Posterior Open-wedge Osteotomy and Glenoid Concavity Reconstruction Using an Implant-free, J-shaped Iliac Crest Bone Graft in Atraumatic Posterior Instability with Pathologic Glenoid Retroversion and Dysplasia: A Preliminary Report

Posterior Glenoid Bone Grafting in the Setting of Excessive Glenoid Retroversion Does Not Provide Adequate Stability in a Cadaveric Posterior Instability Model

BACKGROUND

Excessive glenoid retroversion is a known risk factor for posterior shoulder instability and failure after soft tissue stabilization procedures. Whether excessive glenoid retroversion is a risk factor for failure after posterior glenoid bone grafting is unknown.

PURPOSE

To evaluate the biomechanical effectiveness of posterior iliac crest bone grafting (ICBG) for posterior shoulder instability with increasing glenoid retroversion.

STUDY DESIGN

Controlled laboratory study.

METHODS

Six fresh-frozen cadaveric shoulders had a posterior glenoid osteotomy allowing the glenoid retroversion to be set at 0°, 10°, and 20°. At these 3 preset angles, 4 conditions were simulated consecutively on the same specimen: (1) intact glenohumeral joint, (2) posterior Bankart lesion, (3) 20% posterior glenoid bone defect, and (4) posterior ICBG. Stability was evaluated in the jerk position (60° of glenohumeral anteflexion, 60° of internal rotation) by measuring (A) posterior humeral head (HH) translation (in mm) and (B) peak translational force (in N) necessary for translation of the HH over 25% of glenoid width.

RESULTS

At 0° of retroversion, the ICBG restored posterior HH translation and peak translational force to values comparable with those of the intact condition (P = .649 and P = .979, respectively). At 10° of retroversion, the ICBG restored the peak translational force to a value comparable with that of the intact condition (22.3 vs 24.7 N, respectively; P = .418) but showed a significant difference in posterior HH translation in comparison to the intact condition (4.5 vs 2.0 mm, respectively; P = .026). There was a significant increase in posterior HH translation and significant decrease in peak translational force with the ICBG at 20° of glenoid retroversion compared with the intact condition (posterior HH translation: 7.9 vs 2.0 mm, respectively; P < .006; peak translational force: 15.3 vs 24.7 N, respectively; P = .014).

CONCLUSION

In this cadaveric study, posterior ICBG was able to restore stability to a level comparable to that of the native condition at 0° and to some extent at 10° of retroversion. However, posterior ICBG was not able to provide adequate stability at 20° of glenoid retroversion.

CLINICAL RELEVANCE

Posterior glenoid bone grafting with ICBG should be used with caution when performed in isolation in the setting of posterior instability associated with glenoid bone loss and combined glenoid retroversion of >10°.

Diagnosis and treatment of posterior shoulder instability based on the ABC classification

Posterior shoulder instability (PSI) is less common than anterior shoulder instability, accounting for 2-12% of total shoulder instability cases. However, a much higher frequency of PSI has been recently indicated, suggesting that PSI accounts for up to 24% of all young and active patients who are surgically treated for shoulder instability. This differentiation might be explained due to the frequent misinterpretation of vague symptoms, as PSI does not necessarily present as a recurrent posterior instability event, but often also as mere shoulder pain during exertion, limited range of motion, or even as yet asymptomatic concomitant finding. In order to optimize current treatment, it is crucial to identify the various clinical presentations and often unspecific symptoms of PSI, ascertain the causal instability mechanism, and accurately diagnose the subgroup of PSI. This review should guide the reader to correctly identify PSI, providing diagnostic criteria and treatment strategies.

Differences in Osseous Shoulder Morphology, Scapulothoracic Orientation, and Muscle Volume in Patients With Constitutional Static Posterior Shoulder Instability (Type C1) Compared With Healthy Controls

BACKGROUND

Constitutional static posterior humeral decentering (type C1 according to ABC Classification) has been recognized as a pre-osteoarthritic deformity that may lead to early-onset posterior decentering osteoarthritis at a young age. Therefore, it is important to identify possible associations of this pathologic shoulder condition to find more effective treatment options.

