Clinical and morphological justification of the treatment of purulonecrotic lesion in deep structures of limb distal segment in pig: case report

Surgical pathology of the musculoskeletal system, and in particular the diseases of the limb distal segment in pigs are quite common. Their significant spread leads to economic losses due to culling, compulsory slaughter, short-received pig production and pig crop. The purpose of this work was to reveal clinical and morphological features of limb distal segment diseases in pigs and to study the possibility of preserving their health and productivity. The conservative treatment of purulonecrotic lesions in the deep structures of the limb distal segment in pigs is not promising. It is shown that the best way to treat a given pathology is amputation of a sick limb. The technique of carrying out exarticulation of talus shin consists in separation of soft tissues, capsule and ligaments, ligation of vessels, formation of stump. The postoperative recovery period of the animal body is 25 days.


INTRODUCTION
The introduction of intensive technologies in modern pig breeding allows, at minimal investments, to increase the productivity of pigs and to improve the working conditions of service personnel. Optimization of livestock, material and labor systems increases the efficiency of obtaining healthy pigs. Housing a large number of pigs in group pens and lack of exercise combined with malnutrition increase the risk of the musculoskeletal diseases (Burdenyuk & Vlasenko, 1985;Borisevich, 1991Borisevich, , 2007Podobed et al., 2011, Van de Weerd;Day, 2009). Diseases of the limb distal segment lead to a worldwide decline in producing ability of pigs in different age groups, posing a serious threat to the well-being of replacement and breeding livestock (KilBride et al., 2009).
Analysis of the literature makes it possible to conclude that the surgical pathology of the musculoskeletal system, and in particular the diseases of the limb distal segment in pigs are quite common. Their significant spread leads to economic losses due to culling, compulsory slaughter, short-received pig production and pig crop.

MATERIALS AND METHODS
The investigation was conducted in pig farms of VAT "Smak Myrhorodshchyny" (open jointstock company "Taste of Mirgorod area") in Myrhorod district, Poltava region, Ukraine. The pigs were kept in typical quarters with concrete floors, according to groups: weaning piglets, growing-fattening pigs, replacement pigs and sows. Our research subject was purulonecrotic lesions in the deep structures of the limb distal segment in Large White and Landrace pigs. This pathology is most often recorded in sows after the fourth farrowing, as well as in weaning piglets, mainly on the hind limbs.
The purpose of this work was to reveal clinical and morphological features of limb distal segment diseases in pigs and to study the possibility of preserving their health and productivity. Two pigs were taken for the study. To achieve this goal, we applied a battery of general and specific clinical research methods used in Ukraine. Drugs used for anesthesia: sevoflurane, zoletil, lidocaine, propofoleven, the patients were stable for the entire operation for 2.5 hours, did not show any signs of pain, heart rate 90-95, ventilation mode Simv, CO2 35-45, Fio2 65-70, flow 10ml/kg/min.
Animal housing conditions and experimental research methods complied with the provisions of the European Convention for the Protection of Vertebrate Animals Used for Experimental and Other Scientific Purposes (EES, 1986). The reserch protocol of the courent study was appruved by the Ethic Committee of Poltava State Agrarian Academi (Aprobal number 2020/04.

