Stress Fracture

**Stress fractures** result from the imbalance between bone formation and bone resorption when repetitive stress exceeds the bone's ability to repair. Bones constantly remodel — old bone is broken down (resorption) and new bone is laid down (formation). Normally these processes are balanced, but with excessive repetitive loading, resorption outpaces formation, creating microscopic damage that progresses to small cracks (stress fractures) and eventually complete fractures if loading continues. **Two Types of Stress Fractures:** **Fatigue Fractures (Most Common):** - Normal bone subjected to abnormal repetitive stress - The bone is healthy but the load is excessive - Common in athletes who suddenly increase training - Common in military recruits during basic training - Examples: runner who increases mileage too quickly **Insufficiency Fractures:** - Abnormal (weakened) bone subjected to normal stress - The bone has reduced strength from underlying conditions - Common in older adults with osteoporosis - Common in patients with hormonal abnormalities - Examples: postmenopausal woman with normal walking activity **Risk Stratification by Location:** **Low-Risk Stress Fractures (Heal Well):** - Posteromedial tibia - 2nd-4th metatarsal shafts - Femoral shaft - Pubic ramus - Posterior calcaneus - These typically heal with rest and protected weight bearing **High-Risk Stress Fractures (Need Aggressive Treatment):** - **Femoral neck (anterior/superior)** — risk of complete fracture and avascular necrosis - **Anterior tibia** — "dreaded black line"; high risk of progression and nonunion - **Tarsal navicular** — slow healing; often missed - **Fifth metatarsal (Jones fracture)** — poor blood supply; often nonunion - **Sesamoids** — slow healing - **Pars interarticularis** (lumbar spine) — spondylolysis - These typically require non-weight-bearing or surgical treatment **The Female Athlete Triad / RED-S Connection:** **Female Athlete Triad** (now expanded to RED-S — Relative Energy Deficiency in Sport): - Low energy availability (not enough calories for training) - Menstrual dysfunction (irregular or absent periods) - Low bone mineral density This combination dramatically increases stress fracture risk and represents a major problem in sports requiring leanness (running, gymnastics, ballet, figure skating). Addressing nutrition and menstrual function is essential for prevention and treatment.

## Root Causes **Stress fractures result from imbalance between bone loading and bone repair capacity:** **Mechanical/Activity Factors:** *Training Errors (Most Common):* - **Sudden increase in training volume** (>10% per week) — the most common cause - **Changes in training surface** (track to road, soft to hard) - **Inadequate rest between sessions** - **New activity** — recently active person starting running - **Military basic training** — explains 30% incidence in recruits - **Inadequate progression** in athletic programs *Sport-Specific Risk:* - **Running** — particularly long-distance - **Military training** — marching, running with packs - **Track and field** - **Basketball** — repetitive jumping - **Gymnastics** — pounding force - **Ballet** — repetitive pointe work - **Tennis** — serving (lower spine, foot) **Biomechanical Factors:** - **Foot mechanics**: Cavus foot (high arch) and pes planus (flat foot) - **Leg length discrepancy** (>1 cm increases risk) - **Lower extremity malalignment** - **Inadequate muscle strength** to absorb forces - **Tight calves**: Increased forefoot loading - **Genu varum (bow legs)** or genu valgum (knock knees) **Nutritional/Hormonal Factors:** *Female Athlete Triad / RED-S (Major Risk Factor):* - **Low energy availability** — eating disorders, restriction - **Menstrual dysfunction** — amenorrhea, oligomenorrhea - **Low bone mineral density** — osteopenia, osteoporosis - This combination dramatically increases stress fracture risk *Other:* - **Vitamin D deficiency** (very common, often overlooked) - **Low calcium intake** - **Inadequate caloric intake** for activity level - **Eating disorders** (anorexia, bulimia) - **Hormonal imbalances** (low estrogen, low testosterone) **Medical Risk Factors:** - **Osteoporosis** — increases insufficiency fracture risk - **Hyperparathyroidism** - **Hyperthyroidism** - **Long-term corticosteroid use** - **Selective serotonin reuptake inhibitors (SSRIs)** — emerging evidence - **Proton pump inhibitors** — long-term use affects bone - **Some chemotherapy agents** **Equipment/Footwear:** - **Inadequate shoe support** - **Running shoes >400-500 miles** — degraded cushioning - **Stiff military boots** in recruits - **Pointe shoes** in ballet

