Biomechanical investigation of two plating systems for medial column fusion in foot

Canine ex vivo tarsal arthrodesis: fixation by using a new bone tissue glue

Introduction

Arthrodesis, performed as a salvage surgical procedure to treat intractable joint conditions in dogs and cats, is associated with a high incidence of complications intra and postoperative, proving the need for improved and new techniques in arthrodesis surgery. Adding a new resorbable bone glue to the arthrodesis could potentially add fixation strength and lower complications. The objectives of this experimental ex vivo biomechanical study were therefore to develop a biomechanical test model of partial tarsal arthrodesis and to determine whether the new resorbable bone glue (phosphoserine modified cement) produced measurable fixation strength in canine calcaneoquartal arthrodesis, without orthopedic implants.

Methods

Four biomechanical test models with a total of 35 canine tarsal joints were used. Soft tissues were dissected to 4 different test models with variable contributions from soft tissues. The calcaneoquartal joint was prepared as in vivo arthrodesis and the glue was applied to joint surfaces as a liquid/putty (0.4 cc). After curing for 24 h, a shear force was applied to the joint (1 mm per minute) and the failure strength was recorded.

Results

Calcaneoquartal joints, where all soft tissues had been completely resected and fixated with glue (1-1.5 cm2 joint surface), withstood 2-5 mm of displacement and an average of 100 ± 58 N/cm2 of shear force (Model 1). Similar adhesive fixation strengths were obtained in Model 2 and 3 with increasing contributions from soft tissues (80 ± 44 and 63 ± 23 N/cm2, p = 0.39, ANOVA).

Conclusion

The developed biomechanical model was sensitive enough to measure differences in fixation strengths between different glue formulations. The average fixation strength (60-100 N/cm2) should be strong enough to support short-term load bearing in medium sized canines (20 kg). The developed cadaver biomechanical test model is of potential use for other arthrodesis studies. The new resorbable glue can potentially contribute to stability at arthrodesis surgery, acting as a complement to today's standard fixation, metal implants.

First Tarsometatarsal Joint Fusion in Foot-A Biomechanical Human Anatomical Specimen Analysis with Use of Low-Profile Nitinol Staples Acting as Continuous Compression Implants

Background and Objectives: The aim of this study was to investigate under dynamic loading the potential biomechanical benefit of simulated first tarsometatarsal (TMT-1) fusion with low-profile superelastic nitinol staples used as continuous compression implants (CCIs) in two different configurations in comparison to crossed screws and locked plating in a human anatomical model. Materials and Methods: Thirty-two paired human anatomical lower legs were randomized to four groups for TMT-1 treatment via: (1) crossed-screws fixation with two 4.0 mm fully threaded lag screws; (2) plate-and-screw fixation with a 4.0 mm standard fully threaded cortex screw, inserted axially in lag fashion, and a 6-hole TMT-1 Variable-Angle (VA) Fusion Plate 2.4/2.7; (3) CCI fixation with two two-leg staples placed orthogonally to each other; (4) CCI fixation with one two-leg staple and one four-leg staple placed orthogonally to each other. Each specimen was biomechanically tested simulating forefoot weightbearing on the toes and metatarsals. The testing was performed at 35-37 °C under progressively increasing cyclic axial loading until construct failure, accompanied by motion tracking capturing movements in the joints. Results: Combined adduction and dorsiflexion movement of the TMT-1 joint in unloaded foot condition was associated with no significant differences among all pairs of groups (p ≥ 0.128). In contrast, the amplitude of this movement between unloaded and loaded foot conditions within each cycle was significantly bigger for the two CCI fixation techniques compared to both crossed-screws and plate-and-screw techniques (p ≤ 0.041). No significant differences were detected between the two CCI fixation techniques, as well as between the crossed-screws and plate-and-screw techniques (p ≥ 0.493) for this parameter of interest. Furthermore, displacements at the dorsal and plantar aspects of the TMT-1 joint in unloaded foot condition, together with their amplitudes, did not differ significantly among all pairs of groups (p ≥ 0.224). Conclusions: The low-profile superelastic nitinol staples demonstrate comparable biomechanical performance to established crossed-screws and plate-and-screw techniques applied for fusion of the first tarsometatarsal joint.

Effect of Simulated Bone Resorption on the Biomechanical Performance of Intramedullary Devices for Foot and Ankle Arthrodesis

Midfoot and subtalar arthrodesis surgeries are performed to correct foot deformities and relieve arthritic pain. These procedures often employ intramedullary (IM) devices. The aim of the present study was to evaluate the biomechanical performance of a sustained dynamic compression (SDC) IM device compared to mechanically static devices in withstanding the effects of simulated bone resorption. Mechanically static and SDC IM devices were implanted in simulated bone blocks (n = 5/device). Compressive loads were measured with a custom-made mechanism to simulate bone resorption. The construct bending stiffness was determined from a 4-point bend test. Resorption was simulated by cutting a 1 mm or 2 mm gap in the midpoint of each construct and repeating the loading (n = 6/device). Initial compressive loads after device insertion were greater in the SDC IM devices when compared to the static devices (p < .01). The SDC device was able to sustain compression from 2 mm to 5.5 mm of simulated resorption depending upon device length, while the static devices lost compression within 1 mm of simulated resorption regardless of implant length (p < .001). In the 4-point bend test, the SDC device maintained its bending stiffness during simulated resorption whereas the static device displayed a significant loss in bending stiffness after 1 mm of simulated resorption (p < .001). The SDC device exhibited a significantly higher bending stiffness than the static device (p < .001). The SDC IM device demonstrated superior biomechanical performance during simulated resorption compared to static devices (p < .001). In conclusion, the ability of SDC IM devices to maintain construct stability and sustain compression across the fusion site while adapting to bone resorption may lead to greater fusion rates and overall quicker times to fusion than static IM devices. Surgeons who perform midfoot and subtalar arthrodesis procedures should be aware of a device's ability to sustain compression, especially in cases where bone resorption and joint settling are prevalent postoperatively.

