Modified gait patterns due to cam FAI syndrome remain unchanged after surgery

Musculoskeletal modeling and movement simulation for structural hip disorder research: A scoping review of methods, validation, and applications

Musculoskeletal modeling is a powerful tool to quantify biomechanical factors typically not feasible to measure in vivo, such as hip contact forces and deep muscle activations. While technological advancements in musculoskeletal modeling have increased accessibility, selecting the appropriate modeling approach for a specific research question, particularly when investigating pathological populations, has become more challenging. The purposes of this review were to summarize current modeling and simulation methods in structural hip disorder research, as well as evaluate model validation and study reproducibility. MEDLINE and Web of Science were searched to identify literature relating to the use of musculoskeletal models to investigate structural hip disorders (i.e., involving a bony abnormality of the pelvis, femur, or both). Forty-seven articles were included for analysis, which either compared multiple modeling methods or applied a single modeling workflow to answer a research question. Findings from studies comparing methods were summarized, such as the effect of generic versus patient-specific modeling techniques on model-estimated hip contact forces or muscle forces. The review also discussed limitations in validation practices, as only 11 of the included studies conducted a validation and used qualitative approaches only. Given the lack of information related to model validation, additional details regarding the development and validation of generic models were retrieved from references and modeling software documentation. To address the wide variability and under-reporting of data collection, data processing, and modeling methods highlighted in this review, we developed a template that researchers can complete and include as a table within the methodology section of their manuscripts. The use of this table will help increase transparency and reporting of essential details related to reproducibility and methods without being limited by word count restrictions. Overall, this review provides a comprehensive synthesis of modeling approaches that can help researchers make modeling decisions and evaluate existing literature.

Diagnostic Capability of Intra-Articular Injections for Femoroacetabular Impingement Syndrome: A Systematic Review

OBJECTIVE

To review and critically appraise available literature concerning the diagnostic capability of intra-articular injections for femoroacetabular impingement (FAI) syndrome.

DESIGN

Systematic review.

SETTING

N/A.

PARTICIPANTS

N/A.

INTERVENTIONS

N/A.

MAIN OUTCOME MEASURES

Studies assessing pain relief following intra-articular injections for the diagnosis of FAI syndrome, compared with arthroscopy as diagnostic reference standard, were considered eligible. Searches were performed across 8 databases, and the risk of bias was evaluated through the Quality Assessment of Diagnostic Accuracy Studies tool.

RESULTS

From 489 articles identified, 4 were included for analysis. Intra-articular injections were composed of anesthetic agents (such as lidocaine, bupivacaine, and ropivacaine), combined or not with corticosteroids (triamcinolone and betamethasone). All studies were judged as "at risk of bias", and a substantial heterogeneity was found considering assessment methods and pain relief thresholds for a positive response to intra-articular injections. Overall, 2 studies reported that intra-articular injections presented a high accuracy in determining the presence of FAI syndrome. However, the remaining 2 studies indicated that intra-articular injections might present restricted diagnostic capability to discriminate FAI syndrome from healthy individuals or those with other hip pathologies.

CONCLUSIONS

Based on limited evidence, the diagnostic capability of intra-articular injections for FAI syndrome cannot be supported. It remains unclear which pain relief thresholds are related to a higher diagnostic capability. The combination of anesthetics with corticosteroids should also be further explored, including multiple pain assessments for evaluation of prolonged effects.

Hip joint contact forces are lower in people with femoroacetabular impingement syndrome during squat tasks

It remains unknown if hip joint forces during squat tasks are altered in people with femoroacetabular impingement syndrome (FAIS). The aim of this study is to compare hip joint forces between people with FAIS and healthy controls during double leg squat and single leg squat tasks and within limbs during a single leg squat task in people with FAIS. Kinematic and kinetic data were collected in eight people with FAIS and eight healthy matched controls using 3D motion capture and force plates. AnyBody Modeling System was used to perform musculoskeletal simulations to estimate hip joint angles, forces, and moments for all participants. Estimates were postprocessed with AnyPyTools and converted into normalized time series to be compared using a 1D statistical nonparametric mapping (SnPM) approach. SnPM with an independent samples t-test model was used to compare people with FAIS to controls, while a paired samples model was used to compare involved to uninvolved limb in people with FAIS. Patients demonstrated lower proximodistal force compared to controls (p < 0.01) and compared to the uninvolved side (p = 0.01) for single leg squat. The smaller joint contact forces in people with FAIS compared to controls could represent a strategy of reduced muscle forces to avoid pain and symptoms during this high demand task. These findings when combined with imaging data could help assess the severity of FAIS on hip related function during higher demand tasks.

Hip Contact Forces During Sprinting in Femoroacetabular Impingement Syndrome

PURPOSE

Sprinting often provokes hip pain in individuals with femoroacetabular impingement syndrome (FAIS). Asphericity of the femoral head-neck junction (cam morphology) characteristic of FAIS can increase the risk of anterior-superior acetabular cartilage damage. This study aimed to 1) compare hip contact forces (magnitude and direction) during sprinting between individuals with FAIS, asymptomatic cam morphology (CAM), and controls without cam morphology, and 2) identify the phases of sprinting with high levels of anteriorly directed hip contact forces.

METHODS

Forty-six recreationally active individuals with comparable levels of physical activity were divided into three groups (FAIS, 14; CAM, 15; control, 17) based on their history of hip/groin pain, results of clinical impingement tests, and presence of cam morphology (alpha angle >55°). Three-dimensional marker trajectories, ground reaction forces, and electromyograms from 12 lower-limb muscles were recorded during 10-m overground sprinting trials. A linearly scaled electromyogram-informed neuromusculoskeletal model was used to calculate hip contact force magnitude (resultant, anterior-posterior, inferior-superior, medio-lateral) and angle (sagittal and frontal planes). Between-group comparisons were made using two-sample t -tests via statistical parametric mapping ( P < 0.05).

