Musculoskeletal clinical topic of the month – Calcaneal stress injury

Traumatic calcaneal fractures are often associated with high-velocity impact injury to the heel, with mechanisms such as falling from a height or road traffic accidents. Stress fractures of the heel often present much more insidiously and are not always as clinically obvious.

Biomechanics and force transmission through the Calcaneum

The calcaneus is well designed to sustain high tensile, shearing, and compressive forces. It possesses a thin shell of cortical bone that encloses a highly organised array of trabecular bone. The relatively sparse cancellous bone within the calcaneus leaves space that is filled by blood. This high fluid content helps the calcaneus to function as a hydrodynamic shock absorber during impact.

The calcaneal bone itself is able to dissipate force travelling from the talus downwards, but also the ground contact upwards (see image below). This creates compression and tensile forces across the joint, akin to that of those in the in hip, which can further be split into primary and secondary forces. In addition, there is also a traction force coming from the achilles tendon to the posterior aspect of the heel. 

The complicated crossroad of force distribution makes the prediction and classification of calcaneal stress fractures difficult. 

Calcaneal Stress Fracture Musculoskeletal clinical topic of the month – Calcaneal stress injury
Left image. Load transfer pattern of calcaneus: Body weight (BW), primary compression lines (PC), secondary compression lines (SC), primary tensile lines (PT), secondary tensile lines (ST), Achilles tendon lines (AT) (Adapted from Elsevier, Drake et al., 2015).
Right image. Comparison load transfer pattern of proximal femur. 

Case Presentation

Clinical history;

  • 47 year old male ultrarunner
  • 7-8 month peroid away from running due to midportion right achilles tendinitis
  • Completed a tendon loading programme and resummed running over a peroid of 2 months with gradual increases of milage 
  • Worked from no running to 40-50 miles a week within 2 months of return
  • 10 miles into a run, felt “something go” in left ankle, however continued to run further 10 miles 
  • Unable to weight bear fully on left ankle thereafter with only mild ankle swelling
  • Went to A+E next day, where x-ray of ankle was reported normal (heel not imaged), diagnosed ankle sprain and sent home with RICE advice
  • Presented to LBSM clinic 1 week after injury still unable to fully weight bear due to pain 

Past Medical history;

  • BMI 28
  • Non-smoker
  • No history of previous stress injury
  • Previously good health apart from achilles tendinitis

Exercise history;

  • Ultrarunner
  • Running load in fitness usually 50-60km a week
  • Good variation of training, but more road running since lockdown
  • Good SnC routine

Social history;

  • Acturary 
  • Lives in Bermondsey and runs through central london

Clinical examination;

  • Good range of painfree movement in talo-crual joint and subtalar joints and midfoot
  • No swelling around ankle joint or lateral gutter
  • Tender around posterior talus with “puffiness” in posterior ankle and Kaegers fatpad
  • Traditional heel squeeze test did not reproduce symptoms
  • Posterior imingment signs negative

Point of Care Ultrasound – Left ankle

No effusion in the talo-crual joint. Normal lateral and medial ligaments. No tear in achilles tendon and no signs of retrocalcaneal bursitis. No obvious posterior ankle impingement on dynamic testing. 

Clincial suspicions, differentials and reasoning;

  1. Stress fracture in left talus or calcaneus. Most likely due to length peroid of deloading from the contralateral achilles tendinitis and the fast resumption in returning to high running volumes. All runs were steady state, on pavement and without much variation of training. Heel squeeze test at the posterior heel however was negative. 
  2. Insertional achilles tendinopathy/tear on left side. Possible, as had marked tendinopathic changes on the right side. Was doing all loading programmes bilaterally which should have mitigated this, but could have experienced an acute tear in distal achilles during the run. Was not visible on ultrasound so this differential diagnosis was excluded.
  3. Acute retrocalcaneal bursitis. This can present in runners with acute posterior ankle pain and be very painful. No other risk factors for retrocalcaneal bursitis e.g. obesity, metabolic disease. Was not visible on ultrasound so this differential diagnosis was excluded.
  4. Posterior impingement of the ankle. Unlikely, as patient not getting into extreme or forced plantar flexion positions (e.g dancers, gymanst). No obviously posterior impingement on Ultrasound but require MRI to fully visualise posterior talus and os trigone.

Imaging

MRI T2 weighted showed a superior border calcaneal stress fracture with surrounding bone oedema. 

stress fracture Musculoskeletal clinical topic of the month – Calcaneal stress injury

Diagnosis

Calcaneal stress fracture due to repetitive overloading from rapid return to running post achilles tendinitis on contralateral side.

Management

Rehabilitation

  • First 8 weeks  
    • Aircast boot for immobilisation
    • Limited steps to 2000 day outdoors (with boot)
    • Asked to wear soft slippers or padded trainers indoors
    • Gentle prioceptive exercises and banded exercise for muscle activation
  • 8-12 weeks
    • CT scan to confirm full bony union of fracture and stability across fracture site
    • Reintroduction of strength and condition, weight lifting and calf raises
  • 12 weeks+
    • Gradual return to impact training and pylometric exercises 
    • Walk to run programme
    • Strict running periodised programme to ensure patient is protected from repeat stress injury (e.g. non-consectutive day running)  
    • Biomechanical analysis reveals patient is a “heavy heel striker”
    • Foot wear, orthotics and running style adapted to move ground reaction force away from heel

Medical

  • Calorie and nutritional intake optimised to help fracture healing
  • Interval CT scan at 8 weeks to ensure full union of fracture

Patient Self-monitoring tools

  • LBSM pain and symptom diary
  • LBSM load monitoring diary

Alternative patterns of calneal stress fractures

There are several orthopaedic classifications for traumatic stress fractures including the Sander Classifiction and Essex-Lopresti. There is currently no classification system or studies looking specifically at calcaneum stress fracture patterns.

Most calcaneal fractures will occur due to excessive axial compressive loading and therefore fall along the primary compression lines (red lines in diagram above). However, excessive traction from the achilles tendon injury can also produce stress on the calcaneal (yellow lines in diagram above). This may also lead to potential fracture, particularly in more pylometric based sports. The MRI images below show an achilles based stress fracture in a young jumper. 

Calcaneal Stress Fracture Imaging Musculoskeletal clinical topic of the month – Calcaneal stress injury

Key Summary and learning points – Calcaneal Stress Fractures

  • Calcaneal Stress Fractures should be considered in patients with heel pain participating in lower body impact sports such as running
  • They can be vague in their presentation and may be confused with ankle sprains, achilles tendinitis and plantar fascitis
  • There may be an associated history of low energy availbility or poor bone health
  • There is a varying distribution of calcaneal stress fractures, but they are more common along the primary compression force lines and around the achilles anchor
  • Superior border calcaneal stress fractures may not be positive on squeeze testing
  • No current classification system for calcaneal stress fractures
  • Intra-articular calcaneal fractures are common in traumatic fractures but not for stress fractures
  • If there is an intra-aricular compenent, surgical opinion should be sought for fixation
  • Biomechanical and Medical causes must be investigated to uncover all possible aetiological factors
  • When rehabilitating patients after a peroid of absence from training, remember that bone will have been deloaded and may have lost some density. Be sure to progressively increase and monitor load and volume to avoid stress injury
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