- Email: [email protected]
Effect of rearfoot orthotics on postural sway after lateral ankle sprain
1000
PROSTHETICS/ORTHOTICS/DEVICES
Effect of Rearfoot Orthotics on Postural Sway After Lateral Ankle Sprain Jay Hertel, PhD, ATC, Craig R. Denegar, PhD, ATC, PT, W.E. Buckley, PhD, ATC, Neil A. Sharkey, PhD, Wayne L. Stokes, MD ABSTRACT. Hertel J, Denegar CR, Buckley WE, Sharkey NA, Stokes WL. Effect of rearfoot orthotics on postural sway after lateral ankle sprain. Arch Phys Med Rehabil 2001;82: 1000-3. Objective: To investigate the effects of different rearfoot orthotics on postural sway during unilateral stance after lateral ankle sprain. Design: Repeated-measures 3-factor analysis of variance on postural sway length and velocity in the frontal and sagittal planes with factors being stance leg (injured, uninjured), session (within 3d, 2wk, 4wk postinjury), and condition (6 orthotic conditions). Setting: University biomechanics laboratory. Patients: Fifteen collegiate athletes with acute, unilateral first- or second-degree lateral ankle sprain. Interventions: Balance testing was performed under 6 conditions: (1) shoe only, (2) molded Aquaplast orthotic, (3) lateral heel wedge, (4) 7° medially posted orthotic, (5) 4° laterally posted orthotic, and (6) neutral orthotic. Main Outcome Measures: Postural sway length and postural sway velocity in the frontal and sagittal planes. Results: Significant main effects were found for side and session, but not orthotic condition, for all 4 dependent variables. Postural sway length and velocity were greater on the injured limbs as compared with the uninjured limbs during the first 2 sessions but not during the third session. None of the orthotics significantly reduced postural sway compared with the shoe-only condition after lateral ankle sprain. Conclusions: Rearfoot orthotics, irrespective of design or posting, were ineffective at improving postural sway after lateral ankle sprain. Key Words: Ankle, sprains and strains; Balance; Orthotic devices; Posture; Rehabilitation. © 2001 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation
From the Departments of Kinesiology (Hertel, Denegar, Buckley, Sharkey), Orthopaedics and Rehabilitation (Denegar, Sharkey, Stokes), Penn State Center for Sports Medicine (Denegar, Stokes), Center for Locomotion Studies (Sharkey), Pennsylvania State University, University Park, PA. Accepted in revised form July 18, 2000. Supported by the National Athletic Trainers’ Association Research and Education Foundation and the Robert and Susan Freidman Student Fund. Presented in part at the American Physical Therapy Association Combined Sections Meeting, February 5, 2000, New Orleans, LA. No commercial party having a direct financial interest in the results of the research supporting this article has or will confer a benefit upon the author(s) or upon any organization with which the author(s) is/are associated. Reprint requests to Jay Hertel, PhD, ATC, Penn State University, 269 Recreation Bldg, University Park, PA 16802, e-mail: [email protected]. 0003-9993/01/8207-6205$35.00/0 doi:10.1053/apmr.2001.22349
Arch Phys Med Rehabil Vol 82, July 2001
ATERAL ANKLE SPRAINS are among the most comL mon injuries suffered during competitive and recreational athletics. In sports such as basketball, most experienced 1,2
players have suffered at least 1 lateral ankle sprain at some point in their careers.3 Recurrence rate for lateral ankle sprain has been reported to be as high as 80% among athletes.4 Approximately 30% of those suffering a lateral ankle sprain develop functional instability, or repetitive giving way of the ankle.5 Although lateral ankle sprain is rarely permanently disabling, an association between repetitive ankle sprain and osteoarthritis of the joints about the ankle has been reported.6,7 Despite extensive research, recurrence of lateral ankle sprain remains problematic for athletes and clinicians alike. Two hypotheses have been proposed to describe the cause of recurrent lateral ankle sprain: mechanical instability and functional instability. Mechanical instability, a loss of the structural integrity of the ankle ligaments after injury, is thought to predispose individuals to further injuries because the ankle is allowed to go through a greater range of motion. Mechanical instability has been shown at both the talocrural and subtalar joints after lateral ankle sprains.8 Functional instability is proposed to result because of neuromuscular deficits that occur after lateral ankle sprain. Freeman5 first proposed functional instability as a cause of repetitive lateral ankle sprain when he noted impaired balance in single leg stance among patients after ankle ligament injury. Since then, numerous reports9-13 have identified impaired balance after lateral ankle sprain. Maintenance of balance is typically accomplished by using either the ankle strategy or the hip strategy. The ankle strategy occurs when muscle contractions first occur about the ankle and cause a torque that rotates the body toward the support surface after a perturbation. This strategy is generally used by healthy adolescents and young adults. The hip strategy occurs when hip flexion or extension are performed in the direction of a perturbation, thus causing a force to be generated against the support surface. The hip strategy is not as effective as the ankle strategy and is typically used by the elderly and those