Why Do Some RTSA Patients Have Poor Outcomes?
A recently published study examines potential risk factors for poor recovery of active anterior elevation after reverse total shoulder arthroplasty. But the most valuable pearls for surgeons may be the identification of specific surgical techniques that were used in the poorly performing patient population.
Timothy G. Reish, MD, and Daniel H. Wiznia, MD
Jeon YS, Rhee YG.Factors associated with poor active anterior elevation after reverse total shoulder arthroplasty. J Shoulder Elbow Surg. 2017 Dec 21. pii: S1058-2746(17)30687-0. doi: 10.1016/j.jse.2017.10.027.
Jeon and Rhee, from the College of Medicine, Kyung Hee University, Seoul, Republic of Korea, conducted aretrospective chart review of 76 patients who underwent primary reverse total shoulder arthroplasty (RTSA) using the reverse-type Aequalis prosthesis (Tornier; Montbonnot, France) to treat the following conditions:
- Cuff tear arthropathy
- Rheumatoid arthritis
- Post-traumatic arthritis
- Posti-infectious arthritis
- Proximal humerus fractures
They investigated potential causes of poor outcomes to clarify why RTSA was not successful in some patients. Patients with poor outcomes were identified as those with poor recovery of active anterior elevation after undergoing RTSA.
Patients were evaluated at an average of 34 months after surgery. Potential risk factors collected by Jeon and Rhee were:
- Preoperative pathologic diagnosis leading to surgery
- Presence of preoperative pseudoparalysis
- Patient comorbidities
- Radiographic parameters, including acromiohumeral distance, lateral humeral offset, alteration of humerus lateralization and distalization, and medialization of the center of rotation
- Preoperative deltoid muscle volume assessed on preoperative MRI.
Lateral humeral offset was defined as the distance from the lateral edge of the acromion to the most lateral projection of the greater tuberosity.
Jeon and Rhee found that patients who had increased lateral humeral offset in anRTSA prosthesis designed to be medialized had poor active anterior elevation. Patients with a satisfactory outcome as a group experienced a mean decrease in lateral humeral offset of -2 ± 6 mm, while patients in the unsatisfactory group experienced a mean increase in lateral offset of 3 ±5 mm.
Pre-investigation, Jeon and Rhee had hypothesized that postoperative outcomes would be negatively influenced by:
- Preoperative pseudoparalysis
- Deltoid muscle volume
- Patient comorbidities
They found, however, that none of these parameters negatively impacted outcomes. Instead, patients with increased lateral humeral offset had a statistically significant chance of a poor outcome.
A medialized reverse shoulder prosthesis design – based on Grammont’s principle that a medialized center of rotation tensions the deltoid – improves joint stability and allows patients to flex and abduct the shoulder. A medialized and inferiorly placed center of rotation increases the deltoid’s mechanical advantage by lengthening its fulcrum, which provides for increased shoulder abduction.
Studies examining the outcomes of RSTAperformed with implants based on Grammont’s design concepts have demonstrated satisfactory long-term outcomes. Yet a subset of these patients has experienced poor outcomes. Deltoid muscle strength and function have been considered critical to having a successful outcome. This study showed a non-statistically significant trend that low anterior deltoid muscle volume negatively impacted function.However, the study did not demonstrate any relationship between the pathologic diagnosis leading to surgery and functional outcome or patient comorbidities and functional outcome.
Jeon and Rhee found that patients with an increase in lateral humeral offset had poor active anterior elevation, and theyshowed a trend toward patients with the worst anterior elevation recoveryhaving the highest increase in lateral humeral offset.
Some of the highest-yield surgical advice was hidden within the discussion section of the paper. Jeon and Rhee identified specific surgical techniques in the poorly performing patient population that were found to correlate with an increase in lateral humeral offset:
- High humeral head cuts
- Insufficient insertion of the humeral stem
- Thicker liner insertion
These technical insights are valuable pearls for the surgeon to weigh when conducting the humeral osteotomy, preparing the humerus for the humeral stem, and trialing the polyethylene liners when balancing the joint.
As the factors that influence outcomes of RTSA continue to be elucidated, this study provides new insights regarding which surgical steps are most critical to improving patient outcomes. It is important to note that these findings cannot be extended to lateralized reverse shoulder prosthesis designs, as they were not included in the study.
Timothy G. Reish, MD, is the Director of the Insall Scott Kelly Institute and Clinical Assistant Professor, Division of Sports Medicine, Department of Orthopaedic Surgery, NYU Langone Medical Center – Hospital for Joint Diseases, New York, New York.Daniel H. Wiznia MD, Adult Reconstruction Fellow, Department of Orthopaedic Surgery, Insall Scott Kelly Institute/NYU Langone Medical Center – Hospital for Joint Diseases, New York, New York.
Dr. Reish has disclosed that he is a consultant with Conmed and Arthrex and that he serves on the design team with Catalyst Orthoscience. Dr. Wiznia has no disclosures relevant to this article.