Abstract
In congenital and acquired angular deformities of the coxofemoral joint, hip prosthesis presents considerable difficulties. The aim of this study is to analyse the different surgical solutions for this problem.
In the geographical area of G. Pini Institute, where congenital hip dysplasia is endemic and where also historically the surgical outcome of various types of osteotomy (both acetabular and femoral) have been investigated, this problem has often been encountered. We have evaluated several parameters, also with respect to particular cases in which tailored prosthetic solutions were required, to establish which kind of prosthetic treatment is most reliable today.
From 1994 to 2002 more than 6000 surgical hip prosthesis procedures were carried out at our institute: 750 in dysplastic hips and 112 after osteotomy. In our clinical division we also evaluate patientsin the pre-surgical phase with the DEXA, which gives qualitative and quantitative data about peri-prosthestc bone. After the first period of using standard, customised prostheses with no modular neck, we have progressively increased the use of a modular stem with press-fit cups that guarantee minimal bone sacrifice and a good recovery of articular biomechanics. In particular, with the use of modular components for the head and neck it is easy to reinstate the centre of rotation and achieve good offset and good lower limb length, without “escamotages” such as the use of a larger stem not perfectly inserted in the femoral diaphysis and the non-physiological cup position to avoid the risk of luxation.
We have progressively abandoned the use of PE, which is the cause of debris and should be avoided in angular deformities: in patients under 65 years of age we use ceramic-on-ceramic bearing surfaces with monob-lock insert, whereas in patients over 65 we prefer to use metal-on-metal bearing surfaces (always monoblock).
Deformities caused by the same pathological condition resulting in surgical osteotomy make implantation of standard prosthetic models impossible; our surgical experience suggests the use of different prosthetic models.
The use of custom-made prostheses has progressively been reduced thanks to the development of suitable modular prostheses which suit these patients perfectly.
In the past few years the use of cemented prostheses in these patients has decreased: according to our experience the use of cementless prostheses in relatively young subjects allows a good range of motion but above all it is useful to preserve bone in view of a possible future revision.