RESULTS

No significant differences in magnitude or direction of hip contact forces were observed between FAIS and CAM or between FAIS and control groups during any phase of the sprint cycle. The highest anteriorly directed hip contact forces were observed during the initial swing phase of the sprint cycle.

CONCLUSIONS

Hip contact forces during sprinting do not differentiate recreationally active individuals with FAIS from asymptomatic individuals with and without cam morphology. Hip loading during early swing, where peak anterior loading occurs, may be a potential mechanism for cartilage damage during sprinting-related sports in individuals with FAIS and/or asymptomatic cam morphology.

Pre-operative gait kinematics and kinetics do not change following surgery in adolescent patients with femoroacetabular impingement

BACKGROUND

Femoroacetabular impingement (FAI) is a condition where the femoral head-neck junction collides with the acetabulum. Open or arthroscopic treatment of FAI aims to increase hip motion while reducing impingement during passive or dynamic movements.

RESEARCH QUESTION

What are the biomechanical characteristics of the hip and pelvis in adolescents and young adults diagnosed with FAI syndrome 1) pre-operatively compared to controls and 2) pre- to post-operatively?

METHODS

43 patients with FAI and 43 controls were included in the study. All patients with FAI had cam deformities and underwent unilateral hip preservation surgery (either open or arthroscopic). Pre- and post-operative imaging, patient-reported outcomes, and gait analysis were performed. Joint angles and internal joint moments were evaluated with an emphasis on the pelvis and hip. A comparative analysis was conducted to evaluate the gait patterns before and after surgical treatment, as well as to compare pre-operative gait patterns to a control group.

RESULTS

43 patients with FAI (28 female, 16.5 ± 1.5 yrs) and 43 controls (28 female, 16.0 ± 1.5 yrs) were included. Pre-operative patients with FAI had decreased stride length and walking speed compared to controls, with no significant change following surgery. There were no differences in sagittal and coronal plane hip and pelvis kinematics comparing pre- to post-operative and pre-operative to controls. Pre-operatively, differences in internal hip rotation angle (pre: 3.3˚, post: 3.9˚, controls: 7.7˚) and hip extensor moment (pre: 0.121, post: 0.090, controls: 0.334 Nm/kg) were observed compared to controls with no significant changes observed following surgery.

SIGNIFICANCE

Compensatory movement strategies in pelvic and hip motion are evident during gait in patients with FAI, particularly in the sagittal and transverse planes. These strategies remained consistent two years post-surgery. While surgery improved radiographic measures and patient-reported outcomes, gait did not elicit biomechanical changes following surgical treatment.

Dynamic joint stiffness in individuals with femoroacetabular impingement syndrome pre- and post-hip arthroscopy

BACKGROUND

Patients with hip-related pain often fail to return to their desired level of activity following hip arthroscopy. Lasting biomechanics alterations may be one potential explanation. Dynamic joint stiffness assesses the mechanistic controls of the lower limb during high impact movements, and thus, may provide valuable clinical targets to improving movement and optimizing return to activity after surgery.

METHODS

Twenty-five participants (13 females) with hip-related pain underwent 3D motion capture during a drop jump task before surgery and six months post-operatively. Nineteen healthy controls (9 females) were collected for comparison. Sagittal plane dynamic joint stiffness was calculated during the initial landing phase. Baseline and 6-month dynamic joint stiffness data were compared 1) between males and females with hip-related pain and 2) between individuals with hip-related pain and controls using Wilcoxon Signed-Rank and Mann Whitney U tests. Sexes were analyzed separately.

FINDINGS

From baseline to 6 months post-operatively, females with hip-related pain demonstrated decreased dynamic ankle stiffness (2.26 Nm/deg. [0.61] to 1.84 Nm/deg. [0.43]) (p = .005) and males with hip-related pain demonstrated increased dynamic hip stiffness (2.73 [0.90] to 3.88 [1.73]) (p = .013). There were no differences in dynamic stiffness at any joint between individuals with hip-related pain at either timepoint when compared to controls (p ≥ .099).

INTERPRETATION

Females and males with hip-related pain may demonstrate unique changes in dynamic joint stiffness after surgery, indicating return to activity may follow different trajectories for each sex. Additional work should examine the relationship between hip joint stiffness and treatment outcomes and identify additional movement-related rehabilitation targets.

A Smartphone App Shows Patients Return to Preoperative Gait Metrics 6 Weeks After Hip Arthroscopy, and Gait Metrics Have Low to Moderate Correlations With a Hip-Specific Patient-Reported Outcome Measure

Purpose

The purpose of this study was to use a smartphone app to collect gait metrics in patients undergoing hip arthroscopy for femoroacetabular impingement syndrome (FAIS) and determine when gait metrics return to preoperative levels and if gait metrics correlate with postoperative hip-specific patient-reported outcomes.

Methods

Patients undergoing primary hip arthroscopy for FAIS from August 2021 to December 2022 were prospectively enrolled. Patients downloaded the iPhone app, rHip, at ∼6 months postoperatively, enabling retroactive access to Apple Health data. Gait metrics included step count, step length, and walking speed. Each patient's preoperative baseline was compared to that individual's successive postoperative week metrics. All patients underwent a standard 4-stage rehabilitation protocol. We compared metrics from beginning to end of each phase (i.e., week 1 to 6 for phase 1) and evaluated correlations with patient outcomes.

