Three-Dimensional Printed Anatomical Models Help in Correcting Foot Alignment in Hallux Valgus Deformities

Abstract

Background

Hallux valgus (HV) is the most common pathologic entity affecting the great toe. The goal of corrective surgery is to restore foot mechanics and provide pain relief. The purpose of the study was to create individual angle using life-size foot models with three-dimensional (3D) printing technology to design a section on HV osteotomy.

Materials and Methods

Ten female patients with a diagnosis of HV were included. Radiologic [HV angle and intermetatarsal (IM) angle] and clinical [American Orthopaedic Foot and Ankle Score (AOFAS)] assessment was done pre- and postoperatively. All the operations were planned together with 3D life-size models generated from computed tomography (CT) scans. Benefits of using the 3D life-size models were noted. The 3D model’s perception was evaluated.

Results

The mean AOFAS score, mean HV, and IM angles had improved significantly (P < 0.05). The visual and tactile inspection of 3D models allowed the best anatomical understanding, with faster and clearer comprehension of the surgical planning. At the first tarsometatarsal joint, the HV models showed significantly greater dorsiflexion, inversion, and adduction of the first metatarsal relative to the medial cuneiform. At the first metatarsophalangeal joint, the HV models showed significantly greater eversion and abduction of the first proximal phalanx relative to the first metatarsal. It provided satisfactory results about operation time and blood loss. 3D model’s perception was statistically significant (P < 0.05).

Conclusion

3D models help to transfer complex anatomical information to clinicians, which provide guidance in the preoperative planning stage, for intraoperative navigation. It helps to create a patient-specific angle section on osteotomy to correct IM angle better and improve postoperative foot function. The 3D personalized model allowed for a better perception of information when compared to the corresponding 3D reconstructed image provided.

Introduction

Hallux valgus (HV) is one of the most common and significant diseases of the forefoot among elderly people (2–4%) [1–4]. It occurs with the lateral deviation of the great toe and medial deviation of the first metatarsal. Most feet with HV exhibit hypermobility of the first ray [5–7]. Many studies have investigated HV associated with hypermobility of the first tarsometatarsal joint and the first ray (first metatarsal and medial cuneiform) [8–10]. The first ray forms the medial longitudinal arch, which absorbs the load, acts like a spring, and has a very important function during locomotion [7–12]. Therefore, deformities of the first ray readily disrupt the integrity of the foot structure, possibly leading to the onset of HV [12–15].

HV is a complex deformity including a variety of pathologies on toes [16–19]. This is likely because many aspects of the etiology and pathology of HV remain unclear. There is a female predilection for this condition [11, 16]. Several reports have suggested an age of onset peaking in the 3rd to 5th decades of life, while others have reported a high incidence of onset (46–92%) in the juvenile and adolescent years before skeletal maturation [4, 13]. Occupation shoe wear, genetic predisposition, and pes planus have been implicated as causes of HV in adults with little if any critical supporting evidence. Patients with HV typically complain of over medial eminence, metatarsophalangeal joint pain, intolerance of shoe wear, bursal or skin irritation, ulceration, or infection [1, 2, 9, 18, 19].

There are many foot abnormalities seen in HV. Among these are metatarsus primus varus, first metatarsal pronation, exophytic growth at the distal edge of the metatarsal, hypertrophy of the bursa over medial protrusion and inflammation (bunion), and lateral deviation of the great toe [20–24]. Apart from this, degenerative osteoarthritis, callus formation, sesamoid subluxation at the inferior of the metatarsal edge, and subluxation of the first metatarsophalangeal joint may accompany [13, 25]. Therefore, not only the anatomy of the great toe but also whole foot needs to be analyzed thoroughly [26–30]. For this reason, approximately 130 types of surgical treatment have been defined for HV [22, 26, 31–35]. Chevron osteotomy of the first metatarsal is the most commonly applied procedure. Following osteotomy, development of avascular necrosis, delayed union, or nonunion are among common complications.

