Stephanie Muh, MD
One of the most difficult aspects of shoulder arthroplasty remains the ability to correct glenoid deformity with accurate reaming and positioning of the glenoid implant. Even with experienced surgeons, it remains a challenge to appreciate how much version and inclination is corrected intra-operatively. The success of patient-specific instrumentation (PSI) in total hip and knee arthroplasty has naturally led to the surge of growth of PSI in shoulder arthroplasty. However, the key question of whether PSI is better than standard instrumentation is unknown.
21 of the 22 articles required the assistance of a physical PSI component to be manufactured prior to surgery. It took an average of 10 days to 5 weeks for production once the preoperative plan was completed.
This meta-analysis attempts to determine whether PSI significantly improves implantation accuracy during shoulder arthroplasty. The authors review all the available literature on PSI in shoulder arthroplasty including both cadaveric and clinical studies looking at a variety of available industry manufactured components. A total of 22 articles were compared and all preoperative planning programs were predetermined with a goal of 0 degrees of version and 0 degrees of inclination for total shoulder arthroplasty (TSA) and 5-10 degrees of inferior inclination for rTSA. 21 of the 22 articles required the assistance of a physical PSI component to be manufactured prior to surgery. It took an average of 10 days to 5 weeks for production once the preoperative plan was completed. The authors found that in 91% of articles, the postoperative errors were found to be less than 5 degrees with the assistance of PSI compared to preoperative plans. However, there was only 18% of articles that found PSI significantly reduced glenoid component malposition compared to standard instrumentation. Meta-analysis that directly compared PSI to standard instrumentation was only available for 7 articles (2 clinical, 5 cadaveric). While analysis did demonstrate an improvement in accuracy with PSI, it did not demonstrate any significant difference in accuracy when comparing PSI to standard instruments when looking at differences in version error (3 degrees), inclination error (1 degree) and offset (0.22mm).
I find this meta-analysis extremely useful for my practice. With the recent impetus for PSI hip and knee arthroplasty, it is natural that a similar push would extend to shoulder arthroplasty. However, there are unique challenges in the shoulder including the exposure, smaller bone surface area, and unique three-dimensional aspect of the glenoid that makes large PSI constructs in the shoulder difficult to circumnavigate. From personal experience, it is often difficult to attach the pre-made guides onto the glenoid with precision. Often, osteophytes, calcified labrum, or other soft tissue prevent accurate placement of the guides and therefore compromises the pre-planned procedure. There is also no ability to make an intra-operative adjustment with the guides if intra-operative findings necessitate changes. The meta-analysis also notes that with an experienced surgeon, there is no significant difference between PSI and standard instrumentation in achieving similar accuracy implanting glenoid components. Given the issues of increased additional cost of PSI components, increased operating room time, inability to intra-operatively adjust the preoperative plan, and time delay to surgery for completion of surgery assisted components, I believe the usefulness of PSI needs to be seriously considered when there does not seem to be any substantial advantage in accuracy and postoperative outcomes.
Stephanie Muh, MD, is deputy chief of service in the department of orthopaedics at Henry Ford Hospital West Bloomfield where she specializes in shoulder and elbow reconstruction, rotator cuff repair and arthritis. Dr. Muh completed her residency in orthopaedic surgery at the Henry Ford Hospital and shoulder and elbow fellowship at Case Western Reserve University/University Hospitals of Cleveland.