The suction seal of the hip plays an important role in maintaining hip stability; however, the function of the ligamentum teres in maintaining this seal remains poorly understood. This study aimed to ...evaluate the effectiveness of the hip suction seal in ligamentum teres deficient hips for joint positions occurring during gait.
Six fresh-frozen human cadaveric hips were dissected and mounted to an Instron materials test system. Each specimen was analyzed for average peak distraction force, stiffness, and total energy during hip displacement. Testing was performed in the native intact ligamentum teres state and the deficient ligamentum teres state. Specimens were examined in 20° of flexion, neutral, and 10° of extension.
In the neutral position, the ligamentum teres deficient state displayed a significant decrease in peak distraction force (mean difference: 33.2 N, p < 0.001), average stiffness (mean difference: 63.7 N/mm, p = 0.016), and total energy (mean difference: 82.3 mJ, p = 0.022) compared to the intact controls. In extension, the deficient state exhibited a significant decrease in peak distraction force (mean difference: 42.8 N, p < 0.001) and total energy (mean difference: 72.9 mJ, p = 0.007). In flexion, the deficient state displayed a significant decrease in peak distraction force relative to contols (mean difference: 7.1 N, p = 0.003).
The ligamentum teres plays a significant role in maintaining the suction seal of the hip, with its effect being most prominent when the hip is in neural alignment or in extension. The findings suggest that ligamentum teres deficiency may be a relevant treatment target in the clinical setting.
•The ligamentum teres supports the hip fluid seal.•The hip fluid seal is most prominent in neutral hip alignment or extension.•Ligamentum teres deficiency may be a relevant target for hip stability treatment.
Abstract Large knee adduction moments during gait have been implicated as a mechanical factor related to the progression and severity of tibiofemoral osteoarthritis and it has been proposed that ...these moments increase the load on the medial compartment of the knee joint. However, this mechanism cannot be validated without taking into account the internal forces and moments generated by the muscles and ligaments, which cannot be easily measured. Previous musculoskeletal models suggest that the medial compartment of the tibiofemoral joint bears the majority of the tibiofemoral load, with the lateral compartment unloaded at times during stance. Yet these models did not utilise explicitly measured muscle activation patterns and measurements from an instrumented prosthesis which do not portray lateral compartment unloading. This paper utilised an EMG-driven model to estimate muscle forces and knee joint contact forces during healthy gait. Results indicate that while the medial compartment does bear the majority of the load during stance, muscles provide sufficient stability to counter the tendency of the external adduction moment to unload the lateral compartment. This stability was predominantly provided by the quadriceps, hamstrings, and gastrocnemii muscles, although the contribution from the tensor fascia latae was also significant. Lateral compartment unloading was not predicted by the EMG-driven model, suggesting that muscle activity patterns provide useful input to estimate muscle and joint contact forces.
People with Parkinson's disease (PD) can be classified into tremor dominant (TD) and postural instability and gait difficulty (PIGD) subtypes; the latter group having more impaired gait and increased ...fall risk. While there is some evidence that anti-parkinsonian medication, levodopa, might not improve balance and gait control or reduce fall risk in the PIGD subtype, it is unclear whether the levodopa dosage intake affects gait stability. To address these issues, this study used accelerometry to compare gait stability: (i) during before and after levodopa intake between non-PIGD and PIGD subtypes; (ii) between individuals who took less or >750 mg of levodopa/day.
In 15 non-PIGD (Combination of 13 TD patients and 2 classified as indeterminate subtype) and 23 PIGD participants of similar mean (SD) age ((63.0 (7.6) versus 62.6 (10.0) years, respectively)) and disease-duration (8.9 (8.9) versus 11.3 (4.6) years, respectively), head and trunk stability during gait was examined using anteroposterior, vertical and mediolateral acceleration harmonic ratios (HRs). Participants were assessed before and after a levodopa dose, during typical “off” and “on” periods, respectively.
Two-way analyses of variance (group × medication status) revealed that compared to the non-PIGD subgroup, the PIGD subgroup showed significantly worse head stability (lower anteroposterior HR) in the “off” state, and significantly worse pelvis stability (significantly lower mediolateral and vertical HRs) in the “on” state (p < 0.05 for both). Levodopa was effective in treating most of the disease-related impairments (not bradykinesia) in both groups, (p < 0.05) but improved gait stability (lowered pelvis mediolateral and vertical HRs) only in people with the non-PIGD subtype (p < 0.05) and those taking <750 mg of levodopa/day (p < 0.05).
