Indocyanine Green (ICG) in Present-Day Surgery

Background and Pharmacology

• Fischer's Mastery of Surgery, 8th ed. (pp. 881-882)

Principle Operating Domains

1. Biliary Anatomy Visualization - Laparoscopic Cholecystectomy

• Fischer's Mastery of Surgery, 8th ed. (pp. 889-890); Sabiston Textbook of Surgery (p. 185)

2. Colorectal Surgery - Anastomotic Perfusion Assessment

• Fischer's Mastery of Surgery, 8th ed. (p. 884); SAGES 2025 guidelines (PMID 41249539); PMID 41422225

3. Hepatic Surgery - Tumor Detection and Margin Assessment

• Preoperative liver function testing: The ICG 15-minute retention rate (ICG-R15) is a standard tool to assess hepatic reserve and functional capacity before major hepatectomy, replacing the older constant-infusion clearance technique because of better tolerance.
• Intraoperative tumor identification: ICG (0.25-0.5 mg/kg) is administered 24 hours or more before surgery. Normal hepatocytes clear ICG into bile, while tumor cells - particularly metastases from colorectal and pancreatic cancer - are unable to accumulate ICG. This creates a sharp "dark spot" contrast against fluorescing liver parenchyma that guides resection margins.
• Differential tumor fluorescence: Hepatocellular carcinoma fluoresces less intensely than surrounding parenchyma, while fibrolamellar carcinoma and cholangiocarcinoma display brighter fluorescence than the hepatic background - enabling pathological differentiation.
• A 2024 systematic review and meta-analysis (PMID 38867212) confirmed that ICG-guided laparoscopic hepatectomy achieves significantly better surgical margin status in liver malignancies.
• Fischer's Mastery of Surgery, 8th ed. (pp. 886-887)

4. Sentinel Lymph Node (SLN) Mapping

• Breast cancer: ICG identifies sentinel nodes with 95-100% accuracy under infrared light at 780 nm - superior to older methods. It can be used alone or in combination with blue dye (>90% identification), and serves as an alternative when radioisotope (Tc-99m) is unavailable.
• Gastric cancer: ICG is injected submucosally around the primary lesion endoscopically. Within minutes, lymphatic drainage basins and SLNs light up under NIR, guiding lymphadenectomy. This is particularly valuable in laparoscopic/robotic settings where traditional blue dye or radiotracers are impractical.
• Colorectal cancer: A 2024 meta-analysis (PMID 39542857) found ICG fluorescence imaging significantly increases lymph node yield and improves long-term oncologic outcomes in colorectal cancer surgery.
• Gynecologic oncology: SLN mapping with ICG is now standard in endometrial and cervical cancer, with near-universal adoption in robotic-assisted surgery.
• Bailey and Love's Short Practice of Surgery, 28th ed. (pp. 957-958); Fischer's Mastery of Surgery, 8th ed. (p. 827)

5. Esophageal and Foregut Surgery

• Fischer's Mastery of Surgery, 8th ed. (pp. 890-891)

6. Bariatric Surgery

• Fischer's Mastery of Surgery, 8th ed. (pp. 892-893)

7. Endocrine Surgery - Parathyroid Identification

• Sabiston Textbook of Surgery (pp. 1528-1529)

8. Thoracic Surgery

• Pulmonary nodule localization: Before resection of small or ground-glass pulmonary nodules that are difficult to palpate, ICG is injected endobronchially or percutaneously to mark the target segment, which then fluoresces under NIR and guides the resection plane.
• Intersegmental plane identification: For anatomic segmentectomy, ICG administered intravenously lights up the perfused segment while the target segment to be resected remains dark (or vice versa), precisely delineating the intersegmental boundary.
• Fischer's Mastery of Surgery, 8th ed.; Bailey and Love's, 28th ed. (p. 3007)

9. Urology - Robotic Partial Nephrectomy

• Selective arterial clamping guidance: After IV ICG injection, the specific renal artery branch supplying the tumor can be identified before selective clamping, preserving perfusion to the remaining kidney. A 2024 meta-analysis (PMID 38000056) confirmed improved perioperative outcomes with ICG-guided selective arterial clamping compared to standard RAPN.
• Tumor margin delineation: Renal cortex and tumor tissue can be differentially fluoresced based on their perfusion characteristics.
• Adrenal surgery: ICG helps with intraperitoneal tumor localization during robotic adrenal procedures.

