Purpose: The purpose of this study is to detect the changes occurring occur in patients with adolescent idiopathic scoliosis in terms height and Cobb’s angle during a specific period of time by means of a mathematic model.

Materials and methods: This was a retrospective study of a cohort of 132 girls. The inclusion criteria were the following: adolescent idiopathic scoliosis, Cobb’s angle greater than 10°, follow-up of at least 2 years with half-yearly controls. The variables were: year of onset of menstruation (menarche), height, Cobb’s angle and treatment. The changes in height and Cobb’s angle which occurred with time were adjusted through curved regression models. The gradient was calculated between each of the consecutive time points (first-degree derivative). Growth was considered stable when the gradient changed direction or was illegible.

Results: The cubic measure was found to be best fitted to the height (R2=0.329) and signal-change parameters of the gradient a year after the onset of menstruation (menarche). The force function was the best for Cobb’s angle, albeit with a slight adaptation (R2=0.038). A correlation was found between the mean height and the angles. This value was found to be higher for girls treated with a brace. Comparing the mean heights recorded in one semester with those of the previous semester, one can observe statistically significant differences up to 2.5– 3 years post-menarche.

Conclusions: Cobb’s angle and height in conservatively-treated adolescent idiopathic scoliosis often stabilize 2,5 years and after the onset of menstruation. Patients treated with a brace stabilize when they reach menarche.

Introduction and Objectives: This is a retrospective study on the treatment of lumbar degenerative disk disease (LDDD) using intervertebral arthroplasty. The lack of uniformity in the treatment of LDDD, persistence of pain even with solid fusion, and the possibility of changes over the fusion site have encouraged us to seek other solutions for this condition. Total intervertebral arthroplasty has been proposed as a possible alternative for selected cases of LDDD.

Materials and Methods: Between November 1999 and July 2002, 16 patients with LDDD were treated surgically using third-generation total intervertebral arthroplasty (Link SB Charité III) with a chromium-cobalt alloy and ultra-high molecular weight (UHMW) poly-ethylene. Average follow-up time was 14 months (6-36 months), and average age was 42 years (35–52). There were 11 females and 5 males. All patients underwent radi-olographic studies, CT scan, MRI, and discography (minimum 2 levels). Indications included LDDD of one to three segments, absence of root tension signs, absence of complete disc collapse, and iconography including concordant discography. LDDD was primary in 11 cases and post-discectomy in 5 cases. Surgery was indicated when at least 6 months of conservative treatment failed to yield results. Blood loss and length of hospital stay were compared to a similar group that underwent posterolateral arthrodesis. Pain, function, and degree of disability were evaluated before and after surgery using GEER (1999) instruments for the evaluation of degenerative lumbar pathology. Increase in height of the posterior intervertebral space and segmentary lordosis were also measured.

Results: Preoperative VAS: 7.8; postoperative VAS: 2.3. Disability index (Oswestry) was 41.3% preoperative and 10.8% postoperative. Average increase in height of posterior intervertebral space was 2.4mm, and mean segmental lordosis was 19.5°, which remained constant through the end of the follow-up period. Average hospital stay was 4.8 days (3–15) compared with 7.5 (5–18) for a group of patients who underwent suspended arthrodesis of L4–L5 with a much smaller quantity of blood loss. No infections were found. Complications: One patient developed an epidural haematoma, which was treated conservatively. Another developed a postoperative retroperitoneal haematoma, which was also treated conservatively. In neither case was there an adverse effect on the outcome of the procedure. One patient showed malpositioning of the prosthetic components on follow-up radiographs, with poor clinical progression at one year postoperative. The patient was treated with posterolateral fusion and right L5 foraminotomy. No infections were seen.

Discussion and Conclusions: Treatment of LDDD with intervertrebral arthroplasty was shown to be effective in the short term, if strict guidelines are followed. Aggressive surgical management is highly inferior to conventional arthrodesis. A longer follow-up period is needed to confirm the validity of this treatment. Technical error in malpositioning of the components in one case caused a poor result.