Comparison of Different Internal Implants for Repair of Hind Limb Fracture

Bone fracture is termed as any discontinuity in the integrity of bone structure. Basic principal of treatment of fracture include reduction and retention. Modern age has developed number of methods to treat fracture; one of them is usage of Compression plate that are held in place with the help of screws. Limited Contact Dynamic Compression Plate (LC-DCP) is the new version of Dynamic Compression Plate (DCP) and is better than DCP in terms of providing aid in early healing, playing its role as providing low degree of plate-bone contact and decreased incidence of porosity and better vascularization, which reduces healing time and optimizes callus formation, leading to early healing and return of limb function.


Introduction
Musculoskeletal system holds its importance in the maintenance of body function, biggest of them being support of viscera. Musculoskeletal system includes multiple organs like skin, bones, tendon, ligaments and cartilages. Bones are the main holding framework of body accompanied with ligament and tendon to act as supportive structures. Femur is the largest and longest bone of all and is responsible to bear most of the weight of hind quarter. Any force applied to the bone surpassed the bone strength causes bone fracture. These forces may be physiological forces and non-physiological forces. Non-physiological forces are trauma from an auto mobile, gunshot wound and falls. While physiological forces are weight bearing, muscle contraction and associate functions (Hulse 2003). Overall chances of fracture in dogs are 29.94% (Tercavlioglu 2009). Treatment of fracture has two basic principles; 1-reduction of the fracture fragments, and 2-retention of fractured fragments. Bone plates and screws are one of the many choices to treat fracture. Primary bone plate system is Dynamic Compression Plate (DCP) in which holes are designed in such a way that they cause compression of fracture fragments (Roe 2003). Bone plates and screws are indicated when it is desired to restore the functional ability of affected limb early (Fossum 2003). A modification of DCP is Limited Contact-Dynamic Compression Plate (LC-DCP) and Point-Contact Fixation. LC-DCP has its advantage over DCP as stress is not concentrated at the screw holes with lesser infection rate and early callus formation.
The purpose of this study is to evaluate the latest two plate fixation system; i.e DCP and LC-DCP, in terms of appropriate fracture reduction, implant position, early fracture healing, lesser infection rate, early callus formation and better vascularization of the bone. The results were evaluated on the basis of Radiographic findings and B-Mode Sonography, where by early callus formation evidence and fewer infection rates were admitted in group subjected to LC-DCP. Early callus formation showed better implant and early healing time.

Materials and Methods
The experimental trial was performed on 8 mongrel dogs of either sex. Dogs were divided into two groups, A and B comprising four dogs each. The dogs were assigned names and groups as follow: Group 1: A1, A2, A3, A4 Group 2: B1, B2, B3, B4 In group 1, DCP was applied on long oblique femoral fracture while in group 2, LC-DCP was applied on long oblique femoral fractures.

Pre-operative Examination of Dogs and Medication:
A complete visual and thorough physical examination. Bathing of animals with Luke warm water and antibacterial soaps. Prophylactic measures against rabies in the form of Rabicin vaccine. Fenbendazole at the rate of 6mg/kg body weight for controlling of internal worms and Trichlorphan powder for bathing to control external parasites, examination of femur prior to surgery by 5.0 & 7.5 MHz transducer ultrasonography to eliminate any sort of confusion regarding bone health and condition prior to surgery.

Instrument and Their Preparation
Periosteal elevator, lowman's bone clamp, Bone Plates of 2 sizes (DCP 3.5mm broad & LC-DCP 3.5mm broad), bone drill machine of 2.7 & 3.5mm size, bone saw, 3.5mm screws, bone hammer, depth gauge, bone chisel, 20 gauge orthopedic wire, lag screws 3.5mm fully threaded varying in length between 30mm 32mm and 34mm as per needed, screw driver hexagonal type for 3.5mm screws, bone tape 3.5mm, wire cutter, wire twister along with common surgical pack used for soft tissue surgery including scissors, forceps, needle holders, scalpel handles, artery clamp, muscle retractor, trays, towel and needle plus disposable sterilized surgical blades, gauzes, gloves, caps and masks.
All orthopedic and general surgical instruments were autoclaved prior to use.

Pre-anesthetic Medication
Atropine sulphate and Xylaine I/M as pre-anesthetic & sedative, respectively at the dose rate of 0.02 mg/kg and 0.4 mg/kg body weight before induction of general anesthesia.

