Medical Policies - Surgery

Patient-Specific Cutting Guides and Custom Knee Implants


Effective Date:10-15-2017



Use of custom implants or patient-specific instrumentation (e.g., cutting guides) for joint arthroplasty, including but not limited to use in unicompartmental or total knee arthroplasty, is considered experimental, investigational and/or unproven.


Total knee arthroplasty (TKA; also, called knee replacement) is an established treatment for relief from significant, disabling pain caused by advanced arthritis.

TKA is considered among the most successful medical procedures in the United States regarding the degree of improvement in functional status and quality of life. As a result of the success of TKA, the increase in the aging population, and the desire of older adults to remain physically active, the incidence of TKA is increasing rapidly. It is projected that by 2030, the demand for knee replacement will approach 3.5 million procedures annually. (1)

TKA is performed by removing the damaged cartilage surface and a portion of underlying bone using a saw guided by templates and jigs. The cartilage and bone removed from the distal femur and proximal tibia are replaced with implants that recreate the surface of the joint. Patellar resurfacing may also be performed. Three-dimensional implant alignment (coronal, sagittal, axial) is considered to be critical for joint articulation and implant longevity. Less than 3° deviation from the rotational or mechanical axis, as determined by a straight line through the center of the hip, knee, and ankle on the coronal plane, is believed to minimize the risk of implant wear, loosening, instability, and pain.

The placement of conventional cutting guides (templates and jigs) is based on anatomic landmarks or computer navigation. Use of conventional instrumentation has been shown to result in malalignment of approximately one-third of implants in the coronal plane. (2) Computer-assisted navigation can significantly reduce the proportion of malaligned implants compared with conventional instrumentation, but has a number of limitations including a lack of rotational alignment, increased surgical time, and a long learning curve. Also, no studies have demonstrated an improvement in clinical outcomes with computer-assisted navigation compared with conventional instrumentation.

Custom implants and patient-specific instrumentation (PSI) have been developed as alternatives to off the-shelf implants and conventional cutting guides, with the goal of improving both alignment and surgical efficiency. A number of patient-specific cutting guides and custom implants (with their associated cutting guides) are currently being marketed (see Regulatory Status section). Custom implants and patient specific guides are constructed with the use of preoperative 3-dimensional computed tomography (CT) or magnetic resonance imaging (MRI) scans, which are taken about 4 to 6 weeks before the surgery. The images are sent to the planner/manufacturer to create a 3-dimensional model of the knee and proposed implant. After the surgeon reviews the model of the bone and implants, makes adjustments, and approves the surgical plan, the manufacturer fabricates the custom knee implants and/or disposable cutting guides.

The proposed benefits of using patient-specific implants and instrumentation during TKA include improved alignment, decreased operative time, increased patient throughput, fewer instrument trays, reduced risk of fat embolism and intraoperative bleeding (no intramedullary canal reaming), shorter recovery, reduced postoperative pain, reduced revision rate, and reduced costs. However, the nonsurgical costs of the procedure may be increased due to the requirement for preoperative CT or MRI, preoperative review of the template, and fabrication of the PSI. Also, the patient-specific template relies on the same anatomic landmarks as conventional TKA and does not take soft tissue balancing into account. Thus, evaluation of this technology should also address the reliability of the cutting guides and the need for intraoperative changes such as conversion to conventional instrumentation.

Regulatory Status

A number of patient-specific cutting block systems and custom knee implants have been cleared for marketing by the U.S. Food and Drug Administration (FDA). An example is the single-use, disposable cutting guides designed and manufactured from patient imaging data (MRI/CT). The cutting guides are used to aid the surgeon intraoperatively in making the initial distal femoral and the initial proximal tibial bone cuts during TKA surgery. The cutting guides also establish the references for component orientations. Planning systems (e.g., from Materialise N.V.) for the personalized instruments have also cleared for marketing clearance by the FDA through the 510(k) process.

