Abstract
Background:
Elevated fluid pump pressures during hip arthroscopy have been associated with surgical complications including fluid extravasation, abdominal compartment syndrome, and higher use of pain medication.
Purpose:
To demonstrate the safe use of low pump pressures and to identify factors associated with the need for increased fluid pump pressure during hip arthroscopy.
Study Design:
Case-control study; Level of evidence, 3.
Methods:
A retrospective review was performed on all patients who underwent hip arthroscopy by a single surgeon between 2020 and 2021. Patients maintaining a pump pressure ≤20 mm Hg during surgery were assigned to group A, and patients who required a pump pressure >20 mm Hg at any point during surgery were assigned to group B. Univariate and multivariate analyses were performed to assess for relationships between elevated pump pressure (>20 mm Hg) during hip arthroscopy and the patient’s age, sex, length of surgery, body mass index, Beighton hypermobility score, lateral center edge angle, alpha angle, Tegner activity score, femoral shaft torsion angle, highest systolic blood pressure during surgery, number of suture anchors, and the presence of medical comorbidities (ie, hypertension, clotting disorder, or diabetes mellitus).
Results:
A total of 103 patients (112 hips) were included. Group A consisted of 77 hips (54 female, 23 male) with a mean age of 33.3 years. Group B consisted of 35 hips (19 female, 16 male) with a mean age of 33.6 years. Multivariate regression analysis revealed that mean length of surgery was associated with a need to increase pump pressure (P < .001). On average, for every 1-minute increase in surgery duration, the odds of needing an increase in pump pressure increased by 2.0%. In addition, highest systolic blood pressure during surgery and number of anchors were associated with an elevated pump pressure on univariate analysis (P = .026 and P < .001, respectively).
Conclusion:
For a majority of patients who underwent hip arthroscopy, a pump pressure of 20 mm Hg resulted in adequate visualization for the duration of the case. Increased length of surgery was associated with an elevated pump pressure during hip arthroscopy.
Hip arthroscopy is a rapidly evolving surgical procedure that has experienced a dramatic increase in use as well as expanded indications over the last 2 decades. 16 During hip arthroscopy, irrigation fluid is pumped into the hip joint to allow for surgical visualization. The pressure of the fluid can be manipulated by the surgeon to improve visualization, flush debris, and tamponade bleeding as needed. To date, no standardized pump pressure has been identified. As a result, pump pressures used during hip arthroscopy vary based on surgeon training and preference. When using high pump pressures, the surgeon should consider potential complications. Specifically, elevated pump pressures during hip arthroscopy have been associated with significant complications such as intra-abdominal fluid extravasation, abdominal compartment syndrome, and increased postoperative pain and medication use.3,4,6,9,12-14,17
Current literature assessing patient risk factors associated with the need for elevated pump pressure during hip arthroscopy is sparse, and further investigation is needed. The purpose of this study was to demonstrate the safe use of low pump pressures and to identify patient risk factors associated with the need for increased fluid pump pressure during hip arthroscopy. We hypothesized that prolonged surgery time and an elevated blood pressure during hip arthroscopy would be associated with an increase in fluid pump pressure.
Methods
After institutional review board approval was granted, a retrospective analysis was performed on prospectively collected data for a cohort of patients who underwent hip arthroscopy by the senior author (O.M-D.) between July 2020 and May 2021. Inclusion criteria for patients selected for this study were as follows: (1) persistent hip pain and mechanical symptoms refractory to nonoperative management (physical therapy, nonsteroidal anti-inflammatory drugs, activity modifications, corticosteroid injections) lasting at least 3 months, (2) reproducible clinical examination findings suggestive of impingement and/or instability, and (3) joint-space width >3 mm on all views of plain radiography and cross-sectional imaging. Patients presenting with severe anatomic deformity such as slipped capital femoral epiphysis, Legg-Calvé-Perthes disease, osteochondromatosis, or postdislocation syndrome were excluded from this study. Common indications for referral included femoroacetabular impingement, labral tears, hip instability, acetabular dysplasia, and associated abnormalities of femoral torsion or acetabular version. Revision hip arthroscopies were included in this study.
Outcome Measurements
Pump pressure was recorded throughout surgery, and patients were divided into 2 groups based on the fluid pump pressure required during surgery; patients with a pump pressure ≤20 mm Hg throughout the procedure were assigned to group A, and patients who required a pump pressure >20 mm Hg at any point during surgery were assigned to group B. Demographic and anatomic variables collected included age, sex, length of surgery, body mass index (BMI), Beighton hypermobility score, lateral center edge angle, alpha angle, Tegner activity score, femoral shaft torsion angle, highest systolic blood pressure during surgery, number of suture anchors, and the presence of medical comorbidities (ie, hypertension, clotting disorder, or diabetes mellitus).
