Heterotopic ossification, also known as heterotopic bone formation, is the ectopic formation of lamellar bone within soft tissues such as muscle, ligament, or tendon. It can be genetic or acquired. It is most commonly acquired and can be categorized into 3 etiologies: neurogenic from central nervous system injury; traumatic after burns or high-veloc-ity impact; or orthopedic, entailing fracture fixations, repairs, and joint replacements.1,2 Unfortunately, the exact underlying mech-anism for heterotopic ossification remains unclear. Regardless, it is widely accepted that heterotopic ossification results from a combination of an inflammatory response and differentiation of multipotent cells in the ectopic tissue where bone forms.1-5
When it occurs, heterotopic ossifica-tion can decrease patient satisfacossifica-tion and impact recovery and rehabilitation efforts. It can lead to a variety of complications, ranging from pain and reduced range of motion to ankylosis of the joint.6,7
Inci-dence rates of heterotopic ossification af-ter surgery for different traumatic elbow fractures have varied tremendously in the literature. In 2016, a study of 38 patients by Chen and Bi8 on the outcomes of repair of terrible triad injuries reported an incidence rate of 0% for heterotopic ossification. In 1982, Garland and O’Hollaren9 reported an incidence rate of 89% for heterotopic os-sification in patients with elbow fracture/ dislocation injuries. Neither study used a classification system to define heterotopic ossification. In 2015, Hong et al10 per-formed a study of risk factors of 124 elbow fractures of several different types, finding an overall incidence of heterotopic ossifi-cation of 31%; this study used the Hastings and Graham classification system. Finally, in 2015, Shukla et al11 studied heterotopic ossification formation after elbow frac-tures/dislocations specifically. They found an incidence of 43% and reported hetero-topic ossification data using the modified Brooker classification system.11
The authors believe that there are sev-eral reasons for this variation in the inci-dence of heterotopic ossification, noting the numerous fracture possibilities pres-ent at the elbow joint and the absence of classification or the use of multiple classification systems in particular. To the authors’ knowledge, there is limited literature using a standardized protocol to compile incidence rates of heterotopic ossification after surgical repair of several types of elbow fractures in a comparable manner. As such, the goal of this system-atic review was to use specific inclusion and exclusion criteria to provide updated data on the incidence and prevalence of heterotopic ossification after surgical re-pair of various types of elbow fractures.
A systematic literature review was per-formed in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement. Scopus (EMBASE, MEDLINE, COMPENDEX) and PubMed (MEDLINE) databases were
Heterotopic Ossification After Elbow Fractures
, BS; DaviD
, mD; aSif
, mD, mBa
The authors are from the Sidney Kimmel Medical College (ZJH, DGE) and the Rothman Institute (AMI), Thomas Jefferson University, Philadelphia, Pennsylvania.
The authors have no relevant financial rela-tionships to disclose.
Correspondence should be addressed to: Zachary J. Herman, BS, 1111 South St, Apt C, Philadelphia, PA 19147 (Zjh001@jefferson.edu).
Received: May 4, 2020; Accepted: August 10, 2020.
Heterotopic ossification (HO), a complication after surgical repair of elbow fractures, can result in pain, decreased range of motion, or complete an-kylosis of the joint. This updated systematic review focused on compiling incidence and prevalence rates of HO after surgical repair of various types of elbow fractures. The overall incidence of HO after surgical repair was calculated to be 28.7%, a result comparable with rates in the literature. Fur-ther analysis suggested that the odds of having HO may be less after distal humerus fractures than after proximal radius fractures, terrible triad injuries, and elbow fractures/dislocations. [Orthopedics. 2021;44(1):10-16.]
JANUARY/FEBRUARY 2021| Volume 44 • Number 1 queried for articles using the keywords “elbow”, “fracture”, and “trauma” and the phrase “heterotopic ossification”. The search was kept broad in an attempt to cap-ture all relevant literacap-ture. All articles in print or epub ahead of print were included. The search was limited to articles written in English or easily translatable to English dur-ing a 26-year period, from 1994 to the pres-ent. Initial screening was based on title and abstract, and all articles relevant to the cur-rent review were included for examination. For completeness, the references of the ar-ticles included were also reviewed to ensure accurate data capture. The title and abstract of each article were screened initially for relevance, and then the full text of articles was checked against specific inclusion and exclusion criteria by an independent review-er (Z.J.H.).
