Biomechanical Comparison of Fixation With a Single Screw Versus Two Kirschner Wires in Distal Chevron Osteotomies of the First Metatarsal: A Cadaver Study

Biomechanical comparison of different fixation methods in tibiotalocalcaneal arthrodesis: a cadaver study

BACKGROUND

Various fixation methods are available for tibiotalocalcaneal arthrodesis: nail, plate, or screws. An intramedullary bone stabilization system within a balloon catheter has not previously been used in tibiotalocalcaneal arthrodesis. The aim of this study was to compare the stability of these techniques.

METHODS

Twenty-four lower legs from fresh-frozen human cadavers were used. Tibiotalocalcaneal arthrodesis was performed with a retrograde nail, a lateral locking plate, three cancellous screws, or an intramedullary bone stabilization system. The ankles were loaded cyclically in plantarflexion and dorsiflexion.

RESULTS

For cyclic loading at 125 N, the mean range of motion was 1.7 mm for nail, 2.2 mm for plate, 6.0 mm for screws, and 9.0 mm for the bone stabilization system (P < .01). For cyclic loading at 250 N, the mean range of motion was 4.4 mm for nail, 7.5 mm for plate, 12.1 mm for screws, and 14.6 mm for the bone stabilization system (P < .01). The mean cycle of failure was 4191 for nail, 3553 for plate, 3725 for screws, and 2132 for the bone stabilization system (P = .10).

CONCLUSIONS

The stability of the tibiotalocalcaneal arthrodesis differs depending on the fixation method, with nail or plate showing the greatest stability and the bone stabilization system the least. When three screws are used for tibiotalocalcaneal arthrodesis, the stability is intermediate. As the biomechanical stability of the bone stabilization system is low, it cannot be recommended for tibiotalocalcaneal arthrodesis.

The influence of partial weight bearing on plantar peak forces using three different types of postoperative shoes

BACKGROUND

Therapeutic shoes and partial weight bearing regimes are used after foot surgery to prevent the operated region from excessive load. It remains unclear to which extent partial weight bearing reduces the plantar peak forces. Therefore, we investigated the correlation of weight bearing and plantar peak forces in commonly used therapeutic shoes.

METHODS

Three different weight bearing regimes (20 kg, 40 kg, full weight) were investigated in 20 healthy volunteers. Sensor insoles were used to measure peak forces of the forefoot, midfoot, heel and the complete foot using four kind of shoes (bandage shoe, forefoot relief shoe, short walker and standard sneaker). Peak forces were compared between shoes using one-way ANOVA. The influence of partial weight bearing relative to the peak forces was examined by linear regression analysis.

RESULTS

All therapeutic shoes reduced significantly peak forces of the fore- and midfoot when compared to the reference shoe; the largest reduction was achieved by the forefoot relief shoe (-70 % at forefoot). Weight load and the resulting peak force showed a positive linear correlation for all regions and shoe types. Partial weight bearing significantly reduced the forefoot's force ratio compared to full weight bearing for all shoes except the forefoot relief shoe.

CONCLUSIONS

Partial weight bearing is a strong instrument to reduce plantar peak forces of the forefoot, additionally to the proven offloading effect of therapeutic shoes.

Biomechanical Comparison of a Novel Method of Tricortical Kirschner Wire Fixation of Distal Chevron Osteotomies of the First Metatarsal Versus Traditional Kirschner Wire and Versus Screw Fixation

INTRODUCTION

Traditional Kirschner wire (K-wire) stabilization of first metatarsal distal chevron osteotomy involves 1 cortex of fixation; however, unicortical fixation is associated with a high complication rate, including pin migration. A method of K-wire fixation utilizing 3 cortices may be biomechanically superior and potentially equivalent to single-screw fixation.

METHODS

Cadaveric specimens fixed with tricortical K-wires were tested in both the physiologic and cantilever conditions against specimens fixed with unicortical K-wires (N = 8) and single screws (N = 9) utilizing matched-pair comparison groups. Differences in physiologic and cantilever fixed/intact stiffness ratio and cantilever failure load were determined.

RESULTS

The tricortical fixation specimens had a significantly higher stiffness ratio in cantilever loading than the unicortical fixation specimens (60.50% tricortical, 34.17% unicortical, P = .02) but not in physiologic load (15.34% tricortical, 25.75% unicortical, P = .23). In cantilever failure loading, the tricortical fixation specimens had a significantly higher load to failure than the unicortical fixation specimens (132.81 N tricortical, 58.58 N unicortical, P < .01). Stiffness ratio under physiologic load, cantilever load, and ultimate load to failure were not significantly different between tricortical K-wire and screw-fixation groups.

CONCLUSION

Tricortical K-wire fixation for distal chevron osteotomies is biomechanically superior to traditional unicortical K-wire fixation, and equivalent to single-screw fixation.

LEVELS OF EVIDENCE

Level V: Cadaver study.

