Mini open pedicle subtraction osteotomy
Technique
The osteotomy site is approached with a bilateral open subperiosteal dissection. Thus, it is achieved in a manner similar to an open pedicle subtraction osteotomy (PSO). This strategy overcomes the problem of control of bleeding and the management of neural structures intrinsic to 3-column osteotomies. However, the total soft tissue envelope disruption is similar to a 1-level posterolateral fusion or a 2-level open laminectomy. The surgery caudal to the PSO is performed with MIS transforaminal lumbar interbody fusions (TLIFs) with interbody cages, and potentially with percutaneous iliac screws. Above the PSO site, the construct is achieved with percutaneous screws supplemented with facet or interlaminar fusions.
Videos
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Case series
2016
The mini-open pedicle subtraction osteotomy (PSO) can achieve significant lumbar lordosis, although it is heavily reliant on anterior arthrodesis. Larger studies are needed to compare this approach with an open PSO.
Two patients underwent percutaneous fixation above and below the PSO, and the PSO was performed in a mini-open fashion. The correction was obtained by cantilever.
The patient who underwent the L3 PSO had a prior fusion from T11 to L4 for scoliosis 35 years ago. On presentation at 62 years of age, he had a pelvic incidence of 54°, lumbar lordosis of 23°, sagittal vertical axis of +14 cm, and pelvic tilt of 25°. He underwent an anterior lumbar interbody fusion at L5-S1 followed by a min-open L3 PSO. He had a postoperative lumbar lordosis of 64° (correction of 41°), and his sagittal vertical axis went to +3 cm. His Oswestry Disability Index and visual analog scale scores decreased after surgery. The second patient was 64 years of age and underwent an L1 PSO. He had 43° of kyphosis from T10 to L2. He had a preoperative pelvic incidence of 63°, lumbar lordosis of 35°, pelvic tilt of 24°, and sagittal vertical axis of 3 cm. His postoperative kyphosis improved from 43° to 32°.
The mini-open PSO can achieve significant lordosis, although it is heavily reliant on anterior arthrodesis. Larger studies are needed to compare this approach with an open PSO 1)
Sixteen patients with severe coronal- and/or sagittal-plane deformities were treated in this series. Conservative measures had failed in all cases and patients had undergone a single-level PSO or extended PSO at L-2 or L-3. Fixation was accomplished using percutaneous instrumentation and interbody or facet joint fusions were used at the remaining levels. None of the procedures were aborted or converted to a traditional open procedure. Standard clinical and radiographic measures were used to assess patient outcomes.
Mean age was 68.8 years and mean follow-up duration was 17.7 months. An average of 7.6 levels were fused, and 50% of the patients had bilateral iliac screw fixation, with all constructs crossing both the thoracolumbar and lumbosacral junctions. Operative time averaged 356 ± 50 minutes and there was a mean blood loss of 843 ± 339 ml. The leg visual analog scale score improved from a mean of 5.7 ± 2.7 to one of 1.3 ± 1.6, and the back visual analog scale score improved from a mean of 8.6 ± 1.3 to one of 2.4 ± 2.1. The Oswestry Disability Index score improved from a mean of 50.1 ± 14.4 to 16.4 ± 12.7, representing a mean reduction of 36.0 ± 16.9 points. The SF-36 physical component summary score changed from a mean of 43.4 ± 2.6 to one of 47.0 ± 4.3, and the SF-36 mental component summary score changed from a mean of 46.7 ± 3.6 to 46.30 ± 3.0. Coronal alignment improved from a mean of 27.9 ± 43.6 mm to 16.0 ± 17.2 mm. The lumbar Cobb angle improved from a mean of 41.2° ± 18.4° to 15.4° ± 9.6°, and lumbar lordosis improved from 23.1° ± 15.9° to 48.6° ± 11.7°. Pelvic tilt improved from a mean of 33.7° ± 8.6° to 24.4° ± 6.5°, and the sagittal vertical axis improved from 102.4 ± 73.4 mm to 42.2 ± 39.9 mm. The final lumbar lordosis-pelvic incidence difference averaged 8.4° ± 12.1°. There were 4 patients who failed to achieve less than or equal to a 10° mismatch on this parameter. Ten of the 16 patients underwent delayed postoperative CT, and 8 of these had developed a solid arthrodesis at all levels treated. A total of 6 complications occurred in this series. There were no cases of symptomatic proximal junction kyphosis.
Advancements in minimally invasive technique have resulted in the ability to manage increasingly complex deformities with hybrid approaches. In this limited series, the authors describe the results of utilizing a tissue-sparing mini-open PSO to correct severe spinal deformities. This method was technically feasible in all cases with acceptable radiographic outcomes similar to open surgery. However, high complication rates associated with these deformity corrections remain problematic 2).
Case report
2014
Wang and Madhavan, describe the evolution of a technique for treating thoracolumbar kyphoscoliosis using a mini-open pedicle subtraction osteotomy (PSO) combined with interbody fusion and percutaneous pedicle screws.
The patient underwent a T10 to S1 percutaneous posterior instrumented with an L3 PSO and right L4/5 minimally invasive transforaminal interbody fusion. Clinically, the patient had excellent improvement and regained the ability to ambulate independently for distances of up to one half mile. Imaging demonstrated good correction of coronal imbalance (1.8 to 9.5 cm) and sagittal imbalance (sagittal vertical axis of 22.5 to 7 cm).
The correction of sagittal plane deformities remains difficult using MISS approaches. In this report, we describe a new technique using a mini-open PSO technique to achieve significant improvement in thoracolumbar lordosis 3)