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Chinese Journal of Reparative and Reconstructive Surgery logoLink to Chinese Journal of Reparative and Reconstructive Surgery
. 2019 Jan;33(1):8–12. [Article in Chinese] doi: 10.7507/1002-1892.201808045

单髁关节置换术股骨髓内定位对股骨假体力线影响的影像学研究

Imaging study on effect of femoral intramedullary guide on the alignment of femoral prosthesis in unicompartmental knee arthroplasty

Tao YANG 1, Yihui TU 1,*, Huaming XUE 1, Tong MA 1, Tao WEN 1, Long XUE 1, Fangxing WANG 1, Yu MENG 1
PMCID: PMC8337236  PMID: 30644253

Abstract

Objective

To explore the imaging features of intramedullary guide rod and its influence on the alignment of the femoral prosthesis in unicompartmental knee arthroplasty (UKA).

Methods

Between August 2016 and November 2016, 50 patients (50 knees) with primary anteromedial osteoarthritis were treated with UKA by Oxford MicroPlasty minimally invasive replacement system. There were 10 males and 40 females. The age ranged from 62 to 77 years with an average of 68.8 years. Preoperative varus and flexion deformity angles were (5.22±3.46)° and (7.42±2.65)°, respectively. The knee range of motion (ROM) was (106.85±7.62)°. The Hospital for Special Surgery (HSS) score was 68.26±4.65. The angles between the femoral intramedullary guide rod and the anatomical axis of femur on the coronal and sagittal planes, the femoral component valgus/varus angle (FCVA), the femoral component posterior slope angle (FCPSA), knee varus deformity angle, and knee flexion deformity angle were measured by intra- and post-operative X-ray films. The postoperative ROM and HSS score were measured.

Results

Intraoperative X-ray films measurement showed that the lateral side angles between femoral intramedullary guide rod and femoral anatomical axis were observed on coronal plane, and the angles ranged from 0.28 to 2.06° with an average of 0.96°. While the posterior side angles were observed on sagittal plane, and the angles ranged from 0.09 to 0.48° with an average of 0.23°. The angulations (>1°) between femoral intramedullary part guide rod and outside part of the rod were confirmed in 12 cases (24%) on coronal plane. Postoperative femoral prosthesis were mild varus in 38 patients (76%). The FCVA ranged from –1.76 to 4.08° with an average of 2.21°. The FCPSA ranged from 7.12 to 13.86° with an average of 9.16°. All patients were followed up 22-26 months, with an average of 24.5 months. The incisions healed by first intention. At last follow-up, the varus and flexion deformity angles were (1.82±1.05) and (2.54 ± 1.86)°, respectively. ROM was (124.62±5.85)° and HSS score was 91.58±3.65. There were significant differences between pre- and post-operative parameters (P<0.05). No complication such as dislocation or aseptic loosening of the prosthesis occurred during the follow-up.

Conclusion

UKA by Oxford MicroPlasty minimally invasive replacement system can obtain accurate femoral prosthesis position with the help of intramedullary guide system, and the effectiveness is excellent.

Keywords: Knee joint, unicompartmental knee arthroplasty, femoral intramedullary guide, femoral component alignment

近年来，单髁关节置换术（unicompartmental knee arthroplasty，UKA）广泛用于膝关节单间室骨关节炎的治疗。假体力线是影响 UKA 预后的主要因素之一[1]，研究报道 UKA 术中股骨假体位置偏差高达 32%[2-3]。为解决上述问题，2012 年临床开始采用 MicroPlasty 牛津膝关节微创置换系统（以下简称 MP 系统）进行股骨假体定位[4-5]，并取得了优良的早期疗效[6]。与传统 UKA 术中需术者“手动”股骨侧假体定位不同，MP 系统是通过“铰链式”髓内杆连接器，将股骨髓内导杆和股骨钻孔导引器固定，这种机械式连接理论上使股骨假体力线能符合既定的理想值，从而获得准确的股骨假体位置。目前，关于采用 MP 系统术中股骨髓内定位导杆影像学位置及其对股骨假体力线的影响研究较少。本研究拟通过分析采用 MP 系统行 UKA 的患者术中及术后影像学资料，评估股骨髓内定位导杆实际位置及其对股骨假体力线的影响，为临床手术提供理论依据。报告如下。

1. 临床资料

1.1. 一般资料

患者选择标准：① 原发性膝关节前内侧骨关节炎，并且采用 MP 系统行 UKA；② 疼痛局限于膝关节内侧（髌骨内缘内侧）或伴膝后方疼痛；③ 膝关节屈曲挛缩<15°；④ 膝关节屈曲角度>90°；⑤ 内翻畸形<15° 且可以被动矫正。排除标准：① 类风湿性关节炎、感染性关节炎；② 有膝关节周围骨折或截骨矫形手术史。2016 年 8 月—11 月，共 50 例（50 膝）患者符合选择标准纳入研究。本研究通过医院伦理委员会批准，患者及家属均自愿加入本次研究并签署知情同意书。

