A surgical pin is a slim metal rod that an orthopedic surgeon drives through or alongside a broken bone to hold the fragments in place while they heal. The most common type, the Kirschner wire (K-wire), is a smooth, pointed stainless-steel or titanium wire typically ranging from about 0.9 to 2.8 mm in diameter. Pins can be placed entirely inside the body, left partially protruding through the skin for later removal, or used as part of an external frame that stabilizes the fracture from outside. Despite the rise of plates, screws, and intramedullary nails, pins remain one of the most widely used tools in fracture surgery because they are inexpensive, versatile, and minimally invasive compared with larger implants.
A Brief History of the Surgical Pin
The modern surgical pin traces back to 1909, when the German surgeon Martin Kirschner introduced his wire traction method for treating bone fractures. Kirschner’s wire and the percutaneous pinning technique it made possible revolutionized skeletal traction and fracture fixation in orthopedic surgery.1Europe PMC. Historical remarks on Martin Kirschner and the development of the Kirschner (K)-wire Before that, surgeons relied on bulky external splints or crude traction setups that offered limited control over bone alignment. The K-wire gave them a way to reach fracture fragments through small skin incisions and hold them together with minimal soft-tissue damage. More than a century later, the basic concept has not changed much. The wires got better metallurgy and sharper tips, but the principle of threading a thin metal pin across a fracture line is still a daily workhorse in operating rooms worldwide.
What Pins Are Made Of
Most surgical pins are made from one of three metals: stainless steel, titanium, or nitinol (a nickel-titanium alloy with shape-memory properties). Each has trade-offs. Titanium outlasts stainless steel under low, repetitive stress, which matters in weight-bearing applications where the pin endures many small loading cycles over weeks. Stainless steel, however, performs better under higher acute loads.2PubMed. Nitinol, Stainless Steel, and Titanium Kirschner Wire Durability Material choice also affects imaging. On an MRI scan, stainless-steel hardware creates far larger signal-void artifacts than titanium does, making it harder for radiologists to see the surrounding bone and soft tissue. In one quantitative comparison, steel screws produced artifacts roughly three times the size of titanium screws on a 1.5T MRI, and the gap widened further at 3T field strength.3PubMed Central. Metal artifacts from titanium and steel screws in CT, 1.5T and 3T MR images of the tibial Pilon: a quantitative assessment in 3D That difference often pushes surgeons toward titanium when post-operative MRI monitoring is anticipated.
How Pins Are Used in Wrist Fractures
Distal radius fractures, the classic “broken wrist,” are one of the most common reasons for pin surgery. The technique is straightforward: after the surgeon manually aligns the bone fragments, two or three K-wires are drilled percutaneously (through the skin) across the fracture, and the wrist is immobilized in a cast or splint. In a prospective study of 54 patients treated this way, bony union occurred in every case, and the satisfaction rate was about 91%. The reduction held well over time, with average radial height shifting only about a millimeter between the immediate post-operative X-ray and wire removal.4PubMed Central. Treatment of distal radius fractures with percutaneous pinning and pin-in-plaster
A larger series of 64 patients using a combined conventional and transulnar pinning technique reported radiographic union at an average of about six and a half weeks. Roughly 88% of patients had excellent or good anatomic restoration on X-ray, and functional outcomes were similarly favorable. The most common complication was pin tract infection, which occurred in four patients, followed by loss of reduction and complex regional pain syndrome in two patients each.5Techniques in Orthopaedics. Combined Conventional and Transulnar Percutaneous Pinning of the Displaced Distal Radius Fracture These numbers reflect a general pattern: pinning works reliably for many wrist fractures, though small rates of infection and occasional loss of alignment are an accepted trade-off for a procedure that is fast, cheap, and spares the patient a larger surgery.
