Clinical and radiographic outcomes of open Latarjet procedure in patients aged 40 years or older

Anterior shoulder instability in patients older than 40 years treated with arthroscopic Bankart repair

BACKGROUND

Anterior shoulder instability in adults aged ≥40 years is frequently managed nonoperatively. There is limited published evidence for the surgical management of these patients. This study aims to assess the risk of recurrence and functional outcomes in older adults after arthroscopic Bankart repair (ARB).

METHODS

A retrospective review of patients who underwent ARB by a single surgeon with a minimum of 2-year follow-up was performed. Recurrence, visual analog scale (VAS) score for pain, satisfaction, Subjective Shoulder Value (SSV), Rowe and Constant scores, along with rate, level, and timing of return to work and sport were evaluated.

RESULTS

Overall, 51 patients who underwent ABR were included; there were 35 males (69%). The mean age was 46.9 ± 6.4 years, with mean follow-up of 77.9 ± 32.6 months (range 25-138 months). At final follow-up, 88% (45 of 51) were either satisfied or very satisfied. The mean SSV was 87.4 ± 14, the mean Constant score was 80.4 ± 19.6, and the mean Rowe score was 80.4 ± 19.6, whereas the mean VAS score was 2.2 ± 2.6. Overall, 45 of 47 patients (95.7%) returned to work at a mean of 5.7 ± 4.6 weeks (range 0-16). Of the 43 patients playing sport preoperatively, 81.4% returned to play at a mean of 6.5 ± 3.8 months, and 53.5% returned at the same level. However, only 27.3% of collision and 42.9% of overhead athletes returned at the same level. There were 4 patients (7.8%) who had a postoperative dislocation, all of which were traumatic. There were two revision (3.9%) arthroscopic stabilizations, whereas a total 8 patients (15%) had further procedures.

CONCLUSION

Arthroscopic stabilization in patients older than 40 years results in a high rate of satisfaction, good functional outcomes, and low pain scores at medium- to long-term follow-up. There was a high rate of return to play and work, although most returned to play at a lower level. There was a low rate of recurrent instability and a moderate rate of reoperation, with contact sports being the primary cause of recurrence.

Clinical and radiographic outcomes using standard length of cannulated screws for traditional Latarjet procedure

Background

The purpose of this study was to evaluate the clinical and radiographic outcomes of open traditional Latarjet stabilization using 32-mm-long and 30-mm-long cannulated screws in males and females, respectively, with a minimum of 2 years of follow-up.

Methods

We retrospectively reviewed open Latarjet procedures using cannulated screws of standard length with a minimum of 2 years of follow-up. Functional evaluation was performed with postoperative Rowe and Walch score, visual analog scale for pain and return to sport. Graft healing was assessed with computed tomography scans at 4 to 6 months postoperatively. Patients were divided into 2 groups according to postoperative radiographic measurements: a bicortical or unicortical screw group. The α angle between the shaft of the screw and the glenoid subchondral bone was measured for superior and inferior screws. Level of significance was 0.05. The post hoc power analysis was 0.89.

Results

A total of 69 patients met the criteria for inclusion. Of these patients, 60 (87%) were available for final follow-up (n = 62 shoulders), with a mean age of 28.4 ± 9.5 years (range, 16-55 years) at the time of surgery. Fifty six males (93.3%) and 4 females (6.7%) were included. The mean final follow-up period was a mean of 38 months after the procedure (range, 25-48 months). Eight of 60 patients (13.3%) had persistent apprehension in abduction-external rotation position. One patient (1.7%) had a recurrence of shoulder subluxation. The mean Walch-Duplay score was 90 ± 11.6 points (range, 40-100 points), and the mean Rowe score was 93.4 ± 11 points (range, 50-100 points). The mean visual analog scale score for the evaluation of pain was 0.9 ± 1.3 (range, 0-4). The coracoid healed the glenoid neck in 87.1% (54/62) of the shoulders on the postoperative computed tomography scan. Lower alpha angle for inferior and superior screws had more rate of unicortical fixation (P = .05 and P = .04, respectively). Fourteen of 62 (22.6%) shoulders were found unicortical screws. Six bicortical cases and 2 cases of unicortical screws (25%) showed nonunion (P = .86). There were 2 complications, 1 patient had hematoma that required drainage and 1 case had transient axillary nerve palsy which resolved spontaneously. No complications associated with the hardware were found.

