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Orthopaedic Proceedings
Vol. 103-B, Issue SUPP_1 | Pages 2 - 2
1 Feb 2021
Pizzamiglio C Fattori A Rovere F Poon P Pressacco M
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Background

Stemless prostheses are recognized to be an effective solution for anatomic total shoulder arthroplasty (TSA) while providing bone preservation and shortest operating time. Reverse shoulder arthroplasty (RSA) with stemless has not showed the same effectiveness, as clinical and biomechanical performances strongly depend on the design. The main concern is related to stability and bone response due to the changed biomechanical conditions; few studies have analyzed these effects in anatomic designs through Finite Element Analysis (FEA), however there is currently no study analyzing the reverse configuration. Additionally, most of the studies do not consider the effect of changing the neck-shaft angle (NSA) resection of the humerus nor the proper assignment of spatial bone properties to the bone models used in the simulations. The aim of this FEA study is to analyze bone response and primary stability of the SMR Stemless prosthesis in reverse with two different NSA cuts and two different reverse angled liners, in bone models with properties assigned using a quantitative computed tomography (QCT) methodology.

Methods

Sixteen fresh-frozen cadaveric humeri were modelled using the QCT-based finite element methodology. The humeri were CT-scanned with a hydroxyapatite phantom to allow spatial bone properties assignment [Fig. 1]. Two implanted SMR stemless reverse configurations were considered for each humerus: a 150°-NSA cut with a 0° liner and a 135°-NSA cut with a 7° sloped liner [Fig. 2]. A 105° abduction loading condition was simulated on both the implanted reverse models and the intact (anatomic) humerus; load components were derived from previous dynamic biomechanical simulations on RSA implants for the implanted stemless models and from the OrthoLoad database for the intact humeri. The postoperative bone volume expected to resorb or remodel [Fig. 3a] in the implanted humeri were compared with their intact models in sixteen metaphyseal regions of interest (four 5-mm thick layers parallel to the resection and four anatomical quadrants) by means of a three-way repeated measures ANOVA followed by post hoc tests with Bonferroni correction. In order to evaluate primary stability, micromotions at the bone-Trabecular Titanium interface [Fig. 3b] were compared between the two configurations using a Wilcoxon matched-pairs signed-rank test. The significance level α was set to 0.05.


Orthopaedic Proceedings
Vol. 94-B, Issue SUPP_XLI | Pages 73 - 73
1 Sep 2012
Rupasinghe S Poon P
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The radius has a sagittal and coronal bow. Fractures are often treated with volar anterior plating. However, the sagittal bow is often overlooked when plating. This study looks at radial morphology and the effect of plating the proximal radius, with straight plates then contoured plates bowed in the sagittal plane. We report our findings and their effect on forearm rotation.

Morphology was investigated using fourteen radii. Attention was made to the proximal shaft of the radius and its sagittal bow, from this 6, 7 and 8 hole plates were contoured to fit this bow. A simple transverse fracture was then made at the apex of this bow. Supination and pronation was then compared when plating with a straight plate and a contoured plate. Ten cadavers had the ulna plating at the same level. The effect on rotation of fractures plated in the distal third shaft was also measured

A significant reduction in rotation was found, when a proximal radius fracture was plated with straight plate compared to a contoured plate: 10.8, 12.8, 21.7 degrees (p<0.05 for 6, 7, 8 hole plates). Forearm rotation was decreased further when a longer plate was used. Ulna or distal shaft plating did not reduce rotation.

This study has shown a significant sagittal bow of the proximal shaft of the radius. Plating this with contoured plates in the sagittal plane improves rotation when compared to straight plates. Additional ulna plating is not a source of reduced forearm rotation.


Introduction

Reverse shoulder replacement is a surgical option for cuff tear arthropathy. However scapular notching is a concern. Newer designs of glenospheres are available to reduce scapular notching. Eccentric glenosphere with a lowered centre of rotation have been shown to improve range of adduction in vitro. We hypothesize that the eccentric glenosphere improve clinical outcomes and reduce scapular notching.

