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 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.

The present study investigates the morphometric changes in the hip joint in a surgically induced rabbit model of hip dysplasia through the sectioning of the ligamentum capitis femoris and pelvic limb immobilization. A total of seventeen rabbits were evaluated using radiographic and computed tomographic imaging to measure the following parameters: the femoral angles of anteversion and inclination, length and width indexes of the neck of the femur, and acetabular depth and ventroversion. Significant differences in femoral anteversion angle and acetabular depth were observed, particularly in the group of hip instability surgery with pelvic limb immobilization. The results have shown the influence of hip joint instability in the promotion of femoral anteversion and acetabular shallowing. These findings provide a foundation for future research on naturally occurring or experimentally induced hip dysplasia in rabbits and underscore the model\'s potential for studying the biomechanical and developmental aspects of hip joint disorders.

Hip pain is a prevalent degenerative joint symptoms, imposing a significant global health burden. Hip pain is experiencing an increase in incidences in Korea due to its aging society, and the social burden of hip pain continues to rise as the hip joint is crucial for gait and balance. This study assessed the epidemiology of hip pain in Korea using data from the fifth version of Korea National Health and Nutrition Examination Survey (KNHANES V-5). The research analyzed data from 8,898,044 Koreans to evaluate the prevalence and characteristics of hip pain and abnormal hip X-ray. Variables encompassed medical, demographic, mental, social, and musculoskeletal factors. Descriptive analysis and propensity score matching analyses unveiled characteristics of Koreans experiencing hip pain or showing abnormal hip x-ray. The study provides insights into the epidemiology of hip pain in the entire Korean population, and further suggesting the effective management of hip pain.

OBJECTIVE: It is not uncommon for patients with hip disorders to present with pelvic obliquity (PO), and residual PO after total hip arthroplasty (THA) may not only affect hip joint function but also cause adjacent intervertebral joint disorders. This study aimed to investigate the postoperative PO impact on clinical outcomes and risk factors by comparing patients who had PO after THA to those who did not.
METHODS: A single-center, retrospective cohort study was conducted. A total of 103 patients who underwent THA were included in this study from 2018 to 2020. Demographics, functional outcomes, and spinopelvic parameters were compared between post-THA PO of less than 2° (NT group, 55 patients) and PO of 2° or more (O group, 48 patients). Multivariate analysis was performed using factors with significant differences in univariate analysis.
RESULTS: Postoperative Harris Hip Score Activity was significantly lower in the T group than in the NT group (p = 0.031). Preoperative PO was smaller in the NT group than in the T group (p = 0.001). Preoperative lumbar bending range (LBR) was significantly more flexible in the NT group than in the T group. In the logistic regression analysis, Age (odds ratio 0.957, 95% CI 0.923-0.993, p = 0.020), preoperative PO (odds ratio 1.490, 95% CI 1.100-2.020, p = 0.001), and LBR (odds ratio 0.848, 95% CI 0.756-0.951, p = 0.005) were found to be significant factors.
CONCLUSIONS: Younger age and large preoperative PO, and poor lumbar spine mobility were identified as risk factors for residual postoperative PO.

Canine hip dysplasia (CHD) is a common orthopedic condition, influenced by both genetic and environmental factors. While current breeding programs often rely on ventrodorsal hip-extended (VDHE) radiographs, it is known they fail to accurately assess hip joint laxity. Therefore additional laxity-oriented diagnostic techniques have been developed. This study aims to evaluate the effectiveness of the Vezzoni modified Bädertscher distension device (VMBDD) technique, which quantifies hip joint laxity with the laxity index (LI), as a screening tool in two breeding programs. Data from a Belgian population of assistance dogs (population A) and a French population of guide dogs (population B) were analyzed. The heritability estimates of the LI, estimated using Bayesian statistical methods, were high in both populations (0.83 in population A and 0.82 in population B). Improved screening of parents by combining the VMBDD technique with the VDHE, significantly decreased LI and the prevalence of CHD in their offspring. In population A, when two parents were screened with the VMBDD compared to one, there was an average LI decrease of 0.03 (P<0.05). In population B, when one or both parents were screened with the VMBDD compared to none, the average LI decrease was 0.04 (P< 0.05) and 0.05 (P<0.01), respectively. In population A, screening both parents with the VMBDD in addition to the VDHE, resulted in 82.7% (P< 0.05) lower odds of CHD compared to screening only one parent. In population B, screening one parent led to 72.3% (P<0.05) lower odds of CHD compared to none of the parents being screened. In population B, when both parents were screened with the VMBDD, not a single case of CHD was observed in the puppies. In conclusion, based on these results, the VMBDD technique has the potential to drastically reduce CHD prevalence and is as such an excellent tool for breeding programs.

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