Arthroscopic bone block metal-free fixation for anterior shoulder instability. Short-term functional and radiological outcomes

The Addition of Remplissage to Free Bone Block Restores Translation and Stiffness Compared to Bone Block Alone or Latarjet in a Bipolar Bone Loss Model

PURPOSE

The purpose of this study was to compare glenohumeral stability following a Latarjet, a free bone block (FBB), and a FBB with remplissage for bipolar bone loss.

METHODS

Nine matched pairs of fresh frozen cadavers were tested in a custom biomechanical apparatus with rotation and progressive translational loading. The free bone block group consisted of a distal tibial allograft with an all-suture tape construct. The Latarjet group was performed with the native coracoid and two partially threaded cannulated screws. A bipolar bone loss model was created with 20% glenoid bone loss and an off-track Hill-Sachs lesion. Testing conditions included the 1) native state, 2) bipolar bone loss model, 3) Latarjet, 4) FBB with distal tibial allograft secured with cerclage sutures, and 5) FBB with remplissage. Each condition was tested for translation, humeral head apex shift, stiffness, and dislocation force.

RESULTS

There were no differences in translation, stiffness, or dislocation forced between the FBB alone and Latarjet groups. The FBB with remplissage group demonstrated the lowest anterior-inferior translation at 90° of ER, which was statistically significant compared to Latarjet 20N (P = .013) and compared to the FBB alone at 40N (P = .024) and 50N (P = .011). The FBB with remplissage group was significantly stiffer compared to FBB alone at 90° ER with approximately 60% change in stiffness (P = .028). The force required to dislocate the humeral head after treatment was highest in the FBB with remplissage group, which was statistically significant compared to the FBB alone (P = .003) and Latarjet groups (P = .018).

CONCLUSION

The addition of remplissage to a FBB restores translation and stiffness closer to the intact state compared to a FBB alone or Latarjet in a bipolar bone loss model with an off-track Hill-Sachs lesion. In this model, dislocation force significantly increased with the addition of remplissage to the FBB.

CLINICAL RELEVANCE

This biomechanical study provides evidence that Latarjet and FBB are both acceptable forms of treatment for bipolar bone loss, but stability can be enhanced with the addition of remplissage following glenoid reconstruction.

Metal-Free Fixation for Free Bone-Block Reconstruction of Chronic Anteroinferior Shoulder Instability

Background:

Anterior shoulder instability is common and may cause a considerable effect on quality of life. For cases with glenoid bone loss, there is still a controversial discussion regarding the optimal treatment. Most of the recent methods are using metal implants to attach the needed graft to the glenoid with reported disadvantages such as metal impingement, damage to the humeral head, cartilage destruction, and premature arthritis.

Indications:

(1) Erosion-type defects with significant bone loss (>15%-20%); (2) chronic fragment-type defects if the size of the fragment is not large enough for an anatomical reconstruction; and (3) non-reconstructible, multifragmented acute fragment type of lesions.

Technique Description:

After placing the patient in a lateral decubitus position and fixing the arm in a traction devise, 3 arthroscopic entries are established: a posterior portal, an anterosuperior portal, and an anteroinferior portal. A harvested tricortical iliac crest bone graft is provided with 2 drilling holes which match the drilling holes through the glenoid. The tapes are then placed from the posterior to the anterior side of the glenoid, and then the graft is passed from the anterior to the posterior side, thus compressing the cancellous side of the bone block onto the glenoid defect. A following interconnection of the sutures creates a continuous loop. The end of the tapes was loaded into a pretied racking hitch knot system, which creates sliding knots between the 2 pair of tapes, whereon the knots can be reduced to the glenoid in a symmetrical fashion. Finally, the reconstruction of the anterosuperior labrum can be done, to cover the bone block with enough soft tissue.

Results:

First short-term results show radiographic consolidation after 3 months and an increased median glenoid estimated surface area at 12 months. The functional scores showed good outcomes, and there were no serious complications reported.

Discussion/Conclusion:

The presented arthroscopic reconstruction of the glenoid using a tricortical bone graft and high-strength fiber tapes provides a metal-free technique which results in a high primary stability of the construct and should therefore be considered when treating anterior shoulder instability with significant bone loss.