In this retrospective study, we compared the clinical outcomes of OBS intramedullary fixation with those of plating for treating midshaft clavicle fractures. We revealed that surgical time, intraoperative blood loss and total incision length were significantly greater in the OBS group than in the control group, illustrating that this new technique is convenient and causes minimal trauma. Additionally, there was less pain early after surgery, earlier shoulder joint functional recovery, a shorter fracture healing time and fewer complications in the OBS group than in the LP group, showing that patients benefited more from the less invasive procedure of the OBS intramedullary fixation technique.

In recent years, intramedullary fixation has emerged as a minimally invasive and clinically effective surgical treatment option for midshaft clavicle fractures [12, 14, 20, 21]. However, the double-arch shape and narrow, irregular medullary cavity of the clavicle have hindered the clinical application of intramedullary fixation devices [22, 23]. Furthermore, Harmouchi et al. [24] reported that the Kirschner wires used for fixing intramedullary clavicle fractures were highly prone to displacement; they migrated to critical areas, such as the heart or lungs, causing fatal injuries. To reduce the risks of surgical trauma and postoperative complications, numerous researchers have explored measures to improve this technique [12, 14, 25]. However, the intramedullary fixation devices most commonly used in clinical practice are also prone to problems such as nail loosening, soft-tissue irritation and fixation failure [15]. Moreover, unstable intramedullary fixation greatly limits the treatment of comminuted fractures [12, 14, 15]. Many studies have reported the use of OBS for the extramedullary fixation of clavicle fractures, which potentially facilitates indirect fracture reduction without stripping the periosteum and promotes fracture healing via three-dimensional elastic fixation [26, 27]. However, this approach has some limitations, including increased risks of hematoma, acromioclavicular pain, implant-related pain, and subcutaneous prominence of the nail rod [7]. The novel intramedullary fixation technique described in our study, OBS intramedullary fixation for midshaft clavicle fractures, addresses these problems.

The OBS intramedullary fixation technique has several advantages that make it a promising surgical approach for treating midshaft clavicle fractures. First, this new technique is convenient and causes minimal trauma. The following are advantages. (1) The operation is easy to perform in hospitals due to the small size of the incision and simple operation. (2) The diameter of the connecting rod is only 3 mm, and the rod is flexible and malleable, allowing the rod tail to be easily bent and shaped, while the screws are flexible enough to be inserted from multiple directions. )3) After the fracture has completely healed, a small incision is made at the end of the nail rod for removal. Our study revealed that, compared to plate fixation, OBS intramedullary fixation required smaller surgical incisions and a shorter operation and led to less intraoperative blood loss. At the 1-year follow-up examination, there was no significant difference in the Constant–Murley shoulder score or VAS score between the two groups. Additionally, the OBS group exhibited no scars or numbness at the incision site, indicating improved skin aesthetics and comfort.

Second, the OBS intramedullary fixation technique involves minimally invasive incisions on the lateral and midportion of the clavicle, resulting in minimal surgical trauma. During this procedure, the supraclavicular nerve was avoided. In contrast, steel-plate fixation requires longitudinal incisions along the clavicle, potentially damaging the supraclavicular nerve and causing more surgical trauma [28]. Given the impact of incision choice on the patient’s postoperative skin sensation, recent studies have explored alternative incision placements. Ankers et al. [29] performed a retrospective review and showed that compared to conventional transverse incisions, an oblique incision along Langer’s lines did not reduce the rate of complications following the fixation of displaced middle-third clavicle fractures. Longitudinal vertical incisions or oblique incisions following the nerve course are likely to reduce the risk of injury to iatrogenic supraclavicular nerves [30, 31]. Whether the nerves are protected when these methods are performed depends on the surgeon’s experience, and the implementation of nerve protection strategies is time-consuming [31]. These findings showed that although neither group had significant differences in pain at 6 and 12 months after surgery, the OBS group demonstrated significantly lower VAS pain scores than the LP group at 1 day, 1 week, 1 month and 3 months after surgery. Thus, OBS intramedullary fixation may reduce early and midterm postoperative pain in patients. Moreover, in the present study, the total length of the incision in the OBS group (4.80 ± 0.74 cm) was significantly shorter than that in the LP group (10.54 ± 1.58 cm). None of the patients in the OBS group had surgical incision scarring, whereas 6 patients in the LP group had surgical incision scarring, which indicates that OBS intramedullary fixation has a better cosmetic effect than steel-plate internal fixation. The use of OBS intramedullary fixation for the treatment of midclavicular fractures provides significant pain relief in the early to mid-postoperative period as well as good cosmetic outcomes.

