Michael E. Graham

The Effect of HyProCure Sinus Tarsi Stent on Tarsal Tunnel Compartment Pressures in Hyperpronating Feet

Tarsal tunnel syndrome is characterized by increased pressure in the tarsal tunnel. In hyperpronation, there is excessive abnormal pronation resulting from partial displacement of the talus on the calcaneus. In this study, we hypothesized that hyperpronation caused by talotarsal instability will lead to increased pressure in the tarsal tunnel and porta pedis. We also hypothesized that the pressure in these compartments will decrease following an extra-osseous talotarsal stabilization procedure using HyProCure(®). Pressures in the tarsal tunnel and porta pedis were measured in 9 fresh-frozen cadaver specimens using an intracompartmental pressure monitor system. Pressures were measured with the foot in neutral and hyperpronated position, before and after stabilization using HyProCure. For the tarsal tunnel, pressure in the neutral position with and without HyProCure was 3 ± 3 mm Hg and 4 ± 3 mm Hg, respectively (P = .159). However, for the hyperpronating foot, the pressure decreased from 32 ± 16 mm Hg to 21 ± 10 mm Hg (P < .001) following the placement of HyProCure. In the porta pedis, pressure in the neutral position with and without HyProCure was 2 ± 2 mm Hg and 2 ± 2 mm Hg, respectively (P = .168). However, for the hyperpronating foot, the pressure decreased from 29 ± 15 mm Hg to 18 ± 11 mm Hg (P < .001) following the placement of HyProCure. The pain caused by compression of the posterior tibial nerve in the tarsal tunnel and its branches in the porta pedis, owing to hyperpronation, may be alleviated by implantation of HyProCure.

Extraosseous Talotarsal Stabilization Using HyProCure® in Adults: A 5-year Retrospective Follow-up

The purpose of this retrospective study was to determine long-term functional outcomes and device tolerance achieved in adult patients who chose to undergo an extraosseous talotarsal stabilization procedure HyProCure(®) for the treatment of flexible talotarsal joint deformity. Eighty-three adult patients participated in this study. Postoperative subjective assessment of device performance was evaluated using Maryland Foot Scores, which were collected at a mean follow-up period of 51 months. The mean postoperative Maryland Foot Score was 88 out of 100; postoperatively, 52% of cases reported complete alleviation of foot pain, 69% of cases had no limitations on their foot functional abilities, and 80% of cases reported complete satisfaction with the appearance of their feet. The implant was removed in 7 out of 117 cases (removal rate: 6%) due to prolonged pain of the anterior talofibular ligament (4 cases), psychogenic reaction (2 cases), and postoperative infection (1 case). The long-term positive subjective outcomes and excellent patient satisfaction obtained in this study may imply that extraosseous talotarsal stabilization was effective in stabilizing the talotarsal joint complex and eliminating excessive abnormal pronation, thus reducing pain and improving quality of life of the patients; it represents a possible treatment option for partial talotarsal dislocation in cases with flexible and reducible deformity.

Evaluating Plantar Fascia Strain in Hyperpronating Cadaveric Feet Following an Extra-osseous Talotarsal Stabilization Procedure

Abnormal talotarsal joint mechanics leading to hyperpronation is implicated as one of the most common causes of plantar fasciopathy. In patients with hyperpronating feet, the plantar fascia experiences excessive tensile forces during static and dynamic weight-bearing activities because of excessive medial longitudinal arch depression. For the purposes of this study, we hypothesized that plantar fascia strain in hyperpronating cadaveric feet would decrease after intervention with an extra-osseous talotarsal stabilization (EOTTS) device. A miniature differential variable reluctance transducer was used to quantify the plantar fascia strain in 6 fresh-frozen cadaver foot specimens exhibiting flexible instability of the talotarsal joint complex (i.e., hyperpronation). The strain was measured as the foot was moved from its neutral to maximally pronated position, before and after intervention using the HyProCure(®) EOTTS device. The mean plantar fascia elongation was 0.83 ± 0.27 mm (strain 3.62% ± 1.17%) and 0.56 ± 0.2 mm (strain 2.42% ± 0.88%) before and after intervention, respectively (N = 18, variation reported is ± 1 SD). The average plantar fascia strain decreased by 33%, and the difference was statistically significant with p < .001. From this cadaveric experiment, the reduction in plantar fascia strain suggests that an EOTTS device might be effective in stabilizing the pathologic talotarsal joint complex and the medial longitudinal arch and in eliminating hyperpronation. An EOTTS procedure might offer a possible treatment option for plantar fasciopathy in cases in which the underlying etiology is abnormal talotarsal biomechanics.

