Specialty-related differences in diagnosing hip–spine syndrome: a multi-center retrospective cohort study

Abstract

Background

Hip-spine syndrome (HSS) poses a diagnostic challenge because lumbar degenerative disease, sacro-iliac joint dysfunction, and hip osteoarthritis often produce overlapping symptoms. The suboptimal diagnostic pathways may contribute to adverse clinical outcomes. Earlier work suggested that orthopaedic surgeons more consistently obtain hip imaging than neurosurgeons when treating patients who ultimately require both lumbar and hip operations. Whether this observation holds in a tertiary-care electronic medical-record (EMR) setting remains unknown.

Methods

We queried the Chang Gung Research Database (CGRD), the largest multi-institutional EMR repository in Taiwan, for patients aged 50–85 years who underwent both hip arthroplasty and lumbar surgery within the same 12-month period between 2001 and 2024. Cohorts were categorised as hip-then-spine (HS, n = 58), spine-then-hip (SH, n = 223), or simultaneous procedures (Both, n = 2). SH patients were stratified by the specialty of the spine surgeon: orthopaedic (OS, n = 104) versus neurosurgical (NS, n = 111). Primary outcomes were (1) pre-operative ordering of combined spine + pelvis/hip radiography and (2) documentation of hip pathology before spine surgery. Group differences were analysed with χ² or Student’s t tests (α = 0.05).

Results

Combined spine-and-hip imaging was obtained significantly more often by OS than by NS (73.1% vs. 51.4%; p < 0.001; FDR q-value: 0.002). Hip osteoarthritis or osteonecrosis was recorded pre-operatively in 26.9% of OS cases versus 21.6% of NS cases, a non-significant difference attributable to limited sample size (p = 0.364). The SH:HS ratio showed approximately 4:1, indicating that spine surgery typically precedes hip arthroplasty in routine practice.

Conclusions

Within a tertiary-care EMR database, orthopaedic surgeons were more likely than neurosurgeons to order comprehensive spinopelvic imaging, thereby enhancing detection of hip pathology in patients with suspected HSS. These findings underscore the importance of mandated and standardized pre-operative hip/pelvic imaging before lumbar surgery and support efforts to harmonise diagnostic protocols across specialties.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12891-025-09479-x.

Background

Lumbar spinal stenosis-related referred pain, sacroiliac joint (SIJ) pathology, and degenerative hip osteoarthritis frequently present with overlapping clinical manifestations. Accurate differentiation relies on careful history taking, focused physical and neurologic examinations, and selective local anesthetic blocks [1, 2]. According to the literature, 12.5–17.5% of patients with low-back pain that radiates caudally are found to have concurrent spine and hip disease or a combination of spine pathology and SIJ dysfunction, whereas the simultaneous presence of spine, SIJ, and hip disorders is observed in fewer than 2% of cases [3, 4].

Hip-spine syndrome was first described by Offierski and Macnab in 1983 [5]. Hip–spine syndrome can be stratified into four categories on the basis of the interaction between hip and spinal pathology: simple, mixed, complex, and misdiagnosed. Recent literature highlights the importance of an integrated hip–spine diagnostic approach that begins with a comprehensive history, neurological assessment, and site-specific provocative maneuvers. Every surgeon should be well-versed in both hip- and spine-specific examinations. Radiographic evaluation should routinely include spinopelvic parameters in the standing, upright-seated, and deep-flexed-seated positions to assess dynamic spinopelvic mobility. The EFORT Open review 2023 recommends four standard radiographs over spinopelvic region. These updated imaging protocols improve diagnostic sensitivity and support a more consistent interdisciplinary evaluation between hip and spine specialists [6].

The optimal order of surgical intervention in hip–spine syndrome remains unsettled [7]. Certain studies have linked performing spinal fusion first with a higher incidence of subsequent hip dislocation, whereas some experts contend that addressing the spine first may lower the risk of neural injury [8]. At present, a definitive consensus has yet to be established [9, 10].

