Lumbar Spine Fusion Patients See Similar Improvements in Physical Activity Level to Non-Spine Fusion Patients Following Total Hip Arthroplasty

The Journal of Arthroplasty xxx (2019) 1e6

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Lumbar Spine Fusion Patients See Similar Improvements in Physical Activity Level to Non-Spine Fusion Patients Following Total Hip Arthroplasty Adrian D. Hinman, MD a, *, Maria C.S. Inacio, PhD b, Heather A. Prentice, PhD b, Calvin C. Kuo, MD c, Monti Khatod, MD d, Kern H. Guppy, MD, PhD e, Elizabeth W. Paxton, PhD b a

Department of Orthopaedic Surgery, The Permanente Medical Group, San Leandro, CA Surgical Outcomes and Analysis, Kaiser Permanente, San Diego, CA c Department of Spine Surgery, The Permanente Medical Group, Oakland, CA d Department of Orthopaedic Surgery, Southern California Permanente Medical Group, Los Angeles, CA e Department of Neurosurgery, The Permanente Medical Group, Sacramento, CA b

a r t i c l e i n f o

a b s t r a c t

Article history: Received 9 April 2019 Received in revised form 5 August 2019 Accepted 23 August 2019 Available online xxx

Background: The impact of prior lumbar spinal fusion on the change in physical activity level following total hip arthroplasty (THA) has not been thoroughly examined. Therefore, we sought to compare the change in physical activity level following THA for patients with and without a history of lumbar spine fusion. Methods: Patients who underwent primary elective THA were identified using an integrated healthcare system’s Total Joint Replacement Registry (2010-2013). Prior lumbar spine fusion was identified using the healthcare system’s Spine Registry. Physical activity was self-reported by patients and measured in min/ wk. Generalized linear models were used to evaluate the association between prior spine fusion and the change in physical activity from 1 year pre-THA to 1-2 years post-THA. Results: Of 11,416 THAs, 90 (0.8%) had a history of lumbar spinal fusion. Patients with a prior lumbar fusion had a median physical activity level of 28 min/wk prior to THA compared to 45 min/wk in the patients with no history of lumbar spinal fusion. One year after THA, patients with a history of lumbar spinal fusion reported a median of 120 min/wk of physical activity compared to 150 min/wk for patients without a history of lumbar spinal fusion. The difference in physical activity level change between groups was not statistically significant (estimate ¼ 23.1, 95% confidence interval 62.1 to 15.9, P ¼ .246). Conclusion: Patients with prior lumbar fusion were found to have lower self-reported physical activity levels than patients without spine fusion both before and after THA surgery. However, both groups saw the same degree of improvement in physical activity level following THA. These findings may help in counseling patients who have had a prior lumbar spine fusion and in setting appropriate expectations prior to THA. © 2019 Elsevier Inc. All rights reserved.

Keywords: total hip arthroplasty spine lumbar fusion physical activity registry cohort study

Total hip arthroplasty (THA) is an effective treatment for endstage arthritis of the hip. However, certain predisposing medical

One or more of the authors of this paper have disclosed potential or pertinent conflicts of interest, which may include receipt of payment, either direct or indirect, institutional support, or association with an entity in the biomedical field which may be perceived to have potential conflict of interest with this work. For full disclosure statements refer to https://doi.org/10.1016/j.arth.2019.08.053. * Reprint requests: Adrian D. Hinman, MD, Department of Orthopaedic Surgery, The Permanente Medical Group, 2500 Merced Street, San Leandro, CA 94577. https://doi.org/10.1016/j.arth.2019.08.053 0883-5403/© 2019 Elsevier Inc. All rights reserved.

conditions are known to influence THA outcomes [1,2]. One of these, “hip-spine syndrome”, is well-documented in the literature and describes the coexistence of osteoarthritis of the hip joint and degenerative disc disease of the spine [3,4]. Several studies have found worse postoperative functional outcomes following THA for patients with lumbar spine disease compared to patients without [5e8]. More recent studies have reported on a variety of outcome measures for patients who undergo surgical treatment of lumbar disease before THA, including prosthetic-related complications [9], early complication rates within 90 days [10], dislocations of THA

