Ozgur Dede

Biomechanics and anterior cruciate ligament reconstruction

For years, bioengineers and orthopaedic surgeons have applied the principles of mechanics to gain valuable information about the complex function of the anterior cruciate ligament (ACL). The results of these investigations have provided scientific data for surgeons to improve methods of ACL reconstruction and postoperative rehabilitation. This review paper will present specific examples of how the field of biomechanics has impacted the evolution of ACL research. The anatomy and biomechanics of the ACL as well as the discovery of new tools in ACL-related biomechanical study are first introduced. Some important factors affecting the surgical outcome of ACL reconstruction, including graft selection, tunnel placement, initial graft tension, graft fixation, graft tunnel motion and healing, are then discussed. The scientific basis for the new surgical procedure, i.e., anatomic double bundle ACL reconstruction, designed to regain rotatory stability of the knee, is presented. To conclude, the future role of biomechanics in gaining valuable in-vivo data that can further advance the understanding of the ACL and ACL graft function in order to improve the patient outcome following ACL reconstruction is suggested.

Determination of a Safe Range of Knee Flexion Angles for Fixation of the Grafts in Double-Bundle Anterior Cruciate Ligament Reconstruction: A Human Cadaveric Study

Background For anterior cruciate ligament reconstruction with a double-bundle procedure, one of the major concerns is to not predispose either one of the grafts to risk of failure by overloading. Hypothesis Knee flexion angles between 15° and 45° for anteromedial graft fixation and 15° for posterolateral graft fixation are safe for both grafts in double-bundle anterior cruciate ligament reconstruction. Study Design Controlled laboratory study. Methods Nine human cadaveric knees were tested. The double-bundle anterior cruciate ligament reconstruction was conducted with both grafts fixed at 15° of knee flexion (fixation protocol 15/15) and again with the anteromedial and posterolateral grafts fixed at 45° and 15° of knee flexion (fixation protocol 45/15). For both fixation protocols, the knee kinematics and the in situ forces of the reconstructed anterior cruciate ligament and its individual grafts were measured and collected under an anterior tibial load of 134 N and combined rotatory loads of 10 N·m of valgus and 5 N·m of internal tibial torque. The data from both fixation protocols were compared with those of an intact knee. Results In response to the 2 external loading conditions, both fixation protocols (15/15 and 45/15) could restore the knee kinematics to within 2 mm of the intact knee (although statistically significant differences were found between fixation protocol 15/15 and the intact knee) and the overall in situ forces in the grafts similar to the intact anterior cruciate ligament. In response to the 134-N anterior tibial load, the in situ forces in the anteromedial graft for both fixation protocols did not exceed those of the intact anteromedial bundle. But at 30° and 45° of knee flexion, the in situ forces for fixation protocol 15/15 were 20.7% and 22.1% lower, respectively, when compared with the intact anteromedial bundle. Under combined rotatory loads, the anteromedial graft for fixation protocol 15/15 had in situ forces that were 45% lower than the intact anteromedial bundle at 30° of knee flexion. The in situ force in the posterolateral graft for both fixation protocols did not exceed those of the intact posterolateral bundle, nor were they significantly different from the intact posterolateral bundle at any of the flexion angles tested. Conclusion Both fixation protocols restored knee kinematics without predisposing either graft to failure. Therefore, knee flexion angles between 15° and 45° for graft fixation were found to be safe for the anteromedial graft, while 15° of knee flexion was safe for the posterolateral graft. Clinical Relevance A range of knee flexion angles that is safe for the fixation of both grafts in double-bundle anterior cruciate ligament reconstruction was determined.

Pulmonary and Radiographic Outcomes of VEPTR (Vertical Expandable Prosthetic Titanium Rib) Treatment in Early-Onset Scoliosis