Case-control studies, randomized trials, case series, and prospective and retrospec-tive cohort analyses with patients older than 18 years reporting cases of heterotopic os-sification after elbow fracture and surgical repair were included. To accurately assess and compare the heterotopic ossification, an additional inclusion criterion was use of the Hastings and Graham classification system (class I, radiograph with positive findings for ectopic bone with no function-al impairment clinicfunction-ally; class II, ectopic bone causing subtotal, functional limitation of flexion, extension, pronation, and/or su-pination; class III, ectopic bone with anky-losis of the joint that eliminates motion) for the heterotopic ossification that occurred. The authors chose to only include studies that used the Hastings and Graham classifi-cation system as it was originally designed for evaluation of heterotopic ossification at the elbow.12 Studies that included isolated fracture types or studies with multiple frac-ture types (different classifications, differ-ent anatomic regions about the elbow) that supplied individual patient data specifically delineating which patients with which frac-ture patterns had postoperative heterotopic ossification were also included. Finally, all patients whose data were used in analysis
must have adhered to follow-up protocols in the individual studies.
To obtain information on a broad, gen-eral incidence, no exclusion criteria were applied based on presence or absence of prophylactic measures (radiation therapy/ nonsteroidal anti-inflammatory drug use) or type or severity of elbow fracture. No ex-clusion criteria were applied for type of sur-gical treatment for the elbow injury, age of patients in the studies, underlying calcium metabolism disorder of patients, additional complications besides heterotopic ossifica-tion, or length of follow-up.
Studies were excluded if they did not re-port the specific number of heterotopic ossi-fication formations compared with the total number of elbow fracture repairs. Studies that focused on the treatment of popula-tions entirely with heterotopic ossification were excluded because incidence could not be calculated. Studies that reported the inci-dence of elbow heterotopic ossification af-ter head, spinal cord, or burn injuries (with-out elbow fractures and surgical repair) were excluded. Studies that reported the incidence of heterotopic ossification after surgery indicated for elbow pathology other than a fracture, such as rheumatoid arthritis, osteoarthritis, or tumor, were also excluded.
Ultimately, the included studies were used as evidence for the review. All studies included were assigned a level of evidence using the Oxford Centre for Evidence-Based Medicine table of guidelines and rec-ommendations.13 Additionally, the authors conducted an analysis of potential bias in all included studies using the Risk Of Bias In Non-randomized Studies–of Interven-tions (ROBINS-I) tool14 and the Cochrane risk-of-bias in randomized studies (RoB 2.0) tool.15 Bias results were formatted with the visualization tool for risk of bias assess-ments in a systematic review (robvis) tool.16 Included fracture types were stratified ac-cording to anatomic location about the elbow or injury pattern. Fractures were not stratified by presence or absence of concomitant nerve or ligamentous injury or as being opened or closed. The authors grouped fractures into 6
categories: distal humerus, proximal radius, proximal ulnar, terrible triad injury, elbow fracture/dislocation, and complex fracture without dislocation. The distal humerus cat-egory included distal humerus fractures as well as capitellum and coronal shear frac-tures. Proximal radius fractures included radial head and neck fractures and Essex-Lopresti lesions if present.17 The proximal ulnar group included coronoid process, olec-ranon process, and proximal ulnar fractures. The terrible triad group included fractures with the characteristic features of the “ter-rible triad” injury described by Hotchkiss18 in 1966. This consists of the combination of radial head and coronoid process fractures with an associated elbow dislocation. The elbow fracture/dislocation group consisted of Monteggia-like lesions and any other combination of distal humerus, proximal radius, proximal ulnar, olecranon process, or coronoid process fracture with concomi-tant elbow dislocation that was not otherwise classified as a terrible triad injury.19,20 Final-ly, the complex fracture without dislocation group involved a combination of fractures of 2 or more of the following: olecranon pro-cess, coronoid propro-cess, proximal ulna, radial head/neck, and/or distal humerus without as-sociated elbow dislocation.
Data Extraction and Statistical Analysis Standardized data extraction was per-formed. The overall (combination of all 3 Hastings and Graham classes) incidence of heterotopic ossification was calculated by dividing the total number of cases of het-erotopic ossification by the total number of fractures in the studies. The incidence of heterotopic ossification was calculated separately for those studies that used any form of heterotopic ossification prophy-laxis postoperatively vs those studies that did not. The authors calculated odds ratios and 95% CIs to compare the overall inci-dence of heterotopic ossification with and without the use of prophylaxis. Addition-ally, the overall incidence of heterotopic ossification in the studies was divided ac-cording to Hastings and Graham classes
n Review Article
I, II, and III. Furthermore, Hastings and Graham classes II and III were combined to produce an incidence of “clinically rel-evant” heterotopic ossification, as class I heterotopic ossification has no functional impairment. The incidence of heterotopic ossification by fracture group was also calculated by dividing the number of cas-es of heterotopic ossification in a fracture group by the total number of fractures in that fracture group. Within each fracture group, the prevalence of heterotopic ossi-fication was broken down by Hastings and Graham classes. The authors calculated odds ratios and 95% CIs to compare the overall incidence of heterotopic ossifica-tion by fracture category. Statistical sig-nificance was defined as P<.05 and a 95% CI that did not contain a value of 1.
