An Enhanced Strength Retention Poly(Glycolic Acid)-Poly(l-Lactic Acid) Copolymer for Internal Fixation: In Vitro Characterization of Hydrolysis

Examining the Relationship Between Wound Complications and the Use of Resorbable Plates in Cranial Vault Reconstruction

BACKGROUND

Resorbable plates are commonly used in cranial vault reconstruction surgery. There are few published papers examining their safety profile. The authors examined the prevalence of wound complications associated with the use of resorbable plates (Inion CPS Fixation System) in pediatric patients undergoing cranial vault reconstruction.

METHODS

A retrospective review of patients (n = 182) who underwent cranial vault reconstruction using resorbable plate fixation was undertaken. All procedures were performed by a single Craniofacial Surgeon at the National Pediatric Craniofacial Center from 2008 to 2016. Wound complications were identified from a prospectively maintained database and medical note review. Several key patient characteristics and surgical variables were also recorded and tested for associations with wound complications.

RESULTS

A total of 58.8% (107 of 182) of patients were male with a median age at surgery of 16.2 months. Overall, 12.1% (22 of 182) experienced a postoperative wound complication requiring hospital admission. A total of 2.73% (5 of 182) of the patients that returned to theatre had remnants of plates removed. The authors had a mean time from primary operation to secondary reoperation of 103 days. In univariate statistical analysis, females were more likely to develop a wound complication. However, in stratified analyses excluding patients with an underlying genetic syndrome, increasing age, and lower weight but not gender were associated with wound complications.

CONCLUSIONS

A 12.1% (22 of 182) wound complication rate with the use of the Inion CPS Fixation System was observed. Inion plates appear to have an equivalent safety profile to other fixation devices. Increasing age and lower weight were associated with an increased risk of wound complications in nonsyndromic patients.

Influence of surface modifications on the degradation of standard-sized magnesium plates and healing of mandibular osteotomies in miniature pigs

Biodegradable magnesium alloys are suitable osteosynthesis materials. Despite the alloy composition, surface modifications appear to have an influence on the degradation process and biocompatibility. The aim of this study was to investigate the impact of hydrogenation and fluoridation of the surface in a mandibular osteotomy model. Standard-sized plates and screws were implanted in an osteotomy at the mandibular angle in nine miniature pigs. The plates and screws were harvested together with the adjacent tissues at 8 weeks after surgery and were investigated by micro-computed tomography and histological analysis. The bone healing of the osteotomy was undisturbed, independent of the surface properties. The adjacent bone tissue showed new bone formation at the implant surface; however, formation of some lacunae could be observed. The corrosion was between 9.8% and 11.6% (fluoridated<hydrogenated<non-modified) in histological specimens, while radiologically neither the volume nor the density of the osteosynthesis material was reduced in any treatment group. The soft tissues exhibited full biocompatibility with every surface property. In summary, surface modification by hydrogenation and fluoridation did not significantly influence bone healing, biocompatibility, or corrosion kinetics of the magnesium osteosynthesis at the mandibular angle.

Osteosynthesis of a cranio-osteoplasty with a biodegradable magnesium plate system in miniature pigs

Biodegradable magnesium alloys are a new class of implant material suitable for bone surgery. The aim of this study was to investigate plates and screws made of magnesium for osteosynthesis in comparison to titanium in a cranial fracture model. Implants were used for internal fixation of a cranio-osteoplasty in nine minipigs. Computed tomography was conducted repeatedly after surgery. The implants and the adjacent tissues were harvested 10, 20 and 30weeks after surgery and investigated by micro-computed tomography and histological analysis. The surgical procedure and the inserted osteosynthesis material were well tolerated by the animals, and the bone healing of the osteoplasty was undisturbed at all times. The adjacent bone showed formation of lacunas in the magnesium group, resulting in a lower bone-to-implant contact ratio than that of titanium (72 vs. 94% at week 30), but this did not lead to clinical side effects. Radiological measurements showed no reduction in osteosynthesis material volume, but indicated signs of degradation: distinct volumes within the magnesium osteosynthesis group had lower density in micro-computed tomography, and these volumes increased up to 9% at week 30. The histological preparations showed areas of translucency and porosity inside the magnesium, but the outer shape of the osteosynthesis material remained unchanged. No fracture or loosening of the osteosynthesis devices appeared. Soft tissue probes confirmed sufficient biocompatibility. Given their biodegradable capacity, biocompatibility, mechanical strength and visibility on radiographs, osteosynthesis plates made of magnesium alloys are suitable for internal fixation procedures.

