Rabbit bones are brittle relative to dog and cat bones, and fracture repair carries a high postoperative failure rate.1–4 These failures can occur intraoperatively during the drilling process or, more commonly, fail before bone healing despite appropriate exercise restrictions.4,5 Long bone fractures, particularly of the pelvic limb, are common and are often comminuted.4 These fractures are most often repaired using relatively rigid bridging fixation.2 Primary weight-bearing, plantigrade stance, high motion, and significant overlying soft tissues of the femur make internal fixation with a bone plate and screws desirable over external skeletal fixation.6 A clinical study4 using primarily external skeletal fixation for femur fractures (22/26 fractures) resulted in an unacceptably high nonunion rate of 27%, further supporting the benefit of optimizing internal fixation.
The cause of high postoperative failure after bone plate and screw placement in rabbits has been investigated ex vivo. When drilled by hand, only a 1.1-mm defect, the core diameter of a 1.5-mm screw, did not weaken the rabbit femur beyond 50% of its original torsional strength, considered the acceptable loss in strength for a surgically created defect.1,7 However, when a mechanical testing machine was used to drill with a standard axial load torque, 1.5-mm drill holes, the core diameter of a 2.0-mm screw, could be created without exceeding 50% torsional strength.8 The decrease in bone mechanical performance resulting from drilling with a conventional (standard) surgical drill bit, a Kirschner wire (K-wire), or an acrylic drill bit intended for gradual widening of brittle materials was investigated.8 These data demonstrated that the maximum torque and force to create a hole was greater with the K-wire than either of the drill bits tested, as was the integral of force and displacement. Also, placing the K-wire generated more heat and led to the greatest loss of torsional strength. These results suggest the K-wire was the most damaging of the holes created.8
Previous studies9,10 demonstrate the importance of decreasing mechanical and thermal damage during the drilling process, as intrinsic processes of self-repair can be overwhelmed by the propagation of microcracks and by increasing osteonecrosis. In pigs, microcracks have been demonstrated to form in parallel and transverse to the tool feed direction, with transverse microcracks easily propagating up and down the osteon.11 The microstructure of the bone tissue and bone drilling technique has an influence on microcrack production.12–15 Drilling forces do not necessarily correlate with bone damage, making histologic evaluation imperative to the understanding of the damage caused by drilling.11
The purpose of this study was to histologically evaluate rabbit femoral bone for macro- and microdamage after the creation of bicortical 1.5-mm-diameter holes using a standard surgical drill bit, an acrylic drill bit, and a K-wire. The authors hypothesized that the microdamage of femoral rabbit bone would be greater with the K-wire than the standard surgical and acrylic drill bits.
Methods
Study design
Microdamage caused by drilling with a drill bit (1.5-mm surgical drill bit [DePuy Synthes Vet], 1.5-mm acrylic drill bit [Plexi-Point Drill; Vortex Tool Company Inc], or 1.5-mm K-wire [1.5-mm-diameter half-point wire; Hofmann]) was histologically evaluated using 10 rabbit femora (5 pairs). The geometry of each drill bit and K-wire was described previously.8 Each femur was divided into 4 proximodistal sections, and each test (1.5-mm surgical drill bit, 1.5-mm acrylic drill bit, 1.5-mm K-wire, and intact control) was systematically assigned a location on the bone as described below. Each drill bit or K-wire was cycled for each test to ensure equivocal usage, and each was used no more than 8 times.
Specimen preparation
Skeletally mature female intact New Zealand white rabbits, mean weight of 3.75 kg (range, 3.28 to 4.2 kg), euthanized for reasons unrelated to this study at an outside facility were used. Therefore, no IACUC was needed. Rabbits were frozen whole at −20 °C following euthanasia. Each rabbit was thawed at room temperature, was weighed, and had both femora harvested. The dissected femora were wrapped individually in saline-soaked towels and stored in sealed plastic bags at −20 °C until testing.
The femora were thawed at 4 °C for 24 hours before use. Craniocaudal and lateromedial digital radiographs (NEXT Equine DR Digital Radiography System and HF100/30+ MinXray Generator) of the femora were obtained at 48 kVp and 2 mAs. Femora were excluded from the study if any orthopedic abnormalities were noted including trauma, fracture, neoplasia, or osteoarthritis. Bone dimensions were obtained with digital calipers (Absolute Digital Caliper Series 500) as previously described1 and were recorded.
