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Occult posttraumatic avascular necrosis of hip revealed by MRI
Magnetic Resonance Imnging, Vol. 10, pp. Printed in the USA. All rights reserved.
155-159,
1992 copyright
0730-725w92 $5.00 + .xl 0 1992 Pergamon Press plc
l Case Report
OCCULT POSTTRAUMATIC AVASCULAR NECROSIS OF HIP REVEALED BY MRI JEFFREY C. ALLARD, GUY PORTER, AND ROBERT W. RYERSON Departmentof Radiology, MusculoskeletalSection, University of Miami, Box 016960, Miami, FL, 33101, USA
Three hips with avascular necrosis in two patients had associated traumatic lesions noted on magnetic resonance imaging. Location of stress fracture in two femoral necks and acetabular contusion development prior to avascular necrosis favors these. processes as being etiologic. These cases are particularly noteworthy in that nondisplaced fractures or other musculoskeletal trauma not visible on plain films has rarely been associated with subsequent development of avascular necrosis. Keywords: Magnetic resonance; Avascular necrosis; Fracture; Hip.
2. An 81-year-old woman with multiple medical problems complained of right hip pain. Other than a 1-wk course of steriods, she had no predisposition for the development of AVN. Initial plain films were normal except for involutional osteoporosis [Fig. 2(A)]. Because of worsening pain, MRI was performed 5 mo later, demonstrating bilateral subcapital stress fractures and bilateral AVN [Fig. 2(B) and (C)l. Subsequent plain film examination showed collapse of right femoral head and sclerotic area in both femoral necks consistent with healed stress fractures [Fig. 2(D)]. The patient underwent a total right hip replacement confirming the presence of AVN. Subsequent radiographs have demonstrated similar changes in the left hip, but surgery here is being deferred.
INTRODUCTION MRI is the preferred modality for evaluation of the painful hip when plain films are normal and there is clinical suspicion for avascular necrosis (AVN) or occult fracture. ‘+j Fractures are both a common cause and a common result of AVN.5-8 Subcapital fractures of the femoral neck are especially prone to development of AVN, especially if the fracture is displaced or poorly reduced.’ We report two cases of radiologically occult trauma to the hip revealed with MRI and likely accounting for the development of AVN of the femoral head. CASE REPORTS 1. A 65year-old woman complained of right hip pain after a car accident. Plain films were normal, and MFU showed evidence of superior acetabular T1 and T2 prolongation consistent with a bone contusion [Fig. l(A) and (B)]. Biopsy was performed because of the remote possibility of neoplasm, and results were negative. The patient had gradual decrease in pain over a 4-mo period. Hip pain returned and was severe enough to warrant another MRl 7 mo after the initial trauma. Plain films at this time showed sclerosis of superior acetabulum. MRl showed AVN of femoral head [Fig. l(C) and (D)]. The patient underwent total hip replacement, which confirmed the presence of AVN with secondary degenerative changes. RECEIVED
DISCUSSION The pathogenesis of AVN is dependent on decrease in blood supply to the marrow. Femoral head blood supply originates from retinacular branches of the femoral circumflex arteries and the ligamenturn teres artery.5*7 Fractures of the femoral neck reduce blood supply by interrupting the retinacular vessels and capsular vessels. Hip dislocations reduce blood supply via ligamenturn teres. The small artery within ligamentum teres is an increasingly important source of blood in the elderly hip.7 This vessel, which is a branch of the obturator artery, might also be disrupted in direct acetabular trauma such
l/15/91; ACCEPTED 6128191. 155
156
Magnetic Resonance Imaging 0 Volume 10, Number 1, 1992
Fig. 1. (A) Sag&al MRI (SE 500/20) of right hip shows low signal of superior acetabulum consistent with acetabular contusion.
