Comparison of two cementing techniques: femoral component insertion into early-cure stage cement and insertion into late-cure stage cement in an in vivo model to identify if cement cure stage affects the strength of the bone cement interface.

Bilateral arthroplasties – using only the femoral component - were performed in vivo on paired porcine femora. The femora were harvested and cross-sectioned in preparation for strength testing. Performance was measured by peak load required to push the femoral prosthesis and surrounding cement mantle free of the cancellous bone.

The mean failure load for prostheses inserted into late cure stage cement was 908 N +/− SD 420, whereas the mean failure load for the conjugate early cure stage cement was 503 N +/− SD 342. A paired t-test indicated significantly higher load failure rates in the late cure stage cement versus the early cure stage samples (t=2.37, p< 0.049).

Femoral component insertion into late cure stage cement required statistically significant higher loads for push-out when compared to femoral component insertion into early cure stage cement.

Purpose: To assess patients quality of life, pain, and functional limitations with with endstage ankle arthritis (EAA) and compared this to a similar cohort of patients with endstage hip arthritis (EHA).

Methods: Preoperative data (Short Form SF36) was collected prospectively from patients (n=130) with end stage ankle arthritis and compared to a similar cohort of patients (n=130) with end stage hip arthritis. Patients with ankle arthritis were registered in the Canadian Orthopedic Foot and Ankle Society (COFAS) multi-center study investigating the clinical outcome of ankle arthroplasty and fusion and patients with hip arthritis were randomly selected from the Halifax Joint Replacement Registry Database.

Results: All symptom and functional SF36 subscales for patients with EAA or EHA, were approximately two standard deviations below normal population scores. All differences between ankle and hip SF36 subscales scores were less than 4 points (40% of STD) in both direct and adjusted comparisons. A direct comparison of SF36 scores revealed that patients with EAA had significantly worse mental health according to the SF36 Mental Component Summary Score (MCS) (p= 0.0059), physical limitations with work and daily activities - role physical score (p= < 0.0001), and general health (p= 0.0004). Patients with EHA reported poorer physical function (p= 0.0007) although the Physical Component Summary Score (PCS) for the SF36 was not significant (p= 0.0510). Total Summary SF36, Physical Component Summary (PCS), bodily pain, vitality, role-emotional, social functioning, and mental health subscales were all not significantly different between cohorts (p> 0.05).

Conclusions: Patients with EAA have devastating losses of quality of life, which are comparable to patients with EHA. These findings suggest that increased resources should be directed towards alleviating the severe pain and disability associated with ankle arthritis.

Wrong site surgery is a preventable problem. In 1994 the Canadian Orthopaedic Association (COA) began an educational program initiated to prevent such mistakes from occurring. The purpose of this study was to assess the proportion of orthopedic surgeons who mark their sites preoperatively. This study confirms a high proportion (74.9%) of surgeons in Canada follow the COA guidelines at least occasionally with over half (52.1%) consistently “signing their sites.”

Wrong site surgery is often a catastrophic, but preventable problem. Reports of wrong site surgery have been on the rise in the United States every year since 1995. In 1994 the Canadian Orthopaedic Association (COA) began an educational program initiated to prevent such mistakes from occurring. Their recommendations involved marking the incision site preoperatively. Since that time the claims of wrong site orthopedic surgery have diminished. The purpose of this study was to assess the proportion of orthopedic surgeons who mark their sites preoperatively.

Two hundred orthopedic surgeons across Canada were asked to complete a survey concerning preoperative incision site marking.

A response rate of 89.3% was achieved. Eighty seven (52.1%) stated they always marked their incision site, thirty eight (22.8%) stated they occasionally marked their incision site, while forty two (25.1%) claimed to never mark their incision site preoperatively. Surgeons in academic centers were more likely to sign their sites than their community counterparts (p=0.021) and surgeons in practice longer were less likely to comply with the COA recommendation (p=0.023).

The COA and American Academy of Orthopedic Surgeons (AAOS) have recommended marking incision sites preoperatively in an attempt to reduce wrong site surgery. This study confirms a high proportion (74.9%) of surgeons in Canada follow the COA guidelines at least occasionally with over half (52.1%) consistently “signing their sites.”

We performed a prospective genotype-phenotype study using molecular screening and clinical assessment to compare the severity of disease and the risk of sarcoma in 172 individuals (78 families) with hereditary multiple exostoses. We calculated the severity of disease including stature, number of exostoses, number of surgical procedures that were necessary, deformity and functional parameters and used molecular techniques to identify the genetic mutations in affected individuals. Each arm of the genotype-phenotype study was blind to the outcome of the other. Mutations EXT1 and EXT2 were almost equally common, and were identified in 83% of individuals. Non-parametric statistical tests were used.

There was a wide variation in the severity of disease. Children under ten years of age had fewer exostoses, consistent with the known age-related penetrance of this condition. The severity of the disease did not differ significantly with gender and was very variable within any given family. The sites of mutation affected the severity of disease with patients with EXT1 mutations having a significantly worse condition than those with EXT2 mutations in three of five parameters of severity (stature, deformity and functional parameters). A single sarcoma developed in an EXT2 mutation carrier, compared with seven in EXT1 mutation carriers. There was no evidence that sarcomas arose more commonly in families in whom the disease was more severe.

