A Prospective Randomized Study of Minimally Invasive Total Knee Arthroplasty Compared with Conventional Surgery

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1 This is an enhance PDF from The Journal of Bone an Joint Surgery The PDF of the article you requeste follows this cover page. A Prospective Ranomize Stuy of Total Knee Arthroplasty Compare with Conventional Surgery N. Wülker, J.P. Lambermont, L. Sacchetti, J.G. Lazaró an J. Nari J Bone Joint Surg Am. 2010;92: oi: /jbjs.h This information is current as of July 4, 2010 Supporting ata Commentary Reprints an Permissions Publisher Information Click here to orer reprints or request permission to use material from this article, or locate the article citation on jbjs.org an click on the [Reprints an Permissions] link. The Journal of Bone an Joint Surgery 20 Pickering Street, Neeham, MA

2 1584 COPYRIGHT Ó 2010 BY THE JOURNAL OF BONE AND JOINT SURGERY, INCORPORATED A commentary by Joshua Davi Nelson, MD, PharmD, is available at an as supplemental material to the online version of this article. A Prospective Ranomize Stuy of Minimally Invasive Total Knee Arthroplasty Compare with Conventional Surgery By N. Wülker, PhD, MD, J.P. Lambermont, MD, L. Sacchetti, MD, J.G. Lazaró, MD, an J. Nari, MD Investigation performe at the Orthopaeic Department, Tübingen University Hospital, Tübingen, Germany; University Hospital CHU Anré Vesalé, Montigny-le-Tilleul, Belgium; General Hospital, Policlinico i Moena, Moena, Italy; Hospital Universitario e Fuenlabraa, Fuenlabraa, Mari, Spain; an University Hospital Vall Hebron, Barcelona, Spain Backgroun: Despite intense ebate regaring whether minimally invasive techniques for total knee arthroplasty improve clinical outcomes over stanar techniques, few prospective ranomize trials aressing this ebate are available in the literature. We therefore esigne this multicenter stuy to assess the overall safety an effectiveness of a minimally invasive approach without the use of computer navigation in comparison with conventional knee arthroplasty. Methos: We prospectively ranomize 134 patients (101 women an thirty-three men, with an average age of 70.1 years) to unergo surgery for total knee arthroplasty with use of either minimally invasive knee instruments (sixty-six patients) or a stanar approach (sixty-eight patients). The follow-up perio was one year. Results: On the basis of our sample size, no significant ifference was etecte between the groups in any of the relevant clinical areas assesse: total range of motion, Knee Society total an function scores, an visual analog scores for pain an activities of aily living. Patients who unerwent minimally invasive surgery ha a longer mean surgical time (by 5.6 minutes) an ha less mean bloo loss (by 17 ml). Raiographic measurements emonstrate reliable implant positioning in both groups. Seven patients in each group ha an averse event relate to their proceure. Conclusions: On the basis of the numbers, no significant avantage to minimally invasive total knee arthroplasty over a conventional technique was observe. Greater sample sizes an a longer follow-up perio are require to fully etermine the long-term safety an efficacy of this minimally invasive surgical technique. Level of Evience: Therapeutic Level II. See Instructions to Authors for a complete escription of levels of evience. Stuies of minimally invasive surgery techniques for total knee arthroplasty have resulte in a wie range of clinical results. Although certain analyses have associate minimally invasive surgery approaches with early benefits, such as ecrease pain, improve time to functional recovery, an enhance range of motion 1-6, others have faile to emonstrate any substantial ifferences between these techniques an conventional methos in the postoperative perio 6-8. Unfortunately, only a small number of these stuies have been prospective ranomize comparisons of minimally invasive surgery an conventional total knee arthroplasties, an even fewer have offere such a comparison without the use of computer navigation accompanying the minimally invasive surgery approach 