(B) Coronal MRI (SE 2000/80) shows increased signal in acetabulum consistent with edema or contusion. (C) Coronal MRI (SE 500/20) of pelvis shows low signal in right femoral head consistent with AVN. Note residual low signal in acetabulum correlating with sclerosis on plain films. (D) Coronal MRI (SE 2000/80) shows low signal in femoral head consistent with stage D AVN. as occurred in case 1. No bone displacement was evident in either of our cases, ordinarily a factor mitigating against AVN development. In Gardner’s series of femoral neck fractures, no patient with a nondisplaced fracture had this complication.’ It has heen postulated that an additional mechanism for intracapsular femoral neck fractures to cause AVN is by joint effusion tamponade of the medial femoral circumflex artery.g Nuclear medicine studies have dem-
onstrated diminished flow to the femoral head in patients who had minimally displaced fractures and joint effusions. Aspiration of hemarthrosis to prevent the theoretical complication of AVN has therefore been advocated.g Joint effnsions are also present in cases of AVN totally unrelated to trauma, in which cases they are considered to be the effect rather than the cause.’ Finally, there is evidence to indicate that the etiology of traumatic AVN of the hip is related to venous
&zult posttraumatic avascular necrosis of hip 0 J.C.
ALLARD
ET AL.
157
Fig. 2. (A) Initial plain film of both hips is normal except for demineralization. (B) Coronal MRI (SE 700120) shows transversely oriented low-signal areas in subcapital femoral neck consistent with stress fractures and low signal especially in right femoral neck consistent with AVN. (Figure continued
B
obstruction with secondary intraosseous hypertension. It has been clinically observed that subcapital femoral neck fractures with varus deformity are particularly likely to be complicated by AVN.7*8 An in vivo study of the intraosseous pressures in these fractures demonstrated a pulseless intracapital tracing in one-third, but in two-thirds of cases the intracapital pressures were greater than pressure measurements taken in the intertrochanteric regi0n.s These data would indicate that marrow hypertension is even more important than disruption of arterial inflow and that traumatic venous disruption or obstruction is the likely mechanism for this in-
next page.)
traosseous congestion, which may secondarily lead to ischemia and marrow necrosis. The MRI depiction of hip pathology is largely dependent on low-signal areas within otherwise normal highsignal fatty marrow on T,-weighted images. Vertically oriented low signal due to a high concentration of weight-bearing bony trabeculae should not be confused with a pathologic process, however. Various patterns of AVN have been described.5 Up to 80% of AVN cases demonstrate a characteristic “double-line sign” on T2weighted images, a feature present in both hips of case 2 [Fig. 2(C)].1,6*11The segmental distribution of abnor-
158
Magnetic Resonance Imaging 0 Volume 10, Number 1, 1992 Fig. 2. (cont.) (C) Coronal MRI (SE 2000/70) shows right joint effusion, low signal in femoral head consistent with AVN, and abnormal signal oriented transversely in subcapital regions indicating stress fracture. (D) Follow-up plain film shows collapse and sclerosis of right femoral head due to AVN and sclerosis of both subcapital regions indicating healed stress fractures (white arrows).
ma1 signal, particularly in the anterosuperior aspect of subchondral femoral head, is also useful for diagnosing AVN. 4*6*10-12Subchondral cysts should be differentiated from AVN by their tendency to occur on both sides of the joint space and frequent fluid signal characteriitic on MRI.5 MRI staging of AVN has been described and shown to be useful in the prediction of subchondral fracture development.6*‘2 In addition to the extent of signal abnormality, the center of the AVN lesion is least likely to have fracture when fat signal is present (stage A) and most likely to fracture when fibrous tissue is present (stage D). Intermediate stages have blood (stage B) and fluid signal (stage C). Based on this grading mechanism, both of our patients’ hips which were replaced were
stage D. Plain films or CT scans sometimes demonstrate subchondral collapse in AVN better than MRI, because of improved trabecular imaging. ‘* The role of MRI in diagnosis of traumatic conditions of the hip is less well established than that of diagnosing AVN. Bone bruise is a common entity, particularly about the knee, wherein there is a pattern of marrow edema similar to the pattern seen in the acetabulum of case 1 .* Pathologically, trabecular fracture is suspected. Usually healing ensues with return of normal marrow signal. Occasionally healing with sclerosis or fibrosis, or secondary osteonecrosis may result, resulting in low-signal persistence, as occurred in the acetabulum of case 1. Fractures tend to have a more linear morphology than
Occult posttraumatic avascular necrosis of hip 0 J.C. ALLARO ETAL.
