Background: Hindfoot trauma including ankle and subtalar sprains may be followed by osteochondral lesions and persisting pain originating from posttraumatic arthritis.
Hypothesis: “Acute severe” supination sprains and “mild supination sprains with increasing ligamentous incompetence” of the hindfoot lead to medial ankle and subtalar stress concentrations that may contribute to osteochondral lesions (OCLs) and subsequent arthritis.
Study Design: Controlled laboratory study.
Methods: “Acute severe” sprains and “mild sprains with increasing ligamentous incompetence” (consecutive anterior talofibular ligament [ATFL], calcaneofibular ligament [CFL], and lateral talocalcaneal ligament [LTCL] transections) were simulated in human lower leg specimens (7 different specimens for each condition). The effect on the migration of the center of force (COF) and on the tibiotalar and subtalar pressures at 700-N (acute severe) and 150-N (mild sprain with increasing ligamentous incompetence) axial static and dynamic loads, respectively, was recorded using pressure sensors.
Results: In the “acute severe” sprain, the peak pressure increase reached the level of significance in the ankle (P = .042) and in the subtalar medial facet (P = .046). The ankle COF migrated significantly toward the medial (P = .001) and posterior (P = .023) directions. In the “mild sprain with increasing ligamentous incompetence” condition, the ankle (P = .018) and subtalar (medial facet, P = .022) peak pressure increased significantly with intact ligaments and with all ligaments cut. The ankle COF migrated significantly toward the medial direction when the ATFL and CFL or when all 3 ligaments were severed. The anteroposterior ankle COF migration was anterior when all ligaments were intact or when only the ATFL was severed but posterior when the CFL or when the CFL and the LTCL were severed in addition.
Conclusion: Next to chronic inhomogeneous load distribution in the unstable hindfoot and shear stress during sprains, intra-articular pressure elevation (impact) in the ankle and subtalar joint during hindfoot supination sprains with intact ligaments or incompetent ligaments likely contributes to OCLs of the medial talar dome and the medial subtalar facet.
Clinical Relevance: Intra-articular hindfoot pressure elevation (impact) in “acute severe” and in “mild hindfoot supination sprains with increasing ligamentous incompetence” is substantial for the development of OCLs at the medial midtalar dome and the medial facet of the subtalar joint.
Background: Osteochondral allograft transplantation is technically demanding. It is not always possible to place the surface of the graft perfectly flush with the surrounding cartilage. One must often choose between placing at least some portion of the surface of the graft slightly elevated or recessed. The effect of this choice on joint contact pressure is unknown.
Purpose: This study was undertaken to determine the effect of graft height mismatch on joint contact pressure in the ankle.
Study Design: Controlled laboratory study.
Methods: Ten human cadaveric ankles underwent osteochondral grafting by removal then replacement of an osteochondral plug. Six conditions were tested: intact, graft flush, graft elevated 1.0 mm, graft elevated 0.5 mm, graft recessed 0.5 mm, and graft recessed 1.0 mm. Joint contact pressures were measured with a Tekscan sensor while loads of 200 N, 400 N, 600 N, and 800 N were sequentially applied.
Results: The peak contact pressure at the graft site for the flush condition was not significantly different from the intact condition for either medial or lateral lesions. In contrast, peak pressure on the opposite facet of the talar dome was significantly increased during the flush condition for the medial but not the lateral grafts. Elevated grafts experienced significantly increased contact pressures, whereas recessed grafts experienced significantly decreased pressures. These changes were greater for lateral than for medial lesions. Reciprocal changes in joint contact pressures were found on the opposite facet of the talus with elevated grafts on the lateral side and recessed grafts on the medial side.
Conclusion: Flush graft placement can restore near-normal joint contact pressure. Elevated graft placement leads to significant increases in joint contact pressure at the graft site. Recessed graft placement leads to a transfer of pressure from the graft site to the opposite facet of the talus.
Clinical Relevance: Osteochondral grafts in the talus should be placed flush if possible or else slightly recessed.
Background: Autologous osteochondral transplantation procedures provide hyaline cartilage to the site of cartilage repair. It remains unknown whether these procedures restore native contact mechanics of the ankle joint.
Purpose: This study was undertaken to characterize the regional and local contact mechanics after autologous osteochondral transplantation of the talus.
Study Design: Controlled laboratory study.
Methods: Ten fresh-frozen cadaveric lower limb specimens were used for this study. Specimens were loaded using a 6 degrees of freedom robotic arm with 4.5 N·m of inversion and a 300-N axial compressive load in a neutral plantar/dorsiflexion. An osteochondral defect was created at the centromedial aspect of the talar dome and an autologous osteochondral graft from the ipsilateral knee was subsequently transplanted to the defect site. Regional contact mechanics were analyzed across the talar dome as a function of the defect and repair conditions and compared with those in the intact ankle. Local contact mechanics at the peripheral rim of the defect and at the graft site were also analyzed and compared with the intact condition. A 3-dimensional laser scanning system was used to determine the graft height differences relative to the native talus.
Results: The creation of an osteochondral defect caused a significant decrease in force, mean pressure, and peak pressure on the medial region of the talus (P = .037). Implanting an osteochondral graft restored the force, mean pressure, and peak pressure on the medial region of the talus to intact levels (P = .05). The anterior portion of the graft carried less force, while mean and peak pressures were decreased relative to intact (P = .05). The mean difference in graft height relative to the surrounding host cartilage for the overall population was –0.2 ± 0.3 mm (range, –1.00 to 0.40 mm). Under these conditions, there was no correlation between height and pressure when the graft was sunken, flush, or proud.
Conclusion/Clinical Relevance: Placement of the osteochondral graft in the most congruent position possible partially restored contact mechanics of the ankle joint. Persistent deficits in contact mechanics may be due to additional factors besides graft congruence, including structural differences in the donor cartilage when compared with the native tissue.