The initial search identified 1766 ar-ticles using the keywords. An additional
17 articles were found and included from references of included studies. After du-plicates were removed, 1375 articles re-mained. All articles were screened based on title and abstract. A total of 1174 were excluded due to irrelevance to topic, not being in English, or being older than pub-lication year of 1994. A total of 201 full-text articles were reviewed, with 178 be-ing excluded for failure to meet inclusion criteria. Thus, 23 studies were included for final data analysis.21-43 Figure 1 shows the search details and study selection process.
Of the 23 studies included, there were 1 level II study, 7 level III studies, and 15 level IV studies. Seven were prospective and 16 were retrospective. The 1 randomized trial was assessed as having “some concerns” of bias.24 Of the non-randomized studies, 11 were assessed as having “moderate” risk of bias.21-23,26,29,32-34,38-40 Eleven were assessed as having “serious” risk of bias by the bias assessment tools used.25,27,28,30,31,35-37,41-43
These data are presented in Figure A and Figure B (available in the online version of the article).
Demographic data, study information, and results regarding the incidence of het-erotopic ossification per study are present-ed in Table A (available in the online ver-sion of the article). Overall, 659 fractures were reviewed in 659 patients with a mean age of 51.5 years (range, 18-90 years). All but 1 study42 reported sex. There were 334 males (52.5%) and 302 females (47.5%). The average follow-up was 42 months (range, 9-171 months). The incidence rate of heterotopic ossification (of any class) was found to be 189 per 659 (28.7%).
Seven studies used prophylaxis post-operatively to prevent heterotopic ossifica-tion. This included radiation therapy, in-domethacin, and/or celecoxib.22-24,29,31,33,40 In these studies, the incidence of hetero-topic ossification was 19.9% (43 of 216). The remaining 16 studies did not use any form of heterotopic ossification prophy-laxis.21,25-28,30,32,34-39,41-43 The incidence of heterotopic ossification in this group was 33.0% (146 of 443). Analysis suggested that the odds of heterotopic bone formation are less with any form of prophylaxis than without prophylaxis (odds ratio, 0.51; 95% CI, 0.34-0.75; P=.0006).
Of the total 189 cases of heterotopic os-sification, prevalence by Hastings and Gra-ham classification was as follows: 54.5% (103 cases) class I; 43.9% (83 cases) class II; and 1.6% (3 cases) class III. Addition-ally, the overall incidence of class I, class II, and class III heterotopic ossification was 15.6%, 12.6%, and 0.5%, respectively. The authors found a result of 13.1% when cal-culating the incidence of clinically relevant heterotopic ossification by Hastings and Graham classes II and III (Table 1).
As stated earlier, the fractures in the studies included were grouped according to anatomic region about the elbow or type (Table 2). Fractures in the distal humerus group included distal humerus fractures that were AO/OTA classification A, B, and C (class A, extra-articular; class B, partial
Figure 1. Preferred Reporting Items for Systematic Reviews and Meta-Analyses database search and study selection process.
JANUARY/FEBRUARY 2021| Volume 44 • Number 1 articular; class C, complete articular).44 No studies involving isolated capitellum or coronal shear fractures met inclusion and exclusion criteria. Distal humerus AO/ OTA fractures that included capitellum or coronal shear fracture elements were placed in the distal humerus group as well. There were 367 total fractures; 16 (4.4%) were AO/OTA class A, 8 (2.2%) were AO/ OTA class B, and 343 (93.5%) were AO/ OTA class C. The overall incidence of het-erotopic ossification in the distal humerus fracture group was 21.8% (n=80). Of the heterotopic ossification cases, 42.5% (n=34) were class I and 57.5% (n=46) were class II. There were no class III cases.
Fractures in the proximal radius group consisted of type II and type III radial head fractures by Mason-Johnston classification (type II, fractures with >2 mm displace-ment; type III, comminuted fractures with-out dislocation).45 One study did not use the Mason-Johnston classification but included only radial head fractures that were greater than 2 mm but less than 5 mm displaced. This study was included. The group also contained 1 Essex-Lopresti lesion. There were 132 total fractures: 101 (76.5%) were classified as Mason-Johnston type II or III, 1 (0.8%) was an Essex-Lopresti lesion, and 30 (22.7%) were greater than 2 mm but less than 5 mm displaced but not classified by Mason-Johnston. The overall incidence of heterotopic ossification in the proximal ra-dius group was 31.8% (n=42). Of the het-erotopic ossification cases, 78.6% (n=33) were class I and 21.4% (n=9) were class II. There were no class III cases.
In the terrible triad injury group, the Mason-Johnston classification system was used for radial head fractures and the Re-gan and Morrey classification system (type I, coronoid process tip; type II, fracture of 50% or less of height; type III, fracture of more than 50% of height) was used for coro-noid process fractures.46 There were 97 total fractures. The overall incidence was 42.3% (n=41). Of the heterotopic ossification cases, 61.0% were class I (n=25), 34.1% (n=14) were class II, and 4.9% (n=2) were class III.
