Kenneth J. Guidera

Pediatric Pedicle Screw Placement Using Intraoperative Computed Tomography and 3-Dimensional Image-Guided Navigation

Study Design. A retrospective cohort study reporting the use of intraoperative computed tomography (CT) and image-guided navigation system for the placement of pedicle screws in pediatric compared with adult patients. Objective. To evaluate the accuracy of open pedicle screw placement in pediatric patients using intraoperative CT and 3-dimensional (3D) image-guided navigation. Summary of Background Data. Pedicle screws are widely used in children for the correction of spinal deformity. Navigation systems and intraoperative CT are now available as an adjunct to fluoroscopy and anatomic techniques for placing pedicle screws and verifying screw position. Methods. From 2007 to 2010, 984 pedicle screws were placed in a consecutive series cohort of 50 pediatric patients for spinal deformity correction with the use of intraoperative CT (O-arm, Medtronic, Inc, Louisville, CO) and a computerized navigation system (Stealth, Medtronic, Inc, Louisville, CO). The primary outcome measure for this study is redirection or removal of screw on the basis of the intraoperative CT imaging. During the study period, 1511 screws were placed in adult patients using the same image guidance system. Results. A total of 984 pedicle screws were implanted using real-time navigation, with a mean of 20 screws per patient (range: 2–34). On the basis of intraoperative CT, 35 screws (3.6%) were revised (27 redirected and 8 removed), representing a 96.4% accuracy rate. No patients returned to the operating room because of screw malposition. Of the 1511 screws placed in adult patients, 28 (1.8%) were revised intraoperatively for malposition on CT imaging, for an overall 98.2% accuracy rate. Screw revision thus was more common in the pediatric population (P = 0.008). However, the pediatric screw accuracy rate is significantly higher than the findings from a recent meta-analysis of predominantly nonnavigated screws in children, reporting a 94.9% accuracy rate (P = 0.03). Conclusion. We report 96.4% accuracy in pediatric pedicle screw placement using intraoperative CT and a 3D navigation system. This is similar to other reports and has better accuracy than a recent meta-analysis of nonnavigated screws in children.

Nail Patella Syndrome: A Review of 44 Orthopaedic Patients

Nail patella syndrome is a rare dysplasia with characteristic findings of finger nail abnormalities, hypoplastic patellas, radial head dislocations, and iliac horns. We reviewed the problems and treatment of 44 patients with this syndrome from 13 Shriners Hospital units. The inheritance pattern is autosomal dominant, with foot abnormalities as the chief presenting complaint. All patients were ambulatory. Twenty of the patients underwent knee operations, and 24 underwent operations to correct foot and ankle deformities. Knee extensor realignments and foot posteromedial releases had overall good results. Knee flexion contractures required full posterior capsular releases. Elbow reconstructive procedures were rarely indicated.

Contiguous discitis and osteomyelitis in children.

Magnetic resonance imaging of 16 patients with contiguous discitis and osteomyelitis provided a specific diagnosis and defined the anatomic extent of vertebral and soft-tissue involvement. Altered signal changes were evident in the disc, adjacent vertebra in the end plate and metaphyseal equivalent regions, and the anterior prevertebral tissues. Significant posterior spread and disc herniation were not evident. Fourteen patients had lumbar involvement; two had cervical involvement. The patients were followed-up for an average of 4 years 5 months. Scoliosis has developed in one patient, and four continue to have a loss of lumbar lordosis. By comparing serial roentgenograms, the mean decrease of disc-space height after the acute episode was 43% (range, 51-61%). There was no restitution of normal disc-space height at the latest follow-up roentgenogram in any of the patients. A 14% (average) narrowing of the vertebral foramina was evident in seven cases. In one patient, a fusion progressively developed 7 years after the acute episode (before full skeletal maturity). However, several patients appear to be progressing toward fusion of adjacent vertebra. A study of histologic specimens elucidated vascular anatomy of the immature vertebra that further explain the disease characteristics.

