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Published 12/1/2011
Terry Stanton

Experience is a factor in scoliosis surgery outcomes

Study calls for innovative training, mentorships

Patients with adolescent idiopathic scoliosis (AIS) who undergo surgery performed by surgeons with less than 5 years of experience in practice have significantly higher blood loss, longer surgery times, and lower SRS-22 scores than patients whose surgeons are more experienced, according to a study presented at the 2011 annual meeting of the Scoliosis Research Society.

Presenter Patrick J. Cahill, MD, of the Shriners Hospitals for Children, noted that “the techniques of pedicle screw placement, deformity reduction, and spinal fusion are complex tasks that intuitively cannot be learned easily without repetition and experience.” Although attempts at quantifying the learning curve have been undertaken for other orthopaedic procedures, including several spinal operations, most have focused on how many of the specific procedure the surgeon has performed and not on the surgeon’s overall surgical experience as quantified in terms of years in practice. “The best way to evaluate the effect of experience on outcomes in spinal deformity surgery is as a function of time in practice,” he asserted.

Most learning curve studies are longitudinal studies of single surgeon results that may be confounded by advances in the field, Dr. Cahill said. The study that Dr. Cahill presented, however, is a cross-sectional multicenter analysis of the impact of surgeon experience on AIS surgery.

The 165 patients participating in this study included 133 females and 32 males. All surgeries were posterior-only procedures performed over 1 academic year, with a minimum of 2 years of follow-up. Two groups were created based on the surgeon experience. The young surgeons’ group (YS) comprised patients (n = 17) whose surgeons had less than 5 years experience; the experienced surgeons’ group (ES) consisted of patients (n = 148) whose surgeons had 5 or more years of experience. The YS group had four surgeons; the ES group had five surgeons. The surgeons’ experience in AIS surgery ranged from less than 1 year to 36 years.

Preoperative evaluations included Lenke classification, Cobb angle, thoracic kyphosis, shoulder balance, and health-related quality of life (HRQOL) as measured by SRS-22 score. Surgical variables analyzed included blood loss, levels fused, blood loss per level fused, transfusion rates, and surgery time. Postoperative variables analyzed included Cobb angle, percent Cobb angle correction, thoracic kyphosis, shoulder balance (as expressed in centimeters of difference in shoulder height), and postoperative days until meeting discharge criteria.

Longer procedures, lower HRQOL
The following significant perioperative and 2-year postoperative outcome differences were observed:

  • Surgeons in the YS group fused an average of 1.2 levels more than those in the ES group (P = 0.045).
  • The average blood loss in patients operated on by surgeons in the YS group was more than twice that lost by patients who had more experienced surgeons (2,042 mL vs. 1,013 mL, P < 0.001).
  • Blood loss expressed as a ratio of levels fused was significantly higher in the YS group (173 mL/level in the YS group vs. 102 mL/level in the ES group).
  • Surgeons in the YS group took longer to perform surgery (458 minutes vs. 265 minutes in the ES group, P < 0.001).
  • Patients in the ES group met discharge criteria faster than those in the YS group (5.2 days vs. 5.8 days, P = 0.08).
  • Patients in the YS group had significantly worse overall SRS-22 scores than those in the ES group (4.1 vs. 4.5, P = 0.001). The difference was significant in the domains of pain (P = 0.016), self-image (P = 0.008), and function (P < 0.001).

Other outcomes were similar
No differences were seen for several outcomes, including incidence of complications and postoperative Cobb angle of the major curve and percent correction of the major Cobb angle at 2 years postoperatively. The differences in shoulder asymmetry were not significant preoperatively or at 2-years postoperatively; however, patients in the ES group trended toward better results because they generally had more preoperative and less 2-year postoperative shoulder asymmetry.

Dr. Cahill said these results are similar to those reported in a previous single-surgeon learning curve study, with the exception of the effect of HRQOL. Dr. Cahill’s multisurgeon study found significantly worse outcomes in SRS-22 scores, the first such finding following posterior spinal fusion for AIS.

