Dr. Toda is currently applying for a patent for the novel insole used in this study.
Usefulness of an insole with subtalar strapping for analgesia in patients with medial compartment osteoarthritis of the knee
Article first published online: 14 OCT 2002
Copyright © 2002 by the American College of Rheumatology
Arthritis Care & Research
Volume 47, Issue 5, pages 468–473, 15 October 2002
How to Cite
Toda, Y. and Segal, N. (2002), Usefulness of an insole with subtalar strapping for analgesia in patients with medial compartment osteoarthritis of the knee. Arthritis & Rheumatism, 47: 468–473. doi: 10.1002/art.10669
- Issue published online: 14 OCT 2002
- Article first published online: 14 OCT 2002
- Manuscript Accepted: 18 JAN 2002
- Manuscript Received: 9 MAY 2001
- Clinical trial;
To assess the effect of an insole with subtalar strapping on patients with medial compartment osteoarthritis (OA) of the knee.
Novel lateral wedged insoles with elastic subtalar strapping (the subtalar strapping support group) and ankle supporters with a lateral wedged heel insert (the sock-type ankle support group) were prepared. Eighty-eight female outpatients with knee OA were treated with 1 of the 2 insoles for 8 weeks. Femorotibial angle was assessed by standing radiographs with and without unilateral insole use for each subject. Symptoms of knee OA were evaluated according to the severity index of Lequesne et al at baseline and at the final assessment.
Participants wearing the insole with subtalar strapping (n = 42) demonstrated significantly decreased femorotibial angle (an average of change: −3.1° ± 2.5°, P < 0.0001), but a significant difference was not found in the sock-type ankle support group (n = 46; −0.4° ± 1.1°, P > 0.05). In the subtalar strapping support group, pain during bed rest with full extension of the knee (P < 0.0001), pain after getting up (P = 0.04), pain on getting up from a seated position (P = 0.021), maximum distance walked (P = 0.009), and aggregate severity score (P < 0.0001) were significantly improved compared with baseline. In contrast, significant symptomatic improvement was detected only in the aggregate score (P = 0.016) in the sock-type ankle support group, but not in any of the 10 specific categories.
The lateral wedged insole with subtalar strapping induces correction of the femorotibial angle and symptomatic relief in patients with varus-deformity knee OA.
Osteoarthritis (OA) of the knee is the most common joint disorder, accounting for a large proportion of disability in adults. The Chingford study documented a 12% prevalence of radiologic knee OA and a 6% prevalence of symptomatic knee OA in women aged 45–64 years (1). The total asocial cost of OA in the United States has been estimated at approximately 1% of the gross national product (2). The same trend will likely be observed in other advanced nations. Recently, remarkable progress has been made in surgical techniques, such as high tibial osteotomy and total knee arthroplasty, for treatment of knee OA. However, surgical management is associated with a high cost as well as the potential for serious complications.
One of the first forms of conservative mechanical treatment for patients with medial compartment knee OA was the lateral wedged insole insert. However, Sasaki et al reported that the inserted insole was significantly more effective for knee OA patients with mild joint deformity, and ineffective for those with advanced joint deformity (3). One possible reason for the ineffectiveness of the inserted insole against advanced knee OA is lack of correction of the femorotibial angle (FTA) in patients with varus deformity due to medial compartment knee OA (4). This results in an effect fundamentally different from surgical correction of the FTA with a high tibial osteotomy.
In researching conservative alternatives to surgical correction of the FTA, this limitation of inserted insoles was addressed through the development of a novel lateral wedged insole with elastic strapping of the subtalar joint. In a previous study, 26 knee OA participants, who had been treated with full-length lateral wedged insoles attached at the talonavicular joint, were then treated for 8 weeks with the insole with subtalar strapping (5). Both the FTA and the visual analog scale for global assessment of knee pain were significantly reduced after wearing the insole with subtalar strapping, but not after using the insole with talonavicular strapping. This suggests that the insole with subtalar strapping is a more efficacious conservative therapy for correction of the FTA in patients with genu varum and medial compartment knee OA. Through radiographic measurements with electrical stimulation of the peroneus longus, Vaes et al demonstrated that tape bandages significantly restrict talar tilt (6). Through taping, talar tilt was reduced from 13.3° to 4.9° in their study. Thus, it seems reasonable that if subtalar strapping causes the calcaneous and talus to move together, the FTA may be affected.
