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CASE REPORT

Early Femoral Component Loosening of Constrained Condylar Primary Total Knee Arthroplasties Inserted Without Stems

Samuel J. Macdessi*, Daniel S. Rich**,, Robert L. Buly**, Sarah Walcott-Sapp**, Geoffrey Westrich**

* Orthopedic Surgery, Sydney Knee Specialists, Edgecliff, NSW, Australia
** Department of Orthopedic Surgery, Hospital for Special Surgery, New York, NY

Address for Correspondence:  

Geoffrey Westrich
Department of Orthopedic Surgery
Hospital for Special Surgery
535 E. 70th St.
New York, NY 10021
E-mail: westrichg@hss.edu
Phone: 212-606-1510
Fax: 212-639-9266

Abstract:

Constrained condylar femoral components that do not accept stem extensions have been recently developed in an attempt to minimize the problems associated with diaphyseal stem fixation.  While avoiding stem placement may have clinical advantages, a concern with this concept is that increased stresses on the implant-bone and bone-cement interfaces may lead to early component loosening.  We are reporting four cases of early aseptic femoral component loosening of primary constrained condylar knee arthroplasties in which a stem extension was not used.  Based upon this experience, we suggest caution with the use of constrained condylar implants without stem extensions.

J.Orthopaedics 2008;5(1)e20

 Keywords:

failed total knee replacement; total knee replacement; osteolysis;constrained condylar knee; femoral loosening

Introduction:

There are theoretical benefits and risks associated with the use of constrained condylar femoral components that do not include stem extensions.  This design is intended to provide the additional kinematic stability of a constrained condylar knee prosthesis design in patients with good bone quality who are thought to not require additional stem support.  The system has the potential to minimize certain complications of diaphyseal fixation, but also may increase the possibility of component loosening.  We present four cases of early femoral component loosening in patients who had primary cemented total knee replacements using the same non-modular constrained condylar knee implant without stem extensions.

Case Report :

Case One

A 78 year-old female with a body mass index (BMI) of 29.3 had undergone a right primary cemented knee replacement nine years earlier for varus osteoarthritis.  An Optetrak Non-Modular Constrained Condylar Knee was inserted without stems (Exactech®, Gainesville , FL ) to assist with the marked lateral ligament attenuation with persistent coronal plane imbalance which presented following a medial ligament release.  She had no postoperative instability and the anatomic alignment was 5 degrees of valgus as assessed by postoperative radiographs.  Her knee replacement functioned well for three years but then presented with new onset of left anterior knee pain with weight bearing of one year’s duration. She had sustained several falls in the recent past, one producing a right humeral neck fracture. However, she did not recall any direct trauma to the left knee.  Physical examination revealed a small joint effusion, tenderness over the lateral joint line and pain free arc of motion from 0 to 110 degrees.  She had maintained physiologic valgus alignment of five degrees and no gross coronal plane instability was appreciated clinically.   Some pain was elicited to stress testing.   Radiographs (Figures 1A and 1B) showed an incomplete 2 mm radiolucent line under the anterior flange of the femoral component, but it did not appear loose. 

Figure 1A: These are the anteroposterior radiographs of the left knee four years after primary total knee arthroplasty.  The tibial component is in slight varus.

Figure 1B: These are the lateral radiographs of the left knee four years after primary total knee arthroplasty.  An incomplete radiolucent line is noted under the anterior flange of the femoral component.

The tibial component was noted to be in slight varus alignment.  A three-phase technetium bone scan showed intense uptake around the femoral component only.  Blood indices and aspiration were within normal limits with no evidence of infection.  Revision knee surgery was undertaken, which revealed a grossly loose femoral component and a well-fixed tibial component. There were large contained bone defects involving both femoral condyles.  After preparing the bone surfaces, a new constrained condylar femoral component with distal and posterior augments was inserted along with a diaphyseal press fit stem extension to engage the femoral cortex.  The core implant was cemented distally, while the stem was press fit proximally.  The patient had an uneventful recovery and is now without knee pain at 18 months post revision.

