Computer-assisted surgery (CAS) is a tool developed to allow accurate limb and implant alignment in total knee arthroplasty [TKA]. The strength of the technology is that it allows the surgeon to assess soft tissue balance and ligament laxity in flexion and extension. The accuracy of this ligament balancing technology depends upon an accurate determination of femoral component size. This size is established with intraoperative surface registration techniques. Customised instrumentation (CI) is a measured resection technique in which component size is established on preoperative 3D MRI reconstructions. The purpose of this study is to determine how these two computer-based technologies compare with regard to the accuracy with which femoral component size is established in TKA.

67 TKA were performed using CI and 30 TKA were performed using CAS by a single surgeon. CI-predicted and CAS-predicted femoral component size were compared to actual component selection. The process by which CI and CAS perform an anatomic registration was evaluated.

The CI and CAS systems accurately predicted surgeon-selected femoral component size in 89% and 43% of cases, respectively (p<0.001). The discrepancy between predicted and actual femoral component size with CI and CAS was 0.1 and 0.8 sizes, respectively (p<0.001). The maximum deviation between predicted and actual femoral component size was greater in CAS than in PMI (three sizes versus one size, respectively). The anterior cortex cut was flush in 92% of CI cases. The rotation profile was consistent with Whiteside's line in 95% of CI cases.

The CI system was both more accurate and more precise than the CAS navigation system in predicting femoral component size in TKA. CI utilises preoperative MR imaging to generate femoral component sizing based on optimizing medial-lateral fit with a measured posterior femoral bone resection. CAS utilises surface registration techniques based on anatomic site registration that may be subject to intraoperative measurement error due to difficult visualization (femoral epicondyles), inherent subjectivity (Whiteside's line) or anatomic variation (hypoplastic posterior condyles). CI bases implant sizing solely on reproducing an anatomical fit and a measured resection technique, whereas CAS attempts to balance an anatomic fit with optimal soft tissue balancing. In this study, the surgeon's final component selection was more likely to be in accordance with the CI rather than the CAS sizing algorithm. The CI system was capable of accurate femoral component placement in TKA.

This study suggests that intraoperative surface registration may not be as accurate as preoperative 3D MRI reconstructions for establishing optimal femoral component sizing. Surgeons using intraoperative navigation based surface registration need to be aware of this when making femoral component size selection, establishing ligament balance, and determining femoral rotation.

The focus of deep vein thrombosis (DVT) prophylaxis following total joint arthroplasty has shifted in recent years to the reduction of symptomatic pulmonary emboli (PE). The relative infrequency and presumed delayed occurrence of these events has led many to suggest that the risks of more frequent early postoperative complications of treatment, especially bleeding, be weighed against the benefits of thromboembolic prophylaxis. The purpose of this study was to determine the timing and risk factors associated with the development of symptomatic PE following total hip arthroplasty (THA) and total knee arthroplasty (TKA).

A retrospective analysis was performed of all patients diagnosed with a symptomatic pulmonary embolism following THA and TKA performed from January, 2004 to March, 2008. The records of 4706 patients were reviewed who were operated upon by 7 surgeons, and a total of 58 PE were identified. All patients were managed and treated by an anti-coagulation dosing service. Helical CT Scans were used to make the diagnosis of PE.

The overall incidence of PE was 1.2%, with 1.8% occurring in TKAs and 0.5% occurring in THAs. 48 of the 58 PE patients (83%) were women. 33 patients (57%) had unilateral TKA, 14 (24%) had bilateral TKA and 11 (19%) had THA. The average patient age was 65 (range: 44–88) and BMI was 33.8 (range: 24.7–51.9). There was no apparent correlation between age and BMI with incidence of PE. The PE were diagnosed an average of 4 days (range: 1–46) following surgery. 56 of the 58 patients (97%) were diagnosed by the sixth postoperative day. The average INR at the time of diagnosis was 1.7 (range: 1.0–3.0). There were two mortalities (3%), both of which occurred within the first two postoperative days.

The PE in this study occurred predominantly in women undergoing TKA. There appears to be an urgent need to develop an effective prophylaxis program aimed at preventing PE in the early post-operative period and to identify patients at risk of these PE.

