- Email: [email protected]
Footprint Contact Area and Interface Pressure Comparison Between the Knotless and Knot-Tying Transosseous-Equivalent Technique for Rotator Cuff Repair
Footprint Contact Area and Interface Pressure Comparison Between the Knotless and Knot-Tying Transosseous-Equivalent Technique for Rotator Cuff Repair Sung-Jae Kim, M.D., Ph.D., Sung-Hwan Kim, M.D., Hyun-Soo Moon, M.D., and Yong-Min Chun, M.D., Ph.D.
Purpose: To quantify and compare the footprint contact area and interface pressure on the greater tuberosity between knotless and knot-tying transosseous-equivalent (TOE) repair using pressure-sensitive film. Methods: We used 11 pairs of fresh-frozen cadaveric shoulders (22 specimens), in which rotator cuff tears were created before repair. Each pair was randomized to either conventional medial knot-tying TOE repair (group A) or medial knotless TOE repair using the modified Mason-Allen technique (group B). Pressure-sensitive film was used to quantify the pressurized contact area and interface pressure between the greater tuberosity and supraspinatus tendon. Results: The mean pressurized contact area was 33.2 2.5 mm2 for group A and 28.4 2.4 mm2 for group B. There was a significant difference between groups (P ¼ .005). Although the overall contact configuration of both groups was similar and showed an M shape, group A showed a greater pressurized configuration around the medial row. The mean interface pressure was 0.20 0.02 MPa for group A and 0.17 0.02 MPa for group B. There was a significant difference between groups (P ¼ .001). Conclusions: Contrary to our hypothesis, in this time-zero study, medial knotless TOE repair using a modified MasonAllen suture produced a significantly inferior footprint contact area and interface pressure compared with conventional medial knot-tying TOE repair. Clinical Relevance: Even though we found a statistically significant difference between the 2 repair methods, it is still unknown if this statistical difference seen in our study has any clinical and radiologic significance.
I
n recent years, to enhance healing at the repair site, the transosseous-equivalent (TOE) technique has become a popular method for reattaching rotator cuff tendons to their insertion site on the greater tuberosity of the proximal humerus.1-7 Although the TOE repair technique, also called the suture bridge technique, for arthroscopic rotator cuff repair has shown a substantial
From the Department of Orthopaedic Surgery, Arthroscopy and Joint Research Institute, Severance Hospital, Yonsei University College of Medicine, Seoul, Republic of Korea. The authors report the following potential conflict of interest or source of funding: Y-M.C. receives support from Yonsei University College of Medicine. Faculty research grant (6-2014-0144). Received February 12, 2015; accepted July 10, 2015. Address correspondence to Yong-Min Chun, M.D., Ph.D., Department of Orthopaedic Surgery, Arthroscopy and Joint Research Institute, Severance Hospital, Yonsei University College of Medicine, CPO Box 8044, 134, Shinchon-dong, Seodaemun-gu, Seoul 120-752, Republic of Korea. E-mail: [email protected] Ó 2016 by the Arthroscopy Association of North America 0749-8063/15138/$36.00 http://dx.doi.org/10.1016/j.arthro.2015.07.004
theoretical benefit for restoring footprint contact and pressure compared with other techniques such as singlerow repair or double-row repair, the structural integrity and clinical outcomes of TOE repair are not superior to those of other repair techniques.1,7-9 Indeed, TOE repair shows a higher healing rate at the tendon-bone interface compared with single-row repair.2 However, a unique retear pattern is present after TOE repair; in many cases, failures occurred at the medial row with a well-attached tendon on the greater tuberosity, even though satisfactory healing was obtained at the repair site.1,2,6 As early investigators indicated, potential over-tensioning and strangulation at the medial row due to knot tying in the double-row or suture bridge technique may leave the repaired tendon vulnerable to retearing, although many studies have indicated the biomechanical benefit of medial knots in the construct compared with the knotless construct.2,6,10-13 Although the medial knotless construct in TOE repair may reduce the possibility of over-tensioning and strangulation and subsequent medial-row failure, several investigators have shown mechanical inferiority in stability
Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 32, No 1 (January), 2016: pp 7-12
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such as greater gap formation and failure.10-12 However, Rhee et al.5 retrospectively compared the outcome of arthroscopic TOE repair in a conventional medial knottying group and a knotless group using modified Mason-Allen sutures. The knotless group showed a significantly lower retear rate despite the knotless medial row in the construction. In this study we asked whether medial knotless TOE repair using a modified Mason-Allen suture would provide a footprint contact area and interface pressure on the tendon-bone interface comparable with those of conventional medial knot-tying TOE repair. The purpose of this study was to quantify and compare the footprint contact area and interface pressure on the greater tuberosity between knotless and knot-tying TOE repair using pressure-sensitive film. We hypothesized that medial knotless TOE repair using a modified Mason-Allen suture would produce a footprint contact area and interface pressure that were comparable with those of conventional medial knot-tying TOE repair.