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[11], and patient-reported outcomes (PRO) including pain, healthrelated quality-of-life, and patient satisfaction 1 year after THA [12,13]. One clear indicator of success following orthopedic surgery is patient satisfaction, with satisfaction rates following THA reported to be greater than 90% [14]. In the last decade, interest in patient satisfaction following total joint arthroplasty and spine surgery through use of validated PRO measures has increased [15e18]. The Centers for Medicare & Medicaid Services and large commercial insurance payers now consider the use of PRO necessary for assessing quality [19]. Physical function is a major component in many of these validated PRO measures. Higher patient expectations prior to THA have been found to correlate with improved functional scores following surgery [20]. Most patients undergoing THA and spine surgery expect to see improvements in physical function and activity following surgery. Mancuso et al. [21] found that 95% of patients undergoing THA expected to see improvements in their ability to exercise or play sports and 96% expected to see improvements in their ability to participate in recreational or social activities. Any evaluation of the successful outcome of hip and spine surgery therefore needs to consider the impact of these procedures on physical activity. Physical activity level is a more holistic assessment of a patient’s overall function, unlike other PRO that are validated for subjective measures in specific populations, such as leg pain following lumbar spine surgery or hip pain following THA. Prior studies have used physical activity level to individually evaluate the impact of lumbar stenosis [22], lumbar spine surgery [23], and THA [24e26]. The potential impact of spine surgery prior to THA on change in physical activity level following THA has yet to be evaluated. The objective of this study was to determine whether patients undergoing THA can expect to see an increase in their physical activity level after surgery and whether patients with a history of spine fusion see the same degree of change in physical activity as those without a history of spine fusion. Patients and Methods Study Design and Setting A retrospective cohort study was conducted using data from an integrated healthcare system’s Total Joint Replacement Registry (TJRR) and Spine Registry (SR) [27,28]. The exposure of interest was a history of instrumented lumbar spine fusion. We compared this cohort of patients to a cohort of patients with no reported history of instrumented lumbar spine fusion. The integrated healthcare system covers over 12.2 million lives throughout 8 geographical regions (Colorado, Georgia, Hawaii, Mid-Atlantic, Northern California, Northwest, Southern California, and Washington) in the United States. Data Sources The integrated healthcare system’s unique patient identifiers were used to link information from the electronic medical record and the 2 registries used in this study. The TJRR was established in 2001 and detailed information on its coverage, processes, validation rules, and available data has been published elsewhere [27,28]. In brief, this comprehensive surveillance tool for elective joint arthroplasty procedures covers all 8 geographical regions covered by the integrated healthcare system and reported 95% voluntary surgeon participation in 2011 [28]. The TJRR collects information on the procedure and patient via electronic and paper-based forms completed by surgeons performing the procedure and from other available data sources within the organization. The SR was

