General anaesthesia was induced using injection atropine sulphate @ 0.04 mg/kg I/M as preanaesthetic, followed by injection diazepam hydrochloride @ 0.5 mg /kg I/V and injection propofol @ 4 mg/kg I/V. The animal was intubated and anaesthesia was maintained with isoflurane @ 2-3% MAC using an anaesthetic machine.

The suitable nail according to the diameter and length of fractured bone was selected on basis of the preoperative radiograph. In the open method, a skin incision was given laterally for femur whereas the skin incision was given medially for the tibia. The procedure was carried out as described by Raghunath and Singh (2003). After insertion of the screws, the C-arm exposure was made to evaluate the location of the screws. The separated muscles were then sutured in a standard manner using polyglactin 910 followed by the routine closure of the skin incision using non absorbable suture material.

In closed method, the anatomical site for the insertion of a Steinmann pin was located. A stab incision was given and a small tunnel was created with the help of an instrument awl. Then, an intramedullary pin was inserted through this tunnel. This pin was progressed under the guidance of C-arm, till it reached the proximal segment of bone. Then, the fractured segments were reduced indirectly. After reducing the fracture, the pin was inserted into the distal segment. Subsequently, the pin was removed from bone. In some cases, a reamer of appropriate diameter was inserted through the tunnel hole for the preparation of marrow cavity. The preparation of the cavity facilitated the entry of the nail. Now the nail of appropriate diameter and length was loaded on the Jig and inserted into the prepared marrow cavity in a normograde manner. The holes were drilled in the bone cortices of the proximal and distal segments using the universal drill and sleeve. Then, the screws were fixed in these holes in bone cortices through a nick incision in the skin, fascia and the muscles. The tunnel hole and the nick incision were sutured (Fig. 1).

In all the animals, inj cefotaxime sodium @ 10 mg/kg body weight I/M bid prior to surgery and up to day 7 was administered and inj. meloxicam @ 0.2 mg/kg body weight I/M o.d was administered for 3 days. A Robert Jones bandage was applied on the affected limb to restrict its movement. Anti-septic dressing was done with 5% povidone iodine solution. Skin sutures were removed on day 8 to 12.

Radiographic examination was done prior to surgical procedure to evaluate the type of fracture; then it was conducted after interlocking nailing to assess the level of fracture reduction, alignment of bone fragments and the placement of nail through the bone. Subsequent radiographs were taken post-operatively on day 14, 28, 45 and 60 and were graded using the score card described by Hayashi et al. (2008).

Comparison between the groups for studied attributes was subjected to unpaired t-test whereas, within group values for each parameter were analyzed by one way ANOVA as described by Snedecor and Cochran (1994).

In all dogs, mean values of rectal temperature were found to be reduced after induction of anaesthesia and during the period of surgery (Table 3). The mean values of rectal temperature showed non-significant changes between groups and significant (p<0.05) changes within group at different time intervals in both group of dogs. Base line of temperature 101.36±0.35 and 101.6±0.24⁰F, decreased to 97.31±1.03 and 98.3±0.70^oF during surgery in both the groups. Thereafter, a gradual increase in rectal temperature was observed during recovery of animals from anaesthesia. These finding are in corroboration with English et al. (1991), who reported that a decrease in rectal temperature during anaesthesia may be due to disruption of thermoregulation and heat loss.

In all the dogs, mean values of heart rate were found to be reduced after induction of anaesthesia and during the period of surgery (Table 4). The mean values of heart rate showed significant (p˂0.05) decrease at different time intervals in both the groups. The base line heart rate 104.66±5.92 and 118.33±5.01 (beat/min), decreased to 88.66±4.10 and 95.33±3.22 (beat/min), during surgery in both the groups.

This may be due to severe hypothermia, cardiac conduction abnormalities and severe myocardial depression as described by Haskins (2015). Thereafter, a gradual increase in the heart rate was observed during recovery of animals from anaesthesia. This finding is in accordance with finding of Patil et al. (2017), who also reported a decrease in the heart rate after induction of anaesthesia.

The time taken for the fracture reduction was observed to be longer in group-II (15±1.82 min) than in group-I (9±2.38 min). The mean value of blood loss in group-I (51.65±1.72 g) was higher than in group-II (20.71±1.96 g), hence the intraoperative bleeding was lesser in group-II. Time taken for orthopaedic surgery was observed to be longer in group-II (140±6.55 min) than in group-I (101±6.41 min) (Table 5). Neuropraxia was observed in two cases of group-I, which was managed with conservative treatment.

In all the dogs, mean value of degree of exudation showed gradual decrease at site of suture line from day 3 onwards up to day 14 postoperatively (Table 6). The mean values of degree of exudation varied significantly (p˂0.05) at different intervals in both the groups. Mean value ranged from 0.16±0.16 to 2.00±0.25 at different time intervals in both groups. No exudation was observed on day 14 postoperatively. This finding is in accordance with De´Souza (2012) who observed that complete absence of exudation at fracture site on 15^th postoperative day in dogs.

Radiographic assessment of fracture healing illustrated initial bone union by day 14 and complete union by day 45 and 60 post-operatively (Fig. 2). The mean values of radiographic score in group-II were higher than the values in group-I (Table 7).

This finding is in accordance with findings of Patel et al. (2007) and Manjunatha and Ranganath (2012). They also reported that static intramedullay interlocking nail fixation was successfully applied in a minimally invasive method for long bone diphyseal fracture in dogs. This resulted in early weight bearing and good bone healing as observed on the postoperative radiographs.

The degree of lameness was calculated based on lameness score as stated by Cook et al. (1999). The lameness score started to reduce significantly (p˂0.05) from 5.00±0.00 at day 0 to 0.00±0.00 at day 60 in both the groups. There was a consistent decrease in lameness core at different time intervals in both the groups accompanied by improved weight bearing by the animals (Fig. 3). This improved weight bearing was result of fracture healing after anatomical reduction and fixation of fracture segments (Table 8). At day 3, animals were having significant (p˂0.05) weight bearing on affected limb in group- II, this finding is in accordance with the finding of Mathai et al. (2016) and Manjunatha et al. (2011) who reported that dogs started weight bearing on day 1 itself and showed complete weight bearing by 4^th post-operative day.