Calculating hominin and nonhuman anthropoid femoral head diameter from acetabular size.

Background and purpose Previous population-based registry studies have shown that larger femoral head size is associated with reduced risk of revision for dislocation. However, the previous data have not included large numbers of hip resurfacing arthroplasties or large metal-on-metal (> 36-mm) femoral head arthroplasties. We evaluated the association between femoral component head size and the risk of revision for dislocation after THA by using Finnish Arthroplasty Register data.Patients and methods 42,379 patients who were operated during 1996–2010 fulfilled our criteria. 18 different cup/stem combinations were included. The head-size groups studied (numbers of cases) were 28 mm (23,800), 32 mm (4,815), 36 mm (3,320), and > 36 mm (10,444). Other risk factors studied were sex, age group (18–49 years, 50–59 years, 60–69 years, 70–79 years, and > 80 years), and time period of operation (1996–2000, 2001–2005, 2006–2010).Results The adjusted risk ratio in the Cox model for a revision operation due to dislocation was 0.40 (95% CI: 0.26–0.62) for 32-mm head size, 0.41 (0.24–0.70) for 36-mm head size, and 0.09 (0.05–0.17) for > 36-mm head size compared to implants with a head size of 28 mm.Interpretation Larger femoral heads clearly reduce the risk of dislocation. The difference in using heads of > 36 mm as opposed to 28-mm heads for the overall revision rate at 10 years follow-up is about 2%. Thus, although attractive from a mechanical point of view, based on recent less favorable clinical outcome data on these large heads, consisting mainly of metal-on-metal prostheses, one should be cautious using these implants.

Posterior dislocation continues to be a relatively common complication following total hip arthroplasty. In addition to technical and patient-associated factors, prosthetic features have also been shown to influence stability of the artificial hip joint. In this study, a dynamic model of the artificial hip joint was used to examine the influence of the size of the head of the femoral component on the range of motion prior to impingement and posterior dislocation following total hip replacement. Six fresh cadaveric specimens were dissected, and an uncemented total hip prosthesis was implanted in each. Each specimen was mounted in a mechanical testing machine and loaded with use of a system of seven cables attached to the femur and pelvis that simulated the action of the major muscle groups crossing the hip joint. The hip was taken through a range of motion similar to that experienced when rising from a seated position. The three-dimensional position of the femur at the points of impingement and dislocation was recorded electronically. The range of joint motion was tested with prosthetic femoral heads of four different diameters (twenty-two, twenty-six, twenty-eight, and thirty-two millimeters). Significant associations were noted between the femoral head size and the degree of flexion at dislocation in ten (p = 0.001), twenty (p < 0.001), and thirty (p = 0.003) degrees of adduction. Increasing the femoral head size from twenty-two to twenty-eight millimeters increased the range of flexion by an average of 5.6 degrees prior to impingement and by an average of 7.6 degrees prior to posterior dislocation; however, increasing the head size from twenty-eight to thirty-two millimeters did not lead to more significant improvement in the range of joint motion. The site of impingement prior to dislocation varied with the size of the femoral head. With a twenty-two-millimeter head, impingement occurred between the neck of the femoral prosthesis and the acetabular liner, whereas with a thirty-two-millimeter head, impingement most frequently occurred between the osseous femur and the pelvis. With the particular prosthesis that was tested, increasing the diameter of the femoral head component increased the range of motion prior to impingement and dislocation, decreased the prevalence of prosthetic impingement, and increased the prevalence of osseous impingement. These results suggest that femoral heads with a twenty-eight-millimeter diameter increase the range of motion after total hip replacement. This may be beneficial when additional factors compromising joint stability are encountered.

Preoperative templating in hip arthroplasty surgery is crucial for accurate implant selection and reducing postoperative complications. This study examines whether there is a correlation between femoral head size and shoe size, with the aim of simplifying the preoperative planning process. A total of 14 patients had their shoe size and femoral head size measured. Data were analyzed using linear regression and Pearson's correlation analysis to quantify the relationship between the two variables. The Pearson correlation coefficient revealed a value of 0.80 (p = 0.0007), and the linear regression model showed that 63% of the variation in shoe size was based on femoral head size. The study demonstrates a strong and significant correlation between shoe size and femoral head size. This correlation could potentially be used to develop a simple calculation method, where femoral head size = (shoe size - 23.9) / 0.36, which may streamline preoperative planning in orthopedic surgery and reduce workload. None. None.

