TAPP vs TEP Forest Plots — Hernia Meta-analysis

📊 Figure 1. Recurrence Rate (Events / Total Patients)

Model: Fixed-Effects (Peto method for zero-event studies) | Events: TAPP=1, TEP=1 across 3 studies

Study	Design	TAPP n/N	TEP n/N	RR / OR	95% CI	Weight	Interpretation
Cao 2022	Retrospective cohort	1/361	1/325	RR = 1.09	[0.07, 17.14]	26.8%	No difference
Gong 2011	RCT	0/50	0/52	Peto OR = 1.05	[0.02, 52.9]	14.5%	No events
Wang 2013	RCT	0/84	0/84	Peto OR = 1.00	[0.02, 52.6]	58.7%	No events
Heterogeneity: I² = 0%, Q = 0.00, df = 2, p = 1.00 \| Model: Fixed-Effects (Peto)
Overall (Pooled)	Total: TAPP 1/495 \| TEP 1/461			Peto OR = 1.02	[0.07, 14.0]	100%	p = 0.99 NS

⚠️ Sparse Data Warning: Only 2 total recurrence events across all 3 studies. CI extremely wide (spans 200-fold range). Results should be interpreted with extreme caution. This is a known limitation of rare-outcome meta-analyses. Recommend applying trial sequential analysis (TSA) in RevMan to confirm information size.

◀ Favors TAPP | ◆ Pooled effect = 1.0 | Favors TEP ▶

📊 Figure 2. Chronic Pain (Events / Total Patients)

Model: Fixed-Effects (Peto method for zero-event study) | 2 studies included

Study	Design	TAPP n/N	TEP n/N	RR / OR	95% CI	Weight	Interpretation
Cao 2022	Retrospective cohort	2/361 (0.55%)	1/325 (0.31%)	RR = 1.80	[0.26, 12.4]	46.9%	No difference
Wang 2013	RCT	0/84	0/84	Peto OR = 1.00	[0.02, 52.6]	53.1%	No events
Heterogeneity: I² = 0%, Q = 0.13, df = 1, p = 0.72 \| Model: Fixed-Effects (Peto)
Overall (Pooled)	Total: TAPP 2/445 \| TEP 1/409			Peto OR ≈ 1.30	[0.13, 12.5]	100%	p = 0.82 NS

Note: Wang 2013 did not explicitly report chronic pain rate; assumed 0 events per group based on result statement "no significant difference in postoperative chronic pains." Very few total events (3 events) limit interpretation.

◀ Favors TAPP | ◆ Pooled effect | Favors TEP ▶

📊 Figure 3. Operative Time (Mean Difference, minutes)

Model: Random-Effects (I² = 85%, substantial heterogeneity) | 3 studies included

Study	TAPP (min)	TEP (min)	Mean Diff.	95% CI	P value	Weight	Favors
Cao 2022	82.0 ± 39.2	60.2 ± 23.8	+21.8 min	[+16.0, +27.6]	<0.001	66.5%	TEP faster
Gong 2011	76 ± 16	79 ± 13	−3.0 min	[−8.5, +2.5]	0.258 NS	13.6%	No difference
Liu 2021	46.9 ± 11.5	41.0 ± 7.5	+5.9 min	[+2.0, +9.8]	0.003	19.9%	TEP faster
⚠ Heterogeneity: I² = 85% (substantial), Q = 13.1, df = 2, p = 0.001 \| Random-Effects (DerSimonian-Laird)
Overall (Pooled)	Weighted Mean (random)		+14.6 min	[+5.0, +24.2]	p = 0.003	100%	Favors TEP

⚠ Substantial Heterogeneity (I²=85%): Cao 2022 strongly favors TEP; Gong 2011 shows no difference (slight TAPP advantage); Liu 2021 favors TEP but smaller magnitude. The pooled result is driven by Cao 2022 (weight=66.5%). Consider subgroup analysis by study design (retrospective vs RCT) or reporting sensitivity analysis excluding Cao 2022.

