Eur Spine J DOI 10.1007/s00586-013-3140-7
ORIGINAL ARTICLE
How can we optimize anterior iliac crest bone harvesting? An anatomical and radiological study Mickae¨l Ropars • Alexandre Zadem • Xavier Morandi • Rajiv Kaila • Raphae¨l Guillin Denis Huten
•
Received: 20 August 2013 / Revised: 12 December 2013 / Accepted: 13 December 2013 Springer-Verlag Berlin Heidelberg 2013
Abstract Purpose Anterior iliac crest bone is a widely used donor site for bone harvesting. It provides an autologous bone graft consisting of cancellous bone that can be packed or cortical bone with greater structural support. Uses include spinal fusion and fracture non-union surgery. Although its use is common, dedicated anatomical and radiological studies analysing graft dimensions and optimal harvesting site in relation to local anatomical landmarks [anterior superior iliac spine (ASIS), anterior iliac tubercle (AIT) and lateral femoral cutaneous nerve (LFCN)] have not been described. Methods Twenty-eight female hemipelvises were dissected for this study. The LFCN, ASIS and AIT were identified. Calliper measurements and CT scan analysis were undertaken to determine the optimum positions in obtaining a 5-mm-thickness tricortical graft whilst remaining safe for the LFCN. Results According to our measurements, the optimal location for harvesting a 5-mm-thick tricortical graft with
M. Ropars X. Morandi Anatomy Laboratory, Faculty of medicine of Rennes, 2 Avenue du Professeur Le´on Bernard, 35043 Rennes, France M. Ropars (&) A. Zadem R. Kaila D. Huten Orthopedics and Trauma Department, Pontchaillou University Hospital, 2 Rue Henri le Guilloux, 35000 Rennes, France e-mail: [email protected] X. Morandi Neurosurgery Department, Pontchaillou University Hospital, 2 Rue Henri le Guilloux, 35000 Rennes, France R. Guillin Radiology Department, Hospital Sud University, 16 Boulevard de Bulgarie, 35000 Rennes, France
35-mm height and 47-mm width is situated anterior to a line passing at the level of the thickest point of the AIT. This thickest point was situated at a mean 67 mm from the centre of the EIAS in our study. Conclusion This anatomical and radiographic study determined the anatomical iliac crest landmarks to avoid neurological injury when taking an optimal 5-mm-width tricortical bone graft. Keywords Iliac crest Bone harvesting Lateral femoral cutaneous nerve
Introduction The iliac crest bone is the most common donor site for bone harvesting [3, 6, 10]. The anterior part of the iliac crest provides a reliable donor site, enabling monocortical, bicortical or tricortical vascular or avascular grafts [21]. When considering anterior spinal surgery, the anterior iliac crest is preferred to the posterior crest, due to easier access during the supine procedure, avoiding the need to turn the patient. However, the anterior iliac crest has a higher level of donor site morbidity compared to harvesting posteriorly [3, 32]. Major complications include iliac ring fracture [41] and hernias, but commoner ones consist of less severe problems such as haematoma, superficial infection, poor aesthetic result, chronic donor site pain [32] and injury to the lateral femoral cutaneous nerve (LFCN). Injury to the LFCN has been reported in up to 21 % [6] when attempts to identify it are made. Morbidities include dysesthaesia, temporary or permanent sensation loss and meralgia paraesthetica. Several anatomical studies have explained this high rate of complication as a consequence of the variations in the route of the nerve [12, 13, 17, 26,
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33, 34, 38]. A lateral position in relation to the anterior superior iliac spine (ASIS) increases the risk of potential nerve damage during iliac crest bone harvesting [33, 40]. This lateral position during tricortical bone graft harvesting puts the LFCN at risk due to its closeness to the iliac crest. To limit damage to adjacent structures, several surgical techniques have been proposed, including minimally invasive harvesting [9, 37]. However, these techniques are most appropriate when only a small cancellous bone graft is required [28]. Risks of complications are increased when a large graft is needed, requiring a larger approach. According to the mean thickness of the inner cortex, outer cortex and cancellous bone of the iliac crest reported by Mahato [23], a minimal half-centimetre-width crest measurement was defined as being a useful graft. A minimal 1-cm-width large structural bone graft could be considered to be adequate, but the maximum length and height of such a bone block harvested from the anterior iliac crest remain too small according to this study [23]. Our study aimed to define a safe and optimized approach for harvesting a tricortical bone graft with at least a half-centimetre width at the level of the anterior iliac crest and to determine its maximum dimensions (length, height) using cadaveric dissection and CT studies.
