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MRI of Seemingly Isolated Greater Trochanteric Fractures

¹ Both authors: Department of Radiology, New York Presbyterian Hospital, 622 W 168th St., New York, NY 10032.

Received August 21, 2003; accepted after revision February 2, 2004.

 
Address correspondence to F. Feldman.

Abstract

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OBJECTIVE. The objective of this article is to show that greater trochanteric fractures commonly perceived on routine radiographs as isolated are often neither isolated nor minor and that MR images can serve as a basis for more informed treatment by revealing the actual extent of such fractures in acute posttraumatic settings.

CONCLUSION. A pitfall in diagnosing seemingly isolated greater trochanteric fractures on routinely used imaging techniques lies in the fact that the injuries usually involve a large anatomic area. In our experience, MRI more accurately defines the true geographic extent of greater trochanteric fractures sustained through acute trauma than do radiography and bone scintigraphy and thus could provide a more reliable basis for anticipating complications and for planning appropriate treatment.

Introduction

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Hip fractures have long been recognized as a major public health problem. In addition to requiring immediate orthopedic attention, hip fractures often entail protracted medical, rehabilitative, social, and psychiatric repercussions that directly affect health care economics [1]. In acute emergency settings, initial visualization of hip fractures most often is on radiographs. Bone scintiscans usually play a supplementary role and do not routinely reveal acute hip fractures, particularly in immunosuppressed or older patients in whom renal or circulatory failure contributes to delayed or poor radionuclide concentration. However, MRI, with its increasing acceptance and availability, has most often been used in documenting acute hip fractures that are clinically suspected but totally occult on routine imaging [2–4].

Our study emphasizes a role for MRI in another specific posttraumatic setting. In our experience, the diagnosis of isolated greater trochanteric fractures based on initial radiographs, bone scintiscans, and other commonly used imaging techniques has been misleading. The diagnostic pitfall lies in the failure of these techniques to fully define the geographic extent of these injuries; this deficiency results in masking coexisting and more complex components, invariably leading to underestimation of the injuries. Although the treatment favored for presumed isolated greater trochanteric fracture has most often been nonsurgical [5–11], treatment might be altered if the actual extent of the injury were known. This knowledge is particularly important if immediate or early weightbearing is contemplated for those potentially at risk for displacement, including osteopenic, obese, recalcitrant, or older patients.

Materials and Methods

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We identified 37 consecutive patients (12 men and 25 women; age range, 50–95 years old) who fell while in the hospital or who presented in the emergency department after sustaining a fall between 1990 and 2003. Initial radiographs (and in 10 patients, supplementary bone scintiscans) showed greater trochanteric fractures. These patients also underwent MRI 3–24 hr after the fall on superconductive 1.5-T magnets (Signa, GE Healthcare or, in early cases, Gyroscan or Gyroview, Philips) in the coronal, axial, and sagittal planes. Sequences used included spin-echo T1-weighted (TR range/TE range, 400–700/10–18; on older units, 700/20–30), T2-weighted (2,000/100 on older units) or T2-weighted fast spin-echo with fat saturation (3,200–5,300/72–84; slice thickness, 3 mm; 0.3- to 0.5-gap interspaces; matrix, 256 x 192–256; and number of excitations, 2). Body coils and large fields of view (28–38 cm) were preferred for visualization of contralateral injury.

For earlier hip fracture cases, routine bone scintiscans (five patients), CT scans (five patients; slice thickness, 1–3 mm; sagittal and coronal reconstructions with high-spatial-resolution bone algorithms); and routine tomograms (slice thickness, 1–2 mm;) (Figs. 1A, 1B, 1C, 1D, and 1E) were obtained. However, in view of the well-known ability of MRI to document occult fractures [2–4], patients who have presented more recently have been sent directly to MRI after undergoing routine radiography and discussion with referring physicians.

View larger version (112K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 1A. —70-year-old woman who presented in emergency department with right hip pain after trauma. Anteroposterior radiograph shows only isolated greater trochanteric fracture (arrows).

View larger version (68K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 1B. —70-year-old woman who presented in emergency department with right hip pain after trauma. Radionuclide-enhanced bone scintiscan obtained on same day as A shows radionuclide predominantly concentrated in greater trochanter.

View larger version (180K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 1C. —70-year-old woman who presented in emergency department with right hip pain after trauma. Coronal T1-weighted MR image (TR/TE, 700/30; slice thickness, 5 mm; interslice, 0) shows right greater trochanteric fracture (arrow) extending to intertrochanteric region without involving medial cortex.

