Impact of support instruments in medial closed-wedge distal femoral osteotomy: a finite element analysis.

INTRODUCTION: Medial closed-wedge distal femoral osteotomy (MCWDFO) is a valuable treatment approach for lateral knee osteoarthritis with femoral valgus deformity. Improved results have been reported with the upgrade of surgical techniques and locking plates. However, the risk of nonunion and loss of correction increases in cases of lateral hinge fractures. This study aimed to evaluate the mechanical impact of hinge fractures and support instruments in MCWDFO using finite element analysis (FEA). MATERIALS AND METHODS: Five femur models were developed using Mechanical Finder 11.0 FEA software. We simulated the following models: only a medial locking plate (MLP) (group A); an MLP with a lateral support screw (group B); and an MLP with a lateral support plate (group C). The equivalent stress around the hinge was evaluated and the percentage of the plastic deformation zone was calculated for the hinge area in the no-hinge fracture model. The equivalent stress of the MLP and the degree of displacement were calculated using the hinge fracture model. RESULTS: The percentages of the plastic deformation zone in groups A, B, and C were 18.0 ± 11.7%, 3.3 ± 2.4%, and 2.3 ± 2.8%, respectively. The percentages tended to be lower in groups B and C than in group A. In the hinge fracture model, the mean equivalent stress of the MLP in group C was significantly less than that in group A. In terms of the mean degree of displacement, group A showed more than 1 mm of displacement, which was significantly larger than that of the other groups. CONCLUSION: The support instruments provided stability to the hinge site and reduced the equivalent stress of the main plate in the MCWDFO with hinge fractures. No significant difference was observed between the two instruments in terms of stability.

Effect of bone morphology of the tibia plateau on joint line convergence angle in medial open wedge high tibial osteotomy.

BACKGROUND: Change in the joint line convergence angle (JLCA) of the knee after high tibial osteotomy (HTO) is difficult to predict accurately. Given that any change in JLCA is intra-articular, the shape of the articular surface, including the bone morphology of the proximal tibia, may affect the alignment of the knee joint postoperatively. The purpose of this study was to investigate the relationship between the shape of the tibial plateau and postoperative alignment of the knee joint by focusing on changes in JLCA. METHODS: One hundred and nine knees that underwent HTO were retrospectively reviewed. The shape of the tibial plateau was classified based on the slope of the medial and lateral articular surfaces as depressed, flat (within 3 degrees), or convex (pagoda-like). The relationship between the shape of the tibial plateau and radiological parameters was investigated. RESULTS: The shape of the tibial plateau was depressed in 38 knees, flat in 52 knees, and pagoda-like in 19 knees. There was a moderate correlation between the postoperative change in JLCA and the preoperative hip-knee-ankle angle for knees with a pagoda-shaped tibial plateau (r = 0.56) but not for the other two shapes. CONCLUSIONS: These findings suggest that knees with marked varus deformity before HTO are likely to show more change in JLCA postoperatively if the tibial plateau is pagoda-shaped than if it has a depressed or flat shape. The advantage of focusing on the bone morphology of the proximal tibia is that surgeons can easily perform visual assessment using preoperative radiograph.

Correlation of patient-reported numbness around surgical scars with patient-reported outcome measures and joint awareness after knee replacement: a cohort study.

BACKGROUND: Knee replacement is a very effective and indispensable treatment option for end-stage knee arthritis, and the number of cases has been increasing worldwide. A replaced knee joint without patient joint awareness is thought to be the ultimate goal of artificial knees. Joint awareness reportedly correlates with patient satisfaction. Although numbness around a replaced knee is a minor but common problem, its effect on postoperative outcome is controversial. Joint awareness also is sensitive to subtle abnormalities of the joint, so it must be negatively affected by numbness. Although numbness is minor, it cannot be ignored to further improve knee replacement outcomes. This study investigated the relationship between patient-reported numbness and other patient-reported outcome measures (PROMs), including joint awareness, and kneeling. We developed a numbness score based on a 5-point Likert scale on frequency of numbness, with an intraclass correlation coefficient of 0.76 and higher scores indicating less numbness. METHODS: The numbness score, New Knee Society Score (KSS), Knee Injury and Osteoarthritis Outcome Score (KOOS), Forgotten Joint Score-12 (FJS-12), and other clinical and radiological data from 311 patients (394 primary knee replacements) were analyzed. Kneeling ability was evaluated by using kneeling-specific items in the KSS (KSS-Kneeling). RESULTS: No numbness was found in 170 knees (43.1%), and some degree of numbness was found in the remaining 224 knees (56.9%). The numbness score showed weak-to-moderate correlations with KSS-Symptoms (r = 0.44), KSS-Satisfaction (r = 0.41), KSS-Activities (r = 0.29), and all KOOS subscales (r = 0.23-0.44), and FJS-12 (r = 0.42). Multiple regression analyses suggested that midline incision positively affected the numbness score over the anteromedial incision (p = 0.04) and that a better numbness score (p = 0.001), male sex (p < 0.0001), and better postoperative knee flexion angle (0.04) positively affected kneeling. CONCLUSIONS: The numbness score positively correlated with PROMs and positively affected kneeling. Knee replacements performed via an anteromedial incision may be at higher risk for numbness.

