3rd Time’s the Charm? Managing a Distal Femoral Non-union
After undergoing 2 failed attempts at repairing her closed metadiaphyseal distal femur fracture, a 60-year-old female patient is scheduled for re-revision surgery. What went wrong with the 2 previous procedures?
Brandon J. Yuan, MD
The author has no disclosures relevant to this article.
A 60-year-old, previously active female patient with a history of insulin-dependent diabetes has sustained a closed metadiaphyseal distal femur fracture from a fall down a flight of stairs (Figure 1). She also has a patella fracture, but for the purposes of this discussion, we will ignore the patella injury.
Figure 1. Radiograph showing closed metadiaphyseal distal femur fracture.
The goal of treatment is to gain fixation of the relatively short distal segment and obtain a functional reduction of the limb, restoring length, alignment, and rotation of this comminuted fracture. Due to the degree of comminution, indirect reduction and use of a relatively stable construct would be appropriate.
This fracture can be successfully managed with either a retrograde medullary nail or lateral locked plate. If the distal articular fragment is large enough to accept the nail and 3 or 4 bicortical interlocking screws, my preference is for a retrograde medullary nail.
Another consideration is the fracture pattern: A fracture with simple, non-comminuted fracture lines may necessitate direct reduction and interfragmentary compression, which is often best accomplished with a laterally based implant.
Initial Treatment Decision
The surgeon opted for treatment with a retrograde medullary nail. A cable was also placed, presumably to improve reduction of the large medial segment of comminution.
Use of a medullary implant for this type of comminuted fracture implies relative stability, with expected secondary bone healing with callus. In that case, there is no need for direct reduction of comminuted segments, as long as an excellent functional reduction is obtained. Application of a cable implies increased periosteal stripping of the fracture at this segment, which can lead to impaired fracture healing.
Use of circumferential wires or cables in the distal femur should be done with extreme caution, as the femoral artery and vein lie in close proximity to the posteromedial femur in this location. Note that the distal nail is protruding into the knee joint; ideally the nail would be seated to a slightly more proximal position (Figure 2).
Figure 2. First attempt at repairing the fracture. Radiographs show the distal nail sticking into the knee joint.
Outcome of Initial Treatment
The patient returned to the surgeon 18 months following the procedure with complaints of worsening knee pain and crepitance with knee flexion.
Radiographs (Figure 3) show evidence of:
- Implant failure through the distal interlocking bolts
- Migration of the retrograde medullary implant into the knee
- Non-union at the site of the cerclage cable
Figure 3. Radiographs show failure of the first attempt at fracture repair.
This oligotrophic non-union is likely due to lack of adequate blood flow to the area of the fracture under and near the cable, eventually resulting in late mechanical failure.
What Went Wrong?
- Excessive periosteal stripping and disruption of the local blood supply to the fracture occurred due to unnecessary application of a cerclage cable. Indirect functional reduction was all that was required.
- Incomplete seating of the nail occurred, such that even minimal migration of the nail resulted in significant mechanical knee symptoms.
Prior to a revision procedure for a fracture non-union, the surgeon must rule out underlying infection or endocrine abnormality that may be contributing to delayed bone healing.
If this were my patient, I would preoperatively obtain a C-reactive protein level, erythrocyte sedimentation rate, white blood cell count, and a panel of endocrine labs (vitamin D, thyroid-stimulating hormone, parathyroid hormone, alkaline phosphatase, calcium, and phosphorus). I would also obtain an aspirate of the knee to rule out intra-articular sepsis.
If the laboratory studies and aspirate did not show evidence of infection or endocrine abnormality, I would proceed with the revision surgery.
Goals of the revision procedure should be to:
- Remove the now intra-articular implant and cerclage cable
- Biologically augment the non-union with autograft cancellous bone
- Compress the non-union
These goals can be accomplished with either another retrograde medullary implant, through exchange nailing, or with a laterally based plate.
In this case, however, the surgeon opted for revision to a locked condylar plate (Figure 4). The cerclage cable was removed and local autograft was used for bone grafting.
Figure 4. A locked condylar plate was used for the revision procedure.
The surgeon’s rationale for choosing the laterally based plate was a concern about obtaining adequate fixation in the distal segment with another retrograde nail. The surgeon also noted concerns about shortening the limb through further compression of the non-union.
Two points about this revision surgery. First, I prefer to use autograft bone obtained from a site remote from the non-union site. My preferred site in this case would have been the ipsilateral proximal tibia or iliac crest.
