Preoperative Virtual Planning Combined with 3D-Printed Surgical Guide Technology for Correction of Shepherd’s Crook Deformity: A Case Report

Abstract

Patient: Male, 12-year-old

Final Diagnosis: Fibrous dysplasia

Symptoms: Deformity

Clinical Procedure: —

Specialty: Orthopedics and Traumatology • Surgery

Objective: Rare disease

Background

Shepherd’s crook deformity, a rare and severe skeletal malformation, is characterized by a distinctive shepherd’s crook-like curvature of the proximal femur. This pathological condition manifests as a marked reduction in the femoral neck–shaft angle (typically measuring less than 90 degrees). The deformity is most frequently observed in patients with fibrous dysplasia (FD), where it is a hallmark skeletal manifestation of the disease.

Case Report

A 12-year-old boy presented with progressive deformity of both lower limbs. Physical examination revealed a typical “shepherd’s crook” deformity of both femurs with associated abnormalities of the left tibia and fibula. Radiographic findings confirmed polyostotic fibrous dysplasia affecting multiple bones and causing severe lower-limb malalignment.

Preoperative three-dimensional (3D) CT reconstruction and digital planning were performed to design an individualized osteotomy, and a patient-specific surgical guide was fabricated to ensure accuracy. Postoperative imaging demonstrated restoration of anatomical axes and improved mechanical alignment. Measurements showed a right femoral neck–shaft angle of 125.7°, a left angle of 129.1°, and a residual limb length discrepancy of 9 mm. The patient recovered well without complications.

Conclusions

This case report demonstrates the integration of preoperative virtual surgical planning with 3D-printed patient-specific guides for precise correction of femoral shepherd’s crook deformity, exemplifying the clinical application of digital orthopedic technologies in complex skeletal reconstruction.

Introduction

Shepherd’s crook deformity is an extremely rare and refractory severe skeletal deformity of the proximal femur, characterized by a significantly reduced femoral neck–shaft angle (typically <90°), presenting a shepherd’s-crook-shaped curvature [1,2]. This deformity most frequently occurs in patients with fibrous dysplasia (FD) [3]. FD is primarily caused by mutations in the Gsα gene, where abnormal fibrous tissue replaces normal bone tissue, leading to progressive deformation of weight-bearing long bones such as the femur and tibia [3,4]. For such rare and highly complex deformities, conventional treatments face formidable challenges: conservative management (eg, bisphosphonates) cannot correct structural deformities [5], and traditional open osteotomy is limited by difficult surgical exposure, obscured identification of critical bony landmarks, and high dependence on surgeon experience for precise osteotomy. Reports indicate that for severe structural deformities, traditional osteotomy achieves correction rates typically between 62% and 78%, accompanied by high complication risks, with postoperative complication rates reaching over 30% [6–8].

While digital orthopedic technologies (eg, computer-aided design, virtual surgical planning, 3D printing) demonstrate significant potential in orthopedics, their systematic application for correcting rare and complex skeletal deformities like shepherd’s crook deformity remains scarce in current clinical practice and in the literature. Therefore, this report presents a case of complex polyostotic FD with severe shepherd’s crook deformity, combining preoperative virtual planning with 3D-printed patient-specific guides for the first time to achieve precise correction of this extreme deformity. It successfully demonstrates the breakthrough application and value of preoperative virtual planning combined with 3D-printed surgical guide technology in the accurate correction of high-difficulty deformities. This innovative technology utilizes 3D reconstruction of patient medical imaging data to accomplish personalized osteotomy scheme design, precise angle calculation, 3D simulation of osteotomy planes, and guide-bone surface matching verification, enabling higher correction accuracy for complex skeletal deformities compared to traditional surgery, significantly improving surgical safety and prognosis [9,10]. Through the “digital simulation-physical verification” bidirectional closed-loop optimization model, it enables precise intraoperative guidance for osteotomy, drilling, and internal fixation placement, effectively addressing positioning difficulties caused by absent bony anatomical landmarks in traditional approaches; it also reduces intraoperative C-arm fluoroscopy use and shortens operative time [11]. The successful implementation in this case not only provides a high-precision treatment solution for this rare severe deformity but also highlights the critical value of digital orthopedic technologies in advancing precision orthopedic surgery.

Case Report

Presentation

A 12-year-old boy presented to our hospital with marked deformities of both lower limbs. Orthopedic examination revealed the characteristic “shepherd’s crook” deformity of both femurs, accompanied by deformities of the left tibia and fibula. On physical examination, there was tenderness in both hips, marked limitation of hip joint mobility, and a limping gait. Preoperative imaging confirmed the diagnosis of polyostotic fibrous dysplasia, involving both femurs, the left tibia, and multiple skeletal sites throughout the body, resulting in severe bilateral lower-limb deformities (Figure 1).

Figure 1.

(A) Preoperative X-ray. (B) Preoperative CT scan.

