Division of Orthopedic Surgery

DIVISION OF ORTHOPEDIC SURGERY UNIVERSITY OF OTTAWA

H. K. UHTHOFF ANNUAL RESEARCH DAY

THURSDAY, MAY 2, 2013

THE OTTAWA HOSPITAL – GENERAL CAMPUS MAIN AUDITORIUM

VISITING PROFESSOR

J Mark Wilkinson, PhD, FRCS (Trauma & Orthopedics) Professor of Orthopedics Academic Unit of Bone Metabolism Department of Human Metabolism University of Sheffield Northern General Hospital United Kingdom We are pleased to welcome

J Mark Wilkinson, PhD, FRCS (Trauma &Orthopedics)

as the 2013 H. K. Uhthoff Visiting Professor

Professor Wilkinson received his medical degree in 1991 from Sheffield University, England. After completing a PhD in the metabolic and genetic aspects of joint replacement failure (2001), he undertook orthopedic surgical training posts in Sheffield and fellowship training in lower limb arthroplasty at Wrightington Hospital, and travelling fellowships in Canada, Japan, and Switzerland. He was appointed to an academic Faculty post at Sheffield University in 2007 and to the Chair of Orthopedics in 2012.

Professor Wilkinson’s research focuses on the interaction between joint prostheses and the patient, and the genetic basis of joint disease. He conducted the first clinical trial of bisphosphonate therapy after hip replacement, and was the first to show genetic variability is a risk factor for prosthesis failure. More recently, he was a PI in the arcOGEN study that identified several novel risk loci for osteoarthritis, and is currently conducting the first clinical trial of monoclonal antibody therapy to modulate osteolytic lesion activity.

Professor Wilkinson sits on the Research committees of the British Orthopedic Association and Arthritis Research UK, and has sat as a board member of the Orthopedic Research Society and as chair of its Awards and Recognition Committee. He is currently topic chair for Arthroplasty for its annual meeting, and a member of the Editorial Board of the Journal of Orthopedic Research.

Professor Wilkinson is a recipient of the Robert Jones Gold Medal of the British Orthopedic Association, The McKee Prize of the British Hip Society, and the William Harris Award of the Orthopedic Research Society. He continues an active clinical practice in joint reconstruction and revision surgery with a particular interest in inflammatory arthritis, in addition to his on-going clinical and translational research program. RESIDENT RESEARCH REQUIREMENTS THE DIVISION OF ORTHOPEDIC SURGERY UNIVERSITY OF OTTAWA

1. All residents must participate in a minimum of two research projects during their residency.

2. Research plan and protocol is presented to the Research Visiting Professor in November.

3. Preliminary results are presented to the Division of Orthopedic Surgery Research Committee in early April.

4. The final paper is presented at the H.K. Uhthoff Research Day in April.

5. Papers are chosen for submission to Collins Day in May.

6. Two completed manuscripts must be written in style of the Journal of Bone and Joint Surgery and submitted to the Chairman of the Resident Research Committee, one by the end of the PGY-3 year and one by the end of the PGY-4 year. RESIDENTS/FELLOWS

DIVISION OF ORTHOPEDIC SURGERY

2012 - 2013

PGY-5 PGY- 2

Dr. Derek Butterwick Dr. Christopher Dowding Dr. Sasha Carsen Dr. Heathcliff D’Sa Dr. Michael Creech Dr. Adrian Huang Dr. William Desloges Dr. Brian Le Dr. Marc Prud’homme-Foster Dr. Andrew Tice Dr. Nathan Sacevich Dr. Kristi Wood

PGY-4 PGY- 1

Dr. Natasha Holder Dr. Mitchel Armstrong Dr. Bradley Meulenkamp Dr. Aaron Frombach Dr. Mark Pahuta Dr. John Morellato Dr. Marie-France Rancourt Dr. Caleb Netting Dr. Cai Wadden Dr. Jason Reinglas Dr. Geoffrey Wilkin Dr. Shawn Verma

PGY-3 FELLOWS

Dr. Gillian Bayley Dr. Abdullah Arab Dr. Kelly Hynes Dr. Long Chen Dr. Matthew MacEwan Dr. Mohamed Elkurbo Dr. Ian MacNiven Dr. Krista Goulding Dr. Travis Marion Dr. Liangfu Jiang Dr. Scott McGuffin Dr. Vickas Khanna

Dr. Brendan O’Neill

Dr. Othman Ramadan

Dr. Paul Whittingham-Jones

Dr. Hani Zamil

DIVISION OF ORTHOPEDIC SURGERY

RESIDENCY TRAINING COMMITTEE 2012 – 2013

CHAIRMAN

Dr. Joel Werier

MEMBERS

Dr. Wade Gofton Dr. Ken Kontio Dr. Karl-André Lalonde Dr. Louis Lawton Dr. Allan Liew Dr. Wadih Matar Dr. Peter Thurston

RESIDENT REPRESENTATIVES

Dr. Marc Prud’homme-Foster Dr. Scott McGuffin

DIRECTOR OF RESEARCH

Dr. Peter Lapner ACKNOWLEDGEMENTS

The Division of Orthopedic Surgery greatly acknowledges the support of the H. K. Uhthoff Research Day by the following companies:

Bayer Inc.

Biomet Canada

ConMed Linvatec

Covidien

Depuy/Synthes

KCI Medical Canada Inc.

Kinemedics

Pfizer Canada

Stryker Canada

Tribe Medical Group

Wright Medical (Mr. Trevor Fisher) PROGRAM

0800 Opening Remarks Dr. Joel Werier, Director of the Orthopedic Surgery Residency Training Program, University of Ottawa

0805 Welcome/Introduction of Dr. J Mark Wilkinson Dr. Paul Beaulé, Department of Orthopedic Surgery, University of Ottawa

0810 Genetics of Hip Shape and Osteoarthritis Dr. J Mark Wilkinson, Visiting Professor

0830 Discussion

SESSION I

MODERATOR: Dr. Paul Beaulé

0834 1. Seasonal Variation in Orthopedic Trauma Dr. Matthew MacEwan, PGY-3

0842 Discussion

0846 2. The Use of an Incisional VAC in Sarcoma Surgery – Wounds at Risk Dr. Bradley Meulenkamp, PGY-4

0904 Discussion

0908 3. Supraspinatus and Infraspinatus Fatty Infiltration in Shoulder Arthroplasty: Does it Affect Outcome? Dr. Liangfu Jiang, Clinical Fellow

