This suggests a **Nickel Allergy** (Type IV Hypersensitivity), which has important implications for orthopaedic implant selection. **Nickel Allergy Background**: (1) **Prevalence**: Nickel allergy is common, affecting **10-15% of females** and **2% of males** in the general population. (2) **Mechanism**: Type IV delayed hypersensitivity reaction - nickel acts as a hapten (binds to proteins), triggers T-cell mediated immune response, typically manifests 24-72 hours after exposure. (3) **Clinical manifestation**: Cutaneous contact dermatitis - itchy, red, eczematous rash at sites of metal contact (earrings, watches, belt buckles, cheap jewelry). **Implant Composition - Stainless Steel 316L**: (1) Most orthopaedic stainless steel implants are **316L** alloy, which contains **12-14% Nickel** by weight. (2) Nickel serves a critical metallurgical function - it **stabilizes the austenitic (FCC) crystal structure** at room temperature, which gives stainless steel its desirable properties (ductile, non-magnetic, work-hardenable). (3) Without nickel, the steel would be in the martensitic (BCT) or ferritic (BCC) phase, which are more brittle and less suitable for implants. **Implications for This Patient**: (1) **Risk of implant reaction**: While **cutaneous patch test positivity does not strongly predict deep implant failure** (skin environment differs from deep tissue), patients with **severe nickel allergy** (rash from cheap jewelry, multiple metal sensitivities) have a **theoretical risk** of: (a) **Dermatitis overlying the implant** - eczematous skin reaction over the plate. (b) **Chronic pain** - persistent unexplained pain at the implant site. (c) **Aseptic loosening or implant failure** - controversial, but case reports exist of implant failure attributed to metal sensitivity (though difficult to prove causation, and infection must be excluded). (2) **Debate in the literature**: The correlation between cutaneous nickel allergy and deep implant failure is **controversial**. Most studies show that the majority of patients with nickel allergy tolerate stainless steel implants without problems. However, a subset (estimated 5-10% of nickel-allergic patients) may develop implant-related symptoms. Given this patient has a **clear history of nickel sensitivity** (rash from cheap earrings), I would take this seriously and modify my implant choice. **Decision - Use Titanium Implants**: (1) I would **switch to Titanium alloy implants** (Ti-6Al-4V) for this patient. (2) **Rationale**: (a) Titanium is **Nickel-free** - eliminates the allergen entirely. (b) Titanium has **excellent biocompatibility** - forms a stable TiO₂ (titanium oxide) passive layer, minimal tissue reaction, widely used in total joint replacements and spinal implants. (c) **Lower elastic modulus** (110 GPa for titanium vs 200 GPa for stainless steel) - closer to bone (15-20 GPa), causes **less stress shielding** (bone resorption from load transfer to implant). (d) **Minimal MRI artifact** - if the patient needs future MRI imaging, titanium produces much less artifact than stainless steel. (e) **Equivalent mechanical strength** for fracture fixation - titanium plates and screws provide adequate fixation strength for distal radius fractures. (3) **Downside of Titanium**: (a) **Higher cost** - titanium implants are more expensive than stainless steel (typically 2-3 times the cost). (b) **Less ductile** - cannot be contoured/bent intraoperatively as easily as stainless steel (SS is more malleable and can be shaped on the back table). However, most modern anatomic plates are pre-contoured, so this is less relevant. **Alternative Options (if Titanium Unavailable)**: (1) **Nickel-free stainless steels**: Some manufacturers produce specialized austenitic stainless steels with reduced or no nickel content (using nitrogen or manganese to stabilize austenite instead). These are rare and not widely available. (2) **Non-operative management**: If the fracture pattern allows, consider **closed reduction and casting** to avoid metal implants entirely. However, many distal radius fractures (especially intra-articular, unstable, or dorsally comminuted fractures) are not suitable for non-operative treatment. (3) **Cobalt-Chromium alloys**: Some might suggest this as an alternative, but this is **NOT appropriate** because: (a) Cobalt-Chrome