A Comparative Study on the Use of Lateral Heel Wedge and Lateral Wedge Insole in the Treatment of Medial Compartment Osteoarthritis of Knee with Varus Deformity

INTRODUCTION

Osteoarthritis (OA), which is often erroneously called degenerative joint disease, represents failure of the diarthrodial (i.e., movable synovial) joint. Osteoarthritis, though primarily involves progressive loss of articular cartilage, involves all structures of the joint—subchondral bone, synovial fluid, and synovial membrane are major sites of change in the course of the disease process.¹

Joint involvement is usually asymmetrical with a predilection for weight-bearing joints and of the various common sites, OA knee is the most common, which could be uni-, bi-, or tricompartmental; among which the most common is the medial compartmental OA changes.² Risk factors for OA include age (most important), obesity, bone density, genetics, and gender.³

Extensive research has gone into various facets in the treatment of OA, viz., nonpharmacological, pharmacological, and surgical methods with varying results.

This study was concerned with a particular aspect of nonpharmacological therapy, viz., the use of lateral wedge orthotics of two types in OA of medial compartment of knee with varus deformity. The two types of lateral wedge orthotics are lateral heel wedge and lateral wedge insole.

It has been proved through prior research that patients have benefited from each of the above types of lateral wedge orthotics. This study was aimed to evaluate the effectiveness between them using measuring parameters such as VAS for pain, Western Ontario and McMaster (WOMAC) University Index of OA scale, 50 ft walk time. Statistical tests were performed and conclusion reached based on the research findings.

AIMS AND OBJECTIVES

The aim of the study was to evaluate the effectiveness of shoe correction using lateral wedge orthotics by observing clinical and functional improvement in a comparative study between lateral heel wedge and lateral wedge insole in medial compartment OA of the knee with varus deformity.

MATERIALS AND METHODS

After Institutional Ethics Committee clearance, the individual informed consent was taken from every patient who was included in the study. The study was conducted in the Department of Physical Medicine and Rehabilitation, Institute of Postgraduate Medical Education and Research and Seth Sukhlal Karnani Memorial Hospital, Kolkata, and was carried out for 18 months from February 2011 to August 2012, and a minimum of 28 subjects was the requirement per group. For the purpose of sample size estimation, the pain component of WOMAC index was considered as the primary outcome measure. It was a single-blind randomized parallel group trial. All subjects having grade II or higher Kellgren–Lawrence radiographic severity of tibiofemoral OA along with medial compartment narrowing and varus deformity in standing AP view, pain in the knee for most days in the past month, and pain score of at least 3 on a 0–10 VAS score were included. Patients who were excluded had a history of knee trauma or surgery in the past 6 months, history of other types of arthritis, neurological disease, intra-articular steroid or hyaluronate injection over past 6 months, calcaneovalgus deformity, and everted foot. Parameters studied were WOMAC scale, VAS score, and 50 ft walk time.

STUDY TECHNIQUE

In the study, patients suffering from medial compartment OA of knee with varus deformity were selected for intervention after obtaining informed consent (considering inclusion and exclusion criteria). The selected patients were examined at baseline (visit 1 or V1) using the parameters mentioned above. They were randomly put into two groups (1) group using lateral heel wedge of 1/6th inch (4.23 mm) and (2) group using lateral wedge insole of 1/6th inch (4.23 mm). The wedge insoles and heel wedges were constructed with plain rubber. The patients were examined using the above-mentioned parameters after intervals of 4 weeks (visit 2 or V2) and 8 weeks (visit 3 or V3). Parameters of functional improvement were noted. The results were analyzed according to the standard statistical methods to accomplish the aims and objectives of the study. In all cases, exercises were shown to the patients, which the patients were instructed to practice at home.

RESULTS

Data was normally distributed and summarized using descriptive statistics and represented graphically. Change from baseline (V1) to study end (V3) assessed through repeated-measure analysis of variance (ANOVA) for normally distributed data, Fisher’s F value, and R² value noted in each case to determine the level of significance and comparison. Numerical variables between groups were compared by Student’s t test (Mann–Whitney) where applicable. Tukey’s post hoc tests for ANOVA was conducted for each parameter to observe the fine-grained differences between visits (from V1 to V2, V1 to V3, and V2 to V3) where significance was noted in ANOVA test. All statistical analyses were two tailed and p %3C; 0.05 considered statistically significant.

DEMOGRAPHICS

STATISTICAL RESULTS FOR OUTCOME MEASURES

STATISTICAL RESULT FOR COMFORT LEVEL

Table 10 shows significance between the two groups in the comfort level of using their shoes.

