Submuscular Plating of Pediatric Femur Fractures
Chapter 26
Submuscular Plating of Pediatric Femur Fractures
Ernest L. Sink Benjamin F. Ricciardi
DEFINITION
Submuscular bridge plating is a minimally invasive, soft tissue preserving approach that provides relative stability for length-unstable pediatric diaphyseal femur fractures.
ANATOMY
The distal margin of the vastus lateralis is deep to the iliotibial fascia in line with the proximal pole of the patella.
The fibers of the distal vastus lateralis are oblique, and the muscle is not attached to the bone, providing a plane between the muscle and lateral periosteum of the femur for plate insertion.
PATHOGENESIS
Falls or motor vehicle accidents are the most common mechanisms of injury, representing approximately two-thirds of all pediatric femur fractures.6
Child abuse should be ruled out in pediatric patients with femur fractures, particularly in patients younger than 2 years old.6
NATURAL HISTORY/BACKGROUND
Femur fractures are the most common cause of hospital admission due to orthopaedic trauma for pediatric patients.6
Male patients are more commonly affected relative to female patients, and there is a bimodal age distribution with peaks in young (younger than 4 years old) patients and adolescent patients.
Fracture of the femoral diaphysis is more common than trochanteric or distal femoral locations.
PATIENT HISTORY AND PHYSICAL FINDINGS
History should include age, mechanism of injury (rule out child abuse in patients younger than 2 years old), other locations of pain to rule out concomitant injury, and relevant medical or family history (eg, cerebral palsy and osteogenesis imperfecta increase the risk of low-energy femur fractures).
Physical examination reveals shortening and rotational deformity of the affected extremity with painful range of motion. Neurovascular examination, skin integrity, signs of compartment syndrome should all be carefully assessed.
Concomitant injury should be ruled out because pediatric femur fractures represent high-energy injuries in many cases and can be associated with neurologic, visceral, and other musculoskeletal trauma.
IMAGING AND OTHER DIAGNOSTIC STUDIES
An anteroposterior (AP) and lateral view of the injured femur will diagnose the fractured femur. Imaging should include radiographs of the ipsilateral hip and knee to rule out secondary injuries to the femoral neck or knee joint.
SURGICAL MANAGEMENT
Operative stabilization is the treatment of choice for pediatric femur fractures in most children 5 years and older through skeletal maturity. Flexible elastic nailing is successful for the majority of diaphyseal femur fractures.1, 3 Factors such as comminution, long oblique length-unstable fractures, and children older than the
age of 10 years have resulted in increased complication rates in some series with flexible elastic nailing.7, 10
Therefore, alternative means of stabilization have been suggested for fractures with these characteristics.
Plate osteosynthesis is a proven method to stabilize pediatric fractures. The use of submuscular bridge plating for comminuted femur fractures allows for rigid stabilization, minimally invasive techniques, avoidance of avascular necrosis (AVN) of the femoral head, and stabilization of the diaphyseal/metaphyseal junction.
The procedure is indicated for patients 5 years old to skeletal maturity. The fracture patterns most amenable to bridge plating are comminuted or long oblique length-unstable fractures. Older or heavier children with femoral canals unable to accommodate an intramedullary (IM) nail would also be appropriate candidates (FIG 1).
Submuscular plating is also a reliable option for proximal or distal one-third femur fractures.1 For these fractures, there needs to be room for two to three screws in the proximal or distal diaphyseal region.
It has a relative contraindication in patients that have transverse fractures. We prefer flexible IM nails to bridge plating for transverse or short oblique mid-diaphyseal fractures.
Preoperative Planning
All patients should be carefully evaluated for other injuries including knee or hip injuries. An operating room equipped with traction bed and fluoroscopy is critical.
No preoperative templating is required, as the plate length and contour are chosen under sterile conditions. It is important to have the long plates available and the appropriate screw set.
Finally, evaluating the natural rotation of the contralateral leg is useful as a reference prior to draping.
