Background and Clinical Rationale

Hip fractures are among the most consequential orthopedic injuries in older adults, carrying a disproportionately high burden of morbidity and mortality within the first month following surgical repair. Globally, the incidence of hip fractures continues to rise as populations age, with an estimated 1.6 million cases per year worldwide and projections exceeding 6 million annually by 2050. Among patients who undergo surgery for a hip fracture, 30-day mortality rates in most registries range from 5% to 10%, although individual risk can vary dramatically depending on patient-level factors such as age, comorbidity burden, functional status, and pre-injury living arrangement.

The clinical need for a concise, reliable tool that stratifies short-term mortality risk after hip fracture surgery has been recognized for decades. Accurate prognostication allows clinicians to calibrate perioperative care intensity, guide shared decision-making with patients and families, organize multidisciplinary orthogeriatric co-management, and benchmark institutional outcomes. Several prediction models have been proposed over the years, including the Nottingham Hip Fracture Score, the Almelo Hip Fracture Score, and the National Hip Fracture Database (NHFD) risk model. However, many of these tools require laboratory results, detailed comorbidity lists, or cognitive assessments that may not be readily available at the point of admission or in emergency surgical settings.

The Rotterdam Hip Fracture Mortality Prediction-30 Days (RHMP-30), in its simplified form, addresses this gap by distilling the most consistently predictive clinical variables into a four-item additive point score that can be calculated at the bedside within moments of patient presentation. Originally developed at the Erasmus University Medical Center and affiliated trauma centres in the Netherlands, the RHMP-30 simplified score leverages routinely collected data to generate a composite risk estimate ranging from 0 to 16 points, mapped to four tiered mortality bands.

Development of the Simplified Score

The simplified RHMP-30 emerged from a body of work examining predictors of early mortality following hip fracture surgery in frail elderly populations. Investigators at the Erasmus MC and collaborating institutions retrospectively analyzed cohorts of consecutive hip fracture patients to identify the variables with the strongest, most reproducible associations with death within 30 days of surgery. Through multivariable logistic regression and clinical consensus, four variables were selected for the simplified model: age at injury, sex, American Society of Anesthesiologists (ASA) physical status classification, and pre-injury residential status.

Each of these variables was discretized into clinically meaningful categories and assigned integer point values weighted to approximate their relative contributions to 30-day mortality risk. The resulting additive score was designed for simplicity: no laboratory values, no complex calculations, and no requirement for specialist assessment tools. This design philosophy ensures that the RHMP-30 simplified score can be applied universally, including in resource-limited settings, during after-hours admissions, and in triage environments where comprehensive geriatric assessment is not immediately feasible.

A subsequent multidimensional RHMP-30 model was developed and published in the Journal of Bone and Joint Surgery (2025), employing LASSO regression to select seven predictors (age, sex, ASA 4 status, dementia, serum albumin, Katz Activities of Daily Living total, and nursing home residence) with an area under the receiver operating characteristic curve (AUC) of approximately 0.78 in both training and external validation cohorts. That expanded model requires access to laboratory and functional assessment data not always available at initial presentation, which is why the simplified four-variable score remains widely used as a rapid bedside tool.

Clinical Variables and Point Assignment

Age

Age is the single most heavily weighted variable in the RHMP-30 simplified score, reflecting the well-established exponential increase in perioperative mortality with advancing age in hip fracture patients. The scoring system divides age into five bands:

• Under 60 years: 0 points. Hip fractures in this age group are typically the result of high-energy trauma and occur in patients with fewer baseline comorbidities, resulting in substantially lower 30-day mortality.
• 60 to 69 years: 1 point. The onset of age-related physiological decline begins to contribute measurably to perioperative risk in this decade.
• 70 to 79 years: 2 points. This is the age range in which the majority of hip fractures occur, and mortality risk rises appreciably compared to younger cohorts.
• 80 to 89 years: 4 points. Patients in their eighties carry a substantially elevated risk due to accumulated frailty, multimorbidity, and diminished physiological reserve.
• 90 years and older: 6 points. Nonagenarians and centenarians represent the highest age-related risk tier, with 30-day mortality rates that may exceed 15 to 20% even in otherwise favorable clinical scenarios.

The nonlinear weighting (0, 1, 2, 4, 6) rather than a simple linear increment captures the accelerating nature of age-related risk in this population. The disproportionate jump from the 70s to the 80s and again to the 90s reflects registry data showing that each additional decade of life beyond 70 confers a multiplicative rather than merely additive increment in mortality risk.