Accurate diagnosis is paramount; consequently, pre-operative imaging must be sufficiently comprehensive to encompass both the spine and the hip if the likelihood of correct diagnostic attribution is to be maximized [11, 12]. Prior investigations involving patients with concomitant spinal and hip pathology have compared the performance of orthopaedic and neurosurgical specialists, attributing observed differences chiefly to variations in residency training. Neurosurgeons typically gain more intensive exposure to spinal procedures, whereas orthopaedic surgeons are trained across the full spectrum of spinal as well as appendicular musculoskeletal surgery [13]. Overall, the different diagnostic pathways between specialties may lead to tangible clinical consequences including: Delaying the definitive diagnosis of a coexisting hip or spine condition; Contributing to suboptimal early outcomes after the first operation; Potentially leading to incorrect surgical sequencing. A recent meta-analysis by Huppert et al. (2024) demonstrated that patients undergoing lumbar spinal fusion prior to total hip arthroplasty have a 3-fold increased risk of hip dislocation compared to the reverse sequence [7].

Despite consensus that integrated assessment is essential, there is a lack of EMR-based multicenter evidence on specialty-driven diagnostic variability. To address this gap, we leveraged a large, multi-institutional EMR database to compare specialty-specific diagnostic pathways and preoperative imaging completeness in patients who ultimately required both hip and lumbar surgery. Specifically, we compared orthopaedic and neurosurgical practitioners to ascertain which specialty more consistently orders comprehensive spine–hip imaging and achieves a more thorough and accurate pre-operative diagnosis.

Methods

Data source

This was a retrospective, multi-center study using the Chang Gung Research Database (CGRD). The CGRD is the greatest multi-institutional electronic medical records (EMR) database in Taiwan. It was derived from medical records of Chang Gung Memorial Hospital (CGMH) which is also the largest hospital system alliance in Taiwan. 15-year longitudinal data could be aggregated in detailed standardization format. Not only secondary data from billing order or charge codes, the CGRD has a more comprehensive dataset with original data, which may be better than national database like the Taiwan National Health Insurance Research Database (NHIRD). Compared with the NHIRD and medical-center cohorts in Taiwan, patients captured in the CGRD typically present with higher Charlson Comorbidity Index scores and a greater prevalence of select comorbidities, suggesting that the CGRD is particularly well suited for research on populations with more severe and complex diseases [14]. This study was approved by the Research Ethics Committee of Chang Gung Medical Foundation Institutional Review Board (no. 201801118B0).

Study population

First, we applied predefined diagnostic codes to identify all patients who had concurrent diagnoses of both spinal disorders and hip-joint diseases in CGRD. Preoperative documentation of hip pathology was identified through review of outpatient and inpatient medical records, diagnostic codes (ICD-10 M16, M87), and imaging or follow-up documentation. A case was considered positive if any of these sources indicated hip pathology, including hip osteoarthritis, or avascular necrosis. Combined spine + pelvis/hip radiography was defined as the presence of both lumbar spine (AP and/or lateral) (code 32011 C / 32012 C) and pelvic or hip radiographs—such as KUB (code 32006 C) or pelvis AP (code 32022 C)—that provided visualization of the hip joint. Advanced imaging studies (CT or MRI) were also included when available but were not required. The preoperative time window was defined as imaging performed within six months before surgery, reflecting local clinical practice and health insurance policy.

Next, we identified specific procedure codes, including total hip arthroplasty (64162B), partial hip arthroplasty (64170B), fusion surgery (83043B, 83044B, 83045B, or 83046B), laminectomy (83002–83003 C), or lumbar discectomy (83024 C). We extracted data on patients aged 50–85 who had undergone both hip and spine surgeries within the same 12-month period (total: 463). The age range of 50–85 years was selected based on epidemiological evidence indicating that this window represents the peak incidence of both degenerative lumbar spinal stenosis [15] and end-stage hip osteoarthritis requiring arthroplasty [16]. As noted in seminal reviews on Hip-Spine Syndrome, the concurrence of these two pathologies is predominantly a phenomenon of the aging spine and hip [17].

The inclusion and exclusion criteria

Inclusion

Age 50–85 with undergone both hip and spine surgeries within the same 12-month period.

Exclusion

(1) Hip and/or spine fracture; (2) Benign/malignant tumor; (3) Infections; (4) Complications (surgical/medical); (5) Cervical spine related; (6) No OS/NS clinic 6 months before first surgery.

