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INTRODUCTION The purpose of this study was to evaluate balance function before and after total knee arthroplasty (TKA) using Berg balance scale (BBS). The study also aimed to identify factors associated with balance impairment. MATERIALS AND METHODS Ninety-three knees in 90 patients were prospectively evaluated using their BBS scores, passive knee extension/flexion angles, Visual analogue scale for pain scores, hip-knee-ankle angles, and knee extensor/flexor muscle strengths before and after TKA. A total BBS score of less than 45 indicates an enhanced risk of multiple falls. Multivariate logistic regression models were performed to elucidate factors associated with post-operative BBS score. RESULTS A significant difference in mean pre- and post-operative BBS scores were noted (49.3 ± 6.4 vs. 52.2 ± 4.7) (p

Objectives The concept of locomotive syndrome (LS) and its evaluation method, the LS risk test, have been applied in an integrated manner to capture the decline in mobility resulting from musculoskeletal disorders. The purpose of this study was to evaluate the impact of total knee arthroplasty (TKA) in the elderly with knee osteoarthritis, a common disorder found in LS. Methods A total of 111 patients were registered prior to TKA and postoperatively followed up for 1 year. Three components of the LS risk test (the two-step test, stand-up test, and Geriatric Locomotive Function Scale-25) were assessed pre- and postoperatively. Results After surgery, all three components of the test showed significant improvements from the baseline. The ratio of Stage 3 LS patients (progressed stage of decrease in mobility) reduced from 82.3% to 33.9% postoperatively. There was no significant difference in the degree of change in the scores between the younger (60–74 years) and older (≥75 years) age groups. Conclusions We found that TKA has a major impact in preventing the progression of LS in patients with knee osteoarthritis. The LS risk test is a feasible tool for the longitudinal evaluation of patients with musculoskeletal diseases of varying severity and with multiple symptoms.

The optimal placement within 3 degrees in coronal alignment was reportedly achieved in only 60 to 80% of patients when using an extramedullary alignment guide for the tibial side in total knee arthroplasty (TKA). This probably occurs because the extramedullary alignment guide is easily affected by the position of the ankle joint which is difficult to define by tibial torsion. Rotational direction of distal end of the extramedullary guide should be aligned to the anteroposterior (AP) axis of the proximal tibia to acquire optimal coronal alignment in the computer simulation studies; however, its efficacy has not been proven in a clinical setting. The distal end of the guide can be overly displaced from the ideal position when using a conventional guide system despite the alignment of the AP axis to the proximal tibia. This study investigated the effect of displacement of the distal end of extramedullary guide relative to the tibial coronal alignment while adjusting the rotational alignment of the distal end to the AP axis of the proximal tibia in TKA. A total of 50 TKAs performed in 50 varus osteoarthritic knees using an image-free navigation system were included in this study. The rotational alignment of the proximal side of the guide was adjusted to the AP axis of the proximal tibia. The position of the distal end of the guide was aligned to the center of the ankle joint as viewed from the proximal AP axis (ideal position) and as determined by the navigation system. The tibial intraoperative coronal alignments were recorded as the distal end was moved from the ideal position at 3-mm intervals. The intraoperative alignments were 0.5, 0.9, and 1.4 degrees in valgus alignment with 3-, 6-, and 9-mm medial displacements, respectively. The intraoperative alignments were 0.7, 1.2, and 1.7 degrees in varus alignment with 3-, 6-, and 9-mm lateral displacements, respectively. In conclusion, the acceptable tibial coronal alignment (within 2 degrees from the optimal alignment) can be achieved, although some displacement of the distal end from the ideal position can occur after the rotational alignment of the distal end of the guide is adjusted to the AP axis of the proximal tibia.

This study aimed to evaluate whether preparation of the subtalar joint affects the clinical outcomes after tibiotalocalcaneal arthrodesis using an intramedullary nail with fins for rheumatoid ankle/hindfoot deformity. Fifty-three joints in 51 patients who underwent tibiotalocalcaneal arthrodesis using an intramedullary nail with fins for rheumatoid arthritis at 2 institutions were included. Ten patients were male and 41 were female, with a mean age at surgery and follow-up period of 61.3 years and 71.6 months, respectively. Radiographic bone union was evaluated at the most recent visit. Univariate and multivariable analyses were performed to determine the risk factors associated with nonunion. The mean postoperative Japanese Society for Surgery of the Foot ankle/hindfoot scale was 65.3 (range, 5–84). The tibiotalar nonunion rate was 0%, whereas the subtalar nonunion rate was 43.3% (23 joints). Revision surgery was performed in 5, all of which were due to painful subtalar nonunion. Absence of subtalar curettage and earlier postoperative weightbearing were significantly associated with subtalar nonunion (p = .0451 and p = .0438, respectively). Subtalar nonunion after tibiotalocalcaneal arthrodesis for rheumatoid hindfoot is associated with higher revision rate. To decrease the risk of subtalar nonunion after tibiotalocalcaneal arthrodesis with an intramedullary nail in rheumatoid patients, curettage for the subtalar joint should be performed, and full weightbearing should be delayed until at least 26 days postoperatively.

Aims This study aims to investigate the effects of posterior tibial slope (PTS) on knee kinematics involved in the post-cam mechanism in bi-cruciate stabilized (BCS) total knee arthroplasty (TKA) using computer simulation. Methods In total, 11 different PTS (0° to 10°) values were simulated to evaluate the effect of PTS on anterior post-cam contact conditions and knee kinematics in BCS TKA during weight-bearing stair climbing (from 86° to 6° of knee flexion). Knee kinematics were expressed as the lowest points of the medial and lateral femoral condyles on the surface of the tibial insert, and the anteroposterior translation of the femoral component relative to the tibial insert. Results Anterior post-cam contact in BCS TKA was observed with the knee near full extension if PTS was 6° or more. BCS TKA showed a bicondylar roll forward movement from 86° to mid-flexion, and two different patterns from mid-flexion to knee extension: screw home movement without anterior post-cam contact and bicondylar roll forward movement after anterior post-cam contact. Knee kinematics in the simulation showed similar trends to the clinical in vivo data and were almost within the range of inter-specimen variability. Conclusion Postoperative knee kinematics in BCS TKA differed according to PTS and anterior post-cam contact; in particular, anterior post-cam contact changed knee kinematics, which may affect the patient’s perception of the knee during activities. Cite this article: Bone Joint Res 2020;9(11):761–767.

