This series demonstrates the successful use of the SuperPath approach for THA and most notably, zero dislocations 214 patients one year after surgery. Prosthetic hip dislocation is one of the most common early complications after primary THA, and may be influenced by factors including surgical approach and cup position.[18, 19, 54–58, 20, 47–53] The present study shows that the SuperPath approach may present an opportunity for the surgeon to further reduce dislocation incidence below the reported rates of 2–3%.[1, 2, 11, 3–10] Additionally, the present study demonstrates the ability of CT-assisted navigation to achieve adequate cup position within the classic safe zone as described by Lewinnek et al., despite the decreased visualization that accompanies a smaller incision.[18] It should be noted that dislocation rates have decreased in recent years due to factors such as the increased popularity of larger femoral heads, capsular repair, and increased offset stems, and the impact of surgical approach remains controversial.[59–65]
EBL was 321 cc. Although intraoperative surgeon EBL is often underestimated[66], patients overall experienced small decreases in hemoglobin after surgery (1.6 g/dL), as well as a low rate of intraoperative and postoperative blood transfusions (3.7%). A recent analysis of the Nationwide Inpatient Sample of 2,087,423 THAs found that the rate of allogenic blood transfusion increased from 11.8% in 2000 to 19.0% in 2009.[67] A prospective study of 92 patients randomized to either SuperPATH or the posterior approach THA demonstrated a decreased rate of transfusions with SuperPATH, although the results were not statistically significant.[68] Allogenic blood transfusions have been associated with increased risk of infection after total joint arthroplasty, and the SuperPATH approach may help reduce this risk by reducing blood loss.[69]
Rapid time to ambulation is a theoretical advantage of MIS THA approaches. The vast majority of patients in the present series were ambulatory on POD1, and most (75.7%) were discharged home without home health. Multiple studies have demonstrated similar recovery at home as compared to rehabilitation or skilled nursing facilities after TJA, with or without another person living in the home.[70–76] Bozic et al. reported that post discharge payments account for 36% of total Medicare payments for total joint arthroplasty, of which 70% is consumed by the 49% of patients who are discharged to post acute care facilities.[77] By allowing the majority of patients to discharge home, the SuperPATH approach may enable significant cost savings, findings that were supported by a recent economic analysis by Chow and Finch.[42]
Overall operative time averaged 136 minutes from skin incision to dressing application, but decreased 65 minutes from the first 20 cases to the last 20, which may represent the effect of the initial learning curve. Rasuli and Gofton found that operative time continued to significantly decrease with the SuperPATH approach even at the 50th case, implying a longer learning curve that may require extensive experience to become proficient.[78] A recent retrospective analysis of the National Surgical Quality Improvement Program database reported an average operative time of 94 minutes in 103,000 THAs, which is shorter than reported in the present series.[79] However, operative times did not translate into an unacceptably high rate of infection nor complications in this series.
Adequate visualization is an inherent challenge in MIS THA. There is some evidence that the risk of intraoperative periprosthetic fracture is elevated with MIS approaches for elective THA.[80, 81] However, the present study demonstrated an incidence of 1.4%, which is lower than the 2.95–10.6% reported in other large series.[82–85] The three intraoperative fractures in the present series were all treated successfully using cerclage cables inserted through a smaller secondary incision without compromising the short external rotators. The only other complication attributable to decreased visualization was a return to the OR from PACU after a postoperative radiograph demonstrated a previously unrecognized piece of bone interposed between the prosthetic head and cup.
The present study is limited by several factors. Most notably, the retrospective data comes from a single surgeon who routinely uses the SuperPATH approach at a single institution. Without a control group undergoing a different approach, it is difficult to isolate the effect of the approach itself. Additionally, the number of total patients was relatively small, and prior analysis has shown that a sample size of 3720 patients would be needed to detect a 2% difference in dislocation rates of two different methods of THA with 80% power, leaving our study underpowered.[86] Thus, outcomes may not be generalizable to the broader patient population. Furthermore, telephone follow up was 76.7%, and although the medical records were examined for dislocations or other complications, it is possible that some patients lost to follow up experienced a dislocation that was treated at an outside facility. Larger, prospective studies with a comparison group are warranted to confirm our findings.