[Percutaneous dynamic interspinous stabilisation for the treatment of juxtafacet cysts of the lumbar spine: prospective study].

PURPOSE OF THE STUDY: To present the authors' philosophy on the surgical treatment of juxtafacet cysts of the lumbosacral (LS) spine, with its primary aim of dynamic lumbar stabilisation with an interspinous implant, inserted by a minimally invasive approach, without concurrent exploration of the spinal canal and cyst removal.

MATERIAL AND METHODS: During a 20-month period, ten patients aged between 25 and 70 years (average age, 53.2 years) were indicated for surgical treatment of a juxtafacet cyst by percutaneous insertion of an In-Space interspinous spacer without surgical exploration of the spinal canal. The group comprised six men and four women. At a follow-up of 6 weeks to 18 months, each patient underwent MRI examination of the LS spine and the degree of cyst resorption was assessed. The visual analogue scale (VAS) scores, Oswestry Disability Index (ODI) and range of motion (ROM) values, and a sagittal angle (SA) of the segment treated obtained for the whole group at 3 to 18 months after surgery were compared with the pre-operative va - lues. The surgeon evaluated the effect of surgery on radicular and axial pain.

RESULTS: Complete resorption of the cyst was found in seven patients (70%) and three (30%) showed partial resorption. Complete resolution of radicular symptoms was reported by five patients (50%); five experienced partial relief (50%). Lumbago was relieved completely in three (30%) and partially in seven (70%) patients. The average VAS score was 6.7 points (range, 4-10) pre-operatively and 3.5 (0-8) post-operatively, i.e. it decreased by 3.2 points, which meant an improvement by 48%. The average ODI value was 58.4% (range, 32-80) pre-operatively and 23.9% (0-70) post-operatively, i.e., it decreased by 34.5 percentage points and was an improvement by 59%. The average ROM measures were 5.65 degrees (range, 2°-10°) pre-operatively and 5.55 degrees (0°-19°) post-operatively. The average pre- and post-operative sagittal angles in normal lumbar lordosis were 7.1 degrees (1°-13°) and 6.2 degrees (1°-11°), respectively.

DISCUSSION: The conventional surgical procedure involves cyst extirpation. However, the procedure only relieves nerve root compression but does not remove the cause of juxtafacet cyst development, which is due to facet joint degeneration and instability. This may results in persistent or recurrent clinical symptoms. On the other hand, a reduction of both mobility and loading of the intervertebral joints achieved by implantation of an interspinous spacer is the mechanism allowing for resorption of the cyst and resolution of symptoms.

CONCLUSIONS: 1. The original method of treating juxtafacet cysts of the LS spine by an In-Space interspinous spacer, as presented here, was efficient in all patients and resulted in complete, or at least partial, resorption of the cyst. 2. Segmental mobility and spondyloarthritis are the major aetiological factors of juxtafacet cyst development. 3. Dynamic interspinous stabilisation will reduce loading of the intervertebral joints and will thus allow for cyst resorption and clinical symptom resolution. 4. Percutaneous implantation of an "In-Space" interspinous spacer is a minimally invasive method of dynamic stabilisation that means no restrictions in patients' activities and reduces the length of hospital stay.