BACKGROUND VEPTR (vertical expandable prosthetic titanium rib) expansion thoracoplasty is used to manage thoracic insufficiency syndrome in early-onset scoliosis. Literature regarding the effects of this technique on pulmonary function is scarce. The aim of this study was to report the intermediate-term results of VEPTR expansion thoracoplasty. METHODS Twenty-one children with thoracic insufficiency syndrome underwent VEPTR expansion thoracoplasty from 2002 to 2012 and had complete chart data, preoperative and follow-up radiographs, and pulmonary function tests performed at the index implantation, first expansion, and last expansion. Pulmonary function tests with forced and passive deflation techniques developed for children under general anesthesia were performed prior to the index implantation and each expansion surgery under the same anesthetic conditions. Pulmonary and radiographic parameters were analyzed longitudinally. RESULTS Mean follow-up was six years, and mean age at implantation was 4.8 years. The mean number of expansion procedures per patient was eleven, and the mean number of pulmonary function tests was ten. The mean interval between surgical procedures was 6.4 months. Mean forced vital capacity (FVC) increased from 0.65 to 0.96 L (p < 0.0001). However, the percentage of the predicted FVC decreased from 77% to 58%. Respiratory system compliance normalized on the basis of body weight, Crs/kg, decreased by 39%, from 1.4 to 0.86 mL/cm H2O/kg. The mean Cobb angle before treatment was 80°, and the mean maximum thoracic kyphosis angle was 57° (range, 7° to 107°). The initial coronal correction was maintained at the time of final follow-up (67°); however, there was a trend toward a decrease in the maximum thoracic kyphosis angle (to 66°, p = 0.08). Clinically apparent proximal thoracic kyphosis occurred in four patients, and spinal imbalance occurred in seven. The mean gain in T1-T12 height during the treatment period was 18 mm (2.9 mm/year). CONCLUSIONS FVC improved over time; however, this increase in lung volume did not keep up with the growth of the child, as the percentage of the predicted FVC decreased, and the chest wall stiffness increased. Coronal correction was maintained, but the increase in proximal thoracic kyphosis is concerning. LEVEL OF EVIDENCE Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Serial derotational casting in congenital scoliosis as a time-buying strategy.

Background: Serial casting is an effective treatment modality in early-onset idiopathic scoliosis; however, the role of this method in congenital scoliosis is not well studied. Methods: A total of 11 patients with progressive congenital scoliosis were treated with serial cast application. Age at initial cast application, magnitudes of the congenital, compensatory and sagittal deformities, coronal balance, T1 to T12 height, number of casts and time-in cast per patient, subsequent surgical interventions, and complications were evaluated. Results: Mean age at the first cast application was 40 months, and the average number of cast changes was 6.2 per patient. There were no major complications. The average precasting curve magnitude was 70.7 degrees (range, 44 to 88 degrees) and was significantly reduced to 55.1 degrees (range, 16 to 78 degrees) at the latest follow-up (P=0.005). The average precasting compensatory curve was 55.8 degrees (range, 38 to 72 degrees) and was significantly reduced to 39.8 degrees (range, 23 to 62 degrees) at the latest follow-up (P=0.017). Average T1 to 12 height increased from 12.8 cm at post-first cast to a 14.6 cm at the latest follow-up (P=0.04). Average time in cast was 26.3 months (range, 13 to 49 mo). During the treatment period, none of the patients required surgery for curve progression. Conclusions: Serial derotational casting is a safe and effective time-buying strategy to delay the surgical interventions in congenital deformities in the short-term follow-up. Level of Evidence: Level IV, case series.

Using the freehand pedicle screw placement technique in adolescent idiopathic scoliosis surgery: what is the incidence of neurological symptoms secondary to misplaced screws?

Study Design. Retrospective case series. Objective. This study evaluated the incidence of postoperative neurological symptoms after a freehand pedicle screw insertion technique in idiopathic posterior scoliosis surgery. Summary of Background Data. It is generally accepted that pedicle screws can be inserted by a freehand technique in the thoracic and lumbar spine in patients with adolescent idiopathic scoliosis (AIS) with a very low frequency of major complications. The prevalence of clinically significant screw misplacement, with or without the need for revision surgery is less well defined. Methods. Between January 1, 2000, and October 2, 2012, five hundred fifty-nine patients with AIS had thoracolumbar posterior instrumented spine surgery at the Childrens Hospital of Pittsburgh. Each patients chart and radiographs were reviewed and only those with AIS were included. Patients with neuromuscular and syndromic diagnoses were excluded as well as those with congenital or traumatic etiologies, incomplete charts, less than 3 months of follow-up and those without pedicle screws. The records were studied for complaints of radicular pain, neurological deficit, or severe headache that could be indicative of potential screw misplacement. Results. Four hundred eighty-one patients with 5923 pedicle screws met the inclusion criteria. Nine patients (1.9%) developed symptoms and underwent computed tomographic scanning. Six patients were found to have pedicle screw malposition (8 screws) and 3 of these patients underwent revision surgery. Of the 3 revision patients, 2 presented with radicular symptoms (leg pain) and 1 with an orthostatic headache due to cerebrospinal fluid leakage. At the final follow-up, all revision patients had complete symptom resolution. In total, there were 8 symptomatic, misplaced pedicle screws (0.14%) in 6 patients (1.25%). Conclusion. During a 12-year period in a dedicated pediatric orthopedic hospital using the freehand placement technique, the incidence of symptomatic misplaced pedicle screws was exceedingly low. Level of Evidence: 4

