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Ultrasound Diagnosis of Sleeve Fracture of the Patella
721
CASE REPORTS
doi:10.1057/crad.2000.0114, available online at http://www.idealibrary.com on
Ultrasound Diagnosis of Sleeve Fracture of the Patella A . D IT C H F I E L D , M . A . S A M P S O N , G . R . T A Y L O R * Departments of Clinical Radiology and *Orthopaedic Surgery, Southampton General Hospital, Southampton SO16 6YD, U.K.
The term patella sleeve fracture describes avulsion of the lower pole of an immature patella. A sleeve of cartilage is pulled off the main bony patella, often taking with it a small bony fragment from the lower pole (Fig. 1). Plain radiographs may not be diagnostic. This report describes the use of ultrasound to demonstrate a sleeve fracture of the patella, a technique not previously recorded in this condition. CASE REPORT A healthy 13-year-old boy had sudden onset right knee pain whilst playing football. On examination there was a moderate effusion, tenderness over the inferior pole of the patella and inability to straight leg raise against gravity. The lateral radiograph taken on the day of injury demonstrates a small bone fragment just distal to the inferior pole of the patella (Fig. 2). Ultrasound performed at that time (ATL 3000 with a 10-5 MHz broadband 38 mm linear array) showed the plane of fracture across the inferior patella (Fig. 3, Fig. 4). The avulsed cartilage is seen to include a slender fragment of bone and the fracture line has ®lled with blood. There is 4.5 mm separation between the fragments and a step of 2 mm at the inferior margin. The patient underwent surgical reduction under general anaesthesia. An oblique fracture was identi®ed across the lower pole of the patella on the medial side. The cartilaginous fragment was reattached with suture. After 48 h immobilization in a backslab, to permit review of the wound, the leg was kept in full extension in a plaster cylinder for 6 weeks. Following physiotherapy there has been recovery of full range of movement at the knee with resumption of all normal activities. Follow-up radiographs con®rm consolidation at the fracture site.
DISCUSSION
vigorous extension against resistance often with a background of sporting activity [1,2]. The patient may have a joint effusion with a palpable defect over the lower pole of the patella. In addition to point tenderness, there is inability to fully extend. A high-riding patella indicates that there may be wide disruption of the extensor mechanism [1,2]. When there is diastasis of more than 4 mm between the avulsed fragment and the body of the patella or a step deformity greater than 3 mm, open reduction with or without internal ®xation is recommended [1±4]. Reconstitution of a disrupted extensor mechanism may be necessary. With minimal separation, or when the articular surface has been spared, immobilization in extension may be adequate [1,2,5].
Fig. 1 ± Schematic depiction of fracture across the lower pole of patella with a large cartilaginous `sleeve'.
Following this type of injury, the avulsed fragment comprises more cartilage than bone and causes plain radiology to underestimate the extent of injury or, in some cases, to fail to demonstrate it [1]. The term `sleeve fracture' has been used in recognition of this. Disruption of the articular surface of the patella makes this injury more signi®cant. The typical aetiology is an indirect force transmitted to the patella in vigorous extension, although cases have been recorded following a direct blow to the knee [1,2]. Overall, fractures of the bony patella in children and adolescents are rare, usually taking the form of avulsion of the lower pole, but unusually transverse fractures have also been described [2,3]. Clinically, there is sudden onset anterior knee pain following Author for correspondence; Dr A. Ditch®eld, Radiology Registrar, Department of Clinical Radiology, Southampton General Hospital, Southampton SO16 6YD, U.K.
Fig. 2 ± Lateral radiograph demonstrating distal patellar fragment (arrow). q 2000 The Royal College of Radiologists
722
CLINICAL RADIOLOGY
Fig. 4 ± Line drawing of ultrasound image with patellar tendon (PT), bony patella (P), cartilaginous patella (C) and fracture line (arrow).
CONCLUSION Fig. 3 ± Longitudinal ultrasound showing patellar tendon (PT), patella (P) and fracture line (arrow).
Plain radiographs may not show a sleeve fracture if the distal bony fragment is small. When there is a bone fragment visible, the cartilaginous fragment greatly exceeds it in size. Ultrasound is a rapid, accessible, safe and cost-effective means of imaging soft tissues, cartilage and bony interfaces and of measuring the separation of fragments. The axial resolution of the 10-5 MHz transducer (quoted at 20 dB level relative to peak amplitude) is 0.9 mm at a depth of 20 mm. Magnetic resonance imaging has been used to con®rm the diagnosis and de®ne the cartilaginous injury, including that to the articular surface. Sagittal fast spin echo T2 weighted sequences may show patellar marrow oedema with a hyperintense fracture line within adjacent hypointense cartilage [5].
