Plate-rod Construct Research Articles

Ex vivo biomechanical evaluation of 2.4 mm LCP plate rod constructs versus 2.7 mm LCP applied to the feline tibia.

To compare the stiffness and strength of three plate and rod fixation constructs applied to a feline tibial gap model. Ex vivo study. Thirty-three unpaired tibiae obtained from skeletally mature cats. The tibiae were randomly divided into three groups. The following implants were then applied to the feline tibiae prior to the creation of a 10 mm diaphyseal gap. Group 1: 2.4 mm locking compression plate (LCP) and 1.0 mm intramedullary pin (IMP). Group 2: 2.4 mm LCP and 1.6 mm IMP. Group 3: 2.7 mm LCP. Subsequently, each specimen was tested for torsion, axial compression, and axial load until construct failure. Student's t-tests were used to compare the torsional and axial stiffness, yield load, and maximum axial force. Group 2 had higher axial stiffness than group 3 (p = .013). Group 1 showed a lower maximum axial force and yield point than groups 2 and 3 (p < .01; p < .05, respectively). There were no among-group differences in torsional stiffness. Constructs with a 2.4 mm LCP and 1.6 mm IMP provided the strongest and most rigid constructs in a feline tibia gap model. A plate-rod construct combining a 2.4 mm LCP and a 1.6 mm IMP is appropriate for achieving high implant stiffness and resisting maximum axial force in treatment of tibial fractures in cats.

Comparação biomecânica entre placa de TPLO modificada, placa bloqueada e construção placa-pino intramedular aplicadas medialmente em modelo de fratura proximal em tíbias sintéticas caninas

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.

Analysis of feline humeral fracture morphology and a comparison of fracture repair stabilisation methods: 101 cases (2009-2020).

ObjectivesThe aims of this study were to describe the type, presentation and prognostic factors of feline humeral fractures over a 10-year period and to compare three stabilisation systems for feline humeral diaphyseal fractures.MethodsIn total, 101 cats with humeral fractures presenting to seven UK referral centres between 2009 and 2020 were reviewed. Data collected included signalment, weight at the time of surgery, fracture aetiology, preoperative presentation, fixation method, surgical details, perioperative management and follow-up examinations. Of these cases, 57 cats with humeral diaphyseal fractures stabilised using three different fixation methods were compared, with outcome parameters including the time to radiographic healing, time to function and complication rate.ResultsThe majority of the fractures were diaphyseal (71%), with only 10% condylar. Of the known causes of fracture, road traffic accidents (RTAs) were the most common. Neutered males were over-represented in having a fracture caused by an RTA (P = 0.001) and diaphyseal fractures were significantly more likely to result from an RTA (P = 0.01). Body weight had a positive correlation (r = 0.398) with time to radiographic healing and time to acceptable function (r = 0.315), and was significant (P = 0.014 and P = 0.037, respectively). Of the 57 humeral diaphyseal fractures; 16 (28%) were stabilised using a plate–rod construct, 31 (54%) using external skeletal fixation and 10 (18%) using bone plating and screws only. Open diaphyseal fractures were associated with more minor complications (P = 0.048). There was a significant difference between fixation groups in terms of overall complication rate between groups (P = 0.012). There was no significant difference between fixation groups in time to radiographic union (P = 0.145) or time to acceptable function (P = 0.306).Conclusions and relevanceAll three fixation systems were successful in healing a wide variety of humeral diaphyseal fractures. There was a significantly higher overall complication rate with external skeletal fixators compared with bone plating; however, the clinical impact of these is likely low.

A PLATE-ROD CONSTRUCT FOR REPAIR OF A HUMERAL DIAPHYSEAL FRACTURE IN A BLACK HOWLER MONKEY INFANT

An infant black howler monkey (Alouatta caraya), aged approximately three months, presented with atransverse fracture of the distal third of the right humeral shaft underwent surgical treatment using aplate-rod construct. A 1.00-mm diameter intramedullary pin was used in a retrograde fashion to reduceboth the fracture and plate stress. The plate-rod construct was a seven-hole 1.5-mm veterinary cuttableplate, which was installed following the principles of biological osteosynthesis. The animal presentedno pain in the postoperative exams and used the limb normally. Bone consolidation was observed foreighth weeks after surgery, showing that the treatment was effective.

Posterior atlantoaxial fixation with new subfacetal axis screw trajectory avoiding vertebral artery with customized variable screw placement plate and screws to enhance biomechanics of fixation.

