What Factors Correlate With Length of Stay and Readmission After Limb Lengthening Procedures? A Large-database Study

Abstract

Background

Indications and techniques for limb lengthening procedures have evolved over the past two decades. Although there are several case series reporting on the complications and efficacy of these techniques, limited data are available on length of stay and hospital readmission rates after these procedures.

Questions/purposes

(1) What is the median length of stay after lower limb lengthening procedures, and is variability in patient demographics, preoperative diagnosis, and surgical technique associated with length of stay? (2) What is the 1-year readmission rate after lower limb lengthening procedures? (3) Is variability in patient demographics, preoperative diagnosis, and surgical technique associated with varying rates of hospital readmission?

Methods

Patients who underwent femoral or tibial lengthening from 2005 to 2015 in seven states were identified using the Healthcare Cost and Utilization Project (HCUP) State Inpatient Databases. These databases include a large, diverse group of patients across a wide range of hospitals and socioeconomic backgrounds with inclusion of patients regardless of payer. Between 2005 and 2015, there were 3979 inpatient admissions that were identified as involving femoral and/or tibial lengthening procedures based on ICD-9 procedure codes; of those, 2% (97 of 3979) of the inpatient admissions were excluded from analysis because they had ICD-9 procedure codes for primary or revision hip or knee arthroplasty, and 10% (394 of 3979) of the inpatient admissions were excluded because they involved repeated admissions of patients with previous hospitalization data within the database. This yielded 3488 patients for analysis. The median (interquartile range) age of patients was 18 years (12 to 41), and 42% (1481 of 3488) of patients were women. A total of 49% (1705 of 3469) of patients were children (younger than 18 years), 19% (675 of 3469) were young adults (18 to 34 years), 24% (817 of 3469) were adults (35 to 59 years), and 8% (272 of 3469) were seniors (60 years and older). Length of stay and rates of readmission at 1 year after the lengthening procedure were calculated. Univariate analysis was performed to examine associations between age, race, payment method, underlying diagnosis, bone lengthened, and lengthening technique with length of stay and readmission rate. Factors found to be significantly associated with the outcome variables (p < 0.05) were further examined with a multivariate analyses.

Results

Included patients had a median (IQR) length of hospital stay of 3 days (2 to 4). Given the poor explanatory power of the multivariate model for length of stay (R² = 0.03), no meaningful correlations could be drawn between age, race, underlying diagnosis, lengthening technique, and length of stay. The overall 1-year readmission rate was 35% (1237 of 3488). There were higher readmission rates among adult patients compared with pediatric patients (odds ratio 1.78 [95% confidence interval 1.46 to 2.18]; p < 0.001), patients with government insurance compared with commercial insurance (OR 1.28 [95% CI 1.05 to 1.54]; p = 0.01), and patients undergoing lengthening via external fixation (OR 1.61 [95% CI 1.29 to 2.02]; p < 0.001) or hybrid fixation (OR 1.81 [95% CI 1.38 to 2.37]; p < 0.001) compared with lengthening with internal fixation only.

Conclusion

When counseling patients who may be candidates for limb lengthening, providers should inform individual patients and their caretakers on the anticipated length of hospital stay and likelihood of hospital readmission based on our findings. Adult patients, those with government insurance, and patients undergoing hybrid or external fixator limb lengthening procedures should be advised that they are at greater risk for hospital readmission. The relationship of specific patient-related factors (such as severity of deformity or associated comorbidities) and treatment-related variables (such as amount of lengthening, compliance with physical therapy, or surgeon’s experience) with clinical outcomes after lower limb lengthening and the burden of care associated with hospital readmission needs further study.

Level of Evidence

Level III, therapeutic study.

