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Biomedical subjects

R Kontio

Publications and source records attributed to R Kontio.

12 recordsLinked to original sources
PubMed2005

Biodegradable polydioxanone and poly(l/d)lactide implants: an experimental study on peri-implant tissue response.

Several implants for orbital wall fracture treatment are available at the present, but they have drawbacks: resorption, risk for migration and foreign body reaction. Alloplastic resorbable implants would be advantageous: no removal operation and no donor side morbidity. The purpose of this study was to evaluate the foreign body reaction, capsule formation and mechanical properties of two bioresorbable implants. PDS and SR-P(L/DL)LA mesh sheet (70/30) with solid frame (96/4) implants (SR-P(L/DL)LA 70,96) were placed into subcutaneous tissue of 24 rats. Immunohistochemistry was used to evaluate reactivity for Tn-C, alpha-actin, type I and III collagens and two mononuclear cells: T-cells and monocyte/ macrophage. GPC, DSC and SEM were performed. Student's t-test or nonparametric Kruskall-Wallis test were used for statistical analysis. Histology of peri-implant capsule exhibited an inner cell-rich zone and an outer connective tissue zone around both materials. Tn-C reactivity was high in the inner and alpha-actin in the outer zone. At the end of the study, the difference of type I collagen versus type III collagen reactivity in inner zone was statistically significant (P<0.0001) as was the difference of type I collagen versus type III collagen reactivity in outer zone (P<0.0001). Immunohistochemistry did not reveal any statistical differences of T-cell and monocyte/macrophage reactivity around PDS versus SR-P(L/DL)LA 70,96 implants, nor any differences as a function of time. PDS were deformed totally after 2 months. SR-P(L/DL)LA 70,96 implants were only slightly deformed during the follow up of 7 months. PDS degraded rapidly in SEM observation. Particles were detaching from surface. SEM observation revealed that polylactide implant was degrading from the surface and the inner porous core became visible. The degradation came visible at 7 months. There were cracks in perpendicular direction towards to the long axis of the filaments. M(w) of PDS decreased fast compared to the polylactide implant. Foreign body reaction was minimal to both materials but continued throughout the whole observation period. Mechanically PDS was poor, it looses its shape totally within 2 months. It cannot be recommended for orbital wall reconstruction. New mesh sheet-frame structure (SR-P(L/DL)LA 70,96) approved to be mechanically adequate for orbital wall reconstruction. It seems not to possess intrinsic memory and retains its shape. The resorption time is significantly longer compared to PDS and is comparable to other studied P(L/DL)LA copolymers. Thus, the new polylactide copolymer implant may support the orbital contents long enough to give way to bone growth over the wall defect.

Absorbable Implants↗
PubMed2005

The MDM2 promoter polymorphism SNP309T-->G and the risk of uterine leiomyosarcoma, colorectal cancer, and squamous cell carcinoma of the head and neck.

BACKGROUND: MDM2 acts as a principal regulator of the tumour suppressor p53 by targeting its destruction through the ubiquitin pathway. A polymorphism in the MDM2 promoter (SNP309) was recently identified. SNP309 was shown to result, via Sp1, in higher levels of MDM2 RNA and protein, and subsequent attenuation of the p53 pathway. Furthermore, SNP309 was proposed to be associated with accelerated soft tissue sarcoma formation in both hereditary (Li-Fraumeni) and sporadic cases in humans. METHODS: We evaluated the possible contribution of SNP309 to three tumour types known to be linked with the MDM2/p53 pathway, using genomic sequencing or restriction fragment length polymorphism as screening methods. Three separate Finnish tumour materials (population based sets of 68 patients with early onset uterine leiomyosarcomas and 1042 patients with colorectal cancer, and a series of 162 patients with squamous cell carcinoma of the head and neck) and a set of 185 healthy Finnish controls were analysed for SNP309. RESULTS: Frequencies of SNP309 were similar in all four cohorts. In the colorectal cancer series, SNP309 was somewhat more frequent in women and in patients with microsatellite stable tumours. Female SNP309 carriers were diagnosed with colorectal cancer approximately 2.7 years earlier than those carrying the wild type gene. However, no statistically significant association of SNP309 with patients' age at disease onset or to any other clinicopathological parameter was found in these three tumour materials. CONCLUSION: SNP309 had no significant contribution to tumour formation in our materials. Possible associations of SNP309 with microsatellite stable colorectal cancer and with earlier disease onset in female carriers need to be examined in subsequent studies.

Adult↗
PubMed2004

Are there any complications with bioabsorbable fixation devices? A 10 year review in orthognathic surgery.

