Ron L. Ferguson

A mechanistic classification of closed, indirect fractures and dislocations of the lower cervical spine

Closed, indirect fractures and dislocations of the lower cervical spine occur in families or groups within which there is a spectrum of anatomic damage to a cervical motion segment. This study of 165 cases demonstrates the various spectra of injury, called phylogenies, and develops a classification based on the mechanism of injury. The common groups are compressive flexion, vertical compression, distractive flexion, compressive extension, distractive extension, and lateral flexion. The probability of an associated neurologic lesion relates directly to the type and severity of cervical spine injury. With use of the classification, it is possible to formulate a rational treatment plan for injuries to the cervical spine.

The Galveston technique of pelvic fixation with L-rod instrumentation of the spine.

From April 1978 to October 1982, the authors performed 44 pelvic fixations as part of L-rod Instrumentation of a spinal deformity. Thirty scoliosis and revision scoliosis cases with a minimum of 1 year follow-up were analyzed for changes of the instrumentation with respect to the pelvis, angular changes at the lumbosacral junction, radiolucency about the portions of the rods providing pelvic fixation, and success of lumbosacral fusion. The technique for fixation was different among three groups of patients. A pelvic fixation technique in which the pelvic segments of the rods were longer than 6 cm, completely intraosseous through their iliac course, and within 1.5 cm of the sciatic notch, yielded the best results.

The Galveston Technique for L Rod Instrumentation of the Scoliotic Spine

Many small details of technique are important for achieving an excellent quality L-rod instrumentation of the scoliotic spine. Herein the authors report specifics gleaned from their experience and discuss the basis for them. The optimum approach establishes correctability of the deformity prior to spinal instrumentation, provides secure internal fixation of the spine, and strives for a massive arthrodesis.

A mechanistic classification of thoracolumbar spine fractures.

Thoracolumbar spinal injuries are classified on the basis of the mechanical mode of failure of the vertebral bodies. The fractures are presented in seven categories. Emphasis is placed on the injury component causing the fracture patterns. The choice of instrumentation for surgery is based on the surgeons understanding of these injury patterns.

Biomechanical comparisons of spinal fracture models and the stabilizing effects of posterior instrumentations

In this study, the authors evaluated the stiffness of motion segments in intact spines in two spine fracture models, and with each of five implant systems used for posterior fixation of thoracolumbar spine fractures. The devices represented a cross-section of types, including those employing sublaminar wires with and without laminar hooks, pedicle screws, plates, and rods. Two spine fracture models, one partially and one totally destabilized, were used in the tests of the instrumentation. Stiffness, or the magnitude of load needed to produce a unit displacement of the construct in the direction of the applied load, was measured in flexion, extension, lateral bending, and torsion in combination with a compressive force. Both horizontal plane shear and angular displacements were measured in the two fracture patterns. All evaluations were made by testing the difference in stiffness for statistical significance among groups. The results showed significant differences in stiffness without Instrumentation among intact spines, partly destabilized spines (anterior two-thirds of disk and posterior ligaments removed), and totally destabilized spines (only anterior longitudinal ligament intact). The implant/spine constructs were least stiff relative to the intact spine in torsion, followed in increasing order of stiffness with flexion, lateral bending, and extension. In the Roy-Camille plate with six-screw fixation was found to produce the stiffest construct, followed by wired Harrington rods, C-rods and J-rods, and the Vermont internal fixator. Cyclic loading with stiffness measured before and after cycling indicated that most spinal implants lost stiffness in torsion and lateral bending, and that those tested maintained their initial flexion stiffnesses.

Correlation of static to dynamic measures of lower extremity range of motion in cerebral palsy and control populations.

The question addressed in this study was whether static measurements of hip, knee, and ankle range of motion correlate to dynamic measurements of hip and knee function during gait. Range-of-motion measures of the lower extremities taken during physical examination (static variables) were recorded on 80 adolescents with cerebral palsy and 30 adolescent normal controls. Kinematic measurements collected during gait analysis (dynamic variables) were recorded on the same patients and controls. Results indicated no correlation greater than r = 0.50 (R2 < 0.25) between any static and dynamic variable for either group--cerebral palsy patients or controls. The lack of good correlation of these measures indicates static physical examination variables such as popliteal angle and straight-leg raise are not good predictors of dynamic gait, such as knee-extension and hip-flexion variables measured during ambulation in controls or cerebral palsy populations.

Comprehensive outcomes of surgically treated idiopathic toe walkers.

