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

Superior capsular reconstruction for irreparable posterosuperior rotator cuff tears

Although the superior portion of the shoulder joint capsule is a clearly distinct structure, its ability to prevent vertical humeral head translation in irreparable rotator cuff tears remains controversial. The clinical results of superior capsule reconstruction (SCR) in this context are satisfactory but the radiological outcomes are poor in up to two-thirds of patients. Moreover, there is no proof that SCR is more beneficial than simply doing a subacromial debridement, a partial repair or a tenotomy of the long head of biceps. Furthermore, graft healing is not predictive of success. Given the lack of comparative studies with high level of evidence (level 1 or 2), we cannot conclude that this surgical technique (and its many variants) has a place in our treatment paradigm. Also, it seems that xenografts are no longer being used given the high rate of structural failure seen on MRI and the large number of complications. If the long head of biceps tendon is still intact at the time of surgery, it is a feasible option for SCR given the reasonable cost and minimal complications. If it is not - but the subscapularis tendon is intact or repairable - an allograft or a non-local autograft should be considered, despite its unpredictable clinical results. Surgeons should inform patients of the high rate of radiological repair failure and the worse results if a reverse shoulder arthroplasty should be needed subsequently. Level of evidence: 4.

Superior Capsular Reconstruction Partially Restores Native Glenohumeral Joint Loads In A Dynamic Biomechanical Shoulder Model

PURPOSE

To evaluate the effect of an irreparable posterosuperior rotator cuff tear (PSRCT) on glenohumeral joint loads and to quantify improvement following superior capsular reconstruction (SCR) using an acellular dermal allograft.

METHODS

Ten fresh-frozen cadaveric shoulders were tested using a validated dynamic shoulder simulator. A pressure mapping sensor was placed between the humeral head and glenoid surface. Each specimen underwent the following conditions: (1) native, (2) irreparable PSRCT, (3) SCR using a 3mm-thick acellular dermal allograft. Glenohumeral abduction angle (gAA) and superior humeral head migration (SM) were measured using 3D motion tracking software. Cumulative deltoid force (cDF) and glenohumeral contact mechanics, including contact area (gCA) and contact pressure (gCP), were assessed at rest,15°,30°,45°, and maximum angle of glenohumeral abduction.

RESULTS

The PSRCT resulted in a significant decrease of gAA along with an increase in SM, cDF, and gCP (P<.001, respectively). SCR did not restore native gAA (P<.001), however, SM was significantly reduced (P<.001). Further, SCR significantly reduced deltoid forces at 30° (P=.007) and 45° of abduction (P=.007) when compared to the PSRCT. SCR did not restore native cDF at 30°(P=.015), 45°(P<.001), and maximum angle (P<.001) of glenohumeral abduction. Compared to the PSRCT, SCR resulted in a significant decrease of gCP at 15°(P=.008), 30°(P=.002), and 45°(P=.006). However, SCR did not completely restore native gCP at 45° (P=.038) and maximum abduction angle (P=.014).

CONCLUSION

In this dynamic shoulder model, SCR only partially restored native glenohumeral joint loads. However, SCR significantly decreased glenohumeral contact pressure, cumulative deltoid forces, and superior migration, while increasing abduction motion, when compared to the posterosuperior rotator cuff tear.

CLINICAL RELEVANCE

These observations raise concerns regarding the true joint preserving potential of SCR for an irreparable posterosuperior rotator cuff tear, along with its ability to delay progression of cuff tear arthropathy and eventual conversion to reverse shoulder arthroplasty.

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.

Relationship between the progression of posterosuperior rotator cuff tear size and shoulder abduction function: A cadaveric study via dynamic shoulder simulator

Posterosuperior rotator cuff tear (PSRCT) is one of the most common shoulder disorders in elderly people’s daily life; however, the biomechanical relationship between PSRCT and shoulder abduction function is still controversial. In this study, a total of twelve freshly frozen cadaveric shoulders were included and tested in five conditions: intact rotator cuff, 1/3 PSRCT, 2/3 PSRCT, entire PSRCT, and global RCT. In each condition, extra load (0%, 45%, and 90% failure load) was sequentially added to the distal humerus, and the function of the remaining rotator cuff was mainly evaluated via the middle deltoid force (MDF) required for abduction. It is found that the peak MDF is required for abduction did not differ among the three PSRCT conditions (1/3 PSRCT: 29.30 ± 5.03 N, p = 0.96; 2/3 PSRCT: 29.13 ± 9.09 N, p = 0.98; entire PSRCT: 28.85 ± 7.12 N, p = 0.90) and the intact condition (29.18 ± 4.99 N). However, the peak MDF significantly differed between the global RCT (76.27 ± 4.94 N, p < 0.01) and all PSRCT and intact conditions. Under 45% failure load, the MDF of the entire PSRCT and global tear conditions were significantly increased compared with another status. With the 90% failure load, only the 1/3 PSRCT condition maintained the same shoulder function as the intact rotator cuff. These biomechanical testing jointly suggested that the weight-bearing ability of the shoulder significantly decreased as PSRCT progressed.

Editorial Commentary: Shoulder Superior Capsular Reconstruction Graft Tensioning Between 30° and 40° of Glenohumeral Abduction Is Recommended: The Balance Beam of Superior Capsular Reconstruction

Massive irreparable rotator cuff tears in young, active patients pose a challenging treatment dilemma. Since the relatively recent development of the superior capsular reconstruction (SCR) procedure, the technique has been increasingly used to stave off reverse total shoulder arthroplasty in this demographic. As a result of continued output of supportive literature, both biomechanically and clinically, SCR has been adopted by surgeons despite some technical aspects of the procedure not being fully elucidated. One notable topic of study is the ideal glenohumeral position in which to determine graft length and therefore graft tension. Tensioning inevitably affects glenohumeral joint kinematics, including superior humeral head translation, subacromial contact pressure, and graft healing potential. Although it is currently known that some degree of glenohumeral abduction is necessary for appropriate graft tensioning, and there are some biomechanical studies from our group and other groups that have looked at this, there is not a clinically supported position in which to measure graft length and therefore set graft tension. Well-designed biomechanical studies will serve as the foundation for what is performed clinically. On the basis of the best available evidence, tensioning the graft between 30° and 40° of glenohumeral abduction is recommended and has yielded encouraging clinical outcomes for SCR in our patients.