The successful management of PJI is challenging. In the presence of significant bone loss, these difficulties are multiplied. This adaptation of the CUMARS technique has the versatility to be used as an interim spacer and in some patients as a single stage procedure. This is achieved through a stable cemented construct that preserves bone stock, prevents soft tissue contracture and allows unrestricted mobility. This is evidenced by the extended period between 1st and 2nd stage revision. This is not possible using alternative techniques which have limited rotational and longitudinal stability [15, 20].
Given the small numbers of patients who suffer this complication, the literature on the treatment of PJI in the context of severe proximal femoral bone loss is scarce. Multiple techniques have been described which include the use of cement loaded Kuntscher nails , modular articulating antibiotic spacers , long stem uncemented THA with antibiotic impregnated allograft bone  and endoprostheses . Despite the multitude of surgical descriptions, there are only four comparable case series of more than five patients identified in our literature search [17, 18, 24]. Our study is the largest to report on spacer design in the presence of femoral deficiency with one of the longest follow-ups.
Ben-Lulu et al.  report the use of a femoral antibiotic-impregnated cement spacer mould with a metal endoskeleton that was press fit into a pre-cut reamed intramedullary nail in 11 patients. Patients were allowed to touch-weight bear between 1st and 2nd stage procedures. Infection was eradicated in 90.9% but after only 1.25 years (range 1–1.5 years). Reimplantation was performed on average 3.5 months post 1st stage revision. Excluding death and recurrence of infection, they had two complications (18.2%): one dislocation and one dissociation between the nail and the spacer.
Hsieh et al.  report the outcomes of 8 patients with femoral deficiencies and one with a combined acetabular and femoral deficiency at 4.2 years follow up. They used a custom-made articulating spacer reinforced with Kirschner wires. Patients could touch-weight bear until 2nd stage revision at an average of 3.2 months. They had three spacer related complications including two spacer fractures and a dislocation.
Winkler et al.  treated 37 patients with PJI using uncemented prostheses and antibiotic impregnated bone allograft. Some had extensive femoral bone loss and were given long stems but there was no further analysis of this subset. Overall a high level of infection eradication (92%) was observed. Similar to our study, they advocate this as a single stage procedure with an early repeat 1st stage revision where this fails. The technique is not advised in the presence of Paprosky type 3 acetabular defects.
Finally, in two papers by Alvand and Grammatpolous [1, 24] they report on endoprosthetic replacements used in treating PJI in 40 hip patients with a 5 year follow up. They found an overall infection eradication of 82.5%. Their overall complication rate excluding recurrence and death was 40% however it is unclear which were due to the spacer. The time between 1st and 2nd stage procedures isn’t reported, though the 2nd stage appears to be mandatory in the majority of cases (70%). A proportion (30%) had a planned single stage due to frailty or because the bone stock prohibited formal two stage revision.
This technique has multiple advantages and has been demonstrated successfully in a case-series of 53 patients who have underwent first stage revision using standard primary stems . Firstly, it uses readily available materials that are familiar to surgeons who cement their prostheses without the need to extend the indications of an implant e.g. femoral nail or spend large amounts on endoprostheses. The financial cost to the patient and the hospital of PJI is huge. Vanhegan  and Kapadia  estimate the difference in cost between a septic revision of infected THA and either an aseptic revision or a primary THA to be £10,000 and $63,000 respectively. Hence, managing the financial burden through the use of more cost-effective implants is imperative.
Secondly, the use of cement allows delivery of high levels of localised antibiotics that can be tailored to the appropriate cultured microbiology [12, 27] and avoid the complications associated of systemic administration . The use of antibiotic loaded cement is part of the gold standard for treating PJI .
Thirdly, all patients were allowed to weight bear as tolerated. This functions to maintain bone stock, muscle mass and avoids complications of immobility. Allowing patients greater levels of independence and function is desirable both to facilitate rehabilitation and to reduce the burden on social care.
Fourthly, patients requiring this technique have histories littered with multiple revision surgeries, chronic infections, significant co-morbidities and bone loss. Despite these challenges, this technique achieves high levels of infection eradication comparable to current published literature [1, 17, 18].
Fifthly, this technique preserves overall bone stock. While complications and infection clearance are comparable with those achieved using endoprosthetic replacement, it does maintain options for future revision.
Finally, while the majority of patients have a 2nd stage procedure, it is not mandatory. In our cohort, there was on average 9 months between stages and five patients have cleared infection but have not undergone 2nd stage revision. These implants have survived an average of 3.8 years.
Like many of the papers addressing PJI, it has a number of weaknesses. Firstly, this is a retrospective review although the data are predominantly complete. Secondly, it is a heterogenous group of patients with a variety of presentations. There are also a vast range of primary implant histories. Thirdly, functional scoring was not available for all patients but the comparable eradication and revision rate in similar series serve as a proxy. This underpowered the clinical outcomes analysis, though there was a clear trend in all three measures. These case series are small and only multicentric studies performing the same technique would achieve sufficient statistical power. Fourthly, the acetabular defects and the cups used were different which may affect the results. This demonstrates the versatility of the technique.