In our previous study, standing full-length radiographs were used to analyze the talocalcaneal, talar tilt, and femorotibial angles for each subject with and without a unilateral inserted or a subtalar strapping insole. The talocalcaneal angle was significantly increased for both the subtalar strapping and inserted insole groups compared with no insole. However, the talar tilt angle was significantly decreased only in the subtalar strapping insole group. There was no significant difference in the talar tilt angle with the inserted insole. A significant difference in FTA with insole use was detected in the subtalar strapping group. However, the FTA was not significantly changed in the inserted insole group (7). Further study suggested that the insole with subtalar strapping is more efficacious for younger patients and those with a higher proportion of lean body mass per body weight in the lower extremity, and less efficacious for older patients with sarcopenia (8).
Despite advances in our understanding of the lower extremity anatomic realignment induced by the subtalar strapping insole, specific symptomatic efficacy has not yet been elucidated. It is necessary to qualify whether the anatomic change is clinically significant with respect to patient function and symptoms. Therefore, this study was designed to assess symptomatic relief of knee OA in patients treated with an insole fixed to an ankle supporter or with the insole with subtalar strapping.
PATIENTS AND METHODS
After providing informed consent to participate, 88 female outpatients seen in our orthopedic outcome clinic (OOC) from September to December 2000, who met the American College of Rheumatology criteria for a diagnosis of knee OA, were treated with wedged insoles for 8 weeks (9). All participants were also treated with a nonsteroidal antiinflammatory drug (NSAID; acemetacine, 30 mg) orally twice a day as adjunctive therapy.
Disease duration was based on patients' recollection of the onset of knee pain. Height was measured to the nearest 1 cm using a stadiometer. Weight was measured to the nearest 0.1 kg in a standing position with underwear and robes but without shoes. Body mass index (BMI) was calculated from weight and height as weight (in kilograms) divided by height squared (in meters). The grade of radiographic progression of knee OA was evaluated according to the standard films of Kellgren/Lawrence (K/L) (10).
Each symptom relating to knee OA was evaluated according to the severity index of Lequesne et al (Table 1) (11). Items 1 and 2, concerning pain during nocturnal bed rest and pain after awakening, were evaluated by patient self-report, because patients could not be observed at night or early morning. All other items (Table 1, items 3–10) were assessed under stable conditions by physical therapists who were uninformed of the objective of the study when patients presented to the OOC.
|A. Pain or discomfort|
|1. During nocturnal bedrest with full extension of the knee||1. Bedrest|
|Only on movement or in certain positions||1|
|2. Duration of morning stiffness or pain after getting up||2. Morning stiffness|
|Less than 15 min||1|
|15 min or more||2|
|3. Remaining standing for 30 min increases pain||3. Standing|
|4. Pain on walking||4. Walking|
|Only after walking some distance||1|
|Early after starting||2|
|5. When getting up from sitting position without the help of arms||5. Getting up|
|B. Distance walked|
|6. Maximum distance walked||6. Maximum distance|
|More than 1 km, but limited||1|
|About 1 km (about 15 min)||2|
|From 500 to 900 m (about 8–15 min)||3|
|From 300 to 500||4|
|From 100 to 300||5|
|Less than 100||6|
|C. Activities of daily living*|
|7. Can you go up a standard flight of stairs?||7. Up stairs|
|8. Can you go down a standard flight of stairs?||8. Down stairs|
|9. Can you squat?||9. Squat|
|10. Can you walk on uneven ground?||10. Uneven ground|
Two types of lateral wedged insoles were prepared: urethane wedges with elevations of 6.35 mm (1/4 inch) fixed to an ankle strap (Sofra Wolfer, Taketora Co., Japan) designed to fit around the ankle and subtalar joints (subtalar strapping insole, Figure 1A); and a sock-type ankle supporter with lateral rubber heel wedge insert (Wedge heel supporter, Sanshin-Kosan Co., Japan; Figure 1B).
The urethane used for the subtalar strapping insole was made of PORON L-24 (Rogers Corp, Rogers, CT), had a density of 240 kg/m3, 0.54 MPa pull strength, 115% stretch rate, and 1.8 N/mm rip strength. The urethane wedge or rubber heel wedge was replaced every 2 weeks and proper use of the insoles was confirmed by examination of material wear. The NSAID was prescribed every week and regular usage was maintained in each group.
