David W. Polly

Epidemiology of injuries associated with physical training among young men in the army

It is widely acknowledged that musculoskeletal injuries occur as a result of vigorous physical activity and exercise, but little quantitative documentation exists on the incidence of or risk factors for these injuries. This study was conducted to assess the incidence, types, and risk factors for training-related injuries among young men undergoing Army infantry basic training. Prior to training we evaluated 303 men (median age 19 yr), utilizing questionnaires and measurements of physical fitness. Subjects were followed over 12 wk of training. Physical training was documented on a daily basis, and injuries were ascertained by review of medical records for every trainee. We performed univariate and multivariate analyses of the data. Cumulative incidence of subjects with one or more lower extremity training-related injury was 37% (80% of all injuries). The most common injuries were muscle strains, sprains, and overuse knee conditions. A number of risk factors were identified, including: older age, smoking, previous injury (sprained ankles), low levels of previous occupational and physical activity, low frequency of running before entry into the Army, flexibility (both high and low), low physical fitness on entry, and unit training (high running mileage).

In vivo accuracy of thoracic pedicle screws

Study Design. A retrospective observational study of 279 transpedicular thoracic screws using postoperative computed tomography (CT). Objective. To determine the accuracy of transpedicular thoracic screws. Summary of Background Data. Previous studies have reported the importance of properly placed transpedicular thoracic screws. To our knowledge, the in vivo accuracy of pedicle screw placement throughout the entire thoracic spine by CT is unknown. Methods. The accuracy of thoracic screw placement within the pedicle and vertebral body and the resultant transverse screw angle (TSA) were assessed by postoperative CT. Cortical perforations of the pedicle were graded in 2-mm increments. Screws were regionally grouped for analysis. Results. Forty consecutive patients underwent instrumented posterior spinal fusion using 279 titanium thoracic pedicle screws of various diameters (4.5–6.5 mm). The regional distribution of the screws was 39 screws at T1–T4, 77 screws at T5–T8, and 163 screws at T9–T12. Fifty-seven percent of screws were totally confined within the pedicle. Although medial perforation of the pedicle wall occurred in 14% of screws, in <1% there was >2 mm of canal intrusion. Lateral pedicular perforation occurred in 68% of perforating screws and was significantly more common than medial perforation (P < 0.0005). Seventeen screws penetrated the anterior vertebral cortex by an average of 1.7 mm. Screws inserted between T1 and T4 had a decreased incidence of full containment within the pedicle (P < 0.0005) and vertebral body (P = 0.039) compared with T9–T12. The mean TSA for screws localized within the pedicle was 14.6° and was significantly different from screws with either medial (mean 18.0°) or lateral (mean 11.5°) pedicle perforation (P < 0.0005). Anterior vertebral penetration was associated with a smaller mean TSA of 10.1° (P = 0.01) and with lateral pedicle perforation (P < 0.0005). There were no neurologic or vascular complications. Conclusions. Ninety-nine percent of screws were fully contained or were inserted with either ≤2 mm of medial cortical perforation or an acceptable lateral breech using the “in-out-in” technique. Anterior cortical penetration occurred significantly more often with lateral pedicle perforation and with a smaller mean TSA. The incidence of fully contained screws was directly correlated with the region of instrumented thoracic spine.

A novel classification system for spinal instability in neoplastic disease: an evidence-based approach and expert consensus from the Spine Oncology Study Group.

Study Design. Systematic review and modified Delphi technique. Objective. To use an evidence-based medicine process using the best available literature and expert opinion consensus to develop a comprehensive classification system to diagnose neoplastic spinal instability. Summary of Background Data. Spinal instability is poorly defined in the literature and presently there is a lack of guidelines available to aid in defining the degree of spinal instability in the setting of neoplastic spinal disease. The concept of spinal instability remains important in the clinical decision-making process for patients with spine tumors. Methods. We have integrated the evidence provided by systematic reviews through a modified Delphi technique to generate a consensus of best evidence and expert opinion to develop a classification system to define neoplastic spinal instability. Results. A comprehensive classification system based on patient symptoms and radiographic criteria of the spine was developed to aid in predicting spine stability of neoplastic lesions. The classification system includes global spinal location of the tumor, type and presence of pain, bone lesion quality, spinal alignment, extent of vertebral body collapse, and posterolateral spinal element involvement. Qualitative scores were assigned based on relative importance of particular factors gleaned from the literature and refined by expert consensus. Conclusion. The Spine Instability Neoplastic Score is a comprehensive classification system with content validity that can guide clinicians in identifying when patients with neoplastic disease of the spine may benefit from surgical consultation. It can also aid surgeons in assessing the key components of spinal instability due to neoplasia and may become a prognostic tool for surgical decision-making when put in context with other key elements such as neurologic symptoms, extent of disease, prognosis, patient health factors, oncologic subtype, and radiosensitivity of the tumor.