Sex

Male sex is assigned 2 points in the RHMP-30 simplified score, while female sex receives 0 points. Although women account for approximately 70% of all hip fractures (largely due to higher osteoporosis prevalence and longer life expectancy), men who sustain hip fractures consistently demonstrate higher 30-day mortality rates across virtually all published registries and cohort studies. The reasons for this disparity are multifactorial and include higher prevalence of cardiovascular comorbidities in men at the time of fracture, greater likelihood of delayed presentation, higher rates of alcohol-related cognitive impairment, and differences in postoperative inflammatory and catabolic response. Some analyses also suggest that men are more likely to present with fractures resulting from higher-energy mechanisms and to have higher ASA grades at baseline.

ASA Physical Status Classification

The ASA Physical Status Classification System, originally developed in 1941 and revised multiple times since, provides a standardized global assessment of a patient's pre-anesthetic health. In the RHMP-30 simplified score, the ASA grade is assigned points as follows:

• ASA 1 or 2: 0 points. These classifications encompass healthy patients and those with mild systemic disease that does not impose functional limitations. Hip fracture patients in these categories are relatively uncommon, particularly among elderly cohorts, and carry the lowest perioperative risk.
• ASA 3: 2 points. This classification denotes severe systemic disease with substantive functional limitation but not an immediate threat to life. It is the most frequently assigned ASA grade among elderly hip fracture patients and reflects a moderate elevation in perioperative risk.
• ASA 4: 4 points. Patients with severe systemic disease that is a constant threat to life. This category is strongly predictive of 30-day mortality and is associated with conditions such as unstable angina, decompensated heart failure, severe COPD with home oxygen, active hepatic or renal failure, and severe sepsis.
• ASA 5: 6 points. A moribund patient not expected to survive 24 hours without the operation. While rare in clinical practice for hip fracture, this classification carries the highest individual variable weighting in the score and signals an extremely elevated risk of early death.

The ASA grade functions as a surrogate for the cumulative burden of systemic disease and physiological reserve. Its assignment by the anaesthesia team at the time of preoperative assessment ensures that it is available for every surgical patient, making it an ideal variable for inclusion in a rapid bedside prediction tool.

Pre-Injury Residence

The patient's living situation prior to the hip fracture is the fourth and final variable in the simplified score, categorized as either independent (living at home in the community) or institutionalized (residing in a nursing home, residential care facility, or similar institution). Institutional residence is assigned 2 points, while independent living receives 0 points.

Pre-injury residential status serves as a composite proxy for functional dependence, frailty, cognitive impairment, and social vulnerability. Patients who are already living in institutional care at the time of fracture are, on average, older, more frail, more cognitively impaired, and more dependent in activities of daily living than their community-dwelling counterparts. Multiple studies have demonstrated that institutionalized hip fracture patients have 30-day mortality rates two to three times higher than those of independent-living patients, even after adjustment for age and comorbidity.

This variable is particularly valuable because it captures dimensions of patient vulnerability (functional status, cognitive reserve, social support) that are not directly measured by the other three variables but are nonetheless powerfully predictive of short-term survival.

Score Interpretation and Risk Stratification

The RHMP-30 simplified score sums the points from all four variables to produce a composite score ranging from 0 to a theoretical maximum of 16. This total is then mapped to four risk categories:

Score Range	Risk Category	Approximate 30-Day Mortality
0 to 3	Low risk	~0 to 1%
4 to 7	Intermediate risk	~3 to 6%
8 to 10	High risk	~10 to 18%
11 to 16	Very high risk	>25%

These mortality estimates are approximate and derived from the original development cohort and subsequent validation studies. Actual 30-day mortality in any individual patient or institution may differ based on surgical timing, operative technique, anesthetic approach, postoperative care protocols, and local case-mix characteristics. The risk bands are intended to provide a general framework for clinical stratification rather than precise individual probability estimates.

Clinical Applications

Preoperative Risk Communication and Shared Decision-Making

One of the primary applications of the RHMP-30 is to facilitate transparent, evidence-informed conversations with patients and their families about perioperative risk. When a patient presents with a hip fracture, the care team can rapidly compute the RHMP-30 simplified score and use the resulting risk category to frame discussions about the expected trajectory of care, the possibility of serious complications including death, and the relative urgency of surgical intervention. For patients in the very high risk category, this information may be particularly important in guiding goals-of-care discussions and advance care planning.

Perioperative Care Intensity and Resource Allocation

Hospitals and trauma systems can use RHMP-30 risk stratification to tailor the intensity and configuration of perioperative care. Low-risk patients may be suitable for standard ward-based care with routine monitoring, while high-risk and very high-risk patients may benefit from preoperative optimization by a dedicated orthogeriatric or perioperative medicine service, higher-acuity postoperative monitoring (e.g., step-down or intensive care unit admission), proactive involvement of palliative care for symptom management and advance planning, and early multidisciplinary rehabilitation planning to minimize deconditioning.

