Lower extremity fractures are common in children and adolescents. These injuries can range from low-energy falls from standing height such as toddler fractures to moderate-energy sports-related injuries such as tibial tubercle fractures to high-energy motor vehicle injuries such as floating knees. Many of the unique fracture patterns that occur in growing children are attributable to their changing bony and physeal anatomy. Although growing bone and open physes can allow remodeling after certain fractures, these open physes also provide distinct opportunities for postinjury complications such as premature physeal closure. Pediatric patients are vulnerable to compartment syndrome like adults, particularly after tibial shaft fractures, but they present with increased anxiety, agitation, and increased analgesia requirement.

Patellar fractures in skeletally immature patients are rare and account for less than 2% of all patellar fractures. Patellar sleeve fractures, specifically, make up 57% of patellar fractures in children with a peak incidence at 12.7 years of age. Boys sustain patellar sleeve fractures at a ratio of 3:1 compared with girls.¹ Most patellar sleeve fractures occur at the inferior pole, but superior pole sleeve fractures have been reported.²

The pathogenesis of patellar sleeve fractures occurs because of the direct attachment/blending of extensor mechanism tendon collagen into the cartilage portion of the osteochondral rim at the periphery of the growing patella. Therefore, the mechanism of injury of a patellar sleeve fracture is not a direct blow to the patella, but rather a powerful contraction of the extensor mechanism that separates a circumferential cuff of articular cartilage (deep) and periosteum (superficial) off the bony patella.³

On examination, a patient with a patellar sleeve fracture will have knee swelling/effusion, pain on palpation of the patella, possibly a palpable gap in the extensor mechanism, patella alta (or baja), and inability to perform a straight leg raise. Plain radiographs can usually diagnose the condition, but the findings can be subtle (Figure 1). MRI can confirm the diagnosis and demonstrate the extent of cartilage injury and amount of fragment displacement.⁴

In general, treatment for patellar sleeve fractures is surgical, with the goals of restoring articular surface alignment, reconstructing the extensor mechanism, and correcting patella alta. Surgical treatment
(open reduction and internal fixation [ORIF]) can be accomplished using transosseous fixation with nonabsorbable sutures, tension band wiring with Kirschner wires and nonabsorbable sutures, or reconstruction with suture anchors.¹,³

Proximal tibia physeal fractures are rare, accounting for less than 1% of pediatric fractures.⁵,⁶ These fractures are classified by the Salter-Harris classification system, with Salter-Harris II being the most common (Figure 2). The mechanism of injury is hyperextension of the knee (with resulting posterior displacement of the epiphysis) or hyperflexion (with anterior displacement of the epiphysis).

Salter-Harris I/II fractures can generally be diagnosed on AP/lateral knee radiographs and can be managed with closed or open reduction and long leg cast (LLC) immobilization alone or crossed smooth Kirschner wire fixation and long leg casting for 4 to 6 weeks. Salter-Harris III/IV fractures can also be diagnosed on plain AP/lateral knee radiographs, but CT can be added to evaluate articular displacement. MRI is not routinely used in acute evaluation of this injury but can be used for suspected associated ligamentous injuries. Treatment for Salter-Harris III/IV proximal tibial fractures is closed or open reduction to achieve articular displacement less than 2 mm and stabilization with screws placed parallel to the knee joint avoiding the physis. LLC immobilization should also be used.

There is a high incidence of neurovascular injury (14%) among these proximal tibia physeal fractures (similar to knee dislocation) because the popliteal artery at its trifurcation is tethered to the posterior tibia just below the physis. Therefore, a thorough neurovascular and compartment examination needs to accompany evaluation of this injury.⁷

There is also a high incidence of growth disturbance (premature physeal closure) in approximately 25% of these injuries. Therefore, after healing is achieved,
growth of the proximal tibial physis should be followed with knee radiographs and/or full-length weight-bearing radiographs until the patient reaches skeletal maturity.⁵,⁸

