The use of neck modular adapter is a relative new solution for hip revision arthroplasty. This device assure a lot of advantages for the orthopaedic surgeon because Bioball can be use in different situations in order to solve different complications: hip prosthesis dislocation, correction of length (up to +21mm), save an old stem not mobilized, reduction of operation length.

The hip prosthesis dislocation, in spite of the continuous progress of implants’ materials and design, is still an actual event in the orthopaedic clinical practice, both after total hip replacement or a endoprosthesis. Furthermore, dislocation has an important social-economic impact because of a protracted hospitalization and rehabilitation and elevated costs of an eventual revision. Although using heads with a diameter larger than 28 mm we obtain virtually a greater range of motion, with a contemporary increase of degree necessary to cause the head-neck impingement, the risck of dislocation hasn’t a significant increase using head with a diameter of 22 mm.

Neck modular adapters (Bioball) allow to correct easily the biomechanics parameters of the dislocated prosthesic joint, avoiding the revision of the stem. Other indications for the use of the neck modular adapter are total hip replacement and intraoperatory correction of the limb length. Vantages are the possibilty to obtain a great range of motion through a small thickness of the 12/14 adapter, the possibility to extend the limb length up to 21 mm and to use ceramic heads during revisions, because the combination head/neck has a tribological unweared surface. In fact, in normal conditions, if the stem is not mobilizated, the use of ceramic head is rash; the Bioball adapter, instead, can be used with a old stem, so we can set a ceramic head. Every stem with a Biolox cone can be combined with a metal or ceramic head up to the 5XL size (+21 mm) through a Bioball adapter; in this way the cup is not removed.

We have two kinds of neck modular adapters: 12/14 allow both to extend the neck and to correct the offset, and 14/16 that allow to extend only the neck, because of the largest diameter of the prosthesic neck and the small thickness of the adapter. For these neck modular adapters exist different sizes, from M to 5XL (+21mm). Recently to these two types of Bioball were introduced also solutions for special stems (like for Exeter, ABG I, ABGII, PCA and others) We have also proving heads and necks. The proving and definitive heads have to be of the Bioball system because these are inserted on a modular neck with a no-standard diameter.

In the common practice the use of these adaptors has not to be considered as a routinary procedure, but have to be taken in consideration as a valid aid for orthopaedic surgeon to quickly and less invasively, solve technically demanding procedures with a real benefit for high-surgical risk patients.

Long-term stability of total hip arthroplasty (THA) depends on the integration between osseous tissue and the biomaterial implant. Integrity of the osseous tissue requires the contribution of mesenchymal stem cells and their continuous differentiation into an osteoblastic phenotype.

Some studies, like Wang ML et al., show that chronic exposure to titanium and zirconium oxide wear debris may contribute to decreased bone formation at the bone/implant interface by reducing the population of viable human mesenchymal stem cells (hMSCs) and compromising their differentiation into functional osteoblasts.

On the basis of our good experience in the use of Exeter technique in revision surgery of THA, two years ago we started to utilize bone grafts mixed with growth factors in order to improve grafts incorporation and implant fixation. At the moment we are studying the use of hMSCs during hip revision surgery, employing polyethylene cup to reduce the possible titanium and zirconium oxide debris. hMSCs are obtained with MarrowsStim Concentration Kit (Biomet Biologics Europe) by 60 ml of patient’s bone marrow.

Clinical outcomes and quality of life are evaluated on the basis of Harris Hip Score, Womac score and SF-36 score, while bone graft incorporation features are assessed with post operative computed tomography (CT) examination and further CT controls at two, four and eight months after surgery.

Femoral off-set is the perpendicular distance between femur longitudinal axle and the femoral head’s rotation’s centre. Femoral off-set influences following yardsticks: stability of the joint, range of movement (ROM), muscular forcibleness, solicitations on the femoral component and acetabular component’s usury. From numerous radiographies studies, is shown as off-set is not an indefeasible measure, but an average with a range of variability. Offset is one of the most important yardsticks to consider during the pre-operating planning since, as is broadly documented, it has a positive effect on the functionality of the prosthesis; difficulty remains to individualize the optimal offset value in patient with bilateral coxofemural pathology or carriers of opposite side total hip prosthesis. Modular necks act indipendently in three spatial variables allowing to reach 27 points in the space, disposing of heads with three lenghts the real disponibility become of 81 points.

Usually we estimate the sizes and the orientation of the components manually and through a radiographic intra-operative control in order to choose the best match head-neck.

If we make a minimum mistake in cup position, the use of modular necks allow to correct this failure to obtain the most correct anatomic position producing negligible debris and the reduction of the mechanic stress.

Basing on our experience we think that the possibility to change length and version independently and sequentially is the unique technique avaible to correct the implant’s orientation, even if in our series we have choose neutral neck in most cases. To obtain better functional outcome we are studing a device based on gait analysis and superficial electromyography to calculate pre and post operative off-set. The data that we have achieved are still too few to be able to produce results; if there is possible, presenting them in future editions.