Isokinetic Performance After Cruciate-substituting Ultra-congruent and Posterior Stabilized Total Knee Arthroplasties
Condition: Osteoarthritis, Knee; Knee Arthritis
MeSH terms: Osteoarthritis, Knee
Study type: Interventional

Summary: 
      The choice between ultra-congruent (UC) insert or posterior cruciate ligament-stabilized (PS)
      insert in posterior cruciate ligament (PCL) sacrificing total knee arthroplasty (TKA) remains
      debatable. Despite the potential advantages of the UC insert over PS insert with its
      different design, there are concerns about inferior clinical outcome related to its use.
      Therefore, isokinetic performance was used in this study to objectively evaluate knee
      function after TKA and the clinical scores of the patients were also evaluated. To the best
      of our knowledge, no prospective randomized study has compared the isokinetic performance of
      the knee following the use of UC and PS inserts in TKA. The hypothesis of the present study
      was that compared with the PS insert, the UC insert would be associated with a lower clinical
      outcome and isokinetic performance following TKA.

      A total of 65 patients scheduled to undergo TKA on for primary knee osteoarthritis were
      randomly assigned to either the UC (32 patients) or the PS group (33 patients). The Knee
      Society Score (KSS) and isokinetic performance results of each patient were recorded
      preoperatively and at postoperative 3, 6 and 12 months. The physiatrist performing isokinetic
      tests and patients were blinded to the study.
    

Detailed description: 
      Eligibility of all patients between 55 and 80 years, scheduled to undergo unilateral TKA on
      for primary knee osteoarthritis will be evaluated. The exclusion criteria are rheumatological
      joint diseases, previous knee surgery, neuromuscular diseases, bilateral TKA, or
      insufficiency of collateral ligaments. Patients will be randomized in a 1:1 ratio via
      computer-generated randomization using Microsoft Excel 2016 (Microsoft Corporation, Seattle,
      WA, USA) to be allocated in the UC insert or PS insert group before the operation. Unblinded
      senior resident will implement the randomization. Patients and physiatrists performing
      isokinetic measurements will be blinded to group allocation.

      During the UC and PS operations, Vanguard® Complete Knee System prosthesis (Zimmer Biomet
      Inc., Warsaw, IN, USA) will be implanted using the same surgical technique in all patients.
      The Vanguard anterior-stabilized (AS) insert is a UC deep-dish design with a 10 mm prominent
      anterior lip and 5mm posterior lip. This bone-conserving design prevents anterior femoral
      subluxation because of the prominent anterior lip. The insert design allows it to be used
      with the Vanguard cruciate-retaining femoral component and the highly congruent articulating
      surface increases rotational stability. There is more contact area between the femoral
      component and the weight-bearing surface to decrease the shear stress between the femur and
      polyethylene insert.

      A tourniquet will be inflated to pressure of 300 mmHg after spinal anesthesia. All operations
      will be performed with the same surgical technique by a single senior surgeon. Patellar
      surface arthroplasty will be performed in all the cases. Both femoral and tibial prostheses
      will be implanted with pressured bone cement. A suction drain will be placed inside the knee
      capsule. On the morning of the first day after surgery patients will be mobilized under the
      supervision of the physical therapist. All patients will undergo the same rehabilitation
      procedure during the outpatient period and will be examined by the same physiatrist at the
      regular 3, 6, and 12-month follow-up visits.

      The primary outcome is isokinetic performance, measured as peak knee extensor and flexor
      torque values in Newton-meters, on the operated knee. Measurements wilil be done
      preoperatively and at 3, 6, and 12-month follow-up examinations under the supervision of the
      same physiatrist. At same time points, the Knee Society Score (KSS) will be evaluated as
      well. Isokinetic measurements will be performed using a Biodex System III Isokinetic
      Dynamometer, version 3.03 (Biodex Medical Inc., Shirley, NY, USA) by the same senior
      physiatrist. Patients will be positioned on the dynamometer with the hip in 90° in a sitting
      position for the knee flexion and extension measurements. Lateral movement of the knee will
      be prevented during full extension and flexion of the knee by a thigh strap on the operated
      leg. The physical therapist will help the patients to achieve proper positioning before each
      test. Concentric isokinetic knee flexion-extensions will be assessed at a preset velocity of
      60º/sec, over a range of motion of 0º to 110º for both parameters. A fixed number of 10
      flexion-extension repetitions will be completed by each patient. Instructions will be
      provided, and one trial repetition will then performed by all patients before the
      measurements were taken.

      Sample size estimation will be performed using the extension peak torque as a primary effect
      variable. As there is no similar study with isokinetic measurements regarding this subject, a
      difference in mean values of 10 Nm and standard deviation of 12 Nm were assumed for each
      group. The group sample sizes of 31 and 31 achieved a power of 0.90 to detect a difference of
      10 Nm between the two groups with estimated group standard deviations of 12 for each group
      and with a significance level (alpha) of 0.05 using a two-sided, two-sample test. Considering
      the loss to follow-up, two patients were added to each group. Thus, recruitment will end
      after 33 patients were assigned to either groups. All data will be calculated as mean and
      standard deviation. The Student's t-test will be used for statistical analysis of the patient
      data. Statistical calculations will be performed with SPSS 22.0 software (IBM SPSS Statistics
      for Windows, Version 22.0. Armonk, NY: IBM Corp.). A value of p< 0.05 will be considered
      statistically significant.
    

Intervention name(s): Vanguard® Knee System
Intervention type(s): Device
Intervention description(s): Posterior cruciate ligament retention versus sacrificing is one of the main debates in total knee arthroplasty (TKA) and retention or sacrificing depends on the individual preference of the surgeon during the surgery. Whenever the surgeon decides to sacrifice the posterior cruciate ligament (PCL), another controversial question arises regarding the tibial insert type. While the posterior cruciate ligament-stabilized (PS) insert is widely used as the tibial insert in PCL-sacrificing TKA, it has some disadvantages such as increased polyethylene wear, additional bone resection, breakage of the post and patellar clunk syndrome. The ultra-congruent (UC) insert was designed to prevent bone loss in particular, and the other mentioned disadvantages of the conventional PS insert. However, patients with postoperative hyperextension have been seen to be associated with inferior clinical outcomes and knees become gradually more extended until two years after TKA using the UC insert.
Allocation: Randomized
Intervention model: Parallel Assignment
Intervention model description: Patients were randomized in a 1:1 ratio via computer-generated randomization using Microsoft Excel 2016 (Microsoft Corporation, Seattle, WA, USA) to be allocated in the UC insert or PS insert group before the TKA operation (Figure 1). Unblinded senior resident implemented the randomization. Patients and physiatrists performing isokinetic measurements were blinded to group allocation.
Masking: Double (Participant, Investigator)
Primary purpose: Treatment
Keywords: Ultra-congruent insert; Posterior cruciate ligament-stabilized insert; Isokinetic test; Strength; Total knee arthroplasty