Extensor Indicis Research Articles

Nerve compression after opponensplasty: a cadaveric study

Background: We describe the differences in thumb opposition between different opponensplasty tendon transfers and determine the immediate pressure on the median and ulnar nerves incurred by each transfer. Methods: Using fresh frozen cadavers (8 specimens), opponensplasties were performed using extensor indicis proprius (EIP), flexor digitorum superficialis (FDS) with flexor carpi ulnaris (FCU) pulley, palmaris longus (PL, Camitz procedure), and PL utilizing the thenar fascia as a pulley (PLwP). Each tendon transfer was tensioned, and the thumb flexion, abduction and pronation were measured. The pressure on the median and ulnar nerves were measured for each tendon transfer at varying tensions. Results: There were no differences seen in flexion or pronation between any of the four tendon transfers. FDS, PL and PLwP demonstrated more abduction than the EIP transfer, however differences were less than 10°. EIP and FDS transfers caused significantly more pressure on the median nerve than PL or PLwP at high tendon tensions. Both EIP and FDS tendon transfers caused significantly more pressure on the ulnar nerve than PL or PLwP, and the pressure increased as tension on the transfer increased. No pressure differences were seen between PL and PLwP. Conclusions: No significant differences were seen in thumb flexion or pronation between the four tendon transfers. Differences were seen for abduction with EIP showing the least amount of abduction. EIP and FDS caused more median nerve compression than PL transfers at high tension. Both EIP and FDS tendon transfers cause more ulnar nerve compression than PL transfers at all tensions. Level of Evidence Level: V

An extensor digitorum brevis manus coexisting with the typical extensor indicis muscle: a rare dissection finding.

The forearm extensor muscle and hand extensor tendons are composed of several structures with unique anatomy identified with high morphological variability. During a routine dissection of a 74-year-old donated male cadaver, the right hand was isolated for educational purposes. After carefully dissecting the structures, an accessory muscle was identified. The accessory muscle corresponded to the extensor digitorum brevis manus (EDBM) inserted into the extensor indicis (EI) tendon, which was typically identified. According to the current literature, this occurrence corresponds to a rare variant, with 0.36-0.38% prevalence between the cadaveric studies. Knowledge of the hand extensor musculature is essential for orthopedics and plastic surgeons operating in the region to avoid iatrogenic injury.

Articular Surface Damage Following Headless Intramedullary Nail Fixation of Proximal Phalanx Fractures

Offering the benefits of rigid fixation while minimizing soft tissue dissection, intramedullary implants have become a popular choice among hand surgeons. Their placement often requires traversing or passing in proximity to joint surfaces. This study aimed to assess the damage to the articular cartilage of the base of the proximal phalanx resulting from antegrade placement of threaded headless intramedullary nails. A cadaveric study comparing two techniques for antegrade placement of threaded headless intramedullary nails was conducted in 56 digits. The first entailed a single 2.1 mm intramedullary nail placed via the dorsal base of the proximal phalanx, whereas the second used two 1.8 mm intramedullary nails inserted via the collateral recesses of the phalangeal base. All specimens were analyzed for articular surface damage with the cartilage defect measured as a percentage of total joint surface area. Damage to the extensor tendons was also assessed in a subset of specimens. No significant difference in the percentage of articular surface damage was observed, with an average 3.21% ± 2.34% defect in the single 2.1 mm nail group and a 2.71% ± 3.42% mean defect in the two 1.8 mm nails group. There was no articular surface injury in 18% of digits in each group. Damage to extensor tendons was seen in three (9.4%) specimens and in all cases involved either the extensor indicis proprius or extensor digiti minimi. Hardware insertion using either the dorsal base of the proximal phalanx or the collateral recesses of the phalangeal base both demonstrated minimal articular cartilage damage and infrequent injury to the extensor tendons. With proper technique for antegrade insertion into the proximal phalanx, the cartilage defect observed often encompasses only a small percentage of the overall joint surface area.

An accessory head of the extensor indicis: a rare case report.

