Roger Lyon

Tensile properties of the human femur-anterior cruciate ligament-tibia complex The effects of specimen age and orientation

The structural properties of 27 pairs of human cadaver knees were evaluated. Specimens were equally divided into three groups of nine pairs each based on age: younger (22 to 35 years), middle (40 to 50 years), and older (60 to 97 years). Anterior-posterior displacement tests with the intact knee at 30° and 90° of flexion revealed a significant effect of knee flexion angle, but not of specimen age. Tensile tests of the femur-ACL- tibia complex were performed at 30° of knee flexion with the ACL aligned vertically along the direction of applied tensile load. One knee from each pair was oriented anatomically (anatomical orientation), and the contralateral knee was oriented with the tibia aligned vertically (tibial orientation). Structural properties of the femur-ACL-tibia complex, as represented by the linear stiffness, ultimate load, and energy absorbed, were found to decrease significantly with specimen age and were also found to have higher values in specimens tested in the anatomical orientation. In the younger specimens, linear stiffness (242 ± 28 N/mm) and ulti mate load (2160 ± 157 N) values found when the femur- ACL-tibia complex was tested in the anatomical orien tation were higher than those reported previously in the literature. These values provide new baseline data for the design and selection of grafts for ACL replacement in an attempt to reproduce normal knee kinematics.

A Randomized Clinical Trial of Ibuprofen Versus Acetaminophen With Codeine for Acute Pediatric Arm Fracture Pain

STUDY OBJECTIVE We compare the treatment of pain in children with arm fractures by ibuprofen 10 mg/kg versus acetaminophen with codeine 1 mg/kg/dose (codeine component). METHODS This was a randomized, double-blind, clinical trial of children during the first 3 days after discharge from the emergency department (ED). The primary outcome was failure of the oral study medication, defined as use of the rescue medication. Pain medication use, pain scores, functional outcomes, adverse effects, and satisfaction were also assessed. RESULTS Three hundred thirty-six children were randomized to treatment, 169 to ibuprofen and 167 to acetaminophen with codeine; 244 patients were analyzed. Both groups used a median of 4 doses (interquartile range 2, 6.5). The proportion of treatment failures for ibuprofen (20.3%) was lower than for acetaminophen with codeine (31.0%), though not statistically significant (difference=10.7%; 95% confidence interval -0.2 to 21.6). The proportion of children who had any function (play, sleep, eating, school) affected by pain when pain was analyzed by day after injury was significantly lower for the ibuprofen group. Significantly more children receiving acetaminophen with codeine reported adverse effects and did not want to use it for future fractures. CONCLUSION Ibuprofen was at least as effective as acetaminophen with codeine for outpatient analgesia for children with arm fractures. There was no significant difference in analgesic failure or pain scores, but children receiving ibuprofen had better functional outcomes. Children receiving ibuprofen had significantly fewer adverse effects, and both children and parents were more satisfied with ibuprofen. Ibuprofen is preferable to acetaminophen with codeine for outpatient treatment of children with uncomplicated arm fractures.

A comparative evaluation of the mechanical properties of the rabbit medial collateral and anterior cruciate ligaments.

The biomechanical properties of the medial collateral and anterior cruciate ligaments from 30 New Zealand White rabbits were measured. Because of its complex geometry, the ACL was divided into two portions (medial and lateral) to provide uniform loading. This allowed an examination of the intra-ligamentous properties. A laser micrometer system was used to measure the cross-sectional area for tensile stress and a video dimension analyzer was used to measure the strain. The mechanical properties (stress-strain curves) of the MCL and ACL were different, with the modulus (determined between 4 and 7% strain) in the MCL (1120 +/- 153 MPa) more than twice that of either portion of the ACL (516 +/- 64 and 516 +/- 69 MPa for the medial and lateral portions, respectively). This higher modulus correlated with the more uniform and dense appearance of the collagen fibrils examined with scanning electron microscopy (SEM).

Culture-negative septic arthritis in children.

