INTRODUCTION
The incidence of posttraumatic elbow joint stiffness is relatively high and can negatively affect activities of daily living [1-3]. Elbow trauma carries a 12% risk of joint stiffness and an 8.4% risk amongst those patients who have undergone elbow surgery for trauma, of whom 7.2% require revision contracture release surgery [4,5]. Capsular or ligamentous contractures are a main intrinsic factor affecting posttraumatic stiffness, among which anterior capsular contraction is the leading cause of flexion contracture after an elbow injury [6]. Thickened capsules and myofibroblast proliferation can result in alpha-smooth muscle actin expression as the primary pathology [2,3,7]. Furthermore, recognizing anterior capsular injury patterns is vital for effective treatment and recovery, as different patterns lead to varied outcomes. This concept is well-established in animal models, where specific capsular and ligamentous injury patterns affect outcomes [3,8]. This principle also applies to clinical scenarios, where the mechanism and severity of injury can influence the pattern of capsular disruption. For instance, simple elbow dislocation, which typically results from high-energy injuries, often involves substantial soft tissue disruption, including injuries to the anterior capsule. Existing literature has extensively documented the link between prolonged immobilization after elbow dislocation and increased risk of flexion contracture [9].
Conversely, distal humerus coronal shear (DHCS) fractures, which are often caused by low-energy injuries, usually require surgery to restore elbow joint function [10,11]. While these fractures involve disruption of the articular surface, the degree of soft tissue injury, particularly to the anterior capsule, is presumed to be less severe compared to elbow dislocation. Early range of motion (ROM) exercises after stable internal fixation are regarded as the standard treatment for distal humeral coronal shear fractures to limit stiffness [12]. However, achieving stable fixation of fragmented capitellar and trochlear fractures with posterior comminution is challenging. Thus, adjuvant external immobilization might be needed to attain adequate bone union. Most studies have reported that patients regain functional ROM after coronal shear fractures regardless of the immobilization period [13-16]. This suggests that factors beyond immobilization duration, such as the specific pattern of anterior capsular injury, may play a significant role in determining the risk of flexion contracture.
There are currently no reported outcome results or data on the percentage of patients requiring arthrolysis after long-term immobilization following coronal shear fracture surgery. Hence, developing appropriate treatment guidelines for patients with long-term immobilization for coronal shear fracture is difficult. Long-term immobilization is a potential factor contributing to the development of stiffness after treatment of elbow dislocation [17]. Mehlhoff et al. [9]. reported the impact of immobilization on the development of flexion contracture, comparing the impact of immobilization between less than 14 days and more than 24 days. Flexion contracture development was six-fold higher in the more than 24 days immobilization group (5.1° vs. 30.1°). Recent studies have emphasized that early mobilization is essential in treating elbow dislocation, less than 1 week of immobilization recommended as an appropriate treatment [12,18]. However, the optimal immobilization strategy for DHCS fractures, considering the potential differences in soft tissue injury patterns, remains unclear.
This study aims to address those critical knowledge gaps by evaluating the impact of immobilization duration on clinical outcomes and the development of stiffness in patients with DHCS fractures, comparing early mobilization and long-term immobilization groups. Secondly, we sought to determine the role of elbow anterior capsular injury pattern on the development of flexion contracture by comparing magnetic resonance imaging (MRI) findings between DHCS fracture and elbow dislocation groups.
METHODS
We conducted this study in compliance with the principles of the Declaration of Helsinki. This study was approved by Pohang SM Christianity Hospital Institutional Review Board (No. PSMCHIRB-2023-003). Written informed consent was obtained from the patients.
Coronal Shear Fracture of the Distal Humerus (Group A)
Twenty-eight elbows of 28 patients with DHCS fracture who presented to a single trauma center from January 2007 to December 2017 were enrolled. Inclusion criteria were patients diagnosed with a DHCS fracture who were treated with ORIF and had a minimum follow-up period of 1 year. Patients were excluded if they had a follow-up period of less than 1 year or were aged 70 years or older. One patient was lost to follow-up and six patients older than 70 years were excluded. Therefore, 21 patients (21 elbows) were enrolled in this study. We included all consecutive patients who met the inclusion criteria during the study period to mitigate selection bias. The average age of patients was 53 years (range, 19–70 years). There were two males and 19 females. There were eight right-sided and 13 left-sided injuries. The mean follow-up period was 73 months (range, 22–152 months). Mechanisms of injury were a fall from standing height in 20 elbows and one road traffic collision. All patients underwent surgery within 1 week after trauma.
