Healing rate and clinical outcomes of xenografts appear to be inferior when compared to other graft material in rotator cuff repair: a meta-analysis

Clinical and radiological outcomes between superior capsule reconstruction using allografts or xenografts: a 2-year retrospective comparison study

BACKGROUND

Treating symptomatic, massive, irreparable rotator cuff tears remains challenging and controversial. Superior capsule reconstruction (SCR) using the tensor fascia lata has shown promising clinical results; however, due to donor site morbidity, interest in SCR using other grafts has increased. Yet, no studies have compared allografts with xenografts. In addition, the clinical results of graft tears remain controversial. This study compared the clinical and radiological outcomes of SCR between those with allografts and xenografts.

METHODS

Sixty-seven patients who had undergone SCR with allografts or xenografts between January 2016 and December 2020 were included in this retrospective study. Furthermore, 62 patients were evaluated 2 years postsurgery, with five patients excluded due to loss to follow-up or conversion to reverse shoulder arthroplasty. The Constant, American Shoulder and Elbow Surgeons, and visual analog scale scores, range of motion, and radiological outcomes were evaluated before the surgery and at 6 and 24 months after surgery.

RESULTS

The graft tear rate was 23.08% in the allograft group and 42.86% in the xenograft group at 6 months after surgery; at 2 years postsurgery, the gap further widened to 32.43% and 64%, respectively, showing a significant difference. The graft in the allograft group was thicker than that in the xenograft group, and there were significant differences on the humeral side and in the midsubstance area. The allograft group showed significantly better visual analog scale, Constant, and American Shoulder and Elbow Surgeons scores than the xenograft group 2 years postsurgery. However, the difference in clinical outcomes between the two groups did not surpass minimal clinically important differences.

CONCLUSION

Although arthroscopic SCR using xenografts had significantly lower clinical outcome than allografts, this difference did not reach minimal clinically important differences. Arthroscopic SCR using xenografts showed higher graft tear rates than allografts. Even with partial tears, better results were obtained if the graft continuity was maintained. Additionally, after surgery, the xenograft showed less thickness than the allograft and resulted in more tears, specifically in the midsubstance area.

Midterm outcomes of autologous bridging of rotator cuff tears with an autologous tendon patch (TEAR patch)

BACKGROUND

Large and massive rotator cuff tears and tears after failed surgical repair are a challenging clinical problem with different treatment options. The purpose of the study was to evaluate the midterm outcomes after rotator cuff repair (RCR) with autologous hamstring tendon graft bridging (tissue-enhanced autologous rotator cuff repair [TEAR] patch) with the hypothesis that outcomes would be reasonable and complication rates would be low.

METHODS

This is a retrospective case series study of patients who underwent open RCR using a TEAR patch from June 2015 to March 2019. The exclusion criteria included evidence of cuff tear arthropathy, advanced fatty infiltration, moderate-to-severe arthropathy, and workers compensation board or litigation involved. Clinical outcome measures were Constant score; Disabilities of the Arm, Shoulder and Hand score; Simple Shoulder Test; Subjective Shoulder Value; range of motion (ROM); and manual muscle test for forward elevation, abduction, external and internal rotation, patient satisfaction, and willingness to perform the operation again. Radiographic outcome measures were magnetic resonance imaging, ultrasound, and radiographs: graft integrity and acromiohumeral distance (AHD).

RESULTS

A total of 44 patients were followed (89%) for ≥2 years (45 shoulders, mean age 60.3 years [48-76 years], mean follow-up 4.3 years [2-6 years]). All clinical outcome measures (Constant score, Disabilities of the Arm, Shoulder and Hand score, Simple Shoulder Test, Subjective Shoulder Value, ROM, and manual muscle test) demonstrated significant improvement except active external and internal rotation. At 2 years of follow-up, the mean patient satisfaction was high (12.2 of 15 points), and 33 of 38 patients (73.3%) would perform the operation again. A perfect graft integration was observed in 30 (66.7%), a small gap in 7 (15.6%), a retear in 3 (7%), and a complete failure of the tendon patch in 5 (11%) patients. Graft integrity was strongly correlated with the postoperative AHD (r = 0.599, P = .001) and the gain in AHD (r = 0.599, P = .001) but not with ROM or patient-reported outcome measures or patient satisfaction. Four patients required revision surgeries (3 due to deep infection and 1 for poor function and pain).

