BlueCross and BlueShield of Montana Medical Policy/Codes
Unicondylar Interpositional Spacer as a Treatment of Unicompartmental Arthritis of the Knee
Chapter: Surgery: Procedures
Current Effective Date: November 26, 2013
Original Effective Date: November 26, 2013
Publish Date: August 26, 2013
Description

Interpositional unicondylar spacers are metallic implants that are inserted into the joint space between the affected tibial plateau and femoral condyle.  Instead of being fixed, the spacers are held in place by the geometry of the curved implant, ligament tension, and surrounding soft tissue structures.  Metallic interpositional unicondylar spacers have been developed as possible alternatives to osteotomy or unicompartmental arthroplasty for treatment of unicompartmental knee arthritis.

While osteoarthritis of the knee may involve both medial and lateral components, some patients may have signs or symptoms confined to only one compartment, often as a result of specific injury.  Initial treatment of uni- and bi-compartmental disease is similar, i.e., analgesics, viscosupplementation, and arthroscopic debridement.  If focal cartilage defects are present, other therapies such as autologous chondrocyte or osteochondral transplants may be considered.  When these more conservative therapies fail, surgical interventions may be indicated.

Older patients with arthritis who typically consider total knee replacement are the type of patients who might be considered for unicondylar knee arthroplasty.  The metal-to-plastic unicondylar prosthesis has both tibial and femoral components but leaves intact both cruciate ligaments, the patellofemoral joint, and the opposite compartment, thus preserving nearly normal knee kinematics.  Unicompartmental arthroplasties are typically performed in patients with isolated medial arthritis who are older than 60 years, have a low level of physical activity, and weigh less than 180 pounds. 

Younger patients are usually not considered ideal candidates for total knee arthroplasty since they would be expected to need at least one additional total knee replacement in their lifetimes.  The preferred option for young patients with unicompartmental disease is high tibial osteotomy.  Those with medial compartment disease may also be candidates for unicompartmental arthroplasty or for fixed metallic hemiarthroplasty.  MacIntosh and McKeever hemiarthroplasty devices were used primarily between 1950 and 1970, but their use has decreased with the refinement of total knee arthroplasty procedures.  These devices require bone cuts that might complicate future arthroplasty procedures. 

Metallic interpositional unicondylar spacers have been developed as possible alternatives to osteotomy or unicompartmental arthroplasty.  These devices do not require any bone resection or mechanical fixation for proper function.  Following debridement and resection of the meniscus, the device is fit to the joint space above the affected tibial plateau and held in place by its geometry, ligament tension and the surrounding soft tissue structures.  The uncemented implant adapts to the kinematics of the knee, with a smooth metallic curved surface against which the femur articulates.  Preservation of bone is important for the use of interpositional spacers as a bridge procedure in active young adults or for overweight patients who would not be candidates for unicompartmental arthroplasty.

In 2001, a cobalt alloy device, referred to as a "unicondylar interpositional spacer" or "UniSpacer™" received clearance for marketing through a U.S. Food and Drug Administration (FDA) 510(k) process as an interpositional arthroplasty device, listing the MacIntosh and McKeever prostheses as predicate devices.  The FDA clearance for the UniSpacer device is for "moderate degeneration of the medial compartment of the knee (grade III-IV chondromalacia) with not more than minimal degeneration (grade I-II chondromalacia, no loss of joint space) in the lateral condyle and patellofemoral compartments."  The Orthoglide Medical Knee Implant™, which received 510(k) approval in 2006, is also indicated for “uncemented use in the treatment of moderate degeneration of the medial compartment of the knee,” but for grade II-IV chondromalacia.

Two other interpositional devices have received 510(k) approval, the Oti Unicondular Interpositional Spacer Osteoimplant™ (2002) and the Knee Interpositional Mini-Repair System™ (2003), listing the UniSpacer as a predicate device.  The Knee Interpositional Mini-Repair System is a patient-specific design, with specifications taken from magnetic resonance scans.  These devices are indicated for the uncemented treatment of medial and/or lateral tibial articulating surfaces of the osteoarthritic knee with grade II-IV chondromalacia.

Policy

Each benefit plan, summary plan description or contract defines which services are covered, which services are excluded, and which services are subject to dollar caps or other limitations, conditions or exclusions.  Members and their providers have the responsibility for consulting the member's benefit plan, summary plan description or contract to determine if there are any exclusions or other benefit limitations applicable to this service or supply.  If there is a discrepancy between a Medical Policy and a member's benefit plan, summary plan description or contract, the benefit plan, summary plan description or contract will govern.

Coverage

Unicondylar interpositional spacer is considered experimental, investigational and unproven as a treatment of unicompartmental arthritis of the knee.

