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Functional outcomes after treatments for different types of isolated ulnar coronoid fracture

Abstract Background: Optimal treatments for ulnar coronoid fracture have yet to be determined. We aimed to systematically review treatment efficacy assessed by functional outcomes of patients with isolated ulnar coronoid fracture. Methods: Medline, Cochrane Library, EMBASE, and Google Scholar were searched for studies reporting quantitative outcomes data after surgical treatment for isolated ulnar coronoid fractures up to July 16, 2019. Functional outcomes determined using disabilities of the arm, shoulder and hand score; Mayo elbow performance score (MEPS); and range of motion were systematically reviewed. Results: Six studies with a total of 65 patients with isolated coronoid fracture who had received surgical treatment were included. All studies were of good quality according to a modified Delphi checklist. Most patients had Type II fractures based on Regan-Morrey or O’Driscoll classification. Disabilities of the arm, shoulder and hand scores were reported by 2 studies (mean range 5–17). Four studies reported MEPS (mean range 89–98). One study reported Broberg-Morrey scores, in which 93% patients achieved excellent or good outcomes. Five studies reported range of motion, with mean flexion ranging from 122 to 137 and mean extension ranging from 4.0 to 21 degrees. Quantitative analyses revealed that lateral, medial, or posterior approaches in treating Type II fractures are associated with higher postoperative MEPS and flexion scores than the anteromedial approach. Conclusions: Treatment efficacy assessed by functional outcomes for isolated ulnar coronoid fractures is overall satisfactory. Whether lateral, medial, or posterior approaches lead to more favorable outcomes than the anteromedial approach is inconclusive. Further prospective studies are warranted.


Introduction
The coronoid process is the key osseous stabilizer of the elbow joint. [1] Fractures of the coronoid process are thought to occur due to axial loading of the elbow, and are often associated with elbow dislocation. [2,3] Fractures of the coronoid process are rare, and are associated with concomitant injuries in 2% to 11% of elbow luxations. [4,5] About 58% of the anteromedial coronoid is unsupported by the proximal ulnar metaphysis and diaphysis, and is particularly prone to injury. [6] Fracture type is related to the mechanism of injury, and also may impact the choice of treatment. [7,8] A number of classification methods are used to describe coronoid fractures. Based on involvement of the coronoid process, Regan and Morrey introduced 3 classes: Type I fractures involving the tip of the coronoid, Type II fractures involving more than the tip and <50%of the coronoid, and Type III fractures involving >50% of the coronoid. [9] The O'Driscoll classification system subdivides coronoid injuries based on the location and number of coronoid fragments [10] : Type I is a tip fracture, Type II is an anteromedial facet fracture, and Type III is a fracture through the base of the process. [10] Several scoring systems grade clinical fracture severity of the elbow and functional outcomes, including disabilities of the arm, shoulder and hand (DASH) Score, [11,12] Mayo Elbow Performance Score (MEPS), [13,14] and the Broberg-Morrey rating system. [15] From 23% to 61% of coronoid fractures are treated surgically. [9,16] Although management of coronoid fractures is complex, several surgical interventions addressing different fracture patterns are considered effective treatment options, and current recommendations are to repair all coronoid fractures with elbow instability. [17,18] Stable fixation and ligament repair are considered essential. [19] The surgical approach varies depending on fracture severity and the presence of concomitant injuries (e.g., radial head injury). [18] A lateral approach is usually performed when an associated radial head fracture is present. A medial approach is used for an isolated coronoid fracture. Repairing large coronoid fractures can be challenging. Suture anchors are used for repairing small coronoid process fractures by suturing the bone and anterior capsule to the anterior ulna. [17] Small coronoid fractures can also be treated with elbow immobilization only. [18] Small coronoid fractures with radial head fractures, or with posteromedial instability, can be stabilized by "lasso-type" sutures or suture anchors that incorporate the capsular attachment of the fragment. Larger fragments may require screws, and large anteromedial facet fractures may require plates. [18] Complex Monteggia fractures and trans-olecranon fracture dislocations with bone and soft tissue involvement can only be treated with plates and screws. [18] Arthroscopic-assisted techniques provide open reduction and external fixation. [18] After coronoid stabilization, other components of each specific injury pattern must be treated (e.g., radial head fracture). [18] Although a range of methods are available to manage coronoid process fractures, their effectiveness has not been systematically reviewed to date. Also, optimal treatments according to different coronoid fracture types remain to be determined. We hypothesized that assessing treatments by functional outcomes may reveal important differences between surgical approaches for different types of ulnar coronoid fractures. Given this context, we conducted a systematic review of the literature, aiming to compare the clinical efficacy of treatments for ulnar coronoid fractures and evaluating differences between surgical approaches.

