Study: Arthrotomy added to PAO may avoid impingement

Modified periacetabular osteotomies with an arthrotomy also performed by the orthopaedist who invented the procedure provided better offset correction and less risk of failure at 10-year follow-up compared with the surgeon’s original series using this method to treat developmental dysplastic hip.

The research group of Klaus A. Siebenrock, MD, at Inselspital Bern, Switzerland, has compared two consecutive series of patients after periacetabular osteotomy (PAO) with and without this surgical modification in a retrospective study. All surgeries were previously performed by Reinhold Ganz, MD.

The first series involved 75 PAOs performed between 1984 and 1987 without an arthrotomy and they were compared to the second series, which involved 90 PAOs with an arthrotomy carried out between 1997 and 2000. While the need for optimal acetabular version was emphasized in the latter series, patient demographics and gender were similar in both groups, according to Christoph E. Albers, MD, of Bern, who presented the findings at the 12th EFORT 2011 Congress in Copenhagen.

This research earned the investigators the Gold Free Paper Award, signifying it as the best paper presented at the congress.

The preoperative AP radiograph of a 26-year-old female patient (left) is shown in comparison to the postoperative radiograph (right). A correct 3-D orientation of the acetabulum was achieved resulting in better lateral coverage represented by the increased lateral center edge angle (white lines) and a correct version of the acetabulum shown by the course of the anterior and posterior acetabular wall. Images: Albers CE

“The intraoperative assessment of impingement-free motion improves the long-term result after PAO and key factors for joint preservation seem to be a correct 3-D reorientation of the acetabulum and the correction of head/neck asphericity, if necessary,” Albers said.

Focus on survivorship

This preoperative cross table view shows a decreased head neck offset. The alpha angle (white lines) is preoperatively increased resulting in femoro-acetabular impingement after reorientation of the acetabulum. An additional arthrotomy was performed to improve decreased femoral head neck offset (below) prior to definite fixation of the acetabular fragment. As a result, impingement free range of motion was achieved postoperatively.

Patients in both series were clinically evaluated based on Merle D’Aubigné hip score, ambulation and the anterior impingement test. Using radiographs, investigators evaluated the progression of osteoarthritis (OA) and used computer assistance to radiographically evaluate the extent of femoral head coverage, according to Albers.

Furthermore, investigators performed a Kaplan-Meier survivorship analysis with an endpoint of total hip arthroplasty, OA that progressed or a Merle D’Aubigné score less than 14 points and they also calculated key risk factors for poorer outcome with a PAO using a Cox-regression analysis.

“If necessary, an additional offset correction is performed” in conjunction with the more recent PAOs, which occurred in 56% of those cases or 50 hips, Albers said, noting both groups had a 10-year minimum postoperative follow-up.

Risk factors

Results in the early series showed 77% survivorship, which Albers said was significantly decreased vs. the 86% survivorship in the latest series.

Beyond those factors predictive of surgical success with PAO identified in previous studies, such as advanced age, low preoperative Merle D’Aubigné scores, a limp or advanced OA, “In our series we additionally found that a preoperative positive Trendelenburg sign, a non-spherical head, and preoperatively subluxated hip joint were positively associated with a higher risk of failure,” he said.

Regarding the identified PAO surgical predictive factors, over and under femoral head coverage and excessive anteversion or retroversion were associated with a higher risk of failure, Albers noted, adding he and his colleagues observed significantly better outcomes for the hips in the latter series with additional offset correction. – by Susan M. Rapp

Reference:

• Albers CE, Steppacher SD, Ganz R, et al. Optimal acetabular reorientation and offset correction improve the long term results after periacetabular osteotomy. Paper #2830. Presented at the 12th EFORT Congress 2011. June 1-4. Copenhagen.

• Christoph Albers, MD, can be reached at Inselspital, Bern University Hospital, Department of Orthopaedic Surgery, Freiburgstrasse, CH-3010 Bern, Switzerland; email: christoph.albers@insel.ch.
• Disclosure: Albers has no relevant financial disclosures.

Soren Overgaard

The winning paper from the Bern group is interesting as it presents the very early results of the large series of patients treated with periacetabular osteotomy (PAO) due to dysplasia.

The results, however, have to be treated with caution due to its retrospective design comparing two groups of patients treated differently. The first group of the patient cohort had a PAO from 1984-1987 with reorientation of the acetabular fragment without special notice of the version of the acetabulum and, in some cases, with excessive extension of the fragment. The second group was treated 10 years later and had the acetabulum reorientated with special attention on the version without too much extension and good lateral coverage. In addition, some of the cases had bone resection on the femoral side.

The take-home message is that a good long-term result after PAO probably depends on optimal reorientation of the acetabulum and secondary impingement-free range of motion.

The learning curve also might have played a role together with change in patient selection. Patient reported outcome might be relevant to include in future studies.

— Soren Overgaard, MD, DmSc/PhD
Professor, Head of Research, Department of Orthopaedics and Traumatology
Odense University Hospital, Odense, Denmark
Disclosure: He has no relevant financial disclosures.