established in 2009 and captures records detailing procedure, diagnosis, surgical techniques, implants, and subsequent reoperations of all patients undergoing instrumented spine surgery in 4 regions (ie, Hawaii, Northern California, Northwest, and Southern California) of the integrated healthcare system [28]. Patients who underwent noninstrumented spine surgery were not included in the registry. All information in the SR is captured electronically via quarterly extractions from the patient’s hospitalization and operative records. The electronic health record (EHR), called HealthConnect, was the third data source and is an Epic-based product that was rolled out in 2004 and was fully implemented in all regions in 2008. Study Sample The study cohort was selected using the TJRR. All primary unilateral THA procedures in adult patients (18 years old) performed between January 1, 2010 and December 31, 2013 for any indication in the 3 largest regions (Northern California, Northwest, and Southern California) were identified. This timeframe was chosen because the SR includes patients from January 1, 2009 to December 31, 2013, and we wanted to ensure patients who underwent spine surgery had 1 year of pre-THA follow-up and had stabilized their postoperative activity levels in the recovery period. If patients had more than 1 primary THA during our study period only the first surgery was included in the sample. Exposure of Interest The exposure of interest was a history of an instrumented lumbar spine fusion and was compared to those without a history of an instrumented lumbar spine fusion. Instrumented lumbar spinal procedures included anterior lumbar interbody fusions, posterior lumbar interbody fusions, transforaminal lumbar interbody fusions, and posterior lateral lumbar fusions. All cases were supplemented with pedicle screws. Exposure status (history, no history) was identified through operative dates using the SR and TJRR registries. Our SR identifies patients who have undergone instrumented spine fusions. Any patient who had noninstrumented lumbar spine fusion or underwent lumbar spine fusion at an outside hospital prior to enrolling in our healthcare plan would be captured in the non spine surgery cohort. A lumbar spine operative date prior to the THA operative date was regarded as having a lumbar spine fusion history. Patients with a history of a prior spine surgery in the cervical or thoracic regions were excluded (n ¼ 67). Outcome of Interest The outcome of interest was the change in patient self-reported physical activity (measured in min/wk) from before (within 1 year) to after THA surgery (1-2 years postoperative) [26,29]. In cases where a patient had multiple physical activities reporting dates pre-THA, the average minutes per week was used to capture the average activity level. In cases where the patient had multiple report dates post-THA, we chose the date that had the maximum level of minutes per week to represent the greatest improvement in activity level during this period. We chose to use average physical activity level during the period prior to THA as this period reflects the patient’s baseline status during which they are not recovering from a procedure. During the interval following THA surgery, we chose the highest reported physical activity level because we considered the patients at this point to be in an active state of recovery with changing physical activity levels over time. The EHR system was used to identify the self-reported physical activity level of patients in the study sample. Physical activity information was

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Table 1 Study Cohort Characteristics, Overall and by Prior Spine Fusion Status (2010-2013). Prior Spine Surgery Total Sample

Total N Age at THA (y) Mean (SD) Range Gender Female Male Race/ethnicity Asian Black Hispanic Multiracial Native American Other White THA intraoperative BMI (kg/m2) <30 30-34 35 THA ASA classification 1-2 3 No. of comorbidities at THA 0 1 2 3 4 5 THA surgical indicationa Osteoarthritis Osteonecrosis Other Post-traumatic arthritis THA operative side Left Right THA operative year 2010 2011 2012 2013 Spine surgical indication Deformity Herniated disc/myelopathy/stenosis Other Spondylolisthesis Spinal levels fused 1-2 levels 3 levels Surgical approach Combined Direct anterior Posterior

No History

History

n

(%)

n

(%)