Materials and methods This work was conducted in accordance with the ethical standards set by the committee on human experimentation. We dissected 28 hemipelvises and thighs of formalin-fixed female Caucasian cadavers with a mean age of 71 years (62–78 years) and a mean height of 159 cm (range 150–168 cm). Only prosections that had not been dissected previously were used. An ilio-inguinal approach was used [22] to identify the LFCN in all specimens. The route of the nerve was followed from its pelvic origin until division into its two branches as it exited the pelvis (Fig. 1). The distance from the medial edge of the ASIS to the LFCN along the line of the ilio-inguinal ligament was recorded in millimetres using a calliper. The thickness of the ilium was measured on a vertical line at the level of the ASIS, the thickest point of the anterior iliac tubercle (AIT) and three locations situated 2 and 3 cm posterior to the centre of the ASIS and 2 cm posterior to the thickest point of the AIT to include the entire ‘‘anterior iliac tubercle’’. The thickness of the iliac crest was measured orthogonally to the direction of the iliac crest. Distances between the LFCN in its pelvic origin to the five points were measured during dissections (Fig. 2). Once the bony measurements were performed, the dissected iliac wings were removed using an oscillating saw
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Fig. 1 Endopelvic view of a dissection. LFCN (1), femoral nerve (2) and iliac artery (3) are individualized. Five iliac crest bone points used for measurements (green and blue pins) are shown. Notice the variation of the distance between the iliac crest and LFCN along the endopelvic route
and analysed with a CT scan after removal of the muscular attachments. A bone window (window level 500 HU; window width 2500 HU) and a 1-mm slice thickness were used for the CT scan study. Using 3D reconstructions, the same defined five points were assessed, and the distance from the iliac crest to the inferior limit of the optimal bone graft (e.g., thickness [5 mm) was measured on the five defined vertical lines. The distances from the iliac crest to the LFCN and to the inferior limit of a useful graft at the level of the five points were recorded. This provided data to avoid LFCN injury and useful bony landmarks for harvesting a bone graft of useful thickness [5 mm.
Results In our 28 dissections, we found that the site at which the LFCN exits the pelvis was situated medial to the medial edge of the ASIS in all specimens at a mean 22-mm distance (range 5–50 mm). Nine dissections showed an LFCN ensheathed in the inguinal ligament. The thickest point of the AIT was located at a mean 67 mm (range 53–80 mm) from the ASIS with a mean thickness of 15 mm (range 12–22 mm). No difference was noted between the bony anatomical landmarks and graft thickness found during dissection and CT scan analysis of the iliac wing. The distances from the iliac crest to the LFCN and to the inferior limit of a useful graft at the level of the five points are listed in Table 1. As indicated in Table 1, a safe and useful area can be defined to start at a point situated 2 cm posterior to the ASIS until the level of the thickest part of the AIT. Its mean length was 47 mm and mean depth 35 mm (Fig. 3).
Eur Spine J
Fig. 2 The thickness of the ilium was measured at the level of the anterior superior iliac spine (1), the thickest point of the anterior iliac tubercle (4) and three starting points situated 2 and 3 cm posterior to the centre of the ASIS (2, 3) and 2 cm posterior to the thickest point of the AIT (5). The thickness of the iliac crest was measured
orthogonally to the direction of the iliac crest. A minimal halfcentimetre-width crest measurement was defined as being a useful graft. Distances between the LFCN in its endopelvic portion and those five points were also measured during dissection (a, b, c, d, and e)
Table 1 Distances between iliac crest and LFCN in the endopelvic route and optimal thickness Bony landmarks
Mean distance from the iliac crest to LCFN (measured during dissections) (mm)
Mean distance from the iliac crest to the inferior limit of the optimal bone graft (thickness C5 mm) (mm)
EAIS
22 (5–55)
Non measured
2 cm posterior to EIAS
43 (22–65)
44 (20–65)
3 cm posterior to EIAS
48 (27–68)
42 (24–67)
Centre of the AIT
63 (32–74)
37 (22–65)
2 cm posterior to AIT
[65
24 (13–60)
In most of the cases studied, it was not useful to harvest 2 cm posterior to the thickest point of the AIT, because the height of a useful graft quickly decreased to \30 mm at this level (Fig. 4).
Discussion Autogenous bone graft is routinely harvested from the anterior iliac crest during a wide range of surgical
Fig. 3 CT scan reconstruction of a safe and useful graft. It starts from a point situated 2 cm posterior to the ASIS and ends up at the level of the thickest part of the AIT. Its mean length was 47 mm and its mean depth was 35 mm
procedures. This site offers the possibility of cortical, cancellous and cortico-cancellous bone harvesting, providing a sufficient amount of bone for many indications including maxillofacial reconstruction [1, 2, 7, 8, 16, 24,
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• •
Optimized length of the graft with at least 5-mm-width graft. Optimized height of the graft.
