When Is Less More? Identifying the Right Candidates for Short Fusion in Cervical Deformity Surgery
A multicenter study of 127 patients identifies a specific preoperative measurement that predicts when shorter cervical fusions succeed — and when they fail — offering surgeons a data-driven framework for one of the field's most consequential planning decisions.
OPENING SUMMARY
In cervical deformity surgery, one of the most consequential decisions a surgeon makes is how many vertebral levels to include in the fusion. Longer fusions can address more severe deformity and provide greater stability — but they come at a cost: more blood loss, longer operating time, greater surgical risk, and a more demanding recovery. Shorter fusions offer the appeal of a less invasive procedure with faster recovery, but only if the deformity is corrected adequately and durably. The central question this study addresses is not whether short fusions can work — they can — but for which patients, and how to identify them reliably before surgery. The answer comes down to a single measurable angle.
STUDY SNAPSHOT
Study type – Retrospective review of a prospective cervical deformity database
Number of patients – 127
Short fusion group (SF) – 27 patients (≤4 levels fused, cervical lowest instrumented vertebra)
Long fusion group (LF) – 100 patients (>4 levels fused, LIV caudal to C7)
Primary outcomes – Alignment failure (1-year cSVA >4mm or C2 slope >20°), complications, patient-reported outcomes
Key decision variable – Baseline C2 slope (C2S)
Analytic methods – Propensity score matching by cSVA; decision tree analysis
Follow-up – 1 year
Published in – Spine
PMID – 41603594
DOI – 10.1097/BRS.0000000000005634
WHY THIS MATTERS
Cervical deformity — abnormal alignment of the neck — can cause significant pain, disability, and neurological impairment. Surgical correction involves fusing vertebral levels to restore and maintain proper alignment, but decisions about how extensive that fusion should be involve real tradeoffs. Longer fusions are more likely to achieve and maintain adequate correction in severe deformity, but they expose patients to substantially greater surgical risk. Shorter fusions spare patients much of that risk — but only when the deformity can be adequately corrected and sustained with a limited construct.
Currently, there is limited data to guide surgeons in selecting fusion length for cervical deformity patients. Most decisions rely on a combination of experience, deformity severity, and clinical judgment. This study takes a step toward a more objective, data-driven framework — identifying a specific preoperative radiographic threshold that reliably distinguishes patients likely to do well with a short fusion from those who are likely to fail.
For patients, this kind of evidence matters because it informs conversations about surgical options, realistic expectations, and the genuine tradeoffs between a less invasive and more invasive approach.
KEY FINDINGS
1. Short fusions were dramatically less invasive — when appropriate. Patients who underwent short fusion had a mean estimated blood loss of 131 mL compared to 1,001 mL in the long fusion group — nearly an eightfold difference. Operative time was also substantially shorter (223 minutes vs. 435 minutes). When a short fusion is clinically appropriate, it represents a meaningfully less burdensome surgical experience for the patient.
2. After accounting for baseline deformity severity, short fusion patients reported better functional outcomes. Before propensity score matching, the long fusion group had worse baseline cervical alignment and greater disability — making direct comparison difficult. After matching groups by cervical sagittal vertical axis to create more comparable cohorts, 71% of short fusion patients achieved a clinically meaningful improvement in neck disability scores (NDI MCID), compared to 52% of long fusion patients. This suggests that for appropriately selected patients, shorter fusions can deliver outcomes that are at least comparable to — and in this cohort, somewhat better than — longer constructs.
3. A baseline C2 slope greater than 26° identified patients at high risk of failure with short fusion. Using decision tree analysis, the study identified a C2 slope of 26° as the critical threshold for predicting short fusion outcomes. Patients with a baseline C2 slope above this threshold were 12.4 times more likely to experience postoperative alignment failure than those at or below it — with alignment failure rates of 85% versus 31% respectively. The same group was also 5.1 times more likely to experience a postoperative complication (69% vs. 31%).
4. The C2 slope threshold provides an actionable preoperative decision point. The C2 slope is a standard radiographic measurement available from preoperative cervical imaging. Its identification as the primary predictor of short fusion failure gives surgeons a concrete, measurable criterion to incorporate into surgical planning — moving fusion length selection from a judgment-based decision toward a more evidence-based one.
5. Short fusion should be avoided in patients with a baseline C2 slope greater than 26°. The study's conclusions are direct on this point: the elevated rates of both alignment failure and complication in patients above this threshold support avoiding short fusion as the primary surgical strategy in this subgroup. For these patients, a longer fusion construct appears necessary to achieve durable correction and minimize complication risk.
PRACTICAL IMPLICATIONS
Fusion length selection in cervical deformity now has a clearer evidence base. The identification of the C2 slope threshold of 26° gives surgeons a practical, radiographically measurable criterion for preoperative planning. For patients below this threshold, short fusion is a legitimate and less invasive option that can deliver excellent outcomes. For those above it, the data strongly favor a longer construct.
Preoperative imaging interpretation should include C2 slope assessment in cervical deformity patients. Because the C2 slope is derivable from standard cervical imaging, this threshold can be applied without additional diagnostic workup. Ensuring that preoperative radiographic evaluation includes this measurement — and that it is explicitly factored into surgical planning discussions — is a low-barrier way to apply this study's findings in clinical practice.
Short fusion is not a shortcut — it is a matched strategy. A key message from this study is that short fusion, when applied to the right patient, is not a compromise — it delivers better reported outcomes with far less surgical burden. The goal is not to maximize or minimize fusion length, but to match surgical extent to the patient's deformity profile. The C2 slope threshold helps define that match.
Patients with borderline C2 slope values may warrant particularly careful counseling. The decision tree analysis identifies 26° as the key inflection point, but clinical decisions near any threshold require individualized judgment. Patients with C2 slope values near this boundary should receive especially thorough preoperative discussion about the tradeoffs between approaches and the uncertainty involved.
CONCLUSION
This study provides a clinically useful and actionable framework for one of the most consequential decisions in cervical deformity surgery. By demonstrating that short fusion can achieve excellent outcomes with dramatically less surgical burden — and by identifying a specific, measurable radiographic threshold that predicts when it will fail — the authors have moved the field toward more objective, individualized surgical planning. For surgeons, the C2 slope of 26° is a number worth knowing. For patients, this research supports the possibility of a less invasive surgical option when their deformity profile makes it appropriate — and helps define clearly when it does not.
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