Preoperative Virtual Planning and Guide Preparation

To develop an individualized corrective plan, the surgical team first imported the patient’s imaging data in DICOM format into MIMICS 21.0 software (Materialise, Leuven, Belgium) to construct a 3D model extending from the pelvis to the ankle. The model was then exported in STL format and imported into ImageWare 13.0 software (UGS Corporation, Plano, TX, USA) for detailed evaluation of the lower-limb pathology through model rotation. Baseline reference lines, including the lowest point of the ischial tuberosity, the line connecting the femoral head centers and femoral mechanical axis, as well as the line connecting the knee midpoint, tibial mechanical axis, and ankle midpoint, were established to align the pelvis, femur, and tibia/fibula into the standard anatomical position. This alignment enabled measurement of anatomical parameters (Figure 2, Table 1), simulation of femoral osteotomy, plate placement, and design of surgical guides.

Figure 2.

(A) Sagittal femoral bowing angle. (B) Coronal femoral angle. (C) Femoral anteversion angle. (D) Neck–shaft angle. (E) Femoral angle. (F) Mechanical axis deviation angle. (G) Femur-tibia angle.

Table 1.

Summary of preoperative 3D anatomic measurement parameters.

Parameter	Right side	Left side
Femoral sagittal plane angle	2.13°	29.23°
Femoral frontal (coronal) plane angle	51.49°	47.94°
Anterior tilt angle	0.18°	2.64°
Neck-shaft angle	63.20°	31.42°
Femoral angle	75.59°	70.77°
Angle between force line and axis	19.52°	12.87°
Tibial angle	88.76°	86.19°
Bone-tibial angle	170.03°	169.02°
Hip-knee condylar angle	176.21°	175.29°
Lower-limb length	683.63 mm	704.85 mm

On the precisely aligned 3D model, virtual simulations of femoral osteotomy and corrective plate placement were subsequently performed. By comparing the pathological femur with the contralateral normal femur, the surgical team determined the osteotomy location and angle required to achieve anatomical realignment, and predicted the appropriate plate size and optimal placement strategy. Preliminary assessment of postoperative outcomes was also conducted during the simulation, which informed the design of patient-specific osteotomy and corrective guides (Figure 3).

Figure 3.

(A) Simulation of normal right femur to align the deformed right femur with the normal anatomy. (B) Determination of the proximal subtrochanteric osteotomy line on the right femur. (C) Simulation of subtrochanteric osteotomy correction on the right femur. (D) Identification of the subtrochanteric osteotomy segment on the right femur. (E) Simulation of right femoral osteotomy correction. (F) Simulation of right femoral plate fixation. (G) Drill guide design matching for the right femur. (H) Osteotomy guide design matching for the right femur. (I) Auxiliary correction guide design matching for the right femur.

Finally, all design schemes were exported in STL format and fabricated into physical guide models using a 3D printer (Shining 3D, Hangzhou, China) with photosensitive resin material (Figure 4). The preoperative simulation of the left femur and fibula followed a similar process to that of the right femur; therefore, only the design procedure for the right femur is presented in this report.

Figure 4.

The red, yellow, and blue arrows indicate the deformity correction guide, drilling guide, and osteotomy guide, respectively.

Surgical Treatment

Under general anesthesia with endotracheal intubation, the patient was placed in the lateral decubitus position. A longitudinal incision was made along the lateral aspect of the right hip, followed by stepwise dissection to fully expose the femur. A Kirschner wire was first applied to secure the positioning guide. After confirming accurate placement, the positioning guide was removed and replaced with the corrective guide. Under the guidance of the corrective guide, additional Kirschner wires were inserted to define the placement of the corrective plate. Following accurate localization, femoral osteotomy and corrective realignment were performed using the osteotomy guide. After successful reduction of the femur, the corrective plate was positioned over the pre-placed Kirschner wires and secured with locking screws to complete internal fixation (Figure 5). The osteotomy gap was filled with the resected bone segment and supplemented with osteoinductive grafting (Figure 5D). The incision was then closed in layers. Osteotomy and corrective plate fixation of the left femur and left tibia were performed using the same technique; however, only the right-sided procedure is presented in this report.

Figure 5.

(A) The right femur is exposed. (B) Guide plate is placed for positioning. (C) Guide plate is used to guide osteotomy, and the right femoral proximal plate and proximal hip screws are placed. After reduction, the distal screws of the osteotomy are installed. (D) The osteotomy part is filled with autologous bone and bone induction.

Postoperative 3D Evaluation

Postoperatively, the patient’s lower limbs showed satisfactory symmetrical alignment (Figure 6A). Recovery was uneventful, with no incision infection or other complications. Radiological follow-up at 2 weeks postoperatively was compared with preoperative imaging (Figure 6B). In addition, postoperative CT data were reconstructed in 3D for parameter analysis, which demonstrated favorable restoration of anatomical indices (Table 2). Limb length was nearly balanced, with only mild shortening of approximately 9 mm on the right side. Comparison between pre- and postoperative imaging (Figure 6B), as well as between postoperative 3D models and the preoperative surgical plan (Figure 6C), confirmed a satisfactory corrective outcome.