Originally introduced in 1997, porous tantalum is an attractive alternative metal for orthopaedic implants because of its unique mechanical properties. Porous tantalum has been used in numerous types of orthopaedic implants, including acetabular cups in total hip arthroplasty. The early clinical results from porous tantalum acetabular cups have been promising. The purpose of this study was to evaluate the presence of bone ingrowth and the incidence of osteolytic lesions in the acetabular cup -at 10 year follow up – in patients who had a total hip arthroplasty with a monoblock porous tantalum acetabular cup.

50 consecutive patients underwent a total hip arthroplasty with a monoblock porous tantalum acetabular component. All patients had computed tomography at an average of 10 years of follow-up. The computed tomography scan used a standard, validated protocol to evaluate bony ingrowth in the cup and for the presence of osteolysis.

The computed tomographic scans showed evidence of extensive bony ingrowth, and no evidence of osteolysis.

This study reports the 10-year results of a monoblock porous tantalum acetabular cup. This is the first study to evaluate a porous tantalum acetabular cup with the use of computed tomography. These results show that a porous tantalum monoblock cup has excellent bony ingrowth and no evidence osteolysis at 10 year follow-up. These results suggest that porous tantalum is an attractive material for implantation in young, active patients.

Despite the clinical success of uncemented femoral stems of various types, current issues continue to require repeated examination:

proximal-distal mismatch

A previous study demonstrated that a custom-made (based on CT-scan) short metaphyseal engaging femoral stem design provided stable fixation and reliable bony ingrowth at four-year follow-up. The purpose of this study is to present the minimum two-year clinical and radiographic results obtained with an off-the-shelf metaphyseal filling stem.

An uncemented, metaphyseal engaging femoral stem was inserted in 194 consecutive hips in 181 patients, whose average age was 70 years (range 32–95) and BMI of 28 (range 19–63). The implant, which averaged 94 millimeters in length (range 91–105), was made of titanium alloy with a hydroxyapatite coating on a titanium plasma-spray in the third of the stem.

The average Harris hip score (HHS) was 52 (range 10–80) preoperatively and 91 (range 70–100) postoperatively and no patients experienced thigh pain. Preoperative WOMAC scores averaged 48, compared to a postoperative average of 4. There were no fractures or other complications related to the prosthesis, no radiographic evidence of subsidence, and all stems were radiographically stable on most recent radiographs. The typical pattern of bony ingrowth was that of bone bridging and endosteal condensation at the proximal portion of the stem.

This study demonstrated that the use of an off-the-shelf short femoral stem designed to fit and fill the metaphysis provides reliable clinical and radiographic results at a minimum two-year (average 31 months) follow-up. Short stems may be particularly helpful to surgeons performing total hip arthroplasty using a MIS anterior approach.

The trend toward evidence-based decision-making in orthopedics requires the analysis of large sets of data in real time that can direct clinical decision-making. We have developed an automated web-based electronic data capture (EDC) software system designed to simplify and make more time and cost efficient orthopedic data collection and analysis. The purpose of this study is to validate the radiographic alignment tool of the EDC software system. The goal was to establish the feasibility of using this web-based EDC tool in clinical practice.

Twenty-eight consecutive unilateral TKAs were performed on 28 patients. Coronal mechanical axis and sagittal tibial and femoral axis radiographic measurements were obtained preoperatively and 1 month postoperatively. The radiographs were uploaded to a web-based EDC knee surgery data analysis program that includes a radiographic measurement tool. Two blinded observers analyzed the radiographs; one using a conventional manual measurement tool and the other a web based measurement tool. A paired t-test was used to evaluate measurement variation between observers.

There was no statistically significant difference in pre-operative mechanical axis (.18°, p> .05), postoperative mechanical axis (.25°, p> .05), postoperative femoral component axis (.68°, p> .05), and postoperative tibial component axis (1.07°, p> .05) measurements performed using the manual tool and the web-based software systems.

The results of this study validate the ability of the web-based software system to collect and process radiographic measurements. An automated web-based EDC software system allows for the full integration of patient demographic, radiographic, and peri-operative clinical variables in a fully searchable, instantaneously updatable and easily analyzed database. It is anticipated that this unique approach will allow surgeons to gather a wealth of searchable and quantifiable data that can quickly, accurately, economically, and efficiently shape clinical decisions.

