Yasunori Suda

Effect of tibial coronal inclination on hindfoot kinematics: A biomechanical simulation study

Tibial coronal inclination is often recognized in everyday life, but the compensatory kinematic changes to maintain plantigrade of the hindfoot in response to tibial coronal inclination remain unclear. Lower legs and foot specimens obtained from seven human cadavers were loaded vertically with traction of Achilles’ tendon in different tibial inclinations: 0° (neutral), 5°, and 10° medial inclination, and 5° and 10° lateral inclination. The orientations of the tibia, talus, and calcaneus were recorded under vertical load by a three-dimensional digitizing stylus. The angular changes of the talocrural and subtalar joints in the tibial inclinations from neutral were analyzed. The heights of the origins of the talus and calcaneus were also recorded. As the tibia was medially inclined from neutral, the talocrural joint was significantly more dorsiflexed. The subtalar joint was significantly more inverted, plantarflexed, and internally rotated. However, such significant changes in the joint angles were not observed when the tibia was laterally inclined. The height of the talus decreased as the tibia was medially inclined, but it was vice versa when laterally inclined. The compensatory motions of the hindfoot to tibial medial inclination involved coupled movement of both the talocrural and subtalar joints; such motions flatten the medial foot by decreasing the height of the talus. However, such compensatory capacities of the hindfoot to tibial lateral inclinations were limited. Tibial medial inclination under axial loading affects the kinematics of the hindfoot, and this is an important factor to consider in the treatment of flatfoot as well as foot orthotic/footwear intervention.

Quantification of vertical free moment induced by the human foot–ankle complex during axial loading

Axial loading of the human cadaver lower leg is known to generate eversion of the calcaneus and internal rotation of the tibia if the plantar surface of the foot does not slide on the floor. Such kinematic coupling between calcaneal eversion and internal tibial rotation has been described previously, but no studies have actually quantified the innate ability of the human foot to generate ground reaction moment around the vertical axis of the floor (vertical free moment) due to axial loading of the human cadaver lower leg. This study investigated the vertical free moment generated by eight cadaveric lower leg specimens loaded vertically with traction of the Achilles’ tendon using a six-component force plate. The vertical free moments in all specimens were oriented toward the direction of internal rotation, and the mean magnitude of the vertical free moments was −1.66 N m when an axial load of 450 N was applied. A relatively large ground reaction moment can be applied to the body during walking due to the innate structural mobility of the foot. The structurally embedded capacity of the human foot to generate the vertical free moment may facilitate compensation of the moment generated around the vertical axis of the body during walking due to trunk rotation and leg swing.

Minimally invasive distal linear metatarsal osteotomy combined with selective release of lateral soft tissue for severe hallux valgus

BACKGROUND Minimally invasive techniques for hallux valgus have been widely used to treat mild to moderate hallux valgus deformities. The purpose of this study was to evaluate the clinical and radiographic outcomes of distal linear metatarsal osteotomy (DLMO), which is one of the minimally invasive techniques, for severe hallux valgus. METHODS 95 patients (141 feet) with severe hallux valgus underwent DLMOs. Lateral soft tissue release (LSTR) was performed at the same time for the cases selected by an original manual test. The satisfaction level, the Japanese Society of Surgery of the Foot (JSSF) hallux scale score, and weight-bearing radiographs of the foot were assessed preoperatively and after more than 24 months. In addition, the clinical and radiographic outcomes were compared among three groups divided by the kind of LSTR: no LSTR; manual correction; and open release through skin incision. RESULTS Although the first metatarsal bone was significantly shortened, dorsiflexed, and elevated on postoperative radiographs, the rate of satisfaction was 87.2% (123/141), and the mean JSSF hallux scale score improved significantly from 60.4 (44-73) to 90.4 (65-100). The mean hallux valgus and intermetatarsal angles also improved significantly from 45.5° (40.0-60.0°) to 10.3° (-28.0-40.9°) and from 19.9° (14.0-28.7°) to 8.3° (-1.6-18.5°), respectively. Delayed union (18 feet), metatarsalgia (16 feet), recurrence (22 feet), and hallux varus (22 feet) were observed, and they were more obvious in DLMO combined with open release through a skin incision. CONCLUSIONS DLMO combined selectively with LSTR is an effective procedure for correcting severe hallux valgus. However, the indication for open release with DLMO should be considered carefully.

Radiographic Shape of Foot With Second Metatarsophalangeal Joint Dislocation Associated With Hallux Valgus

Background: Second metatarsophalangeal (MTP) joint dislocation is associated with hallux valgus, and the treatment of complete dislocation can be difficult. The purpose of this study was to radiographically clarify the characteristic foot shape in the presence of second MTP joint dislocation. Methods: Weight-bearing foot radiographs of the 268 patients (358 feet) with hallux valgus were examined. They were divided into 2 groups: those with second MTP joint dislocation (study group = 179 feet) and those without dislocation (control group = 179 feet). Parameters measured included the hallux valgus angle (HVA), first-second intermetatarsal angle (IMA), second MTP joint angle, hallux interphalangeal angle (IPA), second metatarsal protrusion distance (MPD), metatarsus adductus angle (MAA), and the second metatarsal declination angle (2MDA). Furthermore, the dislocation group was divided into 3 subgroups according to second toe deviation direction: group M (medial type), group N (neutral type), and group L (lateral type). Results: The IPA and the 2MDA were significantly greater in the study group than in the control group. By multiple comparison analysis, the IMA was greatest in group M and smallest in group L. The IPA was smaller and 2MDA greater in group N than in group L. The HVA and MAA in group L were greatest, and MPD in group L was smallest. Conclusions: The patients with second MTP joint dislocation associated with hallux valgus had greater hallux interphalangeal joint varus and a second metatarsal more inclined than with hallux valgus alone. The second toe deviated in a different direction according to the foot shape. Level of Evidence: Level III, retrospective comparative study.