- Email: [email protected]
A review of sleeve fractures of the patella in children
The Knee 12 (2005) 3 – 7 www.elsevier.com/locate/knee
Review article
A review of sleeve fractures of the patella in children David M. Hunt*, Naresh Somashekar St. Mary’s Hospital, London W2, UK Received 15 April 2004; accepted 18 August 2004
Abstract Patella fractures are rare in children and the sleeve fracture is a particular form of fracture that only occurs in children where it is the most common patella fracture. It is caused by rapid muscle contraction. Diagnosis may be difficult both clinically and on the X-ray which may look normal if there is no bony fragment. Patella alta is the best sign and ultrasound is very helpful. Awareness of the existence of the injury is all important. This fracture differs from straightforward avulsion because of the bsleeveQ of periosteum which is pulled off the patella and will continue to form bone if not treated thus enlarging or even duplicating the patella. Treatment involves prompt reduction and, usually, internal fixation of the disrupted patella tendon. D 2004 Elsevier B.V. All rights reserved. Keywords: Patella; Sleeve; Periosteum; Osseo-chondral; Ultrasound
Contents 1. Patellar sleeve fractures in children . 2. Incidence . . . . . . . . . . . . . . 3. Pathogenesis. . . . . . . . . . . . . 4. Classification of patella fractures . . 5. Mechanism of injury . . . . . . . . 6. Clinical presentation. . . . . . . . . 7. Investigations . . . . . . . . . . . . 8. Treatment . . . . . . . . . . . . . . 9. Outcome. . . . . . . . . . . . . . . 10. Conclusion . . . . . . . . . . . . . Acknowledgements . . . . . . . . . . . . References . . . . . . . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
1. Patellar sleeve fractures in children A patella fracture in a child is a sufficiently rare occurrence to send trainees to the textbooks and the literature with the idea of producing a case report. It is no surprise then that the literature comprises a haphazard
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
3 3 4 5 5 5 5 6 6 6 6 6
collection of case reports and reviews. In the textbooks, sleeve fractures are included in a general discussion of patella fractures and it is not always pointed out that it is the most common form of patella fracture in the under 16’s [1].
2. Incidence * Corresponding author. Tel.: +44 207 886 1394. E-mail addresses: [email protected], [email protected] (D.M. Hunt). 0968-0160/$ - see front matter D 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.knee.2004.08.002
Patella fractures make up 1% of all fractures in children which is actually the same as in adults, although they are
4
D.M. Hunt, N. Somashekar / The Knee 12 (2005) 3–7
usually thought to be less common in children [1,3]. Of all patella fractures, less than 2% occur in the skeletally immature. They are, then, rare. In children, approximately half the patella fractures are sleeve fractures. A review of the literature of the last 25 years indicates that sleeve fractures make up 57% of all patella fractures in this age group [2,4]. Adolescents are most susceptible, probably related to the intensity of sporting activity, rapid growth with osseochondral transformation at the periphery of the patella and relative patella instability. The peak incidence is 12.7 years (range 8–16) [2]. It is more common in boys occurring at a ratio of 3:1.
3. Pathogenesis The patella begins to ossify at the age of 3. There are multiple small ossification centres in the middle of the patella, possibly as many as six and ossification progresses peripherally with growth [1]. This leaves a rim of soft, intense osseo-chondrous transformation all around the growing patella. In keeping with other parts of the immature skeleton, where ligament or tendon attaches to growing bone, the cartilage blends directly with the collagen of the tendon rather than by the distinct Sharpey’s fibres found in the adult. Injury in the form of a powerful separating force is then more likely to pull cartilage or bone off rather than rupture the tendon. Hence patellar tendon disruption in
Fig. 1. Diagramatic representation of a sleeve fracture. Broad arrow indicates articular cartilage; thin arrow, periosteum and cartilage.
