Prosthetic Head Size Research Articles

The Association of Sacro-Femoro-Pubic Angle and Postoperative Dislocation Following Total Hip Arthroplasty

BackgroundSpino-pelvic orientation may affect dislocation risk following total hip arthroplasty (THA). It can be measured on lateral lumbo-pelvic radiographs. The sacro-femoro-pubic (SFP) angle, measured on an antero-posterior (AP) pelvis radiograph, is a reliable proxy for pelvic tilt, a measurement of spino-pelvic orientation measured on a lateral lumbo-pelvic radiograph. The purpose of this study was to investigate the relationship between SFP angle and dislocation following THA. MethodsAn Institutional Review Board-approved retrospective case-control study was conducted at a single academic center. We matched 71 dislocators (cases) to 71 nondislocators (controls) following THA performed by 1 of 10 surgeons between September 2001 and December 2010. Two authors (readers) independently calculated SFP angle from single preoperative AP pelvis radiographs. Readers were blinded to cases and controls. Conditional logistic regressions were used to identify factors differentiating cases and controls. ResultsThe data did not show a clinically relevant or statistically significant difference in SFP angles after adjusting for gender, American Society of Anesthesiologists classification, prosthetic head size, age at time of THA, measurement laterality, and surgeon. ConclusionWe did not find an association between preoperative SFP angle and dislocation following THA in our cohort. Based on our data, SFP angle as measured on a single AP pelvis radiograph should not be used to assess dislocation risk prior to THA.

The effect of cemented acetabular component geometry on the risk of revision for instability or loosening : a study of 224,874 primary hip arthroplasties from the National Joint Registry.

To determine if primary cemented acetabular component geometry (long posterior wall (LPW), hooded, or offset reorientating) influences the risk of revision total hip arthroplasty (THA) for instability or loosening. The National Joint Registry (NJR) dataset was analyzed for primary THAs performed between 2003 and 2017. A cohort of 224,874 cemented acetabular components were included. The effect of acetabular component geometry on the risk of revision for instability or for loosening was investigated using log-binomial regression adjusting for age, sex, American Society of Anesthesiologists grade, indication, side, institution type, operating surgeon grade, surgical approach, polyethylene crosslinking, and prosthetic head size. A competing risk survival analysis was performed with the competing risks being revision for other indications or death. The distribution of acetabular component geometries was: LPW 81.2%; hooded 18.7%; and offset reorientating 0.1%. There were 3,313 (1.5%) revision THAs performed, of which 815 (0.4%) were for instability and 838 (0.4%) were for loosening. Compared to the LPW group, the adjusted subhazard ratio of revision for instability in the hooded group was 2.31 (p < 0.001) and 4.12 (p = 0.047) in the offset reorientating group. Likewise, the subhazard ratio of revision for loosening was 2.65 (p < 0.001) in the hooded group and 13.61 (p < 0.001) in the offset reorientating group. A time-varying subhazard ratio of revision for instability (hooded vs LPW) was found, being greatest within the first three months. This registry-based study confirms a significantly higher risk of revision after cemented THA for instability and for loosening when a hooded or offset reorientating acetabular component is used, compared to a LPW component. Further research is required to clarify if certain patients benefit from the use of hooded or offset reorientating components, but we recommend caution when using such components in routine clinical practice. Cite this article: Bone Joint J2021;103-B(11):1669-1677.

