Fracture fixation devices are surgical implants and external frames used to hold broken bone fragments in alignment while they heal. They range from metal plates and screws drilled directly into bone to rods threaded inside the marrow canal and external cages bolted through the skin. The choice among them depends on the fracture pattern, the bone involved, and the patient’s overall health, and each category carries distinct trade-offs in stability, complication risk, and whether a second surgery is needed for removal.
Why the Type of Stability Matters
Not all fractures heal the same way, and the fixation device a surgeon picks is designed to steer the healing process in a particular direction. Bone can knit back together through what is called primary healing, where the two broken ends fuse directly without forming a visible callus, or through secondary healing, where a cartilage-rich callus forms around the fracture gap and gradually converts to bone. Rigid fixation, where the device locks the fragments so tightly that almost no motion occurs at the break, favors primary healing. Flexible fixation, which allows controlled micro-motion, encourages the secondary route and the callus formation that comes with it.1PubMed Central. Principles of Fracture Healing and Fixation: A Literature Review Neither pathway is universally better; the best match depends on the fracture’s location and complexity.
This distinction shaped decades of evolving surgical philosophy. Early approaches to internal fixation prioritized absolute stability for every fragment, on the assumption that rigidity was the surest path to union. Over time, surgeons recognized that aggressively manipulating fragments and bolting stiff plates to bone could damage the blood supply, which is just as important for healing as mechanical stability. That realization shifted practice toward methods that preserve blood flow even if they allow slightly more motion at the fracture site.2Injury. Changes in the AO/ASIF principles and methods Today, the guiding principle is to match the device’s stiffness to what the fracture and its surrounding tissue actually need.
Plates and Screws
Plates are the workhorse of fracture fixation. A metal plate is contoured to the bone’s surface and held in place by screws driven through holes in the plate and into the bone on either side of the break. Traditional (non-locking) plates rely on friction between the plate and the bone surface for stability, which means they work best when bone quality is good and the screws can grip firmly.
Locking plates changed the equation. In a locking design, the screw heads thread into the plate itself, creating a fixed-angle connection. This means the plate does not need to be compressed tightly against the bone to stay put. The result is greater stability and higher loads to failure compared with traditional plates, a meaningful advantage in fractures near joints or in bone that has become thin and fragile.3PubMed Central. Evidence for success with locking plates for fragility fractures That said, plate configuration matters as much as plate type. In biomechanical testing of distal humerus fractures, the way two plates are arranged on the bone influences stability more than whether those plates are locking or conventional. Locking plates show their clearest advantage in poor-quality bone or heavily fragmented fractures where conventional screws struggle to hold.4PubMed. A biomechanical evaluation of methods of distal humerus fracture fixation using locking compression plates versus conventional reconstruction plates
Intramedullary Nails
For long-bone fractures of the femur, tibia, or humerus, surgeons often place a metal rod inside the bone’s marrow canal. This intramedullary nail acts as an internal splint, sharing load with the bone while allowing early weight-bearing. Locking screws at each end of the nail keep it from rotating or telescoping inside the canal.
