0
    110
    views

    Management of an Acutely Infected Distal Tibial Stress Fracture

    A 56-year-old female patient has undergone 2 procedures to treat a stress fracture of the distal tibia and fibula. Five months after the second procedure, she notices increasing varus deformity of the right distal leg, as well as swelling, pain, and fluid collection. What went wrong, and how can this case be successfully resolved?

    Author

    Brandon J. Yuan, MD

    Background

    A 56-year-old female patient has significant osteopenia and a history of stress fractures as a consequence of undergoing parathyroidectomy. She also has a history of atrial fibrillation, idiopathic bilateral lower extremity neuropathy, obesity, and bilateral medial unicompartmental knee arthroplasty (UKA) (Figure 1).

    Figure 1. Radiographs of the knee show the previous medial unicompartmental knee arthroplasty with use of screws and cement to augment tibial fixation.

    RELATED: Find past X-Ray Forensics articles here.

    She began having pain in the right distal leg, and radiographs demonstrated a stress fracture of the distal tibia and fibula (Figure 2). The patient was seen at another institution, where she was placed into a removable walking boot and made non-weight-bearing for 5 months.

    Figure 2. Radiographs show a stress fracture of the distal tibia and fibula.

    Initial Treatment

    Despite protected weight-bearing, the patient developed progressive varus deformity of the distal tibia and underwent open reduction and internal fixation 5 months after diagnosis.

    The initial fixation construct was a stout medially based plate-locking plate, presumably to buttress the distal segment from deforming back into varus. When utilizing a medially based plate as a buttress in the distal tibia, the surgeon must ensure that the plate is compressed to the bone at and just proximal to the fracture. Otherwise, the distal fragment is at risk for failing into varus.

    The non-locking screw that was utilized can reduce the plate down to the bone, but it does not appear that the plate was completely compressed to the bone, compromising the stability of the construct (Figure 3).

    Figure 3. Radiographs show that the plate was not completely compressed to the bone.

    Three months after fixation, the patient noted persistent drainage from the wound on the medial aspect of the ankle. She was diagnosed with a deep infection and the treating surgeon elected to perform a debridement with removal of all implants. As evidenced on the radiographs, some increasing varus deformity had developed at this point (Figure 4). Note the space between the plate and the bone proximal to the fracture, indicating that the plate was not effectively buttressing the medial segment from failing into varus.

    Figure 4. Radiographs demonstrate increasing varus deformity 3 months after the initial surgery.

    Intraoperative cultures were positive for methicillin-resistant Staphylococcus aureus (MRSA) and the patient was treated with 6 weeks of intravenous (IV) vancomycin after implant removal. She was placed in a cast and instructed to remain non-weight-bearing until the fracture had healed. The patient was compliant with her restrictions for several months.

    Treatment Considerations for Revision

    Five months later, the patient began to notice increasing varus deformity of the right distal leg, as well as swelling, pain, and fluid collection (Figure 5). At this point, she presented to my clinic. Radiographs revealed progressive deformity primarily through a new fracture just above the previous one, inducing varus and procurvatum deformities (Figure 6).

    Figure 5. Radiographs demonstrate increasing varus deformity 5 months after implant removal.

    Figure 6. Radiographs demonstrate a second distal tibial fracture that is causing progressive deformity.

    To arrive at a treatment plan for a revision procedure, I considered each of her issues – infection, deformity, and metabolic bone disease – separately.

    Infection

    Infection must be adequately treated if an attempt at limb salvage is to be performed. This treatment should include:

    • Thorough operative debridement of all infected and necrotic soft tissue and bone
    • Bone and/or soft tissue biopsy to aid in microbiologic diagnosis and to guide antimicrobial treatment
    • Use of local and IV antibiotics as needed
    • Appropriate soft tissue coverage as needed
    • Temporary stabilization of any unstable osseous injury to help stabilize the soft tissues and assist in wound healing and eradication of the infection

    It was unclear if the patient’s prior infection had been eradicated at this point or if persistent infection was partially the cause of her current symptoms and fluid collection.