There has been a longstanding need for a structural biomaterial that can serve as a bone graft substitute or implant construct and is effective for fixation by bone ingrowth. A porous tantalum material was developed to address these issues. The purpose of this paper and presnetation is to describe the properties and 2 to 5 year clinical results of porous tantalum in various reconstructive orthopaedic procedures.

Porous tantalum has been used to manufacture primary and revision acetabular cups, acetabular augments, tibial and patella implants, patellar augments, structural devices for the treatment of osteonecrosis, and spinal fusion implants. Clinical follow-up includes: 2–5 year clinical and radiographic evaluation of: 414 monoblock cups in primary THA, 36 monoblock cups and 587 revision hemispheres used in revision THR, 16 hips revised with acetabular augments and revision hemispheres; 2 to 4 years for 101 tibial implants used in primary TKR and 69 patellas used in cementless TKR; 2–4 years for 11 patellar augments in salvage TKR, 1–5 years for 53 revision TKRs using knee spacers; 1–4 years for 91 osteone-crosis hip implants; and for 15 cervical fusion cases.

This innovative tantalum implant material with trabecular architecture possesses advantages in stiffness, friction coefficient, porosity, rate and extent of tissue ingrowth, and versatility in manufacturing of structural devices. It has been clinically validated in numerous and diverse reconstructive procedures.

The most reported benefit of TKA navigation technologies has been the reduction in limb and component alignment outliers. This improvement has not been shown to effect clinical outcomes. This study was designed to compare the functional outcomes between computer assisted techniques and manual techniques.

Each group had 60 patients with similar demographics. The average functional outcomes (SF-36, WOMAC, range of motion, pain relief, and knee society score) were the same.

The average scores of the SF-36, Knee Society Score, WOMAC were similar for the two groups. However, fewer patients in Group II reported visual analog pain scores greater than 40 at 6 wks, 3 mos and 6 mos. At 1 yr, the pain scores of the two groups were similar. Fewer patients in Group II had KSS scores less than 70 at 3 months, 80 at 6 months, and 90 at one year, than those in Group I. The average range of motion in Group II was greater by 8 degrees at 4 wks and 3 mos, but equal to the average ROM in Group I at 6 and 12 mos. However, the number of patients with less than 90 degrees of motion at each follow-up period was less in Group II than in Group I at each follow-up period. There were fewer superficial wound infections in Group II than in Group I.

The average functional outcomes were similar; the results indicate a consistent reduction in outliers in most measured parameters of functional outcomes. In particular, the guidelines for administering pain medication and providing physical therapy were similar for the two groups. The results of this study are parallel to the radiographic results comparing TKA’s performed with manual and computer assisted instrumentation. In those studies, a reduction in outliers was consistently associated with the use of computer assisted techniques.

Customization makes it possible to fulfill design requirements during MIS-THA procedures, and has helped define the parameters of fit and fill. This study describes the results of using customization techniques to develop a femoral implant for utilization.

CT-based design criteria for femoral implants has-been developed and used for primary, cement-less, non-minimally invasive THA surgery. Over 1000 procedures performed with these devices have been associated with displaced femoral fractures, and have been revised for septic loosening. This study has 2 parts:

20 implants were designed and implanted with CT-based criteria that utilized the identical fit and fill standards of the custom implants previously established, but had short (< 115 mm), tapered stems;

The stem of these implants was shortened (95–115 mm) and tapered. Implants in both groups were inserted using a single incision, posterior-lateral MIS approach. Patients were followed clinically and radiographically for six months. Immediate full weightbearing and use of a single cane were encouraged.

The use of CT-based customization techniques is helpful for defining design criteria of femoral implants, but the instrumentation for inserting these implants must be adapted to the specific surgery. Customization also facilitates the design and evaluation of CAOS applications for inserting these MIS implants.

Introduction: Hospital accrediting organizations have recently emphasized the evaluation of and response to postoperative pain as the “fifth vital sign”. However, there are no prospective studies describing normal pain patterns after TKA to guide appropriate clinical responses. Similarly, there are no studies describing those at risk for unusual pain.

