Surgical site soft tissue thickness as a predictor of complications following arthroplasty

Table 1 Soft-tissue thickness in total knee arthroplasty

Ref.	Type of study	n	Mean BMI	Mean age	Indications for surgery	Approach	STT measurement definition	Outcomes studied	Results	Inter-rater reliabilities	Challenges
Wagner et al[23]	Retrospective	528	35.5	57.8	Osteoarthritis	Not specified	PFTR measured from radiographs	SSI, BMI, PFTR	Significant association between higher PFTR and increased risk of SSI	Strong agreement (r = 0.952; P < 0.001)	Small number of infections, limited generalizability to non-obese populations
Watts et al[24]	Case-control	116	44.8	62.7	Osteoarthritis	Not specified	PPT and PTT measured from radiographs	SSI, reoperation risk, PPT, PTT	Higher PPT and PTT associated with increased risk of reoperation	Excellent (Pearson coefficients: PPT 095, PTT 098)	Retrospective design, small sample size, potential unaccounted variables
Vahedi et al[22]	Case-control	824	32.5	63.9	Osteoarthritis	Not specified	Medial STT at joint line on AP radiograph; Anterior STT 8 cm above joint line on lateral radiograph	PJI, STT, BMI	Higher medial and anterior STT associated with increased risk of PJI	Excellent (ICC: Anterior STT 094, medial STT 096)	Retrospective design, potential unmeasured confounders, variability in surgical techniques
Shearer et al[28]	Retrospective	4745	32.1	68.3	Osteoarthritis	Not specified	PPT; KAI	PJI, surgical duration	BMI > 35 was strongly associated with PJI; local adipose measures were not significant	Excellent for KAI (inter: 0.94, intra: 0.99), moderate for PPT (inter: 0.75, intra: 0.99)	Variations in measurement techniques, low incidence of PJI, retrospective design
Yu et al[25]	Retrospective	376	30.9	66.2	Osteoarthritis	Not specified	PASTI using femoral and tibial measurements	Minor and major wound complications	High PASTI (> 3.0) associated with more minor complications (tibial OR: 3.89, femoral OR: 2.09); no significant difference in major complications	Excellent for both femoral and tibial PASTI (inter: 0.980/0.984, intra: 0.985/0.967)	Retrospective design, accuracy dependent on standardized X-ray technique, limited by proper lateral radiographs only
Gupta and Kejriwal[26]	Retrospective	494	30.6	71.3	Osteoarthritis	Medial parapatellar	PPT and PTT	Superficial wound complications	PTT ≥ 12 mm associated with lower risk of superficial wound complications (RR: 0.54); PPT not significantly associated	Measurement reliabilities not evaluated in this study, but previous study by Watts et al. noted high reliabilities (PPT: Intra 095, inter 0.92; PTT: Intra 098, inter 0.96)	Retrospective design, non-standardized surgical techniques, dressing types, and rehabilitation protocols, small sample size, no comparison group for BMI ≥ 40 kg/m2
Secrist et al[27]	Retrospective	453	32.9	66	Osteoarthritis	Not specified	LEG ratio: Width of soft tissue envelope divided by bone width on lateral radiographs	90-day postoperative complications	No significant difference in LEG ratio between patients with/without complications; LEG ratio had no utility in predicting complications	Not specified	Retrospective design, novel measurement method not validated in previous studies, did not analyze intraoperative variables, limited to short-term complications

PFTR: Prepatellar fat thickness ratio; SSI: Surgical site infection; BMI: Body mass index; PTT: Pretubercular thickness; PPT: Prepatellar thickness; ICC: Intra-class correlation; PJI: Periprosthetic joint infection; STT: Soft-tissue thickness; KAI: Knee Adipose Index; PASTI: Preoperative Anterior Soft-Tissue Index; OR: Odds ratio; RR: Relative risk; LEG: Lower extremity girth.