Is the magnesium screw as stable as the titanium screw in the fixation of first metatarsal distal chevron osteotomy? A comparative biomechanical study on sawbones models

Background: Distal chevron osteotomy (DCO) is commonly performed in hallux valgus surgery. The fixation of the osteotomy is provided by various implants. The usage of biodegradable implants such as magnesium is gradually increasing due to the advantages they provide. In this study, we aimed to compare the fixation of DCO with magnesium or titanium screw biomechanically. Methods: Twenty sawbones were used. The samples were divided into two equal groups, including ten sawbones for fixation with single headless titanium (group-1) or magnesium screw (group-2). DCO and screw fixations were performed on all samples using the same technique. Biomechanical testing was applied to five samples in each group in cantilever and the other five in a physiological configuration using a computer connected to the electromechanical test machine. The obtained data were evaluated using the Shapiro-Wilk test, Student's t-test and Mann-Whitney U test on the IBM® SPSS (Statistical Package for the Social Sciences) V22.0 software. Significance was accepted at the p < 0.05 level. Results: There was no statistically significant difference between the magnesium screw and the titanium screw in terms of maximum force, maximum displacement and stiffness measurements in cantilever and physiological loadings (p > 0.05 for all). Conclusion: This study found no significant difference in biomechanical stability between the magnesium and titanium screws in DCO fixation on sawbones. Further studies with real bones are needed.

Biomechanical comparison of different fixation methods in metatarsal shaft fractures: A cadaver study

BACKGROUND

Various fixation methods are available for the operative treatment of metatarsal shaft fractures: Kirschner wire, Titanium elastic nail, plate, or an intramedullary bone stabilization system within a balloon catheter. The aim of this study was to compare the stability of these techniques.

METHODS

72 metatarsals II to V from fresh frozen human cadaver feet were used. A shaft fracture was performed and fixed with a 1.6-mm Kirschner wire, a 1.5-mm Titanium elastic nail, a locking 6-hole-plate, or an intramedullary bone stabilization system. In a cantilever configuration, the head of the metatarsals was loaded statically (2 mm/min until failure; all groups) or cyclically (0 to 20 N for 1000 cycles with 10 mm/s, after 1000 cycles 2 mm/min until failure; plate and bone stabilization system).

FINDINGS

The mean failure strength for static loading was 17 N for Kirschner wire, 13 N for Titanium elastic nail, 73 N for plate and 34 N for the bone stabilization system (P < .01). For cyclic loading, the mean cycle of failure was 1000 for plate and 961 for the bone stabilization system (P = .76). The mean failure strength after cyclic loading was 73 N for plate and 48 N for the bone stabilization system (P = .03).

INTERPRETATION

Stability differs depending on the fixation method, with a plate showing the greatest stability and Kirschner wire or Titanium elastic nail the least. The stability of the bone stabilization system for fixing metatarsal shaft fractures is intermediate.

Biomechanical Comparison of 2 Common Techniques of Minimally Invasive Hallux Valgus Correction

BACKGROUND

Hallux valgus is one of the most common surgically corrected forefoot deformities. Compared to open procedures, minimally invasive (MIS) treatment of hallux valgus has resulted in decreased operative time, reduced complication rates, and greater patient satisfaction. Historically, distal chevron osteotomies are the standard for moderate hallux valgus correction. To our knowledge, no studies have evaluated biomechanical strength of transverse and chevron distal first metatarsal osteotomy (DMO) constructs. The purpose of this study was to evaluate the biomechanical strength of these techniques.

METHODS

Eighteen cadaveric specimens (9 matched pairs) were randomized to transverse or chevron DMO. Each technique was performed by a separate fellowship-trained orthopedic foot and ankle surgeon. Radiographic images were analyzed. Biomechanical testing was performed using Instron Mechanical System. Ultimate load to failure, yield load, and stiffness were assessed. A 10-N preload was applied to the sesamoid bones for stability. A coaxial compression rate (10 mm/min) was applied until failure was observed. Mean and standard deviations were compared. All cadaveric specimens were male.

RESULTS

There was no significant difference in percent metadiaphyseal shift between osteotomies (P = .453). The most common mode of failure was fracture at screw insertion site (55.6%), followed by failure at osteotomy site (44.4%). A trend toward increased ultimate load to failure (P = .480), yield load (P = .054), and stiffness (P = .438) among transverse compared to chevron osteotomy was observed, but this difference was not statistically significant.

CONCLUSION

Biomechanical testing demonstrated no significant difference in ultimate load, yield load, and stiffness between MIS transverse and chevron osteotomy constructs; a trend toward increased strength in the transverse osteotomy cohort was observed. Chevron osteotomies may result in early failure by relative ease of cutout through cancellous bone compared to transverse osteotomies in which failure requires cortical cutout.

CLINICAL RELEVANCE

Use of MIS techniques for hallux valgus correction is gaining clinical traction. Although various clinical studies have evaluated outcomes of these MIS techniques, biomechanical studies have been minimal. Specifically, the potential biomechanical benefits of various MIS hallux valgus osteotomy techniques have not been delineated to date. The content of this manuscript is quite timely, given the rise in use of these MIS techniques.