Fractures in the elbow fracture/disloca-tion group consisted of Mason-Johnston type IV (radial head fracture with associ-ated dislocation), Monteggia-like lesions, and any other combination of distal humer-us, olecranon, or coronoid process fracture with an associated elbow dislocation that did not meet criteria for terrible triad in-jury. There were 49 fractures in this group. The incidence of heterotopic ossification was 42.9% (n=21). Of the heterotopic os-sification cases, 47.6% (n=10) were class I, 47.6% (n=10) were class II, and 4.8% (n=1) were class III.
Fractures in the complex fracture with-out dislocation group consisted of com-binations of olecranon process, coronoid process, proximal ulnar, radial head/neck, and/or distal humerus fractures without as-sociated dislocations. There were 14 total fractures in this group. The incidence of
heterotopic ossification was 35.7% (n=5). Of the heterotopic ossification cases, 20.0% (n=1) were class I and 80.0% (n=4) were class II. There were no class III cases.
No studies involving isolated proximal ulnar fractures or isolated coronoid or olec-ranon process fractures met inclusion and exclusion criteria. Any coronoid or olecra-non fracture was sustained in a combina-tion of fractures or as part of an elbow frac-ture/dislocation, Monteggia-like lesion, or terrible triad injury. This group was thus omitted, and the fractures were grouped accordingly.
Additionally, the authors compared the overall incidence of heterotopic ossifica-tion by fracture anatomic region and injury type. Proximal radius fractures (odds ra-tio, 1.67; 95% CI, 1.08-2.61; P=.02), ter-rible triad injuries (odds ratio, 2.63; 95% CI, 1.64-4.22; P=.0001), and elbow
Prevalence and Incidence of Heterotopic Ossification by Hastings and Graham Classification
Class Prevalence Incidence
I (no functional impairment) 54.5% (n=103) 15.6% (n=103) II (subtotal functional impairment of any kind) 43.9% (n=83) 12.6% (n=83) III (ankylosis of the joint eliminating motion) 1.6% (n=3) 0.5% (n=3) Total no. 189 659
Incidence of Heterotopic Ossification by Anatomic Region/ Fracture Type Group
Group No. of HO cases (by Hastings and Graham class) Total no. of fractures Incidence of HO (no./total no.)
Distal humerus 80 (34 class I; 46 class II) 367 21.8% (80/367) Proximal radius 42 (33 class I; 9 class II) 132 31.8% (42/132) Terrible triad 41 (25 class I; 14 class II;
2 class III) 97 42.3% (41/97) Elbow
fracture/disloca-tion 21 (10 class I; 10 class II; 1 class III) 49 42.9% (21/49) Complex fracture
with-out dislocation 5 (1 class I; 4 class II) 14 35.7% (5/14)
Abbreviation: HO, heterotopic ossification. n Review Article
tures/dislocations (odds ratio, 2.69; 95% CI, 1.45-4.99; P=.002) were all associated with a statistically significant higher inci-dence of heterotopic ossification than distal humerus fractures. No other comparisons were associated with statistically signifi-cant increased or decreased incidence of heterotopic ossification (Table 3).
The results of this study suggested an overall incidence rate of 28.7% for hetero-topic ossification and an incidence rate for clinically relevant heterotopic ossification of 13.1% when multiple elbow fracture surgical repair results were compiled. Comparisons, odds ratios, and 95% CIs also suggested a smaller chance of having any heterotopic ossification after surgi-cal repair of distal humerus fractures than after proximal radius, terrible triad, or elbow fracture/dislocation repairs. It was further suggested that there was no differ-ence in the chance of acquiring any het-erotopic ossification after surgical repair of proximal radius fractures, elbow frac-tures/dislocations, terrible triad injuries, or complex elbow fractures.
Limited studies are present in the lit-erature that compile and comment on the incidence of heterotopic ossification after surgical repair of multiple different types of elbow fracture. In 2012, Bauer et
al47 reported a case-control study in two institutions of 786 elbow fractures be-tween 2002 and 2009. The fracture types included distal humerus, isolated radial head, Monteggia lesions, terrible triad, isolated olecranon, and floating elbow in-juries. They set out to quantify the rate of clinically relevant heterotopic ossification after elbow fracture surgery (incidence of heterotopic ossification for Hastings and Graham classes II and III combined). They found an incidence rate of 7%. Comparatively, in the current study, the incidence of clinically relevant hetero-topic ossification for Hastings and Gra-ham classes II and III was 13.1%. Bauer et al47 also broke down the incidence of clinically relevant heterotopic ossification by fracture type. In their results, terrible triad injuries (18%; 14 cases of 76 frac-tures) and floating elbow injuries (36%; 4 cases of 11 fractures) had the highest in-cidence of clinically relevant heterotopic ossification.47 The current study compiled the overall incidence and not the clinically relevant incidence of heterotopic ossifica-tion, yet the terrible triad (42.3%), elbow fracture/dislocation (42.9%), and com-plex fracture without dislocation (35.7%) groups had the highest overall incidences.