Initial plain radiographs, preoperative CT with three-dimensional (3D) reconstruction, and MRI were performed for all elbows. Fractures underwent Dubberley classification based on computed tomography (CT) scans with 3D reconstruction [13]. All MRI images were obtained with 1.5-T scanners (Signa HDx, GE Healthcare; Intera, Philips) within 5 days post-injury. T1- and T2-weighted and T2 fat suppression images were obtained on the sagittal plane, coronal plane, and axial plane concerning the axis of the humerus while it was flexed around 30°–60°. Injury patterns of the anterior elbow joint capsule on the preoperative MRI sagittal scans were classified into proximal stripping, middle displaced, and distal avulsion tears (Fig. 1). All patients were treated with open reduction and internal fixation within a week after the injury. The surgical approach was determined after detailed analysis of the preoperative CT scan.
Surgical Technique
General or regional anesthesia was performed according to patient condition. The approach was determined after analysis of preoperative CT. The extended lateral approach was used in nine elbows [19]. The transolecranon approach was used in 12 elbows where definitive trochlea involvement or severe posterior comminution was seen on the CT scan.
In the elbow of the extended lateral approach, the patient was placed in the supine position on the operating table. An incision was made centered on the lateral epicondyle extending from the anterior aspect of the lateral column of the distal end of the humerus that exposed the supracondylar ridge. We released the origin of the brachioradialis (BR) and extensor carpi radialis longus (ECRL), elevated the muscles, and approached the anterior aspect of the capitellum after incision in the lateral joint capsule. The distal incision was extended using the Kaplan approach between the extensor digitorum communis and extensor carpi radialis brevis (ECRB) as needed. The BR, ECRL, and ECRB were separated from the lateral supracondylar ridges and epicondyle, allowing sufficient space in the anterior capitellum. Care was taken to avoid injury to the lateral ulnar collateral ligament when extending the incision to the distal portion. Additional exposures of the posterior capitellum were necessary if screw fixation was needed in the posterior to anterior direction, an extension of the fracture to the posterior capitellum or a comminuted fracture. To reduce the articular surface, we pulled the lateral side of the triceps tendon to expose the posterior aspect of the capitellum and incised the joint capsule of the postero-lateral side to approach the articular surface. The displaced fragment was reduced, and a K-wire was inserted to fix it temporarily. We used two 4.5-mm cannulated screws and washers and inserted them from the posterior to the anterior. For anterior-to-posterior fixation, two or more headless screws were inserted and fixed. A locking plate was used to fix the posterior comminution. Small fragments that did not affect joint stability were removed. Finally, flexor-extension movement of the elbow and forearm rotation was confirmed to be smooth, and the released tendon was closed.
Olecranon osteotomy was performed in the lateral decubitus position for the posterior approach. The skin was incised to a length of about 15 cm at the posterior of the elbow. In soft tissue dissection, the skin flap was separated from the triceps fascia and olecranon periosteum to prevent circulation disturbance. First, the ulnar nerve was found on the medial triceps side and was separated to protect it. Next, olecranon osteotomy was made as a V shape (chevron) with a distal apex so that it could be easily fixed later. If the osteotomized olecranon was fixed with a cannulated screw, we created a drill hole for the screw before osteotomy. Next, we carried out the osteotomy using a saw blade after finding the position and direction of the osteotomy line so that it could pass through the part of the trochlear notch with no articular cartilage. We completed the osteotomy by using the osteotome to stop the saw just before the joint surface. The osteotomized olecranon was pulled with a towel clip, and the triceps muscle was pulled to the proximal side after dissecting to both sides to expose the posterior aspect of the humerus. At the lateral decubitus position, anterior parts of the capitellum and trochlear fractures were identified by separating the BR and ECRL from the lateral supracondylar ridge, lifting the humerus and incising the lateral joint capsule. At this time, maintaining maximum flexion of the elbow could be used to increase exposure. Fractures were fixed in six elbows using only pins or screws and in six elbows using the plate and other fixation methods.
