Differential suture loading in an experimental rotator cuff repair

An Injectable Calcium Phosphate Bone Graft Substitute Improves the Pullout Strength of Various Suture Anchor Designs in an Osteoporotic Bone Model

Purpose

To compare various suture anchor designs with and without calcium phosphate (CaP) augmentation in an osteoporotic foam block model and decorticated proximal humerus cadaveric model.

Methods

This was a controlled biomechanical study, consisting of 2 parts: (1) an osteoporotic foam block model (0.12 g/cc; n = 42) and (2) a matched pair cadaveric humeral model (n = 24). Suture anchors selected were an all-suture anchor, PEEK (polyether ether ketone)-threaded anchor, and a biocomposite-threaded anchor. For each study arm, one half the samples were first filled with injectable CaP and the other half were not augmented with CaP. For the cadaveric portion, the PEEK- and biocomposite-threaded anchors were assessed. Biomechanical testing consisted of a stepwise, increasing load protocol for a total of 40 cycles, followed by ramp to failure.

Results

For the foam block model, the average load to failure for anchors with CaP was significantly greater when compared with anchor fixation augmented without CaP; the all-suture anchor was 135.2 ± 20.2 N versus 83.3 ± 10.3 N (P = .0006); PEEK was 131 ± 34.3 N versus 58.5 ± 16.8 N (P = .001); and biocomposite was 182.2 ± 64.2 N versus 80.8 ± 17.4 N (P = .004). For the cadaveric model, the average load to failure for anchors augmented with CaP was again greater than anchor fixation without CaP; PEEK anchors went from 41.1 ± 21.1 N to 193.6 ± 63.9 N (P = .0034) and biocomposite anchors went from 70.9 ± 26.6 N to 143.2 ± 28.9 N (P = .004).

Conclusions

Augmenting various suture anchors with CaP has shown to significantly increase pull-out strength and stiffness in an osteoporotic foam block and time zero cadaveric bone model.

Clinical Relevance

Rotator cuff tears are common in the elderly patients, in whom poor bone quality jeopardizes treatment success. Exploring methods that increase the strength of fixation in osteoporotic bone to improve outcomes in this patient population is important.

Effects of Abduction Pillows on Rotator Cuff Repair: A Biomechanical Analysis

BACKGROUND

After rotator cuff repair, some surgeons use abduction pillows to unload or protect the repair construct, while others do not.

QUESTION/PURPOSE

The aim of this study was to determine which type of sling-one with a small or large abduction pillow or one without a pillow-places the repaired rotator cuff in the best position to reduce tension on the supraspinatus.

METHODS

An X-ray study was performed on asymptomatic subjects to determine what position the shoulder is placed in when wearing a sling with or without an abduction pillow. Positions were then reproduced in human cadaveric shoulders using a custom-made testing jig, and tension on the repaired supraspinatus was measured.

RESULTS

X-rays showed that abduction of the glenohumeral joint with a sling was only 4°, with a sling with a small pillow was 13°, and with a sling with a large abduction pillow was 25°. Placing the cadaveric shoulders in the position of a sling with a small abduction pillow caused a reduction in tension on the supraspinatus of 27% anteriorly and 55% posteriorly compared to placing the shoulder in the position of a sling without an abduction pillow; a large abduction pillow caused a further reduction in tension, of 42% anteriorly and 56% posteriorly.

CONCLUSION

These findings show that abduction pillows reduce tension on the repaired supraspinatus tendon.

Clinical outcomes and structural integrity of C-shaped rotator cuff tears after arthroscopic repair: comparison with crescent-shaped tears

Background

We aimed to describe a new C-shaped tear configuration, and to compare clinical outcomes and structural integrity between the C-shaped and the established crescent-shaped small to medium-sized rotator cuff tears after arthroscopic repair.

