Objectives. We studied subchondral intraosseous pressure (IOP) in an animal model during loading, and with vascular occlusion. We explored bone compartmentalization by saline injection. Materials and Methods. Needles were placed in the femoral condyle and proximal tibia of five anaesthetized rabbits and connected to pressure recorders. The limb was loaded with and without proximal vascular occlusion. An additional subject had simultaneous triple recordings at the femoral head, femoral condyle and proximal tibia. In a further subject, saline injections at three sites were carried out in turn. Results. Loading alone caused a rise in subchondral IOP from 11.7 mmHg (. sd. 7.1) to 17.9 mmHg (. sd. 8.1; p < 0.0002). During arterial occlusion, IOP fell to 5.3 mmHg (. sd. 4.1), then with loading there was a small rise to 7.6 mmHg (. sd. 4.5; p < 0.002). During venous occlusion, IOP rose to 20.2 mmHg (. sd. 5.8), and with loading there was a further rise to 26.3 mmHg (. sd. 6.3; p < 0.003). The effects were present at three different sites along the limb simultaneously. Saline injections showed pressure transmitted throughout the length of the femur but not across the knee joint. Conclusion. This is the first study to report changes in IOP in vivo during loading and with combinations of vascular occlusion and loading. Intraosseous pressure is not a constant. It is reduced during proximal arterial occlusion and increased with proximal venous occlusion. Whatever the perfusion state, in vivo load is transferred partly by hydraulic pressure. We propose that joints act as hydraulic pressure barriers. An understanding of subchondral physiology may be important in understanding osteoarthritis and other bone diseases. Cite this article: M. Beverly, S. Mellon, J. A. Kennedy, D. W. Murray. Intraosseous pressure during loading and with vascular occlusion in an animal model. Bone Joint Res 2018;7:511–516. DOI: 10.1302/2046-3758.78.BJR-2017-0343.R2

Objectives. Legg–Calvé–Perthes’ disease (LCP) is an idiopathic osteonecrosis of the femoral head that is most common in children between four and eight years old. The factors that lead to the onset of LCP are still unclear; however, it is believed that interruption of the blood supply to the developing epiphysis is an important factor in the development of the condition. Methods. Finite element analysis modelling of the blood supply to the juvenile epiphysis was investigated to understand under which circumstances the blood vessels supplying the femoral epiphysis could become obstructed. The identification of these conditions is likely to be important in understanding the biomechanics of LCP. Results. The results support the hypothesis that vascular obstruction to the epiphysis may arise when there is delayed ossification and when articular cartilage has reduced stiffness under compression. Conclusion. The findings support the theory of vascular occlusion as being important in the pathophysiology of Perthes disease. Cite this article: M. Pinheiro, C. A. Dobson, D. Perry, M. J. Fagan. New insights into the biomechanics of Legg-Calvé-Perthes’ disease: The Role of Epiphyseal Skeletal Immaturity in Vascular Obstruction. Bone Joint Res 2018;7:148–156. DOI: 10.1302/2046-3758.72.BJR-2017-0191.R1

