Aims. The aim of the study was to compare two methods of calculating pelvic incidence (PI) and pelvic tilt (PT), either by using the femoral heads or acetabular domes to determine the bicoxofemoral axis, in patients with unilateral or bilateral primary hip osteoarthritis (OA). Methods. PI and PT were measured on standing lateral radiographs of the spine in two groups: 50 patients with unilateral (Group I) and 50 patients with bilateral hip OA (Group II), using the femoral heads or acetabular domes to define the bicoxofemoral axis. Agreement between the methods was determined by intraclass correlation coefficient (ICC) and the standard error of measurement (SEm). The intraobserver reproducibility and interobserver reliability of the two methods were analyzed on 31 radiographs in both groups to calculate ICC and SEm. Results. In both groups, excellent agreement between the two methods was obtained, with ICC of 0.99 and SEm 0.3° for Group I, and ICC 0.99 and SEm 0.4° for Group II. The intraobserver reproducibility was excellent for both methods in both groups, with an ICC of at least 0.97 and SEm not exceeding 0.8°. The study also revealed excellent interobserver reliability for both methods in both groups, with ICC 0.99 and SEm 0.5° or less. Conclusion. Either the femoral heads or acetabular domes can be used to define the bicoxofemoral axis on the lateral standing radiographs of the spine for measuring PI and PT in patients with idiopathic unilateral or bilateral hip OA. Cite this article: Bone Joint J 2021;103-B(8):1345–1350

Interest on acetabular version arose from unstable developmental dysplastic hips. Initial studies and clinical observations described the dysplastic hip as being excessively anteverted. The advent of computed tomography allowed further detailed analysis of the acetabulum in the axial plane, yet these studies failed to determine conclusively whether or not the dysplastic acetabulum is abnormally anteverted. Much controversy evolved from different methods of measuring and from the fact that a more anteriorly located acetabular deficiency results in excessive anteversion while a more posteriorly located deficiency in retroversion. It remains inconclusive to what extent acetabular dysplasia is due to a mal-orientation of an otherwise normal configured acetabulum or to a deficient acetabulum which is otherwise normally orientated. Furthermore, the acetabular opening spirals gradually from mild anteversion proximally to increasing anteversion distal to it and therefore render its measurement dependent from pelvic inclination and from the level of the transverse CT scan slice. On an orthograde pelvic X-ray, both, pelvic inclination and rotation can be controlled. Therefore, acetabular version is best estimated from the relationship of the anterior and posterior acetabular rim to each other on an orthograde pelvic X-ray. The main hip pathologies, acetabular rim overload and anterior femoro-acetabular impingement, both occur in the superior part of the acetabulum, the acetabular dome, and that’s where version is best measured. We called this version of the acetabular dome. Interest on retroversion of the acetabular dome arose from analysis of complications such as persistent posterior subluxation after acetabular reorienting procedures. They resulted in the hypothesis that the site of acetabular deficiency may vary and be more posteriorly located in some cases resulting in a rather retroverted than anteverted acetabular dome. In fact, retroversion of the acetabular dome was found to be a characteristic feature of specific hip disorders. A review of ten patients with posttraumatic premature closure of the triradiate cartilage before age 5 showed beside a bowed hemipelvis with lateralized and caudalized acetabulum a mean retroversion of the acetabular dome of 27°. A review of 14 patients suffering from proximal femoral focal deficiency with a functional hip joint revealed a mean retroversion of the acetabular dome of 24°. Typically this was accompanied by femoral retrotorsion and coxa vara. Finally, bladder exstrophy, when treated without pelvic osteotomy, typically end up with externally rotated or retroverted acetabula (Sponseller, 1995) Even in DDH, retroversion of the acetabular dome has been shown to be a significant variation as 40 of 232 such acetabula showed to have a retroverted dome (Li, 2003). Furthermore retroversion typically can result from pelvic osteotomy in childhood as 26 from 97 subjects, who underwent either Salter or Le Coeur osteotomy in childhood ended up with retroverted acetabular domes after closure of the pelvic bone growth plates. In the context of neuromuscular or genetic disorders, dysplastic hips also may have retroverted acetabular domes and may additionally be influenced from fixed spine deformities. Finally, retroverted acetabular domes may be found in otherwise non dysplastic hips. The relevance of acetabular retroversion is both technical and clinical: First, it calls for a more individual approach to acetabular dysplasia because presence of retroversion will affect the manner in which corrective osteotomy will be done. Salter-like reorientation maneuvers will result in worsening the pre-existing posterior deficiency or acetabular rim overload and risk continued posterior subluxation or dislocation of a previously reduced hip (Lee, 1991). Second, anterior overcorrection of a primarily retroverted acetabula may necessitate a further intervention to remove bone from the anterior aspect of the acetabulum or anterior part of the femoral head-neck junction due to limited hip flexion (Crockarell 1999, Myers 1999). Third, evidence that the long-term effect of retroversion of the acetabular dome is harmful is increasing: An association between decreased acetabular anteversion and osteoarthritis was found as soon as 1991 (Menke, 1991) and the prevalence of retroversion among patients with idiopathic hip osteoarthritis has been found to be 20% versus 5% among the general population (Giori, 2003). Furthermore, decreased acetabular and femoral anteversion was found to be a major cause of altered rotation, hip pain and osteoarthritis (Tönnis, 1999). A positive impingement test was the key clinical finding (Reynolds,1999). This anterior impingement of the femoral head-neck junction against the border of the prominent anterior acetabular wall which over a long period of time may lead to fatiguing and destruction of the acetabular labrum and the adjacent cartilage is thought to initiate groin pain and early osteoarthritis. Finally, even for total hip replacement, severe retroversion of the acetabular dome will make surgery more difficult

