This work was aimed at study the role of paraspinal muscles on spinal tensegrity. Four different models of spinal tensegrity breakage with and without injury of the posterior spinal muscle were investigated.

Fifteen minipigs (mean age 6-week) underwent costotransversectomy (CTT) at 5 consecutive vertebral segments. In 4 animals ribs and transverse processes (T7–T11) were removed through a posterior midline approach with complete desinsertion of paraspinal muscles. In other 3 animals, CTT was performed by a posterolateral approach (T6–T10) without detachment of paraspinal muscles. Other 4 minipigs underwent rib resection (T7-T11) throughout a thoracoscopic approach avoiding damage of posterior spinal muscles. A final group of 4 animals, a complete detachment of the paraspinal muscles was performed from T7 to T11 without removing bony structures and leaving in deep surgical wax attached to the spinous and transverse processes to avoid reinsertion of the muscles after surgery. Anatomic specimens were radiologically and macroscopically studied just at sacrifice 5 months after surgery

All 4 animals operated on of CTT by midline posterior approach developed structural spinal deformity with curve convexity at the side of rib removal (mean Cobb angle 34,6°). Animals undergoing CTT by posterolateral approach without paraspinal muscle detachment did not develop any significant spinal deformity. Absence of spinal deformity was also found in those animals in which rib resection was performed by thoracoscopy without injury of the posterior spinal muscles. All 4 animals undergoing detachment of the paraspinal muscles without CTT and application of the surgical wax developed scoliotic curves (mean Cobb angle of 28°).

In conclusion, a new insight on the underlying pathogenic mechanisms of scoliotic curves is given by using this spinal tensegrity model. Isolated damage of the posterior muscle-ligamentous structures around the costotransverse joints breaking muscles spine tensegrity seems to be mandatory to induce scoliotic deformity. Rib removal alone appeared to have less scoliotic inductive implication. The finding questions previous knowledge on scoliosis etiopathogeny.

Introduction and Objectives: The aim of this study is to evaluate the results of the technique described by Ahlgren and Larsson in 1989, presenting our experience with 7 patients.

Materials and Methods: A retrospective study was conducted on the clinical records of 7 adolescents treated in our center beginning in 1991 using the technique described by Ahlgren and Larsson. There were 3 males and 4 females, ranging in age from 13 to 16.5 years (average: 14 years 10 months). All subjects had a history of repeated ankle sprains for 2 to 5 years before surgery. In all cases there was painful instability of the ankle which significantly limited physical activity. In 4 cases, symptoms were present even when walking on level ground. On clinical examination, 3 cases showed significant instability under varus stress, 3 others had moderate instability, and one case had mild instability. Surgical technique was similar in all cases and involved creating a periosteal flap with a distal anterior base, including the fibulotalar and fibulocalcaneal ligaments, which was sutured with tension to the fibula. In 3 cases, this was done with the help of Mitek metal hooks. In 5 of 7 cases, an ossicle of the fibular malleolus visible on the radiographs was removed. Duration of surgery ranged from 30 to 60 minutes, with a mean of 40 minutes. Postoperative immobilisation consisted of a plaster cast used for an average of 45 days, after which time patients progressively returned to normal physical activities. Patients were advised to use an ankle brace. Average follow-up time was 35 months, with a range of 13 to 72 months.

Results: In 5 patients, a subjective improvement in ankle stability was found on examination. Only in one case was there a significant reduction in radiographic instability when the tibiotalar joint was moved from 20° to 8°. One patient developed a superficial infection of the surgical wound which resolved with antibiotic treatment. Two patients suffered sprains within the first year after intervention, but there were no further sprains, and the injuries did not seem to affect the final outcome. However, the outcome of one of these was considered to be only fair due to occasional mild pain which did not limit physical activity. Two cases had poor outcomes due to frequent pain which limited physical activity postoperatively for 2 and 6 years, respectively. However, neither patient had repeat sprains during this period. The remaining 4 cases were considered to have had good results, as the patients were totally asymptomatic and without any limitation of physical activity.

Discussion and Conclusions: This simple, non-aggressive method is an attractive option for use in adolescents. We therefore conclude that more studies are needed to validate its effectiveness.