In 2008, the Smith & Nephew Patient Matched Instrumentation (now called Visionaire™ Patient Matched Instrumentation) was the first patient-specific cutting guide to receive FDA clearance for marketing. Other patient-specific cutting guide systems cleared for marketing include:

MyKnee® Patient Matched Cutting Blocks (Medacta),

Signature™ Planner/Signature Guides (Materialise N.V. and Biomet),

TruMatch® Personalized Solutions (DePuy Orthopaedics),

Prophecy™ Pre-operative Navigation Alignment Guides (Wright Medical Technology), and

Zimmer® Patient Specific Instruments and Zimmer® Patient Specific Instruments Planner (Materialise N.V. and Zimmer).

Custom knee implants with their associated patient-specific cutting guides (iJig® instrumentation, ConforMIS) include:

ConforMIS iTotal® Cruciate Retaining Knee Replacement System (ConforMIS),

ConforMIS iTotal® Posterior Stabilized Knee Replacement System (ConforMIS), or

ConforMIS iUni® Unicondylar Knee Replacement System (ConforMIS).

FDA product codes: JWH, MBH, OIY, OOG.


This policy was created March 2016 and has been updated regularly with searches of the MEDLINE database. The most recent literature update was performed through June 22, 2017.

Assessment of the efficacy for a therapeutic intervention involves a determination of whether an intervention improves health outcomes. The optimal study design for this purpose is a randomized controlled trial (RCT) that includes clinically relevant measures of health outcomes.

Intermediate outcome measures, also known as surrogate outcome measures, may also be adequate if there is an established link between the intermediate outcome and true health outcomes. Nonrandomized comparative studies and uncontrolled studies can sometimes provide useful information on health outcomes but are prone to biases such as noncomparability of treatment groups, placebo effect, and variable natural history of the condition.

A number of RCTs have compared patient-specific instrumentation (PSI) with conventional instrumentation for total knee arthroplasty (TKA). Therefore, this evidence review focuses on systematic reviews that address clinical outcomes. The surrogate outcome measure of a reduction in malalignment may be informative to support improvement with the new technology. However, a reduction in the percentage of malaligned implants has not been definitively shown to result in improved clinical outcomes and is therefore not sufficient to demonstrate an improvement in clinical outcomes. Also, because this is a relatively new technology, no long-term studies are currently available that could provide data on revision rates. It should also be noted that the design of these devices is evolving, and results from older studies may be less relevant for contemporary designs.

Patient-Specific Instrumentation

Systematic Reviews

There are a number of systematic reviews on PSI for total knee arthroplasty. This medical policy will focus on the most comprehensive and relevant analyses.

Thienpont et al. included 20 RCTs and 24 cohort studies (total N=5822 patients) in their 2017 systematic review (see Table 1). (3) The PSI systems used in the RCTs were the Signature (Biomet), Zimmer Patient Specific Instruments (Zimmer), TruMatch (DePuy), Visionaire (Smith & Nephew), and MyKnee (Medacta). Meta-analysis of results for PSI versus conventional total knee arthroplasty indicated modest but statistically significant decreases in the likelihood of malalignment in the mechanical axis and femoral/coronal plane, but increases in malalignment of the tibial/sagittal and tibial/coronal planes (see Table 2). There were minor reductions in total operative time (-4.4 minutes, p=0.002) and blood loss (-37.9 mL, p=0.015) that are of uncertain clinical significance. There was some evidence of publication bias for mechanical axis alignment, but the relative risk did not change after adjusting for bias. In the 6 studies (598 knees) that reported clinical outcomes (follow-up, 6-24 months), PSI was associated with a modest improvement in function (4.3 points) assessed on the Knee Society Score.

Rotational alignment was evaluated in a 2016 systematic review of 6 RCTs by Mannan and Smith. (4) The most commonly used PSI was Trumatch (DePuy). Meta-analysis showed a significant decrease in the risk of femoral rotational malalignment (see Table 2). Only 1 study was identified that evaluated tibial rotational alignment.

The key question considered is whether these modest differences in the number of outliers greater than 3º impacts functional outcomes. This question was addressed in a 2016 meta-analysis by Mannan et al., who identified 5 RCTs and 3 prospective comparative studies that assessed functional outcomes. (5) Meta-analysis indicated that functional outcomes did not differ significantly when measured at up to 24 months after surgery (see Table 3).

