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Orthopaedic Proceedings
Vol. 106-B, Issue SUPP_16 | Pages 32 - 32
19 Aug 2024
Caplash G Caplash Y Copson D Thewlis D Ehrlich A Solomon LB Ramasamy B
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Few surgical techniques to reconstruct the abductor mechanism of the hip have been reported, with outcomes reported only from case reports and small case series from the centres that described the techniques. As in many of our revision THA patients the gluteus maximus was affected by previous repeat posterior approaches, we opted to reconstruct the abductor mechanism using a vastus lateralis to gluteus medius transfer. We report the results of such reconstructions in seven patients, mean age 66 (range, 53–77), five females, presenting with severe abductor deficiency (MRC grade 1–2). Five patients had previous revision THA, two with a proximal femoral replacement, one patient had a primary THA after a failed malunited trochanteric fracture, and one patient had a native hip with idiopathic fatty infiltration of glutei of >90%. All patients had instrumented gait analysis, and surface electromyography (EMG) of the glutei, TFL, and vastus muscles simultaneously before surgery and at each post-op follow-up. Postoperatively, patients were allowed to weight bear as tolerated and were requested to wear an abduction brace for the first six weeks after surgery to protect the transfer. All patients improved after surgery and reached an abductor power of 3 or more. All patients walked without support six months after surgery and were satisfied with the result. Abductor function continued to improve beyond one year of follow-up, and some patients reached an abductor power of 5. EMG demonstrated that the transferred vastus lateralis started firing synchronously with gluteus medius after three months post-surgery, suggesting adaptation to its new function. No knee extension weakness was recorded. One patient complained of lateral thigh numbness and was dissatisfied with the cosmetic look of her thigh after surgery. Our preliminary results are encouraging and comparable with those achieved by the originators of the technique


Orthopaedic Proceedings
Vol. 106-B, Issue SUPP_9 | Pages 2 - 2
16 May 2024
Schwagten K
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Background

Iatrogenic hallux varus is a rare complication after hallux valgus surgery. Operative treatment comprises a wide variety of techniques, of which the reversed transfer of the abductor hallucis tendon is the most recent described technique.

Methods

This paper will present the long-term clinical results of the reversed transfer of the abductor hallucis longus. Therefore, we performed a prospective clinical observational study on 16 female patients. Our hypothesis is that the tendon transfer will persist in a good alignment and patient satisfaction on long term. There is a 100% follow-up rate with a range from 10 to 101 months. Patients were subjected to a clinical examination, three questionnaires and their general satisfaction.


The Bone & Joint Journal
Vol. 106-B, Issue 5 Supple B | Pages 89 - 97
1 May 2024
Scholz J Perka C Hipfl C

Aims. There is little information in the literature about the use of dual-mobility (DM) bearings in preventing re-dislocation in revision total hip arthroplasty (THA). The aim of this study was to compare the use of DM bearings, standard bearings, and constrained liners in revision THA for recurrent dislocation, and to identify risk factors for re-dislocation. Methods. We reviewed 86 consecutive revision THAs performed for dislocation between August 2012 and July 2019. A total of 38 revisions (44.2%) involved a DM bearing, while 39 (45.3%) and nine (10.5%) involved a standard bearing and a constrained liner, respectively. Rates of re-dislocation, re-revision for dislocation, and overall re-revision were compared. Radiographs were assessed for the positioning of the acetabular component, the restoration of the centre of rotation, leg length, and offset. Risk factors for re-dislocation were determined by Cox regression analysis. The modified Harris Hip Scores (mHHSs) were recorded. The mean age of the patients at the time of revision was 70 years (43 to 88); 54 were female (62.8%). The mean follow-up was 5.0 years (2.0 to 8.75). Results. DM bearings were used significantly more frequently in elderly patients (p = 0.003) and in hips with abductor deficiency (p < 0.001). The re-dislocation rate was 13.2% for DM bearings compared with 17.9% for standard bearings, and 22.2% for constrained liners (p = 0.432). Re-revision-free survival for DM bearings was 84% (95% confidence interval (CI) 0.77 to 0.91) compared with 74% (95% CI 0.67 to 0.81) for standard articulations, and 67% (95% CI 0.51 to 0.82) for constrained liners (p = 0.361). Younger age (hazard ratio (HR) 0.92 (95% CI 0.85 to 0.99); p = 0.031), lower comorbidity (HR 0.44 (95% CI 0.20 to 0.95); p = 0.037), smaller heads (HR 0.80 (95% CI 0.64 to 0.99); p = 0.046), and retention of the acetabular component (HR 8.26 (95% CI 1.37 to 49.96); p = 0.022) were significantly associated with re-dislocation. All DM bearings which re-dislocated were in patients with abductor muscle deficiency (HR 48.34 (95% CI 0.03 to 7,737.98); p = 0.303). The radiological analysis did not reveal a significant relationship between restoration of the geometry of the hip and re-dislocation. The mean mHHSs significantly improved from 43 points (0 to 88) to 67 points (20 to 91; p < 0.001) at the final follow-up, with no differences between the types of bearing. Conclusion. We found that the use of DM bearings reduced the rates of re-dislocation and re-revision in revision THA for recurrent dislocation, but did not guarantee stability. Abductor deficiency is an important predictor of persistent instability. Cite this article: Bone Joint J 2024;106-B(5 Supple B):89–97