with balance disorders. Greater use of the hip strategy in maintaining single-leg stance has been reported in young athletes after lateral ankle sprain.14,15 It has been hypothesized that a loss of proprioceptive feedback caused by injury to the afferent receptors in the lateral ankle ligaments may alter the strategy used when maintaining a single-leg stance.5 The use of molded foot orthotics has been shown to be advantageous in improving postural control after lateral ankle sprain, although the exact mechanisms have not been clearly defined.16,17 Orteza et al16 found that molded neutral orthotics improved balance and led to decreased ankle pain while jogging in patients suffering from acute lateral ankle sprain. Guskiewicz and Perrin17 found that orthotics reduced the magnitude of postural sway in various balance tasks in patients suffering acute ankle sprains. It should be noted that the orthotics used in both of these studies were custom fit for each patient.16,17 Stabilization of the subtalar joint with orthotics
1001
ORTHOTICS AND ANKLE SPRAIN, Hertel
may allow the injured individual to return to the ankle strategy of balance maintenance and may be the mechanism by which orthotics help to improve balance after lateral ankle sprain; however, research is needed to validate this hypothesis. The literature concerning the type of orthotics to use in the treatment of lateral ankle sprain is scarce and recommendations are based largely on anecdotal evidence. Clanton18 has anecdotally suggested that a laterally posted heel wedge be used in the conservative treatment of mechanical instability of the subtalar joint. Many clinicians prefer to use neutral orthotics, whereas others use medial or lateral posts. It seems unlikely that these 3 fundamentally different methods of controlling rearfoot position can all be effective in the treatment of lateral ankle sprain. Therefore, this study sought to examine the effects of differently posted rearfoot orthotics on postural control after lateral ankle sprain. METHODS Subjects Fifteen collegiate athletes (8 men, 7 women; age, 21.9 ⫾ 6.2yr; height, 176.5 ⫾ 7.4cm; weight, 74.3 ⫾ 11.2kg) who had suffered unilateral first- or second-degree lateral ankle sprain volunteered as subjects. Nine subjects suffered right lateral ankle sprain, whereas 6 suffered injuries to their left ankles. All subjects signed a human subject consent form approved by the Pennsylvania State University Institutional Review Board. Subjects were either referred to the investigator from intercollegiate or intramural athletic trainers or responded to publicly posted flyers publicizing the study. All subjects were assessed by the same clinician to assure consistency in the grading of injury. Those suffering concurrent fractures or deltoid ligament sprains were excluded. Subjects who had suffered lower extremity fractures or cerebral concussions within the previous 12 months were also excluded, as were individuals who had balance disorders. Subjects were not tested until they were full weight bearing and could consistently maintain a single-leg stance on their injured leg for at least 5 seconds. The uninjured leg served as the control. Subjects were allowed to take medications and perform rehabilitation as recommended by their health care providers. Rehabilitation and medication were allowed to simulate typical clinical conditions. All subjects were instructed in proper care of their lateral ankle sprain with an emphasis placed on rest, cryotherapy, compression, elevation, walking with a normal gait pattern, and a gradual rehabilitation program. Instrumentation Postural control measurements were assessed using a forceplatea interfaced with an IBM-compatible computer using LabVIEW software.b Data were captured at 50Hz, amplified, digitized, and recorded by the computer. The force plate measured the location and magnitude of the 3 components of ground reaction force. Global coordinates of the center of pressure (COP) were subsequently calculated for the frontal plane (X) and sagittal plane (Y) coordinates. Materials Five types of orthotic devices were tested with each subject. Neutral position, molded orthotics made with 1⁄8-inch Roylan Aquaplast-T™c were constructed for both feet of each subject using the methods of orthotic fabrication described by Massie.19 No posting of the molded orthotics was performed. Neutral, as well as both medially (7° post) and laterally (4° post) posted Superfeet Synergizer™ footbed orthoticsd were
each tested, as was the Sprained Ankle Orthotic,e a prefabricated rigid laterally posted heel wedge. A shoe-only condition, with no orthotic intervention, was also used. Subjects wore a pair of their own low-top athletic shoes with the different orthotics. Protocol Subjects were instructed to maintain single-leg stance while standing on the forceplate under 6 conditions: (1) shoe with no orthotic, (2) shoe with molded Roylan Aquaplast-T orthotic, (3) shoe with medially posted orthotic, (4) shoe with laterally posted orthotic, (5) shoe with neutral orthotic, and (6) shoe with sprained ankle orthotic. The order of test conditions and stance leg were performed in a counterbalanced manner to avoid any potential order effects from contaminating the data. The nonstance leg was held in slight hip and knee flexion and was not allowed to touch the stance leg during testing. Arms were folded across the chest, and eyes were open