Risk of stroke after unilateral or bilateral TKA (simultaneous and staged without discharge) in 327,438 matched patients using data from the National Health Insurance Claims for South Korea.

PURPOSE: This study aims to investigate the incidence rate and risk factors of stroke in patients treated with bilateral TKA compared with patients with unilateral TKA. METHODS: In this retrospective nationwide cohort study, we compared patients undergoing unilateral TKA or bilateral TKA using data from the Korean National Health Insurance claims database between January 1, 2009 and August 31, 2017 and included patients older than 40 years of age who underwent primary TKA by the index date as documented primary diagnosis and first additional diagnosis without a history of stroke during the preceding 1 year. We used matched Cox regression models to compare the incidence rate and risk factors of newly acquired stroke among patients treated with unilateral TKA or bilateral TKA after propensity score (PS) matching. RESULTS: In the present study, 163,719 patients who received unilateral TKA were matched to 163,719 patients with bilateral TKA based on PS. The risk of stroke during the study period was lower in patients treated with bilateral TKA than in patients with unilateral TKA (adjusted hazard ratio [HR] 0.79). Patients who received bilateral TKA were at decreased risk of stroke when the following variables were present: advanced age (70-79 years, HR 0.76), female sex (HR 0.75), rural area (HR 0.77), small- or medium-sized hospital (HR 0.75), health insurance (HR 0.77), history of hypertension drug use (HR 0.75), congestive heart failure (HR 0.70), connective tissue disease (HR 0.71), diabetes (HR 0.77), and diabetes with complication (HR 0.76). CONCLUSION: The risk of stroke was lower in patients treated with bilateral TKA than in patients with unilateral TKA. Patients treated with bilateral TKA were at decreased risk of stroke when the following variables were present: age (70-79 years), female sex, health insurance, history of hypertension drug use, and comorbidities, such as congestive heart failure, connective tissue disease, and diabetes.

Increased external rotation of the osteoarthritic knee joint according to the genu varum deformity.

PURPOSE: To evaluate the rotational profile of the lower extremity using computed tomography (CT) in accordance with the degree of varus deformity in medial condyle-affected knee joint osteoarthritis (OA). METHODS: This retrospective study included 1036 patients (872 lower extremities) with end-stage knee OA. The coronal alignment of the lower extremity was measured using standing anteroposterior radiography. The CT parameters of femoral anteversion and tibial torsion were assessed in relation to the knee joint. The axes were the femoral neck axis; the distal femoral axis, which was composed of the anterior trochlear axis, the clinical transepicondylar axis, and the posterior condylar axis; the axis of the proximal tibial condyles; and the bimalleolar axis. RESULTS: There was a tendency for increased external rotation of the knee joint parameters in relation to the hip and ankle joints as varus deformity of the lower extremity increased. The relative external rotational deformity of the knee joint in relation to the hip joint had a positive value with a good correlation. The relative external rotational deformity of the knee joint in relation to the ankle joint also demonstrated a positive value with a good correlation. CONCLUSION: The distal femur and proximal tibia (knee joint) tended to rotate externally in relation to the hip and ankle joint, respectively, as the degree of varus deformity increased. This study identified the relationship between lower extremity varus deformity and rotational deformity of knee joints with OA. LEVEL OF EVIDENCE: III.

Correction to: Use of autogenous onlay bone graft for uncontained tibial bone defects in primary total knee arthroplasty.

After the publication of this article [1] it came to the attention of the authors that there were 2 errors in the results section: 0.0.856 should be 0.856 and "this this difference" should have been "this difference".

Arthroscopic suture bridge fixation technique with multiple crossover ties for posterior cruciate ligament tibial avulsion fracture.

