Fractures of the distal femur are often associated with several factors that can make successful fixation challenging. These include a short segment for distal fixation, lower bone density in the metaphysis, and significant metadiaphyseal comminution.1,2 Open fractures and obesity significantly increase the rate of nonunion and other complications in fractures of the femoral shaft and distal femur.3–7 Open fractures with medial comminution are the most common fracture pattern to progress to nonunion in the distal femur,7 and bone loss is directly correlated with poor outcomes in open femoral fractures.8
Lateral locked plating has improved fixation and maintained reduction of distal femur fractures compared with traditional nonlocking implants. Although this provided a leap forward in the management of these complex injuries,9,10 unfortunately, there continue to be some patient factors and fracture characteristics that have led to a continued risk of nonunion as high as 32%.11 This has led many authors to investigate both risk factors for nonunion and methods to decrease nonunion rates.7,11
Endosteal substitution is the use of an implant placed in the medullary canal to compensate for a structural deficiency in the medial cortex.12–14 This can be accomplished with an intramedullary plate, fibular allograft, or an intramedullary rod and is used in combination with a standard or locked plate. Endosteal substitution has been described in multiple anatomic locations.12–17 This composite fixation is most commonly needed to reconstitute a deficient far cortex in the metadiaphysis to provide additional stability and resist secondary displacement with prolonged or excessive loading during bony healing.
This series describes 2 groups of patients treated with a lateral locked plate and an intramedullary rod used as endosteal substitution. The first group includes acute comminuted or segmental femoral fractures. Composite fixation with an intramedullary rod and lateral locked plate was used at surgeon discretion based on factors including patient body habitus and fracture pattern characteristics such as segmental bone loss and comminution. The second group includes distal femoral nonunions treated with the composite fixation with an intramedullary rod and a lateral locked plate.
A retrospective review was completed of a database of all patients who underwent treatment of fractures of the femur or nonunions with both an intramedullary rod and a lateral locked plate from 2005 to 2016 at a Level I academic trauma center. Current Procedural Terminology codes 27470/27472 and the combination of Current Procedural Terminology 27506/27511 or 27513 identified 9 patients with acute treatment of femoral fractures with intramedullary rod and 10 femur fracture nonunions treated with intramedullary rod and a lateral locked plate. Eight acute fractures and 8 nonunions had adequate follow-up (6 months or until bony union) and complete medical records. The medical record and radiographs were reviewed to identify patient demographics, comorbidities, and clinical characteristics including mechanism of injury, fracture pattern, presence of a segmental bony defect, and implants.
In the nonunion subgroup, time interval from index surgery to nonunion surgery and type of bone graft was also recorded. Initial postoperative coronal and sagittal alignment, time to radiographic union and change in coronal and sagittal alignment were assessed. Postoperative complications including loss or change in alignment, wound dehiscence, deep or superficial infection, nonunion, and reoperation for any reason were recorded. Follow-up time was also recorded. Union was defined as radiographic evidence of healing in 3 of 4 cortices and clinical ambulation without any pain. Time to union and the union rate were also recorded.
A lateral parapatellar approach is used if distal femoral articular reduction is necessary, otherwise a tendon-splitting or medial parapatellar approach for a retrograde rod starting point and a direct lateral incision can be used for submuscular plate insertion. The reduction should proceed with any necessary articular reduction and fixation with independent lag screws in a manner that will avoid the trajectory of an intramedullary implant. The use of images from the contralateral uninjured extremity can be useful for comparison in restoring the coronal and sagittal alignment. At this point, there are 2 options in the order of fixation.
Plate First Technique
Reduction of length, alignment, and rotation can be accomplished through indirect reduction techniques using skeletal traction and strategically placed towel bumps, a universal distractor, or an external fixator. The lateral plate is passed in a submuscular fashion, and if needed, the fixed angle plate can be used as a reduction tool in the coronal plane. Screws in the plate should be placed outside the anatomic axis of the femur to allow for subsequent passage of the intramedullary rod. This means either directing bicortical screws outside the anatomic axis or using unicortical screws. After plate osteosynthesis, the provisional reduction tools and the targeting guide can be removed. At this point, intramedullary rodding can take place in a standard fashion. To create composite fixation, the rod position can be adjusted to allow for variable angle locking screws to be placed through one of the interlocking holes in the distal aspect of the rod. Using the targeting guide for interlocking screws can be helpful to define which plate hole would be best. A proximal screw can sometimes be placed through the plate into the lateral to medial interlocking hole in the rod. A simpler choice is to limit motion of the rod by placing a screw through the plate just proximal to it and additional screws through the plate around the rod or abutting it.
Rod First Technique
Reduction of length, alignment, and rotation can be accomplished through indirect reduction techniques using skeletal traction and strategically placed towel bumps. Percutaneous reduction tools such as Schanz pins, picadors, and bone hooks are used when needed. The intramedullary rod is then placed, and interlocking screws can be placed either medial to lateral or lateral to medial distally. Anterior to posterior interlocking screws can be placed proximally. The variable angle locking plate can then be placed in a submuscular fashion and adjusted so that a variable angle screw can pass through a distal interlocking hole in the rod, and proximally, screws can be placed either through an interlocking hole in the rod or immediately above the rod to prevent proximal migration. An antegrade rod can be placed if the fracture pattern requires it with a locking screw directed through the lateral plate in the distal metaphyseal segment. Proximal screw placement is then accomplished bicortically around the anatomic axis or unicortically abutting the rod. The rod first technique makes it easier to create composite fixation, as it is easier to fine tune plate placement distally.