To compare the incidence, characteristics, treatment course, and clinical outcome of children with culture-negative versus culture-positive septic arthritis, we reviewed all 105 children treated for septic arthritis at our institution from 1990 to 1997. Seventy-six children had a clinical presentation consistent with an isolated joint infection. All underwent a joint aspiration with fluid analysis including culture. All were followed up until resolution of their symptoms. Culture of the synovial aspirates identified an etiologic organism in only 30% of cases. No significant differences existed between the culture-positive and culture-negative groups in most clinical and laboratory criteria. No other diagnoses were demonstrated. All patients underwent joint drainage, received comparable antibiotic therapy, and had complete resolution of their infections. The current literature reports deceptively low rates of 18-48% for culture-negative septic arthritis. Seventy percent of children with clinical findings of septic arthritis had negative synovial fluid cultures. As the two culture groups were comparable and no other diagnoses were demonstrated, the culture-negative cases were likely infections. Thus we recommend the same aggressive treatment in those cases with and without identification of a causative organism.

Ultrastructural Differences Between the Cells of the Medial Collateral and the Anterior Cruciate Ligaments

The anterior cruciate ligament (ACL) does not heal after an interstitial tear, in contrast to the medial collateral ligament (MCL), whose interstitial tears heal readily. The light microscopic and ultrastructural differences between the cells of the two ligaments were studied in rabbit knees to observe the healing characteristics of the two ligaments. A rabbit knee was chosen because the rabbit ACL, like that of humans, does not heal following interstitial injury. The cells populating the MCL have the characteristics of fibroblasts. The cells of the ACL resemble fibrocartilage cells. The phenotypic differences in the cells of the two ligaments may be important determinants of the differences in healing.

Gabapentin use in pediatric spinal fusion patients: a randomized, double-blind, controlled trial.

BACKGROUND: Gabapentin has opioid-sparing effects in adult surgical patients, but no reported studies have involved children and adolescents. In a double-blind, randomized, controlled trial, we examined whether gabapentin decreases postoperative opioid consumption for pediatric spinal fusion patients with idiopathic scoliosis. METHODS: Patients, aged 9 to 18 years, received preoperative gabapentin (15 mg/kg, treatment) or placebo. Anesthesia was standardized. After surgery, all patients received standardized patient-controlled analgesia opioid and continued on either gabapentin (5 mg/kg) or placebo 3 times per day for 5 days. Opioid use was calculated in mg/kg/time intervals. Pain scores and opioid side effects were recorded. RESULTS: Data from 59 patients (30 placebo and 29 gabapentin) did not differ in demographics. Total morphine consumption (mg/kg/h ± SD) was significantly lower in the gabapentin group in the recovery room (0.044 ± 0.017 vs 0.064 ± 0.031, P = 0.003), postoperative day 1 (0.046 ± 0.016 vs 0.055 ± 0.017, P = 0.051), and postoperative day 2 (0.036 ± 0.016 vs 0.047 ± 0.019, P = 0.018). In addition, gabapentin significantly reduced first pain scores in the recovery room (2.5 ± 2.8 vs 6.0 ± 2.4, P < 0.001) and the morning after surgery (3.2 ± 2.6 vs 5.0 ± 2.2, P < 0.05), but otherwise pain scores were not significantly different. There were no differences in opioid-related side effects over the course of the study. CONCLUSION: Perioperative oral gabapentin reduced the amount of morphine used for postoperative pain after spinal fusion surgery, but not overall opioid-related side effects. Initial pain scores were lower in the treatment group. Perioperative use of gabapentin seems to be an effective adjunct to improve pain control in the early stages of recovery in children and adolescents undergoing spinal fusion.

Relationship between Quantec measurement and Cobb angle in patients with idiopathic scoliosis.

