Knee Surg Sports Traumatol Arthrosc DOI 10.1007/s00167-014-2837-4

KNEE

A meta-analysis of minimally invasive and conventional medial parapatella approaches for primary total knee arthroplasty Canfeng Li • Yi Zeng • Bin Shen • Pengde Kang Jing Yang • Zongke Zhou • Fuxing Pei

•

Received: 23 July 2013 / Accepted: 8 January 2014 Ó Springer-Verlag Berlin Heidelberg 2014

Abstract Purpose Minimally invasive surgical (MIS) approaches for total knee arthroplasty (TKA) have become increasingly popular for doctors and patients. They have argued that it decreases post-operative pain, accelerates functional recovery and increases patient satisfaction due to less injury. However, critics are concerned about TKA’s possible effects on component position and with complications, considering the procedure’s limited exposure. The purpose of this study was to summarise the best evidence in comparing the clinical and radiological outcomes between MIS and a conventional approach in TKA. Methods Electronic databases were systematically searched to identify relevant randomised controlled trials (RCTs). Our search strategy followed the requirements of the Cochrane Library Handbook. Methodological quality was assessed, and data were extracted independently by two authors. Results Thirty studies, including 2,536 TKAs, were reviewed: 1,259 minimally invasive and 1,277 conventional exposure TKAs. The results showed that while the MIS group had longer operation times and tourniquet times, it had superior outcomes in KSS (objective and total), range of motion, flexion range of motion, flexion 90° day, straight leg-raising day, total blood loss and decrease in haemoglobin. However, wound-healing problems occurred more frequently in the MIS group. There were no statistically significant differences in other clinical or

C. Li
Y. Zeng
B. Shen (&)
P. Kang
J. Yang
Z. Zhou
F. Pei Orthopedic Department, West China Hospital, Sichuan University, Chengdu, China e-mail: [email protected]

radiological outcomes between the MIS and conventional groups in TKA. Conclusion The preliminary results indicate that the MIS approach provides an alternative to the conventional approach, with earlier rehabilitation but no malpositioning or severe complications. Wound-healing problems can be treated easily and effectively, and the risk also decreases as surgeons become more experienced, and more userfriendly instruments are invented. Potential benefits in medium- and long-term outcomes require larger, multicentre and well-conducted RCTs to confirm. Level of evidence Therapeutic study, Level II. Keywords Minimally invasive approach
Conventional approach
Total knee arthroplasty
Meta-analysis

Introduction With ageing, an increasing number of patients has severe osteoarthritis, which greatly diminishes quality of life. Total knee arthroplasty (TKA) is considered to be the best method for treating advanced osteoarthritis for excellent alleviation of pain, restoration of joint function and improvement in quality of life, with 95 % implant survivorship over 15 years [18, 39, 46, 53]. However, the conventional surgical approach requires an incision of 20–30 cm, which injures the quadriceps tendon and can result in weakness of the extensor mechanism and can adversely affect the blood supply to the patella [20, 50]. In addition, patients complain of post-operative pain and the long period required for functional recovery [18, 26, 46]. Some surgeons have even suggested that TKA can require up to 1 year for rehabilitation to achieve full functional recovery [14]. To address such issues, many surgeons have

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applied the concept of minimally invasive surgery (MIS) in TKA, with smaller skin and capsule incisions, avoidance of patellar eversion and tibiofemoral dislocation and minimisation of knee hyperflexion. These surgeons believe that the MIS approach can effectively relieve post-operative pain, promote faster recovery, improve functional outcomes, reduce hospital lengths of stay and costs and improve cosmetics, as well as increase patients’ satisfaction [56, 58, 60]. Therefore, MIS-TKA has become increasingly popular for both surgeons and patients. Some critics, however, have argued that prolonged the operative and tourniquet times result in disadvantages in blood loss, tourniquet-associated ischaemia, the incidence of infection and delayed wound-healing problems. More importantly, poor exposure and visualisation can increase the risk of misalignment, leading to polyethylene wear, premature loosening and instability and earlier revision [4, 6, 11]. It was reported that the annual number of TKAs performed in the United States alone was projected to increase to 3.48 million by 2030 [29]. Because of less post-operative pain, faster rehabilitation and less unsightly scarring, many patients have requested MIS techniques for their TKAs. However, in the academic field, there remains significant controversy over MIS-TKA, with many clinical studies suggesting conflicting results, including prospective studies and randomised controlled trials (RCTs) [14, 26, 33, 61]. As evidence-based medicine (EBM) has become a tendency in the clinical field, an increasing number of doctors believe that meta-analysis currently provides the most reliable evidence. There have been one systematic review and five meta-analyses published from 2009 to 2012 on this subject [2, 8, 20, 28, 40, 58]. Not only did these

studies have many limitations, but their conclusions were also conflicting (Table 1). Taking all these issues into consideration, we do not yet know whether MIS-TKA offers advantages over conventional TKA. Recently, many new RCTs on this subject have been published without conclusive results [7, 11, 13, 19, 31, 42, 45, 48, 55, 61–63]. Thus, we conducted an updated meta-analysis to investigate whether MIS-TKA was superior to conventional TKA. To perform a thorough and comprehensive assessment of the safety and efficiency of MIS-TKA, we included 30 RCTs (22 level I and 8 level II studies), and we added many new statistical indicators that had not been reported before, such as intraoperative blood loss, drainage, decrease in haemoglobin, transfusions per patient, extensive range of motion, flexion range of motion, flexion 90° day and straight leg-raising day.