Methods Eleven pairs of fresh-frozen cadaveric shoulders (22 specimens) were used. Each pair was randomized to either conventional medial knot-tying TOE repair (group A) or medial knotless TOE repair using modified Mason-Allen suture14 (group B). The inclusion criteria for the specimens were the absence of a rotator cuff tear and no history of surgery on the shoulder. If a rotator cuff tear was found during dissection, the specimen was excluded. The mean age of the specimens was 69.2 9.2 years (range, 49 to 81 years). Before use, the specimens were thawed at room temperature for 24 hours. The humerus was cut at the mid diaphysis, and the soft tissue around the proximal humerus and scapula was removed except for the rotator cuff tendon and muscle. After identification of the supraspinatus, the tendon was sharply detached from the greater tuberosity. To prevent an inadvertent imprint colorization during placement of the pressure-sensitive film between the tendon and greater tuberosity, the entire supraspinatus as well as the anterior infraspinatus was sharply detached. In a previous study, investigators resected the distal 10mm portion of the supraspinatus tendon to simulate the configuration of a rotator cuff tear.7 However, in our pilot study, after resection of a 10-mm portion of the tendon, the remaining medial portion was too thick to colorize the pressure-sensitive film (Prescale measurement film, Ultra Super Low pressure; Fujifilm, Tokyo, Japan) by simulating the repair with the suture bridge technique, although we used the most sensitive pressure film (sensitive range, 0.2 to 0.6 MPa), which was used in previous studies.7,15 Thus we did not resect any portion of the supraspinatus tendon. After detaching the rotator cuff, we removed the remaining soft tissue using rongeurs.
With rasps, the surface of the footprint was made flat and smooth. Then, 2 pilot holes were created, 12 mm apart, along the articular margin using an awl. A 5.0-mm single-loaded suture anchor (Paladin; ConMed Linvatec, Largo, FL) was inserted into each pilot hole. In group A, 2 suture limbs (No. 2 Hi-Fi high strength; ConMed Linvatec) of each anchor were passed through the tendon, about 12 mm medial to the lateral edge, in a mattress suture fashion. To avoid improper colorization during knot tying with a knot pusher, the knot tying for the medial row was performed before the placement of the pressure film. Then, the film was carefully placed at the interface between the tendon and bone. The 2 pilot holes for the lateral row were created 1 cm distal to the lateral edge of the greater tuberosity using an awl. For the TOE repair, 2 limbs (1 limb from each of the 2 medial anchors) were loaded onto the suture anchor (PopLok; ConMed Linvatec) for the lateral row, and the anterior anchor was inserted first. In the same manner, the remaining 2 limbs of each medial anchor were loaded onto the posterior anchor for the lateral row and inserted (Fig 1). To provide uniform tension for this TOE technique, a stress equalization graft tensioner (ConMed Linvatec) was used (Fig 2). Twenty newtons of tension was loaded onto each limb, for a total load of 40 N.7,8 In group B, instead of mattress sutures for the medial row, a modified Mason-Allen suture was used after insertion of 2 anchors. One suture limb from one anchor
Fig 1. Medial knot-tying transosseous-equivalent repair.
FOOTPRINT CONTACT AREA AND INTERFACE PRESSURE
Fig 2. Tensioning device.
was first passed, about 12 mm medial to the lateral edge of the tendon, from the intra-articular space through the tendon to the subacromial space. For the second passage, the surgeon retrieved the suture limb from the subacromial space to the intra-articular space, making about a 10-mm horizontal loop on the bursal side of the tendon. The surgeon made the third passage from the intraarticular space to the subacromial space, passing just medial to the horizontal loop. The remaining one suture limb of the same anchor was passed from the intraarticular space to the subacromial space, just medial to the horizontal hoop (Fig 3A). For the remaining anchor, 2 suture limbs were passed through the tendon in the same manner. Without knot tying, the pressure-sensitive film was placed at the interface between the tendon and bone. In the same manner, lateral fixation through the TOE repair was performed (Fig 3B). All procedures were performed by a single surgeon (Y-M.C) to maintain experimental uniformity. Institutional review board approval was obtained with a waiver of informed consent.
Fig 3. (A) Medial knotless suture passage using a modified MasonAllen suture. (B) Medial knotless transosseous-equivalent repair using a modified Mason-Allen suture.
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Pressure-Sensitive Film Preparation and Analysis of Colorized Contact Area and Interface Pressure The pressure-sensitive films used in this study were composed of 2 sheets. One was a color-developing layer, and the other was coated with a microcapsulecontaining layer. These 2 layers faced each other. As the pressure or pressurized area increased, a stronger color or greater area was fixed. We determined that the adequate film size was 8 20 mm2 as introduced in previous study by Park et al.7 To prevent the film from becoming wet, the 2 facing sheets of the film were sealed with a polyethylene sheet, as in previous studies.7,15 After lateral fixation was performed in both groups, the tension was maintained for 2 minutes and the sutures were cut. Then, the film was removed carefully from the interface. The 2 opposing sheets (color-developing sheet and microcapsule-containing sheet) were separated immediately to prevent inadvertent imprint colorization. For analysis of the colorized imprint film, a digital scanner (Epson Perfection V330 Photo Scanner; Epson, Suwa, Japan) and the Fujifilm pressure-distribution mapping system for Prescale film (FDP-8010E, version 2.01) were used. The colorized imprint was converted into a digital image with a variable-color scale at a resolution of 0.125 mm. The pressurized contact area and interface pressure were calculated. Statistical Analysis Because no previous study has been published regarding this topic, we performed a pilot study with 6 specimens (3 per group) to calculate the sample size. The mean (standard deviation) for each group in the pilot study was 32.7 2.5 mm2 for group A and 29.7 2.1 mm2 for group B. On the basis of these data, we
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found that 22 specimens (11 per group) were required to provide 80% power at an a level of .05. The Mann-Whitney U test was used to compare the pressurized contact area and interface pressure values between groups. Statistical significance was defined at P < .05.
