Lesions of the distal deep digital flexor tendon (DDFT) are frequently diagnosed using magnetic resonance imaging (MRI) in horses with foot pain. The prognosis for horses with DDFT lesions to return to previous levels of performance is poor. Treatment options are limited; consisting of conservative therapy, desmotomy of the accessory ligament of the deep digital flexor tendon, injection of the digital sheath or navicular bursa, navicular bursoscopy or intralesional injection. Intralesional injection of biologic therapeutics shows promise in tendon healing, with increased number of experimental and clinical studies finding positive results. However, accurate injection of DDFT lesions within the hoof is difficult and requires general anesthesia. The Hallmarq open, low-field MRI unit was used to develop an MRI-guided technique to inject structures within the hoof. This procedure has been previously reported for injecting the collateral ligaments of the distal interphalangeal joint. Four clinical cases of deep digital flexor tendinopathy have been treated with MRI-guided injections using a similar technique.
The aim of this study was to evaluate accuracy of a technique for injection of the deep digital flexor tendon within the hoof using MRI-guidance, which could be performed in standing patients. We hypothesized that injection of the DDFT within the hoof could be accurately guided using open low-field MRI to target either the lateral or medial lobe at a specific location. Ten cadaver limbs were positioned in an open, low-field MRI unit to mimic a standing horse. Each DDFT lobe was assigned to have a proximal (adjacent to the proximal aspect of the navicular bursa) or distal (adjacent to the navicular bone) injection. A titanium needle was inserted into each tendon lobe, guided by T1-weighted transverse images acquired simultaneously during injection. Oil-based colored dye was injected as a marker. Post-injection MRI and gross sections were assessed by three blinded investigators experienced in equine MRI. The success of injection as evaluated on gross section was 85% (70% proximal, 100% distal). The success of injection as evaluated by MRI was 65% (60% proximal, 70% distal). There was no significant difference between the success of injecting the medial versus lateral lobe. The major limitation of this study was the use of cadaver limbs with normal tendons. The authors concluded that injection of the DDFT within the hoof is possible using MRI guidance. Future work should be focused on using the techniqe in live horses with tendon lesions, and more clinical studies are needed to determine the most efficacious biologic therapeutic for tendon healing. / Master of Science / The deep digital flexor tendon is a commonly injured soft tissue structure in horses. This tendon inserts on the distal phalanx, within the hoof capsule. At this level, lesions of this tendon are commonly diagnosed with magnetic responance imaging (MRI). Treatment options are limited and consist of stall rest, supportive shoeing and a rehabilitation program. The prognosis for horses to return to previous levels of work is poor. For specific lesions of the tendon, surgery can be performed to explore the navicular bursa which allows access to the dorsal surface of the tendon. Other treatment options include injection of corticosteroids in the digital tendon sheath or navicular bursa or intralesional injection of various biological therapeutics such as stem cells. In recent years, there has been increasing use of biological therapeutics for tendon injury. Research in experimental and clinical studies in horses has shown promise in using stem cells to improve the healing of tendon injuries. However, as the deep digital flexor tendon is not visible using ultrasonography at its most distal aspect within the hoof capsule, alternative techniques are needed to guide placement of a needle. Currently, these other techniques are difficult and require general anesthesia. The Hallmarq open, low-field MRI unit allows for MRI examinations to be performed in the standing horse, which decreases cost, staff involved and risks. We have developed a technique which utilizes open, low-field MRI to guide injection of the deep digital flexor tendon within the hoof capsule, that can be performed in standing horses. This study describes the technique in cadaver limbs and assesses the accuracy of targeting a specific portion of the tendon with the injection. Utilizing low-field MRI a technique was developed to guide injection of the deep digital flexor tendon within the hoof capsule, performed in standing horses. The results suggest that the technique is accurate when used in standing horses to inject the deep digital flexor tendon within the hoof.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/77699 |
| Date | 22 May 2017 |
| Creators | Groom, Lauren M. |
| Contributors | Veterinary Medicine, Barrett, Jennifer G., White, Nathaniel A., Adams, Morton Norris |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Detected Language | English |
| Type | Thesis |
| Format | ETD, application/pdf, application/pdf, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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