UNASSIGNED: IV.

A spontaneous rupture of the extensor pollicis longus (EPL) tendon after a fracture of the distal radius is a known complication in adults. In contrast, there are a paucity of reports concerning EPL tendon ruptures in children and adolescents. The authors present a case of a spontaneous rupture of the EPL tendon in a 15-year-old girl after a non-displaced distal radius fracture. The patient had no predisposing factors including rheumatoid arthritis or steroid injection. During surgery, the EPL tendon was found to be ruptured at the extensor retinaculum (third compartment). Extensor indicis proprius (EIP) to EPL transfer was performed. At the 18-month follow-up, the patient was asymptomatic and showed satisfactory thumb function, with normal active extension.
La rotura espontánea del tendón del extensor largo del pulgar (EPL) tras una fractura distal del radio es una complicación conocida en adultos. En cambio, son escasos los informes sobre roturas del tendón del EPL en niños y adolescentes. Los autores presentan un caso de rotura espontánea del tendón del EPL en una niña de 15 años tras una fractura distal del radio no desplazada. La paciente no presentaba factores predisponentes como artritis reumatoide o inyección de esteroides. Durante la intervención quirúrgica, se descubrió que el tendón del EPL estaba roto a la altura del retináculo extensor (tercer compartimento). Se realizó una transferencia del extensor indicis proprius (EIP) al EPL. A los 18 meses de seguimiento, el paciente estaba asintomático y mostraba una función satisfactoria del pulgar, con una extensión activa normal.

BACKGROUND: The extensor indicis proprius (EIP) tendon is a frequently used donor for a variety of tendon transfers, most commonly for reconstruction of the extensor pollicis longus (EPL). EIP is known to have frequent anatomic variants including split tendons and variations in tendon arrangement.
OBJECTIVE: To characterize the anatomy of the EIP at the level of the extensor retinaculum, where tendon harvest is often performed, and share our preferred technique for EIP to EPL transfer.
METHODS: Twenty-nine fresh-frozen cadaveric forearms without history of forearm or hand injury or surgery were dissected. Tendon circumference and relationship of the EIP and extensor digitorum communis to the index (EDCI) at the metacarpophalangeal (MCP) joint and the distal extensor retinaculum were recorded. Distance from the distal extensor retinaculum to the EIP myotendinous junction was measured.
RESULTS: EIP was ulnar to the EDCI in 96.5% of specimens (28/29) at the distal edge of the extensor retinaculum. In the remaining specimen, EIP was volar to EDCI. Tendon circumference at the distal extensor retinaculum averaged (9.3 mm ± 1.7 mm) for EDCI and 11.1 mm (± 2.7 mm) for EIP (P = 0.0010). The tendon circumference at the index MCP joint averaged 11.0 mm (± 1.7 mm) for EDCI and 10.6 mm (± 2.1 mm) for EIP (P = 0.33). EIP had a greater circumference in 76% (22/29) of specimens at the distal extensor retinaculum whereas EIP had a greater circumference in only 31% (9/29) of specimens at the MCP joint.
CONCLUSIONS: The EIP tendon is frequently ulnar to and greater in circumference than the EDCI at the distal extensor retinaculum, which can be taken into consideration for tendon transfers involving EIP.

We presumed that primary repair would be possible if the extensor pollicis longus (EPL) rupture after volar locking plating (VLP) for distal radius fracture (DRF) was diagnosed earlier. Thus, five cases of EPL ruptures were resolved via primary repair rather than extensor indicis proprius (EIP) transfer, so we reported the clinical outcomes of at least 2 years follow-up since EPL repair. Of 588 consecutive patients with the fractures treated between January 2016 and December 2019, 501 who met out inclusion/exclusion criteria were initially investigated. We informed patients of: (1) the ordinary range of motion of thumb at full wrist flexion/extension; (2) the proper tone of thumb extension compared to the contralateral thumb; and (3) the degree of pain/discomfort during thumb exercise. After discharge, we called each patient monthly commencing at 8 weeks postoperatively to enquire if any of those had worsened, by telephone. Five patients had ruptured EPLs diagnosed at a mean of postoperative-12.8 weeks. Three came to outpatient department for suspected tendon rupture just after telephone survey with the authors. The other two visited after detecting insufficiency in the three items, during the period between telephone inquiries. In four, the torn EPL were encapsulated by tendon sheathes. Extension lag at interphalangeal joint was absent and other clinical outcomes associated with DRF were all satisfactory at final follow-up. Primary repair of EPL rupture (rather than EIP transfer) is possible if patients are properly followed up after VLP for DRF. LEVEL OF EVIDENCE: Level IV, retrospective case series.

The choice of the donor tendon in tendon reconstruction of the hand theoretically influences the results of the surgery because of the interactions of its structure with the healing process. The objective of our study was to specify the surgical bases of vascularized extensor indicis proprius (EIP) in tendon reconstruction of the hand and to present its application from a series of observations. According to our observations, the EIP\'s vascularization arises from a branch of the 2nd dorsal metacarpal artery, 3-4 cm proximally to the metacarpophalangeal joint (MCP). We demonstrate the feasibility and effectiveness of a vascularized EIP graft for finger flexor tendon reconstruction, for defects of the extensor mechanism at the MCP joint level and for reconstruction of the extensor pollicis longus. Our biomimetic approach in tendon reconstruction has led us to factor in the complexity of the tendon and peritendinous structure. The use of vascularized EIP offers theoretical advantages for the tendon healing process, demonstrates encouraging first results with interesting versatility and very low iatrogenicity.

