Intraoperative reliability of the tibial anteroposterior axis "Akagi's Line" in total knee arthroplasty.

Purpose: The tibial anatomical anteroposterior (AP) axis "Akagi's line" was originally defined on computed tomography (CT) in total knee arthroplasty (TKA); however, its intraoperative reproducibility remains unknown. This study aimed to evaluate the intraoperative reproducibility of the Akagi's line and its effect on postoperative clinical outcomes. Methods: This prospective study included 171 TKAs. The rotational angle of the intraoperative Akagi's line relative to the original Akagi's line (RAA) defined on CT was measured. The RAA was calculated based on the tibial component rotational angles relative to the intraoperative Akagi's line measured using the navigation system and CT. The effects of RAA on postoperative clinical outcomes and rotational alignments of components were also evaluated. Results: The mean absolute RAA (standard deviation) value was 5.5° (3.9°). The range of RAA was 22° internal rotation to 16° external rotation. Intraoperative Akagi's line outliers (RAA > 10°) were observed in 14% of the knees (24 knees). In outlier analysis, the tibial component rotation angle was externally rotated 6.5° (5.6°) in the outlier group and externally rotated 3.7° (4.2°) in the nonoutlier group (≤10°), with a significant difference between the two groups. Additionally, the outlier group (RAA > 10°) showed lower postoperative clinical outcomes. Conclusion: The original Akagi's line defined on CT showed insufficient reproducibility intraoperatively. The poor intraoperative detection of Akagi's line could be the reason for the tibial component rotational error and worse postoperative clinical outcomes. Level of Evidence: Level IV, case series.

Factors Associated With a Lateral Ankle Sprain in Young Female Soccer Players: A Prospective Cohort Study.

Background: Previous studies have attempted to determine if certain risk factors can predict the occurrence of a lateral ankle sprain (LAS) in female soccer players. Unfortunately, there is limited evidence with regard to risk factors associated with an LAS in female soccer players. Purpose: To identify intrinsic risk factors for an LAS among young female soccer players. Study Design: Cohort study; Level of evidence, 2. Methods: Participants were 161 young female soccer players in Japan who were evaluated for LAS risk factors during a preseason medical assessment. The assessment included anthropometric, joint laxity, joint range of motion, muscle flexibility, muscle strength, and balance measurements. Each athlete's history of LASs was also collected. The participants were monitored during a single-yearseason for LASs, as diagnosed by physicians. Results: There were 26 instances of an LAS in 25 players (15.5%) during the season. Injured players were significantly more likely to have sustained a previous ankle sprain (P = .045) and demonstrated significantly worse balance than their peers without an LAS during the double- and single-leg balance tests (P = .008 for both). Athletes with lower hamstring-to-quadriceps muscle strength ratios were also significantly more likely to sustain an LAS (P = .02). Conclusion: Poor balance, a low hamstring-to-quadriceps ratio, and a history of ankle sprains were associated with an increased risk of LASs in young female soccer players in the current study. These findings may be useful for developing a program to prevent LASs in this population.

Lower hamstring to quadriceps muscle strength ratio and lower body weight as factors associated with noncontact anterior cruciate ligament injury in male American football players: A prospective cohort study.

Background: Previous studies have aimed to determine the use of certain risk factors in predicting the occurrence of noncontact anterior cruciate ligament (ACL) injuries. Unfortunately, evidence regarding noncontact ACL injuries in male American football players is limited. This prospective cohort study aimed to identify intrinsic risk factors for noncontact ACL injury among male American football players. Methods: This study evaluated 152 male American football players in Japan for potential noncontact ACL injury risk factors during a preseason medical assessment, including anthropometric, joint laxity, and flexibility, muscle flexibility, muscle strength, and balance measurements. A total of 25 variables were examined. Participants were monitored during each season for noncontact ACL injury, as diagnosed by physicians. Results: Noncontact ACL injuries occurred in 11 knees of 11 players (prevalence; 7.1 %). Injured players were significantly more likely to have lightweight (P = 0.049). No statistically significant between-group differences were found for any other variables. Participants with a lower hamstring to quadriceps (H/Q) ratio (P = 0.04) were more likely to sustain noncontact ACL injuries. Conclusion: Lower H/Q ratio and lower body weight were significantly associated with new-onset noncontact ACL injury in male American football players. These findings will help develop strategies to prevent noncontact ACL injuries in male American football players.

