The mean body weight of dogs in group 1 was significantly (p<0.05) higher (12.60±4.25 kg) than in group 2 (9.18±4.34 kg). However, the age was non-significantly different. The average duration of femur fractures in group 1 was significantly (p<0.05) less (2.00±0.82 days) than group 2 (3.60±2.80 days). Since, older fractures require breaking of callus and have muscle contracture with medullary canal filled with newly deposited callus, these were difficult to align and place pins in the medullary cavity. Therefore, end-threaded pinning was the preferred method in old cases.
The group 1 included 4 transverse (Fig 5a and b) and 6 oblique fractures, while group 2 included 4 transverse (Fig 7a and b), 4 oblique and one each of spiral and comminuted fracture (Fig 6a and b). There was no significant difference in the narrowest medullary canal diameter between the group 1 (9.29±3.13 mm) and 2 (7.98±2.35 mm).
Intraoperatively, in group 1, implant placement required significantly (p<0.05) more time (72.4±11.16 min) than in group 2 (60±15.78 min). Placements of two pins in group 1 could be the reason for the prolonged duration of surgery. Single pin fixation has been described as easy, less time consuming technique but is associated with more callus formation and prolonged healing time in supracondylar femur fractures in dogs
(Aithal et al., 1998). The TENS placement was easy but reduction was difficult particularly in oblique femur fractures. A longer incision was required to expose the fracture site and femoral condyles for the placement of TENS.
Immediate postoperative radiographs showed comparable mean fracture reduction scores between the group 1 (1.30±0.95) and 2 (1.20±0.63). In group 2, the implant occupied non-significantly higher per cent of narrowest medullary canal diameter (64.31±9.15%) as compared to group 1 (46.28±13.56%). Radiographs made on day 12 (group 1) revealed clearly visible fracture line with uniform (n=8), non-uniform (n=1) or non-appreciable (n=1) callus.
In group 2, 9 out of 10 dogs presented on day 12 revealed visibility of fracture line, with uniform (n=6), non-uniform (n=1) or no (n=3) callus. Implant was stable in 7 out of 9, one had proximal pin migration (Fig 9) and another had fracture of cranial wall of distal bone fragment due to implant (Fig 7). Besides, two dogs had stifle joint effusions.
Irrespective of technique used, femur fractures had good callus formation by day 45 justifying faster healing of fracture in young dogs and early implant removal.
In group 1, the overall fracture alignment at 45
th day was graded as excellent (2 cases), very good (3 cases) and good (5 cases) and the per cent alignment grades were similar for group 2. The fracture line was visible in 3 and 2 dogs of groups 1 and 2, respectively. The overall callus was smooth in all the cases but not uniform with few sites having excess bridging callus showing remodeling with time. The stifle joint effusions were recorded in only one case of group 1 (due to distal pin migration) and 4 dogs of group 2 on day 45.
When two titanium elastic nails of same diameter are inserted in a dynamic cross intramedullary fashion, symmetrically, the biomechanical stability is achieved from the divergent ‘C’ configuration that creates six points fixation (3 point fixation with each nail)
(Mahar et al., 2004). To achieve this, the nails are pre-curved to approximately three times the narrowest (isthmus) diameter of bone. These nails reduce chances of angulation in both anterio-posterior direction and varus/valgus by achieving axial and rotational stability
(Singh et al., 2006). In the current study, the TENS were not pre-curved but were bent at the distal ends before cutting extra pins that might have added to curvature of the TENS pins.
To assess femur bone length (operated and healthy) between days 0 and 45, statistical analysis using paired “t” test was performed. A significant difference in the bone length of operated and healthy femur was recorded on day 45 as compared to day 0, irrespective of the technique used (Table 1). It was inferred that the use of any fracture fixation technique such as end-threaded pin and TENS for femur lead to reduced bone growth as compared to the growth of contralateral healthy bone. This might be due to the fact that in distal third or supracondylar fractures of young dogs, the distal growth plate might have been damaged during trauma or with internal fracture fixation technique
(Alcantara and Stead, 1975).
As compared to Group 2, the stifle joint ROM was significantly higher on day 12 (p<0.01) and day 60 (p<0.05) in group 1 (Table 2). The group 1 dogs had almost equal ROM of the operated stifle joint compared to the healthy contralateral joint. This could be due to better stability provided by TENS as compared to single end-threaded pin. In contrast,
Gill et al., (2018) reported better functional outcome including ROM of stifle joint in supracondylar fracture repaired with end-threaded pin as compared to cross pinning. Interference of cross pin cut ends with soft tissue and stifle joint was explained as the reason.
During walking, the weight bearing scores in group 1, improved significantly (p<0.01) on day 45 as compared to day 12 (Table 3). Similarly, lameness score was found to be significantly (p<0.05) less on day 45 as compared to day 12 in group 1 (Table 4). These findings are explained due to better stability by TENS as compared to single end-threaded pin.
In group 1, all the dogs had full functional outcome, whereas in group 2, eight dogs had full functional outcome, while one each had acceptable and unacceptable. In group 1, 2 dogs had minor complication of distal and proximal pin migration which resumed normal walk after pin removal (Fig 8).
In group 2 also, minor complications (n=3) of seroma formation (n=2, one had transient sciatic nerve deficit) (Fig 10) and proximal pin migration (n=1) were recorded. All three dogs recovered completely. Sciatic nerve deficit in cases of supracondylar femur fractures repaired using retrograde end-threaded pins has been reported
(Fortere et al., 2007; Gill et al., 2018). Therefore, normograde method of pinning has been recommended in femur fractures
(Palmer et al., 1988). Osteopenic dogs had been reported to have implant related complications
(Kumar et al., 2007), as also reported in one dog of group 2, in this study.
There is lack of published reports on the use of TENS of long bone fracture fixation in veterinary practice. This is the first report of its kind on the successful clinical use of TENS for the stabilization of femoral fractures in dogs.