Progressive degenerative changes in the medial compartment of the knee following lateral unicompartmental arthroplasty (UKA) remains a leading indication for revision surgery. The purpose of this study is to evaluate changes in the congruence and joint space width (JSW) of the medial compartment following lateral UKA. The congruence of the medial compartment of 53 knees (24 men, 23 women, mean age 13.1 years; . sd. 62.1) following lateral UKA was evaluated pre-operatively and six weeks post-operatively, and compared with 41 normal knees (26 men, 15 women, mean age 33.7 years;. sd . 6.4), using an Interactive closest point algorithm which calculated the congruence index (CI) by performing a rigid transformation that best aligns the digitised tibial and femoral surfaces. Inner, middle and outer JSWs were measured by sub-dividing the medial compartment into four quarters on pre- and post-operative, weight bearing tunnel view radiographs. The mean CI of knees following lateral UKA significantly improved from 0.92 . (sd . 0.06) pre-operatively to 0.96 . (sd . 0.02) (p < 0.001) six weeks post-operatively. The mean CI of the healthy control group was 0.99 sd 0.01. Post-operatively, the mean inner JSW increased (p = 0.006) and the outer decreased (p = 0.002). The JSW was restored post-operatively as no significant differences were noted in all three locations compared with the control group (inner JSW p = 0.43; middle JSW p = 0.019, outer JSW p = 0.51). . Our data suggest that a well conducted lateral UKA may improve the congruence and normalise the JSW of the medial compartment, potentially preventing progression of degenerative change. . Cite this article: Bone Joint J 2015;97-B:50–5

Introduction:. The number of medial unicompartmental knee arthroplasties (UKA) performed over the last decade has increased by 30%, as studies have demonstrated improved knee kinematics, range of motion, and decreased perioperative morbidity versus total knee arthroplasty. However, concerns remain regarding the future risk of revision due to lateral compartment degeneration. In patients with a varus mechanical alignment and tibiofemoral subluxation secondary to medial compartment osteoarthritis, the femoral and tibial articular surfaces of the lateral compartment subsequently become incongruous, potentially increasing the focal contact stresses seen with loading. The purpose of this study is to evaluate whether the tibiofemoral congruence of the lateral compartment of the knee is improved following a medial UKA. Methods:. This study is a retrospective review of 192 consecutive medial UKAs included in an IRB-approved, single-surgeon database. All UKAs were performed using a robot-assisted surgical technique. Preoperative and postoperative standing, anteroposterior hip-to-ankle radiographs controlling for lower extremity rotation were performed from which the congruence of the lateral compartment was measured. The preoperative and postoperative degree of articular congruence (congruence index, CI) was calculated using an iterative closest point (ICP)-based software code (Matlab, MathWorks Inc., Natick, MA), specially developed to evaluate congruence of knee compartments. Following digitization of the articular surfaces of the femur and tibia, the code performs a rigid transformation that best aligns the articular surfaces and evaluates the current degree of articular congruence. A congruence index (CI) is then calculated, with a value of 1 indicating complete congruence, and a value of 0 indicating a 100% dislocation of the articular surfaces. A student's t-test was used to compare the preoperative and postoperative values of lateral compartment congruence. Results:. The mean, preoperative congruence index of the lateral compartment was 0.88 (± 0.1), which was improved to 0.93 (± 0.07), following implantation of a medial UKA (p < 0.001). Congruence of the lateral compartment was improved in 158 of the UKAs (83%), while 34 (17%) demonstrated a decrease in the congruence index postoperatively. Conclusion:. Implantation of a medial unicompartmental knee arthroplasty improves the articular surface congruence of the lateral compartment in the majority of patients with isolated, medial compartment osteoarthritis (Figure 1). We hypothesize that this factor, combined with a controlled undercorrection of the overall mechanical alignment, will improved load distribution across the lateral compartment, reduce the risk of focal contact stress points, and decrease the risk of subsequent osteoarthritic degeneration of the lateral compartment. Medial UKA not only resurfaces the medial compartment, but also may treat potential lateral compartment degeneration by improving congruence and load distribution

