Novel Achilles tendon repair technique utilizing an allograft and hybrid external fixator in dogs.

Background: Achilles mechanism rupture is a surgical condition involving primary tenorrhaphy with various described means of surgical augmentation and bolstering. Aim: To report complications and outcomes with a novel Achilles repair technique in dogs using a superficial digital flexor tendon (SDFT) or deep digital flexor tendon (DDFT) allograft. Methods: Medical records were reviewed for dogs with chronic rupture or deterioration of the Achilles mechanism. Fibrous tissue was excised and either primary tenorrhaphy or reattachment of the tendon(s) to the calcaneus was performed. The surgical repair was supplemented by an SDFT or DDFT allograft, and postoperative immobilization was provided using a transarticular hybrid external skeletal fixator. Complications were classified as minor, major, or catastrophic, and function was classified as full, acceptable, or unacceptable, based on established guidelines. Results: Complications occurred with 6 out of 12 repairs, including 1 minor, 6 major, and 2 catastrophic complications. The two catastrophic complications were the recurrence of tarsal hyperflexion and lameness at 20 weeks and 18 months following surgery. Of the 12 surgeries performed, 2 resulted in full function, 8 with acceptable function, and 2 with unacceptable function at last follow-up 17-98 weeks postsurgery (mean = 45 weeks) for a success rate of 10/12 cases. Conclusion: The use of SDFT or DDFT allografts, coupled with an external fixator, can provide a moderate rate of full or acceptable functional outcomes and appears a viable treatment. However, complications were frequent and without a comparison group no conclusions can be drawn about the inferiority or superiority of this technique to other techniques for Achilles mechanism repair in dogs.

Comparison of osteotomy level with three different canine total hip replacement systems.

Background: Numerous cementless total hip replacement (THR) systems are available for application in dogs and one of the potential differences among these systems is the technique for performing a femoral osteotomy and the amount of bone preserved in the calcar region. However, no quantitative comparison of osteotomy level has been performed for canine THRs to date. Aims: To develop and validate a method for quantifying the level of the osteotomy at its most distomedial aspect in conjunction with canine THR and to compare osteotomy level between multiple different THRs. Methods: Immediate post-operative cranial-caudal or caudal-cranial radiographs of 33 dogs treated with 17 Helica and 17 BFX THR were assessed and osteotomy level was quantified using a novel radiographic assessment by 3 independent observers. Correlation among observers was quantified using a Spearman rank order correlation. Osteotomy location was subsequently quantified for an additional 10 Zurich THRs. The osteotomy level for each THR was subsequently compared between Helica, BFX, and Zurich THRs using one-way non-parametric Mann-Whitney rank sum tests and significance set at p < 0.05. Results: R-values assessing correlation between observers were 0.87, 0.72, and 0.60. Osteotomy location was significantly more proximal in conjunction with the Helica (0.75 ± 0.22) versus the BFX (0.97 ± 0.13; p < 0.001) and Zurich (1.1 ± 0.15; p < 0.001) femoral prostheses. Osteotomy location was also significantly more proximal with the BFX prosthesis in comparison to the Zurich THR (p < 0.05). Conclusion: The strong correlations among three different observers indicate that the technique for measuring the location of the distomedial aspect of the osteotomy was acceptably precise. The osteotomies made in conjunction with the short-stemmed Helica implants were significantly more proximal than those made with both of the long-stemmed (BFX and Zurich) femoral prostheses. The distomedial aspect of the osteotomy with the BFX system was significantly more proximal than that with the Zurich THR, indicating that between these two long-stemmed systems the osteotomy level is unique.

Randomized Controlled Trial Comparing Autologous Protein Solution to Hyaluronic Acid Plus Triamcinolone for Treating Hip Osteoarthritis in Dogs.

