Biomechanical comparison of first metatarsophalangeal joint arthrodeses using triple-threaded headless screws versus partially threaded lag screws

Evaluating the Biomechanical Integrity of Various Constructs Utilized for First Metatarsophalangeal Joint Arthrodesis: A Systematic Review

The first metatarsophalangeal (MTP) joint is a frequently loaded joint, handling loads up to 90% of bodyweight. First MTP arthrodesis is a frequently performed procedure designed to improve pain in patients with degenerative MTP joint disease. There are a wide variety of fixation constructs for this procedure without consensus on the most effective method. The purpose of this study was to compare the biomechanical integrity of various constructs utilized for first MTP arthrodesis. A systematic review of the literature was conducted in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. PubMed, CINAHL, MEDLINE, and Web of Science databases were searched from inception to 18 June 2023. Articles discussing the biomechanics of first MTP arthrodesis constructs were included. A total of 168 articles were retrieved. A total of 20 articles involving 446 cadaveric and synthetic bone constructs were included in the final review. Of the six articles comparing dorsal plating with compression screws to crossed interfragmentary screws, five found that dorsal plating had significantly higher stiffness. All three studies assessing shape-memory staples found them to be significantly less stable than crossed screws or dorsal plates alone. Both studies evaluating fully threaded screws found them to be stronger than crossed cancellous screws. Wedge resections have been shown to be 10 times stronger than standard planar or conical excision. Dorsal plating with compression screws is the gold standard for MTP arthrodesis. However, more research into newer methods such as fully threaded screws and wedge resections with an increased focus on translation to clinical outcomes is needed.

Arthroscopic Arthrodesis of the First Metatarsophalangeal Joint in Hallux Valgus Deformity Using Medial and Toe Web Portals

Arthrodesis of the first metatarsophalangeal joint is indicated for severe hallux valgus deformity. Open arthrodesis requires extensive soft-tissue dissection. Recently, a technique of arthroscopic first metatarsophalangeal arthrodesis in hallux valgus deformity has been reported. This approach includes endoscopic lateral release of the first metatarsophalangeal joint via the plantar and toe web portals, followed by arthroscopic arthrodesis of the joint via the medial and dorsolateral portals. Endoscopic lateral release of the first metatarsophalangeal joint can convert the fixed hallux valgus deformity into a flexible one and reduce the stress over the screws and risk of loss of reduction and nonunion. The purpose of this Technical Note is to report a modified technique of arthroscopic first metatarsophalangeal arthrodesis in hallux valgus deformity. In this modified technique, the arthrodesis is performed via the medial and toe web portals and creation of the dorsolateral portal is not needed. A 2.7-mm arthroscope is used for the arthrodesis procedure instead of a 1.9-mm arthroscope. This can improve fluid inflow and visualization.

First Metatarsophalangeal Arthrodesis for the Failed Hallux

Hallux metatarsophalangeal joint (MTPJ) arthrodesis was first described in 1894 by Clutton, who recommended ankylosing the MTPJ to treat painful hallux valgus (HV). He used ivory pegs to stabilize the MTP joint. Surgeons over the last century have modified the procedure and added indications, including hallux rigidus, rheumatoid arthritis, and revision of failed surgeries. This article addresses many common yet challenging clinical scenarios, and a few hot topics, related to hallux MTPJ arthrodesis, including matarsus primus elevatus, severe hallux valgus, avascular necrosis, and infections. The article provides a condensed evidence-based discussion on how to manage these challenges using MTPJ arthrodesis.

Biomechanical Study Concerning the Types of Resection in Arthrodesis of First Metatarsophalangeal Joint

This work concerns a biomechanical study aiming to ascertain the optimal type of joint resection when performing a joint arthrodesis. A 3-dimensional digital model of the first metatarsophalangeal joint including the entire first metatarsal bone and proximal phalanx using CT scans of the forefoot was created. Using this computer model, 4 types of resections; ball-and-socket, flat-on-flat, wedge 90°, and wedge 100° were simulated. Parameters measured using this model were the force necessary to separate the 2 fused surfaces, the surface area of the resected surfaces and the shortening of the first ray. By measuring the reactive force necessary to separate the phalanx from the first metatarsal, the 90° wedge resection was found to be the most stable, with comparable results in the case of the 100° wedge resection. Wedge resections are also more favorable when comparing the shortening of the first ray. Wedge resections, though being more technically difficult to perform prove to be the most stable for metatarsophalangeal joint-1 arthrodesis using this model.

