Influence of Q-angle on Lower-Extremity Running ~inematics

Transcription

1 Journal of Orthopaedic & Sports Physical Therapy 2000;30(5) : Influence of Q-angle on Lower-Extremity Running ~inematics Bryan C. Heiderscheit, MS, PT1 )oseph Hamill, PhD2 Graham E. Caldwell, PhD3 Study Design: Two-group posttest-only comparison. Objective: To assess the influence of the Q-angle on the 3-dimensional lower-extremity kinematics during running. Background: An excessive Q-angle has been implicated in the development of knee injuries by altering the lower-extremity locomotion kinematics. Previous investigations using 2- dimensional analyses during walking did not support this hypothesis. Methods and Measures: We hypothesized that individuals with Q-angles more than 15" would display an increase in reatfoot eversion and tibial internal rotation during running. Thirty-two nonimpaired subjects (men: n = 16, mean age = years; women: n = 16, mean age = years) ran over ground, and 3-dimensional kinematic data were collected from the right lower extremity. Subjects with a Q-angle of 15" or less comprised the 1ow-Q-angle group, whereas those with Q-angles of more than 15" comprised the high- Q-angle group. Segment and joint maximum angles and the times when the maxima occurred during stance were measured. Results: The Q-angle magnitude did not increase the maximum segment or joint angles during running. The groups displayed similar maximum angles for rearfoot eversion (low Q- angle, t 5.0"; high Q-angle, ") and tibial internal rotation (low Q-angle, "; high Q-angle, -6.8 t 5.1"). The high-q-angle group (39.5 t 16.3%) achieved maximum tibial internal rotation later in the stance phase than the 1ow-Q-angle group (28.8 t 10.7%). Conclusions: In support of the previous investigations involving Q-angle influences on kinematics, our study did not reveal any differences between groups in maximum joint or segment angles. The kinematic information did reveal that the high-q-angle group displayed an increase in time to maximum tibial intemal rotation. The impact of this single factor on producing knee injury is unknown. ) Orthop Sports Phys Ther 2000;30: Key Words: segment alignment, 3-dimensional kinematics, tibial rotation I Doctoral candidate, Biomechanics Laboratory Department of Exercise Science, University of Massachusetts, 1 10 Totman Building, Amherst, Mass. : Director, Biomechanics Laboratory, Departn~ent of Exercise Science, University of Massachusetts, 110 Totman Building, Amherst, Mass. Biomechanics Laboratory, Department of Exercise Science, University of Massachusetts, 110 Totman Building, Amherst, Mass. This study was approved by the Institutional Review Board, Human Subjects Committee, School of Public Health and Hedlth Sciences, University of Massachusetts, Amherst. Send correspondence to Bryan Heiderscheit, Biomechanics Laboratory, University of Massachusetts, 1 10 Totman Building, Amherst, MA bcheider@excsci.umass.edu L ower-extremity segment alignment has frequently been implicated in the develop ment of running injuries.~i.~.5.~!~.2~ 23 Various static goniometric measures have been defined to assess the alignment of joints and segments. One such measure, the Qangle, is frequently cited as a possible predictor of knee injury. I I-l4.23.!!5 The Qangle represents the frontal plane angle of the quadriceps' resultant force on the patella and tibial tubero~ity.".'~ It is defined by the intersection of the line from the anterior superior iliac spine to the center of the patella and a line connecting the center of the patella to the tibial tuberosity (Figure 1). The Qangle can be measured reliably,"-" and it provides a reasonable estimate of the quadriceps muscles' angle of pull on the patella in the frontal plane.2" Qangles that vary from 15-20" are often referred to as ex- CeSSive.l:%.142:< The American Orthopaedic Association:' defines "excessive" as Qangles greater than 15". Sexbased differences in Qangle have been reported, with women typically having a larger Qangle.2.1 I.':'.:'" Sub~tnick'~' suggested that an excessive Qangle produces increased foot pronation or rearfoot

2 patella FIGURE 1. Q-angle is defined as the acute angle between a line connecting the anterior superior iliac spine and the midpoint of the patella and a line connecting the midpoint of the patella and the tibial tuberosity. eversion as a result of increased genu valgum. Increased rearfoot eversion has been implicated as a factor that produces various knee injuries.".'based on the anatomical congruency between the talus and tibia,24 increased tibial internal rotation will accompany the increased rearfoot eversion. Therefore, during running the increase in rearfoot eversion suggested to be present with an excessive Qangle should produce increased tibial internal rotation. Kernozek and Greerl%ttempted to verify this theory using a 2dimensional kinematic analysis during walking but were unable to find a relationship between Qangle and rearfoot eversion. The authors concluded that a large Qangle does not predispose an individual to greater maximum rearfoot eversion.'" This investigation of walking kinematics, however, did not address tibial or femoral motion. In addition to altered segment angles, it has been suggested that knee injuries may develop from abnormal timing between the motions of the lowerextremity segments."