Fracture Healing in 37 Dogs and Cats with Implant Failure after Surgery (2013-2018)

Implant failure is common in small animal orthopedics, but risk factors are rarely reported. Our objective was to determine whether abnormal fracture healing was associated with implant failure after fracture fixation in dogs and cats in a consecutive series of cases. Thirty-seven client-owned animals (thirty-two dogs, five cats) diagnosed with implant failure after fracture treatment from January 2013-September 2018 were studied. Medical and radiographic records were retrospectively reviewed to identify patients that underwent fracture fixation using open reduction and internal fixation with subsequent radiographic evidence of implant failure. Area moment of inertia (AMI), plate working length, and bone screw density were determined. Implant failure was found in 39 fractures in 37 animals, representing 23% of fracture cases during the study period. Cases of implant failure were at increased risk of delayed union, malunion, or non-union (p < 0.0001). The most common cause of implant failure was loosening (54%); the second most common was plate failure that included low AMI locking plates (28%). Major complications found in 22/39 fractures (56%) were associated with delayed union (p < 0.01). Surgical revision was performed in 49% of implant failure cases. Complications were most frequently identified after treatment of humeral fractures (26%). We conclude mechanical failure of implants increases the risk for delayed or abnormal fracture healing and often requires revision surgery. Implant AMI should be considered during preoperative planning. Locking plates are associated with implant failure if plate bending stiffness is not sufficient, based on findings from this case series.

Locking Compression Plate Fixation of Feline Acetabular Fractures: Application, Complications and Perioperative Outcome

OBJECTIVES

 The aim of this study was to report the use, complications and perioperative outcome of locking compression plates (LCP) for acetabular fracture fixation in feline patients.

STUDY DESIGN

 Medical records were reviewed for cats presented with acetabular fractures between 2011 and 2019. Only cases that involved open reduction and internal fixation with at least one LCP and had a minimum of 5-week postoperative follow-up were included. Long-term follow-up was based on the Feline Musculoskeletal Pain Index.

RESULTS

 Fifteen cats with 15 acetabular fractures met the inclusion criteria. Locking compression plates were used as a sole method of fixation in 11/15 cases, while with other ancillary implants in 4/15 cases. There were two minor complications related to the LCP consisting of a single screw backing out. Two major perioperative complications not related to the locking implants were described and required further surgical treatment. At the last clinical follow-up (median 46 days: 38-88 days), function was described as full for 7/15 cats, and acceptable for 8/15 cats. The Feline Musculoskeletal Pain Index questionnaire was completed by 9/15 owners at a median of 2,332 days; all owners reported their cats had minimal impairment.

CLINICAL SIGNIFICANCE

 Based on our results, LCP is a suitable implant for acetabular fracture fixation in cats, associated with a satisfactory outcome. Complications were similar to previously reported with other methods.

Biomechanical comparison of a modified TPLO plate, a locking compression plate, and plate-rod constructs applied medially in a proximal gap model in canine synthetic tibias

ABSTRACT The aim of this study was to develop a modified tibial plateau leveling osteotomy (TPLO) plate and to compare its biomechanical properties with a locking compression plate (LCP) and plate-rod constructs for the stabilization of experimentally induced gap fractures in canine synthetic tibias. The tibial models were assigned to either repair with a modified TPLO plate (Group 1), locking compression plate construct (Group 2), or plate-rod construct (Group 3). The specimens were loaded to failure in axial compression, three-point mediolateral and craniocaudal bending. There was no statistical difference between the three groups regarding stiffness (N/mm) and deformation (mm) in axial compression. The modified TPLO plate achieved load to failure similar to the plate-rod construct in craniocaudal bending. There was no significant difference between groups on mediolateral bending tests regarding load to failure and deformation. Furthermore, there was no significant difference in stiffness between groups 1 and 2. In conclusion, the modified TPLO plate had similar mechanical properties to LCP and plate-rod construct in the axial compression and bending tests. Nonetheless, clinical studies with a large population of dogs are required to determine the value of this new implant in proximal tibial fracture repair.

