• Possible indications for a rotating hinge or pure hinge implant in primary total knee arthroplasty (TKA) include collateral ligament insufficiency, severe varus or valgus deformity (> 20°) with relevant soft-tissue release, relevant bone loss, including insertions of collateral ligaments, gross flexion-extension gap imbalance, ankylosis and hyperlaxity.

• The use of hinged implants in primary TKA should be limited to the aforementioned selected indications, especially for elderly patients.

• Potential indications for a rotating hinge or pure hinge implant in revision TKA include infection, aseptic loosening, instability and bone loss.

• Rotating hinge knee implants have a 10-year survivorship in the range of 51% to 92.5%.

• Complication rates of rotating hinge knee implants are in the range of 9.2% to 63%, with infection and aseptic loosening as the most common complications.

• Although the results reported in the literature are inconsistent, clinical results generally depend on the implant design, appropriate technical use and adequate indications.

• Considering that the revision of implants with long cemented stems can be challenging, in the future it would be better to use shorter stems in modular versions of hinged knee implants.

Cite this article: EFORT Open Rev 2019;4:121-132. DOI: 10.1302/2058-5241.4.180056

• With an incidence of 5.8 per 100,000 per year, patellar dislocations are commonly seen in the emergency department. Surprisingly, there are only a few studies available that focus on the results of the different non-surgical treatment options after first-time patellar dislocation. The aim of this review is to provide an overview of the most recent and relevant studies on the rationales and results of the non-surgical treatment for first-time patellar dislocation.

• Patellar instability mainly affects young and active patients, with a peak incidence of 29 per 100 000 per year in adolescents. The medial patellofemoral ligament, a main passive restraint for lateral translation of the patella, is torn in lateral patellofemoral dislocations. Treatment of first-time patellar dislocation can be either conservative or surgical.

• There are two options in conservative management of first-time patellar dislocation: immobilization using a cylinder cast or removable splint, or, second, functional mobilization after applying a brace or patellar tape.

• The current available literature of conservative treatment after a first-time patellar dislocation is little and of low quality of evidence. Conclusions should be drawn with care, new research focussing on non-surgical treatment is therefore strongly needed.

Cite this article: EFORT Open Rev 2019;4:110-114. DOI: 10.1302/2058-5241.4.180016

• Patient-reported instability is a common complaint amongst those with knee arthritis.

• Much research has examined the assessment of self-reported instability in the knee; however, no definitive quantitative measure of instability has been developed.

• This review focuses on the current literature investigating the nature of self-reported instability in the arthritic knee and discusses the possibilities of further investigation.

Cite this article: EFORT Open Rev 2019;4:70-76. DOI: 10.1302/2058-5241.4.170079

• For multifactorial reasons an estimated 20% of patients remain unsatisfied after total knee arthroplasty (TKA).

• Appropriate tension of the soft tissue envelope encompassing the knee is important in total knee arthroplasty and soft tissue imbalance contributes to several of the foremost reasons for revision TKA, including instability, stiffness and aseptic loosening.

• There is debate in the literature surrounding the optimum way to achieve balancing of a total knee arthroplasty and there is also a lack of an accepted definition of what a balanced knee replacement is.

• It may be intuitive to use the native knee as a model for balancing; however, there are many difficulties with translating this into a successful prosthesis.

• One of the foundations of TKA, as described by Insall, was that although the native knee has more weight transmitted through the medial compartment this was to be avoided in a TKA as it would lead to uneven wear and early failure. There is a focus on achieving symmetrical tension and pressure and subsequent ‘balance’ in TKA, but the evidence from cadaveric studies is that the native knee is not symmetrically balanced.

• As we are currently trying to design an implant that is not based on its anatomical counterpart, is it possible to create a truly balanced prosthesis or to even to define what that balance is? The authors have reviewed the current evidence surrounding TKA balancing and its relationship with the native knee.

Cite this article: EFORT Open Rev 2018;3:614-619. DOI: 10.1302/2058-5241.3.180008.

• Despite a good outcome for many patients, approximately 20% of patients experience chronic pain after total knee arthroplasty (TKA).

• Chronic pain after TKA can affect all dimensions of health-related quality of life, and is associated with functional limitations, pain-related distress, depression, poorer general health and social isolation.

• In both clinical and research settings, the approach to assessing chronic pain after TKA needs to be in-depth and multidimensional to understand the characteristics and impact of this pain. Assessment of this pain has been inadequate in the past, but there are encouraging trends for increased use of validated patient-reported outcome measures.

• Risk factors for chronic pain after TKA can be considered as those present before surgery, intraoperatively or in the acute postoperative period. Knowledge of risk factors is important to guide the development of interventions and to help to target care. Evaluations of preoperative interventions which optimize pain management and general health around the time of surgery are needed.

• The causes of chronic pain after TKA are not yet fully understood, although research interest is growing and it is evident that this pain has a multifactorial aetiology, with a wide range of possible biological, surgical and psychosocial factors that can influence pain outcomes.

• Treatment of chronic pain after TKA is challenging, and evaluation of combined treatments and individually targeted treatments matched to patient characteristics is advocated. To ensure that optimal care is provided to patients, the clinical- and cost-effectiveness of multidisciplinary and individualized interventions should be evaluated.

Cite this article: EFORT Open Rev 2018;3:461-470. DOI: 10.1302/2058-5241.3.180004

• Despite the excellent success rates of modern implants, unicompartmental knee arthroplasty (UKA) continues to show relatively high failure and revision rates, especially when compared with total knee arthroplasty (TKA).