Anterior prominence of the femoral condyle varies among prosthesis designs and surgical techniques in total knee arthroplasty.

BACKGROUND: Patellofemoral overstuffing after total knee arthroplasty (TKA) can cause limited range of motion and anterior knee pain. This study compared anterior prominence of femoral components among different prothesis designs in surgical simulation models utilizing the anterior reference (AR) and posterior reference (PR) techniques. METHODS: Surgical simulations were performed using on a three-dimensional planning system preoperative computed tomography data of consecutive 30 patients with knee osteoarthritis scheduled to undergo TKA. Four implant models were used: Attune, Persona, Journey II, and Legion. Rotational alignment was set parallel to the transepicondylar axis and size was selected based on the absence of notch formation in the femoral anterior cortex and the best fit with the shape of the medial posterior femoral condyle. For each combination of surgical technique (AR or PR method) and implant model, measurements were taken of the maximum medial, central, and lateral prominence of the implant from the anterior femoral cortex. RESULTS: Using either the AR or PR method, the medial and central prominences were significantly lower with Journey II than with the other models. The lateral prominence was the lowest with Attune in the AR method. The AR method was associated with significantly less prominence compared with the PR method, regardless of implant model. CONCLUSIONS: The degree of anterior prominence of the femoral implant is affected by the implant design when the AR method is used. The PR method is associated with greater anterior prominence compared with the AR method, and the pitch size is an additional factor in the PR method. Surgeons should be familiar with implant designs, including the thickness of the anterior flange and the available size selections.

No difference in the incidence or location of deep venous thrombosis according to use of pharmacological prophylaxis following total knee arthroplasty.

BACKGROUND: The incidence and characteristics of deep vein thrombosis (DVT) following total knee arthroplasty (TKA) without pharmacologic prophylaxis have not been fully investigated. This study aimed to determine whether there are any differences in the incidence, location, and characteristics of DVT following TKA with pharmacologic prophylaxis and without pharmacologic prophylaxis. METHODS: A total of 156 knees were retrospectively evaluated for DVT following TKA by duplex ultrasound on postoperative day 7, after excluding 60 knees from 216 consecutive knees because of antiplatelet or anticoagulant use before surgery, history of venous thromboembolism, or bleeding risk. The 156 knees included in the analysis were divided into two groups: with pharmacologic prophylaxis (n = 79) and without pharmacologic prophylaxis (n = 77). RESULTS: The overall incidence of DVT was 34% (54/156 knees). DVT was detected in 31.6% of knees with pharmacologic prophylaxis and in 37.6% of knees without pharmacologic prophylaxis; the difference was not statistically significant. Soleal vein thrombus was observed in 74.6% of the knees with DVT and non-floating thrombus was observed in 98.7%. There were no obvious between-group differences in thrombus characteristics such as compressibility, echogenicity, mean vein diameter, and whether the thrombus was attached to the vein wall or free-floating. CONCLUSIONS: No differences were found in the incidence, location, or characteristics of DVT following TKA with or without pharmacological prophylaxis.

Monocortical fixation for locking plate distal screws does not impair mechanical properties in open-wedge high tibial osteotomy.

