CT image evaluation of one-screw fixation in the Latarjet procedure.

BACKGROUND: In the Latarjet procedure, two screws are used for secure fixation. However, when the graft is small, two-screw fixation is technically difficult. The purpose of this study was to evaluate the bone union of one-screw fixation on CT images. METHODS: Ten shoulders with anterior recurrent dislocation underwent the open Latarjet procedure using one-screw fixation combined with arthroscopic Bankart repair. The bone union and the graft position were evaluated on CT images at 3, 6, and 12 months after the operation. RESULTS: Seven of 10 shoulders showed bone union at 3 months after the operation. In two shoulders, the removal of cortex was insufficient, and bone union was observed at 6 months. In one shoulder, the distal part of the graft was not in contact with the glenoid, and bone union was observed at 12 months. In one shoulder, the graft was healed in a 70-degree-rotated position. The average thickness of the graft was 7.2 ± 1.0 mm. CONCLUSION: One-screw fixation in the Latarjet procedure did not show non-union. Sufficient removal of the graft cortex and good contact were needed for early union.

An augmentation suture technique for arthroscopic rotator cuff repair.

The double-row suture technique and the suture-bridge technique have been used for rotator cuff repair to decrease the occurrence of retears. However, when only the degenerated tendon end is sutured, the risk of retear remains. The augmentation suture technique is a new procedure that connects the intact medial tendon to the lateral greater tuberosity, and this approach may protect the initial repair site. The procedures for this technique are as follows: 2 sutures are placed through the medial intact tendon, the cuff tear is repaired by the single-row technique, 2 sutures are pulled laterally over the single-row repair site, and 2 sutures are fixed at the lateral greater tuberosity with a push-in-type anchor. This technique is simple and easy and does not require special equipment. Moreover, this approach can augment the single-row repair technique without creating high tension at the cuff end.

Biomechanical effect of rotator cuff augmentation with an acellular dermal matrix graft: a cadaver study.

BACKGROUND: Acellular human dermal matrix grafts (Graftjacket; Wright Medical Technology, Arlington, TN, USA) are used clinically for rotator cuff augmentation without a detailed understanding of their biomechanical effects. The purpose of this study was to evaluate the effect of augmentation with dermal grafts on the biomechanical effects of rotator cuff repairs. METHODS: Nine matched pairs of human cadaveric shoulders were used. A single-row rotator cuff repair combined with an augmentation graft was performed on one shoulder, and a single-row repair was performed on the contralateral shoulder as a control. An acellular dermal matrix graft was sutured to the tendon medially and fixed to the humerus laterally. The constructs were preloaded at 10 N and then cyclically loaded between 10 and 180 N for 1000 cycles, followed by tensile testing to failure at 1.0 mm/s. FINDINGS: The maximum load of the augmentation group (560.2 N, SD 95.5) was greater than that of the control group (345.7 N, SD 60.8), while the linear stiffness of the augmentation group (65.2 N/mm, SD 15.6) was less than that of the control group (77.2 N/mm, SD 15.7). Reliable gap distance data were not obtained during cyclic loading in 5 of 9 augmented repairs due to the elasticity of the dermal matrix graft. INTERPRETATION: The dermal matrix graft augmentation increased the maximum load but did not increase the linear stiffness. The elasticity of the dermal matrix graft affected the biomechanical effects of the augmented rotator cuff repairs.

Rotator cuff regeneration using a bioabsorbable material with bone marrow-derived mesenchymal stem cells in a rabbit model.

