Introduction: Transient posterolateral subluxation of the lateral femoral condyle has been postulated as a non-contact mechanism of ACL rupture. The consistent location of MRI bone bruises on the anterior half of the lateral femoral condyle and the posterior rim of the lateral tibial plateau in ACL injuries suggest this mechanism of injury. Previous studies utilizing radiographs have investigated and eliminated the possibility of an increase in posterior tibial slope angle as a risk factor for ACL injury. None, however, have specifically measured the slope angle of the lateral tibial plateau. This study was designed to utilize MRI images for specific measurement of the lateral tibial slope angle and investigate this as a risk factor for ACL injuries. Materials & methods: The MRI images of 30 knees with complete ACL ruptures (Group I) and those of 30 knees with an intact ACL were studied. Both groups were age-matched (range 15 to 50 years) and predominantly male. The slope angles of the medial plateau and the lateral tibial plateau were measured separately. Statistical comparison was made between the slope angles of the medial and lateral tibial plateaus within both groups, and between the lateral tibial slope angles of Group I and Group II., using a Student’s t-Test. Results: The mean slope angle of the medial plateau was 3.43 degrees in Group I and 3.67 in Group II. The mean slope angle of the lateral tibial plateau was 6.40 degrees in Group I, and 5.43 in Group II. The difference between medial and lateral slope angles was statistically significant, as well as that between the lateral tibial slopes of Group I and Group II. There was no statistical difference between the mean slope angles of the medial plateau of both groups. Conclusion: There is a significant difference in slope angles of the medial and lateral tibial plateaus, and thus the need to specify the lateral tibial slope angle in determining slope angles as a risk for ACL injuries. While there is a statistically significant difference in lateral tibial slope angles of patients with ACL tears, the actual measured difference of one degree is not clinically useful as a predictor of ACL injury risk

The aim was to report operative complications, radiographic and patient-reported outcomes following lateral tibial plateau fracture fixation augmented with calcium phosphate cement (CPC). From 2007–2018, 187 patients (median age 57yrs [range 22–88], 63% female [n=118/187]) with a Schatzker II/III fracture were retrospectively identified. There were 103 (55%) ORIF and 84 (45%) percutaneous fixation procedures. Complications and radiographic outcomes were determined from outpatient records and radiographs. Long-term follow-up was via telephone interview. At a median of 6 months (range 0.1–138) postoperatively, complications included superficial peroneal nerve injury (0.5%, n=1/187), infection (6.4%, n=12/187), prominent metalwork (10.2%, n=19/187) and post-traumatic osteoarthritis (PTOA; 5.3%, n=10/187). The median postoperative medial proximal tibial angle was 89o (range 82–107) and posterior proximal tibial angle 82o (range 45–95). Three patients (1.6%) underwent debridement for infection and 27 (14.4%) required metalwork removal. Seven patients (4.2%) underwent total knee replacement for PTOA. Sixty percent of available patients (n=97/163) completed telephone follow-up at a median of 6yrs (range 1–13). The median Oxford Knee Score was 42 (range 3–48), Knee injury and Osteoarthritis Outcome Score 88 (range 10–100), EuroQol 5-Dimension score 0.812 (range −0.349–1.000) and Visual Analogue Scale 75 (range 10–100). There were no significant differences between ORIF and percutaneous fixation in patient-reported outcome (all p>0.05). Fixation augmented with CPC is safe and effective for lateral tibial plateau fractures, with a low complication rate and good long-term knee function and health-related quality of life. Percutaneous fixation offers a viable alternative to ORIF with no detriment to patient-reported outcome

