Repair of the entire superior acromioclavicular ligament complex best restores posterior translation and rotational stability

Abstract

Purpose The acromioclavicular ligament complex (ACLC) is the primary stabilizer against horizontal translation with the superior ACLC providing the main contribution. The purpose of this study was to evaluate the speciic regional contributions in the superior half of ACLC, where the surgeon can easily access and repair or reconstruct, for posterior translational and rotational stability. Methods The superior half of ACLC was divided into three regions; Region A (0°-60°): an anterior 1/3 region of the superior half of ACLC, Region B (60°-120°): a superior 1/3 region of the superior half of ACLC, and Region C (120°-180°): a posterior 1/3 region of the superior half of ACLC. Fifteen fresh-frozen cadaveric shoulders were used. Biomechanical testing was performed to evaluate the resistance force against passive posterior translation (10 mm) and the resistance torque against passive posterior rotation (20°) during the following the four conditions. (1) Stability was tested on all specimens in their intact condition (n = 15). ( 2) The ACLC was dissected and stability was tested (n = 15). (3) Specimens were randomly divided into three groups by regions of suturing. Stability was tested after suturing Region A, Region B, or Region C (n = 5 per group). ( 4) Stability was tested after suturing additional regions: Region A + B (0°-120°), Region B + C (60°-180°), or Region A + C (0°-60°, 120°-180°, n = 5 per group). ResultsThe translational force increased after suturing Region A when compared with dissected ACLC (P = 0.025). The force after suturing Region A + B was signiicantly higher compared to the dissected ACLC (P < 0.001). The rotational torque increased after suturing Region A or Region B compared with dissected ACLC (P = 0.020, P = 0.045, respectively). The torque after suturing the Region A + C was signiicantly higher compared to the dissected ACLC (P < 0.001).

Reconstruction of the Acromioclavicular Ligament Complex Using Dermal Allograft: A Biomechanical Analysis

“…Specimen preparation was done in accordance with previously published methods. 4,14,15,[22][23][24] The clavicle and scapula were dissected free of all soft tissue except for the ACLC and CC ligaments. The scapula was trimmed and potted with plaster of Paris in a polyvinyl chloride (PVC) pipe.…”

“…The biomechanical test setup was done in accordance with previously published methods. 14,15 The specimens were positioned anatomically with the scapula secured to a swivel fixture on a X-Y-Z table, whereas the clavicular portion was attached to a custom fixture allowing for anteroposterior translation. A pneumatic cylinder (Bimba, Monee, IL) connected to a 100-lb load cell (Futek, Irvine, CA) was hooked to the custom fixture on the clavicle side to generate an anteroposterior translational force (Fig 4).…”

“…Translational and rotational testing was done in accordance with previously published methods. 14,15 Before testing, 5 cycles with reduced distance (5 mm of displacement) were used for preconditioning to eliminate hysteresis. A linear displacement of 10 mm in the anterior and posterior direction was applied for 15 cycles after preconditioning.…”

“…[4][5][6][7][8][9][10] The acromioclavicular ligament complex (ACLC) has been reported as the primary posterior stabilizer of the AC joint. [11][12][13][14] A previous biomechanical study demonstrated that dissection of the entire ACLC (with intact CC ligaments) reduced the resistance force of the AC joint against posterior translation to less than 25% when compared with the native ligament complex. 12 Similarly, the authors also found the resistance torque was reduced to less than 10% against posterior rotation when compared with the intact ligament.…”

“…15 Their study, along with Beitzel et al, also found that maintaining rotational stability was much more difficult compared with translational following AC joint reconstruction. 4,14 Other previous biomechanical studies have examined the specific contribution of the ACLC and found that the superior half of this complex is the most important for both posterior rotational and translational stability. 14 Using this information, the authors of the current study developed a surgical technique to reconstruct the superior half of the ACLC using dermal allograft.…”