Short-term clinical results of bicruciate-retaining total knee arthroplasty using personalized alignment.

BACKGROUND: Bicruciate-retaining (BCR) prosthesis has been introduced to recreate normal knee movement by preserving both the anterior and posterior cruciate ligaments. However, the use of BCR total knee arthroplasty (TKA) is still debatable because of several disappointing reports. We have been performing BCR TKAs with personalized alignment (PA). This study aimed to reveal the limb alignment and soft tissue balance of FA-BCR TKAs and compare the clinical outcomes of FA-BCR TKAs with those of unicompartmental knee arthroplasty (UKA). METHODS: Fifty BCR TKAs and 58 UKAs were included in this study. The joint component gaps of BCR TKA were evaluated intraoperatively and the postoperative hip-knee-ankle (HKA) angle, medial proximal tibial angle (MPTA), and lateral distal femoral angle (LDFA) were measured using full-length standing radiography. The short-term clinical outcomes of BCR TKAs were compared with those of UKA using the scoring system of 2011 Knee Society Scoring (KSS) and the knee injury and osteoarthritis outcome score (KOOS) at an average of 2 years postoperatively (1-4yeras). RESULTS: The coronal alignment values of PA-BCR TKA were as follows: HKA angle, 177.9° ± 2.3°; MPTA, 85.4° ± 1.9°; and LDFA, 87.5° ± 1.9°. The joint component gaps at flexion angles of 10°, 30°, 60°, and 90° were 11.1 ± 1.2, 10.9 ± 1.4, 10.7 ± 1.3, and 11.2 ± 1.4 mm for the medial compartment and 12.9 ± 1.5, 12.6 ± 1.8, 12.5 ± 1.8 and 12.5 ± 1.7 mm for the lateral compartment, respectively. The patient expectation score and maximum extension angle of PA-BCR TKA were significantly better than those of UKAs. CONCLUSIONS: The short-term clinical outcomes of PA-BCR TKA were comparable or a slightly superior to those of UKAs.

Postoperative quadriceps weakness and male sex are risk factors for patellofemoral articular cartilage lesions after anatomical anterior cruciate ligament reconstruction.

PURPOSE: Patellofemoral (PF) compartment cartilage lesions are a frequent problem after anterior cruciate ligament (ACL) reconstruction. This study aimed to determine the factors that influence PF cartilage lesions after anatomical ACL reconstruction. METHODS: This study enrolled a total of 114 patients who did not manifest PF compartment cartilage lesions during anatomical ACL reconstruction and underwent second-look arthroscopy 18 months postoperatively. Arthroscopy using the International Cartilage Repair Society (ICRS) classification was used to assess cartilage lesions. The correlation between surgical findings, radiographic factors, and clinical factors and change of ICRS grade was analysed. Multivariate regression analysis was conducted to reveal the independent risk factors for PF cartilage lesions among patients' demographic data and parameters that correlated with the change of ICRS grade in the correlation analyses. RESULTS: ICRS grade changes in PF cartilage were significantly correlated with age, sex, quadriceps strength at 1 year postoperatively, hamstrings strength at pre- and 1 year postoperatively, and single leg hop test at 1 year postoperatively. However, no significant correlation was found between the time between injury and surgery, posterior tibial slope angle, pre- and postoperative Tegner activity scale, graft type, initial graft tension, meniscus injury, meniscus injury treatment, pre- and postoperative range of motion, anteroposterior laxity and preoperative quadriceps strength, and the change in ICRS grade. Multivariate regression analysis revealed male (P = 0.019) and quadriceps strength weakness at 1 year postoperatively (P = 0.009) as independent risk factors for PF cartilage lesions. CONCLUSIONS: Quadriceps strength weakness 1 year after ACL reconstruction and males were correlated with a new PF cartilage lesion after anatomical ACL reconstruction, with no significant correlation between bone-patellar tendon-bone autograft, initial graft tension, or extension deficit and new PF cartilage lesion. Rehabilitation that focuses on quadriceps strength after ACL reconstruction is recommended to prevent new PF cartilage lesions. LEVEL OF EVIDENCE: Level IV.