View larger version (87K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 1D. —70-year-old woman who presented in emergency department with right hip pain after trauma. Axial T1-weighted MR image (700/30; slice thickness, 3 mm; interslice, 0) confirms that fracture (arrow) fails to extend to medial femoral cortex.

View larger version (129K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 1E. —70-year-old woman who presented in emergency department with right hip pain after trauma. Anteroposterior tomogram (slice thickness, 2 mm) obtained immediately after injury only shows greater trochanter fracture (arrow) on multiple sections.

Institutional review board category 3 criteria were met because all studies were performed for clinical indications considered acceptable for patient care. Two attending musculoskeletal radiologists retrospectively reviewed all studies in consensus.

Results

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MRI documented isolated greater trochanteric fractures as diagnosed on initial radiographs and bone scintiscans in two (5%) of 37 patients. However, MRI additionally revealed more complex injuries in 35 patients (95%) (Figs. 1A, 1B, 1C, 1D, 1E, 2A, 2B, 2C, 2D, 3A, 3B, 3C, 3D, 4A, 4B, 4C, and 4D). Bone scintiscans acquired in five patients before MRI showed radionuclide concentrated chiefly around the greater trochanter. None of the bone scintiscans definitively showed fracture propagations (Fig. 1B).

View larger version (147K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 2A. —87-year-old man who presented with left hip pain immediately after trauma. Anteroposterior radiograph shows only isolated greater trochanteric fracture (arrow), with fragments displaced upward, medially, and posteriorly.

View larger version (115K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 2B. —87-year-old man who presented with left hip pain immediately after trauma. Axial CT scan (slice thickness, 3 mm) corroborates findings on routine radiograph (A), with fracture (arrows) confined to greater trochanter.

View larger version (112K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 2C. —87-year-old man who presented with left hip pain immediately after trauma. Axial T1-weighted spin-echo MR image (TR/TE, 600/14; slice thickness, 3 mm; interslice section, 0) shows fractured left greater trochanter (arrows) with focally decreased signal.

View larger version (94K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 2D. —87-year-old man who presented with left hip pain immediately after trauma. Coronal T1-weighted spin-echo MR image (600/14; slice thickness, 3 mm; interslice section, 0) shows greater tuberosity fracture (thick arrow) extending to medullary diaphysis (thin arrow).

View larger version (161K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 3A. —60-year-old man who presented with left hip pain after trauma. Anteroposterior radiograph shows only isolated greater trochanteric fracture (arrow), with fragments displaced upward, medially, and posteriorly.

View larger version (72K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 3B. —60-year-old man who presented with left hip pain after trauma. Axial CT scan (slice thickness, 3 mm) obtained with bone algorithm reveals left greater trochanter fracture (arrow) on this and other reconstructed planes.

View larger version (105K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 3C. —60-year-old man who presented with left hip pain after trauma. Axial T1-weighted spin-echo MR image (TR/TE, 600/14; slice thickness, 3 mm; interslice section, 0) shows diminished signal (arrows) confined to left greater trochanter with edema in femoral neck that coincides with CT evidence of isolated injury.

View larger version (88K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 3D. —60-year-old man who presented with left hip pain after trauma. Coronal T2-weighted fast spin-echo fat-suppressed MR image (5,300/90) shows greater trochanter (upper arrow) and intertrochanteric and mid diaphyseal fracture extensions (lower arrows) with associated intramedullary edema.

View larger version (153K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 4A. —87-year-old woman who presented with right hip pain after trauma. Anteroposterior radiograph shows only isolated greater trochanteric fracture (arrow), with fragment displaced upward, medially, and posteriorly.

View larger version (152K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 4B. —87-year-old woman who presented with right hip pain after trauma. Selected axial (B) and coronal (C) reconstructions and sagittal sections (not shown) of axial CT scan (slice thickness, 2 mm) obtained with bone algorithm reveal only nonpropagated greater trochanteric fracture (arrows).

View larger version (114K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 4C. —87-year-old woman who presented with right hip pain after trauma. Selected axial (B) and coronal (C) reconstructions and sagittal sections (not shown) of axial CT scan (slice thickness, 2 mm) obtained with bone algorithm reveal only nonpropagated greater trochanteric fracture (arrows).

