JCLB-03834; No of Pages 7 Clinical Biomechanics xxx (2014) xxx–xxx
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A novel osteotomy in shoulder joint replacement based on analysis of the cartilage/metaphyseal interface Fraser Harrold ⁎, Amar Malhas, Carlos Wigderowitz Department of Orthopaedic and Trauma Surgery, College of Medicine, Dentistry and Nursing, University of Dundee, TORT Centre, Ninewells Hospital and Medical School, Dundee DD1 9SY, Scotland, UK
a r t i c l e
i n f o
Article history: Received 9 February 2014 Accepted 19 August 2014 Keywords: Shoulder Arthroplasty Osteotomy Anatomy Humerus Geometry
a b s t r a c t Background: The accuracy of reconstruction is thought to impact on functional outcome following glenohumeral joint arthroplasty. The objective of this study was to define an area of minimal anatomic variation at the cartilage/ metaphyseal interface of the proximal humerus to optimize the osteotomy of the humeral head, enabling accurate reconstruction with a prosthetic component. Methods: Hand held digitization and 3D surface laser scanning techniques were used to digitize 24 cadaveric arms and determine the normal geometry. Each humeral head was then examined to identify the most consistent anatomical landmarks for the ideal osteotomy plane to optimize humeral component positioning. Findings: The novel, posterior referencing, osteotomy resulted in a mean increase in retroversion of only 0.4° when compared to the original geometry. A traditional anterior referencing osteotomy, by comparison, produced a mean increase in retroversion of 11°. In addition, the novel osteotomy only increased axial diameter by 0.71 mm and head height by 0.02 mm compared to an anterior referencing osteotomy (3.0 mm and 2.7 mm respectively). Interpretation: The traditional osteotomy, referencing the anterior border of the cartilage/metaphyseal interface potentially resulted in an increase in prosthetic head size and retroversion. The novel osteotomy, referencing from the posterior cartilage/metaphyseal interface enabled a more accurate recovery of head geometry. Importantly, the increase in retroversion created by the traditional osteotomy was not replicated with the novel technique. Referencing from the posterior cartilage/metaphyseal interface produced a more reliable osteotomy, more closely matching the original humeral geometry. Level of Evidence: Basic Science, Anatomic study, Computer model. © 2014 Elsevier Ltd. All rights reserved.
1. Introduction Survivorship of shoulder arthroplasty surgery in the literature is encouraging and represents the treatment of choice for degenerative joint diseases of the glenohumeral joint. Studies place the 10 year survivorship of anatomic shoulder replacement (ASR), with revision as an end-point, between 85 and 95% (Haines et al., 2006; Radnay et al., 2007; Raiss et al., 2012; Young et al., 2011). Reverse total shoulder replacement (RTSR) is also reported to have 90% survivorship at 10 years for revision (Guery et al., 2006). Shoulder hemiarthroplasty implants are reported to have 80% 10 year survivorship (Levine et al., 2012; Sperling et al., 1998). When other outcome measures are examined, shoulder arthroplasty surgery is less successful. By 10 years, approximately 50–70% of ASR demonstrate glenoid loosening on radiographic assessment (Haines
⁎ Corresponding author at: University Department of Orthopaedic & Trauma Surgery, Ninewells Hospital & Medical School, Dundee DD1 9SY, Scotland, UK. E-mail address: [email protected] (F. Harrold).
et al., 2006; Young et al., 2011). RTSR have reported lower glenoid loosing at 10 years (~ 20%) but up to 70% display inferior glenoid notching (Guery et al., 2006; Levigne et al., 2011). Patients' satisfaction can also be poor with up to 50% of ASR (Sperling et al., 1998) and 75% of hemiarthroplasty replacements were deemed ‘unsatisfactory’ or ‘unsuccessful’ (Levine et al., 2012). In some series of ASR up to 74% of patients complain of stiffness and 35% complain of instability (Hasan et al., 2002). Evidence in the literature supports the important role that component positioning and glenohumeral alignment play in implant survivorship and function (Hasan et al., 2002; Neer and Kirby, 1982; Norris and Iannotti, 2002; Spencer et al., 2005; Wirth and Rockwood, 1994, 1996). Franta et al. postulated that glenohumeral mal-alignment was the most likely cause of glenoid loosening in their series of 282 unsatisfactoy shoulder arthroplasties (Franta et al., 2007). Underlying, glenohumeral mal-alignment from the original disease process may also play a role. If eccentric glenoid wear is present at the time of the primary arthroplasty, there is an increased risk of glenoid wear in ASR (Haines et al., 2006) and lower patient satisfaction in shoulder hemiarthroplasty surgery (Levine et al., 2012).
http://dx.doi.org/10.1016/j.clinbiomech.2014.08.008 0268-0033/© 2014 Elsevier Ltd. All rights reserved.
Please cite this article as: Harrold, F., et al., A novel osteotomy in shoulder joint replacement based on analysis of the cartilage/metaphyseal interface, Clin. Biomech. (2014), http://dx.doi.org/10.1016/j.clinbiomech.2014.08.008
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The highly variable anatomy of the proximal humerus is an important consideration that modern prosthetic components are designed to accommodate (Boileau and Walch, 1997; Iannotti et al., 1992; Robertson et al., 2000). Failure to address the restoration of glenohumeral alignment (particularly retroversion) is thought to lead to eccentric loading, glenoid wear and glenoid loosening (Figgie et al., 1988; Pearl and Volk, 1996). There may also be a change in the centre of rotation impacting of joint stability (Boileau and Walch, 1997; Pearl and Volk, 1996). Individual humeral retroversion can range from 3° to 40° although the mean is approximately 20° (Harrold and Wigderowitz, 2012). In order to restore an individual's proximal humeral morphology, a precise osteotomy of the humeral head at the level of the anatomical neck is required (Walch and Boileau, 1999). The anterior cartilage/metaphyseal interface is used as a reliable anatomical landmark to facilitate an accurate osteotomy (Pearl and Volk, 1995). Recent evidence has demonstrated that not only is there anatomical variation in the cartilage/metaphyseal landmark but also that the humeral head is not truly spherical (Harrold and Wigderowitz, 2012). An osteotomy that is therefore based on anterior referencing can significantly increase retroversion by 11° (an increase of almost 40%) and decrease component inclination by 5° (Harrold and Wigderowitz, 2013). The purpose of the study was to analyse the cartilage/metaphyseal junction as it relates to the osteotomy and determine the optimum landmarks, with which to perform an osteotomy, to recover humeral head geometry accurately. 2. Methods Twenty-four cadaveric full arms, preserved in formalin, without skeletal abnormality and that had not undergone a previous surgical procedure were disarticulated and all soft tissues removed. Eighteen specimens were matched pairs a further two were right humeri and four were left humeri. There were fourteen females and ten males ranging in age from 68 to 99 years (average, 84 years, SD 8.4 years). A precision reference cube was attached to the greater tuberosity of each humerus to enable two independently collected data sets to be combined (Pfaeffle et al., 1999). The details of data collection have been described, previously, by Harrold and Wigderowitz (Harrold and Wigderowitz, 2012, 2013). For each specimen, the following anatomical landmarks were identified and marked: (1) the circumference of the anatomical neck; (2) the
most superior point of the articular surface at the insertion of the supraspinatus tendon, the corresponding lowest point of the articular surface at the cartilage/metaphyseal interface; (3) the medial epicondyle and the lateral epicondyle. Each specimen was then mounted, rigidly, on a custom-built jig. Two instruments, a Microscribe 3D-X handheld digitizer (Immersion Corp., San Jose, CA, USA) and an Arius3D colour surface laser scanner (Metrologic MTI; Metrologic Instruments, Meylan, France) were used to acquire the data for the surface geometry of each humerus. The precision reference cubes were used as a common reference to transform the Microscribe 3D-X digitizer data to the same coordinate system as the surface scanner data within 3DReshaper software (Technodigit, Gleizé, France). The combined data was then imported into Rhinocerus NURBS modelling software and graphically presented (Fig. 1a and b). For each model the following were constructed: (1) the humeral shaft as a line through the centre of a best fit cylinder representing the proximal humeral data points extending from the surgical neck to the distal insertion of the deltoid; (2) the transepicondylar line between the medial and lateral epicondyles; (3) the articular portion of the humeral head was used to create a sphere which was divided in the saggital and coronal planes to determine the diameter of the head in the two planes; (4) a best fit plane formed and bounded by the circumference of the anatomical neck. The details of model construction have previously been described by Harrold and Wigderowitz (Harrold and Wigderowitz, 2013). The cartilage/metaphyseal interface was divided into 24 discrete points representing a clock face (Fig. 2). The 12 o'clock position was defined as the point along the cartilage/metaphyseal border adjacent to the insertion of the supraspinatus tendon. The 6 o'clock position was defined as the most medial and inferior position of the cartilage/ metaphyseal border. Clockwise and anticlockwise reference numbers were used for left and right specimens, respectively. An ideal osteotomy plane was then created along the cartilage/ metaphyseal interface fulfilling the following criteria: • Replicated the inclination and retroversion angles measured for the original geometry of the humeral head • Replicated head height for the original geometry of the humeral head • Replicated radius of curvature of the original humeral head created from the proximal 80% of the articular surface The constructed graphical model was used to simulate resection of the articular surface based on an idealised prosthetic implant. The simulated osteotomy plane created a frame of reference to analyse the
Cartilage/metaphyseal boundary Upper and lower boundary of best fit cylinder
Shaft axis constructed from best fit cylinder
Best fit sphere constructed from articular surface data
Transepicondylar axis a
b
Figs. 1. a and 1b Model constructed in Rhinocerus NURBS modelling software (1a) with magnified view of the modelled proximal humerus (1b).
