Complete elbow ankylosis secondary to heterotopic ossification: operative management leads to fair to excellent long-term outcomes

Abstract

Background

Heterotopic ossification in the elbow, often caused by trauma or neurogenic factors, can lead to limited range of motion and physical impairment, while severe cases may result in debilitating loss of function. Complete bony ankylosis of the elbow, though rare, presents challenges in treatment due to complex anatomy and high recurrence rates, with limited literature on management and outcomes. This study retrospectively investigates cases of elbow ankylosis secondary to heterotopic ossification, assessing long-term functional outcomes following operative intervention and standardized rehabilitation.

Methods

A retrospective case series was performed on patients who underwent surgical excision of heterotopic ossification of the elbow at our institution. Outcomes of interest were intraoperative flexion-extension arc, flexion-extension arc at the final long-term postoperative follow-up, visual analog scale pain scores at long-term follow-up, and Mayo Elbow Performance scores at long-term follow-up. The Wilcoxon signed-rank test was performed to identify a statistically significant difference between arc of motion achieved intraoperatively and the arc of motion maintained at the final long-term postoperative follow-up.

Results

Between September 1999 and July 2021, 107 patients underwent operative resection for heterotopic ossification around the elbow, with 13 patients (16 elbows) exhibiting complete ankylosis at time of surgery. Patients were followed up for a minimum of 2 years. Long-term outcomes demonstrated an average visual analog scale pain score of 1.4 +/− 1.7, and an average Mayo Elbow Performance score of 85.9 +/−12.8, with 75% of cases maintaining at least 100 degrees of flexion-extension arc at the final long-term postoperative follow-up. On average, the flexion-extension arc of motion at the final follow-up was preserved at 95% of intraoperative levels. Patients did have an average residual flexion contracture of 18 +/− 9 degrees at the final follow-up.

Conclusion

Surgical excision for complete elbow ankylosis secondary to heterotopic ossification presents challenges due to potential complications. Our study shows favorable long-term outcomes in pain scores, range of motion, and Mayo Elbow Performance scores. Despite reported complications in the literature, our series exhibited no adverse events, supporting operative excision as a standard treatment with overall fair to excellent outcomes. Further research, particularly involving multicenter, randomized, prospective studies, is warranted to refine protocols and understand predictors for improved outcomes in this patient population.

Heterotopic ossification (HO) of the elbow results from the formation of extraskeletal mature lamellar bone as a sequela of direct elbow trauma, thermal injuries, or systemic neurogenic factors.^1,10,12,20 The pathophysiology of HO development remains poorly understood; however, it is believed to be related to local inflammatory changes or systemic increases in bone morphogenic proteins expression, particularly in patients with neurologic injury.¹⁴ In most cases, the natural history of elbow HO is self-limiting, with many patients experiencing minimal to no loss of elbow range of motion or physical impairment.²⁴ Contrarily, cases of extensive HO development may lead to severe contractures and deformity which may impede a patient’s ability to perform activities of daily living, particularly in those with dominant arm involvement.^3,20

Rarely, complete bony ankylosis of the elbow can develop, resulting in debilitating loss of function due to loss of free placement of the hand in space and resultant neuropathies from bony encasement.^8,16,19,23 This translates to increased dependence on wrist, shoulder, and spine movement in an attempt to compensate for loss of elbow motion.¹⁶ The treatment of complete bony ankylosis, however, poses a challenge for the treating surgeon due to the complex pathoanatomy and reported high rates of recurrence and complications.^7,13,20 Additionally, given its rarity, there is a relative paucity of available literature on the management of complete ankylosis with a lack of high level of evidence and long-term outcomes.^{2,4,5,19,20,22,23}

This retrospective study aims to report on cases of complete ankylosis of the elbow secondary to heterotopic ossification and evaluate long-term functional outcomes of operative management and a standardized postoperative rehabilitation regimen.

Materials and methods

After receiving approval from our institutional review board, we conducted a retrospective review of case 107 patients who underwent surgical excision of ectopic bone around the elbow. Data were gathered from medical records and imaging. All procedures took place in an inpatient setting at an academic level I trauma center between September 1999 and July 2021 and were performed by fellowship-trained shoulder and elbow surgeons. Indications for surgical excision of heterotopic ossification included painful or restricted active and/or passive elbow motion causing functional debilitation after complete history, physical examination, and radiographic assessment. Patients under 18 years of age, cases of HO lacking complete ankylosis of the elbow preoperatively, and cases with incomplete follow-up outcomes data were excluded from the analysis. After exclusions, 16 elbows (13 patients) with complete ankylosis of the elbow secondary to severe heterotopic ossification and minimum 2-year follow-up remained.