In 2015, Hong et al10 reported a retro-spective analysis from 2007 to 2011 of 124 elbow fractures and the incidence of
het-erotopic ossification after surgical repair. Injury types included terrible triad, floating elbow and combined fractures, elbow frac-tures/dislocations, distal humerus, isolated radial head, isolated olecranon, and Mon-teggia lesions. They found an overall inci-dence of heterotopic ossification of 30.6%. This is comparable with the current study’s overall incidence of 28.7%. Addition-ally, Hong et al10 reported an incidence of clinically relevant heterotopic ossification (Hastings and Graham classes II and III) of 21%. This is higher than the currently re-ported incidence of clinically relevant het-erotopic ossification of 13.1%. Although the samples were small, Hong et al10 found the overall incidence of heterotopic os-sification after surgical repair of distal humerus fractures to be 25% (8 of 32), proximal radius fractures to be 50% (8 of 16), terrible triad injuries to be 58.3% (7 of 12), and floating elbow/combined fractures to be 83.3% (5 of 6). The current study’s reported incidence of heterotopic ossifica-tion after distal humerus fracture repair is comparable, at 21.8%. However, the cur-rent reported incidence rates of heterotopic ossification after proximal radius (31.8%), terrible triad (42.3%), and combined frac-tures (35.7%) are lower than those reported by Hong et al.10
Additionally, in 2014, Wiggers et al48 reported a retrospective review of 284
Odds Ratios, 95% CIs, and P Values for Fracture Grouping Comparisons
Group comparison Odds ratio 95% CI P Statistically significant?
Proximal radius to distal humerus 1.67 1.08-2.61 .02 Yes Terrible triad to distal humerus 2.63 1.64-4.22 .0001 Yes Elbow fracture/dislocation to distal humerus 2.69 1.45-4.99 .002 Yes Complex fracture to distal humerus 1.99 0.65-6.11 .23 No Terrible triad to proximal radius 1.57 0.91-2.70 .11 No Terrible triad to complex fracture 1.32 0.41-4.23 .64 No Elbow fracture/dislocation to terrible triad 1.02 0.51-2.05 .95 No Elbow fracture/dislocation to proximal radius 1.61 0.82-3.15 .17 No Elbow fracture/dislocation to complex fracture 1.35 0.39-4.62 .63 No Complex fracture to proximal radius 1.19 0.38-3.77 .77 No
JANUARY/FEBRUARY 2021| Volume 44 • Number 1 bow fractures from 2001 to 2007. Fracture types included distal humerus, radial head, olecranon, coronoid, and elbow fracture/ dislocation. The study found an overall incidence of heterotopic ossification of 33.8% and an incidence of clinically rel-evant heterotopic ossification of 10%.48 These results are comparable to the current findings for overall incidence of hetero-topic ossification (28.7%) and incidence of clinically relevant heterotopic ossification (13.1%).
Although most have much smaller samples, numerous studies have reported heterotopic ossification incidence rates after isolated fracture types. These rates tend to have large ranges when compared across the literature. For example, in the studies used in the current systematic re-view, the incidence of heterotopic ossifica-tion after isolated distal humerus fracture repair ranged from 4.0% to 41.6%.29,34 The incidence of heterotopic ossification after surgical repair of isolated proximal radius fractures ranged from 0.0% to 52.0%.26,38 The incidence of heterotopic ossifica-tion after terrible triad repair ranged from 27.3% to 58.3%.41,43 The incidence of het-erotopic ossification in the one study with isolated elbow fracture/dislocation was 27.3%.22 Due to the large number of in-dividual studies, their small samples, and different techniques for surgical repair, it is difficult to compare the variable results of these studies for individual fracture types with the current results compiled into a much larger sample.
A limitation of the current study was the inherent nature of a systematic review, which relies on the quality of the indi-vidual studies from which it collects data. This study was also limited by publication bias for the individual studies included and any potential bias introduced by those in-volved in reporting radiologic results. In an attempt to collect general information about multiple fracture types at the elbow, several of the studies included used differ-ent repair mechanisms, had differdiffer-ent pa-tient age ranges and follow-up periods, and
had varied implementation of heterotopic ossification prophylactic measures. Future research should have stricter inclusion cri-teria and exclusion cricri-teria, such as specific fracture types, surgical treatments, patient populations, and use of prophylactic mea-sures, to specify the effect of different variables on the incidence of heterotopic ossification.
