Aims

Periprosthetic fractures (PPFs) around the knee are challenging injuries. This study aims to describe the characteristics of knee PPFs and the impact of patient demographics, fracture types, and management modalities on in-hospital mortality.

The June 2023 Hip & Pelvis Roundup³⁶⁰ looks at: Machine learning to identify surgical candidates for hip and knee arthroplasty: a viable option?; Poor outcome after debridement and implant retention; Can you cement polyethylene liners into well-fixed acetabular shells in hip revision?; Revision stem in primary arthroplasties: the Exeter 44/0 125 mm stem; Depression and anxiety: could they be linked to infection?; Does where you live affect your outcomes after hip and knee arthroplasties?; Racial disparities in outcomes after total hip arthroplasty and total knee arthroplasty are substantially mediated by socioeconomic disadvantage both in black and white patients.

Literature surrounding artificial intelligence (AI)-related applications for hip and knee arthroplasty has proliferated. However, meaningful advances that fundamentally transform the practice and delivery of joint arthroplasty are yet to be realized, despite the broad range of applications as we continue to search for meaningful and appropriate use of AI. AI literature in hip and knee arthroplasty between 2018 and 2021 regarding image-based analyses, value-based care, remote patient monitoring, and augmented reality was reviewed. Concerns surrounding meaningful use and appropriate methodological approaches of AI in joint arthroplasty research are summarized. Of the 233 AI-related orthopaedics articles published, 178 (76%) constituted original research, while the rest consisted of editorials or reviews. A total of 52% of original AI-related research concerns hip and knee arthroplasty (n = 92), and a narrative review is described. Three studies were externally validated. Pitfalls surrounding present-day research include conflating vernacular (“AI/machine learning”), repackaging limited registry data, prematurely releasing internally validated prediction models, appraising model architecture instead of inputted data, withholding code, and evaluating studies using antiquated regression-based guidelines. While AI has been applied to a variety of hip and knee arthroplasty applications with limited clinical impact, the future remains promising if the question is meaningful, the methodology is rigorous and transparent, the data are rich, and the model is externally validated. Simple checkpoints for meaningful AI adoption include ensuring applications focus on: administrative support over clinical evaluation and management; necessity of the advanced model; and the novelty of the question being answered.

Cite this article: Bone Joint J 2022;104-B(12):1292–1303.

Aims

Unicompartmental and total knee arthroplasty (UKA and TKA) are successful treatments for osteoarthritis, but the solid metal implants disrupt the natural distribution of stress and strain which can lead to bone loss over time. This generates problems if the implant needs to be revised. This study investigates whether titanium lattice UKA and TKA implants can maintain natural load transfer in the proximal tibia.

Aims

Metal allergy in knee arthroplasty patients is a controversial topic. We aimed to conduct a scoping review to clarify the management of metal allergy in primary and revision total knee arthroplasty (TKA).

Aims

For many designs of total knee arthroplasty (TKA) it remains unclear whether cemented or uncemented fixation provides optimal long-term survival. The main limitation in most studies is a retrospective or non-comparative study design. The same is true for comparative trials looking only at the survival rate as extensive sample sizes are needed to detect true differences in fixation and durability. Studies using radiostereometric analysis (RSA) techniques have shown to be highly predictive in detecting late occurring aseptic loosening at an early stage. To investigate the difference in predicted long-term survival between cemented, uncemented, and hybrid fixation of TKA, we performed a randomized controlled trial using RSA.

Aims

Our objective is to describe our early and mid-term results with the use of a new simple primary knee prosthesis as an articulating spacer in planned two-stage management for infected knee arthroplasty. As a second objective, we compared outcomes between the group with a retained first stage and those with a complete two-stage revision.

Aims

Second-generation metal-on-metal (MoM) articulations in total hip arthroplasty (THA) were introduced in order to reduce wear-related complications. The current study reports on the serum cobalt levels and the clinical outcome at a minimum of 20 years following THA with a MoM (Metasul) or a ceramic-on-polyethylene (CoP) bearing.

Aims

Antibiotic-loaded bone cements (ALBCs) may offer early protection against the formation of bacterial biofilm after joint arthroplasty. Use in hip arthroplasty is widely accepted, but there is a lack of evidence in total knee arthroplasty (TKA). The objective of this study was to evaluate the use of ALBC in a large population of TKA patients.

Aims

The aim of this study was to give estimates of the incidence of component incompatibility in hip and knee arthroplasty and to test the effect of an online, real-time compatibility check.