Twenty-three dogs with bilateral hip osteoarthritis were used to compare the efficacy of intra-articular injections of autologous protein solution (APS) to hyaluronic acid plus triamcinolone (HAT). Prior to treatment, owner assessments of pain and mobility were obtained using the canine brief pain inventory (CBPI) and Liverpool Osteoarthritis for Dogs (LOAD) questionnaires. Owners were also asked to list all medications used to control signs of pain associated with hip osteoarthritis (OA). In addition, objective kinetic data using a pressure sensitive walkway was used to quantify the relative weight bearing of each of the limbs (total pressure index; TPI). One hip was then selected using a random number generator for injection with HAT and the contralateral hip was injected with APS under the same sedation event. At 1-, 3-, and 6 months following injection, medication usage was recorded and dogs were re-assessed using the CBPI and LOAD questionnaires and using objective gait analysis to determine the TPI. Twenty dogs completed all aspects of the study and statistically significant (p < 0.05) improvements were noted by dog owners at every post-treatment time point in every category of pain and mobility as assessed by the CBPI and LOAD questionnaires. Only 5 dogs, compared to 14 pre-treatment, received any oral NSAID or other analgesic for the duration of the 6-month study period. The TPI, and change in TPI from baseline, were not statistically significantly different between the two treatments at any time point. These data suggest clinical efficacy of both APS and HAT, but fail to show superiority of one treatment vs. the other. The inability to detect a statistically significant difference between the two treatments could be attributable to a true lack of a difference, or a type II statistical error.

Complications with the Zurich Canine Total Hip Replacement System in an Initial Series of Cases Performed by a Single Surgeon.

OBJECTIVE: The aim of this study was to quantify the complications using the Zurich total hip replacement system in an initial series of cases performed by a single surgeon who had experience with other total hip replacement systems. MATERIALS AND METHODS: This was a retrospective study in which complications were classified as major if any treatment was needed or if the outcome was less than near-normal function. Complications that did not warrant treatment and that did not result in function that was inferior to near-normal were considered minor. Outcomes were assessed by radiographic review, physical examination, subjective gait evaluation or, in one case, by objective gait analysis. Bilateral total hip replacements were considered separate procedures. RESULTS: The first 21 procedures in 19 dogs performed by a single surgeon were included. The mean time to follow-up was 48 weeks (range: 8-120 weeks; standard deviation: 36 weeks). Two cases (of 21) experienced major complications including one dog with excess internal femoral rotation during weight bearing and one dog having luxation. One case (of 21) had a minor complication; femoral fracture in the presence of an intact bone plate that maintained alignment and healed without treatment. CLINICAL SIGNIFICANCE: A high rate of successful outcomes with few major complications can be obtained in the initial cases treated using the Zurich total hip replacement system for surgeons with prior experience with other total hip replacement systems.

Outcomes Associated With Osteochondral Allograft Transplantation in Dogs.

The purpose of this study was to retrospectively characterize outcomes and complications associated with osteochondral allograft transplantation for treating chondral and osteochondral lesions in a group of client-owned dogs with naturally-occurring disease. Records were reviewed for information on signalment, treated joint, underlying pathology (e.g., osteochondritis dissecans; OCD), and type, size, and number of grafts used. Complications were classified as "trivial" if no treatment was provided, "non-surgical" if non-surgical treatment were needed, "minor surgical" if a minor surgical procedure such as pin removal were needed but the graft survived and function was acceptable, or "major" if the graft failed and revision surgery were needed. Outcomes were classified as unacceptable, acceptable, or full function. Thirty-five joints in 33 dogs were treated including nine stifles with lateral femoral condyle (LFC) OCD and 10 stifles with medial femoral condyle (MFC) OCD treated with osteochondral cylinders or "plugs." There were 16 "complex" procedures of the shoulder, elbow, hip, stifle, and tarsus using custom-cut grafts. In total there were eight trivial complications, one non-surgical complication, two minor surgical complications, and five major complications for a total of 16/35 cases with complications. Accordingly, there were five cases with unacceptable outcomes, all of whom had major complications while the other 30 cases had successful outcomes. Of the 30 cases with successful outcomes, 15 had full function and 15 had acceptable function. Based on these subjective outcome assessments, it appears osteochondral allograft transplantation is a viable treatment option in dogs with focal or complex cartilage defects. However, no conclusions can be made regarding the inferiority or superiority of allograft transplantation in comparison to other treatment options based upon these data.

