No long-term effects of ultrasound therapy on bioabsorbable screw-fixed lateral malleolar fracture.

BACKGROUND AND AIMS: The present study was initiated to evaluate the long-term effects of low-intensity ultrasound therapy on bioabsorbable screw-fixed lateral malleolar fractures, which has not been studied earlier. PATIENTS AND METHODS: The study design was prospective, randomized, double-blinded, and placebo-controlled. Sixteen dislocated lateral malleolar fractures were fixed with one bioabsorbable self-reinforced poly-L-lactide screw. The patients used an ultrasound device 20 minutes daily for six weeks without knowing it was active (eight patients) or inactive (eight patients). The follow-up time was 18 months. The radiological bone morphology was assessed by multidetector computed tomography (MDCT) scans, the bone mineral density by dual-energy X-ray absorptiometry scans, and the clinical outcome by Olerud-Molander scoring and clinical examination of the ankle. RESULTS: The MDCT scans revealed that all fractures were fully healed, and no differences were observed in radiological bone morphology at the fracture site. The bone mineral density of the fractured lateral malleolus tended to increase slightly during the 18-month follow-up, the increase being symmetrical in both groups. No differences were observed in the clinical outcome or Olerud-Molander scores. CONCLUSIONS: The six-week low-intensity ultrasound therapy had no effect on radiological bone morphology, bone mineral density or clinical outcome in bioabsorbable screw-fixed lateral malleolar fractures 18 months after the injury.

Coralline hydroxyapatite reinforced with polylactide fibres in lumbar interbody implantation.

Porous hydroxyapatite HA blocks reinforced with poly-l/dl-lactide fibres were used to maintain the lumbar disc space and to start to create intercorporeal fusion in 23 growing pigs. In four pigs two emptied non adjacent disc spaces were left open. After 3, 6, 12 and 16 weeks the implanted disc blocks were studied radiologically, histologically, histomorphometrically, microradiographically, and with oxytetracycline fluorescence. In plain films slight to moderate ossification of the implanted disc spaces was detected at 12 and 16 weeks. Resorption of the implants was seen radiologically from 3 weeks and fragmentation from 12 weeks onwards. In microradiographs disintegration of the coralline inner structure started at 3 weeks. Histologically, connective tissue ingrowth was seen inside the porous structure from three weeks onwards. Small amounts of new bone were visible and connective tissue inside the implant increased from a mean of 65.6% at 3 weeks to a mean of 79.4% at 16 weeks histomorphometrically. The bone ingrowth varied from 0.7 to 1.7%. A loss of height in the implanted disc spaces was seen (p < 0.05, linear regression analysis). In control pigs the emptied disc spaces lost their height similarly. The implants used were not strong enough to maintain the lumbar disc height.

Genoprevalence in human tissues of TT-virus genotype 6.

TT virus (TTV) is a newly discovered human virus of high genotypic diversity. TTV is widely distributed among humans, but the possible genotype-related differences in TTV biology are not well known. The prevalence and amount of TTV-DNA, especially of genotype 6, was determined by nested-PCR in various human tissues, and human parvovirus B19, another ssDNA virus, was used as a reference. TTV DNA was detected simultaneously in bile, peripheral blood mononuclear cells (PBMC) and plasma of 77% subjects, in 38% skin samples, in 38% synovial samples and in all (100%) adenoids, tonsils and liver samples. The relative concentrations of TTV-DNA did not vary significantly among the different samples. Genotype 6 TTV-DNA was detected in bile and plasma of one subject (3%), in skin and serum of one subject (8%) and in one liver (5%). The overall prevalence of TTV genotype 6 was 4% in subjects and 4% in sera. TTV genotype 6 was shown to occur in human tissues with no obvious tissue-type or symptom specificity. Parvovirus B19 DNA was detected overall in 38% subjects, and bile was the only sample type tested that did not persistently harbour B19 DNA.

Complications in the first 1,043 operations where self-reinforced poly-L-lactide implants were used solely for tissue fixation in orthopaedics and traumatology.

This is an analysis from one hospital of the first 1043 operations where pure self-reinforced poly-L-lactide (SR-PLLA) implants have been used alone. The operations were performed between 1988 and 1999 and included 407 orthopaedic patients and 636 trauma patients. There was a total of 107 complications. There were 21 infections but no sinus formation. Failure of fixation was seen in 46 patients. In 936 operations the healing was uneventful.

