Abstract. Background. The Oxford Domed Lateral (ODL) Unicompartmental Knee Replacement (UKR) has some advantages over other lateral UKRs, but the mobile bearing dislocation rate is high (1–6%). Medial dislocations, with the bearing lodged on the tibial component wall, are most common. Anterior/posterior dislocations are rare. For a dislocation to occur distraction of the joint is required. We have developed and validated a dislocation analysis tool based on a computer model of the ODL with a robotics path-planning algorithm to determine the Vertical Distraction required for a Dislocation (VDD), which is inversely related to the risk of dislocation. Objectives. To modify the ODL design so the risk of medial dislocation decreases to that of an anterior/posterior dislocation. Methods. The components were modified using Solidworks. For each modification the dislocation analysis tool was used to determine the VDD for medial dislocation (with bearing 0–6mm from the tibial wall). This was compared with the original implant to identify the modifications that were most effective at reducing the dislocation risk. These modifications were combined into a final design, which was assessed. Results. Modifying the tibial component plateau, changing the femoral component width and making the bearing wider medially had little effect on VDD. Shifting the femoral sphere centre medially decreased VDD. Shifting the femoral sphere laterally, increasing tibial wall height and increasing bearing width laterally increased VDD. A modified implant with a femoral sphere centre 3mm lateral, wall 2.8mm higher, and bearing 2mm wider laterally, implanted so the bearing is ≤4mm from the tibial wall with a bearing thickness ≥4mm had a minimum VDD for medial dislocation of 5.75mm, which is larger than the minimum VDD for anterior/posterior dislocation of 5.5mm. Conclusions. A modified ODL design should decrease the dislocation rate to an acceptable level, however, further testing in cadavers is required. Declaration of Interest. (a) fully declare any financial or other potential conflict of interest

Introduction. The highest incidence of recurrent shoulder instability is in young patients, surgical repair can reduce recurrent instability and improve shoulder function. This has led to an increasing rate of stabilisation and use of MRI to identify associated injuries in first time dislocations. MRA has the benefit of distending the joint and is becoming increasingly used. The aim of this study is to establish the sensitivity and specificity of MRA in the investigation of patients with traumatic anterior shoulder dislocations. Methods. A retrospective analysis of patients undergoing both magnetic resonance arthrography and arthroscopy after a traumatic anterior shoulder dislocation between January 2011 and 2014. Images were interpreted by eight musculoskeletal radiologists and arthroscopic findings were obtained from surgical notes and used as a reference. The sensitivity, specificity and positive predictive value for the different injuries were calculated. Results. 60 patients were reviewed; 88% were male, mean age was 28 years (range 18 to 50) and 27% were primary dislocations. The overall sensitivity and specificity of MRA to all associated injuries was 0.9 (CI 0.83–0.95) and 0.94 (CI 0.9–0.96) retrospectively. The lowest sensitivity was seen in osseous Bankart 0.8 (CI 0.44–0.96) and SLAP lesions 0.5 (CI 0.14–0.86). Conclusion. MRA has a high sensitivity when used to identify associated injuries in shoulder dislocation although in 8 patients (13%) arthroscopy identified an additional injury. The overall agreement between MRA and arthroscopic findings was good but identification of GHL and rotator cuff injuries was poor. Level of Evidence. IV. Conflict of Interests. The authors confirm that they have no relevant financial disclosures or conflicts of interest. Ethical approval was not sought as this was a systematic review

Primary traumatic anterior dislocations of the shoulder are common injuries which are complicated by persistent instability in a high proportion of patients. Surgery is successful and has been well described in the literature. Current controversies centre on the role of open and arthroscopic techniques. We describe the outcomes of a new mini-incision surgical (MIS) technique which was developed within our institution. 27 patients with traumatic shoulder instability (2 bilateral) were prospectively entered into a database between June 1998 and March 2008. The mean age was 31 years and the mean follow up period was 53 months. 29 shoulders underwent diagnostic shoulder arthroscopy and mini-incision surgery using a delto-pectoral approach and 3 bio-absorbable anchors. Patients reported no re-dislocation in 24 shoulders (83%). 5 shoulders, including one with a bony Bankart lesion, re-dislocated with additional trauma. One shoulder required revision to a Bristow-Latarjet. Satisfaction was very good in 16 and good in 9 shoulders (83%). 19 patients had minimal or no pain. 8 patients experienced moderate shoulder pain with the other two complaining of severe pain. QuickDASH scores were encouraging. Our technique combines the ability to appreciate all shoulder pathology arthroscopically with the visualisation gained in open Bankart surgery. Functionally, patients do well. The higher than expected re-dislocation rate is concerning. We advise that long term outcomes are needed

Objectives

Intra-articular injections of local anaesthetics (LA), glucocorticoids (GC), or hyaluronic acid (HA) are used to treat osteoarthritis (OA). Contrast agents (CA) are needed to prove successful intra-articular injection or aspiration, or to visualize articular structures dynamically during fluoroscopy. Tranexamic acid (TA) is used to control haemostasis and prevent excessive intra-articular bleeding. Despite their common usage, little is known about the cytotoxicity of common drugs injected into joints. Thus, the aim of our study was to investigate the effects of LA, GC, HA, CA, and TA on the viability of primary human chondrocytes and tenocytes in vitro.

Reported rates of dislocation in hip hemiarthroplasty (HA) for the treatment of intra-capsular fractures of the hip, range between 1% and 10%. HA is frequently performed through a direct lateral surgical approach. The aim of this study is to determine the contribution of the anterior capsule to the stability of a cemented HA through a direct lateral approach.

A total of five whole-body cadavers were thawed at room temperature, providing ten hip joints for investigation. A Thompson HA was cemented in place via a direct lateral approach. The cadavers were then positioned supine, both knee joints were disarticulated and a digital torque wrench was attached to the femur using a circular frame with three half pins. The wrench applied an external rotation force with the hip in extension to allow the hip to dislocate anteriorly. Each hip was dislocated twice; once with a capsular repair and once without repairing the capsule. Stratified sampling ensured the order in which this was performed was alternated for the paired hips on each cadaver.

Comparing peak torque force in hips with the capsule repaired and peak torque force in hips without repair of the capsule, revealed a significant difference between the ‘capsule repaired’ (mean 22.96 Nm, standard deviation (sd) 4.61) and the ‘capsule not repaired’ group (mean 5.6 Nm, sd 2.81) (p < 0.001). Capsular repair may help reduce the risk of hip dislocation following HA.

Cite this article: Bone Joint J 2015;97-B:141–4.

Dislocation remains a major concern after total hip replacement, and is often attributed to malposition of the components. The optimum position for placement of the components remains uncertain. We have attempted to identify a relatively safe zone in which movement of the hip will occur without impingement, even if one component is positioned incorrectly. A three-dimensional computer model was designed to simulate impingement and used to examine 125 combinations of positioning of the components in order to allow maximum movement without impingement. Increase in acetabular and/or femoral anteversion allowed greater internal rotation before impingement occurred, but decreases the amount of external rotation. A decrease in abduction of the acetabular components increased internal rotation while decreasing external rotation. Although some correction for malposition was allowable on the opposite side of the joint, extreme degrees could not be corrected because of bony impingement.

We introduce the concept of combined component position, in which anteversion and abduction of the acetabular component, along with femoral anteversion, are all defined as critical elements for stability.