Aims. The aim of this study was to evaluate cartilaginous patellotrochlear congruence and patellofemoral alignment parameters after deepening trochleoplasty in severe trochlear dysplasia. Patients and Methods. The study group comprised 20 patients (two male, 18 female; mean age 24 years (16 to 39)) who underwent deepening trochleoplasty and medial patellofemoral ligament (MPFL) reconstruction for the treatment of recurrent lateral patellar dislocation due to severe trochlear dysplasia (Dejour type B to D). Pre- and postoperative MRI investigations of the study group were compared with MRI data of 20 age- and gender-matched control patients (two male, 18 female; mean age 27 years (18 to 44)) regarding the patellotrochlear contact ratio, patellotrochlear contact area, posterior patellar edge-trochlear groove ratio, and patellar tilt. Results. Preoperatively, all parameters in the study group indicated significant patellar malalignment, including a reduced patellotrochlear contact ratio (mean 0.38 (0.13 to 0.59) vs mean 0.67 (0.48 to 0.88); p < 0.001), reduced contact area (mean 128 mm. 2. (87 to 190) vs mean 183 mm. 2. (155 to 227); p < 0.001), increased patellar lateralization (mean 0.82 (0.55 to 1.0) vs mean 0.99 (0.93 to 1.1); p < 0.001) and increased patellar tilt (mean 25.8° (8.1° to 43.0°) vs mean 9.1° (0.5° to 16.8°); p < 0.001). Postoperatively, all parameters in the study group improved significantly and reached normal values compared with the control group. The patellotrochlear contact ratio increased to a mean of 0.63 (0.38 to 0.85) (p < 0.001), the contact area increased to a mean of 187 mm. 2. (101 to 255) (p < 0.001), the posterior patellar edge-trochlear groove ratio improved to a mean of 0.96 (0.83 to 0.91) (p < 0.001), and the patellar tilt decreased to a mean of 13.9° (8.1° to 22.1°) (p < 0.001) postoperatively. Conclusion. Deepening trochleoplasty and MPFL reconstruction normalized the patellotrochlear congruence and patellofemoral alignment parameters. Modifying the dysplastic trochlea involves approximating the trochlear morphology to the shape of the patella rather than inducing a patella and trochlea mismatch. Cite this article: Bone Joint J 2019;101-B:325–330

Introduction. Chronic uneven distribution of forces over the articular cartilage, which are present in OA, has been shown to be a risk factor for the development of OA. Certain regions of the articular cartilage will be exposed to increased chronic peak loads, whereas other regions encounter a corresponding relative reduction of transmitted forces. This has a well known influence on cartilage viability and is a precursor of degenerative progression. Congruence of joints has an important impact on force distribution across articular surfaces. Therefore, tibiofemoral incongruence could lead to alterations of load distribution and ultimately to progressive degenerative changes. In clinical practice the routine method for evaluation of progressive OA is analysis of joint space width (JSW) using weight bearing radiographs. Recent studies have suggested that JSW has a strong positive correlation with cartilage compression, volume and meniscal extrusion. Lateral unicondylar knee arthroplasty (UKA) has gained increasing popularity over the last decade in the treatment of isolated unicompartmental osteoarthritis (OA). However, progressive degenerative alterations of the medial compartment following lateral unicompartmental knee arthroplasty remains a leading cause of revision surgery. Therefore, the purpose of this study is to evaluate the medial compartment congruence (MCC) and joint space width (JSW) alterations following lateral UKA. Methods. The MCC of 53 knees following lateral UKA was evaluated on pre- and postoperative radiographs and compared to 41 healthy knees, using an Interative Closest Point (ICP) algorithm. The ICP algorithm calculated the Congruence Index (CI) by performing a rigid transformation that best aligns the digitized tibial and femoral surfaces (figure 1A). Inner, middle and outer JSW was measured by subdividing the medial compartment into four quarters on weight bearing tunnel view radiographs pre- and postoperatively (figure 1B). Results. The measured CI of the healthy control group was 0.99. The pre-operative CI of knees undergoing lateral UKA was 0.92, which significantly improved to 0.96 (p<0.0001) post-operatively (figure 2). Post-operatively the inner JSW increased (p=0.006) and the outer decreased (p=0.002). JSW was restored post-operatively since no significant differences were noted in all three measured post-operative JSW locations compared to the control group (figure 3). Conclusion. Our data suggests that lateral UKA improves MCC and normalizes JSW of the medial compartment, potentially preventing osteoarthritic progression in the uninvolved medial compartment

Objectives. The bony shoulder stability ratio (BSSR) allows for quantification of the bony stabilisers in vivo. We aimed to biomechanically validate the BSSR, determine whether joint incongruence affects the stability ratio (SR) of a shoulder model, and determine the correct parameters (glenoid concavity versus humeral head radius) for calculation of the BSSR in vivo. Methods. Four polyethylene balls (radii: 19.1 mm to 38.1 mm) were used to mould four fitting sockets in four different depths (3.2 mm to 19.1mm). The SR was measured in biomechanical congruent and incongruent experimental series. The experimental SR of a congruent system was compared with the calculated SR based on the BSSR approach. Differences in SR between congruent and incongruent experimental conditions were quantified. Finally, the experimental SR was compared with either calculated SR based on the socket concavity or plastic ball radius. Results. The experimental SR is comparable with the calculated SR (mean difference 10%, . sd. 8%; relative values). The experimental incongruence study observed almost no differences (2%, . sd. 2%). The calculated SR on the basis of the socket concavity radius is superior in predicting the experimental SR (mean difference 10%, . sd. 9%) compared with the calculated SR based on the plastic ball radius (mean difference 42%, . sd. 55%). Conclusion. The present biomechanical investigation confirmed the validity of the BSSR. Incongruence has no significant effect on the SR of a shoulder model. In the event of an incongruent system, the calculation of the BSSR on the basis of the glenoid concavity radius is recommended. Cite this article: L. Ernstbrunner, J-D. Werthel, T. Hatta, A. R. Thoreson, H. Resch, K-N. An, P. Moroder. Biomechanical analysis of the effect of congruence, depth and radius on the stability ratio of a simplistic ‘ball-and-socket’ joint model. Bone Joint Res 2016;5:453–460. DOI: 10.1302/2046-3758.510.BJR-2016-0078.R1

