Biomedical subjects

J Ryhänen

Publications and source records attributed to J Ryhänen.

14 recordsLinked to original sources

PubMed2006

Histomorphometric analysis of poly-L/D-lactide 96/4 sutures in the gastrocnemius tendon of rabbits.

BACKGROUND: Common Achilles tendon ruptures are not usually fixed by bioabsorbable sutures due to limitations in their strength retention properties. Modern technology has made it possible to develop bioabsorbable sutures with prolonged strength retention. AIMS: To evaluate histologically tissue reactions of poly-L/D-lactide (PLDLA) sutures implanted in Achilles tendon of rabbits. MATERIAL AND METHODS: Fifteen rabbits were evaluated at 2, 6 and 12 weeks postoperatively, with five rabbits in each follow-up group. PLDLA monofilament sutures were implanted into the medial gastrocnemius tendon. Polyglyconate monofilament sutures with similar diameter (Maxon 4-0, Cyanamid of Great Britain Ltd., Gosport, UK) were implanted in the contralateral gastrocnemius tendon. The histology was studied in hard-resin embedded samples. The thickness of the formed fibrous tissue capsule was determined histomorphometrically. RESULTS: PLDLA led to formation of significantly thinner fibrous tissue capsule than Maxon sutures of the same diameter. Median thickness (PLDLA vs. Maxon) at two weeks was 5.26 vs.13.22 microm, at six weeks 11.66 vs. 80.97 microm, and at 12 weeks 10.63 vs. 17.59 microm (p<0.01). CONCLUSIONS: During the 12 week follow-up period, PLDLA sutures implanted intratendineously formed thinner fibrous capsule than Maxon sutures of the same diameter. The suture materials were not totally absorbed by 12 weeks.

Animals↗

PubMed2006

Recovery of muscle strength after late repair of distal biceps brachii tendon.

BACKGROUND AND AIMS: Ruptures of the distal part of the biceps brachii tendon are rare. The diagnosis is often delayed and only late repair can be considered. In this study, the recovery of muscle strength after late repair of the distal biceps brachii tendon was evaluated. MATERIALS AND METHODS: Sixteen patients with a ruptured distal biceps brachii tendon were analysed. The mean delay from the primary trauma to the operation was 35 weeks. The tendon was anatomically re-attached with bone anchors. In three cases a tendon graft was needed. The operated arms were immobilised postoperatively for four weeks, after which mobilisation was allowed. Maximal static flexion and supination strength was measured after an average follow-up time of 124 weeks by using a computer-based isokinetic dynamometer. RESULTS: Patient satisfaction and overall muscle strength recovery were very good. Compared to the non-operated side, average flexion strength recovery was 90% and corresponding recovery of supination strength 78%. Weakness on supination remained in the cases where a tendon graft was used. One patient needed a re-operation for a re-rupture. There were three cases of transient paresthesia of the cutaneous nerve. All patients resumed their previous work. CONCLUSION: Late anatomical repair of the biceps brachii tendon restores very good flexion and moderate supination strength. This operation should always be considered when the primary diagnosis is delayed.

Adult↗

PubMed2005

Dupuytren's contracture; increased cellularity--proliferation, is there equality?

BACKGROUND: Dupuytren's disease is a chronic inflammatory process which causes contractures of the fingers by shortening and thickening the palmar fascia. During the proliferative phase, fibroblasts transform into myofibroblasts apparently under the influence of several different factors. The disease usually develops slowly, but in some patients it tends to develop aggressively. The pathogenesis of Dupuytren's disease remains unsolved. In this study, we analyzed some histological characteristics that seem to predict rapid recurrence. MATERIAL AND METHODS: 21 patients were divided into two groups. In 11 patients the disease was classified as aggressive because it had recurred within two years after an operation. In 10 cases it was non-aggressive, as no recurrence had been seen. Five control samples were taken from healthy palmar aponeurosis. The differences in cellularity, collagen, Ki-67, MSA, alpha-SMA and tenascin between the specimens were analyzed using immunohistochemistry. RESULTS: Alpha-SMA and Ki-67 were present more often in the aggressive specimens. Immunohistochemical stainings for macrophages and lymphocytes were negative. CONCLUSION: There may be differences in the histology and/or immunohistochemical appearance of pathological palmar connective tissue cords in aggressive and normal Dupuytren's disease. Further studies are needed to elucidate the pathogenesis of this disease.

