Evoked temporal summation in cats to highlight central sensitization related to osteoarthritis-associated chronic pain: a preliminary study

Non-invasive electroencephalography in awake cats: Feasibility and application to sensory processing in chronic pain

BACKGROUND

Feline osteoarthritis (OA) leads to chronic pain and somatosensory sensitisation. In humans, sensory exposure can modulate chronic pain. Recently, electroencephalography (EEG) revealed a specific brain signature to human OA. However, EEG pain characterisation or its modulation does not exist in OA cats, and all EEG were conducted in sedated cats, using intradermal electrodes, which could alter sensory (pain) perception.

NEW METHOD

Cats (n=11) affected by OA were assessed using ten gold-plated surface electrodes. Sensory stimuli were presented in random orders: response to mechanical temporal summation, grapefruit scent and mono-chromatic wavelengths (500 nm-blue, 525 nm-green and 627 nm-red light). The recorded EEG was processed to identify event-related potentials (ERP) and to perform spectral analysis (z-score).

RESULTS

The procedure was well-tolerated. The ERPs were reported for both mechanical (F3, C3, Cz, P3, Pz) and olfactory stimuli (Cz, Pz). The main limitation was motion artifacts. Spectral analysis revealed a significant interaction between the power of EEG frequency bands and light wavelengths (p<0.001). All wavelengths considered, alpha band proportion was higher than that of delta and gamma bands (p<0.044), while the latter was lower than the beta band (p<0.016). Compared to green and red, exposure to blue light elicited distinct changes in EEG power over time (p<0.001).

COMPARISON WITH EXISTING METHOD

This is the first demonstration of EEG feasibility in conscious cats with surface electrodes recording brain activity while exposing them to sensory stimulations.

CONCLUSION

The identification of ERPs and spectral patterns opens new avenues for investigating feline chronic pain and its potential modulation through sensory interventions.

Predictive and concurrent validity of pain sensitivity phenotype, neuropeptidomics and neuroepigenetics in the MI-RAT osteoarthritic surgical model in rats

Background

Micro-RNAs could provide great insights about the neuropathological mechanisms associated with osteoarthritis (OA) pain processing. Using the validated Montreal Induction of Rat Arthritis Testing (MI-RAT) model, this study aimed to characterize neuroepigenetic markers susceptible to correlate with innovative pain functional phenotype and targeted neuropeptide alterations.

Methods

Functional biomechanical, somatosensory sensitization (peripheral-via tactile paw withdrawal threshold; central-via response to mechanical temporal summation), and diffuse noxious inhibitory control (via conditioned pain modulation) alterations were assessed sequentially in OA (n = 12) and Naïve (n = 12) rats. Joint structural, targeted spinal neuropeptides and differential expression of spinal cord micro-RNAs analyses were conducted at the sacrifice (day (D) 56).

Results

The MI-RAT model caused important structural damages (reaching 35.77% of cartilage surface) compared to the Naïve group (P < 0.001). This was concomitantly associated with nociceptive sensitization: ipsilateral weight shift to the contralateral hind limb (asymmetry index) from -55.61% ± 8.50% (D7) to -26.29% ± 8.50% (D35) (P < 0.0001); mechanical pain hypersensitivity was present as soon as D7 and persisting until D56 (P < 0.008); central sensitization was evident at D21 (P = 0.038); pain endogenous inhibitory control was distinguished with higher conditioned pain modulation rate (P < 0.05) at D7, D21, and D35 as a reflect of filtrated pain perception. Somatosensory profile alterations of OA rats were translated in a persistent elevation of pro-nociceptive neuropeptides substance P and bradykinin, along with an increased expression of spinal miR-181b (P = 0.029) at D56.