PURPOSE: This study examined the clinical outcomes of a newly developed technique, arthroscopic suture bridge fixation with crossover ties of PCL tibial avulsion fracture using two tibial tunnels and a posterior trans-septal portal. METHODS: Records were reviewed of 18 patients (median age 33.5 years, range 13-55 years) with PCL tibial avulsion fractures treated with an arthroscopic suture bridge technique. Knee function before surgery and at last follow-up was evaluated by Lysholm and Tegner scores. A KT-2000 arthrometer was used to evaluate knee stability, and fracture union was assessed by plain radiographs. RESULTS: Mean postoperative Lysholm (P < 0.001) and Tegner (P = 0.011) scores showed significant improvements compared with preoperative scores. Arthrometry showed that the mean side-to-side difference improved significantly, from 7.8 ± 0.8 mm preoperatively to 3 ± 1.2 mm postoperatively (P = 0.012). Radiographic evaluation showed solid union at the fracture site in all 18 patients at last follow-up. CONCLUSION: This new arthroscopic double-tunnel pull-out suture bridge fixation with multiple crossover ties and posterior trans-septal technique for PCL tibial avulsion fracture yielded good clinico-radiological outcomes, including satisfactory stability and fracture site healing. This technique can be a useful treatment option for PCL tibial avulsion fracture even with small comminuted fracture due to compression by the unique crossover configuration mesh of multiple fixation sutures. LEVEL OF EVIDENCE: IV.

Unicompartmental knee arthroplasty fails to completely restore normal gait patterns during level walking.

PURPOSE: Gait analysis is a valuable instrument for measuring function objectively after unicompartmental knee arthroplasty (UKA). However, most gait analysis studies have reported conflicting results for functional assessment after UKA. This meta-analysis compared the gait patterns of UKA patients and healthy controls during level walking. METHODS: Studies were included in the meta-analysis if they recorded vertical ground reaction force (GRF), flexion at initial contact, flexion at loading response, extension at mid-stance, flexion at swing, walking speed, cadence, and stride length in UKA patients or healthy controls. RESULTS: Seven studies met the criteria for inclusion in the meta-analysis. The UKA patients and healthy controls were similar in terms of vertical GRF (95% CI - 0.54 to 0.23; ns), flexion at initial contact (95% CI - 0.47 to 4.96; ns), flexion at loading response (95% CI - 1.29 to 3.69; ns), and flexion at swing (95% CI - 8.85 to 0.40; ns). In contrast, extension at mid-stance (95% CI 0.53 to 4.88; P = 0.01), walking speed (95% CI - 2.13 to - 0.15; P = 0.02), cadence (95% CI - 1.02 to - 0.25; P = 0.001), and stride length (95% CI - 2.02 to - 0.22; P = 0.01) differed significantly between groups. Subgroup analyses revealed that the pooled data were similar between groups: 1st maximum (heel strike), - 0.43 BW (ns); 1st minimum (mid-stance), 0.61 BW (ns); and 2nd maximum (toe off), - 0.46 BW (ns). CONCLUSIONS: There were no significant differences in vertical GRF or overall kinematics in the sagittal plane between UKA patients and healthy controls during level walking. However, the UKA group had a significantly slower walking speed and cadence and a shorter stride length than healthy controls. The current findings suggest that, clinically, UKA fails to completely restore normal gait patterns. LEVEL OF EVIDENCE: Level II, therapeutic study.

Posterior-stabilized inserts are preferable to cruciate-substituting ultracongruent inserts due to more favourable kinematics and stability.