Table 1. Meta-Analyses Characteristics

Study (Year)



N (Range)



Thienpont et al. (2017) (3)



5822 (29-865)

RCTs and cohort

Coronal and sagittal malalignment >3º

Mannan and Smith (2016) (4)



444 (40-128)


Femoral rotational malalignment >3º

Mannan et al. (2016) (5)



828 (48-232)

RCTs and cohort

Functional outcomes

RCT: randomized controlled trial.

Table 2. Meta-Analytic Outcomes for Malalignment



N (knees)

Malalignment (>3º)


95% CI


I2, %

Thienpont et al. (2017) (3)



Coronal mechanical axis


0.65 to 0.95





Tibial/sagittal plane


1.12 to 1.56





Femoral/coronal plane


0.55 to 0.99





Tibial/coronal plane


0.92 to 1.83



Mannan and Smith (2016) (4)



Femoral rotational alignment


0.16 to 0.95



CI: confidence interval; RR: relative risk.

Table 3. Meta-Analytic Results for Functional Outcomes



N (knees)

Functional Outcome Measures

FU, mo


95% CI


I2, %

Mannan et al. (2016) (5)



KSS functional score



-9.31 to 8.88





KSS knee score



-6.15 to 7.95





Range of motion (degrees)



-0.46 to 7.91





Oxford Knee Score



-1.83 to 0.86



CI: confidence interval; FU: follow-up; mo: month; KSS: Knee Society Score; MD: mean difference.

Randomized Controlled Trials

Additional RCTs, published after the search dates of the systematic reviews have compared PSI with conventional instrumentation. In 2016, Boonen et al. reported on a multicenter, double-blind RCT that evaluated clinical outcomes of PSI with the Signature instrumentation. (6) With a total of 180 patients, the trial was powered to detect a clinically significant difference on the Knee Society Score at 2 years. At follow-up, there were no statistically or clinically significant differences between the groups on any of the 5 clinical outcome measures (Knee Society Score, Oxford Knee Score, Western Ontario and McMaster Universities Osteoarthritis Index, visual analog scale score for pain, EuroQol-5D-3L index score, EuroQol-5D-3L VAS health).

Custom Knee Implants

No published RCTs have been identified on custom knee implants. Results from an RCT (NCT02494544) comparing the ConforMIS iTotal (CR) Knee Replacement System with off-the-shelf implants are expected in 2025 (see Table 4).

Ongoing and Unpublished Clinical Trials

Some currently unpublished trials that might influence this review are listed in Table 4.

Table 4. Summary of Key Trials


Trial Name

Planned Enrollment

Completion Date



Randomised Controlled Trial of Patient Specific Instrumentation vs Standard Instrumentation in Total Knee Arthroplasty.


Feb 2020


A Multi-center, Prospective, Randomized Study Comparing Surgical and Economic Parameters of Total Knee Replacement Performed With Single-use Efficiency Instruments With Patient Specific Technique (MyKnee®) Versus Traditional Metal Instruments With Conventional Surgical Technique.


Apr 2020


Patient-specific Positioning Guides (PSPG) Technique Versus Conventional Technique in Total Knee Arthroplasty - a Prospective Randomized Study.


Jan 2024


Attune With TruMatch TM Personalized Solutions Instruments: A Prospective Randomized Controlled Trial Comparing Clinical and Economic Outcomes in Patients With a BMI Between 30 and 50.


Aug 2024


A Prospective, Randomised Control Trial Assessing Clinical and Radiological Outcomes of Patient Specific Instrumentation In Total Knee Arthroplasty.


Dec 2024

NCT 02494544a

A Prospective, Randomized, Multicenter Study to Evaluate the ConforMIS iTotal® (CR) Knee Replacement System Versus Off-the-Shelf Replacement.


Aug 2025



Comparison of Customized Cutting Block (Visionaire™) and Conventional Total Knee Arthroplasty: A Prospective Randomized Control Trial.


May 2014 (Completed)


A Prospective, Randomized, Post-market, Multi-center Study and Cost-effectiveness Analysis of Shape Match Technology


Dec 2018 (Suspended)

NCT: national clinical trial.

a Denotes industry-sponsored or cosponsored trial.

