Post-mortem retrieval of canine, cemented femoral components was analysed to assess the performance of these implants in the dog as a model for human total hip replacement (THR). Mechanical testing and radiological analysis were performed to determine the stability of the implant and the quality of the cement. Thirty-eight implants from 29 dogs were retrieved after time intervals ranging from 0.67 to 11.67 years. The incidence of aseptic loosening was 63.2%, much higher than in human patients (6% in post-mortem studies). Failure of the femoral implants began with debonding at the cement-metal interface, similar to that in implants in man. The incidence of aseptic loosening was much lower in bilateral than in unilateral implants. Significant differences were observed for three different designs of implant. While the dog remains the animal model of choice for THR, results from this study provide insight into interspecies differences in the performance of implants. For example, the performance of THR in dogs should be compared with that in young rather than in elderly human patients.
Osteogenesis imperfecta is a rare inherited disorder of connective tissue which may present with recurrent fractures which are prone to nonunion and malunion resulting in deformity. Some patients develop osteoarthritis of the hip. Formation of hyperplastic callus after recurrent fractures may deform the shape of the femur and preclude the use of standard implants at joint replacement. Replacement can thus be technically demanding.
We present a case of bilateral hip replacement in a patient with osteogenesis imperfecta and hyperplastic callus which was treated by the use of long femoral allografts and cemented femoral stems.
This study investigates and defines the topographic anatomy of the medial femoral circumflex artery (MFCA) terminal branches supplying the femoral head (FH). Gross dissection of 14 fresh–frozen cadaveric hips was undertaken to determine the extra and intracapsular course of the MFCA’s terminal branches. A constant branch arising from the transverse MFCA (inferior retinacular artery; IRA) penetrates the capsule at the level of the anteroinferior neck, then courses obliquely within the fibrous prolongation of the capsule wall (inferior retinacula of Weitbrecht), elevated from the neck, to the posteroinferior femoral head–neck junction. This vessel has a mean of five (three to nine) terminal branches, of which the majority penetrate posteriorly. Branches from the ascending MFCA entered the femoral capsular attachment posteriorly, running deep to the synovium, through the neck, and terminating in two branches. The deep MFCA penetrates the posterosuperior femoral capsular. Once intracapsular, it divides into a mean of six (four to nine) terminal branches running deep to the synovium, within the superior retinacula of Weitbrecht of which 80% are posterior. Our study defines the exact anatomical location of the vessels, arising from the MFCA and supplying the FH. The IRA is in an elevated position from the femoral neck and may be protected from injury during fracture of the femoral neck. We present vascular ‘danger zones’ that may help avoid iatrogenic vascular injury during surgical interventions about the hip.
Cite this article:
Graft-tunnel mismatch of the bone-patellar tendon-bone (BPTB) graft is a major concern during anatomical anterior cruciate ligament (ACL) reconstruction if the femoral tunnel is positioned using a far medial portal technique, as the femoral tunnel tends to be shorter compared with that positioned using a transtibial portal technique. This study describes an accurate method of calculating the ideal length of bone plugs of a BPTB graft required to avoid graft–tunnel mismatch during anatomical ACL reconstruction using a far medial portal technique of femoral tunnel positioning.
Based on data obtained intra-operatively from 60 anatomical ACL reconstruction procedures, we calculated the length of bone plugs required in the BPTB graft to avoid graft–tunnel mismatch. When this was prevented in all the 60 cases, we found that the mean length of femoral bone plug that remained in contact with the interference screw within the femoral tunnel was 14 mm (12 to 22) and the mean length of tibial bone plug that remained in contact with the interference screw within the tibial tunnel was 23 mm (18 to 28). These results were used to validate theoretical formulae developed to predict the required length of bone plugs in BPTB graft during anatomical ACL reconstruction using a far medial portal technique.