Randomization was performed by date of birth. Participants with even numbered dates of birth were treated with the ankle supporter insole and those having odd numbered dates of birth were treated with the insole with subtalar strapping. Each participant was instructed to use the insole whenever wearing shoes, for between 3 and 6 hours each day. This time limitation was due to the fact that nearly all participants were Japanese housewives who remove their shoes in their homes and spend only several hours each day outside wearing shoes. This study was limited to only female subjects because males comprise a minority of the knee OA population, and the duration of insole use would have varied by their occupation (12).
Before entering the 8-week study, standing anteroposterior radiographs of the knee joint were completed. Participants stood on one leg and radiographic analysis was performed for each subject with and without the respective insole in place. The FTA, the angle formed by the axes of the distal one-third of the femur and the proximal one-third of the tibia, was compared between radiographs with and without the insole. The radiographic assessment was completed by 3 orthopedic surgeons prior to being informed of the category of the patients. Each of the 10 items included in the Lequesne Index of Severity was assessed at baseline and followup, and aggregate scores were calculated for participants wearing the insole with subtalar strapping (the subtalar strapping support group) and the ankle supporter insole (the sock-type ankle support group).
Baseline values for age, disease duration, height, weight, BMI, and FTA were compared between the 2 groups using one-way analysis of variance. Radiographic grade was compared between the 2 groups using the chi-square test. The paired t-test was used for paired data to assess for statistically significant differences between the baseline and final assessment for each item, total Lequesne index score, and FTA. Statistical significance level was set at P < 0.05.
Characteristics of the participants.
All participants in both groups completed the 8-week study (i.e., returned for the final followup visit). There were no dropouts. There were 42 participants in the subtalar strapping support group and 46 in the sock-type ankle support group. At the initial assessment, there were no significant differences between the groups for age (P = 0.57), disease duration (P = 0.28), height (P = 0.51), weight (P = 0.40), BMI (P = 0.12), and the distribution of K/L grade (P = 0.25) (Table 2).
|Age, years||Disease duration, years||Height, cm||Weight, kg||Body mass index, kg/m2||Radiographic grade* (No. of cases)|
|Subtalar strapping group, (n = 42)|
|Mean ± SD||64.2 ± 7.5||5.3 ± 5.7||153 ± 6.5||59.7 ± 8.3||25.7 ± 3.3||2 (29)|
|95% CI||61.8–66.6||3.4–7.1||150.9–155.1||57–62.3||24.6–26.7||4 (5)|
|Ankle supporter group, (n = 46)|
|Mean ± SD||65.2 ± 9.0||4 ± 5.0||153.9 ± 5.2||58.2 ± 7.2||24.6 ± 2.9||2 (30)|
|95% CI||62.6–67.9||2.5–5.5||152.3–155.4||56.1–60.4||23.7–25.5||4 (2)|
The mean FTA without an insole in the subtalar strapping support group (182° ± 5°) was higher than that in the sock-type ankle support group (180.2° ± 4.6°), although the difference was not significant (P = 0.094). The angle was decreased after wearing the insole in 34 of 42 patients (81%) in the subtalar strapping support group and 17 of 46 (37%) patients in the sock-type ankle support group. In the subtalar strapping support group, the FTA with insole use (178.9° ± 4.6°) changed an average of −3.1° ± 2.5° with respect to no insole use. In contrast, in the sock-type ankle support group, the FTA (179.8° ± 4.9°) changed by −0.4° ± 1.1° compared with before insole use. These changes represent a significant difference between the subtalar strapping and sock-type ankle support groups (P < 0.0001) (Figure 2).
Comparison of the baseline with the final assessment in each group is shown in Figures 3 and 4. At baseline, the distribution in each of 10 specific categories and the aggregate score was not significantly different between the subtalar strapping and sock-type ankle support groups (P > 0.05). In the subtalar strapping support group, pain during bed rest with full extension of the knee (item 1), pain after getting up (item 2), pain on getting up from a seated position (item 5), maximum distance walked (item 6), and aggregate severity score were significantly improved compared with baseline. However, scores for “walks easily on uneven ground” (item 10) were lower at the final assessment (20 out of 42 cases) than at the baseline assessment (22 out of 42 cases) in the subtalar strapping support group. Thus, the insole with subtalar strapping exacerbated pain with ambulation on uneven ground (Figure 3). Significant symptomatic improvement was detected only in the aggregate score in the sock-type ankle support group, but not in any of the 10 specific categories (Figure 4).
