A combination chemotherapy protocol with MOPP and CCNU consolidation (Tufts VELCAP-SC) for the treatment of canine lymphoma

A chemotherapy protocol using a consolidation phase of alkylating agents was used for treating 94 dogs with lymphoma. Fifty‐seven percent of dogs were in stage V, 63% were ill and 38% had T‐cell lymphoma. The complete remission (CR) rate was 70% and is comparable to results achieved with previously published chemotherapy protocols. Anorexia predicted the remission; of the 40 dogs without anorexia, 35 (88%) achieved CR whereas of 52 dogs with anorexia, 30 (58%) achieved CR. Median first CR duration was 168 days and 1‐ and 2‐year CR rates were 17.4 and 15.5%, respectively. Platelet count affected length of first CR, with a 53.2% reduced chance of coming out of remission with each log increase in platelet count. Median survival time was 302 days. One and 2‐year survival rates were 44 and 13%, respectively. Anorexia and no dose reduction of any drug were independent negative variables. Of 93 dogs with toxicity data, 65 dogs (70%) required a dose reduction. Cyclophosphamide was most commonly reduced with reductions in 31 (38%) of 82 dogs. A dose reduction was significantly more likely in dogs with B‐cell lymphoma than in those with T‐cell lymphoma.     

Determination of threshold concentrations of allergens and evaluation of two different histamine concentrations in canine intradermal testing

The purpose of this study was to determine the optimal histamine concentration and allergen threshold concentrations for canine intradermal testing. Thirty healthy dogs were tested using two different concentrations of histamine and four different concentrations of each allergen. The optimal histamine concentration was determined to be 1:10 000 w/v. The threshold concentration was at least 1750 PNU/mL for all tested grasses, weeds, trees, moulds and insects, except for fleas which was as least 1:500 w/v. For Dermatophagoides pteronyssinus, the optimal threshold concentration was 250 PNU/mL, whereas for Dermatophagoides farinae and Tyrophagus putrescentiae, it was 100 PNU/mL. Threshold concentration for all epidermals except human dander was at least 1250 PNU/mL. The optimal threshold concentration for human dander was 300 PNU/mL. Our results suggest that the currently used 1:100 000 w/v concentration of histamine and the 1000 PNU/mL concentration for most grasses, weeds, trees, moulds, epidermals and insects may not be appropriate for canine intradermal testing.     

Feasibility and repeatability of thermal quantitative sensory testing in normal dogs and dogs with hind limb osteoarthritis-associated pain

The objectives of this study were to determine whether thermal quantitative sensory testing (QST) can be performed in client-owned dogs, is repeatable and whether QST differs between normal dogs and dogs with hind limb osteoarthritis (OA). This clinical, prospective, observational study used clinically normal dogs (n = 23) and dogs with OA-associated hind limb pain (n = 9). Thermal QST was performed in standing dogs using a high-powered light source delivered by a previously validated system. Dogs were tested on two occasions, 2 weeks apart. Five tests were performed on each hind limb at each time point. Repeated measures analysis of variance was used to evaluate the effects of leg, time point and OA/normal status on thermal threshold latencies (TTL). Additionally, paired t tests were used to compare the TTL of left and right limbs within groups and between time points.Thermal thresholds were successfully measured in 32 client-owned dogs without prior training. TTL were significantly different between normal and OA dogs (P = 0.012). There was no difference between limbs (P = 0.744) or time periods (P = 0.572), when analyzed by repeated measures analysis of variance, and no interactions between group and limb, visit and limb, or visit and group. In conclusion, thermal thresholds can be measured in client owned dogs with no prior training and are repeatable from week to week. Further data are required to determine if OA results in thermal hypoalgesia as measured at the distal hind limb and whether this is an indication of central sensitization.     

Evaluation of a 15‐week CHOP protocol for the treatment of canine multicentric lymphoma

Dose intense CHOP protocols have been shown to improve outcome for people with non‐Hodgkin's lymphoma, but evaluation of dose intense CHOP protocols for canine lymphoma is currently limited. The hypothesis of this retrospective study was that a 15‐week dose intense CHOP protocol would have shorter treatment duration with similar efficacy to other doxorubicin‐based multidrug protocols. Thirty‐one client owned dogs with multicentric lymphoma were treated with a 15‐week CHOP chemotherapy protocol with an overall response rate of 100% and a median progression‐free interval (PFI) of 140 days [95% confidence interval (CI) 91–335 days]. Dogs that had two or more treatment delays had significantly prolonged PFI and overall survival in multivariate analysis. Dose intensity did not correlate with patient outcome. Dogs experiencing multiple treatment delays secondary to adverse events may receive their individual maximally tolerated dose while dogs with no adverse events may be underdosed. Future studies should focus on individual patient dose optimization.     

