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

Abstract

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.

First Metatarsophalangeal Joint Arthrodesis: A Narrative Review of Fixation Constructs and Their Evolution

“…This evolving and ever-expanding list of fixation constructs has provided surgeons with many options when selecting hardware for first MTP arthrodesis, each with its own unique benefits and limitations. Current options for fixation devices include screws in various configurations, Kirschner wires (K-wires), Steinmann pins, monofilament wires, biodegradable rods, both locking and non-locking plates, memory compression staples, and various combinations of these fixation devices [7,11,[18][19][20][21].…”

“…Fixation with screws has since changed drastically, but screws are still common means of fixation in first MTP arthrodesis. Currently, screw fixation is primarily in the form of a supplementary lag screw [11,16,20] or as the fixation construct itself, most commonly as a single screw, two parallel screws, or two crossed screws (Figure 1) [7,16,[22][23][24]. Studies have shown these methods of fixation to be acceptable options as they work well in patients with good bone quality and cause less postoperative irritation and discomfort due to their relatively low profile.…”

“…The lower profile of screw fixation is also useful in scenarios in which joint space is limited, such as fixation in children or in cases where deformities prevent the use of plates. Crossed-screw fixation can provide an acceptable amount of biomechanical stability in these scenarios [7,22]. One limitation to the use of screws as a sole fixation construct is that patients must remain non-weight-bearing for a longer period of time than if another construct, such as a plate, or even a combination of constructs is used.…”

“…One limitation to the use of screws as a sole fixation construct is that patients must remain non-weight-bearing for a longer period of time than if another construct, such as a plate, or even a combination of constructs is used. More recent studies are beginning to investigate the use of new types of screws in new configurations in an effort to improve arthrodesis techniques with regard to invasiveness, postoperative complications, fusion rates, stability, and cost of each fixation device [7,22].…”

“…It was originally described by Clutton in 1894 as a treatment for severe cases of hallux valgus, but, over the years, its indications have since expanded [5]. It is now most commonly used as means for surgical treatment of end-stage arthritis of the first MTP joint [6], also known as hallux rigidus, as well as for a salvage operation in the case of previously failed cheilectomy, resection arthroplasty, implant arthroplasty, or severe hallux valgus deformity [7][8][9][10]. As a result of successful outcomes, first MTP arthrodesis has become a standard procedure in the treatment of disorders of the forefoot and first ray [11][12][13][14][15][16].…”