Willy Serlo

Biocompatibility of nickel-titanium shape memory metal and its corrosion behavior in human cell cultures

Nickel-titanium alloy (Nitinol) is a metallic biomaterial that has a unique thermal shape memory, superelasticity, and high damping properties. Nitinol is potentially very useful in orthopedic surgery, for example. At present, there are not enough confirmative biocompatibility data available on Nitinol. The aim of our study was to clarify the primary cytotoxicity and corrosion rate of Nitinol in human cell cultures. Comparisons were made with stainless steel (Stst), titanium (Ti), composite material (C), and control cultures with no test discs. Human osteoblasts (OB) and fibroblasts (FB) were incubated for 10 days with test discs of equal size, 6 x 7 mm. The cultures were photographed and the cells counted. Samples from culture media were collected on days 2, 4, 6, and 8, and the analysis of metals in the media was done using flameless atomic absorption spectrophotometry. The proliferation of FB was 108% (Nitinol), 134% (Ti) (p < 0.02), 107% (Stst), and 48% (C)(p < 0.0001) compared to the control cultures. The proliferation of OB was 101% (Nitinol), 100% (Ti), 105% (Stst), and 54% (C) (p < 0.025) compared to the controls. Initially, Nitinol released more nickel (129-87 micrograms/L) into the cell culture media than Stst (7 micrograms/L), but after 2 days the concentrations were about equal (23-5 micrograms/L versus 11-1 micrograms/L). The titanium concentrations from both Nitinol and Ti samples were all < 20 micrograms/L. We conclude that Nitinol has good in vitro biocompatibility with human osteoblasts and fibroblasts. Despite the higher initial nickel dissolution, Nitinol induced no toxic effects, decrease in cell proliferation, or inhibition on the growth of cells in contact with the metal surface.

Bone healing and mineralization, implant corrosion, and trace metals after nickel–titanium shape memory metal intramedullary fixation

Its shape memory effect, superelasticity, and good wear and damping properties make the NiTi shape memory alloy a material with fascinating potential for orthopedic surgery. It provides a possibility for making self-locking, self-expanding, and self-compressing implants. Problems, however, may arise because of its high nickel content. The purpose of this work was to determine the corrosion of NiTi in vivo and to evaluate the possible deleterious effects of NiTi on osteotomy healing, bone mineralization, and the remodeling response. Femoral osteotomies of 40 rats were fixed with either NiTi or stainless steel (StSt) intramedullary nails. The rats were killed at 2, 4, 8, 12, 26, and 60 weeks. Bone healing was examined with radiographs, peripheral quantitative computed tomography, (pQCT) and histologically. The corrosion of the retrieved implants was analyzed by electron microscopy (FESEM). Trace metals from several organs were determined by graphite furnace atomic absorption spectrometry (GF-AAS) or by inductively coupled plasma-atomic emission spectrometry (ICP-AES). There were more healed bone unions in the NiTi than in the StSt group at early (4 and 8 weeks) time points. Callus size was equal between the groups. The total and cortical bone mineral densities did not differ between the NiTi and StSt groups. Mineral density in both groups was lower in the osteotomy area than in the other areas along the nail. Density in the nail area was lower than in the proximal part of the operated femur or the contralateral femur. Bone contact to NiTi was close. A peri-implant lamellar bone sheet formed in the metaphyseal area after 8 weeks, indicating good tissue tolerance. The FESEM assessment showed surface corrosion changes to be more evident in the StSt implants. There were no statistically significant differences in nickel concentration between the NiTi and StSt groups in any of the organs. NiTi appears to be an appropriate material for further intramedullary use because it has good biocompatibility in bone tissue.