+3' During initial foot-ground contact of running, the rearfoot eversion and knee flexion angles increase to absorb impact shock, with both reaching their maximum angles at mid~tance.'~ Similar to the coupled relationship between rearfoot eversion and tibial internal rotation, tibial internal rotation also accompanies knee flexion. When rearfoot eversion or knee flexion reach their respective maximum angles at different times in the stance phase, knee joint dysfunction may occur as a result of conflicting requirements of the tibia.",:" The increased rearfoot eversion angle that has been suggested to occur with an excessive Qangle may result in the maximum rearfoot eversion angle and maximum tibial internal rotation angle occurring later in the stance phase of running. If the maximum knee flexion angle remains at midstance, an increase in torsional load on the tibiofemoral joint can occur during later stance as the knee extends. The tibia will simultaneously be required to externally rotate with knee extension and internally rotate to accompany the prolonged rearfoot eversion. The purpose of our study was to determine if a direct relationship exists between Qangle and various lowerextremity kinematic variables. We hypothesized that individuals with excessive Qangles would display an increase in rearfoot eversion and tibial internal rotation angles during running. It was also expected that an excessive Qangle would alter the timing of the lowerextremity segment motions (ie, maximum rearfoot eversion and maximum tibial internal rotation occurring later in stance). METHODS Thirty-two nonimpaired subjects (16 men and 16 women) were selected from the University of Massachusetts community. Appropriate sample size was estimated using Cohen case 0 for a minimum statistical power of 80%.' All subjects signed a letter of informed consent approved by the Human Subjects Committee of the University of Massachusetts and completed a participation questionnaire to verify health status. Subject inclusion was dependent on the following criteria: (1) no history of lowerextremity injury within the last 10 years, (2) no use of orthotics, and (3) less than 1.27-cm difference between lengths of the right and left lower extremities. It has been stated that limb length discrepancies less than 1.27 cm do not significantly alter lowerextremity biomechanic^.^' The subjects were evenly divided into four groups based on their sex and measured Qangle. Qangles greater than 15" were defined as excessive based on the findings of Messier et a12:' and the American Orthopaedic Association.:' The men ranged in age from years (mean, years), in body mass from kg (mean, kg), and in height from cm (mean, cm). The women ranged in age from years (mean, 23 -C 3 years), in body mass from kg (mean, kg), and in height from cm (mean, cm). Twosample t tests did not reveal significant group differences for age (t = , df = 30). mass (t = 1.14, df = 30), or height (t = 0.76, df = 30). whereas mass and height displayed significant differences between the sexes (P <.001). A lowerextremity evaluation was performed on each subject by the same physical therapist. The sub- 272 J Orthop Sports Phys Ther.Volume 30. Number 9. May 2000

3 jects were in a weight-bearing position for all goniometric and anthropometric measures. The Qangle was measured from the right lower extremity by placing the goniometer axis at the center of the patella, with the stationary arm aligned to the anterior superior iliac spine and the movable arm aligned to the tibial tuberosity (Figure 1). In addition, right genu valgum and tibial varum were recorded because excessive values of each have been suggested to influence the gait pattern, possibly producing kinematic differences between subjects.!' Genu valgum was measured by placing the goniometer axis at the right anterior knee joint line, with the stationary arm bisecting the tibial segment and the movable arm bisecting the thigh segment. The goniometric axis for the measure of tibial varum was placed at the anterior talocrural joint, with the stationary arm aligned to the vertical and the movable arm aligned to the anterior tibial tuberosity. To establish intratester reliability for each goniometric measure, 10 knees were measured by the physical therapist on 3 consecutive days. Intraclass correlation coefficient (ICC) values ranged from , indicating good intratester reliability. Using a tape measure, lowerextremity length was also determined.