The purpose of this study was to highlight our experience using short-stem THA following failed internal fixation for PFF and to investigate potential risks and complications. No previous study has reported on one-stage short-stem THA in revision surgery after osteosynthetic hardware removal. PROMs and radiological results at the last follow-up were encouraging, along with high satisfaction rates. One patient with early dislocation and fracture of the greater trochanter required a change of the acetabular component and refixation of the greater trochanter. No other revision surgery was needed. Stem survival was 100% at the last follow-up.

Conversion THA is considered a salvage procedure with technical challenges and perioperative complications. Previous attempts were made to classify conversion THA as primary or revision THA. On the one hand, it has been suggested that conversion THA should be considered primary THA because, although it is a technically challenging procedure, it yields fewer orthopaedic complications compared to revision THA [25]. For example, in 2020, a matched cohort study by Vles et al. found that most (72%) of the patients who underwent conversion THA were treated with primary implants and never experienced a major complication [26].

On the other hand, it requires the removal of internal fixation devices and previous implants [9, 27]. Thus, conversion has often been associated with increased operative time and blood loss, increased fracture, dislocation, and infection rates, and lower functional outcome scores compared to primary THA [9]. Potential postoperative complications may therefore negatively influence the revision rate of conversion THA. Gjertsen et al. [28] analysed data from the Norwegian Arthroplasty Registry and found a higher revision rate for THA performed following failed internal fixation compared with acute fracture THA or primary THA. Dislocation and periprosthetic fracture were the most common causes of revision. Leonardsson et al. [6] examined data from the Swedish Hip Arthroplasty Registry and also found a high revision rate when comparing acute THA in fracture and THA performed after failed internal fixation (2.9% vs 4.4%). The most common causes of re-revision were dislocation and periprosthetic fracture, and the type of femoral component and surgical approach influenced the revision risk [6].

To date, in almost all data on conversion THA, either conventional straight stems or revision stems, cementless as well as cemented, were used. As far back as 2004, Zhang et al. reported on 19 patients who underwent conversion THA for failed internal fixation of intertrochanteric fractures [29]. Complications were common, given seven cases of intraoperative fracture of the greater trochanter and three cases of postoperative dislocation. HHS was 79.8 at the latest follow-up. Archibeck et al. published a series of 50 cases following failed internal fixation of proximal femoral fractures with a minimum 2-year follow-up in 2013 [5]. They found 12 patients who had early surgical complications related to the procedure, such as dislocations and periprosthetic fractures. At last follow-up, mean HHS was 81.8.

Over the last decade, short-stem THA has gained popularity in Germany, as well as in large parts of Europe, and is already used in > 10% of all primary cases [30]. Potential advantages compared to conventional THA are bone preservation and soft-tissue sparing [21]. Faster postoperative mobilization and a reduced hospital stay have been reported, as well as less blood loss and lower transfusion rates [31, 32]. Concurrently, indications for short-stem THA have constantly been expanded in recent years [14]. Although the use of short stems in revision surgery is considered off-label use, they may be selected to reduce surgical trauma and preserve as much femoral bone stock as possible.

Coutandin et al. recently introduced the concept of downsizing the femoral component in revision THA in a subset of cases using the same short stem as in the present study, and reported satisfying clinical outcomes and no major complications [15]. Another case series investigated the outcomes of revision surgery of failed hip resurfacing arthroplasty using short-stem THA. The authors concluded that cementless short stems may be considered as a revision implant for experienced surgeons [20]. Furthermore, Bostian et al. [19] published a surgical technique that uses short stems in cases of challenging proximal femoral anatomy, excessive femoral bowing, diaphyseal deformities, and retained implants.

The present case series supports the use of the investigated stem design in conversion THA. Only one case needed re-revision due to dislocation and greater trochanter fracture. None of the short stems had to be revised at the last follow-up. The design of the investigated short stem may account for potential advantages compared with earlier short-stem designs, particularly in cases with reduced bone quality. In addition to the metaphyseal fixation, this stem design enables the surgeon to intentionally choose an additional fit-and-fill in the proximal diaphysis [14] (Fig. 4) by applying a neutral or valgus alignment instead of a varus positioning. This may lead to increased safety for certain indications, such as conversion THA [33]. Moreover, operation time and blood loss could be held at low levels with short stems, and there was no need for blood transfusions, which corresponds to the current literature [32]. Given an HHS of 96.8, the clinical outcomes, including PROMs, were found to be superior compared to the available literature [5, 29].

The results of the present investigation are supported by the only previous study with data on the usage of short-stem THA in conversion THA. De Meo et al. reported conversion THA outcomes after failed fixation of intracapsular compared to extracapsular hip fractures and included seven cases in which a short stem was used [34]. No complications were observed during follow-up. They concluded that the physiological load distribution in the metaphyseal bone may reduce stresses in the cortical region, where the screw holes could create minor resistance points [34].

Although one of the major concerns when using a proximal anchoring short stem in conversion THA following internal fixation is the imminent risk of periprosthetic fracture in the region of prior screw holes, remarkably, there were no intraoperative or early postoperative fractures in the present series.. Archibeck et al. [5] recommended prophylactic cable placement in this region to avoid this issue. Haidukewych and Berry [7] advised bridging the cortical screw holes with long-stemmed femoral implants. Similarly, Winemaker et al. [35] recommended diaphyseal anchorage of the stem. In a biomechanical analysis performed by Chen et al. [36], a bypass of the last screw hole by at least 3 cm was recommended.

However, the superiority of the above-mentioned technical modifications was not substantiated by the results of the current study.

Another crucial step in conversion THA is excluding peri-implant infection as a cause of failed internal fixation. Besides preoperative blood work-up, hip punction is recommended to determine the need for a one- or two-stage conversion THA strategy [37]. Hemmann et al. [38] recently evaluated the infection risk for conversion THA by a one-stage procedure in the absence of clear infection signs. A positive microbiological test result was found in 10% of the cases of one-stage conversion THA, and a postoperative periprosthetic infection rate of 5.8% was reported. The present study only included patients without preoperative proof of a peri-implant infection who qualified for a one-stage procedure, as intraoperative microbiological testing using swabs or sonication was not used routinely at that time. However, no signs of periprosthetic infection were obvious in any patients at the last follow-up, supporting the one-stage strategy in those cases.

The present study has several limitations. First, the retrospective study design and small series are inherent limitations. However, there are almost no data available on the use of short stems in conversion THA, making the present results interesting for the orthopaedic community, even if only a small cohort is represented. Second, the lack of a control group limits a direct comparison to conventional conversion THA. Third, the short-term follow-up does not allow definite conclusions to be drawn about the safety of short-stem THA in revision surgery. Further studies with long-term data and larger populations are needed to confirm these findings. Finally, the current investigation only reflects the results of one stem design.