Aims

The outcomes of total knee arthroplasty (TKA) depend on many factors. The impact of implant design on patient-reported outcomes is unknown. Our goal was to evaluate the patient-reported outcomes and satisfaction after primary TKA in patients with osteoarthritis undergoing primary TKA using five different brands of posterior-stabilized implant.

INTRODUCTION. Medial ball and socket knee designs have a long history but are not yet widely used. The Saiph medial ball and socket knee passed preclinical testing before an introductory cohort of 20 patients were studied in detail for 2 years. Subsequently a multicenter study was undertaken by the developing surgeons. METHODS. We report the minimum 5-year follow-up of the first 102 Saiph knee replacements implanted in Australia as part of a step-wise or phased introduction of this device to the market. These 102 consecutive patients were recruited to the study at two centers in Australia. Revisions, complications and adverse events were collected. Patient reported scores including EQ-5D, Oxford Knee Score (OKS), Knee Injury and Osteoarthritis Outcome Score (KOOS) and Kujala and range of motion satisfaction and forgotten joint score were collected. Data were collected pre-operatively and at one to two years post-operatively and at a minimum of five years. RESULTS. The average age of the patients was 67.2 years (range, 47 to 85) and average BMI was 29. There were 53% female and 47% male patients. There were two revisions performed – one for infection and one for arthrofibrosis. There were no device related failures or adverse events reported. The OKS improved from 21 pre-operatively to 43 post-operatively. KOOS improvement pre-operative to post-operative was 51 to 88 (symptoms), 54 to 94 (pain), 14 to 68 (sport) and 23 to 86 (quality of life). The percentage of patients reporting difficulty negotiating stairs because of their knee decreased from 86% pre-operatively to 5% post-operatively. The percentage of patients reporting a moderate or severe lack of confidence with their knee decreased from 91% pre-operatively to 10% post-operatively. CONCLUSION. This study demonstrates that this knee replacement design is safe and provides early pain relief and improved function. Patient reported outcome scores which improved post-operatively and were maintained at latest follow-up. Further data is being collected as part of a large, multicenter study to show repeatability in non-designer surgeon hands

Total knee arthroplasty (TKA) is widely accepted as a successful treatment option for the pain and limitation of function associated with severe joint disease. The ideal knee arthroplasty implant should provide reliable pain relief and normal levels of functional strength and range of motion. However, there are still a number of implant-specific problems following knee arthroplasty, such as irregular kinematics, polyethylene wear and poor range of motion. MRI and cadaveric studies have highlighted important kinematics during movement of the native knee. In particular, flexion of the joint results in a phenomenon referred to as “roll back and slide”. This essentially describes posterior translation of the femur on the tibia which in turn has a two-fold biomechanical function: to increase the lever arm of the quadriceps and allow clearance of the femur from the tibia in deep flexion. During extension of the joint, the femur rolls forward increasing the lever arm of the hamstrings to act as a brake on hyperextension. Additional rotation of the joint arises in the axial plane. This is attributed to the concave tibial plateau and relatively fixed meniscus on the medial compartment of the joint in comparison to a lateral convex plateau with a mobile meniscus. This asymmetry allows axial rotation of the lateral compartment over the medial compartment by up to 30 degrees. Subsequently, from extension to full flexion the tibia rotates internally on the femur and vice versa. The external rotation of the tibia on the femur that occurs during the terminal degrees of knee extension is often referred to as the “screw home mechanism” and results in tightening of both the cruciate ligaments locking the knee such that the tibia is in a position of maximum stability on the femur. Numerous studies over the past two decades have characterised the in-vivo motions of knee replacements. Major conclusions from these studies are that the motion after knee arthroplasty generally does not replicate normal knee motions. In particular, many kinematic studies of unconstrained devices have demonstrated the femur sliding forwards rather than backwards with flexion. This paradoxical movement is also seen in many posterior cruciate retaining knees. This in turn has a negative outcome in range of movement, particularly in light of fluoroscopic studies highlighting strong positive correlations in weight-bearing flexion with femoral roll back. In contrast knee arthroplasties that retain both cruciate ligaments come closest to replicating normal knee motion and furthermore, provide greater stair climbing stability. It may therefore be presumed that this excessive AP motion in a well-designed prosthesis is attributed to a loss in the natural intrinsic stabilizing structures. A number of studies to date have also highlighted close correlation between knee kinematics and functional strength. Generally, patients with knee replacement exhibit a significant loss of strength compared to normal. The common experimental findings is that knees with the highest intrinsic stability, whether provided by retained ligaments, conforming articular surfaces or post-cam substitution, exhibit the greatest functional strength in high-demand activities in TKA patients. On the basis of this knowledge, it would be intuitive to choose a TKA design that attempts to restore natural knee joint stability. The medially conforming ‘ball and socket’ articulation of the medial tibio-femoral compartment is a design concept thought to provide stability through the complete arc of knee flexion. Clinical and biomechanical data from a number of centers suggests that this has been a successful evolution in TKA that will continue to benefit patients

