The Impact of Conjoint Tendon Resection on Functional Internal Rotation of the Shoulder Following Reverse Shoulder Arthroplasty: A Prospective, Randomized Clinical Trial
Phase: NA
Conditions: Shoulder Injuries, Patient Satisfaction, Internal Rotation Contracture-shoulder
Sponsor: University of Missouri-Columbia

 
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The impact of conjoint tendon lengthening on functional internal rotation of the shoulder 
following reverse shoulder arthroplasty: A prospective, randomized clinical trial 
 
Date: 12 November 2022 
Version: 1 
NCT #: 05753904 
 
Principle Investigator: H. Mike Kim, MD 
Co-Investigator: Charles Gusho, MD 
Research Coordinator: Michael Nguyen  
 
 
 

 
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ABSTRACT 
Introduction 
Reverse total shoulder arthroplasty (RTSA) can reliably restore active forward elevation, 
abduction, and external rotation, which are often lost in patients with massive rotator cuff tears. 
However, functional internal rotation (i.e., functional movements of the hand behind the body) is 
often unsatisfactorily restored and/or lost after RTSA. This study aims to compare the standard 
surgical approach for RTSA to RTSA with conjoint tendon lengthening with the targeted metric 
being postoperative functional internal rotation.  
 
Methods and analysis 
This study will be a prospective, randomized-controlled clinical trial comparing standard of care 
RTSA to RTSA with conjoint tendon lengthening in 64 patients undergoing RTSA by a single 
surgeon. Participants and assessors will not be blinded to intervention. The primary outcome is 
postoperative functional internal rotation. Secondary outcome measures include VAS, ASES, 
SANE, PROMIS, and VR-12 scores, as well as forward elevation and external rotation at the side, 
and complications at any time point. Our null hypothesis is that patients who undergo conjoint 
tendon lengthening during RTSA will have significantly increased functional internal rotation and 
clinically significant improved above-mentioned scores compared to non-resected tendon patients. 
 
Ethics and dissemination 
This study is pending approval by the University of Missouri – Columbia Institutional Review 
Board Committee (2094589) 
 
Discussion 
Completion of this trial will provide evidence on the effectiveness of conjoint tendon lengthening 
for patients undergoing RTSA to improve functional internal rotation. If these patients have 
superior postoperative functional internal rotation, this trial has the capacity to change current 
clinical practice.  
 

 
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BACKGROUND 
It is well known that internal and external rotation of the shoulder are often limited following 
reverse total shoulder arthroplasty (RTSA). RTSA can reliably restore active forward elevation, 
abduction, and external rotation, which are often lost in patients with massive rotator cuff tears. 
However, functional internal rotation (i.e., functional movements of the hand behind the body) is 
often unsatisfactorily restored or even lost after RTSA.1–3 Limited internal rotation has been 
attributed to mechanical impingement of the humeral socket against bony structures or soft tissue. 
Various biomechanical studies have recently analyzed factors influencing functional internal 
rotation. These data suggest that lateralization of the center of rotation, inferior positioning of the 
glenoid component,4–6 a decreased glenosphere size,7 a more varus neck-shaft angle,8 and less 
humeral component retroversion9–12 are positively associated with improved internal rotation. 
However, it is not uncommon to observe limited functional internal rotation despite these 
measures. Limited internal rotation can be disabling for activities such as toileting, pulling up pants 
or shorts, or tucking in a shirt.1–3,13 The authors' intraoperative observation suggests that limited 
internal rotation is caused by soft tissue restraints rather than impingement of the humeral socket 
against bony structures. This observation calls for further research.  
 
 

 
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METHODS 
Study design  
The following protocol has been developed per Standard Protocol Items: Recommendations for 
Interventional Trials guidelines. This study will be a prospective randomized-controlled clinical 
trial (RCT) comparing outcomes after either RTSA or RTSA with conjoint tendon lengthening. 
The trial will be conducted at a single high-volume academic center in Columbia, Missouri. 
Blinding in surgical trials is difficult, and neither surgeons nor participants will be blinded to 
treatment allocation. However, the independent statistician will be blinded to allocation groups. 
 
Recruitment and consent 
The study population will consist of participants undergoing RTSA. Eligible participants will be 
identified at the shoulder and elbow clinic, be invited to take part in the trial, and will be informed 
of study details and provided with written information along with a detailed explanation of the trial 
by a member of the research team. Once a participant agrees to participate, and meets all inclusion 
criteria, they will be enrolled and randomized into one of two groups.  
 
Study participants 
Inclusion criteria 
- 
All patients undergoing primary RTSA 
 
Exclusion criteria 
- 
Revision RTSA 
- 
RTSA for acute proximal humerus fracture or fracture sequela  
 
Baseline measures 
The following will be collected from all participants preoperatively: 
- 
Age 
- 
Sex 
- 
Preoperative functional (operative) shoulder and contralateral shoulder range of motion if 
applicable 
- 
Indication for RTSA 
- 
Associated injuries 
- 
Medical comorbidities 
- 
Residence and ambulatory status 
 
Treatment allocation 
Individuals consenting to participate in the trial will be randomized to RTSA or RTSA plus 
conjoint tendon lengthening. Each patient will receive a study ID, and a computer randomization 
system will be used to allocate patients to receive either of two groups.  
 