Abstract: The treatment of idiopathic toe walking in children can include surgical lengthening of the gastrocnemius/soleus complex after conservative options have been ineffective. Previous outcome reports of surgery for idiopathic toe walkers have largely been limited to assessing the sagittal plane motion of dorsiflexion/plantar flexion with minimal quantitative preoperative and postoperative analysis. The purpose of this study was to comprehensively assess the outcome of idiopathic toe walkers that had been treated surgically. Fourteen children seen in our motion analysis laboratory that underwent gastrocnemius or tendo-Achilles lengthening for idiopathic toe walking were retrospectively reviewed. Preoperatively, this group had significantly greater anterior pelvic tilt than normal, decreased peak knee flexion in swing, greater external foot progression, and the expected increased plantar flexion (P < 0.01). Postoperatively, anterior pelvic tilt decreased by a mean of about 4 degrees (P < 0.01), only for the group that had tendo-Achilles lengthening because the gastrocnemius group was close to normal preoperatively, and peak knee flexion normalized. The foot progression angle of this group did not change from preoperative values and remained significantly more external than normal, although dorsiflexion in stance significantly improved after surgery (indicating the goal of the surgery was achieved). Increased external foot progression in idiopathic toe walkers is apparently due to increased external tibial torsion and/or external hip rotation but was unaffected by gastrocnemius/soleus surgical lengthening. Significant improvement occurred on an overall index of gait variables, indicating surgery can be an effective treatment of idiopathic toe walkers.

A biomechanical study of thoracolumbar spine fractures with bone in the canal. Part III. Mechanical properties of the dura and its tethering ligaments.

Experiments were performed to determine some mechanical properties of the spinal cord-meningeal (SCM) complex and its tethering elements with reference to factors contributing to contact pressure of an anterior mass on the SCM complex with spinal fracture and the development of some means to relieve the pressure. Measurements were made using a combined microload cell and displacement transducer that was passed posteriorly through a hole drilled in vertebra T12 through the interpedicular space and contacted the cord. Loss of nerve roots and anterior ligaments as dural tethers in the lumbar region permitted the SCM complex to fall out of the lordosis of the canal and fail to resist transverse loading. Head and neck flexion increased contact force for a given depth of penetration, particularly in the cervical region. This was consistent with measurements of strain along the dura that was greatest in the cervical region. The dura was found to be elastic, having a failure strain averaging 34% but was uniform in thickness, stiffness, and elastic modulus along its length. The study did not delineate any surgical manipulation other than removal of the anterior mass that would be beneficial when there is anterior compression of the spinal cord.

Comparison of neurologic deficits with atlanto-dens intervals in patients with Down syndrome

Eighty-four patients with Down syndrome had flexion-extension lateral roentgenograms of the C1-C2 articulation for the purpose of dividing the group into subluxators (> or = 4 mm atlanto-dens interval and 2 mm translation) and nonsubluxators (those who did not meet these criteria). Neurologic examinations and chart review were carried out on all patients to ascertain those with a positive neurologic finding or history. Seventeen (20%) were defined as subluxators and 67 (80%) as nonsubluxators. Five (29%) of the subluxators were found to have positive neurologic findings and 18 (27%) of the nonsubluxators had similar types of positive neurologic findings. These percentages are not significantly different. This led us to conclude that positive neurologic findings and an abnormal atlanto-dens interval are not alone adequate criteria to judge need for surgical stabilization of the C1-C2 articulation in patients with Down syndrome.

The pediatric outcomes data collection instrument detects improvements for children with ambulatory cerebral palsy after orthopaedic intervention.

The purpose of this study was to assess whether the Pediatric Outcomes Data Collection Instrument (PODCI) was able to detect changes in function, as perceived by the parents of children and adolescents with cerebral palsy who had undergone lower limb soft tissue and/or bony surgeries. This was a retrospective study of 80 ambulatory patients who were seen in the motion laboratory and classified with the Gross Motor Functional Classification System (GMFCS). Significant changes (P < 0.05) were detected in the PODCI scores for upper extremity function, transfers and mobility, physical function and sports, and global function after surgery, by approximately 4% to 5%, whereas comfort (pain-free) did not significantly change. There was a significant difference in the PODCI scores preoperatively between GMFCS levels I, II, and III for upper extremity function, transfers and mobility, physical function and sports, and global function. Postoperative improvements were of equal magnitude for each GMFCS level. This suggests that the PODCI did not have a ceiling effect for high-functioning children. Age (±10 years) and surgery (soft tissue/soft tissue plus bony) were not significant factors for any of the subcategories preoperative to postoperative. In conclusion, the PODCI detected improvement as perceived by the parents in ambulatory children with cerebral palsy after lower-limb soft tissue and/or bony surgeries in 4 areas by a magnitude of approximately 4% to 5%.