Adult spinal deformity: a very heterogeneous population of patients with different needs

OBJECTIVE The purpose of this study was to analyze and demonstrate the heterogeneity in adult spinal deformity (ASD) populations by baseline health-related quality of life (HRQL) data. METHODS ASD was defined as patients over 18 years of age with any of the following: coronal deformity >20°, sagittal vertical axis (SVA) >5 cm, pelvic tilt >25°, or thoracic kyphosis >60°. Three hundred fifty-two patients meeting the above definition of ASD were analyzed for measures of HRQL (Oswestry disability index [ODI], SRS-22 [Scoliosis Research Society-22], and SF-36 [Short form-36 health survey] questionnaires) at presentation. Age groups were defined as 18-40, 40-60, and >60 years. Deformity was analyzed as either degenerative (DS) or idiopathic (IS) (294 patients; 71 degenerative, 223 idiopathic). RESULTS There were significant differences between age groups--predominantly between the lower age group (18-40) and others--for all HRQL parameters except SRS-22 mental health and SF-36 mental component score. Similarly, HRQL measures for DS and IS deformities were significantly different. Regarding location of main curves, thoracolumbar/lumbar (TL/L) (70.2%) was dominant for the DS group and thoracic (55%) for the IS group. Mean age was 65 years for the DS group and 36 for the IS group, which were significantly different. Radiographic parameters were also significantly different between these groups, with IS patients having more coronal deformity and better sagittal balance. CONCLUSION ASD patients are very heterogeneous at presentation, depending on age and diagnosis. There is a distinct need to stratify ASD as early and late presentation ASD and/or by diagnosis. Patients with IS deformity may be very different from those with DS deformity, even at time of presentation. These differences must be taken into consideration in treatment of these patients, as well as for the analysis of the results of treatment.

Is decreased bone mineral density associated with development of scoliosis?A bipedal osteopenic rat model

BackgroundAn association between adolescent idiopathic scoliosis and osteopenia has been proposed to exist. It is still not clear whether there is such an association and if so, whether osteopenia is a causative factor or a consequence. Our previous pilot studies have suggested the presence of osteopenia in scoliotic animals. The aim of this study was to investigate the development of scoliosis in an unpinealectomized bipedal osteopenic rat model, implementing osteoporosis as a causative factor.MethodsFifty Sprague-Dawley rats were rendered bipedal at the 3rd postnatal week and separated into control (25 rats) and heparin (25 rats receiving 1 IU/gr body weight/day) groups. DEXA scans after 4 weeks of heparin administration showed low bone mass in the heparin group. Anteroposterior and lateral x-rays of the surviving 42 animals (19 in heparin and 23 in control groups) were taken under anesthesia at the 40th week to evaluate for spinal deformity. Additional histomorphometric analysis was done on spine specimens to confirm the low bone mass in heparin receiving animals. Results of the DEXA scans, histomorphometric analysis and radiological data were compared between the groups.ResultsBone mineral densities of rats in the heparin group were significantly lower than the control group as evidenced by both the DEXA scans and histomorphometric analyses. However, the incidence of scoliosis (82% in heparin and 65% in control; p > 0.05) as well as the curve magnitudes (12.1 ± 3.8 in heparin versus 10.1 ± 4.3 degrees in control; p > 0.05) were not significantly different. Osteopenic rats were significantly less kyphotic compared to control specimens (p = 0.001).ConclusionsThis study has revealed two important findings. One is that bipedality (in the absence of pinealectomy) by itself may be a cause of scoliosis in this animal model. Further studies on animal models need to consider bipedality as an independent factor. Secondly, relative hypokyphosis in osteopenic animals may have important implications. The absence of sagittal plane analyses in previous studies makes comparison impossible, but nonetheless these findings suggest that osteopenia may be important in the development of 3D deformity in adolescent idiopathic scoliosis.

Growth-sparing spinal instrumentation in skeletal dysplasia.

