Shin Pain - Ultrarunner

HISTORY: A 64-year-old male ultrarunner presented with a 10-week history of right lateral leg pain that started while training for the Boston Marathon. He was running 55-70 miles per week with 80% at an easy pace. He completed the race but reported limping through the final 16 miles; he self-initiated crutches for 5 days afterwards. Patient reported a ketogenic diet for several years due to resolution of polyarthralgia. He prefers to stay under 30-50 grams of carbs per day and does not use gels or other carbohydrate replacement during long runs. PHYSICAL EXAMINATION: Right leg: Tender to palpation pes anserine, proximal peroneal muscles. No tenderness knee joint line, patellar tendon, fibula, anterior or distal medial tibia, lumbar back. Limited lumbar ROM. No pain with resisted strength testing. Positive single leg hop test (at pes anserine). Neurovascularly intact. Nonantalgic gait. Poor lower quarter stability. BMI 24.41 m/kg2. DIFFERENTIAL DIAGNOSIS: 1. Lumbosacral radiculopathy 2. Tibial stress fracture 3. Fibular stress fracture 4. Pes anserine tendinitis TEST AND RESULTS: Point of care ultrasound: Cortical irregularity and periosteal edema at right proximal medial tibia corresponding to tenderness to sonopalpation X-ray tibia/fibula: No bony abnormality. MRI: Proximal posteromedial tibial stress fracture, Grade 4 Distal anterior tibial stress fracture, grade 4 with long segment anterior cortical thickening and irregularity of the mid to distal right tibia with marrow edema Medial femoral condyle osteochondral lesion DEXA: Osteopenia of femoral neck (T -1.6) and lumbar spine (T -1.4) Labs: Hgb 15.5, ferritin 161, TSH 1.59, free T3 3.2 CMP WNL Total cholesterol 211, LDL 138 Repeat MRI at 8 weeks: Interval decrease in proximal tibial edema with persistent fracture line. Resolution of anterior tibial stress fracture FINAL/WORKING DIAGNOSIS: Proximal posteromedial and distal anterior tibial stress fractures, Grade 4 Secondary diagnosis: relative carbohydrate deficiency TREATMENT AND OUTCOMES: Nonweightbearing for 8 weeks; then gradual weightbearing with start of return to run progression at 12 weeks. Physical therapy Education regarding the influence of both low energy availability and low carbohydrate availability on bone resorption. Referral to sports dietician.