 
Intervention  
All RTSAs will be performed by the attending surgeon (H.M.K) in a standard fashion through a 
deltopectoral approach. The skin will be incised with bovie electrocautery in standard fashion, and 
the dissection will be carried down through the subcutaneous tissue to the level of the shoulder. 
The subscapularis muscle will be incised and reflected to expose the shoulder joint. Following 

 
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surgical removal of the humeral head and reaming of the glenoid cavity, the Perform glenoid and 
humeral components of Tornier Stryker Reverse Shoulder system will be implanted. The sizes and 
offsets of the components will be chosen based on each patient's local anatomy which will vary 
among patients. Each of these surgical steps will be performed in all patients regardless of whether 
they are in the control or investigative group. Following final implant selection, the subscapularis 
tendon will be repaired using three transosseous nonabsorbable sutures whenever there is a 
reparable subscapularis tendon. After definitive implantation of the prosthesis is completed, and 
the subscapularis tendon is reattached, the investigative step will take place. In the control group, 
which is the group receiving a RTSA without conjoint tendon lengthening the subcutaneous tissue 
and skin will be closed in standard fashion. In the investigative group, prior to subcutaneous and 
skin closure, the conjoint tendon will be lengthened by approximately 2 cm. The conjoint tendon 
is comprised of the coracobrachialis and biceps short head tendon, which attach proximally to the 
coracoid process at the level of the shoulder. In the investigative group, as mentioned, the conjoint 
tendon will be released completely via a Z-shaped incision made at a level 2 cm distal to the 
coracoid process and sutured back in a lengthened position using #2 Ethibond suture for the 
patients assigned the conjoint lengthening group. Electrocautery will be used for the lengthening, 
and the underlying muscular portion of the conjoint tendon will be preserved. As mentioned above, 
the control group will not receive this conjoint tendon lengthening. Then, for the investigative 
group following lengthening and like the control group, the wound will be closed in layers, and 
the shoulder will be immobilized in an abduction sling.  
 
Postoperative management 
Postoperatively, patients will wear the sling for 4 weeks, after which supervised physical therapy 
will begin.  
 
Outcome measures 
The primary outcome will be functional internal rotation at six months. Functional internal rotation 
will be measured based on the highest anatomical level that the patient's thumb can reach: 
- 
Side 
- 
Ipsilateral buttock 
- 
Lower lumbar 
- 
Mid-lumbar 
- 
Upper lumbar 
- 
Thoracolumbar junction 
- 
T10 and above 
 
Additional secondary outcome measures and associated timepoints will include:   
- 
Six weeks: pain VAS 
- 
Three months: pain VAS, ASES, SANE, Forward elevation, external rotation at the side 
- 
Six months, one year, and two years: pain VAS, ASES, SANE, PROMIS, VR-12, Forward 
elevation, external rotation at the side  
- 
Complications at any time points: dislocation, severe pain, arm muscle cramping, implant 
loosening, infection, hematoma, medical complications, blood transfusions, non-union, 
mortality rate. Specific surgical complications include wound infections, intraoperative 
fracture, deep surgical infection, and periprosthetic fractures.   
 

 
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Follow-up 
All participants were be surveilled per standard of care at our hospital for the targeted patient 
group. Patients will return for follow-up at two weeks, six weeks, three months, six months, one 
year, and two years. Plain radiographs will be taken at the immediate postoperative (anesthesia 
care unit) setting and at all scheduled follow-up visits. Radiographs obtained in clinic at the 
aforementioned follow-up intervals are standard of care and are not part of the research explicitly. 
For example, all patients regardless of whether they are in the control or investigative group will 
receive radiographs at the above intervals. A member of the research team will review participant 
outcome measures at each appointment.  
 
Sample size calculation 
To reject the null hypothesis that functional internal rotation is equal between groups, 32 subjects 
are needed per group with a power set at 80%, and with a Type 1 error probability of 5%.  
 
 
Data collection and management, and risks 
Data collection will primarily be electronically based. A breach of confidentiality and/or privacy 
is a risk of this study. To prevent this, all collected data will be stored electronically in password-
protected files to protect patient identity and information. All information will be collected and 
reviewed by the research team only. Data will be maintained on a password-protected computer 
that will be accessible only to the study team. No patient identifiers will be maintained in the 
database. Every attempt will be made to minimize missing data. Multiple contact details will be 
taken at recruitment, and a system of reminders plus phone contact if applicable will be made to 
ensure patients make follow-up appointments. Additionally, there is an additional risk of being 
withdrawn from the Standard of Care treatment if they are randomized into the experimental 
condition. Benefits of this procedure included improved functional internal rotation following 
surgery and the potential to change clinical practice. 
 
