Introduction. Due to the commercial launch of newly developed ceramic-on-metal (COM) bearings, we compared the deformation and stresses in the liner with ceramic-on-ceramic (COC), metal-on-metal (MOM) as well as ceramic-on-polyethylene (COP) bearings using a finite-element (FE)-model, analyzing a variety of head size and implant position. Liner deformation in terms of change in inner diameter as well as peak stresses were evaluated. Methods. The FE-model consisting of a commercial THR, the proximal femur and a section of the hemipelvis was created based on our previously published approach. Static load and muscle forces were applied according to the maximum load during gait. Polyethylene was modelled using a nonlinear definition with isotropic hardening, cobalt-chromium was modelled elastic-plastic and ceramic was modelled linear-elastic. Validity of the model was checked using an experimental setup with artificial bone and strain gauges located at the rim of the liner. Implant material (COM vs. COC vs. MOM vs. COP), head size (28 mm vs. 36 mm) and cup position (45° inclination/15° anteversion vs. 60° incl./0° antev.) were varied. Results. The experimental validation showed high correlation between strain measurements and FE-results. Liner deformation was evaluated by change in diameter at different levels. Change in head size had a high influence on cup deformation in COM, COC and MOM bearings, most possibly due to decreased liner thickness using bigger heads. Differences in MOM, COC and COM liner deformation were only in sub-micrometer range and not further evaluated. Evaluation of von Mises stress and minimum principal stress showed high differences between the bearing couples, implant positions and head sizes. COM liner stress was less sensitive to the steep cup position, but principal stress amounts were about ten times higher than in polyethylene liners. Thereby, MOM liners developed about 13 % less peak stress than COM. COC liners showed 11 % to 16 % higher stresses than COM. In accordance with published results, bigger head size correlated with lower principal stresses in the liner. Also, bigger heads were less sensitive to steep cup positions. Discussion. Deformation of the liner in total hip replacement has an important influence on lubrication, wear and clinical long-term success. The deformation occurring during intraoperative impaction and press-fit of the metal shell was not included in this study, hence the results are only valid considering the late postoperative phase when the implant is fully integrated in the bone. The FE-analysis showed no significant difference in liner deformation between COM, COC and MOM bearings. However, principal stresses were slightly higher in COM under the same conditions, but lower than COC

Aims. To evaluate if, for orthopaedic trainees, additional cadaveric simulation training or standard training alone yields superior radiological and clinical outcomes in patients undergoing dynamic hip screw (DHS) fixation or hemiarthroplasty for hip fracture. Methods. This was a preliminary, pragmatic, multicentre, parallel group randomized controlled trial in nine secondary and tertiary NHS hospitals in England. Researchers were blinded to group allocation. Overall, 40 trainees in the West Midlands were eligible: 33 agreed to take part and were randomized, five withdrew after randomization, 13 were allocated cadaveric training, and 15 were allocated standard training. The intervention was an additional two-day cadaveric simulation course. The control group received standard on-the-job training. Primary outcome was implant position on the postoperative radiograph: tip-apex distance (mm) (DHS) and leg length discrepancy (mm) (hemiarthroplasty). Secondary clinical outcomes were procedure time, length of hospital stay, acute postoperative complication rate, and 12-month mortality. Procedure-specific secondary outcomes were intraoperative radiation dose (for DHS) and postoperative blood transfusion requirement (hemiarthroplasty). Results. Eight female (29%) and 20 male trainees (71%), mean age 29.4 years, performed 317 DHS operations and 243 hemiarthroplasties during ten months of follow-up. Primary analysis was a random effect model with surgeon-level fixed effects of patient condition, patient age, and surgeon experience, with a random intercept for surgeon. Under the intention-to-treat principle, for hemiarthroplasty there was better implant position in favour of cadaveric training, measured by leg length discrepancy ≤ 10 mm (odds ratio (OR) 4.08 (95% confidence interval (CI) 1.17 to 14.22); p = 0.027). There were significantly fewer postoperative blood transfusions required in patients undergoing hemiarthroplasty by cadaveric-trained compared to standard-trained surgeons (OR 6.00 (95% CI 1.83 to 19.69); p = 0.003). For DHS, there was no significant between-group difference in implant position as measured by tip-apex distance ≤ 25 mm (OR 6.47 (95% CI 0.97 to 43.05); p = 0.053). No between-group differences were observed for any secondary clinical outcomes. Conclusion. Trainees randomized to additional cadaveric training performed hip fracture fixation with better implant positioning and fewer postoperative blood transfusions in hemiarthroplasty. This effect, which was previously unknown, may be a consequence of the intervention. Further study is required. Cite this article: Bone Jt Open 2023;4(8):602–611

