Keywords
arthroscopic - coracoid graft - instability - Latarjet-Patte - shoulder - computed
tomography
Introduction
The Latarjet technique has proven over the years to be a very effective and reliable
procedure for the surgical treatment of anterior instability of the shoulder, especially
in cases of glenoid bone loss, bipolar (humeral head and anterior glenoid) bone defects,
and revision of surgical failures.[1]
[2]
[3]
[4] Also, the introduction of subscapularis muscle split, described by Patte, improved
the results concerning recovery of external rotation.[5] In 2007, Lafosse et al described the arthroscopic Latarjet procedure (arthro-Latarjet)
as an alternative to traditional open surgical technique with encouraging short-term
results.[6] The proper placement of the coracoid graft on the anterior glenoid neck represents
the most important step of the Latarjet procedure for the restoration of shoulder
stability and maintenance of results over time.[7] However, no clear information exist about efficacy of open and arthroscopic Latarjet
procedure in terms of correct coracoid graft placement.
The purpose of this study was to assess the accuracy of coracoid graft placement in
the open and arthroscopic Latarjet procedure for the treatment of anterior shoulder
instability. The hypothesis of the study was that the difference between the two technique
is not significant.
Methods
Forty-six patients (43 males and 3 females) were prospectively and consecutively enrolled
for this study and divided into two groups: 25 patients were operated with arthroscopic
“arthro-Latarjet” technique (group A) and 21 patients underwent an open Latarjet-Patte
procedure (group B). All of them were suffering from anterior instability of the shoulder
and had an instability severity index score (ISIS) equal to or greater than 6 points.[8]
[9] Exclusion criteria were: age older than 50 years, concomitant rotator cuff tears,
multidirectional instability, and systemic disorders such as autoimmune or rheumatic
diseases.
Arthroscopic technique was performed with five portals: A-D-E-H-M. The open technique
was performed through the deltopectoral approach. The following steps were followed
in both the procedures: coracoid preparation and osteotomy, subscapularis muscle split,
preparation of the anterior glenoid neck, and fixation of the coracoid graft to the
anterior side of the glenoid with two 3.5-mm cannulated titanium screws of length
varying between 36 and 38 mm. In both the groups, we used the arthro-Latarjet instruments
(Mitek, Johnson & Johnson, New Brunswick, New Jersey, United States) for coracoid
graft placement. The same surgeon (A.R.) operated all the patients.
At a minimum 1-year follow-up, all the patients underwent an imaging evaluation with
standard anteroposterior axillary radiographs and a three-dimensional computed tomography
(3D-CT). The following parameters were examined: positioning of the coracoid graft
on the sagittal and coronal plane, placement of the screws with respect to the glenoid
surface, screw length with respect to the anteroposterior width of the glenoid neck,
integration of the bone graft, and signs of osteoarthritis.[10]
Positioning of the coracoid graft on the coronal plane was classified as “adequate”
if the graft was placed in a subequatorial position or “imperfect” if the graft was
placed at the level or over the equator ([Fig. 1]). Positioning of the coracoid graft on the axial plane was classified as “adequate”
if the graft was flat compared with the glenoid surface or moved within 2 to 5 mm
medially (flush graft) or “imperfect” if hanging laterally more than 2 mm compared
with the anterior glenoid edge (proud graft) or shifted medially more than 5 mm compared
with the glenoid edge (recessed graft), ([Fig. 2]).
Fig. 1 Position of the graft compared with equator of the glenoid (three-dimensional computed
tomography [3D-CT] coronal scan).
Fig. 2 Position of the graft compared with anterior glenoid edge (computed tomography [CT]
axial scan).
Screw positioning was assessed on axial CT scans. Screw divergence was measured as
the angle that the screw formed with the articular glenoid surface and was open anteriorly
(convergence angle: the tip of the screw points toward the posterior edge of the articular
surface) or posteriorly (divergence angle: the tip of the screw diverges from the
posterior edge of the articular surface, [Fig. 3]). The divergence angle of the screws should be within 10 to 15 degrees to avoid
injuries to the suprascapular nerve.[11]
Fig. 3 Divergence angle is formed by the screw direction and the tangent to the glenoid
surface (computed tomography [CT] axial scan).
Screw length was assessed for screw tip protrusion from the posterior glenoid neck
and measured in millimeters ([Fig. 4]).
Fig. 4 Measurement of the posterior protrusion of the screw (computed tomography [CT] axial
scan).
Graft integration was defined as the disappearance in the axial CT scans of a separation
between the coracoid graft and the anteroinferior glenoid bone with inability to identify
the two contiguous cortical profiles. Integration was semiquantitatively rated as
partial (limited to a portion varying from 35 to 75% of the contact area between the
graft and the glenoid surface) or complete (if greater than 75%). Nonunion was defined
as persistence of two distinct cortical profiles (graft and glenoid neck) and/or fragmentation
of the graft.