Rationale

Two retrospective reports were identified on the use of the UniSpacer.  The largest group of patients reported was 71 UniSpacer implants in 67 patients (ages ranged from 38-83 and weights ranged from 53-168 kg). (1)  At one-year follow-up, 63 patients (66 knees) still had the implant; the five failed implants (7%) were converted to total knee arthroplasty for inadequate pain relief.  Ten patients (14%) had their implants revised to another size because of persistent pain (n=6) or dislocation (n=4), and 17 patients (24%) required manipulation under anesthesia to correct postoperative arthrofibrosis.  The rate of revision at one year was 21%, with an additional 24% requiring manipulation due to arthrofibrosis. 

Another group reported their experience with 37 UniSpacer implants in 34 patients (ages ranging from 42–75 years) with baseline Knee Society functional and objective rating scales of 69 and 62 points, respectively. (2)  At two-year follow-up, functional and objective ratings had improved by about 10 points; there were no excellent, 10 good, 15 fair, and 12 poor results.  Six of the 12 poor results were due to dislocation, and the 12 were revised to total knee arthroplasty.  There was no significant change in average pain scores (pre: 22, post: 26), with complaints of pain during normal walking for 32 knees and activities limited by pain in 15 patients (41% of implants).  Persistent postoperative swelling was present in nine patients.  No publications were identified on the use of other FDA-approved uncemented spacers. 

Based on the lack of controlled trials, combined with the high proportion of failures and adverse events in the identified retrospective reports, the use of interpositional unicondylar spacers is considered experimental, investigational and unproven.

2009 Update

One prospective study was identified in which 18 consecutive patients with isolated medial compartment osteoarthritis provided informed consent for insertion of a Unispacer knee implant.  Seventeen patients (94%) reported persistent symptoms between three and six months after surgery. (3) At an average 17-month follow-up (range, 3-26 months), 12 (67%) patients had required further interventions, and eight (44%) were classified as implant failures.  The authors described these results as “disappointing.”  While current data indicate that the unicondylar interpositional spacer does not improve the net health outcome, this technology is in an early stage of research and development.  The unicondylar interpositional spacer is considered investigational; a search of peer reviewed literature through July 2009 identified no new clinical trial publications or any additional information that would change the coverage position of this medical policy.

2010 Update

A search of peer reviewed literature through October 2010 identified no new clinical trial publications or any additional information that would change the coverage position of this medical policy.

2013 Update

A search of peer reviewed literature was conducted through July 2013.  No new clinical trial publications or any additional information was identified that would change the coverage position of this medical policy.

Coding

Disclaimer for coding information on Medical Policies

Procedure and diagnosis codes on Medical Policy documents are included only as a general reference tool for each policy. They may not be all-inclusive.

The presence or absence of procedure, service, supply, device or diagnosis codes in a Medical Policy document has no relevance for determination of benefit coverage for members or reimbursement for providers. Only the written coverage position in a medical policy should be used for such determinations.

Benefit coverage determinations based on written Medical Policy coverage positions must include review of the member’s benefit contract or Summary Plan Description (SPD) for defined coverage vs. non-coverage, benefit exclusions, and benefit limitations such as dollar or duration caps.

ICD-9 Codes

715.16, 715.26, 715.36, 715.86, 715.96

ICD-10 Codes

M17.0, M17.10, M17.11, M17.12, M17.2, M17.30, M17.31, M17.32, M17.4, M17.5, M17.9

Procedural Codes: 27599, 29999
References
  1. Hallock, R.H., and B.M. Fell.  Unicompartmental tibial hemiarthroplasty: early results of the UniSpacer knee.  Clinical Orthopaedics and Related Research (2003) (416):154-63.
  2. Sisto, D.J., and I.L. Mitchell.  UniSpacer arthroplasty of the knee.  Journal of Bone Joint Surgery American Volume (2005) 87(8):1706-11.
  3. Bailie AG, Lewis PL, Brumby SA et al. The Unispacer knee implant: early clinical results. J Bone Joint Surg Br 2008; 90-B(4):446-50.
  4. Scott, R.D., Joyce, M.J., et al.  McKeever metallic hemiarthroplasty of the knee in unicompartmental degenerative arthritis.  Long-term clinical follow-up and current indications.  American Journal of Bone and Joint Surgery (1985) 67(2):203-7.
  5. Emerson, R.H., and T. Potter.  The use of the McKeever metallic hemiarthroplasty for unicompartmental arthritis.  American Journal of Bone and Joint Surgery (1985) 67(2):208-12.
  6. Unicondylar Interpositional Spacer as a Treatment of Unicompartmental Arthritis of the Knee- Archived. Chicago, Illinois: Blue Cross Blue Shield Association Medical Policy Reference Manual (2009 July) Surgery 7.01.88.
History
August 2013  New 2013 BCBSMT medical policy.  Unicondylar interpositional spacer is considered experimental, investigational and unproven as a treatment of unicompartmental arthritis of the knee.
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Unicondylar Interpositional Spacer as a Treatment of Unicompartmental Arthritis of the Knee