%' A kinematic analysis of the right thigh, leg, and foot was conducted using a %segment model. Triads, composed of 3 noncollinear hollow polypropylene spheres fastened to a polypropylene base, were securely placed on the lateral surface of the right thigh and leg at midsegment. The triad base was formed to the thigh and leg to maximize surface contact and reduce error due to skin movement artifact. To measure foot motion, individual markers were placed on the lateral surface of the shoe at the heel, the head of the fifth metatarsal, and anterior to the lateral malleolus. Similar techniques have been performed in previous investigations.';" Although marker placement on the shoe does not provide a direct measure of the foot, each subject was individually fit to a shoe such that it was assumed the shoe motion adequately reflected foot motion. All subjects wore running shoes with a standardized midsole to prevent variations in segment movement due to different midsole durometers.!' Two high-speed (200-Hz) video cameras (NAC, Burbank, Calif) and recorders were used to record the subjects running through a calibrated field. The cameras were arranged such that all markers were visible in each camera throughout right foot-ground contact. A fixed right-hand room coordinate system was previously defined using a 1.0-m cube that contained 25 markers of known coordinates. The y-axis of the room coordinate system was in the direction of running, with the z-axis perpendicular to the floor. Before the running trials, a calibration fixture was used to align the segment coordinate systems with the room coordinate sy~tern.~ The subject stood in the fixture such that the longitudinal axis of the foot was aligned to the y-axis of the room coordinate system. A calibration trial was collected for use as a reference for the running trials, thus defining zero angle position of the lowerextremity segments. Subject running velocity was monitored using a digital counter interfaced to photoelectric sensors arranged on each side of the force platform. Men maintained a velocity of 3.8 m/s 2 5%, whereas women maintained 3.6 m/s 2 5%. The difference in running velocity was in regard to the inherent velocity differences found between men and women. The vertical ground reaction force from a force platform (Advanced Mechanical Technologies Inc, Newton, Mass) placed in the running path was interfaced to a lightemitting diode to indicate foot-ground contact. Subjects were instructed not to target the force platform with their right foot in an attempt to minimize alterations in their approach that may bias the collection. Ten trials were recorded for each subject. A trial was deemed acceptable if proper velocity was maintained, and the entire right foot of the subject contacted the force platform. The video data from each camera were analyzed using the Motion Analysis VP 110 Expert Vision System (Motion Analysis Corp, Santa Rosa, Calif). Cartesian coordinates (x, y) were determined for each marker at each frame of the stance phase (heel-strike to to~ff), with a %frame buffer before and after foot-ground contact to minimize filtering effects. A 16-Hz low-pass, fourtha-der, zero lag Butterworth filter was used to eliminate higher frequencies associated with noise. The frequency cutoff was determined by calculating power spectral densities on the marker x and y paths and selecting a common frequency that contained 95% of the signal's power. A direct linear transformation was used to merge the views from the two cameras to reconstruct the Mimensional image.iz7 Using the methods adapted from Areblad et a14 and described by Grood and Suntay? the local segment coordinates were calculated from the marker triads throughout the stance phase. The segment coordinates were oriented with respect to the calibration stance position of the respective subject-producing segment and joint time series. Based on the previous discussion of possible segmental alterations, maximum segment and joint angles and the time at which these maxima occurred were calculated from these curves (see Tables 2 and 3 for a listing of variables). The rearfoot angle was defined as the relative frontal plane angle between the tibia and calcaneus, whereas the knee flexion angle was defined as the relative sagittal plane angle between the tibia and femur. Intraclass correlation coefficients (ICC = MS,,,,, / [MSII,,,, + MS,..i.R])* were conducted on each parame- * MS indicates mean square J Onhop Sports Phys Ther -Volrme 30 Number 5 May

