Biomechanics of tensor fascia lata allograft for superior capsular reconstruction

Patients With Intact Shoulder Superior Capsular Reconstruction Grafts on Ultrasound Show Significant Improvement in Functional Outcomes at Minimum 2-Year Follow-up

Purpose

To assess the utility of using dynamic ultrasound for postoperative evaluation after superior capsular reconstruction (SCR) by evaluating graft integrity and its correlation with clinical outcomes at a minimum 2-year follow-up.

Methods

A retrospective chart review was conducted to identify patients who underwent SCR between July 2015 and July 2020 with a minimum 2-year clinical and ultrasound follow-up. Clinical outcome measures included Simple Shoulder (SS) and American Shoulder and Elbow Surgeon (ASES) scores. Integrity of the SCR graft was evaluated by dynamic ultrasound.

Results

We evaluated 22 shoulders in 21 patients with a mean follow-up of 44.8 months (range, 24-71 months). The graft was found to be intact by ultrasound evaluation in 82% (18/22). Patients with intact grafts had higher mean SS (11.6 vs 7.8, P = .00079) and ASES (91.2 vs 64.1, P = .0296) scores at latest follow-up compared to those with failed grafts. Those with intact grafts also had significant improvement in SS (3.7 vs 11.6, P < .00001) and ASES (23.2 vs 91.2, P < .00001) scores at latest follow-up compared to their preoperative scores. In contrast, patients with graft failure had no significant improvement in SS (6.3 vs 9.0, P = .123) and ASES (40.4 vs 58.3, P = .05469) scores at latest follow-up compared to their preoperative scores. There was no difference between clinical outcomes at 6 to 12 months vs latest follow-up for both SS (P = .11, P = .5) and ASES (P = .27, P = .21) scores.

Conclusions

SCR grafts were found by ultrasound to be intact in 82% of cases. Patients with intact grafts on ultrasound had significant improvement in functional outcome scores while those with graft failure did not. Functional outcome scores suggest that maximal recovery from this procedure occurs by 6 to 12 months.

Level of Evidence

Level IV, therapeutic case series.

Superior Capsular Reconstruction Combined With Lower Trapezius Tendon Transfer Improves the Biomechanics in Posterosuperior Massive Rotator Cuff Tears

BACKGROUND

Surgical treatments for chronic posterosuperior massive rotator cuff tear (MRCT) are still controversial. Superior capsular reconstruction (SCR), which provides a static stabilizer to decrease superior humeral head translation, and lower trapezius tendon transfer (LTTT) with centralization of the humeral head, which prevents superior humeral head migration, are potential surgical options. To date, SCR combined with LTTT has not been fully investigated.

HYPOTHESIS

Restoration of static stabilizer and dynamic stabilizer together would effectively improve shoulder kinematics in posterosuperior MRCT.

STUDY DESIGN

Controlled laboratory study.

METHODS

A custom-made shoulder mechanics testing system was used to test 8 fresh-frozen cadaveric shoulders. The testing conditions were as follows: (1) intact; (2) posterosuperior MRCT (supraspinatus and infraspinatus removed); (3) SCR using the fascia lata; (4) LTTT; and (5) SCR combined with LTTT. The total rotational range of motion (ROM), superior translation, anteroposterior translation, and peak subacromial contact pressure were evaluated at 0°, 30°, and 60° of shoulder abduction. Repeated-measures analysis of variance and Tukey post hoc tests were performed.

RESULTS

The total rotational ROM, superior translation, anteroposterior translation, and peak subacromial contact pressure increased in posterosuperior MRCTs (all, P < .05). The rotational ROM, superior translation, anteroposterior translation, and peak subacromial contact pressure at 0° and 30° of shoulder abduction decreased in SCR (all, P < .05). However, there was no significant improvement in rotational ROM, superior translation, and peak subacromial contact pressure at 60° of shoulder abduction (P > .05). LTTT resulted in a significant decrease in the superior translation, anteroposterior translation, and peak subacromial contact pressure at 0°, 30°, and 60° of shoulder abduction (P < .05). SCR combined with LTTT restored the total rotational ROM, superior translation, anteroposterior translation, and peak subacromial contact pressure at 0°, 30°, and 60° of shoulder abduction (all, P < .05).

