Impacts of external rotators and the ischiofemoral ligament on preventing excessive internal hip rotation: a cadaveric study

Background This study examined the biomechanics of preventing excessive internal hip joint rotation related to the hip flexion angle. Method An intramedullary nail with a circular plate equipped with a protractor was installed in the femur of nine normal hips. The circular plate was pulled by 3.15 Nm of force in the internal rotation direction. The external rotators were individually resected, finally cutting the ischiofemoral ligament. The cutting order of the external rotators differed on each side to individually determine the internal rotation resistance. The external rotators were resected from the piriformis to the obturator externus in the right hips and the reverse order in the left hips. Traction was performed after excising each muscle and ischiofemoral ligament. Measurements were taken at 0°, 30°, and 60° of hip flexion, and the differences from baseline were calculated. Results For the right hip measurements, the piriformis and ischiofemoral ligament resection significantly differed at 0° of flexion (p = 0.02), each external rotator and the ischiofemoral ligament resections significantly differed at 30° of flexion (p < 0.01), and the ischiofemoral ligament and piriformis and inferior gemellus resections significantly differed at 60° of flexion (p = 0.04 and p = 0.02, respectively). In the left hips, the ischiofemoral ligament and obturator externus, inferior gemellus, and obturator internus resections significantly differed at 0° of flexion (p < 0.01, p < 0.01, and p = 0.01, respectively), as did each external rotator and the ischiofemoral ligament resections at 30° of flexion (p < 0.01). Conclusion The ischiofemoral ligament primarily restricted the internal rotation of the hip joint. The piriformis and obturator internus may restrict internal rotation at 0° and 60° of flexion.

P12 Focal myositis—A case series of a rare cause of hip immobility and calf pseudotumor in children

Case report - Introduction Focal myositis is a rare immune-mediated pseudotumour of a single skeletal muscle group. Only around 200 cases have been described in the literature, so little is known about incidence, prevalence, patient management and outcomes. This differs and should not be confused with post-viral myalgia which bears neither the histological changes nor chronicity of focal myositis. Treatment options are centred on immunomodulation and in severe cases surgical management of contractures. Case report - Case description Case 1 A systemically well 7-year-old girl presented with 5-weeks of right calf tenderness and swelling following a short episode of pharyngitis and generalised maculopapular rash. There was no gait abnormality, focal neurology or restriction in activity aside from fatigability on walking distances. There were no skin rashes, joint involvement, eye changes or involvement of other muscles. She had a raised creatine kinase, plasma viscosity and lactate dehydrogenase. Her other blood results were normal including an extended autoimmune screen, immunoglobulins, complement levels, ASOT and titres of mycoplasma, EBV and CMV. MRI showed evidence of extensive inflammation of the gastrocnemius and soleus. A muscle biopsy showed heavy interstitial inflammatory cell infiltrate of predominantly lymphocytes, features of fibre necrosis including phagocytosis and hyalinisation with concurrent fibre regeneration. Case 2 A systemically well 14-year-old presented with 6-months of left-sided hip pain, weight loss and inability to weight-bear without crutches. On examination there was painful fixed limitation of the left hip to 45o on abduction and external rotation with bilateral mild swelling of the proximal interphalangeal (PIP) joints on both upper limbs. Otherwise, there was a full range of movement in all joints, with no rashes or other joint swelling or inflammation. Her blood tests were ANA positive 1:6000 and MRI of her hips demonstrated high T2 signal intensity in the left gluteus minimis and medius, obturator internus, obturator externus in keeping with myositis. Case report - Discussion Case 1 She was initially managed with physiotherapy and anti-inflammatory medications but then developed intermittent right calf pain, restriction in activity and tiptoe walking due to gastrocnemius contractures. She was commenced on an 8-week tapering course of oral steroids and is improving with weekly methotrexate. Case 2 She received a pulse of corticosteroids followed by a course of methotrexate. There was immediate improvement in her PIP joint swellings and within a few weeks she was able to walk without crutches for the first time in 6 months; a surveillance MRI confirmed complete radiographical resolution of myositis. Unfortunately, 18 months after her diagnosis, she had developed anterior uveitis of her left eye with posterior synechiae; this responded well to steroid and cyclopentolate eye drops. Case report - Key learning points We emphasise that clinicians should bear this rare differential diagnosis for in mind for consideration of early conservative management, assessment for uveitis, immunomodulation and possibly surgical correction to improve patient outcome.