Orthogonal views of plain elbow radiographs were taken for preoperative diagnosis and assessment of HO maturation. Mature intramuscular HO is characterized by a well-demarcated radio-dense mass with a zonal ossification process.¹⁴ Advanced stages of HO can become large enough to encase a joint and result in ankylosis (see Fig. 1). Additionally, computed tomography scans were utilized for preoperative planning, assessing ectopic bone morphology, identifying involvement of surrounding neurovascular structures, and pinpointing ossifications directly causing joint ankylosis (see Fig. 2).

Figure 1.

Lateral (A) and anteroposterior (B) radiographs of the left elbow of one patient in this series demonstrating evidence of complete ankylosis secondary to severe heterotopic ossification of the elbow.

Figure 2.

Sagittal (A), Coronal (B), and 3-dimensional reconstruction (C) of a computed tomography scan of the right elbow of one patient in this series demonstrating evidence of complete ankylosis secondary to severe heterotopic ossification of the elbow.

Patient demographics – including age, gender, type of predisposing injury, history of tobacco use, and medical comorbidities – were obtained and included in the analysis (see Table I). Preoperative elbow position measurements of ankylosed elbows were taken using a goniometer. Measurements of maximum flexion-extension arc of motion achieved intraoperatively were measured using a sterile goniometer during the procedure. Preoperative and postoperative ulnar nerve symptoms in those who underwent ulnar nerve transposition at the time of surgical excision were recorded (see Table II).

Table I.

Demographics, comorbid risk factors, and perioperative logistics.

Pt #	Age	Sex	TOB	DM	HTN	Type of injury	IVL (d)	ISL (d)
1	45	M	Yes	Yes	Yes	Burn	208	650
2	33	F	No	No	No	Burn	392	638
3	33	F	No	No	No	Burn	392	881
4	41	F	Yes	No	No	Trauma	290	522
5	31	M	No	No	No	Trauma	118	406
6	31	M	No	No	No	Trauma	118	273
7	71	M	No	Yes	Yes	Burn	335	943
8	59	M	Yes	No	No	Burn	258	439
9	59	M	No	No	No	Burn	163	274
10	40	M	No	Yes	No	Burn	470	622
11	50	M	Yes	Yes	Yes	Trauma	47	65
12	33	M	Yes	No	No	Trauma	121	136
13	27	M	No	No	No	Trauma	79	308
14	44	F	No	Yes	No	Trauma	125	217
15	71	M	Yes	No	Yes	Trauma	178	306
16	40	F	Yes	Yes	Yes	Trauma	185	410

Pt, patient; TOB, tobacco; DM, diabetes mellitus; HTN, hypertension; IVL (d), injury to visit latency (days); ISL (d), injury to surgery latency (days).

Table II.

Assessment of ulnar neuropathy and intraoperative ulnar nerve transposition.

Pt #	Preoperative neuropathy	EMG	Ulnar nerve transposition	Postoperative subjective at most recent follow-up
1	No	Yes	Yes	Has good days and bad days, reports new pain posteriorly
2	Yes	No	Yes	Some improvement
3	No	No	Decompression	Getting better, anterior tightness
4	No	No	Yes	Concerned that the position of her arm is changing, was reassured it was just arthritis
5	No	No	Yes	Doing well
6	Yes	No	Yes	Doing well
7	No	Yes	No	Doing well
8	Yes	No	Decompression	Doing well
9	Yes	No	No	Doing well
10	No	No	Yes	Doing well, minimal pain, significantly increased usage of joint after removal of infected suture
11	Yes	Yes	Neurolysis	Feels good, slight drainage/erythema
12	Yes	No	Yes	7/10 pain, plateau
13	No	No	Decompression	Doing well
14	No	No	Yes	Doing well
15	Yes	Yes	Yes	Doing well
16	No	No	No	N/A

EMG, electromyography.

