ORIGINAL ARTICLE

https://doi.org/10.5005/jojs-10079-1155
Journal of Orthopedics and Joint Surgery
Volume 6 | Issue 2 | Year 2024

Pedobarography Analysis of Foot Pressure Changes in Varus Total Knee Replacement

Harisudhan Raviraja1https://orcid.org/0009-0005-7858-2180, Lokesh K Sekaran2https://orcid.org/0009-0008-4040-6685, Ganesan G Ram3https://orcid.org/0000-0002-2877-293X, Krishna K Jayaraman4https://orcid.org/0009-0007-7071-6257, Vijayaraja Elangovan5https://orcid.org/0000-0002-1854-6496, Dheepan Kumar6https://orcid.org/0009-0005-9931-621X

1–6Department of Orthopaedics, Velammal Medical College Hospital and Research Institute, Madurai, Tamil Nadu, India

Corresponding Author: Harisudhan Raviraja, Department of Orthopaedics, Velammal Medical College Hospital and Research Institute, Madurai, Tamil Nadu, India, Phone: +91 9842991161, e-mail: drharisudhan.hs@gmail.com

Received: 08 January 2023; Accepted: 06 March 2024; Published on: 14 June 2024

ABSTRACT

Introduction: Issues that begin with feet can cause persistent pain in the knees, hips, and back. Misalignments of the foot bones and different constructions in the foot can adjust how a person can walk and how the lower limb bears weight as a person moves. To evaluate the influence of total knee arthroplasty on foot pressure changes in varus osteoarthritic knee using pedobarography.

Methods: It is a prospective study done at Velammal Hospital, Velammal Medical College and Research Institute, Madurai, Tamil Nadu, India, among patients with primary osteoarthritis with varus deformity undergoing total knee replacement (TKR) from April 2021 to 2023. The inclusion criteria are patients with primary osteoarthritis with varus deformity undergoing TKR. Only patients with grade II varus (10–20°) deformities are included. Patients who satisfied the inclusion criteria and were willing to participate in the study filled out the informed consent form, and preoperative (pre-op) and postoperative (post-op) pedobarography was done and analyzed.

Results: Preoperatively, the high-pressure changes were seen in the lateral metatarsal, lateral midfoot, and lateral heel. Postoperatively, there was a significant shift in pressure changes toward medial foot zones, including the hallux, medial metatarsal, central metatarsals, and medial heel.

Conclusion: Posttotal knee replacement, the distribution of foot pressure changes toward the normal foot pressure distribution.

How to cite this article: Raviraja H, Sekaran LK, Ram GG, et al. Pedobarography Analysis of Foot Pressure Changes in Varus Total Knee Replacement. J Orth Joint Surg 2024;6(2):119–124.

Source of support: Nil

Conflict of interest: None

Keywords: Arthroplasty, Foot zones, Heel pressure, Osteoarthritis, Pedobarography.

INTRODUCTION

Issues that begin with feet can cause persistent pain in the knees, hips, and back. Misalignments of the foot bones and different constructions in the foot can adjust how a person can walk and how the lower limb bears weight as a person moves. Similarly, in patients with knee osteoarthritis knee, the distribution of weight-bearing, walking pattern, and balance can cause problems in the foot. Pain, loss of strength in the quadriceps muscles, restricted range of motion, and impaired proprioceptive function are among the underlying causes of these disorders.1,2 These conditions may cause changes in foot pressure in patients with osteoarthritic knee disease. The knee problem is directly proportional to the foot pressure.3

METHODOLOGY

Aim

To evaluate the influence of total knee arthroplasty on foot pressure changes in varus osteoarthritic knee using pedobarography.

METHODS

It is a prospective study done at Velammal Hospital, Velammal Medical College and Research Institute, Madurai, Tamil Nadu, India, among patients with primary osteoarthritis with varus deformity undergoing total knee replacement (TKR) from April 2021 to April 2023. Approval from the Institutional Ethics Committee was obtained. The inclusion criteria are patients with primary osteoarthritis with varus deformity undergoing TKR. Only patients with grade II varus (10–20°) deformities are included. Patients who plan to undergo bilateral TKR are excluded from the study. The exclusion criteria are patients with preexisting foot and ankle pain and deformities, Patients with valgus deformities, patients with hyperextension deformities, patients with limb length discrepancies, patients with inflammatory disorders, patients who have undergone other surgeries in the knee, patients with hip/spinal pathologies. A total of 220 patients were included in the study; we lost 11 patients to follow-up, and one patient expired 3 weeks postoperatively due to a road traffic accident. Hence, we had 208 patients for analysis. The mean age was 64.5 years. We had 146 female and 62 male patients included in the study. 112 patients underwent right TKR while the remaining patients had left TKR.