Results

Fifty patients (40 women; age: 31.9 ± 14.5 years) were included. Patients had significantly reduced step count from postoperative weeks 1 to 5 and improved upon baseline at weeks 13 and 16 to 26. Patients had significantly reduced step length from postoperative weeks 1 to 4 and improved upon baseline at weeks 16 and 20. Patients had significantly lower walking speed from postoperative weeks 1 to 6 and improved upon baseline at week 20 (P < .05). Step count significantly improved over phase 1 rehabilitation (P < .05). Step length and walking speed significantly improved over each of phases 1 to 3 (P < .05 for all). Preoperatively, weak correlations were noted between step length and Patient-Reported Outcomes Measurement Information System (PROMIS) for Physical Function (PF)/Pain, as well as walking speed and Hip Outcome Score-Activities of Daily Living (HOS-ADL)/PROMIS-Pain. At 3 months, moderate correlations were noted between step count and HOS-ADL/12-item international Hip Outcome Tool (iHOT-12), step length and HOS-ADL/PROMIS-PF, and walking speed and HOS-ADL/iHOT-12/PROMIS-PF/PROMIS-Pain. At 6 months, weak to moderate correlations were noted between all 3 gait metrics and HOS-ADL.

Conclusions

A smartphone app was capable of capturing health data gait metrics. Patients undergoing hip arthroscopy for FAIS returned to baseline levels in step count, step length, and walking speed after phase 1 (6 weeks) of rehabilitation. The most consistent correlations between gait metrics and step count were seen at 3 months, although only weak to moderate. Gait metrics similarly had weak to moderate correlations with HOS-ADL at 6 months.

Level of Evidence

Level IV, case series.

Females with hip-related pain demonstrate reduced kinetics at the hip and ankle during terminal stance of gait

BACKGROUND

Individuals with hip-related pain (HRP) commonly report pain with walking and demonstrate altered movement patterns compared to healthy controls (HCs). Individuals with HRP may attempt to reduce pain during walking by decreasing kinetics and joint forces at the hip through increased use of the ankle during pushoff.

RESEARCH QUESTION

Do individuals with HRP have increased kinetics at the ankle and decreased kinetics at the hip during pushoff in gait compared to HCs, and do kinetic patterns differ between males and females with HRP?

METHODS

This retrospective observational study included 42 individuals with HRP and 20 HCs. Participants completed overground gait trials at their self-selected speed while kinematics and kinetics were recorded through a motion capture system and force plates. Peak internal hip and ankle moments and hip flexion and ankle plantarflexion angular impulse during terminal stance were used in general estimating equations for comparison of group by limb interactions for males and females separately, as well as a comparison of males and females within the HRP group.

RESULTS

Females with HRP demonstrated reduced hip flexion impulse on their involved limb (.070 Nm*s/kg*m) compared to female HCs (.083Nm*s/kg*m; p = .032), as well as reduced peak ankle plantarflexion moment (-.94Nm/kg*m) compared to their contralateral limb (-.99Nm/kg*m) and the involved limb of HRP males (-1.00Nm/kg*m) (p ≤ .007). There were no between-limb or between-group differences in hip or ankle peak moments or impulses in males.

SIGNIFICANCE

Females with HRP show decreased kinetics at both the hip and ankle; these patterns were not identified in males. Future investigations should examine whether increasing ankle kinetics during pushoff reduces pain at the hip, as this may be a valuable clinical treatment strategy.

Do patients with femoroacetabular impingement syndrome who undergo hip arthroscopy display improved alpha angle (magnetic resonance imaging) and radiographic hip morphology?

AIMS

To compare (a) the change in radiological bony morphology between participants with femoroacetabular impingement (FAI) syndrome who underwent arthroscopic hip surgery compared to physiotherapist-led non-surgical care and (b) the change in radiological bony morphology between participants with FAI syndrome who underwent arthroscopic hip surgery involving cam resection or acetabular rim trimming or combined cam resection and acetabular rim trimming.

METHODS

Maximum alpha angle measurements on magnetic resonance imaging and Hip2 Norm standardized hip measurements on radiographs were recorded at baseline and at 12 months postoperatively. One-way analysis of covariance and independent T tests were conducted between participants who underwent arthroscopic hip surgery and physiotherapist-led non-surgical care. Independent T tests and analysis of variance were conducted between participants who underwent the 3 different arthroscopic hip procedures.

RESULTS

Arthroscopic hip surgery resulted in significant improvements to mean alpha angle measurements (decreased from 70.8° to 62.1°) (P value < .001, 95% CI -11.776, -4.772), lateral center edge angle (LCEA) (P value = .030, 95% CI -3.403, -0.180) and extrusion index (P value = 0.002, 95% CI 0.882, 3.968) compared to physiotherapist-led management. Mean maximum 1-year postoperative alpha angle was 59.0° (P value = .003, 95% CI 4.845, 18.768) for participants who underwent isolated cam resection. Measurements comparing the 3 different arthroscopic hip procedures only differed in total femoral head coverage (F[2,37] = 3.470, P = .042).

CONCLUSION

Arthroscopic hip surgery resulted in statistically significant improvements to LCEA, extrusion index and alpha angle as compared to physiotherapist-led management. Measured outcomes between participants who underwent cam resection and/or acetabular rim trimming only differed in total femoral head coverage.

