Technique
The Double Endobutton Technique for AC Joint Reconstruction
GROUND BREAKING technique by Dr. Steven Struhl
This page walks through how the reconstruction is actually performed, from exposure through final repair. It is written for the reader who wants to understand the mechanics rather than the summary, which is often a patient facing surgery, sometimes a referring clinician, and occasionally another surgeon.
The procedure is Dr. Struhl’s own. He developed it beginning in 2002, holds United States Patent 8,162,997 for the device, and has performed more than 200 of these reconstructions. Steven Struhl, MD is board certified in orthopedic surgery and separately in sports medicine, completed his sports medicine fellowship at Penn State University, and serves on the faculty of NYU School of Medicine.
The Principle Behind the Construct
Reconstructing a separated AC joint means restoring the connection between the collarbone and the coracoid process of the shoulder blade, replacing coracoclavicular ligaments that have torn completely.
The historical difficulty was never exposure or fixation strength. It was that the constructs used to hold the reduction could loosen, and a repair that loses position at three months looks identical at six weeks to one that holds.
“The problem with the older repairs was never the surgeon’s technique, it was the construct. A knot can slip and a knot can break. Removing the knot entirely removes the most common way these repairs fail.” – Steven Struhl, MD, Board Certified Orthopedic and Sports Medicine Surgeon
The solution is a continuous loop of suture joining two titanium buttons, manufactured to a fixed length rather than tied or tensioned during surgery. With no knot, there is nothing to slip. With a preset length, there is no hand tensioning to under or overcorrect.
How the Procedure Is Performed
Exposure
A single short incision is made over the distal clavicle, giving access to both the collarbone and the coracoid beneath it. The exposure is deliberately limited, since a smaller opening means less soft tissue disruption and a more comfortable early recovery.
Bone Preparation
A channel is drilled through the clavicle and, in axial alignment beneath it, through the base of the coracoid. Alignment matters here more than anywhere else in the procedure, because the two tunnels must line up for the construct to seat correctly and load evenly.
Endobutton Implant
The construct consists of two small titanium buttons joined by a continuous loop of high strength suture. The loop length is selected to match the distance between the top of the clavicle and the underside of the coracoid, which is measured rather than estimated.
Endobutton Passage
The lower button is passed through both tunnels and flipped beneath the coracoid, where it seats against the undersurface of the bone. The upper button remains above the clavicle. Confirming the lower button has flipped and seated flush is a critical checkpoint.
Fixation
With both buttons seated, the construct holds the clavicle in anatomic position without further tensioning. The fixed loop length sets the reduction, which is the central difference from adjustable systems where the surgeon tensions by feel.
Final Repair
The acromioclavicular capsule and the deltotrapezial fascia are repaired over the construct, and biologic augmentation is added through coracoacromial ligament transfer or direct coracoclavicular ligament repair. The hardware holds the reduction while biology creates the durable long term result.
Why Biologic Healing Matters as Much as the Hardware
A construct holds a reduction. It does not, on its own, produce a permanently stable joint. What produces that is dense scar tissue forming between the coracoid and the clavicle over the months after surgery, effectively a new ligament.
In the published outcomes study, MRI in the patients evaluated demonstrated exactly that, dense scar tissue bridging the two bones. That is why the ligament transfer and fascial repair are performed rather than relying on fixation alone, and why the early sling period is protected rather than rushed.
Published Results
Dr. Struhl’s outcomes appeared in The American Journal of Sports Medicine in 2015, following thirty five patients for a mean of 5.2 years, with individual patients followed as long as twelve years.
- Stability: the construct remained stable in all but one patient across the study period.
- Position: eighty seven percent maintained a coracoclavicular interval difference under two millimeters.
- Function: mean Constant and ASES shoulder scores of 98 out of 100.
- Complications: no infections, no fractures, no perioperative complications.
Click here to open and read Dr. Struhl’s published article.
Frequently Asked Questions About the Technique
- Because a knot is a failure point that exists after the surgeon has finished. Knots can slip and suture can break at the knot, and both cause the collarbone to drift back upward months later. A continuous loop with no knot removes that mechanism entirely.
- Adjustable systems let the surgeon tension the construct during surgery, which sounds like an advantage but introduces a mechanism that can loosen afterward. Published reports have documented fixation loss with adjustable loop devices. The fixed length loop cannot lengthen.
- A single short incision over the distal clavicle, considerably smaller than the exposure older open reconstructions required. Most patients find the resulting scar modest and it sits in an area typically covered by clothing.
- Yes. The titanium buttons and the suture loop remain in place. They are small, they sit against bone rather than under skin where they would be felt, and they do not typically require removal.
- The procedure is generally performed on an outpatient basis and most patients go home the same day. Exact operative time depends on whether the injury is acute or chronic and whether additional repair is required alongside the reconstruction.
- Yes, and most patients in the published study were chronic cases. Reconstruction of an older injury is more involved, since retracted tissue must be mobilized, but results were comparable to the acute group. Timing and its effect on the procedure is covered here.
Schedule a Surgical Consultation in New York City
Understanding the procedure is useful, and what most patients actually need is someone to tell them whether they need it, which begins with confirming the grade was measured properly. Dr. Struhl evaluates AC joint injuries at his Manhattan and White Plains offices and reviews outside imaging for patients traveling from elsewhere. Contact our practice at (212) 207-1990 in New York City or (914) 328-4111 in Westchester.
Current technique using a complete two button technique
The procedure is simplified even further by modifying the implant so that both buttons are on the same continuous loop and it is no longer necessary to slide the second button into the loop after it is passed throught the clavicle. The basic steps are the same but now with two buttons on the same loop the passage and deployment is much simpler. The device is passed in the reverse direction from the original technique, being passed from the underside of the coracoid up through the coracoid bone and then the clavicle. Once it exits the clavicle it is simply “flipped” and deployment is complete. The rest of the steps are the same. If extra length is needed then either one or two washers are placed on top of the clavicle and the button sits atop the washer(s).
Contact our practice today to schedule a consultation with Dr. Struhl.