Single focal grade IV cartilage lesion in the knee has a poor healing capacity. Instead these lesions often progress to severe and generalized osteoarthritis that may result in total knee replacement. Current treatment modalities aim at biological repair and, although theoretically appealing, the newly formed tissue is at the best cartilage-like, often fibrous or fibrocartilaginous. This at the expense of sophisticated laboratory resources, delicate surgery and strict compliance from patients. An alternative may be small implants of biomaterial inserted to replace the damaged cartilage. We investigated the response of the opposing tibia cartilage to a metallic implant inserted at different depth into the surrounding cartilage level. Methods. The medial femoral condyle of both knees of 12 sheep, 70–90kg, 2 year of age and from the same breeder, was operated. A metallic implant with an articulating surface of 316L stainless steel, diameter of 7mm, HA plasma sprayed press-fit peg and a tailored radius and contour to the sheep femoral condyle was placed at the most weight-bearing position. The level of the implant was aimed flush, 0,3 and 0,8 mm below surrounding cartilage. The animals were stabled indoors, allowed to move freely and euthanized after 6 and 12 weeks. Postoperatively the knees were high resolution photographed for macroscopic evaluation. The position and depth of the implant were analysed using a laser scan device. Tibial and femoral condyles specimen were decalcified and slices were prepared for microscopic evaluation. Implant position and cartilage damage was assessed from two independent observers using a macroscopic ICRS score and a modified histologic score according to Mankin. Results. 22 tibia condyles showed a variety of cartilage damage ranging from severe damage down to subchondral bone to an almost pristine condition. There was a strong correlation between implant position and damage to opposing cartilage surface. Mankin score correlated significantly with implant position (p<0.001 regression analysis, r. 2. =.45) as did the ICRS score (p<0.001, regression analysis, r. 2. =.67). Implants sitting proud were associated with poor Mankin score. There was no difference between 6-week and 3-months knees. Conclusion. By precise postoperative measurement we have shown that significant imprecision occur; this has never before been studied. We found a distinct correlation between implant position and cartilage damage. These results suggest that further studies of metallic implants, inserted into cartilage defects with the utmost precision regarding the surrounding cartilage, may be warranted

Aims

Proper preoperative planning benefits fracture reduction, fixation, and stability in tibial plateau fracture surgery. We developed and clinically implemented a novel workflow for 3D surgical planning including patient-specific drilling guides in tibial plateau fracture surgery.

Introduction. Dislocation following total hip arthroplasty THA is a major short term complication not infrequently resulting in revision arthroplasty. Malposition of the acetabular component in THA results in a higher rate of dislocation as well as increased wear and osteolysis. The aim of this study was to assess the effect of mode of fixation on positioning of the acetabular component. Patients, materials and methods. For all THAs performed at our hospital in 2008, angle of acetabular inclination was measured using PACS by two independent observers. Interobserver and intraobserver reliability were assessed (Pearson's correlation coefficient, r). We determined whether the number of acetabular components outside the target angle range (eg:45±5°) was significantly different between cemented and cementless THA (chi squared test). An enquiry was made to the National Joint Registry (NJR) in respect to incidence of revision for dislocation of THA using cemented and cementless acetabular components, 2004–2009. Results. During 2008 126 THA were performed, 80 cemented and 46 cementless. There was good reliability of angle measurement (interobserver: r=0.89; intraobserver: r=0.87 and 0.97). More cemented acetabular components were within target angle range compared to cementless (cemented 32/80, cementless 29/46; chi squared=6.39, p<0.05). Using data from NJR comparing the number of primary hip replacement operations with number of revisions due to dislocation found a higher rate for cementless THA, 0.381% (266/69,822) than for cemented, 0.282% (262/92,928) (Odds ratio: 1.35 (95% CI 1.14–1.60; P<0.05). Conclusion. Positioning of the acetabular component is more difficult when using cementless systems as implant position is determined by orientation of reaming whereas with cement there is potential for fine implant position adjustment on insertion. The choice of a cementless acetabular component significantly increases the incidence of dislocation post THA. Acetabular component malposition is likely to be a factor in this increased incidence

Aims

The aim of this study was to investigate if there are differences in outcome between sliding hip screws (SHSs) and intramedullary nails (IMNs) with regard to fracture stability.