Five pairs of femora were used. Each bone was divided into 4 equally spaced locations along the diaphysis of the bone for the drill-type treatment (surgical drill bit, acrylic drill bit, K-wire, and intact control). The location of each treatment was systematically shifted from proximal to distal by one “location” for each bone, choosing left then right of each pair, and the pair was selected randomly. Four (4) pairs of femora were drilled using a surgical drill (4300 cordless driver; Stryker) attached to and controlled by a mechanical testing machine (Model 809 Axial-Torsional Testing System; MTS Systems Corp), and 1 pair was drilled free hand (4300 cordless driver; Stryker). Drilling location was determined by marking the diaphysis of the bone from the lesser trochanter to the proximal aspect of the trochlear groove into 4 equally spaced segments. Bicortical drill holes were created from lateral to medial in the center of each segment under continuous room-temperature water irrigation. Machine drilling was completed as previously outlined; the femoral epiphyses were potted in polymethylmethacrylate (PMMA) for fixation on the mechanical testing system and drilled using a standard axial speed/displacement rate of 0.5 mm/s with the drill bit rotated at 500 rpm.8 Average force was 24 N as measured in a previous study.8 Hand drilling was performed by placing the drill (4300 cordless driver; Stryker) on the bone through an appropriately sized drill guide and only applying the load associated with the weight of the drill (10 N) without additional manual pressure, although hand-arm weight could add up to an additional 10 N when measured in the previous study.8 Drill bits and K-wires were reused, with up to 8 reuses per component.
Histologic preparation
Transverse sections (4 mm thick) of the diaphysis that captured the drill holes were cut using a precision bandsaw (300 CP & 310 saw; Exakt Technologies) and then stained en bloc in basic fuchsin in ascending grades of ethanol (70, 80, 90, then 100%) for 2 days each grade. Sections were infiltrated with glycol methacrylate (Technovit 7200; Exakt Technologies) after dehydration in 100% ethanol. Infiltration was done in sequential concentrations under vacuum and continuous agitation (2 days each: twice in 100% ethanol; 70% ethanol and 30% glycol methacrylate [Technovit 7200; Exakt Technologies]; 30% ethanol and 70% glycol methacrylate; completing 2 then 7 days of 100% glycol methacrylate). Sections were block polymerized with 8 hours of light (Histolux; Exakt Technologies). Hardened blocks were mounted (Technovit 4000 and 7210; Kulzer Technik) on 25 X 75-mm plastic slides, sectioned to 300-µm thickness, and then ground and polished to 40-µm thickness (400 CS grinder [Exakt Technologies] and Buehler MicroPolish II). A glass coverslip was glued (Cytoseal 60; Thermo Fisher Scientific) to the dry slides before imaging under transmitted white light microscopy. All histologic preparation was performed simultaneously by the same personnel to avoid variation in technique.
Data analysis
Images of the diaphysis were acquired on a microscope (Olympus Vanox-T AH-2 Microscope; Evident Corp) at 4X objective by a blinded evaluator. The tissue surrounding the drill hole (0.5 mm from hole edge) was further analyzed at 10X objective. A standard region of interest of bone next to both sides of each hole was created by drawing a line along the hole edge and a second line 250 µm from the edge, and the resultant bone area was calculated. Damaged bone was subjectively defined as regions with visible chips/fractures and with positive basic fuchsin stain emanating from a region that was deformed or peeling away with the appearance of microdamage at a higher magnification (Figure 1). The damaged area was reported as a percentage of the region of interest. The damage in these areas was quantified in each location (cis- or transcortex), drill contact (entrance or exit of the cortex), and total (sum of damage area of both cortices divided by the sum of the standardized total area measured). The cortical thickness was measured from the cis- and transcortex at the same location as the damaged area.
Example of the region of interest used for determination of bone damage area. A standard area of bone next to both sides of the hole was created by drawing a line along the hole edge and a second parallel line 250 μm away, capturing the bone area of that region. The damaged bone area was measured and reported as a percent damage area relative to the standard area. Green outline denotes region of interest, and blue outline denotes damaged region. The damaged areas (% total) were measured by location (cis- or transcortex), drill contact (entrance or exit of the cortex), or total (both cortices). Scale bar = 250 µm.
Citation: American Journal of Veterinary Research 86, 1; 10.2460/ajvr.24.07.0198
Unassociated with the fuchsin stain emanating damaged area defined above, large black cracks were found. The anatomy of the cracks was noted, and the number of these cracks was counted.
