Biomechanical properties of plate constructs for feline ilial fracture gap stabilization

Effect of an Orthogonal Locking Plate and Primary Plate Working Length on Construct Stiffness and Plate Strain in an In vitro Fracture-Gap Model

OBJECTIVE

 The aim of this study was to compare stiffness and strain of an in vitro fracture-gap model secured with a primary 3.5-mm locking compression plate (LCP) at three primary plate working lengths without and with an orthogonal 2.7-mm LCP.

STUDY DESIGN

 Primary plate screw configurations modeled short working length (SWL), medium working length (MWL), and long working length (LWL) constructs. Construct stiffness with and without an orthogonal plate during nondestructive four-point bending and torsion, and plate surface strain measured during bending, was analyzed.

RESULTS

 Single plate construct stiffness was significantly, incrementally, lower in four-point bending and torsion as working length was extended. Addition of an orthogonal plate resulted in significantly higher bending stiffness for SWL, MWL, and LWL (p < 0.05) and torsional stiffness for MWL and LWL (p < 0.05). Single plate construct strain was significantly, incrementally, higher as working length was extended. Addition of an orthogonal plate significantly lowered strain for SWL, MWL, and LWL constructs (p < 0.01).

CONCLUSION

 Orthogonal plate application resulted in higher bending and torsional construct stiffness and lower strain over the primary plate in bending in this in vitro model. Working length had an inverse relationship with construct stiffness in bending and torsion and a direct relationship with strain. The inverse effect of working length on construct stiffness was completely mitigated by the application of an orthogonal plate in bending and modified in torsion.

Use of Locking Plates Fixed with Cortical Screws for Pelvic Fracture Repair in 20 Cats

OBJECTIVE

 The aim of this study is to describe the use of String of Pearls (SOP) plates for the surgical management of feline pelvic fractures, including surgical technique, proposed indications, complications, and outcomes in a cohort of cats.

STUDY DESIGN

 This study is a single-center retrospective clinical case series.

METHODS

 Medical records (2015-2019) of cats presenting for pelvic fractures (n = 33) were reviewed. Type of fracture, preoperative and postoperative imaging, and complications were retrospectively retrieved. Owners were contacted via questionnaire for medium- and long-term follow-up.

RESULTS

 A total of 20 cats met the inclusion criteria. Minor intraoperative complications were encountered in three patients. One patient suffered a major intraoperative complication. Five major complications were encountered postoperatively. These included two greater trochanter osteotomy fixation implant removal and three SOP plate removal. Full function was recovered in all patients according to the owners' assessment.

CLINICAL SIGNIFICANCE

 The use of SOP plates in feline pelvic fractures appears to yield a consistently good outcome with a very low incidence of canal narrowing and screw loosening. SOP plates are easy to contour and to apply along the entire pelvic length.

Biomechanical Tests on Long-Bone Elliptical Medullary-Canal Endoprostheses for Limb Salvage in Dogs

Simple Summary

Currently, more owners look for offering a better quality of life to their pets. In fact, the complete limb amputation seems to be the last option considered by pet owners in surgeries to save their pets’ lives. Although this field is under development in veterinary medicine, we believe that 3D-printed implants for this market sector will improve the advancement in its research by reducing production costs. This would allow the pet owners to select this solution without large expenses, allowing at the same time, advances in this field. For this purpose, mechanical tests have been carried out on implants printed in a high-performance plastic that resembles the resistance of metals—that are traditionally used in veterinary surgery—and the properties of dogs’ bones as well. The results obtained have confirmed that the implants could withstand the dog weight in its different gaits, although further comparative studies on the effect of rotation forces applied during the animal’s change of direction (evaluated at different paces) are required to confirm their suitability.

Abstract

Exo-endoprosthesis is a limb salvage procedure poorly described for animals, as only expensive metal devices have been used so far. Currently, additive manufacturing (AM) can make this type of implant affordable by exploring a wide new range of materials. However, safety factors should be considered and could be related to kinetic and kinematic studies of canine natural gaits. The suitability of a novel inner part of an exo-endoprosthesis manufactured by fuse deposition modeling (FDM) was assessed for long canine bones with an elliptical medullary canal. Polyether ether ketone (PEEK) was the material used as an alternative to metal for veterinary traumatology. Poisson’s ratio of 3D-printed PEEK material and ex vivo mechanical tests of the customized endoprosthesis were performed for the evaluation. The customized endoprostheses had promising outcomes for the radii of 20 kg dogs. Quasistatic mechanical tests of bone-inserted endoprostheses—pure compression tests—reached a maximum force of 1045.0 ± 78.0 N. In fatigue tests, the samples reached 500,000 cycles without failure or detriment to their quasistatic results. These outcomes surpass the natural weight-bearing of dogs, even during a galloping pace. Furthermore, torque tests with different adhesives were performed to obtain reference data for future assessments comparing with natural dog movements.

