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Surgical Revision Rate of Hooks vs. Hybrid vs. Screws vs. ASF/PSF for AIS

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Written by Timothy R. Kuklo, MD, JD, Lawrence G. Lenke, MD, Benjamin Potter, M.D. and David W. Polly, Jr., MD

Abstract from the 2006 SRS Annual Meeting

a - Medtronic Sofamor Danek

Background: Much debate continues on the safety, efficacy and cost of thoracic pedicle screws in AIS to determine the need for repeat surgery; and therefore, the added indirect costs and risks Nonetheless, there are no large series which have evaluated the revision rate of various constructs of additional procedures.

Methods: We retrospectively reviewed the surgical case logs of 1,428 patients with AIS at two institutions from 1990-2004, and the clinical records and radiographs of revision cases. Patients were classified into one of 4 groups: hook constructs, hybrid constructs, all screw constructs, and combined ASF/PSF. Overall, there were 64 (4.5%) returns to the OR, or 54 (3.8%) cases after excluding infections without pseudarthrosis.

Results: Of the 64 revision cases, there were 51 females and 13 males, at an average age at first surgery of 13.9 years (range, 9-18), and an average age at revision of 14.7 (range, 12-23). For the revision cases, the average Cobb was 61.9 (range 44-110 ), and this was not statistically different within the cohorts (p>0.05). In terms of revision rate, all hook constructs had a higher revision rate 2 instrumentation failure when compared to screws, while both hooks and hybrid constructs had an overall higher surgical revision rate when compared to screw constructs or anterior/posterior constructs (all p?0.05; see table). The pseudarthrosis rate trended toward, but did not meet, (added comma) statistical significance between these same groups. (See table)

Conclusions: All pedicle screw constructs have a lower surgical revision rate when compared to hook and hybrid constructs. The hidden costs of these findings should be considered when evaluating instrumentation efficacy.

	N (%)	Dislodged Instrumentation	Pseudarthrosis	Prominent Implant	Infection	Crankshaft	Other	Total
Hooks	389	9 (2.3)**	6/2* (2.1)	3 (0.8)	4 (1.0)	2 (0.5)	1 (0.3)	25 (6.4)**
Hybrid	423	7 (1.7)	10/1* (2.6)	0 (0)	6 (1.4)	0 (0)	1 (0.2)	24 (5.7)**
Screws	295	0 (0)	2 (0.7)	2 (0.7)	1 (0.3)	0 (0)	2 (0.7)	7 (2.4)
ASF/PSF	321	1 (0.3)	3 (0.9)	2 (0.6)	2 (0.6)	0 (0)	0 (0)	8 (2.5)
Total	1428	17	21	7	13	2	4	64 (4.5)