Isolated MPFL Reconstruction Stabilizes Patella Despite High Femoral Anteversion

Managing Patellofemoral Instability Amidst Torsional Malalignment

Recurrent patellar dislocation represents a significant clinical challenge for the practicing orthopedist, often necessitating surgical intervention to prevent long-term joint degeneration and functional decline [1]. While the medial patellofemoral ligament is recognized as the primary soft tissue stabilizer against lateral patellar translation, isolated reconstruction is associated with a complication rate of approximately 26.1 percent [2]. In patients presenting with increased femoral anteversion (an inward twisting of the thigh bone that alters the pull of the quadriceps), surgeons frequently consider combining ligament reconstruction with a derotational distal femoral osteotomy to address the underlying bony malalignment [3, 4]. However, these derotational procedures involve significant surgical morbidity and potential risks, including peroneal nerve injury and hardware-related complications [5]. Although isolated reconstruction generally facilitates a high rate of return to athletic activity, the specific anatomical thresholds that mandate concomitant bony correction remain a subject of active clinical debate [6]. A recent study now offers data on whether isolated ligamentous stabilization is sufficient for patients with high femoral torsion but minimal maltracking.

Patient Selection and Torsional Assessment

The researchers conducted a retrospective cohort study involving 52 consecutive patients who presented with recurrent patellar dislocations and significant femoral malalignment. The study population was relatively young, with a mean age of 19.1 ± 5.9 years, representing a demographic frequently seeking surgical stabilization to maintain an active lifestyle. To be included in the analysis, patients were required to demonstrate femoral anteversion greater than 30 degrees, a threshold often used to justify more invasive derotational osteotomies. Furthermore, the study focused specifically on those with an absent or mild J-sign (the lateral, letter J shaped path the patella takes as the knee moves into full extension). In clinical practice, the J-sign serves as a critical marker for patellar maltracking; its absence or minimal presence suggests that despite bony torsion, the patella remains relatively well-aligned within the trochlear groove during terminal extension. To precisely quantify the degree of rotational deformity, the authors utilized computed tomography to measure several key anatomical parameters. This imaging allowed for the objective assessment of femoral anteversion, tibiofemoral rotation, and tibial external torsion, ensuring a comprehensive view of the lower extremity alignment. Within this specific cohort, the mean femoral anteversion was 35.2° ± 6.5°, confirming that these patients possessed substantial torsional deformities that would typically trigger consideration for bony correction. By isolating patients with high femoral torsion but minimal dynamic maltracking, the study aimed to determine if the soft tissue stabilization of the medial patellofemoral ligament alone could overcome the mechanical disadvantages imposed by a mean anteversion exceeding 35 degrees.

Surgical Intervention and Longitudinal Stability

The researchers utilized a retrospective cohort study design, providing Level 3 evidence (data derived from a non-randomized, controlled trial), to evaluate the efficacy of isolated medial patellofemoral ligament reconstruction in this specific patient population. Between 2018 and 2022, all 52 patients in the study underwent this soft tissue procedure without the addition of bony realignment or derotational osteotomy. This surgical approach focused exclusively on restoring the primary soft tissue tether that prevents lateral patellar displacement, testing whether this single intervention could compensate for the mechanical disadvantage of femoral anteversion exceeding 30 degrees. Clinical and radiological outcomes were rigorously assessed both preoperatively and at a minimum 2-year follow-up to determine the longitudinal viability of the reconstruction. Over a mean follow-up period of 2.4 ± 1.1 years, the primary indicator of surgical success was the prevention of further instability events. The study found that zero redislocations occurred during the follow-up period, suggesting that isolated medial patellofemoral ligament reconstruction can provide sufficient mechanical restraint to maintain patellar stability in patients who lack severe maltracking, even when significant femoral torsion is present. For the clinician, this suggests that the presence of high anteversion alone may not be an absolute indication for invasive derotational osteotomy if the patella tracks well dynamically.

Functional Recovery and Activity Levels

Beyond the absence of redislocations, the researchers observed substantial improvements in patient-reported outcome measures that reflect the daily clinical experience of patellofemoral recovery. The Kujala score, a 100-point instrument specifically designed to evaluate patellofemoral pain and function, increased from a preoperative mean of 58 ± 9 to 88 ± 9 at the final follow-up (P < .001). Similarly, the Lysholm score, which clinicians use to assess knee stability and mechanical symptoms such as locking or swelling, improved from 62 ± 7 preoperatively to 90 ± 11 postoperatively (P < .001). These gains indicate that the reconstruction not only stabilized the joint but also significantly reduced the symptomatic burden of patellofemoral instability, allowing for a more predictable return to routine activities. The restoration of joint stability also translated into a measurable return to physical activity, which is a primary goal for the young, active population typically affected by recurrent dislocations. The Tegner activity scale, which categorizes patients based on their level of sports participation and work-related physical demands, showed that median scores improved from 3 preoperatively to 5 postoperatively (P = .021). This shift suggests that patients were able to progress from light physical activities or sedentary work to more demanding recreational sports. Collectively, these data points demonstrate that isolated medial patellofemoral ligament reconstruction can facilitate a return to higher functional levels in patients with high femoral anteversion, provided they do not exhibit severe patellar maltracking.

Impact of Trochlear Dysplasia on Outcomes

A critical consideration in patellofemoral surgery is the morphology of the trochlea, as a shallow or flat groove can theoretically compromise the success of a soft tissue reconstruction. To determine if the shape of the femoral groove influenced the results of the isolated procedure, outcomes were compared between patients with severe trochlear dysplasia (Dejour type B or D; n = 17) and those without severe trochlear dysplasia (n = 35). Dejour classification is a radiographic system used to grade the severity of the trochlear groove's flatness or convexity, with types B and D representing more significant anatomical abnormalities. This subgroup analysis allowed the researchers to evaluate whether the absence of a deep bony track for the patella would necessitate a more invasive bony realignment in the presence of high femoral torsion. The data indicated that the underlying bony anatomy did not dictate the clinical success of the ligamentous repair. Functional outcomes were comparable between the severe trochlear dysplasia group and the non-severe group (all P > .05), suggesting that the reconstructed ligament provided sufficient medial restraint regardless of the Dejour classification. While the functional scores were similar, radiographic differences remained evident at the final follow-up. Patients with severe trochlear dysplasia had significantly greater postoperative patellar tilt (the angle of the kneecap relative to the femur) compared to those without severe dysplasia, with measurements of 18° ± 5° versus 13° ± 4° (P < .001). Despite this increased tilt, the lack of redislocations and the high functional scores suggest that radiographic alignment does not always correlate perfectly with clinical stability in this patient population, potentially sparing many patients from the risks of more invasive bony procedures.

References

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6. Platt BN, Bowers LC, Magnuson JA, et al. Return to Sport After Medial Patellofemoral Ligament Reconstruction: A Systematic Review and Meta-analysis.. The American journal of sports medicine. 2022. doi:10.1177/0363546521990004