PURPOSE: It is unknown whether the conforming superiority of ultracongruent (UC) inserts over posterior stabilized (PS) inserts, due to an increased anterior lip for prevention of anterior displacement of the condyles during knee flexion, leads to better knee scores or greater knee stability in arthroplasty patients. This meta-analysis compared clinical outcomes, intraoperative kinematics, sagittal stability, and range of motion (ROM) between groups with either UC or PS inserts in primary total knee arthroplasty (TKA). METHODS: Studies that recorded clinical outcomes, intraoperative kinematics, sagittal stability, and ROM in patients who underwent primary TKA with UC or PS inserts were included in the meta-analysis. Subgroup analyses based on differences in flexion angles were performed for intraoperative kinematics. RESULTS: Thirteen studies met the criteria for inclusion in the meta-analysis. The UC and PS insert groups reported similar pain scores (95% CI - 0.15 to 0.16; n.s.) and function scores (95% CI - 0.30 to 0.14; n.s.). In contrast, femoral rotation during flexion (95% CI - 0.06 to 6.35; p = 0.05), posterior femoral translation during flexion (95% CI - 2.74 to - 0.15; p = 0.03), tibial sagittal laxity at 90° (95% CI 2.91 to 7.72; p < 0.0001), and ROM (95% CI - 4.84 to - 1.53; p = 0.0002) differed significantly between the groups. Subgroup analyses revealed that the pooled data for femoral rotation were significantly different between groups: 60°, 4.09 (p < 0.00001); 90°, 7.94 (p < 0.00001); and 120°, 8.16 (p < 0.00001). Furthermore, pooled data for posterior femoral translation were significantly different between groups: 90°, - 3.70 (p < 0.00001); and 120°, - 3.96 (p < 0.00001). CONCLUSIONS: There were no significant differences in clinical outcomes between the groups with UC and PS inserts. However, the UC insert group showed significantly greater external femoral rotation, less posterior femoral translation, greater tibial laxity in the sagittal plane, and less ROM than the PS insert group. Based on the results of the current meta-analysis, in substituting the PCL, PS inserts are preferable to UC inserts due to more favourable kinematics and stability, even though both inserts have equivalent clinical outcomes. LEVEL OF EVIDENCE: Therapeutic study, Level II.

Satisfactory Short-Term Results of Navigation-Assisted Gap-Balancing Total Knee Arthroplasty Using Ultracongruent Insert.

BACKGROUND: The use of highly conforming ultracongruent (UC) polyethylene insert is bone-preserving and became a relatively common alternative to the conventional posterior stabilized total knee arthroplasty (TKA) design. The purpose of this study was to analyze the short-term clinical and radiologic results of UC insert TKA using the navigation-assisted gap-balancing technique. METHODS: Two hundred thirty-three knees were operated with a mean follow-up period of 8.1 years (minimum of 5 years). Radiologic and clinical outcomes were assessed before operation and at latest follow-up using the Knee Society Score and Western Ontario and McMaster Universities Osteoarthritis Index score. For statistical analysis, paired sample t-test and analysis of variance were used. Significance was considered as P < .05. RESULTS: According to the preoperative deformities (valgus, mild varus, and moderate varus), there were 23 cases (9.9%) of valgus deformity, 180 cases (77.3%) of mild varus deformity, and 30 cases (12.9%) of moderate varus deformity. Overall, the results at mean 8.1 years revealed an improvement in mean Knee Society Score (54 ± 12 to 92 ± 3) and mean Western Ontario and McMaster Universities Osteoarthritis Index scores (62 ± 14 to 17 ± 3). Overall, 220 of 233 cases (94.4%) were in neutral alignment (between -3° and +3°) at latest follow-up. There were no migrating or shifting prosthesis that should be considered as possible failure. There was 0% component revision rate. CONCLUSION: Navigation-assisted gap-balancing technique using UC insert TKA had satisfactory short-term outcome. Strict gap-balancing technique using the offset-type-force-controlled-spreader-system aided in the satisfactory results.

Unsatisfactory clinical outcomes of second-generation mobile bearing floating platform total knee arthroplasty: comparing outcomes with fixed bearing after five years minimum.

