Although many orthopaedic ailments and surgeries in general may cause pain, an individual person’s experience as far as severity and duration of pain may differ greatly from that of another in the same clinical condition. In other words, pain is a subjective and individual experience that can change throughout the course of injury and recovery. Pain can be influenced by many factors. Although pain is not a pleasant feeling, it serves several important purposes. One of the most glaring purposes is that pain is a protective sensation that serves to prevent you from actions and stimuli that may cause organ and tissue damage.
All pain is not created equal and pain comes from different sources, is perceived differently depending on the individual, and can have variable severity and duration. Pain can be from mechanical causes (blunt force, cutting, etc.), thermal (heat or cold), and from substances released by the body to combat stress or illness. Through the stimulation of nerve endings at the site of pain, signals are sent to the central nervous system that tell your brain that pain is present. Pain can be present in the absence of an external stimulus as well, such as with neuropathic pain. Neuropathic pain often results in a burning or tingling pain, and may be described as the feeling of an electrical shock. Neuropathic pain results from underlying damage or disturbance to the nerve itself and can be somewhat common in conditions such as poorly controlled diabetes mellitus. Somatoform pain can also contribute in part to the experience of pain in an individual with orthopaedic injury. This may, in part, explain why two people with the same injury will often report very different levels of pain. Somatoform pain is no less significant than other sources of pain and can contribute significantly to discomfort. Traditional treatments for pain (such as opioid medications) may not provide substantial relief for this type of pain. This is one of many situations where alternative treatments to opiods as discussed on the next page may be even more beneficial in pain control. Somatoform pain can be affected by stress and other behavioral and emotional considerations. Phantom pain results from an area of the body that is no longer there. For example, phantom pain can occur in people after the amputation of a leg, where the perception of pain remains present in the former location of that leg even after it is gone. Allodynia is the term given to the sensation of pain in response to a stimulus that would normally not cause pain (such as light touch to the skin).
The benefits of pain are important to understand. When the ability to sense pain from external pressure is diminished in the feet of people with peripheral neuropathy, for example, an offending stimulus may be allowed to remain in place and can lead to direct tissue damage. Patients with peripheral neuropathy may not feel pain from something as simple as a pebble in their shoe. They may stand on that pebble all day long and by the end of the day have a wound (ulcer) develop on the sole of their foot. In an individual with normal sensation that pebble in the shoe would have caused pain and been removed before it was able to cause significant tissue damage. An extreme and rare example of the protective aspects of pain are seen in people who are born without the ability to sense pain (known as congenital analgesia, or CIPA). With this rare genetic disease, most people do not live beyond the age of 25. An inability to sense pain from temperature changes is especially harmful in this disease. Additionally, without the ability to feel injuries, those with CIPA and their caregivers must constantly check for bruises, cuts, etc., because left untreated these wounds can become infected.
Beyond its protective benefits, pain can also be of value as a positive reinforcement for certain aspects of life. The popular term, “no pain, no gain” refers to the muscle pain felt in the aftermath of a strenuous training session. This pain is one sign that you have stressed your muscles beyond your body’s comfort level. When this happens, your body will attempt to adapt and prepare for that stimulus again in the future by repairing itself and becoming larger and stronger.
Although the pain resulting from an orthopaedic injury or surgery is not likely to be pleasurable, it certainly provides protective functions. Most people would rather avoid the pain associated with putting all of their weight on a foot with an unstable ankle fracture and do not attempt to walk after such an injury. This will prevent further injury in many cases that might otherwise occur from the moment of injury to arrival at a hospital. After surgery pain may serve several important functions, depending on the source of that pain. Swelling in the involved limb is common after many orthopaedic procedures. This swelling causes an increase in pressure to the surrounding tissues. In mild cases, the pain associated with this swelling can prompt a person to elevate the limb, which will increase venous return to the heart and ultimately improve blood flow to the area, which in turn brings oxygen to the tissues and aids in healing. In severe cases, the pain associated with swelling into a constricted portion of the limb may alert the patient and his/her physician to the development of possible muscle and nerve damage.
Additionally, pain may play a role in the process of bone healing and new bone formation. In a study by Tomlinson et al published in April of 2017, the authors found that inhibition of the sensory nerve signaling pathway in bone (TrkA) impaired bone formation by reducing the bone formation activity of osteoblasts (bone-forming cells)(1). Tomlinson and colleagues also published a study in 2016 in the journal of Cell Reports that showed TrkA activation led to vascularization and ossification, and blocking this pathway impaired normal bone development during embryogenesis (2). These studies highlight the importance of nerve sensation in bone formation, as well as the detriment that occurs to blocking these sensory nerve pathways.
Notwithstanding the benefits mentioned above, much of the pain surrounding orthopaedic injuries and surgeries causes discomfort, and strategies to decrease pain are desirable. Risks associated with pain reduction strategies (such as medication and procedural side effects) must be taken into account as well when deciding on treatment for pain. For information on strategies to reduce pain, continue on to the next page.
Next Page: Treating and Reducing Pain
References:
- Tomlinson RE, Li Z, Li Z, Minichiello L, Riddle RC, Venkatesan A, Clemens TL. NGF-TrkA signaling in sensory nerves is required for skeletal adaptation to mechanical loads in mice. Proc. Natl. Acad. Sci. U.S.A. 114, E3632–E3641 (2017). Full Text: https://www.pnas.org/content/pnas/114/18/E3632.full.pdf
- Tomlinson RE, Li Z, Zhang Q, Goh BC, Li Z, Thorek DLJ, Rajbhandari L, Brushart TM, Minichiello L, Zou F, Venkatesan A, Clemens TL. NGF-TkrA signaling by snsory nerves coordinates the vascularization and ossification of developing endochondral bone. Cell Rep. 2016 Sep 6;16(10):2723-2735. Full Text: https://www.sciencedirect.com/science/article/pii/S2211124716310348