Positioning of surgical incision in relation to the LFCN
Fig. 4 Posterior CT scan view of a left side anterior iliac crest removed after dissection. Notice the weak thickness of the iliac crest at the posterior and inferior part of the anterior iliac crest, \5 mm for a 25-mm width in this case
31], anterior cervical spine surgery and fracture non-union [35, 36]. The potential quantity of harvested bone is half that compared to the posterior iliac crest, but can be more appropriate in situations that would require repositioning the patient such as when performing posterior spinal surgery [3]. In some procedures including cervical anterior fusion, required harvest amounts are smaller [35] compared to those required in reconstructive oral and maxillofacial surgery [25]. However, bicortical or tricortical grafts of various dimensions are frequently necessary and have motivated the present study, with the purpose of standardizing and optimizing the technique of anterior iliac crest bone harvesting. In this study, a minimum 5-mm thickness was considered as a useful graft. This thickness corresponds with values reported by Mahato [23] to a 2.5mm cortical part (sum of inner and outer cortex) and a 2.5mm cancellous bone graft. Despite the frequent use of anterior iliac crest bone harvesting and its significant rate of complications and morbidity, only a few studies have described the morphology of the anterior part of the ilium and its implications on surgical technique of graft harvesting and occurrence of complications [11, 23]. In practice, only two bony and variable anatomical landmarks can be used: the ASIS and the AIT. Using these two landmarks, we have highlighted four main points in undertaking adequate and safe anterior iliac crest bone harvesting (AICBH): • •
The positioning of surgical incision in relation to the LFCN. Safe distance from the ASIS to the anterior limit of the graft, to prevent stress fracture of the ASIS.
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The surgical incision should be parallel and distal to the iliac crest, beginning at least 2 cm posterior and laterally to the ASIS [6, 27]. This incision preserves the skin around the ASIS, which avoids fibrous scar healing [19] and limits inclusion of a variant of the LFCN course that has been reported in human cadavers by several authors [27, 29, 33, 34]. The LFCN has various courses and locations in relation to the ASIS. The most dangerous type reported by Aszmann et al. [5] occurs in 4 % of cases with the LFCN exiting through the abdominal wall 2–3 cm posterior to the ASIS and crossing the iliac crest. This course is the most superficial location of all types and the most dangerous during AICBH. In the majority of cases, the LFCN exits from the pelvis about 2 cm medially to the ASIS, with variable relationships to the soft tissues (inguinal ligament and sartorius muscle in particular). Safe distance from the ASIS to the anterior limit of the graft The safe distance from the ASIS to the anterior limit of the graft is around 2–3 cm [41]. In our study, iliac thickness at 2 or 3 cm posterior to the ASIS was always [5 mm (Table 1). This indicated that a useful zone for graft harvesting is 2 cm posterior to the ASIS. Interestingly, if the graft is harvested from an area about 30 mm posterior to the ASIS, the risk of fracture at the harvesting site is biomechanically 2.4 times lower than at 15 mm [18] and, furthermore, the LFCN is farther from the iliac wing and less at risk (see Table 1). According to these landmarks, 2 cm appears to be the minimum safe distance and could be increased to 3 cm. Optimized length of the graft The length of a useful graft was \47 mm in our study. Should a graft longer than 50 mm be required, consideration needs to be made to utilize other donor sites such as a fibular or tibial graft, although such long grafts are rarely needed during spine surgery, except in spinal tumour surgery [15]. Additionally, according to our study, the graft should be harvested just anterior to a line passing at the level of the thickest point of the AIT. Murata et al. [29] reported the same and it was emphasized by Ebraheim et al. [14], the ‘‘anterior iliac tubercle’’ being defined as the crest zone situated 3–6 cm posterior to the medial edge of the ASIS.