Heat, Drilling, and Why Technique Matters
When a surgeon drills a pin into bone, the friction generates heat. If the bone temperature rises too high, it can cause thermal necrosis, killing the cells around the pin tract and weakening the hold. How much heat is generated depends on the pin geometry, the drilling technique, and whether irrigation (cooling fluid) is used. A cadaver study found that one-step drilling with a 5.0 mm Schanz pin without irrigation exceeded the thermal-injury threshold in five of eight trials. With irrigation, temperatures dropped significantly. Among the other tested techniques, only one in 24 trials reached damaging temperatures.6PubMed. Cadaveric Study of Bone Tissue Temperature During Pin Site Drilling Using Fluoroptic Thermography
The shape of the wire tip also makes a difference. A comparison of three K-wire point geometries found that trochar-tipped wires produced the highest drilling temperatures (averaging 129°C), diamond tips were in the middle (98°C), and a third design ran considerably cooler at 66°C.7The Journal of Bone and Joint Surgery. British volume. Drilling efficiency and temperature elevation of three types of Kirschner-wire point Surgeons who insert pins regularly care about these details because a loose pin from thermal bone damage can mean a second surgery. The takeaway for patients: the specific hardware and how carefully it is placed matter as much as which implant is chosen.
Insertion technique affects mechanical strength too, not just heat. A biomechanical study comparing four insertion methods for external fixation pins found that bi-cortical self-drilling pins had a 72% increase in maximum failure force compared with uni-cortical self-drilling pins, and an 82% increase over uni-cortical self-tapping pins.8PubMed Central. Biomechanical analysis of four external fixation pin insertion techniques In plain terms, drilling a pin through both walls of the bone’s cortex and using a self-drilling design produces a much stronger anchor.
Pin Tract Infection
Infection around the entry point where a pin exits the skin is the most common complication of any pinning procedure. The pin creates a direct highway between the outside environment and the bone, and bacteria can colonize that tract despite careful cleaning. Rates vary by study and fracture type, but pin tract infection shows up in nearly every published case series of external fixation or percutaneous pinning. Minor infections usually respond to oral antibiotics and improved pin-site care. Deeper infections can require pin removal, intravenous antibiotics, or both.
One problem with measuring how often this happens is that grading systems for pin-site infection are not very reliable. The Checketts’ grading system, the only classification that pairs a visual grading description with a treatment recommendation, showed only poor-to-moderate agreement between surgeons when tested formally. The agreement was even lower for patients with darker skin tones, raising equity concerns about how consistently infections are diagnosed and treated across different populations.9PubMed Central. Inter- and Intra-rater Reliability of the Checketts’ Grading System for Pin-site Infections across All Skin Colours This means that published infection rates from different studies may not be directly comparable, and that real-world detection likely depends on who is looking.
Antibiotic coatings on pins are one approach to reducing infection. Gentamicin-coated polyurethane sleeves designed for external fixation pins released effective concentrations of the antibiotic for up to 26 weeks in laboratory testing. The initial burst delivered pin-tract drug concentrations far beyond what oral or intravenous dosing could achieve, and concentrations stayed above the standard breakpoint for susceptibility for at least 20 weeks.10PubMed. Bactericidal activity of antimicrobial coated polyurethane sleeves for external fixation pins In an animal study, antibiotic-coated pins prevented infection at every pin site except one, while all uncoated control pins became infected.11PubMed. Antibiotic-coated pins for prevention of pin-tract infection: a rabbit study Clinical adoption of these coatings has been slower than the lab results might suggest, partly because of cost and partly because regulatory approval of drug-device combinations adds complexity.
When Pins Migrate
Pin migration is rare but alarming. A K-wire that is not adequately bent, threaded, or anchored can gradually travel through tissue, sometimes ending up far from where it was placed. Documented cases include wires migrating from the clavicle or shoulder region into the heart, and from the lower extremities toward the chest. The exact mechanism is not fully understood, but proposed explanations include muscle contractions, respiratory movements, negative pressure within the chest, and gradual bone resorption around the pin.12PubMed Central. Subcostal wire migration from the left clavicle internal fixation: A case report The migration can occur silently over weeks to years, making it difficult to catch early. In one reported case, a K-wire that had been used to fix a clavicle fracture migrated into the neck, where it endangered major blood vessels and the airway.13PubMed Central. Neck migration of a K-wire following fixation of clavicle fracture: a case report
These cases are dramatic but genuinely uncommon. They are important mostly because they explain why surgeons bend or cap the exposed ends of K-wires, why certain fractures (particularly around the shoulder and clavicle) are increasingly treated with plates rather than pins, and why timely pin removal matters. If you have a protruding K-wire and notice it feels like it has moved, that warrants a prompt call to your surgeon.