still contains **~1% residual Nickel**, and (b) patients with nickel allergy often have **cross-reactivity with Cobalt** (both are common contact allergens), so there is risk of allergic reaction to cobalt-chrome as well. **Counseling the Patient**: I would explain: 'You've mentioned you get a rash from cheap earrings, which suggests you may be allergic to nickel, a metal commonly found in jewelry and in standard stainless steel implants. While most people with nickel allergy tolerate stainless steel implants without problems, there is a small risk that you could develop skin irritation, pain, or implant-related symptoms. To minimize this risk, I recommend using **titanium implants** instead, which do not contain nickel and are very well tolerated. Titanium is more expensive, but I believe it's the safer choice for you given your allergy history. The alternative would be to treat your fracture non-operatively with a cast, but given the fracture pattern, I believe surgical fixation will give you a better outcome.' **Post-Operative Considerations**: (1) **Monitor for metal sensitivity symptoms**: Pain, erythema, dermatitis, chronic swelling at implant site (though these can also indicate infection, so must be worked up appropriately). (2) **Implant removal**: If the patient develops symptoms suggestive of metal sensitivity after implant placement (and infection/other causes excluded), consider **early implant removal** once fracture healed (typically 3-6 months for distal radius). (3) **Patch testing**: Formal nickel patch testing can be performed preoperatively if the history is unclear, but in this case the history is straightforward (rash from cheap earrings = nickel allergy). **Follow-Up Questions and Key Concepts**: (1) **Why is Nickel in stainless steel?** Nickel (12-14%) is added to stainless steel to **stabilize the austenitic (Face-Centered Cubic, FCC) crystal structure** at room temperature. Without nickel, the steel would be martensitic (BCT - body-centered tetragonal) or ferritic (BCC - body-centered cubic), which are more brittle. The austenitic structure gives stainless steel desirable properties: non-magnetic (allows MRI), ductile (can be bent), work-hardenable (gets stronger when cold-worked). (2) **What is the passivation layer?** Stainless steel forms a **Chromium Oxide (Cr₂O₃) passive layer** on its surface (requires at least 10.5% chromium in the alloy, and 316L has 17-20%). This thin, adherent oxide layer protects the underlying metal from corrosion by preventing oxygen and moisture from reaching the base metal. If the layer is scratched or disrupted, it **spontaneously re-forms** in the presence of oxygen (self-healing). However, in **low-oxygen environments** (e.g., under screw heads, in crevices), the passive layer cannot re-form, leading to **crevice corrosion**. (3) **What is stress shielding?** Stainless steel has a high **elastic modulus** (Young's modulus = 200 GPa) compared to bone (15-20 GPa). When a stiff plate is applied to bone, the plate carries most of the load (because it's much stiffer), causing the underlying bone to be **shielded from normal physiological stress**. According to **Wolff's Law** (bone remodels in response to mechanical stress), the unloaded bone undergoes **osteopenia** (bone resorption, decreased density) beneath the plate. This can lead to **refracture** after plate removal, especially if the plate is removed too early. Titanium (modulus 110 GPa) causes less stress shielding than stainless steel. **In Summary**: For this patient with a history of nickel allergy (rash from cheap earrings), I would **use Titanium alloy (Ti-6Al-4V) implants** for her distal radius ORIF to avoid nickel exposure and minimize the risk of implant-related hypersensitivity reactions. Titanium is nickel-free, highly biocompatible, causes less stress shielding, and produces minimal MRI artifact.

