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Several studies have reported better clinical outcomes following kinematically aligned total knee arthroplasty (KA-TKA) than mechanically aligned TKA. Consistent reproduction of a KA-TKA is aided by accurate tibial bone resections using computer navigation systems. This study compares an accelerometer-based portable navigation system with a conventional navigation system on tibial bone resection and clinical outcomes in KA-TKA. This study included 60 knees of patients who underwent primary KA-TKA between May 2015 and September 2017. They were randomly assigned to the OrthoPilot and iASSIST groups. A tibial bone cut was performed with 3 degree varus and 7 degree posterior slope in relation to the mechanical axis in all cases. The tibial component angle (TCA) and posterior slope angle (PSA) were evaluated by postoperative radiography, and those that deviated more than 2 degree were set as outliers. The clinical outcomes were the knee range of motion (ROM) and 2011 Knee Society Score (KSS) evaluated at 1 year postoperation. The groups were compared in terms of the TCA, PSA, number of outliers, ROM, and 2011 KSS ( p  < 0.05). No significant difference was observed between the groups in terms of the mean TCA, PSA, number of outliers, ROM, and categories of the 2011 KSS (objective knee indicators, symptoms, satisfaction, expectations, and functional activities). Although tibial bone cuts were performed with 3 degree varus and 7 degree posterior slope, no significant difference was observed between the OrthoPilot and iASSIST groups in terms of the accuracy of cuts or postoperative clinical result. The iASSIST was found to be a simple and useful navigation system for KA-TKA., Competing Interests: None declared., (Thieme. All rights reserved.)

Background: Lateral unicompartmental knee arthroplasty (UKA) leads to good clinical outcomes for isolated lateral osteoarthritis. However, the impact of the tibial component position on postoperative outcomes in lateral UKA is yet to be determined., Purpose: This study investigated the influence of tibial component malposition on clinical outcomes in lateral UKA., Materials: This was a retrospective study of 50 knees (mean age 73.5 years) who underwent lateral UKA between September 2013 and January 2019. The Oxford Knee Score (OKS), Knee Society Score - Knee (KSSK), and Knee Society Score - Function (KSSF) were evaluated. The coronal alignment, posterior slope of tibial component, tibial component rotation relative to Akagi's line (angle α), and femoral anteroposterior (AP) axis (angle β) were measured postoperatively. The average follow up period was 2.3 (range, 1-4.9) years., Results: Clinical scores were significantly improved after lateral UKA. The mean coronal alignment was 0.9° ± 3.2° varus (range, 9.1° varus to 5.5° valgus), the mean posterior slope was 6.8° ± 3.8° (range, 0.8° to 14.8°). The mean α and β angles, were 4.1° ± 5.8° (range, -9.7° to 16.5°) and 6.7° ± 7.1° (range, -7.0° to 20.5°) external rotation. The angle α had significant negative correlations with postoperative OKS (r = -0.36), KSSK (r = -0.28), and KSSF (r = -0.39), and angle β had significant negative correlations with postoperative OKS (r = -0.34) and KSSK (r = -0.46)., Conclusion: Excessive external rotation of the tibial component could negatively influence the postoperative outcomes of lateral UKA., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Purpose: The aim of this study was to examine and evaluate the factors associated with changes in limb alignment 10 years after total knee arthroplasty (TKA). The hypothesis was that bone morphology and immediate postoperative alignment could be correlated with long-term post-operative alignment changes following TKA., Methods: This study retrospectively analysed 136 consecutive primary TKA cases for varus deformity, performed from 2006 to 2008, that could be followed for at least 10 years postoperatively. Anteroposterior long-leg weight-bearing radiographs were obtained within 1 month and at least 10 years after surgery. The hip-knee-ankle (HKA) angle immediately after surgery was compared with that 10 years later; factors correlating with the change in HKA angle (δHKA) were evaluated., Results: The mean HKA angles were significantly different between immediate and long-term postoperative assessments (0.1° ± 1.9° vs. 1.2° ± 2.9°, p < 0.001). Furthermore, a significant difference was observed in the outlier ratio (> 3° deviation from the 0° of HKA angle) (10% vs. 24%, p = 0.002). δHKA strongly correlated with a higher preoperative tibial plateau tip-to-proximal tibial shaft (TPTPS) angle, higher postoperative HKA angle, lateral distal femoral angle, and lower postoperative medial proximal tibial angle., Conclusion: Varus deformity in the proximal part of the tibia, immediate postoperative varus alignment, and varus position of the femoral and tibial components may lead to varus progression in limb alignment in the long term, even 10 years after TKA; the surgeon should, therefore, weigh the risks of leaving a varus alignment during surgery. Moreover, if the preoperative TPTPS angle is high, the alignment may become varus after TKA, even in patients who have acquired neutral alignment., Level of Evidence: IV.

