What are the Benefits of CAOS for Shoulder Replacement?

Ari R Youderian, MD

Read complete study: Benefit of intraoperative navigation on glenoid component positioning during total shoulder arthroplasty

I have now performed my first 40 shoulder replacement cases with computer assisted orthopaedic surgery (CAOS).  As an early adopter of this technology, the meta-analysis by Sadoghi et al, “Benefit of intraoperative navigation on glenoid component positioning during total shoulder arthroplasty” was very intriguing to me.  The authors reveal seven cases of comparative studies between CAOS and standard shoulder replacement.  The biggest finding was a combined 6 degree difference in glenoid version, but they found limited data and differences in inclination or other parameters.  The study emphasizes the point that navigation will continue to demonstrate improved accuracy in postoperative position, but we are only scratching the surface with the power of this technology.  As a fairly high volume shoulder surgeon, even I can easily see a difference in glenoid placement, angulation and screw positions as I compare my postoperative radiographs from my navigated cases to my pre-navigation cases.

The good news is that CAOS for shoulder replacement is finally here.  This is not the same as patient specific instrumentation; it’s a step further.  The newest CAOS system allows for robust planning, continuous feedback to the surgeon throughout the case and the ability to deviate from the plan but still always know where you are.  The authors make a great point about the added benefit of both accuracy and reliability.  Not only do these systems allow you to place a glenoid within 1mm and degree of your plan, but they will commonly decrease the margin of error.  This is a common theme of eliminating outliers, seen with the knee CAOS systems, especially for those who perform these cases less often.

During my fellowship, CAOS was not available.  My mentor was finishing up his work on the first patient specific navigation system, and we used a robust 3-D planning tool.  I quickly bridged the gap between the standard radiograph and 2-dimensional planning seen in residency to the eye-opening concepts of 3-D, including planning and implementation of glenoid sizing, seating, use of augmented implants, finding the best bone for fixation and bone graft planning in severe deformity cases.

Preoperative planning software has allowed me to more accurately choose glenoid sizes and augmentation, as well as estimate the patient’s native glenoid position.

Since that time, these concepts have permeated in each case that I carefully planned, but I did not have the tools to translate them to the operating room.  Previous studies have demonstrated that the use of preoperative planning software alone adds to the accuracy of glenoid placement.  Preoperative planning software has allowed me to more accurately choose glenoid sizes and augmentation, as well as estimate the patient’s native glenoid position.  In addition, augmented glenoids are much easier to place with CAOS, as the guessing of how much bone to remove and at what angle to start are removed from the equation.  The majority of my decision making is now performed prior to the start of the surgery, and it is then executed more promptly and efficiently during the surgery.

One important clarification that this study does not address is the difference between cadaver studies, virtual studies and in vivo studies.

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What is the Difference in Post-Op Activity Level Between Older and Younger rTSA Patients?

Ryan Simovitch, MD

Read complete study: Younger patients report similar activity levels to older patients after reverse total shoulder arthroplasty

The authors conducted a study to measure a subjective questionnaire that reported type of activities, range of motion, pain and strength. The authors looked at patients younger and older than 65 to determine if there was a difference in activity levels and what the functional differences were in these patient populations. They broke activity level down into low, medium and high demand.

Literature Review:

The authors bring up a good point for surgeons to think about. Older patients are not necessarily inactive patients. The patient population at my practice in South Florida is older demographically, but those patients still enjoy golfing, swimming, lifting weights, cycling, hunting and other similar  activities that place high stresses on shoulder implants.

In my practice, I tend to view physiological age as a more important indicator than chronological age because my experience confirms what the study has above has found. Continue reading

Is rTSA the Solution to Every Patient’s Problem?

Howard Routman, DO

Read the complete study: Causes of poor postoperative improvement after reverse total shoulder arthroplasty

This study reviewed comorbidities and results for higher baseline American Shoulder and Elbow Surgeons (ASES) scores that are correlated with poor post-operative improvement. The study collected data from a total of 150 patients who underwent reverse total shoulder arthroplasty (rTSA) from 2007-2013. A minimum of two-year post-operative ASES scores were included, and poor post-op improvement was defined as a change of ASES score of less than 12 points. Out of the 150 patients, male gender, presence of an intact rotator cuff at the time of surgery, depression, a higher baseline ASES score and higher total number of medical comorbidities were associated with poor post-operative improvement after rTSA. Neither patient age, nor indication for surgery, was found to correlate with poor improvement after rTSA. In general, the study population was older, with an average age of 71.6 +/- 8.8, and the majority of patients were female.

Literature Review:

It should be noted that as the number of rTSAs continues to grow rapidly—due to its success in improving pain and function in most patients—some patients fail to improve clinically. Interestingly, the article also mentioned that patient satisfaction is now frequently linked to hospital and physician reimbursements. This study emphasizes reasons for poor post-operative improvement throughout with baseline pulled  from ASES scores and patient data. Physical examination findings were not a focused component of the analysis.

The temptation to view the rTSA as a panacea that can fix everything is high.  We need to temper our enthusiasm and ensure that we select our patients wisely.

When managing expectations with higher pre-operative ASES scores, I don’t really look at an ASES score pre-operatively as a screening tool, but I appreciate the concept of the ‘delta’ of improvement before surgery.  If a patient’s radiograph shows a classic cuff tear arthropathy, and the patient has maintained overhead elevation and mild pain, the change in function and pain that can be provided with a perfect reverse is minimal.  Ideally, patient selection can help us identify who best benefits from rTSA.  By limiting the indications to patients who cannot elevate beyond 90⁰, and who identify themselves has having quality-of-life-altering pain, we can skew our delta favorably.  The article referenced a study by Wall et al that noted patients who underwent rTSA for primary osteoarthritis had much smaller improvements in range of motion compared with patients who underwent rTSA for rotator cuff tear arthropathy or massive tears. Current expectations for improving post-operative function versus outcomes in patients with high levels of pre-operative function are to be noted.

In a cohort of 31 of my rTSA patients, the average post op ASES score was 82.68 (+/- 18.4), compared to 76 +/- 16.7 as mentioned in the study. Continue reading