BACKGROUND: The purpose of this retrospective study was to analyze and compare the clinical and radiologic outcomes of fixed bearing ultracongruent (UC) insert total knee arthroplasty (TKA) and mobile bearing (MB) floating platform TKA using the navigation-assisted gap balancing technique with a minimum follow-up of five years. METHODS: The study retrospectively enrolled 105 patients who received the UC type fixed bearing insert (group 1) and 95 patients who received the floating platform MB insert (group 2) during the period from August 2009 to June 2012. All surgery was performed using the navigation-assisted gap balancing technique. For strict assessment of gap measurements, the offset-type-force-controlled-spreader-system was used. Radiologic and clinical outcomes were assessed before operation and at the most recent follow-up using the Knee Society Score (KSS) and the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score. For statistical analysis, paired sample t tests were used. A p value less than 0.05 was considered significant. RESULTS: Although the radiologic alignments were satisfactory for both groups (99/105 [94%] cases were neutral for group 1 and 90/95 [94%] for group 2), the functional and total WOMAC scores were inferior in group 2 (p < 0.05). There were two cases of insert breakage in group 2 that required bearing exchange. The Kaplan-Meier survivorship rates for groups 1 and 2 at 77 months were 100.0 and 97.9%, respectively. CONCLUSION: Second-generation MB floating platform TKA cases did not have satisfactory outcomes. There were two cases of insert breakage, which required bearing exchange. Other patients who underwent surgery with second-generation MB floating platform were encouraged to avoid high knee flexion activities, resulting in lower clinical performance.

Diagnostic accuracy of interleukin-6 and procalcitonin in patients with periprosthetic joint infection: a systematic review and meta-analysis.

PURPOSE: Many studies have found associations between laboratory biomarkers and periprosthetic joint infection (PJI), but it remains unclear whether these biomarkers are clinically useful in ruling out PJI. This meta-analysis compared the performance of interleukin-6 (IL-6) versus procalcitonin (PCT) for the diagnosis of PJI. METHODS: In this meta-analysis, we reviewed studies that evaluated IL-6 or/and PCT as a diagnostic biomarker for PJI and provided sufficient data to permit sensitivity and specificity analyses for each test. The major databases MEDLINE, EMBASE, the Cochrane Library, Web of Science, and SCOPUS were searched for appropriate studies from the earliest available date of indexing through February 28, 2017. No restrictions were placed on language of publication. RESULTS: We identified 18 studies encompassing a total of 1,835 subjects; 16 studies reported on IL-6 and 6 studies reported on PCT. The area under the curve (AUC) was 0.93 (95% CI, 0.91-0.95) for IL-6 and 0.83 (95% CI, 0.79-0.86) for PCT. The pooled sensitivity was 0.83 (95% CI, 0.74-0.89) for IL-6 and 0.58 (95% CI, 0.31-0.81) for PCT. The pooled specificity was 0.91 (95% CI, 0.84-0.95) for IL-6 and 0.95 (95% CI, 0.63-1.00) for PCT. Both the IL-6 and PCT tests had a high positive likelihood ratio (LR); 9.3 (95% CI, 5.3-16.2) and 12.4 (95% CI, 1.7-89.8), respectively, making them excellent rule-in tests for the diagnosis of PJI. The pooled negative LR for IL-6 was 0.19 (95% CI, 0.12-0.29), making it suitable as a rule-out test, whereas the pooled negative LR for PCT was 0.44 (95% CI, 0.25-0.78), making it unsuitable as a rule-out diagnostic tool. CONCLUSIONS: Based on the results of the present meta-analysis, IL-6 has higher diagnostic value than PCT for the diagnosis of PJI. Moreover, the specificity of the IL-6 test is higher than its sensitivity. Conversely, PCT is not recommended for use as a rule-out diagnostic tool.

Use of autogenous onlay bone graft for uncontained tibial bone defects in primary total knee arthroplasty.

