Post-traumatic sacroiliac joint remodeling in a pediatric patient: a case report

Abstract

Background

Sacroiliac joint (SIJ) remodeling in pediatric patients following trauma is a rare phenomenon with limited documentation in medical literature. This case report presents a unique instance of post-traumatic SIJ remodeling in an 11-year-old girl following a motorbike accident, highlighting novel imaging findings and successful outcomes achieved through a multidisciplinary approach.

Case presentation

The patient presented ten days post-injury with severe right hemi-pelvic pain and limited leg mobility. Initial imaging revealed dislocation of the right SIJ, along with superior and posterior hemi-pelvic displacement and pubic symphysis separation. Initial attempts at closed reduction were unsuccessful, necessitating surgical intervention with percutaneous SIJ screw placement and external fixation. Despite incomplete reduction, multidisciplinary rehabilitation was initiated. At the three-month follow-up, the patient was walking pain-free, with CT scans showing significant SIJ remodeling as the joint adapted to the sacral surface. The SIJ screw was removed at six months, with the patient returning to full function, equal limb lengths, and no residual deficits.

Conclusions

This case underscores the distinct anatomical and physiological responses of the pediatric SIJ to trauma. Early diagnosis, multidisciplinary management, and careful consideration of growth factors are crucial for favorable outcomes in pediatric post-traumatic SIJ injuries. This report highlights the potential for significant joint remodeling and emphasizes the importance of tailored rehabilitation in pediatric cases.

Background

The sacroiliac joint (SIJ) plays a critical role in load transfer between the spine and lower extremities, which is essential for maintaining pelvic stability and movement [1]. Injuries to the SI joint are relatively rare in children due to its structural resilience and flexibility, but they can have substantial impacts on skeletal development and mobility [2]. However, when trauma occurs-often from high-energy impacts such as motor vehicle accidents or significant falls-pediatric SIJ injuries can lead to complex healing processes, including joint remodeling. Understanding the remodeling of the SIJ after trauma in children is crucial, as their joints differ from those of adults in both anatomy and response to injury. Pediatric bones, which contain growth plates and have a higher cartilage-to-bone ratio, influence both the injury pattern and healing process, often leading to remodeling outcomes that are more variable and less predictable than in adults.

Current literature on pediatric SIJ injuries primarily focuses on fracture dislocations, stability concerns, and general management approaches. However, few studies address the specific process of post-traumatic SIJ remodeling in children. Most research emphasizes conservative management or basic surgical approaches, creating a gap in understanding the natural progression and adaptive remodeling potential of the pediatric SIJ following trauma. This gap is particularly relevant in cases where the SIJ demonstrates the capacity for self-correction or compensatory remodeling in response to incomplete reductions

The aim of this case report is to study the specific remodeling process of the sacroiliac joint in an 11-year-old child who experienced a traumatic dislocation following a motorbike accident. By examining the unique characteristics of this pediatric patient’s injury—including the dislocation of the right SI joint, associated pelvic displacement, and subsequent callus formation-this report provides insights into the mechanisms of pediatric SIJ remodeling, the impact of growth and anatomical adaptation, and the effectiveness of surgical and rehabilitative interventions tailored to a growing child. This study adds to the body of knowledge on SIJ injuries in children and underscores the importance of individualized treatment approaches that consider pediatric-specific healing patterns and long-term functional outcomes.

Case presentation

Initial presentation and diagnosis

An 11-year-old girl was transferred to our hospital ten days after sustaining a pelvic fracture from a motorbike accident. Initially stabilized with a pelvic binder, she presented with pain in the right hemipelvis and was unable to move her leg. X-ray and computed tomography (CT) scans revealed a dislocation of the right SIJ, along with superior and posterior displacement of the hemipelvis and separation of the pubic symphysis (Fig. 1A, B). Consistent with common patterns in pediatric pelvic injuries, a small Thurston-Holland fragment was also noted at the site of the SIJ fracture-dislocation, suggesting periosteal stripping. The sacroiliac joint injury pattern was classified according to the modified Torode classification, which is commonly used for pediatric pelvic injuries. Based on this classification, the injury corresponds to Type IV, involving a fracture-dislocation through the SI joint with associated instability [3].