Figures. 1–4 show preoperative, intraoperative, postoperative, and final x-rays of a nonunion reconstruction of a morbidly obese female, respectively. In this case, the plate first technique was selected.
Adequate follow-up (6 months or until bony union) and complete medical records were located in 8/9 acute fractures and 8/10 nonunions. Union was determined clinically by pain-free ambulation and radiographic healing on ¾ cortices.
Acute Fracture Group
In the acute fracture group, there were 2 male and 6 female patients. There were a total of 13 noncontiguous fractures in these 8 patients. The average patient age was 50 years (range 33–79 years). The average body mass index (BMI) was 44.3 (28.1–60.7).
The average follow-up was 21.6 months (range 3.9–72.8 months). All patients eventually achieved union of all fractures. The average anatomic lateral distal femoral angle (aLDFA) on immediate postoperative imaging was 81.13 degrees. The average aLDFA at final follow-up was 80.63 degrees. Time to union in those who achieved primary union was 108 days (range 72–152 days). Two patients underwent reoperation: 1 patient with a segmental open femoral shaft fracture and associated comminuted open supracondylar femur fracture suffered a nonunion of the femoral shaft; the other patient underwent planned removal of an antibiotic spacer and staged bone grafting and went on to unite uneventfully.
In the nonunion group, there were 5 male and 3 female patients. The average patient age was 54 years (range 46–65 years). The average BMI was 37.9 (range 21–58). Bone graft was used in 7/8 patients (88.9%; Reamer Irrigator Aspirator in 4 patients and iliac crest in 3 patients).
The average follow-up was 16.7 months (range 5.2–29 months). All patients (8/8) achieved union. The average time to union was 145 days (range 71–192 days). The average aLDFA on immediate postoperative imaging was 81.0 degrees. The average aLDFA at final follow-up was 80.5 degrees. No patients underwent reoperation for any reason, and there were no superficial or deep infections.
Endosteal substitution was first described in detail in the book Planning and Reduction Technique in Fracture Surgery by Mast et al. Endosteal substitution has since been described in the proximal humerus, proximal femur, midshaft femur, distal femur, and ankle,12–18 with clinical success in difficult fractures and nonunions. The success achieved by the technique of endosteal substitution has led to the continued expansion of its use since the time of its first description. Cortical substitutes other than plates have been used to create composite fixation. Each has theoretical advantages and disadvantages.
Our study examined the use of an intramedullary rod as an endosteal substitute for a deficient medial cortex in conjunction with a lateral locked plate in the distal femur. We found that this technique resulted in high rates of union and low rates of complications in the treatment of both acute fractures and nonunions of the distal femur. In this series, we found a union rate of 92.3% in fractures and 100% in nonunions of the distal femur in using an intramedullary rod and a lateral locked plate. The only nonunion in the acute fracture group was a type 3 open diaphyseal femur fracture in a morbidly obese man, proximal to a noncontiguous comminuted supracondylar fracture. The supracondylar fracture healed uneventfully, and the diaphyseal fracture healed after reamed exchange rod. There was excellent maintenance of alignment in both groups with the use of a lateral plate and intramedullary rod in this series, with average changes in the aLDFA of ≤0.5 degrees. The additional stability generated by the reconstitution of the medial cortex by the intramedullary rod provides significant resistance to displacement in all planes. Varus displacement and failure, which can be seen at times in the situation of a highly comminuted metadiaphysis or fractures with bone loss,19 was not observed in this series. These results compare favorably with other published reports on the outcomes of both distal femoral fractures and distal femoral nonunion reconstructions.7,11,20–22
Advantages of the intramedullary rod as a cortical substitute compared with an endosteal plate or allograft are numerous. Placement is technically easier and does not require extreme fracture/nonunion site displacement (and therefore potential soft tissue stripping) or require a bony defect at that site for insertion. This makes it a logical biologic choice in an effort to minimize the surgical soft tissue insult. Either an antegrade or retrograde technique is acceptable for the entry site, and both are familiar to most orthopedic surgeons. The moment of inertia of the intramedullary rod is ideal for loading in all planes and the highest for buckling resistance, making it a logical mechanical choice. Removal is also a standardized technique, creating less concern for potential complications and the next step in management if required.
Weaknesses of this study include its retrospective nature and the small sample size. In addition, the indications for the use of this technique in acute fracture treatment or recalcitrant nonunions are unclear. Although these fractures and nonunions healed without changes in alignment, it is possible that other techniques could have been used successfully as well. Our indications for the technique in acute fracture management include morbid and supermorbid obesity and open fractures with bone loss. These have developed from the challenges of treating these patient populations. The challenges of bone loss are well known and described. The challenges of supraphysiologic loads are not as well described. We have experienced mechanical failures in the morbid and supermorbid obese populations using standard techniques and single implants (rod or plate). These implants are designed with factors of safety based on an average population size. Morbid and supermorbid obese patients are at least triple or quadruple the average population size, creating supraphysiologic loading and a higher risk of implant failure. The average BMI in this acute fracture cohort was 44.3. This composite fixation was shown to endure supraphysiologic loads and prolonged revascularization times.
The use of a plate and a rod is not a new idea and has previously been reported in small numbers for nonunion management.16,23,24 This study has the largest sample size and includes acute fractures, differentiating it from previous publications. The description of the technique and principles of endosteal substitution are equally applicable in the management of fractures and nonunions at the risk of mechanical instability due to patient body habitus and/or bone defects. Using an intramedullary rod as a cortical substitute in composite fixation seems to be a safe, effective, and reproducible technique.
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Keywords:Copyright © 2018 Wolters Kluwer Health, Inc. All rights reserved.
cortical substitution; distal femur fracture; obesity; nonunion