Conclusion

The MI-RAT OA model is associated, not only with structural lesions and static weight-bearing alterations, but also with a somatosensory profile that encompasses pain centralized sensitization, associated to active endogenous inhibitory/facilitatory controls, and corresponding neuropeptidomic and neuroepigenetic alterations. This preliminary neuroepigenetic research confirms the crucial role of pain endogenous inhibitory control in the development of OA chronic pain (not only hypersensitivity) and validates the MI-RAT model for its study.

Evaluation of the analgesic efficacy of grapiprant compared with robenacoxib in cats undergoing elective ovariohysterectomy in a prospective, randomized, masked, non-inferiority clinical trial

OBJECTIVES

The main objective of this study was to compare the postoperative analgesic effects of grapiprant with those of robenacoxib in cats undergoing ovariohysterectomy (OVH).

METHODS

In total, 37 female cats (age range 4 months-10 years, weighing ⩾2.5 kg) were enrolled in a prospective, randomized, masked, non-inferiority (NI) clinical trial. Cats received oral robenacoxib (1 mg/kg) or grapiprant (2 mg/kg) 2 h before OVH. Analgesia was assessed via the Feline Grimace Scale (FGS), the Glasgow Composite Measure Pain Scale-Feline (CMPS-F), von Frey monofilaments (vFFs) and pressure algometry (ALG) 2 h before treatment administration, at extubation, and 2, 4, 6, 8, 18 and 24 hours after extubation. Hydromorphone (<8 h postoperatively) or buprenorphine (>18 h postoperatively) were administered to cats with scores of ⩾5/20 on CMPS-F and/or ⩾4/10 on FGS. NI margins for CMPS-F and vFFs were set at 3 and -0.2, respectively. A mixed-effect ANOVA was used for FGS scores (P <0.05). Data are reported as mean ± SEM.

RESULTS

The data from 33 cats were analyzed. The upper limit of the 95% confidence interval (CI) (0.35) was less than the NI margin of 3 for CMPS-F, and the lower limit of the 95% CI (0.055) was greater than the NI margin of -0.2 for vFFs, indicating NI of grapiprant. The FGS scores were greater than baseline at extubation for both treatments (1.65 ± 0.63; P = 0.001); however, there was no difference between treatments. There was no difference between treatments, nor treatment by time interaction, for vFFs (P <0.001). The CMPS-F scores for both treatments were higher at extubation but returned to baseline after 4 h (P <0.001). For ALG, there was no difference in treatment or treatment by time interaction. The robenacoxib group had lower pressure readings at extubation and 6 h compared with baseline.

CONCLUSIONS AND RELEVANCE

These results indicate that grapiprant was non-inferior to robenacoxib for mitigating postsurgical pain in cats after OVH performed via ventral celiotomy. The impact of grapiprant for analgesia in OVH via the flank is unknown.

Owner evaluation of quality of life and mobility in osteoarthritic cats treated with amantadine or placebo

OBJECTIVES

The aim of the study was to determine if amantadine improves owner-identified mobility impairment and quality of life associated with osteoarthritis in cats.

METHODS

Using a blinded, placebo-controlled, randomized, crossover design, 13 healthy client-owned cats with clinical and radiographic evidence of osteoarthritis and owner-identified mobility impairment were studied. Cats received 5 mg/kg amantadine or placebo q24h PO for 3 weeks each with no washout period in between. Locomotor activity was continuously assessed with a collar-mounted activity monitor system, and owners chose and rated two mobility-impaired activities using a client-specific outcome measures (CSOM) questionnaire on a weekly basis. Locomotor activity on the third treatment week was analyzed with two-tailed paired t-tests. The CSOM scores were analyzed using a mixed-effect model and the Bonferroni post-hoc test. Owner-perceived changes in quality of life were compared between treatments using the χ2 test. Statistical significance was set at P <0.05.

RESULTS

Mean ± SD activity counts during the third week of each treatment were significantly lower with amantadine (240,537 ± 53,880) compared with placebo (326,032 ± 91,759). CSOM scores assigned by the owners were significantly better with amantadine on the second (3 ± 1) and third (3 ± 1) weeks compared with placebo (5 ± 2 and 5 ± 1, respectively). A significantly greater proportion of owners reported improvement in quality of life with amantadine compared with placebo.

