(5) Assessment and Validation of Preoperative Three-dimensional Volumetric Analysis to Predict Bone Graft Success in Alveolar Cleft Reconstruction

Abstract: Cleft lip and palate is the most common craniofacial congenital anomaly in the world, affecting 1 in 700 live births.[1] Although alveolar bone grafting (ABG) with autologous iliac crest bone graft (ICBG) remains the standard of care to treat these bony defects, recombinant human bone morphogenetic protein-2 (rhBMP-2) with demineralized bone matrix (DBM) has shown equal graft success compared to ICBG.[2] Despite significant advancements in ABG, reported graft success rates vary widely for both types ranging from 60-80% for ICBG and 54-90% for rhBMP-2.[2-5] Thus, the success of ABG can be attributed to many factors other than graft type, such as preoperative cleft size, cleft phenotype, and timing of repair. We aim to identify the best predictor for successful bony bridge formation in ABG.
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A retrospective review evaluated patients undergoing ABG from 2009-2022. Patients with genetic syndromes, bilateral clefts, and missing postoperative cone beam computed tomography (CBCT) were excluded. The cleft width and 3-dimensional volumetric defect sizes were calculated using preoperative CBCT scans. The area under the curve (AUC) using receiver-operating characteristic (ROC) analysis was used to determine the strongest predictor of graft success among age at ABG, preoperative cleft width, and volumetric size. AUC>0.700 was the marker of adequate sensitivity and specificity.

Of the 583 patients screened, 70 met inclusion criteria and underwent ABG with ICBG (n=32) or rhBMP-2/DBM (n=38). There was no significant difference in failure of bony bridge formation between graft types (ICBG: 25.0%, rhBMP-2/DBM: 39.5%; p=0.199). The AUC of the ROC curve was 0.843 (95% Confidence Interval[CI]: 0.730–0.955), indicating good performance of the model. Across both cohorts, preoperative volumetric size had a larger AUC compared to preoperative cleft width (0.843 vs. 0.695; p=0.013) and age (0.843 vs. 0.649; p=0.033). Individually, volumetric cleft size strongly predicted graft failure among both ICBG (AUC 0.953 [95% CI: 0.885–1.000]) and rhBMP-2/DBM (AUC 0.780 [95% CI: 0.608–0.951]) cohorts. The average follow-up time after ABG among all patients was 26.9±15.9 months.

Our findings identified preoperative volumetric cleft size as the strongest predictor for successful bony bridge formation in ABG. Clinicians can prioritize volumetric analysis via CBCT to better predict graft failure among clefts of varying sizes.

References
1. Vyas T, Gupta P, Kumar S, Gupta R, Gupta T, Singh HP. Cleft of lip and palate: A review. J Family Med Prim Care. 2020;9(6):2621-2625.
2. Hammoudeh JA, Fahradyan A, Gould DJ, et al. A Comparative Analysis of Recombinant Human Bone Morphogenetic Protein-2 with a Demineralized Bone Matrix versus Iliac Crest Bone Graft for Secondary Alveolar Bone Grafts in Patients with Cleft Lip and Palate: Review of 501 Cases. Plastic and Reconstructive Surgery. 2017;140(2):318e - 325e.
3. Kortebein MJ, Nelson CL, Sadove AM. Retrospective analysis of 135 secondary alveolar cleft grafts using iliac or calvarial bone. J Oral Maxillofac Surg. 1991;49(5):493-498.
4. Kimia R, Scott M, Magee L, Jackson OA. Secondary Alveolar Bone Grafting in Patients with Unilateral and Bilateral Complete Cleft Lip and Palate: A Single-Institution Outcomes Evaluation Using Three-Dimensional Cone Beam Computed Tomography. Plastic & Reconstructive Surgery. 2022;149(6):1404-1411.
5. Lee KC, Costandi JJ, Carrao V, Eisig SB, Perrino MA. Autogenous Iliac Crest Versus rhBMP-2 for Alveolar Cleft Grafting: A 14-Year Single-Institution Experience. J Oral Maxillofac Surg. 2021;79(2):431-440.

Figure 1. Preoperative alveolar cleft volume calculation based on the trapezoidal pyramid model
Figure 2. Receiver-operating characteristic curves for predicting bone graft failure based on 3-dimensional alveolar cleft volume, cleft width, and age of repair

Figure 3. Receiver-operating characteristic curves for predicting bone graft failure based on preoperative alveolar cleft volume for each bone graft type