Charles E. Johnston

Pulmonary Function Following Early Thoracic Fusion in Non-Neuromuscular Scoliosis

BACKGROUND While early spinal fusion may halt progressive deformity in young children with scoliosis, it does not facilitate lung growth and, in certain children, it can result in thoracic insufficiency syndrome. The purpose of this study was to determine pulmonary function at intermediate-term follow-up in patients with scoliosis who underwent thoracic fusion before the age of nine years. METHODS Patients who had thoracic spine fusions before the age of nine years with a minimum five-year follow-up underwent pulmonary function testing. Forced vital capacity, forced expiratory volume in one second, and maximum inspiratory pressure were measured and compared with age-matched normal values. Patients with neuromuscular disease, skeletal dysplasias, or preexisting pulmonary disease were excluded, while those with rib malformations were included. The relationships between forced vital capacity and age at the time of surgery, length of follow-up, extent of the fusion, proximal level of the fusion, and revision surgery were studied. RESULTS Twenty-eight patients underwent evaluation. Twenty patients had congenital scoliosis, three had idiopathic scoliosis, three had scoliosis associated with neurofibromatosis, one had congenital kyphosis, and one had syndromic scoliosis. Seventeen patients had one spinal surgery, while eleven had additional procedures. The average age of the patients was 3.3 years at the time of surgery and 14.6 years at the time of follow-up. The average extent of the thoracic spine fused was 58.7%. The average forced vital capacity was 57.8% of age-matched normal values, and the average forced expiratory volume in one second was 54.7%. The forced vital capacity was <50% of normal in twelve of the twenty-eight patients, and two required respiratory support, implying that substantial restrictive lung disease was present. With the numbers studied, no significant correlation could be detected between the age at the time of fusion or the length of follow-up and pulmonary function. The extent of the spine fused correlated with the forced vital capacity (p = 0.01, r = -0.46). Fusions in the proximal aspect of the spine were found to be associated with diminished pulmonary function as eight of twelve patients with a proximal fusion level of T1 or T2 had a forced vital capacity of <50%, but only four of sixteen patients with a fusion beginning caudad to T2 had a forced vital capacity of <50% (p = 0.0004, r = 0.62). CONCLUSIONS Patients with proximal thoracic deformity who require fusion of more than four segments, especially those with rib anomalies, are at the highest risk for the development of restrictive pulmonary disease. Pulmonary function tests should be performed for all patients who have an early fusion. The pursuit of alternative procedures to treat early spinal deformity is merited.

The Prevalence of Back Pain in Children Who Have Idiopathic Scoliosis

A retrospective study of 2442 patients who had idiopathic scoliosis was performed to determine the prevalence of back pain and its association with an underlying pathological condition. Five hundred and sixty (23 per cent) of the 2442 patients had back pain at the time of presentation, and an additional 210 (9 per cent) had back pain during the period of observation. There was a significant association between back pain and an age of more than fifteen years, skeletal maturity (a Risser sign of 2 or more), post-menarchal status, and a history of injury. There was no association with gender, family history of scoliosis, limb-length discrepancy, magnitude or type of curve, or spinal alignment. At the latest follow-up evaluation, 324 (58 per cent) of the 560 patients who had had back pain at presentation had no additional symptoms. Forty-eight (9 per cent) of the 560 patients who had back pain had an underlying pathological condition: twenty-nine patients had spondylolysis or spondylolisthesis, nine had Scheurmann kyphosis, five had a syrinx, two had a herniated disc, one had hydromyelia, one had a tethered cord, and one had an intraspinal tumor. A painful left thoracic curve or an abnormal neurological finding was most predictive of an underlying pathological condition, although only eight of the thirty-three patients who had such findings were found to have such a condition. When a patient with scoliosis has back pain, a careful history should be recorded, a thorough physical examination should be performed, and good-quality plain radiographs should be made. If this initial evaluation reveals normal findings, a diagnosis of idiopathic scoliosis can be made, the scoliosis can be treated appropriately, and non-operative treatment can be initiated for the back pain. It is not necessary to perform extensive diagnostic studies to evaluate every patient who has scoliosis and back pain.

Use of the Pavlik harness in congenital dislocation of the hip: an analysis of failures of treatment

In twenty-five patients, the Pavlik harness failed to obtain or maintain reduction in thirty of thirty-five congenital dislocations of the hip. All of the patients had met the clinical criteria for use of the harness in our institution: they were less than seven months old, the femoral head pointed to the triradiate cartilage on anteroposterior radiographs that were made with the child wearing the harness, and they had no evidence of neuromuscular disease or teratological dislocation. These patients were compared with seventy-one patients (eighty-one dislocations) who had also been treated with the Pavlik harness and in whom a stable reduction was obtained and maintained. Statistically significant risk factors for failure of the harness included an absent Ortolani sign at the initial evaluation, bilateral dislocation, and an age of more than seven weeks before treatment with the harness was begun. All thirty hips in which the harness failed to obtain or maintain reduction had a subsequent attempt at closed reduction after preliminary Bryant traction. Fifteen of these hips were successfully reduced closed, but two later redislocated and needed an open reduction. The remaining fifteen hips needed an open reduction, and two redislocated and needed a second open reduction.