Third, related studies have shown that intramedullary fixation is suitable for preserving the biomechanical characteristics of the normal clavicle, is minimally invasive and does not strip the periosteum, and provides dynamic elastic fixation. Additionally, the healing time of clavicle midshaft fractures and the recovery time of shoulder joints have been reported to be significantly shorter with intramedullary fixation than with plate fixation [32, 33]. In line with these results, our study revealed that the OBS group had a shorter fracture healing time (11.32 ± 1.56 weeks) than the LP group did (15.13 ± 1.26 weeks). Furthermore, the Constant–Murley shoulder scores at 1 month, 3 months and 6 months after surgery were greater in the OBS group (83.21 ± 1.68, 89.68 ± 2.34, and 94.43 ± 1.53, respectively) than in the LP group (71.17 ± 3.11, 85.66 ± 1.57, and 90.20 ± 2.18, respectively), indicating that shoulder joint function was better and functional recovery occurred earlier in the OBS group than in the LP group.

Finally, many studies [8,9,10] have revealed that patients with midshaft clavicle fractures who undergo fixation with steel plates are prone to complications such as a noticeable sensation of subcutaneous protrusion of the plate and hypertrophic scar formation at the incision site due to the subcutaneous location of the clavicle. Moreover, the occurrence rate of nonunion or refracture after plate removal has been consistently underestimated [34]. A retrospective study by Zhu et al. [34] revealed that the refracture incidence rate after plate removal was 6.5% (23/352) in patients with midshaft clavicle fractures fixed with plates, emphasizing the likelihood of this complication in high-risk patients, including those with severe fracture comminution, postmenopausal women, and male smokers. Furthermore, recent biomechanical studies have highlighted the issue of insufficient fixation strength of intramedullary devices for clavicle fractures, while clinical observations have frequently reported problems such as loosening and displacement of intramedullary nails, the protrusion of nail ends that irritate the skin and soft tissue, and the failure of internal fixation [12, 14, 15]. In this study, the observed complication rate in the OBS group was significantly lower than that in the LP group [3.57% (1/28) vs. 17.10% (6/35)] and also lower than previously reported complication incidence rates associated with intramedullary fixation of clavicle fractures [34,35,36]. In the OBS group in our study, 1 patient presented with subcutaneous protrusion of the rod end postoperatively. At 5 months after surgery, this complication resulted in chronic inflammation of the surrounding soft tissue due to subsequent skin damage and exposure of the rod end. This issue may be attributed to the excessive length or inadequate bending of the rod end during surgery, which was further compounded by the patient’s lean physique and limited subcutaneous soft tissue. This complication should be considered and avoided as much as possible in clinical practice.

Under physiological conditions, the clavicle is a non-weight-bearing bone that does not require a strong internal fixation device to maintain a fracture reduction [31, 34]. After fixation, only the tension from the opposing muscles is sufficient to maintain the original alignment of the fracture [32, 35, 37]. The OBS intramedullary fixation technique in this study involved elastic fixation, which is in line with the current “BO” concept of fracture fixation and the cosmetic outcomes desired by the public. In contrast, plate fixation, an eccentric fixation approach, changes the original mechanical transmission mechanism of the clavicle, leading to significant stress shielding [38]. Moreover, the high stiffness of the plate and the sustained stress shielding effect during the later stages of fracture healing affect callus remodeling and might cause delayed fracture healing and reduce bone hardness after healing, potentially resulting in refracture after plate removal [39, 40].

In conclusion, the results of this study showed that the OBS intramedullary fixation technique for midclavicular fractures is not only clinically effective but also advantageous in that it is a simple operation, minimally invasive, and provides good cosmetic outcomes, as it is a method of elastic fixation. This technique is recommended, but there are several limitations of this study. First, this study was retrospective in nature. Nevertheless, the preoperative inclusion criteria were consistent between the two groups. Additionally, all surgeries were performed by the same surgeons, and postoperative management and follow-up examinations were performed using the same approach. Second, the VAS score for pain was limited by subjective factors, and individual differences among the patients might have caused the VAS scores to be biased. Last, the sample size of this study was small. Hence, multicenter large-sample prospective studies are needed to obtain more accurate results.