3D Printing Surgical Guide for Talocalcaneal Coalition Resection: Technique Tip

Morphological characteristics of talocalcaneal coalitions: Anatomical observation, finite element analysis and clinical application

BACKGROUND

The intricate anatomical structure of talocalcaneal coalitions (TCCs) presents significant challenges for clinicians in both diagnosis and treatment. This study aimed to investigate the anatomy, imaging characteristics, and biomechanical properties of TCCs, providing essential references for contemporary clinical diagnosis, treatment, scientific research, and education regarding TCCs.

METHODS

The morphologies of TCCs were examined and classified in intact dry osseous specimens from 131 Asian adults. The imaging characteristics of TCCs were summarized by carefully observing the X-rays and CT scans. Additionally, finite element models of TCCs were established and validated, allowing for the simulation and analysis of stress and strain.

RESULTS

The TCCs were primarily located in the region between the posterior end of sustentaculum tali (ST), the medial port of the tarsal canal, and the medial edge of the posterior talar articular surface (PTF). In comparison to specimens with cartilage and ligament connections, the medial tubercle of osseous connections exhibited significant inward and downward protrusion, while the ST was longer and thicker. Statistically significant differences were noted in the widths of the calcaneus and talus, as well as in the thickness and length of the ST (P < 0.05). CT imaging provided an accurate determination of TCCs' locations, while X-rays revealed the presence of the "C sign" and "duck beak sign" in all osseous connection specimens. Finite element model analysis indicated that stress was primarily concentrated at the osseous connection, which also reduced displacement of the subtalar joint.

CONCLUSIONS

The comprehension of the precise location, anatomical morphological characteristics, imaging features and finite element mechanical properties of TCCs is instrumental in enhancing the diagnosis and treatment of TCCs.

Tarsal coalition in adults

Adult tarsal coalition consists in abnormal union of two or more tarsal bones. Reported incidence ranges between 1 and 13%. It is generally a congenital condition, due to dominant autosomal chromosome disorder, but with some acquired forms following trauma or inflammatory pathology. Poorly specific clinical signs and the difficulty of screening on conventional X-ray may lead to diagnostic failure. The present review of tarsal coalition addresses the following questions: how to define tarsal coalition? How to diagnose it? How to treat it? And what results can be expected? There are 3 types of tarsal coalition, according to the type of tissue between the united bones: bony in pure synostosis, cartilaginous in synchondrosis, and fibrous in syndesmosis. Location varies; the most frequent forms are talocalcaneal (TC) and calcaneonavicular (CN), accounting for more than 90% of cases. Cuneonavicular, intercuneal and cuboideonavicular locations are much rarer, at less than 10%. Tarsal coalition is classically painful, often with valgus spastic flatfoot in young adults. The pain is caused by the biomechanical disturbance induced by the bone, cartilage or fibrous bridges which partially or completely hinder hindfoot and/or midfoot motion. Conventional imaging, with weight-bearing X-ray and CT, is standard practice. Weight-bearing CT is increasingly the gold standard, displaying abnormalities in 3 dimensions. Functional imaging on MRI and tomoscintigraphy assess direct and indirect joint impact at the affected and neighboring joint lines. Non-operative treatment can be proposed, with orthoses, rehabilitation and/or injections. But surgery is the most frequent option: either resection of the bony, cartilaginous or fibrous constructs to restore optimally normal anatomy, or arthrodesis in the affected joint line or the entire joint. Surgery can be open, arthroscopic or percutaneous, depending on the severity of the biomechanical impact on the affected and neighboring joints. Resecting the abnormality is the standard practice in all locations if it affects less than 50% of the talocalcaneal joint line and there is no osteoarthritis to impair the functional outcome. Otherwise, fusion is required. Level of evidence: V; expert opinion.

Midfoot Tarsectomy in Cavovarus: Why PSI Makes a Difference?