0916 Discussion

0920 4. Discriminant Function Analysis Using Geometric Hip Joint and Squat Depth Parameters to Classify Cam FAI K.C. Geoffrey Ng, Graduate Student, Department of Mechanical Engineering, University of Ottawa

0928 Discussion

0932 5. A Systematic Review of the Evidence for Metal Ions as a Diagnostic Test for the Failed Metal-on-Metal Hip Prosthesis Dr. Markian Pahuta, CIP/PGY-4

0940 Discussion

0944 6. A Systematic Review of the Quality of Evidence for the Treatment of Metastatic Spinal Cord Compression Dr. Gillian Bayley, PGY-3

0952 Discussion

Refreshment Break and Exhibits, Royal Room

SESSION II

MODERATOR: Dr. Steven Papp

1041 7. Unicompartmental versus Total Knee Arthroplasty for Isolated Medial or Lateral Osteoarthritis in Patients 75 years of Age or Older Dr. Brendan O’Neill, Clinical Fellow

1049 Discussion

1053 8. Synovial Biopsy as a Diagnostic Tool in Chronic Shoulder Infection: A Pilot Study Dr. Kelly Hynes, PGY-3 1101 Discussion

1105 9. Incidence of Hip Pain in a Prospective Cohort of Asymptomatic Volunteers: Is the Cam Deformity a Risk Factor for Hip Pain? Dr. Vickas Khanna, Clinical Fellow

1113 Discussion

1117 10. A Quantitative Comparison of the Deltopectoral and Deltoid-Splitting Surgical Approaches to the Proximal Humerus Dr. Scott McGuffin, PGY-3

1125 Discussion

1129 11. The Ottawa Orthopedic Orientation Dr. Marie-France Rancourt, PGY-4

1137 Discussion

1141 12. Development and Validation of the Self-Administered Online Assessment of Preferences (SOAP) Tool Dr. Markian Pahuta, CIP/PGY-4

1149 Discussion

1153 13. Societal Valuation of Metastatic Spinal Cord Compression Health States Dr. Markian Pahuta, CIP/PGY-4

1201 Discussion

Lunch and Exhibits, Royal Room SESSION III

MODERATOR: Dr. Hesham Abdelbary

1315 The Importance of Extramuscular and the Measurement of Intramuscular Fat after Rotator Cuff Tear Dr. Hans K. Uhthoff

1325 Discussion

1329 Bone Densitometry around Hip Replacements Dr. J Mark Wilkinson, Visiting Professor

1349 Discussion

1353 14. A Single Centre Preliminary Experience of the Anterior Approach for Total Hip Arthroplasty Dr. Caleb Netting, PGY-1

1401 Discussion

1405 15. Complications of Operative Treatment of Distal Femoral Fractures: Is Osteoarthritis Associated with Increased Rate of Non-Union? Dr. Long Chen, Clinical Fellow

1413 Discussion

1417 16. Predictors of Early Anterior Cruciate Ligament Failure, is Graft Diameter a Factor? Dr. Ian MacNiven, PGY-3

1425 Discussion

1429 17. Migration of a Monoblock Acetabulum in Hip Resurfacing; the Importance of Medial Lucencies Dr. Paul Whittingham-Jones, Clinical Fellow 1437 Discussion

Refreshment Break, Royal Room

SESSION IV

MODERATOR: Dr. Paul Kim

1500 18. Hip Arthroscopy in Patients in Less Than 25 Years of Age: Analysis of Outcomes and Indications for Surgery Dr. Gilliam Bayley, PGY-3

1508 Discussion

1512 19. An Individual Patient Data Meta-Regression of the Short-Term Treatment Effects for Metastatic Spinal Cord Compression Dr. Markian Pahuta, CIP/PGY-4

1520 Discussion

1524 20. An Individual Patient Data Meta-Regression of the Long-Term Treatment Effects for Metastatic Spinal Cord Compression Dr. Markian Pahuta, CIP/PGY-4

1532 Discussion 1536 21. Assessment of Cartilage Proteoglycan Content of Patients with Femoroacetabular Impingement Dr. Adrian Huang, PGY-2

1544 Discussion

1548 Closing Remarks Dr. Peter Lapner, Director of Research, Division of Orthopedic Surgery, University of Ottawa

ABSTRACTS

1. SEASONAL VARIATION IN ORTHOPEDIC TRAUMA

Matthew MacEwan MD, Wade Gofton MD, FRCSC, Allan Liew MD, FRCSC Geoffrey Dervin MD, FRCSC, Steven Papp MD, FRCSC Division of Orthopedic Surgery University of Ottawa, The Ottawa Hospital

Background

Seasonal variation in orthopedic trauma may exist and should be considered when planning orthopedic resources. We reviewed the seasonal demand of the operative fracture cases performed in the Orthopedic on-call Trauma Room at our Level 1 Trauma Centre to examine fluctuations in resource demand throughout the year.

Methods

A fracture database was prospectively collected data at a Level 1 Canadian Academic Trauma Centre was used. A 4 year continuous block was established from August 2007-July 2011. This data was then analyzed for patterns in seasonal variations, time to surgery, length of hospital stay and fracture type.

Results

Between August 2007 and July 2011, 4304 fractures in 3,469 patients required Orthopedic Intervention in the Trauma Room. Significant trends were found with demand varying by month. In general, summer and winter months showed a significant increase in activity as compared to the fall and spring. The six busiest months were December, July, February, March, January, and August. December was the busiest month and over a 4 year averaged 35% higher volume of cases vs our slowest month (October). Variations were also seen in wait time to surgery and length of stay in hospital during busy months.

Conclusions

Seasonal variation exists to a significant degree in Orthopedic Trauma Surgery. Data from this study could be used to support a program in which Orthopedic Trauma Services better match seasonal variation and improve efficiency of care. Increased OR access and resources could be allocated during busy months with some decreases during slower periods 2. THE USE OF AN INCISIONAL VAC IN SARCOMA SURGERY - WOUNDS AT RISK

Brad Meulenkamp MD, Joel Werier MD, FRCSC

Division of Orthopedic Surgery University of Ottawa, The Ottawa Hospital

Backgound

Wound complications following soft tissue sarcoma surgery are frequent. These wounds are at risk due to lengthy operative times, large exposures and dead-spaces, as well as neo-adjuvant or adjuvant treatments with radiotherapy.

