Anterior shoulder dislocation and concomitant fracture of the greater tuberosity

Background Recurrence rates after primary traumatic shoulder dislocation are distinctly high. We hypothesized that concomitant isolated fractures of the greater tuberosity are associated with low rates of persistent instability but decreased range of motion. Methods Between 2007 and 2013, 66 consecutive shoulders in 64 patients were treated for primary shoulder dislocation combined with an isolated fracture of the greater tuberosity with either a nonsurgical (48 shoulders, 72.7%) or surgical (18 shoulders, 27.3%) treatment approach. In all, 55 cases (83.3%) were available for clinical follow-up examination after an average of 59.0 ± 20.7 months (range: 25–96 months) and of these, 48 (72.7%) patients consented to radiological evaluation to determine healing and position of the greater tuberosity. Results The mean range of motion of the affected shoulder was significantly decreased by 9° of elevation (p = 0.016), 11° of abduction (p = 0.048), 9° of external rotation in 0° of abduction (p = 0.005), and 10° of external rotation in 90° of abduction (p = 0.001), compared with the unaffected shoulder. The mean WOSI score was 373 ± 486 points, the mean Constant and Murley score was 75.1 ± 19.4 points, and the mean Rowe score was 83 ± 20 points. Three cases (5.5%) of re-dislocation were reported among the cohort, all of them were due to a relevant trauma. Radiological evaluation revealed anatomically healed fragments in 31 shoulders (65%), dislocation of the fragment in ten shoulders (21%), impaction into the humeral head in four shoulders (8%), and absorption in three shoulders (6%). Conclusion A concomitant isolated fracture of the greater tuberosity leads to low recurrence rates along with a significant decrease in range of motion after primary traumatic anterior shoulder dislocation.


Introduction
The incidence of traumatic shoulder dislocations has been reported to range from 17 to 23.9/100,000 [1][2][3][4]. Recurrence rates after primary dislocation are known to be high and have been shown to depend especially on the patient's age, as patients younger than 40 years have a much higher risk of posttraumatic redislocation compared with those over 40 years [5]. Other risk factors for recurrence include male gender, hyperlaxity, and, to a lesser extent, bony Bankart lesions, nerve palsies, and type of activity [5].
A concomitant fracture of the greater tuberosity (GT) is seen in approximately 20% (range: 15.5-25%) of patients presenting with anterior shoulder dislocation [6][7][8]. Inherent muscle tension of the attached rotator cuff (RC) displaces the fragment dorsally and cranially from the dislocated humeral head fragment [9]. The degree of fragment displacement after reduction has been suggested to be a prognostic factor regarding restitution of shoulder function. While nondisplaced and minimally displaced fractures can be treated conservatively, surgical fixation is indicated for 3-5 mm of displacement, depending on the patient's age and activity level [9][10][11].
Level of evidence: level IV, case series with no comparison group.
We hypothesized that concomitant isolated fractures of the greater tuberosity are associated with low rates of recurrent dislocation but decreased range of motion (ROM) after primary traumatic anterior shoulder instability, as repeatedly mentioned in the literature [7,8,12]. The purpose of this study was to retrospectively evaluate the clinical and radiological outcome of patients treated for anterior glenohumeral (GH) dislocation in combination with an isolated fracture of the GT who underwent either surgical or nonsurgical treatment.

Patients and methods
The current investigation is a retrospective cohort study, approved by the institutional ethics committee (415-EP/73/501-2014).  Morphological classification for greater tuberosity fractures:a avulsion type fracture; b split type fracture; c depression type fracture [21] causes of the trauma were: fall in a domestic setting (n = 25), winter sports accidents (n = 12), fall during leisure time activity without involvement of a vehicle (n = 9), bicycle accident (n = 9), motor vehicle accidents (n = 5), occupational accidents (n = 3), and epileptic seizure (n = 3). In all, 53 patients (55 shoulders, 83%) were available for FU. Five patients (8%) died from an unrelated cause and six patients (9%) could not be contacted because current contact information was lacking. Mean patient age at the time of the initial trauma was 56.5 ± 14.4 years (range: 15-84 years). The mean FU was 59.0 ± 20.7 months (range: 25-96 months).

