Purpose: Cervical arthroplasty is an emerging technology with the potential of motion preservation and reduced adjacent level disease. However, the factors that influence postoperative range of motion (ROM) and patient satisfaction is not fully understood. The aim of this study was to evaluate the influence of disk height on the postoperative motion as well as clinical outcomes.

Method: 167 patients from a multi-center prospective randomized FDA trial with single level ProDisc-C arthroplasty performed were evaluated radiographically utilizing Medical Metrics (QMATM, Medical Metrics, Inc.). Preoperative and postoperative disk height and ROM were measured from standing lateral and flexion-extension radiographs. Of these 167 patients, 19 patients from a single center had clinical outcomes based on ODI and VAS scores evaluated pre and postoperation with a mean follow-up of 22 months. Two-tailed student’s T-test and Spearman’s Rho tests were performed in order to find out if there was any correlation or “threshold” effect between the disk height and ROM.

Results: Patients with less than 4 mm of preoperative disc height had a 1.8° increase in their flexion-extension ROM after TDA as compared to no change in ROM in patients with more than 4 mm of preoperative disc height (p=0.04). Patients with more than 5mm of postoperative disc height have significantly higher postoperative flexion-extension ROM (10.1°) than those with less than 5mm disc height (8.3°, p=0.014). However, patients with more than 7mm of postoperative disc height have significantly lower postoperative lateral bending ROM (4.1°) than those with less than 7mm disc height (5.7°, p=0.04). It appears that the optimal postoperative disc height is between 5 to 7 mm for increased ROM on flexion-extension and lateral bending. No correlation could be found between clinical outcomes and disc height. Similarly, no threshold effect could be found between any specific disc height and ODI or VAS.

Conclusion: Patients with greater disc collapse benefit more in ROM from a TDR. The optimal range to maximize ROM for postoperative disc height is between 5 to 7mm. This optimal range did not translate into better clinical outcome at 2 year follow-up. A longer follow-up will yield if less ROM ultimately leads to worse clinical outcomes.

Combined anterior/posterior scoliosis surgery is the mainstay of scoliosis surgery in large curves with Cobb angle more than 65°, in stiff curves that correct to above 40° only on the pre-operative bending films and in Steersman’s kyphosis greater than 90°. The combined anterior/posterior scoliosis surgery allows better correction of the curve, saving motion segments in the spine and eliminating the occurrence of the crankshaft phenomenon. Video-assisted spinal surgery (VATS) and Mini open thoracotomy, thoracoscopically assisted (MOT-TA) allow for the performing of multi level discectomies and soft tissue release, as an anterior adjunct to posterior spine fusion, through minimal approach to the thoracic spine in scoliosis surgery. During the last year we have begun using the MOT-TA for anterior thoracic spine release and fusion, as the first step in releasing, reducing, and fusing large and stiff scoliotic curves, utilizing standard surgical instrumentation and techniques.

Materials and Methods: Mini-Thoracotomy Thoracoscopic Assisted was performed on 15 patients, age 4 to 48 (mean 20 years old) between January 2000 to present. There was a female predominance (12:3). In the group, 13 patients were scoliosis patients and 2 were kyphosis patients. All patients underwent anterior release and discectomy before performing posterior fusion. A mean of 4 discs (range 3 to 5 discs) was excised at surgery. The mean Cobb angle was 62°. No anterior instrumentation was placed in the first 14 cases. In case No. 15 an anterior crew-rod construct was placed through the mini thoracotomy incision.

Technique: MOT-TA is performed with the patient positioned in a lateral decubitus with the convex side of the scoliotic curve up through a 5–7 cm skin incision above the apical vertebra obliquely from the posterior to the middle axillary line.

Results: There was a short learning curve associated with the technique, which proved to be an easy and straight forward surgical technique. Pre-operative thoracic Cobb angle measured 50°–80° (average 62°) that bends to 30°–66° on the pre-operative thoracic bend films (average 45°). The pot-operative thoracic Cobb angle measured 15°–38° (average 28°). The overall curve correction was 59% on average. The anterior soft tissue releases and discectomies were a quick and relatively “dry” part of the surgery. Estimated blood loss ranged 50–800cc, less than a quarter of the total intra-operative blood loss averaging 220cc out of 1227cc of the total EBL. Anterior surgery time ranged 100 to 170 min averaging 147min for mean of 6.1 discs (range 4 to 9 discs). When compared to the total operative time, the anterior part of the surgery took about a 1/3 of the total surgery time.

Discussion: The results of the study show that the mini open thoracotomy, thoracoscopically assisted, for anterior thoracic spine release and discectomies is a fast, easy to learn technique with a short learning curve leading to complete anterior release, short operative time, allowing same day front and back surgery with no difficulty in performing internal thoracoplasty that results in structural and cosmetically superior outcome. In the hands of an experienced surgeon, the usage of VATS could be an effective and beneficial in scoliosis surgery; however, in the case of less experienced surgeon, who has no experience in thoracoscopic surgery, the MOT-TA could be an elegant and useful way to perform the technically demanding anterior discectomies and releases in severely deformed and rigid scoliotic spine. In our last case we have demonstrated the ability to instrument the anterior spine utilizing the same mini thoracotomy incision, this advance will be carried further to more extensive instrumentation in the future.

In conclusion: Mini open thoracotomy, thoracoscopically assisted, for anterior thoracic spine release and fusion is a faster, easier, cosmetically superior and surgically justified procedure.