HIP
The blood supply to the femoral head after posterior fracture/dislocation of the hip, assessed by CT angiography M. Zlotorowicz, J. Czubak, A. Caban, P. Kozinski, R. BoguslawskaWalecka From The Medical Centre of Postgraduate Education, Warsaw, Poland
The femoral head receives blood supply mainly from the deep branch of the medial femoral circumflex artery (MFCA). In previous studies we have performed anatomical dissections of 16 specimens and subsequently visualised the arteries supplying the femoral head in 55 healthy individuals. In this further radiological study we compared the arterial supply of the femoral head in 35 patients (34 men and one woman, mean age 37.1 years (16 to 64)) with a fracture/dislocation of the hip with a historical control group of 55 hips. Using CT angiography, we identified the three main arteries supplying the femoral head: the deep branch and the postero-inferior nutrient artery both arising from the MFCA, and the piriformis branch of the inferior gluteal artery. It was possible to visualise changes in blood flow after fracture/dislocation. Our results suggest that blood flow is present after reduction of the dislocated hip. The deep branch of the MFCA was patent and contrast-enhanced in 32 patients, and the diameter of this branch was significantly larger in the fracture/dislocation group than in the control group (p = 0.022). In a subgroup of ten patients with avascular necrosis (AVN) of the femoral head, we found a contrast-enhanced deep branch of the MFCA in eight hips. Two patients with no blood flow in any of the three main arteries supplying the femoral head developed AVN. Cite this article: Bone Joint J 2013;95-B:1453–7.
M. Zlotorowicz, MD, PhD, Orthopaedic Surgeon J. Czubak, MD, PhD, Professor, Orthopaedic Surgeon, The Medical Centre of Postgraduate Education, Gruca Teaching Hospital, Department of Orthopaedics, Pediatric Orthopaedics and Traumatology, Konarskiego 13, 05-400 Otwock, Poland. A. Caban, MD, PhD, Orthopaedic Surgeon Gruca Teaching Hospital, Department of Orthopaedics, Konarskiego 13, 05-400 Otwock, Poland. P. Kozinski, MD, PhD, Lecturer R. Boguslawska-Walecka, MD, PhD, Professor Military Institute of Medicine, Department of Radiology, Szaserow 128, 04-141 Warsaw 44, Poland. Correspondence should be sent to Dr M. Zlotorowicz; e-mail: [email protected] ©2013 The British Editorial Society of Bone & Joint Surgery doi:10.1302/0301-620X.95B11. 32383 $2.00 Bone Joint J 2013;95-B:1453–7. Received 8 May 2013; Accepted after revision 2 July 2013
The femoral head receives its blood supply primarily from the medial femoral circumflex artery (MFCA). Of all of the branches of this artery, the deep branch is the most important.1-6 The deep branch terminates as the posterosuperior nutrient arteries, which enter the femoral head via the vascular foramina in the postero-superior and antero-superior quadrants of the femoral head and neck.7 The deep branch and the terminal nutrient arteries can provide all, or nearly all, of the blood supply to the femoral head.8 In a previous study, we identified the three main arteries that provide the blood supply to the femoral head: the deep branch of the MFCA, the postero-inferior nutrient artery originating from the MFCA, and the anastomosis from the inferior gluteal artery.2 The anterior nutrient artery of the femoral neck, which originates from the lateral femoral circumflex artery and the artery of the ligamentum teres, branching from the obturator artery, constitute a minor component of the blood supply to the femoral head.1-4,8,10,11 During posterior dislocation of the hip, arteries supplying the femoral head can be injured when the deep branch passes posterior
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to the obturator externus muscle and anterior to the quadratus femoris muscle.5 The deep branch of the MFCA penetrates the capsule of the joint in the posterior aspect of the trochanteric region and can be kinked or stretched by the dislocated femoral head. Damage to the deep branch after traumatic posterior dislocation leads to avascular necrosis of the femoral head in between 5% and 60% of patients, depending on the delay to hip relocation and severity of fracture/dislocation.12-17 In previous studies, we performed dissection of 16 specimens and analysed 55 CT angiography images of the hip in healthy individuals.1,2 The third phase of our research is the current radiological study, in which the arteries supplying the femoral head in patients following traumatic posterior dislocation of the hip were visualised.
