• Use of articular antibiotic-eluting cement spacers during two-stage revision arthroplasty for prosthetic joint infection (PJI) is a long-established and proven adjunctive technique during first-stage surgery. Articular spacers come in many forms, either static or dynamic. The authors present an instructional review of current evidence regarding their use.

• A total of 45 studies (for spacer use in PJI involving either hip or knee) were analysed for data regarding eradication rate, functional outcomes, mechanical complications and the impact on second-stage surgery. A large number of case series and retrospective cohort studies were retrieved, with only a small number of prospective studies (2).

• High levels of infection eradication were commonly reported (>80%). Outcome scores were commonly reported as indicating good-to-excellent function and pain levels. Second-stage procedures were often not required when dynamic spacers were used. Static spacers were associated with more mechanical complications in both the hip and the knee. In the hip, dynamic spacers were more commonly associated with instability compared to static spacers. Consideration should be given to the use of dual-mobility or constrained definitive acetabular components in these cases at second-stage surgery.

• The use of antibiotic-eluting polymethylmethacrylate articular spacers in two-stage revision for PJI of hip and knee arthroplasty achieves a high rate of infection eradication. Dynamic spacers may confer a variety of benefits compared to static spacers, with a similar rate of infection eradication.

• Acetabular dysplasia is a significant problem in the spectrum of developmental dysplasia of hip. In a younger child, positioning the femoral head into the acetabulum helps in reciprocal remodeling of the acetabulum and correction of dysplasia. In an older child, the remodeling potential is limited and often the acetabular dysplasia needs surgical intervention in the form of a pelvic osteotomy.

• Thus, pelvic osteotomy forms an integral part of surgical management of hip dysplasia. The ultimate goal of these osteotomies is to preclude or postpone the development of osteoarthritis and add more years of life to the native hip.

• Pelvic osteotomies play a pivotal role in normalizing hip morphology. The choice of pelvic osteotomy depends on the age of a child, the type of dysplasia and the status of the tri-radiate cartilage.

• Several types of re-directional and reshaping pelvic osteotomies have been described in the literature to improve the stability and restore the anatomy and biomechanics of the dysplastic hip.

• This article attempts to review the current indications for various pelvic osteotomies with a brief description of their techniques along with the outcomes and complications published thus far. Besides, the guidelines to choose the right pelvic osteotomy are also provided.

• The aim of this systematic review is to assess the role of the prophylactic fixation of contralateral unaffected hip in unilateral slipped capital femoral epiphysis (SCFE) in children, focusing on the possible complications of this surgical procedure.

• A systematic review of medical literature was conducted, according to the Preferred Reporting Items for Systematic review and Meta-Analysis (PRISMA) statement, to analyse the complications of prophylactic contralateral hip fixation in unilateral paediatric SCFE. We registered the complications reported in the included studies, scoring their severity according to the orthopaedic adaptation of Clavien–Dindo classification.

• From 1695 studies primarily identified, 14 studies were finally included: 1 prospective cohort study, 4 retrospective case-control studies and 9 retrospective case series, with a total of 811 children diagnosed with unilateral SCFE and treated on the unaffected contralateral hip. Grade IV complications were very rare (0.37%), while the rate of grade III events was 8%. No death was recorded. The most frequent complication was unplanned further surgery (6.29%) that was an epiphyseal refixation, owing to the physiologic growth of the proximal femur, in 42 cases. Cannulated screws fixation showed to have a lower major complication rate than pinning with K-wires, 5.37% vs 17.95%.

• The prophylactic fixation of contralateral unaffected hip in paediatric unilateral SCFE is a safe procedure. Although a benefit-cost analysis on this topic has not been published yet, considering the low rate of complications, prophylactic hip fixation is a viable option for patients presenting with unilateral SCFE, to prevent the occurrence of severe hip deformity and avoid future invasive surgeries.

• There are advocates of both two-dimensional (2D) and three-dimensional (3D) templating methods for planning total hip replacement.

• The aim of this study was to compare the accuracy of implant size prediction when using 2D and 3D templating methods for total hip arthroplasty, as well as to compare the inter- and intra-observer reliability in order to determine whether currently available methods are sufficiently reliable and reproducible.

• Medline, EMBASE and PubMed were searched to identify studies that compared the accuracy of 2D and 3D templating for total hip replacement.