Purpose: To outline the pattern of normal recovery and identify factors predictive of significant pain after TKA.

Method: Prospective, observational, single surgeon design. Inclusion criteria: primary, cemented TKA for osteoarthritis. Clinical & radiographic measures obtained pre-op and at 1,3,6 and 12 months post-operatively. Predictive factors and post-operative outcomes included body mass index visual analogue scale (VAS), demographics, physical therapy, and component design, alignment and fixation. Psychometric testing included the Beck Depression Inventory and McGill Pain Questionnaire.

Results: 96 patients, 125 knees (mean age = 66, 55.2% women). Mean VAS at pre-op, 1,3, 6 and 12 month visits were 51.1(SD 23.8), 37.4(21.8), 27.0(22.2), 20.8(20.3), and 18.0(21.0), respectively. significant pain (VAS> 40) was reported by 61.51% of patients pre-op, 41.7% at 1 month, 24.0% 3 months, 16.7% 6 months, and 8.3% 12 months. There were no differences in pain based on the type of anesthesia, weight, age or gender. Preoperative elevated depression, anxiety and pain-related suffering descriptors predicted greater pain during the first 6 months after surgery, but did not ultimately affect recovery. Patients who had greater pain (VAS> 40) used more home and outpatient physical therapy (p=0.25).

Conclusion: Contrary to common beliefs, many patients (22%) still experience significant pain up to six months after TKA, despite absence of clinical or radiographic abnormalities. significant pain (VAS > 40mm) after six months may be indicative of an abnormal pain experience. Preoperative pain, depression and suffering are associated with increased early pain andutilization of therapy.

The success of total knee replacement surgery depends critically on proper limb alignment and implant position. Even with contemporary mechanical alignment instrumentation, errors in limb alignment and implant position do occur. To improve upon the accuracy and biomechanical efficacy of conventional surgical instrumentation while limiting the need for substantial pre-operative planning, a non-image-based computer-aided navigation system was developed for total knee replacement surgery. Clinical studies have demonstrated that use of this system, OrthoPilot® (Aesculap AG, Tuttlingen, Germany), for knee replacement surgery can lead to improved limb alignment and implant position.

In this study we investigated the repeatability and sensitivity of the OrthoPilot® computer-aided navigation system for total knee replacement surgery. To assess repeatability, total knee replacement surgeries were simulated on an idealized test bench using identical input parameters and the variation in output measurements was measured. To assess sensitivity, the effect of moderate movement of position sensors on system-level accuracy was measured. The results indicate that (1) the system functions in a highly repeatable manner if it is supplied with repeatable inputs; and (2) unintentional relative movement of position sensors during surgery can substantially affect accuracy of the system outputs.

Because computer-aided navigation systems are powerful tools for orthopaedic surgery, it is important to recognize that their accuracy and precision are highly dependent on pre-operative and intra-operative registration techniques. Like all instrumentation systems, their use is associated with a learning curve, even in the hands of experienced orthopaedic surgeons. The results of this study demonstrate that the OrthoPilot® in an inherently precise instrument that is sensitive to variations in surgical technique. It is critical that the users of these systems (i.e. surgeons) be aware of system sensitivities and pay careful attention to operative techniques required by the system.

Introduction: The consequences of incorrect implant orientation and improper limb alignment in TKR surgery are: 1) accelerated implant wear; 2) early prosthesis loosening; 3) sub optimal clinical function. Although mechanical alignment guides have improved the precision of TKR surgery, it has been estimated that alignment errors of more than 3 degrees occur in at least 10% of TKR even when performed by experienced surgeons using mechanical alignment systems of modern design. The purpose of this study was to determine the accuracy of TKR surgery performed with conventional instruments using a computer assisted navigation system (OrthoPilot) as a measurement tool.

Methods: 35 patients underwent primary TKR performed with a conventional intramedullary, mechanical instrumentation system. Minimal follow-up was 1 year. The OrthoPilot was used to measure: 1) pre-operative limb alignment; 2) pre-operative medial-lateral stability; 3) pre-operative flexion; 4) post-operative alignment; 5) post-operative medial-lateral stability; 6) post-operative flexion. Patients consented to the use of the Ortho-Pilot as part of an Investigation Review Board approved study. Limb and implant alignment were measured on pre- and post-operative x-rays and compared to the alignment results measured by OrthoPilot. Knee society scores were obtained on all patients.

