Mikko Manninen

Complications of plate fixation in fresh displaced midclavicular fractures.

BACKGROUND The role of plate fixation in the management of fresh displaced midclavicular fractures is unsettled. The objective of this study was to evaluate the drawbacks and pitfalls of this treatment method. METHODS We analyzed the complications encountered in 103 consecutive adult patients with severely displaced fresh fractures of the middle third of the clavicle who were treated by open reduction and internal fixation using AO/ASIF plates. These 103 patients accounted for 9.5% of the 1,081 patients with fresh midclavicular fractures seen between 1989 and 1995. The mean age of the 103 patients was 33.4 years (range, 19-62 years). RESULTS Seventy-nine patients had an uneventful recovery, whereas 24 (23%) suffered one or several complications. The major complications included deep infection, plate breakage, nonunion, and refracture after plate removal. The most common of the minor complications was plate loosening resulting in malunion. The infection rate was 7.8%. A total of 14 reoperations were performed because of the complications. Permanent nonunion ensued in two patients. A severely comminuted fracture (relative risk of failure, 5.15) as well as a state of alcohol intoxication on admission (relative risk of failure, 3.12) were identified as markers of increased complication risk. CONCLUSIONS Patient noncompliance with the postoperative regimen could be suspected to have been a major cause of the failures. The high complication rate supports a reserved attitude toward plate fixation of fresh midclavicular fractures. The method should be reserved for patients who have trustworthy personal motives for quick pain relief and functional recovery.

The tissue-implant interface during degradation of absorbable polyglycolide fracture fixation screws in the rabbit femur.

A transverse transcondylar osteotomy of the distal femur was fixed with an axially placed absorbable fracture fixation screw made of polyglycolide (PGA) in 25 rabbits. Changes at the tissue-implant interface accompanying degradation of the screw were examined histologically, histomorphometrically, and microradiographically seven, 20, 40, 80, and 250 days after implantation. At seven days postimplantation, a layer of fibroblasts was seen surrounding the implant, and new bone formation was discernible in the host tissues adjacent to this membranous structure. At 20 days postimplantation, the geometry of the screw was still intact and the tissue-implant boundary was distinct. The first signs of invasion of vascular granulation tissue into the implant were observed 40 days after implantation, at which time the osteotomies were united. The apparent walling-off response by formation of new trabecular bone outlining the PGA profile continued, with the greatest mean trabecular bone volume fraction at the interface, 23.9%, measured at 40 days. A significant decrease in the new bone volume occurred between 40 and 80 days postimplantation. The intensity of the foreign-body reaction seen was histologically moderate. The giant cell count was highest at 80 days postimplantation, when the migratory activity of phagocytic cells had transported intracellular particulate polymeric debris 400-800 microns away from the original tissue-implant boundary. At 250 days postimplantation, no birefringent polymeric material could be seen in the specimens. No contraindications for the clinical application of PGA implants emerged in this study.

Polymeric debris from absorbable polyglycolide screws and pins: Intraosseous migration studied in rabbits

The migration of polymeric particles during degradation of absorbable implants made of polyglycolide was investigated in the cancellous bone of distal rabbit femur by using a transverse osteotomy model. The osteotomy was fixed either with a 4.5 x 25 mm screw or with two 1.5 x 30 mm pins. The histologic sections obtained at 3, 6, 12, and 36 weeks were morphometrically analyzed using polarized-light microscopy. The migration of the polymeric debris into the host-tissues showed two different patterns. On the one hand, particles were in all specimens seen lying intracellularly in phagocytic cells in a regular front close to the original tissue-implant boundary. In addition, in several specimens there occurred expansions filled with largely extracellular polymeric particles that bulged into the hematopoietic bone marrow up to 2.8 mm from the original implant cavity. This kind of particle migration over long distances could not be explained by cellular transport, but may have been caused by an increased osmotic pressure that developed within the implant cavity during depolymerization of polyglycolide.

Shear strength of cancellous bone after osteotomy fixed with absorbable self-reinforced polyglycolic acid and poly-L-lactic acid rods

The right distal femur of 42 adult rabbits was osteotomized and fixed with two 1.5 mm in diameter metallic Kirschner wires, self-reinforced polyglycolic acid (SR-PGA, Biofix®), or self-reinforced poly-L-lactic acid (SR-PLLA) rods. Follow-up times were 6 and 12 weeks. The shear strength of 30 pairs of femora was investigated. The strength of osteotomized bones was compared with the non-osteotomized controls. After six weeks the operated femora had reached 70, 69 and 71% shear strength in metallic, SR-PGA and SR-PLLA groups, respectively. After 12 weeks the shear strength values were 75, 79 and 73%, respectively. There was no statistically significant difference in shear strength values between the groups. Twelve pairs of femora were studied with microradiographic, oxytetracyclic fluorescence, and histologic methods. Normal bone healing was seen in these samples. Metallic and SR-PLLA implants caused slight foreign-body reaction with giant cells and SR-PGA rods led to slight infiltration of macrophages and foam cells.

Intramedullary nailing of the cortical bone osteotomies in rabbits with self-reinforced poly-l-lactide rods manufactured by the fibrillation method

Right femoral, cortical bone osteotomies of 42 rabbits were fixed with fibrillated, self-reinforced (SR) poly-L-lactide (PLLA) rods, 4.5 mm in diameter. Follow-up times were from 3 to 48 wk. None of the rods broke during this period. There was one non-union at three weeks and one non-union at 12 weeks. Radiographic, histologic, microradiographic and oxytetracyclic fluorescence studies showed normal healing. Shear load carrying capacity of the osteotomy plane was measured from 30 bone samples; the shear force at breaking increased during the follow-up time to 450 N, while the mean shear force of intact, left-side control femurs was 440 N. Before shear tests of the bones, the SR-PLLA rods were taken away from the medullary cavities of the femurs. The rods were also tested mechanically. About 25% of the initial 136 MPa shear-strength of the rods was left after 24 wk. The results show that fibrillated SR-PLLA rods are strong enough to be used in intramedullary nailing of femoral cortical bone osteotomies in rabbits.

