Shoulder girdle injuries involving the medial clavicle differ from lateral clavicle injuries with a focus on concomitant injuries and management strategies: A retrospective study based on nationwide routine data.

INTRODUCTION: Although shoulder girdle injuries are frequent, those of the medial part are widely unexplored. Our aim is to improve the knowledge of this rare injury and its management in Germany by big data analysis.
METHODS: The data are based on ICD-10 codes of all German hospitals as provided by the German Federal Statistical Office. Based on the ICD-10 codes S42.01 (medial clavicle fracture, MCF) and S43.2 (sternoclavicular joint dislocation, SCJD), anonymized patient data from 2012 to 2014 were evaluated retrospectively for epidemiologic issues. We analyzed especially the concomitant injuries and therapy strategies.
RESULTS: A total of 114,003 cases with a clavicle involving shoulder girdle injury were identified with 12.5% of medial clavicle injuries (MCI). These were accompanied by concomitant injuries, most of which were thoracic and craniocerebral injuries as well as injuries at the shoulder/upper arm. A significant difference between MCF and SCJD concerning concomitant injuries only appears for head injuries (p = 0.003). If MCI is the main diagnosis, soft tissue injuries typically occur as secondary diagnoses. The MCI are significantly more often associated with concomitant injuries (p < 0.001) for almost each anatomic region compared with lateral clavicle injuries (LCI). The main differences were found for thoracic and upper extremity injuries. Different treatment strategies were used, most frequently plate osteosynthesis in more than 50% of MCF cases. Surgery on SCJD was performed with K-wires, tension flange or absorbable materials, fewer by plate osteosynthesis.
CONCLUSIONS: We proved that MCI are rare injuries, which might be why they are treated by inhomogeneous treatment strategies. No standard procedure has yet been established. MCI can occur in cases of severely injured patients, often associated with severe thoracic or other concomitant injuries. Therefore, MCI appear to be more complex than LCI. Further studies are required regarding the development of standard treatment strategy and representative clinical studies.

Introduction

Clavicle injuries are a common entity of upper extremity injury [1]. A solitary clavicle fracture represents about 2.5–10.0% of all fractures [2-6]. However, most of these injuries are in the midshaft region rather than the medial clavicle [1, 7]. The dislocation of the sternoclavicular joint (SCJD) is often the result of a high velocity force experienced during trauma [5, 8]. Although numerous surgical treatments have been reported, epidemiologic data regarding such injuries in Germany is sparse; this applies particularly to concomitant injuries and therapeutic strategies that have so far been described only in case reports/series or in small studies with a minor level of evidence [9-18].

Nonetheless, medial clavicle injuries (MCI) are quite important, as this anatomic area is the most important articular joint connecting the upper extremity to the trunk. This has an important impact on shoulder-girdle kinematics and stability [19]. Moreover, posterior dislocation of the SCJ is associated with major concomitant complications, such as haematopneumothorax [20], tracheal injuries [21] and (neuro-)vascular compression problems [22].

Given this significance, we present an analysis of current epidemiologic data of medial clavicle fractures (MCF) and SCJD in Germany. The investigation focused primarily on the frequency and importance of MCI and comparing both variants of MCI with each other and with other clavicle injuries concerning concomitant injuries and the treatment strategies applied.

Methods

The retrospective study was approved by the local ethics committee (Medical University Greifswald: BB 007/19). Since the data provided by the German Federal Statistical Office were purely retrospective and anonymized, no experiments on humans or animals had been done. Routine data based on the 10th revision of the International Statistical Classification of Diseases and Related Health Problems (ICD-10 codes) of all German hospitals discounting diagnosis-related groups (DRG) in the scope of application of § 1 of the German hospital finance law (KHEntgG) has been analyzed in detail [23, 24].

All patients released from in-patient settings (including those deceased) were included in this analysis. The ICD-10 codes S42.01, S42.02 and S42.03 (clavicle fracture medial, midshaft and lateral, respectively) in addition to S43.1 and S43.2 (acromioclavicular and sternoclavicular joint dislocations, respectively), including their combinations, were evaluated from 2012 to 2014. We extracted the data of MCI S42.01 and S43.2 from these five shoulder girdle injuries involving the clavicle and focused on them. The lateral clavicle fracture and the acromioclavicular joint dislocation were summarized to the subgroup of lateral clavicle injuries (LCI) for comparison. The retrospective analysis addresses potential concomitant injuries and therapy strategies.

Concerning the concomitant injuries, we also distinguish between main and secondary diagnosis of MCI. Therefore, a patient with multiple injuries was counted once, since we analyzed each of the shoulder-girdle injuries relating to the clavicle for itself and the further injuries were counted as main or secondary diagnosis, vice versa, to the related injury. We focused on chapter XIX of the ICD-10 code, which contains “Injuries, poisoning and certain other consequences of external causes” for the analysis of concomitant injuries and excluded all posttraumatic conditions resulting in the analysis of diagnoses describing only primary injuries (S00-S99) [23]. Soft tissue damage is classified according to the Oestern and Tscherne classification in the ICD-10 code system, which is also used most often in the literature to describe soft tissue injuries in blunt trauma [25].

