Introduction Maquet views are a well established method of determining the axial alignment of the lower limb in the coronal plane and their use in the assessment of total knee replacement is widespread. It is an awkward investigation for both patient and radiographer and we compared them to the information that can be obtained using the new generation of Helical CT scanners.

Results We prospectively studied a cohort of 60 patents undergoing TKR. As part of their routine post-operative follow-up they had a standard series of AP and Lateral radiographs (performed under fluoroscopic control) in addition to the Maquet views and a CT scan of their lower limbs. All plain films were performed at the same hospital by the same group of radiographers, while all CTs were performed on the same scanner using a predetermined protocol, and post processing performed by the same individual. Maquet views gave a good assessment of coronal alignment but were also shown to have a much high interobserver error than CT. Maquet views took on average three times longer for the radiographers to perform than CT, were often repeated as technically demanding, and patients (especially the elderly and infirm) often found it difficult and uncomfortable to comply with the required positioning. CT views on each patient (which incorporated standard slices and a scanogram) took a few minutes of time in the scanner allowing a quick throughput when patients arrived in clinic. Patients were supine, a position they all found easy to adopt, and radiographers reported that they found them less difficult to perform. The femoral and tibial axes were easily determined, and rotation easily assessed from the femoral epicondyles, negating the projection errors due to malrotation that may compromise the accuracy of Maquet views. Radiation dosage for the CT is higher than a single Maquet view, but these are often repeated due to poor exposure, increasing the dosage above that of CT.

Conclusions We have used a spiral CT protocol with much success and feel that its greater accuracy, coupled with the information gained on sagittal alignment and component rotation means that the older Maquet view has now been superceded. We also feel that the amount of information recorded by a single investigation may prove invaluable in subsequent investigation of pain or suspected loosening, and very helpful in planning any required revision.

Scarf osteotomy improves hallux valgus and can be used for deformities with large intermetatarsal angles. It is designed to minimise shortening of the first ray. The aim of this radiographic analysis was to assess the outcome of patients undergoing Scarf osteotomy at the Royal Cornwall Hospital.

The initial 18 consecutive cases performed by the senior author were analysed using the guidelines recommended by the American Foot and Ankle Society. Standardised anterior-posterior radiographs of the foot were compared pre-operatively and at 6 weeks postoperatively. Measurements of the intermetatarsal angle (IMA), hallux valgus angle (HVA), joint congruency angle (JCA), distal metatarsal articular angle (DMAA), sesamoid position and metatarsal length were used to assess any improvement.

The results showed a significant median reduction of the IMA of 70, HVA of 180, JCA of 50, and the DMAA of 30 (all p values < 0.001). The medial sesamoid position in relation to the first metatarsal also improved from a mean value of 2.28 to 1 using the American Foot and Ankle Society grading system. There was no shortening of metatarsal length as measured using the Hardy and Clapham method.

This study shows that the radiographic outcome of Scarf osteotomy at the Royal Cornwall Hospital compares favourably with that found in the literature. It provides effective correction of moderate to large intermetatarsal angles.

We describe the radiographic measurement of the angle of tilt of the patella and relate it to malalignment of the extensor mechanism. The tilt angle is defined as the angle subtended by a line joining the medial and lateral edges of the patella and the horizontal. The radiograph (Merchant type) is taken with the foot pointing up, the lower edge of the film parallel to the ground, and the knee at 30 degrees flexion. The mean tilt angle of a group of patients with signs and symptoms suggesting patellofemoral malalignment was 12 degrees (+/- 6 degrees); in a similar group of control subjects it was 2 degrees (+/- 2 degrees) (p < 0.01). Tilting of 5 degrees was taken to be the limit of normal. For the detection of patellar malalignment, the tilt angle was almost as specific as the congruence angle (92% v 99%) but more sensitive (85% v 25%) and more accurate (89% v 62%).

INTRODUCTION

Femur is one of the bones in humans that exhibit ethnic, racial, and gender difference. Several basic and clinical studies were conducted to explore these variations. Clinical anthropological studies have dealt with the compatibility of femoral prostheses and osteosythesis and materials with the femur. If there is a misalignment between the Total Knee Arthroplasy (TKA) femoral comportment installation position, Range of Motion (ROM) failure and several problems may arise. The aim of this study was to evaluate anterior bowing of the Japanese femur and to assess the adequacy of TKA femoral comportment installation position.