Materials and Methods We analysed 35 CT-angiography images of the hip after fracture-dislocation. All of the examinations were performed after reduction of the posterior dislocation. There were 34 men and one woman with a mean age of 37.1 years (16 to 64). All injuries were unilateral (20 left hips 1453
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Table I. Mechanism of injury, type of acetabulum fracture, associated injuries, time to relocation and the treatment in the fracture/dislocation group (ORIF, open reduction and internal fixation) Characteristic (n, %)
n = 35
Mechanism of injury Motor vehicle accidents Motorcycle accidents Traffic accident – pedestrian Falls from height Sport activities Hit by heavy object Slip Type of fracture Posterior wall of the acetabulum + posterior dislocation Posterior column of the acetabulum + posterior dislocation Transverse fracture + fracture of the posterior wall of the acetabulum + posterior dislocation Associated injuries Other fractures (non-hip) Concussion Haemothorax, pneumothorax, indication for laparotomy Ischiadic nerve paresis Time to relocation < 12 hours 12 to 24 hours > 24 hours Treatment Closed relocation Closed relocation and ORIF with Kocher–Langenbeck approach
and 15 right hips). The mechanism of injury, type of acetabulum fracture, associated injuries, time to relocation and treatment is shown in Table I. From these patients (35 hips), we identified a subgroup of ten patients who developed avascular necrosis (AVN) at minimum 12-month followup. AVN was diagnosed at a mean of 5.2 months (1 to 9) after dislocation. All patients who developed AVN had a delay to relocation of the hip joint > 12 hours (three patients: mean 13 hours (12 to 15); seven patients: mean 15 days (1.5 to 40)). The results from these two groups were compared with the results obtained in the control group (55 hips) as previously described.2 We used a 64-section CT scanner with a scanning thickness of 0.6 mm (LightSpeed VCT 64; General Electric, Van Buren, Michigan). Studies were performed with intravenously administered contrast material as a rapidly injected bolus of 90 ml to 120 ml (Iomeron 400; Bracco, Milan, Italy). We delayed contrast delivery (25 to 30 seconds) to achieve optimal middle-to-late arterial phase imaging, which allowed visualisation of small arteries in the hip region. All of the CT studies were performed for pre-operative planning and evaluation of reduction. Contrast material was administered to visualise the arteries. The acquired data were evaluated using a combination of axial scans, multiplanar reformations (MPR), and postprocessing using the volume rendering technique (VRT) and maximum intensity projection (MIP).18,19 The study had ethical approval.
23 (66) 3 (9) 1 (3) 3 (9) 2 (6) 2 (6) 1 (3) 20 (57) 2 (6) 13 (37) 12 (34) 13 (37) 4 (11) 7 (20) 17 (49) 5 (14) 13 (37) 2 (6) 33 (94)
Statistical analysis. The chi-squared test or Fisher’s exact test was used to compare the frequency of arterial distributions between the groups. The Student’s t-test was used to compare mean values. A p-value of < 0.05 was considered significant. Calculations were done in Stata v.9[1] (Stata Statistical Software, College Station, Texas).
Results In all groups (fracture/dislocation group, avascular necrosis group, and control group), we identified three main arteries supplying the femoral head: the deep branch of the MFCA, the postero-inferior nutrient artery originating from the MFCA, and the piriformis branch of the inferior gluteal artery. We have previously shown that the deep branch can be visualised from its origin at the bifurcation of the MFCA to the superior aspect of the femoral head, where the terminal nutrient arteries enter the femoral head near the cartilaginous margin of the femoral head.1,2 The deep branch was patent and filled with contrast material in 32 scans (91%) in the fracture/ dislocation group, and in 53 scans (96%) in the control group (p = 0.37, Fisher’s exact test). The deep branch in the fracture/ dislocation group is shown in Figure 1. In the fracture/dislocation group, it was possible to visualise the arterial location where the contrast ceased to flow. In one patient, it stopped near the bifurcation of the MFCA (Fig. 2); in another two patients, it stopped 26 mm and 35 mm along the course of the deep branch. In one hip, a fragment of fractured bone near the inferior aspect of the femoral neck blocked the main trunk of the MFCA but the THE BONE & JOINT JOURNAL
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Fig. 1
Fig. 2
Three-dimensional volume-rendering CT reconstruction showing the deep branch of the medial femoral circumflex artery (MFCA); shown from the bifurcation of the MFCA (arrow 1) to its division into the postero-superior nutrient arteries (arrow 2) with a comminuted fracture of the posterior wall and an undisplaced transverse fracture of the acetabulum after reduction of hip dislocation.
