1992, The British Journal of Radiology, 65, 105-111
VOLUME 65 NUMBER 770
FEBRUARY 1992
The British Journal of Radiology Computed tomographic assessment of soft tissue abnormalities following calcaneal fractures By S. A. Bradley, FRCR and A. M. Davies, FRCR Department of Radiology, Birmingham Accident Hospital, Bath Row, Birmingham, UK
(Received 10 January 1991 and in revised form 26 July 1991, accepted 6 August 1991)
Keywords: Calcaneum, Fracture, Computed tomography Abstract. Computed tomographic (CT) examinations of 50 acute calcaneal fractures were compared with a further series of 77 fractures in which the date of injury preceded the CT by 6 months or more. 42 (84%) of the fractures in the acute group and 55 (71%) in the chronic group were classified as intra-articular and they form the basis of this study. The alteration in the position of the peroneal tendons in the two groups was similar, with a 5% or less difference in each category. In the acute group the peroneal tendons were normally located in 40.4% of the cases, entrapped by bone in 11.9%, subluxed in 33.3% and dislocated in 14.2%. Structural abnormalities of the peroneal tendons and surrounding soft tissues were identified in 52.4% of the acute group and in 61.1% of the chronic group. The incidence of partial rupture of the peroneal tendons in the chronic group was approximately one third that in the acute group, but the low incidence of complete tendon rupture remained unchanged. The inference from these observations is that, in the majority of cases, partial peroneal tendon rupture is reversible, whereas complete rupture is not. Seven fractures were common to both series and from this limited group the identification of haemorrhage around the peroneal tendons in the acute phase was shown not to be related to the subsequent development of chronic stenosing tenosynovitis. Various abnormalities of the medial tendons of the hindfoot were identified in 17% of the acute group and in 18% of the chronic group. Following calcaneal fracture, CT in both the immediate post-fracture period and in the late phase can be used to detect and classify the soft tissue changes. The limitations of comparing the two groups in this study are discussed. When dealing with musculoskeletal trauma, there is a tendency for the attending clinician and radiologist to concentrate on the bony abnormalities and overlook the associated soft tissue injuries. Many of the numerous articles published on the use of computed tomography (CT) in the evaluation of acute calcaneal fractures deal principally with fracture patterns illustrated by CT scans imaged on a bone window and only make a brief comment on soft tissue involvement (Guyer et al, 1985; Heger et al, 1985; Pablot et al, 1985; Segal et al, 1985; Gilmer et al, 1986; Hindman et al, 1986; Heuchemer et al, 1988; Lowrie et al, 1988; Crosby & Fitzgibbons, 1990). A few recent studies have emphasized the role of CT in the assessment of tendon trauma following acute calcaneal fractures (Rosenberg et al, 1987) and in their longterm follow-up (Bradley & Davies, 1990), as well as in other soft tissue afflictions of the hindfoot (Rosenberg etal, 1986, 1988a, 1988b, 1988c; Keyseretal, 1988). The purpose of this paper is both to study prospectively with CT the soft tissue changes around the hindfoot in a group of patients presenting with an acute calcaneal fracture, and to compare the findings with a second . Address correspondence to Dr A. M. Davies, Department of Radiology, Birmingham Accident Hospital, Bath Row, Birmingham. Vol. 65, No. 770
group on whom CT examination was performed more than 6 months after sustaining the injury, Patients and methods High resolution CT of the hindfeet was performed on either a Siemens DRH or CR Whole Body Scanner in both the coronal and the axial planes (Smith & Staple, 1983) on a series of 40 patients who had presented with an acute calcaneal fracture within the previous 2 weeks. Contiguous slices measuring 4 mm were obtained and viewed on bone and soft tissue window settings. The CT examinations were subsequently reviewed and observations regarding bone and soft tissue changes recorded. The abnormalities in this acute group were compared with the findings in a second group of 67 patients with calcaneal fractures sustained more than 6 months before CT examination. The majority of the cases in this latter chronic group have been the subject of a study published previously (Bradley & Davies, 1990) and are included in the current paper for the purposes of comparison, CT abnormalities of the soft tissues of the hindfoot were classified either as alterations in the position of the tendons or as alterations in the structural appearances of the tendons and surrounding soft tissues. A normal tendon appears as a well defined, homogeneous, 105