BACKGROUND: The neurovascular bundle containing the deep peroneal nerve has a potential risk of injury during open-wedge high tibial osteotomy (OWHTO), particularly due to drilling for bicortical fixation at distal screw holes. Therefore, monocortical fixation is recommended for distal fixation of a long locking plate as long as good stability is ensured. The purpose of this study was to analyse the biomechanical properties of monocortical fixation of distal locking screws for OWHTO. METHODS: Three-dimensional models of bone and fixation materials simulating OWHTO were created using computed tomographic data of patients and material data of a T-shaped long locking plate and screws. Three of the four distal screws of the locking plate were chosen for a bicortical fixation or monocortical fixation procedure. In addition, loss of correction was assessed by measuring the medial proximal tibial angle (MPTA) in patients who underwent OWHTO with two bicortical and two monocortical distal fixation screws at 1 month and 1 year after surgery. RESULTS: No significant differences in stress were observed in either the normal or osteoporotic bone model between the monocortical and bicortical fixation models, including in the area of the lateral hinge at the osteotomy site. Furthermore, there were no significant differences in MPTA between the early post-operative period and 1-year follow-up. CONCLUSIONS: The monocortical fixation method for three distal screws of the locking plate did not worsen the mechanical properties of fixation for OWHTO using a long locking plate with four proximal and four distal screws. In actual surgery, the number of distal bicortical screws should be reduced based on the patient's condition, taking into account the risk of lateral hinge fracture and unexpected surgical complications. Using at least two bicortical screws would be practical considering the various factors related to reduced fixing ability.

Good Validity and High Internal Consistency of the Forgotten Joint Score-12 in Patients After Medial Opening Wedge High Tibial Osteotomy.

BACKGROUND: The Forgotten Joint Score-12 (FJS-12) was originally developed to assess awareness of an artificial joint. Medial opening wedge high tibial osteotomy (MOWHTO), an alternative surgical method of knee replacement, is a joint-preservation surgery; therefore, joint awareness should be used to evaluate its clinical results. However, FJS-12 has not been validated as a tool to evaluate the postoperative results of MOWHTO. This study aimed to validate FJS-12 in MOWHTO. METHODS: Patients with bilateral knee surgery, previous knee surgery, flexion contracture >15°, varus alignment >20°, and patients without plate removal surgery were excluded. Finally, 71 knees of 71 patients were analyzed, with a mean follow-up of 34.5 months. The FJS-12 score and Knee Injury and Osteoarthritis Outcome Score (KOOS) were obtained, and the floor and ceiling effect of each score was investigated. Cronbach's α was calculated to determine the internal consistency of FJS-12. Spearman's correlation coefficients between FJS-12 and KOOS were calculated to assess convergent validity. RESULTS: There were ceiling effects in 3 KOOS subscales (symptoms [25.4%], pain [15.5%], and activities of daily living [25.4%]) but not in FJS-12 (8.5%). No floor effect was noted in any patient-reported outcome measures. The total Cronbach's α was 0.9457 in FJS-12. FJS-12 showed moderate-to-strong positive correlations with all KOOS subscales (r = 0.64-0.72). CONCLUSION: FJS-12 showed a lower ceiling effect than KOOS and high internal consistency and convergent validity in patients following MOWHTO. With its low ceiling effect, FJS-12 was found to be useful for evaluating patients following MOWHTO.

Noise after total knee arthroplasty has limited effect on joint awareness and patient-reported clinical outcomes: retrospective study.

BACKGROUND: Some patients complain of noise after total knee arthroplasty (TKA). Controversy still exists on how the noise affects the clinical outcomes, including joint awareness, after TKA. The Forgotten Joint Score-12 (FJS-12) measures the clinical outcomes focusing on joint awareness after surgery. The Knee Society Scoring System-2011 (KSS-2011) includes questionnaires for satisfaction, expectation, and functional activities. The aim of this study is to clarify the relationship among FJS-12, KSS-2011, and the noise. Furthermore, the relationship between FJS-12 and KSS-2011 was validated. METHODS: Using FJS-12 and KSS-2011, 295 knees from 225 patients who underwent TKA were retrospectively evaluated. Noise perception was evaluated by a questionnaire with five grades, a method that follows the questionnaire form of FJS-12 ("Are you aware of the noise of your artificial joint?"; never, almost never, seldom, sometimes, mostly). Correlations among FJS-12, KSS-2011, and noise were analyzed. The patients were divided into four groups based on the mechanism of their implant [cruciate retaining, posterior stabilized, cruciate sacrificed, and bicruciate stabilized (BCS)]. FJS-12, KSS-2011, and noise were compared among the groups. RESULTS: A strong correlation was found between FJS-12 and total score of KSS-2011 (0.70; P < 0.001). FJS-12 correlated with KSS-2011 subcategories of "symptoms," "satisfaction," and "standard activities," with correlation coefficients at approximately 0.60. Noise had weak correlations with FJS-12 (0.28; P < 0.001) and KSS-2011 (0.20 P < 0.001). In comparing the TKA mechanisms, BCS had remarkably better KSS-2011 and greater movement range but worse noise scores. CONCLUSIONS: Noise perception after TKA had limited effect on joint awareness and clinical outcomes. FJS-12 correlated strongly with KSS-2011 and associated with satisfaction, residual symptoms, and daily activities, as assessed by KSS-2011 subscores. TRIAL REGISTRATION: This study was approved by the Medical Ethical Committee of the Tokyo Women's Medical University (approval number: 4681 on March 2, 2018).

