股骨近端外侧壁的确切解剖区域、厚度、高度、面积等参数的确定有助于明确骨折分型和相关治疗方案，但目前仍未形成统一的意见，有待于进一步研究。本文是关于外侧壁的厚度的争议和观点。
外侧壁（lateral wall）的概念是由以色列骨科医生Yechiel Gotfried于2004年正式提出的。外侧壁被誉为近20年来股骨转子间骨折治疗的三大重要进展之一（另二项是尖顶距和皮质支撑）。
外侧壁的背景
外侧壁是一个服务于临床的外科概念（surgical concept），特指头颈骨块内固定物（拉力螺钉或螺旋刀片）在股骨干外侧打入部位的骨皮质，即股外侧肌嵴远侧至小转子之间的股骨皮质。 描述外侧壁的参数，包括： 长、宽、高、厚度、面积等几何参数； 骨骼质地强度等生物力学参数； 亦有骨性外侧壁和软组织外侧壁的概念。
外侧壁的厚度
外侧壁厚度（lateral wall thickness）由台湾Hsu等（许承恩，2013）提出。他将外侧壁残留骨质厚度定义为：
在正位X线片上，于大转子无名结节下3cm做一标记点 然后与股骨干呈135°作1条直线，与转子间骨折线相交 骨折线与外侧壁的两点之间的距离（前后侧骨皮质残留长度的平均值）为外侧壁残留骨质厚度（图1）
▲ 图1 X片测量：台湾Hsu等测量的外侧壁厚度，实为沿135°方向，残留的前、后侧皮质长度的平均值，以20.5mm为界 文中所指外侧壁厚度，即是使用DHS时主钉钉道从外侧骨皮质到骨折线的长度。当外侧壁残留骨质厚度<20.5mm时，不应当使用DHS固定。 Hsu等（2015）在进一步的研究中发现，当A2型骨折的外侧壁厚度<22.4mm时，使用DHS加大转子稳定钢板（trochanteric stabilizing plate, TSP）固定，能够有效减小股骨头颈拉力螺钉滑出退钉的距离，可以降低外侧壁破裂的发生率和再次手术率。 外侧壁危险边界的研究，直接改变了AO/OTA学会关于股骨转子间骨折的分型： 2018-AO/OTA分型中，将股骨转子间骨折A1型和A2型，根据外侧壁的残留厚度（以20.5mm为分界线）进行划分，不再依据是否具有内侧小转子骨块进行划分（图2）。对新分类中外侧壁完整的A1型骨折，推荐使用DHS，优点是价格便宜、隐性失血少、效果也挺好。
▲ 图2 左图：2018-AO/OTA股骨转子间骨折分类；右图：A2型厚度d≤20.5mm
争议1——外侧壁的厚度
针对Hsu发表在2013年BJJ的研究，不少学者提出了疑问和讨论（见后附文），总结成10条：
急诊X片质量问题，测量点标定不准确（包括无名结节和骨折线交点）； 下肢外旋的影响，外旋度数不同影响的大小不同，致使作者的结果在均数之外有很大的标准差（标准差比两组之间的均数差别还大）； 下肢牵引内旋位可以增加摄片的质量和测量的准确性，但增加病人的痛苦； 测量没有放大标尺； 打入导针的次数，可能对外侧壁的损坏更为重要； 没有考虑冠状面外侧壁骨折； 测量外侧壁的面积更有价值； 骨骼大小的差别； 在正位上将螺钉打入正中或中下的差别（接受TAD或Cal-TAD的差别）； 称这个测量参数为“外侧壁厚度（lateral wall thickness）”，有歧义，容易误导。【该数据实际上是“残留的前后皮质长度的平均值（图3）（a mean distance of the remnant length of anterior and posterior cortex）”】。
▲ 图3 CT测量：与股骨干呈135°方向（头颈主钉进钉位置），测量前后皮质环的弧长,分为前侧、外侧及后侧三段（anterior cortex, lateral wall cortex, posterior cortex），残留的前壁皮质长度（a）总是大于后壁长度（p）。 Sharma等（2016）发现，当皮质环的前侧部分<2.10cm（相当于前壁残留皮质厚度）时，使用DHS容易发生外侧壁破裂而导致内固定失败。
附一：Hsu等论文的争论（2013发表在BJJ文章）
对Hsu等2013发表在BJJ文章的争论，参阅BJJ杂志网络版： 
1.Comment I
时间: 15 August 2013
作者：Aatif Mahmood, Registrar Orthopaedics；Other Contributors——Gunasekaran Kumar MS Orth, FRCS (Glasg), FRCS (Tr&Orth). Consultant Trauma and Orthopaedics. Royal Liverpool University Hospital 原文：
We read this paper with interest. The concept that lateral wall thickness (LWT) is directly related to the risk of failure of the DHS is logical. However, measuring LWT on the basis of radiographs taken in the emergency department is not easy. Since the distal fragment is externally rotated, identifying the distal end of the innominate tubercle of the greater trochanter becomes difficult. The measurement of LWT will also vary significantly in the same fracture depending on the degree of rotation. In this paper, the difference in LWT of patients with an A2 fracture with and without lateral wall fracture (LWF) was 4.8mm. Measurements were made on radiographs without markers and assumed 120% magnification. It is difficult to assign significance to a figure of 4.8mm when the standard deviation for each group is >5mm. In A1 fractures there was no significant difference in LWT between the groups with and without a LWF but the numbers are