The therapies conducted were analyzed based on the German procedure classification (“Operationen- und Prozedurenschlüssel”; OPS code), which is the official classification for the encoding of operations, procedures and general medical measures [26]. The OPS is available in various versions and formats in German and is updated annually [26]. We focused on the OPS codes of the subdivided categories “operations” (5–01 …5–99) and “operations of movement organs” (5–78 …5–86), and the category “closed reduction and correction of deformities” (8–20…8–22). We analyzed these categories and further description of the targeted part “clavicle,” “sternoclavicular joint” or “others” were inclusion criteria. Thus, the unrelated interventions were excluded. These were surgeries of concomitant injuries at other parts of the body, but related to the case due to an MCI as a main diagnosis. The relevant therapies were, without exception, part of the categories “operations at other bones” (5–78), “reduction of fracture and dislocation” (5–79), “open surgical and other joint operations” (5–80) and “closed reduction and correction of deformities” (8–20…8–22). The data were presented as summarized interventions of MCI as a main and secondary diagnosis. Therefore, all injuries with either surgical or nonsurgical treatment were included.

Statistical analysis was performed using the SPSS software (IBM, version 22, Champaign, IL). The association between type of fracture and frequency of surgery was tested by Pearson’s chi-squared test and, in the case of low cell frequencies (i.e. single cell number < 5), via Fisher’s exact test with an alpha level of 0.05. In some cases, confidence intervals were added. No alpha adjustment for multiple testing was conducted due to the explorative character of the analysis.

Results

We reviewed a total of 114,003 patients who had a diagnosed clavicle injury (). Of these, 12.5% are coded as MCI, n = 13,588 for medial clavicle fractures (S42.01; 11.9%) and n = 676 for SCJD (S43.2; 0.6%) of all clavicle injuries (). This group is used for further investigation. The average patient age for SCJDs was 50.3 (±23.3) years and 47.7 (±22.8) years for MCFs; an average of 67.2% (CI 63.5–70.7%) of SCJD were attributed to males and 32.8% (29.3–36.5%) to females. The sex distribution of MCF was an average of 69.4% (CI 68.6–70.2%) in males and 30.6% (29.9–31.4%) in females.

Prism of distribution of shoulder girdle injuries relating to the clavicle, 2012–2014.

n = number of patients.

Concomitant injuries

MCI are associated with a significantly higher number of concomitant injuries at each anatomic region, apart from wrist and hand injuries, in contrast to LCI (, p = 0.001–0.02). Concomitant injuries of the shoulder and upper arm are the most commonly affected part of the body in MCI and LCI, while the major differences between the medial and lateral shoulder girdle occur in this group and in concomitant thoracic injuries. The ratio of associated injuries overall to the number of diagnoses in the case of MCI is 20.4% higher than LCI. MCI have an average of 1.0 concomitant injuries per case, while LCI have a ratio of 0.8.

Concomitant injuries of medial clavicle and lateral clavicle injuries categorized by the anatomical region.

MCI = medial clavicle injuries; LCI = lateral clavicle injuries; * = significant difference.

With a focus on MCI particularly, the most common concomitant injuries occur regarding the anatomical region affected at the shoulder/upper arm (SCJD 39.5%; MCF 42.2%), as thoracic injuries (SCJD 19.4%; MCF 19.6%) and as craniocerebral injuries (SCJD 14.1%; MCF 18.3%) (). A significant difference between both MCI only appears for concomitant head injuries (p = 0.003).

Concomitant injuries of medial clavicle injuries categorized by the anatomical region affected.

S43.2 = sternoclavicular joint dislocation; S42.01 = medial clavicle fracture; *p = p-value as level of significant difference.

Since every case of MCI as a secondary diagnosis has to be associated with another concomitant injury as a main diagnosis, we further focus on the opposite part. As a main diagnosis, a SCJD is associated with an average of 1.1 further concomitant injuries (). The same applies to MCF, with a mean of 1.1 other diagnosis. These concomitant injuries are most frequently soft tissue injuries in both types of MCI.

Most common concomitant injuries of medial clavicle injuries as a main diagnosis.

Second diagnoses according to MCI as a main diagnosis presented as the five most common second diagnoses for both types of MCI each. S43.2 = sternoclavicular joint dislocation; S42.01 = medial clavicle fracture; x = non-valid, since main ≠ secondary diagnosis at the same time.

The distribution is quite similar for each MCI with special regard to the specific thoracic concomitant injuries (). The two most frequent are, in both cases, an associated serial rib fracture with participation of four or more ribs (MCF 18.2% of all thoracic concomitant injuries; SCJD 14.5%) and a contusion of the thorax (MCF 15.2%; SCJD 17.6%). The thoracic first grade soft tissue injuries differ (MCF 8.3%; SCJD 1.5%) as do fractures of the sternum and first rib (MCF 4.0%; SCJD 9.9%).

