History and Evolution of Spinal Robotics in Pediatric Spinal Deformity.

Robotic assistance in surgical procedures is a valuable tool that enhances the safety and efficacy of invasive surgeries. These devices are divided functionally into surgeon surrogates where the device operates under the direct control of an offsite surgeon, and surgeon adjuncts where the device is an intraoperative guidance tool used in a portion of the procedure. The current state of robotic spine surgery focuses on the latter, addressing the primary task of pedicle screw placement. We would like to share our experience with the Mazor Robotics devices to discuss the underlying concepts, strengths, weaknesses, and results as they pertain to pediatric spine deformity.

CT Radiation Dose Reduction in Robot-assisted Pediatric Spinal Surgery.

STUDY DESIGN: Retrospective consecutive cohort series. OBJECTIVE: The aim of this study was to develop a low-dose computed tomography (CT) protocol for use in robot-assisted pediatric spinal surgery. SUMMARY OF BACKGROUND DATA: CT scans are utilized preoperatively for preoperative planning, by navigation software during robot-assisted surgery, and postoperatively to assess surgical implant placement. Traditionally high radiation doses produced by CT scanning are a concern in the highly radiosensitive pediatric population. METHODS: We developed a low-dose protocol using phantom scans. A cohort of patients undergoing CT scanning using the low-dose protocol was collected. Further, a matching cohort of patients who underwent standard scanning was collected. Image quality was assessed by observer ratings. Radiation doses and image quality metrics were compared for the standard and low-dose protocol patients. RESULTS: Effective dose significantly decreased 84% to 91% depending on patient size and whether the scan was preoperative or postoperative. All scans were compatible with the navigation software. No clinically significant differences in image quality were observed between low-dose and standard patient cohorts. CONCLUSIONS: Task-based CT protocol optimization can produce acceptable image quality with dose comparable to standard two-view radiography. LEVEL OF EVIDENCE: 2.

A rare case of dermatofibrosarcoma protuberans of the forefoot.

Dermatofibrosarcoma protuberans is an extremely rare, potentially malignant tumor type that usually presents on the trunk or proximal extremities. The clinical presentation includes a gradually enlarging painless plaque-like or nodular lesion of the skin with surrounding red to blue discoloration. The diagnosis is based on clinical presentation, computed tomography or magnetic resonance imaging, and biopsy with histologic analysis. An early and timely diagnosis improves chances of complete surgical resection thus improving prognosis. Herein, we present a rare case of dermatofibrosarcoma protuberans with the hopes that its addition to the literature will aid in the earlier recognition of future patients and help prevent this potentially curable disease from becoming deadly.

Accuracy of robot-assisted pedicle screw placement for adolescent idiopathic scoliosis in the pediatric population.

This is a retrospective review of pedicle screw placement in adolescent idiopathic scoliosis (AIS) patients under 18 years of age who underwent robot-assisted corrective surgery. Our primary objective was to characterize the accuracy of pedicle screw placement with evaluation by computed tomography (CT) after robot-assisted surgery in AIS patients. Screw malposition is the most frequent complication of pedicle screw placement and is more frequent in AIS. Given the potential for serious complications, the need for improved accuracy of screw placement has spurred multiple innovations including robot-assisted guidance devices. No studies to date have evaluated this robot-assisted technique using CT exclusively within the AIS population. Fifty patients were included in the study. All operative procedures were performed at a single institution by a single pediatric orthopedic surgeon. We evaluated the grade of screw breach, the direction of screw breach, and the positioning of the patient for preoperative scan (supine versus prone). Of 662 screws evaluated, 48 screws (7.2 %) demonstrated a breach of greater than 2 mm. With preoperative prone position CT scanning, only 2.4 % of screws were found to have this degree of breach. Medial malposition was found in 3 % of screws, a rate which decreased to 0 % with preoperative prone position scanning. Based on our results, we conclude that the proper use of image-guided robot-assisted surgery can improve the accuracy and safety of thoracic pedicle screw placement in patients with adolescent idiopathic scoliosis. This is the first study to evaluate the accuracy of pedicle screw placement using CT assessment in robot-assisted surgical correction of patients with AIS. In our study, the robot-assisted screw misplacement rate was lower than similarly constructed studies evaluating conventional (non-robot-assisted) procedures. If patients are preoperatively scanned in the prone position, the misplacement rate is further decreased.

C-OnSite ® for intraoperative 3D control of pedicular screw positions.