A Comparison of Two Nonoperative Methods of Idiopathic Clubfoot Correction: The Ponseti Method and the French Functional (Physiotherapy) Method

BACKGROUND In the treatment of idiopathic clubfeet, the Ponseti method and the French functional method have been successful in reducing the need for surgery. The purpose of this prospective study was to compare the results of these two methods at one institution. METHODS Patients under three months of age with previously untreated idiopathic clubfeet were enrolled. All feet were rated for severity prior to treatment. After both techniques had been described to them, the parents selected the treatment method. Outcomes at a minimum of two years were classified as good (a plantigrade foot with, or without, a heel-cord tenotomy), fair (a plantigrade foot that had or needed to have limited posterior release or tibialis anterior transfer), or poor (a need for a complete posteromedial surgical release). Two hundred and sixty-seven feet in 176 patients treated with the Ponseti method and 119 feet in eighty patients treated with the French functional method met the inclusion criteria. RESULTS The patients were followed for an average of 4.3 years. Both groups had similar severity scores before treatment. The initial correction rates were 94.4% for the Ponseti method and 95% for the French functional method. Relapses occurred in 37% of the feet that had initially been successfully treated with the Ponseti method. One-third of the relapsed feet were salvaged with further nonoperative treatment, but the remainder required operative intervention. Relapses occurred in 29% of the feet that had been successfully treated with the French functional method, and all required operative intervention. At the time of the latest follow-up, the outcomes for the feet treated with the Ponseti method were good for 72%, fair for 12%, and poor for 16%. The outcomes for the feet treated with the French functional method were good for 67%, fair for 17%, and poor for 16%. CONCLUSIONS Nonoperative correction of an idiopathic clubfoot deformity can be maintained over time in most patients. Although there was a trend showing improved results with use of the Ponseti method, the difference was not significant. In our experience, parents select the Ponseti method twice as often as they select the French functional method.

Treatment of adolescent idiopathic scoliosis using Texas Scottish Rite Hospital instrumentation.

Study Design. To determine the effectiveness of posterior TSRH instrumentation for the treatment of idiopathic scoliosis, 103 patients with a 2-year minimum followup were retrospectively studied. Methods. Patients who underwent operations between October 1988 and April 1991 were evaluated for curve correction, spinal balance, and complications. Age at surgery averaged 14.3 years. Follow-up averaged 2.5 years. Results. Thoracic curve correction averaged 65% in those with King Type III/IV curves and 54% in those with Type II curves. With follow-up, correction loss averaged approximately 13% for each group. Lumbar curve correction after instrumentation in Type I and II curves averaged 48% postop but lost approximately 20% with follow-up. Trunk balance improved 77% toward midline after surgery in those with Type III/IV curves. Improvement in trunk balance was less impressive in patients with Type II curves, particularly after selective thoracic fusions. Thoracic sagittal contour improved 43% for hypokyphotic (<20°) patients but, in the remainder, no significant radiographic change was evident. No neurologic complications occurred. Delayed deep infections developed in ten patients (10%) between 11 and 45 months postoperative. Cultures eventually grew Propionlbacterium acnes, staph epidermidis, or staph coagulese negative in eight patients. Two patients had pseudarthroses. Conclusions. Frontal and sagittal thoracic curve correction can be satisfactorily obtained using TSRH instrumentation. Continued efforts are being made to improve lumbar hook patterns and technique to achieve and maintain better lumbar curve correction.

Biomechanical analysis of pedicle screw instrumentation systems in a corpectomy model

Five different spinal implants, all using pedicle screw attachment to vertebrae, were examined in a one above/ one below corpectomy model, to determine 1) the relative stiffness of each construct, 2) the stresses generated in the implant during loading, and 3) the relative fatigue susceptibility of each implant. Results indicated that the relative axial and torsional stiffnesses were similar for all the implants tested (DKS/Zielke, VSP/Steffee, AO Fixator Interne, Luque plate, AO Notched plate). Hence, each of the devices impart approximately the same stability to the spine in this highly unstable model. Stresses measured at the root of the pedicle screws were found to exceed the endurance limit of stainless steel in those systems in which the pedicle screws were attached rigidly to the plates (VSP/Steffee, AO Fixator Interne). Good agreement was found between the measured stresses and stresses derived from static calculations. Comparisons between the stresses from each implant gave a relative measure of fatigue susceptibility that was validated by in vitro cyclic testing. Implants with stresses exceeding the endurance limit failed during the cyclic test.

