Computer assisted surgery for knee ligament reconstruction
Abstract
This is a protocol for a Cochrane Review (Intervention). The objectives are as follows:
To assess the effects of computer assisted reconstruction surgery versus conventional operating techniques for ACL or PCL deficient knees in adults.
We will test these effects according to the following specific subgroups:
1. System used for CAS (e.g. per‐operative use of X‐rays, pre‐operative use of radiology (CT, MRI, X‐rays), per‐operative landmarks or bone morphing).
2. Type of ligament reconstruction: ACL or PCL, or both.
Background
Description of the condition
The anterior and posterior cruciate ligaments (ACL and PCL) are located within the knee joint. These connect the femur (thigh bone) to the tibia (shin bone) and play a crucial stabilising role. The ACL restrains the anterior translation (forward movement) of the tibia relative to the femur. The PCL restrains posterior translation (backward movement) of the tibia relative to the femur. Both are important also for varus/valgus (sideward) and rotational stability of the knee joint during movement.
ACL injury is a common orthopaedic problem with an annual incidence of approximately 200,000 cases per year in the United States (AAOS 2007). It often results from an abrupt change in direction or rapid deceleration during sports, typically football or skiing. As well as knee instability, an ACL rupture can give rise to recurrent complaints of the knee ‘giving way’ and pain (Noyes 1983), and result in discontinuation or limitation of sporting activities (Barrack 1990a; Barrack 1990b). Although the natural history is not clearly defined, the ACL injury predisposes the knee to chronic instability and further damage, such as meniscal tears, with a consequent impairment to quality of life (Mohtadi 1998). An ACL injury may also predispose to osteoarthritis (Daniel 1994; Sherman 1988).
PCL injury is less common, comprising 1 to 20% of knee ligament injuries. This is most often sustained through a traffic accident (e.g. a dashboard injury) or after athletic trauma (Schulz 2003). Complaints after a PCL injury can include instability or knee pain, especially patellofemoral, and a progression to a degenerative knee (Margheritini 2002).
Description of the intervention
An ACL rupture with recurrent instability is most often treated with a tendon graft reconstruction. The latter comprises reconstruction of the damaged ligament using a strip of tendon, often from the patient's knee (the patellar tendon or hamstring). In most cases, the surgery is done arthroscopically. The primary goal of surgery is to restore a stable knee without extra morbidity. Approximately 100,000 ACL reconstructions are performed annually in the United States (AAOS 2007). Many people with these injuries are treated non‐operatively. These are generally people who have minimal symptoms of instability, are less active or are unwilling or unable to participate in the demanding and protracted post‐surgical rehabilitation protocols (Linko 2005). PCL reconstruction is usually reserved for more complex knee injuries (Peccin 2005).
Navigation systems have recently been introduced to surgery, including orthopaedic surgery. These systems are known as computer assisted surgery (CAS) or computer assisted orthopaedic surgery (CAOS). The most common types use images acquired pre‐operatively by fluoroscopic CT (computerized tomography) or intra‐operatively by fluoroscopy (dynamic X‐rays) or an image‐free system using pre‐specified anatomical landmarks.
During surgery the system uses infrared feedback, enabling orientation of the surgical instruments relative to the anatomical structures of interest. In cruciate ligament reconstruction CAS has the potential to optimise the preparation for grafting, which involves drilling into the femur and tibia to form a bone tunnel, and subsequent placement of the graft. The system also has the capacity to monitor femur and tibia positions and movements. With this information, stability and range of motion can be optimised.
For a clinically successful outcome, an accurate graft placement is essential. This is accomplished by an exact and reproducible tunnel placement. A malposition of the graft can lead to limited range of motion, impingement of and damage to the graft, instability and re‐injury. The most common cause of technical failure of ACL reconstruction is the misplacement of the bone tunnel (Giffin 2001; Nakagawa 2007).
Possible benefits and harms of computer assisted surgery versus conventional surgery
A more reproducible ACL reconstruction with an exact bone tunnel placement is likely to improve the patient outcome, potentially by giving increased knee stability and lowering the risk of complications, especially those associated with limited range of motion, and knee discomfort. However, CAS comes with an increased operating time, an extra investment for the necessary equipment and additional fixation of navigation probes to the patient's leg. As with every new development, using CAS will involve a learning curve for the surgeon. However, compared with traditional surgical techniques this may shorten the learning curve for the novice surgeon (Schep 2005).
Why it is important to do this review
Cruciate ligament reconstruction is a very common orthopaedic procedure. The pressure to implement technological advances is unrelenting. Thus it is important to systematically review the current evidence comparing the effects of computer assisted knee ligament reconstruction versus conventional surgery for the reconstruction of the ACL and / or PCL deficient knee.
Objectives
To assess the effects of computer assisted reconstruction surgery versus conventional operating techniques for ACL or PCL deficient knees in adults.
We will test these effects according to the following specific subgroups:
1. System used for CAS (e.g. per‐operative use of X‐rays, pre‐operative use of radiology (CT, MRI, X‐rays), per‐operative landmarks or bone morphing).
2. Type of ligament reconstruction: ACL or PCL, or both.
Methods
Criteria for considering studies for this review
Types of studies
Randomized controlled trials (RCTs) and quasi‐randomized controlled trials (for example, allocation by hospital record number or date of birth) that compare computer assisted surgery (CAS) with conventional operating techniques not involving CAS.
Types of participants
Skeletally mature people undergoing reconstruction of the ACL, PCL or both ligaments. Trials involving a policy of surgical treatment of other concomitant soft‐tissue knee injuries, such as meniscal tears, in the same operation as cruciate ligament reconstruction will also be included, provided this applies to both groups.
Types of interventions
ACL and / or PCL reconstruction using either CAS or conventional techniques. There is no exclusion on the type of graft or the method of graft fixation.