Second, this surgeon utilized a stiff implant and applied it in a way that would maximize stability and minimize motion at the fracture site. The short working length of this construct would not be a problem if the non-union had been compressed and primary bone healing could be expected.
However it would appear that a gap has been left at the non-union site; as such, primary bone healing cannot occur.
In this high-strain environment, the short working length of the implant only serves to concentrate all the forces in the construct to the area between the 2 screws closest to the non-union.
Outcome of the Revision Procedure
Seven months after revision surgery, the patient again presented with knee pain and subjective instability. Failure of the implant was noted to have occurred directly at the non-union site and through the plate at the site of an empty screw hole (Figure 5).
Figure 5. Radiographs show failure of the revision procedure to repair the fracture non-union.
What Went Wrong?
- Failure of the second procedure likely occurred for 1 primary reason: Although a stiff implant with a short working length is appropriate in the case of a compressed non-union, the gap at the non-union site in this case prohibited primary bone healing. As mentioned above, this construct is too stiff to allow any secondary bone healing to occur. This results in concentration of stress forces at the weak area of the plate, between the screws closest to the non-union. Somewhat predictably, the implant failed by fracturing through the plate at the empty screw hole.
- Secondarily, it could be argued that the use of autograft bone from a site distant from the non-union would have been superior to local autograft.
Re-revision Procedure: Solving the Problem
The patient was referred to our institution for management of a persistent distal femoral non-union with a failed implant.
After ruling out potential infection or endocrine abnormality as above, the re-revision procedure was planned. My primary goal for this surgery was to create a mechanically and biologically favorable environment for union.
As highlighted above, the primary reason for failure of the first revision construct was lack of compression at the non-union site. Compression can be accomplished through use of a retrograde medullary nail or another laterally locked plate.
Given that exposure of the non-union was necessary either way, and that the distal femoral segment had already been exposed to multiple screw paths from prior implants, I elected to treat this non-union with a laterally based locked implant utilizing direct compression with a clamp and extrinsic compression with the plate.
In addition, the non-union occurred at an area of the fracture that had originally undergone increased surgical dissection from the placement of a cable. At best, it had shown only modest biologic healing potential since then. To augment healing, I performed a bone graft from the patient’s ipsilateral iliac crest.
The non-union was exposed and the previous plate removed. The fibrous tissue at the non-union site was debrided back to bleeding bone, and samples were sent for culture (all were negative for infection). The non-union was then bone grafted, aligned, and compressed with a clamp and the plate was applied (Figure 6).
Figure 6. In the re-revision procedure, a clamp was used to compress the non-union and then a plate was applied.
The original alignment of the femur was maintained with a Verbrugge clamp distally. Extrinsic compression was applied through use of screw placed outside the plate at the proximal femur, as well as a second Verbrugge clamp. Given that the prior implant had already gone to the level of the subtrochanteric femur, I elected to span of the entire femur up to the level of the vastus ridge to protect the femur (Figure 7). Compression was supplemented with use of a compression screw proximal to the non-union (Figure 8).
Figure 7. Clamps and screws were used for extrinsic compression at the non-union site.
Figure 8. Compression screw proximal to the non-union.
The procedure restored sagittal alignment of the femur (Figure 9).
Figure 9. Sagittal alignment is restored.
Outcome of the Re-revision Surgery
Postoperatively, the patient’s weight-bearing was protected for 6 weeks and appropriate calcium and vitamin D supplementation was provided (Figure 10).
Figure 10. Postoperative radiographs show alignment of the non-union.
At 12 months after the re-revision surgery, the patient had regained full function and no longer had thigh pain (Figure 11). She still had some symptoms of patellofemoral arthrosis while going up and down stairs.
Figure 11. Radiographs 12 months following the re-revision procedure.
Key Takeaway Points
- Comminuted metadiaphyseal distal femur fractures may be successfully managed with a retrograde medullary nail or lateral locked plate. However basic principles should be followed:
- Comminuted fractures should undergo a functional, indirect reduction and should be stabilized with a construct that allows for micromotion through the zone of the fracture.
- Reduction of comminuted segments is unnecessary, and the use of cerclage cables or wires in the distal femur should only be done with extreme caution.
- Simple fracture or non-union patterns require compression and absolute stability if primary bone healing is to be expected.
- Adding biologic supplementation to selected non-unions is an important consideration. Options include use of the iliac crest, proximal tibia, or calcaneus. Bone graft may also be harvested from the medullary canal of long bones with the use of the reamer-irrigator-aspirator.
Brandon J. Yuan, MD, is an Assistant Professor in the Division of Orthopedic Trauma, Mayo Clinic, Rochester, Minnesota.