Please cite this article as: Harrold, F., et al., A novel osteotomy in shoulder joint replacement based on analysis of the cartilage/metaphyseal interface, Clin. Biomech. (2014), http://dx.doi.org/10.1016/j.clinbiomech.2014.08.008
F. Harrold et al. / Clinical Biomechanics xxx (2014) xxx–xxx
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24
Legend
6
H: Superior pole L: Inferior pole A: Anterior margin P: Posterior margin
12
Fig. 2. Division of the humeral head using 24 increments for left and right specimens.
cartilage/metaphyseal interface; for each specimen, a deviation analysis was performed comparing the point cloud data for the cartilage/ metaphyseal interface to the ideal osteotomy plane. Rhinoceros NURBS modelling software was used to determine the perpendicular distance of each point from the ideal plane (Fig. 3). The degree of
deviation of the cartilage/metaphyseal point cloud data was then measured at each of the twenty-four increments. The analysis was performed on all specimens. The points of least deviation were used as a reference to construct a plane through the humeral head. The new plane was then used to
Points representing the cartilage/calcar interface Graphical representation of the point deviation from the ideal osteotomy plane H •
•
Legend H: Superior pole L: Inferior pole A: Anterior margin P: Posterior margin
A
P
• • L
Shaft axis Ideal osteotomy plane
Fig. 3. Plane constructed based on the idealised osteotomy and a deviation analysis of each point along the cartilage/metaphyseal interface relative to the plane.
Please cite this article as: Harrold, F., et al., A novel osteotomy in shoulder joint replacement based on analysis of the cartilage/metaphyseal interface, Clin. Biomech. (2014), http://dx.doi.org/10.1016/j.clinbiomech.2014.08.008
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simulate an osteotomy and an idealised fully adaptable spherical prosthetic head was constructed and placed on the simulated osteotomy plane. The lengths of the coronal diameter and height of the resected head were used to determine the diameter and head height of the prosthetic head, respectively. The inclination, retroversion, coronal and axial diameters and radii of curvature (total, coronal and axial radii of curvature) were calculated for each specimen and compared to the original humeral head parameters. The distribution of all descriptors was tested for normality using a Shapiro–Wilk's W test. The critical value for the Shapiro–Wilk's W test at the 0.05 level for 24 specimens was 0.916 (Pearson and Hartley, 1972). The data was found to be normally distributed for all parameters. Descriptive statistics were computed for all outcome variables and paired t-tests used to assess the differences between the normal head geometry and prosthetic implant utilizing the novel osteotomy. All the reported P values were two-tailed with P b 0.05 considered to be statistically significant. SPSS 14.0 software package (SPSS Inc., Chicago, Illinois, USA) was used for all statistical analysis. 3. Results The results revealed marked differences between the cartilage/ metaphyseal interface when compared to the ideal osteotomy plane at certain points around the cartilage/metaphyseal interface. The points at the upper and lower poles represented the points of greatest deviation and with the widest confidence intervals. The smallest deviations were noted along the posterior margin of the cartilage/ metaphyseal interface (Fig. 4). Eight positions were identified with deviations of less than 1.5 mm and associated standard deviations of less than 10 mm (Table 1). The interface with least deviation was posteriorly between the 2 o'clock and 4 o'clock positions. Two points were identified anteriorly with small average deviations and narrow standard deviations, between 8 and 9 o'clock and between 10 and 11 o'clock. The points of reference with the least deviation were then used to construct a novel osteotomy plane. On average, the simulated osteotomy resulted in an increase in retroversion of the prosthetic head of 0.4° from 18.5 (SD 9.0°; range, 2.7 to 37.4°) to 18.9 (SD 9°; range, 14.0 to 58.7°) (Table 2). The result was not statistically significant (P = 0.528). There was a statistically significant (P b 0.001) mean decrease in the inclination angle of the prosthetic head on the simulated osteotomy of 3.2° when compared to the inclination of the original humeral head (Mean, 136.9; SD, 4.7°; range, 126.3 to 143.2°). The osteotomy resulted in a mean coronal diameter (Mean, 46.8; SD, 2.5 mm; range, 41.3 to 51.3 mm) that was, on average, 1.9 (SD, 1.6 mm;
Mean deviation (Millimetres)
30.0 20.0 10.0 0.0 0
1
2
3
4
5
6
7
8
9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
-10.0 -20.0 -30.0 -40.0
Clockface Position Fig. 4. Average, standard deviation and 95% confidence intervals for deviation of cartilage/ metaphyseal interface at each clock face reference position from an optimal osteotomy plane.