Diagnostic and procedural ascertainment followed prespecified code lists spanning ICD-9-CM/ICD-10-CM for diagnoses and hospital order codes for surgeries and imaging. The complete code sets used to identify hip/spine diagnoses, operative procedures, and radiographic/advanced imaging orders are provided in Appendix / Supplementary Table S1.S2.S3.S4. In our analytic dataset, key variables—including age, sex, specialty, index surgery type and date, diagnostic codes, and imaging orders/dates—were fully observed at extraction; consequently, no complete-case analysis or imputation was performed [14].

We collected all the remaining patients’ demographic data, including surgeon specialty, the timing and items of radiographic examination and discharge diagnoses. We subsequently stratified the cohort into three groups according to the timing and sequence of their hip and spine surgeries: (1) underwent hip and spine surgery at the same admission (Both), (2) hip surgery prior to spine surgery (HS), and (3) spine surgery prior to hip surgery (SH). Patients in the SH (spine surgery prior to hip surgery) group were further subdivided into (1) spine surgery performed by an orthopedic surgeon (OS) or (2) spine surgery performed by a neurosurgeon (NS).

Statistics

Primary comparisons were evaluated using multivariable logistic regression with imaging utilization. We report odds ratios (ORs) with 95% confidence intervals (CIs). To address multiplicity across related outcomes, we controlled the false discovery rate (FDR) using the Benjamini–Hochberg procedure and report q-values (significant at q < 0.05) in addition to raw P-values [18]. Descriptive statistics of the Both, HS, and SH groups were performed, including age, sex, the items and timing of image, Charlson Comorbidity Index (CCI), and specialty of the surgeon. Differences between the OS and NS groups were assessed using independent Student’s t-test for continuous variables and Chi-Square test for nominal variables. Significance was defined as p < 0.05 in two-tailed testing. We also conducted a post hoc power assessment using the observed sample sizes, two-sided α = 0.05, and the effect estimates from the main comparisons.

Results

From the CGRD, we initially identified 463 patients aged 55–85 who underwent both spine-related surgery and hip arthroplasty within the same 12-month window. After applying the Fig. 1 exclusion criteria (eliminating 180 cases), 283 patients remained for analysis. Among these patients, 2 were included in Both group (hip and spine procedures during the same admission), 58 were categorized in HS group (hip surgery performed before spine surgery), and 223 were included in SH group (spine surgery performed before hip surgery).

Fig. 1.

Flowchart of Patient Identification and Inclusion/Exclusion. A total of 463 patients who underwent both spine and hip surgery within a single 12-month interval were retrieved from the CGRD (Chang Gung Research Database). After excluding 180 cases involving trauma, neoplasm, infection, or procedure-related complications, the remaining patients were allocated to three groups according to surgical sequence. Within the spine-then-hip (SH) group, cases were further stratified by the specialty of the spine surgeon—orthopaedic surgery (OS), neurosurgery (NS), or other subspecialties

All hip operations were carried out by orthopaedic surgeons. Spine procedures were further stratified by surgical specialty into orthopaedic surgeon (OS) and neurosurgical surgeon (NS) subgroups. Comprehensive demographic characteristics, length of stay, interval between the two operations, Charlson Comorbidity Index scores, and genders are collected from this EMR database (Table 1). These patients were aged around 50, and the duration between these 2 admissions was more than 5 months. More females were collected in this cohort.

Table 1.

Demographics, length of stay, and Charlson comorbidity index (CCI) for each group

Characteristics	Hip and Spine Surgery in the Same Admission (Both) (n = 2)		Hip Before Spine Surgery (HS) (n = 58)		Spine Before Hip Surgery (SH) (n = 223)
Age	58.50 (4.95)		65.26 (7.31)		68.84 (8.75)
1st hospital stays	36.0 (41.01)		5.43 (2.11)		8.66 (6.50)
1st + 2nd hospital stays	36.0 (41.01)		15.98 (9.30)		15.10 (9.23)
Duration between admissions	-		195.71 (96.32)		149.15 (93.88)
CCI at 1st admission	0.50 (0.71)		0.40 (0.67)		0.43 (0.88)
CCI at 2nd admission	-		0.74 (1.83)		0.53 (1.16)
Gender	n	%	n	%	n	%
Female	0	0.00	34	58.60	158	70.90
Male	2	100.00	24	41.40	65	29.10

In multivariable models adjusting for age, sex, CCI, surgical year/epoch, and combined hip-focused imaging remained directionally consistent with the unadjusted findings (see Table 2). None of the additional covariates materially changed the magnitude or significance of the specialty effect; after FDR correction, inferences were unchanged. The specialty distribution of surgeons across the study cohorts is different in these three groups (Table 3). Within the SH group, 46.64% of spine operations were performed by orthopaedic surgeons, whereas 49.78% were carried out by neurosurgeons. Overall, only about 15–20% of patients had consulted both orthopaedics and neurosurgery in the preoperative period.