The goal of corrective surgery is to restore foot mechanics and provide pain relief, so that patients can return to their desired activity level. However, confidence in the comprehension of anatomical, pathological, and structural complexities which surgeons require to conduct osteotomies may not always be supported by two-dimensional (2D) imaging alone. Therefore, resections of foot osseous tissue require patient-specific complex anatomical and pathological features.

The 3D models help to transfer complex anatomical information to clinicians, which provide guidance in the preoperative planning stage, for intraoperative navigation and for surgical training purposes [36–38]. 3D printing technology is a kind of individualized and digital method to design operation. The innovative developments in intraoperative stereotactic navigation have added to the accuracy and preciseness for addressing pedal surgery.

The aim of the study was to plan on the surgeon’s ability to reconstruct 2D images into 3D models and plan resection margins and the amount of lateral deviation. Modeling has helped to determine landmarks of the treatment by creating algorithm. The first toes demonstrated the roundness of the first metatarsal head radiographs (the so-called round sign) significantly. Torsion of the metatarsal head with respect to the base has been investigated previously in the field of physical anthropology [4, 11], but no studies have actually tried to identify the possible difference in first metatarsal torsion in 3D patient-specific foot model cases.

The aim of this study is to present the benefits of the guidance of life-like 3D models in presurgical planning for corrective surgery. It has been used to aid in the change of alignment, visualize operative margins, and plan V-shaped osteotomy and the amount of lateral deviation to help to optimize surgical intervention.

Materials and Methods

Patient Characteristics and Clinical and Radiologic Assessments

The study included ten female patients with HV who underwent surgery with the guide of 3D personalized models between 2016 January and 2018 September at our hospital (Fig. 1; Table 2). The inclusion criteria were as follows: (1) patients who underwent an operation after having undergone unsuccessful conservative treatment and (2) those operation made together with 3D personalized models. The exclusion criteria were as follows: patients with a history of prior foot surgery, rheumatoid arthritis, or hallux rigidus. Conservative treatment, including shoe modification, nonsteroidal anti-inflammatory medications, and arch supports, had failed in all the patients. Both feet were examined in all the patients and included inspection and palpation with attention to the posture of the foot, the presence of bunion, the appearance and alignment of the great toes, first/second metatarsophalangeal and ankle joint range of motion, and the first/second-ray mobility. Preoperative standing radiography and preoperative computed tomography (CT) imaging and postoperative standing radiography are taken, and the HV angle, intermetatarsal angle (IM angle), and lateral sesamoid subluxation angle measured for three times by two orthopedic surgeons were evaluated. Classification of severity of HV deformities made according to Table 1. The International Classification of Diseases specific codes (ICD-10), the World Health Organization, Geneva, Switzerland), and the American Orthopaedic Foot and Ankle Score (AOFAS) were used to estimate patient accrual rates [39, 40]. Statistical significance was defined at the 5% (P = 0.05) level.

Fig. 1.

Case of bilateral hallux valgus (a). Preoperative standing radiographs, including the HV angle and the first–second intermetatarsal angle (b)

Table 2.

