Pullout strength of all-suture anchors: effect of the insertion and pulling angle - A biomechanical study -
Author(s):
Oh J. (South Korea (ROK))
,
Oh J. (South Korea (ROK))
Affiliations:
Rhee S.
,
Rhee S.
Affiliations:
Jeong H.
,
Jeong H.
Affiliations:
Yang S.
,
Yang S.
Affiliations:
Itami Y.
,
Itami Y.
Affiliations:
McGarry Michelle H.
,
McGarry Michelle H.
Affiliations:
Lee T.
Lee T.
Affiliations:
ESSKA Academy. Oh J. 05/09/18; 209292; P02-874 Topic: Biomechanics
Prof. Dr. Joo Han Oh
Prof. Dr. Joo Han Oh
Login now to access Regular content available to all registered users.

You can access free regular educational content on the ESSKA Academy by registering as an 'ESSKA Academy User’ here

Access to Premium content is currently a membership benefit.

Click here to join ESSKA or renew your membership.
Abstract
Discussion Forum (0)
Rate & Comment (0)
Objectives: Recently, all-suture anchors (ASA), composed of textile materials without rigid components, were developed to minimize the invasiveness and complications related to the use of rigid materials. The fixation mechanism of ASA differs from that of the conventional suture anchors due to different mechanical properties. Although several biomechanical studies showed no differences in pullout strength, many surgeons concerned about weaker fixation of ASA due to different fixation mechanism. Furthermore, authors experienced the several cases of anchor pullout during knot-tying. Despite the increasing use of ASA, few biomechanical studies have evaluated it surgical techniques, including the insertion angle of ASA to enhance its pullout strength. Therefore, the current study aimed to evaluate the pullout strength of the all-suture anchor, based on the angles of anchor insertion and pulling.

Methods: Synthetic bone analog of two densities (0.16 and 0.32 g/cm3) with 3 mm-thick cortical bone models were used. ASAs were inserted at 45°, 60°, 75°, or 90° and pulled at two angles from the surface: 45° (simulating the physiologic pull of the supraspinatus) and 90° (simulating pulling out during knot-tying). Five consecutive pullout tests for each insertion and pulling angle combination per synthetic bone analog were conducted to evaluate the ultimate load-to-failure and mode-of-failure (80 tests total). Thereafter, 9 matched pairs of human cadaveric humeri with two ASA types were used (insertion angle 45°, 75°, 90°; pulling angle 90°). Nine consecutive tests were conducted for each insertion angle and anchor type (54 tests total).

Results: The pullout strength was significantly higher for high-density than for low-density sawbones (all p<0.05). The pullout strength was higher at the 45° pulling angle than at the 90° (all p<0.05), and was significantly higher at the 90° and 75° insertion angle than at the 45° in both high-density sawbones and cadaveric humeri (all p< 0.05). However, the pullout strength was not significantly different by ASA type (all p >0.05).

Conclusions: ASA showed a stronger pullout strength when pulled in the physiologic direction of the supraspinatus rather than in the knot-tying direction, consistent with the deadman theory. However, stronger pullout strength was observed in the vertically directed insertion angle, not 45°. Therefore, implanting the ASA vertically may be clinically more beneficial not only when performing knot-tying during surgery, but also when the ASA is pulled by the supraspinatus tendon after surgery.

Keywords:
all-suture anchor, shoulder, pullout strength, rotator cuff, deadman theory
Objectives: Recently, all-suture anchors (ASA), composed of textile materials without rigid components, were developed to minimize the invasiveness and complications related to the use of rigid materials. The fixation mechanism of ASA differs from that of the conventional suture anchors due to different mechanical properties. Although several biomechanical studies showed no differences in pullout strength, many surgeons concerned about weaker fixation of ASA due to different fixation mechanism. Furthermore, authors experienced the several cases of anchor pullout during knot-tying. Despite the increasing use of ASA, few biomechanical studies have evaluated it surgical techniques, including the insertion angle of ASA to enhance its pullout strength. Therefore, the current study aimed to evaluate the pullout strength of the all-suture anchor, based on the angles of anchor insertion and pulling.

Methods: Synthetic bone analog of two densities (0.16 and 0.32 g/cm3) with 3 mm-thick cortical bone models were used. ASAs were inserted at 45°, 60°, 75°, or 90° and pulled at two angles from the surface: 45° (simulating the physiologic pull of the supraspinatus) and 90° (simulating pulling out during knot-tying). Five consecutive pullout tests for each insertion and pulling angle combination per synthetic bone analog were conducted to evaluate the ultimate load-to-failure and mode-of-failure (80 tests total). Thereafter, 9 matched pairs of human cadaveric humeri with two ASA types were used (insertion angle 45°, 75°, 90°; pulling angle 90°). Nine consecutive tests were conducted for each insertion angle and anchor type (54 tests total).

Results: The pullout strength was significantly higher for high-density than for low-density sawbones (all p<0.05). The pullout strength was higher at the 45° pulling angle than at the 90° (all p<0.05), and was significantly higher at the 90° and 75° insertion angle than at the 45° in both high-density sawbones and cadaveric humeri (all p< 0.05). However, the pullout strength was not significantly different by ASA type (all p >0.05).

Conclusions: ASA showed a stronger pullout strength when pulled in the physiologic direction of the supraspinatus rather than in the knot-tying direction, consistent with the deadman theory. However, stronger pullout strength was observed in the vertically directed insertion angle, not 45°. Therefore, implanting the ASA vertically may be clinically more beneficial not only when performing knot-tying during surgery, but also when the ASA is pulled by the supraspinatus tendon after surgery.

Keywords:
all-suture anchor, shoulder, pullout strength, rotator cuff, deadman theory
Code of conduct/disclaimer available in General Terms & Conditions

By clicking “Accept Terms & all Cookies” or by continuing to browse, you agree to the storing of third-party cookies on your device to enhance your user experience and agree to the user terms and conditions of this learning management system (LMS).

Cookie Settings
Accept Terms & all Cookies