The Bone & Joint Journal
Vol. 106-B, Issue 5 Supple B | Pages 98 - 104
1 May 2024
Mallett KE Guarin Perez SF Taunton MJ Sierra RJ

Aims

Dual-mobility (DM) components are increasingly used to prevent and treat dislocation after total hip arthroplasty (THA). Intraprosthetic dissociation (IPD) is a rare complication of DM that is believed to have decreased with contemporary implants. This study aimed to report incidence, treatment, and outcomes of contemporary DM IPD.

Methods

A total of 1,453 DM components were implanted at a single academic institution between January 2010 and December 2021: 695 in primary and 758 in revision THA. Of these, 49 presented with a dislocation of the large DM head and five presented with an IPD. At the time of closed reduction of the large DM dislocation, six additional IPDs occurred. The mean age was 64 years (SD 9.6), 54.5% were female (n = 6), and mean follow-up was 4.2 years (SD 1.8). Of the 11 IPDs, seven had a history of instability, five had abductor insufficiency, four had prior lumbar fusion, and two were conversions for failed fracture management.


The Bone & Joint Journal
Vol. 106-B, Issue 5 Supple B | Pages 105 - 111
1 May 2024
Apinyankul R Hong C Hwang KL Burket Koltsov JC Amanatullah DF Huddleston JI Maloney WJ Goodman SB

Aims

Instability is a common indication for revision total hip arthroplasty (THA). However, even after the initial revision, some patients continue to have recurrent dislocation. The aim of this study was to assess the risk for recurrent dislocation after revision THA for instability.

Methods

Between 2009 and 2019, 163 patients underwent revision THA for instability at Stanford University Medical Center. Of these, 33 (20.2%) required re-revision due to recurrent dislocation. Cox proportional hazard models, with death and re-revision surgery for periprosthetic infection as competing events, were used to analyze the risk factors, including the size and alignment of the components. Paired t-tests or Wilcoxon signed-rank tests were used to assess the outcome using the Veterans RAND 12 (VR-12) physical and VR-12 mental scores, the Harris Hip Score (HHS) pain and function, and the Hip disability and Osteoarthritis Outcome score for Joint Replacement (HOOS, JR).


Orthopaedic Proceedings
Vol. 105-B, Issue SUPP_15 | Pages 77 - 77
7 Nov 2023
Dey R Nortje M du Toit F Grobler G Dower B
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Hip abductor tears(AT) have long been under-recognized, under-reported and under-treated. There is a paucity of data on the prevalence, morphology and associated factors. Patients with “rotator cuff tears of the hip” that are recognized and repaired during total hip arthroplasty(THA) report comparable outcomes to patients with intact abductor tendons at THA. The study was a retrospective review of 997 primary THA done by a single surgeon from 2012–2022. Incidental findings of AT identified during the anterolateral approach to the hip were documented with patient name, gender, age and diagnosis. The extent and size of the tears of the Gluteus medius and Minimus were recorded. Xrays and MRI's were collected for the 140 patients who had AT and matched 1:1 with respect to age and gender against 140 patients that had documented good muscle quality and integrity. Radiographic measurements (Neck shaft angle, inter-teardrop distance, Pelvis width, trochanteric width and irregularities, bodyweight moment arm and abductor moment arm) were compared between the 2 groups in an effort to determine if any radiographic feature would predict AT. The prevalence of AT were 14%. Females had statistically more tears than males(18vs10%), while patients over the age of 70y had statistically more tears overall(19,7vs10,4%), but also more Gluteus Medius tears specifically(13,9vs5,3%). Radiographic measurements did not statistically differ between the tear and control group, except for the presence of trochanteric irregularities. MRI's showed that 50% of AT were missed and subsequently identified during surgery. Abductor tears are still underrecognized and undertreated during THA which can results in inferior outcomes. The surgeon should have an high index of suspicion in elderly females with trochanteric irregularities and although an MRI for every patient won't be feasible, one should always be prepared and equipped to repair the abductor tendons during THA