BACKGROUND: The use of autogenous bone graft is a well-known technique for reconstruction of tibial bone defects in primary total knee arthroplasty (TKA). In cases where the size of the bone graft is inappropriate, the stability of bone graft fixation and subsequent bone graft to host bone incorporation may be compromised. We describe a simple and reliable technique of reconstruction in a proximal tibia bone defect at the time of primary TKA by using autogenous onlay bone graft (AOBG). METHODS: Records were reviewed of 19 patients (mean age, 72 years) who underwent primary TKA using AOBG without the additional allogenous bone or metal augments, between August 2013 and August 2014. RESULTS: Mean Knee Society score (KSS) in the 22 knees was significantly higher postoperatively than preoperatively (92 ± 4 vs. 30 ± 7, P < 0.001). The mean range of motion (ROM) in the 22 knees, which was 106 ± 12° preoperatively, improved to 112 ± 10° at last follow-up, but this difference was not significant (P = 0.32). No migration of implants and presence of radiolucent lines at the bone cement-prosthesis interface were observed. Furthermore, the serial radiographs of 19 patients had a mean time of 3.2 months (range, 2.7-4.4 months) for solid union with cross trabeculation between the proximal tibial bone and graft. CONCLUSIONS: This simple AOBG supplement technique may biologically promote graft to host bone healing by enhancing fixation stability without the additional fixatives and assist the surgeon in managing the varying nature of uncontained bone defects. TRIAL REGISTRATION: Trial registration number: KCT0002328 , May 15, 2017.

Intravenous versus topical tranexamic acid administration in primary total knee arthroplasty: a meta-analysis.

PURPOSE: This meta-analysis was designed to compare the effectiveness and safety of intravenous (IV) versus topical administration of tranexamic acid (TXA) in patients undergoing primary total knee arthroplasty (TKA) by evaluating the need for allogenic blood transfusion, incidence of postoperative complications, volume of postoperative blood loss, and change in haemoglobin levels. METHODS: Studies were included in this meta-analysis to check whether they assessed the allogenic blood transfusion rate, postoperative complications including pulmonary thromboembolism (PTE) or deep vein thrombosis (DVT), volume of postoperative blood loss via drainage, estimated blood loss, total blood loss, and change in haemoglobin levels before and after surgery in primary TKA with TXA administered through both the IV and topical routes. RESULTS: Ten studies were included in this meta-analysis. The proportion of patients requiring allogenic blood transfusion (OR 1.34, 95 % CI 0.63-2.81; n.s.) and the proportion of patients who developed postoperative complications including PTE or DVT (OR 0.85, 95 % CI 0.41 to 1.77; n.s.) did not significantly differ between the two groups. There was 52.3 mL less blood loss via drainage (95 % CI -50.74 to 185.66 mL; n.s.), 52.1 mL greater estimated blood loss (95 % CI -155.27 to 51.03 mL; n.s.), and 51.4 mL greater total blood loss (95 % CI -208.16 to 105.31 mL; n.s.) in the topical TXA group as compared to the IV TXA group. The two groups were also similar in terms of the change in haemoglobin levels (0.02 g/dL, 95 % CI -0.36 to 0.39 g/dL; n.s.). CONCLUSIONS: In primary TKA, there are no significant differences in the transfusion requirement, postoperative complications, blood loss, and change in haemoglobin levels between the IV and topical administration of TXA. In addition, results from subgroup analysis evaluating the effect of the times of TXA administration through the IV route suggested that double IV dose of TXA is more effective than single dose in terms of the transfusion requirements and blood loss via drainage. The current meta-analysis indicates that IV administration of 10 mg/kg of TXA 20 min before inflation of the tourniquet followed by 10 mg/kg of TXA 15 min before deflation of the tourniquet is effective and safe. The topical administration of 2 g of TXA mixed with 100 mL of normal saline after wound closure could be an alternative option in patients at greater risk of thromboembolic complications. LEVEL OF EVIDENCE: Meta-analysis, Level III.

Sagittal osteotomy inclination in medial open-wedge high tibial osteotomy.

