Down syndrome (DS) is a condition characterized by triplication of chromosome 21 during the meiosis stage of human embryonic development^1,2). Associated with advanced maternal age³⁾, it occurs in 1.66 per 1,000 births⁴⁾ and is considered the most common survivable chromosomal abnormality in humans⁵⁾. The presence of this extra chromosome is associated with abnormalities affecting the brain, heart, skin, blood, and immune systems⁶⁾. With respect to the musculoskeletal system, DS can be associated with several abnormalities such as atlantoaxial instability, short stature, patellar dislocations, hypermobility, and hip dysplasia⁷⁾.

Hip problems are common and disabling manifestations in those with DS. Occurring in 2%-28% of cases, hip involvement may include hip dysplasia, hip instability, posterior acetabular deficiency, acetabular retroversion, Perthes disease, slipped capital femoral epiphysis, and juvenile rheumatoid arthritis^8,9). The prevalence of most hip problems in DS was found to correlate significantly with walking ability. The outcomes of hip disorders in DS patients are more serious and disabling than similar diagnoses in patients without DS^10-12), and their presence can lead to loss of community ambulation in DS patients after the age of 30 years due to the resulting severe osteoarthritis that may require total hip arthroplasty (THA)⁸⁾.

Several reports have discussed THA in those living with DS. Despite significant improvement in functional outcomes after THA^13-15), various studies report a high incidence of complications including dislocation, infection, periprosthetic fractures, aseptic loosening, and revisions compared to matched controls^16,17). This was attributed to several factors, including the presence of intellectual disabilities, noncompliance with postoperative instructions and rehabilitation protocols, hypotonia, decreased bone density, generalized ligamentous laxity, previous surgery, and the presence of hip deformities^16,17). When it comes to hip hemiarthroplasty (HA) for those with DS in the trauma setting, only three case reports are available^18-20). This study aims to describe the outcomes of hip HA for femoral neck fractures in four individuals (5 hips) with DS and to contribute to the sparse existing literature regarding this procedure in this population.

1. Data Acquisition

A retrospective, Geisinger Institutional Review Board-approved study (No. 2019-0591) was performed to examine the electronic medical records of our health system to identify all patients who had hip HA at Geisinger Medical Center from January 2007 to July 2024. The written informed consent was waived due to the study’s retrospective design. All cases of HA have been independently reviewed and their medical history was examined to extract all the cases of DS among them. This has been confirmed using the procedural codes of surgery and diagnostic International Classification of Diseases (ICD-10).

2. Patients

Out of 2,328 individuals undergoing HA, 4 (0.17%) with DS treated with HA for femoral neck fracture (5 cases) and had complete follow-up records were identified. One of these individuals had bilateral simultaneous HA surgery. Subjects were all males, with a mean age of 49.3 years (range, 26.1-59.7 years) at the time of surgery. The left side was involved in 3 cases. The mean height was 1.54 m (range, 1.44-1.60 m), and the mean weight was 58.8 kg (range, 52.1-73.9 kg). The mean body mass index at the time of surgery was 25.3 kg/m² (range, 22.4-32.5 kg/m²).

One subject (the bilateral case) had chronic epilepsy, one had a known history of chronic patellar dislocation, and another had hypothyroidism, mitral valve replacement, and known osteoporosis. Three subjects were unassisted community ambulators who presented after falls from standing while ambulating and the final subject (the bilateral case) was a limited household ambulator with assistance and presented after having fallen from a chair.

All cases presented to the emergency department accompanied by their relatives or caregivers; three presented with inability to bear weight and hip pain as their presenting symptoms. The chief complaint of one subject was knee pain. In all subjects, there was unclear history about the exact timing of injury. History taking revealed that all the included subjects had been complaining of decreased activity levels over days and up to two weeks before their injury.