Bone & Joint Open
Vol. 4, Issue 8 | Pages 559 - 566
1 Aug 2023
Hillier DI Petrie MJ Harrison TP Salih S Gordon A Buckley SC Kerry RM Hamer A

Aims

The burden of revision total hip arthroplasty (rTHA) continues to grow. The surgery is complex and associated with significant costs. Regional rTHA networks have been proposed to improve outcomes and to reduce re-revisions, and therefore costs. The aim of this study was to accurately quantify the cost and reimbursement for a rTHA service, and to assess the financial impact of case complexity at a tertiary referral centre within the NHS.

Methods

A retrospective analysis of all revision hip procedures was performed at this centre over two consecutive financial years (2018 to 2020). Cases were classified according to the Revision Hip Complexity Classification (RHCC) and whether they were infected or non-infected. Patients with an American Society of Anesthesiologists (ASA) grade ≥ III or BMI ≥ 40 kg/m2 are considered “high risk” by the RHCC. Costs were calculated using the Patient Level Information and Costing System (PLICS), and remuneration based on Healthcare Resource Groups (HRG) data. The primary outcome was the financial difference between tariff and cost per patient episode.


Orthopaedic Proceedings
Vol. 105-B, Issue SUPP_12 | Pages 24 - 24
23 Jun 2023
Byrd JWT Jones KS Bardowski EA
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Partial thickness abductor tendon tears are a significant source of recalcitrant laterally based hip pain. For those that fail conservative treatment, the results of endoscopic repair are highly successful with minimal morbidity. The principal burden is the protracted rehabilitation that is necessary as part of the recovery process. There is a wide gap between failed conservative treatment and successful surgical repair. It is hypothesized that a non-repair surgical strategy, such as a bioinducitve patch, could significantly reduce the burden associated recovery from a formal repair. Thus, the purpose of this study is to report the preliminary results of this treatment strategy.

Symptomatic partial thickness abductor tendon tears are treated conservatively, including activity modification, supervised physical therapy and ultrasound guided corticosteroid injections. Beginning in January 2022, patients undergoing hip arthroscopy for intraarticular pathology who also had persistently symptomatic partial thickness abductor tendon tears, were treated with adjunct placement of a bioinducitve (Regeneten) patch over the tendon lesion from the peritrochanteric space. The postop rehab protocol is dictated by the intraarticular procedure performed. All patients are prospectively assessed with a modified Harris Hip Score (mHHS) and iHOT and the tendon healing response examined by ultrasound.

Early outcomes will be presented on nine consecutive cases.

Conclusions - Will be summarized based on the preliminary outcomes to be reported.


Bone & Joint Open
Vol. 3, Issue 8 | Pages 611 - 617
1 Aug 2022
Frihagen F Comeau-Gauthier M Axelrod D Bzovsky S Poolman R Heels-Ansdell D Bhandari M Sprague S Schemitsch E

Aims

The aim of this study was to explore the functional results in a fitter subgroup of participants in the Hip Fracture Evaluation with Alternatives of Total Hip Arthroplasty versus Hemiarthroplasty (HEALTH) trial to determine whether there was an advantage of total hip arthroplasty (THA) versus hemiarthroplasty (HA) in this population.

Methods

We performed a post hoc exploratory analysis of a fitter cohort of patients from the HEALTH trial. Participants were aged over 50 years and had sustained a low-energy displaced femoral neck fracture (FNF). The fittest participant cohort was defined as participants aged 70 years or younger, classified as American Society of Anesthesiologists grade I or II, independent walkers prior to fracture, and living at home prior to fracture. Multilevel models were used to estimate the effect of THA versus HA on functional outcomes. In addition, a sensitivity analysis of the definition of the fittest participant cohort was performed.


