Total hip replacement (THR) is being considered as one of the most effective medical procedures. Since its introduction, there was a worldwide debate over proper implant selection in terms of size, bearing type and shape. The diameter of used femoral heads components grew throughout the years - from 22 mm in the 1960s to 32 mm in the 2000s, which is the most commonly used size nowadays. In recent years there was a visible use of large femoral heads (>=36mm) in several registers. In the USA there was a significant grow in use of this heads rising from 1% in early 200s to even 58% in 2009. There is a strong evidence data and many researchers concerning range of movement, risk of dislocation, functional results, pain and prosthesis wear depending of femoral head size.

In terms of gait characteristics there are several deviations reported concerning both patients with hip osteoarthritis (OA) and following THR. There is a lack of literature concerning influence of used implants on gait parameters and whether this goal of the surgery can be achieved.

The aim of this study was to assess potential differences of lower limb biomechanics during gait in patients following total hip replacement surgery depending on femoral head diameter and compare them to the normal gait of healthy volunteers. As a secondary outcome authors wanted to inspect correlation between gait parameters and patient-reported outcome.

Total hip replacement (THR) is being considered as one of the most effective medical procedures. Since its introduction, there was a worldwide debate over proper implant selection in terms of size, bearing type and shape. The diameter of used femoral heads components grew throughout the years - from 22 mm in the 1960s to 32 mm in the 2000s, which is the most commonly used size nowadays. In recent years there was a visible use of large femoral heads (>=36mm) in several registers. In the USA there was a significant grow in use of this heads rising from 1% in early 200s to even 58% in 2009. There is a strong evidence data and many researchers concerning range of movement, risk of dislocation, functional results, pain and prosthesis wear depending of femoral head size.

In terms of gait characteristics there are several deviations reported concerning both patients with hip osteoarthritis (OA) and following THR. It is well-proven that those with hip OA have reduced stride length and reduced cadence, reduced gait velocity, and reduced joint excursion. Patients after THR walk with lower hip-abduction moments, sagittal-plane range of motion. It is believed that it might be a consequence of pain-avoidance mechanism developed as an adaptation for joint disease, which is still present after the surgery. What is more, there are publications, which underline that lower limb biomechanics during gait do not return to normal following THR.

However there is a lack of literature concerning influence of used implants on gait parameters and whether this goal of the surgery can be achieved.

According to authors best knowledge this study is the first to ever describe potential differences in gait parameters between THR performed with standard femoral heads (28-32mm) and large ones (>=36mm).

Aim of the study The aim of this study was to assess potential differences of lower limb biomechanics during gait in patients following total hip replacement surgery depending on femoral head diameter and compare them to the normal gait of healthy volunteers. As a secondary outcome authors wanted to inspect correlation between gait parameters and patient-reported outcome.

Inclusion Criteria:

• BMI <35
• Ability to walk for 10 meters
• 60-80 years of age
• Bilateral THR

Exclusion Criteria:

• Revision surgeries before and after THR
• Any other lower limbs surgeries
• Secondary OA
• Neurological disorders
• Cardiac disorders
• Severly impaired balance
• Severe dizziness

The datasets used and/or analyzed during the current study will be available from the corresponding author on reasonable request.

The datasets used and/or analyzed during the current study will be available from the corresponding author on reasonable request.

The datasets used and/or analyzed during the current study will be available from the corresponding author on reasonable request.