CONCLUSIONS AND RELEVANCE

Amantadine significantly decreased activity, but improved owner-identified impaired mobility and owner-perceived quality of life in cats with osteoarthritis. Amantadine appears to be an option for the symptomatic treatment of osteoarthritis in cats.

Feline musculoskeletal ageing: How are we diagnosing and treating musculoskeletal impairment?

PRACTICAL RELEVANCE

An understanding of the process of musculoskeletal ageing - which all senior and geriatric cats will experience - is vital to maintaining the health and welfare of our ageing cat population.

CLINICAL CHALLENGES

Assessment of the feline musculoskeletal system is not always straightforward. Diagnosis of impairment relies on input from owners and veterinarians in terms of visual observation, and clinical and orthopaedic examination, in addition to diagnostic imaging.

AUDIENCE

This review is written for the primary care veterinary team.

AIMS

The goals are to raise awareness and improve clinical diagnosis of musculoskeletal impairment as a result of ageing. The article also reviews therapeutic options and considers the evidence available for the prevention/deceleration of musculoskeletal ageing and impairment.

EVIDENCE BASE

There is good evidence of a high prevalence of osteoarthritis (OA) and degenerative joint disease (DJD) in older cats. There is also good evidence to indicate that functional impairment and chronic pain are sequelae of musculoskeletal disease. However, there is a paucity of information for what is best practice for the management and treatment of musculoskeletal impairment in a clinical situation. There is also a lack of evidence on how prevention of central stimulation of the nervous system caused by musculoskeletal impairment and, in turn the development of chronic pain, can be avoided.

Dietary Supplementation with Palmitoyl-Glucosamine Co-Micronized with Curcumin Relieves Osteoarthritis Pain and Benefits Joint Mobility

Simple Summary

Canine osteoarthritis is a chronic degenerative joint disease and a major cause of elective euthanasia. The disorder increasingly limits joint motion, might cause lameness as well as pain, and impacts quality of life. An unmet need remains for safe and effective therapies for osteoarthritis. Palmitoyl-glucosamine and curcumin are used in animal nutrition. A co-micronized formulation, with the two substances being jointly processed to reduce their particle size and increase the extent to which they can be absorbed, is currently available on the European market. The present study investigated if this formulation could relieve joint pain and benefit mobility. Two well-established rat models of inflammation and osteoarthritis pain were used. Results from the first set of experiments showed that the dietary supplement relieved experimentally induced paw edema, infiltration of inflammatory cells, and decreased sensitivity to painful stimuli (thermal hyperalgesia). In the osteoarthritis model, the supplement proved to protect joint cartilage against degradation and successfully address neuropathic pain (i.e., pain from normally non-painful stimuli). Locomotor function recovered by 45% under supplement administration. The present findings suggest that the dietary supplement with palmitoyl-glucosamine co-micronized with curcumin might help manage osteoarthritis.

Abstract

Chronic mixed pain and orthopedic dysfunction are the most frequently associated consequences of canine osteoarthritis (OA). An unmet need remains for safe and effective therapies for OA. Palmitoyl-glucosamine (PGA) and curcumin are safe and naturally occurring compounds whose use is limited by poor bioavailability. Micronization is an established technique to increase bioavailability. The aim of this study was to investigate if the dietary supplementation with PGA co-micronized with curcumin (PGA-Cur, 2:1 ratio by mass) could limit pathologic process in two well-established rat models of inflammation and OA pain, i.e., subplantar carrageenan (CAR) and knee injection of sodium monoiodoacetate (MIA), respectively. In CAR-injected animals, a single dose of PGA-cur significantly reduced paw edema and hyperalgesia, as well as tissue damage and neutrophil infiltration. The repeated administration of PGA-Cur three times per week for 21 days, starting the third day after MIA injection resulted in a significant anti-allodynic effect. Protection against cartilage damage and recovery of locomotor function by 45% were also recorded. Finally, PGA-cur significantly counteracted MIA-induced increase in serum levels of TNF-α, IL-1β, NGF, as well as metalloproteases 1, 3, and 9. All the effects of PGA-Cur were superior compared to the compounds used singly. PGA-Cur emerged as a useful dietary intervention for OA.