Introduction

Leg length discrepancy can occur secondary to various etiologies and alter gait biomechanics, predispose to back and lower extremity joint pain, and be cosmetically undesirable to the patient and/or their caretakers [10, 24, 33, 53, 54]. Historically, external fixation has been the implant of choice for limb lengthening [16, 18, 20, 23, 39, 49, 51, 53, 54]. However, untoward events associated with external fixation, including soft-tissue transfixation, pin tract infections, joint stiffness, poor cosmesis related to pin sites, and patient discomfort, have led to the development of alternative techniques for limb lengthening [1, 9, 17, 22, 31, 36, 40, 42, 51, 54, 66, 67]. Current techniques of limb lengthening include the use of external fixators, hybrid constructs with the use of both internal and external fixation, and fully implantable internal lengthening nails [33]. Although these techniques can address the leg length discrepancy, they are often associated with a long recovery period and high rate of serious complications postoperatively, including infection, premature consolidation, delayed union, nonunion, malunion, bending or fracture of the lengthening regenerate, loss of joint mobility, residual deformity, pain and implant failure [19, 33, 58].

Previous studies have shown a wide range of length of stay and complications after limb lengthening procedures, with the reported length of stay varying from 4.2 to 50 days [1, 2, 4, 11, 12, 27, 31, 45, 61, 63, 65]; the proportions of patients experiencing complications have varied widely across studies, from 10% to 182% [1, 14-16, 20, 21, 28, 29, 35, 41, 46, 47, 50, 51, 54, 60, 62, 64, 68]. Several patient and surgical factors may contribute to the length of stay and complication rate, including the patient’s age, underlying diagnosis, bone segment lengthened, severity of deformity, and lengthening technique [6, 7, 11, 14, 16, 17, 25, 26, 30-34, 38, 43, 44, 51, 56, 59]. However, to date, most studies exploring the results of limb lengthening procedures are limited to single centers with smaller case series focusing on a specific underlying diagnosis, patient population, or surgical technique, and they do not provide comparative data on length of stay after the index procedure or hospital readmission rates after limb lengthening. Assessing the variability in length of stay and readmission risk for these procedures within a large cohort of patients encompassing patients of various ages, races, socioeconomic circumstances, underlying diagnoses, and lengthening techniques can help provide guidance for appropriate preoperative counseling for shared decision-making and set realistic expectations for patients.

We therefore sought to use a large US healthcare database to ask: (1) What is the median length of stay after lower limb lengthening procedures, and is variability in patient demographics, preoperative diagnosis, and surgical technique associated with varying length of stay? (2) What is the 1-year readmission rate after lower limb lengthening procedures? (3) Is variability in patient demographics, preoperative diagnosis, and surgical technique associated with varying rates of hospital readmission?

Patients and Methods

Study Design and Setting

We conducted a retrospective, comparative large-database study using data from 2005 to 2015. Inpatient data were acquired using the Healthcare Cost and Utilization Project (HCUP) State Inpatient Databases (SID) for the seven states during the periods that were available to us: California, Florida, Maryland, Nebraska, New York, North Carolina, and Utah. The HCUP database is deidentified and has the largest collection of longitudinal hospital care data in the United States with all-payer, encounter-level information [3]. The large size of the SID and inclusion of all-payor data make it a well-suited resource to examine outcomes after these infrequently performed procedures within a diverse group of patients across the country. Furthermore, the inclusion of data points such as diagnosis, race, insurance type, and procedure performed allow for an assessment of various factors that may be associated with length of stay and readmission rate. During this time period, the database used ICD-9 procedure and diagnoses codes and included patient demographics, admission diagnoses, procedures performed, hospital readmissions, readmission diagnosis, and procedures performed during readmission. Only patients who were readmitted for at least one overnight stay were recorded as having a readmission. The details of patients who may have undergone same-day procedures or had emergency department visits were not available.

Patient Selection

A total of 3979 inpatient admissions with ICD-9 procedure codes for limb lengthening of the femur (78.35), limb lengthening of the tibia (78.37), and both from 2005 to 2015 in the states available to us were included for analysis. Two percent (97 of 3979) of all admissions were excluded due to having procedure codes for partial, total, or revision hip arthroplasty, or total or revision knee arthroplasty. Ten percent (394 of 3882) of admissions were subsequently excluded from analysis as they involved repeated admissions of patients with previous hospitalization data within the database. This yielded 88% (3488 of 3979) of the initially identified individuals for analysis.

