Gait analysis and clinical outcomes of anterior and lateral approach total hip arthroplasty: A prospective randomized study

INTRODUCTION

The lateral approach (LA) for total hip arthroplasty (THA) is widely used by orthopedic surgeons but involves releasing part of the gluteus medius, raising concerns about its impact on gait mechanics and delayed recovery postoperatively.^[1-4] The direct anterior approach (DAA) is gaining popularity as an alternative, minimizing soft-tissue dissection using an internervous plane between the tensor fascia latae and sartorius muscle. The DAA is considered minimally invasive due to its shorter incision length and potential to preserve the hip musculature.^[5]

However, the success of THA depends not only on the surgical approach but also on factors like bearing surface and implant placement.^[6] Restoring normal gait is a critical outcome after THA, particularly in the 1^st post-operative year. Gait analysis is a valuable tool for evaluating hip joint function postoperatively.^[7-9]

Our institution has predominantly used the LA for THA for nearly five decades but has recently adopted the DAA, observing differences in early outcomes. The previous studies compared gait mechanics between DAA and LA postoperatively at 3 and 18 months. This prospective randomized trial aims to compare gait mechanics between these approaches using gait analysis starting from 6 weeks postoperatively.

MATERIALS AND METHODS

Forty patients were enrolled in this randomized prospective comparative cohort study between January 2021 and June 2023.

The inclusion criteria comprised skeletally mature adults aged 20–60 with unilateral primary hip osteoarthritis (OA) or osteonecrosis. Participants had to be independent and physically active, defined by their ability to perform daily tasks, climb two flights of stairs, and walk for 15 min.

Exclusion criteria included individuals with bilateral hip involvement, hip conditions other than primary OA or osteonecrosis, prior hip or spine surgery, body mass index (BMI) over 40, chronic uncontrolled comorbidities, psychological disorders, an American Society of Anesthesiologists (ASA) score above 2, chronic neurological deficits affecting gait, limb length discrepancy >1 cm, or post-operative complications that delayed weight bearing.

Gait analysis

A single experienced physical medicine specialist conducted the gait analysis in a laboratory at 6 weeks, 3 months, and 18 months postoperatively. Three-dimensional kinematic and kinetic data were collected using eight high-speed infrared cameras (Qualisys motion analysis system, Oqus 1) at 240 frames per second, two force plates (AMTI), and 26 ten-millimeter passive retroreflective markers. The markers were positioned on specific landmarks of both lower limbs according to the modified Istituto Ortopedico Rizzoli model^[12] [Figure 1].

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Figure 1:

(a-d) Markers placement on the subject.

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During the static trial, six additional calibration markers were placed on each side’s 2^nd metatarsal, medial malleolus, and medial femoral condyle. A static trial was recorded while the subject stood on the first force plate with arms abducted at 90° for 10 s. Body mass, marker orientation, and joint center positions for the knee and ankle were determined, after which the calibration markers were removed. Subjects then walked barefoot over the walkway at their self-selected speed, with at least six clean force plate strikes per lower limb. Three trials per limb were analyzed for consistency.

The static and dynamic trials were processed using the Qualisys Track Manager tool, and data were then extracted with the Visual 3D application. The kinematic and kinetic data were normalized to 51 points through a specialized pipeline.

RESULTS

The study aimed to include 40 patients who had THA, with 20 subjects assigned to each group. However, six patients were excluded due to noncompliance and insufficient follow-up data, resulting in 34 cases being analyzed (16 in the LAG and 18 in the DAAG).

The statistical analysis indicated that age, sex, weight, height, BMI, and ASA class did not significantly influence the VAS and HHS scores [Tables 1-3].

The DAAG had significantly longer surgery times and greater intraoperative blood loss than the LAG. However, the length of hospital stay was similar between the groups [Table 4].

Gait analysis revealed a significant increase in gait speed for DAAG compared to LAG at 6 weeks (Student’s t-test). However, no significant differences were observed between the groups at 3 or 18 months, nor in stride length, step length, stance time, or swing time across all follow-up periods [Table 5].

