Fixation of horizontal maxillary osteotomies with biodegradable self-reinforced absorbable polylactide plates: preliminary results

Totally biodegradable, self-reinforced polylactide plates and titanium miniscrews were used for the fixation of horizontal maxillary osteotomies in 32 patients. In two cases the fixation was unstable because of technical problems. In the others the analysis of cephalometric radiographs between immediate and late postoperative showed very similar figures, indicating postoperative stability. There were no complications in the healing due to this biodegradable osteofixation in these patients.     

Fixation of experimental osteotomies of the distal femur in rabbits with bone cement and cyanoacrylate

Summary A distal femoral osteotomy was fixed with liquid cyanoacrylate and bone cement in 25 rabbits. Follow-up was done at 1, 3, 6, 12, and 24 weeks. The distal portion of each femur was removed, fixed in alcohol, embedded in methylmethacrylate, sawed to 80 m thickness for OTC-fluorescence study and microradiography, and cut to 5-m sections for histological analysis. Radiological and careful microscopic (OTC labeling, microradiographic, and histological) studies showed healing of the osteotomies during the first 6 weeks after operation. However, at 12 and 24 weeks' follow-up only four of ten osteotomies had healed. According to these observations it is obvious that fixation of an osteotomy of the cancellous bone with bone cement and cyanoacrylate does not provide sufficient stability for successful healing.

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Zusammenfassung Die distalen Femurosteotomien von 25 Kaninchen wurden mit Zyanoakrylat und Knochenzement fixiert. Die Nachuntersuchungen fanden nach 1, 3, 6, 12 and 24 Wochen statt. Der distale Teil von jedem Oberschenkelknochen wurde entnommen, in Alkohol fixiert, in Methylmethacrylat gegossen und für die histologischen Studien auf 5 m Dicke geschnitten und für die OTC-Studien und Microradiographie auf 80 m gesägt. Die radiologischen und genauen mikroskopischen (OTC, Mikroradiographie, Histologic) Untersuchungen zeigten, daß die Osteotomien während den ersten sechs Wochen heilten. Später dagegen waren die Resultate ungenügend, denn nur 4 von 10 Osteotomien waren nach 12 and 24 Wochen geheilt. Auf Grund dieser Resultate ist zu schlieBen, daB eine genügend stabile Osteotomie des spongiösen Knochens durch Fixation mit Knochenzement and Zyanoakrylat nicht erreicht und somit die Heilung gestört wurde.

     

Fixation of experimental osteotomies with absorbable polylactic acid screws.

Absorbable screws made of self-reinforced poly-L-lactic acid (SR-PLLA) and poly-DL/L-lactic acid (SR-PDLLA/PLLA) were used for fixation of cancellous bone osteotomies of the distal femur in rabbits. The initial molecular weight of PLLA was 260.000 and that of PDLLA 100.000. The follow-up times were from one week to 96 weeks. Seventy-two rabbits were operated on, 36 in the PLLA group and 36 in the PDLLA/PLLA group. After sacrifice, radiographic, micro-radiographic, histologic, histo-morphometric, and oxytetracycline-labelling studies were performed. In the PLLA group 34/36 (94%) osteotomies and in the PDLLA/PLLA group 31/36 (86%) osteotomies healed without delay or angular deformity. The present investigation shows that absorbable SR-polylactic acid screws are suitable for fixation of weight loading cancellous bone osteotomies in rabbits. Based on these promising results, a clinical study where cancellous bone fractures are fixed with SR-PLLA screws has been started.     

Comparison of the tissue response to absorbable self-reinforced polylactide screws and metallic screws in the fixation of cancellous bone osteotomies: An experimental study on the rabbit distal femur