Conclusion

Open traditional Latarjet procedure using 32-mm-long and 30-mm-long cannulated screws in males and females, respectively, provided good outcomes with acceptable complication rates. Unicortical screws fixation does not have a higher rate of nonunion than bicortical screws.

Over 89% of Patients Return to Work After Undergoing Arthroscopic or Open Latarjet Procedure for Anterior Shoulder Instability: A Systematic Review

PURPOSE

To better define the rate of return to work in patients undergoing Latarjet surgery for anterior shoulder instability.

METHODS

A systematic review was performed in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. PubMed, Cochrane Center Register of Controlled Trials, and Scopus were queried in October 2023 with the following keywords: ((latarjet) OR (anterior shoulder instability)) AND ((work) or (compensation)). Articles were included if they reported return to work in patients (including military members) undergoing Latarjet surgery for traumatic anterior shoulder instability with bone loss and were written in English. This study was registered in Prospero (ID blinded).

RESULTS

Six studies reporting on 419 shoulders were included in the review. Five studies reported on patients in the general population, and 1 reported on military members. Mean age ± standard deviation of patients ranged from 23.1 ± 5.8 to 32.0 ± 12.3 years. Moreover, there were 286 primary Latarjet procedures, 131 revision Latarjet procedures, and 2 unspecified as primary or revision surgery. Mean glenoid bone loss ranged from 14.5% to 22.9%. Return-to-work rates ranged from 89.1% to 100%, with 2 studies reporting all patients were able to return to work. Among military members, 89.1% were able to return to duty. Mean time to return to work ranged from 8.69 to 34.8 weeks after surgery. Four studies also reported return to sport, which ranged from 60.9% to 100%. Mean time for returning to sport varied between 10.0 and 35.2 weeks after the Latarjet procedure.

CONCLUSIONS

Patients with anterior shoulder instability who undergo an arthroscopic or open Latarjet procedure can expect high rates of return to work and sport. All studies reported return-to-work rates over 89%, with 89.1% of military members able to return to duty.

LEVEL OF EVIDENCE

Level IV, systematic review of Level III and Level IV studies.

Rotator Cuff Tears are Significantly More Frequent in Recurrent Shoulder Instability Patients With Initial Dislocation at Age 40 or Older

PURPOSE

To investigate and compare the pathologies and clinical outcomes of patients with traumatic anterior shoulder instability who underwent arthroscopic stabilization at 40 years or older between shoulders with initial dislocation before age 40 years and at 40 years or after.

METHODS

Shoulders that underwent arthroscopic stabilization for recurrent traumatic anterior shoulder instability at 40 years or older with a minimum of 2-year follow-up were included. The subjects were divided into 2 groups according to age at initial dislocation after propensity score matching to reduce potential bias: younger than 40 years (group 1) and 40 years or older (group 2). Radiographic findings, pathologies, clinical outcomes, and complications were compared between the groups.

RESULTS

Group 1 included 56 shoulders in 56 patients (26 men and 30 women) with a mean age of 51 years (range, 40-77 years). Group 2 included 28 shoulders in 28 patients (13 men and 15 women) with a mean age of 51 years (range, 40-77 years). Glenoid bone loss was greater in group 1 than in group 2 (P = .004). Rotator cuff tears were more frequently observed in group 2 than in group 1 (P < .001). Both groups showed significant improvement in the West Ontario Shoulder Instability Index score (P < .001 for each) and flexion (P < .001 for each). The recurrence rate was 4% in group 1 and 7% in group 2.

CONCLUSIONS

Rotator cuff tears are significantly more frequent in recurrent shoulder instability patients with initial dislocation at age 40 or older. Arthroscopic stabilization yielded a low recurrence rate and favorable outcomes with a good return-to-sport rate in patients 40 years or older.

LEVEL OF EVIDENCE

Level III, retrospective comparative prognostic trial.

Postoperative Radiographic Outcomes Following Primary Open Coracoid Transfer (Bristow-Latarjet) Vary in Definition, Classification, and Imaging Modality: A Systematic Review

PURPOSE

To analyze radiographic outcomes by conventional radiography, computed tomography (CT), or both and complication rates of open coracoid transfer at a minimum of 12-months follow-up.