Fixation for atlantoaxial dislocation is a challenging issue, and posterior C1 lateral mass and C2 pars–pedicle screw plate–rod construct is the standard of care for atlantoaxial instability. However, vertebral artery injury remains a potential complication. Recent literature has focused on intraoperative navigation, the O-arm, 3D printing, and recently use of robots for perfecting the trajectory and screw position to avoid disastrous injury to the vertebral artery and enhance the rigidity of fixation. These technological advances increase the costs of the surgery and are available only in select centers in the developed world.Review of the axis bone anatomy and study of the stress lines caused by weight transmission reveal that the bone below the articular surface of the superior facet is consistently dense as it lies along the line of weight transmission A new trajectory for the axis screw 3–5 mm below the midpoint of the facet joint and directed downward and medially avoids the course of the vertebral artery and holds the axis rigidly. Divergent screw constructs are biomechanically stronger. Variable screw placement (VSP) plates with long shaft screws permit manipulation of the vertebrae and realignment of the facets to the correct reduced position with fixation in the compression mode.The video can be found here: https://youtu.be/E1msiKjM-aA

Veterinary Cuttable Plate in a Plate-Rod Construct for Repair of Diaphyseal Femoral Fractures in the Cat.

This study evaluated retrospectively the effectiveness of the veterinary cuttable plate (VCP) in a plate-rod construct, for the treatment of diaphyseal femoral fractures in cats. A total of 29 cats with diaphyseal femoral fracture underwent stabilization with a VCP-rod construct. Fractures were classified as type A (7/29), type B (11/29) and type C (11/29) following the AO classification. Biological osteosynthesis was elected in three type B and 10 type C fractures, and open approach in the other cases. Pin diameter was 2 mm (n = 16) or 2.5 mm (n = 13); this corresponded to a percentage of pin occupation of 39.9 and 53.0% of the intramedullary cavity respectively. The 2.0/2.7-mm VCP and 2-mm screws were used in all cases. The median length of the VCP was 12 holes, and the median number of screws placed in the plate was 6. The median number of cortices engaged per fragment was 6. Ninety-nine percent of the screws were bicortical. Quadriceps contracture was an unacceptable functional outcome in one cat. Follow-up was available in 20 cases. Complete bone healing was assessed in 16/20 cases with a functional outcome considered as full in 17/20, acceptable in 2/20, and unacceptable in 1/20. Telephonic owner outcome assessment was available for five more cats and was considered as full in all cases. The VCP-rod construct is effective to manage all configurations of diaphyseal femoral fracture in cats. The high amount of screw holes per unit length of a VCP allows bicortical screws placement without interfering with the intramedullary rod.

Craniovertebral fixation … a new technique of occipital – cervical fixation

Background: Craniovertebral instability following transoral odontoid excision is usually treated by posterior occipital–cervical fixation using occipital plate and cervical lateral mass fixation with screw rod construct. A patient previously operated for basilar invagination had postoperative infection of both the transoral wound and the posterior implant site which needed removal of the posterior implant earlier.Clinical presentation: The patient presented with severe neck pain, myelopathy, and chronic discharging sinus in the posterior lower aspect the previous neck surgery wound. Reimaging revealed incomplete odontoid excision. He underwent repeat transoral odontoid excision. Treatment of the instability needed occipitocervical fixation avoiding, the atlas, axis (weakened by infection and previous implants), and the infected posterior cervical wound. A new technique using a customized plate rod construct, fixed anteriorly to the mid cervical vertebrae (by a standard mid cervical exposure) with the rods contoured to reach posteriorly through the safe paraspinal corridor and connected with domino connectors to occipital plate rods fixed on either side of midline by additional posterior exposure avoiding the midline scar was planned and executed successfully.Conclusion: This construct transfers the weight of the cranium to the cervical vertebral bodies along the physiological line of weight transmission and can be considered for distraction and reduction of basilar invagination with atlantoaxial dislocation. The technique seems to be safe and reproducible, but will need to tested over time with more cases.

The Pelvic Bridge: A Subcutaneous Approach for Anterior Pelvic Fixation.

