Orthopedics

Feature Article 

Lateralized Center of Rotation and Lower Neck-Shaft Angle Are Associated With Lower Rates of Scapular Notching and Heterotopic Ossification and Improved Pain for Reverse Shoulder Arthroplasty at 1 Year

Ryan Nelson, DO; Jeremiah T. Lowe, BA; Sarah M. Lawler, BA; Megan Fitzgerald, BA; Matthew T. Mantell, MD; Andrew Jawa, MD

Abstract

Heterotopic ossification and scapular notching are common following reverse total shoulder arthroplasty. Compared with the original Grammont-style prosthesis with a medialized center of rotation (COR) and a 155° neck-shaft angle, lateralization of COR and reduction of neck-shaft angle have been associated with decreased incidence of scapular notching. The authors hypothesized that these design features may also be effective in reducing heterotopic ossification after reverse total shoulder arthroplasty. Ninety-seven consecutive patients who underwent reverse total shoulder arthroplasty performed by a single surgeon were included in the study. Forty-eight patients received a Grammont-style prosthesis, and 49 received a prosthesis with either 6 mm or 10 mm of lateral COR offset and a 135° neck-shaft angle. Radiographs at 1-year follow-up were reviewed by 2 surgeons for notching and heterotopic ossification. Patient-reported outcome scores and range of motion were also compared between the groups. More patients in the Grammont-style group showed scapular notching (Grammont, 35.4%; lateral COR, 12.2%; P=.018) and heterotopic ossification (Grammont, 47.9%; lateral COR, 22.4%; P=.009). The lateralized COR group reported lower pain on the visual analog scale (Grammont mean, 1.1; lateral COR mean, 0.5; P=.01) and trended toward better American Shoulder and Elbow Surgeons scores (Grammont mean, 77.2; lateral COR mean, 83.4; P=.05). However, range of motion was similar between the 2 groups. Compared with the Grammont-style prosthesis, the lateralized COR prosthesis with a decreased neck-shaft angle resulted in a lower incidence of both scapular notching and heterotopic ossification as well as better pain scores and a trend toward improved function at 1 year after reverse total shoulder arthroplasty. [Orthopedics. 2018; 41(4):230–236.]

Abstract

Heterotopic ossification and scapular notching are common following reverse total shoulder arthroplasty. Compared with the original Grammont-style prosthesis with a medialized center of rotation (COR) and a 155° neck-shaft angle, lateralization of COR and reduction of neck-shaft angle have been associated with decreased incidence of scapular notching. The authors hypothesized that these design features may also be effective in reducing heterotopic ossification after reverse total shoulder arthroplasty. Ninety-seven consecutive patients who underwent reverse total shoulder arthroplasty performed by a single surgeon were included in the study. Forty-eight patients received a Grammont-style prosthesis, and 49 received a prosthesis with either 6 mm or 10 mm of lateral COR offset and a 135° neck-shaft angle. Radiographs at 1-year follow-up were reviewed by 2 surgeons for notching and heterotopic ossification. Patient-reported outcome scores and range of motion were also compared between the groups. More patients in the Grammont-style group showed scapular notching (Grammont, 35.4%; lateral COR, 12.2%; P=.018) and heterotopic ossification (Grammont, 47.9%; lateral COR, 22.4%; P=.009). The lateralized COR group reported lower pain on the visual analog scale (Grammont mean, 1.1; lateral COR mean, 0.5; P=.01) and trended toward better American Shoulder and Elbow Surgeons scores (Grammont mean, 77.2; lateral COR mean, 83.4; P=.05). However, range of motion was similar between the 2 groups. Compared with the Grammont-style prosthesis, the lateralized COR prosthesis with a decreased neck-shaft angle resulted in a lower incidence of both scapular notching and heterotopic ossification as well as better pain scores and a trend toward improved function at 1 year after reverse total shoulder arthroplasty. [Orthopedics. 2018; 41(4):230–236.]