Knee laxity following anterior cruciate ligament (ACL) injury is a complex phenomenon influenced by various biomechanical and anatomical factors. The contribution of soft tissue injuries – such as ligaments, menisci, and capsule – has been previously defined, but less is known about the effects of bony morphology. (Tanaka et al, KSSTA 2012) The pivot shift test is frequently employed in the clinical setting to assess the combined rotational and translational laxity of the ACL deficient knee. In order to standardise the maneuver and allow for reproducible interpretation, the quantitative pivot shift test was developed. (Hoshino et al, KSSTA 2013) The aim of this study is to employ the quantitative pivot shift test to determine the effects of bone morphology as determined by magnetic resonance imaging (MRI) on rotatory laxity of the ACL deficient knee. Fifty-three ACL injured patients scheduled for surgical reconstruction (36 males and 17 females; 26±10 years) were prospectively enrolled in the study. Preoperative magnetic resonance imaging (MRI) scans were reviewed by two blinded observers and the following parameters were measured: medial and lateral tibial slope, tibial plateau width, femoral condyle width, bicondylar width, and notch width. (Musahl et al. KSSTA 2012). Preoperatively and under anaesthesia, a quantitative pivot shift test was performed on each patient by a single experienced examiner. An image analysis technique was used to quantify the lateral compartment translation during the maneuver. Subjects were classified as “high laxity” or “low laxity” based upon the median value of lateral compartment translation. (Hoshino et al. KSSTA 2012) Independent t-tests and univariate logistic regression were used to investigate the relationship between the pivot shift grade and various features of bone morphology. Statistical significance was set at p<0.05. A high inter-rater reliability was observed in all MRI measurements of bone morphology (ICC=0.72–0.88). The median lateral compartment translation during quantitative pivot shift testing was 2.8mm. Twenty-nine subjects were classified as “low laxity” (2.8mm). The lateral tibial plateau slope was significantly increased in “high laxity” patients (9.3+/−3.4mm versus 6.1+/−3.7mm; p<0.05). No other significant difference in bone morphology was observed between the groups. This study employed an objective assessment tool – the quantitative pivot shift test – to assess the contribution of various features of bone morphology to rotatory laxity in the ACL deficient knee. Increased lateral tibial plateau slope was shown to be a significant independent predictor of high laxity. These findings could help guide treatment strategies in patients with high grade rotatory laxity. Further research into the role of tibial osteotomies in this sub-group is warranted

Type-I fractures of the lateral tibial plateau were simulated by osteotomy in 18 pairs of unembalmed cadaver tibiae. One fracture of each pair was fixed with two lag screws whereas the contralateral site was stabilised with three lag screws, or two lag screws plus an antiglide screw. The lateral plateau was displaced downwards using a servohydraulic materials testing machine and the resulting force and articular surface gap were recorded. Yield load was defined as the maximum load needed to create a 2.0 mm articular offset at the fracture line. The yield loads of the three-lag-screw (307 ± 240 N) and antiglide constructs (342 ± 249 N) were not significantly different from their two-screw control constructs (231 ± 227 and 289 ± 245 N, respectively). We concluded that adding an antiglide screw or a third lag screw did not provide any biomechanical advantage in stabilising these fractures

Purpose of the study: We compared in vitro the efficacy of screw-plate fixation versus double screw fixation on a model of type 2 Schatzker fracture of the lateral tibial plateau. Materials and methods: Ten screw-plate fixations using a lateral prebent plate and 10 double-screw fixations (6.5 mm screws) were made on 10 pairs of non-embalmed cadaver knees after simulation of type 2 Schatzker fractures. The strength of each fixation was tested with a compression device. Criteria indicating failure were displacements greater than 2 mm of one or more fracture lines. The force applied at rupture and the stiffness of each type of fixation were compared. Wilcoxon’s test was used for statistical analysis. Results: Force at rupture and stiffness of the fixation were similar for the two types of fixation. There was no statistical difference (p > 0.05) between the screw-plate and the double-screw fixations. Discussion: Our findings on a model of type 2 Schatzker fractures are in agreement with previous data obtained by other authors working on models of type 1 Schatsker fractures. The biomechanical stability of the double-screw fixation is as good as that obtained with screw-plate fixation for the treatment of fractures of the lateral tibial plateau