In gait kinetics, DAAG showed significantly higher peak hip extension and external rotation moments at 6 weeks compared to LAG, but these differences were not significant at 18 months. Conversely, LAG had a significant decrease in peak hip abduction and internal rotation moments at 6 weeks, which became non-significant at 3 and 18 months [Tables 6 and 7].

In gait kinematics, there were no significant differences in maximal hip flexion or external rotation angles between the two groups throughout the study. At 6 weeks, DAAG had a significantly larger peak hip abduction angle, and a significantly lower peak extension angle compared to LAG, but these differences were not significant at the 3- and 18-month follow-ups [Table 7].

DISCUSSION

The study supports that the DAA leads to less muscle injury and faster post-operative recovery than the LA. HHS, kinematic, and kinetic gait analysis parameters were significantly better in DAAG than LAG in the first 6 weeks but were similar at 3 and 18 months. There was no significant difference in hospital stay length between the groups, but DAAG had longer operation times and greater hemoglobin drops.

At the 6-week follow-up, gait speed was higher in the DAAG compared to the LAG, but other spatiotemporal parameters were similar between the groups in later follow-ups. Similar results were reported by Queen et al.,^[13] Müller et al.,^[7] Pospischill et al.,^[14] and Varin et al.,^[15] who found no significant differences in time-distance parameters at various post-operative points. However, Mayr et al.^[16] and Klausmeier et al.^[17] observed improved time-distance metrics favoring DAAG at 6 weeks, but not at later follow-ups. Varin et al.^[15] noted that spatiotemporal parameters do not directly reflect joint force distribution, moment production, or joint function, urging caution in interpreting these findings.

In our study, the DAAG showed significant improvements in peak hip abduction and internal rotation moments at the 6-week gait analysis compared to LAG. The DAAG also had increased external rotation and extension moments, likely due to compensatory actions of the gluteus medius and maximus after releasing short external rotators in the anterior approach. In contrast, LAG had a smaller internal rotation moment at 6 weeks, possibly due to the surgical technique detaching the anterior third of the gluteus medius and minimus. By 3 and 18 months, no significant differences in hip kinetics were found between the groups.

In hip kinematics, the DAAG exhibited a significant increase in peak hip abduction angle and a lower extension angle at the 6-week follow-up compared to LAG, possibly due to a painful anterior incision. However, these differences were not significant at 3 and 18 months. Studies by Queen et al.,^[13] Müller et al.,^[7] Pospischill et al.,^[14] and Klausmeier et al.^[17] reported no notable changes between groups over time. Varin et al.^[15] found that the DAA had sagittal plane kinematics closer to normal than LA, while Kiss and Illyés^[18] observed reduced hip motion and increased pelvic tilt in LA patients early post-surgery, normalizing within a year. DAA showed quicker recovery and better functional results than LA, as supported by Mayr et al.^[16] and Klausmeier et al.,^[17] particularly at 6-week and 3-month follow-ups.

In the LA, partial detachment of the anterior third of the gluteus medius can weaken abductors, significantly impacting gait kinetics and kinematics early postoperatively.^[19] Queen et al.^[13] found that LAG had a larger adduction moment than the unoperated limb, likely due to pelvic drop during propulsion, indicating weak abductors. Mayr et al.^[16] observed that patients with impaired abductor function compensated by internally rotating their hips, especially within the first 12 weeks post-surgery.

All the studies that compared the DAA and LA are shown in [Table 8].^{[13-18,20-24]} From the results shown, our results align with all the published results.

CONCLUSION

Compared to the direct LA, the DAA for THA has a faster rehabilitation course, better functional outcomes, and significantly improved hip abductors’ kinetics and kinematics in the first 6 weeks postoperatively. However, both surgical approaches are comparable in the longer-term follow-up.

RECOMMENDATIONS

We recommend a systematic review to compare gait analysis outcomes for THA using the LA, DAA, and posterior approach.