Introduction. Application of an external fixator for type B and C pelvic fractures can be life saving. Anteriorly the fixator half pins can be placed in the long and thick corridor of bone in the supra-acetabular region often referred to as the low anterior ex-fix. Pins in this location are favoured as they are more stable biomechanically. The bone tunnel for the low anterior ex-fix can be visualised with an iliac oblique projection intra-operatively. In some cases despite being outside the articular surface it may still be low enough to pass through the capsular attachment of the hip joint on the anterior inferior iliac spine. We aim to provide radiological markers for the most superior fibres of the capsule to help accurate extra-capsular pin placement within the supra-acetabular bone tunnel. Materials and Methods. Thirteen cadaveric pelves, embalmed with the method of Thiel, were used for this study. An image intensifier was positioned to acquire an iliac oblique outlet view, such that the supra acetabular bone tunnel was visualised. This was achieved by positioning the beam 30 degrees cephalad and 20 degrees medial. Both left and right hemipelves were examined in this way. A standard size metallic disc was included in all images with in the acetabulum to allow for image calibration. The proximal most fibres of the hip joint capsule were marked with a K-wire so that their relation to the bone tunnel could be clearly seen on the images. Once all images were acquired they were calibrated and analysed using ImageJ Software to estimate the height and maximum width of the bone tunnel as seen on the images and the vertical distance of the superior most fibres of the capsule from the dome of the acetabulum. Results. The mean height of the bone tunnel was 24.9 mm (SD 4.3 mm, Range 18.9–33.2 mm) and the maximum width of the tunnel was 11.7 mm (SD 2.6 mm, Range 7.6–16.3 mm). The inferior margin of the bone tunnel was on average 7.4 mm (SD 3.4 mm, Range 1.1–14.4 mm) superior to the acetabular dome and the most proximal fibres of the capsule were on average 9.2 mm (SD 2.4 mm, Range 4.7–16.1 mm) superior to the acetabular dome. This meant that on average 3.6 mm (SD 2.1 mm, Range 0.3–8.9 mm) of the inferior portion of the tunnel is within the joint. There was no statistically significant difference between the left and right sides. Conclusion. There is adequate space for two long external fixator pins within the described tunnel. These should be placed in the upper half of the anterior inferior iliac spine. Below this level there is risk of being intra-capsular which can lead to septic arthritis. For this reason we recommend that supra-acetabular pins should be placed at least 16 mm superior to the acetabular dome as visualised on the iliac oblique outlet view

