The Minimally Invasive Anterolateral Approach (MIS-AL)- 11-Year Results of Cementless Total Hip Arthroplasty

The study prospectively assessed the eleven-year outcomes of cementless total hip arthroplasty using the minimally invasive anterolateral approach...


Introduction
Minimally invasive approaches in total hip arthroplasty continue to be a debated topic with a number of controversial views [1,2]. The present paper presents prospective results of cementless total hip arthroplasty over a period of 11 years post-procedure.
Evaluation was performed using the Harris score, monitoring of the level of patient satisfaction, and X-ray scan assessment.

Materials and Methods
The study included a total of 105 patients who had had cementless hip arthroplasty (Allofit cup and CLS stem) using the mini-invasive anterolateral approach. The patients were followed up prospectively for a period of 11 years. Thorough examination prior to, 1 year and 11 years after surgery was performed in 75 evaluated patients. Our finally evaluated study group is made up of 43 men and 32 women with a mean age of 59.5 years at the time of surgery, and aged 70.5 at the time of evaluation. Mean BMI at the time of the joint prosthesis implant procedure was 26.7. Of the above 75 cases, the right and left hip joints were in 38 and 37 patients, respectively.
One patient had re-do surgery 2 years after the primary procedure because of femoral head split fracture, with another patient having re-do surgery for stem loosening. A total of 28 patients failed to respond to our invitation for a final comprehensive assessment and were thus excluded from the group. In our department, total hip arthroplasty using the MIS-AL approach is indicated for non-obese patients (with the main criterion being body fat distribution and not total body weight or BMI) with primary spherical hip joint arthritis.
Contraindications include marked obesity, severe postdysplastic arthritis, severe joint deformities, previous hip joint surgery, and marked limb shortening [3]. The procedure is performed using the MIS-AL approach described in detail by Bertin and Rottinger [4], with the latter modifying the original technique proposed by Keggi [5,6], using a dedicated toolset manufactured by Zimmer Biomet for both cemented and cementless implants.

Technique
The procedure is performed under regional or general anesthesia with the patient in the recumbent position and fixed tightly in the pubic and sacral regions. The incision, measuring 5-8 cm in length, is localized slightly dorsally from the line between the spina iliaca anterior superior and the anterior superior facet of the greater trochanter. Upon fascial dissection, we proceed along

Abstract
The study prospectively assessed the eleven-year outcomes of cementless total hip arthroplasty using the minimally invasive anterolateral approach (MIS-AL). Enrolled into the study were a total of 104 patients who had had total hip arthroplasty using the MIS-AL approach in our center between 1/2005 and 3/2006. A combination of an Allofit cup and CLS stem was used in all patients (Zimmer Biomet). Patients were assessed using the Harris score, school-like performance rating, evaluation of satisfaction levels (in percent), and evaluation of X-ray scans obtained prior to, 1 year, and 11 years after the procedure. Overall, complete assessment was performed in 75 patients. The Harris score was 91.34 and 91.35 at 1 year and 11 years post-surgery, respectively. One patient required re-implantation for damage to the femoral head at 2 years after the primary implantation and another one replacement for stem loosening because of an inappropriately-sized component. There was no case of infection-related stem loosening. Our results showed that, in indicated cases, the MIS-AL approach can be an alternative to the conventional one; however, while the former has comparable mid-term outcomes, they are not superior to those obtained using standard approaches.

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the space between the gluteal medius muscle and tensor fasciae latae. Next, we loosen as much as possible the joint capsule, which is-after placing femoral elevators-ventrally excised and medially dissected. Once the elevators have been placed in the joint above (one sharp elevator) and below the neck (two blunt elevators), subcapital transverse osteotomy of the femoral neck is performed. skin. Once the procedure is over, the patient is transferred to our intensive care unit with verticalization and mobilization started on postoperative day 2. The patient is allowed to immediately load the limb up to 50% of body weight; however, as a rule, based exclusively on subjective sensations. Beginning week 6, the patient is encouraged to progressively proceed to full load using three-points ambulation. Standard antibiotic prophylaxis is performed intraoperatively, with the patient secured with lowmolecular weight heparin while continuing with pharmacological prevention of thromboembolic disease for a period of 6 weeks.
The patients are followed up at intervals of 6 weeks, 4 and 12 months, and 2 years thereafter. All patients were followed up prospectively. Preoperative and postoperative evaluation at 1 and 11 years post-op was performed using the Harris score; also, patients were invited to provide their rating of satisfaction with their current status (in percent), school-like rating of the overall outcome, and asked whether or not they would be willing to have the same procedure on their contralateral joint if needed. Those patients who had had total hip arthroplasty from the standard anterolateral approach previously were asked whether they found the mini-invasive procedure better than, worse than or equal to the standard technique. X-ray scans obtained in the A-P and axial projections were assessed at 1 and 11 years postoperatively. Both intraoperative and postoperative complications were recorded.