Preoperative and postoperative angle values of patients

Patient	Age	Side	Preop. HV angle	Postop. HV angle	Preop. IM angle	Postop. IM angle	Preop. AOFAS	Postop. AOFAS
N.A.	51	L	38.3	16.9	13.8	4.1	Pain: 20/40 Function: 27/45 Alignment: 0/15 Total: 47/100	Pain: 40/40 Function: 40/45 Alignment: 8/15 Total: 88/100
B.T	32	R	41.8	15.6	13.2	8.6	Pain: 20/40 Function: 21/45 Alignment: 0/15 Total: 41/100	Pain: 40/40 Function: 40/45 Alignment: 15/15 Total: 95/100
D.A.	48	L	32	12.4	14.2	7.8	Pain: 30/40 Function: 27/45 Alignment: 0/15 Total: 57/100	Pain: 40/40 Function: 40/45 Alignment: 15/15 Total: 95/100
N.T.	66	R	49.3	15.5	14.4	9	Pain: 20/40 Function: 21/45 Alignment: 0/15 Total: 41/100	Pain: 40/40 Function: 35/45 Alignment: 8/15 Total: 83/100
F.S.	72	R	31.4	13.4	14.1	8.5	Pain: 30/40 Function: 27/45 Alignment: 0/15 Total: 57/100	Pain: 40/40 Function: 40/45 Alignment: 8/15 Total: 88/100
F.K.	25	L	47.8	10.7	14	5.2	Pain: 20/40 Function: 21/45 Alignment: 0/15 Total: 41/100	Pain: 40/40 Function: 40/45 Alignment: 15/15 Total: 95/100
F.Z.	65	R	30.5	11.6	13.5	7.8	Pain: 30/40 Function: 27/45 Alignment: 0/15 Total: 57/100	Pain: 40/40 Function: 40/45 Alignment: 15/15 Total: 95/100
A.T.	71	R	38.6	12.2	14.6	9.5	Pain: 20/40 Function: 27/45 Alignment: 0/15 Total: 47/100	Pain: 40/40 Function: 40/45 Alignment: 15/15 Total: 95/100
S.D.	67	L	35.2	11.3	13.2	5.8	Pain: 30/40 Function: 27/45 Alignment: 0/15 Total: 47/100	Pain: 40/40 Function: 40/45 Alignment: 15/15 Total: 95/100
O.O.	61	L	38.7	9.5	13.3	7.9	Pain: 20/40 Function: 27/45 Alignment: 0/15 Total: 47/100	Pain: 40/40 Function: 40/45 Alignment: 15/15 Total: 95/100
Mean ± SD	59.3 ± 15.8		38.4 ± 6.5	12.9 ± 2.4	13.8 ± 0.5	7.4 ± 1.8	48.2 ± 6.6	92.4 ± 4.4
	Range: 25–72		Range: 30.5–49.3	Range: 9.5–16.9	Range: 13.2–14.6	Range: 4.1–9.5
			P < 0.05		P < 0.05		P < 0.05

HV hallux valgus, IM intermetatarsal, AOFAS American Orthopaedic Foot and Ankle Score

Table 1.

Classification of hallux valgus

Classification of hallux valgus	Hallux valgus angle	Intermetatarsal angle	Lateral sesamoid subluxation (%)
Mild	< 20°	< 11°	< 50
Moderate	20°–40°	11°–16°	50–75
Severe	> 40°	> 16°	> 75

Creating of the Three-Dimensional Models

Before the surgery, 3D model was created for the cases to reshape the great toe and alignment and plan the course of the operation more effectively. With the help of life-size 3D model, misaligned foot was planned preoperatively for the Chevron osteotomy (Figs. 2, 3, 4). 3D model was created with four steps: CT data acquisition, image segmentation, image data editing, and 3D printing. Data for 3D personalized models can be obtained from CT using the Digital Imaging and Communications in Medicine (DICOM) software.

Fig. 2.

Three-dimensional printing foot model with support

Fig. 3.

Detailed view of the first ray and second fingers on 3D foot model

Fig. 4.

Under the first metatarsal head, two sesamoid bones have appeared on three-dimensional model

DICOM data from the CT sections of the patients were imported with the free 3D Slicer (version 4.10.1) software. The appropriate threshold values were segmented and identified. The data images were processed using segmentation and mesh generation tools, and were converted to a standard tessellation language file for printing (Figs. 5, 6a, b). The axis of the tibia was used as the z-axis, the vector product of the line connecting the center of the calcaneus with the head of the second metatarsal bone and the z-axis was used as the x-axis, and the cross product of the z- and x-axes was used as the y-axis.

Fig. 5.

Axial torsion of the head of the first metatarsal and second phalanx malalignment with standard tessellation language files

Fig. 6.

