Abstract. Objective. To estimate the effect of calcar collar contact on periprosthetic fracture mechanics using a collared fully coated cementless femoral stem. Methods. Three groups of six composite femurs were implanted with a fully coated collared cementless femoral stem. Neck resection was increased between groups (group 1 = normal, group 2 = 3mm additional, group 3 = 6mm additional), to simulate failure to obtain calcar collar contact. Periprosthetic fractures of the femur were simulated using a previously published technique. Fracture torque and rotational displacement were measured and torsional stiffness and rotational work prior to fracture were estimated. High speed video recording identified if collar to calcar contact (CCC) occurred. Results between trials where calcar contact did and did not occur where compared using Mann-Whitney U tests. Results. Where CCC occurred versus where no CCC occurred, fracture torque was greater (47.33 [41.03 to 50.45] Nm versus 38.26 [33.70 to 43.60] Nm, p= 0.05), Rotational displacement was less (0.29 [0.27 to 0.39] rad versus 0.37 [0.33 to 0.49] rad, p= 0.07), torsional stiffness was greater (151.38 [123.04 to 160.42] rad. Nm-1 versus 96.86 [84.65 to 112.98] rad.Nm-1, p <0.01) and rotational work was similar (5.88 [4.67, 6.90] J versus 5.31 [4.40, 6.56] J, p= 0.6). Conclusions. Resistance to fracture and construct stiffness increased when a collared cementless stem made contact with the femoral calcar prior to fracture. These results demonstrate that calcar-collar contact and not a calcar collar per se, is crucial to maximising the protective effect of a medial calcar collar on the risk of post-operative periprosthetic fractures of the femur. Declaration of Interest. (a) fully declare any financial or other potential conflict of interest

Although cemented fixation provides excellent results in primary total hip replacement (THR), particularly in patients older than 75 years, uncemented implants are most commonly used nowadays. We compare the rate of complications, clinical and radiological results of three different designs over 75-years-old patients. 433 hips implanted in patients over 75 years old were identified from our Local Joint Registry. Group A consisted of 139 tapered cemented hips, group B of 140 tapered grit-blasted uncemented hips and group C of 154 tapered porous-coated uncemented hips. A 28 mm femoral head size on polyethylene was used in all cases. The mean age was greater in group A and the physical activity level according to Devane was lower in this group (p<0.001 for both variables). Primary osteoarthritis was the most frequent diagnoses in all groups. The radiological acetabular shape was similar according to Dorr, however, an osteopenic-cylindrical femur was most frequently observed in group A (p<0.001). The pre- and post-operative clinical results were evaluated according to the Merle-D'Aubigne and Postel scale. Radiological cup position was assessed, including hip rotation centre distance according to Ranawat and cup anteversion according to Widmer. We also evaluated the lever arm and height of the greater trochanter distances and the stem position. Kaplan-Meier analysis was done for revision for any cause and loosening. The hip rotation centre distance was greater and the height of the greater trochanter was lower in group B (p=0.003, p<0.001, respectively). The lever arm distance was lower in group C (p<0.001). A varus stem position was more frequently observed in group B (p<0.001). There were no intra- or post-operative fractures in group A, although there were five intra-operative fractures in the other groups plus two post-operative fractures in group B and four in group C. The rate of dislocation was similar among groups and was the most frequent cause for revision surgery (8 hips for the whole series). The mean post-operative clinical score improved in all groups. The overall survival rate for revision for any cause at 120 months was 88.4% (95% CI 78.8–98), being 97.8% (95% CI 95.2–100) for group A, 81.8% (95% CI 64.8–98.8) for group B and 95.3% (95% CI 91.1–99.6) for group C (log Rank: 0.416). Five hips were revised for loosening. The overall survival rate for loosening at 120 months was 91.9% (95% CI 81.7–100), being 99.2%(95% CI 97.6–100) for group A, 85.5 (95% CI 69.9 −100) for group B and 100% for group C (Log Rank 0.093). Despite a more osteopenic bone in the cemented group, the rate of peri-prosthetic fractures was higher after uncemented THR in patients older than 75 years. Although the overall outcome is good with both types of fixation, the post-operative reconstruction of the hip, which might be more reliable after cemented fixation, may affect the rate of complications in this population

The use of impaction bone grafting during revision arthroplasty of the hip in the presence of cortical defects has a high risk of post-operative fracture. Our laboratory study addressed the effect of extramedullary augmentation and length of femoral stem on the initial stability of the prosthesis and the risk of fracture. Cortical defects in plastic femora were repaired using either surgical mesh without extramedullary augmentation, mesh with a strut graft or mesh with a plate. After bone impaction, standard or long-stem Exeter prostheses were inserted, which were tested by cyclical loading while measuring defect strain and migration of the stem. Compared with standard stems without extramedullary augmentation, defect strains were 31% lower with longer stems, 43% lower with a plate and 50% lower with a strut graft. Combining extramedullary augmentation with a long stem showed little additional benefit (p = 0.67). The type of repair did not affect the initial stability. Our results support the use of impaction bone grafting and extramedullary augmentation of diaphyseal defects after mesh containment

Objectives

Recent studies have shown that modulating inflammation-related lipid signalling after a bone fracture can accelerate healing in animal models. Specifically, decreasing 5-lipoxygenase (5-LO) activity during fracture healing increases cyclooxygenase-2 (COX-2) expression in the fracture callus, accelerates chondrogenesis and decreases healing time. In this study, we test the hypothesis that 5-LO inhibition will increase direct osteogenesis.

This study explored the relationship between the initial stability of the femoral component and penetration of cement into the graft bed following impaction allografting.

Impaction allografting was carried out in human cadaveric femurs. In one group the cement was pressurised conventionally but in the other it was not pressurised. Migration and micromotion of the implant were measured under simulated walking loads. The specimens were then cross-sectioned and penetration of the cement measured.

Around the distal half of the implant we found approximately 70% and 40% of contact of the cement with the endosteum in the pressure and no-pressure groups, respectively. The distal migration/micromotion, and valgus/varus migration were significantly higher in the no-pressure group than in that subjected to pressure. These motion components correlated negatively with the mean area of cement and its contact with the endosteum.

The presence of cement at the endosteum appears to play an important role in the initial stability of the implant following impaction allografting.