Patient care
Our diagnostic and treatment protocol for patients with GH dislocation and concomitant GT fracture consisted of clinical examination followed by biplane radiographic imaging (true anteroposterior [a. p.] view and y-view) to confirm the diagnosis of GH dislocation and determine position of the humeral head and the fractured greater tuberosity. One careful attempt of closed reduction was usually performed in the emergency room with adequate analgesia. If unsuccessful, the GH dislocation was reduced with the patient under general anesthesia and relax-ation in the operating room to prevent the risk of iatrogenic humeral fractures [13,14]. Clinical examination and radiographic imaging were repeated to identify neurological changes and confirm the reduction as well as fracture morphology of the greater tuberosity. In the case of inconclusive radiographs, an additional computed tomography (CT) scan with three-dimensional (3D) reconstruction to evaluate the fracture morphology and degree of GT displacement was obtained (42 patients).
Nerve injury became evident in seven patients during the initial examination. Of these patients, four were found to have axillary nerve palsy, two had radial nerve palsy with one affecting the brachial plexus. All of them fully

Anterior shoulder dislocation and concomitant fracture of the greater tuberosity. Clinical and radiological results
Abstract Background. Recurrence rates after primary traumatic shoulder dislocation are distinctly high. We hypothesized that concomitant isolated fractures of the greater tuberosity are associated with low rates of persistent instability but decreased range of motion. Methods. Between 2007 and 2013, 66 consecutive shoulders in 64 patients were treated for primary shoulder dislocation combined with an isolated fracture of the greater tuberosity with either a nonsurgical (48 shoulders, 72.7%) or surgical (18 shoulders, 27.3%) treatment approach. In all, 55 cases (83.3%) were available for clinical follow-up examination after an average of 59.0 ± 20.7 months (range: 25-96 months) and of these, 48 (72.7%) patients consented to radiological evaluation to determine healing and position of the greater tuberosity. Results. The mean range of motion of the affected shoulder was significantly decreased by 9°of elevation (p = 0.016), 11°of abduction (p = 0.048), 9°of external rotation in 0°of abduction (p = 0.005), and 10°of external rotation in 90°of abduction (p = 0.001), compared with the unaffected shoulder. The mean WOSI score was 373 ± 486 points, the mean Constant and Murley score was 75.1 ± 19.4 points, and the mean Rowe score was 83 ± 20 points. Three cases (5.5%) of redislocation were reported among the cohort, all of them were due to a relevant trauma.
Radiological evaluation revealed anatomically healed fragments in 31 shoulders (65%), dislocation of the fragment in ten shoulders (21%), impaction into the humeral head in four shoulders (8%), and absorption in three shoulders (6%). Conclusion. A concomitant isolated fracture of the greater tuberosity leads to low recurrence rates along with a significant decrease in range of motion after primary traumatic anterior shoulder dislocation.

Keywords
Shoulder fractures · Conservative treatment · Surgery · Recurrence · Range of motion
Surgical treatment was indicated in (1) patients younger than 65 years of age and displacement greater than 3 mm and in (2) patients older than 65 years and displacement greater than 5 mm on initial CT, measuring the widest distance. Surgical treatment was furthermore indicated for patients with depression-type fractures and an irreducible fragment dis-location after reduction of the dislocated shoulder [10,11].
Otherwise, nonsurgical treatment was advised, consisting of initial immobilization of the GH joint in internal rotation for 4 weeks with an arm sling and weekly clinical and radiological FU examination in our clinic to detect possible late displacement of the GT. This was followed by mobilization of the upper extremity under the guidance of a physical therapist starting with passive ROM and advancing at approximately 6 weeks to active ROM.
Surgical treatment was performed either via percutaneous reduction of the fracture and fixation using cannulated self-tapping 3-mm screws (7 cases; . Fig. 1a) or open reduction and fixation with either cannulated self-tapping 3-mm screws or suture anchors (6 cases; . Fig. 1b) or screw fixation in combina-

Obere Extremität 3 · 2018 213
Original Contribution tion with steel-wire cerclages (5 cases; . Fig. 1c). All procedures were performed or supervised by a senior trauma surgeon. Postoperative care followed the conservative therapy protocol as described earlier.