Benchmarking and Quality Improvement

At the institutional level, the RHMP-30 can be used to risk-adjust 30-day mortality rates for benchmarking and quality improvement purposes. By stratifying patients into risk categories at admission, hospitals can compare their observed mortality against expected rates, identify outlier performance (both positive and negative), and target improvement efforts toward specific subgroups. National hip fracture registries and audit programs can incorporate the RHMP-30 as a standardized risk-adjustment tool to enable fair inter-hospital comparisons.

Triage in Mass Casualty and Resource-Limited Settings

Because the RHMP-30 simplified score requires no laboratory investigations and no specialized assessment tools, it is particularly well-suited for triage in austere or resource-limited environments. In mass casualty scenarios, natural disasters, or settings where laboratory turnaround times are prolonged, the ability to stratify hip fracture mortality risk using only age, sex, ASA status, and residential history represents a significant practical advantage over more complex scoring systems.

Research Stratification

Clinical trials and observational studies focusing on hip fracture outcomes can use the RHMP-30 as a baseline stratification variable to ensure balanced risk distribution across treatment arms, facilitate subgroup analyses by baseline mortality risk, and adjust for confounding in multivariable models. The simplicity and reproducibility of the score make it an attractive option for multi-centre studies where data collection protocols must be minimally burdensome.

The Multidimensional RHMP-30 Model

Building on the simplified four-variable score, a research group led by de Jong and colleagues at the Erasmus MC developed and externally validated a more comprehensive multidimensional RHMP-30 model, published in the Journal of Bone and Joint Surgery in 2025. This expanded model employed LASSO (Least Absolute Shrinkage and Selection Operator) regression, a penalized regression technique that simultaneously performs variable selection and coefficient shrinkage, to identify the optimal set of predictors from a larger pool of candidate variables.

The LASSO-selected multidimensional model includes seven predictors: age (continuous), sex, ASA 4 status (as a binary variable rather than the full ordinal scale), presence of dementia, serum albumin level, Katz Activities of Daily Living (ADL) total score, and nursing home residence. This model achieved an AUC of approximately 0.78 in both the development cohort and an independent external validation cohort, suggesting good discrimination and generalizability.

The multidimensional model offers improved predictive accuracy over the simplified score by incorporating direct measures of nutritional status (albumin), functional dependence (Katz ADL), and cognitive impairment (dementia). However, the requirement for laboratory results and functional assessment data means that the multidimensional model cannot always be applied at the time of initial emergency presentation, making the simplified score a complementary rather than redundant tool.

Comparison with Other Hip Fracture Mortality Prediction Tools

Nottingham Hip Fracture Score (NHFS)

The Nottingham Hip Fracture Score is one of the most widely validated hip fracture mortality prediction tools internationally. It uses seven variables: age, sex, number of comorbidities, abbreviated mental test score, hemoglobin on admission, living in an institution, and presence of malignancy. While the NHFS has demonstrated good discrimination (AUC typically 0.70 to 0.75), it requires a cognitive screening test and an admission hemoglobin, which may not be immediately available. The RHMP-30 simplified score offers the advantage of requiring no laboratory values and no formal cognitive assessment, trading some predictive granularity for ease of use.

Almelo Hip Fracture Score (AHFS)

The Almelo Hip Fracture Score incorporates age, sex, number of active comorbidities, malignancy, and ASA classification. Like the RHMP-30, it can be computed without laboratory values, but it requires enumeration of specific comorbidities and identification of active malignancy, which may involve chart review or collateral history. The RHMP-30 simplifies this further by using only ASA grade (which integrates comorbidity burden) and residential status (which integrates functional reserve).

Hip-Multidimensional Frailty Score (Hip-MFS)

Frailty-based approaches to hip fracture mortality prediction, such as the Hip-MFS, explicitly quantify frailty through instruments like the Clinical Frailty Scale, grip strength, or walking speed. While these tools may capture physiological vulnerability more directly, they require trained personnel to administer frailty assessments and may not be feasible in the acute emergency setting. The RHMP-30 captures frailty indirectly through its residential status and ASA variables, offering a pragmatic trade-off between measurement precision and clinical feasibility.

Limitations and Considerations

While the RHMP-30 simplified score is a valuable rapid-assessment tool, several limitations should be acknowledged when applying it in clinical practice:

