Angled BIO-RSA (bony-increased offset-reverse shoulder arthroplasty): a solution for the management glenoid bone loss and erosion

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Article

Reference

Angled BIO-RSA (bony-increased offset-reverse shoulder arthroplasty): a solution for the management glenoid bone loss and

erosion

BOILEAU, Pascal, et al .

Abstract

Glenoid deficiency and erosion (excessive retroversion/inclination) must be corrected in reverse shoulder arthroplasty (RSA) to avoid prosthetic notching or instability and to maximize function, range of motion, and prosthesis longevity. This study reports the results of RSA with an angled, autologous glenoid graft harvested from the humerus (angled BIO-RSA).

BOILEAU, Pascal, et al . Angled BIO-RSA (bony-increased offset-reverse shoulder arthroplasty): a solution for the management glenoid bone loss and erosion. Journal of Shoulder and Elbow Surgery , 2017, vol. 26, no. 12, p. 2133-2142

DOI : 10.1016/j.jse.2017.05.024 PMID : 28735842

Available at:

http://archive-ouverte.unige.ch/unige:99036

Disclaimer: layout of this document may differ from the published version.

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ORIGINAL ARTICLE

Angled BIO-RSA (bony-increased offset–reverse shoulder arthroplasty): a solution for the

management glenoid bone loss and erosion

Pascal Boileau, MD, PhD

^a,

*, Nicolas Morin-Salvo, MD

^a

, Marc-Olivier Gauci, MD

^a

, Brian L. Seeto, MD, FRCS(C)

^a

, Peter N. Chalmers, MD

^b

, Nicolas Holzer, MD, PhD

^c

, Gilles Walch, MD

^d

aDepartment of Orthopaedic Surgery, iULS (Institut Universitaire Locomoteur & Sport) Hôpital Pasteur 2, University of Nice Sophia-Antipolis, Nice, France

bDepartment of Orthopaedic Surgery, University of Utah, Salt Lake City, UT, USA

cDepartment of Orthopaedic Surgery, Hôpital Universitaire de Genève, Geneva, Switzerland

dDepartment of Orthopaedic Surgery, Centre Orthopédique Santy, Lyon, France

Background: Glenoid deficiency and erosion (excessive retroversion/inclination) must be corrected in reverse shoulder arthroplasty (RSA) to avoid prosthetic notching or instability and to maximize function, range of motion, and prosthesis longevity. This study reports the results of RSA with an angled, autologous glenoid graft harvested from the humerus (angled BIO-RSA).

Methods: A trapezoidal bone graft, harvested from the humerus and fixed with a long-post baseplate and screws, was used to compensate for residual glenoid bone loss/erosion. For simple to moderate (<25°) glenoid defects, standardized instrumentation combined with some eccentric reaming (<15°) was used to reconstruct the glenoid and obtain neutral implant alignment. For severe (>25°) and complex (multiplanar) glenoid bone defects, patient-specific grafts and guides were used after 3-dimensional planning. Patients were reviewed with minimum 2 years of follow-up. Mean follow-up was 36 months (range, 24-81 months).

Preoperative and postoperative measurements of inclination and version were performed in the plane of the scapula on computed tomography images.

Results: The study included 54 patients (41 women, 13 men; mean 73 years old). Fifteen patients had combined vertical and horizontal glenoid bone deficiency. Among E2/E3 glenoids, inclination improved from 37° (range, 14° to 84°) to 10.2° (range−28° to 36°,P<.001). Among B2/C glenoids, retroversion improved from−21° (range,−49° to 0°) to−10.6° (−32° to 4°,P=.06). Complete radiographic incorporation of the graft occurred in 94% (51 of 54). Complications included infection in 1 and clinical aseptic baseplate loosening in 2. Mild notching occurred in 25% (13 of 51) of patients. Constant-Murley and Sub- jective Shoulder Value assessments increased from 31 to 68 and from 30% to 83%, respectively (P<.001).

Conclusion: Angled BIO-RSA predictably corrects glenoid deficiency, including severe (>25°) multiplanar deformity. Graft incorporation is predictable. Advantages of using an autograft

This study was approved by the Institutional Review Board of the Ethical Committee of Centre Orthopédique Santy/Hôpital Jean Mermoz, France (reference study number 2016-18).