Biodegradation and strength retention of poly-L-lactide screws in vivo. An experimental long-term study in sheep.

BACKGROUND AND AIMS: Poly-L-lactide implants have gained popularity in the fixation of fractures and osteotomies in the past decade. The aim of the present experimental long-term study was to examine the degradation and strength retention of self-reinforced poly-L-lactide (SR-PLLA) lag-screws and the bone tissue response. MATERIAL AND METHODS: A total of 27 young adult sheep were used. Self-reinforced poly-L-lactide (SR-PLLA) lag-screws of 6.3 mm were implanted in the left proximal femur of nine sheep. At two, three and five years three of the sheep were sacrificed and the degradation was studied radiologically, microradiographically and histologically. For the strength retention measurements five SR-PLLA lag-screws of 6.3 mm and five lag-screws of 4.5 mm were implanted in the subcutaneous tissue of the five sheep and lag-screws of 6.3 mm for the pull-out test in the left proximal femur of 20 sheep. At 0, 12, 18, 24, 32, and 36 weeks bending and shear strength, molecular weight and pull-out measurements were performed. RESULTS: At five years no SR-PLLA material could be seen. The implant area was surrounded by high density bone with bone ingrowth in the screw area. At 36 weeks the bending strength of the 6.3 mm screws had decreased from 257.9 MPa to 36.4 MPa and the shear strength from 131.8 MPa to 19.8 MPa. The pull-out strength of the lag-screws of 6.3 mm in diameter decreased from 1507 N to 331 N in 24 weeks. CONCLUSIONS: SR-PLLA lag-screws showed high initial values, a controlled strength retention and gradual degradation process making the use of them safe also in demanding fixations.

Long-term results of ankle and triple arthrodeses fixed with self-reinforced polylevolactic acid implants in patients with rheumatoid arthritis.

Self-reinforcing polylevolactic acid (SR-PLLA) implants have been used in arthrodeses of patients with rheumatoid arthritis. No long-term evaluation has been published so far. Two patients (three ankles) with destruction of the ankle joint and seven with destruction of the subtalar joint received ten arthrodeses. One out of three ankle arthrodeses healed and nonunion developed in two. Five out of seven triple arthrodeses attained bony union. Two patients with malunion of the subtalar and talonavicular joints are free of symptoms and need no reoperation. One superficial wound infection healed by oral antibiotics. In one patient, an ankle arthrodesis was performed 6 years after the triple arthrodesis of the left foot. SR-PLLA implants can be used in triple arthrodesis in rheumatoid arthritic patients with good results comparable to those of other studies. The problems with nonunion of ankle arthrodeses noticed in former studies are also attributable to this fixation method.

Bioabsorbable fixation in orthopaedic surgery and traumatology.

Bioabsorbable internal fixation devices were introduced clinically in the treatment of fractures and osteotomies of the extremities at the Department of Orthopaedics and Traumatology, Helsinki University, in 1984. Since November 5, 1984, a total of 3200 patients were managed using bone or ligament fixation devices made of self-reinforced (matrix and fibres of the same polymer) bioabsorbable alpha-hydroxy polyesters. The devices used included cylindrical rods, screws, tacks, plugs, arrows, and wires. The most common indication for the use of bioabsorbable implants was the displaced malleolar fracture of the ankle. Transphyseal fixation with small-diameter, mainly polyglycolide pins was used in children. The postoperative clinical course was uneventful in more than 90% of the patients. The complications included bacterial wound infection in 4% and failure of fixation in 4%. In one-fifth of the latter cases, however, re-operation was not necessary. The occurrence of non-infectious foreign-body reactions two to three months postoperatively has been observed in 2% of the patients operated in the last few years with polyglycolide implants but none of the patients managed with polylactide implants. This inflammatory tissue response often required aspiration with a needle but did not influence the functional or radiologic result of the treatment. Owing to the biodegradability of these internal fixation devices, implant removal procedures were avoided. This results in financial benefits and psychological advantages. Bioabsorbable implants can also be used in open fractures and infection operations.

Treatment of subcapital femoral neck fractures with bioabsorbable or metallic screw fixation. A preliminary report.

