Walter H. Truong

The accuracy of intraoperative O-arm images for the assessment of pedicle screw postion

Study Design. Human cadaveric study. Objective. The objective of the study was to determine the accuracy of intraoperative O-arm images in determining pedicle screw position using open dissection as the gold standard. Summary of Background Data. Pedicle screws are widely used in the treatment of various spinal disorders. Postoperative computed tomographic scans are the imaging gold standard to detect pedicle screw malposition. However, a second procedure is necessary if such malpositioned screws have to be revised. The O-arm is an intraoperative scanner that allows revision of a screw without having to return the patient to the operating room for a separate procedure. No previous studies have looked at the accuracy of intraoperative O-arm images in determining pedicle screw position. Methods. This factorial validation study utilized 9 cadavers in a comparison of intraoperative O-arm images and the dissection gold standard. Four hundred sixteen screws were inserted using 3-dimensional image (O-arm) guidance from C2 to S1. The screw positions were randomized into 3 groups: “IN” (fully contained within the pedicle), “OUT-lateral,” or “OUT-medial.” After screw insertion, O-arm images were obtained and reviewed in a blinded fashion by 3 independent observers. Dissection identified the true position of the screws. Specificity, sensitivity, positive predictive value (PPV), and negative predictive value (NPV) were calculated using dissection results as the gold standard. The interobserver reliability was also determined. Results. The overall accuracy, specificity, sensitivity, PPV, and NPV of O-arm images for the thoracic and lumbar spine were 73%, 76%, 71%, 74%, and 72%, respectively. Accuracy of surgeon perception in the cervical spine was significantly less than in the thoracic and lumbosacral spine. There was substantial interobserver agreement between the 3 readers. Conclusion. Intraoperative O-arm images accurately detect significant pedicle screw violations in the thoracic and lumbosacral spine but are less accurate for the cervical spine.

Predicting the outcome of intramuscular psoas lengthening in children with cerebral palsy using preoperative gait data and the random forest algorithm

This study used the random forest algorithm to predict outcomes of intramuscular psoas lengthening as part of a single event multi-level surgery in patients with cerebral palsy. Data related to preoperative medical history, physical exam, and instrumented three-dimensional gait analysis were extracted from a historic database in a motion analysis center. Data from 800 limbs of patients with diplegic cerebral palsy were analyzed. An index quantifying the overall deviation in pelvic tilt and hip flexion was used to define outcome categories. The random forest algorithm was used to derive criteria that predicted the outcome of a limb. The criteria were applied to limbs that underwent psoas lengthening with outstanding results (accuracy=.78, sensitivity=.82, specificity=.73). The criteria were then validated using an extended retrospective case-control design. Case limbs met the criteria and underwent psoas lengthening. Control limbs met the criteria, but did not undergo psoas lengthening. Over-treated limbs failed the criteria and underwent psoas lengthening. Other-treated limbs failed the criteria and did not undergo psoas lengthening. The rate of good outcomes among Cases exceeded that observed among controls (82% vs. 60%, relative risk=1.37), and far exceeded that observed in Over-treated limbs (27%). Other-treated limbs had good outcomes 52% of the time. Application of the criteria in the future is estimated to increase the overall rate of good pelvis-hip outcomes from 58% to 72% among children with diplegia who undergo single-event multi-level surgery (SEMLS).

Evaluation of conventional selection criteria for psoas lengthening for individuals with cerebral palsy: A retrospective, case-controlled study

Background Psoas lengthening surgery has been advocated to improve hip function in patients with spastic cerebral palsy (CP); however, no uniform or standardized selection criteria have been agreed upon. Our study evaluated a proposed algorithm for selecting patients for psoas surgery to be included as part of a single-event multilevel surgery (SEMLS). Methods A retrospective, case-controlled study was performed on children with CP who underwent a SEMLS and met 2 of 3 of the following proposed selection criteria after gait analysis: (1) maximum hip extension no >8 degrees of flexion, (2) maximum pelvic tilt >24 degrees, and (3) pelvic tilt range of motion >8 degrees. One group had a psoas lengthening surgery as part of their SEMLS (psoas group) and 1 group did not (control group). Among other variables, overall kinematic gait pathology, as measured by the Gait Deviation Index (GDI), Pelvis and Hip kinematic gait pathology, as measured by the Pelvis and Hip Deviation Index (PHiDI), and Gross Motor Function Classification System (GMFCS) levels were compared. Results Eighty-seven sides met 2 of 3 of the proposed selection criteria; 32 in the psoas group and 55 in the control group. Both groups showed improvement in function after SEMLS. There was a significantly greater improvement in GDI for the psoas group in patients with GMFCS levels 3 and 4 (+12.9 vs. +7.7, P=0.02). Odds ratio for “poor outcomes” in PHiDI for the control group compared with the psoas group was 5.1 (95% CI, 1.37-18.95), which was significant. Conclusions Certain patients that met the proposed selection criteria did functionally better if psoas surgery was included as part of their SEMLS, specifically those that were classified as GMFCS levels 3 and 4. The risk of no improvement in hip function after SEMLS was greater if the parameters were met and psoas lengthening was not performed. The differences between the groups were modest by clinical standards, leaving open the possibility that other selection criteria may better differentiate those that would do well and those that would do poorly after psoas surgery. Level of Evidence Retrospective, case-controlled study. Level III.