Introduction

Conventional pre-operative planning for total hip arthroplasty mostly relies on the patient radiologic anatomy for the positioning and choice of implants. This kind of planning essentially remains a static approach since dynamic aspects such as the joint kinematics are not taken into account. Hence, clinicians are not able to fully consider the evolving behavior of the prosthetic joint that may lead to implant failures. In fact, kinematics plays an important role since some movement may create conflicts within the prosthetic joint and even provoke dislocations. The goal of our study was to assess the relationship between acetabular implant positioning variations and resultant impingements and loss of joint congruence during daily activities. In order to obtain accurate hip joint kinematics for simulation, we performed an in-vivo study using optical motion capture and magnetic resonance imaging (MRI).

Aims

The aim of this study was to determine and compare the congruency of the articular surface contact area of the patellofemoral joint (PFJ) during both active and passive movement of the knee with the use of an MRI mapping technique in both the stable and unstable PFJ.

Purpose: The purpose of this work was to compare polyethylene (PE) wear between prostheses with similar function but different congruency of the femoral implant / PE insert and, as a corollary, the mobility of the plateau.

Material and methods: We studied two groups of knee prostheses: prostheses preserving both cruciate ligaments (n = 20), and stabilised prostheses without preservation of the cruciate ligaments (n = 20). Four representative samples of ten patients by type of total knee arthroplasty (TKA) were selected at random among a cohort of 105 patients operated on between 1994 and 1996 with a mean follow-up of five years. All patients were reviewed with AP and lateral radiographs, a view in the plateau plane, and goniometry. Using this random selection, patients in the two groups were comparable for operative age (69 years), diagnosis (degenerative disease), sex ratio, IKS score (> 80/100), and follow-up. The only difference between the two groups was the postoperative goniometry: 180±2° for fixed plateau; 178±3° for mobile plateau (p< 0.05).

Result: Penetration of the femur in the PE insert (U) (after correction for radiographic magnification) was: TKA two cruciates fixed plateau: U=3.5±1.5mm; TKA two cruciates mobile plateau: U=0±1mm (p< 0.001); TKA posterior stabilisation fixed plateau: U=2.5±1mm; TKA posterior stabilisation mobile plateau: U=0 mm (p< 0.001). A difference of more than 3° in the mechanical axis did not show detectable wear in the group of congruent prostheses while for fixed plateau prostheses, wear appeared when the mechanical axis was 180°.

Discussion: Few studies have compared PE wear of TKAs with identical form and function. The random selection allowed us to compare homogeneous groups of patients eliminating selection bias of the retrospective analysis and of the effect of patients lost to follow-up. The highly significant difference between the groups compared avoided potential ß risk. However the quality of the PE and its mode of sterilisation were not known with certainty for the tested implants.

Conclusion: This study demonstrates the importance of congruency as a factor reducing PE wear in TKA. This parameter is more favourable when the postoperative mechanical axis is perfectly corrected.

Aims. Treatment of Weber B ankle fractures that are stable on weightbearing radiographs but unstable on concomitant stress tests (classified SER4a) is controversial. Recent studies indicate that these fractures should be treated nonoperatively, but no studies have compared alternative nonoperative options. This study aims to evaluate patient-reported outcomes and the safety of fracture treatment using functional orthosis versus cast immobilization. Methods. A total of 110 patients with Weber B/SER4a ankle fractures will be randomized (1:1 ratio) to receive six weeks of functional orthosis treatment or cast immobilization with a two-year follow-up. The primary outcome is patient-reported ankle function and symptoms measured by the Manchester-Oxford Foot and Ankle Questionnaire (MOxFQ); secondary outcomes include Olerud-Molander Ankle Score, radiological evaluation of ankle congruence in weightbearing and gravity stress tests, and rates of treatment-related adverse events. The Regional Committee for Medical and Health Research (approval number 277693) has granted ethical approval, and the study is funded by South-Eastern Norway Regional Health Authority (grant number 2023014). Discussion. Randomized controlled trials are needed to evaluate alternative nonoperative treatment options for Weber B/SER4a ankle fractures, as current clinical guidelines are based on biomechanical reasoning. The findings will be shared through publication in peer-reviewed journals and presentations at conferences. Cite this article: Bone Jt Open 2023;4(9):713–719