Comparison of finite helical axis of the knee joint before and after bi-cruciate-preserving knee arthroplasty.

BACKGROUND: Difference in the finite helical axis of the knee joints before and after anterior cruciate ligament-preserving knee arthroplasties such as unicompartmental knee arthroplasty and bi-cruciate-retaining total knee arthroplasty remains unknown. This study compared the knee finite helical axes before and after bi-cruciate-preserving knee arthroplasty. METHODS: Patients undergoing medial unicompartmental knee arthroplasty and bi-cruciate-retaining total knee arthroplasty were included. Under fluoroscopy, participants performed a deep knee bend before and after surgery. A two/three-dimensional registration technique was employed to measure tibiofemoral kinematics. Femoral finite helical axis was calculated in a flexion range of 0-120° using 30° windows (early-, mid-, late-, and deep-flexion phases). FINDINGS: In unicompartmental knee arthroplasty, the preoperative knee vertical angle was larger than the postoperative vertical angle in mid- and deep-flexion phases. The postoperative knee vertical angle was smaller in unicompartmental knee arthroplasty than in bi-cruciate-retaining total knee arthroplasty. In unicompartmental knee arthroplasty, the preoperative horizontal angle was smaller than the postoperative horizontal angle in the early-flexion phase. However, in bi-cruciate-retaining total knee arthroplasty, the preoperative horizontal angle was larger than the postoperative horizontal angle in mid- and deep-flexion phases. The horizontal angle was smaller before unicompartmental knee arthroplasty than that before bi-cruciate-retaining total knee arthroplasty in early-, mid-, and deep-flexion phases. However, the vertical angle was larger after unicompartmental knee arthroplasty than that after bi-cruciate-retaining total knee arthroplasty in the early-flexion phase. INTERPRETATION: The knee finite helical axes before and after unicompartmental knee arthroplasty differed from those before and after bi-cruciate-retaining total knee arthroplasty.

Risk factors for hamstring strain injury in male college American football players -a preliminary prospective cohort study.

BACKGROUND: Given the frequency of hamstring strain injuries (HSI) among male college American football players, several studies have attempted to determine whether certain risk factors can predict their occurrence. However, no consensus on modifiable risk factors for HSIs in male college American football players has yet been reached to prevent these injuries. This study aimed to clarify risk factors for HSI prospectively in college male American football players. METHODS: A total of 78 male college American football players, whose positions were limited to skill positions, were medically assessed for potential risk factors of HSI. The preseason medical assessment included anthropometric measurements, joint laxity and flexibility, muscle flexibility, muscle strength, and balance ability. RESULTS: HSI occurred in a total of 25 thighs from 25 players (32.1%). Injured players had significantly lower hamstring flexibility (p = 0.02) and hamstring to quadriceps strength ratio (H/Q) (p = 0.047) compared to uninjured players. Additionally, injured players had significantly lower general joint laxity scores, especially for the total (p = 0.04), hip (p = 0.007), and elbow (p = 0.04) scores, compared to uninjured players. CONCLUSIONS: Lower hamstring flexibility, lower hamstring to quadriceps strength ratio, and lower general joint laxity score were identified as risk factors for HSI in male college American football players placed in skill positions. The muscle flexibility and H/Q ratio could be useful in preventing HSI in such players.

Intraoperative femoral rotational kinematics are similar in varus and valgus knees during medial pivot total knee arthroplasty.