A deep knowledge of the variations of the posterior forearm musculature is crucial for assessing and diagnosing conditions in this region. Extensor indicis (EI) is one of the muscles in this region, which exhibits diverse anatomical variations. This report documents an extremely unusual form of the EI with an accessory head on the dorsum of the hand. During routine dissection, an extremely rare presentation of the EI was found in the left forearm of a 94-year-old female cadaver. This unusual EI consisted of two muscle bellies. The traditional belly originated from the distal two-thirds of the ulna. The muscle became tendinous around the carpal area, distal to the extensor retinaculum. The tendon was subsequently joined by an accessory muscle belly originating from the distal radioulnar ligament. The EI tendon inserted onto the dorsal expansion of the index finger, ulnar to that of the extensor digitorum. The posterior interosseous nerve innervated the muscle. Herein, we report an extremely rare form of the EI. To our knowledge, EI with an accessory head has only been reported rarely over the past 200 years. Moreover, our report appears to be the first case with photographic details of this anatomical variation. Clinicians should be aware of this variation for proper diagnosis and treatment.

Different Muscles, Lower Cutoff Values: Does it Truly Improve the Diagnostic Sensitivity of Repetitive Nerve Stimulation in Myasthenia Gravis?

ABSTRACT Context: This study evaluated the diagnostic accuracy of repetitive nerve stimulation (RNS) compared with single-fiber electromyography (SF-EMG) in generalized myasthenia gravis (MG). Aims: The aim of the study was to determine the diagnostic sensitivity of RNS in various muscles and assess the effect of varying decrement cutoff values on diagnostic efficacy. Setting and Design: This was a prospective study of 34 confirmed generalized MG patients. Subjects and Methods: RNS was performed on five muscles. Clinical features, autoantibody presence, and SF-EMG jitter rates recorded from the frontalis muscle were analyzed. Patients were classified according to the MG Foundation of America classification. Statistical Analysis: SPSS version 23 was used for descriptive statistics, comparisons of categorical and quantitative data, and correlation analysis, with the significance level set at P < 0.05. Results: Among the patients (58.8% males and mean age = 59.47 ± 13.37 years), SF-EMG detected increased jitter in 91.2%, whereas RNS identified a significant decrease of 50% across at least one muscle. The decremental response was >10% in the abductor digiti minimi (ADM), trapezius, nasalis, abductor pollicis brevis, and extensor indicis proprius muscles in 5.9%, 26.5%, 29.4%, 11.8%, and 29.4% of patients, respectively. A sensitivity improvement at lower decrement values was observed only in the ADM muscle. A significant correlation was found between decreases in the trapezius muscle and seropositivity. Conclusions: Optimal muscle selection improves RNS diagnostic accuracy in MGs. The study recommends incorporating the spinal accessory and radial nerves in RNS due to their high sensitivity, although modifying the decrement cutoff value has a limited overall effect.

An unusual configuration of two anomalies in the extensor digitorum profundus complex in a human.

The extensor digitorum profundus complex underwent degeneration of the ulnar segments during primate adaptation and evolution. This process resulted in the preservation of only the extensor pollicis longus and extensor indicis in some apes, including humans. Consequently, anatomical variations within the digitorum profundus complex in modern humans have been well-documented, with detailed reports on their frequency and patterns in previous studies. Here, we report an unusual arrangement involving two anomalies in the extensor digitorum profundus complex, identified in a 66-year-old Japanese male cadaver. In this cadaver, two accessory muscles differentiated from both the extensor pollicis longus and extensor indicis. Notably, the latter muscle featured a tendon bifurcating towards both the thumb and index fingers, referred to as the extensor pollicis et indicis communis. Under the extensor retinaculum, the tendon of the accessory extensor pollicis longus passed through an independent compartment, whereas that of the extensor pollicis et indicis communis traversed a compartment shared by the extensor indicis and the extensor digitorum communis. Both muscles were innervated by the posterior interosseous nerve. Previous studies have reported that the accessory slip of the extensor pollicis longus and extensor pollicis et indicis communis appear at frequencies of 0.6% and 0.4-1.4%, respectively. However, to the best of our knowledge, a configuration in which both appear simultaneously has not been reported. The data from this case could provide essential insights into the variations in the extensor digitorum profundus complex in humans and non-human primates.

