Comparison of the quadriceps-sparing and subvastus approaches versus the standard parapatellar approach in total knee arthroplasty: a meta-analysis of randomized controlled trials

The studies were included if they were randomized controlled trials (RCTs) comparing the subvastus or quadriceps-sparing approach with the standard parapatellar approach in TKA. Case report, cohort study, quasi-RCT and non-RCT were excluded in this study not considered for inclusion. The included participants should be adult patients who underwent the primary TKA. The extracted outcomes included: KSS and VAS, ROM, lateral retinacular release, straight leg raise, blood loss, operative time, hospital stay and postoperative complications (wound infection, deep vein thrombosis and total complications).

The databases of PubMed, the Cochrane library, EMBASE, Chinese Biomedical Database and ISI Web of Knowledge were searched for the relevant studies from January 1982 to July 2014. The following search strategies were used for literature search: #1, “Arthroplasty, Replacement, Knee” [Mesh]; #2, knee arthroplasty; #3. knee replacement, #4. medial parapatellar; #5. standard OR conventional approach; # 6. subvastus; #7. mini-subvastus; #8. quadriceps-sparing; #9. quad-sparing; #10. quadriceps sparing; #11. #1 OR #2 OR # 3 OR; # 12. #4 OR # 5; # 13. #6 OR #7 OR #8 OR # 9 OR #10; # 11 AND # 12 AND # 13. In addition, the lists of references and Google scholar were also searched for other potential RCTs.

Two authors independently screened the titles and abstracts. If the studies possibly met the inclusion criteria, the full text was retrieved for the final decision. Data extraction was completed by two blind authors. If insufficient data was reported, efforts were made to contact the authors for the additional information. The methodological quality was evaluated using the following items recommended by the Cochrane Collaboration [ 28]: randomization; allocation concealment; blinding of participants; blinding of outcome assessors; incomplete outcome data; selective reporting; and other bias. Each item was classified into “Yes”, “No”, or “Unclear”: “Yes” - low risk of bias, “No” - high risk of bias, “Unclear” - lack of information or unknown risk of bias. Any disagreement in assessments was resolved by discussing with a third author.

The software of Review Manager 5.2.7 [ 28] was used to perform meta-analysis. Odds ratios (OR) and 95 % confidence interval (95 % CI) was calculated to test the overall effects for dichotomous outcomes, and mean difference (MD) and 95 % CI were used for continuous outcomes. Heterogeneity was tested using I ² statistic ( I ²  > 50 % indicating significant heterogeneity, and I ²  ≤ 50 % indicating no significant heterogeneity) [ 29]. If significant heterogeneity ( I ²  > 50 %) was found in the meta-analysis, random-effect model was used, otherwise, using fix-effect model. Subgroup analysis was performed for outcomes with different time points.

The characteristics of the included RCTs were summarized in Table  1. A total of 1633 TKAs were performed in 1578 adult patients (male: 31.8 %; female: 68.2 %). The mean age ranged from 62.5–73.8, the mean BMI ranged from 24.6–30.97, and the follow-up duration ranged from 13 days to 3 years. The patients’ parameters (age, BMI, patient/TKA number, preoperative knee function) were reported similar between groups.

Regarding the methodological quality, all the included studies were randomized using various methods: eight (42.1 %) used the computer-generated random number and seven (36.8 %) used random number table. Allocation concealment was reported in 10 studies (52.6 %); the method of blind was used in 16 studies (84.2 %) (Table 2).

Meta-analysis showed that, when compared with the standard approach, the quadriceps-sparing approach significantly improved KSS at postoperative 3 months (MD = 2.88, 95 % CI [1.17, 4.60], P = 0.001) and 2 years (MD = 1.75, 95 % CI [0.45, 3.06], p = 0.08), and decreased VAS at postoperative 1 week (MD = −0.69, 95 % CI [−1.10, −0.29], P < 0.05). There were no differences in KSS at postoperative 4–6 weeks (MD = −0.91, 95 % CI [−3.08, 1.25], P = 0.41) and VAS at postoperative 4–6 weeks (MD = 0.14, 95 % CI [−0.29, 0.58], P = 0.52) between both groups. No significant heterogeneity was found in the meta-analysis of KSS and VAS ( I ²  ≤ 50 %) (Table  3).

