A computer-assisted solution for acromioplasty is presented. The software allows surgeons
to better plan the surgical procedure by visualizing dynamic simulation of the patient's
shoulder joint during everyday activities. Impingements are dynamically detected and the
exact location and amount of bone to be resected is precisely computed. As a result, the
success of the acromioplasty does not only rely on the surgeon's experience or previous
recommendations, but on quantitative data. Although the clinical validation of this 3D
planning support is currently under evaluation, it may allow to recover more effectively
postoperative joint mobility, to get a better relationship with pain and a better healing
rate of the rotator cuff tendons.

ArthroPlanner: A Surgical Planning Solution for Acromioplasty

Shoulder Impingement Syndrome

Subacromial Impingement Syndrome

Tendon Injuries

Introduction Subacromial impingement of the rotator cuff between the anterior [1] or
lateral acromion [2] and the superior humeral head is a common disorder. This condition
arises when the subacromial space height is too narrow during active elevation or
scaption of the arm above shoulder level due to an abnormal hooked shape or large lateral
extension of the acromion.

In severe cases of impingement syndrome, an arthroscopic acromioplasty surgery is usually
performed to resect the different area of the acromion causing damage to the subacromial
structures. The exact location and the amount of bone to be resected is generally left to
the unique appreciation of the orthopedic surgeon during surgery. To improve the
precision of this resection, surgeons could greatly benefit from a surgical planning
solution that aims at providing precise information about the surgical procedure.
Moreover, since subacromial impingements are the result of a dynamic mechanism, an
effective planning solution should analyze both the morphological joint's structures and
its dynamic behavior during shoulder movements to fully apprehend the patient joint's
condition.

Computer-assisted planning solution "ArthroPlanner" for acromioplasty is nowadays
available. The solution allows to perform standard morphological bony measurements, as
well as 3D simulations of the patient's joint during everyday shoulder activities. The
software computes the precise bone resection (location and amount) based on detected
subacromial impingements during motion.

The goal of this study was thus to compare clinical and radiological results of superior
rotator cuff repair with or without computer-assisted planning. The hypothesis was that
preoperative planning of acromioplasty would allowed more accurate bone resection, would
decrease postoperative impingements and consequently improved postoperative range of
motion and tendon healing.

Methods

We reconstruct the bones of the patient's shoulder joint (scapula and humerus from the
humeral head to the mid-shaft) from a CT image using Mimics software (Materialise NV,
Leuven, Belgium). The bones are then imported into ArthroPlanner software and the
following steps are performed:

First, generic bone models are produced using a template fitting approach that deforms a
bone template with an optimized topology (one for the scapula and one for humerus) to the
reconstructed bone. This allows us in the next steps to exploit anatomical
correspondences and to automatize landmarks and points selection on the mesh.

Second, biomechanical parameters are computed to permit motion description of the
glenohumeral joint. The glenohumeral joint center is automatically calculated by a sphere
fitting technique [3] that fits a sphere to the humeral head using the points of the
proximal humerus model. Bone coordinate systems are established for the scapula and
humerus. based on the definitions suggested by the International Society of Biomechanics
[4] using anatomical landmarks defined on the bone models. Missing landmarks such as the
lateral and medial epicondyles are identified on the CT image.

Third, morphological measurements are performed to analyze individual shoulder anatomy.
The Critical Shoulder Angle [5] and the β angle [6] are calculated, as they are criteria
associated with rotator cuff tears. The angles are computed in 3D based on bony landmarks
and can be, if necessary, interactively adjusted by the user by manipulating 3D handles
in the viewer.

Fourth, motion is applied at each time step to the humerus model with real-time
evaluation of impingement. The minimum humero-acromial distance that is typically used
for the evaluation of subacromial impingement is measured [7]. This distance is
calculated in millimeters based on the simulated bones models positions. A color scale is
also used to map the variations of distance on the scapula surface (red color = minimum
distance, other colors = areas of increased distance). Given the thickness of the
potential impinged tissues, subacromial impingement is considered when the computed
humero-acromial distance is < 6 mm, as suggested in the literature [7]. To test a wide
variability of realistic movements, a motion database of daily activities (e.g., cross
arm, comb hair) is used in addition to standard kinematic sequences (e.g., elevation,
scaption).

Finally, the acromial resection plan is defined based on the 3D simulation results. A
color map is used to represent areas where impingements occurred between the acromion and
humerus (Fig. 1D). The red color denotes the area with the smallest humero-acromial
distance computed over the different motion simulations.

The results at each step of the planning procedure are carefully validated by the user
before continuing to the next ones. At the end of the planning, a PDF report is generated
that contains patient's information and the measurements performed. The bones and the
simulation data are also exported to be used in a simple 3D viewer (Fig. 2) dedicated to
the surgeon. With this viewer, the surgeon is able to play all simulations, observe
impingements dynamically and review the resection plan.

Acromioplasty with planning

Acromioplasty without planning

Accuracy of acromioplasty in relation to preoperative planning (zone 1 anterior, zone 2
lateral, zone 3 medial, zone 4 central).

ultrasound realized by a blinded radiologist. This outcome will be considered as primary
only if the first primary outcome is reached. Otherwise it will considered as a secondary
outcome.

Evaluated by a independent and blind observer with dedicated software

ArthroPlanner: A Surgical Planning Solution for Acromioplasty

About this trial

Study ID

Status

Type

Phase

Placebo

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Trial Timing

What is this trial about?

What are the participation requirements?

Locations

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