Aurélien Mulliez

Usefulness of sonication for diagnosing infection in explanted orthopaedic implants

BACKGROUND Orthopaedic implant infection is a rare but serious complication whose optimal treatment requires an accurate microbiological diagnosis. The objective of this study was to determine whether culturing sonicated explants improved sensitivity compared to culturing standard sonicated soft-tissue samples. HYPOTHESIS Cultures of explant sonication fluid are more sensitive than cultures of soft-tissue sonication fluid in patients with implant infection. METHODS This single-centre retrospective study included all sonication fluid samples from implants explanted in orthopaedic surgery theatres for any reason. The microbiological results of the implant sonication fluid cultures were compared to those of cultures of sonicated soft-tissue and bone samples taken during the same procedure. The primary evaluation criterion was the difference in microorganisms recovered from explant sonication fluids versus fluid/tissue cultures. RESULTS The study included 187 explants removed between September 2009 and June 2015. Of the definite infections, 83% were identified by explant sonication, 86% by fluid/tissue cultures, and 91% by both techniques combined. Explant sonication recovered causative organisms in 10 patients with definite infection but negative fluid/soft tissue cultures. Antibiotic therapy prior to explantation was associated with lower sensitivity of explant sonication (57% vs. 67% for fluid/soft tissue cultures). CONCLUSION Explant sonication improved the diagnosis of infection when combined with fluid/soft tissue cultures. LEVEL OF EVIDENCE IV, retrospective single-centre study.

Complications with cement spacers in 2-stage treatment of periprosthetic joint infection on total hip replacement

INTRODUCTION The aim of the present study was to assess our management of infected total hip replacement in indications for 2-stage surgical treatment according to current guidelines when a cement spacer has been used. The study hypothesis was that the complications rate related to cement spacers is low. MATERIAL AND METHOD A single-center retrospective study included 26 patients receiving a spacer between the two stages of total hip replacement, over a 5 year period. We analyzed the spacers used, mechanical complications, infectious complications and the second stage of surgery. RESULTS During the interval between surgeries, in the 26 patients, there were 19 spacer-related mechanical complications (73% of patients): 11 dislocations (42.3%), 5 spacer fractures (19.2%), 5 femoral bone lyses or fractures (19.2%) and 3 acetabular lyses or fractures (11.5%). In 4 cases, complications were associated. The greater the femoral offset of the spacer, the more frequent were femoral bone lyses or fractures (p=0.05), and the smaller the offset the more frequent were acetabular lyses or fractures (p=0.05). The rates of mechanical complications (p=0.003) and spacer fracture (p=0.02) were significantly greater in older patients. There were 4 cases of reinfection (19%): i.e., an 81% treatment success rate. One reinfection implicated a new bacterium: methicillin-susceptible Staphylococcus aureus. The second surgical stage was significantly longer in complex bipolar revision (p=0.009). CONCLUSION The present results showed a high risk of spacer-related complications, and thus the importance of selection of patients liable to derive real benefit and those for whom a Gilderstone procedure would be preferable. LEVEL OF EVIDENCE IV, retrospective study.

Irradiation at 11 kGy conserves the biomechanical properties of fascia lata better than irradiation at 25 kGy

&NA; The objective of this study was to determine the biomechanical properties of the fascia lata and the effects of three preservation methods: freezing, cryopreservation with dimethylsulfoxide solution and lyophilization; and to compare the effects of low‐dose (11 kGy) and normal‐dose (25 kGy) gamma‐ray sterilization versus no irradiation. 248 samples from 14 fasciae latae were collected. Freezing samples were frozen at −80 °C. Cryopreservation with dimethylsulfoxide solution samples were frozen with 10 cl dimethylsulfoxide solution at −80 °C. Lyophilization samples were frozen at −22 °C and lyophilized. Each preservation group were then randomly divided into 3 irradiation groups. The cryopreservation with dimethylsulfoxide solution samples had significantly worse results in all 3 irradiation conditions. Youngs modulus was lower for the freezing samples (p < 0.001) and lyophilization samples groups (p < 0.001). Tear deformation was lower for the freezing samples (p = 0.001) and lyophilization samples groups (p = 0.003), as was stress at break (p < 0.001 and p < 0.001). Taking all preservation methods together, samples irradiated at 25 kGy had worse results than the 0 kGy and 11 kGy groups in terms of Youngs modulus (p = 0.007 and p = 0.13) and of stress at break (p = 0.006 and p = 0.06). The biomechanical properties of fascia lata allografts were significantly worse under dimethylsulfoxide cryopreservation. The deleterious effects of irradiation were dose‐dependent. HighlightsFirst study about 11 kGy applied to tendonsLarge possible clinical applicationLot of specimen tested

RM Pressfit® cup: good preliminary results at 5 to 8 years follow-up for 189 patients

Aim The RM Classic® cup shows very good results. The RM Pressfit® cup has an equatorial pressfit; it is a monoblock implant without metalback. The aim of this study was to evaluate retrospectively the survival of this implant, monitoring patients for at least 5 years in all consecutive cases operated in our centre. Methods Between February 2006 and December 2008, our department performed 189 consecutive nonselected primary total hip arthroplasties using the RM® Pressfit cup, and all of these were included in the study. The operative technique involved an anterolateral approach. The latest follow-up evaluation was performed at a minimum of 5 years after the index arthroplasty. Results The mean follow-up was 6.5 years (5-8 years). We had preoperative information for 186 of the 189 patients. 102 patients were seen in consultation (54.0%), 46 (24.3%) patients were contacted by phone, 37 (19.6%) patients died, and 4 patients (2.1%) were lost for unknown reasons. Of the 189 arthroplasties, 6 (3.2%) required revision; 4 (2.1%) for infection, 1 (0.5%) for significant haematoma with persistent deglobulisation and 1 (0.5%) for periprosthetic calcification during the 5 to 8 years following the operation. No hip was revised because of aseptic loosening. The mean annual wear rate based on the last follow-up at 5 years minimum was 0.065 mm per year. We observed no migration, 1 femoral loosening and no acetabular loosening. Conclusions Our study finds a good survival rate which is compatible with the 94% at 20 years with RM Classic®. These results are suggestive but must be confirmed with long-term studies.