Minimally Invasive Total Knee Arthroplasty

Updated: May 21, 2017
  • Author: Derek F Amanatullah, MD, PhD; Chief Editor: Erik D Schraga, MD  more...
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Overview

Background

In addition to conventional surgical approaches, total knee arthroplasty (TKA) may be done by means of minimally invasive surgery (MIS). Minimally invasive TKA (MIS-TKA) is often portrayed in the lay community and press as involving a small skin incision. Actually, MIS-TKA is defined by limited soft-tissue and bony dissection. MIS-TKA was developed after the description of unicondylar knee arthroplasty. [1, 2]

Conventional TKA is a successful operation for patients suffering from arthritis of the knee, with a reported complication rate of less than 2% and an implant survivorship of 95% at 10 years. The aim of MIS-TKA is to decrease postoperative pain and shorten the rehabilitation period.

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Indications

MIS-TKA is used as an alternative to conventional TKA. However, there are conflicting data on whether MIS-TKA is an acceptable replacement for or even an improvement on conventional TKA, and no definitive answer to this question is available at present.

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Contraindications

No absolute contraindications exist for MIS-TKA; this procedure is defined by limited soft-tissue and bony dissection. Conventional TKA is probably a more suitable choice for the following patients [3, 4, 5] :

  • Patients with a body mass index (BMI) greater than 40 kg/m 2
  • Patients with severe fixed valgus deformity
  • Patients with severe osteoporosis
  • Patients who have previously undergone knee arthrotomy
  • Patients with rheumatoid arthritis
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Technical Considerations

Complication prevention measures recommended for MIS-TKA are exactly the same as those recommended for conventional TKA and should include the following:

  • Appropriate preoperative screening and clearance
  • Preoperative templating and planning
  • Preoperative administration of antibiotics as recommended by the American Academy of Orthopaedic Surgeons (AAOS)
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Outcomes

Early series comparing MIS-TKA with conventional TKA reported successful outcomes. [6, 7] A randomized controlled trial (RCT) showed significantly shorter hospital stays after MIS-TKA than after conventional TKA. [8] In a retrospective review of 48 knees, MIS-TKA patients were able to complete an active straight leg raise earlier than conventional TKA patients could. [9]  A similar conclusion was reached in a study comparing computer-assisted approaches. [10] A case-control study comparing 32 knees after conventional TKA and after MIS-TKA reported mean Knee Society Scores (KSS) of 94 and 96 and mean functional scores of 90 and 99, respectively. [11]

An RCT that investigated extensor and flexor muscle function after conventional TKA and MIS-TKA found that the MIS-TKA group had a higher knee extensor peak torque at 3, 6, and 12 months postoperatively. [12]  Similarly, another RCT found that the MIS-TKA group had greater hamstring and quadriceps strength at 4 weeks after surgery; however, this difference was not observed at 12 weeks, and no benefit was documented with regard to longer-term strength or functional performance. [13]

Another prospective RCT, which compared conventional TKA with MIS-TKA by using an accelerometer, found that MIS-TKA patients were significantly more active on all postoperative days and that MIS-TKA patients achieved 80% of their preoperative acceleration in about half of the time that conventional TKA patients took to reach this level. [14]  Additionally, a systematic review of 13 randomized controlled trials found that the mean KSS at 6 and 12 weeks postoperatively was higher in the MIS-TKA group but that this difference was lost at 6 months. [15]

Conflicting conclusions demonstrate why there is still no consensus regarding either the noninferiority or the superiority of MIS-TKA as compared with conventional TKA. A prospective RCT found that as expected, incisions were significantly shorter in the MIS-TKA group, but there were no significant differences in the Knee Injury and Osteoarthritis Outcome Score (KOOS), the Oxford Knee Score (OKS), the KSS, and the Short Form (SF)-12 score at 6-week, 1-year, 2-year, and 5-year follow-up evaluations in comparison with conventional TKA. [16]

A meta-analysis of 30 RCTs examined short- to midterm results (<36 months) for MIS-TKA as compared with conventional TKA. [17] Evaluating a total of 2500 TKAs, the authors concluded that the MIS-TKA group had better outcomes with respect to KSS, range of motion, days to straight leg-raise, and total blood loss. However, this benefit was associated with longer operating and tourniquet times, as well as wound-healing complications. Overall, though, there were no significant differences with regard to radiographic evaluation of component positioning with MIS-TKA and conventional TKA.

An RCT that evaluated medium-term results demonstrated that at a mean of 6 years' follow-up, there were no differences between MIS-TKA and conventional TKA in terms of pain, function, malalignment, or revision rates. [18]

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