Application of generalized dynamic neural networks to biomedical data.

This paper reviews the application of continuous recurrent neural networks with time-varying weights to pattern recognition tasks in medicine. A general learning algorithm based on Pontryagin's maximum principle is recapitulated, and possibilities of improving the generalization capabilities of these networks are given. The effectiveness of the methods is demonstrated by three different real-world examples taken from the fields of anesthesiology, orthopedics, and radiology.

Leg lengthening as part of gait improvement surgery in cerebral palsy: an evaluation using gait analysis.

Eleven children with hemiplegic or an asymmetric diplegic cerebral palsy who had a preoperative leg length discrepancy of more than 2.5 cm underwent gait improvement surgery which included leg length equalisation. Sagittal plane kinematics and kinetics before and about 3 years after surgery for the lengthened limb and contralateral limb were evaluated. Preoperatively the unaffected limb had excessive stance phase flexion at the hip and knee, and dorsal flexion at the ankle joint. These changes could be partially reversed to produce a kinematic gait pattern comparable to age matched normal controls on the uninvolved side after equalisation of leg length.

Tibial lengthening over nails in children using modified Ender nails: preliminary results of a new treatment.

Tibial lengthening over nails, using modified Ender nails, was performed in nine children whose mean age at surgery was 12.8 years. The prerequisite for using this technique was the absence of axial malalignment and an indication for tibial lengthening only. Lengthening was not performed in one case due to the development of a compartment syndrome after the tibial osteotomy. Breakage of one interlocking screw without loss of alignment or length was observed in one case. Superficial pin tract infections were observed in two cases. An average of 4.1 cm (range 3-4.5 cm) lengthening of the tibia was achieved in eight of the nine cases. The modified Ender nails used permitted locking at both ends after achieving the desired distraction and permitted early removal of the external fixator. The advantage of this technique is that it permits early removal of the fixator and thus decreases the incidence of fixator related problems and facilitates early rehabilitation.

Effect of derotation osteotomy of the femur on hip and pelvis rotations in hemiplegic and diplegic children.

The purpose of this study was to evaluate hip and pelvis rotations in groups of hemiplegic and diplegic children before and after surgical correction of fixed internal rotation deformity of the hip. Twenty-two children with cerebral palsy (eight diplegia, 14 hemiplegia) having fixed internal rotation deformity at the hip were treated by multilevel surgery which included derotation osteotomy of the femur. Evaluation was done before and at a mean of 3.1 years after surgery using three-dimensional computerized gait analysis. Preoperatively, the patients in the hemiplegia group had a significantly greater compensatory external rotation of the pelvis than those in the diplegic group. Post-operatively there were no significant differences between the two groups. In the hemiplegia group the external rotation of the pelvis was corrected after correction of hip rotation by derotation osteotomy. Patients in the diplegia group showed significant improvements in the hip rotation with no significant change in the pelvis rotation after multilevel surgery.

Preliminary report: resection and interposition of a deepithelialized skin flap graft in tarsal coalition in children.

Six tarsal coalitions in children were managed surgically using a deepithelialized skin flap for interposition after resection of the bony, fibrous or cartilaginous coalition. The advantage of this technique is that due to positioning the skin flap, joint motion can be preserved. The clinical results using the Ankle Hindfoot Scale of the American Orthopedic Foot and Ankle Society were excellent in two and good in four cases. The radiographs at follow-up showed no recurrences of the resected coalitions. This study shows that the use of deepithelialized skin flap interposition is effective in providing pain relief for the patients in symptomatic coalitions.

Gait improvement surgery in diplegic children: how long do the improvements last?

