Correction to Read for Credit #955 question 4

Abstract

Dear Editor MacDermid, As the authors of "An in-depth look at zone III and IV anatomy of the finger extensor mechanism and some clinical implications for use of the relative motion flexion orthosis," 1 We are requesting that the author of Read for Credit Quiz #955 provide the correct answer to question #4. The correct answer is detailed in the article (1) on page 283; left column, line 4. Communication among clinicians and anatomists will improve if universal terminology regarding the structures composing the ex-tensor mechanism (EM) is implemented. This use of universal terminology between scientist and clinician colleagues would lend to better understanding and discussions about the anatomical and functional interactions between the EM's complex tendinous, in-tertendinous, and ligamentous structures. An example is the inappropriate use of the term lateral bands (LBs) instead of conjoined lateral bands (CLBs) when describing the tendinous structures that run on each side of the distal-dorsal end of the proximal phalanx and continue distally past the proximal interphalangeal joint (PIPJ). For this structure, the use of LBs instead of CLBs has lingered for too long and was an important aim for writing our article to distinguish the difference between the LBs and the CLBs. Another important focus of the article was to bring attention to the spiral fibers (SFs), their relationship with the CLBs, and their importance for the proper functioning of the EM. Knowledge of the arrangement of the EM's tendinous and inter-tendinous structures may improve our clinical insight into the EM's function. For example, we point out that intact SFs limit the volar shift of the CLBs (not the LBs) when moving into PIPJ flexion. As shown in Figure 11, the fibers composing the CLBs are derived from both extrinsic fibers from the LBs of the extensor digitorum (ED) and intrinsic fibers from the intrinsic tendon (IT). This is an important distinction between the CLBs and the LBs as the merger of the ex-trinsic fibers (LBs) and intrinsic fibers (IT) is proximal to the PIPJ, while the CLBs continue distally along the PIPJ. The SFs that are located directly over the PIPJ originate from these CLBs, then run dorsal on both sides of the PIPJ and attach to the medial band of the ED and the central slip. The clinical significance of understanding these anatomical relationships lies herein that a zone IV injury (LB/ IT) will probably be managed differently than a zone III EM injury (CLB/SF), and the use of universal (and correct) terminology will improve clinical decision making and communication between surgeons and therapists. Based on our description, the answers to Read for Credit #955 as provided below for question #4 are incorrect: Question #4. The spiral fibers run between the a. dorsal expansionand the EDC b. central slip and the lateral bands c. lumbricales and the interossei d. FDP and the EDC The correct answer should be the SFs are located between the central slip (and the medial slip of the ED) and the CLBs. On a final note, as we endorse the use of universal and precise terminology, we would have preferred that the author of the Read for Credit questions had not used the term EDC but would have followed the article's text, which consistently used ED based on the official International Federation of Societies for Surgery of the Hand and universal anatomical terminology (https://ifssh.info/terminology_hand_ surgery.php/, chapter 1: anatomy).