The SR.2 trial found pre and post-operative radiation therapy to be associated with wound complications rates of 35% and 18%, respectively. Vacuum assisted closure (VAC) is a wound closure device that acts to keep wound beds dry, and to stimulate blood flow to the region. Indications for the use of VAC are expanding, including over closed incisions. We propose that the use of an incisional VAC after sarcoma surgery leads to less wound complications in patients receiving radiation therapy.

Methods

Patients with biopsy proven soft tissue sarcoma were identified through a prospectively collected database. A chart review was performed to identify patients who had received radiation therapy and undergone VAC over a closed incision. Wound complications were defined in keeping with the SR.2 trial, and complication rates were compared to this benchmark within 120 days from surgery.

Results

Over a 3-year period, 23 patients were identified who met the criteria for study. 15 patients had undergone pre-operative radiation, and 8 post-operative radiation. The pre-operative radiation group had a complication rate of 20% (p = .251), while the postoperative group had a rate of 25% (p = .578).

Conclusions

While not reaching statistical significance, pilot data suggests a lower wound complication rate in patients treated with incisional VAC. Even modest decreases in wound complications may translate to health care dollar savings, as well as improved patient outcomes.

3. SUPRASPINATUS AND INFRASPINATUS FATTY INFILTRATION IN SHOULDER ARTHROPLASTY: DOES IT AFFECT OUTCOME?

Peter L.C. Lapner MD, FRCSC, Liangfu Jiang MD Tinghua Zang MSc, George S. Athwal MD, FRCSC

Division of Orthopedic Surgery University of Ottawa, The Ottawa Hospital Background Shoulder arthroplasty yields predictable results for the treatment of glenohumeral arthritis. However, little is known of the natural history of rotator cuff muscle fat infiltration and atrophy after successful functional restoration with shoulder arthroplasty. The purpose of this study, therefore, was to compare pre-operativeto post-operative fatty infiltration (FI) and atrophy of the supraspinatus and infraspinatus muscles following primary shoulder arthroplasty.

Methods Eighty-seven patients, with a mean age of 68 ｱ 11 years, undergoing shoulder arthroplasty were prospectively followed. Computed tomography scans (CT) were conducted preoperatively and at 12 months postoperatively. Outcome variables included the degree of Supraspinatus and Infraspinatus fatty infiltration, Supraspinatus atrophy, shoulder strength, and the WOOS, ASES and Constant outcome scores.

Results

CT imaging and FI assessment was available in 81% (n=72) of the cohort. Beam hardening (metal artifact) prevented post- operative determination of supraspinatus fatty infiltration. Preoperatively, the mean supraspinatus fat infiltration was 15%. Preoperative supraspinatus occupation volume (mean 78%) was not statistically different from the postoperative (mean 67%, p=0.073). Postoperative infraspinatus fat infiltration (7%, p<0.0001) was statistically lower than preoperative (mean 13%).

Preoperatively, greater supraspinatus FI was negatively associated with pre-operative shoulder strength (p=0.0014) and Constant score (p= 0.0012). Postoperative infraspinatus FI was negatively associated with postoperative strength (p=0.021) and Constant (p=0.04). Preoperative supraspinatus occupation volume was positively associated with post-operative Constant (p=0.017) and WOOS (p=0.010). Pre-operative infraspinatus FI was negatively associated with post-operative Constant (p=0.007) and WOOS (p=0.021).

Discussion:

A statistically significant reduction in infraspinatus fat infiltration was observed after shoulder arthroplasty. This may indicate that pain relief after shoulder arthroplasty allows increased function that results in improved muscle quality. Additionally, associations were identified that correlated greater degrees of fat infiltration and atrophy to poorer functional results. 4. DISCRIMINANT FUNCTION ANALYSIS USING GEOMETRIC HIP JOINT

AND SQUAT DEPTH PARAMETERS TO CLASSIFY CAM FAI

K.C. Geoffrey Ng, MASc 1 | Mario Lamontagne, PhD 21 | Michel R. Labrosse, PhD 1 | Kawan S. Rakhra, MD FRCPC 3 | Paul E. Beaulé, MD FRCSC 4

1 Department of Mechanical Engineering, University of Ottawa 2 School of Human Kinetics, University of Ottawa 3 Division of Musculoskeletal Imaging, University of Ottawa 4 Division of Orthopaedic Surgery, University of Ottawa

The severity and risks associated with cam femoroacetabular impingement (FAI) and its deformity is traditionally defined by the alpha angle, with higher values associated with larger cam lesions and aspherical heads. Although other radiographic parameters have been suggested to identify symptoms of cam FAI, it is unclear why many patients with the cam deformity do not exhibit any symptoms of mechanical impingement. Furthermore, symptomatic patients have demonstrated different squat kinematics, leading to higher hip joint stresses. The purpose was to include additional geometric parameters and a maximal squat depth analysis to distinguish which parameters would be more closely associated with symptomatic FAI.

Forty-four male participants were first classified as either: symptomatic FAI (sFAI – cam deformity with symptoms); asymptomatic FAI (aFAI – deformity without symptoms); or control (CON – no deformity, no symptoms). In addition to the alpha angles, participant CT data were blinded and measured for femoral neck-shaft angle, anterior femoral head-neck offset, acetabular version, and centre-edge angle. Three-dimensional hip joint kinematics were collected from each participant’s maximal squat motions. The resultant squat depths were then matched with the unblinded geometric measures. A discriminant function analysis (DFA) was used to identify which parameters were most suitable to classify each participant with their respective subgroup. The DFA determined that radial alpha angle and femoral neck-shaft angle were significantly the most suitable parameters to classify the participants with their respective subgroups. The sFAI participants had significantly smaller femoral neck-shaft angles and could not squat as low (Table 1). The smaller femoral neck-shaft angles, in combination with elevated alpha angles and a decreased femoral head- neck offset, could have contributed to symptoms and distinguishable squat kinematics.

Femoral neck-shaft angle should be included as a radiographic parameter to predict if sFAI would persist, in addition to the conventional alpha angle measurements. Moreover, squat depth could be implemented as a preliminary diagnostic tool. For impingement to occur due to hip joint geometry, symptoms could persist due to a combination of several radiographic parameters. The next step is to evaluate femoral version as a radiographic parameter, since it is known that anteversion can influence hip motion and internal rotation. This would further lead to the association of altered squat kinematics due to the severity, location of the cam deformity, and orientation of the anatomical structures.