The cavovarus foot is a complex deformity that can be treated using multiple surgical procedures, ranging from soft tissue surgery to triple arthrodesis. Among these options, anterior midfoot tarsectomy is a three-dimensional closed-wedge osteotomy, traditionally performed slowly and progressively in a blind fashion, and remaining a challenge for unexperimented surgeons with variable outcomes. As such, we investigated and discussed the use of patient-specific cutting guides (PSCGs) in computer-assisted anterior midfoot tarsectomy in terms of accuracy, reproducibility, and safety.

Diagnostic value of high-frequency ultrasonography for painful talocalcaneal coalition and its complications

OBJECTIVE

To investigate the value of high-frequency ultrasonography in the diagnosis of painful talocalcaneal coalition (TCC) and its complications.

METHODS

Seventy-seven patients (84 feet) with abnormal mass and pain in the medial malleolus were suspected of TCC pre-operatively and examined by high-frequency ultrasonography, radiograph, and CT. The sonographic characteristics of the affected feet were analyzed pre-operatively and compared with the surgical findings.

RESULTS

During the operation, 49 feet with TCC and 35 feet with non-TCC were confirmed; pre-operative ultrasonography diagnosed 48 feet with TCC and 36 feet with non-TCC; taking surgery as the gold-standard, the sensitivity, specificity, accuracy, positive-predictive value and negative-predictive value of ultrasound diagnosis of TCC were 87.8%, 85.7%, 86.9%, 89.6%, and 83.3%, respectively. The two were consistent, with κ = 0.732, p < 0.001. High-frequency ultrasonography had high diagnostic efficacy for TCC, with an area under the receiver operating characteristic curve of 0.867. The accuracy of ultrasound and CT in the diagnosis of TCC was significantly higher than that of radiograph, and the difference was statistically significant (p < 0.0167). High-frequency ultrasound could also accurately diagnose complications of TCC, such as tibial nerve compression and tendon displacement, while CT and radiograph cannot show these complications.

CONCLUSION

High-frequency ultrasonography can accurately diagnose TCC and its complications, and locate the body surface accurately. Therefore, high-frequency ultrasonography can be used as a routine examination method to supplement CT and provide clinical assistance in precise surgery.

ADVANCES IN KNOWLEDGE

This study is the first to use high-frequency ultrasonography to examine TCC and compare its findings with surgical results to explore the diagnostic value of ultrasonography for TCC and its complications.

Application of mixed reality technology in talocalcaneal coalition resection

Objectives

With positive outcomes recorded, the mixed reality (MR) technology has lately become popular in orthopedic surgery. However, there are few studies that specifically address the utility of MR in talocalcaneal coalitions (TCC) resection. Our goal in this retrospective study is to assess certain data while examining the viability of using MR to treat TCC resection.

Methods

Six consecutive patients with TCC diagnosed by computed tomography (CT) for which nonoperative therapy had failed and MR system assisted TCC resection were included in this study from March 2021 to December 2021. The feasibility and accuracy of TCC resection were assessed by post-operation radiography. The American Orthopaedic Foot & Ankle Society (AOFAS) hindfoot score and visual analog scale (VAS) score were used to assess the recovery condition and pain level pre- and post-operation.

Results

The surgeon can accurately resect the TCC according to the preoperatively determined range by superimposing the holographic model with the actual anatomy of the TCC using an MR system. Additionally, no additional x-ray was necessary while operating. Mean follow-up was 10.3 months, with a minimum of 6 months. There is a significant difference between the preoperative AOFAS score of 53.4 ± 3.8 and the 6-month follow-up AOFAS score of 97.3 ± 2.2 (p < 0.05). There is also a significant difference between the preoperative VAS score of 8.1 ± 0.7 and the 6-month follow-up VAS score of 1.7 ± 0.4 (p < 0.05). All individuals had clinical subtalar mobility without stiffness following surgery.

Conclusion

While the TCC resection operation is being performed, the application of MR technology is practicable, effective, and radiation-free, giving surgeons satisfactory support.

