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The Bone & Joint Journal
Vol. 105-B, Issue 11 | Pages 1226 - 1232
1 Nov 2023
Prijs J Rawat J ten Duis K IJpma FFA Doornberg JN Jadav B Jaarsma RL

Aims. Triplane ankle fractures are complex injuries typically occurring in children aged between 12 and 15 years. Classic teaching that closure of the physis dictates the overall fracture pattern, based on studies in the 1960s, has not been challenged. The aim of this paper is to analyze whether these injuries correlate with the advancing closure of the physis with age. Methods. A fracture mapping study was performed in 83 paediatric patients with a triplane ankle fracture treated in three trauma centres between January 2010 and June 2020. Patients aged younger than 18 years who had CT scans available were included. An independent Paediatric Orthopaedic Trauma Surgeon assessed all CT scans and classified the injuries as n-part triplane fractures. Qualitative analysis of the fracture pattern was performed using the modified Cole fracture mapping technique. The maps were assessed for both patterns and correlation with the closing of the physis until consensus was reached by a panel of six surgeons. Results. Fracture map grouped by age demonstrates that, regardless of age (even at the extremes of the spectrum), the fracture lines consolidate in a characteristic Y-pattern, and no shift with closure of the physis was observed. A second fracture map with two years added to female age also did not show a shift. The fracture map, grouped by both age and sex, shows a Y-pattern in all different groups. The fracture lines appear to occur between the anterior and posterior inferior tibiofibular ligaments, and the medially fused physis or deltoid ligament. Conclusion. This fracture mapping study reveals that triplane ankle fractures have a characteristic Y-pattern, and acknowledges the weakness created by the physis, however it also challenges classic teaching that the specific fracture pattern at the level of the joint of these injuries relies on advancing closure of the physis with age. Instead, this study observes the importance of ligament attachment in the fracture patterns of these injuries. Cite this article: Bone Joint J 2023;105-B(11):1226–1232


Bone & Joint Open
Vol. 3, Issue 2 | Pages 158 - 164
17 Feb 2022
Buddhdev P Vallim F Slattery D Balakumar J

Aims. Slipped upper femoral epiphysis (SUFE) has well documented biochemical and mechanical risk factors. Femoral and acetabular morphologies seem to be equally important. Acetabular retroversion has a low prevalence in asymptomatic adults. Hips with dysplasia, osteoarthritis, and Perthes’ disease, however, have higher rates, ranging from 18% to 48%. The aim of our study was to assess the prevalence of acetabular retroversion in patients presenting with SUFE using both validated radiological signs and tomographical measurements. Methods. A retrospective review of all SUFE surgical cases presenting to the Royal Children’s Hospital, Melbourne, Australia, from 2012 to 2019 were evaluated. Preoperative plain radiographs were assessed for slip angle, validated radiological signs of retroversion, and standardized postoperative CT scans were used to assess cranial and mid-acetabular version. Results. In all, 116 SUFEs presented in 107 patients who underwent surgical intervention; 47 (52%) were male, with a mean age of 12.7 years (7.5 to 16.6). Complete radiological data was available for 91 patients (99 hips) with adequate axial CT imaging of both hips. Overall, 82 patients (82%) underwent pinning in situ (PIS), with subcapital realignment surgery (SRS) performed in 17 patients (18%) (slip angles > 75°). Contralateral prophylactic PIS was performed in 72 patients (87%). On the slip side, 62 patients (68%) had one or more radiological sign of retroversion. Tomographical acetabular retroversion was more pronounced cranially than caudally of the acetabulum on both the affected side and the contralateral side (p < 0.001) as expected in the normal population. Increasing severity of the slip was found to be directly proportional to the degree of reduction in cranial and central acetabular version (p < 0.05) in the SUFE hips. Conclusion. Acetabular retroversion is more prevalent in patients with SUFE than previously reported, and have been shown be correlated to the severity of the slip presentation. The presence of radiological signs of acetabular retroversion could be used to justify prophylactic contralateral pinning. Cite this article: Bone Jt Open 2022;3(2):158–164


