Page 27 - KNEETA

KNEETA R asked “Which is your better knee overall?” Again, the medial-pivot

implant was selected as the preferred implant over competitive

Total Knee system design philosophies: 76% of patients preferred the medial-pivot
(MP) to the posterior-stabilized (PS) knee, 76% to a PCL-retaining
(PCL) device, and 61% over a mobile-bearing (MB) implant.
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Patients gave the following

reasons for their preference
Today’s total knee implants for one knee over the other
have revolutionized 1. Felt more NORMAL

the treatment of patients with osteoarthritis. Even though
many devices can tout long-term survivorship data, surgeons have 2. Was STRONGER on stairs
strong opinions on which device they believe is superior.
In 2004, Dr. JW Pritchett authored a paper which was subsequently 3. Felt more STABLE
published in the British Journal of Bone and Joint Surgery. This
study polled 344 patients who underwent bilateral total knee 4. Had FEWER “CLUNKS, POPS, OR CLICKS”

“Which is your better knee overall?” This study showed 77% of
patients preferred the medial-pivot (MP) prosthesis to a posterior-
stabilized (PS) knee and 79% preferred the medial-pivot to a PCL-
retaining (PCL) device. Patients gave the following reasons for their
preference for one knee over the other: 1) felt more normal; 2) was
stronger on stairs; 3) felt more stable; 4) have fewer “clunks”, “pops” 76% of patients
or “clicks.” 7

Historically, patients have dealt with noise associated with knee 76 % preferred the medial
replacements. Literature usually claimed posterior-stabilized pivot (MP) to the
1-3
4
knees as the culprit. This noise seen in posterior-stabilized knees
was usually the result of the cam engaging the post, causing what posterior-stabilized
patients referred to as “clicks.” However, newer studies show that (PS) knee, 76% to a
this noise does not only stem from posterior-stabilized knees, but from
1,3,5
all types of prostheses. Medial-pivot knees have been shown to PCL-retaining (PCL)
be quiet when compared with traditional knee designs. There
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are several key attributes that contribute to the lack of noise in device, and 61% over
medial-pivot implants: an anatomic and deepened patellar track a mobile-bearing
resist and highly conforming medial pivot compartment, which acts
to femoral slide and contributes to the stabilty of the medial-pivot (MB) implant.
device.

Again in 2011, Dr. Pritchett published another patient preference REFERENCES
article, building upon his initial paper. This study now included 1. Niikura T. Patellar clunk syndrome after TKA with cruciate retaining design: a report of
mobile-bearing implants, adding patients to bring his initial 344 two cases. Orthopedics 2008;31:90
patients up to 440. Each patient underwent bilateral total knee 2. Yong-Gon K. Arthroscopic treatment of patellofemoral soft tissue impingement after
posterior stabilized total knee arthroplasty. The Knee 2008;15:36-39
3. Ip D. Natural history and pathogenesis of the patella clunk syndrome. Arch Orthop
Trauma Surg 2004;124(9):597-602
Patient Preference Regarding Their Knee Arthroplasties 4. Hozack WJ. The patellar clunk syndrome: a complication of posterior stabilized total
knee arthroplasty. Clin Orthop 1989;241:203-8
Implant Prefer Prefer Cannot 5. Beight JA, Yao B, Hozack WJ, et al. The patellar ‘clunk’ syndrome after posterior
Type N Procedure 1 Procedure 2 Tell P stabilized total knee arthroplasty. Clin Orthop Relat Res 1994;299:139–142
6. Pritchett JW. Patients prefer a bicruciate-retaining or the medial-pivot total knee
MP vs PS 42 32 (76.2%) 4 (9.5%) 6 (14.3%) <.001 prosthesis. J Arthroplasty. 2011;26(2):224-8.
7. Pritchett J. Patient preferences in knee prostheses. J Bone Joint Surg (Br)
MP vs PCL 50 38 (76.0%) 6 (12.0%) 6 (12.0%) <.001 2004;86(7):979-82
8. Anderson M. Patellofemoral complications after posterior-stabilized total knee
MP vs MB 83 51 (61.4%) 25 (30.1%) 7 (8.4%) .003
Adapted from Pritchett 6 2002;17(4):422-6
SUNTEK
Medical Devices
and Electronic
Products Trade Co. KNEETA® Medial-Pivot Knee System
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