Unusual mechanical complications of unicompartmental low contact stress mobile bearing patellofemoral arthroplasty: a cause for concern?

The Low Contact Stress Patellofemoral Arthroplasty (LCS PFA) is a newer design belonging to the second generation of inlay type implants, addressing the problems encountered in the first generation models (Lubinus & Richard's). The cemented mobile bearing metal backed patellar component in this system is "modular"; allowing interchangeable usage with either the trochlear component in a PFA or the femoral component of a total knee arthroplasty, thus obviating the need for patellar revision during conversion of PFA to TKA. The younger active patient with a PFA may exert extreme joint reaction forces on their patellar implant, rendering early loosening of the patellar implant. The endurance of this implant with repeated flexion beyond 90 degrees is also a concern. We describe a series of three unusual mechanical failures associated with this particular design of metal backed patellar component of the unicompartmental LCS patellofemoral arthroplasty.

Slipped upper femoral epiphysis in a child with spondyloepiphyseal dysplasia tarda: a rare coincidence?

We present a report of a child with Spondyloepiphyseal dysplasia tarda (SED) presenting with non-traumatic, insidious onset hip pain with limited internal rotation. Radiographs revealed a left sided stable slipped upper femoral epiphysis (SUFE). To our knowledge an association between these two pathologies has not been reported previously in the literature and hence a tentative commom etiopathogenesis between SED and SUFE is discussed. Patients who have SED often develop hip pain as part of the natural history of the condition. This case highlights the need to be vigilant regarding the potential for SUFE as a cause of hip pain rather than attributing it to the dysplasia itself in these patients.

Is secondary radiological follow-up of infants with a family history of developmental dysplasia of the hip necessary?

The practice of regular radiological follow-up of infants with a positive family history of developmental dysplasia of the hip is based on the widespread belief that primary acetabular dysplasia is a genetic disorder which can occur in the absence of frank subluxation or dislocation. We reviewed all infants who were involved in our screening programme for developmental dysplasia of the hip, between November 2002 and January 2004, and who had a normal clinical and ultrasound examination of the hip at six to eight weeks of age, but who, because of a family history of developmental dysplasia of the hip, had undergone further radiography after an interval of 6 to 12 months. The radiographs of 89 infants were analysed for signs of late dysplasia of the hip and assessed independently by three observers to allow for variability of measurement. There were 11 infants (11%) lost to follow-up. All the patients had normal radiographs at the final follow-up and none required any intervention. We therefore question the need for routine radiological follow-up of infants with a positive family history of developmental dysplasia of the hip, but who are normal on clinical examination and assessment by ultrasound screening when six to eight weeks old.