A rare case with atypical findings: schwannoma of the radial nerve

A 53-year-old male complained of weakness in the dorsum of the 5-4-3rd fingers of the right hand. The musculus extensor digitorum communis was heavy and the musculus extensor indices proprius was light involved in the needle electroneuromyography study. Radial nerve ultrasonography showed a mass(schwannoma) which located on the radial nerve course after the lateral epicondyle at the elbow level. In conclusion, we should consider radial nerve schwannoma in patients with radial nerve injury and when there is an atypical involvement of the muscles innervated by the radial nerve, we should utilize ultrasonography for evaluation.

Opposition Transfer Using the Extensor Indicis Muscle and the Extensor Pollicis Brevis Tendon

PurposeThis study aimed to introduce a novel technique utilizing the extensor pollicis brevis and extensor indicis proprius tendons as power sources for thumb opposition reconstruction in cases of severe carpal tunnel syndrome (CTS) associated with thenar muscle atrophy. Further, the efficacy of this novel method and the traditional Camitz technique was compared. MethodsPatients with severe CTS and thumb opposition dysfunction who underwent surgery using the novel technique (n = 7, 9 surgeries) or the Camitz technique (n = 8, 8 surgeries) were included in the analysis. The pre- and postoperative palmar abduction angle, thumb–ring finger opposition (T–R) angle, and Kapandji score were assessed. The repeated measures ANOVA and the Mann–Whitney U test were used for statistical analysis. ResultsThe novel technique was associated with a significant postoperative improvement in palmar abduction angle, T–R angle, and Kapandji score. In particular, the T–R angle of patients who underwent surgery using this technique was superior to that of patients who underwent surgery using the Camitz technique. Therefore, the novel technique was highly effective in improving thumb pronation. ConclusionThe novel technique using the extensor pollicis brevis and extensor indicis proprius tendons is promising for thumb opposition reconstruction in severe CTS cases. Unlike the traditional Camitz technique, this approach promotes stable thumb opposition function without requiring a pulley, thereby yielding satisfactory outcomes. Nevertheless, further studies with a larger sample size should be conducted to validate these findings.

Modified Extensor Indicis Proprius Opponensplasty.

Extensor indicis proprius (EIP) opponensplasty is one of the commonly used techniques to restore thumb abduction and opposition in patients with thenar muscle dysfunction from various causes of median nerve palsy. However, its subcutaneous route around the distal ulna may not represent a straight line of pull, and part of the extensor hood sometimes has to be harvested along with the EIP tendon to gain adequate length to reach the insertion. The purpose of the study is to present the alternative method of EIP opponensplasty and report the clinical outcomes. The modified EIP opponensplasty was performed on 16 patients with severe carpal tunnel syndrome. At the final follow-up examination, all patients were able to regain their desired level of activities. The Kapandji score, abduction angle, and the disabilities of the arm, shoulder, and hand score improved in all patients. There were no complications related to harvesting the EIP tendon. Two patients developed finger stiffness, which improved after rehabilitation. This technique is safe and effective for restoring thumb function and can solve the insufficient tendon length problem of the original EIP opponensplasty.

Management of extensor tendon injuries concerning distal radius fractures

IntroductionRupture of the extensor tendons secondary to fractures involving the distal radius is a well-recognized rare complication. In patients with implants particularly, there exists a tendency for attributing the implant as a cause for the tendon rupture. We retrospectively studied the patients with extensor tendon injuries related to distal radius fractures, analyzed the factors leading to the rupture, suggest few preventive measures and describe the management strategy of these ruptures. Materials and methods21 patients who were treated for extensor tendon rupture following distal radius fractures in the period of 2014–2022 were retrospectively analyzed. 19 patients had been managed with surgery and two patients conservatively for the distal radius fracture. The time interval between the fracture fixation and tendon rupture, the time interval between tendon rupture and presentation, the extensor tendons injured and the position of the impinging screws or bony spur in relation to the extensor compartments, necessity for implant removal and modality of tendon reconstruction were studied in these patients. ResultsExtensor pollicis longus was found to be ruptured in all the patients except one patient with Extensor indicis proprius rupture alone. The time interval between the fracture fixation and tendon rupture averaged at 32.5 months. End to end repair of the ruptured tendons was never possible even in patients who presented earlier. 10 patients underwent intertendinous bridge grafting and 11 patients underwent tendon transfer. All the patients achieved full extension of thumb with no donor deficit. ConclusionDistal radius fracture related extensor tendon injuries pose a technical challenge to the surgeon and concern to the patient in the form of recurring surgeries. However, with immediate presentation to the surgeon and their use of appropriately designed management algorithm, these patients could be immensely satisfied with the outcome.

