For a variety of neurosurgical conditions, increasing surgeon and hospital volumes correlate with improved outcomes, such as mortality, complication rates, length of stay, hospital charges, and discharge disposition. Neurosurgeons can improve patient outcomes at the population level by changing practice and referral patterns to regionalize care for select conditions at high-volume specialty treatment centers. Individual practitioners should be aware of where they fall on the volume spectrum and understand the implications of their practice and referral habits on their patients.
Key points
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For a variety of neurosurgical conditions, increasing surgeon and hospital volumes correlate with improved outcomes, such as mortality, complication rates, length of stay, hospital charges, and discharge disposition.
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Neurosurgeons can improve patient outcomes at the population level by changing practice and referral patterns to regionalize care for select conditions at high-volume specialty treatment centers.
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Individual practitioners should be aware of where they fall on the volume spectrum and understand the implications of their practice and referral habits on their patients.
Introduction
Evidence is mounting that patient morbidity and mortality rates decrease when high-volume physicians and centers perform certain medical or surgical procedures ( Tables 1 and 2 ). These volume-outcome relationships (VORs) have been demonstrated for common procedures, such as hip and knee replacements, and more complex procedures, such as pancreaticoduodenectomy and abdominal aortic aneurysm repair. Data such as these have been used to support changes in the delivery of care, with centralization of patients and procedures at specialized centers in efforts to increase volumes and thereby improve overall patient outcomes.
| Specialty | Subspecialty | Author | Stratification | Volume Threshold | Mortality | Disposition | Length of Stay | Complications |
|---|---|---|---|---|---|---|---|---|
| Tumor | All | Long et al, 2003 | Dichotomous | >50/y | RR, 0.71; P <.05 | 6.8 vs 8.8 d; P <.001 | ||
| All | Cowan et al, 2003 | Quartile | >29/y | OR, 0.58; 95% CI, 0.35–0.97; P = .04 | ||||
| All | Nuno et al, 2012 | Quintiles | >139/y | OR, 0.56; 95% CI, 0.37–0.83 | OR, 0.71; 95% CI, 0.59–0.91 | 6.4 vs 8.0 d | ||
| Supratentorial primaries | Barker et al, 2005 | |||||||
| Craniotomy | Quintile | >41/y | OR, 0.75; 95% CI, 0.62–0.90; P = .003 | OR, 0.77; 95% CI, 0.70–0.85; P <.001 | NS | OR, 1.67; 95% CI, 1.13–2.45; P = .009 | ||
| Biopsy | Quintile | >11/y | OR, 0.54; 95% CI, 0.35–0.83; P = .006 | OR, 0.67; 95% CI, 0.56–0.80; P <.001 | 19% shorter; P <.001 | |||
| Trinh et al, | Quartile/decile | >35/y | OR, 0.76; 95% CI, 0.63–0.90; P <.001 | OR, 1.29; 95% CI, 1.21–1.37; P <.01 | OR, 0.93; 95% CI, 0.97–0.99; P = .040 | |||
| Metastasis | Barker, 2004 | Quintile | >17/y | OR, 0.79; 95% CI, 0.59–1.03; P = .09 | OR, 0.75; 95% CI, 0.65–0.86 | |||
| Transsphenoidal pituitary tumors | Barker et al, 2003 | Quartile | >24/y | OR, 0.54; CI, 0.31–0.95; P = .03 | OR, 0.74; 95% CI, 059–0.92; P = .007 | P = .02 | OR, 0.77; 95% CI, 0.61–0.97; P = .03 | |
