Purpose

To review prospectively collected data on patients undergoing primary total hip arthroplasty utilizing two different cementless acetabular components.

To review prospectively collected data on patients undergoing primary total hip arthroplasty utilizing two different cementless acetabular components.

All patients undergoing primary total hip replacement surgery at our institution are entered prospectively into a database which includes history and physical examination, radiology, WOMAC and SF-36 scores. The patients are re-examined, re-x-rayed and re-scored at 3 months, 6 months and 1 year after surgery and yearly thereafter.

Using this database we are able to identify patients who have undergone total hip replacement using one of two geometric variants of the acetabular component. The first design is hemispherical and the second design has a peripheral rim expansion designed to increase initial press-fit stability.

Five hundred and twenty-seven consecutive primary total hip replacements were identified using either of the geometric variants of the acetabular component. Results at a mean of 7 years revealed a 95.6% survivorship with no significant difference between the two component designs with revision for aseptic loosening as the end point. Functional scores between the two groups of patients also demonstrated no statistically significant difference.

Radiologic assessment, however, showed a difference between the two designs. The hemispherical design which matches the reamer line-to-line had 80% complete osseointegration on final radiologic review while the second design with a peripheral rim expansion had only 57% complete osseointegration. This was statistically significant. The peripherally expanded components also had a greater number of screws inserted at the time of surgery, felt by us to be a reflection of initial surgeon dissatisfaction with component stability at the time of insertion of the component.

The difference in screw numbers was also statistically significant. This study demonstrates that a hemispherical design with line-to-line contact between the acetabular component surface and the acetabular bone is statistically superior in terms of bone ingrowth and probably statistically superior in terms of initial press-fit stability when compared to a peripherally expanded component.

Peripherally expanded components appear to offer no advantage over hemispherical components in terms of clinical outcome and are statistically inferior to hemispherical components in radiologic parameters at 7 years follow-up.

Objectives

To assess the effectiveness of a modified tibial tubercle osteotomy as a treatment for arthroscopically diagnosed chondromalacia patellae.

Purpose

To review prospectively collected data on patients undergoing primary total hip arthroplasty utilizing two different cementless acetabular components.

Introduction

Hydroxyapatite (HA) coated femoral stems require a press fit for initial stability prior to osteointegration occurring. However this technique can lead to perioperative femoral fracture.

Introduction: This study aimed to determine the accuracy of computer navigation in simulated fixation of femoral neck and supracondylar femoral fractures using different sizes of guidewires and drills from commercially available cannulated screw systems.

Methods: Simulated fracture fixation was performed with 2.5mm, 2.8mm and 3.2mm threaded guidewires and 3.2mm and 5mm drill bits using 20 4th generation synthetic femurs. The drill or guide wire was inserted in the synthetic femurs, using fluoroscopy based computer navigation (24 drills/guidewires in each group). Pre and postoperative fluoroscopy images were acquired with the C-arm and synthetic bone in the same orientations. Virtual and real wire/drill positions were compared, and errors calculated for each diameter of drill/guidewire (sum AP + Lateral error (mm)). Errors were compared using a general linear model with Tukey adjustment for multiple comparisons. Statistical significance at a two-tailed p-value < 0.05.

Results: The mean error for the 5.0mm drill (3.20mm) was significantly less than all the threaded wires (p< 0.05). The mean error for the 3.2mm drill (5.68mm) was significantly less than the 2.5mm guidewire (9.27mm) p< 0.05, and less than the 2.8mm (8.19mm) and 3.2mm (7.14mm) threaded wires.

Discussion: For cannulated screws, the 3.2mm drill was the most accurate size tested. The most accurate drill, 5mm, would allow solid screw insertion. However, its large size may preclude screw repositioning, and unlike a cannulated screw, would not maintain fracture position whilst the screw was being inserted.

Introduction: This study compared the accuracy of reduction of intra-medullary nailed femoral shaft fractures, comparing conventional and computer navigation techniques.

Methods: Twenty femoral shaft fractures were created in human cadavers, with segmental defects ranging from 9–53mm in length. All fractures were fixed with antegrade 9mm diameter femoral nails on a radiolucent operating table. Five fractures (control) were fixed with conventional techniques. Fifteen fractures (study) were fixed with computer navigation, using fluoroscopic images of the normal femur to correct for length and rotation. The surgeon was blinded to defect size. Two landmark protocols were used in the study group referencing the piriform fossa (Group A, n=10) or proximal shaft axis (Group B, n=5). Postoperative CT scans, blindly reported by a musculoskeletal radiologist, were used to compare femoral length and rotation with the normal leg.

Results were analysed using ANOVA with 95% Confidence Intervals.

