Contrast Medium Controlled Injection in the Navicular Bursa and the Following Bursography in 23 Cases

Contrast Medium Controlled Injection in the Navicular Bursa and the Following Bursography in 23 Cases. Equine palmar foot syndrome or navicular disease is a common cause of chronic front limb lameness. The state-of-the-art magnetic resonance imaging is not available for all patients and ultrasonography is sometimes impossible. Intrabursal medication is an important part of treating the disease. Contrast-enhanced (CE) radiography seems to be another interesting imaging modality. There is no information about the CE dorsoproximal-palmarodistal oblique (DPr-PaDiO) radiographs in living horses. This case study shows the first results of this imaging technique with explanations of the findings. Twenty out of 23 injections were successful. The navicular bursa (NB) and the distal interphalangeal joint were filled with contrast medium (CM) in 1/23. There was CM palmar to the deep digital flexor tendon (DDFT) in addition to the filled NB in 5/20 (25 %) cases. The DPr-PaDiO CE showed alliterations in 7/9 (77.78 %) with a clinical history of lameness. There were two DDFT lesions, one full flexor cortex lesion, three suspected ruptures of the NB and five NB adhesions. The DPr-PaDiO CE X-ray is an inexpensive and highly available additional imaging tool in horses with suspected equine palmar foot syndrome.


Introduction
Equine palmar foot syndrome is a common cause of front limb lameness in the horse [1]. The podotrochlear apparatus is a special anatomic feature in the horse due to the deep digital flexor tendon needing a pulley before the insertion on the distal phalanx.
Alliterations of one of these structures alone or combined lead to pain [2]. Magnetic resonance imaging (MRI) is a favorable method to diagnose the different lesions [3][4][5]. Ultrasound is also an option to diagnose changes in the DIL and DDFT [6,7]. Due to lesions in the soft tissue, X-ray is sufficient to diagnose equine palmar foot syndrome [8]. Contrast radiography with palmaroproximal-palmarodistal oblique views seem to be helpful in diagnosing changes in the DDFT and the flexor surface cartilage [9,10]. Intrabursal medication is one of the widest use practices in navicular disease [11,12].
There are many ways to inject the bursa. The distal palmar approach to the "navicular position," defined as a point on the lateral hoof wall, 1 cm distal to the coronary band, and halfway between the most dorsal and most palmar aspect of the coronary band [12], seems to be very successful. In cadaver limbs, 23/25 (92 %) were injected successful with 1.1 redirection per injection. However, there was also contrast medium (CM) in the distal interphalangeal joint (DIP) in 1/25 (4 %) and palmar to the DDFT in 1/25 (4 %) legs. There is also the possibility to show alliterations in navicular apparatus in cadaver limbs with bursography, especially with the dorsoproximal-palmarodistal oblique view [13]. There is a reported success of 14/17 for NB injections (82.35 %) in living horses [14]. There is no information currently about dorsoproximalpalmarodistal oblique radiographic projections with CM in the NB in living horses. Thus, this case study will show the first results of this technique in living horses.

Materials and Methods
Thirteen horses were chosen for a reason not connected to the study for injection of the NB. Patients were presented in the hospital from 2015 to 2020 and were all warmbloods. Nine horses were injected in both front feet. Only one foot was injected in each of four horses. The NB was injected twice in one horse. There was complete lameness examination data available in seven horses, including a positive distal digital nerve block. The data were collected retrospectively. All horses underwent a distal digital nerve block and a sedation with detomidine and butorphanol. The skin between the heel bulbs was shaved or clipped and washed for 5 min with antibacterial soap and swabbed several times with alcohol. The foot was placed on a standard DP 65° wooden block and held by staff, the same way as for the DPr-PaDiO radiographic projections. An amount of 3 ml Iomeprol 300 mg ID/ml (Imeron The landmark for needle insertion was a point just proximal to the central sulcus of the frog, with the needle directed toward the apex of the frog and parallel to the ground surface of the hoof [10]. The correct placement of the needle was controlled with a latero-medial view. If the needle was not in place, it was redirected and also checked with an latero-medial view until it was correctly placed. The CM was then injected and another latero-medial view was taken to see whether the bursa was filled with CM. Holding the leg still in position, the DPr-PaDiO radiographic projection and a palmaroproximal-palmarodistal oblique (PaPr-PaDiO) radiograph on a standard block were made. All radiographs were acquired with a mobile X-ray tube (TR 90/30, Gierth®, Riesa, Germany) and a direct X-ray detector system (Mark 3 Sound-Eklin® Carlsbad, CA, USA or CXDI-801C, Canon®, Tokyo, Japan). shaped. An adhesion would be represented by a radiolucent area.
As described above, there is a small amount of CM between the navicular bone and the DDFT. If there is an adhesion between those structures mentioned, the dye column will be interrupted. The radiological density of the scar tissue is like soft tissue, therefore, there will be radiolucency.

