This article has Open Peer Review reports available.
Total knee arthroplasties performed with a mini-incision or a standard incision. Similar results at six months follow-up
© Hernandez-Vaquero et al; licensee BioMed Central Ltd. 2010
Received: 25 June 2009
Accepted: 6 February 2010
Published: 6 February 2010
Minimal invasion surgery (MIS) is a recent technique recommended for Total knee arthroplasty (TKA) but demands an effort of the surgeons and the learning curve may be long.
Twenty six MIS-TKA were matched to 36 standard TKA with respect to age, sex, body mass index or preoperative score. All patients suffered from knee osteoarthritis, which had not improved with medical treatment and which presented a less than 10° deformity in the coronal and sagittal radiographic projections. At six months after the surgery a specific questionnaire was completed as well as the KSS (Knee Society rating scale), the generic short-form health questionnaire (SF-12) and a visual analogue scale (VAS).
The MIS technique required more time of surgery (p < 0.001), hospital stay was noticeably shorter (p < 0.05) and drainage volume collected after surgery was significantly higher in the standard technique. We observe a higher frequency in small sizes implants for MIS surgery but no statistically significant differences were found between both groups regarding the radiological alignment of the implant. At six months no differences were found between the groups in range of motion, KSS scores, the physical or mental subscale SF-12, patient's pain perception, satisfaction or subjective improvement.
Minimal invasion surgery in total knee arthroplasty showed no improvement over a standard approach.
Total knee arthroplasty (TKA) is a very successful procedure in the treatment of end-stage arthritis or deformity of the knee. Long-term results for pain relief and functional improvement have been excellent. The procedure, however, traditionally requires an extensile approach. The medial parapatellar arthrotomy is the most common method used to expose the knee. This exposure involves patella eversion and generally is done through large incisions of approximately 20 to 30 cm. Although the long-term results of knee arthroplasty have proven to be excellent, the rehabilitation period often is long and painful . In order to improve the patient's well-being in the immediate postoperative period and to lessen the aesthetic impact, other, less traumatic exposures (MIS-TKA) have been introduced, including the subvastus, midvastus, and lateral arthrotomy. The mini midvastus approach extends from the tibial tubercle to the superior patella and then to the muscle of the vastus medialis, and the muscle fibers are not cut . Although recommendations for the use of this technique are not precisely defined yet, the exclusion criteria for patients to receive the MIS-TKA were rheumatoid arthritis, obesity, severe osteoporosis, valgus-varus deformity greater than 10°, previous arthrotomy on the knee and preoperative knee flexion less than 100°. These techniques aim for a faster recovery of mobility, a shorter postoperative period, a reduction in blood loss, less pain throughout the postoperative period, a lessened aesthetic impact, and to reduce the amount of health resources required by resorting to a smaller incision and a less aggressive technique for soft tissues; they will not, however, impair the good results this procedure achieves.
The purpose of this study is to evaluate the short-term functional and health-related quality of life results of MIS-TKA (mini-mid vastus approach) compared with a traditional TKA using a medial parapatellar exposure. Additionally, this study examines the effect of MIS-TKA on operative time, postoperative well-being, health resources used, radiographic alignment and complications.
Number of TKAs
70.8 (SD, 5.9)
70,5 (SD, 6.9)
32.1 (SD, 6)
30.8 (SD, 3.3)
Previous surgery (*)
4 (range, 0--12)
6 (range, 0--20)
100 (range, 85--130)
106 (range, 75--132)
Surgery duration (min)
Size of incision (cm)
Size of the femoral component
Size of the tibial component
Thickness of the tibial polyethylene insert (mm)
Length of post-operative hospital stay (days)
Blood loss in the immediate post-operative check-up (grams of hemoglobin)
Redon draining (cc)
Number of rescue analgesic doses during immediate post-operative period
Radiographic alignment of the tibial component of the prosthesis/axis on the tibia (degrees)
Radiographic alignment of the femoral component of the prosthesis/axis on the femur (degrees)
Radiographic measurement of the femorotibial axis (degrees)
Use of walking stick or crutches (one, two, none)
Mean time of the surgery for Group B was 103.19 minutes (SD 20.94), while the mean time for Group A was 130 minutes (SD 26.94). This means applying the MIS technique required 26% more time (p < 0.001). The mean size of the length of the cutaneous incision was 11 cm (8-12) for the MIS-TKA Group, and 19 cm (17.5-23) for the Group using the traditional method.