Table 2.

Preoperative KUB and pelvis AP: confounding variables with logistic regression analysis

Characteristics	Univariate				Multivariate
	OR	95% CI		P-value	OR	95% CI		P-value	FDR (q-value)
		Lower	Upper			Lower	Upper
Preoperative KUB
Age	1.03	1.00	1.06	0.044	1.03	1.00	1.06	0.078	0.234
Sex	0.74	0.44	1.22	0.236	0.75	0.44	1.28	0.294	0.310
CCI at 1st admission	1.18	0.85	1.63	0.316	1.27	0.85	1.90	0.244	0.310
CCI at 2nd admission	0.94	0.79	1.13	0.532	0.89	0.72	1.11	0.310	0.310
Surgical year	1.07	1.01	1.13	0.012	1.06	1.00	1.12	0.043	0.234
Preoperative pelvis AP
Age	0.99	0.97	1.02	0.716	0.99	0.96	1.02	0.558	0.622
Sex	1.02	0.60	1.73	0.951	1.15	0.66	2.00	0.622	0.622
CCI at 1st admission	1.26	0.93	1.71	0.135	1.11	0.80	1.55	0.532	0.622
CCI at 2nd admission	1.18	0.98	1.42	0.082	1.17	0.95	1.45	0.136	0.272
Surgical year	1.06	1.00	1.12	0.049	1.07	1.01	1.13	0.026	0.078

* The OR (odds ratio): the odds in the NS relative to the odds in the OS (i.e., NS vs. OS)

• Values are n (%) unless otherwise indicated.; CI = confidence interval; q = FDR-adjusted P-value (Benjamini–Hochberg)

Table 3.

Comparison of the numbers of surgeries performed by orthopedic surgeons and neurosurgeons

	Hip and Spine Surgery in the Same Admission (Both) (n=2)		Hip Before Spine Surgery (HS) (n=58)		Spine Before Hip Surgery (SH) (n=223)
	n	%	n	%	n	%
First surgery by orthopedic surgeon	2	100.00	58	100.00	104	46.64
First surgery by neurosurgeon	0	0.00	0	0.00	111	49.78
Second surgery by orthopedic surgeon	-	-	36	62.07	203	91.03
Second surgery by neurosurgeon	-	-	15	25.86	0	0.00
Orthopedic clinic visit before first surgery (<6 months)	2	100.00	58	100.00	146	65.47
Neurosurgery clinic visit before first surgery (<6 months)	1	50.00	9	15.52	121	54.26
Orthopedic and neurosurgery clinic visits before first surgery	1	50.00	9	15.52	44	19.73

The preoperative imaging patterns across the three cohorts are detailed in Table 4. In the both-group, every patient underwent both spinal radiography and a KUB study. Among the HS group, roughly 40% had a spine X-ray prior to surgery, whereas this proportion rose to 80.27% in the SH group. Conversely, pelvic radiography was far more common in the HS cohort—performed in 81.03% of patients—while only 21.08% of those in the SH group received the same examination. To further assess the impact of having seen both specialties on imaging utilization, we divided the cohort into three groups and compared them in a pairwise manner. Regarding imaging utilization among patients with dual consultations (OS + NS), the patterns for KUB and spine AP resembled those of the NS-only group, whereas pelvis AP utilization was more consistent with the OS-only group (Tables 5 and 6).

Table 4.

