Bead-beating assay during synovial fluid DNA extraction improves real-time PCR accuracy for periprosthetic joint infection.

Polymerase chain reaction (PCR)-based genetic diagnosis is a rapid and sensitive method to diagnose periprosthetic joint infection (PJI). DNA extraction using bead beating is an effective method for collecting bacterial genes in Gram-positive bacteria. We compared the detection accuracy between the conventional and bead-beating DNA extraction assay. The detection rate improved from 86.7% using the conventional method to 95.6% using the bead-beating. Our results suggest that bead-beating during DNA extraction can improve the accuracy of PCR-based genetic diagnosis of PJI.

A Case of Myxoid Pleomorphic Liposarcoma with Rhabdoid Cells: A Diagnostic Pitfall.

Myxoid pleomorphic liposarcoma (MPLS) is an extremely rare tumor listed in the fifth edition of the WHO classification (2020). Histologically, it mainly comprises a mixture of myxoid and pleomorphic liposarcoma-like components. Genetically, it lacks FUS/EWSR1::DDIT3 fusion and MDM2 amplification. Herein, we describe an example of MPLS with rhabdoid cells in a 10-year-old girl who presented with a growing mass in the right inguinal region. The specimen from the wide excision measured 68 mm × 55 mm × 43 mm, and a circumscribed and lobulated mass was observed in the subcutaneous tissue. Histologically, oval-to-short, spindle-shaped, proliferating tumor cells with moderate nuclear atypia and mesh-like capillaries against a myxoid background were noted. Adipocytes were observed focally, while rhabdoid cells were observed multifocally. Immunohistochemically, the tumor showed inconsistent reactivity for desmin but was negative for MYOD1, myogenin, MDM2, and CDK4. Fluorescence in situ hybridization revealed no DDIT3 rearrangement. Despite adjuvant chemotherapy, the tumor metastasized to the thoracic cavity 24 months after excision. The metastatic lesions contained abundant lipoblasts rather than rhabdoid cells, and we concluded this tumor was a MPLS. The presence of rhabdoid cells could be a diagnostic pitfall, and recognizing such a variation in histology would help improve diagnostic accuracy.

Histological and immunohistochemical analyses of osteoclast maturation in giant cell tumor of bone.

INTRODUCTION: Giant cell tumor of bone (GCTB) is a benign but locally aggressive tumor characterized by the occurrence of multinucleated osteoclast-like giant cells that play a key role in GCTB pathogenesis. However, little is known about the molecular mechanisms underlying osteoclast differentiation in GCTB. Denosumab, a human monoclonal antibody against RANKL, is used for GCTB treatment. Here, we performed morphological and immunohistochemical examinations of pre- and post-denosumab treatment changes by analyzing each stage of osteoclast differentiation. METHODS: We retrieved 15 archival cases of GCTB with tumor samples from both pre- and post-denosumab treatment. We selected three immunohistochemical markers from the expression data from a previous single-cell RNA study: FOS, a progenitor osteoclast marker, and JDP2 and NFATc1, mature osteoclast markers. RESULTS: The mean positivity of the markers decreased after denosumab treatment from 11.1% to 8.9% for FOS, from 10.6% to 7.2% for JDP2, and from 10.0% to 0.2% for NFATc1. Only NFATc1 positivity decreased significantly (P < 0.001) after denosumab treatment. CONCLUSIONS: We identified a new differentiation stage of osteoclast maturation, intermediate cell, by comparing histological findings before and after denosumab treatment. We demonstrated that discrepancies exist between histological and molecular data and highlight the need for establishing an integrated definition of osteoclasts considering morphology and marker expression.

Novel Local Antifungal Treatment for Fungal Periprosthetic Joint Infection With Continuous Local Antibiotic Perfusion: A Surgical Technique.

Fungal periprosthetic joint infections are one of the most intractable orthopedic disorders. Continuous local antibiotic perfusion allows direct administration of the antifungal agent micafungin into the local infection area at biofilm-disruptive concentrations, while controlling the dead space in addition to conventional treatment. Although the appropriate use of continuous local antibiotic perfusion requires familiarity with the characteristics of local antibiotic perfusion, it is a versatile treatment modality that can improve the clinical outcomes of fungal periprosthetic joint infection in combination with conventional treatment methods.

A rare case of intra-articular synovial sarcoma of the hip joint: a case report with intra-articular findings via hip arthroscopy.