Feline Femoral Fracture Fixation: What are the options?

PRACTICAL RELEVANCE

The femur is the most commonly fractured bone in cats. Femoral fractures usually result from high-velocity trauma such as a road traffic accident or fall from a height and, as such, are associated with a wide variety of concurrent injuries. The initial focus of treatment should always be on assessment and stabilisation of the major body systems. Once any concurrent injuries have been addressed, all femoral fractures need surgical stabilisation, with the notable exception of greenstick fractures in very young cats, which can heal with cage rest alone. A number of different surgical options are available depending on the fracture type, location, equipment, surgeon experience and owner finances.

CLINICAL CHALLENGES

Femoral fractures can vary hugely in complexity and the small size of feline bones can limit the choice of implants. Furthermore, cats can present unique challenges in the postoperative period due to their active nature and the limited means to control their exercise level.

AUDIENCE

This review is aimed at general and feline-specific practitioners who have some experience of feline orthopaedics, as well as those simply wishing to expand their knowledge.

AIMS

The aim of this review is to help clinicians assess, plan and manage feline femoral fractures. It provides an overview of diagnostic imaging and a discussion of a range of suitable surgical options, including the principles of different types of fixation. It also highlights cat-specific issues, approaches and implants pertinent to the management of these cases.

EVIDENCE BASE

A number of original articles and textbook chapters covering many aspects of femoral fractures in cats and dogs have been published. Where possible, this review draws on information from key feline research and, where necessary, extrapolates from relevant canine literature. The authors also offer practical guidance based on their own clinical experience.

Description of and complications associated with reinforced, free-form external skeletal fixation for treatment of appendicular fractures in cats: 46 cases (2010-2019)

OBJECTIVE

To describe a modified technique for reinforced, free-form external skeletal fixation (rFF-ESF) of appendicular fractures in cats and identify factors associated with development of complications.

ANIMALS

46 cats with fractures repaired with rFF-ESF at Angell Animal Medical Center between 2010 and 2019.

PROCEDURES

Medical records were reviewed for information on signalment, affected bone, fracture location and orientation, degree of comminution, severity (open vs closed), fixator type, number of fixation pins, use of an intramedullary pin (yes vs no), surgeon experience (staff surgeon vs surgical resident), anesthesia time, surgery time, perioperative antimicrobial administration, concurrent surgical procedures, intraoperative complications, postoperative alignment, whether fixator destabilization was performed, and time to complete fixator removal. Postoperative complications were recorded.

RESULTS

43 of the 46 (93%) cats had a successful outcome, with a median time to complete fixator removal of 8 weeks (range, 3 to 61 weeks). Twelve of the 46 (26%) cats had major (n = 3) or minor (9) complications. In univariable analyses, 4 factors were significantly associated with development of postoperative complications: body weight (OR for each 1-kg increase in weight, 1.8), tibial fracture (vs fracture of any other long bone; OR, 16), use of a type 2 fixator (vs a type 1 fixator; OR, 11), and use of destabilization (vs no destabilization; 7).

CONCLUSIONS AND CLINICAL RELEVANCE

Results indicated that rFF-ESF can be successfully used to stabilize a variety of appendicular fractures in cats. Further studies are required to compare rFF-ESF with other fracture fixation methods.

A Retrospective Study of Postoperative Development of Implant-Induced Osteoporosis in Radial-Ulnar Fractures in Toy Breed Dogs Treated with Plate Fixation

OBJECTIVE

 This study aimed to evaluate implant-induced osteoporosis (IIO) development in toy breed dogs treated using internal fixation with digital radiographs as the index of pixel values.

STUDY DESIGN

 There were 226 cases (236 limbs) of toy breed dogs with radial-ulnar fractures. Pixel values were measured on radiographs immediately, 2 weeks and 1 to 12 months after surgery. The ratio of pixel values (PVR) represented the bone mineral areal density based on the humeral condyle in the same image. The dogs were grouped based on the fixation methods, age and status of destabilization.