Materials and methods Literature search A written prospective protocol defined the search strategy, eligibility criteria, quality assessment, data elements of interest and plans for data synthesis and analysis, according to the guidelines described in the Cochrane Handbook for Systematic Reviews. We searched the electronic medical databases, including PubMed, EMBASE and the Cochrane Library, using the following search terms: (total knee arthroplasty or total knee replacement) AND (minimally invasive or mini-incision or less invasive). The last date for our research was 1 February 2013. Moreover, the reference

Table 1 Details of meta-analyses and systematic review published on this subject References

Studies included

Patients

Knees

Statistical indicators

Conclusion

Khanna et al. [28]

28, only 4 RCTs, 14 prospective studies, and 10 retrospective studies. Besides, 10 studies only reported on outcomes of MIS-TKAs

N/S

3,496

13

MIS-TKAs tend to recover faster with higher rate of misaligment

Cheng et al. [8]

13 RCTs or qRCTs

942

980

7

Liu and Yang [40]

15, only 4 RCTs, 11 non-RCTs

1,445

N/S

7

MIS-TKAs dead to faster recovery with more frequent delayed wound healing and infections MIS-TKAs have advantages in length of hospital stay, blood loss, straightleg raise, and ROM

Gandhi et al. [20]

7 RCTs

790

828

2 (Complications and KSS)

MIS-TKAs leads to higher complication rate with similar KSS

Smith et al. [53]

18 RCTs, but 4 studies using computer navigation system, and 1 study comparing mini-MPP with QS

1,561

1,582

27 (Primary outcome: KSS)

Except flexion range of motion, there was no difference between MIS- and standard TKAs

Alcelik et al. [2]

17 RCTs or qRCTs

733

748

10

MIS-TKAs results in superior function in the immediate post-operative period with higher rates of intraoperative complications

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lists of the retrieved studies and relevant reviews were also scrutinised in case we were missing any additional studies that the electronic database search had not found.

chosen for analysis because most of the patients were in the early post-operative stages (less than 3 years). Statistical analysis

Eligibility criteria Study selection was made performed by two reviewers, who scanned the titles and abstracts of all the citations, according to the following inclusive criteria: (1) prospective RCTs; (2) human studies; (3) studies comparing MISTKA with conventional TKA; (4) studies reporting clinical and/or radiological outcomes and (5) studies published in English. The exclusion criteria were as follows: (1) nonrandomised or retrospective studies; (2) animal studies or cadaver studies; (3) studies using the navigation system; and (4) studies without full text available. However, there were no restrictions on minimally invasive technique, type of implant or duration of follow-up. Quality assessment Two reviewers independently assessed the methodological quality of the studies, according to the criteria outlined in the Cochrane Handbook for Systematic Reviews of Interventions, version 5.1.0. If any disagreements occurred, a third reviewer joined the discussion until a consensus was obtained. Methodological quality included six items: sequence generation; allocation sequence concealment; blinding; incomplete outcome data; selective outcome reporting; other potential risks. Each domain was rates as yes, no, or unclear guidelines: yes = low risk of bias; no = high risk of bias; and unclear = unclear risk of bias. Data extraction A data extraction form was predesigned, and the data were independently extracted by two investigators, including data on patient demographics, surgical technique, implant style, follow-up, methodology, clinical outcomes, radiological measurements and complications. The data were checked by a third investigator, and any disagreements were resolved through discussion. The authors of these articles were contacted if necessary to obtain any information. Missing standard deviations were calculated based on the range of values provided in the articles, according to the formula reported by Hozo et al. [21]. In addition, two articles compared three different approaches, including two minimally invasive approaches [6, 33]. To gain more information, we decided to analyse these studies twice, using the same value for the conventional group. Although the times at which the outcomes were measured differed among these studies, the outcomes at final follow-up were

Review Manger (Revman, version 5.1), which the Cochrane Library recommends for preparing and maintaining Cochrane systematic reviews, was used for our data synthesis and analysis. For continuous outcomes, expressed as the means and standard deviations, confidence intervals or ranges, weighted mean differences (WMDs) and 95 % CIs were calculated. For categorical outcome measurements expressing dichotomous outcomes, risk ratios (RRs) and 95 % CIs were calculated. Statistical heterogeneity was tested by the Chi squared test and I-square test. If a P [ 0.1 or I-square statistic less than 50 % was reported, we assumed low statistical heterogeneity, and a fixed-effects model (Mantel–Hansel) was used; otherwise, a randomeffect model was adopted. In addition, publication bias, indicating the potential for negative studies not being published, was assessed through a funnel plot of length of incision. If the funnel plot was asymmetric about the pooled log OR, there was high potential of publication bias versus a plot resembling an inverted funnel, indicating no bias.