95 percentile range, 1.2 to 2.6 mm) narrower than the measured diameter of the original head (Mean, 48.8; SD 3.2 mm; range, 42.7 to 55.1 mm); a result that was statistically significant (P b 0.001). In the saggital plane, a significant difference of 0.7 (SD, 1.6 mm; 95 percentile range, 1.8 to 3.2 mm) was noted between the mean axial diameter of the original head (Mean, 43.6; SD 2.5 mm; range, 38.9 to 49.0 mm) and simulated osteotomy surface (Mean, 44.3; SD, 2.2 mm; range, 40.0 to 47.5 mm) (P = 0.035). Further, a statistically significant difference was found between the axial and coronal diameters of the osteotomised surface of 2.5 (SD, 1.7 mm; range, −2.6 to 4.9 mm) and range within the 95 percentile of between 1.8 and 3.2 mm (p b 0.001). The mean difference between the coronal and axial diameters for the normal humeral head geometry was 5.2 (SD, 2.4 mm; range, 0.6 to 11.6 mm) less than the coronal diameter. The mean head height of the resected segment was almost identical to the original humeral head (P = 0.892). The mean prosthetic head height was 16.9 (SD, 1.6 mm) compared to 16.9 (SD, 1.5 mm) for the original geometry; a mean difference of −0.02 (SD, 0.8 mm). The radii of curvature of the original head (Mean, 24.0; SD, 1.2 mm; range, 22.1 to 26.8 mm) and simulated head, (Mean, 24.7; SD, 1.3 mm; range, 22.3 to 27.8 mm) were statistically different (P b 0.001). In the coronal plane the difference between the idealised prosthetic radius of curvature and the resected segment was 0.1 (SD, 0.2 mm; 95 percentile range, 0.02–0.17 mm) and was statistically significantly different (P =016). Further, in the axial plane a statistically significant difference of 1.7 mm (SD, 1.0 mm) was noted between the prosthesis and original head (Mean, 23.0; SD, 1.1 mm; range, 21.3 to 25.2 mm) (P b 0.001). 4. Discussion The evidence from this study demonstrates that the area with the least anatomic variation is the posterior margin of the cartilage/ metaphyseal interface and not the anterior margin (most commonly used reference) (Pearl and Volk, 1995; Walch and Boileau, 1999). By incorporating this principle into a new posterior referencing osteotomy, the proximal humeral version may be more reliably restored when compared to a traditional anterior referencing osteotomy (Harrold and Wigderowitz, 2013). It has been established, previously, that the cartilage/metaphyseal interface is not a perfect circle forming a cap of a sphere (Harrold and Wigderowitz, 2012, 2013). There is a wide degree of variability of the cartilage/metaphyseal interface when compared to an ideal osteotomy plane. However, the degree of variation at this interface is not consistent. If specific points are chosen, the cartilage/metaphyseal interface could be used as an anatomical landmark for an osteotomy. The results demonstrated that the posterior margin provided the most consistent reference, (3.6 mm variation) while the inferior pole and anterior margin displayed slightly greater variation (4 mm). The greatest variation of the cartilage/metaphyseal interface appeared towards the superior pole of the cartilage surface adjacent to the insertion of the supraspinatus tendon. In extremes of abduction, the glenoid does not make contact with the humeral head at the superior articular surface, seen on all the specimens, under normal conditions. This extension of cartilage may represent an interface between the humeral head and supraspinatus tendon rather than a true articulation with the glenoid (Ateshian et al., 1991; Kelkar et al., 2001; Sahara et al., 2007; Warner et al., 1998). Variations in the cartilage structure based on loading conditions have been reported by a number of authors which may correlate with the topographical variation (Li et al., 2005; Soslowsky et al., 1992). Despite the variation in geometry of the cartilage/metaphyseal interface, a pattern did emerge in which the cartilage/metaphyseal interface approximated to an ideal osteotomy plane and the variability between specimens was small. The computer simulations of the novel osteotomy technique based on three reference points along the
Please cite this article as: Harrold, F., et al., A novel osteotomy in shoulder joint replacement based on analysis of the cartilage/metaphyseal interface, Clin. Biomech. (2014), http://dx.doi.org/10.1016/j.clinbiomech.2014.08.008
F. Harrold et al. / Clinical Biomechanics xxx (2014) xxx–xxx
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Table 1 Descriptive statistics for the deviation of the cartilage/metaphyseal interface from the ideal osteotomy plane (millimetres). Position
H
1
2
3
5
A
7
8
9
10
11
Mean St.dev 95% (Upper) 95% (Lower)
−13.2 10.7 3.6 −32.6
−10.0 9.7 2.2 −27.5
−5.1 6.4 3.3 −15.4
1.1 6.3 8.8 −8.7
4 6.2 6.5 17.5 −3.3
5.4 7.1 14.6 −6.2
3.6 8.2 12.5 −15.3
1.5 8.5 10.6 −10.4
−2.4 8.0 7.6 −14.8
−5.6 6.7 4.2 −15.8
−6.5 8.1 6.5 −18.4
−7.3 12.0 13.9 −22.6
Position
L
13
14
15
16
17
19
20
21
22
23
Mean St.dev 95% (Upper) 95% (Lower)
−4.0 13.6 17.8 −24.4
−2.7 12.0 11.8 −19.8
−3.2 11.7 11.7 −23.3
1.3 9.7 18.0 −9.3
1.4 9.2 14.7 −11.1
1.2 7.1 13.2 −9.2
1.3 6.8 11.7 −11.1
1.4 6.0 9.4 −7.5
−2.8 7.7 8.1 −12.3
−7.3 7.4 1.9 −17.6
−11.3 8.5 1.3 −23.7
cartilage/metaphyseal interface resulted in the removal of a segment of the humeral head that was similar in size to the articular portion of the original head. Further, the osteotomy resulted in only small changes to the orientation of the simulated prosthetic head. The osteotomy resulted in almost identical recovery in the retroversion angle of the prosthetic head when compared to the original humeral head geometry. With the traditional osteotomy, referencing the anterior cartilage/metaphyseal margin, resulted in an average increase in retroversion of 11° (Harrold and Wigderowitz, 2013) (Fig. 5). Although the anterior margin of the cartilage/metaphyseal interface had slightly more variation than the posterior margin (4 mm versus 3.6 mm), simply using the anterior margin as a reference tended to amplify the error in orientation resulting in a significant increase in retroversion. The novel osteotomy resulted in an average increase in retroversion of only 0.4°. Accurate restoration of retroversion is thought to provide a more stable joint with balanced anterior and posterior structures of the rotator cuff (Boileau and Walch, 1997; Pearl and Volk, 1995). Also, the novel osteotomy may avoid creating tension on the posterior capsule, identified by Boileau et al. as a problem (Boileau et al., 2002). Further, the technique may reduce the potential for eccentric loading on the glenoid noted in the traditional cut, minimising the risk of excessive glenoid wear and glenoid loosening (Figgie et al., 1988; Pearl and Volk, 1996). The theoretical risk of damaging the rotator cuff with a retroverted cut, noted by a number of authors (Cofield and Edgerton, 1990; Figgie et al., 1988; Friedman et al., 1989) may also be reduced with the novel technique. There were some similarities between the novel and traditional osteotomy. Both osteotomies produced a reduction in inclination (novel osteotomy 3.2°, traditional osteotomy 4°) that fall within the normal range of translations of the joint centre during active motion and are therefore unlikely to be of clinical significance (Howell et al., 1988; Karduna et al., 1996; Kelkar et al., 2001; Sahara et al., 2007).
P 0.3 6.7 9.1 −8.3
Head height was restored within the 5 mm height deemed to be clinically significant (a variation of 0.02 mm in the novel osteotomy and 2.7 mm in the traditional osteotomy) (Harryman et al., 1995; Williams et al., 2001). Both osteotomies restored the coronal and axial diameters to within 2.6 mm. The radius of curvature in both osteotomies were reproduced to within the 2–3 mm threshold described by Iannotti (Iannotti et al., 1992) and Kelkar (Kelkar et al., 2001). The study was based on previous work using an established modelling technique and may be limited by the sample size; the study was powered to examine the difference between the traditional osteotomy and original head geometry (Harrold and Wigderowitz, 2012, 2013). The variation in results between this study and those of other authors may be associated with the sample size or measurement technique. This could either be the instrumentation selected or the reference points used to define a particular descriptor. Further, the range of data was narrower in this study and, likely, reflects the size of the sample. The principle of using three of the reference points along the cartilage/ metaphyseal interface and, in particular, the posterior cartilage/ metaphyseal margin has been developed by JRI Orthopaedics Ltd in their resurfacing instrumentation. The guidewire inserted into the centre of the humeral head is based on a jig which centres the wire, referencing the posterior cartilage/metaphyseal interface. Similar instrumentation could be used with the addition of a cutting jig attached to the centred guidewire, allowing the osteotomy to be undertaken along the anterior margin of the cartilage/metaphyseal junction but referenced from the posterior margin. 5. Conclusions By applying computer generated simulations, it was possible to identify repeatable reference points along the cartilage/metaphyseal interface to create a posterior referencing osteotomy of the proximal humerus that improved recovery of humeral head geometry in
Table 2 Differences between the geometry of the osteotomised head and original geometry. Original:Idealised
Paired differences Mean
Inclination (deg) Retroversion (deg) Coronal diameter (mm) Axial diameter (mm) Head height (mm) ROC (mm) Axial ROC (mm) Coronal ROC (mm)
3.18 −0.40 1.93 −0.71 −0.02 −0.70 1.70 0.09
Std. dev.
