Introduction and purpose: The failure of a TKP is often due to deficiencies related to alignment, stability or fixation. The purpose of this paper is to determine how loads are distributed when each of two tibial stem models are implanted and to assess those loads densitometrically.

Materials and methods: We analyzed 20 patients with a cemented TKR and divided them into two groups according to whether their tibial stem was cylindrical or cruciform. We studied the evolution of periprosthetic bone density under the internal and external bearings and under the stem. We performed a densitometry after 2 years postop and controls after 3 and 7 years.

Results: In the cylindrical stem group the evolution of mean bone density under the internal bearing after 2 and 3 years was 0.92±0.20 to 0.90±0.19 g/cm2 respectively; mean bone density under the external bearing was 0.97±0.36 to 0.97±0.38 and under the stem it was 1.05±0.25 to 1.08±0.26. In the cruciform group, density under the internal bearing was 0.75±0.08 to 0.71±0.05, under the external one it was 0.89±0.01 to 0.85±0.07 and under the stem it was 1.06±0.06 to 1.04±0.29. In the long term (three patients were lost to follow-up), comparing the cylindrical prostheses to one another, we can say that the evolution under the internal bearing after 2, 3 and 7 years was 0.88, 0.84 and 0.80 g/cm2 respectively; under the external bearing it was 0.79, 0.78 and 0.77 and under the stem it was 0.99, 0.96 and 0.99.

Conclusions: After TKR a progressive loss of bone density is observed. Comparatively, the reduction is greater in the cruciform stem. The internal compartment is the most affected one.

Introduction and Objectives: The purpose of this study is to analyse the clinical and radiographic results of revision total hip prosthesis using femoral stems with diaph-yseal fixation.

Materials and Methods: We assessed failure of the primary prosthesis based on Paprosky’s classification to identify the femoral defect and determine the optimal component for revision, keeping in mind the difficulty of classifying bone defects based on radiographic parameters. The most commonly-used replacement models were KAR revision stems (wide, straight, long necks and hydroxyapatite-coated along the entire length) and Restoration-T3 stems (diaphyseal fixation, modular, fits different necks, Wagner model progression, particularly indicated to facilitate extraction of cement using a buried diaphyseal osteotomy). Clinical evaluation was done using the Merle D’Aubigné and Postel scales modified by Charnley. Radiographic evaluation of prosthetic stability and osseointegration was done using Engh’s criteria, checking for presence or absence of radiolucency, migration, pedestal, and increase or decrease of endosteal and periprosthetic density (calcar, diaphysis, and greater trochanter).

Results: We examined 47 KAR stems and 16 Restoration-T3 stems, with an average follow-up period of 4.1 years (range: 1–9 years) and an average patient age of 69.4 years (range: 40–79 years). Of these, 6 were Paprosky type 1, 36 were type II, 14 were type IIIA, 5 were type IIIB, and 2 were type IV. Average preoperative clinical score was 9.76 points. Aetiology in all cases was aseptic loosening of a primary prosthesis, with the exception of one case of a delayed Corynebacterium infection. There were 2 partial Monk prosthesis revisions and 3 periprosthetic fractures. Average postoperative clinical score was 15.83 points. There were no deep infections or dislocations. Radiolucency was noted in only one case, and no migrations of more than 2 mm were seen. No further stem revisions were required in this series, though we believe a future revision will be necessary in at least one case.

Discussion and Conclusions: The use of femoral stems with diaphyseal fixation is an acceptable alternative in revision surgery of the hip, even in cases of major bone deficit. Modular stems have the added advantage of versatility to adapt to a great variety of prosthetic salvage procedures.