Case Two

A 77 year-old female with a BMI of 30.9 presented three years following right total knee replacement with worsening knee pain.  She suffered from valgus osteoarthritis and had undergone an Optetrak Non-Modular Constrained Condylar Knee replacement without stem extensions (Exactech®, Gainesville , FL ) because of inability to achieve coronal plane balance following collateral ligament release.  Initially, she had no instability, anatomic alignment of 5 degrees, and did well with no pain.  She sustained a fall 6 months prior to presentation with no significant injury but felt her pain had developed since then.  Physical examination revealed a 5 degree flexion contracture and passive flexion to 100 degrees.  There was a boggy effusion present and a suggestion of coronal plane laxity.  Tenderness was elicited around the femoral component.   Radiographs demonstrated a progressive radiolucency under the anterior flange of the femoral component.  Blood indices and aspiration were within normal limits with no evidence of infection.  A technetium bone scan demonstrated increased uptake around the femoral component and a labeled white cell scan to exclude infection was normal.  Revision knee surgery was performed for persistent pain and probable component loosening.  The femoral component was found to be grossly loose.  Significant contained femoral condylar defects from toggling of the component were noted.  Posterior and distal augments were used along with a diaphyseal stem extension on a new constrained condylar femoral component.  Following preparation of the bone the core implant was cemented distally while the stem was press fit proximally.  She made an uneventful post-operative recovery and is now without knee pain 14 months years post revision surgery.

Case Three

A 72 year-old female with a BMI of 37.3 underwent a right Optetrak Non-Modular Constrained Condylar Knee replacement without stem extensions (Exactech®, Gainesville , FL ) for valgus osteoarthritis. She had previously had a successful Exactech® posterior stabilized left total knee replacement. The patient did well initially with no instability. Two years after her first index procedure, she reported that the right knee did not feel like the left and had a tendency to give way.  Radiolucency was noted behind the anterior femoral flange.  Blood indices and aspiration were normal without any evidence of infection.  A three phase technetium bone scan revealed increased uptake around the femoral component, and an MRI suggested a large amount of synovial debris and potential loosening of the patella without loosening of femoral or tibial components.  Because of persistence of symptoms consistent with synovitis, an arthroscopic synovectomy was performed.  The patient’s preoperative symptoms resolved but she still reported “achiness”.  Nine months later she had an episode of giving way and fell.  Radiographs demonstrated translation and tilting of the femoral component.  At the time of revision surgery, the femoral component was grossly loose. Significant contained femoral condylar defects from toggling of the component were present. All other components were stable. Posterior and distal femoral augments were used along with a diaphyseal stem extension on a new constrained condylar femoral component. Following preparation of the bone the core implant was cemented distally while the stem was press fit proximally.  She made an uneventful post-operative recovery and the knee pain resolved completely.  She is now 12 months post revision surgery.

 

Case Four

A 63 year-old male with a BMI of 23.7 presented with severe right knee pain and a medial condyle fracture.  Four years earlier he had undergone a bilateral knee replacement with Optetrak Non-Modular Constrained Condylar Knee replacement without stem extensions (Exactech®, Gainesville , FL ) for varus osteoarthritis with lateral laxity.  He did well initially with no instability, but three and a half years post-operatively developed increasing pain and difficulty walking.  At that time he was diagnosed with a soft tissue problem and treated with anti-inflammatory medication.  Physical examination revealed tenderness, crepitus with range of motion, and a moderate effusion.  Radiographs showed a fracture through the medial condyle of the knee with displacement without any obvious trauma.  Comparison to previous films indicated that the femoral component had clearly shifted in position and loosened.  A CT scan was also performed and demonstrated significant osteolysis in the femur and some ostetolysis beneath the tibial base plate.  Blood indicies and aspiration were normal with no signs of infection.  A DePuy P.F.C. Sigma TC3 knee (DePuy [Johnson and Johnson]. Warsaw, Indiana) with a rotating platform base and a Synthes locking plate for the medial condyle fracture (Synthes, West Chester, PA) were implanted with cement because of the preference of this particular surgeon.  The patient had an uneventful recovery and is currently free of knee pain at 7 months post revision.

Discussion :

The theoretical benefits of avoiding stem extensions with constrained condylar knee replacements include prevention of fat embolism from canal instrumentation, reduction in “end of stem pain”, shorter operating times, less difficult surgery at revision and reduced costs. Certain constrained condylar knees have been developed that do not have a femoral stem extension so as to minimize the violation of distal femoral metaphyseal bone.  These relatively new implants are similar to a posterior-stabilized femoral component except they have a wider and deeper femoral box to accommodate the more conforming tibial polyethylene spine.  The polyethylene in the Optetrak Non Modular Constrained implant is machined from molded block material.  The insert has 1.5° of  medial-lateral motion and 2° internal-external rotation before the femoral and tibial components begin to transfer and share additional constraint.  In all four of these patients Palacos cement (Zimmer®, Warsaw , IN ) was used for fixation.  These three surgeons performed 125 primary total knee replacements with this stemless constrained implant from February 1, 2002 to April 19, 2007 .  These four revisions are the only known cases of femoral component loosening of implants inserted during this time period and represent 3.2% of the total number of implants. Three of the four patients described some traumatic event prior to loosening and subsequent revision.  This compares to a revision rate of 6% for constrained condylar implants using stem extensions (Genesis II, Smith and Nephew, Memphis , TN ; Insall Burnstein CCK, Zimmer, Warsaw , IN ; hinged implant, Biomet, Warsaw , IN ) at our institution over a three year time period2.  Specific data on revision rate for the Optetrak Non-Modular Constrained Condylar Knee replacement with stem extensions is unfortunately not currently available.  