People with the PD PIGD subtype exhibit impaired gait stability that is not improved and frequently worsened by levodopa. New non-pharmaceutical approaches, technological (e.g. cueing) or exercise-based (e.g. balance training) are required to improve or compensate for mediolateral gait instability in this subtype and ultimately prevent falls.
•People with the PIGD subtype have significantly impaired head and trunk stability during gait.•Levodopa improved clinical measures including axial posture in both PIGD and non-PIGD subtypes.•Levodopa worsened mediolateral gait stability in people with the PIGD subtype.•Levodopa did not improve gait stability in participants taking >750 mg of levodopa/day.
Ulnar styloid fractures occur frequently concomitant with distal radial fractures. Although unstable distal radial fractures are mostly surgically treated, ulnar styloid fractures are often ignored. ...Unstable fractures at the base of the ulnar styloid may lead to persistent ulnar pain, due to distal radioulnar joint instability or ulnar styloid non-union.
We retrospectively analyzed a single-surgeon cohort series of surgically treated distal radial fractures on how these concomitant ulnar styloid fractures were regarded: indications for surgery and surgical technique with headless screw fixation.
119 surgically treated distal radial fractures were assessed. 51 (42.8%) of the surgically treated distal radial fractures had a distal ulnar fracture, and more specifically 23 (19.3%) had a base fracture of the ulnar styloid. 9 (7.6%) of the wrists had a base fracture of the ulnar styloid which was considered after distal radial fracture fixation as persistently unstable, during distal radioulnar joint ballottement translation test. This fracture subtype was immediately treated with headless screw fixation, resulting in all cases in bony union, with a mean active pronation of 85°, a mean active supination of 80° and a clinical stable distal radioulnar joint, with minimal ulnar pain after 6 weeks (mean Visual Analogue Scale 1). After at least 12 months, persistent pain did not occur and mean QuickDASH was 2.5.
According to this single-surgeon cohort series, headless screw fixation provides a reliable treatment for unstable base fractures of the ulnar styloid after distal radial fixation.
Objective: The present study is an attempt to determine the various types of bony modifications on the dorsum of the neck of the human tali of both feet due to the continuous habit of squatting in ...humans and correlating these findings to the existing literature. Materials and Methods: 70 tali of unknown sex, obtained from the Department of Anatomy of MVJ Medical College and Research Hospital, Bangalore were used for the study. The dorsal surface of talar neck was carefully examined for the presence of medial and lateral squatting facets, combined facets, continuous gutter shaped facets and extension of trochlear surface. The collected data were tabulated and percentage of each facets and trochlear extensions were calculated. Statistical analysis of data was performed. Results: Out of 70 dry human tali, lateral squatting facets were present in 29 (41.4%) bones and medial squatting facets were seen in 11 (15.7%) bones, gutter shaped facets in 12 (17.1%) tali and combined facet present in 10 (14.2%) tali. Complete absence of facet was observed in 8 tali. Lateral extension of trochlear surface on the dorsum of neck was seen in 60 (85.7%) bones and medial trochlear extension was seen in 8(11.5%) bones. Lateral squatting facets were more common on right side but medial, gutter and combined facets though less frequent were seen more on left side. Lateral extensions were more commonly seen than medial extensions. Conclusion: The knowledge of incidence of these modifications on the dorsal surfaces of neck of the talus acts as a key anthropological factor to identify the racial and regional origin of unclaimed skeleton. Hence the results of this study will be of great help for forensic experts, anthropologist who are handling the unidentified skeletons. KEY WORDS: Squatting Facets, Talus, Trochlear extensions, Sub Talar Joint Stability.
