Use of The Mirror-Image Technique for Patient-Specific Reconstruction of Cuboid Fractures

Introduction

Cuboid fractures are rare but serious injuries that can result in significant disability. The existing literature on cuboid fractures consists mainly of case reports and small case series, covering both adult and pediatric populations [1–3]. In the UK, the yearly incidence of cuboid fractures is about 1.8/10 000 foot fractures [4] and they account for 2–5% of all midfoot fractures in the USA [5]. Most of these fractures are observed as isolated avulsion fractures, with less frequent occurrences of combination with other midfoot fractures, dislocations, or Lisfranc joint injuries [6]. Isolated cuboid fractures present a challenging diagnosis, and many healthcare professionals are unaware of this fracture, which is often overlooked because most cuboid injuries are not severe [7]. However, delayed diagnosis and inappropriate treatment can result in long-term functional deficits and persistent pain.

The cuboid, shaped like a wedge, is an essential element of the lateral column. It is the only midfoot bone supporting the lateral column and significantly contributing to foot stability, and it is involved in all intrinsic movements of the foot [8]. Therefore, a full understanding of its normal anatomy and its relationship to foot biomechanics is essential for accurate diagnosis and favorable prognosis. It joins with the proximal facet of the calcaneus, the medial facet of the lateral cuneiform, and the distal facets of the 4th and 5th metatarsals. In 25% of the population, there is an additional connection with the navicular bone. The dorsal calcaneal and medial cuboidal tuberosities, along with a system of sturdy ligaments, provide stability to the calcaneocuboid joint during weight-bearing [9]. The calcaneocuboid joint has minimal mobility, with all lateral column movement occurring distally at the tarsometatarsal joints. The range of motion of the lateral tarsometatarsal joints can be up to 3 times greater than that of the medial tarsometatarsal joints [10]. The peroneal groove, situated on the plantar surface of the cuboid, extends plantarly and medially towards the point of insertion of the tendon into the first metatarsal. During contraction of the peroneus longus, the cuboid functions as a fulcrum. Furthermore, the lateral plantar artery supplies blood to the cuboid. Open reduction and plate fixation is the standard surgical treatment for displaced cuboid fractures. This method offers a reconstruction that is stable from a biomechanical perspective and enables early mobilization, and accommodates fracture compression. However, the complex anatomy of the cuboid presents challenges to the traditional surgical approach, which relies on surgical experience and comparison with radiographs of the unaffected side. The traditional method may fail to fully restore the anatomical morphology of the cuboid. As a result, the longer operative time required can increase the overall risk, including complications such as infection, skin necrosis, non-union, and chronic pain due to loss of lateral column length and failure to restore joint congruity.

Fortunately, the advent of 3D-printing technology has made it possible to create customized templates prior to surgery, based on either a 3D replica of the patient’s bony anatomy or a mirror-imaged 3D model. This development has significantly reduced the duration of the surgical procedure [11–13]. In our study, we provide a new technique that uses a customized guide template to aid intraoperative reduction. In patients with unilateral displaced cuboid fractures, a CT scan of both cuboids is performed. Using the mirror imaging technique, a mirror-image model of the fractured cuboid is created based on the contralateral side. An individual guide template is then designed using this mirror-image model. The guide is used as an intraoperative reference to achieve anatomical reduction of the fracture.

Material and Methods

INDICATIONS:

This method is specifically recommended for unilateral displaced cuboid fractures requiring surgery. It is particularly useful for fractures with lateral column depression in which attaining anatomical reduction using only open reduction is challenging. In addition, patients with fractures that have poor soft-tissue quality, which can lead to a higher risk of wound complications following open reduction, may benefit from this novel technique, which offers a minimally invasive approach and reduces operative time.

It is important to note that the contralateral uninjured cuboid must be free of any fractures, deformities, or previous surgical procedures to be considered suitable for the creation of an anatomically pre-contoured locking plate template, which will ensure the accuracy and effectiveness of the guide during surgery. Shortening of the cuboid lateral column was more than 3 mm without medial column injuries in this study.

During the operation, the guide serves as a valuable reference for achieving reduction of the lateral column. By using the guide, the surgeon can precisely restore the lateral column’s length and alignment, which improves the stability and functional results of reconstructing the cuboid fracture.