METHODS

A literature search was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, using PubMed, Medline (Ovid), and EMBASE library databases. Inclusion criteria were clinical studies reporting on open Latarjet as the primary surgical procedure(revision coracoid transfer after failed prior stabilization excluded) with postoperative radiographic outcomes at a minimum mean 1-year follow-up. Patient demographics, type of postoperative imaging modality, and radiographic outcomes and complications including graft union, osteoarthritis, and osteolysis were systematically reviewed. Data were summarized as ranges of reported values for each outcome metric. Each radiographic outcome was graphically represented in a Forest plot with point estimates of the incidence of radiographic outcomes with corresponding 95% confidence intervals and I2.

RESULTS

Thirty-three studies met inclusion criteria, with a total of 1,456 shoulders. The most common postoperative imaging modality was plain radiography only (n = 848 [58.2%]), both CT and radiography (n = 287 [19.7%]), and CT only (n = 321 [22.1%]). Overall, the reported graft union rate ranged from 75% to 100%, of which 79.8% (n = 395) were detected on plain radiography. The most common reported postoperative radiographic complications after the open coracoid transfer were osteoarthritis (range, 0%-100%, pooled mean 28%), graft osteolysis (range, 0%-100%, pooled mean 30%), nonunion (range, 0%-32%, pooled mean 5.1%), malpositioned graft (range, 0%-75%, pooled mean 14.75%), hardware issues (range, 0%-9.1%, pooled mean 5%), and bone block fracture (range, 0%-8%, pooled mean 2.1%). Graft healing was achieved in a majority of cases (range, 75%-100%).

CONCLUSION

Postoperative radiographic outcomes after open coracoid transfer vary greatly in definition, classification, and imaging modality of choice. Greater consistency in postoperative radiographic outcomes is essential to evaluate graft healing, osteolysis, and nonunion.

LEVEL OF EVIDENCE

Level IV, systematic review of Level III-IV studies.

All-Arthroscopic Trillat Procedure Using Screw Fixation for Recurrent Shoulder Instability

The Trillat procedure has been described for the management of shoulder instability in younger patients but also for shoulder instability in older patients with irreparable rotator cuff tears. We describe an all-arthroscopic technique using screw fixation. This technique allows for safe dissection, clearance and osteotomy of the coracoid, and direct visualization during screw tensioning and fixation to minimize the risk of subscapularis impingement. We outline our stepwise approach to medialize and distalize the coracoid process using arthroscopic screw fixation and present pearls to avoid fracture through the superior bone bridge.

Factors affecting a patient's experience following the open Latarjet procedure to treat recurrent anterior shoulder instability

The open Latarjet procedure is a widely used treatment for recurrent anterior instability of the shoulder. Although satisfactory outcomes are reported, factors which influence a patient's experience are poorly quantified. The aim of this study was to evaluate the effect of a range of demographic factors and measures of the severity of instability on patient-reported outcome measures in patients who underwent an open Latarjet procedure at a minimum follow-up of two years. A total of 350 patients with anterior instability of the shoulder who underwent an open Latarjet procedure between 2005 and 2018 were reviewed prospectively, with the collection of demographic and psychosocial data, preoperative CT, and complications during follow-up of two years. The primary outcome measure was the Western Ontario Shoulder Instability Index (WOSI), assessed preoperatively, at two years postoperatively, and at mid-term follow-up at a mean of 50.6 months (SD 24.8) postoperatively. The secondary outcome measure was the abbreviated version of the Disabilities of the Arm, Shoulder and Hand (QuickDASH) score. The influence of the demographic details of the patients, measurements of the severity of instability, and the complications of surgery were assessed in a multivariate analysis. The mean age of the patients was 25.5 years (22 to 32) and 27 (7.7%) were female. The median time to surgery after injury was 19 months (interquartile range (IQR) 13 to 39). Seven patients developed clinically significant complications requiring further intervention within two years of surgery. The median percentage WOSI deficiency was 8.0% (IQR 4 to 20) and median QuickDASH was 3.0 (IQR 0 to 9) at mid-term assessment. A minority of patients reported a poorer experience, and 22 (6.3%) had a > 50% deficiency in WOSI score. Multivariate analysis revealed that consumption of ≥ 20 units of alcohol/week, a pre-existing affective disorder or epilepsy, medicolegal litigation, increasing time to surgery, and residing in a more socioeconomically deprived area were independently predictive of a poorer WOSI score. Although most patients treated by an open Latarjet procedure have excellent outcomes at mid-term follow-up, a minority have poorer outcomes, which are mainly predictable from pre-existing demographic factors, rather than measures of the severity of instability.