Therapy strategies

There was a significant difference between MCF and SCJD regarding the fundamental types of operations (): here were significantly (p < 0.001) more removals of osteosynthetic material in the case of MCF (18.9%) compared to SCJD (7.5%) in relation to all interventions regarding SCJD and MCF. After exclusion of all irrelevant coded interventions–also excluding the removals of osteosynthetic material, coded by a related ICD-10 code of MCI in terms of a removal as a main diagnosis–there remained n = 9445 primary operations of MCI ().

Prism of medial clavicle injuries therapies coded by OPS code, 2012–2014.

MCI = medial clavicle injuries; SCJ = sternoclavicular joint; n = number of patients.

There were differences in treatment options within the MCI (). The ratio of primary surgical interventions to the number of injuries was 60.4% for SCJD, while 66.5% were treated surgically in the case of MCF. Both MCI were the domain of open surgical treatment (p < 0.001). While an open surgery was done in 92.2% of all MCF operations in contrast to 89.5% of all SCJD (p < 0.001), a closed procedure was performed in 7.8% of all MCF compared to 10.5% at SCJD (p = 0.049).

Heterogeneous treatment options were performed for both MCI in the case of an invasive surgical strategy with a reduction via osteosynthesis (). Each specific type of osteosynthesis showed significant differences between SCJD and MCF (p < 0.001). While SCJD was a preserve of osteosynthesis via wire or tension flange, more than half of the MCF treated by osteosynthetic procedure received a (locking) plate osteosythesis.

Primary operations with osteosynthesis of medial clavicle injuries sorted for type of osteosynthesis.

Primary operations with osteosynthesis in the case of the coded diagnosis of a medial clavicle injury (S42.01 and S43.2) related to the sternoclavicular joint, clavicle or others sorted for the type of osteosynthesis. The number is presented as a percentage of all surgeries performed with osteosythesis. All types showed a significant difference between both diagnoses. S43.2 = sternoclavicular joint dislocation; S42.01 = medial clavicle fracture; * = p-value as level of significance with p < 0.001.

Discussion

The distribution of MCI is slightly different from the data published in the past: SCJD seem to be less frequent and MCF more frequent than assumed so far [3–5, 7]. Previous work with a large cohort concerning clavicle fractures was limited by not differentiating between the localizations of the fracture [27]. To the best of our knowledge, this is the epidemiologic study with the largest demographic sample analyzed in the literature. It might be that, based on the large cohort, these findings are more powerful than the past data. On the other hand, the advantage of the high number of cases could prove to be problematic. Some authors avoid, for example, specifying confidence intervals or presenting p-values in these cases as it makes relatively small differences significant and simulates a relationship that is purely statistically significant [28].

As we have shown, MCI are more frequently associated with concomitant injuries compared to LCI in all respects. The concomitant injuries of MCI appear predominantly in the upper half of the body, especially at the shoulder/upper arm, thorax and head. In comparison to recent work of clinical retrospective research, the high presence of concomitant injuries at these anatomic regions affected could be proved [15]. The concomitant craniocerebral injuries are significantly more in the case of MCF. This is quite unsuspected because of the assumption that a severe trauma impact leads more often to a SCJD instead of an MCF. However, in this study, we analyzed severely injured patients and monotraumatically injured ones. In order to deliver a more precise insight regarding the role of MCI in severely injured trauma patients with high impact trauma mechanism, further research with a focus on these circumstances is necessary. However, we confirm that MCI might be a hint of a severe thoracic trauma or trauma of the upper half of the body [29]. Therefore, patients with injuries to the medial part of the shoulder girdle should be examined with special care.

With a focus on specific concomitant injuries, there are differences for main and secondary diagnoses especially regarding thoracic injuries, which are often underestimated. The contemporaneous appearance of MCI and thoracic injuries is proved [30, 31]. While soft tissue injuries and costoclavicular injuries are found mostly in cases of MCF, the central localized sternal and first rib injuries occur predominantly with SCJD. This is presumed to be because of the close anatomic distance.

Since one concomitant injury per MCI case is only an average and there do not seem to be many at first glance, this rate is still 20% higher than with LCI and shows, therefore, the complexity of MCI. The frequently coded soft tissue injuries as a secondary diagnosis may be based on the attempt to enlarge the financial results. The minor proportions of several main diagnoses relating to MCI as a secondary diagnosis show their widely dispersed distribution.

There is currently no established protocol of care for sternal end clavicle injuries [32]. Although a new classification system and a proposal for a compulsory standard management for medial clavicle injuries have been published recently, these have not yet been evaluated or validated [15]. The heterogeneity of different treatment options of MCI was clearly identified in this study. Although the SCJD and the MCF are close to each other regarding their location, there are certain differences between the current treatment strategies of MCI.

In detail, the different corresponding anatomic structures of the SCJ and bony medial clavicle were referring to diverse treatments: Comprehensive operations relating to soft tissue, such as sutural surgery, were presented more often in SCJD, while most MCF were treated by plate osteosynthesis. In comparison with recent work of clinical retrospective research, there is a relevant difference to the amount of conservative/operative therapy relating to 68.4% conservatively treated medial injuries [15]. In an international comparison, even fewer surgically treated patients were shown with an amount of little or no MCI surgery in Belgium and Sweden [16, 18].