Tibial tubercle fractures occur with an incidence of less than 1% to 2.7%. They most commonly occur in males nearing skeletal maturity (age 14 to 17 years). In a 2019 study, 63% of the patients with tibial tubercle fractures were overweight.⁹ The mechanism of injury is a forceful eccentric contraction of the extensor mechanism pulling suddenly on a partially open tibial tubercle apophysis. The proximal tibia physis closes from posterior to anterior leaving the anterior portion weaker and susceptible to these injuries with initiating or landing a jump such as during basketball, as discussed in a 2020 study.¹⁰ Osgood-Schlatter disease coexists in 23% of patients with tibial tubercle fractures.¹¹

There are many systems for the classification of tibial tubercle fractures. The classic system is the Watson-Jones classification system: type I is a distal tubercle avulsion, type II is a secondary ossification center fracture that hinges upward at the proximal tibial physis, and type III (the most common type) is a fracture that exits out of the proximal tibial physis into the knee joint. The Ogden modification of this system is frequently used; each of the three types can be classified as either A, nondisplaced/minimally displaced, or B, displaced/comminuted. There are modifications by Ryu/Debenham to add a type IV fracture that exits out the posterior proximal physis and McKoy/Stanitski to add a type V fracture that is a combination of IIIB and IV¹²,¹³ (Figure 3).

Clinical examination includes assessment of knee pain, significant swelling, patella alta, and often inability to perform a straight leg raise. Plain radiographs can diagnose the injury, but CT scan delineates intraarticular extension of the fracture for bony surgical decision making.¹⁴ Because intra-articular injuries can occur along with the fracture in 12% of patients, MRI or direct visualization with arthroscopy/arthrotomy at the time of surgical fixation can help identify these associated soft-tissue injuries.¹⁵

Associated injuries that can occur with tibial tubercle fractures are patellar tendon/quadriceps tendon avulsion (2%), meniscal tear (2%), and compartment syndrome (4% to 20%).⁵,¹¹,¹⁵ Compartment syndrome can occur if the anterior tibial recurrent artery is torn at the time of fracture; and the anterior compartment can be released at the time of ORIF if needed.

Management of nondisplaced tibial tubercle fractures is with long leg casting for 4 to 6 weeks. Treatment of displaced tibial tubercle fractures is with ORIF. The usual screw configuration is at least two anterior-to-posterior partially threaded 4.0-mm cannulated screws (with or without washers) placed parallel to the physis.¹⁴ Useful surgical pearls for placing these screws are to obtain a perfect lateral fluoroscopic image of the tibial tubercle by slightly internally rotating the leg and to remember that the anatomically reduced apophysis may look slightly wide on fluoroscopy because the cartilage of the apophysis looks like a gap (Figure 4).

Outcomes after tibial tubercle fractures are generally very good. A union rate of 98% to 100% is reported, with 94% of patients able to return to preinjury level of activity and 98% achieving full knee range of motion.¹¹ In a 2019 functional outcomes paper, 26% of patients with tibial tubercle ORIF had clinically significant quadriceps weakness and 37% had loss of thigh girth at average 3-year follow-up. These objective findings did not correlate with lower patient-reported outcomes.⁹

Complications occur in 28% of patients with tibial tubercle fractures treated with ORIF: painful hardware necessitating removal (56%), tubercle prominence (18%), refracture (6%), infection (3%), genu recurvatum (4%, all patients were younger than 13 years at the time of injury), and leg length difference (5%).¹¹

Ipsilateral simultaneous fractures of the tibia and femur are referred to as a floating knee. This is a rare combination of injuries that occurs via high-energy mechanisms such as motor vehicle accidents as a passenger (45%) or pedestrian (33%) and all-terrain vehicle (9%) injuries.¹⁶ In a 2019 multicenter study of floating knees, the average age of these patients was 10.2 years, 63% were male, one-third of the patients had at least one open fracture, 90% of the femoral fractures were shaft fractures, and 87% of the tibial fractures were shaft fractures, and the hospital length of stay was 9 days.¹⁶

Classification of floating knees is by the Letts-Vincent classification system: A, both femur and tibia are closed diaphyseal fractures; B, one fracture is diaphyseal and other is metadiaphyseal and both are closed; C, one fracture is epiphyseal and the other is diaphyseal and both are closed; and D, either femoral or tibial fracture is open; E, both femoral and tibial fractures are open.¹⁷