The availability of absorbable fracture-fixation devices for clinical use calls for better knowledge of the reaction of bone tissue to absorbable polyester implants as compared with similar metallic devices. To examine and compare the tissue response to biodegradable and metallic screws within cancellous bone, a transverse transcondylar osteotomy of the distal femur was fixed with absorbable self-reinforced polylevolactide screws in 35 rabbits and with stainless-steel screws in 35 rabbits. New bone formation and consolidation of the osteotomy were examined histologically, histomorphometrically, and microradiographically within standardized sample fields 1,3,6,12,24,36, and 48 weeks postoperatively. The intact contralateral femur served as the control. A vigorous osteoconductive response to the polylevolactide screws was observed at 3 weeks postoperatively, and the osteoid surface fraction was significantly higher in all follow-ups than in the contralateral femora. In the femora with metallic screws, new bone formation was seen 3,6, and 12 weeks postoperatively, but at 24,36, and 48 weeks the osteoid surface fraction did not differ significantly from that of the intact control femora. The total bone area was significantly larger in the femora with self-reinforced polylevolactide screws than in the control bone 6-48 weeks postoperatively; in the femora with metallic screws, this was found only at 6 and 12 weeks. After 48 weeks, the femora fixed with metallic screws had statistically smaller total bone area than the intact control femora. Solid bone union was seen in 84% of the osteotomies in the self-reinforced polylevolactide group and in 76% of those in the metallic group after 3 weeks or more. No signs, of degradation of the self-reinforced polylevolactide implant and only a mild foreign-body reaction with no accumulations of inflammatory cells to either self-reinforced polylevolactide or metallic screws were observed during the follow-up period. Both types of screws seemed to induce an osteostimulatory response around their threads. This phenomenon was transient for metallic screws but lasted for at least 48 weeks for self-reinforced polylevolactide screws. The polylevolactide screw does not seem to cause osteopenia at the implantation site. The fixation properties of both self-reinforced polylevolactide screws and metallic screws appear to be sufficient for the fixation of small fragments of cancellous bone.     

Healing of subcapital femoral osteotomies fixed with self-reinforced poly-L-lactide screws: an experimental long-term study in sheep

Subcapital femoral osteotomies of ten young adult sheep were fixed with two bioabsorbable, self-reinforced, poly- L-lactide (SR-PLLA) lag screws of 4.5 mm in diameter. At 3 weeks radiographs were taken to check the reduction and fixation achieved. After follow-up periods of 12 weeks, 1 year and 3 years with three sheep in each group, and of 7 years and 4 months with one sheep, the sheep were killed, and the healing of the osteotomies, degradation and tissue response of the implants were examined radiographically, histologically and microradiographically. All osteotomies healed with a firm bony union. There was no dislocation or wound infection. Histologically, there was no marked tissue response in the bone tissue. At 12 weeks the implants were grossly intact, at 1 year granulation tissue and new bone formation had started to penetrate into the implant, and at 3 years the implant area was mostly replaced by connective tissue and new bone, but implant material was still seen as little islands surrounded by some lymphocytes. At 7 years and 4 months, the implant material had been degraded and replaced by tight bone. Self-reinforced poly- L-lactide lag screws seem to possess adequate mechanical properties and good biocompatibility for this demanding fixation.     

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

Seven subcapital femoral osteotomies of adult sheep were each fixed with two absorbable selfreinforced 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 ostecotomized bones, at 12 weeks there were no statistically significant differences in the load-carrying capacity between the bones fixed with self-reinforecd 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.     

Pullout strengths of self-reinforced poly-L-lactide (SR-PLLA) rods versus Kirschner wires in bovine femur

OBJECTIVE: To determine the relative amount of fixation of self-reinforced poly-L-lactide (SR-PLLA) rods and Kirschner wires in bovine cancellous bone by comparing their pullout strength DESIGN: An in vitro laboratory study was performed using bovine femurs. Ten two-millimeter-diameter pins of each type were inserted into cancellous bone and then pulled out, using a material testing machine. The maximum force (pullout strength) was selected over other measurements to compare the amount of fixation of the two types of pins. All of the pins were retrieved for microscopic analysis. A paired t test was performed to analyze the differences between the pullout strength of the two types of pins. SETTING: Orthopaedic Bioengineering Laboratory, University of Louisville School of Medicine, Louisville, Kentucky, U.S.A. SPECIMENS: Two young fresh bovine distal femurs, ten two-millimeter-diameter Kirschner wires, ten two-millimeter-diameter bioabsorbable SR-PLLA rods MAIN OUTCOME MEASUREMENTS: Pullout strength in Newtons, and microscopic pin surface aspect after insertion. RESULTS: Significant differences were noted between the maximum force required to remove the two types of pins (p < 0.01) The K-wire mean pullout force was 37.7 N (SD 13.6), and the SR-PLLA rod mean pullout force was 53.6 N (SD 19.3). Microscopic analysis indicated surface modification only on the SR PLLA rods. DISCUSSION: SR-PLLA composites have shown comparable clinical results to their metallic counterparts. In this study, the pullout strength of SR-PLLA rods was compared with that of conventional K-wires. A significant difference (p < 0.01) favoring bioabsorbable pullout strength was noted. The bioabsorbable pin surface modification during insertion is an interesting finding that warrants further investigation as a potential source of improved fixation. CONCLUSION: SR-PLLA rods retain their hold in bovine cancellous bone better than K-wires. This finding offers to the orthopaedic surgeon more information about new pin fixation methods.     