Technique tip: 3D printing surgical guide for pes cavus midfoot osteotomy

BACKGROUND

Pes cavus can be defined as an abnormal elevation of the longitudinal arches, which is often secondary to a muscle imbalance. This deformity affects the foot's three dimensions (3D) and our osteotomies are usually planned on a lateral (two-dimension) X-ray. Are we really considering all the spatial components of the deformity? The aim of this study is to present a technique tip to identify the apical plane of the pes cavus deformity and perform a midfoot dorsal-based wedge resection osteotomy by using customized 3D printed surgical guides.

METHODS

Three patients underwent the presented technique, all for the indication of symptomatic neuromuscular pes cavus with both anterior and posterior deformity.

RESULTS

3D-printed patient-specific guides help the surgeon to minimize human error, improving intraoperative accuracy, while reducing surgical time and intraoperative X-ray exposure.

CONCLUSIONS

Closing wedge midfoot osteotomy to correct anterior pes cavus may be an interesting indication to use customized 3D printed surgical guides.

3D-printed models improve surgical planning for correction of severe postburn ankle contracture with an external fixator

Gradual distraction with an external fixator is a widely used treatment for severe postburn ankle contracture (SPAC). However, application of external fixators is complex, and conventional two-dimensional (2D) imaging-based surgical planning is not particularly helpful due to a lack of spatial geometry. The purpose of this study was to evaluate the surgical planning process for this procedure with patient-specific three-dimension-printed models (3DPMs). In this study, patients coming from two centers were divided into two cohorts (3DPM group vs. control group) depending on whether a 3DPM was used for preoperative surgical planning. Operation duration, improvement in metatarsal-tibial angle (MTA), range of motion (ROM), the American Orthopedic Foot and Ankle Society (AOFAS) scores, complications, and patient-reported satisfaction were compared between two groups. The 3DPM group had significantly shorter operation duration than the control group ((2.0±0.3) h vs. (3.2±0.3) h, P<0.01). MTA, ROM, and AOFAS scores between the two groups showed no significant differences pre-operation, after the removal of the external fixator, or at follow-up. Plantigrade feet were achieved and gait was substantially improved in all patients at the final follow-up. Pin-tract infections occurred in two patients (one in each group) during distraction and were treated with wound care and oral antibiotics. Patients in the 3DPM group reported higher satisfaction than those in the control group, owing to better patient-surgeon communication. Surgical planning using patient-specific 3DPMs significantly reduced operation duration and increased patient satisfaction, while providing similar improvements in ankle movement and function compared to traditional surgical planning for the correction of SPAC with external fixators.

The role of ultrasonography in the diagnosis of talocalcaneal coalitions

BACKGROUND

Patients with talocalcaneal coalitions (TCC) often undergo computed tomography (CT). However, ultrasonography diagnosis of TCC has been seldom done according to the literature.

PURPOSE

To investigate the accuracy of ultrasonography in diagnosing TCC compared to CT.

MATERIAL AND METHODS

Ninety-seven consecutive patients with a clinical suspicion of TCC were included. Ultrasonography was used to assess the classification and complication of TCC. The main sonographic criteria for a positive diagnosis in cases of osseous coalition were the joint space between the medial surface of talar head and the underlying sustentaculum tali of calcaneus disappearing and being replaced by a continuous hyperechoic bony structure. In cases of fibrous coalition, ultrasonography revealed a reduced space of the joint associated with an irregular, angular appearance of its outline and hypoechoic fibrous tissue inside. These data were compared with CT findings. κ statistic was applied to determine the level of agreement. The sensitivity, specificity, positive and negative predictive values, accuracy, and Youden index of ultrasonography as a diagnostic method were assessed.