This study reports the 5-year clinical and radiological outcomes of a simple arthroscopic-assisted technique for Schatzker type II and III tibial plateau fractures, without bone grafting. Forty six patients (46% males, 54% females, average age 48 years, SD 13.6 years), with tibial plateau fractures Schatzker type II (41%) and III (59%), underwent an arthroscopic-assisted technique conceived to use a compacted cancellous bone graft, taken from the medial metaphyseal side of the tibia, and a percutaneous fixation. The patients were prospectively followed-up at one, three and five years from surgery. Independent assessments were carried out using Knee Society Score, HSS score and Rasmussen’s clinical and radiological scores. At 5-year follow-up patients underwent a weight-bearing radiograph of both limbs. At last follow-up evaluation Knee Score (average 93.2, SD 7.7) was excellent in 37 patients (80%), good in six (13%), fair in three (7%). Function Score (average 94.8, SD 8.51) was excellent in 38 patients (83%), good in five (11%), fair in three (6%). HSS score (average 93.4, SD 8.23) was excellent in 41 patients (89%), good in five (11%). The average Rasmussen clinical score was 28.2 (SD 1.4). The radiological Rasmussen score was excellent in five patients (11%), good in 39 (85%) and fair in two (4%). In the weight-bearing radiographs a valgus deviation was present in four patients (8.7%). Arthroscopic-assisted technique for lateral tibial plateau fractures without bone grafting has outcomes encouraging and comparable to the results of other techniques that use either iliac crest graft or bone substitutes

We investigated the stability of seven Schatzker type II fractures of the lateral tibial plateau treated by subchondral screws and a buttress plate followed by immediate partial weight-bearing. In order to assess the stability of the fracture, weight-bearing inducible displacements of the fracture fragments and their migration over a one-year period were measured by differentially loaded radiostereometric analysis and standard radiostereometric analysis, respectively. The mean inducible craniocaudal fracture fragment displacements measured −0.30 mm (−0.73 to 0.02) at two weeks and 0.00 mm (−0.12 to 0.15) at 52 weeks. All inducible displacements were elastic in nature under all loads at each examination during follow-up. At one year, the mean craniocaudal migration of the fracture fragments was −0.34 mm (−1.64 to 1.51). Using radiostereometric methods, this case series has shown that in the Schatzker type II fractures investigated, internal fixation with subchondral screws and a buttress plate provided adequate stability to allow immediate post-operative partial weight-bearing, without harmful consequences

We compared internal fixation augmented with a trabecular metal implant to internal fixation augmented with morcellized bone grafting for depressed lateral tibial plateau fractures. Six cadaveric tibia pairs were prepared and tested on a MTS machine for both cyclic loading and static load to failure. Results showed greater resistance in cyclic loading and load to failure in the trabecular metal group. We found half the loss of reduction of the tibial articular surface compared after cyclic loading over 10 000 cycles. These surprising results show the biomechanical superiority of our trabecular metal construct over the current standard of care. Restoration and maintenance of the plateau surface are the key points in the treatment of tibial plateau fractures. Any deformity of the articular surface jeopardises the future of the knee by causing osteoarthritis and axis deviation. The purpose of this study is to develop a more solid way to fix the Shatzker III fracture and to test a trabecular metal implant in the trauma setting for the first time. Six matched pairs of fresh frozen human cadaveric tibias were fractured and randomly assigned to be treated with either the standard of care (two 4,5mm cortical raft screws augmented with morcellized bone graft) or the new method (the same screws supporting a 2 cm diameter trabecular metal disc placed under the comminuted articular surface). The specimens were tested in cyclic loading and put at load to failure. The trabecular metal construct showed 40% less caudad displacement of the articular surface (1,43 mm vs 0,81 mm) in cyclic loading (p< 0.05). Its mechanical failure occurred at a mean of 3275 N compared to 2650 N for the standard of care construct (p< 0,05). The current study shows the biomechanical superiority of our trabecular metal construct compared to the current standard of treatment with regards to both its resistance to caudad displacement of the articular surface in cyclic loading and its strength at load to failure. Trabecular metal is a good metaphyseal void filler in the studied fracture