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FIG 1 • A,B. Displaced pediatric diaphyseal femur fracture in AP and lateral planes, respectively. C,D. Submuscular bridge plating shows appropriate fracture reduction and restoration of length in in AP and lateral planes, respectively.
A narrow 4.5-mm plate is most often used.
This plate is readily available, easy to contour, and percutaneous screw placement is forgiving.
Many of the currently available implants have the locking or nonlocking screw option.
Although nonlocking screws have been successful, locking screws may have some benefit in osteopenic patients or very proximal or distal fractures, where there is little available room for screws.
In our experience, nonlocking screws achieve enough stability in this age group and allow easier percutaneous screw placement compared with locking screws.
If a locking plate is used, a combination of locking and nonlocking screws are needed to reduce the femur to the plate.
It may be easier to place the locking screws with direct plate exposure rather than percutaneous exposure.
Self-tapping screws are essential for easier percutaneous insertion.
In smaller children, a long, narrow 3.5-mm plate may be used if absolutely necessary, but a 4.5-mm plate will fit most femurs even in the younger children.
The plate length chosen is usually 10 to 16 holes, depending on fracture location and patient size.
The plate commonly spans from just below the greater trochanteric apophysis to the metaphysis of the distal femur.
If possible, the plate length should allow six screw holes proximal and distal to the fracture.
Positioning
Patients are positioned supine on a fracture table.
The normal contralateral leg is extended and slightly abducted to allow a true lateral fluoroscopic image of the fractured femur.
Alternatively, a “well-leg” holder may also be used.
Provisional reduction restoring femoral length and rotation is obtained with boot traction and verified fluoroscopically.
Final alignment is performed with plate fixation as described later.
TECHNIQUES
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Exposure
A small (4 to 7 mm) incision is made at the distal lateral thigh.
The exposure is advanced through the tensor fascia to expose the distal oblique fibers of the vastus lateralis muscle.
Blunt dissection is performed deep to the distal muscle fibers to enter the plane between the vastus lateralis and lateral femur periosteum. This plane is easily entered and allows proximal plate advancement with minimal force.
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Plate Contouring
A table top plate bender contours the plate similar to the lateral femur with a slight bend proximally and distally to accommodate the proximal and distal metaphysis.
The final femoral varus/valgus alignment is that of the plate so it is important to contour the plate as close to anatomic as possible.
The usual practice is to place the precontoured plate on the anterior thigh and use the AP view on the Carm to shadow the plate with the lateral femur cortex checking the plate contour (TECH FIG 1).
In our experience, there has been no significant (>5 degrees) misalignment as a result of incorrect contouring.
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TECH FIG 1 • A. Plate contour is established using the AP view on the C-arm. B. The plate is aligned with the lateral femur cortex.
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Plate Advancement
Blunt dissection is performed deep to the distal muscle fibers to enter the plane between the vastus lateralis and lateral femur periosteum. This plane allows proximal plate advancement with minimal force.
The plate is then slowly tunneled proximally in this plane. A plate-holding clamp may be used to grasp the distal aspect of the plate for guidance.
Care must be taken to keep the plate on the lateral femur, as it is advanced proximally past the fracture to the region of the greater trochanteric apophysis.
The plate may be more difficult to pass along the lateral femur past the fracture. The surgeon may correct this by pulling the plate back and redirecting it.
Fluoroscopy may also aid the surgeon in plate advancement.
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Provisional Plate Fixation
Once the plate is fully advanced, it sits comfortably on the lateral femur; AP and lateral images are obtained to make sure the plate is in a good position in both planes, and the femoral length is restored (TECH FIG 2).
The plate is provisionally fixed to the femur with a Kirschner wire placed in the most proximal and distal screw holes.
If the fracture is “sagging” posteriorly, the femur can be lifted in an anterior direction while a K-wire is placed through the plate to engage the femur in this region.