Surgery

Due to the elective nature of the surgical intervention, timing of the procedure was determined through shared decision-making with the patient based on patient availability and convenience. All surgical procedures were performed under general anesthesia, with the inclusion of an indwelling catheter for both intraoperative and postoperative pain management.²⁰ Decisions regarding the operative approach for each case took into consideration factors such as prior operative incisions, scars from previous burns, the condition of the skin, and the morphology of elbow HO. While a detailed discussion of the specific resection techniques for individual patients is beyond the scope of this report, the surgical incisions employed for each case are outlined in Table III. Details regarding the anatomic location of heterotopic bone in each case are referenced in Table III.

Table III.

Injury date, mechanism, predisposing factors, surgical approach, and anatomic location of heterotopic ossification.

Pt #	Age	Sex	Injury date	Injury pattern	Involved extremity	Predisposing factors	Surgical approach	Anatomic location	Location detail
1	45	M	9/5/2002	60% TBSA flame burn	L	Burn	Medial	Medial and posteromedial	Extending from posteromedial aspect of medial epicondyle of humerus; posteromedial margin of olecranon
2	33	F	12/18/2003	Third degree burns to 80%	R	Burn	Extended posteromedial	Posteromedial	Posteromedial joint line
3	33	F	12/18/2003	Third degree burns to 80%	L	Burn	Medial	Medial and posteromedial	Bridging olecranon and posteromedial humeral metaphysis/epicondyle
4	41	F	3/6/2004	Olecranon fx	L	Trauma	Posterior (prev.)	Posteromedial	Lateral aspect of distal humerus; medial bar; ossification of medial collateral ligament
5	31	M	2/1/2006	Multiple facial fx, Left femur fx, bilateral elbow fx	L	Trauma	Posterior	Posteromedial	Fracture site of ulna and posterior distal humerus superior to olecranon; tip of olecranon
6	31	M	2/1/2006	Multiple facial fx, Left femur fx, bilateral elbow fx	L	Trauma	Posterior	Posteromedial	Medial distal humerus and medial elbow joint
7	71	M	1/6/2006	Circumferential burns	L	Burn	Medial and lateral	Medial and lateral	Bridging bars in posterior joint line, lateral > medial; synostosis between proximal radius and ulna
8	59	M	6/1/2010	80% TBSA burn	R	Burn	Posterior	Medial and lateral	Medial and posterior aspect of distal humerus extending into medial joint margin; medial aspect of coronoid
9	59	M	6/1/2010	80% TBSA burn	L	Burn	Medial	Medial	Medial epicondyle; dorsally from olecranon; anteromedial joint line
10	40	M	08/09/2012	75% TBSA burn	L	Burn	Posterior	Posteromedial	Bridging bone from the medial distal humerus to ulna
11	50	M	9/16/2017	Right proximal humerus fx, left open elbow fx, left ankle fx	L	Trauma	Posterolateral	Posteromedial and anterior	Posterior and anterior aspects of elbow joint
12	33	M	3/12/21	Closed Head Injury and R open intra-articular distal humerus fx	R	Trauma	Posterior	Posteromedial and anteromedial	-
13	26	M	09/12/16	Left femur fx, left radius and ulna fx	L	Trauma	Posteromedial + Lateral	Posteromedial	Posteromedial joint line
14	44	F	7/31/2019	Right Elbow Fracture Dislocation	R	Trauma	Medial and Lateral	Medial and Lateral	HO in anterior and posterior compartments
15	71	M	11/1/2013	Olecranon fx, Medial Ligament Complex Injury	R	Trauma	Posterior	Medial	HO of medial ligamentous complex
16	40	F	6/20/2015	Coronoid Fracture	L	Trauma	Posterolateral	Anterior	Large anterior column of bone blocking motion

HO, heterotopic ossification; TBSA, total body surface area.

Generally, surgical resections were planned based on the anatomic location and morphology of ectopic bone, with the goal of maximizing heterotopic bone removal while safeguarding vital neurovascular structures. In instances where the ulnar nerve was completely encased by bone, a standardized approach to ulnar nerve release was undertaken, utilizing previously published techniques.^21,23

Postoperative management and prevention

On the second postoperative day, bulky dressings and drains were removed. Subsequently, continuous passive motion (CPM) machines were initiated for 12 hours per day following drain removal. Indwelling interscalene anesthesia catheters were utilized in the immediate postoperative period for pain management. Catheters were discontinued 24 hours prior to discharge to ensure patients could tolerate oral pain regimen and passive range of motion upon discharge. Once discharged, patients were provided with a home CPM device and instructed to adhere to the regimen for two weeks postoperatively. A representative of the CPM machine manufacturer accompanied all patients at discharge to ensure proper delivery, functionality of the machines, and understanding of their usage by both the patient and their family.^21,23