Results The results of the initial search retrieved 1,149 citations, and 76 articles were considered potentially eligible for further evaluation after removing the duplications and scanning the titles and abstracts. After reading the full texts for detailed evaluation, 30 studies were included based on our inclusion and exclusion criteria (Fig. 1). The majority of the studies were small, with participant numbers ranging from 15 to 150. Two articles [36, 47] compared three groups (conventional TKA vs. MIS-TKA vs. computerassisted TKA); therefore only the conventional and MIS groups were included for meta-analysis. Regardless of length of follow-up, the type of less invasive technique or implant used, studies were included in our meta-analysis if the outcomes were compared between conventional and minimally invasive approaches. In total, the meta-analysis included 2,477 patients (1,657 women and 636 men) undergoing 2,536 TKAs. There were 1,277 knees that underwent conventional approaches and 1,259 knees that underwent minimally invasive approaches, including 307 knees undergoing subvastus (SV) approaches, 371 knees undergoing mid-vastus (MV) approaches, 270 knees undergoing quadriceps-sparing (QS) approaches and 311 knees undergoing mini-MPP approaches, respectively. Nineteen of the included randomised trials used a cruciatesubstituting technique, and only five used a cruciate-retaining

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Fig. 1 Flow chart shows how articles were selected

Identificatio

Knee Surg Sports Traumatol Arthrosc 567 of records identified through PudMed searching

534 of records identified through Embase searching

48 of records identified through Cochrane library searching

O of record through other sources

Included

Eligibility

Screening

932 of records after duplicates removed

technique. Most of the studies had the patellae resurfaced and used cemented implants. The follow-ups ranged from 2 to 96 months. The post-operative management protocols were similar, and the patients’ demographics were comparable in each citation. Table 2 summarises the details. The level of evidence of the included studies is outlined in Table 3. Among the 30 eligible trials, 22 were level I, and the remaining eight were level II. Except for two [3, 41] prospective studies, all the included trials were RCTs. There were 20 studies reporting adequate methods of randomisation generation, including sealed envelopes, randomised table numbers and computer-generated randomised numbers. Of the 30 articles, 20 studies had blinding methods, but only six citations reported allocation concealment. There was minimal indication of publication bias, as the funnel plot reporting length of incision was symmetrical (Fig. 2). Outcomes of meta-analysis Clinical outcomes The KSS was regarded as our primary outcome for this meta-analysis (Figs. 3, 4, 5). Our study suggested that the MIS group had advantages in total KSS and objective KSS, except for functional KSS, with significant statistical heterogeneity (in five trials, nine trials, and 12 trials, respectively). The HSS score [7, 31], Oxford knee score [31, 41] and WOMAC score [19, 36] were also used for the clinical

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932 of records screened

856 of records excluded

76 of full-text articles assessed eligibility

46 of full-text excluded with reasons

30 of studies included in qualitative synthesis

30 of studies included in qualitative synthesis (Meta-analysis)

assessments of patients; however, there were insufficient data to pool for analysis. As other authors have identified [3, 9–11], there was a significant difference between the two approaches with regard to operative and tourniquet times and incision length, with the MIS group having smaller surgical scars but experiencing longer operative and tourniquet times compared with the conventional group. However, as anticipated, the MIS approach was less disruptive to tissue and caused less trauma, especially to extensor mechanism, and our meta-analysis also found that MIS-TKA offered statistically significant benefits in visual analogue scale (VAS), range of motion (ROM), flexion range of motion, flexion 90° day and straight leg-raising day. There were no significant differences between the surgical groups regarding hospital stay or the extension range of motion. While the differences were not statistically significant in intraoperative blood loss, drainage, estimated blood loss or transfusions per patient, the total blood loss and decrease in haemoglobin were significantly less in the MIS-TKA group, compared to the conventional TKA group. As Table 3 shows, the majority of synthetic outcomes had significant statistical heterogeneity among those studies included, so a random-effects model was chosen for them. Component measurement In contrast to some authors’ concerns [6, 11, 57], our metaanalysis showed that there were no significant differences

Size (K/P)

Kolisek MIS 40/40 CONV 40/40 Tashiro MIS 24/20 CONV 25/21 Kim MIS 120/120 CONV 120/120 Chin MIS 30/30 CONV 30/30 Chin MIS 30/30 CONV 30/30 Han MIS 30/15 CONV 30/15 Chotanaphuti MIS 20/20 CONV 20/20 Karachalios MIS 50/50 CONV 50/50 Karpman MIS 20/20 CONV 19/19 Karpman MIS 20/20 CONV 20/20 Juosponis MIS 35/35 CONV 35/35 Varela-Egocheaga MIS 50/50 CONV 50/50

Study

27/93 27/93 24-Jun 27-Mar 24-Jun 27-Mar 28-Feb 28-Feb 17-Mar 16-Apr 19/31 15/35 13-Jul 10-Sep 12-Aug 10-Sep 30-May 30-May

65.4 (43–68) 65.4 (43–68)

67.4 (56–80) 63.4 (47–80)

69 (57–80) 63.4 (47–80)

66 (SD 3.8) 64 (SD 6.4)

68.4 (58–78) 67.5 (56–80)

71.1 (52–78) 70.8 (54–77)

74 (53–85) 73 (64–80)

73 (56–82) 73 (64–80)

72 (SD 5.5) 71.4 (SD 5 .0) 14/36 13/37

18-Feb 19-Feb

76.1 (65–86) 73.9 (62–86)

68.02 (SD 8.1) 70.64 (SD 7.9)

29/11 24/15

Gender (M/F)

67 (48–84) 70 (54–79)

Age (years)

Table 2 Characteristics of the included studies

30.97 (SD 14.2) 30.62 (SD 3.4)

27.95 (SD 3.2) 29.08 (SD 2.7)

28 (23–37) 29 (22–38)

30 (17–56) 29 (22–38)

32 (27–35) 31.5 (28–35)

N/S

26.9 (SD 2.5) 26.4 (SD 2.7)