Treatment of floating knees has changed over time toward more surgical treatment. Comparison of a historical pediatric floating knee group (1975 to 2003) with a more modern group (2004 to 2014) showed there was more casting done historically. In the more modern group, 91% of the femoral fractures were managed surgically (38% flexible nails, 31% rigid intramedullary nails) and 27% of the tibias were managed with a cast only, whereas 25% of tibias were managed with flexible nailing.¹⁶

Although 93% of the floating knees in the 2019 multicenter study had either excellent or good outcomes after at least 1 year follow-up, complications did occur. The complications were: nonunion (3%), malunion
(9%), and wound complications (10%).¹⁶ In a systematic review of floating knees, complications were: leg length discrepancy (33%), malunion (20%), secondary surgeries (13%), infection (9%), nonunion (7%), and premature physeal closure (3%).¹⁸

As discussed in a 2019 study, tibial shaft fractures account for 15% of all long bone injuries in children, and average age at time of injury is 8 years.¹⁹ Thirty percent of tibial shaft fractures have an associated fibular fracture, usually caused by a higher energy mechanism than isolated tibial fractures. This pattern has a tendency to progress into valgus alignment because of anterolateral muscle overpull. Of the tibial shaft fractures with an intact fibula (lower energy/usually torsional mechanism), varus alignment eventually develops in 60% because of tethering of the fibula and posterior muscle overpull even if the fracture was minimally displaced initially.²⁰ The mechanism of injury ranges from low-energy spiral tibial fractures in younger children who sustain a torsional force with a planted foot to higher energy motor vehicle and collision sports injuries in older adolescents.

A typical presentation of patients with a tibial fracture is pain at the fracture site, possible deformity, variable amount of swelling, and inability to bear weight. The diagnosis of a tibial fracture is made by AP and lateral tibia/fibula radiographs. Sometimes dedicated ankle and knee radiographs are necessary to look for ipsilateral fractures. In a 2020 study of 517 tibial shaft fractures, 4.3% had ipsilateral distal tibial fractures (36% of which were not diagnosed until chart review for the study). The highest incidence of these concurrent fractures occurred in the middle-distal third shaft fracture with spiral or oblique fracture patterns.²¹

Acceptable alignment parameters for tibial shaft fracture in patients younger than 8 years is up to 10° varus or apex anterior (procurvatum) angulation, up to 5° valgus or apex posterior (recurvatum) angulation or rotation, one shaft width (100%) translation, and 10 mm of shortening. In patients older than 8 years, acceptable parameters are up to 5° varus/valgus, apex anterior angulation or rotation, 0% apex posterior angulation, 50% translation, and 5 mm of shortening.¹⁸,²¹,²²

Treatment for many tibial shaft fractures is closed reduction within aforementioned tolerances and casting with weekly radiographic monitoring for 3 weeks to ensure maintenance of acceptable alignment. Traditionally an LLC is worn for 4 to 6 weeks followed by a short leg walking cast or boot for another 4 to 6 weeks.²³ If there is loss of reduction during the course of casting, remanipulation or cast-wedging can be performed. In a 2020 study, 21% of the 75 adolescents treated with closed reduction and casting of tibial shaft fractures needed either remanipulation or cast-wedging in the clinic. A total of 60% of these patients required casting longer than 3 months, especially when both the tibia/fibula were fractured. Only 4% of these patients needed surgical treatment.²¹ This is a much smaller percentage compared with an earlier study of 74 patients with tibial shaft fractures in which 40% needed surgical treatment for loss of reduction during cast treatment. Predictors of failure of casting were initial displacement greater than 20% and presence of both a tibial and fibular fracture.²⁴ Position of the ankle in the cast is important; slight plantar flexion to prevent recurvatum deformity is preferred. The position of the knee in an LLC and weight-bearing status were studied in a prospective randomized study of 81 patients. There was no difference in final angulation or time to union in the group with 10° of knee flexion and weight bearing as tolerated versus the group with 60° of knee flexion and no weight bearing.²⁵ A 2021 comparison of patients age 5 to 17 years with distal third tibial shaft fracture treated with 50 LLCs and 35 short leg casts (SLC) showed that SLC had shorter time to weight bearing (3.3 weeks in SLC group compared with 6.4 weeks in LLC group), shorter time to union (7.4 weeks SLC versus 9.0 weeks LLC) without a difference in final angulation. There were also more cast complications in the LLC group (12% versus 6% in SLC group).²⁶