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Posterior dislocation of the sternoclavicular joint (SCJ), although uncommon, can be life-threatening. Displacement of the clavicular head poses a threat to the vital structures of the mediastinum. We describe the case of a 15-year-old boy with traumatic Salter Harris II medial clavicular fracture with posterior dislocation of the metaphysis resulting in impingement of the aortic arch, left subclavian and common carotid artery, as well as partial obstruction of the brachiocephalic vein. We describe the novel use of video-assisted thoracoscopy to assist with a safe open reduction and fixation of the fracture dislocation. The case highlights the importance of computer tomography imaging for diagnosis of posterior SCJ fracture/dislocations and the early recognition of potential life-threatening complications in the mediastinum.

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BACKGROUND: Patients referred to public orthopaedic clinics can experience long waiting times before assessment. This study aims to evaluate the effectiveness of a collaborative Shoulder/Elbow Triage and Assessment (SHELTA) model of care involving orthopaedic surgeons and physiotherapists to reduce the waitlist and improve service and clinical outcomes for patients on an orthopaedic shoulder/elbow clinic waitlist. METHODS: Patients on the waitlist were triaged by surgeons and physiotherapists and invited to an assessment by experienced physiotherapists. Patients were treated nonoperatively or transferred to orthopaedic management based on clinical discussion. The primary outcome was the number of patients on the waitlist. Secondary outcomes included adverse events, patient satisfaction, re-referral and conversion to surgery rates. Pain, function and patient global impression of change were recorded for participants managed nonoperatively. RESULTS: From July 2019 to December 2019, the waitlist reduced from 451 to 298 patients with no adverse events. Seventy-nine patients could not be contacted and 25 no longer required assessment, and were removed from the waitlist. Nonoperatively managed participants reported satisfaction with the service, a median score of 6 on a 7-point Patient Global Impression of Change scale, change in pain of -2.5/10 (95% CI -3.3, -1.7; P < 0.001) on a numerical pain rating scale, and change in function of -17.4/100 (95% CI: -24.1, -10.8; P < 0.001) on the QuickDASH, indicating improvement. CONCLUSIONS: The SHELTA model of care effectively reduced the number of patients on an orthopaedic shoulder/elbow clinic waitlist with good service and clinical outcomes.

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BACKGROUND: The rotational alignment of the femoral component in total knee arthroplasty (TKA) is regarded as being one of the critical factors associated with its long-term success. Traditionally, the femoral component is aligned parallel to the transepicondylar axis (TEA), perpendicular to the Whiteside's line (WL) or at 3 degrees external rotation to the posterior condylar line (PCL). The aim of this study was to use magnetic resonance imaging (MRI) to evaluate the relationship between these anatomical axes used for femoral component rotation (TEA to WL and PCL to TEA) and identify if any of these relationships were influenced by age, sex or coronal axial deformity (mechanical axis). METHODS: Two hundred and sixty-five patients undergoing preoperative MRI for patient-specific jigs TKA were included in our study. The MRI data were then analysed via preoperative planning software, and values relating to WL, TEA, PCL and coronal axial alignment were generated. RESULTS: The mean age was 66.0 ± 8.7 years. There were 102 men and 163 women. The average mechanical axis (coronal deformity) was 4.2 ± 6.1 degrees of varus. TEA compared with WL was on average 92.6 ± 2.3 degrees. PCL was on average 2.3 ± 1.8 degrees internally rotated to the TEA. The PCL was more internally rotated in women (P < 0.01) and valgus (P < 0.001) knees. There was no significant relationship between age or varus knees when comparing TEA to WL (P > 0.1) and PCL to TEA (P > 0.1). CONCLUSIONS: Our study shows that the previously assumed values for rotational alignment of the femoral component may need to be reviewed. The use of advanced preoperative imaging (e.g. MRI) may aid to overcome this variability and assist surgeons in planning femoral component alignment in TKA.

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BACKGROUND: The failure to restore mechanical alignment and appropriate rotational axis intraoperatively has been described as one of the most common causes of implant failure in total knee arthroplasty (TKA). Both conventional and computer-assisted TKA have their limitations. Patient-specific jigs (PSJ) offer a possible alternative method for TKA. The aim of this study was to investigate if the use of PSJ offers reproducible and accurate orientation of the components in TKA compared with conventional and computer-assisted surgery. METHODS: We conducted a prospective case series looking at 261 consecutive patients undergoing TKA for osteoarthritis using the Signature Patient Specific System (Biomet, North Ryde, NSW, Australia). Each patient underwent a preoperative magnetic resonance imaging for planning. Using a computer software program, specialized femoral and tibial pin placement jigs were generated. Post-operative femoral and tibial component alignment was measured using computed tomography. RESULTS: Of patients, 96.2% achieved femoral rotational alignment ±3 degrees of the transepicondylar axis. Tibial coronal alignment showed 92.7% of cases were 90 ± 3 degrees to the tibial medullary axis. Implant measurements of the posterior tibial slope demonstrated 76.6% of cases were within our accepted 0 to 7 degrees slope and 81.2% of patients had an overall mechanical axis within ±3 degrees of neutral. We also recorded femoral coronal alignment of the last 98 patients of our group and found that 99% were within 90 ± 3 degrees. CONCLUSION: PSJ for TKA shows good accuracy in alignment when compared with conventional TKA. However, improvements in the development of the tibial alignment cutting guides will aid in further increasing its overall accuracy and reproducibility.

