Accessory head of the flexor pollicis longus muscle: anatomical study and clinical significance.

BACKGROUND: The accessory head of the flexor pollicis longus (AHFPL) has an oblique trajectory from medial to lateral aspect of the forearm below the flexor digitorum superficialis muscle and then joins the flexor pollicis longus muscle. When the anterior interosseous nerve (AIN) courses underneath the muscle belly of the AHFPL an entrapment neuropathy may occur, known as anterior interosseous nerve syndrome (AINS). MATERIALS AND METHODS: This descriptive cross-sectional study evaluated 106 fresh upper extremities. When the AHFPL was present, its fascicle was traced up to evaluate the origin site. The morphometric variables were measured using a digital micrometre (Mitutoyo, Japan). The relationship between the AHFLP and the AIN was evaluated. RESULTS: The AHFPL was found in 34 (32.1%) of the 106 forearms. The AHFPL arose from the flexor digitorum superficialis muscle in 16 (47.1%) forearms, the medial epicondyle of the humerus in 10 (29.4%) forearms and the coronoid process of ulna in 8 (23.5%) forearms. The average total length of the AHFPL was 94.11 ± ± 10.33 mm. The AIN was located lateral to the AHFPL in 3 (8.8%) forearms, posterolateral in 7 (20.6%) forearms and posterior in 24 (70.6%) forearms. CONCLUSIONS: This study performed in a South American population sample revealed a prevalence of the AHFPL in a lower range compared to previous studies in North Americans and Asians. The AIN coursed more frequently underneath the muscle belly of AHFPL. This finding has clinical significance in the onset of the AINS and the subsequent surgical procedure for the AIN decompression.

Nervio interóseo anterior: trayecto, distribución e implicancias clínicas / Anterior interosseous nerve: course, distribution and clinical implications

El principal ramo del nervio mediano en el antebrazo es el nervio interóseo anterior (NIA), el cual inerva la mayoría de los músculos del plano profundo del compartimiento anterior del antebrazo. Existen diferentes descripciones sobre el punto de origen y su trayecto del NIA, así como también respecto a ramos comunicantes de este, con otros nervios del antebrazo. Algunas de estas descripciones concuerdan de que el NIA pueda atraparse en su tránsito por los arcos formados en las cabezas de origen de los músculos pronador redondo y flexor superficial de los dedos. El objetivo fue determinar el punto de origen, trayecto, músculos inervados y presencia de ramos comunicantes del NIA con otros nervios del antebrazo. Se utilizaron 30 antebrazos de cadáveres adultos brasileños fijados en formalina pertenecientes al laboratorio de anatomía de la UNCISAL, Maceió, Brasil. El punto de origen del NIA alcanzó un promedio de 46 mm con una desviación estándar de 17,54 mm, distal a la línea biepicondilar. En un 37 % de los casos, este nervio se originó en el tramo existente entre los arcos musculares mencionados y en un 23 % surgió proximal a la ubicación de estos. En todos los casos, el NIA inervó a los músculos flexor profundo de los dedos y pronador cuadrado y en un 93 % también inervó al músculo flexor largo del pulgar. Un caso presentó ramo comunicante entre el NIA y el nervio ulnar. En el 10 % de los casos, presentó la variante muscular cabeza accesoria del músculo flexor largo del pulgar. Todos estos hallazgos deben considerarse al momento de diagnosticar correctamente los diferentes síndromes de atrapamiento que afectan tanto al NIA como al nervio mediano en la región cubital y en el antebrazo. Así mismo, el éxito de procedimientos quirúrgicos de estas regiones está supeditado a un conocimiento detallado del trayecto y distribución de estos nervios.

The main branch of the median nerve in the forearm is the anterior interosseous nerve (NIA), which innervates most of the muscles of the deep plane of the anterior compartment of the forearm. There are different descriptions about the point of origin and its course, which can determine a potential entrapment of it in its transit through the arcs formed in the heads of origin of the pronator round and flexor digitorum of the fingers muscles, as well as with regard to communicating branches of the NIA with other nerves of the forearm. The aim was to determine the point of origin, course, innervated muscles and presence of communicating branches of the NIA with other nerves of the forearm. 30 forearms of Brazilian adult corpses fixed in formalin belonging to the UNCISAL anatomy laboratory were used, Maceió, Brazil. The point of origin of the NIA reached an average of 46 mm with a standard deviation of 17.54 mm, distal to the biepicondilar line. In 37 % of the cases, this nerve originated in the existing section of the muscular arches mentioned and in 23 % it arose proximal to the location of these. In all cases, the NIA inervated the flexor digitorum profundus and pronator quadratus and 93 % also inervated the flexor pollicis longus. One case presented a communicating branch between the NIA and the ulnar nerve. In 10 % of the cases, he presented the variant muscle accessory head of the flexor pollicis longus. All these findings should be considered at the time of correctly diagnosing the different entrapment syndromes that affect both the NIA and the median nerve in the ulnar region and the forearm. Likewise, the success of surgical procedures in these regions is subject to a detailed knowledge of the course and distribution of these nerves.

