Volume 85, Issue 4 , Pages 673-677, April 2004
The effects of different elevations of laterally wedged insoles with subtalar strapping on medial compartment osteoarthritis of the knee1
Article Outline
Abstract
Toda Y, Tsukimura N, Kato A. The effects of different elevations of laterally wedged insoles with subtalar strapping on medial compartment osteoarthritis of the knee. Arch Phys Med Rehabil 2004;85:673–7.
Objective
To assess the radiographic and symptomatic effects of treating patients with medial compartment osteoarthritis (OA) of the knee with laterally wedged insoles with subtalar strapping of varying elevations.
Design
Prospective quasi-experimental evaluation.
Setting
Outpatient clinic in Japan.
Participants
Sixty-two women outpatients with knee OA who were randomized into 3 groups according to their birth dates and wedge elevation.
Interventions
Participants wore laterally wedged insoles with subtalar strapping with elevations of 8, 12, or 16mm for 2 weeks.
Main outcome measures
Standing radiographs were used to analyze the femorotibial angle for each subject, both with and without their respective unilateral insoles. The remission scores of the Lequesne index of severity for knee OA were compared among the 3 groups at the conclusion. Participants were asked to report adverse effects on use of the insoles.
Results
The 16-mm group (n=21) showed a significantly greater valgus correction of the femorotibial angle than the 8-mm group (n=20) (P=.013). The remission score was significantly improved in the 12-mm group (n=21) compared with the 16-mm group (P=.029). Adverse effects were more common in the 16-mm group (9/21, 42.8%) than in the 12-mm (3/21, 14.3%) or 8-mm (2/20, 10%) groups.
Conclusions
The degree of change in femorotibial angle with the insole with subtalar strapping was affected by the tilt of the lateral wedge. For constant routine use, the 8- or 12-mm elevation wedged insoles with subtalar strapping may be more comfortable and effective than the 16-mm elevation wedge.
Keywords: Knee, Orthotic devices, Osteoarthritis, Radiography, Rehabilitation
OSTEOARTHRITIS (OA) OF THE knee affects approximately 6% of adults 30 years of age and older and 11% of adults 65 years of age and older, and it accounts for more disability in the elderly than any other disease.1 Knee OA is more common among women than men.2 Patients with knee OA usually show major involvement in only 1 compartment, with the medial compartment involved nearly 10 times more often than the lateral compartment.3
High tibial osteotomy, mainstay of surgical therapy, is indicated for severe medial compartment knee OA with varus deformity. The operation induces valgus realignment of the femorotibial angle by wedged osteotomy at the tibia. There are, however, numerous severe complications associated with high tibial osteotomy, and reports have been published on intraoperative injury to the popliteal artery, tibial nerve, or peroneal nerve and its branches.4 Magyar et al5 conducted a follow-up study of 308 patients after high tibial osteotomy and reported deep vein thrombosis in 4%, nonunion requiring further surgery in 2%, and pin-track infections in 51%.
One of the first conservative treatments for patients with medial compartment knee OA was an inserted lateral wedged insole. This type of insole, made of sponge rubber material that is inserted into ordinary shoes (inserted insole), has become popular with patients with knee OA.6 Wolfe and Brueckmann7 reported that 82% of their patients with medial knee OA had some lessening of pain with an inserted insole, and Keating et al8 reported that 61% of knees with medial OA had improved pain scores with an inserted insole.
The purpose of the inserted insole is to alter the mechanical alignment of the lower leg by enhancing a valgus correction of the calcaneus. Yasuda and Sasaki9 characterized the mechanism of action of the inserted insole as a reduction of the medial knee joint surface loading with a concurrent reduction in lateral tensile forces. They reported, however, that the femorotibial angle in patients with varus deformity with medial compartment knee OA was not corrected by use of the inserted insole. It is plausible that with the inserted insole, movement of the talus may prevent calcaneal valgus correction, thereby preventing femorotibial valgus correction. Thus, the effect of the inserted insole is fundamentally different from correction of the femorotibial angle with high tibial osteotomy.
