UNASSIGNED: Pediatric hip pain can have orthopedic, infectious, inflammatory, neoplastic, or nonmusculoskeletal etiologies. Organizing the differential diagnosis by symptom chronicity and a determination of intraarticular versus extraarticular pain, as well as the age at pain onset, can be helpful to hone in on the cause. Clinicians should consider plain radiographs in cases of acute trauma, with concern for bony pathology, or in patients with unexplained limp or hip pain, with musculoskeletal ultrasound and magnetic resonance imaging used as advanced imaging when indicated. Relative rest with subsequent strengthening and stretching should be prescribed in nonoperative conditions, though several pediatric hip pain diagnoses require orthopedic or other specialty referral for definitive treatment. This article is a comprehensive review of hip pain etiologies in the pediatric population.

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The primary objective of this study was to develop a custom algorithm to assess three-dimensional (3D) acetabular coverage of the femoral head based on surface models generated from computed tomography (CT) imaging. The secondary objective was to apply this algorithm to asymptomatic young adult hip joints to assess the regional 3D acetabular coverage variability and understand how these novel 3D metrics relate to traditional two-dimensional (2D) radiographic measurements of coverage. The algorithm developed automatically identifies the lateral- and medial-most edges of the acetabular lunate at one-degree intervals around the acetabular rim based on local radius of curvature. The acetabular edges and the center of a best-fit sphere to the femoral head are then used to compute the mean 3D subchondral arc angles and hip joint coverage angles in five acetabular octants. This algorithm was applied to hip models generated from pelvis/hip CT imaging or abdomen/pelvis CT angiograms of 50 patients between 17 and 25 years of age who had no history of congenital or developmental hip pathology, neuromuscular conditions, or bilateral pelvic and/or femoral fractures. Corresponding 2D acetabular coverage measures of lateral center edge angle (LCEA) and acetabular arc angle (AAA) were assessed on the patients\' clinical or digitally reconstructed radiographs. The 3D subchondral arc angle in the superior region (58.0 [54.6-64.8] degrees) was significantly higher (p < 0.001) than all other acetabular subregions. The 3D hip joint coverage angle in the superior region (26.2 [20.7-28.5] degrees) was also significantly higher (p < 0.001) than all other acetabular subregions. 3D superior hip joint coverage angle demonstrated the strongest correlation with 2D LCEA (r = 0.649, p < 0.001), while 3D superior-anterior subchondral arc angle demonstrated the strongest correlation with 2D AAA (r = 0.718, p < 0.001). The 3D coverage metrics in the remaining acetabular regions did not strongly correlate with typical 2D radiographic measures. The discrepancy between standard 2D measures of radiographic acetabular coverage and actual 3D coverage identified on advanced imaging indicates potential discord between anatomic coverage and the standard clinical measures of coverage on 2D imaging. As 2D measurement of acetabular coverage is increasingly used to guide surgical decision-making to address acetabular deformities, this work would suggest that 3D measures of acetabular coverage may be important to help discriminate local coverage deficiencies, avoid inconsistencies resulting from differences in radiographic measurement techniques, and provide a better understanding of acetabular coverage in the hip joint, potentially altering surgical planning and guiding surgical technique.

BACKGROUND: Spinopelvic stiffness (primarily in the sagittal plane) has been identified as a factor associated with inferior patient-reported outcomes (PROs) and increased dislocation risk after THA. Incorporating preoperative spinopelvic characteristics into surgical planning has been suggested to determine a patient-specific cup orientation that minimizes dislocation risk. Sagittal plane radiographic analysis of static postures indicates that patients exhibit a degree of normalization in their spinopelvic characteristics after THA. It is not yet known whether normalization is also evident during dynamic movement patterns, nor whether it occurs in the coronal and axial planes as well.
OBJECTIVE: (1) Does motion capture analysis of sagittal spinopelvic motion provide evidence of normalization after THA? (2) Do changes in coronal and axial plane motion accompany those in the sagittal plane?