27.5 (18.6–34.2) 29.4 (22.7–40)

28.5 (22.1–40) 29.4 (22.7–40)

28.1 (19–36) 28.1 (19–36)

25.5 26.1

32 (19–49) 30 (20–40)

BMI (kg/m2)

OA

OA

OA

OA

OA

OA

OA

OA

OA

OA 113 N 5, R 1

OA

OA

Disease

SV MPP

MV MPP

QS MPP

MV MPP

MV MPP

QS MPP

Mini-MPP MPP

QS MPP

MV MPP

QS MPP

Mini-MPP MPP

MV MPP

Approach

N/S

PS PS

CR CR

CR CR

N/S

PS PS

PS PS

PS PS

PS PS

PS PS

PS PS

PS PS

Cruciate

Yes Yes

Not Not

Yes Yes

Yes Yes

Not Not

N/S

Yes Yes

Yes Yes

Yes Yes

Yes Yes

Yes Yes

Yes Yes

Patellae resurfaced

Yes Yes

Yes Yes

Yes Yes

Yes Yes

Yes Yes

Yes Yes

Yes Yes

Yes Yes

Yes Yes

Yes Yes

Yes Yes

Yes Yes

Cemented

NexGen NexGen

PFC Sigma PFC Sigma

NexGen NexGen

NexGen NexGen

Genesis II Genesis II

N/S

NexGen LPS-Flex NexGen LPS-Flex

NexGen LPS NexGen LPS or PFC Sigma

NexGen LPS or PFC Sigma NexGen LPS or PFC Sigma

NexGen LPS NexGen LPS

NexGen LPS-Flex NexGen LPS

Scorpio PS Scorpio PS

Prosthesis

36

3 3

6 6

6 6

23 23

5.5 5.5

28 28

N/S

N/S

21.5 21.5

16 14

3 3

Follow-up (months)

Knee Surg Sports Traumatol Arthrosc

123

123

Size (K/P)

Hernandez-Vaquero MIS 26/26 CONV 36/36 Pan MIS 35/35 CONV 33/33 Wu¨lker MIS 66/66 CONV 68/68 Lu¨ring MIS 30/30 CONV 30/30 Chalidis MIS 50/50 CONV 50/50 Stevens-Lapsey MIS 22/22 CONV 22/22 Guy MIS 40/40 CONV 40/40 Thienpont MIS 150/150 CONV 150/150 Chiang MIS 30/30 CONV 30/30 Kashyap MIS 25/25 CONV 25/25 Dayton MIS (total 44) CONV Pei-Liang MIS 34/34 CONV 34/34

Study

Table 2 continued

2-May 30-Jun 24-Nov 24-Sep 18/48 15/53 N/S

Apr-46 Jun-44 12-Oct 10-Dec N/S

45/105 50/100

27-Mar 27-Mar 15-Oct 16-Sep N/S

27-Jul 27-Jul

62.5 (54–70) 63.2 (50–75)

70.2 (68–71) 70.1 (68–71)

69 (SD 9) 69 (SD 9)

70.1 (45–85) 71.2 (53–81)

64.6 (SD 8.5) 64 (SD 8.4)

70.2 96.1

68 (56–83) 69 (52–84)

69.7 (SD 5.3) 69.8 (SD 5.4)

71 (51–84) 72 (50–82)

N/S

70.5 (56–78) 70.5 (56–78)

Gender (M/F)

70.8 (SD 5.9) 70.5 (SD 6.9)

Age (years)

N/S

N/S

27.4 (23–32) 27.6 (24–34)

28.6 (SD 3.8) 29.6 (SD 3.5)

30.4 (28–36) 29.8 (26–37)

28.2 (SD 3.0) 28.9 (SD 3.8)

30.5 (SD 5.6) 31.3 (SD 5.1)

34.6 (30.9–42.1) 34.2 (30.4–41.8)

31 (SD 6) 32 (SD 6)

29.3 (28.2–30.4) 29.3 (28.1–30.4)

24.8 (19.5–28.6) 24.6 (19.4–28.2)

32.1 (SD 6) 30.8 (SD 3.3)

BMI (kg/m2)

OA 24 Rhe10

OA

N/S

OA

OA

OA

OA

OA

N/S

N/S

OA

OA

Disease

SV MPP

mini-MPP MPP

SV MPP

QS MPP

mini-MPP MPP

SV MPP

mini-MPP MPP

MV MPP

mini-MPP MPP

MV/mini-MMP MPP

SV MPP

MV MPP

Approach

PS PS

PS PS

CR CR

PS PS

PS PS

N/S

PS PS

CR CR

N/S

N/S

PS PS

CR CR

Cruciate

Not Not

Yes Yes

Not Not

Not Not

Yes Yes

N/S

Yes Yes

N/S N/S

N/S N/S

N/S

Not Not

Yes Yes

Patellae resurfaced

Yes yes

Yes Yes

N/S

Yes Yes

Yes Yes

N/S

Yes Yes

Yes Yes

Yes Yes

N/S

N/S

Yes Yes

Cemented

PFC Sigma PFC Sigma

PFC Sigma PFC Sigma

Maxim Maxim

NexGen LPS-Flex NexGen LPS-Flex

N/S N/S

NexGen LPS-Flex NexGen LPS-Flex

PFC Sigma PFC Sigma

Genesis II Genesis II

PFC Sigma PFC Sigma

Genesis II Genesis II

NexGen LPS NexGen LPS

Triathlon Triathlon

Prosthesis

3

3

24

24

32

12

3

24

12

12

18

6

Follow-up (months)

