E. Antero Mäkelä

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.

Strength retention of self-reinforced drawn poly-L/DL-lactide 70/30 (SR-PLA70) rods and fixation properties of distal femoral osteotomies with these rods. An experimental study on rats

Self-reinforced polylevo-dextro-lactic acid(SR-PLA)70 composite rods,(2 mm×26 mm) were implanted in the dorsal subcutaneus tissue of sixteen rats. Osteotomies of the distal femur were fixed with SR-PLA70 composite rods (2 mm × 15 mm) in 39 rats. The follow-up times varied from 1 week to 1 year. After sacrifice three-point bending and shear tests were performed for subcutaneously placed rods, and radiological, histological, histomorphometrical, microradiographic, and oxytetracycline-fluorescence studies of osteotomized and intact control femora were performed. At 52 weeks the shear strength and flexural modulus of the rods were 41% of the initial value, and the flexural strength was 43% of the initial value. In the osteotomies seven specimens had to be excluded due to postoperative infection or dislocation of the fragment. Six of the thirty-two evaluated osteotomies showed signs of postoperative infection. Twenty-six osteotomies healed uneventfully. No signs of inflammatory or foreign-body reaction were observed. The present investigation demonstrated that the mechanical strength and fixation properties of the SR-PLA70 rods are suitable for fixation of cancellous bone osteotomies in rats. The present article is the first report on successful application of SR-PLA70 rods for fixation of cancellous bone osteotomies studied.

Results of Operative and Nonoperative Treatment of Rockwood Types III and V Acromioclavicular Joint Dislocation A Prospective, Randomized Trial With an 18- to 20-Year Follow-up

Background: The optimal treatment of acute, complete dislocation of the acromioclavicular joint (ACJ) is still unresolved. Purpose: To determine the difference between operative and nonoperative treatment in acute Rockwood types III and V ACJ dislocation. Study Design: Randomized controlled trial; Level of evidence, 2. Methods: In the operative treatment group, the ACJ was reduced and fixed with 2 transarticular Kirschner wires and ACJ ligament suturing. The Kirschner wires were extracted after 6 weeks. Nonoperatively treated patients received a reduction splint for 4 weeks. At the 18- to 20-year follow-up, the Constant, University of California at Los Angeles Shoulder Rating Scale (UCLA), Larsen, and Simple Shoulder Test (SST) scores were obtained, and clinical and radiographic examinations of both shoulders were performed. Results: Twenty-five of 35 potential patients were examined at the 18- to 20-year follow-up. There were 11 patients with Rockwood type III and 14 with type V dislocations. Delayed surgical treatment for ACJ was used in 2 patients during follow-up: 1 in the operatively treated group and 1 in the nonoperatively treated group. Clinically, ACJs were statistically significantly less prominent or unstable in the operative group than in the nonoperative group (normal/prominent/unstable: 9/4/3 and 0/6/3, respectively; P = .02) and in the operative type III (P = .03) but not type V dislocation groups. In operatively and nonoperatively treated patients, the mean Constant scores were 83 and 85, UCLA scores 25 and 27, Larsen scores 11 and 11, and SST scores 11 and 12 at follow-up, respectively. There were no statistically significant differences in type III and type V dislocations. In the radiographic analysis, the ACJ was wider in the nonoperative than the operative group (8.3 vs 3.4 mm; P = .004), and in the type V dislocations (nonoperative vs operative: 8.5 vs 2.4 mm; P = .007). There was no statistically significant difference between study groups in the elevation of the lateral end of the clavicle. Both groups showed equal levels of radiologic signs of ACJ osteoarthritis and calcification of the coracoclavicular ligaments. Conclusion: Nonoperative treatment was shown to produce more prominent or unstable and radiographically wider ACJs than was operative treatment, but clinical results were equally good in the study groups at 18- to 20-year follow-up. Both treatment methods showed statistically significant radiographic elevations of the lateral clavicle when compared with a noninjured ACJ.

Fixation of femoral shaft osteotomy with intramedullary metallic or absorbable rod: an experimental study on growing dogs.

