Denis Huten

Medium-term osteolysis with the Wallaby I ® deep-dished total knee prosthesis

BACKGROUND Highly congruent total knee prostheses were introduced in the 1990s in the hope of decreasing polyethylene wear, thereby minimising loosening and particle-induced peri-prosthetic osteolysis. Despite promising long-term outcomes, substantial rates of aseptic loosening were reported with conventional gamma-irradiated polyethylene inserts, suggesting that highly reticulated polyethylene should be used instead. We assessed medium-term outcomes of the Wallaby I® total knee prosthesis with a deep-dished tibial insert made of conventional gamma-irradiated polyethylene. HYPOTHESIS We hypothesised that the deep-dished Wallaby I® prosthesis was associated with similar or lower rates of aseptic loosening and peri-prosthetic osteolysis compared to posterior-stabilised prostheses. MATERIALS AND METHODS At our institution, 121 consecutive patients underwent total knee arthroplasty (TKA) with a deep-dished cemented prosthesis (Wallaby I®, Sulzer/Centerpulse, Zürich, Switzerland) between 2001 and 2005. Among them, 89 had complete follow-up data over a 4-year period and a mean follow-up of 96 months. We retrospectively analysed the clinical and radiographic IKS scores in these 89 patients. RESULTS Osteolysis with aseptic loosening required revision TKA of 10 knees after a mean follow-up of 81 months. Mean 9-year prosthesis survival was 88±17%. Four inserts exhibited evidence of delamination. A fracture of the postero-medial aspect of the tibial baseplate beneath a zone of insert wear was found in 1 knee and gross mobility of the insert on the baseplate in 6 knees. The other 79 patients had good clinical and radiographic outcomes with a mean range of active knee flexion of 108±15°. DISCUSSION The medium-term outcomes in our study were inferior to those reported with posterior-stabilised tibial components. Sporadic variations in polyethylene quality may explain the cases of osteolysis (shelf oxidation). In addition, the increased shear stresses related to the deep-dish design may increase backside wear, thereby compromising insert fixation to the baseplate. We believe the Wallaby I® prosthesis should no longer be used, and we recommend computed tomography follow-up of patients harbouring this prosthesis. LEVEL OF EVIDENCE Level IV (retrospective study).

Are ligament-tensioning devices interchangeable? A study of femoral rotation

BACKGROUND During total knee arthroplasty (TKA), femoral rotation can be adjusted either in relation to bony landmarks or by tensioning the ligaments with the knee in 90° of flexion. The primary objective of this study was to compare femoral rotations achieved using various ligament-tensioning devices. The secondary objective was to compare these femoral rotations to that indicated by the transepicondylar axis (TEA). MATERIAL AND METHODS We performed 13 posterior-stabilised TKA procedures using HiFit (Ceraver(®)) on cadaver knees. Before performing the posterior condyle cut, we used an original method to measure the femoral rotation induced by five different ligament-tensioning devices (2 with a ratchet mechanism, 1 with screws, 1 force-sensing device, and 1 with spacer blocks) and the central tibio-femoral distance (CTFD). RESULTS Both ratchet tensioners provided significantly greater mean external rotation values (P=0.002), of 4.94° and 4.46°, respectively, compared to the force-sensing and spacer tensioners. Significant differences were found across devices for CTFD, with a mean difference of about 2mm between the ratchet and screw tensioners versus the force-sensing and spacer tensioners. The mean differences in rotations obtained using the tensioners versus the TEA were close to 0° but with standard deviations greater than 4°. CONCLUSION Femoral rotation was dependent on the distraction force applied to the joint. Tensioners that did not measure the distraction force were associated with greater distraction force and external rotation values. The TEA criterion did not reliably indicate good ligament balance. LEVEL OF EVIDENCE Experimental study.

The Use of a Cemented Dual Mobility Socket to Treat Recurrent Dislocation: A Prospective Evaluation

Methods: A prospective series included 51 patients (39 females, 12 males) with a mean age of 71.3 ± 11.5 years presenting with recurrent dislocation (mean 3.3 ± 1.4). The mean number of previous THA was 1.8 ± 1.1 (1-6). A single cup design was used (Medial cup, Aston Medical, France) consisting of a stainless steel outer shell with grooves with a highly polished inner surface articulating with a mobile intermediate polyethylene component with an opening diameter smaller than the 22.2 mm femoral head. No locking ring or other means of constraint was used.

74 Résultats de la prothèse bipolaire humérale dans le traitement de l’ostéonécrose post-traumatique

Introduction L’osteonecrose est une complication grave des fractures de l’extremite superieure de l’humerus. En l’absence d’atteinte de la glene, la prothese humerale est le traitement de choix mais elle se heurte a plusieurs difficultes : cals vicieux ou pseudarthrose des tuberosites, lesions de la coiffe. Notre but etait d’evaluer les resultats de la prothese bipolaire humerale dans le traitement de l’osteonecrose post-traumatique. Materiel et Methodes La serie comportait 15 protheses, pratiquees chez 6 hommes et 9 femmes, âges en moyenne de 68 ans (55-83). 8 fractures avaient ete traitees par osteosynthese (plaques, broches ou clous). L’osteonecrose etait survenue en moyenne 2 annees apres la fracture (4 fragments : 10, 3 fragments : 5). Au moins un tendon etait rompu dans tous les cas. Toutes les necroses ont ete classees selon la classification de Steinberg (Stades 3 : 6 ; stade 4 : 9). L’etat clinique pre et postoperatoire a ete evalue selon Constant et nous avons recherche sur les radiographies au dernier recul des signes de descellement humeral et d’usure glenoidienne. Resultats Le recul moyen etait de 5 ans (3 a 7 ans). Le score de Constant absolu moyen preoperatoire etait de 25 points sur 100, avec 2,5 points pour la douleur, 4,2 pour l’activite, 9,5 pour la mobilite et 0,7 pour la force. Les mobilites actives etaient de 63,8° pour l’elevation anterieure, 45° pour l’abduction et 12° pour la rotation externe. Au dernier recul, le score de Constant absolu moyen postoperatoire etait de 39 points avec 10,3 points pour la douleur, 10,8 pour l’activite, 13,8 pour la mobilite, et 4,1pour la force. L’elevation anterieure moyenne active etait de 83,7°, l’abduction de 70,4° et la rotation externe de 29,1°. Tous les parametres ont ete ameliores significativement (p Discussion La prothese bipolaire humerale procure a moyen terme des resultats modestes dans cette indication. La double mobilite ne procure pas de maniere evidente de meilleurs resultats fonctionnels que les protheses humerales et ne permet pas de prevenir l’usure glenoidienne. Certaines ruptures de coiffe etendues en particulier au tendon du muscle sous-scapulaire exposent a l’instabilite superieure et anterieure et sont une limite de la methode. Elles doivent faire discuter une prothese inversee, notamment chez les sujets âges.