Sleeve fractures of the patella are rare but are underestimated by plain radiology. The diagnosis of a primarily cartilage based injury with assessment of fracture separation and displacement can be made with ultrasound. These ®ndings are helpful in determining management of this fracture. REFERENCES 1 Houghton GR, Ackroyd CE. Sleeve fractures of the patella in children: a report of three cases. J Bone Joint Surg 1979;61:165±168. 2 Ray JM, Hendrix J. The patella in children. J Trauma 1992;32:464±467. 3 Belman DAJ, Neviaser RJ. Transverse fracture of the patella in a child. J Trauma 1973;13:917±918. 4 Crawford AH. Fractures about the knee in children. Orthop Clin North Am 1976;7:639±656. 5 Bates DG, Hresko MT, Jaramillo D. Patellar sleeve fracture: demonstration with MR imaging. Radiology 1994;193:825±827.
doi:10.1053/crad.2000.0116, available online at http://www.idealibrary.com on
Pelvic Fibrosis ± A Rare Variant of Idiopathic Retroperitoneal Fibrosis R . H A S H M I , M . U E T A N I , K . H A Y A S H I , N . N A K A H A R A * , S. F U T A G A W A * , K. YAMAGUCHI*, Y. KAWAHARA* Departments of Radiology, Nagasaki University School of Medicine and *Isahaya Health Insurance Hospital, Isahaya, Nagasaki, Japan
Idiopathic retroperitoneal ®brosis is usually localized around the lower aorta and common iliac arteries in the retroperitoneal space [1,2]. We report a rare case of idiopathic retroperitoneal ®brosis in which the retroperitoneal mass was centred around the rectum and describe the computed tomography (CT) and Author for correspondence: Masataka Uetani, Department of Radiology, Nagasaki University School of Medicine, 1-7-1 Sakamoto, Nagasaki 852-8501, Japan.
magnetic resonance (MR) imaging ®ndings of this atypical presentation. CASE REPORT A 65-year-old man presented with a 3-month history of abdominal fullness and dif®culty in defaecation. There was no history of passage of blood in stools, weight loss, malaise or fatigue. The patient had a past history of gastric carcinoma for which he underwent partial gastrectomy 6 years previously. Eight months before presentation he had an appendectomy. q 2000 The Royal College of Radiologists
CASE REPORTS
doi:10.1057/crad.2000.0114, available online at http://www.idealibrary.com on
Ultrasound Diagnosis of Sleeve Fracture of the Patella A . D IT C H F I E L D , M . A . S A M P S O N , G . R . T A Y L O R * Departments of Clinical Radiology and *Orthopaedic Surgery, Southampton General Hospital, Southampton SO16 6YD, U.K.
The term patella sleeve fracture describes avulsion of the lower pole of an immature patella. A sleeve of cartilage is pulled off the main bony patella, often taking with it a small bony fragment from the lower pole (Fig. 1). Plain radiographs may not be diagnostic. This report describes the use of ultrasound to demonstrate a sleeve fracture of the patella, a technique not previously recorded in this condition. CASE REPORT A healthy 13-year-old boy had sudden onset right knee pain whilst playing football. On examination there was a moderate effusion, tenderness over the inferior pole of the patella and inability to straight leg raise against gravity. The lateral radiograph taken on the day of injury demonstrates a small bone fragment just distal to the inferior pole of the patella (Fig. 2). Ultrasound performed at that time (ATL 3000 with a 10-5 MHz broadband 38 mm linear array) showed the plane of fracture across the inferior patella (Fig. 3, Fig. 4). The avulsed cartilage is seen to include a slender fragment of bone and the fracture line has ®lled with blood. There is 4.5 mm separation between the fragments and a step of 2 mm at the inferior margin. The patient underwent surgical reduction under general anaesthesia. An oblique fracture was identi®ed across the lower pole of the patella on the medial side. The cartilaginous fragment was reattached with suture. After 48 h immobilization in a backslab, to permit review of the wound, the leg was kept in full extension in a plaster cylinder for 6 weeks. Following physiotherapy there has been recovery of full range of movement at the knee with resumption of all normal activities. Follow-up radiographs con®rm consolidation at the fracture site.
DISCUSSION
vigorous extension against resistance often with a background of sporting activity [1,2]. The patient may have a joint effusion with a palpable defect over the lower pole of the patella. In addition to point tenderness, there is inability to fully extend. A high-riding patella indicates that there may be wide disruption of the extensor mechanism [1,2]. When there is diastasis of more than 4 mm between the avulsed fragment and the body of the patella or a step deformity greater than 3 mm, open reduction with or without internal ®xation is recommended [1±4]. Reconstitution of a disrupted extensor mechanism may be necessary. With minimal separation, or when the articular surface has been spared, immobilization in extension may be adequate [1,2,5].