Background: Valgus subsidence (VS) of the tibial component is a rare complication of unicompartmental knee arthroplasty (UKA), and surgeons might consider revision surgery. The present study aimed to identify the factors related to VS of the tibial component after cementless Oxford mobile-bearing UKA., Methods: The study included 120 patients who underwent Oxford mobile-bearing UKA using a cementless tibial component in our center between September 2015 and September 2016. Six showed VS of >2° after surgery. Patients were stratified into 2 groups according to the occurrence of VS of the tibial component (VS group, n = 6; no-subsidence group, n = 114). Postoperative radiographic evaluations were conducted to assess the varus/valgus alignment, rotation, and mediolateral position of the tibial and femoral components. The Oxford Knee Score (OKS) was assessed at 3, 6, and 12 months postoperatively. Positional parameters and sequential change in OKS were compared between the two groups using unpaired t-test (P < .05, statistically significant)., Results: At 3 months postoperatively, an average VS of 3.4° in the VS group was observed, with a significant decrease in OKS. VS was associated with a significantly more medial position and external rotation of the tibial component. After 3 months, VS stopped, and the OKS gradually improved without revision surgery., Conclusions: VS might be caused by the malpositioning of the tibial component. VS of the tibial component after UKA appears to stop, with simultaneous pain relief, even without revision after 3 months postoperatively., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Background: Soft-tissue balance is an important element for the success of total knee arthroplasty; however, the influence of intraoperative soft-tissue balance on knee kinematics in posterior-stabilized-total knee arthroplasty remains unknown. We investigated whether intraoperative soft-tissue balance could influence knee kinematics and flexion angle after posterior-stabilized-total knee arthroplasty., Methods: This study included 30 patients with knee osteoarthritis and varus alignment who underwent posterior-stabilized total knee arthroplasty; intraoperative soft-tissue balance parameters, such as varus ligament balance and joint component gap, were assessed by an offset-type tensor at knee flexion angles of 0°, 10°, 30°, 60°, 90°, 120°, and 135°. Medial and lateral compartment gaps were calculated. The amount of tibial internal rotation was determined between 60° and 135° flexion by the navigation system. Simple linear regression analysis was used to analyze the effects of intraoperative soft-tissue balance on tibial internal rotation. Linear regression analysis was used to assess correlation between tibial internal rotation and postoperative knee flexion angle., Findings: Medial compartment gaps at 60° (r = -0.57, P < 0.05) and 90° (r = -0.60, P < 0.05) of flexion were significantly negatively correlated with tibial internal rotation. Moreover, tibial internal rotation showed a significant correlation with the 2-year postoperative knee flexion angle (r = 0.50, P < 0.05) and improvement in knee flexion angle (r = 0.61, P < 0.05)., Interpretation: Thus, smaller medial compartment gaps at 60° and 90° of flexion play an important role in achieving medial pivot motion with tibial internal rotation; moreover, tibial internal rotation provides a better flexion angle after posterior-stabilized total knee arthroplasty., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Purpose: This study aimed to determine the correlation between the change in joint line height calculated from the resected bone and insert thickness during surgery and the change in limb alignment following unicompartmental knee arthroplasty (UKA). It was hypothesized that joint line elevation is correlated with the change in limb alignment., Methods: A total of 74 consecutive patients diagnosed with either isolated medial compartmental osteoarthritis (38 patients) or spontaneous osteonecrosis of the knee (36 patients) were included. The thickness of the proximal tibial and distal femoral bony cuts was measured during surgery; using these values, the medial joint line elevation of the tibia (MJLET) and medial joint line reduction of the femur (MJLRF) were defined. The correlation between the amount of change in the hip-knee-ankle (HKA) angle before and after surgery (δHKA) and the thickness of the tibial insert (TI), MJLET, or MJLRF were evaluated., Results: The mean values of δHKA, TI, MJLET, and MJLRF were 5.0° ± 2.6°, 8.5 ± 0.8, 4.4 ± 1.3, and 0.0 ± 1.1 mm, respectively. The δHKA had a significant, but weak-positive correlation with the TI (P = 0.02), and moderate-positive correlation with MJLET (P < 0.001). However, no correlation was observed between δHKA and MJLRF., Conclusions: The MJLET measured during surgery had a significant moderate-positive correlation with the change in limb alignment following medial UKA. For clinical relevance, the surgeon can predict postoperative limb alignment after UKA by considering, intraoperatively, both the insert thickness and the depth of resection at the proximal tibia thus minimizing technical error to obtain an optimal alignment after UKA., Level of Evidence: Diagnostic study, level II.