Intraosseous pressure measurements (IOP) are not new. Several authors have struggled to interpret static IOP and to understand arthritis and osteonecrosis pathology. This work uses a combination of simple experiments in vivo to reassess bone and joint physiology. Joint replacement needs to take into account the hydrodynamic conditions that are present in bone. Intraosseous pressure measurements were carried out with vascular occlusion, activity and saline injection in experimental conditions and then in man during walking. RESULTS. 1. Basal IOP has a pulse wave and an underlying respiratory wave (RW). 2. IOP closely reflects systemic vascular changes. 3. Proximal arterial occlusion causes loss of IOP (IOPa) and pulse volume (PV). 4. Proximal vein occlusion causes a rise in IOP (IOPv) with preservation of PV and RW. 5. Physical loading raises IOP with preservation of PV and RW. 6. Load with arterial occlusion caused minimal rise in IOP. Loading with venous occlusion caused an augmented rise in IOP with preservation of the PV. 7. Simultaneous recordings from the femoral head, condyle and upper tibia during vascular occlusion and loading show that the same effects occur at all sites. 8. Simultaneous recording from the femoral head, condyle and upper tibia during saline injection shows pressure is transmitted through bone but not across joints. 9. The Ficat bolus test destroys local circulation. Aspiration is better and preserves local perfusion. 10. Bone health at the needle tip is better assessed by IOPv – IOPa, the perfusion ‘bandwidth’. 11. Upper tibial pressure during standing, slow walking and fast walking shows large IOP changes in vivo. 12. There is probably a physiological subchondral bone blood pump. 13. Anatomical features are present which support this idea. CONCLUSIONS. IOP measurement in isolation is meaningless. With arterial and venous occlusion, perfusion at the needle tip can be studied. Compartment syndrome testing should be similar. Subchondral bone is a compressible perfused sponge with a ‘pumped’ microcirculation. Very high pressures arise in subchondral bone during activity. There are protective modifications of the microcirculation. Failure of subchondral circulation causes arthritis. Arthritis is mainly a ‘vasculo-mechanical’ disease. This work explains the spectrum of arthritis and osteonecrosis, and Perthes, caisson and sickle cell disease patterns. It explains why osteoporosis might protect against arthritis

Thoracic Outlet Syndrome (TOS) is a complex of symptoms representing neurovascular compression in the supraclavicular area and shoulder girdle. Arterial thoracic outlet syndrome represents only 1% of all TOS's. We present two cases of arterial TOS's following internal fixation of clavicular fractures. Two cases of clavicular fractures managed with internal fixation and subsequently diagnosed with symptomatic, position dependent arterial occlusion are presented. The first case of a 16-year-old male treated with an intramedullary compression screw. He developed symptoms and was diagnosed with TOS using dynamic duplex examination performed by a vascular surgeon. Revision surgery was planned to decompress the subclavian artery from the hypertrophic callus at the fracture site. Before this could be performed the patient re-fractured his clavicle and bent the intramedullary screw. This resulted in resolution of the TOS symptoms. Following this second injury the patient went on to unite the fracture. The second case was of a 48-year-old male. He was initially treated non- operatively until the patient reported sensory and motor disturbances involving the hand and forearm. Excess callus was excised and the fracture was fixed using a locking plate. The symptoms improved, but worsened again eight weeks post operatively. Angiogram revealed vascular occlusion on arm abduction. Repeat surgery was performed in conjunction with a vascular surgeon. The plate was removed, vascular structures were released from fibrous tissue in the region of the fracture, and the posterior edge of the clavicle was debrided with a burr to reduce future impingement on vascular structures. Post operatively the TOS symptoms did not recur. Arterial thoracic outlet syndrome is an uncommon complication of trauma involving the clavicle. It can present in the presence or absence of surgical intervention, but can require surgical intervention to resolve