Orthopaedic Proceedings
Vol. 94-B, Issue SUPP_XXIV | Pages 2 - 2
1 May 2012
Cooper A Flowers M
Full Access

Aims. The purpose of this study was to calculate the dislocation rate following open or closed reduction for developmental dysplasia of the hip (DDH) in our unit. In addition we evaluated the posterior neck line as a method of determining hip relocation and assessed the morphology of the dysplastic acetabulum on single slice CT scan. Method. We retrospectively assessed all patients operated on for either open or closed reduction for DDH between August 2007 and August 2009 and evaluated their notes, CT scans and radiographs. The immediate post-operative dislocation rate was calculated, as was the subsequent re-dislocation rate and late subluxation rate. The acetabular morphology was assessed to determine whether the acetabulae were “S” shaped or “C” shaped. A novel method for confirming hip reduction was also appraised. Results. Seventy-five hips were operated on during the study period. The immediate post-operative dislocation rate was 9.3%. There were no subsequent dislocations in any of the patients in whom CT scans had confirmed adequate initial reduction. Two patients went on to develop late subluxation. 98.6% of dysplastic acetabulae displayed an S shaped acetabulum and 1 hip had a virtually flat acetabulum. The posterior neck line test for dislocation had a 85.7% sensitivity and 96.9% specificity. Conclusions. Immediate post-operative CT scan of the hip is a useful investigation following reduction of the hip for DDH. If it can be established that the hip is reduced on the scan it is unlikely to re-dislocate. The S shape of the acetabulum in DDH is consistently present and is a marker of the dysplastic posterior acetabular wall. The posterior neck line is a reliable measure of hip reduction


The Bone & Joint Journal
Vol. 99-B, Issue 5 | Pages 697 - 701
1 May 2017
Massa BSF Guarniero R Godoy Jr RM Rodrigues JC Montenegro NB Cordeiro FG

Aims. This pilot study aimed to evaluate prospectively the use of inlet radiographs of the hip as an alternative method of the assessment of reduction after the surgical treatment of developmental dysplasia of the hip (DDH). Patients and Methods. The children in this study underwent surgery between January 2013 and January 2015. All had inlet radiographs and CT scans post-operatively. Data were analysed by determining inter-observer reliability and intra-observer reproducibility, using the kappa value (K). Differences were settled by discussion between the two observers until a consensus was reached. The sensitivity and specificity of the radiographic and CT results were compared. A total of 26 radiographs were obtained from 23 children, with a mean age of 2.38 years (one to five). Results. Similar high levels of intra- and inter-observer agreement were observed (K = 0.834, 95% confidence interval (CI)). There was a high agreement between the radiographic and CT results (K = 0.834, 5% CI), with excellent sensitivity and a specificity of 95.5%. Conclusion. These results suggest that inlet radiographs may be a reliable method of assessing the reduction of the hip after the surgical treatment of DDH. Cite this article: Bone Joint J 2017;99-B:697–701


The Bone & Joint Journal
Vol. 106-B, Issue 9 | Pages 1008 - 1014
1 Sep 2024
Prijs J Rawat J ten Duis K Assink N Harbers JS Doornberg JN Jadav B Jaarsma RL IJpma FFA

Aims

Paediatric triplane fractures and adult trimalleolar ankle fractures both arise from a supination external rotation injury. By relating the experience of adult to paediatric fractures, clarification has been sought on the sequence of injury, ligament involvement, and fracture pattern of triplane fractures. This study explores the similarities between triplane and trimalleolar fractures for each stage of the Lauge-Hansen classification, with the aim of aiding reduction and fixation techniques.

Methods

Imaging data of 83 paediatric patients with triplane fractures and 100 adult patients with trimalleolar fractures were collected, and their fracture morphology was compared using fracture maps. Visual fracture maps were assessed, classified, and compared with each other, to establish the progression of injury according to the Lauge-Hansen classification.