STATEMENT OF SIGNIFICANCE

To the best of our knowledge this is the first study that used biodegradable magnesium implants for osteosynthesis in a cranial fracture model. The cranio-osteoplasty in miniature pigs allowed in vivo application of plate and screw osteosynthesis of standard-sized implants and the implementation of surgical procedures similar to those conducted on human beings. The osteosynthesis configuration, size, and mechanical properties of the magnesium implants within this study were comparable to those of titanium-based osteosynthesis materials. The results clearly show that bone healing was undisturbed in all cases and that the biocompatibility to hard- and soft tissue was sufficient. Magnesium implants might help to avoid long-term complications and secondary removal procedures due to their biodegradable properties.

Biocomposite Implants Composed of Poly(Lactide-co-Glycolide)/β-Tricalcium Phosphate: Systematic Review of Imaging, Complication, and Performance Outcomes

PURPOSE

To determine the degradation and performance outcomes of poly(lactide-co-glycolide)/β-tricalcium phosphate (PLGA/β-TCP) implants.

METHODS

A MEDLINE and Embase search for randomized or nonrandomized controlled studies and prospective or retrospective case series that used biocomposite interference screws or suture anchors composed of PLGA/β-TCP was performed. Main outcomes included volume of implant resorption and incidence of osteoconductivity at implant sites, imaging findings, adverse events, and the frequency of reoperations.

RESULTS

A total of 13 studies representing 668 patients with either knee or shoulder implants were included. Median follow-up was 28 months (range: 12-37 months). Biocomposite implants lost 88% of their original volume during follow-up. Osteoconductivity at the implant site was identified in 63% of cases. Adverse events included tunnel widening (3%), effusion (5%), and cyst formation (4%). Synovitis was not reported.

CONCLUSIONS

Biocomposite interference screws or suture anchors composed of PLGA/β-TCP almost fully absorb over 3 years while promoting osteoconductivity with few reported adverse events.

LEVEL OF EVIDENCE

Level IV, systematic review of Level I-IV studies.

Absorbable Screws Versus Metallic Screws for Distal Tibiofibular Syndesmosis Injuries: A Meta-Analysis

A meta-analysis was performed to investigate the outcomes between absorbable screw (AS) and metallic screw (MS) fixation for distal tibiofibular syndesmosis injuries (DTSIs). Randomized controlled trials comparing AS versus MS fixation in DTSIs were searched systematically, and the outcomes were analyzed using Review Manager Software, version 5.2. The risk ratio (RR) or mean difference with the 95% confidence interval (CI) was calculated using the fixed effects or random effects model. A total of 16 studies were included in the meta-analysis. No statistically significant difference was found between AS and MS fixation in excellent and good functional recovery rate (RR 1.11, 95% CI 1.00 to 1.23, I(2) = 60%, p = .06), infection (RR 1.66, 95% CI 0.73 to 3.79, I(2) = 0%, p = .23), incidence of pain (RR 0.68, 95% CI 0.24 to 1.92, I(2) = 12%, p = .47), screw broken (RR 0.31, 95% CI 0.03 to 2.93, I(2) = %, p = .31), heterotopic ossification (RR 1.93, 95% CI 0.21 to 17.62, I(2) = 51%, p = .56; 472 cases in 4 studies), fracture healing time (mean difference -1.88, 95% CI -3.51 to -0.26, I(2) = 93%, p = .02,), duration of operation time (mean difference 7.64, 95% CI -3.80 to 19.09, I(2) = 98%, p = .19). The incidence of foreign body reaction was higher with AS fixation (RR 6.07, 95% CI 2.54 to 14.50, I(2) = 0%, p < .001). The reoperation rate was higher with MS fixation (RR 0.08, 95% CI 0.03 to 0.18, I(2) = 77%, p < .01). The functional outcomes of AS were as good as those with MS for DTSIs. Other than the foreign body reaction, the complications occurring after AS fixation were not as serious as those with MS fixation. AS fixation might be a preferable alternative for reconstruction of DTSIs.