Cite this article:
The mechanical performance of the cement-in-cement interface in revision surgery has not been fully investigated. The quantitative effect posed by interstitial fluids and roughening of the primary mantle remains unclear. We have analysed the strength of the bilaminar cement-bone interface after exposure of the surface of the primary mantle to roughening and fluid interference. The end surfaces of cylindrical blocks of cement were machined smooth (Ra = 200 nm) or rough (Ra = 5 μm) and exposed to either different volumes of water and carboxymethylcellulose (a bone-marrow equivalent) or left dry. Secondary blocks were cast against the modelled surface. Monoblocks of cement were used as a control group. The porosity of the samples was investigated using micro-CT. Samples were exposed to a single shearing force to failure.
The mean failure load of the monoblock control was 5.63 kN (95% confidence interval (CI) 5.17 to 6.08) with an estimated shear strength of 36 MPa. When small volumes of any fluid or large volumes were used, the respective values fell between 4.66 kN and 4.84 kN with no significant difference irrespective of roughening (p > 0.05). Large volumes of carboxymethylcellulose significantly weakened the interface. Roughening in this group significantly increased the strength with failure loads of 2.80 kN (95% CI 2.37 to 3.21) compared with 0.86 kN (95% CI 0.43 to 1.27) in the smooth variant. Roughening of the primary mantle may not therefore be as crucial as has been previously thought in clinically relevant circumstances.
We examined the morphology of mammalian hips asking whether evolution can explain the morphology of impingement in human hips. We describe two stereotypical mammalian hips, coxa recta and coxa rotunda. Coxa recta is characterised by a straight or aspherical section on the femoral head or head-neck junction. It is a sturdy hip seen mostly in runners and jumpers. Coxa rotunda has a round femoral head with ample head-neck offset, and is seen mostly in climbers and swimmers.
Hominid evolution offers an explanation for the variants in hip morphology associated with impingement. The evolutionary conflict between upright gait and the birth of a large-brained fetus is expressed in the female pelvis and hip, and can explain pincer impingement in a coxa profunda. In the male hip, evolution can explain cam impingement in coxa recta as an adaptation for running.
Using a modern cementing technique, we implanted 22 stereolithographic polymeric replicas of the Charnley-Kerboul stem in 11 pairs of human cadaver femora. On one side, the replicas were cemented line-to-line with the largest broach. On the other, one-size undersized replicas were used (radial difference, 0.89 mm
CT analysis showed that the line-to-line stems without distal centralisers were at least as well aligned and centered as undersized stems with a centraliser, but were surrounded by less cement and presented more areas of thin (<
2 mm) or deficient (<
1 mm) cement. These areas were located predominantly at the corners and in the middle and distal thirds of the stem. Nevertheless, in line-to-line stems, penetration of cement into cancellous bone resulted in a mean thickness of cement of 3.1 mm (
When Charnley-Kerboul stems are cemented line-to-line, good clinical results are observed because cement-deficient areas are limited and are frequently supported by cortical bone.
We performed a retrospective study to determine
the effect of osteoporosis on the functional outcome of osteoporotic
distal radial fractures treated with a volar locking plate. Between
2009 and 2012 a total of 90 postmenopausal women with an unstable
fracture of the distal radius treated with a volar locking plate
were studied. Changes in the radiological parameters of 51 patients
with osteoporosis (group 1, mean age 66.9, mean T-score –3.16 (
We found that osteoporosis does not have a negative effect on the functional outcome and additional analysis did not show a correlation between T-score and outcome.
Cite this article:
Despite worldwide clinical use of bio-absorbable devices for internal fixation in orthopaedic surgery, the degradation behaviour and tissue replacement of these implants are not fully understood.
In a long-term experimental study, we have determined the patterns of tissue restoration 36 and 54 months after implantation of polyglycolic acid and poly-laevo-lactic acid screws in the distal femur of the rabbit.
After 36 months in the polyglycolic acid group the specimens showed no remaining polymer and loose connective tissue occupied 80% of the screw track. Tissue restoration remained poor at 54 months, the amounts of trabecular bone and haematopoietic elements being significantly lower than those in the intact control group. The amount of trabecular bone within the screw track at 54 months in the polyglycolic acid group was less than in the empty drill holes (p = 0.04). In the poly-laevo-lactic acid group, polymeric material was present in abundance after 54 months, occupying 60% of the cross-section of the core area of the screw track.