Heterotopic ossification (HO) along the long head of the triceps tendon and scapular notching are common following primary reverse total shoulder arthroplasty (RSA). Scapular notching, reportedly occurring in up to 96% of patients,1 has been extensively studied and may be associated with poorer outcomes.2–5 In these studies, the RSA prosthesis is characterized by a glenosphere with a medialized center of rotation (COR) and a 155° neck-shaft angle (NSA), being commonly referred to as the Grammont-style prosthesis. Altered design features, such as a lateral COR offset and lower NSA, have been shown to reduce the prevalence of notching during short-term follow-up.6–10 Although studied far less, HO presents after RSA with a similarly reported incidence as high as 94%.10–14 Recent studies suggest that HO formation is associated with decreased range of motion11 and poorer functional outcomes through 12 months after RSA.4

Scapular notching results from mechanical impingement of the humeral component on the inferior aspect of the scapular neck.2,3 However, the etiology of HO along the triceps after RSA remains unclear. Moreover, the prevalence of HO following anatomic total shoulder arthroplasty is substantially lower than that following RSA—between 15% and 45%.15–17 This has led to speculation that HO is caused by increased traction on the triceps,18 greater soft tissue dissection during the surgical approach,12,13,19 and mechanical irritation of the humeral tray on local soft tissue or on the scapular neck itself.9,11,20

A study by Kempton et al9 compared a reverse prosthesis with no COR offset and a 155° NSA with a prosthesis with 2.5 mm of lateral COR offset and a 143° NSA. The authors reported a significantly higher rate of notching with the former prosthesis (60.7% vs 16.2%). The formation of a gap between the humeral component and the scapula owing to lateralization may limit impingement and thus reduce the incidence of scapular notching.21 In the current study, the same 2.5-mm lateralizing glenosphere paired with a 155° NSA humeral component was compared with a prosthesis with either 6 mm or 10 mm of COR offset and a 135° NSA. Given the increasing evidence that HO has clinical consequences for RSA outcomes, it is important to investigate how prosthesis design can mitigate the frequency of HO formation. Thus, the authors' aim was to compare radiographic and clinical outcomes between the 2 prosthesis designs 1 year after RSA. The authors hypothesized that, in addition to impacting notching rates, lateralized COR and lower NSA may also have an effect on the occurrence of HO after RSA.

Materials and Methods

After institutional review board approval was obtained, a retrospective review of a prospectively maintained database was performed to identify a consecutive series of patients who underwent primary reverse total shoulder replacement by a single surgeon (A.J.) from 2013 to 2015. Surgical indications for RSA include rotator cuff tear arthropathy, massive irreparable rotator cuff tears with pseudoparesis, lack of glenoid bone stock, and advanced glenoid pathology that would not support a polyethylene glenoid implant. Reverse total shoulder arthroplasty was elected for the treatment of rotator cuff arthropathy or advanced glenohumeral osteoarthritis with rotator cuff deficiency. During the study time frame, the surgeon changed prostheses from a Grammont-style design with a 2.5-mm medial COR offset and a 155° NSA (humeral component—Anatomical Shoulder Reverse System; glenoid component—Bigliani/Flatow System; Zimmer, Warsaw, Indiana) to a 6- or 10-mm lateralized design with a 135° NSA (Reverse Shoulder Prosthesis; DJO/Encore Medical Corporation, Austin, Texas). While using the Grammont-style prosthesis, a 36-mm glenosphere was implanted in all patients. After switching to the lateralized implant, the surgeon uniformly implanted a 32-mm glenosphere with 6 mm of lateral COR offset in females and a 36-mm glenosphere with 10 mm of offset in males. No aspect of the surgical technique other than the implants was changed during the study time frame. All RSA surgeries were performed by the surgeon using the delto-pectoral approach. Neither nonsteroidal anti-inflammatory drugs nor intra-articular injections were routinely used as part of the surgeon's postoperative protocol for pain relief. Patients were given home physical therapy exercises with instructions as follows: for 6 weeks postoperatively, no external rotation beyond neutral with sling; at 6 weeks postoperatively, discontinue sling and perform range of motion exercises, including external rotation and behind the back; and at 3 months postoperatively, strengthening exercises permitted and return to all normal activity as tolerated.

