Bone density and functional results after femoral revision with a cementless press-fit stem.

INTRODUCTION: The influence of radiographic bone density changes in the area surrounding a total hip arthroplasty (THA) revision with a cementless press-fit stem is unknown, notably in terms of functional results. We have therefore conducted a study aiming to (1) propose a radiographic method to assess bone density, (2) measure the functional effects of reduced bone density, and (3) determine the factors contributing to these modifications. HYPOTHESIS: A reduction in radiographic bone density has a negative influence on the functional result after revision using a cementless press-fit stem. MATERIAL AND METHODS: We retrospectively assessed 150 THA revisions at a mean follow-up of 6.3 ± 3.2 years (range, 2-15 years). The clinical assessment was based on the Harris Hip Score. Bone density modifications were measured radiographically and the method was evaluated. The change in bone density was classified into two groups: (1) bone density not reduced or < 2 Gruen zones (118 cases [79%]); (2) bone density reduced ≥ 2 zones (32 cases [21%]). The variables showing a potential influence were the Cortical Index (CI), the type of primary stability with the press-fit system, and the femoral implant length. RESULTS: Inter- and intraobserver reliability of radiographic bone density measurement was evaluated as moderate or good (Kappa, 0.58; 0.60 and 0.67, respectively). For the Harris Hip Score at follow-up, there was a borderline statistical relation between stages 1 and 2: for the 118 stage 1 patients, this score was 83.62 ± 11.54 (range, 27-99) versus 78.34 ± 15.98 (range, 62-91) for stage 2 patients (P = 0.09). A CI ≤ 0.44 showed mediocre bone quality contributing to decreased bone density (P < 0.02). On the other hand, there was no statistically significant relation with the type of primary fixation (P = 0.34) or the length of the implant (P = 0.23). CONCLUSIONS: A cementless revision femoral stem can induce a reduction in bone density with possible functional effects. The negative role played by bone scarcity on the functional score is confirmed, and even though the difference is not statistically significant, we suggest using a short stem when this is possible.

Stem subsidence after total hip revision: 183 cases at 5.9 years follow-up.

INTRODUCTION: Secondary subsidence of a revision femoral stem is often a negative predictive sign for successful osseointegration and perfect long-term stability. MATERIALS AND METHODS: We performed a retrospective study in a series of 183 revision total hip replacements between 1996 and 2000 to evaluate the importance and risk factors of secondary subsidence with a cementless press-fit design femoral stem as well as this subsidence's consequences to osseointegration. RESULTS: Secondary subsidence did not occur in 80 cases (53%), was between 0 and 4mm in 41 cases (27%); between 5 and 10mm in 17 cases (12%) and was greater than 10mm in 12 cases (8%). Mean subsidence of all patients was 3mm (0-30). There was a statistically significant negative correlation between subsidence and the quality of osseointegration (P=0.03). There was no significant relationship between component diameter and stem subsidence (P=0.9). The presence of preoperative bone deficiencies did not increase the risk of secondary subsidence (P=0.2). CONCLUSION: In the case of revision with press-fit stems, the importance of secondary subsidence should not be overestimated, because it usually does not negatively affect satisfactory osseointegration.

[Mucoid pseudo-cysts of the sheath of the external popliteal sciatic nerve. Apropos of 2 cases]. / Les pseudo-kystes mucoides de la gaine du nerf sciatique poplité externe. A propos de deux observations

Two cases of paralysis of the etxernal popliteal sciatic nerve are described. They are secondary to the development of a pseudo-cyst containing mucoid matter within the connective tissue sheath of the nerve itself. The authors describe the pathological anatomy of these lesions and discuss their aetiology, favouring the theory of mucoid degeneration of the connective tissues of the nerve sheath. They give brief indication of the clinical symptoms and emphasize the need for early but simplified surgery, ruling out any nerve resection.