Background: The importance of medial compartment stability is recognized in total knee arthroplasty (TKA). To manage the medial extension-flexion gap, the posterior reference position can be changed from conventional posterior center to posterior medial in measured resection techniques. This study aimed to compare the intraoperative soft tissue balance and rotational kinematics between the posterior medial and posterior center reference groups., Methods: We enrolled 57 consecutive patients with varus osteoarthritis undergoing posterior-stabilized (PS) TKA using an image-free navigation system. The detailed surgical plan in both groups and intraoperative kinematics were recorded using navigation, and soft tissue balance measured with an offset-type tensor was statistically compared between groups., Results: Patients were divided into the posterior center reference group (n = 32) and posterior medial reference group (n = 25). The posterior medial and posterior lateral condyles were significantly thicker in the posterior center reference group (P < .05). Although preoperative rotational kinematics were comparable between groups, the tibial rotational position was significantly more externally rotated in the posterior center reference group than in the posterior medial reference group at 45°, 60°, and 90° of flexion (P < .05). The varus angle and joint component gap were significantly smaller in the posterior medial reference group than in the posterior center reference group at 60° and 90° of flexion (P < .05)., Conclusion: The posterior reference position affects intraoperative kinematics and soft tissue balance in navigated PS TKA. Posterior medial reference PS TKA decreases the excessive tibial external rotation during midflexion and increases the flexion stability compared with conventional posterior center reference PS TKA., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Purpose: In clinical practice, people with better femorotibial rotation in the flexed position often achieve a favourable postoperative maximum flexion angle (MFA). However, no objective data have been reported to support this clinical observation. In the present study, we aimed to investigate the correlation between the amount of intraoperative rotation and the pre- and postoperative flexion angles., Methods: Fifty-five patients with varus osteoarthritis undergoing computer-assisted posterior-stabilized total knee arthroplasty (TKA) were enrolled. After registration, rotational stress was applied towards the knee joint, and the rotational angles were recorded by using a navigation system at maximum extension and 90° of flexion. After implantation, rotational stress was applied for a second time, and the angles were recorded once more. The MFA was measured before surgery and 1 month after surgery, and the correlation between the amount of femorotibial rotation during surgery and the MFA was statistically evaluated., Results: Although the amount of tibial rotation at maximum extension was not correlated with the MFA, the amount of tibial rotation at 90° of flexion after registration was positively correlated with the pre- and postoperative MFA (both p < 0.005). However, no significant relationship was observed between the amount of tibial rotation after implantation and the postoperative MFA (n.s.)., Conclusion: The results showed that better femorotibial rotation at 90° of flexion is associated with a favourable postoperative MFA, suggesting that the flexibility of the surrounding soft tissues is an important factor for obtaining a better MFA, which has important clinical relevance. Hence, further evaluation of navigation-based kinematics during TKA may provide useful information on MFA., Level of Evidence: Diagnostic studies, development of diagnostic criteria in a consecutive series of patients, and a universally applied "gold" standard, Level II.

Background: The effect of posterior slope on joint gap in unicompartmental knee arthroplasty (UKA) has yet to be quantified. The purpose of this study was to quantify the effect of the tibial slope on the joint component gap and postoperative range of motion in UKA., Methods: Forty consecutive patients were prospectively enrolled. The correlation between the tibial slope changes and the component gap, the component gap difference between flexion angles, the postoperative extension or flexion angles was examined. The correlation of joint looseness with tibial slope changes and postoperative extension angle was also examined., Results: Increased tibial slope positively correlated with the differences between the component gap at 90° and 10°, 120° and 10°, or 135° and 10° knee flexion angle. Although tibial slope change did not affect postoperative flexion angle, increased tibial slope reduced postoperative extension angle. Moreover, increased tibial slope resulted in decreased joint looseness during 10° of knee flexion and decreased joint looseness during 10° of knee flexion resulted in reduced postoperative extension angle., Conclusions: Increased tibial slope resulted in tight component gap at knee extension compared with that at knee flexion. Furthermore, tight component gap at extension lead to decreased postoperative extension angle. These results indicate that an individual anatomical tibial slope should be considered when tibial sagittal osteotomy was performed and increasing tibial slope should be avoided to achieve full extension angle after UKA., Level of Evidence: II., (Copyright © 2016. Published by Elsevier B.V.)

