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Mini-incision vs. standard incision for THA: a surgical outcome comparison

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Mini-incision vs. standard incision for THA: a surgical outcome comparison

Vol: 3| Issue: 2| Number:55| ISSN#: 2564-2537
Study Type:Meta analysis
OE Level Evidence:1
Journal Level of Evidence:N/A

Mini-Incision versus Standard Incision Total Hip Arthroplasty Regarding Surgical Outcomes: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

PLoS One. 2013 Nov 12;8(11)

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Fourteen prospective randomized control trials in which patients received total hip arthroplasty through mini-incision (MI) or standard incision (SI) were pooled to determine if mini-incision THA was superior to standard incision THA in general, or through a specific surgical approach. The results of the study indicated that mini-incision THA reduced total blood loss and length of hospital stay. Subgroup analysis of the two treatment methods by surgical approach demonstrated that posterior mini-incision THA led to perioperative advantages in surgical duration, blood loss, and hospital stay. A lateral approach MI THA was also noted to be significantly shorter in surgical duration compared to SI THA. No significant differences in pain medication dose, functional outcomes, radiographic outcomes, or complications were found.

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Risk of Bias


Reporting Criteria


Fragility Index


Were the search methods used to find evidence (original research) on the primary question or questions stated?

Was the search for evidence reasonably comprehensive?

Were the criteria used for deciding which studies to include in the overview reported?

Was the bias in the selection of studies avoided?

Were the criteria used for assessing the validity of the included studies reported?

Was the validity of all of the studies referred to in the text assessed with use of appropriate criteria (either in selecting the studies for inclusion or in analyzing the studies that were cited)?

Were the methods used to combine the findings of the relevant studies (to reach a conclusion) reported?

Were the findings of the relevant studies combined appropriately relative to the primary question that the overview addresses?

Were the conclusions made by the author or authors supported by the data and or analysis reported in the overview?

How would you rate the scientific quality of this evidence?

Yes = 1

Uncertain = 0.5

Not Relevant = 0

No = 0

The Reporting Criteria Assessment evaluates the transparency with which authors report the methodological and trial characteristics of the trial within the publication. The assessment is divided into five categories which are presented below.




Accessing Data


Analysing Data





Detsky AS, Naylor CD, O'Rourke K, McGeer AJ, L'Abbé KA. J Clin Epidemiol. 1992;45:255-65

The Fragility Index is a tool that aids in the interpretation of significant findings, providing a measure of strength for a result. The Fragility Index represents the number of consecutive events that need to be added to a dichotomous outcome to make the finding no longer significant. A small number represents a weaker finding and a large number represents a stronger finding.

Why was this study needed now?

The introduction of mini-incision (MI) (defined as 10cm or smaller for the purposes of this study) to total hip arthroplasty remains controversial despite a large amount of existing studies addressing the topic. MI THA may lead to less soft tissue trauma, reduced blood loss, and fewer blood transfusions, along with less postoperative pain after surgery. However, while there are these benefits with the MI treatment, certain risks have been suggested to be associated with its use, such as increased complications due to component malpositioning. Studies comparing MI THA to standard incision (SI) THA have provided varying results on the two treatment methods, possibly due to a lack of exclusion or separation of surgical approach methods. The goal of this meta-analysis was to determine if MI THA was superior to SI THA in general, or through a specific surgical approach.

What was the principal research question?

Is mini-incision THA superior to standard incision THA in general, or through a specific surgical approach?

Study Characteristics -
Data Source:
A search using the internet databases PubMed, Cochrane Library, EMBASE, BIOSIS, and Ovid for articles published up to May 2013 was completed. The reference lists of identified studies were also manually checked to identify other eligible trials.
Index Terms:
("minimally invasive" or "less invasive" or "minimal incision" or "mini-incision" or "MIS") and "hip" and ("replacement" or "arthroplasty" or "THR" or "THA").
Study Selection:
Studies included were 14 prospective randomized control trials that contained patients receiving THA in mini-incision (MI) and standard incision (SI) groups, who were demographically similar and had no statistically significant differences with respect to the variables of age, gender, and BMI. MI THA completed through posterior, posterolateral, lateral, or anterolateral approaches were the only approaches accepted. Comparison with standard or conventional THA was mandatory. The studies also had to contain 1 or more of the following outcomes: surgical outcomes, functional outcomes, radiological outcomes, or complications. Trials were excluded if they were abstracts, did not report outcomes of interest, or used computer navigated treatments. Two reviewers independently assessed each RCT, with disagreements resolved by discussion and consensus.
Data Extraction:
Outcome data from the included studies was extracted independently by two authors, disagreements were resolved by discussion and consensus.
Data Synthesis:
Standardized mean differences with 95% CIs for continues outcome and differences were expressed as risk differences (RDs) with 95% CIs for any dichotomous outcomes. MD and SD were calculated by the Hozo method for any data published as a median. Heterogeneity was determined using the I-squared statistic. Studies with an I-squared statistic of 25-50% were considered to have low heterogeneity, 50-75% moderate heterogeneity, and >75% as high heterogeneity. A fixed effects model was used for studies with low heterogeneity and a random effects model for those with >50% heterogeneity. All pooling was performed using RevMan 5.1 software. A p value <.05 was considered statistically significant.

