Preoperative computer planning and patient-specific instrumentation: "The long-term clinical benefit is unknown and requires further examination prior to the widespread acceptance of these technologies"

Computer-Assisted Preoperative Planning and Patient-Specific Instrumentation for Glenoid Implants in Shoulder Arthroplasty

These authors reviewed the literature on computer-assisted preoperative planning and patient specific instrumentation for glenoid implants in shoulder arthroplasty.

Their bullet points were:

» Glenoid component positioning affects implant survival after total shoulder arthroplasty, and accurate glenoid-component positioning is an important technical aspect.

» The use of virtual planning and patient-specific instrumentation has been shown to produce reliable implant placement in the laboratory and in some clinical studies.

» Currently available preoperative planning software programs employ different techniques to generate 3-dimensional models and produce anatomic measurements potentially affecting clinical decisions.

» There are no published data, to our knowledge, on the effect of preoperative computer planning and patient-specific instrumentation on long-term clinical outcomes.

The last of the above statements is most critical in that the value of these innovations is determined by the   benefit to the patient divided by the cost. See New technologies in anatomic total shoulder: what is their value to the patient? In terms of the value of these innovations, the authors state "high-level clinical outcomes studies are needed to justify the additional time and cost related to the universal use of CT scans, preoperative planning, and the production of PSI guides".

These authors point out that, "planning software is used in other areas of joint arthroplasty, most commonly for total knee arthroplasty. However, published reports have not reached consensus regarding the utility, accuracy, and reproducibility. Various studies have reported more accurate implant positioning with software assisted planning in total knee arthroplasty, but without impacting patient reported outcomes."

Comment: "Precision" and "accuracy" are terms often used in describing the benefits of computer assistance. Precision means the ability to reproduce the same result each time, while accuracy refers to the ability to hit a predefined target. These characteristics are of critical importance in the assembly of microchips or automobiles where the targets are clearly specified and the configuration of the structure entering the assembly line is always identical. In dealing with an arthritic shoulder, neither of these is true: (1) No two arthritic shoulders are the same and (2) while average ± standard deviation values for glenoid version and joint line position in normal shoulders can be defined, evidence is lacking that "reproducing normal anatomy" leads to better outcomes for the patient.

Consider an example from the review where three-dimensional planning was used.

Note that pre-operatively, the arthritic humeral head was centered in the glenoid fossa in both the superior-inferior direction and in the anteroposterior direction.

While the patient-assessed clinical outcome of this case was not presented, the postoperative x-rays show what appears to be superior decentering of the prosthetic humeral head on the glenoid in the AP view and anterior decentering of the humeral head on the glenoid on the axillary view.

Since the value of an innovation is determined by the health outcome that matters to the patient divided by the cost of delivering that outcome, each innovation needs to be put to the test by tracking patient reported measures of comfort and function combined with tracking of the cost of care from the initial encounter through a period of followup that is long enough to capture most adverse outcomes (n.b. this is likely to be 7-10 years for total shoulder arthroplasty). 

The potential divergence between the goal of the surgeon to restore "normal anatomy" and the patient's desire for durable comfort and function is reminiscent of the work of the late Wilton Bunch, who demonstrated that the goal of many scoliosis surgeons was to achieve a straight spine, while the goal of most scoliosis patients was to have a durably comfortable and functional back.

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Here are some videos that are of shoulder interest

Shoulder arthritis - what you need to know (see this link)

The smooth and move for irreparable cuff tears (see this link)

The total shoulder arthroplasty (see this link).

The ream and run technique is shown in this link.

The cuff tear arthropathy arthroplasty (see this link).

The reverse total shoulder arthroplasty (see this link).

Shoulder rehabilitation exercises (see this link).