Adult↗

PubMed2002

Bone morphogenetic protein 3b expressing reindeer antler.

A cDNA sequence of bone morphogenetic protein 3b (BMP-3b) of reindeer antler was produced with degenerative homology primers in polymerase chain reaction (PCR). An in situ hybridization study of BMP-3b mRNA in 1-month-old antler showed expression in most differentiated cells in the antler center. In addition, the bone-inductive capacity of the reindeer antler matrix was evaluated. Decalcified and powdered antler matrix of different stages of antler maturity was implanted in gelatin capsules under the rat dorsal muscle fascia for two implantation periods: 3 and 8 weeks. Allogenic matrix prepared from rat long bones was used as a positive control implant. Heterotopic ossification was evaluated histomorphometrically and densitometrically. Allogenic bone matrix induced rapid osteogenesis and mineral accumulation. Both endochondral and intramembranous ossification was evident, endochondral ossification being the dominant form. Mineral density in the induced ossicle was 115 +/- 48 mg/cm(3) as early as at 3 weeks and 350 +/- 69 mg/cm(3) at 8 weeks. The proportional areas of von Kossa-stained mineral were 3.67 +/- 2.1% and 11.6 +/- 0.07%, respectively. The antler preparations induced mineralization, but significantly less than the allogenic bone matrix. At 8 weeks, mineral density was significantly lower in the cast antler preparation than in the allogenic implants. The morphology of the mineralized areas of the antler preparations showed no ossification.

Animals↗

PubMed2002

Behaviour of nitinol in osteoblast-like ROS-17 cell cultures.

Nickel titanium shape memory metal alloy Nitinol (NiTi) has been used in dental wares and in gastrointestinal surgery. Nitinol is a promising implant material in orthopedics, but its biocompatibility, especially in long-term implantation is not confirmed yet. We studied Nitinol's effect on a cell culture model. Comparisons to stainless steel, pure titanium and pure nickel were performed. The effects of Nitinol on cell death rate, the apoptosis rate and the formation of local contacts were studied on rat osteosarcoma cell line ROS-17 in 48-h cultures. The cell death rate was assessed with combined calcein-ethidium-homodimer labelling. The amount of dead cells 1000 cells were as follows: four in the NiTi, 21 in the Stst, 4.8 in the Ti and 51 in the Ni group. In the NiTi and Ti groups, the number of dead cells was significantly lower (p < or = 0.01) than in Ni group. The rate of apoptosis was detected with TUNEL-assay. The assay results were: 1.93 apoptotic cells 1000 cells in the NiTi, 1.1 in the Stst, 2.98 in the Ti and 0.62 in the Ni group. A comparison of these two results shows that 48% of the dead cells were apoptotic in the NiTi, 56.6 in the Stst, 62% in the Ti and only 1.8% in the Ni group. The focal contacts were stained with a paxillin antibody and counted. There were marked differences in the number of focal contacts per unit area compared to NiTi (774 focal contacts): 335 in Stst (p < or = 0.01), 462 in Ti (p < or = 0.01) and 261 in Ni (p < or = 0.005). Our results show that NiTi is well tolerated by the osteoblastic type ROS-17 cells.

Alloys↗

PubMed2002

Comparison of the bone modeling effects caused by curved and straight nickel-titanium intramedullary nails.

Nitinol (NiTi) shape memory metal alloy makes it possible to prepare functional implants. A curved intramedullary NiTi nail has been shown to cause bending of the bone, bone thickening, increase in cortical area, and reduction in bone longitudinal growth. The purpose of the present study was to find out whether these changes are caused by the bending force of the curved nail or by the intramedullary nailing itself. Pre-shaped intramedullary NiTi nails were implanted in the cooled martensitic form into the medullary cavity of the right femur in 12 rats, where they started to restore their austenitic form, causing a bending force. Straight nails were used as controls in another 12 rats. After 12 weeks, the operated femurs were compared with their non-operated contralateral counterparts and the differences were compared between the groups. Anteroposterior radiographs demonstrated bone bowing only in the curved nail group. Retardation of longitudinal growth was observed in both groups, showing that the growth effect seems to be due to the intramedullary nailing itself. Increase in bone cross-sectional area and cortical thickness were found in both groups. However, this increase was more evident with the curved nail, indicating that the bending force of the functional nail seems to induce these changes.

