Derotational distal femoral osteotomy for patellar dislocation yielded favorable outcomes
Medial patellofemoral reconstruction with derotational distal femoral osteotomy yielded favorable subjective and objective outcomes among patients with recurrent patellar dislocation and increased femoral anteversion, according to results.
Researchers categorized 126 patients (135 knees) with recurrent patellar dislocation and increased femoral anteversion angle into groups based on whether they underwent MPFL reconstruction with (n=66) or without (n=69) derotational distal femoral osteotomy. Researchers measured preoperative and postoperative patellar stability with stress radiography and compared patellar maltracking and patient-reported outcomes between the groups. Researchers performed subgroup analysis by stratifying the results in terms of severity of preoperative patellar maltracking.
Results showed patients who underwent derotational distal femoral osteotomy had significantly lower rates of postoperative MPFL residual graft laxity and residual J-sign compared with the control group. Researchers also found significantly higher Kujala and Lysholm scores in the derotational distal femoral osteotomy group. Patients with a preoperative high-grade J-sign had a significantly lower rate of MPFL residual graft laxity when they underwent derotational distal femoral osteotomy, according to subgroup analysis.
“Bearing in mind the concepts of femoral torsional deformity and patellar maltracking, we believe that cases with concurrent excessive [femoral anteversion angle] FAA and a high-grade J-sign pose a challenged scenario in the [recurrent patellar dislocation] RPD spectrum, as described previously and also observed in the present study,” the authors wrote. “On the basis of our findings, we believe that FAA and patellar tracking should be identified and that their severity should be surgically corrected using more extensive procedures, such as [derotational distal femoral osteotomy] DDFO, rather than using MPFL [reconstruction] alone or with tibial tubercle transfer.”
Perspective
Back to TopWe read the article by ZhiJun Zhang, MD, and colleagues with great enthusiasm as it revealed clinical insights into a surgical approach that has dominated our practices: combined distal femoral osteotomy and tibial tubercle osteotomy/MPFL reconstruction for patients with complex patellofemoral instability. Dedicated to patellofemoral pathology-surgical sports medicine and limb deformity surgery, we have brought our separate skills together to deliver comprehensive surgical plans where osteotomies for valgus and femoral anteversion often accompany surgery to address coronal plane malalignment through tibial tubercle transfer, address incompetent medial structures via MPFL reconstruction and address cartilage defects with cartilage restoration. Historically, femoral anteversion was corrected through a mid-diaphyseal osteotomy fixed with an antegrade intramedullary nail with minimal impact on the extensor mechanism tracking.
We have been performing transverse distal femoral rotational osteotomy to externally rotate the femoral condyles toward the patella while addressing varus or valgus malalignment. This is done with simultaneous MPFL reconstruction, tibial tubercle osteotomy, knee arthroscopy and cartilage restoration work if indicated. Femoral plate position and screw lengths are modified to accommodate the MPFL graft tunnel on the medial femur. Zhang and colleagues provide a sound clinical comparison that echoes the amazing clinical results we have witnessed in our collaborative practice.
Perspective
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The study by ZhiJun Zhang, MD, and colleagues reaffirms what we already hold as true – femoral anteversion adversely affects patella tracking. This issue was studied in depth by Robert Teitge, MD, decades ago. He advocated proximal derotation femoral osteotomies. Patella surgeons departed from Teitge’s brilliant work because most patients fare well with tibial tubercle osteotomies when performed properly. This study has a major flaw in that it was not controlled for those who received Elmslie-Trillat. Also, the investigators falsely assume that a ‘J-sign’ is principally due to excessive anteversion. A ‘J-sign’ merely reflects laterally based force vector and includes elements of trochlea dysplasia, lax MPFL, patella alta, tibial external rotation and medialization of the tribal tubercle in addition to femoral anteversion.
This work is noble, but I find the recommendations too aggressive. A properly performed allograft-based minimally invasive MPFL reconstruction coupled with a meticulous tubercle medialization has served my patients well.
Surgeons are wise to remember that the MPFL is a checkrein and is not devised to “pull” the patella medially. Bone work is necessary. I prefer what is least invasive.
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