Aims: Propose of this study is to evaluate the results of mini open surgical technique in treatment of tibial plateau fractures. Methods: Between September 1999 and September 2000, 10 patients (6 men, 4 women) with closed tibia plateau fractures were treated with arthroscopic and mini open surgical technique. The mean age was 48 (range 28–72 years). The mean follow-up was 26 months (range 20 months to 36 months). Schatzker classiþcation system was used for evaluation and classiþcation of the fracture patterns. Hence, three cases were type 1, four were type 2 and three cases were type 3. The arthroscopy was done in all the cases. No meniscus tears were found in all the patients. The plateau fracture has been reconstructed with elevation, through an antero-medial window in the proximal metaphysis of the tibia, with a particular carrot system. No autograft bone was adopted. We used a percutaneous þxation with AO cannulated screws (1–3 screws). Results: The results were evaluated with the HSS Knee Score System. There were no preoperative and postoperative complications. The results were 80% excellent, 20% good. The average of the Knee Score was 94 (range 78–100) and the average of the Functional Score was 96 (range 80–100). Conclusions: The arthroscopy and the mini open surgical technique create a complete anatomical reduction of articular fractured area with no graft.

Aims. Osteoarthritis (OA) is a common degenerative joint disease. The osteocyte transcriptome is highly relevant to osteocyte biology. This study aimed to explore the osteocyte transcriptome in subchondral bone affected by OA. Methods. Gene expression profiles of OA subchondral bone were used to identify disease-relevant genes and signalling pathways. RNA-sequencing data of a bone loading model were used to identify the loading-responsive gene set. Weighted gene co-expression network analysis (WGCNA) was employed to develop the osteocyte mechanics-responsive gene signature. Results. A group of 77 persistent genes that are highly relevant to extracellular matrix (ECM) biology and bone remodelling signalling were identified in OA subchondral lesions. A loading responsive gene set, including 446 principal genes, was highly enriched in OA medial tibial plateaus compared to lateral tibial plateaus. Of this gene set, a total of 223 genes were identified as the main contributors that were strongly associated with osteocyte functions and signalling pathways, such as ECM modelling, axon guidance, Hippo, Wnt, and transforming growth factor beta (TGF-β) signalling pathways. We limited the loading-responsive genes obtained via the osteocyte transcriptome signature to identify a subgroup of genes that are highly relevant to osteocytes, as the mechanics-responsive osteocyte signature in OA. Based on WGCNA, we found that this signature was highly co-expressed and identified three clusters, including early, late, and persistently responsive genes. Conclusion. In this study, we identified the mechanics-responsive osteocyte signature in OA-lesioned subchondral bone. Cite this article: Bone Joint Res 2022;11(6):362–370

Aims. Commonly performed unicompartmental knee arthroplasty (UKA) is not designed for the lateral compartment. Additionally, the anatomical medial and lateral tibial plateaus have asymmetrical geometries, with a slightly dished medial plateau and a convex lateral plateau. Therefore, this study aims to investigate the native knee kinematics with respect to the tibial insert design corresponding to the lateral femoral component. Methods. Subject-specific finite element models were developed with tibiofemoral (TF) and patellofemoral joints for one female and four male subjects. Three different TF conformity designs were applied. Flat, convex, and conforming tibial insert designs were applied to the identical femoral component. A deep knee bend was considered as the loading condition, and the kinematic preservation in the native knee was investigated. Results. The convex design, the femoral rollback, and internal rotation were similar to those of the native knee. However, the conforming design showed a significantly decreased femoral rollback and internal rotation compared with that of the native knee (p < 0.05). The flat design showed a significant difference in the femoral rollback; however, there was no difference in the tibial internal rotation compared with that of the native knee. Conclusion. The geometry of the surface of the lateral tibial plateau determined the ability to restore the rotational kinematics of the native knee. Surgeons and implant designers should consider the geometry of the anatomical lateral tibial plateau as an important factor in the restoration of native knee kinematics after lateral UKA. Cite this article: Bone Joint Res 2019;8:593–600