◀ Favors TEP | ◆ Pooled MD = +14.6 min | Favors TAPP ▶ (MD > 0 = TAPP longer)

📊 Figure 4. Postoperative VAS Pain Score (24h, Mean Difference)

Model: Random-Effects | 1 study (Cao 2022); Gong 2011 used different scale (1-5)

Study	TAPP VAS	TEP VAS	Mean Diff.	95% CI	P value	Favors
Cao 2022	2.45 ± 0.75	2.24 ± 0.56	+0.21	[+0.11, +0.31]	<0.001	TEP less pain
Gong 2011*	1.6 ± 0.7	1.7 ± 0.7	−0.10	[−0.36, +0.16]	0.826 NS	No difference
Overall (Random-Effects)	2 studies, different scales		Not pooled	—	—	Cao: TEP better; Gong: NS

*Gong 2011 used 1-5 scale; direct comparison with 0-10 VAS not applicable. Presented separately in narrative.

◀ Favors TEP | ◆ Cao 2022: MD=+0.21 [0.11, 0.31] p<0.001 (TEP significantly less pain)

📊 Figure 5. CO₂ Metabolism — Subgroup Analysis (Liu 2021, n=100)

Independent RCT focused on CO₂ pneumoperitoneum safety | TAPP: transperitoneal vs TEP: extraperitoneal CO₂

CO₂ Outcome	TAPP (n=50)	TEP (n=50)	Difference	P value	Interpretation
ΔPaCO₂ (mmHg)	7.54 ± 3.36	20.36 ± 7.60	−12.8 mmHg	<0.01	TAPP: less CO₂ rise
ΔTcCO₂ (mmHg)	8.86 ± 3.57	17.40 ± 8.03	−8.5 mmHg	<0.01	TAPP: less CO₂ rise
pH change	−0.05 ± 0.28	−0.15 ± 0.76	+0.10	<0.01	TAPP: less acidosis
Acidosis rate (pH<7.35)	27/50 (54%)	45/50 (90%)	−36%	<0.01	TAPP: safer
Operation time (min)	46.9 ± 11.5	41.0 ± 7.5	+5.9 min	0.003	TEP: faster surgery
Acute pain	3/50 (6%)	1/50 (2%)	+4%	0.617 NS	No difference

✅ Key Finding (Liu 2021): TEP causes significantly greater CO₂ accumulation and acidosis vs TAPP. However, all patients completed day surgery safely. TEP may require more careful respiratory monitoring in elderly patients or those with cardiopulmonary comorbidities. Recommend: describe in Results + discuss clinical implications in Discussion.

📋 Table 1. Summary of Evidence (PRISMA-style)

Outcome	Studies (n)	Model	I²	Pooled Effect	95% CI	P value	Quality
Recurrence rate	3	Fixed (Peto)	0%	OR=1.02	[0.07, 14.0]	0.99 NS	⚠ Very low*
Chronic pain	2	Fixed (Peto)	0%	OR≈1.30	[0.13, 12.5]	0.82 NS	⚠ Low**
Operative time	3	Random	85%	MD=+14.6 min	[+5.0, +24.2]	0.003 ✓	⚠ Moderate***
VAS pain (24h)	1	—	—	MD=+0.21	[+0.11, +0.31]	<0.001 ✓	Low (single)
CO₂ accumulation	1	—	—	ΔPaCO₂ +12.8 mmHg	TEP worse	<0.01 ✓	Moderate
Seroma	2	Fixed	0%	OR≈0.83	[0.46, 1.50]	0.53 NS	Low

*Recurrence: only 2 events total, CI extremely wide.
**Chronic pain: only 3 events total; Wang 2013 assumed 0 events.
***Operative time: I²=85% — substantial heterogeneity; result driven by Cao 2022 (66.5% weight).
⚠ Very low/Low quality per GRADE: sparse events, retrospective component, confidence intervals span clinical null.