Although synovial sarcoma is a relatively common soft tissue sarcoma, primary intra-articular cases are extremely rare. Herein, we report a case of primary intra-articular synovial sarcoma arising from the hip joint, that was initially treated with hip arthroscopy. A 42-year-old male presented with a history of pain in the left hip for 7 years. Radiography and magnetic resonance imaging revealed the primary intra-articular lesion and simple excision with an arthroscopy was performed. Histological findings revealed spindle cell proliferation with abundant psammoma bodies. SS18 gene rearrangement was confirmed by fluorescence in situ hybridization, and the tumor was diagnosed as synovial sarcoma. Adjuvant chemotherapy and radiotherapy were performed. Local control without metastasis was achieved 6 months after excision. This is the first case of intra-articular synovial sarcoma of the hip joint excised via hip arthroscopy. When an intra-articular lesion is identified, malignancies such as synovial sarcoma should be included in the differential diagnosis.

Giant Cell Tumor of Bone Without Giant Cells with a Long Clinical Course: A Case Report.

Giant cell tumor of bone (GCTB) consists of a mixture of neoplastic mononuclear cells and non-neoplastic cells, including polynuclear giant cells. Recently, with the spread of the immunohistochemical staining marker H3.3 G34W corresponding to specific genetic abnormalities, the histological diversity of GCTB has been recognized. GCTB without giant cells is uncommon, although it has also been reported previously. Herein, we describe a 45-year-old man with GCTB without giant cells who was successfully diagnosed using H3.3 G34W immunohistochemistry. Other unusual findings in GCTB that were identified in this patient include bone and osteoid formation with a long clinical course of 13 years. We also compared the histological findings of the current patient to those who received denosumab therapy.

Rhabdomyosarcoma With FUS::TFCP2 Fusion in the Scalp: A Rare Case Report Depicting Round and Spindle cell Morphology.

Rhabdomyosarcoma (RMS) is a nonepithelial malignant tumor that differentiates into immature skeletal muscle. It is currently classified into 4 main subtypes according to the WHO classification. However, based on clinicopathological and molecular findings, there has been an increasing number of cases that do not fit into any of these subtypes. TFCP2-rearranged RMS is a rare tumor with characteristic clinicopathological findings including a preference for the craniofacial bones, a spindle and epithelioid histomorphology, and positive immunohistochemistry for epithelial markers, ALK, and myogenic markers. In this report, we describe a rare case of RMS with FUS::TFCP2 fusion in the scalp of a 58-year-old man. Histologically, the tumor showed a biphasic pattern, with solid proliferation of round cells in the superficial areas and of spindle cells in the deep areas. Immunohistochemically, tumor cells were positive for pan keratin, myogenic markers (desmin, MYOD1, and myogenin), and ALK. Additionally, fluorescence in situ hybridization using a break-apart FUS probe revealed FUS rearrangement. RMS with FUS::TFCP2 fusion was suspected, and the fusion gene was finally confirmed by target fusion sequencing. We believe that detailed histological, immunohistochemical, and genetic findings were important for the diagnosis. The unique traits of this tumor were the biphasic histological appearance consisting of round and spindle cells and development in the skin and soft tissue.

Effect of Tranilast on the Frequency of Invasive Treatment for Extra-Abdominal Desmoid Fibromatosis.

BACKGROUND: Active surveillance (AS) has been suggested for managing extra-abdominal desmoid fibromatosis (EADF), but a substantial percentage of such patients transitioned to invasive secondary treatments. The anti-keloid medication tranilast is frequently used in Japan but its effectiveness for EADF is not well understood. METHODS: We retrospectively analyzed the medical records of EADF patients treated with tranilast between January 2009 and March 2021. EADF has been reported to shrink spontaneously, so the effects of all drugs must be compared with AS. To assess the effect of tranilast, we compared the clinical courses of patients receiving tranilast with those managed by AS (as identified in a systematic review). A systematic review of AS outcomes was conducted on July 22, 2021, in accordance with PRISMA guidelines. The primary endpoint was rate of conversion to secondary treatment. Secondary endpoints were progression-free survival, objective response rate (ORR), disease control rate (DCR), and adverse events. The rates of conversion to secondary treatment, ORRs, and DCRs were compared between the two groups by using the Fisher exact test. RESULTS: Eighteen patients who received tranilast as initial treatment for EADF were included. Two patients (11.1%) underwent surgical resection for treatment of tumor growth and persistent pain. The rate of conversion to secondary treatment was significantly lower for tranilast than for a pure AS approach (40.1%; p = 0.01). ORR and DCR did not differ between groups. CONCLUSIONS: Tranilast was better than AS for initial management of EADF.