Introduction: To our knowledge there are no published data comparing the actual anteroposterior (AP) and mediolateral (ML) dimensions of the medial and lateral tibial plateau with tibial dimensions of current available tibial designs of unicompartimental arthroplasies (UKA). Inter- and intra-gender specific dimensions may not match current designs. Methods: Medial and lateral tibial plateaus of 42 CTs of cadaveric knees were measured in its AP and ML dimension. There were 25 male and 17 female knees. The results of the measurements were compared to current in the US available UKA systems. Results: Wide variations in all observed articular femoral and tibial surfaces were observed. There are gender and side differences between medial and lateral in respect to the aspect ratio AP/ML:AP length of the female medial tibial plateau is 4.9 cm (Std Dev 0.38, n=25), AP length lateral tibial plateau is 4.5 cm (Std Dev 0.5, n=25), ML width medial plateau is 2.9 cm (Std Dev 0.27, n=25), ML lateral tibial plateau is 3.1 cm (Std Dev 0.21, n=25), AP length of the male medial tibial plateau is 5.5 cm (Std Dev 0.30, n=26), AP length lateral tibial plateau is 4.95 cm (Std Dev 0.34, n=26), ML width medial plateau is 3.3 cm (Std Dev 0.20, n=26), ML width lateral tibial plateau is 3.48 cm (Std Dev 0.24, n=26), All measurements comparing female and male data for medial and lateral surfaces were different (Student-t, p< 0.005). All current available observed UKA match best the female medial plateau, less the male tibial plateau and very poor the male and female lateral tibial plateau. Discussion/Conclusion: Intra- and inter gender differences of morphologic data are shown for all articular surfaces, medial and lateral femur, as well as medial and lateral tibia. Best matches between AP/ML ratio and implants were seen for the medial tibial components and the female medial plateau. Poor matches were observed for the lateral female and male tibial plateau. The common practice of using a right medial tibial implant for the lateral side should be reconsidered. The question if the poor match of current medial tibial components in larger males has a relationship to the inferior clinical results of males undergoing UKA requires more investigation

A total of 20 patients with a depressed fracture of the lateral tibial plateau (Schatzker II or III) who would undergo open reduction and internal fixation were randomised to have the metaphyseal void in the bone filled with either porous titanium granules or autograft bone. Radiographs were undertaken within one week, after six weeks, three months, six months, and after 12 months. The primary outcome measure was recurrent depression of the joint surface: a secondary outcome was the duration of surgery. The risk of recurrent depression of the joint surface was lower (p < 0.001) and the operating time less (p < 0.002) when titanium granules were used. The indication is that it is therefore beneficial to use porous titanium granules than autograft bone to fill the void created by reducing a depressed fracture of the lateral tibial plateau. There is no donor site morbidity, the operating time is shorter and the risk of recurrent depression of the articular surface is less. . Cite this article: Bone Joint J 2015; 97-B:836–41

Several studies have highlighted the relationship between anterior cruciate (ACL) injury and knee geometry particularly tibial slope (TS). However, clinical data are inconsistent, whether the lateral or medial or slopes have a different influence on ACL injury. Our goal was to assess whether the medial, lateral slopes are associated with ACL injury and whether meniscus geometry is associated with ACL injury. In addition, we sought to determine if lateral meniscal height could serve as a simple surrogate measurement for ACL injury risk. A case-controlled study compared 68 patients with an ACL injury and 68 matched nested controls. Radiological analysis of MRI measured the anterior-posterior distance of the medial and lateral plateaus, the tibial slope of both plateaus and meniscus geometry. Groups were compared using a Mann-Whitney test and α < 0 .05. The lateral tibial plateau slope was significantly higher in the ACL injured group (6.92 degrees ±5.8) versus the control group 2.68 ±5.26 (p 0.0001). In addition, the lateral meniscal slope was significantly steeper with (ACL injuries: −1 ±4.7 versus −4.73 ±4.4 (p 0.0001) in the control group. The ACL Injured group had a significantly lower lateral meniscal height 0.76 cm ±0.09, compared to the control group that has 0.88 cm ±0.12 (p 0.0001). The Lateral meniscal height had a sensitivity of 76.47% and specificity 75% for predicting ACL injury using a cut off of. Patients with ACL-injury had significantly higher lateral tibial plateau slope. Lateral meniscus height was found to be an easy measurement to make on MRI with a high specificity for predicting ACL injury. Lateral tibial slope and meniscal Geometry can be used to identify patients with high risk of an ACL injury, that might benefit from further surgery to optimize rotational stability in high-risk patients

