There is an increased risk of fracture following osteoplasty of the femoral neck for cam-type femoroacetabular impingement (FAI). Resection of up to 30% of the anterolateral head–neck junction has previously been considered to be safe, however, iatrogenic fractures have been reported with resections within these limits. We re-evaluated the amount of safe resection at the anterolateral femoral head–neck junction using a biomechanically consistent model. In total, 28 composite bones were studied in four groups: control, 10% resection, 20% resection and 30% resection. An axial load was applied to the adducted and flexed femur. Peak load, deflection at time of fracture and energy to fracture were assessed using comparison groups. There was a marked difference in the mean peak load to fracture between the control group and the 10% resection group (p < 0.001). The control group also tolerated significantly more deflection before failure (p < 0.04). The mean peak load (p = 0.172), deflection (p = 0.547), and energy to fracture (p = 0.306) did not differ significantly between the 10%, 20%, and 30% resection groups. . Any resection of the anterolateral quadrant of the femoral head–neck junction for FAI significantly reduces the load-bearing capacity of the proximal femur. After initial resection of cortical bone, there is no further relevant loss of stability regardless of the amount of trabecular bone resected. Based on our findings we recommend any patients who undergo anterolateral femoral head–neck junction osteoplasty should be advised to modify their post-operative routine until cortical remodelling occurs to minimise the subsequent fracture risk. Cite this article: Bone Joint J 2015;97-B:1214–19

In navigated total hip arthroplasty, the pelvis and the femur are tracked by means of rigid bodies fixed directly to the bones. Exact tracking throughout the procedure requires that the connection between the marker and bone remains stable in terms of translation and rotation. We carried out a cadaver study to compare the intra-operative stability of markers consisting of an anchoring screw with a rotational stabiliser and of pairs of pins and wires of different diameters connected with clamps. These devices were tested at different locations in the femur. Three human cadavers were placed supine on an operating table, with a reference marker positioned in the area of the greater trochanter. K-wires (3.2 mm), Steinman pins (3 and 4 mm), Apex pins (3 and 4 mm), and a standard screw were used as fixation devices. They were positioned medially in the proximal third of the femur, ventrally in the middle third and laterally in the distal portion. In six different positions of the leg, the spatial positions were recorded with a navigation system. Compared with the standard single screw, with the exception of the 3 mm Apex pins, the two-pin systems were associated with less movement of the marker and could be inserted less invasively. With the knee flexed to 90° and the dislocated hip rotated externally until the lower leg was parallel to the table (figure-four position), all the anchoring devices showed substantial deflection of 1.5° to 2.5°. The most secure area for anchoring markers was the lateral aspect of the femur

Aims

The aim of the study was to investigate whether the primary stability of press-fit acetabular components can be improved by altering the impaction procedure.

Aims

The diagnosis of developmental dysplasia of the hip (DDH) is challenging owing to extensive variation in paediatric pelvic anatomy. Artificial intelligence (AI) may represent an effective diagnostic tool for DDH. Here, we aimed to develop an anteroposterior pelvic radiograph deep learning system for diagnosing DDH in children and analyze the feasibility of its application.

The requirement for release of collateral ligaments to achieve a stable, balanced total knee replacement has been reported to arise in about 50% to 100% of procedures. This wide range reflects a lack of standardised quantitative indicators to determine the necessity for a release. Using recent advances in computerised navigation, we describe two navigational predictors which provide quantitative measures that can be used to identify the need for release. The first was the ability to restore the mechanical axis before any bone resection was performed and the second was the discrepancy in the measured medial and lateral joint spaces after the tibial osteotomy, but before any femoral resection.

These predictors showed a significant association with the need for collateral ligament release (p < 0.001). The first predictor using the knee stress test in extension showed a sensitivity of 100% and a specificity of 98% and the second, the difference between medial and lateral gaps in millimetres, a sensitivity of 83% and a specificity of 95%. The use of the two navigational predictors meant that only ten of the 93 patients required collateral ligament release to achieve a stable, neutral knee.

Conventional non-steroidal anti-inflammatory drugs (NSAIDs) and newer specific cyclo-oxygenase-2 (cox-2) inhibitors are commonly used in musculoskeletal trauma and orthopaedic surgery to reduce the inflammatory response and pain. These drugs have been reported to impair bone metabolism. In reconstruction of the anterior cruciate ligament the hamstring tendons are mainly used as the graft of choice, and a prerequisite for good results is healing of the tendons in the bone tunnel. Many of these patients are routinely given NSAIDs or cox-2 inhibitors, although no studies have elucidated the effects of these drugs on tendon healing in the bone tunnel.