Complications Related to Latarjet Shoulder Stabilization: A Systematic Review

BACKGROUND

In cases of recurrent anterior shoulder instability with a glenoid defect, Latarjet procedures are widely used for stabilization. Although complications with this procedure have been reported, few studies have comprehensively analyzed issues related to the Latarjet procedure.

PURPOSE

To identify the overall complication rate of the Latarjet procedure used for anterior shoulder instability and to compare the rate of complications between arthroscopic and open approaches.

STUDY DESIGN

Systematic review; Level of evidence, 4.

METHODS

PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines were followed by using the PubMed, EMBASE, Scopus, and Cochrane Library databases. Data on complications were extracted and classified as intraoperative, postoperative, or instability-related for further analysis. Quality assessments were performed with criteria from the Methodological Index for Nonrandomized Studies (MINORS). A quantitative synthesis of data was conducted to compare the complication rates between arthroscopic and open approaches.

RESULTS

A total of 35 articles were included in this analysis. The MINORS score was 11.89. A total 2560 Latarjet procedures (2532 patients) were included. The overall complication rate was 16.1% (n = 412). The intraoperative complication rate was 3.4% (n = 87) and included a 1.9% (n = 48) incidence of nerve injuries and a 1.0% (n = 25) incidence of iatrogenic fractures. Screw problems, vascular injuries, and conversion arthroscopic to open surgery each occurred at a rate of <1%. The postoperative complication rate was 6.5% (n = 166), and the most common complication was nonunion (1.3%; n = 33). The instability-related complication rate was 6.2% (n = 159) and included a 1.5% (n = 38) rate of redislocation, a 2.9% (n = 75) rate of positive apprehension test, and a 1.0% (n = 26) rate of instability. Overall, 2.6% (n = 66) of patients required an unplanned secondary operation after the initial surgery. The arthroscopic approach was associated with a higher rate of intraoperative complications compared with the open approach (5.0% vs 2.9%; P =.020) and a lower rate of instability-related complications (3.1% vs 7.2%; P < .001).

CONCLUSION

The Latarjet procedure for anterior shoulder instability results in an overall complication rate of 16.1% and a reoperation rate of 2.6%. However, serious complications at short-term follow-up appear rare. When the arthroscopic approach was used, the rate of intraoperative complications was higher, although instability-related complications were lower when compared with the open approach.

The Trillat Procedure for Anterior Glenohumeral Instability

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Anterior glenohumeral instability (AGI) is a challenging condition that requires close attention to osseous and soft-tissue abnormalities. The morphometric variance of the periarticular scapular anatomy may be involved in the pathogenesis of recurrent traumatic anterior instability.

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The Trillat procedure repositions the coracoid medially and downward by a partial wedge osteotomy, mimicking the sling effect of the Latarjet procedure by moving the conjoint tendon closer to the joint line in throwing position. The Trillat procedure decreases the coracohumeral distance without affecting the integrity of the subscapularis muscle and tendon.

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Joint preservation methods, such as the Trillat procedure, may be explored in older patients to treat AGI with simultaneous irreparable rotator cuff tears (RCTs) with a static centered head and a functional subscapularis.

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Shoulder hyperlaxity and instability can be challenging to treat with isolated soft-tissue procedures. In cases without glenoid bone loss, free bone block techniques are ineffective because of the subsequent potential graft resorption, apprehension, or recurrence. The Trillat surgery, in conjunction with an anteroinferior capsuloplasty, seems to be helpful in preventing recurrent instability and in reducing shoulder apprehension.

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Recently, several variations of the original technique have been described. In the future, anatomical, biomechanical, and clinical studies need to be conducted to further evaluate the morphometric characterization of the procedure, enhance the technical features, improve indications, and avoid coracoid impingement and other potential complications with the Trillat procedure.