Introduction. Metatarsocuneiform (MTC) fusion is a standard treatment for arthritis, instability, and deformity of these joint. The MTC fusion achieves a good clinical outcome, but nonunion rates up to 12% have been reported. There are different methods for fixation of first MTC joint arthrodesis. Our aim was to compare the biomechanical characteristic of internal and external fixation constructs. Hypothesis. Plantar plate fixation provides higher construct stiffness and endurance stability than intraosseous fixation. Materials & Methods. Seven pairs of fresh-frozen human specimens were used in a matched pair test. In one foot the MTC joint was supplied with a plantar plate. On the other foot intraosseous-screw fixation was perfomed. The specimen constructs were loaded in a 4 point bending test. Parameters obtained were initial stiffness and number of cycles to failure. Failure was defined as displacement of more than 3 mm plantar gapping. Results. The intraosseous-screw fixation group showed significantly (p=0.002) less cycles to failure (n=2946) than the plantare plate (n=7517). The initial stiffness was 131 N/mm for the plantare plate and 43 N/mm for the intraosseous implant (p=0.005). Discussion & Conclusion. Plantar plate fixation of the first MTC fusion created a stronger and stiffer construct than intraosseous fixation. This was likely due to the plantar and dorsal implant position. A stiffer construct can reduce the risk of non-union and shorten the period of nonweight-bearing

Introduction. The usefulness of minimal invasive hip replacement is frequently discussed but there is a lack of data on the effect of the surgical approach on early results. We wanted to study the effect of the surgical approach on the peri- and early postoperative outcome. Material/Methods. In a prospective case control study 315 elective hip replacements were performed between January 2008 and March 2010. Until March 2009 a lateral transgluteal approach (STD) was used, then the approach was changed to a minimal invasive anterior approach (MIS). All operations were performed in the same routine setting not affected by the approach. Duration of operation, complications and bloodloss were assessed. 1 week postoperatively, independent mobility, stairs, central analgetics were analysed and length of stay was recorded. At 6 and 12 weeks, pain and patients satisfaction (VAS) and the Harris Hip Score were assessed. Pre- and postoperative radiographs were compared for component position and orientation (EBRA). Results. 6 patients (hips) refused participation, 4 were excluded for other reasons. 174 (57%) hips belonged to STD and 131 (43%) to MIS. There were no demographic differences between both groups. Operation time was longer for MIS (109 vs. 123 min, p=.001). At 1 week, MIS patients were more mobile (rising up from bed, p=.009; stairs, p=.015) and time of hospitalisation became shorter (p=.001). At 6 weeks, MIS patients had less pain at motion (p=.013), less limb (p=.001), a higher HHS (p=.007) and were more satisfied (p=.046). The differences remained unchanged after 12 weeks. There was no difference in implant positioning between the groups. Inclination was higher in group MIS [39° (SD 6°) vs. 38° (SD 7°), p=.030], anteversion was lower [21° (SD 8°) vs. 24° (SD 8°), p=.010]. Conclusion. The introduction of the MIS anterior approach was safe. Early rehabilitation was facilitated and clinical results were better. Radiographical results were not impaired by the new approach. We see no disadvantage of the MIS anterior approach. Adaptions in the clinical setup might further facilitate rehabilitation

