Summary: 86 patients with Scheuermann's kyphosis with a minimum 2‐year follow‐up were reviewed for evidence of proximal (33%) or distal (11%) junctional problems. The upper instrumented vertebra should be the proximal end vertebra, or T2 if the spine is in forward sagittal imbalance, and the LIV should be the vertebra below with first lordotic disc, or the SSV if the spine is in global sagittal imbalance.
Introduction: The optimal proximal and distal fusion levels in patients undergoing instrumented spinal fusion for Scheuermann's kyphosis (SK) is still controversial. Previous studies recommend the proximal fusion level to be the proximal end vertebra (PEV) but still 30% of the pts developed proximal junctional kyphosis (PJK). As to the optimal distal fusion level, most of the surgeons select the vertebra below the first lordotic disc. A recent study recommended selection of the sagittal stable vertebra (SSV) as the lowest instrumented vertebra (LIV). However, distal junctional problems (DJP) still may occur even using these criteria.
Methods: 86 pts (53 males/33 females) who underwent instrumentation and correction surgery for SK were reviewed (ave age, 18.3±6.6). Cobb angles were measured on preop lateral standing, initial postop lateral standing, 2yrs postop lateral standing, last F/U lateral standing radiographs.
Results: The mean preop max Cobb angle was 85.8°±11.7, corrected to 54.8°±14.2 postoperatively, maintained at 59.7°±16.8 at last F/U (PJK group: 66.9°±18.3; nonPJK group:56.3°±15.1). The mean correction ratio was 43.6%. PJK occurred in 28 cases (33%). DJP occurred in 11 cases (13%). There was a significant difference in PJK morbidity between the groups regarding fusion levels at or above the PEV and the fusion level below the PEV (p<0.05). Pts with a proximal fusion level at or above T2 had less PJK morbidity vs below T2 (p<0.05). 5 out of the 6 pts with a preop C7 plumbline (C7PL) ≥50mm developed PJK, which was significantly different from pts with C7PL <50mm (p<0.05). There was a significant difference in DJP morbidity between the groups regarding fusion level above the first lordotic disc vs below first lordotic disc (p<0.05). 4 pts had a fusion level below the first lordotic disc but DJP still occurred. All had global sagittal imbalance preop.
Conclusion: In SK, the optimal proximal fusion level is the PEV. It is better to select T2 or above when it is difficult to determine the PEV especially when the C7PL ≥50mm. The optimal distal fusion level is the vertebra below the first lordotic disc. If preop sagittal imbalance exists, the distal fusion level should extend distally to the SSV or one level lower than the first lordotic vertebra.