Effectiveness of Foot Orthotic Devices Used to Modify Pronation in Runners*

Transcription

1 /82/ $02.00/0 THE JOURNAL OF ORTHOPAEDIC AND SPORTS PHYSICAL THERAPY Copyright O 1982 by The Orthopaedic and Sports Physical Therapy Sections of the American Physical Therapy Association Effectiveness of Foot Orthotic Devices Used to Modify Pronation in Runners* MARY M. RODGERS, MS, LPTT, BARNEY F. LEVEAU, PHD, LPT Foot orthotic devices (FOD) are often used to treat excessive pronation and related problems of runners. In order to assess the effectiveness of FOD, 29 runners who used FOD were filmed on an outdoor track during three conditions: 1) barefoot, 2) running shoe, and 3) running shoe plus FOD. The barefoot data were not used because of marked variability. Comparison between the shoe and FOD conditions showed that only two of the six variables were statistically significant at the 0.05 level. Both the maximum angle of pronation and percentage of support time in pronation on the left foot were significantly decreased in the FOD trial. No significant differences were found between the shoe and FOD conditions for the other four variables (pronation velocity on both feet, maximum angle of pronation on the right foot, and percentage of support time spent in pronation on the right foot). The variability of these results support the conclusion that the type of FOD used in this study have questionable effectiveness in the treatment of excessive pronation. Foot orthotic devices (FOD) are often used to correct malalignment, especially excessive pronation and its numerous related problems Orthotic correction of excessive pronation is essentially empirical and clinical results have been 527v ' 2. 13, l5 The high cost of custom-made orthoses ($ per pair) leads many sports medicine personnel to question the practicality of FOD in correcting malalignment. Although many authors have presented views regarding the value of FOD, few research studies have been reported. In one study, Bates et al2 filmed six previously injured runners on a treadmill using rear and side views during three conditions: 1) barefoot, 2) running shoe, and 3) regular shoe plus FOD. These authors found that both the period of pronation and the amount of maximum pronation were significantly less (P = 0.15) in the FOD condition than in the barefoot condition. No significant differences were found between the FOD condition and shoe condition for pronation variables. In an unpublished study, Cavanagh et a1.5 used both a force plate and a ' This study was a winner in the Allied Heaiih Division of the Fifth International Conference on Human Functioning, Biomedical Synergistic Institute, September t This study partially fulfilled the requirements for the Master of Science degree at the University of North Carolina, Chapel Hill. NC. high speed motion camera to examine the effect of felt shoe inserts on the foot position of four symptom-free runners. The authors found that the amount and rate of pronatory movement was reduced with these "soft orthotics." A review of the literature shows an obvious dearth of substantial research to confirm the effectiveness of FOD in modification of foot position in runners. The few research studies which have been reported have small sample size, artificial environment, and uncontrolled variables. The purpose of the current study was to expand objective data regarding the effectiveness of FOD so that sports medicine clinicians might have more information on which to base treatments. For specific definitions used in this study, see the "Appendix." METHOD Twenty-nine male runners, aged 14 to 53 years, participated in this study. The subjects were either volunteers from the local running community or patients of a local podiatrist. All subjects wore individualized semirigid FOD made of polypropylene (as described by ~ rody,~ p. 33). Each subject completed a questionnaire so that sample characteristics, running habits, and reasons for needing a FOD could be identi-

2 JOSPT Fall 1982 FOOT ORTHOTIC DEVICES 8 7 fied. Standard objective measurements of each runner were taken to identify physical characteristics of the subjects. Ankle range measurements were made with the subject supine and prone with feet off the table. Leg length was measured using the distance from the anterior superior iliac spine to the medial malleolus with the subject supine. Each subject wore his own running attire for the study. Reference points on each subject's calf midline, Achilles tendon, mid-calcaneus, and bottom center of the shoe heel cup were marked with a black square of tape marked centrally with a white hole reinforcer, so that a 6-mm-diameter black dot was visible. These markings were similar to those used by Cavanagh et a1.5 Midlines were determined with sliding calipers. The 16- mm camera (1 6-mm motor-drive Teledyne