Quantitative sensory testing with Electronic von Frey Anesthesiometer and von Frey filaments in nonpainful cats: a pilot study

Objective

Measurement of sensory thresholds could represent a complementary tool to behavioural pain scores in cats. The aim of this study was to investigate the feasibility of quantitative sensory testing (QST) with the Electronic von Frey Anesthesiometer (EVF) and von Frey filaments (VFF) in healthy cats, and to assess the limits of agreement (LOA) between the two devices.

Validation of a thermal threshold nociceptive model in bearded dragons (Pogona vitticeps)

Objectives

To validate a thermal threshold (TT) nociceptive model in bearded dragons (Pogona vitticeps) and to document TT changes after administration of morphine.

Use of nociceptive threshold testing in cats in experimental and clinical settings: a qualitative review

ObjectiveThe objective of this study was to review the scientific articles on the use of nociceptive threshold testing (NTT) in cats and to summarize the clinical and experimental applications in this species.Databases usedPertinent literature was searched with PubMed, Scopus, Web of Science, Universitätsbibliothek Basel (swissbib Basel Bern) and Google Scholar. The search was then refined manually based first on article titles and abstracts, and subsequently on full texts.ConclusionsOf the four classical acute nociceptive models used for NTT, thermal and mechanical are most commonly used in cats. Thermal stimulation is applicable in experimental settings and has been used in pharmacodynamics studies assessing feline antinociception. Although mechanical stimulation is currently less used in cats, in the future it might play a role in the evaluation of clinical feline pain. However, the low response reliability after stimulus repetition within a narrow time interval represents a major limitation for the clinical use of mechanical thresholds in this species. Challenges remain when thermal thresholds are used to investigate analgesics that have the potential to affect skin temperature, such as opioids and α2-adrenergic agonists, and when a model of inflammatory pain is reproduced in experimental cats with the purpose of evaluating non-steroidal anti-inflammatory drugs as analgesics.     

Evaluation of a discontinuous treatment protocol (VELCAP-S) for canine lymphoma

Eighty-two dogs with lymphoma received a single 15-week course of chemotherapy, after which treatment was ceased until relapse. Fifty-six dogs (68%) achieved complete remission for a median 1st remission duration of 20 weeks. Forty-eight dogs relapsed, of which 30 repeated the induction cycle. In 22 of these dogs, 1st remission had been short, and they received maintenance chemotherapy; the other 8 dogs received 2 or 3 cycles of induction chemotherapy. Second remission rate for these 30 dogs was 87% (26 dogs). Overall disease control for the 38 dogs that remained on protocol was 44 weeks, which was not markedly shorter than for dogs treated with a previously reported protocol in which maintenance chemotherapy was instituted in all dogs after an identical 1st induction (VELCAP-L). Dogs that were febrile and dogs that were dyspneic were less likely to achieve a complete remission to induction chemotherapy. Of dogs that achieved a complete remission, those that were thrombocytopenic at entry had a shorter 1st remission, and dogs that were anorexic at entry had shorter overall disease control. There was a correlation between 1st remission duration and length of any subsequent remission obtained. The incidence of toxicity was high, particularly after the combination of doxorubicin and vincristine. Dose reductions because of toxicity did not markedly reduce remission duration. We conclude that discontinuous chemotherapy may reduce patient visits in a small number of patients because of long-term disease control. Delaying maintenance chemotherapy until after 2nd remission is achieved does not markedly affect overall disease control.     

Antitumour effects of Liporaxel (oral paclitaxel) for canine melanoma in a mouse xenograft model