PURPOSE: Unlike postoperative changes in posterior tibial slope after medial open-wedge high tibial osteotomy, sagittal osteotomy inclination has not been examined. It has been recommended that the osteotomy line in the sagittal plane be parallel to the medial posterior tibial slope. The purpose of this study was to determine the frequency of parallel osteotomy in medial open-wedge high tibial osteotomy. METHODS: To determine the sagittal osteotomy inclination, the angle between the medial joint line and the osteotomy line was measured in the lateral radiograph. A positive angle value indicates that the osteotomy is anteriorly inclined relative to the medial posterior tibial slope. Correlation between the sagittal osteotomy inclination and posterior tibial slope was also evaluated. RESULTS: The mean sagittal osteotomy inclination was 15.1 ± 7.5°. The majority 87.1 % of knees showed an anterior-inclined osteotomy. There was a significantly positive correlation between the postoperative posterior tibial slope and the sagittal osteotomy inclination (r, 0.33; 95 % confidence interval (CI) 0.19-0.46; P < 0.001). The postoperative change in posterior tibial slope also showed a significantly positive correlation with the sagittal osteotomy inclination (r, 0.35; 95 % CI 0.21-0.47; P < 0.001). CONCLUSION: Although parallel osteotomy in the sagittal plane relative to the medial joint line was planned, only 12.9 % of cases achieved osteotomy parallel to the medial posterior tibial slope in the sagittal plane. Because of high rate of the anterior-inclined osteotomy and their correlations with posterior tibial slope, surgeons should make all efforts to perform parallel osteotomy relative to medial posterior tibial slope. LEVEL OF EVIDENCE: IV.

Changes in coronal alignment of the ankle joint after high tibial osteotomy.

PURPOSE: The purpose of this study was to investigate changes in coronal alignment of the ankle joint after HTO. Our hypothesis was that ankle joint orientation may become more parallel or less parallel to the ground after HTO, and this change may affect ankle symptoms. METHODS: Eighty-six knees were retrospectively analysed after HTO for varus osteoarthritis. Preoperative and follow-up whole-leg radiographs were taken. The hip-knee-ankle (HKA) angle and medial proximal tibial angle (MPTA) were measured to evaluate coronal alignment of the knee. Tibial plafond inclination (TPI), talar inclination (TI), talar tilt (TT), and lateral distal tibial angle (LDTA) were measured to evaluate coronal alignment of the ankle. Patients were divided into two groups: those who exhibited a decrease in the absolute value of TPI and TI after HTO (group A) and those who exhibited an increase in the absolute value of TPI or TI after HTO (group B). Clinical outcomes of the knee and ankle were evaluated pre- and postoperatively. RESULTS: Mean TPI and TI changed from 6.9° ± 3.6° and 8.0° ± 3.8° to 2.8° ± 3.1° and 3.9° ± 3.0° in group A (P < 0.001 for both) and from -1.3° ± 3.7° and 0.6° ± 4.5° to -6.0° ± 4.2° and -4.6° ± 5.9° in group B (P = 0.018 for both). VAS for ankle pain did not change significantly after HTO (n.s.) in group A, whereas those of group B increased significantly after HTO (P = 0.014). CONCLUSION: Ankle joint orientation becomes more parallel or less parallel to the ground after HTO. Smaller preoperative HKA and LDTA result in a more valgus ankle joint orientation after HTO. Ankle symptoms were affected by coronal alignment changes of the ankle after HTO. LEVEL OF EVIDENCE: III.

Tibial nerve neuropathy following medial opening-wedge high tibial osteotomy-case report of a rare technical complication.

A 63-year-old woman developed tibial nerve injury caused by an overlong K wire and 4.5-mm cortical lag screw through the first distal hole below the osteotomy during medial opening-wedge high tibial osteotomy (HTO), leading to a lack of sensation on the sole of the foot with no disturbances in motor functions. The temporary lag screw in the first distal hole below the osteotomy is often inserted by an excessive length in order to compress the potentially fractured opposite cortex. By doing so, posterior neurovascular structures including the tibial nerve and the popliteal vessels can be injured. To avoid this type of injury during medial opening-wedge HTO, proper knee position and appropriate Hohmann retractor position in combination with meticulous insertion of the K wire or screw under fluoroscopic control are essential. In addition, our study reinforces the fact that different presentations of injury to the tibial nerve should be carefully considered in the absence of common diagnostic features, including weakness of the toe flexors and posterior tibial muscle of the leg with intractable pain.

Minimally invasive navigation-assisted versus conventional total knee arthroplasty: a meta-analysis.