Implant loosening is one of the primary mechanisms of failure for hip, knee, ankle and shoulder arthroplasty. Many established implant fixation surfaces exist to achieve implant stability and fixation. More recently, additive manufacturing technology has offered exciting new possibilities for implant design such as large, open, porous structures that could encourage bony ingrowth into the implant and improve long-term implant fixation. Indeed, many implant manufacturers are exploiting this technology for their latest hip or knee arthroplasty implants. The purpose of this research is to investigate if the design freedoms offered by additive manufacturing could also be used to improve initial implant stability – a precursor to successful long-term fixation. This would enable fixation equivalent to current technology, but with lower profile fixation features, thus being less invasive, bone conserving and easier to revise. 250 cylindrical specimens with different fixation features were built in Ti6Al4V alloy using a Renishaw AM250 additive manufacturing machine, along with 14 specimens with a surface roughness similar to a conventional titanium fixation surface. Pegs were then pushed into interference fit holes in a synthetic bone material using a dual-axis materials testing machine equipped with a load/torque-cell (figure 1). Specimens were then either pulled-out of the bone, or rotated about their cylindrical axis before being pulled out to quantify their ability to influence initial implant stability. It was found that additively manufactured fixation features could favourably influence push-in/pull-out stability in one of two-ways: firstly the fixation features could be used to increase the amount pull-out force required to remove the peg from the bone. It was found that the optimum fixation feature for maximising pull-out load required a pull-out load of 320 N which was 6× greater than the least optimum design (54 N) and nearly 3× the maximum achieved with the conventional surface (120 N). Secondly, fixation features could also be used to decrease the amount of force required to insert the implant into bone whilst improving fixation (figure 2). Indeed, for some designs the ratio of push-in to pull-out was as high as 2.5, which is a dramatic improvement on current fixation surface technology, which typically achieved a ratio between 0.3–0.6 depending on the level of interference fit. It was also found that the additively manufactured fixation features could influence the level of rotational stability with the optimum design resisting 3× more rotational torque compared to the least optimum design. It is concluded that additive manufacturing technology could be used to improve initial implant stability either by increasing the anchoring force in bone, or by reducing the force required to insert an implant whilst maintaining a fixed level of fixation. This defines a new set of rules for implant fixation using smaller low profile features, which are required for minimally invasive device design

INTRODUCTION. There is ongoing debate about the possible advantages of unicompartmental (UNI) knee replacement versus total knee replacement (TKR), such as for young, active patients. The purpose of this study was to investigate functional, radiographic, and device survivorship outcomes of UNI knee replacement with a newer generation UNI through 2-years post-op. METHODS. A retrospective review of 188 cemented, fixed bearing unicompartmental (UNI) knee replacements implanted between January 2009 and June 2012 at 3 centers. The purpose of this study was to evaluate the survivorship, reasons for revision, radiographic and clinical results. A chart review was performed to collect demographics, operative details, American Knee Society (AKS) scores and adverse events (AE) through 2-years post-op. Kaplan-Meier (KM) device survivorship rates for the partial knee construct were estimated for post-op years in which at least 40 subjects had later follow-up. The definition of revision was the removal of any component for any reason, and device survivorship was the lack of revision. The time variable was the time to revision if the knee had been revised, or the time to last clinical follow-up or death if the knee had not been revised. The average follow-up was 2.03 years (SD=0.4). The mean age was 64 years (SD=10.5), 56% of the patients were 65 years or younger, mean BMI was 27.5 kg/m2 (SD=4.9), 60% of patients were women, and 89% had a diagnosis of OA (9.6% had AVN). Data were collected through April 2015. RESULTS. The KM device survivorship was 98.7% at 2 years (95% CI: 94.8–99.7%) (Figure 1). There were 3 revisions, 2 of which were prior to 2 years post-op (Figure 2) Overall, there were 23 operative site adverse events, including the 3 revisions. The most common AE was arthralgia (4.3%). There were no observations of lucencies, osteolysis, stress shielding, or femoral notching. At 2-years post-op the average AKS score was 89.9 points (N= 138, SD=11); 84% were in the good to excellent range. The average improvement from pre-op baseline at 2-years was 37.4 (N=117, SD=18). The average improvement in pain was 30 points (N=124, SD=15) on a 0–50 point scale, with 70% having no pain and 20% having mild pain at 2-years. Preoperatively, the average flexion was 118 degrees (N=152, SD=12.7o), which improved to 126 degrees (N=148, SD=9.4 o) at 2-years; average change from pre-op was 7.1 degrees (N=136, SD=12.2 o). Preoperatively, the average extension was 1.9 degrees (N=152, SD=3.6 o) which improved to 0.5 degrees (N=148, SD=1.6 o) at 2-years; average change from pre-op was a 1.4 degree improvement (N=136, SD=3.6 o). DISCUSSION. Overall results demonstrated excellent 2 year survivorship for this newer generation UNI, consistent with published national registry results for the class of UNIs. The clinical results demonstrated excellent pain relief and improvements in motion compared to preoperative. It will be of interest to investigate longer term outcomes of UNI knee replacement in a larger patient population, with a focus on younger, more active patients (younger than 60), perhaps with an emphasis on the quality of life

