Treatment of chronic nonunion of a sternal fracture with bone morphogenetic protein

Surgical management of traumatic sternal body nonunions: Technical tricks and clinical experience

BACKGROUND

Rarely, traumatic sternum fractures may result in nonunion, which can have drastic, negative implications. Literature on traumatic sternal nonunion reconstruction outcomes is limited to case reports. We present the surgical principles and report clinical outcomes for seven patients following surgical reconstruction of a traumatic sternal body nonunion.

METHODS

Consecutive adult patients with a nonunion after a traumatic sternum fracture who underwent reconstruction using locking plate technology and iliac crest bone graft at a Level I trauma center from 2013 to 2021 were identified. Demographic, injury, and surgery data was collected, and postoperative patient-reported outcome (PRO) scores were obtained. Patient-reported outcome scores included the one-question single assessment numeric evaluation (SANE), and the combined 10-question global physical health and global mental health values. Injuries were classified and all fractures were mapped onto a sternum template. Postoperative radiographs were reviewed for union.

RESULTS

Of the study's seven patients, five were female, and the mean age was 58 years. Mechanism of injury included motor vehicle collision (5) and blunt object chest trauma (2). The mean time from initial fracture to nonunion fixation was 9 months. Four of the seven patients achieved in-clinic follow-up at ≥12 months (mean = 14.3 months), while the other three achieved ≥6 months of in-clinic follow-up. Six patients completed outcomes surveys ≥12 months after surgery (mean = 28.9 months). Mean PRO scores at final follow-up included: SANE of 75 (out of 100), and global physical health and global mental health of 44 and 47, respectively (US population mean = 50).Six of seven patients achieved known radiographic union.

CONCLUSION

We describe an effective and practical method of achieving stable fixation in traumatic sternal body nonunions as evidenced by the positive clinical outcomes of a seven-patient series. Despite the variation in presentation and fracture morphology of this rare injury, the surgical technique and principles outlined can serve as a useful tool for chest wall surgeons.

LEVEL OF EVIDENCE

Therapeutic/Care Management; Level IV.

Traumatic sternal fractures: a narrative review

OBJECTIVE

Traumatic sternal fractures are injuries most commonly resulting from a direct blow to the anterior chest wall or forced deceleration. The purpose of this review is to define the clinical significance of these injuries, outline their initial evaluation and work up, and review current treatment strategies available and their outcomes.

BACKGROUND

The diagnosis of traumatic sternal fractures has seen a recent rise, largely due to the increased access to computed tomography (CT) scan. Currently, there are no published guidelines to make recommendations on operative fixation for sternal fractures. This is probably related to the lack of evidence in published literature along with patient heterogeneity.

METHODS

We conducted a non-systematic review of the English literature published from January 2000 to December 2020, including meta-analyses, systematic reviews, case series and case reports regarding the diagnosis, treatment, and complications of traumatic sternal fractures. We critically analyzed the available evidence to provide an overview of the treatment and clinical outcomes of traumatic sternal fractures.

CONCLUSION

Isolated sternal fractures are commonly benign injuries that can be managed conservatively in an outpatient setting. Polytrauma patients with sternal fractures should be carefully screened for possible associated injuries. Surgical stabilization of sternal fractures is feasible and safe, and should be considered in unstable fractures, severe displacement, symptomatic malunion or non-union.

Role of Prx1-expressing skeletal cells and Prx1-expression in fracture repair

The healing capacity of bones after fracture implies the existence of adult regenerative cells. However, information on identification and functional role of fracture-induced progenitors is still lacking. Paired-related homeobox 1 (Prx1) is expressed during skeletogenesis. We hypothesize that fracture recapitulates Prx1's expression, and Prx1 expressing cells are critical to induce repair. To address our hypothesis, we used a combination of in vivo and in vitro approaches, short and long-term cell tracking analyses of progenies and actively expressing cells, cell ablation studies, and rodent animal models for normal and defective fracture healing. We found that fracture elicits a periosteal and endosteal response of perivascular Prx1+ cells that participate in fracture healing and showed that Prx1-expressing cells have a functional role in the repair process. While Prx1-derived cells contribute to the callus, Prx1's expression decreases concurrently with differentiation into cartilaginous and bone cells, similarly to when Prx1+ cells are cultured in differentiating conditions. We determined that bone morphogenic protein 2 (BMP2), through C-X-C motif-ligand-12 (CXCL12) signaling, modulates the downregulation of Prx1. We demonstrated that fracture elicits an early increase in BMP2 expression, followed by a decrease in CXCL12 that in turn down-regulates Prx1, allowing cells to commit to osteochondrogenesis. In vivo and in vitro treatment with CXCR4 antagonist AMD3100 restored Prx1 expression by modulating the BMP2-CXCL12 axis. Our studies represent a shift in the current research that has primarily focused on the identification of markers for postnatal skeletal progenitors, and instead we characterized the function of a specific population (Prx1+ cells) and their expression marker (Prx1) as a crossroad in fracture repair. The identification of fracture-induced perivascular Prx1+ cells and regulation of Prx1's expression by BMP2 and in turn by CXCL12 in the orchestration of fracture repair, highlights a pathway in which to investigate defective mechanisms and therapeutic targets for fracture non-union.

Late complications of chest wall reconstruction: management of painful sternal nonunion

Although rare, sternal nonunion after median sternotomy or traumatic injury is associated with a high rate of morbidity. Pain and sternal clicking are two of the most common complaints and reasons these patients seek evaluation and treatment. Diagnosis of sternal nonunion is based on a thorough history and physical examination and can be confirmed with subsequent radiographic imaging. The treatment for symptomatic sternal nonunion requires stable fixation of the bony fragments and chest wall after the debridement of all nonviable bony and soft tissue by the cardiothoracic or reconstructive surgery team. Multiple fixation techniques have been described and incorporate a wide variety of materials including combinations of wires, cables, pins, bands, staples, and plates. Most recently, several new commercially available plating systems have demonstrated low recurrence and complication rates and resolution of the patient's symptoms on follow-up evaluation. Included in this review are three cases demonstrating the management of symptomatic sternal nonunion using these new techniques and review the history, diagnosis, risk factor, and classification, as well as several of the previously described fixation methods.

Treatment of posttraumatic sternal non-union with a locked sternum-osteosynthesis plate (TiFix)

Only a minority of sternal fractures require osteosynthesis. Unstable non-union of the sternum is a very disabling condition which often requires treatment. The method most often used is tension-wiring. Due to loosening of the tensile strength or wire cut-out, this method often fails. We report the results of locked plate osteosynthesis of sternal non-union and displaced fractures. Over a five-year period, 12 patients have been treated using this method in a multicentre trial. Mean age at trauma was 32.8 years, the implant used in all cases was an 8-hole titanium plate, the fixation of the screws is based on the principles of angular stable fixation.In all cases the index procedure was possible, in all cases there was bony healing at follow-up examination.Multidirectional locked plating offers a reliable method for the successful treatment of sternal nonunion and displaced fractures.