In the Japanese population, the confidence intervals for measurement of the FTA in standing radiographs ranged from 175° to 180° in healthy subjects aged 25–35 years, and the standard value of the angle is considered to be 176° degrees in healthy women (13).
In a previous study, 90 female outpatients with knee OA were treated with the subtalar strapping insole or traditional inserted wedged insoles (7). The insole with subtalar strapping elicited a significant change in the talocalcaneal, talar tilt, and femorotibial angles, while the inserted insole produced a significant change only in the talocalcaneal angle.
Valgus angulation of talocalcaneal angle would be induced by lateral wedges in both insoles. The realignment by insoles with subtalar strapping led to the conclusion that the insole with elastic fixation with tension by bands at the subtalar and ankle joint leads to valgus angulation of the talus, resulting in correction of the FTA in patients with varus deformity of knee OA, and may have a similar therapeutic effect to that of high tibial osteotomy.
In this study, participants wearing the insole with subtalar strapping also demonstrated a significantly decreased FTA. These significant differences were not seen in the participants wearing the sock-type ankle supporter. This suggests that subtalar strapping, but not a simple sock-type ankle supporter, leads to valgus correction of the FTA when combined with a lateral wedged insole.
Results of the current study indicate that the insole with subtalar strapping was more effective than the ankle supporter insole for increasing maximum distance of ambulation and for pain reduction while asleep, upon awakening, and upon standing from a seated position. Further studies will need to address the mechanism by which the insole with subtalar strapping reduces pain. However, one possible hypothesis is that through correction of the FTA, the insole with subtalar strapping may regulate medial compartment loading across the tibiofemoral joint in the standing position. This may lead to reduction of pain on standing up from a seated position and increased ambulation.
It is also notable that participants in the subtalar strapping group reported increased pain with ambulation on uneven ground. This may be related to the decreased freedom of the subtalar joint, leading to increased loading of the knee. In contrast, the less constraining brace may have allowed more movement at the subtalar joint, thus decreasing the stress at the knee.
The current study was limited in that it did not clarify whether symptomatic relief in the subtalar strapping group was attributable to a change in the FTA. The confounding factor was that relief was constant despite the fact that 8 of 42 participants in the subtalar strapping group did not demonstrate a change in the FTA. This small number was not sufficient to allow a chi-squared analysis to evaluate symptomatic relief in this subgroup. Future studies should include a large number of patients to better evaluate symptomatic changes in participants who lack a change in the FTA.
Another area that this study could not address was the possibility of a placebo effect due to the subtalar strapping, unrelated to the lateral-wedged insole. To evaluate such an effect, it would be necessary to provide patients with strapping without an insole. Because this study was completed using Japanese national health insurance, in the context of routine medical care, use of a placebo insole for knee OA patients was not acceptable. Additionally, in this study, participants were not blinded to the treatment. However, participants were not told whether the method of fixation at ankle joint, belt or sock-type, was thought to be important. We believe the appearance did not influence the outcome. Another limitation of this study was that the selection of outpatients resulted in a bias toward inclusion of patients who could walk to our clinic and therefore were more likely to have mild knee OA. Future studies should include a larger number of patients with advanced knee OA to evaluate the effect of subtalar strapping on the FTA in those with more severe disease.
Other directions for future study include a more detailed analysis of the most efficacious material, height of the lateral wedge, and the optimal duration of use of the insole with subtalar fixation. The observation period in this study was 8 weeks. Keating et al (14) reported that participants who attained pain relief with use of the wedges generally noticed relief within the first 3 days to 1 week, and participants who received no relief in the first week generally received no relief with continued use. However, it will be necessary to continue followup to assess treatment efficacy over an extended observation period.
The prevalence of knee OA is increasing due to the escalating proportion of elderly in our society. Therefore, appropriate selection of patients for conservative treatment of knee OA is of increasing importance. It will also be desirable to better characterize the degree to which symptomatic relief of knee OA can be attained through conservative treatment. Through such studies, it will be possible to select patients who may respond to conservative therapy, improving quality of life while simultaneously reducing costs and complications.
This work was reviewed prior to submission by Ryokei Ogawa, MD, Professor Emeritus of Department of Orthopedic Surgery, Kansai Medical University, Moriguchi City, Osaka, Japan.
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