A Modified Technique of Minimally Invasive Cortical Bone Trajectory Screws With U‐Rod for Treatment of Lumbar Spondylolysis

ABSTRACT

Objective

Spondylolysis is a common cause of low back pain, especially in the young athletic population. It involves a defect, either unilateral or bilateral, of the pars interarticularis. Numerous techniques have been developed for the surgical treatment of spondylolysis, each with its own strengths and weaknesses. This article aims to describe a modified minimally invasive technique using cortical bone trajectory screws with a U‐rod to stabilize the lumbar spondylolysis.

Methods

Adult patients who presented between July 2020 and August 2024 with low back pain due to spondylolysis were included in this study. Imaging studies of the lumbar spine were performed to confirm the spondylolysis. All patients were confirmed to be treated conservatively for at least 12 months prior to surgical intervention. A 2.5 cm midline incision was made at the level of the spondylolysis. Under fluoroscopic guidance, two screws were inserted into the level of the spondylolysis in the cortical bone trajectory, and the screws were connected with a U‐shaped bent rod.

Results

Four adult patients (one male, three females) were included. The mean age was 38.5 ± 16.1 years. Average intraoperative blood loss was 6 ± 3 mL. Mean postoperative hospital stay was 3 ± 0.5 days. Both postoperative visual analog scale (VAS) and Oswestry disability index (ODI) scores showed significant improvement. Lumbar spine CT scans performed 1‐year post‐operation confirmed fusion of the pars defect in seven of the eight defects.

Conclusion

We described a modified minimally invasive technique for the treatment of spondylolysis. This approach offers the advantage of being minimally invasive, leading to less blood loss, short hospital stays, and fast recovery. It also requires less technical expertise than traditional pars screw placement and utilizes readily available instrumentations. Patients reported improved pain scores, and imaging confirmed successful fusion of the pars defect.

The U‐rod technique combined with cortical bone trajectory screws is a safe and effective method for the treatment of lumbar spondylolysis.

1. Introduction

Spondylolysis is a common spinal pathology defined as a defect or fracture of the pars interarticularis either unilaterally or bilaterally often at the L5 level. The incidence of spondylolysis varies with age and has been reported to be around 4.4% in childhood and potentially increasing to 6% in adult populations [1]. However, this can vary between different ethnic groups [2]. Gender also plays a role, with males being twice as likely to develop spondylolysis than females [1]. In active sporting populations, where repetitive axial loading and spinal hyperextension are common, the incidence may be as high as 47%–54% [3, 4].

The exact etiology of spondylolysis remains unknown, though both congenital and acquired mechanisms are possible causes [5]. Congenital spondylolysis is thought to result from a defect in the neural arch during early fetal development, leading to incomplete fusion of the pars interarticularis [6]. Conversely, acquired spondylolysis is often linked to acute or repetitive trauma from hyperextension and/or rotation of the lower lumbar spine during sporting activities [3, 4].

Although most patients remain asymptomatic, low back pain is among the most common presentations of spondylolysis, especially during motion which requires extension of the low back. The majority of patients are successfully managed with non‐surgical treatments such as analgesics, physical therapy focusing on core muscle strengthening exercises, and spinal bracing, leading to symptom improvement. Surgical intervention is generally reserved for patients who: (i) do not respond to conservative management for at least 6 months, (ii) have progression of spondylolisthesis, or (iii) develop worsening neurological deficits [7, 8]. The diagnosis primarily relies on imaging studies that reveal pars articularis defects.