RESULTS

 There was a significant decrease in the PVR at 1 to 12 months postoperatively for all cases. There were not any significant differences in PVR of antebrachial fractures between those repaired with plates using locking head screws, cortex screws or a combination of locking and cortex screws. Implant-induced osteoporosis persisted at 1 to 12 months postoperatively in dogs aged ≧6 months, while the PVR increased after 3 months in dogs aged <6 months. Based on the destabilization method, there was a significant increase in the PVR at 3 months in the plate removal group.

CONCLUSION

 This study suggests that IIO occurs in small dogs treated with plates and screws. Moreover, patients aged < 6 months showed an early postoperative recovery of bone mineral areal density. Further, screw and plate removal could contribute to the recovery of bone mineral areal density.

Clinical application of the small I-Loc interlocking nail in 30 feline fractures: A prospective study

OBJECTIVE

To describe medium-term functional outcome after nail osteosynthesis in feline traumatology and report clinically relevant recommendations for I-Loc angle-stable interlocking nail use in cats.

STUDY DESIGN

Prospective clinical study.

SAMPLE POPULATION

Client-owned cats (n = 29).

METHODS

Consecutive cases with femoral, tibial, or humeral fractures were included. Outcome measures included fracture and surgical procedure description, limb alignment, nail size vs body weight (BW), percentage of nail medullary canal (MC) fill, time to limb function at clinical union (CU), and complications. Descriptive statistics were reported and compared with historical data.

RESULTS

Bone distribution was 53.3% femora, 30% tibiae, and 16.7% humeri. There were six epimetaphyseal and 24 diaphyseal fractures. Overall, 67% of fractures were comminuted. Open reduction and minimally invasive techniques were used in 73% and 27% of cases, respectively. Seventeen I-Loc 3 (cat mean BW 4.4 ± 2.2 kg) and 13 I-Loc 4 (cat mean BW 5.2 ± 1.2 kg) nails were placed with mean MC fill of ≤50%. Average time to CU was 7.2 weeks. At CU, lameness had resolved or was mild in every cat, and all cats ultimately regained full limb function. No major complications were encountered.

CONCLUSION

Because of improved CU times, excellent functional outcomes, and low complication rate, our results provide evidence that I-Loc nails are safe and effective for feline traumatology.

CLINICAL SIGNIFICANCE

The I-Loc may be advantageous for fixation of epimetaphyseal fractures. Because of feline bone specific dimensional constraints, I-Loc 3 is likely appropriate for all feline humeri and most tibiae, while I-Loc 4 is well sized for feline femora.

Radiographically confirmed outcomes after fracture repair with a PLS polyaxial locking system in 40 dogs and cats

OBJECTIVE

To report radiographic findings and complications after fracture repair with a new polyaxial locking plate system (PLS polyaxial locking system; Aesculap/B Braun, Tuttlingen, Germany) in dogs and cats.

STUDY DESIGN

Retrospective case review from four veterinary practices.

SAMPLE POPULATION

Twenty-six dogs and 14 cats (40 long bone fractures).

METHODS

Medical and radiographic records of dogs and cats with long bone fractures treated with the PLS were reviewed. Cases were included when operative records were complete and included documentation of radiographic union or complications. Phone interviews of owners were performed for long-term follow-up. Ancillary methods of fracture fixation and associated complications were recorded.

RESULTS

Only two complications were recorded, one of which required a revision surgery. Radiographic follow-up was performed for all fractures. Radiographic union without complications was achieved in 38 of 40 (95%) fractures. Radiographic union was documented before 60 days in 19 of 40 (47.5%) fractures, between 61 and 90 days in 15 of 40 (37.5%) fractures, and after 90 days in six of 40 (15%) fractures. A functional union was observed at a mean time ± SD of 70.8 ± 38.9 days (range, 32-182). One or more ancillary fixation methods were used in 27 of 40 (67.5%) fractures.

