Methyl Methacrylate Complications and Bone Cement Implantation Syndrome

Introduction

• MMA is a monomer primarily used for the creation of acrylic resin and plastics.1 The monomer form appears as a colorless liquid commonly combined with an inhibitor to prevent the initiation of polymerization.
• In its most common form, MMA is used to create, via polymerization, PMMA.
• MMA is a volatile and highly flammable compound.¹

Medical Uses

• In the surgical setting, MMA is most commonly used in orthopedics for cementing joint replacements.
• It is also used as part of the Masquelet technique in orthopedic surgery for lower extremity injuries caused by osteomyelitis.
• In vertebroplasty, it is used via percutaneous injection to restore vertebral body height, reduce pain, and stabilize fractures.
• In dental practice, it is used for the creation of dentures, temporary crowns, and bridges as well as for craniofacial reconstruction.

Complications

• Severe hypercapnia and pulmonary venous embolism from PMMA monomer and polymer are a described but rare complication of vertebroplasty. Clinical findings of embolization include respiratory distress, coughing, hypotension, and decreased end-tidal CO₂.²

• The integrity of latex gloves may be compromised when using MMA. Adverse effects associated with direct contact include numbness, pain, and whitening of fingers.³
• Hepatoxicity associated with vessel necrosis and subcapsular hemorrhage has been described. In-vivo studies have demonstrated diffuse microvesicular hepatic steatosis associated with monomer vapor inhalation.⁴
• Decrease in systolic blood pressure following cement insertion for femoral head replacement with a significant risk of intraoperative hypotension is another complication.
• Acute respiratory irritation from inhalation of MMA has been noted. Long-term effects related to pulmonary function have not been adequately studied.⁵
• Studies have not found a significant correlation between MMA usage and respiratory irritation with subsequent allergic reactions or asthma.
• Bone cement implantation syndrome is also a possible complication (described below).

Bone Cement Implantation Syndrome (BCIS)

• BCIS is characterized by clinical findings ranging from hypoxia, arrhythmias, and hypotension to cardiac arrest.⁶
• It is caused by the release of the MMA monomer into the circulation directly following cementation.
• The pathophysiology of hypotension and cardiac arrest is poorly understood with some studies suggesting a secondary cause of right ventricular failure from increased pulmonary artery pressure.⁶
• The risk is increased in patients with comorbid conditions such as hypertension and obesity as well as with patients who have had a previously uninstrumented femoral canal.⁶
• A grading of BCIS has been proposed based on the severity of symptoms.^6,7
  • Grade 1: moderate hypoxia (SpO₂ less than 94%) or a decrease in systolic arterial pressure more than 20%
  • Grade 2: severe hypoxia (SpO₂ less than 88%) or a decrease in systolic arterial pressure more than 40%, or an unexpected loss of consciousness
  • Grade 3: cardiovascular collapse requiring resuscitation
• Though there is no clear evidence regarding the anesthetic technique for preventing BCIS, one animal study demonstrated that the use of volatile anesthetics generates greater hemodynamic instability with similar embolic loads.^6,7
• Further techniques include increased inspired oxygen concentration at the time of cement insertion.
• Patients at high risk of BCIS should be monitored perioperatively with invasive arterial pressure and central venous catheter.
• The treatment of BCIS is primarily supportive care in line with the treatment of acute right ventricular failure, and includes 100% oxygen, intravenous fluids, inotropes, and pulmonary vasodilators.⁶
• One study demonstrated that the use of bone cement during total knee arthroplasty when using MMA or PMMA led to a transient astroglial injury when monitoring serum levels of S-100B released from glial and Schwann cells compared to controls. However, there were no recorded neurologic abnormalities in the postoperative period compared to controls.⁸

Prevention of Complications

• Appropriate personal protective equipment, including gloves, safety glasses, and a properly fitted N95 mask should be worn.
• Mixing of MMA with the polymerizing agent in a well-ventilated area, preferably under suction if available, has been described to decrease the amount of monomer available in the sample compared to nonventilated mixed samples.
• Correct mixing ratios based on manufacturer’s protocols should be used.
• Mixing should be performed at a slow and stable pace to avoid intense exothermic reactions and excess vaporization.
• Waste material should be disposed properly.
• Contact of material on skin or areas on the patient that do not require the material should be avoided.
• Fluoroscopy in vertebroplasty procedures should be utilized to ensure proper location of injection of the polymer and avoid systemic toxicity.