Background
Distal femur fractures are the second most frequent fracture type of femur fractures with an annual incidence rate of 8.7 per 100,000 [
8,
16]. Among these fractures, the management of intra-articular AO/OTA type 33-C3 femoral fractures of the distal femur are considered to be notably challenging [
4]. This management becomes more challenging in cases with open fractures along with a large bone defect [
12]. Bone defects of the limbs are defined as a bone loss without any new bone formations or areas where regenerated new bone accounts for less than 10% of the bone defect at the extremities. They are typically caused by trauma, chronic osteomyelitis, or malignant tumor resection [
36]. Large bone defects persist as a difficult problem, especially in defects larger than 5 cm where much is still unknown regarding their outcomes, necessitating complex treatment, extensive multidisciplinary resources and expert input [
11,
26].
Surgical procedures ranging from reconstruction and salvage to amputation have all been mentioned in the literature to manage large bone defects. These methods, as well as allografts, direct cancellous autologous bone grafting, and vascularized fibular bone graft, have all been used in previous studies [
17,
23]. The “induced membrane” method for bone reconstruction is a recent development that has piqued the interest of clinicians and basic scientists after 2000 when it was introduced by Masquelet et al. [
22].
There are two stages to the Masquelet method; installation of a cement spacer, massive bone graft, initial debridement, soft-tissue restoration by flaps if necessary, and insertion of polymethylmethacrylate (PMMA) cement spacer are all included in the first stage. At least six to eight weeks after the first stage, the second stage is performed. When the spacer is removed, the membrane is filled with autografts of cancellous tissue [
22]. Fragment stabilization during this induced membrane procedure is needed and Masquelet et al. recommended nailing in large bone defects [
21]; however, nailing is not considered a proper method for C3 distal femoral fractures with articular comminution. Previous studies has reported instability and poor outcomes of these cases following the intramedullary nailing fixation and have recommended plate and screw fixation instead [
10,
14]. On the other hand, biofilm formation is a notable disadvantage of fixations with plate [
15]; This can result in delayed healing, leading to permanent functional loss, or in severe cases, necessitate amputation of the affected limb [
28]. We modified the Masquelet technique by using polypropylene mesh augmentation instead of intramedullary nailing to stabilize the cement beads during the first stage of Masquelet procedure.
In this paper, we present the clinical and radiological outcomes, as well as some interesting findings, of open distal femoral fractures treated early with anatomical plates and the modified Masquelet technique with polypropylene mesh augmentation.
Discussion
There is currently no consensus on the best management strategy for open distal femoral fractures because of their complexity [
27]. The management becomes more difficult in patients with significant bone loss [
12]. Although induced membrane procedures are seen to be a proper method for managing large bone defects, they require a stabilizer which has classically been recommended as an intramedullary nail in large bone defects [
21]; however, using intramedullary retrograde nailing is not recommended for intra-articular AO/OTA type 33-C3 femoral fractures of the distal femur in several studies [
8,
14]. Some reports show that nailing for type C3 is associated with the worse range of motion outcomes among all distal femoral fracture patterns [
1]. Management of type C3 with a new locking intramedullary nail is reported as a reliable fixation method [
42]; however, it is not a standard of care and the nail is not accessible easily worldwide. An external fixator may also be used for stabilization, but it leads to delayed weight bearing and may lead to knee stiffness and further complications in distal femoral fracture management [
5,
20]. However, plating is reported to have favorable outcomes in this regard [
13,
14,
37]. Based on the daily living demands, a different range of motion in the knee joint is required [
39]; this outcome becomes more important while the patient is involved with high activity levels like sports [
3]. For these reasons, we avoided using intra-medullary nailing fixation for any of our cases.
This study found that early fixation of open distal femoral fractures using an anatomical LCP in combination with a modified Masquelet technique along with using propylene surgical mesh resulted in successful clinical and radiographic outcomes. A recent systematic evaluation of 17 studies revealed a significant probability of complication (49.6%) in Masquelet procedures, with a more than 10% non-union rate in cases with bone defect lengths ranging from 0.6 to 26 cm [
30]. However, no complications such as nonunion or infection occurred in any of our cases. When compared to previous studies using the plate for fixation, our findings revealed a considerably earlier union time (159 days) [
7,
9,
32]. This notable discovery may be related to the hard callus formation found by accident in this study using the modified Masquelet approach. It could also be a call to modify the Masquelet technique in the repair of additional fracture sites to obtain a quicker union and better clinical and radiological outcomes.
The PMMA spacer is inserted to act as a foreign body to induce membrane formation. However, it is not without flaws. The exothermic reaction that occurs during this method’s polymerization damages the bone ends and increases the risk of adjuvant toxicity. In some cases, surgical removal is required, which is difficult to handle because it may cause membrane damage [
6,
19]. The arteries and nerves surrounding the bone defect area will not be subjected to heat stress if a substitute material is used that does not cause an exothermic response [
35]. Recent studies have attempted to improve the osteogenic properties of the induced membrane by introducing alternative materials [
19,
40]. In our case series, we filled the bone defect with shell-shaped antibiotic-impregnated PMMA beads after letting the cement get cold outside the patient’s body [
30]. Morelli et al. in their systematic review found that the most common main complications of the Masquelet technique are superficial (4.9%) and deep surgical site infections (4.4%). It is well known that antibiotic beads are used in open fracture reconstructions of the lower extremities [
29,
31]. Also, previous studies showed that antibiotics in spacers can help make membranes thicker by increasing osteogenic gene expression and decreasing bacterial inoculation [
38], and this is the strength of our technique that we could use the antibiotic beads in our cases, and we believe the use of antibiotic beads in our cases along with meticulous debridement of the open fractures may have contributed to the absence of post-operative infections. We also attempted to widen the cross-section of our beads in order to get a better antibiotic release by molding them into shell-shaped beads. This could potentially be one of the reasons for the absence of infection.
The results of PMMA substitute spacer materials such as titanium have been evaluated in some earlier studies, mostly animal studies; however, low union rates with these rough surfaced spacers have been reported [
18]. PMMA substitutes that are less expensive and more easily available can be a good choice for this procedure even in low-income and developing countries; Mathieu et al. published an animal study on rats that used a polypropylene spacer from disposable syringes as a material that met these criteria [
25]. In that animal study, it was shown that polypropylene leads to similar tissue reactions as PMMA, with comparable bone healing characteristics probably in terms of growth factors, histology, and stem cell content [
25]. To the best of our knowledge, there is only one published clinical study that used polypropylene in Masquelet, which reports two cases of metacarpal bone reconstruction following a gunshot wound using polypropylene syringe body instead of PMMA cement [
33]. Polypropylene syringes used in a few previous studies had notable drawbacks. They may not provide the desired stability, and cannot be loaded with antibiotics to prevent infections [
24,
25].
In this investigation, we used surgical mesh wrapped around the cement beads to act as a stabilizer as well as a barrier against surrounding tissue irritation. Additionally, we allowed the cement to cool outside the patient’s body, which prevented tissue irritation. Not only did polypropylene mesh function satisfactorily in membrane induction, but it also has substantial other benefits that make it a potential substitute for PMMA, which is traditionally used in the Masquelet technique.
To the best of our knowledge, this is the first clinical study to evaluate the results of the Masquelet technique using polypropylene mesh and PMMA together. This case series, however, is not without limitations. There is no control group observed, and the sample size is small the results presented here may not be generalizable to a larger population. Further research with larger sample size and a control group may shed a light on various aspects of this bone reconstruction method, particularly on the callus formation noted in our study.
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