to allow visual feedback during the balance task. If the nonstance leg touched the ground, the trial was terminated and repeated again. The length of each trial was 5 seconds and subjects performed 3 trials on each leg with a rest period of 30 seconds between trials. Subjects underwent 3 testing sessions: (1) within 72 hours of return to full weight bearing, (2) 2 weeks after the first session, and (3) 4 weeks after the first session. Statistical Analysis Postural control was quantified with 2 measures of COP displacement in both the frontal and sagittal planes. The 4 dependent variables were the following: frontal plane postural sway length (PSLX), sagittal plane postural sway length (PSLY), root mean square (RMS) of frontal plane sway velocity (VelX), and RMS of sagittal plane sway velocity (VelY). PSX and PSY were determined by calculating the length of the path of the COP in the frontal and sagittal planes, respectively, throughout the entire 250 data point trial using the equation: PS ⫽ i⫺250
冘abs(COP ⫺ COP i
i⫺1
)
RMS values of VelX and VelY were determined by dividing the length between adjacent measurements by .02 seconds for all 250 data points. Because the velocity could be expressed as either a positive or negative value, the RMS of the velocity measures was calculated using the formula:
velRMS ⫽ i⫽250
冑
冘冉 COP ⫺.02COP 冊
2
i
i⫺1
250
Four separate 3-factor analyses of variance were run on the postural control variables with the independent variables being side (injured leg stance vs uninjured), session (day 1, week 2, week 4), and orthotic condition. The level of significance was preset at .05. RESULTS Significant main effects were found for side and session (p ⬍ .05), but not orthotic condition (p ⬎ .05), for all 4 dependent variables. None of the orthotics significantly improved postural sway measures compared with the shoe-only condition after lateral ankle sprain. PSLX data are presented in figures 1–3. Similar trends were also observed for PSLY, VelX, and VelY. All sway measures were significantly higher (p ⬍ .05) on injured limbs as compared with uninjured limbs. Significant improvements in all 4 variables were seen between Arch Phys Med Rehabil Vol 82, July 2001
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ORTHOTICS AND ANKLE SPRAIN, Hertel
Fig 1. Mean PSLX within 3 days under the 6 different orthotic conditions. Significant differences were found between the injured (■) and uninjured (p) limbs (n ⴝ 15) under all conditions (p < .05). No significant differences were found between the different orthotic conditions. Error bars represent 1 standard deviation (SD). Abbreviations: Aqua, Aquaplast; SAO, Sprained Ankle orthotic; Med, medial; Lat, lateral; Neut, neutral.
sessions on both the injured and uninjured limbs (p ⬍ .05). For PSLX, a significant side-by-session interaction (F ⫽ 15.34, df ⫽ 2,28, p ⬍ .0005) was found, indicating that improvements across sessions were greater on the injured limbs as compared with the uninjured limbs (fig 4). No other significant 2- or 3-factor interactions were found (p ⬎ .05). DISCUSSION Postural control during single-leg stance on injured limbs was found to be initially impaired after lateral ankle sprain. However, none of the orthotics examined in this study were able to decrease postural control impairment after injury. Previous studies investigating the effects of rearfoot orthotics on
Fig 2. Mean PSLX at week 2 under the 6 different orthotic conditions. No significant differences were found between the different orthotic conditions. Significant differences (p < .05) were found between the injured (■) and uninjured (p) limbs (n ⴝ 15) for all conditions, except the SAO. Error bars represent 1 SD.
Arch Phys Med Rehabil Vol 82, July 2001
Fig 3. Mean PSLX at week 4 under the 6 different orthotic conditions. No significant differences were found between the different orthotic conditions or between the injured (■) and uninjured (p) limbs (n ⴝ 15) under all conditions. Error bars represent 1 SD.
balance after lateral ankle sprain have used molded orthotics with posting performed specific to foot malalignments (ie, rearfoot valgus, forefoot varus) identified by the investigator.16,17 In the current study, no adjustments were made based on subject malalignments. Instead, 4 differently posted off-theshelf orthotics and 1 custom-molded orthotic without individualized posting were used in an effort to compare the effects of architecturally different orthotics on postural sway. The current investigation is the first to study the effects of orthotic use in the shoe while assessing postural control with a forceplate measuring 3-dimensional ground reaction forces. Two previous studies found improved postural control with the use of orthotics after lateral ankle sprain using different methodologies than those used here. Orteza et al16 assessed postural control with a single axis unstable balance board, whereas Guskiewicz and Perrin17 used a forceplate system that only
Fig 4. Pooled injured and uninjured limb (n ⴝ 15) PSLX and sagittal PSLY across the 3 testing sessions. Injured PSLX within 3 days (■) was significantly higher than weeks 2 (p) and 4 (d) (p < .05). Injured PSLY was significantly higher on day 1 as compared with week 4 (p < .05). Uninjured PSLX was significantly higher on day 1 than week 4. Uninjured PSLY was significantly higher on day 1 than weeks 2 and 4. Error bars represent 1 SD.