Polylactide screws in the fixation of olecranon osteotomies A mechanical study in sheep

We studied absorbable self-reinforced poly-L-lactide screws in the fixation of osteotomies in sheep. A left olecranon osteotomy in 10 sheep was fixed with polylactide screws and in an additional 10 sheep with metallic AO cortical screws. Follow-up times were 6 and 12 weeks. 8 polylactide fixations healed and 2 failed. All metal fixations united; one of them had a fracture of the proximal fragment resulting in malposition. After killing the sheep the olecranons were radiographed and the shear strengths of the osteotomies were compared with those of the non-operated contralateral bones. After 6 weeks the mean comparative strength was 74 percent in the polylactide group and 83 percent in the metallic control group. After 12 weeks the corresponding values were 112 and 47 percent (P less than 0.05). Our study demonstrated that the mechanical weakening of fixed bone can be avoided by using absorbable polylactide screws instead of metallic screws. However, polylactide screws are not recommended for use without external support in places of high mechanical strain.

Mandibular osteotomy fixed with biodegradable plates and screws : an animal study

The objective of the study was to evaluate the use of a totally biodegradable fixation device in the fixation of mandibular osteotomy in sheep. Mandibular unilateral body osteotomies were fixed with biodegradable self-reinforced poly-L-lactide (SR-PLLA) multi-layer plates and screws in nine sheep. The unoperated sides acted as control. The follow-up times were 6, 12 and 24 weeks, after which radiological, mechanical and histological studies were carried out. An analysis of the implanted material was also carried out. The results showed that the SR-PLLA plates and screws were strong enough to fix the osteotomy and that the osteotomies healed mainly with callus formation. Therefore we conclude that SR-PLLA multi-layer plates and screws can be used together successfully in the fixation of mandibular osteotomies without maxillomandibular fixation. However, before they can be used in humans, the size of the plate and screws should be decreased.

Tissue-implant interface at an absorbable fracture fixation plug made of polylactide in cancellous bone of distal rabbit femur

The tissue-implant interface at a self-reinforced poly-l-lactide (SR-PLLA) expansion plug implanted in distal rabbit femoral cancellous bone was studied histologically, histomorphometrically, and microradiographically in 35 rabbits during consolidation of a transverse transcondylar osteotomy fixed with the SR-PLLA expansion plug. The absorbable plug for internal fixation of fractures and osteotomies measured 4.5 mm in diameter and 30 mm in length and had an expandable distal locking blade system. The femoral specimens were harvested in groups of 5–10 rabbits after a follow-up time of 3, 6, 12, and 24 weeks. The intact controlateral femur served as a control. Vigorous osteogenic response to the implant was already observed at 3 weeks postoperatively, and the osteoid surface fraction at 24 weeks was still significantly higher than in the unoperated contralateral femur. Incomplete union of the osteotomy seemed to result in increased fibrous tissue formation at the tissue-implant boundary. No signs of degradation of the SR-PLLA was observed within the entire follow-up period. The number of inflammatory cells at the tissue-implant interface was low. Consequently, the short-term biocompatibility of the implant was deemed acceptable. Clinical application of the expansion plug is being planned.

Self-reinforced poly-l-lactide screws in the fixation of cortical bone osteotomies in rabbits

This study was carried out to test absorbable self-reinforced poly-l-lactide (PLLA) screws as lag screws in the fixation of cortical bone osteotomies. A right tibial osteotomy was performed in 72 rabbits, of which 36 were fixed with 4.5 mm in diameter metallic cortical screws and 36 with self-reinforced PLLA screws manufactured by a sintering method. Follow-up times were 6, 12, and 24 weeks. After killing the rabbits all operated and the control tibias were examined macroscopically and radiographed. Sixty pairs of tibias were tested for shear strength; the rest were evaluated histologically, microradiographically and by oxytetracycline fluorescence. Macroscopically, 97% of the metallic and 44% of the PLLA screw-fixed osteotomies healed well. Radiographically, the metallic group healed significantly better and there were less malpositions than in the PLLA group. The shear strengths of the operated tibias were divided by those of the controls to give comparative shear strengths. The mean comparative shear strengths were 52% at 6, 61% at 12 and 76% at 24 weeks in the metallic group and 38, 49 and 61% in the PLLA group, respectively. No statistically significant difference in shear strength was observed between the groups. A mild foreign-body reaction was found in the histological evaluation in both groups, and normal bone healing was noticed in the microradiography and in the fluorescence studies. In conclusion, the sintered self-reinforced microradiography and in the fluorescence studies. In conclusion, the sintered self-reinforced PLLA screws were insufficiently strong to be used as a single lag screws in the fixation of tibial cortical bone osteotomies in rabbits.

Absorbable polyglycolide screws in internal fixation of femoral osteotomies in rabbits

In 20 rabbits, a transverse distal femoral osteotomy was fixed using a 4.5 by 30-mm absorbable screw made of polyglycolide. No postoperative external support was used. The consolidation of the osteotomy was investigated histologically, morphometrically, and microradiographically in groups of 4 to 6 rabbits that were followed for 3, 6, 12, or 36 weeks. Fourteen osteotomies showed solid bony union; and in 3, several bone trabeculae were seen to bridge a still partially ununited osteotomy. In another 3 rabbits, each with a follow-up time of 12 or 36 weeks, no convincing signs of progressing consolidation could be seen. Only 1 of these rabbits showed displacement of the distal fragment.