View larger version (128K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 4D. —87-year-old woman who presented with right hip pain after trauma. Coronal T1-weighted MR image of right hip (TR/TE, 600/14; slice thickness, 3 mm; interspace, 0) shows fracture emanating from base of greater trochanter (white arrow) to intertrochanteric regions with additional diaphyseal extension on other sections. Note patchy edema in right ilium (black arrow).

MRI performed 3–24 hr after the injury documented various degrees of intramedullary fracture ramifications (Figs. 1A, 1B, 1C, 1D, 1E, 2A, 2B, 2C, 2D, 3A, 3B, 3C, 3D, 4A, 4B, 4C, 4D, 5A, 5B, 5C, and 5D). In this series, 24 of the 27 patients in the eighth and ninth decades of life were most likely to sustain hip fractures. In 22 of 37 patients, the right hip was fractured; 25 of the 37 patients were women. The most common fracture pattern, pattern 1, extended from the superolateral to the inferomedial cortices of the intertrochanteric region. The second most common, pattern 2, displayed the features of pattern 1 plus diaphyseal extension (Figs. 2C, 3D, and 4C). In pattern 3, only the superolateral femoral cortex was involved, with a partial intertrochanteric extension (Figs. 1A, 1B, 1C, 1D, and 1E). The least common pattern, pattern 4, had features of pattern 1 fractures plus superior extension into the femoral neck (Figs. 5A, 5B, 5C, and 5D).

View larger version (12K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 5A. —Illustrations of propagations of greater trochanter fractures seen on MR images of 35 patients. In pattern 1, greater trochanter fracture extends to intertrochanteric region and its lateral and medial cortices (21 patients).

View larger version (15K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 5B. —Illustrations of propagations of greater trochanter fractures seen on MR images of 35 patients. Pattern 2 fracture has characteristics of pattern 1 fracture plus extension of fracture to diametaphysis (11 patients).

View larger version (13K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 5C. —Illustrations of propagations of greater trochanter fractures seen on MR images of 35 patients. In pattern 3, greater trochanter fracture only extends to superolateral cortex of intertrochanteric region (two patients).

View larger version (13K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 5D. —Illustrations of propagations of greater trochanter fractures seen on MR images of 35 patients. Pattern 4 fracture has characteristics of pattern 1 fracture plus superior extension of fracture to base of femoral neck (one patient).

Two of the 37 patients with MRI-corroborated fractures were treated conservatively with bed rest. Five of the remaining 35 patients with intramedullary extension below the intertrochanteric region were poor surgical risks. Ambulation was initially proscribed for these patients, and follow-up was required for 2–3 months until the fractures healed. All 30 remaining patients with intramedullary extension of any kind, without respect to pattern, underwent surgery. Treatment of proximal femoral fractures varies from region to region. In our institution, treatment of complex greater trochanteric fractures seen on MRI was changed from medical to surgical for these 30 patients. Whether fracture-line propagations abutted or extended beyond one or both intertrochanteric cortexes, or whether the propagations were or were not displaced did not affect the decision to perform surgery, as has been noted in some studies [5–7]. In our series, five of 37 patients were deemed poor surgical risks, and two with MRI-corroborated isolated trochanteric fractures were treated conservatively. Therefore, outcome was influenced in the remaining 30 patients who underwent surgery based on MRI findings for intramedullary fracture propagations. Decisions to perform surgery were not influenced by any specific fracture pattern.

Discussion

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Radiographically documented isolated greater trochanteric fractures, as reflected by the sparsity of orthopedic reports and limited textbook coverage of the subject, have been thought to be uncommon [8–15]. Because of their purported rarity, greater trochanteric fractures have been included only incidentally, if at all, in most conventional hip fracture classifications [6–19].

The greater trochanter is most vulnerable at its tip and upper portion, but its fracture mechanisms have been debated [10, 14, 15]. Avulsion of the greater trochanter, with physeal separation, occurs most frequently in children or adolescents in whom muscle violence or twisting are more common causative factors than in adults [10, 14, 20]. Muscle action alone is a doubtful cause of isolated greater trochanter injuries in adults, with direct blows or falls being more likely mechanisms [10, 14].

