Clinical application of gait analysis in hip arthroplasty

Abstract

Gait analysis technology can collect a subject's gait data when walking through motion capture systems, force plates, electromyography (EMG), and sensors. It can now be applied to a variety of medical applications. The authors review the recent advances in gait analysis technology and its current clinical application in hip arthroplasty.

Introduction

Hip arthroplasty can relieve pain, restore joint function and improve the quality of life of patients. Hip arthroplasty is considered to be one of the most successful orthopedic procedures ¹ . There are a variety of tools for postoperative assessment of surgical treatments, of which gait analysis is the most objective. Gait analysis boomed with the rapid development of computer technology during the past two decades, and is now increasingly used in the evaluation of the efficacy of hip replacement. Human body kinematics, kinetics and dynamic electromyography data can be collected through gait analysis systems to quantitatively assess patients' function. Different types of replacement, surgical approaches and other factors impacting on the results can be compared objectively. Thus, gait analysis helps surgeons to choose procedures and rehabilitation programs. The purpose of this review is to summarize recent advances in gait analysis and their clinical application in hip arthroplasty.

Recent advances in gait analysis technology

Styles of gait analysis systems vary. At present they mainly include motion capture systems, force plates, electromyography (EMG), and sensors, including accelerometers, electrogoniometers, gyroscopes and pressure sensors, which are small and portable.

Motion capture systems

Motion capture technology is the most common method for gait analysis. By using optical or electromagnetic systems, it can convert body segmental movements into three‐dimensional digital data. Markers are affixed to the subject and tracked throughout the movement of interest. Typically, passive markers reflect ambient or infrared light; active markers emit light (light‐emitting diodes). Electromagnetic systems are able to detect the position and orientation of the receiver on a body segment relative to an externally fixed transmitter. The coordinate three‐dimensional location of the markers can be determined through a manual or automatic digitization technique. From these position data, velocity and acceleration can be calculated from the time derivative of the position and velocity, respectively ² .

Direct comparisons have indicated that measurements obtained from optical and electromagnetic system show no significant differences and that both are accurate ³ . However the two systems have their own shortcomings. If there are a significant number of markers or an insufficient number of cameras, optical systems are prone to marker occlusion. Electromagnetic systems are subject to interference from metal objects located within or near the capture volume ⁴ . Their accuracy is also affected by the distance between the transmitter and the receiver ⁵ . Both systems need skillful operators, and can be prohibitively expensive. Besides, they have a relatively small capture volume and require a controlled operation environment ⁶ .

Force plates

Force plates are commonly used to measure contact forces between foot and ground during the stance phase of gait. This information can be used to quantify impact forces and loading rates, and to track changes in the center of pressure over time ² . However, because of their relatively small size, they impose constraints on foot placement, the psychological effects of which may lead to gait changes affecting the test results ⁷ . Recently, the development of instrumented treadmills has allowed the rapid collection of ground reaction forces over repeated gait cycles, while eliminating any potential error introduced by psychological effects ⁸ .

EMG

EMG is often used to monitor muscle activity during walking. Through the use of surface or indwelling (fine‐wire) electrodes, it can measure timing and relative intensity of muscle activation. This technique can be used to detect abnormal gait behavior and assess neuromuscular control ² . In addition, the frequency content of the EMG signal can be analyzed to determine relative muscle fatigue, which may be useful for the early detection of potential injuries ⁹ .

Novel EMG systems incorporate technology that allows for data to be transmitted wirelessly or stored in a data logger worn by the subject, avoiding the major drawback of old EMG systems in which data were transmitted via cable, potentially limiting the movements of the subject ² . Another limitation of EMG is cross‐talk between muscles and electrical noise from external sources ¹⁰ . The incorporation of in‐line pre‐amplification devices has greatly reduced the ambient noise in the underlying myographic signal ¹¹ , making a greater signal‐to‐noise ratio possible.

Accelerometers

Accelerometers are used to assess the status of body movements soon after their advent. They are inertial sensors that can directly measure acceleration along single or multiple axes, effectively reducing the error associated with differentiation of displacement and velocity data derived from conventional gait analysis systems. Some accelerometers have the ability to respond to both gravitational acceleration and acceleration caused by movement, which allows them to be used for the measurement of segment orientation under static conditions ¹² . In gait analysis, the concurrent application of electrogoniometers and gyroscope scanning further enhances the utility of accelerometers. The most attractive advantage of accelerometers is that they can record data continuously over stride cycles for a prolonged period of time ⁶ , which neither motion capture systems nor force plates can do.