Noninvasive shape-fitting method quantifies cam morphology in femoroacetabular impingement syndrome: Implications for diagnosis and surgical planning

There are considerable limitations associated with the standard 2D imaging currently used for the diagnosis and surgical planning of cam-type femoroacetabular impingement syndrome (FAIS). The aim of this study was to determine the accuracy of a new patient-specific shape-fitting method that quantifies cam morphology in 3D based solely on preoperative MRI imaging. Preoperative and postoperative 1.5T MRI scans were performed on n = 15 patients to generate 3D models of the proximal femur, in turn used to create the actual and the virtual cam. The actual cams were reconstructed by subtracting the postoperative from the preoperative 3D model and used as reference, while the virtual cams were generated by subtracting the preoperative 3D model from the virtual shape template produced with the shape-fitting method based solely on preoperative MRI scans. The accuracy of the shape-fitting method was tested on all patients by evaluating the agreement between the metrics of height, surface area, and volume that quantified virtual and actual cams. Accuracy of the shape-fitting method was demonstrated obtaining a 97.8% average level of agreement between these metrics. In conclusion, the shape-fitting technique is a noninvasive and patient-specific tool for the quantification and localization of cam morphology. Future studies will include the implementation of the technique within a clinically based software for diagnosis and surgical planning for cam-type FAIS.

Comparison of Walking Biomechanics After Physical Therapist-Led Care or Hip Arthroscopy for Femoroacetabular Impingement Syndrome: A Secondary Analysis From a Randomized Controlled Trial

BACKGROUND

Femoroacetabular impingement syndrome is characterized by chondrolabral damage and hip pain. The specific biomechanics used by people with femoroacetabular impingement syndrome during daily activities may exacerbate their symptoms. Femoroacetabular impingement syndrome can be treated nonoperatively or surgically; however, differential treatment effects on walking biomechanics have not been examined.

PURPOSE

To compare the 12-month effects of physical therapist-led care or arthroscopy on trunk, pelvis, and hip kinematics as well as hip moments during walking.

STUDY DESIGN

Secondary analysis of multi-centre, pragmatic, two-arm superiority randomized controlled trial subsample; Level of evidence, 1.

METHODS

A subsample of 43 participants from the Australian Full randomised controlled trial of Arthroscopic Surgery for Hip Impingement versus best cONventional (FASHIoN trial) underwent gait analysis and completed the International Hip Outcome Tool (iHOT-33) at both baseline and 12 months after random allocation to physical therapist-led care (personalized hip therapy; n = 22; mean age 35; 41% female) or arthroscopy (n = 21; mean age 36; 48% female). Changes in trunk, pelvis, and hip biomechanics were compared between treatment groups across the gait cycle using statistical parametric mapping. Associations between changes in iHOT-33 and changes in hip kinematics across 3 planes of motion were examined.

RESULTS

As compared with the arthroscopy group, the personalized hip therapy group increased its peak hip adduction moments (mean difference = 0.35 N·m/body weight·height [%] [95% CI, 0.05-0.65]; effect size = 0.72; P = .02). Hip adduction moments in the arthroscopy group were unchanged in response to treatment. No other between-group differences were detected. Improvements in iHOT-33 were not associated with changes in hip kinematics.

CONCLUSION

Peak hip adduction moments were increased in the personalized hip therapy group and unchanged in the arthroscopy group. No biomechanical changes favoring arthroscopy were detected, suggesting that personalized hip therapy elicits greater changes in hip moments during walking at 12-month follow-up. Twelve-month changes in hip-related quality of life were not associated with changes in hip kinematics.

Hip kinematics and kinetics in patients with femoroacetabular impingement syndrome before and 1 year after hip arthroscopic surgery. Results from the HAFAI cohort

INTRODUCTION

Patients with femoroacetabular impingement syndrome (FAIS) experience decreased function. Consequently, earlier studies have evaluated gait biomechanics in these patients, but a larger study evaluating gait biomechanics before and after an intervention standardising gait speed is lacking. We aimed at investigating gait kinematics and kinetics in patients with FAIS compared with pain-free controls before and 1 year after hip arthroscopic surgery. Secondary, we aimed at analysing gait pattern separately for the sexes and to investigate associations between peak kinematics and kinetics and the Copenhagen Hip and Groin Outcome Score (HAGOS).

MATERIALS AND METHODS

Sixty patients with FAIS and 30 pain-free controls were tested at a standardised gait speed (1.40 m/s ± 10%). Patients were tested twice: before and 1 year after surgery. Kinematics and kinetics were recorded using infrared high-speed cameras and a force plate. Participants answered HAGOS.

RESULTS

The largest difference among groups was that gait differed between males and females. Neither before nor after surgery could we demonstrate large alterations in gait pattern between patients and pain-free controls. Male patients demonstrated associations between peak kinematics and kinetics and HAGOS Sports function.

CONCLUSIONS

Gait pattern was only vaguely altered in patients with FAIS compared with pain-free controls before and after surgery when using at standardised gait speed. Hence, analysing gait in patients with FAIS does not seem of major importance. Nevertheless, there was an association between HAGOS Sports function and peak kinematics and kinetics in male patients, implying that there could be a clinical importance.

Neuromuscular Consequences of Lumbopelvic Dysfunction: Research and Clinical Perspectives

Injuries involving the lumbopelvic region (ie, lumbar spine, pelvis, hip) are common across the lifespan and include pathologies such as low back pain, femoroacetabular impingement syndrome, labrum tear, and osteoarthritis. Joint injury is known to result in an arthrogenic muscle response which contributes to muscle weakness and altered movement patterns. The purpose of this manuscript is to summarize the arthrogenic muscle response that occurs across lumbopelvic region pathologies, identify methods to quantify muscle function, and propose suggestions for future research. While each lumbopelvic region pathology is unique, there are a few common impairments and a relative consistent arthrogenic muscle response that occurs across the region. Hip muscle weakness and hip joint range of motion limitations occur with both lumbar spine and hip pathologies, and individuals with low back pain are known to demonstrate inhibition of the transversus abdominis and multifidus. Assessment of muscle inhibition is often limited to research laboratory settings, but dynamometers, ultrasound imaging, and electromyography offer clinical capacity to quantify muscle function and inform treatment pathways. Future studies should systematically determine the arthrogenic muscle response across multiple muscle groups and the timeline for changes in muscle function and determine whether disinhibitory modalities improve functional outcomes beyond traditional treatment approaches.