S. A. Bradley and A. M. Davies rounded density of higher attenuation than muscle and is accentuated by surrounding fat. Obliteration of this fat by a soft tissue density indicates either haemorrhage/ granulation tissue in the acute phase, or the scar tissue of chronic stenosing tenosynovitis in the late phase. Distension of the synovial sheath by a halo of low density fluid is characteristic of chronic tenosynovitis. Increased girth of the tendon with heterogeneous areas of decreased attenuation within the tendon substance indicates a partial rupture, whereas a complete rupture is detected by an absence of a portion of the tendon with the defect either replaced by fat or fluid (Rosenberg et al, 1988a; Bradley & Davies, 1990). Results A total of 50 calcaneal fractures were identified in 40 patients of the acute group and 77 fractures were identified in 67 patients of the chronic group. There were 32 (80%) male patients and 8 (20%) female patients in the acute group and 48 (72%) males and 17 (28%) females in the chronic group. The age range in the acute group was 19-81 years with a mean age of 44 years. The age range in the chronic group was 12-83 years with a mean age of 48 years. The plain film incidence of the different types of calcaneal fracture are summarized in Table I according to the Schmidt and Weiner modification of the Rowe and Essex-Lopresti classifications (Essex-Lopresti, 1952; Rowe et al, 1963; Schmidt & Weiner, 1982). 42 (84%) fractures in the acute group and 55 (71 %) in the chronic group were categorized as intra-articular fractures, with involvement of the posterior subtalar joint (Types 4, 5a & 5b of Table I). The remainder of this paper is confined to this intra-articular fracture category. The position of the peroneal tendons for both groups are shown in Figure 1 and illustrated in Figure 2. Structural changes of the peroneal tendons were identified in 22 (52.4%) patients in the acute group and 34 (62%) patients in the chronic group. A breakdown of these changes is shown in Figure 3 (a & b). In all five acute fractures in which haemorrhage alone was identified around the peroneal tendons, the tendons were also Table I. Calcaneal fractures: classification and incidence (Schmidt and Weiner modification of Rowe and Essex-Lopresti classifications), after Berquist & Johnson, 1989 Type
Published incidence
la (tuberosity) lb (sustentaculum) lc (anterior process) Id (infero-lateral) 2 (Achilles avulsion) 3 (linear extra-articular) 4 (linear intra-articular) 5a (tongue depression) 5b (joint depression)
6 3 15 1 4 19
106
Acute group 6
11.7
2
9.1 1.3 2.6 3.9 3.9
8
10-26 5
43-60
Chronic group
28 56
29.8 37.7
Normal/Trapped
Subluxed
10
20
30
40
50
% cases ^ H Acute Fractures
MSSSi Chronic Fractures
Figure 1. Position of the peroneal tendons. shown to be either subluxed or dislocated (Fig. 4a). In nine of the 16 cases in which there was partial rupture of the peroneal tendons, with or without surrounding haemorrhage, the tendons were also shown to be either subluxed or dislocated. Structural changes in or around the peroneal tendons were present in 14 of the 20 acute cases with subluxation or dislocation of the tendons (Fig. 4a & c). Almost half the acute fractures exhibited lateral bony spur formation impinging on the peroneal tendons (Fig. 5), best shown on axial CT. This feature was common in those cases in which the peroneal tendons were trapped by bone in their normal anatomical position. There was otherwise no relationship between the lateral spur formation and the appearances of the peroneal tendons and the surrounding soft tissue. Medially, in the acute group, bony encroachment on the abductor hallucis longus muscle was revealed in four cases, partial rupture of the flexor hallucis longus tendon in two cases and complete rupture of the tibialis posterior tendon in one case. In the chronic group, there was scarring surrounding the flexor hallucis longus tendon in five cases, bony encroachment in two cases and rupture in one case. Rupture of both the flexor hallucis longus and flexor digitorum longus tendons was detected in one case and scar tissue surrounding the tibialis posterior tendon was also detected in one case. In a minority of acute cases further soft tissue injury to the ankle was identified by an ankle joint effusion or superficial haemorrhage adjacent to the lateral malleolus (Fig. 6). Four patients with seven intra-articular fractures were common to both the acute and chronic groups in this study. In one case normal peroneal tendons were present bilaterally on both CT examinations. In one case extensive haemorrhage surrounding the peroneal tendons largely resolved to reveal intact tendons (Fig. 7). In one case scar tissue developed around previously normal peroneal tendons and in another case partial rupture of the peroneal tendons persisted on the second CT examination. Discussion The literature on calcaneal fractures is confusing regarding which factors are significant or of prognostic The British Journal of Radiology, February 1992
CT of soft tissues following calcaneal fractures
Figure 2. Coronal CT, soft tissue window, (a) Acute right calcaneal fracture showing entrapment of the peroneal tendons between the distal fibula and displaced lateral wall of the calcaneum (1). Haemorrhage around the flexor hallucis longus tendon (2) and bony fragments involving the inferior aspect of the abductor hallucis muscle (3). (b) Acute bilateral calcaneal fractures showing subluxation of the left peroneal tendons (4). (c) Bilateral calcaneal fractures, 33 months after injury, showing the peroneal tendons to be trapped on the right and dislocated on the left.
