Augmentation of Distal Biceps Tendon Ruptures With the Lacertus Fibrosus: A Biomechanical Study in a Tendon-Deficient Model

Background: Chronic distal biceps tendon ruptures may require tendon graft augmentation secondary to tendon attrition or retraction. The lacertus fibrosus is a local, cost-effective graft that can be used to supplement reconstruction. Purpose: To compare the biomechanical strength of distal biceps tendon repairs with and without lacertus fibrosus augmentation in a tendon-deficient cadaveric model. Study Design: Controlled laboratory study. Methods: Sixteen fresh-frozen matched cadaveric pairs of elbows were randomized into 2 groups: (1) standard distal biceps tendon repair and (2) tendon-deficient (50% step cut) repair with lacertus fibrosus augmentation. All repairs were completed using an oval bone trough and 2 double-loaded No. 2 braided nonabsorbable sutures in a locked Krackow fashion tied over a lateral bone bridge. For the lacertus augmentation group, the lacertus was wrapped circumferentially in a tubular fashion around the tendon to restore the native size and incorporated into the Krackow suture. All specimens underwent cyclic loading and then were loaded to failure. Displacement, stiffness, load to failure, and mode of failure were recorded. Results: The standard repair and lacertus augmentation groups had similar displacements on cyclic loading (1.66 ± 0.62 vs 1.62 ± 0.58 mm, respectively; P = .894). The stiffness was significantly greater for the standard repair group (21.3 ± 2.5 vs 18.5 ± 3.5 N/mm; P = .044). Both groups provided excellent mean peak load to failure strengths, despite the standard repair group having significantly greater strength (462.4 ± 140.5 vs 377.3 ± 101.1 N; P = .022). The primary mode of failure in the standard repair group was fracture at the bone bridge (n = 5/8) compared with suture pullout (n = 4/8) in the lacertus augmentation group. Conclusion: Lacertus fibrosus augmentation of a tendon-deficient biceps repair was less stiff and had lower mean load to failure compared with repair of the native tendon in this cadaveric model, but these values remained biomechanically acceptable above critical thresholds. Consequently, lacertus fibrosus augmentation is a viable option for chronic distal biceps tendon ruptures with tendon attrition. Clinical Relevance: Chronic distal biceps tendon ruptures may require autograft or allograft reconstruction secondary to tendon scarring, shortening, attrition, and degeneration. The lacertus fibrosus is a cost-effective and low-morbidity local autograft that can be used to augment repairs.

Síndrome del lacertus fibrosus

El lacertus fibrosus del bíceps o expansión aponeurótica del bíceps es una estructura a la que suele prestársele poca atención frente a otras unidades miotendinosas de destacada importancia como el bíceps brachii o el tríceps. Por esta razón, en general es escaso el conocimiento que se tiene de ella respecto a su anatomía, biomecánica, fisiología y, sobre todo, patología; en las descripciones del síndrome del pronador redondo se le menciona de manera incidental. El presente es un estudio descriptivo observacional de tipo retrospectivo hecho con el propósito de revisar la anatomía del lacertus fibrosus, plantear aspectos de su biomecánica y presentar la revisión de una serie de 29 casos identificados a partir de 4 100 historias clínicas realizadas entre el 13 de enero de 2015 y el 12 de febrero de 2020. En la revisión de la literatura hecha para la presente investigación se encontró que dicha patología predominó en las mujeres y en los mayores de 56 años, siendo el principal motivo de consulta el dolor en la cara antero-medial del brazo distal y del codo. Además, se halló que su presentación clínica con frecuencia se acompañaba de los síndromes del pronador redondo y del interóseo posterior.

Biceps, Brachialis, and Triceps

Tendon injuries at the elbow affect mostly the distal biceps and can progressively degenerate over time or rupture in an acute event. The degree of retraction may depend on the integrity of the lacertus fibrosus, a fibrous expansion that merges with the forearm flexor fascia. Biceps disorders are frequently associated with fluid or synovitis of the adjacent bicipital bursa; primary bursal disorders (primary inflammatory synovitis) can also be observed. Distal triceps is less frequently injured than the distal biceps, and tears usually manifest as distal ruptures with avulsion of a small flake of bone from the tip of the olecranon. Brachialis injuries are uncommon and the consequence of sudden muscle stretching during forced elbow hyperextension, as in posterior elbow luxation.