Knee Surg Sports Traumatol Arthrosc

Size (K/P)

18-Sep 18-Sep 28/22 28/4 0/23 0/22 14/31 14/37 0/25 0/25 14/46 15/45

18/19 15/25 14/5 14/4

66.7 (58–77) 68 (58–81)

67 (SD 6) 68 (SD 7)

71.2 (SD 6.5) 69.3 (SD 6.4)

73.8 (55–85) 73.7 (55–86)

69 (55–82) 68 (59–83)

71 (48–80) 70 (52–88)

67 (SD 8) 64 (SD 7)

Gender (M/F)

66.7 (SD 9.6) 66.7 (SD 9.6)

Age (years)

30 (SD 6) 31 (SD 4)

N/S

28 (19–35) 29 (20–35)

N/S

28.4 (SD 5.4) 27.9 (SD 5.1)

27.1 (SD 3) 28.4 (SD 5)

N/S

29.6 (SD 5.6) 29.6 (SD 5.6)

BMI (kg/m2)

OA

OA

OA

OA

N/S

OA

OA

N/S

Disease

SV MMP

MV MPP

SV MPP

QS MPP

SV MPP

MV MPP

QS MPP

MV MPP

Approach

PS PS

N/S

PS PS

PS PS

N/S

PS PS

PS PS

PS PS

Cruciate

Yes yes

N/S

Yes Yes

Yes Yes

Yes Yes

Yes Yes

Yes Yes

Yes Yes

Patellae resurfaced

Yes Yes

N/S

Yes Yes

N/S

N/S

Yes Yes

Yes Yes

Yes Yes

Cemented

PFC Sigma PFC Sigma

PFC Sigma PFC Sigma

NexGen LPS or LPS-Flex NexGen LPS or LPS-Flex

NexGen LPS-Flex NexGen LPS-Flex

N/S N/S

NexGen LPS-Flex NexGen LPS-Flex

N/S N/S

N/S N/S

Prosthesis

2

3

3

N/S

96

12

24

3

Follow-up (months)

MIS mini-invasive group, CONV conventional group, K knee, P patients, M male, F female, OA osteoarthritis, N osteonecrosis, R rheumatoid, MV midvastus, SV subvastus, QS quadriceps sparing, MPP medial parapatellar, CR cruciate retaining, CS cruciate substituting, N/S not specified

Nestor MIS 27/27 CONV 27/27 Yang MIS 25/16 CONV 25/15 Kim 2011 [31] MIS 23/23 CONV 22/22 Pescador MIS 45/45 CONV 51/51 Matsumoto MIS 25/25 CONV 25/25 Boerger MIS 60/60 60/60 CONV Maru MIS 37/37 CONV 40/40 Wegrzyn MIS 18/18 CONV 18/18

Study

Table 2 continued

Knee Surg Sports Traumatol Arthrosc

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Knee Surg Sports Traumatol Arthrosc Table 3 Assessment of risk of bias about the included studies Studies

Adequate randomization method

Allocation concealment

Blinding

Incomplete outcome

Free of selective reporting

Free of other bias

Level of evidence

Kolisek [27]

Yes

Unclear

Unclear

Yes

Unclear

Unclear

Level I

Tashiro [57]

Unclear

Unclear

Unclear

Yes

Unclear

Unclear

Level I

Kim [30]

Yes

Unclear

Yes

Yes

Unclear

Unclear

Level I

Chin [6]

Yes

Yes

Yes

Yes

Unclear

Unclear

Level I

Han [25]

Yes

Unclear

Yes

Yes

Unclear

Unclear

Level I

Chotanaphuti [10]

Unclear

Unclear

Unclear

Yes

Unclear

Unclear

Level I

Karachalios [29] Karpman [33]

Yes Yes

Yes Unclear

Yes Yes

Yes Yes

Unclear Unclear

Unclear Unclear

Level I Level I

Juosponis [26]

Yes

Unclear

Unclear

Yes

Unclear

Unclear

Level I

Varela-Egocheaga [59]

Yes

Unclear

Unclear

Yes

Unclear

Unclear

Level I

Hernandez-Vaquero [24]

Yes

Unclear

Unclear

No

Unclear

Unclear

Level I

Pan [47] Wu¨lker [61]

Yes

Yes

Yes

Yes

Unclear

Unclear

Level I

Yes

Unclear

Yes

No

Unclear

Unclear

Level I

Lu¨ring [36]

Yes

Unclear

Unclear

Yes

Unclear

Unclear

Level I

Chalidis [11]

Yes

Unclear

Unclear

Yes

Unclear

Unclear

Level I

Stevens-Lapsley [52]

Unclear

Yes

Yes

No

Unclear

Unclear

Level I

Guy [19]

Yes

Yes

Yes

Yes

Unclear

Unclear

Level I

Thienpont [55]

Yes

Unclear

Unclear

Yes

Unclear

Unclear

Level II

Chiang [7]

Yes

Unclear

Yes

No

Unclear

Unclear

Level I

Kashyap [34]

Unclear

Unclear

Unclear

Yes

Unclear

Unclear

Level I

Dayton [13]

Yes

Unclear

Yes

Yes

Unclear

Unclear

Level I

Pei-Liang [50] Nestor [45]