Fig. 1

A, B Preoperative X-ray (A) and CT scan (B) showing right sacroiliac joint dislocation with superior and posterior displacement of the right hemipelvis, separation of the pubic symphysis, and a visible Thurston-Holland fragment. The initial assessment revealed a 2 cm pelvic discrepancy. C Postoperative X-ray taken two days after the surgical procedure, showing partial alignment of the pelvis with residual displacement. The percutaneous SIJ screw and external fixation device are visible. D, E Follow-up CT scan on day 16 post-injury showing early signs of callus formation around the right sacroiliac joint (SIJ), indicative of periosteal response and early remodeling. F, G CT scan at the three-month follow-up, showing continued ossification and alignment of the remodeled SIJ with the sacral articular surface. Remodeling contributed to increased joint stability and functional improvement. H Six-month follow-up X-ray showing complete remodeling of the right SIJ, with alignment comparable to the contralateral side. I, J Sagittal CT cuts at six-month follow-up, illustrating the remodeled alignment between the sacral and iliac surfaces. This view confirms the adaptive remodeling of the joint surfaces, highlighting improved congruity critical for long-term joint function

The Keshisyan method was utilized, involving the tracing of two diagonal lines from the edge of the SIJ to the contralateral triradiate cartilage, which revealed a 2 cm discrepancy between the lines (Fig. 1 A).

Surgical intervention

Fourteen days post-injury, surgical intervention was performed due to unsuccessful attempts at closed reduction and persistent instability in the SIJ. The procedure began with the patient positioned supine under general anesthesia. An anterior iliac approach was selected to provide optimal access to the right SIJ.

After making an incision along the iliac crest, soft tissue dissection was carried out to expose the SI joint. Initial attempts at achieving reduction were made using longitudinal skeletal traction in combination with a ball-spike pusher for direct pressure. However, due to the severity of the dislocation and resistance to complete reduction, further stabilization was required.

A percutaneous SIJ screw was then inserted under fluoroscopic guidance to ensure precise placement across the joint. The screw was positioned carefully to avoid the growth plates and critical neurovascular structures, a consideration essential in pediatric cases. For additional stabilization of the pelvis, a rigid external fixateur was applied across the anterior pelvic ring, specifically to stabilize the pubic symphysis and maintain alignment.

Postoperative course and early imaging

Post-fixation, an intraoperative X-ray confirmed the alignment and placement of the fixation devices. Although the reduction was incomplete, the combination of internal and external fixation provided sufficient stability to initiate a carefully monitored rehabilitation program. Key surgical considerations included minimizing disruption to the growth plates and achieving stability without extensive invasive procedures, preserving the potential for natural remodeling in the child’s joint.

Two days postoperatively, an X-ray revealed an incomplete reduction of the pelvis, with residual displacement at the SIJ despite improved alignment (Fig. 1C). A follow-up CT scan indicated ossifications early callus formation around the right SIJ, suggestive of callus formation resulting from periosteal stripping and elevation at the time of injury. Ossification was observed to be developing by day 16 post-injury, with subsequent imaging showing progressive maturation of the callus (Fig. 1D, E). These findings suggest that the heterotopic ossifications, or callus, likely arose as a response to initial trauma and surgical manipulation, contributing to the natural remodeling process.

Postoperative measurements continued to show a 2 cm discrepancy in pelvic diagonal values. A follow-up CT scan initially identified early callus formation as "heterotopic ossification" around the right SIJ. However, this ossification more accurately represents callus formation due to periosteal stripping and elevation from the initial injury—an expected response in pediatric fractures, where the periosteum is more active and significantly contributes to bone healing.