Instrumented measurements inside human femoral nails during daily activities show that the implant bears significant axial forces and bending moments even during seemingly light tasks like sitting or lifting the leg while lying down. As the fracture consolidates, the loads carried by the nail drop by roughly half, confirming that the bone progressively takes over its own weight-bearing job.5PubMed. Loads acting in an intramedullary nail during fracture healing in the human femur In children and adolescents, flexible elastic nails are preferred because they can be inserted without crossing growth plates, preserving the bone’s ability to keep growing. These thinner, more elastic rods rely on the periosteum (the outer bone membrane) staying intact to maintain alignment.6PubMed Central. Atypical use of pediatric flexible nails in the treatment of diaphyseal fractures in adults
Tension Band Wiring and Cerclage Techniques
Some fractures sit where muscles pull the broken fragments apart every time you move. The kneecap is a classic example: the quadriceps muscle above and the patellar tendon below constantly try to separate the upper and lower halves. Tension band wiring handles this by threading a figure-of-eight wire around two parallel pins that cross the fracture. When the knee bends, the wire converts the pulling (tension) force on the front surface of the kneecap into compression on the joint side, pushing the fragments together rather than apart.7Indian Journal of Orthopaedics Surgery. Technique of tension band wiring in patella fracture management-our experience Variations use cannulated screws instead of plain pins, with the wire threaded through the hollow center of each screw, which can improve the construct’s grip on the bone.8PubMed Central. Percutaneous Cannulated Screws with Tension Band Wiring Technique in Patella Fractures
External Fixation
When the soft tissue around a fracture is too damaged for immediate internal surgery, or when a fracture is open with bone piercing through skin, surgeons often turn to external fixation. Pins or wires are drilled through the skin and into bone segments above and below the break, then connected to an external frame. The frame can be a simple bar on one side of the limb (unilateral fixator) or a circular construct with tensioned wires, which is especially useful when gradual correction of deformity or bone lengthening is the goal.9PubMed Central. The mechanics of external fixation
External fixators are often a bridge: they stabilize the fracture during the acute phase and get swapped for internal hardware once swelling and soft-tissue damage settle down. In cases of severe bone loss, circular frames may stay on for months while the bone regenerates. The trade-off is that the pin-skin interface creates a direct pathway for bacteria, making pin-track infection an almost universal risk. These infections range from minor skin irritation treatable with antibiotics and local wound care to deep infections that can loosen the pins, prevent union, or progress to chronic bone infection.10PubMed Central. Prevention and management of external fixator pin track sepsis
Titanium Versus Stainless Steel
Most fracture fixation hardware is made from either stainless steel or titanium alloys. Stainless steel is cheaper and stiffer, which can be an advantage when absolute rigidity is needed but a disadvantage when some flexibility would help callus formation. Titanium is lighter, more flexible, and more biocompatible, meaning the body’s immune response to it is milder.
A systematic review comparing the two metals found clinically meaningful differences. In distal femur plating, patients with stainless steel plates had significantly less callus formation and over six times the odds of nonunion compared with those who received titanium plates. For intramedullary nails, stainless steel showed a higher rate of locking-screw breakage: about 10% of stainless steel nails experienced this complication versus roughly 2% of titanium nails.11PubMed Central. A systematic review of the use of titanium versus stainless steel implants for fracture fixation Screw breakage in a nail is sometimes called autodynamization, where the loss of the locking screws converts a statically locked nail into a dynamic one, which can actually promote healing in some cases but is obviously uncontrolled and unplanned. The trend in modern practice leans toward titanium for most long-bone nails and an increasing share of plates, though stainless steel remains in use where cost is a deciding factor.
Carbon Fiber and Polymer Alternatives
One frustration with metal implants is that they block X-ray imaging around the fracture site, making it harder to judge how well healing is progressing. Carbon fiber-reinforced PEEK (a tough polymer) plates are radiolucent, meaning X-rays pass through them clearly, giving surgeons an unobstructed view of the healing bone. In a multicenter study of proximal humerus fractures, carbon fiber PEEK plates proved as reliable as metal plates while also making intraoperative imaging easier and simplifying hardware removal, since the screws do not cold-weld to the plate the way metal-on-metal constructs sometimes do.12PubMed. Proximal humeral fracture fixation: multicenter study with carbon fiber peek plate Biomechanical testing of these plates against titanium in comminuted tibia fractures showed comparable performance, further supporting the idea that carbon fiber composites are a realistic alternative in certain clinical settings.13PubMed Central. A biomechanical matched-pair comparison of two different locking plates for tibial diaphyseal comminuted fracture: carbon fiber-reinforced poly-ether-ether-ketone (CF-PEEK) versus titanium plates
Another advantage of non-metal implants is that their stiffness can be tuned closer to bone, which reduces stress shielding (more on that below). Composite plates made from carbon fiber and natural fiber in an epoxy matrix have demonstrated less stress shielding than standard clinical metal plates in biomechanical modeling.14PubMed. Biomechanical analysis of a new carbon fiber/flax/epoxy bone fracture plate shows less stress shielding compared to a standard clinical metal plate
Biodegradable Implants
The ideal fixation device would hold a fracture firmly, gradually transfer load back to the healing bone, and then dissolve harmlessly so no removal surgery is needed. That is the promise behind biodegradable implants, typically made from polylactic acid (PLA) or magnesium alloys, sometimes combined. Adding magnesium particles to a PLA matrix helps neutralize the acidic by-products that PLA generates as it degrades and encourages mineral deposition, which could support bone growth.15Composites Science and Technology. Development of PLA/Mg composite for orthopedic implant: Tunable degradation and enhanced mineralization Researchers are working to fine-tune the degradation rate so the implant retains its mechanical strength long enough for the bone to heal. In laboratory tests, composites with magnesium showed that interfacial binding between the metal particles and the polymer weakens over about eight weeks of immersion in simulated body fluid, leading to rapid loss of mechanical properties.16PubMed. Mechanical and degradation properties of biodegradable Mg strengthened poly-lactic acid composite through plastic injection molding Getting the balance right between how fast the material dissolves and how long the fracture needs support remains the central engineering challenge.
