Reliability of stress radiography in the assessment of coronal laxity following total knee arthroplasty

BackgroundStress radiography is used in the valuation of soft tissue laxity following total knee arthroplasty (TKA). However, reliability and agreement is largely unknown.MethodsIn this prospective reliability study, we included 15 participants with prior TKA. Standardized coronal stress radiographs were obtained in both extension and flexion and with both varus and valgus stress. All radiographs were repeated (test–retest). In extension the Telos stress device was used, and flexion radiographs were obtained using the epicondylar-view. Three independent raters measured angulation between femoral and tibial component from all radiographs. Reliability was assessed by intra-class correlation coefficient (ICC) and agreement visualized with Bland–Altman plots and by mean difference and limits of agreement (LOA).ResultsStress radiography in extension showed excellent reliability with ICC = 0.96 (0.95–0.98) and LOA of ± 1.2°. Stress radiography at 80–90° of flexion showed good to excellent reliability when measuring medial laxity with ICC = 0.94 (0.89–0.97) and LOA of ± 1.7°; however, when measuring lateral laxity the reliability was only moderate to good with ICC = 0.70 (0.51–0.84) and LOA of ± 6.3°.ConclusionStress radiography is clinically applicable and the methods described in this study provide excellent reliability for measurement of laxity in extension. The reliability of measurements in flexion is good to excellent when measuring medial laxity but only moderate to good when measuring lateral laxity.     

Antagonist muscle moment is increased in ACL deficient subjects during maximal dynamic knee extension

IntroductionCoactivation of the hamstring muscles during dynamic knee extension may compensate for increased knee joint laxity in anterior cruciate ligament (ACL) deficient subjects. This study examined if antagonist muscle coactivation during maximal dynamic knee extension was elevated in subjects with anterior cruciate ligament (ACL) deficiency compared to age-matched healthy controls.MethodsElectromyography (EMG) and net knee joint moments were recorded during maximal concentric quadriceps and eccentric hamstring contractions, performed in an isokinetic dynamometer (ROM: 90–10°, angular speed: 30°/s). Hamstring antagonist EMG recorded during concentric quadriceps contraction was converted into antagonist moment based on the EMG–moment relationship observed during eccentric agonist contractions.ResultsThe magnitude of antagonist hamstring EMG was 65.5% higher in ACL deficient subjects compared to healthy controls (p < 0.05). Likewise, antagonist hamstring moment expressed in percentage of the measured net extension moment was elevated in ACL deficient subjects (56 ± 8 to 30 ± 6%) compared to controls (36 ± 5 to 19 ± 2%) at 20–50° of knee flexion (0° = full extension) (p < 0.05).DiscussionThe results showed a marked increase in hamstring coactivation towards more extended joint positions. Notably, this progressive rise in coactivation was greater in ACL deficient subjects, which may reflect a compensatory strategy to provide stability to the knee joint in the anterior–posterior plane during isolated knee extension. The present study encourages further investigations of hamstring coactivation in ACL deficient subjects.     

Preoperative rotational assessment of the distal femur with CT may cause femoral component malrotation in TKA

BackgroundBefore total knee arthroplasty (TKA), rotational assessment of the distal femur can be performed using either magnetic resonance imaging (MRI) or computed tomography (CT). Until now, there has been no study comparing the two modalities regarding rotational assessment of the distal femur in the same patients.MethodsWe retrospectively reviewed the preoperative CT and MRI images of 110 knees in 110 patients who underwent TKA. In the axial planes of CT and MRI scan, the posterior condylar axis (PCA), anatomical transepicondylar axis (aTEA), and perpendicular line to anteroposterior axis (pAPA) were identified; the angles between these studied lines were calculated. During TKA, the angles measured on the preoperative CT and MRI were compared with the measurements obtained in the intraoperative field.ResultsThe mean aTEA-PCA angle was 6.2 ± 1.9° with CT and 5.1 ± 1.8° with MRI. The mean pAPA-PCA angle was 4.7 ± 2.1° with CT and 3.5 ± 2.0° with MRI. The mean aTEA-PCA (1.1 ± 1.3°, p = 0.001) and pAPA-PCA (1.2 ± 1.2°, p = 0.012) angles significantly differed between CT and MRI. Intra-operatively, the mean aTEA-PCA angle was 4.7 ± 1.1° and the mean pAPA-PCA angle was 3.2 ± 0.9°. Reliability analysis between the preoperative CT/MRI and the intraoperative measurements gave kappa values of 0.72 for aTEA-PCA and 0.66 for pAPA-PCA with CT, and 0.82 for aTEA-PCA and 0.84 for pAPA-PCA with MRI.ConclusionsPreoperative rotational assessment of the distal femur with CT may cause higher external rotation of femoral component in TKA.     