bone contusion on MRI.3 Location of abnormal signal in femoral neck would also favor fracture rather than AVN. Fractures sometimes have a serpentine course, which if in a subcapital location might be difficult to distinguish from the “bandlike” pattern of AVN.3*5The subsequent plain films in case 2 are sufficiently characteristic for a healed stress fracture to indicate that the signal abnormality on MRI in this area is due to the same process. Increased sensitivity, specificity, and spatial resolution compared to bone scanning should promote MRI into the forefront of occult traumatic imaging. Our two cases, in addition, point out that occult trauma can lead to AVN of the femoral head. This complication has rarely been attributed to trauma when there is no displacement. Perhaps the increased usage of MRI in problematic hip pain cases will reveal additional cases where occult traumatic conditions are revealed, particularly in older patients wherein a history of trauma is not clearly elicited. REFERENCES B.G.; Kressel, H.Y.; Dalinka, M.K.; 1. Coleman, Scheibler, M.L.; Burk, D.L.; Cohen, E.K. Radiographitally negative avascular necrosis: Detection with MR imaging. Radiology 168525-528; 1988. 2. Deutsch, A.L.; Mink, J.H. Magnetic resonance imaging of musculoskeletal injuries. Rd. Clin. North Am. 27(5): 983-1002; 1989. 3. Deutsch, A.L.; Mink, J.H.; Waxman, A.D. Occult fractures of the proximal femur: MR imaging. Radiology 170:
159
113-l 16; 1989. 4. Markisz, J.A.; Knowles, R.J.R.; Altchek, D.W.; Schneider, R.; Whalen, J.P.; Cahill, P.T. Segmental patterns of avascular necrosis of the femoral heads: Early detection with MR imaging. Radiology 162:717-720; 1987. 5. Gillespy, T.; Genant, H.K.; Helms, C.A. Magnetic resonance imaging of osteonecrosis. Radiol. Clin. North Am. 24(2):193-208; 1986. 6. Mitchell, D.G.; Rao, V.M.; Dal&a, M.K.; Spritzer, C.E.; Alavi, A.; Steinberg, M.E.; Fallon, M.; Kressel, H.Y. Femoral head avascular necrosis: Correlation of MR imaging, radiographic staging, radionuclide imaging, and clinical findings. Radiology 162:709-715; 1987. 7. Garden, R.S. Low angle fixation in fractures of the femoral neck. J Bone Joint Surg. 43B:647*3; 1961. 8. Arnoldi, C.C.; Linderholm, H. Fracture of femoral neck: Vascular disturbances in different types of fractures, assessed by measurements of intraosseous pressures. Clin. Orth. Rel. Res. 84:11&127; 1972. 9. Wingstrand, H.; Stromquist, B.; Egund, N.; Gustofson, T.; Nilsson, L.T.; Throngren, K.G. Hemarthrosis in undisplaced cervical fractures. Acta Orthop. Scund. 57:305308; 1986. 10. Lang, P.; Jergesen, H.E.; Moseley, M.E.; Block, J.E.; Chafetz, N.I.; Genant, H.K. Avascular necrosis of the femoral head: High-field-strength MR imaging with histologic correlation. Radiology 169:517-524;1988. 11. Mitchell, D.G.; Joseph, P.M.; Fallon, M.; Hickey, W.; Kressel, H.Y.; Rao, V.M.; Steinberg, M.E.; Dalinka, M.K. Chemical-shift imaging of the femoral head: An in vitro study of normal hips and hips with avascular necrosis. AJR 148:1159-1164; 1987. 12. Mitchell, D.G.; Kressel, H.Y.; Arger, P.H.; Dalinka, M.; Spritzer, C.E.; Steinberg, M.E. Avascular necrosis of the femoral head: Morphologic assessment by MR imaging, with CT correlation. Radiology 161:739-742; 1986.