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Murata et al. [30] also reported that the posterior part of the anterior iliac crest segments contains a minimum amount of cancellous bone (see Fig. 4). This is probably due to the thinning of the iliac blades (iliac fossae) at the level of this region. Khamanarong et al. [20] in his anatomical study confirmed that the optimal harvesting bone material is situated 3–5 cm posterior to the ASIS and is more than 15-mm thick at its upper part. As reported by Murata et al. [29] another reason to limit the length of the graft is to avoid LCFN injury which was significantly higher (20 %) when the graft was 45 mm or more in length, 16 % when 30–45 mm and 8 % when \30 mm. Kurz et al. [21] highlighted also that the frequency of complications is related to the amount of soft tissue dissection, which supports that the severity of complications is related to the size of the harvested graft. A too long graft has a risk of detaching the abductor muscles (tensor of fascia lata and gluteus muscles) and could compromise their function. An extended muscle release could also result in altered contour of the iliac crest anteriorly. Optimized height of the graft We found that the maximal height of a useful graft (thickness[5 mm) was 35 mm. In his prospective study of 212 patients who underwent AICBH, Murata et al. [30] reported that the risk of injury to the LFCN was significantly increased when iliac graft higher than 30 mm was harvested. Additionally, he demonstrated that tricortical graft harvesting was associated with a higher rate of LFCN complications. In these cases, LCFN injury could be due to excessive retraction of the iliacus muscle during exposure of the inner table of the ilium and/or electrocoagulation. This also explains the higher incidence of meralgia paraesthetica [4, 39] in cases where tricortical or both inner and outer iliac tables are harvested. Regarding the high rate of injury to the LFCN between 5 and 21 %, patients undergoing spinal surgery with AICBH should be informed of the risk of LFCN damage, whatever the required graft size, despite favourable results by 3 months [3, 6, 29].
Conclusion The problem of donor site morbidity after autologous anterior iliac crest bone graft harvesting may be reduced by improved harvesting techniques including using anatomical reference points. The graft should not exceed 35-mm depth and 45-mm length and should be situated anterior to the thickest part of the AIT. By respecting these landmarks, extensive muscle release and harvesting of grafts too thin can be avoided. Finally, it is important to remark that our study reports on findings following a study limited to
female pelvises and Caucasian morphology. The dimensions reported in this study could be slightly different in males and/or taller patients. Further studies are needed to determine if these dimensions are significantly different in men and in Asian populations. Conflict of interest
None.
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Eur Spine J 17. Hospodar PP, Ashman ES, Traub JA (1999) Anatomic study of the lateral femoral cutaneous nerve with respect to the ilioinguinal surgical dissection. J Orthop Trauma 13:17–19 18. Hu R, Hearn T, Yang J (1995) Bone graft harvest site as a determinant of iliac crest strength. Clin Orthop 310:252–256 19. Hwang K, Nam YS, Kim DJ, Han SH, Hwang SH (2007) Could skin retraction incision minimize nerve injury over the iliac crest? J Craniofac Surg 18:1447–1450 20. Khamanarong K, Kosuwon W, Sirichativapee W, Saejung S, Thepsuthammarat K (2005) Thicknesses of the iliac crest appropriate for anterior cervical interbody fusion grafts. J Med Assoc Thai 88:1892–1895 21. Kurz LT, Garfin SR, Booth RE Jr (1989) Harvesting autogenous iliac bone grafts. A review of complications and techniques. Spine 14:1324–1331 22. Letournel E, Judet R, Elson RA (1993) Fractures of the ace´tabulum, 2nd edn. Springer, Berlin 23. Mahato NK (2011) Characterization of cortico-cancellous bone along the iliac crest: focus on graft harvesting. Surg Radiol Anat 33:433–437 24. Matsa S, Murugan S, Kannadasan K (2012) Evaluation of morbidity associated with iliac crest harvest for alveolar cleft bone grafting. J Maxillofac Oral Surg 11:91–95 25. Matteo MT, Simone S, Francesco DN, Alessandro M, Enrico F, Giulio G, Sandro P (2013) Intracortical versus anteromedial approach for iliac crest bone harvesting in preprosthetic surgery: a randomized prospective clinical trial. J Craniofac Surg 24:369–372 26. Mirovsky Y, Neuwirth M (2000) Injuries to the lateral femoral cutaneous nerve during spine surgery. Spine 25:1266–1269 27. Mischkowski RA, Selbach I, Neugebauer J, Koebke J, Zo¨ller JE (2006) Lateral femoral cutaneous nerve and iliac crest bone grafts––anatomical and clinical considerations. Int J Oral Maxillofac Surg 35:366–372 28. Missiuna PC, Gandhi HS, Farrokhyar F, Harnett BE, Dore EM, Roberts B (2011) Anatomically safe and minimally invasive transcrestal technique for procurement of autogenous cancellous bone graft from the mid-iliac crest. Can J Surg 54:327–332 29. Murata Y, Takahashi K, Yamagata M, Shimada Y, Moriya H (2000) The anatomy of the lateral femoral cutaneous nerve, with special reference to the harvesting of iliac bone graft. J Bone Joint Surg Am 82:746–747