Biomechanical measures of clinician-defined unsteadiness during a forward stepdown task in individuals post-arthroscopy for femoroacetabular impingement syndrome

BACKGROUND

Patients with femoroacetabular impingement syndrome can present with aberrant movement patterns including unsteady balance. Balance training is included in rehabilitation after hip arthroscopy and may improve quality of movement; however, specific biomechanical measures associated with clinician-defined balance impairments are unknown. We aimed to understand these associations as they may inform targeted rehabilitative interventions.

METHODS

The forward stepdown is a clinical test used to evaluate movement quality, including balance. 23 individuals at least one-year post-arthroscopy for femoroacetabular impingement syndrome and 15 healthy comparisons performed the forward stepdown, recorded by 3-dimensional motion capture and 2-dimensional video. Three physical therapists graded the 2-dimensional video for steadiness. Two-way analyses of variance were used to evaluate the interaction of group (post-arthroscopy/healthy comparison) by steadiness (steady/unsteady), for center of pressure medial-lateral excursion, center of pressure path length, and lateral trunk, pelvis, and lower extremity joint excursions.

FINDINGS

Six (26.1%) participants post-arthroscopy and five (33.3%) healthy comparisons were categorized as unsteady. The odds of being categorized as unsteady were not greater for participants post-arthroscopy (P = 0.72). There were no significant interactions; however, participants with clinician-defined unsteady balance, regardless of group, had significantly greater frontal plane trunk excursion, greater hip excursion, and greater center of pressure path length than those with steady balance (P ≤ 0.006).

INTERPRETATION

The odds of being categorized as unsteady were not greater for individuals post-arthroscopy for femoroacetabular impingement syndrome. Clinician-defined unsteadiness was associated with greater frontal plane trunk and hip motion which may be rehabilitation targets to improve balance during a dynamic single-leg task.

Biomechanics of Cam Femoroacetabular Impingement: A Systematic Review

PURPOSE

To assess how biomechanical gait parameters (kinematics, kinetics, and muscle force estimations) differ between patients with cam-type femoroacetabular impingement (FAI) and healthy controls, through a systematic search.

METHODS

A systematic review of the literature from PubMed, Scopus, and Medline and EMBASE via OVID SP was undertaken from inception to April 2020 using PRISMA guidelines. Studies that described kinematics, kinetics, and/or estimated muscle forces in cam-type FAI were identified and reviewed.

RESULTS

The search strategy identified 404 articles for evaluation. Removal of duplicates and screening of titles and abstracts resulted in full-text review of 37 articles, with 12 meeting inclusion criteria. The 12 studies reported biomechanical data on a total of 173 cam-FAI (151 cam-specific, 22 mixed-type) patients and 177 healthy age-, sex-, and body mass index-matched controls. Patients with cam FAI had reduced hip sagittal plane range of motion (mean difference -3.00° [-4.10, -1.90], P < .001), reduced hip peak extension angles (mean difference -2.05° [-3.58, -0.53] , P = .008), reduced abduction angles in the terminal phase of stance, and reduced iliacus and psoas muscle force production in the terminal phase of stance compared to the control groups. Cam FAI cohorts walked at a slower speed compared with controls.

CONCLUSIONS

In conclusion, patients with cam-type FAI exhibit altered sagittal and frontal plane kinematics as well as altered muscle force production during level gait compared to controls. These findings will help guide future research into gait alterations in FAI and how such alterations may contribute to pathologic progression and furthermore, how such alterations can be modified for therapeutic benefit.

LEVEL OF EVIDENCE

Systematic review of Level III studies.

Muscle and Hip Contact Forces in Asymptomatic Men With Cam Morphology During Deep Squat

Cam morphology is defined as an aspherical femoral head-neck junction that causes abnormal contact of the acetabular rim with the anterior hip. Imaging confirmation of the cam morphology, associated with clinical signs and pain in the hip or groin, is characterized as femoroacetabular impingement (FAI) syndrome. Although some individuals with cam morphology do not experience any symptoms, sparse studies have been done on these individuals. Understanding the way asymptomatic individuals generate muscle forces may help us to better explain the progression of the degenerative FAI process and discover better ways in preventing the onset or worsening of symptoms. The purpose of this study was to compare the muscle and hip contact forces of asymptomatic cam morphology (ACM) and FAI syndrome men compared to cam-free healthy controls during a deep squat task. This prospective study compared 39 participants, with 13 in each group (ACM, FAI, and control). Five deep squatting trials were performed at a self-selected pace while joint trajectories and ground reaction forces were recorded. A generic model was scaled for each participant, and inverse kinematics and inverse dynamics calculated joint angles and moments, respectively. Muscle and hip contact forces were estimated using static optimization. All variables were time normalized in percentage by the total squat cycle and both muscle forces and hip contact forces were normalized by body weight. Statistical non-parametric mapping analyses were used to compare the groups. The ACM group showed increased pelvic tilt and hip flexion angles compared to the FAI group during the descent and ascent phases of the squat cycle. Muscle forces were greater in the ACM and control groups, compared to the FAI group for the psoas and semimembranosus muscles. Biceps femoris muscle force was lower in the ACM group compared to the FAI group. The FAI group had lower posterior hip contact force compared to both the control and ACM groups. Muscle contraction strategy was different in the FAI group compared to the ACM and control groups, which caused different muscle force applications during hip extension. These results rebut the concept that mobility restrictions are solely caused by the presence of the cam morphology and propose evidence that symptoms and muscle contraction strategy can be the origin of the mobility restriction in male patients with FAI.

