Percutaneous acetabuloplasty: a cadaveric study.

Periacetabular osteolysis is a common etiology of prosthesis failure in patients who undergo total hip arthroplasty. These lesions are treated by open and, more recently, percutaneous techniques. The purpose of this study was to determine the relevant surface anatomy and bony landmarks in establishing percutaneous access to periacetabular regions and identifying critical at-risk structures in establishing access. Percutaneous access to the periacetabular region was established superiorly, anteroinferiorly, and posteroinferiorly by using 5 L5-to-mid thigh fixed cadaver pelvises with latex-injected vessels using threaded guidewires. Dissection was completed to identify structures at risk, with the distance from the wires recorded to the nearest millimeter. C-arm position for the optimal visualization and placement of guidewires was recorded. Average distance from the pin and the at-risk structures ranged from 11.2 to 38.7 mm. All 3 approaches allowed for safe percutaneous access to the periacetabular regions without injuring significant anatomical structures. This study established safe starting points and orientation for guidewires and radiograph projections associated with percutaneous access to the periacetabular regions. The findings in this study will be useful for developing minimally invasive approaches to these regions for the treatment of osteolytic lesions of diverse etiology. However, a biomechanical evaluation of the impact of these bony channels on the strength of pelvis under physiological and unanticipated loading must be performed before this technique can be safely translated to clinical practice.

Serum titanium levels after instrumented spinal arthrodesis.

STUDY DESIGN: A retrospective study measuring postoperative serum titanium levels in patients with titanium alloy spinal instrumentation. OBJECTIVE: To determine serum titanium levels in patients after instrumented spinal arthrodesis with implants composed of titanium alloy and to identify potential factors responsible for any increase in ion levels. SUMMARY OF BACKGROUND DATA: Previous studies have documented localized metal debris in the tissues surrounding spinal instrumentation. Systemic distribution of metal debris has also been demonstrated by measuring elevated serum metal ion levels in patients with titanium spinal implants; however, no studies exist on the impact of instrumentation characteristics on serum ion levels. METHODS: Serum titanium concentrations were measured in 30 patients with titanium spinal instrumentation at a mean 26 months after surgery and compared with a control group without metallic implants. Comparisons were made regarding serum titanium levels with respect to specific instrumentation characteristics such as number of pedicle screws used, and the presence of cross connectors or titanium interbody devices. RESULTS.: Serum titanium levels were significantly higher in patients with titanium spinal implants (mean, 2.6 microg/L) when compared with controls (mean, 0.71 microg/L). Subjects who underwent an instrumented arthrodesis of only one spinal segment had decreased serum titanium levels when compared with those who were fused at 2 or more spinal segments (mean, 2.3 vs. 3.1 microg/L) and patients with 4 or less pedicle screws also had decreased serum titanium levels when compared with constructs of 6 to 8 pedicle screws (mean, 2.3 vs. 3.35 microg/L); however, both of these findings were not statistically significant. Patients without cross connectors had a slightly increased serum titanium level when compared with those with connectors (mean, 2.7 vs. 2.44 microg/L); however, this finding was also not statistically significant. Patients with titanium interbody devices had a statistically significant elevation in serum titanium levels when compared with those without (mean, 3.3 vs. 1.98 microg/L). CONCLUSION: Significantly higher serum titanium concentrations were observed in subjects with titanium spinal instrumentation when compared with controls. Continued research is necessary to examine the relationship between Ti interbody devices and cross connectors with regards to serum ion levels.