CONCLUSION

In the cadaveric model, SCR combined with LTTT showed improved shoulder kinematics and contact pressures in the posterosuperior MRCT model compared with SCR or LTTT alone.

CLINICAL RELEVANCE

SCR combined with LTTT may be regarded as an alternative surgical procedure for posterosuperior MRCTs.

Dynamic Superior Capsular Reconstruction for Irreparable Massive Rotator Cuff Tears: Histologic Analysis in a Rat Model and Short-term Clinical Evaluation

BACKGROUND

Superior capsular reconstruction (SCR) has been demonstrated to be a valuable treatment for patients with irreparable massive rotator cuff tears (IMRCTs). However, the torn medial supraspinatus (SSP) tendons, which acted as dynamic stabilizers, were left untreated in conventional SCR, and the dynamic force from the SSP tendon was not restored.

PURPOSE

To evaluate the effect of dynamic SCR (dSCR) on fascia-to-bone healing in a rat model, and to compare the short-term clinical effectiveness of dSCR and SCR using autologous fascia lata (FL) in patients with IMRCTs.

STUDY DESIGN

Controlled laboratory study and cohort study; Level of evidence, 3.

METHODS

A total of 50 rats were divided randomly into 2 groups: the dSCR group and the SCR group (25 rats per group). First, chronic IMRCTs were created, and then the torn tendons in both groups were subjected to SCR using autologous thoracolumbar fascial (TLF) grafts. The remnant of the SSP tendon was sutured to the medial part of the TLF graft in the dSCR group but not in the SCR group. Histologic sections were assessed at 1, 2, 4, 8, and 16 weeks postoperatively. In the clinical study, 22 patients (9 SCR, 13 dSCR) were analyzed. The recovery of shoulder function, including the active range of motion (ROM), visual analog scale (VAS), American Shoulder and Elbow Surgeons score, Constant score, and University of California Los Angeles score, acromiohumeral distance (AHD), and fatty infiltration, was evaluated before surgery and at the last follow-up.

RESULTS

Histologic analysis of the fascia-to-bone junction in the rat model showed that the TLF gradually migrated into tendon-like tissue over the rotator cuff defects in both groups, and the modified tendon maturation score of the fascia-to-bone interface in the dSCR group was higher than that in the SCR group at 4 weeks (12.20 ± 1.30 vs 14.60 ± 1.52; P = .004), 8 weeks (19.60 ± 1.14 vs 22.20 ± 1.10; P = .019), and 16 weeks (23.80 ± 0.84 vs 26.20 ± 0.84 P = .024). The dSCR group showed earlier fibrocartilage cell formation and angiogenesis. In the clinical study, all 22 patients completed a minimum of 12 months of follow-up after surgery, and the mean follow-up duration was 22.89 ± 7.59 months in the SCR group and 25.62 ± 7.32 months in the dSCR group. The patients in both groups showed significant improvements in terms of ROM, shoulder function scores, and AHD. At the last follow-up, abduction (56.67°± 27.39° vs 86.54°± 30.37°; P = .029), external rotation (25.00°± 9.35° vs 33.08°± 8.55°; P = .049), internal rotation cone rank (-2.78 ± 2.44 vs -4.38 ± 1.12; P = .049), VAS (-3.00 ± 0.87 vs -3.92 ± 0.95; P = .031) and Constant (47.89 ± 15.39 vs 59.15 ± 9.74; P = .048) scores, and the AHD improvement degree (3.06 ± 1.41 mm vs 4.38 ± 1.35 mm; P = .039) in the dSCR group were significantly improved compared with those in the SCR group. The results of fatty infiltration at the last follow-up showed that there was significant improvement compared with the preoperative results in both the conventional SCR (P = .036) and the dSCR (P = .001) groups. However, there were no significant differences between the 2 groups (P = .511).