Clinical follow-up evaluation
After obtaining informed consent, the clinical FU was conducted in our outpatient clinic by the principal investigator and supervised by a resident. All patients filled out a questionnaire in order to complete patient history comprehensively. The clinical outcome was determined using the subjective shoulder value (SSV; [15]), Western Ontario Shoulder Instability Index (WOSI; [16]), the Rowe scoring system (Rowe 1988; [17]), and the Constant and Murley score (CS; [18]). With regard to the heterogeneity of our study population, the "ageand gender-adjusted CS" was used [19]. The shoulder-related level of exertion in terms of work and sports was measured with the shoulder activity level (SAL; [20]). Current pain intensity was determined using a 10-part visual analogue scale (VAS 0-10).
Clinical examination included the assessment of the active ROM of both shoulders, which was measured with a goniometer including elevation, abduction (ABD), external rotation (ER), and internal rotation (IR) in 0°and 90°ABD position. Shoulder strength was assessed in 90°ABD position with an IDO isometer (IDO, Innovative Design Orthopaedics Limited, Redditch, Worcestershire, UK).

Radiological evaluation
The type of fracture on imaging following reduction was categorized according to the fragment's morphology into three groups applying a classification system for GT fractures [21]: 1. Avulsion fracture (. Fig. 2a), characterized by small fragments and the presence of a horizontal fracture line caused by a shearing motion of the GT along the glenoid rim and tension of the muscles of the RC.
2. Split fracture (. Fig. 2b), characterized by relatively large fragments and almost vertical fracture line from impaction of the GT on the anterior side of the glenoid. 3. Depression-type fracture (. Fig. 2c), characterized by impaction of the fragment into the humeral head due to collision with the anterior glenoid. Depression-type fractures are distinct from Hill-Sachs lesions as the GT is entirely impacted into the humeral head, while Hill-Sachs lesions affect the posterolateral articular surface of the humeral head [22].
At the final FU, three views of radiographic imaging were obtained (true a. p. view, axillary view, and y-view) to assess bony union, position, and displacement of the GT fragment and accurate articulation of the humeral head with the glenoid. Instability arthropathy was evaluated on true a. p. radiograph views of the shoulder according to the classification system of Samilson and Prieto [23]. FU images were compared with postreduction images to evaluate the development of instability arthropathy. We were able to radiographically examine 48 patients (73%), of whom 32 had undergone nonsurgical treatment and 16 cases had undergone surgical repair. All radiographic analyses were performed by a radiologist and a trauma surgeon.
The ROM measured at FU is presented in . Table 2. No statistically significant differences were detected between the nonsurgical and the surgical group in regard to ROM (elevation: p = 0.177; ABD: p = 0.178; ER neutral position: p = 0.703; ER 90°abduction: p = 0.651; IR 90°abduction: p = 0.307).
The results of the clinical outcome scores are outlined in . Table 3.
No statistically significant difference was detected between the three GT fragment type groups regarding the ROM
Of the initially 20 undisplaced fractures among the nonsurgical group,     Posttreat. after closed reduction or surgical procedures, postred. after closed reduction, pre-/ postsurg. before/after surgery 19 remained in anatomical position and one underwent absorption. Of the initially four dorsally displaced tuberosities, three remained dorsally displaced, whereas one was found to be displaced dorsocranially at final FU. Of the initially two cranially displaced tuberosities, one was found in anatomical position at FU, whereas the other tuberosity was absorbed. Both dorsocranially displaced tuberosities showed no further evidence of subsequent displacement. Review of postoperative radiographs in the surgical group showed three tuberosities with dorsal displacement, one tuberosity with dorsocranial displacement, and two impacted tuberosities, all of which remained in the same displaced position until final radiological FU. Of the ten anatomically reduced tuberosities, nine stayed in anatomical position at FU while one resorbed (. Table 5).

Revisions
Revision surgery was necessary in five of 18 patients (27.8%); all of them were treated with cannulated self-tapping 3-mm screws. One patient who was treated with percutaneous screws sustained screw breakage 13 days after surgery requiring revision surgery. Four other patients (22.2%) underwent removal of surgical implants owing to material migration, which was performed after an average time of 116.5 days (73-167 days). No patient of the nonsurgical group was scheduled for secondary surgical reduction and stabilization of Obere Extremität 3 · 2018 215 the fragment after conservative therapy regime was started.

