Approximately 15% to 25% of adult patients presenting for hip arthroplasty have bilateral disabling hip disease and can potentially benefit from single-stage bilateral total hip arthroplasty (BTHA).¹ Although the majority of total hip arthroplasties (THAs) performed are unilateral, up to 42% of patients develop bilateral disease requiring the replacement of both hips.² Furthermore, the rehabilitation potential can be compromised when both diseased hips are not addressed simultaneously.³

Single-stage BTHA was initially reported by Jaffe and Charnley⁴ in 1971 in a series of 50 cases. Salvati et al⁵ followed with a review of 122 patients who underwent single-stage BTHA compared with staged BTHA performed on a single or separate admission showing equivalent results. Despite the prevalence of bilateral hip disease, the number of single-stage BTHAs remains low. Using National Inpatient Sample data, Rasouli et al⁶ reported that single-stage BTHAs were performed in about 0.75% to 1.1% of the THA cases in the United States.

Several factors make the supine direct anterior approach (DAA) advantageous for single-stage BTHA. The supine position negates the need for repositioning between sides, which can decrease the overall surgical time. It is a true internervous and intermuscular approach that minimizes surgical trauma to important muscle groups that allow for normal hip biomechanics, resulting in faster recovery. The anterior approach has shown less postoperative pain and narcotic use, a shorter length of stay, and faster return to normal gait mechanics compared with the posterior approach.^7,8,9,10,11 Furthermore, studies have shown decreased blood loss with the DAA, which heightens the appeal for ­single-stage BTHA.¹²

There are several potential advantages of performing both hip replacements in a single episode. Rehabilitation can be optimized when both diseased hips are replaced simultaneously, and operative time and overall recovery can be minimized. The cost of care and resource utilization can also be diminished.

The presence of a degenerative hip joint increases the force across ipsilateral adjacent joints as well as all of the contralateral limb joints.¹³ After a unilateral THA, the nonsurgical lower extremity power production is higher preoperatively and at 6 weeks postoperatively. During level walking, the knee and hip joints of the nonsurgical extremity produce more power than those of the surgical side.¹³ This force pattern across different adjacent ipsilateral and contralateral joints does not reach stability until the patient can reach the maximal force across the replaced hip joint; this can take up to a year.¹³ During the gait cycle, after one hip is replaced, the contralateral limb single-stance phase increases from 35% to 37%.¹⁴ Therefore, unilateral THA in these patients will lead to reliance on a diseased hip for ambulation, and patients with bilateral hip joint disease who undergo a staged BTHA do not improve their preoperative maximum walking speed until the second side is replaced.¹⁴

These findings have been supported with patient-reported outcomes. Parvizi et al¹⁵ reported a better Harris Hip Score for patients undergoing single-stage BTHA versus staged BTHA. Gondusky et al¹⁶ reported improved Harris Hip Scores from 49.8 to 97.8 postoperatively after single-stage BTHA, and others also have reported similar trends.^17,18,19 This improved rehabilitation in single-event surgery makes single-stage BTHA an attractive option for young productive patients who want less time away from work. In their series, Kamath et al²⁰ found that patients with bilateral hip disease and full-time jobs were more likely to undergo single-stage BTHA. Retired patients were more likely to undergo staged BTHA.²⁰

Cost savings are another potential advantage of single-stage BTHA. Houdek et al²¹ estimated a 27% reduction in the cost of care for a single-stage BTHA compared with staged BTHA. A single hospitalization and anesthetic could result in lower costs to the health care system as long as other variables, such as
perioperative complications, operating room (OR) time, and resource utilization, are comparable. Martin et al²² compared the cost of single-stage versus staged BTHA in a Canadian population with the anterior approach. They found reduced hospital costs for single-stage BTHA with a mean difference of $1942.50 and a mean savings to the health care system of $2188.24. OR staff and setup accounted for greater than 50% of the savings. They found no clinically significant difference in complications that would offset these cost savings.²² Furthermore, OR and anesthesia time can be a significant source of cost reduction. It has been estimated that 100 minutes of total operation time difference could represent $3700.00.^20,23 Another source of reduction in cost to the health care system comes from the surgical fee; there is a 50% reduction in payment for the second hip.²⁴ Brown et al²⁵ performed a perioperative and financial outcome analysis of single-stage versus two-staged anterior approach THA. They compared the single-stage episode with a single-sided episode in the staged cohort. Not surprisingly, the blood loss, transfusion rate, and length of stay were higher in the single-stage group. Financial analysis showed lower total cost and equivalent reimbursement per hip in the single-stage group, resulting in better profits per hip in the single-stage group.²⁵

