CLINICAL APPROACHES TO THE STEM MOBILIZATION IN THR: OUR EXPERIENCE USING UNCEMENTED STEMS

Abstract

The great diffusion of total hip replacement in young patients has generated as a consequence an increasing in the number of prothesic failing associated with more or less extended bone loss. We mean analyze the various surgical solution to this problem. In the planning of the best surgical treatment the evaluation of the degree of osteolysis is the more correct technique; in fact we have supported the classical radiological exams with the miralometry as DEXA (supplying quantitative data on the periprotesic bone stock). Data obtained in this way allow choosing more carefully the best protheses in the preoperative planning: mid or long stem, with or without bone graft, with or without materials which may promote a bone rehabilitation. Anyway the surgeon should have all the possible protheses solutions as it happens to change the operative plan during the operation. These are the criterion of choice of the revision protheses, keepin’ in consideration data acquired by D.E.X.A.:

1. GIR 1 (loosening and or widing of the femural shaft with reducing of the cortical without interruption of walls): If the mobilized protheses is uncemented and DEXA supplies datas about a good bone stock we try to use a first implant uncemented protheses

2. GIR 2 (widing of the femural shaft with reducing of the cortical with interruption of one wall): In these cases we use two kind of protheses anatomical or not with an oversized stem which increases the stability of the implant.

3. GIR 3 (widing of the femural shaft with reducing of the cortical with interruption of two or more walls): In this cases we prefer using a long stem straight protheses, unless there is an increase of the osteolitic lesion; this protheses allows a stable anchorage thanks the optimized lenghts thus opposing to the rotational strenghts and allowing the transmission of translational strenghts both in the proximal and in the distal direction. The new calcar shape assure better adapting to the bone stock. With the increase of the osteolitic region, according to Wagner’s criteria, we have to change plan in orther to find a better anchorage. In fact SL Wagner protheses regains the coesion with the rehabsorbed bone cavity thus creating a relative stability in the immediate post operatory. Lately a high osteodeformation fills in the bone lacks. For this reason the muscolar insertion shouldn’t be receded around the thick cortical. This uncemented revision stem get anchored through a distal anchorage guaranteed by the conical shape, the stem is straight. The pre operative planning is compulsory in order to evaluate the measure of the osteotomic cut.

4. GIR 4 (massive proximal circumferential bone loss). In the past, in case of complete femoural osteolisys the gold standard was the implant of great resection tumoral-cemented Muller’s stem as well as Kotz’s uncemented stems.

Kotz’s design, on the bases of follow up studies, seem to support Wagner’s theories about the distant anchorage: There is an attempt of periprothesic corticalization even though the huge bone loss. In the last years we have performed a revision modular distally anatomic stem characterized by a metafi sarial leaning on the proximal component.

The weight bearing is progressive on the base of the radiological evolution and DEXA as well. The complete bearing will be allowed only after a sufficient bone restoration.

In our experience uncemented protheses in the stem revision can allow in mid and long term good results expecially keeping in consideration that these patients had already coxofemural problems. The range of motion is difficulty improvable so the results must be weighted on the bases of the previous clinical situation. If patients are monitored in order to operate as soon as possible in case of mobilization, the use of uncemented protheses can be a valid way for the functional recovering of these patients.