Estudio anatómico del fascículo accesorio del músculo flexor largo del pulgar y su relación con el nervio interóseo anterior en individuos brasileños / Anatomical study of the accessory head of the flexor pollicis longus muscle and its relationship to the anterior interosseous nerve in Brazilian individuals

Entre los síndromes de compresión nerviosa en el antebrazo, debido a la presencia de arcos tendinosos de músculos relacionados al trayecto de los nervios que transcurren entre sus capas musculares, se encuentra el del nervio interóseo anterior (NIA). La presencia de variaciones musculares puede generar arcos que ocasionan compresión nerviosa. El objetivo fue establecer la incidencia y morfología del músculo accesorio del flexor largo del pulgar (AFLP) y la relación de éste con el NIA o sus ramos motores. Se utilizaron 30 antebrazos, de cadáveres formolizados de individuos adultos brasileños. El punto de referencia seleccionado para las mediciones fue el epicóndilo medial del humero (EMH). Se observó que tres miembros superiores presentaron el AFLP (10%), en todos ellos se originó en el EMH para terminar insertándose en el tendón del músculo flexor largo del pulgar (FLP). El vientre muscular presentó aspecto fusiforme, el cual tenía un tendón que formó un arco con el FLP. En uno de los casos, este arco se relacionó con el paso del NIA; en los otros dos, lo hizo con los ramos motores que se originan del NIA. Al diagnosticar los síndromes generados por compresión nerviosa se debe considerar la presencia del AFLP, el cual, potencialmente se puede relacionar con el trayecto del NIA o de sus ramos.

Between the syndromes of nerve compression in the forearm, due to the presence of the tendinous arches related to the nerves that pass between its muscle layers, is the anterior interosseous nerve (AIN). The presence of muscular variations can generate arches that cause nerve compression. The aim of our study was to establish the incidence and morphology of the accessory head of flexor pollicis longus muscle (AFPLm) and its relationship with AIN or its branches. Thirty forearms of formalized corpses of adult Brazilians were used. The selected landmark for measurements was the medial epicondyle of the humerus (MEH). It was noted that three upper limbs presented the AFPLm (10%), originated from the MEH to end inserted into the tendon of the flexor pollicis longus muscle. The AFPLm showed fusiform appearance, which had a tendon that formed an arch with the flexor pollicis longus muscle. In one case, this arch was associated with the passage of AIN. In the other two, this arch was related to motor branches originating from the AIN. The diagnosis of nerve compression syndromes should consider the presence of AFLPm, which potentially can be related to the course of the AIN or its branches.

Minimally invasive endoscopic decompression for anterior interosseous nerve syndrome: technical notes.

Anterior interosseous nerve syndrome (Nevin-Kiloh syndrome) is a rare entity caused by compression of the purely motor anterior interosseous nerve in the forearm. Historically, conventional surgical treatment has consisted of open decompression of the nerve. Unfortunately, open decompression is often complicated by scarring and significant morbidity. Endoscopic decompression is an alternative means of surgical intervention in the hands of well-trained surgeons comfortable with soft tissue endoscopy. In this report, we review relevant anatomy, offer technical hints, and present our personal experience with 4 illustrative cases, all with greater than 1.5 years of follow-up. Our patients showed considerable improvement of their symptoms with minimal scarring. No significant complications occurred.