In two elbows, small fragments were fixed using polydioxanone, an absorbable suture with autogenous bone graft, due to severely comminuted fragments that made it impossible to use only standard osteosynthesis (Fig. 2). Postoperative elbow immobilization period was determined by intra-operative assessment of the fracture fixation stability. Early active assistive motion exercises were permitted after less than 3 weeks of immobilization for elbows without fracture fragment mobility on intraoperative assessment. ROM exercises were delayed whilst maintaining long-arm plaster immobilization for more than 3 weeks in elbows with fracture fragment mobility or gaps/displacement under fluoroscopy. After adequate immobilization, progressive active self-assisted joint exercise was undertaken until fracture union was confirmed. Return to work and sporting activities, including physical labor, were allowed if functional ROM was restored and bone union was achieved between 3 and 6 months after surgery.
Postoperatively, 11 elbows (group A1) were permitted early ROM exercise at an average of 11 days (range, 5–14 days). The mean age of group A1 was 49 years (range, 19–70 years). There were 9 female patients in group A1. The mean duration of follow-up was 81 months (range, 25–152 months). A long-arm plaster of Paris cast was used to immobilize the other 10 elbows (group A2) for more than 3 weeks (mean, 26 days; range, 23–29 days) due to insufficient intra-operative fracture fixation stability. All patients in group A2 were female. Their mean age was 58 years (range, 44-69 years). The mean duration of follow-up was 65 months (range, 22–145 months) (Table 1).
Radiographic evaluation with standard orthogonal AP and lateral elbow radiographs was performed postoperatively at 2 weeks, 6 weeks, 12 weeks, 6 months, 1 year, and annually thereafter. Clinical evaluation comprised elbow ROM measurement using a hand-held goniometer with a standardized technique to record flexion contracture, further flexion, and an extension-flexion arc of the elbow joint. To ensure objective evaluation, standardized medical photographs demonstrating full flexion and full extension of the elbow were archived in our institutional database. Patient reported outcomes were evaluated using Mayo Elbow Performance Score (MEPS) and Disabilities of the Arm, Shoulder and Hand (DASH) scores [20]. Clinical and patient-reported outcomes were measured at the last follow-up if revision surgery was not performed. If revision surgery was performed, these outcomes were measured immediately prior to surgery.
Simple Posterolateral Elbow Dislocation (Group B)
We collected data for 30 elbows of 30 patients with posterolateral elbow dislocation who presented to a single trauma center in 2020. MRI was obtained for all elbows in the same manner as group A. Injury sites of the anterior capsule of the elbow joint on post-injury MRI scans were classified as proximal stripping, middle displaced and distal avulsion tears (Fig. 1).
MRI Scan Interpretation
A musculoskeletal radiology-trained radiologist (GCP) and an orthopedic surgeon (KBA) were involved in interpreting the MRI scans for both groups A and B. Regarding inter-observer variability in the observed injury site of the anterior capsule of the elbow joint [21], a final diagnosis was made through a consensus meeting with co-authors. All images were analyzed using the PACS system (Pi-view, INFINITT).
Statistical Analysis
All statistical analyses were performed with Python Version 3.9.0 (Python Software Foundation). Interobserver reliability was determined with Cohen's kappa coefficient. The Mann-Whitney U-test was used to compare postoperative flexion contracture, further flexion, and arc of flexion and extension between group A1 and group A2. Pearson's chi-square and Fisher's exact tests were performed to compare subgroups (group A1, A2) by fracture type and approach. Pearson's chi-square test was also carried out to compare differences in injury site of the anterior capsule of the elbow joint between group A and group B.