When using absorbable internal fixation implants we should recognise that the degradation of the devices will probably not be accompanied by the restoration of normal trabecular bone.
We report the clinical and radiographic outcomes of 208 consecutive femoral revision arthroplasties performed in 202 patients (119 women, 83 men) between March 1991 and December 2007 using the X-change Femoral Revision System, fresh-frozen morcellised allograft and a cemented polished Exeter stem. All patients were followed prospectively. The mean age of the patients at revision was 65 years (30 to 86). At final review in December 2013 a total of 130 patients with 135 reconstructions (64.9%) were alive and had a non re-revised femoral component after a mean follow-up of 10.6 years (4.7 to 20.9). One patient was lost to follow-up at six years, and their data were included up to this point. Re-operation for any reason was performed in 33 hips (15.9%), in 13 of which the femoral component was re-revised (6.3%). The mean pre-operative Harris hip score was 52 (19 to 95) (n = 73) and improved to 80 (22 to 100) (n = 161) by the last follow-up. Kaplan–Meier survival with femoral re-revision for any reason as the endpoint was 94.9% (95% confidence intervals (CI) 90.2 to 97.4) at ten years; with femoral re-revision for aseptic loosening as the endpoint it was 99.4% (95% CI 95.7 to 99.9); with femoral re-operation for any reason as the endpoint it was 84.5% (95% CI 78.3 to 89.1); and with subsidence ≥ 5 mm it was 87.3% (95% CI 80.5 to 91.8). Femoral revision with the use of impaction allograft bone grafting and a cemented polished stem results in a satisfying survival rate at a mean of ten years’ follow-up.
Cite this article:
We report a 30-year-old patient who was involved in a high-velocity road traffic accident and developed a left-sided hemiparesis, which was noted in the post-operative period following bilateral femoral intramedullary nailing. CT scanning of the brain revealed infarcts in the right frontal and parietal lobes in the distribution of the right middle cerebral artery. CT angiography showed occlusion of the right internal carotid artery consistent with internal carotid artery dissection. He was anticoagulated and nine months later was able to walk independently.
An awareness of this injury is needed to diagnose blunt trauma to the internal carotid artery. Even in the absence of obvious neck trauma, carotid artery dissection should be suspected in patients with a neurological deficit in the peri-operative period.
Elastic stable intramedullary nailing (ESIN) is generally acknowledged to be the treatment of choice for displaced diaphyseal femoral fractures in children over the age of three years, although complication rates of up to 50% are described. Pre-bending the nails is recommended, but there are no published data to support this. Using synthetic bones and a standardised simulated fracture, we performed biomechanical testing to determine the influence on the stability of the fracture of pre-bending the nails before implantation. Standard ESIN was performed on 24 synthetic femoral models with a spiral fracture. In eight cases the nails were inserted without any pre-bending, in a further eight cases they were pre-bent to 30° and in the last group of eight cases they were pre-bent to 60°. Mechanical testing revealed that pre-bending to 60° produced a significant increase in the stiffness or stability of the fracture. Pre-bending to 60° showed a significant positive influence on the stiffness compared with unbent nails. Pre-bending to 30° improved stiffness only slightly.
These findings validate the recommendations for pre-bending, but the degree of pre-bend should exceed 30°. Adopting higher degrees of pre-bending should improve stability in spiral fractures and reduce the complications of varus deformity and shortening.
We describe the results of 81 consecutive revision total hip replacements with impaction grafting in 79 patients using a collared polished chrome–cobalt stem, customised in length according to the extent of distal bone loss. Our hypothesis was that the features of this stem would reduce the rate of femoral fracture and subsidence of the stem.
The mean follow-up was 12 years (8 to 15). No intra-operative fracture or significant subsidence occurred. Only one patient suffered a post-operative diaphyseal fracture, which was associated with a fall. All but one femur showed incorporation of the graft. No revision for aseptic loosening was recorded.
The rate of survival of the femoral component at 12 years, using further femoral revision as the endpoint, was 100% (95% confidence interval (CI) 95.9 to 100), and at nine years using re-operation for any reason as the endpoint, was 94.6% (95% CI 92.0 to 97.2).