Bone modeling and cell–material interface responses induced by nickel–titanium shape memory alloy after periosteal implantation

The purpose of this study was to evaluate the new bone formation, modeling and cell-material interface responses induced by nickel-titanium shape memory alloy after periosteal implantation. We used a regional acceleratory phenomenon (RAP) model, in which a periosteal contact stimulus provokes an adaptive modelling response. NiTi has thermal shape memory and superelasticity properties uncommon in other implant alloys. So far, there are insufficient data concerning the biocompatibility of NiTi as a bone implant. NiTi was compared to stainless steel (stst) and Ti-6Al-4V. The test implant was placed in contact with the intact femur periosteum, but it was not fixed inside the bone. Histomorphometry with digital image analysis was used to determine the bone formation and resorption parameters. The ultrastructural features of cell-material adhesion were analysed with scanning electron microscopy (FESEM). A typical peri-implant bone wall modelation was seen due to the normal RAP. The maximum new woven bone formation started earlier (2 weeks) in the Ti-6Al-4V group than in the NiTi (P < 0.01) group, but also decreased earlier, and at 8 weeks the NiTi (P < 0.05) and stst (P < 0.005) groups had greater cortical bone width. At 12 and 26 weeks no statistical differences were seen in the histomorphometric values. The histological response of the soft tissues around the NiTi implant was also clearly non-toxic and non-irritating. Cell adhesion and focal contacts were similar between the materials studied by FESEM. We conclude that NiTi had no negative effect on total new bone formation or normal RAP after periosteal implantation during a 26-week follow-up.

Arthroscopy of the acute traumatic knee in children: Prospective study of 138 cases

We performed diagnostic arthroscopy for acute knee trauma in 138 children and adolescents aged 13 (1-15) years. The compatibility between the clinical examination and the arthroscopic findings was 59 percent. Ligament injuries were found in 32 cases, 14 of which had rupture of the anterior cruciate ligament. The compatibility in the case of ligament injuries was 31 percent. 48 patients had dislocation of the patella, and a displaced osteochondral fragment was seen in 19, 14 of which were radiographically silent. In 37 cases of distortion of the knee a correct diagnosis would have been missed unless arthroscopy had been performed. Arthroscopy is therefore indicated in children with severe distortion of the knee, hemarthrosis and with dislocation of the patella.

Functions and complications of shunts in different etiologies of childhood hydrocephalus

Shunt function and complications in different etiologies of childhood hydrocephalus were studied in a series of 306 patients involving 1102 shunt operations. Shunts in patients with hydrocephalus caused by neoplasms proved to be most prone to shunt complications. The patency time for shunts in these patients was significantly shorter than for shunts in other patient categories [Standard number of deviations (SND) 5.9; P<0.001, Meyer-Kaplan life table analysis]. When the two main groups of infantile hydrocephalus-congenital obstructive hydrocephalus and hydrocephalus caused by perinatal intracerebral hemorrhage-were compared, the latter group proved to be significantly more prone to shunt infections (P<0.01), with an infection rate of 17.8% compared with 8.9% for the former group. The importance of this fact is stressed by the observation that these patients appear to constitute an increasing percentage of hydrocephalic patients. According to the present study, patients with congenital intracranial cysts and hydrocephalus are less prone to shunt complications, i.e., the infection rate is 6.8%, which is significantly less than that of patients with other types of hydrocephalus (P<0.01; chi-square test).

Classification and management of the slit ventricle syndrome

A total of 32 patients with overdrainage of CSF, fulfilling the radiological and clinical criteria for collapsed ventricles (“slit ventricles”), were classified into acute, subacute and chronic forms. The basis of classification into these categories was neurologic symptomatology. The majority (29 patients) originally had a ventriculoatrial shunt and 3 had ventriculoperitoneal shunts. Operative correction was performed in 23 patients (insertion of a high pressure valve in 18 and an antisiphon device in 5). Of these, 5 had acute, 10 subacute, and 6 chronic symptoms. Two patients without symptoms were operated on also. During the follow-up period, which varied from 2 to 11 months, no patient has shown recurrence of the original symptoms of the slit ventricle syndrome; two patients developed subacute signs and an antisiphon device was inserted in addition to the high-resistance valve. On the basis of this series, it is concluded that the slit ventricle syndrome can also develop in patients with an atrioventricular shunt and can be treated by preventing further overdrainage of CSF. Though the results are acceptable by present methods, the need for a servo-regulated shunt persists. The surgical correction should preferably be performed before the acute phase. A flowchart is presented for management of a child with suspected slit ventricles.