Paclitaxel, a member of the taxane family, exhibits antitumour effects by targeting the microtubules in cancer cells. Recently, oral paclitaxel has been developed to overcome the side effects of intravenous paclitaxel administration in human patients. The objective of this study was to investigate the antitumour effects of oral paclitaxel in vitro and in vivo. Three weeks after inoculation, oral paclitaxel (25 and 50 mg/kg) or saline was administered every week for three consecutive weeks. To explore the underlying mechanism, tumour angiogenesis was examined by immunohistochemistry with an anti‐CD31 antibody. Tumour cell apoptosis was detected by Terminal deoxynucleotidyl transferase dUTP Nick‐End Labeling assay, and cell cycle arrest was confirmed by western blot analysis. Oral paclitaxel treatment of canine melanoma cells exerted mediated antiproliferative effects and mediated cell cycle arrest in vitro. In animal experiments, after oral paclitaxel administration, the average tumour size decreased to approximately 30% of that in the control. Histologically, oral paclitaxel showed anti‐angiogenic effects and induced the apoptosis in tumour tissues. Oral paclitaxel also downregulated the intratumoural expression of cyclin D1 and inhibited cell proliferation. The study findings support potential application of oral paclitaxel as a novel chemotherapeutic strategy to treat canine melanoma. This is the first study to investigate the potential of oral paclitaxel as a therapeutic drug against canine tumours.     

Validation of a commercially available enzyme-linked immunosorbent assay (ELISA) for the determination of cortisol in canine plasma samples

Samples were obtained from clinically normal dogs before and after ACTH stimulation and dexamethasone suppression tests. The test kit Enzymun-Test (Boehringer Mannheim) for determining cortisol concentrations in human plasma was used in connection with the analyser system Enzymun-Test (Boehringer Mannheim) System ES300 following the manufacturer's instructions. The intra-assay and inter-assay coefficients of variation were 1.28% and 5.64%, respectively. The mean recovery when assaying samples with a cortisol content of more than 100 nmol/L was 95.41%, but this percentage decreased in samples with lower cortisol levels. The sensitivity of the assay was 2.76 nmol/L. The results of the ACTH stimulation and dexamethasone suppression tests were similar to those published previously. The ELISA method evaluated allows a precise and sensitive determination of cortisol concentrations in canine plasma samples. The major drawback observed was the loss of accuracy at low cortisol concentrations. Since the assay tends then to report lower cortisol concentrations, the generally accepted concentration of 40 nmol/L may not be suitable as the cutoff value in dexamethasone suppression tests.     

Evaluation of a multi‐agent chemotherapy protocol combining lomustine,procarbazine and prednisolone (LPP) for the treatment of relapsed canine non‐Hodgkin high‐grade lymphomas

The standard of care treatment for canine lymphoma is multi‐agent chemotherapy containing prednisolone, cyclophosphamide, vincristine and an anthracycline such as doxorubicin (CHOP) or epirubicin (CEOP). Lomustine, vincristine, procarbazine, and prednisone (LOPP) has been evaluated as a rescue, with encouraging results; however, resistance to vincristine is likely in patients relapsing on CHOP/CEOP, and this agent may enhance LOPP toxicity without improving efficacy. The aim of this study was to evaluate responses to a modified‐LOPP protocol that does not include vincristine (LPP) and is administered on a 21‐day cycle. Medical records of dogs with high‐grade multicentric lymphoma from 2012 to 2017 were reviewed. Dogs with relapsed lymphoma that received LPP as a rescue protocol were enrolled. Response, time from initiation to discontinuation (TTD) and toxicity of LPP were assessed. Forty‐one dogs were included. Twenty‐five dogs (61%) responded to LPP including 12 complete responses (CR) and 13 partial responses (PR). Responders had a significantly longer TTD (P < .001) compared to non‐responders with 84 days for CR and 58 days for PR. Neutropenia was documented in 20 dogs (57%): 12 grade I to II, 8 grade III to IV. Thrombocytopenia was infrequent (20%): 5 grade I to II, 2 grade III to IV. Twelve dogs developed gastrointestinal toxicity (30%): 10 grade I to II and 2 grade III. Nineteen dogs had elevated ALT (59%): 9 grade I to II, 10 grade III to IV. Treatment was discontinued due to toxicity in 8 dogs (19%). The LPP protocol shows acceptable efficacy and toxicity‐profile and minimizes in‐hospital procedures.     

Pressure algometry and thermal sensitivity for assessing pain sensitivity and effects of flunixin meglumine and sodium salicylate in a transient lameness model in sows

