Ann Thorac Surg 2011;91:597-599. doi:10.1016/j.athoracsur.2010.07.083
© 2011 The Society of Thoracic Surgeons
Case Reports
Use of SternaLock Plating System in Acute Treatment of Unstable Traumatic Sternal Fractures
Stephanie S. Chou, BAa,
Matthew J. Sena, MDb,
Michael S. Wong, MDa,*
a Division of Plastic Surgery, University of California Davis Medical Center, Sacramento, California
b Division of Trauma & Emergency Surgery, Department of Surgery, University of California Davis Medical Center, Sacramento, California
Accepted for publication July 26, 2010.
* Address correspondence to Dr Wong, Department of Surgery, Division of Plastic Surgery, University of California Davis Medical Center, 2221 Stockton Blvd, Ste 2123, Sacramento, CA 95817 (Email: michael.wong{at}ucdmc.ucdavis.edu).
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Abstract
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Optimal surgical treatment of unstable sternal fractures is controversial. Wiring provides suboptimal fixation and adaptations of existing non-sternum specific plating systems may be dangerous when rapid sternal reentry is required. We present our experience with the sternal specific fixation system, SternaLock (Biomet Microfixation Inc, Jacksonville, FL), in the acute treatment of transverse sternal body fractures in 2 patients who sustained significant blunt anterior chest wall trauma. SternaLock provides the rigid sternal fixation necessary for reliable fracture healing while offering advantages over other systems with regards to ease of use and safety.
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Introduction
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Traumatic sternal fractures, characterized by severe pain, respiratory compromise, and deformity of the anterior chest wall [1], occur in 3% to 8% of blunt trauma victims [2]. Although most stable fractures heal without sequelae [2], unstable fractures may result in flail chest, intractable pain [1], and sternal nonunion [3]. Sternal wiring has been the traditional surgical approach [4], yet this type of fixation is nonrigid and imperfect.
Currently, no consensus exists for the optimal method of operative fixation of unstable sternal fractures. Mandibular [5] and cervical spinal plates [1] have been adapted for sternal fracture repair; however, design limitations prevent rapid removal when urgent sternal reopening is required. In 2005 Wu and colleagues [3] reported the use of the sternum-specific plating system SternaLock (Biomet Microfixation Inc, Jacksonville, FL) in treating sternal nonunion. This system uses locking titanium plates and screws and provides more rigid fixation than traditional wiring. Its advantages over mandibular and cervical spinal plating systems include a drill-free, self-drilling, self-tapping screw system. It also features an incorporated "cuttable" section, allowing emergent sternal reentry for hemorrhage or tamponade. We report the successful use of SternaLock in the acute treatment of 2 patients with unstable sternal fractures and describe follow-up at 4 months.
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Case Reports
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Patient 1
A 59-year-old man, assaulted to his chest and abdomen, complained of severe sharp pain in his anterior and left lower chest wall, which increased with deep inspiration and palpation. Computed tomography (CT) of the chest demonstrated a nondisplaced, transverse fracture of the upper third of the sternum and numerous rib fractures. Surgical stabilization was performed 9 days after the trauma after sternal instability was confirmed during reexamination.
Patient 2
A 55-year-old woman, who fell from her horse and was subsequently trampled, sustained a severe sternal crush injury. At presentation, she complained of chest pain and exhibited labored deep breathing with palpable sternal instability consistent with a sternal fracture. CT of the chest revealed a displaced midbody sternal fracture (Fig 1). Given the severity of symptoms and instability, she was scheduled for open sternal fixation 6 days after the trauma.
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Fig 1. The preoperative midsagittal view computed tomography scan of patient 2, a 55-year-old woman, demonstrates a displaced midsternal fracture.
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The physical examination and imaging confirmed the presence of a displaced or unstable fracture in both patients, and the need for fixation was determined by the severity of the respiratory and physical limitation. Mobile segments exhibiting some deformity and association with symptoms characterize unstable fractures. Open reduction and internal fixation of the sternum was performed using the SternaLock system (Biomet Microfixation Inc).
