1
Department of Orthopaedics, AlWakra Hospital, Hamad Medical Corporation, Qatar
Corresponding author details:
Mohammed Shabeer
Department of Orthopaedics
AlWakra Hospital Hamad Medical Corporation
Hamad Medical Corporation,Qatar
Copyright:
© 2020 Shabeer M, et al. This is
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the terms of the Creative Commons
Attribution 4.0 international License, which
permits unrestricted use, distribution, and
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original author and source are credited.
We describe a rare case of patellar fracture in a seven year old girl. The case was
reviewed for various aspects such as clinical diagnosis, imaging tests and most suitable
treatment.
Pediatric patellar fractures are relatively uncommon. However, when reported, they
involve patients younger than 16 years [1]. The peak incidence is between 8-12 years of age
[2,3].The reason for this is the relative flexibility of the patella in childhood, which is less
affected by impact and tension forces during quadriceps contraction [4]. The mechanism of
such fractures is either due to direct trauma and/or excessive contraction of the extensor
mechanism. Houghton and Ackroyd [5] elucidated an avulsion-type fracture of the lower
end of the patella; in such fractures a significant chunk of cartilage is avulsed from the
patella affixed to a discreet bone fragment. Such fractures may not be commonly diagnosed,
especially if there is a large hemarthrosis or if radiographs studies aren’t clear about the
fracture line [5,6]. Grogan et al. [7] gave his classification of pediatric patellar fractures
based on their anatomic location. The proximal avulsion fracture, which is the commonest,
involves the patellar upper pole while as the distal end avulsion is commonly traumatic,
just like our case. Medial avulsion injury can be seen after a lateral patellar dislocation. The
avulsion of the superolateral corner of the patella may be mistaken for a bipartite patella [8]
or may be stress induced due to repeated traction of the vastus lateralis muscle [9]. A similar
stress induced injury is the Sinding-Larsen-Johansson disease, due to repeated stress of
the distal patellar end,s causing an incomplete avulsion of the patellar ligament fibers and
subsequent necrosis and calcification [10]. In such cases, MRI of the knee is the diagnostic
modality of choice [11-13] in the detection of this condition in order to avoid later damage
to knee extension or the formation of megapatellas with irregular joint surface [14-16].
A seven year old Ghanaian girl was running at school and she collided with another girl and her right knee hit a concrete pillar. When she presented to the emergency department, she had complaints of pain and swelling right knee and inability to bear weight on the right lower limb. On examination, there was moderate swelling and tenderness over right patella. The patient could not perform an active extension of the knee. Radiographss revealed a patellar fracture.
Patient was admitted to the hospital and was given analgesics and knee immobilizser. She was treated by Open reduction and Internal Fixation using K wires and Tension Band Wiring on the following day. A cylinder slab was advised for 3 weeks post operatively. Immobilisation with plaster was discontinued after 3weeks and Radiographs showed fracture was uniting well. She was referred to physiotherapy and was advised knee mobilisation exercises and partial weight bearing (Figure 1A and 1B).
She was followed up regularly and at 6 weeks clinically there was no tenderness at the fracture site (Figure 2A and 2B).
Her knee ROM was full with full active flexion and extension and she was bearing full weight. Check radiographss showed the complete union of fracture at 6 weeks.
At the last follow up at 6 months, the child was asymptomatic and was advised implant
removal (Figure 3A and 3B).
Radiograph Before Surgery
Figure 1: A) Lateral View, B) AP View
Radiograph After Six Weeks
Figure 2: A) AP View, B) Lateral view
Radiograph After 6months
Figure 3: A) AP View, B) Lateral view
The girl in our case report had an age less than the usually reported age group of patellar fractures in children which is8-12 years [1]. This may be due to a combination of direct and indirect trauma that is the peculiar mechanism of injury which occurred in our patient.
The predominant quandary regarding pediatric patellar fractures is the diagnosis. Often, congenital anomalies may mimic fractures [8,9]. Another issue in such cases is difficulty in gauging the size of the fracture fragments, more so in sleeve-type fractures due to the cartilaginous nature of the patella [3]. Belman and Neviaser [1] reported that missed or delayed diagnoses are common for patellar fractures in children. Sleeve-type patellar fractures often occur in children who take part in activities requiring knee extension force with quadriceps contraction against resistance, with injury occurring on the supporting leg. Hence, this form of injury is unlike those due to direct knee trauma [5].
To be aware of the possibility of such an injury, a good history along with characteristic radiological features should lead to the diagnosis. The avulsed patellar fragment invariably includes a sizable sleeve of cartilage; it is imperative that this fragment must be accurately reduced to re-establish the articular surface of patella [5].
The treatment of paediatric patellar fractures with splints in the lower limb extension can result in a reconstruction of the extensor apparatus, but a patellar deformity can remain (megapatella) with motion restraint, especially in extension [17,18]. Extensor mechanism reconstruction surgery with absorbable sutures has not shown good results [5,18,19]. The most ideal treatment method seems to be the rigid internal fixation of the fracture with emphasis on anatomical reduction and the realignment of the joint cartilage [5]. When bone fragments are small, internal fixation must be performed by a tension band [5,12]. The stability of internal fixation can be augmented by suturing medial and lateral retinacula which is very important. With rigid fixation, active flexion and extension exercises of the knee are initiated as early as possible as soon as the wound has healed and a normal range of movements of the knee was achieved within a few weeks as we observed in our case.
Tsubosaka et al. [19] has reported a case of fracture patella in a 12 year old boy following a skateboard injury. As tension band wiring was unsuccessful, it was treated with trans osseous tunnelling and suturing with ethibond 5 and cerclage wiring of patella.
Ndeleva et al. [20] has reported a case of transverse fracture patella in a 10 year old boy 2 months after a fall. He was treated with tension band wiring.
Johan Kirkegaard et al. [21] has reported a case of fracture patella
in a 11 year old boy which was missed initially and later diagnosed
after 6 weeks with an MRI scan. He was treated with open reduction
and fixation of patella using cerclage and fiber wire sutures.
Although fractures of the patella in children are uncommon, we
should think of it as one of differential diagnoses in cases of acute
knee injuries, especially when the injury was caused by excessive
force such as jumping or sports injuries. The diagnosis can often be
missed in fractures with a very small Avulsed bony fragment. We
suggest MRI scans in doubtful cases for early diagnosis and early
surgical intervention and internal fixation with mobilisation can
achieve excellent results for displaced fractures of the patella.
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