## Treatment Depends on Location and Severity **Treatment varies dramatically based on whether the stress fracture is "high-risk" or "low-risk":** ## Low-Risk Stress Fractures (Most Common) *Locations*: Posteromedial tibia, 2nd-4th metatarsal shafts, femoral shaft, pubic ramus, posterior calcaneus **Treatment Protocol:** *Phase 1 (Weeks 1-2): Pain Reduction* - **Activity cessation** — stop the inciting activity - **Cross-training** — non-weight-bearing alternatives (swimming, cycling, pool running, elliptical) - **Pain monitoring** — use pain as guide; activities causing pain should be avoided - **NSAIDs**: Use cautiously — may impair bone healing (especially long-term) - **Ice** for symptomatic relief *Phase 2 (Weeks 2-6): Protected Loading* - **Pain-free walking** progression - **Pneumatic walking boot** for some metatarsal fractures - **Progressive range of motion** - **Cross-training** intensity may increase - **Calcium and vitamin D supplementation** if deficient *Phase 3 (Weeks 6-8+): Return to Activity* - **Gradual return** to running with walk-run progression - **Start at 50%** of pre-injury volume - **10% weekly progression** rule - **Address underlying causes** (training errors, biomechanics, nutrition) ## High-Risk Stress Fractures (Aggressive Treatment) *Locations and Specific Treatment:* **Femoral Neck Stress Fracture (Anterior/Superior):** - **Risk**: Complete fracture with avascular necrosis - **Treatment**: Often requires surgical fixation (cannulated screws) - **Recovery**: 12+ weeks; cautious return to running **Anterior Tibial Stress Fracture ("Dreaded Black Line"):** - **Risk**: Progression to complete fracture; high nonunion rate - **Treatment**: Non-weight-bearing for 6-8 weeks; possible intramedullary nail surgery - **Recovery**: 4-6 months for return to running **Tarsal Navicular Stress Fracture:** - **Risk**: Slow healing; missed diagnosis common - **Treatment**: Non-weight-bearing in cast for 6-8 weeks; possible surgery - **Recovery**: 4-6 months for full return **Fifth Metatarsal (Jones Fracture):** - **Risk**: Poor blood supply; high nonunion rate - **Treatment**: Often surgical (intramedullary screw) in athletes - **Recovery**: 6-12 weeks (surgical), 12-16 weeks (conservative) **Sesamoid Stress Fracture:** - **Risk**: Slow healing - **Treatment**: Stiff-soled shoe, off-loading pad, possible surgery - **Recovery**: 12+ weeks **Pars Interarticularis (Spondylolysis):** - **Treatment**: Activity modification, brace, physical therapy - **Recovery**: 3-6 months ## Critical Treatment Pearls **Address Underlying Causes (Essential):** *Training:* - Reduce volume by 50%+ initially - Follow 10% rule for progression - Add rest days between hard sessions - Vary surfaces *Biomechanics:* - Correct foot mechanics with appropriate footwear - Address leg length discrepancy - Strengthen weak muscle groups - Improve flexibility *Nutrition:* - **Optimize energy availability** (eat enough for training) - **Adequate calcium**: 1000-1200 mg/day - **Vitamin D**: Optimize blood levels (often need supplementation) - **Address menstrual dysfunction** in female athletes - **Treat eating disorders** if present *Bone Health:* - DEXA scan if recurrent fractures or risk factors - Consider bisphosphonates in some cases (controversial in athletes) - Address hormonal imbalances ## When to Seek Medical Attention **Red flags requiring immediate evaluation:** - Sudden severe pain (possible complete fracture) - Inability to bear weight - Significant deformity - Numbness or weakness - Fever (rule out infection) ## Prevention is Critical The 10-30% recurrence rate emphasizes the importance of addressing underlying causes: - **Smart training progression** (10% rule) - **Adequate recovery time** - **Proper nutrition** (calories, calcium, vitamin D) - **Female Athlete Triad screening** in at-risk populations - **Bone density assessment** in recurrent fractures - **Footwear management** (replace at 400-500 miles) - **Strengthen lower extremity muscles** - **Correct biomechanical issues**