Hip joint and muscle loading for persons with bilateral transfemoral/through-knee amputations: biomechanical differences between full-length articulated and foreshortened non-articulated prostheses.

BACKGROUND: Currently, there is little available in-depth analysis of the biomechanical effect of different prostheses on the musculoskeletal system function and residual limb internal loading for persons with bilateral transfemoral/through-knee amputations (BTF). Commercially available prostheses for BTF include full-length articulated prostheses (microprocessor-controlled prosthetic knees with dynamic response prosthetic feet) and foreshortened non-articulated stubby prostheses. This study aims to assess and compare the BTF musculoskeletal function and loading during gait with these two types of prostheses. METHODS: Gait data were collected from four male traumatic military BTF and four able-bodied (AB) matched controls using a 10-camera motion capture system with two force plates. BTF completed level-ground walking trials with full-length articulated and foreshortened non-articulated stubby prostheses. Inverse kinematics, inverse dynamics and musculoskeletal modelling simulations were conducted. RESULTS: Full-length articulated prostheses introduced larger stride length (by 0.5 m) and walking speed (by 0.3 m/s) than stubbies. BTF with articulated prostheses showed larger peak hip extension angles (by 10.1°), flexion moment (by 1.0 Nm/kg) and second peak hip contact force (by 3.8 bodyweight) than stubbies. There was no difference in the hip joint loading profile between BTF with stubbies and AB for one gait cycle. Full-length articulated prostheses introduced higher hip flexor muscle force impulse than stubbies. CONCLUSIONS: Compared to stubbies, BTF with full-length articulated prostheses can achieve similar activity levels to persons without limb loss, but this may introduce detrimental muscle and hip joint loading, which may lead to reduced muscular endurance and joint degeneration. This study provides beneficial guidance in making informed decisions for prosthesis choice.

Biceps Tenodesis cannot be used as primary treatment option in baseball pitchers with intact rotator cuff muscles.

Background Surgeons remain hesitant to perform biceps tenodesis in athletes with type II superior labrum anterior-to-posterior tears due to the lack of reported clinical outcomes for individual overhead throwing sports and associated concerns that this may predispose the joint to instability. This study aimed to assess the effect of biceps tenodesis on shoulder stability for major overhead throwing sports to aid sport-specific surgical decision-making for athletes with type II superior labrum anterior-to-posterior tears. METHODS: This is a combined modelling and experimental study. Motion data and external forces were measured from 13 participants performing five overhead throwing motions. These data served as input into a musculoskeletal shoulder model that quantifies shoulder stability and muscle loading. FINDINGS: The loading of the long head of the biceps brachii decreases significantly following biceps tenodesis in three overhead throwing motions (p = 0.02). The loss in joint stability following biceps tenodesis is compensated by a non-significant increase in rotator cuff muscle force which maintains shoulder stability across all overhead throwing motions, except baseball pitching (p = 0.01). The presence of a full-thickness supraspinatus tear post biceps tenodesis further decreases shoulder stability in four of the five overhead throwing motions (p = 0.01). INTERPRETATION: The study findings demonstrate that an increase in rotator cuff muscle force maintains joint stability for all overhead throwing motions post biceps tenodesis, except baseball pitching. As the presence of a full-thickness tear of the supraspinatus significantly reduces joint stability, biceps tenodesis may be used as a primary treatment in overhead throwing athletes with intact rotator cuff muscles, except baseball pitchers. LEVEL OF EVIDENCE: Controlled Laboratory Study; Level of Evidence 3.

An Anatomical Atlas-Based Scaling Study for Quantifying Muscle and Hip Joint Contact Forces in Above and Through-Knee Amputees Using Validated Musculoskeletal Modelling.

OBJECTIVE: Customisation of musculoskeletal modelling using magnetic resonance imaging (MRI) significantly improves the model accuracy, but the process is time consuming and computationally intensive. This study hypothesizes that linear scaling to a lower limb amputee model with anthropometric similarity can accurately predict muscle and joint contact forces. METHODS: An MRI-based anatomical atlas, comprising 18 trans-femoral and through-knee traumatic lower limb amputee models, is developed. Gait data, using a 10-camera motion capture system with two force plates, and surface electromyography (EMG) data were collected. Muscle and hip joint contact forces were quantified using musculoskeletal modelling. The predicted muscle activations from the subject-specific models were validated using EMG recordings. Anthropometry based multiple linear regression models, which minimize errors in force predictions, are presented. RESULTS: All predictions showed excellent (error interval c = 0-0.15), very good (c = 0.15-0.30) or good (c = 0.30-0.45) similarity to the EMG data, demonstrating accurate computation of muscle activations. The primary predictors of discrepancies in force predictions were differences in pelvis width (p < 0.001), body mass index (BMI, p < 0.001) and stump length to pelvis width ratio (p < 0.001) between the respective individual and underlying dataset. CONCLUSION: Linear scaling to a model with the most similar pelvis width, BMI and stump length to pelvis width ratio results in modelling outcomes with minimal errors. SIGNIFICANCE: This study provides robust tools to perform accurate analyses of musculoskeletal mechanics for high-functioning lower limb military amputees, thus facilitating the further understanding and improvement of the amputee's function. The atlas is available in an open source repository.