Results: The control and study groups were not statistically different with respect to age of cadaver or size of femoral defect. Results: The mean leg length discrepancy in the study groups were significantly less (3.6mm (95% CI 1.072 – 6.128) and 4.2mm (95% CI 0.63–7.75), compared with 9.8mm (95% CI 6.225 – 13.37) in the control group (p< 0.023). The mean torsional deformities in the study groups were 8.7 degrees (95% CI 4.282 – 13.12) and 5.6 degrees (95% CI -0.65 – 11.85), compared with 9 degrees (95% CI 2.752 – 15.25) in the control group (p=0.650). Within the navigated study group, length discrepancy was similar in subgroups 1 (3.6mm) and 2 (4.2mm). Torsion appeared more accurate in group 2 (5.6 degrees) than group 1 (8.7 degrees), although this was not statistically significant.

Discussion: Computer navigation significantly improves the accuracy of femoral shaft fracture fixation with regard to length. With further modifications to improve reduction of rotational deformity, it may be a useful technique in the treatment of femoral fractures.

The effect of cup geometry in uncemented Total Hip Arthroplasty has not been investigated. We reviewed the radiological and clinical results of 527 primary total hip arthroplasties. We assessed the bone ingrowth potential of two geometric variations of an uncemented cup and compared hydroxyappetite and porous coated shells.

Patients undergoing primary hip arthroplasty between 1997 and 2004 were prospectively entered into an arthroplasty database. Patients were reviewed at 1,2,4,5,8 and 10 years post surgery. Three acetabular shell types were used. These included hemispherical cups with porous or hydroxyapatite coating, and cups with peripheral expansion with porous coating. Radiographs with minimum 1-year follow-up were examined in 542 cases, using digital templating software. Radiographs were assessed for signs of bone in-growth, lucent lines, migration and polyethylene wear. Survivorship analysis was performed using Kaplan-Meier analysis with 95% confidence intervals. Radiological findings and cup type were analysed using Fishers exact test.

Radiological evidence of bone ingrowth was seen in 82% of hemispherical cups, compared with 59% of peripherally expanded cups, which was significant (p,0.05). Bone ingrowth was not affected by the presence of HA coating. The most common diagnoses were osteoarthritis (67%) and avascular necrosis (12%). The mean age was 56 years. Survivorship with revision or impending revision for aseptic loosening was 95.6% at 7 years (95%CI 1.0134-0.8987). The 3 revisions and 1 impending revision for loosening were in patients with avascular necrosis (3) or previous acetabular and femoral osteotomies for DDH (1), with a mean age of 44 years.

Hemispherical shells have improved radiographic outcome in comparison with peripherally expanded components. At 7 years, clinical results are similar for both components.

This study compared the accuracy of reduction of intra-medullary nailed femoral shaft fractures, comparing conventional and computer navigation techniques.

Twenty femoral shaft fractures were created in human cadavers, with segmental defects ranging from 9–53mm in length. All fractures were fixed with antegrade 9mm diameter femoral nails on a radiolucent operating table. Five fractures (control) were fixed with conventional techniques. Fifteen fractures (study) were fixed with computer navigation, using fluoroscopic images of the normal femur to correct for length and rotation. The surgeon was blinded to defect size. Two landmark protocols were used in the study group referencing the piriform fossa (n=10) or proximal shaft axis (n=5). Postoperative CT scans, blindly reported by a musculoskeletal radiologist, were used to compare femoral length and rotation with the normal leg. Results were analysed using the Wilcoxon two-sample test.

The mean leg length discrepancy in the study group was 3.8mm (range 1–9), compared with 9.8mm(range 0–17) in the control group (p=0.076). The mean torsional deformity in the study group was 7.7 degrees (range 20–2) compared with 9 degrees (range 0–22) in the control group (p=0.86). Within the navigated study group, length discrepancy was similar in subgroups A (3.6mm) and B (4.2mm). Torsion appeared more accurate in group B (5.6 degrees) than group A (8.7 degrees), although not significantly.

Computer navigation appears to improve leg length discrepancy following femoral nailing. Technique modification during the study improved rotational accuracy, and with further improvement, will make this technique applicable to femoral fracture fixation.

We retrospectively reviewed 19 femoral non-unions. Age group ranged from 17–72 yrs with mean of 40 yrs. 12 were men and 7 were women. 11 fractures involved diaphysis and 8 involved supracondylar area. 5 cases were infected non-unions. Time from fracture to defini-tive treatment varied from 5 to 88 months (mean 21 months). Open technique was used in 18 cases. In 8 cases we have used autogenous cancellous bone graft and in 3 cases BMP7 was used in addition to bone graft. 9 cases were treated with Ilizarov frame without bone graft, 6 with plate & bone graft, 3 with intramedullary nail and 1 with bone graft alone. Internal bone transport was carried out in 5 cases to achieve limb length equality. Fracture union was achieved in 16 patients with 7 excellent and 8 good results as per ASAMI criteria. 15 cases achieved excellent to good functional results. Because of persistent infection, 2 distal femoral non-unions required transfemoral amputation. Treatment was discontinued due to psychiatric illness in 1 patient with Ilizarov frame. Two of the patients in Supracondylar group developed knee stiffness. Pin tract infection is a common complication in Ilizarov group.