BACKGROUND: Medial-pivot type total knee arthroplasty is designed to reproduce physiological femoral rotational kinematics during knee flexion; however, its rotational kinematics in valgus knees remain unknown. This study's hypothesis is that its kinematics show the similar medial pivot motion in valgus knees as in varus knees. METHODS: This retrospective study included 50 cases of primary medial-pivot type total knee arthroplasty performed with navigation for knee osteoarthritis. Cases were grouped as valgus (n = 20) or varus (n = 30). In valgus knees, surgeons used preoperative manual testing to confirm that alignment was correctable. They evaluated femoral rotational kinematics at maximum extension, 30°, 60°, 90°, and maximum flexion, using a navigation system, both before and after implantation. Finally, intraoperative rotational kinematics, postoperative patient-reported outcomes, and knee range of motion were compared between the two groups. FINDINGS: Before implantation, both valgus and varus knees displayed external femoral rotation relative to the tibia during knee flexion. The rotation magnitude was significantly larger in varus knees at 60°, 90°, and maximum flexion angles compared to valgus knees (P < 0.05). In contrast, after implantation, both groups displayed external femoral rotation of 12-13° during knee flexion with no significant differences between the two groups at any knee flexion angle tested (P > 0.05). Short-term clinical outcomes were comparable between valgus and varus knees. INTERPRETATION: Postoperatively, medial-pivot type total knee arthroplasty for knee osteoarthritis resulted in external femoral rotation during knee flexion. Notably, this occurred even in valgus knees with good short-term clinical outcomes.

Anterior cruciate ligament-deficient knee induces a posterior location of the femur in the medial compartment during squatting.

Although an anterior cruciate ligament (ACL) deficiency induces knee osteoarthritis, particularly in the medial compartment, the kinematics remains partially unclear. This study investigated the in vivo knee kinematics of ACL-deficient and normal knees by comparing them during squatting. This prospective comparative study included 17 ACL-deficient knees and 20 normal knees. The kinematics was investigated under fluoroscopy using a two- to three-dimensional registration technique. The anteroposterior (AP) translation of the medial and lateral sides of the femur, axial rotation of the femur relative to the tibia, and kinematic pathways were evaluated and compared. At first, the medial AP position of the femur translated anteriorly from 0° to midflexion, afterward it translated posteriorly in both ACL-deficient and normal knees. However, the medial AP position of the femur in the ACL-deficient knees was located significantly posteriorly compared with normal knees at 0-110° flexion. The lateral AP position of the femur translated posteriorly from 0° to 150° flexion in both ACL-deficient and normal knees. The lateral AP position of the femur in the ACL-deficient knees was located significantly posteriorly compared with that in normal knees at 0-10° flexion. The femur showed external rotation from 0° to 150° flexion in both ACL-deficient and normal knees. A medial pivot motion and subsequent bicondylar rollback were observed in both knees in the kinematic pathway. In conclusion, the AP position of the femur relative to the tibia was altered due to ACL deficiency, particularly in the medial compartment.

Both Intraoperative Medial and Lateral Joint Stabilities at Midflexion Influence Postoperative Patient-Reported Outcome Measures Following Bi-Cruciate Stabilized Total Knee Arthroplasty.

Bi-cruciate stabilized (BCS) total knee arthroplasty (TKA) was developed to approximate normal knee kinematics and is expected to improve clinical outcomes. However, the effects of soft tissue balance at the medial or lateral compartment on patient-reported outcome measures (PROMs) following BCS TKA are unclear. The purpose of this study was to clarify the relationship between the medial or lateral component gaps and PROMs following BCS TKA. One hundred seventeen knees with varus deformities which underwent BCS TKA were included in this study. They were divided into two groups according to the validated Japanese version of the Knee Injury and Osteoarthritis Outcome Score for each subscale of pain, symptoms, and activities of daily living (ADL) at 1 year postoperatively: group H consisted of patients with ≥90 points and group L consisted of patients with <90 points. Intraoperative medial and lateral joint laxities at 0°, 30°, 60°, 90°, and 120° flexion measured using a tensor device were compared between the two groups in each subscale. In the pain subscale, the medial joint laxities at 30° (p < 0.05) and 60° flexion (p < 0.05) in group H were significantly smaller than those in group L. In the ADL subscale, the medial joint laxity at 60° flexion in group H was significantly smaller than that in group L (p < 0.05). In the symptom subscale, the lateral joint laxity at 60° flexion in group H was significantly smaller than that in group L (p < 0.05). Surgeons should pay attention to the importance of both medial and lateral joint stabilities to achieve better postoperative PROMs following BCS TKA.