Three-dimensional volume-rendering CT reconstruction showing: the contrastenhanced main trunk of the medial femoral circumflex artery (MFCA) with no contrast visible in the deep branch (arrow 1) and the bifurcation of the MFCA with contrast penetration to the descending branch and no contrast visible in the deep branch (arrow 2).
deep branch was filled with contrast through the anastomosis with the obturator artery via the superficial branch of the MFCA (Fig. 3). The contrast-enhanced deep branch (measured 10 mm distally from its bifurcation) had a significantly greater diameter in the fracture/dislocation group than in the control group. The mean diameter was 1.8 mm (1.1 to 2.7) in the fracture/dislocation group and 1.6 mm (1.1 to 2.7) in the control group (p = 0.022, Student’s t-test). The group of terminal branches originating from the deep branch (the postero-superior nutrient arteries) could not be seen because of their small diameter. The postero-inferior nutrient artery originates near the bifurcation of the main trunk of the MFCA and runs straight towards the superior margin of the lesser trochanter. CT angiography showed that the postero-inferior nutrient artery was filled with contrast in eight (23%) in the fracture/dislocation group and six (11%) in the control group (p = 0.13, chi-squared test). The diameter of this vessel is normally so small that it cannot be measured using angiography. We observed the piriformis branch of the inferior gluteal artery in nine hips (26%) in the fracture/dislocation group and in 27 (49%) in the control group (p = 0.027, chi-squared test) (Fig. 4). In the AVN subgroup, we found a contrast-enhanced deep branch of the MFCA with a mean diameter of 1.8 mm (1.4 to 2.4) in eight hips (80%) in comparison with 91% in the whole fracture/dislocation group and 96% in the control group, a postero-inferior nutrient artery in four hips
(40%, 23%, 11% respectively) and an anastomosis with the inferior gluteal artery in one hip (26% in the whole fracture/dislocation group and 49% in the control group). No statistical analyses were performed in the AVN subgroup because of the small sample size.
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Discussion The patients in the fracture/dislocation group demonstrated the same three main vessels supplying the femoral head, which have previously been reported1,2: the deep branch of the MFCA with the terminal postero-superior nutrient arteries, the postero-inferior nutrient artery originating from the MFCA, and the piriformis branch from the inferior gluteal artery. As AVN of the femoral head can be a complication of posterior dislocation of the femoral head in 5% to 60% of patients,12-17 we suspected that the deep branch of the MFCA would not be seen in some patients after traumatic dislocation of the hip, especially in the AVN subgroup of patients, because of rupture or kinking of the extraosseous arteries. However, the deep branch was contrast-enhanced in 32 patients in the fracture/dislocation group (91%), and had a larger mean diameter than that of the control group (1.8 mm versus 1.6 mm, p = 0.022). There was a contrastenhanced postero-inferior nutrient artery in eight hips (23%) in the fracture/dislocation group and six hips (11%) in the control group (p = 0.13). The results for the deep branch of the MFCA suggest that after posterior dislocation, in the majority of cases, there is
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Fig. 3b
Fig. 3a
Fig. 3c
Figure 3a – three-dimensional volume-rendering CT reconstruction showing an injury to the main trunk of the medial femoral circumflex artery (MFCA): no contrast penetration to the main trunk of the MFCA (arrow 1) and a fragment of fractured bone blocking the blood flow (arrow 2). Figures 3b and 3c – maximum intensity projection CT images showing contrast present in the deep branch of the MFCA (c) via the anastomosis with the obturator artery (b) (arrows).
Fig. 4 Three-dimensional volume-rendering CT reconstruction showing the relationship of the anastomosis between the inferior gluteal artery (arrow 1) and the deep branch of the medial femoral circumflex artery (MFCA) (arrow 2) to the posterior wall fracture of the acetabulum after reduction of a dislocated femoral head.
