Pre-operative observations
A higher incidence of fracture was observed in German Shepherd and Non-descript dogs, with the Mean±S.E. values of age (months) of animals of group I and II as 18.20± 10.51 months and 10.00 ± 2.14 months, respectively. Road traffic accident (RTA) being the major cause of fracture among animals in the present study similar to findings of earlier studies
(Braden et al., 1995; Aithal and Singh, 1999; Harasen, 2003; Yaqub, 2001; Tyagi et al., 2021).
The number of males (n=6) was slightly more than females (n=5) in the cases reported. This might be probably because of more active and aggressive nature of males, in addition, there was a preferential keeping of male dogs by the pet owners, which could have also contributed to their more number
(Aithal et al., 1999; Kumar, 2007; Gill et al., 2018; Tyagi et al., 2021). Higher incidence of femur fractures (n=6) was recorded; followed by fracture of tibia (n=3); radius and humerus (n=1) each.
Intra-operative observations
An open reduction with a lateral approach was the technique of choice for diaphyseal, epiphyseal or metaphyseal femoral fracture repair; craniolateral approach was preferred for humeral fracture repair and medial approach was used for tibial fracture repair.
End threaded positive profile and negative profile intramedullary pins, made of stainless steel (316-L), were used (3-5.5 mm in both group) (Table 1 and 2). The end threaded intramedullary pins were inserted in a clockwise manner using Jacob’s chuck and key. While both the pins were passed easily in the distal segment fitting in the cancellous bone, the positive profile end threaded pin was easier to pass and fit in the distal segment as they were self-tapping having screw like action, as also reported by
Chanana et al. (2018).
The pins were used alone except in one case where it was used in conjunction with full cerclage wire (as per the necessity of that case). The pins were cut at the nearest point (leaving 5-10 mm) to where they exited the bone to minimize irritation caused by the pin end.
Altunatmaz et al. (2012) had also left 5 -10 mm pin outside the bone proximally to enable the removal of pin following fracture healing.
Post-operative observations
Post-operatively the surgical wound was cleaned and Modified Robert Jones bandaging was applied in each case. In one case (Case no. 5, group I), modified Thomas splint was applied post operatively for 5 days. The Robert Jones bandage was changed on alternate day upto 5-10 days. In all the cases regular antiseptic dressing with liquid povidone-iodine solution was done and the sutures were removed 10-12 days, post-operatively. Antibiotics, anti-inflammatory drugs along with oral calcium were given to the animals. Surgical wound healed with first intention in all the animals. No complication of wound healing was observed.
The smooth intramedullary pins provide three point fixation, they were anchored at the point of introduction, has contact with the isthmus of the medullary canal and was impacted/screwed into the distal cancellous bone
(Newton and Nunamaker 1985). This was true for end threaded negative profile pins also as their main diameter (MD) was equal to their pitch diameter (PD). However, in case of end threaded positive profile intramedullary pins, it seemed to have only two point fixation. As the main diameter (MD) of end threaded positive profile intramedullary pin was less than pitch diameter (PD), the first fixation was at point of introduction/proximal end of bone and the second was at distal end of the bone (cancellous bone). As the main diameter was less it did not come in contact with bone diaphysis in marrow cavity and pitch diameter was more and this was the area of seating of intramedullary pin in cancellous bone (Contact point).
Weight bearing
The weight bearing and locomotion seemed to be dependent on soft tissue trauma during fracture fixation and irritation caused by the ends of pins or migration of pin. In all the cases partial weight bearing was noticed on 7
th-14
th post-operative day and nearly complete weight bearing was observed in between 40 to 60 post-operative day (except for 2 cases where lameness was observed).These findings were similar with those reported by
Altunatmaz et al., (2012) where the authors used fully threaded intramedullary pins in the treatment of various long bone fracture.
Chanana et al. (2018) also reported weight bearing between 5-15 days after the operation and functional recovery was seen to increase gradually, with full weight-bearing without any signs of complication after day 20.