Lateral posterior tibial slope does not affect femoral but does affect tibial tunnel widening following anatomic anterior cruciate ligament reconstruction using a Bone-Patellar Tendon-Bone graft.

Background: Tunnel widening (TW) after anterior cruciate ligament (ACL) reconstruction has been a research area of interest in ACL reconstruction. In recent years, it has been noted that posterior tibial slope (PTS) affects several types of outcomes after ACL reconstruction including TW. However, the relationships between femoral and tibial TW and between PTS and TW following anatomical ACL reconstruction using a bone-patellar tendon-bone (BTB) graft are often not understood. Therefore, the purpose of this study was to retrospectively clarify the magnitude of femoral and tibial TW and the effect of PTS on TW following anatomical ACL reconstruction using a BTB graft. Methods: A total of 111 patients who underwent isolated ACL reconstructions using BTB grafts were included in this study. Femoral and tibial tunnel aperture areas were measured using three-dimensional computed tomography (3D CT) at 1 week and 1 year postoperatively, and femoral and tibial TW (%) was calculated. Lateral and medial PTS was also measured using 3D CT. Results: As compared with 1 week postoperatively, the mean tibial tunnel aperture areas increased by 30.6% ± 28.5%, and the mean femoral tunnel aperture areas increased by 28.3% ± 27.9% when measured at 1 year postoperatively. Although no significant difference was observed between femoral and tibial TW, a significant positive correlation was noted between femoral and tibial TW (r = 0.240, p = 0.011). A significant correlation was observed only between lateral PTS and tibial TW (r = 0.354, p < 0.001). There was no significant correlation between medial PTS and tibial TW, lateral PTS and femoral TW, or medial PTS and femoral TW. Conclusion: Significant positive correlation was observed between femoral and tibial TW. Steeper lateral PTS correlated with greater tibial TW; on the other hand, medial PTS did not correlate with tibial TW. Although lateral PTS affected tibial TW, it did not affect femoral TW.

The intraoperative gap differences due to joint distraction force differences in total knee arthroplasty are affected by preoperative lower limb alignment and body mass index.

BACKGROUND: Soft tissue balance is important for a good clinical result in total knee arthroplasty. Nevertheless, the appropriate evaluation of the intraoperative gap has not been established. We investigated the relationship between physical characteristics and gap differences due to distraction force, in order to determine whether intraoperative adjustment of the distraction force can be considered based on the physical characteristics of the patient. METHODS: A total of 115 varus knees in which primary total knee arthroplasty was performed were retrospectively evaluated. The component gaps were measured under 60 and 80 N. The gap difference under 60 and 80 N was calculated. We performed a linear regression analysis to determine the correlation between the gap differences and patient parameters. FINDINGS: Each gap was significantly larger under 80 N than under 60 N. The component gap difference is larger in the lateral compartment than in the medial compartment at each knee flexion angle. The gap difference negatively correlated with preoperative hip-knee-ankle angle at a knee flexion of 0° and 120° (r = -0.21, -0.19; p = 0.02, 0.05) and positively correlated with BMI in the lateral compartment at a knee flexion of 90° (r = 0.31, p < 0.001). INTERPRETATION: The difference in the intraoperative gap due to the joint distraction force was affected by the preoperative HKA axis angle and the body mass index in the lateral compartment. Surgeons should consider the effect of preoperative limb alignment and body mass index in interpreting intraoperative gap measurement.

In vivo kinematic comparison of medial pivot total knee arthroplasty in weight-bearing and non-weight-bearing deep knee bending.