These results suggest that a customised cemented polished stem individually adapted to the extent of bone loss and with a collar may reduce subsidence and the rate of fracture while maintaining the durability of the fixation.
Cancellous allograft bone chips are commonly used in the reconstruction of defects in bone after removal of benign tumours. We investigated the MRI features of grafted bone chips and their change over time, and compared them with those with recurrent tumour. We retrospectively reviewed 66 post-operative MRIs from 34 patients who had undergone curettage and grafting with cancellous bone chips to fill the defect after excision of a tumour. All grafts showed consistent features at least six months after grafting: homogeneous intermediate or low signal intensities with or without scattered hyperintense foci (speckled hyperintensities) on T1 images; high signal intensities with scattered hypointense foci (speckled hypointensities) on T2 images, and peripheral rim enhancement with or without central heterogeneous enhancements on enhanced images. Incorporation of the graft occurred from the periphery to the centre, and was completed within three years. Recurrent lesions consistently showed the same signal intensities as those of pre-operative MRIs of the primary lesions. There were four misdiagnoses, three of which were chondroid tumours.
We identified typical MRI features and clarified the incorporation process of grafted cancellous allograft bone chips. The most important characteristics of recurrent tumours were that they showed the same signal intensities as the primary tumours. It might sometimes be difficult to differentiate grafted cancellous allograft bone chips from a recurrent chondroid tumour.
Cite this article:
We determined the midterm survival, incidence of peri-prosthetic fracture and the enhancement of the width of the femur when combining struts and impacted bone allografts in 24 patients (25 hips) with severe femoral bone loss who underwent revision hip surgery. The pre-operative diagnosis was aseptic loosening in 16 hips, second-stage reconstruction in seven, peri-prosthetic fracture in one and stem fracture in one hip. A total of 14 hips presented with an Endoklinik grade 4 defect and 11 hips a grade 3 defect. The mean pre-operative Merle D’Aubigné and Postel score was 5.5 points (1 to 8).
The survivorship was 96% (95% confidence interval 72 to 98) at a mean of 54.5 months (36 to 109). The mean functional score was 17.3 points (16 to 18). One patient in which the strut did not completely bypass the femoral defect was further revised using a long cemented stem due to peri-prosthetic fracture at six months post-operatively. The mean subsidence of the stem was 1.6 mm (1 to 3). There was no evidence of osteolysis, resorption or radiolucencies during follow-up in any hip. Femoral width was enhanced by a mean of 41% (19% to 82%). A total of 24 hips had partial or complete bridging of the strut allografts.
This combined biological method was associated with a favourable survivorship, a low incidence of peri-prosthetic fracture and enhancement of the width of the femur in revision total hip replacement in patients with severe proximal femoral bone loss.
An experimental sheep model was used for impaction allografting of 12 hemiarthroplasty femoral components placed into two equal-sized groups. In group 1, a 50:50 mixture of ApaPore hydroxyapatite bone-graft substitute and allograft was used. In group 2, ApaPore and allograft were mixed in a 90:10 ratio. Both groups were killed at six months. Ground reaction force results demonstrated no significant differences (p > 0.05) between the two groups at 8, 16 and 24 weeks post-operatively, and all animals remained active. The mean bone turnover rates were significantly greater in group 1, at 0.00206 mm/day, compared to group 2 at 0.0013 mm/day (p < 0.05). The results for the area of new bone formation demonstrated no significant differences (p > 0.05) between the two groups. No significant differences were found between the two groups in thickness of the cement mantle (p > 0.05) and percentage ApaPore-bone contact (p > 0.05).
The results of this animal study demonstrated that a mixture of ApaPore allograft in a 90:10 ratio was comparable to using a 50:50 mixture.
Two types of fracture, early and late, have been reported following limb lengthening in patients with achondroplasia (ACH) and hypochondroplasia (HCH).
