Today I will be going through the diagnosis dilemmas we face when treating sesamoid injuries, and the local and global biomechanics to be addressed.
Patients present with pain under the ball of the foot with varying histories. Sometimes the pain is very gradual onset and not too painful (although patients like to minimize their pain for many reasons). The “not too painful” is over level 2, but under level 6. The pain is better since they are not doing their main activity like running, so they can walk without limping. And, sometimes the pain is acute in onset, with high pain levels of 5-7, and definite limping in your offices. When the pain is gradual, we do not think sesamoid fracture, but many sesamoid fractures start this way. When the pain is acute, with high pain walking, we are thinking of fracture, but the office x-rays are negative or show an obvious bi-partite sesamoid, a congenital anomaly. And, there are so many hybrid presentations, I lost count. These are a mixture where pain is low, disability is low, but onset was acute, or pain high, disability high, but onset gradual.
The general rules I have developed for sesamoid injuries are to protect my patients from me making a mistake diagnostically. What are some of these general rules? They include:
- Pain under the first metatarsal head is a sesamoid fracture until proven otherwise in a high impact or overuse activity.
- X-rays make diagnosing sesamoid injuries correctly very confusing, especially in the presence of bi- or tri-partite bones.
- Bi-partite sesamoid bones are easier to fracture than non-bi-partite ones, therefore, the presence of a bi-partite sesamoid probably means you have a sesamoid fracture
- MRI evaluation is standard of care for diagnosing and followup of sesamoid fractures
- The amount of pain is not an indicator of lack of injury, presence of an injury, or lack of healing
- Pain under the first metatarsal head is a sesamoid fracture until proven otherwise in patients with poor eating habits, amenorrhea, low Vitamin D by history, or family history of osteopenia or osteoporosis
Therefore, when in doubt, and your x-rays do not show a fractured sesamoid that you can treat by immobilization, get an MRI. If you can not get an MRI (for many reasons), treat the patient as if you think they have a sesamoid fracture placing them on your sesamoid protocol (last blog post reviewed my protocol with its Top 10).
I know what you are thinking. And yes, you are right. This leads to an over treatment of a patient that may not have a broken sesamoid. This is the state we are in so many times, with so many injuries. I would rather err on over treatment of a possible sesamoid fracture, which ends up having something else, than under treating a sesamoid fracture because that can be devastating to them.
What are the biomechanics involved in sesamoid injuries? Biomechanics will point you to the factors that overload the plantar aspect of the first metatarsal head. This is a great example of why I love biomechanics due to the combinations that patients present with in clinical practice. These biomechanics can help us in our understanding of how they got injured in the first place, and how to treat them so that they just do not go out and break them again. God forbid!!! Podiatry for sure is in the prevention business and cause-reversal is key to preventing injuries re-occurring time and time again. Next week we will begin to discuss the orthotic devices we will need based on these biomechanics. Today, I will just summarize the most common ones to look at in your patient.
These biomechanics are:
- Plantarflexed first rays especially in Everted Forefoot Deformities
- Pes Cavus
- Bunion Formation with Sesamoid Malposition
- Rigid Foot Type (limited subtalar joint Range of Motion)
- Flail Hallux Purchase
- Weak Flexor Hallucis Longus/Brevis
- Hallux Limitus or Rigidus, functional (hopefully) or structural
- Medial column overload (from any source)
- Equinus force with increased metatarsal plantar pressures
- Weak Achilles tendon
Before next week, see if you can imagine why these issues can lead to increased mechanical sesamoid stresses.