The history of knee mechanics studies and the evolution of knee arthroplasty design have been well reported through the last decade (e.g. [1],[2]). Through the early 2000's, there was near consensus on the dominant motions occurring in the healthy knee among much of the biomechanics and orthopaedic communities. However, the past decade has seen the application of improved measurement techniques to permit accurate measurement of natural knee motion during activities like walking and running. The results of these studies suggest healthy knee motion is more complex than previously thought, and therefore, design of suitable arthroplasty devices more difficult. The purpose of this paper is to briefly review the knee biomechanics literature before 2008, to present newer studies for walking and running, and to discuss the implications of these findings for the design of knee replacement implants that seek to replicate physiologic knee motions. Many surgeons point to Brantigan and Voshell [3], an anatomic study of over one hundred specimens focusing on the ligamentous and passive stabilizers of the knee, as being an important influence in their thinking about normal knee function. M.A.R. Freeman and colleagues in London claim particular influence from this work, which motivated their extensive series of MR-based knee studies reported in 2000 [4,5,6]. These papers, perhaps more than any others, are responsible for the common impression that knee kinematics are well and simply described as having a ‘medial pivot’ pattern, where the medial condyle remains stationary on the tibial plateau while the lateral condyle translates posteriorly with knee flexion. Indeed, subsequent studies in healthy and arthritic knees during squatting and kneeling [7,8,9] and healthy and ACL-deficient knees during deep knee bends [10,11] show patterns of motion quite similar to those reported by Freeman and coworkers. These studies make a convincing case for how the healthy knee moves during squatting, kneeling and lunging activities. However, these studies are essentially silent on knee motions during ambulatory activities like walking, running and stair-climbing; activities which most agree are critically important to a high-function lifestyle. In 2008 Koo and Andriacchi reported a motion laboratory study of walking in 46 young healthy individuals and found that the stance phase knee center of rotation was LATERAL in 100% of study participants [12]. One year later, Kozanek et al. published a bi-plane fluoroscopy study of healthy knees walking on a treadmill and corroborated the findings of Koo and Andriacchi, i.e. the center of rotation in healthy knees walking was lateral [13]. Isberg et al. published in 2011 a dynamic radiostereometric study of knee motions in healthy, ACL-deficient and ACL-reconstructed knees during a weight-bearing flexion-to-extension activity, and showed consistent anterior-to-posterior medial condylar translations with knee extension, accompanied by relatively little lateral condylar translation [14]. Hoshino and Tashman reported in 2012 another dynamic radiostereometric analysis of healthy knees during downhill running and concluded “While the location of the knee rotational axis may be dependent on the specific loading condition, during … walking and running … it is positioned primarily on the lateral side of the joint. ”[15] Finally, Claes et al. reported in late 2013 the detailed anatomy of the anterolateral ligament (ALL), another structure serving to stabilize the lateral knee compartment near extension, roughly in parallel with the anterior cruciate ligament (ACL) [16]. Studies since 2008 [9,12–16] show knee motions during walking, running and pivoting activities do not fit the “medial pivot” pattern of motion, but rather point to a “lateral pivot” pattern of knee motion consistent with the stabilizing roles of the ACL and ALL. Having a medial center of rotation in flexion and a lateral center of rotation in extension greatly complicates knee arthroplasty design if the goal is to reproduce kinematics approximating those observed in the natural knee. Consistent kinematics having a fixed center of rotation implies joint stabilizing structures or surfaces, not simply articular laxity allowing the knee to move as forces dictate. Thus, a total knee arthroplasty design seeking to reproduce physiologic motions may need to provide distinct means for controlling tibiofemoral motion in both extension and flexion. Recent studies of natural knee motions have made the implant designer's job more difficult!