Haemorrhage - ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ H
Ch Sten Tenosynov
Partial Rupture ~ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ H
HI
Ch Tenosynovitis
Haem & Part Rupt - ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ H
Ch Partial Rupture
Complete Rupture - ^ H
Complete Rupture
0
5
10
15
20
25
30
0
% cases
(a)
(b)
Figure 3. Structural changes in and around the peroneal tendons in the acute (a) and chronic (b) groups. Vol. 65, No. 770
107
S. A. Bradley and A. M. Davies
(b)
Figure 4. Coronal CT, soft tissue window, (a) Acute calcaneal fracture showing subluxation of the peroneal tendons with obliteration of the surrounding fat by haemorrhage. The loculus of air just lateral to the peroneus longus tendon (arrow) indicates the compound nature of the injury, (b) Acute right calcaneal fracture. The diffuse swelling of the peroneal tendons (arrow) indicates internal disruption due to partial rupture, (c) Acute calcaneal fracture. The central relative lucency within the subluxed tendon sheath indicates complete rupture.
value to the final outcome (Paley & Hall, 1989). Whilst post-traumatic osteoarthrosis of the posterior subtalar joint is arguably the principal cause of morbidity following an intra-articular fracture, another major, longterm complication is injury to the peroneal tendons (Slatis et al, 1979). At the time of injury the downward force of the talus will split the calcaneum into two major fragments. The resultant flattening, with outward splaying of the lateral wall, will displace and damage the 108
peroneal tendons (Palmer, 1948; Essex-Lopresti, 1952). Before the introduction of CT and magnetic resonance imaging (MRI), damage to the peroneal tendons could be either inferred by lateral broadening of the calcaneum or directly visualized by peroneal tenography (Rosenberg et al, 1987). This latter technique is rarely used as it is invasive and difficult to perform in the acute phase when the ankle may be grossly swollen and the tendons displaced. In contrast, CT of the hindfeet is The British Journal of Radiology, February 1992
CT of soft tissues following calcaneal fractures
Figure 5. Axial CT, soft tissue window, (a) Acute right calcaneal fracture with a lateral spur impinging on the peroneal tendons which are swollen and of decreased attenuation indicating internal disruption, (b) Old right calcaneal fracture, 18 months after injury, showing similar appearances to (a).
relatively non-invasive, easy to perform, allows simultaneous assessment of bony and soft tissue structures and can be undertaken in the presence of an external cast. An additional advantage in a patient with a unilateral fracture is that CT of the uninvolved foot, examined simultaneously, can act as a normal control. The confidence with which observations can be made from CT regarding soft tissue abnormalities of the hindfeet is largely a result of the work originating from one institution which, in many instances, included surgical correlation (Rosenberg et al, 1986, 1987, 1988a, 1988b, 1988c). This series, comprising 107 examinations, is to the authors' knowledge, the largest published CT study on calcaneal fractures. The results of the acute intra-articular fracture group agree in many respects with the findings of Rosenberg et al (1987). Bony entrapment of the peroneal tendons was present in 11.9% of the current acute group (Fig. 1) and in 13% of Rosenberg's group. However, Rosenberg identified subluxation or dislocation in only 25% of cases, as opposed to 47.5% in this study (Fig. 1). This discrepancy may be explained, in part, by the fact that in this study there was no distinction between lateral displacement and subluxation of the tendons. Haemorrhage or early scar tissue around the peroneal tendons was present in 21% of Rosenberg's cases as compared with haemorrhage, with or without partial tendon rupture, in 26.2% of the current acute series (Fig. 3a). Rosenberg and his colVol. 65, No. 770
leagues did not identify any structural changes within the peroneal tendons, whereas the current study concluded that partial or complete rupture was present in 40.5% of cases (Fig. 3a). This may be caused by the
Figure 6. Coronal CT, soft tissue window. Acute left calcaneal fracture showing an ankle joint effusion (arrow) and minor haemorrhage around the peroneal tendons.
109
S. A. Bradley and A. M. Davies
(a)
(b)
Figure 7. Coronal CT, soft tissue window. Gross bilateral calcaneal and talar fractures. In the acute phase (a) many of the tendons are surrounded by haemorrhage, (b) 8 months later scar tissue is present but many normal tendons are visible surrounded by fat.
