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The beautifully coordinated functions of the hand depend on the tendon apparatus acting on the articulated skeletal elements. The flexor muscles are situated on the antero-medial aspect of the forearm, with their tendons crossing the wrist and finger joints in a wonderfully arranged system to provide the infinite movements possible. The anatomical details of the extrinsic and intrinsic flexor apparatus are presented, with their functions described as anticipated by their origins, insertions, and the joints they cross and thus can act upon.

Background: This study aimed to develop a classification that precisely describes the extensor carpi ulnaris (ECU) groove morphology.

Methods: Reconstructed axial plane computed tomography scans of the wrists of 200 patients were reviewed. Three groups of groove shape were created based on the position of the deepest point: deviated to the ulnar side (Type U), in the middle of the groove (Type M), and deviated to the radial side (Type R). Groove depth, width, carrying angle, and radius of the curvature were measured using the Picture Archiving and Communication System in a slice in which the ulnar head was the largest.

Results: Type U was present in 88 patients (44%), Type M in 74 patients (37%), and Type R in 38 patients (19%). The average depth, width, carrying angle, and radius of curvature were 2.2 mm, 9.2 mm, 135.8° and 7.0 mm, respectively. Depth, width, and carrying angle were normally distributed. Both depth and width were statistically correlated with the carrying angle; groove depth and width were not correlated. ECU groove shape and depth showed excellent intra- and inter-observer reliabilities; the reliabilities for the width were poor. Therefore, depth subgroups were defined using cutoffs of ±2 standard deviations (SD): d1 (≤-2 SD), ≤1.0 mm; d2 (±SD), 1.1–3.3 mm; and d3 (≥+2 SD), ≥3.4 mm. The 200 wrists were classified as follows: 0.5% Ud1, 40.2% Ud2, 1.3% Ud3, 0.8% Md1, 38.3% Md2, 0.8% Md3, 1.5% Rd1, 16.4% Rd2, and 0.2% Rd3.

Conclusions: The detailed morphology of the ECU groove was classified using three major types and depth subgroups. The Type R ECU groove, which lacks a medial bony buttress, might be more prone to ECU-related injuries. This classification helps to understand the ECU tendon-related injury pathologies and may provide valuable information for treatment decisions; however, further research is necessary.

Tendons and ligaments play an important role to ensure mobility and stability. To correctly understand the characteristics of these fibrous collagenous connective tissues, it is fundamental to highlight their 3D microstructure. In this study a microtomography (microCT) system was used to acquire human hamstring tendons after performing specific preparations to enhance image contrast. Specifically, samples were treated either through chemical dehydration or by 2% of phosphotungstic acid ($PTA$) in water ($H_{2}O$) or in 70% ethanol ($EtOH$) solution. Acquired images were elaborated using dedicated techniques based on 3D Hessian multiscale filter so as to highlight the fibrous structure and identify specific geometric features. For any strategy of sample preparation, the proposed approach resulted to be adequate for identifying fascicle features, thus obtaining structures with diameter in the range of 100–600 $\mu \text{m}$ and proper longitudinal alignment. In conclusion, a novel contrast enhancement microCT protocol was designed and preliminarily validated for the microstructural analysis of fibrous tissues.

The conventional hand tendon zones and subzones do not reflect the actual lengths covered by the involved locus of the tendon during full digital and wrist motion, which warrant reappraisal of the tendon zone concept. Because of the tendon excursions many lacerations should be regarded as multiple zone injuries. Furthermore, the length-spans of glide of the distal tendon stump and of the tendon junction (i.e. the glide zones of tendon injury and repair, respectively) are mostly not of the same length because, due to pulley release and bulkiness of the tenorrhaphy, the glide zone of tendon repair is shorter than that of tendon injury. Therefore, it would be practical to notate the glide zones of the lacerated tendon by indicating the anatomic position of the distal tendon stump and tendon junction in full extension and flexion. This data can be provided separately or along with the conventional tendon zones, e.g. II (A4–C2) or II–III (A2–PA), where A, C, and PA stand for the annular, cruciform, and palmar aponeurosis pulleys, respectively. The conventional tendon zone classification could be improved with a tendon glide zone concept. Documentation of the actual excursions of the distal tendon stump and of the tenorrhaphy interface would prevent misinterpretation of the actual level of tendon injury and repair.

Peritendinous adhesions represent a common problem without a satisfactory solution despite several studies. We have been using a conventional silicone Penrose drain in patients undergoing tenolysis in the hand since 2006. The Penrose drain is wrapped around the segment of the tendon after tenolysis. Therapy is started on the second post-operative day and the Penrose drain removed after one week in the outpatient clinic. We have had good outcomes with this technique. It is inexpensive, readily available and effective.

Level of Evidence: Level V (Therapeutic)

An extensor tendon defect in the hand requires reconstruction to restore extension. We report a 44-year-old woman with a 24-mm extensor tendon defect of the middle finger over the dorsum of the hand that was reconstructed using a composite graft consisting of the triceps tendon and paratenon. This composite graft from the posterior aspect of the distal arm is simple, safe and may be considered in extensor tendon reconstruction.

Level of Evidence: Level V (Therapeutic)

Background: Little is known regarding the effect timing of repair has on extensor tendon repair results. The purpose of this study is to determine if a relationship exists between the time of extensor tendon injury to extensor tendon repair and patient outcomes.

Methods: A retrospective chart review was conducted on all patients that underwent extensor tendon repair at our institution. The minimum time to final follow-up was 8 weeks. Patients were then divided into two cohorts for analysis; those that underwent repair less than 14 days after injury and those that underwent extensor tendon repair at or greater than 14 days after injury. These cohorts were further sub-grouped by zone of injury. Data analysis was then completed using a two-sample t-test assuming unequal variance and ANOVA for categorical data.

Results: A total of 137 digits were included in final data analysis, with 110 digits repaired less than 14 days from injury and 27 digits in the greater than or equal to 14 days to surgery group. For zones 1–4 injuries, 38 digits were repaired in the acute surgery group and eight digits in the delayed surgery group. There was no significant difference in final total active motion (TAM) (142.3° vs. 137.4°). Final extension was also similar between the groups (2.37° vs. 2.13°). For zones 5–8 injuries, 73 digits were repaired acutely, and 13 digits were repaired in delayed fashion. There was no significant difference in final TAM (199.4° vs. 172.7°). Final extension was also similar between the groups (6.82° vs. 5.77°).

Conclusions: We found time from extensor tendon injury to surgical repair did not affect final range of motion when comparing acute repair within 2 weeks from injury or delayed repair greater than 14 days from injury. Additionally, there was no difference in secondary outcomes, such as return to activity or surgical complications.

Level of Evidence: Level IV (Therapeutic)