CONCLUSIONS

Midterm clinical and radiographic outcomes after RCR with graft bridging using a TEAR patch were reasonable. The procedure resulted in improved shoulder function and a high level of patient satisfaction. The revision rate is acceptable in view of the specific patient group and treatment alternatives. The described technique of the TEAR patch can be a valuable alternative to existing methods and a new autograft source for rotator cuff surgeries that need bridging of a tendon defect.

Irreparable Large to Massive Rotator Cuff Tears With Low-Grade Fatty Degeneration of the Infraspinatus Tendon: Minimum 7-Year Follow-up of Fascia Autograft Patch Procedure and Partial Repair

BACKGROUND

In shoulders with irreparable massive rotator cuff tears (RCTs) with high-grade fatty degeneration (Goutallier stage 3 or 4) of the supraspinatus tendon and low-grade fatty degeneration (Goutallier stage 1 or 2) of the infraspinatus tendon (ISP), arthroscopic patch grafting (PG) has been reported as superior to partial repair (PR) regarding the ISP retear rate at short-term to midterm follow-up. However, the longer term outcomes are unclear.

PURPOSE

To compare clinical and structural outcomes in the PG and PR groups at a minimum of 7 years postoperatively.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

We evaluated 24 patients in the PG group and 24 patients in the PR group. We primarily used the Constant score for clinical outcomes and performed magnetic resonance imaging for structural outcomes in the PG and PR groups. The risk factors for a retear of the ISP were identified by univariate and multivariate (forward stepwise selection method) logistic regression analyses. We primarily compared values at midterm follow-up (<4 years) with values at the final follow-up (minimum 7 years) for each patient.

RESULTS

The mean midterm and final follow-up times for the PG group were 41.0 and 95.1 months, respectively, compared with 35.7 and 99.3 months, respectively, for the PR group. We found significant differences for the midterm and final follow-up Constant total scores in the PG and PR groups (midterm follow-up: 79.1 vs 69.9, respectively [P = .001]; final follow-up: 76.0 vs 65.3, respectively [P = .006]) and in the Constant strength scores (midterm follow-up: 14.6 vs 8.5, respectively [P < .001]; final follow-up: 13.1 vs 8.3, respectively [P = .001]). Treatment group (PR) was a significant predictor of an ISP retear in the logistic regression analysis (odds ratio, 3.545; P = .043).

CONCLUSION

Patients with low-grade massive RCTs treated with PG or PR improved significantly in terms of clinical outcomes at the midterm and final follow-up time points. However, Constant scores were significantly better in the PG group at the final follow-up.

Bone healing potential of fascia lata autografts to the humeral head footprint in rotator cuff reconstruction based on magnetic resonance imaging and histologic evaluations

BACKGROUND

The purpose of the study was to evaluate the bone healing potential of fascia lata autograft (FLA) by magnetic resonance imaging (MRI) and histologic analysis.

METHODS

The study included 69 patients assessed by MRI after an FLA patch procedure. Three of the 69 patients underwent a revision procedure after the primary FLA procedure; 1 underwent a second-look arthroscopy and 2 underwent reverse shoulder arthroplasties (RSAs). In the 2 RSA patients, we histologically evaluated greater tuberosities with the repaired graft. Moreover, as a control, we harvested the greater tuberosity with the cuff tendon at the time of RSA for failed open reduction-internal fixation of 4-part proximal humeral fracture. Based on MRI, retear cases were divided into type 1 (the graft did not remain on the greater tuberosity) and type 2 (the graft remained on the greater tuberosity). Histologic sections were evaluated to examine fascia-bone or rotator cuff-bone interfaces.

RESULTS

There were 35 intact repairs: 7 type 1 and 27 type 2 shoulders (type 1 vs. type 2, P < .001). Second-look arthroscopic findings confirmed that the graft was securely attached to the greater tuberosity. Histologic analysis of greater tuberosities in RSA patients showed solid continuity of the graft to the bone, with cells with nuclei in the collagen matrix oriented in parallel. The FLA to bone junction consisted of the FLA, fibrocartilage, and bone, which is similar to the normal cuff tendon to bone junction.