PURPOSE: It is unclear whether the minimally invasive navigation-assisted (MINA) or conventional (CONv) approach for primary total knee arthroplasty (TKA) leads to better clinical and radiographic outcomes. This meta-analysis compared the clinical and radiographic outcomes of the MINA and CONv approaches after primary TKA. It was hypothesized that there was no difference in clinical and radiographic outcomes between the two surgical approaches for primary TKA. METHODS: This meta-analysis reviewed all studies that compared surgical time, incision length, flexion range of motion (ROM), Knee Society Score ( KSS), coronal mechanical axis (CMA), and coronal femoral component angle (CFCA) with various measurement tools, from direct interview to plain radiography, between the MINA and CONv approaches. RESULTS: Five studies met the inclusion/exclusion criteria for the meta-analysis. The findings of this study suggest that surgical time (95 % CI -18.51 to 39.09; n.s.), KSS (95 % CI -8.55 to 30.84; n.s.), CMA (95 % CI -1.01 to 0.54; n.s.), and CFCA (95 % CI -0.91 to 2.97; n.s.) were similar between the two surgical approaches, whereas incision length (95 % CI -5.18 to -3.69; P < 0.001) was significantly shorter in the MINA approach and flexion ROM (95 % CI 14.26-19.01; P < 0.001) was significantly greater in the MINA approach. CONCLUSIONS: There were no significant differences in clinical and radiographic outcomes, including surgical time, KSS, CMA, and CFCA, in patients who underwent MINA and CONv approach for primary TKA, but the MINA approach resulted in a slightly shorter incision length and increased flexion ROM than the CONv approach. Therefore, if particular attention has to be paid to patient's selection with appropriate counselling and surgeon's experience, MINA approach can provide early clinical benefit when compared with CONv approach. Besides, orthopaedic surgeons need to master the MINA and CONv approaches because both approaches have similar clinical and radiographic outcomes. LEVEL OF EVIDENCE: Therapeutic study, Level II.

Myopericytoma around the knee: mimicking a neurogenic tumour.

Myopericytoma is a rare, usually benign soft tissue tumour that arises most commonly in the dermis and subcutaneous soft tissue of the lower extremities. In this article, we present an unusual case of myopericytoma occurring in the deep soft tissue around the knee that mimicked a neurogenic tumour. Myopericytoma can be confused with neurogenic tumour when located in deep soft tissue and adjacent to nerve bundles. Preoperative MRI and colour Doppler ultrasound may help differentiate myopericytoma from neurogenic tumour by revealing the hypervascular nature of the tumour.

Alignment in knee flexion position during navigation-assisted total knee arthroplasty.

PURPOSE: The aim of this study was to demonstrate the lower limb alignment in knee flexion position after navigation-assisted total knee arthroplasty using the gap technique and to identify the correlative factors. METHODS: One hundred and twenty consecutive osteoarthritic knees (120 patients) were prospectively enrolled for intraoperative data collection. All TKA surgeries were performed using the navigation system (OrthoPilot™, version 4.0; B. Braun Aesculap, Tuttlingen, Germany). Before and after final prosthesis implantation, the lower limb navigation alignment in both knee extension (0°) and knee flexion (90°) position was recorded. The knee flexion alignment was divided into three groups: varus, neutral and valgus alignment. To determine the factors of the alignment in knee flexion position, preoperative demographics, radiologic and intraoperative data were obtained. Pearson's correlation (r) analysis was performed to find the correlation. The Knee Society Score and Western Ontario and McMaster Universities Osteoarthritis Index were compared between groups. RESULTS: Although all postoperative extension alignment was within neutral position (between -2° and +2°), postoperative knee flexion alignment was divided into three groups: varus (≤-3°), 24 cases (20 %); neutral (between -2° and +2°), 85 cases (70.8 %) and valgus (≥+3°) alignment, 11 cases (9.2 %). There were a good correlation of alignment in knee flexion position with the rotation of femoral component relative to posterior condylar axis (r = -0.502, p = 0.000) and weak correlations with posterior femoral cut thickness (lateral condyle) (r = 0.207, p = 0.026), medial flexion (90°) gap after femoral component rotation adjustment (r = 0.276, p = 0.003). Other variables did not show correlations. There were no statistical clinical differences between varus, neutral and valgus knee flexion alignment groups. CONCLUSION: About 30 % of the cases showed malalignment of more than 3° in knee flexion position although with neutral alignment in extension position. The knee flexion alignment had a good correlation with the rotation of femoral component relative to posterior condylar axis. Neutral alignment in knee flexion position may be adjusted by femoral component rotation especially by the use of navigation system. LEVEL OF EVIDENCE: IV.