Immediate post-operative period
Hospital stay was noticeably shorter (p < 0.05) for the MIS Group patients (mean: 6.92; SD 1.47) than for the standard Group (mean: 7.88; SD 2.06). The reduction of hemoglobin grams lost in the immediate post-operative period for the MIS Group was 1.87 (mean; SD 0.80), whereas in the other Group the average loss was 2.95 grams (mean; SD 0.80), which is significantly higher (p < 0.001). Drainage volume collected after surgery for Group A was a mean of 621.15 cc (SD 412.22), whereas the figure for the traditional technique was significantly higher, with a mean of 1072.5 cc (SD 440.64).
The number of paracetamol rescue doses set by our hospital for these kind of surgery (which are necessary for the analgesic control during the two days following surgery) was less for those patients belonging to the MIS-TKA Group (mean: 1; SD 1.23) than for those patients who underwent the conventional technique (mean: 1.83; SD: 1.3), showing a significant difference (p < 0.05).
Radiographic alignment of implants
Femoral component (SD)
Tibial component (SD)
Total tibiofemoral coronal (SD)
Total tibiofemoral sagital (SD)
+ 5.7° (2.81)
- 1° (2.46)
+ 5.4° (3.31)
+ 5.5° (2.68)
- 1.6° (2.08)
+ 4.6° (2.98)
Evaluation at six months
Regarding the observed mobility at six months after surgery, no significant differences were observed between both groups. Extension in the MIS Group was -0.96° (SD 2.46), and -0.97° (SD 2.34) in the standard Group. Mean flexion for the MIS Group was 99.62° (SD: 14.55), whereas it was 99.44° (SD 15.3) in the standard group. There were no severe complications which might have altered the clinical or radiographic results. No progressive radiolucencies were found. Care was taken to position patients as uniformly as possible. However, radiographs were obtained without benefit of fluoroscopy, so the true incidence of radiolucent lines beneath the components cannot be stated with certainty.
The percentage of cutaneous complications, all of them slight and easily cured, was similar between both group (11% in the conventional technique group and 11.5% in the MIS group) but delayed wound healing and local soreness was observed in 6% of patients in the MIS group. 15% of the patients who underwent the MIS technique were using a walking stick at six months of follow-up, whereas in the standard technique group that percentage reached 21%, with no statistically significant differences between groups.
Pain as measured with the VAS scale at six months was 2.2 (SD 1.4) for both Groups. Average satisfaction with the same scale was 8.3 (SD 1.9) for the MIS group and 8.2 (SD 1.3) for the traditional technique Group. No statistically significant differences were found, either. At six months of follow-up, the MIS Group scored a mean of 43.9 (SD 10.5) in the physical subscale of the SF-12, whereas the traditional technique Group scored a mean of 44.9 (SD 97.3), with no significant differences. The same happened with the mental subscales: 45.8 (SD 13.4) for the MIS Group and 50.1 (SD 11.4) for the traditional technique Group. KSS scores were 163.4 (SD 31.4) for the MIS Group ad 162.6 (SD 21.4) for the standard technique Group. This difference was not statistically significant.
There have been many studies which have determined the effectiveness of TKA in reducing pain and deformity and improving functionality. Standard TKA has led to consistent, reproducible, and enduring results. Long term success at 10 years or more encompasses survivorship of greater than 90% for many studies, and more than of 80% of patients were satisfied . For many years, clinicians relied exclusively on objective and physical measures of disability in order to assess orthopedic surgical outcomes. Most have assessed outcomes using standardised knee scoring systems such as KSS, but they have poor internal reliability and small effect sizes, and are therefore not good for assessing outcomes in TKA. It seems necessary to add another kind of evaluation, such as a visual scale and a generic questionnaire on quality of life. Works such as that of Bullens et al , show how a comparison between the subjective and objective outcome systems revealed only poor correlations, and this comparison suggests that the concerns and priorities of patients and surgeons can differ.
The outcome measures which we have used (SF-12) is a reliable and validated scoring system which has been used to assess the outcomes of the TKAs [6, 7]. It measures generic health concepts so as to allow for the comparison of several groups. It includes eight variables commonly used in health-related research: physical functioning, bodily pain, general health perception, vitality, social functioning, emotional role and mental health. Results are expressed in two subscales, with scores between 0 and 100, designed to have a mean of 50 and a SD of 10 for the general population. VAS provides additional information about subjective outcome after TKA  and is used frequently in health. We advocate the use of the patient satisfaction VAS system, in addition to the existing evaluating systems.