股骨远端解剖形态性别差异与假体形态设计的关系

目的：通过三维螺旋CT重建正常人膝关节，测量股骨远端相关解剖参数，探讨男女性股骨远端的解剖特点对于关节表面假体形态的不同要求。方法：80侧正常成人膝关节，男性、女性各40侧，年龄18～72岁，行三维螺旋CT扫描，在GE Advantage workstation工作站上进行0．625mm层厚重建，测量股骨经上髁轴线宽度、内外侧髁高度、髁间高度及内外侧滑车前突距离，行模拟截骨后，测量各截骨面高度，比较各测量值性别问的差异。结果：男女性髁间高度、经上髁轴线宽度、外侧髁高度及内侧髁高度均有显著性差异（P〈0．001），男性各值均大于女性。股骨远端横径与纵径的比值亦为男性大于女性（P〈0．001），男性股骨内、外侧滑车前突距离均大于女性，均值差分别为1．2mm和0．7mm，均有显著性差异（P〈0．001）。结论：男女性之间股骨髁形态存在一定差别，股骨远端关节面假体形态的设计应该性别差异化，使假体与截骨面更好的吻合。以提高全膝关节置换术的手术效果。     

Antagonist moment of force during maximal knee extension in pubertal boys: effects of quadriceps fatigue

The examination of the moment exerted by the hamstrings during maximum isokinetic knee extensor tests is useful when comparing isokinetic strength and muscle activity patterns between children and adults. The purpose of this study was to examine the effect of antagonist moment of the hamstrings on the isokinetic moment of the knee extensors in pubertal children and to determine whether this effect is altered following a fatigue task. Eighteen healthy pubertal males [age 14.3 (0.5) years] performed 34 maximal isokinetic concentric efforts of the knee extensors at 60°·s⁻¹. The average moment of force and electromyographic (aEMG) signal of vastus medialis (VM), vastus lateralis (VL) and biceps femoris (BF) at 11–30°, 31–50°, 51–70° and 71–90° of knee flexion were calculated for each repetition. The hamstrings antagonist moment was determined before and after the fatigue task by fitting the aEMG–moment relationship at different levels of muscle effort using second-degree polynomials. The percentage contribution of the antagonist moment to the resultant joint moment ranged from 7.1 % to 60.4 % throughout the range of motion, with the highest percentage observed close to full knee extension (11–30°). The antagonist effect was significantly greater during concentric tests of the knee extensors compared to the corresponding eccentric tests (p<0.05). Following the fatigue test, there was an overall decline of the resultant joint moment, but no changes in the predicted hamstrings moment were observed. These results indicate that when testing maximal knee extensor isokinetic strength in pubertal boys, activity of the hamstrings implies a reduction of the net extensor moment as compared to the isolated capacity of the knee extensors. However, this antagonist effect is not altered following the performance of an isokinetic fatigue knee extension task. Electronic Publication     

Mechanical measures during maximal velocity knee extension exercise and their relation to fibre composition of the human vastus lateralis muscle

Summary A method for measuring the maximal velocity of knee extension exercise is described using a very light lever arm. Instrumentation of the lever arm with a potentiometer and accelerometer also allows for the measurement of peak acceleration, time to peak acceleration, the average rate of development of acceleration (jerk) and peak torque. With this apparatus and surface electromyography, electromechanical delay (EMD) was also determined. This apparatus was tested using 17 female and 10 male subjects, and the measures obtained were related to the percentage of fast twitch fibres (% FT) and the relative area of fast twitch fibres (% FTA) in the vastus lateralis determined from duplicate muscle biopsy samples. Peak velocity of unloaded knee extension averaged 12.1±1.2 and 12.2±1.7 rad · s^–1 for females and males, respectively, and were not significantly different. As well, peak acceleration, time to peak acceleration jerk and EMD values were not significantly different between the female and male subjects, but the mean peak torque for the female subjects (73.5±14.7 N · m) was significantly lower than that for the males (98.4±31.5 N · m). Peak acceleration was significantly correlated with %FT (r=0.40,P=0.04) for the total subject population. None of the other measures was significantly related to either %FT or %FTA for the male and female subjects or the combined population of subjects.     