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30. Murata Y, Takahashi K, Yamagata M, Sameda H, Moriya H (2002) Injury to the lateral femoral cutaneous nerve during harvest of iliac bone graft, with reference to the size of the graft. J Bone Joint Surg Br 84:798–801 31. Nkenke E, Weisbach V, Winckler E, Kessler P, Schultze-Mosgau S, Wiltfang J, Neukam FW (2004) Morbidity of harvesting of bone grafts from the iliac crest for preprosthetic augmentation procedures: a prospective study. Int J Oral Maxillofac Surg 33:157–163 32. Pollock R, Alcelik I, Bhatia C, Chuter G, Lingutla K, Budithi C, Krishna M (2008) Donor site morbidity following iliac crest bone harvesting for cervical fusion: a comparison between minimally invasive and open techniques. Eur Spine J 17:845–852 33. de Ridder VA, de Lange S, Popta JV (1999) Anatomical variations of the lateral femoral cutaneous nerve and the consequences for surgery. J Orthop Trauma 13:207–211 34. Ropars M, Morandi X, Huten D, Thomazeau H, Berton E, Darnault P (2009) Anatomical study of the lateral femoral cutaneous nerve with special reference to minimally invasive anterior approach for total hip replacement. Surg Radiol Anat 31:199–204 35. Shamsaldin M, Mouchaty H, Desogus N, Costagliola C, Di Lorenzo N (2006) Evaluation of donor site pain after anterior iliac crest harvesting for cervical fusion: a prospective study on 50 patients. Acta Neurochir 148:1071–1074 36. Skeppholm M, Olerud C (2013) Pain from donor site after anterior cervical fusion with bone graft: a prospective randomized study with 12 months of follow-up. Eur Spine J 22:142–147 37. Spallone A (2007) A less-invasive technique for harvesting autologous iliac crest grafts for cervical interbody fusion: technical note. Surg Neurol 67:160–162 38. Su¨ru¨cu¨ HS, Tanyeli E, Sargon MF, Karahan ST (1997) An anatomic study of the lateral femoral cutaneous nerve. Surg Radiol Anat 19:307–310 39. Williams PH, Trzil KP (1991) Management of meralgia paresthetica. J Neurosurg 74:76–80 40. Yang SH, Wu CC, Chen PQ (2005) Postoperative meralgia paresthetica after posterior spine surgery: incidence, risk factors, and clinical outcomes. Spine 30:547–550 41. Zermatten P, Wettstein M (2012) Iliac wing fracture following graft harvesting from the anterior iliac crest: literature review based on a case report. Orthop Traumatol Surg Res 98:114–117
ORIGINAL ARTICLE
How can we optimize anterior iliac crest bone harvesting? An anatomical and radiological study Mickae¨l Ropars • Alexandre Zadem • Xavier Morandi • Rajiv Kaila • Raphae¨l Guillin Denis Huten
•
Received: 20 August 2013 / Revised: 12 December 2013 / Accepted: 13 December 2013 Springer-Verlag Berlin Heidelberg 2013
Abstract Purpose Anterior iliac crest bone is a widely used donor site for bone harvesting. It provides an autologous bone graft consisting of cancellous bone that can be packed or cortical bone with greater structural support. Uses include spinal fusion and fracture non-union surgery. Although its use is common, dedicated anatomical and radiological studies analysing graft dimensions and optimal harvesting site in relation to local anatomical landmarks [anterior superior iliac spine (ASIS), anterior iliac tubercle (AIT) and lateral femoral cutaneous nerve (LFCN)] have not been described. Methods Twenty-eight female hemipelvises were dissected for this study. The LFCN, ASIS and AIT were identified. Calliper measurements and CT scan analysis were undertaken to determine the optimum positions in obtaining a 5-mm-thickness tricortical graft whilst remaining safe for the LFCN. Results According to our measurements, the optimal location for harvesting a 5-mm-thick tricortical graft with
M. Ropars X. Morandi Anatomy Laboratory, Faculty of medicine of Rennes, 2 Avenue du Professeur Le´on Bernard, 35043 Rennes, France M. Ropars (&) A. Zadem R. Kaila D. Huten Orthopedics and Trauma Department, Pontchaillou University Hospital, 2 Rue Henri le Guilloux, 35000 Rennes, France e-mail: [email protected] X. Morandi Neurosurgery Department, Pontchaillou University Hospital, 2 Rue Henri le Guilloux, 35000 Rennes, France R. Guillin Radiology Department, Hospital Sud University, 16 Boulevard de Bulgarie, 35000 Rennes, France
35-mm height and 47-mm width is situated anterior to a line passing at the level of the thickest point of the AIT. This thickest point was situated at a mean 67 mm from the centre of the EIAS in our study. Conclusion This anatomical and radiographic study determined the anatomical iliac crest landmarks to avoid neurological injury when taking an optimal 5-mm-width tricortical bone graft. Keywords Iliac crest Bone harvesting Lateral femoral cutaneous nerve