| Meningioma | Curry et al, 2010 | Quartile | >17/y | OR, 0.74; 95% CI, 0.59–0.93 | OR, 0.71; 95% CI, 0.62–0.80 | |||
| Ambekar et al, 2013 | Quartile | >16/y | OR, 0.5; 95% CI, 0.38–0.66; P <.001 | OR, 0.8; 95% CI, 0.74–0.86; P <.001 | ||||
| Acoustic neuroma | Barker et al, 2003 | Quartile | >36/y | NS | OR, 0.47; 95% CI, 0.37–0.58; P <.001 | P = .01 | OR, 0.75; CI, 0.64–0.89, P <.001 | |
| Chordoma | Jones et al, 2014 | Dichotomous | >40 | HR, 0.49; 95% CI, 0.28–0.86; P = .013 | ||||
| Vascular | Aneurysm/SAH | Leake et al, 2011 | ||||||
| Clip | Dichotomous | >20 | P = .001 | P = .0242 | ||||
| Coil | P = .0053 | NS | ||||||
| Johnston, 2000 | ||||||||
| Ruptured | Quartile | >45/y | NS | |||||
| Unruptured | NS | |||||||
| Hattori et al, 2007 | ||||||||
| Ruptured | Tertile | >50/y | NS | |||||
| Unruptured | >50/y | NS | ||||||
| Bardach et al, 2002 | Quartile | >20/y | OR, 0.57; 95% CI, 0.48–0.67; P <.001 | OR, 0.44; 95% CI, 0.36–0.53; P <.001 | OR, 1.21; 95% CI, 1.09–1.33; P = .001 | |||
| Cross et al, 2003 | Quartile | >35/y | OR, 0.71; 95% CI, 0.62–0.83; P <.001 | |||||
| Boogaarts et al, 2014 | Dichotomous | OR, 0.85; 95% CI, 0.72–0.99; P = .00 | ||||||
| Solomon et al, 1996 | Quartile | >30/y | OR, 0.57; 95% CI, 0.27–0.86; P = .009 | NS | ||||
| McNeill et al, 2013 | Continuous, per 100 patients per year | RR, 0.76; 95% CI, 0.67–0.87; P = .009 | ||||||
| Carotid stenosis | Cebul et al, 1998 | Dichotomous | >62/y | OR, 0.29; 95% CI, 0.12–0.69; P = .006 | ||||
| Wennberg et al, 1998 | Tertile | >21/y | 1.7% vs 2.5%; volume OR not reported; P = .001 | |||||
| Cowan et al, 2002 | Tertile | >100/y | NS | |||||
| Pediatrics | Tumor | Smith et al, 2004 | Quartile | >20/y | OR, 0.52; 95% CI, 0.28–0.94; P = .03 | OR, 0.52; 95% CI, 0.39–0.71; P <.001 | NS | |
| VPS | Smith et al, 2004 | Quartile | >121/y | OR, 0.38; 95% CI, 0.18–0.81; P = .01 | NS | |||
| Spine | Dasenbrock et al, 2012 | Quintile | >394/y | NS | NS | NS | NS | |
| Trauma | Clement et al, 2013 | Quintile | >59/y | OR, 0.59; 95% CI, 0.41–0.87 | NS | NS | ||
| Functional | Epilepsy | McClelland et al, 2011 | Dichotomous | |||||
| Englot et al, 2012 | Tertile | >15/y | RR, 0.93; 95% CI, 0.93–097; P <.001 | |||||
| MVD | Kalkanis et al, 2003 | Quartile | >19/y | NS | OR, 0.50; 95% CI, 0.31–0.82; P = .006 | NS | OR, 0.59; 95% CI, 0.35–0.98; P = .04 | |
| DBS | Eskandar et al, 2003 | Quartile | >120/y | OR, 0.14; 95% CI, 0.04–0.49; P = .002 | OR, 0.69; 95% CI, 0.50–0.96; P = .007 | NS | ||
| Sharma et al, 2013 | Quartile | NA | NS | OR, 0.28; 95% CI, 0.14–0.56; P <.001 | NS | |||
| Specialty | Subspecialty | Author | Stratification | Volume Threshold | Mortality | Disposition | Length of Stay | Complications |
|---|---|---|---|---|---|---|---|---|
| Tumor | All | Long et al, 2003 | Dichotomous | >50/y | ||||
| All | Cowan et al, 2003 | Quartile | >21/y | OR, 0.42; 95% CI, 0.22–0.84; P = .01 | ||||
| Supratentorial primaries | Barker et al, 2005 | |||||||
| Craniotomy | Quintile | NA | OR, 0.60; 95% CI, 0.45–0.79; P <.001 | |||||
| Biopsy | Quintile | NA | OR, 0.79; 95% CI, 0.70–0.89; P <.001 | |||||
| Trinh et al, | Quartile/decile | >12/y | OR, 0.43; 95% CI, 0.32–0.55; P <.001 | NS | OR, 0.91; 95% CI, 0.84–0.99; P = .040 | |||
| Metastasis | Barker, 2004 | Quintile | >7/y | OR, 0.49; 95% CI, 0.30–0.80; P = .004 | OR, 0.51; 95% CI, 0.40–0.64 | |||