After a midline incision over the sternum, the fracture site was carefully debrided of any fibrous union, old hematoma, and anterior mediastinal fat to expose healthy bone. Sternal edges were curetted to facilitate better reduction and healing. Bone reduction forceps placed within the surrounding intercostal spaces assisted in the manual reduction of the sternal fracture. Temporary screw placement, to act as posts for wire tightening, facilitated bony reduction (Fig 2). The 8-holed X-plates were oriented vertically (Fig 3), manually contoured to the underlying sternum, and secured using self-drilling, self-tapping screws. Screw length was chosen by adding 2 mm to the thickness of the sternum (as measured on chest CT) at each point of screw placement, accounting for plate thickness. This allowed for bicortical screw purchase for maximum stability while avoiding sternal penetration. The wound was irrigated and the incision was closed in 2 layers.
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Fig 2. Before plate fixation, manual reduction of the sternal fracture in patient 1 was assisted by the use of bone reduction forceps placed within the surrounding intercostal spaces. Two temporary screws were placed to assist with fracture reduction, providing stable posts for wire tightening.
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Fig 3. After fracture reduction was achieved in patient 1, the sternum was rigidly fixed with an 8-holed SternaLock X-plate (Biomet Microfixation Inc, Jacksonville, FL).
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Results
No immediate complications occurred, and a chest CT after the procedure confirmed adequate fracture reduction in both patients (Fig 4). Patient 1 was discharged on postoperative day 1 and patient 2 on postoperative day 4 with oral analgesia for pain control. The 4-month follow-up demonstrated normal wound healing in both patients, with neither complaining of symptoms associated with instability. Both repairs were palpably stable and nontender.
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Fig 4. A midsagittal view postoperative computed tomography scan demonstrates reduction and rigid fixation of the fractured sternum for patient 1.
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Patient 1 continued to require narcotics for the multiple rib fractures but denied any significant sternal pain. He had resumed his daily activities at his last follow-up visit. Patient 2 reported being able to lift weights up to 20 pounds without difficulty, indicating good 4-month recovery, although she had not fully returned to lifting 50-pound hay bales.
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Comment
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Sternal fractures are common after severe chest wall trauma. Most of these are stable nondisplaced fractures that will heal without sequelae. In patients where fracture overlap or instability results in significant respiratory compromise or intractable pain, open reduction and stainless steel wiring has been the mainstay of treatment [4]. Although this technique is less expensive than plating and may be rapidly applied, the nonrigid nature of the wires and the potential for wire pull-through can result in secondary sternal fractures or sternal nonunion [4]. More rigid fixation using a plate and screw system minimizes these risks.
The potential advantages of rigid sternal plate fixation include more secure reduction, faster healing, and lower risk of nonunion [4, 6]. Current off-label adaptations of other plating systems, such as those designed for mandibular [5] and cervical spine fixation, have potentially dangerous limitations when applied to the sternum. Plate thickness makes rapid cutting impossible with standard wire cutters and requires removal of at least half of the screws to allow for sternal separation. Although acute cardiac tamponade and other bleeding complications are uncommon, the time required for screw removal may prove fatal in these circumstances.
To address this problem, specific sternal plating systems such as SternaLock incorporate a thinner "cuttable" section that spans the fracture line and can be easily divided using common wire cutters [3]. Synthes has a sternal fixation system that uses safety-release cotter pins to allow for quick reentry but requires extensive dissection onto the ribs for support [7]. Drill bit trauma with bicortical screws is another potential danger in using Synthes-type plating and those specified for other body parts in the treatment of traumatic sternal fractures. Although bicortical screws are preferred over unicortical screws due to their biomechanical advantage in providing better stabilization, drilling beyond the second cortex of the sternum for screw placement increases risks to the heart and great vessels. SternaLock uses self-drilling and self-tapping screws, eliminating the need for drilling and reducing the chance of injury to mediastinal structures [6].