Table 2 Soft-tissue thickness in total hip arthroplasty

Ref.	Type of study	Approach	STT measurement definition	Inter-rater and inter-observer reliabilities	Outcomes studied	Results
Bell et al[38]	Retrospective case-control analysis	Posterolateral	Skin tosourcil distance; tip of the GT to skin; lateral prominence of GT to skin	Inter-rater reliabilities: Skin to sourcil: 0.966; Tip of GT to skin: 0.958; lateral prominence of the GT to skin: 0.981	Compare interobserver reliability; peritrochanteric fat thickness association with increased wound complications and infection in early post-operative period	No association between peritrochanteric fat and infections/wound complications in primary THA patients
Hohmann et al[29]	Retrospective review	Lateral	Length from bilateral ASISs to the skin surface at a right angle to each ASIS as ASIS-thickness; Length from PS to skin surface at a right angle to the PS as PS-thickness	NR	Examine the relationship between postoperative acetabular cup angles and anterior pelvic STT overlying the anatomical landmarks; investigate the difference between obese patients and normal/overweight patients	No significant relationships between BMI, intraoperative cup placement, or final cup placement for both inclination and anteversion; No significant relationships between STT over either ASIS or pubic tubercle with respect to acetabular cup orientation; no association between inclination/anteversion angles and anterior pelvic soft tissues
Mayne et al[41]	Prospective series	Posterior	FD	NR	Post-THA complications: Dislocation, infection, periprosthetic fracture, wound dehiscence. Comparing with BMI and fat depth	Patients within upper quartile of FD were not at increased risk of developing complications, as compared to patients within lower quartile of FD; patients with highest BMI (≥ 40 kg/m2) had significantly increased risk of complications, as compared to patients with lower BMI (< 40 kg/m2); Patients with highest BMI had significantly greater proportion of post-operative infection, as compared to lower BMI; number of patients within upper quartile of FD was 311, higher than the 60 patients in the BMI ≥ 40 kg/m2 category. Conclusions: Fat depth is not more useful in predicting complications and poor outcomes following THA
Rey Fernandez et al[36]	Case-control study	Posterolateral	Distance from the tip of the GT to the skin following a perpendicular line to the femoral diaphysis in post-operative AP hip radiographs	NR	APJI	Larger STT radiographic measurement associated with higher risk of APJI
Sezgin et al[37]	Retrospective cohort review	Anterolateral	Distance between most lateral point on the GT to the skin, on an axis perpendicular to the anatomical axis of the femur; HFTR: Subcutaneous fat tissue thickness divided by diameter of femoral diaphysis at level just inferior to minor trochanter	Pearson's coefficients: 0.981 (inter-observer), 0.965 (intra-observer)	Use HFTR and determine efficacy as a predictor of failure risk in 1-year post-operative period of primary THA	Increased peri-incisional subcutaneous fat tissue thickness associated with higher risk of failure of THA (i.e. reoperation, revision, death after 1 year)
Sprowls et al[40]	Retrospective cohort review	Anterolateral, posterior, lateral, direct anterior, hueter/smith-peterson	Thickness ratio (lateral/anterior): Lateral and anterior measurements of subcutaneous hip fat were obtained from CT, in slice where femoral head diameter was widest	NR	Compare thickness of subcutaneous fat in lateral hip incision (posterior, lateral, anterolateral approaches) with that of an approach using anterior incision (direct anterior and variations of Hueter or Smith-Peterson approach); examine relationship between BMI and distribution of subcutaneous fat, based on sex and age	Incision STT was greater for lateral hip incision approaches than for anterior incision; Greater BMI was associated with greater distribution of subcutaneous fat around the hip, based on sex and age; Lateral subcutaneous fat is greater in women, regardless of age or BMI
Sprowls et al[38]	Retrospective cohort review	Direct anterior, posterior	Subcutaneous fat depth measurement obtained from superficial extent of fat layer, along lateral skin flap. Anterior and lateral thickness measurements were obtained	NR	Intraoperative thickness of subcutaneous fat at incision site for direct anterior vs posterior approaches; Examine relationship between fat thickness and 90-day post-operative complications	More soft tissue encountered with posterior than direct anterior approach; greater STT was associated with greater rates of re-operation; excess incisional fat was associated with higher rates of wound complications
Suzuki et al[43]	Retrospective observational study	Anterolateral	Length from bilateral ASISs to the skin surface at a right angle to each ASIS. Average of right and left used as the ASIS-thickness; length from PS to skin surface at a right angle to the PS as PS-thickness	Intra- and inter-observer reliabilities > 0.900 (high intraclass correlation coefficient)	Evaluate association between cup alignment errors and obese patients	PS-thickness and ASIS-thickness associated with radiographic anteversion and inclination errors, while BMI only associated with radiographic anteversion errors; PS-thickness and ASIS-thickness both risk factors for cup implantation error of acetabular component using HipCOMPASS technology

ASIS: Anterior superior iliac spine; CT: Computed tomography; FD: Fat depth; GT: Greater trochanter; HFTR: Hip fat thickness ratio; NR: Not reported; PS: Pubic symphysis; STT: Soft-tissue thickness; APJI: Acute periprosthetic joint infection; BMI: Body mass index; THA: Total hip arthroplasty.

Table 3 Soft-tissue thickness and complications in shoulder arthroplasty

Ref.	Type of Study	Approach	Soft-tissue thickness measurement	Inter-rater and inter-observer reliabilities	Outcomes studied	Results
Wu et al[48] (2023)	Retrospective chart review	Reverse shoulder arthroplasties	Distance from the center of the humeral head to the skin. Ratio of the deltoid radius to the humeral head radius. Deltoid size. Subcutaneous tissue size	NR	Length of stay. Operative time. Infection	Greater shoulder soft-tissue thickness is a strong predictor of length of stay, operative time, and postoperative infection in primary reverse shoulder arthroplasties patients

NR: Not reported.

Table 4 Soft-tissue thickness and complications in ankle arthroplasty

Ref.	Type of study	Approach	Soft-tissue thickness measurement	Inter-rater and inter-observer reliabilities	Outcomes studied	Results
Wu et al[56] (2024)	Retrospective Study	Anterior	Posterior distal tibia to the anterior distal tibia (tibial tissue). Lateral process of talus to the head/neck junction of the talus (talus tissue)	Inter-observer Reliabilities: Tibial Tissue: 0.982; Talus Tissue: 0.935	Revision total ankle arthroplasty	Greater soft-tissue thickness was strong predictor of revision total ankle arthroplasty