Treatment of Penile Incarceration by the String Method: 2 Case Reports

We report 2 cases of penile incarceration in a 10-year-old boy and a 40-year-old man. In both cases the penis was encircled by a metallic object. The string method described was successful, rapid, atraumatic and simple to use.

Posterior cranial vault distraction osteogenesis in craniosynostosis: estimated increases in intracranial volume

PurposeTo study distraction osteogenesis of the posterior cranial vault in children requiring increased intracranial volume.Materials and methodsTen patients were treated with cranial distractors. Five children had previously been operated for scaphocephaly and one child for Saether-Chotzen syndrome. Two patients had bilateral coronal suture synostosis with Muenke syndrome and two patients had Apert syndrome. At surgery, the cranial bones were mobilized, the head was widened during surgery, and the segments fixed to each other with distractors. Further expansion at a rate of 1xa0mm/day was performed over 2–4xa0weeks. The cranium was distracted posteriorly from 20 to 30xa0mm.ResultsThe patients all tolerated surgery and distraction well. In all cases, the parents were able to perform the distraction at home. There were no technical problems with the distraction devices. Two cases had minor cutaneous problems, where the distractor penetrated the skin. These cases responded to gentle local wound care measures. At the time of distractor removal, ossification had occurred sufficiently in one of these two cases. In the other case, the device was removed and replaced with a resorbable plate, without any harmful effect on the result. In all cases, sufficient expansion was achieved without causing more cosmetic deformity. Ossification occurred in all cases. This method seems effective, as the calculated increase in intracranial volume was a mean of 20.2% (range 10.2–28.5%).ConclusionsThis preliminary series shows that cranial bone distraction is a useful method for cranial expansion with low morbidity in children with craniosynostosis.

Long-Term Outcome of Fetal Hydrocephaly:

Long-term outcome of 25 fetuses with ventriculomegaly diagnosed before delivery who survived the neonatal period up to school age was examined at 10.1 (standard deviation, 2.6) years of age. Twelve children had normal motor and mental development, seven were severely handicapped, and six showed intermediate outcome. The fetuses with severe handicaps on long-term follow-up had more severe ventricular dilation than the fetuses with good long-term outcomes. Eighteen of the children had surgical treatment, and seven of them had normal long-term development. Thirty percent of surviving fetuses with ventriculomegaly have poor long-term outcomes. In isolated progressive ventriculomegaly, early delivery as soon as fetal lung maturity allows might be reasonable for achievement of better long-term prognosis. (J Child Neurol 1996;11:189-192).

Shunting procedures in the management of intracranial cerebrospinal fluid cysts in infancy and childhood

SummaryWidely diverging opinions on the optimal therapy for intracranial cerebrospinal fluid cysts (CSF), mainly arachnoid cysts and the Dandy-Walker cysts, exist. Excision of the cyst walls in the treatment of the Dandy-Walker cyst has been replaced by shunting procedures, but the recommended method for primary treatment of arachnoid cysts in childhood is still cyst wall excision. Membrane excision is, however, often complicated by recurrence, subsequently requiring shunting-procedures. In a series of 19 cases primary shunting of intracranial CSF cysts proved to be a reliable method. In those cases where hydrocephalus (ventricular dilatation) is present at the time of the primary operation the ventricles should be shunted as well as the cyst. The catheter from the ventricle and that from the cyst should be connected to the same valve, otherwise an increased risk of intracranial herniation exists. The prognosis for infants and children suffering from intracranial CSF cysts is in general good; in 17 out of 19 cases mental development was normal and in 15 out of 19 motor development was normal. The risk of permanent motor damage seems to be particularly high when an arachnoid cyst is located on the quadrigeminal plate.