RESULTS
This study initially included 28 patients with DHCS fractures. Seven patients were excluded due to age or loss to follow-up, resulting in a final sample size of 21 patients (21 elbows). All DHCS fractures achieved bone union within 1-year post-injury in this study. There was a statistically significant difference in Dubberley fracture types between subgroups A1 and A2 (P=0.015). However, there was no statistically significant association between the subgroups (A1 vs. A2) and the Dubberley subtypes (A vs. B), despite a trend suggested by the odds ratio (OR, 6.750; 95% CI, 0.925–49.232; P=0.08). Mean flexion contracture was 2.3° (range, 0°–10°) in group A1, and 8.0° (range, 0°–35°) in group A2. There was no significant difference (P=0.139) between the two subgroups. Mean further flexion and extension-flexion arc were 135.0° (range, 100°–150°) and 133.0° (range, 100°–150°) in group A1 and, 132.7° (range, 100°–145°) and 124.0° (range, 65°–145°) in group A2, respectively. These two subgroups showed no statistically significant differences in further flexion (P=0.770) or flexion-extension arc (P=0.395). Functional outcomes of MEPS and DASH scores were 86 (range, 45–100) and 19.1 (range, 0–59.0) for group A1, and 88 (range, 50-100) and 14.2 (range, 0–61.6) for group A2, respectively. There were also no significant differences in MEPS (P=0.758) or DASH (P=0.101) between the two subgroups (Table 2). Regarding approach, the transolecranon approach was more commonly performed in group A2 (odds ratio, 15.750; 95% CI, 1.424–174.246; P=0.024). There were no significant differences in ROM or clinical outcomes between approach methods (Table 3).
There was strong reliability among the three observers (kappa=0.86) when interpreting the anterior capsular lesion on MRI. The injury pattern of the anterior capsule of group A were proximal stripping tear in 21/21(100%) elbows. In group B, middle displaced tear occurred in 11/30 (37%) elbows and distal avulsion tear in 19/30 (63%) elbows. There was a statistically significant difference between the two groups (P<0.001) (Table 4).
Regarding complications, one elbow in group A2 underwent arthrolysis 1 year after bone union. Data for this elbow was collected before arthrolysis. Avascular necrosis or collapse of the capitellum was observed in seven (39%) elbows. However, these radiographic findings, such as avascular necrosis or capitellar collapse, were observed in some patients but did not negatively influence clinical outcomes.
DISCUSSION
This study primarily aimed to investigate the impact of immobilization duration and anterior capsular injury pattern on flexion contracture in DHCS fractures. Our findings demonstrated that prolonged immobilization of more than 3 weeks did not significantly influence the development of flexion contracture in DHCS fractures, suggesting that factors beyond immobilization duration may play a more critical role. Additionally, we found distinct anterior capsule injury patterns between DHCS fractures and posterolateral elbow dislocations, which may explain the different degrees of flexion contracture in these injuries.
Long-term immobilization is one of the most common causes of elbow stiffness after trauma [2,22-24]. Most reports emphasize that stable internal fixation and early joint motion are mandatory to prevent elbow stiffness after elbow trauma [25,26]. It is often difficult to allow early ROM exercises in coronal shear fractures of the distal humerus with posterior comminution (Dubberley type B), because solid internal fixation is challenging due to osteoporosis or comminution [14,27]. Achieving bone union often requires long-term immobilization [28]. However, there is no evidence of stiffness after long-term immobilization in this type of fracture.
Cutbush et al. [28] reported an elbow series with nonoperative treatment for type 1 capitellar fracture. Eight patients were treated with closed reduction and more than 4 weeks of immobilization. Results were favorable, with mean differences in extension and flexion to the contralateral side of 7.8° and 3.6°, respectively. Although there was no evidence that long-term immobilization inevitably led to the development of stiffness, after long-term immobilization, they insisted that more than 4 weeks of immobilization was an effective treatment for type 1 coronal shear fracture based on their empiric clinical results. A systematic review of the outcomes after fixation of coronal shear fracture showed that stiffness was not a main complication [29]. Furthermore, most articles in the systematic review reported that the total arc of motion did not hinder daily activity regardless of the immobilization period [29]. Therefore, several reports have been unable to provide insight into outcomes after long-term immobilization due to the difficulty of rigid fixation of fracture fragments.