PATIENTS:

This study was approved by the Ethics Committee of Wuhan Fourth Hospital (decision no: KY2024-092-01). Informed consent forms were signed by all patients. According to the above indications, a retrospective analysis was conducted on the data of 10 patients who underwent surgery for cuboid fractures at our clinic between January 2018 and March 2023. The diagnosis of the patients was made based on the X-ray and computed tomography (CT) scan.

3D PRINTING OF THE TEMPLATE:

The primary instrument for collecting data for 3D printing is the CT scan, which captures images of both cuboids at a 0.625 mm slice thickness. This information is archived in the DICOM (Digital Imaging and Communications in Medicine) format. Surgeons may either collaborate with commercial entities that offer specialized 3D printing services or employ in-house 3D printers to develop and fabricate tailored guide templates. An expanding array of commercial services is available, adept at transforming DICOM information into the STL (Standard Triangulation Language) format, which is compatible with 3D printers.

To initiate the 3D printing process, patient approval is secured for the use of their data along with a contract with the 3D printing firm to safeguard the confidentiality of the data and ensure its eradication after the guide’s creation. The DICOM data is then transmitted to the appointed 3D printing service provider, which then reconstructs the 3D model using refined software, notably the Materialise Interactive Medical Image Control System Software (MIMICS) from Materialise in Belgium. The uninjured cuboid is mirrored through a specialized imaging technique to accurately replicate the pre-damaged state of the afflicted cuboid (Figure 1). In addition, the specific locking plate for cuboid fractures is scanned (Figure 2), allowing the lateral surface and anteroposterior articular surface lines of the cuboid to be precisely determined. Finally, a patient-specific template for the cuboid fractures is meticulously designed (Figure 3).

SURGICAL TECHNIQUE AND POSTOPERATIVE MANAGEMENT:

The patient is placed in the supine position on a radiolucent table under lumbar or general anesthesia. Radiographs (Figure 4) show the shortening of the lateral column of the cuboid, while CT scans (Figure 5) help to identify comminuted fractures involving the articular surfaces of the metatarsal and calcaneocuboid.

After sterile draping, a longitudinal incision is made on the lateral dorsum of the foot above the cuboid and along the lateral border of the extensor digitorum brevis muscle. Special care is taken to protect the sural nerve in the vicinity of the incision and to preserve the long and short peroneal tendons and the tendon of the third peroneal muscle throughout the procedure. Care is also taken to protect the flap as it is elevated to access the calcaneocuboid joint close to the lateral wall of the cuboid bone. The fourth–fifth tarsometatarsal joint and the calcaneocuboid joint are fully exposed using a Kirschner wire spreader, allowing clear visualization of the articular cartilage surfaces. Displacement or collapse of the articular surface fracture is often observed.

The next step is reduction of the fracture and elevation of any collapsed bone, followed by temporary fixation with Kirschner wires. The long axis shortening of the cuboid is carefully corrected, and if a bone defect remains after satisfactory reduction, autologous or allograft bone grafting may be performed. The customized guide template is then placed on the lateral side to ensure accurate reduction, particularly in terms of lateral column length and articular surface alignment (Figure 6). Once a satisfactory reduction is confirmed, a special rectangular locking plate is positioned on the outer and upper side of the rectangular and secured with screws. Fluoroscopy is used to verify the adequacy of reduction, fixation and screw length. In the case of midfoot fractures or dislocations, the cuboid reduction and temporary Kirschner wire fixation are performed first, followed by reduction and internal fixation of other fractures and dislocations. Finally, the cuboid is fixed with a plate after the length of the lateral column has been restored.

Once the incision has been closed, a short leg brace is applied to protect the leg. Prophylactic antibiotics are given for 2 days as a routine measure. Non-weight-bearing foot functional exercises are initiated from the first postoperative day, with brace protection applied after each session within 6 weeks postoperatively. The timing of weight-bearing is determined by fracture healing as assessed by regular radiographs at 6, 12, and 24 weeks postoperatively. At final follow-up, patients undergo a questionnaire-based assessment and physical examination, with the American Orthopaedic Foot & Ankle Society (AOFAS) Ankle-Hindfoot Scale used to evaluate treatment efficacy.

STATISTICAL ANALYSIS:

IBM SPSS Statistical software (version 24, IBM, Somers, NY, USA) was used for statistical analysis. The paired-samples t test was used to analyze significant differences in AOFAS between the different time points in the treatment period. Results were presented as mean±SD. P value <0.05 was considered statistically significant.