Fig. 1 ± Schematic depiction of fracture across the lower pole of patella with a large cartilaginous `sleeve'.
Following this type of injury, the avulsed fragment comprises more cartilage than bone and causes plain radiology to underestimate the extent of injury or, in some cases, to fail to demonstrate it [1]. The term `sleeve fracture' has been used in recognition of this. Disruption of the articular surface of the patella makes this injury more signi®cant. The typical aetiology is an indirect force transmitted to the patella in vigorous extension, although cases have been recorded following a direct blow to the knee [1,2]. Overall, fractures of the bony patella in children and adolescents are rare, usually taking the form of avulsion of the lower pole, but unusually transverse fractures have also been described [2,3]. Clinically, there is sudden onset anterior knee pain following Author for correspondence; Dr A. Ditch®eld, Radiology Registrar, Department of Clinical Radiology, Southampton General Hospital, Southampton SO16 6YD, U.K.
Fig. 2 ± Lateral radiograph demonstrating distal patellar fragment (arrow). q 2000 The Royal College of Radiologists
722
CLINICAL RADIOLOGY
Fig. 4 ± Line drawing of ultrasound image with patellar tendon (PT), bony patella (P), cartilaginous patella (C) and fracture line (arrow).
CONCLUSION Fig. 3 ± Longitudinal ultrasound showing patellar tendon (PT), patella (P) and fracture line (arrow).
Plain radiographs may not show a sleeve fracture if the distal bony fragment is small. When there is a bone fragment visible, the cartilaginous fragment greatly exceeds it in size. Ultrasound is a rapid, accessible, safe and cost-effective means of imaging soft tissues, cartilage and bony interfaces and of measuring the separation of fragments. The axial resolution of the 10-5 MHz transducer (quoted at 20 dB level relative to peak amplitude) is 0.9 mm at a depth of 20 mm. Magnetic resonance imaging has been used to con®rm the diagnosis and de®ne the cartilaginous injury, including that to the articular surface. Sagittal fast spin echo T2 weighted sequences may show patellar marrow oedema with a hyperintense fracture line within adjacent hypointense cartilage [5].
Sleeve fractures of the patella are rare but are underestimated by plain radiology. The diagnosis of a primarily cartilage based injury with assessment of fracture separation and displacement can be made with ultrasound. These ®ndings are helpful in determining management of this fracture. REFERENCES 1 Houghton GR, Ackroyd CE. Sleeve fractures of the patella in children: a report of three cases. J Bone Joint Surg 1979;61:165±168. 2 Ray JM, Hendrix J. The patella in children. J Trauma 1992;32:464±467. 3 Belman DAJ, Neviaser RJ. Transverse fracture of the patella in a child. J Trauma 1973;13:917±918. 4 Crawford AH. Fractures about the knee in children. Orthop Clin North Am 1976;7:639±656. 5 Bates DG, Hresko MT, Jaramillo D. Patellar sleeve fracture: demonstration with MR imaging. Radiology 1994;193:825±827.
doi:10.1053/crad.2000.0116, available online at http://www.idealibrary.com on
Pelvic Fibrosis ± A Rare Variant of Idiopathic Retroperitoneal Fibrosis R . H A S H M I , M . U E T A N I , K . H A Y A S H I , N . N A K A H A R A * , S. F U T A G A W A * , K. YAMAGUCHI*, Y. KAWAHARA* Departments of Radiology, Nagasaki University School of Medicine and *Isahaya Health Insurance Hospital, Isahaya, Nagasaki, Japan
Idiopathic retroperitoneal ®brosis is usually localized around the lower aorta and common iliac arteries in the retroperitoneal space [1,2]. We report a rare case of idiopathic retroperitoneal ®brosis in which the retroperitoneal mass was centred around the rectum and describe the computed tomography (CT) and Author for correspondence: Masataka Uetani, Department of Radiology, Nagasaki University School of Medicine, 1-7-1 Sakamoto, Nagasaki 852-8501, Japan.
magnetic resonance (MR) imaging ®ndings of this atypical presentation. CASE REPORT A 65-year-old man presented with a 3-month history of abdominal fullness and dif®culty in defaecation. There was no history of passage of blood in stools, weight loss, malaise or fatigue. The patient had a past history of gastric carcinoma for which he underwent partial gastrectomy 6 years previously. Eight months before presentation he had an appendectomy. q 2000 The Royal College of Radiologists