03/12/2010
AO Technical Commission Approved

Universal Reduction Screws (URS) in the Treatment of Deformities

The indication for surgery of an idiopathic scoliosis according to Cobb should be a thoracic spine of more than 50 and lumbar spine of more than 45. In these cases surgery is necessary, leading to the correction and stabilization of the spine by implant systems. Surgical management of scoliosis is generally intended to prevent further progression of the deformity [1].

Nowadays in modern instrumentation systems, more anchors are used to connect the rod and the spine. This allows individual segmental rotation, resulting in better correction and less frequent implant failures [2]. Segmental pedicle screw constructs are considered the gold standard for deformity correction today [3].

Universal reduction screws (URS) are polyaxial pedicle screws with extended tabs, enabling rod reduction without the use of reduction instruments. The tabs can be broken off after rod reduction. The screw heads allow for a polyaxial adjustment of 90 around 360. The locking cap of the URS is designed as a two-step locking cap. The outer part of the locking cap captures the rod and locks the polyaxiality of the screw, while the inner part of the locking cap locks the rod in place. The individual fixation of the polyaxiality and the rod allows for segmental derotation as well as parallel compression and distraction.

Rod reduction and curve correction will be performed by reducing the locking cap within the extended tabs. As soon as the rod is fully reduced by the locking cap, the rod can be derotated to correct the deformity according to the Cotrel-Dubousset technique [4, 5]. To fine-tune the deformity reduction and to reduce the prominence of the rib hump, individual vertebral bodies can be segmentally rotated with the help of derotation tubes. After final tightening of the screws, the extended tabs are broken off the screw at their indented break-off line.

References

1 Hopf C (2000) [Criteria for treatment of idiopathic scoliosis between 40 degrees and 50 degrees. Surgical vs. conservative therapy]. Orthopde; 29(6):500506. German.

2 Shah SA (2007) Derotation of the spine. Neurosurg Clin N Am; 18(2), 339345.

3 Lehman RA Jr, Lenke LG, Keeler KA, et al (2008) Operative treatment of adolescent idiopathic scoliosis with posterior pedicle screw-only constructs: minimum three year follow-up of one hundred fourteen cases. Spine; 33(14):15981604.

4 Cotrel Y, Dubousset J, Guillaumat M (1988) New universal instrumentation in spinal surgery. Clin Orthop Relat Res; 227:1023.

5 Dubousset J, Cotrel Y (1991) Application technique of Cotrel-Dubousset instrumentation for scoliosis deformities. Clin Orthop Relat Res; 264:103110.

Case provided by Cornelius Wimmer, Vogtareuth, Germany

A 23-year-old man with neurogenic kyphoscoliosis, Cobb angle: 120. Fusion of T7S1 with universal reduction screws. Duration of surgery: 4.5 hours.

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