The site and method of attachment of accelerometers may have an impact on the measurement. Evidence indicates that skin‐mounted accelerometers result in significantly greater peak accelerations than bone‐mounted accelerometers ¹³ .

Electrogoniometers

Electrogoniometers can directly measure the joint angle during the continuous movement. They offer a simple and affordable alternative to motion capture systems, allow the joint angle data to be collected and viewed instantaneously, and prove highly accurate. Because electrogoniometers are affixed to skin, there may be excessive sensor motion, resulting in measurement error ¹⁴ . For prolonged periods of data collection, special suits have been fabricated, which facilitates the attachment of the electrogoniometers with hook and loop fasteners ¹⁵ .

Gyroscopes

Gyroscopes are miniature angular rate sensors that can be attached to individual body segments, providing a direct measurement of segment angular velocity ² . This technology is also inexpensive. Compared with foot pressure sensors, gait parameters measured by gyroscopes have shown less measurement errors ¹⁶ . Gyroscopes are small, portable, have low power consumption ¹⁷ , are easy to attach compared to accelerometers, and are insensitive to gravitational influences ⁶ .

Pressure sensors

Pressure sensors placed in shoes are light‐weight, portable, easy‐to‐use, and can also be used for gait analysis. In contrast to force plates, they are capable of quantifying the distribution of force over the plantar surface of the foot, and providing more detailed information on the loading of the foot during gait. In‐shoe pressure sensors also provide the ability to measure the vertical forces of the foot and to detect typical gait parameters required for gait analysis, such as the heel strike and toe‐off needed to define the stance phase of gait ¹⁸ . Although force plates are considered to be the gold standard for measuring foot forces during gait, they are limited in the number of steps that can be sampled and are typically restricted to a laboratory setting. In‐shoe pressure sensors allow easier collection of data in an environment that facilitates normal gait.

Data obtained from in‐shoe pressure sensors have shown high reliability across multiple trials of the same subject ¹⁹ . However, comparison of the two most popular in‐shoe pressure measurement systems has indicated that the accuracy and precision of these systems may be sensitive to the levels of pressure applied, calibration procedure, duration of pressure application, and length of time that the insole has been used ²⁰ .

Until now, there has been no single gait analysis system that can provide all gait information ²¹ . Researchers are working towards integrating multiple sensors into a device, such as “gait shoes”, which are light‐weight, do not hinder the natural movement of the wearer, and yet are able to detect motion, force, and pressure ²² . It can be predicted that gait analysis systems will keep being updated and being applied more widely.

Clinical application of gait analysis in hip arthroplasty

Comparison of different replacement types

Total hip arthroplasty (THA) is the option for most patients with end‐stage arthritis of the hip. Revisions account for almost 20% of total hip cases in the USA, and this number is growing ²³ . A major advantage of resurfacing hip arthroplasty (RHA) is that bone stock for future revision is retained, which young and active patients prefer. In terms of operative time, blood loss, and clinical success rate, conversion to a THA is more similar to a primary THA than to a revision procedure ²⁴ . Shimmin et al. found no difference in gait characteristics between 14 RHA and 12 THA ²⁵ . Lavigne et al. reported gait data in three distinct groups: RHA, standard THA, and THA using a large diameter femoral head ²⁶ . They found better gait measurements in patients with RHA or with THA using large‐diameter heads than in those with standard THA. Other studies have shown that gaits in patients with RHA are closer to normal than they are in patients with THA ²⁷ , ²⁸ . Mont et al. found improved gait parameters (speed of walking, abduction moments) after RHA when compared to standard hip arthroplasty and osteoarthritic hips ²⁹ . Patients who underwent RHA had greater hip abduction moments, higher clinical survey scores, and greater symmetry in muscular activation 3 months postoperatively in comparison with those who had undergone THA ³⁰ .

Comparison of different surgical approaches

Different approaches are used in hip replacement surgery. Surgeons usually make decisions according to their own operating habits and the specific characteristics of patients. Madsen et al. investigated the influence of the type of surgical approach on 6 months post‐operative gait by comparing the data of patients treated by the modified Mallory anterolateral (AL) approach with that of patients treated by the posterolateral (PL) approach ³¹ . The patients who underwent THA using an AL approach deviated from normal with respect to increased trunk inclination, reduced range of movement in the sagittal plane, and greater loading asymmetry. These findings can be explained by the fact that the AL approach is known to affect the abductor muscle, which plays a crucial role during the single stance phase. Whatling et al. claimed that a group in which the southern posterior approach was used exhibited greater characteristics of non‐pathological gait and better functional ability as compared with a group in which the McFarland‐Osborne direct lateral approach was used ³² . Klausmeier et al. observed no difference between the anterior THA approach and the anterolateral one for most isometric strength and dynamic gait measurements after 6 and 16 weeks ³³ . So far, however, few prospective trials have compared the long‐term results among different surgical approaches using gait analysis.