    Deformity

    Clearly, the deformity needed to be corrected to provide a stable limb for weight-bearing and to minimize the risk of future fractures. Deformity may be corrected by open or closed means and augmented with internal and/or external fixation.

    • If internal fixation is utilized, the proposed surgical field must first be cleared of infection.
    • External fixation can be applied immediately, but in this patient, it carried with it the risk of pin site infection, pin site loosening, and re-fracture due to obesity and poor bone quality.

    Metabolic Bone Disease

    The patient’s history of parathyroidectomy significantly altered her calcium homeostasis and led to significant osteoporosis. Correction of her calcium and phosphorus levels and appropriate treatment of osteoporosis was necessary for optimal healing of this fracture and to prevent future fractures. Given her history of multiple stress fractures, she was also a candidate for anabolic agents, such as a parathyroid hormone (PTH) receptor agonist, to assist with increasing bone density.

    The patient had presented with elevated inflammatory markers and a well-healed incision over the medial distal tibia, but with a palpable fluid collection. Due to her history of MRSA infection, we agreed on a staged approach to treatment, with operative debridement as the first stage and delayed fixation.

    Operative Debridement

    The distal tibia was debrided through the same direct medial incision that was utilized for the previous attempted fixation. Excisional debridement of all infected soft tissue was performed and intraoperative cultures showed no growth.

    For the bony debridement, all necrotic and avascular bone was debrided. No significant necrotic cortical bone was encountered. All remaining bone demonstrated a rich vascular supply intraoperatively and was thus left in place. The fracture was not freely mobile at the time of debridement and no intramedullary debridement was performed. A local antibiotic (vancomycin powder) was left in the wound.

    Partly due to the patient’s large soft tissue envelope, significant healthy soft tissue was available to close the wound primarily without need for soft tissue reconstruction. An external fixator was not placed across the ankle because of the perceived relative stability of the fracture, the large soft tissue envelope, and the patient’s poor bone quality.

    The patient was treated with a 3-week course of IV vancomycin prior to the planned fixation. Had the intraoperative cultures been positive for MRSA, the duration of treatment likely would have been extended.

    In addition, the patient was seen by an endocrinologist and her calcium and phosphorous levels were corrected. She was started on a PTH agonist to manage significant metabolic bone disease and osteopenia.

    Six weeks after debridement, repeat radiographs demonstrated progressive varus and procurvatum deformity through the more proximal fracture (Figure 7). Definitive fixation was planned at this point.

    Figure 7. Radiographs demonstrate progressive varus and procurvatum deformity through the more proximal fracture.

    Operative Plan

    A relatively rigid medially based plate is generally very useful for correcting coronal plane deformity. However, this type of implant had already failed once. Options for augmenting fixation include plates, external fixation, and medullary fixation.

    Adding Multiple Plates

    A posteriorly based plate would have the advantage of being protected by the large posterior soft tissue envelope and would be ideally positioned to resist the sagittal plane deformity. Fixation of the fibula, which is failing in tension, would offer less mechanical advantage than a medial or posterior plate on the tibia.

    External Fixation

    Advantages of external fixation include:

    • Minimizing the need for indwelling implants given the history of infection
    • Maximizing control of deformity correction and compression of the fracture

    External fixation could also be used in combination with a medially based plate to protect the internal fixation. However, the distal segment is relatively small and this patient has already demonstrated exceptionally poor bone quality, making distal segment fixation problematic (but not impossible) if an external fixator were used in isolation. In addition, the patient’s large size and soft tissue envelope increase the risk of pin site complications.

    Medullary Fixation

    The patient’s unicompartmental knee arthroplasty does not preclude the placement of a tibial nail. However, this would likely be inadequate fixation in isolation. Plate fixation could be utilized in addition to medullary fixation to maximize fixation in the short distal segment.

    I elected to use this third option to avoid external fixation and the possible complications associated with use of a fixator in a patient with a very large leg and poor bone quality.