Glenohumeral osteoarthritis was assessed according to Samilson and Prieto grading
system.[12]
Statistical analysis of data was performed with the Mann–Whitney U test for continuous
variables and Fisher's exact test for categorical variables. Significance was set
at p < 0.05.
Results
In group A, on axial CT scans, the graft was “flush” in 24 cases (96%) and “proud”
in 1 (4%); no recessed grafts were found. On sagittal CT scans, graft placement was
adequate (subequatorial) in 20 cases (80%) and imperfect (equatorial) in 5 (20%).
Overall, positioning of the graft was correct (flush and subequatorial) in 19 cases
(76%). No nonunions were found. In group B, the graft was “flush” and subequatorial
(correct positioning) in all cases. Comparison between the groups showed a significant
difference for overall coracoid graft positioning on the coronal plane (p = 0.025).
Graft integration in group A was complete in 19 cases (76%) and partial in 6 (24%).
Graft integration in group B was complete in 18 cases (86%) and partial in 3 (14%).
No significant difference between the groups was observed (p = 0.39).
Assessment of screw placement showed that in group A, screws were parallel to the
glenoid surface in 14 cases (56%) and divergent in 11 (44%). Median divergence angle
was 19.4 degrees (range, 10–32 degrees). In group B, screws were parallel to the glenoid
surface in 16 (76%) and divergent in 5 (24%) cases. Median divergence angle was 11.2
degrees (range, 6–18 degrees). No significant difference between the groups was observed
for screw divergence (p = 0.15). Posterior protrusion of screw was absent in 4 (16%), < 2 mm in 18 (72%),
and ≥ 2 mm in 3 (12%) cases. Median screw protrusion was 1.8 mm (range, 0–3 mm). Screw
posterior protrusion was observed in 76% (19/25) of cases in group A and 71.4% (15/21)
of cases in group B. Posterior protrusion of screws was < 2 mm in 16 cases (76%) and ≥ 2 mm
in 5 cases (24%). Median screw protrusion was 1.8 mm (range, 0–3 mm). The difference
between the groups for posterior protrusion of screw was not significant (p = 0.73).
Assessment of glenohumeral osteoarthritis (OA) according to Samilson and Prieto classification
showed that in group A, OA was absent in 22 (88%) cases, grade 1 in 2 (8%) cases,
and grade 2 in 1 (4%) case. In group B, OA was absent in 15 (71%) cases, grade 1 in
5 (24%) cases, and grade 2 in 1 (5%) case. No significant difference between the groups
was observed for glenohumeral OA (p = 0.26).
Mild signs of glenohumeral OA were observed in 12% of cases (3/25) in group A and
28.6% (6/21) in group B (Fisher's exact test, p = 0.26).
Discussion
Many surgical techniques have been described for the treatment of anterior instability
of the shoulder. The goal of any surgical treatment should be to stabilize the shoulder
without compromising strength or range of motion. In 1954, Latarjet described his
treatment for recurrent dislocation of shoulder by transposing the coracoid process
on the neck of the scapula and securing it with a screw.[13] The method underwent several changes over the years, but the basic procedure remained
unchanged for coracoid osteotomy and fixation to the anterior glenoid neck. The critical
step of the procedure is the proper placement of the coracoid graft to the anterior
glenoid, where it is generally fixed with two 3.5-mm screws, 36 to 38 mm in length.
This size is recommended to prevent nonunion.[14] The efficacy of double screw fixation is mainly related to an improved contact surface
and rotational stability of the graft.[15]
Many authors investigated the bone block position on radiographs. Allain et al[16] observed 53% too lateral bone blocks (proud grafts) and 5% too medial bone blocks
(recessed grafts). Cassagnaud et al[17] reported more than 10% of bone blocks protruding into the joint on CT scans. Hovelius
et al[18] found 36% of bone blocks seated above the equator and 6% bone blocks placed too
medially. Huguet et al[19] found 45% of the grafts protruding into the joint.[19] All these studies demonstrated the importance of the position of the graft, which
is directly related to the outcome. A graft placed too lateral or protruding into
the joint raises OA over time, while a coracoid graft placed too medially and/or above
the equator can generate recurring instability.
Nevertheless, optimal position of the coracoid process grafts is difficult to define;
in general, it is believed that it should be below the equator, not too medial from
the anterior glenoid edge, and less than 2 to 10 mm from the cartilage according to
different authors.[20]
[21] In our study, according to previous reports, we used a careful 3D-CT scan assessment
of some imaging parameters useful to evaluate differences between open and arthroscopic
Latarjet regarding graft placement, fixation, and healing, and found that open procedure
provided better results in terms of positioning of the graft on the coronal plane.
With regard to other parameters, graft integration, posterior screw divergence, posterior
protrusion of the screws, and osteoarthritis, data analysis showed no significant
differences between the groups.