Background

We occasionally come across cortical atrophy of the femur with cemented collarless polished triple-taper stem, a short time after the operation. This study aimed to estimate the radiographs of cemented collarless polished triple-taper stem taken at three, six, twelve, and twenty-four months after the initial operation.

Introduction

In total knee arthroplasty extramedullary tibial guides could not to be as accurate as requested in obtaining proper alignment perpendicular to the mechanical axis. The aim of this study was to determine the accuracy of an accelerometer-based system (KneeAlign 2; OrthAlign Inc, Aliso Viejo, California) as evaluated by post-op X-rays analysis.

Avascular necrosis of the femoral head (AVN) is associated with collapse of the femoral head and arthritic degeneration of the joint. The combination of an implant inserted into the femoral head that provides mechanical support and bone grafting to promote bone formation may offer a possible joint-preserving solution1. Seventeen such procedures were performed between November 2012 and March 2014 during an IRB approved clinical trial. Thirteen out of 18 patients remained unrevised at a minimum of 12 months; the results of radiographic and histological analysis of four revisions are presented.

The investigational device (Figure 1) was developed as a joint preserving treatment for AVN with a clinical grade of IIC or less according to the ARCO grading system2.

The device consisted of a braided spherical Nitinol cage with a Titanium / Nitinol orientation feature. It was implanted using fluoroscopic navigation into a spherical cavity cut into the femoral head via an 11mm diameter access tunnel. Once deployed, the implant was filled with a lightly impacted mixture of autologous bone graft and bone marrow soaked Conduit TCP (DePuy CMW, Blackpool, UK). The implant's purpose was to provide mechanical support to the weakened subchondral surface while the bone graft mixture re-integrated with the host bone.

The retrieved femoral heads were trimmed to leave approximately 3mm of bone around the implant, dehydrated, embedded in methacrylate resin, sectioned and thinned into 50–70µm coronal slices for histological analysis. The following observations were made (Figure 2):

Case 1 (Female, age 70, ARCO IIB, revised after 2 days): The patient was revised for spontaneous sub-trochanteric fracture secondary to osteoporosis. Contact between the native bone and bone graft was observed. Marrow elements and repair tissue were visible within the pores in the graft (Figure 2a).

Case 2 (Male, age 67, ARCO IIIC, revised after 82 days): Two wires were broken but retained within the braided structure. A radiolucent gap caused by the presence of fibrous tissue between the graft mixture and native bone was evident suggesting that the implant was unable to prevent progression in this case.

Case 3 (Female, age 70, ARCO IIC, revised after 482 days): The cavity penetrated the subchondral surface; at revision the implant was found to have breached the articular cartilage. There was partial separation of the proximal osteonecrotic fragment and no evidence of graft revascularisation or remodelling within the implant.

Case 4 (Male, age 42, ARCO IIC, revised after 469 days): There was no indication of bone graft re-integration. Collapse of the necrotic bone and deformation of the implant was diagnosed from 1 year follow-up x-rays.

The thickness of the cement mantle surrounding total hip replacements has been used to predict the incidence of aseptic loosening. However little work has been done regarding the significance of the cement mantle distal to the tip of the femoral prosthesis. Results are reported of a radiographic audit study analyzing the thickness of the distal cement column in primary total hip replacement.

In this study the thickness of cement distal to the tip of the femoral prosthesis was measured from 80 post-op AP radiographs taken over a period of 5 months using both the PACS system and plain film x-rays. The mean thickness was 2cm (max 8cm) (min −1.8cm) with a std dev of 1.7cm.

This study demonstrated the wide variation in the thickness of the distal cement column achieved by surgeons. It also highlighted the fact that while 2–5mm is the generally accepted optimal cement mantle surrounding the femoral prosthesis, there is little guidance from the literature with regards the optimal thickness of the cement mantle distal to the tip of the femoral prosthesis. Further work requires to be undertaken to determine the optimal thickness of cement in this area, as well as changes in local surgical practice to ensure the optimal thickness of cement distally is consistently achieved. A re-audit of this work after alterations of surgical technique is desirable.

Background

We occasionally came across cortical atrophy of femurs with cemented collarless polished triple-taper stem in a short term period. This study aimed to estimate radiographs of cemented collarless polished triple-taper stem taken 6 months after the initial operation.