10. Plastic and Reconstructive Surgery - Flap Perfusion

• Free flap viability: Real-time assessment of arterial inflow and venous outflow in free tissue transfers, allowing early identification of a failing anastomosis before clinical signs develop.
• Perforator mapping: Locating perforator vessels preoperatively or intraoperatively for perforator flap design.
• Pericranial flap viability: Used in head and neck reconstructive surgery and skull base surgery to confirm vascular pedicle integrity.
• Cummings Otolaryngology Head and Neck Surgery (PMID references, p. 3159)

11. Ophthalmology - ICG Angiography

• Evaluate choroidal circulation
• Diagnose polypoidal choroidal vasculopathy, central serous chorioretinopathy, and other macular diseases
• Guide photodynamic therapy targeting
• Kanski's Clinical Ophthalmology, 10th ed. (p. 568-575); The Wills Eye Manual

12. Acute Care and Emergency Surgery

• Evaluating bowel ischemia and viability in emergency laparotomy
• Assessing perfusion of stomas and bowel segments
• Identifying the extent of ischemia in vascular emergencies

Technical Considerations

Current Evidence Level Summary (SAGES 2025)

Key References

• Fischer's Mastery of Surgery, 8th ed. - Chapter 27: Fluorescence-Guided Surgery
• Sabiston Textbook of Surgery - Chapter 11 (Tools section); Chapter on Thyroid Surgery
• Bailey and Love's Short Practice of Surgery, 28th ed. - Chapter 58 (Breast surgery)
• SAGES 2025 Guidelines - PMID 41249539 (strong recommendation for left-sided colorectal anastomosis)
• PMID 38867212 - Meta-analysis: ICG hepatectomy and surgical margin status
• PMID 39542857 - Meta-analysis: ICG lymph node detection in colorectal cancer
• PMID 38000056 - Meta-analysis: ICG-guided selective arterial clamping in partial nephrectomy
• PMID 41422225 - GRADE systematic review: ICG perfusion vs. standard to prevent anastomotic leak

Hyperkalemia: Clinical Features and Management

Definition and Classification

• Rosen's Emergency Medicine (p. 2513); Current Surgical Therapy, 14th ed. (p. 3136)

Pathophysiology

• Transcellular distribution: ~98% of total body K⁺ is intracellular, maintained by the Na⁺/K⁺-ATPase pump. Insulin and β₂-adrenergic stimulation drive K⁺ into cells; metabolic acidosis (by H⁺/K⁺ exchange) drives it out.
• Renal excretion: The primary route of K⁺ elimination, occurring in the distal nephron under aldosterone regulation.

Causes

Pseudohyperkalemia (Spurious)

True Hyperkalemia

• Acute or chronic kidney disease
• Volume depletion / dehydration
• Adrenal insufficiency (Addison disease)
• Hyporeninemic hypoaldosteronism (Type 4 RTA - common in diabetic nephropathy)

• Metabolic acidosis (excluding organic acidoses)
• Insulin deficiency / diabetic ketoacidosis
• Hyperosmolality
• Non-selective β-blockers
• Depolarizing muscle relaxants (succinylcholine) - especially dangerous in burns, crush injury, rhabdomyolysis
• Digitalis toxicity
• Severe exercise, rhabdomyolysis, tumor lysis syndrome, massive hemolysis

• ACE inhibitors and angiotensin receptor blockers (ARBs)
• Potassium-sparing diuretics (spironolactone, amiloride, triamterene)
• NSAIDs
• Cyclosporine
• Heparin, ketoconazole (decrease aldosterone production)
• Potassium supplementation / salt substitutes

• High-K⁺ foods: salt substitutes, dried fruits, nuts, potatoes, tomatoes, spinach, bananas, citrus juices

• Rosen's Emergency Medicine (p. 2513-2514); Washington Manual (pp. 2701-2711); Current Surgical Therapy, 14th ed. (p. 3138)