Radiographic Evaluation of Navicular Position in the Sagittal Plane—Correction Following an Extraosseous Talotarsal Stabilization Procedure

The navicular drop in the sagittal plane on weight-bearing is a valid indicator of foot pronation. Dislocation of the talus on the tarsal mechanism results in hyperpronation, which can lead to excessive navicular drop. The purpose of the present study was to radiographically determine the efficacy of HyProCure(®) in realigning the navicular bone in hyperpronating feet. We hypothesized that following the placement of HyProCure(®), the navicular height would increase significantly compared to its preoperative value. Radiographs of 61 adult patients (86 feet) who received HyProCure(®) without adjunctive hindfoot or midfoot soft tissue or osseous procedures were analyzed. The distance of the navicular with respect to the cuboid was measured from the pre- and postoperative weight-bearing lateral radiographs. Additionally, we measured foot length to normalize the navicular to cuboid distance. The postoperative radiographs were taken at an average follow-up of 17 days. The mean preoperative true navicular to cuboid distance was 19 ± 6 mm as compared to a mean postoperative value of 24 ± 5 mm. The mean pre- and postoperative normalized navicular to cuboid distances were 0.098 ± 0.029 and 0.125 ± 0.027, respectively (± 1 SD). The postoperative increase in the true and normalized navicular to cuboid distance was statistically significant (p < .001). HyProCure(®) was effective in improving the anatomic alignment of the talonavicular joint by reducing excessive navicular drop. This indicates reduction of excessive abnormal pronation and stabilization of the medial column of the foot, which can also lead to reduction in the excessive forces placed on the supporting soft tissue structures.

Effect of extra-osseous talotarsal stabilization on posterior tibial tendon strain in hyperpronating feet.

Posterior tibial tendon dysfunction is considered one of the most common causes of progressive adult acquired flatfoot deformity. The etiology leading to the dysfunction of posterior tibial tendon remains controversial. The purpose of this study was to quantify strain on the posterior tibial tendon in cadaver feet exhibiting hyperpronation caused by flexible instability of the talotarsal joint complex. We hypothesized that posterior tibial tendon strain would decrease after a minimally invasive extra-osseous talotarsal stabilization procedure. A miniature differential variable reluctance transducer was used to measure the elongation of posterior tibial tendon in 9 fresh-frozen cadaver specimens. The elongation was measured as the foot was moved from its neutral to maximally pronated position, before and after intervention with the HyProCure(®) extra-osseous talotarsal stabilization device. The mean elongation of the posterior tibial tendon (with respect to a fixed reference point) was found to be 6.23 ± 2.07 mm and 3.04 ± 1.85 mm, before and after intervention, respectively (N = 27; variation is ± 1 SD). The average elongation reduced by 51% and was statistically significant with p < .001. Strain on the posterior tibial tendon is significantly higher in hyperpronating feet. An extra-osseous talotarsal stabilization procedure reduces excessive abnormal elongation of the posterior tibial tendon by minimizing excessive abnormal pronation. This minimally invasive procedure may thus provide a possible treatment option to prevent or cure posterior tibial tendon dysfunction in patients exhibiting flexible instability of the talotarsal joint complex.

Effect of Extra-osseous Talotarsal Stabilization on Posterior Tibial Nerve Strain in Hyperpronating Feet: A Cadaveric Evaluation