Meta-analysis showed that the quadriceps-sparing and the standard parapatellar approaches had similar results in total complication (MD = 1.00, 95 % CI [0.21, 4.72], P = 0.49), wound infection (MD = 1.21, 95 % CI [0.29, 5.05], P = 0.80), deep vein thrombosis (MD = 0.65, 95 % CI [0.13, 3.31], P = 0.60), ROM from 1 week (MD = 5.79, 95 % CI [−6.26, 17.85], P = 0.35 %)–24 months (MD = −0.18, 95 % CI [−1.91, 1.56], P = 0.84), blood loss (MD = −57.00, 95 % CI [−213.73, 99.73]) and hospital stay (MD = −2.00, 95 % CI [−3.19, −0.81], P = 0.10). However, the quadriceps-sparing approach significantly increased operative time when compared with the standard parapatellar approach (MD = 18.22, 95 % CI [9.92, 26.51], P < 0.05). The heterogeneity was significant in ROM, operative time and hospital stay ( I ²  > 50 %) (Table  3).

Ten RCTs [ 12, 16, 18, 20, 21, 23– 26, 30] comparing the subvastus with the standard parapatellar approach were included for meta-analysis (Table  4).

Meta-analysis showed that the subvastus approach significantly reduced VAS score at postoperative 12 months (MD = −0.14, 95 % CI [−0.28, −0.01], P = 0.04) compared with the standard approach. There were no differences in KSS from postoperative 4 weeks (MD = −1.86, 95 % CI [−8.59, 4.88], P = 0.59)–12 months (MD = 3.25, 95 % CI [−0.60, 7.10]), and VAS from postoperative 1 week (MD = −0.56, 95 % CI [−1.42, 0.29], P = 0.19)–3 months (MD = −0.03, 95 % CI [−0.32, 0.27], P = 0.87) between the standard and subvastus groups (Table  3). Significant heterogeneity was found in KSS (4–6 weeks) and VAS (1 week–3 months) ( I ²  > 50 %).

Meta-analysis showed that the subvastus approach had significant advantages over the standard parapatellar approach in ROM at postoperative 1 week (MD = 3.96, 95 % CI [3.20, 4.72], P < 0.05) and 12 months (MD = 6.80, 95 % CI [0.94, 12.66], P < 0.05), straight leg raise (OR = −2.77, 95 % CI [−4.07, −1.47], P =0.02) and lateral retinacular release (OR = 0.34, 95 % CI [0.14, 0.79], P = 0.01). The two groups showed similar results in ROM at postoperative 4–6 weeks (MD = 3.79, 95 % CI [−0.44, 8.03], P = 0.08) and 3 months (MD = 3.24, 95 % CI [−0.90, 7.38], P = 0.12), total complication (MD = 0.81, 95 % CI [0.44, 1.49], P = 0.49), wound infection (MD = 1.11, 95 % CI [0.40, 3.08]) and blood loss (MD = −100.76, 95 % CI [−223.42, 21.89], P = 0.11) (Table  4).

Two earlier systematic review or meta-analysis [ 1, 40] had compared the clinical efficiency between the subvastus and the standard aprraoch in TKA. However, the authors included quasi-RCT, which reduced the level of the evidence. Additionally, the published meta-analysis only investigated the short-term outcomes. The strengthens of this study included that: (1) the results of our meta-analysis were based on RCTs, which provided high-level evidence for clinical practice; (2) our study first reported a meta-analysis comparing the quadriceps-sparing with the standard approach.

Several limitations should be noted in our study. (1). Although some outcomes were reported in the full text, data was not sufficiently provided to perform meta-analysis. (2) Although efforts were made to minimize the heterogeneity by conducting subgroup analysis, for example, using random-effect model and setting strict inclusion criteria, the heterogeneity among the included studies was still significant in several meta-analyses, which might decrease the reliability of the conclusion. Readers should be cautious for the results when heterogeneity existed. (3) Although all the included RCTs used randomization, some RCTs did not used allocation concealment and blinding to the patients and surgeons, which also might lead to high risks of selection and detection bias; besides, the most RCTs included were performed in single center with small samples, therefore, multi-center RCTs with large-samples are still lacking to verify our conclusion. (4) For a superior approach in TKA, it should include the following criteria: simple technique, sufficient visibility, less complication rates and improve clinical outcomes. Obviously, the quadriceps-sparing or subvastus approach did not involve all the criteria above. Therefore, TKA surgeons should get a balanced perspective for the two approaches.