Anatomical features of tibia and femur: Influence on laxity in the anterior cruciate ligament deficient knee

Background

Until now, there has been a lack of in vivo analysis of the correlation between bony morphological features and laxity values after an anterior cruciate ligament (ACL) injury.

Periprosthetic fractures in the distal femur following total knee replacement: A review and guide to management

The management of distal femoral fractures following a total knee replacement can be complex and requires the equipment, perioperative support and surgical skills of both trauma and revision arthroplasty services. Recent advances in implant technology have changed the management options of these difficult fractures. This article describes the options available and discusses the latest evidence.     

Perceived exertion and maximal quadriceps femoris muscle strength during dynamic knee extension exercise in young adult males and females

The objectives of the present study were to: (1) examine perceived exertion across different target voluntary-contraction intensities; (2) compare perceived exertion ratings with actual target intensities, and (3) compare perceived exertion ratings between males and females. Subjects for this study included 30 healthy, college-aged male (n=15) and female (n=15) volunteers. All subjects were free of orthopedic, cardiopulmonary, systemic and neurological disease. Subjects were evaluated for their one-repetition maximum (1-RM) during inertial knee extension exercise. All subjects then completed, in a random order, two sub-maximal inertial contractions at 20%, 30%, 40%, 50%, 60%, 70%, 80%, and 90% of their 1-RM. Perceived exertion was measured by asking subjects to provide a number that corresponded to the feelings in their quadriceps after completion of the two repetitions, by viewing a modified category-ratio (CR-10) scale. The results showed that males lifted a significantly greater absolute (P<0.05) and relative (P<0.05) amount of mass than females; allometric-modeled strength values also demonstrated significant sex differences. The results revealed a significant intensity main effect (P<0.001) but no significant gender main effect (P=0.97) nor intensity-by-gender interactions (P=0.50) for the perceived exertion responses. The findings demonstrated that perceived exertion was significantly (P<0.05) lower than the specific expected values on the CR-10 scale from 10% to 60% of 1-RM, but was not different from 70% to 90% 1-RM. The results revealed that the increase in perceived exertion was fit to both linear and quadratic trends, and that the exponent of the power function was found to be 1.437 (SD 0.22) for the males, and 1.497 (0.295) for the females. The major findings demonstrate that although males were able to lift more absolute and relative mass than females, the perceptual response to relative load was similar between genders. The increase in perceived exertion, as a function of relative load, showed a strong linear trend; however, enhanced perceptual sensitivity at high contraction intensities was evident from the positively accelerating power function. Electronic Publication     

The effect of medial condylar bone loss of the knee on coronal plane stability--a cadaveric study

IntroductionThe quantitative effects of medial bone loss of the knee on both leg alignment and coronal plane stability are poorly understood.Materials and methodsUtilizing computer navigation, 5 mm bone defects of the medial distal femur (MDF), medial posterior femoral condyle (MPF), and medial tibial plateau (MT) were simulated in 10 cadaveric limbs, and alignment of the knee at various degrees of flexion were analyzed when applying standardized varus and valgus loads.ResultsThe 5 mm MPF defect significantly increased varus laxity at 90° of flexion by 3.3° ± 1.2° (p = 0.019), a 5 mm MDF defect resulted in a 2.2° ± 1.7° (p = 0.037) and a 2.1° ± 1.3° (p = 0.023) increase in laxity at 0° and 30° of flexion, respectively, and a 5 mm MT defect increased varus laxity at all flexion angles by 4.0° to 7.0°, but was only statistically significant at 30° (p = 0.026).DiscussionThis study confirms and quantifies the theories of flexion and extension gap balancing, and pseudolaxity of the medial collateral ligament in the varus knee, the results of which can be used in preoperative planning and intraoperative decision making for both total knee and unicondylar arthroplasty.     

