Can Simple Changes in Splinting Technique Reduce Posterior Heel Contact Pressure?

Background: Lower extremity splints are commonly used for the treatment of foot and ankle injuries and carry the risk of posterior heel pressure injury. Assessing heel contact pressures in a splint may guide clinicians toward specific splint designs that are associated with lower contact pressures.

Questions/purposes: This biomechanical study tested multiple splint characteristics to answer: (1) Which combination of heel position, padding thickness, and padding type (brand) minimizes posterior heel contact pressure? (2) Are there factors while making a splint that are associated with higher contact pressures?

Methods: Twenty legs in 10 volunteer participants (mean ± SD age 30 ± 14 years) without current foot or ankle injury were recruited for this biomechanical study. Three of 10 volunteers were female. A pressure transducer was used over the posterior heel to measure contact pressure in a short leg splint. To answer our first research question about the effects of different splint characteristics, we measured contact pressures with 0, 2, 4, 6, 8, and 10 layers of two undercast padding brands, with both resting the heel down and floating the heel freely by placing the leg on a pillow to keep the splinted heel free of contact. Pressures were compared with a threshold of 32 mm Hg, the pressure of dermal arteriolar capillary collapse. To answer our second research question about factors associated with higher contact pressures, we recorded measurements of abnormal pressure spikes and observed the effect of improperly bunched or folded padding behind the heel.

Results: Mean contact pressure remained above 32 mm Hg when resting the heel down, independent of padding thickness or brand. Floating the heel, by resting the leg on a pillow, with 6, 8, and 10 layers of thicker undercast padding or 8 and 10 layers of thinner padding reduced pressure below the threshold of 32 mm Hg. The mean contact pressure between 8 and 10 layers of padding was not different (10 layers reduced contact pressure by 4 mm Hg more than 8 layers [95% confidence interval -3 to 11]; p = 0.22). Improperly bunched undercast padding behind the heel increased mean contact pressure roughly threefold compared with evenly applied padding (median 270% increase [range 187% to 575%]).

Conclusion: In this study, the best splint configuration consisted of 8 or 10 evenly applied layers of thicker undercast padding when floating the heel. Lower extremity positioning with the heel floating freely appears to be an important modifiable factor to reduce heel dermal pressures. We contend that attention to these details of splint application might reduce the likelihood of pressure ulcers in patients, but future clinical studies of patients with various injuries or other indications for splinting are warranted.

Clinical relevance: These findings may be relevant to orthopaedic surgeons, emergency department and primary care providers, as well as cast technicians, all of whom play a role in mitigating the mechanical factors that contribute to iatrogenic posterior heel pressure ulcers in patients with foot and ankle injuries.