Explanation

Projectiles create direct and indirect injuries. Direct is caused by the wound cavity produced by the projectile’s size and shape. Indirect comes from the temporary cavity produced as tissue expands away from the bullet path. The cavity expands then collapses. 

Fractures can be caused by this indirect cavitation with wedge shape fractures caused by bending away from projectile. Clothing can increase the size and depth of the cavity. These videos show the cavity expansion and then collapse based on the differences in low vs. high velocity.

Low energy example:

https://www.youtube.com/watch?v=NvYWWwylz-I

High energy example:

https://youtu.be/zG48pgYe-Is?t=814

Initial evaluation:

• Just like any distracting injuries, do a full ortho exam on these patients. Be sure to focus on the joint above and below the area of the injured area.

• CT scan to evaluate nearby joints, often helpful to eval the joint above and below

Kinetic energy = 1/2MV^2 (Velocity is the greatest contributor to energy)

Because velocity is the greatest factor in kinetic energy, firearms are classified by velocity:

High velocity = high energy (>2,000 feet per second)

• Rifles

• Shotguns when within 10 feet (wadding from cartridge can become embedded in the body causing infections, have a high suspicion for it)

270 Winchester. FPS >2900. Varies based on the bullet grain (mass of the bullet).

Low velocity = usually lower to medium energy (<2,000 feet per second)

• Handguns

High energy projectiles are linked to a higher risk of infection (41 percent vs. only 9.5 for low-energy) creating larger temporary cavities and soft-tissue injuries.

Treatment:

• High energy

  • Antibiotics

    • Ancef

    • Continue 1st generation cephalosporin 1-3 days post injury

    • Recommends against prophylactic use of aminoglycosides or penicillin

  • Surgery

    • Irrigation, debridement, delayed wound closure typically 3-5 days after injury

• Low energy

  • Antibiotics

    • OTA survey showed that 86% provide routine ancef

  • Surgery

    • If intra-articular bullet fragments

      • Prevents synovitis, joint destruction, elevated lead levels

    • Wound is part of dissection field for fixation

    • Evidence of significant soft-tissue damage

  • No surgery

    • Entry and exit wounds have low incidence of infection (2 percent)

    • Routine surgical debridement is not recommended for arthrotomies without retained fragments or fractures that do not require fixation

      • Though there is common meniscus and chondral damage that may require arthroscopic treatment later on

Unique scenarios

• Acetabular and pelvic ring injuries when projectile violated the bowel

  • Routine fracture debridement has unproven effectiveness in these pelvic injuries

  • Injection rates are high with or without bony debridement

 Here are the answers to the above questions.

 How would you describe this fracture?

• AP view of a femur in a skeletally mature individual showing a distal third comminuted fracture with likely bullet fragments

 What was the velocity of the projectile, high or low?

• Likely High energy, >2,000 feet per second (FPS)

Any more imaging that you would want to get?

• CT scan right lower extremity (RLE). Involving right knee and hip to evaluate the joints.

How would you manage this injury in the trauma bay?

• Ideally get supplies needed ahead of time

  •  Basin, sterile saline, sterile gauze, kerlix (gauze roll), acewrap, traction pin supplies (if needed, not in this case), splint supplies (long posterior leg splint in this case)

• Let the gen surg team do their ABCs, primary and secondary exams (you should do the rectal exam if covering spine)

• I usually jump to “C” because I consider the pelvis to be part of circulation because there can be life-threatening blood loss

• Do a full exam neck to toes

  • Look for any area of open skin, be on high alert because it is sometimes easy to miss open fractures and arthrotomies (open joints)

  • Palpate for pain (can help find fractures)

  • Check Motion (helps find joint dislocations)

  • Motor and sensory (reflexes if covering spine)

  • Vascular (if abnormal consider checking signal with doppler and ABIs)

• Order xrays for any area of concern: Skin abrasions/bruising, Pain, motion abnormality, (it is okay to over x-ray, minimal radiation, cheap, and you don’t want to miss anything)

  • You can order long bone xrays to help survey joints if in a hurry (femurs, tibia/fibula, forearm, humerus). If you think a joint is involved, just get the joint specific xray.

  • You can find fractures underlying mild abrasions (more likely in high energy mechanisms)

• Wash off debris and exam more closely with sterile saline

• Cover with sterile saline soaked gauze

• Add more absorbent gauze, kerlix, and ace wrap

• Splint

What would you do in the operating room?

• What would you do with the bullet fragments?

  • Leave bullet fragments, unless they are in the joint, in the path of dissection, in the spinal canal, or sometimes if likely to cause irritation (superficial)

• What type of fixation would you use and what type of bone healing?

  • secondary  bone healing with a retrograde or anterograde femur nail

• What parameters are essential to restore in the operating room and how would you assess them?

  • Restore length, rotation, alignment (compare with xrays of other side, line up cortical diameters, check both legs if other side isn’t covered by drapes)

  • Check femoral neck under fluoro (femoral neck fractures are common in higher energy femoral shaft fractures)

  • Check knee ligaments (ligamentous knee injuries are common in high energy injuries, trying to get one while the patient is awake is likely not obtainable)

References: 

https://www.aaos.org/aaosnow/2019/nov/clinical/clinical01/