Results/Observations
Twenty-three legs were injected. The NB was successfully The findings are summarized in Table 1. There were two DDFT lesions, one full flexor cortex lesion, three suspected ruptures of the NB and five NB adhesions. Table 1: Table 1 shows the information about the horses, results of the injection and radiographic evaluation. + = positive and -= negative, n.a. = not available.   Horse 11 has a chronic right front limb lameness (3/5). The distal digital nerve block was positive. The radiographs and ultrasound of the tendon in the heel region (not transcuneal) were without significant findings. The owners reported a history of stumbling. Because they did not want to make an MRI, the NB was injected and the additional CE views were obtained. There were several longitudinal (proximo-distal) straight and radiopaque lines in the DPr-PaDiO CE (Figure 3a). The horse was diagnosed with a DDFT tendonitis. Additionally, there was an irregular proximal border of the dye column. The horse was given a poor prognosis for riding but a guarded prognosis for a pasture retirement. A special shoe for DDFT tendonitis was advised. The horse was sound for two months and returned with recurrent lameness after three months.
The suspected tendon tear had enlarged enormously ( Figure 3b) and was not visible in the ultrasound of the pastern region. The prognosis given was now poor. A neurectomy was performed even with the assessment that the chance was very poor and the tendon tear would be progressive. Three months later the horse was euthanized because of lameness when walking.  & 5d). In the lateral view, there was also a radiolucent area in the bursa, which seems to be air from the injection. Therefore, the air presents the proximal border of the NB. Three out of these four legs received 10 mg/1ml triamcinolonacetonide. Figure 4: CE X-rays of horse 1,2 right front; lateral is to the left a. The DPr-PaDiO X-ray shows that the proximal border of the NB has two outer pouches with normal invaginations, which represent the normal synovium of the NB. It is nearly the same in the distal border of the NB. Except for the pooling of CM on the medial site of the navicular bone, this seems to be a normal NB. The CM medial to the bursa has to be a small rupture of the NB; b. The finding is reproducible in the DPr-PaDiO X-ray. In addition, a small pooling of CM lateral to the ridge of the navicular bone is visible C. c) and d) The same projections of a cadaver limb injected with 3 ml CM without medication. The proximal border has two outer pouches and is round-shaped in the lateral view.

Discussion
The injection of the bursa is a crucial part of treating navicular disease [11]. There has been a lot of discussion about whether it is necessary to inject the bursa because medication of the DIP joint will diffuse to the NB anyway [15,16]. Therefore, whether to inject the bursa or not should be considered every time [17]. There can be a case of DDFT tendonitis after injecting the bursa [18]. If the decision to inject the bursa has been made, a contrast study [12] for a successful injection seems to be necessary. In our study, the success rate in living horses with an X-ray-guided injection was successful in 20/23 (86.96 %) cases, which is nearly the same as that reported previously: 14/17 (82.35 %) [14]. The reason for the difference between 23/25 (92 %) [19] and (96/96) 100 % [13] seems to be the movement of a living horse. The horse is able to move in the time between making the lateral X-ray to check the needle placement and the injection. Even with the foot placed on the block, the lifted leg can fluctuate and the connected movement of the DDFT can move the needle.
The bursography revealed a diagnosis in 6/7 cases. In two cases (horse 3 and 11), the prognosis based on the bursography was correct, even though one of these cases did not show marked alliterations in the radiographs. In these cases, a MRI was not necessary and saved the owner money and stress for the horse.
The communication between the NB and the DIP joint, as in horse 1, is also a finding which is perhaps not visible in the MRI. The same applies to the right front leg of horse 12. The rupture of the NB may only be visible in the MRI with CM [20]. The mixture of the CM with another medication could be a problem in evaluating bursographies, as shown in Figure 5. The CM based on iodine had a higher density than other drugs. In addition, it does not seem to be dilutable in other drugs. Therefore, there can be two phases in the bursa: distal the CM and proximal the medication (e.g. triamcinolone), and perhaps air. But no problems seem to occur when mixing the CM with local anesthetics and injecting them into synovial structures [21,22]. One horse in this study developed an acute onset of lameness after the injection. No horse had a septic inflammation. The injection of up to 6 ml in the bursa seems to be safe [20]. This is the first study on the DPr-PaDiO CE in living horses.
No validated statistics could be made because of the low number of cases and the absence of a gold standard. The findings were compared with results from cadaver limbs [13]. Further research should be made to ensure these first results. This study shows that the injection of the NB should always be controlled with CM to be sure if the injection was successful. The bursography could lead to a diagnosis, a safer prognosis and a successful control for intrabursal treatment especially in cases where MRI or ultrasound examinations are not possible.