The Symmetry and Predictive Factors in Two-Stage Bilateral Hip Replacement Procedures

Background: Approximately 10–25% of total hip replacement patients undergo a bilateral procedure. The purpose of this study was to compare selected parameters associated with the first and second hip arthroplasty in patients undergoing two-stage treatment due to bilateral hip osteoarthritis and establish the predictive factors for the second procedure. Methods: This study compared the data on bilateral total hip replacement surgeries conducted in the period between 2017 and 2021 (42 patients). The following parameters from the first and second procedure were compared: the prosthetic stem, head, and insert cup size; type of cup insert; duration of anesthesia; duration of hospitalization; and the number of complications. Results: The mean duration of hospital stay at the time of the first total hip arthroplasty was 5.83 days and 5.4 days during the second stay. The mean stem sizes used during the first and second total hip replacement procedures were 7.11 and 7.09, respectively. The mean sizes of endoprosthetic cups used at the first and second total hip replacement procedures were 52.64 and 53.04, respectively. There were no significant differences between the mean prosthetic head size at the first and second surgery. The cup type used during the first and second surgery showed no difference. The mean duration of anesthesia used during the first and second total hip replacement surgery was 108.09 min and 104.52 min, respectively. We recorded a mean of 0.07 complications per patient at the first surgery and 0.02 at the second surgery. Conclusions: Our study results showed symmetry duration of anesthesia, length of hospital stay, number of complications per patient, stem size, prosthetic head size, cup insert size, and cup insert type at the first and second surgery in patients with two-stage bilateral total hip arthroplasty. We observed a strong correlation between the stem sizes of the first and second hip endoprostheses. There was also a strong correlation between the cup sizes used during the first and second surgery.

The Impingement-free, Prosthesis-specific, and Anatomy-adjusted Combined Target Zone for Component Positioning in THA Depends on Design and Implantation Parameters of both Components.

BackgroundLewinnek’s recommendation for orienting the cup in THA is criticized because it involves a static assessment of the safe zone and because it does not consider stem geometry. A revised concept of the safe zone should consider those factors, but to our knowledge, this has not been assessed.Questions/purposes(1) To determine the shape, size, and location of target zones for combined cup and stem orientation for a straight stem/hemispheric cup THA to maximize the impingement-free ROM and (2) To determine whether and how these implant positions change as stem anteversion, neck-shaft angle, prosthetic head size and target range of movements are varied.MethodsA three-dimensional computer-assisted design model, in which design geometry was expressed in terms of parameters, of a straight stem/hemispheric cup hip prosthesis was designed, its design parameters modified systematically, and each prosthesis model was implanted virtually at predefined component orientations. Functional component orientation referencing to body planes was used: cups were abducted from 20° to 70°, and anteverted from -10° to 40°. Stems were rotated from -10° to 40° anteversion, neck-shaft angles varied from 115° to 143°, and head sizes varied from 28 to 40 mm. Hip movements up to the point of prosthetic impingement were tested, including simple flexion/extension, internal/external rotation, ab/adduction, combinations of these, and activities of daily living that were known to trigger dislocation. For each combination of parameters, the impingement-free combined target zone was determined. Maximizing the size of the combined target zone was the optimization criterion.ResultsThe combined target zones for impingement-free cup orientation had polygonal boundaries. Their size and position in the diagram changed with stem anteversion, neck-shaft angle, head size, and target ROM. The largest target zones were at neck-shaft angles from 125° to 127°, at stem anteversions from 10° to 20°, and at radiographic cup anteversions between 17° and 25°. Cup anteversion and stem anteversion were inverse-linearly correlated supporting the combined-anteversion concept. The range of impingement-free cup inclinations depended on head size, stem anteversion, and neck-shaft angle. For a 127°-neck-shaft angle, the lowest cup inclinations that fell within the target zone were 42° for the 28-mm and 35° for the 40-mm head. Cup anteversion and combined version depended on neck-shaft angle. For head size 32-mm cup, anteversion was 6° for a 115° neck-shaft angle and 25° for a 135°-neck-shaft angle, and combined version was 15° and 34° respectively.ConclusionsThe shape, size, and location of the combined target zones were dependent on design and implantation parameters of both components. Changing the prosthesis design or changing implantation parameters also changed the combined target zone. A maximized combined target zone was found. It is mandatory to consider both components to determine the accurate impingement-free prosthetic ROM in THA.Clinical RelevanceThis study accurately defines the hypothetical impingement-free, design-specific component orientation in THA. Transforming it into clinical precision may be the case for navigation and/or robotics, but this is speculative, and as of now, unproven.

