Keywords shoulder dislocation - shoulder joint/injuries - joint instability - glenoid cavity
- bone transplantation
Keywords shoulder dislocation - shoulder joint/injuries - joint instability - glenoid cavity
- bone transplantation
Introduction
Latarjet surgery is the technique of choice for many surgeons to treat anterior glenohumeral
instability with bone loss.[1 ]
[2 ]
[3 ]
[4 ]
[5 ]
[6 ]
[7 ]
[8 ]
[9 ]
[10 ] It was described in 1954 by Latarjet[11 ] and in 1958 by Helfet.[12 ] Patte and Debeyre[13 ] associated the suture of the coracoacromial ligament with the capsule, and described
the triple effect of this technique: a) bone effect of the coracoid process attached
to the glenoid border; b) tendon anchorage effect on the lower third of the subscapularis;
and c) tensioning effect of the capsule by suturing the coracoacromial ligament to
it. The complications that compromise the outcome of surgery most associated with
graft size are fracture of the graft during its preparation and positioning on the
glenoid border – if it is superior or inferior in excess, the osseous and anchoring
effect of the conjoined tendon is compromised, and if it is positioned in an excessively
lateral position, then overhanging is favored, as well as the consequent glenohumeral
arthrosis.
In the technique described by Walch and Boileau,[14 ] two 4.5-mm malleolar screws are used. Without an adequate distance between the two
holes, and between them and the coracoid process margins, the risk of graft fracture
during preparation or mispositioning during glenoid fixation increases. In 2013, Young
et al[15 ] evaluated the dimensions of the coracoid processes after osteotomy and preparation,
and verified the reproducibility of the 7-millimeter rule, in which the lower hole
in the glenoid is made at least 7 mm from the articular margin to maintain the graft
in a satisfactory position.
The aim of the present study was to compare the dimensions of the osteotomized coracoid
process prepared in Latarjet surgeries with the results obtained by Young et al,[15 ] as well as to verify the viability of the 7-millimeter rule considering the coracoid
graft dimensions obtained from our sample. Our hypothesis was that the grafts collected
from our patients would be smaller than those in the study by Young et al,[15 ] and that the 7-millimeter rule could favor a glenoid graft positioning error.
Materials and Methods
From July 2015 to January 2017, the dimensions of 32 coracoid processes osteotomized
during Latarjet surgeries were measured. One case of intraoperative fracture of the
coracoid process was excluded due to the possibility of failure during the measurement
– totaling 31 evaluated grafts. The surgical indications were patients with signs
and symptoms of anterior glenohumeral instability, with or without glenoid bone erosion.
All surgeries were performed by one of the four surgeons from our service.
The technique used in the patients of the present study was described by Walch and
Boileau[14 ] in 2000, with the subscapularis opening in the direction of its fibers and fixation
of the coracoid process to the glenoid rim with two screws. The only variation of
the surgical technique was in relation to the size and type of screw used – a 4.0-mm
cancellous screw ([Figure 1 ]). After osteotomy of the coracoid process ([Figure 2 ]) and preparation of its inferior face, the intraoperative measurement was made with
an analog caliper by the surgeon, who collected data on the graft dimensions: length
in millimeters (from the tip to the base of the coracoid process, near the conjoint
tendon insertion); width in millimeters (average distance between the two holes made
for fixation; [Figure 3 ]) and thickness in millimeters (from the top edge to the bottom edge of the coracoid
process).
Fig. 1 Latarjet surgery.
Fig. 2 Graft length measurement site; arrow: ideal site for osteotomy of the coracoid process.
Fig. 3 (A ) Location of the width measurement of the graft; (B ) location of the length measurement of the graft. Source: Images of our own authorship.
Data distribution was verified through the Shapiro-Wilk test, and the continuous variables
were expressed as mean and standard deviation. Analysis of variance (ANOVA) for one
factor was performed for comparison of the thickness, length and width between men
and women. The Student t test for independent samples was performed to compare the highest and the lowest
widths among the measurements obtained by the present study and the reference study.[15 ] Values of p = 0.05 were considered statistically significant. The ANOVA was performed using the
International Business Machines Statistical Package for the Social Sciences (IBM SPSS,
IBM Corp., Armonk, NY, US) software, version 21.0, and the t test was calculated using the Microsoft Excel software from the Office package (Microsoft
Corp., Redmond, WA, US).
The present investigation was approved by the Ethics in Research Committee of the
institution that proposed the study under number CAAE 65215317.2.0000.5335. All evaluated
patients signed the informed consent form to take part in the study.
Results
We analyzed the dimensions of 31 coracoid processes of 31 patients submitted to the
Latarjet surgery (27 males and 4 females; 1 case was excluded due to graft fracture
during preparation). The average age of the sample was 30.26 years (18-69 years).
Despite the small number of female participants, there was no statistically significant
difference between the dimensions of the coracoid processes according to gender ([Table 1 ]).
Table 1
Male (n = 27)
Female (n = 4)
p -value
Thickness
8.0 (1.6)
7.2 (1.2)
0.39
Length
22.8 (1.7)
21.7 (2.9)
0.30
Width
14.0 (2.1)
14.5 (2.3)
0.67
The mean length obtained was of 22.6 ± 1.9 mm, 3.8 mm shorter than that obtained by
Young et al.[15 ] The mean thickness was also significantly thinner than that obtained by Young et
al:[15 ] 7.9 ± 1.5 mm, which is 1.3 mm thinner than the one found in the compared work. The
width did not present statistically significant differences in relation to the work
by Young et al[15 ] ([Table 2 ]). These authors performed two width measurements at the height of both holes. In
our study, only one measurement was performed, which was compared with the two measurements
by Young et al,[15 ] but no statistically significant differences were found ([Table 2 ]).