Biomechanical Test of a New Endoprosthesis for Cylindrical Medullary Canals in Dogs

Exo-endoprosthesis is a limb salvage procedure for animals, although only expensive metal devices have been described. Now-a-days, new materials for this type of implant could be considered due to novel and affordable manufacturing techniques. However, a factor of safety (FoS) should be considered. There are kinetic and kinematic studies of canine natural gaits, which can be used to establish an FoS for mechanical tests for new non-metallic devices. Polyetheretherketone (PEEK) is used in different specialties in human medicine. Its mechanical properties (and its close mechanical stiffness to that of bone) make this polymer an alternative to metals in veterinary traumatology. PEEK could also be used in 3D printing. The suitability of a novel inner part of an exo-endoprosthesis manufactured by fuse deposition modeling (FDM) was presented in this study for long canine bones. Mechanical characterization of 3D-printed PEEK material and ex vivo mechanical tests of a customized endoprosthesis were performed to address it. Young's modulus of 3D-printed PEEK suffered a reduction of 30% in relation to bulk PEEK. Customized 3D-printed PEEK endoprostheses had promising outcomes for the tibiae of 20 kg dogs. Pure compression tests of the non-inserted endoprostheses showed a maximum force of 936 ± 199 N. In the bending tests of non-inserted endoprostheses, the PEEK part remained intact. Quasistatic mechanical tests of bone-inserted endoprostheses (compression-bending and pure compression tests) reached a maximum force of 785 ± 101 N and 1,642 ± 447 N, respectively. In fatigue tests, the samples reached 500,000 cycles without failure or detriment to their quasistatic results. These outcomes surpass the natural weight-bearing of dogs, even during a galloping pace. In conclusion, the 3D-printed PEEK part of the endoprosthesis for an exo-endoprosthesis can withstand loading, even during a galloping pace.

Ex vivo comparison of lateral plate repairs of experimental oblique ilial fractures in cats

OBJECTIVE

To determine the biomechanical behavior of different plate systems used for oblique ilial fracture fixation in cats.

STUDY DESIGN

Ex vivo biomechanical study.

SAMPLE POPULATION

Fifty fresh-frozen feline hemipelvises.

METHODS

Standardized simple oblique ilial fractures were created and fixed via lateral plating, using different implant systems (10 fractures in each group) The systems were: (1) the Advanced Locking Plate System (ALPS-5); (2) the Advanced Locking Plate System (ALPS-6.5); (3) the Locking Compression Plate 2.0 (LCP); (4) the FIXIN 1.9-2.5 Series (FIXIN), and (5) the Dynamic Compression Plate 2.0 (DCP). Stepwise sinusoidal cyclic loading was applied until failure (10-mm displacement). The groups were compared with regard to construct stiffness and the number of cycles withstood before 1-, 2-, 5-, and 10-mm displacement.

RESULTS

Bending stiffness was lower in ALPS-5 than in other specimens (P < .05). The ALPS-6.5 specimens withstood more cycles (P < .05) before 2-, 5-, and 10-mm displacement than the ALPS-5 and DCP specimens . The LCP and FIXIN specimens endured more cycles than DCP specimens before displaying 5- and 10-mm displacement (P < .05). The ALPS-6.5, FIXIN, and LCP specimens endured higher loads before failure than the DCP specimens (P < .05). Screw loosening occurred in all nonlocking specimens, and bone slicing occurred in all locking specimens.

CONCLUSION

The DCP and ALPS-5 constructs are less resistant to cyclic loading. Failure in nonlocking specimens involved screw loosening. It involved bone slicing in locking specimens.

CLINICAL SIGNIFICANCE

Both the plate size and the plate-screw interface are key to lateral plating success in cases of feline ilial fractures. The use of locking plates reduces the risk of the screw loosening in such cases.

Clinical outcomes of orthogonal plating to treat radial and ulnar fractures in toy-breed dogs

OBJECTIVES

To describe the results of orthogonal plating (OP) as a treatment for fractures of the radius and ulna in toy-breed dogs.

MATERIALS AND METHODS

The medical records (June 2011 to April 2019) of toy-breeds in which the OP technique using non-locking cuttable plates was employed to treat radial and ulnar fractures were reviewed. The inclusion criteria included a bodyweight of 3.5 kg or less, fracture of the diaphysis of the radius and ulna of one or both forelimbs, and the availability of follow-up radiographs. Revision surgeries were also included.

RESULTS

Fifteen limbs that underwent initial fracture repair and five that underwent revision surgery met the inclusion criteria. The radial and ulnar fractures healed in 19 limbs at the final follow-up. Synostosis of the radius and ulna at the fracture sites was observed in one limb. Re-fracture after cranial plate removal was observed in one case. All dogs exhibited successful return of normal limb function at the final clinical and radiographic follow-up (mean, 104.7 ± 67.1 days; median, 79.5 days; range: 35 to 248 days). Long-term follow-up data obtained via telephone interviews to owners or referring veterinarians were available for 15 cases and confirmed maintenance of normal limb function in all dogs (mean, 32.5 ± 17.6 months; median, 26 months; range: 11 to 69 months).