Inclusion and Exclusion Criteria

Patients were eligible for the study provided that they had a documented 1-year follow-up visit with adequate anteroposterior radiographs, determined as having a true Grashey view with anteroposterior view of the scapula and glenoid baseplate interface, for the evaluation of scapular notching and HO. Preoperatively, patients completed the American Shoulder and Elbow Surgeons (ASES) questionnaire and the visual analog scale (VAS) for pain. At the time of their 1-year follow-up, patients again completed the ASES questionnaire and the VAS for pain. In addition, the surgeon performed a range of motion assessment using a goniometer to measure degrees of forward flexion and external rotation. Revision arthroplasties and RSA performed for the treatment of proximal humerus fractures and nonunions were excluded. Other exclusion criteria were a lack of preoperative or 1-year follow-up data, defined as 12 months (+30 days) from the operative date, for consistent comparison of scapular notching and HO incidence and inadequate radiographs.

Radiographic Analysis

For the purposes of this study, the authors followed the precedent of recent authors who define HO as any ossification along the long head of the triceps tendon regardless of whether it is contiguous or noncontiguous with the inferior aspect of the scapular neck.2,4,10

True anteroposterior radiographs obtained 1 year after RSA were reviewed to evaluate scapular notching and HO. The radiographs were presented in a blinded fashion to 2 fellowship-trained surgeons (R.N., A.J.) using a picture archiving and communications system. Scapular notching was defined as any erosion of the native scapular spine, starting from the inferior aspect. Grading of scapular notching was determined by consensus according to the Sirveaux classification as follows: notching involving only the scapular bone (grade 1), notching contacting the inferior screw of the baseplate (grade 2), notching extending to the superior aspect of the inferior screw of the baseplate (grade 3), and notching extending superior to the inferior screw of the baseplate to include the area under the baseplate (grade 4).5 Heterotopic ossification was graded according to 2 recently established classification systems to ensure accurate and complete description of HO incidence: the first was described by Ko et al11 and the second was a modified Brooker classification8,16,18 (originally for HO of the hip) described by Verhofste et al.14 A summary of the classification systems is provided in Table 1 and Table 2.

Ko et al11 Classification for Heterotopic Ossification

Table 1:

Ko et al11 Classification for Heterotopic Ossification

The Modified Brooker Classification23 for Heterotopic Ossification

Table 2:

The Modified Brooker Classification23 for Heterotopic Ossification

Statistical Methods

All statistical analyses were performed by an experienced biostatistician using SAS version 9.4 software (SAS Institute, Cary, North Carolina). A Shapiro–Wilk test of the data found that the continuous variables of a given time point did not satisfy a normal distribution. A Wilcoxon signed rank test was used to compare both preoperative and postoperative ASES, Quick Disabilities of the Arm, Shoulder and Hand, and VAS pain scores, forward flexion, and external rotation between the 2 groups. Due to the categorical nature of scapular notching and HO, these graded data were analyzed using the chi-square test. A Fisher's exact test was used to compare complication rates between the 2 groups because of the small numbers of complications. The 2-tailed threshold of significance was set at P<.05.

Results

A total of 168 patients underwent RSA performed by the surgeon from April 2013 to November 2015. Of those screened, 97 patients met the inclusion criteria, with 61 being excluded because of lack of 1-year follow-up and 10 because of abnormal diagnoses such as fractures, nonunions, and chronic dislocation. Among those included, 48 received the Grammont-style prosthesis and 49 received the lateral COR prosthesis. The demographic data are summarized in Table 3.

Group Characteristics

Table 3:

Group Characteristics

Scapular Notching

Scapular notching of any grade was observed in 17 patients (35.4%) in the Grammont-style prosthesis group vs 6 patients (12.2%) in the lateral COR prosthesis group (P=.018). Specific data on notching grade according to the Sirveaux classification are provided in Table 4.

Scapular Notching Incidence and Grade by Sirveaux Classification

Table 4:

Scapular Notching Incidence and Grade by Sirveaux Classification

Heterotopic Ossification

Heterotopic ossification of any grade was observed in 23 patients (47.9%) in the Grammont-style prosthesis group compared with 11 patients (22.4%) in the lateral COR prosthesis group (P=.009). Specific data on HO grades according to each classification system are detailed in Table 5. Examples of shoulder radiographs for each prosthesis group with HO are shown in the Figure.

