A biomechanical cadaveric study of patellar tendon allograft as an alternative graft material for superior capsule reconstruction

Glenohumeral Superior Translation and Subacromial Contract Pressure Are Both Improved With Superior Capsular Reconstruction: A Systematic Review and Meta-analysis of Biomechanical Investigations

PURPOSE

To review cadaveric studies evaluating the biomechanical outcomes of superior capsular reconstruction (SCR) with different graft types for the treatment of irreparable rotator cuff (RTC) tears.

METHODS

PubMed, Cochrane, and Embase were queried in January 2022 to conduct this meta-analysis using the following key words: "superior capsule reconstruction," "superior capsular reconstruction," and "biomechanics." Articles were included if they reported glenohumeral superior translation or subacromial contact pressure following SCR in cadaveric RTC tears. The review adhered to the Preferred Reporting Items for Systematic Reviews and Meta-analyses criteria. Number of shoulders, graft types, and biomechanical outcomes were recorded and analyzed with forest plots.

RESULTS

Twelve studies (95 shoulders) were included in the statistical analysis. There was a significant reduction in glenohumeral superior translation following SCR compared with RTC tear across 10 studies (79 shoulders) with standardized mean difference (SMD) -2.48 mm; confidence interval (CI) -3.28 mm, -1.69 mm. The SMD between fascia lata graft and RTC tear was -3.84 mm (CI -4.82 mm, -2.86 mm) and between dermal allograft and RTC tear was -2.05 mm (CI -3.10 mm, -1.00 mm). There was a significant reduction in subacromial contact pressure following SCR compared with RTC tear across 5 studies (55 shoulders) with SMD -3.49 MPa (CI -4.54 MPa, -2.44 MPa). The SMD between fascia lata graft and RTC tear was -3.21 MPa (CI -5.08 MPa, -1.34 MPa) and between dermal allograft and RTC tear was -3.89 MPa (CI -5.91 MPa, -1.87 MPa).

CONCLUSIONS

Independent of graft type, biomechanical studies suggest that SCR improves glenohumeral superior translation and subacromial contact pressure in comparison with RTC tear at time zero. There was no definitive evidence identified in this study to suggest a biomechanically superior SCR graft option.

CLINICAL RELEVANCE

Investigating the biomechanical outcomes of several graft types for superior capsular reconstruction will help surgeons better understand the efficacies of different graft types for use in superior capsule reconstruction surgery.

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.

Human Dermal Allograft Superior Capsule Reconstruction With Graft Length Determined at Glenohumeral Abduction Angles of 20° and 40° Decreases Joint Translation and Subacromial Pressure Without Compromising Range of Motion: A Cadaveric Biomechanical Study

PURPOSE

To compare the biomechanical effects of superior capsule reconstruction (SCR) graft fixation length determined at 20° and 40° of glenohumeral (GH) abduction.

METHODS

Humeral translation, rotational range of motion (ROM), and subacromial contact pressure were quantified at 0°, 30°, and 60° of GH abduction in the scapular plane in 6 cadaveric shoulders for the following states: intact, massive rotator cuff tear, SCR with dermal allograft fixed at 20° of GH abduction (SCR 20), and SCR with dermal allograft fixed at 40° of GH abduction (SCR 40). Statistical analysis was conducted using a repeated-measures analysis of variance and a paired t test (P < .05).

RESULTS

A massive cuff tear significantly increased total ROM compared with the intact state at 0° and 60° of abduction. SCR 20 or SCR 40 did not affect ROM. Compared with the intact state, the massive cuff tear model significantly increased superior translation by an average of 4.6 ± 0.5 mm in 9 of 12 positions (P ≤ .002). Both SCR 20 and SCR 40 reduced superior translation compared with the massive cuff tear model (P < .05); however, SCR 40 significantly decreased superior translation compared with SCR 20 at 0° of abduction (P ≤ .046). Peak subacromial pressure for the massive cuff tear model increased by an average of 486.8 ± 233.9 kPa relative to the intact state in 5 of 12 positions (P ≤ .037). SCR 20 reduced peak subacromial pressure in 2 of 12 positions (P ≤ .012), whereas SCR 40 achieved this in 6 of 12 positions (P ≤ .024).