Introduction The iliac crest bone is the most common donor site for bone harvesting [3, 6, 10]. The anterior part of the iliac crest provides a reliable donor site, enabling monocortical, bicortical or tricortical vascular or avascular grafts [21]. When considering anterior spinal surgery, the anterior iliac crest is preferred to the posterior crest, due to easier access during the supine procedure, avoiding the need to turn the patient. However, the anterior iliac crest has a higher level of donor site morbidity compared to harvesting posteriorly [3, 32]. Major complications include iliac ring fracture [41] and hernias, but commoner ones consist of less severe problems such as haematoma, superficial infection, poor aesthetic result, chronic donor site pain [32] and injury to the lateral femoral cutaneous nerve (LFCN). Injury to the LFCN has been reported in up to 21 % [6] when attempts to identify it are made. Morbidities include dysesthaesia, temporary or permanent sensation loss and meralgia paraesthetica. Several anatomical studies have explained this high rate of complication as a consequence of the variations in the route of the nerve [12, 13, 17, 26,
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33, 34, 38]. A lateral position in relation to the anterior superior iliac spine (ASIS) increases the risk of potential nerve damage during iliac crest bone harvesting [33, 40]. This lateral position during tricortical bone graft harvesting puts the LFCN at risk due to its closeness to the iliac crest. To limit damage to adjacent structures, several surgical techniques have been proposed, including minimally invasive harvesting [9, 37]. However, these techniques are most appropriate when only a small cancellous bone graft is required [28]. Risks of complications are increased when a large graft is needed, requiring a larger approach. According to the mean thickness of the inner cortex, outer cortex and cancellous bone of the iliac crest reported by Mahato [23], a minimal half-centimetre-width crest measurement was defined as being a useful graft. A minimal 1-cm-width large structural bone graft could be considered to be adequate, but the maximum length and height of such a bone block harvested from the anterior iliac crest remain too small according to this study [23]. Our study aimed to define a safe and optimized approach for harvesting a tricortical bone graft with at least a half-centimetre width at the level of the anterior iliac crest and to determine its maximum dimensions (length, height) using cadaveric dissection and CT studies.
Materials and methods This work was conducted in accordance with the ethical standards set by the committee on human experimentation. We dissected 28 hemipelvises and thighs of formalin-fixed female Caucasian cadavers with a mean age of 71 years (62–78 years) and a mean height of 159 cm (range 150–168 cm). Only prosections that had not been dissected previously were used. An ilio-inguinal approach was used [22] to identify the LFCN in all specimens. The route of the nerve was followed from its pelvic origin until division into its two branches as it exited the pelvis (Fig. 1). The distance from the medial edge of the ASIS to the LFCN along the line of the ilio-inguinal ligament was recorded in millimetres using a calliper. The thickness of the ilium was measured on a vertical line at the level of the ASIS, the thickest point of the anterior iliac tubercle (AIT) and three locations situated 2 and 3 cm posterior to the centre of the ASIS and 2 cm posterior to the thickest point of the AIT to include the entire ‘‘anterior iliac tubercle’’. The thickness of the iliac crest was measured orthogonally to the direction of the iliac crest. Distances between the LFCN in its pelvic origin to the five points were measured during dissections (Fig. 2). Once the bony measurements were performed, the dissected iliac wings were removed using an oscillating saw
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Fig. 1 Endopelvic view of a dissection. LFCN (1), femoral nerve (2) and iliac artery (3) are individualized. Five iliac crest bone points used for measurements (green and blue pins) are shown. Notice the variation of the distance between the iliac crest and LFCN along the endopelvic route
and analysed with a CT scan after removal of the muscular attachments. A bone window (window level 500 HU; window width 2500 HU) and a 1-mm slice thickness were used for the CT scan study. Using 3D reconstructions, the same defined five points were assessed, and the distance from the iliac crest to the inferior limit of the optimal bone graft (e.g., thickness [5 mm) was measured on the five defined vertical lines. The distances from the iliac crest to the LFCN and to the inferior limit of a useful graft at the level of the five points were recorded. This provided data to avoid LFCN injury and useful bony landmarks for harvesting a bone graft of useful thickness [5 mm.