BACKGROUND: This study aimed to determine the kinematics of medial pivot total knee arthroplasty by comparing weight-bearing and non-weight-bearing deep knee bending and to evaluate the effect of the weight-bearing state on the kinematics. METHODS: The kinematics of 19 knees were investigated under fluoroscopy during squatting (weight-bearing) and active-assisted knee bending (non-weight-bearing) using two- to three-dimensional registration technique. Accordingly, range of motion, anteroposterior translation for the medial and lateral low contact points, axial rotation of the femoral component relative to the tibial component and kinematic pathway were evaluated. FINDINGS: There was no difference in range of motion between the two states. The medial anteroposterior translation showed no significant movement with no anterior translation in both the weight-bearing and non-weight-bearing from 0° to 90° of flexion. Regarding the lateral anteroposterior translation, a posterior translation was observed during weight-bearing, whereas a slight anterior translation from 0° to 30° of flexion and subsequent posterior translation were found in the non-weight-bearing. Femoral external rotation was observed in the weight-bearing, whereas femoral internal rotation was seen from 0° to 30° of flexion and subsequent femoral external rotation was observed in the non-weight-bearing. The kinematic pathway showed medial pivot motion and subsequent bicondylar rollback in the weight-bearing, whereas only medial pivot motion was observed in the non-weight-bearing. INTERPRETATION: The medial anteroposterior translation of the femur during deep knee bending showed no anterior motion in the two states. The lateral anteroposterior translation and femoral rotation were different in the mid-flexion range between the two states.

Dynamic Postural Stability Is Decreased During the Single-Leg Drop Landing Task in Male Collegiate Soccer Players With Chronic Ankle Instability.

Background: Chronic ankle instability (CAI) is commonly encountered in soccer players. The feelings of instability and anxiety caused by CAI can lead to poor performance, such as difficulty in sharp change of direction during soccer play. The single-leg drop landing (SLDL) task is often used to evaluate dynamic postural stability. Purpose/Hypothesis: The purpose of this study was to clarify whether dynamic stability measured during SLDL is altered in male collegiate soccer players with CAI. The hypothesis was that athletes with CAI would show poor dynamic postural stability. Study Design: Controlled laboratory study. Methods: A total of 103 male collegiate soccer players were recruited, and their limbs were classified based on the new international CAI criteria. All players performed three 5-second SLDL trials on a force plate. The main outcome measures included time to stabilization of the horizontal ground-reaction force (GRF); peak GRF in the vertical, horizontal, and sagittal directions; and trajectory length of the center of pressure during SLDL. Results: Data from 59 CAI limbs and 147 non-CAI limbs were collected in this study. Time to stabilization of horizontal GRF was significantly longer in the CAI limbs (P < .001), and the peak GRFs in all directions were significantly lower in the CAI limbs (vertical, P < .001; horizontal, P < .001; sagittal, P = .001). Additionally, the trajectory length of the center of pressure was significantly greater in the CAI limbs (P = .004). Conclusion: Soccer players with CAI had decreased dynamic postural stability that led them to land softly when performing the SLDL task. Measurement of dynamic postural stability may be useful in the evaluation of CAI. Clinical Relevance: Our findings may be useful for strategies of daily training or as an evaluation tool.

The effects of initial graft tension on femorotibial relationship following anatomical rectangular tunnel anterior cruciate ligament reconstruction using bone-patellar tendon-bone graft.

BACKGROUND: The purpose of this study was to elucidate the effects of the difference of initial graft tension on the femorotibial relationship on an axial plane and its chronological change following anatomical anterior cruciate ligament (ACL) reconstruction. METHODS: A total of 63 patients who underwent anatomical ACL reconstruction were included in this study. The graft was fixed at full knee extension with manual maximum (higher graft tension; group H) and 80 N (lower graft tension; group L) pulls in 31 and 32 patients, respectively. The femorotibial positional relationship in axial computed tomography at 1 week and 1 year postoperatively were retrospectively evaluated. The side-to-side differences (SSDs) and the amount of changes of SSDs over 1 year were compared between groups. RESULTS: The SSDs of the external rotational angle of the tibia in group H were significantly larger than those in group L at postoperative 1 week (2.7 ± 3.9° vs. 0.3 ± 3.3°; P < 0.01). The amount of internal rotational changes of SSDs of the internal-external rotational angles over 1 year in group H was significantly larger than that in group L (-3.6 ± 3.9° vs. - 0.3 ± 2.7°; P < 0.01). No significant differences were observed on the anterior-posterior translation distance and medial-lateral shift distance. CONCLUSION: The application of higher initial graft tension resulted in excessive external rotation of the tibia to the femur at 1 week postoperatively in anatomical ACL reconstruction, and the excessive early external tibial rotation had resolved over 1 year.