BACKGROUND AND AIMS: Cancellous bone fractures and arthrodeses have been treated successfully with bioabsorbable polyglycolide and poly-L-lactide implants. In this study bioabsorbable poly-L-lactide lag screws and metallic screws were compared in the fixation of subcapital femoral neck fractures. PATIENTS AND METHODS: Forty patients with femoral neck fractures were treated by internal fixation using three bioabsorbable self-reinforced poly-L-lactide (SR-PLLA) lag screws of 6.3 mm in diameter and 38 patients using three metallic screws of 7 mm in diameter. In addition, one patient was operated on using two and one using four metallic screws. The patients did not differ in age, body weight or primary dislocation of the fracture. There were six males in the lactide group versus 14 in the metallic fixation group. There were two Garden Stage I, 27 Garden Stage II, nine Garden Stage III, and two Garden Stage IV fractures in both groups. RESULTS: In the Garden I and II fractures there were 5/29 redislocations after SR-PLLA fixation and 8/29 after metallic fixation. In the Garden III fractures there were 4/9 and in the Garden IV fractures 2/2 redislocations in both groups. The ability to walk and the range of movement were better after bioabsorbable fixation. CONCLUSION: Self-reinforced poly-L-lactide lag screws can be used safely to fix subcapital femoral neck fractures in Garden Stage I and II fractures and in younger patients in Garden III fractures.

Integrity and full coding sequence of B19 virus DNA persisting in human synovial tissue.

Primary infection by human parvovirus B19 is often accompanied by arthropathy of varying duration, of which the most severe cases can be indistinguishable from rheumatoid arthritis (RA). While this might seem to imply a role in RA pathogenesis, recent studies have verified long-term persistence of B19 DNA in synovial tissue not only in patients with rheumatoid or juvenile arthritis, but also in immunocompetent, non-arthritic individuals with a history of prior B19 infection. However, the latter data are based on PCR amplification of short segments of DNA, with little sequence information. We determined the nucleotide sequence and examined the integrity of the protein-coding regions of B19 genomes persisting in synovial tissue and compared the results with data from synovial tissues of recently infected patients. In synovium of both previously and recently infected subjects, the viral coding regions were found to be present in an apparently continuous, intact DNA molecule. Comparison with sequences reported from blood or bone marrow showed that the synoviotropism or persistence of the B19 virus DNA was not due to exceptional mutations or particular genotype variants. The synovial retention of full-length viral genomes may represent a physiological process functioning in long-term storage of foreign macromolecules in this tissue.

Comparison of polylactide screw and expansion bolt in bioabsorbable fixation with patellar tendon bone graft for anterior cruciate ligament rupture of the knee. A preliminary study.

In a preliminary study, 24 patients with rupture of the anterior cruciate ligament (ACL) were operated on using implants made of self-reinforced poly-l-lactide (SR-PLLA). The operation method was outside-in bone-tendon-bone reconstruction. In 10 patients the fixation was made with an SR-PLLA screw with a diameter of 6.3 mm, in 12 with an SR-PLLA expansion plug with a diameter of 6.0 mm, and in two cases both implants were used, but these cases were excluded from comparison. The purpose of the study was to evaluate and compare the use and fixation results of these two implants. The follow-up time averaged 3.2 years. Twenty patients attended follow-up. On subjective evaluations, seven of the eight patients following SR-PLLA screw fixation and six of the ten after expansion plug fixation regarded their knee as normal or nearly normal. Arthrometric testing showed the side-to-side difference to average 2. 9 mm following SR-PLLA screw fixation and 2.6 mm after expansion plug fixation (NS). Six of the patients had giving-way symptoms (two after screw fixation and four after plug fixation). The pivot shift test was slightly positive in two patients and positive in one patient after SR-PLLA screw fixation, and in three knees slightly positive and in another three knees positive following expansion plug fixation. Radiography showed variation in the location and orientation of the bone channels. Magnetic resonance imaging was performed in seven cases, and in two cases an edema was found in the tendon of the anterior cruciate ligament graft and in six cases the implants were visible. No statistical difference in results between the SR-PLLA screw and SR-PLLA expansion bolt was noted. Fixation with expansion plug seems technically more challenging, with a tendency to inferior results compared to screw fixation. In the absorbable fixation of a bone-tendon-bone graft there are no metallic artifacts on magnetic resonance imaging and no need to remove the fixation material regarding the revision surgery.