An alternative method to external fixation for the treatment of unstable anterior pelvic ring injuries, termed the pelvic bridge technique, provides equivalent results with fewer complications and is performed using occipital cervical rods subcutaneously, with fixation into the iliac wings and parasymphyseal bone. For preoperative planning, review the appropriate imaging, including radiographs and computed tomography (CT) scans, to mesh the findings on imaging to the clinical picture of the patient and ensure that the patient meets operative criteria and that none of the contraindications are present. Position the patient to facilitate anterior and posterior fixation. Make the incisions necessary to expose the osseous contour where fixation will be utilized. Carefully contour the plate-rod construct, which is necessary to minimize postoperative complications. Use care when inserting the rod as doing so will help to avoid neurovascular complications. To recreate pelvic stability, the pelvic ring needs to heal in as close to anatomic position as possible and there are multiple methods that help to obtain an adequate reduction. Multiple constructs may be used to stabilize the anterior pelvic ring, but the fundamental principle is to attach the 2 hemipelves to achieve stability, and the location where fixation can be achieved depends on the fracture pattern. Ensure meticulous closure to reduce the chance of infection and achieve appropriate soft-tissue coverage over hardware. Early mobilization is a fundamental goal of this procedure, but the time to full weight-bearing is dependent on fracture characteristics and healing. Anterior pelvic internal fixation (APIF) using the pelvic bridge technique has been demonstrated to have significantly fewer complications than APEF2.

An anatomical study of plate-rod fixation in feline tibiae.

To investigate the feasibility of placing bi-cortical cortex (B-cort) or mono-cortical locking screws (M-lock) in a plate-rod construct applied to the feline tibia in combination with different intramedullary (IM) pins. Twenty-four feline tibiae of cats were divided into 4 groups, corresponding to IM pin sizes filling approximately 30% (1.0 mm), 40% (1.4 mm), 45% (1.6 mm), and 50% (1.8 mm) of the medullary canal. Computed tomography (CT) was performed to trace potential screw trajectories in each group. A 12-hole, 2.4 mm locking compression plate was then applied on the medial aspect of the tibia. M-lock and B-cort screws were inserted subsequently in each plate hole. Success rates of screw insertion based on CT analysis and cadaveric simulation were compared with screw type, IM pin diameter, and anatomic location as variables. Screw insertion rates were underestimated on CT compared to cadaveric specimens. During cadaveric simulation, B-cort screws could be inserted in all specimens in the 3 most proximal plate holes and in at least 1 of the 3 distal plate holes. The smallest pin size (30%) allowed placement of a greater number of B-cort screws (P < .05) compared to other pins. Fewer B-cort screws could be inserted in the distal diaphyseal region (P < .05) compared to other regions. A total of 99.3% of M-lock screws could be inserted regardless of IMP size. Plate rod constructs can include bicortical screws in the proximal and distal metaphysis, and monocortical screws in the diaphysis, combined with an IM pin filling up to 50% of the medullary canal.

Effect of monocortical and bicortical screw numbers on the properties of a locking plate-intramedullary rod configuration. An in vitro study on a canine femoral fracture gap model.

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

The effect of intramedullary pin size and plate working length on plate strain in locking compression plate-rod constructs under axial load.

To investigate the effect of intramedullary pin size and plate working length on plate strain in locking compression plate-rod constructs. A synthetic bone model with a 40 mm fracture gap was used. Locking compression plates with monocortical locking screws were tested with no pin (LCP-Mono) and intramedullary pins of 20% (LCPR-20), 30% (LCPR-30) and 40% (LCPR-40) of intramedullary diameter. Two screws per fragment modelled a long (8-hole) and short (4-hole) plate working length. Strain responses to axial compression were recorded at six regions of the plate via three-dimensional digital image correlation. The addition of a pin of any size provided a significant decrease in plate strain. For the long working length, LCPR-30 and LCPR-40 had significantly lower strain than the LCPR-20, and plate strain was significantly higher adjacent to the screw closest to the fracture site. For the short working length, there was no significant difference in strain across any LCPR constructs or at any region of the plate. Plate strain was significantly lower for the short working length compared to the long working length for the LCP-Mono and LCPR-20 constructs, but not for the LCPR-30 and LCPR-40 constructs. The increase in plate strain encountered with a long working length can be overcome by the use of a pin of 30-40% intramedullary diameter. Where placement of a large diameter pin is not possible, screws should be placed as close to the fracture gap as possible to minimize plate strain and distribute it more evenly over the plate.

Effect of screw position on single cycle to failure in bending and torsion of a locking plate-rod construct in a synthetic feline femoral gap model.