*Reprint requests: Pascal Boileau, MD, PhD, iULS (Institut Universitaire Locomoteur & du Sport) Hôpital Pasteur 2, University of Nice-Sophia-Antipolis, 30, Ave de la Voie Romaine, F-06001 Cedex 1 Nice, France.

E-mail address:boileau.p@chu-nice.fr(P. Boileau).

www.elsevier.com/locate/ymse

by-nc-nd/4.0/).

http://dx.doi.org/10.1016/j.jse.2017.05.024 J Shoulder Elbow Surg (2017)■■,■■–■■

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harvested in situ include bone stock augmentation, lateralization, low donor-site morbidity, low relative cost, and flexibility needed to simultaneously correct posterior and superior glenoid defects.

Level of evidence: Level IV; Case Series; Treatment study

creativecommons.org/licenses/by-nc-nd/4.0/).

Keywords: Glenoid bone loss; glenoid erosion; reverse total shoulder arthroplasty; glenoid inclination;

glenoid retroversion; bony-increased offset reverse shoulder arthroplasty (BIO-RSA); bony lateralization

Severe glenoid erosion or deficiency is encountered fre- quently in arthritic patients and presents a challenge to the surgeon performing a reverse shoulder arthroplasty (RSA).²⁹ During RSA, glenoid bone loss needs to be corrected to avoid prosthetic notching or instability and to maximize function, range of motion, and prosthesis longevity.^3,40Failure to correct superior bone loss (ie, Favard type E2, E3) can lead to superior tilt of the baseplate, increased scapular impingement, instability, inferior scapular notching, and medial polyethylene wear.^19,25Biomechanically, superior tilt increases tensile baseplate forces during deltoid contraction and can lead to early loosening.

In osteoarthritis with severe retroversion and biconcavity (ie, Walch type B2) or excessive hypoplastic glenoid retroversion (type C), failure to correct posterior bone loss can lead to retroversion of the baseplate, reduced external rotation, posterior scapular notching, and posteromedial polyethylene wear.^26,27In addition, failure to restore the glenoid bone stock during RSA leads to excessive medialization of the center of rotation. Secondary medialization of the humerus can potentially decrease motion and flexion strength, decrease deltoid wrapping, increase the propensity for instability, and fail to restore the rounded cosmesis of the shoulder.⁵

Historically, options to address glenoid bone defects combined eccentric reaming with glenoid bone grafting with an autograft iliac crest bone graft (ICBG) or allograft or augmented glenoid baseplates.9,17,20,34,43

Our choice, since 2006, has been to use an autologous bone graft harvested from the humeral head to restore the glenoid bone stock and obtain correct alignment of the implant with minimal morbidity.^1,8,18,31 The humeral head autograft may be symmetrical (BIO- RSA) or asymmetrical (angled BIO-RSA), depending on the presence, amount, and orientation of glenoid deficiency. In the latter technique, purpose-designed instrumentation is used to harvest the graft from the humeral head such that it is trapezoidal to match the glenoid bone defect. Potential advantages of this technique include flexibility to reconstruct multiplanar deformity, restoration of glenoid bone stock, and ability to lateralize the center of rotation.

The present study reports the results of angled bony- increased offset-reverse shoulder arthroplasty (BIO-RSA) in addressing glenoid bone deficiency. We sought to determine (1) the amount of glenoid deficiency that can be corrected, (2) the rate of graft incorporation, (3) the rate of scapular notching, and (4) the functional outcomes. We hy- pothesized that the asymmetrical (trapezoidal) autologous bone

graft harvested from the humeral head (1) would incorpo- rate to the native scapula, (2) would restore the glenoid bone stock and allow correct baseplate alignment, and (3) would lateralize the center of rotation and provide good functional results.

Materials and methods Study design

This was a retrospective single-center study including a consecu- tive series of patients that underwent a primary RSA and an angled, autologous humeral head bone graft to address significant glenoid bone loss (Walch A2, B2, C or Favard E2, E3, E4). Exclusion cri- teria were patients who underwent a revision RSA and those who underwent primary RSA and glenoid reconstruction with other sources of bone graft, such as ICBG or allograft.