Comparison of preoperatively arranged imaging studies in each group

Characteristics	Hip and Spine Surgery in the Same Admission (Both) (n = 2)		Hip Before Spine Surgery (HS) (n = 58)		Spine Before Hip Surgery (SH) (n = 223)
	n	%	n	%	n	%
Had spinal AP and spine lateral X-rays before first surgery	2	100.00	23	39.66	179	80.27
Had KUB X-ray before first surgery	2	100.00	30	51.72	139	62.33
Had pelvic X-ray before first surgery	0	0.00	47	81.03	47	21.08

Table 5.

Comparison of preoperative images (both vs OS)

Characteristics	Orthopedic and neurosurgery clinic visits before first surgery (n=54)		Orthopedic clinic visits before first surgery (n=152)		p-value
	n	%	n	%
Had spinal AP and spine lateral X-rays before first surgery	44	81.48	96	63.16	0.017
Had KUB X-ray before first surgery	29	53.70	109	71.71	0.019
Had pelvic X-ray before first surgery	24	44.44	64	42.11	0.873

Table 6.

Comparison of preoperative images (both vs NS)

Characteristics	Orthopedic and neurosurgery clinic visits before first surgery (n=54)		Neurosurgery clinic visit before first surgery (n=77)		p-value
	n	%	n	%
Had spinal AP and spine lateral X-rays before first surgery	44	81.48	64	83.12	0.819
Had KUB X-ray before first surgery	29	53.70	33	42.86	0.286
Had pelvic X-ray before first surgery	24	44.44	6	7.79	<0.001

Diagnosis documentation revealed a marked asymmetry between the cohorts (Table 7). While the HS group had high documentation rates for hip-related pathologies, the SH group demonstrated near-universal documentation of spine disorders but notably low rates of preoperative hip-related diagnoses (all < 18%). This diagnostic gap for hip pathology in the SH group persisted through discharge, with the combined frequency of hip-related diagnoses remaining low at approximately 15%.

Table 7.

Comparison of the diagnoses in each group

Characteristics	Hip and Spine Surgery in the Same Admission (Both) (n = 2)		Hip Before Spine Surgery (HS) (n = 58)		Spine Before Hip Surgery (SH) (n = 223)
	n	%	n	%	n	%
Had spinal disease-related diagnosis before surgery	2	100.00	37	63.79	219	98.21
Had hip osteoarthritis diagnosis before surgery	0	0.00	44	75.86	40	17.94
Had hip osteonecrosis diagnosis before surgery	1	50.00	30	51.72	21	9.42
Had spine-related-diagnosis at first discharge	2	100.00	8	13.79	195	87.44
Had hip-related diagnosis at first discharge (osteoarthritis)	0	0.00	39	67.24	21	9.42
Had hip-related diagnosis at first discharge (osteonecrosis)	1	50.00	26	44.83	11	4.93

We further subdivided the SH group by spine surgeon specialty into orthopedics (OS) and neurosurgery (NS) to examine whether preoperative imaging orders differed between the two specialties (Table 8). In the OS group, 79.81% of patients received spine radiograph before surgery, yet as many as 73.08% underwent a combined study that included a spine X-ray plus either a KUB or pelvic radiograph. By contrast, in the NS group, 81.68% had a spine X-ray, whereas just 51.35% obtained both spine and hip films. After FDR adjustment, the statistical conclusions were unchanged; findings significant at P < 0.05 remained significant at q < 0.05. For the primary imaging outcome, the post hoc power to detect the observed between-specialty difference at α = 0.05 (two-sided) was 0.913, indicating adequate power (> 0.80). When comparing OS and NS imaging utilization in the SH group. The difference was 73.1% − 51.4% = 21.7%. This represents an Absolute Risk Difference of 21.7% points (95% CI: 10.3% to 33.1%) (Fig. 2). Overall, orthopaedic surgeons ordered combined spine-and-hip imaging more frequently, whereas neurosurgeons more often relied on spine radiographs alone—an inter-group difference that reached statistical significance. We further sought to determine whether the trends in preoperative imaging orders paralleled those in diagnostic documentation (Table 9). The pattern persists: patients in the OS group had higher pre-operative rates of both spine-related and hip-related diagnoses than those in the NS group, although the differences did not achieve statistical significance.

Table 8.