PURPOSE

To perform a comprehensive analysis of all parameters reported to be associated with a C1 shoulder-including the osseous shoulder morphology, scapulothoracic orientation, and the muscle volume of the shoulder girdle in a single patient cohort.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

A retrospective, comparative study was conducted analyzing 17 C1 shoulders in 10 patients who underwent magnetic resonance imaging (MRI) with the complete depiction of the trunk from the base of the skull to the iliac crest, including both humeri. The mean age of the patients was 33.5 years, and all patients were men. To measure and compare the osseous shoulder morphology (glenoid version, glenoid offset, humeral torsion, anterior acromial coverage, posterior acromial coverage, posterior acromial height, and posterior acromial tilt) and scapulothoracic orientation (scapular protraction, scapular internal rotation, scapular upward rotation, scapular translation, scapular tilt, and thoracic kyphosis), these patients were matched 1 to 4 according their age, sex, and affected side with shoulder-healthy patients who had received positron emission tomography (PET)-computed tomography. To measure and compare the muscle volume of the shoulder girdle (subscapularis, infraspinatus/teres minor, supraspinatus, trapezius, deltoid, latissimus dorsi/teres major, pectoralis major, and pectoralis minor), patients were matched 1 to 2 with patients who had received PET-MRI. Patients with visible pathologies of the upper extremities were excluded.

RESULTS

The C1 group had a significantly higher glenoid retroversion, increased anterior glenoid offset, reduced humeral retrotorsion, increased anterior acromial coverage, reduced posterior acromial coverage, increased posterior acromial height, and increased posterior acromial tilt compared with controls (P < .05). Decreased humeral retrotorsion showed significant correlation with higher glenoid retroversion (r = -0.742; P < .001) and higher anterior glenoid offset (r = -0.757; P < .001). Significant differences were found regarding less scapular upward rotation, less scapular tilt, and less thoracic kyphosis in the C1 group (P < .05). The muscle volume of the trapezius and deltoid was significantly higher in the C1 group (P < .05).

CONCLUSION

Patients with C1 shoulders differ from healthy controls regarding osseous scapular and humeral morphology, scapulothoracic orientation, and shoulder girdle muscle distribution. These differences may be crucial in understanding the delicate balance of glenohumeral centering.

Arthroscopic Posterior Glenoid Osteotomy

Management of posterior shoulder instability in patients with excessive glenoid retroversion can be challenging. However, a corrective posterior glenoid osteotomy is an option. Although various open techniques are available, minimally invasive and arthroscopy surgery are the most advantageous. This study describes the feasibility and safety of an arthroscopic posterior open wedge glenoid osteotomy using an autologous scapular spine graft along with additional posterior capsulolabral complex reattachment. This procedure is a viable option for patients with symptomatic posterior shoulder instability.

Open treatment of posterior glenoid bone loss and bipolar bone loss

Posterior glenohumeral instability is an increasingly common and challenging orthopaedic problem. While an arthroscopic soft tissue stabilization procedure (i.e., reverse Bankart repair) is effective in treating most cases of posterior instability, this procedure may be inadequate in shoulders with critical posterior glenoid bone loss (GBL), or in cases of an engaging reverse Hill-Sachs lesion. Thus, the purpose of the present manuscript was to report contemporary surgical approaches, techniques, and outcomes for the open treatment of glenoid or humeral head bone loss in posterior instability to help guide clinical decision making. Open osteoarticular augmentation procedures have emerged as a popular option to treat posterior bone loss, with bony auto- and allografts utilized from a variety of donor sites including iliac crest, scapular spine, acromion, distal clavicle, and distal tibia. The combination of glenoid retroversion and bone loss can be addressed with a posterior glenoid opening wedge osteotomy. Bipolar bone loss may be treated with a combination of the aforementioned techniques, in addition to a reverse remplissage, a modified McLaughlin procedure, or various arthroplasty-related options. Although short and mid-term outcomes are dependable, studies reporting long-term outcomes are sparse. Moreover, there is no current consensus regarding the most effective treatment of posterior shoulder instability in the setting of bone loss, and open surgical techniques continue to evolve. Further research is necessary to determine long-term effectiveness of these surgical options.