In our study 60 female Wistar rats were randomly allocated into three groups of 20. One received parecoxib, one indometacin and one acted as a control. In all the rats the tendo-Achillis was released proximally from the calf muscles. It was then pulled through a drill hole in the distal tibia and sutured anteriorly. The rats were given parecoxib, indometacin or saline intraperitoneally twice daily for seven days. After 14 days the tendon/bone-tunnel interface was subjected to mechanical testing.

Significantly lower maximum pull-out strength (p < 0.001), energy absorption (p < 0.001) and stiffness (p = 0.035) were found in rats given parecoxib and indometacin compared with the control group, most pronounced with parecoxib.

The ability to predict load-bearing capacity during the consolidation phase in distraction osteogenesis by non-invasive means would represent a significant advance in the management of patients undergoing such treatment. Measurements of stiffness have been suggested as a promising tool for this purpose. Although the multidimensional characteristics of bone loading in compression, bending and torsion are apparent, most previous experiments have analysed only the relationship between maximum load-bearing capacity and a single type of stiffness. We have studied how compressive, bending and torsional stiffness are related to the torsional load-bearing capacity of healing callus using a common set of samples of bone regenerate from 26 sheep treated by tibial distraction osteogenesis.

Our findings showed that measurements of torsional, bending and compressive stiffness were all suitable as predictors of the load-bearing capacity of healing callus. Measurements of torsional stiffness performed slightly better than those of compressive and bending stiffness.

We retrospectively reviewed the records of 1150 computer-assisted total knee replacements and analysed the clinical and radiological outcomes of 45 knees that had arthritis with a pre-operative recurvatum deformity. The mean pre-operative hyperextension deformity of 11° (6° to 15°), as measured by navigation at the start of the operation, improved to a mean flexion deformity of 3.1° (0° to 7°) post-operatively. A total of 41 knees (91%) were managed using inserts ≤ 12.5 mm thick, and none had mediolateral laxity > 2 mm from a mechanical axis of 0° at the end of the surgery. At a mean follow-up of 26.4 months (13 to 48) there was significant improvement in the mean Knee Society, Oxford knee and Western Ontario and McMaster Universities Osteoarthritis Index scores compared with the pre-operative values. The mean knee flexion improved from 105° (80° to 125°) pre-operatively to 131° (120° to 145°), and none of the limbs had recurrent recurvatum.

These early results show that total knee replacement using computer navigation and an algorithmic approach for arthritic knees with a recurvatum deformity can give excellent radiological and functional outcomes without recurrent deformity.

Finite element analysis was used to examine the initial stability after hip resurfacing and the effect of the procedure on the contact mechanics at the articulating surfaces. Models were created with the components positioned anatomically and loaded physiologically through major muscle forces. Total micromovement of less than 10 μm was predicted for the press-fit acetabular components models, much below the 50 μm limit required to encourage osseointegration. Relatively high compressive acetabular and contact stresses were observed in these models. The press-fit procedure showed a moderate influence on the contact mechanics at the bearing surfaces, but produced marked deformation of the acetabular components. No edge contact was predicted for the acetabular components studied.

It is concluded that the frictional compressive stresses generated by the 1 mm to 2 mm interference-fit acetabular components, together with the minimal micromovement, would provide adequate stability for the implant, at least in the immediate post-operative situation.

The aim of this study was to investigate the possible benefit of large-head metal-on-metal bearing on a stem for primary hip replacement compared with a 28 mm diameter conventional metal-on-polyethylene bearing in a prospective randomised controlled trial. We investigated cemented stem behaviour between these two different bearings using Einzel-Bild-Röntgen-Analyse, clinical and patient reported measures (Harris hip score, Western Ontario and McMaster Universities osteoarthritis index, Short Form-36 and satisfaction) and whole blood metal ion levels at two years. A power study indicated that 50 hips were needed in each group to detect subsidence of > 5 mm at two years with a p-value of < 0.05.

Significant improvement (p < 0.001) was found in the mean clinical and patient reported outcomes at two years for both groups. Comparison of outcomes between the groups at two years showed no statistically significant difference for mean stem migration, clinical and patient reported outcomes; except overall patient satisfaction which was higher for metal-on-metal group (p = 0.05). Metal ion levels were raised above the Medicines and Healthcare products Regulatory Agency advised safety level (7 µg per litre) in 20% of the metal-on-metal group and in one patient in metal-on-polyethylene group (who had a metal-on-metal implant on the contralateral side). Two patients in the metal-on-metal group were revised, one for pseudotumour and one for peri-prosthetic fracture.

Use of large modular heads is associated with a risk of raised whole blood metal ion levels despite using a proven bearing from resurfacing. The head-neck junction or excess stem micromotion are possibly the weak links warranting further research.