Results: No complications were associated with the use of the OrthoPilot. Post-operative pain and function were not affected by the use of the OrthoPilot. Pre-operative angular deformities measured by OrthoPilot ranged from 12 degrees varus to 20 degrees valgus and 12 degrees flexion to 7 degrees hyperextension. Post-operative angular deformities ranged from 2.5 degrees varus to 2 degrees valgus and 5 degrees flexion to 2 degrees hyperextension. Pre-operative medial-lateral laxity ranged from 0 to 10 degrees. Post-operative medial-lateral laxity ranged from 3–5 degrees. Pre-operative flexion ranged from 95 to 125 degrees. Post-operative flexion ranged from 115 to 136 degrees. Movement of the pins that hold the diode containing rigid bodies occurred in 5 cases. Inconsistencies of more than 3 degrees in limb registration by the OrthoPilot occurred in 7 cases. Pre- and post-operative x-ray measurements varied from OrthoPilot measurements by more than 3 degrees in 25 cases. Surgery time with OrthoPilot.

Conclusions: OrthoPilot is safe. No complications occurred attributable to the system. It took approximately 10 cases to establish a consistent registration technique using the OrthoPilot. Pin movement can occur and significantly affects the accuracy of the measurements. The OrthoPilot was useful as a measurement tool for determining the pre- and post-operative alignment, stability and range of motion of a TKR. The use of conventional intramedullary mechanical TKR instruments can result in accurate and reproducible frontal and sagittal limb alignment. X-rays are not accurate for determining pre- and post-operative limb and implant alignment.

Significance: Since DRG-based Medicare payments to hospitals, length of stay (LOS) after Total Knee Arthroplasty (TKA) has declined dramatically. This reduction was accomplished in part by transferring patients to DRG-exempt rehabilitation units. Despite the regular use and expense of inpatient rehabilitation after TKA, there have been no prospective studies defining its efficacy. Purpose: Determine the impact of inpatient rehabilitation on TKA outcome.

Methods: Prospective, observational, single surgeon, single facility design.Inclusion criteria:primary,cemented TKA for OA between 1998–1999. All postoperative and rehabilitative care dictated by clinical protocol. Subjects were evaluated pre-op, at 1,3 and 6 months post-op. Patient (demographics, comorbidities), psychological (depression, anxiety), surgical (implant type, fixation, alignment), resource utilization (LOS, outpatient/home PT visits, rehabilitation LOS), complications, functional (knee flexion, gait, assistive device, Knee Society Score (KSS)) and pain (visual analogue scale, medication use) data obtained. Principle outcomes were pain, knee flexion, function, KSS, number of PT visits.

Results: 125 knees, 56 bilateral. No patient lost to follow-up. Mean age 66 years (36–85). At six months follow-up, postoperative KSS score was 164.4(94–200), flexion 114.3(80–130), VAS 18(SD 21). Patients discharged to rehabilitation had significantly lower preoperative KSS scores (89, SD30) than those discharged to home (104.6, SD24.4)p=035. There were no other differences between groups. Patients discharged directly to home had a greater knee flexion (p=005), walk farther (p=024), climb stairs easier (p=036), and utilized less home physical therapy (p=030) than patients discharged to rehabilitation.

Conclusion: This study was unable to demonstrate a benefit of inpatient rehabilitation after TKA. However, patients transferred to inpatient rehabilitation were less functional before surgery than those discharged home. Further studies are needed to determine if these patients benefit from inpatient rehabilitation versus home care.

Introduction: Osteolysis of the pelvis secondary to polyethylene wear of uncemented acetabular implants has emerged as the most serious and challenging consequence of THR. A very large number of patients have and will continue to receive implants at the risk of being associated with osteolysis. The early detection of osteolysis allows the initiation of treatment programs that preserve bone stock. Because osteolysis occurs and progresses in the absence of clinical symptoms, appropriate follow-up surveillance must be instituted. Our initial study of the usefulness of CT scans in detecting clinically silent and radiographically unobservable osteolysis indicated that x-rays greatly understated the incidence and location of osteolysis. The purpose of this study was to determine the incidence of CT scan identifiable osteolysis in young, active patients with a single cup design and a minimum follow-up of 7 years.