Objectives The purpose of the present study was to evaluate improvement in the Knee Injury and Osteoarthritis Outcome Score (KOOS) after open-wedge high tibial osteotomy (HTO) in comparison with total knee arthroplasty (TKA) in cohorts over age 60 matched by pre-operative age, gender, body mass index (BMI), hip-knee-ankle angle (HKAA), KOOS sub-scores, and osteoarthritis (OA) grade. Methods Propensity score matching was performed between 162 HTO patients and 134 TKA patients. When calculating the propensity score by multivariate logistic regression analysis, the following pre-operative confounders were included: age, gender, BMI, HKAA, KOOS sub-scores, and OA grade. Consequently, a total of 55 patients were included in each group. The Student’s t-test was used to analyse differences in the post-operative KOOS sub-scores between groups. Results After propensity score matching, all matched pre-operative valuables were identical, with no significant differences between the HTO and TKA groups. None of the post-operative KOOS sub-scores at 1 year after surgery showed a significant difference between the HTO and TKA groups. Both groups demonstrated significant and comparable post-operative improvement in every KOOS sub-score. Conclusions In patients over age 60, there was no significant difference in short-term pain relief and improvements in activity and quality of life between HTO and TKA after propensity score matching including pre-operative age, KOOS sub-scores, and OA grade. HTO is a joint preservation procedure that is valid for knee OA even in individuals over age 60.

To assess the usefulness of a whole-leg radiograph standing on lateral-wedge insole (LWI) for predicting the change in joint line convergence angle (JLCA) before vs. after high tibial osteotomy (HTO). Forty knees with medial osteoarthritis underwent open-wedge HTO. Pre-operatively, all patients had whole-leg radiographs taken in three different conditions: supine, standing, and standing on LWI inclined at 20°. A standing whole-leg radiograph was also obtained post-operatively. Radiological measurements including JLCA and percentage of mechanical axis (%MA) were compared. Using pre-operative radiographs, correction angles were calculated with the target %MA at 62.5%. Correlations between the difference in calculated correction angle among the three pre-operative conditions and the change in JLCA before vs. after HTO were assessed. In the pre-operative standing conditions, the mean JLCA of 3.8° was significantly decreased to 3.2° using LWI, which did not differ from post-operative JLCA of 3.1°. Mean %MA significantly shifted laterally from 20.6 to 24.8% using LWI, and was strongly correlated with the change in JLCA (coefficient, 0.83). Calculated correction angles differed significantly among the three pre-operative conditions. The difference in calculated correction angle between standing with and without LWI was strongly correlated to the change in standing JLCA before vs. after HTO (coefficient, 0.73). Larger differences in calculated correction angles between pre-operative radiographs standing with and without LWI predicted larger changes in JLCA after HTO. Whole-leg radiograph standing on LWI is a promising modality for correct pre-operative planning considering patient-specific changes in JLCA before vs. after HTO. IV.

The relative impact of soft tissue balance and knee laxity on clinical outcomes after total knee arthroplasty (TKA) is not fully understood. We analyzed associations among knee laxity, kinematics, and patient-reported outcomes.Knee Society Scores were recorded in 67 patients before and after primary TKA for osteoarthritis with varus deformity (N = 78). Varus and valgus laxity was measured in 78 knees using stress radiographs. Knee kinematics were measured fluoroscopically during stair ascent in 16 knees.On average, varus laxity decreased significantly, and valgus laxity increased significantly after TKA, although the net combined varus-valgus laxity did not change significantly. Postoperatively, the magnitude of valgus laxity correlated significantly with greater patient symptoms and satisfaction scores. Patients with medial pivot kinematics scored higher on patient satisfaction and standard activities.We found that postoperative valgus laxity and medial pivot kinematics were significantly associated with better clinical outcomes. These results emphasize the importance of careful preoperative planning and attention to intraoperative alignment and ligament balancing.

The purpose of this study was to investigate the size differences of 19 different femoral component placements from the standard position in total knee arthroplasty using 3-dimensional virtual surgery.Three-dimensional bone models were reconstructed from the computed tomography data of 101 varus osteoarthritic knees. The distal femoral bone was cut perpendicular to the femoral mechanical axis (MA) in the coronal plane. Twenty different component placements consisting of 5 cutting directions (perpendicular to MA, 3° and 5° extension relative to MA [3°E-MA and 5°E-MA, respectively], and 3° and 5° flexion relative to MA [3°F-MA and 5°F-MA, respectively]) in the sagittal plane, 2 rotational alignments (clinical epicondylar axis [CEA] and surgical epicondylar axis [SEA]), and 2 rotational types of anterior reference guide (central [CR] and medial [MR]) were simulated.The mean anteroposterior dimension of femur ranged from 54.3 mm (5°F-MA, SEA, CR) to 62.5 mm (5°E-MA, CEA, MR). The largest and smallest differences of anteroposterior dimension from the standard position (3°F-MA, SEA, and CR) were 7.1 ± 1.3 mm (5°E-MA, CEA, and MR) and -1.2 ± 0.2 mm (5°F-MA, SEA, and CR), respectively. Multiple regression analysis revealed that flexion cutting direction, SEA, and CR were associated with smaller component size.The femoral component size can be affected easily by not only cutting direction but also the reference guide type and the target alignment. Our findings could provide surgeons with clinically useful information to fine-tune for unintended loose or tight joint gaps by adjusting the component size.

Background: To preserve the ability to perform physical activities among the elderly, the concept of locomotive syndrome and its evaluation method, the locomotive syndrome risk test, have been applied in an integrated manner to capture the decline in mobility resulting from musculoskeletal disorders. During treatment, physicians can use the locomotive syndrome risk test to evaluate the impact of each therapy such as total knee arthroplasty for knee osteoarthritis, a common disorder found in locomotive syndrome. The purpose of this study was to evaluate the impact of total knee arthroplasty in the elderly with respect to locomotive syndrome.Methods: A total of 111 patients were registered at six hospitals prior to total knee arthroplasty and postoperatively followed up for 1 year. Three components of the locomotive syndrome risk test (the two-step test, stand-up test, and geriatric locomotive function scale-25) were assessed together with the EuroQol-5 Dimension scores pre- and postoperatively.Results: Post surgery, all three components of the locomotive syndrome risk test as well as the EuroQol-5 Dimension utility score showed significant improvements from the baseline (two-step test, 1.01±0.25 to 1.12±0.21; stand-up test, 2.02±1.14 to 2.38±1.20; geriatric locomotive function scale-25, 38.3±15.8 to 18.7±16.6, mean ± standard deviation). The ratio of stage 3 locomotive syndrome patients (progressed stage of decrease in mobility, restricting social engagement) reduced from 82.3% to 33.9% postoperatively. There was no significant difference in the degree of change in the three test scores between the younger (60-74 years) and older (≥75 years) age groups. Conclusions: We found that total knee arthroplasty has a major impact in preventing the progression of locomotive syndrome in patients with knee osteoarthritis. The locomotive syndrome risk test is a feasible tool for longitudinal evaluation of patients with musculoskeletal diseases of varying severity and with multiple symptoms.Trial registration: This study was registered as UMIN000023595 (10/08/2016)