Methods

This retrospective study included 102 patients who underwent arthroscopic repair in a single-row fashion for small- to medium-sized rotator cuff tears of either C or crescent shape from March 2009 to June 2014. Visual analogue scale (VAS) pain score, subjective shoulder value (SSV), American Shoulder and Elbow Surgeon (ASES) score, and active range of motion (ROM) were evaluated for functional outcomes. Postoperative magnetic resonance arthrography (MRA) or computed tomographic arthrography (CTA) was performed 6 months postoperatively to assess structural integrity.

Results

After 2 years of follow-up, both groups showed no significant difference in VAS pain score, functional scores, or ROM, although the C-shaped tear group exhibited significantly inferior outcomes 3 months after surgery. There was no significant difference in the re-tear rate on follow-up MRA and CTA between groups A and B (24.4 vs. 19.7%, respectively; p = 0.570). The postoperative stiffness rate was significantly higher in the C-shaped tear group than that in crescent-shaped tear group only at 3-month follow-up point after surgery (26.8 vs. 9.8%, respectively; p = 0.024).

Conclusions

Contrary to our hypothesis, there were no significant differences in functional outcomes and structural integrity between C-shaped and crescent-shaped small- to medium-sized tears 2 years after arthroscopic repair. However, C-shaped tears exhibited significantly worse clinical outcomes, including a higher postoperative stiffness rate than crescent-shaped tears in the early postoperative period at the 3-month follow-up point.

Radiolucent rings around bioabsorbable anchors after rotator cuff repair are not associated with clinical outcomes

PURPOSE

Various researchers have observed small areas of osteolysis after using bioabsorbable anchors in shoulder surgeries. The purpose of this study is to determine whether radiographic perianchor radiolucent rings after rotator cuff repair are associated with the failure of repair and also assess their clinical implications. Further, the most frequent location of the radiolucent rings in the double-row suture bridge configuration was also assessed.

METHODS

One hundred and twenty-nine consecutive patients who underwent arthroscopic rotator cuff repair by suture bridge technique were retrospectively evaluated radiographically and clinically. The number and size of the rings that appeared at each follow-up were recorded. Also, the locations of each ring were recorded as anterior, middle or posterior, and medial or lateral according to the construct of the anchors used for suture bridge technique. The size of the tear, the number of anchors used and age of the patients were compared. Re-tear rates according to ultrasound examinations were also analyzed.

RESULTS

After rotator cuff repair, the mean American Shoulder and Elbow Surgeons (ASES) score increased from 46.7 to 88.0 and the overall re-tear rate was 8.5% (11 cases). Seventy-three patients (56.6%) showed RR (total number of 99 rings) at least once during the course of their follow-up and the rings appeared at a mean period of 18.2 months after surgery. Mean size of the rings initially was 5.6 mm and the rings increased or decreased in mean size of 0.4 mm during mean follow-up of 37 months. No correlation was seen with the number of RRs and the rate of re-tears, number of anchors, size of tears, and clinical outcome as determined by the ASES score. Radiolucent ring measurement reproducibility was confirmed by independent, repeated measurements. The rings appeared mostly at anteromedial anchors (75 rings, 75.8%) and the authors suggest that mechanical factors may play a role for the cause of radiolucent rings.

CONCLUSIONS

The number and the size of RRs around bioabsorbable anchors after rotator cuff repair do not appear to adversely affect the healing and clinical outcome of ARCR. Most radiolucent rings appeared at anteromedial anchors, indicating that mechanical factors may play a role for the radiolucencies.

LEVEL OF EVIDENCE

Case series, level IV.

Does a brace influence clinical outcomes after arthroscopic rotator cuff repair?

PURPOSE

The goal of this study was to report the clinical effects of two different braces after rotator cuff repair.

METHODS

Forty patients who underwent an arthroscopic rotator cuff repair were prospectively allocated in this study. Twenty patients were immobilized in 15° external rotation brace (ER Group), and twenty were immobilised in an internal rotation sling (IR Group). For all patients, four surveys were done: in the immediate pre-operative period (T0), at 1 month (T1), at 3 months (T2) and at 6 months after surgery (T3). Range of motion and pain were evaluated by an independent physician. Self-Assessment Scales [(University California Los Angeles Shoulder Rating Scale (UCLA), Disability of the Arm Shoulder and Hand (DASH), Visual Analog Scale (VAS), Simple Shoulder Test (SST) and Physician Assessment Scale (Constant)] were also administered.

