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Introduction: Periacetabular osteotomy (PAO) is an established treatment for symptomatic acetabular dysplasia in skeletally mature individuals without arthritis. Pelvic nonunion and associated stress fractures are under-reported. Nonunited stress fractures can cause continued buttock pain and pelvic instability. The aim of this study is to report on our experience managing patients with ongoing pain following nonunion of PAO. Patients and methods: 8 patients presented to a tertiary referral pelvic service with symptomatic PAO nonunion between 2015-2018. All patients underwent open reduction internal fixation of the superior pubic ramus nonunion, with ipsilateral iliac autograft, at an average of 48.1 (15–82) months following initial osteotomy. Demographic and perioperative data were recorded. Follow-up was on average to 9.9 months, once union was confirmed radiographically. Results: All patients were female and average age was 31.8 (18–41) years. In 7/8 (87.5%) patients a modified Stoppa approach was successfully utilised. 1 patient required an ilioinguinal approach due to the amount of rotational correction. All patients went on to union at the superior pubic ramus and reported improvement in mechanical symptoms. 5/8 (62.5%) patients were noted to develop union of the posterior column or inferior pubic ramus stress fracture indirectly. 2/8 (25%) patients developed progression of intra-articular pain, despite restoration of pelvic stability. 1 patient required intraoperative transfusion due to femoral vein injury. There were no other complications seen in this series. Conclusions: To our knowledge, this is the largest case series of surgically managed PAO nonunion. Pelvic instability resulting from nonunion and stress fracture can be satisfactorily addressed by mobilising, grafting and plating the nonunion at the superior pubic ramus. The modified Stoppa approach is suitable in most cases, allowing excellent exposure whilst minimising the insult to soft tissues. The altered anatomy of the pelvis following PAO should be anticipated to reduce the risk to nearby neurovascular structures.

Avulsion fractures of the ischial tuberosity usually occur in skeletally immature athletes following eccentric contraction of the hamstrings. When displaced fractures are left untreated, subsequent non-union and proximal hamstring fibrosis may lead to chronic pain and reduced activity. However, the indications for and outcomes of operative fixation when presentation is delayed remain unclear. We report the case of a 14 year old male athlete who presented to our institution 6 weeks after sustaining a displaced ischial tuberosity avulsion fracture. He underwent open reduction and internal fixation using a cannulated screw system via a posterior approach, with excellent results at 18 months follow-up. We report our surgical findings in detail as well as a novel method for post-operatively assessing functional screw head prominence-the seated radiograph.

We carried out metal artefact-reduction MRI, three-dimensional CT measurement of the position of the component and inductively-coupled plasma mass spectrometry analysis of cobalt and chromium levels in whole blood on 26 patients with unexplained pain following metal-on-metal resurfacing arthroplasty. MRI showed periprosthetic lesions around 16 hips, with 14 collections of fluid and two soft-tissue masses. The lesions were seen in both men and women and in symptomatic and asymptomatic hips. Using three-dimensional CT, the median inclination of the acetabular component was found to be 55° and its positioning was outside the Lewinnek safe zone in 13 of 16 cases. Using inductively-coupled plasma mass spectrometry, the levels of blood metal ions tended to be higher in painful compared with well-functioning metal-on-metal hips. These three clinically useful investigations can help to determine the cause of failure of the implant, predict the need for future revision and aid the choice of revision prostheses.

Shoulder instability is a phenomenon, which has a variety of clinical presentations. Its complex nature has until recently been poorly understood. Inadequate understanding of the pathology of instability has been confounded by confusion over definitions and inadequate classification systems. As a result treatment failures have been observed in many of the specific pathologies. We propose a classification system, which challenges previous systems by being all inclusive and recognises that more than one pathology can occur in an individual shoulder. The system takes the form of a triangle with polar groups at each corner and specific subgroups mapped along each axis. It provides a usable framework for clinicians in the management of what can be complex problems.

BACKGROUND AND PURPOSE: Operative findings during revision of metal-on-metal hip arthroplasty (MOMHA) vary widely and can involve massive soft tissue and bone disruption. As a result, planning of theater time and resources is difficult, surgery is challenging, and outcomes are often poor. We describe our experience with revision of MOMHA and provide recommendations for management. PATIENTS AND METHODS: We present the findings and outcomes of 39 consecutive MOMHAs (in 35 patients) revised in a tertiary unit (median follow-up time 30 (12-54) months). The patients underwent a preoperative work-up including CT, metal artifact reduction sequence (MARS) MRI, and blood metal ion levels. RESULTS: We determined 5 categories of failure. 8 of 39 hips had conventional failure mechanisms including infection and impingement. Of the other 31 hips, 14 showed synovitis without significant disruption of soft tissue; 6 had a cystic pseudotumor with significant soft tissue disruption; 7 had significant osteolysis; and 4 had a solid pseudotumor. Each category of failure had specific surgical hazards that could be addressed preoperatively. There were 2 reoperations and 1 patient (2 hips) died of an unrelated cause. Median Oxford hip score (OHS) was 37 (9-48); median change (ΔOHS) was 17 (-10 to 41) points. ΔOHS was similar in all groups-except those patients with solid pseudotumors and those revised to metal-on-metal bearings, who fared worse. INTERPRETATION: Planning in revision MOMHA is aided by knowledge of the different categories of failure to enable choice of appropriate personnel, theater time, and equipment. With this knowledge, satisfactory outcomes can be achieved in revision of metal-on-metal hip arthroplasty.