Effect of extension of the ulnar fingers on force control and muscle activity of the hand during a precision pinch.

Some individuals extend the three ulnar fingers when performing a precision pinch. The aim of the present study was to investigate the mechanisms and effect of the extension of the ulnar fingers during a pinch. When performing a pulp pinch task with the ulnar fingers in two positions (extension and flexion), 27 participants maintained 5% of their maximum force. The mean pinch force, force variability and time taken to reach the targeted force (reaching time) were calculated. Muscle activity was simultaneously measured, using surface electromyography, for nine muscles: the flexor pollicis brevis; abductor pollicis brevis; flexor pollicis longus; first lumbrical; first dorsal interosseous; flexor digitorum superficialis of the index finger; extensor indicis; and extensor digitorum of the index and ring fingers. No significant differences in the mean pinch force or force variability were found. However, the reaching time was significantly shorter (approximately 20% reduction) in the extension position and the activities in the flexor pollicis brevis, first lumbrical, extensor indicis and extensor digitorum of the ring finger were significantly higher. These findings suggest that extending the ulnar fingers during pinching enhances the activity of key muscles involved in the movement and allows for more rapid force exertion.

Variations in the extensor indicis proprius muscle in the Burmese population: implications for hand reconstructive surgery

BackgroundThe use of extensor indicis proprius (EIP) muscle tendon for tendon grafting and transplantation in the management of hand injuries is common. Anatomical variations of the EIP tendons have been reported with variable prevalence and presentation in different populations worldwide. Knowledge of possible variation patterns is crucial in reconstructive surgery. The current study aims to describe the prevalence of anatomical variations of the EIP in the Burmese population. MethodsA total of 50 cadavers (39 males, and 11 females) were dissected. Both upper limbs of each cadaver were observed. The presence of the EIP, the number of tendons, the origin and insertion of the muscle and its relation with the extensor digitorum communis (EDC) were recorded and variations reported. ResultsOf the 100 limbs studied in the 50 cadavers, only 1/100 limb was reported to have an absent EIP muscle and tendon. Of the remaining 99/100 limbs examined, one of them consists of a double tendon, that is, EIP and extensor indicis et medii communis (EIMC) were inserted separately onto the index finger and middle finger respectively on the dorsum of the left hand. Further to this, there is one case in which an extra muscle belly was observed in the EIP tendon, this muscle is commonly known as the extensor digitorum brevis manus muscle. All the EIP variations were observed in the male cadavers only. ConclusionOf the 50 cadavers studied, 3/100 limbs exhibited EIP variations in the current studied population. Population-specific studies on these variations may aid in a better understanding of the different anatomical patterns of the muscles in the dorsum of the hand. This may lead to improved diagnosis and surgical management of injuries to the dorsum of the hand and for the use of the EIP tendon in surgical grafts and transplantations.

Reconstruction of Hand Dorsum Defect Using Double Perforators-Based Anterior Interosseous Artery Island Flap: A Case Report and Description of a New Anterior Interosseous Artery Perforator.

The anterior interosseous artery (AIA) perforator flap is not commonly used in hand dorsum reconstruction compared with alternatives. However, it is a versatile flap with several advantages. Literature on the AIA perforator flap is based on the dorsal septocutaneous branch (DSB), which branches from the AIA and passes through fascia between the extensor pollicis longus (EPL) and extensor pollicis brevis muscles. In the described case, the authors reconstructed a hand dorsum defect in a 78-year-old man using an AIA perforator flap with double perforators supplied by the DSB and a new perforator branching from the distal than DSB. No complication was encountered, and the flap survived completely. A retrospective computed tomography review revealed the presence of the new perforator in 14 of 21 patients. Two types of new perforator were observed. One passed through the ulnar side of the extensor indicis proprius (EIP) muscle and penetrated fascia between the extensor digitorum minimi and extensor digitorum communis tendons, whereas the other passed between the EPL and EIP muscles. This report describes the anatomical location and clinical application of the new AIA perforators. The double perforators-based AIA flap provides a straightforward, reliable means of reconstructing hand dorsum defects.

