human anatomy - What happens to bones that do not heal?

I would like to know the steps the body takes to heal a broken bone and what happens if it cannot heal properly. I am not looking for advice or explanations on resting and not doing activity, I am genuinely interested in understanding the outcome if activity is not stopped

Here is the scenario:

A rock climber develops a pain in the lower part of their middle finger. The pain is not so bad so the climber continues to climb for four weeks, but the pain has not gone away. The climber decides to go to the doctor fearing they have an A2 Pulley tear.

To their surprise the Doctors tests show no A2 pulley tear but rather a minor stress fracture of the Proximal Phalanx. The doctor says stop climbing, however the climber has several trips planned and does not experience any pain while climbing nor a loss of strength or power while climbing. The only time pain is felt is when the lower part of the middle finger is squeezed. Because of this the climber decides to continue climbing as they just love it so much.

Question: What will happen to a stress fracture in the finger if adequate rest is not given?

I understand the first thing the body does is try to stabilize the break and then starts to repair. What happens if it is continually used and not given the chance to properly heal? Will the climber just have a sore spot on their finger for the rest of their life or will it progressively get worse and worse?

Answer

Fracture healing occurrs in several steps:

1. haemorrhage: blood and surrounding cells fill the space created by the fracture.


2. fibrous callus: chondrocytes colonize the fracture space, with neovascularization.


3. bony callus: osteocytes colonize the fracture space and rearrange in woven bone


4. remodelling: in long bones, woven bone is remodelled into lamellar bone and creates a new haversian system

If the fracture is not immobilized enough (not enough rest), several things can happen that are mutually exclusive:

• normal healing: luckily, the bone is not too much mobilized and is able to heal normally


• fracture displacement: the bone heals, but in an incorrect alignment. This gets partially corrected over time, but the correction mechanism is limited, especially in adults.


• pseudarthrosis: the worst case. instead of normal healing, cartilage grows to protect the bony extremities that are mobilized and prevents further healing. This causes pain, and will require surgery in most cases.