What is the impact of scoliotic correction on postoperative shoulder imbalance in severe and rigid scoliosis

Background Although recent studies have investigated the risk factors for PSI, few studies have focused on the impact of scoliotic correction on postoperative shoulder imbalance (PSI), especially in severe and rigid scoliosis (SRS). The purpose of the study was to study the effect of scoliotic correction on PSI in SRS. Methods The preoperative, postoperative, and minimum 2-year follow-up radiographs of 48 consecutive patients with SRS who underwent posterior spinal fusion surgery were evaluated. We regarded radiographic shoulder height (RSH) as a shoulder balance parameter and divided the patients into improved and aggravated groups of PSI from pre- to post-operation and from post-operation to last follow-up, respectively. In addition, patients were divided into nine groups based on the observed changes in PSI after surgery and at follow-up, and the correction rate ratios were calculated among the groups. Independent samples T test and Chi-squared test were performed between the improved and aggravated groups of PSI. Results After surgery, the proximal thoracic curve (PTC) flexibility (P = 0.040), correction rate of the main thoracic curve (MTC) (P = 0.010), and Cobb angle of the lumbar curve (LC) (P = 0.037) were significantly higher, while the ratio of the correction rate of the PTC to the MTC (P = 0.042) was smaller in the aggravated group. At follow-up, the improved group had significantly larger PTC flexibility (P = 0.006), larger ratio of the correction rate of PTC to MTC (P = 0.046), a larger ratio correction rate of PTC to LC (P = 0.027), and a smaller correction rate of LC (P = 0.030). The correction rate ratios of the groups after surgery were as follows: negative to negative (N-N) (1.08) > negative to balance (N-B) (0.96) > negative to positive (N-P) (0.67), B-N (1.26) > B-B (0.94) > B-P (0.89), and P-N (0.34) > P-P (0.83). The order of the correction rate ratio at follow-up was as follows: N-N (0.96) > N-B (0.51), B-B (0.97) > B-P (0.90), and P-B (0.87) > P-P (0.84). Conclusion Harmonizing the correction rate ratio of the PTC, MTC, and LC should be recommended for intraoperative correction and postoperative compensation of PSI. In addition, greater PTC flexibility plays an important role in the spontaneous correction and compensation of PSI in SRS.

Upper End Vertebra of Proximal Thoracic Curve At T1 is a Novel Risk Factor of Postoperative Shoulder Imbalance in Lenke Type 2 Adolescent Idiopathic Scoliosis

Study Design: Retrospective single-center study. Objective: We investigated the risk factors of postoperative shoulder imbalance (PSI) in patients with Lenke type 2 adolescent idiopathic scoliosis (AIS) including the position of preoperative upper end vertebra (UEV). Methods: Seventy-five patients with Lenke type 2 AIS who underwent posterior correction and fusion surgeries from 2008 to 2018 were included. We included only patients whose upper instrumented vertebrae were at T2. The patients were divided into 2 groups based on radiographic shoulder height (RSH) at final follow-up, namely PSI group and non-PSI group, and PSI was defined as RSH > 10 mm. UEV, RSH, Cobb angle, curve flexibility, T1 and T2 tilt, correction rate, Risser grade, Scoliosis Research Society-22 scores, and demographic data were compared between the groups using independent t-tests or chi-square tests. Variables with P value < 0.20 in univariate analysis were assessed in logistic regression analysis. Results: Thirty-four patients in the PSI group and 37 patients in the non-PSI group were analyzed. Univariate analysis revealed that there were more patients with UEV at T1 (PSI: 85%, non-PSI: 54%, P < 0.01) and Risser grade ≥ 3 (PSI: 88%, non-PSI: 62%; P < 0.05) in the PSI group than in the non-PSI group. Logistic regression analysis revealed that UEV at T1 (odds ratio [OR] = 4.1 [1.2–14.4], P < 0.05) and Risser grade ≥ 3 (OR = 3.9 [1.1–14.5], P < 0.05) are significantly associated with PSI. Conclusions: UEV at T1 and Risser grade ≥ 3 at the time of surgery are significant risk factors of PSI.