The mean operative duration from incision to closure was significantly longer in group MIS-TKA, (26% more); this was already referred to in other studies on MIS in ATR [15–18]. Analysing the size of the implants shows that the MIS group requires smaller components more frequently. Although we haven't found evidence in the literature on this finding, this could be due to the smaller size of the incision or to difficulties when measuring those components. We do not know whether that difference may have an eventual impact. Similarly, the width of the polyethylene tray showed that knees treated with MIS tend to require less wide components, although there appears to be no statistical significance.
Hospital stay for patients in Group A was at least one day less than that of patients who underwent the traditional technique. Other authors do mention this circumstance  which helps to make good use of health resources. Blood loss was significantly lower in the MIS Group, both in terms of hemoglobin grams and in the amount of drained blood but the difference in the number of drains in each group could produce a bias in the results of our study. However these data are also in keeping with other studies [8, 10] and are supposedly related to the less aggressive surgery. In any case, none of our patients needed to get a blood transfusion.
It has been suggested that minimally-invasive techniques result in less post-operative pain and a reduced requirement for analgesics. In our study, post-operative pain was indeed lower in the MIS Group and, even though it is difficult to measure this variable, we can at least ascertain that this group required fewer analgesics; without patients and nurses blinded to the procedure, there is too much bias to make much of this finding. In other studies on the MIS-TKA technique, analgesic used are measured as en equivalent with morphine , according to the total amount of analgesics used , or via visual pain scales.
We encountered no major perioperative complications in either group. We observed a greater degree of transitory tumefaction in the edges of the wound in the MIS group; this can be related to the use of separators, and other authors have also mentioned an increase in local wound problems (4 vs. 1) . It is possible that being more careful with the soft parts may had avoided the high number of cutaneous complications.
The alignment of the components measured radiographically with respect to each bone segment to both of them was excellent in both groups. Some authors compare the radiologic outcomes of total knee arthroplasty using the conventional technique with those using MIS techniques. Results were comparable between the mini and control groups , but other authors  showed that technical errors and higher rates of outliers in postoperative alignment were observed. It is possible that using computer assisted surgery may add some advantages to this technique, bringing a special vision of the bone cuts, thus easing their reproducibility and avoiding outlier cases .
At six months of follow-up, results for both groups are similar, and there are no statistically significant differences in none of the parameters. The range of motion in both groups is good at six months; these data are in keeping with other authors, and there is no improvement in recovery in group TKA-MIS, as mentioned in other studies [13, 22] where the minimally invasive technique positively contributes to the early restoration of quadriceps strength and a speedy return to normal functioning. In other studies, manipulation was necessary in 14% of the traditional group compared with 2% in the minimal incision group  but there was no significant difference in range of motion or functional outcome at 1 year after surgery nor was no significant difference in component position or complication rates.
Variables measured with VAS did not show significant differences between both groups in neither of its two subscales (physical and mental). Both groups reported a good quality of life at six months. On the KSS scale, both groups achieved high scores, but there were no statistically significant differences between them.
Overweight (BMI>40), muscular hypertrophy, previous surgery or low patella are considered factors which may hinder this kind of surgery. In our experience, none of them have posed any problem whatsoever nor had any negative impact on surgery.
It is usual that studies appear showing better short-term outcomes for MIS-TKA  regarding the patient's well-being and hospital stay. However, in order to properly gauge the scientific evidence on MIS techniques in ATR, it should be noted that those results have frequently been obtained from expert centers or from surgeons devoted to such techniques . This fact may distort the results, since any complications and the follow-up of TKAs implanted via MIS in general hospitals or non-specialized centers are not analysed. It is possible then that, presently, the MIS technique is more a personal choice of the patient or a commercial demand than a true advancement in TKA placement. The surgeon should look for the minimum size necessary for him to correctly implant a TKA, and look away from showing off he is able to implant arthroplasties with ever smaller incisions. Therefore we recommend the use of a standard arthrotomy with the shortest possible invasion and skin incision. MIS-TKA demands an effort on the part of the surgeon , the learning curve may be unacceptably long for a low-volume arthroplasty surgeon , it takes more intervention length, require longer tourniquet time and special tools are needed to insert the implant.