Numerous surgical methods have been described for the treatment of spondylolysis. Historically, fusion with or without instrumentation of the affected segment was common; however, this will lead to unnecessary motion restriction and the possibility of adjacent‐segment pathology [9, 10]. Consequently, growing interest in direct repair of the fracture or fixation methods without restricting motion has been developed. Several repair techniques exists, including: Buck's direct pars repair [11], Scott's wiring technique [12], Morscher's hook screw technique [13], and the V‐shaped [14] or U‐shaped rod technique [15, 16], each with its own biomechanical strengths. In 2016, a novel technique utilizing cortical bone trajectory (CBT) screws connected by a U‐shaped rod for direct pars repair was first described by Goldstein et al. [16]. This approach provided a minimally invasive solution, and was originally performed with the aid of intraoperative navigation to ensure accurate screw placement. The current study presents a modification of this CBT U‐rod technique, where the screws are inserted using a free‐hand technique confirmed by standard fluoroscopy, making the procedure accessible in institutions without specialized spinal navigation systems.

The purpose of the current study is to: (i) describe a modification of the CBT U‐rod technique using a free‐hand, fluoroscopy‐guided approach to improve global surgical accessibility; (ii) evaluate the clinical efficacy and radiographic fusion rates of this construct in a symptomatic adult cohort; and (iii) establish optimal patient selection criteria and future directions for this motion‐preserving technique. By addressing these areas, we aim to demonstrate the benefits of this low‐profile, navigation‐independent system in facilitating successful direct pars repair.

2. Materials and Methods

This study was approved by the Mackay Memorial Hospital institutional review board with an approval number of 24MMHIS544e. Informed consent was obtained from all patients.

2.1. Patient Selection and Statistical Analysis

Adult patients presenting to a single surgeon at Taitung Mackay Memorial Hospital between July 2020 and Aug 2024 and met the following criteria were included: (i) adult patients with confirmed spondylolysis, unilateral or bilateral, on both X‐ray and lumbar spine computed tomography (CT), (ii) no visible instability of the spondylolysis on dynamic lumbar X‐ray, (iii) absent symptomatic radiculopathy, (iv) no significant disc degeneration on imaging studies, and (v) a history of at least 12 months of conservative therapy prior to surgical intervention. Patients who were under 18 years of age, have symptomatic radiculopathy or spondylolisthesis were excluded. Adolescent patients were excluded from this initial series due to the distinct biomechanical and physiological characteristics of the immature skeleton, including the presence of open apophyses and higher spontaneous healing potential. This study focused specifically on adult symptomatic spondylolysis, where chronic non‐union is more prevalent and CBT with U‐rod construct may provide a more robust fixation point in mature bone.

Demographics, clinical features, visual analogue scale (VAS), Oswestry disability index (ODI; Traditional Chinese version), and perioperative and intraoperative images were collected and analyzed. Graphpad Prism was used for paired statistical analysis. A p‐value of < 0.05 was considered statically significant.

2.2. Surgical Technique

Prior to surgical intervention, all patients underwent a standardized imaging protocol including standing anteroposterior (AP) and lateral X‐rays, dynamic views to rule out gross instability, CT scans for three‐dimensional assessment of the pars defect, and magnetic resonance imaging (MRI) to evaluate disc health and neural compression. Under general anesthesia, the patient was positioned prone on a radiolucent surgical table. A mobile C‐arm fluoroscope was utilized to confirm the surgical level. A 2.5 cm midline incision was then made (Figure 1) over the spinous process of the affected level. Minimal dissection was done to expose the spinous process and the lamina of the target level with careful preservation of the supraspinous ligament (Figure 2).

FIGURE 1.

A 2.5 cm midline incision centered over the spinous process of the affected lumbar level. This minimally invasive corridor allows for bilateral access to the cortical bone trajectory (CBT) entry points while preserving the supraspinous ligament and minimizing paraspinal muscle stripping.

FIGURE 2.

Intraoperative view demonstrating exposure of the spinous process and lamina following minimal soft‐tissue dissection. The structural integrity and continuity of the supraspinous ligament are strictly preserved.