Imaging Protocols and Measurements
After a comprehensive clinical evaluation by the senior author, patients underwent a standardized series of plain radiographs (including cross-table lateral and anteroposterior [AP] pelvic views) as well as preoperative magnetic resonance imaging and whole-pelvis computed tomography scans. Standard AP pelvic films were obtained with the patient positioned supine with the lower extremities internally rotated 15° to maximize femoral neck length. The x-ray beam was directed midway between the anterior superior iliac spine and the pubic symphysis, with a focus-film-distance of 100 cm. Radiographs were determined to be adequate with symmetric obturator foramina and a distance of 1 to 3 cm between the coccyx and pubic symphysis.1,2,19
The lateral center edge angle was determined on weightbearing AP pelvic radiography as described by Ogata et al, 10 as the angle subtended by (1) a vertical line through the center of the femoral head and orthogonal to a transverse line passing through the teardrops of both hips and (2) an oblique line drawn from the center of the femoral head to the lateral weightbearing sclerotic zone (sourcil) of the acetabular rim. Supine AP pelvic radiographs were obtained if there was too much anterior or posterior tilt on the weightbearing films.
Surgical Technique
General anesthesia without the use of tranexamic acid was used in all cases, and systolic blood pressure was maintained <100 mm Hg when possible. The patient was placed in a supine position on top of an antislip foam on a specialized hip distraction table without the use of a perineal post (Pivot Guardian; Stryker). 8 Bony prominences of the foot and ankle were padded, and traction was achieved with the use of a limb positioner affixed to custom-machined table attachment arms enabling unrestricted limb positioning. The operative table was placed in approximately 5° to 12° Trendelenburg. With the aid of fluoroscopy, and after air arthrogram, traction was applied to achieve sufficient distraction between the acetabulum and femoral head. The hip was cannulated using the standard anterolateral and midanterior portals. Then, an interportal capsulotomy was performed. 7 No iliopsoas lengthening was performed in the present cohort. The joint was accessed, and the central compartment pathology was addressed. Traction was then released, the table was brought back to a horizontal position, and the peripheral compartment intervention was undertaken. The fluid pump (CrossFlow Integrated Arthroscopy Pump; Stryker) was maintained at 20 mm Hg throughout the surgical case using saline with epinephrine added at a concentration of 1 mg of epinephrine per 3 L of saline per the senior surgeon’s preference. Meticulous cauterization of bleeding was performed during capsulotomy and during preparation for labral repair/reconstruction to allow for maintenance of a low pump pressure. Pump pressure was increased above 20 mm Hg as needed for bleeding control to improve visualization. Notably, the capsule was closed at the conclusion of all included cases.
Statistical Analysis
Logistic regression was used to determine what factors contributed to the odds of needing an increased pump pressure during hip arthroscopy. Univariate regression analysis was used to determine the linear trends of highest systolic blood pressure on pump pressure, highest systolic blood pressure on length of surgery, and pump pressure on length of surgery. Demographic summary statistics were calculated, and, when appropriate, independent t tests and chi-square tests were used to evaluate pairwise differences between the 2 groups. Residual diagnostic plots were evaluated to ensure the normality of errors. No outcomes or predictors needed to be transformed; thus, results are reported on the original scale. Statistical significance for all analyses was set at α = .05 unless otherwise noted. Analysis was completed using R studio (R Version 4.3.2).
Results
A total of 103 patients (112 hips) were included in the study. Pump pressure was maintained at ≤20 mm Hg in 77 hips (54 female, 23 male) and was increased to >20 mm Hg in 35 hips (19 female, 16 male) (Table 1). No fluid extravasation or abdominal compartment syndrome occurred in either group.
Patient Demographic Characteristics a
Data are presented as mean ± SD unless otherwise noted. Group A consisted of patients maintaining a pump pressure ≤20 mm Hg, and group B consisted of patients in whom pump pressure exceeded 20 mm Hg at any point during surgery. Boldface indicates statistical significance.
Comorbidities included hypertension, diabetes, or clotting disorder.
On logistic regression, length of surgery was found to be significantly longer in group B (289 ± 86.1 minutes) compared with group A (198 ± 58.0 minutes) (P < .001) (Table 1; Figure 1). The alpha angle was significantly greater in group B (66.6° ± 10.7°) compared with group A (61.6° ± 11.4°) (P = .03). The number of suture anchors was also significantly greater in group B (2.8 ± 1.4 anchors) compared with group A (1.5 ± 1.3 anchors) (P < .001). No significant differences in age, sex, BMI, Beighton hypermobility score, lateral center edge angle, femoral shaft torsion angle, highest systolic blood pressure, Tegner activity scores, or proportion of patients with medical comorbidities were identified between groups (Table 1).