ORTHOTICS AND ANKLE SPRAIN, Hertel
assessed vertical ground reaction forces. Our use of a more robust forceplate assessing 3-dimensional ground reaction forces might have been partly responsible for our contradictory results. Additionally, Guskiewicz and Perrin17 had subjects stand on orthotics placed directly on the forceplate; no shoe was used. In our study, the orthotics were placed in the shoe during testing, thus providing a more realistic and relevant assessment of the effects of the orthotics. The improvements in postural sway measures across the 1 month after lateral ankle sprain are consistent with previous studies that followed patients with acute ankle sprains.13 In our study, improvements in postural sway scores were seen across sessions on both the injured and uninjured limbs. This may be explained by 2 possible mechanisms. First, improvements may have been caused by a learning effect, because repetitive trials of the single-leg stance were seen. Previous research has shown improved postural sway with balance training after lateral ankle sprain.16,20,21 The second possibility is that lateral ankle sprain causes central changes in postural control thereby increasing postural sway on both the injured and uninjured limbs. Previous research has documented increased postural sway during unilateral stance on both injured and uninjured limbs.22 Although none of the orthotics used in this study decreased postural sway compared with the shoe-only condition, it remains unknown whether orthotic devices provide stabilization of the rearfoot during dynamic activities. It is possible that increased stabilization may place decreased strain on the lateral talocrural and subtalar ligaments during dynamic activities. If an orthotic were able to stabilize the rearfoot during functional activities in such a way as to decrease repetitive strain on healing ligamentous tissue, mechanical stability of the injured joint or joints may be enhanced, potentially leading to a decreased risk of recurrent lateral ankle sprain. Further research is needed to explore this possibility. CONCLUSION Postural sway length and velocity increased significantly on injured limbs as compared with uninjured limbs after lateral ankle sprain; however, rearfoot orthotics, irrespective of the posting, were unable to improve postural sway. If rearfoot orthotics are effective in the treatment of lateral ankle sprain, as has been expressed anecdotally, it appears unlikely that the mechanisms by which they improve function is related to improved postural control. References 1. Garrick JG, Requa RK. The epidemiology of foot and ankle injuries in sports. Clin Sports Med 1988;17:29-36. 2. Holmer P, Sondergaard L, Konradsen L, Nielsen PT, Jorgenson LN. Epidemiology of sprains in the lateral ankle and foot. Foot Ankle 1994;15:72-4. 3. Smith RW, Reischl SF. Treatment of ankle sprains in young athletes. Am J Sports Med 1986;14:465-71. 4. Yeung MS, Chan K, So CH, Yuan WY. An epidemiological survey on ankle sprain. Br J Sports Med 1994;28:112-6.
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5. Freeman MA. Instability of the foot after injuries to the lateral ligament of the ankle. J Bone Joint Surg Br 1965;47:678-85. 6. Gross P, Marti B. Risk of degenerative ankle joint disease in volleyball players: study of former elite athletes. Int J Sports Med 1999;20:58-63. 7. Harrington DC. Degenerative arthritis of the ankle secondary to long-standing lateral ligament instability. J Bone Joint Surg Am 1979;61:354-61. 8. Hertel J, Denegar CR, Monroe MM, Stokes WL. Talocrural and subtalar joint instability after lateral ankle sprain. Med Sci Sports Exerc 1999;31:1501-8. 9. Tropp H, Odenrick P, Gillquist J. Stabilometry recordings in functional and mechanical instability of the ankle joint. Int J Sports Med 1985;6:180-2. 10. Cornwall MW, Murrell PM. Postural sway following inversion sprain of the ankle. J Am Podiatr Med Assoc 1991;81:243-7. 11. Leanderson J, Wykman A, Eriksson E. Ankle sprain and postural sway in basketball players. Knee Surg Sports Traumatol Arthrosc 1993;1:203-5. 12. Goldie PA, Evans OM, Bach TM. Postural control following inversion injuries of the ankle. Arch Phys Med Rehabil 1994;75: 969-75. 13. Leanderson J, Eriksson E, Nilsson C. Proprioception in classical ballet dancers: a prospective study of the influence of an ankle sprain on proprioception in the ankle joint. Am J Sports Med 1996;24:370-4. 14. Tropp H, Odenrick P. Postural control in single-limb stance. J Orthop Res 1988;6:833-9. 15. Pinstaar A, Brynhildsen J, Tropp H. Postural corrections after standardized perturbations of single leg stance: effect of training and orthotic devices in patients with ankle instability. Br J Sports Med 1996;30:151-5. 16. Orteza LC, Vogelbach WD, Denegar CR. The effect of molded orthotics on balance and pain while jogging following inversion ankle sprain. J Athletic Training 1992;27:80-4. 17. Guskiewicz KM, Perrin DH. Effect of orthotics on postural sway following inversion ankle sprain. J Orthop Sports Phys Ther 1996;23:326-31. 18. Clanton TO. Instability of the subtalar joint. Orthop Clin North Am 1989;20:583-92. 19. Massie DL. Use and fabrication of temporary orthotics. J Athletic Training 1994;29:309-15. 20. Gauffin H, Tropp H, Odenrick P. Effect of ankle disk training on postural control in patients with functional instability of the ankle joint. Int J Sports Med 1988;9:141-4. 21. Bernier JN, Perrin DH. Effect of coordination training on proprioception of the functionally unstable ankle. J Orthop Sports Phys Ther 1998;27:264-75. 22. Tropp H. Pronator weakness in functional instability of the ankle joint. Int J Sports Med 1986;7:291-4. Suppliers a. Bertec Corp, 6185 Huntley Rd, Ste B, Columbus, OH 43229. b. National Instruments Corp, 11500 N Mopac Expwy, Austin, TX 78759. c. Smith & Nephew Inc, PO Box 1005, Germantown, WI 53022. d. Superfeet Worldwide LLC, 1419 Whitehorn St, Ferndale, WA 98248. e. Cramer Products Inc, PO Box 1001, Gardner, KS 66030.