Anesthetic Medication
Animals were anesthetized by using ketamine at the dose rate f 5mg/kg in combination with Xylaine in 2:1 with ketamine. Half dose was given as a bolus while remaining half was given as maintenance anesthesia, with regular checking of vitals. After the surgical stage of anesthesia was achieved operation was begum. Prior to surgery Ringer's Lactate was given at the dose rate of 10 ml/kg body weight.

Preparation of the Patient
Surgical site was clipped and shaved off from lateral and median sides from point of hip to toe. Area was cleaned by using antiseptic scrubbing solution. Sterile surgical drapes were places around the surgical site leaving a rectangular window opened at proposed surgical site. The first layer of drape was placed in four drapes fashion and was secured to the patient skin by towel clamp. The first drape was placed in such fashion that the central opening area covered the limb and whole body of animal. Then four drapes fashion was secured to patient by towel clamp as the patient hind quarter was covered. Entire lower portion of limb was also covered in drapes to ascertain asepsis.

Surgical Technique
For the surgical procedure animal was placed in lateral recumbency with limbs to be operated on top. Femur was exposed through a cranio-lateral approach. Then afterwards, a long oblique fracture was induced; after adequate reduction, the respective bone plate was applied in each group. Femur was exposed by standard surgical protocol and was subjected to a long oblique fracture approximately twice the width of the bone was induced in the femoral mid shaft using bone saw. Induced fracture was stabilized with the help of bone plates. Firstly, it was reduced by using bone clamps with the goals of ideal reduction and preventing bone from rotation. A fully threaded 3.5mm cortical screw was applied in lad fashion, perpendicular to the fractured site for additional stability. Then plates were approximated over bone. Holes were drilled with the help of drill machine and grooves were cut with the help of bone tap. Plates were fixed with the help of cortical screws occupying both cortices of the bone (Roe 2003).
Plated system used in both groups was DCP was applied to Group A LC-DCP was applied to Group B

Insertion of Fully-threaded Cortical Screws in Lag Fashion
A 3.5mm fully-threaded cortical screw was used in dog A4 with 24mm length in lag fashion. Keeping at least 1cm distance from the fractured ends, a gliding hole equal to diameter of screw thread was drilled in near cortex. Threaded hole, equal to diameter of screw core was drilled in far cortex and tapped with 2.7mm bone tap. As screw engages far cortex compression along fracture line was occurred. Hole was drilled so that inserted screw bisected an angle between perpendicular to the axis of bone and perpendicular to fracture line, size of screws was different according to bone diameter.

Post-operative Management
Operated animals were kept in germ-free, ventilated, compatible and bio-secured cages. An average of 500ml Ringer's Lactate solution was infused intravenously BD to combat dehydration and acidosis in first week. From day 2 post operatively, milk and chicken were given as diet to compensate the losses during surgery and to combat the stress during healing procedure. Antibiotic therapy was launched using Ceftriaxone sodium as 500 mg/kg body weight, injected intravenously for 7 days after surgery. For 68 Comparison of Different Internal Implants for Repair of Hind Limb Fracture first five days injection Dicloran sodium was given to relieve from the pain along with injection Pherasym was given as antihistaminic to prevent self-mutilation of the suture line by the patients due to itching. Wound was daily dressed using antiseptic solution (10% pyodine) and mycitracin cream up till complete healing of the suture.
The femur with internal fixation implants (i.e DCP & LC_DCP) were examined by B-mode ultrasonography using 7.5 MHz transducer, on day 1 post-operatively and then after every week, respectively for any complication. During this whole procedure behavior, TPR, feeding, defecation and urination were monitored regularly.

Experimental Parameters
Operated animals were kept for the experimental period of three months and the efficacy of the internal implants were evaluated on the basis of the following parameters.

Physical Evaluation
Gait and lameness analysis, Presence of pain, Vital signs (temperature, pulse, respiration), Signs of osteomyelitis.

Radiographic Findings
The animals were restrained in the lateral recumbency and the radiographs of femurs were obtained through a medial-lateral projection (ACOMA, JAPAN). The radiographs were obtained at an interval of 15-days to examine the progress of callus formation with respect to each plate fixation system. The radiographs also made it convenient to visualize the implant position and ascertain proper reduction of the fracture.

Ultrasonographic Findings
Sonograms were obtained in the lateral recumbency with the help of 7.5 MHz curvilinear transducer through B-mode Ultrasonography (Aloka, JAPAN). Sonograms were recorded at an interval of seven days. For sonographical examination femur was approached from medial side of the thigh, as it is better technique to explore the fracture line (Van Bree, 2005).