Two cases showing lameness in our study were from both groups I and II and (One in each group). In one case in a dog with tibia fracture (Case- 5, group II) the pin was touching the patellar ligament leading to lameness throughout the healing period. However, the dog started very good weight bearing after two days of pin removal. In another case (Case 4, group I), there was fracture of radius and was presented after 30 days of fracture. The delayed presentation of the case was due to COVID-19 outbreak. This particular case was highly infected and regular cleaning and antiseptic dressing of the limb was done with povidone-iodine solution for 7 days which further delayed the surgery. Regular radiographs were taken which showed non-union up to 150 days and there was constant lameness. The late presentation of case seems to be the reason for non-union and thus the non-weight bearing from the affected limb.
Healing and callus formation
The Mean±S.E. values of time for healing (days) were 47.25 ± 6.83 and 54 ± 3.96 days for group I (n=4; one case was of non-healing and thus was omitted from the calculation of healing time) and group II (n=6), respectively. The healing time in group I (Positive profile IMP) was lower than in group II, but the difference was non-significant.
A radiographic follow-up carried out regularly after surgery when a bridge of periosteal callus was seen on post-operative radiographs, it was classified as healed (Fig 1-4). In all the cases healing was evident with a moderate degree of periosteal callus. The pins were not removed till there is evidence of callus formation with healing and proper weight bearing.
Complications/Pin migration
In our present study, pin migration was not observed at any stage in the animals of any of the groups. Rotational forces were overcome by the implant used as the threads were embedded in distal cancellous bone firmly. The results of this study were in relevance with the findings of
Ozsoy (2004) who conducted a study to examine the use of full threaded Steinmann pins for adequate rotational stability and prevention of pin migration when applied in normograde fashion in fractures of the femur, humerus and tibia of cat. However, an earlier study had reported migration of an end threaded negative profile pin
(Chanana et al., 2018). There was no pin migration in any of the cases and there was no bone shortening or fragment collapse in our study. In present study, no any radiological or clinical complications were seen in the healing period of fractures belonging to skeletally immature patients. When a proper size of intra medullary pin was used, possibility of pin migration was reduced. The compression of the fractured segment at the fracture line was evident as the positive profile pin was screwed in to the distal fragment ensuring near normal continuity of the bone length and contour.
It had been reported that the partially threaded pins having a negative profile ending create a weak point in the pin-thread junction and the pin-thread junction must not be near the fracture line
(Olmstead et al., 1995; Denny and Butterworth, 2000). Positive profile pins do not have this problem because the threads were raised above the core diameter of the pin. Thus, there were no stress riser (weak point) at the thread non-thread interface
(Gilley and Gold, 2006) and the implant appeared very sturdy. However in the present study no such complication was observed and pin breakage was recorded neither in group I nor in group II.
Method of implant application and removal
Technique of implant application was same in both the groups and removal of implant was done with the help of Jacob’s chuck and key in an anti-clockwise rotation because of firm grip attained by threads of pins in the cancellous bone at the time of pin removal. A similar procedure was reported by
Piermattei et al., (2006) and
Chanana et al. (2018) i.e. on removing a threaded pin after fracture healing, it was necessary to “unscrew” the pin because bone was grown into the threads and not because the pin was threaded into the bone.
There was no evidence of axial rotation or compression or tension at either of the fracture lines in any of the case. The end-threaded intramedullary pins fitted into the medulla like a screw it provided more effective rotational stability by gripping the spongy bone in the distal diaphysis at the same time. The end threaded intramedullary pin of both profiles (positive and negative) provide a sufficient degree of fixation. Also the complications associated with end threaded negative profile intramedullary pin, which had been reported in an earlier study
(Chanana et al., 2018) were not observed in the present study. There were no case of pin migration in the present study which was the most common complication associated with simple steinmann intramedullary pinning.