Arch Phys Med Rehabil Vol 82, July 2001
PROSTHETICS/ORTHOTICS/DEVICES
Effect of Rearfoot Orthotics on Postural Sway After Lateral Ankle Sprain Jay Hertel, PhD, ATC, Craig R. Denegar, PhD, ATC, PT, W.E. Buckley, PhD, ATC, Neil A. Sharkey, PhD, Wayne L. Stokes, MD ABSTRACT. Hertel J, Denegar CR, Buckley WE, Sharkey NA, Stokes WL. Effect of rearfoot orthotics on postural sway after lateral ankle sprain. Arch Phys Med Rehabil 2001;82: 1000-3. Objective: To investigate the effects of different rearfoot orthotics on postural sway during unilateral stance after lateral ankle sprain. Design: Repeated-measures 3-factor analysis of variance on postural sway length and velocity in the frontal and sagittal planes with factors being stance leg (injured, uninjured), session (within 3d, 2wk, 4wk postinjury), and condition (6 orthotic conditions). Setting: University biomechanics laboratory. Patients: Fifteen collegiate athletes with acute, unilateral first- or second-degree lateral ankle sprain. Interventions: Balance testing was performed under 6 conditions: (1) shoe only, (2) molded Aquaplast orthotic, (3) lateral heel wedge, (4) 7° medially posted orthotic, (5) 4° laterally posted orthotic, and (6) neutral orthotic. Main Outcome Measures: Postural sway length and postural sway velocity in the frontal and sagittal planes. Results: Significant main effects were found for side and session, but not orthotic condition, for all 4 dependent variables. Postural sway length and velocity were greater on the injured limbs as compared with the uninjured limbs during the first 2 sessions but not during the third session. None of the orthotics significantly reduced postural sway compared with the shoe-only condition after lateral ankle sprain. Conclusions: Rearfoot orthotics, irrespective of design or posting, were ineffective at improving postural sway after lateral ankle sprain. Key Words: Ankle, sprains and strains; Balance; Orthotic devices; Posture; Rehabilitation. © 2001 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation
From the Departments of Kinesiology (Hertel, Denegar, Buckley, Sharkey), Orthopaedics and Rehabilitation (Denegar, Sharkey, Stokes), Penn State Center for Sports Medicine (Denegar, Stokes), Center for Locomotion Studies (Sharkey), Pennsylvania State University, University Park, PA. Accepted in revised form July 18, 2000. Supported by the National Athletic Trainers’ Association Research and Education Foundation and the Robert and Susan Freidman Student Fund. Presented in part at the American Physical Therapy Association Combined Sections Meeting, February 5, 2000, New Orleans, LA. No commercial party having a direct financial interest in the results of the research supporting this article has or will confer a benefit upon the author(s) or upon any organization with which the author(s) is/are associated. Reprint requests to Jay Hertel, PhD, ATC, Penn State University, 269 Recreation Bldg, University Park, PA 16802, e-mail: [email protected]. 0003-9993/01/8207-6205$35.00/0 doi:10.1053/apmr.2001.22349
Arch Phys Med Rehabil Vol 82, July 2001
ATERAL ANKLE SPRAINS are among the most comL mon injuries suffered during competitive and recreational athletics. In sports such as basketball, most experienced 1,2
players have suffered at least 1 lateral ankle sprain at some point in their careers.3 Recurrence rate for lateral ankle sprain has been reported to be as high as 80% among athletes.4 Approximately 30% of those suffering a lateral ankle sprain develop functional instability, or repetitive giving way of the ankle.5 Although lateral ankle sprain is rarely permanently disabling, an association between repetitive ankle sprain and osteoarthritis of the joints about the ankle has been reported.6,7 Despite extensive research, recurrence of lateral ankle sprain remains problematic for athletes and clinicians alike. Two hypotheses have been proposed to describe the cause of recurrent lateral ankle sprain: mechanical instability and functional instability. Mechanical instability, a loss of the structural integrity of the ankle ligaments after injury, is thought to predispose individuals to further injuries because the ankle is allowed to go through a greater range of motion. Mechanical instability has been shown at both the talocrural and subtalar joints after lateral ankle sprains.8 Functional instability is proposed to result because of neuromuscular deficits that occur after lateral ankle sprain. Freeman5 first proposed functional instability as a cause of repetitive lateral ankle sprain when he noted impaired balance in single leg stance among patients after ankle ligament injury. Since then, numerous reports9-13 have identified impaired balance after lateral ankle sprain. Maintenance of balance is typically accomplished by using either the ankle strategy or the hip strategy. The ankle strategy occurs when muscle contractions first occur about the ankle and cause a torque that rotates the body toward the support surface after a perturbation. This strategy is generally used by healthy adolescents and young adults. The hip strategy occurs when hip flexion or extension are performed in the direction of a perturbation, thus causing a force to be generated against the support surface. The hip strategy is not as effective as the ankle strategy and is typically used by the elderly and those with balance disorders. Greater use of the