Results

The 10 patients in this study were treated with the mirror-image technique. The basic characteristics of the patients (Table 1) were mean age 43.6±17.9 years, sex distribution (male: female ratio, 6: 4), and injury classification (traffic, trauma, fall). The mean incision length was 5.59±0.5 cm, the mean operative time was 55.6±4.8 min, the mean blood loss was 25.3±3.7 ml, the mean fluoroscopy time was 15.2±2.0 s, and the time to fracture union was 11.7±1.6 weeks.

Comparisons of AOFAS functional scores over time are summarized in Table 2. The mean score was 52.1±2.7 in the preoperative period and 93.1±3.1 at 6 months postoperatively. The AOFAS score was significantly different between the preoperative and the 6-month postoperative scores.

Discussion

Cuboid fractures are often high-energy injuries and are commonly associated with Lisfranc dislocations and other tarsal and metatarsal fractures [8,14–16]. Comminuted fractures of the cuboid, known as nutcracker fractures, typically result from direct impact to the lateral aspect of the foot. The cuboid bone has a pyramidal shape, with the base medial and the apex lateral. It consists of 6 bony surfaces – 3 non-articular and 3 articular [17]. Isolated cuboid fractures are rare and are often associated with complex dislocation fractures involving adjacent bones such as the calcaneus or lateral cuneiform base [18]. Therefore, when diagnosing a cuboid fracture, it is important to consider the possibility of associated fractures in other foot structures and to perform appropriate imaging studies, such as CT or MRI, to avoid missed diagnosis.

Displaced cuboid fractures can result in significant bone shortening and articular surface damage. The lateral tarsometatarsal joints have greater mobility than the 3 medial tarsometatarsal joints [10], making the lateral aspect of the cuboid crucial to maintaining foot stability. Failure to properly restore the lateral column length can result in persistent talar subluxation and long-term joint changes [19]. Non-operative treatment often results in poor outcomes, highlighting the importance of open reduction and internal fixation. The surgical goals are to restore lateral column length, preserve cubo-metatarsal joint mobility, and restore calcaneocuboid joint integrity [20]. Weber and Locher [21] reported good results in 12 compression cuboid fractures by open reduction, bone grafting where necessary, and fixation. Given the critical role of the cuboid, fractures and joint damage should be carefully reduced and fixed with stable internal fixation, and bone grafting may be required in cases of bone defects. Surgical reduction should prioritize restoration of lateral column length, followed by preservation of cubo-metatarsal joint mobility and repair of the calcaneocuboid joint.

Application of patient-specific 3D models or mirror-image technique is not uncommon in orthopedic surgery [13,22,23]. However, mirror-image technique combined with the guide template based on 3D printing have been rarely reported in cuboid fractures. Lateral column length restoration in cuboid fractures is challenging due to the irregular shape of the bone. Previous studies have used radiographic comparisons with the unaffected side for analysis, but this approach is limited to preoperative planning and postoperative comparisons, and achieving consistent symmetry in position and angle is difficult, often requiring repeated fluoroscopy. In the absence of an accurate design or method for anatomical reconstruction, the procedure can result in significant bone shortening and articular surface damage, which can lead to persistent subluxation of the cuboid and long-term joint changes, prolonging operative time and increasing the difficulty of surgery. In our study, we used the mirror principle to contour the posterior surface of the affected side and created a reduction guide plate to assess the reduction in length and articular surface. The use of a specially designed cuboid locking plate provided superior fixation and support for anatomical reconstruction of the cuboid and achieved satisfactory results, with the AOFAS score increasing from 52.1±2.7 to 93.1±3.1 between preoperative and 6 months postoperative assessments.

Of course, our study has some limitations. Firstly, it was a retrospective analysis with a relatively small number of patients. Secondly, humans have left-right symmetry in their limbs and skeleton, with the major exception of the internal organs. This bilateral symmetry is the basis for the use of mirror technology in fracture healing, and it is important to verify the necessary symmetry before using mirror technology. Thirdly, this study obviously lacked this experimental verification. Finally, this study focused primarily on reduction of the lateral surface length and the cubo-metatarsal and calcaneocuboid joint surfaces, without considering repair of the deep peroneal longus tendon groove. Inconsistent repair of this groove may lead to fibrosis and dysfunction of the peroneal longus muscle.

Conclusions

Although our study has the above limitations, we achieved satisfactory function by using the mirror fracture reduction technique and a guide plate. This new method is an alternative consideration for the treatment of cuboid fractures.