Background. Understanding of the pathogenetic mechanisms of non-union can not ignore bone remodelling and its cascade of processes at cellular and biochemical levels culminating in an incomplete structural and functional restoration of the damaged bone.

Osteoprotegerin (OPG) is expressed by osteoblasts and functions as a decoy receptor that is able to control and to regulate osteoclastogenesis and therefore to prevent bone resorption.

The objectives of our study were: to investigate OPG serum levels in shaft fractures non-union compared to controls; to assess the use of OPG as a marker for the early identification of fracture non-unions.

Material and Methods. OPG serum levels were determined in 25 male patients (aged between 20–59 years, mean 35.44 ± 11.53) with a shaft fracture non-union at the time of minimum six months (mean 16.83 ± 10.87) since trauma and age matched with 25 male controls patients (aged 20–59 mean 35.44 ± 11.76) with a shaft fracture healed. All patients were correctly operated with different types of synthesis for complex fractures of a long bone (humerus, femur, tibia). Osteocalcin, bone isoenzyme of alkaline phosphatase and deoxypyridino-line (DPD) were also measured.

Results. OPG levels were significantly higher in non-union cases compared to age matched controls (mean 10.17 ± 3.08 vs 8.54 ± 1.18 U/L; p=0.0084). DPD level was significantly higher in cases respect to controls (mean 7.9 ± 2.74 vs 3.8 ± 1.00 nmolDPD/mmol urinary creatinine excretion; p=0.0001). ROC analysis and the classification for probability cut-off show a very good negative predictive value (84%) for a cut-off of OPG 10 U/L, indicating that all patients having OPG lower than 10 U/L are probably free of non-union. Similarly, for an increase of 1 U/L of OPG there is an increase of probability of being a case of 92%. Higher OPG levels clearly carries a higher risk of non-union, thus indicating the usefulness of OPG evaluation in the follow-up of fractured patients. Larger groups will allow the estimation of the correct level of OPG threshold by age, which we are now able to estimate of about 8 U/L for young patients and 10 U/L for older ones in our population.

Conclusion. Shaft fracture non-union may occur following appropriate osteosynthesis in consequence of a condition of altered bone osteoclastic activity. OPG could be directly involved in the pathogenesis of shaft fractures non-union and seems to be an accurate predictive marker in non-union evaluation.

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.