Opinions regarding primary disruptive muscle after a fracture have ranged from the abductors (i.e., the gluteus minimus and gluteus medius) alone [21] to the abductors plus the external or lateral rotators [20]. Expected patterns of disruption have also been based on insertions alone [14]. Some authors [21] contend that unapposed external rotator muscles such as the gluteus minimus avulse the anterosuperior angle while the gluteus maximus avulses a portion of the posteroinferior angle. Others [10–15] postulate that the gluteus medius alone or in conjunction with the other gluteal muscles avulses the entire trochanter. Because the gluteus medias straddles the fracture line, its contraction has been thought to counteract rather than to contribute to fragment displacement. However, these theoretic results are not consistently seen on routine radiographs because displaced or comminuted fragments in all age groups are similarly directed upward, backward, and inward (Figs. 2A, 2B, 3B, and 3C).

Clinically, pain may be focal, minimal, or initially absent. Ecchymosis may or may not be evident. The absence of a discrepancy in the lengths of a patient's legs or the shortening of the affected side despite radiographic evidence of trochanteric displacement or fragmentation has led to mistaken interpretations of greater trochanteric fractures as coxitis or peritrochanteric bursitis. The paucity of expected acute physical findings combined with underestimation of the extent of injury on radiographs has resulted in incomplete comprehension of the injury, with treatment chiefly consisting of bed rest, abduction with or without traction, casting, or limited weightbearing [6, 10, 22].

In reporting the results of a study somewhat related to ours, Schultz et al. [5] emphasized that "incomplete intertrochanteric fractures, as a previously unrecognized subset of intertrochanteric fractures, were diagnosed unequivocally only on MRI" and that "50% of fractures which crossed the midline in the MRI coronal plane were operated. The 23% which did not undergo surgery constituted the nonsurgical group." These investigators noted the poor correlation between radiographic and MRI findings.

Two smaller studies more directly related to our own confirm the frequent complexity of the seemingly isolated greater trochaneric fractures as evidenced on MRI [6, 7]. Seven of the eight patients studied by Omura et al. [6] had such fractures. None of the eight patients underwent surgery despite "fracture lines leading from the greater trochanter towards the lesser." These researchers also noted that "weightbearing and motion of the hip joint may lead an incomplete trochanteric fracture to progress to a complete fracture." One of their patients was treated with 1 week of bed rest and six, with 1–3 weeks of indirect traction followed by progressive ambulation using walkers. Of the 13 patients studied by Craig et al. [7], 10 were found to have more complex injuries than the apparently isolated greater trochanteric fractures. Six of 10 patients underwent surgery because MRI showed intramedullary fracture extension. Although these researchers noted that "occult hip fractures can lead to disastrous consequences if not diagnosed," four of the 10 patients with "limited extension" and three with isolated greater trochanteric fractures did not undergo surgery. The cases of eight patients with limited follow-up were not further detailed.

In our study, no particular pattern of fracture-line propagation affected which cases the surgeons selected to treat with nonsurgical versus surgical intervention. All 30 patients who had no medical contraindications underwent surgery, regardless of the fracture pattern. The prime criterion for performing surgery was extension of the fracture line beyond the base of the greater trochanter, regardless of propagation pattern. Decisions to perform surgery were influenced neither by inferior diaphyseal or superior metaphyseal involvement nor by the presence or absence of fracture displacement nor by combinations of these conditions.

Our study had the largest cohort of patients to date; however, its limitations lie in the fact that although the patients who were treated nonsurgically (five patients with medical contraindications and two with isolated greater trochanteric fractures) were followed for 2 months after treatment, the healing of their fractures was documented solely on radiographs and by clinical orthopedic evaluation, not on MRI. Identification of more specific criteria for performing surgery or of contraindications to surgery will require larger prospective series, further analysis of the influence of specific fracture patterns on treatment decisions, and clinical follow-up using MRI when economically feasible. With heightened awareness of the complexity of greater trochanteric fractures, radiologists can educate surgical colleagues as to their MRI findings and can continue to add objective data so that MRI-based treatment criteria may evolve.

In conclusion, greater trochanteric fractures perceived as isolated on commonly used imaging studies are frequently neither isolated nor minor injuries. They present a diagnostic pitfall because they are frequently more extensive than they appear on routine radiographs. We found that MRI defined the actual geographic extent of greater trochanteric fractures more accurately than other imaging techniques. Therefore, MRI findings may affect patient outcome and costs by altering previously accepted treatment regimens. Implied savings may also be realized because follow-up to prevent fracture extensions could be decreased and delayed healing, which particularly affects older, nonsurgically stabilized patients, could be shortened.

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This Article Abstract Figures Only Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Feldman, F. Articles by Staron, R. B. Search for Related Content PubMed PubMed Citation Articles by Feldman, F. Articles by Staron, R. B. Social Bookmarking                      What's this?