Bone integration of new stemless hip implants (proxima vs. nanos). A DXA study: preliminary results.

The development of short femoral prostheses has the advantage to preserve bone and soft tissues, restore hip geometry, permit mini-invasive techniques and allow quickly return to an active life, but very few studies described bone reaction to these new designed prostheses. The aim of the present study was to evaluate the osseointegration of two different partial neck retained stemless hip prosthesis at one year after surgery, measured by the changes of periprosthetic bone mineral density (BMD) in 5 regions of interest (ROIs) using a dual-energy X ray absorptiometry (DXA) device. The signs of stress-shielding were evaluated by standard radiographs. Thirty-two uncemented primary total hip arthroplasty (THA) patients allocated into 2 groups were evaluated. In the first group (n=19) a Proxima (De-Puy-J&J) hip stem was implanted. In the second group (n=12) a Nanos (Smith & Nephew) hip stem was used. We found that both the implants preserve metaphyseal bone stock and increase periprosthetic BMD. In Nanos prostheses a significant higher BMD values were observed in region of interest (ROI) 3 and 4 (p<0.05). No differences were found in ROIs 1, 2, and 5. Proxima stem seem to produce a physiological strain distribution in the femur. No signs of stress-shielding were present in both the implants. In conclusion, this preliminary DXA analysis showed a physiological integration of both the stems that reproduces the biomechanical stress of proximal femur. New designed short stem implants showed optimal osseointegration after one year, and therefore appears an excellent alternative to traditional long stem hip prostheses.

[Non-cemented reimplantation of failed hip prosthesis]. / Reimpianti non cementati nei fallimenti delle protesi d'anca.

After reviewing their series of prosthetic revisions and comparing it with other reports in literature, the authors reassess, where possible, classic conservative intervention as well as the indications for cemented prostheses given the poor long-term reliability of the bone-cement interface. The authors emphasize the always more frequent incidence of prosthetic loosening and the resulting need for surgical revision, especially in patients who were under 65 years of age at the time of primary prosthetic replacement. Finally, the authors present their clinical and surgical experience in revision using cementless implants, which they prefer in this type of operation.

[Long-term scintigraphic follow-up study of the hip prosthesis]. / L'indagine scintigrafica nel controllo a distanza delle protesi d'anca.

The authors emphasize the importance of the bone scan in long-term follow-ups of total hip arthroplasty and describe some technical details of the examination. The changes revealed in the bone scan are confirmed by the operative report. Even though the number of patients in the study was relatively small, the fact that the bone scan taken of patients with cementless total hip replacements revealed no pathological changes is considered significant.

[The initial findings in 50 cases of the cementless hip prosthesis]. / Primi rilievi su 50 casi di protesi d'anca non cementate.

The authors, after putting forth several biomechanical premises, discuss their experience in total hip arthroplasty (THA) using a PCA-type press fit cementless prosthesis with partial Madreporic covering. Several cases which demonstrate the versatility of this type of replacement are discussed in depth. Even though the short follow-up precludes definitive conclusions, use of cementless total hip replacements must be considered a valid option in the future, especially in cases of early onset of hip pathology.