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TECH FIG 2 • Once the plate is fully advanced, AP (A) and lateral (B) images are obtained to make sure the plate is in a good position on the lateral femoral cortex in both planes. Femoral length is restored.
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Plate Fixation with Percutaneous Screws
A long plate and correct screw placement is important for construct stability.
A screw should be placed in close proximity to the proximal and distal extent of the fracture.
The remaining screws are placed as far apart as possible. Obtaining maximal screw spread with a long
plate will improve construct stability, as there is a long working length of the plate.
Three screws proximal and three screws distal to the fracture are optimal.
The first screw placed should be near the proximal or distal extent of the fracture, where the femur is furthest from the plate.
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A screw in this area will reduce the femur to the plate and act as a “reduction screw.”
As the screw engages the far cortex, the femur will be reduced to the precontoured plate (TECH FIG 3A,B).
The fracture is “bridged,” and no attempt is made to place a screw to lag the fracture fragments.
The technical aspects of percutaneous screw placement are as follows: Screws are placed using “perfect circles” technique (TECH FIG 3C).
Using the fluoroscopic image in the lateral plane, a no. 15 blade scalpel is placed on the skin over the
hole, then rotated horizontal to the beam through the skin, tensor fascia, and vastus fascia.
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TECH FIG 3 • A,B. As the screw engages the far cortex, the femur will be reduced to the precontoured plate. C. Screws are placed using “perfect circles” technique. Using the fluoroscopic image in the lateral plane, a no. 15 blade scalpel is placed on the skin over the hole, then rotated horizontal to the beam through the skin, tensor fascia, and vastus fascia. D. Using freehand technique, a 3.2-mm drill is placed in the incision, and its location in the desired hole is confirmed with fluoroscopy. The hole is then drilled through both cortices. E. A 0 Vicryl suture is tied around the 4.5-mm fully threaded cortical screw head so it will not be lost in the soft tissue if the screw inadvertently disengages from the screwdriver. The screw is then advanced percutaneously through the plate (F), with fluoroscopy confirmation (G).
Using freehand technique, a 3.2-mm drill is placed in this small incision, and its location in the desired hole is confirmed with fluoroscopy.
The hole is then drilled through both cortices (TECH FIG 3D).
The length of the screw is approximated by placing the depth gauge on the anterior thigh as the image is rotated to the AP view.
A 0 Vicryl suture is tied around the 4.5-mm fully threaded cortical screw head so it will not be lost in the soft tissue if the screw inadvertently disengages from the screwdriver (TECH FIG 3E).
The screw is then placed though the plate and across the femur (TECH FIG 3F,G). The Vicryl ties are cut, and the incisions are closed with absorbable subcuticular sutures after all screws are placed.
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PEARLS AND PITFALLS
Plate
selection
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Narrow 4.5 mm most common; can include locking options if osteopenic or very
proximal/distal fracture; extend from greater trochanteric apophysis to distal metaphysis (10-16 holes)
Plate
contouring
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Bend proximally and distally to accommodate proximal and distal metaphyses.
Should be anatomic to avoid varus/valgus malalignment. Fluoroscopy prior to insertion helps refine plate contour.
Plate
advancement
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Insert between plane of femoral periosteum and vastus lateralis. Remain on
bone to avoid anterior/posterior plate malalignment.
Provisional
fixation
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K-wires help fix and align plate provisionally. Cortical screws help reduce plate
to bone.
Percutaneous ▪ Placed using fluoroscopy and perfect circle technique. Try to obtain six cortices
screw on either side of the fracture. Bridge technique (no lag screws across fracture). placement
POSTOPERATIVE CARE
A soft dressing is applied. We often place the patients in a knee immobilizer for early comfort with mobilization. No casting is required in the early postoperative period.
Active knee range of motion is encouraged as comfort allows.
Patients are kept non-weight bearing or touch-down weight bearing until bridging callus is seen usually at 6 to 10 weeks. Progressive weight bearing is then encouraged.