Heterotopic Ossification Incidence and Grades by 2 Classification Systems

Table 5:

Heterotopic Ossification Incidence and Grades by 2 Classification Systems

Grashey view shoulder radiographs showing heterotopic ossification 1 year postoperatively in a patient with a Grammont-style, reverse total shoulder arthroplasty prosthetic implant with 2.5 mm of lateral offset from the glenoid plane and a 155° neck-shaft angle (A) and a patient with a lateral center of rotation, reverse total shoulder arthroplasty implant with 6 mm of lateral offset and a 135° neck-shaft angle (B).

Figure:

Grashey view shoulder radiographs showing heterotopic ossification 1 year postoperatively in a patient with a Grammont-style, reverse total shoulder arthroplasty prosthetic implant with 2.5 mm of lateral offset from the glenoid plane and a 155° neck-shaft angle (A) and a patient with a lateral center of rotation, reverse total shoulder arthroplasty implant with 6 mm of lateral offset and a 135° neck-shaft angle (B).

Baseline and 1-Year Outcome Measures

Preoperatively, the mean ASES scores were comparable in the 2 groups (Table 6). The mean VAS pain score was significantly lower in the lateral COR group (P=.01) compared with the Grammont-style group, and the mean 1-year ASES scores trended higher (P=.05). Forward flexion and external rotation were similar in the 2 groups (P=.13 and P=.27, respectively).

Patient-Reported Outcome Measures and Range of Motion

Table 6:

Patient-Reported Outcome Measures and Range of Motion

Complications

In the Grammont-style prosthesis group, there was 1 acromial fracture, 1 pulmonary embolism, 1 intraoperative glenoid fracture, and 1 occurrence of a transient neurological lesion that was near completely resolved by 1-year follow-up (8% overall complication rate). In the lateral COR prosthesis group, there was 1 intraoperative humeral fracture and 1 case of delayed superficial wound healing (4% overall complication rate). The difference in complication rates between the groups was not found to be statistically significant (P=.435). There were no patients requiring revision surgery through the time of 1-year follow-up.

Discussion

In addition to evidence that scapular notching is associated with poorer clinical outcomes,3,18,22 recent studies suggest that HO may also have significant clinical consequences.5 When compared with a Grammont-style design with 2.5 mm of COR offset and a 155° NSA, the authors' findings indicate that the incidence of both scapular notching and HO may be reduced with increased lateral COR offset up to 10 mm and a lower NSA of 135°. Moreover, the authors observed marginally better outcomes in the lateral COR group using VAS pain and ASES scores.

Due to the nature of this study, the authors were not able to isolate variables and determine if reductions in notching and HO were due to COR, NSA, or a combination of the 2. However, a study by Kempton et al9 reported a notching rate of 16.2% in a cohort with the same 2.5-mm lateral offset Zimmer glenosphere used in the current study but matched to a different 143° NSA humeral component (cumulative 150° NSA due to a 7° polyethylene liner). In the current cohort, with an identical glenosphere and a higher 155° NSA humeral component, the authors observed a higher notching rate of 35.4%. Although the authors acknowledge the systematic differences between the 2 studies (eg, different surgeons, institutions, and techniques), the interstudy comparison still contributes evidence that lower NSA may be an independent factor associated with lower notching. Additionally, Kempton et al9 reported a notching rate of 60.7% in their cohort with no COR offset and a 155° NSA, whereas the current authors found notching in 35.4% of patients with 2.5 mm of lateralization and a 155° NSA. Thus, the current study offers evidence that lateral COR offset is also an independent factor in notching mitigation. Both conclusions are consistent with biomechanical models published by Gutiérrez et al21 showing that lateral COR offset and lower NSA are independent variables that mitigate adduction deficit, which is related to the mechanical impingement on the scapular neck that causes notching.