Statistical analysis
The damaged area measured using histopathology was compared among drilling methods using a multiway ANOVA with drilling direction (cis- or transcortex) and contact (entrance or exit), the interaction of drill method with direction, and limb as fixed effects. The sampling location from proximal to distal and the cortex thickness were included as a fixed effect but were not significant for damage results when stain-emanating perihole damage was assessed, so they were subsequently removed from the model. Rabbit was included as a random effect and drilling method (hand drilling vs machine drilling) as a fixed effect. Cortical thickness and the number of large black cracks were compared among drilling methods using an ANOVA with drilling direction and sampling location as fixed effects. Pairwise comparisons were made using the Tukey honestly significant difference post hoc tests. Normality of the residuals from the analysis of variance was tested using the Shapiro-Wilk statistic (SAS, version 9.4; SAS Institute Inc). Because all variable residuals were not normally distributed, the variables were rank transformed before obtaining ANOVA outcomes. Linear regressions (Proc Reg; SAS, version 9.4; SAS Institute Inc) were performed to evaluate the association between the stained damage region (total, by contact location or direction), and the number of times each drill or pin was used. Significance was defined as P < .05.
Results
One femur was fractured while machine drilling with the acrylic drill bit and was subsequently excluded from the study. Therefore, 9 rabbit femurs and 36 locations were included in the analyses. Two K-wire and 1 standard drill bit samples were lost during histological processing. The drilling method (free hand vs machine assisted) had no significant effect on histologic damage (fuchsin stain emanating perihole damage) in the ANOVA model, so results were analyzed by combining free-hand and machine-assisted drilling data. There was no significant effect of the proximal-to-distal location of the drill site or cortex thickness on damage, so results excluded proximal-to-distal location from the ANOVA damage model.
Large apparent black cracks around the entire cortex were identified in all machine-drilled samples, running both circumferentially and radially, and were unassociated with adjacent stain intensity (Figure 2). Some cracks appeared associated with Haversian canals and/or lamellar orientation but did not appear associated with the drill holes as there was no more cracking at the drill hole than the entire cortex cross-section. Intact (nondrilled) sections also demonstrated cracking.
A transverse section of intact bone demonstrating the presence of large black cracks. Some appear associated with Haversian canals and/or lamellar orientation but did not appear associated with drill holes in drilled bone sections. There were a higher number of cracks counted in the intact regions of bone. These were only present in bones potted in polymethylmethacrylate for machine drilling and were not present in the bones held and drilled by hand, potentially indicating a detrimental effect of the heat and/or rigidity created by polymethylmethacrylate. Scale bar = 1 mm.
Citation: American Journal of Veterinary Research 86, 1; 10.2460/ajvr.24.07.0198
While no difference was found in the measured area of fuchsin-stained damage, the method of drilling (hand or machine drilling) had a significant effect on the number of large cracks identified in the bone. The 23 machine-drilled sections had a median of 10 cracks (range, 2 to 40) and 8 hand-drilled sections had zero cracks. The median number of the large cracks were 10, 7.5, 15, and 7.5 at the proximal to distal sites, respectively. There was not a directional trend proximal-to-distal nor were there more cracks near the ends that were embedded in PMMA. There was a significant effect of drill type (including nondrilled intact section) on the number of large cracks. The intact section had the largest number of these cracks (median of 15); the acrylic and standard drill bits had a median of 10 and 7.5, respectively; and the K-wire had a median of 5. The cracks did not appear to be emanating from or concentrated near the drill holes but rather distributed throughout the cortex. Pairwise comparisons between drill types were not analyzed further.
The K-wire sections demonstrated a larger percent area of basic fuchsin-stained cracks/damage compared to the acrylic bit and the standard bit (P = .010 and .010, respectively). The K-wire created a larger percent area of damage than the acrylic or standard bit at the ciscortex (P = .001 and <.001), at the entrance of each cortex (P = .029 and .010), and at the exit of each cortex (P = .012 and .024). At the transcortex, the K-wire created more percent damage than the acrylic drill bit (P = .011) and the standard surgical drill bit (P = .051, Figure 3). No statistical difference in percent damage was found between the 2 drill bits regardless of the location measured (P ranging from 0.061 to 0.907; Table 1).
Examples of different degrees and locations of damage created by each test. A—Surgical drill bit was used, creating no damage to the surrounding bone. B—Use of an acrylic drill bit resulting in cracking at the exit point of the transcortex. C—Kirschner wire created the most substantial damage, in this case with cracking noted at both the entrance (arrowhead) and exit (arrow) of the transcortex. Scale bars = 250 μm.