CONCLUSION

The PLS polyaxial locking system was often used with adjunct fixation in this series, and radiographically confirmed healing without complications was documented in most cases.

CLINICAL SIGNIFICANCE

Use of the PLS can result in high success rates for fracture repair in dogs and cats, but ancillary fixation should be strongly considered.

Evaluation of a Feline Bone Surrogate and In Vitro Mechanical Comparison of Small Interlocking Nail Systems in Mediolateral Bending

OBJECTIVE

 The aim of this study was to (1) evaluate bending structural properties of a machined short fibre epoxy (SFE) feline bone surrogate (FBS), (2) compare the bending behaviour of small angle-stable interlocking nails (I-Loc; Targon) and locking compression plates (LCP) and (3) evaluate the effect of implant removal on FBS bending strength.

METHODS

 Part 1: Feline cadaveric femurs (n = 10) and FBS (n = 4) underwent cyclic four-point bending and load to failure. Part 2: Fracture gap FBS constructs (n = 4/group) were stabilized in a bridging fashion with either I-Loc 3 and 4, Targon 2.5 and 3.0, LCP 2.0 and 2.4, then cyclically bent. Part 3: Intact FBS with pilot holes, simulating explantation, (n = 4/group) underwent destructive bending tests. Bending compliance, angular deformation and failure moment (F_M) were statistically compared (p < 0.05).

RESULTS

 Native bone and FBS were similar for all outcome measures (p > 0.05). The smallest and largest bending compliance and angular deformation were seen in the I-Loc 4 and LCP 2.0 respectively (p < 0.05). While explanted Targon FBS had the lowest F_M (p < 0.05), I-Loc and LCP constructs F_M were not different (p > 0.05).

CONCLUSION

 The similar bending properties of short fibre epoxy made FBS and native feline femurs suggest that this model could be used for mechanical testing of implants designed for feline long bone osteosynthesis. The I-Loc constructs smaller angular deformation which also suggests that these implants represent a valid alternative to size-matched Targon and LCP for feline fracture osteosynthesis. The significantly lower F_M of explanted Targon may increase the risk of secondary fracture following implant removal.

Biomechanical Comparison of a Notched Head Locking T-Plate and a Straight Locking Compression Plate in a Juxta-Articular Fracture Model

OBJECTIVE

 This investigation compared the biomechanical properties of a 2.0 mm locking compression notched head T-plate (NHTP) and 2.0 mm straight locking compression plate (LCP), in a simple transverse juxta-articular fracture model.

STUDY DESIGN

 Two different screw configurations were compared for the NHTP and LCP, modelling short (configuration 1) and long working length (configuration 2). Constructs were tested in compression, perpendicular and tension non-destructive four point bending and torsion. Plate surface strain was measured at 12 regions of interest (ROI) using three-dimensional digital image correlation. Stiffness and strain were compared between screw configurations within and between each plate.

RESULTS

 The LCP was stiffer than the NHTP in all three planes of bending and torsion (p < 0.05). The NHTP had greater strain than the LCP during compression bending and torsion at all ROI (p < 0.0005). The short working length was stiffer in all three planes of bending and in torsion (p < 0.05) than the longer working length for both plates. The long working length showed greater strain than the short working length at most ROI.

CONCLUSION

 In this experimental model, a 2.0 mm LCP with two screws in the short fragment was significantly stiffer and had lower plate strain than a 2.0 mm NHTP with three screws in the short fragment. Extending the working length significantly reduced construct stiffness and increased plate strain. These findings may guide construct selection.

Fracture Repair in Cats Using a Conical Coupling Mini 1.9 to 2.5 mm Locking Plate System

OBJECTIVE

 The aim of this study was to retrospectively evaluate the clinical application of the Fixin mini 1.9 to 2.5 system for the treatment of long bone fractures in cats. We proposed that the Fixin mini system would successfully stabilize long bone fractures in cats with a healing time and complication rate similar to those previously reported for feline fractures using other locking bone plate systems.