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BACKGROUND: Böhler's historical tuber-joint angle of the calcaneus has been used since 1931. Surprisingly, there is a paucity of literature on its use. OBJECTIVES: To confirm the normal range for Böhler's angle and determine the angle with the highest accuracy in the diagnosis of calcaneal fractures. METHODS: A retrospective cohort study was performed. The study cohort comprised 424 patients spanning a 5-year period from April 2005 to March 2010. Böhler's angle was measured by two independent observers on lateral x-ray study using the digital angle tool from the Picture Archival and Communication System. Data were analyzed using Stata 8 statistical software package. RESULTS: The mean Böhler's angle in patients without calcaneal fracture was 29.4°. In this group there was no difference in Böhler's angle between male and female patients, left and right feet, or across age. In those patients with calcaneal fractures, a Böhler's angle below 25° was moderately predictive of calcaneal fracture (sensitivity = 100%, specificity = 82%), an angle below 23° was highly predictive of calcaneal fracture (sensitivity = 100%, specificity = 89%), and an angle below 21° was strongly suggestive of calcaneal fracture (sensitivity = 99%, specificity = 99%). A Böhler's angle of ≤ 20° had the highest diagnostic accuracy. CONCLUSION: A Böhler's angle of 20° or less is highly accurate in determining the presence or absence of calcaneal fracture. Böhler's angle serves as a useful screening tool in fracture diagnosis.

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AICAR (5-amino-1-beta-D: -ribofuranosyl-imidazole-4-carboxamide) is an adenosine analog which improves the recovery of the heart after ischemia. In some tissues AICAR enters cells and stimulates AMP-activated protein kinase (AMPK). We explored the mechanism of cardioprotection in isolated rat hearts. We confirmed that AICAR (0.5 mM) applied 10 min prior to a 30-min period of ischemia and present throughout ischemia and reperfusion caused a substantial improvement in the recovery of developed pressure on reperfusion. However, adenosine (100 microM) produced no improvement, suggesting that the mechanism of action of AICAR was not increased endogenous adenosine production. Measurements of intracellular sodium concentration ([Na(+)](i)) showed that AICAR prevented the rapid rise of [Na(+)](i), which normally occurs on reperfusion. Inhibitors of the cardiac sodium-hydrogen exchanger (NHE1) also protect the heart from ischemic damage and also prevent the rapid rise of [Na(+)](i) on reperfusion, suggesting that AICAR might cause the inhibition of NHE1. We tested this possibility on isolated rat ventricular myocytes in which the recovery of pH(i) after NH(4)Cl exposure provides a measure of NHE1 activity. AICAR (0.5 micromM) inhibited NHE1 activity in response to an acid load by about 80%. To test whether the AICAR-induced inhibition of NHE1 arose through adenosine, we used the adenosine receptor blocker 8-sulfophenyltheophylline (8-SPT) and found that it had no measureable effect. To test whether the AICAR-induced inhibition of NHE1 might occur through the activation of AMPK, we measured the activity of two isoforms of AMPK. Surprisingly, activity was reduced, whereas in many other tissues AICAR increases AMPK activity. Furthermore, this effect of AMPK was blocked by 8-SPT, suggesting that the inhibition of AMPK arose through an adenosine-receptor-related pathway. We conclude that AICAR inhibits NHE1 through an unidentified pathway. This inhibition may make a contribution to the cardioprotective effects of AICAR.

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The aim of this study was to further characterize the reduction of myofibrillar Ca2+ sensitivity in mouse muscle which has been observed after fatigue at 37 degrees C. Muscle bundles and single fibres were isolated from mouse flexor digitorum brevis muscle and studied at 37 degrees C. The single fibres were injected with the Ca2+ indicator indo-1. Muscle fatigue was produced by 0.4 s tetani repeated at 4 s intervals until force had fallen to less than 50% of initial. Excitation-contraction coupling was assessed by measuring the cytosolic calcium concentration ([Ca2+]i) during tetani, and the maximum Ca2+-activated force and the myofibrillar Ca2+ sensitivity were estimated from a series of tetani at different stimulation frequencies. Two main results were found. (i) The reduction of Ca2+ sensitivity only occurred when the muscle was intensely stimulated leading to fatigue. When the muscle was rested for 10 min at 37 degrees C there was no significant change in Ca2+ sensitivity. (ii) If the membrane-permeant thiol-specific reducing agent dithiothreitol (0.5 mm) was applied to the muscle for 2 min following the fatigue protocol, the reduction in Ca2+ sensitivity was reversed. Dithiothreitol had no effect on Ca2+ sensitivity in unfatigued preparations. There was no effect of fatigue or dithiothreitol on tetanic [Ca2+]i or on the maximum Ca2+-activated force. These results suggest that intense activity of skeletal muscle at 37 degrees C causes the production of reactive oxygen species which oxidize a target protein. We propose that critical sulphydryl groups on the target protein(s) are converted to disulphide bonds and this reaction reduces Ca2+ sensitivity.

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The mechanisms of muscle fatigue were studied in small muscle bundles and single fibres isolated from the flexor digitorum brevis of the mouse. Fatigue caused by repeated isometric tetani was accelerated at body temperature (37 degrees C) when compared to room temperature (22 degrees C). The membrane-permeant reactive oxygen species (ROS) scavenger, Tiron (5 mM), had no effect on the rate of fatigue at 22 degrees C but slowed the rate of fatigue at 37 degrees C to that observed at 22 degrees C. Single fibres were microinjected with indo-1 to measure intracellular calcium. In the accelerated fatigue at 37 degrees C the tetanic [Ca2+](i) did not change significantly and the decline of maximum Ca2+-activated force was similar to that observed at 22 degrees C. The cause of the greater rate of fatigue at 37 degrees C was a large fall in myofibrillar Ca2+ sensitivity. In the presence of Tiron, the large fall in Ca2+ sensitivity was abolished and the usual decline in tetanic [Ca2+](i) was observed. This study confirms the importance of ROS in fatigue at 37 degrees C and shows that the mechanism of action of ROS is a decline in myofibrillar Ca2+ sensitivity.

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