Spinal Instability Neoplastic Score: An Analysis of Reliability and Validity From the Spine Oncology Study Group

PURPOSE Standardized indications for treatment of tumor-related spinal instability are hampered by the lack of a valid and reliable classification system. The objective of this study was to determine the interobserver reliability, intraobserver reliability, and predictive validity of the Spinal Instability Neoplastic Score (SINS). METHODS Clinical and radiographic data from 30 patients with spinal tumors were classified as stable, potentially unstable, and unstable by members of the Spine Oncology Study Group. The median category for each patient case (consensus opinion) was used as the gold standard for predictive validity testing. On two occasions at least 6 weeks apart, each rater also scored each patient using SINS. Each total score was converted into a three-category data field, with 0 to 6 as stable, 7 to 12 as potentially unstable, and 13 to 18 as unstable. RESULTS The κ statistics for interobserver reliability were 0.790, 0.841, 0.244, 0.456, 0.462, and 0.492 for the fields of location, pain, bone quality, alignment, vertebral body collapse, and posterolateral involvement, respectively. The κ statistics for intraobserver reliability were 0.806, 0.859, 0.528, 0.614, 0.590, and 0.662 for the same respective fields. Intraclass correlation coefficients for inter- and intraobserver reliability of total SINS score were 0.846 (95% CI, 0.773 to 0.911) and 0.886 (95% CI, 0.868 to 0.902), respectively. The κ statistic for predictive validity was 0.712 (95% CI, 0.676 to 0.766). CONCLUSION SINS demonstrated near-perfect inter- and intraobserver reliability in determining three clinically relevant categories of stability. The sensitivity and specificity of SINS for potentially unstable or unstable lesions were 95.7% and 79.5%, respectively.

The accuracy of selective magnetic resonance imaging compared with the findings of arthroscopy of the knee.

The results of selective magnetic resonance imaging of the knee were compared with those of arthroscopy in a prospective series of fifty patients. A specifically designed protocol for imaging, producing T1 sagittal images interleaved at four millimeters while the patients foot was in 20 degrees of external rotation, was utilized. This technique, called selective magnetic resonance imaging, yielded excellent visualization of the posterior cruciate ligament, medial meniscus, and lateral meniscus in all patients. However, in only 76 per cent of the patients was the anterior cruciate ligament well visualized. Compared with arthroscopy, the sensitivity, specificity, and accuracy of selective magnetic resonance imaging were, respectively, 95.8, 100, and 98 per cent for tears of the medial meniscus; 66.7, 95.1, and 90 per cent for tears of the lateral meniscus; undefined, 100, and 100 per cent for tears of the posterior cruciate ligament; and 100, 96.9, and 97.3 per cent for tears of the anterior cruciate ligament, when that ligament was well visualized. Our selective sequence can be performed in fifteen minutes at a cost that is comparable with that of arthrography. It is totally non-invasive and requires no exposure to ionizing radiation. Selective magnetic resonance imaging can be a safe and valuable adjunct to the clinical evaluation of the knee and an aid to efficient preoperative planning.

Rates of infection after spine surgery based on 108,419 procedures: a report from the Scoliosis Research Society Morbidity and Mortality Committee.

Study Design. Retrospective review of a prospectively collected database. Objective. Our objective was to assess the rates of postoperative wound infection associated with spine surgery. Summary of Background Data. Although wound infection after spine surgery remains a common source of morbidity, estimates of its rates of occurrence remain relatively limited. The Scoliosis Research Society prospectively collects morbidity and mortality data from its members, including the occurrence of wound infection. Methods. The Scoliosis Research Society morbidity and mortality database was queried for all reported spine surgery cases from 2004 to 2007. Cases were stratified based on factors including diagnosis, adult (≥21 years) versus pediatric (<21 years), primary versus revision, use of implants, and whether a minimally invasive approach was used. Superficial, deep, and total infection rates were calculated. Results. In total, 108,419 cases were identified, with an overall total infection rate of 2.1% (superficial = 0.8%, deep = 1.3%). Based on primary diagnosis, total postoperative wound infection rate for adults ranged from 1.4% for degenerative disease to 4.2% for kyphosis. Postoperative wound infection rates for pediatric patients ranged from 0.9% for degenerative disease to 5.4% for kyphosis. Rate of infection was further stratified based on subtype of degenerative disease, type of scoliosis, and type of kyphosis for both adult and pediatric patients. Factors associated with increased rate of infection included revision surgery (P < 0.001), performance of spinal fusion (P < 0.001), and use of implants (P < 0.001). Compared with a traditional open approach, use of a minimally invasive approach was associated with a lower rate of infection for lumbar discectomy (0.4% vs. 1.1%; P < 0.001) and for transforaminal lumbar interbody fusion (1.3% vs. 2.9%; P = 0.005). Conclusion. Our data suggest that postsurgical infection, even among skilled spine surgeons, is an inherent potential complication. These data provide general benchmarks of infection rates as a basis for ongoing efforts to improve safety of care.

