Retrotubercle osteotomy may have more favorable results than conventional surgery
According to Seyed Morteza Kazemi, MD, medial opening wedge osteotomy (MOWO) is a “fast, easy, and precise” method for treating the varus knee, but it does have disadvantages. The surgery can cause changes in posterior tibial slope and the height of the patellar tendon, and can lead to patella baja as well as malunion or nonunion.
A modified version of the procedure—the retrotubercle medial opening wedge high tibial osteotomy—can greatly reduce the incidence of complications in some patients, according to the results of a study Dr. Kazemi presented at the 2010 Annual Meeting.
“Compared to conventional MOWO, this new method has less impact on the angles and anatomic axes of the tibial articular surface, the height of the patellar tendon, and the distance between the articular surface and the tibial tubercle,” he said.
Union problems are also reduced “because of the creation of a smaller void and a larger surface area for primary bone healing.”
Conducting the study
Dr. Kazemi and his fellow re-searchers conducted a random-ized, controlled trial between April 2007 and September 2008 at Akhtar Hospital in Tehran, Iran, to compare the results of the two surgical techniques. In the study, 72 patients with varus knees (2 degrees or more of anatomic axis varus without ligament injury) who were candidates for surgery were randomized into two groups: 34 were assigned to the retrotubercle osteotomy group, and 38 were assigned to the conventional osteotomy group. The groups were matched for age and gender. The average age of the patients in the retrotubercle osteotomy group was 28.12 years, and 27.89 years in the conventional osteotomy group.
Patients were evaluated using the two different indices to measure patellar height prior to undergoing surgery. In addition, researchers measured tibial plateau inclination and used lateral radiographs to evaluate the distance between the tibial articular surface and the tibial tuberosity. Patients were examined for periarticular ligament stability, range-of-motion, and Q angle at 30 degrees of flexion.
In addition, the following measurements were taken before and after surgery:
- length of the patellar tendon
- diagonal length of the patella
- perpendicular distance between the lower tip of the patellar articular surface to the tibial plateau
- length of the patellar articular surface
- angle between the proximal articular surface and the anatomic axis of the bone
- distance between the articular surface and the tibial tuberosity.
The measurements were re-checked in both groups on average 13 months (range, 10–21 months) following treatment.
All patients underwent physiotherapy and range-of-motion exercises, and were at full weight bearing at 12 weeks.
Modified osteotomy has favorable results
Although no patients in either group had patella baja prior to surgery, 16 patients (42.1 percent) in the conventional osteotomy group had patella baja after surgery, while no patients in the retrotubercle osteotomy group were diagnosed with patella baja.
Except for diagonal length of the patella and the length of the patellar articular surface, other measures were statistically different between the two groups (p < 0.05) when compared to preoperative measurements. The differences in the mean ratios pre- and postoperatively between the two groups were also statistically significant (p < 0.05).
“Unlike the patients in the conventional osteotomy group, the patients in the retrotubercle group had no significant changes in tibial plateau slope, Q angle, or patellar position after surgery,” explained Dr. Kazemi.
He noted that no delayed unions were observed in the retrotubercle group; however, in the conventional osteotomy group, six cases of delayed union and two cases of nonunion that required a second operation for bone grafting were diagnosed.
“It seems that the mere sliding of the distal segment off the proximal segment does the trick in maintaining the slope of the tibial plateau, thus avoiding the complication of a decrease in patellar height,” said Dr. Kazemi.
Because many different methods exist for correcting the varus deformity, surgery must be individualized to the patient. Nonetheless, said Dr. Kazemi, “We concluded that the retrotubercle medial opening wedge high tibial osteotomy is a suitable method for correcting the varus knee without complications such as patella baja, changes in the Q angle, or changes in the slope of the tibial plateau.”
Dr. Kazemi was the lead author of “A Modified (Retrotubercle) Opening Wedge High Tibial Osteotomy Versus the Conventional Technique.” He reports no conflicts. Coauthors Sohrab Keyhani, MD, and Firooz Madadi, MD, also report no conflicts.
Jennie McKee is a staff writer for AAOS Now. She can be reached at firstname.lastname@example.org