Operative treatment of congenital pseudarthrosis of the clavicle.

Eight children were treated operatively with resection of fibrous pseudarthrosis and sclerotic bone ends, careful dissection and preservation of the periosteal sleeve to maintain continuity, and approximation of bone ends. None had additional bone grafts or internal fixation. All had bridging ossification 6–8 weeks postoperatively, and all were solidly healed by 14 weeks after surgery. Follow-up has ranged from 2 to 14 years, with no evidence of recurrence. Remodeling of the prominence occurred slowly in 2–5 years, with the distal clavicle variably underdeveloped in all patients. Early resection of fibrous pseudarthrosis probably does not require the extensive grafting and internal fixation that has been recommended for older children.

Cotrel-Dubousset instrumentation. Results in 52 patients.

Fifty-two posterior spinal fusions were performed for pediatric idiopathic, congenital, and neuromuscular scoliotic curves. Cotrel-Dubousset instrumentation was used in all patients. Nine had prior anterior spinal releases and fusions. The patterns were mixed, with a predominance of right thoracic curvatures. The average preoperative curve measured 60.6 degrees, with correction to 29. Seven patients required revision surgery, and 17 wore orthoses after operation. There were 17 complications in this group, including hook pullout, prominent hardware, infection, pseudarthrosis, and two cases of broken Cotrel-Dubousset instrumentation rods. Fatigue failure of this instrumentation, secondary to pseudarthrosis, has not been reported previously, and these two cases are presented in detail. The operative morbidity and difficulty were increased in the larger idiopathic curves and in neuromuscular and congenital scoliosis. Cotrel-Dubousset instrumentation is an overall excellent tool for the multiplanar correction of scoliosis and is amenable to revision surgery.

The accuracy of navigation and 3D image-guided placement for the placement of pedicle screws in congenital spine deformity.

Background: Treatment of congenital spine deformity has high surgical risk due to abnormal anatomy and dysmorphic pedicles. We hypothesized that an image-guided navigation system would result in a low rate of screw revision due to malposition. Methods: From 2007 to 2010, 142 screws were placed in 14 consecutive patients with congenital spine deformity using an intraoperative computer tomography (CT) (O-arm) and image-guided navigation system (Stealth). Mean age was 8.8 years (range, 1 to 18 y). Deformities included scoliosis (12), kyphosis (1), and spinal dysgenesis (1). Screws were placed from T2 to S1. An intraoperative CT verified screw position. Need for intraoperative screw revision is the primary outcome measure. Results: Of the 142 screws placed, 1 required revision intraoperatively due to malposition (99.3% screw accuracy rate). The screw was at L3 and was successfully redirected. There were no complications due to screw malposition. This navigated congenital screw accuracy rate (99.3%) is higher than the 94.9% accuracy rate reported for non-navigated screws in all children undergoing pedicle screw fixation in a recent systematic literature review and higher than the reported 96.4% accuracy rate for navigated pedicle screws in children. Kosmopoulos and colleagues found a lower accuracy rate (86.6%) in adult non-navigated screws (P<0.0001) and adult navigated screws (93.7%). Of note, 9 pedicles were noted on navigation to be absent. Despite the goal of bilateral screw placement at each fusion level, 31 of 173 pedicles were left unfilled due to technical impossibility based on intraoperative CT imaging. This represents an 18% screw dropout rate. Conclusions: CT-guided navigation resulted in the successful placement of 142 pedicle screws in patients with congenital deformity and altered anatomy, which represents a 99.3% screw accuracy rate. This is comparable with the screw accuracy rate of 93.7% reported for adult navigated pedicle screws. Further, navigation prevented attempts of screw placement at levels with absent or impassable pedicles. Image-guided navigation and intraoperative CT are valuable tools for the safe placement of pedicle screws in patients with significant congenital spine deformity and altered anatomy. Level of Evidence: IV, Case Series.