RESULTS

Abduction and ER2 (external rotation with arm in abduction) were significantly greater in the ER group at T1, T2 and T3, ER1 (external rotation with arm at side) was significantly greater in the ER group at T1 and T2, IR2 (internal rotation) was significantly greater in the ER group at T1, and FFL (forward flexion) was significantly greater in the ER group at T1. VAS was significantly lower in the ER group at T1 and T2 and T3. About the Self-Assessment Shoulder Scales after 3 and 6 months, no differences were found. SST showed a lesser functional limitation for the ER group at T3.

CONCLUSIONS

Patients operated with isolated superior or posterosuperior rotator cuff tear immobilised with brace in 15° of ER position showed less pain and a better passive range of motion at short time after surgery.

Knotless rotator cuff repair in an external rotation model: the importance of medial-row horizontal mattress sutures

PURPOSE

To evaluate the effect of the addition of 2 horizontal mattress knots to the medial row of a knotless rotator cuff construct on the biomechanical properties in terms of both cyclic and failure testing parameters in an external rotation model.

METHODS

In 8 fresh-frozen human cadaveric shoulders, a knotless transosseous repair was performed, whereas in 8 contralateral matched-pair specimens, 2 horizontal mattress knots were added to the medial-row fixation. A custom jig was used that allowed external rotation (0° to 30°) with loading. A materials testing machine was used to cyclically load repairs from 0 to 180 N for 30 cycles and then to failure. Video digitizing software was used for analysis. Data from paired specimens were compared by use of paired Student t tests.

RESULTS

Ultimate load to failure was significantly higher in the modified construct (549 N v 311 N, P = .01). Linear stiffness in the first cycle, at the 30th cycle, and at failure was significantly higher (P = .02, P = .02, and P = .04, respectively) in the modified construct as well. Energy absorbed by the repaired tissue was significantly less in the modified construct at the first cycle, at the 30th cycle, and at ultimate load to failure (P = .03, P = .02, and P = .04, respectively). Significantly greater anterior gap formation occurred with the knotless technique at the first cycle (4.55 v 1.35) and 30th cycle (7.67 mm v 1.77 mm) (P = .02).

CONCLUSIONS

The modified construct shows improved biomechanical properties when allowing for external rotation during high-load testing. Using an additional horizontal mattress from separate sutures in the medial-row anchors helps to neutralize forces experienced by the repair.

CLINICAL RELEVANCE

The addition of medial-row fixation to a knotless construct will enhance the stability of rotator cuff repairs with the goal of improved patient outcomes.

Suture anchor loading after rotator cuff repair: effects of an additional lateral row

HYPOTHESIS

Our initial hypothesis was that the medial row of double-row rotator cuff repair techniques would bear most of the load on the repaired cuff.

MATERIALS AND METHODS

Six cadaver shoulders underwent simulated rotator cuff repairs using sequential single row, double-row, and suture-bridge repair techniques. Suture tensions at each anchor were measured for several static, simulated shoulder positions by specially designed, instrumented anchors.

RESULTS

Significantly greater suture tensions were measured in the anchors in a single row repair construct than either the double row repair or suture bridge repair construct (P < .001). In the double-row and suture bridge techniques, there was no apparent difference in the loads born by the medial and lateral row anchors. Shoulder abduction from 45 degrees to 60 degrees had little effect on anchor tensions; 45 degrees internal and external rotation significantly (P = .032) increased loads on the anterior and posterior anchors by at least 125%.

DISCUSSION

Forces are transmitted through the entire portion of the tendon at its humeral fixation, loading the lateral anchors as well as the medial row for the techniques studied. This "load sharing" can explain the higher fixation strengths of double row techniques seen experimentally.

CONCLUSION

The magnitude and distribution of anchor suture tensions could have important implications for lateral row fixation devices and post-operative positioning and activity.

LEVEL OF EVIDENCE

Basic Science.