Methods: Between 1990–1995, 117 hips (105 patients) underwent an uncemented total hip replacement with a patient-matched femoral component and a titanium plasma sprayed, multi-holed acetabular shell with a compression molded, polyethylene, irradiated in air. 57 patients underwent a CT scan using a metal subtraction software technique. All patients were classified based on their CT scans: Group I: no osteolysis; Group II: cavitary osteolysis; Group III: segmental osteolysis. All patients had standard AP, Frog – lateral and shoot-through lateral radiographs, performed at the time the CT scan was obtained.

Results: 37.2% of hips were in Group I, 53.5% in Group II and 9.3% in Group III. No patients in Group I had x-ray evidence of osteolysis (i.e. there were no false negative CT scans). 12% of patients in Group II had x-ray evidence of osteolysis. 22% of patients in Group III had x-ray evidence of osteolysis. There was no correlation between the incidence of osteolysis seen on CT scans with: 1) activity level; 2) age; 3) sex; 4) weight, and 5) size of acetabular component. There was no correlation between polyethylene wear measured using the Martel method and pelvic osteolysis. There was a correlation between the length of implantation and pelvic osteolysis. The average follow-up for patients in Group III was 105.5 months (range 85 – 115) vs. 89.4 months (57 – 117) for Group II and 81.5 months (51 – 112) for Group I. Of the patients with follow-up greater than eight years, 25% had Group III osteolysis. No patients have required revision or polyethylene liner exchange thus far.

Discussion: This study indicates that: 1) x-rays are an unreliable method for determining the presence. Location or extent of osteolysis, 2) the incidence of osteolysis based upon CT scans (Group II – III) is 63%; 3) Osteolysis, even if extensive (Group 3) is NOT associated with symptoms; 4) the pattern of osteolysis seen on CT scan strongly suggests that the presence of screws plays an important factor in the process; 5) CT scans are helpful in the planning process for acetabular revision. They allow the precise determination of the location and extent of osteolysis; 6) CT scans are also potentially useful for determining the impact of medical (e.g. alidronate) or surgical (e.g. bone grafting) treatment of osteolysis; 7) CT scans may be very helpful in assessing whether new polyethylenes are associated with reduced osteolysis.

The authors strongly recommend that: 1) a surveillance program be established for careful, regular follow-up of patients with THR in place more than 7 years; 2) CT scans be considered as part of that surveillance program, and 3) cups with screws NOT be used routinely in primary THR surgery.

Osteolysis secondary to polyethylene wear is the most serious aseptic long-term complication following THR. Studies have shown that fixation with screws, modularity and lack of extensive bone ingrowth are associated with increased osteolysis. This study examines the initial experience with a cup designed to address these issues.

One hundred and twenty-seven consecutive primary THR were performed between 1997–1999 using unce-mented monoblock, elliptical, tantalum cup without screw holes. Average follow-up 40 months (range 24 to 61). 79 THR in females, 48 in males. 48% THR hybrid fixed, 52% uncemented. Average age 61.6 years (range 19 to 88). Pre and post-operative clinical assessment with Harris hip score (hhs), WOMAC, SF-36. One independent, blinded observer performed zonal radiographic analysis with modified DeLee and Charnley method.

Average hhs at recent follow-up 93 (range 85 to 100). All shells appear fixed with bone ingrowth. Dome-gaps present in 6 cups post-op; all have filled in. Radiolucencies at follow-up: 4% zone 1, 8% zone 2; none greater than 1 mm. No cup migration. 8 cup related complications: 5 dislocations (4%) 1 subluxation, 2 undisplaced rim fractures (1.7% – no treatment). 3 dislocations, 1 subluxation occurred more than three months post-op. 3 revisions: 1 deep wound infection, 1 liner exchange (using reaming technique), 1 femoral head exchange.