Coloured bone cements have been introduced to make the removal of cement debris easier at the time of primary and revision joint replacement. We evaluated the physical, mechanical and pharmacological effects of adding methylene blue to bone cement with or without antibiotics (gentamicin, vancomycin or both). The addition of methylene blue to plain cement significantly decreased its mean setting time (570 seconds (sd 4) vs 775 seconds (sd 11), p = 0.01), mean compression strength (95.4 MPa (sd 3) vs 100.1 MPa (sd 6), p = 0.03), and mean bending strength (65.2 MPa (sd 5) vs 76.6 MPa (sd 4), p < 0.001) as well as its mean elastic modulus (2744 MPa (sd 97) vs 3281 MPa (sd 110), p < 0.001). The supplementation of the coloured cement with vancomycin and gentamicin decreased its mean bending resistance (55.7 MPa (sd 4) vs 65.2 MPa (sd 5), p < 0.001).The methylene blue significantly decreased the mean release of gentamicin alone (228.2 µg (sd 24) vs 385.5 µg (sd 26), p < 0.001) or in combination with vancomycin (498.5 µg (sd 70) vs 613 µg (sd 25), p = 0.018) from the bone cement. This study demonstrates several theoretical disadvantages of the antibiotic-loaded bone cement coloured with methylene blue.

We split 100 porcine flexor tendons into five groups of 20 tendons for repair. Three groups were repaired using the Pennington modified Kessler technique, the cruciate or the Savage technique, one using one new device per tendon and the other with two new devices per tendon. Half of the tendons received supplemental circumferential Silfverskiöld type B cross-stitch. The repairs were loaded to failure and a record made of their bulk, the force required to produce a 3 mm gap, the maximum force applied before failure and the stiffness. When only one device was used repairs were equivalent to the Pennington modified Kessler for all parameters except the force to produce a 3 mm gap when supplemented with a circumferential repair, which was equivalent to the cruciate.

When two devices were used the repair strength was equivalent to the cruciate repair, and when the two-device repair was supplemented with a circumferential suture the force to produce a 3 mm gap was equivalent to that of the Savage six-strand technique.

This prospective randomised clinical trial evaluated the effect of alternatives for allogeneic blood transfusions after total hip replacement and total knee replacement in patients with pre-operative haemoglobin levels between 10.0 g/dl and 13.0 g/dl. A total of 100 patients were randomly allocated to the Eprex (pre-operative injections of epoetin) or Bellovac groups (post-operative retransfusion of shed blood). Allogeneic blood transfusions were administered according to hospital policy.

In the Eprex group, 4% of the patients (two patients) received at least one allogeneic blood transfusion. In the Bellovac group, where a mean 216 ml (0 to 700) shed blood was retransfused, 28% (14 patients) required the allogeneic transfusion (p = 0.002). When comparing Eprex with Bellovac in total hip replacement, the percentages were 7% (two of 30 patients) and 30% (nine of 30 patients) (p = 0.047) respectively, whereas in total knee replacement, the percentages were 0% (0 of 20 patients) and 25% (five of 20 patients) respectively (p = 0.042).

Pre-operative epoetin injections are more effective but more costly in reducing the need for allogeneic blood transfusions in mildly anaemic patients than post-operative retransfusion of autologous blood.

The management of bone loss in revision replacement of the knee remains a challenge despite an array of options available to the surgeon. Bone loss may occur as a result of the original disease, the design of the prosthesis, the mechanism of failure or technical error at initial surgery. The aim of revision surgery is to relieve pain and improve function while addressing the mechanism of failure in order to reconstruct a stable platform with transfer of load to the host bone. Methods of reconstruction include the use of cement, modular metal augmentation of prostheses, custom-made, tumour-type or hinged implants and bone grafting.

The published results of the surgical techniques are summarised and a guide for the management of bone defects in revision surgery of the knee is presented.

The aim of this biomechanical study was to investigate the role of the dorsal vertebral cortex in transpedicular screw fixation. Moss transpedicular screws were introduced into both pedicles of each vertebra in 25 human cadaver vertebrae. The dorsal vertebral cortex and subcortical bone corresponding to the entrance site of the screw were removed on one side and preserved on the other. Biomechanical testing showed that the mean peak pull-out strength for the inserted screws, following removal of the dorsal cortex, was 956.16 N. If the dorsal cortex was preserved, the mean peak pullout strength was 1295.64 N. The mean increase was 339.48 N (26.13%; p = 0.033). The bone mineral density correlated positively with peak pull-out strength.

Preservation of the dorsal vertebral cortex at the site of insertion of the screw offers a significant increase in peak pull-out strength. This may result from engagement by the final screw threads in the denser bone of the dorsal cortex and the underlying subcortical area. Every effort should be made to preserve the dorsal vertebral cortex during insertion of transpedicular screws.