fact that their original paper was one of the earlier publications concerning CT of tendons and, with only few exceptions, their patients were examined in the axial plane alone (Rosenberg et al, 1987). The authors of the current study do not consider themselves guilty of the overenthusiastic identification of peroneal tendon rupture in light of the more recent literature on the subject (Rosenberg et al, 1988a, 1988b, 1988c). In this study, only a limited comparison of the two groups is possible, as they are not identical in a number of respects. The principal difference is the bias in patient selection. All those patients presenting with an acute calcaneal fracture during the study period underwent CT routinely, whereas the chronic group represents the one third of patients who had agreed to attend for CT following receipt of a written request. Nevertheless, the age range, sex ratio and incidence of the various types of fracture (Table I) do suggest that there are moderate similarities. In particular, the position of the peroneal tendons in patients with intra-articular fractures is remarkable similar for both groups, with less than 5% variation in any of the four categories (Fig. 1). The incidence, in the chronic group, of chronic partial tears of the peroneal tendons of approximately one third that in the acute phase (Fig. 3) would indicate that, in the majority of cases, this change is reversible. A similar incidence of complete tendon rupture in the two groups suggests the contrary (acute group = 2.4%, chronic group = 3.6%). However, the numbers involved are small and there is no conclusive proof in this study that the cases of complete rupture in the chronic group were sustained at the time of the injury. It is likely that many of those patients eligible for the chronic group who declined the invitation to attend for CT were asymptomatic. The majority who did attend were probably motivated by pain and disability, hence the higher incidence of structural changes in the chronic group relative to the acute group. It might be expected that haemorrhage around the 110
peroneal tendons in the acute group (26.2%) (Fig. 4a) would pre-dispose to scar tissue formation (chronic stenosing tenosynovitis) in the chronic group (25%) (Fig. 3). No such association was found either by Rosenberg et al (1987) in their limited follow-up of 10 cases or in the two cases in the current study, common to both groups, which exhibited these features (Fig. 7). Abnormalities of the medial tendons were considerably less common than those affecting the peroneal tendons and were found in 17% and 18% of the acute and chronic cases, respectively. This lower incidence reflects the mechanism of injury in that the anteromedial fragment of the calcaneum, including the sustentaculum, usually remains reduced to the undersurface of the talus without injuring the medial tendons, whereas the postero-lateral fragment displaces laterally thereby damaging the adjacent peroneal tendons. However, damage to the medial tendons does occur and can be demonstrated by CT (Carr, 1990). This study confirms that in both the immediate postfracture period and long after injury CT may be used to detect soft tissue injuries. Whilst haemorrhage around the peroneal tendons appears to be of limited significance and two thirds of peroneal tendon ruptures probably resolve, a full longitudinal study would be necessary to categorize which soft tissue changes are ultimately of definite prognostic significance. There remains considerable controversy regarding the treatment of calcaneal fractures; operative or non-operative. The ability of CT to demonstrate both bony and soft tissue abnormalities means that the technique is of value to the proponents of both modes of management. Three-dimensional CT reconstructions may improve the surgeon's visualization of the fractures before operation (Carr et al, 1990; Allon & Mears, 1991) and direct measurements from CT of calcaneal deformity can be used to assess the surgeon's success in restoring the anatomical congruity of the bony structures (Frahm et al, 1989; Krause & Hedtler, 1990). With regards to the The British Journal of .Radiology, February 1992
CT of soft tissues following calcaneal fractures
soft tissue injuries, MRI may be preferred because of its superior soft tissue contrast resolution (Zeiss et al, 1991), but CT remains an excellent alternative when financial considerations and availability limit access to MRI (Rosenberg et al, 1988a).
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HEDTLER,
W.,
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Morphometric
approach to the evaluation of the os calcis in computed tomography. Fortschritte auf dem gebiete der Rontgenstrahlen und der Nuclearmedizin, 152, 303—306. LOWRIE, I. G., FINLAY, D. B., BRENKEL, I. J. & GREGG, P. J.,
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BERQUIST, T. H. & JOHNSON, K. A., 1989. Radiology of the Foot
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1985. The value of computed tomography in the early assessment of comminuted fractures of the calcaneus: a review of 3 patients. Journal of Pediatric Orthopaedics, 5, 435-438. PALEY, D. & HALL, H., 1989. Calcaneal fracture controversies. Can we put Humpty Dumpty together again? Orthopedic Clinics of North America, 20, 665-677. PALMER, I., 1948. The mechanism and treatment of fractures of the calcaneus. Journal of Bone and Joint Surgery, 30(A), 2-8.
CARR, J. B., NOTO, A. M. & STEVENSON, S., 1990. Volumetric
ROSENBERG, Z. S., FELDMAN, F. & SINGSON, R. D., 1986.
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Peroneal tendon injuries: CT analysis. Radiology, 161, 743-748.