While discussing the hip joint failure, material selection and apposite dimension of the femoral head are a significant concern for the artificial hip replacement. In this context, an attempt was made to optimize both ball head and socket material from different combinations like femoral head (metal)—acetabular liner (Polyethylene) and femoral head (ceramic)—acetabular liner (ceramic) in consideration of a different set of femoral ball head size of 28, 30 and 32 mm. The material and femoral head size were optimized in the perspective of minimum stress that eventually enhances the prosthesis life and minimizes the wear of counter bodies. The hip joint prosthesis was designed in CATIA V5 R17 followed by finite element analysis (FEA) was performed in ANSYS 17.2. Dynamic FEA was performed when the 100 kg human in jogging. A theoretical optimization established the combination of ceramic–ceramic articulating body consists of 30.02 mm ID acetabular liner—30 mm OD femoral head made of zirconia toughened alumina (ZTA) experience less stress and deformation that eventually exhibit very low wear rate per cycle of jogging. This design exhibits 0.93 mm wear depth after 15 years of activity; however, similar theoretical analysis can be done under different degree of dynamic motions. The proposed material and design combination has excellent potential for the development of artificial hip joint prosthesis.

Preoperative planning is an important step before any joint replacement surgery. In developing countries standardised radiographs and planning tools might not be available but nevertheless hemiarthroplasties are performed in certain trauma cases. An equation should be devised to allow a preoperative estimation of the expected femoral head size dimensions in those situations. 35 lower limbs of human cadavers were studied. The estimated femoral head (EFH) size of each femur was obtained by measuring the trochanteric length (TL) (in cm) and using the equation 'EFH = 16 + (0.7 × TL)'. The hip joint was dissected, and the actual size of the femoral head (AFH) was measured on the specimen. There was a correlation between the EFH and AFH (p = 0.0001). Accepting a range of ±3 mm the femoral head size was predicted correctly in 31 hips (89%), for ±4 mm in 33 hips (94%) and for ±5 mm in 35 hips (100%), respectively. A simple tape measurement and the equation Femoral head size = {16 + (0.7 × Trochanteric Length)} ±5 mm gives a rather reliable guess for the expected femoral head size. It might be useful as pre-operative planning tool if no standardised radiographs are available.

Effects of the Femoral Offset and the Head Size on the Safe Range of Motion in Total Hip Arthroplasty

Highly Cross-Linked Polyethylene in Patients 50 Years of Age and Younger: A 20-year Follow-Up Analysis

The stability and durability of total hip reconstruction is dependent on many factors that include the design and anatomic orientation of prosthetic components. An analysis of femoral component head size and acetabular component orientation shows an interdependency of these variables and joint stability. Increased femoral component head size can increase hip stability by increasing the prosthetic impingement-free range of hip motion and by increasing the inferior head displacement required before hip dislocation. Increasing the femoral head size from 22 mm to 40 mm increases the required displacement for dislocation by about 5 mm with the acetabular component at 45 degrees of abduction; however, increasing acetabular component abduction greatly diminishes this stability advantage of larger femoral heads. Vertical acetabular component orientation and femoral component head subluxation are each predicted to more than double the tensile stress with acetabular component polyethylene compared with components at 45 degrees of abduction. With a desirable acetabular component orientation, the use of larger femoral heads may result in improved joint stability and durable use of polyethylene. With high abduction acetabular component orientation, the use of larger femoral heads contributes little to joint stability and contributes to elevated stress within the polyethylene that may result in implant failure.