a detectable increase in the blood flow to the femoral head, seen as a significantly larger arterial diameter on CT-angiography, which could be interpreted as increased blood flow in response to revascularisation after ischaemia.20 Our results show that blood flow was present in the main vessel supplying the femoral head (the deep branch of the MFCA) after reduction of the dislocated hip in 91%. It is not possible to draw conclusions about the blood flow to the femoral head while the hip was dislocated. An initial period of ischaemia may trigger the increase in blood flow to the femoral head that occurs during the later phase as a response to revascularisation and healing. The initial ischaemia may also lead to sub-clinical AVN with increased blood flow.20
After reduction of the dislocated hip, any tension on the deep branch of MFCA which might be compromising perfusion of the femoral head should be relieved and the flow restored. However, blood flow may be blocked if thrombosis occurs.21 We can only speculate what blood flow changes occurs while the hip is dislocated, although our results show that after reduction, the blood flow is restored in most cases rather than blocked. Three patients from the fracture/dislocation group had no blood flow in the deep branch of the MFCA after reduction of the dislocation. Of the three patients, two developed AVN (those two patients had no blood flow in all three main vessels supplying the femoral head) but one did not. This latter patient had a large postero-inferior nutrient artery to the femoral head. In the fracture/dislocation group, there was a contrastenhanced piriformis branch of the inferior gluteal artery in nine hips (26%) compared with 27 hips (49%) in the control group (p = 0.027). This significant difference suggests that posterior dislocation of the hip and the Kocher–Langenbeck exposure of the hip joint can both injure the piriformis branch of the inferior gluteal artery.1,5,22 More surprising suggestions can be made for the AVN subgroup. The results suggest that patients with AVN have, in the majority of cases (80%), increased blood flow in the deep branch of the MFCA, seen as a larger arterial diameter on CTangiography (1.8 versus 1.6). This could be interpreted as the result of revascularisation of the necrotic bone tissue.20 This finding corresponds with the typical sign in scintigraphy performed in the later phase of avascular necrosis.23 We can speculate that the initial ischaemia, while the hip was dislocated, caused the avascular necrosis (all patients from the AVN subgroup had > 12 hours delay before relocation of the hip joint). Two patients (20%) of the AVN subgroup had no contrast material in any of the three main arteries supplying the THE BONE & JOINT JOURNAL
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femoral head. In those two cases (delay in relocation of 13 and 40 days) the blood flow could not be restored after relocation of the hip joint. The present study shows that CT angiography is a good method of visualising the vessels supplying the femoral head in patients after posterior hip dislocation. It was possible to visualise the arterial location at which the contrast ceased to flow. The CT angiography can help to determine the prognosis of the hip joint after posterior dislocation: from the whole group of patients with fracture/dislocation two patients had no blood flow in all three main vessels supplying the femoral head, both of whom developed AVN. The present study showed significant increase in the blood flow in the deep branch of the MFCA in the whole group of patients with fracture/dislocation of the hip; it can be treated as a result of revascularisation after subclinical ischaemia in most patients after posterior dislocation of the hip. Funding for the study was received from the Ministry of Science and Higher Education, Republic of Poland. No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article. This article was primary edited by G. Scott and first-proof edited by J. Scott.
References 1. Zlotorowicz M, Szczodry M, Czubak J, Ciszek B. Anatomy of the medial femoral circumflex artery with respect to the vascularity of the femoral head. J Bone Joint Surg [Br] 2011;93-B:1471–1474. 2. Zlotorowicz M, Czubak J, Kozinski P, Boguslawska-Walecka R. Imaging the vascularisation of the femoral head by CT angiography. J Bone Joint Surg [Br] 2012;94-B:1176–1179. 3. Tucker FR. Arterial supply to the femoral head and its clinical importance. J Bone Joint Surg [Br] 1949;31-B:82–93. 4. Trueta J, Harrison MH. The normal vascular anatomy of the femoral head in adult man. J Bone Joint Surg [Br] 1953;35-B:442–461. 5. Gautier E, Ganz K, Krügel N, Gill T, Ganz R. Anatomy of the medial femoral circumflex artery and its surgical implications. J Bone Joint Surg [Br] 2000;82-B:679– 683.