4 TABLE 1. Goniometric measures of the right lower extremity (mean 2 SD) for the men and women of each group. Between-group statistical analyses (combining men and women) are reported. Low Q-angle, degrees High Q-angle, degrees Men Women Men Women Measure (n = 8) (n = 8) (n = 8) (n = 8) t value* P value Q-angle <.001 t Genu valgum Tibia1 varum * Degrees of freedom equals 30. t P <.05. L O W - l5 - inversion (+) I0 -- = 5.- b -20 eversion (-) Qangb - ~ gqangle h I external rotation (+) L lo T external rotation (+) J internal rotation (-) -U internal rotation (-) Percent of Stance FIGURE 2. Mean segment and joint angles of each group throughout the stance phase of running. Maximum rearfoot eversion, knee flexion, tibial internal rotation, and femoral external rotation are indicated by T. Note the discrepancy between groups for time to maximal tibial internal rotation. ter to determine the reliability between trials of each subject. The ICC values showed high reliability ( ). with 9 of the 14 variables having an ICC above Based on the ICC findings, the means of the 10 trials for each subject were used for filrther analyses. The groups were collapsed across Qangle and 1-way analyses of variance were performed to determine a sex effect (P <.05). Because no effect for sex was found (see "Results"), the remaining statistical analyses were performed with the original 4 groups collapsed across sex into 2 groups: Qangle more than 15' (high Qangle) and Qangle 15" or less (low Qangle). The means for the goniometric and kinematic measures were compared across groups using a 2-sample t test for each of the 14 parameters (P <.05). Finally, the Qangle grouping was ignored, and unweighted least-squares linear regressions were conducted across Qangle to investigate the presence of a linear relationship between Q angle and each kinematic variable that may have been hidden by the grouping factor. RESULTS No significant differences were found between men and women for any of the 14 kinematic parameters (P >.lo), thus justifying the collapse of the original 4 groups into 2. The measured Qangle was significantly different between groups (P <.001; Table 1). No differences between groups were found for the other static goniometric measures, genu valgum and tibial varum (Table 1). Ensemble averages were created from the 10 trials of each subject and averaged to produce grand ensemble averages for each group. Figure 2 displays the grand ensemble segment and joint angle averages for each group as a function of the stance phase. The mean time series of the 2 groups are within 1 SD of each other for each segment angle. The discrete angular measures of the segments (tibia and femur) and joints (rearfoot and knee) showed no significant differences between groups (Table 2). The times to the maximum angle of rearfoot eversion, femoral external rotation, and knee flexion were also consistent across groups (Figure 2 and Table 3). The time to maximum tibial internal rotation, 274 J Orthop Sports Phys TIwr.\'olr~~ne 30. Nwnher.i May 2000

5 TABLE 2. Group angular values of specific segment and joint motion events (mean t SD). Negative values indicate direction of movement. Low Q-angle, degrees High Q-angle, degrees Angular variable (n = 16) (n = 16) t value* P value Rearfoot at touchdown Maximum rearfoot eversion t t ,985 Total rearfoot motion 17.0 t t Maximum tibia1 internal rotation -8.8 t t Maximum tibia1 external rotation t Total tibia1 rotation 15.2 t t Maximum knee flexion 43.3 t t Maximum femoral external rotation 7.9 t t Maximum femoral internal rotation -3.8 t t Total femoral rotation 11.8 t t SO4 * Degrees of freedom equals 30. Group however, showed a significant difference (P <.02), with the high-q-angle group requiring more time for the tibia to reach maximum internal rotation than the low-qangle group. Figure 2 displays the discrepancy of time to maximum tibial internal rotation between the groups. Unweighted least-squares linear regressions were performed across all Qangles to investigate a relation between Qangle and each kinematic parameter that may be hidden by the grouping factor (Table 4). Significant linear trends were present for maximum tibial external rotation and the time to maximum tibial internal rotation (P <.05). However, the correlations between Qangle and any of the kinematic parameters were weak based on the $ values. The strongest correlation was found between Qangle and the time to maximum tibial internal rotation (9 = 0.28; N = 32); however, lthe low $ value indicates the relationship is weak. Maximum tibial external rotation showed the strongest correlation among the angular measures to Qangle ($ = 0.16; N = 32), but again the 9 value is weak. The variation found between subjects for each parameter could not be explained by a linear change in Qangle. DISCUSSION As suggested by Subotnick,"' an excessive Qangle should produce increased rearfoot eversion that in turn would cause an increased tibial internal rotation angle. The excessive tibial internal rotation countered by the naturally antagonistic femoral external rotation could potentially produce a torsional load on the tibiofemoral joint and