Steroid diffusion into the navicular bursa occurs in horses affected by palmar foot pain

Objective evaluation for analgesia of the distal interphalangeal joint, the navicular bursa and perineural analgesia in horses with naturally occurring forelimb lameness localised to the foot

BACKGROUND

The outcome and interpretation of intra-synovial diagnostic analgesia of the distal interphalangeal joint (DIPJ) and the navicular bursa (NB) remain in dispute, and no objective studies have been carried out to establish the percentage of improvement over time from these two analgesia techniques.

OBJECTIVES

To investigate the qualitative and time-dependent outcome of DIPJ-A and NB-A in naturally occurring forelimb lameness.

STUDY DESIGN

Case series.

METHODS

Twenty-three clinical cases with forelimb lameness were evaluated objectively using a body mounted inertial sensor system (BMIS). Lameness was localised to the foot with a palmar digital nerve block and/or an abaxial sesamoidean nerve block on day 1, and analgesia of the DIPJ (DIPJ-A) and NB (NB-A) were performed on days 2 and 3. Improvement following perineural analgesia was measured after 10 min and intra-synovial blocks after 2-, 5- and 10-min. Horses with at least 70% improvement measured objectively after diagnostic analgesia were included in the study.

RESULTS

There was no significant association between improvement following perineural analgesia and the DIPJ-A and NB-A. The mean improvement in the lameness differed between DIPJ-A and NB-A at 2 min (p < 0.001) and at 5 min (p = 0.04), and it was no longer observed after 10 min (p = 0.06). A positive NB-A produced a high degree of improvement that remained stable, whereas the DIPJ-A improved over time.

MAIN LIMITATIONS

Perineural and intra-synovial analgesia were performed without contrast medium to assess the diffusion of mepivacaine.

CONCLUSIONS

Our results suggest that perineural analgesia is not reliable enough to differentiate pain originating from DIPJ and NB. Early evaluation of the DIPJ-A and NB-A can determine the origin of the pain. An improvement following NB-A was constant over time, but an improvement following DIPJ-A varied by up to 10 min.

Mechanical nociceptive assessment of the equine hoof after navicular bursa anesthetic infiltration validated by bursography

The analgesic specificity of navicular bursa (NB) anesthetic infiltration is still questionable. The study aimed to determine the mechanical nociceptive threshold of non-specific analgesia in the dorsal lamellar stratum, as well as in the sole, coronary band, and heel bulbs of the hoof, after navicular bursa anesthetic infiltration. Six healthy horses with no clinical or radiographic changes of the digits and no communication between the NB and the distal interphalangeal joint, were used. After random selection, the NB of one of the forelimbs was infiltrated with 2% lidocaine and the contralateral one with lactated ringer’s solution. Contrast was added to confirm radiographic infiltration. The mechanical nociceptive threshold was determined using a portable pressure dynamometer, before and at various times after the infiltration, in 10 points of the hoof. The effects of time and treatment were verified by ANOVA (P<0.05). There was no statistical difference in the values of the mechanical nociceptive threshold (P>0.05) in all regions evaluated. However, in one of the six hooves that receives lidocaine, complete absence of response to the painful stimulus (maximum force of 6 Kg over an area of 38.46 mm², for a maximum of 4 seconds) was observed in the dorsal lamellae between 30 and 60 min after infiltration. In conclusion, lidocaine infiltration of NB did not promote significant increases in the nociceptive threshold of the sole, coronary band, bulbs of the heel and dorsal lamellae clinically healthy horses. However, the occurrence of analgesia in one of the six hooves subjected to NB anesthesia indicates that the technique may not be fully specific in few horses.

Ex vivo effects of corticosteroids on equine deep digital flexor and navicular fibrocartilage explant cell viability

OBJECTIVE

To investigate the effects of triamcinolone acetonide (TA) and methylprednisolone acetate (MPA) on the viability of resident cells within the fibrocartilage on the dorsal surface of the deep digital flexor tendon (FC-DDFT) and fibrocartilage on the flexor surface of the navicular bone (FC-NB) of horses.

SAMPLE

12 to 14 explants of FC-DDFT and of FC-NB from grossly normal forelimbs of 5 cadavers of horses aged 9 to 15 years without evidence of musculoskeletal disease.

PROCEDURES

Explants were incubated with culture medium (control) or TA-supplemented (0.6 or 6 mg/mL) or MPA-supplemented (0.5 or 5 mg/mL) medium for 6 or 24 hours. Explant metabolic activity and percentage of dead cells were assessed with a resazurin-based assay and live-dead cell staining, respectively, at each time point. Drug effects were assessed relative to findings for the respective control group.

RESULTS

Application of TA (at both concentrations) did not significantly change the cell viability of FC-DDFT explants. For FC-NB explants, TA at 6 mg/mL significantly reduced the metabolic activity and increased the percentage of dead cells at both time points. With either MPA concentration, FC-DDFT and FC-NB explants had reduced metabolic activity and an increased percentage of dead cells at 24 hours, whereas only MPA at 5 mg/mL was cytotoxic at the 6-hour time point.

CONCLUSIONS AND CLINICAL RELEVANCE

In ex vivo explants, TA was less cytotoxic to equine FC-DDFT and FC-NB cells, compared with MPA. Further work is warranted to characterize the drugs' transcriptional and translational effects as well as investigate their cytotoxicity at lower concentrations.