The fact that the young surgeons operated on patients similar to their senior counterparts is “reassuring,” said Dr. Cahill, because this meant that surgeon experience made no difference in identifying indications for surgery.

“The demographic similarity in the two treatment groups dispels the notion that senior surgeons feast on smaller, ‘easier’ curves and leave the difficult cases to their younger partners,” he said. “The converse is also disproven, because younger surgeons were not preferentially given smaller curves as a means of nurturing their skills or protecting them from more challenging cases.”

Dr. Cahill noted several limitations to the study. All of the surgeons, young and experienced, work in academic settings at high-volume centers, and the experienced surgeons are all leaders in the field who have been active in maintaining their knowledge base and keeping their skills updated. “We hesitate to draw conclusions about the effect of surgeon experience on AIS surgery in community settings,” he said.

The academic setting also meant that the young surgeons had experienced senior partners. “We do not know if not having any senior surgeon ‘backup’ had any effect on the results,” he added.

An additional potential flaw in the study is the relatively small number of surgeries performed by the surgeons in the YS group. Because most variables analyzed reached statistical significance despite the relatively small sample size, however, Dr. Cahill believes the validity of the findings is supported. “We cannot objectively explain the small number of cases in this group,” he said. “Is that a sign of institutions slowly bringing along junior surgeons?”

Dr. Cahill said the results are not meant to be used as a means of precluding young surgeons from performing AIS surgery or “as a tool for disparaging other surgeons among the medical community, our patients, or the public.” Rather, the results of this study should encourage the spinal deformity community to develop innovative teaching methods for surgeons beyond the training years.

“Experienced scoliosis surgeons should not see the results of this study as a validation of their lifetime of work but rather a call to continued learning and to mentorship of the young surgeons in the field,” he concluded.

Coauthors of “Youth and Experience: The Effect of Surgeon Experience on Outcomes in AIS Surgery” are Patrick J. Cahill, MD; Joshua M. Pahys, MD; Megan Gresh, MD; Burt Yaszay, MD; Michelle C. Marks, PT, MA; Tracey Bastrom, MA; Baron Lonner, MD; Suken A. Shah, MD; Harry L. Shufflebarger, MD; Peter O. Newton, MD; Randal R. Betz, MD; Amer F. Samdani, MD.

Disclosure information: Dr. Cahill—DePuy, Osteotech, Synthes; Dr. Yaszay—DePuy Spine, K2M, KCI, Synthes, Orthopediatrics; Ms. Marks—DePuy Spine; Dr. Lonner—DePuy Spine, K2M, Axial Biotech, Paradigm, Spine Wave; Dr. Shah—DePuy Spine, Axial Biotech, Globus Medical, MTF, K Spine Inc.; Dr. Shufflebarger—DePuy Spine, Axial Biotech; Dr. Newton—DePuy Spine, Biospace Med, NuVasive; Dr. Betz—DePuy Spine, Synthes, Medtronic, SpineGuard, Osteotech, SpineMedica, Orthovita, Orthocon, Chest Wall & Spine Deformity Study Group; Dr. Samdani—DePuy, Synthes, SpineVision. Dr. Pahys, Dr. Gresh, and Ms. Bastrom reported no conflicts.

Terry Stanton is senior science writer for AAOS Now. He can be reached at tstanton@aaos.org

Bottom Line

  • Few data are available regarding the surgeon learning curve in
    spinal deformity surgery.
  • This study is the first multicenter, multisurgeon study comparing outcomes for patients treated by surgeons at various stages of their careers.
  • Patients of surgeons who had less than 5 years of experience had significantly higher blood loss, longer surgery times, and lower SRS-22 scores than those operated on by more experienced surgeons.
  • Outcomes such as incidence of complications, correction in Cobb angle, and shoulder symmetry did not vary significantly between the two surgical groups.