Biomechanical analysis of minimally invasive crossing screw fixation for calcaneal fractures: Implications to early weight-bearing rehabilitation

Biomechanical role of bone grafting for calcaneal fracture fixation in the presence of bone defect: A finite element analysis

BACKGROUND

The purpose of this study was to compare the biomechanical stress and stability of calcaneal fixations with and without bone defect, before and after bone grafting, through a computational approach.

METHODS

A finite element model of foot-ankle complex was reconstructed, impoverished with a Sanders III calcaneal fracture without bone defect and with moderate and severe bone defects. Plate fixations with and without bone grafting were introduced with walking stance simulated. The stress and fragment displacement of the calcaneus were evaluated.

FINDINGS

Moderate and severe defect increased the calcaneus stress by 16.11% and 32.51%, respectively and subsequently decreased by 10.76% and 20.78% after bone grafting. The total displacement was increased by 3.99% and 24.26%, respectively by moderate and severe defect, while that of posterior joint facet displacement was 86.66% and 104.44%. The former was decreased by 25.73% and 35.96% after grafting, while that of the latter was reduced by 88.09% and 84.78% for moderate and severe defect, respectively.

INTERPRETATION

Our finite element prediction supported that bone grafting for fixation could enhance the stability and reduce the risk of secondary stress fracture in cases of bone defect in calcaneal fracture.

Biomechanical characteristics of Sanders type II and III calcaneal fractures fixed by open reduction and internal fixation and percutaneous minimally invasive fixation

BACKGROUND

This work investigated the differences in the biomechanical properties of open reduction and internal fixation (ORIF) and percutaneous minimally invasive fixation (PMIF) for the fixation of calcaneal fractures (Sanders type II and III calcaneal fractures as examples) through finite element analysis.

METHODS

Based on CT images of the human foot and ankle, according to the principle of three-point fixation, namely the sustentaculum tali, the anterior process and the calcaneal tuberosity were fixed. Three-dimensional finite element models of Sanders type II and III calcaneal fractures fixed by ORIF and PMIF were established. The proximal surfaces of the tibia, fibula and soft tissue were constrained, and ground reaction force and Achilles tendon force loads were added to simulate balanced standing.

RESULTS

The maximum stress was 80.54, 211.59 and 113.88 MPa for the calcaneus, screws and plates in the ORIF group and 70.02 and 209.46 MPa for the calcaneus and screws in the PMIF group, respectively; the maximum displacement was 0.26, 0.21 and 0.12 mm for the calcaneus, screws and plates in the ORIF group and 0.20 and 0.14 mm for the calcaneus and screws in the PMIF group, respectively. The values obtained from the simulation were within the permissible stress and elastic deformation range of the materials used in the model, and there was no significant stress concentration. The maximum stress and displacement of the calcaneus and implants were slightly lower in the PMIF group than in the ORIF group when fixing Sanders type II and III calcaneal fractures.

CONCLUSIONS

This study may provide a reference for optimising the design of implants, the development of individualised preoperative plans and the choice of clinical surgical approach.

Minimally Invasive Treatment of Inversion Shortening Calcaneal Fractures in the "Out-In" Position

OBJECTIVE

Heel fractures need extensive surgical incisions and are challenging to successfully reposition using traditional prying. The goal of this study is to evaluate the clinical effectiveness of using a Kirschner pin-guided distractor to treat inversion shortening calcaneal fractures in the "out-in" position.

METHODS

A total of 40 data from 37 patients with inversion shortened calcaneal fractures from January 2018 to March 2020 were reviewed. Preoperative lateral and axial X-rays and 3D CT were taken to assess the fracture type, and minimally invasive internal fixation was performed in the "out-in" position with distractor repositioning, and intraoperative and postoperative images were taken to assess fracture repositioning and fixation. During the follow-up period, the postoperative functional recovery status was assessed using the VAS score, AOFAS score, and FAOS score. Paired-samples t-test was used for all data comparisons.