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6. Kalhor M, Horowitz K, Gharehdaghi J, Beck M, Ganz R. Anatomic variations in femoral head circulation. Hip Int 2012;22:307–312. 7. Lavigne M, Kalhor M, Beck M, Ganz R, Leunig M. Distribution of vascular foramina around the femoral head and neck junction: relevance for conservative intracapsular procedures of the hip. Orthop Clin North Am 2005;36:171–176. 8. Sevitt S, Thompson RG. The distribution and anastomoses of arteries supplying the head and neck of the femur. J Bone Joint Surg [Br] 1965;47-B:560–573. 9. Kalhor M, Beck M, Huff TW, Ganz R. Capsular and pericapsular contributions to acetabular and femoral head perfusion. J Bone Joint Surg [Am] 2009;91-A:409–418. 10. Howe WW Jr, Lacey T, Schwartz RP. A study of the gross anatomy of the arteries supplying the proximal portion of the femur and the acetabulum. J Bone Joint Surg [Am] 1950;32-A:856–866. 11. Judet J, Judet R, Lagrange J, Dunoyer J. A study of the arterial vascularization of the femoral neck in the adult. J Bone Joint Surg [Am] 1955;37-A:663–680. 12. Sen R, Tripathy S, Gill S, et al. Prediction of posttraumatic femoral head osteonecrosis by quantitative intraosseous aspirate and core biopsy analysis: a prospective study. Acta Orthop Belg 2010;76:486–492. 13. Dwyer A, John B, Singh S, Mam M. Complications after posterior dislocation of the hip Int Orthop 2006;30:224–227. 14. Yue J, Sontich J, Miron S, et al. Blood flow changes to the femoral head after acetabular fracture or dislocation in the acute injury and perioperative periods. J Orthop Trauma 2001;15:170–176. 15. McKee M, Garay M, Schemitsch E, Kreder H, Stephen D. Irreducible fracturedislocation of the hip: a severe injury with a poor prognosis. J Orthop Trauma 1998;12:223–229. 16. Hougaard K, Thomsen P. Coxarthrosis following traumatic posterior dislocation of the hip. J Bone Joint Surg [Am] 1987;69-A:679–683. 17. Hougaard K, Thomsen P. Traumatic posterior dislocation of the hip: prognostic factors influencing the incidence of avascular necrosis of the femoral head. Arch Orthop Trauma Surg 1986;106:32–35. 18. Fishman EK, Ney DR, Heath DG, et al. Volume rendering versus maximum intensity projection in CT angiography: what works best, when, and why. Radiographics 2006;26:905–922. 19. Fishman E, Horton K, Johnson P. Multidetector CT and three-dimensional CT angiography for suspected vascular trauma of the extremities. Radiographics 2008;28:653–667. 20. Catto M. A histological study of avascular necrosis of the femoral head after transcervical fracture. J Bone Joint Surg [Br] 1965;47-B:749–776. 21. Yue J, Wilber J, Lipuma J, et al. Posterior hip dislocation: a cadaveric angiographic study. J Orthop Trauma 1996;10:447–454. 22. Siebenrock K, Tannast M, Bastian J, Keel M. Posterior approaches to the acetabulum. Unfallchirurg 2013;116:221–226. 23. Imhof H, Breitenseher M, Trattnig S, et al. Imaging of avascular necrosis of bone. Euro Radiol 1997;7:180–186.
The blood supply to the femoral head after posterior fracture/dislocation of the hip, assessed by CT angiography M. Zlotorowicz, J. Czubak, A. Caban, P. Kozinski, R. BoguslawskaWalecka From The Medical Centre of Postgraduate Education, Warsaw, Poland
The femoral head receives blood supply mainly from the deep branch of the medial femoral circumflex artery (MFCA). In previous studies we have performed anatomical dissections of 16 specimens and subsequently visualised the arteries supplying the femoral head in 55 healthy individuals. In this further radiological study we compared the arterial supply of the femoral head in 35 patients (34 men and one woman, mean age 37.1 years (16 to 64)) with a fracture/dislocation of the hip with a historical control group of 55 hips. Using CT angiography, we identified the three main arteries supplying the femoral head: the deep branch and the postero-inferior nutrient artery both arising from the MFCA, and the piriformis branch of the inferior gluteal artery. It was possible to visualise changes in blood flow after fracture/dislocation. Our results suggest that blood flow is present after reduction of the dislocated hip. The deep branch of the MFCA was patent and contrast-enhanced in 32 patients, and the diameter of this branch was significantly larger in the fracture/dislocation group than in the control group (p = 0.022). In a subgroup of ten patients with avascular necrosis (AVN) of the femoral head, we found a contrast-enhanced deep branch of the MFCA in eight hips. Two patients with no blood flow in any of the three main arteries supplying the femoral head developed AVN. Cite this article: Bone Joint J 2013;95-B:1453–7.