The heterogeneous treatment might be induced by different subtypes of MCI. A more precise classification of the medial injuries in terms of SCJD and medial clavicle fractures provided in recent work is not possible as this study is based only on routine data [15, 33]. Therefore, an attribution of the different treatment options to any type of classification is not possible. This is why a missing doublecheck referring to the correct radiologic location and a potential miscoding are also potential biases regarding this point [15]. Unfortunately, this problem remains unsolved in our study due to the underlying, purely retrospective anonymized data and, consequently, the lack of traceability of the individual cases. This is an important aspect, since a miscoding of medial clavicle fractures is a frequent issue, especially the mix-up between medial and middle third fractures [15]. Other potential bias that might increase the heterogeneity of treatment strategies and which could not have been prevented due to anonymized data are genetic disorders or oncologic patients with diseases affecting the musculoskeletal system. However, although these patients might be subject to adopted treatment, the number of these special cases is assumed not to be in relation to the total size of the cohort. We also admit that the encryption to OPS code is not unambiguous, since the operations are categorized only by major groups of surgical procedures.

Another possible confounder is coding regarding financial aspects, which could lead to an over-/under-coding of certain primary and secondary diagnoses [34, 35]. In addition, it is necessary to clarify the data from the falsification produced by coding the removals of osteosynthesis material, since there are 7.5% for SCJD and 18.9% for MCF of all relevant operations performed. This could also mix up the primary operated cases and the cases of a removal of osteosynthesis material and, therefore, lead to duplicate counting of the same patient over the years. This is attributed to an attendant and iterated coding of the original main diagnosis in the case of removal of material. The procedures and operations conducted and coded were analyzed. Because these were not the same as the number of cases, more than one procedure/operation per patient and case is possible. Several codes in the case of a complex operation are intended [26]. This could lead to a bias due to multi-coding.

A limitation in ICD and OPS coding is the code “others.” Further differentiation is impossible in such cases. A direct conclusion from OPS code to the injured body part can usually be interpreted by the last number/letter of the code to avoid misinterpretation from OPS code to an actual false and non-corresponding injury. A bias or distortion resulting from changes in coding behavior or in the classification systems over the years are suspected to be marginal. The possibility of coding operations at muscles, tendons, fasciae and bursae (OPS 5–85) was missing for SCJ. Therefore, a small lack of OPS coding system might be possible.

Despite the limitations of this registry research and big data analysis in general, especially concerning the potential bias of an impossible and missing doublecheck for the exactness of coding, our analysis offers new aspects regarding MCIs in Germany. An important aspect that warrants further study is an analysis of combined shoulder girdle injuries, which occurred in these findings in contrast to single ones. An interesting area of investigation would be the distribution among different hospitals relating to the level of health care (basic, regular or maximum) and whether there is a correlation to the treatment strategies chosen. An SCJD is a particularly severe injury with potential concomitant or following complications and co-injuries, as shown. For this reason, the statutory accident insurance in Germany lists this injury in the register for very severe injury procedures with its own number, 7.2, which means a treatment in a specialized level one trauma center [36].

Conclusion

Concomitant injuries are common in MCI. We attribute this fact to the high trauma force, which is often responsible for these entities [15, 27, 29, 37]. Concerning the spectrum of concomitant injuries, we demonstrated a relevant difference between medial and lateral clavicle injuries. MCF and SCJD differ only slightly in this regard. However, the variety of current management strategies of MCI confirms the fact that there is currently no standard therapy of MCI. The status in Germany shows heterogeneous treatment options including operative and conservative therapy with a relevant tendency to surgery.

Concomitant thoracic injuries of medial clavicle injuries.

Concomitant thoracic injuries of sternoclavicular joint dislocations (S43.2) and of medial clavicle fractures (S42.01) are presented as an absolute and relative number in relation to all concomitant thoracic injuries categorized by the specific thoracic injury from 2012 to 2014. ICD = code of the diagnosis by ICD-10; SD = secondary diagnosis; MD = main diagnosis; SD+MD = all diagnoses (secondary and main diagnosis); S43.2 = sternoclavicular joint dislocation; S42.01 = medial clavicle fracture; n = absolute number of cases; % = relative amount in relation to all concomitant thoracic injuries of the respective medial clavicle injury.

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30 Aug 2019

[EXSCINDED]

PONE-D-19-21318

Shoulder girdle injuries involving the medial clavicle differ from lateral clavicle injuries with focus on concomitant injuries and management strategies: A retrospective study based on nationwide routine data

PLOS ONE

Dear Dr. med. Bakir,

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process.

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The authors put many hours in collecting data and preparing this interesting manuscript. The recommended therapeutic procedures for MCF as well as for SCJD are really very heterogenous, which underlines the importance of this study. However, in the present form it cannot be accepted for publication in POLS ONE. Please refer to the careful done reviwes for improvement. As pointed out by both reviewers, I believe that a native speaker could be of great linguistic help.

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Reviewer #1: Dear Autors

Thank you for submitting your paper to this journal.

