Polydioxanone Pins Research Articles

Biomechanical evaluation of novel ultrasound-activated bioresorbable pins for the treatment of osteochondral fractures compared to established methods.

Osteochondral injuries often lead to osteoarthritis of the affected joint. All established systems for refixation of osteochondral defects show certain disadvantages. To address the problem of reduced stability in resorbable implants, ultrasound-activated pins were developed. By ultrasound-activated melting of the tip of these implants, a more secure anchoring is assumed. The aim of the study was to investigate if ultrasound-activated pins can provide secure fixation of osteochondral fragments compared to screws and conventional resorbable pins. In a biomechanical laboratory setting, osteochondral fragments of the medial femoral condyle of sheep were refixated with ultrasound-activated pins [US fused poly(L-lactide-co-D,L-lactide) (PLDLLA) pins], polydioxanone (PDA) pins and conventional titanium screws. Anchoring forces of the different fixation methods were examined, registered and compared concerning shear force and tensile force. Concerning the pull out test, the US fused PLDLLA pins and titanium screws (~122 N and ~203 N) showed comparable good results, while the PDA pins showed significantly lower anchoring forces (~18 N). Examination of shear forces showed a significantly higher anchoring of the screws (~248 N) than the US fused PLDLLA pins (~218 N). Nevertheless, the US fused PLDLLA pins could significantly outperform the PDA pins (~68 N) concerning shear forces. The US fused PLDLLA pins demonstrated a comparable anchorage to the fixation with screws, but were free from the disadvantages of metal implants, i.e. the need for implant removal. The PDA pin application showed inferior biomechanical properties.

Manejo quirúrgico de la inestabilidad acromioclavicular aguda

The surgical management of acute acromioclavicular instability is a common procedure within the pathology of the shoulder. In accordance with the Rockwood classification, an assessment should be made of the presence of a horizontal instability component besides the vertical instability. The treatment of acute acromioclavicular dislocations must be adapted to the demands of the patient. The low grade instabilities (types I and II) are treated conservatively. Those considered high grade (types IV-VI) should be treated surgically within 2-3 weeks from the injury. There is still debate on those of type III. The non-surgical treatment of type III injuries provides functional results at least similar to be able to start professional and sports activities. Among the surgical treatments used are found, open surgery procedures using Kirschner wires, polydioxanone pins, or other types of non-absorbable sutures, or hook plates. Arthroscopic techniques use new implants designed to align and reduce the coracoclavicular space. The advantage of arthroscopy is to be able to review and treat associated lesions in the glenohumeral in the same surgical operation.

Arthroscopic reattachment of osteochondritis dissecans cartilage flaps of the femoropatellar joint: Long‐term results

Long-term efficacy of arthroscopic cartilage reattachment for the treatment of osteochondritis dissecans (OCD) lesions in the equine femoropatellar joint is unknown. To evaluate radiographic outcome and long-term performance of horses undergoing OCD reattachment. Separated OCD cartilage flaps may be reincorporated into the joint surface by reattachment rather than flap removal. Polydioxanone pins were utilised arthroscopically to reattach OCD lesions in 40 of 44 joints from 27 horses. Cartilage was reattached when it had persisting perimeter continuity, the surface was not deeply fissured or irregular, and the cartilage was not protuberant or extensively mineralised. Bone marrow aspirate concentrate was grafted to additional areas denuded of cartilage or alongside reattached cartilage. Breeds included Thoroughbred (n = 18), Quarter Horse (n = 4), Warmblood (n = 3), Standardbred (n = 1) and Arabian (n = 1). Mean age was 9.7 months. Radiographic lesion length was 1.5-6.3 cm. Reattachment alone was used in 32 of 44 affected joints, a combination of debridement and reattachment in 8 joints and debridement alone in 4 joints. One horse was destroyed due to tendon laceration. Of the remaining 26 horses, mean duration of follow-up was 15.6 months (range 2 months-12 years). Radiographic resolution of OCD lesions treated with reattachment was significantly improved at 6 months. Twenty horses had long-term performance data, of which 19 were sound and had reached intended athletic potential. One horse remained lame, and an additional 6 were sound but remained unbroken or were convalescing. Thus, an overall success rate based upon continued soundness in performing horses was 95% (19/20). Cartilage flap reattachment can salvage OCD cartilage by integration with the underlying bone. Extensive OCD cartilage flaps may be salvaged by reattachment which can result in normal radiographic subchondral bone contour and long-term athletic performance.