Results In our 28 dissections, we found that the site at which the LFCN exits the pelvis was situated medial to the medial edge of the ASIS in all specimens at a mean 22-mm distance (range 5–50 mm). Nine dissections showed an LFCN ensheathed in the inguinal ligament. The thickest point of the AIT was located at a mean 67 mm (range 53–80 mm) from the ASIS with a mean thickness of 15 mm (range 12–22 mm). No difference was noted between the bony anatomical landmarks and graft thickness found during dissection and CT scan analysis of the iliac wing. The distances from the iliac crest to the LFCN and to the inferior limit of a useful graft at the level of the five points are listed in Table 1. As indicated in Table 1, a safe and useful area can be defined to start at a point situated 2 cm posterior to the ASIS until the level of the thickest part of the AIT. Its mean length was 47 mm and mean depth 35 mm (Fig. 3).
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Fig. 2 The thickness of the ilium was measured at the level of the anterior superior iliac spine (1), the thickest point of the anterior iliac tubercle (4) and three starting points situated 2 and 3 cm posterior to the centre of the ASIS (2, 3) and 2 cm posterior to the thickest point of the AIT (5). The thickness of the iliac crest was measured
orthogonally to the direction of the iliac crest. A minimal halfcentimetre-width crest measurement was defined as being a useful graft. Distances between the LFCN in its endopelvic portion and those five points were also measured during dissection (a, b, c, d, and e)
Table 1 Distances between iliac crest and LFCN in the endopelvic route and optimal thickness Bony landmarks
Mean distance from the iliac crest to LCFN (measured during dissections) (mm)
Mean distance from the iliac crest to the inferior limit of the optimal bone graft (thickness C5 mm) (mm)
EAIS
22 (5–55)
Non measured
2 cm posterior to EIAS
43 (22–65)
44 (20–65)
3 cm posterior to EIAS
48 (27–68)
42 (24–67)
Centre of the AIT
63 (32–74)
37 (22–65)
2 cm posterior to AIT
[65
24 (13–60)
In most of the cases studied, it was not useful to harvest 2 cm posterior to the thickest point of the AIT, because the height of a useful graft quickly decreased to \30 mm at this level (Fig. 4).
Discussion Autogenous bone graft is routinely harvested from the anterior iliac crest during a wide range of surgical
Fig. 3 CT scan reconstruction of a safe and useful graft. It starts from a point situated 2 cm posterior to the ASIS and ends up at the level of the thickest part of the AIT. Its mean length was 47 mm and its mean depth was 35 mm
procedures. This site offers the possibility of cortical, cancellous and cortico-cancellous bone harvesting, providing a sufficient amount of bone for many indications including maxillofacial reconstruction [1, 2, 7, 8, 16, 24,
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• •
Optimized length of the graft with at least 5-mm-width graft. Optimized height of the graft.
Positioning of surgical incision in relation to the LFCN
Fig. 4 Posterior CT scan view of a left side anterior iliac crest removed after dissection. Notice the weak thickness of the iliac crest at the posterior and inferior part of the anterior iliac crest, \5 mm for a 25-mm width in this case
31], anterior cervical spine surgery and fracture non-union [35, 36]. The potential quantity of harvested bone is half that compared to the posterior iliac crest, but can be more appropriate in situations that would require repositioning the patient such as when performing posterior spinal surgery [3]. In some procedures including cervical anterior fusion, required harvest amounts are smaller [35] compared to those required in reconstructive oral and maxillofacial surgery [25]. However, bicortical or tricortical grafts of various dimensions are frequently necessary and have motivated the present study, with the purpose of standardizing and optimizing the technique of anterior iliac crest bone harvesting. In this study, a minimum 5-mm thickness was considered as a useful graft. This thickness corresponds with values reported by Mahato [23] to a 2.5mm cortical part (sum of inner and outer cortex) and a 2.5mm cancellous bone graft. Despite the frequent use of anterior iliac crest bone harvesting and its significant rate of complications and morbidity, only a few studies have described the morphology of the anterior part of the ilium and its implications on surgical technique of graft harvesting and occurrence of complications [11, 23]. In practice, only two bony and variable anatomical landmarks can be used: the ASIS and the AIT. Using these two landmarks, we have highlighted four main points in undertaking adequate and safe anterior iliac crest bone harvesting (AICBH): • •
The positioning of surgical incision in relation to the LFCN. Safe distance from the ASIS to the anterior limit of the graft, to prevent stress fracture of the ASIS.