Table 1: Summary of geometric and squat depth parameters associated with sFAI, aFAI, and CON, indicating mean and (SD) ______

Group n Axial Alpha Radial Alpha Femoral Neck- Femoral Acetabular Centre- Squat Angle Angle Shaft Angle Offset Version Edge Angle Depth (°) (°) (°) (mm) (°) (°) (% of leg height) sFAI 13 56.9 (9.0) * 65.0 (8.5) * 120.8 (3.8) *@ 7.9 (1.4) 18.0 (5.5) 37.2 (5.0) 45.9 (11.2) aFAI 19 57.3 (10.0) * 67.2 (7.8) * 126.1 (3.8) 8.9 (1.4) 14.3 (3.9) 35.6 (3.8) 39.1 (8.7) CON 12 43.4 (6.4) 50.0 (5.1) 125.2 (2.0) 9.0 (1.4) 17.3 (6.4) 38.3 (7.8) 37.3 (8.8) * significant difference, compared with CON @ significant difference, compared with aFAI

Acknowledgement The authors wish to also thank Kevin D. Dwyer and Giulia Mantovani, from the University of Ottawa, for their help with data processing; and Céline Mollon, from l’École supérieure d’ingénieurs du Luminy, for her research insight.

5. A SYSTEMATIC REVIEW OF THE EVIDENCE FOR METAL IONS AS A DIAGNOSTIC TEST FOR THE FAILED METAL- ON-METAL HIP PROSTHESIS

M. Pahuta MD, J. Smoulders, P. R. Kim MD, FRCSC J. van Susante, P. E. Beaulé MD, FRCSC

Purpose

While delay in diagnosis rarely affected the outcome of the patients with metal-on-polyethylene (MPE) bearings, clinicians and patients with metal-on-metal (MoM) bearings are often faced with difficult choices on whom/when to intervene because of the risk of signiﬁcant soft-tissue destruction. Our objectives were to (1) characterize the temporal pattern of post- operative metal ion levels, and (2) determine if metal ion levels are associated with soft tissue reaction or implant failure.

Methods

We performed an electronic Literature Search of MEDLINE, EMBASE, Cochrane CDSR, Cochrane DARE, Cochrane CENTRAL. A hand search of reference lists from relevant review articles and included articles was also conducted to ensure search completion. Two reviewers performed selection, disagreements were resolved by consensus.

Results

38 articles were included in the final review. Meta-analysis of aggregate ion levels demonstrated a significant temporal trend for both cobalt and chromium serum and whole blood levels. No study described a standardized protocol or regular follow-up to detect soft tissue reactions. Only 15 (42%) of studies described a standardized protocol or regular follow-up to detect implant loosening.

Conclusions

Due to the high risk of measurement bias, there is currently insufficient evidence to support the use of serial ion level measurements in the diagnostic work-up of the painful MoM THA or HR. Future studies should take steps to minimize measurement bias in the detection of soft tissue reactions and implant loosening. 6. A SYSTEMATIC REVIEW OF THE QUALITY OF EVIDENCE FOR THE TREATMENT OF METASTATIC SPINAL CORD COMPRESSION

G. Bayley MD, M. Pahuta MD, C. van Walraven MD, D. Coyle MD J. Werier MD FRCSC, E. Wai MD FRCSC

Purpose

A particularly disabling consequence of cancer is metastatic epidural spinal cord compression (MESCC). There is continuing debate as to whether surgery or radiation is more effective. Only one randomized control trial has been conducted to compare these treatments. We performed a systematic review of the literature to both identify comparative observational studies using prospectively collected data, and to determine if the ratio of medical specialties of the authors was associated with magnitude of the reported outcome in single- arm studies.

Methods

We performed an electronic Literature Search of MEDLINE, EMBASE, Cochrane CDSR, Cochrane DARE, Cochrane CENTRAL. A hand search of reference lists from relevant review articles and included articles was also conducted to ensure search completion. Two reviewers performed selection, disagreements were resolved by consensus.

Results

120 studies reporting prospectively collected data for surgical or radiation treatment for MESCC were included in the final review. No study compared surgery to radiation. There was a significant interaction between the ratio of medical specialty of the authors and intervention being reported.

Conclusions

This study further supports the assertion that naïve treatment comparisons are biased and should not be used to compare the effectiveness of interventions. Given the invasiveness of surgery for MESCC, it is important to collect unbiased evidence.

7. UNICOMPARTMENTAL VERSUS TOTAL KNEE ARTHROPLASTY FOR ISOLATED MEDIAL OR LATERAL OSTEOARTHRITIS IN PATIENTS 75 YEARS OF AGE OR OLDER

Brendan O’Neill MD, FRCSC, Geoffrey Dervin MD, FRCSC Kyle A. Kemp MSc, Sarah Plamondon

Purpose

The treatment of end-stage unicompartmental osteoarthritis (OA) of the knee remains controversial, especially in the elderly population (> 75 years). Unicompartmental knee arthroplasty (UKA) is a less invasive alternative to total knee arthroplasty (TKA) although there are few comparisons between the two treatments in an elderly population within the literature. The purpose of this study is to compare revision rates and patient reported outcomes of UKA and TKA for isolated medial or lateral OA among patients 75 years of age and older.

Methods

Data was collected prospectively on consenting patients as part of a database of all joint arthroplasties at a tertiary care orthopaedic center. Demographic data and cases of revision were documented. Patients completed the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), documenting their self-reported joint pain, stiffness and function. Rates of revision and functional outcomes were then compared between groups.

Results

Between 2001 and 2010, 231 UKA and 453 TKA procedures were performed by six surgeons for isolated medial or lateral knee OA in patients 75 years of age and older. Length of stay was significantly shorter and blood loss was significantly less in the UKA group. However, UKAs were revised more commonly than TKAs. Compared to baseline, both patient groups experienced improvements on all domains of the WOMAC.

Conclusions

The majority of elderly patients with isolated lateral or medial compartment osteoarthritis will benefit from UKA. However, there is an increased probability of revision compared to primary TKA as an index procedure. Close attention to patient selection and technique remain important. 8. SYNOVIAL BIOPSY AS A DIAGNOSTIC TOOL IN CHRONIC SHOULDER INFECTION: A PILOT STUDY

Kelly K. Hynes MD, Adnan Sheikh MD, FRCPC, Peter L.C. Lapner MD, FRCSC

Background

Peri-prosthetic glenohumeral infections are a diagnostic challenge due to the low virulence of Proprionibacterium acnes, the most common infective organism (36 – 70%). Clinical presentation is nonspecific and usually includes pain and stiffness. There are no good pre operative or intraoperative investigations to diagnose peri-prosthetic shoulder infection. Synovial biopsy is a valuable diagnostic tool in peri-prosthetic infections in hips and knees and has been shown to be more valuable that CRP or joint aspiration. We describe a technique for fluoroscopic guided synovial biopsy of the glenohumeral joint as a potential technique for non-invasive diagnosis of indolent shoulder infections. This is a pilot study.