Transforaminal lumbar interbody fusion: Clinical and radiographic results and complications in 100 consecutive patients

Objective: We retrospectively reviewed the results of 100 consecutive transforaminal lumbar interbody fusions (TLIFs) performed at one institution. The preoperative diagnoses included degenerative disk disease (55), spondylolisthesis (41; 22 isthmic, 19 degenerative), and degenerative adult scoliosis (4). There were 64 single-level, 33 two-level, 2 three-level, and 1 four-level TLIF (140 levels). Methods: The fusion mass was assessed by an independent observer using biplanar radiography, whereas clinical outcomes were assessed by means of several established outcome measures. Results: By level, the posterolateral fusion was judged to be probably or definitely solid in 78% of levels, whereas the interbody fusion was radiographically solid in 88% of levels, for an overall 93% fusion success/patient (94%/level). All patients had >24 months of postoperative clinical follow-up, and 82 patients (82%) were available for outcome measure assessment at an average follow-up of 34 months (range 24-61 months) postoperatively. Eighty-one percent of these patients reported a >50% decrease in their symptoms, and 76% of patients were satisfied with their results to the degree that they would have the procedure again. However, a large percentage of patients experienced incomplete relief of their symptoms. Twenty patients sustained minor complications, and there were no major complications. Conclusions: We conclude that TLIF is a safe and effective method of achieving lumbar fusion with a 93% radiographic fusion success and a nearly 80% rate of overall patient satisfaction but frequently results in incomplete relief of symptoms. Complications resulting from the procedure are uncommon and generally minor and transient.

Complications in the surgical treatment of 19,360 cases of pediatric scoliosis: a review of the Scoliosis Research Society Morbidity and Mortality database.

Study Design. Retrospective review of a multicenter database. Objective. To determine the complication rates associated with surgical treatment of pediatric scoliosis and to assess variables associated with increased complication rates. Summary of Background Data. Wide variability is reported for complications associated with the operative treatment of pediatric scoliosis. Limited number of patients, surgeons, and diagnoses occur in most reports. The Scoliosis Research Society Morbidity and Mortality (M&M) database aggregates deidentified data, permitting determination of complication rates from large numbers of patients and surgeons. Methods. Cases of pediatric scoliosis (age ⩽18 years), entered into the Scoliosis Research Society M&M database between 2004 and 2007, were analyzed. Age, scoliosis type, type of instrumentation used, and complications were assessed. Results. A total of 19,360 cases fulfilled inclusion criteria. Of these, complications occurred in 1971 (10.2%) cases. Overall complication rates differed significantly among idiopathic, congenital, and neuromuscular cases (P < 0.001). Neuromuscular scoliosis had the highest rate of complications (17.9%), followed by congenital scoliosis (10.6%) and idiopathic scoliosis (6.3%). Rates of neurologic deficit also differed significantly based on the etiology of scoliosis (P < 0.001), with the highest rate among congenital cases (2.0%), followed by neuromuscular types (1.1%) and idiopathic scoliosis (0.8%). Neur-omuscular scoliosis and congenital scoliosis had the highest rates of mortality (0.3% each), followed by idiopathic scoliosis (0.02%). Higher rates of new neurologic deficits were associated with revision procedures (P < 0.001) and with the use of corrective osteotomies (P < 0.001). The rates of new neurologic deficit were significantly higher for procedures using anterior screw-only constructs (2.0%) or wire-only constructs (1.7%), compared with pedicle screw-only constructs (0.7%) (P < 0.001). Conclusion. In this review of a large multicenter database of surgically treated pediatric scoliosis, neuromuscular scoliosis had the highest morbidity, but relatively high complication rates occurred in all groups. These data may be useful for preoperative counseling and surgical decision-making in the treatment of pediatric scoliosis.