3. Preoperative Assessment and Management Plan

Preoperative assessment of all subjects with physical examination and radiographs revealed displaced femoral neck fractures with variable degrees of either acetabular dysplasia and/or acetabular decreased anteversion or retroversion as evidenced by the presence of crossover sign of acetabular walls in the plain radiographs, which also demonstrated the presence of radiological osteopenia and small pelvic measurements (Fig. 1-3). Pelvic computed tomography scans were performed preoperatively in two patients (3 cases) to assess the acetabular version and configuration (Fig. 2, 3)

Figure 1. (A) Plain pelvic radiograph of a 26-year-old male with Down syndrome who presented with a displaced left femoral neck fracture. Note the bilateral acetabular dysplasia and generalized osteopenia. (B, C) Axial computed tomography scan of the knee showing trochlear dysplasia in the same patient. (D) Twelve-month postoperative follow-up plain pelvic X-ray showing cementless bipolar hip hemiarthroplasty.

Figure 2. (A, B) Plain pelvic X-rays of a 57-year-old male with Down syndrome who presented with displaced bilateral femoral neck fractures. Note the bilateral acetabular retroversion, as noticed by the presence of bilateral crossover sign (A, B). (C) Six-week postoperative follow-up plain pelvic X-ray showing bilateral cementless unipolar hip hemiarthroplasty.

Figure 3. (A-C) Pelvic computed tomography (CT) scan cuts showing variable degrees of decreased acetabular version in different subjects with Down syndrome and displaced femoral neck fractures. (A) This patient has approximately 4.7° and 9.2° of anteversion for the right and left sides respectively. (B) This patient has approximately 1.9° and 7.1° of acetabular retroversion for the right and left sides respectively. Note the acetabular retroversion as clearly shown in this three-dimensional reconstruction CT scan (C).

The decision to proceed for HA, rather than THA in all 5 cases was based primarily on the surgeon’s discretion. The subjects’ intellectual disabilities, limited activity levels (even outdoors), unclear history of previous, repetitive falls, and potentially decreased life expectancy in those living with DS were factored into the management decision. Ultimately, based on the previous factors, including the cognitive impairment of subjects, and given the lower incidence of dislocation in HA compared to THA in trauma patients^21-24), the surgeons decided that HA would be a more suitable management approach. The management decision was made after a full discussion of treatment options and risks and benefits between the surgeon, patient, and patient caregivers.

4. Surgical Procedure

Surgeries were performed by four different surgeons. The anterolateral and posterior approaches were utilized in three and two cases, respectively. During surgery, care was taken to restore the native hip anatomical parameters to preserve the hip capsule, and perform suitable hip capsular and muscle repair, which was performed in all cases with trans-osseous sutures or fiber wires. All cases received uncemented, small-size stems (2nd or 3rd available size). Bipolar HA heads were used in three of the cases and unipolar implants were utilized in the bilateral case. Two cases received femoral head size 41 mm, two cases received size 44 mm and one received a 48-mm size femoral head. No particular intraoperative hardships or complications have been recorded and at the final intraoperative testing, all components were found stable along the tested ranges of motion. Intraoperative C-arm was utilized to verify a concentric reduction of the femoral head into the acetabulum, femoral stem sizing, implant rotation, limb length, and restoration of the femoral offset. The mean surgery duration was 54 minutes (range, 53-58 minutes). The mean blood loss was 250 mL (range, 200-400 mL).

Postoperatively, subjects were scheduled for clinical evaluation at 2 weeks, 6 weeks, and biannually thereafter. Assisted weight bearing as tolerated was begun on postoperative day one, supervised by a physical therapist. The mean length of stay at the hospital was 6.4 days (range, 2-11 days). Three subjects were discharged to home, and one was discharged to a nursing facility. Radiographs, operative reports, and clinical follow-up notes were examined, and any intraoperative or postoperative complications were recorded.

The mean follow-up until the last recorded hospital visit was 15.2 months. One subject expired 32 months after surgery for causes unrelated to their surgery. The other three subjects are alive and ambulating without pain according to the last recorded notes. For those who are alive, the mean duration since the surgery is 24.2 months (range, 7.1-30.2 months).