• Results were screened using the PRISMA flowchart and included studies were assessed for their level of evidence using the Oxford CEBM criteria. Non-randomized trials were critically appraised using the MINORS tool, whilst randomized trials were assessed using the CASP RCT checklist.

• A series of meta-analyses of the data for accuracy were also conducted.

• Ten studies reported that 3D templating is an accurate and reliable method of templating for total hip replacement. Six studies compared 3D templating with 2D templating, all of which concluded that 3D templating was more accurate, with three finding a statistically significant difference.

• The meta-analyses showed that 3D CT templating is the most accurate method.

• This review supports the hypothesis that 3D templating is an accurate and reliable method of preoperative planning, which is more accurate than 2D templating for predicting implant size. However, further research is needed to ascertain the significance of this improved accuracy and whether it will yield any clinical benefit.

• Hip, spine, and pelvis move in coordination with one another during activity, forming the lumbopelvic complex (LPC).

• These movements are characterized by the spinopelvic parameters sacral slope, pelvic tilt, and pelvic incidence, which define a patient’s morphotype.

• LPC kinematics may be classified by various systems, the most comprehensive of which is the Bordeaux Classification.

• Hip–spine relationships in total hip arthroplasty (THA) may influence impingement, dislocation, and edge loading.

• Historical ‘safe zones’ may not apply to patients with impaired spinopelvic mobility; adjustment of cup inclination and version and stem version may be necessary to achieve functional orientation and avert complications.

• Stem design, bearing surface (including dual mobility), and head size are part of the armamentarium to treat abnormal hip–spine relationships.

• Special attention should be directed to patients with adult spine deformity or fused spine because they are at increased risk of complications after THA.

• Robot-assisted total hip arthroplasty (THA), in comparison to conventional THA, improves radiographic outcomes, but it remains unclear whether it alters complication rates, clinical and functional outcomes, and implant survival.

• The purpose of this systematic overview was to summarize the findings of the most recent meta-analyses that compare clinical and surgical outcomes of robot-assisted versus conventional THA.

• Two readers independently conducted an electronic literature search, screening and data extraction from five electronic databases. Inclusion criteria were: meta-analyses evaluating robot-assisted versus conventional THA in terms of radiographic outcomes, clinical and functional scores, and complications and revision rates. The literature search returned 67 records, of which 14 were duplicates and 49 were excluded, leaving three meta-analyses published within the past two years for data extraction and analysis.

• The present overview of meta-analyses suggests that, compared to conventional THA (n = 3011), robot-assisted THA (n = 1813) improves component placement and reduces intraoperative complications. The overview also affirms that robot-assisted THA could extend surgery by 20 minutes, and increases risks of postoperative heterotopic ossification, dislocation, and revision. None of the meta-analyses found significant differences in clinical or functional scores between robot-assisted and conventional THA.

• Future studies and reviews should make a clear distinction between active and semi-active robotic assistance, address technology matureness, and describe the experience of surgeons with robotic assistance.

Cite this article: EFORT Open Rev 2021;6:1157-1165. DOI: 10.1302/2058-5241.6.200121

• To report clinical and radiographic outcomes of primary THA using three-dimensional (3D) image-based custom stems.

• This systematic review was performed according to PRISMA guidelines and registered with PROSPERO (CRD42020216079). A search was conducted using MEDLINE, Embase and Cochrane. Clinical studies were included if they reported clinical or radiographic outcomes of primary THA using 3D image-based custom stems. Studies were excluded if specific to patients with major hip anatomical deformities, or if not written in English.

• Fourteen studies were eligible for inclusion (n = 1936 hips). There was considerable heterogeneity in terms of manufacturer, proximal geometry, coating and length of custom stems. Revision rates ranged from 0% to 1% in the short-term, 0% to 20% in the mid-term, and 4% to 10% in the long-term, while complication rates ranged from 3% in the short-term, 0% to 11% in the mid-term and 0% to 4% in the long-term. Post-operative Harris hip scores ranged from 95 to 96 in the short-term, 80 to 99 in the mid-term, and 87 to 94 in the long-term. Radiographic outcomes were reported in eleven studies, although none reported 3D implant sizing or positioning, nor compared planned and postoperative hip architecture.

• Primary THA using 3D image-based custom stems in unselected patients provides limited but promising clinical and radiographic outcomes. Despite excellent survival, the evidence available in the literature remains insufficient to recommend their routine use. Future studies should specify proximal geometry, length, fixation, material and coating, as well as management of femoral offset and anteversion. The authors propose a classification system to help distinguish between custom stem designs based primarily on their proximal geometry and length.

