Beat Hintermann

Transfer of movement between calcaneus and tibia in vitro

Excessive foot eversion and/or abnormal tibial rotation have been associated with knee injuries. The mechanical coupling of leg and foot, which may be related to the aetiology of knee injuries, is still not well understood. The goal of this study was to determine in vitro, as a function of loading and flexion position of the foot, the movement transfer from calcaneal eversion-inversion to tibial rotation and vice versa occurring in the ankle-joint complex. A lower leg holding and loading device with 6 degrees of freedom was used in the investigation. Fourteen fresh-frozen, foot-leg specimens were tested. The movement transfer from calcaneus to tibia and vice versa differed significantly between the specimens. The transferred movement was not the same for all input modes. Specifically, calcaneal eversion resulted in significant internal tibial rotation; however, internal tibial rotation did not induce any calcaneal eversion. Vertical loading of the tibia and foot flexion position had a major influence on this movement transfer. The amount of calcaneal eversion transferred to internal tibial rotation depends on the individual mechanical coupling at the ankle-joint complex. Therefore excessive pronation, in running for instance, is only critical for high knee loading when coupled with a high movement transfer in the ankle-joint complex. The interindividual differences may also signal difficulties for prosthesis design in total ankle-joint replacement and for the design of shoe orthotics.

Influence of Arthrodeses on Kinematics of the Axially Loaded Ankle Complex during Dorsiflexion/Plantarflexion

The purpose of this study was to quantify the effect of selective arthrodesis (stabilization) of the ankle, subtalar, and talonavicular joints on the rotational movement of the tibia and the calcaneus occurring with dorsiflexion/plantarflexion. Six cadaver foot-leg specimens were investigated using an unconstrained testing apparatus. Simulated ankle joint arthrodesis caused a large increase in tibial rotation and calcaneal eversion-inversion. Subtalar and talonavicular stabilization did not cause as large a rotation.

Influence of Ligament Transection on Tibial and Calcaneal Rotation with Loading and Dorsi-Plantarflexion

The purpose of this study was to quantify the effect of sequential ligament transection (anterior talofibular, calcaneofibular, posterior talofibular, deltoid, and subtalar interosseous ligaments) on the rotational movement of the tibia and the calcaneus as associated with axial loading and dorsi-plantarflexing the foot. Eight cadaver foot-leg specimens were investigated using a unconstrained testing apparatus. As the ankle complex was axially loaded, almost the same internal rotation of the tibia and the same calcaneus eversion was found with and without the various degrees of lateral and medial ligament release; additional sectioning of the subtalar interosseous ligament tremendously increased the resulting tibial and calcaneal rotation. While tibial and calcaneal rotation from foot dorsi-plantarflexing did not alter significantly with transection of the lateral ligaments, almost no tibial and calcaneal rotation occurred after additional sectioning of the deltoid and subtalar interosseous ligament. These results indicate that, after release of the lateral ligaments, the foot becomes partially mechanically disconnected from the tibia by additional transection of the medial ligaments and even further disconnected after transection of the subtalar interosseous ligament.

In Vitro Kinematics of the Axially Loaded Ankle Complex in Response to Dorsiflexion and Plantarflexion

The rotational movements of the tibia and calcaneus that occur with dorsiflexion-plantarflexion and axial loading were studied in cadaver foot-leg specimens using an unconstrained testing apparatus. Independent of the foot flexion position, significant internal rotation of the tibia and eversion of the calcaneus were noted after the ankle complex was axially loaded. Independent of loading, 10° of dorsiflexion resulted in 0.1° of eversion and 2.1° of internal rotation of the tibia. Conversely, 10° of plantarflexion resulted in 1.6° of inversion and 1.3° of external rotation of the tibia. The induced rotational movements of the tibia and the calcaneus differed significantly between the specimens. These results suggest that the foot “axes” did not change by axially loading the ankle complex and they support previous reports that the ankle complex uses different axes for dorsiflexion and plantarflexion.

Influence of selective arthrodesis on the movement transfer between calcaneus and tibia in vitro.