Sow lameness can result in decreased animal health and productivity, and is a significant animal welfare concern. Swine producers and veterinarians lack objective assessment tools to detect lameness. Objectives of this study were to evaluate pressure algometry (PA) and thermal sensitivity (TS) as objective assessment tools for changes in pain sensitivity associated with lameness and to assess analgesic drugs for mitigating lameness pain. Twelve mixed parity crossbred sows were anesthetized and injected with Amphotericin B in the distal interdigital space of both claws of one hind leg to induce transient lameness. Sows were randomly assigned to one of three analgesic treatment groups: (1) Sodium Salicylate (SS; 35 mg/kg per os q.12 h+0.04 ml/kg IM q.24 h sterile saline), (2) Flunixin meglumine (FM; 2.2 mg/kg IM q.24 h), or (3) Control (C; 0.04 ml/kg IM q.24 h sterile saline). All sows received each treatment over three trials with two-wk wash-out periods between trials. Forty-eight h post-induction, analgesic treatments were administered daily for four consecutive d. Pain sensitivity was assessed with PA and TS on each hind leg on d−1, d+1 and d+6 relative to induction (d0). Proc Glimmix of SAS 9.2 was used to analyze the difference between sound (S) and lame (L) legs on each trial day, with a simple effect comparison used to analyze effect of analgesia treatment on d+6. As predicted, S and L legs did not differ on d−1 (P=0.56) and less pressure was tolerated on L legs on d+1 (P<0.001) (Raw Means in kilograms of force: d−1 L 7.2±0.2; d−1 S 7.4±0.2; d+1 L 2.1±0.2; d+1 S 7.7±0.2 kgf). A simple effect comparison of d+6 revealed no differences between FM and C (p=0.90), FM and SS (p=0.17), or SS and C (p=0.07). The TS latency of S versus L legs differed on all trial days (d−1 p=0.02, d+1 p<0.0001, d+6 p<0.01) over all trials. (TS Raw means (s): d−1 L 7.3±0.6; d−1 S 9.1±0.6; d+1 L 3.3±0.2; d+1 S 6.8±0.6; d+6 L 6.0±0.6; d+6 S 8.4±0.7 s), including lame and sound days. In conclusion, these results support PA as an objective non-invasive method for measuring pain sensitivity in sows induced with transient lameness. Sodium salicylate or flunixin meglumine did not reduced pain sensitivity as measured by PA from d+1 to d+6 in this model of induced transient lameness.     

Evaluation of an enzyme-linked immunosorbent assay (ELISA) for the serological diagnosis of canine sarcoptic mange