Humanoid Lower Limb: Design, Analysis, Observer-Based Fuzzy Adaptive Control and Experiment

With flexibility similar to human muscles, pneumatic artificial muscles (PAMs) are widely used in bionic robots. They have a high power-mass ratio and are only affected by single-acting pneumatic pressure. Some robots are actuated by a pair of PAMs in the form of antagonistic muscles or joints through a parallel mechanism. The pneumatic pressure and length of PAMs should be measured simultaneously for feedback using a pressure transducer and draw-wire displacement sensor. The PAM designed by the FESTO (10 mm diameter) is too small to install a draw-wire displacement sensor coaxially and cannot measure muscle length change directly. To solve this problem, an angular transducer is adopted to measure joint angles as a whole. Then, the inertia of the lower limb is identified, and observer-based fuzzy adaptive control is introduced to combine with integrated control of the angular transducer. The parameters of the fuzzy control are optimized by the Gaussian basis neural network function, and an observer is developed to estimate the unmeasured angular accelerations. Finally, two experiments are conducted to confirm the effectiveness of the method. It is demonstrated that piriformis and musculi obturator internus act as agonistic muscle and antagonistic muscles alternatively, and iliopsoas is mainly responsible for strengthening because of the constant output force. Piriformis has a greater influence on yaw and roll angles, while musculi obturator internus is the one that influences the pitch angle the most. Due to joint friction, the dead zone of the high-speed on-off valve, lag of compressed air in the trachea, and coupling among angles are very difficult to realize precise trajectory tracking of the pitch, yaw, and roll angles simultaneously.

Traumatic Obturator Internus and Quadratus Femoris Injury in a Pediatric Patient: A Case Report

We present the case of a 11-year-old White female patient with a traumatic quadratus femoris and obturator internus tear after a sprint while at school. She felt immediate pain, swelling, and point tenderness in her posterosuperior thigh with a severely antalgic gait. Magnetic resonance imaging demonstrated a quadratus femoris tear, obturator internus tear, and ischial spine avulsion fracture. Although a less common etiology for acute hip pain in the pediatric population, traumatic injury to the short external rotators should not be excluded. The prognosis is favorable with a full return to previous activities expected using an appropriate rehabilitation program.

Obturator internus and externus muscle abscess caused by methicillin-resistant Staphylococcus aureus in a 6-year-old boy: A case report

Obturator abscess is a rare condition in children which usually occurs commonly in tropical countries. Because of its rarity, vague symptomatology and a lack of focus about this condition, the diagnosis of obturator abscess is commonly delayed or missed. Hence, physicians should be familiar with this condition and have a high index of suspicion when a patient presents with fever, pain in the thigh, hip or abdomen and a limp on the affected side which are considered as the classic clinical triad of obturator abscess. Herein, we present a 6-year-old previously healthy Russian boy who was on holiday in Sri Lanka. He presented on the third day of the fever associated with pain in the right thigh and abdomen. This is the first reported case of an obturator externus muscle abscess due to methicillin-resistant Staphylococcus aureus in a European boy visiting a tropical country.

Spontaneous Multiple Haematomas in a Patient with Severe COVID-19 Fully Recovered with a Conservative Approach

A significant number of hospitalized patients with COVID-19 are prone to thromboembolic events including deep vein thrombosis, pulmonary embolism, cerebrovascular accident, and myocardial infarction. However, some COVID-19 patients have a higher risk of bleeding that is associated with an increased risk of mortality. We report a 71-year-old woman who was a confirmed case of COVID-19 admitted for pulmonary involvement and complicated acute renal failure. During hospitalization, she suffered from a sudden onset of severe pain in the lower left abdomen as well as a sudden drop in blood pressure and hemoglobin. Haematomas in the left rectus and obturator internus muscle were observed in abdominal and pelvic computed tomography scan. Signs of haemorrhage were also seen in the anterolateral aspect of the bladder with extension to the paracolic, subdiaphragmatic, perihepatic and, perisplenic spaces. The patient was totally recovered by a conservative approach. Bleeding tendency could be a serious complication, especially, in COVID-19 patients with complicated renal failure that receive heparin prophylaxis.