Surgical dislocation of the hip in the treatment of acetabular fractures allows the femoral head to be safely displaced from the acetabulum. This permits full intra-articular acetabular and femoral inspection for the evaluation and potential treatment of cartilage lesions of the labrum and femoral head, reduction of the fracture under direct vision and avoidance of intra-articular penetration with hardware. We report 60 patients with selected types of acetabular fracture who were treated using this approach. Six were lost to follow-up and the remaining 54 were available for clinical and radiological review at a mean follow-up of 4.4 years (2 to 9). Substantial damage to the intra-articular cartilage was found in the anteromedial portion of the femoral head and the posterosuperior aspect of the acetabulum. Labral lesions were predominantly seen in the posterior acetabular area. Anatomical reduction was achieved in 50 hips (93%) which was considerably higher than that seen in previous reports. There were no cases of avascular necrosis. Four patients subsequently required total hip replacement. Good or excellent results were achieved in 44 hips (81.5%). The cumulative eight-year survivorship was 89.0% (95% confidence interval 84.5 to 94.1). Significant predictors of poor outcome were involvement of the acetabular dome and lesions of the femoral cartilage greater than grade 2. The functional mid-term results were better than those of previous reports. Surgical dislocation of the hip allows accurate reduction and a predictable mid-term outcome in the management of these difficult injuries without the risk of the development of avascular necrosis

Aims

The aim of this study was to compare the biomechanical models of two frequently used techniques for reconstructing severe acetabular defects with pelvic discontinuity in revision total hip arthroplasty (THA) – the Trabecular Metal Acetabular Revision System (TMARS) and custom triflange acetabular components (CTACs) – using virtual modelling.

Major bone loss involving the acetabulum can be seen during revision THA due to component loosening, migration or osteolysis and can also occur as a sequela of infected THA. Uncemented highly porous ingrowth acetabular components can be used for the reconstruction of the vast majority of revision cases, especially where small to mid-sized segmental or cavitary defects are present which do not compromise stable mechanical support by the host bone for the cup after bone preparation is complete. A mechanically stable and near motionless interface between the host bone and the implant is required over the initial weeks post-surgery for bone ingrowth to occur, regardless of the type of porous surface employed. As bone deficiency increases, the challenge of achieving rigid cup fixation also increases, especially if the quality of the remaining host bone is compromised. A stepwise approach to enhanced fixation of the highly porous revision acetabular component is possible as follows:. Maximise Screw Fixation. Use of a limited number of screws in the dome only (as routinely occurs with a cluster hole design) is inadequate, except for primary arthroplasty cases or very routine revision cases with little or no bone loss and good bone quality. Otherwise an array of screws across the acetabular dome and continuing around the posterior column to base of the ischium is strongly recommended. This can help prevent early rocking of the cup into a more vertical position due to pivoting on dome screws used alone, via cup separation inferiorly in zone 3. A minimum of 3 or 4 screws in a wide array are suggested and use of 6 or more screws is not uncommon if bone quality is poor or defects are large. Cement the Acetabular Liner into the Shell. This creates a locking screw effect, which fixes the screw heads in position and prevents any screws from pivoting or backing out. Acetabular Augments (vs Structural Allograft). When critical segmental defects are present which by their location or size preclude stable support of the cup used alone, either a structural allograft or highly porous metal augment can provide critical focal support and enhance fixation. Highly porous metal augments were initially developed as a prosthetic allograft substitute in order to avoid the occasional graft resorption and loss of fixation sometimes seen with acetabular allograft use. Cup-Cage Construct. If one or more of the above strategies are used and fixation is deemed inadequate, it is possible to add a ½ or full acetabular cage “over the top” of the acetabular component before cementing a polyethylene liner in place. The full cup cage construct can be used for maximal fixation in cases of pelvic dissociation, alone or in combination with the distraction method as described by Paprosky. Use of a ½ cage is technically simpler and requires less exposure than a full cage, but still greatly enhances rigidity of fixation when transverse screws into the ilium are combined with standard screws in the cup including vertically into the dome. These techniques used in combination with highly porous tantalum implants have allowed durable fixation for the full range of reconstructive challenges and bone defects encountered. Newer 3-D printed titanium highly porous materials have recently been introduced by multiple manufacturers as a potential alternative that may be more cost effective, but these implants and materials will require clinical validation over the years ahead