Síndrome de atrapamiento del nervio interóseo anterior / Trapping syndrome of the anterior interosseous verve

Introducción: el síndrome de atrapamiento del nervio interóseo anterior es una enfermedad que se presenta con poca frecuencia, no obstante, acuden a consulta un mayor número de personas que las reportadas. Esto se debe, entre otros factores, al desconocimiento de la enfermedad, lo cual provoca un diagnóstico erróneo y un tratamiento insuficiente. Objetivo: evaluar los resultados obtenidos con el tratamiento quirúrgico de esta enfermedad. Métodos: se realizó un estudio quasiexperimental en 18 pacientes portadores de un síndrome de atrapamiento del nervio interóseo anterior tratados quirúrgicamente en el servicio de miembros superiores del Complejo Científico Ortopédico Internacional Frank País, entre el Primero de diciembre de 2003 y el 31 de marzo de 2009. Los resultados se evaluaron mediante la aplicación de un score modificado para el grupo de estudio a partir de los score de Cooney y de Shah y Jones. Resultados: la edad promedio del grupo fue de 31,8 años con un rango entre 17 y 58 años, de ellos 14 del sexo femenino y 4 masculino; el tiempo de latencia de 5,7 meses con un rango entre 3 y 9 meses. El dolor, signo de Tinel positivo para el nervio interóseo, se presenta en 100 por ciento de los casos. Los resultados se evaluaron entre buenos y excelentes en 14 pacientes (77, 8 por ciento). En ningún caso fueron evaluados de malos. Conclusiones: el tratamiento quirúrgico es un método de elección eficaz ante un síndrome de atrapamiento del nervio interóseo anterior, que puede verse afectado por un período de latencia prolongado

Introduction: trapping syndrome of anterior interosseous nerve is an uncommon disease, however, a great number than reported came to consultation. This is due to among other factors, to the lack of knowledge of this entity leading to a misdiagnosis and a insufficient treatment. Objective: to assess the results obtained with surgical treatment of this disease. Methods: a quasi-experimental study was conducted in 18 patients diagnosed with trapping syndrome of anterior interosseous nerve operated on the upper extremities services of the Frank País International Orthopedic Scientific Complex from December 1, 2003 to March 31, 2009. Results were assessed by application of a modified score for the study group from the Cooney and Shah and Jones score. Results: the mean age of group was of 31.8 years with a rank between 17 and 58 years which included 14 female patients and 4 male patients; the latency time was of 5.7 months with a rank between 3 and 9 months. The pains, a positive Tinel sign for interosseous nerve; is present in the 100 percent of cases. Results were assessed between good and excellent in 14 patients (77.8 percent). In any case the results were assessed as poor. Conclusions: the surgical treatment is an effective choice method in face a trapping syndrome of anterior interosseous nerve t hat may be involved for a longstanding latency period

Distal anterior interosseous nerve transfer to the deep ulnar nerve and end-to-side suture of the superficial ulnar nerve to the third common palmar digital nerve for treatment of high ulnar nerve injuries: experience in five cases / Transferência do nervo interósseo anterior distal para o ramo profundo do nervo ulnar e sutura término-lateral do nervo ulnar superficial ao terceiro nervo digital comum para tratamento de lesões altas do nervo ulnar: experiência em cinco casos

OBJECTIVE: To demonstrate the results of a double nerve transfer at the level of the hand for recovery of the motor and sensory function of the hand in cases of high ulnar nerve injuries. METHOD: Five patients underwent a transfer of the distal branch of the anterior interosseous nerve to the deep ulnar nerve, and an end-to-side suture of the superficial ulnar nerve to the third common palmar digital nerve. RESULTS: Two patients recovered strength M3 and three cases were graded as M4; recovery of protective sensation (S3+ in three patients and S4 in two) was observed in the fourth and fifth fingers, and at the hypothenar region. The monofilament test showed values of 3.61 or less in all cases and the two-point discrimination test demonstrated values of 7 mm in three cases and 5 mm in two. CONCLUSION: This technique of double nerve transfer is effective for motor and sensory recovery of the distal ulnar-innervated side of the hand.

OBJETIVO: Demonstrar os resultados obtidos com uma dupla transferência nervosa ao nível da mão para tratamento de lesões do nervo ulnar localizadas acima do cotovelo. MÉTODO: Cinco pacientes foram submetidos à transferência do nervo interósseo anterior para o ramo profundo do nervo ulnar, associado à sutura término-lateral do nervo ulnar superficial ao terceiro nervo digital comum. RESULTADOS: Dois pacientes recuperaram força M3 e os outros três casos foram graduados como M4. Recuperação de sensibilidade protetora (S3+ em três pacientes e S4 em dois) foi observada nos quarto e quinto dedos, além da região hipotenar. O teste de monofilamentos demonstrou valores iguais ou menores do que 3,61 em todos os casos e o teste de discriminação de dois pontos apresentou valores de 7 mm em três casos e 5 mm em dois. CONCLUSÃO: A técnica de dupla transferência nervosa é eficaz como modalidade de tratamento para lesões altas do nervo ulnar.