Femoral Offset (3D) in Patients without Osteoarthritis - Index Values from 200 Hip Joints.

INTRODUCTION: Femoral offset (FO) is a crucial parameter for hip joint biomechanics. Reference values for FO are particularly important when joint geometry has to be reconstructed during surgical interventions. Such reference values are scarce in literature and have mainly been obtained from osteoarthritis (OA) patients. The aim of this study was to conduct a patient-specific study of FO without osteoarthritis and to create a dataset of FO index values. MATERIALS AND METHODOLOGY: One hundred (49 female, 51 male; mean age: 59 (18 - 83) years) pelvic computed tomography (CT) scans were analyzed to determine FO in each patient. Bilateral symmetry and correlation between demographic data and FO were analyzed. RESULTS: The mean FO ± SD was different for male (4.36 ± 0.56 cm) and female patients (3.95 ± 0.35 cm) (p <.0001). No Side differences of FO were observed in male and female patients. Significant correlation between height and FO was only observed in male patients. CONCLUSION: The values obtained in this study can be used as index values for the restoration and evaluation of hip geometry. For men, FO can be approximated using the correlation between FO and height.

The sex specificity of hip-joint muscles offers an explanation for better results in men after total hip arthroplasty.

PURPOSE: Choosing a surgical approach for total hip arthroplasty (THA) has a patient-specific impact on peri-operative muscle damage as well as postoperative functional outcome. Women and aged patients increasingly benefit from minimally invasive surgical procedures. For this reason, and due to the distinctly different bony anatomy of men and women, the hypothesis of this study is that muscle distribution around the hip joint is dependent on sex and age. The goal of this study was to analyse hip musculature in men and women and to correlate total muscle volume distribution. METHODS: From 93 computed tomography (CT) scans of the pelvis (45 men, 48 women) volumes of gluteus medius (GMV), gluteus maximus (GXV) and tensor faciae latae (TFL) muscles were measured on both sides of the pelvis. The distribution of muscle volumes was normalised to patient weight and then correlated with sex and age. RESULTS: The measured muscle volumes featured no major differences between the left and the right side. The absolute total volume of the hip-encompassing muscular system (TMV) is bigger in men than in women. Correlations between TMV and collected data were observed in both sexes in relation to body weight and size (men p < .00001; women p 0.001). With increased body weight, the TMV of the male patients increased progressively (women 11.2 cm TMV/kg KG vs. men 17.4 cm TMV/kg KG) (p 0.04). The relative distribution of each muscle volume (GMV, GXV, TFL) around the hip joint showed no major differences with respect to sex and/or age (p 0.986 and 0.996, respectively). CONCLUSIONS: The equal relative muscle distribution in men and women around the hip joint reflects neither sex-related differences observed in clinical outcomes after THA nor bony anatomy. Yet men exhibited more muscle reserves (muscle volume; absolute and in relation to body mass) , which could explain the better outcome in men after THA. Furthermore, this suggests the extraordinary importance of muscle-sparing surgical approaches in women. The results represent the rationale for designing and analysing future studies of sex-specific therapies with regard to hip-joint muscles.

A formula to predict patients' gluteus medius muscle volume from hip joint geometry.

The volume of the gluteus medius muscle (GMV) has been shown to be closely related to hip joint function. A defined relation between joint geometry and GMV would allow a calculation of the patient-specific GMV providing reference values to individually determine the goals for rehabilitation programs after total hip arthroplasty (THA). The aim of this study was to investigate correlations between hip geometry and GMV. One hundred and two (50 female, age: 58.53 (18-86)) pelvic computed tomography (CT) scans were analyzed to determine femoral offset (FO), body weight lever arm (BWLA) and the GMV. Relationships between demographic data, FO and GMV were analyzed using correlation and regression analysis. The mean GMV was found to be 289 ± 72 cm(3), the mean FO measured was 4.14 ± 0.55 cm; and the mean value for BWLA measured was 8.88 ± 0.4 cm. A formula to calculate the GMV with a good coefficient of determination (R(2) = 0.681) (p < 0.0001) was derived. In conclusion, the formula obtained predicts individual GMV with good model fit and could be used to individually determine rehabilitation goals. Moreover, the correlation found could account for a hand in hand development of FO and GMV during growth and a continuous functional relationship thereafter.