Patient disposition
The sampling frame consisted of 361 patients who had undergone primary THA. Fifty-nine cases used HFPC-DM-HA and all of them were included in the cohort. Six patients (10%) were lost to 2-year follow-up (Fig. 2).
Sampling frame characteristics
Acetabular cups used in the sampling frame were 242 (67.0%) standard acetabular cups (STD) and 111 (31.6%) DM. Fifty-nine (16.3%) of DMs were HFPC-DM-HA and 55 (15.2%) were other models (Fig. 2). The overall female/male ratio was 171/190 (47.4%/52.6%) (Table 1) and DM were used significantly more frequently in female than in male (58.8% vs. 41.2%, Fisher exact test p = 0.003). HFPC-DM-HA was used in female more frequently than other DM were, but the difference was not significant (67.8%/49.1%, Fisher exact test: p = 0.057).
Table 1
Cup | Total n (%) | female / male n (%) | age mean (sd) | primary THA n (%) | revision THA n (%) |
HFPC-DM-HA | 59 (16.3) | 40 (68)/ 19 (32) | 78.8 (5.6) | 58 (98) | 0 (0.0) |
Other DM | 55 (15.2) | 27 (49) / 28 (51) | 78.0 (11) | 36 (65) | 18 (33) |
Standard | 242 (67.0) | 101 (41.7) /141 (58.3) | 58.6 (12.2) | 232 (95.9) | 7 (2.9) |
Total | 361 (100) | 171 (47.4) / 190 (52.6) | 65.2 (14.6) | 328 (90.9) | 28 (7.8) |
Mean age at the time of surgery was 65.2 [63.7, 66.7]. Patients treated with STD were significantly younger than patients treated with overall DM (mean difference 19.8 years [17.5, 22.1], p < 0.0001). There was no significant age difference between HFPC-DM-HA and other DM (rank sum test: p = 0.197).
Most cases, i.e. 90.9%, were primary THAs with 7.8% revision THAs. Revisions were performed mainly with other DM (72%) and less frequently with STD (28%) (p < 0.001). No HFPC-DM-HA was used for revision THA (although data was missing for one patient) while 33% of other DM were used for revision THA (p < 0.001).
There was no significant difference in gender (Fisher exact test: p = 0.057) or age distribution (t-test: p = 0.66) between the HFPC-DM-HA cohort and patients treated with other DM.
Patients undergoing primary THA were significantly younger than those undergoing revision THA (mean difference: 8.1 years [1.8, 14.5], p = 0.0134).
The cohort median post-operative time to study follow-up date was 3.0 years (range: 2.7 ; 4.1).
HFPC-DM-HA cohort preoperative characteristics
Median patient age at the time of surgery was 77.5 years (range: 67 ; 92), female/male ratio was 32% / 68% and a median body mass index (BMI) of 25.2 kg.m− 2 (range: 18.4 ; 56.8) (Table 2). The main etiologies were primary osteoarthritis of the hip was (80%) and acetabular protrusio (10%). One patient (2%) had prior surgery of the operated area with prior nail osteosynthesis of a pertrochanteric fracture.
Table 2
Cohort demographics & operative details
Baseline |
| n | mean | sd | min | p25 | p50 | p75 | max |
age (years) | 58 | 78.7 | 5.5 | 67.1 | 74.7 | 77.5 | 81.5 | 92.5 |
height (cm) | 56 | 164.8 | 9.2 | 143 | 159 | 165 | 170.5 | 182 |
weight (kg) | 56 | 74.3 | 24.1 | 48 | 60 | 71.5 | 81.5 | 180 |
BMI (kg/m²) | 56 | 27.1 | 7.0 | 18.4 | 23.5 | 25.2 | 29.6 | 56.8 |
Gender n (%) male / female | 40 (68) / 19 (32) |
Side n (%) right / left | 39 (66) / 20 (34) |
Prior hip surgery n (%) | 1 (2) |
Etiology n (%) primary osteoarthritis of the hip acetabular protrusion rapidly destructive osteoarthritis (RDO) hip dysplasia other causes TOTAL | 47 (80) 6 (10) 3 (5) 1 (2) 2 (3) 59 (100) |
Operative details |
Shell diameter (mm): range | 48 ; 56 |
Bone graft n (%) Cup Stem | 0 (0) 0 (0) |
Associated surgery n (%) none hell repositioning | 58 (98.3) 1 (1.7) |
Operative time (minutes): median & range | 53 (42, 110) |
Intraoperative events/outcomes |
Complications n (%) fracture of greater trochanter, Vancouver class A3 partial facture of greater trochanter & calcar fracture line, Vancouver class A2 calcar fracture line, Vancouver class A2 | 2 (3.4) 1 (1.7) 1 (1.7) |
Hip stability n (%) | excellent 59 (100) / medium 0 (0) |
Operative characteristics
All THAs were performed using an anterior approach and most were on the right side (66%) (Table 2).