Lengthening of Dual Growing Rods and the Law of Diminishing Returns

Study Design. A retrospective multicenter study. Objective. To evaluate the effect of repeated surgical lengthenings and time on spinal growth and Cobb angle in children with early onset scoliosis and dual growing rods. Summary of Background Data. Previous studies have established the effectiveness of dual growing rods for controlling spinal deformity and promoting spinal “growth.” Although anecdotal experience suggests that the effectiveness of repeated lengthenings decreases over time, this has not been previously studied. Methods. Medical records from five different centers were reviewed to identify children treated with dual growing rods for early onset scoliosis who had a minimum of 2-year follow-up and at least three lengthening procedures. Initial radiographs, postimplantation radiographs, and radiographs from before and after each lengthening were measured for T1-S1 distance and Cobb angle. Linear regression and analysis of variance were used for statistical analysis. Results. Thirty-eight patients from five centers met the inclusion criteria. The average age of our patients was 5.7 years (range 1.7–8.9 years); mean follow-up was 3.3 years (range 2–7 years). The average interval between lengthenings was 6.8 months. Cobb angle decreased from a mean value of 74° preoperatively to 36° after the primary implantation and did not change significantly with repeated lengthenings (P = 0.96). After initial implantation, the average annual T1–S1 gain was 1.76 ± 0.71 cm/year. The T1-S1 gain after a given lengthening, however, decreased significantly with repeated lengthenings (P = 0.007). When the effect of time was considered, there was also a significant decrease in T1–S1 gain over time (P = 0.014). Conclusion. There seems to be a “law of diminishing returns” with repeated lengthenings of dual growing rods. Repeated lengthenings still result in a net T1-S1 increase; however, this gain tends to decrease with each subsequent lengthening and over time. This phenomenon may be due to autofusion of the spine from prolonged immobilization by a rigid device.

Frontal plane and sagittal plane balance following Cotrel-Dubousset instrumentation for idiopathic scoliosis.

Postoperative decompensation has been reported following Cotrel-Dubousset instrumentation for right thoracic idiopathic scoliosis. The authors examined balance in the frontal and sagittal planes in 53 patients to determine optimal levels for fusion. King et al Type II curves, particularly larger ones, shifted to the left when the thoracic curve was fused to the stable vertebra or just below. Most Type III curves balanced well regardless of the levels fused. One-third of all patients developed mild radiographic junctional kyphosis at the lower level instrumented, more commonly when instrumentation ended at or above T12. The authors recommend fusing one segment short of the stable vertebra in most Type II curves. Large Type II curves need both curves fused for optimal balance. Type III curves can be fused short of the stable vertebra.

Congenital pseudarthrosis of the tibia: results of technical variations in the charnley-williams procedure.

Background: Results of the Charnley-Williams method of intramedullary fixation for treatment of congenital pseudarthrosis of the tibia have varied, in part because of variations in surgical technique. The outcomes of three variations of this procedure were compared to determine which technique was the most likely to result in union. Methods: The results in twenty-three consecutive patients with congenital pseudarthrosis of the tibia were reviewed at four to fourteen years following initial surgical treatment with an intramedullary rod. Three types of procedures were performed: type A, which consisted of resection of the tibial pseudarthrosis with shortening, insertion of an intramedullary rod into the tibia, and tibial bone-grafting combined with fibular resection or osteotomy and insertion of an intramedullary rod into the fibula; type B, which was identical to type A except that it did not include fibular fixation; and type C, which consisted of insertion of a tibial rod and bone-grafting but no fibular surgery. The outcome was classified as grade 1 when there was unequivocal union with full weight-bearing function and maintenance of alignment requiring no additional surgical treatment; grade 2 when there was equivocal union with useful function, with the limb protected by a brace, and/or valgus or sagittal bowing for which additional surgery was required or anticipated; and grade 3 when there was persistent nonunion or refracture, requiring full-time external support for pain and/or instability. Results: Eleven patients (48%) ultimately had a grade-1 outcome; nine, a grade-2 outcome; and three, a grade-3 outcome. The final outcome was not associated with either the initial radiographic appearance of the lesion or the age of the patient at the time of the initial surgery. The results following type-A and B operations were better than those after type-C procedures. Surgery on an intact fibula resulted in a lower prevalence of grade-3 outcomes than was found when an intact fibula was not operated on (p = 0.05). Transfixation of the ankle joint by the intramedullary rod did not decrease the prevalence of grade-3 outcomes. Conclusions: There is little justification for a type-C operation, as it either resulted in a persistent nonunion or failed to improve an equivocal outcome in every case. Leaving an intact fibula undisturbed to maintain stability or length also was not successful in this series. In addition, the presence of fibular insufficiency (fracture or a pre-pseudarthrotic lesion) was highly prognostic for subsequent valgus deformity (occurring in ten of twelve cases), whether or not the fibula eventually healed.

Mechanical testing of spinal instrumentation.

Clinically, implant failure is often the result of fatigue from continuous cyclic loading. Because of the inadequacies of long-run cyclic testing, fatigue susceptibility of implants was investigated by means of strain measurements and stress analysis under physiologic loads. The implants were equipped with strain gauges during load-deformation testing, and the tensile stress (the component of stress-producing fatigue failure in metals) was calculated for that site on the implant. For metals most often implanted for spinal surgery, such as stainless steel and chrome-cobalt alloys, a stress exists, known as the endurance limit, below which failure will not occur, even if cycled indefinitely. By calculating the tensile stresses in an implant and relating them to the endurance limit, the implants susceptibility to fatigue can be determined at the site of stress analysis without formal cyclic load testing.