RESULTS

Ultrasonography findings were positive in 20 of 97 patients with a clinical suspicion of TCC. The diagnosis was confirmed by CT in 21 patients. There were one false-positive result and two false-negative results by ultrasonography. The κ value was 0.907. The sensitivity, specificity, positive and negative predictive values, accuracy, and Youden index of ultrasonography were 90.5%, 98.7%, 95.0%, 97.4%, 96.9%, and 0.892, respectively.

CONCLUSION

Ultrasonography could be a reliable, accurate, and non-radioactive diagnostic imaging method in diagnosis of patients with suspected TCC.

Evaluation of skin cancer resection guide using hyper-realistic in-vitro phantom fabricated by 3D printing

Skin cancer usually occurs in the facial area relatively exposed to sunlight. Medical imaging can confirm the invasiveness and metastasis of skin cancer, which is used to establish a surgical plan. However, there is no method of directly marking this information on the patient's skin in the operating room. We evaluated a skin cancer resection guide that marks resection areas including safety margins on the patient's skin based on medical images and in-vitro phantom fabricated via 3D printing. The in-vitro phantom, which includes the skull, skin, and five different cancer locations was designed and fabricated based on a CT image of a patient. Skin cancer resection guides were designed using a CT image of an in-vitro phantom, with a safety margin, and four injection points at each cancer. The guide was used to insert 16 cc intravenous catheters into each cancer of the phantom, which was rescanned by CT. The catheter insertion point and angle were evaluated. The accuracy of the insertion points was 2.09 ± 1.06 mm and cosine similarities was 0.980 ± 0.020. In conclusion, skin cancer resection guides were fabricated to mark surgical plans on the patient's skin in the operating room. They demonstrated reasonable accuracies in actual clinical settings.

[Effectiveness of a modified posterior approach for arthroscopic resection on painful talocalcaneal coalition in adults]

OBJECTIVE

To investigate the effectiveness of arthroscopic talocalcaneal coalition resection in painful adults via a modified posterior approach.

METHODS

Between January 2015 and December 2017, 9 patients with painful talocalcaneal coalition accepted arthroscopic resection via the posterior malleolus high lateral observation approach combined with the lower medial operation approach. Of them, 6 were male and 3 were female, aged from 19 to 30 years (mean, 24 years). Among them, 2 cases had no definite local trauma and 7 cases had a history of sprain of foot and ankle. The disease duration ranged from 6 to 30 months, with a median of 12 months. Rozansky classification of talocalcaneal coalition for the 9 patients: 5 cases (5 feet) were type Ⅰ, 2 cases (2 feet) type Ⅱ, and 2 cases (2 feet) type Ⅲ. The patients had no sequelae of limb dysfunction and no limb joint surgery in the past. All the patients received anteroposterior and lateral X-ray films and CT scans of the ankle joint during follow-up. The visual analogue scale (VAS) score and American Orthopaedic Foot and Ankle Society (AOFAS) ankle-hind foot score were used to evaluate the effectiveness.

RESULTS

The operation time was 60-90 minutes (mean, 76 minutes). All patients were followed up 12-24 months (mean, 18 months). All the incisions healed by first intention, without infection, skin necrosis, lower extremity deep vein thrombosis, vascular nerve and tendon injury, bone bridge recurrence, and other complications. The ankle function recovered well and the pain was relieved obviously after operation, and the patients returned to work at 3-5 months after operation, with an average of 3.9 months. At last follow-up, the VAS score was 0.7±0.5, which was significantly improved ( t=20.239, P=0.000) when compared with preoperative score (4.2±0.5); the AOFAS ankle-hind foot score was 94±4, which was significantly improved ( t=-27.424, P=0.000) when compared with preoperative score (62±2). According to AOFAS ankle-hindfoot scoring system, the results were excellent in 7 cases and good in 2 cases at last follow-up.

CONCLUSION

It is more intuitive, more space, and more flexibility for operation via the modified posterior malleolus high lateral observation approach combined with the lower medial operation approach in talocalcaneal coalition. It is feasible to remove talocalcaneal coalition programmatically according to the specific anatomic signs during the operation.