What Pin Removal Feels Like
For percutaneous pins that stick out through the skin, removal is usually done in a clinic rather than an operating room. The surgeon grasps the exposed end with a special instrument and pulls or unscrews the wire. In adults, this is generally well tolerated without anesthesia, and satisfaction with the awake clinic removal approach exceeds 85% in prospective series.14PubMed. Analgesia for Kirschner wire removal in paediatric and adult populations: a narrative review
Children are a different story. The experience can be frightening, and pain levels during removal are meaningful. A randomized trial of 146 pediatric patients found that virtual reality distraction during K-wire removal substantially reduced pain: observers rated pain above a moderate threshold in 43% of the VR group versus 74% of the control group.15PubMed. Effect of virtual reality on pain and stress in children during Kirschner-wire removal after fracture treatment: a randomized clinical trial Other studies have explored which factors worsen pain during pediatric wire removal, evaluating metrics like pulse changes and pain scores before, during, and after the procedure.16PubMed. Analysis of the factors affecting pain level during K-wire removal among pediatric elbow fractures If your child needs pin removal, it is worth asking the treating team about distraction techniques or short-acting pain relief, since the evidence suggests these can make a real difference.
Pins Versus Plates
One question patients often ask is whether they should push for a plate-and-screw construct instead of pins. The answer depends on the fracture. For simple, well-aligned breaks, pins provide adequate stability with less soft-tissue disruption and a faster, cheaper procedure. But for complex, comminuted (multi-fragment) fractures, plates are mechanically superior. A biomechanical study comparing percutaneous pinning to volar locked plating for unstable distal radius fractures found that plates allowed roughly half as much movement across the fracture site as pins (about 1 mm versus 2.5 mm). Pins also showed substantial slipping after repeated stress loading, while plates held steady.17Journal of Hand Surgery. Biomechanical Evaluation of Percutaneous Pinning Versus Volar Fixed-Angle Plating for Dorsally Unstable Distal Radius Fractures
That said, superior biomechanics do not always translate into better patient outcomes. Plates allow earlier movement of the wrist, which is valuable for people who cannot afford a prolonged period in a cast. But in older adults with simpler fracture patterns, pinning can produce equivalent functional results at a fraction of the cost.
Cost and Global Access
Pinning is dramatically cheaper than plating. A cost-effectiveness analysis based on a clinical trial of older adults with distal radius fractures found that total costs averaged about $11,300 for percutaneous pinning versus roughly $16,400 for volar locking plates. Pinning also produced the highest quality-adjusted life-years in that trial, meaning patients did not just save money but had comparable or slightly better outcomes by this measure. External fixation cost about $16,000 and fared worst on quality-adjusted outcomes. Simple casting was cheapest at about $6,800 but is only appropriate for the most stable fractures.18PubMed Central. Cost-Effectiveness of Treatments after Closed Extraarticular Distal Radius Fractures in Older Adults from the WRIST Clinical Trial These figures underline why K-wire pinning remains the dominant fixation method in resource-limited settings. When a hospital cannot afford a $500 locking plate for every wrist fracture, a few dollars’ worth of stainless-steel wire and a plaster cast can produce a well-healed bone.
Tension-Band Wiring
Not all pin-and-wire constructs are simple through-and-through fixations. In fractures of the kneecap (patella), surgeons often use a technique called tension-band wiring, where two parallel K-wires are combined with a figure-of-eight stainless-steel wire loop. The wire converts the pulling force of the quadriceps muscle into compression at the fracture site, pushing the fragments together rather than pulling them apart. How the wire is oriented makes a measurable difference: placing the figure-of-eight loop horizontally with wire twists at the corners improved compression by 63% compared with vertical orientation and eliminated construct failure during cyclic loading. Vertical constructs all failed during the same testing protocol.19PubMed Central. Tension-band wiring of transverse fractures of patella. The effect of site of wire twists and orientation of stainless steel wire loop: a biomechanical investigation This kind of biomechanical detail rarely matters to patients in the moment, but it illustrates how seemingly small surgical decisions about wire placement can determine whether a repair holds or fails.