Research into conservative alternatives to surgical correction of the femorotibial angle has addressed this limitation of the inserted insoles through the development of a lateral wedged insole with elastic strapping of the subtalar joint. This novel insole has resulted in a significant change in the talocalcaneal angle, the talar tilt angle, and the femorotibial angle, whereas the inserted insole alone produced a significant change only in the talocalcaneal angle, as shown in standing radiographs.10 Valgus angulation of the talocalcaneal angle was induced by the lateral wedge with both insoles. The realignment produced by the insole with subtalar strapping led us to conclude that an insole with elastic fixation obtained with tension by a subtalar and ankle joint band causes valgus angulation of the talus, which results in correction of the femorotibial angle, and may have a therapeutic effect similar to that resulting from high tibial osteotomy. Further study suggested that the insole with the subtalar strapping was more effective than the insole without it because it increases the maximum distance of ambulation and reduces pain in patients with medial knee OA while they are asleep, on awakening, and on standing up from a seated position.11
We postulated that if elastic fixation of the wedge with a subtalar and ankle joint band leads to valgus realignment of the femorotibial angle in patients with varus deformity of knee OA, then the change in that angle may be affected by the tilt of wedge. Additionally, we believed it necessary to determine the elevation of the insole with subtalar strapping that best relieved the symptoms of knee OA. Therefore, this study compared the radiographic effect on femorotibial alignment, with the goal being the ability to assess pain improvement by using a clinical index in patients treated with elevations of 8-mm (tilt angle=8.5°), 12-mm (tilt angle=11.2°), and 16-mm (tilt angle=16.8°) laterally wedged insoles with subtalar strapping.
Methods
This study prospectively evaluated patients with knee OA who were treated with lateral wedges with elevations of 8, 12, and 16mm in combination with subtalar strapping. The principal outcome measurements considered were the Lequesne index of severity of knee OA12 and the radiographic bony alignment. Additionally, the side effects and complications associated with the use of the insoles were monitored. This procedures was conducted in accord with the Declaration of Helsinki.13
Subjects were diagnosed as having medial compartment knee OA according to the American College of Rheumatology criteria for a diagnosis of knee OA, medial knee pain, and radiographic osteophyte at the medial joint space of the knee and at least 1 of the following items: age greater than 50 years, morning stiffness lasting more than 30 minutes, or crepitus on motion.14 After their informed consent was obtained, 62 female outpatients with medial compartment knee OA (≥45y; mean age ± standard deviation [SD], 61.8±8.3y) who were treated in our orthopedic outcome clinic in 2002 wore the wedged insoles for 2 weeks.
Participants were treated with a nonsteroidal anti-inflammatory drug (acemetacine, 30mg) orally twice a day as adjunctive therapy. Patients were excluded if they were currently using a wedged insole or other custom-made orthotic in their shoes on a regular basis; if they had a history of congenital foot problems, fused joints, foot deformity, or limitation of range of motion of the subtalar joint; or if they had any significant peripheral or central nervous system disease.
The age, disease duration, height, weight, index of severity for knee OA, and the stage and degree of bone destruction were evaluated at baseline. The disease duration was based on the patients’ recollections of the onset of knee pain. Height was measured to the nearest 1cm by using a stadiometer. Weight was measured to the nearest 0.1kg with subjects standing erect, wearing only underwear and robes. Body mass index (BMI) was calculated from the weight and height (kg/m2).
A research nurse, blinded to the study’s objectives, asked the participants to assess their level of pain with the Lequesne index.12 Radiographs were evaluated for changes characteristic of OA in anteroposterior (AP) views, by using the Kellgren and Lawrence grade, as described in the Atlas of Standard Radiographs.15
The insoles consisted of urethane wedges with elevations of 8mm inclined at 8.5°, 12mm inclined at 11.2°, and 16mm inclined at 16.8°, which were fixed to an ankle sprain supportera designed to fit around the ankle and subtalar joints. The technique performed by using the insole with subtalar strapping was previously reported.10 Three types of insoles with subtalar strapping were manufactured by Taketora.a The urethane was made of PORON L-24,b had a density of 240kg/m3, a pull strength of .54MPa, 115% stretch rate, and 1.8N/mm rip strength. The urethane was wrapped and fixed to the skid by an adhesive elastic bandage with a rough surface (Breabuna) (fig 1).
Fig 1.
Construction of the 3 types of lateral wedge insole. (A) The lateral view of the insole with subtalar strapping; (B) the posterior view of the insole.
In our pilot study, the number of participants who complained of foot sole pain increased when the insole with subtalar strapping was made of sponge rubber, the same material used for the insole. Thus, we used urethane for the lateral wedge of the insole with subtalar strapping. The difference in the comfortable tilt of the wedge between the subtalar strapping and insole inserts may be because of the differences in material.