| Transsphenoidal pituitary tumors | Barker et al, 2003 | Quartile | >6/y | NS | OR, 0.62; 95% CI, 0.41–0.94; P = .02 | P <.001 | OR, 0.76; 95% CI, 0.65–0.89; P = .005 | |
| Meningioma | Curry et al, 2010 | Quartile | >5/y | NS | OR, 0.71; 95% CI, 0.62–0.80 | |||
| Ambekar et al, 2013 | Quartile | >2/y | OR, 0.43; 95% CI, 0.27–0.69; P <.001 | OR, 0.63; 95% CI, 0.56–0.70; P <.001 | ||||
| Acoustic neuroma | Barker et al, 2003 | Quartile | >33/y | NS | OR, 0.46; 95% CI, 0.31–0.67; P <.001 | P = .009 | NS | |
| Vascular | Carotid stenosis | Cebul et al, 1998 | Dichotomous | >21/y | NS | |||
| Cowan et al, 2002 | Tertile | >29/y | OR, 0.53; 95% CI, 0.40–0.71; P ≤.001 | |||||
| Pediatrics | Tumor | Smith et al, 2004 | Quartile | >15/y | NS | OR, 0.70; 95% CI, 0.50–0.98; P = .04 | NS | |
| VPS | Smith et al, 2004 | Quartile | >65/y | OR, 0.30; 95% CI, 0.13–0.69; P = .005 | ||||
| Spine | Dasenbrock et al, 2012 | Quintile | >81/y | NS | NS | −4.4%; 95% CI, −6.1%–2.7%; P <.001 | OR, 0.72; 95% CI, 0.65–0.78; P <.001 | |
| Functional | Epilepsy | McClelland et al, 2011 | Dichotomous | >2/y | NS | |||
| MVD | Kalkanis et al, 2003 | Quartile | >29/y | P <.001 | OR, 0.30; 95% CI, 0.11–0.80; P = .02 | OR, 0.32; 95% CI, 0.13–0.77; P = .01 | ||
| DBS | Eskandar et al, 2003 | Quartile | >20/y | OR, 0.13; 95% CI, 0.03–0.57; P = .01 | NS | NS | ||
| Sharma et al, 2013 | Quartile | >12/y | NS | NS | NS | |||
During the past decade, neurosurgeons have begun to study the impact of surgeon and institutional volume on a variety of outcomes across the neurosurgical subspecialties. Positive relationships have been shown between higher volume and improved length of stay, mortality, complications, charges, and discharge dispositions. This article summarizes current evidence for VORs in neurosurgery to examine the basis for centralization of neurosurgical services. For each subspecialty (tumor, vascular, spine, pediatrics, functional, and neurotrauma), the literature for relevant studies is reviewed, the pertinent VORs that have been studied to date are summarized, and the implications of these data are discussed.
Introduction
Evidence is mounting that patient morbidity and mortality rates decrease when high-volume physicians and centers perform certain medical or surgical procedures ( Tables 1 and 2 ). These volume-outcome relationships (VORs) have been demonstrated for common procedures, such as hip and knee replacements, and more complex procedures, such as pancreaticoduodenectomy and abdominal aortic aneurysm repair. Data such as these have been used to support changes in the delivery of care, with centralization of patients and procedures at specialized centers in efforts to increase volumes and thereby improve overall patient outcomes.
| Specialty | Subspecialty | Author | Stratification | Volume Threshold | Mortality | Disposition | Length of Stay | Complications |
|---|---|---|---|---|---|---|---|---|
| Tumor | All | Long et al, 2003 | Dichotomous | >50/y | RR, 0.71; P <.05 | 6.8 vs 8.8 d; P <.001 | ||
| All | Cowan et al, 2003 | Quartile | >29/y | OR, 0.58; 95% CI, 0.35–0.97; P = .04 | ||||
| All | Nuno et al, 2012 | Quintiles | >139/y | OR, 0.56; 95% CI, 0.37–0.83 | OR, 0.71; 95% CI, 0.59–0.91 | 6.4 vs 8.0 d | ||
| Supratentorial primaries | Barker et al, 2005 | |||||||