Boxplot comparing length of surgery between groups A and B. Group A, pump pressure ≤20 mm Hg throughout case; group B, pump pressure >20 mm Hg at any point during the case.
Univariate Analysis
When not controlling for additional variables, we found an elevated highest systolic blood pressure to be positively associated with an increased pump pressure (R = 0.21; P = .026) (Figure 2). On average, for every 1 mm Hg increase in systolic blood pressure, the pump pressure increased by 0.050 mm Hg (β = 0.050; 95% CI, 0.006-0.094). Additionally, length of surgery was positively associated with pump pressure (R = 0.53; P < .001) (Figure 3). In particular, for every 1-minute increase in length of surgery, the pump pressure increased by 0.02 mm Hg (β = 0.02; 95% CI, 0.014-0.026). Number of suture anchors was associated with the need for an increased pump pressure (β = 0.75; 95% CI, 0.39-1.2). For every additional anchor used, the odds of needing an increase in pump pressure increased by a factor of 2.12 (P < .001). There was no statistically significant finding eliciting an effect of highest systolic blood pressure on length of surgery (P = .052) (Figure 4).
Linear regression model analyzing trend of highest systolic blood pressure on fluid pump pressure.
Linear regression model analyzing trend of length of surgery on fluid pump pressure.
Linear regression model analyzing trend of highest systolic blood pressure on length of surgery.
Multivariate Analysis
When controlling for our given variables, we found that increased length of surgery was positively correlated with the odds of needing increased pump pressure during hip arthroscopy (P < .001) (Table 2). On average, for every 1-minute increase in length of surgery, the odds of needing to increase the pump pressure increased by 2.0% (β = 0.02; eβ = 1.02; 95% CI, 0.01-0.03). Our logistic regression analysis did not reveal a statistically significant effect of sex, BMI, Beighton hypermobility score, lateral center edge angle, alpha angle, Tegner activity score, femoral shaft torsion angle, highest systolic blood pressure, or number of suture anchors on the odds of needing increased pump pressure during arthroscopy (Table 2).
Results of Logistic Regression Model Analyzing the Trends of Multiple Variables on the Odds of Needing an Elevated Pump Pressure a
Log-odds are reported under the coefficient column. Log-odds were exponentiated, and interpretations were made on the original odds scale. SE, standard error.
Discussion
The most important findings of this study are that an elevated systolic blood pressure during hip arthroscopy, an increased number of suture anchors, and increased length of surgery were associated with an increase in fluid pump pressure when not controlling for additional variables. However, when controlling for the given variables, we saw a statistically significant association only between length of surgery and the odds of requiring an elevated fluid pump pressure >20 mm Hg. Additionally, the present study demonstrates the safety and efficacy of using a low pump pressure during hip arthroscopy.
Our findings associating an elevated blood pressure with the need for increased pump pressure are consistent with current trends in the arthroscopy literature. In summarizing the fundamentals of arthroscopy, Walker-Santiago et al 18 identified bleeding as a major cause of visualization deficits. During arthroscopic procedures, the hydrostatic pressure exerted by the arthroscopic fluid serves to counter the hydrostatic pressure exerted by the capillary bed, thus preventing blood from exiting the capillary network and entering the joint space. If a patient’s blood pressure is elevated, the hydrostatic force exerted by the capillary network may exceed that of the irrigation fluid, ultimately leading to increased bleeding into the articular space and decreased visual clarity. 15 To improve visual clarity, surgeons may perform meticulous hemostasis or increase the pump pressure to accommodate for the elevated capillary hydrostatic pressure. 15 As a result, it stands to reason that patients with elevated blood pressure require elevated pump pressure during hip arthroscopy for appropriate tamponade and visualization. Furthermore, we identified a trend associating an elevated highest systolic blood pressure with increased surgery duration when not controlling for additional variables. Our results did not reach statistical significance; however, we suspect this trend is due to increased bleeding secondary to an elevated systolic blood pressure per the aforementioned physiologic characteristics. The increased bleeding may require additional hemostasis to maintain visualization compared with patients who do not have an elevated blood pressure, thus prolonging surgical duration.
