Luke Poore1 and Katja Koeppel2
1The Department of Companion Animal Clinical Studies,
Faculty of Veterinary Science, University of Pretoria, Onderstepoort
2The Department of Production Animal Studies,
Faculty of Veterinary Science, University of Pretoria, Onderstepoort
Fractures of the appendicular skeleton in antelopes have been infrequently reported in the veterinary literature.1-11 The size of South African antelopes varies considerably from a 3 kg dik-dik to a 900 kg giant eland making fracture repair challenging.12
Significant advances in both anaesthetic regimes and fracture fixation technology in the last 15 years have now made fracture repair in these antelopes a viable option. Improvements in knowledge and development of techniques for blood transfusions have also improved the success rate of such surgeries.13 The future development of specialist intensive care units for antelopes in both the pre-operative and post-operative periods will also improve the success rate of fracture fixation surgeries in antelopes.
Advances in Fracture Fixation Techniques with Relevance to Antelopes
The aim of any surgical fracture repair is to reconstruct the original anatomical structures and restore the function of the fractured bone. Plate and screw osteosynthesis has been used in clinical settings since 1886, when Carl Hansman used a monocortical fixator.14
As implantation techniques have since been refined, clinical results have been subsequently improved. By using internal fixation with angular stability, fractures in the metaphyseal region of bone and in osteoporotic bone have been repaired.15 The Synthes Locking Compression Plate (LCP) is part of a stainless steel and titanium plate and screw system that merges locking screw technology with conventional plating techniques. The LCP System has many similarities to existing plate fixation methods, but has some significant improvements. Locking screws provide the ability to create a fixed-angle construct while utilizing familiar Association for the Study of Internal Fixation (AO) plating techniques.
A fixed-angle construct provides advantages in osteoporotic bone or multifragmentary fractures where traditional screw purchase is compromised. This is particularly important in our experience of antelope long bone fractures where open comminuted fractures are over-represented and many fractures have areas of osteoporotic bone present.
Where insufficient screw to bone fixation is available because of poor bone quality in these cases, cyclic loading of conventional plate–bone constructs can lead to secondary loss of fracture alignment and stability.16 Screws are known to be susceptible to pull-out fatigue in the metaphyseal regions of bones, osteoporotic bone, patients having slow bone healing conditions and patients with poor compliance to restricted activity during the post-operative period.17 Antelopes with long bone fractures often present with several of these issues and have poor compliance in the post-operative period.
Locking screws do not rely on plate-bone compression to maintain stability with the screw locking into the plate instead of the screw pulling the bone towards the plate as in conventional plate technology.15 LCP implants have been used in several conditions to aid bone healing and provide quicker and more stable fixation.18
The LCP has uniform hole spacing with load (compression) and neutral screw positions. The Combi holes of locking compression plates are a combination of locking and compression holes. This design allows placement of standard cortex and cancellous bone screws on one side or threaded conical locking screws on the opposite side of each hole. These threaded conical locking screws give superior strength to the implant and this quality is very important during the recovery phase of the anaesthetic and in the post-operative period in antelopes. Due to a lack of habituation, only minimal handling and restraint can be performed, exposing the implants to high stress forces.
In 1958, AO formulated four basic principles, which have become the guidelines for internal fixation. These principles, as applied to the locking compression plate in antelopes are:
Locking compression plates allow restoration of the articular surface by exact screw placement, which is important as many antelope long bone fractures have complicated configurations. Additionally, as the locking plate construct functions as an internal fixator, precise anatomical contouring of the plate is not essential to maintain fracture alignment and stability.16 This is an important factor in antelope fracture fixation as there can often be a delay in identifying fracture cases before referral for repair. Callus formation in the immediate post-injury period in these cases can make accurate plate contouring extremely difficult.
Locking screws create a fixed-angle construct, providing superior angular stability compared to conventional plating techniques.16 This is important for post-surgery management in antelopes where sedation and restraint protocols are difficult to utilise.
Preservation of Blood Supply
The tapered end of the LCP allows sub muscular plate insertion, preserving tissue viability. Limited-contact plate design reduces plate-to-bone contact limiting vascular trauma and insult to the periosteum of the repaired bone.16 These features of the compression plate are important in antelope fractures as the overlying tissues are often compromised, with vascular trauma and bone insult having already occurred.
Early Active Mobilization
The features of the compression plate combined with AO technique creates an environment for bone healing in antelope fracture cases, expediting a return to optimal function. In our opinion, successful rehabilitation of antelopes after fracture fixation, is significantly enhanced with reduced post-operative time.
Fracture Repair in an Adult Sable
The use of a locking compression plate allowed the successful repair of a closed mid metacarpal fracture and non-union of an adult sable cow. The fracture had been treated for approximately 8 weeks before referral to the Onderstepoort Veterinary Academic Hospital (OVAH) with external coaptation in the form of a full limb cast. This treatment had been unsuccessful and resulted in a non-union. A 10 hole locking compression plate was used to repair the fracture with 8 locking screws and one mid cortical screw. (Figure 1 and 2)
Figure 1: The fracture at presentation
Figure 2 a: Repair with a 10 hole 5mm Locking Compression Plate
Figure 2 b: The fracture site 8 weeks post-operatively with the cortical screw removed
Advances in Intra-Operative Care
As implant technology has improved in the last 15 years, knowledge about anaesthetic regimes in South African antelopes has also greatly improved.
The drugs available to veterinarians have been refined and knowledge of physiology in antelope species has improved reducing anaesthetic complication associated with prolonged surgeries. New drug regimens are being developed all the time to improve downtime and reduce stress in the antelope species.
There is a scarcity of information available regarding blood transfusions in antelopes but a group at the University of Pretoria is conducting research in this area. This group recently described the use of bovine blood as a component of a successful blood transfusion regime during fracture repair in a golden wildebeest.13
The OVAH has plans for a dedicated wildlife hospital on the campus at Onderstepoort. Plans have been submitted to build dedicated bomas for carnivores, small and large antelope, buffalo and rhinoceros next to the OVAH in 2018. These facilities will allow refinement of the post-operative care of antelopes undergoing fracture repair and will further improve the success rate of these surgeries.
We would like to thank Dr Charlie Boucher for reviewing this manuscript and Professor Louis Coetzee for his inspirational guidance.
References available at www.vet360.vetlink.co.za