Stress Fractures

Normal Anatomy Bone remodels under wolff’s law Remodelling takes place via mechanotransduction Remodelling is based on the force and load placed through the bone If loading on a bone increases the bone will remodel itself to become stronger and resist the loading If loading on a bone decreases the bone will become less dense and weaker due to the lack of stimulus Remodelling occurs quickly in cancellous bone Remodelling occurs slowly in cortical bone

Pathology Partial or complete fractures resulting from repetitive and excessive mechanical stress on normal bone

Pathology Normal Stress Stress Reaction Stress Fracture Load and stress applied to bone with adequate time to remodel Bone remodels according to Wolff’s Law Stress Reaction Under repetitive loads without sufficient time to remodel bone will fatigue and fail Osteoclastic activity is greater than osteoblastic activity Results in microfractures Stress Fracture Continued stress results in cortical break

Mechanism of Injury Insidious Repeated stress or load e.g running

Risk Factors Intrinsic Female Low bone mineral density Nutritional deficiencies Hormonal irregularities Leg Length discrepancies Genu Valgum Poor lower limb muscle mass Extrinsic Running or jumping sports Rapidly increasing training program Poor training surface Running downhill Poor training footwear Smoking

Classification Location and type of the fracture predictive of healing Compression stress fractures more likely to heal with conservative measures Tension stress fracture usually require surgical intervention Tension forces can displace fracture site creating instability

High Risk Fractures

Femoral Neck Stress Fracture High morbidity in runners Significant complications if missed Fracture completion Avascular necrosis Arthritis changes Anterior hip or groin pain worse with activity Extremes of passive ranges of movement maybe painful Superior aspect of the femoral neck Tensile forces Surgically managed Inferior aspect of the femoral neck Compressive forces Can be managed surgically or conservatively depending on fatigue line

Anterior Tibial Shaft Stress Fracture Tension type stress fracture Poorly localised anterior leg pain Risk of non-union “dreaded black line” anterior tibia radiograph at middle-distal third junction of anterior tibia Initially conservative but surgical management required 60% of the time

Navicular Stress Fracture Common in athletes requiring a “push off” e.g sprinters, middle distance runners Navicular avascular Compression between talus and cuneiform Vague, poorly localized foot pain of medial dorsum of the foot Tenderness “N-spot” on the dorsal navicular Can be managed conservatively if no cortical disruption present, otherwise surgically managed

Talar Neck Stress Fracture Rare Usually report a trauma

5th Metatarsal Stress Fracture Less common metatarsal fracture Usually in the diaphysis on the lateral side and progresses medially Tension type Pain with weight bearing History of trauma or change in routine/environment/footwear Tenderness palpation Surgery considered for Failed conservative management Displaced fracture Elite athlete with need for early return

Low Risk Fractures

Femoral Shaft Stress Fracture Usually proximal third Insidious onset Non-specific pain localised to the groin, thigh or knee Conservatively managed

Pelvic/ Pubic Ramus Stress Fracture Groin pain Pain with single leg stance Most commonly inferior pubic ramus Conservatively managed

Fibula Stress Fracture Diffuse lateral leg pain Usually affect the distal third Conservatively managed

Calcaneus Stress Fracture Heel pain Worse on running and jumping Posterosuperior tenderness on palpation Conservatively managed

2nd -4th Metatarsal Stress Fracture Most commonly 2nd and 3rd metatarsal Forefoot pain on activity Tenderness on palpation

Posteromedial Tibial Stress Fracture Shin pain with weight bearing Focal tenderness over posteromedial tibia Occur posteromedial in the proximal or distal parts Conservatively managed

Subjective Examination Localized area of pain Insidious onset Occurs with activity that gradually gets worse Advanced stages pain could be at rest History of repeated activity

Objective Examination Focal tenderness Pain with percussion

Further Investigation MRI Bone scan CT

Management Management plan determined by location and risk of fracture Guided by surgeon

Conservative Activity modification to a pain free threshold “if it hurts to do it, then don’t do it” Reduce risk factors NSAID’s should be avoided Gradually progress weight bearing activity as pain allows Maintain general body conditioning, fitness and strength with pain free exercise Roughly 4 – 8 weeks for adequate healing

Plan B Surgical interventions depend on site

References Aweid, B., O. Aweid, S. Talibi and K. Porter (2013). "Stress fractures." Trauma 15(4): 308-321. Gallo, R. A., M. Plakke and M. L. Silvis (2012). "Common leg injuries of long-distance runners: anatomical and biomechanical approach." Sports Health 4(6): 485-495. Kahanov, L., L. E. Eberman, K. E. Games and M. Wasik (2015). "Diagnosis, treatment, and rehabilitation of stress fractures in the lower extremity in runners." Open Access J Sports Med 6: 87-95. McCormick, F., B. U. Nwachukwu and M. T. Provencher (2012). "Stress fractures in runners." Clin Sports Med 31(2): 291-306.