Consistent with the current findings regarding HO, Kempton et al9 reported a higher incidence of “inferior scapular neck spur”—which would be considered an HO subtype in the current analysis—in the group with no lateral offset and a 155° NSA. However, the difference was not significant (28.6% vs 16.2%; P=.36) in their sample, which was approximately half the size of the sample in the current study. Notably, the current study's evaluation criteria of HO differ considerably from those of Kempton et al,9 who reported only inferior scapular neck spurs. In each of the current study's groups, close to half of the radiographs with HO were identified as “free-floating,” falling under “subtype B” and “grade 1a” according to the Ko et al11 and modified Brooker23 classifications, respectively (Table 5). These variations of HO do not appear to have been evaluated by Kempton et al,9 which may explain their lower overall incidence.

Two recent studies by Ko et al11 and Verhofste et al14 reported overall HO rates after Grammont-style RSA of 61.6% and 29.5%, respectively. The incidence rate of HO in the current study's Grammont-style group was 47.9%. Lowest of all was the 22.4% incidence of HO in the group with a lateralized COR and 135° NSA. Although HO is a common radiographic finding following RSA, the etiology remains unclear. Several hypotheses exist to explain the phenomenon, which is less prevalent after anatomic total shoulder arthroplasty. These include increased tissue damage from extensive capsular releases,12,13,19 traction on the triceps from lengthening of the arm,18 and mechanical irritation caused by the humeral tray.9,11,20 The current study's findings indicate that lateral offset and lower NSA—proven methods of notching reduction—are effective together in decreasing the incidence of HO. Inferior scapular neck osteophytes are common HO subtypes with both the Ko et al11 and the modified Brooker classifications.23 These formations may be related to the same inferior scapular neck impingement that causes notching, thereby explaining the dual effectiveness of lateralization and lowered NSA. Additionally, arm lengthening and the resulting traction on the triceps, which have been proposed causes of HO, may be mitigated by lateral COR offset. Adequate deltoid tension is achieved with lateral offset rather than inferior translation of the humerus, and arm lengthening is lessened as a result.

The authors did not attempt to evaluate differences in outcomes between those with and without notching or HO owing to sample size limitations. Thus, they cannot comment on the clinical consequences of each phenomenon. Nevertheless, their findings suggest that outcomes may be slightly improved with lateral offset and lower NSA. The Grammont-style group had a significantly higher mean VAS pain score than the counterpart group (1.1 vs 0.5; P=.01), although the authors cannot be sure that this finding is clinically significant. As a result, the mean ASES score in the Grammont group was lower (77.2 vs 83.4; P=.05) at 1-year follow-up. Minimal clinically important change score on the ASES has been reported as a difference of 9 points. Although this may be a true difference in score, it was not clinically significant. Determining whether these differences were related to higher rates of notching and HO in the Grammont group will necessitate further research.

This is the first study comparing HO between a Grammont-style prosthesis and a lateralized design with a 135° NSA. This also is the largest series (n=97) offering an immediate comparison between Grammont-style and more lateralized designs used in surgery performed by a single surgeon. Nevertheless, there are several limitations to this study. The primary limitation was the relatively short-term follow-up of 1 year. Scapular notching tends to present postoperatively in the short term but appears to be a progressive condition beyond 2 years in a substantial subset of RSA patients.2,3,12 Heterotopic ossification, however, may not be progressive beyond 1 year in most cases. Verhofste et al14 showed that HO stabilized after an average of 8 months following RSA. Thus, the findings from the current study's short-term follow-up are likely a strong approximation of notching and HO incidence rates, but may not fully account for the progression of notching to more severe grades at longer follow-up. The difference in lateral offset in men (10 mm) and women (6 mm) was not accounted for with the authors' statistical methods because patients were grouped on a binary of no offset (Grammont) or offset, which could have had an effect on the statistical analysis. Additionally, the authors acknowledge that surgeon experience may have been a minor factor in the different outcomes between groups. Within the study time frame, the Grammont-style prosthesis was used from 2013 to 2014, whereas the lateralized design was used from 2014 to 2015. All other aspects of the surgeon's approach and protocol, however, remained consistent.

The authors did not attempt to evaluate clinical differences between patients with and without notching or HO. Thus, they cannot comment on the findings of Ko et al11 or Verhofste et al,14 who reported decreased forward flexion and poorer outcome scores associated with HO, respectively. Further research is necessary to support the claims that HO is clinically significant.