Randomization was performed by date of birth. Participants with birthday dates evenly divisible by 3 were treated with elevations of 8-mm laterally wedged insoles with subtalar strapping (8-mm group). If dividing participants’ birthday dates by 3 left a remainder of 1, they were treated with insoles with an elevation of 12mm (12-mm group). Similarly, if dividing participants’ birthday by 3 left a remainder of 2, they were treated with insoles with an elevation of 16mm.
Each participant was instructed to use the insole without shoes in their home, for a period of 3 to 6 hours each day. This was done because the majority of Japanese wear shoes outdoors, but not indoors. Nearly all of our participants were Japanese housewives who spend most of each day inside their homes without footwear. Thus, in this study, most patients used the insoles without footwear.
Before initiating the study, standing radiographs of the knee and ankle joints in AP views were completed for baseline comparison. Participants stood on 1 leg (insole side) and radiographic analysis was performed for each subject with and without the respective insole. The femorotibial angle, the angle formed by the axes of the femur and the tibia, was radiographically compared with and without the insole. The radiographic assessment was completed by 3 orthopedic surgeons before they were informed of the patients’ group assignment.
The trial lasted 2 weeks; after which, remission scores of the Lequesne index were compared among the 3 groups. The urethane wedge was replaced every week, and proper use of the insoles was confirmed by the wear on the material. After the study period, participants were asked to report side effects and complications associated with wearing the respective insoles, and the rates of adverse outcomes were compared among the 3 groups.
Statistical analysis
Characteristics at baseline (age, disease duration, height, weight, BMI, femorotibial angle Lequesne index), radiographic changes with and without insoles, and the remission scores of the Lequesne index at the conclusion were compared among the 3 groups by using a 1-way analysis of variance. Radiographic grade and the rate of adverse outcomes were compared by using the chi-square test. Statistical significance levels were considered to be P less than .05.
Results
Participant characteristics
All participants completed the study (ie, returned for the final follow-up visit). There were 20 participants in the 8-mm group, 21 in the 12-mm group, and 21 in the 16-mm group. At the initial assessment, there were no significant differences between the groups in age, disease duration, height, weight, BMI, femorotibial angle, Lequesne index, or distribution of Kellgren and Lawrence grade (P>.05) (table 1). From the appearance of the wear of the material, we judged that each participant had used the insole as instructed.
Table 1. Characteristics of the Participants
| Age (y) | Disease Duration (y) | Height (cm) | Weight (kg) | BMI (kg/m2) | Femorotibial Angle at Baseline (deg) | Radiographic Grade∗ (no. of cases) | |
|---|---|---|---|---|---|---|---|
| 8-mm group (n=20) | |||||||
| Mean ± SD | 61.9±10.6 | 4.3±6.0 | 156.2±8.0 | 62.0±9.9 | 26.6±4.8 | 182.8±5.7 | Grade 2: 11 |
| Median | 59.5 | 1.5 | 154.5 | 59 | 24.8 | 182.5 | Grade 3: 6 |
| 95% CI | 56.9–66.8 | 1.5–7.1 | 152.4–159.9 | 57.3–66.6 | 24.3–28.8 | 180.2–185.4 | Grade 4: 3 |
| 12-mm group (n=21) | |||||||
| Mean ± SD | 61.8±5.5 | 4.4±5.0 | 152.8±4.3 | 60.2±8.0 | 26.2±3.5 | 181.6±4.9 | Grade 2: 17 |
| Median | 62 | 3 | 152 | 60.7 | 27.1 | 181 | Grade 3: 2 |
| 95% CI | 59.2–64.4 | 2.0–6.8 | 150.8–154.8 | 56.6–63.9 | 24.5–27.9 | 179.3–184 | Grade 4: 2 |
| 16-mm group (n=21) | |||||||
| Mean ± SD | 61.7±8.3 | 3.1±3.6 | 152.7±6.7 | 56.8±8.5 | 23.9±2.7 | 181.4±5 | Grade 2: 14 |
| Median | 63 | 1.3 | 150 | 56 | 23.5 | 181.5 | Grade 3: 4 |
| 95% CI | 57.8–65.5 | 1.5–4.8 | 149.7–155.8 | 52.9–60.7 | 22.6–25.1 | 179–183.7 | Grade 4: 3 |
∗ Kellgren-Lawrence grade. |
Radiographic assessment
In the 16-mm group with insole use, the femorotibial angle was reduced by an average of −4.0°±1.7° with respect to noninsole use. However, the femorotibial angle differed by −2.4°±3.2° and −3.2°±2.8° compared with the period before use of an insole in the 8-mm and 12-mm groups, respectively. These changes represented a significant difference between the 8-mm and 16-mm groups (P=.048) (fig 2).