Single absorbable polydioxanone pin fixation for distal chevron bunion osteotomies

The distal chevron osteotomy is a well-established technique for correction of symptomatic mild to moderate metatarsus primus varus with hallux valgus deformity. Fixation of the osteotomy ranges from none to bone pegs, Kirschner wires, screws, or absorbable pins. We evaluated one surgeon's (J.K.D.) results of distal chevron osteotomy fixation with a single, nonpredrilled, 1.3-mm poly-p-dioxanone pin and analyzed any differences in patients with unilateral or bilateral symptomatic metatarsus primus varus with hallux valgus deformities. All osteotomies healed without evidence of infection, osteolysis, nonunion, or necrosis. Equal correction was achieved in unilateral and bilateral procedures. The technique is quick and easy, and adequate fixation is achieved.     

Fixation of distal femoral osteotomies with self-reinforced poly(desamino tyrosyl–tyrosine ethyl ester carbonate) rods: an experimental study on rats

 Self-reinforced poly(desamino tyrosyl–tyrosine ethyl ester carbonate) poly(DTE carbonate) rods (diameter, 2 mm; length, 26 mm) were implanted into the dorsal subcutaneous tissue of 16 rats. Osteotomies of the distal femur were fixed with these rods (2 mm by 15 mm) in 64 other rats. The follow-up times varied from 1 week to 1 year. After sacrifice, three-point bending and shear tests and molecular weight measurements were performed for subcutaneously placed rods. Radiological, histological, histomorphometrical, microradiographic, and oxytetracycline-fluorescence studies of the osteotomized and intact control femurs were performed. At 36 weeks, the bending strength of the rods was nearly at the same level as the initial value, and the shear strength was decreased to about one quarter of the initial value. One of the 64 evaluated osteotomies showed signs of infection at 24 weeks, and there were five failures of fixation. Fifty-eight osteotomies healed uneventfully. No gross signs of inflammatory or foreign-body reactions were observed. The present investigation showed that the mechanical strength and fixation properties of SR-poly(DTE carbonate) rods are suitable for fixation of cancellous bone osteotomies in rats. The present article is the first report on successful application of SR-poly(DTE carbonate) rods for fixation of cancellous bone osteotomies. Received: September 25, 2001 / Accepted: May 7, 2002     

Tibial condylar fractures fixed with totally absorbable, self-reinforced polyglycolide screws

Six patients with displaced split-depression-type tibial condylar fractures were treated with absorbable, self-reinforced polyglycolide screws. One patient underwent reoperation because of an unacceptable primary fracture reduction unrelated to the implant material. The others healed well, with good functional and anatomical results despite one slight redisplacement in a medial condylar fracture treated without plaster cast immobilisation. Absorbable polyglycolide screws seem to be suitable for the fixation of selected tibial condylar fractures. The implant removal operation is thus avoided.     

聚乙烯、钛合金板固定治疗股骨远段粉碎性骨折

目的探讨治疗股骨远段(包括股骨髁间、髁上)粉碎性骨折难题的新方法.方法手术治疗,骨折复位后用钛合金钢板、聚乙烯板组合固定.有骨缺损者加植骨,3～5周后开始膝关节功能锻炼.结果骨折均获愈合,平均愈合时间为7个月.1例开放骨折感染后治愈.末发生膝内、外翻等其他并发症,功能满意.结论两块板组合固定骨折呈中心型固定模式,较符合股骨负重的生物力学原理.双板固定后,可将碎骨块或植入的骨块呈挡板样保护作用,防止移位、离散.增加了内固定强度,抗弯屈、抗扭转应力较单侧钢板好.可以早期锻炼,促进骨折愈合和功能恢复.操作方便,减少了双钢板应力遮挡的副作用.     

Fixation of experimental osteotomy of the distal femur with biodegradable thread in rabbits

A distal femoral osteotomy on 24 rabbits was fixed with biodegradable polyglycolic acid (PGA) thread pulled through drill holes made on both sides of the osteotomy. Follow-up times were one, three, six, 12 and 24 weeks. The distal part of each femur was removed, fixed in alcohol, embedded in methylmethacrylate, sawed to 80 microns thick for oxytetracycline (OTC)-labeling studies and microradiography, and sectioned at 5 microns for histologic studies. As judged by histologic microradiographic, and OTC-labeling studies, 19 of 24 osteotomies were healing normally; after six weeks of follow-up examination, union of 11 of 14 osteotomies was observed on radiographs. On the basis of the present study, PGA threads may be promising for the fixation of osteotomies of the metaphyseal cancellous bone in rabbits.     