Highly crosslinked polyethylene (XLPE) was introduced to decrease periprosthetic osteolysis related to polyethylene wear, a major reason for revision of total hip arthroplasty. However, there are few reports of wear and osteolysis at 10 years postoperatively. (1) What are the linear and volumetric wear rates of XLPE at 10 to 14 years? (2) What is the relationship among linear wear, volumetric wear, and femoral head size? (3) What proportion of hips developed osteolysis and was there a relationship between osteolysis and femoral head size or polyethylene wear? We evaluated a previously reported cohort of 84 hips (72 patients) with one design of an uncemented acetabular component and one electron beam 10-kGy irradiated and remelted XLPE at a mean followup of 11 years (range, 10-14 years). The choice of femoral head size was based on several factors, including the outer diameter size of the acetabular component implanted, the perceived risk of dislocation (including the history of alcohol abuse and patient age), and liner availability from the manufacturer. The femoral head sizes used were 26 mm in 10 hips (12%), 28 mm in 31 hips (37%), 32 mm in 31 hips (37%), 36 mm in eight hips (10%), and 40 mm in four hips (5%). Measurements of linear and volumetric wear were performed in one experienced laboratory by the Martell method and analyzed using the first-to-last method. Standard radiographs, with additional Judet views, were used to detect periprosthetic osteolysis. Statistical analysis of wear and osteolysis compared with head size was performed. For the entire cohort, the median linear wear rate as 0.024 mm/year (95% confidence interval [CI], 0.016-0.030) and the median volumetric wear rate was 12.19 mm(3)/year (95% CI, 6.6-15.7). With the numbers available, we found no association between femoral head size and linear wear rate. However, larger femoral heads were associated with more volumetric wear; 36/40-mm femoral heads had higher volumetric wear (median 26.1; 95% CI, 11.3-47.1) than did 26-mm heads (median 3.1; 95% CI, 0.7-12.3), 28-mm heads (median 12.3; 95% CI, 3.0-19.3), and 32-mm heads (median 12.9; 95% CI, 6.6-16.8; p = 0.02). Small osteolytic lesions were noted in 12 hips (14%), but with the numbers available, there was no association with head size or volumetric wear rates. This uncemented acetabular component and this particular XLPE had low rates of linear and volumetric wear. Small osteolytic lesions were noted at 10 to 14 years but were not related to femoral head size or linear or volumetric wear rates. We recommend additional longer-term clinical followup studies and perhaps alternative imaging studies of patients with XLPE and osteolysis. Level III, therapeutic study.

This article was updated on August 17, 2022, because of previous errors, which were discovered after the preliminary version of the article was posted online. On page 1462, in the first sentence of the Abstract section entitled "Results," the phrase that had read "and 36-mm heads had fewer dislocations than 28-mm (HR = 0.33 [95% CI, 0.16 to 0.68]; p = 0.003), but more dislocations than 32-mm heads (HR for >2 weeks = 2.25 [95% CI, 1.13 to 4.49]; p = 0.021)" now reads "and 36-mm heads had fewer dislocations than 28-mm (HR = 0.33 [95% CI, 0.16 to 0.68]; p = 0.003) and 32-mm heads (HR for ≥2 weeks = 0.44 [95% CI, 0.22 to 0.88]; p = 0.021)." On page 1468, in the last sentence of the section entitled "Acetabular Components with a Diameter of <51 mm," the phrase that had read "and HR for ≥2 weeks = 2.25 [95% CI, 1.13 to 4.49; p = 0.021]) ( Fig. 3 )" now reads "and HR for ≥2 weeks = 0.44 [95% CI, 0.22 to 0.88; p = 0.021]) ( Fig. 3 )." Finally, on page 1466, in the upper right corner of Figure 3 , under "32mm vs 36mm," the second line that had read "2Wks+: HR=2.25 (1.13, 4.49), p=0.021" now reads "2Wks+: HR=0.44 (0.22, 0.88), p= 0.021."