Tibia valga after proximal metaphyseal fractures in childhood: a normal biologic response

Seventeen children with 19 proximal tibial metaphyseal fractures were followed-up between 2 and 7 years after injury. Detailed measurements of the metaphyseal/diaphyseal/metaphyseal distances medially and laterally on the injured and noninjured sides demonstrated overgrowth. In four patients, the medial distance of the injured tibia was longer than the lateral distance, which was the same distance as the uninjured tibia. In 11 patients, there was an overgrowth of both the medial and lateral sides of the injured tibia, compared to the unijured tibia, and in each instance, the medial distance of the injured tibia was always longer than the lateral. In a patient with bilateral metaphyseal fractures, the medial length exceeded the lateral length in both tibias. In the child with metaphyseal and diaphyseal fractures, the medial side of the tibia with the metaphyseal fracture was the longest of the four measurements. In five of six patients with Harris lines, there was distal as well as proximal tibial metaphyseal overgrowth, but the distal line was always parallel to the physis and did not contribute to the valgus angulation. Thus there was not only a generalized increased growth proximally and distally, but there also was an eccentric proximal medial overgrowth in every patient.

Use of the reciprocating gait orthosis in myelodysplasia.

Summary There are advantages to an upright posture and ambulation in pediatric myelodysplasia patients. The reciprocating gait orthosis (RGO) is a useful tool to enable this activity in selected individuals. We evaluated the long-term usage, pitfalls, and contraindications of this orthosis. Mean daily usage was 6.9 h/day, requiring an average of 10 min to don or doff; all patients required assistance. Obesity, advanced age, lack of patient or family motivation, scoliosis, and spasticity were significant negative factors in long-term usage of the RGO. Good upper extremity strength, trunk balance, previous standing or walking, and active hip flexion were important positive variables. Eleven of 21 patients did not persist with long-term usage of this orthosis, averaging 25.8 months of usage. An energy study was performed on three patients, comparing the efficiency of reciprocating gait and swing-through gait. All three were more energy efficient and two were faster with the swing-through gait but each preferred the reciprocating pattern. Care should be taken when selecting patients for RGO usage because not all children with myelomeningocele are able to function effectively with this orthosis.

Pathologic morphology of the dislocated proximal femur in children with cerebral palsy.

We describe the gross and microscopic anatomic changes in the hip that result from the deforming forces in children with neuromuscular imbalance. Twelve dislocated proximal femora that had been resected from children with spastic diplegia or tetraplegia were evaluated with respect to their gross, microscopic, and radiographic structure. The epiphyses were wedge shaped with deformation of the femoral head apparent in all cases. In addition to a severe loss of articular cartilage, a furrowed erosion of epiphyseal bone suggested a sustained, blunt, band-like force across the surface of the hip where it opposed the acetabular labrum. The underlying physis of the capital femur was irregular with aberrant histologic structure, whereas that of the lesser trochanter was hypertrophic and angulated in a superior and anterior direction. A significant degree of valgus was not noticeable in most specimens. In summary, the spastic adductor and iliopsoas, responsible for the changes in the lesser trochanter, work in conjunction with the hip flexor and internal rotator muscles to subluxate the proximal femur. In the process, the superior rim of the acetabulum and capsule causes focal deformation of the superolateral femoral head, creating a fulcrum upon which the hip then progressively subluxates. The indentation locks the femoral head at the lateral acetabular margin, preventing complete dislocation, but leading to bone pain consequent to cartilage erosion.

Ilizarov treatment of congenital pseudarthroses of the tibia

Eleven children with congenital pseudarthrosis of the tibia were treated with the Ilizarov device. This was successful in nine of 11 patients with an average of 322 days in the fixator and 1.6 additional surgeries. Two patients eventually had amputations. These results demonstrate this to be an effective tool for this complex condition, but amputation should be considered if union is not achievable with this method and other procedures have previously been attempted.