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Author Reply to “Regarding “Primary Medial Patellofemoral Ligament Repair Versus Reconstruction: Rates and Risk Factors for Instability Recurrence in a Young, Active Patient Population”

      First and foremost, we would like to thank Dr. Ilahi for his thoughtful commentary on our recent publication.
      • Puzzitiello R.N.
      • Waterman B.
      • Agarwalla A.
      • et al.
      Primary medial patellofemoral ligament repair versus reconstruction: Rates and risk factors for instability recurrence in a young, active patient population.
      Our referenced study comparatively analyzed the outcomes of 32 medial patellofemoral ligament (MPFL) reconstructions and 19 MPFL repairs. At an average follow-up of approximately 5 years, there was a 6.3% re-dislocation rate among reconstructions compared with 36.9% among repairs. The follow-up duration for repair and reconstruction was 6.5 years and 3.7 years, respectively.
      • Puzzitiello R.N.
      • Waterman B.
      • Agarwalla A.
      • et al.
      Primary medial patellofemoral ligament repair versus reconstruction: Rates and risk factors for instability recurrence in a young, active patient population.
      The primary concern mentioned by Dr. Ilahi was the relatively high failure rate, defined as recurrent patellar dislocation, following MPFL repair compared anecdotally with his own surgical experience. He postulates that our inclusion of patients with a single patellar dislocation event could account for this difference. In the current study, there were a significantly greater number of patients with only a single patellar dislocation before surgery in the MPFL repair group (36.9%) compared with the reconstruction group (3.1%). However, previous evidence would suggest that this would actually favor the outcomes of the MPFL repair group. It has previously been observed in the epidemiologic study by Fithian et al.
      • Fithian D.C.
      • Paxton E.W.
      • Stone M.L.
      • et al.
      Epidemiology and natural history of acute patellar dislocation.
      that only 17% of patients who sustain a first-time patellar dislocation event go on to experience a second dislocation, as opposed to the 49% with a history of previous instability who suffered a subsequent dislocation event. Further, it is also possible for patients with a single patellar dislocation to not respond to nonsurgical management without a second dislocation, such as in patients with provocative apprehension or positional subluxation. Nonetheless, there remains a paucity of high-quality studies that attempt to identify the best treatment option for patients after a single patellar dislocation, and this topic remains controversal.
      • Pagliazzi G.
      • Napoli F.
      • Previtali D.
      • Filardo G.
      • Zaffagnini S.
      • Candrian C.
      A Meta-analysis of surgical versus nonsurgical treatment of primary patella dislocation.
      Although the inclusion of these patients in our study may have made our study population less homogenous, it is unlikely that this could explain the high failure rate among MPFL repairs.
      Dr. Ilahi also suggests that it is possible that the suture size and rehabilitation protocol used for the MPFL repair group in our study also may account for the high failure rate. These are 2 variables that could very well influence outcomes for this procedure, but these are factors that are often highly variable among different surgeons for many orthopaedic procedures. It is unlikely that these 2 factors alone could account for such a significantly greater failure rate. However, it is more likely that additional anatomic features, such as patella alta, could influence the unfavorable outcomes after MPFL repair, and this is supported by recent evidence. In our study, we found the average Caton–Deschamps index of the MPFL failures was 1.30, which was significantly greater than the MPFL non-failure group.
      • Puzzitiello R.N.
      • Waterman B.
      • Agarwalla A.
      • et al.
      Primary medial patellofemoral ligament repair versus reconstruction: Rates and risk factors for instability recurrence in a young, active patient population.
      It is also possible that the chronic laxity of MPFL tissue among those with repeated dislocations and trochlear dysplasia may contribute to the high failure rate after MPFL repair, as suggested by Arendt et al.
      • Arendt E.A.
      • Moeller A.
      • Agel J.
      Clinical outcomes of medial patellofemoral ligament repair in recurrent (chronic) lateral patella dislocations.
      As discussed in our published article, the studies by Camp et al.
      • Camp C.L.
      • Krych A.J.
      • Dahm D.L.
      • Levy B.A.
      • Stuart M.J.
      Medial patellofemoral ligament repair for recurrent patellar dislocation.
      and Arendt et al.
      • Arendt E.A.
      • Moeller A.
      • Agel J.
      Clinical outcomes of medial patellofemoral ligament repair in recurrent (chronic) lateral patella dislocations.
      corroborate our high reported rate of recurrent lateral patellar dislocation after MPFL repair. The population in the study of Camp et al.
      • Camp C.L.
      • Krych A.J.
      • Dahm D.L.
      • Levy B.A.
      • Stuart M.J.
      Medial patellofemoral ligament repair for recurrent patellar dislocation.
      included 7 femoral-sided, 8 patellar-sided, 7 both-side tears, and 7 intrasubstance tears repaired by reefing. The overall failure rate in this study was 28%. The study by Arendt et al.
      • Arendt E.A.
      • Moeller A.
      • Agel J.
      Clinical outcomes of medial patellofemoral ligament repair in recurrent (chronic) lateral patella dislocations.
      reported a 46% re-dislocation rate among their MPFL repairs, all of which were initially disrupted at the femoral origin only. There have been several other studies published in recent years that report a wide range of failure rates for MPFL repair,
      • Puzzitiello R.N.
      • Waterman B.