METHODS: Between April 2019 and February 2020, 25 patients agreed to undergo motion capture movement analysis before THA for the treatment of hip osteoarthritis (OA). Of those, 20 underwent the same assessment between 8 and 31 months after THA. Five patients were excluded because of revision surgery (n = 1), contralateral hip OA (n = 1), and technical issues with a force plate during post-THA assessment (n = 3), leaving a cohort total of 15 (median age [IQR] 65 years [10]; seven male and eight female patients). A convenience sample of nine asymptomatic volunteers, who were free of hip and spinal pathology, was also assessed (median age 51 years [34]; four male and five female patients). Although the patients in the control group were younger than those in the patient group, this set a high bar for our threshold of spinopelvic normalization, reducing the possibility of false positive results. Three-dimensional motion capture was performed to measure spinal, pelvic, and hip motion while participants completed three tasks: seated bend and reach, seated trunk rotation, and gait on a level surface. ROM during each task was assessed and compared between pre- and post-THA conditions and between patients and controls. Statistical parametric mapping (SPM) was used to assess the timing of differences in motion during gait, and spatiotemporal gait parameters were also measured.
RESULTS: After THA, patients demonstrated improvements in sagittal spinal (median [IQR] 32° [18°] versus 41° [14°]; difference of medians 9°; p = 0.004), pelvis (25° [21°] versus 30° [8°]; difference of medians 5°; p = 0.02), and hip ROM (21° [18°] versus 27° [10°]; difference of medians 6°; p = 0.02) during seated bend and reach as well in sagittal hip ROM during gait (30° [11°] versus 44° [7°]; difference of medians 14°; p < 0.001) compared with their pre-THA results, and they showed a high degree of normalization overall. These sagittal plane changes were accompanied by post-THA increases in coronal hip ROM (12° [9°] versus 18° [8°]; difference of medians 6°; p = 0.01) during seated trunk rotation, by both coronal (6° [4°] versus 9° [3°]; difference of medians 3°; p = 0.01) and axial (10° [8°] versus 16° [7°]; difference of medians 6°; p = 0.003) spinal ROM, as well as coronal (8° [3°] versus 13° [4°]; difference of medians 5°; p < 0.001) and axial hip ROM (21° [11°] versus 34° [24°]; difference of medians 13°; p = 0.01) during gait compared with before THA. The SPM analysis showed these improvements occurred during the late swing and early stance phases of gait.
CONCLUSIONS: When restricted preoperatively, spinopelvic characteristics during daily tasks show normalization after THA, concurring with previous radiographic findings in the sagittal plane. Thus, spinopelvic characteristics change dynamically, and incorporating them into surgical planning would require predictive models on post-THA improvements to be of use.
METHODS: Level II, prognostic study.

BACKGROUND: The risk of developing avascular necrosis (AVN) in the setting of an unstable slipped capital femoral epiphysis (SCFE) that is undergoing treatment with the modified Dunn procedure is not well understood. In addition, since the Loder classification of unstable is reportedly different than actual intraoperatively observed instability (that is, discontinuity between the femoral head epiphysis and proximal femoral metaphysis), the overall risk of developing AVN, as well as the potential complications of treatment of these patients with the modified Dunn procedure, are unknown.
OBJECTIVE: To evaluate the modified Dunn procedure for the treatment of patients with epiphyseal-metaphyseal discontinuity, we asked: (1) What was the survivorship free from AVN at 10 years? (2) What was the survivorship free from subsequent surgery and/or complications at 10 years? (3) What were the clinical and patient-reported outcome scores?