Our definition of elevated pump pressure in this study was >20 mm Hg, which is substantially lower than pressures reported in the current literature.4,6,13 Studies describing a standardized pump pressure for hip arthroscopy are limited; however, Kocher et al 6 identified a mean pump pressure of 69.42 mm Hg (range, 45-90 mm Hg) as a significant risk factor for intra-abdominal fluid extravasation in patients undergoing hip arthroscopy. Furthermore, the mean reported pump pressure across all hip arthroscopies included in their study was 55.62 mm Hg. 6 Fowler and Owens 4 reported on a case of a 42-year-old man undergoing hip arthroscopy for femoroacetabular impingement who developed abdominal compartment syndrome with the use of fluid pressures between 40 and 60 mm Hg. Shakuo et al 13 reported a case of a 47-year-old man who developed abdominal compartment syndrome after hip arthroscopy for an acetabular fracture. Although the exact pump pressure was not specified, Shakuo et al described “massive bleeding” that required the use of “high perfusion pressure” to control. These reported pump pressures are higher than those used by the senior author of the present study, in which the highest pump pressure used was 60 mm Hg during the capsular closure of only a single case, suggesting that hip arthroscopic surgeons can safely use lower pump pressures without compromising surgical performance. As a result, surgeons should use low pump pressures—facilitated by meticulous hemostasis and minimal Trendelenburg positioning—when performing hip arthroscopy to reduce the risk of surgical complications while not compromising visualization. 11
Our findings identifying an association between increased surgery length and the need for increased pump pressure during hip arthroscopy were consistent with our original hypothesis. Our team suspected that this association was due to increased case complexity, larger cam resections, and/or increased bleeding. More complex cases and cases with large cam lesions are often associated with longer surgical durations and more bleeding. For example, repair or reconstruction of complex labral pathologies may require a longer surgical duration and the use of multiple anchors for fixation compared with routine labral repairs where fewer anchors are used. The increase in number of anchors used not only increases the length of surgery but may lead to more bleeding and the subsequent need for increased pump pressure to maintain adequate tamponade and visualization. Similarly, large cam resections are more time intensive and can lead to increased bleeding and the need for higher pump pressures compared with smaller cam resections. This theory was supported by our univariate analysis suggesting that an increased number of suture anchors may increase the odds of needing to increase pump pressure; however, our multivariate analysis analyzing the effect of anchor count did not reach statistical significance.
In our study, surgical duration was prolonged in both study groups compared with hip arthroscopy durations previously reported in the literature. 9 For many of the surgical procedures included in this study, access, interportal capsulotomy, and portions of the cam resection were performed by a single hip preservation fellow, resulting in an increased overall operative time. All procedures were performed at an academic institution in which medical trainee education is emphasized, which we suspect also contributed to the longer surgical duration. Nonetheless, our findings associating increased surgery duration with increased pump pressure may explain the results demonstrated by Hinzpeter et al, 5 who identified an association between fluid extravasation and longer surgical times. Although not directly assessed in their study, it is possible that their prolonged surgical cases required increased pump pressure, thus leading to increased fluid extravasation, as the authors reported using pump pressures between 40 and 90 mm Hg for all cases. Notably, fluid extravasation was not an issue in our study due to the use of very low pump pressures. The results reported by Hinzpeter et al associating increased fluid extravasation with increased operative time did not reach statistical significance; however, the trend suggests that arthroscopic surgeons should be increasingly aware of pump pressure levels during longer surgical cases to minimize complications.
Limitations
The limitations of this study should be noted. The systolic blood pressure used in statistical analysis was recorded at various stages of the case rather than continuously throughout surgery. Thus, it is possible that the highest systolic blood pressures reported in our study may not accurately reflect the mean blood pressure throughout the procedure. Furthermore, patients were assigned to group B if the pump pressure exceeded 20 mm Hg at any point during surgery. This may have led to grouping of patients who required only a transient elevation in pump pressure with those who remained at an elevated pump pressure for the entirety of a surgical case, thus creating variation within groups and potentially affecting our results. All surgeries performed in this study were done using a postless surgical bed. Therefore, the findings of the present study may not be universally applicable to surgeons who use a perineal post. Last, given the relatively small sample size of the patients in the present study, it was not possible to match patients by demographic and intraoperative factors.
Conclusion
For most hip arthroscopy patients, a pump pressure of 20 mm Hg resulted in adequate visualization for the duration of the case. Additionally, increased length of surgery was associated with an elevated pump pressure during hip arthroscopy.
Footnotes
Final revision submitted January 11, 2025; accepted February 19, 2025.
The authors have declared that there are no conflicts of interest in the authorship and publication of this contribution. AOSSM checks author disclosures against the Open Payments Database (OPD). AOSSM has not conducted an independent investigation on the OPD and disclaims any liability or responsibility relating thereto.
Ethical approval for this study was obtained from Colorado Multiple Institutional Review Board (COMIRB Protocol 12-1385).