M. Zlotorowicz, MD, PhD, Orthopaedic Surgeon J. Czubak, MD, PhD, Professor, Orthopaedic Surgeon, The Medical Centre of Postgraduate Education, Gruca Teaching Hospital, Department of Orthopaedics, Pediatric Orthopaedics and Traumatology, Konarskiego 13, 05-400 Otwock, Poland. A. Caban, MD, PhD, Orthopaedic Surgeon Gruca Teaching Hospital, Department of Orthopaedics, Konarskiego 13, 05-400 Otwock, Poland. P. Kozinski, MD, PhD, Lecturer R. Boguslawska-Walecka, MD, PhD, Professor Military Institute of Medicine, Department of Radiology, Szaserow 128, 04-141 Warsaw 44, Poland. Correspondence should be sent to Dr M. Zlotorowicz; e-mail: [email protected] ©2013 The British Editorial Society of Bone & Joint Surgery doi:10.1302/0301-620X.95B11. 32383 $2.00 Bone Joint J 2013;95-B:1453–7. Received 8 May 2013; Accepted after revision 2 July 2013
The femoral head receives its blood supply primarily from the medial femoral circumflex artery (MFCA). Of all of the branches of this artery, the deep branch is the most important.1-6 The deep branch terminates as the posterosuperior nutrient arteries, which enter the femoral head via the vascular foramina in the postero-superior and antero-superior quadrants of the femoral head and neck.7 The deep branch and the terminal nutrient arteries can provide all, or nearly all, of the blood supply to the femoral head.8 In a previous study, we identified the three main arteries that provide the blood supply to the femoral head: the deep branch of the MFCA, the postero-inferior nutrient artery originating from the MFCA, and the anastomosis from the inferior gluteal artery.2 The anterior nutrient artery of the femoral neck, which originates from the lateral femoral circumflex artery and the artery of the ligamentum teres, branching from the obturator artery, constitute a minor component of the blood supply to the femoral head.1-4,8,10,11 During posterior dislocation of the hip, arteries supplying the femoral head can be injured when the deep branch passes posterior
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to the obturator externus muscle and anterior to the quadratus femoris muscle.5 The deep branch of the MFCA penetrates the capsule of the joint in the posterior aspect of the trochanteric region and can be kinked or stretched by the dislocated femoral head. Damage to the deep branch after traumatic posterior dislocation leads to avascular necrosis of the femoral head in between 5% and 60% of patients, depending on the delay to hip relocation and severity of fracture/dislocation.12-17 In previous studies, we performed dissection of 16 specimens and analysed 55 CT angiography images of the hip in healthy individuals.1,2 The third phase of our research is the current radiological study, in which the arteries supplying the femoral head in patients following traumatic posterior dislocation of the hip were visualised.
Materials and Methods We analysed 35 CT-angiography images of the hip after fracture-dislocation. All of the examinations were performed after reduction of the posterior dislocation. There were 34 men and one woman with a mean age of 37.1 years (16 to 64). All injuries were unilateral (20 left hips 1453
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M. ZLOTOROWICZ, J. CZUBAK, A. CABAN, P. KOZINSKI, R. BOGUSLAWSKA-WALECKA
Table I. Mechanism of injury, type of acetabulum fracture, associated injuries, time to relocation and the treatment in the fracture/dislocation group (ORIF, open reduction and internal fixation) Characteristic (n, %)
n = 35
Mechanism of injury Motor vehicle accidents Motorcycle accidents Traffic accident – pedestrian Falls from height Sport activities Hit by heavy object Slip Type of fracture Posterior wall of the acetabulum + posterior dislocation Posterior column of the acetabulum + posterior dislocation Transverse fracture + fracture of the posterior wall of the acetabulum + posterior dislocation Associated injuries Other fractures (non-hip) Concussion Haemothorax, pneumothorax, indication for laparotomy Ischiadic nerve paresis Time to relocation < 12 hours 12 to 24 hours > 24 hours Treatment Closed relocation Closed relocation and ORIF with Kocher–Langenbeck approach
and 15 right hips). The mechanism of injury, type of acetabulum fracture, associated injuries, time to relocation and treatment is shown in Table I. From these patients (35 hips), we identified a subgroup of ten patients who developed avascular necrosis (AVN) at minimum 12-month followup. AVN was diagnosed at a mean of 5.2 months (1 to 9) after dislocation. All patients who developed AVN had a delay to relocation of the hip joint > 12 hours (three patients: mean 13 hours (12 to 15); seven patients: mean 15 days (1.5 to 40)). The results from these two groups were compared with the results obtained in the control group (55 hips) as previously described.2 We used a 64-section CT scanner with a scanning thickness of 0.6 mm (LightSpeed VCT 64; General Electric, Van Buren, Michigan). Studies were performed with intravenously administered contrast material as a rapidly injected bolus of 90 ml to 120 ml (Iomeron 400; Bracco, Milan, Italy). We delayed contrast delivery (25 to 30 seconds) to achieve optimal middle-to-late arterial phase imaging, which allowed visualisation of small arteries in the hip region. All of the CT studies were performed for pre-operative planning and evaluation of reduction. Contrast material was administered to visualise the arteries. The acquired data were evaluated using a combination of axial scans, multiplanar reformations (MPR), and postprocessing using the volume rendering technique (VRT) and maximum intensity projection (MIP).18,19 The study had ethical approval.
23 (66) 3 (9) 1 (3) 3 (9) 2 (6) 2 (6) 1 (3) 20 (57) 2 (6) 13 (37) 12 (34) 13 (37) 4 (11) 7 (20) 17 (49) 5 (14) 13 (37) 2 (6) 33 (94)
Statistical analysis. The chi-squared test or Fisher’s exact test was used to compare the frequency of arterial distributions between the groups. The Student’s t-test was used to compare mean values. A p-value of < 0.05 was considered significant. Calculations were done in Stata v.9[1] (Stata Statistical Software, College Station, Texas).
