In recent years, the use of computed tomography (CT) has made it possible to obtain without distortion images of axial sections of the patella with the knee in the first 15°–20° of flexion. We performed CT examinations on 27 patients aged between 11 and 17 years. We considered patients who had anterior knee pain with or without a feeling of patellar instability. CT examinations were performed with the knee flexed to 15° with and without quadriceps contraction. The tomograms obtained were analysed considering: (1) the congruence angle (CA), (2) the patellar tilt angle (PTA), (3) the sulcus angle (SA) and (4) trochlear depth (TD). We performed CT examinations on a control group of 20 patients aged between 11 to 17 years. Statistical analysis was performed by using the analysis of variation (ANOVA) test or the Student’s t-test on paired or unpaired data. The difference between control knees and symptomatic knees was significant for all of the CT variables (unpaired t-test). Malalignment detected with the quadriceps relaxed was typed according to the classification of Schutzer et al. as follows: type I – lateralised patella, 13 knees (24.1%); type II – lateralised and tilted patella, 24 knees (44.4%); and type III – tilted patella, 12 knees (22.2%). In 26 knees (48.2%), CT examination with quadriceps in contraction gave the same findings as CT examination with the quadriceps relaxed, i.e. type and severity of malalignment were identical. In the remaining 28 knees (51.8%), CT examination with the quadriceps in contraction gave different results from the CT examination with the quadriceps relaxed. The greater sensitivity and specificity of CT as compared with conventional radiographic methods in the diagnosis of patellofemoral malalignment have been demonstrated. Our results show that there is a relationship between clinical findings and CT data. CT assessment with the quadriceps relaxed permitted us to divide the knees into three types of patellofemoral malalignment. To our knowledge, not many studies have been performed with the quadriceps contracted. In the present study, in 48.2% of knees there were no differences between CT assessment with the quadriceps relaxed and with the quadriceps contracted in either type or severity of malalignment. In contrast, in the remaining 51.8% of symptomatic knees we found differences. Before planning an operation in patients with anterior knee pain with or without patellar instability, CT assessment both with the quadriceps relaxed and contracted permits a reliable documentation of malalignment, permitting the surgeon to select the optimal treatment.
Torsional changes in the lower limbs represent a serious clinical problem. The evaluation of the physiological development of the relationship between femur and tibia in the axial plane is necessary for final assessment. The authors observed 940 patients aged from 4 to 15 years to identify the most important modifications of torsion of the lower limbs during paediatric age. Clinical examination includes assessment in the standing and supine position and observation of the gait features so that the physiological-pathological borderline can be defined, along with peculiar aspects of single and combined deformities, in order to identify indications for osteotomy. The types of torsion are classified as: (1) isolated augmentation of femoral anteversion; (2) isolated reduction of femoral anteversion; (3) isolated medial tibial torsion; (4) isolated lateral tibial torsion; and (5) combined torsion (femoral anteversion combined with lateral tibial torsion). The anatomy and the natural progression of femoral and tibial torsion can be assessed by clinical methods. Radiographic methods such as axial CT views are indicated in cases in which clinical examination does not provide clear information and, in particular, if qualitative and quantitative diagnosis is required in order to establish the therapeutic protocol. The authors conclude by suggesting that the physiological development of torsion should be followed up to skeletal maturity in order to make a general evaluation and to decide on treatment.
The Q angle is defined as the angle formed by a line passing from the anterior-superior iliac spine and the centre of the patella and another line passing this point to the centre of the tibial tuberosity. Normal values reported in the literature for the Q angle widely range between 12.7° (± 0.72°) and 18.8° (± 4.7°). This variability depends on individual anatomical variations and method of measurement as well. In fact, several factors can affect the measurement of Q angle. The correct evaluation is carried out with a goniometer, in supine position and the knee in full extension. Q angle evaluation can be biased by standing position and quadriceps contraction, which can increase the Q angle; in contrast, knee flexion can reduce it. Furthermore, it has been demonstrated that the Q angle increases from external to internal rotation of the tibia, while it decreases from pronation to supination of the foot. Finally, patellar malalignment in the horizontal plane, such as subluxation or dislocation, causes a decrease in the Q angle, as the centre of the patella is laterally shifted. The accuracy of Q angle measurement can be also affected by an error in identifying the anatomical landmarks. An error in Q angle measurement below 5° requires an error in setting the anatomical landmarks of no greater than 2 mm. Several authors have shown that the Q angle is greater in females, as the proximal landmarks are more lateral and a greater valgus alignment is necessary to reestablish a correct mechanical axis of the limb. According to the side, there is no evidence that Q angle is symmetric. The clinical significance of the Q angle is controversial. An increased Q angle was considered for a long time as the main cause of anterior knee pain and an important risk factor for patella subluxation or dislocation. Some authors showed a correlation between Q angle increase and symptomatic patellar chondromalacia. However, others showed no significant differences in Q angle values between symptomatic and asymptomatic patients. Presently, there is not sufficient clinical evidence that an increased Q angle predisposes to knee problems. Furthermore, it is impossible to assert that all the alterations of the extensor mechanism are exclusively due to an increase in the Q angle, as they can depend on other factors, such as: functional overloading of the knee, muscle and ligament insufficiency, bone and chondral morphological changes, malalignment or asymmetric length of the inferior limbs and foot alterations. In conclusion, a homogeneous method of measurement and correct data interpretation are necessary to clarify the conundrum of Q angle. Moreover, it is important to understand that patellofemoral malalignment is not always the cause of knee pain and instability. This can reduce the risk of performing surgical procedures of extensor mechanism realignment that are technically perfect but potentially harmful.