Perioperative Adriamycin plus ifosfamide vs. gemcitabine plus docetaxel for high-risk soft tissue sarcomas: randomised, phase II/III study JCOG1306.

BACKGROUND: This randomised phase II/III trial aimed to determine whether perioperative chemotherapy with gemcitabine plus docetaxel (GD) is non-inferior to the standard Adriamycin plus ifosfamide (AI) in terms of overall survival (OS) in patients with soft tissue sarcoma (STS). METHODS: Patients with localised high-risk STS in the extremities or trunk were randomised to receive AI or GD. The treatments were repeated for three preoperative and two postoperative courses. The primary endpoint was OS. RESULTS: Among 143 enrolled patients who received AI (70 patients) compared to GD (73 patients), the estimated 3-year OS was 91.4% for AI and 79.2% for GD (hazard ratio 2.55, 95% confidence interval: 0.80-8.14, P = 0.78), exceeding the prespecified non-inferiority margin in the second interim analysis. The estimated 3-year progression-free survival was 79.1% for AI and 59.1% for GD. The most common Grade 3-4 adverse events in the preoperative period were neutropenia (88.4%), anaemia (49.3%), and febrile neutropenia (36.2%) for AI and neutropenia (79.5%) and febrile neutropenia (17.8%) for GD. CONCLUSIONS: Although GD had relatively mild toxicity, the regimen-as administered in this study-should not be considered a standard treatment of perioperative chemotherapy for high-risk STS in the extremities and trunk. CLINICAL TRIAL REGISTRATION: jRCTs031180003.

Prevalence and risk factors of preoperative venous thromboembolism in patients with malignant musculoskeletal tumors: an analysis based on D-dimer screening and imaging.

BACKGROUND: Venous thromboembolism (VTE) is a major complication in patients with malignant tumors and orthopedic disorders. Although it is known that patients undergoing surgery for malignant musculoskeletal tumor are at an increased risk of thromboembolic events, only few studies have investigated this risk in detail. Therefore, the aim of this study was to determine the prevalence and risk factors for preoperative VTE in malignant musculoskeletal tumors patients. METHODS: We retrospectively reviewed the medical records of 270 patients who underwent surgical procedures, including biopsy for malignant musculoskeletal tumor, have undergone measurements of preoperative D-dimer levels, and were subsequently screened for VTE by lower extremity venous ultrasonography and/or contrast-enhanced computed tomography scans. Statistical analyses were performed to examine the prevalence and risk factors for VTE. Receiver operating characteristic (ROC) analysis was performed to verify the D-dimer cutoff value for the diagnosis of VTE. RESULTS: Overall, 199 patients (103 with primary soft tissue sarcomas, 38 with primary bone sarcomas, 46 with metastatic tumors, and 12 with hematologic malignancies) were included. D-dimer levels were high in 79 patients; VTE was detected in 19 patients (9.5%). Multivariate analysis indicated that age ≥ 60 years (P = 0.021) and tumor location in the lower limbs (P = 0.048) were independent risk factors for VTE. ROC analysis showed that the D-dimer cutoff value for the diagnosis of VTE was 1.53 µg/mL; the sensitivity and specificity were 89.5% and 79.4%, respectively. CONCLUSIONS: Our study indicated that age and tumor location in the lower limbs were independent risk factors for preoperative VTE in malignant musculoskeletal tumors patients. D-dimer levels were not associated with VTE in the multivariate analysis, likely because they are affected by a wide variety of conditions, such as malignancy and aging. D-dimer is useful for exclusion diagnosis because of its high sensitivity, but patients with high age and tumor location in the lower limbs are a high-risk group and should be considered for imaging evaluation such as ultrasonography regardless of D-dimer levels. TRIAL REGISTRATION: Our study was approved by the institutional review board. The registration number is B200600056 . The registration date was July 13, 2020.

Detection of mecA and 16S rRNA Genes Using Real-Time PCR Can Be Useful in Diagnosing Iliopsoas Abscess, Especially in Culture-Negative Cases: RT-PCR for Iliopsoas Abscess.