A free‐hand CBT was employed for screw placement. Under fluoroscopic guidance, the entry point was created at the junction of the lateral pars interarticularis and the superior border of the transverse process (typically at the 5 o'clock position on the right and 7 o'clock position on the left on true AP view) at the desired level using an 11G diamond‐tip biopsy bone access trocar. The trocar was then carefully advanced in a lateral and cranial direction, ensuring that the pedicle walls were not breached. Adequate positioning of the bone access trocar was then confirmed with both AP and lateral fluoroscopic views. A guide wire was then inserted through the trocar followed by trocar removal. The hole was then tapped to the actual screw diameter to prevent cortical bone fracturing. With the guide wire in place, prior to final placement of the screws, the pars fracture site was visualized and cleared of fibrous and soft tissue. To facilitate biological fusion, the defect and the surrounding cortical bone were lightly decorticated using a 3 mm diamond bur. Approximately 2 cc to 2.5 cc of demineralized bone matrix (DBM; Grafton, Medtronic Inc.) in total was applied to the defect to enhance fracture site healing. Cannulated screws (Voyager, Medtronic Inc.) were then inserted and the guide wire was removed. In our series, screw diameters ranged from 4.5 mm to 5.5 mm and lengths from 30 mm to 35 mm depending on the patient's specific pedicle morphology.

A 4.75 mm cobalt‐chromium‐molybdenum (Voyager, Medtronic Inc.) rod was utilized to create the U‐shaped construct. The rod was bent to a sharp “U” shape configuration with an internal angle of approximately 25°–40° to accommodate the medially situated screw tulips. A small perforating hole was then made in the interspinous ligament to facilitate passing and placement of the U‐shaped curve rod (Figure 3) and hook around the inferior aspect of the spinous process. Finally, the rod was compressed onto the spinous process and the rod was positioned within the tulip head and fixed firmly with setscrews. Final intraoperative AP and lateral fluoroscopic films were taken to confirm proper positioning and hardware integrity of the instrumentation. The incision wound was then closed in layers with absorbable sutures.

FIGURE 3.

The 4.75 mm rod contoured into an “U” shape with acute internal angles of 25°–40°. This sharp configuration is required to bridge the medially situated CBT screw tulips while hooking securely beneath the inferior aspect of the spinous process to create a stable clamping effect.

2.3. Follow‐Up Course

All patients were followed routinely at the out‐patient department. Plain radiographs (Figure 4) were taken at 1, 3, and 6 months post‐operation; CT scan was performed after 1 year post‐operation. VAS scores were recorded prior to surgery and at 1, 3, 6, and 12 months post‐operation. ODI scores were collected before and at one and 6 months after surgery. Bone growth within the pars defect, as observed on CT images, was defined as positive fusion (Figure 5). Complete imaging records for all patients are available in the Supporting Information.

FIGURE 4.

Representative pre‐ and postoperative radiographs of the 40‐year‐old female patient with bilateral L5 pars interarticularis fracture. (a) AP and (b) lateral views prior to surgical intervention; the black and white arrows indicate the pars defect. (c) AP and (d) lateral views at the 3‐month follow‐up for the same patient, demonstrating stable positioning of the bilateral CBT screws and the U‐rod construct. Note the maintenance of the index‐level disc height.

FIGURE 5.

Representative sagittal lumbar spine CT image of the 59‐year‐old male patient with bilateral L5 spondylolysis. (a) Preoperative image; the black arrow indicates the fracture L5 pars interarticularis. (b) One‐year postoperative follow‐up demonstrating bone bridging across the defect (white arrow). This confirms successful biological union facilitated by active decortication and DBM grafting.

3. Results

3.1. Patient Demographics and Perioperative Data

Four patients fulfilling the inclusion criteria were identified and included in this study (Table 1). The cohort had a mean age [±SD] of 38.5 ± 16.1 year‐old (range: 20–59 year‐old); one of whom is male (25%). All patients were active, healthy adults with no significant medical comorbidities. All patients maintained a normal body habitus, with body mass index (BMI) values ranging between 20 and 22 kg/m². All the patients had pars fracture bilaterally and were all at the L5 level. The mean duration of symptom presence prior to surgical intervention was 32.8 ± 14 months. Mean duration of surgery was 146.5 ± 28 min and the average blood loss was 6 ± 3 mL. The average stay in hospital after surgery is 3 ± 0.5 days.