Once bridging callus is apparent on three or four cortices, activity as tolerated and sports is allowed in a graded manner. This is usually between 10 and 14 weeks.
The plate is removed in most patients around 6 months.
Later removal may require a larger incision due to tissue and bone ingrowth.
There are no clear indications for plate removal, although implant prominence, family preference, younger age, and surgeon preference may all influence this decision.8
We are more aggressive with offering plate removal in the younger children, as they have more bony overgrowth and leg growth potential. With adolescents, we approach removal on an individual basis, and family and surgeon preference are factors for removal.
The screws are removed using image guidance, and a dull Cobb elevator is slid along the outer part of the plate to free up surrounding tissue. Then the Cobb with the sharp end directed away from the bone is advanced between the plate and bone freeing up the plate.
Once the plate is completely freed, it can be removed from the distal incision where it was advanced.
Patients are then allowed weight bearing as tolerated and kept from running or sports for 6 weeks.
OUTCOMES
Many series report very high rates of fracture union with low rates of clinically evident malrotation, angulation, or shortening even in heavier patients and comminuted fracture patterns.1, 5, 9, 11
COMPLICATIONS
Reported complications are rare.
Plate failures are rare, and use of a 4.5-mm plate should minimize this complication from occurring.2, 5
Malunion is possible and can be potentially avoided with appropriate plate contouring.
Patients may be at increased risk of postoperative distal femoral valgus deformity, particularly in fractures extending close to the physis, and this may require longitudinal follow-up.4
Nonunion has not been reported, as this technique is best applied in closed comminuted fractures where the fracture region is bridged.
Attention to rotation is important prior to screw placement.
We use the opposite extremity and fracture geometry appearance with fluoroscopy with initial traction setup.
Asymptomatic leg length discrepancies may be present but rarely require any further management.1, 5, 9, 11
Symptomatic hardware may require plate removal in some patients.
REFERENCES
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Abdelgawad AA, Sieg RN, Laughlin MD, et al. Submuscular bridge plating for complex pediatric femur fractures is reliable. Clin Orthop Relat Res 2013;471:2797-2807.
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Becker T, Weigl D, Mercado E, et al. Fractures and refractures after femoral locking compression plate fixation in children and adolescents. J Pediatr Orthop 2012;32:e40-e46.
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Flynn JM, Hresko T, Reynolds RA, et al. Titanium elastic nails for pediatric femur fractures: a multicenter study of early results with analysis of complications. J Pediatr Orthop 2001;21:4-8.
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Heyworth BE, Hedequist DJ, Nasreddine AY, et al. Distal femoral valgus deformity following plate fixation of pediatric femoral shaft fractures. J Bone Joint Surg Am 2013;95:526-533.
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Kanlic EM, Anglen JO, Smith DG, et al. Advantages of submuscular bridge plating for complex pediatric femur fractures. Clin Orthop Relat Res 2004;(426):244-251.
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Loder RT, O'Donnell PW, Feinberg JR. Epidemiology and mechanisms of femur fractures in children. J Pediatr Orthop 2006;26: 561-566.
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Moroz LA, Launay F, Kocher MS, et al. Titanium elastic nailing of fractures of the femur in children. Predictors of complications and poor outcome. J Bone Joint Surg Br 2006;88:1361-1366.
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Pate O, Hedequist D, Leong N, et al. Implant removal after submuscular plating for pediatric femur fractures. J Pediatr Orthop 2009;29:709-712.
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Sink EL, Faro F, Polousky J, et al. Decreased complications of pediatric femur fractures with a change in management. J Pediatr Orthop 2010;30:633-637.
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Sink EL, Gralla J, Repine M. Complications of pediatric femur fractures treated with titanium elastic nails: a comparison of fracture types. J Pediatr Orthop 2005;25:577-580.
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Sink EL, Hedequist D, Morgan SJ, et al. Results and technique of unstable pediatric femoral fractures treated with submuscular bridge plating. J Pediatr Orthop 2006;26:177-181.