Selecting appropriately sized components is important in total knee arthroplasty because they can affect postoperative knee function and pain. This study investigated size differences of 19 different femoral component placements from the standard position by three-dimensional virtual surgery using three-dimensional bone models of 101 varus osteoarthritic knees. Distal femoral bone was cut perpendicular to the femoral mechanical axis (MA) in the coronal plane. Twenty different component placements consisting of five cutting directions (perpendicular to MA, 3° and 5° extension/flexion relative to MA in the sagittal plane), two rotational alignments (clinical and surgical epicondylar axes), and two rotational types of anterior reference guide (central and medial) were simulated. The mean anteroposterior dimension of the standard position was 55.5 mm which means that the difference compared to 19 different methods ranged from -1.2 ± 0.2 mm to 7.1 ± 1.3 mm. Multiple regression analysis revealed that flexion cutting direction, surgical epicondylar axis, and central were associated with smaller component size. In conclusion, the femoral component size can be affected easily by not only cutting direction but also the reference guide type and the target alignment. Our findings could provide surgeons with clinically useful information to fine-tune for unintended loose or tight joint gaps by adjusting the component size.

The purpose of this 3-dimensional (3D) surgical simulation study was to investigate the effects of axial and sagittal hinge axes (hinge axes in the axial and sagittal planes) on medial and lateral posterior tibial slope (PTS) in medial open-wedge high tibial osteotomy (OWHTO), and evaluate the quantitative relationship between hinge axis and PTS change.Preoperative computed tomography data from patients with varus knee deformity were collected. A standard hinge axis (0°) and 12 different hinge axes (6 axial hinge axes and 6 sagittal hinge axes: ±10°, ±20°, and ±30°) were defined in a 3D surgical simulation of OWHTO using a bone model. The differences between before and after simulation surgery in medial and lateral PTS, medial proximal tibial angle, opening gap, and opening wedge angle were measured.In total, 93 varus knees in 93 patients were included for study. Compared with the standard hinge axis, axial hinge axis significantly affected medial and lateral PTS (P.001). In contrast, sagittal hinge axis had no significant effect on medial and lateral PTS (P.05). Every 10° change in axial hinge axis with a mean coronal valgus correction of 10° might result in approximately 1.6° of alteration in PTS. Stepwise regression analysis showed that axial hinge axis is the most significant factors affecting PTS (β coefficient = 0.78, P.001), followed by opening wedge angle (β coefficient = 0.36, P.001) and gap ratio (β coefficient = 0.12, P0.001).Based on our findings of 3D OWHTO simulation, axial hinge axis significantly influences medial and lateral PTS in OWHTO, but sagittal hinge axis has no effect on change in PTS. Every 10° change of axial hinge axis with a 10° coronal valgus correction caused approximately 1.6° change of PTS.Hinge axis in the axial plane significantly affects PTS, but hinge axis in the sagittal plane has no effect on PTS. To maintain PTS, surgeons should make hinge axis at the true lateral position of the tibia in the axial plane. To intentionally alter PTS, an anterolateral axial hinge axis could be used to decrease PTS or a posterolateral axial hinge axis could be used to increase PTS. Opening wedge angle or gap ratio is also useful for intentional modification of PTS.

Coronal whole-leg radiography is generally used for preoperative open-wedge high tibial osteotomy (OWHTO) planning. Nevertheless, malrotational whole-leg radiographs could affect the planning, and the effects could possibly be strengthened by the knee flexed position. Consecutive 51 varus osteoarthritis knees that underwent OWHTO were included. The digitally reconstructed radiography (DRR) images parallel to the surgical epicondylar axis (neutral rotation; NR), 5° and 10° external rotation (ER) or internal rotation (IR), were reconstructed from preoperative CT. Preoperative weight-bearing line percentage (WBL%), medial proximal tibial angle (MPTA), planned opening angle, and planned postoperative MPTA were measured with OWHTO planning in each DRR image. Correlations among the measured differences relative to NR images and knee flexion angle were investigated. As the DRR image shifted from ER to IR, the differences in preoperative WBL% and MPTA gradually increased, whereas those in the opening angle gradually decreased, although all differences in the opening angle were within 0.5° on an average. Opening angle differences remarkably correlated with knee flexion angle, and knees with >10° flexion contracture had >1° difference in 10° ER or IR images. Planned postoperative MPTA had relatively high consistency regardless of whole-leg malrotation. The opening angle measurement using malrotated radiographs less than 10° would be clinically reliable in cases without knee flexion contracture. Nevertheless, extreme care should be taken in cases with >10° knee flexion contracture. The MPTA after medial opening would be a consistent and reliable parameter in whole-leg alignment evaluation.

Varus alignment is known as one of the major causes of medial compartment osteoarthritis (OA). Medial meniscus extrusion also plays a critical role in the in the development of OA. However, studies on the exact relationship between alignment parameters and medial meniscus extrusion are limited. Therefore, this study aimed to investigate this relationship in patients with knee OA. Based on a retrospective analysis of the outpatient magnetic resonance imaging (MRI) database, 190 knees were identified to be examined using weight-bearing, whole-leg radiographs and MRIs within 3 months from the first consultation. Subsequently, various parameters of lower leg alignment were measured, which affected the knee varus in radiographs. Finally, a statistical analysis was performed to assess the relationships between the OA grade, distance of medial meniscus extrusion (MME), and alignment parameters; hip–knee–ankle angle (HKAA), percentage of mechanical axis (% MA), medial proximal tibial angle (MPTA), and joint line convergence angle (JLCA). The subjects were divided according to the presence or absence of MME (Group A: MME distance below 3 mm, Group B: MME distance 3 mm and above) to assess the differences in each alignment parameter correlated with MME distance between the groups. MME distance significantly increased with OA grade progression. HKAA, % MA, MPTA, and JLCA significantly correlated with medial meniscus extrusion distance (r = − 0.21, − 0.23, − 0.16, 0.3, respectively). Multiple regression analysis of each significant alignment combined with age, sex, and body mass index revealed that HKAA, % MA, MPTA, and JLCA were significant independent factors of MME distance (P = 0.008, 0.0026, 0.011, 0.0001, respectively). These significant findings were reinforced in group B. In contrast, the correlation between alignment parameters and medial meniscus extrusion distance was not significant in group A. Varus alignment factors are related to MME distance especially in extruded meniscus knees, as the OA grade progressed. Therefore, the coexistence of varus alignment and MME can be the risk factors for OA progression. As the low MPTA was an independent alignment factor for generating varus alignment, patients with osteoarthritis of the knee with both, low MPTA and MME could be the appropriate candidates for early intervention by high tibial osteotomy. III.