Patients were categorized based on the bone that was lengthened (femur or tibia), lengthening technique (internal, external, or hybrid), and underlying diagnosis based on ICD-9 coding. Demographic factors including age at the time of the initial lengthening procedure, gender, race or ethnicity, and insurance type were included. Patients’ races were categorized based on the administrative claims (hospital billing) submitted by each health system to their respective state based on categories within the database. The available data did not include information on other related important covariates such as income, housing insecurity, or educational attainment. We recorded the length of hospital stay at the time of the index lengthening procedure and hospital readmissions within 30 days, 90 days, and 365 days after the index procedures.

Patients’ Baseline Data

A total of 3488 patients (42% [1481] of whom were women) were included for analysis. The median (interquartile range) age of the patient at the time of the index lengthening procedure was 18 years (12 to 41). The median age of patients undergoing tibial lengthening was 27 years (13 to 49), the median age of those undergoing femoral lengthening was 16 years (11 to 29), and the median age of those undergoing combined femoral and tibial lengthening was 14 years (11 to 19) (p < 0.001) (Table 1). Forty-nine percent (1705 of 3469) of patients were children (younger than 18 years), 19% (675 of 3469) were young adults (18 to 34 years), 24% (817 of 3469) were adults (35 to 59 years), and 8% (272 of 3469) were seniors (60 years and older). Age was unavailable for 1% (19 of 3488) of patients in this dataset. Fourteen percent (485 of 3488) of patients were noted to be Black, 16% (550 of 3488) were Hispanic, 54% (1887 of 3488) were White, and 16% (566 of 3488) were classified as another race or had missing data. Sixty percent (2096 of 3488) of patients had commercial insurance, 30% (1030 of 3488) had government insurance, 2% (80 of 3488) were self-pay, and 8% (282 of 3488) had another or missing payment method.

Table 1.

Demographics of study cohort

Parameter	Femur-only lengthening (n = 1597)	Tibia-only lengthening (n = 1773)	Combined femoral and tibial lengthening (n = 118)	Overall (n = 3488)
Age in years	16 (11-29)	27 (13-49)	14 (11-19)	18 (12-41)
Gender
Women	43 (692)	42 (741)	41 (48)	42 (1481)
Men	55 (878)	57 (1013)	58 (69)	56 (1960)
Unknown	2 (27)	1 (19)	0.8 (1)	1 (47)
Race or ethnicity a
Black	13 (212)	15 (266)	6 (7)	14 (485)
Hispanic	17 (268)	15 (261)	18 (21)	16 (550)
White	53 (839)	55 (973)	64 (75)	54 (1887)
Other or missing	17 (278)	15 (273)	13 (15)	16 (566)
Payor status
Commercial	59 (946)	60 (1063)	74 (87)	60 (2096)
Government	31 (495)	29 (509)	22 (26)	30 (1030)
Self-pay	2 (39)	2 (40)	0.8 (1)	2 (80)
Other or missing	7 (117)	9 (161)	3 (4)	8 (282)

Data presented as median (IQR) or % (n).

^aPatient race was categorized based on the administrative claims submitted by each health system to their respective states, per the database categories.

Classification of Lengthening Technique

Patients were classified as having internal-only, external-only, or hybrid lengthening based on ICD-9 coding (Supplementary Table 1; http://links.lww.com/CORR/A783). Patients who did not have the above codes for internal, external, or hybrid lengthening were noted to have an undetermined technique.

