Kaj Tallroth

Improved accuracy of pedicle screw insertion with computer-assisted surgery : A prospective clinical trial of 30 patients

Study Design. A prospective clinical trial was done to study the accuracy of pedicle screw placement in 30 consecutive computer-assisted orthopedic surgeries. Objectives. To determine the accuracy and clinical applicability of this new method for pedicle screw insertion. Summary of Background Data. Conventional screw insertion techniques have been associated with high pedicle screw malplacement rates in cadaver studies and clinical studies with postoperative computed tomography evaluation. Methods. Thirty transpedicular, low-back, titanium instrumentations were performed with computer-assisted orthopedic surgery. The accuracy of screw placement was evaluated using a sophisticated computed tomography protocol. Results. The total number of pedicle screws was 174. Of these, 139 (79.9%) could be inserted with computer-assisted orthopedic surgery. The malplacement rate of computer-assisted orthopedic surgery screws was 4.3%. In screws that were not inserted by computer-assisted orthopedic surgery, the malplacement rate was 14.3%. One malplaced screw that had not been inserted with computer-assisted orthopedic surgery caused L4 root paresis. Conclusions. The accuracy of pedicle screw placement using computer-assisted surgery proved to be superior to the accuracy obtained when using conventional techniques.

Progression of spondylolisthesis in children and adolescents: A long-term follow-up of 272 patients

The radiologic progression of spondylolisthesis during a long-term follow-up was studied in 272 children and adolescents. There were 134 girls and 138 boys. The mean age at the first visit was 14.3 years (girls, 13.8 years; boys, 14.9 years). The radiologic follow-up time was 14.8 years on average (range, 5–32). The operation was done in 190 patients younger than 20 years of age. Fusion in situ, using a posterior or posterolateral technique, had no statistically significant effect on progression. Surgically treated patients did not differ from conservatively treated patients. Ninety percent of the slip, on average, had already occurred at the time of the first radiologic examination compared with the final amount of slip. More than 10% progression occurred in 62 patients, mainly within the first year postoperatively or after the first examination. Progression of the lumbosacral kyphosis and sinking of the vertebral body was noted in severe slips. Although female gender and dysplasia (spina bifida) at the lumbosacral junction were more frequent in severe slips, they statistically had no value in predicting progression. A wedge form of L5 or sacral rounding also had no prognostic value. These were secondary to the slip and expressed it but did not predict it. The only radiologic variable with predictive value of progression was the percentage amount of the primary slip. In age groups corresponding to the growth spurt in early puberty (girls, 9–12 years; boys, 11–14 years), there was a tendency to progress.

Reproducibility of dual-energy x-ray absorptiometry total and regional body composition measurements using different scanning positions and definitions of regions

Repeated dual-energy x-ray absorptiometry (DEXA) measurements are often performed both in clinical work and in research studies. The aims of the present study were to investigate the repeatability of DEXA total body measurements, to clarify the effect of the scanning positioning of the subject, and to compare the reliability of DEXA measurements of the extremities between automatically and manually defined regions of interest (ROIs). Three DEXA measurements of the total body composition, that is, fat tissue mass, lean tissue mass (LM), and bone mineral content, were performed on 30 male volunteers (mean age, 45.2 years) in addition to measurements of bone mineral density. Using a narrow fan-beam Lunar Prodigy densitometer (GE Lunar, Madison, WI), 3 DEXA scans (2 supine and 1 prone) of the total body were performed. For regional measurements of the right arm and leg, ROIs were set automatically and manually in the supine-supine and supine-prone positions. Repeatability of total body DEXA measurements was excellent for bone mineral content (r = 0.99), LM (r = 0.99), fat tissue mass (r = 1.00), and bone mineral density (r = 0.98) in supine scanning. Change of position from supine to prone slightly decreased the reproducibility of total body measurements. Reproducibility of regional measurements was inferior to total body results; especially in the upper extremity, the repeated automatic LM measurements in supine-supine positions produced r values as low as 0.74 but increased to 0.93 after manual adjustment of the ROIs. To obtain maximal reliability of the composition measurements, we recommend manual checking of machine-made ROIs and, if needed, manual adjustment to avoid measurement errors.

Comparison of radiologic signs and clinical symptoms of spinal stenosis.

Study Design. Clinical findings of spinal stenosis were compared to graded radiologic findings of dural sac narrowing. Objectives. To examine the changes of the dural sac area of the lumbar spine on computerized tomography (CT) performed without and with axial loading, and study the correlations between the radiologic findings and clinical symptoms suggestive of spinal stenosis. Summary of Background Data. Although several studies have been performed regarding the advantage of an external compression device in lumbar CT, to our knowledge, none of these studies have correlated radiologic findings with clinical symptoms. Methods. The cross-sectional areas of the dural sac at the 3 lowest lumbar intravenous spaces, measured by CT both without and with external compression, were correlated to the clinical symptoms suggestive of spinal stenosis in 117 patients and 351 intervertebral levels. Results. No statistically significant correlation between the severity of the clinical symptoms of spinal stenosis and dural cross-sectional areas was found. Neither did the use of an external compression device improve the correlation. Conclusion. Although an external compression simulates the dynamic condition in the back during standing position, it does not eliminate the need to compare the radiologic findings with the clinical symptoms of patients examined because of a suspected narrowing of the spinal canal.