MR imaging in biofix-osteosynthesis.

PURPOSE: Osteosynthesis by means of bioresorbable implants, mostly of self-reinforced poly-L-lactide (SR-PLLA), has been used in humans for about 10 years. The aim of this study was to examine the controversy between histological studies confirming fragmentation of the biomaterial and radiological studies showing no breaking of the material. MATERIAL AND METHODS: Six patients with displaced malleolar fractures operatively treated with biodegradable SR-PLLA screws underwent MR examinations at 1.5 T, immediately postoperatively and after one to two years. RESULTS: The biodegradable osteosynthetic screws were clearly seen on all MR images. Of 12 screws, 6 were broken at the final examination (5 syndesmotic transfixation screws and 1 screw through the growth cartilage). CONCLUSION: The breaking of a biodegradable osteosynthesis is possible to document on MR images.

Treatment of periprosthetic fractures in association with total hip arthroplasty--a retrospective comparison between revision stem and plate fixation.

BACKGROUND AND AIMS: In periprosthetic fracture associated with hip arthroplasty, no consensus exists about the use of plate fixation or revision stem except for cases where the stem is loose in a young patient and a revision is made. The aim of the present retrospective study was to compare two commonly used alternatives for treatment of the fracture--revision arthroplasty and plate fixation. MATERIAL AND METHODS: Seventy-five fractures associated with total hip arthroplasty were treated with revision arthroplasty (N = 40) or compression plate fixation (N = 35). Twenty-one fractures were intraoperative and 54 were postoperative. In revision arthroplasty, cemented (N = 11) and porous-coated (N = 29) stems were sued. Autologous bone grafts were used in 15 revision arthroplasties and 20 plate fixations. The follow-up time was median 20 months (range 12-96 months). RESULTS: Bone grafting at the time of fracture treatment had no significant effect on fracture healing in the present setting. One patient in both groups was operated secondarily because of fracture instability. Five nonunions in the former and 9 nonunions in the latter group were treated by repeated revision and bone graft. In two revision arthroplasties and nine cases with plate fixation, a secondary bone grafting operation was performed for delayed union. In all, 20 secondary operations were needed after prosthesis stem revision and 27 secondary operations after plate fixation (p = 0.014). The need for reoperations was similar in fractures at different levels of the femur. Fracture healing was finally obtained in 39 revision arthroplasties and 34 cases with plate fixation during the follow-up period. CONCLUSIONS: Cases where the prosthesis stem is stable, where its removal would include great risks and, where the biomechanical conditions are optimal, are best treated with plate fixation. In cases where the stem is loose and where a choice is possible, stem revision is preferable to plate fixation.

Absorbable fixation of femoral head fractures. A prospective study of six cases.

BACKGROUND AND AIMS: Fracture of the femoral head associated with a traumatic dislocation of the hip is a rare but severe injury. The methods of the recommended treatment have varied from primary closed or open reduction without fixation to excision of fragments or internal fixation. In our department we have treated other kinds of intra-articular fractures successfully with totally absorbable polyglycolide and poly-L-lactide implants. The aim of this study was to investigate the value of totally absorbable rods and screws in the fixation of the femoral head fractures. MATERIAL AND METHODS: Six femoral head fractures associated with a posterior traumatic dislocation of the hip were treated by open reduction and internal fixation using self-reinforced absorbable polyglycolide (SR-PGA) or poly-L-lactide (SR-PLLA) rods and screws. The follow-up time was 38 months in average (range 6 weeks to 77 months). RESULTS: In three patients the end results were excellent and in one fair. One patient died six weeks after the accident from the consequences of the cerebral injury. In one 61-year-old patient an arthroplasty was performed one year after the primary osteosynthesis, because of avascular necrosis of the femoral head. CONCLUSIONS: Self-reinforced polyglycolide and polylactide implants can be used safely to fix femoral head fractures without the need of implant removal.

Redisplacement after ankle osteosynthesis with absorbable implants.