Purpose: To investigate whether intraoperative kinematics obtained by navigation systems can be divided into several kinematic patterns and to assess the correlation between the intraoperative kinematics with maximum flexion angles before and after total knee arthroplasty (TKA)., Method: Fifty-four posterior-stabilised (PS) TKA implanted using an image-free navigation system were evaluated. At registration and after implantation, tibial internal rotation angles at maximum extension, 30°, 45°, 60°, 90°, and maximum flexion were collected. The rotational patterns were divided into four groups and were examined the correlation with maximum flexion before and after operation., Results: Tibial internal rotation from 90° of flexion to maximum flexion at registration was correlated with maximum flexion angles pre- and postoperatively. The four groups showed statistically different kinematic patterns. The group with tibial external rotation up to 90° of flexion, following tibial internal rotation at registration, achieved better flexion angles, compared to those of another groups (126.7° ± 12.0°, p < 0.05). The group with tibial external rotation showed the worst flexion angles (80.0° ± 40.4°, p < 0.05). Furthermore, the group with limited extension showed worse flexion angles (111.6° ± 8.9°, p < 0.05)., Conclusion: Navigation-based kinematic patterns found at registration predict postoperative maximum flexion angle in PS TKA. Navigation-based kinematics can be useful information during TKA surgery., Level of Evidence: Diagnostic studies, development of diagnostic criteria in a consecutive series of patients and a universally applied "gold" standard, Level II.

Purpose: The sagittal fibular axis serves as an intra-operative landmark during conventional total knee arthroplasty (TKA); however, only a few relevant anatomical studies have been published regarding its use as an extramedullary guide. Furthermore, the correlation between the coronal fibular and tibial mechanical axes in osteoarthritic knees has been only reported once. Here, the hypothesis of this study is that the fibula can be a reliable intra-operative landmark, in the sagittal and coronal planes, among patients with osteoarthritis who have undergone TKA., Methods: Osteoarthritic knees (n = 62) after TKA were evaluated using three-dimensional image-matching software. The angles between the tibial mechanical axis and the fibular shaft axis were measured in the sagittal and coronal planes. Moreover, correlations between the angles and patient-specific factors were evaluated., Results: The mean angle between the tibial mechanical and fibular shaft axes was 2.6° ± 2.3° for posterior inclination in the sagittal plane and 0.9° ± 2.0° for varus inclination in the coronal plane. The percentage of subjects with the fibular shaft axis within 2° of the tibial mechanical axis was 17.7 and 69.3 % in the sagittal and coronal planes, respectively. No patient-specific factors were correlated with the angle between the tibial mechanical and fibular shaft axes., Conclusions: The angle between the tibial mechanical and fibular shaft axes differed among patients, independent of patient-specific factors, and did not appear to be a reliable intra-operative landmark. Surgeons should use values from individual pre-operative evaluations of the axis as reference for conventional TKA., Level of Evidence: Case series with no comparison group, Level IV.

Medial release for varus knee is a key procedure to obtain appropriate soft tissue balance in total knee arthroplasty (TKA). The influence of semimembranosus release during cruciate-retaining (CR) TKA on knee kinematics and clinical outcomes were investigated in consecutive 50 patients (25: semimembranosus release group, 25: minimum release group) with moderate varus osteoarthritis using a navigation system. Semimembranosus release significantly reduced the amount of tibial internal rotation before bone cut and after all prostheses implanted. Despite of no significant differences in clinical scores between the groups, minimum release group exhibited significantly higher postoperative flexion angle compared to the semimembranosus release group. Minimal medial release with avoiding semimembranosus release maintains tibial internal rotation in CR TKA, resulting in achievement of postoperative high flexion angle., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Purpose: The tibia first technique in unicompartmental knee arthroplasty (UKA) may have the advantage that surgeons can obtain a balanced flexion-extension gap. However, changes of the soft tissue tension during UKA have not been elucidated yet. The purpose of this study was to examine the correlation between the soft tissue tension before the femoral osteotomy and after the femoral component is in place using the tibia first technique in UKA., Methods: Thirty UKAs for isolated medial compartmental osteoarthritis or idiopathic osteonecrosis were assessed. The actual values of the proximal and posterior femoral osteotomy were calculated by adding the thickness of the bone saw blades to the thickness of the bony cut. Using a UKA tensor designed to facilitate intra-operative soft tissue tension throughout the range of motion (ROM), the original gap before the femoral osteotomy, the component gap after the femoral osteotomy, and component placement were assessed under 20-lb distraction forces., Results: The mean actual thickness of the distal femoral osteotomy was 6.5 ± 1.3 mm and the posterior femoral osteotomy was 7.4 ± 1.3 mm. The distal thickness of the prosthesis was set to 6.5 mm and the mean posterior thickness of the prosthesis used in this study was 5.8 ± 0.3 mm. There is a positive correlation between the original and component gap throughout the ROM (R > 0.5). The original and component gap showed the same kinematic pattern from full extension to 90° of knee flexion. However, the component gap was significantly higher compared to the original gap after 120° of knee flexion (P < 0.001)., Conclusions: Despite the fact that the component gap values were significantly higher compared to the original gap value in deep flexion, there is a positive correlation between the original and component gap throughout the ROM. The discrepancy during deep flexion was due to the posterior design of the prosthesis that is designed to be thinner than the actual thickness of the posterior osteotomy. These results suggest that the tibia first technique with the tensor have the advantage that surgeons can predict final soft tissue tension before femoral osteotomies with the prosthetic design and help restore natural knee kinematics, potentially improving implant survival and functional outcomes.

