How orthopedic plates and screws work together
Orthopedic plates and screws are internal fixation devices used to stabilize broken, cut, or reconstructed bone so healing can occur in a controlled position. The plate functions as a load-sharing or load-bearing bridge along the bone surface. Screws anchor the plate, compress fracture surfaces, or secure individual fragments directly. Selection is not just a question of implant size. Surgeons consider the fracture pattern, bone quality, anatomy, soft tissue condition, expected loading, and whether the construct should provide absolute stability or controlled relative stability. For readers comparing fixation approaches, this overview fits within broader Fixation topics and should be read as educational industry information, not personal medical advice.
In open reduction and internal fixation, bone fragments are first aligned and then held with implants. The American Academy of Orthopaedic Surgeons describes internal fixation as a method that may use screws, plates, rods, pins, or other devices to hold bone in place. Plates and screws are among the most familiar options because they can be adapted to many anatomical regions, including the forearm, ankle, distal radius, clavicle, pelvis, and periarticular bone.
The implant does not heal the bone by itself. Its role is to maintain reduction, resist displacement, and provide a mechanical environment in which biological healing can proceed. That distinction matters in clinical planning and device evaluation. A construct that is too weak can fail before union, while one that is too stiff or poorly matched to the fracture biology may create a different set of problems.
The fixation goal determines the construct
AO Surgery Reference materials commonly describe plating by function rather than by brand or appearance. A plate with the same general shape can behave differently depending on where it is placed, how it is contoured, which holes are used, and which screws are inserted. For that reason, implant selection starts with fracture mechanics.
| Plating mode | Main purpose | Typical use concept |
|---|---|---|
| Compression plate | Compresses a simple fracture line | Used when the fracture pattern allows close contact between fragments and the goal is absolute stability |
| Neutralization plate | Protects another fixation method | Often supports lag screws so bending and torsional forces do not act directly on the screw alone |
| Bridge plate | Spans a comminuted zone | Maintains length, alignment, and rotation while avoiding unnecessary disturbance of intermediate fragments |
| Buttress plate | Prevents shear displacement | Used where a fragment tends to slide, especially near metaphyseal or joint-adjacent bone |
Absolute stability aims to minimize interfragmentary motion. It is usually associated with primary bone healing and is most relevant to simple fracture patterns that can be compressed. Relative stability allows small, controlled motion and is often used where indirect healing with callus formation is expected, especially in multifragmentary fractures. Neither principle is automatically better; the appropriate method depends on anatomy and fracture configuration.
A common misconception is that a stronger-looking plate always improves fixation. In practice, construct stiffness, working length, screw density, plate length, and soft tissue preservation all influence performance. AO teaching materials note that it is not necessary to fill every plate hole if enough screws are used to maintain reduction until healing. This principle helps explain why many modern fixation constructs look less crowded than older images of fully filled plates.
Locking and non-locking screws are not interchangeable
Screws do more than attach hardware. A conventional non-locking screw pulls the plate toward the bone as it is tightened. That can be useful when the plate is intended to compress the bone or sit closely against the cortex. It also means plate contouring is important, because an inaccurately shaped plate can shift fracture alignment as the screws are tightened.
A locking screw works differently. Its head engages the threaded plate hole, creating a fixed-angle relationship between screw and plate. The construct behaves more like an internal fixator because stability does not depend only on friction between plate and bone. This can be valuable in osteoporotic bone, short metaphyseal segments, periarticular fractures, and situations where preserving blood supply under the plate is important.
However, locking screws are not simply upgraded conventional screws. AO educational material emphasizes that locking screws used in locking mode do not create compression in the same way as eccentrically placed conventional screws in a dynamic compression hole. If compression is needed at a simple fracture line, the surgeon must plan for it with the correct screw type, hole position, lag screw technique, or compression device.
| Feature | Non-locking screw | Locking screw |
|---|---|---|
| Primary stability mechanism | Compresses plate to bone | Locks screw head to plate |
| Need for plate contouring | Higher, because tightening can pull bone to the plate | Lower for plate-to-bone contact, but overall alignment remains critical |
| Compression capability | Can create compression when used eccentrically or as a lag screw | Does not create standard dynamic compression when locked |
| Common advantage | Useful for compression and cost-effective fixation principles | Useful in weak bone and fixed-angle constructs |
| Potential limitation | May lose purchase in poor bone | May produce an overly stiff construct if used without attention to mechanics |
Many modern systems allow a combination of locking and non-locking screws. The key issue is compatibility. Screws, plates, drill bits, depth gauges, torque-limiting drivers, and washers may be designed as a system. Mixing components outside the manufacturer’s instructions can change mechanical performance and may create regulatory or safety issues.
Materials and design factors that affect performance
Regulatory descriptions in the United States identify common metallic materials for bone fixation appliances, including stainless steel, titanium, and cobalt-chromium-molybdenum alloys. ISO standards such as ISO 5832-1:2024 address metallic materials for surgical implants, including wrought stainless steel, by specifying characteristics and test methods. These standards do not mean every plate or screw is the same; they help define material expectations and support consistent evaluation.
Titanium alloys are often associated with corrosion resistance, a lower modulus compared with stainless steel, and favorable imaging behavior. Stainless steel remains widely used because of its strength, manufacturing familiarity, and established clinical history. Cobalt-chromium alloys may appear in certain implant contexts where high strength and wear resistance are important. There is no universal best material. The appropriate choice depends on indication, design, surgeon preference, regulatory clearance, availability, and patient-specific factors such as allergy history.
