An Innovative Partial Resurfacing Implant for Humeral Bone Loss in Shoulder Instability

By Nicholas Frisch, MD; Morgan Jones, MD, MPH; and Anthony Miniaci, MD, FRCSC

Despite the evolution of numerous surgical interventions, shoulder instability continues to be a challenge for orthopaedic surgeons. Partial cap resurfacing is a promising approach to humeral bone defects in select patients with shoulder instability that has been in use at Cleveland Clinic with encouraging preliminary outcomes.

A Difficult Problem

Shoulder instability is a multifaceted problem. Shoulder stability requires a fine balance of both soft-tissue and bony architecture. Anterior shoulder dislocations have long been known to result in a predictable pattern of pathology that includes avulsion of the anterior-inferior labrum from the glenoid, fracture of the anterior-inferior glenoid (bony Bankart lesion) and depression fracture of the posterior-superior humeral head (Hill-Sachs lesion). In a similar fashion, the less common posterior shoulder dislocation can result in analogous pathologies on the posterior glenoid and anterior humeral head (reverse Hill-Sachs lesion). Osseous defects of the humeral head play a significant and well-documented role in the pathoanatomy of chronic shoulder instability. A large defect, a young age and involvement in high-risk athletic activities predispose the patient to recurrent shoulder dislocations and worsening of the injury if not properly treated.

Surgical management options for shoulder instability vary and have been subjected to much debate in the literature and among surgeons. Arthroscopic repair of labral tears and capsule plication is a popular treatment modality. However, mounting evidence from numerous research studies shows high failure rates in patients with chronic instability and in patients with significant bony lesions. The presence of humeral head defects ranges from 65 to 71 percent in first-time dislocators and is as high as 93 to 100 percent in recurrent dislocators. Defects that are smaller than 20 percent relative to the size of the humeral head appear not to pose a significant threat to stability, whereas larger lesions result in a significant increase in recurrent instability.

Surgical Treatment of Humeral Bone Loss

Once the decision is made to address humeral bone loss surgically, there are several options to restore glenohumeral stability. Traditionally, bone grafting procedures range from osteoplasty or osteotomy correction for small defects to bony allograft reconstructions for larger lesions. Although a large allograft provides arguably the best anatomic reconstruction, its complications include graft resorption, possible disease transmission and challenges relating to graft availability. Another option is “remplissage,” in which posterior soft-tissue structures of the shoulder are anchored to the Hill-Sachs defect, but remplissage is a nonanatomic reconstruction that has been shown to decrease shoulder range of motion both in a cadaveric model and when comparing operative and nonoperative shoulders in postoperative patients.

The HemiCAP® partial humeral head resurfacing implant (Arthrosurface Inc., Franklin, Mass.) (Figure 1) is a relatively new alternative for managing both Hill-Sachs and reverse Hill-Sachs lesions in the setting of acute and chronic shoulder instability. This metallic resurfacing implant is an off-the-shelf device available in multiple sizes and multiple radii of curvature to provide a near-anatomic reconstruction while preserving native bone stock.

Figure 1. Intraoperative photograph of a partial cap resurfacing implant used for treatment of a Hill-Sachs lesion.

Our Experience with the Partial Resurfacing Implant

Partial cap resurfacing of humeral bone defects has been used specifically in the setting of shoulder instability for nearly five years at Cleveland Clinic. Our indications for the device include the following:

• A humeral head lesion of at least 25 percent of the total area of the articulating surface
• An engaging Hill-Sachs or reverse Hill-Sachs lesion
• Continued shoulder instability despite previous arthroscopic treatment of soft-tissue structures

Shoulders with deficient glenoid bone stock also undergo a Latarjet procedure at the same time as humeral defect resurfacing (Figure 2). All operations are performed through a deltopectoral approach, except for one case in which a muscle-splitting technique was used.

Figure 2. Postoperative radiograph of a patient with recurrent shoulder instability treated with a combined Latarjet procedure and a partial cap resurfacing implant for a Hill-Sachs defect

Our investigations are ongoing, but results thus far are very encouraging. To date, 21 shoulders in 20 patients (mean age, 34 years; range, 17 to 72 years) have been evaluated, with a mean follow-up of 28.1 months (range, 6 to 56 months). Sixteen of the 21 shoulders have undergone partial cap placement for a Hill-Sachs lesion in anterior shoulder instability, and five have undergone a partial cap placement to treat a reverse Hill-Sachs lesion.

None of the 21 shoulders has suffered a dislocation following HemiCAP implantation. Review of patient-reported outcome scores from both the Short-Form Health Survey (SF-12) and the Musculoskeletal Review of Systems reveals statistical improvement following surgery, and more than 80 percent of patients report a return to activity levels comparable to those before their shoulder injuries. Although these are relatively generic outcomes scores, improvement on these measures indicates overall patient improvement and increased quality of life. All patients undergoing shoulder surgery at Cleveland Clinic now also complete the shoulder-specific Penn Shoulder Score, with preliminary results in our patients showing a similar trend in improvement postoperatively.

Although recurrent glenohumeral instability remains a difficult problem to treat, partial resurfacing arthroplasty of focal defects appears to be a promising technique for managing humeral bone loss.

About the Authors

Dr. Frisch was the chief resident in the Department of Orthopaedic Surgery.

Dr. Jones is a staff surgeon in the Department of Orthopaedic Surgery and the Center for Sports Health. He specializes in sports medicine surgery and arthroscopy of the shoulder, knee, foot and ankle.

Dr. Miniaci is a staff surgeon in the Department of Orthopaedic Surgery and the Cleveland Clinic Sports Health facility. He specializes in shoulder reconstruction, knee reconstruction and cartilage resurfacing.