METHODS: In a retrospective analysis, we identified 159 patients (159 hips) treated with a modified Dunn procedure for SCFE between 1998 and 2020, of whom 97% (155 of 159) had documentation about intraoperatively observed epiphyseal-metaphyseal stability. Of those, 37% (58 of 155) of patients were documented to have intraoperatively observed epiphyseal-metaphyseal discontinuity and were considered eligible for inclusion, whereas 63% (97 of 155) had documented epiphyseal-metaphyseal stability and were excluded. No patients were lost to follow-up before the 2-year minimum. All patients were assessed for survival, but 7% (4 of 58) did not fill out our outcomes score questionnaire. This resulted in 93% (54 of 58) of patients who were available for outcome score assessment. Additionally, 50% (29 of 58) of patients had not been seen within the last 5 years; they are included, but we note that there is uncertainty about their status. The median (range) age at surgery was 13 years (10 to 16), and the sex ratio was 60% (35 of 58) male and 40% (23 of 58) female patients. Sixty-four percent (37 of 58) of patients were classified as acute-on-chronic, and 17% (10 of 58) of patients were classified as acute. Forty-seven percent (27 of 58) of patients presented with severe slips and 43% (25 of 58) of patients with moderate slips based on radiographic classification. All patients underwent surgical hip dislocation with the modified Dunn procedure to correct the slip deformity and provide stabilization. Complications and reoperations were assessed from a review of electronic medical records, and a Kaplan-Meier estimator was used to estimate survivorship free from complications and reoperations at 10 years. Clinical examination results and questionnaire responses were evaluated at minimum 2-year follow-up.
RESULTS: Kaplan-Meier survivorship free from AVN was 93% (95% CI 87% to 100%) at 10 years. Survivorship free from any reoperation was 75% (95% CI 64% to 88%) at 10 years. In addition, survivorship free from complications, defined as development of AVN, reoperation, or a Sink Grade II complication or higher, was 57% (95% CI 45% to 73%) at 10 years. The median (range) Merle D\'Aubigne Postel score was 18 (14 to 18) for the patients who did not develop AVN, and 12 (6 to 16) for the four patients who developed AVN (p < 0.001). The median modified Harris hip score was 100 (74 to 100) in the non-AVN cohort and 65 (37 to 82) in the AVN cohort (p = 0.001). Median HOOS total score was 95 (50 to 100) in the non-AVN cohort and 53 (40 to 82) in the AVN cohort (p = 0.002).
CONCLUSIONS: Although the modified Dunn procedure is technically challenging, this study shows that in experienced hands, patients with who have demonstrated epiphyseal-metaphyseal discontinuity can be treated with a low risk of AVN and subsequent surgery. Referral of these patients to specialists who have substantial expertise in this procedure is recommended to improve patient outcomes. Prospective, long-term observational studies will help us identify these high-risk patients preoperatively and determine the long-term success of this procedure.
METHODS: Level IV, therapeutic study.

An abundance of degrees of freedom (DOF) exist when executing a countermovement jump (CMJ). This research aims to simplify the understanding of this complex system by comparing jump performance and independent functional DOF (fDOF) present in CMJs without (CMJNoArms) and with (CMJArms) an arm swing. Principal component analysis was used on 39 muscle forces and 15 3-dimensional joint contact forces obtained from kinematic and kinetic data, analyzed in FreeBody (a segment-based musculoskeletal model). Jump performance was greater in CMJArms with the increased ground contact time resulting in higher external (p = 0.012), hip (p < 0.001) and ankle (p = 0.009) vertical impulses, and slower hip extension enhancing the proximal-to-distal joint extension strategy. This allowed the hip muscles to generate higher forces and greater time-normalized hip vertical impulse (p = 0.006). Three fDOF were found for the muscle forces and 3-dimensional joint contact forces during CMJNoArms, while four fDOF were present for CMJArms. This suggests that the underlying anatomy provides mechanical constraints during a CMJ, reducing the demand on the control system. The additional fDOF present in CMJArms suggests that the arms are not mechanically coupled with the lower extremity, resulting in additional variation within individual motor strategies.

