基于热力图分析膝骨关节炎(KOA)患者的内翻畸形与胫骨平台下低密度影面积的关联性。

回顾性分析2020年6月至2021年4月广州中医药大学第三附属医院诊断为KOA的患者406例(594膝)的影像学及临床资料。纳入标准：符合KOA影像学和临床表现诊断标准；年龄≥50岁；影像学检查显示力线正常或者膝内翻畸形。排除标准：膝外翻畸形；影像学资料不全；过去半年内曾服用过影响骨代谢药物的患者；因关节外畸形而影响膝关节下肢负重力线者。根据患者负重位下肢全长片测量下肢负重力线，并根据下肢负重力线将患者分为三组：力线正常组(力线位于胫骨髁间嵴)、轻度内翻组(力线位于胫骨内侧平台)和重度内翻组(力线超出胫骨内侧平台)。收集记录患者年龄、身体质量指数(BMI)等指标。将患者的膝关节负重正位片导入E-3D软件，提取胫骨平台下低密度影的轮廓线，通过Image-Pro Plus 6.0软件测量轮廓线内的面积。轮廓线匹配至标准膝关节模型上，采用单因素方差分析比较3组患者年龄、BMI、胫骨平台下低密度影的位置及面积。

406例(594膝)患者中男12例(16膝)，女394例(578膝)，双膝188例，单膝218例；平均年龄(69±8)岁。所有患者均完成测量分析，其中力线正常组66膝，轻度内翻组351膝，重度内翻组177膝。三组患者年龄和BMI差异无统计学意义(均为P>0.05)。比较3组热力图发现，力线正常组的胫骨平台下低密度影位于胫骨平台下正中，其低密度影范围最小；重度内翻组较力线正常组、轻度内翻组两组的低密度影位置最接近胫骨内侧皮质骨，且范围最大。力线正常组的平均面积为(6 568±519)mm²，轻度内翻组平均面积为(7 266±577)mm²，重度内翻组平均面积为(8 240±485)mm²，三组对比差异有统计学意义(F＝293.140，P<0.001)。

胫骨平台下低密度影面积是影响膝骨关节炎患者内翻畸形严重程度的重要危险因素。胫骨平台下低密度影面积与膝骨关节炎患者的内翻畸形严重程度呈正相关。

To analyse the correlation between varus deformity of knee osteoarthritis (KOA) and area of low-density region under tibial plateau on the basis of thermography.

Imaging and clinical data of 406 patients (594 knees) diagnosed with knee osteoarthritis, from June 2020 to April 2021, in our hospital were retrospectively analysed. The inclusion criteria were: those who met the diagnostic criteria in X-ray images and clinical manifestations of KOA; age ≥50 years old; X-ray showed a normal mechanical alignment or otherwise a deformity of genu varum. Exclusion criteria were: genu valgus deformity, incomplete imaging data, those had been taking drugs that affected bone metabolism in last six months and alignment of lower limbs was affected by non-articular deformity. Alignments of lower limbs were measured according to full-length lower limb X-ray in weight-bearing position. The patients were divided into three groups according to the lower limb alignments. The patients were assigned in the normal group while the alignment of lower limb was found across the tibial intercondylar eminence, those in the mild varus group had the alignment of lower limb across the medial tibial plateau and those in the severe varus group were found that the alignment of lower limb extended beyond the medial tibial plateau. A retrospective analysis was performed to compare the age, body mass index (BMI) and other indicators among the three groups. Anteroposterior weight-bearing X-ray images of the knees in three groups were imported into E-3D software to extract the contour of the low-density region under tibial plateau. Area within the contour was then measured and calculated by Image-Pro Plus 6.0 software. The contours were then mapped with the standard knee models and the locations and areas of the low-density regions under tibial plateaux between the three groups were compared by one-way ANOVA.

Of the 406 patients (594 knees), there were 12 males (16 knees) and 394 females (578 knees), including 188 bilateral knees and 218 single knees. The age of the patients was (69±8) years. There were 66 knees in the normal group, 351 knees in the mild varus group and 177 knees in the severe varus group. Comparison of general data of the patients showed that there was no statistically significant difference in age and BMI among the three groups (all P>0.05). Thermographs confirmed that, in the normal group, the low-density region under tibial plateau was located in the middle under the tibial plateau with a smallest size of low-density region in the three groups. Low-density region in the severe varus group was closer to the medial tibial cortical bone and with the largest size than the other two groups. The average area in the normal group was found at (6 568±519) mm², (7 266±577) mm² in the mild varus group and (8 240±485) mm² in the severe varus group. The differences between the three groups were statistically significant (F=293.140, P<0.001).

Low-density region under tibial plateau shown by an X-ray image is an important risk factor of the severity of genu varus deformity in patients with knee osteoarthritis. The region of low-density under tibial plateau is positively correlated with the severity of genu varus deformity in patients with knee osteoarthritis.