Bioabsorbable fixation devices have been used in our departments between November 1991 and November 2001 in orthognathic surgery. The aim of this retrospective study was to assess all complications experienced during this time period, when we have operated 163 patients who have undergone 329 orthognathic osteotomies fixated with bioresorbable devices. No postoperative intermaxillary fixation was used. Light guiding elastics were used for 5 to 7 weeks. Patients' acceptance was generally excellent and very few complications occurred during this follow-up of 10 years. The complications were minor and did not affect the end results of the operations. Minor complications occurred in 14 patients (8.6%). Only one patient (0.6%) had a postoperative infection with elevated infection parameters. The other minor complications consisted mainly of dehiscence of the wound and plate exposure together with granulation tissue in the operation field. The rest of the complications occurred in the beginning of our study, when large screw heads on top of the bone irritated the patient and had to be removed. Insufficient fixation resulted in open bite in three patients (1.8%) in the beginning of the trial use of new devices, which no longer are used. Based on our experience, bioresorbable devices are safe to be used in orthognathic procedures. However, there is a learning curve, as there is with all new methods introduced.

Absorbable Implants↗
PubMed2004

Orbital floor reconstruction with poly-L/D-lactide implants: clinical, radiological and immunohistochemical study in sheep.

In this study the reconstruction capacity of orbital wall in sheep was evaluated when poly-L/D-lactide (PLDLA96) implants were used for large blow-out defects in 18 sheep. The contralateral side, where the defects healed spontaneously, served as controls. The follow-up was 12, 16, 22 and 36 weeks. Healing was evaluated clinically, radiologically, histologically and immunohistochemically. Physiochemical properties of the implants were also studied. At first, the implants were surrounded by elastic capsules, which gradually ossified. At 36 weeks, 60% were still visible and deformed but surrounded by bone. Light microscopy revealed a low grade inflammatory reaction. Expression of Tn-c and cFn was intense throughout the study. Shear strength decreased gradually and was not measurable after 16 weeks. Crystallinity increased steadily from 1.5 to 29.30% and molecular weight decreased from 49,000 to 4186. In CT, the final bony defect was smaller in the reconstructed sides than in the controls. Based on this study it can be concluded that PLDLA96 implant provokes a local inflammation, which does not prevent bone healing. The deformation of the implant, however, indicates that this PLDLA96 plate is not suitable for orbital floor reconstruction.

Absorbable Implants↗
PubMed2001

Effectiveness of operative treatment of internal orbital wall fracture with polydioxanone implant.

Many implants, some made from teflon or silicone, have been used for internal orbital wall reconstruction. Late complications relating to use of such implants have been reported. In this prospective study a polydioxanone (PDS) implant absorbable in vivo was used for internal orbital wall reconstruction. Follow-up involved clinical examination, magnetic resonance imaging (MRI) and computerized tomography (CT). Clinical examinations were undertaken before operation and up to 36 weeks postoperatively. Sixteen consecutive patients (10 pure blow-out fractures, six with associated zygomatic fracture) took part in the study. Prevalences of diplopia, proptosis and enophthalmus were recorded during each follow-up examination. This study revealed no muscle entrapment within the fracture line. Although CT results confirmed bone growth in the internal orbital wall, shape was unsatisfactory, and orbital volume was not reduced. MRI revealed thick scar formations in six cases (37.5%), fibrotic sinuses filled with air or gas in three cases (19%) and a fibrotic sinus with fluid around the PDS in one case (6%). Our results suggest that use of PDS in reconstructing the internal orbital wall is inadvisable.

Absorbable Implants↗
PubMed1998

Fibrous wound repair associated with biodegradable poly-L/D-lactide copolymer implants: study of the expression of tenascin and cellular fibronectin.

Extracellular matrix (ECM) proteins are known to play a role in inflammatory and hyperplastic processes. Our aim in the present study was to study the distribution of tenascin (Tn), cellular fibronectins (cFn) and myofibroblasts around biodegradable poly-L/D-lactide (PLA) implants with monoclonal antibodies (MAb). Ethylene-oxide and gamma-irradiation sterilized PLA plate-type implants were inserted into the dorsal subcutaneous tissue of ten adult rabbits. Follow-up times were 4, 12, 16, 36 and 48 wk. Only some inflammatory cells were observed. In electron microscopy, a close coherence between the implant and the stromal tissue was seen. Immunoreactivity for Tn, cFn and alpha-actin was detected as a distinct layer bordering the implant, regardless of the sterilization method for the first 36 wk. From week 36 onwards, Tn immunoreactivity was downregulated while cFn immunoreactivity still persisted. A moderate upregulation for myofibroblasts was seen on the week 48 specimens, when hydrolysation of PLA implant had started. The persistent content of myofibroblasts, Tn and cFn suggests a prolonged wound healing produced by PLA implants. The absence of Tn at the week 48 specimens suggests that cFn, rather than Tn may be needed for alpha-actin-mediated contraction by myofibroblasts.

Journal Article↗
PubMed1998

Activation of periprosthetic connective tissue in aseptic loosening of total hip replacements.