You submit a scientific paper focusing on the frequency of medial clavicule injuries including medial clavicule fractures as well as dislocations of the sternoclaviular joint. Their cohort included a high number of patients (13588 MCF and 676 SCJD) and therefore the study could be very interresting and could bring up relevant differences between MCF and SCJD as well as between MCI and LCI. The severe problem with this data analysis is, that it is based on numbers related to ICD coding and OPS coding. We all know, that this may significantly falsify data, as coding is sometimes driven by financial and economic interrests. Although some conclusions seem to be logical, I would not take the data as realistic and meaningful. Over and/or undercoding as well as multicoding should be ruled out by looking at the charts and x-rays of the patients to avoid misinterpretation.

If the data are correct and doublechecked, the paper would contribute to a better understanding of shoulder girdle injuries. The paper is well written, the citations are correct and I only would suggest a few revisions.

Page 4 line 55: Change to: This has significant impact on Shoulder girdle kinematics as well as stability.

Page 4 line 60: The investigation focused primarily on the frequency and importance of MCI and comparing both variants as well as comparing MCI with other clavicle injuries concerning concomitant injuries and applied treatment strategies.

Page 5 line 80: chapter XIX is not clear for all readers of the journal.

Page 7 line 102: I would suggest to skip Fig I. The clarification in the text seems to be enough.

Page 8 line 129 to 149: this paragraph could possibly improve by rewriting and shortening by focusing on the relevant data. Why is it so important if the diagnosis is coded as the primary or secundary diagnosis keeping the uncertainty of coding in mind. Under this perspective also figure 5a and 5b could be revised.

Regarding the treatment options it seems very difficult to draw or follow relevant conclusions, as there is no detailed information on the type, classification and pattern of the injury. This should also be provided after analysing the charts and x-rays.

Concluding I want to emphysize, that in my opinion this paper would gain a lot of significance by correction of the data by checking the charts and the x-rays and improve the quality of the basic data to reduce this uncertainty.

Reviewer #2: The authors address the topic of medial clavicle injuries by using a nationwide database.

Abstract

Introduction

I have a little problem with the phrase “general idea”. Please rephrase this sentence into the hypothesis/research question/or the aim of this study.

Methods

Based on ICD-10 codes patients with medial clavicle fractures or SC joint dislocation were evaluated. This methodology could be adequate depending on the research question.

Results

The results section of the abstract need major revision: I recommend English correction by a native speaker. “A significant difference between the both MCI only appears for concomitant head injuries (p=0.003)” This sentence appears incomplete: what groups were compared?

Conclusion

Major language correction, conclusion of MCI being rare with inhomogeneous treatment strategies

Manuscript

Intoduction

The first sentence states clavicle fractures to be a common complication of upper extremity injury. We believe that these fractures are not common complication of other injuries, but are common injuries by themselves. Further, the authors state epidemiologic data regarding such injuries in Germany were sparse and cite 6 articles. This seems inconsistence.

“MCI are quite important as they are the only articular joint of the upper extremity to the trunk” Technically speaking, the scapula-thoracic also serves as an articular joint of the upper extremity to the trunk. Please correct the sentence (e.g. one of the important….)

“This has significant impact on…”, “significant” usually followed by a p-value / a comparison. Please rephrase

I have problems with the last sentence of the Introduction: The investigation focused primarily on the role of MCI in their comparison -> to what? And in comparison to other clavicle injuries concerning concomitant injuries …. This phrase is hard to read. The reader would benefit from substantial revisions with the help of native speaker

Methods

According to the methodology of this article, the authors only evaluated ICD-10 diagnosis an OPS codes.

Please include a definition of shoulder girdle injuries relating to the clavicle

The time frame 2012-2014 should be included in the methods section

Please include inclusion and exclusion criteria: where only surgical treated injuries included, or all injuries (non-surgical treatment). What about genetic disorder, or oncological patients with diseases affecting the musculo-skeletal system: these patients might be subject to adopted treatment that might increase heterogeneity of treatment strategies.

Are multiple injured patients calculated multiple times? E.g. Patient with MCF and, pneumothorax and fracture of the ankle. How is this patient being handled?

Please define soft tissue injury

How where patients handled that were operated several different times due to MCI / MCF?

Results

Figures: Generally, please replace the ICD-10 code with the wording of the injury, eventhough it has been stated in the description, I believe the reader would benefit from stating the text in the graph, rather in the description. X = non valid (where there missing data? NAs?)

How many patients had only the injury to the medial part of the clavicle, or is there always a concomitant injury?

Line 129: Concerning the concomitant injuries in particular… This belongs to the methods section

Line 143: There are also some differences for main as well as for secondary diagnosis with special regard to…. -> Please revise this sentence; don’t use empty phrases such as “There are also some differences”

It appears the results section to be a collection of Figure and Table descriptions…

Discussion

Major English corrections needed

Line 186-187: The authors state that large cohort analysis are more precise: We highly disagree with this statement. The problem with big data analysis, especially when comparing groups has been discussed several times. Further, this study lacks substantial elements of epidemiologic studies: Table 1 approach, patients demographics etc. Citing an article regarding head injuries the authors state “specifying confidence intervals in these cases” to be avoided “as it makes relatively small differences significant and simulates a relationship that is purely statistically significant”. First, this statement holds true for all statistical tests, and tor the p-value. The alpha is arbitrary set at 0.05, and the statistical tests simulate a purely statistical significance. Second, the CI gives way more information than the p-value and should always be preferred.