Clinical Features

Symptoms (often minimal until severe)

ECG Changes (ordered by progressive severity)

Management

1. Stabilize the Cardiac Membrane

• Mechanism: Does NOT lower serum K⁺. Restores the electrical gradient by increasing the depolarization threshold and the calcium gradient across the cardiac membrane, thereby reducing myocyte excitability and narrowing the QRS.
• Onset: 1-3 minutes
• Duration: 30-60 minutes (transient - must be followed by K⁺-shifting agents)
• Repeat if no ECG improvement in 5-10 minutes
• Indication: ECG changes (peaked T waves that are rapidly evolving, absent P waves, wide QRS, sine wave, bradycardia, cardiac arrest attributed to hyperkalemia)

2. Shift Potassium into Cells (Temporizing - does NOT remove K⁺ from body)

• Onset: <15 minutes; peak effect: 30-60 minutes
• K⁺ reduction: ~0.6 mEq/L on average
• Monitor glucose closely for several hours post-therapy

• Dose: 10-20 mg nebulized continuously over 30-60 minutes (4× the normal bronchodilator dose)
• Mechanism: Stimulates Na⁺/K⁺-ATPase pump
• Onset: 15 minutes; K⁺ reduction: 0.5-1.0 mEq/L
• Additive to insulin: Combined insulin + albuterol lowers K⁺ by ~1.2 mEq/L on average
• Not reliable in all patients (some are albuterol-resistant)

• Dose: 50-100 mEq IV (or 3 ampules in 1 L of D5W as isotonic solution)
• Mechanism: Buffers H⁺ extracellularly; K⁺ shifts into cells in exchange
• Only effective in hyperkalemic patients with confirmed concurrent metabolic acidosis - no benefit in non-acidotic patients
• Use as an adjunct, not primary therapy

• Even a few hundred mL can stimulate Na⁺/K⁺-ATPase
• Increases distal Na⁺ delivery to the kidney, promoting K⁺ excretion
• Use judiciously in anuric patients; consult nephrology

3. Remove Potassium from the Body (Definitive)

• Removes K⁺ by at least 1 mEq/L in the first hour and another 1 mEq/L during the next 2 hours
• The only experimentally validated method of reliable K⁺ removal
• Indicated: life-threatening hyperkalemia with renal failure; failure of medical management
• Should be initiated early in patients with renal failure and severe hyperkalemia
• In patients with intact renal function, medical management alone is usually sufficient

• Enhance kaliuresis in patients with intact or recovering renal function
• Particularly useful in rhabdomyolysis or tumor lysis syndrome with intact urine output (combined with saline)
• Not effective acutely in anuric patients

• Oral Kayexalate is contraindicated in bowel obstruction
• Rectal administration is contraindicated in immunosuppressed patients
• The sorbitol vehicle in Kayexalate carries risk of bowel ischemia
• Patiromer and SZC are effective and safe for chronic/recurrent hyperkalemia, particularly in CKD and heart failure patients on RAASi therapy

Summary Treatment Algorithm

Suspected Hyperkalemia
        ↓
Establish IV access + continuous cardiac monitoring
Obtain ECG + serum K⁺ + blood gas
        ↓
ECG changes present?  ──YES──→  CALCIUM GLUCONATE IV (Step 1)
        │                        (10-20 mL of 10% over 2-3 min)
        │
      Both paths proceed to:
        ↓
SHIFT K⁺ INTO CELLS (Step 2) - effects additive:
  • Insulin 10 units IV + 50% dextrose 50 mL IV
  • Nebulized albuterol 10-20 mg
  • NaHCO₃ if acidotic
        ↓
REMOVE K⁺ FROM BODY (Step 3):
  • Furosemide (if urine output present)
  • Patiromer or SZC (chronic/maintenance)
  • Hemodialysis (renal failure or refractory severe hyperkalemia)
        ↓
Address underlying cause + chronic prevention
(dietary restriction, correct acidosis, review offending drugs,
 optimize RAASi with K⁺ binder if tolerated)