Two weeks postoperatively, patients visited the outpatient clinic for wound check, suture removal, and range of motion assessment. To enhance reliability and reproducibility, the senior author conducted all range-of-motion measurements using a goniometer. Following assessment, therapists initiated guided range-of-motion exercises, including active, active-assisted, and passive movements, 5 times per week. CPM usage was subsequently reduced to 6 hours daily. After 6 weeks, CPM machines were discontinued and physical therapy was decreased to 3 sessions per week. By postoperative week 12, patients transitioned from formal physical therapy to a home therapy regimen comprising simple exercises aimed at maintaining and enhancing range of motion.

To prevent recurrence of heterotopic ossification, all patients were prescribed 75 mg of indomethacin orally once daily for 28 days. Weekly follow-up calls were conducted by a clinical nurse or resident physician from the research team during the initial 4 weeks to ensure compliance with physical therapy, HO prophylaxis, and the CPM regimen.^21,23

Long-term follow-up and statistical analysis

The primary endpoint of interest was flexion-extension arc of motion at the final follow-up. The secondary endpoints were the visual analog scale (VAS) pain scores and Mayo Elbow Performance Score (MEPS), a composite functional outcome score that incorporates flexion-extension arc of motion, assessment of gross elbow instability, and patient-reported ability to complete activities of daily living. Long term follow-up consisted of yearly outpatient encounters, which included serial focused history and musculoskeletal examinations. Additionally, MEPS and VAS pain scores were recorded, and elbow range-of-motion assessments were performed using a goniometer (see Table IV). A nonparametric test for 2 dependent samples, namely the Wilcoxon signed-rank test, was performed to assess if there was a statistically significant difference between flexion-extension arc of motion achieved intraoperatively, and the flexion-extension arc of motion maintained at long-term follow-up.

Table IV.

Range of motion, Mayo elbow performance score, and visual analog scale at long-term follow-up.

Preoperative					Surgical approach	Intraoperative			Range of motion at final follow-up			MEPS at final f/u	VAS at final f/u	F/u (y)	Change from preoperative to final F/u
Case #	SI	Ext	Flex	Arc		Ext	Flex	Arc	Ext	Flex	Arc				Ext	Flex	Arc
1	L	70	70	0	Medial	15	95	80	20	80	60	70	1	4	50	10	60
2	R	40	40	0	Extended posteromedial	10	125	115	10	125	115	70	3	18.5	30	85	115
3	L	100	100	0	Posterior	10	140	130	20	130	110	100	0	18	80	30	110
4	L	90	90	0	Posterior	30	135	105	30	135	105	85	2	3	60	45	105
5	R	50	50	0	Posterior	10	130	120	20	120	100	85	3	16.5	30	70	100
6	L	60	60	0	Posterior	20	110	90	20	120	100	85	3	17	40	60	100
7	L	20	20	0	Medial + Lateral	10	80	70	30	120	90	95	0	2	−10	100	90
8	L	120	120	0	Medial	0	120	120	0	140	140	100	0	12.5	120	20	140
9	R	50	50	0	Posterior	10	140	130	5	140	135	90	0	11.5	45	90	135
10	L	90	90	0	Posterior	30	125	95	20	105	85	75	4	9.5	70	15	85
11	L	90	90	0	Posterolateral	0	120	120	10	110	100	60	5	6	80	20	100
12	R	90	90	0	Posterior	−5	135	140	20	125	105	100	0	2	70	35	105
13	L	75	75	0	Posteromedial + Lateral	40	130	90	5	135	130	100	0	6	70	60	130
14	R	80	80	0	Medial + Lateral	0	140	140	25	125	100	100	0	3.5	55	45	100
15	R	70	70	0	Posterior	20	120	100	20	115	95	80	1	2	50	45	95
16	L	90	90	0	Posterolateral	10	130	120	30	140	110	80	1	7	60	50	110
Mean		74	74	0		13	123	110†	18	123	105†	86	1.4	8.7∗	56	49	105

MEPS, Mayo Elbow Performance score; ROM, range of motion; VAS, visual analog scale.

^∗Mean years of follow-up for patients with complete ROM, MEPS, and VAS data.