Arthrodeses of foot and ankle are well established, accepted, and practical methods for treatment of painful joint degeneration, foot deformity, and instability. Consecutive changes in gait and over-use injuries have been explained by the created lever arms and the overall compensatory motion in the neighbouring joints, rather than by changes in the mechanical coupling of foot and tibia. Thus the purpose of this study was to quantify the change of movement transferred from calcaneus to tibia, and vice versa, for selective joint fusions (ankle, subtalar, and talonavicular joints) under different flexion and loading conditions. In six fresh cadaveric foot-leg specimens, transfer of rotational movement between calcaneus and tibia occurred in all arthrodesis conditions. Fusion of the subtalar joint, which is commonly believed to be crucial in the transfer of rotational movement in the ankle joint complex, decreased the movement transfer from calcaneal inversion to external tibial rotation about 71.8% and, vice versa, from external tibial rotation to calcaneal inversion about 35.8%. However, the movement transfer did not change when calcaneal eversion and internal tibial rotation were the input movements. The ankle (talocrural) joint must have more than 1 degree of freedom, since significant movement transfer still occurred when the subtalar joint was fused. It could be that other structures such as ligaments also play an important role in transferring movement. Consequently it may be difficult to predict the effect of a planned arthrodesis since the resulting restriction of motion and movement transfer may be substantially determined by the integrity of the surrounding soft tissue, especially the ligaments.

The subtalar joint: A complex mechanism

Subtalar joint anatomy is complex and can vary significantly between individuals. Movement is affected by several adjacent joints, ligaments and periarticular tendons. The subtalar joint has gained interest from foot and ankle surgeons in recent years, but its importance in hindfoot disorders is still under debate. The purpose of this article is to give a general overview of the anatomy, biomechanics and radiographic assessment of the subtalar joint. The influence of the subtalar joint on the evolution of ankle joint osteoarthritis is additionally discussed. Cite this article: EFORT Open Rev 2017;2:309-316. DOI: 10.1302/2058-5241.2.160050

Chronic Ankle Osteochondral and Chondral Lesions

Osteochondral and chondral lesions of the talus are commonly found following sport related trauma to the ankle joint. Conservative treatment frequently fails, and most patients undergo surgery. Several surgical treatment techniques are available, showing good short and mid-term clinical and radiological results.

The Role of Periarticular Osteotomies in Total Ankle Replacement

Careful radiographic assessment of the talar position, in all three planes, is mandatory to successfully replace an end-stage osteoarthritic ankle associated with a major deformity. As correcting resection cuts for the prosthesis may not be able to restore proper position of the talus within the ankle mortise and provide overall stability of the ankle, additional osteotomies above or below the ankle or selective fusions may be necessary to obtain a well-balanced ankle joint complex. Meticulous realignment of the forefoot and, if necessary, stabilization of the medial arch are also mandatory to achieve a good long-term outcome of total ankle replacement. In summary, the key to success is to use all treatment modalities necessary to restore appropriate alignment of the hindfoot complex.

Osteotomies Around the Ankle

Mal-alignment of the hindfoot has been found to be one of the main risk-factors for ankle joint arthritis. The deviation of the axis leads to an altered load distribution within the joint which eventually causes degenerative wear. Therefore corrective osteotomies around the ankle joint have gained increasing popularity to address early and mid-stage arthritis of the ankle joint.

Revisionen nach endoprothetischer Versorgung des oberen Sprunggelenks

Das Versagen einer Prothese kann u. a. durch die Lockerung einer oder beiden Komponenten bedingt sein. Die Versagerquote liegt bei der neueren Prothesengeneration bei etwa 3 % pro Jahr (Kotnis et al. 2006). Eine kurzlich publizierte systematische Ubersicht hat gezeigt, dass die 5-Jahres- und die 10-Jahres-Uberlebensrate bei 78 % (95 %-CI: 69,0–87,6 %) bzw. bei 77 % (95 %-CI: 63,3–90,8 %). Die haufigste Ursache eines Revisionseingriffs war dabei Lockerung oder Dislokation des Implantats (Haddad et al. 2007). In unserem Patientenkollektiv mit den mittelfristigen Ergebnissen lag die Revisionsquote bei 6,6 % (Hintermann et al. 2004). Die Prothesenlockerung kann sowohl im fruhen initialen postoperativen Verlauf als auch Jahre spater auftreten. Ein progredientes, nicht zu korrigierendes Malalignment kann ebenfalls zu einer Revision fuhren. Eine therapierefraktare ligamentare Instabilitat kann langfristig aufgrund der ungunstigen biomechanischen Situation zu einem Versagen der Prothesenkomponente fuhren. Zu den weiteren Ursachen einer Revision werden Infektionen, periprothetische Frakturen sowie nicht beherrschbare Schmerzzustande gezahlt. Zu beachten sind die teilweise heiklen Weichteilverhaltnisse, die eine mogliche Indikation zu einem Revisionseingriff stellen. Andere, eher seltene Ursachen sind die Metallallergie oder Metallunvertraglichkeit.