Decreased resource utilization helps reduce costs. Rasouli et al⁶ showed a cumulative length of stay for staged BTHA of 6 to 10 days with estimated costs between $63,900 and $111,500 compared with 3 to 4 days in single-stage BTHA with estimated costs between $30,000 and $60,000. Discharge disposition also affects resource utilization, and the DAA for single-stage BTHA has been advantageous, with the majority of patients being discharged home.^{17,19,26,27,28,29}

There remains apprehension for the adoption of single-stage BTHA because older studies showed a potential increase in the rate of the already known complications of THA. Increased blood loss with postoperative anemia and increased need of transfusion are the most common complications reported for single-stage BTHA.¹⁵ Single-stage BTHA was found to be an independent risk factor for allogeneic blood transfusion by Rasouli et al³⁰ with an odds ratio of 3.30. Autologous and allogeneic transfusion carry an associated risk of infection (1.2% vs 12%) and prolonged hospital stays.^31,32 They also found an increased rate of pulmonary embolism (0.45% vs 0.23%), venous thrombotic events (0.35% vs 0.21%), and local complications (4.96% vs 4.54%) in BTHA compared with unilateral THA.⁶ Berend et al³³ reported a higher surgical complication rate for single-stage BTHA; 3.9% of patients required a subsequent hip surgery versus the staged group, which had a 0.5% rate of reoperation. Heterotopic ossification has also been found to be higher in BTHA.^34,35

Regardless of the approach, three recent studies demonstrated the safety of single-stage BTHA compared with staged procedures. Shao et al³⁶ performed a meta-analysis of 13 studies with 17,762 patients in the single-stage group and 46,147 patients in the staged group. Single-stage procedures were associated with fewer major complications and a lower overall hospital stay, with no difference in the other perioperative outcome measures. Houdek et al²¹ reported a shorter overall length of stay and surgical time with equivalent complications, reoperation, and mortality in single-stage BTHA compared with staged BTHA. Taheriazam et al³⁷ performed a prospective randomized trial with 180 patients comparing single versus staged BTHA on American Society of Anesthesiologists (ASA) one or two patients using the lateral approach. Their results showed equivalent clinical outcomes at 1 year without an increase in perioperative complications. These studies have demonstrated that on selected patients single-stage BTHA is safe and potentially associated with less complications than staged procedures, which contrasts with historical data.

Advances in the preoperative optimization of patients, streamlined postoperative protocols, and the introduction of effective medications such as tranexamic acid have made a significant impact on the reported success of single-stage BTHA. Table 17.1 summarizes the patient selection criteria in the reviewed studies. The DAA, with its described unique advantages, could potentially further improve the outcomes of single-stage BTHA.

The supine position of the DAA facilitates the workflow for single-stage BTHA and negates the need for repositioning between sides, which can be time consuming and expose patients to prolonged anesthesia. The procedure can be performed with a single drape and instrument setup or double setup depending on the surgeon’s preference. A meticulous draping strategy must be used for a single setup to avoid sterility breakdown (see Figure 17.1). The authors advocate for a double setup. We use specialized fluoroscopy, which enters the field through the contralateral side, potentially breaching sterility at the site of the subsequent hip replacement (Figure 17.2). For surgeons who prefer a single setup with the use of fluoroscopy, we recommend additional draping to cover the contralateral side with a blue towel after draping. This is then removed before commencement of that side, with repeat ChloraPrep (Becton Dickinson [BD], Franklin Lakes, NJ, USA) skin preparation applied on the second side before commencing the second THA. Finally, the reprepped sterile field is covered with an Ioban drape (3M, St. Paul, MN, USA) just before the second THA is performed. The avoidance of fluoroscopy could further help to mitigate the concern for inadvertent contralateral site contamination during the first THA.

Recreation of leg length after bilateral THA is an important surgical goal. Another benefit from the supine DAA for single-stage bilateral THA is the ability to judge leg length either manually or with the aid of fluoroscopy. For surgeons using a standard operating table, evaluation with palpation of the medial malleoli has been described as an effective method.³⁸ We advocate the use of fluoroscopy to assess leg length, which has been demonstrated to be both reliable and independent of confounding variables such as pelvic tilt, hip, or ankle deformities.³⁹

Furthermore, the use of fluoroscopy improves component positioning. Slotkin et al⁴⁰ reported 88% of their cups were placed within the targeted safe zone for both inclination and anteversion with low variance. A follow-up study showed that the accuracy was not influenced by body mass index (BMI).⁴¹ Lin et al³⁹ compared posterior approach component positioning with DAA fluoroscopic-guided component positioning and found an acceptable acetabular angle achieved in 96% of cases using the DAA compared with 85% of posterior approach cases. Rathod et al⁴² also demonstrated improved acetabular component positioning with less variance than the posterior approach, with greater than 90% mean cup positioning within the safe zone.