A cavovarus foot deformity was simulated in cadaver specimens by inserting metallic wedges of 15° and 30° dorsally into the first tarsometatarsal joint. Sensors in the ankle joint recorded static tibiotalar pressure distribution at physiological load. The peak pressure increased significantly from neutral alignment to the 30° cavus deformity, and the centre of force migrated medially. The anterior migration of the centre of force was significant for both the 15° (repeated measures analysis of variance (ANOVA), p = 0.021) and the 30° (repeated measures ANOVA, p = 0.007) cavus deformity. Differences in ligament laxity did not influence the peak pressure. These findings support the hypothesis that the cavovarus foot deformity causes an increase in anteromedial ankle joint pressure leading to anteromedial arthrosis in the long term, even in the absence of lateral hindfoot instability

To study the effect of ligament injuries and surgical repair we investigated the three-dimensional kinematics of the ankle joint complex and the talocrural and the subtalar joints in seven fresh-frozen lower legs before and after sectioning and reconstruction of the ligaments. A foot movement simulator produced controlled torque in one plane of movement while allowing unconstrained movement in the remainder. After testing the intact joint the measurements were repeated after simulation of ligament injuries by cutting the anterior talofibular and calcaneofibular ligaments. The tests were repeated after the Evans, Watson-Jones and Chrisman-Snook tenodeses. The range of movement (ROM) was measured using two goniometer systems which determined the relative movement between the tibia and talus (talocrural ROM) and between the talus and calcaneus (subtalar ROM). Ligament lesions led to increased inversion and internal rotation, predominantly in the talocrural joint. The reconstruction procedures reduced the movement in the ankle joint complex by reducing subtalar movement to a non-physiological level but did not correct the instability of the talocrural joint

Anatomical atlases document safe corridors for placement of wires when using fine-wire circular external fixation. The furthest posterolateral corridor described in the distal tibia is through the fibula. This limits the crossing angle and stability of the frame. In this paper we describe a new, safe Retro-Fibular Wire corridor, which provides greater crossing angles and increased stability. In a cadaver study, 20 formalin-treated legs were divided into two groups. Wires were inserted into the distal quarter of the tibia using two possible corridors and standard techniques of dissection identified the distance of the wires from neurovascular structures.

In both groups the posterior tibial neurovascular bundle was avoided. In group A the peroneal artery was at risk. In group B this injury was avoided. Comparison of the groups showed a significant difference (p < 0.001).

We recommend the Retro-Fibular wire technique whereby wires are inserted into the tibia mid-way between the posteromedial border of the fibula and the tendo Achillis, at 30° to 45° to the sagittal plane, and introduced from a posterolateral to an anteromedial position. Subsequently, when using this technique in 30 patients, we have had no neurovascular complications or problems relating to tethering of the peroneal tendons.

The biomechanics of the patellofemoral joint can become disturbed during total knee replacement by alterations induced by the position and shape of the different prosthetic components. The role of the patella and femoral trochlea has been well studied. We have examined the effect of anterior or posterior positioning of the tibial component on the mechanisms of patellofemoral contact in total knee replacement. The hypothesis was that placing the tibial component more posteriorly would reduce patellofemoral contact stress while providing a more efficient lever arm during extension of the knee.

We studied five different positions of the tibial component using a six degrees of freedom dynamic knee simulator system based on the Oxford rig, while simulating an active knee squat under physiological loading conditions. The patellofemoral contact force decreased at a mean of 2.2% for every millimetre of posterior translation of the tibial component. Anterior positions of the tibial component were associated with elevation of the patellofemoral joint pressure, which was particularly marked in flexion > 90°.

From our results we believe that more posterior positioning of the tibial component in total knee replacement would be beneficial to the patellofemoral joint.

Post-traumatic arthritis is a frequent consequence of articular fracture. The mechanisms leading to its development after such injuries have not been clearly delineated. A potential contributing factor is decreased viability of the articular chondrocytes. The object of this study was to characterise the regional variation in the viability of chondrocytes following joint trauma. A total of 29 osteochondral fragments from traumatic injuries to joints that could not be used in articular reconstruction were analysed for cell viability using the fluorescence live/dead assay and for apoptosis employing the TUNEL assay, and compared with cadaver control fragments.

Chondrocyte death and apoptosis were significantly greater along the edge of the fracture and in the superficial zone of the osteochondral fragments. The middle and deep zones demonstrated significantly higher viability of the chondrocytes. These findings indicate the presence of both necrotic and apoptotic chondrocytes after joint injury and may provide further insight into the role of chondrocyte death in post-traumatic arthritis.