Lateral-Only Kirschner-Wire Fixation of Type-3 Supracondylar Humerus Fractures in Children with a Special Attention to Technical Issues.

BACKGROUND AND AIMS: Lateral-only Kirschner-wire pinning of supracondylar humerus fracture is superior in avoiding surgery-related ulnar nerve injury. Their disadvantageous effects on stability may be a consequence of inappropriate surgical techniques. We analyzed whether the surgeon's preference for lateral-only fixation is associated with his or her orthopedic competence. We also analyzed the surgical technique-related risk factors of redisplacement. MATERIALS AND METHODS: All children, aged <16 years, with a distal humerus fracture in 2000-2009 were preliminary included (N = 861). Altogether, 24 of the 165 type-3 supracondylar fractures were operated by lateral-only pinning. Loss of reduction in the follow-up was the main outcome, while the close characteristics of the surgical technique and treating surgeon's orthopedic competence were the explanatory variables. RESULTS: Orthopedic surgeons used lateral-only method in 23.5% of the type-3 fractures (N = 16/68), and other surgeons in 8.2% (N = 8/97)(difference = 15.3%, 95% confidence interval = 4.6%-27.6%, p = 0.005). One-third of the lateral-only treated fractures (29.2%, 95% confidence interval = 12.6%-51.1%) redisplaced. Lateral-entry pins that crossed at the level of the fracture were associated with failure (87.5%), while no patient with appropriate pin configuration failed (difference = 87.5%, 95% confidence interval = 52.1%-97.8%). A shorter distance (<5 mm) between the entry points of the pins was associated with redisplacement (80% vs. 15.8%, difference = 64.2%, 95% confidence interval = 16.1%-86.9%). Open reduction (p = 0.07), insufficient (<4 mm) bone contact (p = 0.28), monocortical pins (p = 0.569), low diverging angle (p = 0.13) or parallel pins (p = 1.0), residual coronal displacement (p = 1.0), >5° changed Bauman angle (p = 0.11), rotational displacement (p = 0.25), and the experience or specialty of the surgeon were not associated with redisplacement. CONCLUSION: Lateral-only pins resulted in poor stability in one in three of the patients. Appropriate configuration of the pins was associated with good fracture healing, but crossing the pins at the fracture level and introducing them close to each other were associated with redisplacement. Surgeons with more orthopedic competence selected lateral-only fixation more usually.

Main Clinical Use of Additive Manufacturing (Three-Dimensional Printing) in Finland Restricted to the Head and Neck Area in 2016-2017.

BACKGROUND AND AIMS: Additive manufacturing or three-dimensional printing is a novel production methodology for producing patient-specific models, medical aids, tools, and implants. However, the clinical impact of this technology is unknown. In this study, we sought to characterize the clinical adoption of medical additive manufacturing in Finland in 2016-2017. We focused on non-dental usage at university hospitals. MATERIALS AND METHODS: A questionnaire containing five questions was sent by email to all operative, radiologic, and oncologic departments of all university hospitals in Finland. Respondents who reported extensive use of medical additive manufacturing were contacted with additional, personalized questions. RESULTS: Of the 115 questionnaires sent, 58 received answers. Of the responders, 41% identified as non-users, including all general/gastrointestinal (GI) and vascular surgeons, urologists, and gynecologists; 23% identified as experimenters or previous users; and 36% identified as heavy users. Usage was concentrated around the head area by various specialties (neurosurgical, craniomaxillofacial, ear, nose and throat diseases (ENT), plastic surgery). Applications included repair of cranial vault defects and malformations, surgical oncology, trauma, and cleft palate reconstruction. Some routine usage was also reported in orthopedics. In addition to these patient-specific uses, we identified several off-the-shelf medical components that were produced by additive manufacturing, while some important patient-specific components were produced by traditional methodologies such as milling. CONCLUSION: During 2016-2017, medical additive manufacturing in Finland was routinely used at university hospitals for several applications in the head area. Outside of this area, usage was much less common. Future research should include all patient-specific products created by a computer-aided design/manufacture workflow from imaging data, instead of concentrating on the production methodology.