Fig 2.
Comparison of femorotibial angles with and without insoles at the initial assessment.
Clinical assessments
Compared with the initial assessment, the remission score on the Lequesne index at the final assessment, showed greater improvement in the 12-mm group than in the 8-mm and 16-mm groups, although it was only statistically significant between the 12-mm and 16-mm groups (P=.029).
Although adverse effects were not severe enough to deter participants from continuing to wear the insole, they were more common in the 16-mm group (9/21, 42.8%) than in the 8-mm (2/20, 10%) and 12-mm (3/21, 14.3%) groups. There were significant differences in the rates of adverse effects between the 8-mm and 16-mm groups (P=.003) and between the 12-mm and 16-mm groups (P=.005). The most common side effect in the 16-mm group was foot sole pain (5/9, 55.6%) (table 2).
Discussion
This study’s results support the hypothesis that the change in femorotibial angle produced by the insole with subtalar strapping would be affected by the tilt of the lateral-wedge insole.
Compared with an elevation of 8mm, use of insoles with 16-mm elevation resulted in a significantly greater valgus correction of the femorotibial angle. However, the 16-mm wedge was associated with varying degrees of discomfort. A possible etiology for this higher rate of complications with the 16-mm wedge is the rapid reduction in the femorotibial angle resulting in an acute imbalance of surrounding muscles, which had been compensating for the joint deformity. Although the valgus correction of the femorotibial angle of the 12-mm wedge was smaller than with the 16-mm wedge, the remission score was significantly improved in the 12-mm group compared with that found in the 16-mm group. Thus, the 8- or 12-mm wedge may be more comfortable than the 16-mm wedges for constant normal use.
In a study on inserted insoles, Keating et al8 used lateral heel elevations of 6.35mm. Crenshaw et al16 studied the effects of a 5° laterally wedged inserted insole on knee varus torque during a walking stance period with unimpaired subjects, and they showed that an insole significantly decreased the varus torque by almost 7%.
In our study of the subtalar strapping insole, an insole with an elevation of 12mm (tilt angle=11.2°) or 8mm (tilt angle=8.5°) was comfortable. The inserted insole in combination with subtalar strapping had a more natural form fit to the sole than the insole insert alone.
Although we took radiographs with subjects in the static position, we did not evaluate the dynamic effects on walking of the subtalar strapped insoles with different elevations. However, we recently assessed the effect of the insole with an elevation of 10mm during the dynamic gait phase using foot print analysis.17 The foot angle ipsilateral to the varus deformity in the knee OA group was significantly higher than that in the control group; the angle was significantly reduced after wearing the insole with subtalar strapping, but not when using the insole without subtalar strapping. From these results, we inferred that an insole with subtalar strapping induces an adaptive mechanism that reduces the adductive moment at the knee by decreasing the femorotibial angle and by decreasing the external rotation of the foot position during walking, as was reported by Andriacchi18 after high tibial osteotomy. Future studies should investigate the correlation between the tilt of the insole with subtalar strapping and the change in the femorotibial angle during the gait phase.
The optimal tilt of a lateral wedged insole with subtalar strapping may be affected by age. In our previous study,19 a subtalar strapping insole with an elevation of 10mm was more efficacious for younger patients and patients with a higher lower-extremity proportion of lean body mass to body weight and less efficacious for older patients with sarcopenia. A decrease in lean body mass and an increase in fat are characteristic of the aging process.20 We concluded that the lack of effect on older patients with knee OA may be because of a muscle mass insufficient to preserve the femorotibial angle realignment by the insole with subtalar strapping. Comparing the results of the previous study with those of this study, we believe that a low tilt such as the 8-mm elevation of the insole with subtalar strapping might be better recommended for older patients. Because relatively few patients were in the 3 groups in this study, we could not assess the optimal tilt of the lateral wedge according to age; it will be necessary to evaluate this correlation in a future study.
Recently, remarkable progress has been made in surgical techniques for the treatment of knee OA. However, the majority of patients with knee OA hesitate to undergo surgical treatment. Therefore, if conservative therapy, such as use of an insole, can provide a low-cost, effective complement or alternative to surgical treatment, it will be useful for patients and the health care economy.