Quantitative sensory testing in feline osteoarthritic pain - a systematic review and meta-analysis

Quantitative sensory testing (QST) is a psychophysical test used to quantify somatosensory sensation under normal or pathological conditions including osteoarthritis (OA).

OBJECTIVE

This study aimed to conduct a systematic review and meta-analysis of studies using QST in healthy and osteoarthritic cats, registered at Systematic Review Research Facility (#26-06-2017).

DESIGN

Hierarchical models with random intercepts for each individual study extracted through the systematic review were fit to subject-level data; QST measures were contrasted between healthy and osteoarthritic cats. Four bibliographic databases were searched; quality and risk of bias assessment were performed using pre-established criteria.

RESULTS

Six articles were included; most were of high quality and low risk of bias. Punctate tactile threshold (n = 70) and mechanical temporal summation (n = 35) were eligible for analysis. Cats with OA have lower punctate tactile threshold [mean difference (95%HDI): -44 (-60; -26) grams] and facilitated temporal summation of pain [hazard ratio (95%HDI): 5.32 (2.19; 14) times] when compared with healthy cats. The effect of sex and body weight on sensory sensitivity remained inconclusive throughout all analyses. Due to the correlation between age and OA status, it remains difficult to assess the effect of OA on sensory sensitivity, independently of age.

CONCLUSIONS

Clear and transparent reporting using guidelines are warranted. Similar to people, centralized sensitization is a feature of OA in cats. Future studies should try to elucidate the age effect on feline OA. Research with natural OA in cats is promising with potential to benefit feline health and welfare, and improve translatability to clinical research.

Feline Neuropathic Pain

Neuropathic pain represents the extreme in maladaptive pain processing. In itself, it is a disease in which pain has become exaggerated in some combination of scope, severity, character, field, duration, and spontaneity. It is almost certainly an underappreciated, underdiagnosed cause of possible significant patient morbidity in cats. This article explores the basic mechanisms, recognition, known and suspect syndromes, and prospective treatment of feline maladaptive and neuropathic pain.

Feline Chronic Pain and Osteoarthritis

This article reviews the current knowledge regarding osteoarthritis-related pain in cats as a structure in which to discuss the assessment of chronic pain in the research and clinical settings. The scientific evidence available for current and emerging drug therapies is described. The importance of environmental enrichment and positive emotions to reduce pain, stress, and anxiety as means to promote feline welfare and human-pet bond is discussed.

Pharmacologic Methods: An Update on Optimal Presedation and Euthanasia Solution Administration

Pre-euthanasia sedation or anesthesia offers many benefits. It allows the owners to spend time with their pet before euthanasia, improves safety for the person performing euthanasia and others who are present, decreases stress for the patient, reduces or eliminates the need for physical restraint for intravenous injection. Under anesthesia, non-intravenous routes may be used for administration of euthanasia solutions. Some drugs that do not require injection; the oral transmucosal route is noninvasive and suitable for several drugs or drug combinations. The oral route also is feasible, but there are fewer data available on suitable drugs and doses.

Pain and Problem Behavior in Cats and Dogs

We argue that there is currently an under-reporting of the ways in which pain can be associated with problem behavior, which is seriously limiting the recognition of this welfare problem. A review of the caseloads of 100 recent dog cases of several authors indicates that a conservative estimate of around a third of referred cases involve some form of painful condition, and in some instances, the figure may be nearly 80%. The relationship is often complex but always logical. Musculoskeletal but also painful gastro-intestinal and dermatological conditions are commonly recognized as significant to the animal's problem behavior. The potential importance of clinical abnormalities such as an unusual gait or unexplained behavioral signs should not be dismissed by clinicians in general practice, even when they are common within a given breed. In general, it is argued that clinicians should err on the side of caution when there is a suspicion that a patient could be in pain by carefully evaluating the patient's response to trial analgesia, even if a specific physical lesion has not been identified.