Results The mean pressurized contact area was 33.2 2.5 mm2 for group A (conventional medial knot-tying TOE repair) and 28.4 2.4 mm2 for group B (medial knotless TOE repair using modified Mason-Allen suture). There was a significant difference between groups (P ¼ .005). Although the overall contact configuration of both groups was similar and showed an M shape, group A showed a greater pressurized configuration around the medial row (Fig 4). The mean interface pressure was 0.20 0.02 MPa for group A and 0.17 0.02 MPa for group B. There was a significant difference between groups (P ¼ .001).
Discussion Contrary to our initial hypothesis, conventional TOE repair showed a significantly greater contact area and interface pressure than medial knotless TOE repair. To improve the healing between the tendon and bone after cuff repair, repair techniques have continually evolved. Most recently, TOE repair was introduced; it was expected to provide a wider footprint contact area and better biomechanical properties than other previous techniques.7,8,16 However, although this TOE repair yields comparable or better clinical outcomes and structural integrity, the issue of retearing has not been solved with the TOE technique for cuff repair.1-4,17 In addition, several investigators reported an unusual retear configuration of the repaired rotator cuff after TOE repair.1,2,13 With the conventional single-row repair, many retears occur at the repair site (tendonbone junction). However, with the TOE technique, many retears occur at the musculotendinous junction of the repaired tendon. Trantalis et al.13 first identified medial rotator cuff failure after arthroscopic doublerow repair. They concluded that tension overload with knot tying at the medial row in the double-row
repair was a potential factor that contributed to medial cuff failure. Cho et al.2 compared the retear pattern between single-row repair and the TOE technique and found that the TOE technique has a significantly higher rate of structural failure at the musculotendinous junction rather than at the tendonbone interface. They classified the retear pattern as type 1 (in which failure to heal occurred at the repair site) or type 2 (in which healing was obtained but the retear occurred at the musculotendinous junction); they indicated that unlike single-row repair, type 2 retears mainly occurred after TOE repair, although TOE repair preserves the repaired cuff tissue on the footprint of the rotator cuff. As in double-row repair, they indicated that undue tension may overload the medial row in the suture bridge (i.e., the TOE technique).2 Recently, Rhee et al.5 compared the clinical and radiologic outcomes between a conventional medial knot-tying TOE group and a medial knotless TOE group using a modified Mason-Allen suture for arthroscopic rotator cuff repair. The medial knotless TOE group showed a significantly lower retear rate than the conventional medial knot-tying TOE group. In addition, no medial cuff failure occurred in the medial knotless group. Considering the lower retear rate without medial cuff failure in their knotless group, we thought that our knotless group may have shown a comparable or superior footprint contact area and interface pressure between the tendon and bone to those in the conventional group. However, our study showed that the knotless group had an inferior footprint contact area and interface pressure. Several biomechanical studies have been published regarding the medial knotless technique for double-row or TOE rotator cuff repair.10-12 They verified that the medial knotless construct significantly compromises the biomechanical properties. They also indicated that the medial knot increases the mechanical stability and may promote cuff healing at the repair site.11 However, medial knotless TOE repair using a modified MasonAllen suture appeared to be different from previous reports about medial knotless repair. Modified MasonAllen sutures do not create medial knots. However, considering the lower retear rate in the study by Rhee
Fig 4. Pressurized contact configuration on the footprint between the bone and tendon. An example of a single specimen of each repair type is shown (not an amalgam). The superior area is the medial side of the footprint. (A) Medial knot-tying transosseous-equivalent repair. (B) Medial knotless transosseous-equivalent repair using Mason-Allen suture.
FOOTPRINT CONTACT AREA AND INTERFACE PRESSURE
et al.,5 modified Mason-Allen sutures may support sufficient mechanical stability to obtain healing at the repair site. However, whether the mechanical stability is not as high as that of the medial knot-tying construct is not known. Thus we hypothesized that a modified Mason-Allen suture would provide a footprint contact area and interface pressure that were comparable with those of conventional medial knot-tying TOE repair. However, conventional medial knot-tying TOE repair produced a significantly larger contact area and higher interface pressure than medial knotless TOE repair using a modified Mason-Allen suture. Considering that the study by Rhee et al.5 indicated that the retear rate was higher with conventional TOE repair, which yielded a superior contact area and superior interface pressure in our study, maximizing the contact area may be helpful for healing, although maximizing the contact force might be detrimental if it inhibits the microcirculation of the tendon as it attempts to heal. In addition, in our study, even though the overall contact configuration of both groups was similar and showed an M shape, the conventional medial knot-tying repair group yielded a strong contact pressure around the medial knot-tying region. We think that this pattern of pressure distribution may be related to medial-row failure in conventional suture bridge repair. Limitations Our study has several limitations that should be addressed. First, although we assessed the pressurized contact area and interface pressure between the tendon and bone, this study did not examine the mechanical stability of medial knot and knotless TOE repair, which is subjected to cyclic loading, as was performed in previous studies.8,10-12 Even under cyclic loading, it should be verified whether the current contact area and interface pressure can be maintained. Second, our study was based on a crescent-type tear, which has minimal retraction and good tissue quality. Thus it might not be applicable to tears of various sizes, shapes, and tissue qualities. Third, we used 40 N as the tension value in the lateral row because previous studies used values similar to this.7,8 However, we are not sure whether this value is appropriate in practice. Although we do not use a tensioner in practice and we completely depend on sensing tension with our own hands, we vary the tension loaded onto the lateral row on a caseby-case basis; for osteoporotic bone, we reduce the tension to lower than usual. Fourth, unlike previous studies, our study could not simulate a rotator cuff tear by resection of the distal portion of the supraspinatus. In our pilot study, the remaining medial portion of the supraspinatus was too thick to colorize the pressuresensitive film, although we used the most sensitive film. Fifth, even though there was a statistically
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significant difference in this time-zero study, it is unknown if this result would be clinically significant.