Follow-up

Multidisciplinary rehabilitation guidance resulted in favorable outcomes for the child. One month after the operation, the external fixateur was removed, and the patient began walking with weight-bearing. By the three-month follow-up, the patient was generally walking without pain. Notably, a CT scan revealed that the ossified tissue of the right iliac had undergone remodeling and was now aligned with the sacral articular surface (Fig. 1 F, G).

The SIJ screw was removed after the six-month follow-up. A CT scan revealed that the right SIJ had remodeled anatomically, matching the contralateral SIJ (Fig. 1 H, I, J). The patient experienced no discomfort and had completely returned to pre-injury status. Both lower limbs were of equal length, and the right lower limb had fully compensated for the previously observed 1 cm shortening. This equalization indicates that the remodeling fully compensated for the previously observed 2 cm shortening, restoring normal limb length and alignment.

Clinically, leg length was measured from the umbilicus to the medial malleolus, providing a consistent reference point to account for any residual discrepancy within the SIJ. This method was chosen to avoid potential inaccuracies associated with measurements from the anterior superior iliac spine or the symphysis pubis, particularly due to the incomplete reduction of the dislocation. Using the umbilicus as a reference ensured that any remaining incongruity at the SIJ level did not interfere with the clinical assessment of leg length. Over the follow-up period, this approach demonstrated that the remodeling process effectively compensated for the initial 2 cm discrepancy, ultimately achieving equal limb lengths and restored functional alignment.

Multidisciplinary approach

Following surgical intervention, a multidisciplinary approach was employed to optimize recovery, involving pediatric orthopedic surgeons, physical therapists, and rehabilitation specialists. The team collaboratively developed a phased rehabilitation plan that evolved in line with the child's healing progress and functional goals. In the first month post-surgery, physical therapy focused on pain management, joint mobility, and preventing complications related to immobilization, such as muscle atrophy, with low-impact, non-weight-bearing exercises for unaffected joints. As the healing progressed, the focus shifted to standing and balance exercises, gait training, and strengthening of the core and hip stabilizers. By weeks 8–12, the patient transitioned to full weight-bearing activities, with functional exercises to enhance joint stability and muscle endurance. From weeks 12–24, advanced rehabilitation included plyometric exercises and agility drills to prepare the patient for a return to normal activities. By six months post-operation, the patient achieved full functional recovery, resuming pre-injury activities without restrictions.

Discussion

Children’s joints are more flexible and resilient due to the presence of growth plates and a higher cartilage content. SIJ injuries in children often result from high-energy trauma, such as falls from heights, sports injuries, or motor vehicle accidents. Pediatric pelvic injuries, particularly those involving the SIJ, frequently present as fracture-dislocations through the SIJ. These injuries are often accompanied by a small Thurston-Holland fragment [4], a characteristic periosteal fragment seen in fractures that cross the physis. This injury pattern arises from the unique elasticity and presence of growth plates in pediatric bones, leading to fracture configurations distinct from those in adults. The presence of a Thurston-Holland fragment in this case aligns with common pediatric injury patterns and underscores the need for tailored management strategies. Additionally, children’s higher regenerative capacity supports a faster and more robust healing process.

After an injury, the SIJ undergoes a remodeling process aimed at restoring normal function and stability. The formation of periosteal callus observed in this case, initially identified as heterotopic ossification, is indicative of the typical healing response in pediatric patients. This periosteal reaction occurs due to stripping and elevation of the periosteum during traumatic injury, leading to active callus formation as part of the natural healing process in children. Recognizing this process is essential in pediatric cases to differentiate normal healing patterns from pathological ossification, guiding appropriate management strategies. This process includes the formation of callus around fracture sites, the reorganization of bone tissue, and, in some cases, surgical intervention to correct alignment and ensure stability. Fixation devices, such as screws and external fixateurs, are often used to maintain proper alignment during healing [5,6,7]. Skeletal maturity influences the remodeling process, potentially leading to different long-term outcomes compared to adults. In children, treatment is often non-operative management, with close monitoring of growth and development.