Biomechanical Comparison of Low-Profile Contoured Locking Plate With Single Compression Screw to Fully Threaded Compression Screws for First MTP Fusion

BACKGROUND

Open metatarsophalangeal (MTP) arthrodesis using locked plates produces good clinical outcomes. However, arthroscopic fusion with new-generation fully threaded compression screws is emerging as an alternative. The purpose of this study was to compare low-profile contoured locked plates with fully threaded compression screws for first MTP fusion, in a biomechanical cadaveric model.

METHODS

The first rays of 8 matched pairs of fresh frozen cadaveric feet underwent dissection and dual-energy x-ray absorptiometry (DEXA) scanning to measure bone mineral density (BMD). The "plate" group was prepared with cup-and-cone reamers, and fixation of the MTP joint with 1 compression screw and low-profile dorsal locked plate. The matched-pair "screws" group was prepared through a simulated arthroscopic technique, achieving fixation with 2 new-generation fully threaded compression screws. The plantar MTP gap was recorded with an extensometer during 250 000 90-N cyclic loads followed by a single load to failure.

RESULTS

The screw group demonstrated significantly greater stiffness, 31.6 N/mm (plates) and 51.7 N/mm (screws) (P = .0045). There was no significant difference in plantar gapping or load to failure, 198.6 N (plates) and 290.1 N (screws) (P = .2226). Stiffness and load to failure were highly correlated to BMD for the screw group, r =0.79 and r = 0.94, respectively, but less so for the plate group, r = 0.36 and r = 0.62, respectively. The maximum metatarsal head height measured on the lateral view was strongly correlated with load to failure for both the plate- and screw-only groups (r > 0.9).

CONCLUSION

These data demonstrate that hallux MTP arthrodesis utilizing fully threaded compression screws had similar plantar gapping and load to failure when compared with the low-profile locking plate, but with significantly more stiffness. These results support an increased role of fully threaded screws for MTP arthrodesis using either the arthroscopic or open technique. However, with decreased BMD plate fixation may remain the better fixation choice.

CLINICAL RELEVANCE

Our data suggest that with regard to construct stability, fully threaded headless compression screws may be just as effective as low-profile locking plates, but BMD and MTP joint fluoroscopic measurements should be considered in the decision-making process for fixation.

Headless compression screw for horizontal medial malleolus fractures

BACKGROUND

Horizontal medial malleolus fractures are caused by the application of rotational force through the ankle joint in several orientations. Multiple techniques are available for the fixation of medial malleolar fractures.

METHODS

Horizontal medial malleolus osteotomies were performed in eighteen synthetic distal tibiae and randomized into two fixation groups: 1) two parallel unicortical cancellous screws or 2) two Acutrak 2 headless compression screws. Specimens were subjected to offset axial tension loading. Frontal plane interfragmentary motion was monitored.

FINDINGS

The headless compression group (1699 (SD 947) N/mm) had significantly greater proximal-distal stiffness than the unicortical group (668 (SD 298) N/mm), (P = 0.012). Similarly, the headless compression group (604 (SD 148) N/mm) had significantly greater medial-lateral stiffness than the unicortical group (281 (SD 152) N/mm), (P < 0.001). The force at 2 mm of lateral displacement was significantly greater in the headless compression group (955 (SD 79) N) compared to the unicortical group (679 (SD 198) N), (P = 0.003). At 2 mm of distal displacement, the mean force was higher in the headless compression group (1037 (SD 122) N) compared to the unicortical group (729 (SD 229) N), but the difference was not significant (P = 0.131).

INTERPRETATION

A headless compression screw construct was significantly stiffer in both the proximal-distal and medial-lateral directions, indicating greater resistance to both axial and shear loading. Additionally, they had significantly greater load at clinical failure based on lateral displacement. The low-profile design of the headless compression screw minimizes soft tissue irritation and reduces need for implant removal.

Arthroscopic Arthrodesis of the First Metatarsophalangeal Joint in Hallux Valgus Deformity

Arthrodesis of the first metatarsophalangeal joint is indicated for hallux valgus associated with degenerative changes, severe deformity, or rheumatoid arthritis and those for whom primary hallux valgus surgery has failed. Open approach requires extensive soft tissue dissection. The purpose of this Technical Note was to report the details of arthroscopic arthrodesis of the first metatarsophalangeal joint in severe and rigid hallux valgus deformity. This is a combination of endoscopic lateral release of the first metatarsophalangeal joint and arthroscopic arthrodesis of the joint. Endoscopic lateral release will convert the deformity into a flexible one and facilitate a subsequent arthrodesis procedure.