The rapid detection of etiological agents is important for the successful treatment of iliopsoas abscess (IPA). The purpose of this study was to investigate the clinical utility of a real-time polymerase chain reaction (PCR) that targets the mecA gene for methicillin-resistant staphylococci (MRS) and the 16S rRNA gene for pan-bacteria. Our retrospective diagnostic study included 22 patients exhibiting IPAs and four patients with noninfectious iliopsoas mass regions who underwent computerized tomography or ultrasonography-guided biopsy and/or surgical treatment. Clinical symptoms, serum data, imaging analysis, and tissue microbiological culture were utilized for the diagnosis of IPA. The diagnostic accuracy of real-time PCR was determined based on the diagnosis of IPA and microbiological culture results. The microbiological culture was positive for 12 IPA cases that included 2 MRSA infections. Among 12 culture-positive IPA cases, 16S rRNA-PCR was positive in 12 and MRS-PCR in two. Among 10 culture-negative IPA cases, including 3 TB cases, 16S rRNA-PCR was positive in 8 and MRS-PCR in 2. In noninfectious iliopsoas mass patients, neither 16S rRNA nor MRS-PCR detected bacterial DNA. The sensitivity, specificity, positive predictive, and negative predictive values of 16S rRNA-PCR for diagnosing IPA were 0.91, 1.00, 1.00, and 0.67, respectively, while those for the diagnosis of MRS infection with MRS-PCR were 1.00, 0.92, 1.00, and 0.50, respectively. Real-time PCR targeting bacterial DNA can detect bacterial DNA in culture-negative cases and offer improved detectability of MRS infection in IPA patients.

Clinical and pathological analysis of giant cell tumor of bone with denosumab treatment and local recurrence.

BACKGROUND: Giant cell tumor of bone (GCTB) is a primary bone tumor which comprises giant cells and two types of stromal cells. Recent studies have suggested therapeutic risks of denosumab. No previous studies have reported changes in serum TRACP-5b and SUVmax of 18F-FDG-PET/CT in recurred GCTB after denosumab treatment. Therefore, we assessed the relationship between clinical and pathological features of GCTB which recurred after denosumab treatment. METHODS: We retrospectively reviewed the medical records of 26 patients with GCTB who underwent curettage between 2010 and 2018. Fourteen patients treated with denosumab were defined as the denosumab group. We evaluated TRACP-5b and SUVmax values in the denosumab group. H&E staining and immunohistochemistry for H3.3 G34W were performed for pathological assessment. Twelve patients treated without denosumab were defined as the non-denosumab group and compared with denosumab group. RESULTS: The local recurrence rate in the denosumab group was 57.4%. The mean TRACP-5b and SUVmax values were significantly decreased after denosumab therapy (P < 0.001, 1077 ± 161 to 74 ± 9 mU/dL and 8.88 ± 0.40 to 3.79 ± 0.56, respectively). Both parameters significantly increased with local recurrence. H&E staining after denosumab treatment revealed the disappearance of giant cells and histological changes in stromal cells. Specimens of local recurrence subjected to H&E staining and immunohistochemistry for H3.3 G34W demonstrated almost identical features to those in the first biopsy. CONCLUSION: Although denosumab can prevent GCTB from osteolysis, local recurrence cannot be reduced by denosumab treatment. The clinical and pathological results were almost the same as those before denosumab treatment, suggesting that the changes of GCTB by denosumab are reversible.

Characteristics of Patients with Giant Cell Tumor of Bone and High Serum Tartrate-Resistant Acid Phosphatase 5b Levels: Comparison of Tumor Volume and Clinical Factors.

BACKGROUND: Serum tartrate-resistant acid phosphatase 5b is well known to be increased in giant cell tumors of bone. However, there are only a few studies that analyzed the association with tartrate-resistant acid phosphatase 5b expression in those patients. Therefore, we analyzed the characteristics of patients with giant cell tumors of bone and high tartrate-resistant acid phosphatase 5b expression. METHODS: This retrospective study included 26 patients with giant cell tumors of bone. The correlation between tartrate-resistant acid phosphatase 5b before initial treatment and tumor volume was evaluated. Patients were divided into two groups according to tartrate-resistant acid phosphatase 5b level. Statistical analysis was performed between the two groups. RESULTS: Tartrate-resistant acid phosphatase 5b was elevated in 17/26 patients, and the mean value was 852 mU/dL. There was no correlation with tumor volume (r = 0.034, P = 0.86). The mean age of 34.5 years in the HT group was significantly younger than the mean age of 47.4 years in the LT group (P = 0.040). Pathologically, 19/26 cases showed at least one focal area with features of typical giant cell tumor of bone. Although 11/18 patients in the LT group exhibited relatively noticeable secondary changes, all patients in the HT group exhibited typical features (P = 0.0074). CONCLUSIONS: Tartrate-resistant acid phosphatase 5b levels were not elevated in some giant cell tumors of bone. This study suggested that tartrate-resistant acid phosphatase 5b may be elevated in younger patients and in cases with fewer pathological secondary changes, regardless of tumor volume.