RESULTS

All cases received a mean follow-up of 28.49 ± 3.25 months, and the mean fracture healing time was 7.84 ± 0.71 weeks. The postoperative images showed well-fixed fracture repositioning, and calcaneal height, length, width, and inversion angles were significantly improved. At the final follow-up, the calcaneal height, length, and width recovered from 39.35 ± 4.44mm, 79.35 ± 2.7mm, and 45.75 ± 2.87mm preoperatively to 50.93 ± 3.18mm, 82.23 ± 1.90mm, and 39.67 ± 1.58mm postoperatively (p < 0.001; p < 0.001; p < 0.001). The calcaneus inversion angle restored from 7.73° ± 2.26° to 3.80° ± 1.80° (p < 0.001). Böhler's angle and Gissane's angle improved from 13.13° ± 3.02° and 105.15° ± 8.94° to 27.95° ± 3.41° and 122.85° ± 5.54° (p < 0.001; p < 0.001). No non-healing fractures, osteomyelitis, or traumatic arthritis were observed.

CONCLUSION

Minimally invasive internal fixation with distractor repositioning in the "out-in" position is effective in the treatment of inversion shortening calcaneal fractures while restoring the anatomy and protecting the soft tissue.

Finite element analyses of three minimally invasive fixation techniques for treating Sanders type II intra-articular calcaneal fractures

BACKGROUND AND OBJECTIVE

Calcaneal Sanders type II or III fractures are highly disabling with significant burden. Surgical treatment modalities include open reduction and internal fixation (ORIF) techniques and a variety of minimally invasive surgical (MIS) approaches. ORIF techniques are associated with complications and traditional MIS techniques need extensive intraoperative fluoroscopic procedures. The present study aims to investigate the effects of three different minimally invasive internal fixation (MIIF) techniques used to treat Sanders type II intra-articular calcaneal fractures using finite element analyses.

METHODS

A 64-row spiral computed tomography scan was used to observe the calcaneus of a healthy adult. The scanning data were imported into Mimics in a DICOM format. Using a new model of a Sanders type II-B intra-articular calcaneal fracture, three minimally invasive techniques were simulated. Technique A involved fixation using an isolated minimally invasive locking plate; Technique B used a minimally invasive locking plate with one medial support screw; and Technique C simulated a screw fixation technique using four 4.0-mm screws. After simulating a 640-N load on the subtalar facet, the maximum displacement and von Mises stress of fragments and implants were recorded to evaluate the biomechanical stability of different fixation techniques using finite element analyses.

RESULTS

After stress loading, the maximum displacements of the fragments and implants were located at the sustentaculum tali and the tip of sustentaculum tali screw, respectively, in the three techniques; however, among the three techniques, Technique B had better results for displacement of both. The maximum von Mises stress on the fragments was < 56 Mpa, and stress on the implants using the three techniques was less than the yield strength, with Technique C having the least stress.

CONCLUSION

All three techniques were successful in providing a stable fixation for Sanders type II intra-articular calcaneal fractures, while the minimally invasive calcaneal locking plate with medial support screw fixation approach exhibited greater stability, leading to improved enhancement for the facet fragment; however, screw fixation dispersed the stress more effectively than the other two techniques.

Three-dimensional printed cast assisted screw fixation of calcaneal fractures: a prospective study

BACKGROUND

Treatment of displaced intra-articular calcaneal fractures (DIACFs) with percutaneous screw fixation remains defective in some aspects. A novel three-dimensional (3D) printed cast was devised to assist screw placement. This study assessed the radiological and functional outcomes of 3D-printed cast assisted screw fixation for patients with DIACFs.

METHODS

Patients with unilateral Sanders type II or III DIACFs admitted to a single-centre hospital underwent either 3D-printed cast assisted screw fixation (3D group) or minimally invasive plate fixation (control group) from September 2020 to November 2022. All patients were assessed at one, two, three, and six months of follow-up. Comparison between groups was conducted in operative duration, fluoroscopic times, radiographic measurements of the calcaneus, and the American Orthopaedic Foot and Ankle Society (AOFAS) Ankle-Hindfoot Score.

RESULTS

A total of 32 patients were enrolled (19 in the 3D group versus 13 in the control group). Significant differences were detected between the 3D group and control group in operative duration (53.63±8.95 min, 95.08±8.31 min, P <0.001), fluoroscopic times (7.37±1.21, 16.85±1.57, P <0.001). At a follow-up of six months, the 3D group showed better restoration than the control group in calcaneal width, height, Bohler angle, and AOFAS Ankle-Hindfoot scores (all P <0.001). No significant differences were shown in calcaneal length and Gissane angle (P >0.05). No wound-related complications occurred in either group.