Aims. The mid-term results of kinematic alignment (KA) for total knee arthroplasty (TKA) using image derived instrumentation (IDI) have not been reported in detail, and questions remain regarding ligamentous stability and revisions. This paper aims to address the following: 1) what is the distribution of alignment of KA TKAs using IDI; 2) is a TKA alignment category associated with increased risk of failure or poor patient outcomes; 3) does extending limb alignment lead to changes in soft-tissue laxity; and 4) what is the five-year survivorship and outcomes of KA TKA using IDI?. Methods. A prospective, multicentre, trial enrolled 100 patients undergoing KA TKA using IDI, with follow-up to five years. Alignment measures were conducted pre- and postoperatively to assess constitutional alignment and final implant position. Patient-reported outcome measures (PROMs) of pain and function were also included. The Australian Orthopaedic Association National Joint Arthroplasty Registry was used to assess survivorship. Results. The postoperative HKA distribution varied from 9° varus to 11° valgus. All PROMs showed statistical improvements at one year (p < 0.001), with further improvements at five years for Knee Osteoarthritis Outcome Score symptoms (p = 0.041) and Forgotten Joint Score (p = 0.011). Correlation analysis showed no difference (p = 0.610) between the hip-knee-ankle and joint line congruence angle at one and five years. Sub-group analysis showed no difference in PROMs for patients placed within 3° of neutral compared to those placed > 3°. There were no revisions for tibial loosening; however, there were reports of a higher incidence of poor patella tracking and patellofemoral stiffness. Conclusion. PROMs were not impacted by postoperative alignment category. Ligamentous stability was maintained at five years with joint line obliquity. There were no revisions for tibial loosening despite a significant portion of tibiae placed in varus; however, KA executed with IDI resulted in a higher than anticipated rate of patella complications. Cite this article: Bone Jt Open 2022;3(8):656–665

Aims. It remains controversial whether patellofemoral joint pathology is a contraindication to lateral unicompartmental knee arthroplasty (UKA). This study aimed to evaluate the effect of preoperative radiological degenerative changes and alignment on patient-reported outcome scores (PROMs) after lateral UKA. Secondarily, the influence of lateral UKA on the alignment of the patellofemoral joint was studied. Methods. A consecutive series of patients who underwent robotic arm-assisted fixed-bearing lateral UKA with at least two-year follow-up were retrospectively reviewed. Radiological evaluation was conducted to obtain a Kellgren Lawrence (KL) grade, an Altman score, and alignment measurements for each knee. Postoperative PROMs were assessed using the Kujala (Anterior Knee Pain Scale) score, Knee Injury and Osteoarthritis Outcome Score Joint Replacement (KOOS JR), and satisfaction levels. Results. A total of 140 knees (130 patients) were identified for analysis. At mean 4.1 years (2.0 to 8.5) follow-up, good to excellent Kujala scores were reported. The presence of mild to moderate preoperative patellofemoral joint osteoarthritis had no impact on these scores (KL grade 0 vs 1 to 3, p = 0.203; grade 0 to 1 vs 2 to 3, p = 0.674). Comparable scores were reported by patients with osteoarthritis (Altman score of ≥ 2) evident on either the medial or lateral patellofemoral joint facet (medial, p = 0.600 and lateral, p = 0.950). Patients with abnormal patellar congruence and tilt angles (≥ 17° and ≥ 14°, respectively) reported good to excellent Kujala scores. Furthermore, lateral UKA resulted in improvements to patellofemoral alignment. Conclusion. This is the first study demonstrating that mild to moderate preoperative radiological degenerative changes and malalignment of the patellofemoral joint are not associated with poor patient-reported outcomes at mid-term follow-up after lateral fixed-bearing UKA. Our data suggest that this may be explained by realignment of the patella and thereby redistribution of loads across the patellofemoral joint. Cite this article: Bone Joint J 2020;102-B(6):727–735