Purpose: Medial patellofemoral ligament (MPFL) reconstruction is performed to treat recurrent patellar dislocation (RPD). However, the effectiveness of MPFL reconstruction in patients with a severely lateralised tibial tuberosity remains unknown. In this study, the clinical outcomes of MPFL reconstruction in patients with an increased tibial tuberosity-trochlear groove (TT-TG) distance were examined., Methods: A total of thirty-four patients who underwent MPFL reconstruction for RPD were retrospectively examined. Nineteen patients with a TT-TG distance of >20 mm (increased TT-TG distance group) were compared with 15 patients with a TT-TG distance of <20 mm (control group). Clinical outcomes of MPFL reconstruction were evaluated by occurrence of re-dislocation, Crosby and Insall grading system, apprehension sign, and Kujala and Lysholm scores., Results: None of the patients reported re-dislocation. Apprehension sign remained in three patients in the increased TT-TG distance group and in one patient in the control group. According to the Crosby and Insall grading system, 9 patients (47%) were excellent, 9 (47%) were good, and 1 (5%) was fair to poor in the increased TT-TG distance group, while 6 (40%) were excellent and 9 (60%) were good in the control group. Kujala and Lysholm scores were significantly improved post-operatively in both groups. No significant correlations were observed between TT-TG distance and post-operative Kujala or Lysholm score., Conclusion: Overall clinical outcomes of MPFL reconstruction were favourable even in patients with an increased TT-TG distance. TT-TG distance of >20 mm may not be an absolute indication for medialisation of the tibial tuberosity when performing MPFL reconstruction., Level of Evidence: Case-control study, Level III.

One-staged tibial corrective osteotomy and total knee arthroplasty is a challenging but effective treatment for arthritic knees with extra-articular deformity. Although osteocutaneous thermal necrosis is accepted as a complication of intramedullary reamed nailing following long bone fractures, only 15 cases have been reported in the English literature at present. This report illustrates a rare case of thermal necrosis in a patient undergoing tibial corrective osteotomy coincident with long-stemmed total knee arthroplasty. Excessive reaming with a machine reamer is hypothesized as the cause of this serious complication. In this report, we highlight this rare but serious complication after long-stemmed total knee arthroplasty.

Background: Both kinematically-aligned (KA) total knee arthroplasty (TKA) and bicruciate stabilized (BCS) TKA aim to reproduce the physiological knee kinematics. In this study, we compared the femoro-tibial component rotational mismatch between patients who underwent modified KA-TKA and those who received guided-motion BCS-TKA, and its influence on the clinical outcomes. Methods: In this retrospective study, 77 consecutive patients were included and divided into two groups: subjects who underwent modified KA-TKA with Persona (KA Group; n = 42) and those who received BCS-TKA with JOURNEY II (BCS group; n = 35). Range of motion, the 2011 Knee Society Score (KSS), the rotational alignment of the femoral and tibial components, and the correlations between the rotational mismatch and the 2011 KSS subscales were examined. Results: The postoperative objective knee indicators (P = 0.0157), patient satisfaction (P = 0.0039) and functional activity scores (P = 0.0013) in the KA group were significantly superior to those in the BCS group 1 year postoperatively. There was no significant difference between the two groups observed in the rotational mismatch. In the BCS group, significant negative correlations were identified between the rotational mismatch and objective indicators, patient satisfaction, and functional activity scores but not in the KA group. Conclusions: The short-term clinical results following KA-TKA showed superior objective knee indicators, patient satisfaction and functional activity scores. A negative correlation was observed between component rotational mismatch and the 2011 KSS subscales in the BCS group, compared to no relationship found between the two in the KA group. These findings suggested that KA-TKA has a relatively higher tolerance for rotational mismatch than BCS-TKA. [ABSTRACT FROM AUTHOR]

