Early Return to the OR
Early returns to the OR (<60 d) occurred in 2.2% (11/540) of the patients in the PS group, compared with 3.4% (3/87) in the Hb group (P = 0.43) (Table 2). The most common reason for an early reoperation in the PS group was malpositioned screws 1.7% (9/540), followed by infection 0.4% (2/540). The malpositioned screws presented as follows: 4 patients on routine postoperative CT scans (a single institution used routine postoperative CT scanning and contributed 74 patients), 3 patients radiculopathy, 1 patient transient myelopathy, and 1 patient with loosening. During the reoperation the screws were removed, and additional screws were placed when deemed necessary. Patients' symptoms improved after surgery. Generally, in those patients who underwent routine postoperative CT scanning, screws were removed if there was more than 4 mm of medial penetration into the canal or contact with the aorta, which resulted in vascular indentation. The ultimate decision as to whether or not to remove a screw was made by the surgeon after discussion of the risks and benefits with the family.
In the Hb group, the most common reason for an early reoperation was infection (2.3% [2/87]), followed by malpositioned instrumentation (1.1% [1/87]), which occurred in a patient with hook dislodgment.
Late Return to the OR
Late returns to the OR (>60 d) occurred in 1.3% (7/540) of patients in the PS group, compared with 9.2% (8/87) of those in the Hb group, P < 0.001 (Table 2). The most common reason for a late return in the PS group was infection (1.1% [6/540]), followed by prominent instrumentation (0.2% [1/540]), and pseudarthrosis (0.2% [1/540]). In the Hb group, the most common reason for a late reoperation was prominent instrumentation (3.4% [3/87]), possibly related to older prominent instrumentation), followed by pseudarthrosis (2.3% [2/87]), malpositioned instrumentation secondary to hook migration (2.3% [2/87]), and infection (1.1% [1/87]). During the reoperation for hook migration, the hooks were removed. There was a statistically significant difference in late reoperations between the 2 groups with respect to malpositioned instrumentation (P < 0.05), prominent instrumentation (P < 0.05), and pseudarthrosis (P = 0.05).
Risk for Reoperation
Statistical analysis was performed to identify risk factors for an unplanned return to the OR in patients with AIS treated with PSs (Table 4). Univariate analysis identified preoperative thoracic rib prominence (P < 0.05), estimated blood loss (P < 0.05), amount of cell saver transfused (P < 0.05), and surgical time (P < 0.001) as risk factors for an unplanned return to the OR for patients treated with PSs. There was a trend toward statistical significance of potential risk factors associated with an unplanned reoperation with the preoperative major coronal Cobb angle (P = 0.08), preoperative kyphosis (T5–T12) (P = 0.08), and first erect postoperative distal junctional kyphosis (P = 0.09). Multivariate regression analysis isolated surgical time as an independent risk factor for an unplanned return to the OR in the PS group (P < 0.05).
An analysis of SRS-22 total scores measured preoperatively in the PS group did not reveal any statistically significant differences between patients who subsequently underwent an unplanned return to the OR and those who did not (P = 0.47) (Table 5). Furthermore, subanalysis of the SRS-22 categories did not reveal a statistically significant difference associated with a reoperation (mean pain score P = 0.99, mean self-image score P = 0.37, mean general function score P = 0.64, mean mental health score P = 0.09, and mean satisfaction score P = 0.49).
This study reviewed a prospectively collected multicenter database to identify a consecutive series of patients with AIS who underwent posterior spinal fusion with either PS or Hb constructs with a minimum 2-year follow-up. All returns to the OR were identified and classified on the basis of timing and reason for return. The results suggest that patients with AIS treated with PS constructs have lower rates of return to the OR than those treated with Hb constructs (P < 0.001). In the PS group, most of the reoperations, 58% (n = 11/19), occurred in the early postoperative period (<60 days), and the most common indication was misplaced PSs (n = 9/19). In the Hb group, most of the reoperations, 73% (n = 8/11), occurred in the late postoperative period (>60 d) for pseudarthrosis and prominent instrumentation. In addition, longer operating time was identified as an independent risk factor for complications requiring a return to the OR for the PS group.