Comparison of preoperative imaging studies

	Spine Surgery Was Performed by OS (n = 104)	Spine Surgery Was Performed by NS (n = 111)	p-Value	G-Power a	FDR b (q-value)
Preoperative spinal X-ray<6 months	83 (79.81)	94 (81.68)	0.349	0.064	0.349
Preoperative spine X-ray + KUB or pelvic X-ray <6 months	76 (73.08)	57 (51.35)	<0.001	0.913	0.002

^aG-power: adequately powered at >0.8

^bq, FDR-adjusted P-value by the Benjamini–Hochberg method. Reported q-values are computed within the family of tests shown in this table; significant at q < 0.05

Fig. 2.

Specialty-related difference in the rate of comprehensive pre-operative imaging in the spine-then-hip (SH) cohort. The bar chart compares the percentage of patients in the SH group who received combined spine X-ray plus KUB or pelvic X-ray within six months before their first (spine) surgery, stratified by the specialty of the spine surgeon. Orthopaedic surgeons (OS, n = 104) ordered comprehensive combined imaging significantly more often than neurosurgeons (NS, n = 111). The observed difference of 73.1% vs. 51.4% was statistically significant (p < 0.001), with a calculated G-power of 0.913 and an FDR-adjusted q-value of 0.002. Error bars represent the 95% confidence intervals (CIs). This figure is derived from the primary outcome presented in Table 9

Table 9.

Comparison of diagnoses of spinal or hip disorders

	Spine Surgery Was Performed by OS (n = 104)	Spine Surgery Was Performed by NS (n = 111)	p-Value	G-Power a	FDR b (q-value)
Spine-related diagnosis before surgery	104 (100.00)	108 (97.30)	0.247	0.416	0.364
Hip-related diagnosis before surgery	28 (26.92)	24 (21.62)	0.364	0.147	0.364

^aG-power: adequately powered at >0.8

^bq, FDR-adjusted P-value by the Benjamini–Hochberg method. Reported q-values are computed within the family of tests shown in this table; significant at q < 0.05

While several comparisons did not reach statistical significance, these estimates should be interpreted in light of the available sample size and corresponding confidence-interval widths, which may limit power to detect modest differences. Emphasis is therefore placed on effect sizes and 95% CIs to convey the precision of the estimates.

Further univariate logistic regression analyses were performed, and the odds in the NS group relative to the odds in the OS group was calculated the odds in the OS group was calculated the odds in the OS group was calculated (Table 10). Consistent with our main message, OS and NS did not differ in spine imaging or spine diagnosis rates, whereas the key difference persisted in the ordering of KUB or pelvic AP radiographs.

Table 10.

Comparison of preoperative imaging studies and diagnoses of spinal or hip disorders (NS vs OS)

Characteristics	Univariate
	*OR	95% CI		P-value
		Lower	Upper
Preoperative spinal imaging studies		0.69	2.83	0.350
X-ray (< 6 months)	1.40	0.69	2.83	0.350
X-ray + KUB or pelvic X-ray (< 6 months)	0.39	0.22	0.69	0.001
Diagnoses
Spine-related diagnosis before surgery	0.00	0.00	-	0.999
Hip-related diagnosis before surgery	0.75	0.40	1.40	0.365

* The OR (odds ratio): the odds in the NS relative to the odds in the OS (i.e., NS vs. OS)

• Values are n (%) unless otherwise indicated.; CI = confidence interval

Discussion

Hip-spine disorders demand keen diagnostic acumen: a meticulous history, thorough physical examination, and judicious interpretation of imaging each contribute to a more reliable diagnosis. To complement our prior NHIRD analysis, the present CGRD study examines the same question within a multi-center tertiary-care EMR. Compared with NHIRD’s population breadth, CGRD offers richer clinical detail from subspecialized settings, albeit with a smaller base and greater case complexity (longer median stays and wider inter-operation intervals) [14, 19]. Because the CGMH network is built around such centers, the CGRD arguably captures practice patterns that best represent subspecialized care in Taiwanese medical-center settings [1]. The “combined surgery within 12 months” group was defined based on prior evidence indicating that compensatory changes in spinopelvic relationship after lumbar spine fusion stabilize after approximately one year. Hence, undergoing both LSF and THA within 12 months was considered to represent a period of mutual biomechanical interaction between spine and hip. Patients requiring the second surgery within this interval were interpreted as having unplanned or symptom-driven procedures due to delayed or evolving diagnoses [7, 20, 21].