Femoral rollback at high-flexion during squatting is related to the improvement of sports activities after bicruciate-stabilized total knee arthroplasty: an observational study.

BACKGROUND: In bicruciate-stabilized total knee arthroplasty (BCS-TKA), the relationship between the postoperative kinematics and sports subscales in patient-reported outcome measures (PROMs) remains unknown. The purpose of this study was to determine the relationship between kinematics and sports subscales using the PROMs after BCS-TKA. METHODS: Sixty-one patients with severe knee osteoarthritis were examined at 13.5 ± 7.8 months after BCS-TKA. The patients performed squats under single fluoroscopic surveillance in the sagittal plane. Range of motion of the knee, axial rotation of the femur relative to the tibial component, and anteroposterior (AP) translation of the medial and lateral femorotibial contact points were measured using a 2D-to-3D registration technique. In addition, the relationship between the kinematics and improvement of the sports subscales in the Knee Injury and Osteoarthritis Outcome Score (KOOS) was evaluated. RESULTS: In rotation angle, the femoral external rotation was observed from 0 to 50° of flexion. The amount of femoral external rotation did not correlate with PROMs-SP. In medial AP translation, posterior translation was observed from 0 to 20° and 80-110° of flexion. Mild anterior translation was observed from 20 to 80° of flexion. Beyond 80° of flexion, posterior translation was positively correlated with squatting. In lateral AP translation, posterior translation was observed from 0 to 20° and 80-110° of flexion. Beyond 80° of flexion, posterior translation was positively correlated with running, jumping, twisting/pivoting, and kneeling. CONCLUSION: Femoral rollback at high flexion during squatting may be important to improve sports performance after BCS-TKA.

Proximal tibial morphology is associated with risk of trauma to the posteromedial structures during tibial bone resection reproducing the anatomical posterior tibial slope in bicruciate-retaining total knee arthroplasty.

BACKGROUND: A tibial cut with the native posterior tibial slope (PTS) is a theoretical prerequisite in bicruciate-retaining total knee arthroplasty (BCRTKA) to regain physiological knee kinematics. The present study reveals tibial morphological risk factors of trauma to the posteromedial structures of the knee during tibial bone resection in BCRTKA. METHODS: Fifty patients undergoing BCRTKA for varus knee osteoarthritis were analyzed. A three-dimensional tibial bone model was reconstructed using a computed tomography-based preoperative planning system, and the coronal tibial slope (CTS) and medial PTS (MPTS) were measured. Then, we set the simulated tibial cutting plane neutral on the coronal plane, posteriorly inclined in accordance with the MPTS on the sagittal plane, and 9 mm below the surface of the subchondral cortical bone (i.e., 11 mm below the surface of the cartilage) of the lateral tibial plateau. The association between the tibial morphology and the distance from the simulated cutting plane to the semimembranosus (SM) insertion (Dsm) was analyzed. RESULTS: Of the 50 patients, 19 (38%) had negative Dsm values, indicating a cut into the SM (namely, below the posterior oblique ligament) insertion. The MPTS was negatively correlated with Dsm (r = -0.396, p = 0.004), whereas the CTS was positively correlated with Dsm (r = 0.619, p < 0.001). On multivariate linear regression analysis, the MPTS and CTS were independent predictors of Dsm. CONCLUSION: In the setting of tibial cuts reproducing the native MPTS in BCRTKA, patients with larger PTS and smaller CTS had more risk of trauma to the posteromedial structures.

Effects of a 1-mm difference in bearing thickness on intraoperative bearing movement and kinematics in Oxford unicompartmental knee arthroplasty.

