Locking plates arrived in trauma surgery with a bold promise: fixation that holds in bone where screws alone would strip, loosen and fail. Two decades later the picture is more nuanced and more useful. Locking technology genuinely changed outcomes in osteoporotic bone, periarticular fractures and periprosthetic cases — and a large review literature also documents the fractures where an expensive locking plate adds nothing over a well-applied conventional plate, and a few where it does worse. This post lays out the biomechanics first and the indications second, so the choice between the two becomes a mechanical decision rather than a brand preference. Implant selection for any individual fracture remains the decision of the operating surgeon.
Two different machines
A conventional plate is a clamp. Its screws pull the plate down onto the bone, and friction between plate and bone carries the load. The construct is exactly as strong as that friction interface, which means it depends on bone quality: in dense cortical bone the screw purchase is excellent, and in osteoporotic bone it is not. A locking plate is a scaffold. The screw heads thread into the plate itself, so plate and screws act as one fixed-angle device. Load travels from bone to screw to plate without needing friction, and the bone under the plate keeps its blood supply because the plate never has to be pressed against it. Each screw works alone; one screw loosening does not unload its neighbors.
| Factor | Conventional plate | Locking plate |
|---|---|---|
| Load transfer | Friction between plate and bone | Fixed-angle screw-plate unit |
| Dependence on bone quality | High | Low |
| Fracture compression | Direct, through plate or lag screw | Must be achieved before locking |
| Periosteal blood supply | Compressed under plate | Preserved |
| Plate contouring need | Must fit bone exactly | Approximate fit tolerated |
Where locking plates earn their cost
The evidence summarized in reviews such as the open-access analysis of locking plates in fragility fractures (PMC3145849) points to three consistent winners. Osteoporotic metaphyseal fractures: distal radius, proximal humerus and proximal tibia in poor bone, where conventional screws strip and fixed-angle pegs hold. Periarticular fractures with small articular blocks: the distal femur, the tibial plateau and the distal tibia, where a short metaphyseal segment must be held at an exact angle. And periprosthetic fractures around joint replacements, where unicortical locking screws fix bone that bicortical drilling cannot safely reach. In these settings, locking fixation is the standard of care, and the plate families we stock — the proximal tibia locking plate and the medial distal humerus locking plate among them — are built around it.
Where conventional plating still wins
Simple diaphyseal fractures in good bone remain conventional territory. A transverse forearm or humeral shaft fracture fixed with a properly contoured compression plate heals by direct bone union with a track record no locking plate has beaten — and studies of locking plates used like conventional plates in simple patterns show no benefit and occasional worse union, because a rigid locked bridge over a simple transverse gap can suppress the contact healing the fracture needs. Conventional plating also keeps two unique tools: the lag screw through the plate, which no locking screw can replicate, and intraoperative contouring, which lets the surgeon bend a steel plate to a bone that does not match any factory template. Our conventional lines, such as the medial distal humerus plate, exist for exactly these cases.
Bridge plating: where the biology argument is strongest
Comminuted diaphyseal and metaphyseal fractures — the ones with a zone of fragments that cannot be pieced back together — are treated by bridging, and this is where the two plate philosophies diverge most sharply. A bridge plate spans the comminuted zone without touching it, fixed to healthy bone on either side, and the fracture heals by callus rather than by direct cortical union. Locking plates suit this role naturally: the plate floats off the bone, the periosteum stays perfused, and long plates with few widely spaced screws give the flexible fixation that callus wants. A conventional plate forced into the same role compresses a long segment of periosteum and concentrates stress at its end screws, which is why bridge plating in comminuted fractures has largely moved to locking systems in modern practice. Screw spread matters as much as screw count: filling every hole makes the construct stiff and stress-risers at the fracture ends, while leaving empty holes near the fracture zone spreads the working length of the plate and shares the load.
The combination plate: using both at once
Most modern periarticular plates carry combination holes that accept both screw types, and the skilled use of the two together is where the systems earn their keep. The standard sequence: conventional cortical screws first, to pull the plate to the bone and compress the fracture; locking screws second, to hold the reduction at a fixed angle. Reversing the order — locking first — freezes any gap between plate and bone and makes later compression impossible. The screw inventory behind this workflow sits in our screws and fixation collection, from periarticular cortical screws for the compression step to locking cortical screws for the fixed-angle step.
The honest trade-offs
Locking plates cost more per implant, demand disciplined fluoroscopy because fixed-angle screws cannot be redirected after insertion, and can be harder to remove when bone overgrows the locked interface. Conventional plates demand better bone, exact contouring, and accept a biological cost under the plate. Neither technology forgives a bad reduction: both fix the fracture exactly where the surgeon leaves it. The reviews are consistent on the bottom line — match the fixation principle to the fracture, the bone and the biology, and the implant brand matters far less than the match.
Sourcing locking and conventional systems
BoneCraft is an independent distributor of genuine Zimmer Biomet trauma implants, stocking both locking and conventional plating families across all anatomic regions. Hospitals and distributors building or refreshing a trauma formulary can contact our team for availability and lot documentation.
Frequently asked questions
What is the core difference between a locking and a conventional plate?
A conventional plate works by friction between plate and bone, generated by screw compression. A locking plate works as a fixed-angle scaffold, with screw heads threaded into the plate itself, so it does not depend on friction or bone quality.
Which fractures benefit most from locking plates?
Osteoporotic metaphyseal fractures, periarticular fractures with small joint fragments, and periprosthetic fractures. In these settings fixed-angle fixation outperforms friction-based fixation because the bone cannot supply the screw purchase a conventional plate needs.
When is a conventional plate the better choice?
Simple diaphyseal fractures in good bone, where direct compression and primary bone healing are the goal. Conventional plating also provides lag-screw compression through the plate and allows intraoperative contouring.
Can the two screw types be used in the same plate?
Yes. Combination-hole plates accept both. Conventional screws go first to seat the plate and compress the fracture; locking screws follow to hold the position. Locking first blocks any later compression.
Do locking plates always improve healing?
No. In simple transverse fractures in good bone, an overly rigid locked construct can suppress contact healing. The benefit of locking technology is concentrated in poor bone and periarticular patterns.
Why do locking plates preserve blood supply better?
Because the plate does not need to be pressed against the bone. The periosteal circulation under the plate stays intact, which supports callus formation in bridge plating of comminuted fractures.
Are locking screws weaker than conventional screws?
Locking screws have a thinner core to accommodate the threaded head, so a single locking screw bends or breaks sooner than a solid cortical screw under isolated load. The strength of the locking construct comes from the fixed-angle unit of plate and screws working together, not from the individual screw.
Zimmer Biomet and ZPLP are trademarks of their respective owner. BoneCraft is an independent distributor of genuine Zimmer Biomet products and is not affiliated with, sponsored by, or endorsed by the trademark owner.
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