Surgical interventions are less common in pediatric cases but may be necessary in severe instances or when growth plates are involved. Minimally invasive techniques, such as inserting screws or other fixation devices through small incisions, have become increasingly favored. These methods reduce surgical trauma and recovery time, making them the preferred option when feasible [8, 9].

This case is particularly noteworthy due to several unique aspects of post-traumatic SIJ remodeling in children. It highlights how the distinctive anatomical features of the pediatric SIJ, coupled with the child’s adaptive capacity and potential for new bone formation, led to unique patterns of healing and joint stabilization, different from those observed in adults. Advanced imaging techniques, particularly CT scans, provided detailed visualization, revealing specific remodeling patterns such as irregular bone growth, joint space alterations, and new bone structure formation, which are uncommon in both adults and other pediatric cases. The case also documents the remodeling process over time, demonstrating adaptive responses that contributed to joint stabilization and potentially prevented complications like chronic pain or functional impairment.

Initial imaging performed upon admission showed no evidence of remodeling at the right SIJ. This lack of remodeling is consistent with the early post-injury period, as significant periosteal and bony changes typically do not begin immediately following trauma. The first signs of remodeling were observed on a CT scan taken 16 postinjury, after the joint had been stabilized with a percutaneous SIJ screw and external fixation. The surgical intervention likely triggered the periosteal response, facilitating callus formation and subsequent remodeling. This adaptive response was a result of the combination of stabilization, natural healing processes, and the unique regenerative capacity of pediatric bone.

The initial absence of remodeling prior to surgery is therefore explained by the early phase of injury, during which the body’s healing mechanisms had not yet initiated substantial bone remodeling. The stabilization provided by surgery allowed for proper alignment and load-bearing, which are critical factors in initiating the remodeling process. No additional surgical details were omitted, but the progression observed on day 16 illustrates the typical timeline of callus formation and remodeling in pediatric patients following traumatic injury and stabilization.

This case study, along with its detailed documentation of the diagnosis, contributes significantly to the understanding of pediatric SIJ remodeling. Similar to the work of Donoghue [10], which focuses on the imaging characteristics of pediatric SIJ, this report adds valuable insights into the diagnostic and therapeutic approaches in pediatric SIJ injuries.

The positive outcome for the child was a result of the multidisciplinary collaboration between orthopedic surgeons, radiologists, and rehabilitation specialists. This teamwork provided a comprehensive perspective on the condition and underscored the importance of coordinated integrated care.

The diagnosis and management of post-traumatic SIJ injuries in children present several challenges. First, the atypical presentation of symptoms, such as localized pain, altered gait, and reduced mobility, can easily be mistaken for hip or lower back issues. Additionally, subtle radiographic findings, often masked by skeletal immaturity, make X-rays less effective, necessitating the use of CT or MRI for accurate diagnosis. Developmental variations, including growth plates and increased cartilage, can further obscure the extent of injury on standard imaging, requiring a deep understanding of pediatric anatomy and physiology. Treatment plans must also take into account the child’s growth, with surgical interventions carefully avoiding damage to growth plates to prevent long-term deformities or growth disturbances. Finally, rehabilitation programs must be tailored specifically for children to ensure proper joint function and prevent compensatory injuries, often requiring specialized pediatric physical therapy services. The multidisciplinary approach was essential in providing comprehensive care, with physical therapy tailored to support each stage of healing. The phased Physical Therapist (PT) plan allowed for gradual, safe progression in load-bearing and functional exercises, ensuring the remodeling joint could adapt effectively to stress while preventing complications.

Conclusion

The findings of rare post-traumatic SIJ remodeling in children are marked by specific imaging features that reflect the unique anatomical and physiological responses of the pediatric SI joint to trauma. Recognizing these features is crucial for timely diagnosis and effective management, ultimately leading to better outcomes for affected children.