BACKGROUND: The choice of mobile bearing (MB) thickness is essential for obtaining successful results after mobile-bearing Oxford unicompartmental knee arthroplasty (UKA). This study aimed to investigate the effects of a 1-mm difference in bearing thickness on intraoperative MB movement and intraoperative knee kinematics in Oxford UKAs. METHODS: We prospectively investigated the effects of a 1-mm difference in bearing thickness on intraoperative MB movement and knee kinematics in 25 patients who underwent Oxford UKAs when surgeons didn't know which bearing thickness to choose with 1-mm difference. A trial tibial component that was scaled every 2 mm was used to measure the intraoperative MB movement, and the tibial internal rotation relative to the femur and the knee varus angle was simultaneously evaluated using the navigation system as the knee kinematics. We separately evaluated sets of two MB thicknesses with 1-mm differences, and we compared the intraoperative parameters at maximum extension; 30º, 45º, 60º, and 90º flexion; and maximum flexion between the thicker MB (thick group) and the thinner MB (thin group). RESULTS: The MB in the thin group was located significantly posteriorly at 90º flexion compared with that in the thick group; however, there were no differences at the other flexion angles. There was significantly less tibial internal rotation in the thin group at 90º flexion than that in the thick group; however, there were no differences at the other flexion angles. The knee varus angles in the thick group were significantly smaller than those in the thin group by approximately one degree at all angles other than at 30º and 45º flexion. CONCLUSION: The thicker MB could bring the less posterior MB movement and the more tibial internal rotation at 90º flexion, additionally the valgus correction angle in the thicker MB should be paid attention. These results could help surgeons to decide the thickness of MBs when they wonder the thickness of MB.

Effect of weight-bearing in bicruciate-retaining total knee arthroplasty during high-flexion activities.

BACKGROUND: To evaluate the effect of weight-bearing on the kinematics of the bicruciate-retaining total knee arthroplasty design during high knee flexion activities. METHODS: The kinematics of 21 bicruciate-retaining total knee arthroplasties were evaluated under fluoroscopy, with two- and three-dimensional image registrations, during squatting (weight-bearing) and active-assisted knee flexion (non-weight-bearing). The following variables were measured: knee range of motion, axis of femoral rotation and varus-valgus angle relative to the tibial component, anteroposterior translation of the medial and lateral contact points, and the kinematic pathway of the joint surfaces. FINDINGS: From 20° to 100° of flexion, the femoral external rotation during weight-bearing was larger than that during non-weight-bearing. There were no differences in the varus-valgus angles between the two conditions. From 10° to 50° of flexion, the medial contact point during weight-bearing was located posterior to the point of contact during non-weight-bearing; this difference between the two weight-bearing conditions was significant. From 0° to 90° of flexion, the lateral contact point in weight-bearing was located posterior to the contact point in non-weight-bearing; this difference between the two weight-bearing conditions was also significant. INTERPRETATION: The anteroposterior position of the medial and lateral contact points of the bicruciate-retaining total knee arthroplasty design was significantly more posterior in the mid-range of knee flexion in weight-bearing than in non-weight-bearing. However, no anterior translation of the bicruciate-retaining total knee arthroplasty design was observed. Therefore, bicruciate-retaining total knee arthroplasty appears to have good anteroposterior stability throughout the range of knee flexion, regardless of the weight-bearing condition.

The Association between In Vivo Knee Kinematics and Patient-Reported Outcomes during Squatting in Bicruciate-Stabilized Total Knee Arthroplasty.

Bicruciate-stabilized total knee arthroplasty (BCS TKA) has been developed to improve TKA kinematic performance. However, the relationship between in vivo kinematics and patient-reported outcomes (PROs) has not been well described. This study was performed to clarify the relationship between in vivo kinematics and PROs in a cohort of patients undergoing BCS TKA. Forty knees were evaluated using a two-dimensional to three-dimensional registration technique obtained from sagittal plane fluoroscopy. In vivo kinematics including anteroposterior (AP) translation and tibiofemoral rotation were evaluated. Knee Society scores (KSSs) and Knee injury and Osteoarthritis Outcome Scores (KOOSs) were assessed before and after surgery. Relationships between tibiofemoral kinematics assessed with the knee in different positions of knee flexion and PROs were evaluated using Spearman's correlation analysis. The study demonstrated a significant negative correlation (r = - 0.33) between medial AP translation from minimum flexion to 30 degrees flexion and postoperative KOOS activities of daily living subscale. A significant positive correlation (r = 0.51) was found between the femoral external rotation from minimum flexion to 30 degrees flexion and improvement of the KOOS pain subscale. No correlation was found between the lateral AP translation and PROs. Achieving medial AP and femoral external rotation stability in early flexion may be important in optimizing postoperative PROs.