This is **galvanic corrosion** (also called **bimetallic corrosion**) resulting from **mixing incompatible metals** - specifically, a titanium femoral nail in contact with a stainless steel plate. This is a **preventable iatrogenic complication** caused by fundamental metallurgical principles. The clinical presentation of persistent pain, draining sinus, periosteal reaction, screw loosening, and metallic debris with elevated metal ions (without infection) is classic for **metallosis from galvanic corrosion**. **Diagnosis - Galvanic Corrosion and Metallosis**: (1) **Galvanic corrosion** - accelerated corrosion occurring when two dissimilar metals are in contact in the presence of an electrolyte (body fluids). (2) **Metallosis** - tissue reaction to metal debris and corrosion products, causing synovitis, osteolysis, and implant loosening. (3) **Aseptic** - no infection (negative cultures), but inflammatory reaction from metal particles mimics infection clinically. **What Went Wrong - Electrochemical Series and Galvanic Coupling**: **Fundamental principle**: When two dissimilar metals are in contact in an electrolyte (body fluids = saline solution), a **galvanic cell** (battery) is created. The more **active (anodic)** metal corrodes preferentially, while the more **noble (cathodic)** metal is protected. This is determined by the **electrochemical series** (galvanic series in seawater, which approximates physiological conditions): **Electrochemical Series (Anodic → Cathodic, i.e., Active → Noble)**: **Most Anodic (Corrodes)**: Magnesium → Zinc → Aluminum → **Stainless Steel (Active)** → Nickel → ... → **Titanium (Passive)** → Platinum → Gold **Most Cathodic (Protected)**: In this case: **Titanium** is more **noble (cathodic)** than **Stainless Steel**. **Stainless Steel** becomes the **anode (sacrificial metal)** and corrodes aggressively. **What Happens at the Cellular/Molecular Level**: (1) **Galvanic cell formation**: When titanium nail contacts stainless steel plate in body fluids (electrolyte): **Anode (Stainless Steel)**: Oxidation occurs - metal atoms lose electrons and go into solution as ions: Fe → Fe²⁺ + 2e⁻ (iron oxidation), Cr → Cr³⁺ + 3e⁻ (chromium oxidation), Ni → Ni²⁺ + 2e⁻ (nickel oxidation). **Cathode (Titanium)**: Reduction occurs - accepts electrons from the anode: O₂ + 2H₂O + 4e⁻ → 4OH⁻ (oxygen reduction). (2) **Electron flow**: Electrons flow from the stainless steel (anode) to the titanium (cathode), driving the corrosion reaction. (3) **Result**: The stainless steel corrodes at an **accelerated rate** (much faster than if it were alone), releasing metal ions (Fe, Cr, Ni, Mo) and particles into the surrounding tissues. The titanium is **protected** and does not corrode significantly. **Clinical Consequences**: (1) **Metallosis**: Metal ions and particles accumulate in tissues, causing: **Synovitis** - inflammatory reaction, pain, swelling, joint effusion (if near a joint). **Osteolysis** - metal particles trigger macrophage activation, cytokine release (TNF-α, IL-1), osteoclast activation → bone resorption around implants → implant loosening (explains loosening of distal screws). **Pseudotumor** - mass-like soft tissue reaction (less common with SS/Ti than with Co-Cr). **Staining** - dark discoloration of tissues (black/grey from chromium and nickel oxides). (2) **Implant failure**: The corroded stainless steel loses mechanical integrity - screws may fracture or loosen, plate may weaken. (3) **Systemic metal elevation**: Serum metal ions (chromium, nickel, titanium) may be elevated, though clinical significance is unclear (potential for distant organ toxicity, though rare). (4) **Draining sinus**: Chronic inflammation and metallosis can create a sinus tract draining serous fluid with metal particles (mimics infection, but cultures negative). **Why This Patient?** The **retrograde femoral nail (titanium)** was inserted **through the distal femur** and likely passed **in direct contact with or very close to** the existing **stainless steel distal femoral plate**. At the zone of contact or proximity (where body fluids bridge the two metals), **galvanic corrosion** was initiated. Over 6 months, the stainless steel plate and screws corroded, releasing metal debris, causing metallosis, osteolysis, screw loosening, and eventually sinus formation. **The Cardinal Rule in Orthopaedics - NEVER Mix Metals**: **NEVER use dissimilar metals in the same anatomic region or in contact**. Always use **matched metal systems**: If the original implant is stainless steel, any additional implants should be stainless steel. If the original implant is titanium, any additional implants should be titanium. **Exceptions (where mixing is unavoidable)**: Sometimes in complex reconstructions (e.g., tumor surgery, pelvic trauma), mixing may be necessary. In these cases, try to **separate the metals** physically (e.g., interpose bone graft or soft tissue) to prevent direct contact and minimize galvanic coupling. **Correct Management in This Case - What Should the Registrar Have Done?