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7
The Advanced Locking Plate System (ALPS)

Tomás Guerrero

The Advanced Locking Plate System (ALPS) (Kyon AG^® Zurich, Switzerland) is a locking plate system developed for veterinary use [1–3]. ALPS was developed based on research performed on the point‐contact fixator (PC‐Fix) at the AO Research Institute, in Davos, Switzerland, aiming mainly to preserve blood supply [3–5]. This was accomplished by shaping the underside of the plate for minimal contact with the bone (Figures 7.1 and 7.2), and using only monocortical screws to protect the endosteal blood supply. Stoppers in the drill bits are used to reduce damage to endosteal vasculature.

Image described by caption and surrounding text. — **Figure 7.1** Detail of the back side of a plate showing its shape aimed to minimize plate to bone contact. The locking mechanism between the last screw‐thread and the plate hole is also observed.

Photo of a dog’s limb with retractors displaying good vascularized periosteum. — **Figure 7.2** Good vascularized periosteum is observed after plate removal in a radius.

(Source: Courtesy of Dr. Junga Ogawa)

The Sherman‐shape of the plate is meant to provide uniform bending strength along the plate length and allows for contouring in all planes (Figure 7.3). The screw holes allow for insertion of locking and nonlocking screws. Locking screws must be inserted at a right angle to the plate while nonlocking screws can be angulated 30° in the longitudinal plane and 5° in the transverse plane. Additionally, nonlocking screws can be used to position the plate in compression or neutral functions. If needed, nonlocking screws can be replaced, once fixation is achieved, by the diameter larger locking screws using the same plate holes. The screwheads lock into the plate‐holes by a combination of two mechanisms: (i) partial threads in the plate‐hole that lock with the most proximal thread of the screw (Figure 7.1), and (ii) conical shape of both the screwhead and the plate hole.

The plates are made of grade 4 titanium and the screws are made of a titanium’aluminum‐vanadium alloy (Ti‐6A1–4 V). Four size‐systems, named based in the width of the plates, are available. Each system has two different sizes of plates fitting the same‐size screws: mini (3.5/4 mm), small (5/6.5 mm), medium (8/9 mm), and large (10/11 mm). Details of plate size, locking and cortical screw sizes, and common applications of each system are provided in Table 7.1. A dedicated implant chart is used to evaluate proper implant size (Figure 7.4).