Corrigendum: Outcomes Associated With Osteochondral Allograft Transplantation in Dogs.

[This corrects the article DOI: 10.3389/fvets.2021.759610.].

T1ρ, T2 mapping, and EPIC-µCT Imaging in a Canine Model of Knee Osteochondral Injury.

The dog is the most commonly used large animal model for the study of osteoarthritis. Optimizing methods for assessing cartilage health would prove useful in reducing the number of dogs needed for a valid study of osteoarthritis and cartilage repair. Twelve beagles had critical-sized osteochondral defects created in the medial femoral condyle of both knees. Eight dogs had T1ρ and T2 magnetic resonance imaging (MRI) performed approximately 6 months after defect creation. Following MRI evaluations, all 12 dogs were humanely euthanatized and cartilage samples were obtained from the medial and lateral femoral condyles, medial and lateral tibial plateaus, trochlear groove, and patella for proteoglycan and collagen quantification. Equilibrium partitioning of an ionic contrast (EPIC)-µCT was then performed followed by the histologic assessment of the knees. Correlations between T1ρ, T2, EPIC-µCT and proteoglycan, collagen, and histology scores were assessed using a multivariate analysis accounting for correlations from samples within the same knee and in the same dog. Pearson's correlation coefficients were calculated to assess the strength of significant relationships. Correlations between µCT values and biochemical or histologic assessment were weak to moderately strong (0.09-0.41; p < 0.0001-0.66). There was a weak correlation between the T2 values and cartilage proteoglycan (-0.32; p = 0.04). The correlation between T1ρ values and cartilage proteoglycan were moderately strong (-0.38; p < 0.05) while the strongest correlation was between the T1ρ values and histological assessment of cartilage with a correlation coefficient of 0.58 (p < 0.0001). These data suggest that T1ρ shows promise for possible utility in the translational study of cartilage health and warrants further development in this species. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 38:368-377, 2020.

A Pilot Clinical Study Assessing Treatment of Canine Hip Dysplasia Using Autologous Protein Solution.

Five dogs with bilateral hip dysplasia and without osteoarthritis of other joints were enrolled in this pilot study. Objective kinetic data using a pressure sensitive mat and owner assessments using the canine brief pain inventory (CBPI) and Liverpool Osteoarthritis for Dogs (LOAD) questionnaires were obtained prior to treatment. Enrolled dogs were treated in one hip with autologous protein solution (APS) and the contralateral hip was injected with an equal volume of saline. The hip to be treated was selected using a random number generator. At exactly 28 days following treatment dogs were re-assessed using the pressure sensitive mat and the CBPI and LOAD questionnaires. No dogs were treated with any other medications or supplements throughout the study period. Assessment of the total pressure index (TPI) collected using the pressure sensitive mat showed that the hips treated with APS improved significantly more than hips treated with saline (p = 0.0005) and that the hips treated with APS bore significantly more weight than the hips treated with saline at day 28 (p < 0.05). Statistically significant improvement was noted by owners in "pain" and "function" as assessed by the CBPI as well "mobility at exercise" using the LOAD questionnaire. This pilot study provided proof of principle that APS is beneficial in treating pain and lameness in dogs affected by coxofemoral osteoarthritis.

Effect of propofol and ketamine-diazepam on intraocular pressure in healthy premedicated dogs.