Fig. 2. X-ray of sleeve fracture with new bone forming in the disrupted patella mechanism.
children is at the proximal or distal end by avulsion rather than a mid-substance tear [5]. This is also seen, for example, in avulsion of the epicondyles of the elbow, the tibial tuberosity or even avulsion of the tibial insertion of the anterior cruciate ligament. It is, of course, in keeping with the pain seen in repetitive stress conditions such as Osgood Schlatter’s disease, Sinding–Larsen–Johansson disease or the avulsed fragments seen in children with fixed flexion deformities such as in cerebral palsy or arthrogryposis [6]. What is unique about the sleeve fracture is that it is a complete sleeve or cuff of osseo-potent tissue that is pulled off from the full circumference of the patella. This is articular cartilage on the deep surface and periosteum and cartilage on the superficial surface. This is often not shown clearly in diagrams (Fig. 1). The disruption of the periosteum occurs over the body of the patella. It slides distally taking osseo-potent transformation zone cells from the osseo-chondral zone of the patella with it. This may not result in complete disruption of the quadriceps mechanism but an elongation. The tissue can be all cartilage and periosteum and so will not be visible on X-ray. It means that there is a collection of potent bone-forming tissue at the lower pole of the patella which will go on forming bone resulting in enlargement or even duplication of the patella (Fig. 2) [7]. This differentiates the sleeve fracture from the avulsed osteochondral fragment seen on the medial or lateral side of the patella [8]. The insertion of vastus medialis is so strong and directly into the osseo-chondral zone that cartilage and bone is pulled off. The difference here is that the insertion is transverse or oblique to the line of the fibres of the periosteal sleeve surrounding the patella and a fragment of cartilage and bone is avulsed without the disruption of the periosteal sleeve which occurs with the
D.M. Hunt, N. Somashekar / The Knee 12 (2005) 3–7 Table 1 Classification of patella fractures in children (1) (2) (3) (4) (5) (6)
Medial avulsion fracture Lateral avulsion fracture Separation of bipartite patella Sleeve fracture: lower pole and upper pole Transverse fracture Stellate or comminuted fracture
longitudinal pull of the injury associated with sleeve fractures. The important point is that it is the periosteal sleeve on the subcutaneous surface of the patella which contributes to new bone formation. This raises the issue of the bipartite patella. Is it a fracture or a secondary ossification centre [9,10]? The evidence is in favour of a secondary ossification centre. There is no history of trauma and the bipartite patella is rarely a cause of pain. Pain can occur in overuse situations in enthusiastic athletes and widening of the gap between the fragment and the body of the patella has been described [11]. Also, the fragment can heal after lateral release alone so excision is not needed [12]. The bipartite patella fragment is then a weak spot in the quadriceps mechanism and there is no reason why it should not be pulled off as an acute injury [2], perhaps explaining why it is confused with a fracture. Saupe classified bipartite patella into three types; Type I is a lower pole fragment [10]. It is conceivable that this could be pulled off before it had ossified in a sleeve fracture.
4. Classification of patella fractures Grogan et al. [13] describe 47 patella fractures classifying them all as avulsion fractures. These include upper pole and lower pole fractures (including bipolar), medial and lateral avulsion fractures, transverse and stellate fractures. Separation of bipartite fragments should also be included in a full classification (Table 1). Interestingly, while the sleeve fracture mechanism is described, it is not included as a specific classification. The sleeve fracture is different from the avulsed osteochondral fragment because of the tube of cartilage and periosteum which is pulled off, often without
5
any bone. It is then different from the point of view of diagnosis, treatment and outcome and so should be classified as a separate group.
5. Mechanism of injury Sleeve fractures, like avulsion fractures, are distinct from patella fractures resulting from a direct blow or fall. They are caused by a rapid contraction of the quadriceps on a flexed knee. They usually occur in those involved in explosive acceleration activities such as jumping, although high energy sports such as skateboarding are now common causes [14].
6. Clinical presentation The history is then of the sudden onset of severe pain with an explosive acceleration such as jumping rather than a fall. It may be witnessed by a teacher or trainer. There is pain and a swollen knee with inability to straight leg raise. There are two clues which must be looked for. Firstly, there is a palpable gap at the lower pole of the patella, and secondly, there is patella alta, in that the patella on the affected side will be felt lying more proximally than the patella on the other side. It may not be so easy to demonstrate on X-ray due to difficulty flexing the knee the small amount required to measure true patella alta. If the disruption is minimal, the signs will be minimal. There may be no gap and patella alta will not be obvious and the child soon learns to lift the leg using the fascia lata and internally rotating the limb. These are the cases that result in elongation of the quadricreps mechanism and an elongated patella with an extensor lag. Presentation may be late and so it is no surprise that the diagnosis can be missed.