Validity of surgeon perception of navigated pedicle screw position: a cadaveric study.

Study Design. Human Cadaveric Experimental Study. Objective. To determine the validity of surgeon perception of pedicle screw position inserted using intraoperative three-dimensional (O-arm) image-guided screw insertion. Summary of Background Data. A surgeons ability to detect pedicle wall violations intraoperatively is crucial for optimal pedicle screw placement. Accuracy of use of a probe or sound to assess pedicle breach is not optimal and may require experience. Intraoperative navigation has been shown to improve screw placement accuracy. It has not been shown, however, whether navigation in combination with screw tract palpation can further increase the surgeons ability to detect a pedicle breach in pedicle screw placement in the cervical, thoracic, and lumbosacral spine. Methods. Four hundred eighteen screws were inserted using three-dimensional image guidance transpedicularly from C2 to S1 in 10 fresh frozen cadavers. Screw tracts were created using navigation and then probed. After probing, the surgeon stated whether he perceived that the screw would be in, out laterally, or out medially. After screw insertion for all the levels, open dissection was then performed to determine the actual pedicle screw position. The surgeons perception of screw position was compared to the dissection results. Results. The overall specificity, sensitivity, positive predictive value, and negative predictive value of the surgeon perception of pedicle screw position were 87%, 80%, 78% and 88%, respectively. Accuracy of surgeon perception of pedicle screw position was significantly less than in the cervical spine when compared with thoracic and lumbosacral spine. Conclusion. Surgeon perception of a navigated pedicle screw position is accurate in the thoracic and lumbar spine. Detection of pedicle screw violations by surgeon perception in the cervical spine is less accurate and does not reliably lead to accurate screw placement.

What's New in Pediatric Spine Growth Modulation and Implant Technology for Early-Onset Scoliosis?

Background: Early-onset scoliosis (EOS) affects roughly 1 to 2 out of 10,000 live births per year. Because this subset of patients has a yet to achieve a majority of their skeletal growth, a number of treatment challenges need to be addressed before surgical intervention. If left untreated, EOS can cause a number of problems throughout the patient’s lifespan, particularly in regards to the growth of the thorax and pulmonary development. A wide variety of surgical systems and techniques are available to the treating surgeon. Methods: A review of the orthopaedic literature from 2010 to 2015 relating to pediatric spine growth modulation was performed. Ninety-eight papers were identified and, following exclusion criteria, a total of 31 papers were selected for further review. Results: This paper summarizes the recently published literature regarding growth-friendly spinal implants, the status of their Food and Drug Administration approval labeling as well as the indications, applications, and complications associated with their implementation. Conclusions: There are a growing number of options at the surgeon’s disposal when treating patients with EOS. As surgeons, we must continue to be vigilant in our demand for sound clinical evidence as we strive to provide optimal care for our patients. The rapidly advancing field of spinal growth modulation is exciting. More work must be done to further enhance our ability to predictably modulate growth in the pediatric spine.

Extensor Mechanism Injury in the Pediatric Population—A Clinical Review

The extensor mechanism of the knee-consisting of the four muscles of the quadriceps, the quadriceps tendon, the patella, and the patellar ligament-is essential for lower extremity function during both standing and ambulation. The presence of articular cartilage and growing physes in the pediatric knee, coupled with the generation of significant tensile force, creates an opportunity for pathology unique to the pediatric population.Tibial tubercle fractures and patella injuries are quite rare, and even pediatric-trained orthopaedic surgeons may not be exposed to these injuries on a regular basis. It is the intent of this article to discuss the current literature regarding the mechanism of injury, diagnostic workup, classification, indications for surgical versus non-surgical management, and techniques for operative management for both tibial tubercle and patella (transverse and sleeve) fractures.

Skeletal Anomalies Associated with Esophageal Atresia

Skeletal anomalies are seen in 1.6–55 % of cases of esophageal atresia or tracheoesophageal fistula, usually in the context of the VACTERL association, and may be divided into limb and spinal anomalies. The most common limb anomaly is radial defect/hypoplasia. Congenital spine anomalies may lead to scoliosis, although deformity may also result iatrogenically after thoracotomy. Life expectancy mainly depends on the degree of nonskeletal involvement. Associated skeletal anomalies are typically non-life-threatening, and treatment of such may thus be delayed until medical stabilization is performed and a better understanding of overall prognosis is obtained. For patients with minimal symptoms or limitations secondary to nonskeletal anomalies, the results of treatment of their skeletal anomalies are dependent on the degree of involvement and type of malformation and are expected to be the same as if they occurred in isolated fashion.