Fatigability during repetitive maximal knee extensions in 14-year-old boys

The isokinetic forces, during 50 repeated maximal knee extensions with a constant velocity of 3.14 rad · s^–1, and muscle cross-sectional area (CSA) of the quadriceps femoris muscles were measured for boys aged 14 years (n = 26) and young adult men (n = 26). As representative scores in the maximal session, the mean values of force ( ) of every five consecutive and all trials were calculated. The CSA was measured by using a B-mode ultrasound technique at the midpoint of the thigh length (l _t). The average values of at the 1st–5th contractions were 193 (SEM 12) N for the boys and 303 (SEM 13) N for the young adults. The average decline of with 50 contractions, expressed as a percentage of the value in the 1st–5th trial, was higher in the young adults than in the boys: for the young adults was reduced by 48 (SEM 2.9)%, for the boys by 36 (SEM 3.1)%. The of every five consecutive and all trials were significantly correlated to the product of CSA andl _t (CSA ·l _t) in separate groups: for the boysr = 0.762–0.894 (P < 0.01), for the young adultsr = 0.598–0.837 (P < 0.01). In a trial range between the 1st–5th and 11th–15th contractions, the young adults showed significantly higher values in the ratio of to CSA ·l _t ( · CSA^–1 ·l _t) than the boys. However, the difference between groups of the ratio on and after the 16th–20th trial and for all trials became insignificant. Thus, at least for 50 maximal repeated knee extensions, the 14-year-old boys were inferior to the young adults in their ability to produce force during the earlier sessions even when the difference in muscle size was allowed for. The inferiority in the boys might be attributed to a lower reliance on glycolysis as pointed out in previous biochemical studies.     

Association of knee flexion angle after posterior-stabilized total knee arthroplasty with postoperative tibial external position relative to the femur and the extent of tibial internal rotation from knee extension to flexion

BackgroundThis study evaluated the relationship between preoperative and postoperative knee kinematics, moreover, investigated tibial rotational position and the extent of tibial internal rotation from knee extension to flexion as factors to obtain significant knee flexion after total knee arthroplasty (TKA).MethodsFifty-four patients (60 knees total; 15 males, 16 knees; 39 females, 44 knees) who underwent posterior-stabilized TKA using a navigation system were included. Intraoperative knee kinematics involving tibial rotational position relative to the femur and the extent of tibial internal rotation were examined at two time points: 1) after landmarks registration (pre-TKA) and 2) after skin closure (post-TKA). The relationship between the knee flexion angle at one year postoperatively and intraoperative tibial rotational position, or the extent of tibial rotation among several knee flexion angles calculated with a navigation system were investigated.ResultsThe postoperative knee flexion angle was positively associated with the preoperative flexion angle and intraoperative knee kinematics at post-TKA involving tibial external position relative to the femur at knee extension and the extent of tibial internal rotation from extension to 90° of flexion or to maximum flexion. There was a positive relationship between the extent of tibial internal rotation at pre-TKA and that at post-TKA.ConclusionsThe intraoperative kinematics of the extent of tibial internal rotation at post-TKA was influenced by that at pre-TKA. The greater external position of the tibia relative to the femur at knee extension and the greater extent of tibial internal rotation at post-TKA might lead to good knee flexion angle.     

Prolonged muscle vibration reduces maximal voluntary knee extension performance in both the ipsilateral and the contralateral limb in man

Previous studies have shown that prolonged vibration of the rectus femoris decreases maximal voluntary knee extension performance in the ipsilateral leg. In the present study, measurements of maximal voluntary isometric knee extension contractions with the ipsilateral (right) leg and the contralateral (left) leg were made immediately before and after vibration treatment. Significant reductions in maximal force and maximum rate of force generation occurred in both the ipsilateral and contralateral legs following 30 minutes of continuous vibration at both 30 Hz and 120 Hz, with 30 Hz causing the greatest ipsilateral effects. However, although the level of neural activation (iEMG) of the vibrated muscle (right rectus femoris) was reduced following 30 Hz vibration (P=0.026), there were no significant changes occurring in a synergistic muscle (right vastus lateralis) or in either contralateral muscle. It was concluded that muscle vibration may act through spinal reflex pathways to influence the homonymous motoneuron pool. The effects on contralateral force but not specific muscle iEMG suggest an effect on heteronymous motoneuron pools or an effect acting on central descending drive to contralateral muscles. These findings may have implications for the rehabilitation of patients with an immobilised limb. Electronic Publication     

Sex difference in force generation capacity during repeated maximal knee extensions