Summary of Evidence

For individuals who are undergoing total knee arthroplasty who receive patient-specific cutting guides and custom knee implants, the evidence includes a number of randomized controlled trials, comparative cohort studies, and systematic reviews. Relevant outcomes are symptoms, functional outcomes, and quality of life. Results from the systematic reviews are mixed, finding significant improvements in some measures of implant alignment but either no improvement or worse alignment for other measures. The available systematic reviews are limited by the small size of some of the selected studies, publication bias, and differences in both planning and manufacturing of the patient-specific instrumentation (PSI) systems. Also, the designs of the devices are evolving, and some of the studies may have assessed now obsolete PSI systems. Larger randomized controlled trials examining specific PSI systems and patient-specific implants are in progress and should address some of the limitations of the current literature. Most importantly, trials should demonstrate an improvement in clinical outcome measures. With follow-up currently extending out to 2-years, no functional benefits have been demonstrated. The evidence is insufficient to determine the effects of the technology on health outcomes.


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.


There are no specific codes for these implants or instrumentation. The joint arthroplasty procedure would be reported using the regular CPT codes for that surgery. The preplanning for the surgery may involve magnetic resonance or computed tomography imaging which may help to identify these procedures.


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.


The following codes may be applicable to this Medical policy and may not be all inclusive.

CPT Codes




ICD-9 Diagnosis Codes

Refer to the ICD-9-CM manual

ICD-9 Procedure Codes

Refer to the ICD-9-CM manual

ICD-10 Diagnosis Codes

Refer to the ICD-10-CM manual

ICD-10 Procedure Codes

Refer to the ICD-10-CM manual

Medicare Coverage:

The information contained in this section is for informational purposes only. HCSC makes no representation as to the accuracy of this information. It is not to be used for claims adjudication for HCSC Plans.

The Centers for Medicare and Medicaid Services (CMS) does not have a national Medicare coverage position. Coverage may be subject to local carrier discretion.

A national coverage position for Medicare may have been developed since this medical policy document was written. See Medicare's National Coverage at <>.


1. Kurtz S, Ong K, Lau E, et al. Projections of primary and revision hip and knee arthroplasty in the United States from 2005 to 2030. J Bone Joint Surg Am. Apr 2007; 89(4):780-785. PMID 17403800

2. Computer-assisted navigation for total knee arthroplasty. Chicago, Illinois: Blue Cross and Blue Shield Association - Technology Evaluation Center Assessment Program (2008 February) 22(10):1-4. PMID 18411501

3. Thienpont E, Schwab PE, Fennema P. Efficacy of Patient-Specific Instruments in Total Knee Arthroplasty: A Systematic Review and Meta-Analysis. J Bone Joint Surg Am. Mar 15 2017; 99(6):521-530. PMID 28291186

4. Mannan A, Smith TO. Favourable rotational alignment outcomes in PSI knee arthroplasty: A Level 1 systematic review and meta-analysis. Knee. Mar 2016;23(2):186-190. PMID 26782300

5. Mannan A, Akinyooye D, Hossain F. A Meta-analysis of Functional Outcomes in Patient-Specific Instrumented Knee Arthroplasty. J Knee Surg. Dec 01 2016. (Epub ahead of print) PMID 27907935

6. Boonen B, Schotanus MG, Kerens B, et al. No difference in clinical outcome between patient-matched positioning guides and conventional instrumented total knee arthroplasty two years post-operatively: a multicentre, double-blind, randomised controlled trial. Bone Joint J. Jul 2016; 98-B (7):939-944. PMID 27365472

7. Patient-Specific Cutting Guides and Custom Knee Implants. Chicago, Illinois: Blue Cross Blue Shield Association Medical Policy Reference Manual (August 2017) Surgery 7.01.144.

Policy History:

Date Reason
10/15/2017 Document updated with literature review. Coverage unchanged.
9/1/2016 Reviewed. No changes.
3/15/2016 New medical document. Use of custom implants or patient-specific instrumentation (e. g., cutting guides) for joint arthroplasty, including but not limited to use in unicompartmental or total knee arthroplasty, is considered experimental, investigational and/or unproven.

Archived Document(s):

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