Between 2006 and 2013, 93 patients with severe glenoid erosion or deficiency underwent glenoid bone graft reconstruction during primary RSA implantation. After excluding patients who received an allograft or an ICBG, 63 patients remained who were treated with an angled BIO-RSA. Two patients died, and 7 were lost to follow- up before 2 years, leaving 54 patients (89% of those eligible) who were included in the study. Mean follow-up was 36 months (range, 24-81 months). All patients signed written, informed consent before the procedure.

Angled BIO-RSA concept

The concept of angled BIO-RSA is to use an autologous, trapezoidal bone graft harvested from the humeral head to restore the glenoid bone stock and lateralize the center of rotation of the RSA. The technique provides the flexibility to reconstruct multiplanar deformity (ie, to correct baseplate version and inclination;Fig. 1). Although this is a retrospective study and no prospective protocol was applied, during the study period, we generally used this technique for deformities exceeding 10° to 15°, and smaller deformities were generally corrected with eccentric reaming alone.

Two-dimensional preoperative templating

Our experience has been that preoperative templating is critical to determine the graft thickness necessary to restore a normal or nearly normal inclination and retroversion. Computed tomography (CT) scans of the shoulder were obtained in all patients scheduled for an RSA. We used OsiriX 5.6 software (Pixmeo, Geneva, Switzer- land) for 2-dimensional (2D) preoperative templating. This software provided simple-to-use tools for making linear and angular

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measurements. The modified Friedman method was used to measure the 2D glenoid version.¹⁴

Glenoid inclination was measured using a new method, the reverse shoulder arthroplasty angle or RSA angle. Theβ angle, described by Maurer et al,²⁸is the angle between the line of the glenoid fossa (where an anatomic total shoulder arthroplasty glenoid component would be implanted) and the floor of the supraspinatus fossa. This angle represented the global glenoid inclination. Because an appropriately placed baseplate only occu- pies the inferior portion of the glenoid and because the glenoid has a curvature, the global glenoid inclination provided by theβ angle systematically underestimates the focal inclination at the level of the baseplate. Our experience has been that preoperative planning using the β angle leads to baseplate placement with insufficient correction of superior tilt (Fig. 2,A).

By contrast, the RSA angle is defined as the angle between the inferior glenoid fossa (where a reverse total shoulder arthroplasty baseplate would be implanted) and the perpendicular to the floor of the supraspinatus fossa. Development of the RSA angle provided a method to describe the local, inferior glenoid inclination, which is the inclination relevant to implantation of a baseplate in RSA (Fig. 2,B). With increased graft thickness for lateralization, the graft becomes trapezoidal (Fig. 2,C).

3D preoperative templating

In case of severe (>25°) or multiplanar deformity or erosion, our preference is to use 3D preoperative planning (Glenosys software;

Imascap, Brest, France). Standard preoperative CT images of the patient’s scapula allowed for creation of a 3D virtual model of the patient’s glenoid and accurate and reproducible measurements of version, inclination, bone loss, and bone graft dimensions.^15,30,42 Using algorithms specific to the manufacturer, the virtual model was used to template placement of the guidewire and central peg and to predetermine optimal baseplate positioning (Fig. 3). A patient- specific guide was then fabricated to direct the insertion point and orientation of the central guidewire.

Operative technique

All surgical procedures were performed by the senior author (P.B.) or under his direction. The procedure was done with the patient in the beach chair position and under general anesthesia with an interscalene block. The deltopectoral approach was used in all cases.

Any remaining subscapularis tendon was detached from the lesser tu- berosity and was tagged for reattachment at the end of the procedure, if appropriate. The long head of the biceps tendon was tenodesed in the groove, if still present. The goals of bone grafting were to restore version and inclination to as close to neutral as possible while in- creasing glenoid bone stock and lateralizing the joint line.

For simple to moderate (<25°) glenoid defects, standardized instrumentation combined with some eccentric reaming was used to reconstruct the glenoid and obtain neutral implant alignment (Fig. 4).

After exposure and dislocation of the humeral head, an oscillating saw was used to remove a small amount of bone at the summit of the humeral head, providing a flat surface and removing the subchondral plate. A threaded guidewire was then placed perpendicular to this cut and driven to the lateral cortex of the humerus. A cannulated drill was used to bore a central hole with a diameter of 8 mm.

A bell saw was passed to the desired depth. An oblique cutting guide was then used to harvest bone graft with a 12° angle (12.5 mm thick) and perform the anatomic neck osteotomy. The graft was removed and inserted over the long peg (25 or 30 mm) of the Aequalis baseplate (Wright-Tornier, Memphis, TN, USA).