Method

This is an ongoing randomized controlled double blind prospective clinical trial. Patients 70 years or older at North Shore hospital who have a diagnosis of cuff tear arthropathy and require surgery were consented for this study. Patients were allocated a concentric or eccentric 36 mm glenosphere intraoperatively, using a computer generated randomization contained in a sealed envelope. The surgical technique and post operative rehabilitation were standardized. Patients were followed up by a research nurse and postoperative radiographs were also taken at regular intervals. Clinical assessment include a visual analogue pain score, subjective shoulder rating, American Shoulder and Elbow Society Score, and Oxford shoulder score. Complications were checked for and radiographs were assessed for scapular notching.


Orthopaedic Proceedings
Vol. 93-B, Issue SUPP_III | Pages 378 - 378
1 Jul 2011
Young S Walker C Poon P
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Cuff tear arthropathy represents a challenge to the shoulder arthoplasty surgeon. The poor results of conventional total shoulder arthroplasty in cuff deficient shoulders secondary to glenoid component loosening have meant hemiarthroplasty has traditionally been the preferred surgical option. Recently reverse total shoulder arthroplasty (RSA) has gained increasing popularity due to a clinical perception of an improved functional outcome, despite the absence of comparative data. The aim of this study was to compare the early functional results of Hemiarthroplasty versus RSA in the management of cuff-tear arthropathy.

102 primary hemiarthroplasties performed for cuff tear arthropathy were compared against 102 RSAs performed for the same diagnosis. Patients were identified from the New Zealand National Joint Registry and matched for age, sex, and American Society of Anesthesiologists (ASA) scores. Oxford shoulder scores (OSS) were collected at 6 months and 5 years post operatively and were compared between the two groups, together with mortality and re-revision rates.

There were 51 males and 51 females in each group, with a mean age of 71.6 in the Hemiarthroplasty group and 72.6 in the RSA group. The mean ASA score was 2.2 in both groups. The mean OSS was 31.1 in the hemiar-throplasty group and 38.1 in the RSA group. At follow up, there were 7 revisions in the hemiarthroplasty group and 5 in the RSA group. No difference in mortality was seen between the two groups.

This study provides the first direct evidence of a improved functional outcome of RSA compared to Hemiarthroplasty in the treatment of patients with cuff tear arthropathy. Longer term follow up is needed to confirm that the improved function is maintained, and that late complications such as component loosening remain comparable between the two groups.


Orthopaedic Proceedings
Vol. 93-B, Issue SUPP_III | Pages 379 - 380
1 Jul 2011
Foliaki S Poon P
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Total elbow arthroplasty is usually performed through a posterior approach. The management of the triceps tendon insertion include; Triceps division (V-Y Triceps turn down), Detachment of the Triceps insertion either by triceps splitting (Gschwind approach) or triceps reflecting (Bryan-Morrey approach), or by leaving the Triceps insertion intact (Triceps On approach). The ideal approach needs to meet three broad criteria; firstly it should be quick and easy, secondly it should offer excellent exposure and thirdly it should have low morbidity to the Triceps tendon. An approach that is also versatile provides an additional advantage.

The purpose of this study was to present and discuss the surgical technique of a “new” posterior approach to the elbow. To biomechanically evaluate and compare the strength of the Triceps tendon repair with the Bryan-Morrey approach (recently demonstrated in a cadaveric study to be the strongest of three methods of management of the Triceps tendon).

The Bryan-Morrey and Oxford approach were each performed on fourteen pairs of cadaveric elbows with the two Triceps tendon repairs carried out. The contra-lateral elbow served as the control. The specimens were then mounted on a material testing system and a constant velocity elongation was applied.

This new approach demonstrated a significant reduction in operative time as well as providing excellent exposure suitable for multiple indications. Final analysis of the data using % ultimate strength loss (%USL) compared to the control specimens as the ultimate end point showed this new approach is as strong as the Bryan-Morrey approach with %USL of −40% for both approaches.


Orthopaedic Proceedings
Vol. 92-B, Issue SUPP_I | Pages 222 - 222
1 Mar 2010
Chou J Poon P
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This biomechanical study aims to assess the different designs of glenospheres in SMR reverse total shoulder replacement in the degree of micromotion following dynamic cyclic loading, and its implication for risk of glenoid component loosening. The eccentric designs of glenospheres allowed greater range of motion from improvement in adduction. The eccentric placement of central fixation peg on the glenosphere has raised concerns of increasing micromotion of the baseplate-bone interface during cyclic loading.