3.99 3.05 1.62 1.56 0.79 0.54 0.95 0.18
Std. error mean
0.82 0.62 0.33 0.32 0.16 0.11 0.19 0.07
t
df
Sig. (2-tailed)
3.90 −0.64 5.82 −2.23 −0.14 −6.29 8.74 2.60
23 23 23 23 23 23 23 23
b0.001 0.528 b0.001 0.035 0.892 N0.001 N0.001 0.016
95% Confidence interval Lower
Upper
1.49 −1.69 1.24 −1.37 −0.35 −0.93 1.29 0.02
4.86 0.89 2.61 −0.05 0.31 −0.47 2.10 0.17
Please cite this article as: Harrold, F., et al., A novel osteotomy in shoulder joint replacement based on analysis of the cartilage/metaphyseal interface, Clin. Biomech. (2014), http://dx.doi.org/10.1016/j.clinbiomech.2014.08.008
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F. Harrold et al. / Clinical Biomechanics xxx (2014) xxx–xxx
Fig. 5. A–C. A. Antero-posterior view of the humeral head demonstrating the anterior reference point on the cartilage–metaphyseal junction (dotted line) traditionally used to reference the neck cut. B. Supero-lateral view of the humeral head (deltoid splitting approach) demonstrating a mean 11° over-estimation of retroversion from the true retroversion using anterior referencing alone. C. Posterior referencing with a mean overestimation of true retroversion of 0.4° ((AR), Anterior reference; (PR), Posterior reference; (TR), True retroversion; (LT) lesser tuberosity; (GT), greater tuberosity).
shoulder hemiarthroplasty. Application of the technique in shoulder hemiarthroplasty and total shoulder replacement may improve the overall biomechanics of the glenohumeral arthroplasty and functional outcome. The principle of using three of the reference points along the cartilage/metaphyseal interface and, in particular, the posterior cartilage/metaphyseal margin requires further exploration and development in terms of prosthesis design and instrumentation before applying in-vivo. Conflict of interest statement The authors confirm that there are no financial and personal relationships with other people or organizations that could inappropriately influence (bias) the present work. Acknowledgements This study was partly funded with a grant from the Anonymous Trust, Dundee University. The trust had no part to play in the study other than funding. The Authors wish to thank the Departments of Anatomy at both the University of Dundee and St Andrews University. References Ateshian, G.A., Soslowsky, L.J., Mow, V.C., 1991. Quantitation of articular surface topography and cartilage thickness in knee joints using stereophotogrammetry. J. Biomech. 24, 761–776. Boileau, P., Walch, G., 1997. The three-dimensional geometry of the proximal humerus. Implications for surgical technique and prosthetic design. J. Bone Joint Surg. (Br.) 79, 857–865. Boileau, P., Krishnan, S.G., Tinsi, L., Walch, G., Coste, J.S., Mole, D., 2002. Tuberosity malposition and migration: reasons for poor outcomes after hemiarthroplasty for displaced fractures of the proximal humerus. J. Shoulder Elbow Surg. 11, 401–412. Cofield, R.H., Edgerton, B.C., 1990. Total shoulder arthroplasty: complications and revision surgery. Instr. Course Lect. 39, 449–462. Figgie, H.E.D., Inglis, A.E., Goldberg, V.M., Ranawat, C.S., Figgie, M.P., Wile, J.M., 1988. An analysis of factors affecting the long-term results of total shoulder arthroplasty in inflammatory arthritis. J. Arthroplasty 3, 123–130. Franta, A.K., Lenters, T.R., Mounce, D., Neradilek, B., Matsen 3rd, F.A., 2007. The complex characteristics of 282 unsatisfactory shoulder arthroplasties. J. Shoulder Elbow Surg. 16, 555–562. Friedman, R.J., Thornhill, T.S., Thomas, W.H., Sledge, C.B., 1989. Non-constrained total shoulder replacement in patients who have rheumatoid arthritis and class-IV function. J. Bone Joint Surg. Am. 71, 494–498. Guery, J., Favard, L., Sirveaux, F., Oudet, D., Mole, D., Walch, G., 2006. Reverse total shoulder arthroplasty. Survivorship analysis of eighty replacements followed for five to ten years. J. Bone Joint Surg. Am. 88, 1742–1747. Haines, J.F., Trail, I.A., Nuttall, D., Birch, A., Barrow, A., 2006. The results of arthroplasty in osteoarthritis of the shoulder. J. Bone Joint Surg. (Br.) 88, 496–501. Harrold, F., Wigderowitz, C., 2012. A three-dimensional analysis of humeral head retroversion. J. Shoulder Elbow Surg. 21, 612–617. Harrold, F., Wigderowitz, C., 2013. Humeral head arthroplasty and its ability to restore original humeral head geometry. J. Shoulder Elbow Surg. 22, 115–121. Harryman, D.T., Sidles, J.A., Harris, S.L., Lippitt, S.B., Matsen 3rd, F.A., 1995. The effect of articular conformity and the size of the humeral head component on laxity and
motion after glenohumeral arthroplasty. A study in cadavera. J. Bone Joint Surg. Am. 77, 555–563. Hasan, S.S., Leith, J.M., Campbell, B., Kapil, R., Smith, K.L., Matsen 3rd, F.A., 2002. Characteristics of unsatisfactory shoulder arthroplasties. J. Shoulder Elbow Surg. 11, 431–441. Howell, S.M., Galinat, B.J., Renzi, A.J., Marone, P.J., 1988. Normal and abnormal mechanics of the glenohumeral joint in the horizontal plane. J. Bone Joint Surg. Am. 70, 227–232. Iannotti, J.P., Gabriel, J.P., Schneck, S.L., Evans, B.G., Misra, S., 1992. The normal glenohumeral relationships. An anatomical study of one hundred and forty shoulders. J. Bone Joint Surg. Am. 74, 491–500. Karduna, A.R., Williams, G.R., Williams, J.L., Iannotti, J.P., 1996. Kinematics of the glenohumeral joint: influences of muscle forces, ligamentous constraints, and articular geometry. J. Orthop. Res. 14, 986–993. Kelkar, R., Wang, V.M., Flatow, E.L., Newton, P.M., Ateshian, G.A., Bigliani, L.U., Pawluk, R.J., Mow, V.C., 2001. Glenohumeral mechanics: a study of articular geometry, contact, and kinematics. J. Shoulder Elbow Surg. 10, 73–84. Levigne, C., Garret, J., Boileau, P., Alami, G., Favard, L., Walch, G., 2011. Scapular notching in reverse shoulder arthroplasty: is it important to avoid it and how? Clin. Orthop. Relat. Res. 469, 2512–2520. Levine, W.N., Fischer, C.R., Nguyen, D., Flatow, E.L., Ahmad, C.S., Bigliani, L.U., 2012. Long-term follow-up of shoulder hemiarthroplasty for glenohumeral osteoarthritis. J. Bone Joint Surg. Am. 94, e164. Li, G., Thomson, M., Dicarlo, E., Yang, X., Nestor, B., Bostrom, M.P., Camacho, N.P., 2005. A chemometric analysis for evaluation of early-stage cartilage degradation by infrared fiber-optic probe spectroscopy. Appl. Spectrosc. 59, 1527–1533. Neer 2nd, C.S., Kirby, R.M., 1982. Revision of humeral head and total shoulder arthroplasties. Clin. Orthop. Relat. Res. 189–195. Norris, T.R., Iannotti, J.P., 2002. Functional outcome after shoulder arthroplasty for primary osteoarthritis: a multicenter study. J. Shoulder Elbow Surg. 11, 130–135. Pearl, M.L., Volk, A.G., 1995. Retroversion of the proximal humerus in relationship to prosthetic replacement arthroplasty. J. Shoulder Elbow Surg. 4, 286–289. Pearl, M.L., Volk, A.G., 1996. Coronal plane geometry of the proximal humerus relevant to prosthetic arthroplasty. J. Shoulder Elbow Surg. 5, 320–326. Pearson, E.S., Hartley, H.O., 1972. Biometrika Tables for Statisticians. Cambridge University Press, Cambridge. Pfaeffle, H.J., Fischer, K.J., Manson, T.T., Tomaino, M.M., Herndon, J.H., Woo, S.L., 1999. A new methodology to measure load transfer through the forearm using multiple universal force sensors. J. Biomech. 