Background. In elderly patients with complex proximal humerus fractures and osteoporotic bone reconstruction is not always possible. Although hemiarthroplasty is an alternative, non-union or tuberosity migration can lead to inferior functional results. Implantation of a Reverse Total Shoulder Arthroplasty (RTSA) seems to be an interesting alternative. In the present study we retrospectively analyzed the short-term results of RTSA for complex proximal humerus fractures in the elderly. Methods. From 31.10.2005 to 20.07.2010 RTSA was performed in 29 patients (average age 80 years [67;90], 25 women, 4 man) with subcapital, three- or four-part fracture of the proximal humerus as a primary treatment. All procedures were performed using the Anatomical Inverse Shoulder (Zimmer) with fracture stem. A deltopectoral approach was used in every case with reattachment of the tuberosities. Pain, range of motion, subjected shoulder value (SSV) as well as the Constant score (CS) were used to evaluate shoulder function. Implant positioning and signs of loosening were analyzed on standard x-rays. Results. Included were 23 patients with a minimal follow-up of 12 month. The average follow-up was 17 month (12 month to 5 years). The mean SSV was 81% [40;100]. The absolute CS averaged 67 points [34;84] and the relative CS 97% [52;139]. The mean pain score (VAS) was 13.7 of 15, the mean activity score 18.4 of 20, the mean mobility score 28.6 of 40 and the mean strength score 5.1 of 25. The mean active anterior elevation was 130° [80;160], the mean active abduction 128° [80;170] and the mean active external rotation in 0° abduction 21° [-30;70]. All patients reached the same activity level as before surgery and could return to independent living. The results after 12 month were already comparable to those after 24 month (10 patients). Radiographically no signs of loosening were detected. There was a total of 3 complications and reoperations, two due to a hematoma and one because of a periprosthetic fracture. Conclusions. In elderly patients with complex proximal humerus fractures and osteoporotic bone RTSA seems to be a very satisfactory procedure. The short-term clinical results are excellent and predictable with a rapid postoperative recovery of daily comfort. The complication rate is low and acceptable

Introduction. Total knee replacement has been well-established form of treatment both for osteoarthritis and inflammatory arthritis. Both cemented and uncemented TKR have been used successfully. Since 1977 low contact stress (LCS) mobile bearing knee replacement has been in extensive use. Most of the intermediate and long term results reported are in osteoarthritis1–7. Though there are several studies reporting short term performance of TKR in rheumatoid arthritis8–19 there have been rare reports31 of intermediate to long-term performance of LCS uncemented TKR in rheumatoid arthritis. Methods. Retrospective, non-randomised and consecutive study. Case notes and radiological assessment done. Kaplan meyer survival analysis used. Radiological assessment between initial and final xrays done using T test statistics. Assessement done by two independent observer. Results. 108 knees in 67 patients are collected. 21 patients with 36 knees have died. Only 65 knees in 42 patients had both case notes and xrays which are included in this study. Of this 11 knees in 7 patients were dead. All 65 knees in 42 patients are sero-positive rheumatoid arthritis. Pre-operative bone loss was seen only in 4 knees. Bone loss was in the medial side in 3 knees (4,5 and 8mm respectively) and lateral in 1 knee (1 cm). None of these bone loss needed bone grafting or any special procedures. There was no subsidence in any of the 65 knees. Survival of uncemented LCS TKR in inflammatory arthritis patients is 100%. Aseptic failure is 0%. No infective failure. There is no significant change in the implant position. This is the longest follow for uncemented TKR in inflammatory arthritis ever reported in the literature. Conclusion and Discussion. In conclusion, our study has uniformity, as a single surgeon performed/supervised with senior trainees all the operations and all patients received the same level of post-operative care. Survival of LCS uncemented TKR in inflammatory arthritis patients is 100% up to 15years. This is the longest follow up in this patient population ever reported in the literature. Our study shows excellent survival and comparable to other cemented TKRs in this patient population reported in the literature. This study proves contrary to the general belief that uncemented TKR do poor in inflammatory arthritis due to osteoporotic bone

