No Significant Difference Between Intramedullary and Extramedullary Button Fixation for Distal Biceps Brachii Tendon Rupture After Cyclic Loading in a Cadaver Model

Abstract

To biomechanically compare intramedullary (IM) versus extramedullary (EM) distal biceps button fixation under cyclic loading conditions, which is most representative of postoperative physiologic status. Methods: This controlled laboratory study used 13 fresh-frozen matched paired cadaver elbows. One specimen from each pair was randomized to either IM (unicortical) or EM (bicortical) distal biceps button fixation via onlay technique. A servohydraulic actuator was used to cycle each specimen from full extension to 90 of flexion at 0.5 Hz for 3,000 cycles. All specimens were subsequently loaded to failure to simulate an acute postoperative load. Results: During cyclic loading, the mean change in force from cycle 5 to cycle 3000 was 2.1 AE 3.2 N for the IM group and 0.6 AE 4.2 N for the EM group (P ¼ .19). The increase in tendon gap for the IM group was 1.02 mm and for the EM group was 1.83 mm (P ¼ .37). During failure loading, the IM group had a mean failure load of 154.9 AE 44.5 N and the EM group a mean failure load of 191.1 AE 62.6 N (P ¼ .16). Conclusions: No significant differences exist between the IM and EM techniques in loss of force and tendon gap formation under cyclic loading or load to failure conditions. Thus, IM fixation may adequately facilitate optimal bonetendon apposition, with less risk of iatrogenic injury to the posterior interosseous nerve that can be seen with bicortical extramedullary fixation. Clinical Relevance: The most common major complication following distal biceps repair is PIN palsy. IM fixation may be sufficient in facilitating optimal bone-tendon apposition and healing with onlay technique, while minimizing risk of iatrogenic PIN injury associated with EM fixation.

Tensionable Distal Biceps Tendon Repair With Intramedullary Knotless All-Suture Anchors and FiberLoop w/FiberTag Suture

“…Unicortical drilling and intramedullary placement of fixation devices have demonstrated similar or better biomechanical properties in distal biceps repair pullout strength compared to bicortical drilling and extramedullary button placement, 8 and intramedullary all-suture anchors have demonstrated equal or superior fixation strength compared to intramedullary button. 9 …”

Revision Distal Biceps Tendon Repair Using Original Intramedullary Buttons

“…It has been further validated in several biomechanical studies demonstrating equivalent and in some cases, superior biomechanical strength than suture anchor and extramedullary button fixation. 6 , 7 The greatest advantage of this revision technique is a safe and effective method to use the original intramedullary buttons. This technique could also be performed in other areas of the body where cortical button fixation is utilized such as a revision proximal biceps tenodesis or revision pectoralis major tendon repair.…”

Biomechanical Comparison of Distal Biceps Tendon Repair Techniques: Extracortical Single-Button Inlay Fixation Versus Intracortical Double-Button Onlay Anatomic Footprint Fixation

“…Previous biomechanical studies determined that an intracortical suture anchor construct reduced gap formation by 25% to 47% when compared with the extracortical SB construct, pointing to increased tendon stability at the bicipital tuberosity in the presence of 2 points of tendon fixation. 27,37 Another advantage of the anatomic DB technique is the fact that it follows an onlay repair principle, which allows for appropriate tensioning of the tendon onto the tuberosity, as opposed to various inlay techniques that require insertion of the tendon into approximately 1 cm of the bone, with button fixation on the far cortex of the radius. 3 Ultimate tensile load is indicative of the capacity of a construct to withstand large muscle contractile loads.…”

“…Button pullout, secondary to fracture avulsion, was the primary mode of failure in the anatomic DB group of the present study. Majumdar et al 27 identified elongation and radial fracture to account for 10 of 13 DB construct failures. Siebenlist et al 37 noted that 58% (7 of 12) of intracortical DB constructs failed by fracture avulsion, lower than the 78% (7 of 9) of constructs failing in the same manner in the present study.…”

“…Cyclic loading protocols were performed by applying the amplitude-determined by halving the difference between Instron displacement at 90°of flexion and full extension-in a sinusoidal wave (mean amplitude, 19 mm) for 1000 cycles at 0.5 Hz, in accordance with previous studies. 27,28,31,36,40 Displacement, rather than force, was controlled during cyclic loading testing to replicate elbow motion under a constant distal force. 28,31,36 During testing, gap formation was assessed by measuring the change in displacement at the center of 2 ball bearings, attached directly to the radial tuberosity (distal biceps insertion on the radius) and the distal biceps tendon stump (Figure 4).…”