Several studies have reported on the reoperation rate in patients with AIS ranging from 3.9% to 12.9%.7–11 Although most of these studies categorized their surgical procedures by approach, they did not subdivide them into those patients treated with PSs. To date, Kuklo et al14 published the only study with a substantial number of patients with PSs (n = 295) and comparison group with Hb constructs (n = 423). They reported a 2.4% reoperation rate in the PS group, and a 5.7% reoperation rate in the Hb group. This study showed a reoperation rate of 3.5% in the PS group, compared with 12.6% in the Hb group (P < 0.001). PSs most likely have a lower reoperation rate than Hb constructs because they potentially provide a more stable correction15–19 and thus have a lower incidence of pseudarthrosis and instrumentation dislodgement. This finding was supported by this study (pseudarthrosis: PS = 0.2%, Hb = 2.3%, P = 0.05; prominent instrumentation: PS = 0.2%, Hb = 3.4%, P < 0.05; and late malpositioned instrumentation: PS = 0%, Hb = 2.3%, P < 0.05). In our series, the majority of reoperations in the Hb group occurred later, after 60 days, mainly for pseudarthrosis and instrumentation dislodgement. This was not observed in the patients treated with PSs.
In the PS group, 58% (11/19) of the returns to the OR occurred early (<60 d), and the majority were for misplaced screws (1.7%). Suk et al13 reported a 1.5% rate of PS misplacement in spine deformity, mostly on the convex side of the upper instrumented vertebra with no clinical consequences, but other studies suggest a breach rate as high as 58%.20–24 Results from our institution suggest a free hand PS breach rate closer to 10% on the basis of postoperative CT scans.25 Because the breached screws occurred early in the author's experience, we hypothesize that they are a consequence of the learning curve of placing PSs. In this cohort, instrumentation dislodgement was not observed in patients with PSs, but 3 patients in the Hb cohort experienced this as a reason for a late return to the OR.
Finally, the study isolated longer operating time as an independent risk factor for an unplanned reoperation in patients with AIS treated with PSs. The authors hypothesize that this is likely due to the increased risk of infection with longer operating times.26–29 In the PS group there were 8 reoperations for infection (2 occurred within <60 d, and 6 occurred >60 d). The mean surgical time for these patients was 409.3 ± 255.0 minutes, which was significantly longer than the mean surgical time of all the patients treated with PSs (274.79 ± 120.2 min) (P = 0.02). In addition, although we did not evaluate surgeon experience, it is possible that the more experienced surgeons have shorter operative times. To our knowledge, this is the first study that reports these findings for PS fixation in patients with AIS.
The limitations of this study include the fact that it was a retrospective review of a multicenter database. First, a retrospective analysis was necessary to obtain an appropriate sample size. Second, while the treatment groups were not equal in size, there were no significant differences between the 2 groups with regards to demographic and radiographical parameters. A matched cohort analysis would have drastically reduced our sample size and thus was not performed. Lastly, the mean follow-up time was longer in the Hb group (11.2 yr) than the PS group (4.7 yr). However, all of the reoperations in the Hb group occurred within the mean 4.7-year follow-up time frame of the PS group.
In summary, patients with AIS treated with PS constructs seem to have decreased rates of reoperation when compared with those treated with Hb constructs. In the patients treated with PSs, most of the returns to the OR occurred in the early postoperative period (<60 d) for misplaced PSs. In the patients treated with Hb constructs, most of the reoperations occurred in the late postoperative period (>60 d) for pseudarthrosis and prominent instrumentation. Longer operating times were found to increase the risk of an unplanned return to the OR in patients with AIS treated with PSs.
- Patients with AIS treated with PS constructs seem to have decreased rates of return to the OR when compared with patients with Hb constructs.
- The majority of unplanned reoperations for patients with AIS in the PS group occurred in the early postoperative period (<60 d) for screw misplacement, whereas reoperations for the Hb group occurred late (>60 d), predominantly for pseudarthrosis and prominent instrumentation.
- Longer OR time was identified as an independent risk factor for an unplanned return to the OR in patients with AIS treated with PSs.
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Keywords:© 2013 by Lippincott Williams & Wilkins
scoliosis; adolescent; idiopathic; reoperation; complication; posterior spinal fusion; pedicle screw; hybrid