The Extensor Indicis Proprius Transposition for the Ulnar Collateral Ligament Stabilization in Thumb Hypoplasia Grades II-IIIa.

Congenital upper extremity deformities are rare, the reported incidence is from 0.15% to 0.2%. The thumb is very important for a hand's functionality, as it provides up to 50% of its total performance. Proper pinch grip formation at the age of 12 to 16 months is part of normal development; however, no functional development can affect a child's psychoemotional development. Well-described techniques such as third or fourth superficial flexor transposition can be found in the literature. There is a paucity of studies on using the extensor indicis proprius (EIP) transposition for stabilization of the ulnar collateral ligament for the first metacarpophalangeal joint (MCPJ). Techniques for the usage of EIP tendon for the reconstruction of absent extensor pollicis longus tendon are more commonly practiced as they create abduction and extension for the thumb hypoplasia grade II-IIIa. We performed EIP transposition with subperiosteally fixation for the ulnar collateral ligament stabilization for thumb hypoplasia patients with a mean age of 38 months (11 to 128) and grade II (n=9), grade IIIa (n=4), and grade IIIb (n=1). Long-term follow-up (2 to 10y) for the esthetical and functional study was performed. Patients and parents are satisfied with functional and esthetic outcomes. We believe that the EIP tendon transposition can be an alternative method for thumb hypoplasia patients grade II-IIIa reconstruction.

The Extensor Digiti Quinty (EDQ) Opponensplasty—Revisited

Introduction: The extensor digiti quinty (EDQ) opponensplasty, although previously described, is not widely used by hand surgeons. This tendon transfer was used selectively in cases of combined median-ulnar nerve palsies at our center over the last 4 years, with the primary goal to preserve the extensor indices proprius (EIP) for pinch plasty. We present our technique and the series of 8 patients that underwent EDQ opponensplasty here. Materials and Methods: A retrospective chart review identified patients with combined median-ulnar nerve palsies that underwent EDQ opponensplasty between 2015 and 2019 at our institution by a single surgeon. Primary outcome measures collected were pinch, grip, disabilities of the arm, shoulder, and hand (DASH) scores, thumb position, palmar abduction angle, and thumb span. Secondary outcomes included donor site morbidity and complications. Results: Eight patients (9 hands) ages 21 to 53 underwent EDQ opponensplasty, with an average follow-up of 8 months. Postoperative pinch and grip on the affected side improved from preoperative values. All 9 transfers were functional with the thumb positioned in the palmar plane of the hand. Palmar abduction ranged from 45 to 70 degrees. Motor reeducation was achieved without any difficulty in all patients. No patients had evidence of donor site morbidity. Discussion: The EDQ opponensplasty is satisfactory in achieving thumb opposition in the setting of combined median-ulnar neuropathy, without evidence of donor site morbidity. The EDQ is expendable, has adequate length, an optimal line of pull, minimal donor site morbidity, and leaves the extensor indices proprius available for pinch plasty.

Extensor indicis proprius to extensor pollicis longus transfer in spontaneous rupture of extensor pollicis longus following non displaced fracture distal end radius

Exact incidence of extensor pollicis longus (EPL) ruptures following distal radius fracture is not known. Peculiarly it’s common in nondisplaced fracture of the distal radius with an incidence of EPL rupture of 0.2-5%. Cortical irregularities from distal radius fractures or osteophytes easily abrade the tendon, causing gradual attrition and ultimately rupture. Compromised blood supply is also related to EPL rupture which is supported by microcirculatory anatomic studies. We present a case of 49 year old female who presented with spontaneous rupture of the EPL following a nondisplaced fracture of the distal radius managed by extensor indicis proprius (EIP) transfer. EIP transfer gives promising outcome. Optimum tension of the tendon is crucial for good functional outcome. We recommend suturing the tendon with thumb in extension and wrist in neutral position for optimum tension of tendon to avoid extensor lag and to prevent loss of IP flexion.