A novel osteotomy in shoulder joint replacement based on analysis of the cartilage/metaphyseal interface

BackgroundThe accuracy of reconstruction is thought to impact on functional outcome following glenohumeral joint arthroplasty. The objective of this study was to define an area of minimal anatomic variation at the cartilage/metaphyseal interface of the proximal humerus to optimize the osteotomy of the humeral head, enabling accurate reconstruction with a prosthetic component. MethodsHand held digitization and 3D surface laser scanning techniques were used to digitize 24 cadaveric arms and determine the normal geometry. Each humeral head was then examined to identify the most consistent anatomical landmarks for the ideal osteotomy plane to optimize humeral component positioning. FindingsThe novel, posterior referencing, osteotomy resulted in a mean increase in retroversion of only 0.4° when compared to the original geometry. A traditional anterior referencing osteotomy, by comparison, produced a mean increase in retroversion of 11°. In addition, the novel osteotomy only increased axial diameter by 0.71mm and head height by 0.02mm compared to an anterior referencing osteotomy (3.0mm and 2.7mm respectively). InterpretationThe traditional osteotomy, referencing the anterior border of the cartilage/metaphyseal interface potentially resulted in an increase in prosthetic head size and retroversion. The novel osteotomy, referencing from the posterior cartilage/metaphyseal interface enabled a more accurate recovery of head geometry. Importantly, the increase in retroversion created by the traditional osteotomy was not replicated with the novel technique. Referencing from the posterior cartilage/metaphyseal interface produced a more reliable osteotomy, more closely matching the original humeral geometry. Level of EvidenceBasic Science, Anatomic study, Computer model.

Assessment of Accuracy of Marker Ball Placement in Pre-operative Templating for Total Hip Arthroplasty

We report the accuracy of positioning of the calibration ball in the process of pre-operative templating for total hip arthroplasty (THA). The ball should be placed in the coronal plane of the hip to provide suitable accuracy. We reviewed 112 post-operative THA radiographs where a calibration ball had been placed. We templated the femoral head size of the implant after calibrating the templating system from the ball. The calibrated femoral head diameter was compared to the known prosthetic head size. A percentage error was calculated. Overall, incorrect placement of the calibration ball resulted in a mean percentage error in templating of 6.8% (median 5.7%; range 0–26%). Such error carries implications with the templating process and may result in incorrect component sizes, leg lengths and offset.

Metal-on-metal hip resurfacing: is it forgiven for malorientation?

BackgroundDespite the benefits and clinical success of modern metal-on-metal articulations, there are many concerns about the release of metal ions and their hazardous effects. The exact mechanism and risk factors are a matter of debate. The goal of this prospective study was to evaluate the effect of cup abduction angle and other independent factors (age, sex, prosthetic head size, and period of follow-up) on the levels of serum metal ions in patients after metal-on-metal hip resurfacing (MOMHR) arthroplasty.Patient and methodsBetween January 2010 and June 2013 a total of 50 patients were operated upon and followed up after a unilateral MOMHR, with an average follow-up period of 28.3 months. The patients' ages ranged between 20 and 50 years. There were 24 male and 26 female patients. Clinical and radiological evaluations were made and serum metal ion levels were measured. Correlations between serum metal ion levels and different variables were also evaluated.ResultsThe average preoperative Harris hip score was 46.24. This increased to 90.12 at the end of follow-up. There was a statistically significant increase (P < 0.05) in serum cobalt and chromium levels at the sixth postoperative month, compared with the preoperative levels. However, the condition was significantly (P < 0.05) reversed after the first year. Cup abduction angle was associated with an insignificant effect (P > 0.05) on hip function (Harris hip score) but was associated with a significant increase (P < 0.05) in serum ion levels. Prosthetic head size was associated with a statistically significant (P < 0.05) inverse relation with metal ion levels.ConclusionThe present study found that three main variables had a statistically significant effect on metal ion release: namely, cup orientation, size of the prosthetic head, and period of follow-up. Of them, the only controllable factor that can be carefully addressed during surgical procedures is the first one. Hence, cup inclination during surgery must be considered carefully in order to reduce early failures when performing large-bearing MOMHR.