The purpose of this study was to examine the effects of an intramedullary self-reinforced polyglycolic acid (SR-PGA), self-reinforced poly-L-lactic acid (SR-PLLA) and a metallic rod on growing bone and their applicability in the fixation of a femoral shaft osteotomy in growing dogs. In 5 dogs, 12 weeks of age, a SR-PGA rod and in another 5 dogs a SR-PLLA rod, both 4.7 mm in diameter and 60 mm in length, were introduced into the intramedullary cavity of the right femur to fix a femoral shaft osteotomy. In a third group of 5 dogs the femoral shaft osteotomy was fixed with an intramedullary metallic rod of equal size. The follow-up intervals were 1, 3, 6, 12, 24 and 48 weeks. Solid union of the osteotomy without secondary displacement was seen radiographically 6 weeks after the operation in all dogs. Neither an intramedullary SR-PGA-, SR-PLLA- nor metallic rod caused any significant disturbance to the longitudinal growth of the operated femur. Narrowing of the femoral neck and a slight valgization of the angle between the femoral neck and shaft without any functional disability was seen 48 weeks after the operation.

Healing of physeal fracture after fixation with biodegradable self-reinforced polyglycolic acid pins. An experimental study on growing rabbits

Physeal fractures occur at a frequency of 15% of all long bone fractures in children. Undisturbed continued bone growth is the main goal of the treatment of these fractures. After the operative reduction and fixation, whenever needed, a second operation for the removal of the pins is inevitable. The purpose of this study was to develop a biodegradable fixation device for transphyseal fracture fixation, abolishing the need of removal operation. Epiphyseal separation of the distal femoral physis was made on the right side in 18 five-week-old rabbits. The fixation of the physeal fracture was made with two self-reinforced polyglycolic acid (SR-PGA) pins 1mm in nominal diameter and 25mm in length. The follow-up times were 3, 6, 12, 24, and 28 weeks. The distal femoral growth-plate of both femurs was analyzed by radiographic, microradiographic, oxytetracycline-fluorescence, histological and histomorphometric studies. Histomorphometric studies showed normal features of growth. Two growth-plate-penetrating transcondylar SR-PGA implants, of 1mm in diameter, provided sufficient stability for the fixation of a distal femoral physeal fracture in a growing rabbit, and did not cause any growth disturbance.

The effect of a diagonally placed penetrating biodegradable implant on the epiphyseal plate. An experimental study on growing rabbits with special regard to polydioxanone

Abstract Forty rabbits, five weeks of age, were operated on. In 20 rabbits an oblique drill hole of 3.2mm in diameter was made at an angle of 60° to the growth plate of the right distal femur. In the other 20 rabbits a polydioxanone rod was driven in a similar drill hole. The follow-up times were three, six, 12, and 24 weeks. The distal femoral growth plates of both femurs were analyzed by radiographic, microradiographic, oxytetracycline-fluorescence, histological and histomorphometric studies. Histomorphometric studies served as an excellent means of an exact numerical description of the different cellular areas of the growth plate in experimental studies. An oblique drill hole resulted in permanent growth retardation and varus deformity of the femur in growing rabbit. A diagonally placed PDS-implant caused a similar growth retardation but did not cause any varus deformity. Internal fixation of physeal fractures with biodegradable pins with no need of implant removal appears as an exciting prospect. The fixation device should possess suitable mechanical properties to provide a safe aid for fixation and still be sufficiently flexible to permit uneventful healing process. The pressure of growth was able to break the PDS implant. Further studies are needed for development of biodegradable fixation of physeal fractures.

Healing of epiphyseal fracture fixed with a biodegradable polydioxanone implant or metallic pins. An experimental study on growing rabbits

Abstract Epiphyseal separation of the distal femoral epiphysis was made on the right side in 40 rabbits at five weeks of age. In 20 rabbits the fixation of the epiphyseolysis was made with two Kirschner wires 1.0mm in diameter and in the other 20 rabbits with a centrally placed transepiphyseal polydioxanone implant of 3.2mm in diameter. The follow-up times were three, six, 12 and 24 weeks. The distal femoral growth plate of both femurs was analyzed by radiographic, microradiographic, oxytetracycline fluorescence, histological and histomorphometric studies. Histomorphometric studies served as an excellent means of an exact numerical description of the different cellular areas of the growth plate in experimental studies. The fixation with two Kirschner wires did not cause any growth retardation. A polydioxanone implant of 3.2mm in diameter provided sufficient stability for the fixation of distal femoral physeal fracture in a growing rabbit, but resulted in a growth retardation similar to that after a drill hole of equal bore.

