Total hip arthroplasty (THA) in a patient with subcapital femoral neck fracture and ipsilateral above-knee amputation: A case report

This case report describes the surgical and post-operative challenges encountered following a THA performed for a subcapital femoral neck fracture in a patient with an ipsilateral above-knee amputation.


Introduction
Femoral neck fractures in amputee patients pose a challenge for orthopaedic surgeons and the entire team involved in postoperative rehabilitation.These fractures are uncommon, and the literature on the topic is limited.[1][2][3][4][5][6][7][8][9] Management of femoral neck fractures in patients with above-knee amputations is particularly challenging for the surgeon.[6][7][8][9] This is primarily due to the difficulties involved in the intraoperative management of the femoral stump.The altered anatomy and disuse osteoporosis typical of these patients can lead to diagnostic errors, favor immobilization, make surgical reduction and stabilization more difficult, and ultimately slow down post-operative rehabilitation.[5][6][7][8][9][10] In a patient with a femoral neck fracture who uses an external prosthesis to ambulate, it is essential to prioritize a return to preinjury activities as quickly as possible.
This study presents the case of a patient with a right above-knee amputation who suffered a type 31B1.3AO subcapital fracture on the same side, which was treated with a total hip replacement.

Case report
An 85-year-old male patient presented to the emergency department of our hospital in July 2023 with a low-impact trauma and right hip pain following a fall from the toilet.He was in a septic state with fever, anuria, and asthenia.The patient's past medical history included moderate-grade cardiopathy, COPD, epilepsy, and an indwelling urinary catheter.In 2021, he underwent an above-knee amputation of the right femur due to obliterating vasculopathy of the lower limbs.
At the physical examination the trochanteric and inguinal regions were tender and painful.The overlying skin was intact, with a       well-healed surgical scar at the distal end of the stump, consistent with an above-knee amputation.No peripheral vascular or neurological deficits were apparent.No other injuries were identified.Radiographs showed a type 31B1.3AO subcapital fracture (Figs. 1 and 2).Due to septic shock originating from the indwelling urinary catheter, the patient was admitted to the internal medicine department of our hospital for treatment.
In September 2023, after hemodynamic stabilization, approximately two months after his admission to the emergency department, the patient underwent a pre-operative orthopaedic consultation and was scheduled for a THA.According to a previous infectious disease video consultation, the patient was colonized in the lower urinary tract with Pseudomonas Aeruginosa and Klebsiella pneumoniae mdr despite antibiotic therapy.Therefore, in addition to the usual pre-operative antibiotic prophylaxis used in our center (cefazolin 2 g IV 30 min before surgery), 1 vial of ceftazidime/avibactam 2 g/0.5 g was administered on the evening before surgery and repeated for two days post-operatively, as prescribed by the infectious disease specialist.
A THA was decided upon due to the patient's high functional demand.Prior to the trauma, and despite his numerous comorbidities, the patient was active and regularly exercised with his external prosthesis.
After obtaining informed consent, the procedure was performed under subarachnoid anesthesia, with the patient in the left lateral decubitus position and using a direct lateral approach to the right hip approximately 20 cm long.This was to facilitate the management of the femoral stump during the dislocation maneuvers.No Steinmann pins or other instruments were inserted in anatomic landmarks to facilitate the control of the stump.A 48 mm porous coated uncemented acetabular shell (Adler Ortho) was aligned with the transverse acetabular ligament.A cementless size 4 type femoral stem was inserted (Adler Ortho) and a 28 mm hooded Polyethylene liner was used (Adler Ortho).After trials, a 28 mm femoral head alumina ceramic (Adler Ortho) was impacted and the hip was reduced.
Accurate attention was paid to correctly aligning the femoral stem, respecting its anteversion.The preparation of the femoral canal was possible thanks to the use of a Verbrugge bone-holding forceps, which was used to gently extrarotate the femoral stump.
Since the patella could not be used as a reference point, it was decided to orientate ourselves by palpating the lesser trochanter and, Fig. 6.The patient 6 months after surgery.visually, on the orientation of the femoral canal at the level of the femoral neck osteotomy.
The patient received post-operative antibiotics and anticoagulant therapy, according to departmental protocols.No complications occurred in the post-operative period (Figs. 3 and 4).In the immediate post-operative period, the patient began appropriate physiotherapy: Strengthening of the lower limb muscles, readaptation of the stump to the external prosthesis, progressive re-education of the gait pattern.After two weeks, the patient was able to stand and began to walk with the help of a physiotherapist and appropriate aids (Fig. 5).Three months after the trauma, he was able to walk without aids for short distances.During the first month, the use of the prosthesis was uncomfortable due to significant swelling of the stump, which subsided gradually with the use of an elastic bandage.
At the 6-month follow-up, the amputated limb was in good condition (Figs.6-7).On objective examination, the hip joint was completely mobile, with no pain.No leg length discrepancy was noted when wearing the prosthesis.Radiographs showed wellincorporated femoral and acetabular components without any sign of osteolysis.

Discussion
We have reported a case of subcapital femoral fracture in a patient with above-the-knee amputation.The surgical challenge arises from the reduced lever arm due to the femoral stump, the absence of the patellar landmark to guide the correct anteversion of the femoral stem, and the increased delicacy required in handling the osteoporotic stump [10,11].Despite the waiting period for the Total Hip Arthroplasty (THA) procedure due to the concurrent septic shock condition, the patient showed no clinical or radiographic improvement.Conservative treatment of a femur with a short lever arm may be considered, provided there are no displaced cervical or intertrochanteric fractures [12,13].In our specific case, the severe displacement, pre-existing coxarthrosis, and respect for the patient's functional expectations necessitated a THA surgical treatment.Utmost attention was paid to the surgical access, which, although extensive to facilitate dislocation maneuvers, was extended in such a manner to avoid creating conflict or pressure on the external prosthesis.Postoperatively, physical therapists paid considerable attention to the readjustment of the stump on the external prosthesis.The post-operative edema, associated with that due to disuse from the fractured limb, had caused an increase in the diameters of the stump, consequently making it difficult to comfortably wear the external prosthesis.The use of elastic bandages applied in a manner to achieve gradual compression that stimulated venous return, allowed the readjustment of the stump to the external prosthesis in less than two weeks.Given the results achieved, following careful preoperative planning and considering the patient's functional expectations, we believe it is always appropriate to evaluate surgery in ambulatory above-the-knee amputees, so as to ensure a rapid return to daily activities and social life.