1. Cervical Cerclage (Obstetrics)

• Indications: history of 3+ unexplained second-trimester losses or preterm labor from cervical insufficiency, prior cervical surgical trauma (cone biopsy, LEEP), or a short cervix found on ultrasound in a high-risk pregnancy.
• Techniques:
  • McDonald cerclage - the most common and simplest; a purse-string suture placed at the cervicovaginal junction with monofilament suture.
  • Shirodkar cerclage - a similar but more involved technique with bladder mobilization, suture placed higher on the cervix.
  • Transabdominal cerclage - reserved for cases where transvaginal placement has failed or the cervix is too short/scarred (e.g., after prior trachelectomy).
• Timing: ACOG guidelines recommend elective placement at 14-16 weeks' gestation after confirming fetal viability by ultrasound. It's removed around 37 weeks or with onset of labor.
• Success rate: reported around 75-90% in women with recurrent pregnancy loss when used in a subsequent pregnancy (Pfenninger and Fowler's Procedures for Primary Care).
• Billing: CPT 59320 (cerclage placement), 59871 (removal under anesthesia).

• A 2025 review found repeat cerclage after a failed primary cerclage may reduce pregnancy loss/preterm birth, though evidence quality is limited (PMID: 41202016).
• Combined vaginal progesterone + cerclage may offer added benefit over cerclage alone in some populations (PMID: 37211087).
• In twin pregnancies with short cervix or dilation, cerclage shows benefit for prolonging pregnancy and reducing adverse perinatal outcomes in select subgroups, though earlier single studies found less convincing evidence in unselected twins (PMID: 37535682).

2. Cerclage Wiring (Orthopedic Surgery)

• Common uses:
  • Subtrochanteric femur fracture extension during hip fracture fixation - cerclage wires stabilize a large medial or posteromedial fragment before or during nail/plate insertion.
  • Patellar fractures (tension band wiring).
  • Periprosthetic fractures around a hip or knee implant, where wires or cables secure fragments around a stem.
• Technique notes: wires are passed subperiosteally to protect soft tissue and blood supply, then tightened and twisted or crimped. Care is taken to avoid excessive soft-tissue stripping, which risks devascularizing fragments and delaying union (Rockwood and Green's Fractures in Adults, 10th ed).
• Often combined with a "longitudinal anterior band" technique (e.g., Lotke-Ecker technique) for patellar or periprosthetic fixation.

Metformin Side Effects

• Nausea, diarrhea, crampy abdominal pain
• Metallic taste and dysgeusia
• Loss of appetite / mild weight loss
• These effects are dose-related and tend to abate over time; they can be minimized by titrating the dose slowly and taking metformin with meals (start ~500 mg once daily, titrate up to a max of 2 g/day) - Tintinalli's Emergency Medicine; Lippincott Illustrated Reviews: Pharmacology. A 2024 systematic review/meta-analysis confirms GI adverse events are the dominant tolerability issue in type 2 diabetes patients on metformin (PMID: 39350158).

• Long-term use is associated with 20-30% lower serum B12 levels, thought to occur via lowering transcobalamin I and reduced B12 absorption in the terminal ileum.
• Can worsen or mimic peripheral neuropathy symptoms.
• Goodman & Gilman's Pharmacology and Fuster and Hurst's The Heart recommend periodic B12 monitoring (ideally with serum methylmalonic acid, which is more sensitive/specific) especially if neurologic symptoms develop; The Clozapine Handbook recommends checking B12 yearly in patients on metformin.

• The most significant, though rare, adverse effect - metformin-associated lactic acidosis (MALA), reported at roughly 0.084 cases per 1000 patient-years (Campbell-Walsh-Wein Urology).
• Occurs almost exclusively in the setting of renal insufficiency, since metformin is renally cleared unchanged.
• Mortality from metformin toxicity/overdose has been reported as high as 30% in some series (Comprehensive Clinical Nephrology), and it is among the more common toxicologic indications for extracorporeal renal replacement therapy (dialysis) in poisoning.
• Toxicity can also present with GI symptoms, hypotension, hypoglycemia, hypothermia, and altered mental status (Brenner and Rector's The Kidney).

• eGFR <30 mL/min/1.73 m2 (contraindicated); use caution/dose-adjust between 30-45
• Hepatic insufficiency
• Any form of acidosis, severe hypoxemia
• Alcohol abuse
• Concurrent nephrotoxic agents, especially IV contrast - hold metformin for 48 hours after contrast administration and confirm stable renal function before resuming