Effect of hip angle on anterior hip joint force during gait

REHABILITATION AFTER HIP ARTHROSCOPY AND LABRAL REPAIR IN A HIGH SCHOOL FOOTBALL ATHLETE: A 3.6 YEAR FOLLOW-UP WITH INSIGHT INTO POTENTIAL RISK FACTORS

BACKGROUND

Hip arthroscopy is a common surgical technique for the correction of intraarticular pathology. While surgical success is often determined by anatomical correction, post-operative rehabilitation serves an essential role in restoring pre-morbid activity levels. A paucity of long-term post-operative rehabilitation outcomes exists in the literature lending uncertainty to the long-standing efficacy of interventions and associated risk for future injury.

CASE DESCRIPTION

This case report describes the progress of a male subject 3.6 years after left hip arthroscopy with labral repair. Detailed clinical measures and insight into potential risk factors are presented as a follow-up to a previously published case report.

OUTCOME

A 3.6-year follow-up assessment revealed potential risk factors that may have predisposed the subject to future pathology. The most profound finding was the subject's complaint of contralateral right hip pain and examination findings suggesting intraarticular pathology. His left surgical hip presented with no reported problems or significant findings. The examination also revealed an anterior tilted pelvis, muscle length deficits, and hip muscle weakness which may have contributed to his right hip pain or may be risk factors for future pathology in both hips. It appeared that these impairments affected his gait and performance on functional tests.

DISCUSSION

This case report describes the 3.6 year follow-up for a young adult male subject after unilateral left hip arthroscopy and acetabular labral repair. The re-examination findings and risk factors identified at the follow-up may provide insight into the need for long-term surveillance among post-surgical individuals. Detailed reporting of the long-term effects of a post-operative program after hip arthroscopy is non-existent in the literature and the current findings suggest the potential need for mitigating risk in the non-surgical hip. Future longitudinal studies are needed to develop a consensus on the best interventions for these patients.

LEVEL OF EVIDENCE

4-Case Report.

Gait alterations to effectively reduce hip contact forces

Patients with hip pathology present alterations in gait which have an effect on joint moments and loading. In knee osteoarthritic patients, the relation between medial knee contact forces and the knee adduction moment are currently being exploited to define gait retraining strategies to effectively reduce pain and disease progression. However, the relation between hip contact forces and joint moments has not been clearly established. Therefore, this study aims to investigate the effect of changes in hip and pelvis kinematics during gait on internal hip moments and contact forces which is calculated using muscle driven simulations. The results showed that frontal plane kinetics have the largest effect on hip contact forces. Given the high correlation between the change in hip adduction moment and contact force at initial stance (R(2)  = 0.87), this parameter can be used to alter kinematics and predict changes in contact force. At terminal stance the hip adduction and flexion moment can be used to predict changes in contact force (R(2)  = 0.76). Therefore, gait training that focuses on decreasing hip adduction moments, a wide base gait pattern, has the largest potential to reduce hip contact forces.

Postural correction reduces hip pain in adult with acetabular dysplasia: A case report

Developmental dysplasia of the hip is often diagnosed in infancy, but less severe cases of acetabular dysplasia are being detected in young active adults. The purpose of this case report is to present a non-surgical intervention for a 31-year-old female with mild acetabular dysplasia and an anterior acetabular labral tear. The patient presented with right anterior hip and groin pain, and she stood with the trunk swayed posterior to the pelvis (swayback posture). The hip pain was reproduced with the anterior impingement test. During gait, the patient maintained the swayback posture and reported 6/10 hip pain. Following correction of the patient's posture, the patient's pain rating was reduced to a 2/10 while walking. The patient was instructed to maintain the improved posture. At the 1 year follow-up, she demonstrated significantly improved posture in standing and walking. She had returned to recreational running and was generally pain-free. The patient demonstrated improvement on self-reported questionnaires for pain, function, and activity. These findings suggest that alteration of posture can have an immediate and lasting effect on hip pain in persons with structural abnormality and labral pathology.

Effect of posture on hip angles and moments during gait

Anterior hip pain is common in young, active adults. Clinically, we have noted that patients with anterior hip pain often walk in a swayback posture, and that their pain is reduced when the posture is corrected. The purpose of this study was to investigate a potential mechanism for the reduction in pain by testing the effect of posture on movement patterns and internal moments during gait in healthy subjects. Fifteen subjects were instructed to walk while maintaining three postures: 1) natural, 2) swayback, and 3) forward flexed. Kinematic and force data were collected using a motion capture system and a force plate. Walking in the swayback posture resulted in a higher peak hip extension angle, hip flexor moment and hip flexion angular impulse compared to natural posture. In contrast, walking in a forward flexed posture resulted in a decreased hip extension angle and decreased hip flexion angular impulse. Based on these results, walking in a swayback posture may result in increased forces required of the anterior hip structures, potentially contributing to anterior hip pain. This study provides a potential biomechanical mechanism for clinical observations that posture correction in patients with hip pain is beneficial.