Although not encountered in our 2 patients, osteopenia of the sternum is one situation in which the SternaLock plating system may be less reliable due to weaker screw fixation within the thinner, weaker bone. In such cases, the Sternal Talon (KLS Martin LP, Jacksonville, FL) may have an advantage. This is a 2-piece, titanium, double-footed hook that wraps around both sides of the sternum and pulls the sternum together as the ratcheting mechanism tightens. This may work well for rigid fixation of a midline sternotomy by bringing the 2 halves into approximation. However, this device is not designed for reduction in a craniocaudal direction as was required in these 2 patients.
Despite the SternaLock plating system being designed primarily for stabilization of midline sternotomies, it poses no inherent problems with the stabilization of transverse fractures. The 8-hole X-plate used in our patients allows for 4-screw fixation on each side of the transverse fracture, providing ample bony purchase for stable fixation. It also allows for the treatment of transverse fractures of the hemisternum encountered after wire pull-through seen after traditional wire closure of midline sternotomies.
The SternaLock plating system uses locking plates, providing advantages over compression plates such as reduction in screw backout and loosening. This may help explain the trend away from compression plates to locking systems across the medical device industry. To ensure good compression of the fragments while plating, the system includes a variety of bone reduction forceps.
In these 2 patients, sternal fixation was accomplished in the acute setting. Although the optimal timing of fixation is not known, we believe that earlier fixation optimizes any potential benefit with respect to decreasing the pulmonary morbidity associated with an unstable and painful sternal fracture. In addition, a delay of several weeks may result in a more difficult reduction and a greater operative blood loss as the local inflammatory response to injury progresses.
The performance of open reduction and internal fixation of stable sternal fractures remains controversial. Unlike other bony fractures such as radius or ulnar fractures that can be casted to aid in healing, the sternum cannot because the fractured sternal segments are subjected to movement with each breath. Patients with mobile fractured segments often experience more discomfort. Movement of sternal fractures leads to pain with respiration. These patients are more inclined to splint and avoid deep breaths, thus leading to areas of atelectasis, predisposing to pneumonia [8]. Therefore, to minimize pain and prevent the development of pulmonary complications, we have a low threshold to plate stable sternal fractures. Although there are no definitive studies to date, we and others, such as Ozaki and colleagues [8], believe rigid fixation in sternal closure should result in decreased postoperative pain and infection while accelerating bone healing as motion at the sternotomy site is minimized.
In summary, we present the successful acute treatment of 2 traumatic sternal fractures with open reduction and rigid internal fixation using the SternaLock plating system. We believe this system offers significant advantages over others in ease of use and safety.
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Acknowledgments
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The University of California Davis Department of Surgery receives research support from Biomet Microfixation Inc.
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References
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- Ciriaco P, Casiraghi M, Negri G, et al. Early surgical repair of isolated traumatic sternal fractures using a cervical plate system J Trauma 2009;66:462-464.[Medline]
- Al-Qudah A. Operative treatment of sternal fractures Asian Cardiovasc Thorac Ann 2006;14:399-401.[Abstract/Free Full Text]
- Wu LC, Renucci JD, Song DH. Sternal nonunion: a review of current treatments and a new method of rigid fixation Ann Plastic Surg 2005;54:55-58.[Medline]
- Henderickson SC, Koger KE, Morea CJ, Aponte RL, Smith PK, Levin LS. Sternal plating for the treatment of sternal nonunion Ann Thorac Surg 1996;62:512-518.[Abstract/Free Full Text]
- Richardson J, Franklin G, Heffley S, Seligson D. Operative fixation of chest wall fractures: an underused procedure? Am Surg 2007;73:591-597.[Medline]
- Pai S, Gunja NJ, Dupak EL, et al. In vitro comparison of wire and plate fixation for midline sternotomies Ann Thorac Surg 2005;80:962-968.[Abstract/Free Full Text]
- Huh J, Bakaeen F, Chu D, Wall MJ. Transverse sternal plating in secondary sternal reconstruction J Thorac Cardiovasc Surg 2008;136:1476-1480.[Abstract/Free Full Text]
- Ozaki W, Buchman SR, Iannettoni, MD, Frankenburg BS. Biomechanical study of sternal closure using rigid fixation techniques in human cadavers Ann Thorac Surg 1998;65:1660-1665.[Abstract/Free Full Text]
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Abstract
Introduction