CONCLUSION

The 3D-printed cast assisted screw fixation has shown superiority over minimally invasive plate fixation in the operative duration, fluoroscopic exposure, morphological restoration of the calcaneus, and functional outcomes in the treatment of DIACFs.

Optimal posterior screw placement configuration in Sanders 2B calcaneal fractures: A biomechanical study

BACKGROUND

Calcaneal fractures can be high energy intra-articular injuries associated with joint depression. Challenges to fracture reduction include lateral wall blow out, medial wall overlap, comminution and central bone loss. Secondary deformity such as hindfoot varus alters foot biomechanics. Minimally invasive approaches with indirect reduction of the calcaneal tuberosity to maintain the reduction using posterior screws is routinely being used in the treatment of joint depression fractures. Biomechanically, optimum screw numbers and configuration is not known. Biomechanical studies have evaluated and proposed different screw configurations, however, it is not clear which configuration best controls varus deformity. This study aims to determine the optimum screw configuration to control varus deformity in Sanders 2B calcaneal fractures.

METHODS

Sawbone models were prepared to replicate Sanders type 2-B fracture, with central bone loss and comminution. 0.5 cm medial wedge of the calcaneal tuberosity was removed to create varus instability. After stabilising posterior facet with a single 4 mm partial threaded screw, and applied an 8 hole contoured plate to stabilise the angle of Gissane, inserted one or two 7 mm cannulated partially threaded Charlotte^TM (Wright Medical Technology, Memphis, USA) Headless Multi-use Compression (under image guidance) extra screws to control varus and subsidence deformity of the fracture. Coronal plane displacement of the dissociated calcaneal tuberosity fragment relative to the body when applying 5 N, 10 N and 20 N force was measured in millimetres (mm).

RESULTS

2 screws inserted (one medial screw into the sustentaculum talus from inferior to superior and, one lateral screw into the long axis anterior process) provides the least displacement (0.88 ± 0.390 at 5 N and 1.7 ± 1.251 at 20 N) and the most stable construct (p < 0.05) when compared to other configurations. A single medial screw into the sustentaculum tali (conf. 3) resulted in the least stable construct and most displacement (4.04 ± 0.971 at 5 N and 11.24 ± 7.590 at 20 N) (p < 0.05).

CONCLUSION

This study demonstrates the optimal screw configuration to resist varus in calcaneal fractures using minimally invasive techniques. Optimal stability is achieved using 2 screws; one located along the long axis of the calcaneus (varus control) and the other placed in the short axis directed towards the posterior facet of the calcaneus (control varus and subsidence). Further cadaver research would help evaluate optimal screw placement in simulated fractures to further assess reproducibility.

Optimal posterior screw placement configuration in Sanders 2B calcaneal fractures: A biomechanical study

BACKGROUND

Calcaneal fractures can be high energy intra-articular injuries associated with joint depression. Challenges to fracture reduction include lateral wall blow out, medial wall overlap, comminution and central bone loss. Secondary deformity such as hindfoot varus alters foot biomechanics. Minimally invasive approaches with indirect reduction of the calcaneal tuberosity to maintain the reduction using posterior screws is routinely being used in the treatment of joint depression fractures. Biomechanically, optimum screw numbers and configuration is not known. Biomechanical studies have evaluated and proposed different screw configurations, however, it is not clear which configuration best controls varus deformity. This study aims to determine the optimum screw configuration to control varus deformity in Sanders 2B calcaneal fractures.

METHODS

Sawbone models were prepared to replicate Sanders type 2-B fracture, with central bone loss and comminution. 0.5cm medial wedge of the calcaneal tuberosity was removed to create varus instability. After stabilising posterior facet with a single 4mm partial threaded screw, and applied an 8 hole contoured plate to stabilise the angle of Gissane, inserted one or two 7mm cannulated partially threaded Charlotte™ (Wright Medical Technology, Inc. 5677 Airline Road Arlington, TN) Headless Multi-use Compression (under image guidance) extra screws to control varus and subsidence deformity of the fracture. Coronal plane displacement of the dissociated calcaneal tuberosity fragment relative to the body when applying 5N, 10N and 20N force was measured in millimetres (mm).