n

11,416

100.0

11,326

99.2

90

66.5 (10.8) 18-93

66.4 (10.8) 18-93

(%) 0.8 70.2 (8.7) 47-84

6656 4760

58.3 41.7

6590 4736

58.2 41.8

66 24

73.3 26.7

412 1038 1127 53 25 27 8678

3.6 9.1 9.9 0.5 0.2 0.2 76.4

411 1028 1120 53 25 27 8606

3.7 9.1 9.9 0.5 0.2 0.2 76.4

1 10 7 0 0 0 72

1.1 11.1 7.8 0.0 0.0 0.0 80.0

6960 2857 1599

61.0 25.0 14.0

6901 2837 1588

60.9 25.1 14.0

59 20 11

65.6 22.2 12.2

6980 4096

63.0 37.0

6941 4046

63.2 36.8

39 50

43.8 56.2

1446 2388 2463 1745 1014 942

14.5 23.9 24.6 17.5 10.1 9.4

1440 2372 2444 1727 1006 930

14.5 23.9 24.6 17.4 10.1 9.4

6 16 19 18 8 12

7.6 20.3 24.0 22.8 10.1 15.2

10,787 513 24 61

94.5 4.5 0.2 0.5

10,701 509 24 61

94.5 4.5 0.2 0.5

86 4 0 0

95.6 4.4 0.0 0.0

5057 6358

44.3 55.7

5019 6306

44.3 55.7

38 52

42.2 57.8

1153 1911 3985 4367

10.1 16.7 34.9 38.3

1146 1903 3953 4324

10.1 16.8 34.9 38.2

7 8 32 43

7.8 8.9 35.6 47.8

e e e e

e e e e

e e e e

e e e e

17 56 4 13

18.9 62.2 4.4 14.4

e e

e e

e e

e e

66 24

73.3 26.7

e e e

e e e

e e e

e e e

7 2 81

7.8 2.2 90.0

Missing data: race (n ¼ 56, 0.5%), ASA (n ¼ 340, 3.0%), comorbidities (n ¼ 1418, 12.4%), and operative side (n ¼ 1, <0.1%). ASA, American Society of Anesthesiologists; BMI, body mass index; SD, standard deviation; THA, total hip arthroplasty. a Patient can have more than one surgical indication.

introduced to the EHR’s outpatient encounters “vital signs” recordings in 2009 and was recorded by nursing staff at all visits. Patients report on 2 questions: “On average, how many days per week do you engage in moderate to strenuous exercise (like a brisk walk)?,” for which the response can be 0-7 days; and (2) “On average, how many minutes do you engage in exercise at this level?,” for which the response can be in minutes from 10 to 150 in blocks of 10 minutes, or 150þ if more than 150 per day [27]. Patients with no physical activity information recorded for both preTHA and post-THA timeframes were excluded (n ¼ 8001). Because of this number of missing values, we compared patients with and

without lumbar spine fusion and their missing patterns to assure there was no differential bias between the groups. Covariates Patient age (continuous, per 1 year increment), gender (male vs female), race (Asian, Black, Hispanic, Multiracial, Native American, Other, White), body mass index (35, 30-34.9, <30 kg/ m2), American Society of Anesthesiologist classification (3 vs 12), number of Elixhauser comorbidities (continuous, per 1 unit increment) [30], indication for surgery (osteonecrosis, post-

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Fig. 1. Physical activity level (in min/wk) before and after THA by prior lumbar spine fusion status. Median average physical activity pre-THA in blue, median maximum physical activity 1-y post-THA in red, and median difference between pre-THA and post-THA physical activity levels in green.

traumatic arthritis, osteoarthritis, other), and operative year (continuous, per 1 year increment) were investigated as potential confounders. Statistical Analysis Means, standard deviations, medians, interquartile ranges (IQRs), frequencies, and proportions were used to describe the study cohort. Because change in physical activity from pre-THA to 1-2 years post-THA was not found to be normally distributed, generalized linear models were used to evaluate the association between lumbar spine fusion prior to THA and the change in physical activity level. Crude and adjusted associations of lumbar spine fusion prior to THA with change in physical activity from preTHA to post-THA, including maximum likelihood estimates and P values, are presented. Confounders included in the final adjusted model were defined as covariates that changed the estimate by at least 10% and were associated with outcome of physical activity level change. Data were analyzed using SAS (version 9.4, SAS Institute, Cary, NC). All tests were 2-sided and 0.05 was used as the threshold for statistical significance. Ethics The study was approved by the institutional review board (IRB #5488) before starting the investigation. No external funding was obtained or used.

