By Christina Hall Nettles
Many studies of posterior tibial tendon dysfunction (PTTD), or adult acquired flatfoot disorder, have focused on foot kinematics and benefits of bracing for pain relief and increased ambulation. But new findings from the University of Southern California in Los Angeles suggest clinicians also look higher along the kinetic chain when determining an effective treatment.
A September 2011 Journal of Orthopedic & Sports Physical Therapy study by USC researchers revealed women with PTTD performed significantly fewer single leg heel raises and repeated sagittal and frontal plane nonweight-bearing leg lifts; had at least 27% less hip abduction endurance; showed nearly 40% less hip extensor endurance; and reported a 50% increase in pain after a six minute walk test when compared with age-matched controls. Hip torque and calf muscle strength were also dramatically inferior, and, most interestingly, weakness was apparent in the involved and uninvolved limbs of participants with PTTD.
“The hip deficits that appeared bilaterally were surprising, as our hypothesis was that the hip deficits would be on the same side as the PTTD,” said Lisa M. Noceti-DeWit, DPT, ATC, adjunct instructor of clinical physical therapy at USC. Noceti-DeWit coauthored the study with university colleagues, including Kornelia Kulig, PhD, PT, a Catherine Worthingham fellow. “At this point, our research team is not yet able to speculate why the hip deficits are bilateral. We do feel that clinicians should assess hip strength in women with PTTD and provide appropriate intervention if deficits are found.”
Hip weakness may not be specific to women with PTTD, but reflective of general deconditioning or changes in motor control for a variety of reasons, explained Jeff Houck, PT, PhD, associate professor of physical therapy at New York’s Ithaca College, where he specializes in clinical biomechanics and orthopedics.
“One might ask about knee strength in these patients. If it is also lower, it would indicate more general deconditioning,” Houck said.
General strengthening approaches combined with functional exercises may be helpful, especially from a general health perspective, Houck suggested.
“However, the impact on clinical management of tendinopathy is not determined, therefore the weakness may not be specific to PTTD, but rather a secondary effect,” he said.
Women are three times as likely as men to be diagnosed with PTTD, and the disorder is most frequently found in women in their 50s. PTTD appears to peak during perimenopause, prompting research into female hormonal indicators, including estrogen receptors. A Pennsylvania State College of Medicine study, published in the December 2010 Foot & Ankle International, found no significant gender-related differences in estrogen expression in diseased posterior tibial tendons and no differences in estrogen receptors in diseased tibial tendons versus controls of healthy posterior tibial or flexor digitorum longus tendons. Larger studies may yet explain the role of estrogen in the overall health of tendons and connective tissues.
Houck suggested clinicians be cautious when employing ankle foot orthoses in women with PTTD unless the devices allow some ankle plantar flexion. His studies have shown more restrictive devices may lead to compensatory gait alterations that further weaken the ankle plantar flexors.
“The hip compensation to adapt to a decreased push off may be a stronger hip flexor contraction, resulting in a pull off rather than a push off. The further weakening of the ankle plantar flexors may aggravate the overall condition,” Houck said.
This overemphasis on hip flexion could help explain the reduced hip extensor endurance associated with PTTD in the USC study.
Changes in subtalar motion may also affect hip mechanics in patients with PTTD, Houck added.
“Subtalar inversion/eversion fine-tunes standing balance, and the hip abductors and adductors are major players in maintaining balance. Therefore, losing control at the subtalar joint as a result of PTTD may require some compensations at the hip. This may manifest as lower single leg stance time or increased trunk movements during single leg stance,” he said.
Future targeted studies exploring connections beyond the foot and ankle may elucidate whether existing hip weakness predisposes women to PTTD, or whether PTTD through its various stages complicates movement affecting both hips.
Sponsored by an educational grant from American Orthopedics Manufacturing