Chronic Management and Prevention

• Dietary restriction: Avoid salt substitutes, dried fruits, nuts, bananas, potatoes, tomatoes, spinach, canned fruit/vegetable juices. Boil vegetables rather than steaming.
• Correct metabolic acidosis: Oral sodium bicarbonate or citrate.
• Optimize diuresis: Thiazide or loop diuretics if residual renal function allows.
• Exogenous mineralocorticoid: In hypoaldosteronism states (fludrocortisone).
• Reassess medications: Stop or reduce ACE inhibitors/ARBs, NSAIDs, K-sparing diuretics when clinically safe.
• RAASi management (2025 GUARDIAN-HK European Guidelines, PMID 40685253): Disease-modifying therapies such as RAASi should not simply be stopped when hyperkalemia occurs. Instead, use patiromer or SZC to maintain RAASi at target doses, particularly in heart failure and CKD patients, because the cardiorenal benefits outweigh the risk.

Key Sources

• Rosen's Emergency Medicine (pp. 2113-2205) - Clinical features, ECG classification, management table
• Washington Manual of Medical Therapeutics (pp. 2700-2761) - Causes, diagnosis, treatment doses
• Current Surgical Therapy, 14th ed. (pp. 3136-3143) - Surgical population specifics
• Fischer's Mastery of Surgery, 8th ed. (p. 1405) - Acute treatment summary
• PMID 40685253 - GUARDIAN-HK 2025 European interdisciplinary recommendations on recurrent hyperkalemia (note: erratum published, PMID 41637058)
• PMID 40542996 - Novel potassium binders (patiromer, SZC) systematic review and meta-analysis, 2025

Surgical Drains: Classification, Uses, and Evidence-Based Practice

Historical Perspective

Definition and Purpose

• Prophylactic - placed at the end of a clean or elective procedure to prevent anticipated fluid accumulation
• Therapeutic - placed to treat an existing collection (abscess, haematoma, bile leak)

Classification of Surgical Drains

1. Open Drains (Passive)

• Corrugated drain: A flat, ribbed latex or rubber sheet that creates channels for passive fluid egress. Used in debrided wounds and abscess cavities.
• Penrose drain: A soft, flexible latex or silicone rubber tube available in ¼ to 1 inch diameters; can be cut to length; sutured to skin to prevent migration. Has no collection reservoir - drains into external dressings. Used in scrotal surgery and for subcutaneous fluid prevention during wound closure. Associated with a higher risk of surgical site infection compared to closed systems and therefore removed earlier.

2. Closed Non-Suction Drains (Passive)

• Robinson's drain: A simple soft tube with multiple side holes used within the abdominal cavity to evacuate fluid without the negative pressure hazard of sucking viscera or omentum into the drain. Connected to a drainage bag.
• Urinary catheters and nasogastric tubes are considered specific examples of passive closed drains.
• Pigtail drain: Contains a curled inner portion (deployed by tightening a suture after placement) with small perforations for fluid removal that keep the drain in position. Used for nephrostomy, suprapubic drainage, percutaneous abscess drainage, and pleural collections. Removal requires loosening of the internal suture or transection of the drain to unfurl the coil.

3. Closed Suction Drains (Active)

• Jackson-Pratt (JP) drain: A flat or round perforated internal tube connected to a grenade-shaped compressible bulb. The bulb is compressed to create low negative pressure (~70-170 mmHg). Widely used for intra-abdominal urologic, gynaecologic, and general surgical procedures. The perforated collecting portion is larger than the external tubing, which can cause some discomfort on removal.
• Blake drain: Similar to JP in principle but uses continuous-diameter tubing with longitudinal channels that allow fluid entry via capillary action and negative pressure, rather than side perforations. The uniform diameter may be less uncomfortable during removal. Commonly used in abdominal surgery.
• Redivac (Hemovac): A high-negative-pressure drain used where larger volumes of fluid are anticipated (e.g., after major orthopaedic or vascular procedures). The reservoir is a flat coil-spring container.
• Wound drain with suction: Various proprietary designs used in head and neck surgery, axillary dissection, and after ventral hernia repair.
• T-tube: A specialised T-shaped drain inserted into the common bile duct (CBD) after exploration and stone retrieval, or after repair of a damaged CBD. The horizontal limb sits within the duct; the vertical limb exits externally. It:
  • Drains bile while the sphincter of Oddi is in spasm postoperatively
  • Acts as a safety valve if stones are retained distally
  • Allows T-tube cholangiography to confirm clearance before removal
  • Must remain in situ for at least 2-3 weeks to allow a fistulous tract to form, minimising the risk of biliary peritonitis on removal
  • Before removal: T-tube cholangiogram confirms free bile flow to duodenum; then clamp for 24 hours; if asymptomatic, remove
  • Note: A Cochrane analysis found T-tubes are associated with increased bile leakage, prolonged hospital stay, and cost, with minimal benefit over primary CBD closure
• Campbell-Walsh Wein Urology (pp. 1337-1360); Bailey and Love's Short Practice of Surgery, 28th ed. (pp. 8694-8903)