To evaluate preoperative soft tissue balance for total knee arthroplasty (TKA), varus/valgus stress radiographs has been used in previous studies. While the joint line of femur and tibia is almost parallel in healthy and postoperative knees, osteoarthritis (OA) knees exhibit articular cartilage wear that causes the joint line tilting even in a non-stress condition. Therefore, the exact angle of the joint line might mislead to understand the joint laxity in OA knees. The purpose of this study was to evaluate soft tissue balance in varus OA knees using preoperative stress radiographs under three different constant loads, taking the articular cartilage wear into consideration. One hundred and eighteen varus-deformed OA knees in 102 patients were investigated before primary TKA. Preoperative knee radiographs were obtained in the anteroposterior view with no stress (defined as the neutral condition) and with varus and valgus stresses (5, 10, and 15 kg) in extension. Two different types of joint line angle (JLA), the absolute JLA (an exact angle of joint line) and the relative JLA (the absolute JLA minus the JLA in the neutral condition), were compared for the same load with the paired t test. The absolute JLA was 7.9 ± 1.2°/− 1.5 ± 2.2° under varus/valgus 15 kg stress, 6.7 ± 2.4°/− 0.3 ± 2.1° under varus/valgus 10 kg stress, and 4.7 ± 2.4°/1.1 ± 2.2° under varus/valgus 5 kg stress. Significant differences in the numerical values of the absolute JLA were observed between varus and valgus stresses for each load. The neutral JLA was 3.2 ± 2.0°. The relative JLA was 4.8 ± 2.1°/− 4.7 ± 1.8° under varus/valgus 15 kg stress, 3.5 ± 2.0°/− 3.5 ± 1.8° under varus/valgus 10 kg stress, and 1.5 ± 1.9°/− 2.1 ± 1.8° under varus/valgus 5 kg stress. No significant differences in the numerical values of the relative JLA were observed between varus and valgus stresses for each load. Consideration of cartilage wear allowed knee laxity to be evaluated more precisely in this study than in previous reports. It was shown that medial soft tissue contracture did not always exist, even in varus OA knees. Regarding clinical relevance, surgeons should be aware that underestimating medial soft tissue laxity due to reliance on the absolute JLA might lead to excessive medial tissue release and result in postoperative instability and lower patient satisfaction. IV.

This study aimed to evaluate clinical outcomes and in vivo kinematics of bi-cruciate stabilized (BCS) total knee arthroplasty (TKA), using image-matching techniques. We analyzed tibiofemoral anteroposterior translation, axial rotation, and anterior/posterior cam-post contact for 22 BCS TKAs during squatting and stair-climbing. The functional activities on the 2011 Knee Society Score were significantly improved from 36 to 71. The tibiofemoral translation and axial rotation during squatting/stair-climbing were 16.1 mm/7.1 mm and 2.5° external/1.1° internal, respectively. Anterior/posterior cam-post contacts were observed during squatting (14%/96%) and stair-climbing (27%/96%). In conclusion, BCS TKA produced physiological sagittal plane kinematics during activities with favorable clinical outcomes.

The purpose of this study was to evaluate the relationship between posterior tibial slope and knee kinematics in bi-cruciate stabilized (BCS) total knee arthroplasty (TKA), which has not been previously reported. This computer simulation study evaluated Journey 2 BCS components (Smith & Nephew, Inc., Memphis, TN, USA) implanted in a female patient to simulate weight-bearing stair climbing. Knee kinematics, patellofemoral contact forces, and quadriceps forces during stair climbing (from 86° to 6° of flexion) were computed in the simulation. Six different posterior tibial slope angles (0°–10°) were simulated to evaluate the effect of posterior tibial slope on knee kinematics and forces. At 65° of knee flexion, no anterior sliding of the tibial component occurred if the posterior tibial slope was less than 10°. Anterior contact between the anterior aspect of the tibial post- and the femoral component was observed if the posterior tibial slope was 6° or more. An increase of 10° in posterior tibial slope (relative to 0°) led to a 4.8% decrease in maximum patellofemoral contact force and a 1.2% decrease in maximum quadriceps force. BCS TKA has a wide acceptable range of posterior tibial slope for avoiding knee instability if the posterior tibial slope is less than 10°. Surgeons should prioritize avoiding adverse effects over trying to achieve positive effects such as decreasing patellofemoral contact force and quadriceps force by increasing posterior tibial slope. Our study helps surgeons determine the optimal posterior tibial slope during surgery with BCS TKA; posterior tibial slope should not exceed 10° in routine clinical practice.

The purpose of the present study was to examine the clinical results of surgery for intra-articular calcaneal fractures using a calcaneal locking plate and a bone spreader as a reduction tool. Ten patients with intra-articular calcaneal fractures were treated. An extended lateral approach was used. The reduction of the intra-articular fragments of the posterior facet was temporarily held using a bone spreader and Kirschner wires. Internal fixation was achieved with a locking calcaneal plate. Bohler's angle and Preiss' angle were assessed on the day of injury and the day of the final follow-up examination. The step off and gap of the posterior facet were assessed on the day of injury and the first week after surgery. The functional outcome was evaluated using the American Orthopaedic Foot and Ankle Society ankle hindfoot scale score. The mean Bohler's angle ranged from 2.1° ± 11.0° to 30.4° ± 5.0° (p < .0001), the mean Preiss' angle ranged from 23.5° ± 4.5° to 15.5° ± 2.9° (p < .0001), the mean step off ranged from 4.0 ± 1.9 mm to 0.1 ± 0.2 mm (p = .0002), and the mean gap ranged from 2.6 ± 1.0 mm to 1.2 ± 0.6 mm (p = .0035). The mean American Orthopaedic Foot and Ankle Society Ankle-Hindfoot scale score was 89.2 (range 85 to 100) at a mean of 14.3 months after surgery. Our results suggest that a locking calcaneal plate can be used to restore and reduce an intra-articular calcaneal fracture and achieve good clinical results.