Deep peroneal nerve has a potential risk of injury during open-wedge high tibial osteotomy.

PURPOSE: To assess the risk of injury to the neurovascular bundle on the interosseous membrane of the leg during drilling for distal screw insertion in open-wedge high tibial osteotomy (OWHTO), and to investigate the possible influence of the method of plate placement on the risk. METHODS: This retrospective study involved, 55 patients (32 with a TomoFix plate, 23 with a TriS plate) who underwent postoperative CT scanning of the knee following OWHTO between 2009 and 2018. The angle and position of the locking plate, and the direction of screw insertion relative to the interosseous membrane were analysed. RESULTS: All distal screws had a risk of neurovascular injury. In particular, 25 screws at the #4 hole (45%) had an extended insertion trajectory that intersected with the interosseous membrane. The angle of the proximal part of the TomoFix plate was a significant risk factor. In contrast, methods of TriS plate placement showed no statistically significant differences. CONCLUSIONS: Extended insertion trajectories of distal screws were likely to intersect with the interosseous membrane with the neurovascular bundle potentially on its surface; thus, drilling for bicortical fixation posed a risk of neurovascular injury. The risk increased as the TomoFix plate was placed more medially, suggesting that bicortical drilling must be performed with the utmost attention when the plate is placed at the medial position. Given the particularly high risk at the #3 and #4 screw holes, monocortical fixation of a few distal screws is recommended as long as good stability is ensured.

Patient reported outcomes after high tibial osteotomy show comparable results at different ages in the mid-term to long-term follow-up.

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.

Comparison of the impact of closing wedge versus opening wedge high tibial osteotomy on proximal tibial deformity and subsequent revision to total knee arthroplasty.

PURPOSE: 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. METHODS: 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. RESULTS: The difference in the metaphyseal-diaphyseal angle in the CW-HTO and OW-HTO groups was 0.3° ± 0.2° (p < 0.001). The mechanical axis in the CW-HTO group was shifted laterally by 1.8 ± 1.1 mm relative to that in the OW-HTO group (p < 0.001) on the resection surface in TKA. Finally, the TKA tibial implant was substantially closer to the endosteal cortex in the CW-HTO group (mean 5.6 ± 1.6 mm) than to that in the OW-HTO group (mean 7.3 ± 1.6 mm) (p < 0.001). CONCLUSION: The difference in the post-operative angular deformities of the proximal tibia between CW-HTO and OW-HTO was considered to be clinically irrelevant. The risk of interference between TKA tibial implant and endosteal bone was greater after CW-HTO than after OW-HTO. For clinical relevance, the difference between the two techniques has little influence on subsequent TKA difficulty regarding the proximal tibial deformity, although preoperative planning is obligatory, particularly after CW-HTO, to prevent interference with the tibial implant. LEVEL OF EVIDENCE: II.

The Anteroposterior Axis of the Proximal Tibia Can Change After Tibial Resection in Total Knee Arthroplasty: Computer Simulation Using Asian Osteoarthritis Knees.

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.

Three-dimensional analysis of accuracy of patient-matched instrumentation in total knee arthroplasty: Evaluation of intraoperative techniques and postoperative alignment.