Postoperative excessive external femoral rotation in revision total hip arthroplasty is associated with muscle weakness in iliopsoas and gluteus medius and risk for hip dislocation.

BACKGROUND: Excessive external femoral rotation (FR) can functionally increase stem anteversion (SA) and is often observed at an early stage after surgery in revision total hip arthroplasty (THA). This study was conducted to investigate the prevalence of external FR, identify the factors associated with external FR, and determine the association of FR and other factors with hip dislocation in revision THA. METHODS: We enrolled 51 revision THA patients (55 hip cases). The patient background, angle of anatomical and functional SA, FR angle, sizes and densities of muscles around the hip joint, impingement distance, and consequence of postoperative hip dislocation were assessed by reviewing their medical history and imaging data that includes computed tomography (CT) scans before and after surgery. RESULTS: Forty-five hip cases (81.8%) showed external FR (mean 13.0°). External FR was significantly correlated with anatomical SA (r = - 0.54) and increase in functional SA (r = 0.36), which was significantly correlated with impingement distance (r = 0.46). The independent factors associated with external FR in multivariate analysis were the anatomical SA, CT densities of the psoas, gluteus medius and maximus muscles, and 2-stage revision (R2 = 0.559). During follow-up period, eight cases of revision THA showed hip dislocation. FR, functional SA, impingement distance, CT density of psoas and gluteus medius muscle, body mass index, number of past operation, and ratio of 2-stage revision THA were significantly different between cases with dislocation and non-dislocation. The odds ratio of FR and impingement distance for hip dislocation was identified as 1.061(95% confidence interval (CI): 1.011-1.114) and 0.901 (95% CI 0.820-0.991), respectively. CONCLUSIONS: Revision THA frequently causes an external FR that functionally increases the SA and impingement risk, particularly in hips with 2-stage revision with psoas and gluteus medius muscle atrophy. Patients who have undergone revision THA and have an excessive external FR may require careful monitoring for possible hip dislocation due to hip joint instability and impingement.

G-CSF Production by Undifferentiated Pleomorphic Sarcoma with Leukemoid Reaction Occurred in the Lower Leg: A Case Report.

CASE: A 46-year-old woman presented with a mass in the lower leg and severe leukocytosis. Diffuse uptake in the bones was detected with F-fluorodeoxyglucose positron emission tomography with computed tomography (F-FDG PET/CT) imaging. The serum granulocyte-colony stimulating factor (G-CSF) was elevated, and immunostaining for G-CSF was positive. When diagnosed as G-CSF-producing undifferentiated pleomorphic sarcoma (UPS), a wide resection was performed. The leukocytosis and serum G-CSF were remarkably improved after tumor resection. No local recurrence or metastasis was detected. CONCLUSION: We report the first case of inflammatory UPS in the extremity which demonstrated the neoplastic production of G-CSF. In our case, F-FDG PET/CT, the serum G-CSF, and immunostaining for G-CSF were useful for diagnosis.

[A CASE OF EXTRASKELETAL EWING'S SARCOMA IN THE RETROPERITONEUM].

A 23-year-old man was admitted to our hospital with a huge pelvic tumor. MRI showed a tumor mixed with a solid component and polycystic cyst with maximum diameter of about 20 cm. Percutaneous tumor needle biopsy was performed and diagnosis was Ewing sarcoma. At that time, operation is extremely difficult, so the neoadjuvant chemotherapy with ifosfamide, etoposide, Adriamycin, and vincristine were administered. After 6 courses, MRI showed tumor reduction to maximum diameter of 10 cm. We planned tumor resection with total cystectomy for radical resection, but we also tried to preserve bladder considering the young age and quality of life. Although the bladder was partially resected, tumor resection was succeeded without removing surrounding organs. Histopathological examination revealed viable cells remained, but more than 95% was disappeared and the surgical margins were negative. Here we report a case of extra skeletal Ewing sarcoma in the retroperitoneum that was treated with chemotherapy and surgery without scarifying surrounding organs.

Prognostic factors in elderly osteosarcoma patients: a multi-institutional retrospective study of 86 cases.