The aim of our study was to compare and contrast the effects of two types of mobile-bearing total knee arthroplasties (TKA), namely, the cruciate-retaining (CR) and posterior-stabilized (PS) TKAs, on clinical outcomes and in vivo kinematics during stair climbing.The Press-Fit Condylar Sigma rotating platform was used for both CR and PS TKAs. Patient-reported outcomes were assessed using the 2011 Knee Society Score. Quadriceps muscle strength was evaluated by isokinetic dynamometry. In vivo kinematics were evaluated using periodic sagittal plane radiographic images obtained during stair climbing to quantify anteroposterior (AP) tibiofemoral translation, implant flexion and axial rotation angles using image-matching techniques. Outcomes were evaluated in 20 TKAs, which had been undergone with clinical success, including ten knees with CR types and ten knees with PS types.There were no significant differences between the CR and PS TKA groups (p 0.05) in isometric extensor torque (1.0 ± 0.2 and 1.1 ± 0.6 N m/kg, respectively) or patient-reported score for stair climbing function (4.0 ± 0.5 and 3.8 ± 0.9, respectively). Both types of TKAs showed stable AP translation in the mid range of knee flexion and paradoxical translation in the low range of flexion, with limited rotation, during stair climbing. There were no significant differences between the CR and PS TKA groups (P 0.05) in anterior translation from 80° to 40° of knee flexion (4.2 ± 1.2 and 3.5 ± 1.6 mm, respectively), posterior translation from 40° to 10° of knee flexion (2.3 ± 1.9 and 2.0 ± 1.5 mm, respectively), and total external rotation (2.8° ± 4.9° and 0.5° ± 5.0°, respectively).Both CR and PS types of rotating platform mobile-bearing TKAs provided reproducible knee joint kinematics during stair climbing and equivalent clinical outcomes.IV.

Background We evaluated the effect of cutting surface on the anteroposterior (AP) axis of the proximal tibia using a 3-dimensional (3D) bone model to ensure proper tibial rotational alignment in total knee arthroplasty. Methods 3D bone models were reconstructed from the preoperative computed tomography data of 93 Japanese osteoarthritis knees with varus deformity. The AP axis was defined as the perpendicular bisector of the medial and lateral condylar centers in a 3D coordinate system. Bone cutting of the proximal tibia was performed with various tibial posterior slopes (0°, 3°, 7°) to the mechanical axis, and we compared the AP axes before and after bone cutting. Results The AP axis before bone cutting crossed a point at about 16% (one-sixth) of the distance from the medial edge of the patellar tendon at its tibial attachment. The AP axis after bone cutting was significantly internally rotated at all posterior slopes: 4.1° at slope 0°, 3.0° at slope 3°, and 2.1° at slope 7°. The percentages of cases with differences of more than 3° or 5° were 66.7% and 34.4% at slope 0°, 53.8% and 24.7% at slope 3°, and 38.3% and 11.8% at slope 7°, respectively. Conclusion The AP axis of the proximal tibia may be rotated internally after resection of the proximal tibia in total knee arthroplasty. Hence, surgeons should recognize the effect of changes in the cutting surface on rotational alignment of the proximal tibia.

Background An anterior cruciate ligament (ACL) reconstruction has become more common and the surgical morbidity has decreased, it has been performed not only in younger people to play sports but also middle-aged people, with satisfactory results. Therefore, some patients might have comorbidities for which they take medicines. Especially the medicines, such as systemic steroids, might influence the reconstructed ligament strength and durability. Case report A 49-year-old woman who was taking oral steroids for autoimmune hepatitis suffered a spontaneous ACL injury. She complained of unstable symptoms in the knee despite initial conservative treatment. Then, she was treated operatively with autologous hamstring tendon grafts. Three years postoperatively, her knee remained stable with 1.8 mm side-to-side difference on a Kneelax arthrometer and with 1.6 mm on anterior stress radiographs. There was no rerupture or instability. Conclusion The patient who had received systemic steroids for a long time recovered satisfactorily after the operation, with achievement of knee stability and possibility to prevent degenerative change in the knee joint. ACL reconstruction should be considered even in patients with such medication.

Background Both intra-articular and extra-articular knee alignment pathologies can affect clinical outcomes after high tibial osteotomy. The purpose of this study was to investigate post-operative knee coronal alignment parameters that affect long-term patient-reported outcomes after closed-wedge high tibial osteotomy (CW-HTO). Methods This study included 105 osteoarthritic knees that underwent CW-HTO. Long-term patient-reported outcomes were defined by the 2011 Knee Society Score (KSS) and were collected at an average follow-up of 10.2 years. Post-operative knee coronal alignment parameters, consisting of the femoral tibial angle (FTA), lateral distal femoral angle (LDFA), medial proximal tibial angle (MPTA), tibial plateau inclination (TPI), and joint line convergence angle (JLCA), were measured using standing radiographs of the knee at an average follow-up of 11.0 months. The correlations between these parameters and KSS were then assessed by Spearman's correlation analysis. Comparisons of groups classified by MPTA and TPI cutoff values were performed by the Wilcoxon rank-sum test. Results Post-operative JLCA showed a significant negative correlation with two KSS sub-scores: satisfaction (R = −0.2232, P = 0.022) and total function (R = −0.2059, P = 0.035). There was no significant difference in any KSS sub-score between the “low” groups (MPTA and TPI less than 95 and 5°, respectively) and the “high” groups (MPTA and TPI greater than 98 and 7°, respectively). Conclusions Among knee coronal alignment parameters, a large post-operative residual JLCA, which is an intra-articular varus deformity, was independently associated with worsened long-term clinical outcomes after CW-HTO. Level of evidence Level Ⅳ, Retrospective cohort study.

Extensive soft tissue defects of the ankle are an uncommon but challenging problem that require a combination of reconstructive options. We report the case of a complex injury involving the skin, lateral ankle ligaments, and peroneal tendons that were anatomically reconstructed. A 15-year-old girl was injured in an automobile accident resulting in extensive soft tissue defects and marked instability of her right ankle. The lower two-thirds of the anterior talofibular ligament (ATFL) had segmental defects, and calcaneofibular ligament (CFL) was completely torn, and both peroneal longus and brevis tendons were severely damaged. Initial debridement was performed on the day on injury. Two weeks after injury, the ATFL and CFL were reconstructed using a semitendinosus autograft and suture tape augmentation. Both peroneal tendons were reconstructed using a gracilis autograft. The skin defect (10 × 10 cm) was covered with an anterolateral thigh flap. After removing a short leg cast at 3 weeks postoperatively, the patient started range of motion exercises without using any brace. Weightbearing was allowed at 4 weeks. At the 24-month follow-up examination, she had returned to her preoperative level of work and sports activities.