In most cases, the inferior glenoid rim was still intact and iden- tifiable and was used as landmark to check guidewire placement.

Our aim was to place the guidewire to allow the baseplate to sit flush with the inferior border of the glenoid perpendicular to the line of the floor of the supraspinatus fossa. After insertion of a threaded guidewire into the glenoid vault using the 10° angled guide, a cannulated reamer was used to abrade the glenoid until the subchondral plate was reached, which was typically at a depth of approximate- ly 2 to 5 mm. In our experience, no more than 15° of eccentric reaming can be used to correct abnormal retroversion or inclination, and we avoided excessive reaming. Depending on the depth of the deformity, this reaming technique can create a mildly biplanar Figure 1 Angled BIO-RSA concept. An autologous, trapezoidal bone graft is harvested from the humeral head and used to restore the glenoid bone stock while correcting baseplate version and inclination, and lateralizing the center of rotation. The main advantages of this technique are the flexibility given to reconstruct multiplanar deformity (inclination and retroversion) and the low morbidity of the in situ graft harvesting.

Angled BIO-RSA 3

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glenoid face, which can be overcome through compression of the cancellous bone of the graft against the glenoid face.

The central peg was drilled, and small peripheral drill holes were made into the reamed and unreamed portions of the glenoid face using a threaded guidewire to obtain a complete bleeding bone surface. The long-peg (25 mm or 30 mm) baseplate and trapezoidal bone graft were impacted into the center hole, with the bone graft oriented to fill the defect. Baseplate fixation was performed first with nonlocking compression screws in the superior and inferior holes directed parallel to the central peg. Once compressed, convergent locking screws were placed in the anterior and poste-

rior baseplate holes. Finally, the glenosphere was fixed to the baseplate with both a Morse taper and a countersunk screw. Humeral preparation and implantation was performed using the standard surgical technique described for the Aequalis reversed prosthesis (Wright-Tornier).⁴

For more complex glenoid bone defects or severe glenoid erosion (>25°), or both, patient-specific grafts and guides were used. In these cases, the bell saw was extended deeper into the humeral cancellous metaphysis. A 5-mm osteotome was then passed through an anterior cortical window at the level of the surgical neck to free the bone graft distally. The bone graft was then contoured to fit the defect according to the preoperative 3D-CT plan. The patient-specific guide was used to position the guidewire with the desired inclination and retroversion correction. The high sides (anterior or inferior, or both) of the glenoid surface were slightly reamed with a cannulated reamer (<15°). In these cases of extreme glenoid deformity, in which the circular reamer cannot be flush with the glenoid, unreamed areas were abraded with a curette or a burr to stimulate graft healing. A longer-peg (30- or 35-mm) baseplate was used to fixate the patient- specific angled graft to the native glenoid. The final fixation of the graft was achieved using long screws through the baseplate, span- ning the graft into the native glenoid. After final fixation of the glenoid, the humeral preparation and implantation was completed using the standard technique.

The rehabilitation protocol used for the angled BIO-RSA was no different from that for a standard RSA.⁴

Outcomes assessment

All patients were retrospectively evaluated and radiographed.

Constant-Murley functional scores⁷were measured preoperatively and at each follow-up visit. Range of motion measurements included active forward elevation in the scapular plane, external rotation in adduction, and internal rotation in adduction. Abduction strength was measured with the arm at 90° abduction in the scapular plane using a handheld dynamometer. Patients were asked to estimate the value of their shoulder as a percentage of an entirely normal shoulder preoperatively and at the final follow-up.¹⁶

All patients underwent radiographic and CT evaluation to compare immediate postoperative and final follow-up images. Each radiograph and CT was examined for (1) bone graft healing (absence of a lucent line observed between the humeral bone graft and native glenoid), (2) bone graft resorption or lysis, and (3) inferior scapular notching, which was graded according to the classification system of Sirveaux et al.³⁹Correction of retroversion and inclination was measured according to Friedman’s line¹⁴and the RSA angle, respectively. Minimum follow-up was 2 years.