Between the OS and the NS group, a 22% absolute difference in pre-operative hip imaging is clinically significant. Failing to image the hip in one-fifth of the patients who ultimately require hip surgery constitutes a substantial rate of delayed or missed diagnosis, justifying the need for protocol standardization.

Several mechanisms may contribute to these specialty differences. Training emphasis and routine clinical exposure likely play a role: orthopedic curricula typically span the full musculoskeletal system—including hip pathology evaluation and arthroplasty planning—whereas neurosurgical training prioritizes cranial, cerebrovascular, and spinal disorders, with less emphasis on hip-specific maneuvers and radiographic interpretation. We note that the observed differences are likely not unique to Taiwan. This disparity is likely driven by fundamental differences in residency training. As noted by Daniels et al. (2014) in their analysis of ACGME case logs, orthopedic training emphasizes structural deformity and musculoskeletal biomechanics, whereas neurosurgical training focuses heavily on neural decompression [22].

Previous systematic reviews have confirmed that default order sets significantly influence imaging utilization patterns. Our findings suggest that specialty-specific default pathways in the EMR (e.g., order-set defaults, clinic imaging pathways, and preoperative checklists) may be a key driver of the observed diagnostic gap [23]. We suggest that neurosurgical pathways might involve order-set defaults that prioritize spine-focused imaging, whereas orthopedic clinics may have default pathways (e.g., KUB/Pelvis AP) built into their arthroplasty workup protocols. Finally, clinical focus and thresholds for arthroplasty referral may differ across specialties, shaping the likelihood of ordering combined imaging.

The observed alignment of OS + NS patterns with NS for spine-focused imaging and with OS for pelvic imaging suggests pathway-level influences: patients may receive spine AP radiographs during neurosurgical evaluation, whereas pelvic imaging remains more common in orthopedic visits.

Clinical implications and practical recommendations

1. Standardizing imaging bundles: lumbar AP/lateral and a pelvic/hip view (e.g., KUB or pelvis AP) are ordered together for patients with hip–spine symptoms.

2. Embedding mandatory electronic prompts: document coexisting hip conditions when booking lumbar procedures.

3. Implementing multidisciplinary reviews: spine and arthroplasty surgeons to harmonize examination checklists (hip- and spine-specific provocative maneuvers) and align imaging protocols with contemporary.

Our findings are broadly consistent with prior reports suggesting specialty-related differences in the evaluation of patients with overlapping hip–spine symptoms. In particular, a nationwide claims-based study using the NHIRD reported a similar trend toward greater recognition of hip pathology when hip-focused imaging was obtained in orthopedic settings [19]. In the NHIRD analysis, the pre-operative detection rate of hip osteoarthritis was higher when spine surgery was performed by orthopaedic surgeons—a trend mirrored in the CGRD cohort, although the smaller CGRD sample meant the difference did not reach statistical significance. One plausible explanation is the tertiary-referral nature of the Chang Gung health-care system: many patients may have undergone initial hip assessments at primary or secondary facilities before being referred for definitive care, so those earlier diagnoses were not captured in the CGRD’s electronic records. Consequently, the apparent lack of a statistically significant difference in hip diagnostic rates may reflect under-documentation of hip pathology that had already been recognized outside the CGRD network.

Across both the NHIRD and CGRD datasets, the SH-to-HS ratio consistently falls between 3 : 1 and 4 : 1, highlighting that clinicians most often treat spinal pathology before addressing the hip. Cases in the Both group are too few to support meaningful inference. In practice, the optimal order of intervention when spine and hip disease coexist remains controversial; the critical task is to identify the dominant pain generator, because operating on one site can either relieve—or, in some instances, exacerbate—symptoms arising from the other [24].