^†Per Wilcoxon signed-rank test, there was no significant difference between intraoperative arc and arc at final follow-up (P = .31).

Results

From September 1999 to July 2021, 107 patients underwent operative resection of symptomatic or debilitating heterotopic ossification about the elbow. Of these, 13 patients (16 elbows) were identified to have complete ankylosis of the elbow joint secondary to heterotopic ossification and at least two years of minimum postoperative follow-up. Nine men and four women had an average age of 45 years (range 27-71 years) at time of surgery. Of the 16 total cases, 7 cases resulted from sustaining burns and 9 from direct traumatic injury, and none from closed head injuries. Of the 7 burns, all were thermal burns, none were chemical burns, and the average total body surface area involved was 68% (range 18%-80%). Detailed presentation of patient demographic data is illustrated in Table II. The average time from injury to being seen by an orthopedic shoulder & elbow surgeon was 217 days, while the average time from injury to operative management was 443 days (range 65-943 days).

The patients had at least 2 years of follow-up with the average time from surgery to final follow-up being 8.7 years. At long-term follow-up, VAS and MEPS were recorded. The average VAS pain score at long-term follow-up was 1.4 +/− 1.7, and 9 out of 16 patients (56%) had some residual pain (nonzero VAS) at the final long-term postoperative follow-up. The average MEPS at long-term follow-up was 85.9 +/− 12.8, and 7 out of 16 had excellent outcomes (MEPS of 90 or better), 6 out of 16 had good outcomes (MEPS of 75-89), and 3 had fair outcomes (MEPS of 60-74).

Seven out of 16 patients reported preoperative ulnar nerve neuropathy symptoms including pain, decreased sensation, and weakness. Four of those 7 underwent ulnar nerve transposition at the time of HO surgical excision while the other 3 underwent decompression, neurolysis, or had no operative management, respectively. Seventy-five percent of the symptomatic patients who had an ulnar nerve transposition subjectively reported improvement of symptoms at the final follow-up, while 100% of the symptomatic patients who had either decompression, neurolysis, or no operative management subjectively reported symptomatic improvement at the final follow-up.

Patients undergoing operative resection of HO with complete elbow ankylosis at time of surgery reached an average intraoperative flexion-extension arc of 13 to 123 degrees (110 +/− 21 degrees motion arc). Patients went on to maintain an average increase in elbow flexion-extension arc of 18 to 123 degrees (105 +/− 20 degrees motion arc) at long-term follow-up, which equates to 95% of the total elbow flexion-extension arc achieved intraoperatively. At the 5% level of significance, there was no statistically significant difference between patients’ flexion-extension arc of motion achieved intraoperatively and the flexion-extension arc of motion at long-term follow-up (Wilcoxon signed-rank test, Z = −1.0147, P = .3102). Of note, 75% of patients in this series were able to maintain a minimum of 100 degrees of flexion-extension arc of motion at the final long-term postoperative follow-up. However, in our series of patients who had complete ankylosis prior to surgery, patients had an average residual flexion contracture of 18 +/− 9 degrees at the final long-term postoperative follow-up.

Discussion

Elbow HO with complete ankylosis is a rare and difficult challenge for the treating surgeon given the complex pathoanatomy and high rates of reported complications, including intraoperative fracture, postoperative infection, nerve palsies, delayed wound healing, suboptimal improvement in postoperative range of motion, and HO recurrence.^{2,4,5,7,11,13,19,20,22,23} Given the paucity of literature, it is important to understand the long-term outcomes of operative management to guide treatment, better educate our patients, and manage patient expectations. The purpose of this retrospective study was to evaluate range of motion at long-term follow-up and other functional outcomes of operative excision in 16 cases of elbow HO with complete ankylosis prior to surgery.

Morrey et al¹⁵ previously described the functional motion arc of the elbow including a flexion-extension arc and pronosupination of 100 degrees, respectively, with extension/flexion ranging from 30-130 degrees and pronation/supination from 50 to 50 degrees to complete most activities of daily living. Contrarily, more recent kinematic analyses reported increased elbow flexion (on average 148 degrees) and greater pronation (on average 65 degrees) are necessary to complete contemporary tasks including typing on a keyboard or use of a cellular phone.²⁶ Ultimately, the operative goal is to obtain this minimum amount of motion while reducing risk of aberrant complications. In our series, an average flexion-extension arc of 18 to 123 degrees (motion arc of 105 degrees) was found at final follow-up. Of note, 75% of patients in our series were able to maintain a minimum of 100 degrees of flexion-extension arc of motion, the functional motion arc of the elbow as described by Morrey et al,¹⁵ at the final long-term postoperative follow-up. While several elbows remained short of new standards, this was associated with fair to excellent MEPS in all elbows. More importantly, range of motion postoperatively was maintained at the final follow-up from initial range of motion gains obtained in the operating room (Wilcoxon signed-rank test, Z = −1.0147, P = .3102). This is consistent with prior series by Brouwer et al⁴ and Chen et el.,⁵ who reported flexion/extension arc gains of 95 degrees and 113 degrees, respectively, with similar patient reported outcomes.