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FITZGIBBONS, T.,
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tomography scanning of acute intra-articular fractures of the calcaneus. Journal of Bone and Joint Surgery, 72(A), 852-859. ESSEX-LOPRESTI, P., 1952. Fractures of the os calcis. The mechanism, reduction and results in fractures of the os calcis. British Journal of Surgery, 39, 395-419. FRAHM, VON R., FRITZ, H. & DRESCHER, E., 1989. Changes in
the foot angle after calcaneal fractures. Fortschritte auf dem gebiete der Rbntgenstrahlen und der Nuclearmedizin, 151, 192-195. GlLMER, P. W., HERZENBERG, J., FRANK, J. L., SlLVERMAN, P . , MARTINEZ, S. & GOLDNER, J. L., 1986. Computerised
tomographic analysis of acute calcaneal fractures. Foot and Ankle, 6, 184-193. GUYER, B. H., LEVINSOHN, E. M., FREDRICKSON, B. E., BAILEY,
G. L. & FORMIKEL, M., 1985. Computed tomography of calcaneal fractures: anatomy, pathology, dosimetry and clinical relevance. American Journal of Roentgenology, 145, 911-919. HEGER, L., WULFF, K. & SEDDIQUI, M. S. A., 1985. Computed
tomography of calcaneal fractures. American Journal of Roentgenology, 145, 131-137. HEUCHEMER, VON T H . , BARGON, G., BAUER, G. & MUTSCHLER,
W., 1988. The advantages of using CT for the diagnosis and classification of intra-articular fractures of the os calcis. Fortschritte auf dem gebiete der Rontgenstrahlen und der Nuclearmedizin, 149, 8-14. HINDMAN, B. W., Ross, S. D. K. & SOWERBY, M. R. R., 1986.
Fracture of the talus and calcaneus: evaluation by computed tomography. Journal of Computer Assisted Tomography, 10, 191-196. KEYSER, C. K., GILULA, L. A., HARDY, D. C , ADLER, S. &
VANNIER, M., 1988. Soft-tissue abnormalities of the foot and
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ROSENBERG, Z. S., FELDMAN, F., SINGSON, R. D. & PRICE, G. J.,
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1988a.
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1988b. Ankle tendons: evaluation with CT. Radiology, 166, 221-226. ROSENBERG, Z. S., JAHSS, M. H., NOTO, A. M., SHEREFF, M. J., CHEUNG, Y., FREY, C. C. & NORMAN, A., 1988c. Rupture of
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tomography scanning techniques for the hindfoot. Clinical Orthopedics and Related Research, 177, 34-38. ZEISS, J., EBRAHEIM, N., RUSIN, J. & COOMBS, R. J., 1991.
Magnetic resonance imaging of the calcaneus: normal anatomy and application in calcaneal fractures. Foot and Ankle, 11, 264-273.
11
VOLUME 65 NUMBER 770
FEBRUARY 1992
The British Journal of Radiology Computed tomographic assessment of soft tissue abnormalities following calcaneal fractures By S. A. Bradley, FRCR and A. M. Davies, FRCR Department of Radiology, Birmingham Accident Hospital, Bath Row, Birmingham, UK
(Received 10 January 1991 and in revised form 26 July 1991, accepted 6 August 1991)
Keywords: Calcaneum, Fracture, Computed tomography Abstract. Computed tomographic (CT) examinations of 50 acute calcaneal fractures were compared with a further series of 77 fractures in which the date of injury preceded the CT by 6 months or more. 42 (84%) of the fractures in the acute group and 55 (71%) in the chronic group were classified as intra-articular and they form the basis of this study. The alteration in the position of the peroneal tendons in the two groups was similar, with a 5% or less difference in each category. In the acute group the peroneal tendons were normally located in 40.4% of the cases, entrapped by bone in 11.9%, subluxed in 33.3% and dislocated in 14.2%. Structural abnormalities of the peroneal tendons and surrounding soft tissues were identified in 52.4% of the acute group and in 61.1% of the chronic group. The incidence of partial rupture of the peroneal tendons in the chronic group was approximately one third that in the acute group, but the low incidence of complete tendon rupture remained unchanged. The inference from these observations is that, in the majority of cases, partial peroneal tendon rupture is reversible, whereas complete rupture is not. Seven fractures were common to both series and from this limited group the identification of haemorrhage around the peroneal tendons in the acute phase was shown not to be related to the subsequent development of chronic stenosing tenosynovitis. Various abnormalities of the medial tendons of the hindfoot were identified in 17% of the acute group and in 18% of the chronic group. Following calcaneal fracture, CT in both the immediate post-fracture period and in the late phase can be used to detect and classify the soft tissue changes. The limitations of comparing the two groups in this study are discussed. When dealing with musculoskeletal trauma, there is a tendency for the attending clinician and radiologist to concentrate on the bony abnormalities and overlook the associated soft tissue injuries. Many of the numerous articles published on the use of computed tomography (CT) in the evaluation of acute calcaneal fractures deal principally with fracture patterns illustrated by CT scans imaged on a bone window and only make a brief comment on soft tissue involvement (Guyer et al, 1985; Heger et al, 1985; Pablot et al, 1985; Segal et al, 1985; Gilmer et al, 1986; Hindman et al, 1986; Heuchemer et al, 1988; Lowrie et al, 1988; Crosby & Fitzgibbons, 1990). A few recent studies have emphasized the role of CT in the assessment of tendon trauma following acute calcaneal fractures (Rosenberg et al, 1987) and in their longterm follow-up (Bradley & Davies, 1990), as well as in other soft tissue afflictions of the hindfoot (Rosenberg etal, 1986, 1988a, 1988b, 1988c; Keyseretal, 1988). The purpose of this paper is both to study prospectively with CT the soft tissue changes around the hindfoot in a group of patients presenting with an acute calcaneal fracture, and to compare the findings with a second . Address correspondence to Dr A. M. Davies, Department of Radiology, Birmingham Accident Hospital, Bath Row, Birmingham. Vol. 65, No. 770
group on whom CT examination was performed more than 6 months after sustaining the injury, Patients and methods High resolution CT of the hindfeet was performed on either a Siemens DRH or CR Whole Body Scanner in both the coronal and the axial planes (Smith & Staple, 1983) on a series of 40 patients who had presented with an acute calcaneal fracture within the previous 2 weeks. Contiguous slices measuring 4 mm were obtained and viewed on bone and soft tissue window settings. The CT examinations were subsequently reviewed and observations regarding bone and soft tissue changes recorded. The abnormalities in this acute group were compared with the findings in a second group of 67 patients with calcaneal fractures sustained more than 6 months before CT examination. The majority of the cases in this latter chronic group have been the subject of a study published previously (Bradley & Davies, 1990) and are included in the current paper for the purposes of comparison, CT abnormalities of the soft tissues of the hindfoot were classified either as alterations in the position of the tendons or as alterations in the structural appearances of the tendons and surrounding soft tissues. A normal tendon appears as a well defined, homogeneous, 105
S. A. Bradley and A. M. Davies rounded density of higher attenuation than muscle and is accentuated by surrounding fat. Obliteration of this fat by a soft tissue density indicates either haemorrhage/ granulation tissue in the acute phase, or the scar tissue of chronic stenosing tenosynovitis in the late phase. Distension of the synovial sheath by a halo of low density fluid is characteristic of chronic tenosynovitis. Increased girth of the tendon with heterogeneous areas of decreased attenuation within the tendon substance indicates a partial rupture, whereas a complete rupture is detected by an absence of a portion of the tendon with the defect either replaced by fat or fluid (Rosenberg et al, 1988a; Bradley & Davies, 1990). Results A total of 50 calcaneal fractures were identified in 40 patients of the acute group and 77 fractures were identified in 67 patients of the chronic group. There were 32 (80%) male patients and 8 (20%) female patients in the acute group and 48 (72%) males and 17 (28%) females in the chronic group. The age range in the acute group was 19-81 years with a mean age of 44 years. The age range in the chronic group was 12-83 years with a mean age of 48 years. The plain film incidence of the different types of calcaneal fracture are summarized in Table I according to the Schmidt and Weiner modification of the Rowe and Essex-Lopresti classifications (Essex-Lopresti, 1952; Rowe et al, 1963; Schmidt & Weiner, 1982). 42 (84%) fractures in the acute group and 55 (71 %) in the chronic group were categorized as intra-articular fractures, with involvement of the posterior subtalar joint (Types 4, 5a & 5b of Table I). The remainder of this paper is confined to this intra-articular fracture category. The position of the peroneal tendons for both groups are shown in Figure 1 and illustrated in Figure 2. Structural changes of the peroneal tendons were identified in 22 (52.4%) patients in the acute group and 34 (62%) patients in the chronic group. A breakdown of these changes is shown in Figure 3 (a & b). In all five acute fractures in which haemorrhage alone was identified around the peroneal tendons, the tendons were also Table I. Calcaneal fractures: classification and incidence (Schmidt and Weiner modification of Rowe and Essex-Lopresti classifications), after Berquist & Johnson, 1989 Type
Published incidence
la (tuberosity) lb (sustentaculum) lc (anterior process) Id (infero-lateral) 2 (Achilles avulsion) 3 (linear extra-articular) 4 (linear intra-articular) 5a (tongue depression) 5b (joint depression)
6 3 15 1 4 19
106
Acute group 6
11.7
2
9.1 1.3 2.6 3.9 3.9
8
10-26 5
43-60
Chronic group
28 56
29.8 37.7
Normal/Trapped
Subluxed
10
20
30
40
50
% cases ^ H Acute Fractures
MSSSi Chronic Fractures
