Simultaneous Bilateral Extensor Mechanism Reconstruction for Acute Patellar Tendon Rupture

    Following a fall at home, a 46-year-old male with alkaptonuria and a history of bilateral total knee arthroplasty presents with bilateral knee pain and an inability to actively extend either knee. The surgical plan calls for primary patellar tendon and retinacular repair and reconstruction of the bilateral extensor mechanisms.


    James Fraser, MD, MPH, and Gregory K. Deirmengian, MD


    The authors have no disclosures relevant to this article.


    Alkaptonuria is a rare disease associated with abnormal homogentisic acid metabolism that affects multiple organ systems. A musculoskeletal manifestation of the disease is severe tendinopathy that predisposes patients to tendon rupture. [1]

    Disruption of the extensor mechanism following total knee arthroplasty (TKA) is an infrequent but challenging complication. [2-5] Surgical options for this injury include primary repair, autograft or allograft reconstruction, or reconstruction with a synthetic mesh. [3,5-9]

    Although bilateral extensor mechanism disruption following TKA has been reported in the literature, [7,10] no available case reports have documented the simultaneous Achilles allograft reconstruction of acute bilateral patellar tendon ruptures.

    The aim of this case report is to illustrate the complexity of managing a patient with acute bilateral patellar tendon ruptures many years after TKA.

    Case Report

    Patient Presentation

    A 46-year-old male with a history of alkaptonuria and previously well-performing bilateral TKAs (right knee in 2007, left knee in 2010) presented to an outside hospital after a fall at home. He reported hearing and feeling a “pop” over the anterior aspect of both knees, and was unable to bear any weight following the injury.

    In addition to alkaptonuria, he has a history of multiple prior tendon ruptures, including bilateral Achilles ruptures and a left quadriceps rupture treated with primary repair in 2011. At each previous tendon repair surgery, brittle tissue marred with black discoloration and deposits was described.

    Due to the complex nature of his injury, he was transferred to a tertiary medical center for evaluation and treatment.

    Physical Examination

    • Height: 5 feet, 2 inches; weight: 220 pounds; BMI: 40.2 kg/m2
    • Bilateral knees with 2+ effusions and marked ecchymosis
    • Palpable defects bilaterally over the patellar tendons
    • Well-healed midline incisions over both knees
    • Unable to ambulate or extend either knee
    • Passive range of motion (ROM) bilaterally from 0° to 90°, limited by pain
    • Instability examination limited by pain
    • Bilateral lower extremities with 2+ peripheral pulses
    • Sensation intact to light touch
    • Motor function normal in the sural, saphenous, deep/superficial peroneal, and tibial nerve distributions


    • Mild patella alta bilaterally on radiographs (Figure 1)
    • Patellar tendon disruption on MRI (Figure 2)

    Figure 1. Post-injury, preoperative anteroposterior (AP) and lateral radiographs of the bilateral knees demonstrate mild patella alta bilaterally and well-positioned and aligned cruciate-retaining implants, with no evidence of loosening.

    Figure 2. Representative sagittal T1- and T2-weighted images demonstrate disruption of the patellar tendon from the tibial tubercle.


    • Acute bilateral patellar tendon ruptures with well-fixed, well-functioning bilateral TKA


    The surgical plan was to perform a primary patellar tendon and retinacular repair and reconstruct the bilateral extensor mechanisms with an Achilles allograft bone block.

    Surgery of the Right Knee

    • Using the old incision, the extensor mechanism was exposed.
    • The patellar tendon and retinaculum were found to be torn transversely, but the collateral ligaments were preserved.
    • The knee was exposed with a medial parapatellar arthrotomy.
    • The components were found to be well fixed.
    • A new 12.5-mm rotating polyethylene was placed.
    • With the knee stable, attention was then turned to the allograft reconstruction.
    • A 15×25 mm beveled bone block with a proximal apex was fashioned from the calcaneus on the Achilles allograft tendon and was impacted in a press-fit manner into a similarly shaped trough created at the level of the tibial tubercle (Figure 3).
    • Solid fixation was obtained with the fit of the bone block alone, but supplemental fixation was achieved with 2 cerclage wires.
    • Using Krackow sutures, the remnants of the native patellar tendon were re-approximated to the anterior tibia using bone tunnels.
    • The Achilles allograft was then passed from deep to superficial through a slot created in the patellar tendon just distal to the patella.
    • With the knee forced into maximal extension, the allograft tendon was then sutured to the native quadriceps tendon with interrupted #5 Ethibond sutures.
    • The retinaculum was repaired with a series of #5 Ethibond and #1 Vicryl sutures.
    • A Blake drain was left in the superficial tissues on closure.

    Figure 3. Illustration depicting the press-fit calcaneal bone block (top) and Achilles tendon allograft pass through technique (bottom) that was used. The graft was sutured in full extension with maximal tension.

    Surgery of the Left Knee

    Attention was then turned to the left knee.

    • An identical procedure had been planned for this side, but when the knee was exposed, the surgeon discovered complete incompetence of the medial collateral ligament.
    • At this point, the decision was made to revise to a constrained prosthesis.
    • The existing tibial and femoral components were removed with minimal bone loss and stemmed revision components were placed.
    • A stable knee with full passive ROM was achieved and the new implants were cemented to the bone.
    • The patellar component was found to be stable and was left in place.
    • The same extensor mechanism reconstruction procedure described above was then performed on this knee.

    Tourniquet time was less than 2 hours for each knee.

    Postoperative Follow-Up

    • After closure and dressing application, the bilateral lower extremities were placed in hinged knee braces locked in full extension (Figures 4-5). The braces were to be worn at all times.
    • The patient was transferred in stable condition to the post-anesthesia care unit and then to the orthopedic floor.
    • The patient was made non-weight-bearing in full extension for 8 weeks.
    • He was placed on warfarin for deep vein thrombosis prophylaxis.
    • The patient was discharged to a rehabilitation facility on postoperative day 10.

    Figure 4. Posteoperative AP and lateral views of the right knee.

    Figure 5. Posteoperative AP and lateral views of the left knee.

     Surgical Pearls

    • As expected from the patient’s history, his connective tissues and tendons were stained with a soot-like discoloration and multiple intra-tendinous collections of black particulate debris were noted. These findings should trigger a surgeon to consider the diagnosis of alkaptonuria, which may not always be known preoperatively.
    • Other than alkoptonuria, the patient was a relatively young and healthy male. Consideration was given to a staged reconstruction, but due to the acute nature of his injury, it was decided that bilateral simultaneous reconstructions would be best.
    • Although preoperative history, physical exam, and imaging studies easily diagnosed the patellar tendon disruptions, determining the integrity of the collateral ligaments was more challenging. Having the complete revision set with constrained implants immediately available was key to appropriate intraoperative management of this patient.

    Author Information

    James Fraser, MD, MPH, is an orthopaedic surgery fellow at The Rothman Institute at Thomas Jefferson University. Gregory K. Deirmengian, MD , is a professor at The Rothman Institute at Thomas Jefferson University, Philadelphia, Pennsylvania.

    Adult Reconstruction Section Editor, Rothman Institute Grand Rounds

    Antonia F. Chen, MD, MBA


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