Acetabular bone defects are common in revision total hip arthroplasty and are usually worse than depicted on routine radiographs. These defects may be cavitary, segmental or both. For cavitary and segmental defects with more than 50% host support, our preference is to use a cementless revision acetabular component, supplemented by the use of screw fixation and morselised bone graft. For cavitary and segmental defects with less than 50% host support, the use of an anti-protrusio cage, morselised bone graft and a cemented all polyethylene socket is preferred. Our use of structural allografts is much less common. Indications would include absence of the acetabular dome or posterior column. Our preferred technique is use of the “reverse 7” distal femoral allograft. Whenever a structural allograft is used, we would reinforce this with the use of an anti-protrusio cage. This approach has yielded predictable excellent clinical results

The cemented acetabular component has been essentially abandoned, due to the reliable and durable fixation provided by bone ingrowth into cementless acetabular components of many different designs. A variety of porous surfaces including sintered beads, titanium fibermetal, plasma sprayed titanium, and ultraporous tantalum have been shown to result in significant osteointegration, and provide long term fixation of cementless acetabular components. New ultraporous metals will also likely prove to perform similarly, however, their advantages in the primary THA are unclear. Most currently available cementless acetabular components rely on obtaining initial “interference” or “frictional” fit provided by relative underreaming. Many designs incorporate additional features such as screws, pegs, and fins to limit implant micromotion and augment initial fixation until early tissue ingrowth occurs. “Underreaming” by more than 1 mm has been associated with incomplete component seating and increased incidence of acetabular fracture. Knowledge of the geometry of the component by the surgeon is recommended, since some designs are elliptical and have a built-in degree of interference fit. Screws used to augment acetabular fixation in the primary THA can typically be restricted to the area of the acetabular dome (cluster configuration) and cups with multiple holes are usually unnecessary and may be undesirable as they allow access of wear debris to the acetabular implant-bone interface. In order to minimize backside wear and dissociation of the acetabular liner, modular components need to have a well-designed locking mechanism. Retrieval studies have shown that the peripheral rim of the acetabular liner is most susceptible to oxidative degradation and the integrity of the locking mechanism in this area can be compromised with time. Non-modular, “one piece” components eliminate these concerns, but most of these designs rely on initial frictional fit alone for stability. In the event that the position of a nonmodular component needs to be changed intra-operatively, the quality of frictional fit after repositioning can be diminished and may not be sufficient for implant stability. Modular components that incorporate screws, allow for acetabular component repositioning and adjunctive fixation with screws. Many newer acetabular component designs can accommodate a modular liner for either a metal on polyethylene, ceramic on ceramic or metal on metal bearing

Introduction: We hypothesise that the fixation method of the acetabular component influences stress transmission to the host bone in vivo. We believe that the frequency of appearance of radiolucent lines at the prosthetic rim is directly related to the brake drum effect whereby compressive forces at the dome of a semi-rigid body leads to tensile forces at the rim. Method: A series of miniature pressure transducers were manufactured and positioned at the prosthetic/ bone interface of an acetabular component of a total hip arthroplasty (THA) in a jig designed to replicated the loading conditions of a THA in vivo. The transducers were arranged in a series of five concentric rings spaced from the centre of the acetabular dome to the prosthetic rim. A total of six transducers was used. Three separate experiments were performed: 1. a polyethylene component alone to act as a control. 2. a polyethylene component surrounded by a cement mantle and 3. a polyethylene component surrounded by a metal-back. A separate jig was constructed to provide a cement mantle of the same thickness as the metal back. The stress transmitted to the host bone was measured in each case. Results: The results indicated that successively less stress was transmitted when changing from controls to cemented then to metal-backed cups. Both cemented and uncemented cups demonstrated at the very least absence of compressive forces at the prosthetic rim and in some cases tensile forces, indicating that the brake drum effect is likely

Aims

Custom triflange acetabular components (CTACs) play an important role in reconstructive orthopaedic surgery, particularly in revision total hip arthroplasty (rTHA) and pelvic tumour resection procedures. Accurate CTAC positioning is essential to successful surgical outcomes. While prior studies have explored CTAC positioning in rTHA, research focusing on tumour cases and implant flange positioning precision remains limited. Additionally, the impact of intraoperative navigation on positioning accuracy warrants further investigation. This study assesses CTAC positioning accuracy in tumour resection and rTHA cases, focusing on the differences between preoperative planning and postoperative implant positions.