Patients who met the inclusion criteria and agreed to be included in the study filled out the informed consent form, and preoperative (pre-op) pedobarography was performed.4 The device used for pedobarography was the Tekscan Pedography device, which measured the pedobarographic values both statically and dynamically. In our study, we only measured the static values. Patients were asked to stand barefoot on the platform, which has 1–4 independent pressure-measuring cells per square inch. The foot pressure under both feet is recorded according to the foot zones after 10 seconds. The pressure of the foot is recorded as per the zones of the foot in Figures 1 and 2.5 The computerized pedography foot pressure was measured and tabulated against the zones of the foot.6 Similarly, pedobarography was repeated after 6 weeks post-op. A comparison of the foot pressure before and after surgery is analyzed.

Fig. 1: Zones of foot

Fig. 2: Pressure area as per pedobarography

An independent analyst, who was not part of the clinical and radiographic assessments, did all pedobarographic estimations. For the static investigation, patients were asked to remain on the platform for 10 seconds while they were asked questions to prevent the normal tendency to overpressure on one side of the foot.

RESULTS

The mean pedobarography foot pressure vs the zone of the foot for pre-op varus knee and the posttotal knee arthroplasty results are tabulated in Table 1. The statistical analysis of pre-op and postoperative (post-op) TKR pedobarography values are tabulated in Tables 2 and 3. The mean pedobarography foot pressure based on body mass index (BMI) vs the zones of the foot is tabulated in Table 4. Table 5 compiles the mean age-based and gender-based pedobarography foot pressure vs the zones of the foot.

Table 1: Pre-op and post-op pedobarography values
Foot pressure Very high pressure High pressure Medium pressure Normal pressure Slight contact Null contact
Hallux Pre-op 1.9 53.8 1.9 38.4 3.8 0
Post-op 0 53.8 3.8 41.3 0 0
Toes Pre-op 0 18.26 0 60.5 17.3 3.8
Post-op 0 4.8 0.96 82.6 11.5 0
Medial metatarsal Pre-op 1.9 35.5 25.9 21.1 11.5 0
Post-op 1.9 35.5 25.9 21.15 11.5 0
Central metatarsal Pre-op 1.9 0 2.8 65.3 20.19 9.6
Post-op 0 1.9 14.4 51 32.6 0
Lateral metatarsal Pre-op 32.6 28.8 9.6 26.9 1.9 0
Post-op 2.8 25 20.19 34.61 17.3 0
Medial midfoot Pre-op 0 0 0 0 3.8 96.15
Post-op 0 0 0 0.96 11.5 87.5
Lateral midfoot Pre-op 28.8 24 2.8 30.7 11.5 1.9
Post-op 0 8.6 5.7 40.3 43.2 1.9
Medial heel Pre-op 11.5 47.1 2.8 38.4 0 0
Post-op 10.5 30.76 7.6 51 0 0
Lateral heel Pre-op 51.9 36.5 1.9 9.6 0 0
Post-op 9.6 27 16.3 43.2 3.8 0
Table 2: Statistical analysis of forefoot pre-op and post-op values
Number % Number %
Serial number Variable Mean Pre-op foot test Post-op foot test p-value
1 Hallux Very high pressure 2 1.9 0 0 2.51838
High pressure 56 53.8 56 53.8
Medium pressure 2 1.9 4 3.8
Normal pressure 40 38.4 43 41.3
Slight contact 4 3.8 0 0
Null contact 0 0 0 0
HNP 0 0 1 0.96
2 Toes High pressure 19 18.26 5 4.8 0.006547
Normal pressure 63 60.57 86 82.69
Slight contact 18 17.3 12 11.5
Null contact 4 3.8 0 0
Medium pressure 0 0 1 0.96
3 Medial metatarsal High pressure 36 34.6 37 35.5 0.073908
Medium pressure 5 4.8 27 25.9
Normal pressure 44 42.3 22 21.15
Slight contact 17 16.3 12 11.5
Very high pressure 2 1.9 2 1.9
NMP 0 0 2 1.9
MNP 0 0 2 1.9
4 Central metatarsal Medium pressure 3 2.8 15 14.4 0.014162
High pressure 0 0 2 1.9
Null contact 10 9.6 0 0
Normal pressure 68 65.3 53 51
Slight contact 21 20.19 34 32.6
Very high pressure 2 1.9 0 0
Normal pressure 40 38.4 53 51
Medium pressure 3 2.8 8 7.6
High pressure 49 47.1 32 30.76
5 Lateral metatarsal High pressure 30 28.8 26 25 0.948675
Medium pressure 10 9.6 21 20.19
Normal pressure 28 26.9 36 34.6
Slight contact 2 1.9 18 17.3
Very high pressure 34 32.6 3 2.8