Three-dimensional images indicating motion around each axis (front in a, left side in b). X-axis = vector product of the line connecting the center of the calcaneus with the head of the second metatarsal bone and the z-axis, y-axis = vector product of the x-and z-axes, and z-axis = axis of the tibia. Motion around the x-axis = plantar flexion/dorsiflexion, motion around the y-axis = eversion/inversion, and motion around the z-axis = adduction/abduction

Recorded images were overlaid and modeled in three dimensions in STL format. The STL format 3D model was smoothed with a free “Autodesk Meshmixer (version 3.4.35)” software (Autodesk, San Rafael, California, USA). Movement of the x-axis was defined as plantar flexion–dorsiflexion, movement of the z-axis was defined as adduction–abduction, and movement of the y-axis was defined as eversion–inversion (Fig. 6a, b). Each joint that composes the first ray, namely the talonavicular joint, the medial cuneonavicular joint, the first tarsometatarsal joint, and the first metatarsophalangeal joint, was aligned using its respective proximal bone. Image postprocessing time was approximately 7 h per anatomic misalignment of each foot model.

3D printing technologies include stereolithography, selective laser sintering, inkjet, and fused deposition modeling. Finally, Simplify3D (Version 4.0) software was made available for printing. Proposed models with misalignment together with the topographic neighbors were printed with Mass Portal Pharaoh xd 20 ve Formlabs 2 (Fig. 1). We used PLA White filament 1.75 mm–750 gr for printing process. Each model took approximately 10 h to print.

Surgical Technique

Under spinal anesthesia supine position, anatomical landmarks and the proposed incision were marked on the skin (Fig. 7a, b). Distal incision was made on the capsule opening to the dorsomedial of the first metatarsophalangeal joint (Fig. 8a). After the excision of medial exostosis 1 mm medial to the sagittal sulcus, parallel to the medial aspect of the foot, V-shaped (45°–60°) first metatarsal head was osteotomized in transverse position using Medtronic Midas Rex^® Legend^® Electric Motor with apex of the proposed Chevron osteotomy to the first metatarsophalangeal joint (Fig. 8b). The first metatarsal head slides laterally by around 5^4–6 mm measured from 3D print preoperatively (Fig. 9). The degree of correction was confirmed by intraoperative fluoroscopy. For fixation and rotational stability, fixation of two K-wires was preferred with a 0.062-in. Medial protrusion of the first metatarsal proximal to the osteotomy line was excised. Excess medial capsule was trimmed off, and the capsule was imbricated while holding the toe in a position of reduction. With a 2–0 absorbable suture, the medial capsule closed. The skin was closed with nonabsorbable sutures (Fig. 8c). A derotational bunion dressing was placed around the great toe and midfoot. The postoperative radiograms were taken (Fig. 10). The patients were discharged with a short leg cast to remain nonweight-bearing and advised to elevate the foot above the heart and icing for 10 days.

Fig. 7.

Preoperative condition (a). Planning of osteotomy orientation point and demarcation line at patient’s first ray (b)

Fig. 8.

Application of partial osteotomy to orientation points (a). Navigated instruments allow confirmation of adequate resection before real osteotomy (b). Postoperative position (c)

Fig. 9.

The first metatarsal head shows significantly greater eversion, arrow bunion (a), and orientation point and demarcation line using patient-specific model (b)

Fig. 10.

Postoperative control radiograph at the 1st month [intermetatarsal angle 4.08° (a) and hallux valgus angle 16.9°(b)]

Postoperative Management

Casts were removed and partial weight-bearing was started after 10 days. All stitches were removed at the end of the 2nd week after the operation and. Physical examination including for complications (pin-tract infections, reduction failure, and metatarsophalangeal joint motion) was made 2 weeks after the operation and at the end of the 1st month. The Kirschner wires were excluded removed at the end of 45 days. Low-molecular-weight heparin was given for 30 days. During the 1st year after the operation, the patient was followed at 1 week, 3 weeks, 3 months, 6 months, and 1 year using a self-developed item set for demographic data. At the last follow-up (postoperative 6–18 months), there was no problem at surgical site and loss of reduction.