CONCLUSION

dSCR can promote faster fascia-to-bone healing in a rat model, and the dSCR technique could provide a preferable treatment option for patients with IMRCTs.

CLINICAL RELEVANCE

dSCR might restore the dynamic of SSP in some sense and then improve the fatty infiltration in the SSP.

Arthroscopic Superior Capsular Reconstruction with Tensor Fascia Lata Allograft for Irreparable Rotator Cuff Tears: Clinical and Radiologic Outcomes for a Minimum 1-Year Follow-Up

PURPOSE

To confirm the radiologic and clinical outcomes after performing arthroscopic superior capsular reconstruction (ASCR) using a tensor fascia lata (TFL) allograft.

METHODS

Thirty-three patients with irreparable rotator cuff tears were treated with ASCR with a TFL allograft. The mean age and follow-up period were 62 years and 20.1 months, respectively. TFL allografts were used as 3, 4, and 6 layers, and the graft thickness was 3.7, 3.9, and 5.4 mm, respectively. Range of motion, visual analog scale (VAS) pain score, American Shoulder and Elbow Surgeons score, and Constant score were evaluated preoperatively and at the final follow-up. The pre-, postoperative, and final acromiohumeral distances (AHD) were compared. The graft integrity was checked through a follow-up magnetic resonance imaging at least 6 months after surgery.

RESULTS

Torn grafts were identified in 6 cases (19%). AHD significantly increased from 5.0 to 8.0 mm postoperatively (P < .0001). However, there was no significant difference of 5.0 mm at the final follow-up AHD. Five cases (83%) of torn grafts were induced in the 3-layered graft sheet group, but the difference was not statistically significant (P = .067). Visual analog scale, forward elevation, internal rotation, American Shoulder and Elbow Surgeons, and Constant scores significantly improved at the last follow-up. Two cases of early infection were confirmed and the graft materials were all removed.

CONCLUSIONS

Despite the possibility of early infection, ASCR using TFL allograft is a reliable procedure for the irreparable rotator cuff tear. In particular, if the number of layers of TFL allograft increases, it is judged that it could become a more effective graft.

LEVEL OF EVIDENCE

Level IV, therapeutic case series.

Biomechanical outcomes of superior capsular reconstruction for irreparable rotator cuff tears by different graft materials-a systematic review and meta-analysis

Background

Irreparable rotator cuff tears (IRCT) are defined as defects that cannot be repaired due to tendon retraction, fat infiltration, or muscle atrophy. One surgical remedy for IRCT is superior capsular reconstruction (SCR), which fixes graft materials between the larger tuberosity and the superior glenoid.

Patients and methods

The Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) criteria were followed for conducting the systematic review and meta-analysis. From their inception until February 25, 2022, Pubmed, Embase, and Cochrane Library's electronic databases were searched. Studies using cadavers on SCR for IRCT were also included. The humeral head's superior translation and subacromial peak contact pressure were the primary outcomes. The humeral head's anteroposterior translation, the kind of graft material used, its size, and the deltoid load were the secondary outcomes.

Results

After eliminating duplicates from the search results, 1,443 unique articles remained, and 20 papers were finally included in the quantitative research. In 14 investigations, the enhanced superior translation of the humeral head was documented in IRCTs. In 13 studies, a considerable improvement following SCR was found, especially when using fascia lata (FL), which could achieve more translation restraints than human dermal allograft (HDA) and long head of bicep tendon (LHBT). Six investigations reported a subacromial peak contact pressure increase in IRCTs, which could be rectified by SCR, and these studies found a substantial increase in this pressure. The results of the reduction in subacromial peak contact pressure remained consistent regardless of the graft material utilized for SCR. While there was a statistically significant difference in the change of graft material length between FL and HDA, the change in graft material thickness between FL and HDA was not significant. The humeral head's anterior-posterior translation was rising in IRCTs and could be returned to its original state with SCR. In five investigations, IRCTs caused a significant increase in deltoid force. Furthermore, only one study showed that SCR significantly decreased deltoid force.