Introduction: An intra-medullary cement restrictor is an integral part of modern cementing technique in total hip arthroplasty. Failure of the restrictor to contain cement, flawed surgical technique or dislocation of the restrictor during pressurisation can all result in a deficient cement mantle. A radiographic analysis of hip replacements using a biodegradable restrictor was undertaken to determine the incidence of restrictor failure, the influence of femoral canal morphology on restrictor failure and to describe the cement mantle quality in successful and failed distal cement restriction.

Methods: x-rays from 299 consecutive hip replacements using the amberflex restrictor were analysed. The cortical index, canal-calcar ratio and femoral type, according to Dorr, were recorded. 3 modes of restrictor failure were identified:

Cement leakage –cement was seen to have escaped past the cement restrictor

Results: 84 cases of restrictor failure were observed – 44 dislocations, 24 leakages and 16 penetrations. The mode of failure was not correlated with femoral type, cortical index or canal-calcar ratio. A strong association was found between restrictor failure and grades c and d cement mantles using the chi squared test. A correlation between cortical index, canal-calcar ratio and femoral type was not observed.

Discussion: The ability of a cement restrictor to occlude the femoral canal and resist pressurisation is very important if a good quality cement mantle is to be achieved. Technical error was likely to be an important factor in many of the observed cases of restrictor failure, especially penetrative failure. Surgical technique is more important than femoral morphology in determining the successful use of this restrictor.

Purpose:

Acetabular bone loss during revision total hip arthroplasty (THA) poses a challenge for reconstruction as segmental and extensive cavitary defects require structural support to achieve prosthesis stability. Trabecular metal (TM) acetabular augments structurally support hemispherical cups. Positive short-term results have been encouraging, but mid- to long-term results are largely unknown. The purpose of this study was to determine the continued efficacy of TM augments in THA revisions with significant pelvic bone loss.

Introduction: Drilling of the femoral bone tunnel in anterior cruciate ligament reconstruction may be performed in a transtibial drilling technique or via the anteromedial portal.

Purpose: To determine the accuracy of the radiographic bone tunnel position using either a transtibial or anteromedial drilling technique.

Materials & methods: The postoperative lateral radiographs of 100 patients after anterior cruciate ligament reconstruction were reviewed. In each patient, the femoral bone tunnel was created either through the tibial tunnel or via the anteromedial standard arthroscopy portal. The resulting position of the femoral tunnel was evaluated according to reference values reported by Aglietti (65 % of the cortical femoral A-P distance along Blumenstaat’s line), Amis (60 % of the A-P diameter of the posterior lateral femoral condyle parallel to Blumensaat’s line), and Harner (80 % of the A-P length of Blumensaat’s line). The mean deviation of the radiographic tunnel position from the referenced values was statistically evaluated.

Results: Radiographic bone tunnel positions with transtibial drilling were 62.42 ± 8.36, %, 54.53 ± 8.43 %, and 75.84 ± 9.56 % according to Aglietti, Amis, and Harner, respectively. Bone tunnel positions with anteromedial drilling were 65.46 ± 5.29 %, 59.59 ± 4.18 %, and 79.93 ± 4.24 %, respectively. The mean deviation from the reference values was significantly higher when comparing transtibial to anteromedial drilling. Transtibial drilling resulted in a significantly more anterior bone tunnel position.

Conclusion: Precise bone tunnel placement is a prerequisite for proper postoperative knee function and stability. The results of this study indicate that the accuracy of femoral bone tunnel placement through the anteromedial arthroscopy portal was superior to transtibial drilling. It may therefrore be concluded that drilling the femoral tunnel through the anteromedial portal is recommended when using fixation techniques not depending upon placement of a transtibial guide.