Figure 1. Position of the peroneal tendons. shown to be either subluxed or dislocated (Fig. 4a). In nine of the 16 cases in which there was partial rupture of the peroneal tendons, with or without surrounding haemorrhage, the tendons were also shown to be either subluxed or dislocated. Structural changes in or around the peroneal tendons were present in 14 of the 20 acute cases with subluxation or dislocation of the tendons (Fig. 4a & c). Almost half the acute fractures exhibited lateral bony spur formation impinging on the peroneal tendons (Fig. 5), best shown on axial CT. This feature was common in those cases in which the peroneal tendons were trapped by bone in their normal anatomical position. There was otherwise no relationship between the lateral spur formation and the appearances of the peroneal tendons and the surrounding soft tissue. Medially, in the acute group, bony encroachment on the abductor hallucis longus muscle was revealed in four cases, partial rupture of the flexor hallucis longus tendon in two cases and complete rupture of the tibialis posterior tendon in one case. In the chronic group, there was scarring surrounding the flexor hallucis longus tendon in five cases, bony encroachment in two cases and rupture in one case. Rupture of both the flexor hallucis longus and flexor digitorum longus tendons was detected in one case and scar tissue surrounding the tibialis posterior tendon was also detected in one case. In a minority of acute cases further soft tissue injury to the ankle was identified by an ankle joint effusion or superficial haemorrhage adjacent to the lateral malleolus (Fig. 6). Four patients with seven intra-articular fractures were common to both the acute and chronic groups in this study. In one case normal peroneal tendons were present bilaterally on both CT examinations. In one case extensive haemorrhage surrounding the peroneal tendons largely resolved to reveal intact tendons (Fig. 7). In one case scar tissue developed around previously normal peroneal tendons and in another case partial rupture of the peroneal tendons persisted on the second CT examination. Discussion The literature on calcaneal fractures is confusing regarding which factors are significant or of prognostic The British Journal of Radiology, February 1992
CT of soft tissues following calcaneal fractures
Figure 2. Coronal CT, soft tissue window, (a) Acute right calcaneal fracture showing entrapment of the peroneal tendons between the distal fibula and displaced lateral wall of the calcaneum (1). Haemorrhage around the flexor hallucis longus tendon (2) and bony fragments involving the inferior aspect of the abductor hallucis muscle (3). (b) Acute bilateral calcaneal fractures showing subluxation of the left peroneal tendons (4). (c) Bilateral calcaneal fractures, 33 months after injury, showing the peroneal tendons to be trapped on the right and dislocated on the left.
Haemorrhage - ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ H
Ch Sten Tenosynov
Partial Rupture ~ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ H
HI
Ch Tenosynovitis
Haem & Part Rupt - ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ H
Ch Partial Rupture
Complete Rupture - ^ H
Complete Rupture
0
5
10
15
20
25
30
0
% cases
(a)
(b)
Figure 3. Structural changes in and around the peroneal tendons in the acute (a) and chronic (b) groups. Vol. 65, No. 770
107
S. A. Bradley and A. M. Davies
(b)
Figure 4. Coronal CT, soft tissue window, (a) Acute calcaneal fracture showing subluxation of the peroneal tendons with obliteration of the surrounding fat by haemorrhage. The loculus of air just lateral to the peroneus longus tendon (arrow) indicates the compound nature of the injury, (b) Acute right calcaneal fracture. The diffuse swelling of the peroneal tendons (arrow) indicates internal disruption due to partial rupture, (c) Acute calcaneal fracture. The central relative lucency within the subluxed tendon sheath indicates complete rupture.
value to the final outcome (Paley & Hall, 1989). Whilst post-traumatic osteoarthrosis of the posterior subtalar joint is arguably the principal cause of morbidity following an intra-articular fracture, another major, longterm complication is injury to the peroneal tendons (Slatis et al, 1979). At the time of injury the downward force of the talus will split the calcaneum into two major fragments. The resultant flattening, with outward splaying of the lateral wall, will displace and damage the 108
peroneal tendons (Palmer, 1948; Essex-Lopresti, 1952). Before the introduction of CT and magnetic resonance imaging (MRI), damage to the peroneal tendons could be either inferred by lateral broadening of the calcaneum or directly visualized by peroneal tenography (Rosenberg et al, 1987). This latter technique is rarely used as it is invasive and difficult to perform in the acute phase when the ankle may be grossly swollen and the tendons displaced. In contrast, CT of the hindfeet is The British Journal of Radiology, February 1992
CT of soft tissues following calcaneal fractures
Figure 5. Axial CT, soft tissue window, (a) Acute right calcaneal fracture with a lateral spur impinging on the peroneal tendons which are swollen and of decreased attenuation indicating internal disruption, (b) Old right calcaneal fracture, 18 months after injury, showing similar appearances to (a).