Statistical analysis

Data normality was analyzed with the d’Agostino-Pearson test, and parametric and nonparametric tests were used as appropriate. Pre- operative and postoperative scores and measurements of shoulder mobility were compared. Paired observations were compared using paired Studentttests and Wilcoxon signed rank tests, as appropriate, and unpaired observations were compared using Studentttests and the Mann-WhitneyUtest, as appropriate. Categoric data were compared usingχ²tests and Fisher exact tests, as appropriate, depending on cell populations. Statistical analysis was performed with MedCalc 11.0 software (MedCalc Software, Mariakerke, Belgium).

Figure 2 The reverse shoulder arthroplasty angle (RSA angle) is the angle between the inferior part of the glenoid fossa (where the baseplate is going to be implanted) and the perpendicular to the floor of the supraspinatus fossa. It can be measured on an anteroposte- rior radiograph, on a coronal slice of a reformatted computed tomography scan (like here), or on a 3-dimensional computed tomography scan reconstruction (A). Theβanglemeasures the global glenoid inclination, whereas the RSA angle measures the inferior glenoid inclination (B); when this reference is used for correction of glenoid inclination, the center peg must be parallel to the supraspinatus fossa line and the baseplate perpendicular to it. (Notice that the graft planned with the RSA angle is larger than the graft planned with theβangle.)(C)To provide glenoid baseplate lateralization, the graft must become trapezoidal in shape (instead of triangular).

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Figure 3 Preoperative templating using 3-dimensional computed tomography modeling software (Glenosys; Imascap, Brest, France;) for a patient with severe (>25°) multiplanar glenoid erosion (Walch type C, Favard type E3). The software helps the surgeon choose the optimal baseplate size and orientation, bone graft shape and size (patient-specific bone graft), as well as computing a patient-specific guide for drill- ing and asymmetrical reaming. In this case, 5° of retroversion has been accepted, whereas 8° of inferior inclination has looked for neutralizing superior shearing forces on the baseplate and graft.

Figure 4 A standardized instrumentation (Aequalis [Wright-Tornier] angled BIO-RSA) is used to harvest an asymmetrical bone graft from the humerus and correct moderate (<25°) glenoid defect or erosion. Cannulated bell saw (A) and inclined cutting guide (B) are used to harvest a standardized 12° angulated (trapezoidal shaped) bone graft, which is then placed on a long-peg (25-mm) baseplate (C). To reconstruct the bone loss/erosion and achieve neutral implant alignment, some eccentric reaming of the glenoid is often performed in combination with the use of the asymmetrical bone graft: for example, to correct a moderate (<25°) glenoid defect or erosion in 1 plane, the surgeon can perform 10° of asymmetrical reaming combined with the 12° angled BIO-RSA. To correct a severe (>25°) glenoid defect, a bell saw is inserted deeper in the proximal humerus, and a small osteotome is inserted at surgical neck level to harvest a larger (up to 25 mm) bone graft.

Angled BIO-RSA 5

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Results Demographics

Our cohort included 54 arthritic patients (70% female) with a mean age of 73 years (range, 52-85 years) treated with an angled BIO-RSA. Thirty-one patients received an angled BIO- RSA for cuff-tear arthropathy, 13 for primary glenohumeral osteoarthritis, 6 for rheumatoid arthritis, 2 for postinstability arthropathy, and 2 for fracture sequelae. According to the Walch system,^36,418 shoulders were classified as A2, 15 as B2, and 7 as C. According to the Favard system,¹⁰15 shoulders were classified as E2, 21 as E3, and 3 as E4. Combined vertical and horizontal glenoid bone deficiency was present in 15 patients.

Complications and revisions

Glenoid loosening occurred in 3 patients (5%). Each of these occurred in the first 6 months after the operation. These included 1 infected loosening, 1 traumatic glenoid loosening caused by a fall 4 weeks postoperatively, and 1 glenoid loosening caused by uncorrected superior inclination. The latter 2 patients were revised with revision RSA with ICBG with good results. There was no radiographic humeral loosening or failure.

No patients suffered a postoperative dislocation or subluxation.

One patient sustained a fracture of scapula spine 3 months after surgery, which was treated conservatively. Another patient sustained a pulmonary embolism treated with curative injec- tion of heparin.

Radiologic results

Aside from the 3 patients with glenoid loosening, no other patients showed radiographic signs of baseplate loosening such as lucency around the screws or a change in position of the baseplate.