hip strategy in maintaining single-leg stance has been reported in young athletes after lateral ankle sprain.14,15 It has been hypothesized that a loss of proprioceptive feedback caused by injury to the afferent receptors in the lateral ankle ligaments may alter the strategy used when maintaining a single-leg stance.5 The use of molded foot orthotics has been shown to be advantageous in improving postural control after lateral ankle sprain, although the exact mechanisms have not been clearly defined.16,17 Orteza et al16 found that molded neutral orthotics improved balance and led to decreased ankle pain while jogging in patients suffering from acute lateral ankle sprain. Guskiewicz and Perrin17 found that orthotics reduced the magnitude of postural sway in various balance tasks in patients suffering acute ankle sprains. It should be noted that the orthotics used in both of these studies were custom fit for each patient.16,17 Stabilization of the subtalar joint with orthotics
1001
ORTHOTICS AND ANKLE SPRAIN, Hertel
may allow the injured individual to return to the ankle strategy of balance maintenance and may be the mechanism by which orthotics help to improve balance after lateral ankle sprain; however, research is needed to validate this hypothesis. The literature concerning the type of orthotics to use in the treatment of lateral ankle sprain is scarce and recommendations are based largely on anecdotal evidence. Clanton18 has anecdotally suggested that a laterally posted heel wedge be used in the conservative treatment of mechanical instability of the subtalar joint. Many clinicians prefer to use neutral orthotics, whereas others use medial or lateral posts. It seems unlikely that these 3 fundamentally different methods of controlling rearfoot position can all be effective in the treatment of lateral ankle sprain. Therefore, this study sought to examine the effects of differently posted rearfoot orthotics on postural control after lateral ankle sprain. METHODS Subjects Fifteen collegiate athletes (8 men, 7 women; age, 21.9 ⫾ 6.2yr; height, 176.5 ⫾ 7.4cm; weight, 74.3 ⫾ 11.2kg) who had suffered unilateral first- or second-degree lateral ankle sprain volunteered as subjects. Nine subjects suffered right lateral ankle sprain, whereas 6 suffered injuries to their left ankles. All subjects signed a human subject consent form approved by the Pennsylvania State University Institutional Review Board. Subjects were either referred to the investigator from intercollegiate or intramural athletic trainers or responded to publicly posted flyers publicizing the study. All subjects were assessed by the same clinician to assure consistency in the grading of injury. Those suffering concurrent fractures or deltoid ligament sprains were excluded. Subjects who had suffered lower extremity fractures or cerebral concussions within the previous 12 months were also excluded, as were individuals who had balance disorders. Subjects were not tested until they were full weight bearing and could consistently maintain a single-leg stance on their injured leg for at least 5 seconds. The uninjured leg served as the control. Subjects were allowed to take medications and perform rehabilitation as recommended by their health care providers. Rehabilitation and medication were allowed to simulate typical clinical conditions. All subjects were instructed in proper care of their lateral ankle sprain with an emphasis placed on rest, cryotherapy, compression, elevation, walking with a normal gait pattern, and a gradual rehabilitation program. Instrumentation Postural control measurements were assessed using a forceplatea interfaced with an IBM-compatible computer using LabVIEW software.b Data were captured at 50Hz, amplified, digitized, and recorded by the computer. The force plate measured the location and magnitude of the 3 components of ground reaction force. Global coordinates of the center of pressure (COP) were subsequently calculated for the frontal plane (X) and sagittal plane (Y) coordinates. Materials Five types of orthotic devices were tested with each subject. Neutral position, molded orthotics made with 1⁄8-inch Roylan Aquaplast-T™c were constructed for both feet of each subject using the methods of orthotic fabrication described by Massie.19 No posting of the molded orthotics was performed. Neutral, as well as both medially (7° post) and laterally (4° post) posted Superfeet Synergizer™ footbed orthoticsd were
each tested, as was the Sprained Ankle Orthotic,e a prefabricated rigid laterally posted heel wedge. A shoe-only condition, with no orthotic intervention, was also used. Subjects wore a pair of their own low-top athletic shoes with the different orthotics. Protocol Subjects were instructed to maintain single-leg stance while standing on the forceplate under 6 conditions: (1) shoe with no orthotic, (2) shoe with molded Roylan Aquaplast-T orthotic, (3) shoe with medially posted orthotic, (4) shoe with laterally posted orthotic, (5) shoe with neutral orthotic, and (6) shoe with sprained ankle orthotic. The order of test conditions and stance leg were performed in a counterbalanced manner to avoid any potential order effects from contaminating the data. The nonstance leg was held in slight hip and knee flexion and was not allowed to touch the stance leg during testing. Arms were folded across the chest, and eyes were open to allow visual feedback