Citation: American Journal of Veterinary Research 86, 1; 10.2460/ajvr.24.07.0198
Percent damaged area of region of interest of bone containing damage after bicortical drilling with an acrylic drill bit, standard surgical drill bit, and Kirschner wire.
| Percent damaged area | |||
|---|---|---|---|
| Parameter | Acrylic drill bit | Standard drill bit | Kirschner wire |
| Total cortex | 2.91 (1.36–7.98)a [0.26, 1.39] | 3.16 (0–20.01)a [–0.24, 2.47] | 10.60 (3.43–15.90)b [1.37, 3.52] |
| Ciscortex | 0.55 (0–3.11)a [–0.04, 1.02] | 0.09 (0–0.65)a [–0.01, 0.19] | 2.12 (0.49–5.62)b [0.47, 2.09] |
| Transcortex | 1.53 (0–7.52)a [0.13, 2.13] | 3.16 (0–19.35)a,b [–0.70, 5.26] | 7.08 (2.37–11.46)b [1.70, 5.53] |
| Entrance of cortex | 0.23 (0–3.82)a [–0.01, 0.99] | 0.00 (0–3.16)a [–0.16, 0.74] | 2.31 (1.06–8.16)b [0.83, 3.10] |
| Exit of cortex | 2.02 (0–7.52)a [0.11, 2.22] | 1.01 (0–19.35)a [–0.85, 4.72] | 6.93 (2.37–11.34)b [0.96, 4.89] |
Values are shown as mean (range) and [lower, upper 95% confidence limits].
P < .05. The values within a row that do not share a superscript differ statistically.
There was a significant effect of proximal-to-distal location on cortex thickness (type 3 fixed effects; P < .001). The cortical thickness increased from distal (mean, 1.09 mm) to proximal (mean, 1.31 mm; Table 2). Intact histologic sections were used as a subjective reference to ensure bones appeared physiologically normal and staining accurately reflected microcracks. There were no microcracks, other than large black cracks, in intact sections. Neither drill bit nor K-wire had a significant association of use/reuse with microdamage, including total percent damage and damage based on drilling direction and contact (Figure 4).
Diaphyseal location and cortical thickness of the cis- and transcortices.
| Diaphyseal location | n | Cortical thickness (mm) |
|---|---|---|
| Proximal | 26 | 1.313 (0.131) [1.260, 1.366] |
| Mid proximal | 28 | 1.255 (0.159) [1.194, 1.317] |
| Mid distal | 14 | 1.103 (0.116) [1.059, 1.129] |
| Distal | 24 | 1.094 (0.083) [1.036, 1.170] |
Values are shown as mean (SD) and [lower, upper 95% confidence limits].
Bone location had a significant effect on cortex thickness, with thickness increasing from distal to proximal locations of the femoral diaphysis.
No difference was found with repeated drill bit or Kirschner wire use in total damaged area (%) as defined by fuchsin-emanating regions in the perihole bone. The dots represent the damage area (total) for each sample plotted against number of uses of the respective drill bit. The lines are the best-fit linear regression for each drill type.
Citation: American Journal of Veterinary Research 86, 1; 10.2460/ajvr.24.07.0198
Discussion
The K-wire created more microdamage adjacent to the drill hole to rabbit bone than the acrylic or standard surgical drill bits, supporting the hypothesis. There were no observed differences between bone damage associated with drilling using acrylic or standard surgical drill bits. Large cracks throughout the bone cortex were associated with machine drilling but not hand drilling.
Clinically, fractures repaired with internal bone plate and screws as well as external fixation using K-wire have a high rate of intra- and postoperative failure.2–5 The difference seen between drill types in these data supports that mechanical damage during the drilling process may not be the only factor that leads to postoperative failure, as there is no evidence that external fixation with K-wire is less successful than internal fixation with a bone plate and screws. Later steps in the surgical procedure or subsequent bone necrosis, including the insertion of the screw and/or the rigidity/mechanical behavior of the construct, may contribute to bone weakening and failure and need to be studied.
The success of any surgical repair is dependent on host and environmental factors as well as several mechanical factors, including microcracks that are produced in the bone.14 Rabbit bone has a primary structure with longitudinally oriented vascular canals. Predisposition to crack propagation along that canal network may decrease fracture toughness.16 Iatrogenic microcracks form after surgical drilling in addition to being present as part of the inherent cyclical damage to the bone structure.10,14,15,17,18 Fatigue damage can lead to increased microcracks and decreased bone stiffness and elastic modulus.11,18–21 In humans, this microdamage increases with age and is more common in females, leading to stress fractures after accumulating fatigue damage.10,17,22 In an already brittle bone model, this could indicate that the placement of implants and the location of associated microcracks further add to the brittleness and increased fragility of the bone and perpetuate postoperative failure through stress-fracture-like mechanics.