BACKGROUND: The occurrence of osteosarcoma in elderly patients has recently been increasing, and the outcome is poor. This multi-institutional retrospective study was conducted to investigate clinical features and prognostic factors in patients older than 40 years with osteosarcoma. METHODS: Patients with conventional high-grade osteosarcoma older than 40 years were recruited to this study. Secondary osteosarcoma arising from Paget's disease or irradiated bones was excluded. Information on tumor- and treatment-related factors was collected and statistically analyzed. The median follow-up was 57 months (range 8-244 months) for all surviving patients. RESULTS: A total of 86 patients were enrolled in this study. The median age at diagnosis was 61 years. Surgery and chemotherapy were conducted in 73 and 63 % of all patients, respectively. The 5-year overall and event-free survival rates were 38.8 and 34.0 %, respectively. Tumor site (extremity 57.9 %; axial 19.0 %; p < 0.0001), metastasis at diagnosis (yes 12.2 %; no 48.3 %; p < 0.0091), and definitive surgery (yes 56.2 %; no 10.6 %; p < 0.0001) were associated with overall survival. Although patients without metastasis who received definitive surgery were regarded as good candidates for chemotherapy, the addition of chemotherapy did not have any impact on the outcome (yes 63.4 %; no 65.2 %; p = 0.511). CONCLUSIONS: The present study revealed the distinct clinical features, such as the high incidence of truncal tumors or metastasis at diagnosis, in patients older than 40 years with osteosarcoma. Additionally, prognostic factor analyses revealed that tumor site, metastasis at diagnosis, definitive surgery, and surgical margins were significant prognostic factors, whereas chemotherapy did not influence survival.

Changes in physical function after palliative surgery for metastatic spinal tumor: association of the revised Tokuhashi score with neurologic recovery.

STUDY DESIGN: A retrospective study of patients undergoing palliative surgery for metastatic spinal tumors. OBJECTIVE: To investigate short-term functional recovery and duration of improvement after palliative surgery, to correlate these outcomes with the revised Tokuhashi score, and to examine the relationship between function and neurologic deterioration. SUMMARY OF BACKGROUND DATA: The revised Tokuhashi score is a scoring system used to predict life expectancy for patients with metastatic spinal tumors. The relationship between the revised Tokuhashi score and physical functional improvement after palliative surgery has not been examined previously. METHODS: The clinical charts of 86 patients were reviewed. The Eastern Cooperative Oncology Group Performance Status (ECOG-PS) was used to assess physical function. Each score was documented before surgery and at every month after surgery. The duration of ECOG-PS improvement, defined as the period between surgery and deterioration to the preoperative ECOG-PS grade, was correlated with the revised Tokuhashi score. RESULTS: The ECOG-PS grade improved in 44 (51.1%) patients at 1 month postoperative. When ECOG-PS improvement was found after surgery, it persisted above the preoperative level for an average of 9.3 months. At 1 month postoperative, patients scoring 0 to 8 on the total revised Tokuhashi score had significantly lower ECOG-PS improvement (26 of 55 patients) when compared to patients with higher scores (18 of 27 patients, P < 0.05). In 44 patients with ECOG-PS improvement, the existence of major internal organ metastases significantly shortened the duration of improvement (P < 0.05). CONCLUSION: Palliative surgery benefited half of the patients with metastatic spinal tumor, with a greater probability of benefit found in persons with a higher total revised Tokuhashi score (score 9-15) and/or primary cancers with longer survival times.

Underestimation of varus angulation in knees with flexion deformity.

In order to investigate the change in limb alignment in cases of knee flexion deformity, 17 male volunteers aged from 25 to 35 years with no complaints and no knee disorders were selected. The femorotibial angle (FTA), which is the lateral angle at the intersection between the femoral axis and the tibial axis in an anteroposterior radiograph, was employed as an index of limb alignment. FTA in standing on one leg with and without knee flexion was measured. The mean standing FTA was 179.4+/-19 degrees in full extension, which decreased to 176.9+/-2.5 degrees in a mean flexion position of 18+/-3.3 degrees (range 15-25 degrees ) (P<0.002), and in all cases, standing FTA in flexion was smaller (more valgus-angulated) than that in full extension. There was a significant positive relationship with a straight regression line (D=0.101KFA + 0.296, R=0.8505) between the angle of knee flexion (KFA) and the difference (D) in standing FTA between full extension and knee flexion. We conclude that limb alignment became more valgus-angulated with an increase in flexion deformity.