Introduction

Variably-pitched self-compressing cannulated screws (Acutrak^TM, Acumed, USA) used in human orthopeadics have recently been applied to small animal patients. The full range of veterinary applications for Acutrak^TM screws has not yet been detailed. This study aims to document the technical application, anatomic landmarks, surgical approach, complications and clinical outcomes for a variety of surgical procedures using Acutrak^TM screws in dogs and cats.

Materials and Methods

Humeral condylar fracture (dogs 8, cats 2). Incomplete ossification of the humeral condyle (n=7).

Ununited anconeal process (n=17). Incomplete ossification of the radial carpal bone (n=2). Slipped capital femoral epiphysis (3). Femoral neck fractures (2). Central tarsal bone fracture/luxation (2). Hock fractures/luxation (3). Humeral head fracture (1).

Measurements were taken from orthogonal radiographs of the injuries. The fracture/luxation was reduced and maintained in reduction with forceps. A calibrated guide wire was placed perpendicular to the fissure/fracture line in the optimal position for screw placement and advanced to engage the trans-cortex. A measuring device was placed over the wire in contact with the cis- cortex to calculate screw length. The wire was then driven through the trans-cortex and clamped with a forceps. A cannulated calibrated tapered drill was placed over the wire and advanced to the appropriate depth (not penetrating the trans-cortex). The screw was placed and tightened. Compression can be observed across the fissure.

Results

Four dogs were lost to follow-up. Clinical and radiographic examination between 40 and 75 days post-operatively revealed satisfactory healing in all other cases (43).

Complications: seroma (5), superficial wound breakdown/infection (4), avascular necrosis of the femoral neck (1), and failure (4). One limb was amputated due to unrelated pathology.

Discussion

Acutrak^TM screws are applicable for a wide range of fractures/luxations in small animals and can be recommended for clinical use. Core size of the screw is small by comparison with conventional screws of similar strength and the headless design prevents impingement of joint structures when placed beneath the articular surface. Differential thread pitch and tapered design provides improved interfragmentary compression. Cannulation along a guide wire permits optimal fragment alignment and maximal purchase of the implant. Tapered fully-treaded profile maximises pull-out strength and application by lag technique is not required, thereby minimising surgical approach. The titanium alloy is associated with decreased propensity for immunogenic response and infection risk whilst greater bone contact increases fatigue strength.