OBJECTIVE: To compare the effect of propofol and ketamine/diazepam for induction following premedication on intraocular pressure (IOP) in healthy dogs. STUDY DESIGN: Prospective, quasi-experimental, unmasked, longitudinal. ANIMALS: A total of 61 client-owned dogs. METHODS: Dogs were anesthetized twice with a 4 week washout period. Premedication with dexmedetomidine (5 µg kg-1) and hydromorphone (0.1 mg kg-1) intramuscularly was followed by either propofol (4 mg kg-1) or ketamine (5 mg kg-1) and diazepam (0.25 mg kg-1) intravenously for induction and inhaled isoflurane for maintenance. IOP was measured by applanation tonometry using TonoPen-XL before premedication and after 5, 10, 20 and 30 minutes. IOP was measured again immediately after induction and after 3, 5, 10, 15, 20, 30 and 40 minutes. Data were analyzed using one- or two-way repeated measures ANOVA. RESULTS: No difference was found between right and left IOP (p = 0.45), and data from both the eyes of each dog were averaged and considered as one set of data. Following premedication, IOP was significantly lower at all time points than at baseline when animals were grouped together, mean difference -1.6 ± 0.2 mmHg (p < 0.05). IOP increased immediately (12.2 ± 2.4 mmHg before versus 17.1 ± 3.8 mmHg after) and at 3, 5 (p < 0.001), 10 and 40 minutes (p = 0.009 and 0.045, respectively) after propofol administration. For ketamine/diazepam, IOP was increased immediately post-induction (13.0 ± 2.7 mmHg before versus 14.7 ± 2.8 mmHg after) and at 3, 5 (p < 0.001), 30 and 40 minutes (p = 0.010 and 0.037, respectively). CONCLUSIONS AND CLINICAL RELEVANCE: Sedation with hydromorphone and dexmedetomidine significantly decreased IOP in normal dogs and may be an appropriate choice for dogs that cannot tolerate acute increases in IOP. However, IOP increased significantly after both induction protocols, abolishing the effect of premedication.

Evaluation of Modified Techniques for Toggle Pin Repair of Coxofemoral Luxation in Dogs: A Cadaveric Study.

OBJECTIVES: The primary objective was to assess acetabular articular cartilage damage when an acetabular tunnel is drilled by passing the drill bit through the femoral tunnel. The second objective was to assess the success rate of passing the toggle through the femoral and acetabular tunnels in a single manoeuvre using a toggle delivery device. METHODS: Open bilateral coxofemoral luxations in 16 canine cadavers were repaired by toggle pin technique by a surgical resident (n = 8) and a diplomate surgeon (n = 8). In one hip of each cadaver, the acetabular tunnel was drilled through the femoral tunnel and the toggle was passed in a single manoeuvre using the delivery device. In the contralateral hip, the tunnels were drilled separately, and the toggle was passed through each tunnel separately (resident) or in a single manoeuvre (surgeon). Pelves were examined for acetabular cartilage damage and toggle placement. RESULTS: Cartilage damage did not occur with independent drilling of the acetabulum but occurred in 6/16 hips in which the acetabulum was drilled via the femoral tunnel. Successful deployment of the toggle was obtained in 24/24 hips in which the toggle was passed through the femoral and acetabular tunnels simultaneously using the delivery device, regardless of how the acetabular tunnel was drilled. CLINICAL SIGNIFICANCE: Drilling the acetabular tunnel through the femoral tunnel risks damaging the acetabular cartilage. Success was consistently obtained when passing the toggle through the femoral and acetabular tunnels simultaneously using the toggle delivery device.

Assessment of Canine Autologous Conditioned PlasmaTM Cellular and Transforming Growth Factor-ß1 Content.