Journal Article↗

PubMed2002

Composite implant of native bovine bone morphogenetic protein (BMP) and biocoral in the treatment of scaphoid nonunions--a preliminary study.

BACKGROUND AND AIMS: Bone morphogenetic protein (BMP) has been shown to induce bone formation and union in long bone defects and nonunions. We report a preliminary study of a composite implant consisting of a biocoral frame, carrier collagen and bovine BMP in the treatment of scaphoid nonunions. MATERIAL AND METHODS: Two proximal and eight waist area scaphoid nonunions were treated using BMP/coral implant combined with either the Matti-Russe procedure (2 cases) or an interpositional bone graft fixed with screws or compression fixation pins (8 cases). In two cases only a one piece BMP/coral implant was used as an interpositional graft and in other cases interpositional autograft was used with granular BMP/coral implant placed between the fragments and the graft. RESULTS AND CONCLUSIONS: Only two wrists resulted in complete union. These preliminary results suggest that composite implant of BMP, as used in the present study, may not solve the problems encountered in the treatment of scaphoid nonunions. Poor vascular conditions in scaphoid may not provide enough mandatory osteogenic cells for BMP to function properly. In avascular conditions coral does not resorb edequately and implants may also work as a sequester between the bone graft and the scaphoid bone and therefore actually inhibit the healing process.

Adult↗

PubMed2001

Effect of nickel-titanium shape memory metal alloy on bone formation.

The aim of this study was to determine the biocompatibility of NiTi alloy on bone formation in vivo. For this purpose we used ectopic bone formation assay which goes through all the events of bone formation and calcification. Comparisons were made between Nitinol (NiTi), stainless steel (Stst) and titanium-aluminium (6%)-vanadium (4%) alloy (Ti-6Al-4V), which were implanted for 8 weeks under the fascia of the latissimus dorsi muscle in 3-month-old rats. A light-microscopic examination showed no chronic inflammatory or other pathological findings in the induced ossicle or its capsule. New bone replaced part of the decalcified matrix with mineralized new cartilage and bone. The mineral density was measured with peripheral quantitative computed tomography (pQCT). The total bone mineral density (BMD) values were nearly equal between the control and the NiTi samples, the Stst samples and the Ti-6Al-4V samples had lower BMDs. Digital image analysis was used to measure the combined area of new fibrotic tissue and original implanted bone matrix powder around the implants. There were no significant differences between the implanted materials, although Ti-6Al-4V showed the largest matrix powder areas. The same method was used for measurements of proportional cartilage and new bone areas in the ossicles. NiTi showed the largest cartilage area (p < or = 0.05). Between implant groups the new bone area was largest in NiTi. We conclude that NiTi has good biocompatibility, as its effects on ectopic bone formation are similar to those of Stst, and that the ectopic bone formation assay developed here can be used for biocompatibility studies.

Alloys↗

PubMed1999

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.

Animals↗

PubMed1999

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.

Alloys↗

PubMed1999

Femoral neck is a sensitive indicator of bone loss in immobilized hind limb of mouse.