The Measurement Methods of Movement and Grip Strength in Children with a Previous Upper Extremity Fracture: A Comparative, Prospective Research.

BACKGROUND AND AIMS: Decreased range of motion of the elbow and forearm and decreased grip strength are potential findings following a childhood upper extremity fracture. Clinical follow-up is essential because spontaneous improvement is seen several months after the injury. Freehand measuring with a goniometer and hydraulic dynamometer is used to evaluate clinical result. The new methods are justified in avoiding human typewriting errors, thus improving patient safety. Nevertheless, their feasibility in child patients is unknown. This study aimed to evaluate congruence between the computer-assisted and the free-hand measuring methods. MATERIALS AND METHODS: A total of 59 children with a previous supracondylar humerus fracture were clinically examined by means of free-hand (transparent goniometer and hydraulic dynamometer; Jamar, Lafayette Ltd.) and computer-assisted (E-Link System Packages, Biometrics Ltd.) methods. The range of motion and grip strength were measured separately using both methods. Agreement between the measurements was evaluated using the Bland-Altman method. RESULTS: The results between the two methods were incongruent and the differences between measurements increased along with the mean of measurements in all categories except elbow extension. Rotational range of motions were smaller and grip strength was weaker while measuring with the computer-assisted method. The mean discrepancy was 0.97° (95% confidence interval = -2.46 to 0.53) for elbow extension and 7.97° (95% confidence interval = 6.60-9.33) for elbow flexion. CONCLUSIONS: Grip strength is used to evaluate impairment of hand function. The study method showed slightly lower results in grip strength. Range of motion is essential when evaluating the outcome of supracondylar humerus fracture, while >10° of change in elbow range of motion associate with impaired function. As compared with the gold-standard goniometer, the methods were not congruent. However, all differences were under 10° and probably beyond clinical importance. Because of its advantages in recording the outcomes to electronical charts, the computer-assisted method is recommended option in performing the follow-up of complicated pediatric supracondylar humerus fractures.

Confirmed and Suspected Foreign Body Injuries in Children during 2008-2013: A Hospital-Based Single Center Study in Oulu University Hospital.

INTRODUCTION: Foreign body injuries are common in children. Most of them are not serious but they can be fatal. A suspected foreign body injury in a child results in a high rate of hospitalizations, exposure to radiation, and need for intervention. This study aimed to analyze the current epidemiology of in-hospital or out of hospital treated foreign object injuries and suspected foreign body injuries in children. MATERIAL AND METHODS: All children <16 years of age (N = 152) who suffered or were suspected to suffer (N = 63) from a foreign body injury and were treated in a pediatric trauma unit of Oulu University Hospital, Oulu, Finland, over a 6-year study period (2008-2013) were included. A comprehensive chart review was completed in order to evaluate injury history, age at the time of trauma, treatment and characteristics of the foreign objects. RESULTS: The majority (57.9%, N = 88) of the injuries were found in children <3 years of age. There was a male predominance (60.5%, N = 92). The most common anatomical site where the foreign body was found was the nose (28.9%, N = 44), followed by the esophagus (20.4%, N = 31) and the eye (11.2%, N = 17). Foreign objects were also found in the lower airways (10.5%, N = 16), ear (10.5%, N = 16), bowel (9.9%, N = 15), throat (3.9%, N = 6), stomach (3.9%, N = 6), and urethra (0.7%, N = 1). Various household items were the most common foreign bodies (33.6%, N = 51). Toys in particular caused 22.4% (N = 34) of the injuries. In-hospital intervention was necessary for 38.5% of the patients (N = 58). Intervention was needed in 39.7% (N = 25/63) of the patients who were suspected to suffer from foreign body but did not. There were no fatalities. CONCLUSION: Foreign body injuries treated at the pediatric trauma unit were most common in the youngest children (<3 years of age). Majority (61.8%, N = 94) of the patients were treated non-operatively, without any in-hospital intervention.