Weight-bearing radiography in total hip replacement

Serial anteroposterior (AP) radiographs of the weight-bearing pelvis and hips were taken of 29 patients with total hip replacement (THR). For constant positioning the patient stands with straight knees on a board with a block between the heels. A U-shaped mercury level strapped to the patient provides a horizontal reference line on the radiograph. On the average, individual variation of pelvic tilt in serial films was 1° and pelvic rotation 3.5° confirming satisfactory reproducibility. The horizontal reference enables estimation of pre- and postoperative leg length inequality (LLI) and of the angle of the acetabular cup (AA). Reproducibility allows assessment of the exact position of the femoral component and quantitative evaluation of radiolucency and bone resorption around the prosthetic implant in the follow-up of THR.

Bone cysts containing silicone particles in bones adjacent to a carpal silastic implant

Silastic implants for a wide variety of medical purposes are in current and frequent use worldwide. Only recently there have been reports of the migration of silicone to the surrounding tissues via lymphatics. In the present material of nine cases with carpal implants followed for more than two years, bone cysts developed in the surrounding bones on five occasions. The only cysts so far investigated thoroughly contained foreign body reaction, and silicone could be detected by electron probe microanalysis. A long-term follow-up is suggested whenever these implants are used.

Hyperostosis and osteoarthritis in patients surviving after tetanus

Twenty patients (12 men and 8 women) who had survived tetanus were examined for bone and joint abnormalities, 1–9 years after the disease. The radiographic findings in the elbows were abnormal in 13 out of 20 patients, as were the shoulders of all 3 patients examined. Insertion hyperostoses were found at the elbow and/or in the shoulder region in 5 (25%) of the patients. The hyperostoses were bilateral in 3 patients. One of the patients with hyperostoses also had calcifications in the soft tissue of the elbow. The abnormalities were associated with mild clinical symptoms. Trauma to the periosteum caused by repeated traction of muscular contractions is possibly the causative mechanism. Twelve patients (60%) had osteoarthritis of the elbow joint presumably secondary to the violent stress to the joint.

Spinal stenosis subsequent to juvenile lumbar osteochondrosis

This paper describes eight patients with spinal stenosis associated with marked osteochondrous changes in the vertebral bodies due to juvenile lumbar osteochondrosis (Scheuermanns disease). In no case was the midsagittal or interpedicular diameter of the spinal canal indicative of bony stenosis. On the other hand, in the myelograms the sagittal diameter of the dural sac was in all cases significantly narrowed, a diagnostic sign of central spinal stenosis. Therefore, myelography should always be contemplated when osteochondrous changes are present and spinal stenosis is suspected clinically regardless of whether the spinal canal diameters are normal in plain films.

Metaphyseal sclerosis in patients with chronic renal failure.

We reviewed radiographs of the hands and wrists of 33 patients with immature skeletons and chronic renal disease. Various radiographic manifestations of renal osteodystrophy were seen, including osteopenia in 23 patients (70%), subperiosteal resorption in 20 (61%), distal tuft resorption in 14 (42%), sclerosis of vertebral bodies in 2 (6%), and soft-tissue calcification in 1 (3%). We also noted that 13 patients (39%) exhibited metaphyseal sclerosis adjacent to the growth plates. Five of these 13 showed persistent sclerosis years after the growth plates had fused. None of the patients showed other radiographic changes of rickets, and there was no correlation between the serum calcium, phosphorus, or aluminum levels and the presence of metaphyseal sclerosis. Neither was there any association with the underlying cause of renal failure, method of treatment, presence of a transplant, or type of dialysis. We view this finding as another manifestation of renal osteodystrophy. The importance of distinguishing it from other sclerotic lesions is discussed.

Radiographic changes of the revascularized femoral head

Twenty-two necrotic femoral heads in young adults were radiologically followed-up after grafting with vascularized bone by comparing the preoperative and the postoperative state of the hip joint. Three parameters were observed and followed; the flattening of the femoral head; the degree of osteoarthrosis of the joint; and the degree of incorporation of the graft into the recipient bone. The results, expressed by index figures, showed that the femoral head flattened during the first two years postoperatively; that the maximal incorporation occurred during the same period of time; and that the appearance of postoperative osteoarthrosis was slow during the first year and increased subsequently. This numerical characterization of radiological findings allows systematic individual analysis after revascularization of the femoral head with bone grafts. It is also suited for comparisons between patients, between series of patients and of various treatment techniques. Furthermore, this quantification provides a numerical index that seems to correlate with the outcome of the treated hip joint.