Bracing and Strengthening for Posterior Tibial Tendon Dysfunction

The Foot Function Index (FFI) is a validated disease specific questionnaire that has been used to document outcomes in uncontrolled studies of PTTD. The domains of the 23 item FFI questionnaire include pain, disability, and activity limitations. The scale was originally validated in subjects with foot problems related to rheumatoid arthritis patients, and has subsequently been used to measure outcomes for a variety of foot and ankle problems including plantar fasciitis, diabetes, and PTTD. In clinical trials, the FFI has been used to detect change attributable to orthotics, plantar fasciitis, and brace use in PTTD. The three domains of the FFI include pain (FFI-Pain) range 0 to 90, disability (FFI-Disability) range 0- 90, and activity limitations (FFI-Activity Limitations) range 0 to 50. Each category asks patients to rate items relative to pain with higher scores indicating greater pain. The average of the three scales is the FFI-Total.

Time frame: Measured at Weeks 1, 6, and 12

Population: A power analysis was performed based on previous a previous study. Only the participants that completed the study are included in the analysis. One participant opted to have surgery at 2 weeks from the Brace \& Exercise group. One participant moved overseas and the other resumed cancer treatments bringing the total to 17.

The Short Musculoskeletal Function Assessment Questionnaire (SMFA) is a 46 item self-report questionnaire consisting of the Dysfunction Index, which has thirty-four items, and the Bother index which has 12 items. The Dysfunction index is used for assessment of patient perceptions of functional performance while the Bother index is used to assess patients' perceptions of the degree patients are bothered in broad areas such as recreation and leisure. The responsiveness to change of the SMFA is 10 points out a range of 100 for each scale (Dysfunction, Mobility, and Bother indexes). The SMFA is also particularly suitable for the current investigation due to the presence of a sub-category of questions from the Dysfunction Index that pertains specifically to mobility (i.e. Mobility Index). Lower scores (lowest = 0) indicate better function, mobility, and that patients are less bothered while higher scores (highest = 100) indicate worse function, mobility and that patients are bothered.

Time frame: Measured at Weeks 1, 6, and 12

A 3 dimensional foot kinematic model including the tibia, calcaneus (hindfoot), 1st metatarsal, 2-4th metatarsals and hallux was used to measure foot movement. Six infrared cameras (Optotrak Motion Analysis System, Northern Digital Inc, CAN), synchronized with force plate data (Model 9286, Kistler, Switzerland), were used to collect kinematics (60 Hz) and force (1000 Hz) data with the Motion Monitor software Version 7.24 (Motion Monitor, Innsport Training Inc, USA). Anatomically based coordinate systems were established for each segment using digitized boney landmarks consistent with a previous study. Kinematic data were smoothed using a 4th order, zero phase lag, Butterworth filter with a cut off frequency of 6 Hz. To calculate relative joint angles a Cardan angle Z-X-Y sequence of rotations was used as suggested by Cole et al. The range of possible values varies for each individual and each joint.

Time frame: Measured at Weeks 1,6 and 12

A force transducer (Model SML-200, Interface, Scottsdale, AZ) was connected in series with a resistance plate and oscilloscope (TDS 410A, Tektronix, Beaverton, OR) to display force readings. Participants were seated with their leg in an an air stirrup brace (Aircast, Inc.) mounted on uprights. The air stirrup brace was adjusted so the heel was approximately 10 cm above the resistance plate, resulting in 30 to 45 degrees of ankle plantar flexion depending on foot length. The resistance plate was mounted on ball bearing tracks in the medial/lateral direction and moleskin was used to fit to the general shape of the medial forefoot. The result was that participants could exert maximum effort against the resistance plate (medial direction) with little discomfort. This testing position essentially replicates the manual muscle test position for the posterior tibialis muscle. Force in Newtons was then divided by body mass in kilograms to calculate normalized strength (N/Kg).

Time frame: Measured at Weeks 1, 6, and 12