OBJECTIVE: Anatomical variants in the posterior compartment of forearm and hand are not uncommon. Physicians should be aware of variations in this region for correct diagnosis and treatment of diseased hands.
METHODS: During a routine dissection at our department, an extremely rare case of deep hand extensor muscle was discovered.
RESULTS: A complete extensor digitorum profundus complex was found in the fourth extensor compartment in addition to the extensor indicis proprius. The complex consisted of two muscle bellies originating from the lateral aspect of distal ulna and the adjacent interosseous membrane. The first belly resembled the conventional extensor indicis proprius. The second belly gave off two tendon slips: one inserted to the index and middle fingers and the other formed aponeurosis before inserting to the ring and little fingers.
CONCLUSIONS: To our knowledge, a complete extensor digitorum profundus complex which inserts to all medial four digits has never been reported in humans. Awareness of variations in this region is critical for surgeons operating in the forearm and hand. The present case also provides insights into the evolutionary and developmental origin of these structures.

OBJECTIVE: The extensor indicis proprius (EIP) is a muscle of the forearm that originates from the posterior surface of the ulna and the adjacent interosseous membrane and attaches to the index finger. Many anatomical variations of this muscle have been reported in the literature. The extensor digitorum brevis manus (EDBM) is a variant muscle found on the back of the wrist and hand. These muscle variants should be considered in the context of clinical syndromes and reconstructive hand surgery. The aim of the present study was to describe in detail the normal and variant anatomy of these muscles and propose new systematic classifications.
METHODS: Formol-carbol-fixed Europid upper limbs (n = 176) were examined in the Department of Anatomy, Histology and Embryology at the Medical University of Sofia for variations of the EIP and occurrences of the EDBM.
RESULTS: We found normal anatomy in 147 (84%) of the specimens examined and we measured the length and width of the muscle belly and tendon of the EIP. Variations of the EIP in the other 29 upper limbs (16%) included replacement of the EIP by an EIB, coexistence of the EIP and EIB, presence of accessory tendons, and additional muscles.
CONCLUSIONS: Knowledge of anatomical variations of forearm muscles is important because they can cause clinical syndromes or have implications for reconstructive surgery, most often as tendon transfers in response to functional loss of other forearm muscles.

Proximal or middle lesions of the ulnar or median nerves are responsible for extensive loss of hand motor function. This occurs even when the most meticulous microsurgical techniques or nerve grafts are used. Previous studies had proposed that nerve transfer was more effective than nerve grafting for nerve repair. Our hypothesis is that transfer of the posterior interosseous nerve, which contains mainly motor fibers, to the ulnar or median nerve can innervate the intrinsic muscles of hands. The present study sought to investigate the feasibility of reconstruction of the deep branch of the ulnar nerve and the thenar branch of median nerve by transferring the extensor indicis proprius branch of the posterior interosseous nerve obtained from adult cadavers. The results suggested that the extensor indicis proprius branch of the posterior interosseous nerve had approximately similar diameters and number of fascicles and myelinated nerve fibers to those of the deep branch of ulnar nerve and the thenar branch of the median nerve. These confirm the feasibility of extensor indicis proprius branch of posterior interosseous nerve transfer for reconstruction of the deep branch of the ulnar nerve and the thenar branch of median nerve. This procedure could be a novel and effective method for the functional recovery of the intrinsic muscles of hands after ulnar nerve or median nerve injury.

Complications following extensor indicis proprius (EIP) tendon transfer are loss of strength, independence and mobility in the index finger in extension. The main goal of this study was to measure the index finger\'s independent and dependent extension strength after a tendon transfer. Secondary goals were to determine if the index finger retained the ability to extend independently after the transfer and to evaluate second metacarpophalangeal (MCP) joint mobility. Our study consisted of 19 patients in whom the EIP tendon had been divided proximally to the extensor hood. The EIP tendon was retrieved through a proximal approach at the distal radius level and rerouted towards a recipient tendon. At an average follow-up of 41 months, the average independent extension strength was 5.6N versus 11N on the contralateral side and the dependent strength was 10.9N versus 20N. No patient complained of a loss of extension strength and all had retained independent active extension on the operated index finger. The second MCP joint on the operated side had an independent extension lag of 15.3° compared to the contralateral healthy side and a dependent extension lag of 0.2°. Two patients were impaired in their daily activities when moving the operated index finger. Our results show that EIP harvesting for tendon transfer leads to decreased independent and dependent strength as well as decreased active extension of the second MCP joint. However, the functional impact was negligible and should not compromise the use of the EIP as a tendon transfer.
III.

The goal of this study was to establish a reproducible protocol to measure active extension strength in the index finger. The secondary objectives consisted in correlating the independent or associated index extension strength to the other fingers force of contraction of the extensor indicis propius with hand dominance. The population studied consisted of 24 healthy volunteers, including 19 women and 20 right-handed individuals. The independent and dependent index extension strength in each hand was measured three times with a dynamometer by three examiners at Day 0 and again at Day 7. Intra and inter-examiner reproducibility were, respectively, >0.90 and >0.75 in all cases. The independent extension strength was lower than the dependent one. There was no difference between the independent index extension strength on the dominant and non-dominant sides. The same was true for the dependent strength. Our results show that our protocol is reproducible in measuring independent and dependent index extension strength. Dominance did not come into account.
METHODS: II.