Methods

14 patients (4 females, 10 males) underwent a synovial biopsy in their work up where chronic glenohumeral infection was suspected. This was performed under fluoroscopic guidance. 3 samples of synovial tissue were obtained from the inferior recess using a 20 gauge Cheeba needle. The results were compared to intraoperative tissue cultures, considered the current gold standard.

Results

P. Acnes was the most common infective organism (57%). All positive synovial biopsies had the same result as intraoperative cultures (3/3). Discussion

Despite our small sample size and non-systematic collection of data, this study does show promise that synovial biopsy can be used as a diagnostic technique for shoulder infection. Using the described technique and recommendations obtained from the current literature including number of samples, processing, and incubation time, we plan to carry out a larger study with prospectively gathered data to validate this diagnostic tool.

Conclusion

Synovial biopsy may provide a means of minimally-invasive diagnosis of low-grade shoulder infections; further study is needed in order to fully validate this tool in a area in which there is currently limited ability for pre-operative diagnosis.

9. INCIDENCE OF HIP PAIN IN A PROSPECTIVE COHORT OF ASYMPTOMATIC VOLUNTEERS: IS THE CAM DEFORMITY A RISK FACTOR FOR HIP PAIN?

V. Khanna MD, FRCSC, G. Di Primio MD, FRCPC, K. Rakhra MD, FRCPC A. Caragianis, P. E. Beaulé MD, FRCSC

Purpose : Although cam-type femoroacetabular impingement is commonly associated with labral chondral damage, a large proportion of asymptomatic individuals will have this deformity without being symptomatic. The purpose of this study was to determine the incidence of hip pain in a prospective cohort of individuals who had undergone magnetic resonance imaging in the absence of hip pain.

Methods: Two hundred asymptomatic volunteers who underwent a MRI of both hips were followed for a mean time of 4.4 years (range 4.01-4.95). Thirty were lost to follow-up leaving 170 individuals (77 males, 93 females) with a mean age of 29.5 years (range 25.7 to 45.5 years). All patients were blinded to the results of their MRI. All completed a follow-up questionnaire inquiring about the presence of current hip pain or a history of hip pain lasting greater than 6 weeks since the original MRI. Each patient was asked the draw where the pain was on a body diagram.

Results: Eleven patients (5 males, 6 females; 6.5% of sample; mean age of 29.9 years [range 21.4-41.2 years]) reported at least one episode of hip pain lasting longer than six weeks, of which 3 (1 male, 2 females) had bilateral pain for a total of 14 hips. These 14 hips had a significantly higher alpha angle at both the 3:00 (44.1o [95% Confidence Interval 40.8-46.7o] vs. 40.9o [95% CI 40.1-41.7o]: p=0.03) and 1:30 (54.4o [95% CI 50.0-58.9o] vs. 50.1o [95% CI 49.2-51.0o]: p=0.01) positions when compared to the remaining cohort of patients without hip pain.

Of the 14 limbs with a history of hip pain, 7 (50%) had an asymptomatic cam-type deformity at the time of the original MRI (χ2=13.99, p=0.0002), with a relative risk of 4.3 [95% CI 2.3-7.8], p = 0.001 of subsequently developing hip pain if a cam deformity was present. Of the patients with a previously asymptomatic cam-type deformity, those that went on to develop pain had a greater alpha angle at the 1:30 position, than those who did not develop pain (61.5o [57.3-65.7o] vs. 57.9o [56.9-59.1o] respectively: p = 0.05). A significantly greater proportion of patients (12%) with limited internal rotation ≤20o also went on to develop hip pain compared to the proportion of patients (2.7%) with pain, but internal rotation > 20o (Chi square = 6.7, p = 0.009; Relative Risk = 3.1 [95% CI = 1.6-6.0] p = 0.0008).

Conclusions: Our results indicate that an elevated alpha angle and decreased internal rotation are associated with an increased risk of developing eventual hip pain. However, not all patients with a cam deformity develop hip pain and further research is needed to better define those at greater risk of developing degenerative symptoms.

10. A QUANTITATIVE COMPARISON OF THE DELTOPECTORAL AND DELTOID-SPLITTING SURGICAL APPROACHES TO THE PROXIMAL HUMERUS

William Scott McGuffin MD, Hakim Louati BASc, Peter L.C. Lapner MD, FRCSC, J Pollock MD, FRCSC

Purpose

Operative treatment of proximal humerus fractures requires a balance between adequate fracture visualization to achieve anatomic reduction and careful handling of soft tissues to protect the vascularity of fracture fragments. The goal of this study is to map the total bony surface area exposed with the deltopectoral and deltoid-splitting approaches and quantify the areas using computerized data acquisition techniques. Additionally our study compares the percentage of the greater tuberosity, lesser tuberosity and medial calcar of the humerus visualized during each approach. This allows for objective comparison between the approaches and their ability to access the different anatomic regions of the proximal humerus for fracture fixation.

Methods

Two approaches to the proximal humerus (the deltopectoral and the lateral deltoid-splitting approaches) were concurrently performed on fourteen cadaveric shoulders. At maximal internal and external rotation, the visible bony and articular surface areas were outlined using a drill and burr for each approach. The humeri were then stripped of all soft tissues for scanning. Each proximal humerus was converted into a digitized 3D model using a laser scanner system. The reproduced burr markings were then used to digitally quantify the exposed surface area through each approach.

Results

Overall, the deltopectoral approach exposes approximately 44% greater bony surface area compared to the deltoid-splitting approach. The lesser tuberosity was completely exposed during the deltopectoral approach, compared with 65% visualization during the deltoid-splitting approach. The greater tuberosity was visualized entirely through a deltoid-splitting approach compared with 90% visualization through a deltopectoral approach. The deltopectoral approach permits greater visualization of the anterior medial calcar than the deltoid- splitting approach (55% vs 0%) while the deltoid-splitting approach permits greater exposure of the posterior medial calcar (37% vs 10%).