Reattachment of the articular cartilage component of type 1 subchondral cystic lesions of the medial femoral condyle with polydioxanone pins in 3 horses

3 horses were referred for treatment of subchondral cystic lesions of 1 or both medial femoral condyles. All horses had clinically apparent lameness confirmed to be due to a radiographically evident subchondral cystic lesion of the medial femoral condyle with a large articular component (> 15 mm) and shallow subchondral depth (< 10 mm). Arthroscopic assessment of affected cartilage revealed undulating cartilage with a relatively smooth surface and extensive residual perimeter attachment. Resorbable polydioxanone pins were used arthroscopically to reattach the cartilage overlying the subchondral cystic lesions. A biologic graft (bone marrow aspirate concentrate or allogeneic chondrocytes) was injected into the depths of the cystic cavity following cartilage reattachment. Follow-up examination confirmed radiographic resolution of the lesion and elimination of clinical signs within the treated femorotibial joint. Lesions with a large area of affected articular cartilage have been associated with a decreased rate of return to athletic function following arthroscopic debridement, likely secondary to the loss of subchondral architecture and the production of imperfect fibrocartilage repair. Salvage of the affected cartilage in a select population of horses with progressively expanding but shallow subchondral cystic lesions of the medial femoral condyle is possible and may improve radiographic and clinical outcome.

Mechanical Characteristics of Cortical Bone Pins Designed for Fracture Fixation

Pins constructed from cortical bone may provide a reasonable alternative to other fracture-fixation devices by circumventing some of the complications associated with stainless steel and synthetic biodegradable implants. However, it is unknown whether cortical bone pins provide comparable strength compared to conventional pins. Using four-point bending, we compared the mechanical characteristics of 1.2-mm allogeneic cortical bone pins milled from specific regions of human tibiae and femora to commercially available 1.1-mm diameter stainless steel pins and 1.3-mm diameter polydioxanone pins. We used impact testing to identify mechanical differences in cortical bone pins between gender and harvest site. Cortical bone pins had better mechanical properties in four-point bending compared with polydioxanone pins, but not stainless steel pins. Pins milled from the right tibiae of males had the best bending characteristics. The mechanical performance of 1.2-mm cortical bone pins was comparable to those of stainless steel and polydioxanone pins regardless of site, bone, and gender. The clinical investigation of cortical bone pins as an implant for fracture fixation is warranted based on mechanical testing and comparison to commercially available polydioxanone and stainless steel pins.

距骨における離断性骨軟骨炎に対する自家骨軟骨移植術の１症例

We present a case of a 13-year-old boy with osteochondritis dissecans of the talus, in whom favorable outcomes were obtained by osteochondral autograft transplantation. He underwent arthroscopic fixation of the osteochondral lesions of the talus using polydioxanone pins, but came our hospital due to nonunion. Since pain in the ankle persisted, plain radiography and magnetic resonance imaging were performed. The results suggested stage 3 osteochondritis dissecans of the talus, according to the four-stage classification of Berndt and Hatty. We performed osteochondral autograft transplantation. At the time of writing this report 12 months postoparatively), the patient had experienced no pain and range of motion was not limited. In addition, radiolucency of the talus was restored.

Arthroscopic reattachment of osteochondritis dissecans lesions using resorbable polydioxanone pins.