Conclusion

With IRCT, SCR might significantly decrease the glenohumeral joint's superior and anterior-posterior stability. Despite the risks for donor-site morbidity and the longer recovery time, FL is still the best current option for SCR.

Superior Capsule Reconstruction With Fascia Lata Allograft Has Initial Stiffness and Ultimate Load Comparable to the Native Shoulder Superior Capsule: A Cadaveric Biomechanical Study

PURPOSE

The purpose of this study was to compare the biomechanical characteristics of a fascia lata superior capsule reconstruction (FL-SCR) to the native superior capsule.

METHODS

The native superior capsule of 8 cadaveric shoulders was tested with cyclic loading from 10 to 50 N for 30 cycles in 20° of glenohumeral abduction followed by load to failure at 60 mm/min. Following native superior capsule testing, FL-SCR was performed, which was tested as described for the native capsule. Paired t test was used for statistical analyses with P < .05 for significance.

RESULTS

The stiffness for cycle 1 to 50 N was significantly higher for the native superior capsule compared to the FL-SCR (P = .001). By cycle 30, the stiffness between the two was not statistically different (P = .734). During load to failure, the initial stiffness to 2 mm for the FL-SCR and the native superior capsule was not statistically different (P = .262). The linear stiffness and yield load of the native superior capsule were significantly greater than that of the FL-SCR (94.5 vs 28.0 N/mm, P = .013; 386.9 vs 123.8 N, P = .029). There was no significant difference in ultimate load between the native superior capsule and the FL-SCR (444.9 vs 369.0 N, P = .413).

CONCLUSIONS

FL-SCR has initial stiffness and ultimate load similar to the native superior capsule.

CLINICAL RELEVANCE

The biomechanical properties of FL allograft make it an appealing option as a graft choice for superior capsule reconstruction.

Shoulder Superior Capsular Reconstruction Hybrid Graft Thickness Greater Than Preoperative Acromiohumeral Distance Increases Graft Retear Rate and Subacromial Erosion

PURPOSE

To evaluate the impact of graft thickness on clinical outcomes and graft retear after superior capsular reconstruction (SCR) using a hybrid graft combining both fascia lata autograft and dermal allograft in patients with massive rotator cuff tear (MRCT).

METHODS

Between January 2017 and February 2019, this study enrolled 58 patients with MRCT who underwent SCR using a hybrid graft combining both fascia lata autograft and dermal allograft. We evaluated clinical outcomes and compared differences between the graft intact and the graft retear group. Moreover, subgroup analysis was performed for patients having a preoperative acromiohumeral distance (AHD) less than or equal to the used graft thickness (group 1) and the results were compared with those for preoperative AHD greater than the used graft thickness (group 2).

RESULTS

Fifty-five patients who underwent MRCT with a mean age of 65.1 ± 5.7 years old were followed up during a mean period of 30.5 ± 6.5 (range, 24-37) months. There were significant differences in clinical outcome measures preoperatively and postoperatively (P < .05). There were no significant differences in clinical outcomes between the graft intact and graft retear groups (P > .05). The subgroup analysis revealed that the retear (68.6% vs 30.4%, P = .004) and subacromial erosion rates (91.4% vs 60.9%, P = .005) were significantly greater in for patients having a preoperative AHD less than or equal to the used graft thickness (group 1).

CONCLUSIONS

SCR using a hybrid graft combining both fascia lata autograft and dermal allograft is promising with improved clinical scores (P < .05) irrespective of the graft integrity. The use of a graft with a thickness greater than a patient's preoperative AHD could increase graft retear and subacromial erosion rates after SCR. However, there was no significant difference in clinical outcomes according to the relationship between used graft thickness and preoperative AHD.