Schwartz's Four Indications for a Surgical Drain

1. To collapse surgical dead space in areas of redundant tissue (e.g., neck, axilla)
2. To provide focused drainage of an abscess or grossly infected surgical site
3. To provide early warning of a surgical leak (bowel contents, secretions, urine, air, or blood) - the so-called "sentinel drain"
4. To control an established fistula leak

Arguments For and Against Routine Drainage

Arguments FOR drain use

• Removes collections of purulent material, blood, serous fluid, bile, chyle, pancreatic or intestinal secretions
• Acts as a sentinel signal for postoperative haemorrhage or anastomotic leakage
• Provides a track for long-term drainage and fistula control

Arguments AGAINST routine drain use

• Increases intra-abdominal and wound infection by introducing skin bacteria into the peritoneal cavity (retrograde contamination)
• Delays recovery and increases hospital stay
• Increases abdominal pain
• Decreases pulmonary function (by splinting)
• Can create a false sense of security - a blocked drain may give no output while a significant collection forms
• Active suction (70-170 mmHg negative pressure) may itself promote anastomotic dehiscence by creating suction injury at the anastomotic line - raising the question of whether it is the drain or the anastomosis that fails first
• Schwartz's Principles of Surgery specifically states that "data do not support closed suction drainage to 'protect an anastomosis' or to 'control a leak' when placed at the time of surgery"

Evidence-Based Use by Surgical Procedure

Non-Gastrointestinal Surgery

Gastrointestinal Surgery

Emergency Gastrointestinal Surgery

• Four-quadrant peritoneal contamination: Routine drainage generally beneficial
• Localised peritoneal contamination: More selective approach is appropriate
• The decision must account for clinical state, comorbidities, and availability of round-the-clock interventional radiology for percutaneous drainage if needed

Specific Specialist Uses

Nasogastric Drainage

• Conservative management of paralytic ileus or partial bowel obstruction
• Decompression of stomach before emergency laparotomy
• When postoperative ileus is anticipated after extensive bowel handling
• Feeding route after upper aerodigestive tract procedures

Vacuum-Assisted Closure (VAC/NPWT)

• Decreases local wound oedema
• Promotes granulation tissue formation
• Dramatically improves complex wound healing
• Effectively manages contaminated wounds, fasciotomy sites, abdominal wound dehiscence, and open fractures
• Exposed dura is not a contraindication

Chest Drains (Intercostal Drains)

Percutaneous Image-Guided Drains

• Intra-abdominal and pelvic abscesses
• Loculated infections
• Bilomas, urinomas, lymphoceles
• Drainage of anastomotic leaks This has largely replaced formal surgical re-exploration for accessible fluid collections.

Complications of Surgical Drains

Principles of Drain Removal

• A drain should be removed as soon as its defined objective is achieved - not based on arbitrary volume thresholds alone
• Sentinel (haemostasis) drains: Usually removable at 24 hours if no bleeding
• Infection drains: Remove when infection is subsiding and drainage is minimal
• Post-anastomotic drains: Remove at 3-5 days (they do not prevent anastomotic leak but may allow controlled external drainage if one occurs)
• Closed suction drains: Release the suction before removal to prevent tissue trauma
• T-tubes: Clamp for 24 hours prior to removal after confirming patent cholangiogram; leave in situ minimum 2-3 weeks
• Mastectomy drains: Remove when output <30 mL/day for two consecutive days (typically POD 7-14)
• Longer drain dwell increases infection risk through retrograde bacterial contamination