Despite the current trend favoring surgical treatment of displaced intra-articular calcaneal fractures (DIACFs), studies have not been able to demonstrate superior functional outcomes when compared to non-operative treatment. These fractures are notoriously difficult to reduce. Studies investigating surgical fixation often lack information about the quality of reduction even though it may play an important role in the success of this procedure. We wanted to establish if, amongst surgically treated DIACF, an anatomic reduction led to improved functional outcomes at 12 months. From July 2011 to December 2020, at a level I trauma center, 84 patients with an isolated DIACF scheduled for surgical fixation with plate and screws using a lateral extensile approach were enrolled in this prospective cohort study and followed over a 12-month period. Post-operative computed tomography (CT) imaging of bilateral feet was obtained to assess surgical reduction using a combination of pre-determined parameters: Böhler's angle, calcaneal height, congruence and articular step-off of the posterior facet and calcaneocuboid (CC) joint. Reduction was judged anatomic when Böhler's angle and calcaneal height were within 20% of the contralateral foot while the posterior facet and CC joint had to be congruent with a step-off less than 2 mm. Several functional scores related to foot and ankle pathology were used to evaluate functional outcomes (American Orthopedic Foot and Ankle Score - AOFAS, Lower Extremity Functional Score - LEFS, Olerud and Molander Ankle Score - OMAS, Calcaneal Functional Scoring System - CFSS, Visual Analog Scale for pain - VAS) and were compared between anatomic and nonanatomic DIAFCs using Student's t-test. Demographic data and information about injury severity were collected for each patient. Among the 84 enrolled patients, 6 were excluded while 11 were lost to follow-up. Thirty-nine patients had a nonanatomic reduction while 35 patients had an anatomic reduction (47%). Baseline characteristics were similar in both groups. When we compared the injury severity as defined by the Sanders’ Classification, we did not find a significant difference. In other words, the nonanatomic group did not have a greater proportion of complex fractures. Anatomically reduced DIACFs showed significantly superior results at 12 months for all but one scoring system (mean difference at 12 months: AOFAS 3.97, p = 0.12; LEFS 7.46, p = 0.003; OMAS 13.6, p = 0.002, CFSS 7.5, p = 0.037; VAS −1.53, p = 0.005). Univariate analyses did not show that smoking status, worker's compensation or body mass index were associated with functional outcomes. Moreover, fracture severity could not predict functional outcomes at 12 months. This study showed superior functional outcomes in patients with a DIACF when an anatomic reduction is achieved regardless of the injury severity

Despite the current trend favoring surgical treatment of displaced intra-articular calcaneal fractures (DIACFs), studies have not been able to demonstrate superior functional outcomes when compared to non-operative treatment. These fractures are notoriously difficult to reduce. Studies investigating surgical fixation often lack information about the quality of reduction even though it may play an important role in the success of this procedure. We wanted to establish if, amongst surgically treated DIACF, an anatomic reduction led to improved functional outcomes at 12 months. From July 2011 to December 2020, at a level I trauma center, 84 patients with an isolated DIACF scheduled for surgical fixation with plate and screws using a lateral extensile approach were enrolled in this prospective cohort study and followed over a 12-month period. Post-operative computed tomography (CT) imaging of bilateral feet was obtained to assess surgical reduction using a combination of pre-determined parameters: Böhler's angle, calcaneal height, congruence and articular step-off of the posterior facet and calcaneocuboid (CC) joint. Reduction was judged anatomic when Böhler's angle and calcaneal height were within 20% of the contralateral foot while the posterior facet and CC joint had to be congruent with a step-off less than 2 mm. Several functional scores related to foot and ankle pathology were used to evaluate functional outcomes (American Orthopedic Foot and Ankle Score - AOFAS, Lower Extremity Functional Score - LEFS, Olerud and Molander Ankle Score - OMAS, Calcaneal Functional Scoring System - CFSS, Visual Analog Scale for pain – VAS) and were compared between anatomic and nonanatomic DIAFCs using Student's t-test. Demographic data and information about injury severity were collected for each patient. Among the 84 enrolled patients, 6 were excluded while 11 were lost to follow-up. Thirty-nine patients had a nonanatomic reduction while 35 patients had an anatomic reduction (47%). Baseline characteristics were similar in both groups. When we compared the injury severity as defined by the Sanders’ Classification, we did not find a significant difference. In other words, the nonanatomic group did not have a greater proportion of complex fractures. Anatomically reduced DIACFs showed significantly superior results at 12 months for all but one scoring system (mean difference at 12 months: AOFAS 3.97, p = 0.12; LEFS 7.46, p = 0.003; OMAS 13.6, p = 0.002, CFSS 7.5, p = 0.037; VAS −1.53, p = 0.005). Univariate analyses did not show that smoking status, worker's compensation or body mass index were associated with functional outcomes. Moreover, fracture severity could not predict functional outcomes at 12 months. This study showed superior functional outcomes in patients with a DIACF when an anatomic reduction is achieved regardless of the injury severity