Bone loss in shoulder instability: putting it all together

Glenohumeral bone loss is frequently observed in cases of recurrent anterior and posterior shoulder instability and represents a risk factor for failure of nonoperative treatment. Patients with suspected glenoid or humeral bone loss in the setting of recurrent instability should be evaluated with a thorough history and physical examination, as well as advanced imaging including computed tomography (CT) and/or magnetic resonance imaging (MRI). In cases of both anterior and posterior instability, the magnitude and location of bone loss should be determined, as well as the relationship between the glenoid track (GT) and any humeral defects. While the degree and pattern of osseous deficiency help guide treatment, patient-specific risk factors for recurrent instability must also be considered when determining patient management. Treatment options for subcritical anterior bone loss include labral repair and capsular plication, while more severe deficiency should prompt consideration of bony augmentation including coracoid transfer or free bone block procedures. Concomitant humeral lesions are treated according to the degree of engagement with the glenoid rim and may be addressed with soft tissue remplissage or bony augmentation procedures. While critical and subcritical thresholds of glenoid bone loss guide the management of anterior instability, such thresholds are less defined in the setting of posterior instability. Furthermore, current treatment algorithms are limited by a lack of long-term comparative studies. Future high-quality studies as well as possible modifications in indications and surgical technique are required to elucidate the optimal treatment of anterior, posterior, and bipolar glenohumeral bone loss in the setting of recurrent shoulder instability.

Posterior stability of the shoulder depends on acromial anatomy: a biomechanical study of 3D surface models

PURPOSE

Primary glenohumeral osteoarthritis is commonly associated with static posterior subluxation of the humeral head. Scapulae with static/dynamic posterior instability feature a superiorly and horizontally oriented acromion. We investigated whether the acromion acts as a restraint to posterior humeral translation.

METHODS

Five three-dimensional (3D) printed scapula models were biomechanically tested. A statistical shape mean model (SSMM) of the normal scapula of 40 asymptomatic shoulders was fabricated. Next, a SSMM of scapular anatomy associated with posterior subluxation was generated using data of 20 scapulae ("B1"). This model was then used to generate three models of surgical correction: glenoid version, acromial orientation, and acromial and glenoid orientation. With the joint axially loaded (100N) and the humerus stabilized, an anterior translation force was applied to the scapula in 35°, 60° and 75° of glenohumeral flexion. Translation (mm) was measured.

RESULTS

In the normal scapula, the humerus translates significantly less to contact with the acromion compared to all other configurations (p < .000 for all comparisons; i.e. 35°: "normal" 8,1 mm (± 0,0) versus "B1" 11,9 mm (± 0,0) versus "B1 Acromion Correction" 12,2 mm (± 0,2) versus "B1 Glenoid Correction" 13,3 mm (± 0,1)). Restoration of normal translation was only achieved with correction of glenoid and acromial anatomy (i.e. 75°: "normal" 11 mm (± 0,8) versus "B1 Acromion Correction" 17,5 mm (± 0,1) versus "B1 Glenoid Correction" 19,7 mm (± 1,3) versus "B1 Glenoid + Acromion Correction" 11,5 mm (± 1,1)).

CONCLUSIONS

Persistence or recurrence of static/dynamic posterior instability after correction of glenoid version alone may be related to incomplete restoration of the intrinsic stability that is conferred by a normal acromial anatomy.

LEVEL OF EVIDENCE V

biomechanical study.

Correction of Static Posterior Shoulder Subluxation by Restoring Normal Scapular Anatomy Using Acromion and Glenoid Osteotomies: A Case Report

CASE

A 40-year-old man presented with progressive shoulder pain, associated with static posterior subluxation and mild eccentric glenohumeral osteoarthritis. Compared with a mean statistical shape model of a normal shoulder, the patient's acromion was abnormally high and horizontal, and the glenoid abnormally inclined inferiorly and minimally retroverted. Restoration of normal scapular anatomy using 3-dimensional planned acromial and glenoid osteotomies led to recentering of the joint and full shoulder function up to 24 months postoperatively.

CONCLUSION

The correction of associated acromial and glenoid malformation can revert early static posterior subluxation of the shoulder. Whether successful recentering prevents progression of osteoarthritis remains to be established.

Biomechanical Analysis of Posterior Open-Wedge Osteotomy and Glenoid Concavity Reconstruction Using an Implant-Free, J-Shaped Iliac Crest Bone Graft

BACKGROUND

Posterior open-wedge osteotomy and glenoid reconstruction using a J-shaped iliac crest bone graft showed promising clinical results for the treatment of posterior instability with excessive glenoid retroversion and posteroinferior glenoid deficiency.

PURPOSE

To evaluate the biomechanical performance of the posterior J-shaped graft to restore glenoid retroversion and posteroinferior deficiency in a cadaveric shoulder instability model.