CONCLUSIONS

SCR with dermal allograft fixed at 20° or 40° of GH abduction decreases GH translation and subacromial pressure without decreasing ROM.

CLINICAL RELEVANCE

With an increasing abduction angle for graft fixation, the medial-to-lateral graft length is decreased and the graft tension is effectively increased. Surgeons may increase shoulder stability without restricting ROM by fixing the graft at higher abduction angles. However, surgeons should remain cognizant of potential graft failure due to increased tension.

Biomechanical analysis of progressive rotator cuff tendon tears on superior stability of the shoulder

BACKGROUND

The biomechanical relationship between irreparable rotator cuff tear size and glenohumeral joint stability in the setting of superiorly directed forces has not been characterized. The purpose of this study was to quantify kinematic alterations of the glenohumeral joint in response to superiorly directed forces in a progressive posterosuperior rotator cuff tear model.

METHODS

Nine fresh-frozen cadaveric shoulders (mean age; 58 years) were tested with a custom shoulder testing system. Three conditions were tested: intact, stage II (supraspinatus) tear, stage III (supraspinatus + anterior half of infraspinatus) tear. At each condition, range of motion and humeral head positions were measured with a "balanced" loading condition, and with a superiorly directed force ("unbalanced loading condition"). At each of the 0°, 20°, and 40° of glenohumeral abduction positions, all measurements were made at 0°, 30°, 60°, and 90° of external rotation (ER). Two-way repeated measures analysis of variance with Tukey post hoc tests were performed for statistical analyses.

RESULTS

With the balanced load, no significant change in superior humeral head position was observed in stage II tears. Stage III tears significantly changed the humeral head position superiorly at 30° and 60° ER at each abduction angle compared with the intact condition (P ≤ .028). With superiorly directed load, stage II and stage III tears both showed statistically significant increases in superior translation at all degrees of ER for all degrees of abduction (P ≤ .035), except stage II tears at 0° ER and 40° abduction (P = .185) compared with the intact condition. Stage II tears showed posterior translations with 30° and 60° ER, both at 20° and 40° of abduction. Stage III tears also showed posterior translations with 90° ER for all abduction angles (P ≤ .039).

CONCLUSION

With superiorly directed loads, complete supraspinatus tendon tears created superior translations at all abduction angles, and posterior instability in the middle ranges of rotation for 20° and 40° of abduction. Larger tears involving the anterior half of the infraspinatus tendon caused significant superior and posterior translations within the middle ranges of ER for all abduction angles. In addition to superior instability, posterior translation should be considered when selecting or developing surgical techniques for large posterosuperior rotator cuff tears.

Modified Superior Capsule Reconstruction Using the Long Head of the Biceps Tendon as Reinforcement to Rotator Cuff Repair Lowers Retear Rate in Large to Massive Reparable Rotator Cuff Tears

PURPOSE

To retrospectively assess the clinical outcomes of the patients with large to massive reparable RCTs treated by arthroscopic rotator cuff repair (ARCR) combined with modified superior capsule reconstruction (mSCR) using the long head of biceps tendon (LHBT) as reinforcement with a minimum of 2 years of follow-up.

METHODS

We retrospectively evaluated 40 patients with large to massive reparable RCTs who underwent ARCR and mSCR (group I) between February 2017 and June 2018 (18 patients) or underwent ARCR and tenotomy of LHBT performed at the insertion site (group II) between January 2015 and January 2017 (22 patients). The pain visual analog score (VAS) was assessed preoperatively and 1, 3, 6, 12, 24 months postoperatively. American Shoulder and Elbow Surgeons (ASES) scores, the University of California, Los Angeles (UCLA) shoulder rating scale, and active range of motion (AROM) were assessed before surgery and 6, 12, and 24 months after surgery. The integrity of the rotator cuff and mSCR was evaluated using magnetic resonance images at 12 months postoperatively.

RESULTS

After surgery, both groups had significantly improved in VAS, ASES, UCLA and AROM scores in the final follow-up. There were no significant between-group differences in the characteristics of the patients before surgery. Group I had improved pain relief at 1 month (P < .001) and at 3 months (P < .01) after surgery. For the AROM, group I (flexion, external rotation, internal rotation) demonstrated better improvement than group II 6 months after surgery (all P < .05) and better internal rotation 12 and 24 months after surgery (all P < .05). The mSCR survival rate was 94.4% (17/18). The retear rate of repaired rotator cuffs for groups I and II was 16.7% (3/18) and 40.9% (9/22), respectively, and the differences were significant (P < .046).