** When the patient sustained the proximal femoral shaft fracture above the distal femoral plate: (1) **Option 1 - Remove Distal Femoral Plate (Preferred)**: If the distal femoral fracture was healed (18 months post-ORIF, likely healed), **remove the stainless steel plate entirely**, then insert a **long titanium retrograde nail** or **antegrade femoral nail** to stabilize the entire femur. This avoids mixing metals. (2) **Option 2 - Use Stainless Steel Nail (If Plate Cannot Be Removed)**: If the distal fracture was not fully healed and the plate needed to stay, use a **stainless steel nail** (not titanium) to match the existing plate material. (3) **Option 3 - Plate-on-Plate (Avoid Nail)**: Use a **second stainless steel plate** (matching the original) to bridge the proximal fracture, avoiding the nail entirely. This keeps all hardware as matched stainless steel. What the registrar **should NOT have done** (but did): Insert a **titanium nail** with an existing **stainless steel plate** in situ → guaranteed galvanic corrosion. **Management of the Current Problem**: Now that galvanic corrosion and metallosis have occurred, management is: **Step 1 - Confirm Diagnosis**: (1) **Rule out infection** - despite negative cultures, obtain **extended cultures** (14 days, anaerobes, fungi), consider **sonication of hardware** when removed (improves bacterial detection in biofilm), **histology** for acute inflammatory cells (if infection present). (2) **Serum metal ion levels** - check chromium, nickel, titanium (expect elevated, confirms metallosis). (3) **Advanced imaging**: MRI with **metal artifact reduction sequences (MARS)** - may show soft tissue reaction, pseudotumor, osteolysis (though artifact from metal will limit quality). Ultrasound may show fluid collections. (4) **Aspiration and analysis**: Joint aspiration (if knee involved) - look for metal particles, send for **polarized light microscopy** (metal particles visible), **inductively coupled plasma mass spectrometry (ICP-MS)** for metal ion quantification in fluid. **Step 2 - Surgical Intervention - Remove ALL Hardware**: (1) **Complete hardware removal** is the only definitive treatment: Remove **both the stainless steel plate and the titanium nail** - leaving either one in situ risks recurrent symptoms. (2) **Debridement of metallosis**: Excise stained, necrotic tissues; debride sinus tract; send tissue for culture (rule out superimposed infection) and histology (confirm metallosis - black/grey metal particles in macrophages, chronic inflammation). (3) **Assess fracture healing**: At 24 months post original ORIF (18 months + 6 months), the distal femoral fracture should be healed. At 6 months post proximal fracture fixation, the proximal fracture may not be fully healed. **Intraoperative assessment**: If the proximal fracture is healed, remove all hardware and leave the femur without implants. If the proximal fracture is not healed, need to re-stabilize after hardware removal (see below). (4) **Intraoperative cultures**: Obtain **multiple tissue samples** (at least 3-5) for culture to definitively rule out infection (even though preoperative cultures negative, biofilm-associated infection can be culture-negative). **Step 3 - Fracture Stabilization (If Needed)**: If the proximal fracture is not fully healed and requires continued fixation: (1) **Option 1 - Long Intramedullary Nail** (preferred): Insert a **long antegrade femoral nail** (spanning the entire femur) using **all titanium** or **all stainless steel** (I would prefer **titanium** as it has better biocompatibility and less stress shielding for long-term implantation, and the old hardware is now removed so no mixing issue). (2) **Option 2 - External Fixation** (temporary): If the soft tissues are heavily contaminated with metal debris and there is concern for infection, consider **temporary external fixation** to allow fracture healing while the soft tissues recover, then convert to intramedullary nail once tissues healed. (3) **Option 3 - Locked Plate Fixation** (less ideal): Use a **single-metal plate system** (all titanium or all