Conclusions

The deltopectoral approach provides greater overall exposure to the proximal humerus. It provides adequate visualization of both greater and lesser tuberosities, as well as superior visualization of the medial calcar, and may be superior for three- and four-part proximal humerus fractures. The deltoid- splitting approach provides ideal access to the greater tuberosity and is well-suited for isolated greater tuberosity fractures.

11. THE OTTAWA ORTHOPEDIC ORIENTATION

Marie-France Rancourt MD

Division of Orthopedic Surgery University of Ottawa, The Ottawa Hospital Purpose

First-year orthopedic residents enter a program with varying baseline skills and knowledge. An orientation course would provide a safe environment for the development of core competencies and ensure high quality patient care. The purpose of this study was to evaluate a new intensive orthopedic orientation course designed to increase first-year residents’ orthopedic knowledge, confidence and surgical skills.

Methods

All six first-year residents (R1) completed the five day Ottawa Orthopedic Orientation (O3). The course included multi- disciplinary labs and lectures focused on surgical skills, patient safety, medicine, radiology, and anesthesia as it applies to the management of orthopedic patients. To evaluate the effectiveness of the course, the participants completed a questionnaire, a written exam, and “bell-ringer” test stations. The tests were administered a total of three times: pre-course, immediately post-course, and three months post course as a delayed retention test. Performance was compared with the six second year residents (R2) who had not taken the course but had completed one year of residency, including six months of orthopedic rotations.

Results

Both groups had a mean age of 29 years and had completed a mean of 13 weeks of orthopedic electives prior to residency. The R1s written test mean significantly increased from 48.84% ±13.42 pre-course to 74.19% ± 10.71 post course (p<0.01). This post course score was similar to the R2 mean of 73.39% ± 7.06 and sustained on the retention test, 70.43% ± 8.24.

The R1s demonstrated higher technical skills scores than the R2s (as represented by the AO Principles station) both post course 82% ± 23 vs 41.32% ± 21.56 (p=0.01) and on the retention test 82% ± 16.92 (p<0.01). The R1s test scores were significantly improved post course and sustained on the retention test for 4 of the 6 stations (AO principles, casting, trauma, and ID instrumentation), p<0.05. On a five point Likert Scale questionnaire, the course was shown to decrease anxiety and increase confidence. All inclusive, the course cost approximately 550$ per resident. Conclusions

The R1s who took the course demonstrated equivalent or better post-course scores than the R2s which suggests that this one week course improves residents’ technical and non-technical skills performance. The Ottawa Orthopedic Orientation is logistically manageable and economically feasible while allowing for a rapid improvement of first year residents’ confidence, surgical proficiency, orthopedic knowledge, and patient management skills.

12. DEVELOPMENT AND VALIDATION OF THE SELF-ADMINISTERED ONLINE ASSESSMENT OF PREFERENCES (SOAP) TOOL

M. Pahuta MD, C. Sun, G. Mitera, C. van Walraven MD D. Coyle MD, E. Wai MD, FRCSC, J. Werier MD, FRCSC

Purpose

A particularly disabling consequence of cancer is metastatic epidural spinal cord compression (MESCC). No prospective studies on the treatment of MESCC have collected quality- adjusted-life-year weights (termed utility scores). Utility scores are necessary so that treatments can be evaluated in a holistic patient-centered manner. Our objective was to develop a utility measurement tool, and a module for MESCC.

Methods

We developed a self-administered utility elicitation tool (SOAP) based on the von Morgenstern-Neumann standard gamble method. SOAP can be accessed from a computer or mobile touch-screen device over the internet. It has been developed with modular, freely-available, open-source code so that it can easily be applied to other clinical scenarios. SOAP was piloted with 100 individuals recruited from the orthopaedic fracture clinic. We evaluated the tool in terms of (1) ease of use, (2) stability, (3) discrimination, and (4) logical consistency.

Results

The SOAP tool surpassed benchmarks set by existing self- administered utility elicitation tools.

Conclusion

Therefore, the SOAP tool was judged to be valid for further use.

13. SOCIETAL VALUATION OF METASTATIC SPINAL CORD COMPRESSION HEALTH STATES

M. Pahuta MD, C. van Walraven MD, D. Coyle MD E. Wai MD, FRCSC, J. Werier MD, FRCSC Division of Orthopedic Surgery University of Ottawa, The Ottawa Hospital

Purpose

A particularly disabling consequence of cancer is metastatic epidural spinal cord compression (MESCC). No prospective on the treatment of MESCC have collected utility scores. We sought to collect utilities for the purpose of economic evaluation, therefore, our objective was to measure utilities from the societal perspective.

Methods

We recruited a sample of 822 Canadians from a market research company. Quota sampling was used to ensure that the participants were representative of the Canadian general population in terms of age, gender, and province of residence. Participants were asked to rate 6 health states using the SOAP MESCC module. .

Results

Univariate analysis demonstrated that participants provided ratings consistent with a priori health state rankings. Regression analysis demonstrated that participants valued ambulation, continence, pain, symptoms, and dependence equally.

Conclusion

These studies demonstrate that patient function is not the primary determinant of well-being for cancer patients. This finding has implications for clinical decision making. 14. A SINGLE-CENTRE PRELIMINARY EXPERIENCE OF THE ANTERIOR APPROACH FOR TOTAL HIP ARTHROPLASTY

C. Netting MD, P. E. Beaulé MD, FRCSC, P. R. Kim, MD FRCSC, K. A. Kemp MSc

Purpose

A particularly disabling consequence of cancer is metastatic epidural spinal cord compression (MESCC). No prospective on the treatment of MESCC have collected utility scores. We sought to collect utilities for the purpose of economic evaluation, therefore, our objective was to measure utilities from the societal perspective.

Methods

We recruited a sample of 822 Canadians from a market research company. Quota sampling was used to ensure that the participants were representative of the Canadian general population in terms of age, gender, and province of residence. Participants were asked to rate 6 health states using the SOAP MESCC module. .

Results

Univariate analysis demonstrated that participants provided ratings consistent with a priori health state rankings. Regression analysis demonstrated that participants valued ambulation, continence, pain, symptoms, and dependence equally.

Conclusion

These studies demonstrate that patient function is not the primary determinant of well-being for cancer patients. This finding has implications for clinical decision making.