Comparison between two angular stable locking plates for medial opening-wedge high tibial osteotomy: Decisive wedge locking plate versus TomoFix™.

BACKGROUND: An adequate stable fixation implant should be used for medial opening-wedge high tibial osteotomy (MOWHTO) to promote rapid bone healing without complications. This study compared the radiographic and clinical outcomes as well as plate-specific complications between two angular stable locking plates in patients following MOWHTO. METHOD: This prospective study involved 97 patients (50 with DWL®, group I; 47 with TomoFix™, group II) undergoing MOWHTO for primary medial compartment osteoarthritis between 2010 and 2013. Clinical and radiographic evaluations were performed by using the HSS and WOMAC scores, and calculating mechanical femorotibial angle (mFTA), medial proximal tibial angle (MPTA), joint line convergence angle (JLCA), and posterior tibial slope (PTS) on radiographs both preoperatively and after 3 years. RESULTS: A statistically significant difference was observed for the MPTA at the last follow-up between the two groups (P = 0.033). Additionally, the last follow-up MPTA of group I was associated with the osteotomy technique (P = 0.004) and preoperative JLCA (P = 0.034) whereas the last follow-up MPTA of group II was associated with gender (P = 0.001) and BMI (P = 0.008). Furthermore, the results showed that group I had a higher rate of non-union (4%) compared to that in group II (0%). CONCLUSION: Both locking plates are useful tools in the treatment of medial compartment knee osteoarthritis with varus deformity in young, active patients. However, under special consideration of the complication we found in present study, the TomoFix™ seems to be a better alternative in using the MOWHTO for highly demanding patients.

Does patella position influence ligament balancing in total knee arthroplasty?

PURPOSE: In vivo comparative gap measurements were performed in three different patella positions (reduced, subluxated and everted) using offset-type-force-controlled-spreader-system. METHODS: Prospectively, 50 knees were operated by total knee arthroplasty using a navigation-assisted gap-balancing technique. The offset-type-force-controlled-spreader-system was used for gap measurements. This commercially available instrument allows controllable tension in patella-reduced position. The mediolateral gaps of knee extension (0°) and flexion (90°) angle were recorded in three different patella positions; reduced, subluxated and everted. Any gap differences of more than 3 mm were considered as a meaningful difference. Correlation between the difference with the demographic data, preoperative radiologic alignment and intraoperative data was analysed. For statistical analysis, ANOVA and Pearson's correlation test were used. RESULTS: The gaps in patella eversion demonstrated smaller gaps both in knee extension and flexion position compared to the gaps of patella reduction position. The amount of decreased gaps was more definite in knee flexion position. Statistically significant difference was observed for the lateral gap of patella eversion compared to gap of patella reduction in knee flexion position (p < 0.05). There were notable cases of variability in knee flexion position. Significant portion of 12 (24 %) knees of patella subluxation and 33 (66 %) knees of patella evertion demonstrated either increased or decreased gaps in knee flexion position compared to the gaps of patella reduction position. CONCLUSION: The gaps in patella eversion demonstrated smaller gaps both in knee extension and flexion position compared to the gaps of patella reduction position. The amount of decreased gaps was more definite in knee flexion position. Therefore, the intraoperative patellar positioning has influence on the measurement of the joint gap. Keeping the patella in reduced position is important during gap balancing. LEVEL OF EVIDENCE: I.