Pain characterization and response to palliative care in dogs with naturally-occurring appendicular osteosarcoma: An open label clinical trial

This study aimed to characterize bone cancer pain (quantitative sensory testing (QST), stance asymmetry index, actimetry, scores of pain and quality of life (QoL)) in dogs with appendicular osteosarcoma (OSA), and to evaluate a stepwise palliative analgesic treatment.

The pain profile of thirteen client-owned dogs with OSA was compared with seven healthy dogs. Dogs with OSA were then enrolled in a prospective, open-label, clinical trial. Outcome measures included: primary and secondary mechanical thresholds (MT), conditioned pain modulation (CPM), stance asymmetry index, actimetry (most and least active periods), visual analog scales and QoL. After baseline assessments, stepwise treatment comprised orally administered cimicoxib (2 mg/kg q 24h), amitriptyline (1–1.5 mg/kg q 24h) and gabapentin (10 mg/kg q 8h); re-evaluations were performed after 14 (D14), 21 (D21) and 28 (D28) days, respectively. Statistics used mixed linear models (α = 5%; one-sided). Centralized nociceptive sensitivity (primary and secondary MT, and dynamic allodynia) was recorded in OSA dogs. Healthy dogs had responsive CPM, but CPM was deficient in OSA dogs. Construct validity was observed for the QST protocol. Asymmetry index was significantly present in OSA dogs. The CPM improved significantly at D14. When compared with baseline (log mean ± SD: 4.1 ± 0.04), most active actimetry significantly improved at D14 (4.3 ± 0.04), D21 and D28 (4.2 ± 0.04 for both). When compared with baseline, least active actimetry significantly decreased after treatment at all time-points indicating improvement in night-time restlessness. No other significant treatment effect was observed. Except for tactile threshold and actimetry, all outcomes worsened when gabapentin was added to cimicoxib-amitriptyline. Dogs with bone cancer are affected by widespread somatosensory sensitivity characterized by peripheral and central sensitization and have a deficient inhibitory system. This severe pain is mostly refractory to palliative analgesic treatment, and the latter was only detected by specific and sensitive outcomes.

Quantitative sensory testing in dogs with painful disease: A window to pain mechanisms?

Evaluation of the response to externally applied physical stimuli, such as pressure, heat, or cold is termed quantitative sensory testing (QST). QST may be used to identify and quantify alterations (gain or loss) in function of the sensory systems which detect and mediate these phenomena in both man and animals, and potentially discriminate peripheral and central sensitisation. It has been postulated that evaluation of QST parameters may predict response to analgesics, ultimately increasing the individualisation of treatment for pain. However, while there do appear to be correlations between QST measures and responses to analgesics in man, there is currently insufficient evidence to recommend QST to direct clinical treatments. The use of psychophysical testing, such as QST, in non-verbal subjects presents additional challenges, and requires familiarity with species and individual responses. This narrative review describes the investigations into QST in clinical populations of dogs to date, and discusses the potential benefits and limitations of such testing.

