Locking Plate vs Standard Plate: Which Construct Fits the Fracture

In small animal practice, "locking" is frequently read as a synonym for "better". Mechanically that is not accurate. A locking plate and a standard (non-locking) plate are two different fixation strategies: one behaves as a fixed-angle internal fixator, the other as a compression device held in place by friction between plate and bone. Which one suits a given case depends on the fracture pattern, the bone quality and what the surgeon intends the construct to do.

What each plate actually does

In a standard plate, the screw head seats in the hole and pulls the plate down onto the bone as the screw tightens. Stability therefore depends on how well the plate is contoured to the cortical surface and on the friction generated across that contact. Compression holes in DCP and LC-DCP designs allow the surgeon to generate interfragmentary compression, which is what supports primary bone healing in a simple fracture.

In a locking plate, the screw head threads into the plate hole, so the screw and plate become a single fixed-angle unit. The plate no longer has to be pressed against the cortex to hold position; the construct spans the fracture like an internal fixator, and each screw's angle is locked relative to the plate rather than to the bone surface.

When a locking plate is the better fit

• Comminuted fractures, where the objective is relative stability and callus formation rather than anatomical reconstruction of every fragment.
• Osteopenic or thin-corticed bone, where a fixed-angle screw resists pull-out better than a screw that relies on plate-to-bone friction.
• Sites with a thin soft tissue envelope, where extensive periosteal exposure should be avoided and the plate can be left slightly off the bone.
• Bridging constructs, where the fracture zone is not opened and the plate carries the whole load across the gap.
• Multiple fractures in the same limb that are best managed with one spanning implant instead of several short ones.

When a standard plate is still the right choice

• Simple transverse or short oblique fractures in good bone, where interfragmentary compression and primary healing are the goal.
• Irregular surfaces that require real contouring — a non-locking plate can be shaped to the bone, whereas a locking plate forces the reduction to follow the plate.
• Cost-sensitive, high-volume settings with a predictable case mix, where the extra unit cost of locking implants buys nothing for the fracture at hand.
• Cases with planned early implant removal, where a simpler construct is easier to explant.
• Young, growing patients, where the revision pathway should stay as flexible as possible.

Decision dimensions worth writing down before surgery

• Fracture pattern and mechanical goal — absolute stability with compression, or relative stability with a bridging construct.
• Bone quality and cortical thickness — the limiting factor is usually screw purchase, not plate strength.
• Anatomy and contouring demand — how much the plate must follow the bone determines which design is practical.
• Soft tissue envelope — how much periosteum can be preserved at the approach.
• Instrumentation on hand — locking constructs need matched drill guides and a calibrated torque-limiting driver.
• Surgeon familiarity — outcome is technique-sensitive, and consistency with a known system usually outweighs a theoretical advantage.
• Removal and revision plan — anticipate the second surgery at the first.
• Inventory cost per size — carried stock, not the catalogue price, drives per-case cost.

Where these constructs commonly fail

• Poor contouring with a locking plate. The plate defines alignment, so a badly contoured plate imports a malalignment that cannot be closed by tightening screws.
• A locking screw that is not fully seated. A partially engaged head holds nothing, and a cross-threaded hole cannot be reused reliably.
• Mixing systems from different suppliers. Thread forms differ between manufacturers, so a screw of the same nominal diameter may not lock in another brand's plate.
• Working length too short, or too few screws per fragment. Construct stiffness is dominated by plate span and screw number, not by the locking mechanism itself.
• Screws that barely engage the far cortex, leaving little to resist cyclic load.
• Expecting the locking mechanism to compensate for a fracture gap that is too large — the plate will still fatigue.

What this means for sourcing and inventory

The practical difference between the two systems is not only unit cost. Locking implants require matched instrumentation — dedicated drill guides, calibrated torque-limiting screwdrivers and system-specific depth gauges — and the cost of running two suppliers is usually incompatibility rather than price. A screw that fits one plate will not necessarily lock in another.

Otta Care manufactures locking and non-locking plates on the same production lines to standard AO dimensions, in Ø1.5, 2.0, 2.4, 2.7 and 3.5 mm systems, in titanium and 316L stainless steel, with matching cortical and locking screws and instrument sets. That allows a hybrid inventory — locking for comminuted and osteopenic cases, standard plates for simple compression work — without maintaining two incompatible systems in the same theatre. Because the same facility also produces human orthopaedic implants under ISO 13485, material traceability and machining tolerances follow medical-device practice rather than general machining practice.

Distributors and hospital groups building a size ladder can request the current dimension chart, screw compatibility table and sample plates through our contact page before committing to stock.

Surgical technique and implant selection remain clinical judgements that depend on the individual fracture, bone quality and surgeon experience. This article is written for veterinary professionals as a planning and sourcing reference, not as a treatment protocol.