Conclusions
This study was designed both to evaluate symptomatic and anatomic geometric changes as well as to assess the differences in response rate and the controlling tilt of the lateral wedged insole with subtalar strapping. Insoles with elevations of 16mm resulted in a significantly greater valgus correction of the femorotibial angle than those with elevations of 8mm. However, the 16-mm wedge was associated with a varying degree of discomfort. Although the valgus correction of femorotibial angle of the 12-mm wedge was smaller than that of the 16-mm wedge, the remission score was significantly improved in the 12-mm group compared with 16-mm group. Thus, in routine use, the 12- or 8-mm wedge may be a better compromise for comfort and effectiveness than the 16-mm wedge.
Suppliers
Acknowledgements
We thank Neil Segal, MD, Mayo Clinic, Department of Physical Medicine and Rehabilitation, Rochester, MN, for his contributions to this manuscript.
References
- . Defining arthritis and measuring functional status in elders (methodological issues in the study of disease and physical disability). Am J Public Health. 1990;80:945–949
- . Osteoarthritis of the knee and physical load from occupation. Ann Rheum Dis. 1996;55:677–679
- . Osteoarthritis of the knee (a radiographic investigation). Acta Radiol. 1968;277(Suppl 1):7–72
- . Nerve and vessel injuries during high tibial osteotomy combined with distal fibular osteotomy (a clinically relevant anatomic study). Knee Surg Sports Traumatol Arthrosc. 1999;7:15–19
- . Hemicallotasis open-wedge osteotomy for osteoarthritis of the knee. Complications in 308 operations. J Bone Joint Surg Br. 1999;81:449–451
- . Clinical evaluation of the treatment of osteoarthritis knee using a newly designed wedged insole. Clin Orthop. 1987;181–187 Aug(221)
- . Conservative management of genu valgus and varum with medial/lateral heel wedges. Indiana Med. 1991;84:614–615
- . Use of lateral heel and sole wedges in the treatment of medial osteoarthritis of the knee. Orthop Rev. 1993;19:921–924
- . The mechanics of treatment of the osteoarthritic knee with a wedge insole. Clin Orthop. 1987;162–172 Feb(215)
- . Effect of a novel elastically fixed lateral wedged insole on the subtalar joint of patients with medial compartment osteoarthritis of the knee. J Rheumatol. 2001;28:2705–2710
- . Usefulness of an insole with subtalar strapping for analgesia in patients with medial compartment osteoarthritis of the knee. Arthritis Rheum. 2002;47:468–473
- . Indexes of severity for osteoarthritis of the hip and knee. Validation—value in comparison with other assessment test. Scand J Rheumatol Suppl. 1987;65:85–89 [published errata appear in Scand J Rheumatol 1988;17:following 241; Scand J Rheumatol Suppl 1988;73:1].
- The Declaration of Helsinki. World Med J. 1982;29:86–88
- Guidelines for the medical management of osteoathritis. Part II. Osteoarthritis of the knee. Arthritis Rheum. 1995;38:1541–1546
- . Radiological assessment of osteo-arthritis. Ann Rheum Dis. 1957;16:494–502
- . Effect of lateral-wedged insoles on kinetics at the knee. Clin Orthop. 2000;185–192 Jun(375)
- . Dynamic effect of an elastically strapped lateral wedged insole on subtalar joint in convenient foot print analysis using facsimile paper. Mod Rheumatol. 2003;13:215–219
- . Dynamics of knee malalignment. Orthop Clin North Am. 1994;25:395–403
- . Correlations between body composition and efficacy of lateral wedged insoles for medial compartment osteoarthritis of the knee. J Rheumatol. 2002;29:541–545
- . Cross-sectional age differences in body composition in person 60+ years of age. J Gerontol A Biol Sci Med Sci. 1995;50:M307–M316
- 1 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 authors(s) or upon any organization with which the author(s) is/are associated.
- a. Taketora Co, 18-7 Minanuohi, 3chome, Shinnagawa-ku, Tokyo 140-8558, Japan.
- b. Rogers Co, 1001 N Dobson Rd, Chandler, AZ 85224-6196.
PII: S0003-9993(03)00940-7
doi:10.1016/j.apmr.2003.06.011
© 2004 American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation. Published by Elsevier Inc. All rights reserved.
Volume 85, Issue 4 , Pages 673-677, April 2004