5,7,8. As such, major ebate continues in the orthopaeic community regaring whether minimally invasive surgery techniques are truly beneficial to patients unergoing total knee arthroplasty. We conucte a prospective ranomize multicenter stuy, without the use of computer navigation in the minimally invasive approach or the stanar approach. Our objective was to assess the overall safety an effectiveness of a minimally Disclosure: In support of their research for or preparation of this work, one or more of the authors receive, in any one year, outsie funing or grants of less than $10,000 from Smith an Nephew. Neither they nor a member of their immeiate families receive payments or other benefits or a commitment or agreement to provie such benefits from a commercial entity. J Bone Joint Surg Am. 2010;92: oi: /jbjs.h.01070

3 1585 invasive proceure in comparison with a stanar surgical technique using clinical an raiographic outcomes. We hypothesize that there woul be no ifference between the two surgical techniques. Materials an Methos Following approval of the ethics review boar of each center, patients consente to be inclue in the stuy after receiving comprehensive information regaring the stuy protocol an other etails. Inclusion criteria for this stuy ictate that the patient require either a primary unilateral or bilateral total knee replacement, was eighteen to eighty years ol, provie informe consent, was available for follow-up through at least two years, an was in stable health, meaning free of conitions or treatment for conitions that woul pose an excessive operative risk. Patients were exclue if they were known to have insufficient femoral or tibial bone stock, a boy mass inex of >35 kg/m 2, a faile total or uniconylar knee replacement of the affecte knee, an active local or systemic infection, collateral ligament insufficiency, knee flexion of <90, a fixe flexion eformity of >15, a varus or valgus eformity of >20, an/or an immunosuppressive isorer, such as acquire immunoeficiency synrome (except inflammatory arthritis). The stuy was registere at ClinicalTrials.gov (NCT ). If patients met these inclusion an exclusion criteria, they were ranomize into one of the two treatment groups. Five separate sites participate in this stuy, with five highvolume surgeons performing each operation. Participating surgeons were require to have complete at least ten mini- Fig. 1 Flow iagram of stuy participants. All analyses were performe on the 134 patients (sixty-six in the minimally invasive surgery [MIS] group an sixty-eight in the stanar group) who ha complete oneyear follow-up ata.

4 1586 mally invasive knee arthroplasties prior to this stuy. Each site was provie with a separate ranomization list. From October 14, 2004, until September 28, 2006, 162 patients (Fig. 1) were ranomize into the minimally invasive surgery group (without the concomitant use of computer navigation) an the stanar proceure group. Two patients were eclare lost to follow-up after surgery when the surgeon who performe the operation withrew from the stuy. Aitionally, eleven patients withrew within one year, an fifteen were lost to follow-up at the one-year interval without reason. Therefore, 134 patients (101 women an thirty-three men) were manage operatively an were evaluate. Of the 134 knees, sixty-six unerwent minimally invasive surgery (the minimally invasive group) an sixty-eight ha stanar surgery (the stanar group). Preoperatively, 110 knees (fifty-eight in the minimally invasive group an fifty-two in the stanar group) were reporte as being in varus alignment, twenty-one (six an fifteen, respectively) as being in neutral, an three (two an one, respectively) as being in valgus. There were sixty-eight right knees an sixty-six left knees. No bilateral proceures were performe. One of the patients ranomize to unergo minimally invasive surgery was etermine to have a prohibitively large knee that prevente prosthesis implantation with use of this technique, an therefore the proceure was converte to conventional total knee arthroplasty uring surgery. Surgical Technique All surgeons performe surgery