Results In all groups (fracture/dislocation group, avascular necrosis group, and control group), we identified three main arteries supplying the femoral head: the deep branch of the MFCA, the postero-inferior nutrient artery originating from the MFCA, and the piriformis branch of the inferior gluteal artery. We have previously shown that the deep branch can be visualised from its origin at the bifurcation of the MFCA to the superior aspect of the femoral head, where the terminal nutrient arteries enter the femoral head near the cartilaginous margin of the femoral head.1,2 The deep branch was patent and filled with contrast material in 32 scans (91%) in the fracture/ dislocation group, and in 53 scans (96%) in the control group (p = 0.37, Fisher’s exact test). The deep branch in the fracture/ dislocation group is shown in Figure 1. In the fracture/dislocation group, it was possible to visualise the arterial location where the contrast ceased to flow. In one patient, it stopped near the bifurcation of the MFCA (Fig. 2); in another two patients, it stopped 26 mm and 35 mm along the course of the deep branch. In one hip, a fragment of fractured bone near the inferior aspect of the femoral neck blocked the main trunk of the MFCA but the THE BONE & JOINT JOURNAL
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Fig. 1
Fig. 2
Three-dimensional volume-rendering CT reconstruction showing the deep branch of the medial femoral circumflex artery (MFCA); shown from the bifurcation of the MFCA (arrow 1) to its division into the postero-superior nutrient arteries (arrow 2) with a comminuted fracture of the posterior wall and an undisplaced transverse fracture of the acetabulum after reduction of hip dislocation.
Three-dimensional volume-rendering CT reconstruction showing: the contrastenhanced main trunk of the medial femoral circumflex artery (MFCA) with no contrast visible in the deep branch (arrow 1) and the bifurcation of the MFCA with contrast penetration to the descending branch and no contrast visible in the deep branch (arrow 2).
deep branch was filled with contrast through the anastomosis with the obturator artery via the superficial branch of the MFCA (Fig. 3). The contrast-enhanced deep branch (measured 10 mm distally from its bifurcation) had a significantly greater diameter in the fracture/dislocation group than in the control group. The mean diameter was 1.8 mm (1.1 to 2.7) in the fracture/dislocation group and 1.6 mm (1.1 to 2.7) in the control group (p = 0.022, Student’s t-test). The group of terminal branches originating from the deep branch (the postero-superior nutrient arteries) could not be seen because of their small diameter. The postero-inferior nutrient artery originates near the bifurcation of the main trunk of the MFCA and runs straight towards the superior margin of the lesser trochanter. CT angiography showed that the postero-inferior nutrient artery was filled with contrast in eight (23%) in the fracture/dislocation group and six (11%) in the control group (p = 0.13, chi-squared test). The diameter of this vessel is normally so small that it cannot be measured using angiography. We observed the piriformis branch of the inferior gluteal artery in nine hips (26%) in the fracture/dislocation group and in 27 (49%) in the control group (p = 0.027, chi-squared test) (Fig. 4). In the AVN subgroup, we found a contrast-enhanced deep branch of the MFCA with a mean diameter of 1.8 mm (1.4 to 2.4) in eight hips (80%) in comparison with 91% in the whole fracture/dislocation group and 96% in the control group, a postero-inferior nutrient artery in four hips
(40%, 23%, 11% respectively) and an anastomosis with the inferior gluteal artery in one hip (26% in the whole fracture/dislocation group and 49% in the control group). No statistical analyses were performed in the AVN subgroup because of the small sample size.