The present study was carried out to evaluate a unilateral hind limb immobilization model in the mouse. The right legs of male mice (age 10-12 weeks) were immobilized for 3 weeks against the abdomen by an elastic bandage. Body weight decreased significantly during the immobilization. Peripheral quantitative computed tomography (pQCT) analysis showed that the cross-sectional cortical area (CSA), the bone mineral content (BMC), and the bone mineral density (BMD) of the tibial diaphysis were lower in both legs of the immobilized animals than in age-matched controls, but the difference was mainly due to weight reduction. At the tibial metaphysis, CSA, BMC, and BMD were reduced in both legs of the immobilized animals, even after weight adjustment. At the femoral neck, CSA, BMC, and BMD were significantly lower in both legs of the immobilized animals, and the difference between the hind legs of the immobilized animals was also highly significant. The findings of the pQCT study were in good agreement with the changes in mechanical strength. The tibia was a more sensitive indicator of diaphyseal bone weakening than the femur when measuring the bending breaking force of the diaphysis. The femoral neck showed significantly decreased strength, and the difference between the immobilized leg and the contralateral leg was most clearly seen in lateral loading. We conclude that 3 weeks of hind limb immobilization weakened the tibia and femur significantly compared with their contralateral counterparts. The reduction was more significantly seen in the mechanical bending strength than in the pQCT evaluation, and the femoral neck was the most sensitive indicator of bone weakening.

Animals↗

PubMed1998

In vivo biocompatibility evaluation of nickel-titanium shape memory metal alloy: muscle and perineural tissue responses and encapsule membrane thickness.

Nickel-titanium shape memory alloy (Nitinol) has properties that could be very useful in surgical applications. Thermal shape memory, superelasticity, and high damping properties make such alloys behave differently compared to other implant metals. There has previously been a lack of sufficient evidence on the biocompatibility of Nitinol. The purpose of this study was to evaluate general soft tissue response and biocompatibility to Nitinol in vivo, and to clarify neural and perineural responses, previously unreported. Seventy-five rats were randomized into three groups. Test specimens were implanted into paravertebral muscle and near the sciatic nerve. A comparison was made between Nitinol, stainless steel, and Ti-6Al-4V. The animals were euthanized at 2, 4, 8, 12, and 26 weeks after implantation. General morphologic and histologic observations were made under light microscopy. Semiautomatic computerized image analysis was used to measure the encapsule membrane thickness around the implants. The muscular tissue response to Nitinol was clearly nontoxic, regardless of the time period. The overall inflammatory response to Nitinol was very similar to that of stainless steel and Ti-6Al-4V alloy. There were no necroses, granulomas, or signs of dystrophic soft tissue clacification. The immune cell response to Nitinol remained low. Only a few foreign-body giant cells were present. The detected neural and perineural responses were also clearly nontoxic and nonirritating with Nitinol. No qualitative differences in histology between the different test materials could be seen. At 8 weeks, the encapsule membrane of Nitinol was thicker than that of stainless steel (mean 62 +/- 25 microns vs. 41 +/- 8 microns). At the end of the study, the encapsule thickness was equal to all the materials tested. We concluded that Nitinol had good in vivo biocompatibility after intramuscular and perineural implantation in rats in the 26-week follow-up. Based on the results of the present study, Nitinol appears to have good potential for clinical use.

Animals↗

PubMed1997

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.

Biocompatible Materials↗

PubMed1994

Postoperative pain relief in children. A comparison between caudal bupivacaine and intramuscular diclofenac sodium.

Two hundred and fifty children undergoing herniotomy or orchidopexy under general anaesthesia were randomly allocated to receive pre-operatively either diclofenac sodium 1 mg.kg-1 given intramuscularly or a caudal injection of bupivacaine 0.25% 1 ml.kg-1 with or without adrenaline or no analgesia. Plasma diclofenac and beta-endorphin concentrations were determined in eight and 21 patients respectively. Postoperative pain was assessed by ward nurses who were blinded to the group allocation. Comparison with the control group showed diclofenac to be an effective analgesic. Caudal bupivacaine provided more pain-free children during the early postoperative hours, but later the need for pethidine as rescue analgesic was lower among the children who had received intramuscular diclofenac. Caudal analgesia abolished the stress-induced increase in plasma beta-endorphin level which was found in the children given diclofenac and in those who served as controls. Total plasma clearance of intramuscular diclofenac sodium appears to be higher in children than in adults. A single intramuscular dose of diclofenac significantly reduces the need for an opioid analgesic in children after inguinal herniotomy or orchidopexy, and owing to its long duration of action, it offers an alternative or complementary method of pain relief to caudal analgesia.

Analgesia, Epidural↗