The theoretical risk of using constrained condylar knee replacements without stem extensions is that the interface stresses will be substantially higher and could lead to early implant loosening.  Both Anderson et al.1 and Nazarian et al.4 have reported good intermediate term results when constrained devices were used without stem extensions.  Anderson et al.1 reported 49 patients (55 knees) who had undergone primary total knee replacement with a constrained condylar knee implant without stem extensions.  At an average of 44.5 months follow-up, they found no loosening, one dislocation, and one revision arthroscopy for peripalettar fibrosis.  Nazarian et al.4 reported a rate of loosening of 10.1% for revision total knee replacements using the stemless Insall-Burstein constrained condylar knee implant at a mean follow-up of 4.7 years.  There were 4 cases of tibial loosening and 2 cases of femoral loosening in 55 knees and no significant differences in rate of loosening between patients with implants with zero, one, or two stems.  A study by Easley et al.3 found no loosening at 7.8 years when stem extensions were used with these devices in spite of not attempting to balance the ligaments.  In a recent biomechanical study, Rawlinson et al.5 found that only specimens with reduced bone quality benefited from the addition of a stem.  Appropriate length and diameter were critical in protecting the proximal tibia in these specimens.  To our knowledge, the four patients included in this case study are the only ones who underwent primary total knee arthroplasty with this particular implant and were treated at the same institution for loosening since February of 2002.  This indicates a very low overall incidence of loosening. 

These cases also illustrate the fact that trauma, albeit minor, following knee replacement with these types of implants should be considered a causative risk factor for potential loosening. It should be noted that nothing specific to this particular non stemmed constrained condylar device was found to be contributory to these clinical failures. While overt loosening may not be noted clinically or even radiographically, further imaging studies are warranted.  In each of the cases that we presented, the bone scan was useful to demonstrate femoral component loosening.  Patients that complain of persistent pain in the absence of other definitive sources of pain should have a bone scan to further evaluate the knee prosthesis for occult loosening.  In addition, in every case presented the intraoperative findings were much worse than anticipated, with severe osteolysis, necessitating the use of stems and augments.

Until more definitive evidence exists on the role of stems in constrained condylar knees, we urge caution in the use of non-modular or unstemmed constrained femoral components.  With these stemless devices, the femoral component appears more susceptible to early loosening than the tibial component.  In addition, elderly patients with osteopenic bone may be more at risk for such catastrophic early failure.  Such patients in our practice now receive femoral and tibial stem extensions to better distribute the stresses if a constrained condylar implant is required.

Unfortunately, the authors have noted a trend toward the more cavalier use of stemless constrained femoral components and the lack of an attempt to perform ligament balancing that may avoid these types of prostheses.  While there may be a limited role for stemless constrained knee prostheses in a select patient population (i.e. younger patients with better bone quality), we recommend against the use of unstemmed constrained devices and encourage surgeons to continue to maintain the art of ligament balancing and insertion of a traditional posterior stabilized devices if possible.

Reference :

  1. Anderson JA, Baldini A, MacDonald JH, Pellicci, PM, Sculco TP. Primary Constrained Condylar Knee Arthroplasty without Stem Extension for the Valgus Knee. Clin Orthop Relat Res 2006;442:199-203.

  2. Boettner F, Laskin R, Windsor RE, Haas SB. Hybrid Component Fixation in Revision Total Knee Arthroplasty.  Clin Orthop Relat Res 2006;446:127-131.

  3. Easley ME, Insall JN, Scuderi GR, Bullek DD. Primary Constrained Condylar Knee Arthroplasty for the Arthritic Valgus Knee. Clin Orthop Relat Res 2000;380:58-64.

  4. Nazarian DG, Mehta S, Booth RE. A Comparison of Stemmed and Unstemmed Components in Revision Knee Arthroplasty. Clin Orthop Relat Res 2002;404:256-262. 2002

  5. Rawlinson JJ, Peter LE, Campbell DA, Windsor R, Wright TM, Bartel DL. Cancellous Bone Strains Indicate Efficacy of Stem Augmentation in Constrained Condylar Knees. Clin Orthop Relat Res 2005;440:107-116.

 

 

This is a peer reviewed paper 

Please cite as : Samuel J. Macdessi : Early Femoral Component Loosening of Constrained Condylar Primary Total Knee Arthroplasties Inserted Without Stems  

J.Orthopaedics 2008;5(1)e20

URL: http://www.jortho.org/2008/5/1/e20

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