Heterotopic ossification is a potentially serious complication after surgical repair of elbow fractures. As updates continue in technique, technology, and literature regarding the surgical treatment of elbow fractures, the incidence of complications such as heterotopic ossification must be re-examined. Wide incidence ranges of heterotopic ossification after surgical treatment of the elbow are present in the literature. In the current updated system-atic review, the authors set out to compile various data points on the incidence of heterotopic ossification after several dif-ferent types of fractures about the elbow. Moreover, the authors conclude that their results are similar to those of other stud-ies that have assembled results of larger samples of various elbow fracture repairs. Additionally, the authors conclude that, on the basis of their results, the overall chance of developing heterotopic ossifica-tion may be less after distal humerus frac-tures than after proximal radius fracfrac-tures, terrible triad injuries, and elbow fractures/ dislocations. There may be no statisti-cally significant difference regarding the chance of acquiring heterotopic ossifica-tion after surgical treatment of proximal radius fractures, terrible triad injuries, elbow fractures/dislocations, or complex fractures without dislocation.
1. Shore EM, Kaplan FS. Inherited human diseases of heterotopic bone formation. Nat Rev
Rheuma-tol. 2010;6(9):518-527. https://doi.org/10.1038/ nrrheum.2010.122 PMID:20703219
2. Mujtaba B, Taher A, Fiala MJ, et al. Hetero-topic ossification: radiological and
pathologi-cal review. Radiol Oncol. 2019;53(3):275-284. https://doi.org/10.2478/raon-2019-0039 PMID:31553710
3. Shimono K, Uchibe K, Kuboki T, Iwamoto M. The pathophysiology of heterotopic ossi-fication: current treatment considerations in dentistry. Jpn Dent Sci Rev. 2014;50(1):1-8. https://doi.org/10.1016/j.jdsr.2013.07.003 4. Helms C. Fundamentals of Skeletal
Radiol-ogy. 4th ed. Elsevier; 2014.
5. Medina A, Shankowsky H, Savaryn B, Shu-kalak B, Tredget EE. Characterization of heterotopic ossification in burn patients. J
Burn Care Res. 2014;35(3):251-256. https:// doi.org/10.1097/BCR.0b013e3182957768 PMID:23872497
6. Juarez JK, Wenke JC, Rivera JC. Treatments and preventative measures for trauma-in-duced heterotopic ossification: a review. Clin
Transl Sci. 2018;11(4):365-370. https://doi. org/10.1111/cts.12552 PMID:29697199 7. Meyers C, Lisiecki J, Miller S, et al.
Hetero-topic ossification: a comprehensive review.
JBMR Plus. 2019;3(4):e10172. https://doi. org/10.1002/jbm4.10172 PMID:31044187 8. Chen HW, Bi Q. Surgical outcomes and
complications in treatment of terrible triad of the elbow: comparisons of 3 surgical ap-proaches. Med Sci Monit. 2016;22:4354-4362. https://doi.org/10.12659/MSM.897297 PMID:27841255
9. Garland DE, O’Hollaren RM. Fractures and dislocations about the elbow in the head-injured adult. Clin Orthop Relat Res. 1982;(168):38-41. https://doi.org/10.1097/00003086-198208000-00006 PMID:6809389
10. Hong CC, Nashi N, Hey HW, Chee YH, Murphy D. Clinically relevant heterotopic ossification after elbow fracture surgery: a risk factors study.
Orthop Traumatol Surg Res. 2015;101(2):209-213. https://doi.org/10.1016/j.otsr.2014.10.021 PMID:25701160
11. Shukla DR, Pillai G, McAnany S, Hausman M, Parsons BO. Heterotopic ossification for-mation after fracture-dislocations of the elbow.
J Shoulder Elbow Surg. 2015;24(3):333-338. https://doi.org/10.1016/j.jse.2014.11.037 PMID:25601384
12. Hastings H II, Graham TJ. The classifica-tion and treatment of heterotopic ossificaclassifica-tion about the elbow and forearm. Hand Clin. 1994;10(3):417-437. PMID:7962148 13. OCEBM Levels of Evidence Working Group.