Summary

• Therapeutic drainage of established collections (abscess, haematoma, bile leak) is strongly supported and increasingly performed percutaneously under image guidance
• Prophylactic drainage of clean anastomoses, standard elective colonic, hepatic, and biliary procedures is not routinely indicated and may cause harm
• Selective drainage is appropriate for high-risk anastomoses (oesophageal, pancreatic), major contaminated procedures, and operations creating large dead spaces (neck dissection, axillary surgery)
• ERAS protocols have eliminated many traditional drainage practices (routine NG tubes, routine pelvic drains) from elective surgery

Key Sources

• Bailey and Love's Short Practice of Surgery, 28th ed. (pp. 8694-8903) - Classification, controversy, procedure-specific guidelines, T-tubes, nasogastric drainage, drain removal
• Schwartz's Principles of Surgery, 11th ed. (p. 452) - Four indications for surgical drains; VAC therapy
• Campbell-Walsh Wein Urology (pp. 1337-1360) - Penrose, Jackson-Pratt, Blake, pigtail drain descriptions
• Mulholland and Greenfield's Surgery, 7th ed. (p. 3107-3110) - Mastectomy drain management
• PMID 41246741 (2025 narrative review) - Drain removal timing, criteria, and evidence-based practices

Diagnosis and Evaluation of a Non-Healing Foot Ulcer

Epidemiology and Significance

• Campbell's Operative Orthopaedics, 15th ed. 2026 (p. 5054-5061)

Step 1: Establish the Aetiology - The Differential Diagnosis

Step 2: History Taking

A. Ulcer-Specific History

• Duration - how long has it been present? Any previous episodes?
• Mode of onset - trauma, spontaneous, minor injury unnoticed due to neuropathy
• Pain - painless ulcers suggest neuropathy; severely painful suggest ischaemia
• Prior treatments - antibiotics, dressings, offloading, surgery
• Rate of progression - stable, growing, improving

B. Systemic and Medical History

• Duration and type of diabetes
• Current glycaemic control (HbA1c)
• History of neuropathy (paresthesias, numbness, burning) - patients may deny any pain or trauma preceding the ulcer
• History of prior foot ulcers or amputations (strongest single predictor of recurrence)
• Known retinopathy or nephropathy (renal failure dialysis patients are especially high-risk)
• Impaired vision (reduces self-inspection ability)

• Symptoms of peripheral arterial disease: intermittent claudication, rest pain
• Coronary artery disease, cerebrovascular disease (marker of systemic atherosclerosis)
• Prior vascular interventions (angioplasty, bypass)

• Venous insufficiency, deep vein thrombosis, varicose veins
• Rheumatoid arthritis, vasculitis, Raynaud's disease
• Malignancy (both as immunosuppressant and direct cause via Marjolin's ulcer)
• Immunosuppression (steroids, chemotherapy, transplant drugs)
• Smoking (major vascular risk factor)

C. Medications

• NSAIDs (impair healing, reduce pain perception)
• Steroids (suppress immune response and healing)
• Anticoagulants
• Immunosuppressants

Step 3: Physical Examination

A. General Assessment

• Vital signs: fever, tachycardia, hypotension (systemic sepsis from severe infection)
• Overall nutritional state, BMI
• Signs of systemic disease (diabetes signs, renal disease)

B. Inspect the Patient's Footwear (before removing shoes)

• Undersized shoes create pressure over bony prominences
• Toe box inadequate for forefoot deformities (claw toes, hammer toes)
• Abnormal wear pattern = structural or dynamic foot deformity
• Prominent seams or foreign bodies inside shoe that patient cannot feel = strong neuropathy sign

C. Local Examination of the Ulcer

• Plantar surface / pressure points → neuropathic
• Over metatarsal heads / toes / shins → ischaemic
• Medial/lateral malleolus (gaiter region) → venous
• Measure dimensions in cm (length × width × depth)
• 96% of ulcers <1 cm² heal without amputation vs. only 72% of those >3 cm² (Ince et al.)
• Ulcers showing ≥50% reduction in 4 weeks have significantly better 12-week healing