Stress Shielding
Metal plates and nails are almost always stiffer than the bone they are attached to. When the implant carries most of the mechanical load, the underlying bone “sees” less stress than it normally would. Bone is a living tissue that remodels in response to the forces placed on it: reduce those forces and the bone gradually thins. This process, called stress shielding, can weaken the bone beneath a plate, sometimes leading to bone resorption or a refracture after the hardware is removed.17PubMed Central. Stress analysis in a bone fracture fixed with topology-optimised plates It is particularly relevant in periprosthetic fractures around hip replacements, where the combination of a femoral stem inside the canal and a plate on the outside can create a heavily shielded segment of bone.14PubMed. Biomechanical analysis of a new carbon fiber/flax/epoxy bone fracture plate shows less stress shielding compared to a standard clinical metal plate
Strategies to reduce stress shielding include using lower-stiffness materials like titanium over stainless steel, switching to composite plates, and optimizing the plate’s geometry using computational design so that stiffness varies along its length. None of these fully eliminates the problem, but each nudges the load-sharing ratio closer to what the bone needs to stay healthy.
Infection and Biofilm
Any implanted foreign body increases the risk of infection because bacteria can adhere to its surface and form a biofilm, a slimy layer that is extremely difficult for both the immune system and antibiotics to penetrate. Orthopedic implant-associated infections involve a cascade that starts with proteins from the blood coating the implant surface within minutes, followed by bacterial adhesion, biofilm maturation, and a chronic inflammatory response.18PubMed Central. Antibacterial and Immunomodulatory Coatings for Orthopedic Metal Implants: Biological Rationale, Design Strategies, and Translational Challenges Once a mature biofilm forms, antibiotics alone rarely clear the infection; the implant often has to come out.
External fixator pins are especially vulnerable because each pin creates a permanent breach in the skin. Pin-track infections are so common that some degree of skin irritation around pin sites is practically expected. Most cases respond to local care and oral antibiotics, but severe infections can undermine the pin’s grip in the bone, leading to pin loosening, fracture nonunion, and in the worst scenario, chronic osteomyelitis.10PubMed Central. Prevention and management of external fixator pin track sepsis Research into antibacterial coatings for implants, including silver, copper, and antibiotic-loaded surfaces, is active, though translating laboratory coatings into clinically approved products remains slow.
When Hardware Comes Out
One of the most common questions patients have after a fracture heals is whether the metal needs to be removed. There is no single answer. In many cases, plates and screws stay in permanently without causing problems. Removal becomes an issue when hardware causes pain, limits motion, sits just under thin skin where it can be felt or irritated, or when infection develops. In one study of 83 implant removals, patient request was the most frequent reason the surgery happened, ahead of surgeon-initiated removal or symptomatic hardware.19PubMed Central. Removal of orthopaedic implants: indications, outcome and economic implications
Removal surgery is not without risk. It involves a second anesthetic, a second incision, and complications that include nerve or blood vessel injury and refracture through the empty screw holes. In a series of 83 removal cases, true complications included chronic osteomyelitis in a patient with a previously infected nail, a subsequent refracture, and persistent pain in a few patients who were previously pain-free.20PubMed Central. Indications of implant removal: A study of 83 cases For many patients, leaving well-functioning hardware in place is the safer choice.