Complete incorporation was observed in all patients other than the 3 with complications. Radiographs and CT images demonstrated union between the cancellous bone graft and the surface of the native glenoid in 94% (51 of 54) of the patients.

At final follow-up, 13 patients (25%) had grade 1 to 3 scapular notching. No patients had grade 4 inferior scapular notching.

Correction of glenoid deformity

Preoperative and postoperative CT measurements of inclination and version were performed using the multiplanar reconstruction mode to make our measurements in the plane of the scapula. The correction of glenoid orientation was significant in both planes.

The inclination and version deformity corrections achieved with the angled BIO-RSA, as measured on reformatted 2D CT-scans, are summarized inTable I.

In the 15 patients with combined (vertical and horizontal) glenoid bone loss, the angled BIO-RSA technique allowed simultaneous correction of both the posterior and superior defects. The correction achieved in both planes was statisti- cally significant (Table II,Fig. 5).

Table I Correction of vertical and horizontal deformity of the glenoid as measured with preoperative and postoperative 2-dimensional reformatted CT scans

Variable No. Preoperative Postoperative Pvalue

Mean (range),° Mean (range),°

Glenoid inclination (RSA angle)

Global series 54 27 (5 to 57) 8.6 (−23 to 35) <.0001

Favard E2/E3 39 37 (14 to 84) 10.2 (−28 to 36) <.0001

Glenoid version (Friedman angle)

Global series 54 −12.1 (−49 to+15) −4.7 (−32 to+21) .008

Walch B2/C 30 −21.1 (−49 to 0) −10.6 (−32 to+4) .006

Table II Correction of glenoid orientation in patients with combined (coronal and axial) glenoid deficiencies as measured on reformatted 2-dimensional computed tomography scans

Glenoid orientation Preoperatively Postoperatively Pvalue

Mean (range), ° Mean (range),°

Coronal-plane correction

Inclination (RSA angle) 27.5 (+15 to+40) 11.5 (+4 to+21) .0002

Axial-plane correction Version (corrected

Friedman angle)

18.4 (–49 to+2) 5.6 (–21 to+6) .01

RSA, reverse shoulder arthroplasty.

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Functional results

All patients who received an angled BIO-RSA demonstrated significant functional improvements (Table III). The average gain in active motion was 63° for forward elevation and 12° for external rotation.

Discussion

Acquired bone defects are present in nearly 40% of patients with cuff tear arthropathy and can be significant adverse factors affecting outcomes of shoulder replacement surgery.^11,13,24 Severe glenoid bone loss, usually in the form of excessive

retroversion or superior inclination, or both, must be corrected to optimize outcomes and minimize complications in

RSA.^29,33,44Walch types B2/C (biconcave/hypoplastic) and

Favard E2/E3 (acquired superior defects) pose difficult reconstruction challenges.^29,35 Current options for correcting deformity include eccentric reaming, bone grafting with ICBG or allograft, and augmented glenoid baseplates.9,17,20,32,34,43

Our original surgical option, since 2006, has been to use an angled bone graft harvested from the humeral head (angled BIO- RSA) to restore the glenoid bone stock and obtain correct alignment of the implant with minimal morbidity.

The purpose of the present study was to report the results of angled BIO-RSA in addressing glenoid bone deficiency, including combined (multiplanar) glenoid bone loss. Our 3 hypotheses were verified: (1) the asymmetrical (trapezoidal) autologous bone graft harvested from the humeral head predictably heals and incorporates to the native glenoid, (2) the bone graft restores glenoid bone stock and allows correct baseplate alignment, and (3) the graft allows lateralization of the baseplate and sphere (or at least, avoids its medialization), providing good functional results, comparable to those of RSA in the absence of glenoid deficiency, and avoids complications such as instability and severe scapular notching.