accoring to the technique manuals for the minimally invasive surgery an stanar techniques with use of the specific stanar or minimally invasive Genesis II knee instruments (Smith an Nephew, Memphis, Tennessee) an using an anterior femoral cut first. Both minimally invasive surgery an stanar surgery were performe with use of either a mivastus or meial parapatellar approach. On the basis of consensus among the investigators, minimally invasive surgery was efine as surgery requiring a skin incision of <15 cm an use of specific instrumentation. Spacer blocks were use to confirm ligament balancing in flexion an extension. Intraoperative as well as postoperative pain management was ientical for both the minimally invasive surgery an stanar surgical techniques at each site; however, each site also employe their own pain management protocol. Because each site performe an equivalent number of minimally invasive an stanar arthroplasties an no ifferences were observe between intraoperative an postoperative pain management, this aspect of the surgical technique was not taken into account for this stuy. Postoperative Treatment Walking was begun on the first postoperative ay, with full weight-bearing allowe. Patients were mobilize with use of a walker, which was then replace with a pair of crutches when sufficient stability was attaine. Continuous passive motionwasusefromay1aftersurgery,anrangeof motion was increase as tolerate. Patients were routinely TABLE I Patient Baseline Characteristics Data for Both Groups Parameters Group (N = 66) Stanar Group (N = 68) Age at surgery* (yr) 70.2 ( ) 70.1 ( ) Boy mass inex* (kg/m 2 ) 29.3 ( ) 29.3 ( ) Male patients 18 (27.3) 15 (22.1) Female patients 48 (72.7) 53 (77.9) Primary iagnosis Osteoarthritis 61 (92.4) 60 (88.2) Rheumatoi arthritis 1 (1.5) 3 (4.4) Osteonecrosis 0 (0) 2 (2.9) Posttraumatic arthritis 4 (6) 3 (4.4) Preop. knee score 56.0 ( ) 53.2 ( ) Preop. function score 49.2 ( ) 50.4 ( ) Preop. visual analog pain score Preop. visual analog score for activities of aily living 56.7 ( ) 53.4 ( ) 38.3 ( ) 36.6 ( ) *The values are given as the mean, with the range in parentheses. The values are given as the number of patients, with the percentage in parentheses. The values are given as the mean, with the 95% confience interval in parentheses. ischarge on ay 8 after surgery, with most patients going to an inpatient rehabilitation facility for another two to three weeks afterwars. Follow-up examinations were carrie out at hospital ischarge, at four to six weeks after surgery, an at one year postoperatively. A few patients ha been followe for two years at the early termination point of the stuy. Raiographic measurements inclue the tibial angle (that is, the angle between the tibial axis an the tibial plateau in the coronal plane), the lateral tibial angle (the angle between the tibial axis an the tibial plateau in the sagittal plane), the femoral angle (the angle between the femoral axis an the istal line of the femoral component in the coronal plane), an the overall mechanical axis. These measurements were mae at all stuy intervals. Statistical Analyses Intention-to-treat analysis was use for all clinical outcome variables an was performe by an inepenent bline external statistician. The Stuent t test was use to etermine any ifferences between intraoperative variables an for univariate comparison of postoperative parameters. Treatment comparisons for the continuous postoperative outcome variables were base on a marginal linear moel 9,10, with the preoperative level of a variable use as a part of the outcome vector. Inferences on the correlation structure were base on a likelihoo ratio test. On the basis of these, an unrestricte correlation structure was assume in all moels. Linear contrasts of fitte moel esti-