Our study allows us to assert that the MIS technique does offer some advantages for the immediate post-operative period, including a lesser amount of analgesics, and a shorter hospital stay. However, results at six months after surgery are similar, both in functional assessment and in quality of life for the patient.
- Goble EM, Justin DF: Minimally invasive total knee replacement: principles and technique. Orthop Clin North Am. 2004, 35: 227-234. 10.1016/S0030-5898(03)00113-5.View ArticleGoogle Scholar
- Laskin RS: Minimally invasive total knee replacement using a mini-mid vastus incision technique and results. Surg Technol Int. 2004, 13: 231-238.PubMedGoogle Scholar
- Insall JN, Dorr LD, Scott RD, Scott WN: Rationale of the Knee Society clinical rating system. Clin Orthop. 1989, 248: 13-14.PubMedGoogle Scholar
- Baker PN, Meulen van der JH, Lewsey J, Gregg PJ: The role of pain and function in determining patient satisfaction after total knee Replacement. J Bone Jt Surg Br. 2007, 89-B: 893-900. 10.1302/0301-620X.89B7.19091.View ArticleGoogle Scholar
- Bullens PHJ, van Loon Corme J, de Waal Malefijt MC, Laan RFJM, Veth RPH: Patient Satisfaction After Total Knee Arthroplasty. A Comparison Between Subjective and Objective Outcome Assessments. J Arthroplasty. 2001, 16: 740-747. 10.1054/arth.2001.23922.View ArticlePubMedGoogle Scholar
- Hartley RC, Barton-Hanson NG, Finley R, Parkinson RW: Early patient outcomes after primary and revision total knee arthroplasty. A prospective study. J Bone Joint Surg Br. 2002, 84: 994-999. 10.1302/0301-620X.84B7.12607.View ArticlePubMedGoogle Scholar
- MacDonald SJ, Charron KD, Bourne RB, Naudie DD, McCalden RW, Rorabeck CH: The John Insall Award: gender-specific total knee replacement: prospectively collected clinical outcomes. Clin Orthop. 2008, 466: 2612-2616. 10.1007/s11999-008-0430-1.View ArticlePubMedPubMed CentralGoogle Scholar
- Kelly MJ, Rumi MN, Kothari M, Parentis MA, Bailey KJ, Parrish WM, Pellegrini VD: Comparison of the Vastus-Splitting and Median Parapatellar Approaches for Primary Total Knee Arthroplasty: A Prospective, Randomized Study Surgical Technique. J Bone Joint Surg Am. 2007, 89: 80-92. 10.2106/JBJS.F.01190.PubMedGoogle Scholar
- Chin CPL, Shen Foo LS, Yang KY, Yeo SJ, Lo NN: Randomized Controlled Trial Comparing the Radiologic Outcomes of Conventional and Minimally Invasive Techniques for Total Knee Arthroplasty. J Arthroplasty. 2007, 22: 800-806. 10.1016/j.arth.2006.10.009.View ArticlePubMedGoogle Scholar
- Kolisek FR, Bonutti PM, Hozack WJ, Purtill J, Sharkey PF, Zelicof SB, Ragland PS, Kester M, Mont MA, Rothman RH: Clinical Experience Using a Minimally Invasive Surgical Approach for Total Knee Arthroplasty. Early Results of a Prospective Randomized Study Compared to a Standard Approach. J Arthroplasty. 2007, 22: 8-13. 10.1016/j.arth.2006.06.004.View ArticlePubMedGoogle Scholar
- Karachalios KT, Giotikas D, Roidis N, Poultsides L, Bargiotas K, Malizos KN: Total knee replacement performed with either a mini-midvastus or a standard approach. A prospective randomized clinical and radiological trial. J Bone Joint Surg Br. 2008, 90-B: 584-591. 10.1302/0301-620X.90B5.20122.View ArticleGoogle Scholar
- Kim Y-H, Kim J-S, Kim D-Y: Clinical outcome and rate of complications after primary total knee replacement performed with quadriceps-sparing or standard arthrotomy. J Bone Jt Surg Br. 2007, 89B: 467-470.View ArticleGoogle Scholar