MATERIALS AND METHODS

 Medical records and radiographs of cats with long bone fractures stabilized with the Fixin mini 1.9 to 2.5 system were retrospectively reviewed. Signalment, body weight, bone(s) fractured, region of bone fractured, fracture classification, concurrent orthopaedic injuries, complications, time to functional union, if minimally invasive plate osteosynthesis techniques were used, plate size, number of plates, bone graft use and ancillary methods of fixation were recorded.

RESULTS

 Fifty-six fractures in 54 cats were included. Mean time to radiographic union was 8.8 weeks. Complications were recorded in 8 out of 56 fractures. Major complications occurred in 4 of 56 fractures and minor complications occurred in 4 of 56 fractures.

CONCLUSION

 The Fixin mini 1.9 to 2.5 system had an overall complication rate and time to functional union similar to that of other implant systems used to treat feline long bone fractures and it appears suitable for repair of a wide variety of long bone fracture configurations in cats.

Locking Plate Fixation for Canine Acetabular Fractures

OBJECTIVE

 The aim of this study was to document application of locking plates for stabilization of acetabular fractures along with complications and clinical outcomes. We hypothesized that complications and clinical outcomes would be comparable to historical reports using non-locking plate and screw constructs.

STUDY DESIGN

 Medical records of dogs presented with acetabular fractures at a single referral centre between 2010 and 2018 were reviewed. Cases surgically managed by open reduction and internal fixation, involving placement of at least one locking plate and screws, were included. Signalment, fracture classification, type of implant used, additional methods of stabilization, along with complications and neurological deficits, were collected. Long-term follow-up was based on Liverpool Osteoarthritis in Dogs questionnaire.

RESULTS

 Eighteen acetabula were repaired in 17 dogs. Locking implants were VetLOX (4/18), string-of-pearls (7/18) and locking compression plates (7/18). Locking plates and screws were used as the sole method of fixation in 10/18 acetabula, and as adjunctive fixation with other implants in 8/18 acetabula. Two minor complications and one catastrophic complication were reported. Sixteen of seventeen dogs returned to function with radiographic documentation of fracture healing. Complication rate was comparable to historic reports using non-locking implants. Long-term outcomes assessed by Liverpool Osteoarthritis in Dogs questionnaire were positive in most cases.

CONCLUSION

 Locking plates are a viable means of stabilizing acetabular fractures in dogs and can provide positive clinical outcomes. Surprisingly, problems including inaccurate fracture reduction and implant loosening were not fully avoided by use of locking implants but incidence was low.

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.

Retrospective evaluation of perioperative and short term clinical outcomes in appendicular long bone skeleton fractures repaired via the string of pearls (SOP) locking plate system

BACKGROUND

Internal plate fixation and, more recently, locking plate fixation are commonly used in the repair of fractures in small animal surgery. This retrospective study reviewed the use of the String of Pearls locking plate system in the fixation/repair of appendicular long bone skeleton fractures in 31 small animal veterinary patients (33 fractures).

RESULTS

Major complications necessitating revision surgery occurred in 7/33 (21%), with implant failure as the inciting cause in all cases. Variables corresponding to an unsuccessful outcome were evaluated, and a correlation was found with plates placed in a bridging manner (placed without rigid anatomic reconstruction, p = 0.02) and length of follow-up (p = 0.01).

CONCLUSIONS

The SOP plating system can be used in the repair of appendicular longbone skeletal fractures, however, the authors propose that adjunct fixation, such as intramedullary pin, double plating, or external coaptation would likely improve results and should be considered imperative in cases in which anatomic reconstruction is either not desirable or achievable.

