Topic: Investigating the effect of a humeral head lesion on the biomechanics of the shoulder joint and the impact of allograft reconstruction of the humeral head on shoulder biomechanics and stability
Results: Learning to what degree a lesion causes shoulder instability and whether repairing the defect with allograft reconstruction will restore that stability
Patient Care application of results: Knowledge of when to repair humeral head lesions with allograft in addition to standard surgical repair to improve stability
Simplified patient care application: Zeroing in on when to treat humeral head lesions with allografts to improve shoulder stability after failed standard surgical repair
Shouldering forward for an anatomic solution
OREF-funded study examines shoulder stability
By Jay D. Lenn
Jon K. Sekiya, MD, associate professor of orthopaedic surgery at the University of Michigan, studied electrical engineering in college, but a knee injury related to collegiate wrestling introduced him to the field of orthopaedic surgery and motivated him to change his career plans. He discovered that the problem-solving challenges of clinical practice were equally engaging, and he adds, “I became even more excited when I started getting involved in research and solving bigger problems.”
With funding support from the Musculoskeletal Transplant Foundation, OREF awarded Dr. Sekiya a Research Grant in 2007 to address a long-standing problem: the contribution of a humeral head lesion to recurring shoulder dislocation after a surgical procedure to stabilize the joint. He is investigating the effect of a humeral head lesion on the biomechanics of the shoulder joint and the impact of allograft reconstruction of the humeral head on shoulder biomechanics and stability.
Anatomy of a dislocated shoulder
Dislocation of the ball-and-socket shoulder joint often affects younger patients active in sports or engaged in military activity. When the humeral head shifts forward out of the glenoid cavity, either the humeral head, the rim of the glenoid cavity, or both can suffer damage. The resulting notch or dent in the humeral head, called a Hill-Sachs lesion, appears to affect how well the joint subsequently fits together and functions.
Surgery to stabilize the joint includes procedures that “tighten up” the joint capsule, the fluid-filled structure made of ligaments that encases the joint. Another approach, called the Bristol-Latarjet procedure, relocates a bony projection from the scapula (coracoid process) to the front of the glenoid cavity. This transfer of bone creates a barrier intended to prevent the humeral head from slipping out of the socket.
These corrective procedures are often associated with complications, such as arthritis or limited range of motion in the shoulder — particular problems for patients who hope to resume their prior physical activities. And patients may also have recurring problems with shoulder instability, either shoulder dislocation or subluxation, when the ball does not slip completely out of the socket and then returns to its normal position.
Could lesions lead to instability?
There is ample evidence that a Hill-Sachs lesion may contribute to recurring shoulder instability, but its contribution to the problem has not been well-established. Studies have defined the average size of the lesions and described how the lesion can engage, or “get caught” on, the rim of the socket. But details are still relatively thin about the role of a Hill-Sachs lesion in joint function, the failure of corrective surgery, and recurring shoulder instability.
Standard surgeries to restore stability do not address Hill-Sachs lesions. Although allograft reconstruction is common in knee repair, it hasn’t been used often in shoulders, and little has been published about the effect of humeral head repair on surgical outcomes.
To investigate this issue, Dr. Sekiya and his colleagues are studying cadaver shoulders attached to a robotic device. This system, developed at the Musculoskeletal Research Center of the University of Pittsburgh, where Dr. Sekiya previously served on the faculty, enables the researchers to quantify the stability of the shoulder. Each shoulder is secured to the robotic device, which moves the humerus through various normal positions. Sensors attached at different sites in the shoulder joint provide data about the range of motion, forces at the point of contact between the humeral head and glenoid cavity, and forces within the joint capsule.
One major goal of the study is to determine what degree of injury is detrimental to shoulder stability. “We’re trying to quantify how big a bone defect is, biomechanically, an issue,” stated Dr. Sekiya. After establishing baseline data about each shoulder joint, the researchers create lesions — comparable to typical Hill-Sachs lesions — of increasing size to determine how lesion size affects biomechanical factors.
Putting shoulders in their place
Surgery to restore stability will be either the Bristow-Latarjet procedure or an allograft reconstruction of the humeral head to repair the fabricated lesions. The reconstruction involves the insertion of a bone “wedge” that matches the size of the lesion and is secured with screws.
In the current study, the researchers will conduct a postsurgical analysis of each cadaver shoulder using the robotic system. Dr. Sekiya hypothesizes that, compared with standard surgery, the procedure with allograft reconstruction will better restore joint contact forces, forces in the joint capsule, and motion of the intact shoulder. He believes that restoring the anatomic integrity of the joint will contribute to greater shoulder stability.
Dr. Sekiya noted how valuable the outcome of this research may be to his own clinical experience. “I had a patient who had had three surgeries. He failed two arthroscopies and one open procedure. He presented to me with a huge bone defect that I reconstructed — his glenoid and his humeral head with osteoarticular allografts. And he was finally stable. He had thought he would never be stable again, so he was so happy.”
Fix it the first time
Dr. Sekiya hopes that a better understanding of the impact of Hill-Sachs lesions and the potential of allograft reconstruction could improve clinical decisions. “Let’s get a better understanding of this,” he says. “Let’s fix it the first time. [If the lesion is] big enough, fix it right away.” If the lesion is not “big enough” to contribute to shoulder instability, Dr. Sekiya explained, then a patient can be spared the additional procedure.
Dr. Sekiya noted that OREF played a critical role in helping him move his investigation to the next level. He described the search for sustained funding as essential and an ongoing process. “If you don’t have it, you can’t do the research, you can’t do the pilot phase, you can’t get the next grant.”
Dr. Sekiya hopes this research will lead to a better understanding of how Hill-Sachs lesions may influence shoulder instability and require something other than standard surgical interventions. And equally important, this work may lay the foundation needed for developing subsequent clinical investigations to judge the benefit of allograft reconstructions in the shoulder. Jay D. Lenn is a contributing writer for OREF and can be contacted at email@example.com