Background: Vascular CD34+ cells in anterior cruciate ligament (ACL) tissue have the potential for high proliferation and multilineage differentiation that can accelerate tendon-bone healing. While patient characteristics, such as age, can affect tendon-bone healing, the influence of elapsed time after injury on the healing process is unclear. Hypothesis: Cells obtained during the early phase after injury will exhibit a greater tendon-bone healing potential compared with chronic phase counterparts when applied to an immunodeficient rat model of ACL reconstruction. Study Design: Controlled laboratory study. Methods: Adult human ACL-ruptured tissue was harvested from patients undergoing arthroscopic primary ACL reconstruction and classified into 2 groups based on the time elapsed between injury and surgery: (1) early group (≤3 months from injury) and (2) chronic group (>3 months from injury). In addition, 76 ten-week-old female immunodeficient rats underwent ACL reconstruction, followed by intracapsular administration of one of the following: (1) ACL-derived cells from the early group (n = 5), (2) ACL-derived cells from the chronic group (n = 5), or (3) phosphate-buffered saline (PBS) only (n = 5). During the 8 weeks after surgery, histological (weeks 2, 4, 8), immunohistochemical (week 2), radiographic (weeks 0, 2, 4, 8), and biomechanical (week 8) analyses were performed to evaluate tendon-bone healing. Results: In the early group, the histological evaluation showed early healing, induction of endochondral ossification–like integration, and mature bone ingrowth. Micro–computed tomography showed that the tibial bone tunnels at week 4 and week 8 were significantly reduced in the early group compared with those in the chronic group and PBS group (P < .05). Moreover, biomechanical tensile strength was significantly greater in the early group than in the other groups (P < .05). An accelerated healing potential in the early group was further demonstrated by the enhancement of intrinsic angiogenesis/osteogenesis and human-derived vasculogenesis/osteogenesis. Conclusion: Compared with human ACL-derived cells obtained during the chronic phase, cells obtained during the early phase after injury have a greater tendon-bone healing potential when used in an immunodeficient rat model of ACL reconstruction. Clinical Relevance: During ACL reconstruction surgery, transplanting ACL remnant tissue in the early phase after injury could accelerate and enhance tendon-bone healing. [ABSTRACT FROM AUTHOR]

Purpose: Tibial acceleration during the pivot shift test is a potential quantitative parameter to evaluate rotational laxity of anterior cruciate ligament (ACL) insufficiency. However, clinical application of this measurement has not been fully examined. This study aimed to measure and compare tibial acceleration before and after ACL reconstruction (ACLR) in ACL-injured patients. We hypothesized tibial acceleration would be reduced by ACLR and tibial acceleration would be consistent in the same knee at different time points.Methods: Seventy ACL-injured patients who underwent ACLR were enrolled. Tibial acceleration during the pivot shift test was measured using an electromagnetic measurement system before ALCR and at the second-look arthroscopy 1 year post-operatively. Tibial acceleration was compared to clinical grading and between ACL-injured/ACL-reconstructed and contralateral knees.Results: Pre-operative tibial acceleration was increased stepwise with the increase in clinical grading (P < 0.01). Tibial acceleration in ACL-injured knee (1.9 ± 1.2 m/s(2)) was larger than that in the contralateral knee (0.8 ± 0.3 m/s(2), P < 0.01), and reduced to 0.9 ± 0.3 m/s(2) post-operatively (P < 0.01). There was no difference between ACL-reconstructed and contralateral knee (n.s.). Tibial acceleration in contralateral knees was consistent pre- and post-operatively (n.s.).Conclusion: Tibial acceleration measurement demonstrated increased rotational laxity in ACL-injured knees and its reduction by ALCR. Additionally, consistent measurements were obtained in ACL-intact knees at different time points. Therefore, tibial acceleration during the pivot shift test could provide quantitative evaluation of rotational stability before and after ACL reconstruction.Level Of Evidence: III. [ABSTRACT FROM AUTHOR]