We analyzed the radiographic results of patients treated surgically for flatfoot deformity and who underwent medial cuneiform opening wedge osteotomy as part of the operative procedure. The aim of this study was to confirm the utility of the cuneiform osteotomy as part of the correction of hindfoot and ankle deformity. All patients requiring operative management of flatfoot deformity between January 2002 and December 2007 were prospectively entered in a database. We selected all patients who underwent medial cuneiform opening wedge osteotomy. We measured standardized and validated radiographic parameters on pre and post-operative weight bearing radiographs of the foot. All radiographs were assessed using the digital imaging software package (Siemens). The following measurements were used: lateral talus-1st metatarsal angle; medial cuneiform to floor distance (mm), talar declination angle, calcaneal-talar angle, calcaneal pitch angle, 1st metatarsal declination angle, talonavicular coverage angle, and anteroposterior talus-1st metatarsal angle. Other variables including concomitant surgical procedures, healing of the osteotomy, malunion, and adjacent joint arthritis were also noted. There were 86 patients with a mean age of 36 years (range 9–80). 15 patients had bilateral surgery. The aetiology of the deformity was flexible flat-foot in 48, rupture of the posterior tibial tendon in 41, rigid flatfoot deformity with a fixed forefoot supination deformity in 7, and fixed forefoot varus with metatarsus elevatus in 5. In addition to an opening wedge medial cuneiform osteotomy, a lateral column lengthening calcaneus osteotomy was performed in 80, a gastrocnemius recession in 76, a supramalleolar osteotomy in 2, a triple arthrodesis in 4, a subtalar arthroerisis in 13, excision of an accessory navicular in 6, a tendon transfer in 15 and medial-slide calcaneal osteotomy in 8 patients. The mean lateral talus-1st metatarsal angle improved from 23° to 1°; the mean medial cuneiform to floor distance improved from 20mm to 34mm; the mean talar declination angle improved from 39° to 27°; the mean calcaneal-talar angle improved from 64° to 55°; the calcaneal pitch angle improved from 14° to 23°; the mean 1st metatarsal declination angle improved from 17° to 26°; the mean talonavicular coverage angle improved from 45° to 18°; and the mean anteroposterior talus-1st metatarsal angle improved from 19° to 0° Radiographical analysis confirms that the medial cuneiform opening wedge osteotomy is a reliable and valuable surgical tool in the correction of the forefoot which is associated with flatfoot deformity and that arthrodesis of the 1st metatarsocuneiform joint may not be required to obtain correction of the elevated 1st metatarsal.

The ABG stem (Anatomique Benoist Girard, How-medica) was realized of titanium alloy (TA6V) and it was designed to provide anchoring only at the femour’s metaphyseal portion. The long-term stability is achived by osteointegration of the implant at the metaphyseal region, which is coated with hydroxyapatite (HA) crystals. The plasma-sprayed HA coating has a tickness of 60 μm for the stem.

The current study presents radiographic outcomes of more than one hundred primary uncemented HA stems with a long-term follow-up. One hundred and eleven ABG hip arthroplasties were evaluated with a mean follow-up of 9.8 years. The radiographical findings have been classified observing Engh’s stability criteria according to Gruen’s subdivision of the periprosthetic femoral zones.

Dividing the hips into two different groups (in the first one the prosthesis implanted 11, 12 or 13 years ago and in the second one the prosthesis with a maximum age of 10 years) it’s possible to see as in the first group the radiolucent lines are quite reduced. Among the older prosthesis the percentage of radiolucent lines is 3.1% in zones 3 and 5 and 18.8% in zone 4. For what concerns the younger ones the percentage are 10.1% (zone 3), 21.5% (zone 4) and 15.2% (zone 5).

We believe that there is a load transfer from the metaphyseal to the metadiaphyseal portion of the femur without a worsening of the clinical outcomes. The absence of reactive lines and lucencies around the proximal HA-coated portion of the stem supports an excellent circumferential bony ingrowth in the metaphyseal area of the proximal femur. According to these percentages we can say that there’s less presence of radiolucency in the oldest prosthesis and it could be possible to argue that radiolucent lines tend to reduce along the time. This is probably due to the increase of the strength of the stem anchorage.

Introduction

The advantages of the direct anterior approach (DAA) for total hip arthroplasty include the preservation of external rotators and hip abductors thus leading to quicker recovery times. To our knowledge, there is no objective method in the literature to predict the level of difficulty for femoral exposure through the DAA. It would be beneficial to the surgeon learning the DAA to assess difficulty pre-operatively to avoid prolonged operative times. The purpose of this study was to develop a predictive model of femoral exposure difficulty in the DAA using a combination of demographic data and radiographic measurements.

Introduction: The progression of the collapse is influenced by the extent and location of the necrotic focus of the necrotic femoral head. The authors studied the extent of the necrotic focus on the joint surface by conventional antero-posterior radiographs in neutral position, and antero-posterior radiographs at the 45 degrees flexion position. The differences of the lesions in these two types of radiographs were analyzed.