Parameters affecting baseline hip function in patients with cam-derived femoroacetabular impingement syndrome: data analysis from the German Cartilage Registry

BACKGROUND

Using the database of the German Cartilage Registry (KnorpelRegister DGOU), this study aims to present patient- and joint-related baseline data in a large cohort of patients with cam-derived femoroacetabular impingement syndrome (FAI) and to detect symptom-determining factors.

MATERIALS AND METHODS

Requiring cam morphology as the primary pathology, 362 patients were found to be eligible for inclusion in the study. The assessment of preoperative baseline data was performed using the patient-reported outcome measure-International Hip Outcome Tool (iHOT-33). Descriptive statistics were performed to present baseline data. Univariate and multiple regression with post hoc testing were used to identify patient- and joint-related factors that might affect the preoperative iHOT-33 and its subscores, respectively.

RESULTS

The study collective's mean age was 36.71 ± 10.89 years, with 246 (68%) of them being male. The preoperative mean iHOT-33 total was 46.31 ± 20.33 with the subsection "sports and recreational activities" presenting the strongest decline (26.49 ± 20.68). The parameters "age," "sex," "body mass index" (BMI), and the confirmation of "previous surgery on the affected hip" were identified to statistically affect the preoperative iHOT-33. In fact, a significantly lower mean baseline score was found in patients aged > 40 years (p < 0.001), female sex (p < 0.001), BMI ≥ 25 kg/m² (p = 0.002) and in patients with previous surgery on the affected hip (p = 0.022). In contrast, the parameters defect grade and size, labral tears, and symptom duration delivered no significant results.

CONCLUSIONS

A distinct reduction in the baseline iHOT-33, with mean total scores being more than halved, was revealed. The parameters "age > 40 years," "female sex," "BMI ≥ 25," and confirmation of "previous surgery on the affected hip" were detected as significantly associated with decreased preoperative iHOT-33 scores. These results help to identify symptom-defining baseline characteristics of cam-derived FAI syndrome.

TRIAL REGISTRATION

The German Cartilage Registry is conducted in accordance with the Declaration of Helsinki and registered at germanctr.de (DRKS00005617). Registered 3 January 2014-retrospectively registered. The registration of data was approved by the local ethics committees of every participating institution. Primary approval was given by the ethics committee at the University of Freiburg (No. 105/13). https://www.drks.de/drks_web/navigate.do?navigationId=trial.HTML&TRIAL_ID=DRKS00005617.

Reliability of hip muscle strength measured in principal and intermediate planes of movement

BACKGROUND

Muscle strength testing is widely used in clinical and athletic populations. Commercially available dynamometers are designed to assess strength in three principal planes (sagittal, transverse, frontal). However, the anatomy of the hip suggests muscles may only be recruited submaximally during tasks performed in these principal planes.

OBJECTIVE

To evaluate the inter-session reliability of maximal isometric hip strength in the principal planes and three intermediate planes.

METHODS

Twenty participants (26.1 ± 2.7 years, 50% female) attended two testing sessions 6.2 ± 1.8 days apart. Participants completed 3-5 maximal voluntary isometric contractions for hip abduction, adduction, flexion, extension, and internal and external rotation measured using a fixed uniaxial load cell (custom rig) and commercial dynamometer (Biodex). Three intermediate hip actions were also tested using the custom rig: extension with abduction, extension with external rotation, and extension with both abduction and external rotation.

RESULTS

Moderate-to-excellent intraclass correlation coefficients were observed for all principal and intermediate muscle actions using the custom rig (0.72-0.95) and the Biodex (0.85-0.95). The minimum detectable change was also similar between devices (custom rig = 11-31%; Biodex = 9-20%). Bland-Altman analysis revealed poor agreement between devices (range between upper and lower limits of agreement = 77-131%).

CONCLUSIONS

Although the custom rig and Biodex showed similar reliability, both devices may lack the sensitivity to detect small changes in hip strength commonly observed following intervention.

Pre- and postoperative in silico biomechanics in individuals with cam morphology during stair tasks

BACKGROUND

Osteochondroplasty for cam femoroacetabular impingement is a common treatment to improve hip function and prevent joint degeneration. The purpose was to compare in-silico hip biomechanics during stair tasks in pre- and postoperative patients matched with healthy controls.

METHODS

Ten symptomatic cam femoroacetabular impingement patients performed stair ascent and descent pre- and 2 years postoperatively. Patients were age, and body-mass-index matched to controls. Full-body kinematics and kinetics were computed and, muscle and hip contact forces were estimated using musculoskeletal modeling and static optimization. Stance-phases were time-normalized and compared using statistical non-parametric mapping.

FINDINGS

Preoperatives showed lower hip abduction than controls during stairs ascent (76-100%, P = .007). Pre- and postoperative showed lower hip external rotation compared to controls on stair ascent (Pre-op vs controls: 71-100%, P = .005; Post-op vs controls: 72-100%, P = .01) and stair descent (Pre-op vs controls: 0-62%, P = .001; Post-op vs controls: 0-60%, P = .001). Postoperatives showed lower iliacus force compared to preoperative (1-3%, P = .012) and control (3-6%, P = .008), and higher gluteus maximus and piriformis forces compared to controls during stair descent. Lower postoperative anterior hip contact force (0-7%, P = .004) during descent, and superior (33-35%, P = .018) during ascent compared to controls were observed. Postoperative contact forces were medialized compared to preoperative (0-2%, P = .011) and controls (1-2%, P = .016).

INTERPRETATION

Forcing participants to adhere to standardized step length/rise minimized sagittal kinematic differences between conditions and groups. Persistent reduced hip external rotation postoperatively and minor muscle force adaptations led to reduced superior hip contact force during stair ascent and reduced anterior and more medialized contact forces during stair descent.