RESULTS

2 screws inserted (one medial screw into the sustentaculum talus from inferior to superior and, one lateral screw into the long axis anterior process) provides the least displacement (0.88±0.390 at 5N and 1.7±1.251 at 20N) and the most stable construct (p<0.05) when compared to other configurations. A single medial screw into the sustentaculum tali (conf. 3) resulted in the least stable construct and most displacement (4.04±0.971 at 5N and 11.24±7.590 at 20N) (p<0.05).

CONCLUSION

This study demonstrates the optimal screw configuration to resist varus in calcaneal fractures using minimally invasive techniques. Optimal stability is achieved using 2 screws; one located along the long axis of the calcaneus (varus control) and the other placed in the short axis directed towards the posterior facet of the calcaneus (control varus and subsidence). Further cadaver research would help evaluate optimal screw placement in simulated fractures to further assess reproducibility.

Outcomes of Early Weight Bearing in Displaced Intra-articular Calcaneus Fractures Treated with Screws-Only Fixation Technique

Background

Displaced intraarticular calcaneus fracture indicates surgical treatment. The current trend is open reduction and internal fixation with a plate or multiple screws through the sinus tarsi approach. Most postoperative protocols are prolonged non-weight bearing that causes a high socioeconomic burden. This study aims to determine the safety of the early weight-bearing protocol of screws-only fixation in calcaneal fracture.

Materials and Methods

Evaluate displaced intraarticular calcaneus fractures treated with screws-only technique via the sinus tarsi approach in our institution. The first group, from July 2017 to December 2018, allowed patients to start partial weight bearing as tolerated at 4 weeks after surgery. The second group prospectively from January 2019 to March 2020, which assign patients to keep non-weight bearing for 8 weeks. The functional outcomes (Thai Foot and ankle ability measure subjective form, FAAM) were measured 6 months after surgery. The radiographic outcome (Bohler's angle and Gissane angle) was measured on the first day postoperative and 6 months follow-up, and the changes in these angles were recorded.

Results

There were 28 patients in each group. The outcomes were collected and compared by a T-test. In the early weight-bearing group, The FAAM, Bohler's angle loss, and Gissane's angle change were 76.4 ± 14.8, 2.4 ± 3.5, and 6.6 ± 7.8, respectively. In the delayed weight-bearing group, The FAAM, Bohler's angle loss, and Gissane's angle change were 81 ± 14.8, 2 ± 1.8 and 2.6 ± 6.1, respectively. There was no statistically significant difference in FAAM score, Bohler's angle loss, and Gissane's angle change between early and delayed weight-bearing groups.

Conclusion

Screws fixation in calcaneal fracture may be safe to allow early weight-bearing protocol.

Biomechanical application of finite elements in the orthopedics of stiff clubfoot

BACKGROUND

The purpose of this study was to evaluate the effect of varying the different correction angles of hindfoot osteotomy orthosis on the biomechanical changes of the adjacent joints after triple arthrodesis in adult patients with stiff clubfoot to determine the optimal hindfoot correction angle and provide a biomechanical basis for the correction of hindfoot deformity in patients with stiff clubfoot.

METHODS

A 26-year-old male patient with a stiff left clubfoot was selected for the study, and his ankle and foot were scanned using dual-source computed tomography. A three-dimensional finite element model of the ankle was established, and after the validity of the model was verified by plantar pressure experiments, triple arthrodesis was simulated to analyze the biomechanical changes of the adjacent joints under the same load with "3°" of posterior varus, "0°" of a neutral position and "3°, 6°, 9°" of valgus as the correction angles.

RESULTS

The peak plantar pressure calculated by the finite element model of the clubfoot was in good agreement with the actual plantar pressure measurements, with an error of less than 1%. In triple arthrodesis, the peak von Mises stress in the adjacent articular cartilage was significantly different and less than the preoperative stress when the corrected angle of the hindfoot was valgus "6°". In comparison, the peak von Mises stress in the adjacent articular cartilage was not significantly different in varus "3°", neutral "0°", valgus "3°" and valgus "9°" compared with the preoperative stress.