BACKGROUND: It is questionable that the accuracies of patient-matched instrumentation (PMI) have been controversial, even though many surgeons follow manufacturers' recommendations. The purpose of this study was to evaluate the accuracy of intraoperative procedures and the postoperative alignment of the femoral side using PMI with 3-dimensional (3D) analysis. METHODS: Eighteen knees that underwent total knee arthroplasty using MRI-based PMI were assessed. Intraoperative alignment and bone resection errors of the femoral side were evaluated with a CT-based navigation system. A conventional adjustable guide was used to compare cartilage data with that derived by PMI intraoperatively. Postoperative alignment was assessed using a 3D coordinate system with a computer-assisted design software. We also measured the postoperative alignments using conventional alignment guides with the 3D evaluation. RESULTS: Intraoperative coronal alignment with PMI was 90.9° ± 1.6°. Seventeen knees (94.4%) were within 3° of the optimal alignment. Intraoperative rotational alignment of the femoral guide position of PMI was 0.2° ± 1.6°compared with the adjustable guide, with 17 knees (94.4%) differing by 3° or less between the two methods. Maximum differences in coronal and rotation alignment before and after bone cutting were 2.0° and 2.8°, respectively. Postoperative coronal and rotational alignments were 89.4° ± 1.8° and -1.1° ± 1.3°, respectively. In both alignments, 94.4% of cases were within 3° of the optimal value. The PMI group had less outliers than conventional group in rotational alignment (p = 0.018). CONCLUSIONS: Our 3D analysis provided evidence that PMI system resulted in reasonably satisfactory alignments both intraoperatively and postoperatively. Surgeons should be aware that certain surgical techniques including bone cutting, and the associated errors may affect postoperative alignment despite accurate PMI positioning.

Kinematic analysis of stair climbing in rotating platform cruciate-retaining and posterior-stabilized mobile-bearing total knee arthroplasties.

INTRODUCTION: 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. MATERIALS AND METHODS: 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. RESULTS: 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). CONCLUSIONS: Both CR and PS types of rotating platform mobile-bearing TKAs provided reproducible knee joint kinematics during stair climbing and equivalent clinical outcomes. LEVEL OF EVIDENCE: IV.

Asymmetry in Femoral Tunnel Socket Length During Anterior Cruciate Ligament Reconstruction With Transportal, Outside-In, and Modified Transtibial Techniques.

PURPOSE: To investigate the mismatch between the length at the center and the length on the shortest and longest peripheral sides of the femoral tunnel socket, reamed with the transportal (TP), outside-in (OI), and modified transtibial (TT) techniques, in anterior cruciate ligament (ACL) reconstruction. METHODS: Femoral tunnel drilling was simulated on 3-dimensional bone models from 40 subjects. The tunnel directions used with the TP, OI, and modified TT techniques were previously described. By use of the resulting angle, a femoral tunnel socket of 9 mm in diameter was drilled from the center of the femoral ACL insertion. The virtual femoral tunnel was extracted, and the length mismatch was measured between the center and the shortest and longest peripheral sides of the tunnel socket. RESULTS: The mean socket length mismatch between the center and the shortest peripheral part of the femoral tunnel socket was 4.2 ± 0.9 mm with the TP technique, 5.2 ± 1.3 mm with the OI technique, and 3.2 ± 0.8 mm with the modified TT technique. The mean socket length mismatch between the center and the longest peripheral part of the femoral tunnel socket was 3.5 ± 0.9 mm with the TP technique, 4.8 ± 1.5 mm with the OI technique, and 3.3 ± 1.2 mm with the modified TT technique. The length mismatch was significantly higher when the tunnel socket was created by the OI technique (P < .01). CONCLUSIONS: A length mismatch with the tunnel socket exists after reaming with either the TP, OI, or modified TT technique. In particular, there was a significant increase in length mismatch when the tunnel socket was created by the OI technique, and the length mismatch would easily become greater than 5 mm. The surgeon should recognize this mismatch when it is created and measure the femoral tunnel socket. CLINICAL RELEVANCE: In anatomic ACL reconstruction, a mismatch between the length at the center and the length at periphery of the femoral tunnel socket occurs, and this is increased particularly when using the OI technique. The discrepancy in tunnel length between its center and its periphery could cause an overestimation of the tunnel length that could result in an error in length during graft preparation.

Does knee stability in the coronal plane in extension affect function and outcome after total knee arthroplasty?