Evaluation the Three-Dimensional Model’s Perception

A questionnaire developed by the researchers was used to determine the perceptions of the resident doctors about the 3D model. The questionnaire consists of seven items. The rating of the questionnaire ranges from 0 to 10. In addition, at the end of the questionnaire, the students were asked to open-ended questions whether 1:1 solid model was found useful. Resident doctors were asked to answer the questionnaire by examining the radiograph, the computed tomography image, and the 3D model of the HV case. The internal consistency coefficient was calculated for the reliability study of the questionnaire.

Ethics approval for this study was obtained from our university’s Human Research Ethics Committee (18-5/41).

Results

Reoperative Physical Examination and Clinical Outcome

On examination, there was tenderness around the great toe as medial eminence. Bursal or skin irritation, medial deviation of the first metatarsal lateral deviation of the hallux, pronation of hallux, and splayfoot were found all the cases (Fig. 1a). On physical examination, there was a limitation of the mobility of the second toe at the distal interphalangeal joint, great toe at the metatarsophalangeal joint, and in some (4 patients), callus and bunion on medial edge. In addition, HV and hammertoe deformity were present bilaterally (Figs. 1a, 5, 6a, 7a). The AOFAS improved significantly postoperatively (P < 0.05). Patients’ codes as ICD-10: M20.1, pre- and postoperative AOFAS scores, are listed in Table 2. At the last follow-up (postoperative 6–18 months), there was no problem at surgical site and loss of reduction. Toes were successfully realigned anatomically without damaging the neighboring neurovascular anatomical structures (Fig. 10a, b). No operative complications were reported in all the cases (Fig. 8a, b).

Radiologic Outcome

Successful union was observed at the osteotomy sites in all the patients. There was no delayed union in any patient. In this study, seven patients (70%) were classified as moderate HV and three patients (30%) were classified as severe HV. The mean HV and IM angles significantly decreased from 38.4 ± 6.5° (range 30.5–49.3) and 13.8 ± 0.5° (range 13.2–14.6) preoperatively to 12.9 ± 2.4° (range 9.5–16.9) and 7.4 ± 1.8° (range 4.08–9.5) postoperatively, respectively (P < 0.05 for all) (Table 2).

Patient-Specific Three-Dimensional Model and Benefit Perception

Before the surgery, 3D model was created for the cases to reshape the great toe and alignment and plan the course of the operation more effectively. There was a high degree of correlation between 3D model dimensions and measurements (HV angle, IM angle, and subluxation angle) made on the 3D foot model. The HV angle was measured ranging between 20° and 40° in seven patients and > 40° in three patients, the first–second IM angle as < 16°, and lateral sesamoid subluxation angle as 50–75%.

In the study, the Cronbach’s alpha coefficient calculated for reliability was found to be 0.86. According to this finding, it can be said that the survey is reliable. The Friedman test was applied to compare the perceptions of the residents on the radiograph, computerized tomography, and 3D model. A statistically significant difference was found between the perceptions of residents (P < 0.05). Resident doctors have more positive perceptions about 3D model (Fig. 11). Resident doctors stated that they found a 1:1 solid model useful. These benefits include: they planned the osteotomy site, sesamoid rotation and planning the intervention needed, shortening the operation time, determining the level of osteotomy, ease of deformity, ease of preoperative preparation plan, reduction of bleeding amount, shortening of scopy time, and patient relatives to provide better visual surgery. Surgeons also demonstrated that the 3D personalized model allowed for a better perception of information related to structural depth and spatial relationships when compared to the corresponding 3D reconstructed image provided (Figs. 2, 3, and 4).

Fig. 11.

Perception of the resident doctors on 3D print model

Both surgeons and 3D team believed that 3D life-size model would be useful in the process of identifying a safe surgical pathway, in addition to intraoperative navigation and orientation. It was also suggested that the life-size models might be a useful supplementary tool for surgical team when learning how to interpret multiplanar medical images (Figs. 2, 3, 4, and 7a, b).