We reviewed 25 patients with these conditions who underwent 72 segmental limb lengthening procedures involving the femur and/or tibia, between 2003 and 2011. Gender, age at surgery, lengthened segment, body mass index, the shape of the callus, the amount and percentage of lengthening and the healing index were evaluated to determine predictive factors for the occurrence of early (within three weeks after removal of the fixation pins) and late fracture (> three weeks after removal of the pins). The Mann‑Whitney U test and Pearson’s chi-squared test for univariate analysis and stepwise regression model for multivariate analysis were used to identify the predictive factor for each fracture. Only one patient (two tibiae) was excluded from the analysis due to excessively slow formation of the regenerate, which required supplementary measures. A total of 24 patients with 70 limbs were included in the study.
There were 11 early fractures in eight patients. The shape of the callus (lateral or central callus) was the only statistical variable related to the occurrence of early fracture in univariate and multivariate analyses. Late fracture was observed in six limbs and the mean time between removal of the fixation pins and fracture was 18.3 weeks (3.3 to 38.4). Lengthening of the tibia, larger healing index, and lateral or central callus were related to the occurrence of a late fracture in univariate analysis. A multivariate analysis demonstrated that the shape of the callus was the strongest predictor for late fracture (odds ratio: 19.3, 95% confidence interval: 2.91 to 128). Lateral or central callus had a significantly larger risk of fracture than fusiform, cylindrical, or concave callus.
Radiological monitoring of the shape of the callus during distraction is important to prevent early and late fracture of lengthened limbs in patients with ACH or HCH. In patients with thin callus formation, some measures to stimulate bone formation should be considered as early as possible.
Cite this article:
We report the follow-up at 12 years of the use of the Elite Plus total hip replacement (THR). We have previously reported the results at a mean of 6.4 years. Of the 217 patients (234 THRs), 83 had died and nine had been lost to follow-up. The patients were reviewed radiologically and clinically using the Oxford hip score.
Of the 234 THRs, 19 (8.1%) had required a revision by the final follow-up in all but one for aseptic loosening. Survivorship analysis for revision showed a survival of 93.9% (95% confidence interval (CI) 89.2 to 96.5) at ten years, and of 88.0% (95% CI 81.8 to 92.3) at 12 years. At the final follow-up survival analysis showed that 37% (95% CI 37.3 to 44.7) of the prostheses had either failed radiologically or had been revised. Patients with a radiologically loose femoral component had a significantly poorer Oxford hip score than those with a well-fixed component (p = 0.03). Radiological loosening at 6.4 years was predictive of failure at 12 years.
Medium-term radiographs and clinical scores should be included in the surveillance of THR to give an early indication of the performance of specific implants.
The April 2014 Hip & Pelvis Roundup360 looks at: Recent arthroplasty and flight; whether that squeak could be a fracture; diagnosing early infected hip replacement; impaction grafting at a decade; whether squeaking is more common than previously thought; femoral offset associated with post THR outcomes; and periprosthetic fracture stabilisation.
A total of 31 patients, (20 women, 11 men; mean age 62.5 years old; 23 to 81), who underwent conversion of a Girdlestone resection-arthroplasty (RA) to a total hip replacement (THR) were compared with 93 patients, (60 women, 33 men; mean age 63.4 years old; 20 to 89), who had revision THR surgery for aseptic loosening in a retrospective matched case-control study. Age, gender and the extent of the pre-operative bone defect were similar in all patients. Mean follow-up was 9.3 years (5 to 18).
Pre-operative function and range of movement were better in the control group (p = 0.01 and 0.003, respectively) and pre-operative leg length discrepancy (LLD) was greater in the RA group (p < 0.001). The post-operative clinical outcome was similar in both groups except for mean post-operative LLD, which was greater in the study group (p = 0.003). There was a significant interaction effect for LLD in the study group (p < 0.001). A two-way analysis of variance showed that clinical outcome depended on patient age (patients older than 70 years old had worse pre-operative pain, p = 0.017) or bone defect (patients with a large acetabular bone defect had higher LLD, p = 0.006, worse post-operative function p = 0.009 and range of movement, p = 0.005), irrespective of the group.
Despite major acetabular and femoral bone defects requiring complex surgical reconstruction techniques, THR after RA shows a clinical outcome similar to those obtained in aseptic revision surgery for hips with similar sized bone defects.
Cite this article: