Prof. Dr. Stefano Zanasi performs partial (UNI, BiUNI, BiCOMP) or total knee replacement, robotised partial knee replacement, knee revision surgery.

MIS and Robotised Partial Knee replacement (UNI, BiUNI, BiCOMP) and Innovations in Total Knee Replacement (XR)

1. UNI

Bone stock preservation and tissues respect are the main objectives of a partial knee replacement (UNI/BiUNI/BiCOMP). as well as

  • maintaining/recovering optimal capsulo-ligamentous balancing gives a great advantage from the functional point of view with fastest and maximal recovery , generally within a week , of the passive as well as active ROM;
  • painless, gives shorter recovery time due to anatomical and limited planes of dissection; there’s
  • less incidence of possible complications as fat embolism (no invasion of the medullary). Last, but not least we have
  • the aesthetic advantage of the limited skin incision and
  • normal joint kinematic and gait reproduction, leg’s morphology respect, proprioception maintenance
  • Revision = primary

Advantages of the procedureinclude preservation of uninvolved tissue and bone, reduced operative time, better range of motion, improved gait, increased patient satisfaction.

With appropriate patient selection, careful surgical technique, proper implant design, unicompartmental knee arthroplasty can now be viewed as a procedure with reliable medium to long-term success

Procedure comparisons: UNI VS. HTO

Resurfacing methods are gaining popularity. Results comparing HTO with unicompartmental knee arthroplasty favor the latter.

  • Broughton et al demonstrated good results in 76% of patients in a replacement group and in 43% of patients in an osteotomy group.Range of motion, speed of rehabilitation, and perioperative morbidity were significantly better for unicompartmental knee arthroplasty, and no signs of late deterioration were present.
  • Weale and Newman, after a 12- to 17-year follow-up period, also reported better function and longer survival in the unicompartmental group.Other publications have similarly shown more favorable results with arthroplasty.
  • The functional benefits of unicompartmental knee arthroplasty over HTO have also been demonstrated using gait analysis, with patients displaying a more normal gait and better stair-climbing ability following unicompartmental knee arthroplasty than they did after HTO.
  • If a revision to a total knee arthroplasty becomes necessary, the results are now believed to be generally better if the revision occurs after a failed unicompartmental knee arthroplasty than they are following a failed HTO. (Previous HTO is a contraindication for a unicompartmental knee arthroplasty)

Procedure comparisons: UNI VS. TKA

In the late 1980s, unicompartmental knee arthroplasty waned in popularity, largely because of problems with patient selection, operative technique, and polyethylene wear. Later, as understanding of the procedure and the associated prostheses improved, long-term results of UNI became comparable to those of TKA.

  • Functional outcome with UNI is superior to that with TKA, with the former providing better range of motion and ambulatory function.
  • Laurencin et al found that UNI also results in less pain, more stability, and better stair-climbing ability than does TKA
  • In addition, the cost of the UNI procedure is about 57% that of TKA

In comparison with a TKR, UKR allows:

  • use of smaller implants
  • shorter operative time
  • preservation of both the cruciate ligaments and minimal bone resection
  • maintenance of the anterior cruciate ligament and its mechanoreceptors may produce a better functional result in UKR
  • knee kinematics during flexion following UKR has been shown to more closely resemble the intact knee
  • on the other hand biomechanical studies of TKR have yielded results far from that of a normal knee.
  • Newman et al. presented a randomized study comparing UKR to TKR showing a greater range of motion following UKR
  • Weale et al. documented a superior functional recovery with a higher performance in descending stairs and better patient satisfaction with UKR compared with TKR
  • in a cadaveric study Patil et al. demonstrated normal joint biomechanics after a UKR implantation in a knee

 fig 16, 17

2. Patella femoral joint implant arthroplasty

Osteoarthritis of the patellofemoral joint should be considered as an entity separate from disease in the medial and lateral tibiofemoral compartments of the knee. Not all patients with patellofemoral arthritis have osteoarthritis in the other compartments; arthritis may develop at different times and with different etiologies in the different compartments

Advantages of a PFKR

  • Smaller Incision If the patella and one tibial surface appear healthy, then an incision extending approximately 3" is used to implant the Partial knee replacement components. This is much smaller than the 8" incision required for a total knee; thereby leaving a more pleasing cosmetic appearance after surgery is completed.
  • Less Blood Loss Quite often patients are required to donate blood before total knee replacement providing blood to replace the quantity lost during surgery. The Partial knee replacement technique generally eliminates the need for blood transfusion.
  • Lower Morbidity Benefits of a less invasive procedure include less postoperative discomfort, a shorter hospital stay, less physical therapy, and more rapid healing. Shorter Recovery Time Most partial knee replacement patients walk on their resurfaced knee within a few days of surgery, and are generally released from the hospital within a few days. Within 2-4 weeks most patients are driving an automatic car if the left knee is replaced and resuming most normal daily activities be about six weeks. With a total knee replacement, recovery time can be four to five times longer. Also, with a total knee replacement, extensive physical therapy may be required.
  • Less Bone Removed while retaining the healthy portion of the knee only a few millimeters of bone on one compartment of the knee is removed to properly fit Partial knee replacement implants. In total knee replacement all knee surfaces loose up to 10mms of bone on each of the three compartments. Since Partial knee replacement implants save more bone, future total knee replacement procedures can more easily be performed if necessary.

fig 18,19

3. BiUNI

The principal feature of the Bi-UNI is the use of 2 femoral and 2 tibial indipendent components. In our experience the advantages of this procedure are the same as those regarding UKR: PRESERVATION THE INTERCONDYLAR EMINENCE WITH THE CRUCIATEs, rotational axis respect, bone stock respect, normal patellar level and tracking, normal joint kinematic and gait reproduction, leg’s morphology respect, proprioception maintenance. Obviously a surgical mistake due to the difficulty of the technique or due to the loosening of a component is calculated. Retaining both cruciate ligaments in resurfacing knee arthroplasty appears to maintain the essential features of the normal knee motion: femoral rollback and tibial internal rotation with flexion.

There were no differences in medial kinematics during stairs climbing activity, indicating similar knee function for the UNI and biUNI groups. The close similarity in the pattern and magnitude of medial and lateral condylar translation in the biUNI knees was a surprise, it suggested that larger lateral translation is typical of the cruciate intact knee. Both condyles moved 5mm posterior on the tibia at heel-strike, indicating a dynamic posterior slide of the femur with impact and weight-bearing. The intact knee has an envelope of passive laxity, and these observations suggest that dynamic stabilizers do not eliminate these motions caused by external knee loads. Bicruciate retaining knee arthroplasty, even if it is not commonly performed, appears to provide a high level of function and knee kinematics in patients retaining essential features of the normal Knee .

One of the most common causes of failure in this procedure is a surgical mistake due to the difficult surgical technique. Malposition of the components, intercondylar eminence fracture, wrong ligaments balance and cementation mistakes are possible complications during surgery. Moreover case history showing the advantages and the survival of the Bi-UKR is very rare. This discourages many surgeons to utilize this procedure. But the continuous development of the prosthesis and the instrument accurancy are creating increasingly interest in this prosthetic solution. In our experience possible causes of failure are femoro-patellar degeneration and acquired instability.

ifig 20-28

4. Modular bicompartmental knee arthroplasty

A special consideration in the treatment of arthritic knees is the increased expectation of the more active arthritic population, whether young or old. To adequately serve this population, TKR should not be the first option for midstage arthritic patients with involvement of the medial and patellofemoral joints.

Patient satisfaction is crucial to the arthritic population and should be considered when determining the course of treatment. In 2001, Hawker et al analyzed eligibility requirements for knee arthroplasty: they found that no more than 15% of eligible patients with arthritis would consider arthroplasty. The major reasons patients refused surgical treatment were postoperative pain and disability. In our experience the advantages of this procedure are the same as those regarding UKR: preservation of the cruciates, rotational axis respect, bone stock respect, patellar level and tracking normal joint kinematic reproduction, leg’s morphology respect but with the reduced risk of failure for femoro-patellar joint involvement. Obviously a surgical mistake due to the difficulty of the technique . The indication is a symptomatic or degenerated femoro-patellar joint in a varus or valgus knee arthritis involving a single femoro-tibial compartment. Retention of the cruciate ligaments maintains normal kinematics and proprioception. Because bone and ligaments are conserved, pain relief should be similar to unicondylar knee arthroplasty. Less pain and reduced tissue trauma help to speed recovery and a return of function. Conservation of bone also provides reference landmarks in the event of future revision.

MODULAR BICOMPARTMENTAL PFJ+UNI is suited for the active high-demand patient. However, the same also benefits the less active patient, regardless of age. Retention of the cruciate ligaments maintains normal kinematics and proprioception. Because bone and ligaments are conserved, pain relief should be similar to unicondylar knee arthroplasty. Less pain and reduced tissue trauma help to speed recovery and a return of function. Conservation of bone also provides reference landmarks in the event of future revision. UNI+PFJ is suited for the active high-demand patient.

fig 29-40

5. JOURNEY II XR Total Knee System

Total knee arthroplasty (TKA) is considered the most beneficial and cost-effective treatment for end-stage knee arthritis and is the most frequently performed joint replacement surgery. TKA is also indicated for earlier osteoarthritis (OA) interventions, such as osteotomy or unicompartmental replacement, when additional treatment is warranted.

fig 41-43

One device option available once the decision is made to perform TKA is the JOURNEY II XR Total Knee System. The JOURNEY II XR Total Knee System is designed to be a more "natural feeling" total knee replacement. The goal of the JOURNEY II XR is to enable a higher level of function after total knee replacement by relieving pain and restoring the ability to participate in active lifestyles.

JOURNEY II XR is the next step in the evolution of total knee replacement surgery. By retaining, rather than substituting, the anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL), JOURNEY II XR is designed to combine the greater patient satisfaction of a partial knee replacement with the long-term survivorship and reproducible principles of TKA.

JOURNEY II XR accomplishes this by eliminating the past concerns of bi-cruciate retaining knees through an implant design that reflects more accurate replication of the knee anatomy, a robust tibial baseplate designed for optimal fixation and fatigue strength, the application of Smith & Nephew's VERILAST technology, an advanced bearing surface designed to provide lasting survivorship, . The introduction of enabling technologies such as NAVIO robotics-assisted surgery and VISIONAIRE patient matched adaptive guides to help deliver highly reproducible outcomes

 The retention of the cruciate ligaments may provide patients with more normal feel and stability throughout the range of motion, and may lead to a smoother recovery, improved function, and better patient satisfaction. JOURNEY II total knee system is designed to achieve normal shapes, position and motion. Smith & Nephew created this platform to empower patients to "rediscover normal" following total knee arthroplasty.

 fig 44.45

6. Robotic partial knee replacement (NAVIO)

is a surgical treatment designed to relieve pain in the knee caused by the wear and tear of joint cartilage. The partial knee resurfacing procedure is done using a robotic arm, which lets the surgeon treat only the damaged part of the knee. The precise nature of the procedure means healthy bone and ligaments surrounding the damaged area are spared from trauma. This procedure is best suited for adults suffering knee pain from osteoarthritis in 1 of the 3 knee compartments, but is ineligible for a total knee replacement. The  partial knee resurfacing procedure potentially offers the significative benefit as less damage to surround bone and tissue,  smaller incisions, thus reduced blood loss, less pain, less scarring and faster recovery

During surgery, surgeon guides the NAVIO robotic-arm based on his patient-specific plan. This allows the surgeon to remove only the diseased bone, preserving healthy bone and soft tissue, and assists surgeon in positioning the implant based on patient anatomy.  In the operating room, surgeon will use NAVIO to assist in performing patient surgery based on his personalized pre-operative plan. The NAVIO system also allows surgeon to make adjustments to patient plan during surgery as needed. When the surgeon prepares the bone for the implant, the NAVIO system guides the surgeon within the pre-defined area and helps prevent the surgeon from moving outside the planned boundaries. This helps provide more accurate placement and alignment of patient implant.


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