Minimally invasive (MIS) Tönnis osteotomy- A technical annotation and review of short term results

We detail a modified single incision approach to perform the Tonnis triple pelvic osteotomy by a minimally invasive approach.

12 children underwent minimally invasive Tonnis Osteotomy. There were five boys and seven girls in this study group. Average age was 11 years (9-15 years) at the time of surgery. Mean follow-up was 20.5 months (13-39 months).

The average preoperative Antero-Posterior (AP) Centre Edge (CE) angle was -8.8° (-38.6°-18°), the average post-operative AP CE angle was 29.7° (25.1°-43.7°). The average preoperative lateral CE angle was -4.7° (-16°-0°), the average postoperative Lateral CE angle was 28.5° (21.3°-37.4°). The Sharp's angle before and after surgery were 55.7° (51.3°-66°) and 32.4° (16.1°-40.1°) respectively. The mean Tönnis angle before and after the osteotomy were 28.86° (19.7°-43.4°) and 6.3° (0.5°-9.4°) respectively. There was one major complication with sciatic nerve palsy which is in the recovery phase on followup and six minor complications including two cases of transient lateral femoral cutaneous nerve injury, two cases of ischial non-union, over granulation of the wound in one case, and metalwork irritation in one case.

We have described a minimally invasive Tonnis osteotomy as a viable option based on our results. This technique is recommended for those who are conversant with the traditional pelvicosteotomies.