INTRODUCTION

Despite our best efforts, orthopaedic surgeons do not always achieve desired results in acetabular cup positioning in total hip arthroplasty. New advancements in digital radiography and image analysis software allow contemporaneous assessment of cup position in real-time during the surgical procedure. The purpose of this study was to describe and validate a technique in obtaining a true AP Pelvis radiograph in the lateral decubitus position to accurately assess cup position intra-operatively (Figure 1).

Despite our best efforts, orthopaedic surgeons do not always achieve desired results in acetabular cup positioning in total hip arthroplasty (THA). Although ideal abduction and anteversion angles vary depending on surgeon preference, patient factors and anatomy, studies have shown that improperly positioned cups lead to increased failure rates in THA. While there have been many technological advancements in THA, including using CT-guided and fluoroscopic techniques, the cost for the hospital and time required to use this technology sometimes force hospitals not to use them. New advancements in digital radiography and image analysis software allow contemporaneous assessment of cup position in real-time during the surgical procedure. Intra-operative, or “trial radiographs” with the patient in lateral decubitus position can be digitally manipulated to match pre-operative radiographs obtained with patients in the supine position to enable calculation of the abduction and anteversion angle in these patients. In our single surgeon experience, digital radiography takes approximately 4–6 seconds in order to obtain an AP pelvic radiograph. The use of the software to measure the cup position adds only 1–2 minutes to the operative time and minimises interference with workflow. The adjustments that can be made intra-operatively with this technology allow the surgeon to learn what factors in his surgical approach and technique are useful in achieving the desired component position. This allows the surgeon to have precise control over the cup position during the operation rather than experience disappointment and frustration while viewing the post-operative film. This cost-effective and efficient tool allows the surgeons to achieve the best results for their patients in real time without having to leave the operating room.

The direct anterior approach (DAA) for total hip arthroplasty (THA) has become an extremely familiar concept over the last 8 to 10 years. There has been growing pressure to utilise this approach driven by the lay press, implant manufacturers looking for an edge, as well as from surgeons looking for a marketing advantage. This media and industry presence could leave many surgeons feeling that we delay adoption of the DAA at the risk of losing patients or at minimum must have a good explanation as to why we have chosen not to perform “that surgery where you come in from the front.”

The atmosphere of perceived superiority of DAA has occurred in spite of numerous publications identifying unique risks and complications, including steeply increased complication rates in the “learning curve”, while lacking data identifying its promised advantages when compared to the “modern posterior approach” to THA. It persists despite a recent prospective comparative study that failed to identify any clinical advantages for the anterior THA versus a “mini-posterior” THA and other evidence from state joint registries that has shown the dislocation rate of the DAA is not significantly different from posterior hip approaches.

It essential to understand the considerations that differentiate traditional posterior THA from “modern” posterior-based THA. The advancements made in pain management, rapid rehabilitation and patient education all contribute substantially to the enhanced recovery of the “modern THA”. Furthermore, the extensile exposures such as the Moore, Gibson or Kocher Langenbeck approaches are no longer the type of “posterior” approach that is applied to routine primary THA. Many iterations of posterior-based approaches are now performed with a far more limited and soft tissue preserving approach. It is the purpose of this brief presentation to describe the clinical results of 1000 consecutive hips performed using one such “modern THA,” which has allowed us to obtain early recovery benefits, including the outpatient setting. This is achieved without the additional risk profile assumed with the DAA and with an easily extensile approach. Through these examples we can show that not only is “the back” back, but that for those who were paying attention, it is clear it never really went away.

Acetabular component orientation can directly influence dislocation rates, polyethylene wear, and revision rates. Precise placement has been found to occur in only 38–47% after total hip arthroplasty (THA). The recent introduction of digital radiography (DR) has enabled a paradigm shift in intra-operative imaging technology. Rather than deal with the cumbersome process of chemical image processing we can now acquire a high quality digital image in a matter of seconds. The functionality approaches that of fluoroscopy, or even a C-arm, however, a digital system can operate with lower radiation, higher resolution, and perhaps most importantly a larger field of view. These features make it very suitable for use during surgery. The purpose of this presentation is to illustrate the current intra-operative technique and share the overwhelmingly positive experience gathered over the past five years.

Traditional THA employs use of post-operative radiography for “outcome assessment.” This unfortunately does not allow the surgeon to evaluate the relevant parameters and make necessary adjustments without returning to the operating room. Digital imaging, however, permits intra-operative guidance and “outcome control.” It provides an immediate and complete preview of what the post-operative film will show. There is now an opportunity to optimise component orientation, sizing, apposition, screw position, limb length, and offset, before leaving the operating room. This can be done with minimal intrusion on normal workflow, adding only a few minutes of operating time.

The transgluteal approach (TG) offers a user-friendly alternative to the heavily promoted anterior approach (DA) to total hip arthroplasty (THA). Our purpose is to illustrate the advantages and details of the technique, illustrate the surgical anatomy that differentiates TG from the “traditional posterior” technique, and point out the surprising similarities to the DA.

Unlike the traditional posterior THA, the TG preserves ITB, quadratus, and obturator externus. The conjoined tendon is released, providing direct access to the femur via the piriformis fossa. Direct acetabular access is facilitated either by using a portal through which reaming and cup impaction are performed or offset instrumentation. Intra-operative digital radiography was used in all cases. We present the clinical and radiographic outcome of 850 consecutive primary THA using the TG.