7. Investigations Plain X-rays can be misleading, revealing no bony damage. The clue on X-ray is patella alta which should be
Fig. 3. Ultrasound and schematic appearance of the disrupted bsleeveQ of subcutaneous periosteum and cartilage. Bone may not be present so nothing would be visible on X-ray.
6
D.M. Hunt, N. Somashekar / The Knee 12 (2005) 3–7
looked for specifically. There may be a visible bony fragment at the distal end of the patella (Fig. 3), in which case the diagnosis is easy but it may not be present if the fragment is cartilage and periosteum only. As in all injuries around joints in children, ultrasound should now be thought of before X-ray. It is quick, cheap, easy and safe and in this instance, diagnostic [15]. More sophisticated investigations such as MRI are a luxury but unnecessary [16].
8. Treatment The problem in treatment is the reduction of the injured tissue, to restore the length of the patella tendon and reduce the height of the patella alta. This virtually always means operative reduction. If a bony fragment is visible on X-ray and the displacement is less than 2 mm, closed treatment in a cast in extension is justified but the results of conservative treatment are unsatisfactory [7,14]. Also, simple excision of the bony fragment when present should be avoided, at least in the acute stage as it leaves an irregular lower pole of the patella. In a sleeve fracture, when it is missed at the time of the injury, the new bone formed will be too large to reduce and fix and will have to be removed, emphasising the importance of an awareness of this injury and prompt diagnosis and treatment. Through a midline incision, the periosteum and paratenon are opened in the line of the incision and the lower pole of the patella inspected. There will almost always be a few fragments of cartilage or bone in the avulsed proximal end of the patella tendon. These should be cleaned and the patella brought down. Repair is by whatever is the surgeon’s personal choice. Large transosseous sutures are simple and efficient [1,17]. A modified tension-band wire system can be used or even intra-osseous anchors [14]. If there is a good bone fragment, fixation should be rigid and carefully executed to minimise damage to the delicate nutrient vessels of the patella which enter the patella almost exclusively from the anterior surface and the distal pole, not medially [18]. The particular point about a sleeve fracture is that the periosteum should be carefully replaced over the subcutaneous surface of the patella and held with light tacking sutures. Postoperatively, the limb is immobilised in a cast in full extension for 2 weeks and then a brace, in extension initially, gradually allowing increasing flexion after a month.
9. Outcome Prompt diagnosis and straightforward treatment can be expected to produce an excellent result with full return to all activities, no extensor lag and full flexion. Failure to make the diagnosis can result in permanent disability with patella
alta and subsequent instability, extensor lag, quadriceps wasting and weakness, patella pain associated with osteochondral damage and ossification in the stretched patella tendon giving rise to patella magna or even duplication of the patella [19].
10. Conclusion Sleeve fractures are rare but are the most common form of patella fracture in the under 16 age group. It is a diagnosis that must be considered in an acute knee injury, especially when there has been no contact and the force is explosive force such as jumping. The clinical signs and Xray changes may not be diagnostic. Ultrasound is very helpful. Prompt diagnosis and appropriate treatment which is usually surgical can be expected to result in full functional recovery.
Acknowledgements The authors would like to thank Dr. Adam Ditchfield for the use of the ultrasound picture and accompanying diagram (Fig. 3).
References [1] Sponseller P, Stanitsk C. In: Beaty JH, Kasser JR. editors. 5th ed. Fractures in Children. Philadelphia: Lippincott, Williams and Wilkins. 2001. p.1029. [2] Ray JM, Hendrix T. Incidence, mechanism of injury and treatment of fractures of the patella in children. J Trauma 1992;32:464 – 7. [3] Ogden JA. Skeletal Injury in the Child. Philadelphia7 WB Saunders; 1990. [4] Dai LY, Zhang WM. Fractures of the patella in children. Knee Surg Sports Traumatol Arthrosc 1999;4(7):243 – 5. [5] Peterson L, Stener B. Distal disinsertion of the patellar ligament combined with avulsion fractures at the medial and lateral margins of the patella. Acta Orthop Scand 1976;47:680 – 5. [6] Rosenthal RK, Levine DB. Fragmentation of the distal pole of the patella in spastic cerebral palsy. J Bone Joint Surg Am 1977;59: 934 – 9. [7] Bruijn JD, Sanders RJ, Jansen BR. Ossification in the patellar tendon and patella alta following sports injuries in children. Complications of sleeve fractures after conservative treatment. Arch Orthop Trauma Surg 1993;3(112):157 – 8. [8] Heckman JD, Alkire CC. Distal patellar pole fractures: a proposed common mechanism of injury. Am J Sports Med 1984;12:424 – 8. [9] Ogden JA, McCarthy SM, Jokl P. The painful bipartite patella. J Paediatr Orthop 1982;2(3):263 – 9. [10] Saupe E. Quoted in Bourne MH, Bianco AJ Jr. Bipartite patella in the adolescent, the results of surgical excision. J Paediatr Orthop 1990;10:69. [11] Ishikawa H, Sakurai A, Hirata S. Painful bipartite patella in young athletes: the diagnostic value of skyline views taken in the squatting position and the results of surgical excision. Clin Orthop Relat Res 1994;305:223. [12] Ogata K. Painful bipartite patella: a new approach to operative treatment. J Bone Joint Surg Am 1994;76:573.
D.M. Hunt, N. Somashekar / The Knee 12 (2005) 3–7 [13] Grogan DP, Carey TP, Leffers D, Ogden JA. Avulsion fractures of the patella. J Pediatr Orthop 1990 (Nov.–Dec.);10(6):721 – 30. [14] Houghton GR, Ackroyd CE. Sleeve fractures of the patella in children. J Bone Joint Surg Br 1979;61:165 – 8. [15] Ditchfield A, Sampson MA, Taylor GR. Case reports. Ultrasound diagnosis of sleeve fractures of the patella. Clin Radiol 2000;55(9): 721 – 22. [16] Bates DG, Hresko MT, Jaramillo D. Patellar sleeve fracture: demonstration with MR imaging. Radiology 1994;193(3):825 – 7.
7
[17] Kaar TK, Murray P, Cashman WF. Transosseous suturing for sleeve fracture of the patella; a case report. Ir J Med Sci 1993;162(4):149. [18] Scapinelli R. Blood supply of the human patella: its relation to ischaemic necrosis after fracture. J Bone Joint Surg Br 1967;49: 563 – 70. [19] Yeung E, Ireland J. An unusual double patella. Knee 2004;11: 129 – 31.
Review article
A review of sleeve fractures of the patella in children David M. Hunt*, Naresh Somashekar St. Mary’s Hospital, London W2, UK Received 15 April 2004; accepted 18 August 2004
Abstract Patella fractures are rare in children and the sleeve fracture is a particular form of fracture that only occurs in children where it is the most common patella fracture. It is caused by rapid muscle contraction. Diagnosis may be difficult both clinically and on the X-ray which may look normal if there is no bony fragment. Patella alta is the best sign and ultrasound is very helpful. Awareness of the existence of the injury is all important. This fracture differs from straightforward avulsion because of the bsleeveQ of periosteum which is pulled off the patella and will continue to form bone if not treated thus enlarging or even duplicating the patella. Treatment involves prompt reduction and, usually, internal fixation of the disrupted patella tendon. D 2004 Elsevier B.V. All rights reserved. Keywords: Patella; Sleeve; Periosteum; Osseo-chondral; Ultrasound
Contents 1. Patellar sleeve fractures in children . 2. Incidence . . . . . . . . . . . . . . 3. Pathogenesis. . . . . . . . . . . . . 4. Classification of patella fractures . . 5. Mechanism of injury . . . . . . . . 6. Clinical presentation. . . . . . . . . 7. Investigations . . . . . . . . . . . . 8. Treatment . . . . . . . . . . . . . . 9. Outcome. . . . . . . . . . . . . . . 10. Conclusion . . . . . . . . . . . . . Acknowledgements . . . . . . . . . . . . References . . . . . . . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
1. Patellar sleeve fractures in children A patella fracture in a child is a sufficiently rare occurrence to send trainees to the textbooks and the literature with the idea of producing a case report. It is no surprise then that the literature comprises a haphazard
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
3 3 4 5 5 5 5 6 6 6 6 6
collection of case reports and reviews. In the textbooks, sleeve fractures are included in a general discussion of patella fractures and it is not always pointed out that it is the most common form of patella fracture in the under 16’s [1].