small. Interestingly, all A1 fractures with a LWF healed, whereas two without a LWF failed. The authors have tried to quantify a difficult problem. However, it is not sufficient to have a best cut-off of 20.5mm based on radiographs without magnification markers, with varying rotations of distal femoral shaft fragment and without taking into consideration the effects of other variables. We feel that one of the important factors which increases the risk of LWF is the number of attempts made to pass the guide wire. More attempts mean more 'pepper potting'（类似撒辣椒粉，打成筛网状） of the lateral cortex which increases the risk of fracture. Another factor is an unrecognised coronal LWF, which can be present even in an A1 fracture, which propagates and makes the DHS fixation unstable. 总结成8点： Identifying the distal end of the innominate tubercle of the greater trochanter becomes difficult. The measurement of LWT will also vary significantly in the same fracture depending on the degree of rotation. Measurements were made on radiographs without markers and assumed 120% magnification. In this paper, the difference in LWT of patients with an A2 fracture with and without lateral wall fracture (LWF) was 4.8mm. It is difficult to assign significance to a figure of 4.8mm when the standard deviation for each group is >5 mm. It is not sufficient to have a best cut-off of 20.5mm based on radiographs without magnification markers, with varying rotations of distal femoral shaft fragment and without taking into consideration the effects of other variables. One of the important factors which increases the risk of LWF is the number of attempts made to pass the guide wire. More attempts mean more “pepper potting' of the lateral cortex which increases the risk of fracture. an unrecognised coronal LWF, which can be present even in an A1 fracture, which propagates and makes the DHS fixation unstable.
2.Authors' Reply
原文： We thank Mr Mahmood and Mr Kumar for their interest in our paper. We agree with them that the measurement of lateral wall thickness (LWT) varies with femoral rotation. We think that this effect was also one of the causes of the standard deviation being more than 5mm in the A2 fracture group. However, we believe that, on average, a genuinely thin and narrow lateral wall will be measured as thinner on a radiograph than a thick and broad lateral wall even with some external rotation when the radiograph is taken in the emergency room.
With aninter trochanteric fracture, there are usually two lines projected on the radiographs by the fractured anterior and posterior edges of the cortex. These change their position when radiographs are taken in different degrees of femoral rotation. However, the midline between these two lines is less affected by rotation. By using it as the point of measurement, the effect of femoral rotation on the measurement of LWT is decreased.