We evaluated the results of Cementless Surface Replacement Arthroplasty (CSRA) of the shoulder in 67 patients with advanced glenohumeral destruction who have an intact rotator cuff. Between november 2002 and december 2008, 70 CSRA (32 Copeland/ Biomet and 38 SMRR/ Lima) were implanted in 67 patients. A deltopectoral approach was used in 34 cases and an anterosuperior approach in 36 cases. Patients were assessed using Constant score, a patient satisfaction score and a detailed radiographic analysis. The mean follow up was 3.4 years (range 1 to 7.5 years). The mean Constant score improved preoperatively from 17.6 points (range 2–55) to an average postoperative score of 66.1 (range 13–91). The pain score improved from 1.13 points (range 0–6) to 12.3 points (range 3–15). The forward flexion and external rotation improved from 71° (range 20 to 140) and 0° (range −40 to +45) to 143° (range 60 to180) and 34.4° (range −20 to +60) respectively. Complications included: 1 subscapularis detachment, 5 secondary rotator cuff tear, 1sepsis, 3 patients with shoulder stiffness. No shift in implant position was observed. 11 humeral components developed radiolucencies at the prosthesis-bone interface. The radiographic analysis involved a system of dividing the prosthesis/bone interface into 5 zones. The best clinical results were significantly achieved in patients with necrosis compared with osteoarthritis (Constant Score, ant. elevation, ext. Rotation). Using regression analysis we found that changes in the head-shaft angle position of the implant (valgus/varus placement of the CSRA) significantly predicted the age and sex adjusted Constant score. When the inclination angle of the humeral head decreases, the adjusted Constant score increases. In the same model, we also found that the lateral offset of the humerus significantly predicted the adjusted Constant score. When the lateral offset of the humerus decreases, the adjusted Constant score increases. The medialization of the glenoid significantly and negatively predicted the Constant score. Conclusion. CSRA of the shoulder outcomes have been comparable with those of stemmed arthroplasties. Radiolucent lines occur with follow up and most of the time located in the S1 area. Glenoid wear and humeral head lateralization negatively impact the clinical score. Cementless Shoulder resurfacing is a viable alternative to conventional shoulder arthroplasty

Osteolysis induced by UHMWPE debris has historically been one of the major causes of long term failure of TJR. An increase in concentration of polyethylene particles in the peri-prostheic tissue has been linked to an increased incidence of osteolysis. The dual mobility hip bearing concept mates a femoral head into a polyethylene liner which has an unconstrained articulation into a metal shell. The wear mechanism of the dual mobility hip bearing is distinct from a constrained single articulation design, which may result in a difference in wear debris particles. The aim of this study is to evaluate wear debris generated from a dual mobility hip and compare it to a conventional single articulation design when both are manufactured from sequentially crosslinked and annealed polyethylene. The dual mobility hip (Restoration ADM) incorporated a 28mm CoCr femoral head into a polyethylene liner that articulates against a metal shell (48mm ID). The conventional hip (Trident®) mated a 28mm CoCr femoral head against a polyethylene liner. The polyethylene for all liners was sequentially crosslinked and annealed (X3). A hip joint simulator was used for testing at a rate of 1 Hz with cyclic Paul curve physiologic loading. A serum sample from each testing group was collected. Serum samples were protein digested following the published process by Scott et al. The digested serum was then filtered through a series of polycarbonate filter papers of decreasing size and sputter coated with gold for analysis using SEM. Image fields were randomized and wear debris was compared in terms of its length, width, aspect ration, and equivalent circular diameter (ECD). A total of 149 conventional hip particles and 114 dual mobility hip particles were imaged. Results show a majority of particles are of spherical nature and images do not indicate the presence of fibrillar or larger elongated polyethylene debris. Particle length between designs is not statistically different, while all other comparisons show statistical significance (p<0.05). It is hypothesized that the dual mobility hip system reduces the total amount of cross-shear motion on any one articulation, which aids in the reduction in wear. This design feature may be responsible for the slight difference in morphology of dual mobility wear debris when compared to the constrained hip design. The length of the particles was similar, simply indicating a different shape rather than a marked reduction in overall size. The debris generated is this study was from highly crosslinked polyethylene in two different designs, which produced a very significant decrease in quantity of particles when compared to the quantity of debris from conventional polyethylene. The wear debris was of similar length in both designs and so we do not expect any difference in biological response to debris from either device. The dual mobility design has also shown no effect of cup abduction angle on wear demonstrating forgiveness to implant positioning. This advantage, combined with the low wear rate and similar length wear particles, should lead to good clinical performance of dual mobility cups with sequentially irradiated and annealed polyethylene

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.

Aims

This study describes and compares the operative management and outcomes in a consecutive case series of patients with dislocated hemiarthroplasties of the hip, and compares outcomes with those of patients not sustaining a dislocation.

The spiral blade modification of the Dynamic Hip Screw (DHS) was designed for superior biomechanical fixation in the osteoporotic femoral head. Our objective was to compare clinical outcomes and in particular the incidence of loss of fixation.