Materials and Methods: The conventional antero-posterior radiographs of the neutral position, and the antero-posterior radiographs at the 45 degrees flexion positions in 115 hip joints of 86 patients with non-traumatic osteonecrosis of the femoral head were obtained for this study. These 115 hips showed extensive lesions and could be divided into two groups: Type C-1 or C-2 by classification of the Specific Disease Investigation Committee under the auspices of the Japanese Ministry of Health Labor and Welfare. Type C1 lesions occupy more than the medial 2/3 of the femoral head and C2 lesions extend laterally to the acetabular edge.

Results: At the neutral position, Type C-1 lesions were noted in 42 joints (36%). In these 42 hips, 13 showed Type C-1 (30%) at the 45 degrees flexion position. In contrast, 29 joints (70%) were Type C-2. Type C-2 lesions in 73 joints (64%) were shown in the neutral position. In these 73 hips, Type C-2 lesions were disclosed on 69 joints (95%) in the 45 degrees flexion position and Type C-1 was noted on 4 hips (5%).

Conclusions: Based on these results, the authors propose that location of the lesion on the joint surface varies with different hip positions.

Degenerate chondral surfaces can be assessed in many ways, but arthroscopy is often performed without proper categorisation, mapping, zoning or sizing of lesions. Progression of disease in un-resurfaced compartments is well-recognised to occur, but is only one of several failure mechanism in partial knee replacement.

A validated ‘Functional Zone’ mapping method was used to document articular surface damage in 250 sequential cases of knee arthroscopy in patients over the age of 40. Size, shape, location and severity of each chondral lesion were noted using the Outerbridge classification. Analysis determined rates of involvement of particular compartments and assessed potential for partial replacement or local treatment and also to consider the risk of future progression. Radiographs including antero-posterior standing, postero-anterior flexion views (Rosenberg), lateral and skyline views were graded (Kellgren and Lawrence) and compared with the arthroscopic findings.

Our results showed that out of the 210 knees with Grade 3 or greater damage 13.3% of knees showed ‘isolated’ medial disease of Outerbridge Grade 3 or worse. Isolated lateral disease was noted in 1.4%, patello-femoral disease in 24.3%, bi-compartmental (Medial/PFJ) disease in 30.9% with tibio-femoral and tri-compartmental disease seen in 15.2%. The combination of lateral and patello-femoral disease was seen in 14.8%. Provided that Grade 1 and 2 changes (which were found in other compartments in high percentages) were ignored and ACL status considered, this information seemed to indicate that at the time these procedures were performed, 13.3% of cases were suitable for a medial uni-compartmental device, with sub-analysis of lesion sizes indicating that 17 out of 28 cases (60.7%) were suitable for a localised resurfacing. Lateral uni-compartmental replacement seemed suitable for only 1.4%, patello-femoral replacement in 24.3%, bi-compartmental in 30.9% and total knee replacement in 30%. The mean age for partial resurfacing was 53years and 59 years for total joint replacements.

Radiological analysis found that the antero-posterior standing views had only 66% sensitivity and 73% specificity for the presence of Grade 3 changes or worse in the medial compartment in comparison with Rosenberg views having a sensitivity of 73% and a specificity of 83%. Skyline views had a sensitivity of 56% and 100% specificity.

This study indicates that a large proportion of cases may be suited to local and limited resurfacing. Cases suitable for Patello-femoral and Bi-compartmental replacements were very common, but with the patella-femoral joint's tendency to be more forgiving in terms of symptoms, meaning that indications for uni-compartmental replacement might well be much higher than the arthroscopic findings suggested. On the other hand, the presence of high levels of Grade 1 and 2 changes in other compartments seems to indicate a need for caution particularly in younger patients. This study also indicates a need for better methods of assessing local cartilage health such as enhanced MRI scanning or spectroscopy.

Purpose: Hinged knee prostheses are mainly used for reconstruction after major tumour resection. Aseptic loosening is the main problem with these implants. One of the solutions proposed to reduce the rate of loosening is to add a hydroxyapatite collar on the shaft stems. This work was conducted to study bone ingrowth with a new hinged implant with a hydroxyapatite collar at the junction between the zone of resection and the shaft.