Failed Latarjet Treated With Full Arthroscopic Eden-Hybinette Procedure Using Two Cortical Suture Buttons Leads to Satisfactory Clinical Outcomes and Low Recurrence Rate

PURPOSE

To report clinical and radiologic outcomes of arthroscopic Eden-Hybinette using 2 cortical suture buttons in a series of patients with previous failed Latarjet and persistent glenoid bone loss.

METHODS

Between 2015 and 2019, patients with recurrent anterior instability after failed Latarjet underwent arthroscopic Eden-Hybinette procedure using 2 cortical buttons for graft fixation. Exclusion criteria were open and primary Eden-Hybinette and less than one year follow-up. Functional assessment was performed using Rowe and Walch-Duplay scores, subjective shoulder value, visual analog scale, and degree of satisfaction. Iliac crest bone graft placement and healing were assessed postoperatively with computed tomography imaging.

RESULTS

A total of 17 patients with a mean age of 28 years (range, 21-43 years) at time of revision were included. The mean glenoid bone loss was 23% (range, 18%-42%). Medium or deep Hill-Sachs lesion (Calandra 2 and 3) was present in 65% of cases. At a mean follow-up of 3 ± 1.6 years, all but 1 patient (94%) considered their shoulder stable, and 15 patients (88%) were satisfied or very satisfied. The subjective shoulder value increased from 51% to 87% (P < .05), the Walch-Duplay increased from 23 to 86 points (P < .05), and Rowe scores improved from 30 to 92 points (P < .05). Apprehension was still positive in 3 patients (17.6%), with this percentage being greater in the presence of Hill-Sachs Calandra 3 (P = .02). Postoperative computed tomography scans showed optimal bone autograft position in all patients (below the glenoid equator and flush to the glenoid rim). Iliac crest bone graft healed to the anterior glenoid neck in 16 shoulders (94%). The rate of recurrent instability was 11.7% but only 1 patient required revision surgery (5.8%).

CONCLUSIONS

Arthroscopic Eden-Hybinette using 2 cortical buttons leads to satisfactory clinical outcomes and a low recurrence rate after failed Latarjet, allowing successful reconstruction of the anterior glenoid rim and simultaneous treatment of capsular deficiency and humeral bone loss.

LEVEL OF EVIDENCE

Therapeutic, level IV, retrospective case series.

Incidence and Risk Factors of the Complications Related to the Latarjet Surgery

Objective  The Latarjet procedure is a well-accepted treatment of shoulder instability. This technique is associated with a unique set of complications with overall rates of up to 30%. The purpose of the present study was to investigate the incidence and risk factors associated with complications after open Latarjet procedure. Methods  We retrospectively reviewed 102 patients submitted to open Latarjet procedure. Complications were divided into three types: clinical; graft-related; and screw-related. All of the patients were submitted to radiography and computed tomography (CT). The risk factors analyzed were gender, age, previous surgery, epilepsy, experience of the surgeon. Results  A total of 102 consecutive patients (108 cases) underwent the Latarjet procedure. The mean age was 33.7 years old (18 to 61 years old), with 88 males and 14 females. The overall complication rate was 21.2%, being 12% clinical-related, 7.4% graft-related, and 2.7% screw-related. The most frequent were anterior apprehension (eight cases) and lateral overhang of the graft in six patients. Computed tomography scan at a minimum of 6 months was performed in 79 cases (73%), and graft union occurred in 75 patients (94.9%). There were no cases of instability in the remaining four cases of nonunion. Ten patients (9.2%) required revision surgery. The risk factors associated with complications were epilepsy ( p  = 0.0325), experience of the surgeon ( p  = 0.0499) and patients ≥ 40 years old at the time of the surgery ( p  = 0.0151). There was no correlation with gender and previous surgery. Conclusion  The complication rate following the Latarjet procedure was 21.2%, with 9% requiring revision surgery. Epilepsy, age > 40 years old and experience of the surgeon were risk factors.

Long-term Results of the Arthroscopic Bankart Repair for Recurrent Anterior Shoulder Instability in Patients Older Than 40 Years: A Comparison With the Open Latarjet Procedure

BACKGROUND

Long-term results of the arthroscopic Bankart repair in patients older than 40 years are unknown and may be favorable in terms of postoperative glenohumeral arthritis as opposed to the long-term results of the open Latarjet procedure in patients older than 40 years.

