Mechanical axis following staple epiphysiodesis for limb-length inequality

Area of Science:

• Orthopedic surgery
• Pediatric orthopedics
• Biomechanical analysis

Background:

• Staple epiphysiodesis is a surgical technique used to correct limb-length discrepancies.
• This procedure can lead to complications, including alterations in the lower extremity's mechanical axis.

Purpose of the Study:

• To evaluate the outcomes of staple epiphysiodesis, focusing on changes in the mechanical axis.
• To assess the impact of distal femoral versus proximal tibial staple epiphysiodesis on lower extremity alignment.

Main Methods:

• Retrospective review of 54 patients undergoing staple epiphysiodesis (femur, tibia, or both) between 1990 and 2005.
• Analysis of preoperative, postoperative, and final radiographs to measure limb-length discrepancy, mechanical axis shifts, and angular changes.
• Assessment of staple placement adequacy in postoperative radiographs.

Main Results:

• Fifty percent of patients experienced a mechanical axis shift of 1 cm or more, predominantly varus.
• Proximal tibial and combined epiphyses resulted in significantly greater mechanical axis and zone shifts compared to distal femoral procedures.
• Inadequate staple placement was most common in the proximal-lateral tibia; six patients required corrective high tibial osteotomy for post-stapling varus deformity.

Conclusions:

• Mechanical axis deviation is a frequent complication of staple epiphysiodesis for limb-length discrepancy.
• Proximal tibial and combined procedures often lead to clinically relevant mechanical axis shifts, even with technically adequate placement.
• Distal femoral staple epiphysiodesis may remain a safer option, while proximal tibial staple epiphysiodesis requires careful consideration due to alignment risks.