• Total hip arthroplasty (THA) is one of the most successful surgical procedures – reducing pain and providing functional improvement. However, THA instability is a disabling condition and remains the most common indication for revision THA. To combat the risk of instability, the concept of dual mobility (DM) was developed. This article provides a comprehensive review of DM in the literature.

• Widespread use of first-generation DM was limited due to concern regarding wear of the polyethylene head and the unique complication of intraprosthetic dislocation (IPD). Implant modifications using highly cross-linked, durable polyethylene and a smooth, cylindrical femoral neck have all but eliminated IPD in contemporary DM.

• In multiple studies, DM demonstrates statistically significant reductions in dislocation rates comparative to standard bearing primary THA. These results have been particular promising in high-risk patient populations and femoral neck fractures – where low dislocation rates and improved functional outcomes are a recurrent theme. From an economic perspective, DM is equally exciting – with lower accrued costs and higher accrued utility comparative to standard bearing THA.

• Longer-term clinical evidence and higher-quality prospective comparative studies are required to strengthen current research. Dual mobility may well represent the future gold standard for THA in high-risk patient populations and femoral neck fractures, but due diligence of long-term performance is needed before recommendations for widespread use can be justified.

Cite this article: EFORT Open Rev 2019;4:640-646. DOI: 10.1302/2058-5241.4.180089

• Prosthetic joint infection (PJI) is associated with poor clinical outcomes and is expensive to treat.

• Although uncommon overall (affecting between 0.5% and 2.2% of cases), PJI is one of the most commonly encountered complications of joint replacement and its incidence is increasing, putting a significant burden on healthcare systems.

• Once established, PJI is extremely difficult to eradicate as bacteria exist in biofilms which protect them from antibiotics and the host immune response.

• Improved understanding of the microbial pathology in PJI has generated potential new treatment strategies for prevention and eradication of biofilm associated infection including modification of implant surfaces to prevent adhesion of bacteria.

• Much research is currently ongoing looking at different implant surface coatings and modifications, and although most of this work has not translated into clinical medicine there has been some early clinical success.

Cite this article: EFORT Open Rev 2019;4:633-639. DOI: 10.1302/2058-5241.4.180095

• Robotic total hip arthroplasty (THA) improves accuracy in achieving the planned acetabular cup positioning compared to conventional manual THA.

• Robotic THA improves precision and reduces outliers in restoring the planned centre of hip rotation compared to conventional manual THA.

• Improved accuracy in restoring hip biomechanics and acetabular cup positioning in robotic THA have not translated to any differences in early functional outcomes, correction of leg-length discrepancy, or postoperative complications compared to conventional manual THA.

• Limitations of robotic THA include substantive installation costs, additional radiation exposure, steep learning curves for gaining surgical proficiency, and compatibility of the robotic technology with a limited number of implant designs.

• Further higher quality studies are required to compare differences in conventional versus robotic THA in relation to long-term functional outcomes, implant survivorship, time to revision surgery, and cost-effectiveness.

Cite this article: EFORT Open Rev 2019;4:618-625. DOI: 10.1302/2058-5241.4.180088

• Preoperative planning is mandatory to achieve the restoration of a correct and personalized biomechanics of the hip.

• The radiographic review is the first and fundamental step in the planning. Limb or pelvis malpositioning during the review results in mislead planning.

• Correct templating is possible using three different methods: acetate templating on digital X-ray, digital 2D templating on digital X-ray and 3D digital templating on CT scan.

• Time efficiency, costs, reproducibility and accuracy must be considered when comparing different templating methods. Based on these parameters, acetate templating should not be abandoned; digital templating allows a permanent record of planning and can be electronically viewed by different members of surgical team; 3D templating is intrinsically more accurate. There is no evidence in the few recently published studies that 3D templating impacts positively on clinical outcomes except in difficult cases.

• The transverse acetabular ligament (TAL) is a reliable intraoperative soft tissue reference to set cup position.

• Spine–hip relations in osteoarthritic patients undergoing hip joint replacement must be considered.

Cite this article: EFORT Open Rev 2019;4:626-632. DOI: 10.1302/2058-5241.4.180075

• Many studies in the literature have been carried out to evaluate the various cellular and molecular processes involved in osteogenesis.

• Angiogenesis and bone formation work closely together in this group of disorders. Hypoxia-inducible factor (HIF) which is stimulated in tissue hypoxia triggers a cascade of molecular processes that helps manage this physiological deficiency.

• However, there still remains a paucity of knowledge with regard to how sickle cell bone pathology, in particular avascular necrosis, could be altered when it comes to osseointegration at the molecular level.

• Hypoxia-inducible factor has been identified as key in mediating how cells adapt to molecular oxygen levels.

• The aim of this review is to further elucidate the physiology of hypoxia-inducible factor with its various pathways and to establish what role this factor could play in altering the disease pathophysiology of avascular necrosis caused by sickle cell disease and in improving osseointegration.

• This review article also seeks to propose certain research methodology frameworks in exploring how osseointegration could be improved in sickle cell disease patients with total hip replacements and how it could eventually reduce their already increased risk of undergoing revision surgery.

Cite this article: EFORT Open Rev 2019;4:567-575. DOI: 10.1302/2058-5241.4.180030

• Hip instability following total hip arthroplasty (THA) remains a major challenge and is one of the main causes of revision surgery.

• Dual mobility (DM) implants have been introduced to try to overcome this problem. The DM design consists of a small femoral head captive and mobile within a polyethylene liner.

• Numerous studies have shown that DM implants reduce the rate of dislocation compared to fixed-bearing inserts.

• Early designs for DM implants had problems with wear and intra-prosthetic dislocations, so their use was restricted to limited indications.

• The results of the latest generation of DM prostheses demonstrate that these problems have been overcome. Given the results of these studies presented in this review, surgeons may now consider DM THA for a wider patient selection.

Cite this article: EFORT Open Rev 2019;4:541-547. DOI: 10.1302/2058-5241.4.180045

• Ankylosing Spondylitis (AS) can commonly involve the hip joint and cause significant mobility problems. Total hip arthroplasty (THA) on a single side alone will not restore mobility in patients with bilateral disease.

• We performed a systematic review of the available literature to determine the changes in objective outcome measures and complications of bilateral THA in patients with advanced AS. Four studies, a total of 114 THAs, were included in the study. The average patient age was 32.9 years and the average follow-up time was 59.5 months.

• All studies reported a significant improvement in hip function, patient satisfaction and patient mobility following bilateral THA. Harris Hip Score (HHS) improved by a mean of 60.6 points post-operatively.

• Complications included five intra-operative fractures (4.4%) and three transient nerve palsies (2.6%). There were two dislocations (1.8%) that were successfully managed with closed reduction. Seven hips required revision, with the most common cause being aseptic loosening. Twelve hips (10.5%) developed heterotopic ossification consistent with Brooker Class 1 or 2 with no reports of re-ankylosis.

• This review suggests that bilateral THA is a safe and effective treatment of advanced hip disease in AS. Attention must be paid to the highly demanding technical aspects of this procedure to reduce the risk of significant complications.

• Debate still exists on the ideal prosthesis, fixation method and approach to use but this review presents data from several series of uncemented prostheses that have good post-operative results.

Cite this article: EFORT Open Rev 2019;4:476-481. DOI: 10.1302/2058-5241.4.180047

• Traumatic neurological lesions may lead to development of heterotopic ossification. These cases are classified as ‘neurogenic heterotopic ossifications’ (NHOs). The associated neurological lesions can be caused by cranial trauma or spinal cord injury and may sometimes include a local trauma.

• NHOs that form around the hip joints are of particular interest because they often cause the patient to avoid the sitting position or the resumption of walking.

• Whilst NHO can involve the knee, shoulder and elbow joints, hip-involving NHOs are more numerous, and sometimes develop in close contact with vascular or neurological structures.

• Multi-disciplinary clinical examination is fundamental to evaluate patients for surgical intervention and to define the objectives of the surgery. The best investigation to define an NHO mass is a computerized tomography (CT) scan.

• Resection is performed to liberate a fused joint to provide functionality, and this need not be exhaustive if it is not necessary to increase the range of motion.

• While recurrence does occur post-surgery, a partial resection does not pose a greater risk of recurrence and there are no adjuvant treatments available to reduce this risk.

• The greatest risks associated with NHO surgical resection are infection and haematoma; these risks are very high and must be considered when evaluating patients for surgery.

Cite this article: EFORT Open Rev 2019;4 DOI: 10.1302/2058-5241.4.180098

• Osteonecrosis of the femoral head is a disabling pathology affecting a young population (average age at treatment, 33 to 38 years) and is the most important cause of total hip arthroplasty in this population. It reflects the endpoint of various disease processes that result in a decrease of the femoral head blood flow.

• The physiopathology reflects an alteration of the vascularization of the fine blood vessels irrigating the anterior and superior part of the femoral head. This zone of necrosis is the source of the loss of joint congruence that leads to premature wear of the hip.

• Several different types of medication have been developed to reverse the process of ischemia and/or restore the vascularization of the femoral head. There is no consensus yet on a particular treatment.

• The surgical treatments aim to preserve the joint as far as the diagnosis could be made before the appearance of a zone of necrosis and the loss of joint congruence. They consist of bone marrow decompressions, osteotomies around the hip, vascular or non-vascular grafts.

• Future therapies include the use of biologically active molecules as well as implants impregnated with biologically active tissue.

Cite this article: EFORT Open Rev 2019;4:85-97. DOI: 10.1302/2058-5241.4.180036

• Total hip arthroplasty (THA) is one of the most commonly performed orthopaedic procedures. Some concern exists that trainee-performed THA may adversely affect patient outcomes. The aim of this meta-analysis was to compare outcomes following THA performed by surgical trainees and consultant surgeons.

• A systematic search was performed to identify articles comparing outcomes following trainee- versus consultant-performed THA. Outcomes assessed included rate of revision surgery, dislocation, deep infection, mean operation time, length of hospital stay and Harris Hip Score (HHS) up to one year. A meta-analysis was conducted using odds ratios (ORs) and weighted mean differences (WMDs). A subgroup analysis for supervised trainees versus consultants was also performed.

• The final analysis included seven non-randomized studies of 40 810 THAs, of which 6393 (15.7%) were performed by trainees and 34 417 (84.3%) were performed by consultants. In total, 5651 (88.4%) THAs in the trainee group were performed under supervision. There was no significant difference in revision rate between the trainee and consultant groups (OR 1.09; p = 0.51). Trainees took significantly longer to perform THA compared with consultants (WMD 12.9; p < 0.01). The trainee group was associated with a lower HHS at one year compared with consultants (WMD -1.26; p < 0.01). There was no difference in rate of dislocation, deep infection or length of hospital stay between the two groups.

• The present study suggests that supervised trainees can achieve similar clinical outcomes to consultant surgeons, with a slightly longer operation time. In selected patients, trainee-performed THA is safe and effective.

Cite this article: EFORT Open Rev 2019;4:44-55. DOI: 10.1302/2058-5241.4.180034.