The force generation capacity, during 50 repeated maximal knee extensions with a constant velocity of 3.14 rad · s^–1, and cross-sectional area (CSA) of the quadriceps femoris muscles were determined for untrained women (n = 36) and men (n = 27) aged from 18 to 25 years. As force scores in the maximal repetitions, the mean values of force ( ) of every 5 consecutive and all trials and the percentage of decline of (%D) with 50 contractions were calculated. The CSA was measured by using a B-mode ultrasound technique at the midpoint of the thigh length. The decreased from 303 (SEM 13) N at the 1st–5th trial to 155 (SEM 9) N at the 46th–50th trial for the men, and from 202 (SEM 9) N to 94 (SEM 4) N for the women. The of every 5 consecutive and all trials were significantly correlated to muscle CSA: for the men r = 0.552–0.872 (P < 0.01) and for the women r = 0.609–0.857 (P < 0.01). The men showed significantly higher at every 5 consecutive trials than the women even when calculated per unit muscle CSA ( ·CSA^–1). There were significant correlations between %D and ·CSA^–1 at the 1st–5th trial: r = 0.538 (P < 0.01) for the men and r = 0.631 (P < 0.01) for the women, respectively. The average values of %D were almost the same in both sexes: for the men 48 (SEM 3) % and for the women 52 (SEM 2) %, respectively. However, an ANCOVA calculation on %D, using ·CSA^–1 the 1st–5th trial as the covariate, indicated that the women had significantly higher %D than the men. Thus, the force output during the maximal repetitions was significantly correlated to the CSA of quadriceps femoris in both sexes. The force output was lower in the women than in the men even when the difference in the muscle CSA was allowed for. The women had higher %D than the men when force output per unit muscle CSA during the initial 5 repetitions was compared.     

Varus-valgus laxity correlates with pain in osteoarthritis of the knee

Pain during osteoarthritis (OA) of the knee does not necessarily correlate with the severity of the radiographic grade, and the mechanism of pain has not been completely clarified. The purpose of this study was to evaluate risk factors for pain in the knee OA using epidemiologic analyses. We evaluated 518 out of 4183 people over the age of 40 (156 males and 362 females) from Shinyoshitomi village, Japan. Mean ages were 63.8 years for men and 60.7 years for women. Screening included a physical examination of the knee and a standing AP roentgenogram of the bilateral knee. Radiographic OA was defined as a Kellgren-Lawrence grade 2 or higher. All data were coded and pain risk factors were evaluated using a multiple logistic regression model. Radiographic OA was observed in 18.4% of men and 26% of women. Of these subjects with OA, 10.9% of men and 32.5% of women complained of knee pain. Seven factors-age, gender, BMI, radiographic grade, varus-valgus laxity, torque of quadriceps muscles, and varus-valgus alignment-were evaluated as potential risk factors for pain. A significant increase in the odds ratio was observed with varus-valgus laxity (p=0.005; odds ratio, 3.04). Our results suggest that varus-valgus laxity is a risk factor for pain during knee OA.     

Sectional anatomy of the adrenal gland in the coronal plane

To provide practical anatomic data for the imaging diagnosis and surgical treatment of adrenal disease, we investigated the anatomy of the adrenal gland and its relationships to regional structures using 31 sets of serial coronal sections of upper abdomen of Chinese adult cadavers and correlated coronal magnetic resonance (MR) images of ten upper abdomens of adult healthy volunteers and coronal reconstructed multislice spiral computed tomography (MSCT) images of five patients without lesions in the adrenal gland. The adrenal glands were visualized mainly on the successive coronal sections between 18 mm anterior to the posterior margin of inferior vena cava and 24 mm posterior to the posterior margin of inferior vena cava. In general, the left adrenal gland was visualized two sections earlier than the right adrenal gland. On the plane through the anterior parts of bilateral renal hili (A₁₈), the appearance rate of bilateral adrenal glands was 100%, and the maximal measurements of bilateral adrenal glands were visualized. The length, width, thickness of right adrenal body, thickness of medial limb and lateral limb were, respectively, 34.02 ± 2.12 mm, 10.91 ± 0.89 mm, 5.82 ± 0.26 mm, 2.78 ± 0.08 mm, 2.62 ± 0.06 mm, whereas the measurements of left adrenal gland were 28.31 ± 2.46 mm, 18.40 ± 1.06 mm, 6.84 ± 0.24 mm, 3.02 ± 0.08 mm, 2.86 ± 0.07 mm, respectively. The coronal plane has superior advantage in showing the bilateral adrenal glands. The shapes of adrenal glands are various, whereas the range of adrenal thickness is quite narrow. The thickness of adrenal medial and lateral limbs, especially the thickness of lateral limb are useful for the diagnosis of the bilateral adrenocortical disease.     