At 2–6 years follow-up, dislocation rate was 0.3%, cup abduction 35–50 degrees in 97%, 92% used a cane within 5 days, 61% reported driving within the first post-operative week. No intra-operative trochanteric fractures, nerve injuries, or wound problems were observed. Three calcar fractures were wired. Hospital stay averaged 1.5 days, no patient received a blood transfusion if their pre-operative hematocrit was normal, and 88% of patients were discharged on acetaminophen only.

The TG is a reliable and highly successful alternative to commonly used soft tissue sparing approaches in THA. It permits accelerated recovery while assuring optimal component orientation. The surgeon familiar with the traditional posterior approach can embark on a gradual learning curve that can minimise the complication rate as the surgeon learns the technique.

The recent introduction of digital radiography has enabled a paradigm shift in intra-operative imaging technology. Rather than deal with the cumbersome process of chemical image processing we can now acquire a high quality digital image in a matter of seconds. The functionality approaches that of fluoroscopy, or even a C-arm, however, a digital system can operate with lower radiation, higher resolution, and perhaps most importantly a larger field of view. These features and the greater ability for post-acquisition, digital image enhancement make it very suitable for use during surgery.

The purpose of this presentation is to illustrate the intra-operative technique and share the overwhelmingly positive experience gathered over the past few years.

The current paradigm in total hip arthroplasty (THA) employs use of post-operative radiography for “outcome assessment.” This unfortunately does not allow the surgeon to evaluate the relevant parameters and make necessary adjustments without returning to the operating room. The new paradigm, however, permits intra-operative guidance and “outcome control.” We now have an opportunity to add a “trial radiograph” to our practice of performing a trial reduction. This provides an immediate and complete preview of what the post-operative film will show. There is now an opportunity, during the course of any hip arthroplasty, to optimise component orientation, sizing, apposition, screw position, limb length, and offset, before leaving the operating room. This can be done with minimal intrusion on normal workflow, adding only a few minutes of operating time.

There has been great enthusiasm over the last few years for the mini-anterior, or, the Direct Anterior (DA) approach. As the title of this session suggests there is a perception that there are features of this approach that result in an unusually rapid recovery with “early” return to a high level of function. There have also been claims of improved implant placement and limb length restoration. This is presumably a result of the use of intra-operative imaging. When originally described, it was stated that the DA permitted THA “without cutting any tendons.” The implication was that the alleged unique recovery was due to this particular feature.

Over the last decade I have used a trans-gluteal, direct posterior (DP) approach. Incision into the ITB is not required and quadratus femoris is preserved. The conjoined tendon, occasionally the piriformis, and rarely the obturator externus are released. Over the last 5 years I have used intra-operative digital radiography to guide the procedure.

A review of published DA results indicates at least clinical equivalence with the DP. Recent publications describing DA technique acknowledge that it is required, in most cases, to release conjoined tendon, and possibly piriformis. Personal communication with DA practitioners suggests even more “posterior release” is required. I will illustrate that the DP is a very close anatomic equivalent of the DA. It is therefore the handling of critical anatomic structures along with the use of image guidance that optimise outcome in THA and not mini-anterior or DA exclusively.

Over the last few years low dose digital radiography (DR) has all but replaced traditional chemical image processing. This appears to have created a paradigm shift in the suitability of intraoperative radiographic guidance for total hip arthroplasty. It is the purpose of this publication to describe our preferred technique and assess its reliability in achieving the desired parameters of a successful total hip arthroplasty.

A consecutive prospective evaluation of 150 primary total hip arthroplasties employing intraoperative digital radiography was carried out. An anteroposterior pelvic radiograph with the patient in the lateral decubitus position was obtained for all hips. The orientation of the intraoperative film was matched to that of the preoperative pelvic radiograph. The image was taken after placement of the acetabular component and best estimate of femoral trial size, position, and head and neck length. The DR system produced an image within 6 seconds of exposure. This trial radiograph was then used to make adjustments. Given that the cassette does not have to be moved for image processing, a precise anteroposterior film was obtained by simply adjusting the operating table. Two to three minutes were allotted for each radiograph. Corrections to stem size, cup position, screw length and position, limb length, and offset were made based on this intraoperative radiograph. The final intraoperative image was then compared to a postoperative standard radiograph in supine position at 2 weeks after total hip arthroplasty to verify the accuracy of intraoperative digital radiography. Abduction angle, limb length, offset, and canal fit and fill were assessed for confirmation of the validity of the intraoperative imaging technique.

Acetabular abduction angle was determined with a mean of 43 degrees (range, 35 to 48 degrees). The intraoperative measurement was within 3 degrees of the postoperative measurement in all cases. Adjustment of acetabular cup orientation was performed 10% of the time based on the intraoperative radiograph. Apposition was within 2 mm 100% of the time. Re-seating of the cup was carried out in one hip only. Femoral component was neutral in 92% and between 3 and 5 degrees of varus in 8%. Femoral component was upsized 55% of the time. Intraoperatively measured limb length discrepancy and offset were within 3 mm of the postoperative measurement in all hips.

Intraoperative digital imaging is a reliable tool for achieving the desired radiographic results in THA. The technique is efficient and affordable. The high rate of success in this series suggests that this technology should contribute to a paradigm shift in the standard of care in total hip arthroplasty.