To evaluate the effect of screw position on strength and stiffness of a combination locking plate-rod construct in a synthetic feline femoral gap model. 30 synthetic long-bone models derived from beechwood and balsa wood. 3 constructs (2 locking plate-rod constructs and 1 locking plate construct; 10 specimens/construct) were tested in a diaphyseal bridge plating configuration by use of 4-point bending and torsion. Variables included screw position (near the fracture gap and far from the fracture gap) and application of an intramedullary pin. Constructs were tested to failure in each loading mode to determine strength and stiffness. Failure was defined as plastic deformation of the plate or breakage of the bone model or plate. Strength, yield angle, and stiffness were compared by use of a Wilcoxon test. Placement of screws near the fracture gap did not increase bending or torsional stiffness in the locking plate-rod constructs, assuming the plate was placed on the tension side of the bone. Addition of an intramedullary pin resulted in a significant increase in bending strength of the construct. Screw positioning did not have a significant effect on any torsion variables. Results of this study suggested that, in the investigated plate-rod construct, screw insertion adjacent to the fracture lacked mechanical advantages over screw insertion at the plate ends. For surgeons attempting to minimize soft tissue dissection, the decision to make additional incisions for screw placement should be considered with even more caution.

The effect of intramedullary pin size and monocortical screw configuration on locking compression plate-rod constructs in an in vitro fracture gap model.

To investigate the effect of intramedullary pin size in combination with various monocortical screw configurations on locking compression plate-rod constructs. A synthetic bone model with a 40 mm fracture gap was used. Locking compression plates with monocortical locking screws were tested with no pin (LCP-Mono) and intramedullary pins of 20% (LCPR-20), 30% (LCPR-30) and 40% (LCPR-40) of intramedullary diameter. Locking compression plates with bicortical screws (LCP-Bi) were also tested. Screw configurations with two or three screws per fragment modelled long (8-hole), intermediate (6-hole), and short (4-hole) plate working lengths. Responses to axial compression, biplanar four-point bending and axial load-to-failure were recorded. LCP-Bi were not significantly different from LCP-Mono control for any of the outcome variables. In bending, LCPR-20 were not significantly different from LCP-Bi and LCP-Mono. The LCPR-30 were stiffer than LCPR-20 and the controls. The LCPR-40 constructs were stiffer than all other constructs. The addition of an intramedullary pin of any size provided a significant increase in axial stiffness and load to failure. This effect was incremental with increasing intramedullary pin diameter. As plate working length decreased there was a significant increase in stiffness across all constructs. A pin of any size increases resistance to axial loads whereas a pin of at least 30% intramedullary diameter is required to increase bending stiffness. Short plate working lengths provide maximum stiffness. However, the overwhelming effect of intramedullary pin size obviates the effect of changing working length on construct stiffness.

A comparison between fixation methods of femoral diaphyseal fractures in cats – a retrospective study

To compare the outcome of three different fixation methods and to determine prognostic factors in cats with diaphyseal femoral fractures. Retrospective analysis of case records of cats with diaphyseal femoral fractures surgically corrected using external fixators, bone plate or plate-rod construct. Outcome was evaluated by estimating the time to bone healing and by calculating the complication rate. In total, an external fixator was used in 30 cases, a bone plate in 20 cases and a plate-rod construct in 56 cases. All methods were successful in achieving bone healing without significant differences. There was a significant difference between the categorized complication rates between the treatment groups. The external fixation group had the most complications overall. When only the major and catastrophic complications were taken into account, it had the fewest complications. The plate-rod construct had the fewest complications overall, with most being major complications. The bone plate group had a complication rate between that of the external fixation and plate-rod construct groups. It had the most catastrophic complications in relative terms. There was no statistically significant difference in the time to achieve bone healing but there was a significant difference in categorized complication rates between the groups.

Ex vivo evaluation of the biomechanical effect of varying monocortical screw numbers on a plate-rod canine femoral gap model

To compare the biomechanical behaviour of plate-rod constructs with varying numbers of monocortical screws applied to an ex vivo canine femoral-gap ostectomy model. Twenty Greyhound dog cadaveric femurs. Bone mineral density (BMD) was assessed with dual x-ray absorptiometry. Bones were assigned to four groups. Bones had a 12-hole 3.5 mm locking compression plate with one bicortical non-locking cortical screw in the most proximal and distal plate holes and an intramedullary Steinmann pin applied across a 20 mm mid-diaphyseal ostectomy. Additionally, one to four monocortical non-locking cortical screws were then placed (Groups 1-4 respectively) in the proximal and distal fragments. Stiffness and axial collapse were determined before and after cyclic axial loading (6000 cycles at 20%, 40%, and 60% of mean bodyweight [total: 18000 cycles]). Constructs subsequently underwent an additional 45000 cycles at 60% of bodyweight (total: 63000 cycles). Loading to failure was then performed and ultimate load and mode of failure recorded. The BMD did not differ significantly between groups. Construct stiffness for group 1 was significantly less than group 4 (p = 0.008). Stiffness showed a linear increase with an increasing number of monocortical screws (p = 0.001). All constructs survived fatigue loading. Load-to-failure was not significantly different between groups. Mean load- to-failure of all groups was >1350N. Ex vivo canine large-breed femurs showed adequate stability biomechanically and gradually increasing stiffness with increasing monocortical screw numbers.