Pitfalls in the application of distal femur plates for fractures

Despite design features intended to aid the surgeon in restoring proper alignment, malunion and implant-related problems are relatively common after a distal femur fracture treated with plate fixation. This article presents case examples of these problems followed by a discussion of the relevant distal femoral anatomy, design features of modern locked distal femur plating systems, and technical points necessary to avoid malunion and implant-related problems when using these devices.     

Closed intramedullary osteotomies of the femur

Closed intramedullary osteotomies offer a safe way to correct many femoral deformities. It is the safest method for correcting leg length inequality in adults, having a low infection rate and low complication rate. Unfortunately, the procedure, is technically demanding, requiring great attention by two surgeons. The derotational osteotomy is not nearly as complex; it is a relatively simple procedure for a surgeon experienced in closed intramedullary nailing. Correction is adequate with goniometer measurement, but an interlocking nail is necessary to maintain position. Correction of angulatory deformities is more difficult and requires careful study of anteroposterior, lateral, and oblique radiographs to be certain that the procedure is technically possible. Intramedullary bone grafting is frequently necessary for an open wedge. Distal osteotomies are encumbered by nonunion problems.     

Supracondylar femur osteotomies around the knee

Background

Similar to the re-appreciation of high tibial osteotomy (HTO), supracondylar distal femur varus osteotomy (SCO) for lateral compartment osteoarthritis (OA) of the knee has gained renewed interest as new knowledge has become available on the influence of malalignment on the development, progression and symptoms of OA. Furthermore, the less than optimal results of knee replacements (TKR) in younger patients have also led to renewed interest in joint-preserving treatment options.

Purpose

Varus SCO has not had the same success or widespread use as valgus HTO. The goal in SCO is similar to HTO, to shift the load from the diseased to the healthy compartment, in order to reduce pain, improve function and delay placement of a TKR. Valgus OA however occurs much less frequently than varus OA and varus SCO is considered a technically more demanding procedure. In the past the surgical techniques for SCO were mainly dependent on difficult-to-use implants making the procedure more complex. Complication rates related to the failure of fixation up to 16?% have been reported.

Disussion

The new biplane osteotomy technique fixated with a locking compression plate is very stable; bone healing potential is optimal using this technique and takes 6–8 weeks. Full weight bearing before full bone healing is possible without loss of correction.

Conclusion

In this article, patient selection, planning, surgical techniques, stability of fixation, and bone healing are discussed. Varus supracondylar osteotomy is a viable treatment option for a well-defined patient group suffering from valgus malalignment and lateral compartment osteoarthritis, and in addition may be considered in ligamentous imbalance and lateral patellofemoral maltracking.

     

Intramedullary fixation of cortical bone osteotomies with self-reinforced polylactic rods in rabbits

Summary Osteotomies of the femoral shaft in rabbits were fixed with intramedullary rods made of poly-L-lactic acid (SR-PLLA) and poly-DL/L-lactic acid (SR-PDLLA/PLLA). Follow up was from one week to 2 years. In the PLLA group, in 37 out of 40 osteotomies the fixation was firm and the bone was united. In the PDLLA/PLLA group, the fixation was firm in 30 out of 45, but in 13 of these angular deformity of more than 10° had occurred. The fixation had failed in 15. No inflammatory or foreign body reaction was seen in either group. This study demonstrates that SR-PLLA rods are suitable fixation for cortical osteotomies in rabbits.

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Résumé Les auteurs ont réalisé des ostéotomies de la diaphyse fémorale chez le lapin, qu'ils ont fixées par des tiges intramédullaires faites d'acide poly-L-lactique (APLL) et d'acide poly-DL-L-lactique (APDLL). Les animaux ont été suivis de 1 mois à 2 ans. Dans le groupe APLL, la fixation a été solide et la consolidation obtenue dans 37 des 40 ostéotomies. Dans le groupe APDLL, la fixation a été solide 30 fois sur 45, mais dans 13 de ces cas il s'est produit une angulation de plus de 10°. Il y a eu 15 échecs de fixation. Dans aucun des deux groupes il n'a été observé de phénomènes inflammatoires ni de réactions à corps étranger. Cette étude montre que les tiges d'APLL permettent une fixation efficace de l'ostéotomie corticale chez le lapin.

     

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.