Computer-assisted assessment of lateral column movement following plantar fascial release: a cadaveric study

In patients who fail conservative treatment, releasing the plantar fascia relieves heel pain but destabilizes the lateral column of the foot. After surgery, pain can present in the area of the sinus tarsi, extensor digitorum brevis muscle, between the fourth and fifth metatarsals, and at the calcaneocuboid joint. The precise mechanism and involved structures for this painful compensation remains unclear. The authors hypothesized that the lateral plantar fascial band, bifurcate and cervical ligaments, lateral talocalcaneal ligament, and interosseous talocalcaneal ligament become excessively strained after this surgery. Using eight cadaver lower extremity limbs amputated 7 cm above the ankle joint, structural changes in the foot in response to staged release of the plantar fascia were measured. All ligament, tendon, and osseous structures were exposed along the plantar, medial, and lateral aspects of the foot and ankle. Using a servohydraulic system, compressive loads in increasing increments (50 lbs) were applied along the tibial axis. Tissue and bony structure displacement in the foot was measured using images electronically captured from two fixed cameras and a digital camera following each load change. All measurements were made in pixels and converted to millimeters in a spreadsheet program. Except for plantar fascial measurements, data were expressed as percentage of initial baseline. As expected, increasing compressive loads changed all measurements [repeated measures ANOVA, p<.04]. When releasing the plantar fascia, the inferior sinus tarsi space widened (intact, 85.4+/-10.8%; 1/4 release, 87.7+/-13.0; 1/2 release, 88.3+/-9.2; 3/4 release, 91.2+/-8.8; p<.04). Lateral length increased and medial height decreased, while medial length and lateral height were unchanged as the fascia was sequentially released. Significant movement of the inferior sinus tarsi strained the bifurcate and cervical ligaments, the lateral talocalcaneal ligament, and interosseous talocaneal ligament, which may account for pain following surgery. The initial 1/4 cut of the plantar fascia exerted the greatest mechanical alteration of the foot, suggesting that a partial release may relieve heel pain while optimizing the patient's chances of maintaining structural integrity with 75% of the plantar fascia intact.