RESULTS AND DISCUSSION
Diseases of the deep structures of the hoof ( Figure  1) belong to the group of surgical diseases affecting joint, tendon and bone apparatus of the limb distal segment. First of all, this group includes arthritis and osteomyelitis, that, according to our data (Kirichko et al., 2015;Kirichko & Semirenko, 2016), depending on the age group, account for 0.1 to 4% of all limb diseases in pigs. Arthritis is an inflammation of the joint capsule and adjacent collateral ligaments due to joint tissue trauma or chronic specific infection (chlamydiosis, mycoplasmosis). The tissue of the affected joint is tense on palpation, hot to the touch, there is severe pain reaction. The sick pig lies down, seldom gets up; lameness of III-IV degrees is observed. Excessive fluid in the joint cavity stretches the capsule, forming a fistula for fibrinopurulent exudate to go out. Arthritis was recorded on one or two limbs, in rare cases at all of them.
Osteomyelitis is an inflammation of the bone marrow and bone tissue in the thickness of the cortical layer, followed by its destruction. It occurs due to the significant traumatization of tissues with the microbial contamination of the bone base. Sick pigs are restless, they lose appetite, lameness up to IV-V stages is intensively developed. On palpation, severe pain reaction was observed, the tissues were swollen, and the local temperature was high. X-ray images show characteristic features (Figure 2). The X-ray shows the area of osteolysis of the epiphyseal-diaphyseal part of the metacarpal bone. Bone destruction also extends into the joint cavity, which is characteristic of osteomyelitis and infectious arthritis. Pathological materialthe distal part of the affected limbwas taken from the sick pigs subjected to sanitary slaughter. The material was frozen and longitudinal sections of tissues were performed within the frames of the affected areas (Figure 3-5).    Inflammatory destructive phenomena in the area of the epiphyseal-diaphyseal fusion we observed in other clinical cases as well ( Figure 5). The inflammatory process extends to the cortical layer of the diaphysis of the metacarpal bone, bone marrow, and the metacarpophalangeal joint capsule. The conservative treatment of purulonecrotic lesions in the deep structures of the limb distal segment in pigs is unpromising. The only effective way to treat such a pathology is the removal of the peripheral part of the organ, i.e. amputation. The best long-term results were obtained after hind limb surgery in young animals. For this purpose, an exarticulation tactic of the ankle mortise joint was developed.
The operation can be performed in a pig farm, preparing the animal with a 12 hour fast. After the introduction of the animal into general anesthesia, fixation in the dorsal position, preparation of the operative field and local anesthesia, a circular incision of the skin was performed, 3cm more proximal of the ankle joint. Then the skin was dissected to the tibia. From the caudal side of the limb above the calcaneus, the artery and the saphenous vein were sutured up to the heel muscle. The tibial artery from the cranial side of the limb was stitched with a piercing ligature up to the eponymous muscle. The dorsal ankle artery was stitched with ligature up to the transverse ligament of tibia.
On the cranial side, exarticulation was performed below the transverse ligament of tibia. The heel tendon of the eponymous muscle was dissected close to the head of the calcaneus, taking as much as possible of the connective tissue. All ligaments were separated at the level of the joint middle, exposing the head of the distal part of the tibia and fibula. The cartilage was separated with a raspatory. With single sutures the skin was stitched to the tendons and muscles, then the shape of the suture was corrected. The edges of the skin wound were connected with interrupted stitches, drainage was put in to remove excess exudate. In the postoperative period antibiotics and anti-inflammatory drugs, stimulants and vitamins were used. Throughout the keeping period, the operated animals moved freely on three limbs (Figures. 6, 7), and their weight gain did not differ from that of healthy animals. Figure 6. A 2.5-month-old animal Figure 7. A 6.5-month-old animal

Clinical and morphological…
As complex forms of surgical diseases of the deep structures of the limb distal segment (most often osteomyelitis, purulent arthritis and their complications) with impaired function of the musculoskeletal system in pigs are disclosed, there arises a task for their treatment. Most experts (Timofeev et al., 2007;Vlasenko & Tihonyuk, 1998, Veremej et al., 2010 believe that an effective treatment method can only be the operative one. Surgical treatment should be aimed at eliminating purulonecrotic process by removing the affected tissues within the frames of the healthy ones. In chronic forms of osteomyelitis, treatment is performed surgically (sequestrotomy), using antibiotics and sulfonamides. These authors recommend subperiosteal lesion removal since subsequently it results in periosteal osteogenesis.
Vlasenko & Tihonyuk (1998) for the pathology of the deep structures of the limb distal segment in pigs, recommend the limb amputation by osteotomy. Burdenyuk & Vlasenko (1985) recommend using Roeder's exarticulation technique, saving the main part of the coronet and all the bulb of the heel in pigs. It should also be remembered that after exarticulation of the II and III phalanges of the fingers the postoperative treatment period is longer than after the high amputation (Molokanov et al., 2003). We have tested the technique of high limb amputation in pigs by exarticulation of the ankle mortise joint (Semirenko, 2016). It was this operation that gave the best result in terms of keeping up health and productivity of sick pigs.

CONCLUSION
Thus, limb exarticulation is the only effective treatment for surgical diseases of the deep structures of the limb distal segment in pigs, which allows to preserve the life and productivity of the animal. Ankle mortise joint exarticulation technique involves separation of soft tissues, capsule and ligaments, ligation of vessels, formation of the stump. The postoperative recovery of the animal amounts to 25 days.