The sarcoma risk in EXT1 carriers is similar to the risk of breast cancer in an older population subjected to breast-screening, suggesting that a role for regular screening in patients with hereditary multiple exostoses is justifiable.

Over a five year period 50 patients required combined orthoplastic care out of 987 patients presenting with bone and soft tissue tumours. Thirty men, mean age 51 years, had their treatment reviewed at a mean follow up of 23 months (3–54 months) post surgery. All surviving patients completed the Toronto Extremity Salvage Score.

There were 23 bone and 27 soft tissue sarcomas, 4 were Enneking stage I, 41 stage II and 5 stage III. All tumours were removed by wide resection to achieve microscopically clear margins in 49. 9 endoprostheses were inserted. Soft tissue reconstruction involved 9 local flaps, 13 distant flaps (mainly muscle) and 8 free flaps (including 3 composite osseous flaps). 20 patients received adjuvant radiotherapy and 14 patients received chemotherapy.

Two endoprosthetic replacements required surgery for infection, one distant lap and one free flap required further surgery (6%). The mean disease free interval was 29 months (2–49 months). There were 6 deaths and pulmonary metastases occurred in a further 8 patients. Within this study period there was one episode of local recurrence, but no local recurrence in the group that had radiotherapy. 77% of surviving patients completed the Toronto Extremity Salvage Score and good to excellent function was seen in most cases.

Combined orthoplastic approach facilitates limb sparing surgery and early adjuvant radiotherapy.

To determine whether the spectrum of genetic mutation in Hereditary Multiple Exostoses supports a neoplastic aetiology for this condition.

Historically, experts have been cautious in attributing neoplastic qualities to the osteochondroma. Solomon states ‘[osteochondromas] are not neoplastic in the ordinary sense of the word’; Morton that it ‘is not a tumour but a growth-aberration; Peterson that the ‘osteochondroma is not a true neoplasm’; and Schmale that ‘exostoses are the result of dysplasia of the lateral apect of the growth-plate’. There are, however, several features of osteochondroma behaviour common to other neoplasms which suggest a neoplastic aetiology:

the existence of an autosomal dominant inherited multiple form, in which lesions are histologically identical to the solitary form.

Recent genetic data has supported a fresh look at the neoplastic nature of osteochondromas. EXT1 and EXT2 genes are responsible for Hereditary Multiple Exostoses (HME). EXT1 codes for a protein which alters the synthesis and display of cell-surface heparan sulphate glycosaminoglycans; molecules which affect cellular growth, differentiation, motility and adhesion. Loss-of-function of such a gene may initiate a neoplastic pathogenesis in osteochondromas.

From 1996–1999, 51 families with HME were screened for EXT mutation, with mutations identified in 41 families. EXT mutation was assessed by means of fluorescent single-strand conformational polymorphism (f-SSCP) screening, followed by sequencing analysis.

Results : All missense mutations had previously been reported in the literature. In contrast, only 9 of 34 loss-of function mutations (frame-shift, splice-site and nonsense) had previously been reported.

All frame-shift, splice-site and nonsense mutations are loss-of-function. Missense mutations may result in partial or complete dysfunction if a crucial folding or binding site is involved. Since no missense mutations were new, this suggested their mutation sites are important, and may effectively result in loss-of-function. These data strongly support a tumour suppressor gene function for EXT genes, and a neoplastic pathogenesis for HME.

To identify if disease severity and cancer-risk might depend on genotype in Hereditary Multiple Exostoses (HME).

The discovery that the EXT family of tumour suppressor genes is responsible for Hereditary Multiple Exostoses (HME) now enables correlation of clinical features with genetic defects. Genetic epidemiological studies, such as this, may provide additional data of use to the clinician. In most population-based HME cohorts, the incidence of sarcomatous degeneration has been estimated as 1–5%. This is not high, but occurs at a younger age (on average 2–3 decades younger) than chondrosarcoma in the general population. Genetic stratification might allow a very high-risk subgroup to be identified, within which surveillance for neoplastic change in osteochondromas could be concentrated.

In a pilot study, 29 affected individuals from 17 families with HME were screened for EXT mutation, with mutations identified in 12 families. Pedigrees were obtained and a complete assessment of disease severity made. We have since expanded this cohort; a further 71 affected individuals from 34 families with HME have provided detailed pedigree data and undergone a simple clinical examination to assess number of palpable osteo-chondromas. EXT mutation was assessed by means of fluorescent single-strand conformational polymorphism (f-SSCP) screening, followed by sequencing analysis.

Validation of clinical examination : In those who underwent radiographic examination for clinical purposes, number of palpable osteochondromas correlated strongly with number seen on radiographs at 146 anatomical sites (r= 0.814, p< 0.001), validating the usefulness of clinical examination in a population analysis, and negating the need for a radiographic skeletal survey in individuals at risk from malignant change.

The observation that osteochondromas are more frequent in patients with EXT1 than EXT2 mutations is an important message in genetic counselling. If disease severity and cancer risk is greater in individuals with EXT1 mutation, screening for neoplastic change might be targeted on this group, in which lifetime risk of malignant change in osteochondromas could be increased to between 5% and 10%.