The long-term outcome of childhood supracondylar humeral fractures: A population-based follow up study with a minimum follow up of ten years and normal matched comparisons.

AIMS: We present the clinical and radiographic outcome of 81 children with Gartland type I to III supracondylar humeral fractures at a minimum follow-up of ten years (mean 12.1 years; 10.3 to 16.1) following injury. PATIENTS AND METHODS: The clinical and functional outcomes are compared with normal age- and gender-matched individuals. The population-based study setting was first identified from the institutional registries; the rate of participation was 76%. Controls were randomly selected from Finnish National Population Registry. RESULTS: According to Flynn's criteria, most fractures (75.3%) resulted in a satisfactory ("good or excellent") outcome. Satisfactory recovery was achieved in 75.0% of type I fractures treated by closed splinting (p = 0.013). Type II fractures were associated with both satisfactory (57.7%) and unsatisfactory (42.3%) results, regardless of the type of treatment, although the numbers were small in the sub groups. Most type III fractures were treated operatively, and most (76%) had a satisfactory outcome according to Flynn's criteria (p = 0.015). Compared with none among the normal subjects, flexion of the elbow was reduced by > 10° at long-term follow-up in 20 cases (24.7%, p < 0.001) and 9 (11.1%) had a reduced flexion of > 15° (p = 0.004). In patients who had sustained a type III fracture, the carrying angle was decreased by 35.7% (from 9.8° to 6.3°; p = 0.048). All patients achieved an excellent Mayo Elbow Performance Score (mean 96.4 points). CONCLUSION: The long-term outcome of extension-type supracondylar humeral fractures is generally good, but not exclusively benign, with the potential for long-term pain and ulnar nerve sensitivity, and a decrease in grip strength and range of movement in type II and type III fractures. Bony remodelling cannot be relied upon to correct any residual deformity. In particular, type II fractures have impaired long-term recovery and justify individual consideration in their treatment. Cite this article: Bone Joint J 2016;98-B:1410-17.

Ulnar nerve morbidity as a long-term complication of pediatric supracondylar humeral fracture.

BACKGROUND: Supracondylar humeral fractures are common in children. We studied long-term ulnar nerve symptoms secondary to these fractures and analyzed the treatment for ulnar neuropathy. MATERIALS AND METHODS: The cohort included 91 patients with a supracondylar humeral fracture in childhood, on average 12 years previously, in the geographic catchment area. All the cases were reexamined in regard to ulnar nerve morbidity. Cases with secondary ulnar neuropathy were treated nonoperatively and operatively. RESULTS: Ulnar neuropathy was present in four cases (4.4 %). They all had suffered from a dislocated fracture, and they had been operated primarily. Another three patients had slight ulnar nerve symptoms. Hence, the total prevalence of secondary ulnar nerve morbidity was 7.7 %. A jumping nerve was seen in 9.9 %; 51.6 % had a diminished axial angle. CONCLUSIONS: We report a defined pattern of long-term ulnar nerve morbidity after pediatric supracondylar humeral fracture. The prevalence of neuropathy is alarming in the young population (<25 years of age).

A new mini-invasive technique in treating pediatric diaphyseal forearm fractures by bioabsorbable elastic stable intramedullary nailing: a preliminary technical report.