Presumed Presence of Extensor Indicis et Digiti Medii Communis Muscle in a 70-Year-Old White Male Donor

Forearm extensor muscle variations can be diverse and, in some instances, rare. During a routine anatomical dissection of human cadaveric donors during the 2021 first-year medical gross anatomy course and 2021 graduate nursing advanced anatomy course at the Uniformed Services University of the Health Sciences, bilateral agenesis of the extensor carpi ulnaris muscle was noted in one 70-year-old white male donor. This variation is described as extremely rare in the literature. The presence of an extensor indicis et digiti medii tendon, a variant of the extensor indicis tendon, appeared to be evident in post-dissection photographs on the left hand. The presence of a duplicated extensor indicis proprious tendon appears to be evident on the right hand. However, further inspection of this region was impeded as the body was sent for cremation prior to the variation being identified. The presence of various juncturae tendinum was also noted bilaterally. Reported prevalence of extensor indicis muscle variants ranges from 0.75% to 13%, depending on the specific type or grouping of variations observed. Knowledge of variations in the extensor compartment of the forearm and wrist is crucial for orthopedic surgeons and specialists. Alteration of surgical approaches may be necessary if such a variation is present. Such variations can be options for grafts, resulting in minimal functional change to the grafted area due to the continued existence of other muscles performing similar functions. Knowledge of such variations, and alternative, synonymous names for them, is also important for anatomy instructors, who may need to assist students in identifying these rare variations during anatomical dissection.

Bilateral Digital Extensor Hypoplasia Correction: A Case Report and Systematic Review.

Digital extensor hypoplasia (DEH) is a rare malformation that presents with loss of active finger extension at the metacarpophalangeal (MCP) joints. Descriptions of optimal treatment and outcomes in this population are sparse. We describe successful operative treatment of a child with DEH involving the extensor digitorum communis, extensor digiti minimi, and the extensor indicis proprius tendons. The 5-year-old male patient was referred for severe limitation on bilateral finger extension since birth. He had been previously diagnosed with arthrogryposis and managed conservatively. Due to lack of improvement, magnetic resonance imaging was done evidencing hypoplasia/aplasia of the extensor tendons. The patient underwent successful tendon transfers using extensor carpi radialis longus to the common extensor tendons, and one hand required an additional tenolysis procedure. 2 years postoperatively, his MCP position and finger extension are markedly improved, and he is able to grip objects without limitation or difficulty. The patient returned to full activity without restriction.

A Rare Variation of Extensor Indices Muscle – A Case Report

Abstract The Extensor Indicis muscle is one among the deep muscles of the extensor compartment of the forearm which takes origin from the Posterior surface of the shaft of the ulna below the origin of the extensor pollicislongus, and from the Inter-osseous membrane. It gets inserted close to the head of second metacarpal bone joining with the index tendon of extensor digitorum on its ulnar side and enters the formation of dorsal digital expansion of the index finger. This muscle helps in the Extension of the index finger and also to extend the wrist. During our routine dissection for 1 st BAMS students, in the dissection hall of KAHER’s Shri B.M. Kankanawadi Ayurveda Mahavidyalaya, Belagavi, of a 55 year old male cadaver, variation in the origin of Extensor Indicis muscle was observed. The extensor Indicis muscle was found arising from the Lunate carpal bone and Dorsal Radiocarpal ligament andit further continued as short belly and had its distal attachment on the proximal phalanx of the index finger. Abnormal origin of Extensor IndicisMuscle may possibly be associated with pain and swelling at the back of the hand. This pain may be misinterpreted with other clinical conditions like synovial cyst and ganglion. Knowledge of such rare variations isuseful to clinician and surgeons for therapeutic and surgical procedures.

Anomalous Extensor Indicis Proprius Muscle Extending Beyond the Extensor Retinaculum: A Case Report.

During dissection of the upper limb of a cadaver in preparation for a first-year anatomy course, an extensor indicis proprius (EIP) variant was discovered with its muscle belly extending distal to the extensor retinaculum and beyond what has been previously described in the literature. EIP is commonly used as a tendon transfer for extensor pollicis longus rupture. Few anatomic variants of EIP have been reported in the literature, but such variants should be considered because of their consequences to the success of tendon transfer and potential implications for diagnosis of an otherwise unexplained mass of the wrist.