Study Compares Growth Modulation Techniques for Fixed Flexion Contracture of the Knee

By: Maureen Leahy

Results of a study comparing two growth modulation techniques—tension band plates versus transphyseal screws—for treating fixed flexion contracture of the knee indicated that hardware migration occurred more often in the screws-only construct. The data are presented in Scientific Poster P0246, which was on display Tuesday and Wednesday in Academy Hall B.

“Growth modulation is a well-known method for the correction of pediatric lower extremity angular deformities in the coronal plane. Sagittal deformity correction has been reported but is less common,” said coauthor Philip McClure, MD.

“We compared two anterior distal femoral growth modulation methods for fixed flexion contracture of the knee: anteromedial/anterolateral tension band plates versus anteromedial/anterolateral retrograde transphyseal screws.”

Retrospective review

The authors retrospectively reviewed medical records on 26 patients (39 knees) who underwent insertion of either screws-only or tension band plate constructs into the anterior distal femoral hemiphysis to treat fixed flexion contracture. Patients for whom adequate pre- and postoperative radiographs were not available were excluded.

Overall, 20 patients (average age: 10.7 years; 29 knees) met the inclusion criteria. Among them, nine patients (13 knees) were treated with an anterior tension band plate construct and 11 patients (16 knees) were treated with a screws-only construct.

Preoperative sagittal plane joint orientation angles were evaluated in all patients and again at an average follow-up of 45 months (range: 10–96 months). Incidences of hardware failure and/or migration were also noted.

The researchers found that hardware migration occurred in one of 13 knees treated with a tension band plate and in nine of 16 knees treated with a screws-only construct (P = 0.008). Improvement in sagittal alignment occurred in both groups.

In addition, statistically significant changes were noted in the posterior distal femoral angle in the tension band plate group (P = 0.009) but not in the screws-only group (P = 0.181). There was no significant change in the posterior proximal tibial angle in either group.

Based on the study’s results, the authors concluded that anterior distal femoral growth modulation improved sagittal alignment of the femur without affecting the sagittal alignment of the proximal tibia. They recommended anterior tension-band plating instead of screw placement for sagittal plane growth modulation to treat knee fixed flexion contracture.

“Our study revealed higher failure rates with the screws-only fixation pattern. Retrograde transphyseal screws should not be used for anterior growth modulation. Antegrade screws should be critically evaluated, as the similarities to retrograde fixation raise concern for potentially elevated failure rates,” Dr. McClure said.

“Due to these results,” he explained, “we have abandoned use of retrograde screw fixation for anterior growth modulation. Anterior plates appear to be dependable and are our preferred option at this time. More research is needed to determine the optimal hardware configuration for this technique.”

Dr. McClure’s coauthors of “Growth Modulation for Fixed Flexion Contracture of the Knee: A comparison of Two Techniques” are Hamza M. Alrabai, MD; Martin G. Gesheff, BS; Shawn C. Standard, MD; and John E. Herzenberg, MD.

Maureen Leahy is assistant managing editor of AAOS Now. She can be reached at leahy@aaos.org.

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