Line 190: “Another potential bias…” what has been done to reduce this problem?

The discussion part appears disorganized. Usually, the main results are discussed point by point and one section is dedicated to strengths and limitations. The limitations of this study are discussed in lines 191ff, 228, 247ff, 255. Apparently the author included a “limitation-sentence” at the end of each paragraph. I would not recommend doing so: First, usually Strengths and limitations have one section; Second, with the authors approach, each paragraph/section loses weight, when ended by a “limitation-sentence”

Conclusion:

Line 266: “… the high trauma force which is often responsible for this entities”. I don’t find data in the authors article to support this conclusion. How was the trauma force measured/calculated? Have these data been included?

“on the other hand” empty phrase, discard

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Reviewer #2: No

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11 Oct 2019

Reviewer #1: Dear Autors

Thank you for submitting your paper to this journal.

You submit a scientific paper focusing on the frequency of medial clavicule injuries including medial clavicule fractures as well as dislocations of the sternoclaviular joint. Their cohort included a high number of patients (13588 MCF and 676 SCJD) and therefore the study could be very interresting and could bring up relevant differences between MCF and SCJD as well as between MCI and LCI. The severe problem with this data analysis is, that it is based on numbers related to ICD coding and OPS coding. We all know, that this may significantly falsify data, as coding is sometimes driven by financial and economic interrests. Although some conclusions seem to be logical, I would not take the data as realistic and meaningful. Over and/or undercoding as well as multicoding should be ruled out by looking at the charts and x-rays of the patients to avoid misinterpretation.

If the data are correct and doublechecked, the paper would contribute to a better understanding of shoulder girdle injuries. The paper is well written, the citations are correct and I only would suggest a few revisions.

- Thank you for your kind evaluation. Of course, the problem of miscoding is enormously important. Especially in the analysis of big data, systematic coding bias can lead to wrong conclusions. We described this aspect in our limitations. Although individual cases of miscoding could be a negligible mistake regarding the large study cohort, a potential systematic bias is an important factor. Therefore, we have elaborated this point in the discussion.

Due to the anonymized data underlying this study and the purely retrospective examination, a doublecheck by controlling the x-rays is unfortunately not possible. However, as a conclusion, this is an important study in the future and case-based follow-up studies on this topic should result from this work to avoid miscoding bias and to measure this effect.

Page 4 line 55: Change to: This has significant impact on Shoulder girdle kinematics as well as stability.

Page 4 line 60: The investigation focused primarily on the frequency and importance of MCI and comparing both variants as well as comparing MCI with other clavicle injuries concerning concomitant injuries and applied treatment strategies.

Page 5 line 80: chapter XIX is not clear for all readers of the journal.

- Thank you for your suggestions. We have implemented your suggestions and optimized the formulations.

Page 7 line 102: I would suggest to skip Fig I. The clarification in the text seems to be enough.

- Thank you for this advice. We skipped this figure to avoid duplication.

Page 8 line 129 to 149: this paragraph could possibly improve by rewriting and shortening by focusing on the relevant data. Why is it so important if the diagnosis is coded as the primary or secundary diagnosis keeping the uncertainty of coding in mind. Under this perspective also figure 5a and 5b could be revised.

- We have implemented this note and considered the MCI as a main diagnosis in the current version of the manuscript and the concomitant injuries as a secondary diagnosis only. Consequently, we deleted Figure 5b without replacement.

Regarding the treatment options it seems very difficult to draw or follow relevant conclusions, as there is no detailed information on the type, classification and pattern of the injury. This should also be provided after analysing the charts and x-rays.

Concluding I want to emphysize, that in my opinion this paper would gain a lot of significance by correction of the data by checking the charts and the x-rays and improve the quality of the basic data to reduce this uncertainty.

- In summary, we thank you for the constructive criticism and valuable comments that have improved our work. The main suggestion to control the cases radiologically would of course increase the quality and validity of the work. However, this was and is not possible due to the existing anonymized routine data and was not the aim of this work. The high number of cases analyzed as done in this cohort analysis could not have been achieved in the past, which is proved by previous work on this subject with a significantly smaller number of patients, but radiologically controlled data. Therefore, we believe that despite this limitation, this work has its value because of its large sample size and adds new aspects to the topic.

Nonetheless, we are already in the last steps of planning a prospective, case-controlled follow-up study, in which we follow a similar approach to image-controlled data.

Reviewer #2: The authors address the topic of medial clavicle injuries by using a nationwide database.

Abstract

Introduction

I have a little problem with the phrase “general idea”. Please rephrase this sentence into the hypothesis/research question/or the aim of this study.

Methods

Based on ICD-10 codes patients with medial clavicle fractures or SC joint dislocation were evaluated. This methodology could be adequate depending on the research question.