3D life-like models were revealed the course of the coronal and sagittal plane angles that can extend within bone osteotomy border. It also enabled to designate safe osteotomy corridor while preserving the vascular structures. This provided right and safe guidance and anatomical landmarks for the intervention. 3D life-size models also assisted in the decision making of the fixation of the remainder bone in the foot, following partial osteotomy. In all of our patients, we applied fixation with two Kirschner wires. An orthopedic surgeon was able to confirm that the 3D models could reduce operating time by replacing the need for intraoperative visualization aid, although they both believed in the potential for the models to reduce the chance of intraoperative complications in complex foot misalignment.

The results of this study were not able to confirm whether the size of the printed model had an impact on the viewer’s ability to identify or distinguish the details of foot alignment anatomy. With the help of 3D model, the borders of the partial osteotomy, realigned foot with corrected angles, and bone were observed. Partial osteotomy was planned to perform under 3D patient-specific model guidance without complications (Figs. 7b and 9a–c).

Discussion

Malpracticing corrective pedal surgery may result in a variety of complaints such as continuous foot pain and avascular lesion and has the potential to influence life quality drastically [1, 2, 17, 21, 39]. Before the surgery, the surgeon needs to know the change in the anatomical misalignment of the bone and the deformity caused by the unrelieved foot pain. The use of visualization techniques such as transparency and overlays allows viewers not only to see the great toe in operative field but also the whole foot alignment and their spatial relationships (Figs. 3, 4, 9a, b) [14, 25, 40–42].

Most corrective surgical procedures involve osteotomizing the first metatarsal or fusing its adjacent joints to realign the first ray [12, 17]. However, these procedures have their own trade-offs with regard to the amount of correction that can be provided and length of postoperative recovery [15, 26]. For example, a head or distal osteotomy can only correct mild deformities, since the metatarsal head can only be moved over a limited amount to maintain the desired 60% bone-to-bone contact between the capital fragment and the metatarsal [41, 42]. While a proximal metatarsal osteotomy provides a better IM angle reduction compared with a distal osteotomy, this procedure is associated with complications such as nonunion, malunion, recurrence, avascular necrosis, and first metatarsal shortening [13, 24]. Some proximal osteotomies also require the patient to be either nonweight-bearing or in a boot or sandals for 6 weeks.

Neither the magnitude of the preoperative angular deformity nor increasing age had any association with the magnitude of the first metatarsophalangeal joint range of motion. Constricting shoes and occupation were implicated by all the patients (100%) as a cause of the bunions (Fig. 1a) [3, 4, 18]. A familial history of bunions, bilateral involvement, female gender, a long first metatarsal, and an oval or curved metatarsophalangeal joint articular surface were common findings (Fig. 1a) [33, 39]. Increased first-ray mobility and plantar gapping of the first metatarsocuneiform joint were more common in patients with HV than in the general population (when compared with historical controls) [5, 44].

Hypermobility of the first ray has been reported in various studies [14, 17, 20]. However, besides the present study, only a few studies have investigated the mobility of the intercuneiform 1–2 joint to date, and there are still many unclear points about the mobility of this joint [41–44]. This uncertainty is thought to be attributable to the medial and middle cuneiform in the joint being relatively small, and its mobility is expected to be small. Moreover, on simple radiography, the bone appears different depending on the angle, and it is difficult to evaluate the bone critically because of the lack of anatomical features [2, 3]. There is still debate about whether or not tarsometatarsal joint hypermobility is a major cause of deformity in HV (Figs. 4, 6). The results of this study suggest that HV deformity of the foot causes a significant displacement not only at the tarsometatarsal joint but also at the other joints that constitute the first ray (Figs. 3, 4). This suggests that hypermobility extends across the entire first ray. In addition, there may be a deformity of the second toe similar to hammertoe with a frequency of two patients 20% as in our case. However, the surgical algorithm used in this study enabled us to superimpose, without registering anatomical features, 3D bone models generated from CT images.