CONCLUSION

The results of this study showed that different angles of hindfoot correction in triple arthrodesis did not increase the peak von Mises stress in the adjacent joints, which may not lead to the development of arthritis in the adjacent joint, and a hindfoot correction angle of "6°" of valgus significantly reduced the peak von Mises stress in the adjacent joints after triple arthrodesis.

Modified Ni-Nail and C-Nail systems for intra-articular fractures of the calcaneus: A biomechancial study

OBJECTIVES

We have proposed a novel intramedullary nail (Ni-Nail) by incorporating a sustentaculum tali screw to improve the fixation stability of minimally invasive treatment for calcaneal fractures. This study aimed to evaluate the biomechanical characters of the Ni-Nail system and compare it with traditional C-Nail system.

METHODS

A finite element model of a Sanders type-IIIAB calcaneal fracture was reconstructed and fixed using two intramedullary nail systems, which was validated by a cadaver study. A vertical loading of 700 N was applied to the subtalar joint surfaces, and 525 N Achilles tendon tension was applied to the superior border of the Achilles tuberosity. The von Mises stresses and fracture displacements of both fixation models were evaluated.

RESULTS

The maximum von Mises stress of the screws of Ni-Nail and C-Nail were 27.92 MPa and 57.42 MPa, respectively, while that of the main nail were 67.44 MPa and 53.01 MPa. In addition, the maximum fracture displacement of the Ni-Nail was larger than that of C-Nail by 15.6% (0.37 mm vs.0.32 mm).

CONCLUSIONS

Our static simulation analysis showed that both Ni-Nail and C-Nail demonstrated similar biomechanical stability for calcaneal fixation. The Ni-Nail features a simple structure that is easier to operate and less traumatizing. Future studies may consider to further evaluate the clinical effectiveness by clinical trials and follow-ups.

Significance of the anatomical relationship between the flexor digitorum longus and sustentaculum tali for reconsideration of the talocalcaneonavicular joint stability mechanism

The talocalcaneonavicular joint (TCN-j) is supported by the spring ligament, which has recently been revealed to be part of the joint capsule complex, along with the tendinous sheath of the tibialis posterior and flexor digitorum longus (FDL). Nonetheless, the FDL's role in TCN-j stability has received limited attention. This study aimed to elucidate the positional relationships between the FDL and sustentaculum tali, which comprises the TCN-j. We hypothesized that the FDL runs medial to the sustentaculum tali, and its course significantly changes from the sitting to the standing position. Six ankles from six body donors were investigated, and seven ankles from seven volunteers were assessed using ultrasonography. The FDL was three-dimensionally located inferomedial to the sustentaculum tali. The FDL tendinous sheath was attached to the sustentaculum tali or connected by the tibialis posterior via the tendinous sheath. Based on the in vivo ultrasound image, the FDL location relative to the sustentaculum tali was maintained; however, the curvature of the FDL course was significantly more prominent in standing than in sitting. The FDL force against the bending moment may prevent the excessive eversion of the foot and aid the conventional spring ligament's contribution to TCN-j stability for maintaining the longitudinal arch.

A nomogram for predicting post-operative wound complications after open reduction and internal fixation for calcaneal fractures

The purpose of our study was to determine the risk factors for post-operative wound complications (PWCs) after open reduction and internal fixation (ORIF) for calcaneal fracture and establish a nomogram prediction model. We retrospectively analysed the clinical data of patients who suffered from calcaneal fractures and had been surgically treated for ORIF in our institution between January 2010 and January 2020. Perioperative information was obtained through the electronic medical record system, univariate and multivariate analyses were performed to determine the risk factors of PWCs, and a nomogram model was constructed to predict the risk of PWCs. The predictive performance and consistency of the model were evaluated by the Hosmer -Lemeshow (H-L) test and the calibration curve. In total, 444 patients were enrolled in our study. Multivariate analysis results showed that smoking, limb swelling, angle of incision, and CRP were independent risk factors for skin necrosis. The AUC value for skin necrosis risk was 0.982 (95%CI 0.97-0.99). The H-L test revealed that the normogram prediction model had good calibration ability (P = .957). Finally, we found a correlation between PWCs and smoking, limb swelling, angle of incision, and CRP after ORIF for calcaneal fracture patients. Our nomogram prediction model might be helpful for clinicians to identify high-risk patients, as interventions could be taken early to reduce the incidence of PWCs.

