With the promotion and popularization of early emergency treatment and reconstruction techniques for pelvic fractures, the success rate concerning early management of pelvic fractures has prominently improved, and most displaced unstable pelvic fractures can be reduced and fixed early . However, some severe pelvic fractures do not qualify for early reconstruction due to the need for early rescue for life-threatening massive bleeding and associated injuries [3, 11]. On the one hand, some doctors lack an understanding of the degree of pelvic instability and are unable to apply correct and adequate vector forces to reduce and stabilize the fractures. On the other hand, primary hospitals are limited by the available hardware and techniques, resulting in the occurrence of malunion or nonunion. In our group, one patient with type C1.3 pelvic fracture was not associated with obvious displacement after injury, and was given the conservative treatment of bed rest due to insufficient understanding of the instability of pelvic fracture by the surgeon. One month later, the AP X-ray revealed that the vertical displacement of a unilateral pelvis was 3.9 cm. The patient was given a reduction of femoral skeletal traction. After the failure of traction reduction, the patient with obvious claudication came to our hospital 3.5 months later. Then, in our hospital anterior and posterior pelvic ring osteotomy, longitudinal distraction reduction of the sacrum, anterior ring plate fixation, and posterior ring LPDO were performed. Follow-up at 8 and 15 months after surgery showed no loss of reduction (Fig. 6). The other patient had pubic ramus fractures of an anterior pelvic ring and sacral zone II fractures of a posterior pelvic ring after injury, and significant vertical displacement and symptoms of sacral plexus nerve injury were observed. Because the surgeon was unable to apply correct and adequate vector forces to reduce and stabilize the fractures and was technically limited, only the pubic rami of the anterior ring were fixed in the initial treatment; the vertical displacement of the posterior ring was not reduced, and the sacrum was not fixed. Even two screws on the anterior ring plate were mistakenly inserted into the acetabulum, resulting in claudication, hip and lumbosacral pain in patients for up to 18 months.
In recent years, due to clinical application of the pelvic reduction frame, some pelvic fractures can be treated with closed reduction and minimally invasive fixation in the early stage, with better results and a lower incidence of pelvic malunion or nonunion [12, 13]. However, the application of this new technique has not been popularized, and some complex pelvic fractures are difficult to correct with reduction frames. Thus, pelvic malunion or nonunion still occurs.
The treatment of pelvic malunion or nonunion is challenging for surgeons because of significant intraoperative difficulties and postoperative uncertainty. Few treated cases have been reported in the literature . Therefore, there is no standard treatment strategy for pelvic malunion or nonunion. However, the ultimate goal of pelvic malunion or nonunion remains the same: to restore the integrity and symmetry of the pelvic ring, carefully manage soft tissue, facilitate rapid postoperative recovery and early rehabilitation, and achieve long-term functionality of the hip joint.
Significant vertical displacement deformity is a common reason for patients coming to the hospital with pelvic malunion or nonunion. It is very difficult to correct these deformities. On the one hand, the pelvic ring fracture line has formed a callus, which needs to be converted into a fresh fracture by osteotomy. On the other hand, the severe contracture of soft tissue requires extensive release. Moreover, numerous nerves, blood vessels, and other vital structures surrounding the pelvic region further increase the difficulty of surgery and the risk of treatment.
Surgical treatment of pelvic malunion or nonunion depends on the clinical symptoms, the degree of pelvic vertical displacement, and the requirements of the patients. It is important to ascertain whether the symptoms are related to pelvic malunion or nonunion rather than to other clinical conditions. Pain from mechanical low back pain or an old neurologic injury and dysesthetic pain of neurogenic origin must be excluded . Pain at the site of pelvic fractures is often caused by nonunion, and some pain is caused by nerve injury that occurs during the initial pelvic fracture, which is often difficult to eliminate . We must inform patients that pelvic pain not associated with nonunion or instability is not corrected with this type of surgery . Furthermore, reconstructive surgery involves the risk of many complications, including nerve injury (5.3%), symptomatic venous thrombosis (5.0%), pulmonary embolism (1.9%), and deep wound infection (1.6%) . A hemipelvic displacement of > 1 cm or rotation of 15° to 20° may be not all-inclusive clinically symptomatic, but the integration of these parameters is much more likely to be clinically symptomatic, which may represent malunion . Pelvic fractures with significant displacement often cause gait instability and claudication. All patients in our group had sacral fractures of a posterior pelvic ring, vertical displacement > 2 cm and different degrees of gait abnormalities. The patients had a strong desire for surgery to improve existing symptoms and restore equal lengths of the lower limbs. The authors deem it acceptable for a hemipelvic vertical displacement of ≤1 cm and/or rotation of < 15-20° displacement. However, some studies suggest that surgical correction is indicated for rotational defects greater than 10°, leg length discrepancies greater than 5 mm, and lack of reduction or imperfect facing of sacroiliac articular surfaces .
In the process of reconstruction, the malunion site requires osteotomy, and the scar contracture site requires release. The methods of posterior pelvic ring osteotomy include longitudinal osteotomy of the ilium and sacral osteotomy, which mainly corrects pelvic obliquity and restores lower limb length symmetry [14, 16]. The authors believe that iliac osteotomy is mainly applied to type B pelvic fractures involving the ilium and pelvic obliquity. Given that this group of patients had a sacral fracture (C1.3 or C3.3) of a posterior pelvic ring and significant vertical displacement of a unilateral pelvis, sacral osteotomy is a kind of method to better restore the shape of a pelvis.
Posterior pelvic ring fixation methods include transverse osteosynthesis, vertical osteosynthesis, and triangular osteosynthesis. Transverse osteosynthesis usually involves sacroiliac screws, sacral rods, transiliac and transsacral plates, which show poor shear resistance . Vertical osteosynthesis is LPDO. LPDO with transverse osteosynthesis (triangular osteosynthesis) provides stability against longitudinal displacement and rotation [2, 17]. LPDO was used in all patients in our group. Longitudinal distraction between the lumbar spine and the pelvis directly corrects vertical displacement of a unilateral pelvis. In addition, pelvic malunion or nonunion also needs to be combined with sacrospinous ligament and sacrotuberous ligament release.
The small number of cases in this study precludes statistical analysis and has some limitations. This study is not accurate enough for the measurement of rotational deformity of the pelvis, which will be our main research direction in the future.