BACKGROUND AND AIM: Operative treatment is often indicated in unstable pediatric diaphyseal forearm fractures. Recently minimally invasive reduction and elastic stable intramedullary nailing have been of increasing interest, instead of open reduction and internal fixation with plates. There are several disadvantages of metallic intramedullary implants, such as soft-tissue irritation and a risk of disturbing later imaging. Thus, they are generally removed in later operations. We aimed to develop a new technique to stabilize pediatric forearm fractures by the bioabsorbable intramedullary nailing. MATERIAL AND METHODS: We developed a new, two-stage mini-invasive surgical technique to stabilize the unstable diaphyseal fractures in children. The procedure is bioabsorbable elastic stable intramedullary nailing. Ultra-high-strength bioabsorbable intramedullary nails of poly(lactide-co-glycolide) were manufactured for our purpose. The material has been widely proven to be biocompatible and stable enough for fracture treatment as screws and pins. We have used the new technique in the unstable both-bone diaphyseal forearm fractures in children between the ages of 5 and 15 years. We report the technique and our clinical experience in the series of those three cases that have been followed up for at least 12 months. The present series has been randomized for the procedure instead for titanium elastic stable intramedullary nailing, and the series represents a part of ongoing randomized trial. RESULTS: The reported cases operated by the new technique referred good union in the fractured bones and acceptable alignment in the follow-up. Removal of the implants was not required. No troubles with the procedure or implant per se were noticed, indicating good feasibility. One high-energy refracture occurred half year after the primary trauma. Traditional titanium implants were used to control the refracture. CONCLUSIONS: We report our preliminary experience of a new surgical mini-invasive procedure to stabilize the unstable pediatric forearm shaft fractures by bioabsorbable elastic stable intramedullary nailing. Our clinical experience suggests that the procedure combined with long-arm casting is feasible in treating the pediatric forearm fractures. The technique may bring benefits to handling these challenging fractures. The disadvantages of metallic implants may be avoided. In addition, removal of the implant will not be required. There was one refracture in the series, but it was due to new high-energy trauma. According to our understanding, it was not related to the type of former osteosynthesis. However, ignoring the good preliminary experience, still we do not have results of the superiority of the procedure over traditional elastic stable intramedullary nailing. Our ongoing randomized multicenter study is aimed to determine its long-term outcome against the present golden standard. Nevertheless, due to encouraging preliminary results, we see it necessary to report the technique.

Persistent scrotal pain and suspected orchido-epididymitis of a young boy during pinworm (Enterobius vermicularis) infection in the bowel.

AIM: Pinworm (Enterobius vermicularis) is the most common parasite among mankind. Ectopic pinworm infections in number of organs are broadly reported. The aim of this report is to review the pinworm infection in the scrotum on the basis of our case. METHODS AND RESULTS: Our patient is a young boy with persistent pain in the scrotums together with abdominal symptoms. He underwent several urgent operations. Pinworm was finally found in appendix vermiformis. We hypothesize that concurrent unresponsive orchido-epididymitis was caused by pinworm as well. Eradication happened finally with pyvrinembonate. CONCLUSION: Pinworm is a parasite that lives usually in the bowel. Many ectopic locations, like scrotum, are known. Orchido-epididymitis by pinworm has to be kept in mind when treating boys with persistent scrotal pain.

Using a safety net and following the safety instructions could prevent half the paediatric trampoline injuries.

INTRODUCTION: The number of recreational trampolines in Finnish households has increased. There also appears to be a drastic increase in trampoline-related injuries among paediatric patients. The aim of this study was to quantify and describe trampoline-related injuries in North Finnish paediatric patients. METHODS: A retrospective analysis of medical data was used in the study, covering children 16 years and younger treated for trampoline-related injuries at Oulu University Hospital over a five-month period of time from May 1 to September 30, 2005. Medical records were reviewed and additional details regarding the injuries were obtained by questionnaire. RESULTS: Altogether 76 patients were treated for trampoline-related injuries, which represented 13.4 % of all paediatric accidental trauma patients. In 57 accidents (86 %), there had been multiple jumpers on the trampoline. Twenty-five of the injuries (38 %) had occurred on the trampoline, in 25 cases (38 %) a child had fallen off, in 8 cases (12 %) there had been a collision with another jumper and the person had jumped onto a trampoline from a high platform in 5 incidents (8 %). Only 3 children (5 %) hurt themselves on the trampoline when jumping alone. Orthopaedic procedures requiring general anaesthesia were necessary in a total of 31 cases (41 %). CONCLUSIONS: The study shows that 50 % of traumas (falling off and collisions) could have been avoided by using a safety net and by jumping one at a time. The importance of following safety instructions and the need for a safety net should be emphasised to both the supervising adults and the children.

Treatment of pectus excavatum with bioabsorbable polylactide plates: Preliminary results.