To evaluate (1) the cellular composition of canine ACP™ including using two different preparation protocols with variations on centrifugation time, (2) the effect of different activation protocols on the transforming growth factor (TGF)-ß1 content in the ACP, and (3) patient factors that might influence platelet concentration of the ACP. ACP was made with blood from 15 dogs using a manufacturer-recommended protocol. Each ACP sample was divided into three aliquots that were activated with calcium chloride (CaCl2), human γ-thrombin (HGT), or not activated. TGF-ß1 was quantified in each aliquot using an ELISA and comparisons among activation protocols were performed using a Skillings-Mack test. Correlations between platelet and TGF-ß1 concentration were assessed with a Pearson correlation coefficient. ACP was subsequently prepared from an additional 17 dogs using a slightly modified centrifugation protocol and cellular composition was assessed. Effects of dog age, body weight, and hematocrit were assessed for their potential impact on ACP platelet concentration using a multiple linear regression analysis. The mean increase in platelet concentration in the ACP above that in the whole blood was 1.2× (±std 0.62) and leukocyte concentration was a mean of 26% (0.37) that in the whole blood using the standard protocol. There was a significant (p < 0.01) effect of activation on TGF-ß1 concentrations with mean concentrations of 4,538 (2,317), 14,948 (13,784), and 14,096 (15,210) pg/ml in aliquots that were not activated or were activated with thrombin or CaCl2 respectively. There were significant correlations between the platelet concentration and TGF-ß1 concentration in aliquots that were activated with either thrombin (r = 0.66; p < 0.01) or CaCl2 (r = 0.86, p < 0.0001). The mean increase in platelet concentration was 1.4× (0.62) and the leukocyte concentration was 0.28× (0.13) that in whole blood using the modified ACP preparation protocol. Dog age, body weight, and hematocrit were not significant predictors of ACP platelet concentration. These data show that on average this preparation protocol produces a mildly platelet-concentrated, leukoreduced platelet-rich plasma. Intentional activation had a significant effect on TGF-ß1 concentrations with use of both CaCl2 and thrombin resulting in higher TGF-ß1 concentrations than that obtained in samples that are not activated.

Magnetic resonance imaging diagnosis and arthroscopic treatment of medial meniscal injury in a dog with a palpably stable stifle.

A dog with lameness, stifle effusion, and osteophytes, but in which the stifle retained stability for 10 months after the onset of lameness, was evaluated with 3T magnetic resonance imaging (MRI). Imaging revealed a tear in the caudal meniscotibial ligament of the medial meniscus. Arthroscopy findings correlated well with MRI and a partial meniscectomy was subsequently carried out, without any surgery to stabilize the stifle, and lameness resolved.

Diagnostic par imagerie à résonance magnétique et traitement arthroscopique d'une blessure du ménisque médial chez un chien ayant un grasset stable à la palpation. Un chien présentant de la boiterie, de l'effusion du grasset et des ostéophytes, mais pour lequel le grasset a conservé de la stabilité pendant 10 mois après l'apparition de la boiterie, a été évalué à l'aide de l'imagerie à résonance magnétique (IRM) 3T. L'IRM a révélé une déchirure dans le ligament méniscotibial caudal du ménisque médial. Les résultats de l'arthroscopie présentaient une bonne corrélation avec l'IRM et une méniscectomie partielle a ensuite été réalisée sans chirurgie pour stabiliser le grasset et la boiterie a été résolue.(Traduit par Isabelle Vallières).

Accuracy of Femoral Head and Neck Excision via a Craniolateral Approach or a Ventral Approach.

OBJECTIVES: This study aimed to compare the completeness of femoral head and neck removal via a craniolateral approach or a ventral approach when femoral head and neck excision (FHNE) is performed by a novice veterinarian. METHODS: FHNE was performed on both femurs of 10 canine cadavers with each femur randomized by a coin toss to FHNE via the craniolateral or ventral approach. Computed tomography (CT) of the femurs was performed prior to and following FHNE. The volume of bone that should have been removed with an ideal FHNE, the percentage of this volume that remained following FHNE, time to complete the procedure and the number of technical errors were compared between the two groups. RESULTS: No significant difference (p = 0.88) was found in the volume of bone that should have been removed with an ideal ostectomy when using the two approaches (craniolateral 3,814.7 ± 409.4 mm3; ventral 3,806.2 ± 479.4 mm3), mean excess residual femoral neck (craniolateral 6.0 ± 9.6%; ventral 4.8 ± 6.8%), mean duration of the procedure (craniolateral 19.3 ± 5.4 minutes; ventral 23.7 ± 5.6 minutes) or number of technical errors (craniolateral 0/10; ventral 1/10) between the craniolateral and ventral approach groups. CLINICAL RELEVANCE: The completeness of bone removal was not significantly different when FHNE was performed by a novice veterinarian via a craniolateral or ventral approach.

