Acromioclavicular Fixation Before Coracoclavicular Tunnel Placement and Acromioclavicular Construct Design Improved Reduction and Stability in a Whole-Shoulder Girdle Model: A Pilot Study

Abstract

Background: Reconstruction of the acromioclavicular (AC) ligament after an acute AC dislocation as the first surgical step before coracoclavicular (CC) tunnel placement has been proposed to reduce the risk of postoperative loss of reduction. Additional reconstruction of AC ligamentous complex lesions with different types of bracing constructs has also been described to improve outcomes. Still, the effect of the sequence of surgical steps and the AC bracing construct design on the AC kinematics in a whole-shoulder girdle model has not been reported.

Hypothesis: The primary hypothesis was that postoperative AC joint reduction would improve when the AC joint was reconstructed before CC tunnel placement. The secondary hypothesis was that different AC bracing construct designs affect joint kinematics during physiological motion in a whole-shoulder girdle model.

Study design: Controlled laboratory study.

Methods: Five cadaveric specimens (10 shoulders) were prepared for whole-shoulder mobilization with a robotic manipulator. Joint kinematics was acquired during physiological motions using an optical motion capture system. Recorded parameters were (1) the joint reduction in a resting position, expressed as joint displacements and rotations compared with an intact AC joint, and (2) the joint stability during all tested motions, expressed as joint displacements and rotations. The tested joint conditions were intact AC joint, induced Rockwood type 5 lesion, isolated CC reconstruction, and 4 AC joint bracing construct designs. AC reconstruction was performed before (AC-first technique) and after (CC-first technique) CC tunnel placement in 5 shoulders each.

Results: The AC-first surgical step improved the AC joint reduction in anterior-posterior tilt compared with CC-first (median difference, -9.4°; P < .001). The AC-first surgical step also demonstrated an increased superior-inferior joint reduction with hyperreduction (median difference, 1.6 mm; P = .041) compared with CC-first. Dispersion of joint reduction values was reduced with the AC-first step and particularly for anterior-posterior tilt (IQR difference, -4.8°) and lateral-medial displacement (IQR difference, -3.4 mm). The double vertical bracing construct design increased the AC joint stability compared with other constructs and reached a statistical significance in all rotational displacement (P < .001 to P = .041) as well as in lateral-medial displacement (P = .001 to P = .015).

Conclusion: The AC-first surgical step sequence improved AC joint alignment in the scapular sagittal plane and increased joint hyperreduction. The double vertical bracing construct design achieved the highest joint stability over other tested designs during passive motion.

Clinical relevance: The restoration of the preinjury joint alignment and the optimization of the joint stability may improve outcomes and reduce the risk of construct de-tensioning during the rehabilitation phase.

Keywords: acromioclavicular lesion; bracing construct design; cadaveric specimen; joint kinematics; robotic manipulator; surgical step sequence; whole shoulder.

Figure 1.

Testing setup. (A) Whole-cadaver setup with humerus mobilized by a robotic manipulator. (B) Clusters of reflective markers and related bone pins. (C) Computed tomography scanner. (D) Attachment of the humerus to the robotic manipulator.

Figure 2.

Surgical joint reconstructions. *Coracoclavicular (CC) only: CC drilling and double-button system installation only. (I) Bracing construct design 1: CC only + double vertical suture configuration. (II) Bracing construct design 2: CC only + single anterior vertical suture configuration. (III) Bracing construct design 3: CC only + single horizontal suture configuration. (IV) Bracing construct design 4: CC only + double horizontal suture configuration. AC, acromioclavicular.

Figure 3.

Acromioclavicular joint kinematics of the joint coordinate system. (A) Retraction-protraction of the scapula. (B) Lateral-medial rotation of the scapula. (C) Anterior-posterior tilt of the scapula. (D) Inferior-superior displacement. (E) Anterior-posterior displacement. (F) Lateral-medial displacement.

Figure 4.

Acromioclavicular joint kinematics for each degree of freedom measured on 1 shoulder during thoracohumeral abduction. (A-D) Selected abduction levels corresponding to 30°, 60°, 90°, and 120° of abduction, respectively. CC only, joint only reconstructed with coracoclavicular double-button system; Intact, intact joint condition; Rockwood V, joint in Rockwood type 5 lesion condition.

Figure 5.

Box plots illustrating the surgical step sequence effect on acromioclavicular joint alignment. The colored box spans from the first quartile to the third quartile, with the black line representing the median. Whiskers extend from each quartile to the minimum and maximum values. Black crosses represent outliers. *P < .05; **P < .01. AC-first, inverted surgical step sequence; CC-first, coracoclavicular drilling and double-button system installation before acromioclavicular bracing construct design achievement; n.s., not significant.

Figure 6.

Box plots illustrating the bracing construct design effect on acromioclavicular joint stability. The colored box spans from the first quartile to the third quartile, with the black line representing the median. Whiskers extend from each quartile to the minimum and maximum values. Black crosses represent outliers. *P < .05; **P < .01; ***P < .001. CC only, joint only reconstructed with coracoclavicular double-button system; Native, intact joint condition; Rockwood V, joint in Rockwood type 5 lesion condition.