2. Incidence * Corresponding author. Tel.: +44 207 886 1394. E-mail addresses: [email protected], [email protected] (D.M. Hunt). 0968-0160/$ - see front matter D 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.knee.2004.08.002
Patella fractures make up 1% of all fractures in children which is actually the same as in adults, although they are
4
D.M. Hunt, N. Somashekar / The Knee 12 (2005) 3–7
usually thought to be less common in children [1,3]. Of all patella fractures, less than 2% occur in the skeletally immature. They are, then, rare. In children, approximately half the patella fractures are sleeve fractures. A review of the literature of the last 25 years indicates that sleeve fractures make up 57% of all patella fractures in this age group [2,4]. Adolescents are most susceptible, probably related to the intensity of sporting activity, rapid growth with osseochondral transformation at the periphery of the patella and relative patella instability. The peak incidence is 12.7 years (range 8–16) [2]. It is more common in boys occurring at a ratio of 3:1.
3. Pathogenesis The patella begins to ossify at the age of 3. There are multiple small ossification centres in the middle of the patella, possibly as many as six and ossification progresses peripherally with growth [1]. This leaves a rim of soft, intense osseo-chondrous transformation all around the growing patella. In keeping with other parts of the immature skeleton, where ligament or tendon attaches to growing bone, the cartilage blends directly with the collagen of the tendon rather than by the distinct Sharpey’s fibres found in the adult. Injury in the form of a powerful separating force is then more likely to pull cartilage or bone off rather than rupture the tendon. Hence patellar tendon disruption in
Fig. 1. Diagramatic representation of a sleeve fracture. Broad arrow indicates articular cartilage; thin arrow, periosteum and cartilage.
Fig. 2. X-ray of sleeve fracture with new bone forming in the disrupted patella mechanism.
children is at the proximal or distal end by avulsion rather than a mid-substance tear [5]. This is also seen, for example, in avulsion of the epicondyles of the elbow, the tibial tuberosity or even avulsion of the tibial insertion of the anterior cruciate ligament. It is, of course, in keeping with the pain seen in repetitive stress conditions such as Osgood Schlatter’s disease, Sinding–Larsen–Johansson disease or the avulsed fragments seen in children with fixed flexion deformities such as in cerebral palsy or arthrogryposis [6]. What is unique about the sleeve fracture is that it is a complete sleeve or cuff of osseo-potent tissue that is pulled off from the full circumference of the patella. This is articular cartilage on the deep surface and periosteum and cartilage on the superficial surface. This is often not shown clearly in diagrams (Fig. 1). The disruption of the periosteum occurs over the body of the patella. It slides distally taking osseo-potent transformation zone cells from the osseo-chondral zone of the patella with it. This may not result in complete disruption of the quadriceps mechanism but an elongation. The tissue can be all cartilage and periosteum and so will not be visible on X-ray. It means that there is a collection of potent bone-forming tissue at the lower pole of the patella which will go on forming bone resulting in enlargement or even duplication of the patella (Fig. 2) [7]. This differentiates the sleeve fracture from the avulsed osteochondral fragment seen on the medial or lateral side of the patella [8]. The insertion of vastus medialis is so strong and directly into the osseo-chondral zone that cartilage and bone is pulled off. The difference here is that the insertion is transverse or oblique to the line of the fibres of the periosteal sleeve surrounding the patella and a fragment of cartilage and bone is avulsed without the disruption of the periosteal sleeve which occurs with the
D.M. Hunt, N. Somashekar / The Knee 12 (2005) 3–7 Table 1 Classification of patella fractures in children (1) (2) (3) (4) (5) (6)
Medial avulsion fracture Lateral avulsion fracture Separation of bipartite patella Sleeve fracture: lower pole and upper pole Transverse fracture Stellate or comminuted fracture
longitudinal pull of the injury associated with sleeve fractures. The important point is that it is the periosteal sleeve on the subcutaneous surface of the patella which contributes to new bone formation. This raises the issue of the bipartite patella. Is it a fracture or a secondary ossification centre [9,10]? The evidence is in favour of a secondary ossification centre. There is no history of trauma and the bipartite patella is rarely a cause of pain. Pain can occur in overuse situations in enthusiastic athletes and widening of the gap between the fragment and the body of the patella has been described [11]. Also, the fragment can heal after lateral release alone so excision is not needed [12]. The bipartite patella fragment is then a weak spot in the quadriceps mechanism and there is no reason why it should not be pulled off as an acute injury [2], perhaps explaining why it is confused with a fracture. Saupe classified bipartite patella into three types; Type I is a lower pole fragment [10]. It is conceivable that this could be pulled off before it had ossified in a sleeve fracture.