The Journal of Bone & Joint Surgery British Volume
Vol. 90-B, Issue 1 | Pages 88 - 91
1 Jan 2008
Chung CY Choi IH Cho T Yoo WJ Lee SH Park MS

We carried out a morphometric analysis of the acetabulum following Dega osteotomy in patients with cerebral palsy using three-dimensional CT. We assessed 17 acetabula in 12 patients with instability of the hip. A Dega osteotomy and varus derotation femoral osteotomy were performed in all 17 hips. Three-dimensional CT scans were taken before and approximately one year after operation. Acetabular cover was evaluated using anterosuperior, superolateral and posterosuperior acetabular indices, and the change in the acetabular volume was calculated. Inter- and intra-observer reliability was assessed using the intraclass correlation coefficient. After the osteotomy, the anterosuperior, superolateral and posterosuperior cover had improved significantly towards the value seen in a control group. The mean acetabular volume increased by 68%


Orthopaedic Proceedings
Vol. 97-B, Issue SUPP_9 | Pages 1 - 1
1 Aug 2015
Solomon E Shortland A Lucas J
Full Access

The standard approach of diagnosing and monitoring scoliosis involves using the Cobb angle from posteroanterior (PA) radiograph. This approach has two key limitations: 1) It involves exposing the patients to ionising radiation during a period of heightened radiosensitivity. 2) The 2D x-ray image is a projection image of a 3D deformity and the Cobb angle represents only lateral rotation. 3DUS would overcome both these limitations. We developed a 3DUS system by combining motion capture technology, a conventional 2D ultrasound scanner and bespoke software. An ex vivo experiment and a pilot clinical study were carried out to demonstrate the system's ability in identifying vertebrae landmarks and quantifying the curvature. For the ex vivo validation, a spine phantom was created by 3D-printing a segmented abdo-pelvis CT scan. The spine phantom was then scanned using 3DUS and the level of agreement in the dimensions measured using 3DUS and CT was assessed. An 11 year old female with adolescent idiopathic scoliosis (AIS) was scanned with 3DUS. The SP co-ordinates were projected on a plane of best-fit to compare the curvature angle from 3DUS with the Cobb angle from the x-ray image. The spinous (SP), transverse processes and the laminae demonstrated high echogenicity and were easily identifiable. The difference between the spine phantom inter-SP dimension measurements made in 3DUS and CT was <2.5%. The PA x-ray of the AIS patient revealed 47° (L4-T11) and 52° (T6-T11) curves. 3DUS was able to represent the deformity in 3D revealing complex curvatures in all planes. The curvature angle from derived from 3DUS for the L4-T11 and T6-T11 curves were 132° (48°) and 125° (55°) respectively. The results of this pilot study demonstrate 3DUS as a promising tool for imaging spine curvature


Orthopaedic Proceedings
Vol. 94-B, Issue SUPP_XXIV | Pages 17 - 17
1 May 2012
Geddis C Ali R Fernandes J Madan S
Full Access

The purpose of this study was to determine the oblique plane deformity in slipped upper femoral epiphysis. A retrospective radiographic review was undertaken in patients admitted with a slipped upper femoral epiphysis between March 2008 and October 2010. Patients in whom a CT scan had been performed in addition to plain radiographs were assessed further. Angular deformity in the coronal and sagittal planes were measured by the angle formed between the femoral neck and a line perpendicular to the physis on the AP pelvic radiograph and the axial CT scan respectively. The magnitude and direction of the resultant deformity was defined in the oblique plane. Additional demographic data (gender, age, side, procedure and complications) was collected. Seven girls, average age of 12 (range 10 – 13) and 6 boys, average age of 13 (range 10 – 15) were identified. The slip was bilateral in 2, left sided in 6 and right sided in 5 cases. Two patients were pinned in situ, 8 had surgical dislocation performed to facilitate reduction prior to pinning and 3 patients had secondary procedures performed following in situ pinning. The average angulation in the oblique posteroinferior plane (25 degrees) was less than in the coronal (30 degrees) and the sagittal planes (62 degrees). The average magnitude was 67mm (range 31 – 88). CT is useful adjunct particularly when a frog legged lateral view is not possible because of pain or the fear of further displacement. Determination of the deformity in the oblique plane may aid in positioning of the screw during in situ pinning and may be helpful in identifying patients in whom pinning maybe difficult


The Bone & Joint Journal
Vol. 104-B, Issue 2 | Pages 302 - 308
1 Feb 2022
Dala-Ali B Donnan L Masterton G Briggs L Kauiers C O’Sullivan M Calder P Eastwood DM

Aims

Osteofibrous dysplasia (OFD) is a rare benign lesion predominantly affecting the tibia in children. Its potential link to adamantinoma has influenced management. This international case series reviews the presentation of OFD and management approaches to improve our understanding of OFD.