The results of the present study clearly demonstrated that the first metatarsal head showed a significant eversion in the HV models. We reviewed that the first metatarsal was rotated in the pronated direction [21]. However, the present study clarified that the first metatarsal was not only rotated, but also twisted, in HV cases. The round sign is reportedly observed in HV patients because of larger axial rotation of the entire first metatarsal in the everting direction [13]. To the best of our knowledge, this is the first study based on 3D models providing quantitative evidence that the head of the first metatarsal is more everted with respect to the base in the foot of HV patients.

Taking these findings into account, we designed an analysis system for this study. First, we expected that CT images and 3D models would be essential for detailed 3D evaluation. We reconstructed 3D models of each bone by segmentation and used a surgical algorithm to align bones and quantify displacement in HV. Algorithms for surgical treatment of HV can match the shapes of 3D foot models without using any specified anatomical landmark. In this way, we were able to standardize imaging conditions between patients. We found that, in HV deformity, the first metatarsal exhibited significantly more dorsiflexion relative to the medial cuneiform bone in feet with HV. This reaffirms that patients with HV exhibit hypermobility in the sagittal plane, as described many times before. However, we also found that feet with HV exhibited significantly more inversion and adduction when we evaluated the first tarsometatarsal joint. This suggests that tarsometatarsal joint hypermobility involves motion in all directions, not just the sagittal direction; in other words, hypermobility was 3D.

In addition to tarsometatarsal joint hypermobility, we found significantly greater mobility movement elements in the other joints that constitute the first ray. This suggests that the first-ray hypermobility associated with HV occurs in all of these joints rather than in the tarsometatarsal joint alone. We suggest that correction of the 3D deformity should also be addressed 3D to achieve anatomical restoration with proper function of the foot. The relationship between the first-ray hypermobility and progression of HV and associated deformity is still under debate.

Physical 3D modeling has been identified to support the efficient and effective perception of positional and structural information through the direct visualization of anatomy and pathology [36–38]. In this study, we created ten anatomically accurate, patient-specific 3D foot models with HV from CT data and evaluated their impact in presurgical planning. A strong correlation was noted between the actual measurement on the CT and the measurements on 3D models.

Our results indicate that even experienced orthopedics may potentially benefit from these models for planning complex surgeries. Since the concordance with what was actually performed improved with the 3D model, it is possible that 3D models may facilitate a better anticipation of patient-specific anatomy and better planning for a complex surgery, potentially allowing for less changes to be made in the operating room, therefore reducing the duration of induced ischemia or complications related to complex foot anatomy.

There are some limitations to the present study. We had a small sample size of only ten patients with HV. In addition, we mostly recruited middle-aged women as volunteers, because most of our patients undergoing surgery for HV were middle-aged women. It has been reported that the mechanism for the occurrence of HV could be different for men and women. Analyzing the differences in first metatarsal torsion in HV patients between males and females may bring us closer to the pathology of HV.

It is the first study to use 3D software technology in the treatment of HV patients. 3D personalized life-size models with misalignment help clinicians to understand disease processes and the patient’s anatomy better. Models with life-like tactile and visual characteristics offer multisensory inputs that can enrich and aid in spatial cognition and learning. It is an innovative navigational tool allowing a convenient surgery to the orthopedics while preserving the life quality of the patient. With the help of 3D modeling, creating HV angle in this intervention avoided restraints and provided a lifetime comfort to the patient in work and social life.

This study presents our first clinical experience that we have applied 3D models and computer navigation-assisted corrective surgery for the foot of a series of patients. 3D models enable correcting foot with single-session operation successfully. Correct interpretation of a patient’s anatomy and changes occurring secondary to a disease process are crucial in the preoperative process to ensure optimal surgical treatment.

Conclusion

3D imaging and modeling with corrective surgery represent a safe and helpful tool for osteotomies and may influence surgical treatment plans in selected cases to enable more limited resections. Although point-to-point measurements were not different, 3D personalized models increased the understanding of shape, angle, and anatomy.

Compliance with ethical standards

Conflict of interest

There are no conflicts of interest.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms from the patients. In the form, the patients have given their consent for their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Ethical standard statement

This article does not contain any studies with human or animal subjects performed by the any of the authors.