TABLE 1.

Patient demographics.

	Age (years)	Gender	Duration of symptoms prior to surgery (months)	Level of spondylolysis	Unilateral/bilateral fracture	Body mass index (kg/m2)
Patient 1	59	M	36	L5	Bilateral	22
Patient 2	20	F	14	L5	Bilateral	20.5
Patient 3	35	F	48	L5	Bilateral	21.8
Patient 4	40	F	33	L5	Bilateral	21.6

3.2. Clinical and Functional Outcomes

There was a significant decrease in VAS and ODI scores statistically. Pre‐operatively, the average VAS score is 7 ± 1 which decreased to 2 ± 1 (p < 0.05) at 1 month, 1 ± 1 (p < 0.01) at 3 months, 0 ± 1 (p < 0.01) at 6 months, and 0 (p < 0.001) at 1‐year post‐operation (Figure 6). ODI scores decreased from 58 ± 7 pre‐operatively to 14 ± 6 (p < 0.01) at 1 month and 4 ± 7 (p < 0.01) at 6 months post‐operation (Figure 7). There is also a statistical significance decrease of ODI scores between one and 6 months (p < 0.01).

FIGURE 6.

Visual Analog Scale (VAS) score of patients prior to surgery (7 ± 1) and at 1, 3, 6, and 12 months after surgery. There is a statistical significance in pain reduction as early as 1 month after surgery. All patients had a VAS score of 0 at 12 months post‐operation. (* p < 0.05, **p < 0.01, ***p < 0.001).

FIGURE 7.

Oswestry Disability Index (ODI) scores of patients showing a significant decrease from preoperative status (58 ± 7) to 6 months post‐operation (4 ± 7). This reduction reflects a rapid return to activities of daily living and vocational duties. (**p < 0.01).

3.3. Radiographic Analysis and Postoperative Recovery

Seven out of the eight (87.5%) fractured pars demonstrated radiographic fusion on CT at one‐year follow‐up. Comparison of pre‐ and postoperative dynamic radiographs confirmed that segmental range of motion was preserved, with no significant loss of flexion or extension identified. Additionally, intervertebral disc heights at the index and adjacent levels remained stationary throughout the follow‐up period.

One patient experienced a small wound dehiscence which did not require additional intervention and healed uneventfully within 2 weeks after discharge. One patient complained of mild back soreness, especially after strenuous exercise, until 6 months post‐operation. During the follow‐up period, no breakage or loosening of instrumentation was identified. No patients developed spondylolisthesis, symptomatic radiculopathy, nor motor weaknesses. All patients returned to normal daily activity at 1 month and more active exercises at 6 months post‐operation. The mean interval for return to professional employment was about one month post‐operation; minor variations in vocational reintegration were associated with individual administrative or insurance protocols rather than surgical morbidity.

4. Discussion

4.1. Summary of Findings

Our study demonstrates that the modified free‐hand CBT U‐rod technique is a safe and effective motion‐preserving option for the treatment of adult spondylolysis. The key findings include an 87.5% radiographic fusion rate at 1 year post‐operation and significant improvements in functional scores (VAS and ODI), all achieved via a minimally invasive approach without the need for advanced navigation systems. This suggests that the technique is both clinically robust and technically accessible.

4.2. Pathophysiology and Traditional Treatment Paradigms

Spondylolysis is a relatively common cause of low back pain, particularly among young athletes. Due to its typically benign nature, most patients are treated conservatively, with more than 90% of patients returning to their baseline activity within 6 months [17]. These treatments usually include pain management, physical therapy, activity restriction, and bracing. Spinal bracing is often recommended for 3–6 months, with the best candidate being those in the early stage of defect who commit to at least 3 months of full‐time wear and cessation of sporting activities [18, 19]. The purpose of bracing is to limit movement, especially hyperextension, at the fracture site, thereby supporting bone healing. However, other studies suggest that bracing may not significantly impact the treatment success [20, 21]. Oral non‐steroidal anti‐inflammatory drugs (NSAIDs) and fracture site or facet joint injection have been used to relieve acute pain [22]. Low‐intensity pulsed ultrasound (LIPUS) is a recently emerging intervention with favorable effects [23, 24].