Microcracks formed during drilling can accumulate at a rate beyond the bone’s natural repair mechanism. In bovine bone, the mean length of these iatrogenic cracks was 300 µm, which is subject to creating stress fractures and failure of the bone.15,23 After drilling, microcrack extent and severity are inversely correlated to the pull-out strength of screws, weakening the strength of repair at the screw-bone interface.14 In this study, the K-wire created more microdamage surrounding implantation than either of the drill bits used and therefore, clinically, could lead to poor K-wire stability before adequate bone healing. There was no difference between the damage created by the 2 drill bits, traditional surgical and acrylic, although both created microcracks. The effect of iatrogenic microcracks on fracture healing in brittle rabbit bone is unknown.
The cause of the large black cracks in all machine-drilled samples, but none of the hand-drilled specimens, is unknown and not typically seen from drilling holes in bone.24 The hand-drilled sections were all performed in 1 rabbit, so rabbit variation cannot be excluded, although husbandry and age were similar and there was no other indication of differences between specimens. There are 2 other possible contributing factors. The ends of the femur were potted in PMMA for attachment to the mechanical testing system for machine-drilled, but not hand-drilled, specimens. The fact that there were no cracks in hand-drilled specimens, which were not potted in PMMA for drilling, suggests that potting the bone ends in PMMA and the heat derived from PMMA setting up may have contributed to crack generation. However, large crack distribution did not differ among bone diaphyseal sections closer to the PMMA than other sections. Burr and Stafford24 suggest that bone microdamage can occur during preparation, which could explain the large black cracks. Their study24 concluded that in vivo microdamage exhibits a halo of increased basic fuchsin stain on histology, whereas artifactual microcracks do not. This is consistent with our findings in which basic fuchsin staining cannot be determined due to the black coloration of the large cracks, but no halo of coloration exists surrounding these defects. The cracks were not focal to drilling regions and were seen in intact regions, which had a larger number of cracks than the drilled cross-section. However, the lack of cracks in hand-drilled specimens, which were similarly processed to machine-drilled specimens, indicates that histologic processing including exposure to PMMA and associated heat was not a factor. Second, the magnitude of force applied by the drill bit during drilling may have been different between machine-drilled and hand-drilled specimens, and the machine-drilled specimens were more securely stabilized during drilling than hand-drilled specimens. Consequently, a greater bending moment may have been applied to machine-drilled specimens causing bending deformation and crack formation. Further investigation is required to determine the cause of these cracks. For this study, damage was defined by the region at the drill-hole interface to allow direct comparisons between samples. The large black cracks were considered an unrelated finding to the drill tool and were not defined as damage in this study; however, further studies would be beneficial to determine the cause of these cracks, as they could affect the recommended method for potting and testing rabbit bone samples and for drilling bone in rabbit patients.
There has been no consensus on optimal drill design for cortical bone,25 and the authors sought to examine whether a drill bit designed for acrylic materials may improve the drilling of brittle bone by encouraging a gradual widening of the hole and reducing slippage.26 This was supported by studies27–29 demonstrating that drill specifications, including diameter, cutting face, helix angle, and drill point, are responsible for differing thermal damage to surrounding bone. Thermal damage was not assessed in the current study. However, thermal damage had no effect in a previous study,8 and the acrylic and surgical drill bits created similar microdamage to the surrounding bone.
One bone in this study was drilled by hand, whereas the others were drilled using the testing machine at a constant speed, advancement rate, and position about the thrust axis. Most studies25,27,30–34 evaluating the influence of drill speed and advancement rate have focused on associated thermal changes and bone necrosis without consistent results. This study did not show significant difference in mechanical damage adjacent to the drill hole between the 2 drilling methods, although numbers were limited and bone microstructure variation among the specimens was not assessed. While there was no histologic difference in damage adjacent to the drill hole, previous studies1,8 have shown an improvement in torsional strength to failure when rabbit bone drilling is performed by a loading machine to control for advancement rate and decrease “wobble” that may be created when drilling by hand. While this could indicate that the amount of microdamage is not associated with torsional strength, this should be interpreted cautiously given the small sample size in the current study. Further studies examining the correlation between these factors in rabbit bones are warranted.