Lateral offset may have consequences. These include a loss of the mechanical advantage for the deltoid during abduction24 and increased stress on the acromion associated with a higher risk of acromial stress fracture.25 The authors did not observe specific evidence of these issues in their series, but surgeons should take this into account when selecting an implant.

Conclusion

In this study, the lateralized COR prosthesis showed a lower incidence of HO and scapular notching than the Grammont-style prosthesis. In addition, the authors observed a trend toward better clinical outcomes with the lateralized prosthesis. Further research is needed to determine the optimal degree of lateralization and NSA. However, because of the decreased pain scores and a trend toward improved outcome measures, a lateralized design with an anatomic NSA may be optimal to decrease the HO and notching rates. Adoption of a lateralized implant will depend on whether surgeons are concerned with the incidence and amount of HO in their Grammont-style RSAs, as there is not yet consensus on whether it is important to avoid.

References

  1. Werner CM, Steinmann PA, Gilbart M, Gerber C. Treatment of painful pseudoparesis due to irreparable rotator cuff dysfunction with the Delta III reverse-ball-and-socket total shoulder prosthesis. J Bone Joint Surg Am. 2005; 87(7):1476–1486.
  2. Lévigne C, Boileau P, Favard L, et al. Scapular notching in reverse shoulder arthroplasty. J Shoulder Elbow Surg. 2008; 17(6):925–935. doi:10.1016/j.jse.2008.02.010 [CrossRef]
  3. Lévigne C, Garret J, Boileau P, Alami G, Favard L, Walch G. Scapular notching in reverse shoulder arthroplasty: is it important to avoid it and how?Clin Orthop Relat Res.2011; 469(9):2512–2520. doi:10.1007/s11999-010-1695-8 [CrossRef]
  4. Simovitch RW, Zumstein MA, Lohri E, Helmy N, Gerber C. Predictors of scapular notching in patients managed with the Delta III reverse total shoulder replacement. J Bone Joint Surg Am. 2007; 89(3):588–600. doi:10.2106/JBJS.F.00226 [CrossRef]
  5. Sirveaux F, Favard L, Oudet D, Huquet D, Walch G, Molé D. Grammont inverted total shoulder arthroplasty in the treatment of glenohumeral osteoarthritis with massive rupture of the cuff: results of a multicentre study of 80 shoulders. J Bone Joint Surg Br. 2004; 86(3):388–395. doi:10.1302/0301-620X.86B3.14024 [CrossRef]
  6. Cuff D, Clark R, Pupello D, Frankle M. Reverse shoulder arthroplasty for the treatment of rotator cuff deficiency: a concise follow-up, at a minimum of five years, of a previous report. J Bone Joint Surg Am. 2012; 94(21):1996–2000. doi:10.2106/JBJS.K.01206 [CrossRef]
  7. Cuff D, Pupello D, Virani N, Levy J, Frankle M. Reverse shoulder arthroplasty for the treatment of rotator cuff deficiency. J Bone Joint Surg Am. 2008; 90(6):1244–1251. doi:10.2106/JBJS.G.00775 [CrossRef]
  8. Frankle M, Siegal S, Pupello D, Saleem A, Mighell M, Vasey M. The Reverse Shoulder Prosthesis for glenohumeral arthritis associated with severe rotator cuff deficiency: a minimum two-year follow-up study of sixty patients. J Bone Joint Surg Am.2005; 87(8):1697–1705.
  9. Kempton LB, Balasubramaniam M, Ankerson E, Wiater JM. A radiographic analysis of the effects of prosthesis design on scapular notching following reverse total shoulder arthroplasty. J Shoulder Elbow Surg. 2011; 20(4):571–576. doi:10.1016/j.jse.2010.08.024 [CrossRef]
  10. Kowalsky MS, Galatz LM, Shia DS, Steger-May K, Keener JD. The relationship between scapular notching and reverse shoulder arthroplasty prosthesis design. J Shoulder Elbow Surg. 2012; 21(10):1430–1441. doi:10.1016/j.jse.2011.08.051 [CrossRef]