BACKGROUND: Rotator cuff regeneration using tissue engineering techniques is a challenging treatment in elderly patients with irreparable rotator cuff tears. HYPOTHESIS: A polyglycolic acid sheet scaffold with seeded mesenchymal stem cells (MSCs) may enhance the expression of type I collagen products and increase the mechanical strength of the regenerated tendon in vivo. STUDY DESIGN: Controlled laboratory study. METHODS: A surgically created defect of infraspinatus tendons of rabbits was reconstructed with 2 different materials, a polyglycolic acid (PGA) sheet alone (PGA group) (n = 34) and a PGA sheet seeded with autologously cultured MSCs (MSC group) (n = 34). The authors created a tendon defect model without embedding any graft as the control model (control group) (n = 34). The rabbits were sacrificed at 4, 8, and 16 weeks after the operation and then were histologically evaluated. The rabbits were also biomechanically evaluated by measuring the ultimate failure loads and Young's modulus at 4 and 16 weeks following implantation. RESULTS: In the MSC group, the fibrocartilage layers and Sharpey fibers were found regularly in the insertion site at 8 weeks compared with the PGA group. In control group, thin membranes with many fibroblasts arranged in an irregular pattern linked the end of the torn cuff to the bone without any Sharpey fibers and type I collagen. A large volume of type I collagen was found in comparison with type III collagen at 16 weeks in the MSC group, whereas type III collagen was more prevalent than type I in the PGA group. The tendon maturing score in the MSC group had higher values than the PGA and control groups at 8 and 16 weeks (mean values were 21.0 ± 0.89, 24.0 ± 2.53 in the MSC group; 16.7 ± 2.25, 21.3 ± 2.42 in the PGA group; and 10.2 ± 0.98, 12.2 ± 1.72 in the control group, respectively) (P < .05). The results of the mechanical analysis revealed that the regenerated tendons in the MSC group had better tensile strength than in the PGA and control groups at 16 weeks (mean values were 3.04 ± 0.54 in the MSC group, 2.38 ± 0.63 in the PGA group, and 1.58 ± 0.13 in the control group) (P < .05). CONCLUSION: Bone marrow-derived MSCs were able to regenerate tendon-bone insertions and the tendon belly, including the production of type I collagen, and increased the mechanical strength of the regenerated rotator cuff tendon. CLINICAL RELEVANCE: Rotator cuff regeneration using MSCs is a promising treatment for massive rotator cuff defects.

Biomechanical comparison of lesser tuberosity osteotomy versus subscapularis tenotomy in total shoulder arthroplasty.

BACKGROUND: Total shoulder arthroplasty is traditionally performed through an anterior deltopectoral exposure with subscapularis tenotomy. Postoperative subscapularis dysfunction is common and adversely affects clinical outcomes. Consequently, surgeon interest in lesser tuberosity osteotomy has grown in an effort to improve subscapularis repair strength. This study investigated the biomechanical strength of subscapularis tenotomy vs lesser tuberosity osteotomy in the setting of total shoulder arthroplasty. MATERIALS AND METHODS: Uncemented humeral prostheses were placed in 20 paired upper extremities from 10 cadavers. For each respective cadaver, 1 limb underwent lesser tuberosity osteotomy and the contralateral limb underwent subscapularis tenotomy. The cadaveric specimens then underwent cyclic displacement and maximum load to failure testing. RESULTS: The subscapularis tenotomy specimens exhibited significantly less cyclic displacement (0.8 mm) than the osteotomy group (1.8 mm), with a 95% confidence interval (CI) for the difference of 0.5 to 1.5 mm (P = 0.002). The maximum load to failure was 439 ± 96 N for tenotomy and 447 ± 89 N for osteotomy (95% CI for the difference of -58 to 75), which was not significant (P = .78). CONCLUSION: Lesser tuberosity osteotomy was not significantly stronger than subscapularis tenotomy in maximum load to failure testing, with minimal clinical significance set at 100 N. Subscapularis tenotomy repair showed statistically significant less cyclic displacement than lesser tuberosity osteotomy. Further research is needed to clarify how the biomechanical results immediately after subscapularis tenotomy and lesser tuberosity osteotomy correlate with clinical outcomes.

Engineered tendon with decellularized xenotendon slices and bone marrow stromal cells: an in vivo animal study.

The purpose of this study was to investigate an engineered composite of multilayer acellular tendon slices seeded with bone marrow stromal cells (BMSCs) as a possible solution for tendon reconstruction. BMSCs were harvested from 15 rabbits and infraspinatus tendons were harvested from 17 dogs. The decellularized tendons were sectioned in longitudinal slices with a thickness of 50 µm. The BMSCs were seeded on the slices and then the slices were bundled into one composite. The composite was implanted into a rabbit patellar tendon defect. Tendon slices without BMSCs were implanted into the contralateral patellar tendon as a control. The composites were evaluated by histology and qRT-PCR. The viability of BMSCs was assessed using a fluorescent marker. Histology showed viable cells between the collagen fibres on the cell-seeded side. Analysis by qRT-PCR showed higher tenomodulin, collagen type III, MMP3 and MMP13 expressions and lower collagen type I expression in the cell-seeded composite than in the tendon slices without BMSCs. We conclude that BMSCs can survive in a multilayer composite, express a tendon phenotype and enhance the metabolism of tendon in vivo. This in vivo study suggests a potential utility of this composite in tendon reconstruction.

