Knee Menisci.

The menisci of the knees are semicircular fibrocartilaginous structures consisting of a hydrophilic extracellular matrix containing a network of collagen fibers, glycoproteins, and proteoglycans maintained by a cellular component. The menisci are responsible for more than 50% of load transmission across the knee and increase joint congruity thereby also aiding in fluid film lubrication of the joint. In the United Kingdom, meniscal tears are the most common form of intra-articular knee injury and one of the commonest indications for orthopedic intervention. The management of these injuries is dependent on the location within the meniscus (relative to peripheral blood supply) and the pattern of tear. Removal of meniscus is known to place the knee at increased risk of osteoarthritis; therefore repair of meniscal tears is preferable. However, a significant proportion of tears are irreparable and can only be treated by partial or even complete meniscectomy. More recent studies have shown encouraging results with meniscal replacement in this situation, though further work is required in this area.

Postoperative changes in spinal rod contour in adolescent idiopathic scoliosis: an in vivo deformation study.

STUDY DESIGN: Prospective case series. OBJECTIVE: To evaluate the change in spinal rod contour from before implantation to after surgical correction of thoracic curves in patients with adolescent idiopathic scoliosis. SUMMARY OF BACKGROUND DATA: With segmental pedicle screw spinal instrumentation and vertebral derotation, many authors have reported a loss of thoracic kyphosis postoperatively. Although surgeons anticipate some flattening of the preimplantation rod contour in the sagittal plane, the magnitude of this change in shape has not been documented. METHODS: The concave and convex rod shapes of 5.5-mm ultrahigh-strength steel spinal rods (200 KSI) from patients with thoracic adolescent idiopathic scoliosis (n = 27), which were contoured with benders by the surgeon, were traced prior to insertion. Postoperative (average, 5 weeks) sagittal rod shape was determined from lateral 2-dimensional radiographs. Maximal rod deflection and angle of the tangents to rod end points (Cobb) were measured. Repeated measures analysis of variance assessed differences between pre- and postoperation. RESULTS: The scoliosis of 55° ±14° was corrected 72% to 15° ± 5°. The preinsertion rod shapes were more kyphotic for the concave (45.6°) than for the convex (31.4°) rods. Following correction, the concave rods flattened, with decrease in deflection of 13 mm and reduction in angle of 21° (both P < 0.001). The convex rods increased 1.5 mm in deflection and 2° in angle (P < 0.01, P = 0.18). The sagittal profile was maintained postoperatively as measured from T5-T12: 19° ±14° versus 22° ± 6° (pre vs. post, P > 0.1). CONCLUSION: We found a significant difference between pre- and postoperative rod contour, particularly for concave rods. Rod overcontouring (by ~20° for concave rod) resulted in high degrees of correction without loss of sagittal alignment. The resulting deformations are likely associated with substantial in vivo deforming forces.

Negative pressure therapy for closed spine incisions: a pilot study.

UNLABELLED: Negative pressure therapy (NPT), used on open wounds or postoperative infections, has not been evaluated on closed spinal incisions. This was analyzed after 3 days and 5 days of NPT application using biomechanics and histology in a porcine model. METHODS: In 8 mature miniature pigs, 2 end-to-end midline spine incisions were closed in a standard fashion. Negative pressure (Prevena™ Incision Management System, KCI, San Antonio,TX) was applied to one incision (NPT group) while standard dry dressings were used on the other (control group). After 3 days or 5 days, all incisions underwent biomechanical (eg, failure load, failure energy, and stress), histological, and scar scale evaluation. ANALYSIS: ANOVAs compared the groups (3-day vs 5-day, NPT vs control, P < 0.05). Negative pressure therapy demonstrated a significantly improved scar scale height grade than the control (P = 0.026). Failure load (4.9 ± 4.0 vs 16.5 ± 14.6 N), energy absorbed (8.0 ± 9.0 vs. 26.9 ± 23.0 mJ), and ultimate stress (62 ± 53 vs. 204 ± 118 N/mm2) were lower in the control group. Histological analysis revealed no differences in incision scar width. CONCLUSION: Negative pressure therapy application on closed incisions presented a trend toward improved early healing strength, and in significantly improved incision appearance. Clinically, NPT may improve incision integrity, minimizing the risk of dehiscence or subsequent infection. Patients at high risk of postoperative incision site complications may benefit from primary application of NPT.

An evaluation of fracture stabilization comparing kyphoplasty and titanium mesh repair techniques for vertebral compression fractures: is bone cement necessary?

STUDY DESIGN: In vitro biomechanical investigation using human cadaveric vertebral bodies. OBJECTIVE: To evaluate differences in biomechanical stability of vertebral compression fractures (VCFs) repaired using an expandable titanium mesh implant, with and without cement, as compared with standard balloon kyphoplasty. SUMMARY OF BACKGROUND DATA: Vertebral augmentation, either in the form of vertebroplasty or kyphoplasty, is the treatment of choice for some VCFs. Polymethylmethacrylate, a common bone cement used in this procedure, has been shown to possibly cause injury to neural and vascular structures due to extravasation, embolization, and may be too rigid for an osteoporotic spine. Therefore, suitable alternatives for the treatment of VCFs have been sought. METHODS: Individual vertebral bodies from 5 human cadaveric spines (from T4 to L5) were stripped of all soft tissues, and compressed at 25% of the intact height using methods previously described. Vertebral bodies were then randomly assigned to the following repair techniques: (1) conventional kyphoplasty, (2) titanium implant with cement, (3) titanium implant without cement. All vertebral bodies were then recompressed at 25% of the repaired height. Yield load, ultimate load, and stiffness were recorded and compared in these groups before and after treatment. RESULTS: There were no differences in biomechanical data between intact groups, and between repaired groups. In all 3 treatment groups, yield load and ultimate load of repaired vertebrae were similar to that of intact vertebrae. However, the stiffness following repair was found to be statistically less than the stiffness of the intact vertebral body (P < 0.05 for all comparisons). CONCLUSION: Based on the biomechanical data, the titanium mesh implant with or without cement was similar to polymethylmethacrylate fixation by kyphoplasty in the treatment of VCFs. Avoiding the adverse effects caused by using cement may be the main advantage of the titanium mesh implant and warrants further study.