Aims

The aim of this study was to investigate the association between fracture displacement and survivorship of the native hip joint without conversion to a total hip arthroplasty (THA), and to determine predictors for conversion to THA in patients treated nonoperatively for acetabular fractures.

Introduction: This study was initiated to evaluate cortical and cancellous bone density (BD) changes of the acetabulum after cemented and uncemented total hip arthroplasty (THA) using computer tomography (CT)-assisted osteodensitometry in-vivo. Materials and Methods: 15 cemented ZCA Pfannen cups (Zimmer, USA) (age 78 years) and 21 press-fit Trilogy cups (Zimmer, USA) (age 72 years) were implanted by one surgeon. All hips were investigated by a standardized CT-mode (slice thickness 2 mm, table feed 5 mm, extended CT-scale). 6 CT-scans at the level of the cup and 4 scans above the dome of the cup were analyzed 2 weeks and 2 years after surgery. Cancellous and cortical bone mineral density (BMD) (CaHA mg/ml) were elaborated with a special software tool (CAPPA postOP, CAS Innovations AG, Erlangen). Results: 2 years after index operation cemented cups showed mild cancellous BD loss (−8% to −20%) and no significant cortical BD changes cranial, significant cortical (−4% to −20%) and cancellous (−16% to −44%) BD loss ventral and no significant BD changes dorsal to the cup. For press-fit cups we observed highly significant (p< 0,01) cancellous BD loss in all sectors (−17% to −53%), cortical BD loss ventral and dorsal to the cup (−12% to −23%) and very limited BD loss cranial (−4% to −13%) to the cup. Conclusions CT-assisted osteodensitometry allows a thorough assessment of the actabular bone in-vivo. Different patterns of stress shielding were observed for cemented and press-fit cups. For the press-fit cup high BD loss for both cortical and cancellous bone was observed in all areas adjacent to the pelvic implant, except for cortical BD at the acetabular dome, suggesting fixation of the cup in the cranial cortical bone. Comparetively less BD loss was seen for cemented cups in all sectors, especially for cancellous bone, suggesting a more physiological stress transfer to both cortical and cancellous pelvic bone

Peri-prosthetic bone loss may contribute to aseptic loosening after THA. The aims of this randomised controlled trial extension study were to study the effect of pamidronate therapy on Peri-prosthetic bone mineral density (BMD) and Peri-prosthetic osteolysis over 5 years after primary THA. 50 patients were enrolled in the study in 1998. All received a hybrid THA (Ultima-TPS stem, Plasmacup) for osteoarthritis. Subjects were randomised to receive either 90mg of pamidronate or placebo by intravenous infusion on the 5. th. post-operative day. At 5 years 36 patients (41 Hips: placebo n=21, pamidronate n=20) returned for measurement of BMD and clinical and plain radiographic assessment. Five patients had died and nine had withdrawn from the study. The effect of pamidronate in maintaining femoral bone mass in the region of the calcar previously reported at 2 years was maintained at 5 years (Gruen zone 6 pamidronate versus placebo ANOVA P=0.038; Gruen zone 7 ANOVA P=0.048). No differences in pelvic BMD were found between treatment groups at 5 years. Harris hip scores used to evaluate clinical outcome did not show any significant difference between the 2 groups over the 5-year period. (Mann Whitney p> 0.05). Isolated expansile osteolytic lesions were identified on AP radiographs of the hip at 5 years in 4 patients (2 placebo, 2 pamidronate; P> 0.05). One patient had a 5x9mm lytic lesion in the region of the femoral calcar, and 3 patients had pelvic lytic lesions in the region of the acetabular dome (largest measuring 20x10mm). Single-dose peri-operative pamidronate therapy preserves femoral calcar bone mass over a 5 year period after THA. However, although the number of subjects with osteolysis is small, we have seen no difference in the rate of osteolytic lesions between treatment groups. Long term study of this patient group is required to examine the rate of aseptic loosening between the treatment groups