All HFPC-DM-HA were press-fit without the use of cement, screws or bone grafting. All had a PE liner fitted with a CoCr alloy femoral head. Acetabular shell diameters ranged from 48 to 56 mm and the most frequent used diameter range (54%) was 50 to 54 mm. Femoral stems were all cementless (100%).
One patient required intra-operative additional procedure for shell repositioning after testing.
Median operative time was 53 minutes (range: 42 ; 110). All prostheses presented excellent intraoperative stability. Four patients presented intraoperative periprosthetic fractures or fracture lines without need for additional treatment.
Primary endpoint: Implant survival
Two patients required revision of their hip prosthesis including the HFPC-DM-HA. One was caused by a fall that caused a fracture of the operated area (Vancouver class A) on postoperative day-8. The other was caused by a surgical site infection on postoperative day-7.[12, 13]
The Kaplan-Meier cumulative survival rate of HFPC-DM-HA at 2-year follow-up was 96.6% [87.1, 99.1] with a total time at risk of 131.2 years (Fig. 3). That rate was calculated over the initial cohort of 59 patients taking into account the 2 known failures, 1 death and the 7 patients lost to follow-up.
Secondary endpoints: Postoperative implant or procedure-related complications
Post-operative adverse events, whether related or not to the procedure or implant, were reported in 39 patients (66%) presented (Table 3). Nineteen patients (32%) presented postoperative complications that were adjudicated as procedure and/or implant related. These included the 2 events that caused prosthetic hip revision described previously, 13 with pain in the ipsilateral hip, pelvis or thigh and 4 with surgical scar-related problems. No prosthetic dislocation including IPD was reported during follow-up.
Table 3
– HHS - mHHS – Serious adverse events
HHS | n | min | max | median | mean | sd | 95% CI |
HHS preoperative | 55 | 21.3 | 95.2 | 44.7 | 49.5 | 19.1 | [44.3,54.6] |
HHS 1-year | 57 | 40.0 | 100.0 | 88.6 | 84.6 | 14.3 | [80.8,88.4] |
range of motion preoperative | 59 | 2.3 | 5.0 | 4.4 | 4.3 | 0.6 | [4.1,4.4] |
range of motion 1-year | 58 | 3.6 | 5.0 | 4.8 | 4.7 | 0.3 | [4.6,4. 8] |
mHHS: preoperative | 59 | 7 | 87 | 36 | 39.7 | 19.5 | [34.6,44.7] |
mHHS: 1-year | 57 | 31 | 91 | 81 | 75.8 | 14.3 | [72.1,79.6] |
mHHS: 2-year | 51 | 31 | 91 | 91 | 86.7 | 10.6 | [83.7,89.7] |
Patients with post-operative severe adverse events n (%) |
description | 1-year | 2-year | Overall |
none | 31 | 24 | 15 (25.4) |
dislocation | 0 | 0 | 0 (0) |
pain in the ipsilateral hip, pelvis or thigh | 7 | 8 | 5 (8.5) |
scar-related problem | 4 | 1 | 4 (6.8) |
surgical site infection | 1 | 0 | 1 (1.7) |
fall and fracture of the operated area (Vancouver class A) | 1 | 0 | 1 (1.7) |
cup insufficient fixation | 1 | 0 | 1 (1.7) |
psoas syndrome or tendonitis | 1 | 0 | 1 (1.7) |
pain in the ipsilateral knee | 3 | 1 | 4 (6.8) |
spinal problem or sciatica | 3 | 2 | 5 (8.5) |
disease, trauma or operation of contralateral hip | 2 | 3 | 5 (8.5) |
unrelated death | 0 | 1 | 1 (1.7) |
other | 3 | 12 | 11 (18.6) |
missing | 2 | 7 | |
Secondary endpoints: Functional outcomes
HHS and mHHS were closely correlated preoperatively (R-squared: 0.9993, p < 0.0001,) and at 1-year follow-up (R-squared: 0.9995, p < 0.0001, Fig. 4). Detailed analysis of scores showed that the change in HHS was mostly driven by the change in mHHS items. This suggested that the mHHS at 2-year follow-up could be reasonably compared to prior measurements, although the range of motion and deformation subscores were not available at 2-year follow-up. Pre- and postoperative HHS and mHHS summary in Table 3
Mean within-patient HHS increased from preoperative baseline to 1-year follow-up by 34.4 [28.5, 40.4] (Wilcoxon signed-rank test p < 0.0001). Mean within-patient mHHS increased from baseline to 1-year follow-up by 35.4 [29.6, 41.1] (p < 0.0001) and from baseline to 2-year follow-up by 46.5 [40.3, 52.8] (p < 0.0001).