Post-cam clunk syndrome after posterior stabilized total knee arthroplasty as a sign of early femoral component loosening.

Soft tissue impingements are well-known complications of total knee arthroplasty. The impingements usually occur between the medial or lateral femoral component and tibial insert, and between the patella and femoral components. We report a rare case of impingement of the soft tissue between the femoral intercondylar fossa and post of the polyethylene insert, which caused pain and walking disability. After the surgery for the arthroscopic removal of the soft tissue, the symptoms disappeared. However, prosthetic loosening of the femur occurred several months after the arthroscopic surgery, requiring revision surgery. We would propose to call this symptom as post-cam clunk syndrome.

Tibiofemoral rotational alignment affects flexion angles in navigated posterior-stabilized total knee arthroplasty.

PURPOSE: To investigate the tibiofemoral rotational profiles during navigated posterior-stabilized (PS) total knee arthroplasty (TKA) and investigate the effect on post-operative maximum flexion angles. METHODS: Twenty-five subjects, treated with navigated PS TKA, were enrolled, and the effect of posterior cruciate ligament (PCL) resection and component implantation on tibiofemoral rotational kinematics was statistically evaluated. Then, the effect of rotational alignment changes on the post-operative maximum angles was retrospectively examined in 96 subjects using the multiple regression analysis. RESULTS: Tibial internal rotation was significantly increased in full extension (p < 0.01 and <0.001, respectively) and at 60° and 90° flexion (p < 0.05) after PCL resection, which further increased after implantation, compared with that before resection. The amount of tibial internal rotation from 90° flexion to maximum flexion was significantly decreased after PCL resection and implantation, compared with that before resection (p < 0.05). The internal changes in the rotational alignment were independent factors for the minimal improvement in the post-operative maximum flexion angles (R 2 = 0.078, p = 0.0067). CONCLUSION: PCL resection changed the tibial rotational alignment and decreased the amount of tibial internal rotation. The implantation of PS components further increased the internal rotational alignment and could not compensate for the tibiofemoral rotation. Finally, the internal changes in rotational alignment affected the improvement of the maximum flexion angles, suggesting that rotational alignment is an important factor for improving post-operative maximum flexion angles. LEVEL OF EVIDENCE: II.

Prothrombin time-international normalized ratio is a useful marker for edoxaban efficacy in preventing venous thromboembolism after total knee arthroplasty.

BACKGROUND: Deep vein thrombosis (DVT) is one of the main complications following total knee arthroplasty (TKA). In this study, oral administration of 15 mg edoxaban (a factor Xa inhibitor) once daily for 14 days efficiently prevented the incidence of DVT. Our hypothesis was that prothrombin time-international normalized ratio (PT-INR) on the third postoperative day could predict the incidence of DVT following TKA. METHODS: In this study, 286 subjects were enrolled and divided into two groups according to the presence or absence of DVT. Several variables [age, body mass index, postoperative D-dimer level, PT-INR, and functional recovery findings (standing)] were analysed to determine the predictors of DVT, and for DVT diagnosis, ultrasonography was performed for seven days after surgery. RESULTS: The PT-INR levels were significantly higher in the group that did not develop DVT (p = 0.01). Further analysis with logistic regression analysis and receiver operating characteristic curve was performed. The PT-INR on the third postoperative day was an independent factor of the incidence of DVT (odds ratio 0.210; p = 0.035). The cut-off PT-INR was calculated to be 1.425. CONCLUSION: PT-INR level is a useful marker in determining whether 15 mg edoxaban administration can prevent DVT after TKA. It is suggested that increment of edoxaban to control PT-INR over the cut-off point might prevent the incidence of DVT.

Inaccurate rotational component position in image-free navigated unicompartmental knee arthroplasty.