Study Design. Retrospective case series. Objective. To report the outcomes of distraction-based, growth-sparing spinal instrumentation in patients with skeletal dysplasia. Summary of Background Data. Patients with skeletal dysplasia with spinal deformity often undergo early fusion, further compromising an already small chest. Nonfusion techniques may provide a safe alternative and allow for thoracic growth. Methods. Between 2004 and 2010, 12 children with a diagnosis of various types of skeletal dysplasia underwent growth-sparing spinal instrumentation for severe spinal deformities. The mean duration of treatment with growing rods was 57 months (42–84 mo). Nine patients were treated with growing rods (8 dual, 1 single), and 3 were treated with vertical expandable prosthetic titanium rib (VEPTR; Synthes). Preoperative, initial postoperative, and final follow-up anteroposterior and lateral spine radiographs were measured for magnitude of deformity, junctional kyphosis, and implant failure. Results. The major curve Cobb angle improved from a mean of 79° preoperatively to a mean of 41° at the last follow-up (52%). There was a decrease in mean thoracic kyphosis from 77° preoperatively to 64° at final follow-up and an increase in mean lumbar lordosis from 58° preoperatively to 63° at final follow-up. The mean space available for the lungs increased by 26 mm on the concave and 24 mm on the convex side. Six patients required revision surgery for proximal junctional kyphosis. There were 4 rod failures and 6 hook and 8 screw dislodgements. One patient with vertical expandable prosthetic titanium rib had failed rib fixation that required revision. Conclusion. Growth-sparing spinal instrumentation in patients with skeletal dysplasia and severe spinal deformity has a high complication and revision rate, and surgeons should closely monitor these patients. The complication rate is comparable with previous reports on patients with other diagnoses. However, deformities were well controlled, some trunk growth was achieved, and fusion surgery was delayed in all cases. Level of Evidence: 4

2014 Update on the 'growing spine surgery' for young children with scoliosis.

Purpose of review Spinal fusion procedures that are the mainstay of the treatment of progressive or severe curves in adolescents and adults are not suitable for most young children as there is a large magnitude of remaining growth. Early spinal fusion stunts the growth of the thorax and may interfere with the development of the lungs. Therefore, in children with early-onset scoliosis, ‘growth friendly’ instrumentation systems have been utilized to control the deformity while allowing the growth of the spine and the thoracic cage. Recent findings The experience with growing rods has been increasing, along with expanding indications. Several self-lengthening instrumentation systems have been introduced aiming for guided spinal growth. There has been considerable progress in the clinical and laboratory studies using magnetically controlled growing rod constructs. Growing rods and vertical expandable prosthetic titanium rib (VEPTR) systems provide deformity control while allowing for spinal growth along with a risk of spontaneous vertebral fusions. VEPTR may cause rib fusions as the implants overlie the thoracic cage and, therefore, the use in pure spinal deformities is controversial. Summary There have been exciting recent advances concerning the treatment of spinal deformities in young children. Despite these advances, the surgical treatment of early-onset scoliosis remains far from optimal and more development is on the way.

Anterior and Posterior Vertebral Column Resection Versus Posterior-only Technique: A Comparison of Clinical Outcomes and Complications in Congenital Kyphoscoliosis.

Study Design: Retrospective cohort. Objective: The purpose of this study is to compare the anterior-posterior surgery to posterior-only vertebra resection for congenital kyphoscoliosis in pediatric patients. Summary of Background Data: Vertebral column resection is a very powerful correction technique mainly used in the treatment of severe and rigid spinal deformities. The technique can be applied with combined anterior and posterior vertebral column resection (APVCR) or posterior-only vertebral column resection (PVCR) approaches. PVCR has gained popularity recently due to several apparent advantages, but APVCR is still believed by some to be a viable alternative, despite the use of an anterior exposure. Materials and Methods: A retrospective chart and radiographic review was performed including the patients with congenital kyphoscoliosis up to 16 years of age who were operated on by a single senior surgeon in our department after 2005. The data included surgical time, estimated blood loss, duration of hospital and postoperative intensive care unit stay, intraoperative and postoperative complications. Preoperative, postoperative, and follow-up radiographs were evaluated for scoliosis, kyphosis, and spinal balance. Results: Twenty-six patients (20 girls, 6 boys) met the inclusion criteria. APVCR was performed on 17 (median age, 13.2 y) and PVCR on 9 (median age, 10.7 y). Scoliosis correction at the time of last follow-up was 54.3% and 52.6% for APVCR and PVCR, respectively, whereas the average kyphosis correction was 25.4 degrees in APVCR and 30.1 degrees in PVCR group. Surgical time, hospital stay, and estimated blood loss were all significantly higher in the APVCR group, whereas the complication rates were similar. No neurological or vascular complications were encountered. Conclusions: This study showed that although the operative time and surgical blood loss were higher with APVCR, there were no major complications and the radiologic outcomes were similar between APVCR and PVCR. APVCR should be considered as an acceptable technique especially in deformities where PVCR would be technically difficult or at the beginning of the spine surgeon’s learning curve. Level of Evidence: Level III.