Assessment of the effects of gabapentin on activity levels and owner-perceived mobility impairment and quality of life in osteoarthritic geriatric cats

OBJECTIVE Toevaluate effects of gabapentin on activity levels and owner-perceived mobility impairment and quality of life (QOL) in osteoarthritic geriatric cats. DESIGN Blinded, placebo-controlled, randomized crossover-design study. ANIMALS 20 osteoarthritic cats (≥ 10 years old). PROCEDURES Cats received gabapentin (10 mg/kg [4.5 mg/lb]) or placebo treatment, PO, every 12 hours for 2 weeks, followed by the alternate treatment (with no washout period). Activity was assessed with a collar-mounted accelerometer. A client-specific outcome measure (CSOM) questionnaire was used weekly to collect owner assessments of 3 selected activities in which their cats had impaired mobility; QOL ratings (worse, the same, or improved) following crossover to each treatment and for the overall study period were collected at the end of the investigation. Activity counts, CSOM and QOL data, and deterioration in impaired activities (ie, decrease of ≥ 2 points in CSOM scores) associated with treatment crossover were assessed statistically. Adverse events were recorded. RESULTS Gabapentin administration was associated with significantly lower mean daily activity counts (48,333 vs 39,038 counts/d) and significantly greater odds (approx 3-fold change) of CSOM ratings indicating improvement in impaired activities, compared with results for the placebo treatment. A greater proportion of cats had deterioration in impaired activities after the crossover from gabapentin to placebo than when the opposite occurred, but the proportion of cats with worsened QOL did not differ between sequences. Adverse events were noted for 10 cats (9 that completed the study) during gabapentin treatment (sedation, ataxia, weakness, and muscle tremors) and 1 cat during placebo treatment (lethargy). CONCLUSIONS AND CLINICAL RELEVANCE Gabapentin treatment was associated with improvement in owner-identified impaired activities of osteoarthritic cats. Activity levels were lower than those during placebo treatment, and sedation was the most common adverse effect.

Refinement of the Montreal Instrument for Cat Arthritis Testing, for Use by Veterinarians: detection of naturally occurring osteoarthritis in laboratory cats

Objectives Feline osteoarthritis causes pain and disability. Detection and measurement is challenging, relying heavily on owner report. This study describes refinement of the Montreal Instrument for Cat Arthritis Testing, for Use by Veterinarians. Methods A video analysis of osteoarthritic (n = 6) and non-osteoarthritic (n = 4) cats facilitated expansion of scale items. Three successive therapeutic trials (using gabapentin, tramadol and oral transmucosal meloxicam spray) in laboratory cats with and without natural osteoarthritis (n = 12-20) permitted construct validation (assessments of disease status sensitivity and therapeutic responsiveness) and further scale refinements based on performance. Results Scale osteoarthritic sensitivity improved from phase I to phase III; phase III scale total score ( P = 0.0001) and 4/5 subcategories - body posture ( P = 0.0006), gait ( P = 0.0031), jumping (0.0824) and global distance examination ( P = 0.0001) - detected osteoarthritic cats. Total score inter-rater (intra-class correlation coefficients [ICC] = 0.64-0.75), intra-rater (ICC = 0.90-0.91) and overall internal consistency (Cronbach's alpha = 0.85) reliability were good to excellent. von Frey anesthesiometer-induced paw withdrawal threshold increased with gabapentin in phase I, in osteoarthritic cats ( P <0.001) but not in non-osteoarthritic cats ( P = 0.075). Night-time activity increased during gabapentin treatment. Objective measures also detected tramadol and/or meloxicam treatment effects in osteoarthritic cats in phases II and III. There was some treatment responsiveness: in phase I, 3/10 subcategory scores improved ( P <0.09) in treated osteoarthritic cats; in phase II, 3/8 subcategories improved; and in phase III, 1/5 subcategories improved ( P <0.096). Conclusions and relevance The revised scale detected naturally occurring osteoarthritis, but not treatment effects, in laboratory cats, suggesting future potential for screening of at-risk cats. Further study is needed to confirm reliability, validity (disease sensitivity and treatment responsiveness) and clinical feasibility, as well as cut-off scores for osteoarthritic vs non-osteoarthritic status, in client-owned cats.

Translational pain assessment: could natural animal models be the missing link?