CLINICAL SIGNIFICANCE

OP allowed the successful open reduction of radial and ulnar fractures, facilitating bone union in both the radius and ulna and a return to normal limb function in a series of toy-breed dogs.

Comparison of Single versus Double Lateral Plating in Treatment of Feline Ilial Fractures Using Veterinary Cuttable Plates

OBJECTIVE

 The aim of this study was to compare the frequency of implant failure and the extent of pelvic canal narrowing associated with the fixation of ilial fractures in cats with a single veterinary cuttable plate (SLP) or double veterinary cuttable plates (DLP) applied to the lateral surface of the ilium.

STUDY DESIGN

 Radiographic evaluation of feline ilial fractures plated laterally using SLP or DLP. Pelvic canal narrowing directly postoperatively and at 6 weeks follow-up was objectively measured using the sacral index (SI). Radiographs were evaluated for implant failure and fracture healing.

RESULTS

 Seventy-seven cats satisfied the inclusion criteria. Twenty-nine fractures were treated with a SLP and 48 with DLP. Implant failure occurred significantly more (p = 0.001) in the SLP group (14/29) compared with the DLP group (6/48). Follow-up SI was significantly different between the two groups (p = 0.048, SLP median: 1.0 range: 0.83-2.4, DLP median: 0.98; range: 0.76-1.45). Median change in SI was -0.04 (range: -1.4-0.05) in the SLP group and 0.0 (range: -0.23-0.23) in the DLP group. This difference was significantly different (p = 0.031).

CONCLUSION

 DLP leads to significantly less implant failure and significantly less pelvic canal narrowing compared with SLP. This difference in pelvic canal narrowing was small and the clinical relevance remains unclear.

Short-term outcomes of 59 dogs treated for ilial body fractures with locking or non-locking plates

OBJECTIVE

To determine the influence of plating systems on the clinical outcomes in dogs treated for ilial fractures.

DESIGN

Retrospective study.

ANIMALS

Fifty-nine dogs (63 hemipelves).

METHODS

Radiographs and medical records of dogs with ilial fractures presented to Iowa State University between 2003 and 2019 were reviewed. After fracture reduction, fractures were fixed with a locking plate system (LPS) or non-locking plate system (NLS). Perioperative, long-term complications, and follow-up data were recorded. The frequency of implant failure and pelvic collapse were compared using a logistic and linear regression analysis, respectively. Where the univariate test was statistically significant, a multivariate analysis across categories was performed to identify statistically different categories.

RESULTS

LPS and NLS implants were used in 25/63 and 38/63 hemipelves, respectively. Median follow-up time was 8 weeks (3-624 weeks). Implant failure occurred in 18/63 (29%) of fracture repairs, consisting of 17 with NLS and 1 with LPS. Revision surgery was recommended in five cases of implant failure, all with NLS. The probability of implant failure was higher when fractures were fixed with NLS (p = .0056). All other variables evaluated did not seem to influence outcome measures.

CONCLUSION

The variable with the most influence on the outcomes of dogs treated for ilial fractures consisted of the fixation method (NLS vs. LPS). Fractures repaired with NLS were nearly 20 times more likely to fail than those repaired with LPS.

CLINICAL RELEVANCE

Surgeons should consider repairing ilial body fractures in dogs with LPS to reduce the risk of short-term implant failure.

Mechanical comparison of two small interlocking nails in torsion using a feline bone surrogate

OBJECTIVE

To compare the torsional behavior of two small angle-stable interlocking nails (I-Loc and Targon) with that of locking compression plates (LCP). To evaluate the effect of implant removal on the torsional strength of feline bone surrogates.

STUDY DESIGN

Experimental.

SAMPLE POPULATION

Fracture gap constructs and intact explanted bone surrogates.

METHODS

Fracture gap constructs were stabilized with one of six implants (I-Loc 3 and 4, Targon 2.5 and 3.0, LCP 2.0 and 2.4) and then cyclically tested in torsion (n = 4/group). To simulate implant removal, intact surrogates with implant-specific pilot holes were then twisted to failure (n = 4/group). Torsional compliance (TC; °/Nm), angular deformation (AD; °), and failure torque (F_T ; Nm) were statistically compared (P < .05).

RESULTS

The I-Loc 4 had the smallest TC and AD of all constructs (P < .05). The largest TC (P < .05) was seen with the LCP 2.0. The Targon 2.5 had the largest AD (P < .05) secondary to locking interface slippage. Targon surrogates F_T were the lowest of all groups (P < .05). Conversely, there was no difference between the F_T of the I-Loc, LCP, and intact surrogates (P > .05).

CONCLUSION

We showed that I-Loc nails provided greater torsional stability than size-matched Targon nails and LCPs. Conversely, Targon 2.5 locking interface slippage may jeopardize that construct's stability. Furthermore, the significantly reduced bone surrogate torsional strength provided evidence that the large Targon bolt holes increased the risk of postexplantation iatrogenic fracture.

CLINICAL SIGNIFICANCE

Our results provide evidence to conclude that the small I-Loc nails may be valid alternatives to other osteosynthesis options for feline fracture repair.