In all, 46% (1597 of 3488) patients underwent femoral lengthening, 51% (1773 of 3488) patients underwent tibial lengthening, and 3% (118 of 3488) patients underwent combined femoral and tibial lengthening. Of the 1597 patients who underwent femur-only lengthening, 1086 had a specified lengthening technique. Of the patients with specified lengthening technique, 42% (457 of 1086) underwent internal lengthening, 38% (410 of 1086) underwent external lengthening, and 20% (219 of 1086) underwent hybrid lengthening (Fig. 1A). Of the 1773 patients who underwent tibia-only lengthening, 1477 had specified lengthening technique. Of the patients with specified lengthening technique, 14% (203 of 1477) underwent internal lengthening, 69% (1018 of 1477) underwent external lengthening, and 17% (256 of 1477) underwent hybrid lengthening (Fig. 1B).

Fig. 1.

A-B (A) The distribution of lengthening technique used for femoral lengthening procedures is shown. (B) The distribution of lengthening technique used for tibial lengthening procedures is shown. This excludes lengthening procedures with unspecified techniques or types of fixation.

Classification of Underlying Diagnosis

The underlying diagnosis was determined using ICD-9 admission codes and regrouped for congenital and posttraumatic diagnoses (Supplementary Table 2; http://links.lww.com/CORR/A784). Patients whose diagnosis did not fit into either of these two categories were classified as having another diagnosis. For patients whose diagnosis fit multiple categories, the first recorded admission diagnosis was considered as the primary diagnosis. Twenty-three percent (800 of 3488) were classified as having a congenital diagnosis, 21% (724 of 3488) with a posttraumatic diagnosis, and 56% (1964 of 3488) had another diagnosis.

Ethical Approval

Ethical approval for this study was not sought because we used a public database.

Statistical Analysis

We used descriptive statistics to describe the study population. We calculated rates of hospital readmission at 30 days, 90 days, and 365 days after the index procedure. Continuous variables (age, length of stay) were assessed for normality utilizing Shapiro-Francia test. Because these variables violated the normality assumption, we made comparisons with the Mann-Whitney U/Wilcoxon rank sum test. We performed univariate analyses to examine associations between age, race, health insurance, underlying diagnosis, bone lengthened, and lengthening technique with the outcome variables of length of stay and 1-year readmission rate. Multivariate models were generated utilizing variables that were significant on univariate analyses (p < 0.05). We performed a multiple linear regression analysis to evaluate any associations between age, race, insurance, diagnosis, bone lengthened, fixation method, and length of hospital stay at the time of the initial lengthening. Logistic regression was used to evaluate any associations between age, insurance, diagnosis, bone lengthened, fixation method, and readmission rate. Goodness-of-fit testing was performed on logistic regression with the method of Hosmer-Lemeshow with 10° of freedom. We calculated area under the curve for logistic regression models. The data analysis was performed in Stata version 16 (StataCorp). Statistical significance was set at p < 0.05 for all analyses.

Results

Length of Stay and Associated Factors

The median (IQR) length of stay at the time of the index lengthening procedure was 3 days (2 to 4), and there were no meaningful associations between patient demographic factors, diagnosis, bone lengthened, and lengthening technique. Given the poor explanatory power of the multivariate model for length of stay (R² = 0.03), no meaningful correlations between age, race, underlying diagnosis, lengthening technique and length of stay could be drawn (Table 2).

Table 2.

Multiple linear regression analysis for the outcome of length of stay in days after the index procedure

Variable	Correlation coefficient (95% CI)	p value
Age (reference = pediatric)
Adult	1.24 (0.30 to 2.17)	0.01
Race (reference = White) a
Hispanic	2.25 (1.13 to 3.37)	< 0.001
Black	1.65 (0.55 to 2.75)	0.003
Insurance/payor (reference = commercial)
Government (Medicare, Medicaid)	1.14 (0.23 to 2.04)	0.014
Self-pay	0.61 (-2.24 to 3.45)	0.68
Dx (reference = other)
Congenital	-0.36 (-1.38 to 0.66)	0.49
Trauma	2.20 (1.13 to 3.27)	< 0.001
Bone (reference = tibia)
Femur	0.66 (-0.22 to 1.54)	0.14
Fixation (reference = internal)
Hybrid	0.44 (-0.77 to 1.67)	0.47
External	1.06 (0.05 to 2.07)	0.04

In all, 1969 patients with data points for all variables were included for analysis; the regression formula demonstrated poor correlation between age, race, insurance, underlying diagnosis, bone lengthened, fixation type, and length of stay (R² = 0.038; p < 0.001), and therefore, no reliable conclusions could be drawn from the model.