- Tashiro Y, Miura H, Matsuda S, Okazaki K, Iwamoto Y: Minimally Invasive versus Standard Approach in Total Knee Arthroplasty. Clin Orthop. 2007, 463: 144-150.PubMedGoogle Scholar
- Han I, Seong SC, Lee S, Yoo JH, Lee MC: Simultaneous Bilateral MIS-TKA Results in Faster Functional Recovery. Clin Orthop. 2008, 466: 1449-1453. 10.1007/s11999-008-0216-5.View ArticlePubMedPubMed CentralGoogle Scholar
- Bonutti PM, Mont MA, Kester MA: Minimally invasive total knee arthroplasty: a 10-feature evolutionary approach. Orthop Clin North Am. 2004, 35: 217-226. 10.1016/j.ocl.2004.02.001.View ArticlePubMedGoogle Scholar
- Reid JB, Guttmann D, Ayala M, Lubowitz JH: Minimally invasive surgery - total knee arthroplasty. Arthroscopy. 2004, 20: 884-889.View ArticlePubMedGoogle Scholar
- Hoo Kim Y, Sohn KS, Kim JS: Short-Term Results of Primary Total Knee Arthroplasties Performed with a Mini-Incision or a Standard Incision. J Arthroplasty. 2006, 21: 712-718. 10.1016/j.arth.2005.09.001.View ArticleGoogle Scholar
- Laskin RS: Minimally invasive total knee arthroplasty: the results justify its use. Clin Orthop. 2005, 440: 54-59. 10.1097/01.blo.0000186562.08685.a2.View ArticlePubMedGoogle Scholar
- Bonutti PM, Mont MA, McMahon M, Ragland PS, Kester M: Minimally Invasive Total Knee Arthroplasty. J Bone Jt Surg Am. 2004, 86A: 26-32.Google Scholar
- Hsuan-Ti Huang H, Yuan Su J, Chang Je-Ken, Chen Chung-Hwan, Wang Gwo-Jaw: Early Clinical Outcome of Minimally Invasive Quadriceps-Sparing Total Knee Arthroplasty Report of a 2-Year Follow-Up. J Arthroplasty. 2007, 22: 1007-1012. 10.1016/j.arth.2007.03.021.View ArticlePubMedGoogle Scholar
- Bonutti PM, Dethmers D, Ulrich SD, Seyler TM, Mont MA: Computer Navigation-assisted versus Minimally Invasive TKA. Benefits and Drawbacks. Clin Orthop. 2008, 466: 2756-2762. 10.1007/s11999-008-0429-7.View ArticlePubMedPubMed CentralGoogle Scholar
- Dalury DF, Mulliken BD, Adams MJ, Lewis C, Saunder RR, Bushey JA: Early recovery after total knee arhroplasty performed with and without patellar eversion and tibial translation. A prospective randomized study. J Bone Jt Surg Am. 2009, 91: 1339-1343. 10.2106/JBJS.H.00435.View ArticleGoogle Scholar
- McAllister AC, Stepanian JD: The Impact of Minimally Invasive Surgical Techniques on Early Range of Motion After Primary Total Knee Arthroplasty. J Arthroplasty. 2008, 23: 10-18. 10.1016/j.arth.2007.01.011.View ArticlePubMedGoogle Scholar
- Berger RA, Sanders S, D'Ambrogio E, Buchheit K, Deirmengian C, Paprosky W, Della Valle CJ, Rosenberg AG: Minimally invasive quadriceps-sparing TKA: results of a comprehensive pathway for outpatient TKA. J Knee Surg. 2006, 19: 145-148.PubMedGoogle Scholar
- Haas SB, Cook S, Beksac B: Minimally invasive total knee replacement through a mini midvastus approach: a comparative study. Clin Orthop. 2004, 428: 68-73. 10.1097/01.blo.0000147649.82883.ca.View ArticlePubMedGoogle Scholar
- Berend KR, Lombardi AV: Avoiding the potential pitfalls of minimally invasive total knee surgery. Orthopedics. 2005, 28: 1326-1330.PubMedGoogle Scholar
- King J, Stamper DL, Schaad DC, Leopold SS: Minimally Invasive Total Knee Arthroplasty Compared with Traditional Total Knee Arthroplasty Assessment of the Learning Curve and the Postoperative Recuperative Period. J Bone Joint Surg Am. 2007, 89: 1497-1503. 10.2106/JBJS.F.00867.View ArticlePubMedGoogle Scholar
- The pre-publication history for this paper can be accessed here:http://www.biomedcentral.com/1471-2474/11/27/prepub
This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.