Abstract
A primary goal of shoulder arthroplasty is to place the components in anatomic version. However, traditional instrumentation does not accommodate glenoid wear patterns. Therefore, many investigators have attempted to use computer modeling or CT-based algorithms to create custom targeting guides to achieve this goal.
There are some recent studies investigating the use of custom guides. Iannotti et al. published in JBJS-American in 2012 on the use of patient specific instrumentation. There were 31 patients included in the study. The authors found that the planning software and patient specific instrumentation were helpful overall, but particularly of benefit in patients with retroversion in excess of 16 degrees. In this group of patients, the mean deviation was 10 degrees in the standard surgical group and 1.2 degrees in the patient specific instrumentation group.
Throckmorton presented a study at the AAOS in 2014 on 70 cadaveric shoulders. There was one high volume surgeon (>100 shoulder arthroplasties a year), two middle volume surgeons (20–50 shoulder arthroplasties a year), and two low volume surgeons (less than 20 shoulder arthroplasties per year). Overall, the custom guide was significantly more accurate than standard instrumentation. The custom guides were found to be especially more accurate among specimens with associated glenoid wear. There were no strong trends to indicate consistent differences between high, medium, and low volume surgeons. The authors concluded that custom guides have narrower standard deviation and fewer significant errors than standard instrumentation.
Custom guides continue to evolve for use in shoulder arthroplasty including some guides that allow the surgeon to decide intra-operatively between anatomic shoulder arthroplasty and reverse arthroplasty. Additional studies will be necessary to further define the role of patient specific instrumentation in practice.