Figure 6.

(A) Preoperative (A1) and postoperative (A2) clinical photographs of the lower extremity. (B) Preoperative (B1) and postoperative (B2) digital radiographs (DR). (C) Comparison between virtual surgical planning results and actual surgical results.

Table 2.

Summary of postoperative 2-week 3D anatomic measurement data.

Parameter	Right side	Left side
Anteversion angle (°)	27.76	10.41
Neck-shaft angle (°)	125.72	129.07
Femoral angle (°)	78.45	71.28
Angle between mechanical axis and anatomical axis (°)	6.18	5.53
Tibial angle (°)	170.03	169.02
Femoro-tibial angle (°)	170.03	169.02
Hip-knee-condylar angle (°)	176.21	175.29
Lower-limb length (mm)	707.25	716.25
Shortening difference (mm)	9 mm shortening

Discussion

We performed a literature review comparing our corrective approach versus other reported methods, showing significant our approach has advantages in precision, surgical efficiency, and safety.

Correction Precision

Common methods for shepherd’s crook deformity often use open closing-wedge osteotomies or Ilizarov external fixation frames. However, these techniques exhibit high dependence on anatomical landmark identification, where osteotomy angles and plate placement are significantly influenced by the surgeon’s experience and technical skill, resulting in substantial individual variability and error margins [12–14]. In contrast, this case used more refined preoperative simulation: not only designing patient-specific osteotomy and correction guides, but also conducting detailed comparisons of physiological and anatomical parameters of the affected limb. This scientific approach to surgical planning significantly improved the accuracy of osteotomy angles and orthopedic steel plate positioning.

Surgical Risks and Intraoperative Radiation Exposure Risks

After osteotomy, traditional surgical methods often require multiple intraoperative C-arm fluoroscopy to confirm the correction effect, which prolongs the operation time and increases the risk of radiation. Wan et al combined 3D printed guides with DHS internal fixation. The results showed that compared with the traditional group, the operation time of the guide group was shortened by about 25%, and the number of intraoperative fluoroscopies was reduced by nearly 50% [15]. In this case, 3 complementary guides were innovatively designed: the drilling positioning guide enabled the osteotomy guide and the reduction guide to be precisely positioned during surgery, shortening the operation time. The customized reduction guide enabled the orthopedic steel plate to be precisely aligned, and accurate correction could be achieved without intraoperative C-arm fluoroscopy, further shortening the operation time, minimizing the radiation exposure of patients and medical staff, and achieving the best correction effect.

Currently, preoperative virtual planning combined with 3D-printed guide technology has been applied in total hip arthroplasty and scoliosis correction surgeries, improving intraoperative precision and postoperative outcomes [16–18]. However, research on this technology for correcting bilateral shepherd’s crook deformity remains scarce; the success of this case provides critical reference value for this field. Despite significant advantages, the technology still faces limitations: prolonged guide design and printing cycles currently restrict its use in orthopedic emergency surgeries [19], and guides require high-precision matching with patient-specific anatomy, making imaging data accuracy and guide fabrication precision essential [20]. Additionally, orthopedic surgeons need specialized training to achieve proficiency, requiring a substantial learning curve. To overcome these barriers, future efforts should streamline guide design workflows, accelerate printing processes, implement standardized manufacturing protocols to reduce production time, and enhance clinical accessibility [21].

In summary, this case not only verifies the feasibility of preoperative virtual planning combined with 3D-printed guide technology for correcting shepherd’s crook deformity, but also appears particularly rare due to its severe deformity characteristics in the bilateral lower limbs. We successfully overcame the limitations of traditional surgery – dependence on the surgeon’s experience and expertise, and the need for repeated intraoperative fluoroscopy – achieving precise osteotomy and placement of orthopedic steel plates, significantly shortening operative time and reducing radiation exposure. This report not only fills the research gap in digital orthopedic technology for bilateral shepherd’s crook deformity correction, but also provides a new reference model for clinical treatment of complex skeletal deformities.

Conclusions

This case validates that preoperative virtual planning combined with patient-specific 3D-printed guides effectively enhances surgical precision, reduces intraoperative radiation exposure frequency, significantly shortens operative time, and mitigates risks of intraoperative bleeding and complications in complex skeletal deformity correction. The literature demonstrates that similar techniques achieve higher accuracy, reduced blood loss, and shorter operative duration when applied to complex anatomical sites – including high tibial osteotomy, spinal, elbow, and distal radius procedures. This case further confirms the method’s replicability and scalability, providing orthopedic surgeons with a mature, safe, and efficient treatment protocol.