In posterior-stabilized (PS) total knee arthroplasty (TKA), unexpected wear and fracture of the tibial post due to anterior post impingement have been reported. The purpose of this study was to determine the contact stress on the anterior aspect of the tibial post in four contemporary TKA designs. We evaluated one bi-cruciate stabilized design (Journey II) and three mobile-bearing PS designs (Vanguard RP, PFC Sigma RP, and NexGen LPS Mobile). The contact conditions at the anterior aspect of the tibial post were determined upon application of a posterior force of 100N to individual implants. Each measurement was sequentially performed five times, and the data were compared within and across designs using analysis of variance and a post-hoc test. The contact stress of the Journey II and Vanguard RP was less than the compressive yield stress for polyethylene (10MPa) at all tested flexion angles and degrees of rotation. The PFC Sigma RP did not show anterior tibial post impingement under any experimental conditions. The NexGen LPS Mobile demonstrated bilateral edge loading at the anterior tibial post and exceeded 10MPa of contact stress in some test conditions. Thus, the differences among implants in terms of the dimensions of the femoral anterior cam or intercondylar notch and the anterior aspect of the tibial post in the axial and sagittal planes led to significant differences in contact conditions. The present study helps the surgeon to be more aware that various contact conditions of the anterior aspect of the tibial post can occur in individual TKA designs.

The purpose of this study was to assess the differences in proximal tibial deformity between closing wedge (CW) and opening wedge (OW) high tibial osteotomy (HTO) and their effects on the difficulty of total knee arthroplasty (TKA) conversion. Surgical simulations of CW-HTO and OW-HTO were performed on the same 3D computer-aided design knee models reconstructed from computed tomographic datasets of patients (median age 77 years; range 55–87 years; 40 knees) with medial osteoarthritis or osteonecrosis, and proximal tibial deformities were analysed. Subsequent TKA conversion was simulated in both CW and OW models, and the interference between the tibial implant and endosteal cortex was assessed. The difference in the metaphyseal–diaphyseal angle in the CW-HTO and OW-HTO groups was 0.3° ± 0.2° (p

Purpose Participation in specific activities requires complex ranges of knee movements and activity-dependent kinematics. The purpose of this study was to investigate dynamic knee kinematics during squat and golf swing using image-matching techniques. Methods Five healthy males performed squats and golf swings under periodic X-ray images at 10 frames per second. We analyzed the in vivo three-dimensional kinematic parameters of subjects' knees, namely the tibiofemoral flexion angle, anteroposterior (AP) translation, and internal–external rotation, using serial X-ray images and computed tomography-derived, digitally reconstructed radiographs. Results During squat from 0° to 140° of flexion, the femur moved about 25mm posteriorly and rotated 19° externally relative to the tibia. Screw-home movement near extension, bicondylar rollback between 20° and 120° of flexion, and medial pivot motion at further flexion were observed. During golf swing, the leading and trailing knees (the left and right knees respectively in the right-handed golfer) showed approximately five millimeters and four millimeters of AP translation with 18° and 26° of axial rotation, respectively. A central pivot motion from set-up to top of the backswing, lateral pivot motion from top to ball impact, and medial pivot motion from impact to the end of follow-through were observed. Conclusions The medial pivot motion was not always recognized during both activities, but a large range of axial rotation with bilateral condylar AP translations occurs during golf swing. This finding has important implications regarding the amount of acceptable AP translation and axial rotation at low flexion in replaced knees. Level of evidence IV

Background:Metatarsalgia is frequently associated with hallux valgus. The aim of this study was to evaluate how the relative length and position of the first metatarsal head influenced metatarsalgia and plantar callosities beneath the lesser metatarsal heads.Methods:A retrospective analysis of the clinical data and radiographs of 102 cases was performed at a mean follow-up of 16 months after biplane interlocking osteotomies. Clinical evaluation was made using the Japanese Society for Surgery of the Foot (JSSF) hallux scale. Radiologic evaluation was made with standard weight-bearing anteroposterior radiographs, and the hallux valgus angle (HVA), intermetatarsal 1-2 angle (IMA), distal metatarsal articular angulation (DMAA), and the sesamoid position were evaluated. Relative first metatarsal length (RML) was determined according to Nilsonne/Morton’s technique.Results:The mean preoperative HVA decreased from 37 to 3 degrees, and the mean IMA from 17 to 4 degrees. The mean JSSF-hallux score improved from 56 to 96 points. The mean preoperative area of plantar callosities decreased from 3.1 to 1.5 mm2. Sixty percent of metatarsalgia cases improved, and 85% of painless callosities disappeared postoperatively. Among radiologic parameters, postoperative RML was most significantly associated with JSSF score ( P < .0001) and the presence of postoperative metatarsalgia ( P < .0001). Receiver operating characteristic analysis revealed that the RML cut-off point was −3 mm for avoiding metatarsalgia, with an area under the curve of 0.88, a specificity of 88%, and a sensitivity of 85%.Conclusion:Preservation of relative first metatarsal length during first metatarsal osteotomy was important to prevent postoperative metatarsalgia.Level of Evidence:Level IV, retrospective case series.

The purpose of our study was to evaluate the accuracy of the tibial bone cut in total knee arthroplasty using the anterior tibial border as a guide compared to using bony and soft tissue landmarks of the ankle joint. The extramedullary alignment guide was set parallel to a line connecting the proximal and distal one-thirds of the anterior border of the tibia while the rotational direction of the distal end of the guide was adjusted to the anteroposterior axis of the proximal tibia. Significant differences were detected in the ideal coronal tibial component angles with improvements from 87.2% to 95.9%. The anterior tibial border was a reliable landmark in total knee arthroplasty in clinical practice, as shown by our previous computer simulation.

Background Few studies have evaluated the impact of age on patient-reported outcomes in the long-term follow-up after high tibial valgus osteotomy (HTO). The purpose of this study is to assess the association between age at surgery and patient-reported clinical outcomes in the mid-term to long-term follow-up of HTO. Materials and methods We mailed the 2011 Knee Society score (KSS) questionnaires to 234 consecutive patients (295 knees) who had undergone closing-wedge HTO, and 158 patients (202 knees, 68.5%) returned a completed questionnaire. The cohort was divided into two groups depending on the age at the time of surgery, and pairs matched the follow-up period and sex was created. The mean follow-up period was approximately 12 years. KSS scores at the final follow-up were compared between two groups using the Student t test and chi-square test, and the survival rates were calculated using Kaplan–Meier survival curves. Results The symptom, satisfaction, and expectation scores were not significantly different between the ≤64-year-old patients and ≥65-year-old patients. The functional activities score was significantly lower in older patients than in younger patients. The overall survival rates of HTO were 99.1 ± 0.4% at 5 years, 94.4 ± 1.2% at 10 years, and 84.6 ± 2.7% at 15 years. There was no significant difference in the survival rate after HTO between the two groups divided by the age (p = 0.602). Conclusions Pain relief and satisfaction after HTO in older patients were comparable to those in younger patients in the mid-term to long-term follow-up, although the functional activity was affected by age.