during the balance task. If the nonstance leg touched the ground, the trial was terminated and repeated again. The length of each trial was 5 seconds and subjects performed 3 trials on each leg with a rest period of 30 seconds between trials. Subjects underwent 3 testing sessions: (1) within 72 hours of return to full weight bearing, (2) 2 weeks after the first session, and (3) 4 weeks after the first session. Statistical Analysis Postural control was quantified with 2 measures of COP displacement in both the frontal and sagittal planes. The 4 dependent variables were the following: frontal plane postural sway length (PSLX), sagittal plane postural sway length (PSLY), root mean square (RMS) of frontal plane sway velocity (VelX), and RMS of sagittal plane sway velocity (VelY). PSX and PSY were determined by calculating the length of the path of the COP in the frontal and sagittal planes, respectively, throughout the entire 250 data point trial using the equation: PS ⫽ i⫺250
冘abs(COP ⫺ COP i
i⫺1
)
RMS values of VelX and VelY were determined by dividing the length between adjacent measurements by .02 seconds for all 250 data points. Because the velocity could be expressed as either a positive or negative value, the RMS of the velocity measures was calculated using the formula:
velRMS ⫽ i⫽250
冑
冘冉 COP ⫺.02COP 冊
2
i
i⫺1
250
Four separate 3-factor analyses of variance were run on the postural control variables with the independent variables being side (injured leg stance vs uninjured), session (day 1, week 2, week 4), and orthotic condition. The level of significance was preset at .05. RESULTS Significant main effects were found for side and session (p ⬍ .05), but not orthotic condition (p ⬎ .05), for all 4 dependent variables. None of the orthotics significantly improved postural sway measures compared with the shoe-only condition after lateral ankle sprain. PSLX data are presented in figures 1–3. Similar trends were also observed for PSLY, VelX, and VelY. All sway measures were significantly higher (p ⬍ .05) on injured limbs as compared with uninjured limbs. Significant improvements in all 4 variables were seen between Arch Phys Med Rehabil Vol 82, July 2001
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ORTHOTICS AND ANKLE SPRAIN, Hertel
Fig 1. Mean PSLX within 3 days under the 6 different orthotic conditions. Significant differences were found between the injured (■) and uninjured (p) limbs (n ⴝ 15) under all conditions (p < .05). No significant differences were found between the different orthotic conditions. Error bars represent 1 standard deviation (SD). Abbreviations: Aqua, Aquaplast; SAO, Sprained Ankle orthotic; Med, medial; Lat, lateral; Neut, neutral.
sessions on both the injured and uninjured limbs (p ⬍ .05). For PSLX, a significant side-by-session interaction (F ⫽ 15.34, df ⫽ 2,28, p ⬍ .0005) was found, indicating that improvements across sessions were greater on the injured limbs as compared with the uninjured limbs (fig 4). No other significant 2- or 3-factor interactions were found (p ⬎ .05). DISCUSSION Postural control during single-leg stance on injured limbs was found to be initially impaired after lateral ankle sprain. However, none of the orthotics examined in this study were able to decrease postural control impairment after injury. Previous studies investigating the effects of rearfoot orthotics on
Fig 2. Mean PSLX at week 2 under the 6 different orthotic conditions. No significant differences were found between the different orthotic conditions. Significant differences (p < .05) were found between the injured (■) and uninjured (p) limbs (n ⴝ 15) for all conditions, except the SAO. Error bars represent 1 SD.
Arch Phys Med Rehabil Vol 82, July 2001
Fig 3. Mean PSLX at week 4 under the 6 different orthotic conditions. No significant differences were found between the different orthotic conditions or between the injured (■) and uninjured (p) limbs (n ⴝ 15) under all conditions. Error bars represent 1 SD.
balance after lateral ankle sprain have used molded orthotics with posting performed specific to foot malalignments (ie, rearfoot valgus, forefoot varus) identified by the investigator.16,17 In the current study, no adjustments were made based on subject malalignments. Instead, 4 differently posted off-theshelf orthotics and 1 custom-molded orthotic without individualized posting were used in an effort to compare the effects of architecturally different orthotics on postural sway. The current investigation is the first to study the effects of orthotic use in the shoe while assessing postural control with a forceplate measuring 3-dimensional ground reaction forces. Two previous studies found improved postural control with the use of orthotics after lateral ankle sprain using different methodologies than those used here. Orteza et al16 assessed postural control with a single axis unstable balance board, whereas Guskiewicz and Perrin17 used a forceplate system that only
Fig 4. Pooled injured and uninjured limb (n ⴝ 15) PSLX and sagittal PSLY across the 3 testing sessions. Injured PSLX within 3 days (■) was significantly higher than weeks 2 (p) and 4 (d) (p < .05). Injured PSLY was significantly higher on day 1 as compared with week 4 (p < .05). Uninjured PSLX was significantly higher on day 1 than week 4. Uninjured PSLY was significantly higher on day 1 than weeks 2 and 4. Error bars represent 1 SD.