Mechanical loosening which begins with early-onset migration of the prosthesis is the major reason for failure of the Souter-Strathclyde elbow replacement. In a prospective study of 18 Souter-Strathclyde replacements we evaluated the patterns of migration using roentgen stereophotogrammetric analysis. We had previously reported the short-term results after a follow-up of two years which we have now extended to a mean follow-up of 8.2 years (1 to 11.3). Migration was assessed along the co-ordinal axes and overall micromovement was expressed as the maximum total point movement. The alignment of the prosthesis and the presence of radiolucent lines were examined on conventional standardised radiographs.

All the humeral components showed increased and variable patterns of migration at the extended follow-up and four humeral components were revised. The maximum total point movement at two years in the revised prostheses was 1.8 mm (sd 1.0) and in the non-revised 0.7 mm (sd 0.5, p = 0.01). Most humeral components migrated into external rotation resulting in an anterior and varus tilt. The ulnar components remained stable.

We have evaluated the effect of the short-term administration of low therapeutic doses of modern COX-2 inhibitors on the healing of fractures.

A total of 40 adult male New Zealand rabbits were divided into five groups. A mid-diaphyseal osteotomy of the right ulna was performed and either normal saline, prednisolone, indometacin, meloxicam or rofecoxib was administered for five days. Radiological, biomechanical and histomorphometric evaluation was performed at six weeks.

In the group in which the highly selective anti-COX-2 agent, rofecoxib, was used the incidence of radiologically-incomplete union was similar to that in the control group. All the biomechanical parameters were statistically significantly lower in both the prednisolone and indometacin (p = 0.01) and in the meloxicam (p = 0.04) groups compared with the control group. Only the fracture load values were found to be statistically significantly lower (p = 0.05) in the rofecoxib group. Histomorphometric parameters were adversely affected in all groups with the specimens of the rofecoxib group showing the least negative effect.

Our findings indicated that the short-term administration of low therapeutic doses of a highly selective COX-2 inhibitor had a minor negative effect on bone healing.

The object of this study was to develop a method to assess the accuracy of an image-free total knee replacement navigation system in legs with normal or abnormal mechanical axes. A phantom leg was constructed with simulated hip and knee joints and provided a means to locate the centre of the ankle joint. Additional joints located at the midshaft of the tibia and femur allowed deformation in the flexion/extension, varus/valgus and rotational planes. Using a digital caliper unit to measure the coordinates precisely, a software program was developed to convert these local coordinates into a determination of actual leg alignment. At specific points in the procedure, information was compared between the digital caliper measurements and the image-free navigation system. Repeated serial measurements were undertaken. In the setting of normal alignment the mean error of the system was within 0.5°. In the setting of abnormal plane alignment in both the femur and the tibia, the error was within 1°. This is the first study designed to assess the accuracy of a clinically-validated navigation system. It demonstrates in vitro accuracy of the image-free navigation system in both normal and abnormal leg alignment settings.

We have investigated whether control of balance is improved during stance and gait and sit-to-stand tasks after unilateral total hip replacement undertaken for osteoarthritis of the hip.

We examined 25 patients with a mean age of 67 years (sd 6.2) before and at four and 12 months after surgery and compared the findings with those of 50 healthy age-matched control subjects. For all tasks, balance was quantified using angular measurements of movement of the trunk.

Before surgery, control of balance during gait and sit-to-stand tasks was abnormal in patients with severe osteoarthritis of the hip, while balance during stance was similar to that of the healthy control group. After total hip replacement, there was a progressive improvement at four and 12 months for most gait and sit-to-stand tasks and in the time needed to complete them. By 12 months, the values approached those of the control group. However, trunk pitch (forwards-backwards) and roll (side-to-side) velocities were less stable (greater than the control) when walking over barriers as was roll for the sit-to-stand task, indicative of a residual deficit of balance.

Our data suggest that patients with symptomatic osteoarthritis of the hip have marked deficits of balance in gait tasks, which may explain the increased risk of falling which has been reported in some epidemiological studies. However, total hip replacement may help these patients to regain almost normal control of balance for some gait tasks, as we found in this study. Despite the improvement in most components of balance, however, the deficit in the control of trunk velocity during gait suggests that a cautious follow-up is required after total hip replacement regarding the risk of a fall, especially in the elderly.

We have managed 21 patients with a fracture of the tibia complicated by bone and soft-tissue loss as a result of an open fracture in 10, or following debridement of an infected nonunion in 11, by resection of all the devitalised tissues, acute limb shortening to close the defect, application of an external fixator and metaphyseal osteotomy for re-lengthening. The mean bone loss was 4.7 cm (3 to 11). The mean age of the patients was 28.8 years (12 to 54) and the mean follow-up was 34.8 months (24 to 75).

All the fractures united with a well-aligned limb. The mean duration of treatment for the ten grade-III A+B open fractures (according to the Gustilo-Anderson classification) was 5.7 months (4.5 to 8) and for the nonunions, 7.6 months (5.5 to 12.5). Complications included one refracture, one transient palsy of the peroneal nerve and one equinus contracture of 10°.