• Granulating (healthy, red) vs. sloughy (yellow/grey) vs. necrotic/eschar (black)
• Exposed tendon (Wagner grade II), exposed bone (Wagner III)

• Punched-out, undermined, with surrounding callus → neuropathic
• Sloping, irregular → healing or venous
• Raised, everted, firm, bleeds easily → suspect malignancy (Marjolin's ulcer)

• Shiny, taut skin without hair growth → peripheral arterial disease
• Dry, scaly skin → autonomic neuropathy (anhidrosis)
• Erythema, swelling, calor → infection/cellulitis (measure extent from ulcer edge)
• Lipodermatosclerosis, haemosiderin staining, varicosities → venous disease
• Corns or calluses → precursors to ulcer formation from abnormal pressure

• Insert a sterile, blunt metallic probe into the ulcer
• A hard, gritty sensation on contact = positive probe-to-bone → strong indicator of osteomyelitis
• Sensitivity 60%, Specificity 91%, LR+ 6.4
• Positive predictive value ~90% in hospitalised diabetics with chronic deep foot ulcers

D. Foot Deformity Assessment

• Claw toes, hammer toes → motor neuropathy (intrinsic muscle wasting)
• Fat pad migration distally (normal fat pad displaced from metatarsal heads)
• Rocker-bottom deformity → Charcot neuroarthropathy (midfoot collapse)
• Hallux valgus, prominent metatarsal heads
• Hindfoot alignment with weight bearing (varus/valgus)
• Atrophy of extensor digitorum brevis → motor neuropathy

E. Vascular Examination

• Inspection: colour (pallor, cyanosis, rubor), hair loss, shiny skin, nail dystrophy, gangrene
• Elevation test: elevation pallor; dependent rubor (Buerger's test)
• Temperature: warm foot = infection or neuropathy; cold foot = ischaemia
• Pulses: femoral, popliteal, dorsalis pedis, posterior tibial - absence indicates PAD
• Capillary refill time (>3 seconds = impaired perfusion)

F. Neurological Examination (Neuropathic Foot)

• Inability to feel a 5.07 monofilament (10g pressure) is one of the most predictive risk factors for foot morbidity
• Standard testing: 10 sites on the plantar foot
• Quick alternative: 4.5g monofilament beneath both first metatarsal heads gives equivalent results
• "You cannot examine the feet of your diabetic patients too often, and you cannot examine them with their shoes on!"

• Vibration sense: 128 Hz tuning fork at first MTP joint and medial malleolus
• Proprioception testing
• Deep tendon reflexes (absent ankle reflex = peripheral neuropathy)
• Two-point discrimination

• Reduced ankle dorsiflexion with knee in extension (but not in flexion) = gastrocnemius contracture
• Equal reduction in both positions = Achilles tendon contracture
• Both increase forefoot pressure loading, predisposing to ulceration

Step 4: Ulcer Classification

Wagner-Meggitt Classification (most widely used)

Brodsky Depth-Ischaemia Classification (adds vascular assessment)

IDSA/IWGDF Infection Severity Classification

Step 5: Investigations

A. Vascular Assessment

• Normal: 0.9 - 1.2
• Values >1.3 = non-compressible (calcified) vessels - falsely elevated in diabetics
• ABI <0.5 = ulcer unlikely to heal without vascular intervention
• Ankle systolic pressure >60 mmHg (diabetics need >90 mmHg) required for healing
• ABI difference >0.15 between limbs = significant, warrants further investigation

• Normal toe/brachial index: >0.7
• Toe pressure >40 mmHg = associated with wound healing
• Absolute toe pressure should be >70 mmHg for healing

• Triphasic = normal
• Biphasic = moderate PAD
• Monophasic = severe PAD

• 40 mmHg = adequate perfusion for healing

• <20 mmHg = severe ischaemia, healing unlikely

B. Neurological Assessment

• Semmes-Weinstein monofilament (10g) - primary screening tool
• Neurothesiometer/biothesiometer - quantifies vibration perception threshold (VPT >25 V = high risk)
• Nerve conduction studies/electromyography - reserved for complex cases (rarely needed in routine practice)

