The learning curve of the direct anterior approach is 100 cases: an analysis based on 15,875 total hip arthroplasties in the Dutch Arthroplasty Register

BACKGROUND AND PURPOSE

In the last decade, the direct anterior approach (DAA) for total hip arthroplasty (THA) has become more popular in the Netherlands. Therefore, we investigated the learning curve and survival rate of the DAA in primary THA, using data from the Dutch Arthroplasty Register (LROI).

PATIENTS AND METHODS

We identified all patients who received a primary THA using the DAA in several high-volume centers in the Netherlands between 2007 and 2019 (n = 15,903). Procedures were ordered per surgeon, using date of operation. Using the procedure number, operations were divided into 6 groups based on the number of previous procedures per surgeon (first 25, 26-50, 51-100, 101-150, 151-200, > 200). Data from different surgeons in different hospitals was pooled together. Revision rates were calculated using a multilevel time-to-event analysis.

RESULTS

Patients operated on in group 1-25 (hazard ratio [HR] 1.6; 95% CI 1.1-2.4) and 26-50 (HR 1.6; CI 1.1-2.5) had a higher risk for revision compared with patients operated on in group > 200 THAs. Between 50 and 100 procedures the revision risk was increased (HR 1.3; CI 0.9-1.9), albeit not statistically significant. From 100 procedures onwards the HR for revision was respectively 1.0 (CI 0.6-1.6) and 0.8 (CI 0.5-1.4) for patients in operation groups 101-150 and 151-200. Main reasons for revision were loosening of the stem (29%), periprosthetic infection (19%), and dislocation (16%).

INTERPRETATION

We found a 64% increased risk of revision for patients undergoing THA using the DAA for the first 50 cases per surgeon. Between 50 and 100 cases, this risk was 30% increased, but not statistically significant. From 100 cases onwards, a steady state had been reached in revision rate. The learning curve for DAA therefore is around 100 cases.

MRI Assessment of Muscle Damage After the Posterolateral Versus Direct Anterior Approach for THA (Polada Trial). A Randomized Controlled Trial

BACKGROUND

There is controversy in literature whether the direct anterior approach (DAA) results in less muscle damage compared with the posterolateral approach (PLA) for total hip arthroplasty. The aim of this randomized controlled trial was to assess muscle damage between these two approaches.

METHODS

Forty-six patients were included. Muscle atrophy, determined with the Goutallier classification, and muscle surface of twelve muscles were analyzed on magnetic resonance imaging images made preoperatively and one year postoperatively. Differences in component placement after DAA or PLA were assessed on radiographs. Harris hip scores and Hip disability and Osteoarthritis and Outcome Score were used as functional outcomes.

RESULTS

External rotator musculature was damaged in both approaches. After PLA, the obturator muscles showed significantly more atrophy and a decrease in muscle surface. After DAA, the tensor fascia latae showed an increased muscle atrophy and the psoas muscle showed a decreased muscle surface. An increase in muscle surface was seen for the rectus femoris, sartorius, and quadratus femoris after both approaches. The muscle surface of the gluteus medius and iliacus was also increased after PLA. No difference in muscle atrophy was found between the approaches for these muscles. The inclination angle of the cup in PLA was significantly higher. No differences were found in functional outcomes.

CONCLUSION

Different muscle groups were affected in the two approaches. After PLA, the external rotators were more affected, whereas the tensor fascia latae and psoas muscles were more affected after DAA.

Flow cytometric assessment of leukocyte kinetics for the monitoring of tissue damage

Leukocyte populations quickly respond to tissue damage, but most leukocyte kinetic studies are not based on multiparameter flow cytometry. We systematically investigated several blood leukocyte populations after controlled tissue damage. 48 patients were assigned to either an anterior or posterolateral total hip arthroplasty. Peripheral blood was collected pre-operatively and at 2 h, 24 h, 48 h, 2 and 6 weeks postoperatively and assessed by flow cytometry for absolute counts of multiple leukocyte populations using standardized EuroFlow protocols. Absolute counts of leukocyte subsets differed significantly between consecutive time points. Neutrophils increased instantly after surgery, while most leukocyte subsets initially decreased, followed by increasing cell counts until 48 h. At two weeks all leukocyte counts were restored to pre-operative counts. Immune cell kinetics upon acute tissue damage exhibit reproducible patterns, which differ between the leukocyte subsets and with "opposite kinetics" among monocyte subsets. Flow cytometric leukocyte monitoring can be used to minimally invasively monitor tissue damage.

Rare presentation of Brodie's abscess in the acromion process and the value of the penumbra sign

A 17-year-old male patient presented with a swelling on his right shoulder 1 week after a fall. MRI revealed a superficial fluid collection of the acromion and trapezius muscle, with slight enhancement of the wall. The swelling burst open spontaneously after failed conservative therapy and was treated with surgical drainage and antibiotics. Tissue cultures showed a Staphylococcus aureus 1 year later, he presented with local red discolouration and a recurrent painful swelling that fluctuated at palpation. Radiographs showed a lytic lesion of the acromion process. MRI showed a sinus in the lytic cavity and a penumbra sign, which helped to identify this extremely rare occurrence of Brodie's abscess in the acromion process that was breaking through to the subcutaneous fat. The abscess was treated successfully with surgical drainage and intravenous antibiotics. In retrospect, the first MRI showed a small cortical indentation, with slight oedema of the acromion process.

The design of a randomised controlled trial to evaluate the (cost-) effectiveness of the posterolateral versus the direct anterior approach for THA (POLADA - trial)

Background

Total hip arthroplasty (THA) is one of the most successful orthopaedic procedures. Because of the increasing number of THAs, a growing demand for faster recovery and a greater emphasis on cost-effectiveness, minimally invasive THAs have been introduced in the last decades. The direct anterior approach is a minimally invasive, tissue-sparing approach in which intermuscular planes are used. Theoretically, this approach should result in a faster recovery of physical functioning and higher health-related quality of life.

Methods/design

A randomised controlled trial will be performed. Patients will be randomly allocated to undergo THA by means of the anterior or posterolateral approach. Both the intervention and control group will consist of two subgroups: 1) patients with a good bone stock who will receive an uncemented femoral stem, and 2) patients with a poor bone stock who will receive a cemented femoral stem. Patients between 18 and 90 years with primary or secondary osteoarthritis will be included. Physical functioning and health-related quality of life will be assessed by means of questionnaires. Additionally, performance based tests will be performed to objectively assess the physical functioning. Cost-effectiveness will be assessed by obtaining data on medical costs in and outside the hospital and other nonmedical costs. Measurements will take place preoperatively, two and six weeks, three months and one year postoperatively.

Discussion

There is some evidence that the anterior approach results in reduced tissue damage and faster recovery in the direct postoperative period, compared to the posterolateral approach. However, there is still a lack of well-designed studies that have confirmed the better outcomes and cost-effectiveness of the anterior approach. Therefore, the purpose of this study is to assess the physical functioning, health related quality of life and the cost-effectiveness of the anterior approach, compared to the conventional posterolateral approach.

Trial registration

Netherlands Trial Registry, number 5343 (registration date April 12, 2015)

Electronic supplementary material

The online version of this article (doi:10.1186/s12891-016-1322-2) contains supplementary material, which is available to authorized users.