32, 1331–1335. Radnay, C.S., Setter, K.J., Chambers, L., Levine, W.N., Bigliani, L.U., Ahmad, C.S., 2007. Total shoulder replacement compared with humeral head replacement for the treatment of primary glenohumeral osteoarthritis: a systematic review. J. Shoulder Elbow Surg. 16, 396–402. Raiss, P., Schmitt, M., Bruckner, T., Kasten, P., Pape, G., Loew, M., Zeifang, F., 2012. Results of cemented total shoulder replacement with a minimum follow-up of ten years. J. Bone Joint Surg. Am. 94, e1711-10. Robertson, D.D., Yuan, J., Bigliani, L.U., Flatow, E.L., Yamaguchi, K., 2000. Threedimensional analysis of the proximal part of the humerus: relevance to arthroplasty. J. Bone Joint Surg. Am. 82-A, 1594–1602. Sahara, W., Sugamoto, K., Murai, M., Tanaka, H., Yoshikawa, H., 2007. The three-dimensional motions of glenohumeral joint under semi-loaded condition during arm abduction using vertically open MRI. Clin. Biomech. 22, 304–312 (Epub 2006 Dec 29). Soslowsky, L.J., Flatow, E.L., Bigliani, L.U., Mow, V.C., 1992. Articular geometry of the glenohumeral joint. Clin. Orthop. 181–90. Spencer Jr., E.E., Valdevit, A., Kambic, H., Brems, J.J., Iannotti, J.P., 2005. The effect of humeral component anteversion on shoulder stability with glenoid component retroversion. J. Bone Joint Surg. Am. 87, 808–814. Sperling, J.W., Cofield, R.H., Rowland, C.M., 1998. Neer hemiarthroplasty and Neer total shoulder arthroplasty in patients fifty years old or less. Long-term results [see comments]. J. Bone Joint Surg. Am. 80, 464–473. Walch, G., Boileau, P., 1999. Prosthetic adaptability: a new concept for shoulder arthroplasty. J. Shoulder Elbow Surg. 8, 443–451. Warner, J.J., Bowen, M.K., Deng, X.H., Hannafin, J.A., Arnoczky, S.P., Warren, R.F., 1998. Articular contact patterns of the normal glenohumeral joint. J. Shoulder Elbow Surg. 7, 381–388.
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Please cite this article as: Harrold, F., et al., A novel osteotomy in shoulder joint replacement based on analysis of the cartilage/metaphyseal interface, Clin. Biomech. (2014), http://dx.doi.org/10.1016/j.clinbiomech.2014.08.008
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A novel osteotomy in shoulder joint replacement based on analysis of the cartilage/metaphyseal interface Fraser Harrold ⁎, Amar Malhas, Carlos Wigderowitz Department of Orthopaedic and Trauma Surgery, College of Medicine, Dentistry and Nursing, University of Dundee, TORT Centre, Ninewells Hospital and Medical School, Dundee DD1 9SY, Scotland, UK
a r t i c l e
i n f o
Article history: Received 9 February 2014 Accepted 19 August 2014 Keywords: Shoulder Arthroplasty Osteotomy Anatomy Humerus Geometry
a b s t r a c t Background: The accuracy of reconstruction is thought to impact on functional outcome following glenohumeral joint arthroplasty. The objective of this study was to define an area of minimal anatomic variation at the cartilage/ metaphyseal interface of the proximal humerus to optimize the osteotomy of the humeral head, enabling accurate reconstruction with a prosthetic component. Methods: Hand held digitization and 3D surface laser scanning techniques were used to digitize 24 cadaveric arms and determine the normal geometry. Each humeral head was then examined to identify the most consistent anatomical landmarks for the ideal osteotomy plane to optimize humeral component positioning. Findings: The novel, posterior referencing, osteotomy resulted in a mean increase in retroversion of only 0.4° when compared to the original geometry. A traditional anterior referencing osteotomy, by comparison, produced a mean increase in retroversion of 11°. In addition, the novel osteotomy only increased axial diameter by 0.71 mm and head height by 0.02 mm compared to an anterior referencing osteotomy (3.0 mm and 2.7 mm respectively). Interpretation: The traditional osteotomy, referencing the anterior border of the cartilage/metaphyseal interface potentially resulted in an increase in prosthetic head size and retroversion. The novel osteotomy, referencing from the posterior cartilage/metaphyseal interface enabled a more accurate recovery of head geometry. Importantly, the increase in retroversion created by the traditional osteotomy was not replicated with the novel technique. Referencing from the posterior cartilage/metaphyseal interface produced a more reliable osteotomy, more closely matching the original humeral geometry. Level of Evidence: Basic Science, Anatomic study, Computer model. © 2014 Elsevier Ltd. All rights reserved.
1. Introduction Survivorship of shoulder arthroplasty surgery in the literature is encouraging and represents the treatment of choice for degenerative joint diseases of the glenohumeral joint. Studies place the 10 year survivorship of anatomic shoulder replacement (ASR), with revision as an end-point, between 85 and 95% (Haines et al., 2006; Radnay et al., 2007; Raiss et al., 2012; Young et al., 2011). Reverse total shoulder replacement (RTSR) is also reported to have 90% survivorship at 10 years for revision (Guery et al., 2006). Shoulder hemiarthroplasty implants are reported to have 80% 10 year survivorship (Levine et al., 2012; Sperling et al., 1998). When other outcome measures are examined, shoulder arthroplasty surgery is less successful. By 10 years, approximately 50–70% of ASR demonstrate glenoid loosening on radiographic assessment (Haines
⁎ Corresponding author at: University Department of Orthopaedic & Trauma Surgery, Ninewells Hospital & Medical School, Dundee DD1 9SY, Scotland, UK. E-mail address: [email protected] (F. Harrold).
et al., 2006; Young et al., 2011). RTSR have reported lower glenoid loosing at 10 years (~ 20%) but up to 70% display inferior glenoid notching (Guery et al., 2006; Levigne et al., 2011). Patients' satisfaction can also be poor with up to 50% of ASR (Sperling et al., 1998) and 75% of hemiarthroplasty replacements were deemed ‘unsatisfactory’ or ‘unsuccessful’ (Levine et al., 2012). In some series of ASR up to 74% of patients complain of stiffness and 35% complain of instability (Hasan et al., 2002). Evidence in the literature supports the important role that component positioning and glenohumeral alignment play in implant survivorship and function (Hasan et al., 2002; Neer and Kirby, 1982; Norris and Iannotti, 2002; Spencer et al., 2005; Wirth and Rockwood, 1994, 1996). Franta et al. postulated that glenohumeral mal-alignment was the most likely cause of glenoid loosening in their series of 282 unsatisfactoy shoulder arthroplasties (Franta et al., 2007). Underlying, glenohumeral mal-alignment from the original disease process may also play a role. If eccentric glenoid wear is present at the time of the primary arthroplasty, there is an increased risk of glenoid wear in ASR (Haines et al., 2006) and lower patient satisfaction in shoulder hemiarthroplasty surgery (Levine et al., 2012).
http://dx.doi.org/10.1016/j.clinbiomech.2014.08.008 0268-0033/© 2014 Elsevier Ltd. All rights reserved.