We had no reported complications in our series by the final long-term postoperative follow-up. Despite this, operative excision for elbow HO is not without inherent risk, with several publications reporting complication rates ranging from 9% to 22.6%.^{2,4,5,11,19,20,22,23} Complications reported include intraoperative fracture, postoperative infection, nerve palsies, delayed wound healing, HO recurrence, and suboptimal improvement in postoperative range of motion.^{2,4,5,11,19,20,22,23} A systematic review by Lee et al¹¹ reported higher rates of complications and poorer outcomes in patients with brain injury. In their series of 32 patients with both ankylosis and partially restricted range of motion, Salazar et al²⁰ found suboptimal outcomes in patients with obesity, hypertension, and absence of ulnar nerve transposition. Improved outcomes, however, have been noted with standardized postoperative protocols including heterotopic ossification prophylaxis, adequate postoperative pain management, and the use of continuous passive motion therapy.^11,20

In our practice, operative excision for bony ankylosis of the elbow in the setting of HO remains standard of care, with overall fair to excellent outcomes reported in literature. Albeit, several other treatment options have been reported with positive outcomes, particularly in patients with advanced arthritis and low labor demand. There are several reports of total elbow arthroplasty in the setting of complete bony ankylosis with overall favorable short term outcomes.^6,9,17 However, high rates of implant failure and reoperation in patients younger than 65 in addition to activity restrictions imposed postoperatively may limit its clinical application for laborers and younger post-traumatic patients.^18,25 Chen et al⁵ additionally reported on positive outcomes in 5 patients with HO elbow ankylosis who underwent concomitant radial head replacement at time of operative excision. However, further studies are necessary to determine its clinical benefit given a limited sample size and lack of appropriate comparative analysis with HO excision alone.

This study is not without limitation due to its retrospective nature. Given the rarity of complete bony ankylosis of the elbow secondary to HO, large prospective cohorts are not feasible in addition to limiting our sample size for analysis. Consequently, we did not believe multivariate analysis for the assessment of postoperative outcomes would provide statistical benefit due to limited power. Additionally, our patient population included a wide range of final follow-up time ranging from 2 years to 18.4 years postoperatively, which may fail to identify further detriments in patient reported outcomes and postoperative range of motion gains in those with shorter follow-up times. Furthermore, due to incomplete follow-up data, we did not evaluate and report on pronosupination in this study nor were we able to formally assess preoperative and postoperative ulnar nerve symptoms with grading systems such as the Dellon classification or McGowan classification. Lastly, at the time of establishing the patient exclusion criteria we did not account for factors that could have affected elbow function and range of motion besides HO such as significant skin and soft tissue contracture in those with burn injuries. Future studies would benefit by incorporating a more comprehensive exclusion criterion. Despite this, we believe that our findings of maintained flexion-extension range of motion arc gains obtained in the operating room by final follow-up paired with good patient reported outcome scores provides clinical insight that benefits of operative excision remain present at long-term follow-up. Further studies may benefit from the involvement of multiple centers with a focus on developing standardized protocols to optimize long-term outcomes, patient satisfaction and reduce overall healthcare costs.

Conclusion

Operative excision of heterotopic ossification in patients with complete bony ankylosis of the elbow demonstrates good elbow function and low pain scores by long-term follow-up with maintenance of range of motion arcs obtained intraoperatively. Future prospective, multicenter studies may provide further insight on risk factors for complete ankylosis of the elbow in the setting of HO and predictors for improved postoperative outcomes in this patient population.

Disclaimers:

Funding: No funding was disclosed by the authors.

Conflicts of interest: The authors, their immediate families, and any research foundation with which they are affiliated have not received any financial payments or other benefits from any commercial entity related to the subject of this article.