155-159,
1992 copyright
0730-725w92 $5.00 + .xl 0 1992 Pergamon Press plc
l Case Report
OCCULT POSTTRAUMATIC AVASCULAR NECROSIS OF HIP REVEALED BY MRI JEFFREY C. ALLARD, GUY PORTER, AND ROBERT W. RYERSON Departmentof Radiology, MusculoskeletalSection, University of Miami, Box 016960, Miami, FL, 33101, USA
Three hips with avascular necrosis in two patients had associated traumatic lesions noted on magnetic resonance imaging. Location of stress fracture in two femoral necks and acetabular contusion development prior to avascular necrosis favors these. processes as being etiologic. These cases are particularly noteworthy in that nondisplaced fractures or other musculoskeletal trauma not visible on plain films has rarely been associated with subsequent development of avascular necrosis. Keywords: Magnetic resonance; Avascular necrosis; Fracture; Hip.
2. An 81-year-old woman with multiple medical problems complained of right hip pain. Other than a 1-wk course of steriods, she had no predisposition for the development of AVN. Initial plain films were normal except for involutional osteoporosis [Fig. 2(A)]. Because of worsening pain, MRI was performed 5 mo later, demonstrating bilateral subcapital stress fractures and bilateral AVN [Fig. 2(B) and (C)l. Subsequent plain film examination showed collapse of right femoral head and sclerotic area in both femoral necks consistent with healed stress fractures [Fig. 2(D)]. The patient underwent a total right hip replacement confirming the presence of AVN. Subsequent radiographs have demonstrated similar changes in the left hip, but surgery here is being deferred.
INTRODUCTION MRI is the preferred modality for evaluation of the painful hip when plain films are normal and there is clinical suspicion for avascular necrosis (AVN) or occult fracture. ‘+j Fractures are both a common cause and a common result of AVN.5-8 Subcapital fractures of the femoral neck are especially prone to development of AVN, especially if the fracture is displaced or poorly reduced.’ We report two cases of radiologically occult trauma to the hip revealed with MRI and likely accounting for the development of AVN of the femoral head. CASE REPORTS 1. A 65year-old woman complained of right hip pain after a car accident. Plain films were normal, and MFU showed evidence of superior acetabular T1 and T2 prolongation consistent with a bone contusion [Fig. l(A) and (B)]. Biopsy was performed because of the remote possibility of neoplasm, and results were negative. The patient had gradual decrease in pain over a 4-mo period. Hip pain returned and was severe enough to warrant another MRl 7 mo after the initial trauma. Plain films at this time showed sclerosis of superior acetabulum. MRl showed AVN of femoral head [Fig. l(C) and (D)]. The patient underwent total hip replacement, which confirmed the presence of AVN with secondary degenerative changes. RECEIVED
DISCUSSION The pathogenesis of AVN is dependent on decrease in blood supply to the marrow. Femoral head blood supply originates from retinacular branches of the femoral circumflex arteries and the ligamenturn teres artery.5*7 Fractures of the femoral neck reduce blood supply by interrupting the retinacular vessels and capsular vessels. Hip dislocations reduce blood supply via ligamenturn teres. The small artery within ligamentum teres is an increasingly important source of blood in the elderly hip.7 This vessel, which is a branch of the obturator artery, might also be disrupted in direct acetabular trauma such
l/15/91; ACCEPTED 6128191. 155
156
Magnetic Resonance Imaging 0 Volume 10, Number 1, 1992
Fig. 1. (A) Sag&al MRI (SE 500/20) of right hip shows low signal of superior acetabulum consistent with acetabular contusion.