Analysis of Preoperative and Operative Factors Influencing Postoperative Shoulder Imbalance in Lenke Type 1 Adolescent Idiopathic Scoliosis

Background Postoperative shoulder imbalance is a common complication in adolescent idiopathic scoliosis and may impair patient satisfaction. The little data in the literature on the prediction and treatment of postoperative shoulder imbalance is incongruous. According to some studies, postoperative shoulder imbalance depends on the superior instrumented vertebral bodies, skeletal maturity, extent of correction and flexibility of the major curve. Question Can preoperative radiological parameters from X-ray and traction films as well as correction of the curves be used to identify a factor impacting on postoperative shoulder imbalance? Material and Methods Prospective data in adolescent idiopathic scoliosis with thoracic curve (Lenke type 1), operated on between 2015 and 2018 at a scoliosis centre, were analysed retrospectively based on full-length X-rays of the spine (pre-/postOP and follow-up (FU)) and preoperative-traction films: age; correction of proximal, main and lumbar curve; shoulder height [mm]; clavicle angle [°]; T1 tilt [°]; coronal plumb line deviation [mm]. The findings were expressed as means with standard deviation. Changes in parameters over time (postOP-FU) were compared by t test (significance level α = 0.05). The correlation between preOP parameters and extent of correction with postoperative shoulder imbalance (≥ 15 mm) was determined by Pearson correlation and regression classification analysis. Outcomes 55 patients with adolescent idiopathic scoliosis, mean age of 15 ± 1.4 years. The FU-rate after a mean of 15 months was 80% (n = 44). Correction of proximal, main and lumbar curve: 47.0%, 75.8% and 68.8%, respectively, without statistically significant change (Δ) in FU (p > 0.05). Shoulder height was − 11.0 ± 12.7 mm (preOP), 15.5 ± 13.4 mm (postOP), 10.1 ± 10.6 mm (FU) (p < 0.05). 38% of those with adolescent idiopathic scoliosis had preOP right shoulder elevation; 55% (postOP) and 32% (FU) respectively had postoperative shoulder imbalance (left shoulder elevation). Strong statistical correlation was found for Δshoulder position (FU-preOP) with pre-OP shoulder position (r = − 0.7), and Δshoulder position (pre-OP traction films) (r = 0.5) with pre-OP clavicle angle (r = − 0.5). On regression classification analysis, 81.8% of cases did display postoperative shoulder imbalance if proximal curve correction was ≤ 64.4%; main and lumbar curve correction, Δshoulder elevation (preOP traction films) played a secondary role. Discussion One common complication even in Lenke type 1 adolescent idiopathic scoliosis is postoperative shoulder imbalance. Preoperative planning should include traction films, preoperative shoulder position and clavicle angle to avoid postoperative shoulder imbalance. Moderate correction of proximal curve is critical for postoperative shoulder balance.

An analysis of preoperative shoulder and neck balance and surgical outcome in 111 adolescent idiopathic scoliosis patients with two subtypes of Lenke 1 curves

OBJECTIVEThe incidence of postoperative shoulder imbalance following posterior spinal fusion (PSF) is still high in Lenke 1 curves despite following current treatment recommendations for upper instrumented vertebra (UIV) selection. The objective of this retrospective study was to identify differences in preoperative shoulder balance and to report the surgical outcome of two subtypes of Lenke 1 curves (flexible vs stiff) in patients with adolescent idiopathic scoliosis (AIS).METHODSThe authors grouped patients’ curves as Lenke 1–ve (flexible) when their preoperative proximal thoracic side bending (PTSB) Cobb angle was < 15° and as Lenke 1+ve (stiff) when the PTSB Cobb angle was 15°–24.9°. The authors hypothesized that these two subtypes had distinct preoperative and postoperative shoulder and neck balance following PSF using pedicle screw constructs.RESULTSFifty patients had Lenke 1 (flexible) curves and 61 had Lenke 1 (stiff) curves. The mean preoperative T1 tilt for patients with Lenke 1 (flexible) was −4.9° ± 5.3°, and for those with Lenke 1 (stiff) curves it was −1.0° ± 5.3° (p < 0.001). Mean cervical axis (CA) was −0.1° ± 3.2° for Lenke 1 (flexible) curves and 2.3° ± 3.5° for Lenke 1 (stiff) curves (p < 0.001). Preoperative radiographic shoulder height (RSH) and clavicle angle (Cla-A) were similar between the two curve subtypes. Following surgery, there were significant differences between the subtypes in terms of T1 tilt (p < 0.001), RSH (p = 0.014), and Cla-A (p = 0.031). Interestingly, 41.0% of patients with a Lenke 1 (stiff) curve had +ve T1 tilt compared to 2.0% in Lenke 1 (flexible) group. Moreover, 26.2% of patients with the Lenke 1 (stiff) curve had +ve RSH compared to 12.0% of those with Lenke 1 (flexible) curves. And, 24.6% of patients with Lenke 1 (stiff) had +ve Cla-A compared to 10.0% of those with Lenke 1 (flexible) curves.CONCLUSIONSLenke 1 (flexible) and Lenke 1 (stiff) curves had distinct preoperative T1 tilt and CA measurements. Following PSF, the authors noted +ve T1 tilt in 41% of patients with Lenke 1 (stiff) curves versus 2.0% in those with Lenke 1 (flexible) curves. The authors also noted a significant difference in postoperative RSH and Cla-A measurements.