camera, model DBM-45, Teledyne Camera System, Arcadia, CA) with electronically calibrated timing lights was placed in the plane of running motion and leveled at a height which permitted visualization of the lower third of the runner's legs. This height and the camera-subject distance were kept constant for all filming. Each runner was filmed at 120 frames per second using a 50-mm lens from a posterior view during three randomly sequenced conditions. The three conditions were: 1) running barefoot (B), 2) running shoes with FOD (FOD), and 3) running in running shoes (S). Some shoes had no arch because the entire insole had been removed to allow room for the FOD inside the shoes. In those cases, a foam arch cookie was used to replace the missing insole. The present investigation attempted to make the experimental environment as similar as possible to the runner's natural environment. For this reason, the subjects were filmed on an outdoor track wearing their own individual shoes and FOD. Each runner ran on the straight portion of an outdoor (Rubaturf surface) track. The subjects were instructed to run at a comfortable pace (7-8 minutes per mile) and to keep the speed between the three trials as constant as possible. At least 50 yards were allowed for the subjects to achieve a constant speed before entering the 20-foot filming zone. At least two support phases of each foot were filmed for each condition. The toe-out angles of the first nine subjects were filmed and calibrated so that perspective error was ruled out. The data were collected from the film using a Vanguard Motion Analyzer (Vanguard Instru- ment Corp., Melville, NY). The heel of the foot could not be directly measured except in the barefoot trials. Subjects were instructed to tie their shoes securely to minimize possible movement of the heel within the shoe cup. The following assumptions, used by Cavanagh et al.,5 were made for this study: 1) that no relative movement existed between the shoe and foot, and 2) that the rearfoot angle represents ankle inversion and eversion. All timed calculations were based on the electronically calibrated internal timing lights of the camera. The running speed of each trial was determined from the film speed and the number of frames between the points where the subject first crossed into and out of the marked 20-foot filming zone. Frame numbers were recorded for a support phase of each foot during each of the three conditions (barefoot, shoe, FOD). Calculations for support time spent in pronation (PS) and angular velocity of pronation (PV) were based on the film speed and the frame numbers for the following: foot strike, begin pronation (neutral position), maximum pronation, end pronation (neutral position), and toe-off. The maximum angular displacement in pronation (MP) was directly measured from the film using the Vanguard grid and the reference markers on each subject's calf midline, Achilles tendon, midcalcaneus, and bottom center of shoe heel cup (see Fig. 1 ). In order to determine if speed should be used as a co-variable in the analysis, the relationships between speed and each of the three variables (PS, PV, and MP) were tested using the Spearman correlation. This statistical procedure Pronat ion Neutral Supination Position Fig. 1. Method of measuring angles of pronation and supination on right lower extremity.

3 88 RODGERS AND LEVEAU JOSPT Vol. 4, No. 2 showed no significant variability in the speed among subjects and trials; therefore speed was not used as a co-variable. The normality of the data was tested for each dependent variable for right and left feet at each of the three trials using the Shapiro-Wilk W Statistic." These tests showed that normality could not be assumed and that nonparametric methods of statistical analysis should be used. The Average External Spearman Rank Correlation was used to test the null hypothesis against the alternative ordered hypothesis (B > S > FOD). Signed rank tests for B-S differences and for S- FOD differences were used to further investigate the differences between the conditions. four had a short left leg and eight had a short right leg. The reasons given by subjects for needing FOD are contained in Table 2. The average speed for each subject for each trial showed little variation (Table 3). The means and standard deviations for each variable and each foot are shown in Table 3. The large standard deviations necessitated use of the Average External Rank Spearman Correlation to determine if the hypothesized relationship (B > S > FOD) was valid. Based on these statistical results, the null hypothesis (no difference between the three conditions) could not be rejected. The results of the signed rank tests (Table 4) show that only two of the six dependent variables for the shoe condition were larger than the values for the FOD RESULTS