On a two-dimensional radiograph, the LWT is a measurement which evaluates both lateral wall thickness and width, which is an important predictor of post-operative fracture of the lateral wall. The cut-off value 20.5mm is based only on radiological measurement. We believe that there are still many factors which contribute to post-operative lateral wall fracture such as bone matrix density, BMI and the number of attempts made to pass the guide wire (thanks to Dr Mahmood and Mr Kumar forraising this point), and we hope that a further study with a multifactorial analysis of lateral wall fracture can be performed.
3.Comment II
时间: 2 October 2013
作者：Qing Li, S-C Du, S-M Chang，李清，杜守超，张世民 原文： First, the lateral femoral wall, also called trochanteric lateral wall, is defined anatomically as the lateral femoral cortex distal to the vastus ridge. The real thickness of the lateral wall is the thickness of the lateral cortex. However, the concept defined by the authors is actually a mean distance between the fracture line and the lateral cortex, which contains the lateral femoral cortex and the remaining anterior and posterior cortex. So the definition itself is rather puzzling and somewhat misleading.
Second, the lateral wall provides natural lateral cortical support to the head-neck fragment. When a pertrochanteric fracture is fixed with a sliding compression hip screw, loss of support of the lateral wall leads to uncontrollable sliding of the hip screw, which will initially cause excessive lateral displacement of the head-neck fragment and medial displacement of the shaft, and finally result in cut-out of the lag screw from the femoral head, or pull-out of the cortical screws from the femoral shaft.1,2 The diameter of a DHS socket is 16mm, so about 200mm2 of the lateral cortex is removed when a surgeon implants a sliding hip screw.1 The maneuver per se damages the integrity of the lateral wall. We think the area of lateral wall (height × width) may be of greater use to estimate the risk of lateral wall disruption peri-operatively.3 As the fracture line in pertrochanteric fractures runs obliquely from the greater to the lesser trochanter, the distance measured by the authors may be directly related to the size of the lateral wall and can therefore also reflect the integrity of the lateral cortex.
Third, from a clinical perspective of the lateral wall, we agree with the authors' suggestion that intertrochanteric fractures are classified into three types: intact, vulnerable, and fractured. If the lateral wall is intact (AO/OTA subtype-31A1and A2.1), the incidence of lateral wall fracture after surgery is low. The use of a DHS is appropriate and safe in these types of fracture. When the lateral wall is vulnerable (AO/OTA subtype-31-A2.2 and A2.3), iatrogenic lateral wall rupture can occur intra-operatively, especially in osteoporotic patients. Under these circumstances, we prefer to use a cephalomedullary nail or percutaneous compression plate to a DHS. If the lateral wall has already fractured pre-operatively (AO/OTA subtype-31A3), the consensus of opinion is to use an intramedullary nail.
附二：Hsu等论文的争论（2015发表在INJURY的文章） 针对Hsu发表在2015年INJURY的论文，亦有读者评论LETTER-TO-EDITOR：
时间: 2016
作者：Sun LL, Li Q, Chang SM，孙莅伦，李清，张世民 来源：Sun LL, Li Q, Chang SM. The thickness of proximal lateral femoral wall. Injury.2016, 47(3): 784-785. 原文： We read with great interest the article by Hsu et al.1 entitled “Trochanter stabilising plate improves treatment outcomes in AO/OTA 31-A2 intertrochanteric fractures with critical thin femoral lateral walls” (Injury 2015; 46:1047-53). The authors demonstrated that lateral wall thickness is the main risk factor for postoperative lateral wall fracture by DHS fixation, and using TSP with critically thin lateral wall thickness of <2.24cm can significantly decrease the rate of failure and reoperation. However, we have some different views and would like to comment on some points about the concept of lateral wall thickness. First, the lateral femoral wall, also called the lateral femoral cortex, or trochanteric lateral wall,2-5 is defined anatomically as the lateral cortex proximal to the vastus ridge and distal to the plane of the lesser trochanter. The area can provide a nature buttress for the femoral head-neck fragment and fixation. The real thickness of the lateral wall should be the exact thickness of the lateral cortex, which is usually 2-4mm in CT measurement (Fig.1). But the concept defined by the authors is actually a mean distance between the fracture line and the lateral cortex, which contains the lateral femoral cortex and the remaining anterior and posterior cortex, i.e. the sum of the remnant length of anterior and posterior cortical wall plus the lateral wall thickness.1,6 So the definition itself is different from the original meaning and maybe somewhat of misleading.