Uncemented monoblock, elliptical tantalum cup without holes provides secure, symptom-free fixation at 4 years. No complications associated with use of tantalum. Elliptical shape associated with dome gaps, all of which appeared to fill by 3 months. Monoblock design results in increased polyethylene lip prominence associated with 6 cases of instability. Effect of prominent rim on impingement and long-term wear requires careful follow-up.

Pelvic osteolysis secondary to polyethylene wear is a major complication following THR. Identification of implant specific characteristics associated with osteolysis is essential. The purpose of this study is to compare incidence of CT scan identifiable osteolysis in 2 groups of young, active patients following THR; one with multi-holed acetabular shells with screws, one with cups without screw holes.

Between 1990–1993, 77 patients (85 hips) underwent THR with a cementless titanium, multi-holed shell with screws, modular, compression molded polyethylene and an uncemented titanium femoral stem. Average follow-up: 9 years, average age at surgery: 51 years. Between 1984–1987, 163 patients (183 hips) underwent THR with a cementless cobalt-chrome, solid shell, modular, heat-pressed polyeth-ylene liner and uncemented cobalt-chrome femoral stem. Average follow-up: 16 years, average age at operation: 52 years. All polyethylene was irradiated in air. At most recent follow-up, CT scans with metal suppression software was obtained to evaluate incidence of pelvic osteolysis. Patients classified: Group 1-no osteolysis, Group 2-cavitary osteolysis, Group 3-segmental osteolysis.

Patients with titanium, multi-holed shells had: Group 1-50.0%, Group 2-38.7%, and Group 3-11.3%. Patients with cobalt-chrome, solid shells had: Group 1-59.3%, Group 2-33.3% and Group 3-7.4%.

Although the patients with solid cups had much longer follow-up, less secure capture mechanism, less congruency between polyethylene and shell, and heat-pressed polyethylene, the incidence and extent of pelvic osteolysis was less than in the patients with multi-holed shell with screws. The presence of 6.5 mm cancellous screws is a serious independent risk factor for pelvic osteolysis following THR.

Many recent studies emphasise the importance of surgical technique for achieving long-lasting, pain-free, optimally functioning TKR. However, little information exists in the accuracy with which each step of the TKR procedure is performed using current instrumentation. This study examines the accuracy with which each step of the TKR procedure using current, intramedullary instrumentation.

Twenty primary TKR were performed using a current, intramedullary instrumentation system. The accuracy of each femoral and tibial cut and the accuracy of the final frontal and sagittal limb alignment were measured using an image-free computer assisted navigation system. The system made it possible to measure: 1) frontal femoral implant alignment; 2) sagittal femoral implant alignment; 3) femoral implant rotational alignment; 4) frontal tibial implant alignment; 5) sagittal tibial implant alignment; 6) frontal limb alignment; 7) sagittal limb alignment. Alignment results are expressed in terms of the mechanical axis. Optional results are a frontal and sagittal axis of 90° relative to the mechanical axis. The optimal femoral rotational alignment is 3 degrees externally rotated from the posterior femoral condyles or zero degrees externally rotated from Whitesides line.

The alignment results were: 1) frontal femoral alignment: 89° (range 87 to 92°); 2) sagittal femoral alignment: 89 (range 88 to 193°); 3) femoral rotational alignment: 1° external rotation vs. femoral condyle; 2 degrees internally rotated vs. Whitesides line (range 0.5° to 3.5°); 4) frontal tibial alignment: 88° (87° to 93°); 5) sagittal tibial axis: 87° (range 86° to 91°); 6) frontal limb alignment: 179° (range 177 to 181°); 7) sagittal limb alignment 179° (range 174 to 180°).

Intramedullary instrumentation allows reasonably accurate and reproducible frontal limb alignment. There is a tendency to leave the limb in slight flexion when using intramedullary instruments. There is also a consistent tendency to internally rotate the femur with current anterior –posterior alignment guides and to excessively posteriorly flex the tibial component, although almost all of the 20 TKR’s resulted in final limb alignment within 3 degrees of frontal and sagittal axes. Very few (4) TKR’s were performed in which all of the measured steps were within 3 degrees of the optimal position.