Correlation of the clinical and in vitro degradation characteristics of a poly(L-lactic acid): poly(glycolic acid) copolymer by mini meta-analysis

Absorbable internal fixation devices have built a successful clinical history in a variety of applications throughout the skeleton. Their appeal lies in their ability to lose strength and mass in a predictable reproducible manner, consistent with the healing process. Most of the evidence for their degradation properties, however, is derived from in vitro and animal studies. These methods approximate only the human clinical condition, and there are few such data available directly from patients. To better understand the absorption profile of an 85:15 poly(L-lactic acid):poly(glycolic acid) copolymer in humans, a "mini meta-analysis" was performed on 2 published studies: (1) a clinical study that followed reduction in CT image density of a cross-pin for ligament reconstruction over a 2-year interval, and (2) an in vitro study that measured the hydrolysis and strength loss of test specimens over a 10- to 11-month interval in a phosphate-buffered saline at 37 °C. The CT image density profile grossly approximated the in vitro tensile modulus profile with both quantities retaining at least half of their initial value at 44 to 52 weeks, but bore little resemblance to the rapid decreases in inherent viscosity (a measure of average molecular weight) and elongation to break (a measure of ductility), which were at half their initial values by 32 to 36 weeks. Because of the inherent difficulty in directly measuring absorbable implant degradation in patients on a routine basis, investigators should seize opportunities such as this in an effort to close the knowledge gap regarding absorbable implant degradation in humans as much as possible.

Perspectives on resorbable osteosynthesis materials in craniomaxillofacial surgery

Since introduction to the clinics in the 1990s, resorbable osteosynthesis systems have undergone extensive improvements in order to establish their use as a standard treatment, especially in craniomaxillofacial surgery. However, the development of osteosynthesis systems made of poly(α-hydroxy acid) polymers has been hindered by the lack of information on the mechanical properties and biocompatibility of these materials. Moreover, magnesium-based degredable osteosynthesis materials have not yet been integrated into clinical practice owing to biocompatibility problems. Osteosynthesis systems made from nonresorbable titanium alloys have shown excellent biocompatibility, stability and individual fitting to the implant bed, so these materials are currently considered the 'gold standard'. The procedure of plate removal has been subjected to intense scrutiny and controversy. Bioresorbable materials are indicated for special conditions, such as osteosynthesis of the growing skull or orbital floor reconstructions. This paper presents an overview of the currently available and investigated resorbable osteosynthesis materials in comparison with the nonresorbable 'gold standard' titanium. The main problem areas such as sterilization, biocompatibility and stability are highlighted and perspectives for further improvements are provided.

Combined use of titanium mesh and resorbable PLLA-PGA implant in the treatment of large orbital floor fractures

BACKGROUND

A variety of alloplastic permanent and resorbable materials have been successfully used in orbital floor reconstruction; nevertheless, they both have shown disadvantages in the reconstruction of large orbital floor defects. We believe that, by combining both types of implants, the disadvantages could be diminished.

METHODS

This is a retrospective study that included all patients with large orbital floor defects (>2 × 2 cm), pure or in association with other facial fractures, treated in our service with the combined use of titanium mesh and the resorbable implant LactoSorb.

RESULTS

We included 20 patients, 7 had pure blowout fractures and the rest had other associated maxillofacial fractures. All of them had a large orbital floor defect with entrapment of periorbital tissue and herniation into the maxillary sinus. Mean hospital stay was 2 days, and our follow-up period was for at least 3 months. Seventeen patients had complete coverage of their floor defect with restoration of orbital volume, normal globe position, and full extraocular motility. We report 3 cases of enophthalmos and 2 cases of ectropion. Follow-up tomographic scans showed incomplete implant coverage of the orbital floor in 2 cases and a misplaced implant in the other. Subsequent operation was needed for correction.

CONCLUSIONS

We believe that the combination of both implants is a good option for the reconstruction of large orbital floor defects. It takes full advantage of their intrinsic properties while at the same time lowers the disadvantages of their individual use. Complications were attributed to technical errors and not to the combination of both materials.