Total hip replacement is a major surgical procedure with several complications and a mortality rate of 1–2%. (1) Sir John Charnley, the English orthopedic surgeon who developed the basic principles of the artificial hip joint, is considered the father of total hip replacement. He developed hip replacements in the mid-to-late 1960s. Approximately 500,000 THAs are performed annually in the U.S. alone. Primary total hip arthroplasty (THA) is expected to increase by 71% to 635,000 by 2030 (2). Test metals included gold foil and a cobalt-chromium-molybdenum (Co-Cr-Mo) alloy, which were later used as dental materials. The use of steel to repair cracks was documented by 1804 (3). By the 1950s, McKee and Ferrar introduced the first one-piece metal-to-metal joint, initially in stainless steel but later changing to Co-Cr-Mo (4). Cobalt alloys were accepted by the biomaterials community in the 1950s and early 1960s. The alloys currently used in orthopedics include mainly iron-based alloys (stainless steel), cobalt-based alloys, and titanium-based alloys (5). Recently, the mechanism of implant failure has become the subject of intense research as the life expectancy and lifespan of such implants are increasing (6). In 1988, approximately 11 million people in the United States owned at least one medical implant. Joints accounted for 44% of all medical implants. The proportion of people using a fixation device and joint prosthesis with one or more problems was 33.2% and 31.6%, respectively. The demand for such medical device implants is expected to increase in the coming years (7). Uncemented femoral stems were classified in 2011 by Khanuja et al. (8). In 2020, that classification system was modified by Kheir et al (9) to include short stems. These systems defined 7 major implant types, further broken down by stem geometry, cross-sectional properties, and surface characteristics. Although these classification systems allow for a structured discussion of cementless stems by their functional outcome, the specificity with which they classify stems based on geometry, cross-sectional properties, surface characteristics, and length makes it difficult to classify several new stems. The majority of cementless femoral stems are made of titanium, aluminum vanadium alloy, or cobalt-chromium molybdenum alloy, with the vast majority being titanium aluminum vanadium alloy. A randomized controlled trial of 423 primary THAs demonstrated that titanium stems are associated with lower rates of thigh stress and pain compared with cobalt-chromium stems (10). Albrektsson et al (11) demonstrated that osteoinduction, osteoconduction, and osseointegration resulted from the biocompatibility and lower modulus of elasticity of titanium alloy (100 GPa), which more closely resembles cortical bone (20 GPa) compared with cobalt-chromium (220 GPa). Despite typical excellent clinical outcomes, THA is often associated with less than physiological proximal load transfer and predominantly diaphyseal fixation. This phenomenon has been associated with thigh pain and proximal stress shielding, which, according to a study by Jo et al. (12), analyzed 240 primary uncemented THAs, occurring in 11.3% of patients. Both Ishii et al. and Nam et al. reported that poor canal filling along the stem is likely responsible for this insufficient osseointegration and subsequent thigh pain (13,14). Shorter stems were later introduced and may allow for more physiological proximal load transfer (15).

Material and Methods:

An ambispective, longitudinal cohort study was conducted. Patients postoperatively after total hip arthroplasty from 2016 to December 2024 were included. Patients were treated with long, splined, conical uncemented stems compared to porous-coated cylindrical stems. Patients were identified in the outpatient clinic of the joint department.

An exhaustive search was conducted in the operating room logbook and the hospital's medical archive to identify patients, schedule appointments with follow-up radiographs, and assess functional status and pain using the Harris Hip Score and the Visual Analogue Scale (VAS) for pain.

Results:

Our sample consisted of 48 patients, 52.08% women and 47.92% men, respectively, 25 women and 23 men (Figure 1).

Figure 1: Shows the prevalence of gender, with the female gender having the highest prevalence.

Among the diagnoses reported at the first primary prosthesis surgery were hip osteoarthritis (47.92%), Hip dysplasia (6.25%), basal-vein fracture (12.50%), subcapital fracture (6.25%), transcervical fracture (18.75%), osteonecrosis secondary to fracture (6.25%), and cutout of a centromedullary nail (2.08%) (Figure 2).

Figure 2: The diagnoses of the first primary prosthesis surgery are reported, with coxarthrosis as the most common preoperative diagnosis.

Among the etiologies for revision, there were periprosthetic fractures (31.25%) (15 patients in total), periprosthetic infections (27.08%) (13 patients in total), aseptic loosening (25%) (12 patients in total), and instability (16.67%) (8 patients in total) (Figure 3).

Figure 3:The etiologies of revision prosthesis surgery are reported. Periprosthetic fractures are reported to be the most common cause of prosthetic revision.

Among the outcomes for our dependent variables (pain and function). In the evaluation of pain of the revision femoral component with the fluted conical stem, a total of 24 postoperative patients were obtained, the asymptomatic patients represented were 31.25% and with pain 18.75%. In the end, this represents 50%. Regarding the femoral component revision with the cylindrical stem with extensive porous coating, a total of 24 postoperative patients were obtained. Within the reported results, 33.33% were asymptomatic and 16.67% had pain. This ultimately represents a total of 50%. Based on these results, pain was not statistically significant, with a p value of 0.76 (Figure 4).

Figure 4: The image shows the pain assessment of the revision femoral component with a fluted conical stem versus a cylindrical stem with extensive porous coating. The results are not statistically significant.

The other dependent variable studied was function based on the Harris Hip Scale. When comparing different femoral revision components, our results showed a total of 24 patients with a fluted conical stem (50%) and 24 patients with a cylindrical stem with extensive porous coating (50%). Within the fluted conical stem, good function was achieved in 29.17% of cases, favorable in 16.67%, excellent in 2.08%, and poor in 2.08%. On the other hand, the cylindrical stem with extensive porous coating achieved good function in 14.58% of cases, favorable in 16.67%, and excellent in 18.75%. Based on these functional results, there is statistical significance, with a p < 0.021, and we recommend extensively coated cylindrical stems for function. (Figure 5)

Figure 5: In the reported image, the variable studied was the function based on the Harris Hip scale, with the fluted conical stem vs. cylindrical stem with extensive porous coating, which have statistical significance and recommending cylindrical stems with extensive coating.