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Medacta - Model GMK- Sphere - Total Knee System

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Patient expectations are not as well fulfilled by TKA as by total hip replacement with fewer knee patients achieving a “forgotten joint” replacement.  Studies show that around 20% of TKA patients are not satisfied[1, 2, 3].  Excessive A/P motion may result in anterior knee pain and continued swelling. In many P/S designs, the stabilizing mechanism only engages after 70-80° of flexion leaving the knee vulnerable to A/P instability during the most commonly encountered functional activities.

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PATIENT SATISFACTION

In a study in which patients had a conventional CR or PS in one knee and a medially stabilized device in the other, 76% preferred the knee with the “ball in socket” medial compartment[5]. Patients reported:

  • It feels more normal
  • It is stronger when ascending/descending stairs
  • It has superior single-leg weight bearing
  • It  feels more stable during flexion and overall
  • There are fewer clunks, pops and clicks
GMK SPHERE

Based on the knee anatomy and kinematic studies performed by Prof. Michael Freeman and Prof. Vera Pinskerova[6], the GMK Sphere is an innovative total knee implant designed to deliver maximum functional stability with the goal of increasing TKA patient satisfaction during activities of daily living and decreasing post-operative knee pain.

RESPONSIBLE INNOVATION
Medacta is committed to providing innovative and safe solutions for patients with an evidence-based approach.
GMK Sphere was tested over 3 years prior to launch through an intensive evaluation program including in vitro and in vivo trials and Laboratory tests

STABILITY

GMK Sphere features a fully congruent medial compartment providing:

  1. High stability throughout the range of motion[7,10,11]
  2. No paradoxical motion between femur and tibia[7,10,11]
  3. No implant-related “mid-flexion” instability[7,10,11]
NATURAL PATELLAR TRACKING

GMK Sphere can replicate the natural kinematics of the healthy knee[7]:

  1. Trochlea groove lateralized by 2 mm to enable natural patella tracking[9]
  2. Flattened medial trochlear wall prevents patello-femoral overstuffing minimizing retinacular tension[8]
  3. Anatomic patellar implant with medialized dome allows for optimal bony coverage with reduced soft tissue tension, improved stability and contact area[12]
ANATOMIC FIT

Extensive anthropometric research on a unique global database containing more than 15,000 CT and MRI scans of knees validated the[12]:

  1. Range of 13 femoral sizes with 2 mm increments that best fit a broad spectrum of anatomic profiles
  2. Anatomically shaped tibial baseplate
  3. Range of inserts with 1 mm increments
  4. The combination of 13 femoral sizes and inserts with 1 mm increments allows the surgeon to “fine tune” ligament balance and improve stability throughout the range of motion.
PATIENT-SPECIFIC KINEMATICS

GMK Sphere accommodates the best pattern of kinematic motion for each patient rather than imposing an assumed “norm”[11]. This is achieved with:

  1. “Ball in socket” stability throughout the range of motion in the medial compartment[7,10,11]
  2. Freedom of movement in the lateral compartment[10,11]