Failure of analgesic drugs in clinical development is common. Along with the current "reproducibility crisis" in pain research, this has led some to question the use of animal models. Experimental models tend to comprise genetically homogeneous groups of young, male rodents in restricted and unvarying environments, and pain-producing assays that may not closely mimic the natural condition of interest. In addition, typical experimental outcome measures using thresholds or latencies for withdrawal may not adequately reflect clinical pain phenomena pertinent to human patients. It has been suggested that naturally occurring disease in veterinary patients may provide more valid models for the study of painful disease. Many painful conditions in animals resemble those in people. Like humans, veterinary patients are genetically diverse, often live to old age, and enjoy a complex environment, often the same as their owners. There is increasing interest in the development and validation of outcome measures for detecting pain in veterinary patients; these include objective (eg, locomotor activity monitoring, kinetic evaluation, quantitative sensory testing, and bioimaging) and subjective (eg, pain scales and quality of life scales) measures. Veterinary subject diversity, pathophysiological similarities to humans, and diverse outcome measures could yield better generalizability of findings and improved translation potential, potentially benefiting both humans and animals. The Comparative Oncology Trial Consortium in dogs has pawed the way for translational research, surmounting the challenges inherent in veterinary clinical trials. This review describes numerous conditions similarly applicable to pain research, with potential mutual benefits for human and veterinary clinicians, and their respective patients.

Chronic maladaptive pain in cats: A review of current and future drug treatment options

Despite our increasing understanding of the pathophysiology underlying chronic or maladaptive pain, there is a significant gap in our ability to diagnose and treat the condition in domestic cats. Newer techniques being used to identify abnormalities in pain processing in the cat include validated owner questionnaires, measurement of movement and activity, and measurement of sensory thresholds and somatomotor responses. While some data are available evaluating possible therapeutics for the treatment of chronic pain in the cat, most data are limited to normal cats. This review details our current understanding of chronic or maladaptive pain, techniques for the detection and measurement of the condition and the associated central nervous changes, as well as an overview of the data evaluating potential therapeutics in cats.

Analgesic efficacy of tramadol in cats with naturally occurring osteoarthritis

OBJECTIVES

This study aimed to (1) compare outcome assessments in normal and osteoarthritic cats and (2) evaluate the analgesic efficacy of tramadol in feline osteoarthritis (OA), in a prospective, randomised, blinded, placebo-controlled, crossover design.

METHODS

Twenty cats were included after clinical examination, blood work and full body radiographs were performed. In Phase 1, outcome assessments aimed to differentiate normal (n = 5; i.e. exempt of any radiographic and clinical sign of OA) from OA (n = 15) cats. In Phase 2, OA cats were treated twice daily with a placebo (PG: cornstarch 15 mg) or tramadol (TG: 3 mg/kg) orally for 19 days, with a 3-month washout period between treatments. Evaluations were performed in normal and OA cats at baseline and consisted of: 1) peak vertical force (PVF) after staircase exercise; 2) telemetered night-time motor activity (NMA); and 3) response to mechanical temporal summation (RMTS). After treatment, PVF, NMA and RMTS evaluations were repeated in OA cats. Data were analysed with mixed model methods with an alpha-threshold of 5%.

RESULTS

Phase 1: 1) PVF (% of body weight; mean ± SD) was higher in normal (59 ± 10.5) than in OA cats (50.6 ± 5.7) (p = 0.005); 2) NMA (no unit) was not different between groups; 3) RMTS (number of stimuli; median (range)) was higher in normal [29.5 (23.5-30)] than in OA cats [14 (8.5-28)] (p < 0.0001). Phase 2: PVF, NMA and RMTS presented a treatment effect (p = 0.024, p = 0.008 and p = 0.018, respectively). No clinically important adverse-effects were observed.

CONCLUSION

Outcome assessments such as kinetics (PVF) and evaluation of central sensitisation (RMTS) are discriminant of OA status. Mobility measured by NMA was not discriminant of OA status, however it increased in OA cats with tramadol treatment. Nociceptive hypersensitivity quantified by RMTS was evident in OA cats and was responsive to tramadol treatment.