HNP, hallux normal pressure; NMP, null metatarsal pressure; MNP, metatarsal normal pressure

Table 3: Statistical analysis of midfoot and hindfoot pre-op and post-op values
Number % Number %
Serial number Variable Mean Pre-op foot test Post-op foot test p-value
1 Medial midfoot Normal pressure 0 0 1 0.96 0.048975
Null contact 100 96.15 91 87.5
Slight contact 4 3.8 12 11.5
2 Lateral midfoot High pressure 25 24 9 8.6 0.649781
Medium pressure 3 2.8 6 5.7
Null contact 2 1.9 2 1.9
Normal pressure 32 30.76 42 40.38
Slight contact 12 11.5 45 43.2
Very high pressure 30 28.8 0 0
3 Medial heel Very high pressure 12 11.5 11 10.5 0.174108
Normal pressure 40 38.4 53 51
Medium pressure 3 2.8 8 7.6
High pressure 49 47.1 32 30.76
4 LH High pressure 38 36.5 28 27 0.938446
Medium pressure 2 1.9 17 16.3
Normal pressure 10 9.6 45 43.2
Very high pressure 54 51.9 10 9.6
Slight contact 0 0 4 3.8

LH, lateral heel

Table 4: Pedobarography values based on BMI
Foot pressure Very high pressure High pressure Medium pressure Normal pressure Slight contact Null contact
Hallux BMI <25 1 7 0 7 1 0
BMI 25.1–29.9 1 34 0 22 1 0
BMI ≥30 1 15 0 12 2 0
Toes BMI <25 0 2 0 11 2 1
BMI 25.1–29.9 0 10 0 37 10 1
BMI ≥30 0 3 0 19 5 2
Medial metatarsal BMI <25 0 10 0 4 2 0
BMI 25.1–29.9 1 21 2 23 11 0
BMI ≥30 1 9 2 12 2 0
Central metatarsal BMI <25 0 6 0 12 2 2
BMI 25.1–29.9 1 0 1 38 13 5
BMI ≥30 1 0 1 19 4 5
Lateral metatarsal BMI <25 0 8 0 8 2 0
BMI 25.1–29.9 17 17 5 17 2 0
BMI ≥30 12 7 5 6 0 0
Medial midfoot BMI <25 0 0 0 0 1 15
BMI 25.1–29.9 0 0 0 0 2 56
BMI ≥30 0 0 0 0 1 29
Lateral midfoot BMI <25 3 3 0 5 4 1
BMI 25.1–29.9 16 16 1 17 7 1
BMI ≥30 10 7 1 13 5 1
Medial heel BMI <25 3 6 0 7 0 0
BMI 25.1–29.9 7 28 2 22 0 0
BMI ≥30 6 10 1 13 0 0
LH BMI <25 6 6 0 4 0 0
BMI 25.1–29.9 32 21 1 4 0 0
BMI ≥30 37 28 2 7 0 0

LH, lateral heel, BMI, body mass index

Table 5: Pedobarography values based on age and gender
Foot pressure VHP HP MP NP SC NC
Hallux Age <65 1 34 0 22 1 0
Age >65 0 10 0 4 2 0
Male 0 10 0 37 10 1
Female 0 10 0 4 2 0
Toes Age <65 1 9 2 12 2 0
Age >65 0 0 0 12 2 2
Male 1 21 2 23 11 0
Female 0 0 0 12 2 2
Medial metatarsal Age <65 1 0 1 19 4 5
Age >65 0 10 0 4 2 0
Male 0 0 0 0 2 56
Female 0 3 0 19 5 2
Central metatarsal Age <65 12 7 5 6 0 0
Age >65 1 9 2 12 2 0
Male 16 16 1 17 7 1
Female 1 9 2 12 2 0
Lateral metatarsal Age <65 0 0 0 0 1 29
Age >65 1 0 1 19 4 5
Male 1 9 2 12 2 0
Female 1 34 0 22 1 0
Medial midfoot Age <65 17 17 5 17 2 0
Age >65 0 10 0 4 2 0
Male 1 34 0 22 1 0
Female 7 28 2 22 0 0
Lateral midfoot Age <65 0 0 0 0 2 56
Age >65 0 0 0 12 2 2
Male 0 10 0 37 10 1
Female 32 21 1 4 0 0
Medial heel Age <65 0 10 0 4 2 0
Age >65 6 10 1 13 0 0
Male 17 17 5 17 2 0
Female 1 9 2 12 2 0
LH Age <65 0 0 0 12 2 2
Age >65 37 28 2 7 0 0
Male 0 0 0 0 2 56
Female 1 0 1 19 4 5