A finite element analysis study based on valgus impacted femoral neck fracture under diverse stances

The aim of the study was to determine the biomechanical environment of patients who suffer from valgus impacted femoral neck fracture. With the help of computational modeling, both of finite element hip fracture and normal three-dimensional model were reconstructed from a patient with hip fracture. The predicted stress distribution was compared between before and after fracture. After the fracture, during standing and the gait, the fracture site has a greater change in stress distribution due to the shortening of the femoral neck. The largest stress occurs at the middle and lower end of the femoral shaft, which occurs from toe off to deceleration during the whole gait. After the fracture, greater stress on the femoral head will result in a worse mechanical environment for the femur. The stress peak value of the femoral shaft is larger than the unfractured side and the stress distribution is uneven. From the results of gait analysis, it is concluded that the increase of concentrated stress and the change of stress distribution will cause the possibility of secondary fractures at the middle and lower ends of the femoral shaft when there is an accident in the case of existing fracture.

Biomechanical Analysis of a Novel Double-Point Fixation Method for Displaced Intra-Articular Calcaneal Fractures

The development of minimally invasive procedures and implant materials has improved the fixation strength of implants and is less traumatic in surgery. The purpose of this study was to propose a novel “double-point fixation” for calcaneal fractures and compare its biomechanical stability with the traditional “three-point fixation.” A three-dimensional finite element foot model with a Sanders type IIIAB calcaneal fracture was developed based on clinical images comprising bones, plantar fascia, ligaments, and encapsulated soft tissue. Double-point and three-point fixation resembled the surgical procedure with a volar distal radius plate and calcaneal locking plate, respectively. The stress distribution, fracture displacement, and change of the Böhler angle and Gissane’s angle were estimated by a walking simulation using the model, and the predictions between the double-point and three-point fixation were compared at heel-strike, midstance, and push-off instants. Double-point fixation demonstrated lower bone stress (103.3 vs. 199.4 MPa), but higher implant stress (1,084.0 vs. 577.9 MPa). The model displacement of double-point fixation was higher than that of three-point fixation (3.68 vs. 2.53 mm). The displacement of the posterior joint facet (0.127 vs. 0.150 mm) and the changes of the Böhler angle (0.9° vs. 1.4°) and Gissane’s angle (0.7° vs. 0.9°) in double-point fixation were comparably lower. Double-point fixation by volar distal radius plates demonstrated sufficient and favorable fixation stability and a lower risk of postoperative stress fracture, which may potentially serve as a new fixation modality for the treatment of displaced intra-articular calcaneal fractures.

Finite element method based parametric study of Gastrocnemius-soleus recession: implications to the treatment of midfoot-forefoot overload syndrome

Gastrocnemius-soleus recession has been used to treat midfoot-forefoot overload syndrome and plantar fasciitis induced by equinus of the ankle joint. A controlled and selective amount of recession is imperative to maintain muscle strength and stability. The objective of this study was to conduct a parametric study to quantify the relationship between the level of recession and plantar fascia stress. A finite element model of the foot-ankle-shank complex was reconstructed from magnetic resonance and computed tomography images of a 63-year-old normal female. The model was validated by comparing modeled stresses to the measured plantar pressure distribution of the model participant during balanced standing. The midstance and push-off instants of walking stance were simulated with different levels and combinations of gastrocnemius-soleus recession resembled by different amounts of muscle forces. Halving the muscle forces at midstance reduced the average plantar fascia stress by a quarter while reducing two-third of the muscle forces at push-off reduced the average fascia stress by 18.2%. While the first ray of the plantar fascia experienced the largest stress among the five fasciae, the stress was reduced by 77.8% and 16.9% when the load was halved and reduced by two-third at midstance and push-off instants, respectively. Reduction in fascia stress implicates a lower risk of plantar fasciitis and other midfoot-forefoot overload syndromes. The outcome of this study can aid physicians to determine the amount of gastrocnemius-soleus recession towards patients with vdifferent levels of plantar fascia overstress. A detailed three-dimensional modelling on the plantar fascia is warranted in future study.