C. Laboratory Investigations

D. Microbiological Assessment

1. Do NOT culture clinically uninfected ulcers - commensal bacteria will mislead
2. Do NOT swab the wound surface - superficial swabs are unreliable for identifying deep organisms
3. Cleanse and debride the wound first before obtaining the specimen
4. If purulent secretions present: aspirate with a sterile needle/syringe
5. Gold standard: tissue specimen by scraping the base of the debrided ulcer with a sterile scalpel or dermal curette
6. Deep infections: bone biopsy (see below)

• Mild/acute infections: Usually monomicrobial - Staphylococcus aureus, Streptococcus spp.
• Moderate: S. aureus, Streptococcus, Enterobacteriaceae, anaerobes
• Severe/chronic infections: Polymicrobial (3-5 isolates) including anaerobes; gram-negative organisms (including Pseudomonas) overrepresented
• MRSA present in at least 15-30% of foot ulcers

E. Imaging

Plain Radiograph (first-line, always obtain)

• Demineralisation, loss of normal bone trabecular pattern
• Periosteal reaction
• Cortical erosion, destruction of joint spaces
• Gas in soft tissues (gas-forming organisms)
• Charcot arthropathy (joint destruction, fragmentation, subluxation)
• Foreign bodies

MRI (investigation of choice for suspected osteomyelitis)

• Sensitivity 90%, Specificity 79% (LR+ 5.1, LR- 0.12)
• Most accurate imaging test for osteomyelitis in the diabetic foot
• Findings: decreased T1 signal, increased T2/STIR signal in bone marrow
• Distinguishes soft tissue infection, abscess, septic arthritis from osteomyelitis
• Useful for surgical planning once diagnosis confirmed
• Limitation: differentiating osteomyelitis from Charcot arthropathy can be difficult
• Weight-bearing radiographs → MRI if soft-tissue abscess or osteomyelitis suspected

CT Scanning

• Shows bone architecture in multiple planes, sequestra, cortical disruptions
• Useful for surgical planning for deformity correction
• Not routinely used in isolation for evaluation; weight-bearing CT excellent for Charcot planning

Bone Scintigraphy

PET/CT

• FDG-PET shows increased uptake at sites of active inflammation
• Mixed evidence vs. MRI; insufficient evidence to recommend routine use currently

Complete Imaging Summary for Osteomyelitis (Table 91.3 - Campbell's Orthopaedics):

F. Diagnosing Osteomyelitis - Evidence-Based Approach

• Needle bone biopsy: sensitivity 87%, specificity 93% (LR+ 12.4, LR- 0.14) but subject to sampling error

1. Probe-to-bone positive, AND
2. Elevated inflammatory markers, AND
3. Abnormal plain radiograph

Step 6: Multidisciplinary Assessment

Step 7: Assessment of Factors Impairing Healing

Key Prognostic Points

• Ulcers ≥50% reduced in area after 4 weeks of treatment = significantly better 12-week healing outcomes
• Ulcers infected + ischaemic: 90× more likely to require amputation
• Presence of infected ulcer: 40-55% chance of some form of amputation
• Patient education reduces lower extremity amputation risk by 50-85%
• A 5-year survival of only 56% after first DFU - aggressive management is warranted

Key Sources

• Campbell's Operative Orthopaedics, 15th ed. 2026 - Chapter 91: Diabetic Foot (pp. 5054-5061): History, physical exam, Wagner/Brodsky classification, ABI, imaging, osteomyelitis
• Symptom to Diagnosis: An Evidence-Based Guide, 4th ed. (pp. 10495-10676): Disease highlights, risk factors, infection classification, osteomyelitis diagnostic LRs, microbiology
• Bailey and Love's Short Practice of Surgery, 28th ed. (p. 7443-7484): Diabetic foot infection, clinical presentation, MRI, probe-to-bone
• Schwartz's Principles of Surgery, 11th ed. - Chronic wounds chapter
• PMID 37302121 - IWGDF 2023 Guidelines on Prevention of Foot Ulcers in Diabetes (Practice Guideline + Systematic Review)