Search strategy
Medline, Cochrane, EMBASE, and Google Scholar databases were searched from inception to July 16, 2019. The Medline search was performed using the term "ulnar coronoid fractures." and Cochrane and EMBASE searches with the term "coronoid fracture." The availability of the abstract and the publication language (English) were used as filters in Medline and EMBASE searches.
This study was performed in accordance with the "participants, intervention, comparison, outcomes, study design" criteria. Published clinical studies in English (S) were considered for inclusion in the review; the included clinical studies must report follow-up of patients who had ulnar coronoid fractures (P) and received surgical or non-surgical treatment with or without a control group (I and C); the included clinical studies must report functional outcomes (O) after treatment. Studies focused on complex elbow injuries were excluded. Letters, commentaries, editorials, proceedings, and personal communications were also excluded. The reference lists of included studies were handsearched to identify other potentially relevant studies.
For this review, the "Preferred Reporting Items for Systematic Reviews and Meta-Analyses" (PRISMA) checklist was complete, and a PRISMA 2009 flow diagram was produced to demonstrate the process of study selection. [20]

Study selection and data extraction
Data were extracted by 2 independent reviewers who consulted with a third reviewer to resolve any uncertainties and discrepancies of eligibility. The following information/data were extracted from studies that met the inclusion criteria: the name of the first author, year of publication, study design, number, sex, and age of patients, Regan-Morrey classification for coronoid fractures, O'Driscoll classification system for coronoid injuries, mechanism of injury, time from injury to surgery, treatment approaches for ulnar coronoid fractures, and functional outcomes (measured by DASH score; MEPS, Broberg-Morrey score, and range of motion [ROM]). Ethical approval for a systematic investigation (gathering published information) was not required.

Quality assessment
The quality of the included studies was assessed by the modified 18-item Delphi checklist. [21] Quality assessment (QA) score was obtained by counting how many items the included study met. The maximum QA score was 18.

Main outcome measures
The primary outcome of the present review is treatment efficacy, which was assessed by patients' functional outcomes as measured by DASH scores, MEPS, Broberg-Morrey scores, and ROM.

Statistical analysis
The efficacy of surgical approaches was evaluated based on posttreatment functional outcomes measured by DASH, MEPS, flexion, extension, pronation and supination. All effect sizes were summarized or calculated using mean, variance, and 95% confidence intervals (CIs) for each group and subgroup. Pooled effects were calculated as mean with variance and 95%CIs for overall analysis and for subgroup analysis. A 2-tailed P value < .05 was established as statistical significance.

Search results
A total of 169 potential studies were identified in the initial literature search (Fig. 1). Of these, 139 were excluded for not being relevant after reviewing titles and abstracts. Thirty studies underwent full-text review, and 24 were excluded for not investigating surgical treatments, not reporting quantitative outcomes, or investigating coronoid fractures involving complex elbow injuries or terrible triad injuries. Finally, 6 studies were included in the systematic review.

Study characteristics
The main characteristics of the 6 included studies [5,[22][23][24][25][26] are summarized in Table 1. The number of patients in the studies ranged from 5 to 18 (total = 65). The patients' ages ranged from 14.9 to 39.4 years. More than 61% of the patients were male. The  (Table 1).

Surgical management and functional outcomes
Adams et al (2007) [26] retrospectively reviewed the outcomes of 7 patients with coronoid fractures who were treated arthroscopically (Table 1). Four fractures were Type II and 3 were Type III by Regan-Morrey classification. Fracture fixation included plate and screws after arthroscopic reduction (n = 1), screws (n = 2), threaded Steinmann pins (n = 2). In 2 cases, only fracture debridement was performed. All patients reported good function and no pain after an average follow-up of 31.8 months. ROM averages were: 9°for flexion, 133°for extension, 87°for pronation, and 79°for supination. MEPS was 100 (excellent) in 5 patients (Table 2).