PURPOSE

To analyze our long-term results of the arthroscopic Bankart repair for recurrent anterior shoulder instability in patients older than 40 years of age and to compare these results with previously published long-term results of the Latarjet procedure in a cohort of similar age.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

A total of 35 consecutive patients (36 shoulders) with a mean age of 47 years (range, 40-69) at time of the arthroscopic Bankart repair were studied at a mean 13.2 years (range, 8-18) after surgery. Clinical and radiographic results were then compared with those of our previous study of 39 consecutive patients (40 shoulders) of a same age group who had been treated for the same pathology with an open Latarjet procedure.

RESULTS

Six shoulders (17%) sustained a recurrent shoulder dislocation after a mean 5.3 years; subluxation occurred in 3 shoulders (8%); and apprehension persisted in 3 shoulders (8%). Revision surgery was performed in 8 patients (22%): 2 Bankart and 6 open Latarjet. The relative preoperative Constant score and Subjective Shoulder Value were significantly improved (P < .001) at final follow-up. Arthropathy of stabilization was advanced in the shoulders of 16 patients (47%) and had progressed by at least 2 grades in 21 patients (62%). There were significantly higher rates of redislocation and subluxation when compared with the open Latarjet procedure (9 vs 3; P = .037), and the mean final Subjective Shoulder Value was significantly lower in the Bankart group (86% vs 91%; P = .011). There were no significant differences in final advanced arthropathy (16 vs 14; P = .334) and revision rates (8 vs 7; P = .409) when compared with the Latarjet procedure.

CONCLUSION

Arthroscopic Bankart repair for recurrent anterior shoulder instability in patients older than 40 years was associated with reliable pain relief and patient satisfaction similar to that after the open Latarjet procedure. Restoration of stability was significantly less successful and development of arthropathy no better than the open Latarjet procedure in patients older than 40 years.

Predicting Failure After Primary Arthroscopic Bankart Repair: Analysis of a Statistical Model Using Anatomic Risk Factors

PURPOSE

The purpose of this study was to establish and analyze a simplified scoring system based on anatomic imaging measurements to predict recurrent instability after primary arthroscopic shoulder capsulolabral repair.

METHODS

All patients undergoing primary arthroscopic anterior capsulolabral repair of the shoulder were reviewed. Patients were contacted and charts were reviewed for endpoint of recurrent instability and return to prior level of activity. Predictive variables for recurrent instability studied included age, sex, amount of glenoid bone loss, intact anterior articular arc (IAAA), glenohumeral tracking (off-track), contact sports and overhead sports participation.

RESULTS

540 patients met inclusion criteria and follow-up data with magnetic resonance imaging data were available for 337 shoulders. Average follow-up was 6.2 years(range 3.4-9.3 years). Symptomatic recurrent instability occurred in 102 patients (30.3%) and 68% of contacted patients returned to pre-injury activities. In univariate analysis, age under 21 years, off-track lesions, IAAA <150°, and glenoid bone loss (GBL) of 10% or greater displayed an increased risk of recurrent instability. Multivariable analysis showed these factors remained significant: age <21 (odds ratio [ratio] 2.37), off-track glenoid (OR 2.86), IAAA <150 (OR 3.90), and GBL ≥10% (OR 7.47). A scoring system assigning 1 point each for age and off-track lesions, 2 points for IAAA <150, and 4 points for GBL >10% yielded 79% sensitivity, 75% specificity, 58% positive predictive value, and 89% negative predictive value using a probability value of 20 percent for recurrent instability.

CONCLUSION

At mid-term follow-up, recurrent shoulder instability following primary arthroscopic anterior capsulolabral repair was 30% in this series. Younger age, glenoid bone loss of 10% or more, IAAA <150° and off-track glenoid lesion conferred the greatest risk for postoperative instability. We propose a scoring system assigning 1 point for age, 1 point for off-track lesions, 2 points for IAAA <150, and 4 points for GBL >10%. This schema demonstrated moderate accuracy for predicting recurrent instability when using a cutoff threshold score above 2 points for failure.

LEVEL OF EVIDENCE

Level III, Retrospective Cohort Study.