Evaluation of outcome reporting trends for femoroacetabular impingement syndrome- a systematic review

PURPOSE

The aim of this systematic review was to evaluate the trends in the literature regarding surgical treatment for femoroacetabular impingement syndrome (FAIS) and to present which patient-reported outcome-measures (PROMs) and surgical approaches are included.

METHODS

This systematic review was conducted with the PRISMA guidelines. The literature search was performed on PubMed and Embase, covering studies from 1999 to 2020. Inclusion criteria were clinical studies with surgical treatment for FAIS, the use of PROMs as evaluation tool and studies in English. Exclusion criteria were studies with patients < 18 years, cohorts with < 8 patients, studies with primarily purpose to evaluate other diagnoses than FAIS and studies with radiographs as only outcomes without using PROMs. Data extracted were author, year, surgical intervention, type of study, level of evidence, demographics of included patients, and PROMs.

RESULTS

The initial search yielded 2,559 studies, of which 196 were included. There was an increase of 2,043% in the number of studies from the first to the last five years (2004-2008)-(2016-2020). There were 135 (69%) retrospective, 55 (28%) prospective and 6 (3%) Randomized Controlled Trials. Level of evidence ranged from I-IV where Level III was most common (44%). More than half of the studies (58%) originated from USA. Arthroscopic surgery was the most common surgical treatment (85%). Mean follow-up was 27.0 months (± 17 SD), (range 1.5-120 months). Between 1-10 PROMs were included, and the modified Harris Hip Score (mHHS) was most commonly used (61%).

CONCLUSION

There has been a continuous increase in the number of published studies regarding FAIS with the majority evaluating arthroscopic surgery. The mHHS remains being the most commonly used PROM.

Review of musculoskeletal modelling in a clinical setting: Current use in rehabilitation design, surgical decision making and healthcare interventions

BACKGROUND

Musculoskeletal modelling is a common means by which to non-invasively analyse movement. Such models have largely been used to observe function in both healthy and patient populations. However, utility in a clinical environment is largely unknown. The aim of this review was to explore existing uses of musculoskeletal models as a clinical intervention, or decision-making, tool.

METHODS

A literature search was performed using PubMed and Scopus to find articles published since 2010 and relating to musculoskeletal modelling and joint and muscle forces.

FINDINGS

4662 abstracts were found, of which 39 relevant articles were reviewed. Journal articles were categorised into 5 distinct groups: non-surgical treatment, orthoses assessment, surgical decision making, surgical intervention assessment and rehabilitation regime assessment. All reviewed articles were authored by collaborations between clinicians and engineers/modellers. Current uses included insight into the development of osteoarthritis, identifying candidates for hamstring lengthening surgery, and the assessment of exercise programmes to reduce joint damage.

INTERPRETATION

There is little evidence showing the use of musculoskeletal modelling as a tool for patient care, despite the ability to assess long-term joint loading and muscle overuse during functional activities, as well as clinical decision making to avoid unfavourable treatment outcomes. Continued collaboration between model developers should aim to create clinically-friendly models which can be used with minimal input and experience by healthcare professionals to determine surgical necessity and suitability for rehabilitation regimes, and in the assessment of orthotic devices.

BOPS: a Matlab toolbox to batch musculoskeletal data processing for OpenSim

This paper presents Batch OpenSim Processing Scripts (BOPS), a Matlab toolbox for batch processing common OpenSim procedures: Inverse Kinematics, Inverse Dynamics, Muscle Analysis, Static Optimization, and Joint Reaction Analysis. BOPS is an easy-to-use and highly configurable tool that aims to reduce the time required to process large datasets, thus fostering the adoption of musculoskeletal modeling and simulations in daily practice. Its graphical user interface includes pre-defined setup files and has been designed to fulfill the needs of different research projects by simplifying the customization of the procedures, facilitating the analysis, and boosting research group collaborations. BOPS is released under Apache License 2.0, and its source code is freely available on SimTK and GitHub.

Trunk, pelvis and lower limb walking biomechanics are similarly altered in those with femoroacetabular impingement syndrome regardless of cam morphology size

BACKGROUND

Studies of walking in those with femoroacetabular impingement syndrome have found altered pelvis and hip biomechanics. But a whole body, time-contiuous, assessment of biomechanical parameters has not been reported. Additionally, larger cam morphology has been associated with more pain, faster progression to end-stage osteoarthritis and increased cartilage damage but differences in walking biomechanics between large compared to small cam morphologies have not been assessed.

RESEARCH QUESTION

Are trunk, pelvis and lower limb biomechanics different between healthy pain-free controls and individuals with FAI syndrome and are those biomechanics different between those with larger, compared to smaller, cam morphologies?

METHODS

Twenty four pain-free controls were compared against 41 participants with FAI syndrome who were stratified into two groups according to their maximum alpha angle. Participants underwent three-dimensional motion capture during walking. Trunk, pelvis, and lower limb biomechanics were compared between groups using statistical parametric mapping corrected for walking speed and pain.

RESULTS

Compared to pain-free controls, participants with FAI syndrome walked with more trunk anterior tilt (mean difference 7.6°, p < 0.001) as well as less pelvic rise (3°, p < 0.001), hip abduction (-4.6°, p < 0.05) and external rotation (-6.5°, p < 0.05). They also had lower hip flexion (-0.06Nm⋅kg^-1, p < 0.05), abduction (-0.07Nm⋅kg^-1, p < 0.05) and ankle plantarflexion moments (-0.19Nm⋅kg^-1, p < 0.001). These biomechanical differences occurred throughout the gait cycle. There were no differences in walking biomechanics according to cam morphology size.