Abstract The purpose of this study was to evaluate a serodiagnostic test (enzyme-linked immunosorbent assay; ELISA) for sarcoptic mange in dogs and to characterize the assay antigen, based on the mite Sarcoptes scabiei var. vulpes. The ELISA, applied to sera from 359 dogs suspected of having sarcoptic mange, showed a sensitivity and specificity of 92 and 96%, respectively. Sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) of the antigen employed in the ELISA revealed polypeptide bands with molecular weights ranging between 14 and 164 kDa. In Western blot analyses antigens of molecular weights between 62 and 64 kDa dominated. Particularly dominant were antigens of 164 and 147 kDa. These were found to have isoelectrical points in the range of 5.7–6.9. Sera from dogs infected with Cheyletiella sp., Demodex canis, Linognathus setosus and Otodectes cynotis, as well as from dogs allergic to fleas, were negative in the ELISA. Résumé— Le but de cette étude est d'évaluer un test sérologique ELISA pour le diagnostic de la gale sarcoptique chez le chien et de caractériser l'antigène révélateur, extrait de l'acarien Sarcoptes scabiei var. vulpes. Le test ELISA, lors d'une étude conduite avec les sérums de 359 chiens suspects de gale sarcoptique a démontré une sensibilité et une spécificité de 92 et 96%, respectivement. L'électrophorèse en gel polyacrilamide dodécyl sulfate de sodium de l'antigène utilisé dans l'ELISA a révélé des bandes polypeptidiques de poids moléculaire compris entre 14 et 164 kDa. Dans l'analyse en Western blot, les antigènes de poids moléculaire compris entre 62 et 164 kDa étaient les plus abondants, notamment ceux de 164 et 147 kDa. Ces derniers ont des points isoélectriques compris entre 5.7 et 6.9. Les sérums de chiens infectés par des Cheyletiella sp. Demodex canis, Linognathus setosus et Otodectes cynotis, ou par des chiens allergiques aux puces, se sont révélés négatifs en ELISA. [Bornstein, S., Thebo, P., Zakrisson, G. Evaluation of an enzyme-linked immunosorbent assay (ELISA) for the serological diagnosis of canine sarcoptic mange (Evaluation d'un test ELISA pour le diagnostic sérologique de la gale sarcoptique canine). Veterinary Dermatology 1996; 7 : 21–28.] Resumen El objetivo de este estudio fue el de evaluar una pruba serodiagnóstica (prueba de inmunoadsorción ligada a enzima; ELISA) para la sarna sarcóptica en el perro y caracterizar el antigeno prueba, basado en el ácaro Sarcoptes scabei, var. vulpes. El ELISA, aplicado a sueros de 359 perros sospechosos de padecer sarna sarcóptica, mostró una sensibilidad y especificidad del 92 y 96%, respectivamente. La electroforesis en gel de poliacrilamida dodecil sulfato sódico (SDS-PAGE) del antigeno usado en el ELISA reveló bandas de polipétidos con peso molecular entre 14 y 164 kDa. En el análisis Western blot, predominaron los antigenos de pesos moleculares entre 62 y 164 kDa. Los antigenos entre 164 y 147 kDa fueron especialmente predominantes. Estos tuvieron puntos isoeléctricos entre 5.7 y 6.9. Los sueros de perros infectados por Cheyletiella sp., Demodex canis, Linognathus setosus y Otodectes cynotis, asi como el de perros alérgicos a las pulgas fueron negativos en el ELISA. [Bornstein, S., Thebo, P., Zakrisson, G. Evaluation of an enzyme-linked immunosorbent assay (ELISA) for the serological diagnosis of canine sarcoptic mange (Evaluation de una prueba de immunoadsorcion ligada a enzima (ELISA) para el diagnostico serologico de la sarna sarcóptica canina). Veterinary Dermatology 1996; 7 : 21–28.] Zusammenfassung— Ziel dieser Studie war, einen Serodiagnostiktest (Enzyme-Linked-Immunosorbent-Assay, ELISA) für Sarkoptesräude des Hundes zu überprüfen und das Testantigen zu charakterisieren, das auf der Milbe Sarcoptes scabiei var. vulpes basiert. Der ELISA-Test, der bei den Sera von 359 Hunden mit Sarkoptesverdacht angewendet wurde, zeigte eine Sensitivität von 92% bzw. 96%. Die Natriumdodecylsul-fatpolyacrylamid-Gelelektrophorese (SDS-PAGE) des Antigen, das im ELISA verwendet wurde, zeigte Polypeptid-Banden mit Molekulargewichten zwischen 14 und 164 kDa. In der Wester-blot-Analyse dominierten Antigene mit einem Molekulargewicht zwischen 62 und 164 kDa. Besonders dominierend waren Antigene von 164 und 147 kDa. Bei diesen stellte man isoelektrische Punkte im Bereich von 5,7 bis 6,9 fest. Die Sera von Hunden, die mit Cheyletiella sp., Demodex canis, Linognathus setosus und Otodectes cynotis infiziert waren, fielen ebenso wie die Hunde mit Allergie auf Flöhe im ELISA negativ aus. [Bornstein, S., Thebo, P., Zakrisson, G. Evaluation of an enzyme-linked immunosorbent assay (ELISA) for the serological diagnosis of canine sarcoptic mange (Die Auswertung eines Enzym-Linked-Immunosorbent-Assay (ELISA) für die serologische Diagnose der kaninen Sarkoptesräude). Veterinary Dermatology 1996; 7 : 21–28.]     

Canine prostate specific esterase (CPSE) as an useful biomarker in preventive screening programme of canine prostate: CPSE threshold value assessment and its correlation with ultrasonographic prostatic abnormalities in asymptomatic dogs

Due to the increased attention that pet‐owners devote to their animals and to the improved veterinary care, investigations regarding methods to early detect prostatic disorders that might affect canine life quality have been performed. Canine prostate specific esterase (CPSE) concentration was reported to be higher in dogs suffering from prostatic diseases. This study aimed to estimate the CPSE threshold as a biomarker to early identify prostatic diseases in asymptomatic dogs. The ultrasonographic examination of the prostate was performed in 19 dogs (6–40 kg; 1–5 years) with no symptoms of prostatic diseases. Dogs were grouped according to the presence (Group A) or absence (Group B) of prostatic disorders at the ultrasound (altered appearance, the presence of cysts or irregular borders). For each dog, a venous blood sample was collected to measure serum CPSE and the ratio between calculated and normal expected prostatic volume was assessed for each dog. The CPSE data were statistically analysed (t test, p < .05), and the CPSE threshold in blood serum between groups was calculated by ROC. In 11 dogs, ultrasonography showed signs of prostatic abnormalities (Group A, 2–5 years), while no signs were detected in eight dogs (Group B, 1–3 years). The calculated/estimated volume ratio resulted greater than 1.5 in Group A dogs. The CPSE was statistically different between groups (p < .0001): higher in Group A (mean = 184.9, SD = 126 ng/ml) than in Group B (38.9 ± 22.1 ng/ml). The cut‐off CPSE threshold was 52.3 ng/ml (ROC, AUC = 0.974, SE 95.6%, SP 89.2%). This study suggests that CPSE serum concentration higher than 50 ng/ml in asymptomatic dogs is associated with ultrasonographic alterations and increased the prostatic size (volume by 1.5 times greater than the normal size). As the onset of prostatic disorders often remains asymptomatic, the rapid assessment of CPSE could be suitable for selecting preventively those animals that would require further accurate evaluation.     