PURPOSE: The aim of the present study was to clarify whether varus-valgus laxities under static stress in extension, femoral condylar lift-off during walking, and patient-reported outcomes after total knee arthroplasty (TKA) were correlated with each other. METHODS: Ninety-four knees, which had undergone posterior-stabilized TKA, were analysed. The varus-valgus laxity during knee extension was measured using a stress radiograph. New Knee Society Score (KSS) questionnaires were mailed to all patients. Correlations between the values of stress radiographs and KSS were analysed. Additionally, continuous radiological images were taken of 15 patients while each walked on a treadmill to determine condylar lift-off from the tibial tray using a 3D-to-2D image-to-model registration technique. Correlations between the amount of lift-off and either the stress radiograph or the KSS were also analyzed. RESULTS: The mean angle measured was 5.9 ± 2.7° with varus stress and 5.0 ± 1.6° with valgus stress. The difference between them was 0.9 ± 2.8°. Varus-valgus laxities, or the differences between them, did not show any statistically significant correlation with either component of the KSS (p > 0.05). The average amount of femoral condylar lift-off during walking was 1.4 ± 0.8 mm (medial side) and 1.3 ± 0.6 mm (lateral side). The amount of lift-off did not correlate with either varus-valgus laxities or the KSS (p > 0.05). CONCLUSIONS: No correlations were found among varus-valgus laxities under static stress in extension, femoral condylar lift-off during walking, or patient-reported outcomes after well-aligned TKA. This study suggests that small variations in coronal laxities do not influence lift-off during walking and the patient-reported outcomes. LEVEL OF EVIDENCE: IV.

The coronal alignment after medial unicompartmental knee arthroplasty can be predicted: usefulness of full-length valgus stress radiography for evaluating correctability.

PURPOSE: We aimed to clarify whether the coronal alignment after medial unicompartmental knee arthroplasty (UKA) is predictable using preoperative full-length valgus stress radiography. METHODS: Thirty-seven consecutive patients with a mean age of 71.5 ± 7.0 years awaiting medial UKA were recruited. Full-length weight-bearing radiographs of the lower limbs were obtained pre- and postoperatively. Preoperative full-length valgus stress radiography in the supine position was also performed, and the transition of the hip-knee-ankle angle (HKAA) and the weight-bearing ratio were assessed. The tibia first cut technique was used, and the distal femur was cut parallel to the cutting surface of the proximal tibia during surgery. RESULTS: The mean postoperative HKAA was 2.0° ± 2.1° varus, and the mean weight-bearing ratio was 43.1 ± 7.7 %; each of these parameters demonstrated significantly strong correlations with the values on the preoperative valgus stress radiographs (p < 0.01), while the correlation between the postoperative alignment and the preoperative standing alignment without stress was moderate (p < 0.01). The postoperative alignment was slightly undercorrected compared to that observed on the valgus stress radiographs (p < 0.05), and no knees exhibited evident overcorrection compared to that on the valgus stress radiographs. CONCLUSION: Preoperative valgus stress radiography is useful for evaluating the correctability of varus deformities and predicting the postoperative coronal alignment. For clinical relevance, performing preoperative valgus stress radiography would help to more precisely select patients and, when combined with the tibia first cut technique, aid in achieving the expected knee alignment and avoid severe undercorrection or overcorrection. LEVEL OF EVIDENCE: Diagnostic study, Level II.

Ischio-pubic stress fracture after peri-acetabular osteotomy in patients with hip dysplasia.

PURPOSE: Ischio-pubic stress fracture is one of the potential complications after peri-acetabular osteotomy (PAO) in patients with hip dysplasia. The purpose of this study was to examine the prevalence of and risk factors for ischio-pubic fractures following PAO. METHODS: A total of 296 hips in 275 patients who underwent transposition osteotomy of the acetabulum between 2001 and 2012 were retrospectively reviewed. Patient characteristics and radiographic parameters were compared between patients with and without fracture. RESULTS: Fourteen ipsilateral hips (4.7%) in 14 female patients had fracture of the inferior pubic ramus (11 hips) or the ischial ramus (three hips) on the same side as the surgery at an average of 4.6 weeks after PAO. Multivariate analysis indicated that younger age at operation (odds ratio of 1.43 per five years, p = 0.0169) and greater degree of correction (odds ratio of 1.98 per five degrees, p = 0.0005) were significantly associated with ischio-pubic fracture as independent risk factors. All fractures healed conservatively with partial weight-bearing. CONCLUSIONS: Younger female patients and greater deformity corrections increased the risk of ischio-pubic stress fracture after PAO.