condition. The values of the left MP and left PS Subject characteristics and physical measure- were significantly less with the FOD when ments are shown in Table 1. Of the 29 subjects, pared to the shoe. No significant difference was TABLE 1 found between the shoe and FOD conditions for Subject characteristics the other 4 variables. The subjects appeared to be uncomfortable with running barefoot on the Characteristic Range Median track which may have affected the barefoot data. Age (years) Height 5'4"-6'3~1 5'1 0" Because of the variability of the barefoot data, Weight (~b) only comparisons between the shoe and FOD Best mile run time 4:09-6: conditions are reported. Physical measurements Dorsiflexion DISCUSSION Plantar flexion Pronation (eversion) 5-1 5" 12" The present investigation attempted to make Supination (inversion) 10-40' 19' Navicular (arch) height the experimental environment as similar as posweight-bearing (cm) sible to the runner's natural environment. For this reason, the subjects were filmed on an out- TABLE 2 door track instead of a treadmill and wore their Reasons cited by subjects for requiring FOD assistance own shoes and FOD. Although a certain amount Reasons for getting FOD of variability was introduced by this approach, Of runners Percentage the authors view the study to be more accurate Knee pain I in reflecting the average runner's response to Foot and/or ankle pain FOD than those studies which artificiallv con- Shin splints Other trolled those variables. The variability of the barefoot data in this study may reflect the ab- TABLE 3 Means and standard deviations for each variable and each condition Varible Barefoot Shoe FOD MP, right 6.85' f 2.57" 7.98' ' 7.58' ' MP, left 8.06' ' 8.89" f 3.60' 7.96" f 3.09' PS, right (%) t f PS, left (%) f f f PV, right (radians/sec) 9.68 f f f 5.49 PV, left (radians/sec) 9.05 f f f 6.62 Running speed-) (ft/sec) 14.4 f f * Mean 2 SD. t Speed within filming zone of 20 feet.

4 JOSPT Fall 1982 FOOT ORTHOTIC DEVICES 89 TABLE 4 Signed rank tests comparing barefoot versus shoe and shoe versus FOD Variable Barefoot versus Shoe Shoe versus FOD T-score P T-score P MP, right MP, left : PS, right PS, left ' PV, right PV, left * Significant difference, p normal condition of running barefoot on a track. The subjects did not run long enough to fatigue any muscular control they may have automatically used to prevent potentially painful foot positions. Variability within the sample reflected the criteria used for selecting subjects. The subjects were male, ran regularly, and used FOD. No attempt was made to select subjects who were excessive pronators, although the conditions which necessitated the runners' use of FOD were related to excessive pronation. Since few data have been collected on FOD function, data from runners with different diagnoses should be more representative of the FOD-wearing population. The present study supports the findings by Bates et al.' of no significant differences between the shoe and FOD conditions. The results of the two studies are similar despite differences in procedures. Based on a pilot study and the results of other published studies, the treadmill was not used in the present study because it altered foot mechanics. Although speed is more difficult to control on the track, the present study has less speed differential than the Bates et al. study.' The use of the track, and of the runner's own shoes and FOD made the present study more similar in environment to the runner's everyday running situation. The larger sample size of 29 subjects (compared with six subjects) and use of a significance level of P = 0.05 (compared to P = 0.15) provided a more sound statistical analysis. The study of Bates et al.' evaluated only the subjects' right feet, assuming both feet to be the same. The present study found marked differences between left and right feet which may have been related to leg length discrepancies. Despite these experimental differences, the present study supports the results of the Bates et al. study.' The present study conflicts with the findings by Cavanagh et of significant differences between the shoe and FOD conditions. The felt pads used by Cavanagh et al. produced significant decreases in pronatory measurements, whereas the FOD used in the present study did not. Comparison between layers of soft felt and the semirigid FOD is questionable. The three layers of felt pad which were inserted in the runner's regular shoe were quite thick (1 8 millimeters compressed to 9.5 millimeters). Cavanagh et al. used "four symptom-free recreational runners" (a small sample size) and did not control their running speed. The data were not tested to determine significant differences between the shoe and FOD conditions. The present study found significant differences only on the left foot and only for MP