ORTHOTICS AND ANKLE SPRAIN, Hertel
assessed vertical ground reaction forces. Our use of a more robust forceplate assessing 3-dimensional ground reaction forces might have been partly responsible for our contradictory results. Additionally, Guskiewicz and Perrin17 had subjects stand on orthotics placed directly on the forceplate; no shoe was used. In our study, the orthotics were placed in the shoe during testing, thus providing a more realistic and relevant assessment of the effects of the orthotics. The improvements in postural sway measures across the 1 month after lateral ankle sprain are consistent with previous studies that followed patients with acute ankle sprains.13 In our study, improvements in postural sway scores were seen across sessions on both the injured and uninjured limbs. This may be explained by 2 possible mechanisms. First, improvements may have been caused by a learning effect, because repetitive trials of the single-leg stance were seen. Previous research has shown improved postural sway with balance training after lateral ankle sprain.16,20,21 The second possibility is that lateral ankle sprain causes central changes in postural control thereby increasing postural sway on both the injured and uninjured limbs. Previous research has documented increased postural sway during unilateral stance on both injured and uninjured limbs.22 Although none of the orthotics used in this study decreased postural sway compared with the shoe-only condition, it remains unknown whether orthotic devices provide stabilization of the rearfoot during dynamic activities. It is possible that increased stabilization may place decreased strain on the lateral talocrural and subtalar ligaments during dynamic activities. If an orthotic were able to stabilize the rearfoot during functional activities in such a way as to decrease repetitive strain on healing ligamentous tissue, mechanical stability of the injured joint or joints may be enhanced, potentially leading to a decreased risk of recurrent lateral ankle sprain. Further research is needed to explore this possibility. CONCLUSION Postural sway length and velocity increased significantly on injured limbs as compared with uninjured limbs after lateral ankle sprain; however, rearfoot orthotics, irrespective of the posting, were unable to improve postural sway. If rearfoot orthotics are effective in the treatment of lateral ankle sprain, as has been expressed anecdotally, it appears unlikely that the mechanisms by which they improve function is related to improved postural control. References 1. Garrick JG, Requa RK. The epidemiology of foot and ankle injuries in sports. Clin Sports Med 1988;17:29-36. 2. Holmer P, Sondergaard L, Konradsen L, Nielsen PT, Jorgenson LN. Epidemiology of sprains in the lateral ankle and foot. Foot Ankle 1994;15:72-4. 3. Smith RW, Reischl SF. Treatment of ankle sprains in young athletes. Am J Sports Med 1986;14:465-71. 4. Yeung MS, Chan K, So CH, Yuan WY. An epidemiological survey on ankle sprain. Br J Sports Med 1994;28:112-6.
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5. Freeman MA. Instability of the foot after injuries to the lateral ligament of the ankle. J Bone Joint Surg Br 1965;47:678-85. 6. Gross P, Marti B. Risk of degenerative ankle joint disease in volleyball players: study of former elite athletes. Int J Sports Med 1999;20:58-63. 7. Harrington DC. Degenerative arthritis of the ankle secondary to long-standing lateral ligament instability. J Bone Joint Surg Am 1979;61:354-61. 8. Hertel J, Denegar CR, Monroe MM, Stokes WL. Talocrural and subtalar joint instability after lateral ankle sprain. Med Sci Sports Exerc 1999;31:1501-8. 9. Tropp H, Odenrick P, Gillquist J. Stabilometry recordings in functional and mechanical instability of the ankle joint. Int J Sports Med 1985;6:180-2. 10. Cornwall MW, Murrell PM. Postural sway following inversion sprain of the ankle. J Am Podiatr Med Assoc 1991;81:243-7. 11. Leanderson J, Wykman A, Eriksson E. Ankle sprain and postural sway in basketball players. Knee Surg Sports Traumatol Arthrosc 1993;1:203-5. 12. Goldie PA, Evans OM, Bach TM. Postural control following inversion injuries of the ankle. Arch Phys Med Rehabil 1994;75: 969-75. 13. Leanderson J, Eriksson E, Nilsson C. Proprioception in classical ballet dancers: a prospective study of the influence of an ankle sprain on proprioception in the ankle joint. Am J Sports Med 1996;24:370-4. 14. Tropp H, Odenrick P. Postural control in single-limb stance. J Orthop Res 1988;6:833-9. 15. Pinstaar A, Brynhildsen J, Tropp H. Postural corrections after standardized perturbations of single leg stance: effect of training and orthotic devices in patients with ankle instability. Br J Sports Med 1996;30:151-5. 16. Orteza LC, Vogelbach WD, Denegar CR. The effect of molded orthotics on balance and pain while jogging following inversion ankle sprain. J Athletic Training 1992;27:80-4. 17. Guskiewicz KM, Perrin DH. Effect of orthotics on postural sway following inversion ankle sprain. J Orthop Sports Phys Ther 1996;23:326-31. 18. Clanton TO. Instability of the subtalar joint. Orthop Clin North Am 1989;20:583-92. 19. Massie DL. Use and fabrication of temporary orthotics. J Athletic Training 1994;29:309-15. 20. Gauffin H, Tropp H, Odenrick P. Effect of ankle disk training on postural control in patients with functional instability of the ankle joint. Int J Sports Med 1988;9:141-4. 21. Bernier JN, Perrin DH. Effect of coordination training on proprioception of the functionally unstable ankle. J Orthop Sports Phys Ther 1998;27:264-75. 22. Tropp H. Pronator weakness in functional instability of the ankle joint. Int J Sports Med 1986;7:291-4. Suppliers a. Bertec Corp, 6185 Huntley Rd, Ste B, Columbus, OH 43229. b. National Instruments Corp, 11500 N Mopac Expwy, Austin, TX 78759. c. Smith & Nephew Inc, PO Box 1005, Germantown, WI 53022. d. Superfeet Worldwide LLC, 1419 Whitehorn St, Ferndale, WA 98248. e. Cramer Products Inc, PO Box 1001, Gardner, KS 66030.
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