Methods

A retrospective review at three paediatric tertiary centres identified 101 cases of tibial OFD in 99 patients. The clinical records, radiological images, and histology were analyzed.


Orthopaedic Proceedings
Vol. 94-B, Issue SUPP_XXIV | Pages 4 - 4
1 May 2012
de Gheldere A Hashemi-Nejad A Calder P Tennant S Eastwood D
Full Access

Purpose. To document the success rate of closed reduction and soft tissue release in the treatment of bilateral true dislocation in developmental dysplasia of the hip (DDH). Methods. Case-note review of 22 children (44 hips) with idiopathic bilateral hip dislocation referred to a tertiary centre before walking age. The management protocol was as follows: . Examination under general anaesthesia, arthrogram, closed reduction and appropriate soft tissue release (adductors/psoas), application of a ‘frog’ cast. CT scan at 2 weeks to confirm reduction. Change of cast and arthrogram at 6 weeks to confirm improving position and stability. Cast removal at 12 weeks, and application of an abduction brace for 6 weeks. Treatment failure could occur on day 1 (failure of reduction), at week 2 (failure to maintain reduction), at week 6, or after cast removal. Results. Median age at presentation was 3.8m (2w-7.5m). 19/22 were girls. 7 had a caesarean section for breech presentation, 16/22 had had prior Pavlik harness treatment. All hips were Tonnis 2 or more. Mean age at surgery was 7 months (range 3-12m). 9/44 hips failed on day 1. 13/44 hips failed at 2 weeks. 1/44 hip failed at 6 weeks. 8/22 patients had bilateral failure. 7/22 patients maintained a unilateral hip reduction and 7/22 patients maintained a bilateral reduction after treatment. Mean follow-up was 25m (range 6-71m). 1 patient has bilateral AVN. Successful results were not associated with presentation, previous treatment given, the level of dislocation (Tonnis) or patient age at time of treatment. Conclusion. Following a successful initial reduction, this protocol failed to maintain reduction in 13/35 (40%) hips at 2 weeks: significantly worse than our presented results for unilateral dislocation. Significance. With our current protocol, the percentage chance of reducing at least one of bilateral idiopathic dislocated hips is 64% (14/22) but parents should be told that there is only a 1:3 chance of a successful outcome for both hips following closed reduction


Bone & Joint Open
Vol. 2, Issue 8 | Pages 594 - 598
3 Aug 2021
Arneill M Cosgrove A Robinson E

Aims

To determine the likelihood of achieving a successful closed reduction (CR) of a dislocated hip in developmental dysplasia of the hip (DDH) after failed Pavlik harness treatment We report the rate of avascular necrosis (AVN) and the need for further surgical procedures.

Methods

Data was obtained from the Northern Ireland DDH database. All children who underwent an attempted closed reduction between 2011 and 2016 were identified. Children with a dislocated hip that failed Pavlik harness treatment were included in the study. Successful closed reduction was defined as a hip that reduced in theatre and remained reduced. Most recent imaging was assessed for the presence of AVN using the Kalamchi and MacEwen classification.


The Bone & Joint Journal
Vol. 103-B, Issue 5 | Pages 999 - 1004
1 May 2021
Pollet V Bonsel J Ganzeboom B Sakkers R Waarsing E

Aims

The most important complication of treatment of developmental dysplasia of the hip (DDH) is avascular necrosis (AVN) of the femoral head, which can result in proximal femoral growth disturbances leading to pain, dysfunction, and eventually to early onset osteoarthritis. In this study, we aimed to identify morphological variants in hip joint development that are predictive of a poor outcome.