LH, lateral heel; VHP, very high pressure; HP, high pressure; MP, medium pressure; NP, normal pressure; SC, slight contact; NC, null contact

DISCUSSION

Pedobarography is a noninvasive technique that empowers the estimation of strain between the foot and the floor.7 Pedobarography examination shows the dissemination of plantar strain of the foot.8 Notwithstanding the clinical assessment of the patient, we get exceptionally valuable data about the condition of the foot and the kind of strain. Pedobarography is widely used in gait analysis and biomechanics, diabetic offloading, sports medicine and rehabilitation, pre- and posttreatment evaluation, and orthotic prescription. There are two types—static and dynamic. In our study, we used computerized static pedobarography. Everything is straightforwardly associated with the personal computer framework modified to perform an investigation of the foot.9 By programming investigation, we acquire three-layered pictures of the foot and circulation of strain, specifically the region of the foot with a similar tension, just as geographical linkage so that we can decide certain “hot” and “cold” zones of low and high tension.

Men and women have different musculoskeletal features. This is a significant factor that can cause issues in other areas of the body. It also increases the risk of deformities in the lower extremities, such as dynamic pes planus, pes cavus, increased hindfoot inversion, etc.10 A better understanding of sex and age-related foot pressure will reduce the risk of injury in the foot. Age and sex did not cause any significant changes in foot pressure. Foot pressure was equal in both groups when compared to pre-op and post-op foot pressure. Postoperatively, 120 out of 208 patients (57.69%) of the patients had ankle and foot pain.

Body Mass Index

Increased loading of the feet might be classified based on duration as temporary, short-term, and long-term. Temporarily, for example, carrying weight in the back while pregnant is a short-term condition. At the same time, persistent weight gain is a long-term condition. There are many studies that deal with the temporary and short-term outcomes of foot pressure, but there is minimal evidence for high BMI with foot pressure.11 From our study, it is evident that higher BMI patients are associated with significant high-pressure changes over lateral metatarsal and lateral heel zones.

Varus

Preoperatively, the high-pressure changes were seen in the lateral metatarsal, lateral midfoot, and lateral heel. Postoperatively, there was a significant shift in pressure changes toward medial foot zones to the hallux, medial metatarsal, central metatarsals, and medial heel. The pictorial representation of change in foot pressure is evident in Figure 3.

Fig. 3: Preoperative (pre-op) vs post-op foot pressure pedobarography image

Ankle Pain

When combined with knee osteoarthritis, concurrent foot pain can worsen disability and symptom severity.3 Due to an increase in medial knee compartmental loading, knee varus may raise the risk of developing osteoarthritis in the knee. In order to guarantee that the foot is plantigrade to the ground throughout the walking stance phase, they may also induce enhanced foot pronation. Postoperatively, 60% of the patients had pain in the ankle due to the disuse of the tarsal bones.

The study’s shortcomings are short-term follow-up—some patients still had knee pain, and hence, it may have influenced the post-op foot test. Only grade II varus was studied, and only static pedobarographic images were analyzed.

CONCLUSION

Patients with varus osteoarthritic knees are associated with disuse osteoporosis of the foot. This occurs due to improper foot pressure distribution. Post-TKR, the distribution of foot pressure changes toward the normal foot pressure distribution. Thus, the disuse of osteoporosis can be reversed.

Clinical Significance

This research illuminates the critical role of total knee arthroplasty in addressing not only the functional aspects of varus knee deformity but also its implications for disuse osteoporosis. The findings contribute valuable insights to orthopedic practice, emphasizing the holistic benefits of TKA beyond joint functionality.

ORCID

Harisudhan Raviraja https://orcid.org/0009-0005-7858-2180

Lokesh K Sekaran https://orcid.org/0009-0008-4040-6685

Ganesan G Ram https://orcid.org/0000-0002-2877-293X

Krishna K Jayaraman https://orcid.org/0009-0007-7071-6257

Vijayaraja Elangovan https://orcid.org/0000-0002-1854-6496

Dheepan Kumar https://orcid.org/0009-0005-9931-621X

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