Debridement of osteochondritis dissecans (OCD) cartilage lesions results in fibrocartilage and imperfect hyaline repair tissue, and forms a permanent irregularity to the subchondral bone plate. To evaluate the clinical, radiographic and outcome effects of OCD cartilage flap reattachment for select lesions as an alternative to OCD debridement. Separated cartilage flaps resulting from OCD lesions may be re-incorporated into the hyaline cartilage surface by reattachment rather than debridement and removal. Resorbable polydioxanone pins were used to reattach OCD flap lesions in 16 joints of 12 horses. Criteria for attachment, rather than removal, included an unmineralised cartilage flap on preoperative radiographs and a relatively smooth surface with some residual perimeter attachment at surgery. There were 12 subjects, 6 males and 6 females, 7 Thoroughbred or Standardbred weanlings, 3 Warmbloods, 1 Arabian and 1 Quarter Horse, mean age at surgery 6.8 months. All horses had effusion of the affected femoropatellar joint (n = 9), tarsocrural joint (n = 1) or fetlock (n = 2). Radiographic lesions varied in length between 1.8-6.3 cm; reattachment was used in 16 of 18 affected joints and the OCD cartilage was not satisfactory for salvage in 2 stifles. Number of pins required was 2-10. One horse was subjected to euthanasia due to a tendon laceration 8 weeks after surgery; of the remaining 11 horses, mean duration of follow-up was 3.9 years (range 4 months-8 years). Nine of these were sound and had entered work, while 2 were sound but remained unbroken 4 and 6 months post operatively, respectively. Radiographic resolution of the OCD lesion occurred in 14 of 16 pinned joints in the 9 horses with long-term follow-up. The 2 remaining joints had a 3 and a 5 mm mineralised flap in the original defect sites. This study indicated cartilage flap reattachment was an alternative to removal in selected OCD lesions. Relatively smooth OCD cartilage flaps may be salvaged by reattachment and can result in normal radiographic subchondral contour and a high likelihood of athletic performance. Further case numbers are required to determine which lesions are too irregular or contain too much mineral for effective incorporation after reattachment.

Polydioxanone Biodegradable Pins in the Knee

Biodegradable solid implants have been developed as an alternative to metallic orthopedic fixation. In animal models, implants degrade within and are replaced by bone. This study documents the resorption of these devices in human patients with MR imaging. One hundred seventy-five 1.3-mm biodegradable pins made of polydioxanone were used to secure a total of 59 osteochondral allografts of the knee. Patients with the pins underwent scanning on a 1.5-T unit with 3.3- to 4-mm contiguous T1-weighted spin-echo (TR/TE, 600/15), fat-saturated proton density-weighted (3000/40), T2-weighted fast spin-echo (3000/63), and three-dimensional spoiled gradient-recalled (47/7; flip angle, 60 degrees ) sequences at 3, 6, 12, 24, or 36 months after surgery. Eighty-nine pins were imaged on multiple occasions. Two osteoradiologists interpreted the MR examinations. More than 80% of the pin channels were visible at 3 and at 6 months after surgery. By 24 months, only 20% of the pin channels were visible, with the remainder having been replaced by bone. At 3 months, nearly 40% of the pins were associated with adjacent marrow edema. Edema generally diminished, involving less than 20% of pins at later time points. Focal cartilage defects were evident at 32% of the pin insertion sites during the first 6 months, but these defects were present in only 4% of the insertion sites thereafter. Biodegradable polydioxanone pins usually resorb completely by 24 months. Marrow edema, presumably representing inflammation related to pin resorption, is infrequent and tends to resolve. Cartilage defects related to pin placement heal spontaneously.

Correction of hallux abductus valgus by Mitchell's metatarsal osteotomy: comparing standard fixation methods with absorbable polydioxanone pins

Thirty-nine Mitchell's first metatarsal osteotomies were performed in 28 individuals with hallux abductus valgus at two centres. Seventeen osteotomies were stabilized with standard fixation (Vicryl ® bone suture or K wire) and 22 were fixated with absorbable polydioxanone Orthosorb ® Absorbable Pins (Johnson & Johnson Orthopaedics, Bracknell, UK). Patients were assessed preoperatively and at 3, 6 and 12 months postoperatively. Clinical evaluation was undertaken by an independent assessor unaware of the fixation method with radiographic assessment performed by the consultant. On review, one patient (one foot) that received absorbable fixation was lost to follow-up and another was last seen 4 months postoperatively. Average follow-up was 10.7 months (2–24 months). There was no statistical difference between the two groups in terms of age or weight. Statistical analysis by Mann-Whitney U test revealed no significant difference between the treatment and control groups for first metatarsophalangeal joint (MTPJ) range of motion, hallux valgus angle, intermetatarsal angle, hallux rotation and first to second metatarsal length ratio both preoperatively and postoperatively. Analysis of the patients combined by signed rank test revealed no significant change in the first MTPJ range of motion but there was a significant reduction in the hallux valgus angle, intermetatarsal angle, hallux rotation and first to second metatarsal ratio following surgery. The average postoperative hallux valgus angle (17.1°) suggests that the Mitchell's metatarsal osteotomy is less effective for large preoperative deformities. There was no evidence of foreign body reaction, persistent or increased pin tract lucency or sinus formation in any patients receiving absorbable fixation. One foot required removal of the K wire fixation. In conclusion, absorbable polydioxanone pins present no additional complications to those associated with standard fixation methods and avoids the possible need for a second procedure to remove metalwork.