15. COMPLICATIONS OF OPERATIVE TREATMENT OF DISTAL FEMORAL FRACTURES: IS OSTEOARTHRITIS ASSOCIATED WITH INCREASED RATE OF NON-UNION?

L. Chen MD, S. Papp MD FRCSC, W. Gofton, MD FRCSC, A. Liew MD FRCSC

Purpose The treatment of distal femoral fractures remains a significant surgical challenge. The purpose of this study was to review the distal femoral fractures treated operatively in our hospital between January 2009-December 2011 to determine the type and rate of complications and to compare this with the literature. The mechanical construct was also evaluated for factors including total construct length, working length, and screw type.

Results

Forty-five patients with 45 distal femur fractures were identified. 31 study patients with 31 fractures including 5 periprosthetic fractures had sufficient radiographic and clinical follow-up. The average time for union was 5.9 months. The overall union rate without reoperation was 74%. There were 8 non-unions (26%) requiring reoperation, including 5 with hardware failure (16%) and 1 patient that required 2 revisions (3%). Within the union group, there were 6 delayed unions (19%) which healed after 6 months. There were 3 (10%) infections requiring irrigation and debridement. The ratio of working length to total construct length was similar between the non-union and united groups. The usage of locked vs non locked screws proximally in the femoral shaft was also similar between groups.

In the non-union group, there were 3 patients (38%) with concomitant knee osteoarthritis compared with 5 patients (22%) in the united group.

Conclusion

Degenerative changes of the knee may generate more stress at the fracture site and be associated with an increased rate of non- union or hardware failure. 16. PREDICTORS OF EARLY ANTERIOR CRUCIATE LIGAMENT FAILURE, IS GRAFT DIAMETER A FACTOR?

I. MacNiven MD, D. Johnson MD, FRCSC

Purpose

To evaluate whether decreased hamstring autograft size leads to early anterior cruciate ligament (ACL) failure.

Methods

1259 consecutive patients undergoing primary arthroscopic ACL reconstruction with four-strand hamstring autograft from July 1999 to July 2012 were evaluated. Graft size, gender, patient age, and KT 1000arthrometer readings were recorded, along with whether subsequent ACL revision was performed.

Results

The 1259 patients comprised of 736 male and 491 female patients and ranged in age from 12 to 60 years (mean, 30.7 years). Follow up was completed on average until 24 months post operation. There were no failures in grafts greater than 8.0mm, 12 of 597 (2%) with 7.5mm or 8mm grafts, and 20 of 488 (4%) with grafts less than or equal to 7.0mm in diameter (P value of 0.004). 19 of 32 (59%) of failures occurred in men. The average age in the failure population was 28.4 years and in the non-failures was 30.8 years. Conclusions

Decreased hamstring autograft size was a predictor of ACL failure. Use of hamstring grafts of 8.0mm in diameter or less was associated with higher revision rates. Graft size may be an important variable in predicting the outcome of primary ACL reconstructions performed with hamstring autograft.

17. MIGRATION OF A MONOBLOCK ACETABULUM IN HIP RESURFACING; THE IMPORTANCE OF MEDIAL LUCENCIES

P. Whittingham-Jones MD, FRCSC, R. Roda P. R. Kim MD, FRCSC, P. E. Beaulé MD FRCSC

Purpose

It can be difficult to fully seat a monoblock Acetabulum during hip resurfacing. This has the potential for uncertainty in the results in both the short and long terms. Einzel Bild Roentgen Anlayse (EBRA) is a validated method of assessing the radiographic seating and migration of these components. The follow up of 196 hips, of which 120 met the inclusion criteria, is presented.

Results

Initially at first post-operative radiograph, 37 (30.8%) cups showed lucencies. 28 (46.6%) of 60 components with 2 year follow-up had exceeded the total migration threshold of >0.5mm per year after 2 years.

Conclusions

Initial post-operative lucencies appear not to be predictive for prosthesis migration, loosening requiring revision, nor for clinical outcome. The observation of components exceeding the migration threshold raises concerns about long term performance, however this study demonstrates that medial lucencies seen after hip resurfacings achieve the same clinical outcome and are not at increased risk of early loosening compared to components with no lucencies. 18. HIP ARTHROSCOPY IN PATIENTS IN LESS THAN 25 YEARS OF AGE: ANALYSIS OF OUTCOMES AND INDICATIONS FOR SURGERY

Gillian Bayley MD, Paul E. Beaulé MD, FRCSC

Purpose

Hip Arthroscopy has been shown to be a beneficial procedure for patients with mechanical hip symptoms mainly associated with femoroacetabular impingement. Recent literature has demonstrated improved quality of life following hip arthroscopywith older patients and those with moderate and severe cartilage damage having a poorer outcome. The purpose of this study was to review the clinical indications and outcome after hip arthroscopyin patients less than 25 years of age.

Methods

Sixty patients under the age of 25underwent hip arthroscopy performed by a single surgeon from October 2005 to March 2012; 7 were bilateral. All data was collected prospectively. Mean age at the time of procedure was 20.5 (16-25 range). There were 23 male and 37 female. All patients had a minimum one year follow-up. Indication for arthroscopy included isolated labral tear (25), femoral acetabular impingement (FAI) (36), hip dysplasia (4), avascular necrosis (AVN) (1) and snapping hip (1). Outcome data was prospectively collected using UCLA (University of California at Los Angeles) Activity Scale, HOOS (Hip Disability and Osteoarthritis Outcome Score), and the Marx Activity Scale. Following measurements were made on radiographs: lateral center edge angle, Tonnis angle, alpha angle. Tonnis grade was used to determine degree of arthritis. At the time of surgery the following procedures were done: labral debridement alone in 22; debridements and chondro- osteoplasty 42; and labral repair alone in 3.

Results At a mean follow-up of 1.56 years (range 1-5 years), the mean UCLA activity score improved from 6.9 (± 2.5) to 8.1 (± 2.3). Mean HOOS score went from 65.5 (± 23.9) to 79.7 (± 21.1). One patient underwent total hip arthroplasty for AVN, one underwent pelvic acetabular osteotomy for hip dysplasia, and one underwent femoral osteotomy for FAI.Complications included two lateral femoral cutaneous nerve deficits and one deep vein thrombosis. Six patients had persistent pain requiring repeat scope for labral repair.

Conclusions

Hip Arthroscopy in adolescent patients can improve function and quality of life with minimal morbidity. A large percentage (25/60) will have isolated labral pathology. As techniques such as labral repairs and reconstructions continue to evolve clinical results may further improve.

