HIP ISSN 1120-7000 Hip Int 2017; 27 (5): 500-504 © 2017 Wichtg Publishing ORIGINAL RESEARCH ARTICLE risk, comorbidity rate, and a poorer rehabilitaton potental (5). It is important to note that there is another THA popula- ton with a near identcal set of technical problems, the so- called “complex primary” THA patents. These patents have bony defects discovered on radiographs or sometmes during the procedure itself, these again tend to be older and sufer from chronic diseases. Many approaches have been taken to try to overcome the difcultes of bone loss in revision THA to achieve a natural joint locaton. This includes the development of large acetab- ular cups and augments. These acetabular cups are usually fxed by fricton with a porous metal coat directly in contact with the pelvic surface, with or without the aid of cancellous screws. With high levels of bone loss in the pelvis, large ac- etabular cups and augments can act to eliminate the space caused by acetabular defects, thus improving the biomechan- ical functon of the revised joint (6). More recent developments to improve the long-term sta- bility of the joint include the development of large trabecular metal (TM) acetabular cups and augments. TM is sometmes known as porous metal, is rather ill-defned but generally re- garded as any metal-based material used in arthroplasty with a microstructure allowing at least an 80% porosity through- out the thickness of the component and similar to the archi- tecture of trabecular bone. TM confers beneft by: providing DOI: 10.5301/hipint.5000503 The impact of trabecular metal on hip centre of rotaton in revision and complex primary hip arthroplasty, a radiological review Carl O’Brien 1 , Cillian J. Keogh 1 , Ailish Hannigan 2 , Stephen Brennan 1 , Cian Kennedy 1 , Rehan Gul 1 , James A. Harty 1 1 Department of Orthopaedics, Cork University Hospital, Cork - Republic of Ireland 2 Department of Statstcs, Graduate Entry Medical School, University of Limerick, Cork - Republic of Ireland Introducton Total hip arthroplasty (THA) is a resoundingly successful procedure, but with an ageing populaton, the need for revi- sion has become increasingly prevalent (1-3). Revision THA presents a considerable technical challenge to surgeons. Many patents sufer from severe bone loss, which hampers the achievement of good integraton of the prosthesis with bone in a locaton that is bio-mechanically stable. This is es- pecially relevant with the acetabular cup, where surgeons ofen fnd large bony defects or incongruity at the pelvis (4). In the post-operatve period, patents with revision THA are faced with a much higher risk of aseptc loosening and contn- ued joint pain when compared to their primary THA counter- parts. This patent populaton also has a higher anaesthetc ABSTRACT Introducton: Total hip arthroplasty (THA) is a very successful procedure. Revision THA is becoming increasingly common. Recent developments to improve outcomes include the development of large trabecular metal (TM) acetabular cups and augments. There is a paucity of data on the beneft of these new techniques. Methods: A single-centre retrospectve review consistng of a radiological review of post-op revision THA antero- posterior pelvis. Data collecton was performed using the Irish Natonal Orthopaedic Register (INOR) and from a previous project. We used a technique developed by Fessy et al in 1999 to measure the centre of rotaton (COR) of the hip. We then compared our study to that of a study measuring the COR of healthy natve hips. Results: 127 revision THA analysed. Natve COR calculated by Fessy et al showed a mean horizontal (x) axis 33.6 mm (standard deviaton [SD] 5.74) and a vertcal (y) axis 16.4 mm (SD 4.67). Non-TM revisions showed a mean x axis of 29 mm (SD 3.9) and y axis 17.9 (SD 5.9). TM Augments had a mean x axis 29.2 mm (SD 7.9) and y axis of 21.5 (SD 8.4). TM Cups alone had a mean x axis 27 mm (SD 6.9) and y axis 22 mm (SD 10.18). Conclusions: COR of TM implants showed considerable deviaton from the norm. Non-TM implants showed a COR within acceptable physiological range. TM components consistently failed to restore a natural COR in our cohort. The implicatons of this remain uncertain but must be considered in any decision to use TM. Keywords: Centre of rotaton, Hip arthroplasty, Radiological, Total, Hip arthroplasty, Trabecular metal Accepted: February 11, 2017 Published online: July 1, 2017 Corresponding author: Cillian J. Keogh Department of Trauma and Orthopaedic Surgery Cork University Hospital Wilton, Cork, Republic of Ireland cillianjkeogh@RCSI.ie