Histopathology
A histopathological study was also conducted. At the end of 12 week of surgery the site was opened surgically, plates were removed, and evidence of neo-vascularization was assessed in Group A (DCP) the bone showed lesser vascularization in areas of plate bone contact and plate screw insertion. Comparably in group B (LC-DCP) implants showed evidence of decreased cortical porosity and decreased denuded areas at plate-bone interface and at site of screw insertion.

Physical Findings
Gait and lameness analysis, presence of pain, vital signs (temperature, pulse, respiration)

Assumption
From above table it is assumed that in 50% animals three-legged lameness was shown, while in other 50% marked lameness was shown. Lameness is recovered in research trial in dogs A2 and A4. While dog A1 showed mall-union and dog A3 expired in 3 rd week.

Assumption
From above table it is assumed that lameness is absent in 75% of animals. While in 25% it is severe. B3 was expired later due to osteomyelitis.

Pain Grading
All dogs showed normal routine without exhibit of severe pain except for dog A1 and A3 in Group A (DCP) and B3 in group B (LC-DCP). But these dogs responded well to Diclofenac sodium injection very next day. Response to pain was recorded in according to following scale.

Assumption
From above table it is assumed that there was severe pain in 50% animals and moderate pain in other 50% animals at start. Later on, controlled but A1 had pain throughout the trial.

Assumption
From above table it is assume that 75% experimental animals had moderate pain and just 25% had severe pain which was controlled later in research trial. Key: Mean of DCP is 44.444 which are more than 4.166 of LC-DCP and P≤ 1.566Ḛ-07(00000001.566) which shows P value is less than 0.05 the value of α so it shows that the both groups had not equal lameness score and group B(LC-DCP) have less lameness as compared to Group A(DCP)  From table it is concluded that signs of pain were severe in Group A (DCP) and in group B (LC-DCP) pain signs were less comparably.

Radiographic Findings
Radiographs were obtained for each dog by positioning each dog in lateral recumbancy with medio-lateral projection (ACOMA JAPAN DF-50) at an interval of two weeks of examine the callus formation subjected to each fixation plate system.

Ultrasonographic Findings
Sonograms were also obtained in the lateral recumbancy with the help of 7.5 MHz curvilinear transducer through B-mode ultrasonography (Aloka JAPAN S900) to access signs of early healing. Sonograms were recorded at an interval of one week.

Histopathology
Present project was also evaluated by histopathological studies. At the end of 12 week the site was opened surgically, the plates were removed, and evidence of neo-vascularization was assessed in Group A (DCP), the bone showed lesser vascularization in areas of plate bone contact and plate screw insertion. Comparably in group B (LC-DCP) implants showed evidence of decreased cortical porosity and decreased denuded areas at plate bone interface and at the site of screw insertion.

Discussion
The present experiment was conducted to compare two implants and internal fixation of femoral fractures. Their efficacy (DCP & LC-DCP) was evaluated based on lameness at walk and trot, pain scoring, ultrasonography, radiography and histopathological basis. Both groups were evaluated and group B (2 nd gave clear indications that LC-DCP resulted in quicker recovery as compared to Group A (DCP). All dogs of Group B (LC-DP) showed modern pain signs and recovered well with time span as compared to Group A (DCP). Radiographic and ultrasonographic evaluation of dogs A2 and A4 in Group A showed good callus formation, while dog A1 suffered osteomyelitis in 3 rd week. Dog A3 expired in third week post operatively. Contrastingly, in group B, reduction and fixation of fractured fragments was ideal and dogs regained 100% limb function early in the healing phase, as evidenced by callus formation and complete bone union. Besides this histopathological examination at the end of 12 th week showed evidence of superiority of LC-DCP over DCP. In Group A bone showed lesser vascularization and in the areas of plate bone contact and plate screw insertion. Comparably in Group B implants showed evidence of decreased cortical porosity and decreased denuded areas at the plate-bone interface and at site of screw insertion.

Conclusions
Based on present experimental trail on dogs, it was concluded that the use of Limited Contact Dynamic Compression Plate (LC-DCP) holds an edge over the conventional Dynamic Compression Plate. LC-DCP promises low degree of plate-bone contact and decreased incidence of osteo-porosity and better vascularization, which reduces healing time and optimizes callus formation, leading to early return of limb function as evidenced through all the parameters specially ultrasonography, radiography and histopathology.