In our method, the four different designs of glenospheres were tested; 36mm concentric (Standard), 36mm eccentric, 44mm concentric and 44 eccentric glenospheres. Each glenosphere underwent a thousand cycles of shear loading at four different positions of humeral abduction. The micromotion of each glenosphere baseplate were measured and compared. The 36mm eccentric glenopshere has overall the highest degree of micromotion; its degree of movement was well below the accepted 150 micrometer as the threshold for bony ingrowth inhibition.


Orthopaedic Proceedings
Vol. 92-B, Issue SUPP_I | Pages 221 - 221
1 Mar 2010
Young S Turner P Everts N Segal B Poon P
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Treatment of complex proximal humeral fractures remains controversial. In situations where accurate fracture reduction and fixation cannot be obtained, arthroplasty may be the preferred surgical option. The traditional operation of hemiarthroplasty in these situations is technically challenging, and a good functional outcome is dependent on reduction and healing of the tuberosities. Reverse Shoulder Arthroplasty (RSA) has been suggested as an alternative, and we sought to analyse and compare functional outcomes following the two procedures.

Ten patients who underwent hemiarthroplasty for acute fracture of the proximal humerus between 1999 and 2003 were reviewed. All fractures were assessed intraoperatively for open reduction and internal fixation of the fracture, but deemed to be unsuitable for fixation. From 2003 our management in this clinical situation changed, and ten subsequent patients underwent reverse shoulder arthroplasty using the S.M.R. reverse shoulder prosthesis (Systema Multiplana Randell, Lima, Italy). Clinical and radiological follow up was carried out at a mean of 31 months (hemiarthroplasty patients) and 15 months (RSA patients) post operatively.

Subjectively seven of 10 patients in the reverse group and seven of 10 patients in the hemiarthroplasty group rated their outcome as ‘very good’ or ‘excellent’. The mean ASES scores were 65 (range 40–88) in the reverse group and 67 (26–100) in the hemiarthroplasty group. The mean Oxford shoulder score was 29 (15–56) in the reverse group and 22 (12–34) in the hemiarthroplasty group. The mean active forward elevation in the hemiarthroplasty group was 108° (range 50–180) and in the reverse group 115° (45–40), and active external rotation 49° (5–105) and 48° (10–90) respectively. Differences in outcome scores between the two groups were not statistic ally significant (p value> 0.05).

This study provides the first direct comparison between RSA and hemiarthroplasty for complex proximal humeral fractures. The expected functional gains with Reverse shoulder arthroplasty were not seen, suggesting its use as the primary treatment for acute fracture should remain guarded.


Orthopaedic Proceedings
Vol. 91-B, Issue SUPP_II | Pages 339 - 340
1 May 2009
Misur P Poon P
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Septic arthritis of the knee is an uncommon complication of arthroscopic anterior cruciate ligament reconstruction, with a reported incidence ranging from 0.14% to 1.7% in recent publications. In this study, we assess the clinical presentation, management and early outcome of patients with septic arthritis of the knee following anterior cruciate ligament reconstruction. Literature on this uncommon complication is sparse.

The North Shore and Auckland City Hospital Orthopaedic databases were searched and 13 patients were identified as having been treated for septic arthritis of the knee following anterior cruciate ligament reconstruction in the period from July 2002 to August 2006. Their clinical records were reviewed to compile information regarding their presentation and management. Five of these patients were also recalled for clinical follow-up at an average time of 16 months. We reviewed knee range of motion, stability, functional testing in vertical and horizontal jumps and radiographic changes. Clinical outcomes were further assessed using the Tenger, Lysholm and International Knee Documentation Committee Scores.

The patients reviewed had a mean age of 26 years and presented to hospital at an average of 16 days after their autologous ACL reconstruction surgery. All had initial elevation of inflammatory markers with a mean CRP of 189mg/L (68 – 295) and mean ESR of 71mm in one hr (10 – 112.) Mean peripheral WCC on presentation was 12.3 (9.5 – 22.4.) Initial knee aspirates were performed on all patients and yielded a mean specimen WCC of 60,900 x 106/L. Of the 13 patients, six had S. epidermidis, three had S. aureus, two Propioniobacterium acnes and one Serratia marcescens. No organism was cultured from one patient’s aspirate. The study patients underwent an average of two surgical interventions, the first being arthroscopic washout in each case. Six patients subsequently underwent open knee joint washouts, four of these having their cruciate grafts removed.