No intraoperative or postoperative complications were recorded. At the time of the last follow-up, all subjects were ambulating without pain; three were ambulating independently with assistive devices and one (the bilateral case, bilateral anterolateral hip approach) had limited bed-to-chair ambulation with assistance, which was essentially like their preinjury activity levels. The mean calculated Parker Mobility Index score²⁵⁾ (a composite measurement of the patient’s mobility indoors, outdoors, and during shopping) for all the cases was 5.2 (range, 3-7). Only one subject (the youngest, 26.1 years) had completed subjective outcome scores at his last clinical visit postoperatively, and the reported pain scale, HOOS JR (Hip Disability and Osteoarthritis Outcome Score for Joint Replacement), EuroQol (a standardized measure for quality of life developed by the EuroQol group in Europe), and PROMIS (Patient Reported Outcomes Measurement Information System) physical health scores were 0, 100, 0.88, and 67.7, respectively, indicating excellent functional results. None of the cases suffered dislocations, infections, or periprosthetic fractures and none have been revised for any cause. No radiological complications (e.g., acetabular erosion, stem loosening, fracture, and heterotopic ossification) were observed up until the final follow-up.

This is a report of four individuals living with DS who had five hip HA for femoral neck fractures. After a mean duration of 24.2 months since the surgery, no subjects developed complications; all had returned to their preinjury functional status without revision.

With an increasing life expectancy in individuals living with DS, THA has been more commonly used in those with trisomy 21 to manage advanced hip degenerative changes²⁶⁾. There have been several reports that discussed the outcomes of THA in DS, with variable conclusions. Skoff and Keggi²⁷⁾ reported on 8 cases of THA in subjects with DS and all of them demonstrated significant clinical improvement without complications after a mean follow-up of 4.3 years. Kosashvili et al.¹⁴⁾ reported on 9 THAs in seven subjects with DS and noted that two required revisions at a mean of 9.9 years postoperatively, due to aseptic loosening and trauma. The authors used constrained liners in 6 hips. Amanatullah et al.¹⁶⁾ reported on 21 THAs in those living with DS. The authors reported four revisions (19.0%) for aseptic loosening at a mean follow-up of 5.8 years. Gross et al.²⁸⁾ looked at 26 THAs in DS subjects and found survival of 85% at a mean of 106-month follow-up when considering aseptic loosening as the endpoint. Hernandez et al.²⁶⁾ have retrospectively compared the outcomes of THA in 128 subjects with DS versus a matched group of 521,532 THA in those without DS and found primary THA in those with DS is associated with increased 90-day revision and periprosthetic fracture at 2 years. In a systematic review, Sha et al.¹⁷⁾ found that the 5-year cumulative revision rate of primary THA in DS was 7.5%, twice as high as age-matched control. They also found that medical and surgical complications were 3 times higher in DS subjects than matched controls. Considering previous studies, THA appears to carry a high risk of complications compared to subjects without DS. This could be attributed to multiple factors, including young age, lack of compliance, history of previous surgery, hyperlaxity, hip deformities, and the associated medical, immune, and endocrine comorbidities. Again, DS subjects are more prone to repeated falls and trauma, joint dislocation, and infection which may prevent surgeons from offering THA¹⁶⁾.

In the setting of hip trauma, there is a lack of evidence regarding the proper management in cases of displaced femoral neck fractures in those living with DS. When it comes to HA in this population, only three case reports exist (Table 1). McGillion and Shetty¹⁸⁾ reported on a case of unilateral displaced femoral neck fracture in a 58-year-old female with DS that was managed with bipolar HA without reported complications. Marsh et al.¹⁹⁾ reported on a case of bilateral femoral neck fracture in a 66-year-old male with DS and epilepsy who was successfully managed with bilateral, cementless unipolar HA, without reporting on the follow-up course or duration. Díaz et al.²⁰⁾ also reported on bilateral simultaneous HA in a 56-year-old male with DS and epilepsy and reported no complications at 4 years. This current report describes similar outcomes in four individuals living with DS. In our report, three cases had an anterolateral approach and two had a posterior approach without any identifiable difference in outcomes. Regardless of the utilized technique, care should be given to the positioning of the femoral components, considering the tendency towards acetabular retroversion and slightly increased femoral anteversion in subjects with DS²⁹⁾.

Table 1 . Literature Review about Hip Hemiarthroplasty (HA) in Individuals Living with Down Syndrome.