Plate Fixation in Midfoot and Ankle Charcot Neuroarthropathy

Surgical reconstruction of Charcot arthropathy in the foot and ankle is extremely difficult. The fundamentals of reconstruction are necessary to provide adequate outcome. Removing and resecting the diseased bone is needed along with good anatomic alignment and rigid fixation. This reconstructive surgery is not only difficult from medical management point of view but also involves patient compliance and good technical components of the surgery from the surgeon. The surgeon must have skills with internal and external fixation, a good understanding of lower extremity vascular disease, and a good understanding of infectious disease and plastic surgical techniques of the lower extremity.

Plantar Plating for Medial Naviculocuneiform Arthrodesis in Progressive Collapsing Foot Deformity

Background:

Medial column procedures are commonly used to treat progressive collapsing foot deformity (PCFD) reconstruction. The aim of this research is to present the clinical results of plantar plating for medial naviculocuneiform (NC) arthrodesis when NC joint pathology contributes to medial arch collapse. The authors hypothesized that lag screws with a plantar neutralization plate would result in a satisfactory NC joint fusion rate.

Methods:

A single-surgeon, retrospective case series was performed on patients with flexible PCFD who underwent NC arthrodesis using lag screws and a contoured neutralization plate applied plantarly across the medial NC joint as part of PCFD reconstruction. Thirteen patients (11 females, 2 males; mean age 53.1 [34-62] years) between 2016 and 2019 were identified for inclusion. Mean follow-up was 25.2 ± 12.7 months. Preoperative and postoperative anteroposterior talo–first metatarsal angle, lateral talo–first metatarsal angle, talonavicular coverage angle, and calcaneal pitch were measured. Union was evaluated radiologically. AOFAS midfoot scores were recorded at final follow-up.

Results:

All parameters demonstrated a significant improvement. Fusion was confirmed in 11 of 13 patients (85%) at a mean 5.7 ± 2.1 months. One patient required a revision of their NC fusion because of symptomatic nonunion. There were no cases of symptomatic plantar hardware.

Conclusion:

The results of this small cohort series suggest that lag screw with plantar plate NC arthrodesis yielded generally improved short-term radiographic and clinical outcomes in PCFD patients with medial arch collapse through the NC joint.

Level of Evidence: Level IV, retrospective case series.

Locked Dorsal Compression Plate Arthrodesis for Degenerative Arthritis of the Midfoot

Midfoot arthrodesis is the accepted surgical treatment for symptomatic midfoot arthritis. The published literature has focused on joint-spanning static fixation. Several companies have developed diamond-shaped locked dorsal compression plates, which allow for longitudinal joint compression. After dorsal plate insertion, a spreader device opens the arms of the plate mediolaterally, which allows the plate to compress longitudinally. This work describes outcomes of such locked dorsal compression plates for midfoot arthritis at a single institution. We reviewed 62 patients who underwent midfoot arthrodesis for symptomatic midfoot arthritis using locked dorsal compression plates over a 7-year period. A total of 173 joints were spanned for fusion. The primary outcome measure was radiographic union and visual analog scale pain scores. Characteristics of patients who experienced nonunion versus those who had union were evaluated. Of the 173 joints, there was a 81.5% fusion rate (141/173 joints) and 14 patients experienced nonunion. There was a statistically significant difference in the average number of joints spanned in patients with nonunion (3.6) and patients with union (2.5) (p = .02). Locked dorsal compression plate arthrodesis is a viable technique for achieving midfoot fusion. This mechanical method of compression does not, however, lend itself to improved fusion rates compared with prior reports. A greater number of arthrodesis sites is associated with a higher nonunion rate. Emerging technology using newer materials and improved biomechanical designs may show improved results.

Biomechanical Comparison of Intramedullary Beaming and Plantar Plating Methods for Stabilizing the Medial Column of the Foot: An In Vitro Study

Charcot neuroarthropathy often results in a rocker-bottom foot deformity, which leads to ulceration, infection, and amputation. Surgical techniques to reconstruct the medial column include intramedullary beaming and plantar plating, with disagreement regarding which approach provides a stronger construct with superior stability and fixation. The objective of the present cadaveric study was to compare the construct rigidity and strength of beaming and plantar plating of the medial column of 5 paired bilateral feet. Cannulated titanium beams and plates were implanted in the right and left feet, respectively. The specimens underwent interval testing to generate load-displacement and load-strain curves, cyclic loading at low loads, and then were loaded to failure. The beamed and plated specimens had statistically similar stiffness (p = .80) with a mean of 11.1 ± 3.9 N/mm and 11.3 ± 5.9 N/mm, respectively. The beamed and plated specimens had a statistically similar mean strain of -164 ± 75.1 µε and -208 ± 87.8 µε on the dorsal (p = .45) and 92 ± 90.4 µε and 221 ± 100.5 µε on the plantar (p = .08) surfaces of the first metatarsal. Three beamed specimens failed from talus fracture (60%), and 2 beams plastically deformed (40%). Two plated specimens failed from talus fracture (40%), and 3 experienced screw pullout (60%). The beamed and plated specimens withstood a mean load to failure of 234 ± 111.4 N and 140 ± 68.9 N, respectively, with the difference statistically significant (p = .04). Overall, beaming was more robust than plantar plating, because it was less sensitive to specimen size and bone quality.