Results

The results section of the abstract need major revision: I recommend English correction by a native speaker. “A significant difference between the both MCI only appears for concomitant head injuries (p=0.003)” This sentence appears incomplete: what groups were compared?

Conclusion

Major language correction, conclusion of MCI being rare with inhomogeneous treatment strategies

- Thank you for your feedback. We followed your suggestions, reformulated the abstract and it was edited by a native speaker.

Manuscript

Intoduction

The first sentence states clavicle fractures to be a common complication of upper extremity injury. We believe that these fractures are not common complication of other injuries, but are common injuries by themselves. Further, the authors state epidemiologic data regarding such injuries in Germany were sparse and cite 6 articles. This seems inconsistence.

- We have worked on the ambiguity in the formulations and thank you for the advices. The six quoted articles confirm our statement, which we have related to both sentences more clearly: the topic has been described only in case reports / series or small studies with minor level of evidence in the past.

“MCI are quite important as they are the only articular joint of the upper extremity to the trunk” Technically speaking, the scapula-thoracic also serves as an articular joint of the upper extremity to the trunk. Please correct the sentence (e.g. one of the important….)

“This has significant impact on…”, “significant” usually followed by a p-value / a comparison. Please rephrase

I have problems with the last sentence of the Introduction: The investigation focused primarily on the role of MCI in their comparison -> to what? And in comparison to other clavicle injuries concerning concomitant injuries …. This phrase is hard to read. The reader would benefit from substantial revisions with the help of native speaker

- We clarified the noted parts and revised them.

Methods

According to the methodology of this article, the authors only evaluated ICD-10 diagnosis an OPS codes.

Please include a definition of shoulder girdle injuries relating to the clavicle

The time frame 2012-2014 should be included in the methods section

- We presented the two aspects addressed in the method section of the first submitted draft (line 81-84). Since this was obviously not sufficiently highlighted and to clarify the definition, we have adapted this part.

Please include inclusion and exclusion criteria: where only surgical treated injuries included, or all injuries (non-surgical treatment). What about genetic disorder, or oncological patients with diseases affecting the musculo-skeletal system: these patients might be subject to adopted treatment that might increase heterogeneity of treatment strategies.

Are multiple injured patients calculated multiple times? E.g. Patient with MCF and, pneumothorax and fracture of the ankle. How is this patient being handled?

- We have re-sorted the inclusion and exclusion criteria, which were already mentioned in the first draft, to make them more recognizable (line 81-91, 106-114). We have implemented this for ICD 10 codes and OPS codes.

We gratefully took note of the aspect of patients with genetic disorder or oncological patients and included them in the discussion (line 251-255).

Please define soft tissue injury

- We have added a corresponding explanation in the methods section of the manuscript. In the case of the corresponding coding, the classification of the soft tissue damage of Tscherne and Oestern was used.

How where patients handled that were operated several different times due to MCI / MCF?

- Multiple coding is an important and potential confounding factor. Therefore, this problem has been addressed in our discussion (line 267-277).

Results

Figures: Generally, please replace the ICD-10 code with the wording of the injury, eventhough it has been stated in the description, I believe the reader would benefit from stating the text in the graph, rather in the description. X = non valid (where there missing data? NAs?)

- Thank you for your advice. We improved the comprehensibility and replaced the name of the ICD-10 code with the abbreviation of the injury.

The non-valid data refers to the fact that an injury, in the case mentioned the MCF, can not be both main and secondary diagnosis at the same time. We have completed and executed this in the picture caption.

How many patients had only the injury to the medial part of the clavicle, or is there always a concomitant injury?

- As described in Figure 1 (former Figure 2), 13,588 MCF occurred: 8762 as a main diagnosis, 4826 as a secondary diagnosis. n = 16 out of 296 patients with SCJD as a major diagnosis had a MCF as a secondary diagnosis. Therefore, MCF is present as a single diagnosis as well. MCF is not always present as a concomitant injury.

Line 129: Concerning the concomitant injuries in particular… This belongs to the methods section

- Due to your advice, we have moved the paragraph mentioned to the methods section (line 86-89).

Line 143: There are also some differences for main as well as for secondary diagnosis with special regard to…. -> Please revise this sentence; don’t use empty phrases such as “There are also some differences”

- We optimized the sentence accordingly, thank you very much for your advice.

It appears the results section to be a collection of Figure and Table descriptions…

- Thank you for your comment. Since, according to the journal's guidelines, the submission is prescribed like this, the description of the table and the figures have to be integrated into the text as done. Since the results are already presented via figures and tables, we passed on a detailed description of the results in the text of the result section, since we wanted to avoid duplication of data presentation.

Discussion

Major English corrections needed

Line 186-187: The authors state that large cohort analysis are more precise: We highly disagree with this statement. The problem with big data analysis, especially when comparing groups has been discussed several times. Further, this study lacks substantial elements of epidemiologic studies: Table 1 approach, patients demographics etc. Citing an article regarding head injuries the authors state “specifying confidence intervals in these cases” to be avoided “as it makes relatively small differences significant and simulates a relationship that is purely statistically significant”. First, this statement holds true for all statistical tests, and tor the p-value. The alpha is arbitrary set at 0.05, and the statistical tests simulate a purely statistical significance. Second, the CI gives way more information than the p-value and should always be preferred.