The Bone & Joint Journal
Vol. 104-B, Issue 5 | Pages 598 - 603
1 May 2022
Siljander MP Gausden EB Wooster BM Karczewski D Sierra RJ Trousdale RT Abdel MP

Aims

The aim of this study was to evaluate the incidence of liner malseating in two commonly used dual-mobility (DM) designs. Secondary aims included determining the risk of dislocation, survival, and clinical outcomes.

Methods

We retrospectively identified 256 primary total hip arthroplasties (THAs) that included a DM component (144 Stryker MDM and 112 Zimmer-Biomet G7) in 233 patients, performed between January 2012 and December 2019. Postoperative radiographs were reviewed independently for malseating of the liner by five reviewers. The mean age of the patients at the time of THA was 66 years (18 to 93), 166 (65%) were female, and the mean BMI was 30 kg/m2 (17 to 57). The mean follow-up was 3.5 years (2.0 to 9.2).


Bone & Joint Research
Vol. 11, Issue 2 | Pages 102 - 111
1 Feb 2022
Jung C Cha Y Yoon HS Park CH Yoo J Kim J Jeon Y

Aims

In this study, we aimed to explore surgical variations in the Femoral Neck System (FNS) used for stable fixation of Pauwels type III femoral neck fractures.

Methods

Finite element models were established with surgical variations in the distance between the implant tip and subchondral bone, the gap between the plate and lateral femoral cortex, and inferior implant positioning. The models were subjected to physiological load.


Bone & Joint Open
Vol. 2, Issue 9 | Pages 696 - 704
1 Sep 2021
Malhotra R Gautam D Gupta S Eachempati KK

Aims

Total hip arthroplasty (THA) in patients with post-polio residual paralysis (PPRP) is challenging. Despite relief in pain after THA, pre-existing muscle imbalance and altered gait may cause persistence of difficulty in walking. The associated soft tissue contractures not only imbalances the pelvis, but also poses the risk of dislocation, accelerated polyethylene liner wear, and early loosening.

Methods

In all, ten hips in ten patients with PPRP with fixed pelvic obliquity who underwent THA as per an algorithmic approach in two centres from January 2014 to March 2018 were followed-up for a minimum of two years (2 to 6). All patients required one or more additional soft tissue procedures in a pre-determined sequence to correct the pelvic obliquity. All were invited for the latest clinical and radiological assessment.


The Bone & Joint Journal
Vol. 103-B, Issue 7 Supple B | Pages 66 - 72
1 Jul 2021
Hernandez NM Hinton ZW Wu CJ Lachiewicz PF Ryan SP Wellman SS

Aims

Modular dual mobility (MDM) acetabular components are often used with the aim of reducing the risk of dislocation in revision total hip arthroplasty (THA). There is, however, little information in the literature about its use in this context. The aim of this study, therefore, was to evaluate the outcomes in a cohort of patients in whom MDM components were used at revision THA, with a mean follow-up of more than five years.

Methods

Using the database of a single academic centre, 126 revision THAs in 117 patients using a single design of an MDM acetabular component were retrospectively reviewed. A total of 94 revision THAs in 88 patients with a mean follow-up of 5.5 years were included in the study. Survivorship was analyzed with the endpoints of dislocation, reoperation for dislocation, acetabular revision for aseptic loosening, and acetabular revision for any reason. The secondary endpoints were surgical complications and the radiological outcome.


The Bone & Joint Journal
Vol. 103-B, Issue 7 Supple B | Pages 129 - 134
1 Jul 2021
Ayekoloye CI Abu Qa'oud M Radi M Leon SA Kuzyk P Safir O Gross AE

Aims

Improvements in functional results and long-term survival are variable following conversion of hip fusion to total hip arthroplasty (THA) and complications are high. The aim of the study was to analyze the clinical and functional results in patients who underwent conversion of hip fusion to THA using a consistent technique and uncemented implants.

Methods

A total of 39 hip fusion conversions to THA were undertaken in 38 patients by a single surgeon employing a consistent surgical technique and uncemented implants. Parameters assessed included Harris Hip Score (HHS) for function, range of motion (ROM), leg length discrepancy (LLD), satisfaction, and use of walking aid. Radiographs were reviewed for loosening, subsidence, and heterotopic ossification (HO). Postoperative complications and implant survival were assessed.


Bone & Joint Research
Vol. 10, Issue 4 | Pages 250 - 258
1 Apr 2021
Kwak D Bang S Lee S Park J Yoo J

Aims

There are concerns regarding initial stability and early periprosthetic fractures in cementless hip arthroplasty using short stems. This study aimed to investigate stress on the cortical bone around the stem and micromotions between the stem and cortical bone according to femoral stem length and positioning.