Of the five patients recalled for clinical review, three rated their IKDC knee performance as being significantly worse than their uninjured side. Mean IKDC scores were 63.5 for the affected knee and 97.3 for the contralateral knee. Mean Lysholm knee score was 71.8 at follow-up. Tenger scores prior to ACL reconstruction averaged 4.4, compared to 5.6 on review. Radiographs demonstrated evidence of arthritis that was not apparent pre-operatively in four of the five review patients. These individuals lacked an average 2.8 degrees of extension and 13.4 degrees flexion in comparison to their contralateral knee. Two patients demonstrated clinical instability on examination. The mean single-legged hopping distance was 62.9% horizontally and 96.4% vertically, when comparing the affected knee to the contralateral side.

Staphylococcus epidermidis was the most common pathogen identified in this study. Most patients presenting with this complication will require two or more operative procedures and a prolonged course of intravenous antibiotics. The symptomatic and functional outcomes of septic arthritis associated with recent ACL reconstruction are highly variable, but were found to be worse in those patients requiring graft removal to eradicate their infections. Despite their young age, most of those patients undergoing clinical review had radiographic evidence of early osteoarthritis.


Orthopaedic Proceedings
Vol. 91-B, Issue SUPP_II | Pages 340 - 340
1 May 2009
Everts N Astley T Ball C Poon P
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Reverse shoulder arthroplasty has been used to treat arthritis of the shoulder with no rotator cuff. The purpose of this study is to review the short term outcome of reverse shoulder arthroplasty performed at North Shore Hospital.

Between 2003 and 2007, 54 consecutive patients were treated with the SMR reverse shoulder prosthesis. Patients were assessed using the visual analogue pain score, patient satisfaction rating, the American Shoulder and Elbow Society Shoulder score, the Oxford shoulder score, the Short Form – 12, and by radiographs. We also reviewed clinical and radiographic complications.

Nine patients underwent surgery for fracture, two for chronic dislocation and 43 for cuff tear arthropathy, including four revisions. The mean age at surgery was 77.8 years (range 54–91 years). 53 of the implanted prostheses were SMR (Lima Orthotec) and one was a Delta (De Puy). Patient assessment is still in progress, but findings so far show very favourable early outcomes.

We report a large consecutive series of patients who had the reverse prothesis at North Shore hospital. To the best of our knowledge, there has been no previous publication of results of the SMR reverse prosthesis


Orthopaedic Proceedings
Vol. 91-B, Issue SUPP_II | Pages 340 - 340
1 May 2009
Chou J Anderson I Astley T Poon P
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Reverse total shoulder replacement is a viable surgical option for Cuff Tear Arthropathy. Short term results have been promising. Longer term follow-up has demonstrated a high rate of scapular notching. This is attributed to mechanical impingement between the humeral cup and scapular neck when the arm is fully adducted. The long term sequelae of scapular notching are unclear but there is concern that it may compromise fixation of the glenoid component and affect functional outcomes.

Design modifications to address this problem include the newly available eccentric glenospheres and larger diameter glenospheres. These glenospheres are designed to offer greater ranges of motion and theoretically may reduce the risk of impingement and notching. The purpose of this biomechanical study is to demonstrate the difference in range of motions with each design of glenosphere. To our knowledge there is no published literature evaluating this design differences.

The SMR (Lima Orthotec) reverse total shoulder prothesis was implanted into a synthetic bone model (Sawbones, Pacific Laboratories, Vashon, Washington). Four different types of glenospheres (Standard 36 mm, Eccentric 36 mm, Standard 44 mm, Eccentric 44 mm) were then implanted into the same model which was fixed on a measurement table. The precision coordinate measurement device (FARO-Arm, SO6/Rev22, FARO Technologies Inc., Lake Mary, Florida) was used to establish the centres of rotation and ranges of motion.

To date, the collection of data has just been completed, but the data are yet to be analysed. In conclusion, this is a biomechanical study evaluating the ranges of motion and risk of notching, comparing different designs of glenospheres in Reverse Total Shoulder Joint Replacement.


Orthopaedic Proceedings
Vol. 91-B, Issue SUPP_II | Pages 337 - 338
1 May 2009
Poon P Gross A
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Management of massive acetabular defects in revision hip arthroplasty is challenging. The current generation reconstruction cages in combination with either morcellised or structural allograft bone have given promising results. However, a significant number fail due to failure of biological fixation of the cage, resulting in fatigue fracture of the cage. Trabecular metal has the potential to enhance biologic fixation. The purpose of this paper is to introduce this new surgical technique of combining a cage with a shell of trabecular metal and present the early results.