Menisci are crucial structures for knee homeostasis: they provide increase of congruence between the articular surfaces of the distal femur and tibial plateau, bear loading, shock absorption, lubrication, and proprioception. After a meniscal lesion, the golden rule, now, is to save as much meniscus as possible: only the meniscus tissue which is identified as unrepairable should be excised and meniscal sutures find more and more indications. Several different methods have been proposed to improve meniscal healing. They include very basic techniques, such as needling, abrasion, trephination and gluing, or more complex methods, such as synovial flaps, meniscal wrapping, or the application of fibrin clots. Basic research of meniscal substitutes has also become very active in the last decades. The features needed for a meniscal scaffold are: promotion of cell migration, it should be biomimetic and biocompatible, it should resist forces applied and transmitted by the knee, it should slowly biodegrade and should be easy to handle and implant. Several materials have been tested, that can be divided into synthetic and biological. The first have the advantage to be manufactured with the desired shapes and sizes and with precise porosity dimension and biomechanical characteristics. To date, the most common polymers are polylactic acid (PGA); poly-(L)-lactic acid (PLLA); poly- (lactic-co-glycolic acid) (PLGA); polyurethane (PU); polyester carbon and polycaprolactone (PCL). The possible complications, more common in synthetic than natural polymers are poor cell adhesion and the possibility of developing a foreign body reaction or aseptic inflammation, leading to alter the joint architecture and consequently to worsen the functional outcomes. The biological materials that have been used over time are the periosteal tissue, the perichondrium, the small intestine submucosa (SIS), acellular porcine meniscal tissue, bacterial cellulose. Although these have a very high biocompatibility, some components are not suitable for tissue engineering as their conformation and mechanical properties cannot be modified. Collagen or proteoglycans are excellent candidates for meniscal engineering, as they maintain a high biocompatibility, they allow for the modification of the porosity texture and size and the adaptation to the patient meniscus shape. On the other hand, they have poor biomechanical characteristics and a more rapid degradation rate, compared to others, which could interfere with the complete replacement by the host tissue. An interesting alternative is represented by hydrogel scaffolds. Their semi-liquid nature allows for the generation of scaffolds with very precise geometries obtained from diagnostic images (i.e. MRI). Promising results have been reported with alginate and polyvinyl alcohol (PVA). Furthermore, hydrogel scaffolds can be enriched with growth factors, platelet-rich plasma (PRP) and Bone Marrow Aspirate Concentrate (BMAC). In recent years, several researchers have developed meniscal scaffolds combining different biomaterials, to optimize the mechanical and biological characteristics of each polymer. For example, biological polymers such as chitosan, collagen and gelatin allow for excellent cellular interactions, on the contrary synthetic polymers guarantee better biomechanical properties and greater reliability in the degradation time. Three-dimensional (3D) printing is a very interesting method for meniscus repair because it allows for a patient-specific customization of the scaffolds. The optimal scaffold should be characterized by many biophysical and biochemical properties as well as bioactivity to ensure an ECM-like microenvironment for cell survival and differentiation and restoration of the anatomical and mechanical properties of the native meniscus. The new technological advances in recent years, such as 3D bioprinting and mesenchymal stem cells management will probably lead to an acceleration in the design, development, and validation of new and effective meniscal substitutes

Introduction. Up to 15 % of patients report anterior knee pain (AKP) after a total knee arthroplasty (TKA). The correlation of radiographic patellar measurements and post-operative AKP remains controversial. The purpose of this study was to determine whether any radiographic measurements can predict anterior knee pain after TKA. Methods. We performed a retrospective analysis of data on 343 patients who underwent a primary unilateral TKA between 2009–2012 at a single institution. Post-operative radiographs were evaluated with standing anteroposterior, lateral, and merchant views. Radiographic assessment was performed to assess posterior offset, Insall Salvati ratio, Blackburne, PP angle, Patella thickness, Congruence angle, Patella tilt, and patella displacement. Clinical function was assessed by the Kujala anterior knee pain scale at a minimum of 5 years. Patients were asked if they currently had anterior knee pain post-operatively by responding “yes” or “no.” There were 264 females and 79 males; the mean age at surgery was 64.2 ± 9.7 (range, 42–92 years) years; the mean BMI 31±5.8 kg/m. 2. (range, 18.8–49 kg/m. 2. ). Results. Of the 343 patients, 46 patients (13.4%) patients suffered persistent AKP at a minimum 5 years follow-up. Radiographic measurements were performed. Although we had large variations in congruence angle, patellar tilt and patellar displacement, these variations had no correlation with anterior knee pain (p=0.885). We were not able to detect statistical significance among clinical outcome Kujala score and patient reported AKP (p=0.713) at minimum 5 year follow-up. Discussion. Persistent anterior knee pain is troubling to patients and surgeons. Clinicians often get concerned when they see variability in these radiographic findings. Our findings suggest that variations in radiographic parameters do not predict anterior knee pain following total knee replacement surgery. For figures, tables, or references, please contact authors directly