Differences in the electromyographic activity of the hamstring muscles during maximal eccentric knee flexion

This study investigated the effects of the knee joint angle and angular velocity on hamstring muscles’ activation patterns during maximum eccentric knee flexion contractions. Ten healthy young males (23.4 ± 1.3 years) performed eccentric knee flexion at constant velocities of 10, 60, 180, and 300 deg/s in random order. The eccentric knee flexion torque and the surface electromyographic (EMG) activity of the biceps femoris (BF), semitendinosus (ST), and semimembranosus (SM) muscles were measured. The results of torque during 10 deg/s were lower than the faster velocities. No significant change was found in eccentric torque output and the EMG amplitude with change in the faster test velocities, although those values showed a decreasing tendency as the knee approached extension. Furthermore, the EMG amplitude of the BF decreased significantly as the knee approached extension, although the EMG activity of the ST and SM remained constant. These results suggest that the neural inhibitory mechanism might be involved in decreasing in maximal voluntary force and hamstring muscles activation toward the knee extension during high-velocity eccentric movement and therefore subjects have difficulties to maintain high eccentric force level throughout the motion. Moreover, the possible mechanism reducing the BF muscle activation as the knee approaches extension was architectural differences in the hamstring muscles, which might reflect each muscle’s function.     

膝关节股骨远端软骨硬化前后力学性能分析

目的建立膝关节有限元模型,研究正常及软骨硬化情况下膝关节的应力、应变变化,为临床治疗膝关节骨性关节炎提供参考。方法通过Mimics、ANSYS等软件结合正常膝关节CT扫描图像数据,建立膝关节三维有限元模型,并施加350 N压力载荷,设定软骨硬化前后相关的材料参数,分析膝关节主要组织的应力、应变改变情况。结果膝关节股骨远端软骨硬化后,关节软骨的减震和传递负荷等作用基本消失;股骨应力、应变变化量最大,受力分布极不均匀,股骨前端应力、应变较内、外侧髁明显,整体受力也有明显增加;半月板的应力、应变值最大。结论长期的软骨破坏会影响关节软骨营养代谢,导致骨性关节炎疾病进一步恶化。研究结果可以较好阐释骨性关节炎发病过程和机理,同时为建立参数化研究系统提供相关数据。     

Normalized EMG to normalized torque relationship of vastus intermedius muscle during isometric knee extension

The purpose of the present study was to investigate the electromyography (EMG) to torque relationship of the vastus intermedius (VI) muscle. Thirteen healthy men performed maximal voluntary contraction (MVC) and submaximal contraction during isometric knee extension at 10% of the MVC to 90% of the MVC at intervals of 10% of the MVC level. Surface EMG was detected from four muscle components of the QF muscle group, i.e., VI, vastus lateralis (VL), vastus medialis, and rectus femoris (RF) muscles. Normalized muscle activation in the VI muscle was significantly lower than in the VL muscle at a lower torque level (20 and 40% of MVC) and significantly lower compared to the RF muscle at a higher torque level (from 60 to 90% of MVC). These results suggest that neuromuscular activation in the VI muscle is not consistent with the other components of QF muscle group during submaximal knee extension contractions.     

Intraosseous leiomyosarcoma arising in the epiphysis of the distal femur

Herein, we present a rare case of intraosseous leiomyosarcoma arising in the epiphysis of the distal femur and showing unusual radiographic features. A 44-year-old man presented with a pain in the left knee joint. Computed tomography revealed an intraosseous lesion with slightly increased attenuation and a thin marginal sclerotic rim in the femoral medial condyle. The signal of the lesion was hypointense on T1-weighted magnetic resonance (MR) images and hyperintense on fat-suppressed T2-weighted MR images. After gadolinium administration, the signal of the lesion was moderately and diffusely enhanced. The histological diagnosis of leiomyosarcoma was made based on a preoperative core biopsy specimen. Microscopic examination of the resected specimen revealed an ill-defined intraosseous tumor composed of proliferated atypical and mildly pleomorphic smooth muscle cells permeating among the bone trabeculae with only focal destruction of the bone trabeculae and low mitotic activity, indicating low grade leiomyosarcoma. The bone trabeculae at the periphery of the tumor were mildly thickened and anastomosed with a rim of an increased number of osteoblasts. Systemic examination showed no tumorous lesions in other anatomical sites. Leiomyosarcomas rarely present in the bone as a diffuse intertrabecular growth, even in low grade tumors.