Adequate reduction & stabilization is key to success. Non-unions without any complications can be treated with exchange nail or open reduction and plating. Ilizarov method is effective for non-unions complicated by distal location, infection and bone loss. Psychological assessment is important before considering Ilizarov method of treatment.

Introduction We report the clinical and radiographic outcome of a consecutive series of 138 hydroxyapatite coated total knee replacements with a mean follow up of 11 years (10–13 years)

Method and Results These patients were entered into a prospective study. There were 74 females and 32 males. Indications for surgery were osteoarthritis in 131 knees, rheumatoid arthritis in 5 knees and pigmented villo-nodular synovitis in 2 knees. The mean age of the patient was 72.5 years at the time of surgery. All living patients (76 knees) were examined and X rayed. A current Hospital for Special Surgery knee score (mean 83 points) was obtained for comparison with the preoperative profile (mean 55 points).The knee status of deceased patients was known within the year of death. No patient was lost to follow up. Radiological evaluation, assessed according to the method described by the Knee Society, revealed no loosening in surviving patients, and there are no impending revisions. Seven prostheses have been revised, giving a cumulative survival rate of 93 percent at 13 years.

Discussion. We believe this to be the longest follow up report available for an hydroxyapatite coated knee replacement, and the first using the Insall Burstein knee. Results can thus be compared with the identical prosthesis using cemented fixation. Further modifications would be likely to improve reliability.

We have prospectively followed 100 consecutive HA coated knee replacements performed from 1990–1992. The prostheses was a cruciate sacrificing IB II, with HA coating on the femoral and tibial components. The average age at surgery was 72.5 years [32–92]. The indications for surgery was predominantly osteoarthritis [93 cases]. 3 knees required cemented tibial components at surgery and were excluded from the series. All knees were mobilised full weight bearing postoperatively.

Patients were reviewed annually with radiographic and clinical evaluation [Hospital for Special Surgery Knee score]. There was no loss to follow-up and at most recent review 48 people [60 knees] were alive. Of these, 47 knees had a final radiographic examination; the remaining knees were assessed clinically but did not attend hospital.

Using revision or need for revision as the endpoint for failure, 6 knees have been revised giving a 10 year survival of 92% [CI 0.96–0.76]. 3 tibial and 2 femoral components underwent aseptic loosening. 1 revision was for infection and 1 for technical errors.

Using pain as the endpoint for survival, 5 surviving knees [9.3%] complained of moderate or severe pain at rest or during exercise and could be regarded as failures.

There is a very low incidence of radiolucent lines at the prostheses-bone interface with 11 radiolucent zones of < 1mm under the tibial component [knee society radiological evaluation]. 72% of cases demonstrated evidence of bone-prostheses bonding with ‘spot welds’ or buttress formation.

Overall the survival at ten years is comparable with cemented fixation. We believe the evidence of bone-prostheses bonding and absence of radiolucent lines indicates that the surviving knees will continue to function well.

The aim of this study was to assess the outcome of patients who underwent ElmslieTrillat antero-medial tibial tubercle transfer for treatment of persistent symptomatic anterior knee pain due to chondromalacia patellae.

We performed a prospective analysis of 23 patients who underwent Elmslie-Trillat antero-medial tibial tubercle transfers over a five year period for chronic anterior knee pain and an arthroscopic diagnosis of chondromalacia patellae. All patients who presented with anterior knee pain underwent an initial period of physiotherapy and all patients whose symptoms persisted following physiotherapy underwent arthroscopic assessment. Patients who continued to experience debilitating symptoms despite this initial treatment and who also had a diagnosis of chondromalacia patellae from arthroscopic assessment were listed for an Elmslie-Trillat tibial tubercle anteromedialisation. Patients who gave a history of instability or dislocation were excluded. The average age of patients undergoing surgery was 34 years (21–48 years) and the average time between arthroscopic diagnosis and surgery was 14 months. All patients who underwent surgery had pre and post operative KuJala patellofemoral scoring. The average pre-operative score was 54 (30–78) and post operative score 76 (46–100). The average post operative assessment was 25 months (6–62 months). Twenty one patients had improved post operative scores with one having a worse score and one score remaining unchanged following surgery. Nineteen patients felt that their symptoms had improved, three felt that there had been no change and one felt that they were worse after surgery. When asked if the improvement in symptoms had been worthwhile nineteen stated that they would undergo surgery again if in the same situation and four stated that they would not.

The treatment of symptomatic chondromalacia patellae remains a challenge. Although a more selective approach to individuals with anterior knee pain is widely advocated in the literature this study demonstrates that good results can still be achieved in patients treated empirically with a tibial tubercle anteromedialisation.