      • Agarwalla A.
      • et al.
      Primary medial patellofemoral ligament repair versus reconstruction: Rates and risk factors for instability recurrence in a young, active patient population.
      ,
      • Arendt E.A.
      • Moeller A.
      • Agel J.
      Clinical outcomes of medial patellofemoral ligament repair in recurrent (chronic) lateral patella dislocations.
      • Camp C.L.
      • Krych A.J.
      • Dahm D.L.
      • Levy B.A.
      • Stuart M.J.
      Medial patellofemoral ligament repair for recurrent patellar dislocation.
      • Christiansen S.E.
      • Jakobsen B.W.
      • Lund B.
      • Lind M.
      Isolated repair of the medial patellofemoral ligament in primary dislocation of the patella: A prospective randomized study.
      • Boddula M.R.
      • Adamson G.J.
      • Pink M.M.
      Medial reefing without lateral release for recurrent patellar instability: Midterm and long-term outcomes.
      • Nam E.K.
      • Karzel R.P.
      Mini-open medial reefing and arthroscopic lateral release for the treatment of recurrent patellar dislocation: A medium-term follow-up.
      • Dragoo J.L.
      • Nguyen M.
      • Gatewood C.T.
      • Taunton J.D.
      • Young S.
      Medial patellofemoral ligament repair versus reconstruction for recurrent patellar instability: Two-year results of an algorithm-based approach.
      and this may perhaps be the result of the conflation of several repair techniques at separate locations along MPFL, as mentioned by Dr. Ilahi, as well as greater variability in tissue quality. The study by Sillanpää et al.,
      • Sillanpää P.J.
      • Peltola E.
      • Mattila V.M.
      • Kiuru M.
      • Visuri T.
      • Pihlajamäki H.
      Femoral avulsion of the medial patellofemoral ligament after primary traumatic patellar dislocation predicts subsequent instability in men: A mean 7-year nonoperative follow-up study.
      although limited to the small sample size (n = 35), indeed shows us that patellar dislocation occurs at varying rates based on location of the tear, with femoral avulsions being most likely to re-dislocate.
      In contrast, MPFL reconstruction has been shown in recent literature to demonstrate a very low failure rate at short- and medium-term follow-up, with great reproducibility.
      • Sappey-Marinier E.
      • Sonnery-Cottet B.
      • O'Loughlin P.
      • et al.
      Clinical outcomes and predictive factors for failure with isolated MPFL reconstruction for recurrent patellar instability: A series of 211 reconstructions with a minimum follow-up of 3 years.
      • Erickson B.J.
      • Nguyen J.
      • Gasik K.
      • Gruber S.
      • Brady J.
      • Shubin Stein B.E.
      Isolated medial patellofemoral ligament reconstruction for patellar instability regardless of tibial tubercle-trochlear groove distance and patellar height: Outcomes at 1 and 2 years.
      • Schneider D.K.
      • Grawe B.
      • Magnussen R.A.
      • et al.
      Outcomes after isolated medial patellofemoral ligament reconstruction for the treatment of recurrent lateral patellar dislocations.
      As to Dr. Ilahi’s point that MPFL reconstruction alters patellofemoral joint pressure to be several times greater than the native state, this is a point that is conceptionally possible but has inconsistently been demonstrated in previous biomechanical studies. As mentioned by Dr. Ilahi, Rood et al.
      • Rood A.
      • Hannink G.
      • Lenting A.
      • et al.
      Patellofemoral pressure changes after static and dynamic medial patellofemoral ligament reconstructions.
      found that static reconstruction increased contact pressures, whereas dynamic reconstructions did not. In contrast, Melegari et al.
      • Melegari T.M.
      • Parks B.G.
      • Matthews L.S.
      Patellofemoral contact area and pressure after medial patellofemoral ligament reconstruction.
      found that MPFL reconstructions did not alter patellofemoral contact area or contact pressures compared with native knees. Further yet, several other biomechanical studies have demonstrated that contact pressures in the patellofemoral joint are only increased in the setting of technical error, such as using nonisometric fixation points,
      • Elias J.J.
      • Cosgarea A.J.
      Technical errors during medial patellofemoral ligament reconstruction could overload medial patellofemoral cartilage.
      graft overtensioning,
      • Beck P.
      • Brown N.A.
      • Greis P.E.
      • Burks R.T.
      Patellofemoral contact pressures and lateral patellar translation after medial patellofemoral ligament reconstruction.
      and tensioning at the incorrect angle of knee flexion.
      • Lorbach O.
      • Zumbansen N.
      • Kieb M.
      • et al.
      Medial patellofemoral ligament reconstruction: Impact of knee flexion angle during graft fixation on dynamic patellofemoral contact pressure—a biomechanical study.
      Nonetheless, it is difficult to extrapolate this laboratory evidence to the clinical setting, as there is not enough long-term evidence to show the effects of MPFL reconstruction on long-term patellofemoral joint health.
      In a recent editorial by Dr. Jack Farr, he suggests “If the site of medial restraint injury is discrete, repair may have similar outcomes of reconstruction... [but] Patient-/injury-specific factors and comorbidities must be identified and ranked for risk of recurrent instability.”
      • Farr J.
      Editorial Commentary: What is the optimal management of first and recurrent patellar instability? Patellofemoral instability management continues to evolve.
      We agree that in the proper setting, MPFL repair may still be a viable option in carefully selected patients with symptomatic lateral patellar instability. However, a large and growing body of evidence currently supports a swing of the pendulum toward MPFL reconstruction for the treatment of patellofemoral instability.

      Supplementary Data

      References

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