^aPatients’ race was categorized based on the administrative claims submitted by each health system to their respective state per the database categories.

Readmission Rate

The readmission rate at 1 year was 35% (1237 of 3488). The readmission rate at 30 and 90 days was 7% (232 of 3488) and 18% (644 of 3488), respectively.

Factors Associated With Readmission

After controlling for potentially confounding variables such as length of stay, insurance, diagnosis, bone lengthened, and lengthening technique, a greater likelihood of readmission at 1 year was seen among adult patients (odds ratio 1.78 [95% confidence interval 1.46 to 2.18]; p < 0.001), in patients with government insurance (OR 1.28 [95% CI 1.05 to 1.54]; p = 0.01), and in patients who underwent external fixation (OR 1.61 [95% CI 1.29 to 2.02]; p < 0.001) or hybrid fixation (OR 1.81 [95% CI 1.38 to 2.37]; p < 0.001) compared with internal fixation-only lengthening (Table 3). Patients with a longer length of stay were found to have a greater likelihood of readmission at 1 year, although this difference was small and of unknown clinical importance (OR 1.06 [95% CI 1.04 to 1.08]; p < 0.001). We found no associations between race, underlying diagnosis, and bone lengthened with readmission at 1 year.

Table 3.

Multivariable logistic regression for all-cause 365-day readmissions after the index lengthening procedure

Variable	Odds ratio (95% CI)	p value
Age category (reference = pediatric)
Adult	1.78 (1.46-2.18)	< 0.001
Length of stay (days)	1.06 (1.04-1.08)	< 0.001
Insurance/payor (reference = commercial)
Government (Medicare, Medicaid)	1.28 (1.05-1.54)	0.01
Self-Pay	1.08 (0.64-1.82)	0.70
Dx (reference = other)
Congenital	0.89 (0.71-1.11)	0.30
Trauma	0.93 (0.74-1.17)	0.52
Bone (reference = tibia)
Femur	1.00 (0.83-1.21)	0.96
Fixation (reference = internal)
Hybrid	1.81 (1.38-2.37)	< 0.001
External	1.61 (1.29-2.02)	< 0.001

In all, 2367 patients were included for analysis; the area under the curve = 0.64; goodness-of-fit testing by the method of Hosmer-Lemeshow demonstrates p = 0.78.

Discussion

Limb lengthening procedures are associated with frequent complications [1, 14, 16, 20, 33, 41, 47, 51, 54, 62]. Although smaller studies have examined the frequency of complications as a function of patient factors and surgical techniques [11, 34, 46, 48], we are not aware of any studies on the length of stay and inpatient readmissions after limb lengthening for a diverse group of patients with varying demographics, diagnoses, and surgical techniques. As limb lengthening procedures see wider use, we believe our preliminary findings can be used for preoperative patient counseling and can help guide patient, surgeon, hospital administration, and payor expectations. Providers should emphasize to patients and other stakeholders that these lower limb lengthening procedures are often associated with multiple-day hospital admissions and a high rate of inpatient hospital readmission within the first year after the initial lengthening procedure. Moreover, adult patients, those with government insurance, and those undergoing lengthening via external fixation and hybrid fixation should be counseled that they have a higher likelihood of readmission compared with children and those undergoing internal lower limb lengthening.