▲ Fig. 1. The exact thickness of lateral femoral wall, measured on axial CT image of a 77-year-old man with pertrochanteric fracture. The thickness was 2.1mm. Second, the lateral wall is a natural lateral cortical support to the head-neck fragment. When a pertrochanteric fracture (A1 and A2) is fixed by sliding compression hip screw, loss of the support of lateral wall will lead to uncontrollable sliding of the hip screw, initially resulting in excessive lateral displacement of the head-neck fragment and medial displacement of the femoral shaft, and finally result in lag screw cut-out from the femoral head, or cortical screw pull-out from the femoral shaft. The diameter of DHS socket is 16mm, that is to say, about 200mm2 lateral cortex is removed when the surgeon put in the sliding hip screw. The maneuver per se damages the integrity of the lateral wall. We think the area of lateral wall (height times width) may be a more valuable parameter to estimate the risk of lateral wall rupture peri-operatively.4 As the fracture line in pertrochanteric fractures runs in oblique along the greater-lesser trochanter direction, the distance measured by the authors may have a positive relationship to the size of the lateral wall, therefore it can also reflect the integrity of the lateral cortex.1
Third, with a clinical perspective of the lateral wall, we agree with the suggestion to classify the intertrochanteric fractures into three types: intact, vulnerable, and fractured. If the lateral wall is intact (AO/OTA subtype-31A1and A2.1), the incidence of lateral wall fracture after surgery is low. DHS is valid and safe in these types of fractures. When the lateral wall is vulnerable(AO/OTA subtype-31-A2.2 and A2.3), the lateral wall is compromised, iatrogenic lateral wall rupture could be happen during operative procedure, especially in osteoporotic patients. We prefer to use cephalomedullary nail or PCCP to DHS. If the lateral wall is already fractured pre-operatively (AO/OTA subtype-31A3), consensus has been made to use intramedullary nail by most surgeons.
参考文献：
1. C.E. Hsu, Y.C. Chiu, S.H. Tsai, T.C. Lin, M.H. Lee, K.C. Huang.Trochanter stabilising plate improves treatment outcomes in AO/OTA 31-A2 intertrochanteric fractures with critical thin femoral lateral walls. Injury, 46 (2015), pp. 1047-1053. 2. Y. Gotfried. The lateral trochantericwall: a key element in the reconstruction of unstable pertrochanteric hipfractures. Clin Orthop Relat Res, 425 (2004), pp. 82-86. 3. G.I. Im, Y.W. Shin, Y.J. Song. Potentially unstable intertrochanteric fractures. J Orthop Trauma, 19 (2005), pp. 5-9. 4. H. Palm, S. Jacobsen, S. Sonne-Holm, P. Gebuhr.Integrity of the lateral femoral wall in pertrochanteric hip fractures: an important predictor of a reoperation. J Bone Joint SurgAm, 89-A (2007), pp. 470-475. 5. Z. Ma, S.M. Chang. Letter tothe editor: where is the lateral femoral wall? IntOrthop, 38 (2014), pp. 2645-2646. 6. C.E. Hsu, C.M. Shih, C.C. Wang, K.C. Huang. Lateral femoral wall thickness: a reliable predictor of post-operativelateral wall fracture in pertrochanteric fractures. Bone Joint J, 95-B (2013), pp. 1134-1138. — END —
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