A new technique for physiodesis using photodynamic therapy

[Growth modulation through hemiepiphysiodesis : Novel surgical techniques: risks and progress]

The correction of angular deformities of the lower limb is a key task in paediatric orthopaedic surgery. The growth potential of the physis can be employed for the correction of these malalignments in childhood and adolescence. Hemiepiphysiodesis (HED) is a surgical technique used for growth modulation by permanent or temporary asymmetrical arrest of the growth plate. In permanent HED, exact timing of the procedure is mandatory to achieve optimal correction. Temporary HED through tension band devices such as two-hole-plates or flexible staples has been established as the treatment of choice for growth guidance with excellent results. Implant-associated complications have been significantly reduced through implant modifications. Several experimental procedures have the potential to achieve growth modulation even without the requirement of surgical intervention.

Closing the growth plate: a review of indications and surgical options

PURPOSE OF REVIEW

The purpose is to review the indications for epiphysiodesis in the treatment of pediatric limb length discrepancies; provide an update on current diagnostic, planning, and surgical techniques; and to introduce possible future alternatives.

RECENT FINDINGS

Retrospective comparative studies have failed to demonstrate superiority of one epiphysiodesis technique over the others. EOS low-dose biplanar X-ray and smartphone growth prediction applications are improving our ability to diagnose and plan treatment for leg length discrepancy. Arthroscopically guided percutaneous epiphysiodesis and radiofrequency ablation are newer techniques that are still under investigation.

SUMMARY

Epiphysiodesis is the treatment of choice for children with predicted leg length discrepancies between 2-5 cm, provided that the physes are open with sufficient growth remaining. The most common epiphysiodesis techniques are performed percutaneously and either ablate the physis with drills/curettes or use metal implants to tether the physis and prevent further growth. Surgical treatment is typically ambulatory in nature, and allows for early return to weight bearing. In modern series, complication rates are less than 10%, with the majority being minor complications. Further high-quality prospective research is needed to determine the optimal epiphysiodesis surgical technique.

The benefits of photodynamic therapy on vertebral bone are maintained and enhanced by combination treatment with bisphosphonates and radiation therapy

Photodynamic therapy (PDT) has been shown to ablate tumors within vertebral bone and yield short-term improvements in vertebral architecture and biomechanical strength, in particular when combined with bisphosphonate (BP) treatment. Longer-term outcomes of PDT combined with current treatments for skeletal metastases are essential to understand its therapeutic potential. The objective of this study is to evaluate the response of vertebrae to PDT after a longer (6-week) time period, alone and combined with previous BP or radiation treatment (RT). Sixty-three female rnu/rnu rats were randomized to six treatment groups: untreated control, BP-only, RT-only, PDT-only, combined BP + PDT and combined RT + PDT. L2 vertebrae were structurally analyzed through µCT-based analysis, axial compressive load-to-failure testing and histological analysis of morphology, osteoid formation and osteoclast activity. Combined BP + PDT treatment yielded the largest improvements in bone architecture with combined RT + PDT treatment yielding similar findings, but of a lesser magnitude. Mechanically, ultimate force and stress were correlated to stereological parameters that demonstrated a positive structural effect from combinatory treatment. Increased osteoid formation was observed in both combination therapies without any significant differences in osteoclast activity. Overall, multimodality treatment demonstrated a sustained positive effect on vertebral structural integrity, motivating PDT as a minimally-invasive adjuvant treatment for spinal metastases.

Surgical epiphysiodesis indications and techniques: update

PURPOSE OF REVIEW

To present a summary of epiphysiodesis indications and to report most recent advances in the field, along with their clinical relevance.

RECENT FINDINGS

Percutaneous epiphysiodesis using transphyseal screws (PETS) and guided growth using eight plates represent the most recent techniques used for hemiepiphysiodesis.

SUMMARY

PETS and guided growth have yielded very good results and low rates of complications and are the current standard for the management of angular deformities of the lower extremities in children. Permanent percutaneous epiphysiodesis remains the preferred method for the treatment of limb length discrepancies.

Effects of photodynamic therapy on the structural integrity of vertebral bone

STUDY DESIGN

This study investigates the effects of photodynamic therapy (PDT) on the structural integrity of vertebral bone in healthy rats.

OBJECTIVE

To determine the short-term (1 week) and intermediate term (6 weeks) effects of a single PDT treatment on the mechanical and structural properties of vertebral bone.

SUMMARY OF BACKGROUND DATA

Spinal metastasis develops in up to one-third of all cancer patients, compromising the mechanical integrity of the spine and thereby increasing the risk of pathologic fractures and spinal cord damage. PDT has recently been adapted to ablate metastatic tumors in the spine in preclinical animal models. However, little is known about the effects of PDT on the structural integrity of vertebral bone.

METHODS

A single PDT treatment was administered to healthy Wistar rats at photosensitizer and light doses known to be effective in athymic rats bearing human breast cancer metastases. At both 1 and 6 weeks posttreatment, changes in trabecular architecture, global stiffness and strength of vertebrae were quantified using micro-CT stereological analysis and axial compression testing.

RESULTS

At 6 weeks, there was a significant increase in bone volume fraction (to 55.7 +/- 11.1% vs. 38.5 +/- 6.4%, P < 0.001) and decrease in bone surface area-to-volume ratio (16.9 +/- 5.0/mm vs. 22.8 +/- 4.5/mm, P = 0.001), attributed to trabecular thickening (130 +/- 40 microm vs. 90 +/- 20 microm, P < 0.001). Similar trends were found at 1 week after PDT. There was a significant increase in stiffness from control (306 +/- 123 N/mm) at 1 week (399 +/- 150 N/mm, P = 0.04) and 6 weeks (410 +/- 113 N/mm, P = 0.05) post PDT. There was a positive trend toward increased ultimate stress at 1 week, which became statistically significant at 6 weeks compared with control (39.3 +/- 11.3 MPa vs. 27.5 +/- 9.5 MPa control, P = 0.002).

CONCLUSION

Not only may PDT be successful in ablating metastatic tumor tissue in the spine, but the positive effects of PDT on bone found in this study suggest that PDT may also improve vertebral mechanical stability.