The Oxford levels of evidence 2. Oxford Centre for Evidence-Based Medicine. Ac-cessed April 23, 2020. https://www.cebm.net/ index.aspx?o=5653
14. Sterne JA, Hernán MA, Reeves BC, et al. ROBINS-I: a tool for assessing risk of bias in non-randomised studies of interven-tions. BMJ. 2016;355:i4919. https://doi. org/10.1136/bmj.i4919 PMID:27733354 15. Sterne JAC, Savovic J, Page MJ, et al. RoB 2:
n Review Article
a revised tool for assessing risk of bias in ran-domised trials. BMJ. 2019;366:l4898. https:// doi.org/10.1136/bmj.l4898 PMID:31462531 16. McGuinness LA. Robvis: an R package and
web application for visualising risk-of-bias as-sessments. Accessed April 23, 2020. https:// github.com/mcguinlu/robvis
17. Essex-Lopresti P. Fractures of the radial head with distal radio-ulnar dislocation; report of two cases. J Bone Joint Surg Br. 1951;33(2):244-247. https://doi.org/10.1302/0301-620X.33B2.244 PMID:14832324
18. Hotchkiss R. Fractures and dislocations of the elbow. In Rockwood CA, Green DP, Heckman RW, Bucholz JD, eds. Rockwood
and Green’s Fractures in Adults. 4th ed. Lip-pincott Williams & Wilkins; 1966:980-981. 19. Bado JL. The Monteggia lesion. Clin Orthop
Relat Res. 1967;50(50):71-86. PMID:6029027 20. Laun R, Wild M, Brosius L, Hakimi M.
Mon-teggia-like lesions: treatment strategies and one-year results. GMS Interdiscip Plast Reconstr
Surg DGPW. 2015;4:Doc13. PMID:26734535 21. Popovic N, Gillet P, Rodriguez A, Lemaire
R. Fracture of the radial head with associated elbow dislocation: results of treatment using a floating radial head prosthesis. J Orthop
Trauma. 2000;14(3):171-177. https://doi. org/10.1097/00005131-200003000-00004 PMID:10791667
22. Stein DA, Patel R, Egol KA, Kaplan FT, Tejwani NC, Koval KJ. Prevention of het-erotopic ossification at the elbow following trauma using radiation therapy. Bull Hosp Jt
Dis. 2003;61(3-4):151-154. PMID:15156818 23. Gofton WT, Macdermid JC, Patterson SD,
Faber KJ, King GJ. Functional outcome of AO type C distal humeral fractures.
J Hand Surg Am. 2003;28(2):294-308. https://doi.org/10.1053/jhsu.2003.50038 PMID:12671863
24. Shin SJ, Sohn HS, Do NH. A clinical com-parison of two different double plating meth-ods for intraarticular distal humerus fractures.
J Shoulder Elbow Surg. 2010;19(1):2-9. https://doi.org/10.1016/j.jse.2009.05.003 PMID:19574065
25. Burkhart KJ, Mattyasovszky SG, Runkel M, et al. Mid- to long-term results after bipolar ra-dial head arthroplasty. J Shoulder Elbow Surg. 2010;19(7):965-972. https://doi.org/10.1016/j. jse.2010.05.022 PMID:20846619
26. Chien HY, Chen AC, Huang JW, Cheng CY, Hsu KY. Short- to medium-term out-comes of radial head replacement arthro-plasty in posttraumatic unstable elbows: 20 to 70 months follow-up. Chang Gung Med J. 2010;33(6):668-678. PMID:21199612 27. Frattini M, Soncini G, Corradi M, Panno
B, Tocco S, Pogliacomi F. Mid-term re-sults of complex distal humeral fractures.
Musculoskelet Surg. 2011;95(3):205-213. https://doi.org/10.1007/s12306-011-0132-9 PMID:21484440
28. Schmidt-Horlohé K, Wilde P, Bonk A, Becker L, Hoffmann R. One-third tubular-hook-plate osteosynthesis for olecranon osteotomies in distal humerus type-C frac-tures: a preliminary report of results and complications. Injury. 2012;43(3):295-300. https://doi.org/10.1016/j.injury.2011.06.418 PMID:21782172
29. Tian D, Jing J, Qian J, Li J. Comparison of two different double-plate fixation methods with olecranon osteotomy for intercondylar fractures of the distal humeri of young adults.
Exp Ther Med. 2013;6(1):147-151. https://doi. org/10.3892/etm.2013.1102 PMID:23935736 30. Giannicola G, Polimanti D, Gumina S, Cinotti
G. Use of fine-threaded K-wires in the treatment of coronoid fractures in complex elbow insta-bility. Orthopedics. 2013;36(10):e1233-e1238. https://doi.org/10.3928/01477447-20130920-12 PMID:24093696
31. Berschback JC, Lynch TS, Kalainov DM, Wysocki RW, Merk BR, Cohen MS. Clinical and radiographic comparisons of two different radial head implant designs. J Shoulder
El-bow Surg. 2013;22(8):1108-1120. https://doi. org/10.1016/j.jse.2013.02.011 PMID:23659806 32. Yoon A, King GJ, Grewal R. Is ORIF superior
to nonoperative treatment in isolated displaced partial articular fractures of the radial head?