Conclusions Contrary to our hypothesis, in this time-zero study, medial knotless TOE repair using a modified MasonAllen suture produced a significantly inferior footprint contact area and interface pressure compared with conventional medial knot-tying TOE repair.
Acknowledgment The authors thank Dong-Su Jang (medical illustrator, Medical Research Support Section, Yonsei University College of Medicine, Seoul, Republic of Korea) for help with the figures.
References 1. Cho NS, Lee BG, Rhee YG. Arthroscopic rotator cuff repair using a suture bridge technique: Is the repair integrity actually maintained? Am J Sports Med 2011;39: 2108-2116. 2. Cho NS, Yi JW, Lee BG, Rhee YG. Retear patterns after arthroscopic rotator cuff repair: Single-row versus suture bridge technique. Am J Sports Med 2010;38: 664-671. 3. Frank JB, ElAttrache NS, Dines JS, Blackburn A, Crues J, Tibone JE. Repair site integrity after arthroscopic transosseous-equivalent suture-bridge rotator cuff repair. Am J Sports Med 2008;36:1496-1503. 4. Kim KC, Shin HD, Cha SM, Lee WY. Comparison of repair integrity and functional outcomes for 3 arthroscopic suture bridge rotator cuff repair techniques. Am J Sports Med 2013;41:271-277. 5. Rhee YG, Cho NS, Parke CS. Arthroscopic rotator cuff repair using modified Mason-Allen medial row stitch: Knotless versus knot-tying suture bridge technique. Am J Sports Med 2012;40:2440-2447. 6. Voigt C, Bosse C, Vosshenrich R, Schulz AP, Lill H. Arthroscopic supraspinatus tendon repair with suturebridging technique: Functional outcome and magnetic resonance imaging. Am J Sports Med 2010;38:983-991. 7. Park MC, ElAttrache NS, Tibone JE, Ahmad CS, Jun BJ, Lee TQ. Part I: Footprint contact characteristics for a transosseous-equivalent rotator cuff repair technique compared with a double-row repair technique. J Shoulder Elbow Surg 2007;16:461-468. 8. Park MC, Tibone JE, ElAttrache NS, Ahmad CS, Jun BJ, Lee TQ. Part II: Biomechanical assessment for a footprintrestoring transosseous-equivalent rotator cuff repair technique compared with a double-row repair technique. J Shoulder Elbow Surg 2007;16:469-476. 9. Tuoheti Y, Itoi E, Yamamoto N, et al. Contact area, contact pressure, and pressure patterns of the tendon-bone interface after rotator cuff repair. Am J Sports Med 2005;33:1869-1874. 10. Busfield BT, Glousman RE, McGarry MH, Tibone JE, Lee TQ. A biomechanical comparison of 2 technical variations of double-row rotator cuff fixation: The
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importance of medial row knots. Am J Sports Med 2008;36:901-906. 11. Leek BT, Robertson C, Mahar A, Pedowitz RA. Comparison of mechanical stability in double-row rotator cuff repairs between a knotless transtendon construct versus the addition of medial knots. Arthroscopy 2010;26: S127-S133. 12. Chu T, McDonald E, Tufaga M, Kandemir U, Buckley J, Ma CB. Comparison of completely knotless and hybrid double-row fixation systems: A biomechanical study. Arthroscopy 2011;27:479-485. 13. Trantalis JN, Boorman RS, Pletsch K, Lo IK. Medial rotator cuff failure after arthroscopic double-row rotator cuff repair. Arthroscopy 2008;24:727-731.
14. Gerber C, Schneeberger AG, Beck M, Schlegel U. Mechanical strength of repairs of the rotator cuff. J Bone Joint Surg Br 1994;76:371-380. 15. Kim SJ, Kim SH, Lee SK, Lee JH, Chun YM. Footprint contact restoration between the biceps-labrum complex and the glenoid rim in SLAP repair: A comparative cadaveric study using pressure-sensitive film. Arthroscopy 2013;29:1005-1011. 16. Park MC, Elattrache NS, Ahmad CS, Tibone JE. “Transosseous-equivalent” rotator cuff repair technique. Arthroscopy 2006;22:1360.e1-1360.e5. 17. Kim KC, Shin HD, Cha SM, Park JY. Comparisons of retear patterns for 3 arthroscopic rotator cuff repair methods. Am J Sports Med 2014;42:558-565.