BACKGROUND: Two-dimensional image guidance and navigation can help to reduce the number of misplaced pedicle screws, but do not completely prevent misplacement. This experimental, retrospective, non-inferiority study was designed to evaluate and compare the efficacy of a novel 3D imaging technique versus conventional postoperative CT-scan, for intra-operative determination of pedicle screw position accuracy. METHODS: The capacity of C-OnSite® to intraoperatively assess screw placement was evaluated in 28 clinical cases and 23 deliberately misplaced screws in a cadaver model, and compared to placement accuracy determined by standard CT. The position of each implant, as viewed by both modalities, was graded by three neurosurgeons, one orthopaedic-surgeon and one radiologist. The intermodal variance determined the difference between CT- and C-OnSite® results for each observer, while the inter-observer variance measured the difference between ratings of the same modality by different observers. RESULTS: C-OnSite® successfully assessed 120/138 screws (25/28 cases). Mean procedural fluoroscopy time was 132 ± 51 s, and 40 ± 16s per C-OnSite® scan. The average inter-modality variance was ,15 % with mismatches >1° between C-OnSite® and the gold-standard imaging technique in only 2 % of the comparisons. Average inter-observer variances were about similar (12 % for CT and 18 % for C-OnSite®), with deviations of >1° reaching 1 % for CT and 3 % for C-OnSite®. Individual variances between experienced only observers differed even less. CONCLUSIONS: C-OnSite® is a feasible, reliable and intuitive means of intraoperatively visualizing pedicle screw positions and might render the majority of postoperative CTs superfluous. C-OnSite® might help avoid re-operations for screw re-positioning.

Effect of botulinum toxin type A on gait of children who are idiopathic toe-walkers.

The purpose of this study was to determine the effects of botulinum toxin type A treatment on ankle muscle activity during gait of children who are idiopathic toe-walkers. Five children who were idiopathic toe-walkers with a mean age was 4.34 years participated. Gait of the subjects was evaluated prior to, 20 days following, and 12 months following bilateral botulinum toxin type A injection of the gastrocnemius and soleus muscles. Subjects received physical therapy following the 20-day evaluation. Dependent variables were type of foot contact pattern and duration of swing-phase tibialis anterior activity and onset of stance-phase gastrocnemius relative to ground contact. Prior to treatment 51% of foot contacts were with the toe (heel just off the ground) or were digitigrade, while the remaining contacts were flat foot or heel strike. At approximately 20 days following treatment, only 8% of foot contacts were toe contact or digitigrade. Prior to treatment, mean gastrocnemius onset was 30 ms prior to foot contact and the duration of swing-phase tibialis anterior was only 345 ms. Following treatment (and a more normal foot contact pattern), mean gastrocnemius onset followed ground contact by 36 ms and tibialis anterior duration increased through terminal swing and into the loading response. The posttreatment improvement was maintained at 12-month follow-up. It appears that botulinum toxin type A treatment normalizes the ankle EMG pattern during gait and a more normal foot-strike pattern is obtained. These data are discussed in terms of a neuromotor rationale for the rehabilitation of children who are idiopathic toe-walkers to maintain posttreatment improvements.

Intrinsic pedal musculature support of the medial longitudinal arch: an electromyography study.

Much of the work describing support of the medial longitudinal arch has focused on the plantar fascia and the extrinsic muscles. There is little research concerning the function of intrinsic muscles in the maintenance of the medial longitudinal arch. Ten healthy volunteer adults served as subjects for this study, which was approved by the University Investigational Review Board. The height of the navicular tubercle above the floor was measured in both feet while subjects were seated with the foot in a subtalar neutral position and then when standing in a relaxed calcaneal stance. Subtalar neutral was found by palpating for talar congruency. Recordings of muscle activity from the abductor hallucis muscle were performed while the subjects maintained a maximal voluntary contraction in a supine position by plantarflexing their great toes. An injection of lidocaine (1% with epinephrine) was then administered by a Board-certified orthopedic surgeon in the region of the tibial nerve, posterior and inferior to the medial malleolus. Measurements were repeated and compared by using a paired t test. After the nerve block, the muscle activity was 26.8% of the control condition (P =.011). This corresponded with an increase in navicular drop of 3.8 mm. (P =.022). The observation that navicular drop increased when the activity of the intrinsic muscles decreased indicates that the intrinsic pedal muscles play an important role in support of the medial longitudinal arch.

Interbody allograft in a skeletally immature spine model.

The objective of this cadaveric biomechanical study was to establish further bovine spines as models for evaluating lumbar interbody allografts and to provide guidance for their use in pediatric humans. It is unknown whether interbody allografts can be used in the pediatric spine without failure of the host vertebral bone. Allografts were placed in cow and calf spines and loaded in compression. The cow spines were much stronger and stiffer than the calf, but moderate in vivo activities were estimated to result in loads on the allograft constructs that would result in host bone failure. Bovine spines were established as suitable models for the compressive behavior of interbody allografts in the human spine, when bone density is considered. Interbody allografts should continue to be used with adjunctive instrumentation so as to preclude host bone failure.