19. AN INDIVIDUAL PATIENT DATA META- REGRESSION OF THE SHORT- TERM TREATMENT EFFECTS FOR METASTATIC SPINAL CORD COMPRESSION

M. Pahuta MD, R. Patchell, E. Maranzano, C. van Walraven MD, D. Coyle MD, J. Werier MD, FRCSC, E. Wai MD, FRCSC ← ← Division of Orthopedic Surgery ← University of Ottawa, The Ottawa Hospital ←

Purpose A particularly disabling consequence of cancer is metastatic epidural spinal cord compression (MESCC). There is continuing debate as to whether surgery or radiation is more effective. Only one head-to-head randomized control trial has been conducted to evaluate these treatments. To improve the generalizability of this one trial, we conducted an indirect treatment comparisons meta-regression, of immediate treatment effects.

Methods

Three comparative randomized controlled trials were identified by a systematic review of the literature which evaluated two of: “split-course” radiotherapy (a total of 30 Gy over several fractions); “short-course” radiotherapy (16 Gy in 2 fractions), “single-course” radiotherapy (8 Gy in 1 fraction); and circumferential surgical decompression. The authors of these studies provided individual patient data. A Bayesian, multinomial logit random effects, individual patient data, indirect treatment comparison, meta-regression model was developed. Covariates in the model included: age, tumor histology, gender, and functional score. We investigated a (1) baseline categories, (2) adjacent categories, (3) continuation ratio, and (4) cumulative logit model for the data

Results

The analysis included a total of 416 patients. An unordered multinomial model demonstrated the best calibration and discrimination. Surgical treatment increased the rate of ambulation, but had no impact survival. Treatment effect was not modified by any covariate.

Conclusion

These results indicate that in the short-term, surgery is superior to radiation. 20. AN INDIVIDUAL PATIENT DATA META- REGRESSION OF THE LONG-TERM TREATMENT EFFECTS FOR METASTATIC SPINAL CORD COMPRESSION

M. Pahuta MD, R. Patchell, E. Maranzano, C. van Walraven MD, D. Coyle MD, J. Werier MD, FRCSC, E. Wai MD, FRCSC ← ← Division of Orthopedic Surgery ← University of Ottawa, The Ottawa Hospital ←

Purpose

A particularly disabling consequence of cancer is metastatic epidural spinal cord compression (MESCC). There is continuing debate as to whether surgery or radiation is more effective. Only one head-to-head randomized control trial has been conducted to evaluate these treatments. To improve the generalizability of this one trial, we conducted an indirect treatment comparisons meta-regression, of long-term treatment effects.

Methods

Three comparative randomized controlled trials were identified by a systematic review of the literature which evaluated two of: “split-course” radiotherapy (a total of 30 Gy over several fractions); “short-course” radiotherapy (16 Gy in 2 fractions), “single-course” radiotherapy (8 Gy in 1 fraction); and circumferential surgical decompression. The authors of these studies provided individual patient data. A Bayesian, multistate random effects, individual patient data, indirect treatment comparison, meta-regression model was developed. Covariates in the model included: age, tumor histology, gender, and functional score. We investigated a (1) time-homogenous, (2) time-inhomogenous, and (3) semi markov model for the data.

Results

The analysis included a total of 334 patients. A time- homogenous markov model demonstrated the best calibration and discrimination. Treatment had no effect on the transition from ambulation, or the transition to death.

Conclusion

These results indicate that in the long-term, surgery and radiation are equivalent.

21. ASSESSMENT OF CARTILAGE PROTEOGLYCAN CONTENT OF PATIENTS WITH FEMOROACETABULAR IMPINGEMENT

Adrian Huang MD, Andrew D. Speirs MSc, Paul E. Beaulé MD, FRCSC

← Division of Orthopedic Surgery ← University of Ottawa, The Ottawa Hospital ← Purpose: Degeneration of cartilage within articular joints is a pathological feature of osteoarthritis. Femoroacetabular impingement (FAI), a condition of abnormal contact between the articular surfaces of the femur and acetabulum, has been widely associated with early onset osteoarthritis of the hip. Proteoglycan plays a critical role in regulating fluid pressure and supporting contact stresses in articular cartilage. The purpose of this study was to quantitatively compare the proteoglycan content, as measured by glycosaminoglycan (GAG), of the cartilage in the cam-FAI deformity in surgical patients compared to normal cartilage from cadaver controls.

Methods: Osteochondral plugs were taken during surgery from the cam deformity of 11 patients undergoing surgical correction of symptomatic cam-FAI. Control specimens were harvested from eight cadavers at approximately the same location on the peripheral antero-lateral weight-bearing surface. The GAG content of the specimens were then histologically compared using the model presented by Martin et al (Ann Biomed Eng 1999).

In this method, Safranin-O binds to chondroitin sulfate, a GAG abundant in cartilage, allowing it to be visualized and quantitatively compared. Specifically, the specimens were fixed in formalin, decalcified in EDTA and then sectioned to 7um thick. They were then stained with Safranin-O, which binds specifically and stoichiometrically with proteoglycan. This model allows for quantitative comparison of GAG content whereby the red content (Rc) of the sample is linearly correlated with the amount of GAG present in the sample when viewed under 4x microscopic magnification. Here, the red content was sampled by depth coordinate with superficial and deep zones analyzed. These zones corresponded to the superficial 30% and deep 70% of the tissue specimens

Results: In general, the RC in the cartilage of surgical patients was lower than that of the cadaveric controls, correlating to a decrease in the GAG content of the surgical subjects. In the surgical specimens, RC ranged from 0 – 31.9 in the superficial layer and 0 – 139.6 in the deep. Mean RC of the superficial zone was 17.5 in the surgical specimens compared to 88.6 in controls. In the deep zone, the mean superficial and deep R C values were 52.4 vs. 129.2. The lower RC values indicate a severe depletion of GAG content, by 80.2% in the superficial zone and 59% in the deep zone. For the full thickness, mean

Rcvalues were 64% lower in the surgical specimens compared to controls. Notably, some surgical specimens exhibited no GAG content.

Conclusion: These results show large compositional differences in the cartilage of surgical FAI versus control specimens. The lower GAG content is expected to result in lower cartilage stiffness and higher permeability in surgical specimens. GAG depletion is likely induced by abnormal contact stresses involved in FAI and supports the pathomechanism of FAI as the cause of hip arthritis.