thereby contribute to a knee injury. Based on our findings, this chain of events does not appear to occur. Neither the magnitude of the foot eversion angle nor the tibial internal rotation angle was significantly altered as a result of increased Qangle. These findings are consistent with other investigations that have attempted to establish a similar relationship. In a 2dimensional kinematic analysis, Kernozek and GreerIF' monitored the Qangle and rearfoot motion throughout the walking cycle. Only a weak relationship was found between the static Qangle and the kinematic parameters. Using a 3dimensional analysis, Stergiou et a12* investigated the relation between tibial rotation and Qangle and found no differences between subjects with patellofemoral pain syndrome, subjects with a history of patellofemoral pain syndrome, and nonimpaired subjects. One possible explanation for these findings lies in the measure of the Qangle. Traditionally, the Qangle is measured statically and used as a predictor of dynamic dysfunction. Previous investigations have demonstrated static measures to be poor predictors of dynamic dysfi~nction.'~';' Although the Qangle was not included in these prior investigations, a dynamically measured Qangle may provide more information than one measured statically. It should be TABLE 3. Percentage of stance when the maximum segment and joint angles occurred for each group (mean t SD). Low Q-angle, degrees High Q-angle, degrees Temporal variable (n = 16) (n = 16) t value* P value Maximum rearfoot eversion t Maximum tibia1 internal rotation 28.8 t t t Maximum knee flexion 39.1 t Maximum femoral external rotation t * Degrees of freedom equals 30. t P <.05 Grow J Orthop Sports P ly Ther*Volume 30. Nunlher 5- May 2000

6 TABLE 4. Unweighted least-squares linear regression results for each kinematic variable. Each linear regression was conducted independent of the others. Variable Intercept Coefficient r r' F value* P value Rearfoot at touchdown Maximum rearfoot eversion I33 Total rearfoot motion ,551 Maximum tibia1 internal rotation I45 Maximum tibia1 external rotation t Total tibia1 rotation Maximum knee flexion Maximum femoral external rotation Maximum femoral internal rotation I24 Total femoral rotation lime to maximum rearfoot eversion lime to maximum tibia1 internal rotation t lime to maximum knee flexion Time to maximum femoral external rotation N = 32 for all variables. t P <.05. noted, however, that Kernozek and GreerlVailed to find a relationship between rearfoot motion and Q angle measured either statically or dynamically. Subotnick'sa argument for altered segment and joint kinematics as a result of an excessive Qangle depended on an increased genu valgus angle. Namely, the increased genu valgum angle associated with the excessive Qangle would produce the increased rearfoot eversion and tibial internal rotation angles. Although the Qangles were significantly different between the groups of this investigation, the genu valgum angles were not. The lack of group difference among the angular measures during running may be a result of the similar genu valgum angles. Furthermore, these results suggest that an increased Qangle may not simply reflect the frontal plane alignment of the femur and tibia. Rather, the Qangle appears to be influenced by the position of the patella and the rotation of the tibia. Neither of these variables was quantified among the subjects of this investigation. The method used for calculating the time to maximum tibial internal rotation (and for all other temporal measures) was based on a single point at which the greatest tibial internal rotation angle occurred. The segment curves displayed in Figure 2 indicate that the determination of maximum tibial internal rotation for the high4angle group may not be best represented by a single point. From approximately 3040% of stance, the high-qangle group shows less than 1.0' change in the tibial rotation angle. This lack of change may be perceived as the high-qangle group reaching maximum tibial internal rotation at 30% of stance and remaining in maximum internal rotation until 60% of stance. This interpretation would negate any difference in time to maximum tibial internal rotation between groups, since the 2 time intervals would overlap. However, the high4 angle group would remain in maximal tibial internal rotation for a greater percentage of stance (30%) compared with the low-qangle group (10%). Previous investigations into lowerextremity timing demonstrated a synchronous relation between the occurrences of maximum rearfoot and knee flexion angle~.~.~' Tibia1 and femoral rotations, however, were not assessed in these studies. Based on the anatomical constraints at the talocrural and tibiofemoral joints, both the tibia and femur would be expected to reach their respective rotation maxima synchronous with rearfoot eversion and knee flexion. The articular congruency at the talocrural joint results in the tibia reaching maximum internal rotation simultaneous with rearfoot eversion. Figure 3 displays the Low Qangle High Qangle FIGURE 3. Percentage of stance at which maximum segment and joint angles occur. The low-q-angle group reached maximal tibial internal rotation before the high*-angle group (dark bars, P <.01), whereas the other variables were similar between groups. IR indicates internal rotation; ER. external rotation. J Orthop Sports Phys Ther.Volume 300Nurnber 5-May 2000