Large angular correction of arithmetic coronal alignment is associated with residual lateral laxity after total knee arthroplasty in varus knees for Japanese patients.

Purpose: One of the most common types of coronal plane alignment of the knee (CPAK) is type I, which is characterised by varus alignment and apex distal joint line obliquity. The purpose of this study was to evaluate the association of changes in arithmetic hip-knee-ankle angle (aHKA) with both postoperative joint laxity and patient-reported outcome measures (PROMs) in patients with CPAK type I following mechanical alignment (MA) total knee arthroplasty (TKA). Methods: Of 111 consecutive knees in 92 patients with osteoarthritis who underwent primary TKA, 80 knees (72.0%) with CPAK type I phenotype preoperatively were evaluated. All TKAs were performed to achieve neutral MA by a medial stabilising gap balancing technique. Pre- to postoperative change in aHKA was defined as ΔaHKA. The 80 CPAK type I knees were divided into a larger ΔaHKA group (>7°) and a smaller ΔaHKA group (≤7°). PROMs, including the Knee Society Score and Forgotten Joint Score-12, were assessed before and 2 years after surgery. Pre- and postoperative joint laxity was assessed using a Telos arthrometer. Results: Twenty-two knees showed a larger ΔaHKA, and postoperative lateral joint laxity in varus stress was significantly greater in these patients than in those with a smaller ΔaHKA (6.8° vs. 4.5°, p = 0.006). There were no significant differences between the groups in PROMs (p = n.s.). Conclusions: Postoperative lateral laxity was associated with larger aHKA changes than smaller aHKA changes in CPAK type I knees after TKA. However, no statistically significant differences in PROMs were found according to the amount of change in aHKA. Level of Evidence: Level III.

Surgical Technique and Preliminary Outcomes of Double-Level Osteotomy for Valgus Deformity.

Background: Data are limited regarding the surgical technique or outcomes of double-level osteotomy (DLO) combining medial closing-wedge distal femoral osteotomy and medial closing-wedge high tibial osteotomy in patients with moderate-to-severe valgus deformity. Purpose/Hypothesis: To describe the surgical technique and assess the short-term outcomes and surgical accuracy of DLO in patients with a moderate or severe valgus deformity. It was hypothesized that this technique would result in good clinical outcomes with precise deformity correction. Study Design: Case series; Level of evidence, 4. Methods: Eight patients (mean age, 44.2 ± 10.9 years) with a moderate or severe valgus knee treated with DLO (9 knees; mechanical tibiofemoral angle [mTFA], 10.3°± 3.5°) were included. The mean follow-up was 25.1 ± 11.1 months. Preoperative to postoperative changes in radiographic parameters (mTFA, mechanical lateral distal femoral angle, mechanical medial proximal tibial angle, joint line convergence angle) and clinical scores (Hospital for Special Surgery score, Oxford Knee Score, Lysholm score) were assessed. Surgical accuracy was calculated by subtracting the achieved postoperative correction from the preoperatively planned targeted correction. Results: The mTFA changed significantly from 10.3°± 3.5° preoperatively to -1.8°± 3.4° postoperatively (P < .001); the mechanical lateral distal femoral angle and mechanical medial proximal tibial angle changed significantly by 5.1°± 2.7° and 5.9°± 2.2°, respectively (P < .001 for both); and the posterior distal femoral angle decreased significantly from 85.9°± 3.1° to 84.2°± 2.4° (P < .01). There was no significant difference between pre- and postoperative joint line convergence angles (3.3°± 2.3° to 2.6°± 2.1°). The accuracy of the correction was high: the mTFA achieved postoperatively differed from the mTFA planned preoperatively by a mean of 2.7°± 1.9° (range, 0.6°-6.6°). Significant pre- to postoperative improvement was seen for all outcome scores (Hospital for Special Surgery, from 67 ± 11 to 93 ± 4; Oxford Knee Score, from 29 ± 7 to 43 ± 3; Lysholm, from 41 ± 24 to 89 ± 8; P < .001 for all). Conclusion: High surgical accuracy was achieved, and patients who underwent varus DLO for valgus knees showed improved knee function at short-term follow-up. Varus DLO can be a surgical option to restore the optimal alignment and joint line obliquity in patients with moderate or severe valgus malalignment.