Limitations

There are several limitations to our study. We were unable to ascertain certain kinds of clinically relevant information, such as severity of the limb deformity, amount of lengthening performed, adherence to physical therapy regimens, or surgeon experience, all of which may impact the risk of postoperative complications and hospital readmission [33, 52]. Lack of such details likely contributed to the poor explanatory power of our regression model for length of stay. Although this is a large limitation of the study, we believe that our study still allows meaningful conclusions to be drawn on the relative impact that age, gender, race, insurance, underlying diagnosis, and lengthening technique have on readmissions. Future studies should build on our preliminary findings and study the potential association of these additional variables with length of stay and hospital readmission. Although we were able to evaluate endpoints according to race and insurance type, the database we used did not provide a number of potentially important covariates such as income, housing insecurity, or education level, and without those elements, our ability to draw associations between socioeconomic elements and endpoints of interest was correspondingly limited. Additionally, information on the lengthening technique was unavailable for 24% of our patients, which limits the strength of the conclusions we can draw from our analysis. We included these patients to allow for a better determination of the overall readmission rate and length of stay after limb lengthening procedures, but excluded them for the purposes of our multivariate analysis to ascertain the impact of lengthening technique on length of stay and readmissions more clearly.

Our dataset was restricted to patients who were readmitted as inpatients and excluded those with untoward events after limb lengthening who may have been treated as an outpatient or underwent same-day procedures. Even though we did not capture those outpatient admissions in our study, we believe that the rate of inpatient readmissions is a valuable data point. As is often the case with such study designs, because of a lack of details on the clinical course of the patients, we were unable to classify complications according to severity or clinical outcomes [16, 54, 55]. Additionally, given the multiple diagnoses associated with hospital admission and surgical procedures, we chose the first listed orthopaedic diagnosis to categorize the etiology of limb shortening. Although such assumptions and the use of broader categories for underlying diagnosis and lengthening technique may have impacted our ability to draw conclusions regarding specific diagnoses and specific lengthening devices, we believe that our findings can serve as a guide for providers performing lengthening procedures.

Our readmission data was also limited to 1 year, which precludes information on complications and procedures performed at later timepoints. We believe that the first postoperative year is the time when complications and readmissions are most likely to occur after these procedures, giving our data value despite the lack of longer term follow-up. Finally, a disproportionate percentage of our data were obtained from California, Florida, and New York, as data from these states were available to us for most of our study period and they likely had a higher number of lower limb lengthening procedures per year compared with other states. This may limit the generalizability of our study, both nationally and internationally. However, by capturing overall data from a diverse set of patients from seven states, we believe that we were able to include a sufficiently diverse group of patients in the United States.

Length of Stay and Associated Factors

The median length of hospital stay for the index lengthening procedure in our cohort was 3 days. This is lower than the previously reported length of stay after such procedures (4.2 days to 50 days) [1, 2, 4, 11, 12, 27, 31, 45, 61, 63, 65]. Several of these studies were performed in other countries, where longer inpatient hospital stay may be more common because of less administrative constraints from payors. Two prior studies that we are aware of have mentioned length of stay after limb lengthening procedures in the United States. One case series of 37 patients undergoing limb lengthening found that the Wagner lengthening group had a longer length of stay compared with those undergoing Ilizarov lengthening (50 days versus 38 days) [1]. In 2014, a more recent study reported a median length of stay of 7 days (internal lengthening) versus 9.4 days (external lengthening) within a pediatric cohort [11]. Based on our findings, we believe the duration of hospitalization after lower extremity limb lengthening procedures in the United States is shorter than previously reported within most hospital systems. Providers can counsel patients on the median length of stay after these procedures based on our findings. As our study only included data from 2005 to 2015, it is possible that the current median length of stay may be even shorter with further improvements in pain control strategies and emphasis on early postoperative mobilization [8]. We found no difference in the length of stay based on the patients’ gender or bone segment (femur versus tibia) lengthened. After controlling for potentially confounding variables including age, insurance type, bone lengthened, and lengthening technique, we found that there were no meaningful associations between these variables and length of stay. It is likely that several additional variables not included in this study such as severity of deformity, availability and frequency of physical therapy, and surgeon experience are important factors in determining length of stay. Further studies incorporating these additional variables, which are collected prospectively, will be required to better understand any associations of patient factors with length of stay.