• Derived from specific populations: The original development and validation cohorts were drawn from Dutch trauma centres. While the included variables (age, sex, ASA, residential status) are biologically and clinically universal, the specific point weightings and mortality band estimates may not perfectly calibrate to populations with substantially different demographics, healthcare systems, or surgical practices.
• Limited discrimination in intermediate ranges: As with most simplified scoring systems, the RHMP-30 provides the clearest prognostic separation at the extremes (very low and very high scores) and may be less discriminating in the intermediate range (scores of 4 to 7), where individual patient factors not captured by the four variables may exert substantial influence.
• Does not capture surgical timing or technique: The score is computed based on preoperative characteristics and does not account for potentially modifiable perioperative factors such as time from admission to surgery, choice of surgical technique (arthroplasty versus internal fixation), type of anesthesia (general versus neuraxial), intraoperative blood loss, or postoperative complications. These factors are known to influence 30-day mortality independently.
• ASA grade subjectivity: The ASA Physical Status Classification, while widely used, is subject to inter-rater variability. Different anesthesiologists may assign different ASA grades to the same patient, introducing a source of measurement imprecision into the RHMP-30 score. Standardized ASA assignment protocols and examples can mitigate but not eliminate this variability.
• Binary residential classification: The RHMP-30 dichotomizes pre-injury residence into independent versus institutional, which does not capture the full spectrum of living arrangements (e.g., assisted living, sheltered housing, supported independent living with home care). Patients receiving intensive home-based care services may have risk profiles closer to institutional residents than to fully independent community dwellers.
• No incorporation of fracture-specific features: The score does not differentiate between fracture types (intracapsular versus extracapsular, displaced versus undisplaced), which may carry different prognostic implications depending on the operative approach required.
• Static preoperative assessment: The RHMP-30 provides a single preoperative risk estimate and does not update dynamically based on the patient's clinical trajectory. A patient who deteriorates rapidly in the perioperative period or who develops a major complication (e.g., pulmonary embolism, myocardial infarction, surgical site infection) may have an actual risk far exceeding their initial RHMP-30 estimate.

Integration into Orthogeriatric Care Pathways

The optimal use of the RHMP-30 is as one component of a comprehensive orthogeriatric care pathway rather than as a standalone decision-making tool. Modern hip fracture management emphasizes a multidisciplinary approach involving orthopedic surgery, anesthesia, geriatric medicine, nursing, physiotherapy, occupational therapy, social work, and, where appropriate, palliative care. The RHMP-30 can serve as an initial triage and communication tool within this framework, helping to direct patients to the appropriate level of care and initiate the right conversations from the earliest moments of the clinical encounter.

When used alongside clinical judgment, comprehensive geriatric assessment (when feasible), and institutional protocols, the RHMP-30 simplified score enhances rather than replaces the nuanced, individualized approach to perioperative risk management that characterizes high-quality orthogeriatric care. Clinicians should interpret the score in the context of the whole patient, recognizing that no four-variable model can fully capture the complexity of an individual's health trajectory after a hip fracture.

Special Populations

Younger Patients with High-Energy Fractures

Hip fractures in patients under 60 years of age are most commonly the result of high-energy mechanisms such as motor vehicle collisions, falls from height, or sporting injuries. These patients typically receive 0 age points in the RHMP-30 but may carry significant mortality risk from associated polytrauma, traumatic brain injury, or hemorrhagic shock. The RHMP-30 was not specifically designed or validated for high-energy trauma patients, and its predictive accuracy in this subgroup is uncertain. Clinicians should exercise caution when applying the score to younger patients with complex injury patterns.

Patients with Cognitive Impairment

Dementia and delirium are highly prevalent among elderly hip fracture patients and are independently associated with increased 30-day mortality. The simplified RHMP-30 does not include a direct measure of cognitive status, although the residential status variable (institutional versus independent) partially captures this dimension, as patients with advanced dementia are more likely to reside in nursing home or institutional care. The multidimensional RHMP-30 model addresses this limitation by including dementia as an explicit predictor, and clinicians managing patients with known or suspected cognitive impairment may wish to consider the expanded model when feasible.

Patients with Pathological Fractures

Hip fractures occurring through pathological bone (e.g., metastatic disease, primary bone tumors, Paget's disease) represent a distinct clinical entity with different prognostic considerations. The RHMP-30 was developed in cohorts predominantly comprising osteoporotic fragility fractures and may not accurately estimate 30-day mortality in patients with underlying malignancy or other pathological bone conditions. These patients may require disease-specific prognostic tools in addition to or instead of the RHMP-30.

Practical Workflow for RHMP-30 Application

The following stepwise approach is suggested for integrating the RHMP-30 into routine hip fracture care:

1. Identify the patient: Confirm the diagnosis of an acute hip fracture requiring surgical repair.
2. Ascertain the four variables: Record the patient's age, sex, ASA physical status (assigned by the anesthesia team at preoperative assessment), and pre-injury residential status (independent community dwelling versus institutional care).
3. Compute the score: Sum the corresponding point values for each variable to obtain the total RHMP-30 simplified score (range 0 to 16).
4. Identify the risk category: Map the total score to the appropriate mortality risk band (low, intermediate, high, or very high).
5. Communicate the result: Share the risk category with the patient, family, and multidisciplinary team. Use the result to guide discussions about perioperative expectations, care intensity, and, where appropriate, goals-of-care planning.
6. Document: Record the RHMP-30 score and risk category in the patient's clinical notes to support continuity of care, quality auditing, and research.