Dual mobility design use in preventing total hip replacement dislocation following tumor resection.

INTRODUCTION: Total hip replacement (THR) following hip tumor resection incurs a high risk of dislocation. We assessed the incidence of dislocation associated with use of a dual mobility cup,and the functional results achieved. HYPOTHESIS: Use of a dual mobility cup would reduce the risk of THR instability following hip tumor resection. MATERIAL AND METHODS: We analyzed dislocation rates in a retrospective series of 71 dual mobility cup THRs implanted following the resection of a tumor hip condition: 33 primary bone tumors and 38 bone metastases. The presenting pathology was diagnosed anatomically, and surgery classified in terms of adopted abductor system strategy. Functional results were assessed in terms of pain (analgesia on the World Health Organisation [WHO] scale), assisted walking and Musculoskeletal Tumor Society (MSTS) score. RESULTS: An overall rate of 9.8% dislocation was observed, taking into account all etiologies and contexts together. More precisely, this rate resulted from a compound figure of 5.2% in bone metastasis and 15% in primitive bone tumor. Dislocation risk depended lesson etiology than on the surgical management of the abductor system, being 3.5% in the case of abductor conservation, 9.5% in the case of abductor sectioning/reinsertion, and 18%in case of gluteus medius muscle or nerve resection. Functional improvement was consistently observed, especially in bone metastasis. At the maximal follow-up, 32 patients were not using analgesics, six were taking WHO class III analgesics, 10 class II and 23 class I. Mean MSTS score was 68.1% +/- 23.5% in bone metastasis and 59.6% +/- 17.5% in primary bone tumor.Fourteen patients could walk without assistance, 33 with a single cane, 15 with two canes and eight with a walker; one patient had not been able to resume walking. DISCUSSION: In these indications, dual mobility cups use lead to lower dislocation rates than those reported in the literature. It proved especially effective in the case of bone metastasis and consolidation surgery. In the case of primary bone tumor, it failed to prevent dislocation following acetabular resection, especially when involving the abductor muscles and/or abductor innervation, although it provided lower dislocation rates, comparable to those experienced with other techniques, when applied to limited resection. LEVEL OF EVIDENCE: IV. Retrospective therapeutic study.

[Are sacrospinal and sacrotuberal ligaments involved in sacro-iliac joint stability?]. / Rôle biomécanique des ligaments sacroépineux et sacrotubéral sur la stabilité de l'articulation sacro-iliaque Anatomie et étude expérimentale originale.

OBJECTIVES: Surgery of pudendal nerve entrapment needs the section of both sacrospinal and sacrotuberal ligaments. We asked about the potential side effect of such a section especially on sacro-iliac joint stability. MATERIAL AND METHODS: We performed a cadaveric anatomical and biomechanical study concerning six sacro-iliac joints. Joints were tested on a plateform, and results were analysed with a logiciel (Medai((R))), both especially developped for, before and after sacrospinal and sacrotuberal section. RESULTS: The computered analysis of our results proved that sacro-iliac joint has a significant range of motion, specially in youngs. Results obtained confirmed that there is no statistical difference (p<0.05) between the mobility of sacro-iliac joint with or without sacrospinal and sacrotuberal ligaments. CONCLUSION: This original experimental biomechanical study is the first able to test the influence or sacrospinal and sacrotuberal section on sacro-iliac joint stability. The section of those ligaments has no significant experimental consequence on the sacro-iliac joint stability and cannot create a postoperative instability.