Study	No. of patients	Intervention	Outcomes
Mcgillion and Shetty18) (2008)	1 (left hip), 58-year-old female	• Cemented bipolar hemiarthroplasty through the direct lateral approach. • Postoperatively, immediate weight bearing as tolerated was started.	No complications at 6-week follow-up.
Marsh et al.19) (2010)	1 (both hips), 66-year-old male, epilepsy, and dementia The timing of the injury was unknown.	• Bilateral, simultaneous cementless unipolar hemiarthroplasty through the direct lateral approach. • Postoperatively, immediate weight bearing as tolerated was started.	No complications (duration not mentioned).
Díaz et al.20) (2019)	1 (both hips), 56-year-old male, epilepsy, diabetes mellitus, dementia, and bilateral pneumonia The timing of the injury was unknown.	• Bilateral, simultaneous cemented unipolar hemiarthroplasty one week after admission after controlling the medical condition. • During the immediate postoperative period, bilateral plaster boot splints, with legs abducted, were used for three weeks to avoid implant instability due to patient hypermobility. • Rehabilitation started 2 months after surgery.	Regained preinjury activity level, ambulating unassisted. No complications until the patient deceased 4 years later.
Current study	4 patients (5 hips, 1 bilateral); One patient (the bilateral case) had chronic epilepsy, and one other patient had hypothyroidism, mitral valve replacement, and known osteoporosis.	• Three cases received uncemented bipolar and two cases received uncemented unipolar HA. • Postoperatively, assisted weight bearing as tolerated was initiated on postoperative day one, supervised by a physical therapist.	One patient expired 32 months after surgery for causes unrelated to their surgery. The other three patients are alive and ambulating without pain. Postoperatively, all patients regained their pre-injury activity levels.

Surgeons should consider the version of the native femoral neck and acetabulum to find the best implant position that allows for a stable prosthesis. Restoration of femoral offset, choosing the appropriate femoral head size, and proper soft tissue repair should be carefully performed to compensate for the inherently present risk factors for instability in subjects with DS. Intraoperative C-arm utilization can be a useful tool to restore hip biomechanics and ensure proper implant placement. In cases with severe acetabular dysplasia (Fig. 1A and D, right hip) or intraoperatively if the HA components were found to be unstable due to soft tissue laxity, acetabular retroversion or marked dysplasia, it may be reasonable to shift the decision to THA, preferably dual mobility THA given their lower dislocation risk^30-33). The availability of dual mobility THA set may be advantageous in DS subjects who are planned for HA in case the surgeon changes the decision intraoperatively.

Several critical issues, related to surgical preparation and optimization should be addressed in those with DS given the unique associated potential medical and anatomical changes in DS. Despite an increased life expectancy for those with DS—from 35 years in the 80s to about 60 years at present—an increase mostly attributed to the improved care of congenital heart disease and advances in surgical techniques^34-37), a standardized protocol for preoperative evaluation in those with DS patient does not exist, and literature surrounding this topic remains sparse. A recent narrative review by Malinzak et al.³⁶⁾ published in 2021 delves into the common comorbidities associated with pediatric DS and how each progresses with age, along with the preoperative and intraoperative anesthetic management of adults with DS.

DS patients have characteristic facial features, such as midface hypoplasia, micrognathia, macroglossia, and small upper airways, laryngotracheal or subglottic stenosis, among others. These features are known to increase the prevalence of obstructive sleep apnea and upper respiratory tract infections in those with DS as compared to the general population population^34,38). These features also may increase difficulty in obtaining airway management in the operating room³⁴⁾. Again, these anatomic features, along with the presence of hypotonia or brain stem dysfunction in those with DS may lead to multilevel airway collapse or central sleep apnea intraoperatively³⁹⁾. Therefore, it is essential to elicit a detailed and comprehensive airway history, gather intubation records, and arrange for an airway exam to be performed by a member of the interdisciplinary team.