STUDY DESIGN

Controlled laboratory study.

METHODS

A posterior glenoid open-wedge osteotomy was performed in 6 fresh-frozen shoulders, allowing the glenoid retroversion to be set at 0°, 10°, and 20°. At each of these 3 preset angles of glenoid retroversion, the following conditions were simulated: (1) intact joint, (2) posterior Bankart lesion, (3) 20% posteroinferior glenoid deficiency, and (4) posterior J-shaped graft (at 0° of retroversion). With the humerus in the Jerk position (60° of glenohumeral anteflexion, 60° of internal rotation), stability was evaluated by measuring posterior humeral head (HH) translation (in mm) and peak translational force (in N) to translate the HH over 25% of the glenoid width. Glenohumeral contact patterns were measured using pressure-sensitive sensors. Fixation of the posterior J-graft was analyzed by recording graft micromovements during 3000 cycles of 5-mm anteroposterior HH translations.

RESULTS

Reconstructing the glenoid with a posterior J-graft to 0° of retroversion significantly increased stability compared with a posterior Bankart lesion and posteroinferior glenoid deficiency in all 3 preset degrees of retroversion (P < .05). There was no significant difference in joint stability comparing the posterior J-graft with an intact joint at 0° of retroversion. The posterior J-graft restored mean contact area and contact pressure comparable with that of the intact condition with 0° of retroversion (222 vs 223 mm2, P = .980; and 0.450 vs 0.550 MPa, P = .203). The mean total graft displacement after 3000 cycles of loading was 43 ± 84 µm, and the mean maximal mediolateral graft bending was 508 ± 488 µm.

CONCLUSION

Biomechanical analysis of the posterior J-graft demonstrated reliable restoration of initial glenohumeral joint stability, normalization of contact patterns comparable with that of an intact shoulder joint with neutral retroversion, and secure initial graft fixation in the cadaveric model.

CLINICAL RELEVANCE

This study confirms that the posterior J-graft can restore stability and glenohumeral loading conditions comparable with those of an intact shoulder.

Arthroscopic Posterior Articular Coverage and Shift (PACS) Procedure for Treatment of Preosteoarthritic Constitutional Static Posterior Shoulder Instability (Type C1)

BACKGROUND

Different joint-preserving techniques for treatment of preosteoarthritic, constitutional static (type C1) posterior shoulder instability (PSI) have been proposed, including posterior glenoid open wedge osteotomy and bone graft augmentation. However, the techniques are demanding, the reported complication and reoperation rates are high, and posterior decentering cannot reliably be reversed.

PURPOSE

To assess the clinical and radiological longitudinal outcomes of patients with type C1 PSI after arthroscopic posterior articular coverage and shift (PACS) surgery.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

We performed a retrospective analysis of a prospective database with longitudinal follow-up including 14 shoulders in 13 patients who underwent an arthroscopic PACS procedure for symptomatic preosteoarthritic constitutional static posterior instability (type C1) with previous failed nonoperative treatment. Patients were clinically evaluated before surgery and at 3, 6, 12, and 24 months postoperatively in terms of satisfaction and pain levels as well as standardized physical examination, Subjective Shoulder Value (SSV), Western Ontario Shoulder Instability Index (WOSI) score, Constant score, and Rowe score. Preoperative, postoperative, and follow-up magnetic resonance imaging scans were obtained in all patients. A paired 2-sample t test was used to compare changes in continuous variable parameters over time. Correlation analyses were performed using the Pearson correlation coefficient.

RESULTS

All outcome scores and the pain level improved significantly from preoperatively to postoperatively, and the improvement was sustained over the follow-up period of 2 years (pain level, 6.4 preoperatively vs 3.3 at 2 years, P < .001; SSV, 40 vs 70, P = .001; WOSI, 33 vs 56, P = .001; Constant, 70 vs 79, P = .049; Rowe, 52 vs 76, P < .001). The mean glenohumeral and scapulohumeral subluxation indices were significantly lower in the early postoperative period compared with preoperative measurements (glenohumeral, 52% ± 6% vs 58% ± 10%, P = .02; scapulohumeral, 70% ± 8%; vs 77% ± 9%, P = .002, respectively); however, they returned to baseline values at follow-up (57% ± 7% vs 58% ± 10%, P = .7; 75% ± 6% vs 77% ± 9%, P = .4, respectively). A high scapulohumeral subluxation index, excessive glenoid retroversion, and increased posterior positioning of the humeral head in relation to scapular blade axis and older age were correlated with worse clinical outcomes.