Magnetic resonance imaging with T1ρ mapping is used to quantify the amount of glycosaminoglycan in articular cartilage, which reflects early degenerative changes. The purposes of this study were to evaluate early degenerative changes in knees after anterior cruciate ligament (ACL) reconstruction by comparing T1ρ values before and 2 years after surgery and investigate whether surgical factors and clinical outcomes are related to differences in T1ρ values. Fifty patients who underwent unilateral primary ACL reconstruction were evaluated using T1ρ mapping before and 2 years after surgery. Three regions of interest (ROIs) were defined in the cartilage associated with the medial (M) and lateral (L) weight-bearing areas of the femoral condyle (FC) (anterior: MFC1 and LFC1, middle: MFC2 and LFC2, and posterior: MFC3 and LFC3). Two ROIs associated with the tibial plateau (T) were defined (anterior: MT1 and LT1, and posterior: MT2 and LT2). T1ρ values within the ROIs were measured before and 2 years after surgery and compared using the paired t test. Correlations between the difference in T1ρ values at these two time points and patient characteristics, presence of a cartilaginous lesion, graft type, and postoperative anteroposterior laxity were also evaluated using Pearson’s and Spearman’s correlation coefficients. There was a significant increase in T1ρ before versus 2 years after surgery in the MT1, MT2, LFC1, and LT1 areas, and a significant decrease in the LFC3 and LT2 areas. There was a significant correlation between postoperative anterior-posterior laxity and a postoperative increase in T1ρ values in the MFC3 (r = 0.37, P = 0.013) and MT2 (r = 0.35, P = 0.021) areas. Increases in T1ρ values in the MFC2 area were negatively correlated with KOOS symptoms (ρ = − 0.349, P = 0.027) and quality of life (ρ = − 0.374, P = 0.017) subscale scores. Early degenerative changes in medial articular cartilage were observed with T1ρ mapping at 2 years after ACL reconstruction. Postoperative anterior-posterior laxity is correlated with an increase in T1ρ values in the posteromedial femur and tibia. An increase in T1ρ values in the central medial femoral condyle was associated with knee symptoms. III.

The purpose of this study was to define various anteroposterior axes of the tibial component as references and to evaluate their accuracy and variability using virtual surgery. It was hypothesized that (1) Akagi’s Line could result in high accuracy and low variability in varus osteoarthritic knees; (2) anteroposterior axes defined by using the tibial bony cutting surface as a landmark might be good substitutes for Akagi’s Line; and (3) extra-articular bony landmarks might influence the variability of the anteroposterior axis. Three-dimensional bone models were reconstructed from the preoperative computed tomography data of 111 osteoarthritic knees with varus deformities. Seven different anteroposterior axes of the tibial component were defined: Akagi’s Line, Axis MED, Axis 1/6MED, Axis 1/3MED, Axis of Oval Shape, Axis of Anterior Crest, and Axis Second Metatarsus. The rotational mismatch angle was measured between the tibial anteroposterior axis and the line perpendicular to the transepicondylar axis projected on the cutting surface (positive value: external rotation of the tibial anteroposterior axis). The average rotational mismatch angles (referring to the projected anatomical/surgical epicondylar axes) were − 2.7° ± 5.8°/1.0° ± 6.0° (Akagi’s Line), − 4.2° ± 7.7°/− 0.5° ± 7.8°, 2.9° ± 7.2°/6.6° ± 7.2°, 9.8° ± 7.0°/13.5° ± 6.8° (Axis MED, Axis 1/6MED, Axis 1/3MED), − 5.1° ± 7.9°/− 1.4° ± 7.8° (Axis of Oval Shape), and 19.3 ± 9.5°/23.0° ± 9.6°, − 2.0° ± 11.3°/1.7° ± 11.4° (Axis Anterior Crest, Axis Second Metatarsus), respectively. Akagi’s Line provided the best accuracy and least variability in varus osteoarthritic knees. Axis 1/6MED and Axis MED are good substitutes for Akagi’s Line due to the difficulty of identifying the attachment site of the posterior cruciate ligament after the proximal tibia has been cut. Extra-articular bony landmarks should not be used for alignment due to their high variability. This study will aid surgeons in choosing the proper anteroposterior axis of the tibial component to reduce rotational mismatch and thus achieve good clinical knee outcomes. III.

ObjectivesBecause there have been no standard methods to determine pre-operatively the thickness of resection of the proximal tibia in unicompartmental knee arthroplasty (UKA), information about the relationship between the change of limb alignment and the joint line elevation would be useful for pre-operative planning. The purpose of this study was to clarify the correlation between the change of limb alignment and the change of joint line height at the medial compartment after UKA.MethodsA consecutive series of 42 medial UKAs was reviewed retrospectively. These patients were assessed radiographically both pre- and post-operatively with standing anteroposterior radiographs. The thickness of bone resection at the proximal tibia and the distal femur was measured radiographically. The relationship between the change of femorotibial angle (δFTA) and the change of joint line height, was analysed.ResultsThe mean pre- and post-operative FTA was 180.5° (172.2° to 184.8°) and 175.0° (168.5° to 178.9°), respectively. The mean δFTA was 5.5° (2.3° to 10.1°). The joint line elevation of the tibia (JLET) was 4.4 mm (2.1 to 7.8). The δFTA was correlated with the JLET (correlation coefficient 0.494, p = 0.0009).ConclusionsThis study indicated that there is a significant correlation between the change of limb alignment and joint line elevation. This observation suggests that it is possible to know the requirement of elevation of the joint line to obtain the desired correction of limb alignment, and to predict the requirement of bone resection of the proximal tibia pre-operatively. Cite this article: Bone Joint Res 2015;4:128–133

We used a musculoskeletal model validated with in vivo data to evaluate the effect of tibial posterior slope on knee kinematics, quadriceps force, and patellofemoral contact force after posterior-stabilized total knee arthroplasty. The maximum quadriceps force and patellofemoral contact force decreased with increasing posterior slope. Anterior sliding of the tibial component and anterior impingement of the anterior aspect of the tibial post were observed with tibial posterior slopes of at least 5° and 10°, respectively. Increased tibial posterior slope contributes to improved exercise efficiency during knee extension, however excessive tibial posterior slope should be avoided to prevent knee instability. Based on our computer simulation we recommend tibial posterior slopes of less than 5° in posterior-stabilized total knee arthroplasty.