Material and methods: Twenty-nine massive prostheses with a hydroxyapatite collar were implanted between 1998 and 2001. Nine patients were excluded from the analysis because follow-up was less than two years. This retrospective analysis thus compared twenty massive prostheses with twenty matched hinged GUEPAR prostheses without a collar. Bony ingrowth was measured on plain x-rays (two orthogonal views) at 6, 12, 24, and 36 months. Filling of the gap between the bone and the implant was also assessed. Signs of loosening were noted.

Results: Mean bony ingrowth in implants with a hydroxyapatite collar was 6.58 mm at 6 months 9.84 mm at 12 months, 12.3 mm at 24 months and 13.25 mm at 36 months. Mean bony ingrowth in the implants without a hydroxyapatite collar was 1.65 mm at 6 months, 3.31 mm at 12 months, 4.8 mm at 24 months and 4.35 mm at 36 months. In the implants with a collar, gap filling was partial in five cases and total in 15. In implants without a collar, there was no gap filling in eight cases, partial filling in two cases and total filling in fifteen cases.

Discussion: Prostheses with a hydroxyapatite collar enable better radiological bony ingrowth than observed in implants without a hydroxyapatite collar. Gap filling is better for prostheses with a collar. There was no case of loosening at last follow-up for implants with a hydroxyapatite collar.

Conclusion: In light of these results, shaft anchorage appears to be better with implants with a hydrosyapatite collar. Confirmation of improvement in clinical outcome and lower rate of aseptic loosening will require longer follow-up.

Purpose: Uncertain position of the acetabular implant has been the cause of dysfunction in certain cases of total hip arthroplasty (THA). Classical computed tomographic analysis of anteversion has certain limitations. Integrated reconstruction of positions at risk allows a better diagnostic approach.

Material and methods: We studied 46 THA because of posterior malposition (n=17, anterior subluxation in the standing position in twelve, and true dislocation in five) and anterior malposition (n=29, posterior subluxation in sixteen and true dislocation in thirteen). Two groups of 70 naïve hips and a group of 56 THA with no functional problem served as controls. The position of the acetabulum was studied on optimised computed tomography slices reconstructing the planes of analysis for the standing, sitting and reclining positions. The reference planes for the slices was given by the sacral tilt angle measured on the lateral views of the patient in the corresponding positions. The optimised computed tomographic measurements of anteversion were compared with the classical measures. None of the patients had abnormal femoral anteversion and/or an oblique pelvis and/or leg length discrepancy greater than 10 mm. The frontal inclination of the acetabular implants was 40°–50°.

Results: In the naïve hips, acetabular anteversion varied: 19.2 with the conventional method, 15.7 in the standing position and 31 in the sitting position. In the THA controls, anteversion measurements differed: 21.3 with the conventional method, 21.4 in the standing position and 35.8 in the sitting position. In the THA with a posterior malposition, 18/29 could not be explained by the conventional measurement, but the optimised measurement enabled an understanding in 17 hips (defective anteversion in the sitting position).

Discussion: Changes in pelvis orientation between the sitting and standing positions modifies real anteversion of the cup. In particular, subjects with THA tend to have a spontaneous posterior tilt of the pelvis related to trunk ageing. This element should be taken into account for the analysis of both major and minor THA dysfunction.

Introduction: In cases of small and middle size osteonecrosis on conventional antero-posterior (AP) radiographs, we studied the extent of the lesion on AP radiographs at the 45 degrees flexion position for lesions of the anterior area of the femoral head.

Materials and Methods: Classification of Japanese organizing committee was applied for the extent of the lesion on joint surface. Type A lesions occupy the medial one-third or less; Type B, the medial two-thirds or less; Type C-1 occupies more than the medial two-thirds; and Type C-2 extends laterally to the acetabular edge at the neutral position on conventional AP radiographs. Thirty-three hips (25 patients) with small or middle size lesions (Type A;11, Type B;22) were studied. On AP radiographs taken at the 45 degrees flexion position, the extent of the lesion was studied in 33 hips.

Results: Seven of 11 hips of Type A on neutral position showed Type A lesions. For the remaining 4 hips, 2 were Type B, 2 were on Type C-1 at 45 degrees flexion position. For 22 hips with Type B on neutral position, 6 were Type B, 12 were Type C-1, 4 were Type C-2 found at the 45 degrees flexion position.

Discussion: AP radiographs at the 45 degrees flexion position revealed more extensive necrotic area in cases of small and middle size lesions comparing with the neutral position. This finding may be related to progression of the disease.