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

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.