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Tissue engineering of articular cartilage usually requires the isolation and culture of chondrocytes. Previous studies have suggested that enzymatic isolation may alter the metabolic activity and growth rate of chondrocytes. This study examined the effects of 4 common isolation protocols on chondrocyte gene expression, morphology, and total cell yield immediately following the digest (t = 0) and after 2 culture periods (24 h and 1 week). Cartilage explants were digested using 1 of 4 protocols: (1) 6-h collagenase digest, (2) 22-h collagenase digest, (3) 45-min trypsin digest followed by a 3-h collagenase digest, or (4) 1.5-h pronase digest followed by a 3-h collagenase digest. Gene expression levels for glyceraldehyde-3-phosphate dehydrogenase, type I collagen, type II collagen, aggrecan, superficial zone protein, matrix metalloproteinase- 1, and tissue inhibitor of metalloproteinase-1 were measured at t = 0 h, 24 h, and 1 week using quantitative reverse transcriptase-polymerase chain reaction. In this study, cell yield was greatest for the 22-h collagenase and pronase-collagenase digests. However, the data indicate that a 6-h collagenase digest has the fewest gene expression changes compared to native cells. For tissue engineering, data from this study suggest that when cell yield is critical, a 22-h collagenase digest is preferable, but when obtaining cells closest to native chondrocytes is more desired, the 6-h collagenase digest is more beneficial.

Level III-retrospective cohort study.

Object Significant lumbar kyphosis is frequently observed in patients with myelomeningocele and has been associated with increasing functional impairment, decreased abdominal volume, respiratory impairment, discomfort, and skin ulcerations overlying the prominent gibbus. Treatment of severe kyphotic deformities can include kyphectomy, with or without ligation of the thecal sac, with posterior spinal fixation. However, most series have reported a high rate of morbidity and complications associated with surgical intervention for correction of kyphosis in patients with myelomeningocele. The authors describe a technique in which pedicle screw (PS)–only constructs are used without transection of the thecal sac to treat severe kyphosis successfully, with minimal morbidity. Methods The authors retrospectively reviewed medical records and radiographic images in 2 patients with myelomeningoceles in whom kyphectomies had been performed at the authors' institution between January 2007 and July 2010. They also reviewed the existing literature for case reports or published series of patients with myelomeningocele treated with kyphectomies, to evaluate the outcomes. Results Both patients were male and had thoracic-level myelomeningoceles that had been repaired at birth, with associated paraplegia. Neither patient had any significant scoliotic deformity associated with the kyphosis, and both had fixation from T-9 to the ilium, which was performed using PS constructs, along with L1–2 kyphectomies. The patient in Case 1 was 20 years old and was treated for progressive kyphosis and an ulcerated nonhealing wound over the gibbus. The patient in Case 2 was 10 years old and was treated for progressive pain and functional impairment. The 2 patients had a mean correction of 63%, with a mean correction of kyphotic deformity from 136° to 51°. Neither patient developed any complication in the short term postoperatively, whereas published series have reported high complication rates, including wound infection, poor wound healing, CSF leakage, pseudarthrosis, and shunt malfunction. Conclusions Severe kyphotic deformities in patients with myelomeningocele can be safely treated using PS-only constructs without ligation of the thecal sac. Further evaluation with a larger sample and longer follow-up are needed to detect any associated complications, such as proximal junctional kyphosis. Further evaluation may also validate whether PS-only constructs permit successful outcomes with a shorter construct and fewer instrumented levels.