The painful hip has been a topic of study that has evolved from the beginning of the last century to the present. The clinical approach is complex, and requires a systematization process associated with good questioning, clinical maneuvers with their corresponding interpretation, and complementary imaging studies. The understanding of hip pathology, especially in young adults, is highly simplified and sometimes underdiagnosed, therefore, not treated in a timely manner. The prevalence of painful hip is more common in males (49 to 55%) than in females (25 to 28%), and the causes may vary according to demographic characteristics and the history of each patient. Bryan Kelly, made a topographic and anatomical description of the approach to the painful hip according to the theory or system of the layers: I. Osteochondral layer; II. Inert layer; III. Contractile layer; and IV. Neuro-mechanical layer. This system helps us understand the anatomical site of pain and its clinicopathological correlation. The semiological approach to hip pain is the fundamental pillar for differential diagnosis. We can divide it according to its topography into anterior, lateral and posterior, as well as according to its chronology and characteristics. The physical examination should be carried out systematically, starting from a generalized inspection of gait and posture to the evaluation of specific signs for alterations in each layer, which evoke pain with specific postures and ranges of mobility, or weakness and alterations in the arc of mobility of the joint. Image evaluation is initially recommended with radiographic projections that evaluate different planes, both coronal, sagittal and axial, complemented with panoramic views, and eventually dynamic sagittal ones if necessary. Requesting specific studies such as tomography to evaluate bone structure and reserve, or simple MRI when there is suspicion of soft tissue affection, or failing that, arthroresonance for joint pathology, will depend on the clinical symptoms and radiographic findings.
La cadera dolorosa ha sido un tema de estudio que ha evolucionado desde principios del siglo pasado hasta la actualidad. El abordaje clínico es complejo y exige un proceso de sistematización asociado a un buen interrogatorio, maniobras clínicas con su interpretación correspondiente y estudios de imagen complementarios. El entendimiento de la patología de cadera, sobre todo en adulto joven, es altamente simplificado y en ocasiones infradiagnosticado, por lo tanto, no tratado en tiempo y forma. La prevalencia de cadera dolorosa es más frecuente en el sexo masculino (49 a 55%) que en el femenino (25 a 28%), y las causas pueden variar de acuerdo a características demográficas y a los antecedentes de cada paciente. Bryan Kelly realizó una descripción topográfica y anatómica del abordaje de la cadera dolorosa de acuerdo con la teoría o sistema de las capas: I. Capa osteocondral; II. Capa inerte; III. Capa contráctil; y IV. Capa neuromecánica. Este sistema nos ayuda a entender el sitio anatómico del dolor y su correlación clínico-patológica. El abordaje semiológico del dolor de cadera es el pilar fundamental para el diagnóstico diferencial. Podemos dividirlo de acuerdo con su topografía en anterior, lateral y posterior, así como de acuerdo a su cronología y características. La exploración física debe realizarse de manera sistemática, iniciando desde inspección generalizada, de la marcha y postura hasta la evaluación de signos específicos para alteraciones en cada capa, los cuales evocan dolor con posturas y arcos de movilidad específicos, o bien debilidad y alteraciones en el arco de movilidad de la articulación. La evaluación por imagen se recomienda inicialmente con proyecciones radiográficas que evaluen diferentes planos, tanto coronal, sagital y axial, complementado con panorámicas, y eventualmente sagitales dinámicas de ser necesarios. Solicitar estudios específicos como tomografía para evaluar estructura y reserva ósea, o bien, resonancia simple cuando hay sospecha de afección a tejidos blandos, o en su defecto, artrorresonancia para patología articular, dependerá de la clínica y los hallazgos radiográficos.

OBJECTIVE: People with Marfan syndrome (MFS) have clinical symptoms of hip pain, but to date, there is limited knowledge about hip-related structural abnormalities in these patients. Therefore, the purpose of this cross-sectional study was to assess hip-related structural abnormalities and patient-reported outcomes (PRO) in a cohort of patients with MFS compared to healthy controls.
