Transverse sternal nonunion is a rare but disabling complication that occurrs mainly after a traumatic sternal fracture or a rarely-performed transverse sternotomy [
1]. The rate of nonunion is less than 1% after sternal fractures, while the condition becomes more common after a transverse sternotomy, with the rate of 6.8%, and thus represents an important chronic complication [
7,
8]. A transverse thoracosternotomy (known as a Clamshell incision) is typically used in double-lung transplantations as it provides excellent access to the heart, lungs, and the great vessels [
8,
9]. Due to multidirectional movements with tension and compression forces that act in all planes, fixation of the transverse sternotomy, sternal fracture, or transverse nonunion remains a challenge [
1,
2]. There is limited published data on transverse sternal nonunion, especially after a sternotomy, mostly involving case reports or small case series [
1,
10,
11]. Different fixation materials and techniques were described to fix transverse fractures, osteotomies, or nonunions, with tension wiring and plating being the most commonly performed [
2,
7,
10]. Tension wires, which are still typically used to close a median sternotomy, often fail when used for a transverse sternotomy closure, which also was the case in our patient during the early postoperative period. A sternal notching technique should be considered when a transverse sternotomy is performed. The technique was described as the modification of sternal transection from transverse to inverted V-shaped. It allows for a more precise fit of the sternal fragments at closure, provides better stability, and possibly lowers the transverse sternal nonunion rate [
12]. When using cerclage wires, the crossed wiring closure technique reduced the incidence of sternal dehiscence compared to the uncrossed technique [
13]. In their comparative study, Qin-Yun Ma and co-workers showed a significantly higher sternal healing rate in the plated group compared to the tension-wired group after a transverse sternotomy [
14]. Biomechanical advantages of sternal plating were previously shown in a cadaveric study [
15]. Other authors also reported good functional outcomes of sternal plating with a high rate of union, mainly after using one or two parallel locking plates [
2,
6,
8,
9,
11,
16,
17]. In contrast to conventional plating, locking implants with screws locked in the plate (angularly stable fixation) better resist continuous multidirectional forces that act on the construct during breathing. Additionally, monocortical locking screws can be a safer option to prevent an iatrogenic injury to the vital retrosternal structures. But on the other hand, they provide less purchase than bicortical locking screws, especially in a weaker bone [
6,
11]. A review of the published literature done by Schulz et al. [
18] showed good results for the most locking plate systems that were used and a review from Klei et al. from 2018 confirmed that plating was the most common type of fixation after sternal fractures (83%), with a reasonable consolidation and low complication rate [
10,
18]. In our case, the patient had a symptomatic postoperative chest wall defect because of transverse sternal nonunion combined with a rib resection. The nonunion was previously unsuccessfully treated with tension wiring and one-third tubular plate fixed with conventional, non-locking screws. Following available published data, we fixed the nonunion with a locking plate. Due to the anatomical conditions, we did not use one or two regular longitudinal 3.5 mm locking plates. Instead, we decided to use a single, stronger locking plate that is typically used to fix distal tibial fractures, which we shaped to the bone. As our patient was tall and obese, the plate appeared to be well sized. The broad ending of the plate with multiple locking screws applied in different directions provided a strong purchase in a deformed proximal fragment. The sternal defect was also bone grafted with a tricortical iliac crest autograft. Bone grafting was advocated for and performed in some other published cases of transverse sternal nonunion with a bone defect [
1,
2,
19,
20]. Common late complications of the sternal plating are local pain and irritation caused by the prominent material, requiring removal of the plate in 15.4% and 27% of the patients, respectively [
5,
11]. There were no implant-related problems in our case and therefore no need for plate removal.
In conclusion, we presented a rare case of a patient with a symptomatic postoperative chest wall defect resulting from transverse sternal nonunion after a transverse thoracosternotomy (clamshell incision) and concomitant rib resection. We believe that addressing both the transverse sternal nonunion and the chest wall defect after rib resection with a properly sized and shaped locking plate with bone grafting and a dual mesh membrane, respectively, was important for a favourable outcome in our patient.