This study investigated bone regeneration in the femoral neck canal of osteoporotic rats using a novel animal model. A calcium sulphate (CS)/hydroxyapatite (HA) carrier was used to deliver a bisphosphonate, zoledronic acid (ZA), locally, with or without added recombinant human bone morphogenic protein-2 (rhBMP-2). Twenty-eight-week-old ovariectomized Sprague-Dawley rats were used. A 1 mm diameter and 8 mm long defect was created in the femoral neck by drilling from the lateral cortex in the axis of the femoral neck, leaving the surrounding cortex intact. Three treatment groups and one control group were used: (1) CS/HA alone, (2) CS/HA + ZA (10 μg) (3) CS/HA + ZA (10 μg) + rhBMP-2 (4 μg), and (4) empty defect (control). The bone formation was assessed at 4 weeks post surgery using in vivo micro computed tomography (micro-CT). At 8 weeks post surgery, the animals were sacrificed, and both defect and contralateral femurs were subjected to micro-CT, mechanical testing, and histology. Micro-CT results showed that the combination of CS/HA with ZA or ZA + rhBMP-2 increased the bone formation in the defect when compared to the other groups and to the contralateral hips. Evidence of new dense bone formation in CS/HA + ZA and CS/HA + ZA + rhBMP-2 groups was seen histologically. Mechanical testing results showed no differences in the load to fracture between the treatments in either of the treated or contralateral legs. The CS/HA biomaterial can be used as a carrier for ZA and rhBMP-2 to regenerate bone in the femoral neck canal of osteoporotic rats.

Background and purpose — Postoperative muscle strength and component alignment are important factors affecting functional results after total knee arthroplasty (TKA). We are not aware of any studies that have investigated the relationship between them. We therefore investigated whether coronal malalignment of the mechanical axis and/or of individual implant components would affect knee muscle strength and function 1 year after TKA surgery.Patients and methods — We included 120 consecutive osteoarthritis (OA) patients admitted for TKA. Preoperative active range of motion (ROM) of the knee, patient age, sex, and BMI were recorded and the Knee Society score (KSS) and knee joint extensor/flexor muscle strength were assessed. At 1-year follow-up, the mechanical and coronal component alignment was measured from a postoperative long standing radiograph, and ROM, KSS, and muscle strength measurements were taken in 91 patients. Functional outcome and muscle strength measurements were compared between normally aligned and malaligned TKA groups.Results — 29 of 91 TKAs were malaligned, i.e. they deviated more than 3° from the neutral mechanical axis. 18 femoral components and 15 tibial components were malaligned. Before surgery, the malaligned and normally aligned groups were similar regarding sex distribution, BMI, ROM, KSS, and muscle strength. At the 1-year follow-up, the differences between the groups regarding knee joint function and muscle strength were small, not statistically significant, and barely clinically relevant.Interpretation — Moderate varus/valgus malalignment of the mechanical axis or of individual components has no relevant clinical effect on function or muscle strength 1 year after TKA surgery.

Background: Available interventions for preventing fragility hip fractures show limited efficacy. Injection of a biomaterial as bone substitute could increase the fracture strength of the hip. This study aimed to show the feasibility of injecting a calcium sulfate/hydroxyapatite based biomaterial in the femoral neck and to calculate the consequent change in strength using the finite element method. Methods: Five patients were injected with 10 ml calcium sulfate/hydroxyapatite in their femoral neck. Quantitative CT scans were taken before and after injection. Five additional patients with fragility hip fractures were also scanned and the images from the non-fractured contralateral sides were used. Finite element models were created for all proximal femora with and without injection and the models were tested under stance and sideways fall loading until fracture. The change in fracture strength caused by the injection was calculated. Additionally, perturbations in volume, location, and stiffness of the injected material were created to investigate their contribution to the fracture strength increase. Findings: The 10 ml injection succeeded in all patients. Baseline simulations showed theoretical fracture strength increases of 0-9%. Volume increase, change in location and increase in stiffness of the material led to increases in fracture strength of 1-27%, −8-26% and 0-17%, respectively. Altering the location of the injection to a more lateral position and increasing the stiffness of the material led to increases in fracture strength of up to 42%. Interpretation: This study shows that an injection of calcium sulfate/hydroxyapatite is feasible and can theoretically increase the hip's fracture strength.

This study aims to test the feasibility of the Fracture and Mortality Risk Evaluation (FAME) Index. Patients and methods: Two academic centers in Lithuania and Turkey participated in this retrospective study conducted between November 2018 and July 2019. A total of 100 consecutive patients (22 males, 78 females; mean age 78.9 years; range, 45 to 100 years) with low energy proximal femur fractures admitted for surgery were included in the study. Fracture Risk Assessment tool (FRAX) and the Sernbo scores were calculated and patients were classified into one of the nine subcategories of the FAME Index. Results: Demographics and FAME Index classifications were similar between centers. Patients with high risk of fracture and low risk of mortality accounted for 18% of all patients, which is the FAME Index subcategory to theoretically benefit from cancellous bone augmentation during internal fixation of a fragility hip fracture the most. Conclusion: The FAME Index was successfully applied in clinical emergency setting utilizing a simple form, and demonstrated promising potential in stratification of hip fractures most suitable for screw and device augmentation. Larger studies with at least one-year of follow-up are warranted to verify the validity of FAME Index.