Purpose. Proximal femoral osteotomy is an attractive joint preservation procedure for osteonecrosis of the femoral head. The purpose of this study was to investigate the cause of failure of proximal femoral osteotomy in patients with osteonecrosis of the femoral head. Patients and Methods. Between 2008 and 2014, proximal femoral osteotomy was performed by one surgeon in 13 symptomatic hips. Ten trans-trochanteric rotational osteotomies (anterior: 7, posterior: 3) and 3 intertrochanteric curved varus osteotomy were performed. Of the patients, 9 were male and 1 was female, with a mean age at surgery of 36.9 years (range, 25–55 years). The mean postoperative follow-up period was 38 months (range, 12–72 months). Three patients (4 hips) had steroid-induced osteonecrosis, and 7 (9 hips) had alcohol-associated osteonecrosis. At 6 postoperative weeks, partial weight bearing was permitted with the assistance of 2 crutches. At more than 6 postoperative months, full weight bearing was permitted. Patients who had the potential to achieve acetabular coverage of more than one-third of the intact articular surface on preoperative hip radiography, computed tomography, and magnetic resonance imaging were considered suitable for this operation. A clinical evaluation using the Japanese Orthopaedic Association (JOA) scoring system and a radiologic evaluation were performed. Clinical failure was defined as conversion to total hip arthroplasty (THA) or progression to head collapse and osteoarthritis. The 13 hips were divided into two groups, namely the failure and success groups. Results. The mean preoperative JOA score was 59 points. The score in the success group (7 hips) improved to 89 points at the time of final follow-up. In the failure group (6 hips), 5 hips were converted to THA because of progression to secondary collapse or osteoarthritis in a mean postoperative period of 35 months (range, 24–51 months). After converting to THA, good clinical and radiographic results were achieved, except in 1 patient who had incomprehensible severe pain around the affected hip. Advanced osteoarthritis was observed in 1 hip awaiting THA. Various factors cause failure of proximal femoral osteotomy, such as difficulty in controlling the underlying disease with less than 10 mg of steroid (Fig. 1), overuse of the affected hip within 6 postoperative months without the physician's consent, vascular occlusion after total necrosis of the femoral head as a result of damage to the nutritional vessel during or after the operation, and incorrect judgement of the indication of the operation and the extent of the intact load-bearing area. Conclusion. We think that full weight bearing should be permitted postoperatively only after more than 6 months, and heavy work and sport, only after more than 1 year. Efforts should be made to improve surgeons' skill in proximal femoral osteotomy and accurate judgement of imaging data. For steroid-induced osteonecrosis of the femoral head, proximal femoral osteotomy is an acceptable procedure for relieving pain if the underlying disease can be controlled with not more than 5 mg of steroid

Introduction and Aims: Vertebral artery patency is not routinely documented in cervical fractures and dislocations. The incidence of vertebral artery injuries following cervical trauma is unknown, as they are rarely symptomatic. Vertebrobasilar insufficiency may be catastrophic and such vascular occlusion should be identified and treated early. Method: One hundred and eighteen patients who sustained fractures and dislocations of the cervical spine between January 1996 and February 2001 were evaluated and subjected to MRI (magnetic resonance imaging) and MRA (magnetic resonance angiography). The average age was 34 years and there were 30 females. Seventy patients had unifacet dislocations, 10 burst fractures and 38 bifacetal dislocations. Forty-five patients had neurological deficit. Seven patients died within the first six weeks of injury. Reduction and surgical fusion were performed on 115 patients. None of the patients had signs/symptoms of vertebrobasilar ischaemia. MRA was repeated in six patients three years post-injury. Results: Vertebral artery injury was diagnosed in 20 patients (23.6 %) – one patient had bilateral injury. Diagnosis was based on the loss of normal flow void on MRI and confirmed on MRA. Twelve patients with vascular compromise had unifacetal dislocations, two had burst fractures and six bifacetal dislocations. Thrombosis was present in 13 patients, three patients had intimal tears and five dissections (one patient with bilateral injury). The patient with bilateral injury also had significant neurological deficit (frankel C), confusion that resolved in 24 hours and evidence of cerebellar infarct. She had no symptoms of vertebrobasilar insufficiency and recovered full neurological function. Repeat MRA in six patients showed no evidence of recanalisation. Conclusion: VAI was more common in unifacet dislocations, emphasising the effect of a rotation force predisposing to vascular injury. We recommend early diagnosis of vertebrobasilar insufficiency. Future anterior cervical surgery in patients with VAI should be undertaken with caution

Aims

Avascular femoral head necrosis in the context of gymnastics is a rare but serious complication, appearing similar to Perthes’ disease but occurring later during adolescence. Based on 3D CT animations, we propose repetitive impact between the main supplying vessels on the posterolateral femoral neck and the posterior acetabular wall in hyperextension and external rotation as a possible cause of direct vascular damage, and subsequent femoral head necrosis in three adolescent female gymnasts we are reporting on.

Objectives

In order to ensure safety of the cell-based therapy for bone regeneration, we examined in vivo biodistribution of locally or systemically transplanted osteoblast-like cells generated from bone marrow (BM) derived mononuclear cells.