Our first hypothesis is confirmed: despite the advanced age of the patients (73 years), at a mean 3 years of follow-up, 94% of the grafts incorporated to the native scapula. We observed only 3 patients with glenoid loosening: 1 after early trauma, 1 secondary to a technical mistake (persistent superior inclination), and 1 secondary to infection. Our results confirm that even in elderly patients, an autologous bone graft harvested from the humeral head reliably and predictably fuses to the native glenoid in RSA. These results are in agree- ment with previous reports on the use of autografts in RSA^1,2,18,25and our prior results with standard (nonangled) BIO-RSA for patients without glenoid deficiency.⁴These results are not surprising: Jones et al²³recently demonstrated a higher rate of graft incorporation in RSA for autografts compared with allografts (86% complete or partial incorporation for autografts vs. 66% for allografts). Furthermore, compared with anatomic shoulder arthroplasty, the RSA presents a favorable environment for glenoid graft incorporation. Immediate graft fixation and compression are obtained by the combination of the long-peg baseplate and screws in the native scapula, and compression forces (after 30° of abduction) are favorable to graft healing and incorporation .⁴

Figure 5 Examples of correction of glenoid bone loss or erosion obtained with the BIO-RSA.(A)Posterior asymmetric bone graft used to correct excessive (49°) retroversion in a Walch type C glenoid.

Notice the neutral implant alignment and complete bone graft healing 33 months after surgery.(B)Superior asymmetric bone graft used to correct excessive (45°) superior erosion in Favard type E1 glenoid.

In the vertical plane, the goal is to place the central peg parallel to the supraspinatus fossa line (ie, to negate the RSA angle and there- fore neutralize the superior shearing forces), whereas the baseplate is placed flush to the inferior glenoid rim (to avoid inferior scapular notching). Notice the absence of (A) posterior or (B) inferior scapular notching, thanks to the bony lateralization.

Table III Functional results

Variable Preoperative Postoperative Pvalue

Mean (range) Mean (range)

Active forward elevation,° 85 (20-140) 148 (80-170) <.001

Active external rotation,° 12 (−20 to 60) 24 (−20 to 70) <.001

Active internal rotation S1 (0-T12) L4 (GT-D8) <.001

Constant-Murley score, points 31 (9-62) 68 (30-89) <.001

Subjective Shoulder Value, % 30 (10-60) 83 (0-100) <.001

Angled BIO-RSA 7

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Our second hypothesis is also confirmed: the angled BIO- RSA technique allows for correction of severe glenoid deficiency, including retroversion or inclination of 25° or more, and provides the flexibility needed to reconstruct multiplanar deformity (Tables I and II). Our study demonstrates that patients with severe Walch B2/C and/or Favard E2/E3 glenoid deformities can reliably undergo RSA with this technique. Si- multaneous correction of posterior and superior glenoid defects in patients with combined (multiplanar) glenoid bone loss is undoubtedly one of the main advantages of using a cancellous bone graft. Other advantages of the angled BIO-RSA technique include minimal donor-site morbidity (compared with ICBG^6,12), no potential for disease transmission (compared with allograft²¹), and no additional cost (compared with allograft or augmented baseplate^22,34). In comparison, augmented baseplates do not have this flexibility because they allow correction in only 1 plane. Only a patient-specific augmented baseplate could be used to correct a complex multiplanar deformity; however, the process to build such an implant is more complex and expensive. In addition, it does not offer the possibility to reconstruct the glenoid bone stock.

Finally, our third hypothesis is verified: Functional outcomes were good, similar to those with standard RSA without glenoid bone deficiency.^1,8,18,31No prosthetic dislocation was observed in the present series, and all parameters of the Constant-Murley score significantly improved (Table III). The angled BIO-RSA not only allows correction of severe glenoid erosion but also provides lateralization of the glenoid component (or at least, avoids glenoid medialization). This results in great postoperative motion, improved shoulder contour, absence of instability, and a relatively low rate of scapular notching.

Although no severe scapular notching (grade 4) was observed in the present series, we still observed a 25% rate of mild (grade 1 to 3) scapular notching. All cases of scapular notching were observed with the use of the small (36-mm) sphere and large (29-mm) baseplate (the small [25-mm] baseplate was not available at the time of this series). These results confirm that lateralization alone is not sufficient to avoid scapular notching and that a minimum of 5 mm of inferior overhang is also needed.^1,5,26Nowadays, we constantly achieve this 5 mm of inferior overhang (in addition to glenoid lateralization) by matching the baseplate and sphere sizes: we use a 25-mm baseplate with the 36-mm glenosphere and the 29- mm baseplate with the 42-mm sphere. Since the recent release of the 25-mm baseplate, we have observed a dramatic decrease in the rate of scapular notching. In addition, inferior eccentric sphere and lateralized humeral implants are available today.