Purpose: To quantify and compare the footprint contact area and interface pressure on the greater tuberosity between knotless and knot-tying transosseous-equivalent (TOE) repair using pressure-sensitive film. Methods: We used 11 pairs of fresh-frozen cadaveric shoulders (22 specimens), in which rotator cuff tears were created before repair. Each pair was randomized to either conventional medial knot-tying TOE repair (group A) or medial knotless TOE repair using the modified Mason-Allen technique (group B). Pressure-sensitive film was used to quantify the pressurized contact area and interface pressure between the greater tuberosity and supraspinatus tendon. Results: The mean pressurized contact area was 33.2 2.5 mm2 for group A and 28.4 2.4 mm2 for group B. There was a significant difference between groups (P ¼ .005). Although the overall contact configuration of both groups was similar and showed an M shape, group A showed a greater pressurized configuration around the medial row. The mean interface pressure was 0.20 0.02 MPa for group A and 0.17 0.02 MPa for group B. There was a significant difference between groups (P ¼ .001). Conclusions: Contrary to our hypothesis, in this time-zero study, medial knotless TOE repair using a modified MasonAllen suture produced a significantly inferior footprint contact area and interface pressure compared with conventional medial knot-tying TOE repair. Clinical Relevance: Even though we found a statistically significant difference between the 2 repair methods, it is still unknown if this statistical difference seen in our study has any clinical and radiologic significance.
I
n recent years, to enhance healing at the repair site, the transosseous-equivalent (TOE) technique has become a popular method for reattaching rotator cuff tendons to their insertion site on the greater tuberosity of the proximal humerus.1-7 Although the TOE repair technique, also called the suture bridge technique, for arthroscopic rotator cuff repair has shown a substantial
From the Department of Orthopaedic Surgery, Arthroscopy and Joint Research Institute, Severance Hospital, Yonsei University College of Medicine, Seoul, Republic of Korea. The authors report the following potential conflict of interest or source of funding: Y-M.C. receives support from Yonsei University College of Medicine. Faculty research grant (6-2014-0144). Received February 12, 2015; accepted July 10, 2015. Address correspondence to Yong-Min Chun, M.D., Ph.D., Department of Orthopaedic Surgery, Arthroscopy and Joint Research Institute, Severance Hospital, Yonsei University College of Medicine, CPO Box 8044, 134, Shinchon-dong, Seodaemun-gu, Seoul 120-752, Republic of Korea. E-mail: [email protected] Ó 2016 by the Arthroscopy Association of North America 0749-8063/15138/$36.00 http://dx.doi.org/10.1016/j.arthro.2015.07.004
theoretical benefit for restoring footprint contact and pressure compared with other techniques such as singlerow repair or double-row repair, the structural integrity and clinical outcomes of TOE repair are not superior to those of other repair techniques.1,7-9 Indeed, TOE repair shows a higher healing rate at the tendon-bone interface compared with single-row repair.2 However, a unique retear pattern is present after TOE repair; in many cases, failures occurred at the medial row with a well-attached tendon on the greater tuberosity, even though satisfactory healing was obtained at the repair site.1,2,6 As early investigators indicated, potential over-tensioning and strangulation at the medial row due to knot tying in the double-row or suture bridge technique may leave the repaired tendon vulnerable to retearing, although many studies have indicated the biomechanical benefit of medial knots in the construct compared with the knotless construct.2,6,10-13 Although the medial knotless construct in TOE repair may reduce the possibility of over-tensioning and strangulation and subsequent medial-row failure, several investigators have shown mechanical inferiority in stability
Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 32, No 1 (January), 2016: pp 7-12
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such as greater gap formation and failure.10-12 However, Rhee et al.5 retrospectively compared the outcome of arthroscopic TOE repair in a conventional medial knottying group and a knotless group using modified Mason-Allen sutures. The knotless group showed a significantly lower retear rate despite the knotless medial row in the construction. In this study we asked whether medial knotless TOE repair using a modified Mason-Allen suture would provide a footprint contact area and interface pressure on the tendon-bone interface comparable with those of conventional medial knot-tying TOE repair. The purpose of this study was to quantify and compare the footprint contact area and interface pressure on the greater tuberosity between knotless and knot-tying TOE repair using pressure-sensitive film. We hypothesized that medial knotless TOE repair using a modified Mason-Allen suture would produce a footprint contact area and interface pressure that were comparable with those of conventional medial knot-tying TOE repair.