The study emphasises that current intramedullary instrumentation does not result in a high incidence of accuracy when each step of the procedure is measured. Computer assisted techniques permit measurement of the steps of the TKR procedure with a high degree (error < 1°) of accuracy. Longevity, pain-relief and funtion should be related to the total accuracy with which TKR are performed.

Introduction: The impaction grafting technique appears to be a very useful method for revising failed THA with extensive cavitary proximal femoral bone loss. However, its use with short, polished stems has been associated with femoral fractures, stem subsidence and instability. This study describes a new surgical impaction grafting technique and reports the results using blasted femoral stems of variable lengths, with variable head-neck offsets and lengths.

Methods – Results: Fifteen revision THA using an impaction grafting technique were performed. Minimum follow-up was five years. Preoperative diagnosis was aseptic loosening of cemented femoral stems in 11 cases, and uncemented stems in four cases. Thirteen of the 15 revision cases with impaction grafting were cemented. Three revision cases were performed using stems less than 150 mm in length, the remainder utilised stems from 165 mm – 315 mm in length. Neck lengths of the revision implants ranged from 40 – 80 mm, including four calcar replacements. Intraoperative fractures occurred in two cases and were successfully treated with cerclage wires. There were two postoperative fractures, both in patients with stems less than 150 mm. Both were successfully treated with plates and onlay allografts. At most recent follow-up, all patients were pain-free. All patients were ambulating unlimited distances. Two patients required canes. All stems were well fixed radiographically with no evidence of progressive radiolucencies or subsidence. The graft appeared to be incorporating. The surgical technique consists of: 1.) removal of previously failed implant and cement; 2.) placement of cerclage wires around femur into which graft will be impacted; 3.) introduction of impacted allograft; 4.) radially impacting with tapered, polished, smooth straight impactors to a distance into femur that permits firm engagement with endosteal cortex for a distance of at least 3 cm; 5.) use of polished, smooth broaches to create final shape of cavity; 6.) trial reduction using polished broaches; and 7.) insertion of implant with or without cement.

Discussion – Conclusions: This report describes a new technique for impaction grafting in revision THA. This study suggests that the use of rough surfaced, long femoral stems with variable head-neck lengths and offsets in conjunction with the impaction grafting technique may reduce the incidence of subsidence, femoral fractures, and dislocations that can occur when this revision technique is used with short, polished stems.

Bone loss can be treated in one of two general ways. Missing bone can be replaced either with bone graft applied to the host bone or augmentations attached to the revision implants. The ideal treatment of bone defects during revision TKR surgery: 1) makes immediate full weight bearing possible; 2) provides longterm support for the implants; 3) Restores original bone stock.

Bone grafts achieve these goals when the defects are CAVITARY. Therefore, bone grafts rather than metal augmentation devices are the surgical treatment of choice when these types of defects are encountered during revision TKR surgery.

Although bone grafts may achieve these goals when the defects are SEGMENTAL, the results are uncertain and more difficult to achieve. Metal augmentations make possible immediate full weight bearing and provide reliable long-term support for revision TKR implants. When these augments are made of Tantalulm, a metal with 80% porosity, the restoration of bone stock is also possible.

There are advantages and drawbacks to each approach. The advantages of bone grafts are that they: 1) restore bone stock; 2) are relatively inexpensive (especially if autogenous graft is used); 3) can be applied with relatively simple instrumentation; and 4) allow defects of a wide variety of sizes and shapes to be treated. The disadvantages of bone grafts are that they: 1) have limited application in large, segmental defects where structural support is necessary; 2) do not always unite predictably, particularly when the host bone is osteopenic or when angular deformities exist; 3) are shaped and inserted without the benefit of precise instrumentation; and 4) may require limited weight bearing or restricted activity for a period of time following surgery. The advantages of augmentation devices are that they: 1) can be manufactured in a wide variety of shapes and sizes; 2) provide immediate stable fixation; and 3) can be inserted using precise cutting instruments. Therefore, the indications for metal augmentation devices are: 1) uncontained defects (segmental) that require structural support for the knee implant; 2) knees with osteopenic bone or large angular defects; and 3) older patients in whom the importance of immediate mobilization and unrestricted weight-bearing is more important than the restoration of bone stock.