Results
Of the original 104 patients enrolled, 28 were lost to followup or failed to present for all examinations at the pre-defined In no case was the cup implanted in retroversion. One cup was evaluated as inadequately buried; however, became fully integrated without clinical complications. In nine patients, the stem was inserted off the optimal position. In five cases, mild varus deformity of up to 2° was noted, another two stems were in 5° and 7° varus deformity, two stems were inserted in 2° and 4° valgus deformity.
None of the patients experienced endoprosthesis luxation, developed infectious complications, thrombosis or embolism. Two patients had postoperative wound revision for hematoma.
The average surgical time from transporting the patient to the operating theater to covering the wound was 94 minutes (57-124). Baseline evaluation was performed using the Harris score.
However, the Harris score was not designed to assess the joint

Discussion
In fact, the mini-invasive approach in total hip arthroplasty is not a revolution in endoprosthetics, but an alternative for a vessels. These measures helped reduce the incidence of the above errors. Another most important finding is that there was not a single case of an early infectious complication. We believe an advantage of the mini-invasive approach is the reduction of the surgical wound area, being 4 to 5 times smaller thus reducing the risk of surgical field contamination. The procedure is much more challenging in obese patients where body fat distribution is the critical factor. Jackson [9] reported that, while the Harris score in obese patients was lower, the level of patient satisfaction and total endoprosthesis durability was the same in the mid-term horizon.
In our own prospective study [10] comparing the quality of life at 1 year post-procedure using the conventional and mini-invasive techniques and the SF-36 questionnaire, we documented identical outcomes in either group. Some items in the Harris score focus on patient overall mobility. Our patient set included those with spinal injury, arthritis affecting other joints, subtalar arthrodesis as well as a patient after contralateral lower limb above-the-knee amputation, who could not achieve complete assessment despite optimal outcome; another factor not to be neglected was the effect of aging at the time of individual assessment on the patients´ overall status, which was why decided to ask our patients to rate their level of satisfaction with the outcome. The average Harris score at 11 years had virtually not changed since that of one-year follow-up.
There was a slight worsening of the level of satisfaction in percent and school-like performance rating. An important finding was that infection, neurological problem, no problems with healing or differences in the incidence of complications or numbers of blood transfusion; nonetheless, patients operated on using the miniinvasive approach were leaner. Teet [15] published the results of 73 mini-incision and 54 standard procedures with a follow-up of 4.5 years without a difference between the patient groups. The first to publish a prospective study assessing the posterior mini-invasive approach were Floren [16]. In their paper, the authors compared clinical versus X-ray scan outcomes of patients 10 to 13 years after endoprosthesis implantation using the posterior mini-invasive approach with data presented by authors using the conventional approach but the same implant type. The postoperative Harris score was 92.3, 57% of patients exhibited bone atrophy in the area surrounding the proximal part of the stem on the X-ray scan, with radiolucent zones in the areas of the stem and cup identified in 14% and 11% of cases, respectively. There was no case of aseptic loosening of the implant. These authors consider the mini-invasive approach comparable with standard approaches as reported in earlier papers. In their controlled study, Howell [17] compared data of 50 patients receiving implants from the mini-invasive anterolateral approach with data of 57 patients operated on using the standard approach. As the former patient group showed shorter operating times, smaller blood losses, and shorter hospital stays, the authors consider the mini-invasive technique safe. In their well-documented prospective randomized study comparing 209 patients operated on using either the mini-invasive posterior or the standard 16-cm approach, Ogonda [18] did not document any benefits in any of the end points such as hemoglobin levels, X-ray scan assessment, length of hospital stay, level of pain, or any of the identical. An advantage of the latter is the possibility to extend the procedure to the standard approach. The mini-invasive technique must never be used at the expense of proper component centering.
The procedure should be undertaken by an erudite surgeon with sufficient experience based on a reasonable number of procedures.
Another advantage is that the mini-invasive approach allows to use both, cementless or cemented, implants.
Given the short-and mid-term outcomes and spectrum of patients in our center, we continue to regard the conventional anterolateral approach as the golden standard for the majority of patients. Further studies are warranted to definitively establish the position of the MIS-AL approach within the range of procedures performed in our center.