Bioabsorbable Pins and Screws
The idea of a pin that dissolves after the bone heals is appealing: no removal surgery, no retained metal, and no interference with future imaging. Bioabsorbable implants made from polymers like polylactic acid have been available for years. Newer magnesium-based screws are gaining attention because magnesium is a natural element in bone and, in theory, should be absorbed cleanly.
Clinical results have been mixed. In a study of 22 patients with radial head fractures treated with magnesium bioabsorbable screws, all achieved bone union at an average of about 10 weeks, functional scores were high, and grip strength was nearly identical between the treated and untreated hands.20PubMed Central. Results of the Use of Bioabsorbable Magnesium Screws for Surgical Treatment of Mason Type II Radial Head Fractures The practical advantage is clear: patients avoid a second operation to remove hardware. But a study comparing magnesium and titanium screws for a different procedure found that remnants of the magnesium screws were still visible on X-ray even after more than five years, raising questions about whether “bioabsorbable” lives up to its name in practice.21PubMed Central. Titanium Versus Bioabsorbable Magnesium Headless Compression Screw Fixation for Tibial Tubercle Osteotomy
In pediatric hip surgery, bioabsorbable pins have been compared directly to K-wires for a pelvic osteotomy used to treat developmental dysplasia of the hip. Radiological outcomes were comparable, and no implant-related complications were identified in the bioabsorbable group, though the study was small and follow-up was limited.22PubMed. Bioabsorbable pin versus kirschner wire fixation in the salter innominate osteotomy for the treatment of developmental dysplasia of the hip The technology is promising but not yet a universal replacement for metal. Surgeons tend to reserve bioabsorbable options for fractures where the mechanical demands are modest and a second removal surgery would be particularly burdensome.
Pins in Children’s Fractures
Children’s bones are still growing, which creates a unique challenge: a metal implant that crosses a growth plate can potentially disturb growth. For most pediatric fractures treated with K-wires, the pins are removed within a few weeks, well before they could cause lasting growth disturbance. But in certain complex fractures near the growth plate, surgeons have explored alternative approaches. One group described using a locking plate with transphyseal screws for pathologic fractures of the proximal femur in children, reporting high stability without significant growth restriction.23MDPI Children / PubMed Central. Stabilisation of Pathologic Proximal Femoral Fracture near the Growth Plate with Use of a Locking Plate and Transphyseal Screws This runs against the traditional teaching that screws should never cross a growth plate, though it applies to a narrow set of circumstances where the fracture itself already threatens the growth plate’s function.
Imaging After Pin Placement
If you need an MRI while you still have metal pins or wires in place, the type of metal matters enormously. CT scans are fairly tolerant of both titanium and steel, with artifacts of only a couple of millimeters regardless of the material. But on MRI, stainless-steel screws produced artifacts averaging nearly 11 mm on a 1.5T scanner and over 15 mm at 3T, large enough to completely obscure the nearby joint surface. Titanium artifacts were about a third that size.3PubMed Central. Metal artifacts from titanium and steel screws in CT, 1.5T and 3T MR images of the tibial Pilon: a quantitative assessment in 3D Radiologists can reduce artifact size by adjusting MRI sequences, using fast spin-echo techniques with high spatial resolution, and orienting the frequency-encoding gradient so that the distortion falls away from the area of interest.24PubMed. Metal artifact reduction in musculoskeletal magnetic resonance imaging In practice, this means that if you have titanium hardware and need a post-operative MRI, the scan is usually interpretable with some adjustments. If you have steel, CT may be the better imaging choice.
Surgical Pins in Veterinary Medicine
Surgical pins are not exclusive to human orthopedics. Veterinarians use intramedullary pins and external fixation frames routinely to repair long-bone fractures in dogs and cats. The principles are the same: a metal rod inside the bone’s marrow cavity provides alignment, and external fixation pins through the skin add stability. A comparison of fixation techniques in dogs found that a rigid interlocking nail-and-plate construct produced better bone healing than an intramedullary pin combined with external fixation. One younger dog in the pin-and-frame group developed pin migration during healing, echoing the same complication seen in human patients.25Ukrainian Journal of Veterinary and Agricultural Sciences. Comparison between new design interlocking nail with plate fixation and intramedullary pin with external skeletal fixation in long bone fracture in the dogs If your pet has ever come home with metal rods sticking out of a casted leg, the device family is the same one orthopedic surgeons have used on humans since 1909.