The outcome of complex acetabular reconstruction was evaluated in twenty-one patients who were confined to a wheelchair or bed because of pain from acetabular metastases. Reconstruction rings were used where bone loss exceeded 50% of the acetabulum. Six roof reinforcement-rings, eight ilioischial-rings and eight Harrington reconstructions were performed. All but two patients(90%) became ambulatory without pain. Median survival was nine months. Two patients underwent acetabular revision for recurrence. These results support the role of acetabular reconstruction for palliation of pain in appropriate patients with acetabular metastases. Metastatic disease of the acetabulum is painful and disabling. Operative intervention is indicated in certain patients with pathologic fractures, and non-responders to adjuvant treatment. The functional outcome of hip arthroplasty with reconstruction rings was evaluated in twenty-one patients with acetabular metastases between 1989 and 2001. Preoperatively all patients were confined to a wheelchair or bed and used significant narcotic medications. Preoperative radiotherapy was employed in eighteen cases (90%) and 30% had undergone chemotherapy. AAOS classification of the acetabular lesion revealed: six-type II, seven-type III and eight-type IV deficiencies. All cases required a reconstruction ring due to bone loss exceeding 50% of the acetabular dome. Six roof reinforcement rings, eight ilioischial rings and eight Harrington reconstructions with rings were performed in this group. Determination of the reconstructive technique was based on preoperative computerized tomography and intraoperative examination of the acetabular deficiency. All but two patients (90%) became ambulatory without significant pain. Eleven patients used a walker or two canes and nine walked with one or no canes. Median survival was nine months and patients with visceral involvement had a shorter duration. Eight early post-operative complications developed in six patients (29%). In two patients the acetabular construct failed with cup migration due to locally recurrent disease; both were successfully revised. The results of complex acetabular reconstruction for metastatic disease validate its role for palliation of pain and to improve ambulatory status. Preoperative planning with computerized tomography can assist in classifying acetabular bone loss and determining optimal reconstruction technique

Aims

Implant waste during total hip arthroplasty (THA) represents a significant cost to the USA healthcare system. While studies have explored methods to improve THA cost-effectiveness, the literature comparing the proportions of implant waste by intraoperative technology used during THA is limited. The aims of this study were to: 1) examine whether the use of enabling technologies during THA results in a smaller proportion of wasted implants compared to navigation-guided and conventional manual THA; 2) determine the proportion of wasted implants by implant type; and 3) examine the effects of surgeon experience on rates of implant waste by technology used.

Aims

The main advantage of 3D-printed, off-the-shelf acetabular implants is the potential to promote enhanced bony fixation due to their controllable porous structure. In this study we investigated the extent of osseointegration in retrieved 3D-printed acetabular implants.

As our understanding of hip function and disease improves, it is evident that the acetabular fossa has received little attention, despite it comprising over half of the acetabulum’s surface area and showing the first signs of degeneration. The fossa’s function is expected to be more than augmenting static stability with the ligamentum teres and being a templating landmark in arthroplasty. Indeed, the fossa, which is almost mature at 16 weeks of intrauterine development, plays a key role in hip development, enabling its nutrition through vascularization and synovial fluid, as well as the influx of chondrogenic stem/progenitor cells that build articular cartilage. The pulvinar, a fibrofatty tissue in the fossa, has the same developmental origin as the synovium and articular cartilage and is a biologically active area. Its unique anatomy allows for homogeneous distribution of the axial loads into the joint. It is composed of intra-articular adipose tissue (IAAT), which has adipocytes, fibroblasts, leucocytes, and abundant mast cells, which participate in the inflammatory cascade after an insult to the joint. Hence, the fossa and pulvinar should be considered in decision-making and surgical outcomes in hip preservation surgery, not only for their size, shape, and extent, but also for their biological capacity as a source of cytokines, immune cells, and chondrogenic stem cells.

Cite this article: Bone Joint Res 2020;9(12):857–869.

Aims

This single-centre observational study aimed to describe the results of extensive bone impaction grafting of the whole acetabular cavity in combination with an uncemented component in acetabular revisions performed in a standardized manner since 1993.

Aims

Displaced, comminuted acetabular fractures in the elderly are increasingly common, but there is no consensus on whether they should be treated non-surgically, surgically with open reduction and internal fixation (ORIF), or with acute total hip arthroplasty (THA). A combination of ORIF and acute THA, an approach called ’combined hip procedure’ (CHP), has been advocated and our aim was to compare the outcome after CHP or ORIF alone.