Focus is on ultrasound, hip strength
By Jordana Bieze Foster
Research presented in February at the Combined Sections Meeting of the American Physical Therapy Association highlighted underappreciated clinical characteristics of posterior tibial tendon disorder that could influence patient management.
Tendon thickness as measured using high-frequency ultrasound may help determine which patients with Stage II PTTD are most likely to benefit from conservative interventions and which might be better candidates for surgery, according to research from Upstate Medical University in Syracuse, NY.
Ultrasound imaging identified 12 Stage II patients with abnormal tendon thickening, seven with tendon enlargement and five with tendon atrophy. Mean tendon cross sectional area was 39.7 mm2; those with tendon enlargement averaged 53.4 mm2 while those with atrophy averaged 24.6 mm2.
Tendon thickness was not visibly evident prior to imaging, nor were there apparent functional differences between subjects at presentation. However, the researchers did observe significant kinematic differences between the two groups. Patients with tendon enlargement demonstrated significantly greater range of motion for hindfoot inversion/eversion, forefoot plantar/dorsiflexion, and total excursion; forefoot abduction/adduction did not differ significantly between groups.
Although PTTD is typically thought to be associated with tendon enlargement as the result of degeneration, the Syracuse findings show that tendon atrophy also occurs. The kinematic differences related to relative tendon thickness could help explain inconsistencies in patient response to exercise interventions, and knowing the cross sectional area of an individual patient’s tendon could facilitate more effective patient management.
“Targeted exercises to move the foot may be possible in the tendon enlargement group, and conservative or alternative treatments may be indicated,” said Christopher Neville, PT, PhD, an assistant professor of physical therapy at Upstate Medical University, who presented the results at the Combined Sections Meeting. “The tendon atrophy group may be surgical candidates, or if they don’t have surgery, the goal of treatment may be to protect the secondary structures that maintain foot posture and stability.”
A second study from the University of Southern California suggests that practitioners may also want to consider proximal joint kinetics in their patients with PTTD.
After anecdotally noting increased frontal plane motion at the hip in patients being seen for PTTD, researchers compared hip and calf muscle performance in 17 female patients with Stage I PTTD and 17 healthy matched controls. Patients reported a history of symptoms lasting from six months to one year.
They found that the PTTD patients demonstrated significantly lower levels of strength and endurance across the board, with 33.8% less hip extensor torque, 38.5% less hip extensor endurance, 28.5% less hip abduction torque, 27% less hip abduction endurance, and 62.9% less calf muscle strength. Interestingly, these effects were seen in the uninvolved limb as well as the involved limb. The PTTD patients also covered significantly less distance on the six minute walk test (497 m vs 571 m) and reported as much as a 50% increase in pain following the test.
These two sets of findings may be related, said Lisa M. Noceti-DeWit, DPT, ATC, adjunct instructor of clinical physical therapy at USC, who presented her group’s findings at the Combined Sections Meeting. The researchers theorize that because the PTTD patients walk more slowly, their muscles—all the way up the lower extremity—are being underutilized and over time lose their strength and endurance capacity.
“Walking does not depend solely on the actions of the foot and ankle,” Noceti-DeWit said.
The researchers are unable to tell from this study whether the decreased walking velocity occurred as a result of the pain of PTTD or whether other mechanisms may have been involved. Nevertheless, the findings suggest that practitioners treating patients with PTTD should not limit their focus to the most distal aspects of the lower extremity.