Medial Wedge Insoles to Improve Gait in Persons After Total Hip Replacement

The study will test the hypothesis, that the use of medial wedge insoles in people participating in comprehensive rehabilitation between 1-6 months after total hip replacement, and not having a varus deformity of the knee or symptomatic arthrosis of the medial knee compartment, will improve patient's functioning, the symmetry of gait and stance compared to persons using sham insoles.

The participants will undergo a 6-week program of in-patient rehabilitation aimed at: pharmacologic and non-pharmacologic pain management, improvement of vascular function, cardiopulmonary function, functions of skeletal muscles, range of motion and stability of peripheral joints, gait function, body position. The rehabilitation program will also address individual needs with psychotherapy and vocational therapy.

The study will help to identify correlations between gait parameter change and functional improvement during the rehabilitation following THR.

Study participants will be provided with individually made corrective medial wedge insoles or sham insoles and instructed to use them during gait training and everyday activities.

Functional parameters will be examined at the study entry, at the end of 6 weeks of intervention, and 6 weeks following discharge.

Principal indications for total hip replacement (THR) include hip arthritis - degenerative or inflammatory (91%), fractures of femoral neck (5%), avascular necrosis (2%) and hip dysplasia (2%). Weight-bearing exercises (including treadmill training) are important to improve both impairment and ability to function.

Rationale of testing the effect of medial wedge insoles after THR:

Valgus deformity of the lower limb and insufficiency of the gluteus medius muscle lead to femoral adduction. In patients after a total hip replacement (THR), it will transfer the ground force to the prosthesis cup in the adduction position.

The application of corrective insoles is a simple, inexpensive, and non-invasive intervention that may be easily integrated into daily activities to promote health benefits, provide comfort, and prevent acute and chronic injuries, as well as correct biomechanical deficiencies in the musculoskeletal system (including valgus knee ). An important effect of the insoles is to support the preferred movement pattern and, as a result, reduce unnecessary muscle activity in gait, and decrease fatigue and energy expenditure. The use of insoles can therefore be a valuable addition to gait function exercises. Typically, hindfoot corrective insoles are used with a wedge that corrects the heel between 5-15 degrees. Smaller correction wedge angles are unable to correct the valgus moment and affect the center of pressure (CoP) projection during walking, while wedges with a larger correction angle cause discomfort.\[5\] Medial wedge insoles increase heel inversion, reduce internal tibial rotation, transfer the CoP medially to the knee joint, and increase the knee and hip abduction moment.

Insufficiency of the gluteus medius muscle causing pelvic descent and internal rotation of the thigh is typical for hip arthritis, especially after THR using the posterior, posterolateral, or direct lateral approach. It was found that the use of medial wedge insoles promotes the activation of the gluteus medius during dynamic activities, although Bird et al. did not confirm this effect in people with low back pain.

Gait symmetry and voluntary walking speed belong to important gait quality parameters measured in patients after THR. Many variables illustrating gait symmetry such as ..step length, step time, time of load changes, foot rotation, time of gait phases, as well as temporal and spatial distribution of forces exerted by specific foot parts may be reliably measured with a treadmill instrumented with force sensors.

To identify publications on the effectiveness of corrective insoles after THR, an analysis of the Pubmed, Medline Central, and Scifinder literature databases was carried out using the key phrase: (("hip" AND ("replace\*" OR "plast\*" or "simple\*")) AND ( "insole\*" OR ("foot AND "correc\*"))) Identified (November 15, 2019) in databases; Medline Central: 20 records, Scifinder: 73 records, and Pubmed: 66 records. 159 records were reviewed in the title analysis stage, 9 records were eliminated as repeated, 150 records were eliminated as not related to the use of insoles after THR.

Evidence on the usefulness of supination insoles in people with arthritis of the lower limb, and also in people after hip arthroplasty is warranted.