LEVEL OF EVIDENCE

Level IV, therapeutic case series.

In Vitro Simulation of Shoulder Motion Driven by Three-Dimensional Scapular and Humeral Kinematics

In vitro simulation of three-dimensional (3D) shoulder motion using in vivo kinematics obtained from human subjects allows investigation of clinical conditions in the context of physiologically relevant biomechanics. Herein, we present a framework for laboratory simulation of subject-specific kinematics that combines individual 3D scapular and humeral control in cadavers. The objectives were to: (1) robotically simulate seven healthy subject-specific 3D scapulothoracic and glenohumeral kinematic trajectories in six cadavers, (2) characterize system performance using kinematic orientation accuracy and repeatability, and muscle force repeatability metrics, and (3) analyze effects of input kinematics and cadaver specimen variability. Using an industrial robot to orient the scapula range of motion (ROM), errors with repeatability of ±0.1 mm and <0.5 deg were achieved. Using a custom robot and a trajectory prediction algorithm to orient the humerus relative to the scapula, orientation accuracy for glenohumeral elevation, plane of elevation, and axial rotation of <3 deg mean absolute error (MAE) was achieved. Kinematic accuracy was not affected by varying input kinematics or cadaver specimens. Muscle forces over five repeated setups showed variability typically <33% relative to the overall simulations. Varying cadaver specimens and subject-specific human motions showed effects on muscle forces, illustrating that the system was capable of differentiating changes in forces due to input conditions. The anterior and middle deltoid, specifically, showed notable variations in patterns across the ROM that were affected by subject-specific motion. This machine provides a platform for future laboratory studies to investigate shoulder biomechanics and consider the impacts of variable input kinematics from populations of interest, as they can significantly impact study outputs and resultant conclusions.

The best options in superior capsular reconstruction

Irreparable massive rotator cuff tears cause pain, loss of function, and a decrease in range of motion, which cause serious disturbances in daily life. Young patients, in particular, are active and have relatively high functional requirements, and their surgical options are limited. Superior capsular reconstruction (SCR) was first proposed for irreparable massive rotator cuff tears, good clinical results have been reported in short-term follow up. Since then, SCR has been used increasingly worldwide for irreparable massive rotator cuff tears, and various studies have been published on clinical outcomes, biomechanical outcomes, surgical techniques, and graft types. This article reviews the optimal graft and surgical options for improving clinical outcomes in SCR.

Load-to-failure characteristics of patellar tendon allograft superior capsule reconstruction compared with the native superior capsule

Background

The potential use of a patellar tendon allograft for superior capsular reconstruction has been demonstrated biomechanically; however, there are concerns regarding compromised fixation strength owing to the longitudinal orientation of the fibers in the patellar tendon. Therefore, the purpose of this study was to compare the fixation strength of superior capsule reconstruction using a patellar tendon allograft to the intact superior capsule.

Methods

The structural properties of the intact native superior capsule (NSC) followed by superior capsular reconstruction using a patellar tendon allograft (PT-SCR) were tested in eight cadaveric specimens. The scapula and humerus were potted and mounted onto an Instron testing machine in 20 degrees of glenohumeral abduction. Humeral rotation was set to achieve uniform loading across the reconstruction. Specimens were preloaded to 10 N followed by cyclic loading from 10 N to 50 N for 30 cycles, then load to failure at a rate of 60 mm/min. Video digitizing software was used to quantify the regional deformation characteristics.