Preoperative planning in revision total knee replacement is important to simplify the surgery for the implant representative, operating room personnel and the surgeon. In revision knee arthroplasty, many implant options can be considered. This includes cemented and cementless primary and revision tibial and femoral components, with posterior cruciate retention or resection, and either with no constraint, varus/valgus constraint, or with rotating hinge bearings. One may also need femoral and tibial spacers, metaphyseal augments, or bulk allograft. It is important to preoperatively determine which of these implants you may need. If you schedule a revision total knee and ask the implant representative to “bring everything you've got, just in case,” they will have to bring a delivery van full of instruments and implants. Ideally, the least constraint needed should be used. This requires determination of the status of the collateral ligaments preoperatively. If there is instability present, use physical examination with confirmation from radiographs. Predict the constraint needed and have the next level as a back-up. Substitution for the posterior cruciate ligament is usually needed for most revisions. Intraoperative determination of the joint line position is difficult due to lack of anatomic landmarks. Having intact collateral ligaments with an appropriate anatomic joint line position will usually negates the need for increased implant constraint. Radiographically, one can determine the appropriate joint line position relative to the existing femoral component to simplify the surgery. Preoperative review of radiographs should determine the amount and location of bone loss. This will help determine if having cementless and/or primary components available can be eliminated. Larger defects may warrant having metallic augments or bulk graft present. Determine if bony deficiencies will mandate use of stems. Most revision knee implants can be conservatively cemented with diaphyseal engaging press-fit stems. Occasionally, one may not need to revise all components, so the surgeon needs to be familiar with the implants they are revising. Consider having some or all compatible components available. Excellent preoperative planning will minimises the need to bring in an excessive number of instruments and implants. It will help assure that the patient has a stable revision knee and simplify the surgery for all participants

Obesity is a global epidemic of 2.1 billion people and a well known cause of osteoarthritis. Joint replacement in the obese attracts more complications, poorer outcomes and higher revision rates. It is a reversible condition and the fundamental principles of dealing with reversible medical conditions prior to elective total joint replacement should apply to obesity. The dilemma for orthopaedic surgeons is when to offer surgery in the face of a reversible condition, which if treated may obviate joint replacement and reduce the risk and severity of obesity related disease in both the medical arena and the field of orthopaedics.

Pre-operative planning in revision total knee replacement is important to simplify the surgery for the implant representative, operating room personnel and the surgeon. In revision knee arthroplasty, many implant options can be considered. This includes cemented and cementless primary and revision tibial and femoral components, with posterior cruciate retention or resection, and either with no constraint, varus/valgus constraint, or with rotating hinge bearings. One may also need femoral and tibial spacers, metaphyseal augments, or bulk allograft. It is important to pre-operatively determine which of these implants you may need. If you schedule a revision total knee and ask the implant representative to “bring everything you've got, just in case,” they will have to bring a delivery van full of instruments and implants. Ideally, the least constraint needed should be used. This requires determination of the status of the collateral ligaments pre-operatively. If there is instability present, use physical examination with confirmation from radiographs. Predict the constraint needed and have the next level as a back-up. Substitution for the posterior cruciate ligament is usually needed for most revisions. Intra-operative determination of the joint line position is difficult due to lack of anatomic landmarks. Having intact collateral ligaments with an appropriate anatomic joint line position will usually negate the need for increased implant constraint. Radiographically, one can determine the appropriate joint line position relative to the existing femoral component to simplify the surgery. Pre-operative review of radiographs should determine the amount and location of bone loss. This will help determine if having cementless and/or primary components available can be eliminated. Larger defects may warrant having metallic augments or bulk graft present. Determine if bony deficiencies will mandate use of stems. Most revision knee implants can be conservatively cemented with diaphyseal engaging press-fit stems. Occasionally, one may not need to revise all components, so the surgeon needs to be familiar with the implants they are revising. Consider having some or all compatible components available. Excellent pre-operative planning will minimise the need to bring in an excessive number of instruments and implants. It will help assure that the patient has a stable revision knee and simplify the surgery for all participants