Please cite this article as: Harrold, F., et al., A novel osteotomy in shoulder joint replacement based on analysis of the cartilage/metaphyseal interface, Clin. Biomech. (2014), http://dx.doi.org/10.1016/j.clinbiomech.2014.08.008
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The highly variable anatomy of the proximal humerus is an important consideration that modern prosthetic components are designed to accommodate (Boileau and Walch, 1997; Iannotti et al., 1992; Robertson et al., 2000). Failure to address the restoration of glenohumeral alignment (particularly retroversion) is thought to lead to eccentric loading, glenoid wear and glenoid loosening (Figgie et al., 1988; Pearl and Volk, 1996). There may also be a change in the centre of rotation impacting of joint stability (Boileau and Walch, 1997; Pearl and Volk, 1996). Individual humeral retroversion can range from 3° to 40° although the mean is approximately 20° (Harrold and Wigderowitz, 2012). In order to restore an individual's proximal humeral morphology, a precise osteotomy of the humeral head at the level of the anatomical neck is required (Walch and Boileau, 1999). The anterior cartilage/metaphyseal interface is used as a reliable anatomical landmark to facilitate an accurate osteotomy (Pearl and Volk, 1995). Recent evidence has demonstrated that not only is there anatomical variation in the cartilage/metaphyseal landmark but also that the humeral head is not truly spherical (Harrold and Wigderowitz, 2012). An osteotomy that is therefore based on anterior referencing can significantly increase retroversion by 11° (an increase of almost 40%) and decrease component inclination by 5° (Harrold and Wigderowitz, 2013). The purpose of the study was to analyse the cartilage/metaphyseal junction as it relates to the osteotomy and determine the optimum landmarks, with which to perform an osteotomy, to recover humeral head geometry accurately. 2. Methods Twenty-four cadaveric full arms, preserved in formalin, without skeletal abnormality and that had not undergone a previous surgical procedure were disarticulated and all soft tissues removed. Eighteen specimens were matched pairs a further two were right humeri and four were left humeri. There were fourteen females and ten males ranging in age from 68 to 99 years (average, 84 years, SD 8.4 years). A precision reference cube was attached to the greater tuberosity of each humerus to enable two independently collected data sets to be combined (Pfaeffle et al., 1999). The details of data collection have been described, previously, by Harrold and Wigderowitz (Harrold and Wigderowitz, 2012, 2013). For each specimen, the following anatomical landmarks were identified and marked: (1) the circumference of the anatomical neck; (2) the
most superior point of the articular surface at the insertion of the supraspinatus tendon, the corresponding lowest point of the articular surface at the cartilage/metaphyseal interface; (3) the medial epicondyle and the lateral epicondyle. Each specimen was then mounted, rigidly, on a custom-built jig. Two instruments, a Microscribe 3D-X handheld digitizer (Immersion Corp., San Jose, CA, USA) and an Arius3D colour surface laser scanner (Metrologic MTI; Metrologic Instruments, Meylan, France) were used to acquire the data for the surface geometry of each humerus. The precision reference cubes were used as a common reference to transform the Microscribe 3D-X digitizer data to the same coordinate system as the surface scanner data within 3DReshaper software (Technodigit, Gleizé, France). The combined data was then imported into Rhinocerus NURBS modelling software and graphically presented (Fig. 1a and b). For each model the following were constructed: (1) the humeral shaft as a line through the centre of a best fit cylinder representing the proximal humeral data points extending from the surgical neck to the distal insertion of the deltoid; (2) the transepicondylar line between the medial and lateral epicondyles; (3) the articular portion of the humeral head was used to create a sphere which was divided in the saggital and coronal planes to determine the diameter of the head in the two planes; (4) a best fit plane formed and bounded by the circumference of the anatomical neck. The details of model construction have previously been described by Harrold and Wigderowitz (Harrold and Wigderowitz, 2013). The cartilage/metaphyseal interface was divided into 24 discrete points representing a clock face (Fig. 2). The 12 o'clock position was defined as the point along the cartilage/metaphyseal border adjacent to the insertion of the supraspinatus tendon. The 6 o'clock position was defined as the most medial and inferior position of the cartilage/ metaphyseal border. Clockwise and anticlockwise reference numbers were used for left and right specimens, respectively. An ideal osteotomy plane was then created along the cartilage/ metaphyseal interface fulfilling the following criteria: • Replicated the inclination and retroversion angles measured for the original geometry of the humeral head • Replicated head height for the original geometry of the humeral head • Replicated radius of curvature of the original humeral head created from the proximal 80% of the articular surface The constructed graphical model was used to simulate resection of the articular surface based on an idealised prosthetic implant. The simulated osteotomy plane created a frame of reference to analyse the
Cartilage/metaphyseal boundary Upper and lower boundary of best fit cylinder
Shaft axis constructed from best fit cylinder
Best fit sphere constructed from articular surface data
Transepicondylar axis a
b
Figs. 1. a and 1b Model constructed in Rhinocerus NURBS modelling software (1a) with magnified view of the modelled proximal humerus (1b).
Please cite this article as: Harrold, F., et al., A novel osteotomy in shoulder joint replacement based on analysis of the cartilage/metaphyseal interface, Clin. Biomech. (2014), http://dx.doi.org/10.1016/j.clinbiomech.2014.08.008
F. Harrold et al. / Clinical Biomechanics xxx (2014) xxx–xxx
3
24
Legend
6
H: Superior pole L: Inferior pole A: Anterior margin P: Posterior margin
12
Fig. 2. Division of the humeral head using 24 increments for left and right specimens.
cartilage/metaphyseal interface; for each specimen, a deviation analysis was performed comparing the point cloud data for the cartilage/ metaphyseal interface to the ideal osteotomy plane. Rhinoceros NURBS modelling software was used to determine the perpendicular distance of each point from the ideal plane (Fig. 3). The degree of
deviation of the cartilage/metaphyseal point cloud data was then measured at each of the twenty-four increments. The analysis was performed on all specimens. The points of least deviation were used as a reference to construct a plane through the humeral head. The new plane was then used to
Points representing the cartilage/calcar interface Graphical representation of the point deviation from the ideal osteotomy plane H •
•
Legend H: Superior pole L: Inferior pole A: Anterior margin P: Posterior margin
A
P
• • L
Shaft axis Ideal osteotomy plane
Fig. 3. Plane constructed based on the idealised osteotomy and a deviation analysis of each point along the cartilage/metaphyseal interface relative to the plane.
Please cite this article as: Harrold, F., et al., A novel osteotomy in shoulder joint replacement based on analysis of the cartilage/metaphyseal interface, Clin. Biomech. (2014), http://dx.doi.org/10.1016/j.clinbiomech.2014.08.008
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simulate an osteotomy and an idealised fully adaptable spherical prosthetic head was constructed and placed on the simulated osteotomy plane. The lengths of the coronal diameter and height of the resected head were used to determine the diameter and head height of the prosthetic head, respectively. The inclination, retroversion, coronal and axial diameters and radii of curvature (total, coronal and axial radii of curvature) were calculated for each specimen and compared to the original humeral head parameters. The distribution of all descriptors was tested for normality using a Shapiro–Wilk's W test. The critical value for the Shapiro–Wilk's W test at the 0.05 level for 24 specimens was 0.916 (Pearson and Hartley, 1972). The data was found to be normally distributed for all parameters. Descriptive statistics were computed for all outcome variables and paired t-tests used to assess the differences between the normal head geometry and prosthetic implant utilizing the novel osteotomy. All the reported P values were two-tailed with P b 0.05 considered to be statistically significant. SPSS 14.0 software package (SPSS Inc., Chicago, Illinois, USA) was used for all statistical analysis. 3. Results The results revealed marked differences between the cartilage/ metaphyseal interface when compared to the ideal osteotomy plane at certain points around the cartilage/metaphyseal interface. The points at the upper and lower poles represented the points of greatest deviation and with the widest confidence intervals. The smallest deviations were noted along the posterior margin of the cartilage/ metaphyseal interface (Fig. 4). Eight positions were identified with deviations of less than 1.5 mm and associated standard deviations of less than 10 mm (Table 1). The interface with least deviation was posteriorly between the 2 o'clock and 4 o'clock positions. Two points were identified anteriorly with small average deviations and narrow standard deviations, between 8 and 9 o'clock and between 10 and 11 o'clock. The points of reference with the least deviation were then used to construct a novel osteotomy plane. On average, the simulated osteotomy resulted in an increase in retroversion of the prosthetic head of 0.4° from 18.5 (SD 9.0°; range, 2.7 to 37.4°) to 18.9 (SD 9°; range, 14.0 to 58.7°) (Table 2). The result was not statistically significant (P = 0.528). There was a statistically significant (P b 0.001) mean decrease in the inclination angle of the prosthetic head on the simulated osteotomy of 3.2° when compared to the inclination of the original humeral head (Mean, 136.9; SD, 4.7°; range, 126.3 to 143.2°). The osteotomy resulted in a mean coronal diameter (Mean, 46.8; SD, 2.5 mm; range, 41.3 to 51.3 mm) that was, on average, 1.9 (SD, 1.6 mm;
Mean deviation (Millimetres)
30.0 20.0 10.0 0.0 0
1
2
3
4
5
6
7
8
9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
-10.0 -20.0 -30.0 -40.0
Clockface Position Fig. 4. Average, standard deviation and 95% confidence intervals for deviation of cartilage/ metaphyseal interface at each clock face reference position from an optimal osteotomy plane.