The purpose of this study was to quantify the effect of the flexor carpi ulnaris and the extensor carpi ulnaris muscles on distal radioulnar joint stability. The anteroposterior ulnar head ...translation in relation to the radius was measured sonographically when the forearm was in a neutral resting position and when the hand was actively pressed on to a surface, with and without intentional flexor carpi ulnaris and extensor carpi ulnaris activation, while also being monitored by an electromyogram. Data on 40 healthy participants indicated a mean anteroposterior translation in the distal radioulnar joint of 4.1 mm (SD 1.08) without and 1.2 mm (SD 0.54) with muscle activation. Our results indicate that intentional ulnar forearm muscle activation results in 70% less anteroposterior ulnar head translation and greater distal radioulnar joint stability. Therefore, the flexor carpi ulnaris and extensor carpi ulnaris muscles serve as dynamic stabilizers of the distal radioulnar joint. This finding may be clinically significant since ulnar forearm muscles strengthening may increase distal radioulnar joint stability.
To compare the responses in knee joint muscle activation patterns to different perturbations during gait in healthy subjects.
Nine healthy participants were subjected to perturbed walking on a ...split-belt treadmill. Four perturbation types were applied, each at five intensities. The activations of seven muscles surrounding the knee were measured using surface EMG. The responses in muscle activation were expressed by calculating mean, peak, co-contraction (CCI) and perturbation responses (PR) values. PR captures the responses relative to unperturbed gait. Statistical parametric mapping analysis was used to compare the muscle activation patterns between conditions.
Perturbations evoked only small responses in muscle activation, though higher perturbation intensities yielded a higher mean activation in five muscles, as well as higher PR. Different types of perturbation led to different responses in the rectus femoris, medial gastrocnemius and lateral gastrocnemius. The participants had lower CCI just before perturbation compared to the same phase of unperturbed gait.
Healthy participants respond to different perturbations during gait with small adaptations in their knee joint muscle activation patterns. This study provides insights in how the muscles are activated to stabilize the knee when challenged. Furthermore it could guide future studies in determining aberrant muscle activation in patients with knee disorders.
Approximately 9% of shoulder girdle injuries involve the acromioclavicular joint (ACJ). There is no clear gold standard or consensus on surgical management of these injuries, in part perpetuated by ...our incomplete understanding of native ACJ biomechanics. We have therefore conducted a biomechanical study to assess the stabilizing structures of the ACJ in superior-inferior (SI) translation and anterior-posterior (AP) translation.
Twenty fresh frozen cadaveric specimens were prepared and mounted onto a robotic arm. The intact native joint was tested in SI translation and AP translation under a 50-N displacing force. Each specimen was retested after sectioning of its stabilizing structures in the following order: investing fascia, ACJ capsular ligaments, trapezoid ligament, and conoid ligament. Their contributions to resisting ACJ displacements were calculated.
In the intact native ACJ, mean anterior displacement of the clavicle was 7.9 ± 4.3 mm, mean posterior displacement was 7.2 ± 2.6 mm, mean superior displacement was 5.8 ± 3.0 mm, and mean inferior displacement was 3.6 ± 2.6 mm. The conoid ligament was the primary stabilizer of superior displacement (45.6%). The ACJ capsular ligament was the primary stabilizer of inferior displacement (33.8%). The capsular ligament and conoid ligament contributed equally to anterior stability, with rates of 23% and 25.2%, respectively. The capsular ligament was the primary contributor to posterior stability (38.4%).
The conoid ligament is the primary stabilizer of superior displacement of the clavicle at the ACJ and contributes significantly to AP stability. Consideration should be given to reconstruction of the ACJ capsular ligament for complete AP stability in high-grade and horizontally unstable ACJ injuries.
Joint Instability and Osteoarthritis Blalock, Darryl; Miller, Andrew; Tilley, Michael ...
Clinical Medicine Insights: Arthritis and Musculoskeletal Disorders,
01/2015, Letnik:
2015, Številka:
2015
Journal Article, Book Review
Recenzirano
Odprti dostop
Joint instability creates a clinical and economic burden in the health care system. Injuries and disorders that directly damage the joint structure or lead to joint instability are highly associated ...with osteoarthritis (OA). Thus, understanding the physiology of joint stability and the mechanisms of joint instability-induced OA is of clinical significance. The first section of this review discusses the structure and function of major joint tissues, including periarticular muscles, which play a significant role in joint stability. Because the knee, ankle, and shoulder joints demonstrate a high incidence of ligament injury and joint instability, the second section summarizes the mechanisms of ligament injury-associated joint instability of these joints. The final section highlights the recent advances in the understanding of the mechanical and biological mechanisms of joint instability-induced OA. These advances may lead to new opportunities for clinical intervention in the prevention and early treatment of OA.
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