| Craniotomy | Quintile | >41/y | OR, 0.75; 95% CI, 0.62–0.90; P = .003 | OR, 0.77; 95% CI, 0.70–0.85; P <.001 | NS | OR, 1.67; 95% CI, 1.13–2.45; P = .009 | ||
| Biopsy | Quintile | >11/y | OR, 0.54; 95% CI, 0.35–0.83; P = .006 | OR, 0.67; 95% CI, 0.56–0.80; P <.001 | 19% shorter; P <.001 | |||
| Trinh et al, | Quartile/decile | >35/y | OR, 0.76; 95% CI, 0.63–0.90; P <.001 | OR, 1.29; 95% CI, 1.21–1.37; P <.01 | OR, 0.93; 95% CI, 0.97–0.99; P = .040 | |||
| Metastasis | Barker, 2004 | Quintile | >17/y | OR, 0.79; 95% CI, 0.59–1.03; P = .09 | OR, 0.75; 95% CI, 0.65–0.86 | |||
| Transsphenoidal pituitary tumors | Barker et al, 2003 | Quartile | >24/y | OR, 0.54; CI, 0.31–0.95; P = .03 | OR, 0.74; 95% CI, 059–0.92; P = .007 | P = .02 | OR, 0.77; 95% CI, 0.61–0.97; P = .03 | |
| Meningioma | Curry et al, 2010 | Quartile | >17/y | OR, 0.74; 95% CI, 0.59–0.93 | OR, 0.71; 95% CI, 0.62–0.80 | |||
| Ambekar et al, 2013 | Quartile | >16/y | OR, 0.5; 95% CI, 0.38–0.66; P <.001 | OR, 0.8; 95% CI, 0.74–0.86; P <.001 | ||||
| Acoustic neuroma | Barker et al, 2003 | Quartile | >36/y | NS | OR, 0.47; 95% CI, 0.37–0.58; P <.001 | P = .01 | OR, 0.75; CI, 0.64–0.89, P <.001 | |
| Chordoma | Jones et al, 2014 | Dichotomous | >40 | HR, 0.49; 95% CI, 0.28–0.86; P = .013 | ||||
| Vascular | Aneurysm/SAH | Leake et al, 2011 | ||||||
| Clip | Dichotomous | >20 | P = .001 | P = .0242 | ||||
| Coil | P = .0053 | NS | ||||||
| Johnston, 2000 | ||||||||
| Ruptured | Quartile | >45/y | NS | |||||
| Unruptured | NS | |||||||
| Hattori et al, 2007 | ||||||||
| Ruptured | Tertile | >50/y | NS | |||||
| Unruptured | >50/y | NS | ||||||
| Bardach et al, 2002 | Quartile | >20/y | OR, 0.57; 95% CI, 0.48–0.67; P <.001 | OR, 0.44; 95% CI, 0.36–0.53; P <.001 | OR, 1.21; 95% CI, 1.09–1.33; P = .001 | |||
| Cross et al, 2003 | Quartile | >35/y | OR, 0.71; 95% CI, 0.62–0.83; P <.001 | |||||
| Boogaarts et al, 2014 | Dichotomous | OR, 0.85; 95% CI, 0.72–0.99; P = .00 | ||||||
| Solomon et al, 1996 | Quartile | >30/y | OR, 0.57; 95% CI, 0.27–0.86; P = .009 | NS | ||||
| McNeill et al, 2013 | Continuous, per 100 patients per year | RR, 0.76; 95% CI, 0.67–0.87; P = .009 | ||||||
| Carotid stenosis | Cebul et al, 1998 | Dichotomous | >62/y | OR, 0.29; 95% CI, 0.12–0.69; P = .006 | ||||
| Wennberg et al, 1998 | Tertile | >21/y | 1.7% vs 2.5%; volume OR not reported; P = .001 | |||||
| Cowan et al, 2002 | Tertile | >100/y | NS | |||||
| Pediatrics | Tumor | Smith et al, 2004 | Quartile | >20/y | OR, 0.52; 95% CI, 0.28–0.94; P = .03 | OR, 0.52; 95% CI, 0.39–0.71; P <.001 | NS | |
| VPS | Smith et al, 2004 | Quartile | >121/y | OR, 0.38; 95% CI, 0.18–0.81; P = .01 | NS | |||
| Spine | Dasenbrock et al, 2012 | Quintile | >394/y | NS | NS | NS | NS | |
| Trauma | Clement et al, 2013 | Quintile | >59/y | OR, 0.59; 95% CI, 0.41–0.87 | NS | NS | ||
| Functional | Epilepsy | McClelland et al, 2011 | Dichotomous | |||||
| Englot et al, 2012 | Tertile | >15/y | RR, 0.93; 95% CI, 0.93–097; P <.001 | |||||
| MVD | Kalkanis et al, 2003 | Quartile | >19/y | NS | OR, 0.50; 95% CI, 0.31–0.82; P = .006 | NS | OR, 0.59; 95% CI, 0.35–0.98; P = .04 | |
| DBS | Eskandar et al, 2003 | Quartile | >120/y | OR, 0.14; 95% CI, 0.04–0.49; P = .002 | OR, 0.69; 95% CI, 0.50–0.96; P = .007 | NS | ||
| Sharma et al, 2013 | Quartile | NA | NS | OR, 0.28; 95% CI, 0.14–0.56; P <.001 | NS | |||
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