Strength retention of drawn self-reinforced polyglycolide rods and fixation properties of the distal femoral osteotomies with these rods. An experimental study on rats

Drawn self-reinforced polyglycolide (SR-PGA) rods, Ø 2 mm and 26 mm long, were implanted in the dorsal subcutaneus tissue of 16 rats. Osteotomies of the distal femur were fixed with SR-PGA rods (2 mm by 15 mm) in another 38 rats. The follow-up times varied from one week to one year. After sacrifice, three-point bending and shear tests were performed for subcutaneously placed rods. Radiological, histological, histomorphometrical, microradiographic, and oxytetracycline-fluorescence studies of osteotomized and intact control femora were also performed. At three weeks the flexural strength of the rods was 50% of the initial value, and the flexural modulus was 46% of the initial value. Five osteotomy specimens had to be excluded due to dislocation or non-union. One of the 33 evaluated osteotomy specimens showed signs of postoperative infection. Thirty-two osteotomies healed uneventfully. No gross signs of inflammatory or foreign-body reaction were observed. The amount of osteoid surface and active osteoid formation surface reached their highest value in the histomorphometrical analysis at 24 weeks. The present investigation demonstrated that the mechanical strength and fixation properties of the drawn SR-PGA rods are suitable for fixation of cancellous bone osteotomies in rats. The present article is the first report on the successful application of drawn SR-PGA rods for fixation of cancellous bone osteotomies.

Application of a self-reinforced polyglycolic acid (SR-PGA) membrane to the closure of an abdominal fascial defect in rats

The suitability of a polyglycolic acid (PGA) membrane to fascial closure was tested in 40 rats. To induce collagen synthesis, a fascial strip from the vastus lateralis muscle was applied to the peritoneal side of the PGA membrane. A midline laparotomy was performed, and the incision was covered with the membrane fixed at the edges. The animals were sacrificed at 3, 6, 12, and 28 weeks, at which time macroscopical, histological, and electron microscopical findings, as well as the results of breaking force tests were evaluated. Fascial augmentation had no effect on the results. Ventral hernias were observed in 37.5% of the cases, half of which were observed after 6 weeks postoperatively. In one case, intestinal adhesions to the membrane were found. Inflammatory reaction during the follow-up was moderate and lasted up to 12 weeks. Breaking force decreased up to 6 weeks, after which it slightly increased without reaching the breaking force level of the control animals.

Effect of totally absorbable implant volume on wound infection rate: Study of 2500 operated fractures, osteotomies, and ligament injuries

Between November 1984 and January 1994 in our department, a total of 2500 patients were treated with totally absorbable internal fixation devices. We studied these patients and analyzed results with regard to the volume of the absorbable implants and the development of wound infection. Of the 2500 patients 2044 were trauma patients and 456 were operated on for orthopedic disease. In 1466 patients treated with implants made of self-reinforced polyglycolic acid (SR-PGA) only, the patients who developed wound infection had a higher implant volume (P=0.07) than those who did not; this difference was close to statistical significance. In the 446 patients who received only implants made of self-reinforced poly-l-lactic acid (SR-PLLA), the 5 who developed wound infection had a mean implant volume more than three times that of the non-infected patients (P=0.01). We found that in the patients treated with the earlier SR-PGA implants, which contained a green staining material, there was no correlation between implant volume and incidence of wound infections. On the other hand, both the non-stained SR-PGA implants, which have been in clinical use since 1989, and the SR-PLLA implants, seem to be more predictable in terms of wound infections. We believe that this difference, is largely due to the lower level of tissue reactions with these newer implants.