SURGICAL MANAGEMENT OF APPENDICULAR LONG-BONE FRACTURES IN FREE-RANGING FLORIDA PANTHERS ( PUMA CONCOLOR CORYI): SIX CASES (2000-2014)

The clinical outcomes of six free-ranging Florida panthers ( Puma concolor coryi) that underwent surgical stabilization of appendicular long-bone fractures (three femoral fractures, one tibial and one tibial and fibular fracture and two radial and ulnar fractures) were evaluated. These panthers presented to the University of Florida from 2000-2014. Estimated age of the panthers ranged from 0.5 to 4.5 yr, and weights ranged from 22 to 65 kg. Causes of injuries were vehicular collision ( n = 4) and capture related ( n = 2). All panthers underwent open reduction and fracture stabilization. Fixation failure necessitated three subsequent surgeries in one panther. Five panthers survived the immediate postoperative period, and all of these panthers' fractures obtained radiographic union (range, 8-36 [mean, 22] wk). The five surviving panthers underwent convalescence for 7-14 mo at White Oak Conservation Center before being released back into the wild; however, one panther was killed when hit by a car 3 days after release. The remaining four panthers were tracked for up to 106 mo in the wild and successfully integrated back into the native population. Surgical stabilization of appendicular long-bone fractures in free-ranging Florida panthers can be successful, but must take into account the stress that a large, undomesticated felid will place on the stabilized limb during convalescence as well as the difficulties involved in rehabilitating a wild panther in captivity.

Management of feline tibial diaphyseal fractures using orthogonal plates performed via minimally invasive plate osteosynthesis

Objectives The objective was to assess the medium- and long-term outcomes (radiographic and owner questionnaire) of feline tibial diaphyseal fractures with orthogonal plate fixation via a minimally invasive plate osteosynthesis (MIPO) approach. Methods Medical records and radiographs of cats that had tibial diaphyseal fractures stabilised with orthogonal plates were obtained (2012-2016). Immediate postoperative radiographs were reviewed to assess the construct configuration and follow-up radiographs (where available) were used to assess bone healing and implant-related complications. An owner-completed questionnaire (feline musculoskeletal pain index [FMPI]) was used at a minimum of 6 months following surgery to assess the cats' ability to perform normal activities. Results Eight feline tibial diaphyseal fractures met the inclusion criteria. One major complication was observed, most likely due to an operative technical error. There were no further complications following revision surgery. Six of the eight cases that had radiographic follow-up either had clinical bone union or showed evidence of bone healing. All cases were classified as successful according to FMPI. Conclusions and relevance Orthogonal plating of feline tibial diaphyseal fractures via an MIPO approach resulted in successful outcomes and a lower complication rate compared with previously reported techniques.

Effect of monocortical and bicortical screw numbers on the properties of a locking plate-intramedullary rod configuration

Objectives: To evaluate the effect of varying the number and configuration of locking bicortical and monocortical screws on a plate-rod construct using a mid-diaphyseal femoral ostectomy model.

Methods: Thirty Greyhound femurs were assigned to six groups (A-F). An intramedullary pin was placed in each bone following which a 3.5 mm locking plate was applied with six differing locking screw configurations. Groups A to C had one bicortical screw in the most proximal and distal plate holes and one to three monocortical locking screws in the proximal and distal fragments. Groups D to F had no bicortical screws placed and two to four monocortical locking screws in proximal and distal fragments. Each construct was axially loaded at 4 Hz from a preload of 10 Newtons (N) to 72 N, increasing to 144 N and 216 N, each of 6000 cycles with a further 45,000 cycles at 216 N to simulate a three to six week postoperative convalescence period. Constructs were then loaded to failure.

Results: No construct suffered screw loosening or a significant change in construct stiffness during cyclic loading. There was no significant difference in load to failure of any construct (p = 0.34), however, less variation was seen with monocortical constructs. All constructs failed at greater than 2.5 times physiological load, and failure was by bending of the intramedullary pin and plate rather than screw loosening or pull-out.

Clinical significance: Axially loaded locking monocortical plate-rod constructs applied to the canine femur may confer no difference biomechanically to those employing locking bicortical screws.