Results The final sample consisted of 11,416 THAs from 3 regions, 38 hospitals, and 202 joint replacement surgeons. Of the 11,416 patients who underwent primary THA during the study period, 90 (0.8%) had a prior instrumented lumbar spine fusion and 11,326 had no history of instrumented lumbar spine fusion. Spine fusion procedures occurred 122-1634 days (0.3-4.5) prior to the THA procedure, with the median time being 1.4 years prior to surgery (IQR 0.7-2.6). The study cohort characteristics by prior spine fusion status are in Table 1. The mean age at THA for the total study sample was 66.5 years old (standard deviation ¼ 10.8) and the majority of patients were female (58.3%), white (76.4%), with a body mass index <30 kg/m2 (61.0%), an American Society of Anesthesiologist classification between 1 and 2 (63.0%), and had osteoarthritis as the THA indication (94.5%). Of the patients with prior lumbar spine fusion, most procedures were done for herniated discs/myelopathy/stenosis (62.2%) using a posterior approach (90.0%). Median pre-THA physical activity level was 45 (IQR 0-130) min/wk for patients without prior spine fusion and 28 (IQR 0-98) min/wk for those with a history of prior spine fusion (Figure 1). One year after THA, the median physical activity level increased to 150 (IQR 40-270) and 120 (IQR 0-180) min/wk, respectively. After adjusting for identified confounders, no difference was observed in the change in pre-THA to post-THA physical activity level when patients with a prior fusion were compared to those without a prior fusion (estimate ¼ 23.1, 95% confidence interval 62.1 to 15.9, P ¼ .246) (Table 2).

Table 2 Crude and Adjusted Estimates for Change in Physical Activity (in min/wk) After THA Surgery by Prior Lumbar Spine Fusion Status (N ¼ 11,371)a.

Prior fusion vs no prior fusion

Crude Estimate (95% CI)

P Value

Adjusted Estimate (95% CI)b

P Value

19.4 (55.5 to 16.6)

.291

23.1 (62.1 to 15.9)

.246

CI, confidence interval; THA, total hip arthroplasty. a Change in physical activity is calculated as the difference from maximum post-THA physical activity and average pre-THA physical activity. n ¼ 45, 0.4% patients missing either pre-THA or post-THA physical activity data to calculate change in physical activity. b Adjusted for number of comorbidities.

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Discussion Although outcomes following THA are predictably positive, certain physiologic and anatomic patient characteristics are known to be associated with increased rates of complications and worse functional outcomes [1,2,31]. Spinal fusion can alter spinopelvic biomechanics and consequently complicate THA outcomes [32e34]. Patients undergoing THA surgery expect to see improvements in physical function and activity level and preoperative expectations correlate with patient satisfaction following THA surgery. Consequently, we sought to determine the change in patient-reported physical activity (measured in min/wk) from preTHA to post-THA and whether this change differed between patients with and without a history of lumbar spine fusion. Although patients with a history of lumbar fusion had a lower level of physical activity both before and after THA, improvements in physical activity level post-THA were observed for both groups and the absolute increase in physical activity level was similar between groups. This finding suggests that lumbar disc disease has an independent negative impact on physical activity level, but this does not reduce the positive impact of THA surgery on improvements in physical activity level. Prior studies analyzing change in physical activity level following THA have reported conflicting findings. Two registrybased studies reported increased physical activity levels following THA [26,35], while 1 observational cohort study and 2 metaanalyses found no improvements following surgery [36e38]. Furthermore, 1 meta-analysis reported that postoperative physical activity levels following THA remained lower than baseline physical activity levels of healthy controls [36]. Recent studies have examined the influence of prior lumbar fusions following THA. Studies using Medicare data found a higher rate of complications for patients with lumbar fusions, including hip dislocations, revisions, loosening, and prosthetic-related complications [9,11,39]. The complication rate was shown to correlate with the number of levels fused. Barry et al. [10] found similar results for the early (<90 days) postoperative outcomes including hip complications, readmissions, reoperations, distance walked on postoperative day 1, length of stay, and discharge disposition. Two additional studies found worse PRO measures, less satisfaction, and more pain for THA patients who had prior spine surgery [12,13]. In general, these 2 studies found similar results to ours in that prior lumbar spine surgery negatively impacts post-THA outcomes. However, we need to acknowledge the difference in these studies compared to ours. Eneqvist et al. [12] included all lumbar spine surgeries, which meant a heterogenous mixture of fusion and nonfusion patients. Their outcome measures were also different from the ones evaluated in the present study, theirs included the visual analog scale (VAS) for hip pain, the Euro-Qol 5D health status questionnaire, and the VAS score addressing general health (Euro-Qol VAS). Loh et al. [13] used the Short Form-36 and the Western Ontario and McMaster Universities Arthritis Index score. The equivalence between these outcomes and physical activity has not been established. Chapman et al. [40] pointed out that after lumbar spine surgery, pain may not be the only factor responsible for changes in physical activity, but rather a more holistic measure should be considered. These are 2 distinct outcome measures that may correlate but are not equivalent. Patients may have low satisfaction for a variety of reasons that are distinct from their physical activity level. Moreover, using Short Form-36 and Western Ontario and McMaster Universities Arthritis Index, neither of which have an established minimal clinically important difference in the THA population [13], limits the conclusions made based on these outcome measures. We acknowledge that there are limitations to this cohort study. Because our study is retrospective, there is potential for selection bias. As our SR only identifies instrumented spine fusions, it is