The effect of site of implantation and animal age on properties of polydioxanone pins.

Absorbable polymeric orthopaedic pins (Orthosorb) of 2.0 mm diameter were implanted at different sites in mature (3.5 kg, > 5 months) and immature (5 weeks old) rabbits (total 36) for 2, 4, and 5 weeks. The sites of implantation were the medullary canal of the femur, muscles of the thigh and subcutaneous tissue of the dorsum. In mature rabbits, 1.3 mm diameter pins were also implanted in the medullary canal of the femur. The shear strength of the pins harvested from the rabbits, was measured at each time period using a fixture that shears the pins into three parts symmetrically about the load axis. In both mature and immature rabbits the rate of degradation in mechanical properties was higher in the medullary canal of bone than in the muscle and in the subcutaneous tissue (p < 0.05). The strength retention was lower in immature than in mature rabbits after 4 and 5 weeks. The 1.3-mm pins had higher initial strength (174.7 +/- 7 MPa), higher strength retention and slower degradation within the medullary canal of femur of mature rabbits as compared to the 2.0-mm pins (157.5 +/- 4.8). DSC and X-ray diffraction results of control and implanted pins showed higher initial crystallinity and a wider range of crystallite size in the 1.3-mm pins. After 5 weeks in vivo, the crystallinity increased indicating degradation within the amorphous phase. The smaller crystallites underwent recrystallization to form larger crystallites. The results indicate that site of implantation and age of recipient influence the degradation and associated effects on mechanical properties of absorbable implants. The size of the implant, though important in determining its properties, should be considered in association with its microstructure, which also plays an important role in determining strength and strength retention of absorbable polymeric systems.

A Comparison of Four Different Methods of Fixation of Osteochondral Fragments

SummaryFixation methods for osteochondral shell grafts were studied using replace-ment of a femoral trochlear autograft in rabbits as the model. Twenty skeletally mature rabbits were divided into four groups with five rabbits in each. The articular cartilage of the femoral trochlea, including 2.0 mm of subchondral bone, was removed using a sagittal bone saw. The grafts were immediately reattached using either small Kirschner pins (K-pins), polydioxanone pins (PDP), polydioxanone suture (PDS), or polymethylmethacrylate (PMMA) cement. Six months postoperatively the rabbits were killed and the graft sites compared to the contralateral control using radiography, gross examination, Safranin-O and H &amp; E staining, and sulphate-35 radioactive uptake. Mild degenerative joint changes were evident radio-graphically in all of the operated joints. Articular surface defects at the graft sites were common and included small craters and erosions; a few had larger areas devoid of cartilage. Defects associated with the pin entrance sites were common in the K-pin and PD P groups. The PDS group had the least number of animals with articular surface defects. Safranin-O staining was complete in the PDS group, partial or complete in the K-pin and PD P groups, and partial in all of the joints in the PMM A group. H &amp; E preparations of the cartilage sections were graded from 1 (normal cartilage) to 5 (multiple fissures, severe degradation). The PDS group had a mean (SD) score of 1.8 (0.8), the PD P group 2.4 (1.1), the K-pin group 2.5 (1.3), and the PMM A group 4.6 (0.6). The scores for the PMM A group were significantly greater then the scores for the other groups (p &lt;0.05). The mean (SD) for radioactive counts per minute/mg tissue in treated graft sites as a percent of control was PDS: 130 (83); PDP : 115 (14); K-pins: 92 (42); PMMA : 91 (29). The relative percentages for radioactive uptake were not significantly different (P &gt;0.05). Graft fixation using PDS, PDP, or K-pins was technically easy to perform and the results were generally satisfactory. Fixation using PMM A was technically demanding and histological evidence of moderate to severe cartilage degradation was present in all treated joints.Femoral trochlear autografts in rabbits were used to study fixation methods for osteochondral graft fragments. Six months after the operations the graft sites were evaluated using radiographs, gross examination, Safranin-O and H &amp; E staining, and sulphate-35 radioactive uptake. Grafts stabilized using polydioxanone suture had the least number of articular surface defects and the most complete Safranin-O staining.