In a series of 197 consecutive patients over the age of 50 years treated with DHS-blades (blades) and 242 patients treated with conventional DHS (screw) for AO/OTA 31.A1 or A2 intertrochanteric fractures were identified from a prospectively compiled database in a level 1 trauma centre. Using propensity score matching, two groups comprising 177 matched patients were compiled and radiological and clinical outcomes compared. In each group there were 66 males and 111 females. Mean age was 83.6 (54 to 100) for the conventional DHS group and 83.8 (52 to 101) for the blade group.

Loss of fixation occurred in two blades and 13 DHSs. None of the blades had observable migration while nine DHSs had gross migration within the femoral head before the fracture healed. There were two versus four implant cut-outs respectively and one side plate pull-out in the DHS group. There was no significant difference in mortality and eventual walking ability between the groups. Multiple logistic regression suggested that poor reduction (odds ratio (OR) 11.49, 95% confidence intervals (CI) 1.45 to 90.9, p = 0.021) and fixation by DHS (OR 15.85, 95%CI 2.50 to 100.3, p = 0.003) were independent predictors of loss of fixation.

The spiral blade design may decrease the risk of implant migration in the femoral head but does not reduce the incidence of cut-out and reoperation. Reduction of the fracture is of paramount importance since poor reduction was an independent predictor for loss of fixation regardless of the implant being used.

Cite this article: Bone Joint J 2015;97-B:398–404.

Systemic antibiotics reduce infection in open fractures. Local delivery of antibiotics can provide higher doses to wounds without toxic systemic effects. This study investigated the effect on infection of combining systemic with local antibiotics via polymethylmethacrylate (PMMA) beads or gel delivery.

An established Staphylococcus aureus contaminated fracture model in rats was used. Wounds were debrided and irrigated six hours after contamination and animals assigned to one of three groups, all of which received systemic antibiotics. One group had local delivery via antibiotic gel, another PMMA beads and the control group received no local antibiotics. After two weeks, bacterial levels were quantified.

Combined local and systemic antibiotics were superior to systemic antibiotics alone at reducing the quantity of bacteria recoverable from each group (p = 0.002 for gel; p = 0.032 for beads). There was no difference in the bacterial counts between bead and gel delivery (p = 0.62).

These results suggest that local antibiotics augment the antimicrobial effect of systemic antibiotics. Although no significant difference was found between vehicles, gel delivery offers technical advantages with its biodegradable nature, ability to conform to wound shape and to deliver increased doses. Further study is required to see if the gel delivery system has a clinical role.

Cite this article: Bone Joint J 2015;97-B:1423–7.

We treated 108 patients with a pertrochanteric femoral fracture using either the dynamic hip screw or the proximal femoral nail in this prospective, randomised series. We compared walking ability before fracture, intra-operative variables and return to their residence. Patients treated with the proximal femoral nail (n = 42) had regained their pre-operative walking ability significantly (p = 0.04) more often by the four-month review than those treated with the dynamic hip screw (n = 41). Peri-operative or immediate post-operative measures of outcome did not differ between the groups, with the exception of operation time. The dynamic hip screw allowed a significantly greater compression of the fracture during the four-month follow-up, but consolidation of the fracture was comparable between the two groups. Two major losses of reduction were observed in each group, resulting in a total of four revision operations.

Our results suggest that the use of the proximal femoral nail may allow a faster postoperative restoration of walking ability, when compared with the dynamic hip screw.

We created virtual three-dimensional reconstruction models from computed tomography scans obtained from patients with acetabular fractures. Virtual cylindrical implants were placed intraosseously in the anterior column, the posterior column and across the dome of the acetabulum. The maximum diameter which was entirely contained within the bone was determined for each position of the screw. In the same model, the cross-sectional diameters of the columns were measured and compared to the maximum diameter of the corresponding virtual implant.

We found that the mean maximum diameter of virtual implant accommodated by the anterior columns was 6.4 mm and that the smallest diameter of the columns was larger than the maximum diameter of the equivalent virtual implant.

This study suggests that the size of the screw used for percutaneous fixation of acetabular fractures should not be based solely on the measurement of cross-sectional diameter and that virtual three-dimensional reconstructions might be useful in pre-operative planning.