Comparison of functional outcomes by surgical approach and fracture types
The results of quantitative analyses revealed that MEPSs were significantly influenced by the anteromedial approach (pooled mean MEPS = 95.5; 95%CI: 93.4 to 97.6, P < .001) and the LMP www.md-journal.com Table 1 Characteristics of studies included in the systematic review. Chen et al. Medicine (2020) 99: 19 Medicine Table 2 Functional outcomes of included studies.      When stratified by MEPS for different approaches, patients with Type II fractures who received the LMP approach had a higher MEPS than those receiving the anteromedial approach (mean MEPS = 96.6; 95%CI: 94.5 to 98.7 vs 93.0; 95%CI: 87.6 to 98.4) ( Table 5). Patients who received the LMP approach also had better flexion and extension than did those receiving the anteromedial approach (pooled mean flexion = 136.2; 95%CI: 131.5 to 140.9 vs 129; 95%CI: 123.8 to 134.2; pooled mean extension = 26.25 (95%CI: 11.6 to 40.9 vs 4; 95%CI: 0.6 to 7.4) ( Table 5).

Quality assessment
Results of the 18-item Delphi quality assessment are shown in Table 6. Studies with QA scores ranging from 9 to 15 were classified as good quality. QA results indicated that the articles selected for this system review were of good quality.

Discussion
We systematically reviewed the functional outcomes of patients who underwent surgical treatments for isolated ulnar coronoid fracture, and compared these outcome scores between specific surgical approaches. The results suggest that the current surgical treatments provide satisfactory functional outcomes as measured by DASH scores and MEPS. In addition, results of quantitative analyses showed that in patients with Type II coronoid fracture alone, those who received the LMP approach had higher MEPS and flexion scores than did those receiving the anteromedial approach.
Prior reviews have summarized treatments and prognoses for coronoid fractures, with most indicating that treatment is determined based on fracture characteristics. [18,[27][28][29] However, precisely how to handle small fractures is controversial. Two reviews suggested that surgery may not be needed for small coronoid fractures, particularly those that do not involve capsular attachments; instead authors suggest that they should   be treated only with immobilization. [28,29] In contrast, other studies have suggested that all fractures, regardless of size, should Table 6 Quality assessment of included studies with modified 18-item Delphi technique. Is the hypothesis/aim/objective of the study clearly stated in the abstract, introduction, or methods section?
Are the characteristics of the participants included in the study described?
Were the cases collected in more than one centre?
Are the eligibility criteria (inclusion and exclusion criteria) to entry the study explicit and appropriate?
Were participants recruited consecutively?
Did participants enter the study at a similar point in the disease?
Was the intervention clearly described in the study?
Were outcomes measured before and after intervention?
Were the statistical tests used to assess the relevant outcomes appropriate?
Was the loss to follow-up reported?
Does the study provide estimates of the random variability in the data analysis of relevant outcomes?
Are the conclusions of the study supported by results?
Are both competing interest and source of support for the study reported?  be surgically treated when instability exists, and even small or comminuted fractures should be treated with suture fixation. [17,27,29] Beingessner et al [30] even suggested that suture repair of the coronoid did not correct instability and that suture fixation may not be necessary for small (Type I) fractures with an intact radial head and intact lateral sided ligaments. Other authors state that small coronoid fractures without elbow instability will not require surgical treatment except when they become symptomatic loose bodies. [17] Clearly, all coronoid fractures require careful long-term follow-up to monitor recovery status and intervene as needed.
The majority of coronoid fractures are Type II, which should be treated surgically based on fracture characteristics. [17,27,29] We found that among patients with Type II fractures alone, patients who received the LMP approach had a higher MEPS and flexion score than those who received the anteromedial approach. However, the causal relationship is uncertain, and it cannot be concluded whether patients who had inferior outcomes received the anteromedial approach or the anteromedial approach actually causes inferior outcomes.
Complications that may occur following treatment include loss of ROM, osteoarthritis, heterotopic ossification, calcification, elbow instability, and paresthesias. [27] Younger patients tend to have fewer post-treatment symptoms. [17] Early postoperative mobilization should be performed, as prolonged immobilization (3-4 weeks) is associated with poor results, including loss of ROM, pain, persistent stiffness, and loss of function. [17,27] Early physical therapy and ROM exercise may help to strengthen muscle groups that play a role in muscle stability. [17,29] The present systematic review has several limitations, especially that all included studies were retrospective. Another limitation is that only 6 studies with a relatively small patient number were included in the present systematic review. These limitations suggest an urgent need for future well-designed prospective studies. In addition, although we have performed a quantitative analysis to compare patients' functional outcomes between LMP and anteromedial approaches, it remains inconclusive because cross-sectional retrospective analysis does not allow inference of causal relationship. Finally, complications were not evaluated in this review.

Conclusion
Surgical treatments for isolated ulnar coronoid fractures result in good functional outcomes generally. Whether the LMP approach leads to more favorable functional outcomes than the anteromedial approach remains inconclusive. Further well-designed prospective studies with larger samples are highly warranted.