BACKGROUND/OBJECTIVE: The success of unicompartmental knee arthroplasty (UKA) is highly dependent on the accuracy of component and leg alignment. Computer-assisted surgery is gaining popularity in total knee arthroplasty with numerous studies reporting improved accuracy and decreased variability in implant position and postoperative limb alignment compared with conventional techniques. However, literature evaluating the accuracy of computer-navigated UKA is limited. Therefore, this study aimed to investigate the accuracy of component positions in navigated UKA using a three-dimensional (3D) image-matching system. To the best of our knowledge, this study is the first to evaluate the accuracy of implant-placement position in UKA using 3D image-matching systems. METHODS: Twenty-three knees in 22 patients (9 men, 13 women) underwent computer-assisted UKA performed by a senior surgeon from 2011 to 2013. All surgeries were performed with measured resection techniques using an image-free-navigation system. We recorded the coronal, sagittal, and rotational bone-resection angles towards the mechanical axis in the distal femur and proximal tibia using image-free navigation intraoperatively. The coronal, sagittal, and rotational alignments of the femoral and tibial components were also measured using the 3D image-matching system, and the accuracy of the navigated UKA was evaluated. The rotational alignment of the femur and tibia was defined as surgical epicondylar axis and Akagi's line, and a deviation over 3° from the AA was defined as an outlier. RESULTS: We observed coronal outliers for the femoral component in four of the 23 patients, and for the tibial component in three of the 23 patients. We also observed sagittal outliers for the femoral component in five of 23 patients, and for the tibial component in three of the 23 patients. Twenty-two tibial components were placed in external rotation relative to the rotational reference line. CONCLUSION: In both coronal and sagittal alignments, there were a definite proportion of outliers. The ratio of outliers in rotational alignment was especially higher than that in coronal and sagittal alignments. In UKA, the identification of bony landmarks is difficult because of the small operation field. Therefore, careful surface mapping of particular bony landmarks is necessary, and it is not enough to use image-free navigation system in UKA.

Factors affecting intraoperative kinematic patterns and flexion angles in navigated total knee arthroplasty.

PURPOSE: To investigate the factors affecting intraoperative kinematics, as measured with a navigation system, and their effect on maximum flexion angles during total knee arthroplasty (TKA). METHOD: One hundred posterior stabilised (PS) TKAs performed using an image-free navigation system were evaluated. Tibial internal rotation angles at maximum extension, 30°, 45°, 60°, 90°, and maximum flexion were collected at registration and after implantation. The varus angles from the coronal mechanical axis were also collected. The rotational patterns were divided into four groups to investigate whether flexion contracture and varus deformity affected the kinematic patterns, and correlated with the maximum pre- and post-operative flexion angles. RESULTS: At registration, the flexion angles at maximum extension differed significantly between the kinematic groups; the flexion angle at maximum extension at registration was negatively correlated with the pre-operative maximum flexion angle (R(2) = 0.226, p < 0.0001) and the post-operative maximum flexion angle (R(2) = 0.059, p = 0.0167). Varus deformity at registration also differed significantly between the kinematic groups; varus deformity at registration was negatively correlated with the pre-operative maximum flexion angle (R(2) = 0.087, p = 0.0036) and post-operative maximum flexion angle (R(2) = 0.101, p = 0.0027). CONCLUSION: Navigation-based measurements in patients undergoing PS TKA indicated that pre-operative flexion contracture and varus deformity are negatively correlated with both pre- and post-operative maximum flexion angles. The results may improve the ease with which surgeons can interpret intraoperative kinematics, by providing a multi-dimensional perspective. With further knowledge regarding intraoperative kinematics, it might be possible to improve surgical approach, prosthesis design, and clinical outcomes. LEVEL OF EVIDENCE: II.

Surgical management of the peroneus quartus muscle for bilateral ankle pain: a case report.

The peroneus quartus muscle is an accessory muscle seen in the lateral compartment of the lower leg. Although the peroneus quartus muscle is asymptomatic in general, it sometimes becomes pathologic. We present the rare case of bilateral ankle pain with crepitation caused by the peroneus quartus muscle. Magnetic resonance imaging should be considered to assist with diagnosing this condition. Foot and ankle surgeons should consider it in the preoperative differential diagnosis when patients present with posterior ankle pain.

Evaluation of implant alignment in navigated unicompartmental knee arthroplasty: a comparison of 2D and 3D imaging.

This study aimed to compare two-dimensional (2D) and three-dimensional (3D) methods for evaluating implant alignment in navigated UKA. Nineteen UKAs in 18 subjects (7 men) were performed using an image-free navigation system. Coronal and sagittal implant alignments were assessed using radiographs (2D evaluation) and 3D image-matching software. The accuracy of 2D evaluation was compared with that of 3D evaluation. A deviation > 3° from the 3D evaluation was defined as an outlier. In the 2D evaluation, outliers for the femoral component were observed in both the coronal plane (6/19 subjects) and the sagittal plane (3/19 subjects). In UKA, assessment of the implant position might be misjudged because of the design of the implant, especially for the femoral component; 3D methods are ideal for assessment of implant alignment.