Unclear Unclear

Unclear Unclear

Yes Yes

Yes No

Unclear Unclear

Unclear Unclear

Level I Level I

Yang [63]

Yes

Unclear

Yes

Yes

Unclear

Unclear

Level I

Kim [31]

Yes

Unclear

Yes

No

Unclear

Unclear

Level I

Pescador [48]

Unclear

Unclear

Unclear

No

Unclear

Unclear

Level I

Matsumoto [42]

Unclear

Unclear

Yes

Yes

Unclear

Unclear

Level I

Boerger [3]

Unclear

Unclear

Yes

Yes

Unclear

Unclear

Level II

Maru [41]

Unclear

Unclear

Yes

Yes

Unclear

Unclear

Level II

Wegrzyn [62]

Unclear

Unclear

Yes

Yes

Unclear

Unclear

Level I

Low low risk of bias, High high risk of bias, Unclear Unclear risk of bias, RCT randomization control trial, CCT clinical control trial

between the two groups in leg alignment (valgus), femoral anterior/lateral angle, tibia anterior/lateral angle or patellae component angle. The heterogeneity of these outcomes was also high, except for the last one (Table 3).

heterogeneity of these complications was low, so a fixedeffects model was chosen.

Discussion Complications Although there were significant differences in the risks of skin necrosis/delayed wound-healing problems in the MIS group compared with the conventional group (Fig. 6), there were no significant differences with regard to superficial wound infection, deep infection, DVT or other complications, such as fractures, femoral notching, peroneal nerve palsy, stiffness requiring manipulation, polities tendon injury, knee instability and so on. Table 4 shows that the

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The most important finding of the present study was that although there was a significant lengthening of operative and tourniquet times compared with conventional TKA, MIS-TKA had advantages in KSS (objective and total), total blood loss, VAS, ROM, flexion range of motion, flexion 90° day and straight leg rising day, all of which resulted in patients achieving faster recovery. The two groups had the same outcomes for prosthesis radiographic measurements and complications, except for skin necrosis/

Knee Surg Sports Traumatol Arthrosc

Fig. 2 Funnel plot demonstrating minimal publication bias from length of incision outcome

delayed wound-healing problems, which were treated easily and effectively and decreased as surgeons became more experienced and more user-friendly instruments were invented. Therefore, we believe that the minimally invasive approach does offer significant early clinical benefits over the conventional approach in TKA, and this information could be important and valuable to both surgeons and their patients when making shared medical decisions regarding TKA. There is no doubt that TKA is the best method for treating advanced osteoarthritis. It can effectively relieve pain, restore joint function and improve quality of life [18,

46, 53]. However, conventional TKA can cause quadriceps mechanism disturbance, patellar eversion, tibiofemoral joint dislocation, suprapatellar pouch interruption and extensive soft tissue disruption. These issues result in postoperative pain, late rehabilitation, longer hospital stays and even extensor weakness [14, 20, 26, 50], all of which can decrease the satisfaction of both patients and surgeons. Since the concept of minimally invasive surgery has been applied in TKA, it has become increasingly popular among orthopedic surgeons and patients. Increasing numbers of patients ask for an MIS approach after reading about its potential advantages, which include minimal surgical trauma to reduce post-operative pain and accelerate the body’s healing and functional rehabilitation. There is not yet a universally accepted definition for minimally invasive surgery. Most authors have defined a modified MIS approach as a skin incision less than 14 cm, with less invasive arthrotomy, avoidance of patellar eversion, avoidance of tibiofemoral dislocation and hyperflexion, minimal disruption of the extensor mechanism, and less muscle and soft tissue damage [42, 61, 63]. Theoretically, there is less blood loss, less post-operative pain, earlier rehabilitation, and shortened hospital stays and recovery time, as well as lower medical costs. Although there was no difference in post-operative serum levels of various biochemical enzymes, indicating the degree of muscle damage between MIS and the conventional approach [45], many recently published studies have

Fig. 3 Objective KSS forest plot analysis (pre- and post-operation, respectively)

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Knee Surg Sports Traumatol Arthrosc

Fig. 4 Funtional KSS forest plot analysis (pre- and post-operation, respectively)

Fig. 5 Total KSS forest plot analysis (pre- and post-operation, respectively)

shown superior quadriceps strength of the knee postoperatively with the MIS approach [19, 30, 45, 47]. In addition, in control cohort studies performed by Peter et al. [51] and Dabboussi et al. [14], the MIS approach was found to be superior to the conventional approach in terms of KSS, ROM, post-operative pain, blood loss, quadriceps

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strength, straight leg raising and length of stay. Moreover, those better clinical outcomes mentioned above have also been confirmed without any malpositioning or complications in several randomised prospective studies [8, 9, 17, 33, 34, 52, 62], which were considered to offer the best clinical evidence at present. In addition, our meta-analysis