  11. Ko JK, Tompson JD, Sholder DS, Black EM, Abboud JA. Heterotopic ossification of the long head of the triceps after reverse total shoulder arthroplasty. J Shoulder Elbow Surg. 2016; 25(11):1810–1815. doi:10.1016/j.jse.2016.03.006 [CrossRef]
  12. Melis B, DeFranco M, Lädermann A, et al. An evaluation of the radiological changes around the Grammont reverse geometry shoulder arthroplasty after eight to 12 years. J Bone Joint Surg Br.2011; 93(9):1240–1246. doi:10.1302/0301-620X.93B9.25926 [CrossRef]
  13. Roche CP, Marczuk Y, Wright TW, et al. Scapular notching and osteophyte formation after reverse shoulder replacement: radiological analysis of implant position in male and female patients. Bone Joint J. 2013; 95-B(4):530–535. doi:10.1302/0301-620X.95B4.30442 [CrossRef]
  14. Verhofste B, Decock T, Van Tongel A, De Wilde L. Heterotopic ossification after reverse total shoulder arthroplasty. Bone Joint J. 2016; 98-B(9):1215–1221. doi:10.1302/0301-620X.98B9.37761 [CrossRef]
  15. Boehm TD, Wallace WA, Neumann L. Heterotopic ossification after primary shoulder arthroplasty. J Shoulder Elbow Surg. 2005; 14(1):6–10. doi:10.1016/j.jse.2004.04.007 [CrossRef]
  16. Kjaersgaard-Andersen P, Frich LH, Søjbjerg JO, Sneppen O. Heterotopic bone formation following total shoulder arthroplasty. J Arthroplasty. 1989; 4(2):99–104. doi:10.1016/S0883-5403(89)80061-0 [CrossRef]
  17. Sperling JW, Cofield RH, Steinmann SP. Shoulder arthroplasty for osteoarthritis secondary to glenoid dysplasia. J Bone Joint Surg Am. 2002; 84(4):541–546. doi:10.2106/00004623-200204000-00005 [CrossRef]
  18. Simovitch RW, Zumstein MA, Lohri E, Helmy N, Gerber C. Predictors of scapular notching in patients managed with the Delta III reverse total shoulder replacement. J Bone Joint Surg Am. 2007; 89(3):588–600. doi:10.2106/JBJS.F.00226 [CrossRef]
  19. ElMaraghy A, Devereaux M. Medial wear of the polyethylene component associated with heterotopic ossification after reverse shoulder arthroplasty. Can J Surg. 2008; 51(5):E103–E104.
  20. Boileau P, Watkinson D, Hatzidakis AM, Hovorka I. Neer Award 2005. The Grammont reverse shoulder prosthesis: results in cuff tear arthritis, fracture sequelae, and revision arthroplasty. J Shoulder Elbow Surg. 2006; 15(5):527–540. doi:10.1016/j.jse.2006.01.003 [CrossRef]
  21. Gutiérrez S, Comiskey CA IV, Luo ZP, Pupello DR, Frankle MA. Range of impingement-free abduction and adduction deficit after reverse shoulder arthroplasty: hierarchy of surgical and implant-design-related factors. J Bone Joint Surg Am. 2008; 90(12):2606–2615. doi:10.2106/JBJS.H.00012 [CrossRef]
  22. Sirveaux F, Favard L, Oudet D, Huquet D, Walch G, Molé D. Grammont inverted total shoulder arthroplasty in the treatment of glenohumeral osteoarthritis with massive rupture of the cuff: results of a multicenter study of 80 shoulders. J Bone Joint Surg Br.2004; 86(3):388–395. doi:10.1302/0301-620X.86B3.14024 [CrossRef]
  23. Brooker AF, Bowerman JW, Robinson RA, Riley LH Jr, . Ectopic ossification following total hip replacement: incidence and a method of classification. J Bone Joint Surg Am. 1973; 55(8):1629–1632. doi:10.2106/00004623-197355080-00006 [CrossRef]
  24. Henninger HB, Barg A, Anderson AE, Bachus KN, Burks RT, Tashjian RZ. Effect of lateral offset center of rotation in reverse total shoulder arthroplasty: a biomechanical study. J Shoulder Elbow Surg.2012; 21(9):1128–1135. doi:10.1016/j.jse.2011.07.034 [CrossRef]
  25. Wong MT, Langohr GDG, Athwal GS, Johnson JA. Implant positioning in reverse shoulder arthroplasty has an impact on acromial stresses. J Shoulder Elbow Surg. 2016; 25(11):1889–1895. doi:10.1016/j.jse.2016.04.011 [CrossRef]