The Quantec Spinal Imaging System (QSIS) is a raster stereography used to measure three-dimensional trunk images. The Q angle, a coronal plane measurement generated by the Quantec Spinal Imaging System (QSIS), was compared with the Cobb angle in assessment of scoliosis curve magnitude. One hundred forty-nine patients with idiopathic scoliosis were evaluated using both the Quantec system and plane radiographs. The Cobb and Q angles demonstrated significant correlation in the thoracic region (r = 0.65, p < 0.05), lumbar region (r = 0.63, p < 0.05), and in the thoracolumbar region (r = 0.70, p < 0.05). The difference between the Q and Cobb angles was small when the Cobb angle was <21 degrees with less than 6 degrees of axial surface rotation, as measured by the QSIS method. For smaller curves with minimal rotation, there is close correlation between the Cobb angle and the Quantec angle.

Functional classification of patients with idiopathic scoliosis assessed by the Quantec system: a discriminant functional analysis to determine patient curve magnitude.

Study Design. A stepwise discriminant analysis was used to define a spinal deformity score based on three-dimensional measurements by the Quantec spinal image system (raster stereophotograph). Objective. To provide functional classification of spinal deformity in patients with mild idiopathic scoliosis without using radiographs. Summary of Background Data. Most studies classify the degree of spinal deformity in terms of coronal plane radiograph without analyzing transverse rotation. To the authors’ knowledge, no studies investigating classification of spinal deformity in idiopathic scoliosis using Quantec system measurements have been documented. Methods. In this study, 129 patients with a single curve and 119 patients with a double curve were divided into three groups according to Cobb angle: Group 1 (less than 10°), Group 2 (10–20°), and Group 3 (greater than 20°). Results. The patients were assigned to the group with the highest scores after application of a stepwise discriminant analysis. The accuracy of the classification system by functional scores for the patients with a single curve was 85% for Group 1, 63.5% for Group 2, and 71.7% for Group 3. The accuracy of classification by functional scores for the patients with a double curve was 87.1% for Group 2 and 76.1% for Group 3. Conclusion. The back surface image study is a method for providing a quantitative assessment of mild spinal deformity, allowing evaluation of patients by integrated three-dimensional parameters with no reference to radiographs.

Kinematic and kinetic evaluation of the ankle joint before and after tendo achilles lengthening in patients with spastic diplegia.

Fourteen patients, at a mean age of 9.1 years (range 4.1-16.6 years), who had spastic diplegic cerebral palsy were evaluated before and after tendo Achilles lengthening (TAL). Follow-up (by gait analysis) after TAL ranged from 8 to 30 months. A Vicon motion analysis system with six CCD cameras and two AMTI force plates provided three-dimensional measurements of joint motion and moments. The TAL procedure resulted in normal passive dorsiflexion of the ankle joint with the knee at 0 degrees of extension and 90 degrees of flexion, reduced plantarflexion during swing phase, and reduced premature plantarflexor moment. However, 10 degrees greater than normal dorsiflexion of the ankle joint during mid-stance phase was indicative of a mild calcaneal gait pattern. The TAL procedure improved lower extremity function as documented by both kinematic and kinetic analysis in cerebral palsy.

The effects of therapeutic vs. high‐intensity ultrasound on the rabbit growth plate

Six of 6‐week‐old NZ rabbits underwent ultrasound treatment using a therapeutic dose (0.5 W/cm) and other six were treated with a higher dose (2.2 W/cm2) to the lateral aspect of the left knee joint for 20 min per day and a total of six weeks. The right knee joint served as a control. The goal of this study is to see if the therapeutic dose and high dose (approximately 45‐fold therapeutic dose) will have toxic effects on the physis. Histological review appeared normal growth plate in the therapeutic group. In the high dosage group three of six cases displayed flattening of the distal femoral epiphysis and wedging of the proximal tibial plateau and indistinct growth plate lines. It is of interest to note that there are opening radiolucent area in the lateral aspect on the femoral metaphysis in five of six cases, where bone resorption has taken place. Histological results showed that there are disordered arrays of the cartilaginous cells in the proliferative zone. The height of the lateral physis in the high dose group is not only greater than that in the therapeutic dose (1083.8 vs. 500.3 μm), but also greater than that in their contralateral control (530.7 μm) (P < 0.05). This short‐term study demonstrates that high dose ultrasound has profound pathologic effects in growing bone. Therapeutic doses of ultrasound do not have an adverse effect on bone growth in the short‐term follow‐up.