Mechanical axis following staple epiphysiodesis for limb-length inequality.

BACKGROUND: Staple epiphysiodesis is an option for the treatment of limb-length discrepancies, but it is not without complications. The purpose of this study was to review the outcomes of staple epiphysiodesis, including changes in the mechanical axis. METHODS: The study included patients who underwent, between 1990 and 2005, staple epiphysiodesis of the femur or tibia, or both, to address limb-length discrepancy. We reviewed preoperative, postoperative, and final long standing anteroposterior radiographs of fifty-four patients to assess limb-length discrepancy, shifts in the mechanical axis, changes in the mechanical axis zone, and changes in the anatomic lateral distal femoral angle and the medial proximal tibial angle. Postoperative radiographs were also reviewed to assess the adequacy of staple placement. RESULTS: Three staple epiphysiodesis groups were identified: fifteen patients who underwent a distal femoral staple epiphysiodesis, eighteen who underwent a proximal tibial procedure, and twenty-one who underwent combined distal femoral and proximal tibial procedures. Fifty percent (twenty-seven) of the fifty-four patients showed a shift in the mechanical axis of > or =1 cm as compared with the preoperative measurement. Eighty-nine percent of these large shifts were varus in nature. The proximal tibial and combined epiphysiodeses resulted in significantly larger shifts in the mechanical axis (p = 0.002 and p = 0.006, respectively) and zone changes (p = 0.009 and p = 0.006, respectively) than did the distal femoral procedures. Six patients ultimately underwent a high tibial osteotomy to correct a post-stapling varus deformity. The proximal-lateral aspect of the tibia was by far the most common location for inadequate staple placement. CONCLUSIONS: Mechanical axis deviation is common following staple epiphysiodesis for the treatment of limb-length discrepancy. Proximal tibial and combined distal femoral and proximal tibial staple epiphysiodeses, even if done well technically, lead to clinically relevant shifts in the mechanical axis of the lower extremity more than half of the time. Distal femoral staple epiphysiodesis may still be a safe option for the treatment of limb-length discrepancy, but we advise caution when utilizing proximal tibial staple epiphysiodesis to treat limb-length inequality.

Double inactivation of NF1 in tibial pseudarthrosis.

Osseous abnormalities, including long-bone dysplasia with pseudarthrosis (PA), are associated with neurofibromatosis type 1 (NF1). Prospectively acquired tissue from the PA site of two individuals with NF1 was used for immunohistochemical characterization and genotype analysis of the NF1 locus. Typical immunohistochemical features of neurofibroma were not observed. Genotype analysis of PA tissue with use of four genetic markers (D17S1863, GXALU, IN38, and 3NF1-1) spanning the NF1 locus demonstrated loss of heterozygosity. These results are the first to document double inactivation of NF1 in PA tissue and suggest that the neurofibromin-Ras signal transduction pathway is involved in this bone dysplasia in NF1.

Medial compartment syndrome of the foot: an unusual complication of spine surgery.

STUDY DESIGN: Descriptive case report. OBJECTIVES: To report the case of a child with medial compartment syndrome of the foot following posterior spinal instrumentation and fusion. SUMMARY OF BACKGROUND DATA: No previous study has reported medial compartment syndrome of the foot following spinal surgery. METHODS: A 15-year-old female with progressive idiopathic scoliosis was taken for posterior instrumentation and fusion. The patient had a history of severe postexertional cramping in the feet following athletics. Surgery progressed uneventfully and the patient was continuously monitored with somatosensory-evoked potentials, which showed no changes. In the recovery room, the patient complained of severe cramping in one foot that was similar to her postexertional cramping. This was lessened with massage and ketorolac. Soreness continued in the foot into postoperative day one and then increased overnight. On the morning of postoperative day 2, pressure in the medial compartment was found to be 97 mm Hg and she was taken for fasciotomy, which found necrosis of the abductor hallucis muscle, and all other compartments of the foot were normal. RESULTS: At the 6-month follow-up, the patient is doing well with no known sequelae. CONCLUSION: This was a very rare case of medial compartment syndrome of the foot following spine surgery. We believe that the patient had a predisposition, whether neurologic or vascular, toward cramping in the foot and that this activity was stimulated by the nerve stimulation during the evoked potential monitoring. Although the patient had thoracic epidural analgesia after surgery, it was not felt to have contributed to the development or result of the compartment syndrome. We strongly advocate for checking patients feet and legs during surgery for overactivity and stress the need for a high index of suspicion for compartment syndrome for unexplained pain after surgery.