Results

During cyclic loading, there was no difference found in stiffness between PT-SCR and NSC (cycle 1 - PT-SCR: 12.9 ± 3.6 N/mm vs. NSC: 22.5 ± 1.6 N/mm; P = .055 and cycle 30 - PT-SCR: 27.3 ± 1.4 N/mm vs. NSC: 25.4 ± 1.7 N/mm; P = .510). Displacement at the yield load was not significantly different between the two groups (PT-SCR: 7.0 ± 1.0 mm vs. NSC: 6.5 ± 0.3 mm; P = .636); however, at the ultimate load, there was a difference in displacement (PT-SCR: 20.7 ± 1.1 mm vs. NSC: 8.1 ± 0.5 mm; P < .001). There was a significant difference at both the yield load (PT-SCR: 71.4 ± 2.2 N vs. NSC: 331.6 ± 56.6 N; P = .004) and the ultimate load (PT-SCR: 217.1 ± 26.9 N vs. NSC: 397.7 ± 62.4 N; P = .019). At the yield load, there was a difference found in the energy absorbed (PT-SCR: 84.4 ± 8.9 N-mm vs. NSC: 722.6 ± 156.8 N-mm; P = .005), but no difference in energy absorbed was found at the ultimate load.

Conclusions

PT-SCR resulted in similar stiffness to NSC at lower loads, yield displacement, and energy absorbed to ultimate load. The ultimate load of the PT-SCR was approximately 54% of the NSC, which is comparable with the percent of the ultimate load in rotator cuff repair and the intact supraspinatus at time zero.

Superior Capsular Reconstruction Provides Sufficient Biomechanical Outcomes for Massive, Irreparable Rotator Cuff Tears: A Systematic Review

PURPOSE

To critically review the literature reporting biomechanical outcomes of superior capsular reconstruction (SCR) for the treatment of massive and/or irreparable rotator cuff tears.

METHODS

A systematic review was performed following PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-analyses) guidelines using the PubMed, MEDLINE, and Cochrane Library databases in August 2020. Cadaveric studies were assessed for glenohumeral translation, subacromial contact pressure, and superior humeral translation comparing SCR with an intact cuff with reference to a torn control state.

RESULTS

A total of 15 studies (142 shoulders) were included in our data analysis. SCR showed improvements in superior humeral translation, subacromial contact force, and glenohumeral contact force when biomechanically compared with the massive and/or irreparably torn rotator cuff. No statistically significant differences were found between SCR and the intact rotator cuff regarding superior humeral translation (standard mean difference [SMD], 2.09 mm vs 2.50 mm; P = .54) or subacromial contact force (SMD, 2.85 mPa vs 2.83 mPa; P = .99). Significant differences were observed between SCR and the intact cuff for glenohumeral contact force only, in favor of the intact cuff (SMD, 1.73 N vs 5.45 N; P = .03).

CONCLUSIONS

SCR may largely restore static restraints to superior humeral translation in irreparable rotator cuff tears, although active glenohumeral compression is diminished relative to the intact rotator cuff.

CLINICAL RELEVANCE

Investigating the biomechanical outcomes of SCR will help surgeons better understand the effectiveness of this treatment option.

Editorial Commentary: Superior Capsular Reconstruction Works Biomechanically but Should Be Used Selectively for Genuinely Irreparable Tears

Superior capsular reconstruction (SCR) has undergone extensive biomechanical and clinical study. Systematic review of biomechanical studies has shown that SCR functions to depress the humeral head and improve the glenohumeral register, which provides proof of concept. Clinical studies have shown the short-term effectiveness of SCR, but this is influenced by graft type and thickness, as well as surgical technique. These studies are mostly flawed because follow-up is brief, postoperative imaging is often lacking, and the results may not be generalizable. Multiple systematic reviews pooling the results of these various clinical studies have mostly produced diluted conclusions that are not clinically helpful. To date, there is a dearth of comparative studies to help guide the selection of SCR over other treatment options such as subacromial balloon spacer, partial repair with or without augmentation, tendon transfer, reverse shoulder arthroplasty, or even continued nonoperative care. Additionally, SCR is a salvage operation rather than an expedient alternative to careful mobilization of a rotator cuff tear for primary repair. Ultimately, large-scale, long-term imaging-based comparative clinical studies, rather than additional systematic clinical or biomechanical reviews, must provide the evidence needed to determine the precise indications and optimal technique for SCR.