Types of outcome measures
Primary outcomes
1. Functional assessment
2. Return to previous activity level, including level of sport participation
3. Patient‐derived quality of life measure
Where possible, data from validated and other commonly used knee scores and self‐rated measures of function will be sought. These include the Tegner scale (Tegner 1985), Lysholm scale (Lysholm 1982), IKDC (International Knee Documentation Committee) subjective part (Irrgang 2001), the Cincinnati knee scales (Noyes 1989), KOOS (Knee injury and Osteoarthritis Outcome Score) (Roos 1998) and the ACL Quality of Life (Mohtadi 1998) outcome measure.
Secondary outcomes
1. Tunnel positions and positioning of the graft
2. Static stability measures (KT arthrometer or other stability assessment devices)
3. IKDC objective part (International Knee Documentation Committee) (Irrgang 2001)
4. Range of motion
5. Strength testing (Cybex muscle testing or equivalent)
6. Pain, stability and knee function
7. Recurrent injury with and without re‐operation
8. Radiological osteoarthritis
9. Adverse outcomes, complications
Resource use: Cost data and data on the use of resources, including operation time, will also be collected.
Where available, we will collect data on the experience level of the surgeons involved in the trial.
Timing of outcome assessment
Where possible, outcome assessment will carried out for:
1. Short term (within six months of ACL/PCL reconstruction)
2. Intermediate term (between six months to two years of ACL/PCL reconstruction)
3. Long term (more than two years after ACL/PCL reconstruction)
Search methods for identification of studies
Electronic searches
We will search the Cochrane Bone, Joint and Muscle Trauma Group Specialised Register (to present), the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library, current issue), MEDLINE (1966 to present), EMBASE (1980 to present) and CINAHL (1982 to present). There will be no constraints based on publication status or language.
In MEDLINE (OVID ONLINE), the first two levels of the optimal trial search strategy (Higgins 2006) will be combined with the subject specific search. The complete search strategy is shown in Appendix 1. The search strategies that will be used in EMBASE (OVID ONLINE), CINAHL (OVID ONLINE) and The Cochrane Library (Wiley InterScience) are shown in Appendix 2, Appendix 3 and Appendix 4 respectively.
We will also search the WHO International Clinical Trials Registry Platform Search Portal and the Current Controlled Trials Meta Register for ongoing and recently completed trials.
Searching other resources
We will search reference lists of articles. The bibliographies of relevant papers identified by the search strategy will be checked. Where appropriate and possible, the corresponding authors of studies identified by the search strategies will be contacted to obtain other relevant studies not previously included for review.
Data collection and analysis
Selection of studies
Two review authors (DM and MR) will independently assess potentially eligible trials identified by the search strategy. A third reviewer (JV) will be consulted if there is a disagreement. If necessary, the trial authors will be contacted for more information.
Data extraction and management
Two review authors (DM and MR) will use pre‐piloted data extraction forms to independently extract the data. They will compare the data extracted for each study to achieve consensus. A third reviewer (JV) will resolve disagreements. When necessary, authors of individual trials will be contacted directly to complete data forms or clarify methodology.
Assessment of risk of bias in included studies
Two review authors (DM and MR) will independently assess the risk of bias of included studies using the Cochrane Collaboration's risk of bias tool (Higgins 2008). As well as the items from the six domains listed in the tool (sequence generation; allocation concealment; blinding of participants, personnel and outcome assessors; incomplete outcome data; selective outcome reporting), we will also assess performance bias, specifically in terms of surgeon's experience with techniques being compared, and selection bias, specifically in terms of important differences in baseline characteristics such as other knee injuries. Any unresolved disagreement between the two authors will be arbitrated by the other reviewer (JV).
Measures of treatment effect
For each study, risk ratios with accompanying 95% confidence intervals will be calculated for dichotomous outcomes, and mean differences and 95% confidence intervals will be calculated for continuous outcomes.
Dealing with missing data
We will attempt to contact trial investigators for missing data. Where appropriate, we will perform intention‐to‐treat analyses to include all people randomised to the intervention groups. We will investigate the effect of drop outs and exclusions by conducting worse and best scenario analyses. Unless missing standard deviations can be derived from confidence interval data, we will not assume values in order to present these in the analyses.
Assessment of heterogeneity
The Forest plots will be visually examined for heterogeneity and the chi‐squared test and I‐squared statistic will be considered. If there is a lot of heterogeneity we will either not pool at all or will consider using a random‐effects model.
Assessment of reporting biases
If sufficient data are available, we will attempt to assess publication bias by preparing a funnel plot. We will try to pursue trials listed in clinical trial registers to help to avoid publication bias.
Data synthesis
If appropriate, results of comparable groups of trials will be pooled. We will initially use the fixed‐effect model and 95% confidence intervals. However, if there is a diversity of clinical and methodological characteristics in the included studies, we may use the random‐effects model. We will use standardised mean differences for pooling data based on different units of measurement.
Subgroup analysis and investigation of heterogeneity
Heterogeneity will be explored by subgroup analyses. Our planned subgroup analyses will be by the type of reconstruction, whether the ACL or PCL was an isolated injury or not, and CAS system used. For the latter, we will attempt to compare for the CAS system used: e.g. with or without preoperative use of fluoroscopy and pre‐operative use of radiological data as X‐rays, CT or MRI. To test whether the subgroups are statistically significantly different from one another, we will test the interaction using the technique outlined in Altman 2003.
Sensitivity analysis
Where possible, we will perform sensitivity analyses to explore the effects of various aspects of trial and review methodology, including the effects of missing data, whether allocation was concealed, and surgeon's experience. We will use the test of interaction to establish whether the subgroups are statistically significantly different (Altman 2003).