BACKGROUND/PURPOSE: Pectus excavatum usually is corrected by thoracoplasty using metal plates. Recently bioabsorbabe polylactide plates have been developed. The aim of this study was to compare outcome after use of metal and bioasorbable plates in thoracoplasty performed for correction of pectus excavatum. METHODS: Eighty-three children (<16 years old) underwent thoracoplasty (Sulamaa's technique). In 75 patients, metallic plates, and in 8 patients, self-reinforced poly-L-lactide (SR-PLLA) plates, were used. Seven patients in the SR-PLLA group and 13 patients in the metal plate group were assessed 0.5 to 13 years postoperatively. RESULTS: The mean operating time was 121 minutes in the metal plate group, and 87 minutes in the SR-PLLA plate group. In the metal plate group, complications were pain caused by instability of the metal plates (n = 17), wound infection (n = 3), recurrence of deformity (n = 3), postoperative pain (n = 3), pneumothorax (n = 1), and nonspecific postoperative fever (n = 1). Thirteen patients underwent reoperation to refix the position of the metallic plates. In the SR-PLLA group, one case of pneumothorax occurred, and plate fragment palpability caused local pain in one patient. Cosmetic results and lung function values were similar. CONCLUSION: Our preliminary results show that bioabsorbable plates are a useful option in the treatment of pectus excavatum in children.

Use of self-reinforced polylactide osteosynthesis devices in craniofacial surgery: a long-term follow-up study.

Self-reinforced polylactic acid or polylactide (SR-PLA) is a biodegradable polymer, which is strong enough to fix weight-bearing cortical bone fractures and osteotomies. We report our experience and follow-up of the use of SR-PLA plates in 15 clinical cranioplasties. Two of the cases are described in greater detail. In one of them SR-PLA plates were used in addition to titanium plates, and in the other an SR-PLA plate fixed with mini-titanium screws was used as the only fixation material. In the other patients SR-PLA plates or wire were used in addition to titanium. So far no complications have been observed in these 15 patients. The only small superficial fistula was associated with a titanium plate and titanium screws. The longest follow-up has been over eight years. Recent results show metal-like deformation properties in addition to complete late resorption, making SR-PLA osteosynthesis devices promising for use in craniofacial surgery.

Developments in craniomaxillofacial surgery: use of self-reinforced bioabsorbable osteofixation devices.

Because of the problems associated with the conventional osteofixation devices used in craniomaxillofacial surgery, absorbable devices present an appealing alternative. Devices made of the polymers polylactide, polyglycolide, and their copolymers (PLGA and P[L/DL]LA) are currently the most commonly used. Ultrahigh-strength implants can be manufactured from these polymers with the self-reinforcing technique. Over the authors' almost two decades of study, both in experimental and clinical settings, self-reinforced devices have proved to be biocompatible, easy to handle, and mechanically strong, even for the fixation of femoral neck fractures. In craniomaxillofacial surgery, the authors have used self-reinforced devices for over 8 years without complications. Because of the more favored degradation characteristics, currently the copolymeric self-reinforced devices (P[L/DL]LA, Biosorb FX and PLGA, Biosorb PDX; Elite Performance Technologies, Solana Beach, Calif.) represent the advancing front in the application of absorbable devices in craniomaxillofacial surgery. The authors' share their experience and their studies of self-reinforced devices, which possess the highest strength and ductility of all bioabsorbable products.

A new technique for correction of trigonocephaly in an infant: application of an absorbable endocranial plate.

We report on a new method of cranial bone osteofixation using absorbable material, which is applied endocranially to avoid the application of a thick, cosmetically inferior system epicranially in the frontal area. This is especially important in the correction of deformity in trigonocephaly cases. A 9-month-old boy presented with a prominent trigonocephalic deformity. Cranioplasty was performed, in which a supraorbital bar (bandeau) was removed, reinforced with a self-reinforced polylactide (SR-PLA) plate and reshaped to correct the deformity. The plate was applied on the inner side of the bony bar, with its ends fixed epicranially to the temporal bones by means of SR-PLA miniscrews. 3-D CT scans and rapid prototypes were used to evaluate the results. Stable and secure fixation was obtained, and the cosmetic result appeared excellent. No complications occurred during the postoperative period of 1 year. Hence, stabilisation of cranial bone can be achieved endocranially using an absorbable plate and screws, with an encouraging cosmetic result. The method is thought to be reliable.