Knee Surg Sports Traumatol Arthrosc

Fig. 6 Delay wound-healing problems forest plot analysis

similarly demonstrated that patients undergoing less invasive approaches had better KSS scores (objective and total), less post-operative pain, less blood loss, better ROM and flexion range of motion, and earlier 90° knee flexion and straight leg raising, all of which reflect these patients achieving earlier rehabilitation, likely increasing their satisfaction compared to that with conventional TKA. In a study by White et al. [60], it was suggested that such earlier rehabilitation might be associated with shorter hospital stays. However, we did not found such a relationship in our study. This difference might be related to differences in pre-operative preparation, nursing programs and discharge criteria at different institutions. In addition, we believe that hospital stay is largely determined by patient factors, such as age, co-morbidities, family status, financial situation, social insurance and so on. We also found no significant difference in Knee Society function scores (functional KSS), similar to a recent study by Bonutti et al. [5], who suggested that the best method for assessing this improved outcome was not functional KSS but muscle strength testing, such as isokinetic/isometric muscle strength, ambulation and straight leg-raising time. Less invasive approaches result in shorter incisions and limited knee arthrotomy, without patellar eversion, dislocation of the tibiofemoral joint or hyperflexion. We believe that this approach should result in less damage to muscle and soft tissue and should keep the posterior capsule and the collaterals intact. It could also reduce blood loss, decreases in haemoglobin and transfusion requirements. The proponents of MIS-TKA often cite the advantage of less blood loss to support its use. Our results showed that although intraoperative blood loss, drainage, estimated blood loss and blood transfused per patient were not significant, the total blood loss and early post-operative decrease in haemoglobin were statistically less in the MIS group, which could also have resulted in earlier rehabilitation for patients. These findings were consistent with the outcomes of other authors’ reports [8], in which the MIS approach also involved less blood loss and earlier rehabilitation.

Due to a smaller incision and limited exposure, it is difficult to achieve bone resection and implant placement. Therefore, intuitive optimisation of a ‘‘mobile window’’ is essential, and more surgical steps are required during the procedure to achieve sufficient visualisation of anatomical landmarks and ascertain accurate resection and placement. These time-consuming procedures result in longer operation and tourniquet times than with the conventional approach. Karpman et al. [33] and Cheng et al. [9] reported that prolonged operation times and tourniquet times could lead to increased tourniquet-associated ischaemia and the potential risk of wound contamination due to significant exposure to the outside environment. In addition, there must be greater tension on the wound margins from stronger retraction, which can cause more abrasion of the skin edges and can increase wound-healing problems. Hernandez-Vaquero et al. [24] observed a greater degree of transitory tumefaction on the edges of the wounds in the MIS group. Similarly, our meta-analysis identified longer operation times and tourniquet times, as well as a higher rate of wound-healing problems in the MIS group versus the conventional group. However, we do not believe that wound-healing problems, which can be treated effectively, constitute sever complications. Furthermore, as we all know, there is a significant learning curve requiring orthopaedic surgeons to finish at least 50 operations independently [35]. As surgeons become increasingly familiar with the less invasive procedures and the special instruments used, the operation time and tourniquet time should shorten. Some authors [4, 10, 26] have confirmed our view, finding no difference in surgical time after surgeons complete the learning curve. Hence, we do not believe that these disadvantages have a severe influence on MIS-TKA; on the contrary, its advantages outweigh these disadvantages. The major concerns about the MIS approach are negative radiological measurement outcomes and high rates of complications because of the limited exposure, as well as the difficult steps of bone resection and implant placement mentioned above. Due to the difficulties induced by limited

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Knee Surg Sports Traumatol Arthrosc Table 4 Meta-analysis results of outcomes, prosthesis measurements and complications following MISTKA, compared to conventional TKA Outcomes

Studies

Knees total

Overall effect MIS

CONV

P value

Heterogeneity

WMD/OR

95 % CI

I2 (%)

P value

Clinical outcomes Objective KSS Pre-operation

8

637

317

320

n.s.

0.58

-4.35, 5.50

83

0.00001

Post-operation

9

607

303

304

0.00001

1.98

0.07, 3.88

60

0.010

Pre-operation

11

1,161

581

580

n.s.

0.02

-2.53, 2.57

69

0.0003

Post-operation Total KSS

12

1,197

599

598

n.s.

1.99

-0.94, 4.92

90

0.00001

Pre-operation

2

200

100

100

n.s.

4.29

-1.28, 9.87

0

Post-operation

5

358

174

184

0.0001

6.45

3.20, 9.69

40

0.15

5

368

201

167

0.0001

-1.22

-1.83, -0.61

77

0.002

Operation time (min)

18

1,532

778

754

0.00001

11.19

6.48, 15.90

94

0.00001

Tourniquet time (min)

12

1,215

620

595

0.001

8.94

3.45, 14.42

94

0.00001

Incision length (cm)

14

1,133

584

549

0.00001

-4.74

-6.36, -3.12

99

0.00001

Hospital stay (day)

10

1,145

563

582

n.s.

-0.93

-2.31, 0.45

98

Intraoperative blood loss (ml)

5

573

286

287

n.s.

0.43

-18.46, 19.32

0

Drainage (ml)

7

706

348

358

n.s.

-15.97

-165.64, 133.70

94

0.00001

Estimate blood loss (ml)

3

418

230

188

n.s.

-24.00

1,462.77, 229.99

97

0.00001

Total blood (ml)

6

451

227

224

0.00001

-81.21

-95.73, -66.68

45

0.11

Drop of haemoglobin (g/dl)

6

698

341

357

n.s.

-0.68

-1.30, -0.06

93

0.00001

Blood transfusion per patient (unit)

4

318

180

138

n.s.

0.34

-0.29, 0.96

90

0.00001

ROM Extension range of motion

6 6

470 616

235 300

235 316

0.0001 n.s.