DROPOUT

Of the 30 and 33 cases for lateral heel wedge and lateral wedge insoles, respectively, included in the study, 2 and 5 cases did not report for follow-up and dropped out of the study. Thus, the final sample population was 28 per group. The dropout numbers in both groups suggest that compliance in insole users is less.

DISCUSSION

The effectiveness of using lateral heel wedges⁴ and lateral wedge insoles^5–7 in the treatment of medial compartment OA of knee with varus deformity has been studied for long. But there is lack of studies which compares the effectiveness between these orthotics. This study focused on OA knee prevalent in older population as shown in Figure 1, and majority of patients were female as depicted in Figure 2. Obesity is a contributing factor as shown in Figure 3, indicating leaning toward the overweight side of the bell curve. As shown in Figure 4, majority of the patients were in Kellgren–Lawrence grade III.

Statistical analysis of primary outcome measures shows significant results for 50 ft walk time for both heel and insole wedge user groups from baseline V1 to V2 and from V1 to V3, but significance was observed only for the insole group from V2 to V3. Appreciable reduction in average 50 ft walk time (2.82 seconds) was noticed for the group using lateral wedge insole from baseline to V3 as depicted in Tables 1 and 2. For VAS pain score, considerable reduction in pain was observed from V1 to V2 for both groups. Heel user group shows insignificance across V2 and V3, but in insole user group significance was also seen from V2 to V3 visit as depicted in Tables 3 and 4. In addition, Tables 5 and 6, which show WOMAC pain score, exhibit similar statistical significance in both groups, i.e., from mean baseline to V2 pain reduction is similar in both groups, but mean V2 to V3 pain reduction is appreciable for the insole user group, though not statistically significant. Statistical study of WOMAC stiffness score as shown in Tables 7 and 11 shows insignificant change in score for lateral heel wedge user group but significance is observed for V1 to V2 visit and V1 to V3 visit for insole user group and slight increase in stiffness from V2 to V3. Tables 8 and 9 which depicts statistical study of WOMAC functional score shows there is significant improvement from V1 to V2 and V1 to V3 visit for both groups, whereas the change from V2 to V3 in both cases was insignificant.

In statistical result for comfort level, as shown in Table 10 and Figure 5, it is clear that heel wedge users are more comfortable with their modified shoes compared to full-length lateral wedge insole users.

Thus, per the above findings, there is a trade-off between higher efficiency of biomechanical effects of full-length wedge insole with the greater comfort and comparatively slightly less efficiency of heel wedge orthotics.⁸ The decision to use the type of shoe modification should therefore be customized per the patients’ typical requirements and shoe usage pattern.

LIMITATIONS

The limitations of this study and further research interests are-

• Most of the patients being female, ideal shoe wearing time that is around 5–6 hours per day to bring appreciable change in outcome parameters was not adhered to due to the household chores required of them, where wearing shoes at home is generally not possible.
• Compliance of the patient was an area of concern for various causes like sociocultural issues and also for comfort factor where wearing lateral wedged insole was more inconvenient than wearing lateral heel wedges.
• A longer time period longitudinal study for determining the comparative efficacy of the two groups can be more beneficial than the present 8 weeks’ study.
• Lateral wedge insoles reduce the external knee adduction moment (EKAM). However, in some cases an increase in EKAM is seen.⁹ Understanding the role of ankle joint in every case will throw more light on this subject. This was not in the scope of this study and can be investigated later. Moreover, the relation between the decrease in medial knee loading and the subsequent reduction in pain is inconsistent and can be studied further.¹⁰
• The 1/6th inch wedge orthotics was chosen, as the wedge angle remains within 6° with the inserts and heel for various shoe sizes for the subjects.¹¹ This leads to greater compliance. However, steeper and milder angled wedge orthotics can be used and a comparative study can be carried out between them.

CONCLUSION

Comparing the outcome measures, it was seen that for both lateral wedge insole and lateral heel wedge users, a significant improvement was observed in most of the parameters, whereas slightly greater significance was seen in lateral wedge insole user group. But it was also observed that though sharper angled insoles provided greater efficacy, this was less comfortable, leading to less compliance. In conclusion, it can be affirmed that wedge insoles and heels offer great potential as simple, inexpensive treatment strategies for knee OA in the early stages. However, keeping in mind the various limitations of this approach, it can be deduced that further research is needed to determine the precise estimation of efficacy and the responsiveness of diverse patient groups to this mode of OA management.

DISCLOSURE STATEMENT

This study was not funded by any governmental or nongovernmental organization or any pharmaceutical company, and no financial or other benefit was related to this study, and there was no commitment or agreement or scope of benefit from any commercial entity.

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