Evaluation of a commercially available human C-reactive protein (CRP) turbidometric immunoassay for determination of canine serum CRP concentration

Background: Serum C-reactive protein (CRP) is an acute phase marker in dogs that is useful for the diagnosis and monitoring of inflammatory disease. Rapid, reliable, and automated assays are preferable for routine evaluation of canine serum CRP concentration.
Objective: The aim of this study was to evaluate whether canine serum CRP concentration could be measured reliably using an automated turbidometric immunoassay (TIA) designed for use with human serum.
Methods: A commercially available TIA for human serum CRP (Bayer, Newbury, UK) was used to measure canine serum CRP concentration. Cross-reactivity of antigen was evaluated by the Ouchterlony procedure. Intra-and interassay imprecision was investigated by multiple measurements on canine serum samples and serum pools, respectively. Assay inaccuracy was investigated by linearity under dilution and comparison of methodologies (canine CRP ELISA, Tridelta Development Ltd, Kildare, UK). Then the assay was applied to serum samples from 14 clinically healthy dogs, 11 dogs with neoplasia, 13 with infections, 8 with endocrine or metabolic diseases, and 10 with miscellaneous diseases.
Results: Cross-reactivity between canine serum CRP and the anti-human CRP antibody was found. Intra-and interassay imprecision ranged from 5.2% to 10.8% and 3.0% to 10.2%, respectively. Serum CRP concentration was measured in a linear and proportional manner. There was no significant disagreement and there was linear correlation of the results in the comparison of methodologies, except for a slight proportional discrepancy at low CRP concentrations (<10 μg/mL). Dogs with infections had a significantly higher concentration of serum CRP than did all other dogs, and dogs with neoplasia had a significantly higher concentration of serum CRP than did clinically healthy dogs.
Conclusions: Canine serum CRP concentration can be measured reliably using the commercially available TIA designed for human CRP.     

Mechanical performance of a screw-type veterinary suture anchor subjected to single load to failure and cyclic loads

OBJECTIVE: To characterize the mechanical performance of a veterinary bone anchor under static and cyclic loads. STUDY DESIGN: Mechanical testing study. ANIMALS: Cadaveric canine humeri. METHODS: Humeri (6 pairs) were collected from skeletally mature dogs (mean [+/-SD] age, 17.2+/-2.1 months; weight, 20.8+/-1.5 kg). Bone anchors were inserted in the proximal metaphysis using nylon, and were longitudinally extracted. For the opposite humerus, anchors were subjected to longitudinal cyclic load (50% of the load at failure of their pair) for 1200 cycles then longitudinally loaded to failure. Anchors were then installed in a similar and adjacent area of these 2(nd) humeri with nylon and cyclically tested perpendicular to the axis of anchor insertion (100% of the longitudinal holding power of their pair) for 1200 cycles, then perpendicularly loaded to failure. Paired t-tests were used to compare holding power before and after longitudinal cyclic testing. RESULTS: Longitudinal holding power of the screw-type anchor in the proximal humerus was 385+/-30 N. Anchor pullout was the only mode of failure. Anchors in the paired humeri did not fail after 1200 cycles of 50% longitudinal loading, and post-cycle holding strength was not different (335+/-87 N; P=.32). Perpendicularly loaded anchors did not fail after 1200 cycles of 100% of opposite longitudinal holding strength, and had post-cycle perpendicular holding strengths of 514+/-72 N. Suture breakage was the mode of failure. CLINICAL RELEVANCE: Bone anchor holding strength is dependent on orientation of suture load. Screw-type bone anchor holding strength was not affected by longitudinal cyclic loading, and holding strengths of approximately 385 N can be expected in metaphyseal bone of large-breed mature dogs. Perpendicularly loaded anchors have higher failure loads, and holding strength of approximately 514 N can be expected in metaphyseal bone of the proximal humerus.