and PS. Cavanagh et al. examined only the right foot of each subject. Cavanagh et al. calculated PV based on the time from foot strike to MP, while the present study's calculations were based on the time from neutral position to MP. The soft inserts used by Cavanagh et al.' appeared to be more effective than the semirigid orthoses used in the Bates et al. study' and in this study. Although several articles have been published emphasizing the values of orthotic devices, these articles have not presented the detailed method of study and analysis needed for scientific scrutiny. More investigation is needed to significantly support or refute the use of orthotic devices for runners. The present study attempted to use improved methods in examining the FOD; however, the results do not conclusively prove or disprove the effectiveness of the FOD. More investigation of the FOD employing larger samples and controlled variables are needed. In addition, the function of pronation in normal and abnormal running gaits should be studied. Left and right foot data should be compared and related to specific biomechanical function. Runners who have successfully eliminated their pain with FOD use should be examined. A future study based on collected data should examine the relationship between runners' injuries and the effectiveness of FOD treatment. CONCLUSIONS 1) The maximum angle of pronation and percentage of support time in pronation on the left foot were significantly decreased in the FOD condition when compared to the shoe condition. 2) The pronation velocity on both feet, maxi-

5 90 RODGERS AND LEVEAU JOSPT Vol. 4, No. 2 mum angle of pronation on the right foot, and percentage of support time in pronation of the right foot showed no significant difference between the shoe and FOD conditions. 3) The variability of these results indicate that the effectiveness of the FOD used in this study is questionable. APPENDIX Neutral position-bisection of heel parallel to bisection of calf midline Pronation-eversion of the calcaneus relative to the midline of the calf. Measurement used to approximate the true action of pronation Supination-inversion of the calcaneus relative to the midline of the calf. Measurement used to approximate the true action of supination Begin pronation-neutral position of calcaneus when moving from a supinated to a pronated p~sition.'.~,~ Maximum pronation-position of greatest eversion of calcaneus relative to the calf midline 1.2,5 End pronation-neutral position of calcaneus when moving from a pronated to a supinated position.'. 2, Foot orthotic device (FOD-appliance placed between the foot and shoe to modify foot position during the support phase of gait.2,15.'7 Support phase-part of running cycle from foot strike until toes leave ground.14 Foam cookie-oval-shaped foam arch found in the insole of most running shoes. Appreciation is extended to John Yack for his assistance with this study. REFERENCES 1. Bates BT, Osternig LR, Mason BR, et al.: Functional variability of the lower extremity during the support phase of running. Med Sci Sports 11 : , Bates BT, Osternig LR, Mason BR, et al.: Foot orthotic devices to modify selected aspects of lower extremity mechanics. Am J Sports Med 7: , Brody DM: Running Injuries. ClBA Clin Symp 32(4):1-36, Buchbinder MR, Napora NJ, Biggs EW: The relationship of abnormal pronation to chondromalacia of the patella in distance runners. J Am Podiatry Assoc 69: , Cavanagh PR, Clarke T, Williams K, et al.: An evaluation of the effect of orthotics force distribution and rearfoot movement during running. Presented at the American Orthopaedic Society for Sports Medicine Meeting, Lake Placid, NY, June, lnman VT. Mann RA: Biomechanics of the foot and ankle. In: lnman VT, Duvries, HL (eds), Surgery of the Foot, Ed 4, pp St. Louis: The CV Mosby Co, James SL, Bates BT. Osternig LR: Injuries to runners. Am J Sports Med 6:40-50, Jernick S. Heifitz NM: An investigation into the relationship of foot pronation to chondromalacia patellae. Arch Podiatr Med Foot Surg (Suppl II) pp 1-31, Mann RA, lnman VT: Phasic activity of intrinsic muscles of the foot. J Bone Joint Surg 64A: , Mann RA, Baxter DE. Lutter LD: Running symposium. Foot 8 Ankle 1 : , , Netter J, Wasserman W: Applied Linear Statistical Models. Georgetown, Ontario: Richard D. Irwin, Inc, Root ML, Orien WP, Weed JH: Normal and Abnormal Function of the Foot. Los Angeles: Clinical Biomechanics Corp, Rose GK: Correction of the pronated foot. J Bone Joint Surg 44L: , Slocum DB, James SL: Biomechanics of running. JAMA 205: , Subotnick SI: The abuses of orthotics in sports medicine. Phys Sports Med 3: Wright DG, Desai SM, Henderson WA: Action of the subtalar and ankle joint complex during the stance phase of walking. J Bone Joint Surg 46A: , Yale I: Podiatric Medicine. Ed 2. Baltimore: Williams 8 Wilkins, 1980