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. 2019 Nov 7;4(4):2473011419884274.
doi: 10.1177/2473011419884274. eCollection 2019 Oct.

Anatomy of the Distal End of Flexor Digitorum Longus Tendon and Percutaneous Release Technique: A Cadaveric Study

Baofu Wei  1   2   3 , Ruoyu Yao  4   3 , Annunziato Amendola  2
Affiliations

Anatomy of the Distal End of Flexor Digitorum Longus Tendon and Percutaneous Release Technique: A Cadaveric Study

Baofu Wei et al. Foot Ankle Orthop. .

Abstract

Background: The transfer of flexor-to-extensor is widely used to correct lesser toe deformity and joint instability. The flexor digitorum longus tendon (FDLT) is percutaneously transected at the distal end and then routed dorsally to the proximal phalanx. The transected tendon must have enough mobility and length for the transfer. The purpose of this study was to dissect the distal end of FDLT and identify the optimal technique to percutaneously release FDLT.

Methods: Eight fresh adult forefoot specimens were dissected to describe the relationship between the tendon and the neurovascular bundle and measure the width and length of the distal end of FDLT. Another 7 specimens were used to create the percutaneous release model and test the strength required to pull out FDLT proximally. The tendons were randomly released at the base of the distal phalanx (BDP), the space of the distal interphalangeal joint (SDIP), and the neck of the middle phalanx (NMP).

Results: At the distal interphalangeal (DIP) joint, the neurovascular bundle begins to migrate toward the center of the toe and branches off toward the center of the toe belly. The distal end of FDLT can be divided into 3 parts: the distal phalanx part (DPP), the capsule part (CP), and the middle phalanx part (MPP). There was a significant difference in width and length among the 3 parts. The strength required to pull out FDLT proximally was about 168, 96, and 20 N, respectively, for BDP, SDIP, and NMP.

Conclusion: The distal end of FDLT can be anatomically described at 3 locations: DPP, CP, and MPP. The tight vinculum brevis and the distal capsule are strong enough to resist proximal retraction. Percutaneous release at NMP can be performed safely and effectively.

Clinical relevance: Percutaneous release at NMP can be performed safely and effectively during flexor-to-extensor transfer.

Keywords: BDP; FDLT; NMP; plantar capsule; vinculum brevis.

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Conflict of interest statement

Declaration of Conflicting Interests: The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article. ICMJE forms for all authors are available online.

Figures

Figure 1.
Figure 1.
Model of cutting off the distal end of flexor digitorum longus tendon (FDLT) at different levels. Cutting at base of the distal phalanx (BDP): (A1) anteroposterior view; (A2) lateral view. Cutting at space of the distal interphalangeal joint (SDIP): (B1) anteroposterior view; (B2) lateral view. Cutting at neck of the middle phalanx (NMP): (C1) anteroposterior view; (C2) lateral view. (D) Relationships among the 3 cutting levels: 1, FDLT; 2, proximal part of the vinculum brevis; 3, head of the middle phalanx; 4, BDP; 5, flexor digital brevis tendon; 6, capsule. Line a: BDP; line b: SDIP; line c: NMP.
Figure 2.
Figure 2.
Method, establishment, and equipment used in the biomechanical test.
Figure 3.
Figure 3.
Relationship between the neurovascular bundle and the distal end of flexor digitorum longus tendon (FDLT) (the left second toe). 1, fat pad; 2, pulp artery; 3, distal transverse arch; 4, proper plantar digital artery; 5, distal end of the FDLT; 6, pulley; and 7, proper plantar digital nerve.
Figure 4.
Figure 4.
Division of the distal part of flexor digitorum longus tendon (FDLT) (left third toe): (A) anteroposterior view; (B) Lateral view. 1, FDLT; 2, distal interphalangeal joint (DIP); 3, base of the distal phalanx (BDP); 4, proximal interphalangeal joint (PIP); 5, proximal part of the vinculum brevis; 6, FDLT; 7, capsule of the DIP. Abbreviations: DPP, distal phalanx part; CP, capsule part; MPP, middle phalanx part.
Figure 5.
Figure 5.
(A) Cutting at the base of the distal phalanx (BDP). (B) Cutting at the space of the distal interphalangeal joint (SDIP). (C) Cutting at the neck of the middle phalanx (NMP).
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