- Thank you for your detailed comment on this topic. We discuss this problem of the big data analysis in the relevant section of the discussion. We mention the problem of a high number of cases in terms of the significance of statistical tests. Confidence intervals have been added to Table 1. We also supplemented epidemiological data regarding age and sex distribution for a better overview on patients’ demographics (line 128-130).

Line 190: “Another potential bias…” what has been done to reduce this problem?

- Unfortunately, this problem remains unsolved due to the underlying, purely retrospective anonymized data and consequently the lack of traceability of the individual cases. We added this explanation to this part of the discussion.

The discussion part appears disorganized. Usually, the main results are discussed point by point and one section is dedicated to strengths and limitations. The limitations of this study are discussed in lines 191ff, 228, 247ff, 255. Apparently the author included a “limitation-sentence” at the end of each paragraph. I would not recommend doing so: First, usually Strengths and limitations have one section; Second, with the authors approach, each paragraph/section loses weight, when ended by a “limitation-sentence”

- Many thanks for this conclusive proposal, which we have gladly implemented in this form. We revised the part of the discussion and changed its structure.

Conclusion:

Line 266: “… the high trauma force which is often responsible for this entities”. I don’t find data in the authors article to support this conclusion. How was the trauma force measured/calculated? Have these data been included?

“on the other hand” empty phrase, discard

- We gratefully accepted the comment to our ambiguous phrase and clearly marked the corresponding line as our hypothesis and conclusion. An analysis of the trauma mechanism was not part of this study. In addition, we have also revised this section linguistically.

- In conclusion, we would like to thank you for the constructive evaluation. We have realized the main suggestion of a linguistic revision by a native speaker. We believe that, in spite of the remaining methodological optimization suggestions, this work is nevertheless worth publishing, since it contains aspects that have received little attention in the past regarding MCI. These aspects have been examined in this study analyzing a large cohort.

Submitted filename: PLOS ONE_Response to Reviewers.docx

Click here for additional data file.

14 Oct 2019

Shoulder girdle injuries involving the medial clavicle differ from lateral clavicle injuries with a focus on concomitant injuries and management strategies: A retrospective study based on nationwide routine data

PONE-D-19-21318R1

Dear Dr. Bakir,

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Additional Editor Comments (optional):

Thank you for answering to all reviewers comments.

Reviewers' comments:

18 Oct 2019

PONE-D-19-21318R1

Shoulder girdle injuries involving the medial clavicle differ from lateral clavicle injuries with a focus on concomitant injuries and management strategies: A retrospective study based on nationwide routine data

Dear Dr. Bakir:

I am pleased to inform you that your manuscript has been deemed suitable for publication in PLOS ONE. Congratulations! Your manuscript is now with our production department.

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Table 1

Number of particular primary interventions for medial clavicle injuries and the difference between the injury entities.

Category of treatment	Type of treatment	OPS code	S43.2		S42.01		Significance
			n	%(CI)	n	%(CI)	p
Closed treatment	closed reduction without osteosynthesis	8–200 ff.	37	9.1(6.7–12.3)	65	0.7(0.6–0.9)	< 0.001
	closed reduction of fracture/ epiphyseal injury with osteosynthesis	5–790	2	0.5(0.1–17.7)	643	7.1(6.6–7.7)	< 0.001
	closed reduction of joint dislocation with osteosynthesis	5-79a	4	1.0(0.4–2.5)	1	<0.1(0.0– < 0.1)	< 0.001
Open treatment	open reduction of simple fracture at small bone	5–795	34	8.3(6.0–11.4)	2703	30.0(29.0–30.9)	< 0.001
	open reduction of multi-fragmentary fracture at small bone	5–796	33	8.1(5.8–11.1)	5504	61.0(59.9–61.9)	< 0.001
	open reduction of joint dislocation	5-79b	172	42.1(37.5–47.0)	40	0.4(0.3–0.6)	< 0.001
	open joint surgery	5–800	37	9.1(6.7–12.3)	19	0.2(0.1–0.3)	< 0.001
	open surgery at joint cartilage or meniscus	5–801	8	2.0(1.0–3.8)	7	<0.1(<0.1–0.2)	< 0.001
	open surgical refixation at capsular-ligamental system of other joints	5–807	64	15.7(12.5–19.5)	50	0.6(0.4–0.7)	< 0.001
Others	other joint surgeries	5–809	17	4.1(2.6–6.6)	5	<0.1 (< 0.1–0.1)	< 0.001
Total			408	100.0	9037	100.0

Only injuries related to sternoclavicular joint, clavicle or others were analyzed from 2012–2014 (n = 9445). Non-primary treatments, such as removal of osteosynthesis, have been excluded. The higher value is highlighted in bold. S43.2 = sternoclavicular joint dislocation; S42.01 = medial clavicle fracture; n = number of patients; % = percentage; CI = confidence interval; p = p-value as level of significance.