Introduction and Aims: A number of x-ray appearances have been identified as indicative of discoid menisci. None are reliable or statistically significant. The purpose of this paper is to identify a reliable radiographic sign, diagnostic of the discoid lateral meniscus. Method: The anteroposterior view radiographs of 14 knees in 13 patients with arthroscopically proven discoid meniscus were studied. Ages ranged from 11 to 26, with a mean age of 18.4 ± 4.84 years, right to left ratio 9/5, male to female ratio 8/5. Fifteen normal knees in 14 people were used as a control group, age from 11 to 30, mean age 16.20 ± 6.41, right to left ratio 8/7, male to female ratio 6/8. The parameters measured were: Lateral Joint Space (LJS); Height of the Lateral Tibial Spine (LTS); change of the Medial Tibial Spine (MTS); Height of Fibular Head (HFH); changes of the Edge of the Lateral Tibial Plateau (ELTP), cupping of the lateral tibial plateau, and squaring of the lateral femoral condyle. Results: There was no significant difference between the two groups in LJS, height of LTS, cupping of the lateral tibial plateau, and squaring off of the lateral femoral condyle. There was a difference between the two groups in HFH which was statistically significant at an absolute value of p = 0.033, but not significant in normalised value p = 0.056. The medial tibial spine was sharpened in three patients. There were 12 positive changes on ELTP out of 14 patients (85.71%) in the discoid group, while only one positive of 15 (6.67%) in the normal group, and the difference between the two groups was statistically significant at p< 0.01. The diagnosis parameters were Sensitivity (Se) = 85.71%, Specificity (Sp) = 93.33%, Positive predictive value (PV+) = 92.31%, Negative predictive value (PV−) = 87.50%, Correct rate (ñ) = 89.66%. The typical change on the edge of lateral tibial plateau is sharpening and/or formation of a spur. Conclusion: Sharpening with spur formation on the edge of lateral tibial plateau is a diagnostic radiological sign of a discoid lateral meniscus

Computer Assisted Total Knee Arthroplasty (CAS TKR) has been shown to provide excellent and reproducible limb mechanical alignment. CAS TKR has also been demonstrated to reduce limb alignment variance and outliers. Previous studies have shown improved mechanical alignment both radiographically and clinically. Specifically, CAS TKR has been shown to result in alignment deviations less than 3 degrees from neutral mechanical femoral and tibial axes. Furthermore, CAS TKR also permits any significant pre-operative tibial deformity to be quantified prior to performing tibial osteotomies. In this study, we describe the use of computer navigation to quantify the amount of bone loss on the medial or lateral tibial plateau and the subsequent use of this data to assess the need for augmentation with tibial wedges. Two hundred and thirty consecutive primary computer assisted total knee arthroplasties were performed by one senior surgeon (L.P.) at Northwestern Memorial Hospital. In all cases, the tibial deformity was quantified and recorded intraoperatively using computer navigation software. The deformity was recorded in the navigation software by inputting the lowest point on the deformed tibial plateau and the mid point on the non-deformed tibial plateau using navigation markers. After Institutional Review Board approval was obtained, a retrospective review of the patient operative reports and patient charts was performed. Operative reports were reviewed to identify cases with the difference between the values of medial and lateral tibial plateaus exceeded thirteen millimeters and cases when tibial augmentation was performed. In cases utilising medial or lateral tibial augmentation, pre operative and post operative anterior posterior and lateral knee radiographs and long leg standing anterior posterior radiographs were reviewed to measure the joint line restoration and final mechanical limb alignment. All two hundred and thirty operative dictations and patient charts were reviewed. In seven cases, the difference between the values of the medial and lateral tibial plateaus was greater than thirteen millimeters. In all seven cases, tibial augmentation was utilized in order to prevent resection of tibial bone in excess of fourteen millimeters. In cases with a difference of medial and lateral tibial plateau values of less than thirteen millimeters, no tibial augmentation was utilised. For the seven cases using tibial augmentation, preoperative and post-operative knee and long standing radiographs were reviewed to examine joint line restoration and final limb alignment. In all seven patients, joint line restoration was successful within 4 millimeters and long standing radiographs revealed excellent limb alignment. Computer Assisted Total Knee Arthroplasty has already been shown to provide excellent limb alignment and reduce variance and outliers. We demonstrate that Computer Assisted Total Knee Arthroplasty in patients with significant tibial deformities can help assess and the amount of bone loss on the medial or lateral tibial plateaus. Excessive tibial resection to restore the mechanical axis and joint line can be avoided by quantifying the amount of tibial bone loss prior to osteotomy. Thus, Computer Assisted Total Knee Arthroplasty can successfully restore the joint line and overall limb alignment with conservative bone resection in patients with significant pre-operative tibial deformities