(B) Coronal MRI (SE 2000/80) shows increased signal in acetabulum consistent with edema or contusion. (C) Coronal MRI (SE 500/20) of pelvis shows low signal in right femoral head consistent with AVN. Note residual low signal in acetabulum correlating with sclerosis on plain films. (D) Coronal MRI (SE 2000/80) shows low signal in femoral head consistent with stage D AVN. as occurred in case 1. No bone displacement was evident in either of our cases, ordinarily a factor mitigating against AVN development. In Gardner’s series of femoral neck fractures, no patient with a nondisplaced fracture had this complication.’ It has heen postulated that an additional mechanism for intracapsular femoral neck fractures to cause AVN is by joint effusion tamponade of the medial femoral circumflex artery.g Nuclear medicine studies have dem-
onstrated diminished flow to the femoral head in patients who had minimally displaced fractures and joint effusions. Aspiration of hemarthrosis to prevent the theoretical complication of AVN has therefore been advocated.g Joint effnsions are also present in cases of AVN totally unrelated to trauma, in which cases they are considered to be the effect rather than the cause.’ Finally, there is evidence to indicate that the etiology of traumatic AVN of the hip is related to venous
&zult posttraumatic avascular necrosis of hip 0 J.C.
ALLARD
ET AL.
157
Fig. 2. (A) Initial plain film of both hips is normal except for demineralization. (B) Coronal MRI (SE 700120) shows transversely oriented low-signal areas in subcapital femoral neck consistent with stress fractures and low signal especially in right femoral neck consistent with AVN. (Figure continued
B
obstruction with secondary intraosseous hypertension. It has been clinically observed that subcapital femoral neck fractures with varus deformity are particularly likely to be complicated by AVN.7*8 An in vivo study of the intraosseous pressures in these fractures demonstrated a pulseless intracapital tracing in one-third, but in two-thirds of cases the intracapital pressures were greater than pressure measurements taken in the intertrochanteric regi0n.s These data would indicate that marrow hypertension is even more important than disruption of arterial inflow and that traumatic venous disruption or obstruction is the likely mechanism for this in-
next page.)
traosseous congestion, which may secondarily lead to ischemia and marrow necrosis. The MRI depiction of hip pathology is largely dependent on low-signal areas within otherwise normal highsignal fatty marrow on T,-weighted images. Vertically oriented low signal due to a high concentration of weight-bearing bony trabeculae should not be confused with a pathologic process, however. Various patterns of AVN have been described.5 Up to 80% of AVN cases demonstrate a characteristic “double-line sign” on T2weighted images, a feature present in both hips of case 2 [Fig. 2(C)].1,6*11The segmental distribution of abnor-
158
Magnetic Resonance Imaging 0 Volume 10, Number 1, 1992 Fig. 2. (cont.) (C) Coronal MRI (SE 2000/70) shows right joint effusion, low signal in femoral head consistent with AVN, and abnormal signal oriented transversely in subcapital regions indicating stress fracture. (D) Follow-up plain film shows collapse and sclerosis of right femoral head due to AVN and sclerosis of both subcapital regions indicating healed stress fractures (white arrows).
ma1 signal, particularly in the anterosuperior aspect of subchondral femoral head, is also useful for diagnosing AVN. 4*6*10-12Subchondral cysts should be differentiated from AVN by their tendency to occur on both sides of the joint space and frequent fluid signal characteriitic on MRI.5 MRI staging of AVN has been described and shown to be useful in the prediction of subchondral fracture development.6*‘2 In addition to the extent of signal abnormality, the center of the AVN lesion is least likely to have fracture when fat signal is present (stage A) and most likely to fracture when fibrous tissue is present (stage D). Intermediate stages have blood (stage B) and fluid signal (stage C). Based on this grading mechanism, both of our patients’ hips which were replaced were
stage D. Plain films or CT scans sometimes demonstrate subchondral collapse in AVN better than MRI, because of improved trabecular imaging. ‘* The role of MRI in diagnosis of traumatic conditions of the hip is less well established than that of diagnosing AVN. Bone bruise is a common entity, particularly about the knee, wherein there is a pattern of marrow edema similar to the pattern seen in the acetabulum of case 1 .* Pathologically, trabecular fracture is suspected. Usually healing ensues with return of normal marrow signal. Occasionally healing with sclerosis or fibrosis, or secondary osteonecrosis may result, resulting in low-signal persistence, as occurred in the acetabulum of case 1. Fractures tend to have a more linear morphology than
Occult posttraumatic avascular necrosis of hip 0 J.C. ALLARO ETAL.