5 1587 TABLE II Intraoperative Data Parameters Group* (N = 66) Stanar Group* (N = 68) P Value Tourniquet time (min) 72.3 ( ) 67.1 ( ) Duration of operation (min) 79.6 ( ) 74.0 ( ) Bloo loss (ml) 428 ( ) 445 ( ) Incision length (mm) ( ) ( ) <0.001 *The values are given as the mean, with the 95% confience interval in parentheses. mates were constructe an use to test the hypotheses of interest. Two-taile tests were use throughout. Two-sie p values of <0.05 were consiere to inicate significance. Source of Funing Smith an Nephew (Memphis, Tennessee) provie reimbursements to the stuy centers for ocumentation of the case report forms only. Results Patient emographics, preoperative Knee Society total an function scores, visual analog scores for pain an activities of aily living, an range of motion were comparable between the groups (Table I). The overall objective intraoperative results were similar for the stanar an minimally invasive groups (Table II). The length of incision in extension was a mean (an stanar eviation) of ± 5.9 mm in the minimally invasive group compare with ± 8.5 mm in the stanar group. Other intraoperative inices were similar for the groups. The mean bloo loss was 428 ± 289 ml (95% confience interval, 359 to 498 ml) in the minimally invasive group compare with 445 ± 308 ml (95% confience interval, 372 to 518 ml) in the stanar group. The mean uration of surgery was 80 ± 19 minutes (95% confience interval, 75.0 to 84.2 minutes) for the minimally invasive group an 74 ± 22 minutes (95% confience interval, 68.7 to 79.3 minutes) for the stanar group. Data obtaine uring the hospital stay inicate similarity between the groups in terms of range of motion at ay 3 an at ischarge, although patients in the minimally invasive group ha a mean range of motion at ay 3 of nearly 7 better than those in the stanar group (73.9 [95% confience interval, 69.9 to 77.9 ] compare with 67.1 [95% confience interval, 61.9 to 72.4 ]) (Table III). Patients in the minimally invasive group ha a mean baseline knee score of 56.0 (95% confience interval, 52.3 to 59.8), improving to 62.6 (95% confience interval, 56.9 to 68.2) at ischarge, 88.8 (95% confience interval, 85.4 to 92.1) at four to six weeks, an 86.3 (95% confience interval, 81.0 to 91.6) at one year. Patients in the stanar group ha a mean baseline knee score of 53.2 (95% confience interval, 49.5 to 57.0), improving to 64.8 (95% confience interval, 58.8 to 70.9) at ischarge, 85.7 (95% confience interval, 82.4 to 89.1) at four to six weeks, an 84.0 (95% confience interval, 79.0 to 89.0) at one year (see Appenix). Similar outcomes were also note between the groups in terms of the function score, the visual analog pain score, the visual analog activities of aily living score, an range of motion (see Appenix), inicating that, on the basis of the available numbers, there was no ifference in these postoperative parameters between the two surgical techniques. The ifference in mean function score between the minimally invasive group an the stanar group was 1.12 (95% confience interval, 7.02 to 4.78) at baseline, 1.87 (95% confience interval, 3.12 to 6.87) at ischarge, 8.72 (95% confience interval, 1.89 to 15.55) at four to six weeks, an 4.71 (95% confience interval, 0.46 to 9.89) at one year. The ifference in the mean activities of aily living scores between the minimally invasive an the stanar group was 1.78 (95% confience interval, 6.63 to 10.20) at baseline, 4.68 (95% confience interval, 2.63 to 11.99) at ischarge, 8.04 (95% confience interval, 1.15 to 14.94) at four to six weeks, an 2.85 (95% confience interval, to 4.39) at one year. The confience intervals of the function score an the activities of aily living score i not contain the value zero at the four to six-week interval. Because of multiple testing an the correlations between the tests, these results were not significant. We foun no significant ifference in outcomes up to one year after surgery between patients manage with the minimally invasive technique an those manage with the stanar technique. Raiographic measurements emonstrate reliable implant positioning in both groups without any changes uring the follow-up perio. Both the tibial an femoral implant an- TABLE III Range of Motion During Hospital Stay Group* Stanar Group* P Value Day ( ) 67.1 ( ) Discharge 93.9 ( ) 90.8 ( ) *The values are given in egrees as the mean, with the 95% confience interval in parentheses.