Study design:

A single-center randomized control trial to observe the effect of medial wedge corrective insoles on gait characteristics in persons after THR will be performed in the Rehabilitation Department of the National Institute of Geriatrics, Rheumatology and Rehabilitation, Warsaw, Poland. The trial will involve 100 patients admitted 1-6 months after THR. Consecutive patients fulfilling inclusion criteria will be invited to participate. Participants will be randomly allocated in:

1. Intervention group: the patients will be provided with corrective medial wedge insoles (with hard 10-degree medial wedge)
2. Control group: the patients will be provided with sham medial wedge insoles (with pliable10 degree medial wedge)

Participants' age, sex, time since THR, cause of THR, body height and weight, Q angle, intermalleolar distance, and lower extremities length discrepancy will be measured at the study entry. All insoles will be fabricated individually. The design of insoles will comply with the participant's foot size and needs with regard to lower limb length discrepancy elimination. The participants will be recommended to use the insoles during all therapeutic activities and daily activities during the duration of the program. The participants will undergo a 6-week rehabilitation program provided in the Rehabilitation Department of the National Institute of Geriatrics, Rheumatology and Rehabilitation. The program will be aimed at: pharmacologic and non-pharmacologic pain management, improvement of vascular function, cardiopulmonary function, functions of skeletal muscles, range of motion and stability of peripheral joints, gait function, and body position. The rehabilitation program will also address individual needs with psychotherapy and vocational therapy. The following parameters will be assessed by a blinded researcher in the specific time points (1) 3rd day following delivery of insoles; (2) completion of the 6-week rehabilitation program; (3) follow-up 6 weeks after completion of the rehabilitation program:

Pain intensity (recently and on average during the preceding week), distress produced by pain (recently and on average during the preceding week), and interference of pain with everyday activities (Pain Rating Scale by the British Pain Society, the Polish version; © The British Pain Society 2006), passive ranges of motion of hip, knee, and ankle joints, pain, stiffness, and physical functional disability (Western Ontario and McMaster Universities - WOMAC scale), osteoarthritis-specific symptoms and physical functional disability (The Lequesne OA index), Gait variables: voluntary speed, step time symmetry, time of load change heel to forefoot symmetry, foot rotation symmetry, length symmetry, step width, stance phase symmetry, load response symmetry, single limb support symmetry, swing phase symmetry and variables illustrating the centre of pressure displacement (length of gait line symmetry, single limb support line symmetry, lateral deviation of the center of pressure, anteroposterior position of the center of pressure) (obtained by Zebris Medical Rehawalk software on HP Cosmos Mercury FDM-THP-M2i treadmill), Stance variables: Centre of Pressure path length, 95% confidence ellipse area, symmetry of average forces, Patient's satisfaction with insoles will be assessed at the completion of the study, Dropout rate and adverse effects.

Statistical analysis

Normally distributed data will be described by means and standard deviation and statistically tested using the Student t-test and ANOVA. Data not normally distributed will be described by medians and ranges and statistically tested using non-parametric methods such as Wilcoxon's test and the Kruskal-Wallis test. The frequency will be compared using Fisher's exact test. The normality of data will be tested using the Shapiro-Wilk test. The symmetry of gait and stance will be analyzed using different symmetry indices (such as Symmetry ratio, Symmetry index, Gait asymmetry, and Symmetry angle). The correlations between gait parameter change and functional improvement will be analyzed using Spearman's rank correlations coefficient and Fisher's exact test.

Significance of the results:

The evidence of the beneficial effect of medial wedge insoles on the functioning of patients after THR may result in a recommendation for the use of routine use of such devices after THR. The study will help to identify correlations between gait parameter change and functional improvement during the rehabilitation following THR.

Eligibility Criteria:
Inclusion Criteria:

* Clinical diagnosis of primary or secondary hip coxarthrosis or proxmal hip facture
* Total Hip replacement made from posterior or lateral surgical approaches
* Total Hip replacement made less 1-6 months prior to study entry

Exclusion Criteria:

* Total Hip replacement made from anterior or anterolateral approach
* Total Hip replacement made less than 1 month or more than 6 months prior to study entry
* Varus knee (Q angle below 5 degrees in males and below 10 degrees in females
* Symptomatic arthritis of medial compartment of the knee
* Use of corrective insoles (excluding insoles for limb length discrepancy compensation)
* Inability to walk for one minute
* Neurologic conditions
* History of hip prosthesis dislocation
* Cognitive dysfunction (MoCa Score below 26)
* Lack of shoes with a stiff heel counter