In our experience, preoperative planning is the key to success for bone grafting in RSA. We systematically use 2D or 3D CT images, or both, to measure glenoid bone loss and to anticipate baseplate and bone graft positioning.^3,37,38In the axial plane, we use the corrected Friedman line (or plane of the scapula) for the best glenoid implant alignment: our goal is to implant the baseplate within 10° of neutral version. In

the coronal plane, our goal is to implant the baseplate perpendicular to the floor of the supraspinatus fossa (ie, the peg parallel to the line of the supraspinatus fossa). As men- tioned above, the RSA angle measures focal inferior glenoid inclination and thus is helpful to accurately determine the size and shape of bone graft needed to compensate for superior inclination in RSA (Fig. 2).

For simple (1 plane) and moderate (<25°) glenoid bone loss, we used standardized instrumentation combined with slight eccentric reaming to achieve glenoid reconstruction and implant alignment. For instance, in a patient with a cuff tear arthritis, to compensate for a 22° glenoid superior bone loss (22° of superior inclination), we achieve 10° of correction using inferior eccentric reaming, whereas the additional correction is achieved through a standardized 12° angled bone graft (Fig. 4). Fixation of the graft is of paramount impor- tance: a long-pegged baseplate (≥25 mm) is used to ensure that the peg contacts a minimum of 10 mm of native glenoid for immediate secure fixation and early ingrowth. Long screws (35 to 45 mm) are also necessary to fixate the baseplate to both the graft and the scapula. For more severe glenoid erosion (>25°) or complex (multiplanar) glenoid bone defects, 3D preoperative planning with CT scans and dedicated planning software (Glenosys) is useful to quantify the glenoid erosion, to plan the depth of reaming, the thickness and shape of the graft, and the position of the baseplate. In these cases, a longer- pegged glenoid component (30- or 35-mm) and longer screws may be necessary to obtain graft fixation and incorporation.

This study has several limitations. This is a retrospective, single-center study without a control group, and only midterm results are reported. In addition, only a single implant was used, and this technique may not be as successful with other implants.

We included a variety of indications within our cohort. This increases generalizability but may limit internal validity.

Bone graft resorption may occur with longer follow-up.

RSA, however, provides rigid bone graft fixation under com- pressive forces with the help of the baseplate and screws, which makes us believe that there is low risk of further resorption or lysis of the autograft with extended follow-up.

Most patients with clinical loosening after RSA experience this complication within the first 2 years postoperatively.²¹ Based on our extensive experience with the standard BIO- RSA (since starting in 2006 we have operated on >1000 patients with this technique), our opinion is that significant resorption or lysis will not occur with extended follow-up.

A limit of this technique is that it cannot be used for revision of a previous arthroplasty or when there is necrosis or absence of the humeral head; in this case, we use allograft or an augmented baseplate.

Strengths of our study are that, to our knowledge, this is the largest reported series of patients with humeral autograft used to reconstruct significant glenoid deficiencies during RSA with a minimum of 2 years of follow-up. Furthermore, the methods used to assess graft incorporation and complications are robust: radiographs and CT images were both used

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to evaluate preoperative bone loss, postoperative graft incorporation, glenoid loosening, and scapular notching.

Conclusion

The angled BIO-RSA is a viable and simple solution to address severe glenoid bone loss during RSA. The humeral head is an excellent source of autograft: the graft constantly and predictably incorporates. The asymmetrical (trapezoidal) autologous bone graft, harvested from the humeral head, allows restoration of glenoid bone stock, and correction of baseplate alignment with minimal morbidity. The angled BIO-RSA technique provides the flexibility needed to reconstruct multiplanar deformity. In addition, the graft allows lateralization of the baseplate and sphere, providing good functional results, comparable to those of RSA in the absence of glenoid deficiency. Other advantages include the lack of donor-site morbidity (compared to ICBG), the absence risk of disease transmission (compared to allograft), and low cost (compared to augmented baseplate or allograft). The patient is his or her own donor, and the graft is located in situ.

Disclaimer

Pascal Boileau and Gilles Walch receive royalties from Wright, are involved in the development of the software (Glenosys) used in the present study, and are sharehold- ers of Imascap. All of the other authors, their immediate families, and any research foundations with which they are affiliated have not received any financial payments or other benefits from any commercial entity related to the subject of this article.

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