Effects of extraosseous talotarsal stabilization on the biomechanics of flexible flatfoot subtalar joints in children: a finite element study

<p class="abstract"><strong>Background:</strong> Objective of the study was to generate an experimental foundation for the clinical application of extraosseous talotarsal stabilization (EOTTS) in treatment of flexible flatfeet in children by investigating the biomechanical characteristics of flexible flatfoot and the effects of EOTTS on hindfoot biomechanics.</p><p class="abstract"><strong>Methods:</strong> Three-dimensional finite element models of the foot and ankle complex were generated from computer tomography images of a volunteer’s left foot in three states: normal, flexible flatfoot, and post-EOTTS. After validation by X-ray, simulated loads were applied to the three models in a neutral position with both feet standing.</p><p class="abstract"><strong>Results:</strong> In the flexible flatfoot model, the contact stress on the subtalar joint increased and contact areas decreased, resulting in abnormal stress distribution compared to the normal model. However, following treatment of the foot with EOTTS, these parameters returned to close to normal. Subtalar joint instability leads to a flexible flat foot. Based on this study, it is proposed that EOTTS can restore the normal function of the subtalar joint in and is an effective treatment for flexible flatfoot in children. We and many clinical data studies provide evidence for sinus tarsi implants in pediatric patients. It is showed that the formation of flexible flatfoot is induced by subtalar joint instability.</p><p class="abstract"><strong>Conclusions:</strong> Because of the EOTTS provides the best biomechanical solution to subtalar joint instability, the EOTTS became an effective form for subtalar joint instability treatment.</p>

The reliability of clinical assessment of distal radioulnar joint instability

Accurate assessment of distal radioulnar joint (DRUJ) stability is increasingly recognized as an important part of clinical examination of the wrist. The ability of 30 specialist UK hand surgeons to clinically determine the stability of four volunteers’ wrists was assessed. Volunteers’ wrist stability had previously been confirmed with a validated measurement rig. Use of the wrist ballottement test as the primary examination technique yielded a positive predictive value of 81%, a negative predictive value of 55%, a specificity of 94% and a sensitivity of only 24%, for the detection of DRUJ instability. No correlation between background speciality (orthopaedic versus plastic surgery), nor years of clinical experience was found. Clinical assessment of DRUJ instability among experienced clinicians appears unreliable and instability is typically under recognized. Previous research to date using this clinical assessment method as a parameter of success is therefore brought into question. Level of evidence: IV

Acromioclavicular Joint Instability on Cross-Body Adduction View: The Biomechanical Effect of Acromioclavicular and Coracoclavicular Ligaments Sectioning

Background The relationship between acromioclavicular (AC) joint dislocation, corresponding radiological evaluation, and ligament injuries remains controversial. We hypothesized that AC and trapezoid ligament injuries induce AC joint instability, and the clavicle can override the acromion on cross-body adduction view without conoid ligament injury. We aimed to investigate how biomechanically sectioning the AC and coracoclavicular (CC) ligaments contributes to AC joint instability in the cross-body adduction position using fresh-frozen cadaver models. Methods Six fresh-frozen cadaveric shoulders were used in this study, comprising five male and one female specimen, with a mean age of 68.7 (range, 51–87) years). The left side of the trunk and upper limb, and the cervical and thoracic vertebrae and sternum were firmly fixed with an external fixator. The displacement of the distal end of the clavicle relative to the acromion was measured using an electromagnetic tracking device. We simulated AC joint dislocation by sequential resection of AC ligament, AC joint capsule, and CC ligaments in the following order of stages. Stage 0: Intact AC and CC ligaments and acromioclavicular joint capsule; stage 1: Completely sectioned AC ligament and joint disc; stage 2: Sectioned trapezoid ligament; and stage 3: Sectioned conoid ligament. The superior clavicle displacement related to the acromion was measured in the horizontal adduction position, and clavicle overriding on the acromion was assessed radiologically at each stage. Data were analyzed using a one-way analysis of variance and post-hoc tests. Results Superior displacement was 0.3 mm at stage 1, 6.5 mm at stage 2, and 10.7 mm at stage 3. On the cross-body adduction view, there was no distal clavicle overriding at stages 0 and 1, and distal clavicle overriding was observed in five cases (5/6: 83%) at stage 2 and in six cases (6/6: 100%) at stage 3. Conclusion We found that AC and trapezoid ligament sectioning induced AC joint instability and that the clavicle could override the acromion on cross-body adduction view regardless of conoid ligament sectioning. AC and trapezoid ligament injuries may lead to significant AC joint instability, and the distal clavicle may subsequently override the acromion.