An abnormal lateral position of the tibial tuberosity causes distal malalignment of the extensor mechanism of the knee and can lead to lateral tracking of the patella causing anterior knee pain or objective patellar instability, characterised by recurrent dislocation. Computer tomography is used for a precise pre-operative assessment of the tibial tubercle-trochlear groove distance. A distance ...

Patellar instability is a known but catastrophic complication after total knee arthroplasty (TKA). The occurrence of bilateral dislocation of the patella after TKA is exceedingly rare. It may present as anterior knee pain, and diagnosis can easily be made clinically or by plain radiographs. Early diagnosis with surgical realignment and repair of the extensor mechanism can provide good outcomes ...

We present a case of superior dislocation of the patella trapped by interlocked osteophytes. Unlike previous reports, in which the mechanism resulted from a blow to the inferior pole, it is postulated that increased load on the extensor mechanism, combined with patella alta and patellofemoral osteophytes, caused locking of the knee in extension.

We investigated the clinical and radiological outcome of trochleaplasty for recurrent patellar dislocation in association with trochlear dysplasia in 38 consecutive patients (45 knees) with a mean follow-up of 8.3 years (4 to 14). None had recurrence of dislocation after trochleaplasty. Post-operatively, patellofemoral pain, present pre-operatively in only 35 knees, became worse in 15 (33.4%), ...

Patellofemoral arthroplasty is an infrequently used surgical technique because of its controversial results. In an attempt to improve the results, a design with a mobile-bearing poliethylene patellar component has been developed. We describe a clinical case with an unusual complication: the dislocation of poliethylene from the metal backing; and accordingly, we carried out a literature review o...

Superior dislocation of the patella is a rare diagnosis, which usually occurs after a trivial trauma. It usually requires manipulation with analgesics or may even need anaesthesia. We report a case of spontaneous reduction of the dislocation, which lead us to believe that this may be more common in the community than has been reported.

The effect of strain reversal on hardening due to high pressure torsion (HPT) was investigated using commercially pure aluminium. Hardening is lower for cyclic HPT (c-HPT) as compared to monotonic HPT (m-HPT). When using a cycle consisting of a rotation of 90° per half cycle, there is only a small increase in hardness if the total amount of turns is increased from 1 to 16. Single reversal HPT (...

In the light of recent progress in coarsening the discrete dislocation mechanics, we consider two questions relevant for the development of a mesoscale, size-dependent plasticity: (i) can the phenomenological expression for size-dependent energy, as quadratic form of Nye's dislocation density tensor, be justified from the point of view of dislocation mechanics and under what conditions? (ii) ho...