Controversy surrounds wear data from laboratory hip simulator studies, whether derived from water-based or serum-based studies or whether a major design parameter such as the size of the femoral head has an effect on the volume of wear particulate released. To investigate these relationships, we studied cup wear in water- and serum-based lubricants using as our standard the polytetrafluoroethylene (PTFE) data derived by Charnley. To model Charnley's clinical experience, PTFE acetabular cups were used in sets of three each of four sizes of CoCr femoral heads: 22.25-, 28-, 32-, and 42-mm diameters. Six criteria were used to evaluate the performance of the lubricants against clinical accuracy and scientific methods. The PTFE wear data from the serum-based tests was consistently linear with the duration of the test, exhibited a precision within +/-3% about the average for each set of three cups, and copious amounts of wear debris were clearly seen circulating and settling to the bottom of the wear chambers. The wear data clearly demonstrated Charnley's thesis that volume of wear increases with regard to the size of the femoral head in a linear manner. This increase was considered satisfactory at 9%/ mm. However, in terms of clinical accuracy, the simulator wear rates averaged 3 to 4 times greater than the comparable clinical data for wear magnitude. Thus, the serum-based tests satisfied three of the six criteria used. The PTFE wear data from the water-based tests was generally nonlinear, continually increasing with test duration. These wear trends were examined in three discrete phases to estimate the changing wear rates. By the end of the tests, the wear rates had increased from 1.3 to 3.9 times, with the 42-mm heads showing the greatest change. The resulting precision was never better than +/-26% and deteriorated to +/-70%. In terms of clinical accuracy, the water-based wear rates varied from 2 to 7 times less than the Charnley PTFE wear magnitudes, averaging 4 times less. The water-based data did not satisfactorily model the relationship between increased wear with increased head size. Minimal PTFE wear debris was observed, and what did emerge after thousands of wear cycles appeared as streamers up to 30 mm long and up to 5 mm wide. When these detached, they floated up to the surface where they could be separated into smaller particulates. A similar phenomenon was noted for polyethylene wear tests conducted with water lubrication. Thus the water-based tests satisfied none of the six validation criteria evaluated. These data raise serious doubts as to the validity of testing implant and material combinations in water as a predictor of clinical performance. Bovine serum was not totally satisfactory, but the wear data did model some of the important clinical characteristics of hip joint behavior.

To compare associations between anthropometric and lifestyle factors and femoral head cartilage volume/thickness and radiographic features of osteoarthritis (OA) and to provide evidence of construct validity for magnetic resonance imaging (MRI) assessment of femoral cartilage volume and thickness. We studied a cross-sectional sample of 151 randomly selected subjects (79 men, 72 women; mean age 63 years) from the Tasmanian Older Adult Cohort Study. A sagittal T1-weighted fat-suppression MRI scan of the right hip was performed to determine femoral head cartilage volume, cartilage thickness, and size. An anteroposterior radiograph of the pelvis with weight bearing was performed and scored for radiographic evidence of OA in the right hip. Other factors measured were height, weight, leg strength, serum vitamin D levels, and bone mineral density. Hip cartilage volume was significantly associated with female sex, body mass index, and femoral head size, whereas hip cartilage thickness was significantly associated only with the size of the femoral head. Only female sex was significantly associated with the total radiographic OA score and the joint space narrowing (JSN) score, but not the osteophyte score. Radiographic JSN of the hip, especially axial JSN (but not osteophytes), was significantly correlated with hip cartilage volume and thickness. Femoral head cartilage volume and thickness have modest but significant construct validity when correlated with radiographic findings. Furthermore, the generally stronger associations with volume compared with radiographic OA suggest that MRI may be superior at identifying risk factors for hip OA.

Developmental dysplasia of the hip (DDH) is known to result in smaller femoral head size in toddlers; however, alterations in femoral head size and growth have not been documented in infants. To determine with ultrasound (US) whether femoral head size and growth are altered in infants (younger than 1year of age) with severe DDH. We identified all patients at our tertiary care children's hospital from 2002 to 2014 who underwent US for DDH. We included studies with at least one hip with severe DDH, defined as <25% coverage of the femoral head, and excluded teratological DDH. We constructed a control group of randomized patients with normal US studies. Two pediatric radiologists blinded to diagnosis measured bilateral femoral head diameter. Inter-reader variability and femoral head diameter difference between dislocated and contralateral normal femoral heads were evaluated. Mean femoral head diameters were compared across types of hip joint; femoral head growth rates per month were calculated. Thirty-seven children with DDH (28 female) were identified (median age: 33days). The control group contained 75 children (47 female) with a median age of 47days. Fifty-three of the 74 hips in the study group had severe DDH. Twenty-four children with DDH had completely dislocated hips (nine bilateral, five with contralateral severe subluxations). Thirteen other children had severe subluxation, two bilaterally. There was good inter-reader agreement in the normal femoral head group and moderate agreement in the severe DDH group. In the study group, severe DDH femoral head diameter was significantly smaller than their contralateral normal hip. Severe DDH femoral head diameter was significantly smaller than normal femoral head diameter in the control group. The severe DDH femoral head growth rate was slightly less but not significantly slower than normal femoral head growth rate in the study group. On US during infancy, femoral head size is significantly reduced in severe cases of DDH.

