Search

Study Design: Biomechanical testing of the pullout strengths of pedicle screws placed by two different techniques in adult human cadaveric cervical spines., Objectives: To determine whether there is a significant difference in screw purchase of two commonly proposed methods of cervical pedicle screw insertion., Summary of Background Data: Wiring techniques remain the gold standard for posterior cervical fixation. However, absent or deficient posterior elements may dictate the use of alternative fixation techniques. Cervical pedicle screws have been shown to have significantly higher pullout strength than lateral mass screws., Methods: Fifty fresh disarticulated human vertebrae (C3-C7) were evaluated with computed tomography for anatomic disease and pedicle morphometry. The right and left pedicles were randomly assigned to either a standard method or the Abumi insertion method. In the latter technique the cortex and cancellous bone of lateral mass are removed with a high-speed burr, which provides a direct view of the pedicle introitus. The pedicle is then probed and tapped and a 3.5-mm cortical screw inserted. Each screw was subjected to a uniaxial load to failure., Results: There was no significant difference in the mean pullout resistance between the Abumi (696 N) and standard (636.5 N) insertion techniques (P = 0.41). There was no difference in pullout resistance between vertebral levels or within vertebral levels. Two (4%) minor pedicle wall violations were observed., Conclusion: In selected circumstances pedicle screw instrumentation of the cervical spine may be used to manage complex deformities and patterns of instability. Surgeons need not be concerned about reduced screw purchase when deciding between the Abumi method and its alternatives.

Study Design: Independently assessed radiographic and anatomic comparison of device implantation methods., Objectives: To compare the relative accuracy of two techniques of inserting cervical pedicle screws., Summary of Background Data: In an attempt to define the anatomic risks of cervical pedicle screw insertion, image-guided stereotactic technology was shown to be superior to some other methods in vitro.- Meanwhile, in vivo experience with Abumi's technique of screw insertion has had few clinically relevant instances of screw malposition. There has been no direct comparison between current image-guided technology and Abumi's fluoroscopically assisted technique., Methods: The pedicles (C3-C7) of human cadaveric cervical spines were instrumented with 3.5-mm screws with either of two techniques. Cortical integrity and potential neurovascular injury were independently assessed by computed tomographic (CT) scans and anatomic dissection. A cortical breach was considered "critical" if the screw encroached on any vital structure. If any part of the screw violated the cortex of the pedicle but no vital structure was at risk for injury, the breach was classified as "noncritical.", Results: In Group I (StealthStation; Sofamor-Danek, Memphis, TN), 82% of screws were placed in the pedicle, and 18% had a critical breach. In Group II (Abumi technique), 88% of screws were placed in the pedicle, and 12% had a critical breach. No statistically significant differences were demonstrated between each group (P = 0.59). Regarding pedicle dimensions and safety of insertion, a critical pedicle diameter of 4.5 mm was determined to be the size below which a critical breach was likely, but above which there was a significantly greater likelihood for safe screw placement. The most common structure injured in each group was the vertebral artery., Conclusions: The use of a computer-assisted image guidance system did not enhance safety or accuracy in placing pedicle screws compared with Abumi's technique. Both techniques have a noteworthy risk of injuring a critical structure if inserted into the pedicles with a diameter of less than 4.5 mm. Under laboratory conditions, pedicles with a diameter of more than 4.5 mm have a significantly greater likelihood of being safely instrumented by either technique. These data indicate that cervical pedicle screw placement is feasible, but it should be reserved for selected circumstances with clear indications and in the presence of suitable pedicle morphology.

Study Design: This was a human cadaver study of the accuracy of biplanar roentgenography in determining pedicle screw position., Objective: To determine the independent accuracy of radiologic evaluation of screw placement and to determine if there are any particular screw malpositions that are more likely to produce a false sense of acceptable screw position., Summary of Background Data: Other investigators have reported the correlation between radiologic evaluation and anatomic dissection. However, in those studies the radiologic evaluation was not independent of the surgeons placing the screws. There has been no comment in the literature regarding particular screw malpositions that would lead the surgeon into a false sense of successful screw placement., Methods: Pedicle screws were placed in cadaver spines, and biplanar roentgenograms of the specimens were evaluated by independent observers. The results of the roantgenogram evaluation then were compared to those of the anatomic dissection., Results: The accuracy of roentgenogram evaluation varied from 73% to 83%, depending on the experience of the surgeon grading the roentgenograms. Screws misplaced medially into the spinal canal are more likely to give the surgeon a false sense of successful screw placement., Conclusions: The surgeon must not rely solely on the roentgenograms, but instead continue to use tactile sensory skills, anatomic knowledge, and additional modalities such as electromyography monitoring.

Study Design: This case-control study was undertaken to determine if relatives of patients who had been admitted for surgery for degenerative disc disease-related problems were at increased risk for lower back pain or sciatica., Objectives: To determine if familial factors play a role in placing a person at risk for development of degenerative disc disease of the lumbar spine., Summary of Background Data: It is known that smoking and various occupational factors can place a person at risk for degenerative disc disease problems. It is not known if a familial predisposition may also exist., Methods: The family members and relatives of 65 patients who had undergone surgery for lumbar degenerative disc disease were interviewed with a standardized questionnaire and compared with a control group of 67 patients who had been admitted to hospital for non-spine-related orthopedic procedures. The same interview and standardized questionnaire was used for both groups by a single observer., Results: In the study group of 65 patients who had undergone surgery for degenerative disc disease, 44.6% were noted to have a positive family history, whereas 25.4% of the patients in the control group had a positive family history. Eighteen and one-half percent of relatives in the study group had a history of having spinal surgery, compared with only 4.5% of the control group., Conclusions: The results indicate that a familial predisposition to degenerative disc disease can exist along with other risk factors.

This study was done to define and characterize those adult patients with scoliosis who will have problems of pain and/or progression leading to a surgical procedure and to review the results of these surgical procedures. The authors reviewed the cases of 49 adult patients who had undergone surgical treatment for scoliosis (average follow-up, 34 months; range, 24-140 months). The patients were categorized according to age, which allowed analysis of the data comparing age and the incidence and level of pain, age versus the degree of curvature, and age versus the incidence of progression. The relative incidence of pain and progression as indications for surgery were found to vary with respect to age. In the younger groups, progression was more often the indication for surgery than in the older groups. The younger groups also had larger curves than did the older groups, on average. The degree of pain was not found to correlate with the magnitude of the deformity. Surgical complications occurred in 20 patients; however, 14 of these were minor complications during the perioperative period, which did not result in any sequelae. Surgical treatment can be done with a relatively low serious complication rate and good results in terms of pain relief and reasonable correction of the deformity.