Methods

We retrospectively reviewed all patients who developed AVN after DDH treatment, either by closed and/or open reduction, at a single institution between 1984 and 2007 with a minimal follow-up of eight years. Standard pelvis radiographs obtained at ages one, two, three, five, and eight years, and at latest follow-up were retrieved. The Bucholz-Ogden classification was used to determine the type of AVN on all radiographs. Poor outcome was defined by Severin classification grade 3 or above on the latest follow-up radiographs and/or the need for secondary surgery. With statistical shape modelling, we identified the different shape variants of the hip at each age. Logistic regression analysis was used to associate the different modes or shape variants with poor outcome.


The Bone & Joint Journal
Vol. 102-B, Issue 12 | Pages 1760 - 1766
1 Dec 2020
Langlais T Hardy MB Lavoue V Barret H Wilson A Boileau P

Aims

We aimed to address the question on whether there is a place for shoulder stabilization surgery in patients who had voluntary posterior instability starting in childhood and adolescence, and later becoming involuntary and uncontrollable.

Methods

Consecutive patients who had an operation for recurrent posterior instability before the age of 18 years were studied retrospectively. All patients had failed conservative treatment for at least six months prior to surgery; and no patients had psychiatric disorders. Two groups were identified and compared: voluntary posterior instability starting in childhood which became uncontrollable and involuntary (group VBI); and involuntary posterior instability (group I). Patients were reviewed and assessed at least two years after surgery by two examiners.


The Bone & Joint Journal
Vol. 100-B, Issue 6 | Pages 811 - 821
1 Jun 2018
Fu K Duan G Liu C Niu J Wang F

Aims

The aim of this study was to investigate the changes in femoral trochlear morphology following surgical correction of recurrent patellar dislocation associated with trochlear dysplasia in children.

Patients and Methods

A total of 23 patients with a mean age of 9.6 years (7 to 11) were included All had bilateral recurrent patellar dislocation associated with femoral trochlear dysplasia. The knee with traumatic dislocation at the time of presentation or that had dislocated most frequently was treated with medial patellar retinacular plasty (Group S). The contralateral knee served as a control and was treated conservatively (Group C). All patients were treated between October 2008 and August 2013. The mean follow-up was 48.7 months (43 to 56). Axial CT scans were undertaken in all patients to assess the trochlear morphological characteristics on a particular axial image which was established at the point with the greatest epicondylar width based on measurements preoperatively and at the final follow-up.


The Bone & Joint Journal
Vol. 100-B, Issue 8 | Pages 1117 - 1124
1 Aug 2018
Eamsobhana P Chalayon O Kaewpornsawan K Ariyawatkul T

Aims

Delayed diagnosis is a well-known complication of a Monteggia fracture-dislocation. If left untreated, the dislocated radial head later becomes symptomatic. The purposes of this study were firstly, to evaluate the clinical and radiological results of open reduction of the radial head and secondly, to identify the factors that may affect the outcome of this procedure.

Materials and Methods

This retrospective study evaluated 30 children with a chronic Monteggia lesion. There were 18 boys and 12 girls with a mean age of 7.4 years (4 to 13) at the time of open reduction. The mean interval to surgery, after the initial fracture, was 23.4 months (6 to 120). Clinical grading used a Kim modified elbow score: radiological outcome was recorded. The effect of the patient’s age, gender, duration from initial injury, Bado classification, and annular ligament reconstruction were analyzed. The mean follow-up was 42.2 months (15 to 20).


The Bone & Joint Journal
Vol. 100-B, Issue 3 | Pages 396 - 403
1 Mar 2018
Messner J Johnson L Taylor DM Harwood P Britten S Foster P

Aims

The aim of this study was to report the clinical, functional and radiological outcomes of children and adolescents with tibial fractures treated using the Ilizarov method.

Patients and Methods

Between 2013 and 2016 a total of 74 children with 75 tibial fractures underwent treatment at our major trauma centre using an Ilizarov frame. Demographic and clinical information from a prospective database was supplemented by routine functional and psychological assessment and a retrospective review of the notes and radiographs.