METHODS: Nineteen individuals with MFS (17 females, 39.8±11.5 years) and 19 age, sex, and body mass index-matched healthy, asymptomatic individuals (17 females, 36.2±12.5 years) underwent radiographic imaging and unilateral hip MRI. The Scoring Osteoarthritis with MRI (SHOMRI) technique was used to assess hip-related morphological abnormalities between the MFS and control groups. All participants completed the Hip disability and Osteoarthritis Outcome Score (HOOS) to assess hip-related symptoms, pain, and function during activities of daily living (ADL) and quality of life (QOL).
RESULTS: The MFS group exhibited higher lateral center edge angles (p < .001). Despite similar severity of femoral cartilage damage (p = 1.0), the MFS group exhibited a higher severity (p = 0.046) of acetabular cartilage degeneration (1.21±1.08) compared to the controls (0.53±1.02). There were no between-group differences in severity of labral pathology, subchondral cysts, or edema. Individuals with MFS also self-reported significantly lower HOOS symptoms (p = 0.003), pain (p = 0.014), ADL (p = 0.028), and QOL (p = 0.014) sub-scores, indicating worse hip-related PRO in MFS.
CONCLUSIONS: Our study results suggest that individuals with MFS exhibit early signs of acetabular cartilage degeneration and poor hip-related clinical outcomes compared to healthy individuals. Future work should investigate the underlying biomechanical mechanisms associated with hip joint degeneration in the MFS population.

The accurate estimation of lower-limb joint angles and moments is crucial for assessing the progression of orthopedic diseases, with continuous monitoring during daily walking being essential. An inertial measurement unit (IMU) attached to the lower back has been used for this purpose, but the effect of IMU misalignment in the frontal plane on estimation accuracy remains unclear. This study investigated the impact of virtual IMU misalignment in the frontal plane on estimation errors of lower-limb joint angles and moments during walking. Motion capture data were recorded from 278 healthy adults walking at a comfortable speed. An estimation model was developed using principal component analysis and linear regression, with pelvic accelerations as independent variables and lower-limb joint angles and moments as dependent variables. Virtual IMU misalignments of -20°, -10°, 0°, 10°, and 20° in the frontal plane (five conditions) were simulated. The joint angles and moments were estimated and compared across these conditions. The results indicated that increasing virtual IMU misalignment in the frontal plane led to greater errors in the estimation of pelvis and hip angles, particularly in the frontal plane. For misalignments of ±20°, the errors in pelvis and hip angles were significantly amplified compared to well-aligned conditions. These findings underscore the importance of accounting for IMU misalignment when estimating these variables.

Background and Objectives: Repetitive ankle sprains lead to mechanical instability of the ankle. Patients with chronic ankle instability may experience decreased muscle strength and limited postural control. This study investigated the effects of a hip-strengthening exercise program on muscle strength, balance, and function in patients with chronic ankle instability. Materials and Methods: A total of 30 patients participated in the study and were randomly assigned to the two groups. Among the 30 participants, 14 were assigned to the hip joint-strengthening exercise group and 16 to the control group. The experimental group underwent a hip-strengthening exercise program and received training for 40 min per session twice a week for four weeks. The control group received the same frequency, duration, and number of sessions. Measurements were performed before and after the training period to assess changes in hip strength, balance, and function. Results: In the within-group and between-group comparisons, both groups showed significant differences in hip joint strength, static balance, dynamic balance, and function (FAAM; foot and ankle ability measures) (p < 0.05). Statistically significant differences were observed in the time × group interaction effects among the hip abductors and external rotation in hip joint strength, path length in static balance, posterolateral and posteromedial in dynamic balance, and FAAM-ADL and FAAM-SPORT functions (p < 0.05). Conclusions: Accordingly, this study confirmed that hip joint-strengthening exercises have a positive effect on the strength, balance, and function of patients with chronic ankle instability, and we believe that hip joint-strengthening exercises will be recommended as an effective intervention method for patients suffering from chronic ankle instability.