The relationship of femoral torsion and lower limb injury

Abstract

Research about femoral torsion has existed since the late 1980’s with the focus on developing a method to measure femoral torsion. Identifying the degree of femoral torsion has become important because excessive antetorsion of the femur has been associated with hip pathology. In addition, it is important to identify the degree of femoral torsion prior to placement of a hip prosthesis and prior to derotational osteotomy for children with congenital excessive femoral antetorsion, which is seen in cerebral palsy, hip dysplasia and Blount’s disease. The gold standard for measuring femoral torsion is a CT scan, which is invasive therefore limiting its usage especially in children. While research on femoral torsion has been narrowed to hip pathology and correcting deformity, excessive femoral antetorsion is thought to impact structures distal to the hip therefore increasing the risk of developing lower limb injury. Since the relationship between femoral torsion and lower limb injury is unknown, a systematic review is presented in Chapter 2 that looked at the relationship between femoral torsion and other hip characteristics as a risk factor for lower limb injury. Excessive range of external rotation and increased strength may increase the risk of lower limb stress fracture and patellofemoral pain. Weaker hip external rotators and stronger hip abductors were found to significantly increase the risk of developing patellofemoral pain. Greater range of hip external rotation was also found to be a factor in increasing the risk of lower limb stress fracture however the figure is too small to be considered a clinically worthwhile effect. Although hip strength and hip range of motion were found to be risk factors for lower limb injury, no prospective study investigating the relationship between femoral torsion and lower limb injury was found. Therefore, one of the aims of this thesis was to provide preliminary data to uncover this relationship. Another aim of the work presented in this thesis was to develop a new ultrasound imaging protocol to assess femoral shaft torsion utilising a new landmark on the greater trochanter, ‘the ridge’. The protocol showed excellent intra-rater reliability (ICC2,1 = 0.98; 95% CI 0.97 to 0.99), and inter-rater reliability (ICC2,1 = 0.97; 95% CI 0.95 to 0.98). Fifty per cent of the measurements were within 1o both within and between raters and within 2.7o for 80% of the measurements. The largest difference between raters was 9.3o. Standard error of measurement (SEM) was 0.5 degrees and 0.6 degrees respectively for intra-rater and inter-rater reliability measurements. The excellent reliability supports its usage in the clinical setting. This work is presented in chapter 3. Consequently, using the newly developed reliable method, the relationship between femoral torsion and hip proprioception was examined in healthy adults (n=40). Hip proprioceptive acuity was measured using an active reproduction of movement in three different angles; 10% of neutral, 50% or mid-range and 90% of maximum external rotation. Greater range of medial shaft torsion was found to be associated with better hip proprioceptive acuity only at the angle near the end of maximum external rotation (r=-0.325, p=0.04) not at 10% (r=0.019, p=0.909) and 50% (r=0.116, p=0.478). The detail of this study is described in chapter 4 of this thesis. A cross-sectional study investigated the relationship between femoral shaft torsion and lower limb injury in dancers (n=80). No difference was found in the magnitude of femoral shaft torsion between injured and non-injured dancers (p = 0.94). The relationship between femoral shaft torsion and eight other hip measures was also investigated. Femoral shaft torsion was found to have a very weak, negative correlation with range of hip external rotation (r = -0.034, p=0.384) and turnout (r = -0.066, p=0.558). The association between femoral shaft torsion with all other variables was also found to be very weak. This study is described in detail in Chapter 5. Overall the results of the studies documented in this thesis: describe the development of a novel femoral torsion measurement tool, identify femoral shaft torsion as a measurable component of femoral torsion, and provide preliminary data and inferences regarding the relationship between femoral torsion, distal lower limb injury and lower limb proprioceptive acuity in a high risk population of dancers. It is proposed that future research will determine the extent to which femoral torsion poses a lower limb injury risk, which will inform the modification of screening protocols. The findings of this thesis will also assist clinicians to direct their prophylactic management to joints and soft tissues at risk. If a time-frame for development of FT can be identified, modified training loads may be investigated to enhance optimal FT and determine whether this minimises injury risk. This new information therefore will also provide a basis for future research that would likely be in longitudinal studies establishing relationships, hence providing useful information for coaches and clinicians regarding designing alternative methods of training in preventing lower limb injuries. The body of knowledge provided by this thesis will also inform researchers in determining the measures of the hip to be used in future research which might be worthwhile investigating in relation to lower limb injury.