• These higher rates of failure and revision are mainly observed during the early (< 5 years) post-operative period and are often due to incorrect indications and/or surgical errors.

• The correct clinical and radiological indications for UKA have therefore been analysed and correlated as far as possible with the principal mechanisms and timing of failures of UKA.

Cite this article: EFORT Open Rev 2018;3:442-448. DOI: 10.1302/2058-5241.3.170060

• Total knee arthroplasty (TKA) in patients affected by poliomyelitis is technically challenging owing to abnormal anatomical features including articular and metaphyseal angular deformities, external rotation of the tibia, excessive valgus alignment, bone loss, narrowness of the femoral and tibial canals, impaired quadriceps strength, flexion contractures, genu recurvatum and ligamentous laxity. Little information is available regarding the results and complications of TKA in this challenging group of patients.

• We carried out a systematic review of the literature to determine the functional outcome, complications and revision rates of TKA in patients with poliomyelitis-affected knees. Six studies including 82 knees met the inclusion criteria and were reviewed. The mean patient age was 63 years (45 to 85) and follow-up was 5.5 years (0.5 to 13).

• All studies reported significant improvement in knee function following TKA. There were six failures requiring revision surgery in 82 cases (7%) occurring at a mean of 6.2 years (0.4 to 12). The reasons for revision surgery were aseptic loosening (17%, n=1), infection (33%, n=2), periprosthetic fracture (17%, n=1) and instability (33%, n=2). Thirty-six knees had a degree of recurvatum pre-operatively (44%), which was in the range of 5° to 30°. Ten of these knees (28%) developed recurrent recurvatum post-operatively.

• The findings support the use of TKA in patients with poliomyelitis-affected knees. The post-operative functional outcome is similar to other patients; however, the revision rate is higher. Quadriceps muscle power appears to be an important prognostic factor for functional outcome and the use of constrained implant designs is recommended in the presence of less than antigravity quadriceps strength.

Cite this article: EFORT Open Rev 2018;3:358-362. DOI: 10.1302/2058-5241.3.170028

• An age younger than 60 years, a body weight of 180 lb (82 kg) or more, performing heavy work, having chondrocalcinosis and having exposed bone in the patellofemoral (PF) joint are not contraindications for unicompartmental knee arthroplasty (UKA).

• Severe wear of the lateral facet of the PF joint with bone loss and grooving is a contraindication for UKA.

• Medial UKA should only be performed in cases of severe osteoarthritis (OA) as shown in pre-operative X-rays, with medial bone-on-bone contact and a medial/lateral ratio of < 20%.

• The post-operative results of UKA are generally good. Medium-term and long-term studies have reported acceptable results at 10 years, with implant survival greater than 95% for UKAs performed for medial OA or osteonecrosis and for lateral UKA, especially when fixed-bearing implants are used.

• When all implant-related re-operations are considered, the 10-year survival rate is 94%, and the 15-year survival rate is 91%.

• Aseptic loosening is the principal failure mechanism in the first few years in mobile-bearing implants, whereas OA progression causes most failures in later years in fixed-bearing implants.

• The overall complication rate and the comprehensive re-operation rate are comparable in both mobile bearings and fixed bearings.

• The survival likelihood of the all-polyethylene UKA implant is similar to that of metal-backed modular designs for UKA.

• Notable cost savings of approximately 50% can be achieved with an outpatient UKA surgery protocol. Outpatient surgery for UKA is efficacious and safe, with satisfactory clinical results thus far.

Cite this article: EFORT Open Rev 2018;3:363-373. DOI: 10.1302/2058-5241.3.170048

• High tibial osteotomy (HTO) is a relatively conservative surgical option in the management of medial knee pain. Thus far, the outcomes have been variable, and apparently worse than the arthroplasty alternatives when judged using conventional metrics, owing in large part to uncertainty around the extent of the correction planned and achieved.

• This review paper introduces the concept of detailed 3D planning of the procedure, and describes the 3D printing technology that enables the plan to be performed.

• The different ways that the osteotomy can be undertaken, and the varying guide designs that enable accurate registration are discussed and described. The system accuracy is reported.

• In keeping with other assistive technologies, 3D printing enables the surgeon to achieve a preoperative plan with a degree of accuracy that is not possible using conventional instruments. With the advent of low dose CT, it has been possible to confirm that the procedure has been undertaken accurately too.

• HTO is the ‘ultimate’ personal intervention: the amount of correction needed for optimal offloading is not yet completely understood.

• For the athletic person with early medial joint line overload who still runs and enjoys life, HTO using 3D printing is an attractive option. The clinical effectiveness remains unproven.

Cite this article: EFORT Open Rev 2018;3 DOI: 10.1302/2058-5241.3.170075.

• In suitable patients, unicompartmental knee arthroplasty (UKA) offers a number of advantages compared with total knee arthroplasty. However, the procedure is technically demanding, with a small tolerance for error. Assistive technology has the potential to improve the accuracy of implant positioning.

• This review paper describes the concept of detailed UKA planning in 3D, and the 3D printing technology that enables a plan to be delivered intraoperatively using patient-specific instrumentation (PSI).

• The varying guide designs that enable accurate registration are discussed and described. The system accuracy is reported.

• Future studies need to ascertain whether accuracy for low-volume surgeons can be delivered in the operating theatre using PSI, and reflected in improved patient reported outcome measures, and lower revision rates.

Cite this article: EFORT Open Rev 2018;3 DOI: 10.1302/2058-5241.3.180001