2.49 0.00

1.25, 3.72 -0.72, 0.73

70 51

0.005 0.07

Flexion range of motion

11

1,008

517

491

0.0001

5.20

2.88, 7.51

74

0.0001

90° Knee flexion (day)

5

534

265

269

0.0001

-2.18

-3.22, -1.14

97

0.00001

Straight leg raising (day)

8

822

410

412

0.00001

-1.87

-2.68, -1.06

97

0.00001

Functional KSS

VAS

0.59

0.00001 0.67

Prosthesis measurements Bad Leg alignment (valgus)

6

646

317

329

n.s.

0.49

-0.02, 1.01

71

0.004

a angle

10

928

463

465

n.s.

-0.59

-3.17, 2.00

99

0.00001

B angle

10

928

463

465

n.s.

0.13

-0.47, 0.74

85

0.00001

C angle

7

563

281

282

n.s.

-0.53

-1.17, 0.10

60

0.02 0.0001

D angle Patellar component angle

8

534

267

267

n.s.

-0.39

-0.99, 0.22

78

2

190

145

145

n.s.

0.72

-0.31, 1.75

5

0.31 1.00

Complications Skin necrosis/delay wound healing Superficial wound infection Deep infection DVT Other complications

7

611

305

306

0.03

2.95

1.09, 7.93

0

10

901

460

441

n.s.

0.77

0.36, 1.62

0

0.71

4

429

225

204

n.s.

1.37

0.35, 5.37

0

0.77

10 9

868 876

434 437

434 439

n.s. n.s.

0.70 1.28

0.33, 1.48 0.70, 2.33

0 0

0.77 0.47

MIS minimally invasive surgery, CONV conventional, WMD weighted mean difference, OR odds ratio, CI confidence interval, KSS knee society score, VAS visual analogue scale, ROM range of motion, DVT deep venous thrombosim, n.s. non-significant

working space, MIS-TKA could lead to ligament imbalance [42], which results in knee instability. Misalignment can lead to abnormal patellar tracking, increased polyethylene wear, early loosening and poor functional outcomes [11, 12]. In a study by Goodman et al. [17], there were

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more cement voids and more retained cement debris in the minimally invasive cohort, leading to increased osteolysis and third body polyethylene wear. Michael et al. [41] also suggested that this decreased exposure could result in cement voids around the femoral component anterior

Knee Surg Sports Traumatol Arthrosc

flange and posterior condyles, which could cause premature femoral component loosening. However, our metaanalysis found no significant differences in implant position or complications, except wound-healing problems, and our results were consistent with the findings of previously published meta-analyses [9]. Smith et al. [53] conducted a meta-analysis, finding no differences in component position or complications. Alcelik et al. [2] found higher intraoperative complications, and Gandhi et al. [20] found a higher post-operative complications rate in the MIS group. However, only 17 and 9 studies were included in their research, respectively, far fewer than in our present study of 30 RCTs. Without question, our findings were more reliable. Many studies have proved that computerassisted navigation systems do improve the mechanical leg axis or component orientation in TKA [10, 12, 15, 36]. The role of computer navigation in complementing these minimally invasive techniques requires further study. The limitations of this meta-analysis are as follows. Only studies published in English were included, which might have caused language bias. Most of the outcomes showed significant heterogeneity among the studies included. This heterogeneity might have resulted from a difference in types of MIS approaches, less invasive instruments, implant selection and the patients’ demographics. In addition, most of the trials focused on shortterm outcomes, which might have been insufficient for comparing differences in medium- and long-term outcomes between the two groups. However, our meta-analysis had several advantages. First, we conducted a thorough literature search of RCTs or qRCTs (Level I or II) and finally included 30 studies. Second, the funnel plots for pooled estimates were significantly symmetrical, indicating no publication bias. Third, a total of 32 statistical indicators were selected for this meta-analysis to perform comprehensive and systematic assessments of the safety and efficiency of MIS-TKA. Above all, the theory that patients who underwent MIS-TKA would achieve better outcomes and faster rehabilitation was proved without any malpositioning or severe complications. The results of this meta-analysis are consistent with those of two other meta-analyses [12, 40], suggesting that patients who underwent MIS-TKA had better outcomes and faster recovery, without negative radiographic measurements or severe complications. Hence, MIS-TKA was recommended for clinical orthopaedic surgeons based on this most current evidence. There are various MIS-TKA approaches, including MV, SV, QS and mini-MPP, but we have not yet found any systematic reviews or meta-analyses comparing two different MIS approaches. Niki et al. [43] suggested that lateral MIS-TKA achieved comparable or superior results to medial MIS-TKA. Another study, published by Lee et al. [37], showed that navigation-

assisted MV and navigation-assisted mini-MPP resulted in similar outcomes. However, they recommend the miniMPP approach over the MV approach because it is more familiar to surgeons and is easier to convert to the conventional approach when necessary. Thus, we suggest that the choice of MIS approach should depend on the surgeon’s experience and patient’s characteristics.

Conclusion In conclusion, our meta-analysis of currently available evidence suggested that there are advantages of MIS-TKA over conventional TKA, in terms of earlier rehabilitation and no malpositioning or severe complications. Even if the risk of wound-healing problems was greater in the MIS group, these complications could not only be treated easily and effectively, but they would also decrease as surgeons become more experienced and more user-friendly instruments are invented. However, potential benefits regarding medium- and long-term outcomes will require larger, multicentre and well-conducted RCTs to confirm. Acknowledgments This research was funded by the China Health Ministry Program (201302007). No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article.

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