4. Classification of patella fractures Grogan et al. [13] describe 47 patella fractures classifying them all as avulsion fractures. These include upper pole and lower pole fractures (including bipolar), medial and lateral avulsion fractures, transverse and stellate fractures. Separation of bipartite fragments should also be included in a full classification (Table 1). Interestingly, while the sleeve fracture mechanism is described, it is not included as a specific classification. The sleeve fracture is different from the avulsed osteochondral fragment because of the tube of cartilage and periosteum which is pulled off, often without
5
any bone. It is then different from the point of view of diagnosis, treatment and outcome and so should be classified as a separate group.
5. Mechanism of injury Sleeve fractures, like avulsion fractures, are distinct from patella fractures resulting from a direct blow or fall. They are caused by a rapid contraction of the quadriceps on a flexed knee. They usually occur in those involved in explosive acceleration activities such as jumping, although high energy sports such as skateboarding are now common causes [14].
6. Clinical presentation The history is then of the sudden onset of severe pain with an explosive acceleration such as jumping rather than a fall. It may be witnessed by a teacher or trainer. There is pain and a swollen knee with inability to straight leg raise. There are two clues which must be looked for. Firstly, there is a palpable gap at the lower pole of the patella, and secondly, there is patella alta, in that the patella on the affected side will be felt lying more proximally than the patella on the other side. It may not be so easy to demonstrate on X-ray due to difficulty flexing the knee the small amount required to measure true patella alta. If the disruption is minimal, the signs will be minimal. There may be no gap and patella alta will not be obvious and the child soon learns to lift the leg using the fascia lata and internally rotating the limb. These are the cases that result in elongation of the quadricreps mechanism and an elongated patella with an extensor lag. Presentation may be late and so it is no surprise that the diagnosis can be missed.
7. Investigations Plain X-rays can be misleading, revealing no bony damage. The clue on X-ray is patella alta which should be
Fig. 3. Ultrasound and schematic appearance of the disrupted bsleeveQ of subcutaneous periosteum and cartilage. Bone may not be present so nothing would be visible on X-ray.
6
D.M. Hunt, N. Somashekar / The Knee 12 (2005) 3–7
looked for specifically. There may be a visible bony fragment at the distal end of the patella (Fig. 3), in which case the diagnosis is easy but it may not be present if the fragment is cartilage and periosteum only. As in all injuries around joints in children, ultrasound should now be thought of before X-ray. It is quick, cheap, easy and safe and in this instance, diagnostic [15]. More sophisticated investigations such as MRI are a luxury but unnecessary [16].
8. Treatment The problem in treatment is the reduction of the injured tissue, to restore the length of the patella tendon and reduce the height of the patella alta. This virtually always means operative reduction. If a bony fragment is visible on X-ray and the displacement is less than 2 mm, closed treatment in a cast in extension is justified but the results of conservative treatment are unsatisfactory [7,14]. Also, simple excision of the bony fragment when present should be avoided, at least in the acute stage as it leaves an irregular lower pole of the patella. In a sleeve fracture, when it is missed at the time of the injury, the new bone formed will be too large to reduce and fix and will have to be removed, emphasising the importance of an awareness of this injury and prompt diagnosis and treatment. Through a midline incision, the periosteum and paratenon are opened in the line of the incision and the lower pole of the patella inspected. There will almost always be a few fragments of cartilage or bone in the avulsed proximal end of the patella tendon. These should be cleaned and the patella brought down. Repair is by whatever is the surgeon’s personal choice. Large transosseous sutures are simple and efficient [1,17]. A modified tension-band wire system can be used or even intra-osseous anchors [14]. If there is a good bone fragment, fixation should be rigid and carefully executed to minimise damage to the delicate nutrient vessels of the patella which enter the patella almost exclusively from the anterior surface and the distal pole, not medially [18]. The particular point about a sleeve fracture is that the periosteum should be carefully replaced over the subcutaneous surface of the patella and held with light tacking sutures. Postoperatively, the limb is immobilised in a cast in full extension for 2 weeks and then a brace, in extension initially, gradually allowing increasing flexion after a month.