Accuracy and efficacy of thoracic pedicle screws in curves more than 90

Study Design. Retrospective study of large-magnitude thoracic curves (≥90°) treated with pedicle screw constructs. Objective. To evaluate the results of pedicle screw constructs for thoracic curves ≥ 90° in terms of sagittal and coronal correction/efficacy, as well as accuracy and safety of thoracic pedicle screw placement. Summary of Background Data. Thoracic pedicle screw constructs continue to become increasingly more common; however, the debate continues about the safety and efficacy of these constructs because of their perceived increased risk of neurologic injury and the increased cost of spinal instrumentation. Methods. Since 1998, all patients with adolescent idiopathic scoliosis, or adult progression of adolescent idiopathic scoliosis, a thoracic curve ≥ 90° and a minimum 2-year follow-up who were treated with pedicle screw constructs were included in this study. Standing anteroposterior (or posteroanterior), lateral and bending preoperative radiographs, and anteroposterior (or posteroanterior) and lateral postoperative radiographs were evaluated for curve magnitude, flexibility, and postoperative correction to assess the efficacy of these constructs in the immediate postoperative period and at latest follow-up. Postoperative CT scans were evaluated for screw accuracy using established 2-mm increments (intrapedicular, 0–2 mm breach, 2–4 mm breach, > 4 mm breach). Preoperative plans were also reviewed to evaluate the ability to place a pedicle screw at each planned level in these large-magnitude curves. Results. Twenty patients with thoracic curves ≥ 90° and an average follow-up of 3.3 years (range, 2.0–5.2 years) were included in the study. All patients underwent a posterior spinal fusion with a pedicle screw only construct. The average preoperative main thoracic curve measured 100.2° (range, 90°–133°), with an average side-bender of 71.6° (29% flexibility). The average postoperative main thoracic curve was 32.3° (68% correction). A total of 352 thoracic screws were placed in the 20 cases (17.6 screws/case). Screw accuracy (either intrapedicular or <2 mm breach) was 96.3% (339 of 352 screws) by postoperative CT scanning. Ten screws were considered to have a breach between 2 and 4 mm (3 medial, 7 lateral), while three screws were > 4 mm (2 medial, 1 lateral). The two medial screws were the only placed screws that were removed (0.57%). Overall, 94% of planned screws (352 of 374 screws) were placed according to the preoperative plan. There were no incidences of screw or instrumentation failure. Of note, there was a temporary decrease in motor-evoked potentials during curve correction in 2 cases; however, there were no identifiable neurologic complications. Conclusions. Thoracic pedicle screw constructs can be safely used for large-magnitude curves. Curve correction (68%) is powerful for these curves, which are stiff and difficult to manage. Correction should be performed carefully with consideration given to convex compression for cases with concomitant hyperkyphosis for these “at risk” spinal cords. Screw accuracy (96.3%) was excellent in this review. The authors found that screws can consistently be placed according to the preoperative plan even in these large-magnitude curves.

Straight-Forward Versus Anatomic Trajectory Technique of Thoracic Pedicle Screw Fixation : A Biomechanical Analysis

Study Design. A biomechanical study on cadaveric thoracic vertebrae using pullout strength, insertional torque, and bone mineral density to determine the optimal sagittal trajectory of thoracic pedicle screws. Objective. To perform a biomechanical study on cadaveric thoracic vertebrae using insertional torque, pullout strength, and bone mineral density to determine the optimal biomechanical sagittal trajectory for placement thoracic pedicle screws. We compared the straight-forward (paralleling the vertebral endplate) with anatomic trajectory (directed along the true anatomic axis of the pedicle). Methods. Thirty cadaveric thoracic vertebrae were harvested and evaluated with dual-energy x-ray absorptiometry to assess bone mineral density. Matched, fixed-head pedicle screws were then randomly assigned by side and placed using the straight-forward or anatomic technique under fluoroscopic visualization while recording the maximum insertional torque. Pullout strength testing was then performed. Results. The maximum insertional torque for the straight-forward technique was 2.58 ± 0.14 (SE) in pounds, whereas the anatomic technique averaged 1.86 ± 0.14 (SE) in pounds (P = 0.0005). The maximum insertional torque at the neurocentral junction for the straight-forward technique averaged 1.89 ± 0.17 (SE) in-lbs. (73% of maximum insertional torque), whereas the anatomic trajectory averaged 1.39 ± 0.11 (SE) in pounds (75% of maximum insertional torque) (P = 0.007). The average pullout strength using a straight-forward trajectory was 611 ± 50 (SE) N compared to the anatomic trajectory, which averaged 481 ± 54 (SE) N (P = 0.034). The pullout strength correlated with mean bone mineral density for both the straight-forward (r = 0.461, P = 0.027) and anatomic (r = 0.598, P = 0.004) techniques. Conclusions. The straight-forward technique results in a 39% increase in maximum insertional torque and a 27% increase in pullout strength compared to the anatomic technique. The maximum insertional torque at the neurocentral junction resulted in a 36% increase using the straight-forward technique versus the anatomic trajectory. Bone mineral density directly correlates with pullout strength for both techniques.