CONCLUSIONS

These results indicate that a fresh cellular FLA has good to excellent bone healing potential.

In Vivo Evaluation of Different Collagen Scaffolds in an Achilles Tendon Defect Model

In the present study, a newly introduced bovine cross-linked collagen scaffold (test material) was investigated in vivo in an Achilles tendon defect model and compared to a commercially available porcine collagen scaffold (control material). In total, 28 male Sprague Dawley rats (about 400 g) were examined. The defined Achilles tendon defect of 5 mm of the right hind limb was replaced by one of the scaffold materials. After euthanasia, the hind limbs were transected for testing. Biomechanical evaluation was carried out via tensile testing (n = 8 each group, observation time: 28 days). Nonoperated tendons from the bilateral side were used as a control (native tendon, n = 4). For the histological evaluation, 12 animals were sacrificed at 14 and 28 days postoperatively (n = 3 each group and time point). Stained slices (Hematoxylin & Eosin) were evaluated qualitatively in terms of presence of cells and cell migration into scaffolds as well as structure and degradation of the scaffold. All transected hind limbs were additionally analyzed using MRI before testing to verify if the tendon repair using a collagen scaffold was still intact after the observation period. The maximum failure loads of both scaffold materials (test material: 54.5 ± 16.4 N, control: 63.1 ± 19.5 N) were in the range of native tendon (76.6 ± 11.6 N, p ≥ 0.07). The stiffness of native tendons was twofold higher (p ≤ 0.01) and the tear strength was approximately fivefold higher (p ≤ 0.01) compared to the repaired tendons with both scaffolds. Histological findings indicated that neither the test nor the control material induced inflammation, but the test material underwent a slower remodeling process. An overall repair failure rate of 48% was observed via MRI. The experimental data of the newly developed test material showed similar outcomes compared to the commercially available control material. The high repair failure rate indicated that MRI is recommended as an auxiliary measurement tool to validate experimental data.

Biomechanical, Biochemical, and Cell Biological Evaluation of Different Collagen Scaffolds for Tendon Augmentation

Tendon augmentation is increasingly clinically relevant due to rising amount of tendon ruptures because of the aging and more demanding population. Therefore, newly developed scaffolds based on bovine epoxide stabilized collagen maintaining the native fibril-like collagen structure were characterized and compared to two commercially available porcine collagen scaffolds. For biomechanical testing (ultimate load, ultimate stress, stiffness, and elastic modulus), bovine collagen scaffolds were hydrated and compared to reference products. Cell viability and proliferation were assessed by seeding human primary fibroblasts on each collagen-based scaffold and cultured over various time periods (3 d, 7 d, and 14 d). Live/dead staining was performed and metabolic cell activity (WST-1 assay) was measured. Biochemical degradability was investigated by enzymatic digestion. The bovine collagen scaffold showed significantly enhanced biomechanical properties. These persisted over different rehydration times. Cell biological tests revealed that the bovine collagen scaffolds support reproducible cell colonization and a significant increase in the number of viable cells during cultivation. The results are comparable with the viability and proliferation rate of cells grown on porcine reference materials. With regard to biochemical degradability, all tested materials showed comparable resistance to enzymatic degradation in vitro. Due to imitating the natural tendon structure the new scaffold material is supposed to provide beneficial effects in future clinical application.

Rise of the Pigs: Utilization of the Porcine Model to Study Musculoskeletal Biomechanics and Tissue Engineering During Skeletal Growth

Large animal models play an essential role in the study of tissue engineering and regenerative medicine (TERM), as well as biomechanics. The porcine model has been increasingly used to study the musculoskeletal system, including specific joints, such as the knee and temporomandibular joints, and tissues, such as bone, cartilage, and ligaments. In particular, pigs have been utilized to evaluate the role of skeletal growth on the biomechanics and engineered replacements of these joints and tissues. In this review, we explore the publication history of the use of pig models in biomechanics and TERM discuss interspecies comparative studies, highlight studies on the effect of skeletal growth and other biological considerations in the porcine model, and present challenges and emerging opportunities for using this model to study functional TERM.