6 1588 TABLE IV Postoperative Raiographic Measurements Discharge Group* Stanar Group* P Value One Year Group* Stanar Group* P Value Implant positioning Femoral angle 94.6 ( ) 95.6 ( ) ( ) 94.9 ( ) Tibial angle 89.5 ( ) 89.0 ( ) ( ) 89.3 ( ) Lateral tibial angle 88.2 ( ) 87.8 ( ) ( ) 88.3 ( ) Anatomical axis Tibiofemoral alignment 4.2 ( ) 4.6 ( ) ( ) 4.2 ( ) *The values are given in egrees as the mean, with the 95% confience interval in parentheses. gles, as well as the anatomical axis, were comparable between the minimally invasive an stanar surgical technique groups (Table IV). Lateral femoral angles were not measure. Fourteen patients (seven in the minimally invasive group an seven in the stanar group) ha averse events that were relate to the proceure. One perioperative fracture of the meial femoral conyle occurre in the stanar group an one tibial fracture occurre in the minimally invasive group. Postoperatively, six patients ha limite flexion an unerwent manipulation uner anesthesia (four in the stanar group an two in the minimally invasive group). One patient in the stanar group ha a local (containe to the involve knee an not systemic) bacterial infection, which was treate with antibiotics. Two patients in the minimally invasive group complaine of pain with uncertain etiology. Skin necrosis (3 cm along the scar) was observe in one patient in the minimally invasive group. Finally, two patients (one in each group) complaine of knee instability. Discussion In total knee arthroplasty, a skin incision of at least 9 cm is require to accommoate the implant. However, the cutoff between a normal an a minimal incision is not clearly efine. We utilize a mean incision length of 12.4 ± 2.4 cm in the minimally invasive group in comparison with 18.6 ± 3.6 cm in the stanar group. Generally, an incision must be shorter than 14 to 15 cm to be accepte as a minimal incision 4,11,12. With conventional incisions for total knee arthroplasty often alreay being shorter than 20 cm, the ifference between the two approaches is marginal an certainly cannot be consiere truly innovative. Some patients may not be caniates for minimally invasive surgery because of anatomical variants, in particular having a large amount of soft tissue surrouning the knee. Intraoperative bloo loss is a major concern in stanar total knee arthroplasty, with a resulting increase in the risk of infection, flui overloa, an increase uration of hospitalization associate with bloo transfusion 13.Proponentsof minimally invasive total knee arthroplasty often cite the ability to reuce bloo loss through the use of small incisions to support its use, an this benefit has been note in some stuies 7,14. In our stuy, the reuce incision employe for patients manage with minimally invasive surgery was not associate with a reuction in bloo loss. This result is consistent with that observe by Kolisek et al. 8. The potential benefits of ecrease bloo loss can be offset by the prolongation of operative times that has been observe with other minimally invasive techniques 5,7,15. On the basis of the available numbers in our analysis, the uration of surgery for both groups was not significantly ifferent, which is similar to results reporte in other stuies 6,8. The range-of-motion results showe a slight, although insignificant, avantage for the minimally invasive group at ay 3. By the time the patients ha been ischarge, however, range of motion was nearly ientical between the groups. Although there was a tren towar better range of motion with the minimally invasive approach at four to six weeks, this avantage ha almost completely isappeare at the time of the one-year follow-up (111 for the minimally invasive group compare with 108 for the stanar group; see Appenix). Dalury an Dennis also note a minor early avantage in range of motion in a group of patients unergoing minimally invasive total knee arthroplasty, which similarly isappeare with longer follow-up 16. However, a separate analysis of arthroplasty with the Genesis II knee components inicate improve range of motion at one year postoperatively for those unergoing a minimally invasive proceure through a mivastus approach compare with a control group manage with use of a stanar technique (125 compare with 116, respectively) 1. In a separate retrospective analysis of more than 300 patients, range of motion was again note to improve substantially with a minimally invasive mivastus approach at both one an two years postoperatively 2. No clinically relevant ifference was note between our stuy groups in the area of patient-reporte outcomes. There was no relevant ifference in any of the four scoring outcomes: knee scores, function scores, visual analog pain scores, an the visual analog scores for the activities of aily living. Confience intervals were use to express statistical variation an ranom