Cite this article: EFORT Open Rev 2021;6:1166-1180. DOI: 10.1302/2058-5241.6.210053

• The purpose of this study was to compare the accuracy and the inter- and intra-observer reliability of preoperative digital 2D templating in prosthesis size prediction for the planning of cemented or uncemented THA.

• This study was registered in the NIHR PROSPERO database (ID: CRD42020216649) and conducted according to the PRISMA guidelines. A search of electronic databases in March 2021 found 29 papers overall. The quality of evidence was assessed using the IHE Quality Appraisal of Case Series Studies Checklist and the CASP Randomised Controlled Trials Checklist. A meta-analysis was conducted, and the accuracy was presented as proportions and the inter- and intra-observer reliability were measured using intraclass correlation coefficients (ICC).

• Accuracy within one prosthesis size (±1) for cemented stems was 0.89 (95% confidence interval (CI) 0.83–0.95), cemented cups 0.78 (95% CI 0.67–0.89), uncemented stems 0.74 (95% CI 0.66–0.82) and uncemented cups 0.73 (95% CI 0.67–0.79) (test of group differences: p = 0.010). Inter-observer reliability (ICC) for uncemented cups was 0.88 (95% CI 0.85–0.91), uncemented stems 0.86 (95% CI 0.81–0.91), cemented stems 0.69 (95% CI 0.54–0.84) and cemented cups 0.68 (95% CI 0.55–0.81) (test of group differences: p = 0.004). Due to lack of data, intra-observer reliability (ICC) could only be calculated for uncemented prostheses, which for the stems was 0.90 (95% CI 0.88–0.92) and for the cups was 0.87 (95% CI 0.83–0.90) (test of group differences: p = 0.124).

• The accuracy of preoperative digital templating is greater for cemented prostheses, but the inter-observer reliability is greater for uncemented prostheses. The intra-observer reliability showed a high level of agreement for uncemented prostheses.

Cite this article: EFORT Open Rev 2021;6:1020-1039. DOI: 10.1302/2058-5241.6.210048

• Total hip arthroplasty is performed more frequently in younger patients nowadays, making long-term bone stock preservation an important topic. A mechanism for late implant failure is periprosthetic bone loss, caused by stress shielding around the hip stem due to different load distribution. Short stems are designed to keep the physical loading in the proximal part of the femur to reduce stress shielding. The aim of this review is to give more insight into how short and anatomic stems behave and whether they succeed in preservation of proximal bone stock.

• A systematic literature search was performed to find all published studies on bone mineral density in short and anatomic hip stems. Results on periprosthetic femoral bone mineral density, measured with dual-energy X-ray absorptiometry (DEXA), were compiled and analysed per Gruen zone in percentual change.

• A total of 29 studies were included. In short stems, Gruen 1 showed bone loss of 5% after one year (n = 855) and 5% after two years (n = 266). Gruen 7 showed bone loss of 10% after one year and –11% after two years. In anatomic stems, Gruen 1 showed bone loss of 8% after one year (n = 731) and 11% after two years (n = 227). Gruen 7 showed bone loss of 14% after one year and 15% after two years.

• Short stems are capable of preserving proximal bone stock and have slightly less proximal bone loss in the first years, compared to anatomic stems.

Cite this article: EFORT Open Rev 2021;6:1040-1051. DOI: 10.1302/2058-5241.6.210030

• Modular neck (MN) implants can restore the anatomy, especially in deformed hips such as sequelae of development dysplasia.

• Early designs for MN implants had problems with neck fractures and adverse local tissue, so their use was restricted to limited indications.

• Results of the latest generation of MN prostheses seem to demonstrate that these problems have been at least mitigated.

• Given the results of the studies presented in this review, surgeons might consider MN total hip arthroplasty (THA) for a narrower patient selection when a complex reconstruction is required.

• Long MN THA should be avoided in case of body mass index > 30, and should be used with extreme caution in association with high offset femoral necks with long or extra-long heads. Cr-Co necks should be abandoned, in favour of a titanium alloy connection.

• Restoring the correct anatomic femoral offset remains a challenge in THA surgeries.

• MN implants have been introduced to try to solve this problem. The MN design allows surgeons to choose the appropriate degree and length of the neck for desired stability and range of motion.

Cite this article: EFORT Open Rev 2021;6:751-758. DOI: 10.1302/2058-5241.6.200064