Distal chevron osteotomy with lateral release for moderate to severe hallux valgus patients aged sixty years and over

PURPOSE

To analyze the outcome of distal chevron metatarsal osteotomy (DCMO) with lateral release for moderate to severe hallux valgus patients aged 60 years or more.

METHODS

Consecutive 77 DCMOs in 54 patients were evaluated. Average age at operation was 65.1 ± 4.3 (range 60~79) years; the mean follow-up period was 20.5 ± 14.2 (range 12~93) months. Hallux valgus angle (HVA), first to second inter-metatarsal angle (IMA), and lateral sesamoid grades were measured. Considering the weak bone quality of the patients, fixation failures such as pin migration, callus formation, delayed union, and first metatarsal bone shortening were reviewed. Osteoarthritis (OA) of the first metatarsophalangeal joint (MTPJ), limitation of 1st MTPJ motion (LOM), and transfer metatarsalgia were also reviewed.

RESULTS

HVA, IMA, and sesamoid grades were improved at three months and final follow-up. The mean HVA was 36.9° ± 7.0° preoperatively and 6.8° ± 7.1° at final follow-up. The mean correction angle of HVA was 31.3° ± 8.5° at three months and 30.1° ± 8.9° at final follow-up. The mean IMA was 16.3° ± 3.0° pre-operatively and 7.7° ± 2.7° at final follow-up. Hallux varus deformity was observed in three feet. Instability of osteotomy site was observed in one foot. Mean metatarsal shortening length was 1.26 ± 2.1 mm at three month follow-up. There were no cases of transfer metatarsalgia after operation. OA was observed in four feet post-operatively. LOM was observed in ten feet (13.0%). There were no instances of re-fracture or avascular necrosis (AVN).

CONCLUSION

Despite concerns about aggravation of OA and fixation failure, distal chevron osteotomy with lateral release was safe on patients aged 60 years and over.

Incidence and Risk Factors for Pin Site Infection of Exposed Kirschner Wires Following Elective Forefoot Surgery

BACKGROUND

Kirschner wires (K-wires) are commonly utilized for temporary metatarsal and phalangeal fixation following forefoot procedures. K-wires can remain in place for up to 6 weeks postoperatively and are at risk for complications. This study investigated the incidence of infectious complications of exposed K-wires after forefoot surgery and identifies risk factors for these complications.

METHODS

A single-surgeon retrospective chart review of forefoot surgeries from 2007 to 2017 was undertaken. Inclusion criteria were adult patients (≥18 years) undergoing elective forefoot surgery with the use of exposed K-wires. Incidence of pin site infectious complication, defined as cellulitis, or pin site drainage and/or migration/loosening of the pin was noted. Patient demographic and perioperative data were analyzed, along with the number of K-wires placed per procedure. Mann-Whitney U and chi-square tests were performed to determine predictive factors related to pin site infection rates, with a multivariable model with significant factors subsequently performed. Two-thousand seventeen K-wires in 1237 patients were analyzed.

RESULTS

There were 35 pin site infections for a rate of 1.74%. Combined forefoot procedures (507 pins in 229 patients) had a pin site infection rate of 4.93% (N = 25), followed by lesser metatarsal osteotomies (667 pins in 446 patients) at 1.05% (N = 7), then hammertoe corrections (694 pins in 421 patients) at 0.43% (N = 3), and no pin site infections with chevron osteotomies (149 pins in 141 patients). Male sex, body mass index (BMI), current smoker, and number of pins were significant risk factors (P ≤ .05). Additionally, there were 23 non-infection-related K-wire complications. No long-term sequelae were encountered based on any complications.

CONCLUSION

K-wires are commonly used for temporary immobilization of the smaller bones of the forefoot following deformity correction. Male sex, BMI, current smoker, and number of pins were significant risk factors for pin site infection, with a higher rate of infection with 2 or more pins placed.

LEVEL OF EVIDENCE

Level IV, case series.

Biomechanical comparison of conventional versus modified technique in distal chevron osteotomies of the first metatarsal: A cadaver study

BACKGROUND

Distal chevron osteotomy can be performed using a conventional or a modified technique. The aim of this biomechanical study was to compare the stability of the two techniques.

METHODS

Eighteen first metatarsals from nine pairs of fresh frozen human cadaver feet were used. A distal chevron osteotomy was performed using the conventional technique in group 1 (n=9) and using the modified technique in group 2 (n=9). The head of the first metatarsals was loaded in two different configurations (cantilever and physiological), using a materials testing machine.

RESULTS

In the cantilever configuration, the relative stiffness of the osteosynthesis in comparison with intact bone was 60% (±21%) in group 1 and 65% (±25%) in group 2 (p=0.61). In the physiological configuration, it was 47% (±29%) in group 1 and 47% (±21%) in group 2 (p=0.98). The failure strength in the cantilever configuration was 235N (±128N) in group 1 and 210N (±107N) in group 2 (p=0.47).

CONCLUSIONS

The conventional and the modified technique for distal chevron osteotomy in the treatment of hallux valgus show a comparable biomechanical loading capacity in this cadaver study.