Readmission Rate

The overall 1-year readmission rate in our study was 35% (1237 of 3488). It is difficult to compare our rate of readmission with that of other studies because to the best of our knowledge, no previous study has reported this measure. Given the lack of a single, well-accepted classification of complications in patients undergoing limb lengthening, there is wide variability in the reported complication rate, ranging from 10% to 182% [1, 14-16, 21, 28, 29, 35, 41, 46, 47, 50, 51, 54, 60, 62, 64, 68]. Because many complications do not result in readmission, our readmission rate is understandably lower than the complication rate reported in most studies. However, as readmission can represent a substantial hurdle for patients, it is important for providers to counsel patients preoperatively on this probability so they may better prepare themselves after the lengthening procedure. Surgeons seeking to build a limb lengthening practice should recognize the high rate of readmission and ensure that they have the necessary infrastructure and resources to manage patients after these challenging procedures. Further studies should explore the most frequent causes for inpatient readmission to allow for a better understanding of which patients are at higher risk and how these readmissions may be better prevented in the future. Although readmission may be unavoidable in certain situations, these patients may continue to benefit from closer follow-up and specialized care to ensure better outcomes.

Factors Associated With Readmission

When controlling for length of stay, insurance type, underlying diagnosis, and bone lengthened, adulthood (versus childhood), government insurance (versus commercial insurance), and hybrid or external lengthening (versus internal lengthening) were associated with a higher readmission rate. First, adult patients were more likely to be readmitted compared with children. Younger patients have been reported to have a lower rate of complications, in both femoral and tibial lengthening [16, 17, 33, 51]. This is likely because there were fewer comorbidities and better biologic potential in children than in adults. Patients with government insurance were also more likely to be readmitted compared with patients with commercial insurance. These patients may have fewer resources at their disposal, less access to postdischarge rehabilitation facilities, or less frequent outpatient follow-up visits, which may contribute to a higher rate of readmission. Patients undergoing hybrid and external lengthening had a greater likelihood of readmission at 1 year, respectively, than did those undergoing internal lengthening. Several studies have noted fewer complications with internal lengthening than with other techniques [11, 13, 15, 21, 37, 46, 50, 64]. This may be partially attributed to a lower infection rate with intramedullary fixation and better tolerance of an intramedullary device than with an external fixator. Although we were able to control for potential confounders such as age, underlying diagnosis, and bone lengthened, patients undergoing treatment with hybrid fixation and external fixators may also have more complex and/or severe deformities than those undergoing internal fixation-only lengthening, which may contribute to a higher rate of readmission. When counseling patients preoperatively, providers should emphasize that being an adult and undergoing hybrid and external fixator lengthening may increase the likelihood of hospital readmission. Recognizing this difference in readmission rate may also help providers identify higher risk patients as they undergo lengthening procedures.

We found no difference in readmission rates between patients undergoing femoral versus tibial lengthening, which is consistent with studies that have noted similar overall complication rates between the two procedures [17, 33, 68]. We did not find a difference in readmission rates based on patient gender and are not aware of any prior studies that have examined this association. It has been noted that limb lengthening in patients with an underlying congenital diagnosis may be more difficult and associated with a higher complication rate [1, 5, 20, 57]. In the present database study, we did not find an association between congenital etiology and a higher readmission rate.

Conclusion

Limb lengthening procedures of the femur and tibia are complex procedures that are associated with multiple-day hospital admissions and a high readmission rate at 1 year. As surgeons help patients prepare to undergo these operations, it is important to emphasize that they may experience hospital readmissions during their clinical course. Adult patients, patients with government insurance, and those undergoing hybrid or external fixator lengthening are at particularly high risk for inpatient readmission and should be counseled accordingly. Future studies should build on these findings by incorporating additional variables, such as the severity of limb shortening/deformity, amount of lengthening required, compliance with physical therapy, surgeon’s clinical training and surgical volume, overall treatment cost, and patient-reported outcomes, to allow for a more nuanced understanding of potential factors impacting patients undergoing lower limb lengthening.