Biomechanical effect of increased number of suture strands on rotator cuff repair in a bovine model.

OBJECTIVE: This study aimed to investigate if there was a link between the biomechanical properties and the number of suture strands in repairing a rotator cuff (RC) tear in a bovine model using the transosseous technique. METHODS: Fifty-four fresh tendons from bovine (mean age: 7.1 ± 0.5 months; range 6.5-7.5 months) and 1 humeral head from porcine (8.5 months) were used in this study. All the specimens had no apparent abnormalities. Using the transosseous structure, the RC tendon was detached from the greater tuberosity and randomly assigned to 3-strand, 4-strand, 5-strand, and 6-strand groups, with the glenohumeral abducted at 0° and 90°. Biomechanical tests were conducted to compare the groups' differences in the failure mode, pull-toextension load in the 1-, 2-, and 3-mm formations, and the maximum load. The analysis of variance test was performed to compare the results. Statistical significance was set at P < .05. RESULTS: No significant difference was observed among the groups concerning the tendon characteristics (all P ≥ .05). At 90° shoulder abduction, a significant difference was detected in the load between 3- and 5-strand groups for 1-mm gap formation (P=.049). No statistical differences were noted in the load at the gap displacements in the 1-, 2-, and 3-mm formations at 0° and 90° shoulder abduction (all P > .05). The maximum failure load and extension in maximal tension increased with the number of sutures. CONCLUSION: The maximum load and ultimate extension increase with the number of sutures at both positions. The number of sutures was not an influencing factor of gap formation. Regarding the tear size and tension of the RC, choosing the appropriate number of strands individually instead of excessively increasing the number of sutures is advocated for RC repair.

Anatomical and Interpositional Bursa Preservation Showed Similar Improved Tendon to Bone Healing Compared With the Bursa Removal in a Rat Rotator Cuff Tear Model.

PURPOSE: To compare the effects of anatomical preservation (AP) and interpositional preservation (IP) of subacromial bursa tissue on tendon-to-bone healing in a rat model of rotator cuff tear. METHODS: In this study, 48 male Sprague-Dawley rats (average weight 283 g) underwent bilateral supraspinatus tendons severed by sharp incision and repaired immediately. The subacromial bursa tissues were completely removed in 16 rats, who served as the control (CON) group. The other 32 rats were randomly divided into 2 groups AP and IP between tendon and bone. Eight rats of each group were sacrificed for bilateral shoulders at 3 and 9 weeks after the operation, including 5 rats for biomechanical tests and 3 for histologic analysis. RESULTS: No significant differences in terms of biomechanical properties were observed among the groups 3 weeks after surgery. At 9 weeks, the maximum load and stiffness of the AP (32.95 ± 6.33 N, P = .029; 12.49 ± 3.17 N/mm, P < .001; respectively) and IP (33.58 ± 8.47 N, P = .015; 11.63 ± 2.84 N/mm, P = .010, respectively) groups were significantly superior to that of the CON group (26.59 ± 4.47 N; 8.42 ± 2.33 N/mm, respectively). More organized collagen and more mature tendon insertion were observed in AP and IP groups at the interface at 9 weeks, which means better tendon-to-bone healing compared with the CON group. CONCLUSIONS: The subacromial bursa plays a positive role in tendon-bone healing. Either anatomical preservation or interpositional preservation between tendon and bone can similarly facilitate the process of healing. CLINICAL RELEVANCE: Considering the additional surgical time and surgical manipulation, preserving the subacromial bursa at the anatomical position seems to be a better way to promote rotator cuff healing.

Absorbable suture knots on the supraspinatus tendon prevent adverse effects of nonabsorbable suture knots in a rat model.

PURPOSE: To compare the absorbable and nonabsorbable suture knots on the tendon on bone-to-tendon healing during the early phase in a rat rotator cuff tear (RCT) model. METHODS: Fifty-two male Sprague-Dawley rats (10 weeks old; mean weight, 380 g) were used in this study, and 51 of them were randomly assigned into three groups: absorbable suture group (ASG, n = 22), nonabsorbable suture group (NSG, n = 22), and sham surgery group (SSG, n = 7), and the remaining rat was used to take surgical pictures. Bilateral supraspinatus tendon tears were created and repaired immediately in ASG and NSG. Three rats from ASG and NSG were killed for Western blot and histological evaluation at 3 days, 1 week, and 4 weeks after surgery. At 4 weeks, four rats from each group were killed for biomechanical test, and three rats from SSG were used for histological evaluation. RESULTS: Absorbable suture knots on the tendon completely degraded at 4 weeks. However, nonabsorbable suture knots remained intact between the tendon and articular side. ASG showed a stronger inflammatory reaction at 3 days and 1 week, but a weaker reaction at 4 weeks as confirmed by gross observation and Western blot. Besides, ASG showed superior biomechanical properties in terms of maximum load to failure and stiffness at 4 weeks. Modified Bonar score revealed superior maturity for tissue healing in ASG to that in NSG at 4 weeks. Furthermore, inferior bone-to-tendon interface and weakest link formation were observed in NSG on histologic images. CONCLUSION: Absorbable suture knots on the tendon contributed to better mechanical properties compared with the nonabsorbable one after rotator cuff repair.

Length Changes in the Interosseous Membrane During Forearm Rotation: A 3-Dimensional Study In Vivo.

PURPOSE: The length change of the interosseous membrane (IOM) during forearm rotation has not been fully studied. To explore the meaning of length change in the distal oblique band (DOB), the distal accessory band (DAB), and the proximal, middle, and distal parts of the central band (CBP, CBM, and CBD, respectively), we investigated the length change in these ligaments at maximum pronation, 45° of pronation, neutral position, 45° of supination, and maximum supination in vivo. METHODS: The images of the right forearms from 6 healthy volunteers were obtained by computed tomography scanning at the 5 above-mentioned rotation positions. We created 3-dimensional models of the radius and ulna, DOB, DAB, and central band based on the points of origin and insertion. Finally, the length of each ligament was estimated from the points of insertions and origins registered on the 3-dimensional models. RESULTS: The DAB and CBD lengths increased significantly from maximum pronation to 45° of pronation. The DOB length increased significantly from 45° of pronation to neutral position and decreased significantly from 45° of supination to maximum supination. The DAB and CBM lengths increased significantly from neutral position to 45° of supination. The DAB length decreased significantly from 45° of supination to maximum supination. For the CBP, no difference in length was observed during forearm rotation. CONCLUSIONS: The DOB becomes taut at neutral position, and the central band, especially the CBP, is nearly isometric. The findings indicate that the DOB may provide the primary stabilization of the distal radioulnar joint and that the central band is the key stabilizer during forearm rotation. CLINICAL RELEVANCE: Surgeons may pay attention to the DOB when a patient incurs a distal radioulnar joint injury, and the CBP may be the optimal location for IOM reconstruction.