Advantages of minimally invasive surgical (MIS) techniques for hip arthroplasty include reduction of damage to muscles and tendons and rapid rehabilitation and recovery. MIS approaches include two‐incision, mini‐posterior, and mini‐anterolateral. In a randomized prospective study comparing the two‐incision approach with a mini‐posterior one, Pagnano et al. examined the variables of velocity, cadence, step length, stride length, and single‐leg stance, as well as hip moments derived from force plate data ³⁴ . The authors concluded there was no evidence that the early functional outcome of the two‐incision MIS approach was superior to that of the mini‐posterior approach. Meneghini et al. performed a randomized, prospective study that demonstrated no discernable difference among the three MIS surgical approaches in the early postoperative gait parameters of single‐leg stance time, surgical limb‐loading rate, and abductor torque ³⁵ . The mini‐anterolateral approach showed a decrease in the 6‐week mean value of all three kinetic variables (vertical ground reaction force, limb‐loading rate, and abductor torque). These findings suggest that the mini‐anterolateral approach probably continues to result in greater hip abductor muscle injury in the early postoperative period compared with the other two MIS approaches, which do not intentionally violate the abductors.

While MIS approaches for hip arthroplasty remain controversial, some investigators have reported that MIS techniques result in more rapid recovery ³⁶ , ³⁷ . However, an increased rate of complications has been reported with MIS techniques, particularly with the two‐incision approach ³⁸ , ³⁹ . A recent prospective study assessed early pain and function after THA through a mini‐posterior or a standard posterior approach. Gait analysis was performed preoperatively and 6 weeks postoperatively to determine the kinematic variables of velocity, cadence, and single‐leg support. There was no difference between the two groups after 6 weeks ⁴⁰ . Bennett et al. found no differences between the groups 6 weeks postoperatively in terms of velocity, step length, stride length, and duration of stance phase ⁴¹ , ⁴² . However, these studies did not report kinetic force data, which is effective in quantifying antalgic gait after THA.

Gait analysis in limb length discrepancy (LLD) after THA

LLD after THA is common and difficult to avoid. The most frequent complications are limping, lumbar pain, neurological damage, patient dissatisfaction, and the need for contralateral shoe lifts for correction ⁴³ , ⁴⁴ , ⁴⁵ , ⁴⁶ . LLD is also an important factor constraining gait recovery. The extent to which LLD impairs motor activity is still controversial. The study of Lai et al. showed that, with a discrepancy greater than 2 cm, there was a marked reduction in walking speed and in the length of the step for congenital hip dislocation ⁴⁷ . However, the rhythm of gait was equal to that with corrected discrepancy. Benedetti et al. found that a leg length inequality in the range of 1–20 mm did not impair the symmetry of time–distance parameters and of hip kinematics and kinetics during gait and climbing stairs ⁴⁸ .

Other relevant research in gait analysis

Metal‐on‐metal large‐femoral‐head THA is becoming more and more popular. It has been reported that a well‐designed and well‐manufactured metal‐on‐metal bearing surface predictably decreases the generation of wear particles ⁴⁹ , ⁵⁰ . Theoretically, a large‐diameter femoral head effectively reduces impingement and ensures a larger range of movement. Zhou et al. collected gait data for primary THA using 28 mm metal‐on‐polyethylene heads (conventional group) and for THA (large head replacement group) using metal‐on‐metal femoral heads with an average size of 45 mm ⁵¹ . The results suggested that large‐diameter femoral heads in THA provide better early gait restoration than conventional femoral heads.

Dissatisfaction after THA is linked to complications caused by co‐morbidities, radiographic loosening, and poor prosthetic alignment. However, for some individuals, the underlying cause may be related to soft tissue problems such as muscular weakness and muscle tightness, which are less evident clinically and/or radiographically and for which there are often no standard treatment algorithms. Bhave et al. found that three‐dimensional gait studies are valuable in identifying problems after THA and help to direct customized rehabilitation modalities ⁵² .

The visual, accurate and reliable data obtained by gait analysis technology provide an important reference in hip arthroplasty, and can inform choices concerning replacement type, surgical approach and rehabilitation program. With continuing advancement in biomechanics and information processing, it is expected that gait analysis system will become more prolific, affordable, and important in hip arthroplasty in the near future.