本组男 10 例，女 40 例；年龄 62～77 岁，平均 68.8 岁。体质量指数 22.87～24.31 kg/m2，平均 23.72 kg/m2。膝内翻畸形角度为（5.22±3.46）°，屈曲畸形角度为（7.42±2.65）°；膝关节活动度（range of motion，ROM）为（106.85±7.62）°；美国特种外科医院（HSS）评分为（68.26±4.65）分。膝关节炎病程 3～8 年，平均 5.6 年。

1.2. 手术方法

本组手术均由同一术者参照 MP 系统操作步骤完成，采用美国 Biomet 公司 Oxford 第 3 代单髁假体。蛛网膜下腔阻滞麻醉下，患肢取半截石位，即屈髋 30° 置于托腿架上，大腿根部捆扎止血带。屈膝 90°，从髌骨内缘至关节线下 3 cm 处作切口，切除内侧半月板前半部分以及髌骨后脂肪垫，检查前交叉韧带功能。切除股骨内髁内侧缘、髁间窝内外侧缘、髁间窝顶部、内侧副韧带下方和股骨内侧髁后外缘的全部骨赘。将间隙测厚器插入内侧间室中央，插入胫骨锯切导向器，使其长轴与胫骨长轴平行。使用 G 形夹连接股骨间隙测厚器和胫骨锯切导向器，胫骨导向器紧贴胫骨前缘，咬合 G 形夹，将 3 个部件锁定后用螺钉固定导向器。松开 G 形夹，与测厚器一并取出。将锯片插入靠近内侧髁外侧缘髁间窝，在内侧胫骨脊顶点内侧、前交叉韧带止点边缘，指向髂前上棘，垂直向下进行截骨。插入内侧副韧带拉钩，使用摆锯水平截骨完成胫骨平台截骨。膝关节屈曲 45°，在股骨髁间凹前内侧缘及后交叉韧带止点前方 1 cm，紧贴股骨髁间凹内侧壁沿线上朝向髂前上棘钻孔[7-8]，插入髓内导杆，如遇到阻力，切勿用敲击等暴力强行插入。C 臂 X 线机透视满意后，插入股骨钻孔导向器，将髓内杆连接器分别插入髓内导杆及股骨钻孔导向器的侧孔中，调节并确认导向器位于股骨内髁中央后进行股骨钻孔，将股骨后髁截骨导向器插入钻孔内，切除股骨髁后关节面。余股骨髁的碾磨及屈伸间隙平衡等均按照操作手册完成。

1.3. 观测指标

将术中股骨髓内导杆 X 线片及术后膝关节正侧位 X 线片导入 Winning Health TView v6.1.0 软件（上海金仕达卫宁软件股份有限公司）。测量参数：① 股骨髓内导杆与股骨髓腔解剖轴线在冠状位的夹角（α），定义内侧交角为负值、外侧交角为正值；② 股骨髓内导杆与股骨髓腔解剖轴线在矢状位的夹角（β），定义在前方交角为负值、后方交角为正值；③ 股骨假体内外翻角（femoral component valgus/varus angle，FCVA）：假体力线和机械轴夹角，定义内翻为正值、外翻为负值；④ 股骨假体屈曲角（femoral component posterior slope angle，FCPSA）：股骨假体力线和股骨解剖轴线的夹角。见图 1。

图 1.

Schematic diagram of X-ray films

X 线片测量示意图

a、b. 股骨髓内导杆与股骨解剖轴线（M）的夹角；c. FCVA；d. FCPSA

a, b. Angle between the femoral intramedullary rod and femoral anatomical axis (M); c. FCVA; d. FCPSA

图 1

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1.4. 统计学方法

采用 SPSS20.0 统计软件进行分析。数据以均数±标准差表示，手术前后比较采用配对 t 检验；检验水准 α=0.05。

2. 结果

术中 X 线片测量：股骨髓内导杆与髓腔解剖轴线在冠状位均呈外侧交角，α 为 0.28～2.06°，平均 0.96°；在矢状位均呈后方交角，β 为 0.08～0.48°，平均 0.13°。本组股骨髓内导杆在冠状位上均未在股骨髓腔解剖轴线，更靠近股骨内侧皮质；12 例（24%）冠状位上股骨髓内导杆的髓内段和髓外段部分存在成角形变（>1°），形变角为 1.37～4.26°，平均 2.35°。术后 X 线片测量：股骨假体内翻 38 例（76%），FCVA 为–1.76～4.08°，平均 2.21°；FCPSA 为 7.12～13.86°，平均 9.16°。所有股骨假体力线均在推荐范围内。

患者术后切口均Ⅰ期愈合，未出现早期手术相关并发症。50 例均获随访，随访时间 22～26 个月，平均 24.5 个月。末次随访时，膝内翻畸形角度为（1.82±1.05）°、屈曲畸形角度为（2.54±1.86）°，与术前比较差异均有统计学意义（t=27.419，P=0.000；t=15.878，P=0.000）。ROM 为（124.62±5.85）°，HSS 评分为（91.58±3.65）分，与术前比较差异均有统计学意义（t=14.426，P=0.000；t=21.074，P=0.000）。随访期间均未出现衬垫脱位、假体无菌性松动等并发症。见图 2。

图 2.