relatively non-invasive, easy to perform, allows simultaneous assessment of bony and soft tissue structures and can be undertaken in the presence of an external cast. An additional advantage in a patient with a unilateral fracture is that CT of the uninvolved foot, examined simultaneously, can act as a normal control. The confidence with which observations can be made from CT regarding soft tissue abnormalities of the hindfeet is largely a result of the work originating from one institution which, in many instances, included surgical correlation (Rosenberg et al, 1986, 1987, 1988a, 1988b, 1988c). This series, comprising 107 examinations, is to the authors' knowledge, the largest published CT study on calcaneal fractures. The results of the acute intra-articular fracture group agree in many respects with the findings of Rosenberg et al (1987). Bony entrapment of the peroneal tendons was present in 11.9% of the current acute group (Fig. 1) and in 13% of Rosenberg's group. However, Rosenberg identified subluxation or dislocation in only 25% of cases, as opposed to 47.5% in this study (Fig. 1). This discrepancy may be explained, in part, by the fact that in this study there was no distinction between lateral displacement and subluxation of the tendons. Haemorrhage or early scar tissue around the peroneal tendons was present in 21% of Rosenberg's cases as compared with haemorrhage, with or without partial tendon rupture, in 26.2% of the current acute series (Fig. 3a). Rosenberg and his colVol. 65, No. 770
leagues did not identify any structural changes within the peroneal tendons, whereas the current study concluded that partial or complete rupture was present in 40.5% of cases (Fig. 3a). This may be caused by the
Figure 6. Coronal CT, soft tissue window. Acute left calcaneal fracture showing an ankle joint effusion (arrow) and minor haemorrhage around the peroneal tendons.
109
S. A. Bradley and A. M. Davies
(a)
(b)
Figure 7. Coronal CT, soft tissue window. Gross bilateral calcaneal and talar fractures. In the acute phase (a) many of the tendons are surrounded by haemorrhage, (b) 8 months later scar tissue is present but many normal tendons are visible surrounded by fat.
fact that their original paper was one of the earlier publications concerning CT of tendons and, with only few exceptions, their patients were examined in the axial plane alone (Rosenberg et al, 1987). The authors of the current study do not consider themselves guilty of the overenthusiastic identification of peroneal tendon rupture in light of the more recent literature on the subject (Rosenberg et al, 1988a, 1988b, 1988c). In this study, only a limited comparison of the two groups is possible, as they are not identical in a number of respects. The principal difference is the bias in patient selection. All those patients presenting with an acute calcaneal fracture during the study period underwent CT routinely, whereas the chronic group represents the one third of patients who had agreed to attend for CT following receipt of a written request. Nevertheless, the age range, sex ratio and incidence of the various types of fracture (Table I) do suggest that there are moderate similarities. In particular, the position of the peroneal tendons in patients with intra-articular fractures is remarkable similar for both groups, with less than 5% variation in any of the four categories (Fig. 1). The incidence, in the chronic group, of chronic partial tears of the peroneal tendons of approximately one third that in the acute phase (Fig. 3) would indicate that, in the majority of cases, this change is reversible. A similar incidence of complete tendon rupture in the two groups suggests the contrary (acute group = 2.4%, chronic group = 3.6%). However, the numbers involved are small and there is no conclusive proof in this study that the cases of complete rupture in the chronic group were sustained at the time of the injury. It is likely that many of those patients eligible for the chronic group who declined the invitation to attend for CT were asymptomatic. The majority who did attend were probably motivated by pain and disability, hence the higher incidence of structural changes in the chronic group relative to the acute group. It might be expected that haemorrhage around the 110
peroneal tendons in the acute group (26.2%) (Fig. 4a) would pre-dispose to scar tissue formation (chronic stenosing tenosynovitis) in the chronic group (25%) (Fig. 3). No such association was found either by Rosenberg et al (1987) in their limited follow-up of 10 cases or in the two cases in the current study, common to both groups, which exhibited these features (Fig. 7). Abnormalities of the medial tendons were considerably less common than those affecting the peroneal tendons and were found in 17% and 18% of the acute and chronic cases, respectively. This lower incidence reflects the mechanism of injury in that the anteromedial fragment of the calcaneum, including the sustentaculum, usually remains reduced to the undersurface of the talus without injuring the medial tendons, whereas the postero-lateral fragment displaces laterally thereby damaging the adjacent peroneal tendons. However, damage to the medial tendons does occur and can be demonstrated by CT (Carr, 1990). This study confirms that in both the immediate postfracture period and long after injury CT may be used to detect soft tissue injuries. Whilst haemorrhage around the peroneal tendons appears to be of limited significance and two thirds of peroneal tendon ruptures probably resolve, a full longitudinal study would be necessary to categorize which soft tissue changes are ultimately of definite prognostic significance. There remains considerable controversy regarding the treatment of calcaneal fractures; operative or non-operative. The ability of CT to demonstrate both bony and soft tissue abnormalities means that the technique is of value to the proponents of both modes of management. Three-dimensional CT reconstructions may improve the surgeon's visualization of the fractures before operation (Carr et al, 1990; Allon & Mears, 1991) and direct measurements from CT of calcaneal deformity can be used to assess the surgeon's success in restoring the anatomical congruity of the bony structures (Frahm et al, 1989; Krause & Hedtler, 1990). With regards to the The British Journal of .Radiology, February 1992
CT of soft tissues following calcaneal fractures
soft tissue injuries, MRI may be preferred because of its superior soft tissue contrast resolution (Zeiss et al, 1991), but CT remains an excellent alternative when financial considerations and availability limit access to MRI (Rosenberg et al, 1988a).
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