Those with DS have an increased risk of congenital heart disease. Therefore, each person with DS must undergo individualized risk assessment based on known cardiac disease or endocardial cushion defects. For example, Malinzak³⁶⁾ recommends an updated echocardiogram, along with BNP testing, before surgery if one has not been done since childhood screening. Malinzak³⁶⁾ stated that any test abnormality, new murmur, or signs of heart failure or pulmonary hypertension should trigger a referral to a cardiologist for a full evaluation and may require electrocardiogram or Holter monitoring, implantable loop recorders for proper preoperative risk assessment as it relates to cardiac comorbidities³⁵⁾.

Detailed history regarding the chronically administered medications in those with DS should be obtained preoperatively, to avoid interactions with anesthetic drugs. For example, many with DS take centrally-acting acetylcholinesterase inhibitors for the management of early-onset dementia which may interact with neuromuscular blockade and lead to reversal of anesthesia. These medications, as well as other neuromodulating drugs, may need to be stopped before surgery after considering the risk-benefit assessment⁴⁰⁾.

Along with the cognitive impairment, DS is associated with an increased risk of conductive or sensorineural hearing impairment, vision issues, autism, depression, and dementia which may present difficulties when attempting to communicate for informed consent and discuss the operative details preoperatively, and may increase risk of delirium, behavioral problems, and non-adherence to postoperative restrictions after the surgery. Despite this, it is important to note that an adult with DS is considered consentable and able to make medical decisions unless otherwise declared⁴¹⁾. It is essential to address those with DS directly, listen intently to their story and subjective symptoms in conjunction with input from caregivers and family members, and pay particular interest in gaining the confidence and trust of the patient to best accomplish shared decision-making when deciding upon treatment plans. It is also important to coordinate and share the operative details, postoperative protocols for wound care, follow-up visits, and activity modifications along with fully elaborating on the potential complications of the surgery in light of the individual’s physical and cognitive impairments with the family members and caregivers to ensure adherence to the operative precautions and achieve sensible expectations^37,41).

Those with DS are known to have an increased risk of radiographic atlantoaxial instability (up to 14%), while only 1%-2% are symptomatic⁴⁰⁾. Utilization of preoperative routine cervical radiographs for screening in asymptomatic patients with negative neurological examination is controversial^41,42); however, both flexion/extension and standard neutral cervical spine radiographs should be obtained if there are any symptoms or concerns for atlantoaxial instability³⁹⁾. Regardless of preoperative cervical spine radiographic screening, cervical spine positioning precautions, and in-line stabilization should be performed during intubation³⁶⁾. It is important to note; however, that symptoms such as hyperreflexia, clumsiness, clonus, ataxia, and diminished fine motor skills may be influenced or caused by other comorbidities such as Alzheimer’s disease or early-onset dementia, for example³⁶⁾.

Infection risk may also be increased in this population, particularly dental and respiratory-based infections since they have innate impairments to their cellular and humoral immunity. This may put them at higher risk of pneumonia, respiratory failure, and bronchitis as compared to adults without DS³⁸⁾. In fact, pneumonia is the cause of death in up to half of adults with DS, and this risk increases with age³⁶⁾. Postoperatively, special attention to pulmonary hygiene, mobilization, and avoidance of recumbency is critical in this population to mitigate the risks of developing severe and potentially fatal infectious complications of the upper respiratory tract^36,38).

Another important concern in DS trauma patients is the identification of the appropriate clinical history particularly regarding the time of injury. In all the included cases in this study there was adelay in presentations after injury. Notably in our study, one subject had a positive history of epilepsy. Since 55% of older adults with DS suffer from seizures⁴³⁾ and given the high incidence of decreased bone mineral density in this population^18,44), potentially associated musculoskeletal injuries should always be suspected in those with DS presenting with seizures and for noncommunicative patients in pain¹⁸⁾. With consideration of fracture displacement, limited baseline activity level, and cognitive impairment, HA seems to be a viable treatment option for displaced femoral neck fractures⁴⁵⁾ in those with DS and no signs of hip osteoarthritis.

HA could be a good option for the management of displaced femoral neck fractures in those living with DS. More studies reviewing a larger number of cases for longer-term follow-up are required to more comprehensively assess outcomes and drawbacks.

No funding to declare.

No potential conflict of interest relevant to this article was reported.