Clin Orthop Relat Res. 2014;472(7):2105-2112. https://doi.org/10.1007/s11999-014-3541-x PMID:24577616
33. Zhang C, Zhong B, Luo CF. Comparing ap-proaches to expose type C fractures of the distal humerus for ORIF in elderly patients: six years clinical experience with both the triceps-spar-ing approach and olecranon osteotomy. Arch
Orthop Trauma Surg. 2014;134(6):803-811. https://doi.org/10.1007/s00402-014-1983-y PMID:24777538
34. Foruria AM, Lawrence TM, Augustin S, Mor-rey BF, Sanchez-Sotelo J. Heterotopic ossifica-tion after surgery for distal humeral fractures.
Bone Joint J. 2014;96-B(12):1681-1687. https:// doi.org/10.1302/0301-620X.96B12.34091 PMID:25452373
35. Burkhart KJ, Gruszka D, Frohn S, et al. [Locking plate osteosynthesis of the radial head fractures: clinical and radiological results]. Unfallchirurg. 2015;118(11):949-956. https://doi.org/10.1007/ s00113-014-2562-y PMID:25432670
36. Phadnis J, Banerjee S, Watts AC, Little N, Hearnden A, Patel VR. Elbow hemiarthro-plasty using a “triceps-on” approach for the management of acute distal humeral fractures.
J Shoulder Elbow Surg. 2015;24(8):1178-1186. https://doi.org/10.1016/j.jse.2015.04.010 PMID:26117619
37. Van Hoecke E, Van De Vijver A, Van Glab-beek F, Gielen J. Long term results after bi-polar radial head arthroplasty. Acta Orthop
Belg. 2016;82(2):382-388. PMID:27682304 38. Lópiz Y, González A, García-Fernández
C, García-Coiradas J, Marco F. Commi-nuted fractures of the radial head:
resec-tion or prosthesis? Injury. 2016;47(suppl 3):S29-S34. https://doi.org/10.1016/S0020-1383(16)30603-9 PMID:27692103 39. Chou YC, Hsu YH, Yu YH, Wu CC.
Triceps-reflecting anconeus pedicle approach with double precontoured locking plate fixation is efficient in the treatment of orthopaedic trauma association type C distal humer- us fracture. Injury. 2016;47(10):2240-2246. https://doi.org/10.1016/j.injury.2016.06.036 PMID:27424532
40. Tarallo L, Mugnai R, Rocchi M, Capra F, Catani F. Mason type III radial head fractures treated by anatomic radial head arthroplasty: is this a safe treatment option? Orthop Traumatol Surg Res. 2017;103(2):183-189. https://doi.org/10.1016/j. otsr.2016.10.017 PMID:27940249
41. Mazhar FN, Ebrahimi H, Jafari D, Mirzaei A. Radial head resection versus prosthetic ar-throplasty in terrible triad injury: a retrospec-tive compararetrospec-tive cohort study. Bone Joint
J. 2018;100-B(11):1499-1505. https://doi. org/10.1302/0301-620X.100B11.BJJ-2018-0293.R1 PMID:30418065
42. Gregori M, Zott S, Hajdu S, Braunsteiner T. Preserving the radial head in comminuted Mason type III fractures without fixation to the radial shaft: a mid-term clinical and radio-graphic follow-up study. J Shoulder Elbow
Surg. 2019;28(11):2215-2224. https://doi. org/10.1016/j.jse.2019.07.036 PMID:31630752 43. Zaidenberg EE, Abrego MO, Donndorff AG, Bo-retto JG, De Carli P, Gallucci GL. Treatment of terrible triad injuries at a mean follow-up of nine years. Shoulder Elbow. 2019;11(6):450-458. https://doi.org/10.1177/1758573218809375 PMID:32269605
44. Meinberg EG, Agel J, Roberts CS, Karam MD, Kellam JF. Fracture and dislocation clas-sification compendium—2018. J Orthop
Trauma. 2018;32(suppl 1):S1-S170. https:// doi.org/10.1097/BOT.0000000000001063 PMID:29256945
45. Johnston GW. A follow-up of one hundred cases of fracture of the head of the radius with a review of the literature. Ulster Med J. 1962;31:51-56. PMID:14452145
46. Regan W, Morrey BF. Classification and treatment of coronoid process fractures.
Orthopedics. 1992;15(7):845-848. https:// doi.org/10.3928/0147-7447-19920701-09 PMID:1630968
47. Bauer AS, Lawson BK, Bliss RL, Dyer GS. Risk factors for posttraumatic heterotopic os-sification of the elbow: case-control study.
J Hand Surg Am. 2012;37(7):1422-9.e1, 6. https://doi.org/10.1016/j.jhsa.2012.03.013 PMID:22551954
48. Wiggers JK, Helmerhorst GT, Brouwer KM, Niekel MC, Nunez F, Ring D. Injury complexity factors predict heterotopic os-sification restricting motion after elbow trauma. Clin Orthop Relat Res. 2014;472(7): 2162-2167. https://doi.org/10.1007/s11999-013-3304-0 PMID:24078170