Methods

In total, 12 femoral finite element models (FEMs) were constructed and tested in walking and stair-climbing. Femoral stems of three different lengths and two different positions were simulated, assuming press-fit fixation within each FEM. Stress on the cortical bone and micromotions between the stem and bone were measured in each condition.


Orthopaedic Proceedings
Vol. 103-B, Issue SUPP_3 | Pages 19 - 19
1 Mar 2021
Mazor A Glaris Z Goetz T
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Thumb Carpometacarpal (CMC) arthritis is a common pathology of the hand. Surgical treatment with thumb reconstruction is well described. Retrospective outcomes have been described for multiple techniques, suggesting patient satisfaction with multiple different techniques. The Thompson technique uses a slip of Abductor Pollicis Longus for suspension and interposition as well as excision of the trapezium. Retrospective outcomes suggest good patient satisfaction. We describe the improvement in Patient rated outcomes scores (PROS) and changes in pinch and grip strength in a prospectively collected cohort of patients treated with a modification of the Thompson technique. To assess changes in Patient-Rated Wrist Evaluation (PRWE) and Disabilities of the Arm, Shoulder, and Hand (QDASH) scores, as well as to determine the percentage of patients that surpassed the Minimal Clinically Important Difference (MCID) figure that has been described in the literature for these tests. In addition, measurements for evaluation of pinch and grip strength prior to surgery, at six, and at twelve months follow-up were done. Between June 2016 and February 2019, a consecutive prospective series of Thirty-seven LRTI procedures with APL suspension arthroplasty (Thompson technique) were performed on 34 patients with osteoarthritis of the thumb CMC joint (24 women / 13 men; age 63±8.553). All surgeries were performed by the senior surgeon. Data was collected as part of a wrist pain database. Patients failing conservative treatment and electing surgical management of thumb arthritis were enrolled into the database. Patients were evaluated pre-operatively with the PRWE and QDASH questionnaires and grip and pinch strength measurements, and postoperatively at 6 and 12 months. The MCID for QDASH and PRWE is 14 and will be evaluated at the same time points for each patient. Paired student T-test was used to determine differences in the means. Data are presented as mean ± SD unless stated otherwise. Differences with p<.05 were considered significant. Compared to the pre-operative assessment, at six months, the means of PRWE pain score and PRWE functional score decreased significantly (32.824 SD±10.721 vs. 19.265 SD±12.268 and 30.262 SD±10.050 vs. 16.431 SD± 9.697 respectively, n=34,, p<0.05). 69% of the patients surpassed the MCID of 14 six months after the surgery. In addition, QDASH mean score also dropped from 56.108 to 32.219 (SD± 21.375 n=32. p<0.05) at six months. At one year, 76% of the patients were above the MCID of 14. The mean scores of these three questionnaires did not show significant change between six and twelve months. Compared to the initial pre-operative assessment, we found no statistically significant difference in the means of grip strength, point pinch, and lateral key pinch at six and twelve months. Thumb reconstruction with APL suspension arthroplasty demonstrates significant improvement in pain and functionality. No significant improvement in grip and pinch strength is observed, even at one year postoperatively


Orthopaedic Proceedings
Vol. 102-B, Issue SUPP_11 | Pages 58 - 58
1 Dec 2020
Ranson J Nuttall G Paton R
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Aims & Background. Congenital Talipes Equinovarus (CTEV) is the most common congenital musculoskeletal birth defect affecting 1 in 1000 births per annum. We have compared our surgical results to the British Society of Children's Orthopaedics (BSCOS) published guidelines. Methods. Between, 2006–16, patients who were referred for treatment of pathological CTEV were audited. Data from a combination of Clinical Portal, Orthotic Patient Administration System and Surgical Elogbook were assessed. In addition, the degree of deformity was classified by the Harrold & Walker method at the time of diagnosis (senior author). Most of this information was recorded prospectively and analysed retrospectively. Ponseti technique was the method of treatment. Results. 96 patients assessed (133 feet). There were 78 males and 18 females, 37 patients were affected bilaterally and 11 had associated syndromes. There were 23 Harrold & Walker (H&W) 1, 28 H&W 2 and 82 H&W 3 classification feet. Average time period in Ponseti boots and bars was 14.4 months (95% CI 12.9–15.9), average time in all types of bracing of was 17.1 months (95% CI 14.8–14.8). Number and rate of surgeries performed were as follows: 77 Tendoachilles release (63.1%), 19 Tibialis Anterior Transfer (5.6%), 15 Radical Release (12.3%), revision 25 Surgery (20.5%) & 5 Abductor Hallucis Release (4.1%). Conclusion. The audit confirms that the unit meets most of the current BSCOS guidelines. All surgical procedures apart from radical release surgery fall within accepted limits. This may be due, in part, to the syndromal cases. We do however demonstrate a significantly reduced average time period in bracing compared to that recommended by BSCOS. There are multiple reasons for this discrepancy including non-compliance and poor splint tolerance (child refusing to use). We feel this work demonstrates a reduced period in bracing can be achieved whilst maintaining standards of treatment


