Copyright © 2008 by The Journal of Bone and Joint Surgery, Inc.

Commentary & Perspective

Commentary & Perspective on
"A New Minimally Invasive Transsartorial Approach for Periacetabular Osteotomy"
by Anders Troelsen, MD, et al.

Commentary & Perspective by
Reinhold Ganz, MD*,
University of Bern, Gümligen, Switzerland

Posted March 2008

The authors sought to minimize the tissue trauma associated with the Bernese periacetabular osteotomy through the use of a new approach. The execution of the osteotomies was constantly monitored with fluoroscopy. The approach was used in 125 consecutive hips over a period of twenty-nine months; ninety-four hips were finally selected to comprise a well-defined study group, with a follow-up that ranged from 2.0 to 4.3 years. All patients had undergone surgery with hypotensive epidural anesthesia. The duration of surgery averaged 73.1 minutes; the median perioperative blood loss was 250 mL, and the mean reduction of hemoglobin was 33 g/L. There were no major vascular or nerve complications, no observed instances of unintended extension of the osteotomy, and no wound infections requiring surgical intervention. All procedures were performed by one surgeon, and no particular learning curve was identified. The median length of the hospital stay was eight days.

Concerning radiographic outcome, the median center-edge angle improved from 15° preoperatively to 34° postoperatively, and the median acetabular index angle of Tönnis decreased from 17° preoperatively to 3° postoperatively. There were two hips with Tönnis grade-1 osteoarthritis that had to be converted to total hip arthroplasty 1.8 years and 2.7 years after the index surgery.

The authors concluded that their minimally invasive approach for periacetabular osteotomy is safe, relatively fast, associated with minimal tissue trauma and blood loss, and highly satisfactory with regard to acetabular correction.

There is little question that the technique of any procedure has room for improvement and that the initiative taken by this group of authors may well prove to become, as a whole or in parts, a step forward in the surgery of spatial correction of the human acetabulum. However, important conclusions of this paper are really assumptions and have not been proven with the data presented. The only quantified information with regard to minimal invasion is a skin incision of 7 cm. Only a magnetic resonance imaging study would allow some quantification of true invasion of tissues and/or muscles by comparing muscle integrity during open dissection with a knife with muscle integrity during blunt dissection with a periosteal elevator. Furthermore, the reduced overall blood loss is probably more related to the hypotensive anesthesia than to the minimal incision surgery. Blood loss during open dissection for periacetabular osteotomy is also minimal, so blood loss during execution of the osteotomies should be the same whether the exposure is minimal or classic. A mean operative time of 73.1 minutes for acetabular reorientation for minor or moderate dysplasia is short. An experienced surgeon performing an open dissection may need twenty to twenty-five minutes more for a hip with similar morphological characteristics; however, that amount of time includes the time needed to chart the position of the acetabulum with use of intraoperative anteroposterior pelvic radiographs for more spatial precision and also includes the time needed to perform capsulotomy and intraarticular revision, which are necessary in seven of ten cases. The length of hospital stay is similar for both procedures.

The authors repeatedly assert the importance of gaining an accurate spatial correction of the osteotomized acetabulum (a lateral center-edge angle of 30° to 40° and a Tönnis angle that is never <0°). Acetabular version is mentioned as important; however, no preoperative or postoperative information about prevalence and amount is given. They conclude that their technique allows for optimal correction, and they present data for the frontal plane in Table 2 with preoperative and postoperative overall values. However, in electronic Figures E7-A and E7-B, in which the authors report the preoperative and postoperative angles of each hip, there are several undercorrections and overcorrections, some of which are substantial enough to be considered a complication of the procedure. In addition, one might question the reason(s) for the need to perform two early conversions to total hip arthroplasty of two hips with Tönnis grade-1 osteoarthritis, since this grade of osteoarthritis is unlikely to be associated with rapid degeneration after a satisfactory acetabular correction.

A final remark deals with a recommendation made toward the end of the paper. The authors are basically saying that, in order to shorten the learning curve associated with their technique, an inexperienced surgeon should first learn the open technique of performing periacetabular osteotomy before learning the described new technique, even though the new technique is contrasted to the open procedure as being markedly different in many technical aspects. A statement such as this may even give rise to an ethical discussion.

In summary, the primary conclusions that the new approach for periacetabular osteotomy is minimally invasive and satisfactory with regard to correction are not sufficiently proven by the data provided.

*The author did not receive any outside funding or grants in support of his research for or preparation of this work. Neither he nor a member of his immediate family received payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, division, center, clinical practice, or other charitable or nonprofit organization with which the author, or a member of his immediate family, is affiliated or associated.