Fourteen patients (mean age 63, range 45 to 82 years) with massive contained defects underwent revision arthroplasty with a cup cage by the senior author (AEG). Complications, functional status (WOMAC, Oxford hip score and SF36) and radiographs were assessed. Post operative radiographs were assessed for evidence of construct migration, resorption and or remodelling of allograft bone. Remodelling was defined by the presence of bony trabeculae crossing the allograft host junction. Lucent lines were assessed. Allograft resorption was defined as loss of graft height on comparable radiographic views. An implant was defined as loose if there was evidence of construct migration or component fracture.

The mean follow up was 21 months (range one to 38 months). Complications included one death and one recurrent dislocation requiring revision to a capture liner. Average pre and post operative WOMAC scores were 61 and 17 points respectively. Oxford hip scores were an average of 45 pre-operatively and 24 post-operatively. SF-36 averaged 351 pre-op and 601 post-op. All implants were stable. Minor radiolucent lines were found around the inferior flange of the cage in six patients. Minor graft resorption occurred in two patients. All but one showed graft remodelling. All patients were ambulant.

The early results of this new technique for treating a complex problem show excellent rates of initial implant stability and bone graft remodelling.


Orthopaedic Proceedings
Vol. 91-B, Issue SUPP_II | Pages 341 - 341
1 May 2009
Pandit S Astley T Ball C Poon P
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Avulsion of the distal biceps tendon is an uncommon clinical entity accounting for 3% of all biceps tendon injuries. Various surgical techniques for its repair have been reported, however, the optimal technique is unknown. The two-incision technique is used by three upper limb surgeons at North Shore Hospital. There has been some concern regarding the risk of heterotopic bone formation with this technique. We present a review of a series of patients with distal biceps tendon ruptures treated with the modified two-incision technique to identify and describe any complications that we encountered and also assess the clinical, functional and radiological outcomes of our patients.

Over a 4-year period from 2002–2006, 42 distal biceps tendons repairs using the two-incision technique were identified from the hospital database. All 42 patients were males with an average age of 51.9 years. Patients were followed-up prospectively and reviewed at a clinic where they filled out the SF-12 questionnaire and a Mayo Elbow Performance Score was assessed. Clinical assessment was carried out with regards to their range of flexion-extension and their pronation-supination. All peripheral nerves were examined. Isokinetic elbow flexion-extension and forearm pronation-supination were measured and compared to the unaffected extremity. X-rays were taken to identify heterotrophic ossification or proximal radioulnar synostoses.

Our review, so far, indicates a good clinical and functional outcome in most of our patients. We identified one patient with heterotrophic bone formation requiring excision. Two patients had a transient lateral ante-brachial cutaneous nerve parasthesia and two patients had re-ruptures following surgery.

This study represents a relatively large series of patients. Our results reveal that the two-incision technique is an effective surgical option for the repair of ruptured distal biceps tendons. We found that radioulnar synostoses and heterotrophic ossification are rare following the muscle splitting modification of the two-incision technique.


Orthopaedic Proceedings
Vol. 87-B, Issue SUPP_I | Pages 30 - 30
1 Mar 2005
Twaddle BC Poon P Monnig J
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The aim of this study was to determine the outcome of patients treated with Achilles tendon rupture randomized to surgical or non-surgical treatment where both groups received the same early motion and weight bearing rehabilitation protocol.

Fifty patients between the ages of 18 and 50 years with a clinical diagnosis of Achilles tendon rupture were randomized to surgical or conservative treatment. All injuries had occurred within ten days. Both groups received the same rehabilitation program with initial cast immobilization then splintage in a removable orthosis with ankle motion commencing at two weeks. Patients completed the MFAI, a validated outcome questionnaire and clinical assessment including range of motion and calf squeeze response at 2, 6 and 12 weeks, 6 months and one year.

There was no difference between the surgical and non-surgical groups for difference in dorsiflexion and plantar flexion between the injured and non-injured sides. There was no difference in the MFAI quality of life scores for either treatment group. There was the same number of re-ruptures in both groups. There were no infections in the operated patients.

Early motion rehabilitation after Achilles tendon rupture results in similar functional results and patient satisfaction in both surgically and non-surgically treated patients.