Plate geometry is equally important. A plate may be straight, pre-contoured, anatomic, tubular, reconstruction-style, low-contact, periarticular, or designed with combination holes. Some plates have elongated holes for dynamic compression; others have threaded holes for locking screws; many have both. Reduced-contact designs aim to limit pressure on the bone surface, but they still require correct placement and a suitable fixation strategy.
Screw design also varies. Cortical screws usually have threads suited to dense cortical bone, while cancellous screws are shaped for softer metaphyseal or cancellous bone. Cannulated screws accept a guidewire. Headless compression screws can be used where a prominent screw head would interfere with a joint surface or tendon path. In plate fixation, the screw’s diameter, length, thread form, head design, and drive interface all affect purchase and fatigue behavior.
Regulatory and testing context in the United States
For U.S. device regulation, non-spinal fixation plates and screws are generally handled as Class II orthopedic devices when they fit the relevant definitions. Under 21 CFR 888.3030, metallic bone fixation appliances can include plates and associated fasteners. Under 21 CFR 888.3040, smooth or threaded metallic bone fixation fasteners include devices used for fracture fixation, reconstruction, and related purposes. FDA product classification records list fixation plates and bone screws under orthopedic review categories.
The FDA issued final guidance in April 2022 for orthopedic fracture fixation plates under the Safety and Performance Based Pathway. That pathway allows certain 510(k) submitters to use FDA-identified performance criteria to support substantial equivalence rather than relying only on direct performance comparison to a predicate device. In November 2024, FDA also issued final guidance for orthopedic non-spinal bone plates, screws, and washers in 510(k) submissions, along with performance criteria guidance for non-spinal metallic bone screws and washers. See also: Implants.
These documents are important because they indicate what information regulators may expect around indications, materials, mechanical testing, labeling, sterilization, and system compatibility. They do not rank implants by clinical superiority and should not be read as marketing claims. FDA guidance documents generally describe the agency’s current thinking and are not legally binding unless specific regulatory requirements are cited.
For industry readers, the regulatory lesson is direct: a fixation implant is evaluated as a device with a defined indication, material specification, mechanical performance profile, and labeling. A plate-and-screw system intended for a small bone, a long bone shaft, or a periarticular fracture may require different evidence even if the basic concept looks similar.
Clinical considerations after implantation
After plates and screws are implanted, the construct must survive long enough for biological healing. Load sharing changes over time. Early on, the implant may carry substantial stress. As callus forms or the fracture consolidates, more load transfers through the healing bone. Delayed union or nonunion can leave the plate exposed to repetitive loading for too long, increasing the risk of screw loosening or implant fatigue.
Possible complications discussed in orthopedic education include infection, loss of reduction, irritation from prominent hardware, stiffness, nonunion, malunion, and implant breakage. These risks vary widely by injury severity, surgical technique, patient health, smoking status, bone quality, soft tissue injury, infection risk, rehabilitation, and adherence to weight-bearing restrictions.
Patients often ask whether hardware must be removed. AAOS patient education notes that hardware often does not need removal after healing, although removal may be advised in selected cases. Reasons can include pain, soft tissue irritation, infection management, growth-related issues in younger patients, or planned staged treatment. Removal is still a surgical decision with its own risks, so it should not be assumed to be routine.
Imaging follow-up is also part of the clinical picture. X-rays can show alignment, screw position, plate integrity, and progression of healing. They cannot always explain pain or soft tissue symptoms by themselves. Decisions about activity progression, weight bearing, and rehabilitation depend on the surgeon’s assessment of both the fixation and the patient’s recovery.
How to evaluate information about fixation implants
Because orthopedic plates and screws are widely used, online information often blends education, marketing, and patient anecdotes. A practical review should ask specific questions rather than look for a single best implant.
- What is the indication? A distal radius plate, clavicle plate, ankle plate, and femoral shaft plate solve different mechanical problems.
- What stability principle is intended? Compression, neutralization, bridge, and buttress constructs are not interchangeable.
- What screw types are compatible? Locking, non-locking, variable-angle, cannulated, and cancellous screws require system-specific planning.
- What material standard or specification is referenced? Material names alone are less useful than recognized specifications and validated manufacturing controls.
- What testing supports the claim? Bending strength, fatigue behavior, torsional performance, insertion torque, and pullout data may be relevant depending on the device.
- What does the labeling allow? Indications, contraindications, sterilization status, MRI information, and single-use instructions matter.
The most useful content is specific about mechanics and careful with claims. Statements such as “locking is always better” or “titanium always outperforms stainless steel” are too broad. Better analysis explains the clinical problem, the fixation principle, the evidence source, and the limitation of the conclusion.
Frequently asked questions
What are orthopedic plates and screws used for?
They are used to hold bone fragments, osteotomy sites, or reconstructed bone in a planned alignment while healing occurs. Plates provide structural support along the bone, and screws secure the plate or compress fragments.
Are locking plates better than standard plates?
Not always. Locking constructs can be helpful in weak bone, periarticular fractures, and fixed-angle fixation, but conventional screws remain important for compression and many standard fixation principles. The fracture pattern determines the better approach.
Do plates and screws have to be removed after healing?
Often they remain in place if they are not causing problems. Removal may be considered for pain, irritation, infection, or other surgeon-assessed reasons, but it is not automatically required.
Can every fracture be treated with plates and screws?
No. Some fractures are better treated with casting, intramedullary nails, external fixation, joint replacement, or other methods. Treatment depends on fracture location, displacement, soft tissue condition, patient health, and functional needs.
Why are FDA and ISO references relevant?
They help readers understand the regulatory and material framework behind fixation devices. They do not prove that one implant is clinically superior, but they support consistent evaluation of materials, performance, and submission information.