Repeatability of quantitative sensory testing in healthy cats in a clinical setting with comparison to cats with osteoarthritis

Objectives

The aim of this study was to evaluate the repeatability of quantitative sensory tests (QSTs) in a group of healthy untrained cats (n = 14) and to compare the results with those from cats with osteoarthritis (n = 7).

Methods

Peak vertical force (PVF) and vertical impulse were measured on a pressure plate system. Thermal sensitivity was assessed using a temperature-controlled plate at 7°C and 40°C. Individual paw lifts and overall duration of paw lifts were counted and measured for each limb. Paw withdrawal thresholds were measured using manual and electronic von Frey monofilaments (MVF and EVF, respectively) applied to the metacarpal or metatarsal pads. All measurements were repeated twice to assess repeatability of the tests.

Results

In healthy cats all tests were moderately repeatable. When compared with cats with osteoarthritis the PVF was significantly higher in healthy hindlimbs in repeat 1 but not in repeat 2. Cats with osteoarthritis of the forelimbs showed a decrease in the frequency of paw lifts on the 7°C plate compared with cats with healthy forelimbs, and the duration of paw lifts was significantly less than healthy forelimbs in the first repeat but not in the second repeat. Osteoarthritic limbs had significantly lower paw withdrawal thresholds with both MVF and EVF than healthy limbs.

Conclusions and relevance

QSTs are moderately repeatable in untrained cats. Kinetic gait analysis did not permit differentiation between healthy limbs and those with osteoarthritis, but thermal sensitivity testing (cold) does. Sensory threshold testing can differentiate osteoarthritic and healthy limbs, and may be useful in the diagnosis and monitoring of this condition in cats in the clinical setting.

Preliminary Validation and Reliability Testing of the Montreal Instrument for Cat Arthritis Testing, for Use by Veterinarians, in a Colony of Laboratory Cats

Simple Summary

Feline osteoarthritis (OA) is challenging to diagnose. A pain scale was developed for use by veterinarians, in association with their physical examination, and tested for reliability and validity. The scale items were: Interaction with the examiner, Exploration of the room, Body Posture, Gait, Body Condition, condition of Coat and Claws, and abnormal Findings or Cat Reaction upon joint Palpation. Expert review supported the scale content. Two studies using laboratory-housed cats found the most promising results for Gait and Body Posture, in terms of distinguishing between OA and non-OA cats, repeatability of results, and correlations with objectively measured kinetics (weight-bearing).

Abstract

Subtle signs and conflicting physical and radiographic findings make feline osteoarthritis (OA) challenging to diagnose. A physical examination-based assessment was developed, consisting of eight items: Interaction, Exploration, Posture, Gait, Body Condition, Coat and Claws, (joint) Palpation–Findings, and Palpation–Cat Reaction. Content (experts) and face (veterinary students) validity were excellent. Construct validity, internal consistency, and intra- and inter-rater reliability were assessed via a pilot and main study, using laboratory-housed cats with and without OA. Gait distinguished OA status in the pilot (p = 0.05) study. In the main study, no scale item achieved statistically significant OA detection. Forelimb peak vertical ground reaction force (PVF) correlated inversely with Gait (Rho_s = −0.38 (p = 0.03) to −0.41 (p = 0.02)). Body Posture correlated with Gait, and inversely with forelimb PVF at two of three time points (Rho_s = −0.38 (p = 0.03) to −0.43 (p = 0.01)). Palpation (Findings, Cat Reaction) did not distinguish OA from non-OA cats. Palpation—Cat Reaction (Forelimbs) correlated inversely with forelimb PVF at two time points (Rho_s = −0.41 (p = 0.02) to −0.41 (p = 0.01)), but scores were highly variable, and poorly reliable. Gait and Posture require improved sensitivity, and Palpation should be interpreted cautiously, in diagnosing feline OA.