Methods Eleven pairs of fresh-frozen cadaveric shoulders (22 specimens) were used. Each pair was randomized to either conventional medial knot-tying TOE repair (group A) or medial knotless TOE repair using modified Mason-Allen suture14 (group B). The inclusion criteria for the specimens were the absence of a rotator cuff tear and no history of surgery on the shoulder. If a rotator cuff tear was found during dissection, the specimen was excluded. The mean age of the specimens was 69.2 9.2 years (range, 49 to 81 years). Before use, the specimens were thawed at room temperature for 24 hours. The humerus was cut at the mid diaphysis, and the soft tissue around the proximal humerus and scapula was removed except for the rotator cuff tendon and muscle. After identification of the supraspinatus, the tendon was sharply detached from the greater tuberosity. To prevent an inadvertent imprint colorization during placement of the pressure-sensitive film between the tendon and greater tuberosity, the entire supraspinatus as well as the anterior infraspinatus was sharply detached. In a previous study, investigators resected the distal 10mm portion of the supraspinatus tendon to simulate the configuration of a rotator cuff tear.7 However, in our pilot study, after resection of a 10-mm portion of the tendon, the remaining medial portion was too thick to colorize the pressure-sensitive film (Prescale measurement film, Ultra Super Low pressure; Fujifilm, Tokyo, Japan) by simulating the repair with the suture bridge technique, although we used the most sensitive pressure film (sensitive range, 0.2 to 0.6 MPa), which was used in previous studies.7,15 Thus we did not resect any portion of the supraspinatus tendon. After detaching the rotator cuff, we removed the remaining soft tissue using rongeurs.
With rasps, the surface of the footprint was made flat and smooth. Then, 2 pilot holes were created, 12 mm apart, along the articular margin using an awl. A 5.0-mm single-loaded suture anchor (Paladin; ConMed Linvatec, Largo, FL) was inserted into each pilot hole. In group A, 2 suture limbs (No. 2 Hi-Fi high strength; ConMed Linvatec) of each anchor were passed through the tendon, about 12 mm medial to the lateral edge, in a mattress suture fashion. To avoid improper colorization during knot tying with a knot pusher, the knot tying for the medial row was performed before the placement of the pressure film. Then, the film was carefully placed at the interface between the tendon and bone. The 2 pilot holes for the lateral row were created 1 cm distal to the lateral edge of the greater tuberosity using an awl. For the TOE repair, 2 limbs (1 limb from each of the 2 medial anchors) were loaded onto the suture anchor (PopLok; ConMed Linvatec) for the lateral row, and the anterior anchor was inserted first. In the same manner, the remaining 2 limbs of each medial anchor were loaded onto the posterior anchor for the lateral row and inserted (Fig 1). To provide uniform tension for this TOE technique, a stress equalization graft tensioner (ConMed Linvatec) was used (Fig 2). Twenty newtons of tension was loaded onto each limb, for a total load of 40 N.7,8 In group B, instead of mattress sutures for the medial row, a modified Mason-Allen suture was used after insertion of 2 anchors. One suture limb from one anchor
Fig 1. Medial knot-tying transosseous-equivalent repair.
FOOTPRINT CONTACT AREA AND INTERFACE PRESSURE
Fig 2. Tensioning device.
was first passed, about 12 mm medial to the lateral edge of the tendon, from the intra-articular space through the tendon to the subacromial space. For the second passage, the surgeon retrieved the suture limb from the subacromial space to the intra-articular space, making about a 10-mm horizontal loop on the bursal side of the tendon. The surgeon made the third passage from the intraarticular space to the subacromial space, passing just medial to the horizontal loop. The remaining one suture limb of the same anchor was passed from the intraarticular space to the subacromial space, just medial to the horizontal hoop (Fig 3A). For the remaining anchor, 2 suture limbs were passed through the tendon in the same manner. Without knot tying, the pressure-sensitive film was placed at the interface between the tendon and bone. In the same manner, lateral fixation through the TOE repair was performed (Fig 3B). All procedures were performed by a single surgeon (Y-M.C) to maintain experimental uniformity. Institutional review board approval was obtained with a waiver of informed consent.
Fig 3. (A) Medial knotless suture passage using a modified MasonAllen suture. (B) Medial knotless transosseous-equivalent repair using a modified Mason-Allen suture.
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Pressure-Sensitive Film Preparation and Analysis of Colorized Contact Area and Interface Pressure The pressure-sensitive films used in this study were composed of 2 sheets. One was a color-developing layer, and the other was coated with a microcapsulecontaining layer. These 2 layers faced each other. As the pressure or pressurized area increased, a stronger color or greater area was fixed. We determined that the adequate film size was 8 20 mm2 as introduced in previous study by Park et al.7 To prevent the film from becoming wet, the 2 facing sheets of the film were sealed with a polyethylene sheet, as in previous studies.7,15 After lateral fixation was performed in both groups, the tension was maintained for 2 minutes and the sutures were cut. Then, the film was removed carefully from the interface. The 2 opposing sheets (color-developing sheet and microcapsule-containing sheet) were separated immediately to prevent inadvertent imprint colorization. For analysis of the colorized imprint film, a digital scanner (Epson Perfection V330 Photo Scanner; Epson, Suwa, Japan) and the Fujifilm pressure-distribution mapping system for Prescale film (FDP-8010E, version 2.01) were used. The colorized imprint was converted into a digital image with a variable-color scale at a resolution of 0.125 mm. The pressurized contact area and interface pressure were calculated. Statistical Analysis Because no previous study has been published regarding this topic, we performed a pilot study with 6 specimens (3 per group) to calculate the sample size. The mean (standard deviation) for each group in the pilot study was 32.7 2.5 mm2 for group A and 29.7 2.1 mm2 for group B. On the basis of these data, we
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found that 22 specimens (11 per group) were required to provide 80% power at an a level of .05. The Mann-Whitney U test was used to compare the pressurized contact area and interface pressure values between groups. Statistical significance was defined at P < .05.
