spinal implant system.