In aseptic loosening of initially well inserted total hip prostheses, implant wear debris and cyclic mechanical loading lead to a foreign body type of chronic inflammatory reaction, then to osteolysis, and finally to loosening of the implant. In the present work the reactive and adaptive changes of the periprosthetic tissues and pseudojoint were characterized by analysis of the local cell proliferation. Immunohistochemical demonstration of proliferating cells was performed by application of affinity purified rabbit antihuman Ki-67 antibodies to periprosthetic tissues obtained from revision operations for loose total hip prostheses. The fibrous areas and, in particular, the cell rich, vascular areas of the interface tissue (between implant and bone) and the pseudocapsule around aseptically loosened implants contained higher numbers of proliferating cells than the tissues around well fixed implants. In addition, the pseudosynovial lining occasionally contained some Ki-67 positive proliferating cells. Somewhat surprisingly, proliferating vascular endothelial cells were relatively rare. These findings suggest that reactive (interface tissues) and adaptive (pseudojoint and capsule formed around the artificial joint) tissue changes in loosening total hip prostheses comprise proliferation of local fibroblastlike cells. It is concluded that periprosthetic tissues of the loosened total hip prosthesis represent activated mesenchymal tissue.

Adult↗
PubMed1997

Microvascular free flaps in head and neck cancer surgery in Finland 1986-1995.

Microvascular free tissue transfer has in many cases replaced classic flap techniques and is now an established workhorse for head and neck reconstructions. In this retrospective study the over 300 patients, who had microvascular free flap reconstructions in head and neck cancer surgery in Finland during a 10-year period (1986-1995) were reviewed. The operations were performed in the University Hospitals by plastic surgeons, ENT specialists or maxillofacial surgeons. The cases consisted of defects resulting from resection of oral cavity tumors (63%), mid- or upper-face and skullbase tumors (20%) and hypopharyngo-esophageal tumors (17%). The series includes a wide range of flap types and analyses flap outcome and complications. A total of 313 cases was reconstructed by 317 flaps (forearm flaps 47%, latissimus dorsi flaps 19%, free jejunum or colon transfers 15%, free iliaca crest flaps 8% and other flaps 11%). Thrombosis of one of the vessels and haematoma were the most frequent causes of failure in microvascular free tissue transfer. A total flap necrosis occurred in 27 (8.5%) and a partial necrosis in 12 (4%) patients. The most reliable flap in terms of survival was the radial forearm flap. The ever-improving success of microvascular free tissue transfer has made it a useful procedure for head and neck reconstructions. There is also a growing need for microvascular team surgery in the field of head and neck cancer therapy.

Female↗
PubMed1988

Primary reconstruction of the mandible in cancer surgery. A report of 13 reconstructions according to the principles of rigid internal fixation.

This study comprises 30 patients with extensive oral cancer invading the mandibular bone. In each case, large segmental composite resections were performed and the mandibles primarily reconstructed, according to the principles of rigid internal fixation. All but one of the reconstructions were successful and the functional and cosmetic results were excellent or good in 12 patients. The results indicate that primary reconstruction can be performed without major complications. Bone transplantation may be omitted or postponed to a later date. The fact that tracheostomy and intermaxillary fixation can be avoided, is a major advantage for these patients.

Adult↗
PubMed1988

Sports-related maxillofacial fractures in a hospital material.

Sports-related maxillofacial fractures were analysed in 80 patients, accounting for 5.6% of all patients with facial bone fractures, treated during the 5-year period 1981-1985. 55% of the patients had 1 or more mandibular fractures and 45% had midface fractures. 6% of the patients had multiple injuries. The most common causes of injury were collision and fall. Soccer and ice hockey turned out to be the most hazardous sports, although sports-related maxillofacial fractures were less severe than those related to other causes. The need for oral and facial protection among athletes involved in contact sports is discussed.

Adolescent↗
PubMed1986

Rigid internal fixation of mandibular fractures--an analysis of 45 patients treated according to the ASIF method.

A report is given of 45 patients with fractures of the mandible treated by the method of rigid internal fixation. In a majority of cases, there were either absolute or relative contraindications for an IMF. Most of the fractures plated were body fractures of the mandible, followed by angular, and symphysis fractures. In 4 cases, the fractures, caused by gunshots, were compound ones. In these, extensive soft tissue reconstructions were also performed. In a majority of the patients, good primary healing was observed, and the mean hospitalization time was only 4.4 days. The infection rate of 13% was, however, relatively high, and a few disturbances were seen with respect to motor and sensory function of the lower lip. Slight occlusal dysharmonies were registered in 23%, on an average of 22 weeks postoperatively, but these could be adjusted with a minimum of grinding. It was concluded that bone plating is a useful method in the treatment of several different types of mandibular fractures including the severe compound ones. The method can be especially recommended in cases in which an IMF is contraindicated or should be avoided. The possibilities for decreasing the frequency of postoperative infections are discussed.

Adolescent↗