Are Knotted or Knotless Techniques Better for Reconstruction of Full-Thickness Tears of the Superior Portion of the Subscapularis Tendon? A Study in Cadavers

Abstract

BackgroundKnotted and knotless single-anchor reconstruction techniques are frequently performed to reconstruct full-thickness tears of the upper portion of subscapularis tendon. However, it is unclear whether one technique is superior to the other.Questions/purposes(1) When comparing knotless and knotted single-anchor reconstruction techniques in full-thickness tears of the upper subscapularis tendon, is there a difference in stiffness under cyclic load? (2) Are there differences in cyclic gapping between knotless and knotted reconstructions? (3) Are there differences in the maximal stiffness, yield load, and ultimate load to failure? (4) What are the modes of failure of knotless and knotted reconstruction techniques?MethodsEight matched pairs of human cadaveric shoulders were dissected, and a full-thickness tear of the subscapularis tendon (Grade 3 according to the Fox and Romeo classification) was created. The cadavers all were male specimens, with a median (range) age of 69 years (61 to 75). Before biomechanical evaluation, the specimens were randomized into two equal reconstruction groups: knotless single anchor and knotted single anchor. All surgical procedures were performed by a single orthopaedic surgeon who subspecializes in sports orthopedics and shoulder surgery. With a customized set up that was integrated in a dynamic material testing machine, the humeri were consecutively loaded from 10 N to 60 N, from 10 N to 100 N, and from 10 N to 180 N for 50 cycles. Furthermore, the gapping behavior of the tear was analyzed using a video tracking system. Finally, the stiffness, gapping, maximal stiffness, yield loads, and maximum failure loads of both reconstruction groups were statistically analyzed. Failure was defined as retearing of the reconstructed gap threshold due to rupture of the tendon and/or failure of the knots or anchors. After biomechanical testing, bone quality was measured at the footprint of the subscapularis using microCT in all specimens. Bone quality was equal between both groups. To detect a minimum 0.15-mm difference in gap formation between the two repair techniques (with a 5% level of significance; α = 0.05), eight matched pairs (n = 16 in total) were calculated as necessary to achieve a power of at least 90%.ResultsThe first study question can be answered as follows: for stiffness under cyclic load, there were no differences with the numbers available between the knotted and knotless groups at load stages of 10 N to 60 N (32.7 ± 3.5 N/mm versus 34.2 ± 5.6 N/mm, mean difference 1.5 N/mm [95% CI -6.43 to 3.33]; p = 0.55), 10 N to 100 N (45.0 ± 4.8 N/mm versus 45.2 ± 6.0 N/mm, mean difference 0.2 N/mm [95% CI -5.74 to 6.04]; p = 0.95), and 10 N to 180 N (58.2 ± 10.6 N/mm versus 55.2 ± 4.7 N/mm, mean difference 3 N/mm [95% CI -5.84 to 11.79]; p = 0.48). In relation to the second research question, the following results emerged: For cyclic gapping, there were no differences between the knotted and knotless groups at any load levels. The present study was able to show the following wi...

Limited Biomechanical Evidence Behind Single Row Versus Double Row Repair of Subscapularis Tears: A Systematic Review

“…Three studies 28 , 32 , 33 used the Fox-Romeo 34 classification system to recreate type II (complete tear of the upper 25%) and III (complete tear of the upper 50%) tears of the subscapularis, 1 study 31 used the Lafosse classification 8 to recreate type II tears (complete tear of the upper 1/3), and 2 studies created complete full-thickness tears 29 , 30 ( Table 2 ). Of the included studies, two 28 , 29 compared single-row and double-row repair, one 30 compared single-row to transosseous repair, and 3 studies 31 , 32 , 33 used only single-row suture anchor constructs. Two studies compared knotted and knotless single-row repairs.…”

“…Single-row repair in the current review used either 1 or 2 double-loaded suture anchors and were knotless or tied with variations of mattress or modified Mason-Allen stitches. Sgroi et al 32 compared knotted and knotless single-row repair for Fox-Romeo III subscapularis tears and found no significant differences in biomechanical properties for both constructs. Likewise, Borbas et al 31 compared 3 different single-row constructs (knotted lasso-loop mattress, knotted mattress, and knotless suture tape) for Lafosse II subscapularis tears and found that the constructs resulted in similar ultimate load, gap formation, and stiffness.…”

“…Sgroi et al. 32 compared knotted and knotless single-row repair for Fox-Romeo III subscapularis tears and found no significant differences in biomechanical properties for both constructs. Likewise, Borbas et al.…”

“…Of these, 12 articles underwent full text review, resulting in six articles that were included and analyzed (Fig 1). [28][29][30] According to the QUACS, three studies were excellent (>11/13), 28,31,32 and 3 studies were of substantial (9/13 or 10/13) quality. 29,30 The number of specimens per study ranged from 6 to 18 for a total of 63 specimens and 104 shoulders included in this review.…”

“…Two studies compared knotted and knotless single-row repairs. 31,32 The 4 studies 28,[31][32][33] published most recently used bioabsorbable suture anchors, whereas titanium suture anchors were used in the other 2 studies (Table 2). 29,30 Double-row repairs used three 28 or four 29 suture anchors.…”