Multilayer tendon slices seeded with bone marrow stromal cells: a novel composite for tendon engineering.

The ideal scaffold for tendon engineering would possess the basic structure of the tendon, native extracellular matrix, and capability of cell seeding. The purpose of this study was to assess the tissue engineering potential of a novel composite consisting of a decellularized multilayer sliced tendon (MST) scaffold seeded with bone marrow stromal cells (BMSC). BMSC and infraspinatus tendons were harvested from 20 dogs. The tendons were sectioned in longitudinal slices with a thickness of 50 microm. The slices were decellularized, seeded with BMSC, and then bundled into one composite. The composite was incubated in culture media for 14 days. The resulting BMSC-seeded MST was evaluated by qRT-PCR and histology. The BMSC viability was assessed by a fluorescent tracking marker. Histology showed that the seeded cells aligned between the collagen fibers of the tendon slices. Analysis by qRT-PCR showed higher tenomodulin and MMP13 expression and lower collagen type I expression in the composite than in the BMSC before seeding. BMSC labeled with fluorescent tracking marker were observed in the composite after culture. Mechanical testing showed no differences between scaffolds with or without BMSC. BMSC can survive in a MST scaffold. The increased tenomodulin expression suggests that BMSC might express a tendon phenotype in this environment. This new composite might be useful as a model of tendon tissue engineering.

Augmentation of tendon attachment to porous ceramics by bone marrow stromal cells in a rabbit model.

Tendon attachment to interconnected porous calcium hydroxyapatite ceramics (IP-CHA) with cultured bone marrow stromal cells (BMSC) was analysed. The purpose of this study was to evaluate whether BMSC in IP-CHA could augment the tendon attachment to IP-CHA histologically and biomechanically. Eighteen Japanese white rabbits were used. Cultured BMSCs were subcultured in IP-CHA. The grafted tendon and IP-CHA with BMSC complex were implanted in a bone defect of the knee [BMSC(+) group]. In the contralateral knee, a tendon and IP-CHA without BMSC complex were implanted [BMSC(-) group]. Histological findings of the interface between the tendon and IP-CHA were similar in the two groups 3 weeks after the operation. However, 6 weeks after the operation, more abundant bone formation around the tendon was observed in the BMSC(+) group. The direct apposition of the tendon to bone in pores and collagen fibre continuity between the tendon and fibrous tissue in pores were observed. In biomechanical evaluation, the maximum pull-out load of the tendon from the IP-CHA in the BMSC(+) group was significantly higher than that in the BMSC(-) group 6 weeks after the operation. BMSCs cultured in IP-CHA could augment tendon attachment to IP-CHA.

Effects of interconnecting porous structure of hydroxyapatite ceramics on interface between grafted tendon and ceramics.

The purpose of this study was to evaluate histologically and biomechanically the interface between porous hydroxyapatite ceramics and a tendon grafted into ceramics, and to compare the interface in two ceramics with different porous structures: interconnected porous calcium hydroxyapatite ceramics (IP-CHA) with an effective porosity index (interpore diameter > 20 microm) of 63.6%, and porous calcium hydroxyapatite ceramics with less interconnection (HA-L) with an effective porosity index of 5.5%. The tendon-IP-CHA complex and the tendon-HA-L complex were implanted into the bone defects made in both knees of rabbits. With IP-CHA, abundant fibrous tissue, including vessels and collagen fiber continuity, was observed inside interface-region pores. The amount of osseous tissue in interface-region pores increased over time, and at 24 weeks after operation, the tendon was in direct contact with the osseous tissue in IP-CHA. With HA-L, the amount of fibrous tissue in interface-region pores was low and did not increase. The results of biomechanical analysis revealed that the maximum tendon pull-out load from IP-CHA was significantly higher than that from HA-L. With the porous hydroxyapatite ceramics having highly interconnecting porous structure, a bioactive interface was achieved between ceramics and grafted tendon. On the basis of these results, we conclude that bone defects, including tendon insertion, can be reconstructed using IP-CHA.