Biplane video X-ray (BVX) – with models segmented from magnetic resonance imaging (MRI) – is used to directly track bones during dynamic activities. Investigating tibiofemoral kinematics helps to understand effects of disease, injury, and possible interventions. Develop a protocol and compare in-vivo kinematics during loaded dynamic activities using BVX and MRI. BVX (60 FPS) was captured whilst three healthy volunteers performed three repeats of lunge, stair ascent and gait. MRI scans were performed (Magnetom 3T Prisma, Siemens). 3D bone models of the tibia and femur were segmented (Simpleware Scan IP, Synopsis). Bone poses were obtained by manually matching bone models to X-rays (DSX Suite, C-Motion Inc.). Mean range of motion (ROM) of the contact points on the medial and lateral tibial plateau were calculated using custom MATLAB code (MathWorks). Results were filtered using an adaptive low pass Butterworth filter (Frequency range: 5-29Hz). Gait and Stair ascent activities from one participant's data showed increased ROM for medial-lateral (ML) translation in the medial compartment but decreased ROM in anterior-posterior (AP) translation when comparing against the same translations on the lateral compartment of the tibial plateau. Lunge activity showed increased ROM for both ML and AP translation in the medial compartment when compared with the lateral compartment. These results highlight the variability in condylar translations between different activities. Understanding healthy in-vivo kinematics across different activities allows the determination of suitable activities to best investigate the kinematic changes due to disease or injury and assess the efficacy of different interventions. Acknowledgements: This research was supported by the Engineering and Physical Sciences Research Council (EPSRC) doctoral training grant (EP/T517951/1)

Aims. Mobile-bearing unicompartmental knee arthroplasty (UKA) with a flat tibial plateau has not performed well in the lateral compartment, leading to a high rate of dislocation. For this reason, the Domed Lateral UKA with a biconcave bearing was developed. However, medial and lateral tibial plateaus have asymmetric anatomical geometries, with a slightly dished medial and a convex lateral plateau. Therefore, the aim of this study was to evaluate the extent at which the normal knee kinematics were restored with different tibial insert designs using computational simulation. Methods. We developed three different tibial inserts having flat, conforming, and anatomy-mimetic superior surfaces, whereas the inferior surface in all was designed to be concave to prevent dislocation. Kinematics from four male subjects and one female subject were compared under deep knee bend activity. Results. The conforming design showed significantly different kinematics in femoral rollback and internal rotation compared to that of the intact knee. The flat design showed significantly different kinematics in femoral rotation during high flexion. The anatomy-mimetic design preserved normal knee kinematics in femoral rollback and internal rotation. Conclusion. The anatomy-mimetic design in lateral mobile UKA demonstrated restoration of normal knee kinematics. Such design may allow achievement of the long sought normal knee characteristics post-lateral mobile UKA. However, further in vivo and clinical studies are required to determine whether this design can truly achieve a more normal feeling of the knee and improved patient satisfaction. Cite this article: Bone Joint Res 2020;9(7):421–428