Instead of reducing plantar loading during jumping and landing, use of a rigid carbon graphite footplate among healthy active participants increased the load under the lateral column of the foot, according to study results published in Gait & Posture.
“Metatarsal stress fractures comprise a quarter of all stress fractures of the foot. The incidence of fifth metatarsal stress fractures have never been well-defined in the literature; however, this type of fracture is difficult to heal and results in substantial loss of time from sport. However, little is known about the factors that relate to the mechanism of metatarsal loading during jumping,” the researchers wrote. “The goal of this study was to quantify the effect of a rigid carbon graphite footplate on plantar loading during the takeoff and landing of a jump. If the carbon graphite footplate is capable of decreasing loads beneath the lateral column of the foot, it could be used to unload the foot following fifth metatarsal stress fractures during recovery and to reduce the high rate of recurrent injury when the athlete returned to full sport participation.”
Plantar loading
Researchers recruited 19 recreational male athletes who had no history of lower extremity injury in the past 6 months and no foot or ankle surgery in the past 3 years. They completed 7 jumping tasks while wearing a standard running shoe and then the shoe plus the carbon graphite footplate (CGF) while plantar loading data were recorded. To examine differences between the two footwear conditions for both takeoff and landing, the researchers used a series of paired t-tests. Researchers randomized the testing order for test condition.
Participants were given a 30-second rest period between trials and a 5-minute rest period between testing conditions. Researchers divided the foot into eight anatomical regions for analysis: heel (or rearfoot), medial midfoot, lateral midfoot, medial forefoot, middle forefoot, lateral forefoot, hallux and the lesser toes.
Study results showed the contact area in the medial midfoot and forefoot statistically decreased when participants wore the CGF. Also, the CGF decreased force-time integral beneath the medial midfoot, as well as reduced the maximum force. Researchers found the CGF produced a significantly greater force-time integral and a significantly greater maximum force beneath the middle and lateral forefoot. The medial and middle forefoot also had a significantly greater maximum force when participants wore the CGF.
“Hopefully through this work clinicians will no longer use this type of footplate during the healing phase from a fifth metatarsal stress fracture since the results did not indicate that the load was reduced beneath that area of the foot,” Robin M. Queen, PhD, assistant professor of orthopedic surgery and director of the Michael W. Krzyzewski Performance Lab at Duke University, told O&P Business News.
Future research
According to the researchers, the interaction of loading the fracture and healing is not well understood and the use of the CGF may improve healing through the initiation of bone remodeling. Increasing loads beneath the lateral column with the CGF would need to be examined in future studies among patients with fifth metatarsal stress fractures while monitoring the healing process.
The researchers also believe other factors can increase plantar loading and create risk factors for fifth metatarsal fractures. Shear force may exist between the foot, shoe and rigid carbon footplate, and could be a key factor in tissue and bone injury. Both axial loading and shear stresses may affect healing from a fifth metatarsal stress fracture and therefore need to be further studied to understand the risk of potential injury during various athletic maneuvers.
“Future work in this area needs to focus on ways of unloading the fifth metatarsal or the lateral column of the foot during dynamic tasks both in patients who are recovering from injury as well as athletes who are at increased risk of these types of stress fractures,” Queen said. — by Casey Tingle
Disclosure: Queen has no relevant financial disclosures.