Ko et al11 Classification for Heterotopic Ossification

Type or SubtypeRadiographic Findings
Type
  1Distal extent of the osteophyte is proximal to the line from the medial portion of the humeral tray parallel to the lateral border of the scapula
  2Distal extent of the osteophyte is at or distal to the line from the medial portion of the humeral tray parallel to the lateral border of the scapula
Subtype
  A(Impinging) Humeral component would impinge on the osteophyte with the shoulder in adduction to neutral
  B(Free-floating) Osteophyte is not contiguous with the lateral border of the scapula
  C(Notching) There is presence of scapular notching
  D(Ankylosis) Osteophyte appears to be bridging from the scapula to the humerus

The Modified Brooker Classification23 for Heterotopic Ossification

GradeRadiographic Findings
1aIslands of bone within the soft tissues around the shoulder
1bBone spurs on the inferior scapular neck
1cIncomplete ankylosis of the shoulder
2Combination of a bone spur on the inferior scapular neck together with a bone island(s) about the soft tissues of the shoulder
3Complete ankylosis of the shoulder

Group Characteristics

CharacteristicProsthesisP

Grammont-style (n=48)Lateral Center of Rotation (n=49)
Sex, No..08
  Women2736
  Men2113
Age, mean±SD, y69.3±7.971.6±7.0.12
Body mass index, mean±SD, kg/m229.6±5.730.7±8.3.45

Scapular Notching Incidence and Grade by Sirveaux Classification

Sirveaux ClassificationProsthesis, No.P

Grammont-styleLateral Center of Rotation
Grade 1145
Grade 231
Grade 300
Grade 400
Overall notching incidence17 (35.4%)6 (12.2%).018

Heterotopic Ossification Incidence and Grades by 2 Classification Systems

Classification SystemProsthesis, No.P

Grammont-styleLateral Center of Rotation
Ko et al11
  Type 1146
  Type 295
    Subtype A (impinging)57
    Subtype B (free-floating)104
    Subtype C (notching)80
    Subtype D (ankylosis)00
Modified Brooker23
  Grade 1a114
  Grade 1b96
  Grade 1c00
  Grade 231
  Grade 300
Overall heterotopic ossification incidence23 (47.9%)11 (22.4%).009

Patient-Reported Outcome Measures and Range of Motion

Parameter, Mean±SDProsthesisP

Grammont-styleLateral Center of Rotation
ASES score
  Preoperative35.6±15.532.4±15.5.86
  1 year postoperative77.2±15.583.4±12.8.05
VAS pain score
  Preoperative6.4±2.36.2±2.3.61
  1 year postoperative1.1±1.50.5±1.0.01
Forward flexion
  Preoperative77.6°±34.7°86.9°±29.2°.16
  1 year postoperative134.6°±23.0°132.4°±16.3°.13
External rotation
  Preoperative29.1°±13.9°27.5°±10.7°.52
  1 year postoperative35.1°±18.5°40.6°±9.4°.27
Authors

The authors are from New England Baptist Hospital (RN, JTL, SML, MF, MTM, AJ), Boston, and the Boston Sports and Shoulder Center (JTL, SML, MF, AJ), Waltham, Massachusetts.

Dr Nelson, Mr Lowe, Ms Lawler, Ms Fitzgerald, and Dr Mantell have no relevant financial relationships to disclose. Dr Jawa is a paid consultant and speaker for DJO Global.

Correspondence should be addressed to: Andrew Jawa, MD, Boston Sports and Shoulder Center, 840 Winter St, Waltham, MA 02451 ( AndrewJawa@gmail.com).

Received: September 28, 2017
Accepted: April 23, 2018
Posted Online: June 18, 2018

10.3928/01477447-20180613-01

Sign up to receive

Journal E-contents