Seventy-four mobile bearing total knee arthroplasties (LCS) without patellar resurfacing were analysed in 54 patients who were followed for a minimum of one year. We examined the congruence angle on Merchant’s view, the component rotation to the epicondylar line of the femur on computed tomography(CT), the femorotibial angle on weight-bearing anteroposterior radiograph to assess the contributing factors for the patellofemoral malalignment. The statistical analysis was performed by ANOVA test, student t test, and chi sguare test. The patellofemoral pain was noted in 17 knees(23%). The incidence of patellofemoral pain was significantly increased in the knee when its congruence angle was more than 16 degrees (p=0.034). But the pain did not correlate with the status of the articular cartilage of the patella on operation. The average congrunce angle was 4¢ªdegrees preoperatively and 24.2 degrees postoperatively. The congruence angle in 29 knees with lateral release was significantly lower than that in 45 knees without lateral release (p=0.037). All femoral components were internally rotated on CT scan with average of 6.7 degrees. More significant increase of the congruence angle was observed in 42 knees with femoral or tibial component rotation than in 15 knees with normal or minimal rotation of both components(p=0.017). Pre-operative congruence angle and postoperative femorotibial angle also affected the patellofemoral alignment, which increased postoperative congruence angle respectively. Based on our findings, it seems that the excessive internal rotation of one component and excessive valgus of the femorotibial angle should be avoided to prevent the patellofemoral maltracking. We believe that “no thumb test” should be done carefully and the lateral release performed without hesitation if patellar tracking is a concern

Known risk factors for early periprosthetic femur fracture (PFF) following total hip arthroplasty (THA) include poor bone quality, surgical approach and cementless implants. The association between femoral component size and alignment and the risk of early PFF is not well described. We evaluated radiographic parameters of femoral component sizing and alignment as risk factors for early PFF. From 16,065 primary cementless THA, we identified 66 cases (0.41%) of early PFF (<90 days from index THA) at a single institution between 2016–2020. The stem was unstable and revised in all cases. We matched 60 cases of early PFFs (2:1) to 120 controls based on femoral component model, offset, surgical approach, age, BMI, and sex. Mean age was 67 years; 60% were female. Radiographic assessment of preoperative bone morphology and postoperative femoral component parameters including stem alignment, metaphyseal fill, and medial congruence with the calcar. A multivariable logistic regression was built to identify radiographic risk factors associated with early PPF. Markers of poor preoperative bone quality including canal calcar ratio (p=0.003), canal flare index (p<0.001), anteroposterior canal bone ratio (CBR) (p<0.001) and lateral CBR (p<0.001) were statistically associated with PFF. Valgus alignment (23% versus 12%) (p<0.001) was more prevalent in the PFF group compared to controls, as well as varus alignment of the implant (57% versus 43%). Distance between the medial aspect of the implant and the calcar was greater in cases of PFF (2.5 mm versus 1.4 mm) (p<0.001). Multivariate analysis demonstrated that valgus implant alignment (Odds Ratio (OR) 5) and medial implant-calcar incongruity (OR 2) increased the risk of early PFF. Medial implant-calcar incongruity and valgus alignment of the femoral component were risk factors for early PFF following cementless THA after controlling for age, sex, BMI, approach, proximal femoral morphology, and implant design

Introduction: Total knee replacement has become a common procedure with good clinical results. Today many different designs of the femoral component of bicondylar endoprostheses are offered by industry. The femoral components show similar designs however different angles and length of the cross sections are specific. Because of these design differences the preoperative planning and sparing bone resection are difficult at the revision surgery. The aim of this experimental study was to compare the design of femoral components at their cross section contours to find congruence and differences of common bicondylar endoprostheses to prove the possibility of design exchange during revision surgery. Material and method: Ten femoral components (e.motion. ®. , Genesis II, Genia. ®. , Innex. ®. , LCS. ®. , Multigen Plus, NexGen. ®. , P.F.C. ®. , Scorpio. ®. , Vanguard. ®. ) of similar implant size were analysed with regard to their cross section design. Therefore the constructional properties of the inner surface (direction and length of cross sections) of the components were determined. The components were scanned with a three-dimensional laser scanner and were transferred to two dimensional CAD models to the lateral and frontal view in order to compare the inner contours. The contours of the cross sections were overlaid with congruence of the posterior and anterior cross section of all components at lateral view. Results: Four of the ten analysed femoral components showed good congruence of the cross sections. Here, only a few additional bone resections or extra bone cement have to be done at the diagonal cross sections to change the femoral design among each other. Four other components show wide differences between the inner contours in comparison to the first four components especially at their posterior and diagonal cross sections. Two components can not be compared with the others due to their diagonal distal cross section. Discussion: The numerical results shows good congruence of cross section contours of some analysed femoral components. Furthermore there were clear design differences which complicate the exchange of the femoral component at revision surgery. The use of an elementary inner contour of femoral components of bicondylar endoprostheses could be an advantage for revision arthroplasty in regard to bone sparing surgical treatment