In the uncommon event of failed conservative treatment, surgical intervention may be required. It is reported to be necessary in about 9% of spondylolysis cases [18]. Surgical intervention is indicated when: the patient has failed conservative treatment after 6 months, persistent back pain due to spondylolysis after 6–12 months, neurological deficits, and worsening spondylolisthesis [5, 25, 26, 27]. Two major surgical categories exist, fusion or direct repair of fracture, with various modifications having been developed for symptomatic spondylolysis repair. Although surgical fusion was once the treatment of choice, its popularity has declined due to the restriction in range of motion at the fused segment. However, there are still situations where fusion might be more beneficial than direct repair (Table 2).

TABLE 2.

Comparison of segmental fusion and direct pars repair surgery in the treatment of spondylolysis.

	Surgical fusion	Direct repair
Suggested indications	Grade I or greater spondylolisthesis Dysplastic or abnormal pars anatomy Degenerated intervertebral disc or facet	Young, active athletes No significant/low grade spondylolisthesis (although patients with Grade I spondylolisthesis has been treated with success) No significant disc (Pfirrmann Grade I or II) or facet degeneration
Advantages	Better stability of the fused segment Correct lumbar lordosis No significant learning curve for most spine surgeons	May be minimally invasive depending on method selected Preserve range of motion Reduced risk of adjacent segment degeneration
Disadvantages	Reduced range of motion at fused segment Possible adjacent segment degeneration in the future	Unable to correct lordosis Elevated failure rates if pars dysplasia or abnormal anatomy Learning curve for certain method May not correct spondylolisthesis

4.3. Comparison of Established Direct Repair Modalities

Numerous direct repair techniques have been described over the past half‐century. In 1968, Kimura first described a method for the direct repair of the spondylolysis with bone grafting at the defect without the aid of instrumentation [28]. The patients were instructed to remain supine on bed for several weeks and were then fixed in an external cast for up to 6 months duration. Two years later, Buck described a technique by using screw insertion through the pars interarticularis for direct fixation of the defect [11]. This technique is technically challenging and leaves little margin for error, particularly at the L5 level, where the defect may have varying orientations. Although difficult, this technique has a high reproducible success rate [29, 30, 31]. Scott wiring is a technique where a wire is looped anterior to the transverse process, which is subsequently wrapped around the spinous process thereby stabilizing the defect and facilitating bone repair [12]. This outcome associated with this technique has been variable [32, 33, 34]; with some authors reporting improved fusion with modifications by incorporation of pedicle screws combined with wire fixation of the spinous process [35]. Conversely, other research has highlighted suboptimal results in patients older than 25 years of age [36]. In the original Morscher repair, hooks were first placed at the inferior aspect of the lamina of the vertebral arch and screws were inserted through the hook to the base of the superior articular process [37]. This technique offers the advantage of being suitable for pars dysplasia. However, this technique has been reported to have higher failure and complication rates [33, 38]. The pedicle screw‐based technique is another method similar to the Morscher repair with acceptable fusion rates. The screws were placed in the pedicle instead of the superior articulate process and the spinous process was stabilized with either a wire [35], cable system [39], hook [40], or a V‐ [14]/U‐shaped rod [15]. This method has a shorter learning curve as most spine surgeons are familiar with pedicle screw placement and has been reported in a previous review to have the highest fusion rate of over 90% [26]. A 2018 meta‐analysis by Mohammed et al., encompassing 46 studies and over 900 patients, established pooled fusion rates across various repair modalities: 83.5% for Buck's technique, 81.6% for Scott's wiring, and 77.7% for the Morscher screw‐hook [33]. Notably, pedicle screw‐based constructs demonstrated the highest efficacy at 90.2%, a benchmark that our modified CBT screws with U‐rod technique closely mirrors with a fusion rate of 87.5%, while providing the distinct advantage of a minimally invasive approach. A summarized table presenting the advantages and disadvantages of different techniques is provided (Table 3).