Re-dislocation
Three cases (5.5%) of traumatic re-dislocation were reported among the study population, of which two cases were related to an epileptic seizure (bilateral redislocation in one patient). One case occurred during a traumatic skiing accident as the patient fell onto the previously injured shoulder. The formerly fractured GT remained stable during this second dislocation episode. All of the cases were observed in the conservative group.

Discussion
The principal finding of the current study was that a concomitant isolated fracture of the greater tuberosity in cases with traumatic anterior shoulder dislocation was associated with a low recurrence rate but decreased ROM compared with the contralateral shoulder at mid-term FU.
In general, recurrent shoulder instability is the most common complication following primary shoulder dislocation with recurrence rates of up to 96% in adolescents [24]. Rates of recurrence are known to vary depending to a great degree upon the patient's age, with recurrence rates of 54% in patients below 30 years and 12% for older patients [25]. The recurrence rate in this study cohort was much lower. A possible explanation might be the presence of the concomitant tuberosity fracture in all cases, which seems to reduce the risk for recurrence as previously described [10]. Other possible explanations are that the concomitant fracture of the greater tuberosity reduces the joint compression forces during the dislocation episode, which in return reduces the risk for damage to the anterior glenoid rim and anterior capsulolabral structures. Another explanation might be the observed loss of end-range of motion, which can also reduce the risk for instability [9,10]. ROM, especially in external rotation and abduction, was significantly decreased on the affected side of our study patients compared with the nonaffected shoulder. No differences in ROM were seen in cases with surgical treatment compared with cases with conservative therapy when the aforementioned surgical indication criteria were applied. The mean loss of external rotation of approximately 10°in our study cohort is comparable to the outcomes after stabilization surgery for anterior shoulder instability [26].
The low recurrence rate of approximately 5.5% in the current study could partially also be explained by age-related factors. With increasing age, there is a higher risk of concomitant damage to bony structures such as the greater tuberosity during shoulder dislocation, which is most likely associated with reduced bone density at the proximal humerus. Therefore, in this study cohort primary shoulder dislocation occurred at an age of 40 years or older in about three out of four cases, which is much higher than the typically younger age at which primary traumatic dislocations occur [4]. Since the risk of recurrence decreases with increasing age at primary dislocation [5], the higher average age of the patients in this study can be considered as a confounder leading to a low recurrence rate.
Radiographic analysis at final FU revealed a low risk for secondary fragment displacement after both conservative and surgical treatment. In some cases, secondary fragment absorption was observed. Potential reasons for the absorption might be secondary dislocation with loss of strain on the tuberosity, lack of vascularity, or low-grade infection in the surgical cases.
Considering that the secondary displacement rate was low, the functional outcome was comparable, and the recurrence rate was low, conservative treatment in patients younger than 65 years and displacement less than 3 mm and in patients older than 65 years and displacement less than 5 mm seems to be justified, of course always taking into account the patient specific activity level, general health status, and severity of symptoms as well [27].
Evaluation of radiographs made after reduction of the GH dislocation with regard to morphological properties [21] of the fractured GT fragments demonstrated similar properties of avulsion type fragments (43.9%) and split type fragments (39.4%), whereas only a small proportion of impression type fractures were observed (16.7%). The proportions show almost the same distribution as those presented by Mutch et al. in their study in 2014 of 199 cases (avulsion type, 39%; split type, 41%; impression type, 20%; [21]). Statistical evaluation did not show any significant difference among these three subgroups regarding ROM and clinical outcome scores at FU.

Limitations
The study has limitations typical of retrospective investigations. A control group of primary dislocations without concomitant fracture of the greater tuberosity was not available. Moreover, CT measurements of the distance between the tuberosity fragment and the intact proximal humerus were not available in all cases. Measuring the dislocation distance on radiographs might have limited reliability. Furthermore, no ultrasound examination or magnetic resonance imaging of the RC was made at FU, which could have offered more explanations for the loss of ROM.
Another limitation is the rather low number of surgical cases, which can result in a lack of statistical power when comparing results with the nonsurgical group.

Practical conclusion
4 Anterior GH dislocation with concomitant isolated fracture of the GT results in diminished joint mobility but low recurrence of instability. 4 ROM in any direction was significantly decreased compared with the contralateral shoulder, regardless of whether the surgical or conservative treatment approach was followed.