In vitro Effects of Methylprednisolone Acetate on Equine Deep Digital Flexor Tendon-Derived Cells

Primary deep digital flexor tendon (DDFT) pathologies and those accompanying degenerative changes of navicular bone fibrocartilage are major causes of lameness associated with navicular disease. Intrasynovial corticosteroids are mainstay in the treatment due to the anti-inflammatory effects, but their effect on DDFT cell biosynthesis are unknown. The objective of this in-vitro study was to investigate the effects of methylprednisolone acetate (MPA) on cells isolated from the dorsal fibrocartilaginous region of forelimb DDFTs (DDFT-derived cells) of 5 horses (aged 11–17 years). Non-adherent aggregate cultures were established from third passage cells over a 72 to 96-h duration prior to treating with medium containing 0 (control), 0.05 and 0.5 mg/mL MPA for 24 h. Tendon and cartilage extracellular matrix (ECM) related gene expression, cell aggregate and culture medium GAG contents, culture medium collagen and MMP-3 and−13 concentrations were measured. After 24 h of treatment, only the higher MPA concentration (0.5 mg/mL) significantly down-regulated tendon ECM related genes; whereas, both MPA doses significantly down-regulated cartilage ECM related genes. MPA treatment did not affect the total GAG content of DDFT-derived cells or total GAG, soluble collagen and MMP-3 and−13 contents in culture medium compared to untreated controls. Future studies to determine the response of DDFT-derived cells with longer exposure times to corticosteroids and in the presence of inflammatory cytokines are necessary. These results are a first step in assessing the effects of intrasynovial medications on equine DDFT, for which currently no information exists.

Recent advances in conservative and surgical treatment options of common equine foot problems

Foot problems are very common causes of lameness in horses. With the recent diagnostic advances to evaluate and treat foot pathology as well as to monitor response to therapy, it is now possible to more accurately evaluate the effectiveness of many of these treatments. This review details some of the recent advances of the most common conservative and surgical treatment options for foot problems in horses, including an overview of evidence on the efficacy to support the use of these treatment options and on factors that may affect prognosis.

Response of three digital anesthetic technics in horses with forelimb hoof lameness

ABSTRACT The presented study aimed to assess objectively the response of distal interphalangeal joint (DIJ), navicular bursa (NB) and deep digital flexor tendon sheath (DDFTS) anesthesia in horses with forelimb hoof lameness; and evaluate if the presence of radiographic abnormalities on navicular bone could interfere on blocks’ results. Fifteen horses with lameness improvement above 70% after palmar digital nerve (PDN) block were selected for this study. Blocks were assessed separately on five consecutive trials at seven different time-points. The fifth trial was performed to evaluate the influence of exercise on preexisting lameness. Most of horses (73.33%) presented pain related to the podotrochlear apparatus based on clinical and lameness exam and blocks’ responses. NB and DIJ anesthesia differed on the frequency of horses with lameness improvement above 70% only at 10min (p=0.03), and both differed from DDFTS block until 30’(p<0.05). The blocks’ response was variable along the time and the highest means for NB, DIJ and DDFTS were observed at 5-10 minutes (’), 15-20’ and 10-15’ respectively.Exercise had low interference on lameness intensity since no improvement above 50% was observed and an increase on lameness intensity over time was identified in seven horses. Variable grades of navicular bone radiographic lesions were observed in 14 horses, although these lesions had no interference on blocks’ response (p>0.05). The NB and DIJ blocks had similar responses and both were superior to DDFTS anesthesia, coincident with a major prevalence of podotroclear apparatus abnormalities in this equine population.

Pain Management in Horses

There has been great progress in the understanding of basic neurobiologic mechanisms of pain, but this body of knowledge has not yet translated into new and improved analgesics. Progress has been made regarding pain assessment in horses, but more work is needed until sensitive and accurate pain assessment tools are available for use in clinical practice. This review summarizes and updates the knowledge concerning the cornerstones of pain medicine (understand, assess, prevent, and treat). It highlights the importance of understanding pain mechanisms and expressions to enable a rational approach to pain assessment, prevention, and management in the equine patient.

An ultrasound-guided, tendon-sparing, lateral approach to injection of the navicular bursa

BACKGROUND

Navicular disease in the horse often requires injection of the navicular bursa. We have developed an ultrasound-guided, lateral needle approach to navicular bursocentesis, which avoids penetration of the deep digital flexor tendon (DDFT) and the need for radiographic control.

OBJECTIVES

To describe and evaluate the feasibility and efficacy of an ultrasound-guided, lateral bursocentesis technique.

STUDY DESIGN

Cadaveric and in vivo experiments.

METHODS

The navicular bursa in 62 cadaveric forelimbs of 31 horses and in both forelimbs of 26 live horses, positioned with the foot flexed in a navicular block, were submitted to lateral, ultrasound-guided injection of 1.5 ml radiocontrast agent. Lateromedial radiographs were taken to locate the contrast. A second injection of 0.5 ml methylene blue was administered during needle withdrawal in cadaveric limbs to investigate the needle pathway during dissection.

RESULTS

Contrast agent was successfully deposited in the navicular bursa in 104 of 114 (91%) limbs and in the navicular bursa alone in 89 of 114 (78%) limbs. Dissection showed no evidence of penetration of the DDFT in cadaver limbs. Failure to inject the navicular bursa was significantly associated with poor quality of the ultrasound image (P = 0.04) and resulted in aberrant injection of the distal interphalangeal joint in five of 114 (4%) limbs, the peribursal soft tissues in four of 114 (4%) limbs and the digital flexor tendon sheath in one of 114 (0.9%) limbs. Synovial fluid was observed at the needle hub in 58% of live horses.

MAIN LIMITATIONS

It is unknown whether injection results obtained in the limbs of horses without disease can be extrapolated to horses with clinical disease of the podotrochlear apparatus. The localisation of contrast medium on radiographs may not accurately reflect the behaviour of local anaesthetic solution or therapeutic medications injected in the navicular bursa.

CONCLUSIONS

This lateral, ultrasound-guided technique for injecting the navicular bursa is effective, does not penetrate the DDFT and avoids exposure of personnel to radiation.