Gait improvement surgery in ambulatory children with cerebral palsy performed as single-event multilevel surgery is today a well-established modality of treatment, but follow-up studies are lacking. Preoperative and follow-up gait analysis data of 32 diplegic children who underwent single-event multilevel surgery for gait improvement between 1995 and 1998 were evaluated retrospectively. Relevant sagittal plane kinematic parameters of the hip, knee, and ankle joint and time-distance parameters were considered for outcome measures in this study. Postoperative gait analysis was performed three times in all the cases: after discontinuation of the dynamic AFOs (mean 1.0 +/- 0.3 years), after discontinuation of the night splints (mean 2.3 +/- 0.7 years), and at least 1.5 years after discontinuation of physiotherapy and splints (mean 4.4 +/- 1.1 years). The aim of the study was to ascertain whether the improvements in gait function were maintained over these examinations. The authors found that gait function continued to change over 1, 2, and 3 years of follow-up. A general decrease in gait function was measurable in this collective between the first postoperative and the second postoperative evaluations. The results indicate that evaluation of gait improvement surgery in cerebral palsy performed at a minimum of 3 years after surgery would give the most predictive outcome of treatment.

Phenotypes of the N88S Berardinelli-Seip congenital lipodystrophy 2 mutation.

Recently, two missense mutations (N88S, S90L) in the Berardinelli-Seip congenital lipodystrophy gene have been identified in autosomal dominant distal hereditary motor neuropathy and Silver syndrome. We report the phenotypic consequences of the N88S mutation in 90 patients of 1 large Austrian family and two unrelated German families. Variation in the clinical and electrophysiological phenotype enabled us to distinguish six subtypes. In 4.4%, the disorder was not penetrant. Twenty percent of the patients were subclinically affected; some of these patients could only be detected by pathological nerve conduction studies. A distal hereditary motor neuropathy type V phenotype characterized by predominant hand muscle involvement was found in 31.1%, whereas 14.5% showed typical Silver syndrome with amyotrophy of the small hand muscles and spasticity of the lower extremities. Moreover, the phenotype present in 20% was compatible with Charcot-Marie-Tooth disease. In 10%, the clinical diagnosis of pure or complicated hereditary spastic paraparesis was made. Electrophysiological studies showed an axonal neuropathy but also chronodispersion of compound motor action potentials and conduction blocks. Sensory nerve conduction studies were rarely pathological. Our study indicates that the dominant N88S mutation in the Berardinelli-Seip congenital lipodystrophy gene 2 leads to a broad spectrum of motor neuron disorders.

Improving generalization capabilities of dynamic neural networks.

This work addresses the problem of improving the generalization capabilities of continuous recurrent neural networks. The learning task is transformed into an optimal control framework in which the weights and the initial network state are treated as unknown controls. A new learning algorithm based on a variational formulation of Pontrayagin's maximum principle is proposed. Under reasonable assumptions, its convergence is discussed. Numerical examples are given that demonstrate an essential improvement of generalization capabilities after the learning process of a dynamic network.

Treatment of unicameral calcaneal bone cysts in children: review of literature and results using a cannulated screw for continuous decompression of the cyst.

Nine unicameral bone cysts of the calcaneus in children were managed surgically using the technique of continuous decompression with titanium cannulated cancellous screws. The average age of the patients at surgery was 12.8 years. At follow-up a minimum of 2 years after surgery, eight cysts showed complete healing; one patient showed healing with residuals. Irritation at the screw insertion site necessitated early removal of the screw in one patient; implant-related problems were not observed in the other patients. Patients were allowed to bear weight after surgery. Implant extraction was performed after full consolidation of the cyst and was uneventful in all patients. A review of the literature and the different treatment modalities used for managing calcaneal cysts is also presented.

Multilevel surgery in spastic diplegia: evaluation by physical examination and gait analysis in 25 children.

Gait improvement surgery was performed on 25 ambulatory children with the diplegic type of cerebral palsy. Multiple soft tissue and bony procedures were performed (mean 8.2 procedures) according to criteria defined on the basis of physical examination and gait analysis. Relevant physical examination findings and kinematic and kinetic data in the sagittal plane were evaluated before surgery and at least 3 years after surgery. Physical examination showed a reduction in the ankle plantar-flexor power and in the range of hip flexion and ankle plantarflexion after surgery. Analysis of gait data showed significant improvements in the sagittal plane kinematics and the power generation at the hip and the ankle. At the knee joint there was maintenance of power of the flexor and extensor group of muscles on physical examination, with significant improvements in the kinematics after surgery. The authors conclude that well-selected surgery improves function of the spastic muscle. The importance of assessing clinical, kinematic, and kinetic data together for proper evaluation of gait is stressed.