Numerous studies address surgical sequencing in hip–spine syndrome—i.e., spine-first versus hip-first—as well as the associated radiographic (spinopelvic) parameters. In contrast, the present study focuses on whether the preoperative imaging portfolio is sufficient to ensure the accuracy and completeness of the preoperative diagnosis. Among patients who underwent both lumbar spine surgery and total hip arthroplasty within a single year, the vast majority of hip pathologies were not identified prior to spine surgery, primarily due to inadequate imaging of the hip/pelvis. As a result, many patients experienced suboptimal symptom relief after spine procedures, necessitating further evaluation during which the hip lesion was ultimately recognized; subsequent hip surgery then produced meaningful clinical improvement. Prior reports suggest that surgical sequencing and spinopelvic parameters can affect postoperative alignment and recovery in patients with concurrent hip and spine pathology, highlighting the need to evaluate how diagnostic pathways influence outcomes [21]. This study did not evaluate downstream outcomes (e.g., delayed diagnosis, revision surgery, dislocation, readmissions, or other complications) as a function of preoperative imaging completeness. Future work will link imaging completeness to clinically relevant endpoints to define the prognostic value of standardized preoperative imaging pathways.

We also found that imaging-ordering practices vary by specialty training. Notably, the magnitude of specialty-related differences within this tertiary-care hospital system was smaller than that observed in the nationwide database, suggesting reduced inter-specialty variability in tertiary-center practice. Several limitations merit mention. First, its retrospective design and coding-based case identification introduce the possibility of misclassification. Second, unmeasured confounders (e.g., surgeon-level practice styles, order-set changes, local access to advanced imaging, and referral patterns) could bias observed associations. Third, the long time-span raises concern for secular trends in technology and pathways despite our epoch-stratified considerations. Fourth, we did not capture functional outcomes or patient-reported measures, and therefore cannot determine whether imaging patterns translated into improved clinical results. Although the CGRD is the largest single-system database in Taiwan, it still represents only a segment of the national population when compared with the NHIRD. Because the CGRD captures care delivered mainly at tertiary medical centers, many patients arrive after comprehensive work-ups in primary or secondary facilities, a referral pattern that may introduce diagnostic bias even as it reflects real-world practice. That said, the CGRD’s granular documentation allows for extensive cross-checking, which helps to minimize—but not completely eliminate—these sources of bias. Some non-significant findings may reflect limited statistical power rather than the absence of an association. Furthermore, the long-term retrospective design spanning 23 years (1996–2018) introduces a potential for temporal bias. During this extended period, healthcare infrastructure underwent significant changes, including the gradual implementation of Electronic Medical Record (EMR) systems and the continuous evolution of imaging technology and protocols. These system-wide changes can undoubtedly cause secular trends in diagnostic and ordering behaviors over time. We explicitly note this design limitation and call for future prospective studies to validate our findings using current EMR systems.

Conclusions

This study aimed to delineate how orthopaedic surgeons and neurosurgeons differ in diagnosing hip–spine syndrome, using the completeness of pre-operative imaging and the pattern of diagnostic codes as proxies for diagnostic accuracy and, ultimately, for enhancing treatment success. Orthopedic surgeons were more likely to order combined spine and pelvis/hip imaging, which may facilitate recognition of hip pathology in patients with overlapping hip–spine symptoms. Importantly, spine surgeons should explicitly consider the possibility of concomitant hip pathology before proceeding and ensure a sufficiently comprehensive preoperative work-up—including targeted pelvis/hip imaging—to support accurate diagnosis and surgical planning.

Abbreviations

HSS

Hip–spine syndrome

EMR

Electronic medical-record

CGRD

Chang Gung Research Database

SIJ

Sacroiliac joint

NHIRD

Taiwan National Health Insurance Research Database

CCI

Charlson Comorbidity Index

Authors' contributions

Chao-Chien Chang: writing-Original Draft & Editing; Feng-Chih Kuo: methodology & data analysis; Fu-Shine Yang: resources & methodology; Cheh-Yung Chang: resources; Chieh-Cheng Hsu: resources & Investigation; Meng-Ling Lu: resources & methodology; Re-Wen Wu: resources & Investigation; Tsung-Cheng Yin (corresponding author): Conceptualization,methodology & review.

Funding

There is no funding support in this study.

Data availability

The datasets used and/or analyzed during the current study are available from the corresponding author and first author on reasonable request.

Declarations

Ethics approval and consent to participate

The need for informed consent was waived by the Ethics Committee/Institutional Review Board of the Institutional Review Board of Chang Gung Medical Foundation has approved this study (IRB No. 201801118B0). This study was conducted in accordance with the Declaration of Helsinki and its later amendments.

Consent for publication

Not applicable.

Competing interests

The authors declare no competing interests.