PurposeThe purpose of this study was to evaluate if the femoral head's size has an impact on dislocation rates following total hip arthroplasty (THA).Materials and MethodsFive hundreds forty-three THA performed using a posterolateral approach in our hospital and followed up more than 6 months were included in this study. We evaluated dislocation rates based on the size of femoral head (28 mm vs. over 32 mm) and further investigated the dislocation rates classified into primary and revision surgery. Patient-related and surgical factors were reviewed to evaluate risk factors impacting dislocation rates.ResultsDislocation occurred in 9.6% of cases (n=52; 32 males and 20 females). Of this dislocation group, 36 were treated with femoral heads 28 mm in diameter (9.8% of all patients treated with 28 mm femoral heads) and 16 were treated with femoral heads 32 mm and over (9.1% of all patients treated with femoral heads of at least 32 mm). The percentages of patients experiencing dislocation were not significantly different among the two groups (i.e., 28 mm vs. ≥32 mm). However, after revision surgery, the dislocation rate in the 28-mm group was significantly higher than the ≥32-mm group (P<0.05). In a case-control study comparing dislocation and non-dislocation groups, the risk of dislocation was 6 times higher in patients with habitual alcohol intake, and 9.2 times higher in patients with a neuropsychiatric disorder (P<0.05).ConclusionPatient factors are considered to have a more significant impact on dislocation rates following THA than the size of femoral head.

Purpose In general, the amount and rate of linear wear are associated with femoral head size in the conventional UHMWPE acetabular liner. The smaller the femoral head, the higher the linear wear rate. The aim of this study is to verify the relationship between wear rate and femoral head size and the polyethylene cup thickness. Materials and Methods We conducted a retrospective review of all patients who had undergone primary cementless total hip arthroplasty using the conventional UHMWPE (HGP2) acetabular liner between July 1992 and December 2002. 128 hips (34 hips of female, 94 hips of male) of 64 patients who had 28 mm femoral head with different polyethylene acetabular linear thickness and 102 hips (41 hips of female, 61 hips of male) of 81 patients with 22 mm femoral head were included. Patients were assessed clinically and radiographically at postop 6 weeks, 3 months, 6 months and annually thereafter. Clinical assessment was performed using Harris Hip Score. Radiographic analysis included measurement of acetabular component position, polyethylene wear using a validated radiographic technique (Dorr method). Their mean age at the time of operation was 45.3 (24–81) years old and mean follow-up period was 10.8 (96–144 months) years. Results At a mean of 10.8 years, clinical results as determined by Harris Hip Score did not differ in different liner thickness and head sizes. For male, the linear wear rate was 0.139 mm/y in 22 mm femoral head group, 0.137 mm/y in 28 mm femoral head group. For female, the linear wear rate was 0.136 mm/y in 22 mm femoral head group, 0.169 mm/y in 28 mm femoral head group. In 28 mm femoral head group, the each linear wear rate of 6.2, 7.2, 8.2, 9.2, 10.2, 11.2, 12.2, 13.2, 14.2, 15.2 and 16.2 mm of thickness of PE liner was 0.223, 0.197, 0.190, 0.182, 0.130, 0.104, 0.095, 0.086, 0.070, 0.064 and 0.059 mm/y, respectively. In 22 mm group, the linear wear rate of 6.1, 7.1, 9.1, 10.1, 11.1, 12.1, 13.1, 14.1 and 15.1 mm thickness of PE liner was 0.172, 0.164, 0.148, 0.139, 0.137, 0.138, 0.123, 0.122 and 0.114 mm/y, respectively. The thinner the liner, the larger the linear wear rate. If the thickness of PE liner was less than 9 mm, the larger femoral head, the higher the linear wear rate. But, if thickness of liner was more than 10 mm, the larger femoral head, the lower the linear wear rate. If the liner thickness was less than 13 mm, volumetric wear rate was larger in 28 mm than 22 mm femoral head group. Conclusions The linear wear rate of conventional PE liner is not high in the articulation with smaller metal head and the volumetric wear rate is not high in the articulation with larger metal head constantly. This study demonstrated that if the conventional PE liner is thin(less than 10 mm), larger metal head(28 mm) can induce higher linear wear rate than smaller metal head, and if the thickness of conventional PE is more than 13 mm, the volumetric wear rate of liner with larger metal head is lower than that of smaller head.