Limited range of motion of hip resurfacing arthroplasty due to unfavorable ratio of prosthetic head size and femoral neck diameter

Background and purpose Hip resurfacing arthroplasty is being used more and more frequently. The small ratio in size between the resurfaced femoral head and the relatively thick femoral neck raises the question of whether the range of motion is sufficient, particularly with regard to the high mobility required by younger patients. We analyzed motion in a CAD model.Methods Three-dimensional CAD models of the natural hip were created from CT scans and 8 designs of hip resurfacing prostheses (head diameter between 42 mm and 54 mm combined with a hemispherical cup) were implanted in a virtual sense. We simulated 3 different leg positions and the range of motion was evaluated, considering five different implant positions.Results The range of motion of the hip resurfacing designs analyzed was far below the range of motion of stemmed total hip prostheses. None of the resurfacing prostheses provided flexion movements of 90° without impingement. The average range of motion of hip resurfacing arthroplasty was 31–48° below the range of motion of a stemmed total hip replacement with 32-mm head diameter.Interpretation The range of motion of the hip resurfacing designs examined was substantially less than that of a conventional total hip prosthesis. Since impingement of the femoral neck on the acetabular component increases the risk of neck fractures, of dislocation and of subsequent implant loosening, the design and position of the implant should be considered before using hip resurfacing arthroplasty as a standard treatment for younger patients.

Hemiarthroplasty of the hip for fracture—What is the appropriate sized femoral head?

Caliper measurement of the excised femoral head is a standard technique for determination of prosthetic head size during hemiarthroplasty for displaced femoral neck fractures. To evaluate the accuracy of the caliper method of hemiarthroplasty head sizing by comparing it to the native joint congruency (JC) at the weight bearing surface. The diameters of femoral heads in 10 cadaver hip joints were measured by using a caliper at the head equator. Cast moulds were prepared from both the acetabulum and the femoral head in each joint. Every mould's exact spherical diameter at the weight bearing region was measured by a computerised coordinate measuring machine (MNC B231 MITUTOYO). All specimens were coded to ensure that future examination was carried out in a blind manner. Native JC mismatch was determined by subtracting the diameter of the femoral cement mould from that of the acetabular one. Similarly, JC mismatch was calculated for the caliper measurements. The average native JC mismatch (0.36+/-0.29mm, range 0.03-0.82mm, median 0.29mm) was found significantly smaller (p=0.03) than following caliper measurements (0.72+/-0.37mm, range 0.37-1.46mm, median 0.6mm). Routine caliper measured downward size rounding enhanced (p=0.004) this mismatch (0.98+/-0.44mm, range 0.37-1.96mm, median 1.01mm), while upward rounding (0.48+/-0.46mm, range -0.06 to 1.15mm, median 0.41mm) helped mitigate this tendency. Caliper measurements tend to undersize the actual sphere diameter of the femoral head at the weight bearing region. Upward rounded prosthesis should be selected in order to compensate for this propensity.

Acetabular Diameter Measurement Determines Proper Prosthetic Head Size in Hemiarthroplasty for Femoral Head Osteonecrosis

In hemiarthroplasty for femoral head osteonecrosis, collapse and deformity may make femoral head measurement difficult, thus, precluding the selection of an appropriate prosthetic head. We describe a method for measuring the acetabular diameter using acetabular sizing gauges to estimate the prosthetic head size. We evaluated the precision of this method and found it to be highly accurate and reliable.