In replacing the human knee, we attempt to reproduce the stability of the normal knee so that the knee will feel as close to normal as possible to the patient. To answer the question, “Which features matter?” we must first examine the stability of the normal knee. Compliance and stiffness: Stability is measured as “force-displacement” behavior. That is, a force is applied to the knee and the relative motion is measured. Engineers refer to the curves generated by this type of experiment as “stiffness”. Because stiffness is not a term that orthopaedists like to hear when referring to a knee, the inverse term “compliance” often is used. Ligament stress-strain: The force-displacement test for ligaments is called a “stress-strain” curve and shows three regions of force-displacement response. Early in loading a small force causes considerable displacement. This is called the “toe region” of the curve. After a certain amount of displacement, the ligament enters the “elastic region” of the curve and becomes markedly more stiff. Finally, if enough force is applied, the ligament begins to fail at its “yield point”. Ligaments “live” in the toe region of the stress-strain curve. This can be seen clinically when, in response to varus-valgus and anteroposterior stress, the tibia moves relative to the femur until it is stopped by tension in the ligament. This is the ligament moving from the toe region into the elastic region. Compliance of the knee: In a number of studies done in the 1970s, the compliance of the knee was found to be least to both varus-valgus and anteroposterior loads in full extension. In flexion, compliance increases particularly to varus-valgus stress. This implies that the ligamentous structures about the knee are most tight in extension and become more lax in flexion. When external load is applied to the knee, either in the form of muscle contraction or bearing weight, the compliance of the knee decreases (i.e., it becomes more stiff and more stable). Loading will decrease the tension in the ligaments, yet the knee is less compliant. The only way this can happen is by the geometry of the surfaces imparting the stability. The conclusion from these studies is that the human knee, when moving in the usual plane of motion, is stabilised by the geometry of the surfaces, or the congruency of the femur and tibia. Ligaments are recruited to limit motion when forces outside the plane of motion (“out-of-plane” loads) are applied to the knee. These loads move the knee ligaments from the toe region into the elastic region of their stress-strain curve. Two kinds of total knee prosthesis design: Most total knees are designed to have little or no congruence between the femur and tibia, likely because of the worry about “kinematic conflict” that dates to the four-bar-linkage model of knee motion first proposed by Zuppinger in 1907. In these types of total knees, the ligaments are tensioned (i.e., “balanced”) so that they do the job done in the normal knee by congruence. A few total knees are designed for congruence between the femur and tibia, either in just the medial compartment or in both compartments. The answer to the question, “What is needed for total knee stability?” For non-congruent knee prostheses, the ligaments must be balanced or tensioned into the elastic portion of the stress-strain curve so that the knee is stable. The ligaments must remain in the elastic region indefinitely or the knee will be unstable. For congruent knee prostheses, the ligaments can be left in the toe region and rely, similar to the normal knee, on the geometry of the surfaces to provide stability and allow the ligaments to be recruited for out-of-plane loads. The ligaments must not be left too loose, lest the knee be unstable to out-of-plane loads but must not be as tight as is done with ligament tensioning prostheses

This study looks at the long-term outcome and morbidity following non-operative management of both-columns fractures (BCF) with secondary congruence. A retrospective review was carried out of all both-columns acetabular fractures managed non-operatively from 1984 to 2004. Patients were clinically assessed using a modified Merle d’Aubigne (Matta’s modification) score and quality of life assessed using the SF-36 health survey. The results of the SF-36 scores for this group of patients were compared with the UK normative values and the student t-test was applied to compare the respective means. All these patients were managed according to the senior consultant’s protocol. Original acetabular radiographs were examined to confirm the classification had been correct. Late radiographs were inspected for the presence of union, avascular necrosis, non-union, secondary osteoarthritis (OA) and heterotopic ossification. In the last 20 years, 57 patients have been managed non-operatively. 10 had died from unrelated causes and 16 were lost to, or declined follow-up. This left 31 patients available for assessment with at least 12 months following injury. The age at the time of injury ranged from 14 – 89 years. The majority of injuries were sustained in road traffic accidents. The mean hip score was 15.5. 72% of the clinical scores were in excellent or good categories at the time of review. The SF-36 scores were not statistically significantly different from the normal population (P< 0.05). All fractures had clinically and radiologically united at follow-up. Surprisingly, there were no cases of heterotopic ossification or avascular necrosis. 4 patients developed secondary OA of the hip. Most of the BCF demonstrate ‘secondary congruence’ after the injury assessed on Judet and pelvic radiographs. Good clinical outcomes with minimal complications can be achieved with conservative management of such fractures with secondary congruence, particularly in the older patients