Anteroposterior and lateral X-ray films of a 72-year-old female patient with medial compartment osteoarthritis of the left knee

患者，女，72 岁，左膝内侧间室骨关节炎正侧位 X 线片

a. 术前；b. 术中；c. 术后 2 年

a. Before operation; b. During operation; c. At 2 years after operation

图 2

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3. 讨论

UKA 股骨假体位置多采用股骨髓内定位方法确定，由于微创小切口下术野暴露有限，股骨假体精准定位仍有一定困难，而假体位置直接影响着术后疗效[5, 9-13]。采用 MP 系统定位股骨假体准确性主要与 3 个因素有关，导杆直径、长短和股骨开髓点位置[14]，其中股骨开髓点位置是最重要因素。既往研究认为，股骨开髓点为股骨滑车中心或稍偏内和股骨髁后交叉韧带止点的前方，但具体位置报道较少且无定论。MP 系统推荐在股骨髁间凹前内侧缘前方 1 cm，髁间凹内侧壁沿线上钻孔开髓[8]。我们术中发现部分患者股骨髁间凹存在明显骨赘增生，需要剔除骨赘后进行开髓点定位。因此，为了提高定位的精准性，本组选择在髁间凹内侧壁沿线上，股骨髁间凹前内侧缘及后交叉韧带止点前方 1 cm 作为股骨开髓点。

目前关于股骨髓内定位导杆位置的影像学研究较少，本研究发现股骨髓内导杆在冠状位上并不完全位于股骨髓腔解剖轴线，而更靠近股骨内侧皮质。股骨髓内导杆与髓腔解剖轴线在冠状位上均呈外侧交角，平均角度为 0.96°；在矢状位上呈后方交角，平均角度为 0.13°。我们认为股骨髓内导杆平行于股骨髓腔解剖轴线。此外，有 12 例（24%）股骨髓内导杆的髓内段和髓外段在冠状位上存在成角形变（>1°），我们分析可能受患者体位、术野范围较小等因素影响，术中髂前上棘的准确判定相对困难，髓内导杆的插入方向存在不确定性，当插入的髓内导杆远端达髓腔内骨皮质时会产生侧向应力，进而导致导杆形变；其次，股骨干侧弯等畸形一定程度影响股骨髓内导杆顺利插入，因此对解剖学异常的特殊患者，我们推荐术前行下肢全长 X 线片，进行详细术前准备。

文献报道 UKA 术后股骨假体位置偏差率相对较高[2-3, 15]，假体力线不良可引起假体撞击，增加聚乙烯衬垫的磨损率，衬垫的磨损最大可达每年 0.08 mm[10]。Kang 等[11]的有限元分析发现，股骨组件内外翻畸形会影响衬垫、外侧间室、副韧带张力，尤其当偏差超过 9° 时。Oxford 研究团队推荐股骨假体力线应平行于下肢机械轴，冠状位上股骨假体内、外翻 ±10° 范围可以接受，矢状位上与股骨解剖轴呈屈曲 10°（屈曲 15°～伸 0° 范围）[11, 16]。本组术后 X 线片测量发现股骨假体轻度内翻 38 例（76%），但所有股骨假体力线均在推荐范围内，未受股骨髓内导杆位置及形变的影响。除了选择最佳的股骨开髓点、精确的截骨以外，还应确保股骨假体位置尽可能在胫骨假体中线上。如果股骨假体位置偏内，衬垫易向膝内侧滑移，不仅会刺激软组织，还可能导致衬垫旋转和脱位[11, 16]。Dunn 等[17]研究报道，UKA 髓内定位技术可以获得良好的术后力线及长期疗效。本组末次随访时患者膝关节内翻和屈曲畸形角度、ROM 及 HSS 评分均较术前有显著改善。随访期间均未出现衬垫脱位、假体无菌性松动等并发症。

但是，本研究存在一些不足，如病例数较少，无下肢全长 X 线片，未考虑股骨干畸形等因素，患者年龄分布较窄，也未考虑性别、身高及体质量差异及对假体位置的影响。因此，需要大样本量进一步探究最佳的股骨髓内定位技术。

Funding Statement

上海市卫生和计划生育委员会临床研究专项课题（201840187）

Clinical Research Project of Shanghai Health and Family Planning Commission (201840187)

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