The present study attempted to analyze whether long-term immobilization treatment resulted in undesirable functional outcomes or ROM by including 10 elbows in which immobilization was intentionally performed for more than 3 weeks due to difficulty achieving stable internal fixation intra-operatively. In this series, the flexion contracture was 2° (range, 0°–10°) in the early mobilization group and 8° (range, 0°–35°) in the long-term immobilization group at final follow-up, with no statistically significant differences (P=0.151); MEPS and DASH were not significantly different either (P=0.758, and P=0.101, respectively). Although the early mobilization group showed no stiffness in any elbows, and the long-term immobilization group had one elbow with more than 30° of flexion contracture (10%), there was no statistically significant difference between the two groups. Furthermore, the elbow with more than 30° flexion contracture had arthrolysis 1 year after union and had remnant flexion contracture post-arthrolysis of 20° at the last follow-up. Therefore, this study demonstrated that more than 4 weeks of long-term immobilization caused less posttraumatic stiffness than expected. This insight could be useful clinically when stable fixation of the fracture fragment is challenging in DHCS fracture, emphasizing that long-term immobilization is another option for adjuvant treatment.
Contracture in the posterior band of the medial collateral ligament is an established cause of flexion limitation and fibrosis in the anterior capsule is the leading cause of flexion contracture. Immobilization over 4 weeks following simple elbow dislocation is a primary factor in the development of flexion contracture [9]. A recent randomized controlled study demonstrated that immobilizing the elbow in a plaster cast for 3 weeks can lead to worse outcomes regarding flexion contracture compared to initiating mobilization 3 days after reduction [30,31]. These findings indicate the importance of early mobilization in cases of simple elbow dislocation. However, long-term immobilization after DHCS fracture did not demonstrate a severe problem in the present study compared to flexion contracture after simple elbow dislocation. While MRI of simple elbow dislocation indicated distal avulsion and middle displaced tears in the anterior capsule, DHCS fracture manifested proximal stripping tears in all elbows (Fig. 1). This suggests two hypotheses for differences in flexion contracture. Firstly, the injury site in the anterior capsule is relevant to the development of flexion contracture. Hildebrand et al. [7] and Germscheid and Hildebrand [32] reported regional variation in myofibroblast number. In the contracted elbow, the number of myofibroblasts in the anterior capsule was seven-fold higher than that in the posterior capsule. Thus, there might be a difference in the number of myofibroblasts between proximal and distal ends of the anterior capsule. Secondly, the injury pattern of the DHCS fracture was more quiescent than simple elbow dislocation because most of such fractures result from low-energy injuries [11]. Compared to middle displaced or distal avulsion tears observed in simple elbow dislocations, the proximal stripping tears in elbows with DHCS fracture did not show a significant gap between the anterior surface of the humerus and the anterior capsule. Therefore, we hypothesize that a more severe pattern of anterior capsular injury results in more severe flexion contracture. While further research is needed, we cautiously conjecture that if the tear pattern of the anterior capsule can be identified via MRI, it may be possible to predict the likelihood and severity of flexion contracture. Furthermore, immobilization may be more appropriately viewed as a secondary cause that exacerbates issues stemming from soft tissue problems, such as anterior capsular rupture, rather than being the primary cause of flexion contracture.
This study has some limitations. Firstly, there are inherent drawbacks to a retrospective study with such a small number of DHCS fractures presenting during the study period. However, we added a comparative study model to identify the cause of flexion contracture with regard to anterior capsular tear to overcome this limitation. Second, selection bias could be another limitation of this study. Results demonstrated that more severe elbow fractures were included in group A2, indicating that we prioritized immobilizing these injuries in a clinical situation. However, results showed no significant differences regardless of the immobilization period. Third, we used two distinct approaches without regard to fracture configuration. Approach can influence flexion contracture of the elbow joint. If performing a transolecranon approach, posterior capsular structures will be iatrogenically damaged. Release of the posterior capsule also affects flexion contracture. However, results showed no significant differences between the two approaches in terms of the development of flexion contracture. Lastly, prospective studies with larger sample sizes are warranted to investigate the relationship between anterior capsular injury pattern and flexion contracture development in other types of fractures.
CONCLUSIONS
This study demonstrated that longer immobilization (>3 weeks) did not significantly affect the development of flexion contracture after DHCS fracture. The pattern of anterior capsule injury differed between DHCS fracture and posterolateral elbow dislocation. This suggests that anterior capsule injury pattern may be a more important factor than immobilization duration in the development of flexion contracture after DHCS fracture or elbow dislocation. Therefore, immobilization could be an appropriate adjuvant treatment for DHCS fractures where stable fixation is difficult to achieve.
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