Results The mean pressurized contact area was 33.2 2.5 mm2 for group A (conventional medial knot-tying TOE repair) and 28.4 2.4 mm2 for group B (medial knotless TOE repair using modified Mason-Allen suture). There was a significant difference between groups (P ¼ .005). Although the overall contact configuration of both groups was similar and showed an M shape, group A showed a greater pressurized configuration around the medial row (Fig 4). The mean interface pressure was 0.20 0.02 MPa for group A and 0.17 0.02 MPa for group B. There was a significant difference between groups (P ¼ .001).
Discussion Contrary to our initial hypothesis, conventional TOE repair showed a significantly greater contact area and interface pressure than medial knotless TOE repair. To improve the healing between the tendon and bone after cuff repair, repair techniques have continually evolved. Most recently, TOE repair was introduced; it was expected to provide a wider footprint contact area and better biomechanical properties than other previous techniques.7,8,16 However, although this TOE repair yields comparable or better clinical outcomes and structural integrity, the issue of retearing has not been solved with the TOE technique for cuff repair.1-4,17 In addition, several investigators reported an unusual retear configuration of the repaired rotator cuff after TOE repair.1,2,13 With the conventional single-row repair, many retears occur at the repair site (tendonbone junction). However, with the TOE technique, many retears occur at the musculotendinous junction of the repaired tendon. Trantalis et al.13 first identified medial rotator cuff failure after arthroscopic doublerow repair. They concluded that tension overload with knot tying at the medial row in the double-row
repair was a potential factor that contributed to medial cuff failure. Cho et al.2 compared the retear pattern between single-row repair and the TOE technique and found that the TOE technique has a significantly higher rate of structural failure at the musculotendinous junction rather than at the tendonbone interface. They classified the retear pattern as type 1 (in which failure to heal occurred at the repair site) or type 2 (in which healing was obtained but the retear occurred at the musculotendinous junction); they indicated that unlike single-row repair, type 2 retears mainly occurred after TOE repair, although TOE repair preserves the repaired cuff tissue on the footprint of the rotator cuff. As in double-row repair, they indicated that undue tension may overload the medial row in the suture bridge (i.e., the TOE technique).2 Recently, Rhee et al.5 compared the clinical and radiologic outcomes between a conventional medial knot-tying TOE group and a medial knotless TOE group using a modified Mason-Allen suture for arthroscopic rotator cuff repair. The medial knotless TOE group showed a significantly lower retear rate than the conventional medial knot-tying TOE group. In addition, no medial cuff failure occurred in the medial knotless group. Considering the lower retear rate without medial cuff failure in their knotless group, we thought that our knotless group may have shown a comparable or superior footprint contact area and interface pressure between the tendon and bone to those in the conventional group. However, our study showed that the knotless group had an inferior footprint contact area and interface pressure. Several biomechanical studies have been published regarding the medial knotless technique for double-row or TOE rotator cuff repair.10-12 They verified that the medial knotless construct significantly compromises the biomechanical properties. They also indicated that the medial knot increases the mechanical stability and may promote cuff healing at the repair site.11 However, medial knotless TOE repair using a modified MasonAllen suture appeared to be different from previous reports about medial knotless repair. Modified MasonAllen sutures do not create medial knots. However, considering the lower retear rate in the study by Rhee
Fig 4. Pressurized contact configuration on the footprint between the bone and tendon. An example of a single specimen of each repair type is shown (not an amalgam). The superior area is the medial side of the footprint. (A) Medial knot-tying transosseous-equivalent repair. (B) Medial knotless transosseous-equivalent repair using Mason-Allen suture.
FOOTPRINT CONTACT AREA AND INTERFACE PRESSURE
et al.,5 modified Mason-Allen sutures may support sufficient mechanical stability to obtain healing at the repair site. However, whether the mechanical stability is not as high as that of the medial knot-tying construct is not known. Thus we hypothesized that a modified Mason-Allen suture would provide a footprint contact area and interface pressure that were comparable with those of conventional medial knot-tying TOE repair. However, conventional medial knot-tying TOE repair produced a significantly larger contact area and higher interface pressure than medial knotless TOE repair using a modified Mason-Allen suture. Considering that the study by Rhee et al.5 indicated that the retear rate was higher with conventional TOE repair, which yielded a superior contact area and superior interface pressure in our study, maximizing the contact area may be helpful for healing, although maximizing the contact force might be detrimental if it inhibits the microcirculation of the tendon as it attempts to heal. In addition, in our study, even though the overall contact configuration of both groups was similar and showed an M shape, the conventional medial knot-tying repair group yielded a strong contact pressure around the medial knot-tying region. We think that this pattern of pressure distribution may be related to medial-row failure in conventional suture bridge repair. Limitations Our study has several limitations that should be addressed. First, although we assessed the pressurized contact area and interface pressure between the tendon and bone, this study did not examine the mechanical stability of medial knot and knotless TOE repair, which is subjected to cyclic loading, as was performed in previous studies.8,10-12 Even under cyclic loading, it should be verified whether the current contact area and interface pressure can be maintained. Second, our study was based on a crescent-type tear, which has minimal retraction and good tissue quality. Thus it might not be applicable to tears of various sizes, shapes, and tissue qualities. Third, we used 40 N as the tension value in the lateral row because previous studies used values similar to this.7,8 However, we are not sure whether this value is appropriate in practice. Although we do not use a tensioner in practice and we completely depend on sensing tension with our own hands, we vary the tension loaded onto the lateral row on a caseby-case basis; for osteoporotic bone, we reduce the tension to lower than usual. Fourth, unlike previous studies, our study could not simulate a rotator cuff tear by resection of the distal portion of the supraspinatus. In our pilot study, the remaining medial portion of the supraspinatus was too thick to colorize the pressuresensitive film, although we used the most sensitive film. Fifth, even though there was a statistically
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significant difference in this time-zero study, it is unknown if this result would be clinically significant.