Frontal head posture in shunt-treated hydrocephalic patients.

OBJECTS: The aim of this study was to evaluate frontal head posture in shunt-treated hydrocephalic patients and its relation to the sidedness of the shunt device. METHODS: Natural head position and frontal cephalograms of 55 shunt-treated Finnish hydrocephalic patients and 33 healthy Finnish subjects were analysed using a computerised digitising program (X-METRIX). The following reference angles were used: ORB/HOR, indicating the head position related to the true horizontal; CER/VER, indicating the cervical position related to the true vertical; and CER/CR, indicating the craniocervical position. CONCLUSIONS: The results showed an increased skewness of the head in the shunt-treated subjects, which was not related to the shunt side.

Post-traumatic findings of the spine after earlier vertebral fracture in young patients: clinical and MRI study.

STUDY DESIGN: A study comparing magnetic resonance imaging findings of degenerative changes in intervertebral discs in young patients with previous wedge-shaped compression fracture and age-matched and sex-matched control subjects. OBJECTIVES: To find out the role of fractures in disc degeneration and to assess the clinical outcome of the patients. SUMMARY OF BACKGROUND DATA: Several experimental studies have postulated that trauma is one of the major reasons for disc degeneration. Wedge compression fractures in vertebrae of children have been considered insignificant, but this has not been verified in the literature. METHODS: Fourteen patients 8.8 to 20.8 years of age (mean, 15.5 years) with a history of wedge-shaped vertebral compression fracture at least 1 year previously (mean, 3.8 years) and asymptomatic healthy control subjects were studied by thoracolumbar spine magnetic resonance imaging. The patients also underwent a clinical examination. RESULTS: Eight (57%) of the 14 patients had disc degeneration, and seven of them had it at the trauma level. Of these 7 subjects, 6 also had endplate damage at this level. The association between endplate damage and adjacent intervertebral disc degeneration was significant (P < 0.01). Only 2 of the patients were symptomatic. In the control group, only 1 subject had disc degeneration with endplate changes and disc herniation. CONCLUSIONS: The patients had more disc degeneration than did those in the control group. Endplate injury was strongly associated with disc degeneration. No correlation between previous vertebral fracture and back pain was seen in this study.

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.

Comparison of self-reinforced poly-L-lactide and steel wire in fixation of sternotomy in rabbits.

BACKGROUND AND AIMS: To investigate the healing of sternotomies fixed with biodegradable self-reinforced poly-L-lactide (SR-PLLA) wire and comparing it with steel wire fixation. MATERIAL AND METHODS: Sixteen rabbits (15 Chinchilla and one New Zealand White rabbit) were operated on. Two parallel holes of 1.5 mm in diameter were drilled in the sternum at the level of the second and third rib and similar holes of 0.8 mm were drilled at the level of the third and fourth rib. A transverse sternotomy was created between both drill hole pairs. The sternotomy with larger drill holes was fixed with 1.1-mm thick SR-PLLA wire. The sternotomy between the smaller drill holes was fixed using 2.0 steel wire. The animals were sacrificed at 2, 7, 26 and 52 weeks postoperatively and specimens were taken, radiographed and studied by both light and scanning electron microscopy. RESULTS: One rabbit died at four months postoperatively as a result of gastrointestinal problems. No other complications were seen. The SR-PLLA wire was slowly degraded. There was no disturbance of bone healing. The implants were surrounded by a fibrous tissue capsule, which also contained chronic inflammatory cells. Both SR-PLLA and steel wires provided sufficient fixation security. No differences in the healing of the sternotomies were observed between SR-PLLA and steel wire fixation. CONCLUSIONS: SR-PLLA wires are biocompatible and useful for sternotomy fixation. They may be suitable for use in clinical applications.

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.