stainless steel) if IM nailing not feasible, but this leaves large implant burden and higher infection risk given the soft tissue damage. **Step 4 - Post-Operative Management**: (1) **Antibiotics**: If infection cannot be definitively excluded (despite negative cultures, there is a draining sinus and inflammation), consider empiric antibiotics (e.g., vancomycin + 3rd generation cephalosporin) until final intraoperative cultures finalize. If cultures are negative at 14 days and histology shows only metallosis (not acute inflammation), stop antibiotics. (2) **Monitor metal ion levels**: Recheck serum chromium, nickel, titanium at 3, 6, 12 months - expect levels to decline after hardware removal. (3) **Rehabilitation**: Once fracture healed and hardware removed, standard post-operative rehab. (4) **Counsel patient**: Explain that this was a **preventable complication** from mixing metals, that removing all hardware should resolve symptoms (pain, swelling, sinus), and that future surgeries should use matched metals only. **Prognosis**: With complete hardware removal and debridement: (1) **Symptoms should resolve** - pain, swelling, sinus should improve over 3-6 months. (2) **Fractures should heal** - if sufficient time has passed (18 months distal, 6 months proximal), likely healed or nearly healed. If additional fixation needed, fractures should heal with appropriate stabilization. (3) **Metal ion levels should normalize** - within 6-12 months of hardware removal. (4) **Functional outcome** - should return to baseline or near-baseline function once healed and hardware removed. **Teaching Points - Metallurgy Principles**: **1. Galvanic Series (Corrosion Susceptibility in Physiological Fluids)**: **Most Active (Anodic, Corrodes)**: Magnesium alloys → Zinc → Aluminum alloys → **Stainless Steel 316L** → Nickel → Cobalt-Chrome → **Titanium (passive)** **Most Noble (Cathodic, Protected)**: In a galvanic couple (two dissimilar metals in contact), the more active metal (higher on the list) becomes the **anode** and corrodes, while the more noble metal (lower on the list) becomes the **cathode** and is protected. **2. Galvanic Corrosion Severity Factors**: (1) **Potential difference** - the further apart the metals are in the galvanic series, the more severe the corrosion. Stainless steel + titanium have a moderate potential difference, causing significant galvanic corrosion. (2) **Anode-to-cathode area ratio** - if a small anode (e.g., SS screw) contacts a large cathode (e.g., Ti nail), the corrosion current is concentrated on the small anode, causing very rapid corrosion. Conversely, large anode + small cathode = slower corrosion. (3) **Electrolyte conductivity** - body fluids (saline) are excellent conductors, facilitating galvanic corrosion. (4) **Proximity** - metals must be in contact or very close proximity (within mm) in the presence of electrolyte for galvanic corrosion. Distant implants (e.g., SS plate in forearm + Ti plate in ankle) do not have galvanic coupling. **3. Types of Corrosion in Orthopaedic Implants**: (1) **Galvanic corrosion** - from dissimilar metals (discussed above). (2) **Crevice corrosion** - in low-oxygen crevices (e.g., under screw heads, plate-bone interface) where the passive layer cannot re-form. Stainless steel is particularly susceptible. (3) **Fretting corrosion** - from micromotion between contacting surfaces (e.g., plate-screw interface), mechanical disruption of passive layer with each motion cycle → repeated re-passivation and disruption → corrosion. (4) **Pitting corrosion** - localized breakdown of passive layer creating deep pits. Molybdenum in 316L SS provides pitting corrosion resistance (chloride ions in body fluids promote pitting, molybdenum inhibits). **Summary and Key Message**: **NEVER mix dissimilar metals in orthopaedic surgery**. Stainless steel + titanium in contact → galvanic corrosion (SS corrodes) → metallosis → osteolysis → implant failure → patient morbidity. In this case, the titanium nail should NOT have been inserted with the stainless steel plate in situ. The correct approach was to **remove the SS plate first** (if fracture healed) or **use a stainless steel nail** (if plate needed to stay). Treatment now requires **complete hardware removal** and debridement, with possible re-fixation using **matched metal hardware only**.