7 TABLE 5. Post hoc power analysis results for each kinematic variable except time to maximum tibial internal rotation. Variable Pooled variance Effd size Power* Rearfoot at touchdown Maximum rearfoot eversion Total rearfoot motion Maximum tibia1 internal rotation Maximum tibia1 external rotation Total tibia1 rotation Maximum knee flexion Maximum femoral external rotation Maximum femoral internal rotation Total femoral rotation Time to maximum rearfoot eversion Time to maximum knee flexion Time to maximum femoral external rotation * n = 16 per group; a =.05. time during the stance phase that various maximum angles of the lowerextremity segments occurred for both groups. The high-qangle group seemed to verify the previous arguments, since the segment angles reached their respective maxima nearly simultaneously. In the low-qangle group, however, maximum tib ial internal rotation was achieved before maximum foot eversion and knee flexion based on the single point calculation of the maximum. This apparent group difference between the synchronization of the specific lowerextremity events, however, was not evident under statistical analysis. The appropriateness of 15" to distinguish between normal and excessive Qangles can also be questioned. No consistent value exists for defining a normal Q angle based on a review of literature ~2-5.'5.!2X.W In these studies, a range of 11-17" can be found among nonimpaired subjects and a range of 12-19" among subjects with pathological findings. This disparity among the various investigations suggests that a single point discriminator to define an excessive Qangle may not be suitable. An assessment based on a continuum of the Qangle may be more beneficial; however, the results of the linear regression do not support this claim. Based on the correlation coefficients, little of the variation found in the kinematic parameters could be explained by the differences in Qangle. The lack of significant group differences suggests that an excessive Qangle does not alter the magnitude of rearfoot eversion or tibial internal rotation angles. It should be noted, however, that the chance of type I1 statistical error exists based on post hoc power analyses. The effect size for many of the variables was small, resulting in low statistical power (Table 5). Although the a priori power analysis suggested that the sample size for this study was adequate, it should be emphasized that the post hoc power analysis indicated that these results should be viewed with caution. Further, the significance of the Qangle as a clinical measure has been questioned.":" Caylor et a15 in- vestigated the relationship between Qangle and anterior knee pain syndrome. Measurement of the Q angles between symptomatic and asymptomatic sub jects revealed minimal difference in magnitude, leading the authors to conclude that anterior knee pain syndrome is a multiple-factor dysfunction. Thus, measurement of the Qangle alone may not be sufficient to identify pathological conditions. The external rotation of the femur during the early stance phase of running is a finding that is contrary to previous investigations that report femoral internal rotation during the initial stance of walking."jx Unlike walking, the contralateral pelvis undergoes a forward progression during the early stance phase of running. This early progression could result in accompanying external rotation of the femur. CONCLUSION No relationship was found between the magnitude of the Qangle and maximum rearfoot eversion or tibial internal rotation. These findings fail to support the notion that an excessive Qangle alters maximum rearfoot eversion or tibial and femoral rotation during running. The high-q-angle group, however, required greater time to reach maximum tibial internal rotation than the 1ow-Q-angle group. The potential impact that the tibial rotation timing difference may have on producing knee injuries associated with running is uncertain. ACKNOWLEDGMENTS The authors thank Dr Richard van Emmerik and Dr David Tiberio for their assistance with the manuscript preparation. REFERENCES 1. Abdel-Aziz YI, Karara HM. Direct linear transformation from comparator coordinates into object space coordi- J Orthop Sports Phys Ther Volume SO Number 5 May 2000

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