What were the important findings?

  • Eleven studies (n=1039) were included in a meta-analysis of surgical duration. Overall, no significant difference was found between the MI and SI THA regarding surgical duration (WMD -2.32 min [95%CI -6.98, 2.33]; p=0.33, I-squared=90%). Based on surgical approach, significantly shorter surgical durations were noted for MI THA using a posterior approach (WMD, -5.56 min [95%CI -8.45. -2.67] p<0.001; I-squared=0%) or lateral approach (WMD -15.56 min [95%CI -20.91, -10.21]; p<0.001; I-squared=0%). The difference between groups was not significant for postero- or anterolateral approaches (p>0.05)
  • Eleven trials (n=556) were suitable for meta-analysis for total blood loss. Overall, total blood loss was significantly lower in the MI group compared to SI THA (WMD -111.51 mL [95%CI -201.83, -21.18]; p=0.02; I-squared= 84%). Based on approach subgroups, the only approach which displayed statistically significantly lower total blood loss with MI THA was a posterior approach (WMD -54.46 mL [95%CI -107.20, -1.73]; p=0.04; I-squared= 0%).
  • Six trials (n=528) were pooled to analyze doses of pain medication. No significant difference regarding pain medication doses between treatment arms were found (SMD -0.14 [95%CI -0.47, 0.19]; p=0.40; I-squared= 68%). Pooling was only possible for the posterior approach subgroup, which also displayed no significant differences between MI and SI THA (SMD -0.08 [95%CI -0.40, 0.24]; p=0.61, I-squared 42%)
  • Results from 5 studies (n=522) indicated a significantly reduced length of hospital stay with MI THA when compared to patients receiving SI THA (WMD -0.38 days [95%CI -0.67, -0.08]; p=0.01). Subgroup analysis of two RCTs revealed a significant difference between groups for posterior approach in terms of hospital stay (WMD -0.40 days [95% CI -0.74, -0.06]; p=0.002).
  • Ten trials (n=917) were pooled to compare functional outcome in the two treatment arms. No significant difference between the groups was found (WMD 0.72 [95%CI -0.79 to 2.23]; p=0.35). Subgroup analyses based on surgical approaches also revealed no significant difference.
  • No significant differences between MI and SI groups were found when looking at outliers of acetabular cup abduction (5 trials; p=0.56), outliers of cup anteversion (2 trials; p=0.69), outliers of femoral prosthesis position (9 trials; p=0.27), femoral offset (3 trials; p=0.15), or leg length discrepancy (4 trials; p=0.75). Results from one study indicated a significant difference between posterolateral MI and SI subgroups regarding femoral offset (WMD 3.00mm [95%CI 0.40, 5.60]; p=0.02).
  • No significant difference between groups regarding infection (p=0.25), dislocation (p=0.60), nerve injury (p=0.24) proximal femoral fracture (p=0.61), DVT (p=0.25) component loosening (p=0.38), revision (p=0.40) or heterotopic ossification (p=0.58) were found.

What should I remember most?

Results of the meta-analysis indicated that mini-incision THA reduced total blood loss and length of hospital stay, particularly when a posterior approach was used. Mini-incision THA using a lateral surgical approach also appeared to significantly reduce operative time. No significant differences in pain medication dose, functional outcomes, radiographic outcomes, or complications were found.

How will this affect the care of my patients?

While no definite conclusion can be made on the superiority of mini-incision THA to standard incision THA, the evidence presented suggests that posterior mini-incision THA may reduce surgical duration, blood loss, and hospital stay. The follow-up durations of the included studies ranged from 1.5 months to 5 years; thus subsequent long-term analyses of mini-incision versus standard incision THA are warranted to determine the efficacy of these treatments over an extended period of time. More sufficiently-powered trials are also needed to gain a better perspective of the potential differences between these treatment methods.

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