TABLE 3.

Comparison of the strengths and limitations of various direct pars repair techniques.

	Advantage	Disadvantage
Buck repair	High fusion rates reported Minimally invasive with correct instrument and hardware Less blood loss Fast recovery Can be performed even in patients with grade I spondylolisthesis	Minimal room for error leading to screw misplacement or loosening Less room for bone graft placement Technically demanding Not suitable for pars dysplasia Increased difficulty at the L5 level
Scott wiring repair	Less technical demanding Effortless collection of instruments required Defect surfaces are fully engaged in bone fusion process without instrument disruption	Not minimally invasive with greater muscle dissection Increased difficulty at L5 level (especially when transverse process is close to sacrum) Possible nerve root injury Wire breakage Mixed fusion results (poor success rate in patient > 25 years old)
Morscher screw‐hook repair	Less soft tissue damage compared to Scott wiring repair Can be used in pars dysplasia May allow adequate bone grafting	Not minimally invasive Mixed fusion results Higher complication rates (screw or hook loosening; nerve irritation; pseudoarthrosis)
Pedicular screw‐based method (wire, cable, hook, or V‐/U‐shaped rod)	High fusion rates Less learning curve Can be used in pars dysplasia	Not minimally invasive Screw‐hook combination may have difficult placement of abnormal lamina
Cortical bone trajectory (CBT) screw with U‐shaped rod	Minimally invasive Minimal blood loss Short hospital stays Can be used even in pars dysplasia Possibly high fusion rate	Learning curve for CBT screw placement Additional curvature bending of the rod needed (rod bent into a more acute angle)

In 2016, Goldstein et al. published a case report introducing a novel minimally invasive method for the direct repair of spondylolysis. This approach involves placing two CBT screws at the level of the pars defect guided by navigation assistance, followed by stabilizing the defect with a U‐shaped rod beneath the spinous process and applying compression to the defect to promote bone fusion without using bone graft [16]. The case demonstrated complete fusion at 1 year, with successful removal of the instrumentation at 16 months. In the present report, a modified version of this method was used. First, navigation guidance was not utilized, and the cortical screws were inserted using a free‐hand technique and portable fluoroscope confirmation. This modification reduces the need for specialized equipment and can be performed in institutions lacking spinal navigation systems. Second, the pars defect site was lightly decorticated, and DBM grafting was applied at the defect to encourage bone fusion.

In this series, three of the four patients were female, which is not consistent with the 2:1 ratio presented in the literature [1, 2]. All patients presented with spondylolysis at the L5 level, which is compatible with the literature suggesting over 90% of spondylolysis being at this level and decreases with every caudal level [41]. Seven of the eight fracture sites (87.5%) demonstrated signs of fusion during image follow‐up after 1 year. This result is also consistent with a previous review of different direct repair methods showing around 80%–90% of fusion rate using other repair methods [33]. The non‐union fracture site was observed in the eldest patient within the group, who was 59 years old. A previous report suggested that younger age may be a positive factor influencing fusion outcome [31]. Both VAS and ODI score showed a statistically significant reduction since 1 month post‐operation. This result is in consistence with another pedicle‐based U‐rod method [14, 42, 43]. In addition, we do not routinely remove implants unless patients become symptomatic. To date, no patient has requested removal of the instrumentation despite image confirmation of healed defects.