A total of 1202 fractures of the ankle were treated with absorbable implants made of polyglycolide/polylactide copolymer or self-reinforced polyglycolide and/or self-reinforced polylactide between November 5, 1984, and January 12, 1994. A redisplacement after fixation was diagnosed in 30 patients (2.5%). The redisplacement occurred in 8 of 934 (0.9%) simple ankle fractures and in 22 of 268 (8.2%) severer ankle fractures. A breakage or loosening of the absorbable implant was verified at reoperation in 8 cases and was suspected in another 9. A technical failure was the main reason in 13 cases. A reoperation was performed for 25 patients. The absorbable implants seem to provide a secure fixation in the majority of ankle fractures, but the use of these implants showed unsatisfactory results in unstable and comminuted fractures.

Bone mineral density in fractures treated with absorbable or metallic implants.

Absorbable fixation devices have been clinically used in the fracture treatment for over ten years. No studies have been published where bone mineral density has been measured after bone consolidation comparing absorbable and metallic fixation. In this study the bone mineral density was measured after operative ankle fracture treatment with absorbable self-reinforced polyglycolic acid (SR-PGA) screws (14 patients) or with absorbable self-reinforced polylactic acid (SR-PLLA) screws (eight patients) compared with metallic fixation (17 patients). The overall results were radiologically good in every group. A statistically significant difference in the bone mineral density (BMD) was found only in the distal tibial metaphysis between SR-PGA screw and metallic fixation. The BMD increased in the distal tibia after SR-PGA screw fixation by an average 18.3%. The average change of BMD in the distal tibia after SR-PLLA screw fixation decreased by 6.4% while after metallic fixation the average change of MBD decreased by 18.6%. Bone mineral density measurements in the present study may indicate osteogenetic capacity of polyglycolide implants in the bone after fracture or osteotomy fixation. On the other hand, metallic implants showed negative effects to the bone.

Comparison of the fixation of subcapital femoral neck osteotomies with absorbable self-reinforced poly-L-lactide lag-screws or metallic screws in sheep.

Seven subcapital femoral osteotomies of adult sheep were each fixed with two absorbable self-reinforced poly-L-lactide lag-screws, and seven other osteotomies were each fixed with two metallic cancellous bone screws. At 3 and 12 weeks, radiographs were taken and callus formation, displacement, and union were evaluated. At 12 weeks, the animals were killed and strength measurements were carried out. According to the radiographs, union was achieved in six of seven osteotomies in both groups, while after 3 weeks one fixation in both the group treated with absorbable screws and the group treated with metallic screws had failed. There were no statistical differences between the groups with respect to callus formation or displacement. Regarding the strength of the osteotomized bones, at 12 weeks there were no statistically significant differences in the load-carrying capacity between the bones fixed with self-reinforced poly-L-lactide screws and those fixed with metallic screws. These results showed that self-reinforced poly-L-lactide screws, which have been used successfully in fractures and osteotomies in cancellous bone, are strong enough to support this more demanding fixation of weight-bearing bones.

Osteochondritis dissecans of the knee fixed with biodegradable self-reinforced polyglycolide and polylactide rods in 24 patients.

Over a period of 7 years (1987-1994), 24 cases of osteochondritis dissecans of the knee were treated with self-reinforced polyglycolic acid (SR-PGA) and polylactic acid (SR-PLLA) rods. Rods measuring 1.1 mm, 1.5 mm and 2 mm in diameter, and 20-40 mm in length were used in the fixation of the fragment depending on the size of the lesions. There were 23 patients with osteochondritis dessicans in the medial and 1 in the lateral femoral condyle. The average age of the patients was 25 years (range: 16-48). Follow-up was for 3.3 years (range: 1-7.6). There were 6 lesions in situ, 3 early separations, 11 were partially detached, and there were 4 loose bodies. SR-PGA rods were used in 12 patients, SR-PLLA rods in 11 patients, and both SR-PGA and SR-PLLA rods in 1 patient. The rod in each case was inserted subchondrally and in 9 cases arthroscopically, using a special instrument. In our study, the clinical result was excellent in 13 patients, good in 6, fair in 1 and poor in 4. On radiological assessment the fragment had healed in 19 cases. Synovitis occurred in 1 patient in the SR-PGA group (1/13): the effusion continued for 6 months postoperatively but, after treatment by needle aspiration, there were no symptoms at follow-up 4.2 years later. We conclude that SR-PGA and SR-PLLA rods can be used intra-articularly for the adequate fixation of osteochondritis dissecans.

Totally absorbable fixation in the treatment of fractures of the distal femoral epiphyses. A prospective clinical study.