Bone & Joint 360
Vol. 9, Issue 6 | Pages 5 - 11
1 Dec 2020
Sharma V Turmezei T Wain J McNamara I


Orthopaedic Proceedings
Vol. 102-B, Issue SUPP_5 | Pages 32 - 32
1 Jul 2020
Horga L Henckel J Fotiadou A Laura AD Hirschmann A Hart A
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Background. Over 30 million people run marathons annually. The impact of marathon running on hips is unclear with existing literature being extremely limited (only one study of 8 runners). Aim and Objectives. We aimed to better understand the effect of marathon running on the pelvis and hip joints by designing the largest MRI study of asymptomatic volunteers. The objectives were to evaluate the pelvis and both hip joints before and after a marathon. Materials and Methods. This was a prospective cohort study, Fig.1. We recruited 44 asymptomatic volunteers who were registered for the Richmond Marathon. They were divided into novice and experienced marathoners, Fig.2. All volunteers underwent 3T MRI of pelvis and hips with Dixon sequences 4 months before, and within 2 months after the marathon. Outcome measures were: 1. change in radiological score of each hip joint structure and muscle from the pre- to the post-marathon MRI; 2. change in the self-reported hip function questionnaire score (HOOS) between the two timepoints. Results Pre-marathon, Asymptomatic novice marathoners' hips showed few joint abnormalities (cartilage, bone marrow, labrum), while minimal fatty muscle atrophy of the abductors and CAM-type hip impingement were common (68%; 34%, respectively). Experienced marathoners had no cartilage lesions and slightly lower prevalences of abnormalities than novice runners. Post-marathon, Hip joint cartilage, bone edema and labrum did not worsen in neither novice nor experienced marathoners. Abductor muscles were unaffected post-marathon. Self-reported hip outcomes were not significantly different after the run for both groups. Conclusion. This is the largest MRI study of long-distance runners. We showed that marathon running has no negative impact on the pelvis and hip joints. For any figures or tables, please contact the authors directly


Orthopaedic Proceedings
Vol. 102-B, Issue SUPP_7 | Pages 85 - 85
1 Jul 2020
Cornish J Zhu M Young S Musson D Munro J
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No animal model currently exists for hip abductor tendon tears. We aimed to 1. Develop a large animal model of delayed abductor tendon repair and 2. To compare the results of acute and delayed tendon repair using this model.

Fourteen adult Romney ewes underwent detachment of gluteus medius tendon using diathermy. The detached tendons were protected using silicone tubing. Relook was performed at six and 16 weeks following detachment, histological analysis of the muscle and tendon were performed. We then attempted repair of the tendon in six animals in the six weeks group and compared the results to four acute repairs (tendon detachment and repair performed at the same time). At 12 weeks, all animals were culled and the tendon–bone block taken for histological and mechanical analysis.

Histology grading using the modified Movin score confirmed similar tendon degenerative changes at both six and 16 weeks following detachment. Biomechanical testing demonstrated inferior mechanical properties in both the 6 and 16 weeks groups compared to healthy controls.

At 12 weeks post repair, the acute repair group had a lower Movin's score (6.9 vs 9.4, p=0.064), and better muscle coverage (79.4% of normal vs 59.8%). On mechanical testing, the acute group had a significantly improved Young's Modulus compared to the delayed repair model (57.5MPa vs 39.4MPa, p=0.032)

A six week delay between detachment and repair is sufficient to produce significant degenerative changes in the gluteus medius tendon. There are significant histological and mechanical differences in the acute and delayed repair groups at 12 weeks post op, suggesting that a delayed repair model should be used to study the clinical problem.