Excessive abnormal strain or tension on the posterior tibial nerve in feet exhibiting talotarsal instability has been considered one of the possible etiologic factors of tarsal tunnel syndrome. The suggested treatment options in such cases include stabilization of the talotarsal joint complex in a corrected position, which might help minimize the abnormal forces placed on the posterior tibial nerve due to over stretching. The primary goal of this study was to quantify strain on the posterior tibial nerve in feet exhibiting hyperpronation caused by talotarsal instability, before and after an extra-osseous talotarsal stabilization (EOTTS) procedure. We hypothesized that the excessive strain placed on the posterior tibial nerve in hyperpronating cadaveric feet would be reduced significantly after intervention using the HyProCure(®) EOTTS device. Posterior tibial nerve strain was quantified in 9 fresh-frozen cadaver specimens. A miniature differential variable reluctance transducer was used to measure nerve elongation as the foot was moved from its neutral to a maximally pronated position, before and after intervention. The mean elongation of the posterior tibial nerve (with respect to a fixed reference point) decreased by 43% after the EOTTS procedure (i.e., from 5.91 ± 0.91 mm to 3.38 ± 1.20 mm; N = 27). The reduction was statistically significant at p < .001. HyProCure(®) was effective in stabilizing the talotarsal joint complex, thus reducing the excessive amount of strain placed on the posterior tibial nerve. Clinical implications of this study suggest the use of EOTTS devices in the treatment of tarsal tunnel syndrome.

Surgical Treatment of Hyperpronation Using an Extraosseous Talotarsal Stabilization Device: Radiographic Outcomes in 70 Adult Patients

The purpose of this study was to determine radiographic correction achieved in adult patients treated with an extraosseous talotarsal stabilization (EOTTS) procedure. Patients diagnosed with flexible/reducible talotarsal joint dislocation (partial) underwent surgical correction with the HyProCure(®) EOTTS device. Preoperative and postoperative weightbearing radiographs taken in the anteroposterior (AP) and lateral views for a total 95 feet (in 70 patients) were analyzed to determine standardized radiographic angles, and to quantify the correction obtained after the EOTTS procedure. Postoperative radiographs were taken at an average follow-up of 17 days from the surgery date. The mean preoperative and postoperative talar second metatarsal angles (measured from the AP radiographs) were 24.8° ± 1.0° and 5.8° ± 0.9°, respectively, that is, mean decrease by 19°. The mean preoperative and postoperative talar declination angles (measured from the lateral radiographs) were 25.1° ± 0.7° and 19.4° ± 0.5°, respectively, that is, mean decrease by 5.7°. The mean preoperative and postoperative calcaneal inclination angles (measured from the lateral radiographs) were 21° ± 0.7° and 21.8° ± 0.7°, respectively, that is, mean increase by 0.8°. Postoperatively, the talar second metatarsal and talar declination angles were reduced to average values reported in the literature for normal feet. This study shows the efficacy of a minimally invasive EOTTS procedure in restoring the normal angular relationships between hindfoot and forefoot osseous structures on weightbearing, in both the transverse and sagittal planes. This indicates stabilization of the talotarsal joint complex and elimination of hyperpronation, which may lead to reduced pain, improved foot functional abilities, and patient satisfaction.

Validation of the Talar–Second Metatarsal Angle as a Standard Measurement for Radiographic Evaluation

BACKGROUND Radiographs provide valuable information for assessing osseous foot deformities and aid in accurate diagnosis. The radiographic angular measurements can be used to establish a relationship between the forefoot and the hindfoot that will present valuable information about normal versus pathologic alignment of the foot. The talar-first metatarsal (T1M) angle is frequently used as one of these angles in this capacity; however, there are limitations to the anteroposterior T1M angle. We present a more consistent, reproducible, and accurate measurement for determining foot abnormalities in the transverse plane using the T2M angle instead of the T1M angle. METHODS Seventy feet in 35 participants (12 men and 23 women) were considered for this study. Individuals were selected on the basis of the established inclusion and exclusion criteria. Anteroposterior radiographs were taken in the angle and base of gait, the neutral calcaneal stance position (NCSP), and the resting calcaneal stance position (RCSP). Three observers measured these angles using three different methods. RESULTS The mean ± SD T2M angle was 2.95° ± 7.16° in NCSP and 18.61° ± 7.21° in RCSP. No significant differences were found among the measurements made by the three observers using slightly varying procedures in NCSP and RCSP (P > .05). The intraclass correlation coefficients among the measurements were 0.905 in NCSP and 0.937 in RCSP. Bland-Altman plots showed very good agreement between the measurements made by the three observers. CONCLUSIONS The anteroposterior T2M angle gives a consistent and reproducible measurement that provides accurate information about foot alignment.