CONCLUSION

Over the follow-up period of 2 years, the PACS procedure significantly improved outcome scores in patients who had preosteoarthritic constitutional static posterior shoulder instability, especially in younger patients with less severe glenoid retroversion and posterior decentering of the humeral head. However, similar to other techniques, the PACS procedure needs to be considered a symptomatic therapy that does not reverse the underlying cause or stop the progressive pathology.

Comprehensive management of posterior shoulder instability: diagnosis, indications, and technique for arthroscopic bone block augmentation

Recurrent posterior glenohumeral instability is an entity that demands a high clinical suspicion and a detailed study for a correct approach and treatment. Its classification must consider its biomechanics, whether it is due to functional muscular imbalance or to structural changes, volition, and intentionality.

Due to its varied clinical presentations and different structural alterations, ranging from capsule-labral lesions and bone defects to glenoid dysplasia and retroversion, the different treatment alternatives available have historically had a high incidence of failure.

A detailed radiographic assessment, with both CT and MRI, with a precise assessment of glenoid and humeral bone defects and of glenoid morphology, is mandatory.

Physiotherapy focused on periscapular muscle reeducation and external rotator strengthening is always the first line of treatment. When conservative treatment fails, surgical treatment must be guided by the structural lesions present, ranging from soft tissue repair to posterior bone block techniques to restore or increase the articular surface.

Bone block procedures are indicated in cases of recurrent posterior instability after the failure of conservative treatment or soft tissue techniques, as well as symptomatic demonstrable nonintentional instability, presence of a posterior glenoid defect >10%, increased glenoid retroversion between 10 and 25°, and posterior rim dysplasia. Bone block fixation techniques that avoid screws and metal allow for satisfactory initial clinical results in a safe and reproducible way.

An algorithm for the approach and treatment of recurrent posterior glenohumeral instability is presented, as well as the author’s preferred surgical technique for arthroscopic posterior bone block.

Long-term results after posterior open glenoid wedge osteotomy for posterior shoulder instability associated with excessive glenoid retroversion

BACKGROUND

Treatment of posterior shoulder instability (PSI) associated with excessive glenoid retroversion is a rare, challenging problem in shoulder surgery. One proposed technique is posterior open wedge glenoid osteotomy to correct excessive glenoid retroversion as described by Scott. However, this operation is rarely performed, and limited long-term outcomes using this approach are available. The goal of this study was to analyze the long-term outcomes of posterior open wedge glenoid osteotomy for PSI associated with excessive glenoid retroversion.

METHODS

Six consecutive patients (7 shoulders) with a mean age of 24 years (range 19-34) were treated with posterior open wedge glenoid osteotomy for PSI associated with a glenoid retroversion greater than 15° and followed up clinically and radiographically at a mean age of 15 years (range 10-19).

RESULTS

Recurrent, symptomatic PSI was observed in 6 of 7 shoulders (86%). One necessitated revision with a posterior (iliac crest) bone block procedure and was rated as a failure and excluded from functional analysis. One patient rated his result as excellent, 3 as good, 1 as fair, and 1 as unsatisfactory. Mean relative Constant Score (CS%) was unchanged from preoperation to final follow-up (CS% = 72%) and pain did not significantly decrease (Constant Score = 7-10 points; P = .969). The mean Subjective Shoulder Value (SSV) improved postoperatively, but with 6 patients the improvement did not reach statistical significance (SSV = 42%-67%, P = .053) and the total Western Ontario Shoulder Instability Index averaged 30% at the final follow-up. Mean glenoid retroversion of all 7 shoulders was corrected from 20° (range 16°-26°) to 3° (range -3° to +8°) (P = .018). In the 5 shoulders with preoperative static posterior subluxation of the humeral head, the humeral head was not recentered. All 7 shoulders showed progression of glenoid arthritic changes.

CONCLUSIONS

Posterior open wedge glenoid osteotomy for PSI associated with excessive glenoid retroversion neither reliably restored shoulder stability nor recentered the joint or prevent progression of osteoarthritis. Alternative treatments for PSI associated with excessive glenoid retroversion have to be developed and evaluated.