SIGNIFICANCE

Results do not support the hypothesis that larger cam morphology is associated with larger differences in walking biomechanics but did demonstrate general differences in trunk, pelvis and lower limb biomechanics between those with FAI sydrome and pain-free controls. Altered external biomechanics are likely the result of complex sensory-motor strategy resulting from pain inhibition or impingement avoidance. Future studies should examine internal loading in those with FAI sydnrome.

Hip Muscle Forces and Contact Loading During Squatting After Cam-Type FAI Surgery

BACKGROUND

The purpose of this study was to compare muscle forces and hip contact forces (HCFs) during squatting in patients with cam-type femoroacetabular impingement (cam-FAI) before and after hip corrective surgery and with healthy control participants.

METHODS

Ten symptomatic male patients with cam-FAI performed deep squatting preoperatively and at 2 years postoperatively. Patients were matched by age and body mass index to 10 male control participants. Full-body kinematics and kinetics were computed, and muscle forces and HCFs were estimated using a musculoskeletal model and static optimization. Normalized squat cycle (%SC) trials were compared using statistical nonparametric mapping (SnPM).

RESULTS

Postoperatively, patients with cam-FAI squatted down with higher anterior pelvic tilt, higher hip flexion, and greater hip extension moments than preoperatively. Preoperative patients demonstrated lower anterior pelvic tilt and lower hip flexion compared with the participants in the control group. Postoperative patients showed increased semimembranosus force compared with their preoperative values. Preoperative forces were lower than the control group for the adductor magnus, the psoas major, and the semimembranosus; however, the preoperative patients showed greater inferior gluteus maximus forces than the patients in the control group, whereas the postoperative patients did not differ from the control patients. Higher posterior, superior, and resultant HCF magnitudes were identified postoperatively in comparison with the preoperative values. Preoperative posterior HCF was lower than in the control group, whereas the postoperative posterior HCF did not differ from those in the control group.

CONCLUSIONS

Higher postoperative anterior pelvic tilt was associated with an indication of return to closer to normal pelvic motion, which resembled data from the control group. Lower preoperative anterior pelvic tilt was associated with muscle force imbalance, indicated by decreased semimembranosus and increased gluteus maximus forces. The overall increased postoperative muscle forces were associated with improved pelvic mobility and increased HCFs that were comparable with the control-group standards.

CLINICAL RELEVANCE

Muscle forces and HCFs may be indicative of postoperative joint health restoration and alleviated symptoms.

Sex-specific sagittal and frontal plane gait mechanics in persons post-hip arthroscopy for femoroacetabular impingement syndrome

Postoperative gait mechanics in persons with femoroacetabular impingement syndrome (FAIS) remain understudied as a treatment outcome despite observed, yet inconclusive, preoperative gait abnormalities. Females with FAIS demonstrate worse preoperative patient-reported hip function and altered hip mechanics when compared with males; it is unknown whether these sex differences persist postarthroscopy. The purpose of this study was to compare sex-specific gait kinematics between persons at least 1 year postarthroscopy for FAIS and healthy comparisons. General linear models with estimating equations were used to evaluate the effect of (a) limb and sex within each group, and (b) limb and group within each sex for peak sagittal and frontal plane trunk, pelvis, and hip kinematics during stance phase of gait. Analyses were covaried by gait speed. Seventeen females and eight males an average 2.5 years postarthroscopy (1.1-7.2 year) for FAIS were compared with healthy females (n = 7) and males (n = 5). Females in the FAIS group presented with an average of 4.6° more anterior pelvic tilt, and 4.8° less hip extension compared with healthy females (P ≤ .03) and 8.6° less trunk flexion, 4.8° more anterior pelvic tilt, 3.1° more pelvic drop, and 7.5° more hip flexion than males with FAIS (P ≤ .03). Males in the FAIS group presented with 2.9° less pelvic drop, and 3.2° less hip adduction than healthy males. Preoperative gait mechanics were not collected and thus changes in mechanics could not be evaluated. This study is significant to clinicians who treat patients postarthroscopy to consider sex-specific gait impairments.

Short term outcomes of hip arthroscopy on hip joint mechanics and cartilage health in patients with femoroacetabular impingement syndrome

BACKGROUND

Femoroacetabular acetabular impingement syndrome consists of abnormal hip joint morphology resulting in painful hip joint impingement. Hip arthroscopy corrects the abnormal morphology and reduces clinical symptoms associated with femoroacetabular impingement syndrome yet the effects of hip arthroscopy on gait mechanics and cartilage health are not well understood.

METHODS

Ten femoroacetabular impingement syndrome patients and 10 matched asymptomatic controls underwent gait analysis consisting of three-dimensional hip joint kinematics and kinetics. Femoroacetabular impingement syndrome patients underwent gait analysis and quantitative magnetic resonance imaging of the surgical hip joint before and seven months post-surgery. Patient reported outcomes were obtained from all study participants and were used to quantify hip joint pain, function and quality of life.

FINDINGS

Prior to surgery, femoroacetabular impingement syndrome patients demonstrated hip joint kinematics or kinetics as the control group. After surgery, femoroacetabular impingement syndrome patients exhibited improved patient reported outcomes, similar hip joint kinematic patterns, increased hip flexion and decreased hip extension moment impulses within the surgical limb. The femoroacetabular impingement syndrome patients that ambulated with increased HFMI post-surgery demonstrated a decrease in femoral cartilage T1ρ and T2 values.

INTERPRETATION

Femoroacetabular impingement syndrome patients exhibited improved clinical symptoms yet ambulated with altered sagittal plane hip joint loading after hip arthroscopy. Increased hip flexion moment impulse post-surgery was associated with improved cartilage health within the surgical limb. These study findings suggest that sagittal plane hip joint loading at short-term follow-up after hip arthroscopy is associated with cartilage health and may be an important biomechanical parameter in post-operative rehabilitation programs.