Table 2
General measurements (n = 31)
General measurements of the reference study (n = 76)
p -value
Thickness
7.9 (1.5)
9.2 (1.4)
< 0.001*
Length
22.6 (1.9)
26.4 (2.9)
< 0.001*
Width
14.0 (2.1)
14.1 (1.8) - superior
0.93
13.3 (1.8) - inferior
0.06
The dimensions of the graft compared with the reference work according to gender showed
that in males the average length obtained was of 22.8 ± 1.7 mm, 3.8 mm shorter than
that obtained by Young et al;[15 ] the mean thickness was also inferior, but no statistically significant difference
was found in relation to the width ([Table 3 ]). In females, the graft dimensions were like those found in the reference study,
with no statistically significant difference ([Table 4 ]). There were no complications related to graft looseness or pseudarthrosis.
Table 3
Males (n = 27)
Males in the reference study (n = 67)
p -value
Thickness
8.0 (1.6)
9.4 (1.4)
< 0.001*
Length
22.8 (1.7)
26.6 (2.7)
< 0.001*
Width
14.0 (2.1)
14.3 (1.7) - superior
0.47
13.4 (1.7) - inferior
0.15
Table 4
Females (n = 4)
Females in the reference study (n = 9)
p -value
Thickness
7.2 (1.2)
8.8 (1.6)
0.09
Length
21.7 (2.9)
24.8 (4.1)
0.13
Width
14.5 (2.3)
12.6 (1.0) - superior
0.20
12.2 (1.9) - inferior
0.14
Discussion
The mean dimensions of the coracoid process obtained in the present study were 22.6 mm
(18-26 mm) in length, 14.0 mm (11-20 mm) in width, and 7.9 mm (6-11 mm) in thickness.
Regarding the study by Young et al,[15 ] lower values for thickness and length were obtained, as detailed in the results
([Tables 2 ] e [3 ]). When the data were analyzed separately according to gender, there was no difference
in graft dimensions in females ([Table 4 ]). There was no statistically significant difference regarding width in either sex,
which makes the 7-millimeter rule valid in our patients. By this subjective rule,
which is based only on the authors' experience, the lower hole is made 7 mm from the
glenoid border, with no need to locate it through graft prepositioning, which has
no scientific evidence in the literature. In our sample, no statistically significant
differences were observed in graft dimensions according to gender, unlike previous
studies.[15 ]
[16 ]
Our hypothesis, which is based on the smaller size of our grafts, is that larger screws
would increase the fragility of the prepared coracoid process. The fracture rate of
the coracoid process published in the literature is low, ranging from 1.5 to 7%.[17 ]
[18 ] Athwal et al[17 ] observed that the area between the two holes was the most fragile region, but there
is no defined distance between these holes. Young et al[15 ] obtained a mean distance of 7.8 ± 1.9 mm between the holes. For arthroscopic surgery,
Lafosse and Boyle[5 ] developed a guide with 9 mm between the holes. In the present study, this distance
was not measured, but it is possible to state that since the evaluated grafts had
a shorter length, the interval between the two holes also tends to be shorter, increasing
the risk of fracture. When using a smaller drill (with 2.5 mm), which differs from
the technique described by Walch and Boileau,[14 ] which uses 3.2-mm drills, the risk of fracture is probably reduced. In our sample,
there were no complications, such as loosening or pseudarthroses, related to the use
of 4.0-mm cancellous screws instead of 4.5-mm malleolar screws.
Dolan et al[19 ] evaluated the dimensions of the coracoid process in scapulas of fresh cadaver specimens
without performing osteotomy, and they obtained similar values for the width, but
values that were 5.9 mm longer in relation to the length. This difference was expected
due to technical difficulties in performing osteotomy exactly at the base of the coracoid
process, preserving the insertion of the coracoclavicular ligaments during the surgical
procedure. Comparing our results with those of Young et al,[15 ] we obtained similar width values, but significantly smaller values in relation to
length and thickness. A likely explanation would be the technical differences in performing
the osteotomy and preparing the lower face of the coracoid process. The dimensions
of the inferior face of the coracoid graft may be more influenced by the technical
ability in contrast to the width, but this hypothesis still needs confirmation. Another
hypothesis already demonstrated in other studies,[20 ] would be the difference in bone structure between the populations evaluated, but
this is less likely.
One of the critical moments of Latarjet surgery is the placement of the graft at the
glenoid border.[21 ] Walch and Boileau[14 ] first drill the lower hole at approximately 7 mm from the edge of the glenoid. According
to the results obtained in the present study, this technique could be applied to our
patients, since the width of the grafts was similar to that obtained by Young et al.[15 ]
The present study has some limitations. Firstly, the surgeries were not performed
by the same surgeon, and each surgeon's technical skill may alter the point of the
osteotomy. Secondly, it was not possible to verify whether the use of a 3.2-mm drill
would make the graft more fragile. Thirdly, like the surgical technique, the measurement
was not made by the same surgeon, and there may be differences regarding the measurement
point. Some complications of Latarjet surgery are related to graft problems,[6 ]
[12 ]
[21 ]
[22 ] among them fractures, mispositioning, loosening and pseudoarthroses, which can lead
to the recurrence of instability. Many of these complications can be avoided with
a good knowledge of anatomy and of the surgical technique, enabling a good exposure
to measure the accurate size of the graft and a fixation in the correct spot of the
glenoid. Therefore, we think it is essential to use specific instruments for this
surgery.
Conclusion
In the sample studied, similar dimensions were obtained when compared to the reference
work[15 ] considering the coracoid graft width; but the same did not occur for the length
and thickness values, which were lower than in our study. In addition, the 7-millimeter
rule proposed by other authors was viable in our patients.