9. Outcome Prompt diagnosis and straightforward treatment can be expected to produce an excellent result with full return to all activities, no extensor lag and full flexion. Failure to make the diagnosis can result in permanent disability with patella
alta and subsequent instability, extensor lag, quadriceps wasting and weakness, patella pain associated with osteochondral damage and ossification in the stretched patella tendon giving rise to patella magna or even duplication of the patella [19].
10. Conclusion Sleeve fractures are rare but are the most common form of patella fracture in the under 16 age group. It is a diagnosis that must be considered in an acute knee injury, especially when there has been no contact and the force is explosive force such as jumping. The clinical signs and Xray changes may not be diagnostic. Ultrasound is very helpful. Prompt diagnosis and appropriate treatment which is usually surgical can be expected to result in full functional recovery.
Acknowledgements The authors would like to thank Dr. Adam Ditchfield for the use of the ultrasound picture and accompanying diagram (Fig. 3).
References [1] Sponseller P, Stanitsk C. In: Beaty JH, Kasser JR. editors. 5th ed. Fractures in Children. Philadelphia: Lippincott, Williams and Wilkins. 2001. p.1029. [2] Ray JM, Hendrix T. Incidence, mechanism of injury and treatment of fractures of the patella in children. J Trauma 1992;32:464 – 7. [3] Ogden JA. Skeletal Injury in the Child. Philadelphia7 WB Saunders; 1990. [4] Dai LY, Zhang WM. Fractures of the patella in children. Knee Surg Sports Traumatol Arthrosc 1999;4(7):243 – 5. [5] Peterson L, Stener B. Distal disinsertion of the patellar ligament combined with avulsion fractures at the medial and lateral margins of the patella. Acta Orthop Scand 1976;47:680 – 5. [6] Rosenthal RK, Levine DB. Fragmentation of the distal pole of the patella in spastic cerebral palsy. J Bone Joint Surg Am 1977;59: 934 – 9. [7] Bruijn JD, Sanders RJ, Jansen BR. Ossification in the patellar tendon and patella alta following sports injuries in children. Complications of sleeve fractures after conservative treatment. Arch Orthop Trauma Surg 1993;3(112):157 – 8. [8] Heckman JD, Alkire CC. Distal patellar pole fractures: a proposed common mechanism of injury. Am J Sports Med 1984;12:424 – 8. [9] Ogden JA, McCarthy SM, Jokl P. The painful bipartite patella. J Paediatr Orthop 1982;2(3):263 – 9. [10] Saupe E. Quoted in Bourne MH, Bianco AJ Jr. Bipartite patella in the adolescent, the results of surgical excision. J Paediatr Orthop 1990;10:69. [11] Ishikawa H, Sakurai A, Hirata S. Painful bipartite patella in young athletes: the diagnostic value of skyline views taken in the squatting position and the results of surgical excision. Clin Orthop Relat Res 1994;305:223. [12] Ogata K. Painful bipartite patella: a new approach to operative treatment. J Bone Joint Surg Am 1994;76:573.
D.M. Hunt, N. Somashekar / The Knee 12 (2005) 3–7 [13] Grogan DP, Carey TP, Leffers D, Ogden JA. Avulsion fractures of the patella. J Pediatr Orthop 1990 (Nov.–Dec.);10(6):721 – 30. [14] Houghton GR, Ackroyd CE. Sleeve fractures of the patella in children. J Bone Joint Surg Br 1979;61:165 – 8. [15] Ditchfield A, Sampson MA, Taylor GR. Case reports. Ultrasound diagnosis of sleeve fractures of the patella. Clin Radiol 2000;55(9): 721 – 22. [16] Bates DG, Hresko MT, Jaramillo D. Patellar sleeve fracture: demonstration with MR imaging. Radiology 1994;193(3):825 – 7.
7
[17] Kaar TK, Murray P, Cashman WF. Transosseous suturing for sleeve fracture of the patella; a case report. Ir J Med Sci 1993;162(4):149. [18] Scapinelli R. Blood supply of the human patella: its relation to ischaemic necrosis after fracture. J Bone Joint Surg Br 1967;49: 563 – 70. [19] Yeung E, Ireland J. An unusual double patella. Knee 2004;11: 129 – 31.