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Discussion The patients in the fracture/dislocation group demonstrated the same three main vessels supplying the femoral head, which have previously been reported1,2: the deep branch of the MFCA with the terminal postero-superior nutrient arteries, the postero-inferior nutrient artery originating from the MFCA, and the piriformis branch from the inferior gluteal artery. As AVN of the femoral head can be a complication of posterior dislocation of the femoral head in 5% to 60% of patients,12-17 we suspected that the deep branch of the MFCA would not be seen in some patients after traumatic dislocation of the hip, especially in the AVN subgroup of patients, because of rupture or kinking of the extraosseous arteries. However, the deep branch was contrast-enhanced in 32 patients in the fracture/dislocation group (91%), and had a larger mean diameter than that of the control group (1.8 mm versus 1.6 mm, p = 0.022). There was a contrastenhanced postero-inferior nutrient artery in eight hips (23%) in the fracture/dislocation group and six hips (11%) in the control group (p = 0.13). The results for the deep branch of the MFCA suggest that after posterior dislocation, in the majority of cases, there is
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M. ZLOTOROWICZ, J. CZUBAK, A. CABAN, P. KOZINSKI, R. BOGUSLAWSKA-WALECKA
Fig. 3b
Fig. 3a
Fig. 3c
Figure 3a – three-dimensional volume-rendering CT reconstruction showing an injury to the main trunk of the medial femoral circumflex artery (MFCA): no contrast penetration to the main trunk of the MFCA (arrow 1) and a fragment of fractured bone blocking the blood flow (arrow 2). Figures 3b and 3c – maximum intensity projection CT images showing contrast present in the deep branch of the MFCA (c) via the anastomosis with the obturator artery (b) (arrows).
Fig. 4 Three-dimensional volume-rendering CT reconstruction showing the relationship of the anastomosis between the inferior gluteal artery (arrow 1) and the deep branch of the medial femoral circumflex artery (MFCA) (arrow 2) to the posterior wall fracture of the acetabulum after reduction of a dislocated femoral head.
a detectable increase in the blood flow to the femoral head, seen as a significantly larger arterial diameter on CT-angiography, which could be interpreted as increased blood flow in response to revascularisation after ischaemia.20 Our results show that blood flow was present in the main vessel supplying the femoral head (the deep branch of the MFCA) after reduction of the dislocated hip in 91%. It is not possible to draw conclusions about the blood flow to the femoral head while the hip was dislocated. An initial period of ischaemia may trigger the increase in blood flow to the femoral head that occurs during the later phase as a response to revascularisation and healing. The initial ischaemia may also lead to sub-clinical AVN with increased blood flow.20
After reduction of the dislocated hip, any tension on the deep branch of MFCA which might be compromising perfusion of the femoral head should be relieved and the flow restored. However, blood flow may be blocked if thrombosis occurs.21 We can only speculate what blood flow changes occurs while the hip is dislocated, although our results show that after reduction, the blood flow is restored in most cases rather than blocked. Three patients from the fracture/dislocation group had no blood flow in the deep branch of the MFCA after reduction of the dislocation. Of the three patients, two developed AVN (those two patients had no blood flow in all three main vessels supplying the femoral head) but one did not. This latter patient had a large postero-inferior nutrient artery to the femoral head. In the fracture/dislocation group, there was a contrastenhanced piriformis branch of the inferior gluteal artery in nine hips (26%) compared with 27 hips (49%) in the control group (p = 0.027). This significant difference suggests that posterior dislocation of the hip and the Kocher–Langenbeck exposure of the hip joint can both injure the piriformis branch of the inferior gluteal artery.1,5,22 More surprising suggestions can be made for the AVN subgroup. The results suggest that patients with AVN have, in the majority of cases (80%), increased blood flow in the deep branch of the MFCA, seen as a larger arterial diameter on CTangiography (1.8 versus 1.6). This could be interpreted as the result of revascularisation of the necrotic bone tissue.20 This finding corresponds with the typical sign in scintigraphy performed in the later phase of avascular necrosis.23 We can speculate that the initial ischaemia, while the hip was dislocated, caused the avascular necrosis (all patients from the AVN subgroup had > 12 hours delay before relocation of the hip joint). Two patients (20%) of the AVN subgroup had no contrast material in any of the three main arteries supplying the THE BONE & JOINT JOURNAL
THE BLOOD SUPPLY TO THE FEMORAL HEAD AFTER POSTERIOR FRACTURE/DISLOCATION OF THE HIP, ASSESSED BY CT ANGIOGRAPHY
femoral head. In those two cases (delay in relocation of 13 and 40 days) the blood flow could not be restored after relocation of the hip joint. The present study shows that CT angiography is a good method of visualising the vessels supplying the femoral head in patients after posterior hip dislocation. It was possible to visualise the arterial location at which the contrast ceased to flow. The CT angiography can help to determine the prognosis of the hip joint after posterior dislocation: from the whole group of patients with fracture/dislocation two patients had no blood flow in all three main vessels supplying the femoral head, both of whom developed AVN. The present study showed significant increase in the blood flow in the deep branch of the MFCA in the whole group of patients with fracture/dislocation of the hip; it can be treated as a result of revascularisation after subclinical ischaemia in most patients after posterior dislocation of the hip. Funding for the study was received from the Ministry of Science and Higher Education, Republic of Poland. No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article. This article was primary edited by G. Scott and first-proof edited by J. Scott.
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