**5. Clinical results of the BDSF-method**

88 Injury and Skeletal Biomechanics

length of 13 cm.

cortex the stress is mainly tensile.

**A** equal to 1.63 kN (163.63 kg). The load on the fragile lateral cortex (**point B**) is estimated as

With *the BDSF method* **(case 2.)**, with increasing the angle of the implant towards the diaphysis, the distance between points **A** and **B** increases by 4 cm to reach up to 9.5 cm (a = 9.5 cm). That is why, the load on the cortex decreases significantly. Given the same body weight of 100 kg, the load acting on the medial supporting point is estimated as **A** equal to 1.36 kN (136.84 kg) or with *16.38% less than conventional methods*, and on the lateral supporting point the load is estimated as **B** equal to 0.36 kN (36.84 kg) or with *42.11% less than conventional methods.* The distal screw normally applied with the BDSF method has a

The lateral cortex stress state around point **B** is complex. It is subjected to compressive stress in a proximal direction, and to horizontal tensile stress as well. In the lower part of the

**Figure 4.** Fixation of the femoral neck: a. Conventional method; b. The BDSF-method. [12]

These forces of tension are responsible for the occurrence of subtrochanteric fracture as a complication of the screw fixation. As it was mentioned, these forces of tension are decreased by 42% with the BDSF-method, compared to the conventional methods of fixation. Besides, with the BDSF-method the entry points of the screws are located wide apart from each other (from 2 to 4 cm), which leads to dispersion of the tension stress on the

**B** equal to 0.63 kN (63.63kg), directed in the opposite direction (proximally).

The BDSF-method was introduced in 2007 and it was applied by different surgeons since than. From a series of 178 patients, who underwent surgical treatment, 88 were studied [12]. Inclusion criteria was having late control x-rays and examinations after discharge with questionnaires filled-in. Out of the 88 studied patients, 27(30.68%) were male and 61(69.31%) - female patients; the average age was 76.9 (with the youngest patient at the age of 38 and the eldest at the age of 99). Grouping patients by age: 18 patients (20.45%) were at the age of under 69; 27 patients (30.68%) were at the age of 70 to 79; 37 patients (42.04%) were at the age of 80 to 89; 5 patients (5.68%) were at the age of 90 to 95 ; 1 patient (1.13%) was aged 95 to 100. More than one concomitant disease, which influences the results of Harris Hip Score, was found in 21 patients (23.86%). The average follow-up period is 8.06 months.

The Garden classification was used for classifying of the fractures as follows:

Garden type I: 3 (3.41%); Garden type IІ: 1 (1.14%); Garden type IІІ: 9 (10.23%); Garden type IV: 75 (85.02%).

*Results.* From the studied 88 patients fracture union was registered in 87 patients (98.86%) and failure in 1 patient (1.13%).

*Assessment* according to the Harris Hip Score (modified): Poor results – in 10 patients (11.36%). Fair results – in 20 patients (22.72%). Good results – in 21 patients (23.86%). Excellent results – in 37 patients (42.04%).

*The average* Harris Hip Score is 84.26 points [13].