95 percentile range, 1.2 to 2.6 mm) narrower than the measured diameter of the original head (Mean, 48.8; SD 3.2 mm; range, 42.7 to 55.1 mm); a result that was statistically significant (P b 0.001). In the saggital plane, a significant difference of 0.7 (SD, 1.6 mm; 95 percentile range, 1.8 to 3.2 mm) was noted between the mean axial diameter of the original head (Mean, 43.6; SD 2.5 mm; range, 38.9 to 49.0 mm) and simulated osteotomy surface (Mean, 44.3; SD, 2.2 mm; range, 40.0 to 47.5 mm) (P = 0.035). Further, a statistically significant difference was found between the axial and coronal diameters of the osteotomised surface of 2.5 (SD, 1.7 mm; range, −2.6 to 4.9 mm) and range within the 95 percentile of between 1.8 and 3.2 mm (p b 0.001). The mean difference between the coronal and axial diameters for the normal humeral head geometry was 5.2 (SD, 2.4 mm; range, 0.6 to 11.6 mm) less than the coronal diameter. The mean head height of the resected segment was almost identical to the original humeral head (P = 0.892). The mean prosthetic head height was 16.9 (SD, 1.6 mm) compared to 16.9 (SD, 1.5 mm) for the original geometry; a mean difference of −0.02 (SD, 0.8 mm). The radii of curvature of the original head (Mean, 24.0; SD, 1.2 mm; range, 22.1 to 26.8 mm) and simulated head, (Mean, 24.7; SD, 1.3 mm; range, 22.3 to 27.8 mm) were statistically different (P b 0.001). In the coronal plane the difference between the idealised prosthetic radius of curvature and the resected segment was 0.1 (SD, 0.2 mm; 95 percentile range, 0.02–0.17 mm) and was statistically significantly different (P =016). Further, in the axial plane a statistically significant difference of 1.7 mm (SD, 1.0 mm) was noted between the prosthesis and original head (Mean, 23.0; SD, 1.1 mm; range, 21.3 to 25.2 mm) (P b 0.001). 4. Discussion The evidence from this study demonstrates that the area with the least anatomic variation is the posterior margin of the cartilage/ metaphyseal interface and not the anterior margin (most commonly used reference) (Pearl and Volk, 1995; Walch and Boileau, 1999). By incorporating this principle into a new posterior referencing osteotomy, the proximal humeral version may be more reliably restored when compared to a traditional anterior referencing osteotomy (Harrold and Wigderowitz, 2013). It has been established, previously, that the cartilage/metaphyseal interface is not a perfect circle forming a cap of a sphere (Harrold and Wigderowitz, 2012, 2013). There is a wide degree of variability of the cartilage/metaphyseal interface when compared to an ideal osteotomy plane. However, the degree of variation at this interface is not consistent. If specific points are chosen, the cartilage/metaphyseal interface could be used as an anatomical landmark for an osteotomy. The results demonstrated that the posterior margin provided the most consistent reference, (3.6 mm variation) while the inferior pole and anterior margin displayed slightly greater variation (4 mm). The greatest variation of the cartilage/metaphyseal interface appeared towards the superior pole of the cartilage surface adjacent to the insertion of the supraspinatus tendon. In extremes of abduction, the glenoid does not make contact with the humeral head at the superior articular surface, seen on all the specimens, under normal conditions. This extension of cartilage may represent an interface between the humeral head and supraspinatus tendon rather than a true articulation with the glenoid (Ateshian et al., 1991; Kelkar et al., 2001; Sahara et al., 2007; Warner et al., 1998). Variations in the cartilage structure based on loading conditions have been reported by a number of authors which may correlate with the topographical variation (Li et al., 2005; Soslowsky et al., 1992). Despite the variation in geometry of the cartilage/metaphyseal interface, a pattern did emerge in which the cartilage/metaphyseal interface approximated to an ideal osteotomy plane and the variability between specimens was small. The computer simulations of the novel osteotomy technique based on three reference points along the
Please cite this article as: Harrold, F., et al., A novel osteotomy in shoulder joint replacement based on analysis of the cartilage/metaphyseal interface, Clin. Biomech. (2014), http://dx.doi.org/10.1016/j.clinbiomech.2014.08.008
F. Harrold et al. / Clinical Biomechanics xxx (2014) xxx–xxx
5
Table 1 Descriptive statistics for the deviation of the cartilage/metaphyseal interface from the ideal osteotomy plane (millimetres). Position
H
1
2
3
5
A
7
8
9
10
11
Mean St.dev 95% (Upper) 95% (Lower)
−13.2 10.7 3.6 −32.6
−10.0 9.7 2.2 −27.5
−5.1 6.4 3.3 −15.4
1.1 6.3 8.8 −8.7
4 6.2 6.5 17.5 −3.3
5.4 7.1 14.6 −6.2
3.6 8.2 12.5 −15.3
1.5 8.5 10.6 −10.4
−2.4 8.0 7.6 −14.8
−5.6 6.7 4.2 −15.8
−6.5 8.1 6.5 −18.4
−7.3 12.0 13.9 −22.6
Position
L
13
14
15
16
17
19
20
21
22
23
Mean St.dev 95% (Upper) 95% (Lower)
−4.0 13.6 17.8 −24.4
−2.7 12.0 11.8 −19.8
−3.2 11.7 11.7 −23.3
1.3 9.7 18.0 −9.3
1.4 9.2 14.7 −11.1
1.2 7.1 13.2 −9.2
1.3 6.8 11.7 −11.1
1.4 6.0 9.4 −7.5
−2.8 7.7 8.1 −12.3
−7.3 7.4 1.9 −17.6
−11.3 8.5 1.3 −23.7
cartilage/metaphyseal interface resulted in the removal of a segment of the humeral head that was similar in size to the articular portion of the original head. Further, the osteotomy resulted in only small changes to the orientation of the simulated prosthetic head. The osteotomy resulted in almost identical recovery in the retroversion angle of the prosthetic head when compared to the original humeral head geometry. With the traditional osteotomy, referencing the anterior cartilage/metaphyseal margin, resulted in an average increase in retroversion of 11° (Harrold and Wigderowitz, 2013) (Fig. 5). Although the anterior margin of the cartilage/metaphyseal interface had slightly more variation than the posterior margin (4 mm versus 3.6 mm), simply using the anterior margin as a reference tended to amplify the error in orientation resulting in a significant increase in retroversion. The novel osteotomy resulted in an average increase in retroversion of only 0.4°. Accurate restoration of retroversion is thought to provide a more stable joint with balanced anterior and posterior structures of the rotator cuff (Boileau and Walch, 1997; Pearl and Volk, 1995). Also, the novel osteotomy may avoid creating tension on the posterior capsule, identified by Boileau et al. as a problem (Boileau et al., 2002). Further, the technique may reduce the potential for eccentric loading on the glenoid noted in the traditional cut, minimising the risk of excessive glenoid wear and glenoid loosening (Figgie et al., 1988; Pearl and Volk, 1996). The theoretical risk of damaging the rotator cuff with a retroverted cut, noted by a number of authors (Cofield and Edgerton, 1990; Figgie et al., 1988; Friedman et al., 1989) may also be reduced with the novel technique. There were some similarities between the novel and traditional osteotomy. Both osteotomies produced a reduction in inclination (novel osteotomy 3.2°, traditional osteotomy 4°) that fall within the normal range of translations of the joint centre during active motion and are therefore unlikely to be of clinical significance (Howell et al., 1988; Karduna et al., 1996; Kelkar et al., 2001; Sahara et al., 2007).