Fixation in Osteoporotic Bone
Thin, porous bone is the enemy of screw purchase. In patients with osteoporosis, screws can strip out of bone that is too weak to grip them, leading to implant loosening and fixation failure. Locking plates help because the screws lock to the plate rather than relying entirely on bone friction, but even locking constructs can fail when bone mineral density is very low.
In the spine, where pedicle screws anchor rods that stabilize vertebral fractures, surgeons sometimes inject bone cement (polymethylmethacrylate, or PMMA) through or around the screws to increase their hold. A meta-analysis comparing cement-augmented pedicle screws to conventional screws in patients with osteoporotic spondylolisthesis found that the augmented group had significantly lower pain scores, better functional outcomes, higher rates of spinal fusion, and dramatically lower rates of screw loosening.21Frontiers in Surgery. Bone cement-augmented vs. conventional pedicle screws for osteoporotic lumbar spondylolisthesis: a meta-analysis The trade-off is the risk of cement leakage. Liquid cement can escape into the spinal canal or the veins around the vertebra, and in rare cases, cement emboli travel to the lungs. A case report documented a 70-year-old patient who developed pulmonary embolism from cement that leaked during augmented pedicle-screw placement.22PubMed Central. Cement-Augmented Pedicle Screw Fixation in Patients with Osteoporosis : Safety, Efficacy and Complications Factors that influence how well augmentation works include the volume of cement injected, the severity of bone loss, the screw design, and the injection technique.23PubMed Central. The Biomechanical Properties of Cement-Augmented Pedicle Screws for Osteoporotic Spines
3D-Printed and Patient-Specific Implants
Standard plates come in a limited set of sizes and shapes, and surgeons bend them intraoperatively to match the patient’s anatomy. That works well for straightforward fractures, but complex reconstructions involving bone loss or unusual geometry can push off-the-shelf hardware to its limits. Three-dimensional printing now allows surgeons to design implants from a CT scan of the individual patient’s anatomy, producing a device that fits precisely without any intraoperative bending.
In complex lower-extremity reconstruction, a cohort of fifteen patients treated with 3D-printed titanium cages achieved an 87% fusion rate, with thirteen of fifteen patients healing successfully. Nearly all had previously failed conventional surgery or had major bone loss from trauma. Without the custom implant, their options would have involved large bone grafts and multiple operations.24PubMed Central. Clinical applications of custom 3D printed implants in complex lower extremity reconstruction Beyond custom cages, 3D-printed models of the fracture itself are being used for preoperative planning. Surgeons can rehearse the reduction on a physical replica, pre-bend plates to fit, and walk into the operating room with a detailed roadmap. This approach has been shown to reduce surgical time and improve fracture alignment compared with conventional planning.25Frontiers in Surgery. Treatment of complex limb fractures with 3D printing technology combined with personalized plates: a retrospective study of case series and literature review
Implantable Sensors for Monitoring Healing
Judging when a fracture has healed enough for full weight-bearing is surprisingly subjective. Surgeons rely on X-rays and physical examination, both of which have limitations. A novel approach places a small strain sensor directly onto the fixation plate at the time of surgery. The sensor includes a tiny cantilevered pin and an internal scale. As the bone heals and takes on more load, the plate bends less, and the pin’s position shifts. That shift is visible on a standard X-ray, giving an objective, quantitative readout of how much load the plate is still carrying versus how much the bone has taken back. Early results indicate this kind of sensor could provide a reliable clinical measure for deciding when a patient is ready to return to full activity.26Scientific Reports. Implantable strain sensor to monitor fracture healing with standard radiography If validated in larger trials, implantable sensors could replace guesswork with data, reducing both premature loading (which risks refracture) and unnecessary prolonged restrictions (which slow rehabilitation).