Purpose The purpose of this study is to elucidate how the rotational malalignment of prosthesis after total knee arthroplasty affects the rotational kinematics in a weight-bearing condition. Methods In this study of 18 knees replaced with the posterior stabilizing fixed-bearing system, which has a relatively low-restricting design, rotational angles between the femoral and tibial components and between the femur and tibia during stair climbing were evaluated in vivo in three dimensions using radiologically based image-matching techniques. Rotational alignments of the components were assessed by postoperative CT. The correlations between the rotational alignments and the rotational angles during stair climbing were evaluated. Results Rotational alignment of the tibial component significantly correlated with rotational angles between the components as well as between bones during stair climbing. Rotational malalignment of the tibial component toward internal rotation caused a rotational mismatch of the tibial component toward internal rotation relative to the femoral component in 0° extension and caused a rotational mismatch of the tibia (bone) toward external rotation relative to the femur (bone). The knee in which the tibial component was placed close to the AP axis of the tibia did not show any rotational mismatch between either components or bones. Conclusions Rotational alignment of the tibial component affects the kinematic rotation of the replaced knee during a weight-bearing condition even though using a low-restricting designed surface, and the AP axis can be a reliable reference in determining rotational alignment for the tibial component.

Patient satisfaction has become an important parameter for assessing overall outcomes after total knee arthroplasty (TKA). The level of difficulty in performing activities of daily life that affects overall patient satisfaction is unknown. We therefore evaluated the influence of difficulty in performing activities of daily life on patient satisfaction and expectations. The 2011 Knee Society Knee Scoring System Questionnaire was mailed to patients who had undergone TKA with 375 patients completing and returning it. We evaluated the relationship between the ability to perform daily activities, as assessed via the questionnaire, and patient satisfaction and expectations of the same score in each patient using linear regression analysis. We also determined which activities affected patient satisfaction and expectations using multivariate linear regression analyses. All patient-derived functional activities correlated significantly with the patient satisfaction score. In particular, “climbing up or down a flight of stairs” followed by “getting into or out of a car,” “moving laterally (stepping to the side)” and “walking and standing” correlated strongly with patient satisfaction by linear regression analysis and were revealed to have significant contributions to patient satisfaction by multivariate linear regression analysis. Regarding expectations, all patient-derived functional activities correlated significantly with the patient expectation score, although none of the correlation coefficients was very high. “Squatting,” followed by “walking and standing,” contributed to the patient expectation score by multivariate linear regression analysis. Activities related to walking and standing are some of the most basic movements and basic demands for patients. In addition, “climbing up or down a flight of stairs,” “getting into and out of a car” and “squatting” are very important and distressing activities that significantly correlate with patient satisfaction after TKA.

Prediction of the risk of osteoarthritis in asymptomatic active patients with an isolated injury of the posterior cruciate ligament (PCL) is difficult. T1ρ magnetic resonance imaging (MRI) enables the quantification of the proteoglycan content in the articular cartilage. The purpose of this study was to evaluate subclinical cartilage degeneration in asymptomatic young athletes with chronic PCL deficiency using T1ρ MRI. Six athletes with chronic PCL deficiency (median age 17, range 14–36 years) and six subjects without any history of knee injury (median age 31.5, range 24–33 years) were recruited. Regions of interest were placed on the articular cartilage of the tibia and the distal and posterior areas of the femoral condyle, and T1ρ values were calculated. On stress radiographs, the mean side-to-side difference in posterior laxity was 9.8 mm. The T1ρ values at the posterior area of the lateral femoral condyle and the superficial layer of the distal area of the medial and lateral femoral condyle of the patients were significantly increased compared with those of the normal controls (p

This study aimed to evaluate the effects of two types of total knee arthroplasty (TKA) designs: posterior-stabilized (PS) and bicruciate-stabilized (BCS) on in vivo kinematics during gait. Continuous X-ray images of the gait were taken using a flat panel detector for 23 PS and BCS TKAs. We analyzed the tibiofemoral implant flexion angle, anteroposterior (AP) translation, axial rotation, and anterior/posterior cam-post contact using image-matching techniques. Double knee actions were demonstrated for the PS and BCS design (35 and 61%, respectively, p = 0.08). The tibiofemoral AP positions were significantly more posterior at peak extension (− 1.7 ± 2.2 and 1.0 ± 2.5 mm, respectively, p

Placement of tibial component is expected to fulfill both maximum surface coverage and recommended anterior–posterior (AP) alignment in total knee arthroplasty (TKA). The purpose of this study is to evaluate the effect of the tibial baseplate shape on AP axis. Virtual surgery of TKA was performed with three-dimensional bone models reconstructed from 77 osteoarthritis varus knees. Two differently designed tibial baseplates, symmetrically and anatomically, were set to the cut surface under posterior slopes of 0°, 3°, and 7°. The AP axes were defined by connecting the geometrical center of the cut surface with the medial edge (axis MED) and medial 1/3 (axis 1/3MED) of patella tendon attachment. We evaluated the overhang rates as well as the most fitting AP axis which passes through the geometric center. Overhang rates when aligned to axis MED were 12–25% for the symmetrical-type group and 13–22% for the anatomical-type group. Overhang rates when aligned to axis 1/3MED were 42–48% for the symmetrical-type group and 3–7% for the anatomical-type group. The most fitting AP axis of tibial baseplate was located 2.5° external to axis MED for the symmetrical-type group and around 3.3° internal to axis 1/3MED for the anatomical-type group. Symmetrically or anatomically designed tibial baseplates have their own favored AP axis and specific performance on coverage. When aligned to axis 1/3MED, anatomically designed tibial baseplates will effectively lower the mismatch rates compared to a symmetrically designed tibial baseplate. Orthopaedic surgeons are expected to place the tibial components to the cut surface during TKA with full understanding of the features between different baseplate designs, AP axes, and posterior slopes for an ideal tibial rotational position.

To investigate the optimal starting points for drilling on the lateral femoral condyle for better coverage of the anatomical footprint of the anterior cruciate ligament (ACL) using the outside-in (OI) technique in a single-bundle ACL reconstruction. Femoral tunnel drilling was simulated on three-dimensional bone models from 40 subjects by connecting the centre of the ACL footprint with various points on the lateral femoral surface. The percentage of the femoral footprint covered by apertures of the virtual tunnel sockets with 9 mm diameter was calculated for each tunnel. The mean percentages of the femoral footprint covered by the apertures of the virtual tunnel sockets were significantly higher when drilled at 2 and 3 cm from the lateral epicondyle on a 45° line and a 60° line anterior from the proximal–distal axis than the other points. However, articular cartilage damage was occurred in nine subjects at 3 cm on a 60° line and eight subjects at 3 cm on a 45° line. Posterior wall blowout occurred in five subjects at 3 cm on a 45° line. Thus, OI drilling at 3 cm from the epicondyle has a risk of these complications. During the OI drilling of the femoral tunnel, connecting the centre of the anatomical footprint of the ACL and the entry drilling point at 2 cm from the lateral epicondyle on between the 45° line and the 60° line anterior from the proximal–distal axis provides an oval-shaped socket aperture that covers and restores the native ACL footprint as nearly as possible. III.