Head injury triggers humoral cascade that contributes to enhanced fracture healing: study

Orthopaedic aphorism teaches that fractures of long bones when associated with head injuries frequently heal with excessive callus and at a faster rate than normal.

Praveen Ravi et al have found in a new study that head injury triggers a humoral cascade invloving interleukin-6, parathyroid hormone, growth hormone, and prolactin that contributes to enhanced fracture healing.

The researchers conducted the study to evaluate the effects of a traumatic head injury on bone healing in adults with a diaphyseal fracture of the lower limb at Department of Orthopaedics, SRM Medical College and Research Institute, SRM Nagar, Potheri, Chengalpattu, Tamil nadu, India.

Fiveteen patients with a closed fracture of tibia or femur and associated head injury (cases) and 15 patients with a closed fracture of tibia or femur without an associated head injury (controls) were included in the study.

All patients were evaluated in terms of various serum parameters, including IL-6, growth hormone, PTH, LDH, prolactin levels, and ALP. Head injuries were graded as mild, moderate, or severe. Ventilatory support if required was noted. Serum prolactin was repeated at 5 weeks. Patients were followed up with serial radiographs, and the volume of callus formed was calculated and compared.

The volume of callus formed was calculated using the formula:

2 × π × r1 × (r2 − r1) × L where 'r1' is the radius of the bone and 'r2' the radius of bone plus callus and 'L is the length of the callus.

The observations in the study were:

• The mean value of growth hormone, interleukin-6 levels, and prolactin levels at 5 weeks were found to be higher in patients with head injuries, and the difference was highly significant (p=0.001).

• The severity of head injury also correlated proportionately with the spike in IL-6 levels.

• There was more pronounced callus formation in patients with head injury group when compared to the controls. This difference was significant at all intervals.

• There was higher volume of callus noted at the end of 6 months in patients with severe head injury (GCS7).

• The patients with severe head injury were naturally under ventilator support for a prolonged period compared to those with moderate head injury. It was thus indiscernible if the excess callus observed is due to the humoral cascade or as an effect of prolonged ventilation.

• Patients with head injuries show elevated parathyroid hormone levels, growth hormone levels at the time of injury, and elevated prolactin levels 5 weeks after the trauma—all of which might contribute to enhanced osteogenesis.

• Interleukin-6 levels are also elevated and the levels correlate to severity of head injury.

The authors concluded that there is enhanced fracture healing with exuberant callus formation in patients with long bone fractures when associated with a head injury. Serum alkaline phosphatase, calcium, and vitamin D3 levels are unlikely to contribute in the enhanced fracture healing. Patients with head injuries show elevated parathyroid hormone levels, growth hormone levels at the time of injury, and elevated prolactin levels 5 weeks after the trauma—all of which might contribute to enhanced osteogenesis.Interleukin-6 levels are also elevated and the levels correlate to severity of head injury and, therefore, have a pivotal role in the humoral cascade triggered following head injury that causes enhanced fracture healing.

Further reading:

Correlation Between Traumatic Brain Injuries and Callus Formation in Long bone Fractures

Praveen Ravi, Jambu Nageswaran, Muthumanickam Ramanujam, Sundar Suriyakumar, Elancheral Ayanambakkam Nambi.

Indian Journal of Orthopaedics (2022) 56:837–846

https://doi.org/10.1007/s43465-021-00594-0