The Bone & Joint Journal
Vol. 98-B, Issue 5 | Pages 715 - 720
1 May 2016
Mifsud M Abela M Wilson NIL

Aims

Although atlantoaxial rotatory fixation (AARF) is a common cause of torticollis in children, the diagnosis may be delayed. The condition is characterised by a lack of rotation at the atlantoaxial joint which becomes fixed in a rotated and subluxed position. The management of children with a delayed presentation of this condition is controversial. This is a retrospective study of a group of such children.

Patients and Methods

Children who were admitted to two institutions between 1988 and 2014 with a diagnosis of AARF were included. We identified 12 children (four boys, eight girls), with a mean age of 7.3 years (1.5 to 13.4), in whom the duration of symptoms on presentation was at least four weeks (four to 39). All were treated with halo traction followed by a period of cervical immobilisation in a halo vest or a Minerva jacket. We describe a simple modification to the halo traction that allows the child to move their head whilst maintaining traction. The mean follow-up was 59.6 weeks (24 to 156).


The Bone & Joint Journal
Vol. 98-B, Issue 11 | Pages 1548 - 1553
1 Nov 2016
Tennant SJ Eastwood DM Calder P Hashemi-Nejad A Catterall A

Aims

Our aim was to assess the effectiveness of a protocol involving a standardised closed reduction for the treatment of children with developmental dysplasia of the hip (DDH) in maintaining reduction and to report the mid-term results.

Methods

A total of 133 hips in 120 children aged less than two years who underwent closed reduction, with a minimum follow-up of five years or until subsequent surgery, were included in the study. The protocol defines the criteria for an acceptable reduction and the indications for a concomitant soft-tissue release. All children were immobilised in a short- leg cast for three months. Arthrograms were undertaken at the time of closed reduction and six weeks later. Follow-up radiographs were taken at six months and one, two and five years later and at the latest follow-up. The Tönnis grade, acetabular index, Severin grade and signs of osteonecrosis were recorded.


The Bone & Joint Journal
Vol. 96-B, Issue 9 | Pages 1269 - 1273
1 Sep 2014
Kitoh H Mishima K Matsushita M Nishida Y Ishiguro N

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: Bone Joint J 2014;96-B:1269–73.


The Bone & Joint Journal
Vol. 96-B, Issue 8 | Pages 1124 - 1129
1 Aug 2014
Segaren N Abdul-Jabar HB Hashemi-Nejad A

Proximal femoral varus osteotomy improves the biomechanics of the hip and can stimulate normal acetabular development in a dysplastic hip. Medial closing wedge osteotomy remains the most popular technique, but is associated with shortening of the ipsilateral femur.

We produced a trigonometric formula which may be used pre-operatively to predict the resultant leg length discrepancy (LLD). We retrospectively examined the influence of the choice of angle in a closing wedge femoral osteotomy on LLD in 120 patients (135 osteotomies, 53% male, mean age six years, (3 to 21), 96% caucasian) over a 15-year period (1998 to 2013). A total of 16 of these patients were excluded due to under or over varus correction. The patients were divided into three age groups: paediatric (< 10 years), adolescent (10 to 16 years) and adult (> 16 years). When using the same saw blades as in this series, the results indicated that for each 10° of angle of resection the resultant LLD equates approximately to multiples of 4 mm, 8 mm and 12 mm in the three age groups, respectively.

Statistical testing of the 59 patients who had a complete set of pre- and post-operative standing long leg radiographs, revealed a Pearson’s correlation coefficient for predicted versus radiologically observed shortening when using a wedge of either 10° or 20° of 0.93 (p <  0.001). The 95% limits of agreement from the Bland–Altman analysis for this subgroup were –3.5 mm to +3.3 mm. It has been accepted that a 10 mm discrepancy is clinically acceptable.

This study identified a geometric model that provided satisfactory accuracy when using specific saw blades of known thicknesses for this formula to be used in clinical practice.

Cite this article: Bone Joint J 2014;96-B:1124–9