Conclusions Contrary to our hypothesis, in this time-zero study, medial knotless TOE repair using a modified MasonAllen suture produced a significantly inferior footprint contact area and interface pressure compared with conventional medial knot-tying TOE repair.
Acknowledgment The authors thank Dong-Su Jang (medical illustrator, Medical Research Support Section, Yonsei University College of Medicine, Seoul, Republic of Korea) for help with the figures.
References 1. Cho NS, Lee BG, Rhee YG. Arthroscopic rotator cuff repair using a suture bridge technique: Is the repair integrity actually maintained? Am J Sports Med 2011;39: 2108-2116. 2. Cho NS, Yi JW, Lee BG, Rhee YG. Retear patterns after arthroscopic rotator cuff repair: Single-row versus suture bridge technique. Am J Sports Med 2010;38: 664-671. 3. Frank JB, ElAttrache NS, Dines JS, Blackburn A, Crues J, Tibone JE. Repair site integrity after arthroscopic transosseous-equivalent suture-bridge rotator cuff repair. Am J Sports Med 2008;36:1496-1503. 4. Kim KC, Shin HD, Cha SM, Lee WY. Comparison of repair integrity and functional outcomes for 3 arthroscopic suture bridge rotator cuff repair techniques. Am J Sports Med 2013;41:271-277. 5. Rhee YG, Cho NS, Parke CS. Arthroscopic rotator cuff repair using modified Mason-Allen medial row stitch: Knotless versus knot-tying suture bridge technique. Am J Sports Med 2012;40:2440-2447. 6. Voigt C, Bosse C, Vosshenrich R, Schulz AP, Lill H. Arthroscopic supraspinatus tendon repair with suturebridging technique: Functional outcome and magnetic resonance imaging. Am J Sports Med 2010;38:983-991. 7. Park MC, ElAttrache NS, Tibone JE, Ahmad CS, Jun BJ, Lee TQ. Part I: Footprint contact characteristics for a transosseous-equivalent rotator cuff repair technique compared with a double-row repair technique. J Shoulder Elbow Surg 2007;16:461-468. 8. Park MC, Tibone JE, ElAttrache NS, Ahmad CS, Jun BJ, Lee TQ. Part II: Biomechanical assessment for a footprintrestoring transosseous-equivalent rotator cuff repair technique compared with a double-row repair technique. J Shoulder Elbow Surg 2007;16:469-476. 9. Tuoheti Y, Itoi E, Yamamoto N, et al. Contact area, contact pressure, and pressure patterns of the tendon-bone interface after rotator cuff repair. Am J Sports Med 2005;33:1869-1874. 10. Busfield BT, Glousman RE, McGarry MH, Tibone JE, Lee TQ. A biomechanical comparison of 2 technical variations of double-row rotator cuff fixation: The
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importance of medial row knots. Am J Sports Med 2008;36:901-906. 11. Leek BT, Robertson C, Mahar A, Pedowitz RA. Comparison of mechanical stability in double-row rotator cuff repairs between a knotless transtendon construct versus the addition of medial knots. Arthroscopy 2010;26: S127-S133. 12. Chu T, McDonald E, Tufaga M, Kandemir U, Buckley J, Ma CB. Comparison of completely knotless and hybrid double-row fixation systems: A biomechanical study. Arthroscopy 2011;27:479-485. 13. Trantalis JN, Boorman RS, Pletsch K, Lo IK. Medial rotator cuff failure after arthroscopic double-row rotator cuff repair. Arthroscopy 2008;24:727-731.
14. Gerber C, Schneeberger AG, Beck M, Schlegel U. Mechanical strength of repairs of the rotator cuff. J Bone Joint Surg Br 1994;76:371-380. 15. Kim SJ, Kim SH, Lee SK, Lee JH, Chun YM. Footprint contact restoration between the biceps-labrum complex and the glenoid rim in SLAP repair: A comparative cadaveric study using pressure-sensitive film. Arthroscopy 2013;29:1005-1011. 16. Park MC, Elattrache NS, Ahmad CS, Tibone JE. “Transosseous-equivalent” rotator cuff repair technique. Arthroscopy 2006;22:1360.e1-1360.e5. 17. Kim KC, Shin HD, Cha SM, Park JY. Comparisons of retear patterns for 3 arthroscopic rotator cuff repair methods. Am J Sports Med 2014;42:558-565.