P 0.3 6.7 9.1 −8.3
Head height was restored within the 5 mm height deemed to be clinically significant (a variation of 0.02 mm in the novel osteotomy and 2.7 mm in the traditional osteotomy) (Harryman et al., 1995; Williams et al., 2001). Both osteotomies restored the coronal and axial diameters to within 2.6 mm. The radius of curvature in both osteotomies were reproduced to within the 2–3 mm threshold described by Iannotti (Iannotti et al., 1992) and Kelkar (Kelkar et al., 2001). The study was based on previous work using an established modelling technique and may be limited by the sample size; the study was powered to examine the difference between the traditional osteotomy and original head geometry (Harrold and Wigderowitz, 2012, 2013). The variation in results between this study and those of other authors may be associated with the sample size or measurement technique. This could either be the instrumentation selected or the reference points used to define a particular descriptor. Further, the range of data was narrower in this study and, likely, reflects the size of the sample. The principle of using three of the reference points along the cartilage/ metaphyseal interface and, in particular, the posterior cartilage/ metaphyseal margin has been developed by JRI Orthopaedics Ltd in their resurfacing instrumentation. The guidewire inserted into the centre of the humeral head is based on a jig which centres the wire, referencing the posterior cartilage/metaphyseal interface. Similar instrumentation could be used with the addition of a cutting jig attached to the centred guidewire, allowing the osteotomy to be undertaken along the anterior margin of the cartilage/metaphyseal junction but referenced from the posterior margin. 5. Conclusions By applying computer generated simulations, it was possible to identify repeatable reference points along the cartilage/metaphyseal interface to create a posterior referencing osteotomy of the proximal humerus that improved recovery of humeral head geometry in
Table 2 Differences between the geometry of the osteotomised head and original geometry. Original:Idealised
Paired differences Mean
Inclination (deg) Retroversion (deg) Coronal diameter (mm) Axial diameter (mm) Head height (mm) ROC (mm) Axial ROC (mm) Coronal ROC (mm)
3.18 −0.40 1.93 −0.71 −0.02 −0.70 1.70 0.09
Std. dev.
3.99 3.05 1.62 1.56 0.79 0.54 0.95 0.18
Std. error mean
0.82 0.62 0.33 0.32 0.16 0.11 0.19 0.07
t
df
Sig. (2-tailed)
3.90 −0.64 5.82 −2.23 −0.14 −6.29 8.74 2.60
23 23 23 23 23 23 23 23
b0.001 0.528 b0.001 0.035 0.892 N0.001 N0.001 0.016
95% Confidence interval Lower
Upper
1.49 −1.69 1.24 −1.37 −0.35 −0.93 1.29 0.02
4.86 0.89 2.61 −0.05 0.31 −0.47 2.10 0.17
Please cite this article as: Harrold, F., et al., A novel osteotomy in shoulder joint replacement based on analysis of the cartilage/metaphyseal interface, Clin. Biomech. (2014), http://dx.doi.org/10.1016/j.clinbiomech.2014.08.008
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F. Harrold et al. / Clinical Biomechanics xxx (2014) xxx–xxx
Fig. 5. A–C. A. Antero-posterior view of the humeral head demonstrating the anterior reference point on the cartilage–metaphyseal junction (dotted line) traditionally used to reference the neck cut. B. Supero-lateral view of the humeral head (deltoid splitting approach) demonstrating a mean 11° over-estimation of retroversion from the true retroversion using anterior referencing alone. C. Posterior referencing with a mean overestimation of true retroversion of 0.4° ((AR), Anterior reference; (PR), Posterior reference; (TR), True retroversion; (LT) lesser tuberosity; (GT), greater tuberosity).
shoulder hemiarthroplasty. Application of the technique in shoulder hemiarthroplasty and total shoulder replacement may improve the overall biomechanics of the glenohumeral arthroplasty and functional outcome. The principle of using three of the reference points along the cartilage/metaphyseal interface and, in particular, the posterior cartilage/metaphyseal margin requires further exploration and development in terms of prosthesis design and instrumentation before applying in-vivo. Conflict of interest statement The authors confirm that there are no financial and personal relationships with other people or organizations that could inappropriately influence (bias) the present work. Acknowledgements This study was partly funded with a grant from the Anonymous Trust, Dundee University. The trust had no part to play in the study other than funding. The Authors wish to thank the Departments of Anatomy at both the University of Dundee and St Andrews University. References Ateshian, G.A., Soslowsky, L.J., Mow, V.C., 1991. Quantitation of articular surface topography and cartilage thickness in knee joints using stereophotogrammetry. J. Biomech. 24, 761–776. Boileau, P., Walch, G., 1997. The three-dimensional geometry of the proximal humerus. Implications for surgical technique and prosthetic design. J. Bone Joint Surg. (Br.) 79, 857–865. Boileau, P., Krishnan, S.G., Tinsi, L., Walch, G., Coste, J.S., Mole, D., 2002. Tuberosity malposition and migration: reasons for poor outcomes after hemiarthroplasty for displaced fractures of the proximal humerus. J. Shoulder Elbow Surg. 11, 401–412. Cofield, R.H., Edgerton, B.C., 1990. Total shoulder arthroplasty: complications and revision surgery. Instr. Course Lect. 39, 449–462. Figgie, H.E.D., Inglis, A.E., Goldberg, V.M., Ranawat, C.S., Figgie, M.P., Wile, J.M., 1988. An analysis of factors affecting the long-term results of total shoulder arthroplasty in inflammatory arthritis. J. Arthroplasty 3, 123–130. Franta, A.K., Lenters, T.R., Mounce, D., Neradilek, B., Matsen 3rd, F.A., 2007. The complex characteristics of 282 unsatisfactory shoulder arthroplasties. J. Shoulder Elbow Surg. 16, 555–562. Friedman, R.J., Thornhill, T.S., Thomas, W.H., Sledge, C.B., 1989. Non-constrained total shoulder replacement in patients who have rheumatoid arthritis and class-IV function. J. Bone Joint Surg. Am. 71, 494–498. Guery, J., Favard, L., Sirveaux, F., Oudet, D., Mole, D., Walch, G., 2006. Reverse total shoulder arthroplasty. Survivorship analysis of eighty replacements followed for five to ten years. J. Bone Joint Surg. Am. 88, 1742–1747. Haines, J.F., Trail, I.A., Nuttall, D., Birch, A., Barrow, A., 2006. The results of arthroplasty in osteoarthritis of the shoulder. J. Bone Joint Surg. (Br.) 88, 496–501. Harrold, F., Wigderowitz, C., 2012. A three-dimensional analysis of humeral head retroversion. J. Shoulder Elbow Surg. 21, 612–617. Harrold, F., Wigderowitz, C., 2013. Humeral head arthroplasty and its ability to restore original humeral head geometry. J. Shoulder Elbow Surg. 22, 115–121. Harryman, D.T., Sidles, J.A., Harris, S.L., Lippitt, S.B., Matsen 3rd, F.A., 1995. The effect of articular conformity and the size of the humeral head component on laxity and
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Please cite this article as: Harrold, F., et al., A novel osteotomy in shoulder joint replacement based on analysis of the cartilage/metaphyseal interface, Clin. Biomech. (2014), http://dx.doi.org/10.1016/j.clinbiomech.2014.08.008