CONCLUSIONS

ARCR combined with mSCR using LHBT as reinforcement may lead to a lower retear rate and earlier functional recovery than conventional ARCR with tenotomy of LHBT for large to massive reparable RCTs.

LEVEL OF EVIDENCE

Level III, retrospective therapeutic comparative trial.

A new approach to superior capsular reconstruction with hamstring allograft for irreparable posterosuperior rotator cuff tears: a dynamic biomechanical evaluation

BACKGROUND

Superior capsular reconstruction (SCR) treatment of massive, symptomatic, irreparable rotator cuff tears (RCTs) has become a more recently used procedure. However, there is a lack of consensus surrounding optimal graft choice for the SCR technique, and current dermal grafts have increased cost and are technically challenging because of a need for multiple implants. The purpose of this study was to biomechanically investigate a biological lower-cost alternative as a support for the superior capsule reconstruction concept: an isolated semitendinosus tendon (STT) allograft and a combination graft with the long head of the biceps tendon (LHBT) in an established massive posterosuperior RCT cadaver model.

METHODS

Ten fresh-frozen cadaveric shoulders (53.3 ± 12.4 years: range: 26-65) were tested on an established dynamic shoulder simulator using dynamic muscle loading. Cumulative deltoid forces, maximum abduction angle, and superior humeral head translation were compared across 4 testing conditions: (1) intact state, (2) massively retracted (Patte III), irreparable posterosuperior RCT, (3) SCR repair using an STT allograft, and (4) SCR repair using a combined STT-LHBT repair.

RESULTS

Intact shoulders required a mean deltoid force of 154.2 ± 20.41 N to achieve maximum glenohumeral abduction (55.3° ± 2.3°). Compared with native shoulders, the maximum abduction angle decreased following a massively retracted posterosuperior RCT by 52% (28.3° ± 8.4°; P < .001), whereas the cumulative deltoid forces increased by 48% (205.3 ± 40.9 N; P = .001). The STT repair and the STT-LHBT repair improved shoulder function compared with the tear state, with a mean maximum abduction angle of 30.6° ± 9.0° and 31.8° ± 7.7° and a mean deltoid force of 205.3 ± 40.9 N and 201.0 ± 34.0 N, respectively, but this was not statistically significant (P > .05). The STT-LHBT repair significantly improved the range of motion with respect to the tear state (P = .04).

CONCLUSIONS

In a dynamic shoulder simulator model, both the STT and the STT-LHBT repair techniques improved glenohumeral joint kinematics in an amount similar to previously reported "traditional" SCR techniques for treatment of an irreparable posterosuperior RCT.

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.

Biomechanics of tensor fascia lata allograft for superior capsular reconstruction

BACKGROUND

We hypothesized that in a cadaveric massive rotator cuff tear (MCT) model, a fascia lata (FL) allograft superior capsular reconstruction (SCR) would restore subacromial contact pressure and humeral head superior translation without limiting range of motion (ROM). Therefore, the objective of this study was to compare these parameters between an intact rotator cuff, MCT, and allograft FL SCR.

METHODS

Eight fresh cadavers were studied using a custom shoulder testing system. ROM, superior translation, and subacromial contact pressure were measured in each of 3 states: (1) intact rotator cuff, (2) MCT, and (3) MCT with SCR.

RESULTS

Total ROM was increased in the MCT state at 60° of abduction (P = .037). FL SCR did not restrict internal or external rotational ROM. Increased superior translation was observed in the MCT state at 0° and 30° of humeral abduction, with no significant difference between the intact cuff and FL SCR states. The MCT state significantly increased mean subacromial contact pressure at 0° of abduction with 30° and 60° of external rotation, and FL SCR restored this to intact levels. Peak subacromial contact pressure was increased for the MCT state at 0° of abduction with 30° and 60° of external rotation, as well as 30° of abduction with 30° of external rotation.

CONCLUSION

This study demonstrates a tensor FL allograft preparation technique for use in SCR. After MCT, FL SCR restores ROM, superior translation, and subacromial contact pressure to the intact state.

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.