The Use of the String of Pearls Locking Plate System in the Stabilisation of a Comminuted Calcaneal Fracture in a Giant Breed Dog

An eight-year-old male Pyrenean mountain dog was presented with a comminuted fracture of the right calcaneus following motor vehicle trauma. The fracture was stabilised with a plate-rod construct, using the String of Pearls locking plate system and an intramedullary pin. Healing was uncomplicated.

Application of full-scale three-dimensional models in patients with rheumatoid cervical spine

Full-scale three-dimensional (3D) models offer a useful tool in preoperative planning, allowing full-scale stereoscopic recognition from any direction and distance with tactile feedback. Although skills and implants have progressed with various innovations, rheumatoid cervical spine surgery remains challenging. No previous studies have documented the usefulness of full-scale 3D models in this complicated situation. The present study assessed the utility of full-scale 3D models in rheumatoid cervical spine surgery. Polyurethane or plaster 3D models of 15 full-sized occipitocervical or upper cervical spines were fabricated using rapid prototyping (stereolithography) techniques from 1-mm slices of individual CT data. A comfortable alignment for patients was reproduced from CT data obtained with the patient in a comfortable occipitocervical position. Usefulness of these models was analyzed. Using models as a template, appropriate shape of the plate-rod construct could be created in advance. No troublesome Halo-vests were needed for preoperative adjustment of occipitocervical angle. No patients complained of dysphasia following surgery. Screw entry points and trajectories were simultaneously determined with full-scale dimensions and perspective, proving particularly valuable in cases involving high-riding vertebral artery. Full-scale stereoscopic recognition has never been achieved with any existing imaging modalities. Full-scale 3D models thus appear useful and applicable to all complicated spinal surgeries. The combination of computer-assisted navigation systems and full-scale 3D models appears likely to provide much better surgical results.

Orthopedic clinical techniques femur fracture repair

Femur fractures occur commonly in cats and dogs following substantial trauma. Fractures of the femur may be categorized as capital physeal, femoral neck, trochanteric, subtrochanteric, diaphyseal, supracondylar or condylar or distal physeal. Most femur fractures are closed due to the heavy overlying muscle, unless due to a penetrating injury such as a gunshot wound. Femur fractures are generally not amenable to conservative repair, and some kind of internal fixation is generally required. Implant systems suitable for repair of femur fractures include bone plates, interlocking nails, plate-rod construct, lag screws, pins and wires and external fixators. Fractures may be repaired using anatomic reduction and rigid fixation or using the principles of biologic osteosynthesis. Biologic osteosynthesis is particularly effective for highly comminuted fractures because vascular supply and soft tissue attachments to bone fragments are preserved, speeding the formation of bone callus. Articular fractures should be anatomically reduced and rigidly stabilized to reduce the chance of progressive osteoarthritis.

Use of a plate-rod construct and principles of biological osteosynthesis for repair of diaphyseal fractures in dogs and cats: 47 cases (1994-2001).

To determine outcome for dogs and cats with diaphyseal fractures in which a plate-rod construct was used for fracture repair. Retrospective study. 35 dogs and 12 cats. Medical records and radiographs were reviewed to obtain information concerning signalment, fracture severity, construct design, time to radiographic union, complications, and outcome. Clients were contacted by telephone to obtain information on complications, limb usage, and overall satisfaction with the procedure. 31 femoral, 9 humeral, and 7 tibial fractures were assessed. Thirteen fractures consisted of 2 fragments, 22 consisted of 3 to 5 fragments, and 12 consisted of > 5 fragments. Forty-six of 47 (98%) fractures reached union. Mean +/- SD times to radiographic union were 7.5 +/- 2.7 weeks for the dogs and 4.8 +/- 1.3 weeks for the cats. There were 4 short-term, minor complications and 15 long-term complications (2 major and 13 minor). Owners of 21 of 30 dogs (70%) and 9 of 12 cats reported that their animals had normal limb function. Twenty-six of 28 dog owners (93%) and 12 of 12 cat owners indicated that they were satisfied with results of the procedure. As surgery time increased, time to union also increased. Time to union for fractures with > 5 fragments was significantly shorter than time to union for fractures with < or = 5 fragments. Results suggest that plate-rod constructs can successfully be used for repair of diaphyseal fractures of a wide range of severity in dogs and cats.