Data analysis 
The primary outcome (i.e., functional internal rotation at six months) will be compared between 
the groups using Mann-Whitney U test. Other range of motion data (i.e., forward elevation and 
external rotation at the side), pain VAS, ASES, SANE, PROMIS, and VR-12 will be compared 
using either independent t-test or Mann-Whitney U test depending on the normality of data 
distribution of each variable. The correlations between functional internal rotation and all other 
variables will be analyzed using Spearman rank correlation or Pearson correlation.  
 
Patient and public involvement 
Patients who undergo RTSA often have limitation of functional shoulder internal rotation 
following surgery. However, there are no literature that discuss conjoint tendon lengthening as a 
possible therapeutic intervention. The current research question was developed to address this, and 
patients were not involved in the design, recruitment, or conduct of this study. The future results 
of this trial will be available through publication in a peer-reviewed journal, and at meetings if 
applicable.  
 
 
 

 
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ETHICS AND DISSEMINATION 
Safety  
While this trial compares a new surgical intervention technique with the current standard of care, 
serious adverse events are not anticipated, and therefore a data safety monitoring board will not be 
established at the commencement of this trial. Following conclusion of the trial, participant follow-
up will follow local participating institute guidelines.  
 
The potential risk of patients enrolled in this study stems from potential side effects of conjoint 
tendon lengthening, which has not been studied or reported previously to our best knowledge.  
1. Although there are no published studies describing exactly the same procedure, there is one 
published study that showed good clinical outcomes with no complications following conjoint 
tendon release. Tashjian et al. reported significantly improved anterior shoulder pain with no 
complications following a conjoint tendon release procedure in patients who were experiencing 
anterior shoulder pain after RTSA [Tashjian RZ, Frandsen JJ, Christensen GV, Chalmers PN. 
Conjoint tendon release for persistent anterior shoulder pain following reverse total shoulder 
arthroplasty. JSES Int. 2020 Jul 31;4(4):975-978. doi: 10.1016/j.jseint.2020.07.005. PMID: 
33345243; PMCID: PMC7738564].  
2. Additionally, the Latarjet procedure is a procedure that the orthopaedic community has been 
doing for anterior shoulder instability for decades. This procedure involves cutting the coracoid 
process and moving it distally, which has essentially the same effect as a conjoint tendon 
release/lengthening. There have been no reports or my anecdotal experience of complications 
related to the conjoint tendon (e.g., biceps muscle cramping, loss of biceps or other muscle 
strength, etc) following this procedure. This can be indirect evidence that releasing/lengthening 
the conjoint tendon has no major or minor consequences. 
3. Lastly, the PI (H. Mike Kim, MD) has been performing this conjoint tendon lengthening on his 
primary RTSA patients for last 6 months, and there has been no complications. There has been no 
decreased biceps muscle strength, biceps cramping pain, instability of the prosthesis, hematoma, 
neurovascular injuries, or infection. In fact, the patients seem to be outperforming in many aspects 
those patients who did not receive a conjoint tendon lengthening.  For example, they seem to have 
better improvement of pain and range of motion especially in internal rotation. 
 
Ethics 
Any protocol modifications will be reported to the IRB, trial registry, protocol database, and 
individual participants. All adverse events will be reported to the IRB committee as well, and 
confidentiality of individuals involved in the trial will be maintained as discussed above.  
 
Dissemination 
The results of the study will be presented at national orthopaedic meetings and the results will be 
published in an orthopaedic, biomechanical, or surgical research journal following completion of 
the trial.  
 
 
 

 
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DISCUSSION 
A recently study by Horchreiter et al.14 found that active extension of at least 40° is a prerequisite 
for satisfactory functional internal rotation after RTSA, with an average loss of 16° of active 
extension following RTSA compared to the contralateral unaffected side. Our clinical and 
biomechanical observation is that the conjoint tendon becomes tight with extension, which appears 
to be the main limiting factor for extension and ultimately internal rotation after RTSA. Based on 
this observation and the study by Horchreiter et al., we hypothesize that the conjoint tendon is a 
factor limiting extension and internal rotation after RTSA, and that releasing/lengthening the 
conjoint tendon may increase extension and affect the prosthetic joint biomechanics. To this end, 
we proposed a prospective randomized clinical trial in which we will randomize patients who 
undergo primary RTSA into two groups, conjoint tendon lengthening group vs. control group, and 
compare various clinical outcome measures including functional internal rotation at multiple 
postoperative time points. We hypothesized that conjoint tendon lengthening will have 
significantly greater extension and functional internal rotation of the shoulder following RTSA 
compared to the control group. This trial has the capacity to find a safe and effective way to 
improve functional internal rotation after RTSA. If so, a novel surgical application of this concept 
may lead to a substantial improvement in the disabling limitation of internal rotation following 
RTSA. Limitations of this study include the lack of blinding of surgeon, participants, and research 
assessors who have access to operative notes. Blinding was not used in this study as it is impossible 
to blind the participating surgeon to operative technique. 
 
Inclusion of participants into the trial will commence in January 2023, with data collection 
expected to be complete by the end of 2025. With follow up of two years, the data will be expected 
to be presented around 2026.  
 
 

 
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