We utilized a 4.75 mm screw‐rod system in preference to the standard 5.5 mm system for two primary reasons. First, the lower profile and footprint of the 4.75 mm screw tulips minimizes iatrogenic soft tissue trauma during construct placement, adhering to minimally invasive principles. Second, the small diameter of the 4.75 mm rod facilitates easier contouring, allowing for the precise, acute bending angles required for the U‐rod configuration. Despite the smaller diameter, the construct provided sufficient rigid fixation to promote union in 87.5% of our cases.

4.4. Proposed Indications and Contraindications

The advantage of this technique is that (i) it is less equipment demanding and may be performed at most institutions that perform routine spinal surgeries, (ii) the technique is minimally invasive thus will have less blood loss, shorter hospital stay, and faster recovery time compared to traditional open direct repair techniques, (iii) active decortication and DBM grafting are placed at the fractured site to promote fracture site fusion, (iv) can be performed with different orientation of pars defect and even with pars dysplasia, and (v) preserve segmental motion at the level of instrumentation. Several disadvantages of this technique include (i) learning curve for CBT screw placement, and (ii) the rod must be bent to an acute internal angle in order to fit within the rather medially situated tulips of the screw. To ensure the success of this motion‐preserving technique, strict patient selection is paramount. Based on our clinical experience and the biomechanical nature of the construct, we propose the following selection criteria for optimal results: (i) symptomatic spondylolysis, either unilateral or bilateral, failed after 12 months of conservative treatment, (ii) absent spondylolisthesis with no gross instability on dynamic X‐rays, and (iii) preserved disc height (Pfirrmann Grade I or II). Absolute contraindications: (i) spondylolisthesis or gross instability on dynamic X‐rays, (ii) significant intervertebral disc degeneration (Pfirrmann Grade ≥ IV), and (iii) symptomatic foraminal stenosis requiring extensive decompression that would compromise the screw entry point.

4.5. Limitations and Future Directions

Several limitations are present in the current study. The mean age of the patients in this series is older and no patient under 18 years of age was included. The study was performed at a single‐center and is the experience of a single surgeon. The unrepresentative gender ratio in our cohort is likely a reflection of our specific regional demographic and the small sample size. The limited patient population size and lack of control group in this report prevent high‐powered statistical conclusions and necessitate the need for future larger clinical studies.

Future research should prioritize prospective, multi‐center trials with larger cohorts to validate the long‐term clinical durability and radiographic fusion rates of this modified free‐hand CBT U‐rod technique. Comparative studies against traditional pedicle‐based repairs are warranted to establish the objective benefits of this approach. Furthermore, investigating the safety and efficacy of this low‐profile construct in adolescent populations may expand the surgical indications for pediatric patients who remain symptomatic despite exhaustive conservative management.

5. Conclusion

A diverse array of surgical techniques has been documented in the literature, reflecting the absence of consensus on an optimal procedure for spondylolysis. This article presents a modified minimally invasive technique using CBT screws with a bent U‐shaped rod for the direct repair of spondylolysis. This technique is simple and safe, requiring only general spinal surgery resources commonly available in most institutions. The cases presented within this report demonstrate satisfactory clinical outcomes, including significant pain reduction post‐operation. Its minimally invasive nature also results in minimal blood loss, a short hospital stay, and a rapid recovery to normal daily activities. Further studies are needed to validate this technique.

Author Contributions

Lincoln Liu: conceptualization, methodology, investigation, validation, supervision, writing – review and editing, writing – original draft, formal analysis, data curation. Hung‐Chang Chang: writing – review and editing, data curation, formal analysis. Cheng‐Neng Chen: writing – review and editing, formal analysis, data curation. He‐Shu Ku: writing – review and editing, formal analysis, data curation.

Funding

The authors have nothing to report.

Conflicts of Interest

The authors declare no conflicts of interest.

Supporting information

Data S1: Full imaging data for the patient cohort (N = 4).

Data Availability Statement

The data that support the findings of this study are available on request from the corresponding author. The data are not publicly available due to privacy or ethical restrictions.