    Definitive Fixation Procedure

    The deformity was first corrected, using a medially based, precontoured plate to resist the tendency of the fracture to fail into varus (Figure 8). The fracture was compressed with a clamp and the plate was brought down to the bone on the proximal fragment with a second clamp. Because of the patient’s poor bone quality, I elected to use large clamps with a relatively large surface area of contact with bone to prevent comminuting the fracture. The use of a non-locking screw to reduce the plate down to the bone above the fracture would have relied on the purchase of the screw into the cortical bone in this area. A clamp can accomplish the same goal in patients with compromised bone quality. Note that the fracture is intentionally reduced in slight valgus by over-contouring the plate (Figure 9).

    Figure 8. Radiographs show the medially based, precontoured plated used to correct the deformity.

     

    Figure 9. Radiographs show the use of 2 large clamps to compress the fracture and bring the plate down to the bone on the proximal fragment.

    Next, the starting point for the tibial nail was identified around the patient’s medial UKA. Note the iatrogenic proximal fibula fracture due to correction of the distal tibial deformity (Figure 10). The guidewire for the nail was passed into the center of the plafond distally. Three non-locking screws in the medial plate distally were strategically placed anteriorly to act as blocking screws and to prevent the sagittal plane deformity (Figure 11). The nail was passed down across the fracture and 2 interlocking bolts were placed through the nail distally, outside the plate.

    Figure 10. Radiographs show the iatrogenic proximal fibula fracture due to correction of the distal tibial deformity.

    Figure 11. Radiographs show 3 non-locking screws in the medial plate distally.

    The unicortical screws in the plate above the fracture were removed and the fracture was compressed by back-slapping the nail. Non-locking screws were again placed around the nail proximally (Figure 12). The distal screws in the medially plate were individually exchanged for locking screws to compensate for the patient’s compromised bone quality. Lastly, a 5.0 interlocking screw was placed laterally to the nail in the distal segment to act as blocking screw and further resist varus deformity of the distal segment (Figure 13).

    Figure 12. Radiographs show that non-locking screws were placed around the tibial nail proximally.

    Figure 13. Radiographs show that a 5.0 interlocking screw (red arrow) was placed laterally to the nail in the distal segment.

    Final radiographs demonstrated restoration of alignment of the tibia (Figure 14). The fracture was also augmented with a proximal tibial autograft obtained through an opening created at the time of tibial nailing. Nine months after revision surgery, alignment was maintained and the fracture was nearly completely united (Figure 15).

    Figure 14. Radiographs show that alignment of the tibia has been restored.

    Figure 15. Radiographs show that the fracture is nearly completely united 9 months after revision surgery.

    Key Points

    • Treatment of the infected fracture must be systematic, whether it is a relatively acute case, such as this one, or a case of chronic osteomyelitis. Initial operative treatment must involve debridement of all infected and necrotic soft tissue and bone, appropriate sampling of bone and soft tissue for microbiologic diagnosis, use of local and IV antibiotics, osseous stabilization, and appropriate soft tissue coverage. In retrospect, this patient may have benefited from stabilization with an external fixator at the time of the initial debridement to prevent the increasing deformity that developed.
    • Simple fracture patterns (particularly those treated with direct reduction and plate fixation) do well with interfragmentary compression and rigid stabilization.
    • Although periarticular locked plates can be very useful in treating certain articular fractures, the surgeon must have adequate understanding of how the plate is applied and how it affects the stability of the overall construct. Initial fixation in this patient could have been improved by more effectively reducing the plate down to the bone on the medial aspect of the tibia, allowing the plate to more effectively buttress the distal segment.
    • When considering the approach for non-union surgery, the reason for the lack of healing must first be ascertained. Infection, metabolic bone disease, and inadequate stabilization may have all contributed in this case. A staged approach was utilized but surgery could have been performed in a single stage with an external fixator, or even in a single stage with internal fixation, given that the intraoperative cultures ultimately showed no growth. Either way, the revision approach must address the infection, the metabolic bone disease, and the mechanical and biologic shortfalls of the prior construct to avoid the same complications. It is likely that the correction of the patient’s calcium and phosphorus homeostasis and augmentation with a PTH agonist played a large a role in the success of the revision surgery.

    Author Information

    Brandon J. Yuan, MD, is an Assistant Professor in the Division of Orthopedic Trauma, Mayo Clinic, Rochester, Minnesota.

    Disclosure

    The author has no disclosures relevant to this article.