Nine adolescent patients with a femoral fracture involving the physeal plate were treated by using self-reinforced absorbable polyglycolide (SR-PGA) and poly-L-lactide (SR-PLLA) screws with a follow-up for an average of 2 years and 2 months. During the follow-up all but one of the femurs became skeletally mature. In two of nine patients a clinically significant growth disturbance occurred. The average length difference of the femurs was -5 mm (ranging from +8 mm(-)-41 mm). One valgus deformity was noted. In four patients a lengthening and in four patients a shortening of the operated femur were registered at the end of follow-up. Open reduction and fixation with absorbable screws seem to be suitable for the fixation of distal femoral fractures in adolescents.

Strength of the fixation of patellar tendon bone grafts using a totally absorbable self-reinforced poly-L-lactide expansion plug and screw. An experimental study in a bovine cadaver.

In a bovine cadaver study, bone-tendon-bone graft fixation strength with different graft geometry and fixation devices was measured to evaluate the fixation strength of totally absorbable implants: a 6.0-mm expansion plug and 6.3-mm screw both made of self-reinforced polylactide (SR-PLLA). Comparison was made with 6.5-mm AO cancellous screw. Maximum tensile force to dislodge the bone plug from the bone tunnel was recorded. First, two preliminary tests were performed. In the first test, triangular bone plugs were used (9-mm diameter). The direction of the pull force was parallel to the bone tunnel. The maximum tensile forces were 786 N in femoral insertions and 625 N in tibial insertions, mean. After this, we evaluated the influence of change in the pullout direction. In the second test, a circular bone plug was used with no fixation but the direction of the pull force was parallel to the tibial or femoral axis and the bone plug (10-mm diameter) was in a 30 degrees to 40 degrees angle to the direction of the pull force and it was compressed to the tunnel (9-mm diameter). The maximum tensile forces were 783 N in femoral insertions and 695 N in tibial insertions, mean. In the final third test, we used a curved saw in harvesting the graft. This made a half-circular bone block with a diameter of 12 mm. The maximum tensile force to dislodge the bone plug from the bone tunnel was recorded and the pull force was in a 30 degrees to 40 degrees angle to the tunnel. The results were evaluated with Student's t-test and Mann-Whitney U-test. With the AO screw, the maximum tensile force to dislodge the bone plug from the bone tunnel was 2,113 +/- 407 N (mean +/- standard deviation) and it was better than the fixation strength of the SR-PLLA expansion plug, 1,379 +/- 328 N (P = .009, t-test) and better than the fixation strength of SR-PLLA screw, 1,454 +/- 230 N (P = .007, t-test). However, the maximum tensile force of both SR-PLLA implants in all measurements in the third test were above 1,100 N and it seems that the initial strength of totally absorbable implants is enough for the clinical use.

Absorbable devices in the fixation of fractures.

Totally absorbable internal fracture fixation devices were introduced clinically in the treatment of fractures and osteotomies of the extremities at our department in 1984. A total of 2,500 patients were managed using bone or ligament fixation devices made of self-reinforced (matrix and fibers of same polymer) absorbable alpha-hydroxy polyesters between November 5, 1984, and January 12, 1994. The devices used included cylindrical rods or pins, screws, tacks, plugs, and wires. The most common indication for the use of absorbable implants was displaced malleolar fracture of the ankle. Transphyseal fixation with small-diameter polyglycolide pins was used in children. The postoperative clinical course was uneventful in over 90% of the patients. The complications included bacterial wound infection in 3.6% and failure of fixation in 3.7%. In one-fifth of these cases, however, reoperation was not necessary. The occurrence of noninfectious foreign-body reactions 2 to 3 months postoperatively has been observed in 2.3% of the patients operated in the last years with polyglcolide implants but in none of the patients with polylactide implants. This inflammatory tissue response often required aspiration with a needle or small incision but did not influence the ultimate functional or radiologic result of treatment. Owing to the biodegradability of these internal fixation devices, over 1,000 implant removal procedures were avoided during the 9-year period under review, allowing medical personnel at these facilities to focus on other procedures. Avoidance of removal procedures results in financial benefits and psychological advantages. The benefits of absorbable implants for war surgery are the same as for civilian life. Absorbable implants can also be used in open fractures and infection operations.