bone contusion on MRI.3 Location of abnormal signal in femoral neck would also favor fracture rather than AVN. Fractures sometimes have a serpentine course, which if in a subcapital location might be difficult to distinguish from the “bandlike” pattern of AVN.3*5The subsequent plain films in case 2 are sufficiently characteristic for a healed stress fracture to indicate that the signal abnormality on MRI in this area is due to the same process. Increased sensitivity, specificity, and spatial resolution compared to bone scanning should promote MRI into the forefront of occult traumatic imaging. Our two cases, in addition, point out that occult trauma can lead to AVN of the femoral head. This complication has rarely been attributed to trauma when there is no displacement. Perhaps the increased usage of MRI in problematic hip pain cases will reveal additional cases where occult traumatic conditions are revealed, particularly in older patients wherein a history of trauma is not clearly elicited. REFERENCES B.G.; Kressel, H.Y.; Dalinka, M.K.; 1. Coleman, Scheibler, M.L.; Burk, D.L.; Cohen, E.K. Radiographitally negative avascular necrosis: Detection with MR imaging. Radiology 168525-528; 1988. 2. Deutsch, A.L.; Mink, J.H. Magnetic resonance imaging of musculoskeletal injuries. Rd. Clin. North Am. 27(5): 983-1002; 1989. 3. Deutsch, A.L.; Mink, J.H.; Waxman, A.D. Occult fractures of the proximal femur: MR imaging. Radiology 170:
159
113-l 16; 1989. 4. Markisz, J.A.; Knowles, R.J.R.; Altchek, D.W.; Schneider, R.; Whalen, J.P.; Cahill, P.T. Segmental patterns of avascular necrosis of the femoral heads: Early detection with MR imaging. Radiology 162:717-720; 1987. 5. Gillespy, T.; Genant, H.K.; Helms, C.A. Magnetic resonance imaging of osteonecrosis. Radiol. Clin. North Am. 24(2):193-208; 1986. 6. Mitchell, D.G.; Rao, V.M.; Dal&a, M.K.; Spritzer, C.E.; Alavi, A.; Steinberg, M.E.; Fallon, M.; Kressel, H.Y. Femoral head avascular necrosis: Correlation of MR imaging, radiographic staging, radionuclide imaging, and clinical findings. Radiology 162:709-715; 1987. 7. Garden, R.S. Low angle fixation in fractures of the femoral neck. J Bone Joint Surg. 43B:647*3; 1961. 8. Arnoldi, C.C.; Linderholm, H. Fracture of femoral neck: Vascular disturbances in different types of fractures, assessed by measurements of intraosseous pressures. Clin. Orth. Rel. Res. 84:11&127; 1972. 9. Wingstrand, H.; Stromquist, B.; Egund, N.; Gustofson, T.; Nilsson, L.T.; Throngren, K.G. Hemarthrosis in undisplaced cervical fractures. Acta Orthop. Scund. 57:305308; 1986. 10. Lang, P.; Jergesen, H.E.; Moseley, M.E.; Block, J.E.; Chafetz, N.I.; Genant, H.K. Avascular necrosis of the femoral head: High-field-strength MR imaging with histologic correlation. Radiology 169:517-524;1988. 11. Mitchell, D.G.; Joseph, P.M.; Fallon, M.; Hickey, W.; Kressel, H.Y.; Rao, V.M.; Steinberg, M.E.; Dalinka, M.K. Chemical-shift imaging of the femoral head: An in vitro study of normal hips and hips with avascular necrosis. AJR 148:1159-1164; 1987. 12. Mitchell, D.G.; Kressel, H.Y.; Arger, P.H.; Dalinka, M.; Spritzer, C.E.; Steinberg, M.E. Avascular necrosis of the femoral head: Morphologic assessment by MR imaging, with CT correlation. Radiology 161:739-742; 1986.