Comparison of Platelet-Rich Plasma, Stromal Vascular Fraction (SVF), or SVF with an Injectable PLGA Nanofiber Scaffold for the Treatment of Osteochondral Injury in Dogs.

Stromal vascular fraction (SVF) contains a small number of mesenchymal stem cells and has been used as a treatment for osteoarthritis and cartilage injury. Due to limited evidence of successful cartilage regeneration with injected stem cell therapies, there is interest in combining cellular therapies with injectable scaffolding materials to increase intra-articular residence times of stem cells and improve tissue regeneration. However, the safety of intra-articular injection of SVF combined with injectable scaffolds is unestablished. Also, it is unclear if SVF therapy is superior to more easily prepared biologics, such as platelet-rich plasma (PRP). The purpose of this study was to assess the safety of SVF when combined with an injectable poly(L-lactide-co-glycolide) nanofiber scaffold and to provide a comparison of SVF therapy to PRP. A total of 12 Beagles had osteochondral defects created in both medial femoral condyles and 4 dogs each were allocated to treatment groups of SVF (n = 4), SVF plus PLGA scaffolding (n = 4), or leukoreduced PRP (n = 4). One knee in each dog received treatment, and the contralateral knee was sham treated with saline. Dogs were assessed over a 6-month period, and outcome measures included functional, radiographic, biochemical, and histological assessments. PRP treatment resulted in improvements in lameness scores and objective kinetic assessments of function. There were no statistically significant improvements in function, cartilage biochemical composition, or histology for SVF-treated knees. The combination of SVF and the injectable PLGA scaffold had worse outcomes than other groups including sham treatment based upon functional, biochemical, and histological assessments, raising concerns over the safety of this scaffold for intra-articular injection.

Sustained Release of Transforming Growth Factor-ß1 from Platelet-Rich Chondroitin Sulfate Glycosaminoglycan Gels.

Activated platelet-rich plasma (PRP), also referred to as platelet-rich fibrin (PRF), has been used to augment numerous techniques of cartilage repair in the knee but does not always result in superior quality of repair tissue. One possible reason that PRF does not consistently result in excellent cartilage regeneration is the transiency of growth factor provision with PRF. The objective of this study was to compare the release of transforming growth factor (TGF)-ß1 from PRF and from PRP combined with a novel chondroitin sulfate glycosaminoglycan (CS-GAG) gel. PRP was prepared from nine healthy dogs and split into two aliquots: one activated with bovine thrombin and calcium chloride (CaCl2) to form PRF and the other aliquot was used to rehydrate a lyophilized CS-GAG gel. Both PRF and the CS-GAG gels were incubated in media for 13 days and media were collected, stored, and replaced every 48 hours and the concentration of TGF-ß1 quantified in the media using an enzyme-linked immunosorbent assay. Concentrations of TGF-ß1 in the media were up to three times greater with the CS-GAG gels and were significantly (p < 0.05) greater than with PRF on days 3, 5, 7, 9, and 13. Furthermore, TGF-ß1 elution was still substantial at day 13 with the use of the CS-GAG gels. Additional in vitro work is warranted to characterize TGF-ß1 elution from this CS-GAG gel with human PRP and to determine whether the use of these CS-GAG gels can augment cartilage repair in vivo.

Correction of antebrachial angulation-rotation deformities in dogs with oblique plane inclined osteotomies.