Effect of increased pushoff during gait on hip joint forces

Anterior acetabular labral tears and anterior hip pain may result from high anteriorly directed forces from the femur on the acetabulum. While providing more pushoff is known to decrease sagittal plane hip moments, it is unknown if this gait modification also decreases hip joint forces. The purpose of this study was to determine if increasing pushoff decreases hip joint forces. Nine healthy subjects walked on an instrumented force treadmill at 1.25 m/s under two walking conditions. For the natural condition, subjects were instructed to walk as they normally would. For the increased pushoff condition, subjects were instructed to "push more with your foot when you walk". We collected motion data of markers placed on the subjects' trunk and lower extremities to capture trunk and leg kinematics and ground reaction force data to determine joint moments. Data were processed in Visual3D to produce the inverse kinematics and model scaling files. In OpenSim, the generic gait model (Gait2392) was scaled to the subject, and hip joint forces were calculated for the femur on the acetabulum after computing the muscle activations necessary to reproduce the experimental data. The instruction to "push more with your foot when you walk" reduced the maximum hip flexion and extension moment compared to the natural condition. The average reduction in the hip joint forces were 12.5%, 3.2% and 9.6% in the anterior, superior and medial directions respectively and 2.3% for the net resultant force. Increasing pushoff may be an effective gait modification for people with anterior hip pain.

Rehabilitation after labral repair and femoroacetabular decompression: criteria-based progression through the return to sport phase

Rehabilitation following hip arthroscopy for femoroacetabular impingement (FAI) and labral-chondral dysfunction has evolved rapidly over the past 15 years. There have been multiple commentaries published on rehabilitation following hip arthroscopy without any published standardized objective criteria to address the advancement of the athlete through the phases of rehabilitation. The purpose of this clinical commentary is to describe a criteria driven algorithm for safe integration and return to sport rehabilitation following hip arthroscopy. The criteria based program allows for individuality of the athlete while providing guidance from early post-operative phases through late return to sport phases of rehabilitation. Emphasis is placed on the minimum criteria to advance including healing restraints, patient reported outcomes, range of motion, core and hip stability, postural control, symmetry with functional tasks and gait, strength, power, endurance, agility, and sport-specific tasks. Evidence to support the criteria will be offered as available. Despite limitations, this clinical commentary will offer a guideline for safe return to sport for the athlete while identifying areas for further investigation.

LEVEL OF EVIDENCE

5.

Gait considerations in patients with femoroacetabular impingement

The literature describing the characteristic features of femoroacetabular impingement (FAI) has been on the rise, increasing awareness of this pathology in the young, active population. The physical therapist should consider FAI as a contributing factor to anterior hip pain, impairments, and functional deficits of the lower quarter. The dynamic interplay of anatomical variations, pain, and muscle function and their effects on gait in patients with FAI, however, is poorly understood. Small sample populations and variability in radiological, demographic, and clinical presentations in those with FAI have precluded meaningful insight into gait analysis and FAI, reiterating the need for further research in this domain. The purpose of this clinical commentary is to review the literature that defines normal gait at the hip joint and abnormal gait as a result of FAI and labral pathology or surgery aimed at correcting it. Secondarily, the authors aim to offer clinicians a strategy to progress the post-surgical patient to normal, unassisted gait while reducing the risk for anterior hip pain. Lastly, the authors of this commentary aim to identify specific areas for future research directed at therapeutic interventions in patients with FAI and those who have undergone surgery to correct it.

LEVEL OF EVIDENCE

5.

Invariant hip moment pattern while walking with a robotic hip exoskeleton

Robotic lower limb exoskeletons hold significant potential for gait assistance and rehabilitation; however, we have a limited understanding of how people adapt to walking with robotic devices. The purpose of this study was to test the hypothesis that people reduce net muscle moments about their joints when robotic assistance is provided. This reduction in muscle moment results in a total joint moment (muscle plus exoskeleton) that is the same as the moment without the robotic assistance despite potential differences in joint angles. To test this hypothesis, eight healthy subjects trained with the robotic hip exoskeleton while walking on a force-measuring treadmill. The exoskeleton provided hip flexion assistance from approximately 33% to 53% of the gait cycle. We calculated the root mean squared difference (RMSD) between the average of data from the last 15 min of the powered condition and the unpowered condition. After completing three 30-min training sessions, the hip exoskeleton provided 27% of the total peak hip flexion moment during gait. Despite this substantial contribution from the exoskeleton, subjects walked with a total hip moment pattern (muscle plus exoskeleton) that was almost identical and more similar to the unpowered condition than the hip angle pattern (hip moment RMSD 0.027, angle RMSD 0.134, p<0.001). The angle and moment RMSD were not different for the knee and ankle joints. These findings support the concept that people adopt walking patterns with similar joint moment patterns despite differences in hip joint angles for a given walking speed.