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possible that our non-spine fusion history group contained patients who had undergone noninstrumented spine fusion. However, nearly 100% of all lumbar spine fusions performed in our institution are instrumented, and with only 90 cases of spine fusion out of more than 11,000 THA, the impact of the inclusion of these few cases on the non-spine fusion history cohort would be extremely limited. It is possible that a patient underwent a lumbar spine fusion at a different institution or had one prior to the initiation of the implementation of the SR and was misclassified as not having a prior lumbar spine fusion. However, healthcare plan members have little incentive to seek care outside of the integrated healthcare system. Furthermore, any misclassification of prior spine fusion patients would bias effect estimates toward the null value of zero. Additionally, patients with diagnoses of spinal stenosis and degenerative changes of the spine who have not had prior spine surgery have been shown to have worse postoperative outcomes following THA. Our non-spine fusion cohort may have included some of these patients, which in turn would have influenced the reported physical activity levels of the non-spine fusion cohort, again biasing the effect estimates toward the null value of zero. Reported physical activity is subjective, relying on patients’ recall of their daily activity. To our knowledge, this is the first study to evaluate patient-reported physical activity for those undergoing 2 different surgical procedures, specifically prior spine fusion and THA. Further study is necessary to validate its use for evaluating the influence of a prior surgical procedure on a current procedure. Finally, due to the limited number of THA patients with prior lumbar fusions, subgroup analysis to determine the effect of number of levels fused, or the type of approach for the fusions (eg, anterior lumbar interbody fusions and posterior lumbar interbody fusions), could not be done. The strengths of the present study include the use of our institution’s TJRR and SR, which prospectively capture information on a predefined set of data, increasing internal validity. Furthermore, members in our integrated healthcare system have been found to be representative of the geographic regions served [41,42], increasing generalizability. Conclusions Patients with prior instrumented lumbar spine fusion were found to have lower baseline self-reported physical activity levels than patients without. However, patients with prior lumbar spine fusion saw the same degree of improvement in physical activity level following THA as patients without a history of prior lumbar spine fusion. These findings may help in counseling patients who have had a prior lumbar spine fusion and in setting appropriate expectations prior to THA. Acknowledgments The authors acknowledge the Kaiser Permanente orthopedic surgeons who contribute to the Kaiser Permanente Total Joint Replacement Registry, as well as orthopedic spine surgeons and neurosurgeons who also contributed to the Kaiser Permanente Spine Registry. We also like to acknowledge the Surgical Outcomes and Analysis Department staff, who coordinate registry operations including Jessica E. Harris, MS and Brian H. Fasig, PhD for their ongoing support of these registries. References [1] MacWilliam CH, Yood MU, Verner JJ, McCarthy BD, Ward RE. Patient-related risk factors that predict poor outcome after total hip replacement. Health Serv Res 1996;31:623e38.

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