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The surgical incision should be parallel and distal to the iliac crest, beginning at least 2 cm posterior and laterally to the ASIS [6, 27]. This incision preserves the skin around the ASIS, which avoids fibrous scar healing [19] and limits inclusion of a variant of the LFCN course that has been reported in human cadavers by several authors [27, 29, 33, 34]. The LFCN has various courses and locations in relation to the ASIS. The most dangerous type reported by Aszmann et al. [5] occurs in 4 % of cases with the LFCN exiting through the abdominal wall 2–3 cm posterior to the ASIS and crossing the iliac crest. This course is the most superficial location of all types and the most dangerous during AICBH. In the majority of cases, the LFCN exits from the pelvis about 2 cm medially to the ASIS, with variable relationships to the soft tissues (inguinal ligament and sartorius muscle in particular). Safe distance from the ASIS to the anterior limit of the graft The safe distance from the ASIS to the anterior limit of the graft is around 2–3 cm [41]. In our study, iliac thickness at 2 or 3 cm posterior to the ASIS was always [5 mm (Table 1). This indicated that a useful zone for graft harvesting is 2 cm posterior to the ASIS. Interestingly, if the graft is harvested from an area about 30 mm posterior to the ASIS, the risk of fracture at the harvesting site is biomechanically 2.4 times lower than at 15 mm [18] and, furthermore, the LFCN is farther from the iliac wing and less at risk (see Table 1). According to these landmarks, 2 cm appears to be the minimum safe distance and could be increased to 3 cm. Optimized length of the graft The length of a useful graft was \47 mm in our study. Should a graft longer than 50 mm be required, consideration needs to be made to utilize other donor sites such as a fibular or tibial graft, although such long grafts are rarely needed during spine surgery, except in spinal tumour surgery [15]. Additionally, according to our study, the graft should be harvested just anterior to a line passing at the level of the thickest point of the AIT. Murata et al. [29] reported the same and it was emphasized by Ebraheim et al. [14], the ‘‘anterior iliac tubercle’’ being defined as the crest zone situated 3–6 cm posterior to the medial edge of the ASIS.
Eur Spine J
Murata et al. [30] also reported that the posterior part of the anterior iliac crest segments contains a minimum amount of cancellous bone (see Fig. 4). This is probably due to the thinning of the iliac blades (iliac fossae) at the level of this region. Khamanarong et al. [20] in his anatomical study confirmed that the optimal harvesting bone material is situated 3–5 cm posterior to the ASIS and is more than 15-mm thick at its upper part. As reported by Murata et al. [29] another reason to limit the length of the graft is to avoid LCFN injury which was significantly higher (20 %) when the graft was 45 mm or more in length, 16 % when 30–45 mm and 8 % when \30 mm. Kurz et al. [21] highlighted also that the frequency of complications is related to the amount of soft tissue dissection, which supports that the severity of complications is related to the size of the harvested graft. A too long graft has a risk of detaching the abductor muscles (tensor of fascia lata and gluteus muscles) and could compromise their function. An extended muscle release could also result in altered contour of the iliac crest anteriorly. Optimized height of the graft We found that the maximal height of a useful graft (thickness[5 mm) was 35 mm. In his prospective study of 212 patients who underwent AICBH, Murata et al. [30] reported that the risk of injury to the LFCN was significantly increased when iliac graft higher than 30 mm was harvested. Additionally, he demonstrated that tricortical graft harvesting was associated with a higher rate of LFCN complications. In these cases, LCFN injury could be due to excessive retraction of the iliacus muscle during exposure of the inner table of the ilium and/or electrocoagulation. This also explains the higher incidence of meralgia paraesthetica [4, 39] in cases where tricortical or both inner and outer iliac tables are harvested. Regarding the high rate of injury to the LFCN between 5 and 21 %, patients undergoing spinal surgery with AICBH should be informed of the risk of LFCN damage, whatever the required graft size, despite favourable results by 3 months [3, 6, 29].
Conclusion The problem of donor site morbidity after autologous anterior iliac crest bone graft harvesting may be reduced by improved harvesting techniques including using anatomical reference points. The graft should not exceed 35-mm depth and 45-mm length and should be situated anterior to the thickest part of the AIT. By respecting these landmarks, extensive muscle release and harvesting of grafts too thin can be avoided. Finally, it is important to remark that our study reports on findings following a study limited to
female pelvises and Caucasian morphology. The dimensions reported in this study could be slightly different in males and/or taller patients. Further studies are needed to determine if these dimensions are significantly different in men and in Asian populations. Conflict of interest
None.
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