OBJECTIVE: To describe oblique plane inclined osteotomies and report preliminary data on outcomes in dogs treated for antebrachial angulation-rotation deformities. STUDY DESIGN: Retrospective clinical study. ANIMALS: Six antebrachii from 5 dogs. METHODS: Records of dogs with antebrachial angulation-rotation deformities treated with oblique plane inclined osteotomies were reviewed. Postoperative frontal, sagittal, and transverse plane alignments were assessed subjectively, and alignment in the frontal and sagittal planes was quantified on radiographs. Outcomes were classified based on owner's and veterinarian's evaluation as full, acceptable, and unacceptable function. Complications were classified as minor, major, or catastrophic. RESULTS: Limb alignment was subjectively considered excellent in 1 case, good in 3 cases, and fair in 2 cases. Osseous union was achieved in all cases (mean 10.5 weeks; range, 6-13 weeks). Outcomes were assessed by the veterinarian as return to full function in 5 cases and acceptable function in 1 case at the final in-hospital follow-up (mean 44 weeks; range, 6-124 weeks). All owners classified their dogs as returning to full function at the final phone/email interview (mean 107 weeks; range, 72-153 weeks). Implants were removed due to infection or irritation in 3/6 limbs, while the other 3 limbs had minor dermatitis secondary to postoperative external coaptation. No catastrophic complications occurred. CONCLUSION: Oblique plane inclined osteotomies led to a successful outcome in all 6 limbs, but the technique can be challenging and does not always lead to optimal alignment. Future refinement of this technique could focus on the development of patient-specific osteotomy guides to improve accuracy and precision.

Use of a Cyclooxygenase-2 Inhibitor Does Not Inhibit Platelet Activation or Growth Factor Release From Platelet-Rich Plasma.

BACKGROUND: It remains unestablished whether use of cyclooxygenase (COX)-2 inhibitors impairs platelet activation and anabolic growth factor release from platelets in platelet-rich plasma (PRP). PURPOSE: The purpose of this study was to assess the effects of a COX-2 inhibitor on platelet activation and anabolic growth factor release from canine PRP when using a clinically applicable PRP activator and to determine whether a 3-day washout would be sufficient to abrogate any COX-2 inhibitor-related impairment on platelet function. STUDY DESIGN: Controlled laboratory study. METHODS: Ten healthy dogs underwent blood collection and PRP preparation. Dogs were then administered a COX-2 inhibitor for 7 days, after which PRP preparation was repeated. The COX-2 inhibitor was continued for 4 more days and PRP preparation performed a third time, 3 days after discontinuation of the COX-2 inhibitor. Immediately after PRP preparation, the PRP was divided into 4 aliquots: 2 unactivated and 2 activated using human γ-thrombin (HGT). One activated and 1 unactivated sample were assessed using flow cytometry for platelet expression of CD62P and platelet-bound fibrinogen using the canine activated platelet-1 (CAP1) antibody. The 2 remaining samples were centrifuged and the supernatant assayed for transforming growth factor-ß1 (TGF-ß1), platelet-derived growth factor-BB (PDGF-BB), and thromboxane B2 (TXB2) concentrations. Differences in platelet activation and TGF-ß1, PDGF-BB, and TXB2 concentrations over the 3 study weeks were evaluated using a 1-way repeated-measures ANOVA, and comparisons between activated and unactivated samples within a study week were assessed with paired t tests. RESULTS: There were no statistically significant ( P > .05) effects of the COX-2 inhibitor on percentage of platelets positive for CD62P or CAP1 or on concentrations of TGF-ß1, PDGF-BB, or TXB2. All unactivated samples had low levels of activation or growth factor concentrations and significantly ( P < .05) greater activation and growth factor concentrations in HGT-activated samples. CONCLUSION: This COX-2 inhibitor did not impair platelet activation, growth factor release, or TXB2 production in this canine PRP when using HGT as an activator. Studies are warranted to determine whether COX-2 inhibitors affect platelet activation and growth factor release from human PRPs. CLINICAL RELEVANCE: These results suggest that there is no need to withhold a COX-2 inhibitor before PRP preparation, particularly if thrombin is going to be used to activate the PRP. This is clinically relevant information because many patients who are candidates for PRP therapy for treatment of musculoskeletal injury are also using COX-2 inhibitors.