While these samples were tested by drilling at a central/bisecting point of the diaphysis, rabbit femora are not cylindrical, and the drill bit may not have been perfectly perpendicular to the bone cortex. The influence of this on drilling biomechanics and subsequent damage to the surrounding bone is unknown, although this degree of variation is likely clinically relevant.
Drill bits and K-wire were used repeatedly in this study, with up to 8 uses per component. The damaged area did not differ with reuse in this study, and the reuse of drill bits and K-wire likely reflects many clinical settings.35 Numerous studies36–39 have evaluated the repeated use of drill bits in bone models, demonstrating decreased bone cell viability, bone tissue damage, increased heat production, and increased cutting force and torque associated with increased drill bit wear, primarily along the cutting edge. These studies evaluated repeated drilling over 30–100 uses, likely supporting that 8 uses would be less critical. Specifically with rabbit bones, cell viability was not altered until the 30th usage of a drill bit, and increased soft tissue damage and bone heating were caused after 50 reuses.36,37 A previous study8 using rabbit femora demonstrated temperature increases at the ciscortex more notably with a K-wire compared to the standard drill bit. While this is consistent with increased microfractures associated with the K-wire, another study11 demonstrated no direct association between heat and microdamage. Further research is warranted to determine relationships between drill/pin reuse, thermal damage, microdamage, and healing potential of brittle rabbit bones.
Further studies are required to determine if the most damaging surgical step occurs later in the fracture repair procedure, either during screw insertion or due to the biomechanical properties of the plate-screw-bone construct itself. Microdamage around a drill hole has been associated with decreased screw pull-out strength in human bone, but the effects of screw placement itself on the integrity of the bone were not analyzed.14 As the cutting parameters and amount of required bone clearance vary between surgical screw designs, the damaging/biomechanical effect of screw insertion on bone likely also varies. Variance in bone biomechanical performance has been demonstrated in veterinary studies30 evaluating unique screw designs. Another screw variable that may affect the strength of the construct is the thread pitch. This is particularly relevant in bones with thin cortices as seen in rabbit bone. Cortical screws, with a larger thread pitch than locking screws, may have very few threads engaging the cortices, likely contributing to decreased resistance to screw pullout. Locking screws and smooth pins do not depend on thread engagement in cortices. Yet, locking screws used in clinical rabbit patients are associated with catastrophic failure postoperatively.2 The stiffness of the locking construct may be too rigid for brittle rabbit bone because a stiff implant leads to increased stress at specific bone-implant interfaces relative to a compliant implant. This is a previously recognized issue in human osteoporotic bone, and work is being done to dynamize implant design to better distribute the stress at the bone-implant interface.40 The brittleness of the repaired bone construct may, in contrast, be the primary issue weakening bone and resulting in catastrophic failure during the recovery period. In this case, repairing these fractures with something less rigid such as nonmetallic implants may be superior.41 This could be supported by the clinical success of pins/external fixation, despite creating more damage at the pin-bone interface, as it creates a more compliant construct and allows some micromotion in the construct at the pin-bone interface.
This study was limited by its ex vivo nature and the limited sample size, particularly associated with hand drilling versus machine drilling. Further studies are required to demonstrate in this species whether the presence and severity of microdamage is associated with the ultimate strength of a construct. Additional studies can also determine if later steps in implant placement, such as screw insertion and screw design, are associated with further damage to the peri-implant bone.
This study demonstrates that more microdamage is created when a K-wire is drilled through brittle rabbit bone than when standard surgical or acrylic drill bits are used. Further investigation is warranted to determine whether other stages of the surgical repair or the fixation method itself is responsible for increased damage and weakening of the bone resulting in an unacceptably high clinical failure rate.
Acknowledgments
The authors acknowledge that a pathologist will be used in future manuscripts with histology. Testing was performed at the JD Wheat Veterinary Orthopedic Research Laboratory, School of Veterinary Medicine, University of California-Davis. The authors thank Celina Bravo, Catalina Laughrin, and Justin Irvin for technical assistance.
Disclosures
The authors have nothing to disclose. No AI-assisted technologies were used in the generation of this manuscript.
Funding
This work was supported by grants from the Center for Companion Animal Health, School of Veterinary Medicine, University of California-Davis.
ORCID
A. Massie https://orcid.org/0000-0002-0598-4200
D. Marcellin-Little https://orcid.org/0000-0001-6596-5928
P.-Y. Chou https://orcid.org/0000-0002-0344-5465
S. Stover https://orcid.org/0000-0002-2111-7887
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