Bilateral'naya kompressiya sredinnogo nerva aponevrozom dvuglavoj myshcy plecha na urovne loktevogo sustava (Lacertus-sindrom)

Kompressiya sredinnogo nerva aponevrozom dvuglavoj myshcy plecha (lacertus fibrosus) na urovne loktevogo sustava, ili Lacertus-sindrom, — redkaya patologiya, kotoruyu slozhno obnaruzhit' s pomoshch'yu instrumental'nyh metodov issledovaniya. V literature otsutstvuyut svedeniya o raspostranennosti dannogo sindroma, chetkie algoritmy ego diagnostiki i lecheniya, chto zatrudnyaet postanovku diagnoza i naznachenie effektivnogo lecheniya. Lacertussindrom soprovozhdaetsya polozhitel'nym scratch collapse test i trebuet differencial'noj diagnostiki s sindromom karpal'nogo kanala. Predstavlen klinicheskij sluchaj pacienta s bilateral'noj kompressiej sredinnogo nerva aponevrozom dvuglavoj myshcy plecha na urovne loktevogo sustava, izlozheny kriterii diagnostiki Lacertus-sindroma, sposob operativnogo lecheniya. Rezul'taty ispol'zovannoj hirurgicheskoj taktiki: ischeznovenie boli, parestezij i onemeniya v zone innervacii sredinnogo nerva, vosstanovlenie sily myshc do urovnya M5 po SHkale ocenki myshechnoj sily MRC — svidetel'stvuyut o vysokoj effektivnosti predlagaemogo hirurgicheskogo lecheniya Lacertus-sindroma.

Bilateral lacertus fibrosus entrapment of median nerve at the elbow (Lacertus syndrome)

Lacertus fibrosus entrapment of the median nerve at the elbow, or Lacertus syndrome, is a rare pathology, which is difficult to detect by instrumental examination methods. Literary sources provide no information on the syndrome prevalence, as well as on precise diagnosis and treatment algorithms, which makes it difficult to establish the diagnosis and appoint the effective treatment. Lacertus syndrome is characterized by positive scratch collapse test; differential diagnosis is required to distinguish it from carpal tunnel syndrome. Clinical case of bilateral lacertus fibrosus entrapment of the median nerve at the elbow is reported, Lacertus syndrome diagnosis criteria and surgical treatment method are set out. The results of the surgical tactics used are as follows: pain, paresthesia and numbness in the innervation field of the median nerve have vanished, the muscle strength has been restored to level М5 in accordance with MRC muscle strength scale. These results demonstrate high efficiency of the proposed lacertus syndrome surgical treatment.

Distal biceps hook test – Sensitivity in acute and chronic tears and ability to predict the need for graft reconstruction

Background The aim of this study was to assess the sensitivity of distal biceps hook test – O’Driscoll hook test – in a retrospective series of acute and chronic distal biceps tendon tears and investigate the ability of the test to predict the need for graft reconstruction. Methods We retrospectively evaluated 234 consecutive distal biceps tendon tears operated in a single centre. The result of O’Driscoll hook test and perioperative findings of distal biceps were documented in standard fashion. Results The perioperative and O’Driscoll hook test data were available in 202 cases. The sensitivity for the distal biceps hook test was 78% in all tears and 83% in complete tears. The sensitivity was significantly lower in partial tears (30%) and in cases where lacertus fibrosus was found to be intact (45 %). When O’Driscoll hook test was positive and the delay from initial injury to operative intervention was eight weeks or more, there was over 75% probability of achilles tendon allograft reconstruction. When O’Driscoll hook test was negative, the probability of reconstruction even after 12 weeks’ delay was only 20%. Discussion O’Driscoll hook test is useful when establishing distal biceps tendon tear diagnosis, but a negative test does not exclude rupture. In delayed cases, a positive test may predict the need for reconstruction.