The aim of this study is to mathematically approximate the shape of the femoral articulating line and compare radiuses of condylar curves within and between males and females. Ten male and ten female participants were included in the study. Radiuses of medial and lateral condylar curves were calculated from the side view knee X-ray by original mathematical equation. Average radiuses of condylar curves were between 4.5 and 1.7 cm medially, and between 3.2 and 1.8 cm laterally, for 0 degrees and 90 degrees flexion contact point respectively. Males had longer curve radiuses of both condyles (p < 0.05). Differences turned out to be statistically insignificant after adjusting to body height. Even small changes in the joint geometry during lifetime could make a joint susceptible to osteoarthritis or injuries. Approximation of the radiuses of femoral condyle curves is a useful method in anthropometric, radiological and virtual calculations of the knee geometry, and other ellipsoidal structures in human body, like wrist, scull segments, dental arches, etc.

We compared kinetic characteristic of unipolar, bipolar and total hip endoprostheses, implanted after dislocated femoral neck fracture. Ninety patients were divided into three groups (30 patients in each group); a group with unipolar partial hip endoprosthesis (UPEP), a group with bipolar partial hip endoprosthesis (BPEP) and a group with total hip endoprosthesis (TEP). The patients from different groups were paired by parameters which could influence the long term functional result: follow up period, comorbidities, functional capabilities before injury, etc. After the average follow up 3.8 +/- 1.9 years, a measuring of range of hip motions (ROM) was conducted. The largest mean amplitudes in flexion (104 degrees), extension (13 degrees), abduction (35 degrees) and external rotation (38 degrees) was achieved BPEP, the largest adduction (14 degrees) was achieved UPEP, and internal rotation (34 degrees) TEP. Differences in ROMs are partially related to the clinical parameters such as: level of the hip pain, gait pattern, age and rehabilitation period (P < 0.05). Measuring of ROMs is the most reliable part of the clinical exam and it does not depend on subjectivity of patient, as opposed to other clinical parameters (level of pain, walking distance, aids usage, etc). The results obtained are favorable for the bipolar hip endoprosthesis, and they can be related to the biomechanical differences between the three types of hip endoprostheses. Kinetic advantages of the BPEP as compared to the UPEP, can be explained by the BPEP's structure: two-level mobility and a thinner neck which delays impingement in the late motion phase. In comparison to the TEP, clinical advantages of the BPEP can be attributed to less extensive surgery and scarring.