7 1589 error. Because the sample sizes in both groups were rather small, we ha broa 95% confience intervals for all key outcomes. The 95% confience intervals for the point estimates (ifferences of the mean between the minimally invasive an stanar groups) typically containe the value zero. This means that there was no ifference between the groups, with the exception of the function score an the visual analog score for the activities of aily living at the four to six-week interval, which inicate slightly better results for the minimally invasive group. A power analysis was not conucte a priori for the stuy. Hence, these results must be interprete carefully. However, 95% confience intervals of the ifferences in means between the groups provie an inication as to how much variability exists in the measure effect as well as the irection of the measure effect. The 95% confience interval of the ifference in means for the function score at ischarge was relatively small. The sample size was probably large enough for this variable to rule out the possibility of any large an clinically relevant effects. Variability was higher for the function score at other time points an for the visual analog activities of aily living score throughout the entire postoperative perio. These confience intervals i not exclue relevant clinical effects between the groups; further investigation is therefore neee to confirm these results. Our original plan calle for all patients to be followe for two years. The stuy was terminate after one year of follow-up since the initial clinical avantages of minimally invasive surgery have been shown to ecrease over time. With no clinical ifference observe uring the first postoperative year, it was very unlikely that such a ifference woul occur between the first an the secon year. As with all other outcomes employe in our analysis, the literature has escribe a wie variety of clinical results with minimally invasive techniques. Bonutti et al. observe similarity in mean Knee Society scores between minimally invasive an stanar groups 12. Kolisek et al. also observe similar scores between these two techniques 8 at the time of the threemonth follow-up. Seon an Song ientifie significantly improve scores on a 10-point visual analog pain scale on postoperative ay 3 for patients who ha been ranomize to minimally invasive surgery in comparison with patients who ha a stanar approach, but the scores obtaine at two weeks inicate equivalence between the cohorts 6. Noting the lack of a clear benefit in other similar stuies, some authors have taken a strong position against the use of minimally invasive techniques 17. However, a clinically relevant avantage for patients manage with minimally invasive surgery in postoperative scoring has been note by others 1,3. Variances in the follow-up time points utilize in these stuies preclue a proper comparison with our results, although the iversity in outcomes woul appear to attest to the iniviualize nature of these separate minimally invasive techniques. Implant misalignment has been cite as a potential risk factor with minimally invasive surgery techniques by Dalury an Dennis, who note varus malalignment (<87 ) of the tibial component in four of thirty patients who unerwent total knee arthroplasty with minimally invasive surgery 16. Raiographic ata in our stuy inicate reliable implant positioning regarless of the surgical technique employe. Our results appear to be more consistent with what can commonly be expecte with minimally invasive total knee arthroplasty, as a number of stuies have also observe comparable raiographic results between minimally invasive an stanar techniques 3,6,8,15. Minimally invasive total knee replacement is technically more emaning than the use of stanar surgical techniques. Even though the present stuy emonstrate no failure in the placement of the prosthesis in the minimally invasive group, less experience surgeons may encounter ifficulty. Our stuy has several limitations. We acknowlege that the stuy was unerpowere, given the small clinical ifferences in the primary outcomes between the groups. For example, with the 3 ifference in range of motion at one year between the groups in our analysis, a sample size of 300 subjects per group woul have been require to show significance. Although our stuy showe small effect sizes that were almost consistently in favor of the minimally invasive group, we o not believe they were large enough to be of clinical relevance. Aitionally, proponents of minimally invasive techniques often cite their positive impact on several quality-of-life outcomes, incluing length of hospital stay, reliance on pain meications, an the nee for inpatient rehabilitation following ischarge. Our stuy was not esigne to assess any of these outcomes. In conclusion, on the basis of the available patient numbers, our stuy faile to note a significant avantage for minimally invasive total knee arthroplasty over a conventional technique in any of the outcomes we measure. As we await the results of ranomize prospective stuies with greater sample sizes an longer follow-up perios to bring further clarity to this ebate, we recommen a more measure approach an simply avise surgeons to carefully weigh the theoretical avantages of minimally invasive surgery against stanar techniques before eciing on the proper surgical approach. Appenix Graphs epicting Knee Society scores, pain scores, activity scores, an range of motion for both the stuy groups are available with the electronic version of this article on our web site at jbjs.org (go to the article citation an click on Supporting Data ). n N. Wülker, PhD, MD Orthopaeic Department, Tübingen University Hospital, Hoppe-Seyler-Strasse 1-3, Tübingen, Germany. aress: wuelker@me.uni-tuebingen.e

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