Meeting NewsPerspective

Length of tibial tubercle distalization does not impact patella stabilization surgery outcomes

BOSTON — Tibial tubercle distalization led to high rate of normalization of patellar height measurements, with a patellar stabilization of 94%, according to a presenter at the American Orthopaedic Society for Sports Medicine Annual Meeting.

“MPFL reconstruction and distalization of tibial tubercle in the setting of the patellar alta prevents good outcomes in active population with the diagnosis of chronic lateral patellar instability,” Andrew Schmiesing, MD, said during his presentation. “Residual patella alta is not associated with recurrent instability for patients who undergo these procedures and length of distalization does not correlate with clinical outcomes or complications with the exception of increasing distalization the was associated with arthrofibrosis.”

Schmiesing and colleagues retrospectively collected data on 89 patients who underwent distalization of the tibial tubercle for recurrent lateral patella dislocation. All patients underwent concurrent medial patellofemoral ligament reconstruction. Demographics, preoperative and postoperative imaging measurements related to patella alta and trochlear dysplasia on MRI and plain radiographs, recurrent lateral patella dislocations and complications, including fracture and knee arthrofibrosis, were collected. Investigators assessed the Caton-Deschamps index on sagittal radiographic imaging. The goal of the surgery was to have a final Caton-Deschamps index between 1 and 1.2, and the maximum distance moved 15 mm in severe patella alta cases.

Results showed preoperatively the IS ratio was 1.5, the Caton-Deschamps ratio was 1.4, the lateral patella tilt was 24.7°, the tibial tuberosity-trochlear groove was 18.6 mm, the sulcus angle 158° and the patellar-trochlear index was 29%. The mean Caton-Deschamps index was 1.09 postoperatively. Investigators noted that, on average, the amount of distalization was 9.8.

There were 13 patients with residual patella alta, of which one patient redislocated. The case with the most extreme residual patella alta had a Caton-Deschamps of 1.97 preoperatively and was distalized 15 mm. No patellar baja was observed.

Frank recurrent patellar dislocation was seen in six patients. In these patients, the average postoperative patellar height was 1.11. This demonstrated that residual patella alta did not cause redislocation, according to researchers. Tibia fracture did not correlate with the amount of distalization.

There were 11 patients in with arthrofibrosis that required manipulation. The mean distalization in these patients was 11.8 mm. The distance was significantly different compared with patients who did not need manipulation. – by Monica Jaramillo

Reference:

Schmiesing A, et al. Abstract 61. Presented at: American Orthopaedic Society for Sports Medicine Annual Meeting; July 11-14, 2019; Boston.

Disclosure: Schmiesing reports no relevant financial disclosures.

BOSTON — Tibial tubercle distalization led to high rate of normalization of patellar height measurements, with a patellar stabilization of 94%, according to a presenter at the American Orthopaedic Society for Sports Medicine Annual Meeting.

“MPFL reconstruction and distalization of tibial tubercle in the setting of the patellar alta prevents good outcomes in active population with the diagnosis of chronic lateral patellar instability,” Andrew Schmiesing, MD, said during his presentation. “Residual patella alta is not associated with recurrent instability for patients who undergo these procedures and length of distalization does not correlate with clinical outcomes or complications with the exception of increasing distalization the was associated with arthrofibrosis.”

Schmiesing and colleagues retrospectively collected data on 89 patients who underwent distalization of the tibial tubercle for recurrent lateral patella dislocation. All patients underwent concurrent medial patellofemoral ligament reconstruction. Demographics, preoperative and postoperative imaging measurements related to patella alta and trochlear dysplasia on MRI and plain radiographs, recurrent lateral patella dislocations and complications, including fracture and knee arthrofibrosis, were collected. Investigators assessed the Caton-Deschamps index on sagittal radiographic imaging. The goal of the surgery was to have a final Caton-Deschamps index between 1 and 1.2, and the maximum distance moved 15 mm in severe patella alta cases.

Results showed preoperatively the IS ratio was 1.5, the Caton-Deschamps ratio was 1.4, the lateral patella tilt was 24.7°, the tibial tuberosity-trochlear groove was 18.6 mm, the sulcus angle 158° and the patellar-trochlear index was 29%. The mean Caton-Deschamps index was 1.09 postoperatively. Investigators noted that, on average, the amount of distalization was 9.8.

There were 13 patients with residual patella alta, of which one patient redislocated. The case with the most extreme residual patella alta had a Caton-Deschamps of 1.97 preoperatively and was distalized 15 mm. No patellar baja was observed.

Frank recurrent patellar dislocation was seen in six patients. In these patients, the average postoperative patellar height was 1.11. This demonstrated that residual patella alta did not cause redislocation, according to researchers. Tibia fracture did not correlate with the amount of distalization.

There were 11 patients in with arthrofibrosis that required manipulation. The mean distalization in these patients was 11.8 mm. The distance was significantly different compared with patients who did not need manipulation. – by Monica Jaramillo

Reference:

Schmiesing A, et al. Abstract 61. Presented at: American Orthopaedic Society for Sports Medicine Annual Meeting; July 11-14, 2019; Boston.

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Disclosure: Schmiesing reports no relevant financial disclosures.

    Perspective

    The surgical decision-making in patients with patellofemoral instability is further compounded when the structural risk factor of patella alta is added to the more common extensor mechanism malalignment seen in this patient population.  The lack of clinical outcome data to guide us, as well as concerns for potential overload of the patellofemoral joint contact pressures with distalization, has led to reservations in adding this structural alteration in an effort to improve patellofemoral mechanics.

    This study by Schmiesing and colleagues demonstrated the clinical stability achieved when adding this component to the surgical procedure, using a defined goal (Caton-Deschamps [C-D] index between 1 to 1.2) and maximum distalization (15 mm). The six patients with recurrent patella dislocation had a C-D index of 1.11, demonstrating that re-dislocation may not be related to patellar height but some additional structural factor. The increased risk of arthrofibrosis requiring manipulation was seen in those with a distalization of greater than 11m may be related to the altered patellofemoral forces or potentially increased surgical dissection for the procedure and further evaluation of this is warranted. While prior studies have shown some evidence of decreased C-D indices in isolated medial patellofemoral ligament reconstruction, understanding if there is a further decreased ratio with the combined procedure also warrants further evaluation.

    Publication of the full manuscript to further understand the preoperative planning, surgical technique, technical pearls and clinical outcome scores will add to the knowledge base and surgical options for the treatment of this challenging patient population.

     

     

    • Michael J. Medvecky, MD
    • Associate professor
      Section chief of sports medicine
      Department of orthopedics & rehabilitation
      Yale University School of Medicine
      New Haven, Connecticut

    Disclosures: Madvecky reports no relevant financial disclosures.

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